X-ray reflectivity, diffraction and grazing incidence small angle X-ray scattering as complementary methods in the microstructural study of sol–gel zirconia thin films

X-ray reflectometry, X-ray diffraction and grazing incidence small angle X-ray scattering have been complementary used to fully characterize zirconia (ZrO2) thin films obtained by the sol–gel route. The films were synthesized on various sapphire (Al2O3), silicon (Si) and glass mirrorpolished wafers by a dip-coating process in a zirconia precursor sol. Versus the synthesis parameters as alkoxide sol concentration, withdrawal speed and annealing temperature, the microstructure of the layer is managed and its different microstructural parameters such as thickness, mass density, crystalline phase, grain size and spatial arrangement have been determined. The as prepared layers are amorphous. During a thermal treatment at low temperature (<1000 -C), the layers thickness decreases while their mass density increases. Simultaneously the zirconia precursor crystallises in the zirconia tetragonal form and the coating is made of randomly oriented nanocrystals which self organise in a dense close-packed microstructure. At low temperature, this microstructural evolution is similar whatever the substrate. Moreover, the layer evolves as the corresponding bulk xerogel showing that the presence of the interface does not modify the thermal microstructure evolution of the layer which is controlled by a normal grain growth leading to relatively dense nanocrystalline thin films

Systematic comparison of trip distribution laws and models

Trip distribution laws are basic for the travel demand characterization needed in transport and urban planning. Several approaches have been considered in the last years. One of them is the so-called gravity law, in which the number of trips is assumed to be related to the population at origin and destination and to decrease with the distance. The mathematical expression of this law resembles Newton's law of gravity, which explains its name. Another popular approach is inspired by the theory of intervening opportunities which argues that the distance has no effect on the destination choice, playing only the role of a surrogate for the number of intervening opportunities between them. In this paper, we perform a thorough comparison between these two approaches in their ability at estimating commuting flows by testing them against empirical trip data at different scales and coming from different countries. Different versions of the gravity and the intervening opportunities laws, including the recently proposed radiation law, are used to estimate the probability that an individual has to commute from one unit to another, called trip distribution law. Based on these probability distribution laws, the commuting networks are simulated with different trip distribution models. We show that the gravity law performs better than the intervening opportunities laws to estimate the commuting flows, to preserve the structure of the network and to fit the commuting distance distribution although it fails at predicting commuting flows at large distances. Finally, we show that the different approaches can be used in the absence of detailed data for calibration since their only parameter depends only on the scale of the geographic unit.Comment: 15 pages, 10 figure

Phénoménologie et psychanalyse, une problématique "parenté"?

International audienceIl s'agira de faire état, en amont de la question d’un dialogue possible, de ce qui a été jusqu’à maintenant peu évoqué dans les divers articles de cet ouvrage, à savoir de ce qui sépare ces deux champs théoriques : la phénoménologie et la psychanalyse. Non pas dans le but de réfuter la possibilité de tout dialogue entre ces deux discours (l’altérité n’a jamais rendu impossible le dialogue puisque celui-ci naît d’un écart). Mais dans le but de mettre en question la « parenté » de l’une avec l’autre. C’est en effet par ce terme que Merleau-Ponty désignait le rapport de la phénoménologie et de la psychanalyse, souhaitant même, disait-il, « aggraver » cette parenté. Dans sa Préface à Hesnard de 1961 , il affirme à cet égard qu’elles « se dirigent toutes deux vers la même latence », soutenant par là que la quête de l’une et de l’autre à défaut d’adopter une méthode semblable comportent un même horizon. On ne s’étonne pas assez de ce rapprochement qu’opère Merleau-Ponty entre ce que la phénoménologie a nommé le pré-réflexif et la psychanalyse l’inconscient. Aussi s’agira-t-il premièrement de faire entendre l’originalité d’une telle affirmation dans le contexte phénoménologico-psychanalytique. Puis d’ouvrir des pistes pour envisager les difficultés qui demeurent à supposer une telle parenté si l’on souhaite conserver son tranchant à l’invention freudienne

Using neutral cline decay to estimate contemporary dispersal: a generic tool and its application to a major crop pathogen

Dispersal is a key parameter of adaptation, invasion and persistence. Yet standard population genetics inference methods hardly distinguish it from drift and many species cannot be studied by direct mark-recapture methods. Here, we introduce a method using rates of change in cline shapes for neutral markers to estimate contemporary dispersal. We apply it to the devastating banana pest Mycosphaerella fijiensis, a wind-dispersed fungus for which a secondary contact zone had previously been detected using landscape genetics tools. By tracking the spatio-temporal frequency change of 15 microsatellite markers, we find that σ, the standard deviation of parent–offspring dispersal distances, is 1.2 km/generation1/2. The analysis is further shown robust to a large range of dispersal kernels. We conclude that combining landscape genetics approaches to detect breaks in allelic frequencies with analyses of changes in neutral genetic clines offers a powerful way to obtain ecologically relevant estimates of dispersal in many species

A Universal Model of Commuting Networks

We test a recently proposed model of commuting networks on 80 case studies from different regions of the world (Europe and United-States) and with geographic units of different sizes (municipality, county, region). The model takes as input the number of commuters coming in and out of each geographic unit and generates the matrix of commuting flows betwen the geographic units. We show that the single parameter of the model, which rules the compromise between the influence of the distance and job opportunities, follows a universal law that depends only on the average surface of the geographic units. We verified that the law derived from a part of the case studies yields accurate results on other case studies. We also show that our model significantly outperforms the two other approaches proposing a universal commuting model (Balcan et al. (2009); Simini et al. (2012)), particularly when the geographic units are small (e.g. municipalities).Comment: 11 pages, 5 figure

Tweets on the road

The pervasiveness of mobile devices, which is increasing daily, is generating a vast amount of geo-located data allowing us to gain further insights into human behaviors. In particular, this new technology enables users to communicate through mobile social media applications, such as Twitter, anytime and anywhere. Thus, geo-located tweets offer the possibility to carry out in-depth studies on human mobility. In this paper, we study the use of Twitter in transportation by identifying tweets posted from roads and rails in Europe between September 2012 and November 2013. We compute the percentage of highway and railway segments covered by tweets in 39 countries. The coverages are very different from country to country and their variability can be partially explained by differences in Twitter penetration rates. Still, some of these differences might be related to cultural factors regarding mobility habits and interacting socially online. Analyzing particular road sectors, our results show a positive correlation between the number of tweets on the road and the Average Annual Daily Traffic on highways in France and in the UK. Transport modality can be studied with these data as well, for which we discover very heterogeneous usage patterns across the continent.Comment: 15 pages, 17 figure

Les anomalies climatiques associées à ENSO ont-elles une influence au voisinage de la Nouvelle-Calédonie ?

Ce rapport présente l'étude de quatre paramètres observés autour de la Nouvelle Calédonie (27°S-17°S et 160°E-170°E) sur la période 1972-1992. Les paramètres étudiés sont la température et la salinité de surface de la mer, les vents et précipitations. Il en résulte des informations précises sur les caractéristiques moyennes et sur les cycles annuels de ces paramètres. Les variations interannuelles de ces paramètres sont également quantifiées et il est établi qu'elles présentent une bonne correspondance avec le phénomène ENSO (El Nino Southern Oscillation). Cette étude a été effectuée au sein du groupe SURTROPAC (Surveillance du Pacifique Tropical) du centre ORSTOM de Nouméa, de mars à juin 1995. (Résumé d'auteur

Is spatial information in ICT data reliable?

An increasing number of human activities are studied using data produced by individuals' ICT devices. In particular, when ICT data contain spatial information, they represent an invaluable source for analyzing urban dynamics. However, there have been relatively few contributions investigating the robustness of this type of results against fluctuations of data characteristics. Here, we present a stability analysis of higher-level information extracted from mobile phone data passively produced during an entire year by 9 million individuals in Senegal. We focus on two information-retrieval tasks: (a) the identification of land use in the region of Dakar from the temporal rhythms of the communication activity; (b) the identification of home and work locations of anonymized individuals, which enable to construct Origin-Destination (OD) matrices of commuting flows. Our analysis reveal that the uncertainty of results highly depends on the sample size, the scale and the period of the year at which the data were gathered. Nevertheless, the spatial distributions of land use computed for different samples are remarkably robust: on average, we observe more than 75% of shared surface area between the different spatial partitions when considering activity of at least 100,000 users whatever the scale. The OD matrix is less stable and depends on the scale with a share of at least 75% of commuters in common when considering all types of flows constructed from the home-work locations of 100,000 users. For both tasks, better results can be obtained at larger levels of aggregation or by considering more users. These results confirm that ICT data are very useful sources for the spatial analysis of urban systems, but that their reliability should in general be tested more thoroughly.Comment: 11 pages, 9 figures + Appendix, Extended version of the conference paper published in the proceedings of the 2016 Spatial Accuracy Conference, p 9-17, Montpellier, Franc

Le jeu comme trompe-l'oeil et la dénégation

International audienceContrarily to M. Klein and D.W. Winnicott, who, generally speaking, look favorably on play in the cure, for us it appears impossible to talk about play in general without considering that there exist several types of play. Also, following the examples of J. Piaget for developmental psychology and R. Caillois for sociology, we propose a Freudian “structural classification of play,” and we distinguish three types of plays: play based on the mechanism of negation (Verneinung), play based on the mechanism of disavowal (Verleugnung), and play based on the mechanism of foreclosure (Verwerfung). This article develops the first type of play based on the mechanism of negation – which is what studies of play typically allude to – that we will call “trompe-l’œil” play. In order to illustrate this category, we will study the horse game played by “Little Hans” in Freud's famous analysis, which immediately follows the young patient's phobia. We maintain that the transition from phobic symptom to play is the result of an intervention of the Law. Play based on the mechanism of negation veils the reality of castration, and succeeds the child to move beyond merely being played upon by his fantasy – as in the case of the phobic symptom – allowing him instead to play with his fantasy. Here, the “trompe-l’œil” game can be considered therapeutic, or, at least, its emergence can be considered the effect of the analyst's therapeutic intervention.Contrairement à M. Klein et D.W. Winnicott qui envisagent, de manière générale, le jeu de manière favorable à la cure, il nous apparaît comme impossible de parler du jeu en général sans considérer qu’il existe plusieurs types de jeux. Aussi, comme J. Piaget l’avait proposé pour la psychologie développementale et R. Caillois pour la sociologie, proposons-nous une « classification structurale des jeux » qui épouse le champ freudien et repérons-nous trois types de jeux : les jeux fondés sur le mécanisme de la dénégation (Verneinung), les jeux fondés sur le mécanisme du déni (Verleugnung) et les jeux fondés sur le mécanisme de la forclusion (Verwerfung). Dans cet article est développé le premier type de jeu fondé sur le mécanisme de la dénégation – celui auquel les études sur « le » jeu font en général allusion – que nous appellerons un jeu « trompe-l’œil ». Afin d’illustrer cette catégorie, c’est le jeu du cheval du « petit Hans », célèbre psychanalyse de Freud, qui succède immédiatement à la phobie, qui est étudié. Nous soutenons que le passage du symptôme phobique au jeu résulte d’un rappel de la loi. Le jeu fondé sur le mécanisme de la dénégation, en tant que permettant de voiler la castration, permet à l’enfant de ne plus être totalement joué par son fantasme – comme dans le symptôme phobique – mais de jouer de son fantasme. En cela, le jeu « trompe-l’œil » peut être considéré comme thérapeutique ou, au moins, son émergence comme l’effet d’une intervention thérapeutique de l’analyste