The role of environmental stochasticity in a toxic phytoplankton-non-toxic phytoplankton-zooplankton system

2003 ◽  
Vol 14 (8) ◽  
pp. 775-792 ◽  
Author(s):  
R. R. Sarkar ◽  
J. Chattopadhayay
Keyword(s):  
Environmental Stochasticity ◽  
Toxic Phytoplankton

scholarly journals Heterogeneity in susceptible–infected–removed (SIR) epidemics on lattices

2010 ◽  
Vol 8 (55) ◽  
pp. 201-209 ◽  
Author(s):  
Franco M. Neri ◽  
Francisco J. Pérez-Reche ◽  
Sergei N. Taraskin ◽  
Christopher A. Gilligan
Keyword(s):  
Control Strategies ◽  
Random Variable ◽  
Environmental Stochasticity ◽  
Two Dimensional ◽  
Epidemic Threshold ◽  
Heterogeneous Model ◽  
Non Invasive ◽  
Mean And Variance ◽  
Invasion Threshold

The percolation paradigm is widely used in spatially explicit epidemic models where disease spreads between neighbouring hosts. It has been successful in identifying epidemic thresholds for invasion, separating non-invasive regimes, where the disease never invades the system, from invasive regimes where the probability of invasion is positive. However, its power is mainly limited to homogeneous systems. When heterogeneity (environmental stochasticity) is introduced, the value of the epidemic threshold is, in general, not predictable without numerical simulations. Here, we analyse the role of heterogeneity in a stochastic susceptible–infected–removed epidemic model on a two-dimensional lattice. In the homogeneous case, equivalent to bond percolation, the probability of invasion is controlled by a single parameter, the transmissibility of the pathogen between neighbouring hosts. In the heterogeneous model, the transmissibility becomes a random variable drawn from a probability distribution. We investigate how heterogeneity in transmissibility influences the value of the invasion threshold, and find that the resilience of the system to invasion can be suitably described by two control parameters, the mean and variance of the transmissibility. We analyse a two-dimensional phase diagram, where the threshold is represented by a phase boundary separating an invasive regime in the high-mean, low-variance region from a non-invasive regime in the low-mean, high-variance region of the parameter space. We thus show that the percolation paradigm can be extended to the heterogeneous case. Our results have practical implications for the analysis of disease control strategies in realistic heterogeneous epidemic systems.

scholarly journals Dynamics induced by environmental stochasticity in a phytoplankton-zooplankton system with toxic phytoplankton

2021 ◽  
Vol 18 (4) ◽  
pp. 4101-4126
Author(s):  
He Liu ◽  
◽  
Chuanjun Dai ◽  
Hengguo Yu ◽  
Qing Guo ◽  
...  
Keyword(s):  
Environmental Stochasticity ◽  
Toxic Phytoplankton

The role of avoidance by zooplankton for survival and dominance of toxic phytoplankton

2012 ◽  
Vol 11 ◽  
pp. 144-153 ◽  
Author(s):  
Subhendu Chakraborty ◽  
Sabyasachi Bhattacharya ◽  
Ulrike Feudel ◽  
J. Chattopadhyay
Keyword(s):  
Toxic Phytoplankton

Modeling the Role of Toxic Substances in a Phytoplankton-Toxic Phytoplankton-Zooplankton System

2013 ◽  
Vol 726-731 ◽  
pp. 1600-1603
Author(s):  
Jiang Lin Zhao ◽  
Min Zhao
Keyword(s):  
Mathematical Model ◽  
Numerical Analysis ◽  
Functional Response ◽  
Significant Influence ◽  
Toxic Substances ◽  
Bifurcation Diagrams ◽  
Toxic Phytoplankton ◽  
Dynamical Complexity

In this paper, a mathematical model has been proposed, which consists of three variables: non-toxic phytoplankton (NTP), toxin producing phytoplankton (TPP) and zooplankton. In this model, an Monod- Haldane functional response is utilized to identify the grazing process of zooplankton due to the phytoplankton toxicity. The product of square of TPP density with square of NTP density is to depict the allelopathic influence on NTP. Numerical analysis indicates that the phytoplankton toxicity has a significant influence on the dynamical complexity and species biomass level through bifurcation diagrams. All these results are expected to be of significance in exploration of the dynamical complexity of ecosystems.

Harmful algal blooms in fresh and marine water systems: The role of toxin producing phytoplankton

2016 ◽  
Vol 09 (03) ◽  
pp. 1650043 ◽  
Author(s):  
Nilesh Kumar Thakur ◽  
S. K. Tiwari ◽  
Ranjit Kumar Upadhyay
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Functional Responses ◽  
Toxic Phytoplankton ◽  
Space And Time ◽  
Spatially Distributed ◽  
High Predation ◽  
Predator Switching ◽  
Parameter Values

In this paper, we have investigated a model with three interacting species: non-toxic phytoplankton, toxic phytoplankton and zooplankton with Holling type II and III functional responses over the space and time. The role of toxin producing phytoplankton (TPP) has been studied. We have presented the theoretical analysis of pattern formation in spatially distributed population with local diffusion. The paper highlights the heterogeneity of HABs over space and time. The choice of parameter values and the functional response is important to study the effect of TPP, also it would depend more on the nonlinearity of the system. With the help of numerical simulations, we have observed the spatial and spatiotemporal patterns for plankton system. This study demonstrates that TPP plays an important role in controlling the dynamics. We have observed that prey’s anti-predator efforts promote predator switching. It has been found that high predation of TPP helps for the coexistence of toxic, non-toxic phytoplankton and zooplankton population.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor

Role of the allergist in diagnosis and management of patients with uveitis

JAMA ◽  
1966 ◽  
Vol 195 (3) ◽  
pp. 167-172 ◽  
Author(s):  
T. E. Van Metre
Keyword(s):  
Diagnosis And Management

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

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