Procesos aleatorios en modelación matemática

Repasamos brevemente un modelo simple de caminata aleatoria para modelar el comportamiento colectivo de muchas partículas y el problema asociado con la causalidad de la ecuación de difusión obtenida en el límite difusivo

Método de Newton y el trazado de rayos

Se aplica la teoría de rayos en un medio con estratos homogéneos (velocidades y espesores constantes) para obtener una formulación matemática con la que se puedan determinar los puntos xi donde los rayos interactúan con las interfases de las capas. La formulación utiliza el método de Newton en su forma matricial para obtener de manera iterativa las posicione

Simulación numérica del cálculo de la tortuosidad en la alfombra de Sierpinski

La tortuosidad es un parámetro importante para la descripción del flujo de fluidos en medios porosos, y se ha demostrado que los medios porosos en la naturaleza tienen características fractales. La alfombra de Sierpinski es un fractal exactamente similar a sí mismo, que ha sido utilizado para simular medios porosos fractales. En el presente trabajo se ha diseñado un autómata celular para el cálculo de la tortuosidad de la alfombra de Sierpinski. Para este fractal se ha calculado la tortuosidad de forma analítica y se han realizado aproximaciones. El resultado de este diseño de autómata ha sido excelentes aproximaciones a los resultados analíticos. A partir de ello se calculan otras tortuosidades de fractales que no tienen hasta ahora, respuestas analíticas. El presente modelo puede tener potencial en el análisis de las propiedades de transporte en otros medios porosos

Simulación de flujo laminar para estimar la tortuosidad en la alfombra de Sierpinsk

Este trabajo se centra en la simulación numérica de flujo laminar para estimar la tortuosidad en una estructura geométrica fractal denominada alfombra de Sierpinski, a menudo usada para simular medios porosos sintéticos. La tortuosidad se describe como la medida de las formas irregulares o sinuosidad de los caminos, y es un parámetro muy importante para las Ciencias de la Tierra desde la Geología hasta la Ingeniería Petrolera, por su gran variedad de aplicaciones. En este estudio, se utiliza el software Comsol Multiphysics para resolver las ecuaciones que gobiernan el flujo laminar lo que permite analizar el movimiento de los fluidos a través de la alfombra de Sierpinski. Los resultados permiten obtener información valiosa sobre la eficiencia de un fluido para transportarse a través de una estructura fractal, lo que puede ser relevante en diversas áreas de investigación. Esta metodología da estimaciones de la tortuosidad comparables a las que se obtienen con otras metodologías de la literatura

Head dimensions of brahman and their crossbred bull spermatozoa are affected by cryopreservation

The objective of this study was to determine the effect of cryopreservation on morphometrics characteristic of Brahman and their crossbred bull sperm heads. Five ejaculates were collected from 4 bulls and diluted at 30°C in a skim milk-egg yolk extender. Two microscope slides were prepared from single extended sperm samples prior to freezing in nitrogen vapors, and another one after thawing, sperm smears were prepared as described above. All slides were air dried and stained with Hemacolor®. Sperm-head dimensions for a minimum of 150 sperm heads/samples were analysed from each sample by means of the Sperm-Class Analyser ® (SCA), and the mean measurements recorded. A GLM procedure was performed to evaluate the effect of ryopreservation on sperm head morphometric dimensions. Bull sperm heads were significantly (P<0.001) smaller in frozenthawed spermatozoa than in the extended samples for length (9.00 μm vs. 9.43 μm), width (4.82 μm vs. 5.13 μm), perimeter (32.46 μm vs. 33.69 μm) and area (36.20 μm� vs. 39.97 μm�) for all bulls. Also, differences (P<0.001) were found within all bulls for whole morphometric parameters. The individual variability of sperm head measurements across all bulls ranged from 5.9% to 10.2% for fresh and thawed samples, respectively. In conclusion, the present study indicate that cryopreservation of bull semen did affect the morphometry to reduce the dimensions of Brahman and crossbred bull sperm heads. The differences among bulls may be indicative of the individual bull resistance to the cryopreservation process

Cabbage and fermented vegetables : From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT(1)R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT(1)R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.Peer reviewe

Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity

Actualidad y prospectiva de la investigación científica en el Centro Universitario Amecameca de la Universidad Autónoma del Estado de México

Con responsabilidad, se organizó un programa cuya finalidad fuera publicitar con transparencia dichos avances, a través de un esfuerzo de rendición de cuentas a la comunidad inmediata, la universitaria, y a la comunidad abierta, la sociedad que la principal referencia para tal efecto. El programa se concretiza a través del presente libro, conformado con una inspiración de investigación multidisciplinaria; sin embargo, para llegar a tal fin, el reto es realizar el proceso de búsqueda y generación de conocimiento transitando hacia la colaboración de los cuerpos académicos, que puedan construir nuevos conocimientos fortalecidos por la convergencia de diferentes campos del saber. En consecuencia, la primera etapa de esta estrategia es la publicidad de los trabajos investigativos ejercidos, para hacer un balance al día, pero también proyectar el futuro de cada campo y área del conocimiento. La organización explicativa está organizada por tres bloques representativos del quehacer en la generación de conocimiento del Centro Universitario, un primer bloque centra el interés en las humanidades, educación y sustentabilidad; el segundo bloque lo integra la reflexión científica sobre la construcción democrática, derechos humanos y equidad de género; en el tercer segmento se destina a la seguridad alimentaria, salud pública y sistemas agropecuarios. La actualidad de la investigación eleva la producción lograda y lo que en el momento se encuentra en construcción y los alcances que produce para la docencia, la investigación misma, y para la sociedad en general. La prospectiva es un área que todos los capítulos desarrollan con el propósito de delinear los alcances innovadores por andar en teoría, metodología e incluso en los saberes mismo

A New Deterministic Gasket Fractal Based on Ball Sets

F.H.-Z. thanks FCFM-UNACH and the support from CONACyT through the program “Investi gadoras e investigadores por México”, Cátedra 873. M.A.A.-L. thanks CONACyT for the postdoc toral grant 839412 and FCFM-UNACH for sup porting his research stay.In this paper, we propose a new gasket fractal constructed in a deterministic iterated function system (IFS) way by means of interacting ball and square sets in R 2 . The gasket consists of the ball sets generated by the IFS, possessing also exact self-similarity. All this leads to a direct deduction of other properties and a clear construction methodology, including a dynamic geometry procedure with an open-source construction protocol. We also develop an extended version of the fractal in Rn. Some resulting config urations consisting of stacked 2D-fractals are plotted. We discuss about potential applications of them in some areas of science, focusing mainly on percolation models. Guidelines for future work are also provided

A Quadratic–Exponential Model of Variogram Based on Knowing the Maximal Variability: Application to a Rainfall Time Series

Variogram models are a valuable tool used to analyze the variability of a time series; such variability usually entails a spherical or exponential behavior, and so, models based on such functions are commonly used to fit and explain a time series. Variograms have a quasi-periodic structure for rainfall cases, and some extra steps are required to analyze their entire behavior. In this work, we detailed a procedure for a complete analysis of rainfall time series, from the construction of the experimental variogram to curve fitting with well-known spherical and exponential models, and finally proposed a novel model: quadratic–exponential. Our model was developed based on the analysis of 6 out of 30 rainfall stations from our case study: the Río Bravo–San Juan basin, and was constructed from the exponential model while introducing a quadratic behavior near to the origin and taking into account the fact that the maximal variability of the process is known. Considering a sample with diverse Hurst exponents, the stations were selected. The results obtained show robustness in our proposed model, reaching a good fit with and without the nugget effect for different Hurst exponents. This contrasts to previous models, which show good outcomes only without the nugget effect