Academic literature on the topic 'Slow-wave oscillations'
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Journal articles on the topic "Slow-wave oscillations"
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Mölle, Matthias, Oxana Yeshenko, Lisa Marshall, Susan J. Sara, and Jan Born. "Hippocampal Sharp Wave-Ripples Linked to Slow Oscillations in Rat Slow-Wave Sleep." Journal of Neurophysiology 96, no. 1 (July 2006): 62–70. http://dx.doi.org/10.1152/jn.00014.2006.
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Slow oscillations originating in the prefrontal neocortex during slow-wave sleep (SWS) group neuronal network activity and thereby presumably support the consolidation of memories. Here, we investigated whether the grouping influence of slow oscillations extends to hippocampal sharp wave-ripple (SPW) activity thought to underlie memory replay processes during SWS. The prefrontal surface EEG and multiunit activity (MUA), along with hippocampal local field potentials (LFP) from CA1, were recorded in rats during sleep. Average spindle and ripple activity and event correlation histograms of SPWs were calculated, time-locked to half-waves of slow oscillations. Results confirm decreased prefrontal MUA and spindle activity during EEG slow oscillation negativity and increases in this activity during subsequent positivity. A remarkably close temporal link was revealed between slow oscillations and hippocampal activity, with ripple activity and SPWs being also distinctly decreased during negative half-waves and increased during slow oscillation positivity. Fine-grained analyses of temporal dynamics revealed for the slow oscillation a phase delay of approximately 90 ms with reference to up and down states of prefrontal MUA, and of only approximately 60 ms with reference to changes in SPWs, indicating that up and down states in prefrontal MUA precede corresponding changes in hippocampal SPWs by approximately 30 ms. Results support the notion that the depolarizing surface-positive phase of the slow oscillation and the associated up state of prefrontal excitation promotes hippocampal SPWs via efferent pathways. The preceding disfacilitation of hippocampal events temporally coupled to the negative slow oscillation half-wave appears to serve a synchronizing role in this neocorticohippocampal interplay.
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Nakariakov, Valery M., and Dmitrii Y. Kolotkov. "Magnetohydrodynamic Waves in the Solar Corona." Annual Review of Astronomy and Astrophysics 58, no. 1 (August 18, 2020): 441–81. http://dx.doi.org/10.1146/annurev-astro-032320-042940.
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The corona of the Sun is a unique environment in which magnetohydrodynamic (MHD) waves, one of the fundamental processes of plasma astrophysics, are open to a direct study. There is striking progress in both observational and theoretical research of MHD wave processes in the corona, with the main recent achievements summarized as follows: ▪ Both periods and wavelengths of the principal MHD modes of coronal plasma structures, such as kink, slow and sausage modes, are confidently resolved. ▪ Scalings of various parameters of detected waves and waveguiding plasma structures allow for the validation of theoretical models. In particular, kink oscillation period scales linearly with the length of the oscillating coronal loop, clearly indicating that they are eigenmodes of the loop. Damping of decaying kink and standing slow oscillations depends on the oscillation amplitudes, demonstrating the importance of nonlinear damping. ▪ The dominant excitation mechanism for decaying kink oscillations is associated with magnetized plasma eruptions. Propagating slow waves are caused by the leakage of chromospheric oscillations. Fast wave trains could be formed by waveguide dispersion. ▪ The knowledge gained in the study of coronal MHD waves provides ground for seismological probing of coronal plasma parameters, such as the Alfvén speed, the magnetic field and its topology, stratification, temperature, fine structuring, polytropic index, and transport coefficients.
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Mizrahi-Kliger, Aviv D., Alexander Kaplan, Zvi Israel, and Hagai Bergman. "Desynchronization of slow oscillations in the basal ganglia during natural sleep." Proceedings of the National Academy of Sciences 115, no. 18 (April 16, 2018): E4274—E4283. http://dx.doi.org/10.1073/pnas.1720795115.
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Slow oscillations of neuronal activity alternating between firing and silence are a hallmark of slow-wave sleep (SWS). These oscillations reflect the default activity present in all mammalian species, and are ubiquitous to anesthesia, brain slice preparations, and neuronal cultures. In all these cases, neuronal firing is highly synchronous within local circuits, suggesting that oscillation–synchronization coupling may be a governing principle of sleep physiology regardless of anatomical connectivity. To investigate whether this principle applies to overall brain organization, we recorded the activity of individual neurons from basal ganglia (BG) structures and the thalamocortical (TC) network over 70 full nights of natural sleep in two vervet monkeys. During SWS, BG neurons manifested slow oscillations (∼0.5 Hz) in firing rate that were as prominent as in the TC network. However, in sharp contrast to any neural substrate explored thus far, the slow oscillations in all BG structures were completely desynchronized between individual neurons. Furthermore, whereas in the TC network single-cell spiking was locked to slow oscillations in the local field potential (LFP), the BG LFP exhibited only weak slow oscillatory activity and failed to entrain nearby cells. We thus show that synchrony is not inherent to slow oscillations, and propose that the BG desynchronization of slow oscillations could stem from its unique anatomy and functional connectivity. Finally, we posit that BG slow-oscillation desynchronization may further the reemergence of slow-oscillation traveling waves from multiple independent origins in the frontal cortex, thus significantly contributing to normal SWS.
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Jaar, Olivier, Mathieu Pilon, Julie Carrier, Jacques Montplaisir, and Antonio Zadra. "Analysis of Slow-Wave Activity and Slow-Wave Oscillations Prior to Somnambulism." Sleep 33, no. 11 (November 2010): 1511–16. http://dx.doi.org/10.1093/sleep/33.11.1511.
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Niethard, Niels, Hong-Viet V. Ngo, Ingrid Ehrlich, and Jan Born. "Cortical circuit activity underlying sleep slow oscillations and spindles." Proceedings of the National Academy of Sciences 115, no. 39 (September 12, 2018): E9220—E9229. http://dx.doi.org/10.1073/pnas.1805517115.
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Slow oscillations and sleep spindles are hallmarks of the EEG during slow-wave sleep (SWS). Both oscillatory events, especially when co-occurring in the constellation of spindles nesting in the slow oscillation upstate, are considered to support memory formation and underlying synaptic plasticity. The regulatory mechanisms of this function at the circuit level are poorly understood. Here, using two-photon imaging in mice, we relate EEG-recorded slow oscillations and spindles to calcium signals recorded from the soma of cortical putative pyramidal-like (Pyr) cells and neighboring parvalbumin-positive interneurons (PV-Ins) or somatostatin-positive interneurons (SOM-Ins). Pyr calcium activity was increased more than threefold when spindles co-occurred with slow oscillation upstates compared with slow oscillations or spindles occurring in isolation. Independent of whether or not a spindle was nested in the slow oscillation upstate, the slow oscillation downstate was preceded by enhanced calcium signal in SOM-Ins that vanished during the upstate, whereas spindles were associated with strongly increased PV-In calcium activity. Additional wide-field calcium imaging of Pyr cells confirmed the enhanced calcium activity and its widespread topography associated with spindles nested in slow oscillation upstates. In conclusion, when spindles are nested in slow oscillation upstates, maximum Pyr activity appears to concur with strong perisomatic inhibition of Pyr cells via PV-Ins and low dendritic inhibition via SOM-Ins (i.e., conditions that might optimize synaptic plasticity within local cortical circuits).
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Kaltiainen, Hanna-Leena, Liisa M. Helle, Hanna M. L. Renvall, and Nina H. Forss. "Slow-Wave Oscillations in Awake Healthy Subjects." Journal of Clinical Neurophysiology 33, no. 4 (August 2016): 367–72. http://dx.doi.org/10.1097/wnp.0000000000000251.
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Wei, Yina, Giri P. Krishnan, and Maxim Bazhenov. "Neuronal plasticity during sleep slow wave oscillations." BMC Neuroscience 15, Suppl 1 (2014): P216. http://dx.doi.org/10.1186/1471-2202-15-s1-p216.
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Valderrama, Mario, Benoît Crépon, Vicente Botella-Soler, Jacques Martinerie, Dominique Hasboun, Catalina Alvarado-Rojas, Michel Baulac, Claude Adam, Vincent Navarro, and Michel Le Van Quyen. "Human Gamma Oscillations during Slow Wave Sleep." PLoS ONE 7, no. 4 (April 4, 2012): e33477. http://dx.doi.org/10.1371/journal.pone.0033477.
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Amini, B., J. W. Clark, and C. C. Canavier. "Calcium Dynamics Underlying Pacemaker-Like and Burst Firing Oscillations in Midbrain Dopaminergic Neurons: A Computational Study." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2249–61. http://dx.doi.org/10.1152/jn.1999.82.5.2249.
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A mathematical model of midbrain dopamine neurons has been developed to understand the mechanisms underlying two types of calcium-dependent firing patterns that these cells exhibit in vitro. The first is the regular, pacemaker-like firing exhibited in a slice preparation, and the second is a burst firing pattern sometimes exhibited in the presence of apamin. Because both types of oscillations are blocked by nifedipine, we have focused on the slow calcium dynamics underlying these firing modes. The underlying oscillations in membrane potential are best observed when action potentials are blocked by the application of TTX. This converts the regular single-spike firing mode to a slow oscillatory potential (SOP) and apamin-induced bursting to a slow square-wave oscillation. We hypothesize that the SOP results from the interplay between the L-type calcium current (ICa,L) and the apamin-sensitive calcium-activated potassium current ( I K,Ca,SK). We further hypothesize that the square-wave oscillation results from the alternating voltage activation and calcium inactivation of I Ca,L. Our model consists of two components: a Hodgkin-Huxley-type membrane model and a fluid compartment model. A material balance on Ca2+ is provided in the cytosolic fluid compartment, whereas calcium concentration is considered constant in the extracellular compartment. Model parameters were determined using both voltage-clamp and calcium-imaging data from the literature. In addition to modeling the SOP and square-wave oscillations in dopaminergic neurons, the model provides reasonable mimicry of the experimentally observed response of SOPs to TEA application and elongation of the plateau duration of the square-wave oscillations in response to calcium chelation.
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Amzica, Florin, and Dag Neckelmann. "Membrane Capacitance of Cortical Neurons and Glia During Sleep Oscillations and Spike-Wave Seizures." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2731–46. http://dx.doi.org/10.1152/jn.1999.82.5.2731.
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Dual intracellular recordings in vivo were used to disclose relationships between cortical neurons and glia during spontaneous slow (<1 Hz) sleep oscillations and spike-wave (SW) seizures in cat. Glial cells displayed a slow membrane potential oscillation (<1 Hz), in close synchrony with cortical neurons. In glia, each cycle of this oscillation was made of a round depolarizing potential of 1.5–3 mV. The depolarizing slope corresponded to a steady depolarization and sustained synaptic activity in neurons (duration, 0.5–0.8 s). The repolarization of the glial membrane (duration, 0.5–0.8 s) coincided with neuronal hyperpolarization, associated with disfacilitation, and suppressed synaptic activity in cortical networks. SW seizures in glial cells displayed phasic events, synchronized with neuronal paroxysmal potentials, superimposed on a plateau of depolarization, that lasted for the duration of the seizure. Measurements of the neuronal membrane capacitance during slow oscillating patterns showed small fluctuations around the resting values in relation to the phases of the slow oscillation. In contrast, the glial capacitance displayed a small-amplitude oscillation of 1–2 Hz, independent of phasic sleep and seizure activity. Additionally, in both cell types, SW seizures were associated with a modulatory, slower oscillation (≈0.2 Hz) and a persistent increase of capacitance, developing in parallel with the progression of the seizure. These capacitance variations were dependent on the severity of the seizure and the distance between the presumed seizure focus and the recording site. We suggest that the capacitance variations may reflect changes in the membrane surface area (swelling) and/or of the interglial communication via gap junctions, which may affect the synchronization and propagation of paroxysmal activities.
Dissertations / Theses on the topic "Slow-wave oscillations"
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Liang, Yuqi. "Complex spatiotemporal dynamics and wave propagation of the slow oscillations in the mouse cerebral cortex." HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/651.
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The brain is a complex system which consists of billions of neuron cells and gives rise to diverse neural dynamics spatially and temporally. Spontaneous neural activities construct the foundation for various cognitive processing. However, caused by the limitation spatiotemporal resolution and coverage of recording methods in experiments, the organization of spatiotemporal dynamics of the self-organized brain activity remains largely unknown. Current experimental technique can optically image population voltage transients generated by pyramidal neurons across cortical layer 2/3 of the mouse dorsally with a genetically encoded voltage indicator. Such data provided unique opportunities to investigate the structure- dynamics relationship to elucidate the mechanisms of spontaneous brain activity. The aim of this thesis is to develop a systematic understanding of spatiotemporal mechanism in the mouse cortex by analyzing voltage imaging data, in collaboration with neuroscientist Dr. Knöpfel from the Imperial College London. Local oscillation properties such as duration, amplitude and oscillation forms were studies on the cortex-wide scale and be compared among brain states. Wakefulness modulated the excitability of the neural activity which influenced the duration of the oscillation and the transition of different half wave types. Relatively larger amplitude of parietal cortex reflected stronger neural activity determined by structural hierarchy. Motifs of the oscillations showed consistency in different brain states which indicated typical pathways of the wave propagations. Dynamical properties of various waves and their interactions in sedated mice were investigated. Based on phase velocity fields, there were only a small number of large-scale, cortex-wide plane wave and synchrony (standing wave) patterns during Up-Down states. Interactions of local sources and sinks can generate saddles, and interactions of local wave patterns with large plane waves can induce a change of their wave propagating direction. Local wave patterns emerged at preferred spatial locations. Specifically, sources were predominantly found in cortical regions with high cumulative input through the underlying connectome. The findings revealed the principled spatiotemporal dynamics of Up-Down states and associated them with the large-scale cortical connectome. Waking from deep anesthesia to consciousness increased the number of local wave patterns and made the spatiotemporal dynamics more complex. Although the active state increased the wave propagation speeds, the average speed decreased because of the interaction and collapse of wave patterns. Not affected by the brain states, the two principal modes with the highest variance remained stable. The first mode represented the large waves spreading across the cortex forward or backward while the second mode corresponded to the waves propagating in opposite direction in the frontal and parietal cortex. An infra-slow frequency of the wave number might reflect the bold flow and oxygenation. The characterizations presented in this thesis can be used to predict and guide measurement and analysis of large-scale brain activity. The analysis of cortex-wide neural dynamical patterns builds foundation for further investigation of their functional implications.
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McKillop, Laura. "Sleep slow wave oscillation : effect of ageing and preceding sleep-wake history." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:a3c762ab-cbc0-4095-86db-99e04dc7e84f.
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Sleep is well-established to become more superficial and fragmented as we age, with deficits in cognitive processing also commonly observed. While effects have been identified in both humans and mice (used in this thesis), there are important species differences in these findings and importantly, very little is known about the neural dynamics underlying these changes. By integrating several state-of-the-art approaches from putative single unit electrophysiological recordings to behavioural and pharmacological assessments, this thesis aimed to provide novel insights into the neural mechanisms involved in the age-dependent changes in sleep and cognition in mice. Firstly, this thesis investigated the neural activity underpinning the known global sleep changes that occur with ageing. Surprisingly, the majority of neuronal measures quantified in this study were resilient to the effects of ageing. Therefore the global sleep disruptions identified with ageing are unlikely to arise from changes in local cortical activity. Secondly, diazepam injection was found to suppress neural activity, in addition to previously reported effects on electroencephalography (EEG). Subtle differences in the effects of diazepam were identified across age groups, which may account for the variability seen in the efficacy of benzodiazepines in older individuals. Thirdly, ageing and sleep deprivation were found to have only a few effects on performance in a spatial learning task, the Morris water maze (MWM). Suggesting that spatial learning may be fairly resilient to the effects of ageing and sleep deprivation. Finally, this thesis presents preliminary analyses that showed mice were able to perform two novel paradigms of the visual discrimination task, suggesting their suitability in studying the link between ageing, sleep and cognition. Together the studies presented in this thesis provide insights into the differences between global and local mechanisms affected by ageing. Only by understanding local mechanisms will we be able improve on current treatments aimed at helping with the unwanted effects of healthy ageing, such as cognitive decline and sleep disruptions.
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Aumann, Dominic [Verfasser]. "Comparative effects of anodal and cathodal slow oscillating transcranial direct current stimulation during slow wave sleep on EEG activity / Dominic Aumann." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2016. http://d-nb.info/1084030128/34.
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Jaar, Olivier. "Analyse de l’activité en ondes lentes et des oscillations lentes précédant le somnambulisme." Thèse, 2010. http://hdl.handle.net/1866/12824.
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Diverses études se sont penchées sur les paramètres EEG du sommeil en ondes lentes, y compris l’activité en ondes lentes en lien avec le somnambulisme, mais les résultats se révèlent inconsistants et contradictoires. Le premier objectif de la présente étude était d’analyser quantitativement l’EEG en sommeil en mesurant les fluctuations de puissance spectrale en delta (1-4 Hz) et delta lent (0.5-1 Hz) avant des épisodes de somnambulisme. Le second était de détecter les oscillations lentes (> 75 μV, fréquence d'environ 0.7-0.8 Hz) et très lentes (> 140 μV, fréquence d'environ 0.7-0.8 Hz) afin d'examiner leur changement d'amplitude et de densité avant de tels épisodes. Suite à une privation de sommeil de 25 heures, les enregistrements polysomnographiques de 22 adultes atteints de somnambulisme ont été scrutés. L’analyse des 200 secondes avant les épisodes révèle que ceux-ci ne sont pas précédés d’une augmentation graduelle de puissance spectrale en delta ni en delta lent, tant sur les dérivations frontale, centrale que pariétale. Toutefois, une hausse statistiquement significative de la densité des oscillations lentes et des oscillations très lentes a été observée au cours des 20 sec immédiatement avant le début des épisodes. Reste à déterminer le rôle exact de ces paramètres de l’EEG en sommeil par rapport à la manifestation et au diagnostic des parasomnies en sommeil lent.Several studies have investigated slow-wave sleep EEG parameters, including slow-wave activity (SWA) in relation to somnambulism, but results have been both inconsistent and contradictory. The first goal of the present study was to conduct a quantitative analysis of sleepwalkers’ sleep EEG by studying fluctuations in spectral power for delta (1-4 Hz) and slow delta (0.5-1 Hz) before the onset of somnambulistic episodes. A secondary aim was to detect slow wave oscillations to examine their changes in amplitude and density prior to behavioral episodes of somnambulism. Twenty-two adult sleepwalkers were investigated polysomnographically following 25 h of sleep deprivation. Analysis of patients’ sleep EEG over the 200 sec prior to the episodes’ onset revealed that the episodes were not preceded by a gradual increase in spectral power for either delta or slow delta over frontal, central, or parietal leads. However, time course comparisons revealed significant changes in the density of slow and very slow wave oscillations, with significant increases occurring during the final 20 sec immediately preceding episode onset. The specificity of these sleep EEG parameters for the occurrence and diagnosis of NREM parasomnias remains to be determined.
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Perrault, Rosemarie. "Analyse de l'activité en ondes lentes et des oscillations lentes chez les somnambules." Thèse, 2014. http://hdl.handle.net/1866/11302.
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Le somnambulisme est une parasomnie commune, caractérisée par des éveils incomplets lors des stades de sommeil lent, au cours desquels les individus atteints présentent des comportements moteurs d’une complexité variable accompagnés de confusion et d’un jugement altéré. La littérature actuelle suggère que ce trouble serait associé à des particularités de l’activité en ondes lentes et des oscillations lentes, deux indices de l’intégrité du processus homéostatique et de la profondeur du sommeil. Toutefois, en raison de certaines lacunes méthodologiques dans les études existantes, le rôle de ces marqueurs électroencéphalographiques dans la pathophysiologie du somnambulisme reste à éclaircir.
Notre premier article a donc investigué d’éventuelles anomalies de l’activité en ondes lentes et des oscillations lentes chez les somnambules, en comparant leur sommeil au cours de la nuit entière à celui de participants contrôles. De plus, comme les somnambules semblent réagir différemment (en termes de fragmentation du sommeil notamment) des dormeurs normaux à une pression homéostatique accrue, nous avons comparé l’activité en ondes lentes et les oscillations lentes en nuit de base et suite à une privation de sommeil de 38 heures. Les résultats de nos enregistrements électroencéphalographiques chez 10 somnambules adultes et neuf participants contrôles montrent une élévation de la puissance spectrale de l’activité en ondes lentes et de la densité des oscillations lentes en nuit de récupération par rapport à la nuit de base pour nos deux groupes. Toutefois, contrairement à plusieurs études précédentes, nous ne n’observons pas de différence entre somnambules et dormeurs normaux quant à l’activité en ondes lentes et aux oscillations lentes pour aucune des deux nuits. Au-delà ce certaines considérations méthodologiques ayant pu contribuer à ce résultat inattendu, nous croyons qu’il justifie un questionnement sur l’hétérogénéité des somnambules comme population.
Notre deuxième article s’est penché sur les facteurs électroencéphalographiques transitoires susceptibles d’être associés au déclenchement des épisodes de somnambulisme. Nous avons comparé les fluctuations d’activité en ondes lentes et des oscillations lentes dans les minutes avant des épisodes de somnambulisme spontanés (c.a.d.: non associés à un stimulus identifiable) à celles survenant avant des éveils normaux comparables chez 12 somnambules adultes. Nous montrons que, comparativement aux éveils normaux, les épisodes de somnambulisme sont précédés d’un sommeil plus profond, tel qu’indiqué par une plus grande densité spectrale de l’activité en ondes lentes et une plus grande densité des oscillations lentes. Cet approfondissement du sommeil, spécifique aux épisodes de somnambulisme, semble survenir sur un laps de temps relativement long (>3 minutes), et non abruptement au cours des secondes précédant l’épisode. Ces données ouvrent un questionnement quant aux mécanismes en jeu dans la survenue des épisodes de somnambulisme spontanés.
Globalement, cette thèse suggère que des phénomènes liés à l’activité en ondes lentes et aux oscillations lentes seraient liés au déclenchement des épisodes de somnambulisme, mais que des études supplémentaires devront être menées afin de délimiter le rôle précis que ces marqueurs jouent dans la pathophysiologie du somnambulisme.Sleepwalking is a common parasomnia characterized by sudden but incomplete arousals out of non-rapid eye movement sleep during which predisposed individuals display motor behaviours of various complexity, accompanied by mental confusion and altered judgement. A growing body of evidence suggests that this condition could be associated with atypical patterns in slow wave activity and slow oscillations, both markers of the integrity of the homeostasis process and of sleep intensity. However, due to methodological limitations in past studies, the role of these electroencephalographic markers in the pathophysiology of sleepwalking remains unclear. Our first article aimed at describing slow wave activity and slow oscillations abnormalities in sleepwalkers by comparing whole night sleep in 10 adult sleepwalkers and 9 control participants. In addition, since past studies have shown that increased homeostatic pressure has differential effects on sleepwalkers versus normal controls (e.g., in terms of sleep fragmentation), we compared slow wave activity and slow oscillations during baseline sleep and recovery sleep after 38 hours of sleep deprivation in patients and controls. Results show that sleep deprivation increases slow wave activity power density and slow oscillations density in both groups. However, contrary to our predictions, no group differences were noted on any of the two nights on slow wave activity or slow oscillations. Beyond methodological considerations which may partially account for this unexpected result, this study opens questions as to the homogeneity of sleepwalkers as a clinical population. Our second study focused on transient electroencephalographic fluctuations that may be associated with the onset of sleepwalking episodes. We compared slow wave activity and slow oscillations fluctuations in the moments leading up to spontaneous (that is, occurring without an identifiable internal or external stimuli) somnambulistic episodes recorded in the sleep laboratory in 12 adult sleepwalkers and comparing these patterns to those observed prior to non-behavioural awakenings observed in the same patients. We showed that when compared to non-behavioural awakenings from the same sleep stage and sleep period, somnambulistic episodes were preceded by deeper sleep, as indicated by higher slow wave activity power density and slow oscillations density. This deepening of sleepwalkers’ sleep occurs over a relatively long period of time (>3 minutes) before the episode, rather than abruptly in the seconds preceding episode onset. These findings raise key questions about fundamental mechanisms involved in the occurrence of spontaneously recorded somnambulistic episodes. Taken as a whole, the results from the work presented in this thesis show that electrophysiological processes related to slow wave activity and slow oscillations play a role in the occurrence of somnambulistic episodes. However, the functional significance of these electroencephalographic markers in the pathophysiology of sleepwalking remains to be clarified.
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Orendáčová, Mária. "Akustická stimulácia pomalovlnného spánku a jej vplyv na konsolidáciu pamäti u ľudí trpiacich nespavosťou." Master's thesis, 2019. http://www.nusl.cz/ntk/nusl-404974.
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Slow-wave sleep plays an important role in consolidation of declarative memory. From electrophysiological point of view, this process is dependent on a common occurrence and mutual integration of neocortical slow oscillations (< 1 Hz), hippocampal sharp-wave ripples (150-250 Hz) and thalamo-cortical sleep spindles (10-15 Hz). Previous studies demonstrated that periodic acoustic stimulation by pink noise pulses applied at frequency of sleep slow oscillation during slow wave sleep leads to prolongation of slow wave sleep and to enhancement in declarative memory performance in normal sleepers. Our study investigated this kind of periodic acoustic stimulation in its relation to sleep architecture and declarative memory of people suffering from insomnia due to which there often comes to a reduction in slow wave sleep which positively correlates with worsening of declarative memory performance. Our aim was to investigate if this kind of comparatively non-invasive brain stimulation has a potential to increase a total length of slow wave sleep and enhance declarative memory performance in insomnia. Our study revealed acoustic stimulation neither improved declarative memory performance nor it increased total length of slow-wave sleep. No positive association was found between level of declarative memory...
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Wolansky, Trisha. "Characterisation of the sleep-related slow oscillation in the neocortical - entorhinal - hippocampal bidirectional circuit." Phd thesis, 2009. http://hdl.handle.net/10048/789.
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Our ability to recall information and events is astounding and dependent on the medial temporal lobe (MTL) memory system. The synaptic interconnections between the neocortex (nCTX), entorhinal cortex (EC), and hippocampus (HPC) are the anatomical basis of this memory system. The electrophysiological basis of memory formation in this system is largely unknown, but the activity patterns that occur during slow wave sleep (SWS) are thought to play an important role. One prominent activity pattern that occurs during SWS is the slow oscillation (SO). It is a large-amplitude rhythm of ~1Hz that was first described in the nCTX and only occurs during SWS and deep anaesthesia. Using the urethane-anaesthetised rat, I provide the first description of the SO in the HPC in Chapter 2. I found that the SO in the HPC was dynamically coordinated with that in the nCTX. Because the EC is the anatomical interface between the nCTX and HPC, I hypothesised that it could be responsible for this coordination. Chapter 3 characterises the SO in the EC and its coordination with both the nCTX and HPC. My results suggested that the synaptic interconnections between the nCTX and HPC via the EC were not solely responsible for SO coordination across these structures. Another possibility is that SO coordination across the nCTX, EC, and HPC occurs via the nucleus reuniens thalami (NReu). In Chapter 4, I delivered trains of electrical stimulation to the frontal cortex (fCTX) to enhance the SO in the nCTX and assess any effect in the HPC. In addition, I delivered the same stimulation trains directly to the medial prefrontal cortex (mpfCTX) and NReu. I found that repeated stimulation in each structure entrained the hippocampal SO. I also found that repeated stimulation of the fCTX and mpfCTX enhanced SO coordination across the nCTX and HPC, but repeated stimulation of the NReu did not. My results suggested that SO coordination across the nCTX and HPC occurs via both the EC and NReu. Understanding the coordination of SO activity across these structures will provide insight to the electrophysiological basis of the MTL memory system and the role of SWS in its function.
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Wolansky, Trisha Denise. "Characterisation of the sleep-related slow oscillation in the neocortical - entorhinal - hippocampal bidirectional circuit." 2009. http://hdl.handle.net/10048/789.
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Thesis (Ph.D.)--University of Alberta, 2009.A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosphy, Centre for Neuroscience. Title from pdf file main screen (viewed on November 6, 2009). Includes bibliographical references.
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Ferreira, Tiago. "Catch the dream Wave : Propagation of Cortical Slow Oscillation to the Striatum in anaesthetised mice." Thesis, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150574.
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Under anaesthesia or in deep sleep, different parts of the brain have a distinctive slow oscillatory activity, characterised by states of high membrane potential and intensive spiking activity, the Up-states; followed by hyperpolarisation and quiescence, the Down-states. This activity has been previously described in vitro and in vivo in the cortex and the striatum, across several species. Here, we look into it, during anaesthesia, in the mouse brain. Using whole-cell patch-clamp recordings of cortical cells, it was possible to compare different signal processing methods used to extract the Up-and- Down states in extracellular recordings of the cortex. Our results show that the method based on the Multi-Unit Activity (> 200Hz) have better ac- curacy than High-Gamma Range (20 100Hz) or wavelet decomposition (< 2Hz band). After establishing the most robust method, this was used to compare the intracellular recordings of striatal cells to different parts of the cortex. The results obtained here support a functional connection between the dorsolateral striatal neurons and the ipsilateral barrel field. They also support a functional connection between dorsomedial striatal cells and the primary visual cortex. The analysis of delay between recordings allowed to establish temporal relationships between the contralateral barrel field, the ipsilateral barrel field, and the dorsolateral striatum; and between the ipsilateral barrel field, the ipsilateral primary visual field and the dorsomedial striatum.External Advisor: Dr. Ramon Reig, from Karolinska Institutet
Books on the topic "Slow-wave oscillations"
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Zeitlin, Vladimir. Geostrophic Adjustment and Wave–Vortex (Non)Interaction. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198804338.003.0008.
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The fundamental process of geostrophic adjustment is treated by the method of multi-scale asymptotic expansions in Rossby number and fast-time averaging (which is explained), first in the barotropic one-layer case, and then in the baroclinic two-layer case. Together with the standard quasi-geostrophic regime of parameters, the frontal (or semi-) geostrophic regime is considered. Dynamical separation of slow and fast motions is demonstrated in both regimes. The former obey quasi-geostrophic or frontal-geostrophic equations, thus providing formal justification of the heuristic derivation of Chapter 5. Fast motions are inertia-gravity waves in quasi-geostrophic case, and inertial oscillations in the frontal-geostrophic case. Geostrophic adjustment is also considered in the presence of coastal, topographic, and equatorial wave-guides, and, again, separation of fast and slow motions is demonstrated, the latter now including long Kelvin waves in the first case, long topographic waves in the second case, and long Kelvin and Rossby waves in the third case.
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Jones, Barbara E. Neuroanatomical, neurochemical, and neurophysiological bases of waking and sleeping. Edited by Sudhansu Chokroverty, Luigi Ferini-Strambi, and Christopher Kennard. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199682003.003.0004.
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Neurons distributed through the reticular core of the brainstem, hypothalamus, and basal forebrain and giving rise to ascending projections to the cortex or descending projections to the spinal cord promote the changes in cortical activity and behavior that underlie the sleep–wake cycle and three states of waking, NREM (slow wave) sleep, and REM (paradoxical) sleep. Forming the basic units of these systems, glutamate and GABA cell groups are heterogeneous in discharge profiles and projections, such that different subgroups can promote cortical activation (wake/REM(PS)-active) versus cortical deactivation (NREM(SWS)-active) by ascending influences or behavioral arousal with muscle tone (wake-active) versus behavioral quiescence with muscle atonia (NREM/REM(PS)-active) by descending influences. These different groups are in turn regulated by neuromodulatory systems, including cortical activation (wake/REM(PS)-active acetylcholine neurons), behavioral arousal (wake-active noradrenaline, histamine, serotonin, and orexin neurons), and behavioral quiescence (NREM/REM(PS)-active MCH neurons). By different projections, chemical neurotransmitters and discharge profiles, distinct cell groups thus act and interact to promote cyclic oscillations in cortical activity and behavior forming the sleep-wake cycle and states.
Book chapters on the topic "Slow-wave oscillations"
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Highton, David, Arnab Ghosh, Ilias Tachtsidis, Clare Elwell, and Martin Smith. "Analysis of Slow Wave Oscillations in Cerebral Haemodynamics and Metabolism Following Subarachnoid Haemorrhage." In Advances in Experimental Medicine and Biology, 195–201. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0620-8_26.
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Destexhe, A., and D. Contreras. "The Fine Structure of Slow-Wave Sleep Oscillations: from Single Neurons to Large Networks." In Sleep and Anesthesia, 69–105. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0173-5_4.
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Krueger, James M., James M. Clinton, Bradley D. Winters, Mark R. Zielinski, Ping Taishi, Kathryn A. Jewett, and Christopher J. Davis. "Involvement of cytokines in slow wave sleep." In Slow Brain Oscillations of Sleep, Resting State and Vigilance, 39–47. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-444-53839-0.00003-x.
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Van Der Werf, Ysbrand D., Ellemarije Altena, José C. Vis, Teddy Koene, and Eus J. W. Van Someren. "Reduction of nocturnal slow-wave activity affects daytime vigilance lapses and memory encoding but not reaction time or implicit learning." In Slow Brain Oscillations of Sleep, Resting State and Vigilance, 245–55. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-444-53839-0.00016-8.
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"Slow-Wave Oscillation (SWO)." In Encyclopedia of Computational Neuroscience, 2729. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4614-6675-8_100553.
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Sultanov, Murad, Ulduz Hashimova, and Khadidja Ismailova. "Brain and Behaviour: Quantitative Analysis among Youth Men using Mobile EEG System." In Bulletin of Medical and Clinical Research, 40–49. IOR INTERNATIONAL PRESS, 2020. http://dx.doi.org/10.34256/br2015.
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The present article explores the relationship between the EEG rhythms' oscillations and the personality traits in a group of young males (soccer players and sport students). EEG was recorded by a single-channel wireless EEG system in the prefrontal cortex. Personality traits were identified in accordance with Eysenck's personality questionnaire. The regression model was used to analyse the EEG rhythms as possible predictors for Eysenck's personality traits. The findings of the study highlighted two slow rhythms that can be considered as predictors for personality traits, specifically: delta wave – for extraversion with negative slope, which could be related to mood, and theta wave – for neuroticism with negative slope, which could be related to inhibition. Those EEG patterns could condition preference for certain behavioural strategies in accordance with type of temperament. In addition, for two EEG high-frequency rhythms, association was revealed with personality traits: for beta rhythm as a hypothetical predictor for neuroticism, and for gamma rhythm – for lie. The statistically significant relationship between the slow bands with neuroticism and extraversion indicate to influences of the emotion-generating and reticular brain structures. In conclusion, the prefrontal cortex's background EEG activity can reflect preference of certain behavioural strategies, which are formed in accordance with individual type of temperament. This implies that study further examined probability association between the higher frequency bands (beta and gamma) and personality traits, which would be achieved in future researches. In addition, the data derived from a single-channel wireless system equipment demonstrated results, which is close to EEG recorded by conventional lab-based equipment.
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Sultanov, Murad, Ulduz Hashimova, and Khadidja Ismailova. "Brain and Behaviour: Quantitative Analysis among Youth Men using Mobile EEG System." In Bulletin of Medical and Clinical Research, 40–49. IOR INTERNATIONAL PRESS, 2020. http://dx.doi.org/10.34256/br2015.
Full textAbstract:
The present article explores the relationship between the EEG rhythms' oscillations and the personality traits in a group of young males (soccer players and sport students). EEG was recorded by a single-channel wireless EEG system in the prefrontal cortex. Personality traits were identified in accordance with Eysenck's personality questionnaire. The regression model was used to analyse the EEG rhythms as possible predictors for Eysenck's personality traits. The findings of the study highlighted two slow rhythms that can be considered as predictors for personality traits, specifically: delta wave – for extraversion with negative slope, which could be related to mood, and theta wave – for neuroticism with negative slope, which could be related to inhibition. Those EEG patterns could condition preference for certain behavioural strategies in accordance with type of temperament. In addition, for two EEG high-frequency rhythms, association was revealed with personality traits: for beta rhythm as a hypothetical predictor for neuroticism, and for gamma rhythm – for lie. The statistically significant relationship between the slow bands with neuroticism and extraversion indicate to influences of the emotion-generating and reticular brain structures. In conclusion, the prefrontal cortex's background EEG activity can reflect preference of certain behavioural strategies, which are formed in accordance with individual type of temperament. This implies that study further examined probability association between the higher frequency bands (beta and gamma) and personality traits, which would be achieved in future researches. In addition, the data derived from a single-channel wireless system equipment demonstrated results, which is close to EEG recorded by conventional lab-based equipment.
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Sanders, Kenton M., and Tamas Ördög. "Properties of Electrical Rhythmicity in the Stomach." In Handbook of Electrogastrography. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195147889.003.0006.
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Gastric peristaltic contractions are the basis for emptying of solids from the stomach. These events begin in the mid to high corpus region, develop into a ring around the stomach, and spread down the length of the stomach to the pylorus. The pressure wave resulting from gastric peristalsis pushes the contents of the stomach toward the pyloric sphincter, but a nearly simultaneous contraction of the ring of muscle in the pyloric canal and the terminal antrum ultimately forces much of the food in the retrograde direction, toward the body of the stomach. Sheer forces that develop as a result of this forceful retropulsion cause mechanical disruption of solid particles. Repetitive peristaltic contractions (e.g., in the human these events occur about 3 times per minute), over a period of time, reduces ingested foods to small particles. The action of gastric peristalsis in the distal stomach facilitates emptying and the reduced particle diameter aides in chemical digestion of foods in the small intestine. Pathophysiological conditions that disrupt or disorganize gastric peristalsis can impair or delay normal gastric emptying. Gastric peristaltic contractions result from depolarization of the plasma membranes of smooth muscle cells. For many years it has been known that gastric muscles display periodic (or rhythmic) electrical activity in which membrane potential oscillates between negative potentials and more depolarized levels. The oscillations in membrane potential are known as electrical slow waves (see Color Figs. 2.1 and 2.2 in separate color insert). Slow waves are generated within the tunica muscularis of the proximal corpus along the greater curvature of the stomach, and these events spread around the circumference and down the stomach to the pylorus. A greater velocity of propagation around the stomach than down the stomach causes development of a ring of excitation, and this is the electrical basis underlying gastric peristaltic contractions. Studies have shown that electrical slow waves are generated by specialized pacemaker cells, known as interstitial cells of Cajal (ICCs). The main pacemaker ICCs in the stomach form a dense network of electrically coupled cells between the circular and longitudinal muscle layers of the corpus and antrum.
Conference papers on the topic "Slow-wave oscillations"
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Balakirev, V. A., D. Y. Sidorenko, G. V. Sotnikov, and Y. V. Tkach. "Excitation of UHF oscillations in a magnetically insulated slow-wave line." In XVI International Symposium on Discharges and Electrical Insulation in Vacuum, edited by Gennady A. Mesyats. SPIE, 1994. http://dx.doi.org/10.1117/12.174576.
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Nihei, Yasunori, Takeshi Kinoshita, and Weiguang Bao. "Non-Linear Wave Forces Acting on a Body of Arbitrary Shape Slowly Oscillating in Waves." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67486.
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In the present study, non-linear wave loads such as the wave drift force, wave drift damping and wave drift added mass, acting on a moored body is evaluated based on the potential theory. The body is oscillating at a low frequency under the non-linear excitation of waves. The problem of interaction between the low-frequency oscillation of the body and ambient wave fields is considered. A moving coordinate frame following the low frequency motion is adopted. Two small parameters, which measure the wave slope and the frequency of slow oscillations (compared with the wave frequency) respectively, are used in the perturbation analysis. So obtained boundary value problems for each order of potentials are solved by means of the hybrid method. The fluid domain is divided into two regions by an virtual circular cylinder surrounding the body. Different approaches, i.e. boundary element method and eigen-function expansion, are applied to these two regions. Calculated nonlinear wave loads are compared to the semi-analytical results to validate the present method.
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Forouzanfar, Mohamad, Fiona C. Baker, Ian M. Colrain, and Massimiliano de Zambotti. "Electroencephalographic Slow-Wave Activity During Sleep in Different Phases of Blood Pressure and Respiration Oscillations." In 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC). IEEE, 2019. http://dx.doi.org/10.1109/embc.2019.8857490.
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Kinoshita, Takeshi, and Weiguang Bao. "Nonlinear Wave Loads Affected by the Low-Frequency Oscillations in the Horizontal Plane." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37342.
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To investigate the effects of the low-frequency oscillations on the nonlinear wave loads, the interaction of the low-frequency oscillations with the ambient wave fields is considered. The frequency of the slow oscillations is assumed to be much smaller than the wave frequency. Perturbation expansion based on two small parameters, i.e. the incident wave amplitude and the low frequency, is performed to simplify the problem. Nonlinear wave loads including the wave drift damping and wave drift added mass are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface. The problem is solved for a uniform circular cylinder by means of the Green’s theorem and semi-analytical solutions are presented. The far field conditions for each order of potentials are proposed to ensure the existence of a unique solution. The restriction on the validation of the solutions is discussed.
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Biskup, N., L. Balicas, K. Maki, S. Tomic, D. Jerome, and J. M. Fabre. "Slow quantum oscillations in the semimetallic spin density wave ground state of the organic conductor (TMTSF)/sub 2/NO/sub 3/." In International Conference on Science and Technology of Synthetic Metals. IEEE, 1994. http://dx.doi.org/10.1109/stsm.1994.835912.
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do Carmo, Lucas H. S., Pedro C. de Mello, Edgard B. Malta, Guilherme R. Franzini, Alexandre N. Simos, Rodolfo T. Gonçalves, and Hideyuki Suzuki. "Analysis of a FOWT Model in Bichromatic Waves: An Investigation on the Effect of Combined Wave-Frequency and Slow Motions on the Calibration of Drag and Inertial Force Coefficients." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18239.
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Abstract The choice of drag and inertia coefficients are critical for the evaluation of hydrodynamic loads in slender cylinders using either Morison’s equation or an approach where viscous forces are simply added to the results of potential theory. Many studies available in the literature have considered fixed cylinders under the action of (two dimensional) sinusoidal currents, showing that the average values of drag and added mass coefficients can be correlated with the Keulegan-Carpenter and Reynolds numbers. However, when the semi-empirical models are used for the analysis of Floating Offshore Wind Turbines (FOWTs), many other aspects of the flow may play an important role, such as the spatial variations of the wave flow over the hull, three-dimensional flow effects associated with the floater motions, the presence of heave plates, among others. The present work is based on a case-study involving a simplified version of the floater of a semi-submersible FOWT and deals with cases where the incoming flow is composed of more than one frequency and body motions are a combination of periodic components with very different frequencies (wave frequency and slow-drift motions). In this case, the choice of proper coefficients for the Morison’s approach becomes somewhat puzzling, to say the least. The objective is to understand how the more complex flow and the coexistence of different frequencies affect the hydrodynamic forces and whether proper values of force coefficients can indeed be obtained from simplified model tests performed in the absence of incoming waves, such as forced oscillations and decay tests. For doing so, the paper analyses the results of an experimental campaign performed with the model scale floater (1:80) composed of four vertical circular columns. Three sets of tests are taken into account: forced oscillations of the hull, free decays of the moored model, and motions under the action of waves (monochromatic and bichromatic). The first two are used to assess the values of added mass and drag coefficients (and also for obtaining linearized damping levels), while the third group of tests helps to evaluate the accuracy of the motions predicted when using these coefficients in frequency-domain computations.
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Salenger, Gary D., and Alexander F. Vakakis. "Analytic Study of Discreteness Effects in a String Resting on a Periodic Array of Vibro-Impact Supports." In ASME 1997 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/detc97/vib-3924.
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Abstract We analyze the forced oscillations of an infinite string supported by an array of vibro-impact supports. The envelope of the excitation possesses ‘slow’ and ‘fast’ scales and is periodic with respect to the ‘fast’ scale. The ‘fast’ spatial scale is defined by the distance between adjacent nonlinear supports. To eliminate the singularities from the governing equations of motion that arise due to the discrete nature of the supports, we employ the nonsmooth transformations of the spatial variable first introduced in (Pilipchuk, 1985) and (Pilipchuk, 1988). Thus, we convert the problem to a set of two nonhomogeneous nonlinear boundary value problems which we solve by means of perturbation theory. The boundary conditions of these problems arise from ‘smoothness conditions’ that are imposed to guarantee sufficient differentiability of the results. The transformed system of equations is simplified using regular perturbation and harmonic balancing. Standing solitary wave solutions reflecting the discreteness effects inherent in the discrete foundation are calculated numerically for the unforced system.
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Baik, Chan-Wook, So Yeon Jun, Ho Young Ahn, Seogwoo Hong, Joo Ho Lee, Yongsung Kim, Sang Hun Lee, SeGi Yu, and Jong-Min Kim. "Return loss measurement of a microfabricated slow-wave structure for backward-wave oscillation." In 2010 35th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2010). IEEE, 2010. http://dx.doi.org/10.1109/icimw.2010.5612565.
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Bao, Weiguang, Takeshi Kinoshita, and Motoki Yoshida. "Nonlinear Wave Loads Acting on Cylinder Array Slowly Oscillating in Diffraction and Radiation Wave Fields." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67363.
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The problem of a circular cylinder array slowly oscillating in both diffraction and radiation wave fields is considered in the present work. As a result of the interaction between the wave fields and the low-frequency motion, nonlinear wave loads may be separated into the so-called wave-drift added mass and damping. They are force components proportional to the square of the wave amplitude but in phase of the acceleration and velocity of the low-frequency motion respectively. The frequency of the slow oscillation is assumed to be much smaller than the wave frequency. Perturbation expansion based on two time scales and two small parameters is performed to the order to include the effects of the acceleration of the low-frequency motion. Solutions to these higher order potentials are suggested in the present work. Wave loads including the wave drift added mass and damping are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface.
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Armaoğlu, Evren, and Paolo Monti. "Advantages of Using a Time-Domain Approach for Dynamic Positioning (DP) Pipelay Studies." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23040.
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Normally, the DP capability of a vessel is calculated through the use of static force equilibrium programs in which the dynamic effects are either not taken into account or taken into account by empirical load amplification factors. However, competitive and safe S-laying of large diameter pipelines in deep waters lead to large and long pipe lay vessels for which DP requirements are demanding. The power/propulsion requirement of the vessel needs to be considered from an early stage especially when accounting for the pipe laying equipment demands. This imposes a need for detailed dynamic analysis of the lay vessel. This analysis needs to include the slow drift oscillations counteracted by DP and the analysis in entirety needs to ensure the pipe string integrity is maintained. To this purpose Saipem developed in-house a time-domain simulator (FIPLA – Fully Integrated Pipe LAying) that employs all environmental forces (i.e. wind, wave, current) as well as the pipe tension on the vessel. It is used to assess the DP performances and laying capabilities of pipe lay vessels in harsh dynamic environments as well as critical areas for operations. The software can also be used to assess the performance of the vessel in case of failure of thrusters, power generators or bus bars, study DP Control System improvements, and assess the interaction between vessel, tensioner and pipe in deep and shallow waters. This paper focuses on the advantages of using dynamic simulations as an enhancement to the static DP capability charts, to produce detailed information for the DP Operator (DPO) in terms of setting of the DP parameters and to analyze critical laying events. This information can be used together with the weather forecast and can help getting the best performance out of the DP system in harsh environments, reducing downtime, improving operability and ensuring a safe operation.