Multiple wave solutions in a diffusive predator-prey model with strong Allee effect on prey and ratio-dependent functional response

A thorough analysis is performed in a predator-prey reaction-diffusion model which includes three relevant complex dynamical ingredients: (a) a strong Allee effect; (b) ratio-dependent functional responses; and (c) transport attributes given by a diffusion process. As is well-known in the specialized literature, these aspects capture adverse survival conditions for the prey, predation search features and non-homogeneous spatial dynamical distribution of both populations. We look for traveling-wave solutions and provide rigorous results coming from a standard local analysis, numerical bifurcation analysis, and relevant computations of invariant manifolds to exhibit homoclinic and heteroclinic connections and periodic orbits in the associated dynamical system in $R^4$. In so doing, we present and describe a diverse zoo of traveling wave solutions; and we relate their occurrence to the Allee effect, the spreading rates and propagation speed. In addition, homoclinic chaos is manifested via both saddle-focus and focus-focus bifurcations as well as a Belyakov point. An actual computation of global invariant manifolds near a focus-focus homoclinic bifurcation is also presented to enravel a multiplicity of wave solutions in the model. A deep understanding of such ecological dynamics is therefore highlighted.Comment: 35 pages, 22 figure

Interrogation of Ion-Neutral Complexes by Trapped Ion Mobility-Mass Spectrometry and Theoretical Calculations

In the present study, the fundamentals of molecular ion trapping and the application of trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) to the separation and identification of molecular components in complex mixtures are shown. In particular, ion-neutral complexes lifetimes, relative stability, binding energies and candidate structures are described for common explosives during TIMS-MS, as well as the effect of the micro-environment, during complex sample analysis. A novel TIMS-MS workflow was developed for the detection of both inorganic residues (IGSR; inorganic gunshot residues) and organic residues (OGSR) of firearm discharge residue from skin swabs, capable of high specificity and short analysis time (few min) from a small sample size (µL). The TIMS-MS workflow provided fast, post-ionization, high resolution mobility (RIMS ~ 150–250) and mass separations (RMS ~ 20–40k) with isotopic pattern recognition. In addition, for the first time, liquid chromatography, trapped ion mobility spectrometry and mass spectrometry are combined for fast separation, identification and quantitation of labile juvenile hormones (JHs) with increased sensitivity and confidence levels. In particular, the use of the parent ion and in-source diagnostic fragment ions in a LC-TIMS-MS workflow was developed, complemented with novel extraction and labeled standards for the detection and quantitation of JHs in biological samples

Modelagem e simulação da dinâmica populacional do mosquito Aedes aegypti

This work aims to report a descriptive research on the Aedes aegypti mosquito behavior through computational simulations. The motivation for this work comes from the crescent impact of the species in society. We hope that a realistic simulation can provide information that helps decision taking in the control of dengue, zika and chikungunya. Initially, a mathematical model is developed based on the literature and known biological factors. Parameters like maturation rate and mortality are proposed as time and spatial variables based on biological knowledge about the Ae. aegypti mosquito found in the literature. An additional analysis will be made in some parameters to fit the model using experimental data. After that, we propose to work in the model numerically. The finite volume method will be used to obtain theorical results in respect to the proliferation and behaviour of mosquitoes in an urban area modeled on the city of Juiz de Fora. The final results show how the climate factors dependence is essential to model’s realism, and guide us to new paths like the study of insecticide application in urban area. While the application can already be seen with the current implementation, the measurement of the parameters of the used substances in this technique is proposed as a future work.Busca-se desenvolver neste trabalho modelos computacionais e matemáticos para a ecologia do mosquito Aedes aegypti. O trabalho justifica-se pelo impacto crescente da disseminação de doenças transmitidas pela espécie. Espera-se que os modelos possam contribuir no fornecimento de informações para tomada de decisões no controle da dengue, zika e chikungunya. Em um primeiro momento, desenvolve-se um modelo matemático baseado em ideias propostas na literatura e fatores biológicos já conhecidos. Parâmetros como taxa de emergência dos mosquitos e mortalidade serão propostos como variáveis no tempo e no espaço a partir dos conhecimentos biológicos sobre o Ae. aegypti presentes na literatura. Uma análise adicional será feita em cima de alguns parâmetros para obter valores com base em dados experimentais. Propõe-se em seguida trabalhar com o modelo matemático numericamente. Será utilizado o método de volumes finitos para a obtenção de resultados teóricos a respeito da proliferação e comportamento dos mosquitos em uma área urbana modelada com base na cidade de Juiz de Fora. Os resultados mostram como a dependência de fatores climáticos é essencial para que o modelo represente melhor a realidade, e sugere novos caminhos a serem seguidos como o estudo da aplicação de inseticidas na área urbana. Embora esta aplicação já possa ser visualizada na implementação atual, fica como um trabalho futuro a mensuração dos parâmetros relativos às substâncias utilizadas nesta técnica de controle.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Influência da pressão capilar em escoamentos bifásicos com espuma em meios porosos

Foam injection is one of the studied methods for advanced oil recovery. This method has great potential for application in the Brazilian pre-salt reservoirs. The technique consists of injecting foam into the reservoir (or creating it in situ). This technique aims to reduce gas mobility to provide more uniform and efficient sweeping in the reservoir. Foam models are typically described as a system containing a conservation law for the mass of water and a balance law for the amount of foam. In previous works, assuming a fixed surfactant concentration, the authors present traveling wave solutions for this model. Inspired by adsorption phenomena, we proposed a modification for this model to consider a variable surfactant concentration. By analyzing this modified model analytically, looking for solutions in the form of traveling waves, we found that it may lead to non-physical solutions. Besides, the numerical and analytical obtained solutions did not match. This has motivated us to study the influence of capillarity on the first-order-kinetic model. In the present work, we discuss how the kinetic model behaves under two capillary pressure simplifications. In the first, we approximate the capillary diffusion in both system equations by a constant. In the second, we approximate the capillary diffusion in the water conservation equation by a constant and neglect the capillary diffusion in the foam balance, motivated by the fact that bubble diffusion in the gas phase is lower than water-gas diffusion. We look for analytical solutions in both cases as traveling waves and validate them with numerical simulations. The obtained solutions show abrupt drops in the foam texture. Such decay have already been described in the literature in simulations and assumed to be numerical errors. Other studies justify that this decay represent physical phenomena. In this context, the present work is one of the pioneers to describe that phenomenon analytically.Injeção de espuma é um dos métodos estudados para a recuperação avançada de petróleo. Este método possui um grande potencial de aplicação no pré-sal brasileiro. A técnica consiste em injetar espuma no reservatório (ou criá-la in situ). O objetivo da técnica é reduzir a mobilidade do gás e possibilitar uma varredura mais uniforme e eficiente do reservatório. Modelos de espuma são tipicamente descritos por um sistema contendo uma lei de conservação para a massa de água e uma lei de balanço para a quantidade de espuma. Em trabalhos anteriores, supondo que a concentração de surfactante é fixa, buscou-se soluções na forma de onda viajante para este modelo. Inspirados por fenômenos como adsorção, propusemos uma modificação deste modelo para considerar a concentração de surfactante variável. Ao estudar analiticamente este modelo modificado, buscando soluções na forma de ondas viajantes, constatamos que é possível ter soluções não físicas. Além disso as soluções obtidas numericamente e analiticamente não coincidiram. Isso motivou o estudo da influência da capilaridade no modelo cinético de primeira ordem. No presente trabalho, discutimos como o modelo cinético se comporta sob duas simplificações da pressão capilar. Na primeira, aproximamos a difusão capilar em ambas as equações do sistema por uma constante. Na segunda, aproximamos a difusão capilar na equação de conservação de água por uma constante e desconsideramos a difusão capilar no balanço de espuma, motivado pelo fato de que a difusão de bolhas em fase gasosa é menor em relação à difusão água-gás. Em ambos os casos, buscamos soluções analíticas na forma de ondas viajantes e as validamos com simulações numéricas. As soluções obtidas apresentaram quedas abruptas na textura de espuma. Tais quedas já foram descritas na literatura em simulações computacionais e foram atribuídas a erros numéricos. Outros trabalhos justificam que estas quedas representam fenômeno físicos. Neste sentido o presente trabalho é um dos pioneiros a demonstrar este fenômeno analiticamente

Ultrasensitive detection of toxocara canis excretory-secretory antigens by a nanobody electrochemical magnetosensor assay.

peer reviewedHuman Toxocariasis (HT) is a zoonotic disease caused by the migration of the larval stage of the roundworm Toxocara canis in the human host. Despite of being the most cosmopolitan helminthiasis worldwide, its diagnosis is elusive. Currently, the detection of specific immunoglobulins IgG against the Toxocara Excretory-Secretory Antigens (TES), combined with clinical and epidemiological criteria is the only strategy to diagnose HT. Cross-reactivity with other parasites and the inability to distinguish between past and active infections are the main limitations of this approach. Here, we present a sensitive and specific novel strategy to detect and quantify TES, aiming to identify active cases of HT. High specificity is achieved by making use of nanobodies (Nbs), recombinant single variable domain antibodies obtained from camelids, that due to their small molecular size (15kDa) can recognize hidden epitopes not accessible to conventional antibodies. High sensitivity is attained by the design of an electrochemical magnetosensor with an amperometric readout with all components of the assay mixed in one single step. Through this strategy, 10-fold higher sensitivity than a conventional sandwich ELISA was achieved. The assay reached a limit of detection of 2 and15 pg/ml in PBST20 0.05% or serum, spiked with TES, respectively. These limits of detection are sufficient to detect clinically relevant toxocaral infections. Furthermore, our nanobodies showed no cross-reactivity with antigens from Ascaris lumbricoides or Ascaris suum. This is to our knowledge, the most sensitive method to detect and quantify TES so far, and has great potential to significantly improve diagnosis of HT. Moreover, the characteristics of our electrochemical assay are promising for the development of point of care diagnostic systems using nanobodies as a versatile and innovative alternative to antibodies. The next step will be the validation of the assay in clinical and epidemiological contexts

Estudo das propriedades de variação total para dois métodos de elementos finitos: Runge-Kutta Galerkin descontínuo e misto-híbrido

The present work aims to study the properties Total Variation Diminishing (TVD), Total Variation Diminishing in the Means (TVDM) and Total Variation Bounded in the Means (TVBM) of a Strong-Stability-Preserving Runge-Kutta Discontinuous Galerkin (SSP-RKDG) method developed to solve differential problems with a convective nature written in the form of conservation laws. The TVD and Total Variation Bounded (TVB) properties of a mixed and hybrid finite element method built to solve convection and diffusion problems are also investigated. The motivation for this study is to verify the adequacy of the methods to the simulation of foam injection for enhanced oil recovery. The stability and convergence properties of the schemes were studied, concluding that it is necessary to implement flux limiters in the approximate solutions so that the SSPRKDG method satisfies the TVD, TVDM and/or TVBM properties. The investigation on the SSP-RKDG method was substantially developed from the works [16] and [25]. A general structure of the method is presented, going through the spatial discretization via the Discontinuous Galerkin method and the use of explicit and stable SSP Runge-Kutta methods for the treatment of the temporal variable; some demonstrations of results are made in detail in order to guarantee stability properties of the methods with and without flux limiters. For the mixed and hybrid method, the study was based on the works [55] and [30]. The analysis for this method was aimed to verify the stability property in specific cases.O presente trabalho tem por objetivo estudar as propriedades Total Variation Diminishing (TVD), Total Variation Diminishing in the Means (TVDM) e Total Variation Bounded in the Means (TVBM) de um método Strong-Stability-Preserving Runge-Kutta Discontinuous Galerkin (SSP-RKDG) desenvolvido para resolver problemas diferenciais com natureza convectiva escritos na forma de leis de conservação. São investigadas também as propriedades TVD e Total Variation Bounded (TVB) de um método de elementos finitos misto e híbrido construído para resolver problemas de convecção e difusão. A motivação para este estudo é a verificação da adequação dos métodos à simulação da injeção de espuma para a recuperação avançada de petróleo. Foram estudadas as propriedades de estabilidade e convergência dos esquemas, concluindo a necessidade da implementação de limitadores de fluxo nas soluções aproximadas para que o método SSP-RKDG satisfaça as propriedades TVD, TVDM e/ou TVBM. A investigação do método SSP-RKDG foi substancialmente desenvolvida a partir dos trabalhos [16] e [25]. É apresentada uma estrutura geral do método, passando pela discretização espacial via método de Galerkin Descontínuo e pela utilização de métodos explícitos e estáveis SSP Runge-Kutta para o tratamento da variável temporal. Algumas demonstrações de resultados que garantem propriedades de estabilidade dos métodos com e sem limitadores de fluxo são feitas de maneira detalhada. Para o método misto híbrido, o estudo teve como norte os trabalhos [55] e [30]. A análise para este método esteve voltada à verificação da propriedade de estabilidade de casos específicos.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio