Hopf Bifurcation Analysis of Pathogen-Immune Interaction Dynamics With Delay Kernel

The aim of this paper is to study the steady states of the mathematical models with delay kernels which describe pathogen-immune dynamics of infectious diseases. In the study of mathematical models of infectious diseases it is important to predict whether the infection disappears or the pathogens persist. The delay kernel is described by the memory function that reflects the influence of the past density of pathogen in the blood and it is given by a nonnegative bounded and normated function k defined on [ 0, ∞ ). By using the coefficient of the kernel k, as a bifurcationparameter, the models are found to undergo a sequence of Hopf bifurcation. The direction and the stability criteria of bifurcation periodic solutions are obtained by applying the normal form theory and the center manifold theorems. Some numerical simulation examples for justifying the theoretical results are also given

Environmental impact of mining activity in Bor area as indicated by the distribution of heavy metals and bacterial population dynamics in sediment

The environmental impact of inorganic pollution is pronounced in water adjacent to Bor Copper Smelter Complex (RTB Bor, Serbia), with Cu, Zn, Pb, and As being the main determinants of aquatic pollution pattern. Communities of microorganisms present in the sediments are mainly affected by heavy metal pollution. Some groups of bacteria can be considered pollution bio-indicators, due to their sensibility and ability to bioaccumulate heavy metals, thus contributing to reducing pollution. This study investigates the relationships between trace element accumulation and heterogeneity in sediment bacteria community structure found in water streams adjacent to the Bor Copper Smelter Complex (RTB Bor, Serbia). Our results showed no contamination with copper, zinc, nickel, iron, and chromium, but did show a low to moderate contamination with lead and a moderate to high contamination with arsenic in aquatic sediments within the area of interest. Spatial heterogeneity in sediment-associated bacterial communities did not relate significantly to location of sampling sites, except for iron reducing bacteria. Iron reducing bacteria and nitrifying bacteria were the best distinguishing groups of bacteria. However, only iron reducing bacteria were significantly influenced by sampling locations. The iron reducing bacteria has correlated negatively with the degree of sediment contamination with lead, and therefore, we suggest that this group of bacteria could serve as potential bio-indicators of inorganic water contamination in Bor RTB area

Environmental impact of mining activity in Bor area as indicated by the distribution of heavy metals and bacterial population dynamics in sediment

The environmental impact of inorganic pollution is pronounced in water adjacent to Bor Copper Smelter Complex (RTB Bor, Serbia), with Cu, Zn, Pb, and As being the main determinants of aquatic pollution pattern. Communities of microorganisms present in the sediments are mainly affected by heavy metal pollution. Some groups of bacteria can be considered pollution bio-indicators, due to their sensibility and ability to bioaccumulate heavy metals, thus contributing to reducing pollution. This study investigates the relationships between trace element accumulation and heterogeneity in sediment bacteria community structure found in water streams adjacent to the Bor Copper Smelter Complex (RTB Bor, Serbia). Our results showed no contamination with copper, zinc, nickel, iron, and chromium, but did show a low to moderate contamination with lead and a moderate to high contamination with arsenic in aquatic sediments within the area of interest. Spatial heterogeneity in sediment-associated bacterial communities did not relate significantly to location of sampling sites, except for iron reducing bacteria. Iron reducing bacteria and nitrifying bacteria were the best distinguishing groups of bacteria. However, only iron reducing bacteria were significantly influenced by sampling locations. The iron reducing bacteria has correlated negatively with the degree of sediment contamination with lead, and therefore, we suggest that this group of bacteria could serve as potential bio-indicators of inorganic water contamination in Bor RTB area

Environmental impact of mining activity in Bor area as indicated by the distribution of heavy metals and bacterial population dynamics in sediment

The environmental impact of inorganic pollution is pronounced in water adjacent to Bor Copper Smelter Complex (RTB Bor, Serbia), with Cu, Zn, Pb, and As being the main determinants of aquatic pollution pattern. Communities of microorganisms present in the sediments are mainly affected by heavy metal pollution. Some groups of bacteria can be considered pollution bio-indicators, due to their sensibility and ability to bioaccumulate heavy metals, thus contributing to reducing pollution. This study investigates the relationships between trace element accumulation and heterogeneity in sediment bacteria community structure found in water streams adjacent to the Bor Copper Smelter Complex (RTB Bor, Serbia). Our results showed no contamination with copper, zinc, nickel, iron, and chromium, but did show a low to moderate contamination with lead and a moderate to high contamination with arsenic in aquatic sediments within the area of interest. Spatial heterogeneity in sediment-associated bacterial communities did not relate significantly to location of sampling sites, except for iron reducing bacteria. Iron reducing bacteria and nitrifying bacteria were the best distinguishing groups of bacteria. However, only iron reducing bacteria were significantly influenced by sampling locations. The iron reducing bacteria has correlated negatively with the degree of sediment contamination with lead, and therefore, we suggest that this group of bacteria could serve as potential bio-indicators of inorganic water contamination in Bor RTB area