Reference based contrast functions in a semi-blind context

International audienceWe deal with blind signal extraction in the framework of a convolutive mixture of independent sources. Considering so-called reference signals, we generalize former identifiability conditions. Based on this result, we propose to incorporate some a priori information in the references. We show the validity of reference based contrast functions in two semi-blind situations. The results are confirmed by computer simulation

Would adults with autism be less likely to bury the survivors? An eye movement study of anomalous text reading

In a single eye movement experiment we investigated the effects of context on the time course of local and global anomaly processing during reading in adults with Autism Spectrum Disorder (ASD). In one condition short paragraph texts contained anomalous target words. Detection of the anomaly was only possible through evaluation of word meaning in relation to the global context of the whole paragraph (Passage Level Anomalies). In another condition the anomaly could be detected via computation of a local thematic violation within a single sentence embedded in the paragraph (Sentence Level Anomalies).For the sentence level anomalies the ASD group, in contrast with the typically developing (TD) group, showed early detection of the anomaly as indexed by regressive eye movements from the critical target word upon fixation. Conversely, for the passage level anomalies, and in contrast with the ASD group, the TD group showed early detection of the anomaly, with increased regressive eye movements once the critical word had been fixated.The reversal of the pattern of regression path data for the two groups, for the sentence and passage level anomalies, is discussed in relation to cognitive accounts of ASD

High precision self-alignment using liquid surface tension for additively manufactured micro components

Self-assembly of components using liquid surface tension is an attractive alternative to traditional robotic pick-and-place as it offers high assembly accuracy for coarse initial part placement. One of the key requirements of this method is the containment of the liquid within a designated binding site. This paper looks to expand the applications of self-assembly and investigates the use of topographical structures applied to 3D printed micro components for self-assembly using liquid surface tension. An analysis of the effect of edge geometry on liquid contact angle was conducted. A range of binding sites were produced with varying edge geometries, 45-135°, and for a variety of site shapes and sizes, 0.4 - 1 mm in diameter, and 0.5 x 0.5 – 1 x 1 mm square. Liquid water droplets were applied to the structures and contact angles measured. Significant increases in contact angle were observed, up to 158°, compared to 70° for droplets on planar surfaces, demonstrating the ability of these binding sites to successfully pin the triple contact line at the boundary. Three challenging self-assembly cases were examined, 1) linear initial component misplacement >0.5 mm, 2) angular misplacement of components, 3) 2 misplacement of droplet. Across all three assembly cases the lowest misalignments in final component position, as well as highest repeatability, were observed for structures with actual edge geometries <90° (excluding 45° nominal), where the mean magnitude of misalignment was found to be 31 μm with 14 μm standard deviation

A 3D-printed polymer micro-gripper with self-defined electrical tracks and thermal actuator

This paper presents a simple fabrication process that allows for isolated metal tracks to be easily defined on the surface of 3D printed micro-scale polymer components. The process makes use of a standard low cost conformal sputter coating system to quickly deposit thin film metal layers on to the surface of 3D printed polymer micro parts. The key novelty lies in the inclusion of inbuilt masking features, on the surface of the polymer parts, to ensure that the conformal metal layer can be effectively broken to create electrically isolated metal features. The presented process is extremely flexible, and it is envisage that it may be applied to a wide range of sensor and actuator applications. To demonstrate the process a polymer micro-scale gripper with an inbuilt thermal actuator is designed and fabricated. In this work the design methodology for creating the micro-gripper is presented, illustrating how the rapid and flexible manufacturing process allows for fast cycle time design iterations to be performed. In addition the compatibility of this approach with traditional design and analysis techniques such as basic finite element simulation is also demonstrated with simulation results in reasonable agreement with experimental performance data for the micro-gripper

Attention mechanisms in the CHREST cognitive architecture

In this paper, we describe the attention mechanisms in CHREST, a computational architecture of human visual expertise. CHREST organises information acquired by direct experience from the world in the form of chunks. These chunks are searched for, and verified, by a unique set of heuristics, comprising the attention mechanism. We explain how the attention mechanism combines bottom-up and top-down heuristics from internal and external sources of information. We describe some experimental evidence demonstrating the correspondence of CHREST’s perceptual mechanisms with those of human subjects. Finally, we discuss how visual attention can play an important role in actions carried out by human experts in domains such as chess

A feeding guild indicator to assess environmental change impacts on marine ecosystem structure and functioning.

Integrating food web indicators into ecological status assessments is central to developing effective management measures that can improve degraded ecosystems. This is because they can reveal how ecosystems respond to environmental change that cannot be inferred from studying habitat, species or assemblages alone. However, the substantial investment required to monitor food webs (e.g. via stomach contents analysis) and the lack of internationally agreed approaches to assessing them has hampered their development. Inventories of trophic interactions have been collated world-wide and across biomes, and can be applied to infer food web structure and energy flow. Here, we compile a new marine dataset containing 8,092 unique predator–prey interactions from 415,294 fish stomachs. We demonstrate how feeding guilds (i.e. groupings based on diet and life stage) could be defined systematically and in a way that is conducive to their application internationally across ecosystems; and apply them to the North Sea fish assemblage to demonstrate their responsiveness to anthropogenic pressures. We found evidence for seven distinct feeding guilds. Differences between guilds were related to predator size, which positively correlated with piscivory, phylogeny, with multiple size classes of a species often in the same guild, and habitat, as pelagic, benthic and shallow-coastal foraging was apparent. Guild biomasses were largely consistent through time at the North Sea-level and spatially aggregated at the regional level with change relating to changes in resource availability, temperature, fishing and the biomass of other guilds. This suggests that fish biomass was partitioned across broad feeding and environmental niches, and changes over time were governed partly by guild carrying capacities, but also by a combination of covariates with contrasting patterns of change. Management of the North Sea ecosystem could therefore be adaptive and focused towards specific guilds and pressures in a given area. Synthesis and applications. We propose a food web indicator which has been explicitly called for to inform policy via food web status assessment as part of the European Union's Marine Strategy Framework Directive and the indicator toolkit supporting The Convention for the Protection of the Marine Environment of the North-East Atlantic (the ‘OSPAR Convention’)

Star and Planet Formation with ALMA: an Overview

Submillimeter observations with ALMA will be the essential next step in our understanding of how stars and planets form. Key projects range from detailed imaging of the collapse of pre-stellar cores and measuring the accretion rate of matter onto deeply embedded protostars, to unravelling the chemistry and dynamics of high-mass star-forming clusters and high-spatial resolution studies of protoplanetary disks down to the 1 AU scale.Comment: Invited review, 8 pages, 5 figures; to appear in the proceedings of "Science with ALMA: a New Era for Astrophysics". Astrophysics & Space Science, in pres

Hamiltonian Theory of the FQHE: Conserving Approximation for Incompressible Fractions

A microscopic Hamiltonian theory of the FQHE developed by Shankar and the present author based on the fermionic Chern-Simons approach has recently been quite successful in calculating gaps and finite tempertature properties in Fractional Quantum Hall states. Initially proposed as a small-$q$ theory, it was subsequently extended by Shankar to form an algebraically consistent theory for all $q$ in the lowest Landau level. Such a theory is amenable to a conserving approximation in which the constraints have vanishing correlators and decouple from physical response functions. Properties of the incompressible fractions are explored in this conserving approximation, including the magnetoexciton dispersions and the evolution of the small-$q$ structure factor as \nu\to\half. Finally, a formalism capable of dealing with a nonuniform ground state charge density is developed and used to show how the correct fractional value of the quasiparticle charge emerges from the theory.Comment: 15 pages, 2 eps figure

Lowest-Landau-level theory of the quantum Hall effect: the Fermi-liquid-like state

A theory for a Fermi-liquid-like state in a system of charged bosons at filling factor one is developed, working in the lowest Landau level. The approach is based on a representation of the problem as fermions with a system of constraints, introduced by Pasquier and Haldane (unpublished). This makes the system a gauge theory with gauge algebra W_infty. The low-energy theory is analyzed based on Hartree-Fock and a corresponding conserving approximation. This is shown to be equivalent to introducing a gauge field, which at long wavelengths gives an infinite-coupling U(1) gauge theory, without a Chern-Simons term. The system is compressible, and the Fermi-liquid properties are similar, but not identical, to those in the previous U(1) Chern-Simons fermion theory. The fermions in the theory are effectively neutral but carry a dipole moment. The density-density response, longitudinal conductivity, and the current density are considered explicitly.Comment: 32 pages, revtex multicol

Spinal macrophages resolve nociceptive hypersensitivity after peripheral injury

Peripheral nerve injury induces long-term pro-inflammatory responses in spinal cord glial cells that facilitate neuropathic pain, but the identity of endogenous cells that resolve spinal inflammation has not been determined. Guided by single-cell RNA sequencing (scRNA-seq), we found that MRC1+ spinal cord macrophages proliferated and upregulated the anti-inflammatory mediator Cd163 in mice following superficial injury (SI; nerve intact), but this response was blunted in nerve-injured animals. Depleting spinal macrophages in SI animals promoted microgliosis and caused mechanical hypersensitivity to persist. Conversely, expressing Cd163 in spinal macrophages increased Interleukin 10 expression, attenuated micro- and astrogliosis, and enduringly alleviated mechanical and thermal hypersensitivity in nerve-injured animals. Our data indicate that MRC1+ spinal macrophages actively restrain glia to limit neuroinflammation and resolve mechanical pain following a superficial injury. Moreover, we show that spinal macrophages from nerve-injured animals mount a dampened anti-inflammatory response but can be therapeutically coaxed to promote long-lasting recovery of neuropathic pain