6,258 research outputs found

    NMDA Receptor Blockade Specifically Impedes the Acquisition of Incentive Salience Attribution

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    Glutamatergic signaling plays an important role in learning and memory. Using Pavlovian conditioned approach procedures, the mechanisms that drive stimulus-reward learning and memory have been investigated. However, there are instances where reward-predictive stimuli can function beyond being solely predictive and can be attributed with “motivational value” or incentive salience. Using a Pavlovian conditioned approach procedure consisting of two different but equally predictive stimuli (lever vs. tone) we investigated the role NMDA receptor function has in the attribution of incentive salience. The results revealed that the administration of MK-801, an NMDA receptor antagonist, during acquisition of Pavlovian conditioned approach promoted goal-tracking to a lever stimulus, while control animals learned to sign-track. Moreover, within the same animals, the use of a tone stimulus elicited goal-tracking responses that were unaffected by MK-801 pretreatments. Furthermore, a lever CS that elicited sign-tracking served as a more robust conditioned reinforcer than a tone CS that elicited goal-tracking or a lever CS that elicited goal-tracking via MK-801 pretreatments. Collectively, these results demonstrate that NMDA receptor antagonism can alter the stimulus-reward relationship learned and prevent the attribution of incentive salience, rather than impede general learning

    QUASIANALYTICAL ESTIMATES OF INDUCTANCE USING SUBCONDUCTOR METHODS

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    Subconductor methods or partial wire methods yield reliable results for conductor parameters such as inductance, capacitance, conductance and resistance and can be used to estimate these parameters for conductor configurations involving complex geometries which cannot be handled using analytical methods. The values of inductances obtained using partial wire method are critically compared with values obtained using analytical methods

    QUASIANALYTICAL ESTIMATES OF INDUCTANCE USING SUBCONDUCTOR METHODS

    Get PDF
    Subconductor methods or partial wire methods yield reliable results for conductor parameters such as inductance, capacitance, conductance and resistance and can be used to estimate these parameters for conductor configurations involving complex geometries which cannot be handled using analytical methods. The values of inductances obtained using partial wire method are critically compared with values obtained using analytical methods

    Hard X-ray Variability of AGN

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    Aims: Active Galactic Nuclei are known to be variable throughout the electromagnetic spectrum. An energy domain poorly studied in this respect is the hard X-ray range above 20 keV. Methods: The first 9 months of the Swift/BAT all-sky survey are used to study the 14 - 195 keV variability of the 44 brightest AGN. The sources have been selected due to their detection significance of >10 sigma. We tested the variability using a maximum likelihood estimator and by analysing the structure function. Results: Probing different time scales, it appears that the absorbed AGN are more variable than the unabsorbed ones. The same applies for the comparison of Seyfert 2 and Seyfert 1 objects. As expected the blazars show stronger variability. 15% of the non-blazar AGN show variability of >20% compared to the average flux on time scales of 20 days, and 30% show at least 10% flux variation. All the non-blazar AGN which show strong variability are low-luminosity objects with L(14-195 keV) < 1E44 erg/sec. Conclusions: Concerning the variability pattern, there is a tendency of unabsorbed or type 1 galaxies being less variable than the absorbed or type 2 objects at hardest X-rays. A more solid anti-correlation is found between variability and luminosity, which has been previously observed in soft X-rays, in the UV, and in the optical domain.Comment: 9 pages, 7 figures, accepted for publication in A&
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