07/13/1989 - Winters Commissioned

Solo tenendo conto della dimensione storica dei fenomeni analizzati e del contesto istituzionale in cui essi si collocano, la teoria economica può essere un potente strumento di lettura della realtà. Questa visione ha da sempre caratterizzato la ricerca di Roberto Artoni e ha costituito fonte di ispirazione per generazioni di studenti oggi attivi nell'accademia e nelle istituzioni, sia in Italia sia all'estero. La prima parte del volume presenta una serie di saggi nei quali alcuni dei suoi allievi riflettono sugli sviluppi dell'economia pubblica degli ultimi anni ripercorrendo i temi che più hanno segnato l'attività scientifica di Artoni. La seconda sezione raccoglie i suoi più recenti contributi sull'evoluzione dell'economia italiana, sul ruolo dello Stato sociale, sulle origini della crisi economica e sulla difficoltà degli economisti di prevederla e di interpretarla

Crack paths in soft thin sheets

Highly deformable materials (elastomers, gels, biological tissues, etc.) are ubiquitous in nature as well as in technology. The understanding of their flaw sensitivity is crucial to ensure a desired safety level. Fracture failure in soft materials usually occurs after the development of an uncommon crack path because of the non-classical near-tip stress field and the viscous effects. In a neo-Hookean material, the true opening stress singularity along the crack path (evaluated normal to the crack line) is of the order , while it is of the order ahead of the crack tip, promoting the appearance of a crack tip splitting leading to a tortuous crack. In the present paper, experimental tests concerning the fracture behavior of highly deformable thin sheets under tension are discussed, and the observed crack paths are interpreted according to the crack tip stress field arising for large deformations. The study reveals that higher strain rates facilitate the development of a simple Mode I crack path, while lower strain rates induce a mixed Mode in the first crack propagation stage, leading to the formation of new crack tips. The above described behavior seems to not be affected by the initial crack size

fracture toughness of highly deformable polymeric materials

Abstract: A fundamental requirement for safety design of structural components is flaw tolerance. In this field, the soft materials have a unique ability to bear external loads despite the presence of defects, due to their pronounced deformability. Unlike traditional materials, which have an enthalpic elasticity, the mechanical response of a polymer-based material is governed by the state of internal entropy of a molecular network which has a great ability to rearrange the material structure and shape so to minimize the local detrimental effect of flaws. For a correct estimation of the fracture toughness of these materials, a proper knowledge of this entropic effect is needed. In the present research, the mechanical behaviour up to failure of silicone-based cracked plates is examined by taking into account the time-dependent effects. Experimental and theoretical aspects are discussed in order to understand the defect tolerance of such materials

Considerazioni sul patto di stabilità e crescita

Le regole di politica fiscale derivano da una specifica teoria macroeconomica. Originariamente, le regole sono state proposte nell’ambito della rivoluzione keynesiana. Dal 1997 regole quantitative sono state adottate dall’UE, in coerenza con la teoria macroeconomica oggi dominante. Questo articolo analizza gli effetti di regole quantitative sulla finanza pubblica italiana

Defect tolerance in soft materials

Abstract The ability of materials to withstand defects like cracks, notches or generic geometric discontinuities, is usually indicated as flaw tolerance, and is a crucial aspect of the safety assessment of structural components. Flaw tolerance in soft materials can be substantially different from that in traditional ones. As a matter of fact, the capacity of highly deformable materials to undergo large deformations with a significant rearrangement of the molecular network at the miscroscale in highly stressed regions can enhance such an ability, leading to an erroneous underestimation of their safety level against defect-driven failure, if traditional methods of analysis are employed. In the present research work, the mechanics of highly deformable notched plates is considered from the fail-safety point-of-view. Experimental, numerical and theoretical remarks are made in order to explain the mechanism of defect resistance in such a class of materials from a physically-based point-of-view

Chromosomal diversification in ribosomal DNA sites in Ancistrus Kner, 1854 (Loricariidae, Ancistrini) from three hydrographic basins of Mato Grosso, Brazil

Populations of seven Ancistrus species were analyzed from streams and rivers of three hydrographic Brazilian basins. All populations showed different diploid numbers (2n), fundamental numbers (FNs), and karyotypes. Some representatives of Loricariidae have 2n = 54 chromosomes, which is very likely an ancestral cytotaxonomic characteristic, but many other representatives show extensive karyotype diversification. In the Ancistrus species studied, extensive karyotypic differentiation, which is generally associated with chromosome number reduction and rearrangement of the ribosomal RNA gene (rDNA) sites, was verified. Chromosomal locations of 18S and 5S rDNA were jointly detected using fluorescence in situ hybridization (FISH). In all the Ancistrus species analyzed, 18S rDNA sites were detected only on one chromosome pair, though this differed among species. 5S rDNA was located on 1–3 chromosome pairs either separately or in synteny with 18S rDNA in four of the seven species/populations. Hence the karyotype differentiation in Ancistrus species could be associated with a morphological speciation process, suggesting that chromosome fusions, inversions, deletions, duplications, and heterochromatination could contribute to the karyotype evolution of these neotropical armored catfishes

Overcoming inertia : drivers of the outsourcing process

Almost all managers have directly or indirectly been involved in the practice of outsourcing in recent years. But as they know, outsourcing is not straightforward. Outsourcing inertia, when companies are slow to adapt to changing circumstances that accommodate higher outsourcing levels, may undermine a firm’s performance. This article investigates the presence of outsourcing inertia and the factors that help managers overcome it. Using statistical evidence, we show that positive performance effects related to outsourcing can accumulate when circumstances change. This is then followed by rapid increases in outsourcing levels (i.e. outsourcing processes). We investigate what gives rise to these outsourcing processes through follow-up interviews with sourcing executives, which suggest five drivers behind outsourcing processes: managerial initiative (using outside experience); hierarchy (foreign headquarters); imitation (of competitors and of similar firms); outsider advice (from external institutions); knowledge sources (using external information). These five drivers all offer scope for managerial action. We tie them to academic literatures and suggest ways of investigating their presence and impact on the outsourcing process. Overall, we conclude that while economizing factors play a key role in explaining how much firms outsource, it is socializing factors that tend to drive outsourcing processes

Ensino-aprendizagem em aulas práticas sobre os conteúdos "˜órgãos dos sentidos' e "˜sistema nervoso': relato de uma experiência

Muitas vezes, aprende-se não se preocupando com a natureza desse processo que é complexo, passando esse conhecimento a diante de forma apenas teórica. A formação atual dos profissionais da educação brasileira tem melhorado ao longo dos anos, mas ainda apresenta muitas deficiências. Por isso, mais do que nunca, é necessária a capacitação continuada dos professores. Com isso, se torna possí­vel a renovação das aulas nas escolas, onde o docente ensina aos alunos por meio da observação e investigação com aulas práticas. Essas aulas práticas são de imensa importância para o processo de ensino-aprendizagem dos estudantes. O presente trabalho foi realizado na Escola Estadual José de Anchieta localizada no municí­pio de União da Vitória – PR, durante o perí­odo de dois meses na turma do nono ano, em 2016. Foram feitas no total seis aulas práticas com os alunos, intercaladas de aulas teóricas, para que com isso instigasse a curiosidade dos estudantes e tivesse uma melhoria na aprendizagem desses. Com isso, incentivar os professores e os alunos com aulas diferenciadas é essencial para que haja uma melhora no ensino nas escolas, sendo assim a chave à investigação dos conteúdos de aula, correlacionando-os com vivências de seu cotidiano

Crack paths in soft thin sheets

Highly deformable materials (elastomers, gels, biological tissues, etc.) are ubiquitous in nature as well as in technology. The understanding of their flaw sensitivity is crucial to ensure a desired safety level. Fracture failure in soft materials usually occurs after the development of an uncommon crack path because of the non-classical near-tip stress field and the viscous effects. In a neo-Hookean material, the true opening stress singularity along the crack profile is of the order of , while it is of the order of  ahead of the crack tip, promoting the appearance of a crack tip splitting leading to a tortuous crack. In the present paper, experimental tests concerning the fracture behavior of highly deformable thin sheets under tension are discussed, and the observed crack paths are interpreted according to the crack tip stress field arising for large deformations. The study reveals that higher strain rates facilitate the development of a simple Mode-I crack path, while lower strain rates induce a mixed Mode in the first crack propagation stage, leading to the formation of new crack tips. The above described behavior seems to not be affected by the initial crack size