Search results for "Extinction"
showing 10 items of 458 documents
Cross-reinstatement by cocaine and amphetamine of morphine-induced place preference in mice
2005
The cross-reinstatement by psychostimulants of a conditioned place preference (CPP) induced by morphine was evaluated in mice. In Experiment 1, we examined the effects of a single dose of cocaine and amphetamine on a previously extinguished morphine CPP. After acquisition of CPP induced by morphine (40 mg/kg), animals underwent daily extinction sessions of 15 min duration until the CPP was extinguished. Subsequently, animals received a non-contingent injection of cocaine (25 mg/kg) or amphetamine (4 mg/kg), which produced the reinstatement of the extinguished morphine-induced CPP. In Experiment 2, we evaluated the reinstating effects of several priming doses of cocaine (Experiment 2A) or am…
A multi-instrument approach for characterizing the atmospheric aerosol optical thickness during the STAAARTE/DAISEX-99 campaign
2002
This work deals with the retrieval of the aerosol optical thickness (AOT) needed to carry out the atmospheric correction of remote sensing data measured in Barrax (Spain) on 4 June 1999 in the framework of 1999 Digital Airbone Imaging Spectrometer Experiment (DAISEX'99). The AOT was estimated through three approaches based on: spectral extinction of direct solar irradiance at ground level, airborne nephelometer measurements at different altitudes, and backscatter lidar in the lower troposphere. We found extremely low AOT values due to a cold Atlantic front that swept across the Iberian Peninsula from west to east producing light rain over the test area on 2 June 1999. The results were solar…
Combined impacts of the Allee effect, delay and stochasticity: Persistence analysis
2020
Abstract We study a combined influence of the Allee effect, delay and stochasticity on the base of the phenomenological Hassell mathematical model of population dynamics. This bistable dynamical model possesses a wide variety of regimes, both regular and chaotic. In the persistence zone, these regimes coexist with the trivial equilibrium that corresponds to the extinction of the population. It is shown that borders of the persistence zone are defined by the crisis and saddle-node bifurcation points. Noise-induced transitions from the persistence to the extinction are studied both numerically and analytically. Using numerical modeling, we have found that the persistence zone can decrease and…
Hippocampal theta activity, learning and behavioral tendencies
2014
Trace eyeblink conditioning is a method that models a declarative, awareness-dependent form of learning. Hippocampal theta activity, an approximately 3.5 - 8.5 Hz oscillatory pattern in rabbits, has been associated with learning-related phenomena: arousal, attentional processes and association forming. In some studies theta-contingent training, given during a brain state rich in hippocampal theta oscillation, has improved the initial learning in trace eyeblink conditioning. However, other laboratories have failed to replicate this effect. This study explored the effects of theta-contingent conditioning and extinction on learning, and the connection between the magnitude of spontaneous hippo…
Long-wavelength monolithic GaInNAs vertical-cavity optical amplifiers
2004
We report on the continuous-wave amplification characteristics of an optically pumped 1.3-μm multiple-quantum-well GaInNAs-GaAs vertical-cavity semiconductor optical amplifier (VCSOA). The VCSOA structure was monolithically grown by molecular beam epitaxy and operated in reflection mode in a fiber-coupled system. The maximum on-chip gain attained, limited by the onset of laser action, was 15.6 dB at 196 mW of 980-nm pump power. For a chip gain of 10.4 dB, the optical bandwidth was 10.8 GHz and the saturation output power was -9 dBm. By varying the pump laser power, a maximum extinction ratio of 22.3 dB was obtained. Temperature-controlled tuneable operation of the device is also presented a…
Record Phase Sensitive Extinction Ratio in a Silicon Germanium Waveguide
2015
A binary step-like phase response and phase-sensitive extinction ratio in excess of 28dB under CW pump operation was demonstrated in a 20mm-long low birefringence SiGe waveguide, using a polarization-assisted phase sensitive amplifier scheme.
Cascadability and reshaping properties of a saturable absorber inserted inside a RZ transmission line for future 160-Gbit/s all-optical 2R-regenerato…
2007
International audience; In this prospective work, we analyze the behavior of a quantum-well microcavity saturable absorber component cascaded into a 100-km SMF RZ transmission line in order to annihilate the ghost-pulse phenomenon in the following simplified “...010101...” 160-Gbit/s 2-bit pattern at 1555 nm. Recirculating-loop experiments show a maximal ghost-pulse extinction up to 11.6 dB as well as an intensity extinction ratio enhancement higher than 6 dB over at least 800 km of propagation.
Plasmonics co-integrated with silicon nitride photonics for high-sensitivity interferometric biosensing
2019
We demonstrate a photonic integrated Mach-Zehnder interferometric sensor, utilizing a plasmonic stripe waveguide in the sensing branch and a photonic variable optical attenuator and a phase shifter in the reference arm to optimize the interferometer operation. The plasmonic sensor is used to detect changes in the refractive index of the surrounding medium exploiting the accumulated phase change of the propagating Surface-Plasmon-Polariton (SPP) mode that is fully exposed in an aqueous buffer solution. The variable optical attenuation stage is incorporated in the reference Si3N4 branch, as the means to counter-balance the optical losses introduced by the plasmonic branch and optimize interfe…
Modalités évolutives du genre bullatimorphites (Ammonitina) au Bathonien-Callovien (Jurassique moyen) en Europe occidentale
1999
Abstract The genus Bullatimorphites, (macroconchs Bullatimorphites, Kheraiceras; microconchs Bomburites, Schwandorfia, Spbaeroptycbius, Treptoceras), is characterized by an ontogenesis with three morphologic phases: serpenticone, sphaerocone and ellipticone. Within the successive populations, the relative development of these morphologies allows the defined species to be placed in an evolutive and stratigraphic lineage. The history of the genus comprises five steps: 1) emergence (Early Middle Bathonian), 2) first gradual evolution (Middle-Upper Bathonian), 3) first morphological diversification (Uppermost Bathonian), 4) second gradual evolution, 5) second morphological diversification and e…
Marine Ostracods of the Upper Miocene of the Well Ashtart 1 (Gulf of Gabès, Southeastern Tunisia)
1988
We studied the ostracod fauna from a Late Miocene-Early Pliocene interval 600 m thick, in Ashtart 1, an offshore well in the Gulf of Gabes, southeastern Tunisia. Most of the 131 samples analyzed contained rich and much diversified populations of marine ostracods. In fact, 212 species have been found, belonging to 70 genera. Among them, eight genera, 122 species and subspecies, considered as new, will be described elsewhere. In spite of contamination, usual in oil wells due to caving from higher levels previously drilled, some stratigraphical and palaeoenvironmental features have been established. The last occurrence datum of a selected group of species has been defined with accuracy, and so…