Professor Wiesław Szlenk (1935-1995)
Influence of diffusion on interactions between malignant gliomas and immune system
We analyse the influence of diffusion and space distribution of cells in a simple model of interactions between an activated immune system and malignant gliomas, among which the most aggressive one is GBM Glioblastoma Multiforme. It turns out that diffusion cannot affect stability of spatially homogeneous steady states. This suggests that there are two possible outcomes-the solution is either attracted by the positive steady state or by the semitrivial one. The semitrivial steady state describes...
Jan Poleszczuk – the Winner of the Polish Mathematical Society’s Prize
Jan Poleszczuk was born on 19th of October 1986 in Warsaw in a family of humanists. His parents and older brother are sociologists. Maybe a little out of contrariness he decided to study mathematics. However, it is possible that he was influenced by his father's fascination with statistical tools. Choosing a bachelor's seminar he decided to combine ''tradition with modernity'', registered for ''Biomathematics and Game Theory'' and his first idea was to use Lesli matrices, which are typically used...
Mathematical models in epidemiology and immunology
The article contains no abstract
National Conference Applications of Mathematics to Biology and Medicine
It is unbelievable that this year we will meet at the National Conference Applications of Mathematics to Biology and Medicine for the 24th time. The initiator, chairman of the Scientific Committee and tireless participant of all previous conferences is Prof. Mariusz Ziółko who in the 1970s participated in the Schools of Mathematical Modeling in Biology organized by Prof. Adam Łomnicki, an outstanding biologist and ecologist from the Jagiellonian University. In 1994, M. Ziółko suggested to Prof....
XXV National Conference on Mathematics Applied to Biology and Medicine
A round anniversary is a reflection-friendly moment ... Like last year, I~would like to start with ``I can not believe that...'' This time, however, it will be more personally. Therefore -- I can not believe that it has been 25 years since I walked through the empty (yes, it is unbelievable as well!) streets of Zakopane to the resort where the First National Conference Applications of Mathematics to Biology and Medicine took place. At the end of my journey with quite a heavy backpack (clearly, you...
Co możemy opisać układem dynamicznym?
In this paper we present several examples of simple dynamical systemsdescribing various real processes. We start from well know Fibonaccisequence, through Lotka-Volterra model of prey-predator system, love affairdynamics, ending with modelling of tumour growth.
Complementary analysis of the initial value problem for a system of o.d.e. modelling the immune system after vaccinations
Complementary analysis of a model of the human immune system after a series of vaccinations, proposed in [7] and studied in [6], is presented. It is shown that all coordinates of every solution have at most two extremal values. The theoretical results are compared with experimental data.
Periodic dynamics in a model of immune system
The aim of this paper is to study periodic solutions of Marchuk's model, i.e. the system of ordinary differential equations with time delay describing the immune reactions. The Hopf bifurcation theorem is used to show the existence of a periodic solution for some values of the delay. Periodic dynamics caused by periodic immune reactivity or periodic initial data functions are compared. Autocorrelation functions are used to check the periodicity or quasiperiodicity of behaviour.
Angiogenesis process with vessel impairment for Gompertzian and logistic type of tumour growth
We propose two models of vessel impairment in the process of tumour angiogenesis and we consider three types of treatment: standard chemotherapy, antiangiogenic treatment and a combined treatment. The models are based on the idea of Hahnfeldt et al. that the carrying capacity for any solid tumour depends on its vessel density. In the models proposed the carrying capacity also depends on the process of vessel impairment. In the first model a logistic type equation is used to describe the neoplastic...
Influence of time delays on the Hahnfeldt et al. angiogenesis model dynamics
We study the influence of time delays on the dynamics of the general Hahnfeldt et al. model of an angiogenesis process. We analyse the dynamics of the system for different values of the parameter α which reflects the strength of stimulation of the vessel formation process. Time delays are introduced in three subprocesses: tumour growth, stimulation and inhibition of vessel formation (represented by endothelial cell dynamics). We focus on possible destabilisation of the positive steady state due...
Stability switches for some class of delayed population models
We study stability switches for some class of delay differential equations with one discrete delay. We describe and use a simple method of checking the change of stability which originally comes from the paper of Cook and Driessche (1986). We explain this method on the examples of three types of prey-predator models with delay and compare the dynamics of these models under increasing delay.
Models of interactions between heterotrophic and autotrophic organisms
We present two simple models describing relations between heterotrophic and autotrophic organisms in the land and water environments. The models are based on the Dawidowicz & Zalasiński models but we assume the boundedness of the oxygen resources. We perform a basic mathematical analysis of the models. The results of the analysis are complemented by numerical illustrations.
Time delays in proliferation and apoptosis for solid avascular tumour
The role of time delays in solid avascular tumour growth is considered. The model is formulated in terms of a reaction-diffusion equation and mass conservation law. Two main processes are taken into account-proliferation and apoptosis. We introduce time delay first in underlying apoptosis only and then in both processes. In the absence of necrosis the model reduces to one ordinary differential equation with one discrete delay which describes the changes of tumour radius. Basic properties of the...
Some remarks on modelling of drug resistance for low grade gliomas
In this paper we present a version of a simple mathematical model of acquiring drug resistance which was proposed in Bodnar and Foryś (2017). We based the original model on the idea coming from Pérez-García et al. (2015). Now, we include the explicit death term into the system and show that the dynamics of the new version of the model is the same as the dynamics of the second model considered by us and based on the idea of Ollier et al. (2017). We discuss the model dynamics and its dependence on...
Ananysis of a predator-prey model with disease in the predator species
In the paper we analyse a diffusive predator-prey model with disease in predator species proposed by Qiao et al. (2014). In the original article there appears a mistake in the procedure of the model undimensionalisation. We make a correction in this procedure and show that some changes in the model analysis are necessary to obtain results similar to those presented by Qiao et al.We propose corrected conditions for global stability of one of existing equilibria -- disease free steady state and endemic...
O pewnym ciekawym zastosowaniu modelu Lotki-Volterry
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Logistic equations in tumour growth modelling
The aim of this paper is to present some approaches to tumour growth modelling using the logistic equation. As the first approach the well-known ordinary differential equation is used to model the EAT in mice. For the same kind of tumour, a logistic equation with time delay is also used. As the second approach, a logistic equation with diffusion is proposed. In this case a delay argument in the reaction term is also considered. Some mathematical properties of the presented models are studied in...
A modified van der Pol equation with delay in a description of the heart action
In this paper, a modified van der Pol equation is considered as a description of the heart action. This model has a number of interesting properties allowing reconstruction of phenomena observed in physiological experiments as well as in Holter electrocardiographic recordings. Our aim is to study periodic solutions of the modified van der Pol equation and take into consideration the influence of feedback and delay which occur in the normal heart action mode as well as in pathological modes. Usage...
Model of AIDS-related tumour with time delay
We present and compare two simple models of immune system and cancer cell interactions. The first model reflects simple cancer disease progression and serves as our "control" case. The second describes the progression of a cancer disease in the case of a patient infected with the HIV-1 virus.
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