Model-free reconstruction of neuronal network connectivity from calcium imaging signals

A systematic assessment of global neural network connectivity through direct electrophysiological assays has remained technically unfeasible even in dissociated neuronal cultures. We introduce an improved algorithmic approach based on Transfer Entropy to reconstruct approximations to network structural connectivities from network activity monitored through calcium fluorescence imaging. Based on information theory, our method requires no prior assumptions on the statistics of neuronal firing and neuronal connections. The performance of our algorithm is benchmarked on surrogate time-series of calcium fluorescence generated by the simulated dynamics of a network with known ground-truth topology. We find that the effective network topology revealed by Transfer Entropy depends qualitatively on the time-dependent dynamic state of the network (e.g., bursting or non-bursting). We thus demonstrate how conditioning with respect to the global mean activity improves the performance of our method. [...] Compared to other reconstruction strategies such as cross-correlation or Granger Causality methods, our method based on improved Transfer Entropy is remarkably more accurate. In particular, it provides a good reconstruction of the network clustering coefficient, allowing to discriminate between weakly or strongly clustered topologies, whereas on the other hand an approach based on cross-correlations would invariantly detect artificially high levels of clustering. Finally, we present the applicability of our method to real recordings of in vitro cortical cultures. We demonstrate that these networks are characterized by an elevated level of clustering compared to a random graph (although not extreme) and by a markedly non-local connectivity.Comment: 54 pages, 8 figures (+9 supplementary figures), 1 table; submitted for publicatio

Scientific, Technical and Economic Committee for Fisheries (STECF) - Report of the Working Group (SGECA 10-01) on the discussion of methodologies, indicators and format of the 2010 Annual Economic Report (AER)

STECF-SGECA 10-01 convened in Copenhagen during the 8-11th of February 2010 to discuss and seek agreement on the content, indicators, methodologies and format of the 2010 Annual Economic Report (AER). The latest (DCF) data call requirements and how they affect the contents of the AER were also clarified. The availability of new economic and transversal variables are for the first time available under the DCF meant there was an opportunity to include new indicators and variables in the report and also modify the existing ones if necessary, implying significant changes to some or all chapters of the report. Therefore, proposals for improved contents and the overall structure were discussed. In addition, the economic policy advice needs related to the AER were specified, so that the information contained in the report could be appropriately designed with the end users in mind.JRC.DG.G.4-Maritime affair

The relevance of aerosol in the retrieval of tropospheric NO2 from satellite - a study of model data applicability

Nitrogen dioxide (NO2) is a key pollutant in the troposphere, being one of the main precursors of tropospheric ozone, and source of nitric acid, as well as contributing to global climate change. Tropospheric NO2 vertical columns can be determined from satellite observations, although some uncertainties are still associated with the retrieval process. The conversion from measured slant columns to vertical columns is accomplished with airmass factors (AMF) that are determined by radiative transfer (RT) models. While the measurement (instrumental) conditions are well assessed, improvement is still needed regarding the a priori information of atmospheric characteristics required for the estimation of AMFs (e.g., vertical distribution of the gas, aerosol loading and clouds). This thesis presents a sensitivity study focused on the impact of aerosol on the tropospheric NO2 AMF. Optical properties, size distribution, and vertical distribution of the aerosol were varied within several scenarios. Overall, the results show a tendency for two main opposite effects. On the one hand, enhancement of the measurement sensitivity occurs by means of multiple scattering, when aerosol is mixed with the trace gas. On the other hand, a shielding effect by an aerosol layer located above the NO2 is also verified. The identified pivotal factors for the AMF calculations were the relative vertical distribution of aerosol and NO2, the aerosol optical depth and the single scattering albedo, as well as the surface reflectance. A case study was developed, focusing on the impact on the NO2 measurements of volcanic ash emitted from Eyjafjallajökull during the spring of 2010. Aerosol and NO2 data from the EURAD chemical transport model (CTM) were used to design scenarios for the RT calculations. A small variation of AMFs was found, revealing that, in the days and region analysed, the satellite observations of NO2 were not significantly affected by the mentioned eruption. Nonetheless, it was verified that the conclusions of the study are dependent on the accuracy of the CTM data, and on the approach employed to account for (and determine) aerosol optical properties. Such findings highlight the potential challenges that can be faced in the future if model data are used in satellite retrievals. In addition, a model evaluation performed within the GEMS project is described, where global stratospheric and tropospheric NO2 columns predicted by two chemical transport models MOZART and TM5 are compared with SCIAMACHY observations. The evaluation exercise allowed for the identification of flaws in the model systems, showing problems with the prediction of high levels of pollution in some regions (e.g., East-Asia), and with the simulation of NO2 concentrations during biomass burning events

29th Plenary Meeting Report of the Scientific, Technical and Economic Committee for Fisheries (Plen-08-03)

The Scientific, Technical and Economic Committee for Fisheries held its 29th plenary on 3-7 November 2008 in Brussels. The terms of reference included both assessments of STECF working group reports and additional requests submitted to the STECF by the Commission. Topics dealt with ranged from fisheries economics to stock review issues.JRC.G.4-Maritime affair

Non-Deployable Miniaturized Quadslot Antenna for Cubesats

The combination of the structural panels of a 1U cubesat and their air gaps can form a quadslot antenna. This type of antenna eliminates the need for a deployment mechanism and reduces the risk of a disconnection from the satellite. The electrical field constructs in an air gap at the corner of two panels, and when all four panels are powered the antenna emits a semi-omnidirectional radiation pattern similar to a dipole. Unlike a dipole, it can radiate up to 5dB of gain instead of 2.15dB. Another benefit to this antenna is its ability to have sensors and or solar cells on the panels without interfering with the radiation pattern. This is because each panel serves two electrical purposes: increasing the electrical length to reduce frequency and providing space for miscellaneous electrical hardware. Overall, this type of antenna provides the same capability as an L-dipole or patch antenna without sacrificing space, increasing cost, or cumulating more risk. The design allows for a variety of flexibility in frequency, bandwidth, physical size, or construction. This was designed and developed at California Polytechnic State University

Estimation of Shelf-Slope Exchanges Induced by Frontal Instability Near Submarine Canyons

The dynamics associated with the propagation of unstable waves along a density front and their interaction with submarine canyons are simulated and analyzed with a fine-resolution three-dimensional primitive equation coastal ocean model. Simulations consider flow in an alongshore density front over two bottom topographies: an idealized straight shelf and a shelf incised by a canyon. The stationary circulation over the idealized shelf exhibits a geostrophic balance that is perturbed when the canyon topography is introduced. Enhanced cross-shore and vertical motions are produced as a result of the front-canyon interaction. A second set of simulations consider the effect of a small perturbation superimposed on the frontal circulation which develops growing meanders. In this case, the perturbation over the shelf grows rapidly by baroclinic instability into a steepened backward breaking wave characterized by significant cross-shore and vertical motions. The canyon topography accelerates or slows the development of the perturbation depending on the relative position of the unstable waves and the canyon. Finally, we use model results to determine the shelf-slope exchanges based on two methodologies. The first method computes the water transported across the shelf break while the second accounts for cross-shore displacements of water. The application of both approaches reveals that not all water transported across the shelf break is effectively exchanged between the shelf and the open ocean. However, cross-shore and vertical motions are enhanced by the unstable front and the submarine canyon leading to a large exchange between shelf and open ocean waters

Ultrastructural and cytochemical study on vitellogenesis in the diphyllidean cestode Echinobothrium euterpes (Echinobothriidae) and its phylogenetical implications

The first description of vitellogenesis in the Diphyllidea is presented in this paper. Though the type of vitellogenesis and mature vitellocyte in Echinobothriumeuterpesappear to be unique among the Eucestoda, however, they somewhat resemble that observed in the two orders of the lower cestodes, Tetraphyllidea and Proteocephalidea. Vitellocyte maturation is characterized by: (1) an increase in cell volume; (2) extensive development of short, parallel, frequently concentric cisternae of GER that produce dense proteinaceous granules; (3) development of Golgi complexes engaged in packaging this material; (4) progressive formation of saturated lipid droplets; their continuous enlargement and fusion; (5) formation of small accumulations of glycogen particles scattered between and among lipid droplets in the cytoplasm of maturing vitellocytes; (6) concentration of dense proteinaceous granules in the peripheral layer of cytoplasm, around the cell plasma membrane; and (7) vacuolization of cytoplasm of mature vitellocytes accompanied by a rapid increase in its volume. A new,unreported type of dense proteinaceous granules, situated around the limiting plasma membranes of mature vitellocytes, is described. Vitellogenesis evidently differs from that with typical shell-globules and shell-globule clusters previously reported in other taxa of lower cestodes. Cytochemical staining with periodic acidthiosemicarbazide-silver proteinate for glycogen indicates a strongly positive reaction for glycogen particles between and around largeunsaturated lipid droplets of the maturing and mature vitellocytes. Some hypotheses concerning the interrelationship between this pattern of vitellogenesis, possible mode of egg formation, embryonic development and diphyllidean life cycle, and their phylogenetic implications are drawn and discussed.publishe

Functional ultrastructure and cytochemistry of vitellogenesis and mature vitellocytes of the digenean Cainocreadium labracis (Dujardin, 1845), parasite of Dicentrarchus labrax (L., 1758)

Vitellogenesis and vitellocytes of Cainocreadium labracis were studied by transmission electron microscopy (TEM) and TEM cytochemistry. Four developmental stages were distinguished during vitellogenesis: (I) stem cell of high nucleo-cytoplasmic ratio; (II) early differentiation with chief activity focused on the beginning of protein synthesis and shell globule formation; (III) advanced differentiation with rapid intensification of protein synthesis, progressive fusion of single shell globules into large globule clusters, and formation of unsaturated lipid droplets surrounded by β-glycogen particles; and (IV) mature vitellocyte. Early vitellogenesis with vitellocyte maturation consists of: (1) increase in cell volume; (2) increased development of large, parallel cisternae of GER with production of proteinaceous granules; (3) development of small Golgi complexes that package granules; and (4) within vacuoles, progressive enlargement of proteinaceous granules into shell globule clusters formed during vitellogenesis. Three types of inclusions accumulate in large amounts in mature vitelline cells: (1) shell globule clusters, importantcomponentintheformationofeggshell;(2)numerousunsaturatedlipiddroplets.Thoughfewer,therearealsodiphasic droplets consisting of saturated and unsaturated lipids in the same droplet, and (3) a relatively small amount of β-glycogen particles, usually surround a few groups of lipid droplets. The β-glycogen and lipid droplets are nutritive reserves for embryogenesis. General pattern and functional ultrastructure of vitellogenesis greatly resemble those observed in some lower cestodes, such as bothriocephalideans and diphyllobothrideans. Variations and differences in the amount of lipids and of glycogen during vitellogenesis in lower cestodes and other trematodes are compared and discussed