COMPARATIVE ANALYSIS BASED ON SIMULATION FOR THE DESIGN OF LASER TERRESTRIAL MOBILE MAPPING SYSTEMS

International audienceOver the past decade, laser terrestrial Mobile Mapping Systems (MMS) have been developing for the digitizing of outdoor environments. While the applications of MMS are various (urban security, road control, virtual world, entertainment, etc.), one may imagine that for each application the system designs could be different. Hence, a comparative analysis of different designs may be useful to find the best solution adapted to each application. We present in this paper a methodology based on the use of a simulator, to compare several designs of MMS and to improve the design. We illustrate it in the case of urban architecture digitizing

SIMULATION BASED COMPARATIVE ANALYSIS FOR THE DESIGN OF LASER TERRESTRIAL MOBILE MAPPING SYSTEMS

Over the past decade, laser terrestrial Mobile Mapping Systems (MMS) have been developed for the digital mapping of outdoor environments. While the applications of MMS are various (urban security, road control, virtual world, entertainment, etc.), one may imagine that for each application the system designs could be different. Hence, a comparative analysis of different designs may be useful to find the best solution adapted to each application. The objective of this paper is to propose a methodology to compare point-cloud data quality from different MMS designs by modifying spatial configuration of laser imaging system. For this methodology, we define several quality criteria such as precision, resolution, completeness. We illustrate this in the case of urban architecture digital mapping based on the use of a simulator

In situ associations between marine photosynthetic picoeukaryotes and potential parasites - a role for fungi?

Photosynthetic picoeukaryotes (PPEs) are important components of the marine picophytoplankton community playing a critical role in CO2 fixation but also as bacterivores, particularly in the oligotrophic gyres. Despite an increased interest in these organisms and an improved understanding of the genetic diversity of this group, we still know little of the environmental factors controlling the abundance of these organisms. Here, we investigated the quantitative importance of eukaryotic parasites in the free-living fraction as well as in associations with PPEs along a transect in the South Atlantic. Using tyramide signal amplification-fluorescence in situ hybridization (TSA-FISH), we provide quantitative evidence of the occurrence of free-living fungi in open ocean marine systems, while the Perkinsozoa and Syndiniales parasites were not abundant in these waters. Using flow cytometric cell sorting of different PPE populations followed by a dual-labelled TSA-FISH approach, we also demonstrate fungal associations, potentially parasitic, occurring with both pico-Prymnesiophyceae and pico-Chrysophyceae. These data highlight the necessity for further work investigating the specific role of marine fungi as parasites of phytoplankton to improve understanding of carbon flow in marine ecosystems

An Approximation algorithm for scheduling Trees of Malleable Tasks

This work presents an approximation algorithm for scheduling the tasks of a parallel application. These tasks are considered as malleable tasks (MT in short), which means that they can be executed on several processors. This model receives recently a lot of attention, due mainly to their practical use for implementing actual parallel applications. Most of the works developed within this model deal with independent MT for which good approximation algorithms have been designed. This work is devoted to the case where MT are linked by precedence relations. We present a 1+epsilon approximation algorithm (for any fixed epsilon) for the specific structure of a tree. This preliminary result should open the way for further investigations concerning arbitrary precedence graphs of M

The Missing Step of Pottery chaîne opératoire : Considering Post-firing Treatments on Ceramic Vessels Using Macro- and Microscopic Observation and Molecular Analysis

Post-firing treatments, produced by the interaction of an organic material with the hot surface of a ceramic, are frequently described in ethnographic literature, but have rarely been identified in archaeological ceramic assemblages. In order to address this question, this paper describes a methodology that combines macro- and microscopic observation and molecular analysis. The study of experimental ceramic vessels provided diagnostic tools to identify the type of substances, their liquid or solid state, and their mode of application and attested that the post-firing treatments do not completely waterproof the ceramics. The difficulty to observe macro- and microscopic evidence of post-firing treatments when pots are fired in reducing atmosphere suggests that these processes are probably underestimated in archaeological assemblages. Furthermore, the identification of molecular thermal transformation markers, such as ketones, calls into question their classical interpretation as markers for the cooking of fatty content. This pioneering work highlights the complexity of studying post-firing treatments, which leave small traces that are easily missed or misinterpreted. In order to address this issue, we propose a multi-analytical approach, which can serve as a basis for future studies to explore the full diversity of post-firing treatments mentioned in ethnoarchaeological literature

Virus, bactéries et protistes pathogènes du phytoplancton, le rôle insoupçonné des parasites dans le fonctionnement des écosystèmes aquatiques

International audienceMicroscopiques, les parasites sont la plupart du temps invisibles, mais présents partout. Ils infectent tous les organismes du monde vivant. La dernière décennie a révélé une incroyable diversité chez les parasites viraux, bactériens et eucaryotes. Ceux infectant le phytoplancton pourraient avoir une importance capitale dans la dynamique des populations algales et dans le fonctionnement des écosystèmes aquatiques, mais leur rôle est encore très largement méconnu à ce jour (Brussaard, 2004). Sur ces questions, la recherche ne fait que commencer

A global perspective on marine photosynthetic picoeukaryote community structure

A central goal in ecology is to understand the factors affecting the temporal dynamics and spatial distribution of microorganisms and the underlying processes causing differences in community structure and composition. However, little is known in this respect for photosynthetic picoeukaryotes (PPEs), algae that are now recognised as major players in marine CO2 fixation. Here, we analysed dot blot hybridisation and cloning–sequencing data, using the plastid-encoded 16S rRNA gene, from seven research cruises that encompassed all four ocean biomes. We provide insights into global abundance, α- and β-diversity distribution and the environmental factors shaping PPE community structure and composition. At the class level, the most commonly encountered PPEs were Prymnesiophyceae and Chrysophyceae. These taxa displayed complementary distribution patterns, with peak abundances of Prymnesiophyceae and Chrysophyceae in waters of high (25:1) or low (12:1) nitrogen:phosphorus (N:P) ratio, respectively. Significant differences in phylogenetic composition of PPEs were demonstrated for higher taxonomic levels between ocean basins, using Unifrac analyses of clone library sequence data. Differences in composition were generally greater between basins (interbasins) than within a basin (intrabasin). These differences were primarily linked to taxonomic variation in the composition of Prymnesiophyceae and Prasinophyceae whereas Chrysophyceae were phylogenetically similar in all libraries. These data provide better knowledge of PPE community structure across the world ocean and are crucial in assessing their evolution and contribution to CO2 fixation, especially in the context of global climate change