A trajectory generation module for 2D and 2D1/2 environment

International audienceA trajectory generation module for a mobile robot in a 2D environment and for a robot arm in a 2D1/2 environment made of low height objects placed on a work surface is discussed. For the mobile robot, the problem of driving into a narrow corridor is solved by means of a backtracking process. Obstacle avoidance is carried out by taking into account only the wrist and the end effector of the robot. This allows the determination of a grasping configuration of convex and concave objects, and allows the choice of the shortest, collision-free trajectory

Physical, chemical, and microbiological characteristics of microbial mats (KOPARA) in the South Pacific atolls of French Polynesia

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20–40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2–3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats. Les tapis microbiens qui se développent dans des mares saumâtres et hyposalines en pourtour de deux atolls de la Polynésie Française (Rangiroa et Tetiaroa) ont été étudiés intensivement au cours des trois dernières années. Un suivi comparatif de ces tapis (appelés kopara en Polynésien) a montré des similitudes remarquables dans leur composition et leur structure. À cause de l'absence de fer, la couleur des pigments reste visible dans toute la profondeur des tapis (20 à 40 cm de profondeur), avec des alternances de vert, pourpre et rose. Les profils d'oxygène, de sulfure et de redox montrèrent l'anoxie des tapis dès 2 à 3 mm de profondeur. Les analyses des pigments et des lipides bactériens ont montré que tous les tapis consistaient en des couches stratifiées de cyanobactéries (principalement Phormidium, Schizothrix et Scytonema) et de bactéries phototrophes pourpres et vertes. Ces dernières cohabitent avec des bactéries sulfato-réductrices (Desulfovibrio et Desulfobacter) ainsi que d'autres bactéries hétérotrophes. Les observations microscopiques ont montré l'influence de la salinité sur la diversité bactérienne des différents tapis principalement pour les bactéries pourpres non sulfureuses. Des analyses de matériaux organiques et d'exopolymères ont également été réalisées. Les différences et les similitudes entre les tapis sont discutées du point de vue géomorphologique, chimique et microbiologique de façon à fournir des critères de classification des tapis microbiens de Polynésie

Production of Hydrogen from α-1,4- and β-1,4-Linked Saccharides by Marine Hyperthermophilic Archaea ▿ †

Nineteen hyperthermophilic heterotrophs from deep-sea hydrothermal vents, plus the control organism Pyrococcus furiosus, were examined for their ability to grow and produce H2 on maltose, cellobiose, and peptides and for the presence of the genes encoding proteins that hydrolyze starch and cellulose. All of the strains grew on these disaccharides and peptides and converted maltose and peptides to H2 even when elemental sulfur was present as a terminal electron acceptor. Half of the strains had at least one gene for an extracellular starch hydrolase, but only P. furiosus had a gene for an extracellular β-1,4-endoglucanase. P. furiosus was serially adapted for growth on CF11 cellulose and H2 production, which is the first reported instance of hyperthermophilic growth on cellulose, with a doubling time of 64 min. Cell-specific H2 production rates were 29 fmol, 37 fmol, and 54 fmol of H2 produced cell−1 doubling−1 on α-1,4-linked sugars, β-1,4-linked sugars, and peptides, respectively. The highest total community H2 production rate came from growth on starch (2.6 mM H2 produced h−1). Hyperthermophilic heterotrophs may serve as an important alternate source of H2 for hydrogenotrophic microorganisms in low-H2 hydrothermal environments, and some are candidates for H2 bioenergy production in bioreactors