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1
Ozur, Anastasiia. "Thalamic modulation of the cortisal slow oscillation." Master's thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/27030.
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Il est bien établi que le thalamus joue un rôle crucial dans la génération de l'oscillation lente synchrone dans le cortex pendant le sommeil lent. La puissance des ondes lente / delta (0.2-4 Hz) est un indicateur quantifiable de la qualité du sommeil. La contribution des différents noyaux thalamiques dans la génération de l’activité à ondes lentes et dans sa synchronisation n'est pas connue. Nous émettons l'hypothèse que les noyaux thalamiques de premier ordre (spécifiques) influencent localement l’activité à ondes lentes dans les zones corticales primaires, tandis que les noyaux thalamiques d'ordre supérieur (non spécifiques) synchronisent globalement les activités à ondes lentes à travers de larges régions corticales. Nous avons analysé les potentiels de champ locaux et les activités de décharges de différentes régions corticales et thalamiques de souris anesthésiées alors qu'un noyau thalamique était inactivé par du muscimol, un agoniste des récepteurs GABA. Les enregistrements extracellulaires multi-unitaires dans les noyaux thalamiques de premier ordre (VPM) et d'ordre supérieur (CL) montrent des activités de décharges considérablement diminuées et les décharges par bouffées de potentiels d'action sont fortement réduites après inactivation. Nous concluons que l'injection de muscimol réduit fortement les activités de décharges et ne potentialise pas la génération de bouffées de potentiel d'action à seuil bas. L'inactivation des noyaux thalamiques spécifiques avec du muscimol a diminué la puissance lente / delta dans la zone corticale primaire correspondante. L'inactivation d'un noyau non spécifique avec le muscimol a significativement réduit la puissance delta dans l'ensemble du cortex étudié. Nos expériences démontrent que le thalamus a un rôle crucial dans la génération de l'oscillation lente corticale.It is well established that thalamus plays a crucial role in the generation of the synchronous slow oscillation in the cortex during non-REM sleep. The slow/delta power (0.2-4 Hz) is the main measured factor of the quality of sleep. However, the contribution of different thalamic nuclei to the generation of the slow wave activities and its synchronization is not known. We hypothesized that the first-order (specific) thalamic nuclei provide a control of slow waves in primary cortical areas, while higher-order (non-specific) thalamic nuclei may synchronize the slow-wave activities across wide cortical regions. We analyzed local field potentials and spiking activities from different cortical and thalamic areas of anesthetized mice while a thalamic nucleus was inactivated by the GABA-agonist muscimol. Extracellular multiunit recordings in first-order (VPM) and higher-order (CL) thalamic nuclei show dramatically decreased spiking activity and strongly reduced burst firing after inactivation with muscimol. We conclude that the injection of muscimol strongly reduced the spiking activity and does not potentiate the generation of low-threshold spike mediated bursts. Inactivation of specific thalamic nuclei with muscimol decreased the slow/delta power in the corresponding primary cortical area. The inactivation of a non-specific nucleus with muscimol significantly reduced the delta power in all investigated cortical areas. Our experiments demonstrate that the thalamus is required for the fine tuning of the cortical slow oscillation.
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Betterton, Ruth Traer. "Modulation of hippocampal gamma oscillations by acetycholine." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.691259.
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Neuronal oscillations involve the rhythmic, synchronous firing of populations of cells across a range of frequencies. Gamma oscillations (30 - 100Hz) occur during attention, sensory processing and learning and memory. Acetylcholine (ACh) release in the hippocampus is associated with increases in gamma oscillatory power and disruption of cholinergic inputs to the hippocampus and selective knockout of ACh receptor subtypes (AChRs) alter oscillatory activity. This suggests that ACh has a role in the modulation of gamma oscillations. To investigate this process we have utilised both in vitro brain slice and mathematical models.
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Ma, Rui, Martin Kreißig, Florian Protze, Frank Ellinger, Purbawati, Ruiz-Calaforra, Hem, and Ursula Ebels. "Spin Toqure Oscillator Based BFSK Modulation." IEEE / Institute of Electrical and Electronics Engineers Incorporated, 2017. https://tud.qucosa.de/id/qucosa%3A35059.
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This work presents a spin torque nano-oscillator (STNO) based binary frequency shift keying (BFSK) modulation schema implemented on a printed circuit board (PCB). Maximal input data rate reaches 20 Mbit/s. Depending on the STNO used, carrier frequency can range from 1 to 10 GHz. Both DC and AC currents flowing through the STNO can be tuned between 0 to 4 mA. Using one magnetic tunnel junction (MTJ) STNO, a 380 MHz frequency shift around the center frequency 9 GHz was observed, when the modulated current was toggled between 0.8 mA and 1.2 mA at a rate of 20 Mbit/s. This is the first work demonstrating that the STNOs are applicable for BFSK modulation on the wireless application level.
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Iemi, Luca [Verfasser]. "Spontaneous neural oscillations bias perception by modulating baseline excitability / Luca Iemi." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2017. http://d-nb.info/1148425292/34.
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Gehlhaar, Robert. "Terahertz oscillation and stimulated emission from planar microcavities." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1184931926949-93266.
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In the past decades, the miniaturization in optics led to new devices with structural sizes in the range of the light wavelength, where the photonic modes are con- fined and the number of states is limited. In the smallest microcavities, i.e. micrometer sized optical resonators, the propagation of only one mode is permitted that is simultaneously amplified internally. This particularly strong enhancement of the electric field is directly related to the quality factor of the cavity. By introducing an optical dipole into a high-Q microcavity, the spontaneous emission is amplified at the cavity mode frequency enabling stimulated emission in an inverted system. Although some of theses cavity e®ects can only be understood by quantum elec- trodynamic theory, most mechanisms are accessible by classical and semi-classical approaches. In this thesis, one-dimensional planar microcavities with quality factors up to 4500 have been fabricated by physical vapor deposition of dielectric thin films and organic active materials. A new cavity design based on anisotropic dielectric mirrors grown by oblique angle deposition microcavities with two energetically shifted orthogonally polarized modes is presented. The application of these anisotropic structures for terahertz di®erence signal generation is demonstrated in spectrally and time resolved transmission experiments, where optical beats with repetition rates in the terahertz range are observed. Optically pumped organic vertical cavity surface emitting lasers (VCSELs) have been realized by applying an organic solid state laser compound and high reflectance distributed Bragg reflectors. These lasers combine a very low laser threshold with small beam divergence and good stability. A transfer of the anisotropic design towards an organic VCSEL results in the generation of two perpendicularly polarized laser modes with a splitting adjustable by the fabrication conditions. The observation of an oscillation of two laser modes in a photomixing experiment proves a phase coupling mechanism. This demonstrates the potential of the anisotropic cavity design for a passive or active component in a terahertz radiation source or frequency generator. Furthermore, microcavities with two and three coupled resonators are investigated. By the application of time-resolved transmission experiments, spatial oscil- lations of the internal electric field - photonic Bloch oscillations - are successfully demonstrated. In combination with the anisotropic microcavities, this is a second concept for the modulation of transmitted light with terahertz frequencies. All experiments are accompanied by numerical or analytical models. Transmission experiments of continuously incident light and single laser pulses are compared with transfer matrix simulations and Fourier transform based approaches. For the modeling of emission experiments, a plane wave expansion method is successfully used. For the analysis of the organic VCSEL dynamics, we apply a set of rate equations that explains the gain switching process.
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Haggerty, Daniel Christopher. "Noradrenergic modulation of rat hippocampal neuronal oscillations in vitro." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500920.
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Neuronal oscillations have been implicated in various cognitive functions in vivo and can be correlated to a variety of behavioural states. Hippocampal gamma (20-80 Hz) and theta (4-15 Hz) frequency neuronal oscillations have been reported to play a role in memory and representation of visuospatial information. Noradrenaline, a neurotransmitter released during arousal, is an important factor in information acquisition and ma}g of novel spatial information. The aim of this thesis was to investigate the cellular mechanisms by which noradrenaline modulates hippocampal gamma and theta frequency oscillations in the hippocampus in vitro.
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Fano, Silvia [Verfasser]. "Histaminergic modulation of gamma oscillations in rat hippocampus / Silvia Fano." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1035182475/34.
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Soukharev, Boris E., and Lon L. Hood. "Possible solar modulation of the equatorial quasi-biennial oscillation: Additional statistical evidence." AMER GEOPHYSICAL UNION, 2001. http://hdl.handle.net/10150/624003.
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Although the quasi-biennial oscillation (QBO) in the equatorial zonal wind is dominantly driven by wave forcing originating in the troposphere, a recent study suggests that certain properties of the QBO may vary slightly on the 11-year solar cycle timescale [Salby and Callaghan, 2000]. Here we report further statistical investigation using both equatorial wind data for levels from 50 to 1 hPa and longterm proxy solar ultraviolet flux time series (10.7-cm solar radio flux and sunspot numbers). Spectral analysis of the solar time series yields evidence for a significant spectral peak at periods between 25 and 30 months, approximately equivalent to the mean QBO period, as had also been noted by earlier authors [Shapiro and Ward, 1962]. Cross-spectral analysis of the 10.7-cm solar radio flux and equatorial zonal wind time series shows significant coherency at the QBO period at all available pressure levels. The phase lag of the wind data relative to the solar flux at the QBO period ranges from 0–1 months near the stratopause (1 hPa) to 20–24 months in the lower stratosphere (50 hPa). The nearly inphase relationship near the stratopause suggests a possible modulation of the QBO at this level by the radiative and photochemical effects of solar ultraviolet variations. The amplitudes of the solar variations at the QBO period tend to be larger under solar maximum than under solar minimum conditions. Composite analysis of the westerly and easterly phases of the equatorial zonal wind shows subtle but consistent differences in the durations of the westerlies and easterlies between solar maximum and minimum conditions.
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Copie, François. "Modulation instabilities in dispersion oscillating passive fiber-ring cavities." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10111/document.
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Ces travaux de thèse portent sur l’instabilité paramétrique survenant dans les cavités optiques fibrées passives en anneau, induite par une modulation longitudinale de la dispersion chromatique. Dans les cavités optiques, le processus d’instabilité modulationnelle est connu pour être susceptible de déstabiliser l’état stationnaire et de le transformer en un train stable d’impulsions. Nous décrivons dans ce travail comment une variation longitudinale de la dispersion à l’intérieur de la cavité enrichie la dynamique de ce type de dispositif en engendrant un régime d’instabilité paramétrique. Nous détaillons l’étude théorique de ce nouveau mécanisme ce qui nous permet d’en identifier les signatures spectrales et temporelles, parmi lesquels, la génération de multiples pics de résonances dans le spectre optique et l’apparition d’une dynamique de doublement de période dans le domaine temporel. Nous avons réalisé de tels résonateurs afin de confirmer expérimentalement nos prédictions. Le modèle que nous avons retenu consiste à réaliser un anneau en soudant entre elles des fibres uniformes présentant des dispersions différentes. En terme de résultats, nous avons tout d’abord observé pour la première fois l’apparition des instabilités modulationnelle et paramétrique dans un même système, pour ensuite s’intéresser à leur dynamique. Cette dernière est accessible grâce à des méthodes de détection en temps réel à la fois spectrale et temporelle. Nous avons ainsi pu observer avec une précision remarquable l’émergence des instabilités, le doublement de période associé au régime paramétrique ainsi que l’apparition d’un nombre record de résonances paramétriques dans notre systèmeThis thesis work deals with the parametric instability occurring in passive optical fiber-ring cavities, which is induced by a longitudinal modulation of the chromatic dispersion. In optical cavities, the modulation instability process is known to potentially destabilize the stationary state and turn it into a stable train of pulses. We describe in this work how a longitudinal variation of the dispersion inside the cavity enriches the dynamics of this type of device by entailing a regime of parametric instability. We detail the theoretical study of this new mechanism, which allows us to identify its spectral and temporal signatures, among which, the generation of multiple resonance peaks in the optical spectrum and the appearance of a period doubling dynamics in the time domain. We have realized such resonators in order to confirm experimentally our predictions. The model we have chosen simply consists in building a ring by splicing together uniform fibers characterized by different dispersions. In terms of results, we first observed the emergence of both modulational and parametric instabilities in the same system, before investigating their dynamics. The latter is accessible thanks to real-time spectral and temporal detection methods. We thus observed with remarkable precision the emergence of the instabilities, the period doubling associated to the parametric regime and the appearance of a record number of parametric resonances in our system
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Hood, Lon L. "QBO/solar modulation of the boreal winter Madden-Julian oscillation: A prediction for the coming solar minimum." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/624342.
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The Madden-Julian oscillation (MJO), also known as the 30-60day oscillation, is the strongest of the intraseasonal climate oscillations in the tropics and has significant derivative effects on extratropical circulation and intraseasonal climate. It has recently been shown that the stratospheric quasi-biennial oscillation (QBO) modulates the amplitude of the boreal winter MJO such that MJO amplitudes are larger on average during the easterly phase (QBOE) than during the westerly phase (QBOW). A major possible mechanism is the decrease in static stability in the lowermost stratosphere under QBOE conditions resulting from relative upwelling associated with the QBO-induced meridional circulation. Here evidence is presented that tropical upwelling changes related to the 11year solar cycle also modulate the boreal winter MJO. Based on 37.3years of MJO amplitude data, the largest amplitudes and occurrence rates, and the weakest static stabilities in the tropical lower stratosphere, occur during the QBOE phase under solar minimum (SMIN) conditions while the smallest amplitudes and strongest static stabilities occur during the QBOW phase under solar maximum (SMAX) conditions. Conversely, when the QBO and solar forcings are opposed (QBOW/SMIN and QBOE/SMAX), the difference in occurrence rates becomes statistically insignificant. During the coming solar minimum, at least one additional winter in the QBOE/SMIN category should occur (possibly as early as 2017/2018) during which especially large MJO amplitudes are expected and an initial test of these results will be possible. Plain Language Summary An ongoing issue in climate science is the extent to which upper atmospheric processes, including solar forcing, can influence tropospheric climate. It has recently been shown that an internal oscillation of the stratosphere, the quasi-biennial oscillation, can modulate the amplitude and occurrence rate of intraseasonal climate oscillations in the tropical Pacific during northern winter. These intraseasonal oscillations, the most important of which is the 30-60day Madden-Julian oscillation, have significant derivative effects on climate outside of the tropics, including impacts on rainfall events over the continental United States. Here evidence is presented that the amplitude of the Madden-Julian oscillation during northern winter is also modulated by the 11year solar cycle. The modulation is such that amplitudes and occurrence rates are largest under solar minimum conditions when the quasi-biennial oscillation is in its easterly phase and smallest under solar maximum conditions when the quasi-biennial oscillation is in its westerly phase. However, the available time record (37.3years of satellite measurements) is limited. During the coming solar minimum, at least one additional winter in the solar minimum/easterly category should occur (possibly as early as 2017/2018) during which larger-than-average amplitudes are expected and an initial test of the proposed relationship will be possible.
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Ponomarenko, Alexei. "High frequency oscillations in hippocampus and amygdala modulation by ascending systems /." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968526209.
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Carroll, Matthew J. "First Order Self-Oscillating Class-D Circuit with Triangular Wave Injection." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2303.
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An investigation into performance improvements to the modulator stage of a class-D amplifier is conducted in this thesis. Two of the standard topologies, namely class-D open-loop pulse-width modulation (PWM), and the improved self-oscillating feedback system are benchmarked against a topology which includes both a hysteretic comparator in a feedback loop and triangle wave injection. Circuit performance is analyzed by comparing how the triangle injection circuit handles known issues with open-loop and self-oscillating circuits. Using this analysis, it is shown that the triangle injection topology offers an improved power supply rejection ratio relative to open-loop PWM and reduces distortion generated by frequency modulation characteristic of the self-oscillating topology.
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Boucetta, Soufiane. "Modulation of intrinsic and synaptic excitability during sleep oscillations and electrographic seizures." Thesis, Québec : Université Laval, 2005. http://www.theses.ulaval.ca/2005/22551/22551.pdf.
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Pietersen, Alexander Nicolaas Johannes. "Adenosinergic modulation of hippocampal gamma oscillations : from single cell to whole animal." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1041/.
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Gamma oscillations, synchronous network activity between 30 and 100 Hz, have been linked to higher cognitive functions. Adenosine receptor modulation has been shown to alter cognitive function in animals and humans. In this thesis the effects of adenosine receptor modulation on in vitro and in vivo hippocampal gamma oscillations were investigated as well as the underlying mechanisms. \(A_1\)-receptor activation selectively decreased gamma oscillations while blocking \(A_1\)-receptors and activating \(A_{2A}\)-receptors increased gamma oscillations. Increasing endogenous adenosine levels suppressed gamma oscillations while decreasing endogenous adenosine levels facilitated gamma oscillations in vitro. Sharp electrode current clamp and whole-cell voltage clamp experiments showed that \(A_1\)-receptor activation hyperpolarised resting membrane potential, reduced firing rate and EPSP amplitude and shifted the IPSC reversal potential to more negative potentials. Blocking \(A_1\)-receptors increased pyramidal cell excitability and increased excitatory synaptic transmission. The results in vivo were more ambiguous but \(A_1\)-receptor activation decreased power in all frequency bands indicating that adenosine receptors can modulate hippocampal gamma oscillations in vivo. \(A_1\)-receptor blockage had no consistent effect on in vivo hippocampal gamma oscillations. Adenosine receptors modulate gamma oscillations in rodent hippocampal slices but are difficult targets for developing treatments that have cognitive benefits because of their ambiguous effects in vivo.
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Boucetta, Soufiane, and Soufiane Boucetta. "Modulation of intrinsic and synaptic excitability during sleep oscillations and electrographic seizures." Master's thesis, Université Laval, 2005. http://hdl.handle.net/20.500.11794/18026.
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Le présente mémoire fournit des nouvelles évidences montrant la modulation de l’excitabilité neuronale intrinsèque et synaptique, et la conséquence de cette modulation sur l’activité neuronale durant à la fois, les oscillations lentes du sommeil, et les crises électrographiques in vivo chez des animaux anesthésiés. Nous effectuons des enregistrements intracellulaires simultanés de neurones corticaux et des potentiels de champs locaux au niveau du gyrus suprasylvien à l’intérieur du cortex associatif pariétal (aires : 5, 7 et 21). Nous suggérons que la fluctuation de la concentration extracellulaire du calcium durant les oscillations lentes du sommeil module à la fois, l’excitabilité intrinsèque et synaptique des neurones corticaux, ainsi par conséquent, elle module affecte la relation d’input-output de ces neurones. L’apparition durant les oscillations lentes du sommeil, des crises de type Lennex-Gastaut qui sont générées corticalement, nous a permet d’étudier les propriétés spatio-temporelles des ondes paroxysmiques rapides associées avec ce type de crises. Nous suggérons que les ondes paroxysmiques rapides apparaissent comme des oscillations quasi-indépendantes même dans les localisations corticales voisines, suggérant leur origine focal.Le présente mémoire fournit des nouvelles évidences montrant la modulation de l’excitabilité neuronale intrinsèque et synaptique, et la conséquence de cette modulation sur l’activité neuronale durant à la fois, les oscillations lentes du sommeil, et les crises électrographiques in vivo chez des animaux anesthésiés. Nous effectuons des enregistrements intracellulaires simultanés de neurones corticaux et des potentiels de champs locaux au niveau du gyrus suprasylvien à l’intérieur du cortex associatif pariétal (aires : 5, 7 et 21). Nous suggérons que la fluctuation de la concentration extracellulaire du calcium durant les oscillations lentes du sommeil module à la fois, l’excitabilité intrinsèque et synaptique des neurones corticaux, ainsi par conséquent, elle module affecte la relation d’input-output de ces neurones. L’apparition durant les oscillations lentes du sommeil, des crises de type Lennex-Gastaut qui sont générées corticalement, nous a permet d’étudier les propriétés spatio-temporelles des ondes paroxysmiques rapides associées avec ce type de crises. Nous suggérons que les ondes paroxysmiques rapides apparaissent comme des oscillations quasi-indépendantes même dans les localisations corticales voisines, suggérant leur origine focal.
The present memoir provides new evidences showing the modulation of intrinsic and synaptic excitability of cortical neurons, and the consequence of this modulation on neuronal activity during both slow sleep oscillations and electrographic seizures in vivo in anaesthetized animals. We performed simultaneous recordings of cortical neurons with local field potentials in suprasylvian gyrus within parietal associative cortex (area 5, 7 and 21). We suggest that the fluctuation of extacellular calcium concentration during slow sleep oscillations, modulates both intrinsic and synaptic excitability cortical neurons, thus by consequence modulates the input-output relationship of these neurons. The occurrence during slow-wave sleep of cortically generated Lennox-Gastaut type of seizures admits us to study the spatio-temporal properties of paroxysmal fast runs associated with this type of seizures. We suggest that fast runs appeared as quasi-independent oscillations even in neighbouring cortical locations suggesting their focal origin.
The present memoir provides new evidences showing the modulation of intrinsic and synaptic excitability of cortical neurons, and the consequence of this modulation on neuronal activity during both slow sleep oscillations and electrographic seizures in vivo in anaesthetized animals. We performed simultaneous recordings of cortical neurons with local field potentials in suprasylvian gyrus within parietal associative cortex (area 5, 7 and 21). We suggest that the fluctuation of extacellular calcium concentration during slow sleep oscillations, modulates both intrinsic and synaptic excitability cortical neurons, thus by consequence modulates the input-output relationship of these neurons. The occurrence during slow-wave sleep of cortically generated Lennox-Gastaut type of seizures admits us to study the spatio-temporal properties of paroxysmal fast runs associated with this type of seizures. We suggest that fast runs appeared as quasi-independent oscillations even in neighbouring cortical locations suggesting their focal origin.
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Banghua, Zhou, and Huang Mingsheng. "A Dielectric Resonator Stabilized Frequency Modulation Oscillator in the S-Band." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/611725.
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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, CaliforniaWith the development of the airborne telemetry technique, it will be demanded that the transmitting sets on the missiles are more reliable and smaller. A frequency modulation (FM) oscillator stabilized with a dielectric resonator (DR), which can operates in the S-band directly, is presented. The FM oscillator is of simple circuit, reliable operation in the stabilization, small size, light weight and low cost. It will have a certain prospect of application in the airborne telemetry transmitting sets.
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Wójtowicz, Anna Maria [Verfasser]. "Local and systemic modulation of hippocampal oscillations and synaptic plasticity / Anna Maria Wójtowicz." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2011. http://d-nb.info/1025239008/34.
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Hollnagel, Jan-Oliver [Verfasser]. "Modulation of fast neuronal network oscillations in the hippocampal formation / Jan-Oliver Hollnagel." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2017. http://d-nb.info/1126503681/34.
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Glykos, Vasileios. "Generation and modulation of network oscillations on the rodent prefrontal cortex in vitro." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2187.
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Fast network oscillations (~12-80 Hz) are recorded extensively in the mammalian cerebral cortex in vivo which local and distant neuronal populations orchestrate their firing activity to process cognitive-related information. The rat medial prefrontal cortex (mPFC) is considered to be functionally and anatomically homologous to the primate in vitro studies have demonstrated that the mPFC can sustain carbachol-induced persistent beta1 or kainate-induced transient low gamma frequency oscillations. We wished to establish an in vitro paradigm of carbachol (10 μM) / kainate (200 objective to investigate the distribution patterns and the mechanisms of these oscillations. Then we assessed the modulatory effects of the ascending catecholamine systems on fast network oscillations with exogenous application of Persistent fast network oscillations in the ventral mPFC were stronger, more rhythmic but slower (~25 Hz) than oscillations in the dorsal mPFC (~28 Hz). The regional difference in the oscillation amplitude was correlated to the strong regions in the mPFC, oscillations were stronger in layer 5. Oscillations relied on GABA, kainate but not AMPA receptors. In the ventral mPFC, network oscillations A were also dependent on NMDA receptor-mediated synaptic transmission. μM) reduced the oscillation strength and rhythmicity in the ventral mPFC. Instead, dopamine increased the power and rhythmicity of network oscillations in the dorsal mPFC. The region-dependent dopamine effect was correlated to the induced effects on synaptic inhibition and neuronal firing. μM) reduced the osc caused no effect on the dorsal mPFC.
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Vossen, Alexandra Yvonne. "Modulation of neural oscillations and associated behaviour by transcranial Alternating Current Stimulation (tACS)." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/7958/.
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Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation method that involves the application of weak electric currents to the scalp. tACS has the potential to be an inexpensive, easily administrable, and well-tolerated multi-purpose tool for cognitive and clinical neuroscience as it could be applied to establish the functional role of rhythmic brain activity, and to treat neural disorders, in particular those where these rhythms have gone awry. However, the mechanisms by which tACS produces both "online" and "offline" effects (that is, those that manifest during stimulation and those that last beyond stimulation offset) are to date still poorly understood. If the potential of tACS is to be harnessed effectively to alter brain activity in a controlled manner, it is fundamental to have a good understanding of how tACS interacts with neuronal dynamics, and of the conditions that promote its effect. This thesis describes three experiments that were conducted to elucidate the mechanisms by which tACS interacts with underlying neural network activity. Experiments 1 and 2 investigated the mechanism by which tACS at alpha frequencies (8 12 Hz, α-tACS) over occipital cortex induces the lasting aftereffects on posterior α power that were previously described in the literature. Two mechanisms have been suggested to underlie alpha power enhancement after α tACS: entrainment of endogenous brain oscillations and/or changes in oscillatory neural networks through spike timing-dependent plasticity (STDP). In Experiment 1, we tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment characteristics. To this end, we used a novel, intermittent α-tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and individual alpha frequency (IAF). Alpha aftereffects were successfully replicated with enhanced α power after intermittent stimulation compared to sham. These aftereffects did not exhibit any of the expected characteristics of prolonged entrainment in that they were independent of tACS phase-continuity and did not show stable phase alignment or synchronisation to the stimulation frequency. These results indicate that prolonged entrainment is insufficient to explain the aftereffects and suggest that the latter emerge through some form of network plasticity. To clarify the nature of these plasticity mechanisms, we then aimed to assess whether STDP could explain the α power increase. We developed a conceptual STDP model that predicted bi-directional changes in α power depending on the relative mismatch between the tACS frequency and IAF. After observing in Experiment 1 that tACS at frequencies slightly lower than the IAF produced α enhancement, Experiment 2 used a similar intermittent protocol that manipulated tACS frequency to be either slightly lower or higher than IAF to respectively enhance or suppress α activity. In addition, a control condition with continuous stimulation aimed to replicate previous results from other groups. However, we did not observe a systematic α power change in any of the active conditions. The lack of consistency between the two experiments raises concerns regarding the reproducibility and effect size of tACS aftereffects. The third experiment investigated the mechanism of online effects and tested predictions that were based on the assumption that entrainment is the underlying process mediating behavioural changes during tACS. We capitalised on two well-described phenomena: firstly, the association between α power lateralisation and visuospatial attention, and secondly, the fluctuation of perceptual performance with α phase. Specifically, the experiment tested whether event-related α-tACS applied over right parieto-occipital cortex can induce a visuospatial bias in a peripheral dot detection task that would reflect α power lateralisation, and whether detection performance depends on the phase of the tACS waveform. In control trials either no tACS or 40 Hz-tACS (gamma) was applied to make use of the putative opposing roles of alpha and gamma oscillations in visual processing. As expected from lateralised enhancement of alpha oscillations, visual detection accuracy was weakly impaired for targets presented in the left visual field, contralateral to tACS. However, this effect was neither frequency specific nor waveform phase-dependent. Therefore, it is unlikely that the negative effect of tACS on visuospatial performance reflects entrainment. Overall, the results of these experiments only partially met our hypotheses. Experiment 1 produced the α enhancement that was expected based on the literature while the follow-up experiment failed to reproduce these results under similar conditions. This outcome demonstrates at best that tACS aftereffects on α activity are not robust, may vary widely across individuals, and might be extremely sensitive to small changes in experimental parameters and state variables. The results of the third experiment call into question the assumption of online entrainment as basis for the observed behavioural effect. These findings point to the need for improved methodology, for more systematic and exhaustive exploration of the relative effects of tACS across different parameter settings, tasks, and individuals; and for the replication of promising but thus far often anecdotal results. They also inspire guidelines for more informative experimental designs.
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Gillies, Martin John. "Modulation of excitation as a mechanism of oscillation frequency transition in the hippocampus in vitro." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403026.
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Cristofori, Irène. "Modulations physiologiques et comportementales de la douleur sociale." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00845406.
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La douleur sociale est une forme de douleur non physique dérivant de la perception de l'exclusion sociale. L'importance de la compréhension de ses modulations comportementales et neuronales est fondamentale, car ses conséquences sur le long terme peuvent être très néfastes. Dans ce travail de thèse, j'ai exploré ces aspects à travers une étude comportementale à l‟aide d‟enregistrements par SCR (Skin Conductance Recording), et trois études en iEEG (électro-encéphalographie intracrânienne) chez des patients épileptiques. La première étude comportementale a exploré la direction dans laquelle l'exclusion sociale est influencée par une récompense et ses réactions sur le long terme. Ainsi, la récompense monétaire altère l'équilibre social et augmente l‟activité électrodermale. La personne ayant été exclue met alors en oeuvre des mécanismes de vengeance en défavorisant la personne qui l‟a exclue précédemment. Les études en iEEG ont été une fenêtre unique d'exploration du cerveau lors de différentes types de modulation de l'exclusion. Dans la première étude en iEEG, nous avons observé que la douleur sociale produit une activation des oscillations thêta (3-7 Hz), lors de d'exclusion, dans l'insula, l'ACC, le cortex préfrontal et le gyrus fusiforme. La deuxième étude iEEG s'est intéressée aux modulations produites par la douleur sociale dans BA 19 et BA 17 présentant des P1 d'amplitude majeure lors de l'observation des photos du joueur qui exclut. La troisième étude en iEEG a exploré la réponse neuronale de l'influence d'une variable monétaire lors de l'exclusion. Nos résultats démontrent que l'insula postérieure présente une activation thêta indépendante du fait que l'exclusion soit positive (exclusion et gain d'argent) ou encore négative (exclusion et perte d'argent), à la différence de l'insula antérieure, active seulement lors d'une exclusion négative
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Jahani, Amirhossein. "Examen des modulations de l’activité bêta liées aux composantes sensorimotrice et cognitive de l’adaptation motrice." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0678.
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Les oscillations cérébrales dans la bande de fréquences bêta (15-35Hz) sont observées dans des tâches très diverses, allant de l’exécution d’un mouvement simple à des tâches perceptives et cognitives complexes. Ici, notre objectif a été de déterminer si des activités EEG bêta spatialement distinctes (i.e. observées au sein de circuits neuronaux différents) pouvaient être identifiées dans le cadre d’une tâche d’adaptation motrice. En effet, par exemple pour atteindre une cible visuelle en portant des lunettes prismatiques, qui décalent toute la scène visuelle latéralement, au moins deux types de mécanismes adaptatifs entrent en jeu : des processus d’adaptation sensorimotrice automatiques/implicites et des mécanismes cognitifs/explicites permettant de réduire les erreurs motrices en quelques essais. Nos observations suggèrent fortement que, dans le cadre d’une tâche d’adaptation motrice, l’activité bêta dans les régions latérales centro-pariétales reflète des processus adaptatifs automatiques/implicites, alors que l’activité au sein des aires motrices médiales est modulée en relation avec des mécanismes cognitifs de contrôle du mouvementBrain oscillations in the beta frequency band (15-35Hz) are observed in a wide range of tasks, from simple movements to complex perceptual and cognitive tasks. Here, our objective was to determine whether spatially distinct beta-band EEG activities (i.e. observed within different neural circuits) could be identified in the context of a motor adaptation task. For example, to reach a visual target while wearing prismatic glasses, shifting the entire visual scene laterally, at least two types of adaptive mechanisms come into play: automatic/implicit sensorimotor adaptation processes and cognitive/explicit mechanisms, which allow reducing motor errors within a few trials. Our observations strongly suggest that, in the context of a motor adaptation task, beta activity within lateral centro-parietal regions reflects automatic/implicit adaptive processes, while activity within medial motor areas is modulated in relation to cognitive mechanisms of movement control
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Lepousez, Gabriel. "Physiologie de la somatostatine dans le bulbe olfactif de souris : des interneurones somatostatinergiques à la modulation du comportement olfactif." Paris 6, 2009. http://www.theses.fr/2009PA066490.
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Le neuropeptide somatostatine est largement exprimé dans le cerveau et son rôle modulateur via ses six récepteurs est bien établi dans les fonctions neuroendocriniennes et cognitives. La présence de la somatostatine et de ses récepteurs dans le système olfactif, et leur déclin dans plusieurs maladies neurodégénératives associées à des troubles précoces du sens de l’odorat, suggèrent que ce peptide participe au traitement de l’information olfactive. Notre travail démontre que, dans le bulbe olfactif de souris, la somatostatine est exprimée par des interneurones de van Gehuchten précisément situés dans la partie interne de la couche plexiforme externe. Ces interneurones sans axone établissent des synapses dendrodendritiques réciproques avec les dendrites latérales des cellules de projection du bulbe, les cellules mitrales. En agissant sur les récepteurs sst2 exprimés par leurs dendrites, la somatostatine influence la transmission synaptique dendrodendritique entre cellules principales et cellules granulaires qui est l’origine d’oscillations gamma dans le réseau neuronal bulbaire (40-100 Hz). Les variations de la puissance de ces oscillations induites par le blocage ou l’activation du récepteur sst2 sont associées à des modifications du seuil de discrimination olfactive. Ainsi, nos résultats démontrent que la libération endogène de somatostatine participe à la modulation des oscillations gamma bulbaires et à la discrimination olfactive. Ce travail ouvre donc des perspectives sur l’implication de la somatostatine dans le traitement de l’information sensorielle et dans le fonctionnement des réseaux neuronaux du télencéphale.
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Reiter, Matt J. "Partial Penetration Fiber Laser Welding on Austenitic Stainless Steel." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243339754.
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Zong, Weikai. "Amplitude and frequency modulations of oscillation modes in hot B subdwarf and white dwarf stars from Kepler photometry." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30306/document.
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Les interactions non linéaires entre modes de pulsation, induisant des modulations d'amplitude et de fréquence, sont difficiles à mettre en évidence avec les télescopes au sol en raison des temps caractéristiques en jeu, de l'ordre de la semaine, du mois, ou même de l'année. L'avènement des télescopes spatiaux comme KEPLER (opéré par la NASA) a considérablement changé la donne en apportant de nouvelles données pour ce domaine de recherche. Dans cette thèse, nous analysons les données photométriques obtenues avec KEPLER pour 24 étoiles compactes pulsantes, incluant 18 étoiles sous-naines de type B (sdB) et 6 naines blanches. Nous établissons que les modulations d'amplitude et de fréquence des modes d'oscillation sont un phénomène courant dans ces étoiles. Nous étudions en particulier deux étoiles : KIC 0862602, une naine blanche pulsante de type DB, et KIC 10139564, une étoile sdB variable à courtes périodes. KIC 0862602 et KIC 10139564 ont été observées sans interruption par KEPLER en cadence rapide pendant deux années pour la première et plus de trois ans pour la seconde. En analysant en détail ces données photométriques de très haute précision, nous mettons en évidence différents types de comportements affectant les composantes de triplets induits par la rotation stellaire. Les fréquences et amplitudes de ces modes montrent des variations soi périodiques soi irrégulières, ou demeurent constantes. Ces comportements peuvent être connectés à ceux prédits par les équations d'amplitude dans le cas de couplages non linéaires résonants entre modes, en particulier pour les temps caractéristiques des modulations. De plus, nous montrons que les modes en résonance constituant les triplets peuvent également interagir avec des modes extérieurs par le biais d'autres formes de résonances telle que la résonance à trois modes v 0 ~ v 1 + v 2 , une situation qui n'est pas prise en compte dans le cadre théorique existant. Ces études apportent pour la première fois une preuve claire de l'existence de mécanismes de couplages non linéaires entre modes d'oscillations dans les pulsateurs compacts. Cette découverte résonne comme un avertissement pour les projets visant à mesurer les taux de changement des périodes dus à l'évolution dans les étoiles compactes en général. Les modulations de fréquence d'origine non linéaire peuvent potentiellement empêcher toute mesure fiable de ces taux, à moins de corriger ces effets auparavant. Les modulations observées caractérisées dans cette thèse apportent un regard nouveau sur "l'astérosismologie non linéaire" et appellent à revisiter les méthodes d'analyse des courbes de lumière pour en extraire les modes d'amplitude et de fréquence variables. Dans un futur proche, nous anticipons davantage d'attention portée à ces phénomènes non inéaires dans différents types d'étoiles pulsantes observées depuis l'espace, ainsi qu'un regain d'intérêt pour la théorie non linéaire des oscillations stellaires en généralNonlinear mode interactions, inducing amplitude and frequency modulations, are difficult to observe from ground-based telescopes as these typical timescales of the modulations are of the order of weeks, months, or even years. The launch of space telescopes such as Kepler (operated by NASA) has tremendously changed the situation by providing new data for this research field. In this thesis, we analyze the Kepler photometric data observed for 24 compact pulsators, including 18 hot B subdwarf (sdB) stars and six white dwarf stars. We find that it is a common phenomenon that oscillation modes in these pulsating stars show amplitude and/or frequency variations. We focus in particular on two stars, KIC 08626021, a DB white dwarf, and KIC 10139564, a short period sdB star. KIC 08626021 and KIC 10139564 have been monitored by Kepler in short-cadence mode for nearly two years and more than three years without interruption, respectively. By analyzing in depth these high-quality photometric data, we find that the modes within triplets induced by rotation clearly reveal different types of behaviors : their frequency and amplitude may exhibit either periodic or irregular modulations, or remain constant. These various behaviors can be linked to those predicted within the amplitude equation formalism in the case of the nonlinear resonant mode coupling mechanism, particularly for the modulation timescales. Furthermore, we find that the triplet resonance modes can also interact with outside modes through other types of resonances such as the three-mode resonance v 0 ~ v 1 + v 2 , which is not considered within the current nonlinear theoretical frameworks. These findings constitute the first clear evidence of nonlinear resonant mode couplings occurring in compact pulsators. This should resonate as a warning to projects aiming at measuring the evolutionary change rate of pulsation periods in compact stars in general. Nonlinear modulations of the frequencies can potentially jeopardize any attempt to measure reliably such rates, unless they can be corrected beforehand. The observed modulations characterized in this thesis provide new insights to "nonlinear asteroseismology" and call for new methods to process the signals of variable modes from the observed light curves. We foresee that increasing attention will focus on these nonlinear phenomena in various types of pulsating stars observed from space in the near future, thus reviving interest in the nonlinear oscillation theory in general
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Moratti, Stephan. "Modulation of stimulus driven neuronal oscillations by the emotional and motivational significance of visual stimuli." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975676911.
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Никольский, Валерий Евгеньевич. "Синергетические реакционно-массообменные процессы в газожидкостных аппаратах и топливных агрегатах химической технологии." Thesis, Украинский государственный химико-технологический университет, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24524.
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Диссертация на соискание ученой степени доктора технических наук по специальности 05.17.08 – процессы и оборудование химической технологии. – Национальный технический университет "Харьковский политехнический институт" Министерства образования и науки Украины, Харьков, 2016 г.
Диссертационная работа посвящена решению актуальной инжиниринговой научно-технической проблемы: разработать современные энергоэффективные экологически чистые технологии, средства генерирования и потребления тепловой энергии с применением систем рекуперации теплоты на основе синергетического единства аппаратурно-технологического оформления процессов и системного подхода. В работе разработаны научно-методологические основы и практические способы повышения эффективности использования топлива в газожидкостных аппаратах и топливных агрегатах химической технологии за счет интенсификации тепловых процессов в их рабочем пространстве. С позиции совершенствования топливо– и материалосберегающих техники и технологий созданы новые конструкции газожидкостных аппаратов и топливных агрегатов. На их основе синтезированы экологически чистые энергоэффективные технологические системы (ЭТС), приемлемые для химической технологии и других сфер промышленности, коммунального, сельского хозяйства, отвечающие современным энергетическим и экологическим требованиям. Систематизированы методы интенсификации гетерогенных процессов в теплотехнологических аппаратах; предложены новые перспективные РТ и АК методы интенсификации и обоснована целесообразность их практического использования при синтезе новых ЭТС на базе синергетически совмещенных реакционно-разделительных процессов (обеспечение неоднофазности, наложение электрических и магнитных полей на контактирующие фазы, оптимизация параметров пульсаций в гетерогенных системах, одно- и многотипное комбинирование теплогенерирующих аппаратов, обеспечение многократных входных и концевых эффектов, соударения, закручивания, взаимной эжекции контактирующих фаз и их осциллирования, циклический подвод энергии). Разработанные и приведенные в диссертации аппараты, технологические процессы и оборудование широко внедрены на предприятиях Минхимпрома, Минметаллургии, Минавтопрома, Минкоммунхоза Украины и стран СНГ.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Нікольський, Валерій Євгенович. "Синергетичні реакційно-масообмінні процеси в газорідинних апаратах і паливних агрегатах хімічної технології." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24517.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.08 – процеси та обладнання хімічної технології. – Національний технічний університет "Харківський політехнічний інститут" Міністерства освіти і науки України, Харків, 2016 р.
Дисертаційна робота присвячена вирішенню актуальної інжинірингової науково-технічної проблеми: розробити сучасні енергоефективні екологічно чисті технології, засоби генерування та споживання теплової енергії із застосуванням систем рекуперації теплоти на основі синергетичної єдності апаратурно-технологічного оформлення процесів і системного підходу. У роботі розроблено науково-методологічні основи та практичні способи підвищення ефективності використання палива в газорідинних апаратах і паливних агрегатах хімічної технології за рахунок інтенсифікації теплових процесів в їх робочому просторі. З позиції вдосконалення паливо- і матеріалозберігаючих техніки і технологій створено нові конструкції газорідинних апаратів і паливних агрегатів. На їх основі синтезовано екологічно чисті енергоефективні технологічні системи (ЕТС), прийнятні для хімічної технології та інших сфер промисловості, комунального, сільського господарства, які відповідають сучасним енергетичним та екологічним вимогам. Розроблено високоефективну контактно-модульну систему (КМС), обладнану апаратами зануреного горіння (АЗГ) з багатократною інверсією і модуляцією коливань контактуючих фаз для потреб теплопостачання промислових будівель і споруд, житлових і сільськогосподарських комплексів, яка виключає використання котельних і бойлерних установок з утилізацією теплоти продуктів згоряння, тепловою потужністю 200, 400, 600, 1000, 2000 кВт і вище залежно від потреби в генерованій теплоті. Витрати на обігрівання будівель і споруд при використанні пристрою знижуються в 2,5-2,8 рази в порівнянні з традиційними способами обігрівання. КМС пройшла державні тепло-екологічні випробування, які підтвердили її високу енергоефективність, екологічність, надійність в роботі. Отримано технічні умови на серійне її виготовлення і експлуатацію в різних галузях народного господарства. Розроблені і наведені в дисертації апарати, технологічні процеси і устаткування широко впроваджені на підприємствах Мінхімпрому, Мінметалургіі, Мінавтопрому, Мінкомунгоспу України та країн СНД.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Rosenthal, Glenn K. "A DSP IMPLEMENTED DIGITAL FM MULTIPLEXING SYSTEM." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/613103.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaRecent advancements in high-speed Digital Signal Processing (DSP) concepts and devices permit digital hardware implementation of relatively high-frequency signal processing, which formerly required analog circuitry. Systems utilizing this technology can provide a high degree of software programmability; improved reproducibility, reliability, and maintainability; immunity to temperature induced drift errors; and compare favorably in cost to their analog counterparts. This paper describes the DSP implementation of a software programmable, digital frequency multiplexed FM system providing up to 4 output multiplexes, containing up to 36 subcarrier channels extending up to 4 MHZ, and accommodating modulating frequencies up to 64 kHz. System overall design goals and the implementation of these goals are presented.
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Courtemanche, Richard. "Oscillations locales dans le cervelet, organisation, modulation et synchronisation avec le cortex cérébral lors du mouvement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0025/NQ51945.pdf.
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Rohenkohl, Gustavo. "Temporal orienting in the human brain : neural mechanisms of control and modulation." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:95d78d46-6398-48ce-8ff9-30b4fd192e3f.
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The main aim of the experiments reported in this thesis was to explore the neural mechanisms underlying the temporal orienting of attention. In Chapter 3, I explored the possible dissociation between exogenous and endogenous temporal orienting by comparing reaction times to targets appearing after rhythmic or symbolic cues. Behavioural results provided evidence for the existence of dissociable exogenous and endogenous types of temporal orienting of attention. The experiment in Chapter 4 combined spatiotemporal expectations using rhythmic moving cues to test the modulatory effect of exogenous temporal orienting in the brain. Specifically, I used EEG to test the effect of temporal orienting on perceptual and motor stages of target analysis, as well as on anticipatory oscillatory brain activity. The time-frequency analysis revealed that rhythmic cues can entrain slow brains oscillations, providing a putative mechanism for enhancing the perceptual processing of expected events. Spatiotemporal expectations also modulated the amplitude of visual responses and the timing and amount of preparatory motor activity. In Chapter 5, I used a novel task to explore the neural modulatory effects of spatial and temporal expectations acting in isolation or in coordination. For the first time, the analysis of early visual responses demonstrated that temporal expectations alone, independently of spatial orienting, can enhance early visual perceptual processes. The time-frequency analysis in this experiment showed a desynchronisation of alpha oscillations focused over central-parietal electrodes induced by rhythmic cues that were independent of spatial expectations. When rhythmic cues carried spatiotemporal information, the alpha desynchronisation also spread over contralateral occipital electrodes. In Chapter 6, fMRI was used to test the possible neural dissociation between motor and temporal orienting. The results confirmed the large overlap between these two processes, but also indicated independent behavioural and neural effects of temporal orienting. Temporal orienting activated the left IPS across motor conditions, further implicating the left IPS in temporal orienting. Based on the results of these experiments, directions for future studies are discussed.
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Rheims, Sylvain. "Initiation et modulation des oscillations physiologiques et pathologiques dans le néocortex immature : rôle de la transmission GABAergique." Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22069.pdf.
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La période néonatale est marquée par la survenue d'oscillations neuronales spontanées jouant un rôle primodial dans la maturation fonctionnelle du cerveau et par une susceptiblité particulière aux crises d'épilepsie. Il a été suggéré qu'il existe un lien entre les mécanismes qui sous-tendent la génération d'oscillations physiologiques et d'oscillations pathologiques. Bien que les crises du nourrisson impliquent un réseau néocortical, les propriétés qui concourent à majorer l'excitabilité du néocortex immature sont peu connues. Plus spécifiquement, le rôle du GABA dans le néocortex néonatal est débattu. Au cours de notre thèse, nous avons étudié les mécanismes impliqués dans l'initiation et la modulation des oscillations physiologiques et pathologiques dans le néocortex immature en centrant sur le rôle de la transmission GABAergique. Nous montrons : (i) que le néocortex immature possède intrinsèquement un niveau d'excitabilité élevé qui prédomine dans les couches cellulaires profondes, (ii) que le GABA peut avoir une action excitatrice et pro-épileptogène, mais que celle-ci est physiologiquement modulée par l'état métabolique sous la forme d'une régulation négative par le corps cétoniques, (iii) que la répétition des activités inter-ictales peut modifier les propriétés intrinsèques de ces réseaux et faciliter la génération d'activités épileptiques, et (iv) que la modulation du GABA par l'état du métabolisme énergétique pourrait représenter un mécanisme d'adaptation de l'activité cérébrale à l'environnement du sujet. Au total, nous proposons que le néocortex immature a un niveau d'excitabilité intrinsèquement élevé qui peut-être modulé par la transmission GABAergique. La présence physiologique de taux élevés de corps cétoniques ou leur majoration à titre thérapeutique peut permettre d'abaisser l'action excitatrice du GABA et de moduler négativement la survenue d'oscillations physiologiques ou d'activités épileptiques.
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Li, Wangzhe. "Photonic Generation of Microwave and Millimeter Wave Signals." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24026.
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Photonic generation of ultra-low phase noise and frequency-tunable microwave or millimeter-wave (mm-wave) signals has been a topic of interest in the last few years. Advanced photonic techniques, especially the recent advancement in photonic components, have enabled the generation of microwave and mm-wave signals at high frequencies with a large tunable range and ultra-low phase noise. In this thesis, techniques to generate microwave and mm-wave signals in the optical domain are investigated, with an emphasis on system architectures to achieve large frequency tunability and low phase noise.
The thesis consists of two parts. In the first part, techniques to generate microwave and mm-wave signals based on microwave frequency multiplication are investigated. Microwave frequency multiplication can be realized in the optical domain based on external modulation using a Mach-Zehnder modulator (MZM), but with limited multiplication factor. Microwave frequency multiplication based on external modulation using two cascaded MZMs to provide a larger multiplication factor has been proposed, but no generalized approach has been developed. In this thesis, a generalized approach to achieving microwave frequency multiplication using two cascaded MZMs is presented. A theoretical analysis leading to the operating conditions to achieve frequency quadrupling, sextupling or octupling is developed. The system performance in terms of phase noise, tunability and stability is investigated. To achieve microwave generation with a frequency multiplication factor (FMF) of 12, a technique based on a joint operation of polarization modulation, four-wave mixing and stimulated-Brillouin-scattering-assisted filtering is also proposed. The generation of a frequency-tunable mm-wave signal from 48 to 132 GHz is demonstrated. The proposed architecture can even potentially boost the FMF up to 24.
In the second part, techniques to generate ultra-low phase noise and frequency-tunable microwave and mm-wave signals based on an optoelectronic oscillator (OEO) are studied. The key component in an OEO to achieve low phase noise and large frequency-tunable operation is the microwave bandpass filter. In the thesis, we first develop a microwave photonic filter with an ultra-narrow passband and large tunability based on a phase-shifted fiber Bragg grating (PS-FBG). Then, an OEO incorporating such a microwave photonic filter is developed. The performance including the tunable range and phase noise is evaluated. To further increase the frequency tunable range, a technique to achieve microwave frequency multiplication in an OEO is proposed. An mm-wave signal with a tunable range more than 40 GHz is demonstrated.
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Xie, Ruichao. "A novel Wide-Area control strategy for damping of critical frequency oscillations via modulation of active power injections." Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/67983.
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Cette thèse propose une nouvelle stratégie d'amortissement des oscillations de fréquence critiques par la modulation de l'injection rapide de puissances actives, qui ouvre la voie à l'utilisation d'actionneurs géographiquement dispersés, par exemple des ressources énergétiques distribuées (DERs), dans le contrôle des basses fréquences dynamique de l'angle du rotor du réseau électrique, qui comprend les oscillations interzones et les oscillations de fréquence transitoire. La méthode proposée intègre ces deux dynamiques différentes dans un cadre basé sur un système linéaire invariant dans le temps, dans lequel le contrôle de l'oscillation de fréquence transitoire est traduit en contrôle de la dynamique de mode commun du système. A cet effet, un examen attentif de la relation entre la variation transitoire de fréquence et la dynamique du mode commun est effectué; Les simulations montrent que le mode commun définit la forme d'un changement transitoire de faible signal de fréquence. La méthode de contrôle proposée vise à utiliser efficacement la réserve de marche limitée des DERs existants pour atténuer ces oscillations. Ceci est réalisé en découplant les actions de commande d'amortissement à différents endroits en utilisant les signaux d'oscillation du mode concerné comme commandes de puissance. Une base théorique pour cette commande de modulation découplée est fournie. Techniquement, les signaux d'oscillation modale souhaités sont filtrés en combinant linéairement les fréquences de l'ensemble du système, ce qui est déterminé par la technique (LQRSP). Avec la stratégie proposée, la modulation de chaque injection de puissance active peut être conçue efficacement en tenant compte de la limite de réponse et de la capacité de sortie en régime permanent du dispositif de support. Dans le cadre proposé, le signal de commande pour la commande de fréquence primaire est automatiquement déterminé dans une direction de commande (presque) optimale; des expériences montrent que ce signal a tendance à être la vitesse du système vue par le point d'injection de puissance. La commande modulante découplée a tendance à isoler les actions de commande pour les oscillations interzones et les oscillations de fréquence transitoire, ce qui atténue grandement les préoccupations concernant l'interaction entre la commande de ces deux types de dynamiquesThis dissertation provides a novel wide-area control strategy for damping of critical frequency oscillations via modulation of fast active power injections, which paves the way for the utilization of large-scale geographically dispersed actuators, e.g., distributed energy resources (DERs), in the control of power system low-frequency rotor angle dynamics, this includes the inter-area oscillations and the transient frequency swing. The proposed method incorporates these two different dynamics into a linear time invariant (LTI) system based control framework, in which the control of the transient frequency swing is translated into the control of the system common mode dynamics. For this purpose, a careful examination of the relationship between the transient frequency swing and the common mode dynamics is carried out; extensive simulations show that the common mode defines the shape of a small-signal transient frequency swing. The proposed control method pursues an efficient utilization of the limited power reserve of existing DERs to mitigate these oscillations. This is accomplished by decoupling the damping control actions at different sites using the oscillation signals of the concerned mode as the power commands. A theoretical basis for this decoupled modulating control is provided. Technically, the desired sole modal oscillation signals are filtered out by linearly combining the system-wide frequencies, which is determined by the linear quadratic regulator based sparsity-promoting (LQRSP) technique. With the proposed strategy, the modulation of each active power injection can be effectively engineered considering the response limit and steady-state output capability of the supporting device. In the proposed control framework, the power command signal for the primary frequency control is determined in a (near) optimal control sense; experiments show that this signal tends to be the system speed seen by the power injection point. Importantly, the decoupled modulating control tends to isolate the control actions for the inter-area oscillations and the transient frequency swing, thereby greatly relieving the concern about the interaction between the control of these two types of dynamics.
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Herculano-Houzel, Suzana. "Modulation of neuronal synchronous oscillations : dynamic variation with level of cortical activation and long-term use-dependent modification." Paris 6, 1999. http://www.theses.fr/1999PA066610.
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Mueller, Jerel Keith. "Advancing Transcranial Focused Ultrasound for Noninvasive Neuromodulation of Human Cortex." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56578.
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Ultrasound waves are mechanical undulations above the threshold for human hearing, and have been used widely in both the human body and brain for diagnostic and therapeutic purposes. Ultrasound can be controlled using specially designed transducers into a focus of a few millimeters in diameter. Low intensity ultrasound, such as used in imaging applications, appears to be safe in adults. It is also known that ultrasound waves can penetrate through the skull and be focused within the brain for ablation purposes, employing the heat generation properties of high intensity focused ultrasound. High intensity focused ultrasound is thus used to irreversibly ablate brain tissue in localized areas without observable damage to intermediate tissue and vasculature. Ablation with high intensity focused ultrasound guided by magnetic resonance imaging is used for abolishing brain tumors, and experimentally for pain.
Low intensity ultrasound can be utilized beyond imaging in neuroscience and neurology by focusing the ultrasound beam to investigate the structure and function of discrete brain circuits. In contrast to high intensity focused ultrasound, the effects of low intensity focused ultrasound on neurons are reversible. Considering the volume of work on high intensity focused ultrasound, low intensity focused ultrasound remains decidedly underdeveloped. Given the great potential for impact of low intensity focused ultrasound in both clinical and scientific neuromodulation applications, we sought to advance the use of low intensity focused ultrasound for noninvasive, transcranial neuromodulation of human cortex.
This dissertation contains novel research on the use of low intensity transcranial focused ultrasound for noninvasive neuromodulation of human cortex. The importance of mechanical forces in the nervous system is highlighted throughout to expand beyond the stigma that nervous function is governed chiefly by electrical and chemical means. Methods of transcranial focused ultrasound are applied to significantly modulate human cortical function, shown using electroencephalographic recordings and behavioral investigations of sensory discrimination performance. This dissertation also describes computational models used to investigate the insertion behavior of ultrasound across various tissues in the context of transcranial neuromodulation, as ultrasound's application for neuromodulation is relatively new and crudely understood. These investigations are critical for the refinement of device design and the overall advancement of ultrasound methods for noninvasive neuromodulation.Ph. D.
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Zhou, Dawei. "Development of active integrated antennas and optimization for harmonic suppression antennas : simulation and measurement of active antennas for amplifiers and oscillators and numerical solution on design and optimization of active patch antennas for harmonic suppression with adaptive meshing using genetic algorithms." Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4763.
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The objectives of this research work are to investigate, design and implement active integrated antennas comprising active devices connected directly to the patch radiators, for various applications in high efficiency RF front-ends, integrated oscillator antennas, design and optimization of harmonic suppression antennas using a genetic algorithm (GA). A computer-aided design approach to obtain a class F operation to optimizing the optimal fundamental load impedance and designing the input matching circuits for an active integrated antenna of the transmitting type is proposed and a case study of a design for 1.6 GHz is used to confirm the design principle. A study of active integrated oscillator antennas with a series feed back using a pseudomorphic high electronmobility transistor (PHEMT) confirms the design procedure in simulation and measurement for the oscillator circuit connected directly to the active antenna. Subsequently, another design of active oscillator antenna using bipolar junction transistor (BJT) improves the phase noise of the oscillation and in addition to achieve amplitude shift keying (ASK) and amplitude modulation (AM) modulation using the proposed design circuit. Moreover, the possibility of using a sensor patch technique to find the power accepted by the antenna at harmonic frequencies is studied. A novel numerical solution, for designing and optimizing active patch antennas for harmonic suppression using GA in collaboration with numerical electromagnetic computation (NEC), is presented. A new FORTRAN program is developed and used for adaptively meshing any planar antenna structure in terms of wire grid surface structures. The program is subsequently implemented in harmonic suppression antenna design and optimization using GA. The simulation and measurement results for several surface structures show a good agreement.
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Alayrangues, Julie. "Etude des réponses oscillatoires bêta aux erreurs de mouvements : dissociation fonctionnelle et spatiale des modulations de puissance bêta observées pendant la période de préparation et après le mouvement." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0090/document.
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À ce jour, le rôle des oscillations bêta n’a pas encore été clairement établi. Des travaux récents ont montré que l’activité bêta pendant la préparation du mouvement et celle suivant son exécution sont différemment modulées par les erreurs de mouvements. L’objectif du présent travail a été double : premièrement, déterminer si les modulations de puissance bêta pré- et post-mouvement recrutent des substrats cérébraux différents, deuxièmement, mieux cerner la nature des processus neuronaux reflétés. Grâce à une approche par analyse en composantes indépendantes, nous suggérons fortement que les réponses oscillatoires, aux erreurs cinématiques, observées avant et après le mouvement sont sous-tendues par des structures distinctes, respectivement clairement latéralisées et médiales. De plus, en contrastant différentes tâches motrices, nous montrons que ni l’une ni l’autre des deux activités bêta ne reflètent des mécanismes en lien direct avec les sorties motricesThe role of beta oscillations has not been clearly established yet. Recent work has shown that the beta activities observed during the preparation phase and after the movement are differently affected by movement errors. The aim of this thesis was twofold: first, to determine whether or not the pre- and post-movement beta power modulations recruit common neural substrates; second, to better understand the nature of the reflected neural processes. Using an independent component analysis approach, we strongly suggest that oscillatory responses to kinematic errors, observed before and after movement, are underpinned by distinct neural structures, respectively clearly lateralized and medial. Moreover, by contrasting different motor tasks, we show that neither of the two beta activities reflects mechanisms directly related to the output of the motor command
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Eden, Dorcas Claudia. "The role of serotonin and synaptic plasticity in the generation and modulation of hippocampal gamma-frequency (20-80Hz) oscillations in vitro." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519634.
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Sharma, Arvindh R. "Liquid Jet in Oscillating Crossflow: Characterization of Near-Field and Far-Field Spray Behavior." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439281517.
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Liang, Pengfei. "The modified Synchronization Modulation technique revealed mechanisms of Na,K-ATPase." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7846.
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The Na/K pumps are essential for living system and widely expressed in all eukaryotic cell membranes. By actively transporting sodium ions out of and potassium ions into the plasma membrane, Na/K pumps creates both an electrical and a chemical gradient across the plasma membrane, which are crucial for maintaining membrane potential, cell volume, and secondary active transporting of other solutes, etc.
Previously, oscillating electric field with a frequency close to the mean physiological turnover rate was used to synchronize and modulate the Na/K pump molecules. Results showed that the turnover rate of Na/K pumps can be accelerated by folds. However, this what we called first generation synchronization modulation (SM) technique can only synchronize sodium and potassium translocations into their corresponding half cycles. The detailed location of each sodium extrusion and potassium intrusion can not be determined. As a result, the synchronized pumps were uniformly distributed, generating steady-state macroscopic currents.
Based on these studies, Dr.Chen developed a new generation synchronization modulation technique. The waveform of original SM by adding an overshoot pulse at the end of each half cycle. This overshoot pulse has a function of energy barrier which will force all of the Na/K pumps into the same state in the pumping cycle until the membrane polarity change. As a result, Na/K pump molecules are not only synchronized into half cycles of oscillating electric field, but individual steps of the pumping cycle. Accordingly, transient pump currents or so called 'pre-steady state' pump currents are generated, from which some detailed information abut the mechanism of Na/K pumps can be dissected.
In this dissertation, we firstly characterized the synchronized pump currents by modified SM. The results showed that transient currents were induced at the beginning of each half cycle as expected. The ratio between positive and negative transient currents was close to 3:2, stoichiometric number of Na/K pump. Moreover, the transient currents were significantly reduced in the presence of ouabain in a time dependent manner. In addition, by gradually increasing the frequency of SM electric field in a step-wise fashion, the synchronized pump current can be modulated to the corresponding level. Next,we utilized this technique to study some detailed mechanisms of Na/K pump, including single channel configuration in transmembrane domain and extracellular D2O effect on the turnover rate.
Lastly, we extended our study to applications of this new technique and found that the modified Synchronization Modulation technique can significantly hyperpolarize the membrane potential of skeletal muscle fiber in both physiological and high potasssium conditions. During intensive exercise, the interstitial potassium ions are accumulated and temporarily reach a high level, which will attenuate the contraction force and induce muscle fatigue. Na/K pumps are crucial in the maintenance of skeletal muscle excitability and contractility by restoring the Na and K concentration gradients. By accelerating the turnover rate of Na/K pumps, SM can efficiently re-establish the membrane potential and enhance skeletal muscle contractivity, which unleashes its potential in improving certain pathological conditions, such as exercise-induced hyperkalemia.
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Cibot, Carole. "Variabilité décennale dans le Pacifique tropical et modulation basse fréquence de l'activité ENSO." Toulouse 3, 2004. http://www.theses.fr/2004TOU30211.
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El Niño Southern Oscillation (ENSO), phénomène climatique ayant pour siège le Pacifique tropical, oscille à des périodes caractéristiques comprises entre 3 et 7 ans. Son intensité s'avère de plus modulée à basse fréquence (à des échelles de temps décennales à inter-décennales). Cette thèse se propose d'étudier, à l'aide d'un modèle couplé global de circulation générale, la variabilité décennale du Pacifique tropical et son lien avec la modulation basse fréquence de l'activité ENSO. Les résultats remettent en cause l'hypothèse communément admise selon laquelle la modulation basse fréquence d'ENSO est due aux fluctuations décennales des caractéristiques de l'état moyen, et suggèrent de remplacer les raisonnements habituels de "cause à effet" par des raisonnements de "connections" entre échelles de tempsThe El Niño Southern Oscillation (ENSO), climate phenomenon located in the tropical Pacific, is a coupled ocean-atmosphere mode with a dominant time scale between 3 and 7 years. In addition, the amplitude of ENSO is low-frequency modulated, on a decadal to interdecadal time-scale. The objective of this thesis is to study the tropical decadal variability in a global atmosphere-ocean coupled general circulation model, and his link with the low frequency modulation of ENSO activity. Results question the commonly accepted hypothesis that low frequency modulations of ENSO are due to decadal changes of the mean state characteristics, and suggest that it seems more appropriate to reason in terms of time scale interactions rather than in terms of direct causal relationships
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Bendahmane, Mounir. "Modulation par le jeûne de la représentation spatiotemporelle d'une odeur de nourriture et d'une odeur nouvelle dans le bulbe olfactif du rat." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00737493.
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L'olfaction est importante pour de nombreuses fonctions vitales comme la reproduction, les interactions sociales, la détection des aliments et le comportement alimentaire. Toutefois, l'impact nutritionnel sur le système olfactif n'a pas été précisément décrit. Dans ce contexte, le sujet de cette thèse consistait en l'étude des effets du jeûne sur la représentation spatiotemporelle des odeurs dans le bulbe olfactif principal (BO), une structure assurant la première étape du codage de l'information olfactive dans le cerveau.Dans le BO, les caractéristiques des molécules odorantes sont représentées sous forme d'activitéspatiale et temporelle respectivement dans la couche glomérulaire et celles des cellules mitrales et granulaires. Pour étudier le codage spatial au niveau glomérulaire, nous avons utilisé l'imagerie optique du signal intrinsèque qui permet de cartographier l'activité évoquée sur la surface du BO en réponse à des odeurs. Pour étudier le codage temporel des odeurs, nous avons enregistré les variations spécifiques de l'activité oscillatoire du potentiel de champ local (LFP) dans les couches profondes.Nous avons testé les réponses aux odeurs chez des rats mis à jeun pendant 17 heures par rapport aux rats nourris ad libitum. Nous avons utilisé deux stimuli olfactifs à des concentrations différentes: la première (odeur commerciale d'arôme d'amande) est associée à la nourriture car elle est préalablement incorporée dans une pâte sucrée présentée aux rats quotidiennement ; le second (hexanal), est une molécule odorante pure, nouvelle et neutre pour eux. L'utilisation de ces odeurs dans une gamme de concentrations faibles nous a permis d'étudier les modifications de seuil d'activation du BO. Nous avons analysé les deux types de représentation spatiale et temporelle chez des rats anesthésiés, à jeun versus nourris. Nous avons observé que les cartes spatiales et les changements des profils oscillatoires évoqués dans le BO sont présents pour les deux types de stimuli à de faibles concentrations chez tous les rats à jeun mais pas chez tous les animaux nourris. Par contre, pour les fortes concentrations d'odeurs, nous avons observé plus de réponses chez les animaux nourris. Nous avons conclu que le jeûne affecte profondément le seuil d'activation spatiotemporelle du BO.Nous avons alors cherché à identifier les candidats moléculaires qui pourraient déclencher cetteplasticité olfactive à jeun. Nous avons analysé dans le BO la variation de l'expression des récepteurs à deux hormones satiétogènes, la leptine et l'insuline, mais n'avons pas trouvé de changement significatif entre les deux groupes de rats. En outre, l'injection intrapéritonéale de leptine n'a pas inversé le profil oscillatoire induit chez des rats à jeun. Nous avons conclu que la leptine n'agit pas à elle seule dans la signalisation de l'état nutritionnel qui induit la plasticité bulbaire. Nous avons également cherché des modifications spécifiques des circuits du BO pendant le jeûne et avons obtenu des données préliminaires intéressantes sur la plasticité astrocytaire. Enfin, nous avons mené un nouveau projet sur le rôle des endocannabinoïdes dans la prise alimentaire. Le THC est un agoniste des récepteurs CB1 aux endocannabinoïdes qui induit une hyperphagie. Les CB1 étant présents dans le BO, nous avons testé ses effets sur l'activité oscillatoire chez des souris à jeun. Nous avons trouvé que le THC inhibe la désensibilisation olfactive qui est déclenchée chez les souris contrôle par la présentation d'odeurs répétées.
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Murphy, Simon J., Maxwell Moe, Donald W. Kurtz, Timothy R. Bedding, Hiromoto Shibahashi, and Henri M. J. Boffin. "Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/627133.
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The orbital parameters of binaries at intermediate periods (10(2)-10(3) d) are difficult to measure with conventional methods and are very incomplete. We have undertaken a new survey, applying our pulsation timing method to Kepler light curves of 2224 main-sequence A/F stars and found 341 non-eclipsing binaries. We calculate the orbital parameters for 317 PB1 systems (single-pulsator binaries) and 24 PB2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. The method reaches down to small mass ratios q approximate to 0.02 and yields a highly homogeneous sample. We parametrize the mass-ratio distribution using both inversion and Markov-Chain Monte Carlo forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q approximate to 0.2. While solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6 sigma) population of extreme-mass-ratio companions (q < 0.1) to our intermediate-mass primaries. Across periods of 100-1500 d and at q > 0.1, we measure the binary fraction of current A/F primaries to be 15.4 per cent +/- 1.4 per cent, though we find that a large fraction of the companions (21 per cent +/- 6 per cent) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9 per cent +/- 2.1 per cent over the same parameter space. Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5 per cent for primaries M-1 < 0.8 M-circle dot, but then increases linearly with log M-1, demonstrating that natal discs around more massive protostars M-1 greater than or similar to M-1(circle dot) become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution.
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Dal, Maso Fabien. "Implication du cortex moteur primaire dans la régulation de la coactivation musculaire. Etude de la modulation des oscillations corticales et des interactions cortico-musculaires." Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00911700.
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La coactivation est un phénomène musculaire fondamental pour la stabilisation et la protection des articulations lors de contractions volontaires et joue un rôle essentiel dans le contrôle du mouvement. De nombreuses études ont montré que des mécanismes supraspinaux et spinaux contribuent à la régulation de la coactivation musculaire, mais l'implication du cortex moteur primaire (M1) est encore mal connue. Les modulations des oscillations corticales et des interactions cortico-musculaires ont été étudiées lors de contractions isométriques à différents niveaux de forces chez des participants présentant différents niveaux de coactivation musculaire en raison de leur spécialité sportive (entraînement en force (ST) vs. en endurance (ED)). Chez les ST, une moindre coactivation musculaire est associée à une plus grande activation du M1, ce qui pourrait s'expliquer par le contrôle d'un plus grand nombre de muscles, notamment des muscles antagonistes. Grâce à une méthode novatrice pour analyser les interactions cortico-musculaires, nous montrons qu'il existe un couplage entre le M1 est les muscles antagonistes chez l'ensemble des participants et dans toutes les directions de contraction. Cependant, la magnitude des interactions cortico-musculaires avec les muscles antagonistes est plus faible qu'avec les muscles agonistes, ce qui pourrait s'expliquer par une plus grande implication des mécanismes spinaux dans la régulation de la coactivation musculaire. L'estimation des moments musculaires agoniste et antagoniste à l'aide d'un modèle biomécanique EMG-assisté ouvre la perspective d'étudier directement les corrélats cérébraux des moments musculaires. Dans leur ensemble, nos résultats, obtenus à l'aide d'une approche combinant biomécanique et neurosciences, ont mis en évidence l'implication directe du M1 dans la régulation de la coactivation musculaire lors de contractions isométriques volontaires.
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Böhm, Claudia [Verfasser], Andreas [Gutachter] Draguhn, Dietmar [Gutachter] Schmitz, and Richard [Gutachter] Kempter. "Hippocampal circuits : pyramidal cell diversity During hippocampal oscillations and serotonergic modulation of O-LM interneurons / Claudia Böhm ; Gutachter: Andreas Draguhn, Dietmar Schmitz, Richard Kempter." Berlin : Lebenswissenschaftliche Fakultät, 2016. http://d-nb.info/1121075827/34.
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Dal, Maso Fabien. "Implication du cortex moteur primaire dans la régulation de la coactivation musculaire : étude de la modulation des oscillations corticales et des interactions cortico-musculaires." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/3292/.
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La coactivation est un phénomène musculaire fondamental pour la stabilisation et la protection des articulations lors de contractions volontaires et joue un rôle essentiel dans le contrôle du mouvement. De nombreuses études ont montré que des mécanismes supraspinaux et spinaux contribuent à la régulation de la coactivation musculaire, mais l'implication du cortex moteur primaire (M1) est encore mal connue. Les modulations des oscillations corticales et des interactions cortico-musculaires ont été étudiées lors de contractions isométriques à différents niveaux de forces chez des participants présentant différents niveaux de coactivation musculaire en raison de leurs spécialités sportive (entraînement en force (ST) vs. En endurance (ED)). Chez les ST, une moindre coactivation musculaire est associée à une plus grande activation de M1, ce qui pourrait s'expliquer par le contrôle d'un plus grand nombre de muscles, notamment des muscles antagonistes. Grâce à une méthode novatrice pour analyser les interactions cortico-musculaires, nous montrons qu'il existe un couplage entre M1 est les muscles antagonistes chez l'ensemble des participants et dans toutes les directions de contraction. Cependant, la magnitude des interactions cortico-musculaires avec les muscles antagonistes est plus faible qu'avec les muscles agonistes, ce qui pourrait s'expliquer par une plus grande implication des mécanismes spinaux dans la régulation de la coactivation musculaire. L'estimation des moments musculaires agoniste et antagoniste à l'aide d'un modèle biomécanique EMG-assisté ouvre la perspective d'étudier directement les corrélats cérébraux des moments musculaires. Dans leur ensemble, nos résultats, obtenus à l'aide d'une approche combinant biomécanique et neurosciences, ont mis en évidence l'implication directe de M1 dans la régulation de la coactivation musculaire lors de contractions isométriques volontairesMuscular coactivation is fundamental in stabilizing and protecting the articulations during voluntary contractions and plays an important role in movement control. Numerous studies have shown the contribution of supraspinal and spinal mechanisms to the regulation of muscular coactivation but the implication of the primary motor cortex (M1) is still unclear. We studied the modulation of cortical oscillations and cortico-muscular interactions during isometric contractions in athletes having different levels of muscular coactivation as a consequence of their training orientation (strength (ST) vs. Endurance (ED). We found that in ST, reduced muscular coactivation was associated with greater M1 activation, which could be explained by the control of a greater number of muscles, including antagonist muscles. Using a novel method to analyze cortico-muscular interactions, we show that M1 is directly involved in the control of antagonist muscles in all participants. However, the magnitude of cortico-muscular interactions with antagonist muscles was lower than in agonist muscles, which could be explained by a greater involvement of spinal mechanisms in the regulation of muscular coactivation. The estimation of agonist and antagonist muscle group moments opens the perspective to investigate the cerebral correlates of the modulation of muscular torque. Our results obtained through an approach combining biomechanics and neurosciences highlighted the involvement of M1 in the regulation of the muscular coactivation during isometric voluntary contractions
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Madureira, Heider Marconi Guedes. "Study and design of CMOS RF power circuits and modulation capabilities for communication applications." Thesis, reponame:Repositório Institucional da UnB, 2015. http://www.theses.fr/2015BORD0093/document.
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Dans l’ère des systèmes de communication multi-standards, le besoin des circuits en radio fréquence (RF) flexibles et reconfigurables pousse l´industrie et le monde académique vers la recherche d´architectures alternatives d’émetteurs et de récepteurs RF. Dans cette thèse, nous nous intéressons aux émetteurs RF flexibles. Nous présentons une architecture basée sur l’utilisation d’un oscillateur de puissance composé d´un amplificateur de puissance dans une boucle de rétroaction positive. Pour des raisons de compatibilité avec des circuit numériques et dans le but de minimiser les coûts de fabrication, nous avons choisi la technologie CMOS. Ce choix génère des difficultés de conception des circuits en RF à cause des faibles tensions de claquage. Cette contrainte de conception a motivé le choix de la classe EF2 pour l’amplificateur de puissance afin de réduire le stress en tension sur les transistors. Nous présentons la conception de cet amplificateur de puissance de classe EF2, ainsi que la conception de l’oscillateur de puissance. Nous validons cette architecture avec une implémentation en technologie CMOS 0.13um de STMicroelectronics. Nous démontrons le bon comportement par une campagne de mesures des circuits fabriqués. Ce circuit répond aux contraintes de flexibilité de modulation et de puissance de sortie. Il peut donc être utilisé pour différents standards de communications. Les limitations inhérentes de cette architecture sont discutées et une modélisation mathématique est présentéeThis work presents the study, design and measurement of RF circuits aiming communication applications. The need for flexible and reconfigurable RF hardware leads to the need of alternative transmitter architectures. In the center of this innovative architecture, there is thepower oscillator. This circuit is composed of a power amplifier in a positive feedback loop soit oscillates. As the circuit under study is mainly composed of a power amplifier, a study on power amplifier is mandatory. Modern CMOS technologies impose difficulties in the efficient RF generation due to low breakdown voltages. In order to reduce the voltage stress on the transistors, wave form-engineering techniques are used leading to the use of class EF2. Thedesign and measurement of a class EF2 power amplifier and power oscillator are shown. Thecircuits were implemented in standard STMicroelectronics 0.13um CMOS. Correct behaviorfor the circuits was obtained in measurement, leading to a first implementation of class EF2 inRF frequencies. From a system perspective, the proposed architecture is shown to be flexible and able to generate different modulations without change in the hardware. Reconfigurability is shown not only in modulation but also in output power level. The limitations of this architecture are discussed and some mathematical modeling is presented
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Olivier, Jean-Christophe. "Modélisation et Conception d'un Modulateur Auto-Oscillant Adapté à l'Emulation d'Organes de Puissance." Phd thesis, Université de Nantes, 2006. http://tel.archives-ouvertes.fr/tel-00134615.
Full textAbstract:
Les travaux présentés dans ce mémoire portent sur l'optimisation de la structure et de la commande de systèmes d'émulation de puissance, appelés Charges Actives. Afin de présenter de très bonnes performances dynamiques ainsi qu'une très grande robustesse, ces Charges Actives utilisent des modulateurs et régulateurs de courant (MRC) et de tension (MRT). Ces procédés font partie de la classe des régulateurs auto-oscillant et sont donc par nature fortement non-linéaires. Aussi, pour que leur application à la Charge Active soit optimale, le premier point abordé dans ce mémoire traite de la modélisation de ces régulateurs et de l'identification des différents problèmes éventuels, inhérents à leurs non-linéarités. Il est alors apparut que des phénomènes de synchronisation et d'instabilité de la fréquence de commutation peuvent apparaître si certaines conditions ne sont pas respectées. Le second point abordé est la généralisation de ces procédés de modulation à des systèmes quelconques, basée sur une méthode de synthèse en mode de glissement. De cette étude, une nouvelle structure de modulation et de régulation de tension est proposée, permettant de répondre plus efficacement aux problématiques posées par la Charge Active. Les résultats expérimentaux obtenus sur un prototype de Charge Active montrent les très grandes performances de ce nouveau procédé, contribuant ainsi à l'amélioration de la qualité et de la précision des anciennes et nouvelles générations de Charges Actives.