About the role of chaos and coarse graining in Statistical Mechanics

We discuss the role of ergodicity and chaos for the validity of statistical laws. In particular we explore the basic aspects of chaotic systems (with emphasis on the finite-resolution) on systems composed of a huge number of particles.Comment: Summer school `Fundamental Problems in Statistical Physics' (Leuven, Belgium), June 16-29, 2013. To be published in Physica

Conformations, hydrodynamic interactions, and instabilities of sedimenting semiflexible filaments

The conformations and dynamics of semiflexible filaments subject to a homogeneous external (gravitational) field, e.g., in a centrifuge, are studied numerically and analytically. The competition between hydrodynamic drag and bending elasticity generates new shapes and dynamical features. We show that the shape of a semiflexible filament undergoes instabilities as the external field increases. We identify two transitions that correspond to the excitation of higher bending modes. In particular, for strong fields the filament stabilizes in a non-planar shape, resulting in a sideways drift or in helical trajectories. For two interacting filaments, we find the same transitions, with the important consequence that the new non-planar shapes have an effective hydrodynamic repulsion, in contrast to the planar shapes which attract themselves even when their osculating planes are rotated with respect to each other. For the case of planar filaments, we show analytically and numerically that the relative velocity is not necessarily due to a different drag of the individual filaments, but to the hydrodynamic interactions induced by their shape asymmetry.Comment: 9 pages, 7 figures in Soft Matter (2015

Rock brasileiro na década de 1970: contracultura e filosofia hippie

No presente artigo procuramos tecer algumas reflexões sobre as práticas culturais surgidas em meados dos anos 1960 e que estiveram presentes na década de 1970, como a cultura de massa e a contracultura, observando as categorias de análise produzidas pelo pensamento jo-vem do período no Brasil e no mundo, ou seja, as manifestações dos hippies e consecutivamente underground, que influenciaram e originaram o rock brasileiro da década de 1970

Interações espaciais e inserção de Ampére-PR na divisão territorial do trabalho a partir do setor moveleiro

In the context of the industrialization of the state of Paraná, Ampére began to experience industrial dynamism from the 1970s onwards and over time has stood out in two industrial segments: clothing and furniture, which have important companies on the state and national stage in these industrial sectors. This text seeks to explore the interactions that Ampére has with the furniture segment and how this municipality fits into the territorial division of labor (DTT). In order to achieve this objective, the Socio-Spatial Formation (SSF) category (SANTOS, 1977) was used as a theoretical guide, along with bibliographical reviews on the subject, fieldwork and consultation and analysis of industrial and economic data. The main results are: since the consolidation of the furniture production sector in Ampére during the 2000s, the municipality has established connections with practically all the states of the federation and has more frequent exports and imports, mainly involving countries in South America, Africa and Asia.Num contexto de industrialização do estado do Paraná, Ampére passa a ter dinamismo industrial a partir dos anos 1970 e ao longo do tempo vai se destacando em dois segmentos industriais: confecções e móveis, os quais apresentam empresas importantes nos cenários estadual e nacional desses setores industriais. Esse texto procura explorar as interações que Ampére realiza a partir do segmento moveleiro e como esse município se insere na divisão territorial do trabalho (DTT). Para cumprir com o objetivo, tomou-se a categoria de Formação Sócio-Espacial (FSE) (SANTOS, 1977) como norte teórico, conjuntamente com revisões bibliográficas sobre o tema, trabalho de campo e consulta e análise de dados industriais e econômicos. Destacam-se como principais resultados: a partir da consolidação do setor de produção de móveis em Ampére durante os anos 2000, o município passou a estabelecer conexões com praticamente todos os estados da federação e realizar exportações e importações mais frequentes, envolvendo, sobretudo, países da América do Sul, da África e da Ásia

How Sperm Beat and Swim: From Filament Deformation to Activity

Understanding the dynamics of microbiological swimmers is a key element on the way to discovering biological mechanisms, to develop new sophisticated bio-mimetic technologies, e.g., artificial microswimmers, and to design novel microfluidic devices, e.g., for diagnosis applications. In this work, we focus on the dynamics of microswimmers with a slender flexible body, for which the spermatozoon is one of the best biological representatives. The overarching theme of our investigation is the relation between elasticity and dynamics of semiflexible filaments, their hydrodynamic interactions and active motion. We first study the dynamics of one, two and three sedimenting filaments in a viscous fluid. The dynamics of a settling filament is simpler than that of the beating flagellum because it is dominated only by the passive elastic restoring force. It allows a fundamental understanding of the dynamics generated by the competition of elastic and hydrodynamic forces. At the same time, the settling dynamics is of technological importance as it may suggest, e.g., new purification techniques. We find that the settling plane of an isolated semi-flexible filament is not always stable. When the external field is strong enough, the system encounters two (subsequent) dynamical transitions that break the planarity and chirality of the filament shape. New stationary settling shapes are found that correspond to drift and helical trajectories. Investigations with more filaments show that the settling dynamics may be much more rich than expected already at fields generated by modern centrifuges. Sperm cells are composed of a mostly spherical head and a whip-like appendage called flagellum. The flagellum has an oscillatory movement that sustains a traveling wave from the head to the tail. The motion of the flagellum provides the thrust needed to propel the spermatozoon and generates a complex flow field. As an essential step toward understanding the hydrodynamic cooperation between spermatozoa, we analyze high-speed experimental recording of pinned human sperm (in collaboration with researchers at the research center CAESAR, Bonn) and develop a minimal model of realistic beating. We infer the flagellum internal forces and, in the future, the generated flow field. It turns out that the model needs not to be complex and not to explicitly account for the observed left-right asymmetries in the rotational motion around the pinning point. The simulation closely reproduces the flagellum tracks recorded by high-speed video-microscopy, and the appropriate parameters are, thus, estimated directly from the experimental recordings. This is a new approach to extract also forces from the observed data in addition to the kinematics, as done by other established techniques. The inspection of high-speed recording of human spermatozoa also leads us to suggest a novel mechanism to control the swimming direction of spermatozoa via higher harmonic components of the beating frequency. The proposed mechanisms explain the usual circular trajectories by a shape anisotropy, a curved flagellum or a bent midpiece. Although it may look puzzling at first that higher beating frequency break a spatial symmetry, we show that a simple model can explain the observed behavior and match simulations with experiments. The beating pattern is not due to a predefined sinusoidal pacemaker, as used in the previous model. Instead, it is believed that the molecular motors distributed along the flagellum reach a self-organized state that generates the required force-pattern. Different models have been proposed to explain how the beating pattern is generated by a feedback system between molecular forces and flagellum shapes; however, explicit simulations lead to unexpected buckling instabilities. Thus, we present a simple mathematical (and later computational) model that is not bounded to a specific biomechanical hypothesis on the traits of the molecular motors. The resulting model highlights the difference between different feedback responses that couple the axoneme shape to the molecular motors forces. Among the possible models, we choose the model with the smoothest and the most regular behavior as we expect that, because of the variability of the biological environment and of the resilience of spermatozoa in the most disparate conditions, any representative model of active beating should not display ill-defined behaviors. The model is applied to the fascinating and contemporary investigation of the active response of the beating pattern to controlled perturbations. By numerical integration of the model, we quantify how the beating pattern (amplitude, frequency and wave vector) is affected by the medium viscosity and we show that it is possible to entrain the beating frequency to an external periodic force as generated in experimental setup or by other, surrounding, spermatozoa. This top-down approach provides a simple reference model that allows both investigation of small scale details and investigation of large cooperative assemblies of swimmers

La prise en charge de la douleur par le personnel soignant d'un service d'hémato-oncologie en France

Cette étude est le résultat d’une enquête de terrain dans un service hospitalier d’hémato-oncologie dans le sud de la France. L’objet de cette recherche a été façonné et réorienté par le terrain. Les difficultés liées aux négociations de mon arrivée dans le service et le « blocage » du terrain, font partie intégrante de l’analyse de la nature même d’un terrain en milieu hospitalier. L’étude reconstruit la vie du personnel de service, ses logiques internes, les rapports interpersonnels au sein de la hiérarchie hospitalière, les différents rythmes du travail, la construction des frontières entre professionnels et patients, les stratégies de « défense » et de solidarité interne d’un personnel soignant en contact directe avec la chronicité de la maladie et la mort. La recherche d’un équilibre entre investissement personnel et « juste distance » est le produit d’un « savoir-faire » et d’un « savoir-être » empiriques des soignants, cherchant à gérer à la fois la douleur des patients que leur propre charge émotionnelle

Francesco BENIGNO, La mala setta: alle origini di mafia e camorra, 1859-1878

Le débat historiographique sur les organisations criminelles italiennes du XIXe siècle est relancé d’une manière novatrice par Francesco Benigno, professeur de méthodologie de la recherche historique de l’Université de Teramo. Après la parution de son article « L’imaginaire de la secte », dans Annales. Histoire, science sociales (2013/3), l’auteur a poursuivi cette direction de recherche jusqu’à son dernier livre, La mala setta, dans lequel il étudie le crime organisé italien de la seconde mo..

Efectos de los distintos tipos de esfuerzos en el rendimiento económico de un proyecto de una empresa manufacturera electrónica radicada en Ushuaia

En este trabajo se investiga si existe una relación entre i) la mano de obra laboral intensiva dedicada a la fabricación de los productos, ii) la mano de obra laboral intelectual que se aboca al desarrollo inherente de las EMS y iii) los resultados económicos de distintos proyectos de una empresa radicada en Ushuaia, Tierra del Fuego, con el fin de proporcionar un enfoque desde otra perspectiva ante la decisión del ingreso de nuevos empleados

De l’Apennin aux Maremmes : le processus de réglementation de la mobilité transfrontalière à l’époque napoléonienne

Cet article a pour objectif d’analyser le processus de réglementation de la mobilité transfrontalière des populations de l’Apennin septentrional vers les plaines de la Maremme à l’époque napoléonienne. La perspective méthodologique adoptée pour étudier les pratiques et les techniques de contrôle des flux migratoires saisonniers tient compte des travaux historiographiques les plus récents sur les procédures d’identification personnelle. En outre, il a été possible de souligner le rôle central joué à cette époque par le consulat du Royaume d'Italie à Livourne. En effet, le consul avait la double fonction de surveiller et, en même temps, de protéger les migrants saisonniers italiens au travail dans les départements toscans annexés à l’Empire.This article intends to analyze the regulatory process of the cross-border mobility of mountain populations in the Northern Apennines towards the Maremma plains in the Napoleonic era. The methodological perspective adopted to investigate the practices and techniques for controlling seasonal migration flows takes into account the most recent historiographical works on personal identification procedures. Finally, it highlights the central role played by the Consulate of the Kingdom of Italy in Livorno. In fact, the consul had the dual functions of monitoring and, at the same time, protecting Italian seasonal migrants at work in the Tuscan departments annexed to the Empire.Riassunto : Con quest’articolo si intende analizzare il processo di regolamentazione della mobilità transfrontaliera delle popolazioni montane dell’Appennino settentrionale verso le pianure maremmane in età napoleonica. La prospettiva metodologica adottata per l’indagare delle pratiche e delle tecniche di controllo dei flussi migratori stagionali tiene conto dei più recenti lavori storiografici sulle procedure di identificazione personale. È stato inoltre possibile fare emergere il ruolo centrale giocato dal consolato del Regno d’Italia a Livorno. Il console infatti aveva la duplice funzione di sorvegliare e, al contempo, di proteggere e tutelare i migranti stagionali italiani al lavoro nei dipartimenti Toscani annessi all’Impero

Os saberes do professor de Geografia

Neste texto procuramos identificar quais são os saberes que qualificam o professor de Geografia, ou seja, os conhecimentos que esses profissionais mobilizam para exercerem seu trabalho. Destarte, usamos a pesquisa bibliográfica, centrando-se fundamentalmente nas contribuições de Tardif. Para ser professor de Geografia são necessários diversos saberes, tanto das ciências educacionais quanto da ciência geográfica. Ademais, constatamos que os professores produzem seus próprios saberes no exercício da profissão, ainda que esses sejam amplamente desvalorizados. Partilhamos da ideia de que os professores de Geografia possuem um papel imprescindível na formação cidadã dos estudantes, pelo fato da profissão ser essencialmente humana e por essa ciência possibilitar uma leitura das contradições que o espaço geográfico apresenta. Este trabalho, no que se refere a sua contribuição, buscou trazer uma discussão teórica relevante no estudo dos saberes profissionais dos professores de Geografia, almejando contribuir no processo de superação com a concepção predominante da racionalidade técnica