Analyse et simulation topologiques en géographie, application à l’étude des migrations interrégionales

Le modèle d'Analyse et de Simulation Topologique est à l'analyse de système ce que l'analyse de régression multiple est à l'analyse multivariée. Pour un système de flux ce modèle détermine les gains effectués par tous les noeuds dépendants pour tout changement de flux dans le noeud principal ; il détermine l'importance des diverses lignes de transmission entre les éléments et il permet de connaître la sensibilité d'un élément aux variations de flux sur tout arc du réseau. C'est un modèle qui pourrait s'avérer très utile pour des études d'interdépendance systémique ou pour une recherche sur les lignes de transmissions d'un phénomène de diffusion. C'est une technique très intéressante également pour mesurer l'évolution d'un réseau et connaître les éléments qui ont tendance à être refoulés en marge du système par d'autres qui prennent de l'importance.À titre d'illustration, le modèle a été appliqué à l'étude des migrations de populations en France pour les années 1962-68, dans le cadre des régions de programme.The A.S.T. model, Analyse et Simulation Topologique, does for system analysis what multiple regression does for multivariate analysis. For an origin-destination table this model determines the gains effected by the dependent elements of the System for any change in the independent ; it calculates the transmission links and gains, and it also establishes the sensitivity of any element to fluctuations in any arc of the network. It is a model which should prove of considerable interest for studies of repercussion effects of flow fluctuations, or for the analysis of transmission flows in a diffusion process. It should also prove of value for the study of the evolution of a system to establish which elements are gaining in influence and which are being relegated to the outer fringes.As an illustration, the model was applied to the study of the flow patterns of French migrant populations for the period 1962-68, by planning region

Black-body photon clustering by semi-classical means

If stimulated emission could be turned off then only uncorrelated photons would be emitted from black bodies and the photon counting statistics would be Poissonian. Through the process of stimulated emission, some fraction of the photons emitted from a black body are correlated and thus emitted in clusters. This photon clustering can be calculated by semi-classical means. The corresponding results are in agreement with quantum theory.Comment: 10 pages, 2 figures, 1 table. Added proof that stimulated-emission produced photon clustering at the source leads to the Hanbury Brown and Twiss effect without invoking photon-photon interference. Fixed unit mistakes in the left hand side of Eqs (4), (6), (7), and (9

Vessels in a Rhododendron ferrugineum (L.) population do not trace temperature anymore at the alpine shrubline

Introduction Mean xylem vessel or tracheid area have been demonstrated to represent powerful proxies to better understand the response of woody plants to changing climatic conditions. Yet, to date, this approach has rarely been applied to shrubs. MethodsHere, we developed a multidecadal, annually-resolved chronology of vessel sizes for Rhododendron ferrugineum shrubs sampled at the upper shrubline (2,550 m asl) on a north-facing, inactive rock glacier in the Italian Alps. Results and DiscussionOver the 1960-1989 period, the vessel size chronology shares 64% of common variability with summer temperatures, thus confirming the potential of wood anatomical analyses on shrubs to track past climate variability in alpine environments above treeline. The strong winter precipitation signal recorded in the chronology also confirms the negative effect of long-lasting snow cover on shrub growth. By contrast, the loss of a climate-growth relation signal since the 1990s for both temperature and precipitation, significantly stronger than the one found in radial growth, contrasts with findings in other QWA studies according to which stable correlations between series of anatomical features and climatic parameters have been reported. In a context of global warming, we hypothesize that this signal loss might be induced by winter droughts, late frost, or complex relations between increasing air temperatures, permafrost degradation, and its impacts on shrub growth. We recommend future studies to validate these hypotheses on monitored rock glaciers

Discovering Effective Policies for Land-Use Planning with Neuroevolution

How areas of land are allocated for different uses, such as forests, urban areas, and agriculture, has a large effect on the terrestrial carbon balance, and therefore climate change. Based on available historical data on land-use changes and a simulation of the associated carbon emissions and removals, a surrogate model can be learned that makes it possible to evaluate the different options available to decision-makers efficiently. An evolutionary search process can then be used to discover effective land-use policies for specific locations. Such a system was built on the Project Resilience platform and evaluated with the Land-Use Harmonization dataset LUH2 and the bookkeeping model BLUE. It generates Pareto fronts that trade off carbon impact and amount of land-use change customized to different locations, thus providing a potentially useful tool for land-use planning

Annual Ring Widths in the Arctic-Alpine Dwarf-Shrub Species Betula nana - Dataset from Long-Term Alpine Ecosystem Research in Central Norway (LTAER-NO)

Here we present a Data Paper with microscopically measured data on ring widths of the arctic-alpine dwarf shrub species Betula nana L. from Central Norway. We intend to continuously update the dataset in the future with further ring width measurements of this widespread shrub species.publishedVersio

Estudo epidemiológico de sintomas osteomusculares em cirurgiões-dentistas do Distrito Federal

O Objetivo foi verificar a distribuição de sintomas osteomusculares nos cirurgiõesdentistas ativos do Distrito Federal. Materiais e métodos: Estudo transversal realizado com cirurgiões-dentistas, no qual verificou-se a ocorrência de sintomas osteomusculares em 12 regiões anatômicas, por meio do questionário Nórdico. Tal questionário foi modificado para permitir a medida de variáveis demográficas, ocupacionais e hábitos e estilo de vida. Os dados foram analisados pela estatística descritiva, com prevalência, média e desvio-padrão no Statistical Package for Social Science (SPSS) versão 17.0 para Windows, com nível de significância de p≤0,05. Resultados: Participaram do estudo 100 cirurgiões-dentistas com média de idade de 34,8 ± 8,2 anos, sendo 63 do sexo feminino. O tempo de atuação na profissão foi de 11,6 ± 7,7 anos. Da amostra 52 sujeitos eram praticantes de atividade física, 20 executavam outra ocupação profissional e 35 colaboravam com as atividades domésticas. O uso do microcomputador foi relatado por 75 participantes e a grande maioria (91%) referiu algum quadro álgico relacionado ao trabalho. As regiões de maior prevalência de dor foram cervical (79%), lombar (73%), seguido de ombro (70%) e punho/mão (65%). Conclusão: o cirurgião-dentista pertence a uma área profissional predisposta a desenvolver complicações osteomusculares. As posturas viciosas e os instrumentos de trabalho podem ser fatores de risco para o aparecimento de dores, principalmente em membros superiores e coluna vertebral

Rapidly Prepared Nanocellulose Hybrids as Gas Barrier, Flame Retardant, and Energy Storage Materials

Cellulose nanofibril (CNF) hybrid materials show great promise as sustainable alternatives to oil-based plastics owing to their abundance and renewability. Nonetheless, despite the enormous success achieved in preparing CNF hybrids at the laboratory scale, feasible implementation of these materials remains a major challenge due to the time-consuming and energy-intensive extraction and processing of CNFs. Here, we describe a scalable materials processing platform for rapid preparation (<10 min) of homogeneously distributed functional CNF−gibbsite and CNF−graphite hybrids through a pH-responsive self-assembly mechanism, followed by their application in gas barrier, flame retardancy, and energy storage materials. Incorporation of 5 wt % gibbsite results in strong, transparent, and oxygen barrier CNF−gibbsite hybrid films in 9 min. Increasing the gibbsite content to 20 wt % affords them self-extinguishing properties, while further lowering their dewatering time to 5 min. The strategy described herein also allows for the preparation of freestanding CNF−graphite hybrids (90 wt % graphite) that match the energy storage performance (330 mA h/g at low cycling rates) and processing speed (3 min dewatering) of commercial graphite anodes. Furthermore, these ecofriendly electrodes can be fully recycled, reformed, and reused while maintaining their initial performance. Overall, this versatile concept combines a green outlook with high processing speed and material performance, paving the way toward scalable processing of advanced ecofriendly hybrid material

Nanocellulose and PEDOT:PSS composites and their applications

The need for achieving sustainable technologies has encouraged research on renewable and biodegradable materials for novel products that are clean, green, and environmentally friendly. Nanocellulose (NC) has many attractive properties such as high mechanical strength and flexibility, large specific surface area, in addition to possessing good wet stability and resistance to tough chemical environments. NC has also been shown to easily integrate with other materials to form composites. By combining it with conductive and electroactive materials, many of the advantageous properties of NC can be transferred to the resulting composites. Conductive polymers, in particular poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS), have been successfully combined with cellulose derivatives where suspensions of NC particles and colloids of PEDOT:PSS are made to interact at a molecular level. Alternatively, different polymerization techniques have been used to coat the cellulose fibrils. When processed in liquid form, the resulting mixture can be used as a conductive ink. This review outlines the preparation of NC/PEDOT:PSS composites and their fabrication in the form of electronic nanopapers, filaments, and conductive aerogels. We also discuss the molecular interaction between NC and PEDOT:PSS and the factors that affect the bonding properties. Finally, we address their potential applications in energy storage and harvesting, sensors, actuators, and bioelectronics