Stability analysis of reaction-diffusion models on evolving domains: the effects of cross-diffusion

This article presents stability analytical results of a two component reaction-diffusion system with linear cross-diffusion posed on continuously evolving domains. First the model system is mapped from a continuously evolving domain to a reference stationary frame resulting in a system of partial differential equations with time-dependent coefficients. Second, by employing appropriately asymptotic theory, we derive and prove cross-diffusion-driven instability conditions for the model system for the case of slow, isotropic domain growth. Our analytical results reveal that unlike the restrictive diffusion-driven instability conditions on stationary domains, in the presence of cross-diffusion coupled with domain evolution, it is no longer necessary to enforce cross nor pure kinetic conditions. The restriction to activator-inhibitor kinetics to induce pattern formation on a growing biological system is no longer a requirement. Reaction-cross-diffusion models with equal diffusion coefficients in the principal components as well as those of the short-range inhibition, long-range activation and activator-activator form can generate patterns only in the presence of cross-diffusion coupled with domain evolution. To confirm our theoretical findings, detailed parameter spaces are exhibited for the special cases of isotropic exponential, linear and logistic growth profiles. In support of our theoretical predictions, we present evolving or moving finite element solutions exhibiting patterns generated by a short-range inhibition, long-range activation reaction-diffusion model with linear cross-diffusion in the presence of domain evolution

A PRACTICAL APPROACH TO MODEL BANKING RISKS USING LOSS DISTRIBUTION APPROACH (LDA) IN BASEL II FRAMEWORK

In Basel II Capital Accord, the Advanced Measurement Approaches (AMA) is stated as one of the pillar stone methods for calculating corporate risk reserves. One of the common yet cumbersome methods is the one known as loss distribution approach (cf. [Chernobai A S, Rachev S T and Fabozzi F J, (2007)]. In this article, we present an easy to implement scheme through electronic means and discuss some of the mathematical problems we encountered in the process together with proposed solution methods and further sought on the issues.loss distribution approach, corporate risk, Basel II principles

Domain-growth-induced patterning for reaction-diffusion systems with linear cross-diffusion

In this article we present, for the first time, domain-growth induced pat- tern formation for reaction-diffusion systems with linear cross-diffusion on evolving domains and surfaces. Our major contribution is that by selecting parameter values from spaces induced by domain and surface evolution, patterns emerge only when domain growth is present. Such patterns do not exist in the absence of domain and surface evolution. In order to compute these domain-induced parameter spaces, linear stability theory is employed to establish the necessary conditions for domain- growth induced cross-diffusion-driven instability for reaction-diffusion systems with linear cross-diffusion. Model reaction-kinetic parameter values are then identified from parameter spaces induced by domain-growth only; these exist outside the classical standard Turing space on stationary domains and surfaces. To exhibit these patterns we employ the finite element method for solving reaction-diffusion systems with cross-diffusion on continuously evolving domains and surfaces

Cross-diffusion in reaction-diffusion models: analysis, numerics and applications

Cross-diffusion terms are nowadays widely used in reaction-diffusion equations encountered in models from mathematical biology and in various engineering applications. In this contribution we review the basic model equations of such systems, give an overview of their mathematical analysis, with an emphasis on pattern formation and positivity preservation, and finally we present numerical simulations that highlight special features of reaction-cross-diffusion models

Procesamiento de datos climáticos de alta resolución temporal para simulacio nes diarias de un agroecosistema complejo

Ecosystem services, such as natural pest control, are essential tools to be incorpora ted in future agricultural methodologies. In this paper we focus on the processing of climate data series that feed to a system of computer models simulating daily inte ractions of a pest and its predator, in a dynamic landscape, the olive grove. We filled hourly climate data series and converted them to daily climate series using R langua ge. The methodology used produces acceptable climate data series for the system to run and allows to segregate specific periods of the day while maintaining daily tem poral resolution. We expect this paper can be helpful when dealing with similar data and purpose.Los servicios ecosistémicos, como por ejemplo el control natural de plagas, son her ramientas que se deberán promover en las futuras metodologías agrícolas. En este artículo nos enfocamos en el procesamiento de datos climáticos, necesarios para el funcionamiento de un sistema de modelos que hace simulaciones computacionales diarias de la interacción entre una plaga y su predador, en un paisaje dinámico, el olivar. Completamos las series horarias de datos climáticos y las convertimos a series diarias, usando lenguaje R. La metodología utilizada produce datos climáticos acept ables para el funcionamiento del sistema y permite segregar periodos específicos del día manteniendo una resolución temporal diaria. Esperamos que este artículo pueda ser útil en casos similares.info:eu-repo/semantics/publishedVersio

O impacto do marketing de influência em empresas Born Global

We live in a world where social networks are the consumer's window to commerce and the gateway for many companies to other countries. On social networks we have digital influencers, which can be considered a vehicle between the brand and the consumer. It is important to understand how these situations are interconnected, for such, this study aims to investigate the impact of influencer marketing on Born Global companies. The chosen methodology was mixed, using the interview technique and the questionnaire survey. Interviews were conducted with 5 influencers and 5 Born Global companies, as well as a public questionnaire to understand the impact from the 3 points of view. One would predict that, with the increase in popularity of digital influencers, influencer marketing would be a strategy used by most companies. It was possible to see that influencer marketing has a positive reception from the public and a positive impact on Born Global companies. It was also found that this is an area that companies are still exploring and figuring out how to best approach and monetize, however there was a consensus in all companies about the importance of the use of influencer marketing as a marketing strategy when the goal is fast internationalization. Due to the growth trend of both digital influencers and Born Global companies, this is undoubtedly a topic that needs to be studied in greater depth.Vivemos num mundo em que as redes sociais são a janela do consumidor para o comércio e a porta de entrada de muitas empresas noutros países. Nas redes sociais temos também os influenciadores digitais, que podem ser considerados um veículo entre a marca e o consumidor. É importante perceber como estas situações se interligam, para tal, este estudo tem como propósito investigar o impacto do marketing de influência nas empresas Born Global. A metodologia escolhida foi mista recorrendo à técnica da entrevista e ao inquérito por questionário. Foram realizadas entrevistas a 5 influenciadores e 5 empresas Born Global, assim como um questionário ao público para compreender este impacto do ponto de vista das 3 perspetivas. Seria de prever que, com o aumento de popularidade dos influenciadores digitais, o marketing de influência fosse uma estratégia utilizada por maior parte das empresas. Foi possível perceber que o marketing de influência tem uma recetividade positiva por parte do público e um impacto positivo em empresas Born Global. Constatou-se ainda que esta é uma área que as empresas ainda estão a explorar e a perceber como abordar da melhor maneira e rentabilizar, no entanto, foi consensual em todas as empresas a importância da utilização do marketing de influência como estratégia de marketing quando o objetivo é a internacionalização rápida. Pela tendência de crescimento, tanto dos influenciadores digitais, como das empresas Born Global, este é sem dúvida um tema que necessita de ser estudado com maior profundidade

Comparison of reconstruction methods for water supply systems flow rate time series

Trabalho apresentado em International Conference on Water Energy Food and Sustainability (ICoWEFS 2021), 10 -12 maio, 2021, onlineThe purpose of this paper is to compare the performance of five univariate models for the reconstruction of flow rate time series. Errors in the measurements may occur due to problems in the sensor or in the communication system with data logger, thus generating missing data in the flow rate time series. The presence of missing values in flow rate data restricts its use in network operation processes. The performance of seasonal ARIMA, Standard and double seasonality Holt-Winters, and original and improved Quevedo approach are assessed. The analysis is made considering a real Portuguese case study and 1- month of flow rate data at 1-hour and 10-minute period. The holidays compared to the weekdays show great differences in consumption patterns. For this reason, the effect of forecasting holidays is assessed. Obtained results evidence that the improved Quevedo model can cope with different time step intervals and type of day being forecasted, with a reduced computation time.N/

Hidrópsia fetal imune

Mestrado Integrado em MedicinaMaster Degree in Medicin

Antioxidant and bioactive compounds of two wild edible mushrooms from Northeast of Portugal: Boletus poliporus and Boletus regius

Free radicals are produced in the normal natural metabolism of aerobic cells, mostly in the form of reactive oxygen species (ROS). Maintenance of equilibrium between free radicals production and antioxidant defenses is an essential condition for normal organism functioning [1 ,2]. Although almost all organisms are equipped with antioxidant defense, the antioxidant supplements, or natural products containing bioactive compounds, may be used to help reduce oxidative damage to the human body (3]. Indeed, natural matrices with antioxidant activity, in particular mushrooms, are used to aid the endogenous protective system, increasing interest in the antioxidative role of functional foods or nutraceutical products (2]. The present study describes the antioxidant properties and bioactive compounds of wild edible mushrooms (Boletus porosporus and Boletus regius) collected in Northeast of Portugal (Bragança). The antioxidant properties were assessed through the evaluation of the reducing power, radical scavenging activity and lipid peroxidation inhibition of the samples. The individual profiles of organic acids and phenolic compounds were obtained by high performance liquid chromatography coupled to photodiode array detector (HPLC-POA) and the tocopherols were characterized by HPLC-fluorescence.The Boletus regius sample revealed the best results in all the antioxidant activity assays, with the highest reducing power, highest scavenging activity and highest lipid peroxidation inhibition. Phenolic acids and a related compound (cinnamic acid) were found in both studied species and B. regius revealed the highest content in total phenolic compounds (23.49 mg/1 00 g dw), mainly due to the presence of two possible flavonoids. The highest levels of total tocophero ls were found in B. regius (763.80 j.Jg/1 00 g dw). The highest content in quinic and oxalic acids were found in B. porosporus(1.93 and 0.34 g/1 00 g dw, respectively), while B. regius revealed the highest level of citric acid (3.32 g/1 00 g dw).The results suggest that species of wild mushrooms from Northeast Portugal are a potential source of antioxidants to be explored.FCT and COMPETE/QREN/EU: project PTOC/AGR-ALI/110062/2009, PEst-PTDC/AGRALI/110062/2009 CIMO strategic project and L B. grant (BPD/4609/2008

Dynamics of Shadow System of a Singular Gierer–Meinhardt System on an Evolving Domain

From Springer Nature via Jisc Publications RouterHistory: received 2020-02-28, accepted 2020-10-23, registration 2020-11-12, online 2020-12-18, pub-electronic 2020-12-18, pub-print 2021-02Publication status: PublishedFunder: Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa; doi: http://dx.doi.org/10.13039/501100005856; Grant(s): UID/MAT/04561/2019Funder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/J016780/1Funder: Horizon 2020; doi: http://dx.doi.org/10.13039/501100007601; Grant(s): 642866Abstract: The main purpose of the current paper is to contribute towards the comprehension of the dynamics of the shadow system of a singular Gierer–Meinhardt model on an isotropically evolving domain. In the case where the inhibitor’s response to the activator’s growth is rather weak, then the shadow system of the Gierer–Meinhardt model is reduced to a single though non-local equation whose dynamics is thoroughly investigated throughout the manuscript. The main focus is on the derivation of blow-up results for this non-local equation, which can be interpreted as instability patterns of the shadow system. In particular, a diffusion-driven instability (DDI), or Turing instability, in the neighbourhood of a constant stationary solution, which then is destabilised via diffusion-driven blow-up, is observed. The latter indicates the formation of some unstable patterns, whilst some stability results of global-in-time solutions towards non-constant steady states guarantee the occurrence of some stable patterns. Most of the theoretical results are verified numerically, whilst the numerical approach is also used to exhibit the dynamics of the shadow system when analytical methods fail