Littérature scientifique sur le sujet « Spike phase/time analysis »
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Articles de revues sur le sujet "Spike phase/time analysis"
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Liu, Moutian, et Lixia Duan. « In-phase and anti-phase spikes synchronization within mixed Bursters of the pre-Bözinger complex ». Electronic Research Archive 30, no 3 (2022) : 961–77. http://dx.doi.org/10.3934/era.2022050.
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<abstract><p>In this paper, the transition from anti-phase spike synchronization to in-phase spike synchronization within mixed bursters is investigated in a two-coupled pre-Bözinger complex (pre-BötC) network. In this two-coupled neuronal network, the communication between two pre-BötC networks is based on electrical and synaptic coupling. The results show that the electrical coupling accelerates in-phase spike synchronization within mixed bursters, but synaptic coupling postpones this kind of synchronization. Synaptic coupling promotes anti-phase spike synchronization when electrical coupling is weak. At the same time, the in-phase spike synchronization within dendritic bursters occurs earlier than that within somatic bursters. Asymmetric periodic somatic bursters appear in the transition state from anti-phase spikes to in-phase spikes. We also use fast/slow decomposition and bifurcation analysis to clarify the dynamic mechanism for the two types of synchronization.</p></abstract>
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Wang, Jiaoyan, Xiaoshan Zhao et Chao Lei. « Pulse Inputs Affect Timings of Spikes in Neurons with or Without Time Delays ». International Journal of Nonlinear Sciences and Numerical Simulation 20, no 3-4 (26 mai 2019) : 257–67. http://dx.doi.org/10.1515/ijnsns-2017-0070.
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AbstractInputs can change timings of spikes in neurons. But it is still not clear how input’s parameters for example injecting time of inputs affect timings of neurons. HR neurons receiving both weak and strong inputs are considered. How pulse inputs affecting neurons is studied by using the phase-resetting curve technique. For a single neuron, weak pulse inputs may advance or delay the next spike, while strong pulse inputs may induce subthreshold oscillations depending on parameters such as injecting timings of inputs. The behavior of synchronization in a network with or without coupling delays can be predicted by analysis in a single neuron. Our results can be used to predict the effects of inputs on other spiking neurons.
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Kong, Fanze, et Qi Wang. « Stability, free energy and dynamics of multi-spikes in the minimal Keller-Segel model ». Discrete & ; Continuous Dynamical Systems 42, no 5 (2022) : 2499. http://dx.doi.org/10.3934/dcds.2021200.
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<p style='text-indent:20px;'>One of the most impressive findings in chemotaxis is the aggregation that randomly distributed bacteria, when starved, release a diffusive chemical to attract and group with others to form one or several stable aggregates in a long time. This paper considers pattern formation within the minimal Keller–Segel chemotaxis model with a focus on the stability and dynamics of its multi-spike steady states. We first show that any steady-state must be a periodic replication of the spatially monotone one and they present multi-spikes when the chemotaxis rate is large; moreover, we prove that all the multi-spikes are unstable through their refined asymptotic profiles, and then find a fully-fledged hierarchy of free entropy energy of these aggregates. Our results also complement the literature by finding that when the chemotaxis is strong, the single boundary spike has the least energy hence is the most stable, the steady-state with more spikes has larger free energy, while the constant has the largest free energy and is always unstable. These results provide new insights into the model's intricate global dynamics, and they are illustrated and complemented by numerical studies which also demonstrate the metastability and phase transition behavior in chemotactic movement.</p>
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GRZYWACZ, NORBERTO M., et EVELYNE SERNAGOR. « Spontaneous activity in developing turtle retinal ganglion cells : Statistical analysis ». Visual Neuroscience 17, no 2 (mars 2000) : 229–41. http://dx.doi.org/10.1017/s0952523800172050.
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We report on the temporal properties of the spontaneous bursts of activity in the developing turtle retina. Quantitative statistical criteria were used to detect, cluster, and analyze the temporal properties of the bursts. The interburst interval, duration, firing rate, and number of spikes per burst varied widely among cells and from burst to burst in a single cell. Part of this variability was due to the positive correlation between a burst's duration and the interburst interval preceding that burst. This correlation indicated the influence of a refractory period on the bursts' properties. Further evidence of such a refractoriness came from the bursts' auto-covariance function, which gives the tendency of a spike to occur a given amount of time after another spike. This function showed a positive phase (between ≈10 ms and 10 s) followed by a negative one (between 10 s and more than 100 s), suggestive of burst refractoriness. The bursts seemed to be propagating from cell to cell, because there was a long (symmetrically distributed) delay between the activation of two neighbor cells (median absolute delay = 2.3 s). However, the activity often failed to propagate from one cell to the other (median safety factor = 0.59). The number of spikes per burst in neighbor cells was statistically positively correlated, indicating that the activity in the two cells was driven by the same excitatory process. At least two factors contribute to the excitability during bursts, because the positive phase of the cross-covariance function (similar to auto-covariance but for two cells) had a temporally asymmetric fast component (1–3 ms) followed by a temporally symmetric slow component (1 ms to 10 s).
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Lindsey, B. G., Y. M. Hernandez, K. F. Morris, R. Shannon et G. L. Gerstein. « Dynamic reconfiguration of brain stem neural assemblies : respiratory phase-dependent synchrony versus modulation of firing rates ». Journal of Neurophysiology 67, no 4 (1 avril 1992) : 923–30. http://dx.doi.org/10.1152/jn.1992.67.4.923.
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1. The objective of this work was to determine whether configurations of midline brain stem neural assemblies change during the respiratory cycle. 2. Spike trains of several single neurons were recorded simultaneously in anesthetized, paralyzed, bilaterally vagotomized, artificially ventilated cats. Data were analyzed with cross-correlational and gravity methods. 3. Sequential samples from each of eight groups of neurons known to contain synchronously discharging neurons exhibited temporal variations in that synchrony. 4. Gravity analysis of short (less than 200-s) samples of spike train data revealed 20 pairs of clustered particles that were not predicted from cross-correlation analysis of the parent data sets (greater than 20 min). 5. Twenty-nine groups of three to eight simultaneously monitored neurons, each with at least two synchronously discharging neurons, were analyzed for evidence of respiratory phase-dependent modulation of that coordinated activity. Spikes from successive interleaved inspiratory and expiratory intervals were analyzed separately. 6. Neurons pairs in 11 groups were more synchronous during the inspiratory interval; six groups had pairs that were more synchronous during the expiratory period. In two groups, different pairs were synchronous in different respiratory phases. In 11 of the 26 pairs that exhibited phase-dependent differences in synchrony, neither neuron had a respiratory-modulated firing rate as judged by either the cycle-triggered histogram or an analysis of variance of their firing rates. 7. Configurations of respiratory-related brain stem neural networks changed with time and the phases of breathing. Neurons with no apparent respiratory modulation of their individual firing rates collectively exhibited respiratory phase-dependent modulation of their impulse synchrony.(ABSTRACT TRUNCATED AT 250 WORDS)
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Kim, J. H., J. J. Wang et T. J. Ebner. « Climbing fiber afferent modulation during treadmill locomotion in the cat ». Journal of Neurophysiology 57, no 3 (1 mars 1987) : 787–802. http://dx.doi.org/10.1152/jn.1987.57.3.787.
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The relationship of the climbing fiber afferent discharge to the unperturbed and perturbed step cycle was evaluated in the cat. Following a precollicular-premamillary decerebration, cats walked spontaneously on a motorized treadmill. Purkinje cells were recorded extracellularly and simple and complex spikes were discriminated. Right forelimb displacement, biceps and triceps EMG activity, as well as treadmill velocity, were also monitored. In some animals pressure measurements of the contact of the footpad with the treadmill were obtained. Cells were studied during both “normal” and perturbed locomotion. The perturbation consisted of a braking of the treadmill at different phases in the step cycle. Histograms of the simple and complex spike activity, and averages of the right forelimb displacement, biceps, and triceps EMG activity and treadmill velocity were constructed. The complex spike activity of 163 Purkinje cells was averaged through a minimum of 50 sweeps in either normal and/or perturbed locomotion. Statistical analysis revealed that the probability of the climbing fiber afferent discharge in 54% of the cells (36/67) studied during normal locomotion was significantly modulated with the step cycle. For most Purkinje cells the onset of the increase in climbing fiber afferent discharge was coupled to triceps activity and the onset of stance phase. A group of cells exhibited complex spike discharge in association with biceps onset and swing. These observations suggest that complex spike discharge occurs preferentially at the phase transition periods in the step cycle when the trajectory of the forelimb changes from swing to stance or stance to swing. During treadmill braking 51% of the cells exhibited complex spike modulation (70/137). A number of different patterns of climbing fiber afferent modulation occurred. The most common pattern was an increase in complex spike discharge with the resumption of the treadmill movement and locomotion. Analysis of the time of these periods of increased climbing fiber activity suggests that, although in some cells the response is coupled to the treadmill onset, in other cells the modulation occurs at longer latencies. Subsequent analysis aligning the EMG, displacement, and treadmill velocity signals with the times of the climbing fiber afferent discharge suggested some responses were coupled to the reinitiation of the locomotor cycle. The second most common pattern was an increase in climbing fiber afferent discharge at the onset of the perturbation. Also, in some cells, complex spike discharge decreased during the period in which the step cycle was arrested.(ABSTRACT TRUNCATED AT 400 WORDS)
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Liang, Mei, Pengyu Jia et Tengfei Guo. « Analysis of a Single-Phase Transformerless Bidirectional PFC ». Energies 15, no 22 (8 novembre 2022) : 8329. http://dx.doi.org/10.3390/en15228329.
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This paper presents a single-phase transformerless bidirectional power factor corrector (PFC). A capacitor is inserted into a conventional full-bridge PFC by connecting the ac line terminal and a terminal of DC voltage. The functions of this inserted capacitor have two roles: to bypass the common-mode leakage current from the stray capacitor; to form an LCL filter to reduce the inductor current ripple. A hybrid modulation method is employed in this PFC. The unipolar switching scheme is applied to modulate the PFC, which can achieve high efficiency. Meanwhile, an additional modulation is inserted into the blank time of low-frequency switches to decrease the changing speed of the voltage on the inserted capacitor, and to decrease the spike on the inductor current and leakage current. The performance of the PFC is experimentally verified using a 5 kW prototype.
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Burkitt, A. N., et G. M. Clark. « Analysis of Integrate-and-Fire Neurons : Synchronization of Synaptic Input and Spike Output ». Neural Computation 11, no 4 (1 mai 1999) : 871–901. http://dx.doi.org/10.1162/089976699300016485.
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A new technique for analyzing the probability distribution of output spikes for the integrate-and-fire model is presented. This technique enables us to investigate models with arbitrary synaptic response functions that incorporate both leakage across the membrane and a rise time of the postsynaptic potential. The results, which are compared with numerical simulations, are exact in the limit of a large number of small-amplitude inputs. This method is applied to the synchronization problem, in which we examine the relationship between the spread in arrival times of the inputs (the temporal jitter of the synaptic input) and the resultant spread in the times at which the output spikes are generated (output jitter). The results of previous studies, which indicated that the ratio of the output jitter to the input jitter is consistently less than one and that it decreases for increasing numbers of inputs, are confirmed for three classes of the integrate-and-fire model. In addition to the previously identified factors of axonal propagation times and synaptic jitter, we identify the variation in the spike-generating thresholds of the neurons and the variation in the number of active inputs as being important factors that determine the timing jitter in layered networks. Previously observed phase differences between optimally and suboptimally stimulated neurons may be understood in terms of the relative time taken to reach threshold.
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Sawczuk, A., R. K. Powers et M. D. Binder. « Spike frequency adaptation studied in hypoglossal motoneurons of the rat ». Journal of Neurophysiology 73, no 5 (1 mai 1995) : 1799–810. http://dx.doi.org/10.1152/jn.1995.73.5.1799.
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1. We studied spike frequency adaptation of motoneuron discharge in the rat hypoglossal nucleus using a brain stem slice preparation. The characteristics of adaptation in response to long (60 s) injected current steps were qualitatively similar to those observed previously in cat hindlimb motoneurons. The discharge rate typically exhibited a rapid initial decline, characterized by a linear frequency-time relation, followed by a gradual exponential decline that continued for the duration of current injection. However, a more systematic, quantitative analysis of the data revealed that there were often three distinct phases of the adaptation rather than two. 2. The three phases of adaptation (initial, early, and late) were present in at least one 60-s trial of repetitive firing in all but a small number of motoneurons. Initial adaptation was limited to the first few spikes except in a few trials (7%) in which there was no initial adaptation. The time course of the subsequent decline in rate could be adequately described by a single-exponential function in about half of the trials (48%). In the remaining trials this subsequent decline in frequency was better described as the sum of two exponential functions: an early phase, lasting < 2 s, and a late phase, which lasted for the duration of the discharge period. 3. The magnitude of initial adaptation was correlated with the initial firing frequency (i.e., the reciprocal of the 1st interspike interval). The magnitudes of the early and late phases of adaptation were correlated with the firing frequency reached at the end of initial adaptation. Neither the magnitudes nor the time courses of the three phases were correlated with other membrane properties such as input resistance, rheobase, or repetitive firing threshold. 4. The slope of the frequency-current (f-I) curve was steeper in the initial phase (first 2-5 spikes) than in either the early (< 2 s) or late (> 2 s) phases of adaptation as previously reported by other investigators. In the absence of early adaptation, a steady state for the f-I slope was reached by 0.7-1 s, the time typically reported in studies of repetitive discharge. However, when early adaptation was present (50% of the trials), a steady-state value for the f-I slope was not reached until the cell had discharged for > 1 s. 5. To characterize the time course of firing rate recovery from the adaptive processes, the current was turned off for periods of < or = 10 s during the course of a 60-s trial.(ABSTRACT TRUNCATED AT 400 WORDS)
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Zheng, Xiaoyan, Lecheng Tian, Yan Qi, Xin Zhao et Dongxiao Lu. « Preparation and Characterization of Wheat Spike CuO Array Thin Film ». Nano 16, no 05 (29 avril 2021) : 2150057. http://dx.doi.org/10.1142/s1793292021500570.
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In this paper, the Cu/Cu2O/CuO three-phase coexistence system was obtained by one-step electrochemical deposition method, and CuO nanowheat spike array film was successfully prepared by annealing treatment eventually. Field emission scanning electron microscopy (FESEM) was used to characterize the growth evolution of the synthesized product by adjusting the concentration of copper acetate and the deposition time. The results showed that the concentration of copper acetate plays a key effect on the morphology of the sample. X-ray diffraction (XRD) results exhibited that the synthesized samples (Cu/Cu2O/CuO three-phase) have good crystallinity. With the increase of annealing temperature, the sample changed from Cu/Cu2O/CuO three-phase to CuO single-phase gradually. In addition, the UV–Vis, Nyquist plots and photoelectrochemical analysis were employed for characterization of the samples annealed at different temperatures. These studies showed that the samples annealed at 350∘C exhibit the best photoelectric properties.
Thèses sur le sujet "Spike phase/time analysis"
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TROMBIN, FEDERICA. « Mechanisms of ictogenesis in an experimental model of temporal lobe seizures ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/11032.
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Epilepsy is not a single disorder, but presents with a surrounding of symptoms that are not always of immediate identification and classification. About 50 million people worldwide have epilepsy. Seizures are more likely to occur in young children, or people over the age of 65 years.
The mainstay of treatment of epilepsy is preventive anticonvulsant medication with anti epileptic drugs (AED). Despite the proven efficacy of most of these drugs, it is estimated that over 30% of people with epilepsy do not reach complete seizure control, and this category of patients is eligible for surgical therapy. Among them, people suffering from focal seizure and in particular temporal lobe epilepsy are candidates for surgery. In recent years, surgical ablation of the epileptogenic focus has been rewarded as the best way to cure seizures in patients with intractable focal epilepsy.
Diagnostic scalp and intracranial stereo-EEG recordings can provide direct information from the epileptogenic focus and surrounding areas in order to circumscribe the zone to be surgically removed. Data obtained from the analysis of the patients' EEG brought to the identification of specific ictal patterns which in turn helped to better classify the already clinically defined seizure types. These patterns can be reproduced in animal models of epilepsy and/or seizures.
Focal seizures in the temporal lobe of the isolated in vitro guinea pig brain can be induced by perfusion of proconvulsant drugs. The electrophysiological recordings from the limbic structures of this animal model inform about the mechanisms leading to seizure onset (ictogenesis) and their progression. These phenomena are being studied both from a neuro-physiological and functional point of view; also histology and other anatomo-functional techniques give us a global idea of the activities occurring in different brain compartments during seizure-like events.
The ultimate goal of this research will be to further clarify the causes for which a focal seizure is generated and the regulatory mechanisms that govern the different patterns similar to those identified in humans.
Intracellular recordings from principal neurons in the superficial and deep layers of the entorhinal cortex showed a different involvement of these two regions in seizure initiation and development. We demonstrate that at seizure onset there is a strong activation of GABAergic interneuron (Gnatkovsky et al., 2008). This finding points to a primary role of GABAergic inhibition in seizure generation.
We further showed that slow potentials recorded during the first steps of ictal activity are a typical sign of modifications of ionic composition of the extracellular medium and describe very well the shape of low voltage shifts with fast activity (Trombin et al., in preparation).
Spikes shape identified by intracellular recordings during seizures was also analyzed to evaluate the epileptogenic network. The correlation of AP changes during seizures with the field potential and the increase in extracellular [K] clearly indicates both neuronal and non-neuronal processes, take place during the initiation and the termination of a seizure (Trombin et al, in preparation).
Taken together all these data point out a multi-factorial scenario in which inhibitory networks play a crucial role in seizure generation, in association with changes in glial function and extracellular homeostasis. The impairment of one of these elements can be a triggering event in the development of seizures (ictogenesis), and can start in turn a cascade of permanent modifications that maintain an hyper-excitability condition, leading to epileptogenesis. The precise knowledge of each passage needed to transform a normal tissue into an epileptogenic one is a fundamental achievement in order to recognize and classify the different syndromic manifestations of epilepsy. Further, the possibility to interfere with one of the above mentioned processes is of evident relevance for the modulation of seizure beginning and establishment.
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Na, Yu. « Stochastic phase dynamics in neuron models and spike time reliability ». Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7383.
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The present thesis is concerned with the stochastic phase dynamics of neuron models and spike time reliability. It is well known that noise exists in all natural systems, and some beneficial effects of noise, such as coherence resonance and noise-induced synchrony, have been observed. However, it is usually difficult to separate the effect of the nonlinear system itself from the effect of noise on the system's phase dynamics. In this thesis, we present a stochastic theory to investigate the stochastic phase dynamics of a nonlinear system. The method we use here, called ``the stochastic multi-scale method'', allows a stochastic phase description of a system, in which the contributions from the deterministic system itself and from the noise are clearly seen. Firstly, we use this method to study the noise-induced coherence resonance of a single quiescent ``neuron" (i.e. an oscillator) near a Hopf bifurcation. By calculating the expected values of the neuron's stochastic amplitude and phase, we derive analytically the dependence of the frequency of coherent oscillations on the noise level for different types of models. These analytical results are in good agreement with numerical results we obtained. The analysis provides an explanation for the occurrence of a peak in coherence measured at an intermediate noise level, which is a defining feature of the coherence resonance. Secondly, this work is extended to study the interaction and competition of the coupling and noise on the synchrony in two weakly coupled neurons. Through numerical simulations, we demonstrate that noise-induced mixed-mode oscillations occur due to the existence of multistability states for the deterministic oscillators with weak coupling. We also use the standard multi-scale method to approximate the multistability states of a normal form of such a weakly coupled system. Finally we focus on the spike time reliability that refers to the phenomenon: the repetitive application of a stochastic stimulus to a neuron generates spikes with remarkably reliable timing whereas repetitive injection of a constant current fails to do so. In contrast to many numerical and experimental studies in which parameter ranges corresponding to repetitive spiking, we show that the intrinsic frequency of extrinsic noise has no direct relationship with spike time reliability for parameters corresponding to quiescent states in the underlying system. We also present an ``energy" concept to explain the mechanism of spike time reliability. ``Energy" is defined as the integration of the waveform of the input preceding a spike. The comparison of ``energy" of reliable and unreliable spikes suggests that the fluctuation stimuli with higher ''energy" generate reliable spikes. The investigation of individual spike-evoking epochs demonstrates that they have a more favorable time profile capable of triggering reliably timed spike with relatively lower energy levels.
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Brinson, L. C. Knauss Wolfgang Gustav. « Time-temperature response of multi-phase viscoelastic solids through numerical analysis / ». Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-10292003-112909.
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Vannicola, Catherine Marie. « Analysis of medical time series data using phase space analysis a complex systems approach / ». Diss., Online access via UMI:, 2007.
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Thakkar, Kairavee K. « A Geometric Analysis of Time Varying Electroencephalogram Vectors ». University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613745734396658.
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Nasr, Walid. « Analysis and Approximations of Time Dependent Queueing Models ». Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26090.
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Developing equations to compute congestion measures for the general G/G/s/c queueing model and networks of such nodes has always been a challenge. One approach to analyzing such systems is to approximate the model-specified general input processes and distributions by processes and distributions from the more computationally friendly family of phase-type processes and distributions. We develop numerical approximation methods for analysis of general time-dependent queueing nodes by introducing new approximations for the time-dependent first two moments of the number-in-system and departure-count processes.Ph. D.
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Sole, Christopher J. « Analysis of Countermovement Vertical Jump Force-Time Curve Phase Characteristics in Athletes ». Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etd/2549.
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The purposes of this dissertation were to examine the phase characteristics of the countermovement jump force-time curve between athletes based on jumping ability, examine the influence of maximal muscular strength on the countermovement jump force-time curve phase characteristics of athletes, and to examine the behavior of the countermovement jump force-time curve phase characteristics over the course of a training process in athletes of varying strength levels. The following are the major findings of these dissertations. The analysis of athletes by jumping ability suggested that proficient jumpers are associated with greater relative phase magnitude and phase impulse throughout the phases contained in the positive impulse of the countermovement jump force-time curve. Additionally, phase duration was not found to differ between athletes based on jumping ability or between male and female athletes. The analysis of athletes based on maximal muscular strength suggested that only unweighted phase duration differs between strong and less-strong athletes. Interestingly, in both investigations based on jumping ability and maximal strength indicated the relative shape of the stretching phase representing the rise in positive force was related to an athlete’s jumping ability (jump height). The results of the longitudinal analysis of countermovement jump force-time phase characteristics identified that these variables can be frequently assessed throughout a training process to provide information of regarding an athlete performance state. Furthermore, based on the contrasting behaviors of many of the countermovement jump force-time curve phase characteristics over time, an athlete’s level of muscular strength may influence how these characteristics are expressed in the context of a training process.
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Malvestio, Irene. « Detection of directional interactions between neurons from spike trains ». Doctoral thesis, Universitat Pompeu Fabra, 2019. http://hdl.handle.net/10803/666226.
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An important problem in neuroscience is the assessment of the connectivity
between neurons from their spike trains. One recent approach developed for
the detection of directional couplings between dynamics based on recorded
point processes is the nonlinear interdependence measure L. In this thesis we
first use the Hindmarsh-Rose model system to test L in the presence of noise
and for different spiking regimes of the dynamics. We then compare the
performance of L against the linear cross-correlogram and two spike train
distances. Finally, we apply all measures to neuronal spiking data from an
intracranial whole-night recording of a patient with epilepsy. When applied
to simulated data, L proves to be versatile, robust and more sensitive than
the linear measures. Instead, in the real data the linear measures find more
connections than L, in particular for neurons in the same brain region and
during slow wave sleep.Un problema important en la neurociència és determinar la connexió entre neurones utilitzant dades dels seus trens d’impulsos. Un mètode recent que afronta la detecció de connexions direccionals entre dinàmiques utilitzant processos puntuals és la mesura d’interdependència no lineal L. En aquesta tesi, utilitzem el model de Hindmarsh-Rose per testejar L en presència de soroll i per diferents règims dinàmics. Després comparem el desempenyorament de L en comparació al correlograma lineal i a dues mesures de trens d’impulsos. Finalment, apliquem totes aquestes mesures a dades d’impulsos de neurones obtingudes de senyals intracranials electroencefalogràfiques gravades durant una nit a un pacient amb epilèpsia. Quan utilitzem dades simulades, L demostra que és versàtil, robusta i més sensible que les mesures lineals. En canvi, utilitzant dades reals, les mesures lineals troben més connexions que L, especialment entre neurones en la mateixa àrea del cervell i durant la fase de son d’ones lentes.
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Love, Christina Elena. « Design and Analysis for the DarkSide-10 Two-Phase Argon Time Projection Chamber ». Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/214821.
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PhysicsPh.D.
Astounding evidence for invisible "dark" matter has been found from galaxy clusters, cosmic and stellar gas motion, gravitational lensing studies, cosmic microwave background analysis, and large scale galaxy surveys. Although all studies indicate that there is a dominant presence of non-luminous matter in the universe (about 22 percent of the total energy density with 5 times more dark matter than baryonic matter), its identity and its "direct" detection (through non-gravitational effects) has not yet been achieved. Dark matter in the form of massive, weakly interacting particles (WIMPs) could be detected through their collisions with target nuclei. This requires detectors to be sensitive to very low-energy (less than 100 keV) nuclear recoils with very low expected rates (a few interactions per year per ton of target). Reducing the background in a direct dark matter detector is the biggest challenge. A detector capable of seeing such low-energy nuclear recoils is difficult to build because of the necessary size and the radio- and chemical- purity. Therefore it is imperative to first construct small-scale prototypes to develop the necessary technology and systems, before attempting to deploy large-scale detectors in underground laboratories. Our collaboration, the DarkSide Collaboration, utilizes argon in two-phase time projection chambers (TPCs). We have designed, built, and commissioned DarkSide-10, a 10 kg prototype detector, and are designing and building DarkSide-50, a 50 kg dark matter detector. The present work is an account of my contribution to these efforts. The two-phase argon TPC technology allows powerful discrimination between dark matter nuclear recoils and background events. Presented here are simulations, designs, and analyses involving the electroluminescence in the gas phase from extracted ionization charge for both DarkSide-10 and DarkSide-50. This work involves the design of the HHV systems, including field cages, that are responsible for producing the electric fields that drift, accelerate, and extract ionization electrons. Detecting the ionization electrons is an essential element of the background discrimination and gives event location using position reconstruction. Based on using COMSOL multiphysics software, the TPC electric fields were simulated. For DarkSide-10 the maximum radial displacement a drifting electron would undergo was found to be 0.2 mm and 1 mm for DarkSide-50. Using the electroluminescence signal from an optical Monte Carlo, position reconstruction in these two-phase argon TPCs was studied. Using principal component analysis paired with a multidimensional fit, position reconstruction resolution for DarkSide-10 was found to be less than 0.5 cm and less than 2.5 cm for DarkSide-50 for events occurring near the walls. DarkSide-10 is fully built and has gone through several campaigns of operation and upgrading both at Princeton University and in an underground laboratory (Gran Sasso National Laboratory in Assergi, Italy). Key DarkSide two-phase argon TPC technologies, such as a successful HHV system, have been demonstrated. Specific studies from DarkSide-10 data including analysis of the field homogeneity and the field dependence on the electroluminescence signal are reported here.
Temple University--Theses
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McCullough, Michael Paul. « Phase space reconstruction : methods in applied economics and econometrics / ». Online access for everyone, 2008. http://www.dissertations.wsu.edu/Dissertations/Spring2008/M_McCullough_122707.pdf.
Texte intégralLivres sur le sujet "Spike phase/time analysis"
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Lam, Alex W. Wavelet time-frequency analysis of phase-shift-key modulated signals. Monterey, Calif : Naval Postgraduate School, 1994.
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United States. National Aeronautics and Space Administration., dir. Doppler indices of gas phase formation in hypobaric environments : Time-intensity analysis. Houston, Tex : National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, 1991.
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Wang, Risheng. A phase-space approach to atmospheric dynamics based on observational data : Theory and applications. Berlin : D. Reimer, 1994.
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Time-frequency analysis and synthesis of linear signal spaces : Time-frequency filters, signal detection and estimation, and range-Doppler estimation. Boston : Kluwer Academic Publishers, 1998.
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Paulo, Ribeiro, dir. Time-varying waveform distortions in power systems. Chichester, West Sussex, U.K : Wiley, 2009.
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National Aeronautics and Space Administration (NASA) Staff. Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging. Independently Published, 2018.
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Liu, Mingyan, et Zongding Hu. Nonlinear Analysis and Prediction of Time Series in Multi-Phase Reactors. Springer, 2014.
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Ribeiro, Paulo F. Time-Varying Waveform Distortions in Power Systems. Wiley & Sons, Incorporated, John, 2009.
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Wendling, Fabrice, Marco Congendo et Fernando H. Lopes da Silva. EEG Analysis. Sous la direction de Donald L. Schomer et Fernando H. Lopes da Silva. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228484.003.0044.
Texte intégralRésumé :
This chapter addresses the analysis and quantification of electroencephalographic (EEG) and magnetoencephalographic (MEG) signals. Topics include characteristics of these signals and practical issues such as sampling, filtering, and artifact rejection. Basic concepts of analysis in time and frequency domains are presented, with attention to non-stationary signals focusing on time-frequency signal decomposition, analytic signal and Hilbert transform, wavelet transform, matching pursuit, blind source separation and independent component analysis, canonical correlation analysis, and empirical model decomposition. The behavior of these methods in denoising EEG signals is illustrated. Concepts of functional and effective connectivity are developed with emphasis on methods to estimate causality and phase and time delays using linear and nonlinear methods. Attention is given to Granger causality and methods inspired by this concept. A concrete example is provided to show how information processing methods can be combined in the detection and classification of transient events in EEG/MEG signals.
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Dawid, Herbert, Simon Gemkow, Philipp Harting, Sander van der Hoog et Michael Neugart. Agent-Based Macroeconomic Modeling and Policy Analysis. Sous la direction de Shu-Heng Chen, Mak Kaboudan et Ye-Rong Du. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780199844371.013.19.
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This chapter introduces the Eurace@Unibi model, one of the agent-based simulation models that are relatively new additions to the toolbox of macroeconomists, and the research that has been done within this framework. It shows how an agent-based model can be used to identify economic mechanisms and how it can be applied to spatial policy analysis. The assessment is that agent-based models in economics have passed the proof-of-concept phase and it is now time to move beyond that stage. It has been shown that new kinds of insights can be obtained that complement established modeling approaches. The chapter concludes by pointing toward some potentially fruitful areas of agent-based macroeconomic research.
Chapitres de livres sur le sujet "Spike phase/time analysis"
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Ashida, Go, Hermann Wagner et Catherine E. Carr. « Processing of Phase-Locked Spikes and Periodic Signals ». Dans Analysis of Parallel Spike Trains, 59–74. Boston, MA : Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-5675-0_4.
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Eggermont, Jos J. « Pair-Correlation in the Time and Frequency Domain ». Dans Analysis of Parallel Spike Trains, 77–102. Boston, MA : Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-5675-0_5.
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Tetzlaff, Tom, et Markus Diesmann. « Dependence of Spike-Count Correlations on Spike-Train Statistics and Observation Time Scale ». Dans Analysis of Parallel Spike Trains, 103–27. Boston, MA : Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-5675-0_6.
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Rao, T. Subba, et M. Yar. « Demodulation of phase modulated signals ». Dans Developments in Time Series Analysis, 414–24. Boston, MA : Springer US, 1993. http://dx.doi.org/10.1007/978-1-4899-4515-0_27.
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Chen, JingJie, et YongPing Zhang. « Fuel Consumption Estimation for Climbing Phase ». Dans Time Series Analysis and Forecasting, 231–43. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-96944-2_16.
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Halliday, David M., et Jay R. Rosenberg. « Time and Frequency Domain Analysis of Spike Train and Time Series Data ». Dans Modern Techniques in Neuroscience Research, 503–43. Berlin, Heidelberg : Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-58552-4_18.
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Krémé, A. Marina, Valentin Emiya et Caroline Chaux. « Phase Reconstruction for Time-Frequency Inpainting ». Dans Latent Variable Analysis and Signal Separation, 417–26. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-93764-9_39.
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Galán, Roberto F. « Cellular Mechanisms Underlying Spike-Time Reliability and Stochastic Synchronization : Insights and Predictions from the Phase-Response Curve ». Dans Phase Response Curves in Neuroscience, 237–55. New York, NY : Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0739-3_10.
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Oprisan, Sorinel Adrian. « Existence and Stability Criteria for Phase-Locked Modes in Ring Networks Using Phase-Resetting Curves and Spike Time Resetting Curves ». Dans Phase Response Curves in Neuroscience, 419–51. New York, NY : Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0739-3_17.
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Humphry, L. H. « Phase reconstruction for time-domain analysis of uncertain structures ». Dans IUTAM Symposium on the Vibration Analysis of Structures with Uncertainties, 255–67. Dordrecht : Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0289-9_19.
Texte intégralActes de conférences sur le sujet "Spike phase/time analysis"
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Ciampa, Francesco, et Michele Meo. « Imaging non-classical elastic nonlinearities using reciprocal time reversal and phase symmetry analysis ». Dans SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, sous la direction de Tribikram Kundu. SPIE, 2012. http://dx.doi.org/10.1117/12.915715.
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Grilli, Simonetta, Pietro Ferraro, Marella de Angelis, Sergio De Nicola, Domenico Alfieri, Melania Paturzo, Paolo De Natale, Lucia Sansone et Giovanni Pierattini. « Real-time phase-contrast analysis of domain switching in lithium niobate by digital holography ». Dans Optical Science and Technology, the SPIE 49th Annual Meeting, sous la direction de Katherine Creath et Joanna Schmit. SPIE, 2004. http://dx.doi.org/10.1117/12.560632.
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Zhong, Kai, Zhongwei Li, Yusheng Shi et Congjun Wang. « Analysis of solving the point correspondence problem by trifocal tensor for real-time phase measurement profilometry ». Dans SPIE Optical Engineering + Applications, sous la direction de Joanna Schmit, Katherine Creath, Catherine E. Towers et Jan Burke. SPIE, 2012. http://dx.doi.org/10.1117/12.929211.
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Krishnan, Shankar, et Suresh V. Garimella. « Thermal Management of Transient Power Spikes in Electronics : Phase Change Energy Storage or Copper Heat Sinks? ? » Dans ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35169.
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A transient thermal analysis is performed to investigate thermal control of power semiconductors using phase change materials, and to compare the performance of this approach to that of copper heat sinks. Both the melting of the phase change material under a transient power spike input, as well as the resolidification process, are considered. Phase change materials of different kinds (paraffin waxes and metallic alloys) are considered, with and without the use of thermal conductivity enhancers. Simple expressions for the melt depth, melting time and temperature distribution are presented in terms of the dimensions of the heat sink and the thermophysical properties of the phase change material, to aid in the design of passive thermal control systems. The simplified analytical expressions are verified against more complex numerical simulations, and are shown to be excellent tools for design calculations. The suppression of junction temperatures achieved by the use of phase change materials when compared to the performance with copper heat sinks is illustrated. Merits of employing phase change materials for pulsed power electronics cooling applications are discussed.
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Testorf, M. E., B. C. Jobst, J. K. Kleen, A. Titiz, S. Guillory, R. Scott, K. A. Bujarski, D. W. Roberts, G. L. Holmes et P. P. Lenck-Santini. « Joint time-frequency analysis of EEG signals based on a phase-space interpretation of the recording process ». Dans SPIE Optical Engineering + Applications, sous la direction de Philip J. Bones, Michael A. Fiddy et Rick P. Millane. SPIE, 2012. http://dx.doi.org/10.1117/12.930279.
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Lee, Minsuk, Youngjae Won, Byungjun Park et Seungrag Lee. « The study on the parallel processing based time series correlation analysis of RBC membrane flickering in quantitative phase imaging ». Dans SPIE BiOS, sous la direction de Gabriel Popescu et YongKeun Park. SPIE, 2017. http://dx.doi.org/10.1117/12.2253458.
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Tong, Zhiting, Feng Lin, Jingyi Chen et Chaoqun Nie. « The Self-Induced Unsteadiness of Tip Leakage Vortex and Its Effect on Compressor Stall Inception ». Dans ASME Turbo Expo 2007 : Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27010.
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The self-induced unsteadiness of tip leakage vortex (TLV), which appears in a compressor rotor working in a range of operating points on its characteristics, from wide-open throttle all the way to the stall limit, is investigated experimentally. The research aims are twofold, to clarify the three modes in TLV development process through experimental evidences and to explore the effect of this in-blade TLV unsteadiness on stall inception. In the first half of the paper, in order to detect the unsteadiness and ensure its existence in the experimental environment (not just in computational results), phase-locked Mean and Root-Mean-Square (RMS) contours are used to track the time-averaged trajectories of the TLV, while a power spectral density (PSD) analysis provides a means to identify the magnitude and the frequency of the oscillation. With all of the above, the three modes of the TLV development, which are steady, in-blade unsteady and cross-blade unsteady TLV, can be clearly demonstrated. In the second half of this paper, various tip jet injections are applied to test the effects of the unsteady TLV on stall inception. It is found that a spike stall precursor is originated from circumferential locations where the strongest unsteady TLV are. At those locations, tip jet injections that are designated to directly alter the characteristics of TLV improve the stall margin effectively. Further, the injections are arranged over the rotor tip in difference axial locations and switched on at different points of compressor characteristic, demonstrating that if the injection misses the tip vortices or interferes with TLV too late, little or even no improvement in stall margin can be gained. These results show that the unsteady TLV are closely related to spike stall inception in this single rotor, which implies that the initiation of compressor stall could be manipulated by properly altering the characteristics of TLV unsteadiness.
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Brusa, Eugenio G. M., Nicola Bosso, Nicolò Zampieri, Stefano Morsut et Maurizio Picciotto. « Electromechanical Coupled Response of the AC Electric Arc Furnace Structures During the Scrap Melting Process ». Dans ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82366.
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Prediction of structural dynamics of the Electric Arc Furnace (EAF) is rather difficult, because of a number of phenomena occurring during the scrap melting process. Three large electrodes, corresponding to each phase of a AC circuit, are lowered by the main mast towards the scrap to activate the melting process, induced by the electric arc. Electric current fed to each electrode produces a strong magnetic field and applies an electromechanical force on the other electrodes. Arc voltage looks irregular upon time, even because of the scrap motion within the vessel and temperature growth. The vertical position of the mast is controlled by an hydraulic actuator. Nevertheless, a heavy vibration of the structures affects the regularity of the melting process. A fully coupled model of the whole system is herein proposed, through a multi-physics approach. A first analytical approach, describing the electric circuit of the whole system, is implemented into a Multi Body Dynamics (MBD) model of the EAF, while a reduced Finite Element Method (FEM) model of the flexible structures is used for a preliminary optimization of the design parameters. Electromechanical forces due to the mutual induction among the electrodes are computed and the dynamic response of the system is investigated. Proposed model allows a first refinement of the EAF design, although a complete experimental validation on the real machine has to be performed, in spite of problems due the extremely difficult accessibility of structures during the melting process.
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Deacy, James S., Milind Rao, Sean Smith, Anthony J. Petrella, Peter J. Laz et Paul J. Rullkoetter. « Combined Rigid-Deformable Modeling of Lumbar Spine Mechanics ». Dans ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19672.
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Finite element (FE) models of the spine have been used to assess natural and pathological spine mechanics and evaluate performance of various fusion and posterior stabilization devices [1–3]; however, analysis times may be prohibitive for clinical and design phase assessments. Muscle-actuated, rigid body models have also been developed and used to estimate spinal loading conditions during simulated activities [4]. Although rigid body dynamics platforms typically require less computational time, they are unable to evaluate internal stresses and strains in deformable structures. This study proposes to develop a combined rigid – deformable surrogate spine model where the behavior of the intervertebral disc, facet cartilage and ligaments are replicated by simulated mechanical constraint at desired levels. The explicit FE platform is able to accommodate the spectrum of representations, including fully deformable, fully rigid body, implanted, or any combination. Accordingly, the objective of the current study was to assess the ability of a combined rigid-deformable spine model to accurately reproduce the behavior of the fully deformable representation in the natural state with improved computational efficiency. Specifically, this study compared results for a lumbar (L1-L5) spine under follower load and moment conditions for representations ranging from fully deformable to fully rigid. The combined rigid-deformable model includes the deformable disc, facet cartilage contact, ligament representations at L4-L5, while the other levels are modeled using a simplified mechanical constraint.
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Shimazaki, Hideaki, Shun-ichi Amari, Emery N. Brown et Sonja Grun. « State-space analysis on time-varying correlations in parallel spike sequences ». Dans ICASSP 2009 - 2009 IEEE International Conference on Acoustics, Speech and Signal Processing. IEEE, 2009. http://dx.doi.org/10.1109/icassp.2009.4960380.
Texte intégralRapports d'organisations sur le sujet "Spike phase/time analysis"
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Lam, Alex W. Wavelet Time-Frequency Analysis of Phase-Shift-Key Modulated Signals. Fort Belvoir, VA : Defense Technical Information Center, septembre 1994. http://dx.doi.org/10.21236/ada285791.
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Shishlo, Andrei, et Chun Wong. Time-of-Flight Calculations with Multiple Beam Phase Monitors : Calibration, Jitter Analysis & ; Energy Measurement. Office of Scientific and Technical Information (OSTI), avril 2022. http://dx.doi.org/10.2172/1864413.
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Soloviev, Vladimir, Oleksandr Serdiuk, Serhiy Semerikov et Arnold Kiv. Recurrence plot-based analysis of financial-economic crashes. [б. в.], octobre 2020. http://dx.doi.org/10.31812/123456789/4121.
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The article considers the possibility of analyzing the dynamics of changes in the characteristics of time series obtained on the basis of recurrence plots. The possibility of using the studied indicators to determine the presence of critical phenomena in economic systems is considered. Based on the analysis of economic time series of different nature, the suitability of the studied characteristics for the identification of critical phenomena is assessed. The description of recurrence diagrams and characteristics of time series that can be obtained on their basis is given. An analysis of seven characteristics of time series, including the coefficient of self-similarity, the coefficient of predictability, entropy, laminarity, is carried out. For the entropy characteristic, several options for its calculation are considered, each of which allows the one to get its own information about the state of the economic system. The possibility of using the studied characteristics as precursors of critical phenomena in economic systems is analyzed. We have demonstrated that the entropy analysis of financial time series in phase space reveals the characteristic recurrent properties of complex systems. The recurrence entropy methodology has several advantages compared to the traditional recurrence entropy defined in the literature, namely, the correct evaluation of the chaoticity level of the signal, the weak dependence on parameters. The characteristics were studied on the basis of daily values of the Dow Jones index for the period from 1990 to 2019 and daily values of oil prices for the period from 1987 to 2019. The behavior of recurrence entropy during critical phenomena in the stock markets of the USA, Germany and France was studied separately. As a result of the study, it was determined that delay time measure, determinism and laminarity can be used as indicators of critical phenomena. It turned out that recurrence entropy, unlike other entropy indicators of complexity, is an indicator and an early precursor of crisis phenomena. The ways of further research are outlined.
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Conrady, Morgan, Markus Bauer, Kyoo Jo, Donald Cropek et Ryan Busby. Solid-phase microextraction (SPME) for determination of geosmin and 2-methylisoborneol in volatile emissions from soil disturbance. Engineer Research and Development Center (U.S.), octobre 2021. http://dx.doi.org/10.21079/11681/42289.
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A method is described here for the concentration and determination of geosmin and 2-methylisoborneol (2-MIB) from the gaseous phase, with translation to field collection and quantification from soil disturbances in situ. The method is based on the use of solid-phase microextraction (SPME) fibers for adsorption of volatile chemicals from the vapor phase, followed by desorption into a gas chromatograph-mass spectrometer (GC-MS) for analysis. The use of a SPME fiber allows simple introduction to the GC-MS without further sample preparation. Several fiber sorbent types were studied and the 50/30 μm DVB/CAR/PDMS was the best performer to maximize the detected peak areas of both analytes combined. Factors such as extraction temperature and time along with desorption temperature and time were explored with respect to analyte recovery. An extraction temperature of 30 ◦C for 10 min, with a desorption temperature of 230 ◦C for 4 min was best for the simultaneous analysis of both geosmin and 2-MIB without complete loss of either one. The developed method was used successfully to measure geosmin and 2-MIB emission from just above disturbed and undisturbed soils, indicating that this method detects both compounds readily from atmospheric samples. Both geosmin and 2-MIB were present as background concentrations in the open air, while disturbed soils emitted much higher concentrations of both compounds. Surprisingly, 2-MIB was always detected at higher concentrations than geosmin, indicating that a focus on its detection may be more useful for soil emission monitoring and more sensitive to low levels of soil disturbance.
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Wagner, D. Ry, Eliezer Lifschitz et Steve A. Kay. Molecular Genetic Analysis of Flowering in Arabidopsis and Tomato. United States Department of Agriculture, mai 2002. http://dx.doi.org/10.32747/2002.7585198.bard.
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The primary objectives for the US lab included: the characterization of ELF3 transcription and translation; the creation and characterization of various transgenic lines that misexpress ELF3; defining genetic pathways related to ELF3 function regulating floral initiation in Arabidopsis; and the identification of genes that either interact with or are regulated by ELF3. Light quality, photoperiod, and temperature often act as important and, for some species, essential environmental cues for the initiation of flowering. However, there is relatively little information on the molecular mechanisms that directly regulate the developmental pathway from the reception of the inductive light signals to the onset of flowering and the initiation of floral meristems. The ELF3 gene was identified as possibly having a role in light-mediated floral regulation since elj3 mutants not only flower early, but exhibit light-dependent circadian defects. We began investigating ELF3's role in light signalling and flowering by cloning the ELF3 gene. ELF3 is a novel gene only present in plant species; however, there is an ELF3 homolog within Arabidopsis. The Arabidopsis elj3 mutation causes arrhythmic circadian output in continuous light; however, we show conclusively normal circadian function with no alteration of period length in elj3 mutants in dark conditions and that the light-dependent arrhythmia observed in elj3 mutants is pleiotropic on multiple outputs regardless of phase. Plants overexpressing ELF3 have an increased period length in constant light and flower late in long-days; furthermore, etiolated ELF3-overexpressing seedlings exhibit a decreased acute CAB2 response after a red light pulse, whereas the null mutant is hypersensitive to acute induction. This finding suggests that ELF3 negatively regulates light input to both the clock and its outputs. To determine whether ELF3's action is phase dependent, we examined clock resetting by light pulses and constructed phase response curves. Absence of ELF3 activity causes a significant alteration of the phase response curve during the subjective night, and overexpression of ELF3 results in decreased sensitivity to the resetting stimulus, suggesting that ELF3 antagonizes light input to the clock during the night. Indeed, the ELF3 protein interacts with the photoreceptor PHYB in the yeast two-hybrid assay and in vitro. The phase ofELF3 function correlates with its peak expression levels of transcript and protein in the subjective night. ELF3 action, therefore, represents a mechanism by which the oscillator modulates light resetting. Furthermore, flowering time is dependent upon proper expression ofELF3. Scientifically, we've made a big leap in the understanding of the circadian system and how it is coupled so tightly with light reception in terms of period length and clock resetting. Agriculturally, understanding more about the way in which the clock perceives and relays temporal information to pathways such as those involved in the floral transition can lead to increased crop yields by enabling plants to be grown in suboptimal conditions.
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Gelb, Jr., Jack, Yoram Weisman, Brian Ladman et Rosie Meir. Identification of Avian Infectious Brochitis Virus Variant Serotypes and Subtypes by PCR Product Cycle Sequencing for the Rational Selection of Effective Vaccines. United States Department of Agriculture, décembre 2003. http://dx.doi.org/10.32747/2003.7586470.bard.
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Objectives 1. Determine the serotypic identities of 40 recent IBV isolates from commercial chickens raised in the USA and Israel. 2. Sequence all IBV field isolates using PCR product cycle sequencing and analyze their S 1 sequence to detennine their homology to other strains in the Genbank and EMBL databases. 3. Select vaccinal strains with the highest S 1 sequence homology to the field isolates and perform challenge of immunity studies in chickens in laboratory trials to detennine level of protection afforded by the vaccines. Background Infectious bronchitis (IB) is a common, economically important disease of the chicken. IB occurs as a respiratory form, associated with airsacculitis, condemnation, and mortality of meat-type broilers, a reproductive form responsible for egg production losses in layers and breeders, and a renal form causing high mortality in broilers and pullets. The causative agent is avian coronavirus infectious bronchitis virus (IBV). Replication of the virus' RNA genome is error-prone and mutations commonly result. A major target for mutation is the gene encoding the spike (S) envelope protein used by the virus to attach and infect the host cell. Mutations in the S gene result in antigenic changes that can lead to the emergence of variant serotypes. The S gene is able to tolerate numerous mutations without compromising the virus' ability to replicate and cause disease. An end result of the virus' "flexibility" is that many strains of IBV are capable of existing in nature. Once formed, new mutant strains, often referred to as variants, are soon subjected to immunological selection so that only the most antigenically novel variants survive in poultry populations. Many novel antigenic variant serotypes and genotypes have been isolated from commercial poultry flocks. Identification of the field isolates of IBV responsible for outbreaks is critical for selecting the appropriate strain(s) for vaccination. Reverse transcriptase polymerase chain reaction (RT-PCR) of the Sl subunit of the envelope spike glycoprotein gene has been a common method used to identify field strains, replacing other time-consuming or less precise tests. Two PCR approaches have been used for identification, restriction fragment length polymorphism (RFLP) and direct automated cycle sequence analysis of a diagnostically relevant hypervariab1e region were compared in our BARD research. Vaccination for IB, although practiced routinely in commercial flocks, is often not protective. Field isolates responsible for outbreaks may be unrelated to the strain(s) used in the vaccination program. However, vaccines may provide varying degrees of cross- protection vs. unrelated field strains so vaccination studies should be performed. Conclusions RFLP and S1 sequence analysis methods were successfully performed using the field isolates from the USA and Israel. Importantly, the S1 sequence analysis method enabled a direct comparison of the genotypes of the field strains by aligning them to sequences in public databases e.g. GenBank. Novel S1 gene sequences were identified in both USA and Israel IBVs but greater diversity was observed in the field isolates from the USA. One novel genotype, characterized in this project, Israel/720/99, is currently being considered for development as an inactivated vaccine. Vaccination with IBV strains in the US (Massachusetts, Arkansas, Delaware 072) or in Israel (Massachusetts, Holland strain) provided higher degrees of cross-protection vs. homologous than heterologous strain challenge. In many cases however, vaccination with two strains (only studies with US strains) produced reasonable cross-protection against heterologous field isolate challenge. Implications S1 sequence analysis provides numerical similarity values and phylogenetic information that can be useful, although by no means conclusive, in developing vaccine control strategies. Identification of many novel S1 genotypes of IBV in the USA is evidence that commercial flocks will be challenged today and in the future with strains unrelated to vaccines. In Israel, monitoring flocks for novel IBV field isolates should continue given the identification of Israel/720/99, and perhaps others in the future. Strains selected for vaccination of commercial flocks should induce cross- protection against unrelated genotypes. Using diverse genotypes for vaccination may result in immunity against unrelated field strains.
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Tarko, Andrew P., Qiming Guo et Raul Pineda-Mendez. Using Emerging and Extraordinary Data Sources to Improve Traffic Safety. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317283.
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The current safety management program in Indiana uses a method based on aggregate crash data for conditions averaged over several-year periods with consideration of only major roadway features. This approach does not analyze the risk of crashes potentially affected by time-dependent conditions such as traffic control, operations, weather and their interaction with road geometry. With the rapid development of data collection techniques, time-dependent data have emerged, some of which have become available for safety management. This project investigated the feasibility of using emerging and existing data sources to supplement the current safety management practices in Indiana and performed a comprehensive evaluation of the quality of the new data sources and their relevance to traffic safety analysis. In two case studies, time-dependent data were acquired and integrated to estimate their effects on the hourly probability of crash and its severity on two selected types of roads: (1) rural freeways and (2) signalized intersections. The results indicate a considerable connection between hourly traffic volume, average speeds, and weather conditions on the hourly probability of crash and its severity. Although some roadway geometric features were found to affect safety, the lack of turning volume data at intersections led to some counterintuitive results. Improvements have been identified to be implemented in the next phase of the project to eliminate these undesirable results.
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Al-Qadi, Imad, Egemen Okte, Aravind Ramakrishnan, Qingwen Zhou et Watheq Sayeh. Truck Platooning on Flexible Pavements in Illinois. Illinois Center for Transportation, mai 2021. http://dx.doi.org/10.36501/0197-9191/21-010.
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Truck platoons have many benefits over traditional truck mobility. Truck platoons have the potential to improve safety and reduce fuel consumption between 5% and 15%, based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Therefore, expected fuel savings would be significant for trucks. Deployment of truck platoons within interstate highways may have a direct effect on flexible pavement performance, as the time between consecutive axle loads (i.e., resting time) is expected to decrease significantly. Moreover, platoons could potentially accelerate pavement damage accumulation due to trucks’ channelized position, decreasing pavement service life and increasing maintenance and rehabilitation costs. The main objective of this project was to quantify the effects of truck platoons on pavements and to provide guidelines to control corresponding potential pavement damage. Finite-element models were utilized to quantify the impact of rest period on pavement damage. Recovered and accumulated strains were predicted by fitting exponential functions to the calculated strain profiles. The results suggested that strain accumulation was negligible at a truck spacing greater that 10 ft. A new methodology to control pavement damage due to truck platoons was introduced. The method optimizes trucks’ lateral positions on the pavements, and an increase in pavement service life could be achieved if all platoons follow this optimization method. Life cycle assessment and life cycle cost analysis were conducted for fully autonomous, human-driven, and mixed-traffic regimes. For example, for an analysis period of 45 years, channelized truck platoons could save life cycle costs and environmental impacts by 28% and 21% compared with human-driven trucks, respectively. Furthermore, optimum truck platoon configuration could reduce life cycle costs and environmental impacts by 48% and 36%, respectively, compared with human-driven trucks. In contrast, channelized traffic could increase pavement roughness, increasing fuel consumption by 15%, even though platooning vehicles still benefit from reduction in air drag forces. Given that truck platoons are expected to be connected only in the first phase, no actions are required by the agency. However, in the second phase when truck platoons are also expected to be autonomous, a protocol for driving trends should be established per the recommendation of this study.
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Lam, Terence, et Keith Gale. Construction frameworks in the public sector : Do they deliver what they promise ? Property Research Trust, novembre 2021. http://dx.doi.org/10.52915/sbuk7331.
Texte intégralRésumé :
We demonstrate that the use of Performance Frameworks for the procurement of construction projects by public sector organizations in the UK (specifically, in England) leads to significantly improved outcomes in terms of time, cost, quality, sustainability and closer relationships, than the traditional ‘open tender’ approach of procuring discrete projects, individually. We identify the factors that lead to such improvements. We label these: supplier’s task performance factors (project staff, execution approach, competence of firm and structure of firm); supplier’s contextual performance factors (trust and collaboration, culture and conscious behaviour); and client’s organisational factors (incentives, performance monitoring, procurement approach and communication). And we offer a performance improvement model that will help project managers to select the most appropriate suppliers at the procurement phase, to achieve successful project outcomes. The model can also be used to drive project performance further, by adopting client’s organisational factors during the procurement and construction phases. By applying the research conclusions, suppliers will be able to focus on communicating their strengths in the relevant aspects of task and contextual performance for technical tender proposals, and so increase the value of their services and the probabilities of winning work. And the analysis can be used by policy makers to help in drafting regulations and legislation on formal frameworks, in ways that will improve the delivery of policy objectives.
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Delwiche, Michael, Boaz Zion, Robert BonDurant, Judith Rishpon, Ephraim Maltz et Miriam Rosenberg. Biosensors for On-Line Measurement of Reproductive Hormones and Milk Proteins to Improve Dairy Herd Management. United States Department of Agriculture, février 2001. http://dx.doi.org/10.32747/2001.7573998.bard.
Texte intégralRésumé :
The original objectives of this research project were to: (1) develop immunoassays, photometric sensors, and electrochemical sensors for real-time measurement of progesterone and estradiol in milk, (2) develop biosensors for measurement of caseins in milk, and (3) integrate and adapt these sensor technologies to create an automated electronic sensing system for operation in dairy parlors during milking. The overall direction of research was not changed, although the work was expanded to include other milk components such as urea and lactose. A second generation biosensor for on-line measurement of bovine progesterone was designed and tested. Anti-progesterone antibody was coated on small disks of nitrocellulose membrane, which were inserted in the reaction chamber prior to testing, and a real-time assay was developed. The biosensor was designed using micropumps and valves under computer control, and assayed fluid volumes on the order of 1 ml. An automated sampler was designed to draw a test volume of milk from the long milk tube using a 4-way pinch valve. The system could execute a measurement cycle in about 10 min. Progesterone could be measured at concentrations low enough to distinguish luteal-phase from follicular-phase cows. The potential of the sensor to detect actual ovulatory events was compared with standard methods of estrus detection, including human observation and an activity monitor. The biosensor correctly identified all ovulatory events during its testperiod, but the variability at low progesterone concentrations triggered some false positives. Direct on-line measurement and intelligent interpretation of reproductive hormone profiles offers the potential for substantial improvement in reproductive management. A simple potentiometric method for measurement of milk protein was developed and tested. The method was based on the fact that proteins bind iodine. When proteins are added to a solution of the redox couple iodine/iodide (I-I2), the concentration of free iodine is changed and, as a consequence, the potential between two electrodes immersed in the solution is changed. The method worked well with analytical casein solutions and accurately measured concentrations of analytical caseins added to fresh milk. When tested with actual milk samples, the correlation between the sensor readings and the reference lab results (of both total proteins and casein content) was inferior to that of analytical casein. A number of different technologies were explored for the analysis of milk urea, and a manometric technique was selected for the final design. In the new sensor, urea in the sample was hydrolyzed to ammonium and carbonate by the enzyme urease, and subsequent shaking of the sample with citric acid in a sealed cell allowed urea to be estimated as a change in partial pressure of carbon dioxide. The pressure change in the cell was measured with a miniature piezoresistive pressure sensor, and effects of background dissolved gases and vapor pressures were corrected for by repeating the measurement of pressure developed in the sample without the addition of urease. Results were accurate in the physiological range of milk, the assay was faster than the typical milking period, and no toxic reagents were required. A sampling device was designed and built to passively draw milk from the long milk tube in the parlor. An electrochemical sensor for lactose was developed starting with a three-cascaded-enzyme sensor, evolving into two enzymes and CO2[Fe (CN)6] as a mediator, and then into a microflow injection system using poly-osmium modified screen-printed electrodes. The sensor was designed to serve multiple milking positions, using a manifold valve, a sampling valve, and two pumps. Disposable screen-printed electrodes with enzymatic membranes were used. The sensor was optimized for electrode coating components, flow rate, pH, and sample size, and the results correlated well (r2= 0.967) with known lactose concentrations.