Extrinsic fluctuations in the p53 cycle

Friday, Nov 8, 2024

Fluctuations are inherent to biological systems, arising from the stochastic nature of molecular interactions, and influence various aspects of system behavior, stability, and robustness. These fluctuations can be categorized as intrinsic, stemming from the system’s inherent structure and dynamics, and extrinsic, arising from external factors, such as temperature variations. Understanding the interplay between these fluctuations is crucial for obtaining a comprehensive understanding of biological phenomena. However, studying these effects poses significant computational challenges.

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Global stability for a mosquito-borne disease model with continuous-time age structure in the suscep- tible and relapsed host classes

Wednesday, Nov 6, 2024

Mosquito-borne infectious diseases represent a significant public health issue. Age has been identified as a key risk factor for these diseases, and another phenomenon reported is relapse, which involves the reappearance of symptoms after a symptom-free period. Recent research indicates that susceptibility to and relapse of mosquito-borne diseases are frequently age-dependent. This paper proposes a new model to better capture the dynamics of mosquito-borne diseases by integrating two age-dependent factors: chronological age and asymptomatic-infection age.

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Site percolation threshold of composite square lattices and its agroecology applications

Monday, Jan 1, 2024

We analyze the percolation threshold of square lattices comprising a combination of sites with regular and extended neighborhoods. We found that the percolation threshold of these composed systems smoothly decreases with the fraction of sites with extended neighbors. This behavior can be well-fitted by a Tsallis q-Exponential function. We found a relation between the fitting parameters and the differences in the gyration radius among neighborhoods. We also compared the percolation threshold with the critical susceptibility of nearest and next-to-nearest neighbor monoculture plantations vulnerable to the spread of phytopathogen.

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Final size of the epidemic for metapopulation vector-borne diseases

Sunday, Oct 1, 2023

There is an increasing worldwide concern on the several diseases transmitted by vectors like Dengue, Zika, or Chikungunya. Thus, in recent years studies about the calculation of summary measurements such as the final size of the epidemic have acquired importance. In particular, this quantity allows estimating the impact that the disease has on the affected population. However, advances in calculating analytical expressions to estimate this measure in the case of infectious transmitted by vectors have been scarce.

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Analysis and Bayesian estimation of a model for Chikungunya dynamics with relapse: An outbreak in Acapulco, Mexico

Thursday, Sep 21, 2023

Chikungunya is a vector-borne viral disease transmitted by Aedes aegypti and Aedes albopictus mosquitoes. It does not have any specific treatment, and there is no vaccine. Recent epidemiological data have indicated that a relapse of the infection can occur within three months of the initial infection; however, until now, mathematical models for the spread of the disease have not considered this factor. We propose a mathematical model for the transmission of the Chikungunya virus that considers relapse.

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Mathematical model for the aquatic stage of Aedes aegypti considering variable egg-hatching rate and inter-specific competition between larval stages.

Tuesday, Aug 1, 2023

Mosquito-borne diseases like dengue, Zika, and chikungunya, carried by Aedes aegypti mosquitoes, pose significant health threats. Controlling these diseases primarily involves reducing mosquito populations. Current approaches rely on simplistic measures to decide on actions like mosquito fogging or larval control. Adult mosquito numbers are often estimated from aquatic populations due to easier counting. While these methods have provided some assistance, there’s a need for improvement. Existing risk and population models overlook the various developmental stages of Aedes aegypti and their complex interactions.

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Epidemic local final size in a metapopulation network as indicator of geographical priority for control strategies in SIR type diseases

Friday, Nov 19, 2021

The main limitation on designing epidemic control strategies lies in their economic and social costs. Thus, a practical and efficient approach takes into consideration these factors. Most epidemics evolve in a structured population, being the geographical structure the most evident. In this situation, having a criteria for identifying the most effective locations where control measures can optimize available resources is desirable. In this paper, a regional index based on the final epidemic size predicted by a metapopulation model is proposed.

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A mathematical model to calculate the population of Mammuthus columbi (Mammalia, Proboscidea, Elephantidae) during the Late Pleistocene in the Valsequillo Basin, Puebla, Mexico

Friday, Aug 6, 2021

(imagen de Francisco Javier Jimenez colores de Soni Sánchez Orgaz) Mathematical models are a helpful tool that can help palaeoecology research advance in similar ways as the ones already used in theoretical ecology. In this article, we use a mathematical model based on differential equations to estimate the past Mammuthus columbi population in the Valsequillo Basin, Puebla, Mexico. We calibrated the model based on the biological and etiologic parameters of the African elephant Loxodonta africana.

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Estrategias de movilidad basadas en la teoría de percolación para evitar la diseminación de enfermedades: COVID-19

Tuesday, Jun 1, 2021

La movilidad de las personas es uno de los principales factores que propician la propagaci ´on espacial de epidemias. Las medidas de control epidemiol´ogico basadas en la restricci´on de movilidad son generalmente poco populares y las consecuencias econ´omicas pueden llegar a ser muy grandes. Debido a los altos costos de estas medidas, es de gran relevancia tener estrategias globales que optimicen las medidas minimizando los costos. En este trabajo, se calcula el umbral de percolaci´on de la propagaci´on de enfermedades en redes.

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A mathematical model of anarchy in bees

Wednesday, Jul 1, 2020

Functional worker sterility in queenright honey bees (Apis mellifera ) is fostered by the colony-level costs of this behavior. However, anarchy in the beehive can occur when a fraction of workers lay eggs, which, if reared, will develop into males (drones). Because males do not gather resources but still consume them, they represent an additional energic cost for the colony. This small number of anarchic worker-laid eggs is normally found and eaten by non-anarchic bees via worker policing, a controlling mechanism induced by queen’s pheromones.

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Control strategies for a population dynamics model of Aedes aegypti with seasonal variability and their effects on dengue incidence

Tuesday, Dec 17, 2019

Aedes aegypti female mosquitoes are the principal transmitters of dengue and other vector-borne infections. This species is closely associated with human habitation, due to its blood-feeding habits and the presence of breeding sites widely available around households. In this paper, we introduce a mathematical model for the life cycle of Aedes aegypti mosquitoes comprising two stages, aerial and aquatic, that reflects seasonal changes in the mosquito abundance. This model is further amended by three season-dependent control actions.

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The risk matrix of vector-borne diseases in metapopulation networks and its relation with local and global R0

Tuesday, Jun 5, 2018

The basic reproduction number R0 is an index worldwide commonly used by public health organizations as a key estimator of the severity of a given epidemic. In this work we use a Lagrangian approach to model vector-borne diseases (SIR-SI) into a metapopulation network in order to derive an expression of the basic reproduction number and we analyze its dependency on human mobility. We prove that this index can be computed by evaluating the spectral radius of the risk matrix W, whose entries Wij are the number of secondary cases in patch j produced by the inclusion of a single infected human in patch i.

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Vector-borne disease risk indexes in spatially structured populations

Sunday, Feb 18, 2018

There are economic and physical limitations when applying prevention and control strategies for urban vector borne diseases. Consequently, there are increasing concerns and interest in designing efficient strategies and regulations that health agencies can follow in order to reduce the imminent impact of viruses like Dengue, Zika and Chikungunya. That includes fumigation, abatization, reducing the hatcheries, picking up trash, information campaigns. A basic question that arise when designing control strategies is about which and where these ones should focus.

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Increased efficiency in the second-hand tire trade provides opportunity for dengue control

Wednesday, Oct 25, 2017

Dengue fever is increasing in geographical range, spread by invasion of its vector mosquitoes. The trade in second-hand tires has been implicated as a factor in this process because they act as mobile reservoirs of mosquito eggs and larvae. Regional transportation of tires can create linkages between rural areas with dengue and disease-free urban areas, potentially giving rise to outbreaks even in areas with strong local control measures. In this work we sought to model the dynamics of mosquito transportation via the tire trade, in particular to predict its role in causing unexpected dengue outbreaks through vertical transmis- sion of the virus across generations of mosquitoes.

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Seasonality on the life cycle of Aedes aegypti mosquito and its statistical relation with dengue outbreaks

Monday, Jun 5, 2017

Aedes aegypti is the most common and important vector that transmits dengue disease. It has been observed that its abundance is one of the main factors influencing dengue incidence and hence the importance of studying its population dynamics. By means of a dynamical model, in this work, we study the effects temperature and precipitation in the abundance of the mosquito Aedes aegypti . We also analyze the corre- lation between mosquito and dengue outbreaks using historical data of 8 Mexican regions and the role of diapause in seasonality outbreaks.

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Relative ranges of mating and dispersal modulate Allee thresholds in sessile species

Friday, May 26, 2017

Sessile organisms, including plants and benthic macrofauna, are often restricted in the ranges over whichthey are able to reproduce and disperse. This leads to spatial patterning within populations, causing theeffective population density around each individual to depart from the average across its range. This hasimportant implications for population dynamics, in particular the minimum density at which populationsare able to maintain positive growth (the Allee threshold). Here we compare the population dynamics ofspecies with three syndromes — spatially restricted mating, dispersal or both — against a null model ofa species with no spatial limitations.

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On the dynamics of dengue virus type 2 with residence times and vertical transmission

Friday, Jul 8, 2016

A two-patch mathematical model of Dengue virus type 2 (DENV-2) that accounts for vectors’ vertical transmission and between patches human dispersal is introduced. Dispersal is modelled via a Lagrangian approach. A host-patch residence-times basic reproduction number is derived and conditions under which the disease dies out or persists are established. Analytical and numerical results highlight the role of hosts’ dispersal in mitigating or exacerbating disease dynamics. The framework is used to explore dengue dynamics using, as a starting point, the 2002 outbreak in the state of Colima, Mexico.

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Asymmetric competition causes multimodal size distributions in spatially structured populations

Monday, Nov 30, 2015

Plant sizes within populations often exhibit multimodal distributions, even when all individuals are the same age and have experienced identical conditions. To establish the causes of this, we created an individual-based model simulating the growth of trees in a spatially explicit framework, which was parametrized using data from a long-term study of forest stands in New Zealand. First, we demonstrate that asymmetric resource competition is a necessary condition for the formation of multimodal size distributions within cohorts.

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Spatial Complementarity and the Coexistence of Species

Monday, Dec 22, 2014

Coexistence of apparently similar species remains an enduring paradox in ecology. Spatial structure has been predicted to enable coexistence even when population-level models predict competitive exclusion if it causes each species to limit its own population more than that of its competitor. Nevertheless, existing hypotheses conflict with regard to whether clustering favours or precludes coexistence. The spatial segregation hypothesis predicts that in clustered populations the frequency of intra-specific interactions will be increased, causing each species to be self-limiting.

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Renewal stochastic processes with correlated events: Phase transitions along time evolution

Thursday, Mar 3, 2011

We consider renewal stochastic processes generated by nonindependent events from the perspective that their basic distribution and associated generating functions obey the statistical-mechanical structure of systems with interacting degrees of freedom. Based on this fact we look briefly into the less-known case of processes that display phase transitions along time. When the density distribution ψn(t ) for the occurrence of the nth event at time t is considered to be a partition function, of a “microcanonical” type for n “degrees of freedom” at fixed “energy” t , one obtains a set of four partition functions of which that for the generating function variable z and Laplace transform variable , conjugate to n and t , respectively, plays a central role.

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