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Статті в журналах з теми "Single spike"
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Panchev, Christo, and Stefan Wermter. "Spike-timing-dependent synaptic plasticity: from single spikes to spike trains." Neurocomputing 58-60 (June 2004): 365–71. http://dx.doi.org/10.1016/j.neucom.2004.01.068.
Повний текст джерела
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S B, Jadhav, Vichare S V, and Katwate S M. "Evaluation of Hybrids and Cultivars of Single type Tuberose (Polianthes tuberosa)." Journal of Horticultural Sciences 15, no. 1 (June 30, 2020): 67–71. http://dx.doi.org/10.24154/jhs.2020.v15i01.009.
Повний текст джерелаАнотація:
Hybrids and cultivars of single type tuberose was evaluated to fulfill the need to develop new hybrids as demanded by commercial growers. Evaluation of fifteen genotypes showed significant variation in growth, floral and bulb characters. Cultivar Arka Prajwal was significantly superior over all genotypes, which recorded least number of days for opening of 1st floret (78.55 days) with maximum diameter of spike (1.18 cm), length of floret (6.05 cm), weight of individual floret (3.12 g) and weight of spike (121.43 g).The hybrid genotype L1P4 (Variegated X Phule Rajani) was observed to be superior in terms of rachis length (39.78 cm), inter-nodal length (7.25 cm), length of bulb (8.09 cm), diameter of bulb (3.76 cm) and diameter of bulb-lets (1.85 cm). Among the hybrid genotypes L1P4 also recorded maximum plant height (116.39 cm), spike length (109.58 cm), weight of cut spike (105.08 g) and vase life (11.00 days). However, it was foundto be at par for number of florets per spike (57.25), length of floret (5.92 cm) and number of spikes per clump (10.14) with all other cultivars and hybrids tested. From the overall performance, it was found that the cultivar Arka Prajwal was the best. Genotype L1P4 found promising for loose as well as cut flower production because of its number of florets, inter-nodal length and spikes per clump which are important characters considering loose flower for taking maximum number of pickings. However, characters such as rachis length, spike length, vase life and weight of spike which are imperative for cut flowers are also noted superior in genotype L1P4.
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S B, Jadhav, Vichare S V, and Katwate S M. "Evaluation of Hybrids and Cultivars of Single type Tuberose (Polianthes tuberosa)." Journal of Horticultural Sciences 15, no. 1 (June 30, 2020): 67–71. http://dx.doi.org/10.24154/jhs.v15i1.785.
Повний текст джерелаАнотація:
Hybrids and cultivars of single type tuberose was evaluated to fulfill the need to develop new hybrids as demanded by commercial growers. Evaluation of fifteen genotypes showed significant variation in growth, floral and bulb characters. Cultivar Arka Prajwal was significantly superior over all genotypes, which recorded least number of days for opening of 1st floret (78.55 days) with maximum diameter of spike (1.18 cm), length of floret (6.05 cm), weight of individual floret (3.12 g) and weight of spike (121.43 g).The hybrid genotype L1P4 (Variegated X Phule Rajani) was observed to be superior in terms of rachis length (39.78 cm), inter-nodal length (7.25 cm), length of bulb (8.09 cm), diameter of bulb (3.76 cm) and diameter of bulb-lets (1.85 cm). Among the hybrid genotypes L1P4 also recorded maximum plant height (116.39 cm), spike length (109.58 cm), weight of cut spike (105.08 g) and vase life (11.00 days). However, it was foundto be at par for number of florets per spike (57.25), length of floret (5.92 cm) and number of spikes per clump (10.14) with all other cultivars and hybrids tested. From the overall performance, it was found that the cultivar Arka Prajwal was the best. Genotype L1P4 found promising for loose as well as cut flower production because of its number of florets, inter-nodal length and spikes per clump which are important characters considering loose flower for taking maximum number of pickings. However, characters such as rachis length, spike length, vase life and weight of spike which are imperative for cut flowers are also noted superior in genotype L1P4.
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Lu, Maolin. "Single-Molecule FRET Imaging of Virus Spike–Host Interactions." Viruses 13, no. 2 (February 21, 2021): 332. http://dx.doi.org/10.3390/v13020332.
Повний текст джерелаАнотація:
As a major surface glycoprotein of enveloped viruses, the virus spike protein is a primary target for vaccines and anti-viral treatments. Current vaccines aiming at controlling the COVID-19 pandemic are mostly directed against the SARS-CoV-2 spike protein. To promote virus entry and facilitate immune evasion, spikes must be dynamic. Interactions with host receptors and coreceptors trigger a cascade of conformational changes/structural rearrangements in spikes, which bring virus and host membranes in proximity for membrane fusion required for virus entry. Spike-mediated viral membrane fusion is a dynamic, multi-step process, and understanding the structure–function-dynamics paradigm of virus spikes is essential to elucidate viral membrane fusion, with the ultimate goal of interventions. However, our understanding of this process primarily relies on individual structural snapshots of endpoints. How these endpoints are connected in a time-resolved manner, and the order and frequency of conformational events underlying virus entry, remain largely elusive. Single-molecule Förster resonance energy transfer (smFRET) has provided a powerful platform to connect structure–function in motion, revealing dynamic aspects of spikes for several viruses: SARS-CoV-2, HIV-1, influenza, and Ebola. This review focuses on how smFRET imaging has advanced our understanding of virus spikes’ dynamic nature, receptor-binding events, and mechanism of antibody neutralization, thereby informing therapeutic interventions.
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Scott, John W., and Lisa Sherrill. "Effects of Odor Stimulation on Antidromic Spikes in Olfactory Sensory Neurons." Journal of Neurophysiology 100, no. 6 (December 2008): 3074–85. http://dx.doi.org/10.1152/jn.90399.2008.
Повний текст джерелаАнотація:
Spikes were evoked in rat olfactory sensory neuron (OSN) populations by electrical stimulation of the olfactory bulb nerve layer in pentobarbital anesthetized rats. The latencies and recording positions for these compound spikes showed that they originated in olfactory epithelium. Dual simultaneous recordings indicated conduction velocities in the C-fiber range, around 0.5 m/s. These spikes are concluded to arise from antidromically activated olfactory sensory neurons. Electrical stimulation at 5 Hz was used to track changes in the size and latency of the antidromic compound population spike during the odor response. Strong odorant stimuli suppressed the spike size and prolonged its latency. The latency was prolonged throughout long odor stimuli, indicating continued activation of olfactory receptor neuron axons. The amounts of spike suppression and latency change were strongly correlated with the electroolfactogram (EOG) peak size evoked at the same site across odorants and across stimulus intensities. We conclude that the curve of antidromic spike suppression gives a reasonable representation of spiking activity in olfactory sensory neurons driven by odorants and that the correlation of peak spike suppression with the peak EOG shows the accuracy of the EOG as an estimate of intracellular potential in the population of olfactory sensory neurons. In addition, these results have important implications about traffic in olfactory nerve bundles. We did not observe multiple peaks corresponding to stimulated and unstimulated receptor neurons. This suggests synchronization of spikes in olfactory nerve, perhaps by ephaptic interactions. The long-lasting effect on spike latency shows that action potentials continue in the nerve throughout the duration of an odor stimulus in spite of many reports of depolarization block in olfactory receptor neuron cell bodies. Finally, strong odor stimulation caused almost complete block of antidromic spikes. This indicates that a very large proportion of olfactory axons was activated by single strong odor stimuli.
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Herfst, Lucas J., and Michael Brecht. "Whisker Movements Evoked by Stimulation of Single Motor Neurons in the Facial Nucleus of the Rat." Journal of Neurophysiology 99, no. 6 (June 2008): 2821–32. http://dx.doi.org/10.1152/jn.01014.2007.
Повний текст джерелаАнотація:
The lateral facial nucleus is the sole output structure whose neuronal activity leads to whisker movements. To understand how single facial nucleus neurons contribute to whisker movement we combined single-cell stimulation and high-precision whisker tracking. Half of the 44 stimulated neurons gave rise to fast whisker protraction or retraction movement, whereas no stimulation-evoked movements could be detected for the remainder. Direction, speed, and amplitude of evoked movements varied across neurons. Protraction movements were more common than retraction movements ( n = 16 vs. n = 4), had larger amplitudes (1.8 vs. 0.3° for single spike events), and most protraction movements involved only a single whisker, whereas most retraction movements involved multiple whiskers. We found a large range in the amplitude of single spike-evoked whisker movements (0.06–5.6°). Onset of the movement occurred at 7.6 (SD 2.5) ms after the spike and the time to peak deflection was 18.2 (SD 4.3) ms. Each spike reliably evoked a stereotyped movement. In two of five cases peak whisker deflection resulting from consecutive spikes was larger than expected when based on linear summation of single spike-evoked movement profiles. Our data suggest the following coding scheme for whisker movements in the facial nucleus. 1) Evoked movement characteristics depend on the identity of the stimulated neuron (a labeled line code). 2) The facial nucleus neurons are heterogeneous with respect to the movement properties they encode. 3) Facial nucleus spikes are translated in a one-to-one manner into whisker movements.
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Doron, Guy, and Michael Brecht. "What single-cell stimulation has told us about neural coding." Philosophical Transactions of the Royal Society B: Biological Sciences 370, no. 1677 (September 19, 2015): 20140204. http://dx.doi.org/10.1098/rstb.2014.0204.
Повний текст джерелаАнотація:
In recent years, single-cell stimulation experiments have resulted in substantial progress towards directly linking single-cell activity to movement and sensation. Recent advances in electrical recording and stimulation techniques have enabled control of single neuron spiking in vivo and have contributed to our understanding of neuronal coding schemes in the brain. Here, we review single neuron stimulation effects in different brain structures and how they vary with artificially inserted spike patterns. We briefly compare single neuron stimulation with other brain stimulation techniques. A key advantage of single neuron stimulation is the precise control of the evoked spiking patterns. Systematically varying spike patterns and measuring evoked movements and sensations enables ‘decoding’ of the single-cell spike patterns and provides insights into the readout mechanisms of sensory and motor cortical spikes.
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Gong, Xiajing, Wu Li, and Hualou Liang. "Spike-field Granger causality for hybrid neural data analysis." Journal of Neurophysiology 122, no. 2 (August 1, 2019): 809–22. http://dx.doi.org/10.1152/jn.00246.2019.
Повний текст джерелаАнотація:
Neurotechnological innovations allow for simultaneous recording at various scales, ranging from spiking activity of individual neurons to large neural populations’ local field potentials (LFPs). This capability necessitates developing multiscale analysis of spike-field activity. A joint analysis of the hybrid neural data is crucial for bridging the scales between single neurons and local networks. Granger causality is a fundamental measure to evaluate directional influences among neural signals. However, it is mainly limited to inferring causal influence between the same type of signals—either LFPs or spike trains—and not well developed between two different signal types. Here we propose a model-free, nonparametric spike-field Granger causality measure for hybrid data analysis. Our measure is distinct from existing methods in that we use “binless” spikes (precise spike timing) rather than “binned” spikes (spike counts within small consecutive time windows). The latter clearly distort the information in the mixed analysis of spikes and LFP. Therefore, our spectral estimate of spike trains is directly applied to the neural point process itself, i.e., sequences of spike times rather than spike counts. Our measure is validated by an extensive set of simulated data. When the measure is applied to LFPs and spiking activity simultaneously recorded from visual areas V1 and V4 of monkeys performing a contour detection task, we are able to confirm computationally the long-standing experimental finding of the input-output relationship between LFPs and spikes. Importantly, we demonstrate that spike-field Granger causality can be used to reveal the modulatory effects that are inaccessible by traditional methods, such that spike→LFP Granger causality is modulated by the behavioral task, whereas LFP→spike Granger causality is mainly related to the average synaptic input. NEW & NOTEWORTHY It is a pressing question to study the directional interactions between local field potential (LFP) and spiking activity. In this report, we propose a model-free, nonparametric spike-field Granger causality measure that can be used to reveal directional influences between spikes and LFPs. This new measure is crucial for bridging the scales between single neurons and neural networks; hence it represents an important step to explicate how the brain orchestrates information processing.
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Zhang, Rui, Dianlei Han, Guolong Yu, Haitao Wang, Haibao Liu, Haibin Yu, and Jianqiao Li. "Bionic research on spikes based on the tractive characteristics of ostrich foot toenail." SIMULATION 96, no. 9 (June 10, 2020): 713–23. http://dx.doi.org/10.1177/0037549720927080.
Повний текст джерелаАнотація:
Inspired by the superior fixed and traction characteristics of ostrich foot toenails, we devised, optimized and manufactured the single structure and group arrangement of a new-style bionic spike for sprint shoes to improve athletic performance. The tractive performance of the bionic spike was tested by finite element analysis and experimental verification. The optimized single structure of the bionic spike had a top slope angle of 13° and the radius of the medial groove of 7.3 mm. Compared with the conventional conic spike, the maximal and stable extrusion resistances of the single bionic spike decreased by about 25% and 40% respectively, while the maximal and stable horizontal thrusts increased by about 16% and 10%, respectively. In addition, the arrangement of the bionic spikes was also optimized. Compared with the conventional spike group, the maximal and stable extrusion resistances of the bionic spike group decreased by 11.0% and 6.2%, respectively, while the maximal and stable horizontal thrusts increased by 20.0% and 16.0%, respectively. The current results may provide useful mechanical information that can help develop a better design of athletic shoes with the potential for advanced performance.
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Park, In Yong, Junsik Eom, Hanbyol Jang, Sewon Kim, Sanggeon Park, Yeowool Huh, and Dosik Hwang. "Deep Learning-Based Template Matching Spike Classification for Extracellular Recordings." Applied Sciences 10, no. 1 (December 31, 2019): 301. http://dx.doi.org/10.3390/app10010301.
Повний текст джерелаАнотація:
We propose a deep learning-based spike sorting method for extracellular recordings. For analysis of extracellular single unit activity, the process of detecting and classifying action potentials called “spike sorting” has become essential. This is achieved through distinguishing the morphological differences of the spikes from each neuron, which arises from the differences of the surrounding environment and characteristics of the neurons. However, cases of high structural similarity and noise make the task difficult. And for manual spike sorting, it requires professional knowledge along with extensive time cost and suffers from human bias. We propose a deep learning-based spike sorting method on extracellular recordings from a single electrode that is efficient, robust to noise, and accurate. In circumstances where labelled data does not exist, we created pseudo-labels through principal component analysis and K-means clustering to be used for multi-layer perceptron training and built high performing spike classification model. When tested, our model outperformed conventional methods by 2.1% on simulation data of various noise levels, by 6.0% on simulation data of various clusters count, and by 1.7% on in-vivo data. As a result, we showed that the deep learning-based classification can classify spikes from extracellular recordings, even showing high classification accuracy on spikes that are difficult even for manual classification.
Дисертації з теми "Single spike"
1
Miller, Christopher L. "Variation in single kernel hardness within the wheat spike." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/925.
Повний текст джерела
2
Benda, Jan. "Single neuron dynamics." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2002. http://dx.doi.org/10.18452/14684.
Повний текст джерелаАнотація:
Das Neuron ist das zentrale Element in der Informationsverarbeitung im Nervensystem. In dieser Arbeit werden verschiedene Aspekte der Spikegenerierung sowohl theoretisch als auch experimentell untersucht. Phasen-Rotatoren verschiedener Komplexität werden zur Vorhersage von Spikezeitpunkten vorgestellt. Die Kennlinie eines Neurons wird dabei als wichtiger Parameter für diese Modelle verwendet, damit diese leicht auf echte Neurone anwendbar sind. Die Phasenantwortkurve als ein zweiter wichtiger Aspekt der Spikedynamik wird zur Erweiterung der Modelle verwendet. Solange ein Neuron in seinem überschwelligen Bereich gereizt wird, erweisen sich die Phasenrotatoren als gute Beschreibung des Spikeverhaltens. Es wird jedoch gezeigt, daß bei einer Stimulierung mit Strömen, die um die Schwelle des Neurons herum fluktuieren, diese Modelle, genauso wie alle anderen eindimensionalen Modelle einschließlich des Intergrate-and-fire Neurons, versagen. Feuerraten Adaptation kann in vielen Neuronen beobachtet werden. Es wird ein allgemeines phänomenologisches Modell für die Feuerrate adaptierender Neurone aus den Eigenschaften verschiedene Ionenströme, die Adaptation verursachen, hergeleitet. Dieses Modell ist durch die Kennlinien und einer Adaptations-Zeitkonstanten vollständig definiert. Mit Hilfe des Modells können die Eigenschaften der Adaptation als Hochpassfilter quantifiziert werden. Weiterhin wird die Rolle der Adaptation bei der Unterdrückung von Hintergrundrauschen diskutiert. Sowohl die Phasenrotatoren als auch das Adaptationsmodell werden an auditorischen Rezeptorzellen der Wanderheuschrecke und dem AN1, ein primäres auditorisches Interneuron der Grille {Teleogryllus oceanicus}, getestet. In beiden Fällen stimmen die Modelle gut mit den experimentelle Daten überein. Es wird mit Hilfe der Modelle gezeigt, daß Adaptation in den Rezeptorzellen durch Ionenströme des Spikegenerators verursacht wird, während in dem Interneuron der Eingang schon adaptatiert. Zusätzlich wird der Einfluß der Feuerraten-Adaptation auf die Gesangserkennung analysiert.The single neuron is the basic element of information processing in nervous systems. In this thesis several properties of the dynamics of the generation of spikes are investigated theoretically as well as experimentally. Phase oscillators of different complexity are introduced as models to predict the timing of spikes. The neuron's intensity-response curve is used as a basic parameter in these models to make them easily applicable to real neurons. As a second important aspect of the spiking dynamics, the neuron's phase-resetting curve is used to extend the models. The phase oscillators turn out to be a good approximation of the spiking behavior of a neuron as long as it is stimulated in its super-threshold regime. However, it is shown by comparison with conductance-based models that these models, as well as all other one-dimensional models including the common integrate-and-fire model, fail, if the neuron is stimulated with currents fluctuating around its threshold. Spike-frequency adaptation is a common feature of many neurons. For various ionic currents, as a possible reason for adaptation, a general phenomenological model for the firing rate of adapting neurons is derived from their biophysical properties. This model is defined by the neuron's intensity-response curves and an adaptation time-constant. By means of this model the high-pass properties of spike-frequency adaptation can be quantified. Also the role of adaptation in supression of background noise is discussed. Both the phase oscillators and the adaptation-model are tested on auditory receptor neurons of locusts and the AN1, a primary auditory interneuron of the cricket {Teleogryllus oceanicus}. In both cases the models are in good agreement with the experimental data. By means of the models it is shown that adaptation in the receptor neurons is caused by ionic currents of the spike generator while in the interneuron it is the input which is already adapting. In addition, the influence of spike-frequency adaptation on the recognition of courtship songs is analysed.
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Du, Nan, Mahdi Kiani, Christian G. Mayr, Tiangui You, Danilo Bürger, Ilona Skorupa, Oliver G. Schmidt, and Heidemarie Schmidt. "Single pairing spike-timing dependent plasticity in BiFeO3 memristors with a time window of 25ms to 125µs." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171458.
Повний текст джерелаАнотація:
Memristive devices are popular among neuromorphic engineers for their ability to emulate forms of spike-driven synaptic plasticity by applying specific voltage and current waveforms at their two terminals. In this paper, we investigate spike-timing dependent plasticity (STDP) with a single pairing of one presynaptic voltage spike and one postsynaptic voltage spike in a BiFeO3 memristive device. In most memristive materials the learning window is primarily a function of the material characteristics and not of the applied waveform. In contrast, we show that the analog resistive switching of the developed artificial synapses allows to adjust the learning time constant of the STDP function from 25ms to 125μs via the duration of applied voltage spikes. Also, as the induced weight change may degrade, we investigate the remanence of the resistance change for several hours after analog resistive switching, thus emulating the processes expected in biological synapses. As the power consumption is a major constraint in neuromorphic circuits, we show methods to reduce the consumed energy per setting pulse to only 4.5 pJ in the developed artificial synapses.
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Malvestio, Irene. "Detection of directional interactions between neurons from spike trains." Doctoral thesis, Universitat Pompeu Fabra, 2019. http://hdl.handle.net/10803/666226.
Повний текст джерелаАнотація:
An important problem in neuroscience is the assessment of the connectivity
between neurons from their spike trains. One recent approach developed for
the detection of directional couplings between dynamics based on recorded
point processes is the nonlinear interdependence measure L. In this thesis we
first use the Hindmarsh-Rose model system to test L in the presence of noise
and for different spiking regimes of the dynamics. We then compare the
performance of L against the linear cross-correlogram and two spike train
distances. Finally, we apply all measures to neuronal spiking data from an
intracranial whole-night recording of a patient with epilepsy. When applied
to simulated data, L proves to be versatile, robust and more sensitive than
the linear measures. Instead, in the real data the linear measures find more
connections than L, in particular for neurons in the same brain region and
during slow wave sleep.Un problema important en la neurociència és determinar la connexió entre neurones utilitzant dades dels seus trens d’impulsos. Un mètode recent que afronta la detecció de connexions direccionals entre dinàmiques utilitzant processos puntuals és la mesura d’interdependència no lineal L. En aquesta tesi, utilitzem el model de Hindmarsh-Rose per testejar L en presència de soroll i per diferents règims dinàmics. Després comparem el desempenyorament de L en comparació al correlograma lineal i a dues mesures de trens d’impulsos. Finalment, apliquem totes aquestes mesures a dades d’impulsos de neurones obtingudes de senyals intracranials electroencefalogràfiques gravades durant una nit a un pacient amb epilèpsia. Quan utilitzem dades simulades, L demostra que és versàtil, robusta i més sensible que les mesures lineals. En canvi, utilitzant dades reals, les mesures lineals troben més connexions que L, especialment entre neurones en la mateixa àrea del cervell i durant la fase de son d’ones lentes.
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Landry, Richard Spencer Jr. "Simulating the Affects of Glutamatergic Afferents on the Firing Pattern of Midbrain Dopamine Neurons." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/299.
Повний текст джерелаАнотація:
A computational model of a midbrain dopamine neuron was extended in this study to include a response to random excitatory afferent input by incorporating the receptor components AMPA and NMDA. In a diagonal band where average glutamatergic and tonic gabaergic input is roughly balanced, both single spike firing and bursting can be observed. Simulated SK channel block strengthens the correlation between pattern and rate and increases the number of spikes fired in bursts by increasing the spikes per burst. A simulated doubling of the AMPA/NMDA ratio leads to a frequency increase that becomes more prominent at high firing rates, and an increase in the percent spikes fired in bursts. Changes in pattern and rate are poorly correlated in the model. Manipulations of the neuron greatly depend on the background level of synaptic inputs, suggesting that interpretation of population data from dopamine neurons requires taking variability into account rather than averages.
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Herrera-Valdez, Marco Arieli. "Relationship Between Nearly-Coincident Spiking and Common Excitatory Synaptic Input in Motor Neurons." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/196051.
Повний текст джерелаАнотація:
The activities of pairs of mammalian motor neurons (MNs) receiving varying degrees of common excitatory synaptic input were simulated to study the relationship between nearly-coincident spiking and common excitatory drive. The somatic membrane potential of each MN was modeled using a single compartment model. Each MN was modeled toreceive synaptic contacts from hundreds of pre-synaptic fibers. The percentage of pre-synaptic fibers that diverged to supply both MNs of a pair with common synaptic input could be varied from 0 (no common inputs) to 100% (all common inputs). Spikes trains on separate re-synaptic fibers were independent of one another and were modeled as realizations of renewal processes with mean firing rates (10 - 50Hz) resembling that associated with supra-spinal input. Maximum synaptic conductances and time constants were varied across synapsesto match experimentally observed somatic EPSPs. The number of active pre-synaptic fibers to each MN was adjusted in order that the firingrates of MNs were between 8 and 15 Hz. For each common input condition, 100 s of concurrent spiking activity of the MNs was usedto construct cross-correlation histograms. The sizes of the central peaks in the histograms were quantified using both the k' (Ellaway and Murthy 1985) and CIS (Nordstrom et al. 1992) indices ofsynchrony. Monotonically increasing linear relationships between the proportion of common synaptic input and the magnitude of synchronywere observed for both indices. For example, the model predicted that 10% common input would yield a CIS value of 0.27 whereas 100% commoninput would yield a CIS value of 1.5. These values are within the range of values observed experimentally. These results, therefore,provide a means to translate measures of nearly-coincident spiking into plausible renditions of synaptic connectivity.
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Telenczuk, Bartosz. "Crossing the scales." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16404.
Повний текст джерелаАнотація:
Während seiner normalen Funktion generiert das Gehirn starke elektrische Signale, die technisch gemessen werden können. Das schon seit über einem Jahrhundert bekannte Phänomen ermöglicht es die Signalverarbeitung im Gehirn räumlich und zeitlich zu beobachten. Heute versteht man die zellulären Prozesse die zur Generierung der elektrischen Signale in einzelnen Neuronen führen. Jedoch rekrutieren die meisten neuronalen Ereignisse große Populationen von Zellen, dessen Aktivität zeitlich und räumlich koordiniert ist. Diese Koordinierung führt dazu, dass ihre elektrische Aktivität auch weit von den Quellen gemessen werden kann, sodass die Beobachtung des Gehirns auch nicht invasiv auf der Schädeloberfläche mittels dem sogenannten Elektroenzephalogramm (EEG) möglich ist. Der zeitliche Verlauf des Signals hängt nicht nur von den Eigenschaften einzelner Zellen ab sondern auch von ihrer Wechselwirkung mit anderen Neuronen, die oft komplex oder gar nicht bekannt ist. Diese Komplexität verhindert die Auswertung der gemessen Signale im Bezug auf die Anzahl von aktiven Neuronen, die Art der Antwort (Inhibition, Exzitation), die Synchronisationsstärke und den Einfluss anderer aktiver Prozesse (wie zum Beispiel: Lernen, Aufmerksamkeit usw.). In dieser Arbeit werden die Zusammenhänge zwischen diesen mikroskopischen Parametern (einzelne Neurone) und ihrer makroskopischen Wirkung (EEG) experimentell, datenanalytisch und theoretisch untersucht.During its normal function the brain generates strong and measurable electric signals. This phenomenon, which has been known for more than a century, makes it possible to investigate the signal processing in the brain. Nowadays the cellular processes taking part in the generation of the electric signals are well understood. However, most of the neuronal events recruit large populations of cells, whose activities are coordinated spatially and temporally. This coordination allows for summation of activities generated by many neurons leading to extracellular electric signals that can be recorded non-invasively from the scalp by means of electroencephalography (EEG). The temporal structure of the EEG signal does not depend only on the properties of single neurons, but also on their interactions that may be very complex. The complexity hinders the evaluation of the recoded signal with respect to the number of active neurons, the type of response, the degree of synchronisation and the contribution of other processes (such as, learning and attention). In the thesis, the relations between the microscopic (single-neuron) and their macroscopic (EEG) properties will be investigated by means of experimental, data-analytic and theoretical approaches.
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Blankenburg, Sven. "Theoretical mechanisms of information filtering in stochastic single neuron models." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17577.
Повний текст джерелаАнотація:
Die vorliegende Arbeit beschäftigt sich mit Mechanismen, die in Einzelzellmodellen zu einer frequenzabhängigen Informationsübertragung führen können. Um dies zu untersuchen, werden Methoden aus der theoretischen Physik (Statistische Physik) und der Informationstheorie angewandt. Die Informationsfilterung in mehreren stochastischen Neuronmodellen, in denen unterschiedliche Mechanismen zur Informationsfilterung führen können, werden numerisch und, falls möglich, analytisch untersucht. Die Bandbreite der betrachteten Modelle erstreckt sich von reduzierten strombasierten ’Integrate-and-Fire’ (IF) Modellen bis zu biophysikalisch realistischeren leitfähigkeitsbasierten Modellen. Anhand numerischer Untersuchungen wird aufgezeigt, dass viele Varianten der IF-Neuronenmodelle vorzugsweise Information über langsame Anteile eines zeitabhängigen Eingangssignals übertragen. Der einfachste Vertreter der oben genannten Klasse der IF-Neuronmodelle wird dahingehend erweitert, dass ein Konzept von neuronalem ’Gedächtnis’, vermittelst positiver Korrelationen zwischen benachbarten Intervallen aufeinander- folgender Spikes, integriert wird. Dieses Model erlaubt eine analytische störungstheoretische Untersuchung der Auswirkungen positiver Korrelationen auf die Informationsfilterung. Um zu untersuchen, wie sich sogenannte ’unterschwelligen Resonanzen’ auf die Signalübertragung auswirken, werden Neuronenmodelle mit verschiedenen Nichtlinearitäten anhand numerischer Computersimulationen analysiert. Abschließend wird die Signalübertragung in einem neuronalen Kaskadensystem, bestehend aus linearen und nichtlinearen Elementen, betrachtet. Neuronale Nichtlinearitäten bewirken eine gegenläufige Abhängigkeit (engl. "trade-off") zwischen qualitativer, d.h. frequenzselektiver, und quantitativer Informations-übertragung, welche in allen von mir untersuchten Modellen diskutiert wird. Diese Arbeit hebt die Gewichtigkeit von Nichtlinearitäten in der neuronalen Informationsfilterung hervor.Neurons transmit information about time-dependent input signals via highly non-linear responses, so-called action potentials or spikes. This type of information transmission can be frequency-dependent and allows for preferences for certain stimulus components. A single neuron can transmit either slow components (low pass filter), fast components (high pass filter), or intermediate components (band pass filter) of a time-dependent input signal. Using methods developed in theoretical physics (statistical physics) within the framework of information theory, in this thesis, cell-intrinsic mechanisms are being investigated that can lead to frequency selectivity on the level of information transmission. Various stochastic single neuron models are examined numerically and, if tractable analytically. Ranging from simple spiking models to complex conductance-based models with and without nonlinearities, these models include integrator as well as resonator dynamics. First, spectral information filtering characteristics of different types of stochastic current-based integrator neuron models are being studied. Subsequently, the simple deterministic PIF model is being extended with a stochastic spiking rule, leading to positive correlations between successive interspike intervals (ISIs). Thereafter, models are being examined which show subthreshold resonances (so-called resonator models) and their effects on the spectral information filtering characteristics are being investigated. Finally, the spectral information filtering properties of stochastic linearnonlinear cascade neuron models are being researched by employing different static nonlinearities (SNLs). The trade-off between frequency-dependent signal transmission and the total amount of transmitted information will be demonstrated in all models and constitutes a direct consequence of the nonlinear formulation of the models.
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Darling, Ryan Daniel. "Single Cell Analysis of Hippocampal Neural Ensembles during Theta-Triggered Eyeblink Classical Conditioning in the Rabbit." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1225460517.
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Nguyen, Van Dong. "Speciation analysis of butyl- and phenyltin compounds in environmental samples by GC separation and atomic spectrometric detection." Doctoral thesis, Umeå : Department of Chemistry, Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-892.
Повний текст джерелаКниги з теми "Single spike"
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Stănescu, Nichita. Wheel with a single spoke: And other poems. New York: Archipelago Books, 2012.
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1971-, Cotter Sean, ed. Wheel with a single spoke: And other poems. New York: Archipelago Books, 2012.
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3
Soto, Pedro Juan. Spiks. 8th ed. Rio Piedras, Puerto Rico: Editorial Cultural, 1989.
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4
D, McSherry Frank, Waugh Charles, and Greenberg Martin Harry, eds. More Dixie ghosts: More haunting, spine-chilling stories from the American South. Nashville: Rutledge Hill Press, 1994.
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5
1946-, Codrescu Andrei, and Rosenthal Laura 1958-, eds. Thus spake the Corpse: An Exquisite corpse reader, 1988-1998. Santa Rosa, CA: Black Sparrow Press, 1999.
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Clauser, Marina, Andrea Grigioni, and Mario Landi, eds. Peperoncini. Florence: Firenze University Press, 2010. http://dx.doi.org/10.36253/978-88-8453-951-9.
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The chili pepper is a spice and medicinal remedy used since ancient times by the American peoples who were the first to undertake the domestication of 5 species belonging to the genus Capsicum (Solanaceae): Capsicum (Solanaceae): Capsicum annuum, C. baccatum, C. chinense, C. frutescens e C. pubescens. After the sixteenth century the chili pepper became similarly popular in other continents and today the five species number many reference pod-types and over 3,000 varieties. The book describes their uses in the different spheres of cuisine (aromatic, spicy and colourful), medicine (antioxidant and digestive for internal use, rubefacient and anti-rheumatic for external use) and ornamentation (cut branches, floral compositions, border plants, splashes of colour).
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Klinger, Leslie S., ed. Sherlock Holmes anotado: Relatos II. Spain: Akal, 2011.
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Sampath, Gopalan, and S. K. Srinivasan. Stochastic Models for Spike Trains of Single Neurons. Springer London, Limited, 2013.
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Warman, Cy. Last Spike and Other Railroad Stories. IndyPublish.com, 2006.
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Warman, Cy. The Last Spike and Other Railroad Stories. Wildside Press, 2006.
Знайти повний текст джерелаЧастини книг з теми "Single spike"
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Eder, K. "A Supervised Learning Rule for the Single Spike Model." In ICANN ’94, 789–92. London: Springer London, 1994. http://dx.doi.org/10.1007/978-1-4471-2097-1_187.
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Houghton, Conor, and Thomas Kreuz. "Measures of Spike Train Synchrony: From Single Neurons to Populations." In Multiscale Analysis and Nonlinear Dynamics, 277–97. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527671632.ch13.
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Lu, Renxiang, and Johnn Judd. "Effect of Bridge Skew on the Analytical and Experimental Responses of a Steel Girder Highway Bridge." In Lecture Notes in Civil Engineering, 70–81. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1260-3_7.
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AbstractThis study examines the effect of bridge skew on the load rating and natural frequencies of a steel girder skewed highway bridge. The analytical load rating was determined based on a line-girder model and the AASHTO bridge design specification. The experimental load rating was determined based on a series of calibrated-weight truck runs. The analytical natural frequency was determined based on correlating the single span response to a continuous span response. The experimental natural frequency was obtained based on the free vibration response from the calibrated-weight truck. The frequency associated with the first spike of the frequency domain plot was identified using a Fast Fourier Transformation. The results show that the analytical load ratings and natural frequencies differed from the experimental values primarily due to effect of bridge skew, which caused the actual load path to be significantly shorter than the bridge span length that was used in the analytical calculations.
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Thompson, George H., and Jochen P. Son-Hing. "Single Growing Rods." In The Growing Spine, 441–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-540-85207-0_35.
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Slavici, Andrei. "Pyogenic Infection Following Single Level Nucleotomy." In Spine Surgery, 339–44. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-98875-7_41.
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Thompson, George H., and Behrooz A. Akbarnia. "Single and Dual Traditional Growing Rods." In The Growing Spine, 645–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-48284-1_38.
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Poulter, Gregory T. "Single Position Front–Back Surgery." In Advanced Robotic Spine Surgery, 31–42. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9781003081715-5.
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Nangunoori, Raj, Jacob L. Goldberg, Joseph A. Carnevale, Lynn McGrath, Sertac Kirnaz, and Roger Härtl. "Navigation Guided Single-Stage Lateral Surgery." In Technical Advances in Minimally Invasive Spine Surgery, 11–22. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-0175-1_2.
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Murray, Gisela, Chun-Po Yen, and Juan S. Uribe. "Single Versus Dual Incisions for Lateral Retroperitoneal Approach." In Lateral Access Minimally Invasive Spine Surgery, 101–2. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-28320-3_13.
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Nam, Han Ga Wi, Chun-Kun Park, and Kangtaek Lim. "Cervical Multilevel Foraminotomy Using Single Incision." In Advanced Technique of Endoscopic Cervical and Thoracic Spine Surgery, 39–50. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1133-2_4.
Повний текст джерелаТези доповідей конференцій з теми "Single spike"
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Taylor, Brady, Amar Shrestha, Qinru Qiu, and Hai Li. "1S1R-Based Stable Learning through Single-Spike-Encoded Spike-Timing-Dependent Plasticity." In 2021 IEEE International Symposium on Circuits and Systems (ISCAS). IEEE, 2021. http://dx.doi.org/10.1109/iscas51556.2021.9401644.
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Stanojevic, Ana, Evangelos Eleftheriou, Giovanni Cherubini, Stanislaw Wozniak, Angeliki Pantazi, and Wulfram Gerstner. "Approximating Relu Networks by Single-Spike Computation." In 2022 IEEE International Conference on Image Processing (ICIP). IEEE, 2022. http://dx.doi.org/10.1109/icip46576.2022.9897692.
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Liu, Tao, Lei Jiang, Yier Jin, Gang Quan, and Wujie Wen. "PT-spike: A precise-time-dependent single spike neuromorphic architecture with efficient supervised learning." In 2018 23rd Asia and South Pacific Design Automation Conference (ASP-DAC). IEEE, 2018. http://dx.doi.org/10.1109/aspdac.2018.8297383.
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Stanojevic, Ana, Stanislaw Wozniak, Guillaume Bellec, Giovanni Cherubini, Angeliki Pantazi, and Wulfram Gerstner. "Equivalence of ReLU and Single-Spike Neural Networks." In Neuromorphic Materials, Devices, Circuits and Systems. València: FUNDACIO DE LA COMUNITAT VALENCIANA SCITO, 2023. http://dx.doi.org/10.29363/nanoge.neumatdecas.2023.051.
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Dick, Matthew G., David S. McConnell, and Hans C. Iwand. "Experimental Measurement and Finite Element Analysis of Screw Spike Fatigue Loads." In ASME/IEEE 2007 Joint Rail Conference and Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/jrc/ice2007-40090.
Повний текст джерелаАнотація:
Screw spikes, also known as coach screws, are an advanced alternative to common cut spikes for track fastening. Despite their ability to secure tie plates with a clamp load and utilization of high strength steels, they are still susceptible to bending fatigue failure from lateral wheel loads. A novel method of measuring these bending loads on screw spikes was developed and implemented to characterize the load environment of the screw spikes. Results indicated that measured peak bending loads under lateral wheel loads reached as high as 10,000 lbs for individual spikes, while others carried no load whatsoever. A finite element model was developed to determine the tensile stress fields created by the measured bending loads. A good correlation was found between the FEA model predicted point of highest stress and the location of fracture. Through the testing and analysis it was determined that lateral wheel loads are not distributed evenly among the four screw spikes of a single tie plate. Instead, it was found that one spike carried nearly no load while the spike opposite of it carried more load. Using the finite element analysis it was determined that the spike exposed to the higher loading was subjected to tensile stresses above its endurance limit, which would eventually lead to a bending fatigue failure.
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Harrison, Alan K. "The Spike Dynamics Source Model for Ejecta in the FLAG Code." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5455.
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Abstract The Lagrangian hydrocode FLAG employs a subgrid model to represent the ejection of particulate mass (“ejecta”) from a shocked metal surface. With a conforming mesh used in typical simulations, the calculations of ejecta production, properties and launch are carried out independently on each mesh face lying on the surface of the metal. Based on experimental evidence [1] that ejecta production is greatest when the shock releases to the liquid state, the ejection process is modeled as a Richtmyer-Meshkov instability (RMI) of the liquid metal surface, in which the metal spikes that form break up to become ejecta. The model applies to the case in which surface perturbations such as machining grooves can be well approximated as a single-mode sinusoidal perturbation; in this case the RMI spikes are actually sheets. The FLAG model includes (1) a description of RMI spike and bubble growth rates [2] and (2) the Self-Similar Velocity Distribution (SSVD) model of the velocity field within a spike as varying linearly from zero (in the fluid frame) at the base to a maximum value at the tip [3]. We report here on the improvement of this model by incorporating (3) a spike breakup treatment based on the Taylor Analogy Breakup (TAB) model [5], as extended to apply to sheet breakup [6,7], and (4) a new model for the inflow of metal into the base of the spikes. Combining all these elements allows us to self-consistently reconcile the evolving shape of the spikes (elongation and thinning) with the inflow, and with the corresponding properties of the bubbles, under the assumption of incompressibility. Since the model describes the motion of each fluid element into and along the spike, and subsequent fragmentation of the spike into ejecta, it predicts not only mass ejection rate but also the sizes and velocities of the particles launched in this process. We describe the new self-consistent model and its implementation in FLAG.
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Thorbergsson, P. T., H. Jorntell, F. Bengtsson, M. Garwicz, J. Schouenborg, and A. J. Johansson. "Spike library based simulator for extracellular single unit neuronal signals." In 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2009. http://dx.doi.org/10.1109/iembs.2009.5333847.
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Lopes, M. V., E. Aguiar, E. Santana, E. Santana, and A. K. Barros. "ICA feature extraction for spike sorting of single-channel records." In 2013 ISSNIP Biosignals and Biorobotics Conference: Biosignals and Robotics for Better and Safer Living (BRC). IEEE, 2013. http://dx.doi.org/10.1109/brc.2013.6487468.
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Simpson, Alexander K., and John P. Longley. "An Experimental Study of the Inception of Rotating Stall in a Single-Stage Low-Speed Axial Compressor." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27181.
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There are two established mechanisms, spike and modal inception, by which rotating stall is initiated in an axial flow compressor. Whilst the “Critical incidence hypothesis” and the “Zero slope criterion” are useful ideas in explaining the different stability boundaries for spikes and modes they do not provide the designer with a predictive tool. A detailed experimental investigation utilising a single-stage low-speed compressor is presented in which the aerodynamic environment of a rotor blade row is changed (rotor geometry is held fixed) so that it exhibited both spike and modal inception upon throttling into stall. The dominant mechanism of stall inception was found to be dependent on both the inlet flowfield and the downstream stator. The measurements are analysed and show that the meridional acceleration across the tip region of the rotor influences the mechanism by which rotating stall is incepted. This research is presented as a contribution towards the prediction of the stall inception mechanism.
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Goodhand, Martin N., and Robert J. Miller. "Compressor Leading Edge Spikes: A New Performance Criterion." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59205.
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Compressor blades often have a small ‘spike’ in the surface pressure distribution at the leading edge. This may result from blade erosion, manufacture defects or compromises made in the original design process. This paper investigates the effect of these spikes on profile loss and presents a criterion to ensure they are not detrimental to compressor performance. In the first part of the paper two geometries of leading edge are tested. One has a small spike, typical of those found on modern compressors; the other has no spike, characteristic of an idealized leading edge. Testing was undertaken on the stator of a single-stage low speed compressor. The time-resolved boundary layer was measured using a hot-wire micro traversing system. It is shown that the presence of the small spike changes the time resolved transition process on the suction surface, but that this results in no net increase in loss. In the second part of the paper, spike height is systematically changed using a range of leading edge geometries. It is shown that below a critical spike height the profile loss is constant. If the critical spike height is exceeded, the leading edge separates and profile loss rises by 30%. Finally a criterion is developed, based on the total diffusion across the spike. Three different leading edge design philosophies are investigated. It is shown that if the spike diffusion factor is kept below 0.1 over the blade’s incidence range, performance is unaffected by leading edge geometry.
Звіти організацій з теми "Single spike"
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Parise, Mattia. Single Spoke Resonators: String Assembly and Mechanical Design. Office of Scientific and Technical Information (OSTI), January 2020. http://dx.doi.org/10.2172/1596027.
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Asante, Kofi Takyi. Political Economy of the Oil Palm Value Chain in Ghana. Institute of Development Studies (IDS), March 2021. http://dx.doi.org/10.19088/apra.2021.008.
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Oil palm (Elaeis guineensis) is of strategic importance to the Ghanaian economy. It is the second most important industrial crop after cocoa and is used widely in local food preparation as well as in industrial processing. In spite of its importance, however, oil palm has consistently underperformed since the early twentieth century. This paper conducts a value chain analysis of the crop, foregrounding the political economy factors that shape the performance of the sector. It draws on a combination of in-depth interviews conducted in March 2020 with a variety of value chain actors and a review of the secondary literature. Additionally, between late May and early June 2020, twelve further interviews were conducted as part of a rapid market survey to assess the impact of the COVID-19 pandemic on the value chain.
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Crouch, Rebecca, Jared Smith, Bobbi Stromer, Christian Hubley, Samuel Beal, Guilherme Lotufo, Afrachanna Butler, et al. Preparative, extraction, and analytical methods for simultaneous determination of legacy and insensitive munition (IM) constituents in aqueous, soil or sediment, and tissue matrices. Engineer Research and Development Center (U.S.), August 2021. http://dx.doi.org/10.21079/11681/41480.
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No standard method exists for determining levels of insensitive munition (IM) compounds in environmental matrices. This project resulted in new methods of extraction, analytical separation and quantitation of 17 legacy and 7 IM compounds, daughter products of IM, and other munition compounds absent from USEPA Method 8330B. Extraction methods were developed for aqueous (direct-injection and solid-phase extraction [SPE]), soil, sediment, and tissue samples using laboratory-spiked samples. Aqueous methods were tested on 5 water sources, with 23 of 24 compounds recovered within DoD QSM Ver5.2 limits. New solvent extraction (SE) methods enabled recovery of all 24 compounds from 6 soils within QSM limits, and a majority of the 24 compounds were recovered at acceptable levels from 4 tissues types. A modified chromatographic treatment method removed analytical interferences from tissue extracts. Two orthogonal high-performance liquid chromatography-ultraviolet (HPLC-UV) separation methods, along with an HPLC–mass spectrometric (HPLC-MS) method, were developed. Implementing these new methods should reduce labor and supply costs by approximately 50%, requiring a single extraction and sample preparation, and 2 analyses rather than 4. These new methods will support environmental monitoring of IM and facilitate execution of risk-related studies to determine long-term effects of IM compounds.
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Rosenfeld. L51741 Development of a Model for Fatigue Rating Shallow Unrestrained Dents. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), September 1997. http://dx.doi.org/10.55274/r0010337.
Повний текст джерелаАнотація:
The ability to fatigue-rate dents in line pipe is important for three reasons. First, field failures give evidence that fatigue crack growth occurs in dents under certain circumstances in spite of the fact that plain dents are generally thought to have little effect on the integrity of natural gas pipelines based on the results of single-cycle burst tests. Second, many operators are discovering large numbers of dents on the bottom quadrants of their pipe associated with rocks and backfill loads. Guidance is needed for discerning dents for which excavation and inspection is economically wasteful and counterproductive to pipeline safety from those dents for which further action would be beneficial. Third, fatigue life may be a more rational basis for rating the severity of a dent than present criteria which rely solely on dent depth with a maximum depth of 6 percent of the pipe diameter as a generally accepted limit. In some cases deeper dents might be permitted to remain in service, while in other cases, shallower dents should be repaired. The goal of this project was to develop guidelines for pipeline operators to assess the severity of dents on the basis of their fatigue life in-service. The assessment uses pipeline operating pressures and simple geometric measurements of the dent.
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Dasberg, Shmuel, Jan W. Hopmans, Larry J. Schwankl, and Dani Or. Drip Irrigation Management by TDR Monitoring of Soil Water and Solute Distribution. United States Department of Agriculture, August 1993. http://dx.doi.org/10.32747/1993.7568095.bard.
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Drip irrigation has the potential of high water use efficiency, but actual water measurement is difficult because of the limited wetted volume. Two long-term experiments in orchards in Israel and in California and several field crop studies supported by this project have demonstrated the feasibility of precise monitoring of soil water distribution for drip irrigation in spite of the limited soil wetting. Time Domain Reflectometry (TDR) enables in situ measurement of soil water content of well defined small volumes. Several approaches were tried in monitoring the soil water balance in the field during drip irrigation. These also facilitated the estimation of water uptake: 1. The use of multilevel moisture probe TDR system. This approach proved to be of limited value because of the extremely small diameter of measurement. 2. The placement of 20 cm long TDR probes at predetermined distances from the drippers in citrus orchards. 3. Heavy instrumentation with neutron scattering access tubes and tensiometers of a single drip irrigated almond tree. 4. High resolution spatial and temporal measurements (0.1m x 0.1m grid) of water content by TDR in corn irrigated by surface and subsurface drip. The latter approach was accompanied by parametric modelling of water uptake intensity patterns by corn roots and superimposed with analytical solutions for water flow from point and line sources. All this lead to general and physically based suggestions for the placement of soil water sensors for scheduling drip irrigation.
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Thompson, Joseph. How WASH Programming has Adapted to the COVID-19 Pandemic. Institute of Development Studies (IDS), December 2020. http://dx.doi.org/10.19088/slh.2021.001.
Повний текст джерелаАнотація:
Since first appearing at the end of 2019, the novel coronavirus disease (COVID-19) has spread at a pace and scale not seen before. On 11 March 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. A rapid response was called for, and actors across the globe worked quickly to develop sets of preventative measures to contain the disease. One mode of transmission identified early on in the crisis was via surfaces and objects (fomites) (Howard et al. 2020). To combat this, hand hygiene was put forward as a key preventative measure and heralded as ‘the first line of defence against the disease’ (World Bank 2020). What followed was an unprecedented global focus on handwashing with soap. Health messages on how germs spread, the critical times at which hands should be washed, and methods for correct handwashing were shared (Centers for Disease Control and Prevention 2020). Political leaders around the world promoted handwashing and urged people to adopt the practice to protect against the coronavirus. The primary and secondary impacts of COVID-19 have affected people and industries in a variety of different ways. For the WASH sector, the centring of handwashing in the pandemic response has led to a sudden spike in hygiene activity. This SLH Rapid Topic Review takes stock of some of the cross-cutting challenges the sector has been facing during this period and explores the adaptations that have been made in response. It then looks forwards, thinking through what lies ahead for the sector, and considers the learning priorities for the next steps.
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Thompson, Joseph. How WASH Programming has Adapted to the COVID-19 Pandemic. The Sanitation Learning Hub, Institute of Development Studies, December 2020. http://dx.doi.org/10.19088/slh.2021.0015.
Повний текст джерелаАнотація:
Since first appearing at the end of 2019, the novel coronavirus disease (COVID-19) has spread at a pace and scale not seen before. On 11 March 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. A rapid response was called for, and actors across the globe worked quickly to develop sets of preventative measures to contain the disease. One mode of transmission identified early on in the crisis was via surfaces and objects (fomites) (Howard et al. 2020). To combat this, hand hygiene was put forward as a key preventative measure and heralded as ‘the first line of defence against the disease’ (World Bank 2020). What followed was an unprecedented global focus on handwashing with soap. Health messages on how germs spread, the critical times at which hands should be washed, and methods for correct handwashing were shared (Centers for Disease Control and Prevention 2020). Political leaders around the world promoted handwashing and urged people to adopt the practice to protect against the coronavirus. The primary and secondary impacts of COVID-19 have affected people and industries in a variety of different ways. For the WASH sector, the centring of handwashing in the pandemic response has led to a sudden spike in hygiene activity. This SLH Rapid Topic Review takes stock of some of the cross-cutting challenges the sector has been facing during this period and explores the adaptations that have been made in response. It then looks forwards, thinking through what lies ahead for the sector, and considers the learning priorities for the next steps.
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Drayton, Paul, Jeffrey Panek, Tom McGrath, and James McCarthy. PR-312-12206-R01 FTIR Formaldehyde Measurement at Turbine NESHAP and Ambient Levels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2016. http://dx.doi.org/10.55274/r0011014.
Повний текст джерелаАнотація:
Since formaldehyde is ubiquitous (e.g., naturally formed through atmospheric chemistry even if not directly emitted), there is also the potential that atmospheric levels and atmospheric chemistry are not adequately understood.� That avenue of investigation may provide important information that could be important in assessing formaldehyde health risk, source contribution, and ultimately regulatory criteria for gas-fired combustion sources.� In 2002 and 2003, the pipeline industry conducted turbine formaldehyde testing using refined FTIR methods and a dedicated measurement system, which indicated exhaust formaldehyde below 100 ppb and near the method detection limit.� Anecdotal data from that test program showed ambient levels similar to turbine exhaust in some cases.� For example, during the industry test program, a serendipitous finding observed that ambient formaldehyde concentrations varied and were independent of turbine operation.� Instead, naturally occurring emissions from an adjacent corn field appeared to spike the ambient concentration to levels higher than formaldehyde exhaust levels, depending on whether there was direct sunlight or shading from a cloud (i.e., due to �naturally occurring� formaldehyde from vegetation and/or other organics and ambient photochemistry that forms formaldehyde).� Evidence of �high� ambient formaldehyde levels (relative to turbine exhaust) would be a powerful counterargument to restrictive formaldehyde regulations. If ambient levels are similar to (or higher than) in-stack formaldehyde for turbines, then a NESHAP requiring catalytic control of turbine formaldehyde results in a significant burden without� environmental benefit, while also negatively impacting turbine efficiency and environmental impacts associated with catalyst construction, installation, operation, cleaning, and disposal.� Similarly, if ambient formaldehyde is significantly higher (in at least some circumstances) than currently available ambient data suggests, there could be implications for perceived formaldehyde risk and the basis, need for, and stringency of formaldehyde reductions from turbines or other combustion sources.� In a more far-reaching impact, ambient FTIR data could provide additional insights on atmospheric reactions that not only impact formaldehyde issues, but also ozone (and NOx control issues) because of the importance of formaldehyde and hydrocarbon chemistry in ambient ozone formation. These determinations are challenged by the ability to accurately measure formaldehyde at levels less than 100 parts per billion (ppbv).� Ambient measurements rely on �batch methods� subject to error (due to the inherent instability and reactivity of formaldehyde), and those methods do not provide real-time continuous results.� Extractive Fourier Transform Infrared (FTIR) methods were developed for combustion exhaust formaldehyde measurement, but measuring the ultra-low levels from turbines, commensurate with the NESHAP standard of 90 ppb, is challenging.� This project was intended assess ambient formaldehyde levels as compared to the NESHAP standard and acquire additional ambient measurement data using FTIR testing.
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Ostersetzer-Biran, Oren, and Jeffrey Mower. Novel strategies to induce male sterility and restore fertility in Brassicaceae crops. United States Department of Agriculture, January 2016. http://dx.doi.org/10.32747/2016.7604267.bard.
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Abstract Mitochondria are the site of respiration and numerous other metabolic processes required for plant growth and development. Increased demands for metabolic energy are observed during different stages in the plants life cycle, but are particularly ample during germination and reproductive organ development. These activities are dependent upon the tight regulation of the expression and accumulation of various organellar proteins. Plant mitochondria contain their own genomes (mtDNA), which encode for rRNAs, tRNAs and some mitochondrial proteins. Although all mitochondria have probably evolved from a common alpha-proteobacterial ancestor, notable genomic reorganizations have occurred in the mtDNAs of different eukaryotic lineages. Plant mtDNAs are notably larger and more variable in size (ranging from 70~11,000 kbp in size) than the mrDNAs in higher animals (16~19 kbp). Another unique feature of plant mitochondria includes the presence of both circular and linear DNA fragments, which undergo intra- and intermolecular recombination. DNA-seq data indicate that such recombination events result with diverged mitochondrial genome configurations, even within a single plant species. One common plant phenotype that emerges as a consequence of altered mtDNA configuration is cytoplasmic male sterility CMS (i.e. reduced production of functional pollen). The maternally-inherited male sterility phenotype is highly valuable agriculturally. CMS forces the production of F1 hybrids, particularly in predominantly self-pollinating crops, resulting in enhanced crop growth and productivity through heterosis (i.e. hybrid vigor or outbreeding enhancement). CMS lines have been implemented in some cereal and vegetables, but most crops still lack a CMS system. This work focuses on the analysis of the molecular basis of CMS. We also aim to induce nuclear or organellar induced male-sterility in plants, and to develop a novel approach for fertility restoration. Our work focuses on Brassicaceae, a large family of flowering plants that includes Arabidopsis thaliana, a key model organism in plant sciences, as well as many crops of major economic importance (e.g., broccoli, cauliflower, cabbage, and various seeds for oil production). In spite of the genomic rearrangements in the mtDNAs of plants, the number of genes and the coding sequences are conserved among different mtDNAs in angiosperms (i.e. ~60 genes encoding different tRNAs, rRNAs, ribosomal proteins and subunits of the respiratory system). Yet, in addition to the known genes, plant mtDNAs also harbor numerous ORFs, most of which are not conserved among species and are currently of unknown function. Remarkably, and relevant to our study, CMS in plants is primarily associated with the expression of novel chimericORFs, which likely derive from recombination events within the mtDNAs. Whereas the CMS loci are localized to the mtDNAs, the factors that restore fertility (Rfs) are identified as nuclear-encoded RNA-binding proteins. Interestingly, nearly all of the Rf’s are identified as pentatricopeptide repeat (PPR) proteins, a large family of modular RNA-binding proteins that mediate several aspects of gene expression primarily in plant organelles. In this project we proposed to develop a system to test the ability of mtORFs in plants, which are closely related to known CMS factors. We will induce male fertility in various species of Brassicaceae, and test whether a down-relation in the expression of the recombinantCMS-genes restores fertility, using synthetically designed PPR proteins.
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Swanson, David, and Celia Hampton-Miller. Drained lakes in Bering Land Bridge National Preserve: Vegetation succession and impacts on loon habitat. National Park Service, January 2023. http://dx.doi.org/10.36967/2296593.
Повний текст джерелаАнотація:
The northern coastal plain of Bering Land Bridge National Preserve (BELA) lost lakes at an alarming rate over the first two decades of this century, including four lakes over 100 ha in size in 2018-2019 alone. To understand the effects of these lake drainages, we sampled vegetation of these lakes in 2019 (a reconnaissance visit) and 2021 (for the installation of permanent vegetation monitoring plots). We used these data to summarize the changes that occurred in the first three years after drainage, and to create vegetation maps from 3-m resolution satellite images coinciding with the visit dates. We used time series of these satellite images to study the rate of drainage and vegetation colonization on the lakes. We analyzed our existing data from older drained lake basins (estimated to be more than 200 years since drainage) and reviewed the literature on vegetation change in drained lakes to understand the vegetation changes that are likely in the future. Finally, we used a model of lake occupancy by loons developed by Mizel et al. (2021) to predict the effect of the 2018-2019 lake drainages on available loon habitat, using both our detailed maps of the four sampled drained lakes, and also data on all drained lakes over most of northern BELA derived from Landsat satellite images. Our results show that the four study lakes drained early in the summer, before the end of June, in 2018 (3 lakes) and 2019 (one lake). A combination of record warm weather and heavy snowfall made 2018 and 2019 especially favorable for lake drainage: thaw subsidence probably enlarged existing drainage outlet channels from the lakes, and large amounts of spring snowmelt runoff deepened the outlet channels by thermal erosion (the combination of thaw and erosion). Drainage exposed moist loamy sediment on the lake bottoms that was rapidly colonized by plants. Substantial vegetation cover developed by late summer in the same year as lake drainage in one lake, in the first post-drainage summer in a second lake, and during the 2nd year after drainage in the remaining two lakes. The first vegetation communities to develop consisted of just one or two dominant species, notably Eleocharis acicularis (spike rush), Equisetum arvense (horsetail), and/or Tephroseris palustris (mastodon flower). Other important early species were Arctophila fulva (pendant grass) and Rorippa palustris (yellow cress). By year 3, the communities had become more diverse, with significant cover by taller wetland graminoid species, including A. fulva, Eriophorum scheuchzeri, and Carex aquatilis. Frozen soil was observed in most locations on the lakes in July of 2021, suggesting that permafrost was forming on the lake bottoms. Comparison of the three-year trends in vegetation change with data from older lake basins suggest that ultimately most lake basins will develop wet tundra communities dominated by Carex aquatilis and mosses, with various low shrub species on acid, peat-dominated soils and permafrost; however, this process should take several centuries. The loon habitat model suggests that drainage essentially eliminated the potential habitat for Yellow-billed Loons on the four study lakes, because the residuals ponds were too small for Yellow-billed Loons to take flight from. A total of 17 lakes drained in northern BELA in 2018-2019. As a result, the potential Yellow-billed Loon nesting habitat in northern BELA probably decreased by approximately 2%, while habitat for Pacific Loons decreased less, by about 0.6%. Habitat for the more abundant Red-throated Loons probably increased slightly as a result of lake drainage, because of their ability to use the small residual ponds created by lake drainage.