6,635 research outputs found

    Neural activity associated with the passive prediction of ambiguity and risk for aversive events

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    In economic decision making, outcomes are described in terms of risk (uncertain outcomes with certain probabilities) and ambiguity (uncertain outcomes with uncertain probabilities). Humans are more averse to ambiguity than to risk, with a distinct neural system suggested as mediating this effect. However, there has been no clear disambiguation of activity related to decisions themselves from perceptual processing of ambiguity. In a functional magnetic resonance imaging (fMRI) experiment, we contrasted ambiguity, defined as a lack of information about outcome probabilities, to risk, where outcome probabilities are known, or ignorance, where outcomes are completely unknown and unknowable.Wemodified previously learned pavlovian CSstimuli such that they became an ambiguous cue and contrasted evoked brain activity both with an unmodified predictive CS(risky cue), and a cue that conveyed no information about outcome probabilities (ignorance cue). Compared with risk, ambiguous cues elicited activity in posterior inferior frontal gyrus and posterior parietal cortex during outcome anticipation. Furthermore, a similar set of regions was activated when ambiguous cues were compared with ignorance cues. Thus, regions previously shown to be engaged by decisions about ambiguous rewarding outcomes are also engaged by ambiguous outcome prediction in the context of aversive outcomes. Moreover, activation in these regions was seen even when no actual decision is made. Our findings suggest that these regions subserve a general function of contextual analysis when search for hidden information during outcome anticipation is both necessary and meaningful

    Non-lethal PCR genotyping of single Drosophila

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    In Drosophila, genetic techniques relying on stochastic chromosomal rearrangements involve the generation and screening of a large number of fly stocks to isolate a few lines of interest. Here, we describe a PCR-based method allowing non-lethal molecular characterization of single flies. Using this procedure, individual candidate recombinant animals can be genotyped and selected one generation earlier than with extant methodology and, importantly, before stocks are established. This advance should significantly facilitate several of the most fundamental and routine techniques in Drosophila genetics

    A 12 μm ISOCAM survey of the ESO-Sculptor field

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    We present a detailed reduction of a mid-infrared 12 μm (LW10 filter) ISOCAM open time observation performed on the ESOSculptor Survey field (Arnouts et al. 1997, A&AS, 124, 163). A complete catalogue of 142 sources (120 galaxies and 22 stars), detected with high significance (equivalent to 5σ), is presented above an integrated flux density of 0.24 mJy. Star/galaxy separation is performed by a detailed study of colour-colour diagrams. The catalogue is complete to 1 mJy and, below this flux density, the incompleteness is corrected using two independent methods. The first method uses stars and the second uses optical counterparts of the ISOCAM galaxies; these methods yield consistent results. We also apply an empirical flux density calibration using stars in the field. For each star, the 12 μm flux density is derived by fitting optical colours from a multi-band χ^2 to stellar templates (BaSel-2.0) and using empirical optical-IR colour-colour relations. This article is a companion analysis to our 2007 paper (Rocca-Volmerange et al. 2007, A&A, 475, 801) where the 12 μm faint galaxy counts are presented and analysed per galaxy type with the evolutionary code PÉGASE.3

    The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation

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    Context. Multi-wavelength galaxy number counts provide clues to the nature of galaxy evolution. The interpretation per galaxy type of the mid-IR faint counts obtained with ISO and Spitzer, consistent with the analysis of deep UV-optical-near IR galaxy counts, provide new constraints on the dust and stellar emission. Discovering the nature of new populations, such as high redshift ultra-luminous (≥10^(12) L_⊙) infrared galaxies (ULIRGs), is also crucial for understanding galaxy evolution at high redshifts. Aims. We first present the faint galaxy counts at 12 μm from the catalogue of the ISO-ESO-Sculptor Survey (ISO-ESS) published in a companion article (Seymour et al. 2007a, A&A, 475, 791). They go down to 0.31 mJy after corrections for incompleteness. We verify the consistency with the existing ISO number counts at 15 μm. Then we analyse the 12 μm (ISO-ESS) and the 24 μm (Spitzer) faint counts, to constrain the nature of ULIRGs, the cosmic star formation history and time scales for mass buildup. Methods. We show that the “normal” scenarios in our evolutionary code PÉGASE, which had previously fitted the deep UV-opticalnear IR counts, are unsuccessful at 12 μm and 24 μm. We thus propose a new ULIRG scenario adjusted to the observed cumulative and differential 12 μm and 24 μm counts and based on observed 12 μm and 25 μm IRAS luminosity functions and evolutionary optical/mid-IR colours from PÉGASE. Results. We succeed in simultaneously modelling the typical excess observed at 12 μm, 15 μm (ISO), and 24 μm (Spitzer) in the cumulative and differential counts by only changing 9% of normal galaxies (1/3 of the ellipticals) into ultra-bright dusty galaxies evolving as ellipticals, and interpreted as distant ULIRGs. These objects present similarities with the population of radio-galaxy hosts at high redshift. No number density evolution is included in our models even if minor starbursts due to galaxy interactions remain compatible with our results. Conclusions. Higher spectral and spatial resolution in the mid-IR, together with submillimeter observations using the future Herschel observatory, will be useful to confirm these results

    The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation

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    Context. Multi-wavelength galaxy number counts provide clues to the nature of galaxy evolution. The interpretation per galaxy type of the mid-IR faint counts obtained with ISO and Spitzer, consistent with the analysis of deep UV-optical-near IR galaxy counts, provide new constraints on the dust and stellar emission. Discovering the nature of new populations, such as high redshift ultra-luminous (≥10^(12) L_⊙) infrared galaxies (ULIRGs), is also crucial for understanding galaxy evolution at high redshifts. Aims. We first present the faint galaxy counts at 12 μm from the catalogue of the ISO-ESO-Sculptor Survey (ISO-ESS) published in a companion article (Seymour et al. 2007a, A&A, 475, 791). They go down to 0.31 mJy after corrections for incompleteness. We verify the consistency with the existing ISO number counts at 15 μm. Then we analyse the 12 μm (ISO-ESS) and the 24 μm (Spitzer) faint counts, to constrain the nature of ULIRGs, the cosmic star formation history and time scales for mass buildup. Methods. We show that the “normal” scenarios in our evolutionary code PÉGASE, which had previously fitted the deep UV-opticalnear IR counts, are unsuccessful at 12 μm and 24 μm. We thus propose a new ULIRG scenario adjusted to the observed cumulative and differential 12 μm and 24 μm counts and based on observed 12 μm and 25 μm IRAS luminosity functions and evolutionary optical/mid-IR colours from PÉGASE. Results. We succeed in simultaneously modelling the typical excess observed at 12 μm, 15 μm (ISO), and 24 μm (Spitzer) in the cumulative and differential counts by only changing 9% of normal galaxies (1/3 of the ellipticals) into ultra-bright dusty galaxies evolving as ellipticals, and interpreted as distant ULIRGs. These objects present similarities with the population of radio-galaxy hosts at high redshift. No number density evolution is included in our models even if minor starbursts due to galaxy interactions remain compatible with our results. Conclusions. Higher spectral and spatial resolution in the mid-IR, together with submillimeter observations using the future Herschel observatory, will be useful to confirm these results

    The Proposed Referendum Amendment

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