Foam as a geometer

Foams are found everywhere: in nature, in technology, in our home. They are examples of cellular materials: assemblies or clusters of cells (from Latin cella: a small compartment or enclosed region) packed together so that they fill space without gaps. Foams come in different kinds. Ordinary liquid foam is an experimental system that solves some difficult geometry problems

Prevalence of unstable attractors in networks of pulse-coupled oscillators

We present and analyze the first example of a dynamical system that naturally exhibits attracting periodic orbits that are \textit{unstable}. These unstable attractors occur in networks of pulse-coupled oscillators where they prevail for large networks and a wide range of parameters. They are enclosed by basins of attraction of other attractors but are remote from their own basin volume such that arbitrarily small noise leads to a switching among attractors.Comment: 5 pages, 3 figure

Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential

The S-wave effective range parameters of the neutron-deuteron (nd) scattering are derived in the Faddeev formalism, using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-nucleon force, yielding the observed value of the doublet scattering length and the correct differential cross sections below the deuteron breakup threshold. This conclusion is consistent with the previous result for the triton binding energy, which is nearly reproduced by fss2 without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy

Promover a fluência em leitura: um estudo com alunos do 2º ano de escolaridade

Neste artigo são analisados os resultados de um Programa de Promoção da Fluência em Leitura (PPFL), implementado junto de 74 alunos do 2º ano de escolaridade de um Agrupamento Escolar do norte de Portugal. O PPFL é constituído por 22 sequências didáticas, elaboradas a partir de 22 textos (9 narrativos, 4 informativos e 9 poemas). Cada sequência foi operacionalizada em sessões de 10 a 15 minutos, durante 22 semanas, em ciclos de cinco dias (quinta-feira a quarta-feira). Em cada semana foi trabalhado apenas uma sequência didáctica (i.e. um texto). Foi utilizado um design quase experimental, com grupo experimental e grupo de controlo e com pré e pós-teste. Os sujeitos foram avaliados através de um teste de fluência de leitura – o Teste de Fluência em Leitura (TFL) –, considerando as variáveis velocidade e precisão. Os resultados evidenciam diferenças significativas a favor do grupo experimental, que superou as diferenças iniciais que se registavam no pré-teste. A análise qualitativa do impacto do PPFL aponta para um incremento na motivação para ler, no envolvimento da família e para a mudança de práticas por parte dos professores envolvidos.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), PortugalFundos Nacionais através da FCT (Fundação para a Ciência e a Tecnologia) e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) no âmbito do CIEC (Centro de Investigação em Estudos da Criança, da Universidade do Minho) com a referência POCI-01-0145-FEDER-00756

Alice in Accounting Land: The Adventure of Two Economic Historians in Accounting Records of the 19th Century

This article aims to share our experience of working with São Paulo's municipal budgets published during the 19th century and discuss the difficulties of using this kind of source to analyze the municipal public finance from a historical perspective. The budget laws published draw the researcher's attention because they are abundant and relatively easy to work with, providing a huge documentary set that may be used as a means for studies in the fields of economic history, political history, and cultural history within the imperial period. These laws are printed, therefore, readable, and easily accessible through the digital web portal Acervo Histórico da Assembleia Legislativa do Estado de São Paulo Historical Collection of the São Paulo State Legislative Assembly]. They detail the origins and destinations of public resources, municipality by municipality, allowing the researcher to reconstruct the financial life of municipalities, identifying changes in time and space of the fortunes of the 19th-century São Paulo state communities. However, may we really trust these budgets? Conversations and collaborations between two researchers showed that these accessible, readable, and abundant sources are not as appropriate as they seem at first glance. This article reports our troubled and even contradictory journey into the world of municipal public accounting, in order to detail our findings and provide a warning on these sources. A comparative methodology between budget laws and handwritten balance sheets was used at time intervals of 1, 2, and 3 years, in search of correlations and adjustment patterns between budgeted and spent amounts of money. Our experience has shown that budget laws do not have much in common with the actual financial experience of municipalities within the imperial period, therefore, they are not the most appropriate sources to know the financial daily life in the 19th-century São Paulo state villages