Improved cellular automata model shows that indirect apoptotic cell death due to vascular damage enhances the local control of tumors by single fraction high-dose irradiation

We investigated the effects of indirect apoptotic cell death due to vascular damage on tumor response to a single large dose with an improved two-dimensional cellular automata model. The tumor growth was simulated by considering the oxygen and nutrients supplied to the tumor through the blood vessels. The cell damage processes were modeled by taking account of the direct cell death and the indirect death due to the radiation-induced vascular damages. The radiation increased the permeation of oxygen and nutrients through the blood vessel or caused the breakdown of the vasculature. The amount of oxygen in cancer cells affected the response of cancer cells to radiation and the tumor growth rate after irradiation. The lack of oxygen led to the apoptotic death of cancer cells. We calculated the tumor control probability (TCP) at different radiation doses, D, the probability of apoptotic death, PO2_ap, the threshold of the oxygen level for indirect apoptotic death, O2t, the average oxygen level in cancer cells, [O2]av, and the vessel survival probability after radiation damage, Pv. Due to the vessel damage, indirect cell death led to a 4% increase in TCP for the dose ranging from 15 Gy to 20 Gy. TCP increased with increasing PO2_ap and O2t due to increased apoptotic death. The variation of TCP as a function of [O2]av exhibited the minimum at [O2]av of 2.7%. The apoptosis increased as [O2]av decreased, leading to an increasing TCP. On the other hand, the direct radiation damage increased, and the apoptosis decreased for higher [O2]av, resulting in a higher TCP. We showed by modeling the radiation damage of blood vessels in a 2D CA simulation that the indirect apoptotic death of cancer cells, caused by the reduction of the oxygen level due to vascular damage after high dose irradiation, increased TCP.

Effect of Interactions between Vehicles and Mid-Block Crosswalks on Traffic Flow and CO2 Emission

Unsignalized mid-block raised crosswalks have been adopted as inclusive transport strategies, providing humps to reduce vehicles’ speed to promote drivers to yield to pedestrians. The interaction between vehicles and pedestrians can induce local jams that can merge to become a gridlock. The purpose of this paper is to investigate the interaction between vehicles and the mid-block raised crosswalk, analyzing its effects on traffic flow, instantaneous CO2 emissions, and energy dissipation. A pedestrian–vehicle cellular automata model was developed, where a single-lane road with a mid-block raised crosswalk is considered. The lane boundaries were controlled with the injections rate (α) and extraction rate (β), while the pedestrians’ entrance was controlled with the rate (αp). The system’s phase diagram was constructed, identifying four phases: maximum current, jamming, congestion, and gridlock. All observed phase transitions are of the second order. The transition from maximum current (or jamming) phase to gridlock phase is not noticed. Moreover, since the crosswalk is a bottleneck, the gridlock phase takes place when the pedestrians’ influx exceeds a critical value (αp > 0.8). The study also revealed that the crosswalk is the main precursor of energy dissipation and CO2 emissions, whose major effects are observed during the jamming phase.

Dynamics Study of Constant DI and Constant TR Control for Cardiac Alternans Based on a Two Dimensional Cellular Automata Model

As a precursor for cardiac arrhythmias such as atrial and ventricular fibrillations, which could cause sudden cardiac death (SCD), cardiac alternans is essentially an unstable heart rhythm with alternating long and short action potential durations (APD) of cardiac myocytes that usually occurs under fast pacing conditions. In this paper, the constant TR control method based on global pseudo-electrocardiogram (ECG) is studied and compared with the local constant diastolic interval (DI) control method using a 2-dimensional (2-D) cellular automata model (CAM), aiming at preventing or eliminating cardiac alternans before arrhythmias. The results show that both the constant TR and constant DI control methods are effective in stabling the alternans to a smaller basic cycle length (BCL). Also, the efficacy of the two control approaches depends on the “decrease step” Δ in the downsweep protocol, and a smaller Δ could significantly improve their performance. Besides, in general, constant TR control is superior to constant DI control in alternans prevention when a relatively large Δ is adopted.

Digital Training Platform for Comprehensive Traffic Simulation

The paper deals with the development of software for traffic flow simulation combining the widest spectrum of mathematical approaches used in this field. Macro- and microscopic models, models of cellular automata as well as different numerical methods of their computer implementation are incorporated into a digital platform. Original developments of the authors of the paper such as quasi-gas dynamic traffic model and multilane cellular automata model take the main place. Potential users of the software are students and researchers. The platform possesses an intuitive graphical interface ensuring interactivity. Microsoft Visual Studio with C# is chosen as the development environment, the Unity 3D engine is employed for visualization and collaboration with WinForm projects. In the future, the platform can be transformed into a network computer laboratory providing access to information resources via Internet.

GoZone: A Numerical Model for Travelling Fires Based on Cellular Automata Concept

Fires in large compartments tend to burn locally and to move across the floor over a period of time; this particular behaviour has been discovered to challenge the assumption of uniform gas temperature in the fire compartment. Recent studies on fires in large compartments have led to the now widely known concept of “travelling fires”. Several models have been proposed to describe the evolution in time of travelling fires. Although these models represented an innovative step in the field of travelling fires, the major drawbacks of these models can be found in the simplification of fire dynamics (constant spread rate, 1D imposed fire path) and limited field of application (rectangular based geometries). The purpose of this paper is to present a numerical model of travelling fire. The model was based on an improved zone model combined with a cellular automata model. The software GoZone, in which the model was implemented, is intended to be a practical solution to analyse fires in large compartments of potentially any shape. GoZone is aimed to describe the complex dynamics of the fire from ignition to a phase of growing localised fire that may eventually travel in the compartment, possibly followed by a flashover. The main sub models comprising GoZone are presented. A comparison is given with the results of under ventilated fire test 2 of the BST/FSR 1993 test series and with respect to the Veselì travelling fire test is shown. GoZone shows a promising capacity to represent fires in a large compartment in both air and fuel controlled fire conditions.