In this paper, a discrete version of continuous non-autonomous predator-prey model with infected prey is investigated. By using Gaines and Mawhin's continuation theorem of coincidence degree theory and the method of Lyapunov function, some sufficient conditions for the existence and global asymptotical stability of positive periodic solution of difference equations in consideration are established. An example shows the feasibility of the main results.
Dynamical behavior of a boundary layer separation is studied using both theoretical analysis and experimental approach. The dynamical nature of the phenomenon is demonstrated on a simple case of a boundary layer in adverse pressure gradient studied experimentally. The Time-Resolved PIV technique was used to study instantaneous structure of the separation region and its time development. Distinctive coherent structures and their dynamical behavior were identified using the BOD method. and Obsahuje seznam literatury
To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-a, IL-10 and finally also IL-1b. Productions of IL-12 and INF-g are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1b and TNF-a significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-g were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-g, besides IL-1b, TNF-a, IL-6 and IL-10. Productions of IL-1b, IL-6 and TNFa increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-g begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines., L. Janský, P. Reymanová, J. Kopecký., and Obsahuje bibliografii
To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-a, IL-10 and finally also IL-1b. Productions of IL-12 and INF-g are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1b and TNF-a significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-g were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-g, besides IL-1b, TNF-a, IL-6 and IL-10. Productions of IL-1b, IL-6 and TNFa increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-g begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines., L. Janský, P. Reymanová, J. Kopecký., and Obsahuje bibliografii
This paper is an introduction to dynamics of dianalytic self-maps of nonorientable Klein surfaces. The main theorem asserts that dianalytic dynamics on Klein surfaces can be canonically reduced to dynamics of some classes of analytic self-maps on their orientable double covers. A complete list of those maps is given in the case where the respective Klein surfaces are the real projective plane, the pointed real projective plane and the Klein bottle.
The dominant forces determining the motion of interplanetary particulates are gravitation, solar radiation pressure and Lorentz force. The latter two becoming significant for micron- and submicron- sized particles. In situ measurements by spaceprobes, microcrater distributions and remote observations both in the IR and visible wavelength range have established the mass frequency and spatial distribution of dust particles in interplanetary space. Consequences of the Poynting-Robertson effect and mutual collisions on these distributions and the contributions of various sources (interstellar dust, asteroids and comets) are discussed. It is shown that the contribution from a distributed source of large particles in the inner solar system is most important. Collisions between these meteor sized particles (m > 10^-5 g) produce large amounts of zodiacal light particles (10^-5 g to 10^-10 g) and
β-meteoroids (m < 10^-10 g) which leave the solar system on hyperbolic orbits. At the present time the Poynting-Robertson effect transports into the inner solar system less than 10% of the zodiacal light particles which are produced by collisions from bigger particles.
In arid and semiarid ecosystems, plant interspaces are frequently covered by communities of cyanobacteria, algae, lichens and mosses, known as biocrusts. These crusts often act as runoff sources and are involved in soil stabilization and fertility, as they prevent erosion by water and wind, fix atmospheric C and N and contribute large amounts of C to soil. Their contribution to the C balance as photosynthetically active surfaces in arid and semiarid regions is receiving growing attention. However, very few studies have explicitly evaluated their contribution to organic carbon (OC) lost from runoff and erosion, which is necessary to ascertain the role of biocrusts in the ecosystem C balance. Furthermore, biocrusts are not resilient to physical disturbances, which generally cause the loss of the biocrust and thus, an increase in runoff and erosion, dust emissions, and sediment and nutrient losses. The aim of this study was to find out the influence of biocrusts and their removal on dissolved and sediment organic carbon losses. One-hour extreme rainfall simulations (50 mm h-1) were performed on small plots set up on physical soil crusts and three types of biocrusts, representing a development gradient, and also on plots where these crusts were removed from. Runoff and erosion rates, dissolved organic carbon (DOC) and organic carbon bonded to sediments (SdOC) were measured during the simulated rain. Our results showed different SdOC and DOC for the different biocrusts and also that the presence of biocrusts substantially decreased total organic carbon (TOC) (average 1.80±1.86 g m-2) compared to physical soil crusts (7.83±3.27 g m-2). Within biocrusts, TOC losses decreased as biocrusts developed, and erosion rates were lower. Thus, erosion drove TOC losses while no significant direct relationships were found between TOC losses and runoff. In both physical crusts and biocrusts, DOC and SdOC concentrations were higher during the first minutes after runoff began and decreased over time as nutrient-enriched fine particles were washed away by runoff water. Crust removal caused a strong increase in water erosion and TOC losses. The strongest impacts on TOC losses after crust removal occurred on the lichen plots, due to the increased erosion when they were removed. DOC concentration was higher in biocrust-removed soils than in intact biocrusts, probably because OC is more strongly retained by BSC structures, but easily blown away in soils devoid of them. However, SdOC concentration was higher in intact than removed biocrusts associated with greater OC content in the top crust than in the soil once the crust is scraped off. and Consequently, the loss of biocrusts leads to OC impoverishment of nutrient-limited interplant spaces in arid and semiarid areas and the reduction of soil OC heterogeneity, essential for vegetation productivity and functioning of this type of ecosystems.
Organic matter properties of soils were studied in a territory covered by Stagnosols after afforestation. We quantified the impact of afforestation on the amount and distribution of free organic matter, microaggregates (unstable and stable under low-intensity sonification) and their components in the upper horizons of former arable soils overgrown by different species of forest vegetation. The duration of 45 years after afforestation was revealed to be not sufficient for a complete renewal of soil humus state, which appears only after till 115 years of the duration of forest cenosis. The carbon storage in light fractions remains lower by 21–40 % relative to that of forest soil, including significant losses of free organic matter (42–58 %) and occluded organic matter (12–33 %), which present the most active part of soil organic matter. The positive impact of the deposit regime, expressed by a sharp improvement of the carbon cycle balance, is reflected by the Cunstable/Cstable ratio, which decreases from 6.2 in arable soil to 2.4 on average in forest stands.
We consider autonomous systems where two scalar differential equations are coupled with the input-output relationship of the Preisach hysteresis operator, which has an infinite-dimensional memory. A prototype system of this type is an LCR electric circuit where the inductive element has a ferromagnetic core with a hysteretic relationship between the magnetic field and the magnetization. Further examples of such systems include lumped hydrological models with two soil layers; they can also appear as a component of the recently proposed models of population dynamics. We study dynamics of such systems near an equilibrium point. In particular, we show and examine a similarity in the behaviour of trajectories between the system with the Preisach memory operator and a planar slow-fast ordinary differential equation. The nonsmooth Preisach operator introduces a singularity into the system. Furthermore, we classify the robust equilibrium points according to their stability properties. Conditions for stability, instability and partial stability are presented. A robust partially stable point simultaneously attracts many trajectories and repels many trajectories (a behaviour which is not generic for smooth ordinary differential equations). We discuss implications of such local dynamics for the excitability properties of the system.