Estudo de padrões de clusters surgidos em uma dinâmica de perseguição e fuga

A stochastic agent-based model was developed to study the motion and cluster formation in systems made up of prey and predators. A discrete virtual lattice was set up, where two types of agents could move, one type behaving as prey and was designed to move away from the second type, which acted like a predator. In this model, the primary goal was to study the movement patterns formed by the chase dynamics keeping fixed the number of these individuals in each simulation. The move rules were based on the asymmetric random walk, which applied to these two types of agents to change their behaviors to perform a Brownian motion when they are far apart. However, the chase dynamics got more intense when these two types got close. To analyze the conditions in which the clusters emerge, the initial concentrations of the two types of agents were varied, and the σ parameter acted like a mediator, amplifying or attenuating the “forces” of attraction/repulsion between the individuals. The simulations revealed the migration patterns of randomly spawned agents in the lattice, and we counted the number of the clusters on average over time.Foi desenvolvido um modelo estocástico baseado em agentes, com o objetivo de estudar a movimentação e a formação de clusters em sistemas, composto por presas e predadores. Uma rede virtual discretizada foi montada, onde se movimentaram dois tipos de agentes, sendo que um deles se locomoveu como presa e foi programado para se afastar do segundo tipo, que se comportou como predador. Neste modelo, como o interesse principal foi estudar os padrões formados pela dinâmica de perseguição, as proporções destes agentes foram mantidas fixas em cada simulação. As regras de movimentação foram baseadas em uma caminhada aleatória assimétrica, que fez com que os dois tipos de agentes, com seus respectivos comportamentos, executassem um movimento browniano quando muito afastados. Porém, a dinâmica de perseguição começou a ficar mais intensa quando estes dois se aproximaram. Para analisar as condições nas quais os clusters emergem, foram variadas as concentrações dos dois tipos de agentes e de um parâmetro σ, que atuou como um mediador, amplificando ou atenuando as “forças” de atração/repulsão entre os indivíduos. Foram realizadas simulações que revelaram padrões de movimentação de agentes inicialmente posicionados de forma aleatória na rede, assim como a contagem do número médio de clusters ao longo do tempo

A smooth path to plot hydrogen atom via Monte Carlo method.

In this paper, we show how to build a basic computer program using the Monte Carlo method to display the hydrogen atomic orbitals. For this, in a heuristic way, we applied a von Neumann acceptance-rejection method in simple problems of potential wells, and we end with the hydrogen orbitals representation. In this technique, we spread points uniformly on the 1D and 2D charts of probability density distributions, then we filtered points under these ?curves or surfaces?, and we extended this logic to 3D cases. Throughout the work, we also made some comments to help beginner students better understand the term ?wave function? present in the Schr?dinger equation. Also, we made all source code available at a third-party platform, for any purpose under the MIT license. Keywords: hydrogen atom, quantum mechanics, Monte Carlo method, Neumann acceptance-rejection method

ENXERTO ALVEOLAR UTILIZANDO LUMINA POROUS® E BIOMATERIAL DE FIBRINA: RELATO DE CASO

O Concentrado de plaquetas de segunda geração foi desenvolvido por Choukroun, para utilização em cirurgia oral e maxilofacial e, no âmbito da odontologia, tem vários campos de aplicação, como aumento de tecido ósseo para implantologia, levantamento do seio maxilar, enxerto de alvéolos, cirurgias periodontais estéticas, entre outros

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data