65 research outputs found

    On the origin of the reactor antineutrino anomalies in light of a new summation model with parameterized β−\beta^{-} transitions

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    We investigate the possible origins of the norm and shape reactor antineutrino anomalies in the framework of a summation model (SM) where β−\beta^{-} transitions are simulated by a phenomenological Gamow-Teller β\beta-decay strength model. The general trends of the discrepancies to the Huber-Mueller model on the antineutrino side can be reproduced both in norm and shape. From the exact electron-antineutrino correspondence of the SM model, we predict similar distortions in the electron spectra, suggesting that biases on the reference fission-electron spectra could be at the origin of the anomalies

    Integration of Parallel Opposing Memories Underlies Memory Extinction.

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    Accurately predicting an outcome requires that animals learn supporting and conflicting evidence from sequential experience. In mammals and invertebrates, learned fear responses can be suppressed by experiencing predictive cues without punishment, a process called memory extinction. Here, we show that extinction of aversive memories in Drosophila requires specific dopaminergic neurons, which indicate that omission of punishment is remembered as a positive experience. Functional imaging revealed co-existence of intracellular calcium traces in different places in the mushroom body output neuron network for both the original aversive memory and a new appetitive extinction memory. Light and ultrastructural anatomy are consistent with parallel competing memories being combined within mushroom body output neurons that direct avoidance. Indeed, extinction-evoked plasticity in a pair of these neurons neutralizes the potentiated odor response imposed in the network by aversive learning. Therefore, flies track the accuracy of learned expectations by accumulating and integrating memories of conflicting events.S.W. was funded by a Wellcome Principal Research Fellowship (200846/Z/16/Z), by the Gatsby Charitable Foundation (GAT3237), and by the Bettencourt-Schueller Foundation. J.F. was supported by the DFG (FE 1563/1-1). G.S.X.E.J. was funded by Medical Research Council. D.D.B. funded by HHMI. G.S.X.E.J., D.D.B., and S.W. were funded by a Wellcome Collaborative Award (203261/Z/16/Z)

    Friends and Foes from an Ant Brain's Point of View – Neuronal Correlates of Colony Odors in a Social Insect

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    Background: Successful cooperation depends on reliable identification of friends and foes. Social insects discriminate colony members (nestmates/friends) from foreign workers (non-nestmates/foes) by colony-specific, multi-component colony odors. Traditionally, complex processing in the brain has been regarded as crucial for colony recognition. Odor information is represented as spatial patterns of activity and processed in the primary olfactory neuropile, the antennal lobe (AL) of insects, which is analogous to the vertebrate olfactory bulb. Correlative evidence indicates that the spatial activity patterns reflect odor-quality, i.e., how an odor is perceived. For colony odors, alternatively, a sensory filter in the peripheral nervous system was suggested, causing specific anosmia to nestmate colony odors. Here, we investigate neuronal correlates of colony odors in the brain of a social insect to directly test whether they are anosmic to nestmate colony odors and whether spatial activity patterns in the AL can predict how odor qualities like ‘‘friend’’ and ‘‘foe’’ are attributed to colony odors. Methodology/Principal Findings: Using ant dummies that mimic natural conditions, we presented colony odors and investigated their neuronal representation in the ant Camponotus floridanus. Nestmate and non-nestmate colony odors elicited neuronal activity: In the periphery, we recorded sensory responses of olfactory receptor neurons (electroantennography), and in the brain, we measured colony odor specific spatial activity patterns in the AL (calcium imaging). Surprisingly, upon repeated stimulation with the same colony odor, spatial activity patterns were variable, and as variable as activity patterns elicited by different colony odors. Conclusions: Ants are not anosmic to nestmate colony odors. However, spatial activity patterns in the AL alone do not provide sufficient information for colony odor discrimination and this finding challenges the current notion of how odor quality is coded. Our result illustrates the enormous challenge for the nervous system to classify multi-component odors and indicates that other neuronal parameters, e.g., precise timing of neuronal activity, are likely necessary for attribution of odor quality to multi-component odors

    Online testing of AC motor for predictive maintenance

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    International audienceAbstract – Insulation failure is one of the major causes of electrical machine destruction. The proposed paper shows that it is now possible to perform on-line monitoring of AC machines by detecting slight variations of high frequency parameters of stator windings. The system is based on low-level magnetic field measurements in the vicinity of the machine in the 1-10MHz range. The paper describes an on-line monitoring system, able to detect slight variations of high frequency characteristics of stator windings that depends on machine insulation aging

    High Frequency Behavior of AC Machine: Application of Turn Insulation Aging Diagnostic

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    International audienceThe stator insulation breakdown is a major cause of AC machine failures. Ground insulation defaults are easily detected by classical systems based on the leakage current measurements, however the turn to turn insulation degradations are more difficult to detect. For large machines, on-line methods, based on partial discharge detection and analysis, give good results but they cannot be used for low-voltage machines fed by adjustable speed drives (ASD). This paper presents a new monitoring system able to detect slight variations of high frequency resonances in the winding of a working machine fed by an industrial inverter. The new system works in association with statistical data on accelerated aging of the magnet wire. Index Terms — AC machines, Life estimation, Machine windings, Rotating machine insulation, Power system monitoring

    On-line Testing of AC Motor Insulation Quality for Predictive Maintenance

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    International audienceA new monitoring system able to give information on the insulation aging of an AC motor is presented. The principle is based on experiments on earlier aging of many specimens of a standard magnet wire under thermal and electrical stresses. These measurements show a correlation between the breakdown voltage, the probability of failure at rated voltage and the change in capacitance. In motor windings, the turn to turn capacitance increase yields changes in the high frequency resonances. The new system consists in detecting small variations of these resonances on a working machine fed by the grid or by an adjustable speed driv

    Robust Diagnostics of Stator Insulation Based on High Frequency Resonances Measurements

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    International audienceThe stator insulation breakdown is a major cause of ac machine failures. Ground insulation defaults are easily detected by classical systems based on leakage current measurements, however the turn-to-turn insulation degradations are more difficult to detect. For large machines, on-line methods, based on partial discharge detection and analysis, give good results but they cannot be used for low-voltage machines fed by adjustable speed drives (ASD). Previously, it has been shown by some of the authors that it was possible to estimate the aging of an ac machine winding thanks to HF measurements of current or magnetic field. In this paper, it is proposed to exploit conjointly all these different estimations to obtain a more robust and reliable diagnostic. The merging of the different estimations being realized through the belief functions framework, this approach is tested on real measurements

    Diagnostic Based on High Frequency Resonances and Information Fusion

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    International audienceThe stator insulation breakdown is a major cause of AC machine failures. Ground insulation defaults are easily detected by classical systems based on leakage current measurements, however the turn-to-turn insulation degradations are more difficult to detect. For large machines, on-line methods, based on partial discharge detection and analysis, give good results but they cannot be used for low-voltage machines fed by adjustable speed drives (ASD). A new monitoring system able to detect slight variations of high frequency resonances in the winding of a working machine fed by an industrial inverter was presented in [1]. Several measurements can be used in order to estimate the aging of an AC machine winding (HF measurements of current or magnetic field) [2]. When a measure, also called a piece of information, is precise and certain, no other measure is necessary. However, such a measure is rarely obtained in real world application. Information fusion consists then in merging, or exploiting conjointly, several imperfect sources of information to make proper decision. Various frameworks can be used to model the fusion, e.g., probability theory, possibility theory, belief functions [3,4]. In this paper, different measurements of the aging of an AC machine winding are combined in the latter frame. This approach is tested on real measurements
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