Seasonal and multiannual dynamics of rodent species number under the influence of climate factors and anthropic modifications

The research was carried out in agricultural experiment stations in the central area of the Republic of Moldova during a period of 35 years. It was determined that cyclic oscillations with an interval of 3-4 years are not typical of Microtus arvalis, as can be seen in other parts of the area. Intense anthropogenic influence determines the type of numerical dynamics. A certain periodicity is observed in the species Mus spicilegus, but during the last 30 years the dynamics has become acyclic. In the populations of the species Apodemus sylvaticus there was a more pronounced periodicity of the oscillation of the herd, once every two years.

Freshwater Populations, Interactions, and Networks

Freshwater ecosystems are never static and a species list alone hides that dynamism. Species come and go; populations wax and wane, so basic understanding of the numerical dynamics is necessary to separate ‘natural’ change from anthropogenic-induced change. Numerical changes in species or populations give clues, unravelling details of the changes. For example, quantifying life histories in changing populations or commonalities such as strategies in species changes is often necessary. Community characteristics, such as indices for vegetation or water quality, provide a different perspective on dynamics. Both population and community studies are now greatly assisted by environmental genetics, or eDNA. Ecosystems are made up of patches, as are landscapes, such that the patch dynamics often indicates much about the changing biological dynamics and networks. Energy to make ecosystems function is a small fraction of the solar energy that hits the earth; a far higher fraction is transformed by the vegetation of the ecosystem into latent heat of evaporation and is stored in water vapour. In its absence or reduction, that solar energy is transformed into heat, raising the temperature of the land and air.

Artifacts in time-resolved Kelvin probe force microscopy

Kelvin probe force microscopy (KPFM) has been used for the characterization of metals, insulators, and semiconducting materials on the nanometer scale. Especially in semiconductors, the charge dynamics are of high interest. Recently, several techniques for time-resolved measurements with time resolution down to picoseconds have been developed, many times using a modulated excitation signal, e.g., light modulation or bias modulation that induces changes in the charge carrier distribution. For fast modulation frequencies, the KPFM controller measures an average surface potential, which contains information about the involved charge carrier dynamics. Here, we show that such measurements are prone to artifacts due to frequency mixing, by performing numerical dynamics simulations of the cantilever oscillation in KPFM subjected to a bias-modulated signal. For square bias pulses, the resulting time-dependent electrostatic forces are very complex and result in intricate mixing of frequencies that may, in some cases, have a component at the detection frequency, leading to falsified KPFM measurements. Additionally, we performed fast Fourier transform (FFT) analyses that match the results of the numerical dynamics simulations. Small differences are observed that can be attributed to transients and higher-order Fourier components, as a consequence of the intricate nature of the cantilever driving forces. These results are corroborated by experimental measurements on a model system. In the experimental case, additional artifacts are observed due to constructive or destructive interference of the bias modulation with the cantilever oscillation. Also, in the case of light modulation, we demonstrate artifacts due to unwanted illumination of the photodetector of the beam deflection detection system. Finally, guidelines for avoiding such artifacts are given.

Multi-Stability, Limit Cycles, and Period-Doubling Bifurcation with Reaction Systems

Quantitative models may exhibit sophisticated behaviour that includes having multiple steady states, bistability, limit cycles, and period-doubling bifurcation. Such behaviour is typically driven by the numerical dynamics of the model, where the values of various numerical parameters play the crucial role. We introduce in this paper natural correspondents of these concepts to reaction systems modelling, a framework based on elementary set theoretical, forbidding/enforcing-based mechanisms. We construct several reaction systems models exhibiting these properties.