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

Data standardization of plant–pollinator interactions

Background: Animal pollination is an important ecosystem function and service, ensuring both the integrity of natural systems and human well-being. Although many knowledge shortfalls remain, some high-quality data sets on biological interactions are now available. The development and adoption of standards for biodiversity data and metadata has promoted great advances in biological data sharing and aggregation, supporting large-scale studies and science-based public policies. However, these standards are currently not suitable to fully support interaction data sharing. Results: Here we present a vocabulary of terms and a data model for sharing plant–pollinator interactions data based on the Darwin Core standard. The vocabulary introduces 48 new terms targeting several aspects of plant–pollinator interactions and can be used to capture information from different approaches and scales. Additionally, we provide solutions for data serialization using RDF, XML, and DwC-Archives and recommendations of existing controlled vocabularies for some of the terms. Our contribution supports open access to standardized data on plant–pollinator interactions. Conclusions: The adoption of the vocabulary would facilitate data sharing to support studies ranging from the spatial and temporal distribution of interactions to the taxonomic, phenological, functional, and phylogenetic aspects of plant–pollinator interactions. We expect to fill data and knowledge gaps, thus further enabling scientific research on the ecology and evolution of plant–pollinator communities, biodiversity conservation, ecosystem services, and the development of public policies. The proposed data model is flexible and can be adapted for sharing other types of interactions data by developing discipline-specific vocabularies of termsinfo:eu-repo/semantics/publishedVersio

Redes de fusíveis livres de escala para simulação de fratura em materiais compósitos.

O problema de fraturas de materiais compósitos tem sua relevância destacada devido ao amplo emprego de materiais compostos por fases distintas, usados para atender necessidades específicas e aliar custo e funcionalidade. O tratamento teórico desses tipos de materiais inclui modelos simplificados, mas que envolvem cálculos muitas vezes impraticáveis para a obtenção de respostas práticas de interesse. Como alternativa, modelos de rede para meios não homogêneos oferecem a possibilidade de se introduzir a simulação computacional como uma ferramenta viável para se obter predições ou respostas qualitativas para o comportamento mecânico de materiais compósitos. Um dos modelos mais bem sucedidos nessas últimas duas décadas é certamente o modelo da rede de fusíveis. Ele se dispõe a embutir a desordem em escala mesoscópica, explorando a analogia entre a lei de Ohm para a condução com a lei de Hooke para materiais elásticos. Dessa forma, tem-se uma rede composta de nós interligados por fusíveis, os quais podem vir a queimar, criando falhas no material à medida que se aumenta a voltagem que se aplica às extremidades da rede. É o análogo de um material onde trincas crescem e coalescem à medida que se lhe aplica uma tensão, com a vantagem de que se troca a abordagem tensorial do problema mecânico pela relação linear entre corrente e voltagem em resistores. Esse modelo tem sido historicamente aplicado usando-se redes quadradas, cúbicas ou triangulares, mas sempre regulares. A introdução da desordem é feita pela remoção prévia de ligações (diluição) da rede ou de se atribuir estatisticamente resistências ou limites de tolerâncias diferentes aos fusíveis. A tese que se defende aqui é a de que redes livres de escala possam servir para descrever o problema de fratura sem que se lance mão da introdução ad hoc da desordem. Para isso, é necessário se inventar novas formas para pensar o carregamento de uma rede livre de escala, baseando-se em suas propriedades topológicas e não geométricas, uma vez que a localização dos nós não tem significado claro nessas redes. As redes livres de escala são caracterizadas pela existência de muitos nós com pouquíssimas ligações e de um ou poucos hubs altamente conectados. Identificados os papéis de nós centrais e periféricos nessas redes, propusemos três modos de carregamento que revelaram perfis de resposta da curva constitutiva semelhantes a casos clássicos de materiais reforçados por fibras e de alta porosidade. Investigando as propriedades dessas redes, inclui-se simulações com redes apolonianas (também livres de escala) e redes aleatórias, também na classe das redes complexas. Adicionou-se o papel da atribuição de resistências segundo várias distribuições estatísticas e o que se revelou foi a distinção de classes de universalidades definidas apenas pelos modos de carregamento.The study of fracture of composite materials has a distinguished relevance due the broad and ever increasing use of multiphase materials to attend specific needs and/or combine cost and functionality. Theoretical approach to the issue include simplified models, yet many times mathematically unfeasible, providing information of little practical use. As an alternate approach, lattice models for non-homogeneous media give the possibility of employing computer simulation to provide predictions or qualitative answers for the mechanical behaviour of composite materials. The random fuse network has been for sure one of the most successful lattice models in the last two decades. It places resistive fuses connecting nodes in a lattice, exploring the analogy between Ohms law for conduction and Hooke’s law for elasticity. As an external voltage, placed between two extremities of the network, increases, fuses will burn opening flaws in the lattice. It is the analogous to cracks growing and/or coalescing in a material as it is tracted, with the advantage of dealing with a scalar electrical problem, as opposed to the tensorial mechanical problem. This model has been historically used with square, cubic or triangular lattices, but always regular lattices. Disorder, thought in a mesoscopic scale, is introduced by removing fuses a priori (dilution) or statistically giving the fuses different conductances or current thresholds. This work proposes that scale-free networks of fuses can describe the fracture process in composite materials without the use of ad hoc introduced disorder. This novel approach requires new ways of thinking the loading of a network based on its topology instead of its geometry, since node spatial localization has no clear meaning for this sort of network. Scale-free networks are characterized by the existence a highly connected node (hub) and a huge amount of poorly connected nodes, resulting in a power-law distribution of connectivities among nodes. Identified the roles of central (most connected) and peripheral (least connected) nodes, three load modes are proposed and tested, providing responses similar to classical cases of composite materials – fiber reinforced and highly porous. Further investigating the proprieties of these networks, simulations were also performed with other complex networks: apolonian networks (which are also scale-free) and random networks. Several conductance distribution were also tested, which revealed the distinction of universality classes defined only by the load modes

Scale-free fuse network and its robustness.

The robustness and reliability of scale-free networks are tested as a fuse network. The idea is to examine the robustness of a scale-free network when links are irreversibly removed after failing. Due to inherent characteristics of the fuse network model, the sequence of links removal is deterministic and conditioned to fuse tolerance and connectivity of its ends. It is a different situation from classical robustness analysis of complex networks, when they are usually tested under random fails and deliberate attacks of nodes. The use of this system to study the fracture of elastic material brought some interesting results

Random resistivity network calculations for cuprate superconductors with an electronic phase separation transition.

The resistivity as a function of temperature for high temperature superconductors is very unusual and, despite its importance, lacks a unified theoretical explanation. It is linear with the temperature for overdoped compounds but it falls more quickly as the doping level decreases. The resistivity of underdoped cuprates increases like that of an insulator below a characteristic temperature where it shows a minimum. We show that this overall behavior can be explained by calculations using an electronicphase segregation into two main component phases with low and high electronic densities. The total resistance is calculated from the various contributions through several processes of random picking of the local resistivities and using a common statistical random resistor network approach

Competing orders and the resistivity curves of cuprate superconductors.

The resistivity as function of temperature of high temperature superconductors (HTSC) is an important property of cuprates but it still lacks a widely accepted explanation. Here we show that the overall behavior of an entire series can be explained by calculations using an electronic phase segregation into two main component phases

Computational simulation of binary compounds of carbon nanotubes and amphiphilics in aqueous solution by Monte Carlo method.

Carbonnanotubes have been subject of intensive research because of their outstanding physical properties. The problem of dissolving the aggregation of tubes in bundles formed by strong van der Waals force is addressed in this study. A complete understanding about carbonnanotubes properties is necessary in order to obtain a process of detachment that cause no damage to the tubes. Detachment can be promoted by means of amphiphilic adsorption in water solution. We have studied this phenomenon by means MonteCarlosimulation. The algorithm used was Metropolis algorithm. The analysis of equilibrium was done by means of structure function

Critical behavior of a probabilistic cellular automaton describing a biological system.

We study nonequilibrium phase transitions occurring in aprobabilisticcellularautomaton which describes one part of the immune system. In this model, each site can be occupied by three type of cells and the immune response under parasitic infections is described in terms of two parameters p and r. The local rules governing the evolution of this automaton possess “up–down” symmetry similar to Ising models. Performing Monte Carlo simulations on square and cubic lattices we verify that the model displays continuous kinetic phase transitions with spontaneous symmetry breaking. We present detailed simulations and analysis of the criticalbehavior. Our results indicate that the model belongs to the Ising universality class, supporting the “up–down” conjecture

Simulations of populations of Sapajus robustus in a fragmentedlandscape.

The study of populations subject to the phenomenon of loss and fragmentation of habitat, transformingcontinuous areas into small ones, usually surrounded by anthropogenic matrices, has been the focus ofmany researches within the scope of conservation. The objective of this study was to develop a com-puter model by introducing modifications to the renowned Penna model for biological aging, in order toevaluate the behavior of populations subjected to the effects of fragmented environments. As an objectof study, it was used biological data of the robust tufted capuchin (Sapajus robustus), an endangered pri-mate species whose geographical distribution within the Atlantic Rain Forest is part of the backdrop ofintense habitat fragmentation. The simulations showed the expected behavior based on the three mainaspects that affects populations under intense habitat fragmentation: the population density, area andconformation of the fragments and deleterious effects due the low genetic variability in small and isolatedpopulations. The model showed itself suitable to describe changes in viability and population dynamicsof the species crested capuchin considering critical levels of survival in a fragmented environment andalso, actions in order to preserve the species should be focused not only on increasing available area butalso in dispersion dynamic