Arboreal ants use the "Velcro® principle" to capture very large prey

Plant-ants live in a mutualistic association with host plants known as "myrmecophytes" that provide them with a nesting place and sometimes with extra-floral nectar (EFN) and/or food bodies (FBs); the ants can also attend sap-sucking Hemiptera for their honeydew. In return, plant-ants, like most other arboreal ants, protect their host plants from defoliators. To satisfy their nitrogen requirements, however, some have optimized their ability to capture prey in the restricted environment represented by the crowns of trees by using elaborate hunting techniques. In this study, we investigated the predatory behavior of the ant Azteca andreae which is associated with the myrmecophyte Cecropia obtusa. We noted that up to 8350 ant workers per tree hide side-by-side beneath the leaf margins of their host plant with their mandibles open, waiting for insects to alight. The latter are immediately seized by their extremities, and then spread-eagled; nestmates are recruited to help stretch, carve up and transport prey. This group ambush hunting technique is particularly effective when the underside of the leaves is downy, as is the case for C. obtusa. In this case, the hook-shaped claws of the A. andreae workers and the velvet-like structure of the underside of the leaves combine to act like natural VelcroH that is reinforced by the group ambush strategy of the workers, allowing them to capture prey of up to 13,350 times the mean weight of a single worker

Parcellaires et habitat antiques des forêts du plateau de Haye en Lorraine : bilan et perspectives

Les vestiges antiques conservés sous couvert forestier sur le plateau de Haye en Lorraine, principalement des vestiges agraires et parcellaires associés à de l'habitat, font l'objet de travaux depuis une quinzaine d'années, menés par une équipe d'archéologues et de chercheurs forestiers. Cet article vise à faire un rapide bilan de l'état d'avancement de ce dossier sous forme d'un état des lieux et en ouvrant sur les questions qui peuvent intéresser le programme RurLand

Dynamics of the association between a long-lived understory myrmecophyte and its specific associated ants

Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant–plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant–ant species. In exchange, plant–ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients

Clumping and the Interpretation of kpc-scale Maps of the Interstellar Medium: Smooth H I and Clumpy, Variable H_2 Surface Density

Many recent models consider the structure of individual interstellar medium (ISM) clouds as a way to explain observations of large parts of galaxies. To compare such models to observations, one must understand how to translate between surface densities observed averaging over large (~kpc) scales and surface densities on the scale of individual clouds (~pc scale), which are treated by models. We define a "clumping factor" that captures this translation as the ratio of the mass-weighted surface density, which is often the quantity of physical interest, to the area-weighted surface density, which is observed. We use high spatial resolution (sub-kpc) maps of CO and H I emission from nearby galaxies to measure the clumping factor of both atomic and molecular gas. The molecular and atomic ISM exhibit dramatically different degrees of clumping. As a result, the ratio H_2/H I measured at ~kpc resolution cannot be trivially interpreted as a cloud-scale ratio of surface densities. H I emission appears very smooth, with a clumping factor of only ~1.3. Based on the scarce and heterogeneous high-resolution data available, CO emission is far more clumped with a widely variable clumping factor, median ~7 for our heterogeneous data. Our measurements do not provide evidence for a universal mass-weighted surface density of molecular gas, but also cannot conclusively rule out such a scenario. We suggest that a more sophisticated treatment of molecular ISM structure, one informed by high spatial resolution CO maps, is needed to link cloud-scale models to kpc-scale observations of galaxies

FactoRing: Asynchronous TSN-compliant Network with low bounded Jitters for Industry 4.0

Time-Sensitive Networking (TSN) describes a set of features extending the functionalities and Quality of Service (QoS) of standard Ethernet to enable determinism, reliability and reconfigurability, key requirements for Industry 4.0. The TSN profile for industrial automation (IEC/IEEE 60802 standard) defines specific options to favor reliability and reconfigurability. Nevertheless, there are multiple possible options for scheduling to guarantee determinism. Today, the scheduling standards in TSN can be categorized according to the implemented communication paradigm: asynchronous or synchronous. This paradigm is of utmost importance to quantify the synchronization need and the reconfigurability effort. The main contribution of this work is the specification of an asynchronous TSN-compliant network for Industry 4.0, FactoRing, that bridges the gap between both paradigms to guarantee low bounded jitters and latencies, without the need of synchronization and complex network planning. Moreover, FactoRing supports ring-based topologies to significantly reduce installation wiring and costs. In this paper, we first present the main industry 4.0 requirements and assess the ability of recommended TSN mechanisms for industrial automation versus such requirements. Afterwards, we detail the main features of Factoring including QoS, reliability and reconfiguration management. Finally, preliminary results on performance metrics like jitters, latencies and buffer usage are discussed and the first conclusions on the promises of Factoring to meet Industry 4.0 requirements are derived

Apport du lidar à la connaissance de l’histoire de l’occupation du sol en forêt de Haye

Le potentiel archéologique des forêts est fort, notamment en raison de la bonne conservation des vestiges sous forme de micro-reliefs, mais les prospections archéologiques sont gênées par le couvert forestier, ce qui freine l’étude des sites. Une méthode de télédétection assez récente, le scanneur laser aéroporté ou lidar, permet de s’affranchir d’une partie des contraintes physiques et permet le repérage et la cartographie des vestiges. Cette technique a été appliquée au massif forestier de Haye, qui couvre 116 km2, à côté de Nancy, durant l’hiver 2006-2007. Elle a permis des apports considérables par rapport aux méthodes de prospection traditionnelles au sol jusque-là utilisées pour étudier les structures agraires et parcellaires et les habitats antiques qui y sont conservés. Ces apports ont porté sur de nombreux points : nette augmentation du nombre de vestiges découverts, amélioration de la localisation des vestiges initialement cartographiés au topofil et à la boussole ou au GPS, apports morphologiques et chronologiques, etc. Nous avons mis au point une méthode de cartographie et élaboré un référentiel de vestiges archéologiques et de structures morphologiques diverses, adaptés à l’analyse et à l’interprétation des données lidar. Au final, cette technique rend possible un véritable changement d’échelle dans l’étude des sites archéologiques et permet d’esquisser dans ses grandes lignes l’histoire de l’occupation du sol de l’actuel massif forestier de Haye.The archaeological potential of forests is high, mainly because of good conservation of the remains in the form of microreliefs, but the archaeological surveys are hampered by the forest cover, which slows the study of sites. A method of remote sensing, airborne laser scanning (lidar), overcomes some of the physical constraints and allows the identification and mapping of the remains. This technique was applied to Haye Forest, near Nancy, which covers 116 km2, in the winter of 2006-2007. Compared to traditional ground surveys, lidar improved substantially the study of ancient agrarian structures and settlements preserved in the forest. The mains inputs were: increase in the number of remains found, improved location of the remains originally mapped using topofil and compass or GPS, morphological and chronological informations, etc. We have developed a mapping method and a reference framework for archaeological remains and morphological structures, suitable for the analysis and interpretation of lidar data. Finally, this technique makes possible a real change of scale in the study of forest sites and allows to sketch in broad outline the land-use history of the Haye Forest

Le massif forestier, objet pertinent pour la recherche archéologique. L’exemple du massif forestier de Haye (Meurthe-et-Moselle)

La forêt constitue un milieu avec un potentiel archéologique très fort, notamment du fait de la bonne conservation des vestiges, mais aussi de certaines propriétés chimiques des sols. En revanche, la forêt représente en elle-même un milieu très contraignant pour les études archéologiques, qui a parfois empêché ou ralenti ces études. Les nouveaux outils à la disposition des archéologues, notamment le LiDAR pour la télédétection, mais aussi les collaborations interdisciplinaires permettent aujourd'hui de réinvestir ce milieu en changeant d'échelle. Le massif forestier par sa grande surface a en effet une échelle pertinente pour aborder l'étude d'un terroir, pour peu qu'il soit assez ancien pour avoir fossilisé des vestiges antiques ou médiévaux par exemple. Ces questions sont abordées en se basant sur l’exemple du massif forestier de Haye, massif de 11600 ha localisé en périphérie de l’agglomération nancéienne, qui fait l’objet d’études interdisciplinaires depuis une dizaine d’années.Forests are areas of high archaeological potential, particularly because of the good preservation of the remains and also because of certain chemical properties of the soil. However, forest cover is a very restraining obstacle for archaeological surveys and has sometimes hindered or even stopped them. Archaeologists now possess new tools, in particular airborne laser (LiDAR) for remote sensing but also interdisciplinary collaborative work, that enable a rediscovery of this major part of the territory, at a new scale. Forest massifs (contiguous forest areas) are a relevant scale to tackle the study of a terroir due to their large surface area, particularly if the land is old enough to have fossilized antique or medieval remains for example. Here, we develop the historical analysis of the Haye forest, situated on the outskirts of Nancy and having a total area of 11600 hectares. It has been the subject of interdisciplinary studies for the last ten years, which allowed the discovery of one of the largest Roman agricultural landscape in France.Der Wald ist eine Umgebung mit einem sehr hohen archäologischen Potential, besonders wegen der guten Erhaltung der Überreste, aber auch aufgrund gewisser chemischer Eigenschaften des Bodens. Im Gegensatz dazu ist der Wald an sich eine sehr einschränkendes Milieu für archäologische Untersuchungen, das manchmal seine Untersuchung verhindert oder verlangsamt. Die neuen, den Archäologen zur Verfügung stehenden Werkzeuge, vor allem LiDAR zur Fernerkundung, aber auch die interdisziplinäre Zusammenarbeit erlauben nun dieses Milieu in anderem Maβstab zu erkunden. Der Waldkomplex durch seine große Oberfläche hat in der Tat den geeigneten Maßstab, um die Studien vor Ort anzugehen, wenn er nur alt genug ist, um zum Beispiel antike und mittelalterliche Überreste bewahrt zu haben. Diese Fragen werden am Beispiel des Waldes von Haye angegangen, einem Waldkomplex von 11 600 ha in der Nähe der Stadt Nancy, der seit zehn Jahren Gegenstand interdisziplinärer Studien ist