Portfolios

  1. Home    /
  2. Portfolios
post-image

An exact moment-based approach for high-order chemical reaction–diffusion networks: From

Thursday, Jan 1, 2026

Biochemical systems are inherently stochastic, particularly those with small-molecule populations. The spatial distribution of molecules plays a critical role and requires the inclusion of spatial coordinates in their analysis. Stochastic models such as the chemical master equation are commonly used to study these systems. However, analytical solutions are limited to specific cases, and stochastic simulations require significant computational resources. To mitigate these challenges, approximation methods, such as the moment approach, reduce the system to a set of ordinary differential equations, thereby lowering the computational requirements.

Continue Reading
post-image

Fluctuation-induced corrections to the Hill

Thursday, Jan 1, 2026

Gene regulatory networks are essential for understanding the mechanisms underlying genetic disorders. However, traditional models based on deterministic Hill functions (without fluctuations) often fail to capture critical stochastic effects, particularly in small systems in which molecular fluctuations play a significant role. In this study, we introduced a modified Hill function derived from the stochastic dynamics of ligand-receptor interactions. By performing a second-order expansion of the chemical master equation, we derived a set of ordinary differential equations governing the mean concentrations and covariances.

Continue Reading
post-image

Hepatic Fat

Thursday, Jan 1, 2026

Background/Objectives: High liver fat content is closely associated with hepatic disease and multiple comorbidities including cancer, diabetes and cardiovascular accidents. Therefore, accurate quantification of hepatic steatosis, especially of borderline cases, is essential for clinical management. Although MRI non-invasively assesses hepatic steatosis, current approaches remain limited by the data variability introduced through use of region-of-interest measurements or classification models that predict discrete fat grades without providing uncertainty estimates. This study proposes a probabilistic approach for hepatic steatosis quantification based on combining a neural network and beta distribution, enabling prediction of hepatic fat percentage with corresponding confidence intervals.

Continue Reading
post-image

Local epidemic control through mobility restrictions

Thursday, Jan 1, 2026

Epidemic severity indices that incorporate disease information are essential tools for decision-makers, as these indices allow the design and evaluation of possible control strategies in advance of implementation in susceptible populations. In spatially structured settings, indices that consider human mobility provide valuable information on the spread of infectious diseases and the potential impact of mobility restrictions during outbreaks. In this context, the final epidemic size in metapopulation models serves as an effective measure of outbreak severity in geographical terms.

Continue Reading
post-image

Oscillation criteria in large-scale gene regulatory networks with intrinsic fluctuations

Thursday, Jan 1, 2026

Gene Regulatory Networks (GRNs) with feedback are essential components of many cellular processes and may exhibit oscillatory behavior. Analyzing such systems becomes increasingly complex as the number of components increases. Since gene regulation often involves a small number of molecules, fluctuations are inevitable. Therefore, it is important to understand how fluctuations affect the oscillatory dynamics of cellular processes, as this will allow comprehension of the mechanisms that enable cellular functions to remain even in the presence of fluctuations or, failing that, to determine the limit of fluctuations that permits various cellular functions.

Continue Reading
post-image

A fast validation test of gene regulatory network models via the Fokker

Wednesday, Jan 1, 2025

Since Waddington proposed the concept of the “epigenetic landscape” in 1957, researchers have developed various methodologies to represent it in diverse processes. Studying the epigenetic landscape provides valuable qualitative information regarding cell development and the stability of phenotypic and morphogenetic patterns. Although Waddington’s original idea was a visual metaphor, a contemporary perspective relates it to the landscape formed by the basins of attraction of a dynamical system describing the temporal evolution of protein concentrations driven by a gene regulatory network.

Continue Reading
post-image

Actualización del registro de los meso y megamamíferos del Pleistoceno

Wednesday, Jan 1, 2025

An updated list of Pleistocene meso- and megamammals taxa recorded in the State of Puebla is presented based on a review of the scien fic literature published from 1891 to 2024, covering 123 years. For this purpose, only mesomammals (species with a body mass range of 10-99 kg) and megamammals (body masses between 100-10,000 kg) were considered. In total, 33 species were recorded, belonging to 29 genera, 19 families, and six orders (Xenarthra, Roden a, Carnivora, Ar odactyla, Perissodactyla, and Proboscidea).

Continue Reading
post-image

First population analysis in Hadrosauroid

Wednesday, Jan 1, 2025

The study of biological population densities through direct measurements is one of the pillars of modern ecology; however, it does not apply to extinct fauna without modern extant representatives, as is the case with non-avian, plant-eating dinosaurs such as the Hadrosauroidea. On the other hand, mathematical models of population dynamics have also been used to estimate population density without the need for direct measurements. These models, however, require knowledge of population shift rates that are typically obtained through diverse observations.

Continue Reading
post-image

Relationship between Decimal

Wednesday, Jan 1, 2025

The Hill function is relevant for describing enzyme binding and other processes in gene regulatory networks. Despite its theoretical foundation, based on the mechanism of ligand–receptor binding, it is often used as a proper fitting function with a noninteger Hill coefficient in the description of gene expression. In this study, we explicitly considered intermediate processes in the transcription factor binding sites and mesoscopic concentration fluctuations, which, in contrast to the case of a single binding site without conformal states or all-or-none binding, lead to a noninteger Hill coefficient for the transcription rate.

Continue Reading
post-image

Stability analysis under intrinsic fluctuations: a second-moment perspective of gene regulatory networks

Wednesday, Jan 1, 2025

Gene regulatory networks with negative feedback play a crucial role in conferring robustness and evolutionary resilience to biological systems. However, the discrete nature of molecular components and probabilistic interactions in these networks are inherently subject to fluctuations, which pose challenges for stability analysis. Traditional analysis methods for stochastic systems, like the Langevin equation and the Fokker–Planck equation, are widely used. However, these methods primarily provide approximations of system behavior and may not be suitable for systems that exhibit non-mass-action kinetics, such as those described by Hill functions.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

Bayesian Estimation of the Basic Reproductive Number in a Chikungunya Outbreak in Acapulco, Guerrero

Friday, Nov 1, 2024

Chikungunya is a vector-borne viral disease caused by the mosquitoes Aedes aegypti and Aedes albopictus. There is no specific medical treatment or available vaccine. This work presents a host-vector model that considers two age structures: chronological age and asymptomatic infection age. This model accounts for variability in the relapse period and susceptibility to the chikungunya virus. From this system of integro-differential equations, a particular case is derived in the form of ordinary differential equations (ODEs).

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

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.

Continue Reading
post-image

Schrodinger-Pauli

Thursday, Jan 1, 2004

A non-relativistic equation for spin-3/2 particles is proposed and the gyromagnetic ratio for charged spin-3/2 particles is determined.

Continue Reading

ENTONCES, ¿ QUE OPINAS ?

Si estás interesado en colaborar durante un POSDOC, un POSGRADO o realizando la TESIS

Contáctame