A method for the reconstruction of unknown non-monotonic growth functions in the chemostat

We propose an adaptive control law that allows one to identify unstable steady states of the open-loop system in the single-species chemostat model without the knowledge of the growth function. We then show how one can use this control law to trace out (reconstruct) the whole graph of the growth function. The process of tracing out the graph can be performed either continuously or step-wise. We present and compare both approaches. Even in the case of two species in competition, which is not directly accessible with our approach due to lack of controllability, feedback control improves identifiability of the non-dominant growth rate.Comment: expansion of ideas from proceedings paper (17 pages, 8 figures), proceedings paper is version v

Calcium- and polyphosphate-containing acidic granules of sea urchin eggs are similar to acidocalcisomes, but are not the targets for NAADP

Acidocalcisomes are acidic calcium-storage compartments described from bacteria to humans and characterized by their high content in poly P (polyphosphate), a linear polymer of many tens to hundreds of Pi residues linked by high-energy phosphoanhydride bonds. In the present paper we report that millimolar levels of short-chain poly P (in terms of Pi residues) and inorganic PPi are present in sea urchin extracts as detected using 31P-NMR, enzymatic determinations and agarose gel electrophoresis. Poly P was localized to granules randomly distributed in the sea urchin eggs, as shown by labelling with the poly-P-binding domain of Escherichia coli exopolyphosphatase. These granules were enriched using iodixanol centrifugation and shown to be acidic and to contain poly P, as determined by Acridine Orange and DAPI (4′,6′-diamidino-2-phenylindole) staining respectively. These granules also contained large amounts of calcium, sodium, magnesium, potassium and zinc, as detected by X-ray microanalysis, and bafilomycin A1-sensitive ATPase, pyrophosphatase and exopolyphosphatase activities, as well as Ca2+/H+ and Na+/H+ exchange activities, being therefore similar to acidocalcisomes described in other organisms. Calcium release from these granules induced by nigericin was associated with poly P hydrolysis. Although NAADP (nicotinic acid–adenine dinucleotide phosphate) released calcium from the granule fraction, this activity was not significantly enriched as compared with the NAADP-stimulated calcium release from homogenates and was not accompanied by poly P hydrolysis. GPN (glycyl-L-phenylalanine-naphthylamide) released calcium when added to sea urchin homogenates, but was unable to release calcium from acidocalcisome-enriched fractions, suggesting that these acidic stores are not the targets for NAADP

Three-Dimensional Neurophenotyping of Adult Zebrafish Behavior

The use of adult zebrafish (Danio rerio) in neurobehavioral research is rapidly expanding. The present large-scale study applied the newest video-tracking and data-mining technologies to further examine zebrafish anxiety-like phenotypes. Here, we generated temporal and spatial three-dimensional (3D) reconstructions of zebrafish locomotion, globally assessed behavioral profiles evoked by several anxiogenic and anxiolytic manipulations, mapped individual endpoints to 3D reconstructions, and performed cluster analysis to reconfirm behavioral correlates of high- and low-anxiety states. The application of 3D swim path reconstructions consolidates behavioral data (while increasing data density) and provides a novel way to examine and represent zebrafish behavior. It also enables rapid optimization of video tracking settings to improve quantification of automated parameters, and suggests that spatiotemporal organization of zebrafish swimming activity can be affected by various experimental manipulations in a manner predicted by their anxiolytic or anxiogenic nature. Our approach markedly enhances the power of zebrafish behavioral analyses, providing innovative framework for high-throughput 3D phenotyping of adult zebrafish behavior

Calcul de l'énergie déposée et analyse de la cinétique d'échauffement dans ZnTe et MgZnTe sous bombardement électronique pulsé

Corrélativement à l'étude de l'émission laser de ZnTe et MgZnTe excités par faisceau d'électrons pulsé, nouus présentons le calcul de l'énergie déposée dans ces cristaux et nous analysons la cinétique d'échauffement associée. Les profils de densité d'énergie déposée et les profondeurs de pénétration des électrons sont déterminés en simulant les trajectoires électroniques par une méthode de Monte-Carlo pour des énergies de faisceau de 15 keV à 60 keV. La connaissance de la capacité thermique massique et de la conductivité thermique de ZnTe en fonction de la température permet de calculer la cinétique d'échauffement des échantillons pour des durées de quelques nanosecondes et des profondeurs de quelques micromètres. La température initiale des échantillons couvre le domaine 10 K-300 K et les densités de puissance étudiées sont dans la gamme 75 kW/cm2-1,6 MW/cm2. La méthode d'analyse permet de séparer dans l'excitation la contribution de l'énergie et celle de la densité de courant. Les résultats obtenus mettent en évidence un confinement thermique et montrent en particulier que l'échauffement superficiel est plus élevé à basse température en dépit d'une forte diffusion (Δ T # 40 K en 10 ns) et que à haute température cet échauffement peut s'avérer plus important pour 15 keV que pour 60 keV