Further insights into the interareal connectivity of a cortical network

Over the past years, network science has proven invaluable as a means to better understand many of the processes taking place in the brain. Recently, interareal connectivity data of the macaque cortex was made available with great richness of detail. We explore new aspects of this dataset, such as a correlation between connection weights and cortical hierarchy. We also look at the link-community structure that emerges from the data to uncover the major communication pathways in the network, and moreover investigate its reciprocal connections, showing that they share similar properties

A Surprise Occurrence in Acoustic Bottom Backscatter Measurements Conducted in the Eastern Bering Sea

Acoustic backscatter measurements at different frequencies were made in the eastern Bering Sea in August 2006 from the NOAA Ship Fairweather. The measurements consisted of approximately 2,250 nm of trackline acoustic backscatter data from a 100 kHz RESON model 8111; 2,250 nm of trackline acoustic backscatter data from a 40 kHz Reson model 8160; 750 nm of trackline acoustic backscatter data from a 455 kHz Klein model 5410; and 750 nm of trackline acoustic backscatter data from a 180 kHz pre-production Klein model 7180. The two Klein systems were each towed SW-NE once along the same specified 750 nm of tracklines. The two RESON systems were each operated twice SW-NE and once NE-SW along the same tracklines as the Klein systems. The acoustic backscatter was typically what might be expected from a flat, featureless expanse of fine grained sediments. However, there was a chance encounter with an embedded community of gastropods that was documented both with bottom grab samples and video footage of the seabed. The presence of the embedded community of gastropods drastically changed the level and angle dependence of the backscatter. This paper presents a comparative analysis of the backscatter properties of the gastropod community that were observed at 40 kHz, 100 kHz, 180 kHz and 455 kHz

E-voting in Brazil - the risks to democracy

Literature has shown that countries with strong democratic traditions, such as the United States and Canada, are not yet using electronic voting systems intensively, due to the concern for and emphasis on security. It has revealed that there is no such thing as an error-free computer system, let alone an electronic voting system, and that existing technology does not offer the conditions necessary for a reliable, accurate and secure electronic voting system. In this context, then, what are the risks of e-voting to democracy? In what ways, if at all, can more fragile, less mature democracies be buttressed with e-voting systems? As a key component of e-democracy, it seems that e-voting technologies are to become more secure and increasingly reliable in the near future and will indeed be adopted in many countries. In what ways, if at all, will the introduction of such systems increase voter confidence in the political system, promote citizen engagement in political life, and nurture the evolution of democracy? If both e-voting and edemocracy are emerging based on popular demand - that is, as a demand-driven alternative to current processes, then there is no doubt that they are likely to enhance and improve the efficiency of traditional democracy. However, if e-voting technology is being introduced based on a supply-driven fashion - the technology exists therefore it should and must be implemented - then the implications for democracy should be considered. Brazil's introduction of e-voting offers a cautionary tale of supply-driven technological implication. The purpose of this paper is to demonstrate how the introduction of e-voting in Brazil is highly risky to democracy due to the lack of emphasis on security and the lack of a sociallyinformed and socially driven approach to technological innovation. The Brazilian example illustrates the democratic implications of a market-driven approach. The lack of a technology strategy designed to promote and extend democratic principles is not surprising given the closed door, market-based negotiations that led to the adoption of e-voting in Brazil. The promise, and indeed, the imperative of a democratic, voter-centered approach as an alternative for the development of an electronic voting system, is explored in the paper

Nonequilibrium Stefan-Boltzmann law

We study thermal radiation outside equilibrium. The situation considered consists of two bodies emitting photons at two different temperatures. We show that the system evolves to a stationary state characterized by an energy current which satisfies a Stefan-Boltzmann-like law expressing it as the difference of the temperatures to the fourth power of the emitters . The results obtained show how the classical laws governing the thermal radiation at equlibrium can be generalized away from equilibrium situations.Comment: 9 pages, 1 figure. To be published in J. Noneq. Ther

A Generalized Approach to Complex Networks

This work describes how the formalization of complex network concepts in terms of discrete mathematics, especially mathematical morphology, allows a series of generalizations and important results ranging from new measurements of the network topology to new network growth models. First, the concepts of node degree and clustering coefficient are extended in order to characterize not only specific nodes, but any generic subnetwork. Second, the consideration of distance transform and rings are used to further extend those concepts in order to obtain a signature, instead of a single scalar measurement, ranging from the single node to whole graph scales. The enhanced discriminative potential of such extended measurements is illustrated with respect to the identification of correspondence between nodes in two complex networks, namely a protein-protein interaction network and a perturbed version of it. The use of other measurements derived from mathematical morphology are also suggested as a means to characterize complex networks connectivity in a more comprehensive fashion.Comment: 10 pages, 2 figur

Predicting the connectivity of primate cortical networks from topological and spatial node properties

The organization of the connectivity between mammalian cortical areas has become a major subject of study, because of its important role in scaffolding the macroscopic aspects of animal behavior and intelligence. In this study we present a computational reconstruction approach to the problem of network organization, by considering the topological and spatial features of each area in the primate cerebral cortex as subsidy for the reconstruction of the global cortical network connectivity. Starting with all areas being disconnected, pairs of areas with similar sets of features are linked together, in an attempt to recover the original network structure. Inferring primate cortical connectivity from the properties of the nodes, remarkably good reconstructions of the global network organization could be obtained, with the topological features allowing slightly superior accuracy to the spatial ones. Analogous reconstruction attempts for the C. elegans neuronal network resulted in substantially poorer recovery, indicating that cortical area interconnections are relatively stronger related to the considered topological and spatial properties than neuronal projections in the nematode. The close relationship between area-based features and global connectivity may hint on developmental rules and constraints for cortical networks. Particularly, differences between the predictions from topological and spatial properties, together with the poorer recovery resulting from spatial properties, indicate that the organization of cortical networks is not entirely determined by spatial constraints

Automatic Construction of Acoustic Themes for Benthic Habitat Mapping at Stanton Banks, UK

In recent years, many attempts have been made to develop automatic methods for segmentation of hydroacoustic remote sensing data acquired by multibeam echosounders (MBES) in order to generate quantitative estimates of the spatial distribution of seafloor relief, bottom type and composition. The majority of the segmentation methods presented so far have been based on image processing techniques, which assume implicitly the existence of an image. This limits their ability to unambiguously discriminate seafloor properties, as the primary observation of an MBES is not backscatter imagery or mosaics, but rather backscatter angular response. Mosaics are only projections of the original observations, with resulting loss of information. The method we are developing is fully automatic and attempts to segment the acoustic remote sensing data simultaneously in the image-textural space and in the angular-response space. The output of this automatic procedure is a thematic map, where the individual themes have boundaries defined at the mosaic image resolution, but still have sufficient angular coverage to allow for seafloor characterization. Angular Range Analysis (ARA) inversion is then applied to the average angular response of individual themes, generating estimates of the acoustic impedance, acoustic roughness and mean grain size of the seafloor within the theme. The technique described above is applied to a Simrad EM1002 95kHz MBES dataset acquired from a study area covering an offshore reef at Stanton Banks, UK. The results are compared to still-images, grab samples and previous habitat maps existent in the area, to asses the ability of the acoustic theme segmentation to discriminate benthic habitats