Articles de revues : « 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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.

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Noyama, Hiroki, Yuto Yoshikai, Kiyoshi Kotani et Yasuhiko Jimbo. « Mathematical Analysis of Multiple Spike Time Series Synchronized in Phase with Collective Theta Wave Using Neural Cell Model ». IEEJ Transactions on Electronics, Information and Systems 140, n^o 9 (1 septembre 2020) : 1050–56. http://dx.doi.org/10.1541/ieejeiss.140.1050.

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Xu, Datao, Xinyan Jiang, Xuanzhen Cen, Julien S. Baker et Yaodong Gu. « Single-Leg Landings Following a Volleyball Spike May Increase the Risk of Anterior Cruciate Ligament Injury More Than Landing on Both-Legs ». Applied Sciences 11, n^o 1 (25 décembre 2020) : 130. http://dx.doi.org/10.3390/app11010130.

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Volleyball players often land on a single leg following a spike shot due to a shift in the center of gravity and loss of balance. Landing on a single leg following a spike may increase the probability of non-contact anterior cruciate ligament (ACL) injuries. The purpose of this study was to compare and analyze the kinematics and kinetics differences during the landing phase of volleyball players using a single leg (SL) and double-leg landing (DL) following a spike shot. The data for vertical ground reaction forces (VGRF) and sagittal plane were collected. SPM analysis revealed that SL depicted a smaller knee flexion angle (about 13.8°) and hip flexion angle (about 10.8°) during the whole landing phase, a greater knee and hip power during the 16.83–20.45% (p = 0.006) and 13.01–16.26% (p = 0.008) landing phase, a greater ankle plantarflexion angle and moment during the 0–41.07% (p < 0.001) and 2.76–79.45% (p < 0.001) landing phase, a greater VGRF during the 5.87–8.25% (p = 0.029), 19.75–24.14% (p = 0.003) landing phase when compared to DL. Most of these differences fall within the time range of ACL injury (30–50 milliseconds after landing). To reduce non-contact ACL injuries, a landing strategy of consciously increasing the hip and knee flexion, and plantarflexion of the ankle should be considered by volleyball players.

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Blackburn, C. C., et M. B. Sachs. « Classification of unit types in the anteroventral cochlear nucleus : PST histograms and regularity analysis ». Journal of Neurophysiology 62, n^o 6 (1 décembre 1989) : 1303–29. http://dx.doi.org/10.1152/jn.1989.62.6.1303.

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1. The responses of neurons in the anteroventral cochlear nucleus (AVCN) of barbiturate-anesthetized cats are characterized with regard to features of their responses to short tone bursts (STBs; 25 ms). A "decision tree" is presented to partition AVCN units on the basis of post-stimulus time histogram (PSTH) shape, first spike latency, and discharge rate and regularity calculated as functions of time during responses to STBs. The major classes of AVCN units (primary-like, primary-like-with-notch, chopper, and onset) have been described previously; in this paper, special attention is given to clarifying and systematizing boundaries between classes. Certain types of "unusual" units that may be confused with units in one of the major classes are also examined. 2. When STBs are presented synchronously (constant phase at onset), PSTHs of responses to very-low-frequency (less than 1.0 kHz) tones are difficult if not impossible to resolve into the classes listed above because all unit types phase-lock to low-frequency tones. However, when STBs are presented asynchronously, the responses of units with low best frequencies can be categorized on the basis of PSTH shape and first spike latency. 3. Primary-like, primary-like-with-notch, and onset units are distinguished primarily on the basis of PSTH shape. These three unit types have comparable minimum first spke latencies and synchronization to tones. One type of "unusual" response poses a particular hazard with respect to the generation of uncontaminated primary-like populations. Such "unusual" units have PSTHs that appear primary-like; these units are, however, distinguished by their unusually long first spike latencies. Unlike primary-like units, these "unusual" units show extremely poor synchronization to tones. 4. Chopper units are defined as having an initial response that is highly regular, resulting in the characteristic multimodal PSTH. "Unusual" units with multimodal PSTHs but whose initial responses are not highly regular (measured by the reproducibility of the initial firing pattern in response to multiple repetitions of a STB) are eliminated from the chopper populations. 5. In barbiturate-anesthetized cats, at least three patterns of chopper response can be distinguished on the basis of temporal patterns of rate and regularity adaptation. "Sustained" choppers show no adaptation of instantaneous rate (measured by the inverse of the mean interspike interval), and their discharge remains highly regular throughout the response. "Transiently adapting" choppers undergo a very rapid (less than 10 ms) decrease in instantaneous rate accompanied by a sharp increase in discharge irregularity.(ABSTRACT TRUNCATED AT 400 WORDS)

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Yassine, M., F. Piron, R. Mochkovitch et F. Daigne. « Time evolution of the spectral break in the high-energy extra component of GRB 090926A ». Astronomy & ; Astrophysics 606 (octobre 2017) : A93. http://dx.doi.org/10.1051/0004-6361/201630353.

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Aims. The prompt light curve of the long GRB 090926A reveals a short pulse ~10 s after the beginning of the burst emission, which has been observed by the Fermi observatory from the keV to the GeV energy domain. During this bright spike, the high-energy emission from GRB 090926A underwent a sudden hardening above 10 MeV in the form of an additional power-law component exhibiting a spectral attenuation at a few hundreds of MeV. This high-energy break has been previously interpreted in terms of gamma-ray opacity to pair creation and has been used to estimate the bulk Lorentz factor of the outflow. In this article, we report on a new time-resolved analysis of the GRB 090926A broadband spectrum during its prompt phase and on its interpretation in the framework of prompt emission models. Methods. We characterized the emission from GRB 090926A at the highest energies with Pass 8 data from the Fermi Large Area Telescope (LAT), which offer a greater sensitivity than any data set used in previous studies of this burst, particularly in the 30−100 MeV energy band. Then, we combined the LAT data with the Fermi Gamma-ray Burst Monitor (GBM) in joint spectral fits to characterize the time evolution of the broadband spectrum from keV to GeV energies. We paid careful attention to the systematic effects that arise from the uncertainties on the LAT response. Finally, we performed a temporal analysis of the light curves and we computed the variability timescales from keV to GeV energies during and after the bright spike. Results. Our analysis confirms and better constrains the spectral break, which has been previously reported during the bright spike. Furthermore, it reveals that the spectral attenuation persists at later times with an increase of the break characteristic energy up to the GeV domain until the end of the prompt phase. We discuss these results in terms of keV−MeV synchroton radiation of electrons accelerated during the dissipation of the jet energy and inverse Compton emission at higher energies. We interpret the high-energy spectral break as caused by photon opacity to pair creation. Requiring that all emissions are produced above the photosphere of GRB 090926A, we compute the bulk Lorentz factor of the outflow, Γ. The latter decreases from 230 during the spike to 100 at the end of the prompt emission. Assuming, instead, that the spectral break reflects the natural curvature of the inverse Compton spectrum, lower limits corresponding to larger values of Γ are also derived. Combined with the extreme temporal variability of GRB 090926A, these Lorentz factors lead to emission radii R ~ 1014 cm, which are consistent with an internal origin of both the keV−MeV and GeV prompt emissions.

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Machonis, Philip R., Matthew A. Jones et Catherine Kwik-Uribe. « Analysis of Cocoa Flavanols and Procyanidins (DP 1–10) in Cocoa-Containing Ingredients and Products by Rapid Resolution Liquid Chromatography : Single-Laboratory Validation ». Journal of AOAC INTERNATIONAL 97, n^o 1 (1 janvier 2014) : 166–72. http://dx.doi.org/10.5740/jaoacint.13-034.

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Abstract Recently, a multilaboratory validation (MLV) of AOAC Official Method 2012.24 for the determination of cocoa flavanols and procyanidins (CF-CP) in cocoa-based ingredients and products determinedthat the method was robust, reliable, and transferrable. Due to the complexity of the CF-CP molecules, this method required a run time exceeding 1 h to achieve acceptable separations. To address this issue, a rapid resolution normal phase LC method was developed, and a single-laboratory validation (SLV) study conducted. Flavanols and procyanidins with a degree of polymerization (DP) up to 10 were eluted in 15 min using a binary gradient applied to a diol stationary phase, detected using fluorescence detection, and reported as a totalsum of DP 1–10. Quantification was achieved using (-)-epicatechin-based relative response factors for DP 2–10. Spike recovery samplesand seven different types of cocoa-based samples were analyzed to evaluate the accuracy, precision, LOD, LOQ, and linearity of the method. The within-day precision of the reported content for the samples was 1.15–5.08%, and overall precision was 3.97–13.61%. Spike-recovery experiments demonstrated recoveries of over 98%. The results of this SLV were compared to those previously obtained in the MLV and found to be consistent. The translation to rapid resolution LC allowed for an 80% reduction in analysis time and solventusage, while retaining the accuracy and reliability of the original method. The savings in both cost and time of this rapid method make it well-suited for routine laboratory use.

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Roddey, J. C., et G. A. Jacobs. « Information theoretic analysis of dynamical encoding by filiform mechanoreceptors in the cricket cercal system ». Journal of Neurophysiology 75, n^o 4 (1 avril 1996) : 1365–76. http://dx.doi.org/10.1152/jn.1996.75.4.1365.

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1. The stimulus/response properties of 20 mechanosensory receptors in the cricket cercal sensory system were studied using electrophysiological techniques. These receptors innervated filiform hairs of various lengths and directional selectivities. Previous studies have characterized the sensitivity of such cells to the direction of air currents and to the amplitude of sinusoidal stimuli. In the experiments reported here, the quantity and quality of information encoded in the receptors' elicited responses about the dynamics of more complex air current waveforms were characterized. 2. Based on a white analysis of receptor response properties, the median frequency of each receptor's frequency tuning curve was found to be strongly correlated with the length of its associated mechanosensory hair. The receptors connected to hairs > 900 microns encoded frequencies below approximately 150 Hz very accurately and the receptors connected to shorter hairs encoded progressively higher bands of frequencies. These results were interpreted within the constraints imposed by the biomechanics of the air current-to-cercus boundary. 3. The encoding accuracy was expressed in the information theoretic units of bits/second, which characterizes the information transmission rate of a receptor. The information rates of the neuronal spike trains ranged from 75 to 220 bits/s. The information transmission rate was not correlated with the length of the mechanosensory hair. The average amount of information transmitted per action potential was negatively correlated with receptor hair length and ranged between 0.6 and 3.1 bits/spike. Decoding of the receptor responses was restricted to linear transformations of the spike trains. 4. The stimulus/response latencies of the different receptors ranged between 5 and 11 ms, and the integration time of the receptors ranged between 8 and 30 ms. The latency of a receptor was only weakly correlated with the length of its associated hair, and a receptor's integration time was correlated with hair length. 5. The stimulus/response phase difference for receptor cells that innervated hairs longer than approximately 800 microns increased with frequency > 50 Hz. The phase responses for receptor cells connected to hairs < 800 microns did not vary for frequencies > 50 Hz.

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Rekling, J. C., J. Champagnat et M. Denavit-Saubie. « Electroresponsive properties and membrane potential trajectories of three types of inspiratory neurons in the newborn mouse brain stem in vitro ». Journal of Neurophysiology 75, n^o 2 (1 février 1996) : 795–810. http://dx.doi.org/10.1152/jn.1996.75.2.795.

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1. The electrophysiological properties of inspiratory neurons were studied in a rhythmically active thick-slice preparation of the newborn mouse brain stem maintained in vitro. Whole cell patch recordings were performed from 60 inspiratory neurons within the rostral ventrolateral part of the slice with the aim of extending the classification of inspiratory neurons to include analysis of active membrane properties. 2. The slice generated a regular rhythmic motor output recorded as burst of action potentials on a XII nerve root with a peak to peak time of 11.5 +/- 3.4 s and a duration of 483 +/- 54 ms (means +/- SD, n = 50). Based on the electroresponsive properties and membrane potential trajectories throughout the respiratory cycle, three types of inspiratory neurons could be distinguished. 3. Type-1 neurons were spiking in the interval between the inspiratory potentials (n = 9) or silent with a resting membrane potential of -48.6 +/- 10.1 mV and an input resistance of 306 +/- 130 M omega (n = 15). The spike activity between the inspiratory potentials was burst-like with spikes riding on top of an underlying depolarization (n = 11) or regular with no evidence of bursting (n = 12). Hyperpolarization of the neurons below threshold for spike initiation did not reveal any underlying phasic synaptic activity, that could explain the bursting behavior. 4. Type-1 neurons showed delayed excitation after hyperpolarizing square current pulses or when the neurons were depolarized from a hyperpolarized level. This membrane behavior resembles the response seen in other CNS neurons expressing an IA. The response to 1-s long depolarizing pulses with a large current strength showed signs of activation of an active depolarizing membrane response leading to a transient reduction in the spike amplitude. The relationship between the membrane potential and the amplitude of square current pulses (Vm-I) showed a small upward rectification below -70 mV, and spike adaptation throughout a 1-s pulse had a largely linear time course. 5. Type-1 neurons depolarized and started to fire spikes 398 +/- 102 ms (n = 20) before the upstroke of the integrated XII nerve discharge. The inspiratory potential was followed by fast hyperpolarization, a short fast-repolarizing phase (1,040 +/- 102 ms, n = 5) and a longer slow-repolarizing phase (lasting until the next inspiratory discharge). 6. Type-2 neurons were spiking in the interval between the inspiratory potentials with no evidence of bursting behavior and had an input resistance of 296 +/- 212 M omega (n = 26). The response to hyperpolarizing pulses revealed an initial sag and postinhibitory rebound depolarization. This membrane behavior resembles the response seen in other CNS neurons expressing an Ih. The Vm-I relationship was linear at depolarized potentials and showed a marked upward rectification below -60 mV. Spike trains elicited by 1-s long pulses showed a pronounced early and late adaptation. 7. Type-2 neurons depolarized and started to fire spikes 171 +/- 87 ms (n = 23) before the upstroke of the integrated XII nerve discharge. The inspiratory potential had a variable amplitude from cell to cell and was followed by a short hyperpolarization in the cells displaying a large amplitude inspiratory potential.(ABSTRACT TRUNCATED AT 250 WORDS)

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Bazaliiskii, V. I., A. A. Tyutrin et A. W. Weber. « Morphological Analysis of the Bone Serrated Points from Early Neolithic Complexes of Shamanka 2 Burial Ground ». Bulletin of the Irkutsk State University. Geoarchaeology, Ethnology, and Anthropology Series 35 (2021) : 17–51. http://dx.doi.org/10.26516/2227-2380.2021.35.17.

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An analysis of the bone serrated points from the burial complexes of Shamanka 2 burial ground is presented. The origin of the collection makes it “ritual”, which may explain the large number of undamaged items. Several spikes have been broken intentionally at the time of their interment. Supposedly, several points have been specifically made for interment. In accordance with the morphological analysis, we have identified two groups of serrated spikes: (I) detachable tools and (II) non-detachable tools. Differences in structural elements of the stopper-line determine 7 types of harpoons (95 items), and variations in base structure define 2 types of points of leisters, javelins, spears etc. (6 items), while 15 fragments of blade were excluded from the analysis. Harpoons of the Type I-1 and Type I-2 are divided into 9 varieties, in accordance with structural elements of the blade. Harpoons of the Type I-3 are divided into 2 subtypes due to differences in structural elements of the shaft. Harpoons of the I-4 – I-7 types are represented by only 1 item for each type and are considered to be individual tools. Group I (harpoons) consist mostly of tools with an orifice for line lashing (89 items). Harpoons that feature stopper-line structural elements without through hole are represented here by only 6 items. II-2 type points with a unilaterally beveled base represent most non-detachable barbed tools – 5 items. II-1 type points with a wedgelike base (in a profile) consist of only 1 item. The designated types and varieties of Shamanka II cemetery barbed spikes correlate with items from different synchronous and asynchronous sites of both bordering and substantially remote regions. Serrated points are found mainly in male burials but absent in children's burials. Chronologically, 111 barbed spikes relate to the Phase 1 of the Shamanka 2 cemetery functioning. Five more spikes were recorded in 3 burials of the Phase 2. Barbed spikes of the chronological Phase 2 are represented with 4 items of the I-1.4 variety from burials No. 108-1 and 64-2, as well as 1 item of the I-2-1 variety from a grave No. 49. The last artifact probably represents an ideal model of two-row harpoons with symmetrically situated barbs and a sword-like spike. Harpoons with a curved blade (Type I-1.4) were registered only in burials of the chronological Phase 2. The barbed spikes of the I-1 and I-2 types, which feature a stopper-line with through holes and lateral projections, correlate with a definition of harpoons of the Kitoi type.

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Jansen, Rene F., Anton W. Pieneman et Andries ter Maat. « Pattern Generation in the Buccal System of Freely BehavingLymnaea stagnalis ». Journal of Neurophysiology 82, n^o 6 (1 décembre 1999) : 3378–91. http://dx.doi.org/10.1152/jn.1999.82.6.3378.

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Central pattern generators (CPGs) are neuronal circuits that drive active repeated movements such as walking or swimming. Although CPGs are, by definition, active in isolated central nervous systems, sensory input is thought play an important role in adjusting the output of the CPGs to meet specific behavioral requirements of intact animals. We investigated, in freely behaving snails ( Lymnaea stagnalis), how the buccal CPG is used during two different behaviors, feeding and egg laying. Analysis of the relationship between unit activity recorded from buccal nerves and the movements of the buccal mass showed that electrical activity in laterobuccal/ventrobuccal (LB/VB) nerves was as predicted from in vitro data, but electrical activity in the posterior jugalis nerve was not. Autodensity and interval histograms showed that during feeding the CPG produces a much stronger rhythm than during egg laying. The phase relationship between electrical activity and buccal movement changed little between the two behaviors. Fitting the spike trains recorded during the two behaviors with a simple model revealed differences in the patterns of electrical activity produced by the buccal system during the two behaviors investigated. During egg laying the bursts contained less spikes, and the number of spikes per burst was significantly more variable than during feeding. The time between two bursts of in a spike train was longer during egg laying than during feeding. The data show what the qualitative and quantitative differences are between two motor patterns produced by the buccal system of freely behaving Lymnaea stagnalis.

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Abbasi, Hamid, Alistair J. Gunn, Laura Bennet et Charles P. Unsworth. « Latent Phase Identification of High-Frequency Micro-Scale Gamma Spike Transients in the Hypoxic Ischemic EEG of Preterm Fetal Sheep Using Spectral Analysis and Fuzzy Classifiers ». Sensors 20, n^o 5 (5 mars 2020) : 1424. http://dx.doi.org/10.3390/s20051424.

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Premature babies are at high risk of serious neurodevelopmental disabilities, which in many cases are related to perinatal hypoxic–ischemic encephalopathy (HIE). Studies of neuroprotection in animal models consistently suggest that treatment must be started as early as possible in the first 6 h after hypoxia–ischemia (HI), the so-called latent phase before secondary deterioration, to improve outcomes. We have shown in preterm sheep that EEG biomarkers of injury, in the form of high-frequency micro-scale spike transients, develop and evolve in this critical latent phase after severe asphyxia. Real-time automatic identification of such events is important for the early and accurate detection of HI injury, so that the right treatment can be implemented at the right time. We have previously reported successful strategies for accurate identification of EEG patterns after HI. In this study, we report an alternative high-performance approach based on the fusion of spectral Fourier analysis and Type-I fuzzy classifiers (FFT-Type-I-FLC). We assessed its performance in over 2520 min of latent phase EEG recordings from seven asphyxiated in utero preterm fetal sheep exposed to a range of different occlusion periods. The FFT-Type-I-FLC classifier demonstrated 98.9 ± 1.0% accuracy for identification of high-frequency spike transients in the gamma frequency band (namely 80–120 Hz) post-HI. The spectral-based approach (FFT-Type-I-FLC classifier) has similar accuracy to our previous reverse biorthogonal wavelets rbio2.8 basis function and type-1 fuzzy classifier (rbio-WT-Type-1-FLC), providing competitive performance (within the margin of error: 0.89%), but it is computationally simpler and would be readily adapted to identify other potentially relevant EEG waveforms.

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Koželj, Saša, et Stuart N. Baker. « Different phase delays of peripheral input to primate motor cortex and spinal cord promote cancellation at physiological tremor frequencies ». Journal of Neurophysiology 111, n^o 10 (15 mai 2014) : 2001–16. http://dx.doi.org/10.1152/jn.00935.2012.

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Neurons in the spinal cord and motor cortex (M1) are partially phase-locked to cycles of physiological tremor, but with opposite phases. Convergence of spinal and cortical activity onto motoneurons may thus produce phase cancellation and a reduction in tremor amplitude. The mechanisms underlying this phase difference are unknown. We investigated coherence between spinal and M1 activity with sensory input. In two anesthetized monkeys, we electrically stimulated the medial, ulnar, deep radial, and superficial radial nerves; stimuli were timed as independent Poisson processes (rate 10 Hz). Single units were recorded from M1 (147 cells) or cervical spinal cord (61 cells). Ninety M1 cells were antidromically identified as pyramidal tract neurons (PTNs); M1 neurons were additionally classified according to M1 subdivision (rostral/caudal, M1r/c). Spike-stimulus coherence analysis revealed significant coupling over a broad range of frequencies, with the strongest coherence at <50 Hz. Delays implied by the slope of the coherence phase-frequency relationship were greater than the response onset latency, reflecting the importance of late response components for the transmission of oscillatory inputs. The spike-stimulus coherence phase over the 6–13 Hz physiological tremor band differed significantly between M1 and spinal cells (phase differences relative to the cord of 2.72 ± 0.29 and 1.72 ± 0.37 radians for PTNs from M1c and M1r, respectively). We conclude that different phases of the response to peripheral input could partially underlie antiphase M1 and spinal cord activity during motor behavior. The coordinated action of spinal and cortical feedback will act to reduce tremulous oscillations, possibly improving the overall stability and precision of motor control.

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LONGTIN, ANDRÉ. « NONLINEAR FORECASTING OF SPIKE TRAINS FROM SENSORY NEURONS ». International Journal of Bifurcation and Chaos 03, n^o 03 (juin 1993) : 651–61. http://dx.doi.org/10.1142/s0218127493000556.

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The sequence of firing times of a neuron can be viewed as a point process. The problem of spike train analysis is to infer the underlying neural dynamics from this point process when, for example, one does not have access to a state variable such as intracellular voltage. Traditional analyses of spike trains have focussed to a large extent on fitting the parameters of a model stochastic point process to the data, such as the intensity of a homogeneous Poisson point process. This paper shows how methods from nonlinear time series analysis can be used to gain knowledge about correlations between the spiking events recorded from periodically driven sensory neurons. Results on nonlinear forecastability of these spike trains are compared to those on data sets derived from the original data set and satisfying an appropriately chosen null hypothesis. While no predictability, linear or nonlinear, is revealed by our analysis of the raw data using local linear predictors, it appears that there is some predictability in the successive phases (rather than intervals) at which the neurons fire.

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Lee, Jia-You, Jheng-Hung Chen et Kuo-Yuan Lo. « An Interleaved Phase-Shift Full-Bridge Converter with Dynamic Dead Time Control for Server Power Applications ». Energies 14, n^o 4 (6 février 2021) : 853. http://dx.doi.org/10.3390/en14040853.

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A compact and high-efficiency power converter is the main business of today’s power industry for server power applications. To achieve high efficiency with a low-output ripple, an interleaved phase-shift full-bridge (PSFB) converter is designed, built, and tested for server power applications in this study. In this paper, dynamic dead time control is proposed to reduce the switching loss in the light load condition. The proposed technique reduces the turn-off switching loss and allows a wide range of zero-voltage switching. Moreover, the current ripple of the output inductor can be reduced with the interleaved operation. To verify the theoretical analysis, the proposed PSFB converter is simulated, and a 3 kW prototype is constructed. The experimental results confirm that the conversion efficiency is as high as 97.2% at the rated power of 3 kW and 92.95% at the light load of 300 W. The experimental transient waveforms demonstrated that the voltage spike or drop is less than 2 V in the fast-fluctuating load conditions from 0% load to 60% load and 40% load to 100% load.

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Lou, J. S., et J. R. Bloedel. « Responses of sagittally aligned Purkinje cells during perturbed locomotion : relation of climbing fiber activation to simple spike modulation ». Journal of Neurophysiology 68, n^o 5 (1 novembre 1992) : 1820–33. http://dx.doi.org/10.1152/jn.1992.68.5.1820.

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1. The purpose of these experiments is to test the hypothesis that the synchronous activation of sagittally aligned Purkinje cells by a physiologically relevant stimulus is associated with an increase in the simple spike responses of the same neurons. 2. This hypothesis was tested using a perturbed locomotion paradigm in decerebrate locomoting ferrets. The responses of 3-5 sagittally aligned Purkinje cells were recorded simultaneously in response to the intermittent perturbation of the forelimb during swing phase. A data analysis is introduced, the real time postsynaptic response (RTPR), that permits the quantification of the simple spike responses of Purkinje cells in a manner that can be related to their complex spike responses on a trial-by-trial basis. 3. The data support the above hypothesis by illustrating that the amplitude of the combined simple spike responses across the population of Purkinje cells is correlated with the extent to which their climbing fiber inputs are synchronously activated. These findings together with an analysis of the gain-change ratio support the view that the synchronous climbing fiber input may be responsible for mediating this increased responsiveness. 4. More generally, the data suggest that the task- and/or behaviorally dependent activation of sagittal strips of climbing fiber inputs may provide a mechanism whereby the responsiveness of discrete populations of Purkinje cells can be selectively regulated, specifying the groups of neurons that will be most dramatically modulated by mossy fiber inputs activated by the same conditions.

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Barrio, L. C., A. Araque, V. Abraira et W. Buno. « Intracellular analysis of excitatory-inhibitory synaptic interactions in crayfish stretch receptors ». Journal of Neurophysiology 66, n^o 3 (1 septembre 1991) : 894–904. http://dx.doi.org/10.1152/jn.1991.66.3.894.

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1. To determine the membrane mechanisms underlying the interactions between inhibitory postsynaptic potentials (IPSPs) and excitatory inputs, we investigated, at the membrane potential level, the combined influences of low-frequency (0.05-0.50 Hz) imposed sinusoidal transmembrane currents (termed sine currents), representing the excitatory drive, and trains of regular (3-30/s) IPSPs. The two simplest possible neuron systems exemplified by the slowly and rapidly adapting stretch receptors of crayfish (RM1 and RM2, respectively) were used. 2. At constant elongation the RM1 and RM2 behaved as a pacemaker and a neuron without self-sustained oscillations, respectively, but in dynamic conditions uninhibited controls and IPSP sine current interactions were essentially identical in both RMs. Controls showed the usual smooth variation of the RM firing rate in response to the gradually varying excitatory input. IPSP effects were characterized by the expected overall reduction of the postsynaptic firing rate. More important, special effects were also present, such as the simple fixed alternations of IPSP and postsynaptic spikes (e.g., 1 IPSP, 1 postsynaptic or 1:1; 1 IPSP, 2 postsynaptic or 1:2; 2 IPSPs, 1 postsynaptic spike or 2:1), where interspike intervals were more constant than uninhibited controls and where the sensitivity to the excitatory input was reduced to small values, and the sudden firing rate discontinuities consisting of instantaneous discharge accelerations or decelerations (termed "jumps") between successive alteration ratios, where sensitivity increased to large values. Therefore with inhibition the RM firing rate varied discontinuously in response to the gradually changing input, and the discharge rate could take one of several discrete values by switching between different alteration ratios. 3. At the alternations the times elapsed between an IPSP and the closest spike before (phase, phi) or after it (cophase, theta) increased and decreased, respectively, with increasing excitation. The major membrane potential modification that accompanied the interactions at the alternations was the gradual increase of the post-IPSP slope as a function of excitatory drive, which reduced the time to reach the firing level or theta. 4. Inhibition introduced subtle and complex nonlinear modifications in the coding of convergent excitatory input. The most notable nonlinearity was the discontinuous variations of the firing rate as a function of the gradually changing excitatory input. Effects were due to voltage interactions occurring at the extrasynaptic membrane, with a decisive involvement of the spike generator and insignificant participation of the shunting action of IPSPs. The results provide yet another example of the predominant influence of intrinsic membrane properties in determining the effects of synaptic-evoked activity.(ABSTRACT TRUNCATED AT 400 WORDS)

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Terpos, Evangelos, Marianna Politou, Theodoros N. Sergentanis, Andreas Mentis, Margherita Rosati, Dimitris Stellas, Jenifer Bear et al. « Anti–SARS-CoV-2 Antibody Responses in Convalescent Plasma Donors Are Increased in Hospitalized Patients ; Subanalyses of a Phase 2 Clinical Study ». Microorganisms 8, n^o 12 (28 novembre 2020) : 1885. http://dx.doi.org/10.3390/microorganisms8121885.

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We evaluated the antibody responses in 259 potential convalescent plasma donors for Covid-19 patients. Different assays were used: a commercial ELISA detecting antibodies against the recombinant spike protein (S1); a multiplex assay detecting total and specific antibody isotypes against three SARS-CoV-2 antigens (S1, basic nucleocapsid (N) protein and receptor-binding domain (RBD)); and an in-house ELISA detecting antibodies to complete spike, RBD and N in 60 of these donors. Neutralizing antibodies (NAb) were also evaluated in these 60 donors. Analyzed samples were collected at a median time of 62 (14–104) days from the day of first symptoms or positive PCR (for asymptomatic patients). Anti-SARS-CoV-2 antibodies were detected in 88% and 87.8% of donors using the ELISA and the multiplex assay, respectively. The multivariate analysis showed that age ≥50 years (p < 0.001) and need for hospitalization (p < 0.001) correlated with higher antibody titers, while asymptomatic status (p < 0.001) and testing >60 days after symptom onset (p = 0.001) correlated with lower titers. Interestingly, pseudotype virus-neutralizing antibodies (PsNAbs) significantly correlated with spike and with RBD antibodies by ELISA. Sera with high PsNAb also showed a strong ability to neutralize active SARS-CoV-2 virus, with hospitalized patients showing higher titers. Therefore, convalescent plasma donors can be selected based on the presence of high RBD antibody titers.

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Kraskov, Alexander, Rodrigo Quian Quiroga, Leila Reddy, Itzhak Fried et Christof Koch. « Local Field Potentials and Spikes in the Human Medial Temporal Lobe are Selective to Image Category ». Journal of Cognitive Neuroscience 19, n^o 3 (mars 2007) : 479–92. http://dx.doi.org/10.1162/jocn.2007.19.3.479.

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Local field potentials (LFPs) reflect the averaged dendrosomatic activity of synaptic signals of large neuronal populations. In this study, we investigate the selectivity of LFPs and single neuron activity to semantic categories of visual stimuli in the medial temporal lobe of nine neurosurgical patients implanted with intracranial depth electrodes for clinical reasons. Strong selectivity to the category of presented images was found for the amplitude of LFPs in 8% of implanted microelectrodes and for the firing rates of single and multiunits in 14% of microelectrodes. There was little overlap between the LFP- and spike-selective microelectrodes. Separate analysis of the power and phase of LFPs revealed that the mean phase was category-selective around the θ frequency range and that the power of the LFPs was category-selective for high frequencies around the γ rhythm. Of the 36 microelectrodes with amplitude-selective LFPs, 30 were found in the hippocampus. Finally, it was possible to readout information about the category of stimuli presented to the patients with both spikes and LFPs. Combining spiking and LFP activity enhanced the decoding accuracy in comparison with the accuracy obtained with each signal alone, especially for short time intervals.

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Zeng, Hongliu. « Geologic significance of anomalous instantaneous frequency ». GEOPHYSICS 75, n^o 3 (mai 2010) : P23—P30. http://dx.doi.org/10.1190/1.3427638.

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Anomalous frequency spikes derived from complex-trace analysis have long been considered more as a flaw of algorithms than a valuable seismic attribute. However, synthetic models and field data show that instantaneous frequency spikes are clearly linked to physical models that could help geologic interpretations of seismic data. Frequency spikes are related to relative amplitude minima along a seismic trace that occur either at the merging point of the top and base reflections of a wedge (type I) or at the tip of the wedge (type II). A type II spike is indicative of a seismically thin bed (average [Formula: see text] or thinner in this study; [Formula: see text] denotes wavelength), although the bed thickness tends to decrease with the data frequency and bed spacing in a multibed acoustic-impedance profile (in the range of [Formula: see text] to [Formula: see text] in this study). Interpretive values of instantaneous frequency include recognizing thin reservoirs that are otherwise difficult to detect, mapping relative thickness changes of lithofacies, detecting lithofacies boundaries and faults, and locating a stratal discontinuity or flow barrier. Uncertainties caused by type I spikes, noise-derived fake spikes, and the lack of lithologic and time-stratigraphic information can be reduced by integrating well data, local geologic models, lithology-indicative seismic attributes (e.g., 90°-phase data), and facies-oriented seismic displays (e.g., stratal slices).

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Ma, Cong, Bin Liu et Hong Liang. « Lattice Boltzmann simulation of three-dimensional fluid interfacial instability coupled with surface tension ». Acta Physica Sinica 71, n^o 4 (2022) : 044701. http://dx.doi.org/10.7498/aps.71.20212061.

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In this paper, the development of three-dimensional fluid interfacial Rayleigh-Taylor (RT) instability coupled with the surface tension was numerically studied using the mesoscopic lattice Boltzmann method. We mainly analyzed the influence of surface tension on fluid interfacial dynamics and spike/bubble late-time growth. The numerical experiments show that there exists the critical surface tension (<inline-formula><tex-math id="M3">\begin{document}$\sigma_{\rm{c}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20212061_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20212061_M3.png"/></alternatives></inline-formula>) in the three-dimensional RT instability, above which the RT phenomenon does not appear and below which it would take place. It is found that the critical surface tension increases with the fluid Atwood number and the corresponding numerical predictions show good agreements with those of the theoretical analysis <inline-formula><tex-math id="M4">\begin{document}${\sigma_{\rm{c}}}= {{({{\rho_{\rm{h}}}-{\rho_{\rm{l}}}})g}}/{{{k^2}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20212061_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20212061_M4.png"/></alternatives></inline-formula>. In addition, we can find that increasing surface tension reduces the roll-up of the interface and the complexity of interfacial structure, also preventing the breakup of the interface into the individual droplets. The late-time dynamics of phase interface change from the asymmetric development to the symmetry with respect to the middle axis. When the surface tension is sufficiently low, the spike and bubble amplitudes almost no longer change with it, and further increasing the surface tension can slow down the growth of the spike and bubble amplitudes. Furthermore, we can observe that the development of the high-Reynolds-number RT instability under different surface tensions can also be divided into four distinct stages, including the linear growth, saturated velocity growth, reacceleration, and chaotic mixing. The spike and bubble grow with approximately constant velocities at the saturated stage and their asymptotic values are consistent with those of the modified potential flow theory. In the following, the spike and bubble driven by the increasing Kelvin-Helmholtz vortices are accelerated such that their evolutional velocities exceed the solutions of the potential flow model at the reacceleration stage. The reacceleration stage cannot last infinitely and the spike and bubble velocities at the late time fluctuate with time, implying that the growth of the RT instability enters into the chaotic mixing stage. By numerical analysis, we demonstrate that the three-dimensional RT instability at the chaotic mixing stage has a quadratic growth and also report that the spike and bubble growth rates decrease with the surface tension in general.

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Joris, P. X. « Envelope coding in the lateral superior olive. II. Characteristic delays and comparison with responses in the medial superior olive ». Journal of Neurophysiology 76, n^o 4 (1 octobre 1996) : 2137–56. http://dx.doi.org/10.1152/jn.1996.76.4.2137.

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1. Spike rates of cells in the cat's lateral superior olive (LSO) depend on interaural level differences (ILDs) and envelope interaural time differences (ITDs) of amplitude-modulated tones presented to both ears. We previously proposed that these sensitivities arise from a common mechanism, which is the IE binaural interaction (Inhibited by the contralateral and Excited by the ipsilateral ear). As a further test of that proposal and to gain a better understanding of the importance of this ITD-sensitivity, responses to monaural and binaural modulation are compared here over a range of modulation frequencies. 2. At low modulation frequencies, LSO-IE cells respond maximally when the envelopes of the amplitude-modulated stimuli at the two ears are out-of-phase by a half-cycle. This phase difference changes in a systematic way, which varies from cell to cell, when modulation frequency is increased. Mean interaural phase, measured over a range of modulation frequencies, was subjected to a characteristic delay analysis. Two measures were extracted: characteristic delay, which reflects differences in conduction delay between ipsi- and contralateral pathways, and characteristic phase, which reflects their sign of interaction. Most characteristic delays were within the physiological range of ITDs. There was a small bias toward positive delays, indicating a longer conduction time for the contralateral pathway. Characteristic phases were tightly distributed approximately 0.5 cycles, consistent with the proposed IE mechanism for ITD-sensitivity. 3. Increases in the modulation frequency of binaural stimuli beyond approximately 300 Hz consistently caused a profound decrease in average spike rate, as well as a decrease in the modulation of spike rate by ITD. The upper limit of ITD-sensitivity was 800 Hz. Sensitivity to envelope ITDs therefore is limited to a much lower range of frequencies than sensitivity to ITDs in fine-structure, e.g., as found in the medial superior olive (MSO), which operates up to several kilo Hertz. 4. A small sample of high-frequency EE cells (excited by both ears) in MSO also was tested with binaural amplitude-modulated stimuli. MSO-EE cells showed weak envelope ITD-sensitivity over a limited range of modulation frequencies. Consistent with the EE interaction, characteristic phases clustered approximately 0 cycles. 5. Mean interaural phase was compared with the phase of responses to monaural modulation. The difference between the ipsilateral and contralateral phases correlated well with the phase measured binaurally, both for LSO and MSO cells. 6. Many features of LSO-IE responses were mimicked by the simplest possible computer model, consisting of subtraction and rectification of low-pass filtered envelope waveforms. Differences between model and physiological results are suggestive of a temporal limitation in the binaural interaction that creates the ITD-sensitivity. 7. These results provide additional evidence for LSO ITD-sensitivity paralleling human psychophysical results. The stimulus boundaries within which ITD-sensitivity occurs suggest that it has a limited role in free-field conditions. It is traditionally thought that, to contribute to the perceived change in spatial location of a sound source, the LSO needs to show a change in overall firing rate summed across cells. This is achieved with small ILDs, but requires large ITDs, because the latter cue is less potent in single cells and has varied effects across cells by virtue of differences in characteristic delay.

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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 ? » Journal of Electronic Packaging 126, n^o 3 (1 septembre 2004) : 308–16. http://dx.doi.org/10.1115/1.1772411.

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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 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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Lindsey, B. G., L. S. Segers, K. F. Morris, Y. M. Hernandez, S. Saporta et R. Shannon. « Distributed actions and dynamic associations in respiratory-related neuronal assemblies of the ventrolateral medulla and brain stem midline : evidence from spike train analysis ». Journal of Neurophysiology 72, n^o 4 (1 octobre 1994) : 1830–51. http://dx.doi.org/10.1152/jn.1994.72.4.1830.

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1. Considerable evidence indicates that neurons in the brain stem midline and ventrolateral medulla participate in the control of breathing. This work was undertaken to detect and evaluate evidence for functional links that coordinate the parallel operations of neurons distributed in these two domains. 2. Data were from 51 Dial-urethan-anesthetized, bilaterally vagotomized, paralyzed, artificially ventilated cats. Planar arrays of tungsten microelectrodes were used to monitor simultaneously spike trains in two or three of the following regions: n. raphe obscurus-n. raphe pallidus, n. raphe magnus, rostral ventrolateral medulla, and caudal ventrolateral medulla. Efferent phrenic nerve activity was recorded to indicate the phases of the respiratory cycle. Electrodes in the ventral spinal cord (C3) were used in antidromic stimulation tests for spinal projections of neurons. 3. Spike trains of 1,243 neurons were tested for respiratory modulated firing rates with cycle-triggered histograms and an analysis of variance with the use of a subjects-by-treatments experimental design. Functional associations were detected and evaluated with cross-correlograms, snowflakes, and the gravity method. 4. Each of 2,310 pairs of neurons studied included one neuron monitored within 0.6 nm of the brain stem midline and a second cell recorded in the ventrolateral medulla; 117 of these pairs (5%) included a neuron with a spinal projection, identified with antidromic stimulation methods, that extended to at least the third cervical segment. Short-time scale correlations were detected in 110 (4.7%) pairs of neurons. Primary cross-correlogram features included 40 central peaks, 47 offset peaks, 4 central troughs, and 19 offset troughs. 5. In 14 data sets, multiple short-time scale correlations were found among three or more simultaneously recorded neurons distributed between both midline and ventrolateral domains. The results suggested that elements of up to three layers of interneurons were monitored simultaneously. Evidence for concurrent serial and parallel regulation of impulse synchrony was detected. Gravitational representations demonstrated respiratory-phase dependent synchrony among neurons distributed in both brain stem regions. 6. The results support a model of the brain stem respiratory network composed of coordinated distributed subassemblies and provide evidence for several hypotheses. 1) Copies of respiratory drive information from rostral ventrolateral medullary (RVLM) respiratory neurons are transmitted to midline neurons. 2) Midline neurons act on respiratory-related neurons in the RVLM to modulate phase timing. 3) Impulse synchrony of midline neurons is influenced by concurrent divergent actions of both midline and ventrolateral neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

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Sullivan, W. E. « Classification of response patterns in cochlear nucleus of barn owl : correlation with functional response properties ». Journal of Neurophysiology 53, n^o 1 (1 janvier 1985) : 201–16. http://dx.doi.org/10.1152/jn.1985.53.1.201.

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Response patterns of neurons in the cochlear nuclei of the barn owl (Tyto alba) were studied by obtaining poststimulus time histograms (PSTHs) and interspike interval histograms for the response to short tone bursts at the neuron's characteristic frequency. The observed response patterns can be classified according to the scheme developed for neurons of the mammalian cochlear nuclear complex (22). Neurons of the magnocellular cochlear nucleus (n. magnocellularis), which respond in a phase-locked manner to sinusoidal signals and do not show large increases in spike discharge rate with changes in stimulus intensity (26), have "primarylike" (PSTH) discharge patterns and broad interspike interval histograms. This indicates that magnocellular neurons have irregular firing patterns, with the timing of individual spikes being dependent on the phase of the stimulus waveform. Neurons of the angular cochlear nucleus (n. angularis), which show little or no phase-locking and large increases in spike rate with increasing intensity (26), had almost exclusively "transient chopper" discharge patterns. The interspike interval histograms of these angular units are sharp, indicating that their discharge is very regular. At the onset of the response where the chopper pattern is observed, both discharge regularity and rate-intensity sensitivity are at their maximum levels. Several "onset" units were isolated in the angular cochlear nucleus, but no "pauser" or "buildup" units were seen. Also, all of the units in the angular nucleus had monotonic rate-intensity functions. Thus no neural response patterns typical of mammalian dorsal cochlear nucleus units were observed. The relationship of response pattern type to neural function is discussed in relation to the acoustic cues used by the owl for two-dimensional sound localization. The primarylike, phase-locked discharge of magnocellular units is undoubtedly involved in the analysis of interaural differences in stimulus phase, which the owl uses for horizontal localization. There is strong evidence suggesting that the angular nucleus is involved in processing stimulus intensity information, which is important for determining sound elevation (due to asymmetries in vertical directionality of the owl's external ears). The predominant chopper patterns seen in the angular nucleus suggest that in the owl, this response type is correlated with stimulus intensity processing. Similarities in both anatomy and physiology suggest that the magnocellular nucleus is analogous to the spherical cell or bushy cell population of the anterior division of the mammalian anteroventral cochlear nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

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Smith, J. C., J. J. Greer, G. S. Liu et J. L. Feldman. « Neural mechanisms generating respiratory pattern in mammalian brain stem-spinal cord in vitro. I. Spatiotemporal patterns of motor and medullary neuron activity ». Journal of Neurophysiology 64, n^o 4 (1 octobre 1990) : 1149–69. http://dx.doi.org/10.1152/jn.1990.64.4.1149.

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1. An analysis of the spatial and temporal patterns of activity of neurons of the respiratory motor-pattern generation system in an in vitro neonatal rat brain stem-spinal cord preparation is presented. Impulse discharge patterns of spinal and cranial moto-neurons as well as respiratory neurons in the medulla were analyzed. Patterns of motoneuronal discharge were characterized at the population level from recordings of motor-nerve discharge and at the single-cell level from intracellular recordings. These patterns were compared to patterns generated in the neonatal rat and adult mammal in vivo to establish the correspondence between in vitro and in vivo states. 2. The in vitro system generated a complex spatiotemporal pattern of spinal and cranial motoneuron activity during inspiratory (I) and expiratory (E) phases of the respiratory cycle. The respiratory cycle consisted of three distinct phases of neuronal activity (I, early E, and late E phase) similar to the temporal organization of the cycle in the intact mammal. The spike discharge pattern of motoneurons during the I phase consisted of a rapidly peaking-slowly decrementing discharge envelope with a high degree of synchronization on a time scale of 25-50 ms (approximately 20-40 Hz). A similar pattern was generated in the neonate in vivo under conditions comparable with the in vitro state (i.e., nervous system isolated from mechanosensory afferent inputs). However, the I-phase-motoneuron discharge pattern and cycle-phase durations differed from those characteristic of the intact neonatal or adult systems in vivo. This difference could be accounted for primarily by removal of vagal mechanosensory afferent inputs. 3. The synaptic drive potentials of spinal motoneurons during the I phase in vitro consisted of a rapidly peaking-slowly decrementing potential envelope similar in shape to the spike-frequency histogram of single motoneurons and the envelope of the motoneuron-population discharge. The drive potentials had prominent high-frequency amplitude fluctuations superimposed on the slower drive-potential envelope that were temporally correlated with the generation of motoneuron action potentials. The dominant frequency components of these fast-membrane-potential oscillations (20-35 Hz) were similar to the frequency components of the amplitude fluctuations in the motoneuron-population discharge. One class of medullary neurons with I-phase discharge also exhibited a rapidly peaking-slowly decrementing pattern of impulse discharge and synaptic drive potential with similar high-frequency components.(ABSTRACT TRUNCATED AT 400 WORDS)

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Kitama, Toshihiro, Tomohiro Omata, Akihito Mizukoshi, Takehiko Ueno et Yu Sato. « Motor Dynamics Encoding in Cat Cerebellar Flocculus Middle Zone During Optokinetic Eye Movements ». Journal of Neurophysiology 82, n^o 5 (1 novembre 1999) : 2235–48. http://dx.doi.org/10.1152/jn.1999.82.5.2235.

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We investigated the relationship between eye movement and simple-spike (SS) frequency of Purkinje cells in the cerebellar flocculus middle zone during the optokinetic response (OKR) in alert cats. The OKR was elicited by a sequence of a constant-speed visual pattern movement in one direction for 1 s and then in the opposite direction for 1 s. Quick-phase-free trials were selected. Sixty-six cells had direction-selective complex spike (CS) activity that was modulated during horizontal (preferring contraversive) but not vertical stimuli. The SS activity was modulated during horizontal OKR, preferring ipsiversive stimuli. Forty-one cells had well-modulated activity and were suitable for the regression model. In these cells, an inverse dynamics approach was applied, and the time course of the SS rate was reconstructed, with mean coefficient of determination 0.76, by a linear weighted superposition of the eye acceleration (mean coefficient, 0.056 spikes/s per deg/s2), velocity (5.10 spikes/s per deg/s), position (−2.40 spikes/s per deg), and constant (mean 34.3 spikes/s) terms, using a time delay (mean 11 ms) from the unit response to the eye response. The velocity and acceleration terms contributed to the increase in the reconstructed SS rates during ipsilateral movements, whereas the position term contributed during contralateral movements. The standard regression coefficient analyses revealed that the contribution of the velocity term (mean coefficient 0.81) was predominant over the acceleration (0.03) and position (−0.17) terms. Forward selection analysis revealed three cell types: Velocity-Position-Acceleration type ( n = 27): velocity, position, and acceleration terms are significant ( P < 0.05); Velocity-Position type ( n = 12): velocity and position terms are significant; and Velocity-Acceleration type ( n = 2): velocity and acceleration terms are significant. Using the set of coefficients obtained by regression of the response to a 5 deg/s stimulus velocity, the SS rates during higher (10, 20, and 40 deg/s) stimulus velocities were successfully reconstructed, suggesting generality of the model. The eye-position information encoded in the SS firing during the OKR was relative but not absolute in the sense that the magnitude of the position shift from the initial eye position (0 deg/s velocity) contributed to firing rate changes, but the initial eye position did not. It is concluded that 1) the SS firing frequency in the cat middle zone encodes the velocity and acceleration information for counteracting the viscosity and inertia forces respectively, during short-duration horizontal OKR and 2) the apparent position information encoded in the SS firing is not appropriate for counteracting the elastic force during the OKR.

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Lee, S. G., S. Kim et H. Kook. « Synchrony and Clustering in Two and Three Synaptically Coupled Hodgkin–Huxley Neurons with a Time Delay ». International Journal of Bifurcation and Chaos 07, n^o 04 (avril 1997) : 889–95. http://dx.doi.org/10.1142/s0218127497000686.

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Synchrony and clustering in phase dynamics of two and three Hodgkin–Huxley neurons coupled globally by excitatory synapses with a time delay have been studied by numerical simulations and bifurcation analysis. In particular, we have obtained phase diagrams for the synchronous state and various cluster states in the parameter space of the synaptic coupling strength, G syn , and the synaptic time delay, τd, by computing the phase shifts of action potential spikes. In the weak coupling limit the computed phase diagrams are found to be consistent with the results of phase model analysis. The bifurcation analysis shows the phase model predictions break down at G syn ~ 0.3 and new complex phase dynamics appear. For all numbers of neurons explored, the critical time delay at which the nature of synaptic coupling changes completely is found to be typically about 2–4 msec, which may have some implications in modeling cortical dynamics.

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Li, Zhongzeng, Kendall F. Morris, David M. Baekey, Roger Shannon et Bruce G. Lindsey. « Multimodal Medullary Neurons and Correlational Linkages of the Respiratory Network ». Journal of Neurophysiology 82, n^o 1 (1 juillet 1999) : 188–201. http://dx.doi.org/10.1152/jn.1999.82.1.188.

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This study addresses the hypothesis that multiple sensory systems, each capable of reflexly altering breathing, jointly influence neurons of the brain stem respiratory network. Carotid chemoreceptors, baroreceptors, and foot pad nociceptors were stimulated sequentially in 33 Dial-urethan–anesthetized or decerebrate vagotomized adult cats. Neuronal impulses were monitored with microelectrode arrays in the rostral and caudal ventral respiratory group (VRG), nucleus tractus solitarius (NTS), and n. raphe obscurus. Efferent phrenic nerve activity was recorded. Spike trains of 889 neurons were analyzed with cycle-triggered histograms and tested for respiratory-modulated firing rates. Responses to stimulus protocols were assessed with peristimulus time and cumulative sum histograms. Cross-correlation analysis was used to test for nonrandom temporal relationships between spike trains. Spike-triggered averages of efferent phrenic activity and antidromic stimulation methods provided evidence for functional associations of bulbar neurons with phrenic motoneurons. Spike train cross-correlograms were calculated for 6,471 pairs of neurons. Significant correlogram features were detected for 425 pairs, including 189 primary central peaks or troughs, 156 offset peaks or troughs, and 80 pairs with multiple peaks and troughs. The results provide evidence that correlational medullary assemblies include neurons with overlapping memberships in groups responsive to different sets of sensory modalities. The data suggest and support several hypotheses concerning cooperative relationships that modulate the respiratory motor pattern. 1) Neurons responsive to a single tested modality promote or limit changes in firing rate of multimodal target neurons. 2) Multimodal neurons contribute to changes in firing rate of neurons responsive to a single tested modality. 3) Multimodal neurons may promote responses during stimulation of one modality and “limit” changes in firing rates during stimulation of another sensory modality. 4) Caudal VRG inspiratory neurons have inhibitory connections that provide negative feedback regulation of inspiratory drive and phase duration.

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Ito, Hiroyuki, Pedro E. Maldonado et Charles M. Gray. « Dynamics of Stimulus-Evoked Spike Timing Correlations in the Cat Lateral Geniculate Nucleus ». Journal of Neurophysiology 104, n^o 6 (décembre 2010) : 3276–92. http://dx.doi.org/10.1152/jn.01000.2009.

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Precisely synchronized neuronal activity has been commonly observed in the mammalian visual pathway. Spike timing correlations in the lateral geniculate nucleus (LGN) often take the form of phase synchronized oscillations in the high gamma frequency range. To study the relations between oscillatory activity, synchrony, and their time-dependent properties, we recorded activity from multiple single units in the cat LGN under stimulation by stationary spots of light. Autocorrelation analysis showed that approximately one third of the cells exhibited oscillatory firing with a mean frequency ∼80 Hz. Cross-correlation analysis showed that 30% of unit pairs showed significant synchronization, and 61% of these pairs consisted of synchronous oscillations. Cross-correlation analysis assumes that synchronous firing is stationary and maintained throughout the period of stimulation. We tested this assumption by applying unitary events analysis (UEA). We found that UEA was more sensitive to weak and transient synchrony than cross-correlation analysis and detected a higher incidence (49% of cell pairs) of significant synchrony (unitary events). In many unit pairs, the unitary events were optimally characterized at a bin width of 1 ms, indicating that neural synchrony has a high degree of temporal precision. We also found that approximately one half of the unit pairs showed nonstationary changes in synchrony that could not be predicted by the modulation of firing rates. Population statistics showed that the onset of synchrony between LGN cells occurred significantly later than that observed between retinal afferents and LGN cells. The synchrony detected among unit pairs recorded on separate tetrodes tended to be more transient and have a later onset than that observed between adjacent units. These findings show that stimulus-evoked synchronous activity within the LGN is often rhythmic, highly nonstationary, and modulated by endogenous processes that are not tightly correlated with firing rate.

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Chari, Ajai, Amitabha Mazumder, Lauren Ditrio, Zachary Galitzeck et Sundar Jagannath. « A Phase II Trial of TBL 12 Sea Cucumber Extract in Patients with Untreated Asymptomatic Myeloma »,. Blood 118, n^o 21 (18 novembre 2011) : 3992. http://dx.doi.org/10.1182/blood.v118.21.3992.3992.

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Abstract Abstract 3992 Background: Patients with smoldering multiple myeloma (MM) may remain asymptomatic (ASx) for variable amounts of time and are therefore typically monitored without treatment. Chemoprevention trials using thalidomide have found the toxicity to be prohibitive and longer follow up is needed for the early systemic treatment with lenalidomide and dexamethasone of high risk ASxMM. Based on encouraging preclinical data with bioactive food supplements in MM curcumin (Bharti et al., Blood 2003), resveratrol (Bhardwaj et al, Blood 2006), and a component of green tea extract (Shammas et al, Blood 2006) many patients are already using these agents without definitive proof of efficacy or safety. The sphingolipids/glycosides contained in sea cucumbers have also been shown preclinically to have a number of antitumor properties including antiangiogenesis direct tumor cytotoxicity, and also of particular relevance to MM, the inhibition of osteoclastogenesis (Kariya et al, Carb Res 2004). TBL12, an extract of sea cucumber, has been commercially available since 1981 and used by human subjects as a food supplement without any reported toxicities. We therefore designed a pilot phase II study to determine the safety and efficacy of TBL12 in patients with ASxMM and here we present updated data. Methods: Patients were required to have ASxMM with measurable disease, defined as monoclonal immunoglobulin spike (m-spike) on serum electrophoresis of ≥ 1 g/dL and/or urine m spike of ≥ 200 mg/24 hours. If non-secretory, then abnormal free light chains (FLC) were required. A total of 20 patients with ASxMM were given open label TBL12, formulated as a liquid gel (manufactured by Unicorn Pacific Corporation, IND 103,543) to be kept frozen until the time of consumption. Patients ingested 2 units of 20 ml twice per day, for a total of 80 units per day. Disease parameters were monitored monthly and treatment was continued until disease progression. Results: 23 patients were screened, with 3 failures, and the remaining 20 patients proceeded with study treatment. The median age of the patient was 58 years (range 22–75), with 11 males and 9 females. The phenotypes were 14 IgG, 5 Ig A, and one kappa light chain. Generally, this was a population at high risk for progression of disease (PD), with 14 patients having a serum m spike > 3 g/dl and bone marrow plasma cells (BM PC) > 10%. The median BM PC for all patients was 38% (range 10 to 90). (With the additional high risk criteria of a FLC ratio <0.125 or >8, 13 patients were high risk.) Of the remaining 6 patients, all had immunoparesis and 4 had markedly elevated FLC ratios (range 307-incalculable) and the remaining 2 patients had 9.2 g urine m spike and an IgA phenotype. Compliance was excellent and the treatment was well tolerated with only grade 1 nausea. There was one SAE, a pneumococcal pneumonia requiring admission, which was felt to be unrelated to study treatment. A total of 9 patients remain on treatment, having completed a median of 24 monthly cycles of TBL12 (range 20–30 cycles). The median progression free survival (PFS) has not been reached by Kaplan-Meyer survival analysis, including for high risk patients. The best response to date has been a minimal response (MR) for 5 cycles. 3 patients are on intermittent bisphosphonates therapy q 3–12 months for osteoporosis or equivocal bone lesions unchanged since screening. 8 patients came off study for PD after a median of 7.5 cycles (range 2–18). The reasons for PD include: 1 hypercalcemia, 1 acute renal insufficiency (after 2 cycles with 9.2g urine m spike at screening), 2 for anemia (one after 3 cycles with 90% BM PC at screening), and 1 for a new bony lesion on MRI. 2 patients withdrew consent after cycle 6 and 8, and 1 was removed after cycle 13 due to investigator discretion after the pneumococcal pneumonia SAE. Conclusions: In this pilot study of high risk ASxMM patients, TBL12 is well tolerated and 9 (45%) patients remain on treatment with one MR noted. The expected rate of PD for high risk ASxMM is 52% at 2 years (Dispenzieri et al, Blood 2008) and to date, median PFS has not been reached in this study. Also, of note, in contrast to 10 of 16 pts in the placebo arm of lenalidomide in ASxMM study developing bone PD (Mateos et al, ASH 2009), only 1 patient in this study has bone PD. This may reflect anti-osteoclastogenesis effects of TBL12 observed in vitro. Further studies are required. Disclosures: No relevant conflicts of interest to declare.

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Steriade, M., et F. Amzica. « Dynamic coupling among neocortical neurons during evoked and spontaneous spike-wave seizure activity ». Journal of Neurophysiology 72, n^o 5 (1 novembre 1994) : 2051–69. http://dx.doi.org/10.1152/jn.1994.72.5.2051.

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1. We investigated the development from patterns of electroencephalogram (EEG) synchronization to paroxysms consisting of spike-wave (SW) complexes at 2–4 Hz or to seizures at higher frequencies (7–15 Hz). We used multisite, simultaneous EEG, extracellular, and intracellular recordings from various neocortical areas and thalamic nuclei of anesthetized cats. 2. The seizures were observed in 25% of experimental animals, all maintained under ketamine and xylazine anesthesia, and were either induced by thalamocortical volleys and photic stimulation or occurred spontaneously. Out of unit and field potential recordings within 370 cortical and 65 thalamic sites, paroxysmal events occurred in 70 cortical and 8 thalamic sites (approximately 18% and 12%, respectively), within which a total of 181 neurons (143 extracellular and 38 intracellular) were simultaneously recorded in various combinations of cell groups. 3. Stimulus-elicited and spontaneous SW seizures at 2–4 Hz lasted for 15–35 s and consisted of barrages of action potentials related to the spiky depth-negative (surface-positive) field potentials, followed by neuronal silence during the depth-positive wave component of SW complexes. The duration of inhibitory periods progressively increased during the seizure, at the expense of the phasic excitatory phases. 4. Intracellular recordings showed that, during such paroxysms, cortical neurons displayed a tonic depolarization (approximately 10–20 mV), sculptured by rhythmic hyperpolarizations. 5. In all cases, measures of synchrony demonstrated time lags between discharges of simultaneously recorded cortical neurons, from as short as 3–10 ms up to 50 ms or even longer intervals. Synchrony was assessed by cross-correlograms, by a method termed first-spike-analysis designed to detect dynamic temporal relations between neurons and relying on the detection of the first action potential in a spike train, and by a method termed sequential-field-correlation that analyzed the time course of field potentials simultaneously recorded from different cortical areas. 6. The degree of synchrony progressively increased from preseizure sleep patterns to the early stage of the SW seizure and, further, to its late stage. In some cases the time relation between neurons during the early stages of seizures was inversed during late stages. 7. These data show that, although the common definition of SW seizures, regarded as suddenly generalized and bilaterally synchronous activities, may be valid at the macroscopic EEG level, cortical neurons display time lags between their rhythmic spike trains, progressively increased synchrony, and changes in the temporal relations between their discharges during the paroxysms.(ABSTRACT TRUNCATED AT 400 WORDS)

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Yu, Tzu-Hsien, Shuo-Ping Hsieh, Chien-Ming Su, Feng-Jung Huang, Chien-Che Hung et Lih-Ming Yiin. « Analysis of Leafy Vegetable Nitrate Using a Modified Spectrometric Method ». International Journal of Analytical Chemistry 2018 (5 août 2018) : 1–6. http://dx.doi.org/10.1155/2018/6285867.

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A quick and cost-effective method to analyze leafy vegetable nitrate on spectrometry was developed and compared with a standard method using high performance liquid chromatography (HPLC). This method was designed to use ion-exchange solid phase extraction (SPE) cartridges in reducing interference from organic matrices to meet the criterion of an existing method for analyzing nitrate in wastewater. Nine vegetables (bok coy, cabbage, celery, Chinese cabbage, Chinese kale, lettuce, mustard green, pak choi, and water spinach) were selected for the method testing with three replicates being conducted for each vegetable. The nitrate contents ranged from 800 to 4,300 μg/g, with bok coy, celery, and pak choi being the highest. Data derived from spectrometry and HPLC were close to each other with most relative errors being within ±10% and were highly correlated with an R square value of 0.969. Stability testing and spike analysis resulted in a mean coefficient of variation lower than 6% and a mean recovery rate of 83.7%, suggesting reliability of the method. In addition, both the cost and time consumption for using this method were lower than the standard method using HPLC or ion chromatography, making this spectrometric method a good alternative for analysis of leafy vegetable nitrate.

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Kapustnikov, A. A., M. V. Sysoeva et I. V. Sysoev. « The Modeling of Spike-Wave Discharges in Brain with Small Oscillatory Neural Networks ». Mathematical Biology and Bioinformatics 15, n^o 2 (15 septembre 2020) : 138–47. http://dx.doi.org/10.17537/2020.15.138.

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A pathology of coupling architecture in the thalamo-cortical system is considered the main cause of absence epilepsy, the eletroencephalographic primary manifestation of which are spike-wave discharges. The immediate cause of the discharges may be in increase of intracortical connectivity or external stimulation of cortex or thalamus. At the same time, the mechanisms of discharge termination are still not clear; so from the point of view of the dynamical system theory, the spike-wave discharge can be considered as a long transient process. In this paper, we propose a simple mathematical model of network with 14 identical Fitzhugh–Nagumo neurons, which is organized in accordance with modern ideas about thalamo-cortical brain network. In this model, long transients in response to short-term pulse driving from a separate neuron, representing the nervus trigeminus, are shown to be possible. Bifurcation analysis reveals such transients to develop in the system approximately the bifurcation of the cycle birth from the condensation of phase trajectories. The model may be useful for detailed studies of the thalamo-cortical system. It also can be used to investigate effects of electrical brain stimulation and pharmacological interventions, and to test the methods for evaluating connectivity in brain.

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Parida, Satyabrata, Hari Bharadwaj et Michael G. Heinz. « Spectrally specific temporal analyses of spike-train responses to complex sounds : A unifying framework ». PLOS Computational Biology 17, n^o 2 (22 février 2021) : e1008155. http://dx.doi.org/10.1371/journal.pcbi.1008155.

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Significant scientific and translational questions remain in auditory neuroscience surrounding the neural correlates of perception. Relating perceptual and neural data collected from humans can be useful; however, human-based neural data are typically limited to evoked far-field responses, which lack anatomical and physiological specificity. Laboratory-controlled preclinical animal models offer the advantage of comparing single-unit and evoked responses from the same animals. This ability provides opportunities to develop invaluable insight into proper interpretations of evoked responses, which benefits both basic-science studies of neural mechanisms and translational applications, e.g., diagnostic development. However, these comparisons have been limited by a disconnect between the types of spectrotemporal analyses used with single-unit spike trains and evoked responses, which results because these response types are fundamentally different (point-process versus continuous-valued signals) even though the responses themselves are related. Here, we describe a unifying framework to study temporal coding of complex sounds that allows spike-train and evoked-response data to be analyzed and compared using the same advanced signal-processing techniques. The framework uses a set of peristimulus-time histograms computed from single-unit spike trains in response to polarity-alternating stimuli to allow advanced spectral analyses of both slow (envelope) and rapid (temporal fine structure) response components. Demonstrated benefits include: (1) novel spectrally specific temporal-coding measures that are less confounded by distortions due to hair-cell transduction, synaptic rectification, and neural stochasticity compared to previous metrics, e.g., the correlogram peak-height, (2) spectrally specific analyses of spike-train modulation coding (magnitude and phase), which can be directly compared to modern perceptually based models of speech intelligibility (e.g., that depend on modulation filter banks), and (3) superior spectral resolution in analyzing the neural representation of nonstationary sounds, such as speech and music. This unifying framework significantly expands the potential of preclinical animal models to advance our understanding of the physiological correlates of perceptual deficits in real-world listening following sensorineural hearing loss.

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Lashkari, Saleh, Ali Moghimi, Hamid Reza Kobravi et Mohamad Amin Younessi Heravi. « A Novel Spike-Wave Discharge Detection Framework Based on the Morphological Characteristics of Brain Electrical Activity Phase Space in an Animal Model ». International Clinical Neuroscience Journal 8, n^o 4 (30 octobre 2021) : 180–87. http://dx.doi.org/10.34172/icnj.2021.36.

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Background: Animal models of absence epilepsy are widely used in childhood absence epilepsy studies. Absence seizures appear in the brain’s electrical activity as a specific spike wave discharge (SWD) pattern. Reviewing long-term brain electrical activity is time-consuming and automatic methods are necessary. On the other hand, nonlinear techniques such as phase space are effective in brain electrical activity analysis. In this study, we present a novel SWD-detection framework based on the geometrical characteristics of the phase space. Methods: The method consists of the following steps: (1) Rat stereotaxic surgery and cortical electrode implantation, (2) Long-term brain electrical activity recording, (3) Phase space reconstruction, (4) Extracting geometrical features such as volume, occupied space, and curvature of brain signal trajectories, and (5) Detecting SDWs based on the thresholding method. We evaluated the approach with the accuracy of the SWDs detection method. Results: It has been demonstrated that the features change significantly in transition from a normal state to epileptic seizures. The proposed approach detected SWDs with 98% accuracy. Conclusion: The result supports that nonlinear approaches can identify the dynamics of brain electrical activity signals.

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Rowat, Peter F., et Priscilla E. Greenwood. « Identification and Continuity of the Distributions of Burst-Length and Interspike Intervals in the Stochastic Morris-Lecar Neuron ». Neural Computation 23, n^o 12 (décembre 2011) : 3094–124. http://dx.doi.org/10.1162/neco_a_00209.

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Using the Morris-Lecar model neuron with a type II parameter set and K+-channel noise, we investigate the interspike interval distribution as increasing levels of applied current drive the model through a subcritical Hopf bifurcation. Our goal is to provide a quantitative description of the distributions associated with spiking as a function of applied current. The model generates bursty spiking behavior with sequences of random numbers of spikes (bursts) separated by interburst intervals of random length. This kind of spiking behavior is found in many places in the nervous system, most notably, perhaps, in stuttering inhibitory interneurons in cortex. Here we show several practical and inviting aspects of this model, combining analysis of the stochastic dynamics of the model with estimation based on simulations. We show that the parameter of the exponential tail of the interspike interval distribution is in fact continuous over the entire range of plausible applied current, regardless of the bifurcations in the phase portrait of the model. Further, we show that the spike sequence length, apparently studied for the first time here, has a geometric distribution whose associated parameter is continuous as a function of applied current over the entire input range. Hence, this model is applicable over a much wider range of applied current than has been thought.

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Dahbi, Mohamed, Said Doubabi et Ahmed Rachid. « Current Spikes Minimization Method for Three-Phase Permanent Magnet Brushless DC Motor with Real-Time Implementation ». Energies 11, n^o 11 (19 novembre 2018) : 3206. http://dx.doi.org/10.3390/en11113206.

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Due to their high efficiency and low cost of maintenance, brushless DC motors (BLDCMs) with trapezoidal electromotive forces (back-EMFs), have become widely used in various applications such as aerospace, electric vehicles, industrial uses, and robotics. However, they suffer from large current ripples and current spikes. In this paper, a new method for minimizing current spikes appearing during BLDCM start-up or sudden set point changes is proposed. The method is based on controlling the MOSFET gates of the motor driver using R-C filters. These filters are placed between the PWM control signal generator and the MOSFET gates to smooth these control signals. The analysis of the proposed method showed that the R-C filter usage affects the BLDCM steady-state performances. To overcome this limitation, the R-C filter circuit was activated only during current spikes detection. The effectiveness of the proposed method was analytically analyzed and then validated through simulation and experimental tests. The obtained results allowed a reduction of 13% in current spikes amplitude.

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VLACHOMITROU, M., et N. PELEKASIS. « Short- to long-wave resonance and soliton formation in boundary-layer interaction with a liquid film ». Journal of Fluid Mechanics 660 (12 juillet 2010) : 162–96. http://dx.doi.org/10.1017/s0022112010002612.

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Dynamic interaction between a boundary layer of air and a liquid film is investigated in this paper. The low air-to-film-viscosity ratio is considered in which case the boundary layer is quasi-steady on the time scale within which interfacial waves develop. The base flow consists of a boundary layer that drags a film of constant shear. Linear analysis, in the context of triple-deck theory, predicts the formation of a wavepacket of capillary waves that advances and spreads with time. The Froude number of de-/anti-icing fluids or water interacting with air falls well within the supercritical regime, i.e. Fr > FrCr. Numerical simulations of such flow systems were performed in the context of triple-deck theory, and they do not exhibit wave saturation or formation of uniform wavetrains. The long-term interaction is mainly dependent on film inertia as this is characterized by parameter = (μ/μf)2(ρf/ρ), which involves film and air viscosity and density ratios, and the dimensionless film thickness, H0, and shear, λ, provided by the base flow. Weakly nonlinear analysis taking into consideration mean drift, i.e. generation of long waves, due to self-interaction of the linear wave to O(ϵ2) in amplitude of the initial disturbance, reveals resonance between the wavepacket predicted by linear theory and long waves when the group velocity of the former happens to coincide with the phase velocity, H0λ, of long interfacial waves. Numerical simulations with anti-icing fluids and water verify this pattern. In both cases, long waves eventually dominate the dynamics and, as they are modulated with time, they lead to soliton-type structures. Anti-icing fluids eventually exhibit oscillatory spikes whose mean value never exceeds 2H0, roughly. Water films exhibit a single spike that keeps growing, thus generating a large separation bubble.

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Menon, Vidya, Masood A. Shariff, Victor Perez Gutierrez, Juan M. Carreño, Bo Yu, Muzamil Jawed, Marcia Gossai et al. « Longitudinal humoral antibody response to SARS-CoV-2 infection among healthcare workers in a New York City hospital ». BMJ Open 11, n^o 10 (octobre 2021) : e051045. http://dx.doi.org/10.1136/bmjopen-2021-051045.

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ObjectiveDynamics of humoral immune responses to SARS-CoV-2 antigens following infection suggest an initial decay of antibody followed by subsequent stabilisation. We aim to understand the longitudinal humoral responses to SARS-CoV-2 nucleocapsid (N) protein and spike (S) protein and to evaluate their correlation to clinical symptoms among healthcare workers (HCWs).DesignA prospective longitudinal study.SettingThis study was conducted in a New York City public hospital in the South Bronx, New York.ParticipantsHCWs participated in phase 1 (N=500) and were followed up 4 months later in phase 2 (N=178) of the study. They underwent SARS-CoV-2 PCR and serology testing for N and S protein antibodies, in addition to completion of an online survey in both phases. Analysis was performed on the 178 participants who participated in both phases of the study.Primary outcome measureEvaluate longitudinal humoral responses to viral N (qualitative serology testing) and S protein (quantitative Mount Sinai Health System ELISA to detect receptor-binding domain and full-length S reactive antibodies) by measuring rate of decay.ResultsAnti-N antibody positivity was 27% and anti-S positivity was 28% in phase 1. In phase 1, anti-S titres were higher in symptomatic (6754 (5177–8812)) than in asymptomatic positive subjects (5803 (2825–11 920)). Marginally higher titres (2382 (1494–3797)) were seen in asymptomatic compared with the symptomatic positive subgroup (2198 (1753–2755)) in phase 2. A positive correlation was noted between age (R=0.269, p<0.01), number (R=0.310, p<0.01) and duration of symptoms (R=0.434, p<0.01), and phase 1 anti-S antibody titre. A strong correlation (R=0.898, p<0.001) was observed between phase 1 titres and decay of anti-S antibody titres between the two phases. Significant correlation with rate of decay was also noted with fever (R=0.428, p<0.001), gastrointestinal symptoms (R=0.340, p<0.05), and total number (R=0.357, p<0.01) and duration of COVID-19 symptoms (R=0.469, p<0.001).ConclusionsHigher initial anti-S antibody titres were associated with larger number and longer duration of symptoms as well as a faster decay between the two time points.

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Yoo, Jingon, Soobin Han, Bumjun Park, Sonam Sonwal, Munirah Alhammadi, Eunsu Kim, Sheik Aliya et al. « Highly Specific Peptide-Mediated Cuvette-Form Localized Surface Plasmon Resonance (LSPR)-Based Fipronil Detection in Egg ». Biosensors 12, n^o 11 (23 octobre 2022) : 914. http://dx.doi.org/10.3390/bios12110914.

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Herein, we have developed peptide-coated gold nanoparticles (AuNPs) based on localized surface plasmon resonance (LSPR) sensor chips that can detect fipronil with high sensitivity and selectivity. The phage display technique has been exploited for the screening of highly specific fipronil-binding peptides for the selective detection of the molecule. LSPR sensor chips are fabricated initially by attaching uniformly synthesized AuNPs on the glass substrate, followed by the addition of screened peptides. The parameters, such as the peptide concentration of 20 µg mL−1 and the reaction time of 30 min, are further optimized to maximize the efficacy of the fabricated LSPR sensor chips. The sensing analysis is performed systematically under standard fipronil solutions and spike samples from eggs. The developed sensor has shown excellent sensitivity towards both standard solutions and spike samples with limit of detection (LOD) values of 0.01 ppb, respectively. Significantly, the developed LSPR sensor chips offer distinct features, such as a facile fabrication approach, on-site sensing, rapid analysis, cost-effectiveness, and the possibility of mass production, in which the chips can be effectively used as a promising and potential on-site detection tool for the estimation of fipronil.

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Krasnikov, D. A., I. V. Demchak et E. S. Khudoleeva. « Determination of residual dimethylaminopropylamine in aminopropylamides of fatty acid using high-performance liquid chromatography ». Industrial laboratory. Diagnostics of materials 87, n^o 4 (23 avril 2021) : 21–25. http://dx.doi.org/10.26896/1028-6861-2021-87-4-21-25.

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A procedure for determination of the residual content of N,N-dimethyl-1,3-propanediamine (DMAPA) during synthesis of N,N-dimethylaminopropylamides of fatty acids (DMAPA FA) from coconut oil has been developed. The analysis was performed using high performance liquid chromatography on a Shimadzu LC-20 Prominence device equipped with a diode array detector and reversed phase column GL Sciences Inertsil ODS-3. Precolumn derivatization was carried out with a 13% — dansyl chloride (5-(dimethylamino)naphthalene-1-sulfonyl chloride) solution in acetone to increase the analyte response. The selected composition of the mobile phase — acetonitrile and triethylamine phosphate buffer solution (pH 3.0) in a volume ratio of 2:3 and optimized chromatographic conditions provided a clear peak of DMAPA with a retention time of 8.7 – 8.9 min. The proposed method provides determination of 0.02 – 10% DMAPA in DMAPAFA samples. Correctness of the procedure was confirmed in spike tests. The results obtained can be used for assessing the degree of conversion of starting materials in the synthesis of N,N-dimethylaminopropylamides of fatty acids, as well as for forecasting the content of N,N-dimethyl-1,3-propanediamine in the products on their base.

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