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1

Bursting electrical activity in pancreatic beta cells caused by Ca(2+)- and voltage-inactivated Ca2+ channels.  

PubMed Central

We investigate the hypothesis that two classes of Ca2+ currents, one quickly inactivated by Ca2+ and one slowly inactivated by voltage, contribute to bursting electrical activity in pancreatic islets. A mathematical model of these currents is fit to the experimental whole-cell current-voltage and inactivation profiles, thereby fixing the Ca2+ conductance and all activation and inactivation parameters. Incorporating these currents into a model that includes delayed rectifier K+ channels and ATP-sensitive K+ channels, we show that only abnormal bursting is obtained. Modification of activation parameters to increase Ca2+ channel open times, as suggested by experiment, yields a more robust bursting similar to that observed in intact islets. This reinforces the suggestion that in addition to ATP-sensitive K+ channels, Ca2+ channels may serve as glucose sensors in the beta cell.

Keizer, J; Smolen, P

1991-01-01

2

Study of the EEG phenomenon of high-frequency bursts in the neocortical electrical activity of dogs in the process of alimentary instrumental learning  

Microsoft Academic Search

We studied the electroencephalographic (EEG) phenomenon of high-frequency (HF) bursts (within the limits of 60–170 cycle,\\u000a 70–80 ?V) in the electrical activity (EA) of the brain (1–200 Hz) of dogs in the process of alimentary instrumental conditioning.\\u000a These bursts appeared at the stage of generalization in a number of neocortical areas in the interstimulus intervals at the\\u000a background EA, which

V. N. Dumenko; M. K. Kozlov

1997-01-01

3

Spiking Signatures of Spontaneous Activity Bursts in Hippocampal Cultures  

PubMed Central

Dense dissociated hippocampal cultures are known to generate spontaneous bursting electrical activity which can be recorded by multielectrode arrays. We have analyzed spatio-temporal profiles of the distribution of spikes in the bursts recorded after 2?weeks in vitro. We have found a statistically significant similarity between the spiking patterns in sequential bursting events, we refer to these spiking patterns as spiking signatures. Such spiking signatures may appear in different parts of the bursts, including the activation patterns – the first spike times in the bursts, and deactivation patterns – the last spike times in the bursts. Moreover, these patterns may display apparent time scaling, e.g., they may be replayed in the subsequent bursts at different speeds, while preserving the spiking order. We discuss how such properties of the bursts may be associated with the formation of repeatable signaling pathways in cultured networks in vitro.

Pimashkin, Alexey; Kastalskiy, Innokentiy; Simonov, Alexander; Koryagina, Ekaterina; Mukhina, Irina; Kazantsev, Victor

2011-01-01

4

Shaping bursting by electrical coupling and noise.  

PubMed

Gap-junctional coupling is an important way of communication between neurons and other excitable cells. Strong electrical coupling synchronizes activity across cell ensembles. Surprisingly, in the presence of noise synchronous oscillations generated by an electrically coupled network may differ qualitatively from the oscillations produced by uncoupled individual cells forming the network. A prominent example of such behavior is the synchronized bursting in islets of Langerhans formed by pancreatic ?-cells, which in isolation are known to exhibit irregular spiking (Sherman and Rinzel, Biophys J 54:411-425, 1988; Sherman and Rinzel, Biophys J 59:547-559, 1991). At the heart of this intriguing phenomenon lies denoising, a remarkable ability of electrical coupling to diminish the effects of noise acting on individual cells. In this paper, building on an earlier analysis of denoising in networks of integrate-and-fire neurons (Medvedev, Neural Comput 21 (11):3057-3078, 2009) and our recent study of spontaneous activity in a closely related model of the Locus Coeruleus network (Medvedev and Zhuravytska, The geometry of spontaneous spiking in neuronal networks, submitted, 2012), we derive quantitative estimates characterizing denoising in electrically coupled networks of conductance-based models of square wave bursting cells. Our analysis reveals the interplay of the intrinsic properties of the individual cells and network topology and their respective contributions to this important effect. In particular, we show that networks on graphs with large algebraic connectivity (Fiedler, Czech Math J 23(98):298-305, 1973) or small total effective resistance (Bollobas, Modern graph theory, Graduate Texts in Mathematics, vol. 184, Springer, New York, 1998) are better equipped for implementing denoising. As a by-product of the analysis of denoising, we analytically estimate the rate with which trajectories converge to the synchronization subspace and the stability of the latter to random perturbations. These estimates reveal the role of the network topology in synchronization. The analysis is complemented by numerical simulations of electrically coupled conductance-based networks. Taken together, these results explain the mechanisms underlying synchronization and denoising in an important class of biological models. PMID:22450571

Medvedev, Georgi S; Zhuravytska, Svitlana

2012-02-01

5

Calculation of heating and burst phenomena in electrically exploded foils  

Microsoft Academic Search

A method is presented for computing the transient current and temperature distributions in electrically exploded foils. The model employed is applicable up until the time of burst. Calculations are presented for Al, Cu, and Au foils showing good agreement with experimental current waveforms and burst times over a wide range of capacitor-bank charging voltages and for varying foil cross sections.

J. D. Logan; R. S. Lee; R. C. Weingart; K. S. Yee

1977-01-01

6

DNA fragmentation induced by Intense Burst Sinusoidal Electric Fields  

Microsoft Academic Search

It is a well known fact that intense electric fields with frequencies exceeding MHz ranges cause intracellular effect to mammalian cells. We have used the Intense Burst Sinusoidal Electric Field (IBSEF) which is narrow band spectra, to put the electrical energy into biological cells efficiently. We have experimentally demonstrated here the presence of intense electric fields inside the cell membrane,

N. Nomura; Y. Yamamoto; R. Hayashi; K. Uto; S. Katsuki; H. Akiyama; I. Uchida; S. I. Abe; H. Takano

2007-01-01

7

Identifying Crucial Parameter Correlations Maintaining Bursting Activity  

PubMed Central

Recent experimental and computational studies suggest that linearly correlated sets of parameters (intrinsic and synaptic properties of neurons) allow central pattern-generating networks to produce and maintain their rhythmic activity regardless of changing internal and external conditions. To determine the role of correlated conductances in the robust maintenance of functional bursting activity, we used our existing database of half-center oscillator (HCO) model instances of the leech heartbeat CPG. From the database, we identified functional activity groups of burster (isolated neuron) and half-center oscillator model instances and realistic subgroups of each that showed burst characteristics (principally period and spike frequency) similar to the animal. To find linear correlations among the conductance parameters maintaining functional leech bursting activity, we applied Principal Component Analysis (PCA) to each of these four groups. PCA identified a set of three maximal conductances (leak current, Leak; a persistent K current, K2; and of a persistent Na+ current, P) that correlate linearly for the two groups of burster instances but not for the HCO groups. Visualizations of HCO instances in a reduced space suggested that there might be non-linear relationships between these parameters for these instances. Experimental studies have shown that period is a key attribute influenced by modulatory inputs and temperature variations in heart interneurons. Thus, we explored the sensitivity of period to changes in maximal conductances of Leak, K2, and P, and we found that for our realistic bursters the effect of these parameters on period could not be assessed because when varied individually bursting activity was not maintained.

Doloc-Mihu, Anca; Calabrese, Ronald L.

2014-01-01

8

Bursts of active transport in living cells  

NASA Astrophysics Data System (ADS)

This study of cargo motion in living cells, performed with nm resolution and an unprecedented large database, shows that the instantaneous speed of active transport deviates pervasively from the average speed yet with striking statistical regularity over several decades of time and space. The experimental approach involves single-particle tracking and special wavelet-based methods to discriminate active transport from passive diffusion, thus quantifying the instantaneous speed of endosomal and lysosomal active transport in living cells at times just longer than the motor stepping time. Pervasive bursts of acceleration stem from viscoelastic relaxation of the cytoplasm, the individual bursts displaying a time-averaged shape that we interpret to reflect stress buildup followed by rapid release. These statistical regularities did not change in response to changing the experimental conditions, specifically to changing the cell line and motor type, or to overexpressing microtubule binding proteins, thus indicating redundancy in regulation of cellular active transport. The power law of scaling is the same as seen in driven jammed colloids, powders, and magnetic systems, and is consistent with a simple heuristic argument. The implied regulation of active transport by environmental obstruction in the cytoplasm extends the classical notion of "molecular crowding."

Wang, Bo; Kuo, James; Bae, Sung Chul; Granick, Steve

2011-03-01

9

Genesis and Control of bursting activity in a neuronal model  

NASA Astrophysics Data System (ADS)

Neurons are observed in one of four fundamental activity modes: silence, sub-threshold oscillations, tonic spiking, and bursting. Neurons exhibit various activity regimes and regime transitions that reflect their complement of ionic channels and modulatory state. The leech presents unique opportunities for experimental and theoretical studies on the dynamics of neuronal activity. The central pattern generator controlling the leech's heartbeat contains identified pairs of mutually inhibitory neurons. Bursting activity of neurons is an oscillatory activity consisting of intervals of repetitive spiking separated by intervals of quiescence. It has been observed in neurons under normal and pathological conditions. Neurons which are capable of generating bursting activity endogenously play an important role in motor control and other brain functions. Burst duration, interburst interval and spike frequency are crucial temporal characteristics of bursting activity and thus have to be regulated. Application of the bifurcation theory of dynamical systems suggests new mechanism of how bursting activity can be generated by neurons and how burst duration can be regulated. Here we describe two mechanisms for the transition between tonic spiking and bursting. First mechanism describes a smooth, continuous and reversible transition from tonic spiking into bursting in a model neuron. The burst duration increases with no bound as 1/(a-a0)^1/2, where a0 is a parameter determining the transition. The characteristic features of this mechanism are that (a) the burst duration can be made arbitrarily long while (b) inter-burst interval does not depend on the parameter. The second mechanism is concerned with bi-stability where simultaneous tonic spiking and bursting activities co-exist in a neuron. The mechanism is based on a saddle-node periodic orbit bifurcation with non-central homoclinic orbits. This bifurcation describes a transition between three qualitatively different types of dynamics of a neuron. If one varies the control parameter a towards the critical value a0 at which the transition from the bistability region to the region where only tonic spiking is observed, the burst duration of the bursting activity becomes proportional to ln(a-a0). The interburst interval does not correlate with the burst duration. In terms of neuron's activity these two mechanisms describe a biophysically plausible means for regulation of burst duration. We show how this bifurcation can be found in a Hodgkin-Huxley type model of a neuron and how to identify control parameters determining properties of bursting activity. The work is supported by NIH NS 43098.

Cymbalyuk, Gennady

2005-11-01

10

Identifying repeating motifs in the activation of synchronized bursts in cultured neuronal networks  

Microsoft Academic Search

Cultured neuronal networks cultivated on micro-electrode arrays are a widely used tool for the investigation of network mechanisms, providing structural framework for long-term recordings of network electrical activity, as well as the network reaction to electrical or chemical stimulations. The typical activity pattern of the culture takes the form of synchronized bursting events (SBEs), in which a large fraction of

Nadav Raichman; Eshel Ben-Jacob

2008-01-01

11

Solar Radio Bursts, Proton Events and Geomagnetic Activity.  

National Technical Information Service (NTIS)

The relationships between type II, type IV, microwave bursts and geomagnetic activity have been studied using data from various observatories compiled in the Solar-Geophysical Data over the period 1968-1982. It is found that type II bursts follow the tren...

S. S. Degaonkar

1984-01-01

12

Bursting synchronization dynamics of pancreatic ?-cells with electrical and chemical coupling.  

PubMed

Based on bifurcation analysis, the synchronization behaviors of two identical pancreatic ?-cells connected by electrical and chemical coupling are investigated, respectively. Various firing patterns are produced in coupled cells when a single cell exhibits tonic spiking or square-wave bursting individually, irrespectively of what the cells are connected by electrical or chemical coupling. On the one hand, cells can burst synchronously for both weak electrical and chemical coupling when an isolated cell exhibits tonic spiking itself. In particular, for electrically coupled cells, under the variation of the coupling strength there exist complex transition processes of synchronous firing patterns such as "fold/limit cycle" type of bursting, then anti-phase continuous spiking, followed by the "fold/torus" type of bursting, and finally in-phase tonic spiking. On the other hand, it is shown that when the individual cell exhibits square-wave bursting, suitable coupling strength can make the electrically coupled system generate "fold/Hopf" bursting via "fold/fold" hysteresis loop; whereas, the chemically coupled cells generate "fold/subHopf" bursting. Especially, chemically coupled bursters can exhibit inverse period-adding bursting sequence. Fast-slow dynamics analysis is applied to explore the generation mechanism of these bursting oscillations. The above analysis of bursting types and the transition may provide us with better insight into understanding the role of coupling in the dynamic behaviors of pancreatic ?-cells. PMID:24427201

Meng, Pan; Wang, Qingyun; Lu, Qishao

2013-06-01

13

The 2008 May burst activation of SGR1627-41  

Microsoft Academic Search

In 2008 May, the soft gamma-ray repeater (SGR) SGR1627-41 resumed its bursting activity after nearly a decade of quiescence. After detection of a bright burst, Swift pointed its X-ray telescope in the direction of the source in less than five hours and followed it for over five weeks. In this Letter, we present an analysis of the data from these

P. Esposito; G. L. Israel; S. Zane; F. Senziani; R. L. C. Starling; N. Rea; D. M. Palmer; N. Gehrels; A. Tiengo; A. de Luca; D. Götz; S. Mereghetti; P. Romano; T. Sakamoto; S. D. Barthelmy; L. Stella; R. Turolla; M. Feroci; V. Mangano

2008-01-01

14

Respiratory burst activity in bronchopulmonary dysplasia and changes with dexamethasone.  

PubMed

The first objective of this study was to evaluate longitudinal changes in respiratory burst activity in circulating neutrophils and monocytes in infants of less than 30 weeks of gestation with respiratory distress syndrome (RDS), and to examine differences in neonates who subsequently developed bronchopulmonary dysplasia (BPD) compared with those neonates who did not. The second objective was to investigate the effects of dexamethasone on respiratory burst activity in neutrophils and monocytes. We measured burst activity on neutrophils and monocytes in fresh heparinized blood in response to E. coli, N-formyl-met-leu-phe (fMLP), and phorbol 12-myristate 13-acetate stimulation on days 3, 7, 14, and 21 of life, before and 2-3 days after initiating a 6-day course of dexamethasone treatment. Infants with RDS participating in the study were followed until discharge, and were classified as non-BPD and either 1) BPD d28, reflecting their oxygen requirement at day of life 28, or 2) BPD 36 weeks, reflecting oxygen dependence at 36 weeks' corrected gestational age. The diagnosis of BPD was supported by radiological changes of BPD. The percentage of activated neutrophils producing a respiratory burst increased in all premature infants with increasing postnatal days during the first 28 days of life, when the physiological stimulus E. coli was used as an activator (P < 0.02). There was no significant difference in respiratory burst activity measured either as percent activation or as mean fluorescence intensity between non-BPD and BPD infants after adjusting for the difference in weight and gestational age between the two groups. The treatment of premature infants with dexamethasone was associated with decreased activation of neutrophils (P < 0.005) when E. coli was used as a stimulus. In conclusion, a significant increase in neutrophil respiratory burst activity occurs during the first month of life in very low birth weight infants. Greater pulmonary damage in BPD cannot be attributed to reduced burst activity in either neutrophils or monocytes. Dexamethasone treatment was associated with decreased neutrophil respiratory burst activity. PMID:12687597

Ballabh, Praveen; Simm, M; Kumari, J; Califano, C; Aghai, Z; Laborada, G; Sison, C; Cunningham-Rundles, S

2003-05-01

15

Phase-dependent stimulation effects on bursting activity in a neural network cortical simulation  

PubMed Central

Summary Purpose A neural network simulation with realistic cortical architecture has been used to study synchronized bursting as a seizure representation. This model has the property that bursting epochs arise and cease spontaneously, and bursting epochs can be induced by external stimulation. We have used this simulation to study the time-frequency properties of the evolving bursting activity, as well as effects due to network stimulation. Methods The model represents a cortical region of 1.6 mm × 1.6 mm, and includes seven neuron classes organized by cortical layer, inhibitory or excitatory properties, and electrophysiological characteristics. There are a total of 65, 536 modeled single compartment neurons that operate according to a version of Hodgkin-Huxley dynamics. The intercellular wiring is based on histological studies and our previous modeling efforts. Results The bursting phase is characterized by a flat frequency spectrum. Stimulation pulses are applied to this modeled network, with an electric field provided by a 1 mm radius circular electrode represented mathematically in the simulation. A phase dependence to the post-stimulation quiescence is demonstrated, with local relative maxima in efficacy occurring before or during the network depolarization phase in the underlying activity. Brief periods of network insensitivity to stimulation are also demonstrated. The phase dependence was irregular and did not reach statistical significance when averaged over the full 2.5 seconds of simulated bursting investigated. This result provides comparison with previous in vivo studies which have also demonstrated increased efficacy of stimulation when pulses are applied at the peak of the local field potential during cortical afterdischarges. The network bursting is synchronous when comparing the different neuron classes represented up to an uncertainty of 10 msec. Studies performed with an excitatory chandelier cell component demonstrated increased synchronous bursting in the model, as predicted from experimental work. Conclusions This large scale multi-neuron neural network simulation reproduces many aspects of evolving cortical bursting behaviour as well as the timing-dependent effects of electrical stimulation on that bursting.

Kudela, Pawel; Weinberg, Seth; Bergey, Gregory K.; Franaszczuk, Piotr J.

2009-01-01

16

Periodic bursting activities of locus coerulleus neurons in the rat.  

PubMed

Unit activity of locus coeruleus (LC) neurons in rats was investigated. After the animal recovered from anesthesia, the spontaneous activity exhibited periodic bursting discharges at about 15-30 s intervals. The oscillation was observed to last for a long time (1-3 h). It is suggested that many LC neurons exhibited the oscillation synchronously during stress in the awake animal. PMID:6980040

Akaike, T

1982-05-13

17

Quantifying bursting neuron activity from calcium signals using blind deconvolution.  

PubMed

Advances in calcium imaging have enabled studies of the dynamic activity of both individual neurons and neuronal assemblies. However, challenges, such as unknown nonlinearities in the spike-calcium relationship, noise, and the often relatively low temporal resolution of the calcium signal compared to the time-scale of spike generation, restrict the accurate estimation of action potentials from the calcium signal. Complex neuronal discharge, such as the activity demonstrated by bursting and rhythmically active neurons, represents an even greater challenge for reconstructing spike trains based on calcium signals. We propose a method using blind calcium signal deconvolution based on an information-theoretic approach. This model is meant to maximise the output entropy of a nonlinear filter where the nonlinearity is defined by the cumulative distribution function of the spike signal. We tested our maximum entropy (ME) algorithm using bursting olfactory receptor neurons (bORNs) of the lobster olfactory organ. The advantage of the ME algorithm is that the filter can be trained online based only on the statistics of the spike signal, without any assumptions regarding the unknown transfer function characterizing the relation between the spike and calcium signal. We show that the ME method is able to more accurately reconstruct the timing of the first and last spikes of a burst compared to other methods and that it improves the temporal precision fivefold compared to direct timing resolution of calcium signal. PMID:23711821

Park, In Jun; Bobkov, Yuriy V; Ache, Barry W; Principe, Jose C

2013-09-15

18

Diffuse theta activity and spindle-like bursts during coma after cardiac arrest.  

PubMed

An usual combination of diffuse theta activity with intermittent bursts of spindle-like activity, followed by 2-3 Hz rhythmic discharges and lasting about 7 seconds, was noted in a coma patient after cardiac arrest. We speculate that the theta pattern coma and spindle-like bursts originated in the pontine region, and that those bursts in turn triggered or recruited rhythmic slow-wave complexes similar to absence discharges. PMID:8681468

Ganji, S S; Henry, R; Furlow, J

1996-04-01

19

Electrical Conduction Activity  

NSDL National Science Digital Library

This resource provides an introductory activity on electrical conduction. As the module states, "electrical conduction, the movement of electrical charges, is a mechanism for passing energy and signals from one place to another." The activity covers concepts such as insulators, conductors, semiconductors, superconductors, and ballistic conduction at nanoscale. This module allows students to test their knowledge as they go.The other educational modules in this series can be found here. Instructors and students are encouraged to sign up with the Electron Technologies site here before starting to use these materials.

2012-10-02

20

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans.  

PubMed

Previous studies in humans attempting to assess sympathetic vascular transduction have related large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) to associated changes in limb vascular resistance. However, such procedures do not provide insight into the ability of MSNA to dynamically control vascular tone on a beat-by-beat basis. Thus we examined the influence of spontaneous MSNA bursts on leg vascular conductance (LVC) and how variations in MSNA burst pattern (single vs. multiple bursts) and burst size may affect the magnitude of the LVC response. In 11 young men, arterial blood pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 min of supine rest. Signal averaging was used to characterize percent changes in LVC for 15 cardiac cycles following heartbeats associated with and without MSNA bursts. LVC significantly decreased following MSNA bursts, reaching a nadir during the 6th cardiac cycle (single bursts, -2.9 ± 1.1%; and multiple bursts, -11.0 ± 1.4%; both, P < 0.001). Individual MSNA burst amplitudes and the total amplitude of consecutive bursts were related to the magnitude of peak decreases in LVC. In contrast, cardiac cycles without MSNA bursts were associated with a significant increase in LVC (+3.1 ± 0.5%; P < 0.001). Total vascular conductance decreased in parallel with LVC also reaching a nadir around the peak rise in arterial blood pressure following an MSNA burst. Collectively, these data are the first to assess beat-by-beat sympathetic vascular transduction in resting humans, demonstrating robust and dynamic decreases in LVC following MSNA bursts, an effect that was absent for cardiac cycles without MSNA bursts. PMID:23292718

Fairfax, Seth T; Padilla, Jaume; Vianna, Lauro C; Davis, Michael J; Fadel, Paul J

2013-03-01

21

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans  

PubMed Central

Previous studies in humans attempting to assess sympathetic vascular transduction have related large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) to associated changes in limb vascular resistance. However, such procedures do not provide insight into the ability of MSNA to dynamically control vascular tone on a beat-by-beat basis. Thus we examined the influence of spontaneous MSNA bursts on leg vascular conductance (LVC) and how variations in MSNA burst pattern (single vs. multiple bursts) and burst size may affect the magnitude of the LVC response. In 11 young men, arterial blood pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 min of supine rest. Signal averaging was used to characterize percent changes in LVC for 15 cardiac cycles following heartbeats associated with and without MSNA bursts. LVC significantly decreased following MSNA bursts, reaching a nadir during the 6th cardiac cycle (single bursts, ?2.9 ± 1.1%; and multiple bursts, ?11.0 ± 1.4%; both, P < 0.001). Individual MSNA burst amplitudes and the total amplitude of consecutive bursts were related to the magnitude of peak decreases in LVC. In contrast, cardiac cycles without MSNA bursts were associated with a significant increase in LVC (+3.1 ± 0.5%; P < 0.001). Total vascular conductance decreased in parallel with LVC also reaching a nadir around the peak rise in arterial blood pressure following an MSNA burst. Collectively, these data are the first to assess beat-by-beat sympathetic vascular transduction in resting humans, demonstrating robust and dynamic decreases in LVC following MSNA bursts, an effect that was absent for cardiac cycles without MSNA bursts.

Fairfax, Seth T.; Padilla, Jaume; Vianna, Lauro C.; Davis, Michael J.

2013-01-01

22

60 Hz electric field changes the membrane potential during burst phase in pancreatic ?-cells: in silico analysis.  

PubMed

The production, distribution and use of electricity can generate low frequency electric and magnetic fields (50-60 Hz). Considering that some studies showed adverse effects on pancreatic ?-cells exposed to these fields; the present study aimed to analyze the effects of 60 Hz electric fields on membrane potential during the silent and burst phases in pancreatic ?-cells using a mathematical model. Sinusoidal 60 Hz electric fields with amplitude ranging from 0.5 to 4 mV were applied on pancreatic ?-cells model. The sinusoidal electric field changed burst duration, inter-burst intervals (silent phase) and spike sizes. The parameters above presented dose-dependent response with the voltage amplitude applied. In conclusion, theoretical analyses showed that a 60 Hz electric field with low amplitudes changes the membrane potential in pancreatic ?-cells. PMID:24643285

Neves, Gesilda F; Silva, José R F; Moraes, Renato B; Fernandes, Thiago S; Tenorio, Bruno M; Nogueira, Romildo A

2014-06-01

23

Role of the axodendritic tree in the functioning of Helix bursting neurons: generation of pacemaker activity and propagation of action potentials along the axon  

Microsoft Academic Search

The purpose of this study was to determine the role of the axodendritic tree in the generation of bursting pacemaker activity in the identified Helix RPa1 neuron, which is homologous to the Aplysia R15 cell, and propagation of action potentials along the axons. In doing so, I used recording of RPa1 neuron electrical activity after cutting off the right or

N. I Kononenko

2000-01-01

24

Leukocytes respiratory burst activity as indicator of innate immunity of pacu Piaractus mesopotamicus.  

PubMed

The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT) to formazan as a measure of the production of reactive oxygen species (ROS). In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions. PMID:23917573

Biller-Takahashi, J D; Takahashi, L S; Saita, M V; Gimbo, R Y; Urbinati, E C

2013-05-01

25

Age-Related Increase in Electromyography Burst Activity in Males and Females  

PubMed Central

The rapid advancement of electromyography (EMG) technology facilitates measurement of muscle activity outside the laboratory during daily life. The purpose of this study was to determine whether bursts in EMG recorded over a typical 8-hour day differed between young and old males and females. Muscle activity was recorded from biceps brachii, triceps brachii, vastus lateralis, and biceps femoris of 16 young and 15 old adults using portable surface EMG. Old muscles were active 16–27% of the time compared to 5–9% in young muscles. The number of bursts was greater in old than young adults and in females compared to males. Burst percentage and mean amplitude were greater in the flexor muscles compared with the extensor muscles. The greater burst activity in old adults coupled with the unique activity patterns across muscles in males and females provides further understanding of how changes in neuromuscular activity effects age-related functional decline between the sexes.

Theou, Olga; Edwards, Darl; Jones, Gareth R.; Jakobi, Jennifer M.

2013-01-01

26

2006-2007 Active Phase of Anomalous X-Ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts,and Burst Spectral Features.  

National Technical Information Service (NTIS)

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first se...

F. P. Gavriil R. Dib V. M. Kaspi

2011-01-01

27

Study to assess the effects of nuclear surface burst electromagnetic pulse on electric power systems. Phase I, final report  

Microsoft Academic Search

The surface burst of a nuclear device, within the continental United States, can expose nearby portions of the civilian electric utility system to transient, source region electromagnetic pulse (SREMP). This threat is in addition to any coincident, non-SREMP damage to the system due to craterization, fireball, blast wave and radiation. The unique properties of the civilian electric power system, such

J. R. Legro; N. C. Abi-Samra; A. R. Hileman; F. M. Tesche

1985-01-01

28

Calmodulin and calmodulin kinase II mediate emergent bursting activity in the brainstem respiratory network (preB?tzinger complex)  

PubMed Central

Emergence of persistent activity in networks can be controlled by intracellular signalling pathways but the mechanisms involved and their role are not yet fully explored. Using calcium imaging and patch-clamp we examined the rhythmic activity in the preBötzinger complex (preBötC) in the lower brainstem that generates the respiratory motor output. In functionally intact acute slices brief hypoxia, electrical stimulation and activation of AMPA receptors transiently depressed bursting activity which then recovered with augmentation. The effects were abrogated after chelation of intracellular calcium, blockade of l-type calcium channels and inhibition of calmodulin (CaM) and CaM kinase (CaMKII). Rhythmic calcium transients and synaptic drive currents in preBötC neurons in the organotypic slices showed similar CaM- and CaMKII-dependent responses. The stimuli increased the amplitude of spontaneous and miniature excitatory synaptic currents indicating postsynaptic changes at glutamatergic synapses. In the acute and organotypic slices, CaM stimulated and ADP inhibited calcium-dependent TRPM4 channels and CaMKII augmented synaptic drive currents. Experimental data and simulations show the role of ADP and CaMKII in the control of bursting activity and its relation to intracellular signalling. I propose that CaMKII-mediated facilitation of glutamatergic transmission strengthens emergent synchronous activity within preBötC that is then maintained by periodic surges of calcium during the bursts. This may find implications in restoration and consolidation of autonomous activity in the respiratory disorders.

Mironov, S L

2013-01-01

29

BURST AND PERSISTENT EMISSION PROPERTIES DURING THE RECENT ACTIVE EPISODE OF THE ANOMALOUS X-RAY PULSAR 1E 1841-045  

SciTech Connect

The Swift/Burst Alert Telescope detected the first burst from 1E 1841-045 in 2010 May with intermittent burst activity recorded through at least 2011 July. Here we present Swift and Fermi/Gamma-ray Burst Monitor observations of this burst activity and search for correlated changes to the persistent X-ray emission of the source. The T {sub 90} durations of the bursts range between 18 and 140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8-25) x 10{sup 38} erg, which is on the low side of soft gamma repeater bursts. We find that the bursting activity did not have a significant effect on the persistent flux level of the source. We argue that the mechanism leading to this sporadic burst activity in 1E 1841-045 might not involve large-scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.

Lin Lin [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Goegues, Ersin; Kaneko, Yuki [Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli-Tuzla, Istanbul 34956 (Turkey); Van der Horst, Alexander J. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Watts, Anna L.; Wijers, Ralph A. M. J.; Van der Klis, Michiel [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, 1090 GE Amsterdam (Netherlands); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, Houston, TX 77251 (United States); Woods, Peter M. [Corvid Technologies, Huntsville, AL 35806 (United States); Barthelmy, Scott; Gehrels, Neil; Mcenery, Julie [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Michael Burgess, James; Chaplin, Vandiver; Goldstein, Adam; Guiriec, Sylvain; Preece, Robert D. [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Granot, Jonathan [Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Tierney, David, E-mail: lin198361@gmail.com [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)

2011-10-10

30

Functional Imaging of Human Vestibular Cortex Activity Elicited by Skull Tap and Auditory Tone Burst  

NASA Technical Reports Server (NTRS)

The aim of the current study was to characterize the brain activation in response to two modes of vestibular stimulation: skull tap and auditory tone burst. The auditory tone burst has been used in previous studies to elicit saccular Vestibular Evoked Myogenic Potentials (VEMP) (Colebatch & Halmagyi 1992; Colebatch et al. 1994). Some researchers have reported that airconducted skull tap elicits both saccular and utricle VEMPs, while being faster and less irritating for the subjects (Curthoys et al. 2009, Wackym et al., 2012). However, it is not clear whether the skull tap and auditory tone burst elicit the same pattern of cortical activity. Both forms of stimulation target the otolith response, which provides a measurement of vestibular function independent from semicircular canals. This is of high importance for studying the vestibular disorders related to otolith deficits. Previous imaging studies have documented activity in the anterior and posterior insula, superior temporal gyrus, inferior parietal lobule, pre and post central gyri, inferior frontal gyrus, and the anterior cingulate cortex in response to different modes of vestibular stimulation (Bottini et al., 1994; Dieterich et al., 2003; Emri et al., 2003; Schlindwein et al., 2008; Janzen et al., 2008). Here we hypothesized that the skull tap elicits the similar pattern of cortical activity as the auditory tone burst. Subjects put on a set of MR compatible skull tappers and headphones inside the 3T GE scanner, while lying in supine position, with eyes closed. All subjects received both forms of the stimulation, however, the order of stimulation with auditory tone burst and air-conducted skull tap was counterbalanced across subjects. Pneumatically powered skull tappers were placed bilaterally on the cheekbones. The vibration of the cheekbone was transmitted to the vestibular cortex, resulting in vestibular response (Halmagyi et al., 1995). Auditory tone bursts were also delivered for comparison. To validate our stimulation method, we measured the ocular VEMP outside of the scanner. This measurement showed that both skull tap and auditory tone burst elicited vestibular evoked activation, indicated by eye muscle response. Our preliminary analyses showed that the skull tap elicited activation in medial frontal gyrus, superior temporal gyrus, postcentral gyrus, transverse temporal gyrus, anterior cingulate, and putamen. The auditory tone bursts elicited activation in medial frontal gyrus, superior temporal gyrus, superior frontal gyrus, precentral gyrus, inferior and superior parietal lobules. In line with our hypothesis, skull taps elicited a pattern of cortical activity closely similar to one elicited by auditory tone bursts. Further analysis will determine the extent to which the skull taps can replace the auditory tone stimulation in clinical and basic science vestibular assessments.

Noohi, Fatemeh; Kinnaird, Catherine; Wood, Scott; Bloomberg, Jacob; Mulavara, Ajitkumar; Seidler, Rachael

2014-01-01

31

Plasticity of burst firing in subiculum induced by synergistic activation of metabotropic glutamate and acetylcholine receptors  

PubMed Central

Summary Subiculum, which is the primary efferent pathway of hippocampus, participates in memory for spatial tasks, relapse to drug abuse, and temporal lobe seizures. Subicular pyramidal neurons exhibit low-threshold burst firing driven by a spike after-depolarization. Here we report that burst firing can be regulated by stimulation of afferents projections to subiculum. Unlike synaptic plasticity in these and other neurons, burst plasticity did not require synaptic depolarization, activation of AMPA or NMDA receptors, or action potential firing. Rather, enhancement of burst firing required synergistic activation of group I, subtype 1 metabotropic glutamate receptors (mGluRs) and muscarinic acetylcholine receptors (mAChR). When either of these receptors was blocked, a suppression of bursting was revealed, which in turn was blocked by antagonists of group I, subtype 5 mGluRs. These results indicate that the output of subiculum can be strongly and bidirectionally regulated by activation of glutamatergic inputs within the hippocampus and cholinergic afferents from the medial septum.

Moore, Shannon J.; Cooper, Donald C.; Spruston, Nelson

2009-01-01

32

Effect of oestrous cycle on the oxidative burst activity of blood polymorphonuclear leucocytes in cows.  

PubMed

Blood polymorphonuclear leucocyte (PMN) oxidative burst activity, plasma cortisol levels, and the total and differential white blood cells counts (WBC) of six cycled dairy cows were evaluated for a period of 24 days, three times a week; on Mondays, Wednesdays and Fridays. The PMN oxidative burst was indirectly evaluated by flow cytometry, measuring the intracellular oxidation of 2',7'-dichlorofluorescein diacetate to 2',7' dichlorofluorescein (DCF) by H2O2-production. Results are presented as the mean fluorescence intensity (MFI) of DCF. Cow's oestrous cycle was evaluated by following the plasma progesterone levels using a radioimmunoassay method. Levels of cortisol in the plasma were measured using a fluorimetric method. The oxidative burst activity of PMN, represented a maximum value (MFI=117.6+/-7.4) during the oestrous period. A fall was then observed, in which a steady state was observed during the lutheinic phase of the oestrous cycle, reaching the minimum value [MFI=73.2+/-11.2 (pburst activity was observed. Our results demonstrated that the oestrous cycle might influence directly, or indirectly, the immune system of cows, by altering the oxidative burst of PMN. PMID:19000223

Chaveiro, A; Moreira da Silva, F

2009-12-01

33

Neurons of the nucleus tractus solitarius, in vitro, generate bursting activities by solitary tract stimulation  

Microsoft Academic Search

Extracellular recordings of the activity of nucleus tractus solitarius (NTS) neurons were performed on rat brainstem slice preparations. Neurons localized in the medial part of the lateral NTS, which displayed a synaptic response to single pulse stimulation of the tractus solitarius (TS), generated bursting activity following repetitive TS stimulation (20–50 Hz frequency, 100–600 ms duration). According to their patterns of

F. Tell; L. Fagni; A. Jean

1994-01-01

34

Electric vehicle activities  

NASA Astrophysics Data System (ADS)

The data and information collected for the Public Service Electric and Gas Company's (PSE&G) electric vehicle demonstration program were intended to support and enhance DOE's Electric and Hybrid Vehicle Site Operator Program. The DOE Site Operator Program is focused on the life cycle and reliability of Electric Vehicles (EV's). Of particular interest are vehicles currently available with features that are likely to be put into production or demonstrate new technology. PSE&G acquired eight GMC Electric G-Vans in 1991, and three TEVans in 1993, and conducted a program plan to test and assess the overall performance of these electric vehicles. To accomplish the objectives of DOE's Site Operator's test program, a manual data collection system was implemented. The manual data collection system has provided energy use and mileage data. From September 1991 to October 1994 PSE&G logged 69,368 miles on eleven test vehicles. PSE&G also demonstrated the EVs to diverse groups and associations at fifty seven various events. Included in the report are lessons learned concerning maintenance, operation, public reactions, and driver's acceptance of the electric vehicles.

Delmonaco, J. L.; Pandya, D. A.

1995-02-01

35

Influence of spontaneously occurring bursts of muscle sympathetic nerve activity on conduit artery diameter.  

PubMed

Large increases in muscle sympathetic nerve activity (MSNA) can decrease the diameter of a conduit artery even in the presence of elevated blood pressure, suggesting that MSNA acts to regulate conduit artery tone. Whether this influence can be extrapolated to spontaneously occurring MSNA bursts has not been examined. Therefore, we tested the hypothesis that MSNA bursts decrease conduit artery diameter on a beat-by-beat basis during rest. Conduit artery responses were assessed in the brachial (BA), common femoral (CFA) and popliteal (PA) arteries to account for regional differences in vascular function. In 20 young men, MSNA, mean arterial pressure (MAP), conduit artery diameter, and shear rate (SR) were continuously measured during 20-min periods of supine rest. Spike-triggered averaging was used to characterize beat-by-beat changes in each variable for 15 cardiac cycles following all MSNA bursts, and a peak response was calculated. Diameter increased to a similar peak among the BA (+0.14 ± 0.02%), CFA (+0.17 ± 0.03%), and PA (+0.18 ± 0.03%) following MSNA bursts (all P < 0.05 vs. control). The diameter rise was positively associated with an increase in MAP in relation to increasing amplitude and consecutive numbers of MSNA bursts (P < 0.05). Such relationships were similar between arteries. SR changes following MSNA bursts were heterogeneous between arteries and did not appear to systematically alter diameter responses. Thus, in contrast to our hypothesis, spontaneously occurring MSNA bursts do not directly influence conduit arteries with local vasoconstriction or changes in shear, but rather induce a systemic pressor response that appears to passively increase conduit artery diameter. PMID:23832696

Fairfax, Seth T; Padilla, Jaume; Vianna, Lauro C; Holwerda, Seth H; Davis, Michael J; Fadel, Paul J

2013-09-15

36

Cell-free activation of the respiratory burst oxidase by protein kinase C.  

PubMed

In intact neutrophils, phorbol ester treatment activates the respiratory burst oxidase, the enzyme responsible for O2-production by phagocytes. This effect is thought to be dependent on protein kinase C and on the phosphorylation of p47phox. In this paper, we report that protein kinase C activates the respiratory burst oxidase in a cell-free system consisting of isolated neutrophil cytosol and membrane. Oxidase activation required a highly active protein kinase C, recombinant p47phow and ATP, and was inhibited by the protein kinase C inhibitors H-7 and GF-109203X. PERIl depletion of cytosolic ATP by dialysis reduced oxidase activation by over 50% In contrast, neither protein kinase C inhibitors nor ATP depletion affected oxidase activation by SDS. These findings strongly suggest that in the cell-free system, the oxidase can be activated by the phosphorylation of p47phox. PMID:8673472

el-Benna, J; Park, J W; Ruedi, J M; Babior, B M

1995-01-01

37

Detection of Spectral Evolution in the Bursts Emitted During the 2008-2009 Active Episode of SGR J1550 - 5418  

NASA Technical Reports Server (NTRS)

In early October 2008, the Soft Gamma Repeater SGRJ1550 - 5418 (1E1547.0 - 5408, AXJ155052 - 5418, PSR J1550 - 5418) became active, emitting a series of bursts which triggered the Fermi Gamma-ray Burst Monitor (GBM) after which a second especially intense activity period commenced in 2009 January and a third, less active period was detected in 2009 March-April. Here we analyze the GBM data of all the bursts from the first and last active episodes. We performed temporal and spectral analysis for all events and found that their temporal characteristics are very similar to the ones of other SGR bursts, as well the ones reported for the bursts of the main episode (average burst durations 170ms). In addition, we used our sample of bursts to quantify the systematic uncertainties of the GBM location algorithm for soft gamma-ray transients to less than or equal to 8 degrees. Our spectral analysis indicates significant spectral evolution between the first and last set of events. Although the 2008 October events are best fit with a single blackbody function, for the 2009 bursts an Optically Thin Thermal Bremsstrahlung (OTTB) is clearly preferred. We attribute this evolution to changes in the magnetic field topology of the source, possibly due to effects following the very energetic main bursting episode.

von Kienlin, Andreas; Gruber, David; Kouveliotou, Chryssa; Granot, Jonathan; Baring, Matthew G.; Gogus, Ersin; Huppenkothen, Daniela; Kaneko, Yuki; Lin, Lin; Watts, Anna L.; Bhat, Narayana; Guiriec, Sylvain; van der Horst, Alexander J.; Bissaldi, Elisabetta; Greiner, Jochen; Meegan, Charles A.; Paciesas, William S.; Preece, Robert D.; Rau, Arne

2012-01-01

38

Burst suppression probability algorithms: state-space methods for tracking EEG burst suppression  

PubMed Central

Objective Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily identify burst suppression periods, analysis algorithms require long intervals of data to characterize burst suppression at a given time and provide no framework for statistical inference. Approach We introduce the concept of the burst suppression probability (BSP) to define the brain’s instantaneous propensity of being in the suppressed state. To conduct dynamic analyses of burst suppression we propose a state-space model in which the observation process is a binomial model and the state equation is a Gaussian random walk. We estimate the model using an approximate expectation maximization algorithm and illustrate its application in the analysis of rodent burst suppression recordings under general anesthesia and a patient during induction of controlled hypothermia. Main result The BSP algorithms track burst suppression on a second-to-second time scale, and make possible formal statistical comparisons of burst suppression at different times. Significance The state-space approach suggests a principled and informative way to analyze burst suppression that can be used to monitor, and eventually to control, the brain states of patients in the operating room and in the intensive care unit.

Chemali, Jessica; Ching, ShiNung; Purdon, Patrick L; Solt, Ken; Brown, Emery N

2013-01-01

39

Metachronal propagation of motoneurone burst activation in isolated spinal cord of newborn rat  

PubMed Central

Adequate locomotor and postural activity in mammals results from the coordinated activation of assemblies of spinal cord networks. In order to assess the global functioning of spinal circuitry, multisite recordings were made from an isolated spinal cord preparation of the newborn rat. Motor activity, elicited in a disinhibited network by bath-applying strychnine (glycinergic blocker) and bicuculline (GABAergic blocker), consisted of slow spontaneous bursting. Under these conditions, the recorded bursts were coordinated in 1: 1 relationships at all segmental levels. For each cycle, a leading segment initiated the activity that then propagated in a metachronal way through adjacent segments along the length of spinal cord. There was both regional non-linearity and directional asymmetry in this burst propagation: motor bursts propagated most rapidly in the thoracic spinal cord and the rostro-caudal wave travelled faster than the caudo-rostral one. Propagation involved both long projecting fibres and local intersegmental connections. These results suggest that the mammalian spinal cord contains propriospinal pathways subserving a metachronal transmission of motor information and that normally it may be involved in coordinating various parts of the body. The simple model developed here could be useful in unravelling more general mechanisms of neuronal circuit coupling.

Cazalets, Jean-Rene

2005-01-01

40

Solar Cycle Variations of the Occurrence of Coronal Type III Radio Bursts and a New Solar Activity Index  

NASA Astrophysics Data System (ADS)

The results of studies of solar cycle variations of the occurrence rate of coronal type III radio bursts are presented. The radio spectra are provided by the Learmonth Solar Radio Observatory (Western Australia), part of the USAF Radio Solar Telescope Network (RSTN). It is found that the occurrence rate of type III bursts strongly correlates with solar activity. However, the profiles for the smoothed type III burst occurrence rate differ considerably from those for the sunspot number, 10.7 cm solar radio flux, and solar flare index. The type III burst occurrence rate (T3BOR) is proposed as a new index of solar activity. T3BOR provides complementary information about solar activity and should be useful in different studies including solar cycle predictions and searches for different periodicities in solar activity. This index can be estimated from daily results of the Automated Radio Burst Identification System (ARBIS). Access to data from other RSTN sites will allow processing 24-hour radio spectra in near-real time and estimating true daily values of this index. It is also shown that coronal type III bursts can even occur when there are no visible sunspots on the Sun. However, no evidence is found that the bursts are not associated with active regions. It is also concluded that the type III burst productivity of active regions exhibits solar cycle variations.

Lobzin, V. V.; Cairns, I. H.; Robinson, P. A.

2011-12-01

41

Phagocytosis and respiratory burst activity of haemocytes from the ivory snail, Babylonia areolata.  

PubMed

Haemocytes from the ivory snail, Babylonia areolata phagocytized Saccharomyces cerevisiae and Vibrio parahaemolyticus after 30 min. Haemocytes phagocytized V. parahaemolyticus at a greater rate than they phagocytized S. cerevisiae. The phagocytic rate (PP) of V. parahaemolyticus by granulocytes to was a little higher than that of S. cerevisiae. The phagocytic index (PI) of V. parahaemolyticus by granulocytes was significantly higher than that of S. cerevisiae. The same was true of hyalinocytes. The PP of granulocytes was significantly higher than that of hyalinocytes for each pathogen. No difference in PI was observed in granulocytes and hyalinocytes. Two defense mechanisms of B. areolata were quantified using flow cytometry. Haemocyte phagocytosis was quantified using fluorescent microbeads and respiratory burst activity was measured using H2O2 increases detected by 2', 7'-dichlorofluorescein diacetate. Both phagocytosis and respiratory burst activity of the haemocytes increased over time. After 90 min the phagocytic rate no longer increased. In the case of respiratory burst, the greatest increase in fluorescence occurred between 30 and 120 min, no further increase was seen after 120 min. These results showed unequivocally that a native (unstimulated) haemocyte oxidative burst was active in B. areolata. The aim of this study was to further the knowledge of immunology in gastropods. PMID:23664911

Di, Guilan; Zhang, Zhaoxia; Ke, Caihuan

2013-08-01

42

Modulation of calcium currents by electrical activity.  

PubMed

Electrical activation of mouse dorsal root ganglion (DRG) neurons in cultures for 1-2 days produced a downregulation of voltage sensitive calcium currents, which persisted for > or = 24 h after stimulation was terminated. This regulation varied with different patterns of activation. Both the magnitude and time course of regulation of the low-threshold voltage-activated (LVA) and high-threshold voltage-activated (HVA) currents were differentially sensitive to neural impulse activity. Tonic stimulation at 0.5 Hz did not affect the HVA currents, but 2.5 Hz did produce a significant decrease. Phasic stimulation (10 Hz for 0.5 s every 2 s) with an average frequency of 2.5 Hz produced significantly more downregulation of HVA currents than did the tonic 2.5-Hz stimulation. The efficacy of phasic stimulation varied inversely with the interval between bursts. Thus phasic stimulation of 10 Hz for 0.5 s but delivered every 4 s produced no effects on HVA currents. Stimulation optimal for downregulation of Ca2+ currents also produced a decreased binding by the DRG neurons of an L-type Ca2+ channel antagonist. This suggests a downregulation by electrical activity of the number of Ca2+ channels, rather than an alteration in a constant number of channels. Depression of LVA currents was produced by all stimulus patterns tested, including 0.5-Hz tonic stimulation. Chronic stimulation with a stimulation pattern that downregulated Ca2+ currents also produced a slowing of the increase in intracellular Ca2+ (as measured by Fura-2/AM) that is produced acutely by repetitive stimulation. This is consonant with earlier studies of intracellular Ca2+ concentration kinetics in growth cones. PMID:8899630

Li, M; Jia, M; Fields, R D; Nelson, P G

1996-10-01

43

Neuronal bursting induced by NK3 receptor activation in the neonatal rat spinal cord in vitro.  

PubMed

Intracellular recording from lumbar motoneurons and extracellular recording from ventral roots of the neonatal rat isolated spinal cord were used to study the mechanisms responsible for the excitation mediated by NK3 tachykinin receptors. The selective NK3 agonists senktide or [MePhe7]neurokinin B induced a slow depolarization with superimposed oscillations (mean period +/- SD was 2.8 +/- 0.8 s) that, in the majority of cases, showed left-right alternation at segmental level and were synchronous between L2 and L5 of the same side. During agonist wash out (5-20 min) a delayed form of hyperexcitability emerged consisting of bursts lasting 8 +/- 2 s (average interburst interval 55 +/- 21 s) with superimposed oscillations usually with homosegmental alternation and heterosegmental synchronicity. Such bursting was accompanied by depression of GABAergic dorsal root potentials evoked by dorsal root stimulation and of the recurrent inhibitory postsynaptic potential recorded from motoneurons. Despite bursting, motoneuron membrane potential returned to baseline while input resistance was increased. Bursts were a network-dependent phenomenon triggered by previous NK3 receptor activation because bursting was suppressed by glutamate receptor antagonists and was insensitive to motoneuron membrane potential or subsequent application of an NK3 receptor antagonist. NK3 receptors operated synergistically with N-methyl-D-aspartate (NMDA) and 5-hydroxytryptamine (5-HT) to trigger fully alternating locomotor-like rhythms while NK3 receptor antagonism disrupted the same rhythm. In summary, in the neonatal rat spinal cord NK3 receptors could trigger rhythmic activity predominantly with alternation at segmental level but with synchronous coupling between ipsilateral motor pools. NK3 receptor activation could also facilitate fictive locomotor patterns induced by NMDA and 5-HT. PMID:11731550

Marchetti, C; Nistri, A

2001-12-01

44

Measurement of Leaked High-Frequency Burst Electric Field and EMI Evaluation for Cardiac Pacemaker in Fusion Facility  

NASA Astrophysics Data System (ADS)

In this study, we measured the time variation of burst electric fields leaked from a heating device in the ion cyclotron range of high-frequency in an experimental fusion facility, and analyzed their statistical characteristics such as the amplitude probability distribution (APD) and crossing rate distribution (CRD). As a result, we found that the variation of the leaked electric field level is very irregular, far from the normal distribution. Moreover, the leaked electric field variation with time may reach 400 times in one second to cross its mode value. Although so, the maximum electric field intensity itself is much smaller than the ICNIRP safety guideline. In addition, we also evaluated the possibility of electromagnetic interference to an implanted cardiac pacemaker in the measured electromagnetic environment. We found that even in the worst case the interference voltage induced in the output of the pacemaker sensing circuit does still not exceed the threshold for a malfunction.

Yamanaka, Yukio; Wang, Jianqing; Fujiwara, Osamu; Uda, Tatsuhiko

45

Lysogen stability is determined by the frequency of activity bursts from the fate-determining gene  

PubMed Central

The ability of living cells to maintain an inheritable memory of their gene-expression state is key to cellular differentiation. Bacterial lysogeny serves as a simple paradigm for long-term cellular memory. In this study, we address the following question: in the absence of external perturbation, how long will a cell stay in the lysogenic state before spontaneously switching away from that state? We show by direct measurement that lysogen stability exhibits a simple exponential dependence on the frequency of activity bursts from the fate-determining gene, cI. We quantify these gene-activity bursts using single-molecule-resolution mRNA measurements in individual cells, analyzed using a stochastic mathematical model of the gene-network kinetics. The quantitative relation between stability and gene activity is independent of the fine details of gene regulation, suggesting that a quantitative prediction of cell-state stability may also be possible in more complex systems.

Zong, Chenghang; So, Lok-hang; Sepulveda, Leonardo A; Skinner, Samuel O; Golding, Ido

2010-01-01

46

Dendritic calcium activity precedes inspiratory bursts in preB?tzinger Complex neurons  

PubMed Central

Medullary interneurons of the preBötzinger Complex (preBötC) assemble excitatory networks that produce inspiratory related neural rhythms, but the importance of somatodendritic conductances in rhythm generation is still incompletely understood. Synaptic input may cause Ca2+ accumulation post-synaptically to evoke a Ca2+-activated inward current that contributes to inspiratory burst generation. We measured Ca2+ transients by two-photon imaging dendrites while recording neuronal somata electrophysiologically. Dendritic Ca2+ accumulation frequently precedes inspiratory bursts, particularly at recording sites 50–300 ?m distal from the soma. Pre-inspiratory Ca2+ transients occur in ‘hotspots’, not ubiquitously, in dendrites. Ca2+ activity propagates orthodromically toward the soma (and antidromically to more distal regions of the dendrite), at rapid rates (300–700 ?m/s). These high propagation rates suggest that dendritic Ca2+ activates an inward current to electrotonically depolarize the soma, rather than propagate as a regenerative Ca2+ wave. These data provide new evidence that respiratory rhythmogenesis may depend on dendritic burst-generating conductances activated in the context of network activity.

Del Negro, Christopher A.; Hayes, John A.; Rekling, Jens C.

2010-01-01

47

Calcium-activated nonspecific cation current and synaptic depression promote network-dependent burst oscillations  

PubMed Central

Central pattern generators (CPGs) produce neural-motor rhythms that often depend on specialized cellular or synaptic properties such as pacemaker neurons or alternating phases of synaptic inhibition. Motivated by experimental evidence suggesting that activity in the mammalian respiratory CPG, the preBötzinger complex, does not require either of these components, we present and analyze a mathematical model demonstrating an unconventional mechanism of rhythm generation in which glutamatergic synapses and the short-term depression of excitatory transmission play key rhythmogenic roles. Recurrent synaptic excitation triggers postsynaptic Ca2+-activated nonspecific cation current (ICAN) to initiate a network-wide burst. Robust depolarization due to ICAN also causes voltage-dependent spike inactivation, which diminishes recurrent excitation and thus attenuates postsynaptic Ca2+ accumulation. Consequently, activity-dependent outward currents—produced by Na/K ATPase pumps or other ionic mechanisms—can terminate the burst and cause a transient quiescent state in the network. The recovery of sporadic spiking activity rekindles excitatory interactions and initiates a new cycle. Because synaptic inputs gate postsynaptic burst-generating conductances, this rhythm-generating mechanism represents a new paradigm that can be dubbed a ‘group pacemaker’ in which the basic rhythmogenic unit encompasses a fully interdependent ensemble of synaptic and intrinsic components. This conceptual framework should be considered as an alternative to traditional models when analyzing CPGs for which mechanistic details have not yet been elucidated.

Rubin, Jonathan E.; Hayes, John A.; Mendenhall, Jeffrey L.; Del Negro, Christopher A.

2009-01-01

48

Burst and Persistent Emission Properties during the Recent Active Episode of the Anomalous X-ray Pulsar 1E 1841-045.  

National Technical Information Service (NTIS)

SWift/BAT detected the first burst from 1E 1841-045 in May 2010 with intermittent burst activity recorded through at least July 2011. Here we present Swift and Fermi/GBM observations of this burst activity and search for correlated changes to the persiste...

A. Goldstein A. Von Kienlin A. J. Van Der Horst A. L. Watts C. Kouveliotou D. Tierney E. Gogus J. Granot J. Mcenery J. M. Burgess L. Lin M. Van Der Klis M. G. Baring N. Gehrels P. M. Woods R. A. M. J. Wijers R. D. Preece S. Barthelmy S. Guiriec S. N. Zhang V. Chaplin Y. Kaneko

2011-01-01

49

Theta burst stimulation reduces disability during the activities of daily living in spatial neglect.  

PubMed

Left-sided spatial neglect is a common neurological syndrome following right-hemispheric stroke. The presence of spatial neglect is a powerful predictor of poor rehabilitation outcome. In one influential account of spatial neglect, interhemispheric inhibition is impaired and leads to a pathological hyperactivity in the contralesional hemisphere, resulting in a biased attentional allocation towards the right hemifield. Inhibitory transcranial magnetic stimulation can reduce the hyperactivity of the contralesional, intact hemisphere and thereby improve spatial neglect symptoms. However, it is not known whether this improvement is also relevant to the activities of daily living during spontaneous behaviour. The primary aim of the present study was to investigate whether the repeated application of continuous theta burst stimulation trains could ameliorate spatial neglect on a quantitative measure of the activities of daily living during spontaneous behaviour. We applied the Catherine Bergego Scale, a standardized observation questionnaire that can validly and reliably detect the presence and severity of spatial neglect during the activities of daily living. Eight trains of continuous theta burst stimulation were applied over two consecutive days on the contralesional, left posterior parietal cortex in patients suffering from subacute left spatial neglect, in a randomized, double-blind, sham-controlled design, which also included a control group of neglect patients without stimulation. The results showed a 37% improvement in the spontaneous everyday behaviour of the neglect patients after the repeated application of continuous theta burst stimulation. Remarkably, the improvement persisted for at least 3 weeks after stimulation. The amelioration of spatial neglect symptoms in the activities of daily living was also generally accompanied by significantly better performance in the neuropsychological tests. No significant amelioration in symptoms was observed after sham stimulation or in the control group without stimulation. These results provide Class I evidence that continuous theta burst stimulation is a viable add-on therapy in neglect rehabilitation that facilitates recovery of normal everyday behaviour. PMID:22831781

Cazzoli, Dario; Müri, René M; Schumacher, Rahel; von Arx, Sebastian; Chaves, Silvia; Gutbrod, Klemens; Bohlhalter, Stephan; Bauer, Daniel; Vanbellingen, Tim; Bertschi, Manuel; Kipfer, Stefan; Rosenthal, Clive R; Kennard, Christopher; Bassetti, Claudio L; Nyffeler, Thomas

2012-11-01

50

Analyzing the origin of spontaneous synchronized burst in cultured neuronal networks on MEA  

NASA Astrophysics Data System (ADS)

Many mammalian neuronal networks, such as Central Nervous System (CNS), fire single spikes and complex spike burst. In fact, the conditions for triggering burst are not well understood. In the paper multi-electrode array (MEA) is used to record the spontaneous electrophysiology activity of cultured rat hippocampal neuronal networks for long-term. The transition from single spikes to burst is observed on networks that is cultured about 3 weeks and quickly fire before burst activity. The firing rate during burst is lower than that before burst, but the difference of inter spike intervals (ISIs) between the two firing patterns is not distinctness. Moreover, the electrical activities on neighboring electrodes show strong synchrony during burst activity. In a word, the generation of burst requires that network has a sufficient level of excitation as well as the balance by synaptic inhibition.

Chen, Chuanping; Chen, Lin; Lin, Yunsheng; Zeng, Shaoqun

2006-03-01

51

Peritoneal Dialysis Fluid Inhibition of Polymorphonuclear Leukocyte Respiratory Burst Activation Is Related to the Lowering of Intracellular pH  

Microsoft Academic Search

In order to elucidate the mechanism of peritoneal dialysis fluid inhibition of cell functions, laboratory-prepared fluids were used to investigate the specific influences of low pH and high lactate concentration on neutrophil viability, phagocytosis, respiratory burst activation and leukotriene B4 (LTB4) generation. In the absence of any reduction of viability, respiratory burst activation, stimulated by serum-treated zymosan (STZ), was significantly

Tomasz Liberek; Nicholas Topley; Achim Jörres; Meryl M. Petersen; Gerald A. Coles; Gerhard M. Gahl; J. D. Williams

1993-01-01

52

Cardiac-locked bursts of muscle sympathetic nerve activity are absent in familial dysautonomia  

PubMed Central

Familial dysautonomia (Riley–Day syndrome) is an hereditary sensory and autonomic neuropathy (HSAN type III), expressed at birth, that is associated with reduced pain and temperature sensibilities and absent baroreflexes, causing orthostatic hypotension as well as labile blood pressure that increases markedly during emotional excitement. Given the apparent absence of functional baroreceptor afferents, we tested the hypothesis that the normal cardiac-locked bursts of muscle sympathetic nerve activity (MSNA) are absent in patients with familial dysautonomia. Tungsten microelectrodes were inserted percutaneously into muscle or cutaneous fascicles of the common peroneal nerve in 12 patients with familial dysautonomia. Spontaneous bursts of MSNA were absent in all patients, but in five patients we found evidence of tonically firing sympathetic neurones, with no cardiac rhythmicity, that increased their spontaneous discharge during emotional arousal but not during a manoeuvre that unloads the baroreceptors. Conversely, skin sympathetic nerve activity (SSNA), recorded in four patients, appeared normal. We conclude that the loss of phasic bursts of MSNA and the loss of baroreflex modulation of muscle vasoconstrictor drive contributes to the poor control of blood pressure in familial dysautonomia, and that the increase in tonic firing of muscle vasoconstrictor neurones contributes to the increase in blood pressure during emotional excitement.

Macefield, Vaughan G; Norcliffe-Kaufmann, Lucy; Axelrod, Felicia B; Kaufmann, Horacio

2013-01-01

53

Phagocytosis and Respiratory Burst Activity in Lumpsucker (Cyclopterus lumpus L.) Leucocytes Analysed by Flow Cytometry  

PubMed Central

In the present study, we have isolated leucocytes from peripheral blood, head kidney and spleen from lumpsucker (Cyclopterus lumpus L.), and performed functional studies like phagocytosis and respiratory burst, as well as morphological and cytochemical analyses. Different leucocytes were identified, such as lymphocytes, monocytes/macrophages and polymorphonuclear cells with bean shaped or bilobed nuclei. In addition, cells with similar morphology as described for dendritic cells in trout were abundant among the isolated leucocytes. Flow cytometry was successfully used for measuring phagocytosis and respiratory burst activity. The phagocytic capacity and ability were very high, and cells with different morphology in all three leucocyte preparations phagocytised beads rapidly. Due to lack of available cell markers, the identity of the phagocytic cells could not be determined. The potent non-specific phagocytosis was in accordance with a high number of cells positive for myeloperoxidase, an enzyme involved in oxygen-dependent killing mechanism present in phagocytic cells. Further, high respiratory burst activity was present in the leucocytes samples, verifying a potent oxygen- dependent degradation. At present, the specific antibody immune response could not be measured, as immunoglobulin or B-cells have not yet been isolated. Therefore, analyses of the specific immune response in this fish species await further clarification. The present study presents the first analyses of lumpsucker immunity and also the first within the order Scopaeniformes.

Haugland, Gyri T.; Jakobsen, Ragnhild Aakre; Vestvik, Nils; Ulven, Kristian; Stokka, Lene; Wergeland, Heidrun I.

2012-01-01

54

Group I mGluR Activation Enhances Ca2+-Dependent Nonselective Cation Currents and Rhythmic Bursting in Main Olfactory Bulb External Tufted Cells  

PubMed Central

In the main olfactory bulb, activation of Group I metabotropic glutamate receptors (mGluRs) by olfactory nerve stimulation generates slow (2 Hz) oscillations near the basal respiratory frequency. These oscillations arise in the glomerular layer and may be generated, in part, by the intrinsic neurons, the juxtaglomerular neurons. We investigated the physiological effects of Group I mGluR agonists on one population of juxtaglomerular neurons, external tufted (ET) cells, which rhythmically burst at respiratory frequencies and synchronize the intraglomerular network. Electrophysiological studies in rat MOB slices demonstrated that mGluR agonist DHPG amplified the strength of ET cell spike bursts, principally by increasing the number of spikes/burst. Voltage clamp and Ca2+-imaging studies showed that DHPG elicits a Ca2+-dependent non-selective cation current (ICAN) in the dendrites of ET cells triggered by Ca2+ release from internal stores. The DHPG effects on bursting and membrane current were attenuated by flufenamic acid and SKF96365, agents known to antagonize ICAN in a variety of neurons. DHPG also elicited slow membrane current oscillations and spikelets in ET cells when synaptic transmission and intrinsic membrane channels were inoperative. These findings indicate that DHPG may passively (by increasing burst strength) or actively (by increasing conductance of gap junctions) enhance the strength of electrical synapses between ET cells. Taken together, these findings indicate that activation of group I mGluRs on the dendrites of ET cells play a key role in the generation of slow rhythmic oscillation in the glomerular network, which is in turn tuned to sniffing of the animal in vivo.

Dong, Hong-Wei; Hayar, Abdallah; Callaway, Joseph; Yang, Xiang-Hong; Nai, Qiang; Ennis, Matthew

2013-01-01

55

Emergence of Population Bursts from Simultaneous Activation of Small Subsets of preB?tzinger Complex Inspiratory Neurons  

PubMed Central

During rhythmic movements, central pattern generators (CPGs) trigger bursts of motor activity with precise timing. However, the number of neurons that must be activated within CPGs to generate motor output is unknown. In the mammalian breathing rhythm, a fundamentally important motor behavior, the preBötzinger Complex (preBötC) produces synchronous population-wide bursts of activity to control inspiratory movements. We probed mechanisms underlying inspiratory burst generation in the preBötC using holographic photolysis of caged glutamate in medullary slices from neonatal mice. With stimulation parameters determined to confine photoactivation to targeted neurons, simultaneous excitation of 4–9 targeted neurons could initiate ectopic, endogenous-like bursts with delays averaging 255 ms, placing a critical and novel boundary condition on the microcircuit undelying respiratory rhythmogenesis.

Kam, Kaiwen; Worrell, Jason W.; Ventalon, Cathie; Emiliani, Valentina; Feldman, Jack L.

2013-01-01

56

Modeling Electrically Active Viscoelastic Membranes  

PubMed Central

The membrane protein prestin is native to the cochlear outer hair cell that is crucial to the ear's amplification and frequency selectivity throughout the whole acoustic frequency range. The outer hair cell exhibits interrelated dimensional changes, force generation, and electric charge transfer. Cells transfected with prestin acquire unique active properties similar to those in the native cell that have also been useful in understanding the process. Here we propose a model describing the major electromechanical features of such active membranes. The model derived from thermodynamic principles is in the form of integral relationships between the history of voltage and membrane resultants as independent variables and the charge density and strains as dependent variables. The proposed model is applied to the analysis of an active force produced by the outer hair cell in response to a harmonic electric field. Our analysis reveals the mechanism of the outer hair cell active (isometric) force having an almost constant amplitude and phase up to 80 kHz. We found that the frequency-invariance of the force is a result of interplay between the electrical filtering associated with prestin and power law viscoelasticity of the surrounding membrane. Paradoxically, the membrane viscoelasticity boosts the force balancing the electrical filtering effect. We also consider various modes of electromechanical coupling in membrane with prestin associated with mechanical perturbations in the cell. We consider pressure or strains applied step-wise or at a constant rate and compute the time course of the resulting electric charge. The results obtained here are important for the analysis of electromechanical properties of membranes, cells, and biological materials as well as for a better understanding of the mechanism of hearing and the role of the protein prestin in this mechanism.

Roy, Sitikantha; Brownell, William E.; Spector, Alexander A.

2012-01-01

57

Origin of Initial Burst in Activity for Trichoderma reesei endo-Glucanases Hydrolyzing Insoluble Cellulose*  

PubMed Central

The kinetics of cellulose hydrolysis have longbeen described by an initial fast hydrolysis rate, tapering rapidly off, leading to a process that takes days rather than hours to complete. This behavior has been mainly attributed to the action of cellobiohydrolases and often linked to the processive mechanism of this exo-acting group of enzymes. The initial kinetics of endo-glucanases (EGs) is far less investigated, partly due to a limited availability of quantitative assay technologies. We have used isothermal calorimetry to monitor the early time course of the hydrolysis of insoluble cellulose by the three main EGs from Trichoderma reesei (Tr): TrCel7B (formerly EG I), TrCel5A (EG II), and TrCel12A (EG III). These endo-glucanases show a distinctive initial burst with a maximal rate that is about 5-fold higher than the rate after 5 min of hydrolysis. The burst is particularly conspicuous for TrCel7B, which reaches a maximal turnover of about 20 s?1 at 30 °C and conducts about 1200 catalytic cycles per enzyme molecule in the initial fast phase. For TrCel5A and TrCel12A the extent of the burst is 2–300 cycles per enzyme molecule. The availability of continuous data on EG activity allows an analysis of the mechanisms underlying the initial kinetics, and it is suggested that the slowdown is linked to transient inactivation of enzyme on the cellulose surface. We propose, therefore, that the frequency of structures on the substrate surface that cause transient inactivation determine the extent of the burst phase.

Murphy, Leigh; Cruys-Bagger, Nicolaj; Damgaard, Heidi Delcomyn; Baumann, Martin J.; Olsen, S?ren Nymand; Borch, Kim; Lassen, S?ren Flensted; Sweeney, Matt; Tatsumi, Hirosuke; Westh, Peter

2012-01-01

58

Electrical measurements over active thunderstorms  

NASA Technical Reports Server (NTRS)

During the summer of 1986, the air conductivity and the vertical electric field were measured over active thunderstorms from a high altitude U-2 airplane. The conductivity at 20 km remained relatively steady above storms with variations less than + or - 15 percent while vertical electric fields in excess of 5 kV/m were regularly observed. Estimates of the storm generator current and the C.T.R. Wilson (i.e., conduction) current can be obtained using the current densities derived from the conductivity and field measurements and integrated over area. Upward flowing currents of 0.05 to 7.7 A were observed with an average of 2.2 A. More importantly, the U-2 data show that the storm current varies linearly with flash rate, therefore, the average charge transfer per discharge should be independent of storm development or activity.

Blakeslee, Richard J.; Christian, Hugh J.; Vonnegut, Bernard

1988-01-01

59

Predictive Features of Persistent Activity Emergence in Regular Spiking and Intrinsic Bursting Model Neurons  

PubMed Central

Proper functioning of working memory involves the expression of stimulus-selective persistent activity in pyramidal neurons of the prefrontal cortex (PFC), which refers to neural activity that persists for seconds beyond the end of the stimulus. The mechanisms which PFC pyramidal neurons use to discriminate between preferred vs. neutral inputs at the cellular level are largely unknown. Moreover, the presence of pyramidal cell subtypes with different firing patterns, such as regular spiking and intrinsic bursting, raises the question as to what their distinct role might be in persistent firing in the PFC. Here, we use a compartmental modeling approach to search for discriminatory features in the properties of incoming stimuli to a PFC pyramidal neuron and/or its response that signal which of these stimuli will result in persistent activity emergence. Furthermore, we use our modeling approach to study cell-type specific differences in persistent activity properties, via implementing a regular spiking (RS) and an intrinsic bursting (IB) model neuron. We identify synaptic location within the basal dendrites as a feature of stimulus selectivity. Specifically, persistent activity-inducing stimuli consist of activated synapses that are located more distally from the soma compared to non-inducing stimuli, in both model cells. In addition, the action potential (AP) latency and the first few inter-spike-intervals of the neuronal response can be used to reliably detect inducing vs. non-inducing inputs, suggesting a potential mechanism by which downstream neurons can rapidly decode the upcoming emergence of persistent activity. While the two model neurons did not differ in the coding features of persistent activity emergence, the properties of persistent activity, such as the firing pattern and the duration of temporally-restricted persistent activity were distinct. Collectively, our results pinpoint to specific features of the neuronal response to a given stimulus that code for its ability to induce persistent activity and predict differential roles of RS and IB neurons in persistent activity expression.

Sidiropoulou, Kyriaki; Poirazi, Panayiota

2012-01-01

60

Spontaneous Electrical Activity in the Human Fetal Cortex in vitro  

PubMed Central

Our knowledge about the developing human cerebral cortex is based on the analysis of fixed postmortem material. Here we utilize electrical recordings from unfixed human postmortem tissue to characterize the synaptic physiology and spontaneous network activity of pioneer cortical neurons (“subplate neurons”). Our electrophysiological experiments show that functional glutamate or GABA ionotropic receptors are expressed on human subplate (SP) neurons as early as 20 gestational weeks. Extracellular (synaptic) stimulations evoked postsynaptic potentials in a very small fraction of SP neurons, suggesting that functional synaptic contacts are rare at mid-gestation. Although synaptic inputs were scarce, we regularly observed spontaneous (unprovoked) electrical activity among human SP neurons, comprised of sustained plateau depolarizations and bursts of action potential firing, which resembled cortical UP and DOWN states in the adult neocortex. Plateau depolarizations and bursts of AP firing are thought to depend on the mature morphology and physiology of adult cortical network. However, our current data reveal that similar cortical rhythm is generated by a very immature ensemble of human fetal neurons. In the relative absence of sensory inputs, as in development in utero, or in slow wave sleep (i.e. throughout the entire lifespan), the spontaneous slow oscillatory pattern (UP and DOWN states) is a fundamental aspect of human cortical physiology.

Moore, Anna R.; Zhou, Wen-Liang; Jakovcevski, Igor; Zecevic, Nada; Antic, Srdjan D.

2011-01-01

61

Characterization of inward currents and channels underlying burst activity in motoneurons of crab cardiac ganglion.  

PubMed

Large cell motoneurons in the Cancer borealis cardiac ganglion generate rhythmic bursts of action potentials responsible for cardiac contractions. While it is well known that these burst potentials are dependent on coordinated interactions among depolarizing and hyperpolarizing conductances, the depolarizing currents present in these cells, and their biophysical characteristics, have not been thoroughly described. In this study we used a combined molecular biology and electrophysiology approach to look at channel identity, expression, localization, and biophysical properties for two distinct high-voltage-activated calcium currents present in these cells: a slow calcium current (ICaS) and a transient calcium current (ICaT). Our data indicate that CbCaV1 is a putative voltage-gated calcium channel subunit in part responsible for an L-type current, while CbCaV2 (formerly cacophony) is a subunit in part responsible for a P/Q-type current. These channels appear to be localized primarily to the somata of the motoneurons. A third calcium channel gene (CbCaV3) was identified that encodes a putative T-type calcium channel subunit and is expressed in these cells, but electrophysiological studies failed to detect this current in motoneuron somata. In addition, we identify and characterize for the first time in these cells a calcium-activated nonselective cationic current (ICAN), as well as a largely noninactivating TTX-sensitive current reminiscent of a persistent sodium current. The identification and further characterization of these currents allow both biological and modeling studies to move forward with more attention to the complexity of interactions among these distinct components underlying generation of bursting output in motoneurons. PMID:23576706

Ransdell, Joseph L; Temporal, Simone; West, Nicole L; Leyrer, Megan L; Schulz, David J

2013-07-01

62

A Codimension-2 Bifurcation Controlling Endogenous Bursting Activity and Pulse-Triggered Responses of a Neuron Model  

PubMed Central

The dynamics of individual neurons are crucial for producing functional activity in neuronal networks. An open question is how temporal characteristics can be controlled in bursting activity and in transient neuronal responses to synaptic input. Bifurcation theory provides a framework to discover generic mechanisms addressing this question. We present a family of mechanisms organized around a global codimension-2 bifurcation. The cornerstone bifurcation is located at the intersection of the border between bursting and spiking and the border between bursting and silence. These borders correspond to the blue sky catastrophe bifurcation and the saddle-node bifurcation on an invariant circle (SNIC) curves, respectively. The cornerstone bifurcation satisfies the conditions for both the blue sky catastrophe and SNIC. The burst duration and interburst interval increase as the inverse of the square root of the difference between the corresponding bifurcation parameter and its bifurcation value. For a given set of burst duration and interburst interval, one can find the parameter values supporting these temporal characteristics. The cornerstone bifurcation also determines the responses of silent and spiking neurons. In a silent neuron with parameters close to the SNIC, a pulse of current triggers a single burst. In a spiking neuron with parameters close to the blue sky catastrophe, a pulse of current temporarily silences the neuron. These responses are stereotypical: the durations of the transient intervals–the duration of the burst and the duration of latency to spiking–are governed by the inverse-square-root laws. The mechanisms described here could be used to coordinate neuromuscular control in central pattern generators. As proof of principle, we construct small networks that control metachronal-wave motor pattern exhibited in locomotion. This pattern is determined by the phase relations of bursting neurons in a simple central pattern generator modeled by a chain of oscillators.

Barnett, William H.; Cymbalyuk, Gennady S.

2014-01-01

63

Active Galactic Nuclei, Gamma Ray Bursts and ultra high energy cosmic rays  

NASA Astrophysics Data System (ADS)

The importance of explaining and achieving the highest observed cosmic ray energies by the first order Fermi acceleration mechanism in a given astrophysical environment, is a recurring theme in astroparticle physics. We discuss the acceleration of cosmic rays in relativistic shock formations, focusing on numerical studies concerning proton acceleration efficiency by subluminal and superluminal shocks, emphasising on the dependence of the scattering model, shock Lorentz factor and the angle between the magnetic field and the shock front. We present a diffuse cosmic ray prediction model, where results are compared with the measured flux of cosmic rays at the highest energies. We show that while steeper Active Galactic Nuclei spectra provide an excellent fit, Gamma Ray Burst spectra being flatter can hardly explain the highest energy observed flux. Our model explains well the first evidence of a correlation between the cosmic ray flux above 5.7 x 10^10 GeV and the distribution of Active Galactic Nuclei provided by AUGER. Gamma Ray Bursts seem not to account for the origin of the highest cosmic ray energies, nevertheless, neutrino production is expected in these sources either in mildly or highly relativistic shocks. It is interesting to note that superluminal shocks in relativistic astrophysical environments may be observable via neutrino and photon fluxes, rather than as proton contributors. For this purpose observations from current gamma-ray and neutrino observatories is important.

Meli, A.; Becker, J.; Quenby, J. J.,

64

Praseodymium activation detector for measuring bursts of 14MeV neutrons  

NASA Astrophysics Data System (ADS)

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of praesodymium, an element that has a single, naturally occurring isotope (Pr-141), a significant (n,2n) cross section, and decays by positron emission. Neutron fluences are measured by using the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay product. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma Focus Laboratory fusion sources. Comparisons with lead, copper, beryllium and silver activation detectors have been performed. The detection method allows measurement of 14 MeV neutrons with a total error of +/- 10%.

Meehan, B. T.; Hagen, E. C.; Ruiz, C. L.; Cooper, G. W.

2009-08-01

65

Calcium and Glycolysis Mediate Multiple Bursting Modes in Pancreatic Islets  

PubMed Central

Pancreatic islets of Langerhans produce bursts of electrical activity when exposed to stimulatory glucose levels. These bursts often have a regular repeating pattern, with a period of 10–60 s. In some cases, however, the bursts are episodic, clustered into bursts of bursts, which we call compound bursting. Consistent with this are recordings of free Ca2+ concentration, oxygen consumption, mitochondrial membrane potential, and intraislet glucose levels that exhibit very slow oscillations, with faster oscillations superimposed. We describe a new mathematical model of the pancreatic ?-cell that can account for these multimodal patterns. The model includes the feedback of cytosolic Ca2+ onto ion channels that can account for bursting, and a metabolic subsystem that is capable of producing slow oscillations driven by oscillations in glycolysis. This slow rhythm is responsible for the slow mode of compound bursting in the model. We also show that it is possible for glycolytic oscillations alone to drive a very slow form of bursting, which we call “glycolytic bursting.” Finally, the model predicts that there is bistability between stationary and oscillatory glycolysis for a range of parameter values. We provide experimental support for this model prediction. Overall, the model can account for a diversity of islet behaviors described in the literature over the past 20 years.

Bertram, Richard; Satin, Leslie; Zhang, Min; Smolen, Paul; Sherman, Arthur

2004-01-01

66

How Long does a Burst Burst?  

NASA Astrophysics Data System (ADS)

Several gamma-ray bursts (GRBs) last much longer (~hours) in ?-rays than typical long GRBs (~minutes), and it has recently been proposed that these "ultra-long GRBs" may form a distinct population, probably with a different (e.g., blue supergiant) progenitor than typical GRBs. However, Swift observations suggest that many GRBs have extended central engine activities manifested as flares and internal plateaus in X-rays. We perform a comprehensive study on a large sample of Swift GRBs with X-Ray Telescope observations to investigate GRB central engine activity duration and to determine whether ultra-long GRBs are unusual events. We define burst duration t burst based on both ?-ray and X-ray light curves rather than using ?-ray observations alone. We find that t burst can be reliably measured in 343 GRBs. Within this "good" sample, 21.9% GRBs have t burst >~ 103 s and 11.5% GRBs have t burst >~ 104 s. There is an apparent bimodal distribution of t burst in this sample. However, when we consider an "undetermined" sample (304 GRBs) with t burst possibly falling in the gap between GRB duration T 90 and the first X-ray observational time, as well as a selection effect against t burst falling into the first Swift orbital "dead zone" due to observation constraints, the intrinsic underlying t burst distribution is consistent with being a single component distribution. We found that the existing evidence for a separate ultra-long GRB population is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion. We also discuss the theoretical implications of our results. In particular, the central engine activity duration of GRBs is generally much longer than the ?-ray T 90 duration and it does not even correlate with T 90. It would be premature to make a direct connection between T 90 and the size of the progenitor star.

Zhang, Bin-Bin; Zhang, Bing; Murase, Kohta; Connaughton, Valerie; Briggs, Michael S.

2014-05-01

67

Activity of plant extracts on the respiratory burst and the stress protein synthesis.  

PubMed

Aqueous, methanol and dichloromethane extracts from Artemisia copa, Baccharis grisebachii, Baccharis incarum, Baccharis latifolia, Mutisia kurtzii and Pluchea sagittalis, plants used in the Traditional Medicine of South America, are studied for activity on the respiratory burst and the inducible heat shock protein of 72 kD (hsp72) synthesis. Activity on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as on hsp72 synthesis was measured by flow cytometry in human neutrophils. Cells were stimulated using hydrogen peroxide, phorbol-12-myristate-13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (FMLP) for ROS generation, and sodium nitroprusside (SNP) or PMA in the presence of calmodulin inhibitor W-13 for RNS. The production of hsp72 was induced by heat, PMA, H2O2 and SNP. The best inhibitory activity was shown by the dichloromethane extracts of Baccharis grisebachii and Pluchea sagittalis that were active in all the assays. The aqueous extract of Pluchea sagittalis was also active in most assays. The aqueous extract from Mutisia kurtzii caused a clear increase of the hsp72 production and showed prooxidant activity. PMID:11292237

Pérez-García, F; Marín, E; Adzet, T; Cañigueral, S

2001-01-01

68

Activities Report in Electrical Science.  

National Technical Information Service (NTIS)

Research in acoustics; electromechanics; photometry; systems engineering; materials science; electrical metrology; and time, frequency and electromagnetic metrology is summarized. Television communication; image processing; standards; and calibration tech...

1985-01-01

69

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

NASA Astrophysics Data System (ADS)

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation <10 MeV and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of 141Pr, an element that has a single, naturally occurring isotope, a significant n,2n cross-section, and decays by positron emission that result in two coincident 511 keV photons. Neutron fluences are thus inferred by relating measured reaction product decay activity to fluence. Specific sample activity is measured using the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay products. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma Focus Laboratory fusion sources. Lead, copper, beryllium, and silver activation detectors were compared. The detection method allows measurement of 14 MeV neutron yield with a total error of ?18%.

Meehan, Tim; Hagen, E. C.; Ruiz, C. L.; Cooper, G. W.

2010-08-01

70

Bursting as a source for predictability in biological neural network activity  

NASA Astrophysics Data System (ADS)

The role of bursting as a unit of neural information has received considerable support in the recent years. Experimental evidence shows that in many different neural systems, e.g. visual cortex or hippocampus, bursting is essential for coding and processing. We have recently demonstrated (Menendez de la Prida et al., 1996) the spontaneous presence of bursts in in vitro hippocampal slices from newborn animals, providing a good system to investigate bursting dynamics in physiological conditions. Here we analyze the interspike intervals (ISIs) of five intracellularly recorded cells from immature hippocampal networks. First, we test the time series against Poisson processes, typical of pure random behavior, using the Kolmogorov-Smirnov test. Only {2}/{5} records strongly deviate from Poisson process. Nonlinear diction tests are then applied to compare original series with its Gaussian-scaled random phase surrogates and signs of short time predictability are observed ( {1}/{5}). This predictability is originated by the intrinsic structure of bursts, in an otherwise purely random process, and can be removed completely by eliminating the bursts from the original time series. Here we introduce this method of eliminating bursts to get insight into the nonlinear dynamics of firing. Also the interburst intervals are indistinguishable from pure noise. The analysis of unstable periodicities within the bursts in the original ISIs shows that signs of nonlinearities can be statistically differentiated from their surrogate realizations (Pierson-Moss method). We discuss the computational implication of these results.

Menendez de la Prida, L.; Stollenwerk, N.; Sanchez-Andres, J. V.

71

Bursting as a source for predictability in biological neural network activity  

NASA Astrophysics Data System (ADS)

The role of bursting as a unit of neural information has received considerable support in the recent years. Experimental evidence shows that in many different neural systems, e.g. visual cortex or hippocampus, bursting is essential for coding and processing. We have recently demonstrated (Menendez de la Prida et al., 1996) the spontaneous presence of bursts in in vitro hippocampal slices from newborn animals, providing a good system to investigate bursting dynamics in physiological conditions. Here we analyze the interspike intervals (ISIs) of five intracellularly recorded cells from immature hippocampal networks. First, we test the time series against Poisson processes, typical of pure random behavior, using the Kolmogorov-Smirnov test. Only 2/(5) records strongly deviate from Poisson process. Nonlinear prediction tests are then applied to compare original series with its Gaussian-scaled random phase surrogates and signs of short time predictability are observed (1/(5)). This predictability is originated by the intrinsic structure of bursts, in an otherwise purely random process, and can be removed completely by eliminating the bursts from the original time series. Here we introduce this method of eliminating bursts to get insight into the nonlinear dynamics of firing. Also the interburst intervals are indistinguishable from pure noise. The analysis of unstable periodicities within the bursts in the original ISIs shows that signs of nonlinearities can be statistically differentiated from their surrogate realizations (Pierson-Moss method). We discuss the computational implication of these results.

de La Prida, L. Menendez; Stollenwerk, N.; Sanchez-Andres, J. V.

1997-02-01

72

Transient period of correlated bursting activity during development of the mammalian retina  

Microsoft Academic Search

Summary The refinement of early connections in the visual path- way requires electrical activity in the retina before the onset of vision. Using a multielectrode array, we have shown that the spontaneous activity of cells in the neona- tal ferret retina is correlated by patterns of periodically generated traveling waves. Here, we examine develop- mental changes in the characteristics of

R Wong; C. J. Shatz

1993-01-01

73

Electrical activation of the human vestibulo-sympathetic reflex.  

PubMed

Muscle sympathetic nerve activity (MSNA) is modulated on a beat-to-beat basis by the baroreflex. Vestibular input from the otolith organs also modulates MSNA, but characteristics of the vestibulo-sympathetic reflex (VSR) are largely unknown. The purpose of this study was to elicit the VSR with electrical stimulation to estimate its latency in generating MSNA. The vestibular nerves of seven subjects were stimulated across the mastoids with short trains of high frequency, constant current pulses. Pulse trains were delivered every fourth heartbeat at delays of 300-700 ms after the R wave of the electrocardiogram. Vestibular nerve stimulation given 500 ms after the R wave significantly increased baroreflex-driven MSNA, as well as the diastolic blood pressure threshold at which bursts of MSNA occurred. These changes were specific to beats in which vestibular stimulation was applied. Electrical stimulation across the shoulders provided a control condition. When trans-shoulder trials were subtracted from trials with vestibular nerve stimulation, eliminating the background baroreflex-driven sympathetic activity, there was a sharp increase in MSNA beginning 660 ms after the vestibular nerve stimulus and lasting for about 60 ms. The increase in the MSNA produced by vestibular nerve stimulation, and the associated increase in the diastolic blood pressure threshold at which the baroreflex-driven bursts occurred, provide evidence for the presence of a short-latency VSR in humans that is likely to be important for the maintenance of blood pressure during rapid changes in head and body position with respect to gravity. PMID:16308690

Voustianiouk, Andrei; Kaufmann, Horacio; Diedrich, André; Raphan, Theodore; Biaggioni, Italo; Macdougall, Hamish; Ogorodnikov, Dmitri; Cohen, Bernard

2006-05-01

74

Discrete Pattern of Burst Stimulation in the Ventrobasal Thalamus for Anti-Nociception  

PubMed Central

The thalamus has been proposed to play a role in sensory modulation via switching between tonic and burst dual firing of individual neurons. Of the two firing modes, altered burst firing has been repeatedly implicated with pathological pain conditions, which suggests that maintaining a certain form of thalamic burst could be crucial for controlling pain. However, specific elements of burst firing that may contribute to pain control have not yet been actively investigated. Utilizing the deep brain stimulation (DBS) technique, we explored the effects of bursting properties in pain control by electrically stimulating the ventrobasal (VB) thalamus in forms of burst patterned to test different aspects of bursts during the formalin induced nociception in mice. Our results demonstrated that electrical stimulations mimicking specific burst firing properties are important in producing an anti-nociceptive effect and found that the ?3 ms interval between burst pluses (intra-burst-interval: IntraBI) and ?3 pulses per burst were required to reliably reduce formalin induced nociceptive responses in mice. Periodicity of IntraBI was also suggested to contribute to anti-nociception to a limited extent.

Huh, Yeowool; Cho, Jeiwon

2013-01-01

75

Calcium-activated non-selective cation currents are involved in generation of tonic and bursting activity in dopamine neurons of the substantia nigra pars compacta.  

PubMed

Nigral dopamine neurons are transiently activated by high frequency glutamatergic inputs relaying reward-predicting sensory information. The tonic firing pattern of dopamine cells responds to these inputs with a transient burst of spikes that requires NMDA receptors. Here, we show that NMDA receptor activation further excites the cell by recruiting a calcium-activated non-selective cation current (ICAN) capable of generating a plateau potential. Burst firing in vitro is eliminated after blockade of ICAN with flufenamic acid, 9-phenanthrol, or intracellular BAPTA. ICAN is likely to be mediated by a transient receptor potential (TRP) channel, and RT-PCR was used to confirm expression of TRPM2 and TRPM4mRNA in substantia nigra pars compacta.We propose that ICAN is selectively activated during burst firing to boost NMDA currents and allow plateau potentials. This boost mechanism may render DA cells vulnerable to excitotoxicity. PMID:21486760

Mrejeru, Ana; Wei, Aguan; Ramirez, Jan Marino

2011-05-15

76

Calcium-activated non-selective cation currents are involved in generation of tonic and bursting activity in dopamine neurons of the substantia nigra pars compacta  

PubMed Central

Abstract Nigral dopamine neurons are transiently activated by high frequency glutamatergic inputs relaying reward-predicting sensory information. The tonic firing pattern of dopamine cells responds to these inputs with a transient burst of spikes that requires NMDA receptors. Here, we show that NMDA receptor activation further excites the cell by recruiting a calcium-activated non-selective cation current (ICAN) capable of generating a plateau potential. Burst firing in vitro is eliminated after blockade of ICAN with flufenamic acid, 9-phenanthrol, or intracellular BAPTA. ICAN is likely to be mediated by a transient receptor potential (TRP) channel, and RT-PCR was used to confirm expression of TRPM2 and TRPM4 mRNA in substantia nigra pars compacta. We propose that ICAN is selectively activated during burst firing to boost NMDA currents and allow plateau potentials. This boost mechanism may render DA cells vulnerable to excitotoxicity.

Mrejeru, Ana; Wei, Aguan; Ramirez, Jan Marino

2011-01-01

77

Intracellular free calcium regulates the onset of the respiratory burst of human neutrophils activated by phorbol myristate acetate.  

PubMed

Thapsigargin was used to study the regulation of different static calcium level ([Ca2+]i) on the respiratory hurst of human neutrophils stimulated with phorbol myristate acetate (PMA). The result showed that the onset time of the respiratory hurst was obviously reduced by elevation of static [Ca2+]i but is still much longer than that stimulated with N-formylmethionylleucylphenylalanine (fMLP). To find the reason, the onset times of the respiratory burst stimulated with fMLP, 1,2-dioctanoyl-sn-glycerol (DiC8), and PMA were determined at different static [Ca2+]i. It turns out that although DiC8 was unable to induce the respiratory burst at low [Ca2+], the onset time of DiC8-stimulated response at high [Ca2+]i was almost the same as that stimulated with fMLP. The study revealed that the fast onset of the fMLP-stimulated respiratory burst in comparison with PMA-stimulated response is not only due to the transient rise of [Ca2+]i, but is also due to the higher efficiency of diacylglycerol (DAG) in activating protein kinase c (PKC). The determining step in governing the onset of a respiratory burst is the activation of PKC. PMID:10376809

Hu, T H; Bei, L; Qian, Z M; Shen, X

1999-05-01

78

The Effects of Plantago major on the Activation of the Neutrophil Respiratory Burst.  

PubMed

Plantago major is a common plant that grows worldwide in temperate zones and is found in fields, lawns, and on the roadsides. Its leaves and seeds have been used in almost all parts of the world for centuries as a wound healer, analgesic, antioxidant, and antibiotic, as well as an immune system modulator, antiviral, antifungal, and anti-inflammatory agent. Baicalein and aucubin are the two most biologically active components of P. major, and both have been shown to have antioxidant, anti-inflammatory, and anticancer properties. Neutrophils have a pivotal role in wound healing and inflammation. Their principal mechanism of host defense is the killing of pathogens via the production of reactive oxygen species (ROS). The aim of the present study was to determine the in vitro effects of P. major extract, baicalein, and aucubin on human neutrophil respiratory burst activity. The cytotoxicity of the agents was assessed by lactate dehydrogenase (LDH) assays. A standard luminol-dependent chemiluminescence (CL) assay was utilized to monitor the respiratory burst of the neutrophils after exposure to P. major extract and its two active ingredients, baicalein and aucubin. Three replicates per group were included in each of the three runs of the experiments and analysis of variance (ANOVA) was used for statistical analysis. P. major and baicalein were not toxic to the cells at any of the concentrations examined. Aucubin was toxic to the cells only at the highest concentration tested (P = 0.0081). However, genistein was toxic to the cells at all of the concentrations examined except for the lowest concentration of 16.9 ?g/ml (P = 0.985). P. major (-0.10 ± 0.11), aucubin (0.06 ± 0.16), baicalein (-0.10 ± 0.11), and genistein (-0.18 ± 0.07) all significantly (P < 0.0001) inhibited ROS production from the neutrophils. P. major extract inhibited neutrophil ROS production, as did aucubin and baicalein. Therefore, these components should be investigated further with relation to the regulation of destructive ROS production in conditions such as periodontal disease. PMID:24716188

Reina, Elaine; Al-Shibani, Nouf; Allam, Eman; Gregson, Karen S; Kowolik, Michael; Windsor, L Jack

2013-10-01

79

UNUSUAL CENTRAL ENGINE ACTIVITY IN THE DOUBLE BURST GRB 110709B  

SciTech Connect

The double burst, GRB 110709B, triggered the Swift/Burst Alert Telescope (BAT) twice at 21:32:39 UT and 21:43:45 UT, respectively, on 2011 July 9. This is the first time we observed a gamma-ray burst (GRB) with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations of this unusual GRB and its afterglow. If the two events originated from the same physical progenitor, their different time-dependent spectral evolution suggests they must belong to different episodes of the central engine, which may be a magnetar-to-BH accretion system.

Zhang Binbin; Burrows, David N.; Meszaros, Peter; Falcone, Abraham D. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Zhang Bing [Department of Physics, University of Nevada, Las Vegas, NV 89154 (United States); Wang Xiangyu [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Stratta, Giulia; D'Elia, Valerio [ASI-Science Data Center, Via Galileo Galilei, I-00044 Frascati (Italy); Frederiks, Dmitry; Golenetskii, Sergey [Ioffe Physico-Technical Institute, Laboratory for Experimental Astrophysics, 26 Polytekhnicheskaya, St Petersburg 194021 (Russian Federation); Cummings, Jay R.; Barthelmy, Scott D.; Gehrels, Neil [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Norris, Jay P., E-mail: bbzhang@psu.edu [Physics Department, Boise State University, 1910 University Drive, Boise, ID 83725 (United States)

2012-04-01

80

Unusual Central Engine Activity in the Double Burst GRB 110709B  

NASA Astrophysics Data System (ADS)

The double burst, GRB 110709B, triggered the Swift/Burst Alert Telescope (BAT) twice at 21:32:39 UT and 21:43:45 UT, respectively, on 2011 July 9. This is the first time we observed a gamma-ray burst (GRB) with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations of this unusual GRB and its afterglow. If the two events originated from the same physical progenitor, their different time-dependent spectral evolution suggests they must belong to different episodes of the central engine, which may be a magnetar-to-BH accretion system.

Zhang, Bin-Bin; Burrows, David N.; Zhang, Bing; Mészáros, Peter; Wang, Xiang-Yu; Stratta, Giulia; D'Elia, Valerio; Frederiks, Dmitry; Golenetskii, Sergey; Cummings, Jay R.; Norris, Jay P.; Falcone, Abraham D.; Barthelmy, Scott D.; Gehrels, Neil

2012-04-01

81

Measurement of respiratory burst products, released or retained, during activation of professional phagocytes.  

PubMed

Activation of professional phagocytes, potent microbial killers of our innate immune system, is associated with an increase in cellular consumption of molecular oxygen (O2). The consumed O2 is utilized by an NADPH-oxidase to generate highly reactive oxygen species (ROS) by a one electron reduction, initially generating superoxide anion (O2 (-)) that then dismutates to hydrogen peroxide (H2O2). The ROS are strongly bactericidal molecules but may also cause tissue destruction, and are capable of driving immune competent cells of both the innate and the adaptive immune systems into apoptosis. The development of basic techniques to measure/quantify ROS generation by phagocytes during activation of the respiratory burst is of great importance, and a large number of methods have been used for this purpose. A selection of methods, including chemiluminescence amplified by luminol or isoluminol, the absorbance change following reduction of cytochrome c, and the fluorescence increase upon oxidation of PHPA, are described in detail in this chapter with special emphasis on how to distinguish between ROS that are released extracellularly, and those that are retained within intracellular organelles. These techniques can be valuable tools in research spanning from basic phagocyte biology to more clinically oriented research on innate immune mechanisms and inflammation. PMID:24504962

Bylund, Johan; Björnsdottir, Halla; Sundqvist, Martina; Karlsson, Anna; Dahlgren, Claes

2014-01-01

82

Magnetotail Flow Bursts: Association to Global Magnetospheric Circulation, Relationship to Ionospheric Activity and Direct Evidence for Localization  

NASA Technical Reports Server (NTRS)

A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the UVI instrument of POALR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between BBFs and ionospheric activity observed by UVI even when ground magnetic signatures were absent, suggesting that low ionospheric conductivity at the active sector may be responsible for this observation. During the second substorm no significant flux transport was evidenced past WIND in stark contrast to GEOTAIL and despite the small intersatellite separation ((3.54, 2.88, -0.06) Re). Throughout the intervals studied there were significant differences in the individual flow bursts at the two satellites, even during longitudinally extended ionospheric activations. We conclude that the half-scale-size of transport bearing flow bursts is less than 3 Re.

Angelopoulos, V.; Phan, T. D.; Larson, D. E.; Mozer, F. S.; Lin, R. P.; Parks, G. K.; Brittnacher, M. J.; Germany, G. A.; Spann, J. F., Jr.

1998-01-01

83

The activated SA and JA signaling pathways have an influence on flg22-triggered oxidative burst and callose deposition.  

PubMed

The first line of defense in plants against pathogens is induced by the recognition of microbe-associated molecular patterns (MAMP). Perception of bacterial flagellin (flg22) by the pattern recognition receptor flagellin-sensing 2 (FLS2) is the best characterized MAMP response, although the underlying molecular mechanisms are not fully understood. Here we studied the relationship between salicylic acid (SA) or jasmonic acid (JA) signaling and FLS2-mediated signaling by monitoring flg22-triggered responses in known SA or JA related mutants of Arabidopsis thaliana (L.) Heynh. The sid2 mutant, impaired in SA biosynthesis, had less basal FLS2 mRNA accumulation than the wild type, which correlated with suppression of early flg22 responses such as ROS production and induction of marker genes, WRKY29 and FRK1. The JA-signaling mutants, jar1 and coi1, exhibited an enhanced flg22-triggered oxidative burst and more callose accumulation than the wild type, and pretreatment with SA or coronatine (COR), a structural mimic of JA-isoleucine, altered these flg22-induced responses. Nonexpressor of pathogenesis-related genes 1 (NPR1) acted downstream of SID2 and required SA-dependent priming for the enhanced flg22-triggered oxidative burst and callose deposition. Activation of JA signaling by COR pretreatment suppressed the flg22-triggered oxidative burst and callose accumulation in a coronatine insensitive 1 (COI1) dependent manner. COR had a negative effect on flg22 responses but only the flg22-triggered oxidative burst depended on SA-JA/COR signaling antagonism. Thus the activated SA and JA signaling pathways have an influence on flg22-triggered oxidative burst and callose deposition. These results may explain how SA and JA signaling are cross talked for regulation of flg22-triggered responses. PMID:24586453

Yi, So Young; Shirasu, Ken; Moon, Jae Sun; Lee, Seung-Goo; Kwon, Suk-Yoon

2014-01-01

84

A Chandra observation ~20 hrs before the renewed bursting activity of SGR 1627-41  

Microsoft Academic Search

Following the Swift detection of the reactivation of SGR 1627-41 (Palmer et al., GCN #7777; Woods et al., ATEL #1549; Golenetskii et al., GCN #7778), we searched for serendipitous pre-bursts X-ray observations of the region. Chandra observed the field of this SGR on 2008-05-27 UT 12:57:00 (Obs-ID 9007), ˜20 hours before the first burst detected by BAT from SGR 1627-41.

A. Tiengo; N. Rea; M. Klein-Wolt; R. Wijnands; G. L. Israel; P. Esposito; S. Zane; R. Starling; S. Mereghetti; A. De Luca; D. Gotz

2008-01-01

85

The synergistic tumoricidal activity of anticancer drugs and oxidative burst-triggered macrophages  

Microsoft Academic Search

The anticancer drugs adriamycin (ADR) and actinomycin D (AMD) were tested for their effect on the oxidative burst (OB) of mouse peritoneal macrophages (MPM) and on the killing of tumor cells by OB-stimulated MPM. The oxidative burst of MPM determined by hydrogen peroxide (H2O2) production was severely impaired by ADR (10 µg\\/ml) and AMD (40 µg\\/ml) after a 1 h

Simcha Marcovitch; Yona Keisari

1985-01-01

86

Project BudBurst  

NSDL National Science Digital Library

Project BudBurst is an interactive website that has people recording their observations of growing plants. You monitor the plants progress and record it on the website. there is a section for teachers about how to implement BudBurst in the classroom, and it includes classroom activities for grades Kindergarten to 12th grade. This section includes activities on how to observe plants, climate affect on plants, and an activity on ecosystems and biomes.

2007-01-01

87

Electricity/Electronics Systems. Laboratory Activities.  

ERIC Educational Resources Information Center

This electricity/electronics guide provides teachers with learning activities for secondary students. Introductory materials include an instructional planning outline and worksheet, an outline of essential elements, a list of objectives, a course description, and a content outline. The guide contains 35 modules on the following topics: electrical

Sutherland, Barbara, Ed.

88

Electric Utility Solar Energy Activities. 1976 Survey.  

National Technical Information Service (NTIS)

The report presents the results of a survey to determine the scope and extent of solar energy projects sponsored by electric utilities. Brief descriptions of the active operations along with information contacts are listed for each participating utility. ...

L. D. Cleary

1977-01-01

89

Flow cytometry analyses of phagocytic and respiratory burst activities and cytochemical characterization of leucocytes isolated from wrasse (Labrus bergylta A.).  

PubMed

We have isolated leucocytes from peripheral blood (PBL), head kidney (HKL) and spleen (SL) of wrasse (Labrus bergylta A.) and studied the innate immune responses phagocytosis and respiratory burst using flow cytometry. Further, we have characterized the phenotypic properties of the leucocytes by cytochemical staining. We could differentiate between several subsets of leucocytes; lymphocytes, monocytes/macrophages, neutrophils, eosinophils, basophils and small leucocytes that might be precursor or immature cells. One striking observation was the eosinophils which were present among HKL, PBL and SL. The neutrophils had rounded, bean shaped or bi-lobed nuclei and resembled neutrophils in Atlantic cod (Gadus morhua L.) and lumpsucker (Cyclopterus lumpus L.), but were different from the polymorphonucleated neutrophils in Atlantic salmon (Salmo salar L.) and humans. Basophils were observed, but they were rare. Phagocytosis and respiratory burst activities were detected among different cell types. Highest phagocytic activity was observed among monocytes/macrophages and small leucocytes. Several different subtypes had ability to perform an oxygen-dependent degradation of microbes, measured as respiratory burst activity. Knowledge of the basic properties of wrasse's leucocytes and innate immunology can benefit further studies on its adaptive immune responses. PMID:24798992

Haugland, Gyri T; Rønneseth, Anita; Wergeland, Heidrun I

2014-07-01

90

Exocytosis of neutrophil granule subsets and activation of prolyl isomerase 1 are required for respiratory burst priming.  

PubMed

This study tested the hypothesis that priming the neutrophil respiratory burst requires both granule exocytosis and activation of the prolyl isomerase Pin1. Fusion proteins containing the TAT cell permeability sequence and either the SNARE domain of syntaxin-4 or the N-terminal SNARE domain of SNAP-23 were used to examine the role of granule subsets in TNF-mediated respiratory burst priming using human neutrophils. Concentration-inhibition curves for exocytosis of individual granule subsets and for priming of fMLF-stimulated superoxide release and phagocytosis-stimulated H2O2 production were generated. Maximal inhibition of priming ranged from 72 to 88%. Linear regression lines for inhibition of priming versus inhibition of exocytosis did not differ from the line of identity for secretory vesicles and gelatinase granules, while the slopes or the y-intercepts were different from the line of identity for specific and azurophilic granules. Inhibition of Pin1 reduced priming by 56%, while exocytosis of secretory vesicles and specific granules was not affected. These findings indicate that exocytosis of secretory vesicles and gelatinase granules and activation of Pin1 are independent events required for TNF-mediated priming of neutrophil respiratory burst. PMID:23363774

McLeish, Kenneth R; Uriarte, Silvia M; Tandon, Shweta; Creed, Timothy M; Le, Junyi; Ward, Richard A

2013-01-01

91

Exocytosis of Neutrophil Granule Subsets and Activation of Prolyl Isomerase 1 are required for Respiratory Burst Priming  

PubMed Central

This study tested the hypothesis that priming the neutrophil respiratory burst requires both granule exocytosis and activation of the prolyl isomerase, Pin1. Fusion proteins containing the TAT cell permeability sequence and either the SNARE domain of syntaxin-4 or the N-terminal SNARE domain of SNAP-23 were used to examine the role of granule subsets in TNF-mediated respiratory burst priming using human neutrophils. Concentration-inhibition curves for exocytosis of individual granule subsets and for priming of fMLF-stimulated superoxide release and phagocytosis-stimulated H2O2 production were generated. Maximal inhibition of priming ranged from 72% to 88%. Linear regression lines for inhibition of priming versus inhibition of exocytosis did not differ from the line of identity for secretory vesicles and gelatinase granules, while the slopes or the y-intercepts were different from the line of identity for specific and azurophilic granules. Inhibition of Pin1 reduced priming by 56%, while exocytosis of secretory vesicles and specific granules was not affected. These findings indicate that exocytosis of secretory vesicles and gelatinase granules and activation of Pin1 are independent events required for TNF-mediated priming of neutrophil respiratory burst.

McLeish, Kenneth R.; Uriarte, Silvia M.; Tandon, Shweta; Creed, Timothy M.; Le, Junyi; Ward, Richard A.

2013-01-01

92

Aluminum induces oxidative burst, cell wall NADH peroxidase activity, and DNA damage in root cells of Allium cepa L.  

PubMed

Plants under stress incur an oxidative burst that involves a rapid and transient overproduction of reactive oxygen species (ROS: O(2) (•-) , H(2) O(2) , (•) OH). We hypothesized that aluminum (Al), an established soil pollutant that causes plant stress, would induce an oxidative burst through the activation of cell wall-NADH peroxidase (NADH-PX) and/or plasma membrane-associated NADPH oxidase (NADPH-OX), leading to DNA damage in the root cells of Allium cepa L. Growing roots of A. cepa were treated with Al(3+) (800 ?M of AlCl(3) ) for 3 or 6 hr without or with the pretreatment of inhibitors specific to NADH-PX and NADPH-OX for 2 hr. At the end of the treatment, the extent of ROS generation, cell death, and DNA damage were determined. The cell wall-bound protein (CWP) fractions extracted from the untreated control and the Al-treated roots under the aforementioned experimental conditions were also subjected to in vitro studies, which measured the extent of activation of peroxidase/oxidase, generation of (•) OH, and DNA damage. Overall, the present study demonstrates that the cell wall-bound NADH-PX contributes to the Al-induced oxidative burst through the generation of ROS that lead to cell death and DNA damage in the root cells of A. cepa. Furthermore, the in vitro studies revealed that the CWP fraction by itself caused DNA damage in the presence of NADH, supporting a role for NADH-PX in the stress response. Altogether, this study underscores the crucial function of the cell wall-bound NADH-PX in the oxidative burst-mediated cell death and DNA damage in plants under Al stress. PMID:22865669

Achary, V Mohan M; Parinandi, Narasimham L; Panda, Brahma B

2012-08-01

93

Respiratory burst activity of intestinal macrophages in normal and inflammatory bowel disease.  

PubMed Central

Macrophages isolated from normal mucosa (greater than 5 cm from tumour) and inflamed mucosa (from patients with inflammatory bowel disease) of colon and ileum were studied for their ability to undergo a respiratory burst as assessed by reduction of nitroblue tetrazolium to formazan. Using phorbol myristate acetate (PMA) and opsonised zymosan as triggers, only a minority (median: 8% for zymosan and 9% for PMA) of macrophages isolated from normal colonic mucosa demonstrated release of oxygen radicals. In contrast, a significantly greater (median: 17% for zymosan and 45% for PMA) proportion of macrophages isolated from inflamed colonic mucosa were able to undergo respiratory burst. Studies with normal and inflamed ileum showed similar results. Stimulation of macrophages isolated from normal colon with interferon-gamma produced only a small increase in the proportion of cells showing release of oxygen radicals. We conclude that the respiratory burst capacity of majority of macrophages isolated from normal colon and ileum is downregulated and a greater proportion of macrophages isolated from inflamed colon and ileum are able to undergo a respiratory burst. Images Fig. 2

Mahida, Y R; Wu, K C; Jewell, D P

1989-01-01

94

Yeast ?-glucan stimulates respiratory burst activity of Atlantic salmon ( Salmo salar L.) macrophages  

Microsoft Academic Search

Previous studies have shown that head kidney macrophages isolated from glucan injected rainbow trout (Oncorhychus mykiss) and Atlantic salmon (Salmo salar L.) have increased ability to kill Aeromonas salmonicida. The present work was aimed at investigating the in vitro effects of glucan on the respiratory burst and bactericidal potential of Atlantic salmon head kidney macrophages. Salmon macrophages were incubated for

Jorunn B. Jørgensen; Børre Robertsen

1995-01-01

95

Unusual Central Engine Activity in the Double Burst GRB 110709B.  

National Technical Information Service (NTIS)

The double burst, GRB 110709B, triggered Swift/BAT twice at 21:32:39 UT and 21:43:45 UT, respectively, on 9 July 2011. This is the first time we observed a GRB with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations...

A. D. Falcone B. Zhang B. B. Zhang D. Frederiks D. N. Burrows G. Stratta J. R. Cummings N. Gehrels P. Meszaros S. Golenetskii S. D. Barthelmy V. D'Elia X. Y. Wang

2011-01-01

96

FAST OPTICAL VARIABILITY OF A NAKED-EYE BURST-MANIFESTATION OF THE PERIODIC ACTIVITY OF AN INTERNAL ENGINE  

SciTech Connect

We imaged the position of the naked-eye burst, GRB080319B, before, during, and after its gamma-ray activity with sub-second temporal resolution using the TORTORA wide-field camera. The burst optical prompt emission, which reached 5.3 mag, has been detected, and its periodic optical variability has been discovered in the form of four equidistant flashes with a duration of several seconds. We also detected a strong correlation (r {approx} 0.82) between optical and gamma-ray light curves with a 2 s delay of the optical emission with respect to the gamma-ray emission. The revealed temporal structure of the optical light curve in comparison with the gamma-ray light curve can be interpreted in the framework of the model of shell collisions in the ejecta containing a significant neutron component. All observed emission features reflect the non-stationary behavior of the burst internal engine-supposedly, a hyperaccreting solar-mass black hole formed in the collapse of a massive stellar core.

Beskin, G.; Karpov, S. [Special Astrophysical Observatory, Nizhniy Arkhyz, Karachaevo-Cherkesia (Russian Federation); Bondar, S. [Institute for Precise Instrumentation, Nizhniy Arkhyz, Karachaevo-Cherkesia (Russian Federation); Greco, G. [Astronomical Observatory of Bologna, INAF (Italy); Guarnieri, A.; Bartolini, C.; Piccioni, A. [Astronomical Department of Bologna University, Bologna (Italy)

2010-08-10

97

Mimicking muscle activity with electrical stimulation  

NASA Astrophysics Data System (ADS)

Functional electrical stimulation is a rehabilitation technology that can restore some degree of motor function in individuals who have sustained a spinal cord injury or stroke. One way to identify the spatio-temporal patterns of muscle stimulation needed to elicit complex upper limb movements is to use electromyographic (EMG) activity recorded from able-bodied subjects as a template for electrical stimulation. However, this requires a transfer function to convert the recorded (or predicted) EMG signals into an appropriate pattern of electrical stimulation. Here we develop a generalized transfer function that maps EMG activity into a stimulation pattern that modulates muscle output by varying both the pulse frequency and the pulse amplitude. We show that the stimulation patterns produced by this transfer function mimic the active state measured by EMG insofar as they reproduce with good fidelity the complex patterns of joint torque and joint displacement.

Johnson, Lise A.; Fuglevand, Andrew J.

2011-02-01

98

Extracellular K+ in the supraoptic nucleus of the rat during reflex bursting activity by oxytocin neurones.  

PubMed Central

1. We have investigated changes in extracellular potassium concentration [K+]o in the supraoptic nucleus of lactating rats and in particular those that occur during the intense burst of firing by the oxytocin neurones involved in the milk ejection reflex. 2. Double-barrelled K(+)-selective microelectrodes containing a highly selective sensor based on valinomycin were lowered through the exposed cortex towards the supraoptic nucleus (SON) of female rats anaesthetized with urethane. The mean resting [K+]o in the hypothalami of five rats was 2.4 mM, S.D. = 0.3 mM. 3. Where the reference barrel recorded extracellular action potentials from an oxytocin cell, the reflex burst of firing (4 s, typical maximum 50 Hz) was accompanied by a mean increase in [K+]o (delta[K+]o) of 0.22 mM (S.E.M. = 0.02 mM, fifty-seven bursts in eight cells in seven rats). The rise in [K+]o did not begin more than 0.1 s before the onset of the burst, and began to fall from its maximum during the burst. Slow field potentials, indicative of spatial buffering of K+, were undetectable (less than 50 microV). When the electrode was advanced in steps, the amplitudes of both delta[K+]o and the action potential declined steeply to about 10% over a distance of 20 microns: K+ from oxytocin cells appears to be prevented from dispersing freely through the extracellular space of the SON. 4. When the electrode recorded action potentials from a vasopressin cell, delta[K+]o during an oxytocin cell burst was very small: 0.021 mM (S.E.M. = 0.005 mM). At other sites in the SON, where antidromic stimulation evoked a field potential but no action potential, delta[K+]o was 0.047 +/- 0.005 mM. We conclude that the reason oxytocin bursts do not affect vasopressin cells is that [K+]o rises very little around vasopressin cells. A fortiori, since the increases in [K+]o were very small except where action potentials from oxytocin cells were recorded, they can make no significant contribution to synchronizing the onsets of bursts in oxytocin cells that are not contiguous. 5. A standard antidromic stimulation from the pituitary stalk, at 40 Hz for 4 s, which stimulated both oxytocin neurones and vasopressin neurones, caused a delta[K+]o of 0.17-1.8 mM, the variation being mainly from rat to rat. The larger delta[K+]o values were accompanied by slow negative potentials of up to 1.5 mV, there was a gradient in delta[K+]o decreasing towards the pia at the inferior limit of the SON, and there was a slow increase in [K+] in the subarachnoid space.(ABSTRACT TRUNCATED AT 400 WORDS)

Coles, J A; Poulain, D A

1991-01-01

99

Respiratory burst activity of phagocytic cells isolated from the mammary glands and blood of camels (Camelus bactrianus).  

PubMed

The oxidative burst activity of phagocytic cells isolated from camel blood and mammary glands was studied using a chemiluminescence (Cl) assay. The polymorphonuclear leucocytes (PMNL) isolated from camel blood mounted a luminol-dependent Cl response upon stimulation with opsonized zymosan or opsonized Staphylococcus aureus. These responses showed an overall similarity to those described in other mammalian species. The leucocytes isolated from the mammary glands mounted Cl responses similar to those observed with blood PMNL but to a lower magnitude. Like the Cl responses of blood cells, the Cl responses induced by mammary gland leucocytes were associated with degranulation and the release of lysosomal enzymes such as myeloperoxidase (MPO). PMID:9084231

Cooray, R; Abdurahaman, O A; Bornstein, S; Holmberg, O; Aström, G

1997-03-01

100

Electrical activity enhances neuronal survival and regeneration.  

PubMed

The failure of regeneration in the central nervous system (CNS) remains an enormous scientific and clinical challenge. After injury or in degenerative diseases, neurons in the adult mammalian CNS fail to regrow their axons and reconnect with their normal targets, and furthermore the neurons frequently die and are not normally replaced. While significant progress has been made in understanding the molecular basis for this lack of regenerative ability, a second approach has gained momentum: replacing lost neurons or lost connections with artificial electrical circuits that interface with the nervous system. In the visual system, gene therapy-based 'optogenetics' prostheses represent a competing technology. Now, the two approaches are converging, as recent data suggest that electrical activity itself, via the molecular signaling pathways such activity stimulates, is sufficient to induce neuronal survival and regeneration, particularly in retinal ganglion cells. Here, we review these data, discuss the effects of electrical activity on neurons' molecular signaling pathways and propose specific mechanisms by which exogenous electrical activity may be acting to enhance survival and regeneration. PMID:19721179

Corredor, Raul G; Goldberg, Jeffrey L

2009-10-01

101

Brain Electrical Activity Changes and Cognitive Development.  

ERIC Educational Resources Information Center

This study investigated the relationship of cognitive developmental changes to physiological and anatomical changes by measuring both types of data within the same subjects. Cortical electrical activity was measured in 24 males between 10 and 12 years of age. Event-related potentials (ERPs) were recorded from midline scalp electrodes during a…

Hartley, Deborah; Thomas, David G.

102

Electrical activity and development of neural circuits  

Microsoft Academic Search

A distinct feature of the nervous system is the intricate network of synaptic connections among neurons of diverse phenotypes. Although initial connections are formed largely through molecular mechanisms that depend on intrinsic developmental programs, spontaneous and experience-driven electrical activities in the developing brain exert critical epigenetic influence on synaptic maturation and refinement of neural circuits. Selective findings discussed here illustrate

Li I. Zhang; Mu-ming Poo

2001-01-01

103

Topological entropy and the controlled effect of glucose in the electrical activity of pancreatic ?-cells  

NASA Astrophysics Data System (ADS)

Insulin secretion from electrically coupled ?-cells is governed by bursting electrical activity. In response to stimulatory concentrations of glucose, the membrane potential of pancreatic ?-cells may experience a transition from bursting-spiking oscillations to continuous spiking oscillations. This transition can be chaotic but becomes more and more regular with an increase in glucose. In the presence of chaos, the inhability to predict the behavior of dynamical systems suggests the application of chaos control methods, when we are more interested in obtaining attracting time periodic motion. In this article, we focus our attention on a specific mathematical model from the literature that mimics the glucose-induced electrical activity of pancreatic ?-cells (Deng, 1993 [7]). Firstly, using results of symbolic dynamics, we characterize the topological entropy and the parameter space ordering of the kneading sequences, associated with one-dimensional maps that reproduce significant aspects of the model dynamics. The analysis of the variation of this numerical invariant allows us to quantify and to distinguish different chaotic regimes. Finally, we show that chaotic orbits of the system can be controlled, without changing their orbital properties, and be turned into desired limit cycles. The control is illustrated by an application of a feedback control technique developed by Romeiras, Grebogi, Ott and Dayawansa (1992) [13]. This work provides an illustration of how our understanding of biophysically motivated models can be directly enhanced by the theory of dynamical systems.

Duarte, Jorge; Januário, Cristina; Martins, Nuno

2009-11-01

104

Scale-free bursting in human cortex following hypoxia at birth.  

PubMed

The human brain is fragile in the face of oxygen deprivation. Even a brief interruption of metabolic supply at birth challenges an otherwise healthy neonatal cortex, leading to a cascade of homeostatic responses. During recovery from hypoxia, cortical activity exhibits a period of highly irregular electrical fluctuations known as burst suppression. Here we show that these bursts have fractal properties, with power-law scaling of burst sizes across a remarkable 5 orders of magnitude and a scale-free relationship between burst sizes and durations. Although burst waveforms vary greatly, their average shape converges to a simple form that is asymmetric at long time scales. Using a simple computational model, we argue that this asymmetry reflects activity-dependent changes in the excitatory-inhibitory balance of cortical neurons. Bursts become more symmetric following the resumption of normal activity, with a corresponding reorganization of burst scaling relationships. These findings place burst suppression in the broad class of scale-free physical processes termed crackling noise and suggest that the resumption of healthy activity reflects a fundamental reorganization in the relationship between neuronal activity and its underlying metabolic constraints. PMID:24806681

Roberts, James A; Iyer, Kartik K; Finnigan, Simon; Vanhatalo, Sampsa; Breakspear, Michael

2014-05-01

105

Unusual Central Engine Activity in the Double Burst GRB 110709B  

NASA Technical Reports Server (NTRS)

The double burst, GRB 110709B, triggered Swift/BAT twice at 21:32:39 UT and 21:43:45 UT, respectively, on 9 July 2011. This is the first time we observed a GRB with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations of this unusual GRB and its afterglow. If the two events are from the same physical origin, their different time-dependent spectral evolution suggest they must belong to different episodes of the central engine, which may be a magnetar-to-BH accretion system.

Zhang, Bin-Bin; Burrows, David N.; Zhang, Bing; Meszaros, Peter; Stratta, Giulia; D'Elia, Valerio; Frederiks, Dmitry; Golenetskii, S.; Cummings, Jay R.; Wang, Xiang-Yu; Falcone, Abraham D.; Barthelmy, Scott D.; Gehrels, Neil

2011-01-01

106

The Type III Radio Burst Occurrence Rate as a New Solar Activity Index: Rieger-Type periodicity  

NASA Astrophysics Data System (ADS)

The type III radio burst occurrence rate (T3BOR) strongly correlates with solar activity and was recently proposed as a new index of solar activity. This index can provide complementary information and may be useful in different studies including solar cycle predictions and searches for different periodicities in solar activity. The first observations of a Rieger-type periodicity with the period of 156 days in the daily T3BOR are presented. This periodicity was detected during the time interval from 22 June 2000 to 31 December 2003. This interval partially contains maximum and the declining phase of solar cycle 23. The radio spectra were provided by the Learmonth Solar Radio Observatory in Western Australia, part of the USAF Radio Solar Telescope Network (RSTN).

Lobzin, V. V.; Cairns, I. H.

2012-12-01

107

Magnetogastrographic detection of gastric electrical response activity in humans  

Microsoft Academic Search

The detection and characterization of gastric electrical activity has important clinical applications, including the early diagnosis of gastric diseases in humans. In mammals, this phenomenon has two important features: an electrical control activity (ECA) that manifests itself as an electric slow wave (with a frequency of 3 cycles per minute in humans) and an electrical response activity (ERA) that is

Andrei Irimia; William O Richards; L Alan Bradshaw

2006-01-01

108

Long-Range Temporal Correlations in the EEG Bursts of Human Preterm Babies  

PubMed Central

The electrical activity in the very early human preterm brain, as recorded by scalp EEG, is mostly discontinuous and has bursts of high-frequency oscillatory activity nested within slow-wave depolarisations of high amplitude. The temporal organisation of the occurrence of these EEG bursts has not been previously investigated. We analysed the distribution of the EEG bursts in 11 very preterm (23–30 weeks gestational age) human babies through two estimates of the Hurst exponent. We found long-range temporal correlations (LRTCs) in the occurrence of these EEG bursts demonstrating that even in the very immature human brain, when the cerebral cortical structure is far from fully developed, there is non-trivial temporal structuring of electrical activity.

Hartley, Caroline; Berthouze, Luc; Mathieson, Sean R.; Boylan, Geraldine B.; Rennie, Janet M.; Marlow, Neil; Farmer, Simon F.

2012-01-01

109

Long-range temporal correlations in the EEG bursts of human preterm babies.  

PubMed

The electrical activity in the very early human preterm brain, as recorded by scalp EEG, is mostly discontinuous and has bursts of high-frequency oscillatory activity nested within slow-wave depolarisations of high amplitude. The temporal organisation of the occurrence of these EEG bursts has not been previously investigated. We analysed the distribution of the EEG bursts in 11 very preterm (23-30 weeks gestational age) human babies through two estimates of the Hurst exponent. We found long-range temporal correlations (LRTCs) in the occurrence of these EEG bursts demonstrating that even in the very immature human brain, when the cerebral cortical structure is far from fully developed, there is non-trivial temporal structuring of electrical activity. PMID:22363669

Hartley, Caroline; Berthouze, Luc; Mathieson, Sean R; Boylan, Geraldine B; Rennie, Janet M; Marlow, Neil; Farmer, Simon F

2012-01-01

110

The influence of single bursts versus single spikes at excitatory dendrodendritic synapses.  

PubMed

The synchronization of neuronal activity is thought to enhance information processing. There is much evidence supporting rhythmically bursting external tufted cells (ETCs) of the rodent olfactory bulb glomeruli coordinating the activation of glomerular interneurons and mitral cells via dendrodendritic excitation. However, as bursting has variable significance at axodendritic cortical synapses, it is not clear if ETC bursting imparts a specific functional advantage over the preliminary spike in dendrodendritic synaptic networks. To answer this question, we investigated the influence of single ETC bursts and spikes with the in vitro rat olfactory bulb preparation at different levels of processing, via calcium imaging of presynaptic ETC dendrites, dual electrical recording of ETC -interneuron synaptic pairs, and multicellular calcium imaging of ETC-induced population activity. Our findings supported single ETC bursts, versus single spikes, driving robust presynaptic calcium signaling, which in turn was associated with profound extension of the initial monosynaptic spike-driven dendrodendritic excitatory postsynaptic potential. This extension could be driven by either the spike-dependent or spike-independent components of the burst. At the population level, burst-induced excitation was more widespread and reliable compared with single spikes. This further supports the ETC network, in part due to a functional advantage of bursting at excitatory dendrodendritic synapses, coordinating synchronous activity at behaviorally relevant frequencies related to odor processing in vivo. PMID:22277089

Masurkar, Arjun V; Chen, Wei R

2012-02-01

111

The atmospheric electric global circuit. [thunderstorm activity  

NASA Technical Reports Server (NTRS)

The hypothesis that world thunderstorm activity represents the generator for the atmospheric electric current flow in the earth atmosphere between ground and the ionosphere is based on a close correlation between the magnitude and the diurnal variation of the supply current (thunderstorm generator current) and the load current (fair weather air-earth current density integrated over the earth surface). The advantages of using lightning survey satellites to furnish a base for accepting or rejecting the thunderstorm generator hypothesis are discussed.

Kasemir, H. W.

1979-01-01

112

Electricity  

NSDL National Science Digital Library

5th Grade Electricity Try this Using Electricity Activity. Don't forget to follow the directions! Use this to learn more about electricity: Blobz Guide to Electricity Follow the directions closely! Learn more about Electricity with Electricity Tech-Topics. ...

Lerdahl, Miss

2010-02-23

113

Inhibitory effect of macabarterin, a polyoxygenated ellagitannin from Macaranga barteri, on human neutrophil respiratory burst activity.  

PubMed

An ellagitannin with a 2,4-acyl group, named macabarterin (1), and a new ellagic acid glycoside, 3-O-methylellagic acid 4-O-?-d-xylopyranoside (2), were isolated from the stem bark extract of Macaranga barteri along with five known phenolic compounds, ellagic acid (3), 3-O-methylellagic acid (4), gallic acid (5), methyl gallate (6), and scopoletin (7). The structures of 1 and 2, as well as those of the known compounds, were elucidated on the basis of spectroscopic data and by comparison with reported data. Compounds 1-5 and 7 were tested for their anti-inflammatory potential in a cell-based respiratory burst assay, compound 1 being found an inhibitor of the superoxides produced in the cellular system. PMID:19006373

Ngoumfo, Rostand Manfouo; Ngounou, Georges Eric; Tchamadeu, Chimene Victoire; Qadir, Muhammad Irfan; Mbazoa, Celine Djama; Begum, Afshan; Ngninzeko, Fernande Ngounou; Lontsi, David; Choudhary, Muhammad Iqbal

2008-11-01

114

The Stored Energy of Gravitational Collapse Powers Gamma Ray Bursts, Active Galactic Nuclei and Jets  

NASA Astrophysics Data System (ADS)

The recent discovery of almost 100% polarization of the prompt gamma ray emission from GRB021206 (1) confirms my ````Strong'' Magnetic Field'' model (SMF). In SMF, Storage Ring (SR) particles were accelerated during the gravitational collapse of the pregalactic/prequasar plasma that is permeated by a large-scale primordial magnetic field (2.3). The enormous, intense, slender, relativistic, stable, coherent Astrophysical Storage Ring stores a small fraction of the gravitational collapse energy in an almost radiationless state, unless disturbed. Galactic morphology varies as the ratio of magnetic energy to rotational energy in each object. GRB are due to a ``rock'' i.e. white dwarf,ordinary star,neutron star,planet,etc. falling through the SR and being rapidly vaporized into a hot plasma fireball. The fireball speeds on into the huge organized magnetic field surrounding the current ring, thus generating very highly polarized prompt gamma ray emission from the synchrotron radiation process. The timing fits the GRB observations. A ``rock'' racing at 1000 km/sec across a 20,000 km path in the beam produces a twenty second burst. Tracking across a short chord yields a short burst. Typical currents in space are sometimes made of many slender filaments. Thus the puzzling less than one millisecond spikes observed in some GRB are simply describing the structure of that particular SR at that time. 1. W. Coburn & S. E. Boggs, Nature 423, 425 (2003) 2. H. D. Greyber in After the Dark Ages:When Galaxies Were Young, AIP Conf. Proc. 470, eds. S. Holt & E. Smith, (1998) 3. H. D. Greyber in a Space Telescope Science Institute Report from their 2001 Spring Symposium, ``The Dark Universe: Matter, Energy and Gravity'', ed. Mario Livio, published March 2003.

Greyber, Howard

2004-05-01

115

Phosphatidylinositol 4,5-bisphosphate regulates inspiratory burst activity in the neonatal mouse preB?tzinger complex  

PubMed Central

Neurons of the preBötzinger complex (preBötC) form local excitatory networks and synchronously discharge bursts of action potentials during the inspiratory phase of respiratory network activity. Synaptic input periodically evokes a Ca2+-activated non-specific cation current (ICAN) postsynaptically to generate 10–30 mV transient depolarizations, dubbed inspiratory drive potentials, which underlie inspiratory bursts. The molecular identity of ICAN and its regulation by intracellular signalling mechanisms during inspiratory drive potential generation remains unknown. Here we show that mRNAs coding for two members of the transient receptor potential (TRP) family of ion channels, namely TRPM4 and TRPM5, are expressed within the preBötC region of neonatal mice. Hypothesizing that the phosphoinositides maintaining TRPM4 and TRPM5 channel sensitivity to Ca2+ may similarly influence ICAN and thus regulate inspiratory drive potentials, we manipulated intracellular phosphatidylinositol 4,5-bisphosphate (PIP2) and measured its effect on preBötC neurons in the context of ongoing respiratory-related rhythms in slice preparations. Consistent with the involvement of TRPM4 and TRPM5, excess PIP2 augmented the inspiratory drive potential and diminution of PIP2 reduced it; sensitivity to flufenamic acid (FFA) suggested that these effects of PIP2 were ICAN mediated. Inositol 1,4,5-trisphosphate (IP3), the product of PIP2 hydrolysis, ordinarily causes IP3 receptor-mediated ICAN activation. Simultaneously increasing PIP2 while blocking IP3 receptors intracellularly counteracted the reduction in the inspiratory drive potential that normally resulted from IP3 receptor blockade. We propose that PIP2 protects ICAN from rundown by interacting directly with underlying ion channels and preventing desensitization, which may enhance the robustness of respiratory rhythm.

Crowder, Erin A; Saha, Margaret S; Pace, Ryland W; Zhang, Honglu; Prestwich, Glenn D; Del Negro, Christopher A

2007-01-01

116

Participation of a persistent sodium current and calcium-activated nonspecific cationic current to burst generation in trigeminal principal sensory neurons.  

PubMed

The properties of neurons participating in masticatory rhythmogenesis are not clearly understood. Neurons within the dorsal trigeminal principal sensory nucleus (dPrV) are potential candidates as components of the masticatory central pattern generator (CPG). The present study examines in detail the ionic mechanisms controlling burst generation in dPrV neurons in rat (postnatal day 8-12) brain stem slices using whole cell and perforated patch-clamp methods. Nominal extracellular Ca(2+) concentration transformed tonic discharge in response to a maintained step pulse of current into rhythmical bursting in 38% of nonbursting neurons. This change in discharge mode was suppressed by riluzole, a persistent Na(+) current (INaP) antagonist. Veratridine, which suppresses the Na(+) channel inactivation mechanism, induced rhythmical bursting in nonbursting neurons in normal artificial cerebrospinal fluid, suggesting that INaP contributes to burst generation. Nominal extracellular Ca(2+) exposed a prominent afterdepolarizing potential (ADP) following a single spike induced by a 3-ms current pulse, which was suppressed, but not completely blocked, by riluzole. Application of BAPTA, a Ca(2+) chelator, intracellularly, or flufenamic acid, a Ca(2+)-activated nonspecific cationic channel (ICAN) antagonist, extracellularly to the bath, suppressed rhythmical bursting and the postspike ADP. Application of drugs to alter Ca(2+) release from endoplasmic reticulum also suppressed bursting. Finally, voltage-clamp methods demonstrated that nominal Ca(2+) facilitated INaP and induced ICAN. These data demonstrate for the first time that the previously observed induction in dPrV neurons of rhythmical bursting in nominal Ca(2+) is mediated by enhancement of INaP and onset of ICAN, which are dependent on intracellular Ca(2+). PMID:23883859

Tsuruyama, Kentaro; Hsiao, Chie-Fang; Chandler, Scott H

2013-10-01

117

Calcium responses to synaptically activated bursts of action potentials and their synapse-independent replay in cultured networks of hippocampal neurons.  

PubMed

Both synaptic N-methyl-d-aspartate (NMDA) receptors and voltage-operated calcium channels (VOCCs) have been shown to be critical for nuclear calcium signals associated with transcriptional responses to bursts of synaptic input. However the direct contribution to nuclear calcium signals from calcium influx through NMDA receptors and VOCCs has been obscured by their concurrent roles in action potential generation and synaptic transmission. Here we compare calcium responses to synaptically induced bursts of action potentials with identical bursts devoid of any synaptic contribution generated using the pre-recorded burst as the voltage clamp command input to replay the burst in the presence of blockers of action potentials or ionotropic glutamate receptors. Synapse independent replays of bursts produced nuclear calcium responses with amplitudes around 70% of their original synaptically generated signals and were abolished by the L-type VOCC blocker, verapamil. These results identify a major direct source of nuclear calcium from local L-type VOCCs whose activation is boosted by NMDA receptor dependent depolarization. The residual component of synaptically induced nuclear calcium signals which was both VOCC independent and NMDA receptor dependent showed delayed kinetics consistent with a more distal source such as synaptic NMDA receptors or internal stores. The dual requirement of NMDA receptors and L-type VOCCs for synaptic activity-induced nuclear calcium dependent transcriptional responses most likely reflects a direct somatic calcium influx from VOCCs whose activation is amplified by synaptic NMDA receptor-mediated depolarization and whose calcium signal is boosted by a delayed input from distal calcium sources mostly likely entry through NMDA receptors and release from internal stores. This article is part of a Special Issue entitled: 12th European Symposium on Calcium. PMID:23360982

Bengtson, C Peter; Kaiser, Martin; Obermayer, Joshua; Bading, Hilmar

2013-07-01

118

Detection of bursting activity with INTEGRAL/SPI-ACS, possibly from 1E 2259+586 or SGR 1806-20  

NASA Astrophysics Data System (ADS)

We report on a possible detection of bursting activity (tentatively from the magnetars 1E 2259+586 or SGR 1806-20) with the SPI Anti-Coincidence System (ACS) on-board INTEGRAL. From 2012-04-19T12:03:10 to 2012-04-21 06:28:49 UTC, the ACS detected 25 short (from 50ms to 8s) bursts at a significance level of 5-10 sigma (peak count-rate of 1×104 - 1×105 counts/s on 50 ms time bin).

Savchenko, V.; Mereghetti, S.; Ferrigno, C.; Bozzo, E.; Courvoisier, T. J.-L.; Goetz, D.; Borkowski, J.; Kienlin, A. von; Rau, A.; Zhang, X.; Beckmann, V.

2012-05-01

119

Burst kinetics and redox transformations of the active site manganese ion in oxalate oxidase: implications for the catalytic mechanism.  

PubMed

Oxalate oxidase (EC 1.2.3.4) catalyzes the oxidative cleavage of oxalate to carbon dioxide and hydrogen peroxide. In this study, unusual nonstoichiometric burst kinetics of the steady state reaction were observed and analyzed in detail, revealing that a reversible inactivation process occurs during turnover, associated with a slow isomerization of the substrate complex. We have investigated the underlying molecular mechanism of this kinetic behavior by preparing recombinant barley oxalate oxidase in three distinct oxidation states (Mn(II), Mn(III), and Mn(IV)) and producing a nonglycosylated variant for detailed biochemical and spectroscopic characterization. Surprisingly, the fully reduced Mn(II) form, which represents the majority of the as-isolated native enzyme, lacks oxalate oxidase activity, but the activity is restored by oxidation of the metal center to either Mn(III) or Mn(IV) forms. All three oxidation states appear to interconvert under turnover conditions, and the steady state activity of the enzyme is determined by a balance between activation and inactivation processes. In O(2)-saturated buffer, a turnover-based redox modification of the enzyme forms a novel superoxidized mononuclear Mn(IV) biological complex. An oxalate activation role for the catalytic metal ion is proposed based on these results. PMID:17210574

Whittaker, Mei M; Pan, Heng-Yen; Yukl, Erik T; Whittaker, James W

2007-03-01

120

DEFENSE EVOLUTION IN THE GRACILARIACEAE (RHODOPHYTA): SUBSTRATE-REGULATED OXIDATION OF AGAR OLIGOSACCHARIDES IS MORE ANCIENT THAN THE OLIGOAGAR-ACTIVATED OXIDATIVE BURST  

Microsoft Academic Search

Combined phylogenetic, physiological, and biochemical approaches revealed that differences in defense-related responses among 17 species belonging to the Gracilariaceae were consistent with their evolutionary history. An oxidative burst response resulting from activation of NADPH oxidase was always observed in two of the subgenera of Gracilaria sensu lato (Gracilaria, Hydropuntia), but not in Gracilariopsis and in species related to Gracilaria chilensis

Florian Weinberger; Marie-Laure Guillemin; Christophe Destombe; Myriam Valero; Sylvain Faugeron; Juan A. Correa; Georg Pohnert; Constanze Pehlke; Bernard Kloareg; Philippe Potin

2010-01-01

121

Cytoplasts Made from Human Blood Polymorphonuclear Leukocytes with or without Heat: Preservation of Both Motile Function and Respiratory Burst Oxidase Activity  

Microsoft Academic Search

Anucleate fragments (cytoplasts) from polymorphonuclear leukocytes (PMN) are simplified systems that can be used to elucidate specific pathways by which cell function is altered. PMN cytoplasts in current use are defective either in activatable respiratory burst oxidase activity or in motile function. By centrifugation of PMN on discontinuous gradients of Ficoll without cytochalasin B, we have created granule-poor cytoplasts in

Stephen E. Malawista; Gretchen van Blaricom

1987-01-01

122

Antibody dependent oxidative burst and phagocytosis of Plasmodium falciparum merozoites by activated neutrophils: a functional antibody assay for malaria vaccine candidates  

Microsoft Academic Search

To prioritize merozoite surface protein (MSP) malar ia vaccine candidates for clinical testing, functional assays are needed to evaluate natural an d vaccination-induced antibody responses. A new functional antibody assay is described based on antibody dependent oxidative bursts and phagocytosis of merozoites (ADPm) by activated polymorphonuclear neutrophils (PMN), detected by chemiluminescence monitored with luminol. In meso and holoendemic areas, ADPm

Charlotte Joos; Laurence Marrama; Hannah E. J. Polson; Sandra Corre; Antoine-Marie Diatta; Babacar Mbengue; Babacar Diouf; Jean-François Trape; Adama Tall; Shirley Longacre; Ronald Perraut

123

Burst activity and ultrafast activation kinetics of CaV1.3 Ca2+ channels support presynaptic activity in adult gerbil hair cell ribbon synapses  

PubMed Central

Auditory information transfer to afferent neurons relies on precise triggering of neurotransmitter release at the inner hair cell (IHC) ribbon synapses by Ca2+ entry through CaV1.3 Ca2+ channels. Despite the crucial role of CaV1.3 Ca2+ channels in governing synaptic vesicle fusion, their elementary properties in adult mammals remain unknown. Using near-physiological recording conditions we investigated Ca2+ channel activity in adult gerbil IHCs. We found that Ca2+ channels are partially active at the IHC resting membrane potential (?60 mV). At ?20 mV, the large majority (>70%) of Ca2+ channel first openings occurred with an estimated delay of about 50 ?s in physiological conditions, with a mean open time of 0.5 ms. Similar to other ribbon synapses, Ca2+ channels in IHCs showed a low mean open probability (0.21 at ?20 mV), but this increased significantly (up to 0.91) when Ca2+ channel activity switched to a bursting modality. We propose that IHC Ca2+ channels are sufficiently rapid to transmit fast signals of sound onset and support phase-locking. Short-latency Ca2+ channel opening coupled to multivesicular release would ensure precise and reliable signal transmission at the IHC ribbon synapse.

Zampini, Valeria; Johnson, Stuart L; Franz, Christoph; Knipper, Marlies; Holley, Matthew C; Magistretti, Jacopo; Masetto, Sergio; Marcotti, Walter

2013-01-01

124

Quantitative panoramic imaging of epicardial electrical activity.  

PubMed

Fluorescent imaging with voltage- and/or calcium-sensitive dyes has revolutionized cardiac physiology research. Here we present improved panoramic imaging for optically mapping electrical activity from the entire epicardium of the Langendorff-perfused rabbit heart. Combined with reconstruction of the 3D heart surface, the functional data can be conveniently visualized on the realistic heart geometry. Methods to quantify the panoramic data set are introduced by first describing a simple approach to mesh the heart in regular grid form. The regular grid mesh provides substrate for easy translation of previously available non-linear dynamics methods for 2D array data. It also simplifies the unwrapping of curved three-dimensional surface to 2D surface for global epicardial visualization of the functional data. The translated quantification methods include activation maps (isochrones), phase maps, phase singularity, and electric stimulus-induced virtual electrode polarization (VEP) maps. We also adapt a method to calculate the conduction velocities on the global epicardial surface by taking the curvature of the heart surface into account. PMID:18654852

Lou, Qing; Ripplinger, Crystal M; Bayly, Philip V; Efimov, Igor R

2008-10-01

125

Role of Electrical Activity in Promoting Neural Repair  

PubMed Central

The nervous system communicates in a language of electrical activities. The motivation to replace function lost through injury or disease through electrical prostheses has gained traction through steady advances in basic and translational science addressing the interface between electrical prostheses and the nervous system. Recent experiments suggest that electrical activity, signaling through specific molecular pathways, promotes neuronal survival and regeneration. Such data suggests that electrical prostheses, in addition to replacing lost function, may slow underlying degenerative disease or induce regenerative response. Here we review these data with a focus on retinal neurons, and discuss current efforts to translate this effect of electrical activity into clinically applicable treatments.

Goldberg, Jeffrey L.

2012-01-01

126

Computer program for intestinal spike bursts recognition.  

PubMed

A FORTRAN program has been developed for locating intestinal spike bursts and for estimating their strength. Tested against human scanning, the reliability rate was 92% and the misrecognition rate was 2.5%. This program was applied to the automatisation of the Migrating Myoelectric Complex analysis. A first method computed the percentage of Basic Electrical Rhythm (BER) cycles with superimposed spike bursts. A second one was based on the evaluation of spike bursts strength. PMID:573450

Pousse, A; Mendel, C; Kachelhoffer, J; Grenier, J F

1979-07-01

127

Pumping of high-pressure CO2 laser media via a fast-burst reactor and electrical sustainer  

Microsoft Academic Search

The Sandia Pulse Reactor (SPR II) is used to preionize an atmospheric CO2 laser medium with an applied electrical sustainer field. The small-signal gain and sustainer currents were measured for several mixtures and pressures. Small-signal gain coefficients approaching 0.04 cm?1 were measured at approximately atmospheric pressures.

D. A. McArthur; G. H. Miller; P. B. Tollefsrud

1973-01-01

128

Electrical activation of ion mass doped phosphorous.  

PubMed

In this study, three different crystalline states of silicon were prepared to be doped with phosphorous by IMD, amorphous, poly crystalline and single crystalline silicon. The dose was controlled by IMD duration time and heat treatment for electrical activation was done in RTA and Furnace. In case of RTA, annealing temperature was controlled by the duration time of power application. In case of a single crystal substrate, the resistance was measured to be 20-50 omega/square depending on the dose and annealing temperature. In case of poly crystal, we could observe segregation of the dopant at grain boundaries, which caused increase of the resistance with increase of annealing temperature. In case of amorphous silicon thin film, this phenomenon could not be observed due to lack of the grain boundaries and the minimum resistance of this work was about 300 omega/square, which was about the same to that in a poly silicon thin film. PMID:24245195

Lee, Yong-Woo; Yun, Seung-Jae; Son, Se Wan; Byun, Chang-Woo; Joo, Seung-Ki

2013-10-01

129

Electrical signatures of martian dust activity  

NASA Astrophysics Data System (ADS)

Several past observations of Mars in the microwave have displayed anomalous radio emissions. In particular, the 1.35 cm VLA observations of the Tharsis and Amazonis regions of Mars (the Stealth region) on February 19, 1995 (1) indicated largest discrepancy between model and the derived radio brightness temperature during the time of local noon to 4 p.m., the period in which dust devils are most frequent and strongest (2, 3). The 2 and 6 cm VLA observations in November 1983 (4) exhibited an anomalous microwave emission that was concentrated mainly in a region of the south hemisphere bounded by the Hellas and Argyre Plantia, well known regions of large dust activity. And, the 2.8 cm observations with the 46 m Algonquin Radio Observatory in December 1975 and January 1978 (5, 6, 7) showed a strong variation in the martian radio brightness temperature between the two periods and a large temporal variation during the 1978 campaign. Preliminary indications are that the observed anomalies in the radio brightness temperatures may be related to the 1978 dust storm on Mars. Because the abovementioned anomalous radio emissions have strong correlation with martian dust activity, we suggest that these anomalies are in fact electromagnetic radiation produced by martian dust devils and dust storms. Triboelectric charging of saltating and colliding dust particles produce strong electrical fields in terrestrial dust devils and dust storms. Discharges resulting from the breakdown of these electrical fields generate wideband electromagnetic radiation that can be detected by nearby radio receivers. Similar phenomena are expected to be even more important on Mars, because martian dust devils and dust storms are much larger and stronger than terrestrial, and electrical discharges occur at much lower potential in the thin martian atmosphere. References: (1) Ivanov et al., Icarus 133, 163, 1998; (2) Sinclair, J. Atmos. Sci. 30, 1599, 1973; (3) Renno et al., J. Atmos. Sci. 55, 3244, 1998; (4) Rudy et al., Icarus 71, 159, 1987; (5) Andrew et al., ApJ 213, L131, 1977; (6) Andrew et al., ApJ 220, L61, 1978; (7) Doherty et al., ApJ 233, L165, 1979.

Wong, A. S.; Renno, N. O.; Atreya, S. K.

2003-04-01

130

Spiking-bursting activity in the thalamic reticular nucleus initiates sequences of spindle oscillations in thalamic networks.  

PubMed

Recent intracellular and local field potential recordings from thalamic reticular (RE) neurons in vivo as well as computational modeling of the isolated RE nucleus suggest that, at relatively hyperpolarized levels of membrane potentials, the inhibitory postsynaptic potentials (IPSPs) between RE cells can be reversed and gamma-aminobutyric acid-A (GABA(A)) -mediated depolarization can generate persistent spatio-temporal patterns in the RE nucleus. Here we investigate how this activity affects the spatio-temporal properties of spindle oscillations with computer models of interacting RE and thalamocortical (TC) cells. In a one-dimensional network of RE and TC cells, sequences of spindle oscillations alternated with localized patterns of spike-burst activity propagating inside the RE network. New sequences of spindle oscillations were initiated after removal of I(h)-mediated depolarization of the TC cells. The length of the interspindle lulls depended on the intrinsic and synaptic properties of RE and TC cells and was in the range of 3-20 s. In a two-dimensional model, GABA(A)-mediated 2-3 Hz oscillations persisted in the RE nucleus during interspindle lulls and initiated spindle sequences at many foci within the RE-TC network simultaneously. This model predicts that the intrinsic properties of the reticular thalamus may contribute to the synchrony of spindle oscillations observed in vivo. PMID:10938329

Bazhenov, M; Timofeev, I; Steriade, M; Sejnowski, T

2000-08-01

131

Antioxidant activity of bisabolol: inhibitory effects on chemiluminescence of human neutrophil bursts and cell-free systems.  

PubMed

Human polymorphonuclear neutrophils (PMN), reactive oxygen species (ROS) and inflammatory reactions are closely interrelated, and increasing attention is being given to the search for new synthetic or natural antioxidant agents, capable of reducing ROS and consequent inflammation. It has been claimed that bisabolol (a monocyclic sesquiterpene alcohol) has an antioxidant/anti-inflammatory activity, but this has almost exclusively been investigated using chemical or biochemical tests. We studied the ability of bisabolol to interfere with ROS production (luminol-amplified chemiluminescence, LACL) during human PMN respiratory bursts induced by both corpusculate(Candida albicans)and soluble stimulants (N-formyl-methionyl-leucyl-phenylalanine, fMLP). LACL was also used to test cell-free systems (SIN-1 and H2O2/HOCl(-) systems) in order to investigate the presence of scavenging activity. After C. albicans stimulation, significant concentration-dependent LACL inhibition was observed at bisabolol concentrations ranging from 7.7 to 31 microg/ml; after the fMLP stimulus, significant LACL inhibition was observed at bisabolol concentrations ranging from 3.8 to 31 microg/ml. A similar effect was observed in the SIN-1 and H2O2/HOCl(-) systems. These findings draw the attention to the possible medical use of bisabolol as a means of improving the antioxidant network and restoring the redox balance by antagonising oxidative stress. PMID:19096233

Braga, Pier Carlo; Dal Sasso, Monica; Fonti, Elena; Culici, Maria

2009-01-01

132

Electrical and mechanical activity of the longitudinal muscle of the anterior mesenteric artery of the domestic fowl  

PubMed Central

1. The electrical activity and changes in tension of the longitudinal muscle of the anterior mesenteric artery (LMAMA) of the domestic fowl were recorded simultaneously using the sucrose-gap method. 2. Spontaneous activity consisted of recurring contractions each accompanied by a burst of action potentials. 3. In quiescent preparations, brief electrical stimuli, acetylcholine, or barium chloride produced contractions with the appearance of action potentials. Larger concentrations of barium chloride or acetylcholine produced depolarization and action potentials ceased although contraction was maintained. Whenever depolarization without action potentials occurred, it was associated with a smooth contraction, whereas action potentials were always accompanied by small rapid contractions super-imposed upon the main contraction. 4. When the tone was raised with barium chloride (and in the presence of hyoscine) continuous action potentials occurred; under these circumstances brief electrical stimuli or noradrenaline produced relaxation, cessation of action potentials, and hyperpolarization.

Bolton, T. B.

1968-01-01

133

Magnetism and Electricity Activity "Attracts" Student Interest  

ERIC Educational Resources Information Center

Electricity and magnetism are intimately linked, this relationship forming the basis of the modern electric utility system and the generation of bulk electrical energy. There is rich literature from which to teach students the basics, but nothing drives the point home like having them learn from firsthand experience--and that is what this…

Roman, Harry T.

2010-01-01

134

Integrated electric alternators/active filters  

NASA Astrophysics Data System (ADS)

In response to energy crisis and power quality concerns, three different methodologies to integrate the concept of active filtering into the alternators are proposed. Wind energy, due to its free availability and its clean and renewable character, ranks as the most promising renewable energy resource that could play a key role in solving the worldwide energy crisis. An Integrated Doubly-fed Electric Alternator/Active filter (IDEA) for wind energy conversion systems is proposed. The proposed IDEA is capable of simultaneously capturing maximum power of wind energy and improving power quality, which are achieved by canceling the most significant and troublesome harmonics of the utility grid and power factor correction and reactive power compensation in the grid. The back-to-back current regulated power converters are employed to excite the rotor of IDEA. The control strategy of rotor-side power converter is based on position sensorless field oriented control method with higher power density. Analysis and experimental results are presented to demonstrate the effectiveness of the proposed IDEA. In the next step, an integrated synchronous machine/active filter is discussed. The proposed technology is essentially a rotating synchronous machine with suitable modification to its field excitation circuit to allow dc and ac excitations. It is shown that by controlling the ac excitation, the 5 th and 7th harmonics currents of the utility are compensated. The proposed method is cost effective because it can be applied to existing standby generators in commercial and industrial plants with minimal modification to the excitation circuits. To boost the gain of harmonic compensatory, an advanced electric machine is proposed. An Asymmetric Airgap Concentrated Winding Synchronous Machine (AACWSM) with ac and dc excitation was designed and employed. It is shown that the AACWSM with its unique design, in addition to power generation capability, could be used to compensate the most dominant current harmonics of the utility. The proposed AACWSM can compensate for the 5th and 7th harmonics currents in the grid by controlling the ac field excitation. In addition, the 11th and 13th harmonics currents are also significantly reduced. This system can be used at medium and low voltages for generation or motoring mode of operation.

Towliat Abolhassani, Mehdi

135

Active seat isolation for hybrid electric vehicles  

NASA Astrophysics Data System (ADS)

A feasibility study in the use of induced strain actuators for active seal isolation is described. The focus of the work is the isolation of lightweight automotive seats for hybrid-electric vehicles. The feasibility study is based on a numerical analysis of a three-degree-of-freedom vibration model of the seat. Mass and inertia properties are based on measurements from a powered seat that is found in current model year automobiles. Tradeoffs between vertical acceleration of the seat, actuator stroke requirements, and isolation frequency are determined through numerical analysis of the vibration model. Root mean square accelerations and actuator strokes are computed using power spectral densities that model broadband excitation and road excitation that is filtered by the vehicle suspension. Numerical results using the road excitation indicate that factors of two to three reduction in vertical acceleration are achieved when the active isolation frequency is reduced to approximately 1 Hz with damping factors on the order of 10 to 30 percent critical. More significant reductions are achieved in the case of broadband floor excitation. Root mean square actuator strokes for both case are int he range of 0.4 to 50 mm. Root mean square accelerations in the vertical direction are consistent with the levels found in standard comfort curves.

Leo, Donald J.; Malowicki, Mark; Buckley, Stephen J.; Naganathan, Nagi G.

1999-07-01

136

Using the active collimator and shield assembly of an EXIST-type mission as a gamma-ray burst spectrometer  

NASA Astrophysics Data System (ADS)

The Energetic X-Ray Imaging Survey Telescope (EXIST) is a mission design concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to register hard X-rays in the energy region from 10 keV to 600 keV. A partially active or fully active anti-coincidence shield/collimator with a total area of between 15 m2 and 35 m2 will be used to define the field-of-view of the CZT detectors and to suppress the background of cosmic-ray-induced events. In this paper, we describe the use of a sodium activated cesium iodide shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT 4 to simulate the interactions of photons and cosmic rays with the spacecraft and the instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield/collimator achieves a ? F_?-sensitivity of 3 × 10-9 erg cm-2 s-1 and 2 × 10-8 erg cm-2 s-1 at 100 keV and 600 keV, respectively. The sensitivity is well matched to that of the coded mask telescope.The broad energy coverage of an EXIST-type mission with active shields will constrain the peak of the spectral energy distribution (SED) for a large number of GRBs. The measurement of the SED peak may be key for determining photometric GRB redshifts and for using GRBs as cosmological probes.

Garson, A., III; Krawczynski, H.; Grindlay, J.; Fishman, G. J.; Wilson, C. A.

2006-09-01

137

Intracellular Free Calcium Regulates the Onset of the Respiratory Burst of Human Neutrophils Activated by Phorbol Myristate Acetate  

Microsoft Academic Search

Thapsigargin was used to study the regulation of different static calcium level ([Ca2+]i) on the respiratory burst of human neutrophils stimulated with phorbol myristate acetate (PMA). The result showed that the onset time of the respiratory burst was obviously reduced by elevation of static [Ca2+]i but is still much longer than that stimulated with N-formylmethionylleucylphenylalanine (fMLP). To find the reason,

Tian-Hui Hu; Ling Bei; Zhong-Ming Qian; Xun Shen

1999-01-01

138

In vitro effect of the reproductive hormones on the oxidative burst activity of polymorphonuclear leucocytes from cows: a flow cytometric study.  

PubMed

In this study, the effect of reproductive hormones and substances with hormonal activity on the oxidative burst activity of blood polymorphonuclear leucocytes (PMN) high yielding dairy cows was evaluated. Different concentrations of: progesterone, oestradiol 17?, FSH, LH, GnRH, cortisol and PGF2? were incubated in vitro for 4 h with PMN of seven high milk yielding cows, during the period of anoestrous postpartum. Controls were run in parallel in which each hormone was replaced by its solvent. After incubation with hormones the competence of PMN to generate H(2) O(2) was monitored by flow cytometry. A down-regulation on the oxidative burst activity of PMA-stimulated PMN was observed when cells were incubated with progesterone. Significant (p ? 0.001) differences between control and progesterone incubated cells were observed from 6.56 ?g/ml. The same predisposition was observed when PMNs were incubated with cortisol. Besides for all concentrations employed, a decrease in the burst activity was observed, only beyond 0.19 mg/ml, statistical differences between the results obtained by the control and the cortisol incubated cells were obtained. Concerning oestradiol 17?, an increase on H(2) O(2) -production was observed when PMN were incubated with 15 pg/ml and 45 pg/ml of this steroid (p ? 0.05), followed by a depression of the cell's activity when unphysiological concentrations were employed. Significant (p ? 0.05) differences between the obtained with the control and oestradiol 17? incubated cells were observed only in the highest concentration of oestradiol. No statistical differences were observed in the metabolic burst activity of PMN incubated with FSH, GnRH and LH when compared with the results obtained by the control. PMID:19788527

Chaveiro, A; Moreira da Silva, F

2010-10-01

139

BURSTCALC (A BURST CALCulator).  

National Technical Information Service (NTIS)

BURSTCALC is an arithmetic calculator which accepts inputs in Burst format and produces their sum, difference, product and quotient in Burst format, too. It uses simple counting techniques on the incoming Bursts in order to compute the desired arithmetic ...

E. Bracha

1975-01-01

140

Elevation of rainbow trout Oncorhynchus mykiss macrophage respiratory burst activity with macrophage-derived supernatants  

Microsoft Academic Search

A variety of supernatants were prepared by stimulating rainbow trout Oncorhynchus mykiss head kid- ney macrophages with lipopolysaccharide (LPS), tumor necrosis factor a (TNF-ct), or a leucocyte-derived macro- phage-activating factor (1-MAF), individually and in com- bination. If generated using a 12-h stimulation period,

Seon I. Jang; Laura J. Hardie; Christopher J. Secombes

141

Membrane association of Rac is required for high activity of the respiratory burst oxidase.  

PubMed

NADPH-dependent superoxide generation can be reconstituted in a cell-free system using recombinant cytosolic factors (p47-phox, p67-phox, and Rac) plus flavocytochrome b558. Rac1 and Rac2 are closely related small GTPases, differing primarily in the C-terminal 10 residues where Rac1 but not Rac2 contains a polybasic sequence. In their nonisoprenylated forms, Rac1 was highly effective in reconstituting NADPH oxidase activity (low EC50, high Vmax), whereas Rac2 was only minimally effective (high EC50, low Vmax). In contrast, low concentrations of isoprenylated Rac1 and Rac2 both supported high rates of superoxide generation. Like full length Rac2, truncated forms of both Rac1 and Rac2 in which the C-terminal 10 residues were eliminated were poorly activating, pointing to the C terminus of Rac1 as a determinant of activity. Mutation of single positively charged residues in the C terminus of nonisoprenylated Rac1 markedly reduced its ability to support superoxide generation, affecting both its EC50 and the Vmax. In contrast, mutation or truncation of the C terminus failed to affect the activation of PAK, a Rac-regulated protein kinase. The EC50 for Rac1 increased with increasing salt concentrations, whereas that of Rac2 was independent of salt, implicating the involvement of electrostatic forces for the former. Using flavocytochrome b558 reconstituted into phosphatidylcholine vesicles, the EC50 for Rac1 but not Rac2 decreased (increased binding) when an acidic phospholipid (phosphatidylinositol) was present, supporting a role for the Rac1 polybasic C terminus in binding to the membrane. A model in which Rac must associate simultaneously both with p67-phox and with the membrane to activate the NADPH oxidase can account for the above observations. PMID:8961931

Kreck, M L; Freeman, J L; Abo, A; Lambeth, J D

1996-12-10

142

Platelet-Derived Growth Factor Stimulates Phagocytosis and Blocks Agonist-Induced Activation of the Neutrophil Oxidative Burst: A Possible Cellular Mechanism to Protect against Oxygen Radical Damage  

Microsoft Academic Search

The effect of platelet-derived growth factor (PDGF) on agonist-induced activation of the superoxide-generating oxidative burst in human neutrophils was tested. PDGF had no effect on the resting level of superoxide generation but inhibited both the rate and the extent of fMet-Leu-Phe-stimulated superoxide production in a dose-dependent manner. The concentration required to inhibit the response by 50% was 95 ± 26

Emily Wilson; Scott M. Laster; Linda R. Gooding; J. David Lambeth

1987-01-01

143

[Alpha-bursts and K-complex: phasic activation pattern during spontaneous recovery of correct psychomotor performance at difference stages of drowsiness].  

PubMed

It is known that phasic activation processes reveal themselves by different electrophysiological patterns depending on the sleep depth. Alpha bursts are an electrophysiological manifestation of arousal at the initial stage of sleep, whereas at the II stage K-complex becomes the main arousal pattern. We have shown earlier that during light drowsiness spontaneous recovery of correct psychomotor test performance (after an error) by a sitting subject is accompanied by EEG alpha bursts. The aim of this work was to study the EEG phasic activation pattern at deeper drowsiness during test performance by a subject in a lying position. Subjects had to press sensitive button in a lying position with closed eyes with self-paced oral counting of pressings. The experiment lasted for 40 min; EEG, EOG, and button pressing were recorded. It was shown that recovery of correct performance after errors at deeper drowsiness was accompanied by two types of EEG phasic activation patterns (PAP-1 and PAP-2). The alpha frequency component was always present in both PAP-1 and PAP-2. PAP-1 were observed at early stages of drowsiness and consisted of high-amplitude alpha bursts and EEG activity of higher frequency. PAP-2 were recorded at deeper stages and consisted of K-complexes with superposition of PAP-1. At first (medium level of drowsiness) the alpha bursts were superposed on the late slow K-complex components. With further deepening of drowsiness the early fast components of K-complex were also observed. The early appearance of K-complex during test performance at drowsiness seems to be associated with the urgent run of brain arousal systems, which at spontaneous falling asleep are in operation at the II sleep stage. PMID:14598558

Dorokhov, V B

2003-01-01

144

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

Microsoft Academic Search

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is sensitive to neutrons with energies above 10MeV; importantly, it is insensitive to gamma radiation <10MeV and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of 141Pr, an element that has a single, naturally occurring isotope,

Tim Meehan; E. C. Hagen; C. L. Ruiz; G. W. Cooper

2010-01-01

145

Praseodymium activation detector for measuring bursts of 14MeV neutrons  

Microsoft Academic Search

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of praesodymium, an element that has a single, naturally

B. T. Meehan; E. C. Hagen; C. L. Ruiz; G. W. Cooper

2009-01-01

146

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

Microsoft Academic Search

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation <10 MeV and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of 141Pr, an element that has a single, naturally

Tim Meehan; E. C. Hagen; C. L. Ruiz; G. W. Cooper

2010-01-01

147

A brain-machine interface for control of burst suppression in medical coma.  

PubMed

Burst suppression is an electroencephalogram (EEG) marker of profound brain inactivation and unconsciousness and consists of bursts of electrical activity alternating with periods of isoelectricity called suppression. Burst suppression is the EEG pattern targeted in medical coma, a drug-induced brain state used to help recovery after brain injuries and to treat epilepsy that is refractory to conventional drug therapies. The state of coma is maintained manually by administering an intravenous infusion of an anesthetic, such as propofol, to target a pattern of burst suppression on the EEG. The coma often needs to be maintained for several hours or days, and hence an automated system would offer significant benefit for tight control. Here we present a brain-machine interface (BMI) for automatic control of burst suppression in medical coma that selects the real-time drug infusion rate based on EEG observations and can precisely control the burst suppression level in real time in rodents. We quantify the burst suppression level using the burst suppression probability (BSP), the brain's instantaneous probability of being in the suppressed state, and represent the effect of the anesthetic propofol on the BSP using a two-dimensional linear compartment model that we fit in experiments. We compute the BSP in real time from the EEG segmented into a binary time-series by deriving a two-dimensional state-space algorithm. We then derive a stochastic controller using both a linear-quadratic-regulator strategy and a model predictive control strategy. The BMI can promptly change the level of burst suppression without overshoot or undershoot and maintains precise control of time-varying target levels of burst suppression in individual rodents in real time. PMID:24110002

Shanechi, Maryam M; Chemali, Jessica J; Liberman, Max; Solt, Ken; Brown, Emery N

2013-01-01

148

Ambroxol inhibits neutrophil respiratory burst activated by alpha chain integrin adhesion.  

PubMed

The purpose of the present study was to investigate the possible anti-oxidant effect(s) of Ambroxol on neutrophils activated by ligand-binding of the drug with membrane-associated adhesion integrin CD11a and to estimate dose-response changes in oxygen free radical production. The amount of free radical production by anti-CD11a- and anti-CD4-coated neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP) and challenged with increasing concentration of Ambroxol, was evaluated within a time frame of 90 minutes. A significant dose-dependent effect response of Ambroxol on O2? production by cells coated with anti-CD11a antibody was observed. This preliminary study opens a new perspective on the therapeutic role of Ambroxol as an antioxidant drug and for its potential use in controlling oxidative stress, particularly in leukocyte-dependent inflammation. PMID:24355223

Peroni, D G; Moser, S; Gallo, G; Pigozzi, R; Tenero, L; Zanoni, L; Boner, A L; Piacentini, G L

2013-01-01

149

Transcriptional burst frequency and burst size are equally modulated across the human genome  

PubMed Central

Gene expression occurs either as an episodic process, characterized by pulsatile bursts, or as a constitutive process, characterized by a Poisson-like accumulation of gene products. It is not clear which mode of gene expression (constitutive versus bursty) predominates across a genome or how transcriptional dynamics are influenced by genomic position and promoter sequence. Here, we use time-lapse fluorescence microscopy to analyze 8,000 individual human genomic loci and find that at virtually all loci, episodic bursting—as opposed to constitutive expression—is the predominant mode of expression. Quantitative analysis of the expression dynamics at these 8,000 loci indicates that both the frequency and size of the transcriptional bursts varies equally across the human genome, independent of promoter sequence. Strikingly, weaker expression loci modulate burst frequency to increase activity, whereas stronger expression loci modulate burst size to increase activity. Transcriptional activators such as trichostatin A (TSA) and tumor necrosis factor ? (TNF) only modulate burst size and frequency along a constrained trend line governed by the promoter. In summary, transcriptional bursting dominates across the human genome, both burst frequency and burst size vary by chromosomal location, and transcriptional activators alter burst frequency and burst size, depending on the expression level of the locus.

Dar, Roy D.; Razooky, Brandon S.; Singh, Abhyudai; Trimeloni, Thomas V.; McCollum, James M.; Cox, Chris D.; Simpson, Michael L.; Weinberger, Leor S.

2012-01-01

150

Status of State Electric Industry Restructuring Activity  

NSDL National Science Digital Library

Click on a state to view the current status of electric industry restructuring. Each report includes regulatory orders, legislation, investigative studies, and links to state regulatory commissions, major utilities, and tables on restructuring issues.

151

OPTICAL SPECTRAL PROPERTIES OF SWIFT BURST ALERT TELESCOPE HARD X-RAY-SELECTED ACTIVE GALACTIC NUCLEI SOURCES  

SciTech Connect

The Swift Burst Alert Telescope survey of active galactic nuclei (AGNs) is providing an unprecedented view of local AGNs ((z) {approx} 0.03) and their host galaxy properties. In this paper, we present an analysis of the optical spectra of a sample of 64 AGNs from the nine month survey, detected solely based on their 14-195 keV flux. Our analysis includes both archived spectra from the Sloan Digital Sky Survey and our own observations from the 2.1 m Kitt Peak National Observatory telescope. Among our results, we include line ratio classifications utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities, and Hbeta-derived black hole masses. As in our X-ray study, we find the type 2 sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities) with lower accretion rates than the type 1 sources. We find that the optically classified low-ionization narrow emission line regions, H II/composite galaxies, and ambiguous sources have the lowest luminosities, while both broad-line and narrow-line Seyferts have similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O III] luminosities, we find that both the observed and extinction-corrected [O III] luminosities are weakly correlated with X-ray luminosity. In a study of the host galaxy properties from both continuum fits and measurements of the stellar absorption indices, we find that the hosts of the narrow-line sources have properties consistent with late-type galaxies.

Winter, Lisa M.; Keeney, Brian [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO (United States); Lewis, Karen T. [Department of Physics and Astronomy, Dickinson College, Carlisle, PA (United States); Koss, Michael; Veilleux, Sylvain; Mushotzky, Richard F. [Department of Astronomy, University of Maryland, College Park, MD (United States)

2010-02-10

152

THE 60 MONTH ALL-SKY BURST ALERT TELESCOPE SURVEY OF ACTIVE GALACTIC NUCLEUS AND THE ANISOTROPY OF NEARBY AGNs  

SciTech Connect

Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of {approx}2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent {approx}5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to {approx}10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9{sup +4.1}{sub -2.9} Multiplication-Sign 10{sup -5} Mpc{sup -3} for objects with a de-absorbed luminosity larger than 2 Multiplication-Sign 10{sup 42} erg s{sup -1}. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local ({<=}85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions.

Ajello, M.; Madejski, G. M. [Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Alexander, D. M. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Greiner, J.; Burlon, D. [Max-Planck-Institut fuer Extraterrestrische Physik, P.O. Box 1312, 85741, Garching (Germany); Gehrels, N. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-04-10

153

The 60 Month All-sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of nearby AGNs  

NASA Astrophysics Data System (ADS)

Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of ~2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent ~5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to ~10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9+4.1 - 2.9 × 10-5 Mpc-3 for objects with a de-absorbed luminosity larger than 2 × 1042 erg s-1. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local (<=85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions.

Ajello, M.; Alexander, D. M.; Greiner, J.; Madejski, G. M.; Gehrels, N.; Burlon, D.

2012-04-01

154

Glucose-induced electrical activities and insulin secretion in pancreatic islet ?-cells are modulated by CFTR.  

PubMed

The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in ?-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca(2+) oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse ?-cells or RINm5F ?-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 ?-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in ?-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy. PMID:25025956

Guo, Jing Hui; Chen, Hui; Ruan, Ye Chun; Zhang, Xue Lian; Zhang, Xiao Hu; Fok, Kin Lam; Tsang, Lai Ling; Yu, Mei Kuen; Huang, Wen Qing; Sun, Xiao; Chung, Yiu Wa; Jiang, Xiaohua; Sohma, Yoshiro; Chan, Hsiao Chang

2014-01-01

155

Glucose-induced electrical activities and insulin secretion in pancreatic islet ?-cells are modulated by CFTR  

PubMed Central

The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in ?-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca2+ oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse ?-cells or RINm5F ?-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 ?-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in ?-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy.

Guo, Jing Hui; Chen, Hui; Ruan, Ye Chun; Zhang, Xue Lian; Zhang, Xiao Hu; Fok, Kin Lam; Tsang, Lai Ling; Yu, Mei Kuen; Huang, Wen Qing; Sun, Xiao; Chung, Yiu Wa; Jiang, Xiaohua; Sohma, Yoshiro; Chan, Hsiao Chang

2014-01-01

156

The AtrbohD-Mediated Oxidative Burst Elicited by Oligogalacturonides in Arabidopsis Is Dispensable for the Activation of Defense Responses Effective against Botrytis cinerea1[W][OA  

PubMed Central

Oligogalacturonides (OGs) are endogenous elicitors of defense responses released after partial degradation of pectin in the plant cell wall. We have previously shown that, in Arabidopsis (Arabidopsis thaliana), OGs induce the expression of PHYTOALEXIN DEFICIENT3 (PAD3) and increase resistance to the necrotrophic fungal pathogen Botrytis cinerea independently of signaling pathways mediated by jasmonate, salicylic acid, and ethylene. Here, we illustrate that the rapid induction of the expression of a variety of genes by OGs is also independent of salicylic acid, ethylene, and jasmonate. OGs elicit a robust extracellular oxidative burst that is generated by the NADPH oxidase AtrbohD. This burst is not required for the expression of OG-responsive genes or for OG-induced resistance to B. cinerea, whereas callose accumulation requires a functional AtrbohD. OG-induced resistance to B. cinerea is also unaffected in powdery mildew resistant4, despite the fact that callose accumulation was almost abolished in this mutant. These results indicate that the OG-induced oxidative burst is not required for the activation of defense responses effective against B. cinerea, leaving open the question of the role of reactive oxygen species in elicitor-mediated defense.

Galletti, Roberta; Denoux, Carine; Gambetta, Stefano; Dewdney, Julia; Ausubel, Frederick M.; De Lorenzo, Giulia; Ferrari, Simone

2008-01-01

157

Neutrophil Respiratory Burst Activation.  

National Technical Information Service (NTIS)

The studies on the two forms of chronic granulomatous disease (CGD) have revealed that at least two factors are involved in the action of the NADPH:O2 oxido-reductase. One is a cytochrome b558 and the other a 47-kDa phosphoprotein. In the thesis the quest...

I. M. Kramer

1988-01-01

158

Desynchronization of electrically evoked auditory-nerve activity by high-frequency pulse trains of long durationa)  

PubMed Central

Rubinstein et al. [Hear. Res. 127, 108–118 (1999)] suggested that the neural representation of the waveforms of electric stimuli might be improved by introducing an ongoing, high-rate, desynchronizing pulse train (DPT). A DPT may desynchronize neural responses to electric stimulation in a manner similar to spontaneous activity in a healthy ear. To test this hypothesis, responses of auditory-nerve fibers (ANFs) to 10-min-long electric pulse trains (5 kpps) were recorded from acutely deafened, anesthetized cats. Stimuli were delivered via an intracochlear electrode, and their amplitude was chosen to elicit a response in most ANFs. Responses to pulse trains showed pronounced adaptation during the first 1–2 min, followed by either a sustained response or cessation of spike discharges for the remainder of the stimulus. The adapted discharge rates showed a broad distribution across the ANF population like spontaneous activity. However, a higher proportion of fibers (46%) responded to the DPT at rates below 5 spikes/s than for spontaneous activity, and 12% of the fibers responded at higher rates than any spontaneously active fiber. Interspike interval histograms of sustained responses for some fibers had Poisson-like (exponential) shapes, resembling spontaneous activity, while others exhibited preferred intervals and, occasionally, bursting. Simultaneous recordings from pairs of fibers revealed no evidence of correlated activity, suggesting that the DPT does desynchronize the auditory nerve activity. Overall, these results suggest that responses to an ongoing DPT resemble spontaneous activity in a normal ear for a substantial fraction of the ANFs.

Litvak, Leonid M.; Smith, Zachary M.; Delgutte, Bertrand; Eddington, Donald K.

2008-01-01

159

Desynchronization of electrically evoked auditory-nerve activity by high-frequency pulse trains of long duration  

NASA Astrophysics Data System (ADS)

Rubinstein et al. [Hear. Res. 127, 108-118 (1999)] suggested that the neural representation of the waveforms of electric stimuli might be improved by introducing an ongoing, high-rate, desynchronizing pulse train (DPT). A DPT may desynchronize neural responses to electric stimulation in a manner similar to spontaneous activity in a healthy ear. To test this hypothesis, responses of auditory-nerve fibers (ANFs) to 10-min-long electric pulse trains (5 kpps) were recorded from acutely deafened, anesthetized cats. Stimuli were delivered via an intracochlear electrode, and their amplitude was chosen to elicit a response in most ANFs. Responses to pulse trains showed pronounced adaptation during the first 1-2 min, followed by either a sustained response or cessation of spike discharges for the remainder of the stimulus. The adapted discharge rates showed a broad distribution across the ANF population like spontaneous activity. However, a higher proportion of fibers (46%) responded to the DPT at rates below 5 spikes/s than for spontaneous activity, and 12% of the fibers responded at higher rates than any spontaneously active fiber. Interspike interval histograms of sustained responses for some fibers had Poisson-like (exponential) shapes, resembling spontaneous activity, while others exhibited preferred intervals and, occasionally, bursting. Simultaneous recordings from pairs of fibers revealed no evidence of correlated activity, suggesting that the DPT does desynchronize the auditory nerve activity. Overall, these results suggest that responses to an ongoing DPT resemble spontaneous activity in a normal ear for a substantial fraction of the ANFs.

Litvak, Leonid M.; Smith, Zachary M.; Delgutte, Bertrand; Eddington, Donald K.

2003-10-01

160

Electric Utility Solar Energy Activities, 1978 Survey.  

National Technical Information Service (NTIS)

The results of a survey to determine the scope of solar energy projects sponsored by electric utilities in the United States are presented. Brief descriptions of 600 projects being conducted by 165 utility companies are given. Also included are a list of ...

W. L. York

1979-01-01

161

Structure and electrical activity of planar defects in EFG ribbons  

NASA Technical Reports Server (NTRS)

Optical, electron beam induced current (EBIC), and transmission electron microscopy were used to study the structure and electrical activity of planar defects in EFG silicon. What appears to be twin boundaries by both optical microscopy plus etching, and by EBIC are in reality systems of microtwins, some of which are only a few atomic lattice planes thick. The electrical activity of planar defects appears to be correlated with emission of dislocations especially at termination points. Impurity effects may also play a role. Twin boundaries per se appear not to be electrically active.

Ast, D. G.

1979-01-01

162

Biomagnetic Techniques for Assessing Gastric and Small Bowel Electrical Activity  

NASA Astrophysics Data System (ADS)

Recent advances in electrophysiology of the gastrointestinal tract have emphasized the need for methods of noninvasive assessment of gastric and small intestinal electrical activity (GEA and IEA). While the cutaneous electrogastrogram (EGG) may reveal the frequency dynamics of gastric electrical activity, other parameters important for characterizing the propagating electrical activity are not available from EGG recordings. Recent studies on the electroenterogram (EENG) are promising, but low-conductivity abdominal layers have complicated the identification of small intestinal electrical rhythms in cutaneous recordings. The magnetogastrogram (MGG) and magnetoenterogram (MENG) are able to characterize gastric and intestinal electrical activity noninvasively in terms of its frequency, power and characteristics of its propagation. Superconducting QUantum Interference Device (SQUID) magnetometers are used to detect the minute magnetic fields associated with electrical activity of the gastrointestinal syncytium formed by interstitial cells of Cajal and smooth muscle networks. Changes in GEA and IEA that occur in response to disease or abnormal conditions are reflected in MGG and MENG signals. Magnetic methods for assessing the electrical activity of the stomach and small bowel thus show great clinical promise.

Bradshaw, L. Alan

2004-09-01

163

An electrically active microneedle array for electroporation  

PubMed Central

We have designed and fabricated a microneedle array with electrical functionality with the final goal of electroporating skin’s epidermal cells to increase their transfection by DNA vaccines. The microneedle array was made of polymethylmethacrylate (PMMA) by micromolding technology from a master PDMS mold, followed by metal deposition, patterning using laser ablation, and electrodeposition. This microneedle array possessed sufficient mechanical strength to penetrate human skin in vivo and was also able to electroporate both red blood cells and human prostate cancer cells as an in vitro model to demonstrate cell membrane permeabilization. A model to predict the effective volume for electroporation with respect to applied voltages was constructed from finite element simulation. This study demonstrates the mechanical and electrical functionalities of the first MEMS-fabricated microneedle array for electroporation, designed for DNA vaccine delivery.

Choi, Seong-O; Kim, Yeu Chun; Park, Jung-Hwan; Hutcheson, Joshua; Gill, Harvinder S.; Yoon, Yong-Kyu; Prausnitz, Mark R.; Allen, Mark G.

2010-01-01

164

An electrically active microneedle array for electroporation.  

PubMed

We have designed and fabricated a microneedle array with electrical functionality with the final goal of electroporating skin's epidermal cells to increase their transfection by DNA vaccines. The microneedle array was made of polymethylmethacrylate (PMMA) by micromolding technology from a polydimethylsiloxane (PDMS) mold, followed by metal deposition, patterning using laser ablation, and electrodeposition. This microneedle array possessed sufficient mechanical strength to penetrate human skin in vivo and was also able to electroporate both red blood cells and human prostate cancer cells as an in vitro model to demonstrate cell membrane permeabilization. A computational model to predict the effective volume for electroporation with respect to applied voltages was constructed from finite element simulation. This study demonstrates the mechanical and electrical functionalities of the first MEMS-fabricated microneedle array for electroporation, designed for DNA vaccine delivery. PMID:20012696

Choi, Seong-O; Kim, Yeu Chun; Park, Jung-Hwan; Hutcheson, Joshua; Gill, Harvinder S; Yoon, Yong-Kyu; Prausnitz, Mark R; Allen, Mark G

2010-04-01

165

Demonstrating Electrical Activity in Nerve and Muscle. Part I  

ERIC Educational Resources Information Center

Describes a demonstration for showing the electrical activity in nerve and muscle including action potentials, refractory period of a nerve, and fatigue. Presents instructions for constructing an amplifier, electronic stimulator, and force transducer. (GS)

Robinson, D. J.

1975-01-01

166

Electrical Activation Studies of Ion Implanted Gallium Nitride.  

National Technical Information Service (NTIS)

A comprehensive and systematic electrical activation study of Si- implanted GaN was performed as a function of ion implantation dose, anneal temperature, and implantation temperature. Additionally, Mg-implanted GaN was also investigated. Temperature-depen...

J. A. Fellows

2001-01-01

167

Demonstrating Electrical Activity in Nerve and Muscle. Part II  

ERIC Educational Resources Information Center

Describes the construction of an amplifier and force transducer that can be used to demonstrate electrical activity in nerve and muscle using the gastrocnemius muscle and sciatic nerve of the frog. (MLH)

Robinson, D. J.

1976-01-01

168

Electrical activity modulates growth cone guidance by diffusible factors.  

PubMed

Brief periods of electrical stimulation of cultured Xenopus spinal neurons resulted in a marked alteration in the turning responses of the growth cone induced by gradients of attractive or repulsive guidance cues. Netrin-1-induced attraction was enhanced, and the repulsion induced by myelin-associated glycoprotein (MAG) or myelin membrane fragments was converted to attraction. The effect required the presence of extracellular Ca(2+) during electrical stimulation and appeared to be mediated by an elevation of both cytoplasmic Ca(2+) and cAMP. Thus, electrical activity may influence the axonal path finding of developing neurons, and intermittent electrical stimulation may be effective in promoting nerve regeneration after injury. PMID:11239434

Ming, G; Henley, J; Tessier-Lavigne, M; Song, H; Poo, M

2001-02-01

169

Mid-infrared Properties of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. Emission-line Diagnostics  

Microsoft Academic Search

We compare mid-infrared emission-line properties from high-resolution Spitzer spectra of a hard X-ray (14-195 keV) selected sample of nearby (z < 0.05) active galactic nuclei (AGNs) detected by the Burst Alert Telescope (BAT) aboard Swift. The luminosity distribution for the mid-infrared emission lines, [O IV] 25.89 mum, [Ne II] 12.81 mum, [Ne III] 15.56 mum, and [Ne V] 14.32\\/24.32 mum,

K. A. Weaver; M. Meléndez; R. F. Mushotzky; S. Kraemer; K. Engle; E. Malumuth; J. Tueller; C. Markwardt; C. T. Berghea; R. P. Dudik; L. M. Winter; L. Armus

2010-01-01

170

A? adenosine receptor modulation of chemically and electrically evoked lumbar locomotor network activity in isolated newborn rat spinal cords.  

PubMed

It is not well-studied how the ubiquitous neuromodulator adenosine (ADO) affects mammalian locomotor network activities. We analyzed this here with focus on roles of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX)-sensitive A(1)-type ADO receptors. For this, we recorded field potentials from ventral lumbar nerve roots and electrically stimulated dorsal roots in isolated newborn rat spinal cords. At ? 25?M, bath-applied ADO slowed synchronous bursting upon blockade of anion-channel-mediated synaptic inhibition by bicuculline (20 ?M) plus strychnine (1 ?M) and this depression was countered by DPCPX (1 ?M) as tested at 100 ?M ADO. ADO abolished this disinhibited rhythm at ? 500 ?M. Contrary, the single electrical pulse-evoked dorsal root reflex, which was enhanced in bicuculline/strychnine-containing solution, persisted at all ADO doses (5 ?M-2 mM). In control solution, ? 500 ?M ADO depressed this reflex and pulse train-evoked bouts of alternating fictive locomotion; this inhibition was reversed by 1 ?M DPCPX. ADO (5 ?M-2 mM) did not depress, but stabilize alternating fictive locomotion evoked by serotonin (10 ?M) plus N-methyl-d-aspartate (4-5 ?M). Addition of DPCPX (1?M) to control solution did not change either the dorsal root reflex or rhythmic activities indicating lack of endogenous A(1) receptor activity. Our findings show A(1) receptor involvement in ADO depression of the dorsal root reflex, electrically evoked fictive locomotion and spontaneous disinhibited lumbar motor bursting. Contrary, chemically evoked fictive locomotion and the enhanced dorsal root reflex in disinhibited lumbar locomotor networks are resistant to ADO. Because ADO effects in standard solution occurred at doses that are notably higher than those occurring in vivo, we hypothesize that newborn rat locomotor networks are rather insensitive to this neuromodulator. PMID:22824428

Taccola, G; Olivieri, D; D'Angelo, G; Blackburn, P; Secchia, L; Ballanyi, K

2012-10-11

171

In vitro electrical activity in canine colon  

Microsoft Academic Search

In vitro slow wave activity was studied in strips of right and left canine colon with silver\\/silver chloride electrodes. Using visual and computer analysis, slow wave frequency and coupling was assessed between different recording sites and the effect of a cholinergic agonist on coupling and frequency was determined. A regular slow wave was always found to be present. Frequency in

N L Shearin; K L Bowes; Y J Kingma

1979-01-01

172

Smoke Extracts and Nicotine, but not Tobacco Extracts, Potentiate Firing and Burst Activity of Ventral Tegmental Area Dopaminergic Neurons in Mice  

PubMed Central

Nicotine prominently mediates the behavioral effects of tobacco consumption, either through smoking or when taking tobacco by snuff or chew. However, many studies question the exclusive role of nicotine in these effects. The use of preparations containing all the components of tobacco, such as tobacco and smoke extracts, may be more suitable than nicotine alone to investigate the behavioral effects of smoking and tobacco intake. In the present study, the electrophysiological effects of tobacco and smoke on ventral tegmental area dopaminergic (DA) neurons were examined in vivo in anesthetized wild-type (WT), ?2-nicotinic acetylcholine receptor (nAChR) knockout (?2?/?), ?4?/?, and ?6?/? mice and compared with those of nicotine alone. In WT mice, smoke and nicotine had similar potentiating effects on DA cell activity, but the action of tobacco on neuronal firing was weak and often inhibitory. In particular, nicotine triggered strong bursting activity, whereas no bursting activity was observed after tobacco extract (ToE) administration. In ?2?/? mice, nicotine or extract elicited no modification of the firing patterns of DA cells, indicating that extract acts predominantly through nAChRs. The differences between DA cell activation profiles induced by tobacco and nicotine alone observed in WT persisted in ?6?/? mice but not in ?4?/? mice. These results would suggest that tobacco has lower addiction-generating properties compared with either nicotine alone or smoke. The weak activation and prominent inhibition obtained with ToEs suggest that tobacco contains compounds that counteract some of the activating effects of nicotine and promote inhibition on DA cell acting through ?4?2*-nAChRs. The nature of these compounds remains to be elucidated. It nevertheless confirms that nicotine is the main substance involved in the tobacco addiction-related activation of mesolimbic DA neurons.

Marti, Fabio; Arib, Ouafa; Morel, Carole; Dufresne, Virginie; Maskos, Uwe; Corringer, Pierre-Jean; de Beaurepaire, Renaud; Faure, Philippe

2011-01-01

173

Electrostatic charging of electrically active spacecraft  

NASA Technical Reports Server (NTRS)

A model is presented which predicts the temporal behavior of the ionospheric charging of spacecraft which eject energetic positive ions. The dynamic interaction of the spacecraft with the space-plasma environment is modelled as an equivalent electrical circuit consisting of a variable capacitor in parallel with two current sources. The spacecraft/space-plasma sheath is modelled as a variable capacitor containing positive-ion space charge. The ejection of energetic positive ions from the spacecraft represents a current source which charges the capacitor. Return current collected from the space-plasma sheath to the spacecraft is modelled as a variable current source which discharges the capacitor. The model can predict the temporal behavior of sheath movement, spacecraft potential, and space-plasma return current for a wide range of altitude, duty cycle, and ejected positive-ion current. Experimentally measured charging results, obtained for the Satellite Positive Ion Beam System (SPIBS) rocket flight, are accurately predicted by the model. Anticipated vehicle charging levels are presented for neutral-particle-beam platforms operating with a net, unneutralized, positive-ion-current component present in the emitted neutral-particle beam.

Matossian, J. N.; Beattie, J. R.

1986-01-01

174

Electrostatic charging of electrically active spacecraft  

NASA Astrophysics Data System (ADS)

A model is presented which predicts the temporal behavior of the ionospheric charging of spacecraft which eject energetic positive ions. The dynamic interaction of the spacecraft with the space-plasma environment is modelled as an equivalent electrical circuit consisting of a variable capacitor in parallel with two current sources. The spacecraft/space-plasma sheath is modelled as a variable capacitor containing positive-ion space charge. The ejection of energetic positive ions from the spacecraft represents a current source which charges the capacitor. Return current collected from the space-plasma sheath to the spacecraft is modelled as a variable current source which discharges the capacitor. The model can predict the temporal behavior of sheath movement, spacecraft potential, and space-plasma return current for a wide range of altitude, duty cycle, and ejected positive-ion current. Experimentally measured charging results, obtained for the Satellite Positive Ion Beam System (SPIBS) rocket flight, are accurately predicted by the model. Anticipated vehicle charging levels are presented for neutral-particle-beam platforms operating with a net, unneutralized, positive-ion-current component present in the emitted neutral-particle beam.

Matossian, J. N.; Beattie, J. R.

1986-10-01

175

The effect of beta-glucan administration on macrophage respiratory burst activity and Atlantic salmon, Salmo salar L., challenged with amoebic gill disease--evidence of inherent resistance.  

PubMed

Previous studies have demonstrated that beta-glucans stimulate Atlantic salmon, Salmo salar L., head kidney macrophages both in vitro and in vivo and increase protection against various pathogens. Based on our previous work that showed potent immunostimulatory CpG motif-containing oligodeoxynucleotides increased resistance to amoebic gill disease (AGD), the present study investigated the immunostimulatory effects of three commercial beta-glucan-containing feeds and their ability to increase resistance to AGD. All three commercial beta-glucans were able to stimulate the respiratory burst activity of Atlantic salmon head kidney macrophages in vitro, albeit at different times and concentrations. However, dietary incorporation of the beta-glucans was unable to stimulate the in vivo respiratory burst activity of head kidney macrophages, or serum lysozyme production, and did not increase resistance against AGD. However, this trial showed for the first time that a small subpopulation of Atlantic salmon subjected to a severe AGD infection was able to resist becoming heavily infected and furthermore survive the challenge. PMID:15960658

Bridle, A R; Carter, C G; Morrison, R N; Nowak, B F

2005-06-01

176

Intracellular shunting of O2? contributes to charge compensation and preservation of neutrophil respiratory burst in the absence of voltage-gated proton channel activity  

PubMed Central

Proton efflux via voltage-gated proton channels (Hv1) is considered to mediate the charge compensation necessary to preserve NADPH oxidase activity during the respiratory burst. Using the Hv1 inhibitor Zn2+, we found that the PMA-induced respiratory burst of human neutrophils is inhibited when assessed as extracellular production of O2? and H2O2, in accordance with literature studies, but, surprisingly, unaffected when measured as oxygen consumption or total (extracellular plus intracellular) H2O2 production. Furthermore, we show that inhibiting Hv1 with Zn2+ results in an increased production of intracellular ROS. Similar results, i.e. decreased extracellular and increased intracellular ROS production, were obtained using a human granulocyte-like cell line with severely impaired Hv1 expression. Acidic extracellular pH, which dampens proton efflux, also augmented intracellular production of H2O2. Zinc caused an increase in the rate but not in the extent of depolarization and cytosolic acidification indicating that mechanisms other than proton efflux take part in charge compensation. Our results suggest a hitherto unpredicted mechanism of charge compensation whereby, in the absence of proton efflux, part of O2? generated within gp91phox in the plasma membrane is shunted intracellularly down electrochemical gradient to dampen excessive depolarization. This would preserve NADPH oxidase activity under conditions such as the inflammatory exudate in which the acidic pH hinders charge compensation by proton efflux.

Decleva, Eva; Menegazzi, Renzo; Fasolo, Alba; Defendi, Federica; Sebastianutto, Michele; Dri, Pietro

2013-01-01

177

ACTIVE CONTROL STICK DRIVEN BY A PIEZO ELECTRIC MOTOR  

Microsoft Academic Search

An Active Control Stick (ACS) realized by a travelling wave type ultrasonic motor (USM) is presented. In contrast to the conventional side stick in modern aircrafts, which is only operated by a passive mechanic feedback, forces can be reproduced artificially by an active con- trol stick. Ultrasonic motors are more compact as conventional electrical geared motors and combine features such

T. Schulte; H. Grotstollen; H.-P. Schöner; J.-T. Audren

1999-01-01

178

Mathematical Approach for Modeling the Uterine Electrical Activity  

NASA Astrophysics Data System (ADS)

The aim of physiological modeling of the uterine electrical activity generated at cellular level is to understand the main physiological uterine contractile mechanisms, in particular, the propagation mechanisms and their relationship with the uterine EMG signal recorded externally from the abdominal wall of the pregnant women. In this present paper, we model the electrical activity simulated at its cellular level. This model is built in three steps: first we built a model based on the formulation of Hodgkin and Huxley and adapted to the specificities of the uterine cell. The second step was the integration of the cellular model in a two-dimensional propagation model by using the reactiondiffusion equations in order to simulate the propagation of the uterine activity at the tissue level. Finally, a simplified version of the space-time integration of the electrical activity was used to build a first example of the uterine EMG.

Chkeir, Aly; Moslem, Bassam; Rihana, Sandy; Germain, Guy; Marque, Catherine

179

Control of bursting synchronization in networks of Hodgkin-Huxley-type neurons with chemical synapses  

NASA Astrophysics Data System (ADS)

Thermally sensitive neurons present bursting activity for certain temperature ranges, characterized by fast repetitive spiking of action potential followed by a short quiescent period. Synchronization of bursting activity is possible in networks of coupled neurons, and it is sometimes an undesirable feature. Control procedures can suppress totally or partially this collective behavior, with potential applications in deep-brain stimulation techniques. We investigate the control of bursting synchronization in small-world networks of Hodgkin-Huxley-type thermally sensitive neurons with chemical synapses through two different strategies. One is the application of an external time-periodic electrical signal and another consists of a time-delayed feedback signal. We consider the effectiveness of both strategies in terms of protocols of applications suitable to be applied by pacemakers.

Batista, C. A. S.; Viana, R. L.; Ferrari, F. A. S.; Lopes, S. R.; Batista, A. M.; Coninck, J. C. P.

2013-04-01

180

Theoretical ellipsoidal model of gastric electrical control activity propagation.  

PubMed

A theoretical model of electric current propagation in the human stomach is developed using an approach in which the shape of the organ is assumed to be a truncated ellipsoid whose dimensions can be determined from anatomic measurements. The gastric electrical activity is simulated using a ring of isopotential electric current dipoles that are generated by a pacemaker situated in the gastric corpus. The dipoles propagate in the direction of the pylorus at a frequency of three cycles per minute. The advantages of employing ellipsoids in the analytical formulation of this gastric model are discussed in addition to the realism and usefulness of the approach. PMID:14682818

Irimia, Andrei; Bradshaw, L Alan

2003-11-01

181

A "Spike-Based" Grammar Underlies Directional Modification in Network Connectivity: Effect on Bursting Activity and Implications for Bio-Hybrids Systems  

PubMed Central

Developed biological systems are endowed with the ability of interacting with the environment; they sense the external state and react to it by changing their own internal state. Many attempts have been made to build ‘hybrids’ with the ability of perceiving, modifying and reacting to external modifications. Investigation of the rules that govern network changes in a hybrid system may lead to finding effective methods for ‘programming’ the neural tissue toward a desired task. Here we show a new perspective in the use of cortical neuronal cultures from embryonic mouse as a working platform to study targeted synaptic modifications. Differently from the common timing-based methods applied in bio-hybrids robotics, here we evaluated the importance of endogenous spike timing in the information processing. We characterized the influence of a spike-patterned stimulus in determining changes in neuronal synchronization (connectivity strength and precision) of the evoked spiking and bursting activity in the network. We show that tailoring the stimulation pattern upon a neuronal spike timing induces the network to respond stronger and more precisely to the stimulation. Interestingly, the induced modifications are conveyed more consistently in the burst timing. This increase in strength and precision may be a key in the interaction of the network with the external world and may be used to induce directional changes in bio-hybrid systems.

Zullo, Letizia; Chiappalone, Michela; Martinoia, Sergio; Benfenati, Fabio

2012-01-01

182

The Formation and Merger of Compact Objects in the Central Engine of Active Galactic Nuclei and Quasars: Gamma-Ray Burst and Gravitational Radiation  

NASA Astrophysics Data System (ADS)

The production rate of compact objects, i.e., neutron stars (NSs) and black holes (BHs), in active galactic nuclei (AGNs) and quasars (QSOs), where frequent supernova explosions are used to explain the high metallicity, is very high because of the interaction between the accretion disk and main-sequence stars in the nucleus of the quasar. The compact object red giant (RG) star binaries can be easily formed because of the large captured cross section of the RG stars. The (NS/BH, NS/BH) binary can be formed after the supernova explosion of the (NS/BH, RG) binary. Intense transient gamma-ray emission (gamma-ray burst) and gravitational radiation can result from the merger of these two compact objects. Collision between the helium core (Hc) of the RG and the BH may also take place and may also result in long-duration gamma-ray bursts but no gravitational waves. We estimate that the merger rate of (NS/BH, NS/BH) binaries and (Hc, BH) is proportional to the metal abundance N V/C IV and can be as high as 10-3 [(N V/C IV)/0.01] yr-1 per AGN/QSO.

Cheng, K. S.; Wang, Jian-Min

1999-08-01

183

Burst-by-burst laser frequency monitor  

NASA Technical Reports Server (NTRS)

The invention is a system for real-time frequency monitoring and display of an RF burst where the burst frequency is analyzed and displayed on a burst-by-burst basis in order to allow for frequency control. Although the invention was made for monitoring the laser frequency of a LIDAR system, it has other applications where realtime monitoring is required. The novelty of the invention resides in the use of a counter that is reset at the beginning of each unit time of monitoring and then gated for a unit of time. The invention also has an LED bar graph for displaying the measure of frequency at the end of each unit time in either a bar length mode or a moving dot mode. In the latter mode, the operator makes necessary adjustments to maintain the dot at the center of the bar graph.

Esproles, Carlos (inventor)

1994-01-01

184

The serotonergic inhibition of slowly bursting cells in the intergeniculate leaflet of the rat.  

PubMed

Electrophysiological studies combined with local neurotoxic lesions were conducted on anaesthetized rats in order to determine whether the dorsal raphe nucleus (DRN) inhibits the intergeniculate leaflet (IGL) of the lateral geniculate nucleus by means of innervation by serotonin-containing fibres. In the control animals, electrical stimulation of the DRN induced the long-latency and long-lasting inhibition of the neuronal firing of the IGL cells that are characterized by rhythmic, slow-bursting activity in light conditions. The electrical destruction of the DRN resulted in an increase in the firing rate of the recorded IGL cells, whilst at the same time not affecting the rhythmic, bursting pattern of the activity. In the second group of animals, local neurotoxic lesion of serotonergic fibres was performed by injection of the toxin 5,7-dihydroxytryptamine into the IGL. After 10 days of postoperative recovery, electrophysiological experiments were performed on the toxin-treated rats. In these animals, electrical stimulation as well as electrical lesion of the DRN did not induce any change in the firing of the slowly bursting cells in the 5,7-dihydroxytryptamine-injected IGL. The results obtained provide evidence that inhibition of the IGL slowly bursting cells, by innervation from the dorsal raphe, is mediated by the release of serotonin. Furthermore, the observed serotonergic inhibition of the light-dependent activity of slowly bursting cells can contribute to the neuronal mechanism gating the information that flows through this nucleus to the vestibular, visuomotor, circadian and sleep/arousal systems, with which the IGL is strongly interconnected. PMID:17156203

Blasiak, T; Siejka, S; Raison, S; Pevet, P; Lewandowski, M H

2006-11-01

185

Enormous enhancement of electric field in active gold nanoshells  

NASA Astrophysics Data System (ADS)

The electric field enhancement properties of an active gold nanoshell with gain material inside have been investigated by using Mie theory. As the gain coefficient of the inner core increases to a critical value, a super-resonance appears in the active gold nanoshell, and enormous enhancements of the electric fields can be found near the surface of the particle. With increasing shell thickness, the critical value of the gain coefficient for the super-resonance of the active gold nanoshell first decreases and then increases, and the corresponding surface enhanced Raman scattering (SERS) enhancement factor (G factor) also first increases and then decreases. The optimized active gold nanoshell can be obtained with an extremely high SERS G factor of the order of 1019–1020. Such an optimized active gold nanoshell possesses a high-efficiency SERS effect and may be useful for single-molecule detection.

Jiang, Shu-Min; Wu, Da-Jian; Wu, Xue-Wei; Liu, Xiao-Jun

2014-04-01

186

Q-Burst Origins in Africa  

NASA Astrophysics Data System (ADS)

The generation of electromagnetic transient signatures in the SR frequency range (Q-bursts) from the energetic lightning originating in Africa were intensively studied during the AMMA (African Monsoon Multidisciplinary Analysis) field program centered on Niamey, Niger in 2006. During this wet season many active westward- moving MCSs were observed by the MIT C-band Doppler radar. The MCSs exhibited a gust front, a leading squall line and a large spatially-extended (100-200 km) stratiform region that often passed over the observation site. Many transient events were recorded in association with local lightning both with a slow antenna and a DC electric field mill installed near the radar. During the gust front and squall line traverse, the majority of lightning exhibited normal polarity. A remarkable transition of polarity is observed once the radar site is under the stratiform region and a pronounced radar bright band has had time to develop. The majority of the ground flashes then exhibit a positive polarity (positive ground flash). In particular, very intense positive ground flashes (often topped with spider lightning structure) are registered when the radar "hbright band"h is most strongly developed. These positive flashes exhibit a large DC field change in comparison to ones observed during the earlier squall line passage. Video observations of nighttime events support the existence of the lateral extensive spider lightning. Daytime events exhibit thunder durations of a few minutes. ELF Q-bursts were recorded at MIT's Schumann resonance station in Rhode Island U.S.A. (about 8 Mm distance from Niamey) associated with several large well-established positive ground flashes observed locally near Niamey. The event identification is made by accurate GPS timing and arrival direction of the waves. The onset times of the Q-burst are in good agreement with the electric field measurement near Niamey. The arrival directions of the waves are also in good agreement assuming the lightning source near Niamey. Those Q- bursts were generated when the radar observed the bright band in the stratiform region. Africa stands out among the three tropical chimneys in its production of large and energetic positive ground flashes in several independently produced maps of global lightning activity. Comparison of the morphology of convection in radar field programs in Niamey and in Brazil (LBA Program, 1999) have shown far more squall line activity with accompanying stratiform regions in Africa. A large ratio of positive to negative ground flashes in Africa has been documented by the global mapping of Q-bursts, and is consistent with production of positive lightning in the prevalent stratiform regions behind active squall lines. In contrast, a predominance of large negative ground flashes is observed in the Maritime Continent where many lightning sources are located close to (or over) the ocean, and where vigorous continental-style squall lines are relatively scarce. The global maps from Rhode Island U.S. and Moshiri Japan show similar tendency in the distribution of lightning polarity.

Boldi, R.; Hobara, Y.; Yamashita, K.; Hayakawa, M.; Satori, G.; Bor, J.; Lyons, W. A.; Nelson, T.; Russell, B.; Williams, E.

2006-12-01

187

Fast optical response to electrical activation in peripheral nerves  

NASA Astrophysics Data System (ADS)

Complex neuronal structures and interactions make studying fast optical signals associated with brain activation difficult, especially in non-invasive measurements that are further complicated by the filtering effect of the scalp and skull. We have chosen to study fast optical signals in the peripheral nervous system to look at a more simplified biological neuronal structure and a system that is more accessible to non-invasive optical studies. In this study, we recorded spatially resolved electrical and optical responses of the human sural nerve to electrical stimulation. A 0.1 ms electrical stimulation was used to activate the sural nerve. Electrical signals were collected by an electromyogram machine and results showed an electrical response spanning a distance of 8 mm across the nerve. Optical signals were collected by a two-wavelength (690 and 830 nm) near-infrared spectrometer and displayed a characteristic decrease in intensity at both wavelengths. Data were taken at multiple positions and then reproduced five times. The average optical data over the five trials showed an optical signal that was spatially consistent with the electrical response to sural nerve stimulation.

Chen, Debbie K.; Tong, Yunjie; Sassaroli, Angelo; Bergethon, Peter R.; Fantini, Sergio

2007-03-01

188

Estimates of the global electric circuit from global thunderstorm activity  

NASA Astrophysics Data System (ADS)

The World Wide Lightning Location Network (WWLLN) has a global detection efficiency around 10%, however the network has been shown to identify 99% of thunderstorms (Jacobson, et al 2006, using WWLLN data from 2005). To create an estimate of the global electric circuit activity a clustering algorithm is applied to the WWLLN dataset to identify global thunderstorms from 2009 - 2013. The annual, seasonal, and regional thunderstorm activity is investigated with this new WWLLN thunderstorm dataset in order to examine the source behavior of the global electric circuit. From the clustering algorithm the total number of active thunderstorms is found every 30 minutes to create a measure of the global electric circuit source function. The clustering algorithm used is shown to be robust over parameter ranges related to real physical storm sizes and times. The thunderstorm groupings are verified with case study comparisons using satellite and radar data. It is found that there are on average 714 × 81 thunderstorms active at any given time. Similarly the highest average number of thunderstorms occurs in July (783 × 69) with the lowest in January (599 × 76). The annual and diurnal thunderstorm activity seen with the WWLLN thunderstorms is in contrast with the bimodal stroke activity seen by WWLLN. Through utilizing the global coverage and high time resolution of WWLLN, it is shown that the total active thunderstorm count is less than previous estimates based on compiled climatologies.

Hutchins, M. L.; Holzworth, R. H.; Brundell, J. B.

2013-12-01

189

Electrical-power-system data base for consumables analysis. Volume 1: Electrical equipment list, activity blocks, and time lines  

NASA Technical Reports Server (NTRS)

A standardized data base is described which consists of a space shuttle electrical equipment list, activity blocks defining electrical equipment utilization, and activity-block time lines for specific mission analyses. Information is presented to facilitate utilization of the data base, to provide the basis for the electrical equipment utilization to enable interpretation of analyses based on the data contained herein.

Pipher, M. D.; Green, P. A.; Wolfgram, D. F.

1975-01-01

190

Electricity  

NSDL National Science Digital Library

This Topic In Depth explores some of what the Web has to offer on the subject of electricity.The first site from Thinkquest.org called Electricity Online (1) gives an excellent overview, with topics ranging from circuits and transformers to electricity's discovery and history. The site even contains games, activities, and quizzes. The second site, Edison's Miracle of Light (2) from PBS.org, is a companion site to a PBS special of the same name. The site explores the life and accomplishments of one of the 19th century's greatest inventors, offering a timeline, recordings, and more. From Clark Public Utilities of Clark County Washington, the next site is called Electricity (3). This Web site offers information from a public utilities perspective, with subjects like electrical safety, how electricity gets to your home, what it costs to run appliances, and so on. Next, from the US Department of Energy, is a site that offers an Overview of the Electric Power Industry (4). Here, visitors can find information, data, publications, statistics, and more relating to electric power in the US. The fifth site from ExploreScience.com is called Multimedia Activities (5) and contains just that. Geared towards students, the four interactive lessons include an introduction to electricity and magnetism, an introduction to plasma, coulomb force, and lissajous figures. The next site, provided by the BBC, is another interactive learning site, called Activity Electricity (6). Users click through a lesson about circuits and current, answering questions along the way. The site also contains a fact sheet and quiz. From NASA, the Dataset Information site (7) contains data archived and cataloged by the Global Hydrology Resource Center relating to lighting. Several datasets from varying sources are available for free and include such things as Long Range Cloud to Ground Data. The last site is offered by the Canada Science and Technology Museum and is called Background Information for Electricity (8). This Web site for kids offers simple descriptions and illustrations about electricity, who discovered it, conductors and insulators, fuses, and more. The electricity workshop link also contains lesson plans and additional student activities.

Brieske, Joel A.

2002-01-01

191

Disturbances in the US electric grid associated with geomagnetic activity  

NASA Astrophysics Data System (ADS)

Large solar explosions are responsible for space weather that can impact technological infrastructure on and around Earth. Here, we apply a retrospective cohort exposure analysis to quantify the impacts of geomagnetic activity on the US electric power grid for the period from 1992 through 2010. We find, with more than 3? significance, that approximately 4% of the disturbances in the US power grid reported to the US Department of Energy are attributable to strong geomagnetic activity and its associated geomagnetically induced currents.

Schrijver, Carolus J.; Mitchell, Sarah D.

2013-05-01

192

A Non-Triggered Burst Supplement to the BATSE Gamma-Ray Burst Catalogs  

NASA Technical Reports Server (NTRS)

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) with a real-time burst detection (or "trigger") system running onboard the spacecraft. Under some circumstances, however, a GRB may not activate the onboard burst trigger. For example, the burst may be too faint to exceed the onboard detection threshold, or it may occur while the onboard burst trigger is disabled for technical reasons. This paper is a catalog of such "non-triggered" GRBs that were detected in a search of the archival continuous data from BATSE. It lists 873 non-triggered bursts that were recorded between 1991 December 9.0 and 1997 December 17.0. For each burst, the catalog gives an estimated source direction, duration, peak flux, and fluence. Similar data are presented for 50 additional bursts of unknown origin that were detected in the 25-50 keV range; these events may represent the low-energy "tail" of the GRB spectral distribution. This catalog increases the number of GRBs detected with BATSE by 48% during the time period covered by the search.

Kommers, J.; Lewin, W. H.; Kouveliotou, C.; vanParadijs, J.; Pendleton, G. N.; Meegan, C. A.; Fishman, G. J.

1998-01-01

193

Active Electric Imaging: Body-Object Interplay and Object's "Electric Texture"  

PubMed Central

This article deals with the role of fish's body and object's geometry on determining the image spatial shape in pulse Gymnotiforms. This problem was explored by measuring local electric fields along a line on the skin in the presence and absence of objects. We depicted object's electric images at different regions of the electrosensory mosaic, paying particular attention to the perioral region where a fovea has been described. When sensory surface curvature increases relative to the object's curvature, the image details depending on object's shape are blurred and finally disappear. The remaining effect of the object on the stimulus profile depends on the strength of its global polarization. This depends on the length of the object's axis aligned with the field, in turn depending on fish body geometry. Thus, fish's body and self-generated electric field geometries are embodied in this “global effect” of the object. The presence of edges or local changes in impedance at the nearest surface of closely located objects adds peaks to the image profiles (“local effect” or “object's electric texture”). It is concluded that two cues for object recognition may be used by active electroreceptive animals: global effects (informing on object's dimension along the field lines, conductance, and position) and local effects (informing on object's surface). Since the field has fish's centered coordinates, and electrosensory fovea is used for exploration of surfaces, fish fine movements are essential to perform electric perception. We conclude that fish may explore adjacent objects combining active movements and electrogenesis to represent them using electrosensory information.

Caputi, Angel A.; Aguilera, Pedro A.; Pereira, Ana Carolina

2011-01-01

194

Pressure vessel burst test program - Initial program paper  

NASA Technical Reports Server (NTRS)

The current status of a pressure vessel burst test program, aimed at the study of the blast waves and fragmentation characteristics of ruptured gas-filled pressure vessels, is reported. The program includes a series of test plans, each involving multiple bursts with burst pressures ranging to 7500 psig. The discussion covers the identification of concerns and hazards, application of the data generated, and a brief review of the current methods for assessing vessel safety and burst parameters. Attention is also given to pretest activities, including completed vessel and facility/instrumentation preparation and results of completed preliminary burst tests.

Cain, Maurice R.; Sharp, Douglas E.; Coleman, Michael D.; Webb, Bobby L.

1990-01-01

195

Remote monitoring of biodynamic activity using electric potential sensors  

NASA Astrophysics Data System (ADS)

Previous work in applying the electric potential sensor to the monitoring of body electrophysiological signals has shown that it is now possible to monitor these signals without needing to make any electrical contact with the body. Conventional electrophysiology makes use of electrodes which are placed in direct electrical contact with the skin. The electric potential sensor requires no cutaneous electrical contact, it operates by sensing the displacement current using a capacitive coupling. When high resolution body electrophysiology is required a strong (capacitive) coupling is used to maximise the collected signal. However, in remote applications where there is typically an air-gap between the body and the sensor only a weak coupling can be achieved. In this paper we demonstrate that the electric potential sensor can be successfully used for the remote sensing and monitoring of bioelectric activity. We show examples of heart-rate measurements taken from a seated subject using sensors mounted in the chair. We also show that it is possible to monitor body movements on the opposite side of a wall to the sensor. These sensing techniques have biomedical applications for non-contact monitoring of electrophysiological conditions and can be applied to passive through-the-wall surveillance systems for security applications.

Harl, C. J.; Prance, R. J.; Prance, H.

2008-12-01

196

[Study on dewatering of activated sludge under applied electric field].  

PubMed

For an electro-dewatering process of activated sludge (AS), the effect of pH and conductivity of AS, flocculation conditioning and operation factors of horizontal electric field (voltage magnitude, method of applying electric field and distance between plates) were investigated, and the corresponding optimum electro-dewatering conditions were also obtained. The results showed that the best electro-dewatering effect was achieved for AS without change of its pH value (6.93) and conductivity (1.46 mS x cm(-1)). CPAM conditioning could lead to the increase of 30%-40% in the dewatering rate and accelerate the dewatering process, whereas a slight increase in the electro-dewatering rate. The electro-dewatering rate for conditioned AS reached 83.12% during an electric field applied period of 60 minutes, while this rate for original AS could be 75.31% even the electric field applied period extended to 120 minutes. The delay of applying the electric field had an inhibition effect on the AS electro-dewatering rate. Moreover, the optimum conditions for AS electro-dewatering were followed: CPAM dose of 9 g x kg(-1), electric field strength of 600 V x m(-1), distance between the two plates of 40 mm, dehydration time of 60 minutes. Under above optimum conditions the AS electro-dewatering rate could approach to 85.33% and the moisture content in AS decreased from 99.30% to 95.15% accordingly. PMID:23379170

Ji, Xue-Yuan; Wang, Yi-Li; Feng, Jing

2012-12-01

197

An Overview of Electric Propulsion Activities at NASA  

NASA Technical Reports Server (NTRS)

This paper provides an overview of NASA s activities in the area of electric propulsion with an emphasis on project directions, recent progress, and a view of future project directions. The goals of the electric propulsion programs are to develop key technologies to enable new and ambitious science missions and to transfer these technologies to industry. Activities include the development of gridded ion thruster technology, Hall thruster technology, pulsed plasma thruster technology, and very high power electric propulsion technology, as well as systems technology that supports practical implementation of these advanced concepts. The performance of clusters of ion and Hall thrusters is being revisited. Mission analyses, based on science requirements and preliminary mission specifications, guide the technology projects and introduce mission planners to new capabilities. Significant in-house activity, with strong industrial/academia participation via contracts and grants, is maintained to address these development efforts. NASA has initiated a program covering nuclear powered spacecraft that includes both reactor and radioisotope power sources. This has provided an impetus to investigate higher power and higher specific impulse thruster systems. NASA continues to work closely with both supplier and user communities to maximize the understanding and acceptance of new technology in a timely and cost-effective manner. NASA s electric propulsion efforts are closely coordinated with Department of Defense and other national programs to assure the most effective use of available resources. Several NASA Centers are actively involved in these electric propulsion activities, including, the Glenn Research Center, Jet Propulsion Laboratory, Johnson Space Center, and Marshall Space Flight Center.

Dunning, John W., Jr.; Hamley, John A.; Jankovsky, Robert S.; Oleson, Steven R.

2004-01-01

198

Model of Gamma Frequency Burst Discharge Generated by Conditional Backpropagation  

Microsoft Academic Search

Maler. Model of gamma frequency burst discharge generated by conditional backpropagation. J Neurophysiol 86: 1523-1545, 2001. Pyramidal cells of the electrosensory lateral line lobe (ELL) of the weakly electric fish Apteronotus leptorhynchus have been shown to produce oscillatory burst discharge in the g-frequency range (20 - 80 Hz) in response to constant depolarizing stimuli. Previous in vitro studies have shown

BRENT DOIRON; RAY W. TURNER; LEONARD MALER; A. Longtin

2010-01-01

199

Neutrino bursts from gamma-ray bursts  

NASA Technical Reports Server (NTRS)

If gamma-ray bursts originate at cosmological distances, as strongly indicated by the results from Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO), then ultrarelativistic ejecta are the likely consequence of the highly super-Eddington luminosity of the sources. If the energy injection rate varies with time, then the Lorentz factor of the wind also varies, and the shells of ejected matter collide with each other. The collisions between baryons produce pions which decay into high-energy photons, electrons, electron positron pairs, and neutrino pairs. The bulk Lorentz factor of approximately 300 is required if our model is to be compatible with the observed millisecond variability. The strongest gamma-ray bursts are observed to deliver approximately 10(exp -4) ergs/sq cm in 100-200 keV photons. In our scenario more energy may be delivered in a neutrino burst. Typical neutrinos may be approximately 30 GeV if the protons have a Maxwellian energy distribution, and up to approximately TeV if the protons have a power-law distribution. Such neutrino bursts are close to the detection limit of the DUMAND II experiment.

Paczynski, Bohdan; Xu, Guohong

1994-01-01

200

Organization of electrical activity in the canine pyloric canal.  

PubMed Central

1. The electrical activity of the canine gastroduodenal junction was investigated using cross-sectional muscle preparations and intracellular recording techniques. 2. Spontaneous electrical slow waves were recorded from antral and pyloric cells but not from duodenal cells adjacent to the pyloric region. Slow waves were generated in the antrum and propagated to the pyloric region via the circular layer. Pyloric slow waves consisted of an upstroke phase, a plateau phase and oscillations superimposed upon the plateau, whereas antral slow waves had smooth plateau potentials. 3. Within the pylorus slow waves decayed in amplitude with distance from the myenteric border of the circular muscle; the majority of pyloric circular cells were normally electrically quiescent. 4. The longitudinal muscle in the pylorus was electrically coupled and paced by the circular muscle. In longitudinal cells slow waves were usually of long duration with multiple spikes superimposed upon the plateau phase. 5. Nifedipine (10(-8) to 10(-5) M) decreased slow waves amplitude and duration. Tetraethylammonium ions (TEA; 10 mM) increased the duration of slow waves, caused spiking activity during the plateau phase and also elicited spiking in the quiescent regions. 6. The results suggest that gastric slow waves pace the myenteric portion of the circular muscle layer and the longitudinal layer of the pylorus, but do not traverse the gastroduodenal junction, nor pace the majority of cells within the circular muscle of the pylorus. Other excitatory mechanisms are necessary to activate these regions and to co-ordinate their motility with gastric motility.

Sanders, K M; Vogalis, F

1989-01-01

201

Electrical activation of PAN-Pt artificial muscles  

NASA Astrophysics Data System (ADS)

Activated polyacrylonitrile (PAN) fibers are known to elongate and contract when immersed in caustic and acidic solutions, respectively. The change in length for these pH activated fibers is greater than 100% and are comparable in strength to human muscle, yet need of strong acids and bases for actuation has limited the use of PAN fibers as linear actuators or artificial muscles. Increasing the conductivity of PAN by depositing platinum within the fibers has allowed for electrical activation of PAN artificial muscles when it is placed in an electrochemical cell. The electrolysis of water in such a cell produces hydrogen ions at a PAN anode, thus locally decreasing the pH and causing the PAN muscle to contract. Reversing the electric field allows the PAN muscle to elongate. A 40% change in PAN muscle length in less than 10 minutes is observed when it is placed as an electrode in a 10 mM NaCl electrolyte solution and connected to a 20 volt power supply. These initial results indicate potential in developing electrically activated PAN muscles and linear actuators, which would be much more applicable than chemically activated PAN.

Schreyer, H. Brett; Shahinpoor, Mohsen; Kim, Kwang J.

1999-05-01

202

Auditory perception of music measured by brain electrical activity mapping.  

PubMed

The brain electrical activity of right-handed normal subjects was studied while they were exposed to auditory stimulation of the music type. The material presented was a note, a scale and a melody, recorded on magnetic tape. Each stimulus condition lasted 45 sec. The first 30 sec were analysed using brain electrical activity mapping in the delta (1-4 Hz), alpha (8-12 Hz) and beta 2 (18-24 Hz) frequency bands. The results showed significant bilateral reaction differences for all conditions, showing a left midtemporal activation predominance for the note and scale conditions, but a right midtemporal and frontal predominance for the melody. The results are discussed in terms of functional specialization for different levels of processing. PMID:3431673

Breitling, D; Guenther, W; Rondot, P

1987-01-01

203

Active RF Pulse Compression Using An Electrically Controlled Semiconductor Switch  

SciTech Connect

First we review the theory of active pulse compression systems using resonant delay lines. Then we describe the design of an electrically controlled semiconductor active switch. The switch comprises an active window and an overmoded waveguide three-port network. The active window is based on a four-inch silicon wafer which has 960 PIN diodes. These are spatially combined in an overmoded waveguide. We describe the philosophy and design methodology for the three-port network and the active window. We then present the results of using this device to compress 11.4 GHz RF signals with high compression ratios. We show how the system can be used with amplifier like sources, in which one can change the phase of the source by manipulating the input to the source. We also show how the active switch can be used to compress a pulse from an oscillator like sources, which is not possible with passive pulse compression systems.

Guo, Jiquan; Tantawi, Sami; /SLAC

2007-01-10

204

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-Ray Bursts (GRBs) are now known to be the most powerful explosions in the Universe. I will summarize the history of observations of GRBs, and how we came to know that the sources are so distant. I will also give an overview of the most prominent theories as to the cause of bursts.

Meegan, Charles A.; Six, N. Frank (Technical Monitor)

2002-01-01

205

Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

Prologue C. Kouveliotou, R. A . M. J. Wijers and S. E. Woosley; 1. The discovery of the gamma-ray burst phenomenon R. W. Klebesadel; 2. Instrumental principles E. E. Fenimore; 3. The BATSE era G. J. Fishman and C. A. Meegan; 4. The cosmological era L. Piro and K. Hurley; 5. The Swift era N. Gehrels and D. N. Burrows; 6. Discoveries enabled by multi-wavelength afterglow observations of gamma-ray bursts J. Greiner; 7. Prompt emission from gamma-ray bursts T. Piran, R. Sari and R. Mochkovitch; 8. Basic gamma-ray burst afterglows P. Mészáros and R. A. M. J. Wijers; 9. The GRB-supernova connection J. Hjorth and J. S. Bloom; 10. Models for gamma-ray burst progenitors and central engines S. E. Woosley; 11. Jets and gamma-ray burst unification schemes J. Granot and E. Ramirez-Ruiz; 12. High-energy cosmic rays and neutrinos E. Waxman; 13. Long gamma-ray burst host galaxies and their environments J. P. U. Fynbo, D. Malesani and P. Jakobsson; 14. Gamma-ray burst cosmology V. Bromm and A. Loeb; 15. Epilogue R. D. Blandford; Index.

Kouveliotou, Chryssa; Wijers, Ralph A. M. J.; Woosley, Stan

2012-11-01

206

BATHYMYSIS - THE BURST AUV  

Microsoft Academic Search

A technical description of the Bathymysis is given. The Bathymysis is the AUV put forward by the Bath University Racing Submarine Team (BURST) for the 2006 SAUC-E competition. BURST is principally a student group, although postgraduates, academic staff and technicians are involved as well. The main components of the submarine are discussed, highlighting the major design considerations and decisions that

K. M. Collins; G. Brindlinger; A. L. Coxon; G. M. Klimaytys; C. P. Pattinson; P. R. Riggs; C. L. Wallis

207

Meteor burst communications  

Microsoft Academic Search

The characteristics of meteor burst communications are described and compared to those of HF and satellite systems. The two generic types of MB systems, broadcast and channel-probing systems, are explained. In systems using the broadcast protocol, the transmitter knows nothing about the occurrence of bursts or trails and transmits continuously for a sufficient duration to permit all recipients to receive

Davras Yavuz

1990-01-01

208

Electrical activation of artificial muscles containing polyacrylonitrile gel fibers.  

PubMed

Gel fibers made from polyacrylonitrile (PAN) are known to elongate and contract when immersed in caustic and acidic solutions, respectively. The amount of contraction for these pH-activated fibers is 50% or greater, and the strength of these fibers is shown to be comparable to that of human muscle. Despite these attributes, the need of strong acids and bases for actuation has limited the use of PAN gel fibers as linear actuators or artificial muscles. Increasing the conductivity by depositing platinum on the fibers or combining the fibers with graphite fibers has allowed for electrical activation of artificial muscles containing gel fibers when placed in an electrochemical cell. The electrolysis of water in such a cell produces hydrogen ions at an artificial muscle anode, thus locally decreasing the pH and causing the muscle to contract. Reversing the electric field allows the PAN muscle to elongate. A greater than 40% contraction in artificial muscle length in less than 10 min is observed when it is placed as an electrode in a 10 mM NaCl electrolyte solution and connected to a 10 V power supply. These results indicate potential in developing electrically activated PAN muscles and linear actuators, which would be much more applicable than chemically activated muscles. PMID:11710194

Schreyer, H B; Gebhart, N; Kim, K J; Shahinpoor, M

2000-01-01

209

Burst synchronization transitions in a neuronal network of subnetworks.  

PubMed

In this paper, the transitions of burst synchronization are explored in a neuronal network consisting of subnetworks. The studied network is composed of electrically coupled bursting Hindmarsh-Rose neurons. Numerical results show that two types of burst synchronization transitions can be induced not only by the variations of intra- and intercoupling strengths but also by changing the probability of random links between different subnetworks and the number of subnetworks. Furthermore, we find that the underlying mechanisms for these two bursting synchronization transitions are different: one is due to the change of spike numbers per burst, while the other is caused by the change of the bursting type. Considering that changes in the coupling strengths and neuronal connections are closely interlaced with brain plasticity, the presented results could have important implications for the role of the brain plasticity in some functional behavior that are associated with synchronization. PMID:21456852

Sun, Xiaojuan; Lei, Jinzhi; Perc, Matjaz; Kurths, Jürgen; Chen, Guanrong

2011-03-01

210

Transparent selective illumination means suitable for use in optically activated electrical switches and optically activated electrical switches constructed using same  

DOEpatents

A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch. 11 figures.

Wilcox, R.B.

1991-09-10

211

Pharmacological block of the electrogenic sodium pump disrupts rhythmic bursting induced by strychnine and bicuculline in the neonatal rat spinal cord.  

PubMed

The cellular mechanisms underlying rhythmic bursts induced in the isolated neonatal rat spinal cord by bath application of strychnine and bicuculline (which block glycine- and gamma-aminobutyric acid-A-receptor-mediated inhibition, respectively) were probed with pharmacological tools. Such spontaneous bursts were recorded either intracellularly from lumbar motoneurons or extracellularly from ventral roots. As previously described, these network-driven events consisted of large-amplitude depolarizations arising abruptly from baseline with a highly regular period (on average 28 s). Burst episodes (lasting on average 7 s) comprised several oscillations and appeared synchronously on flexor and extensor motoneuron pools of both sides of the spinal cord. Their diffuse location made convenient to use bath-applied substances in the attempt to selectively block distinct membrane processes operating through the network. Application of apamin (0.4 microM) shortened both cycle period and burst duration without changing their regular rhythmicity. Similar results were obtained with carbachol (10 microM). Cs+ (4 mM) reversibly hyperpolarized the motoneuron membrane potential and largely increased burst duration, which was characterized by a long series of repetitive oscillatory waves. Cycle period and rhythmicity remained unaltered. Ouabain (10 microM), strophanthidin (4 microM), or K(+)-free solutions disrupted rhythmic bursting, which was fragmented into irregularly occurring paroxysmal activity mixed with short depolarizing events, still developing simultaneously on both sides of the spinal cord. Bursting activity eventually ceased after approximately 30-40 min of application of ouabain or strophanthidin. Prolonged washout of strophanthidin or K(+)-free solutions reestablished regular bursting patterns, whereas no recovery from ouabain was observed. At the time of strong depression of bursting, it was still possible to evoke bursts by single electrical pulses applied to the segmental dorsal root. Antidromic spikes of motoneurons could still be evoked by ventral root stimulation. These results demonstrate that, in a spinal bursting network mainly made up by excitatory processes, blockers of slow Ca(2+)-dependent K+ currents, such as apamin or carbachol, or of the slow inward rectifier, such as Cs+, did not suppress rhythmicity, suggesting that these conductances simply contributed to control cycle period and/or burst duration. Conversely, pharmacological blockers of the electrogenic Na+ pump such as ouabain, strophanthidin, or K(+)-free solutions severely disrupted all characteristics of rhythmic bursting. It is proposed that the operation of the electrogenic Na+ pump of premotoneurons was a crucial element for rhythmic bursting. PMID:9120558

Ballerini, L; Bracci, E; Nistri, A

1997-01-01

212

Electrical activation of the human vestibulo-sympathetic reflex  

Microsoft Academic Search

Muscle sympathetic nerve activity (MSNA) is modulated on a beat-to-beat basis by the baroreflex. Vestibular input from the otolith organs also modulates MSNA, but characteristics of the vestibulo-sympathetic reflex (VSR) are largely unknown. The purpose of this study was to elicit the VSR with electrical stimulation to estimate its latency in generating MSNA. The vestibular nerves of seven subjects were

Andrei Voustianiouk; Horacio Kaufmann; André Diedrich; Theodore Raphan; Italo Biaggioni; Hamish MacDougall; Dmitri Ogorodnikov; Bernard Cohen

2006-01-01

213

Multiscale modelling of human gastric electric activity: can the electrogastrogram detect functional electrical uncoupling?  

PubMed

During recent years there has been a growing interest in the assessment of gastric electrical health through cutaneous abdominal recordings. The analysis of such recordings is largely limited to an inspection of frequency dynamics, and this has raised doubts as to whether functional gastric electrical uncoupling can be detected using this technique. We describe here a computational approach to the problem in which the equations governing the underlying physics of the problem have been solved over an anatomically detailed human torso geometry. Cellular electrical activity was embedded within a stomach tissue model, and this was coupled to the torso using an equivalent current source approach. Simulations were performed in which normal and functionally uncoupled (through the introduction of an ectopic antral pacemaker) gastric slow wave activity was present, and corresponding cutaneous electrogastrograms were produced. These were subsequently analysed using the currently recommended techniques, and it was found that the functionally uncoupled situation was indistinguishable from normal slow wave activity using this approach. PMID:16407476

Buist, M L; Cheng, L K; Sanders, K M; Pullan, A J

2006-03-01

214

Type III Radio Bursts at Long Wavelengths: STEREO/Waves Observations and Future Prospects for Inner Heliospheric Missions  

NASA Astrophysics Data System (ADS)

We investigate solar type III radio bursts observed by the S/Waves instruments on-board the STEREO spacecraft. These instruments provides us with goniopolarimetric (GP, also referred to as direction-finding) measurements between 125 kHz and 1975 kHz while amplitudes of electric field fluctuations are recorded up to 16 MHz. We have investigated large number of type III radio bursts from May 2007 till July 2010. Some of them have been associated with solar flares within the NOAA directory of active regions. That allows us to determine a source position of bursts when the electron density model of LeBlanc et al. (1998) has been considered. We have also located a region of type III radio bursts by triangulating the position using GP measurements. Observed type III radio bursts generally propagate in the solar equatorial plane. Our results indicate that the maximum flux density occurs at ~ 800 kHz. Future solar missions (e.g., Solar Orbiter and Solar Probe Plus) will provide new insights into properties of type III radio bursts as for instance sampling the region where this latter maximum occurs.

Krupar, V.; Santolik, O.; Maksimovic, M.; Cecconi, B.

2011-12-01

215

A Nontriggered Burst Supplement to the BATSE Gamma-Ray Burst Catalogs  

NASA Astrophysics Data System (ADS)

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) with a real-time burst detection (or ``trigger'') system running on-board the spacecraft. Under some circumstances, however, a GRB may not activate the on-board burst trigger. For example, the burst may be too faint to exceed the on-board detection threshold, or it may occur while the on-board burst trigger is disabled for technical reasons. This paper describes a catalog of 873 ``nontriggered'' GRBs that were detected in a search of the archival continuous data from BATSE recorded between 1991 December 9.0 and 1997 December 17.0. For each burst, the catalog gives an estimated source direction, duration, peak flux, and fluence. Similar data are presented for 50 additional bursts of unknown origin that were detected in the 25-50 keV range; these events may represent the low-energy ``tail'' of the GRB spectral distribution. This catalog increases the number of GRBs detected with BATSE by 48% during the time period covered by the search.

Kommers, Jefferson M.; Lewin, Walter H. G.; Kouveliotou, Chryssa; van Paradijs, Jan; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.

2001-06-01

216

Age-related changes in visually evoked electrical brain activity.  

PubMed

Whereas much is known about the degenerative effects of aging on cortical tissue, less is known about how aging affects visually evoked electrical activity, and at what latencies. We compared visual processing in elderly and young controls using a visual masking paradigm, which is particularly sensitive to detect temporal processing deficits, while recording EEG. The results show that, on average, elderly have weaker visual evoked potentials than controls, and that elderly show a distinct scalp potential topography (microstate) at around 150 ms after stimulus onset. This microstate occurred irrespective of the visual stimulus presented. Electrical source imaging showed that the changes in the scalp potential resulted from decreased activity in lateral occipital cortex and increases in fronto-parietal areas. We saw, however, no evidence that increased fronto-parietal activity enhanced performance on the discrimination task, and no evidence that it compensated for decreased posterior activity. Our results show qualitatively different patterns of visual evoked potentials (VEPs) in the elderly, and demonstrate that increased fronto-parietal activity arises during visual processing in the elderly already between 150 and 200 ms after stimulus onset. The microstate associated with these changes is a potential diagnostic tool to detect age-related cortical changes. PMID:21538705

Plomp, Gijs; Kunchulia, Marina; Herzog, Michael H

2012-05-01

217

On vortex bursting  

NASA Technical Reports Server (NTRS)

Vortex bursting is studied by means of visualization. The physical behavior of the phenomenon is emphasized, and its similarity with boundary layer separation or wake bursting becomes apparent. The essential influence of an increasing pressure gradient on the initiation, the position and the type of bursting is clearly confirmed. The evolution of the phenomena as a function of several parameters is analyzed in the case of delta wings, alone or installed on aircraft models, and compared with the results of similar wind tunnel or flight tests.

Werle, H.

1984-01-01

218

5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxy-4H-chromen-4-one (MSF-2) suppresses fMLP-mediated respiratory burst in human neutrophils by inhibiting phosphatidylinositol 3-kinase activity.  

PubMed

Respiratory burst mediates crucial bactericidal mechanism in neutrophils. However, undesirable respiratory burst leads to pathological inflammation and tissue damage. This study investigates the effect and the underlying mechanism of 5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxy-4H-chromen-4-one (MSF-2), a lignan extracted from the fruit of Melicope Semecarprifolia, on fMLP-induced respiratory burst in human neutrophils and suggests a possible therapeutic approach to ameliorate disease associated with neutrophil hyperactivation. MSF-2 inhibited fMLP-induced neutrophil superoxide anion production, cathepsin G release and migration in human neutrophils isolated from healthy volunteers, reflecting inhibition of phosphatidylinositol 3-kinase (PI3K) activation. Specifically, PI3K/AKT activation results in migration, degranulation and superoxide anion production in neutrophils. MSF-2 suppresses PI3K activation and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) production, and consequently inhibits downstream activation of PDK1 and AKT. Further, PI3K also stimulates respiratory burst via PLC-dependent elevation of intracellular calcium. MSF-2 reduces fMLP-mediated PLC?2 activation and intracellular calcium accumulation notably through extracellular calcium influx in a PI3K and PLC-dependent manner. However, MSF-2 is not a competitive or allosteric antagonist of fMLP. Additionally, in an in vivo study, MSF-2 prevents fMLP-induced neutrophil infiltration and inflammation in mice. In conclusion, MSF-2 opposes fMLP-mediated neutrophil activation and inflammation by inhibiting PI3K activation and subsequent activation of AKT and PLC?2. PMID:20945388

Liao, Chang-Hui; Chen, Jih-Jung; Lin, Jieru Egeria; Liu, Chia-Hsin; Tseng, Ching-Ping; Day, Yuan-Ji

2011-06-01

219

Electrical Activity of Convective Events During MAP Experiment  

NASA Astrophysics Data System (ADS)

The Mesoscale Alpine Programme (MAP) overall objective was to improve the forecast of severe meteorological events over mountainous terrain (intense precipitation, strong winds and altitude turbulence). During the Special Observing Period (SOP), from September 7 until November 15, 1999, 14 countries got involved in an intensive field experiment over Central Europe. The research group in atmospheric electricity of the Laboratoire d'Aerologie (Toulouse-France), based in Northern Italy in the Lago Maggiore Target Area (LMTA), conducted two kinds of investigations on electrical activity: i) the characterization of the surface precipitation electric current produced by convective rain; ii) the study of cloud-to-ground lightning flash production in relation with dynamics and microphysics. Measurements of electric field, precipitation current density, and rainfall parameters were performed at the ground. Several days of the period provided substantially charged rainfall of both polarities. The average proportions of each polarity are close but the negative one is slightly larger (54 %). During the deeply convective event on September 17, 1999, the precipitation current density is firstly positive (negative charges brought to the surface), reaches more than 100 nA m-2 and changes its polarity when the rainfall rate is maximum (up to 200 mm h-1). In the case of several shallow convective cells passing over the experimental site on October 3, both charge polarities were observed on the rain produced by electrified cells: first the negative one and then the positive one. A very tight correlation between electric field and precipitation current is observed at the ground, displaying the mirror image effect. The ground electric field appears to be due to the cloud charge whose polarity is opposed to that carried down by the rainfall. For the second study, we use data collected during Intensive Observing Period (IOP) 2a of the SOP around the Lago Maggiore Target Area. IOP 2a was the most electrically active during the MAP-SOP. It undergoes 75 % of the total CG activity measured during the whole period. Thundercells were strongly and vertically developed (cloud top reaching over 12 km of altitude) and produced large amounts of rainfall and some hail. Doppler and polarimetric radar data allowed us to retrieve the 3-D wind and radar reflectivity fields (from two synchronous Doppler radar) and particle types fields in the thundercells (from the S-Pol polarimetric radar). Both polarities of CGs are distinguished in each case of study correlation. We first study temporal and spatial correlation from the global activity over the region. Then, we consider the temporal correlation between CG rates and dynamics or microphysics for 5 individual cells. We observe very strong correlation between CGs and the presence of Graupel-Hail mixture, which is in good agreement with the non-inductive charging mechanism. CGs seem to be located at the vertical of large radar reflectivity values and located around the maximum vertical velocities. We particularly study two individual cells, in order to better understand their different electrical behaviors: the first one mainly produced negative CGs, and the second one produced 64 % of positive CGs in the second phase of its lifetime. We observe the association of positive CGs with severe weather and especially the presence of hail and strong vertical velocities.

Chauzy, S.; Coquillat, S.; Seity, Y.; Soula, S.

2002-12-01

220

Electric field activated nonlinear anisotropic charge transport in doped polypyrrole  

NASA Astrophysics Data System (ADS)

Electric field activated nonlinear transport is investigated in polypyrrole thin film in both in-plane and out-of-plane geometries down to 5 K and strong anisotropy is observed. A morphological model is suggested to explain the anisotropy through inter-chain and intra-chain transport. The deviation from the variable range hopping at low temperature is accounted by fluctuation assisted transport. From Zabrodaskii plots, it is found that electric field can tune the transport from insulating to metallic regime. Glazman-Matveev model is used to describe the nonlinear conduction. Field scaling analysis shows that conductance data at different temperature falls on to a single curve. Nonlinearity exponent, mT and characteristic length, LE are estimated to characterize the transport in both the geometries.

Varade, Vaibhav; Anjaneyulu, P.; Suchand Sangeeth, C. S.; Ramesh, K. P.; Menon, R.

2013-12-01

221

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment.

Bunshah, Rointan (Los Angeles, CA); Nath, Prem (Troy, MI)

1982-01-01

222

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation is disclosed. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment. 1 fig.

Bunshah, R.; Nath, P.

1982-06-22

223

Electrically controlled molecular recognition harnessed to activate a cellular response.  

PubMed

Seamless embedment of electronic devices in biological systems is expected to add the outstanding computing power, memory, and speed of electronics to the biochemical toolbox of nature. Such amalgamation requires transduction of electronic signals into biochemical cues that affect cells. Inspired by biology, where pathways are directed by molecular recognition, we propose and demonstrate a generic electrical-to-biological transducer comprising a two-state electronic antigen and a chimeric cell receptor engineered to bind the antigen exclusively in its "on" state. T-cells expressing these receptors remain inactivated with the antigen in its "off" state. Switching the antigen to its "on" state by an electrical signal leads to its recognition by the T-cells and correspondingly to cell activation. PMID:21985491

Artzy-Schnirman, Arbel; Blat, Dan; Talmon, Yael; Fishler, Rami; Gertman, Dori; Oren, Ravit; Wolchinsky, Ron; Waks, Tova; Benhar, Itai; Eshhar, Zelig; Sivan, Uri; Reiter, Yoram

2011-11-01

224

Burst synchronization detection system  

NASA Technical Reports Server (NTRS)

System uses digital logic and a voltage-controlled oscillator to obtain appropriate horizontal and vertical sync signals from the sync bursts contained in the original transmitted signal. It is useful in systems that exhibit considerable single amplitude fluctuation.

Lipoma, P. C.; Seay, B. P., Jr.

1970-01-01

225

INTEGRAL burst alert service  

NASA Technical Reports Server (NTRS)

The detection, accurate positioning, and spectral analysis of cosmic gamma ray bursts is an objective of the International Gamma Ray Astrophysics Laboratory (INTEGRAL) mission. Due to their unpredictable nature, gamma ray bursts can only be observed in serendipity mode. In order to allow and promote multiwavelength follow-up observations of such events, it is desirable to make the information available to the astrophysics community with a minimum delay through the use of Internet. Ideally, the data dissemination should occur within a few seconds of the start of the burst event so that follow up observations can proceed while gamma rays are still being emitted. The technical feasibility of building such a system to disseminate INTEGRAL burst alerts in real time is currently under consideration, the preliminary results of which are presented. It is concluded that such an alert service is technically feasible.

Pedersen, H.; Jennings, D.; Mereghetti, S.; Teegarden, B.

1997-01-01

226

Ga-implantation in Ge: Electrical activation and clustering  

SciTech Connect

The electrical activation and clustering of Ga implanted in crystalline Ge was investigated in the (0.3-1.2)x10{sup 21} Ga/cm{sup 3} concentration range. To this aim, Ge samples implanted with 50 keV gallium, and annealed at several temperatures up to 650 deg. C, have been subjected to a detailed structural and electrical characterization. The substrate was maintained at 77 K during implantation to avoid the formation of the honeycomb structure that occurs during implantation at room temperature of heavy ions at high fluence. Secondary ion mass spectrometry analyses indicated a negligible Ga diffusion and dopant loss during the thermal annealing. The carrier concentration in the recrystallized samples measured by Hall effect showed a maximum concentration of active Ga of approx6.6x10{sup 20} Ga/cm{sup 3}. A remarkable Ga deactivation occurred with increasing the annealing temperature from 450 to 650 deg. C although the sheet resistance did not change considerably in this temperature range. It turned out that the carrier concentration reduction is balanced by the enhancement of the hole mobility that exhibits a steep variation with the concentration of the ionized scattering centers in this range. A simple model is proposed to explain the experimental results taking into account the thermally activated Ga clustering. These studies, besides clarifying the mechanism of Ga deactivation in Ge, can be helpful for the realization of future generation devices based on Ge.

Impellizzeri, G.; Mirabella, S.; Irrera, A.; Grimaldi, M. G. [MATIS CNR-INFM and Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, 95123 Catania (Italy); Napolitani, E. [MATIS CNR-INFM and Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, 35131 Padova (Italy)

2009-07-01

227

Electrical activation studies of ion implanted gallium nitride  

NASA Astrophysics Data System (ADS)

A comprehensive and systematic electrical activation study of Si-implanted gallium nitride (GaN) was performed as a function of ion implantation dose, anneal temperature, and implantation temperature. Additionally, Mg-implanted GaN was also investigated. Temperature-dependent Hall effect measurements and photoluminescence (PL) spectra were used to characterize the samples. GaN wafers capped with AlN were implanted at room temperature and at 800°C with 200 keV Si ions at doses ranging from 1 x 1013 to 5 x 1015 cm-2 and annealed from 1050 to 1350°C for 5 min to 17 sec in flowing nitrogen. The optimum anneal temperature for samples implanted with the higher Si doses is around 1350°C, exhibiting nearly 100% electrical activation efficiency. Exceptional mobilities and carrier concentrations were obtained on all Si implanted samples. PL spectra revealed nearly complete implantation damage recovery as well as the nature of the yellow luminescence plaguing nearly all Si-doped GaN. Additionally, GaN wafers were implanted with Mg and various coimplants and annealed from 1100 to 1350°C. All of the Mg-implanted and most of the Mg coimplanted GaN samples became extremely resistive, and did not show definite p-type conductivity even after annealing at 1350°C, remaining highly resistive even at a sample temperature as high as 800 K. A dominant 2.36 eV green luminescence band observed in the PL spectra of all Mg implanted samples is attributed to a Mg-related deep complex DAP transition. The inefficient electrical activation of Mg acceptors implanted into GaN is attributed to these Mg-related deep complexes.

Fellows, James Andrew

228

[Changes of brain electric activity under general anaesthesia (author's transl)].  

PubMed

The comparison of the influence of HAL, NLA and EHA on the electrical activity of the brain by help of a vigilo-somnogram shows equal directed curves. That is to say that the effect of general anesthesia is to be seen in a inhibition of the central nervous system, from which in the first line the orienting reticular system and pain processing centres of the limbic system are concerned. It has to be emphasized that the sleep-EEG and the EEG of general anaesthesia have a certain similarity but no identity; so the sleep state of the EEG should not be transferred to the anaesthesia states. PMID:7425263

Grabow, L; Pyhel, N

1980-07-01

229

Vasoactive intestinal peptide and electrical activity influence neuronal survival  

SciTech Connect

Blockage of electrical activity in dissociated spinal cord cultures results in a significant loss of neurons during a critical period in development. Decreases in neuronal cell numbers and SVI-labeled tetanus toxin fixation produced by electrical blockage with tetrodotoxin (TTX) were prevented by addition of vasoactive intestinal peptide (VIP) to the nutrient medium. The most effective concentration of VIP was 0.1 nM. At higher concentrations, the survival-enhancing effect of VIP on TTX-treated cultures was attenuated. Addition of the peptide alone had no significant effect on neuronal cell counts or tetanus toxin fixation. With the same experimental conditions, two closely related peptides, PHI-27 (peptide, histidyl-isoleucine amide) and secretin, were found not to increase the number of neurons in TTX-treated cultures. Interference with VIP action by VIP antiserum resulted in neuronal losses that were not significantly different from those observed after TTX treatment. These data indicate that under conditions of electrical blockade a neurotrophic action of VIP on neuronal survival can be demonstrated.

Brenneman, D.E.; Eiden, L.E.

1986-02-01

230

Transient electrical activity accompanying rock under indentation loading  

NASA Astrophysics Data System (ADS)

Enomoto, Y. and Hashimoto, H., 1992. Transient electrical activity accompanying rock under indentation loading. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 337-344. Laboratory experiments have been conducted to investigate the geoelectrodynamics associated with rock fractures in the earth's crust. That is, when rocks were subjected to indentation fracturing in two ways, the electric charges generated were detected; namely, (1) a direct charge collection method using an electroconductive indenter serving as the collecting electrode (referred to as near-field test), and (2) an indirect collection method in which an electrode was placed on rocks at a specific distance from the indentation fracture zone (referred to as far-field test). As near-field test results, higher electric charge signals were detected during the loading cycle when cracking occurred around the indent on granite and on moist andesite. Also in the far-field test, the charge signal propagating through the rock during fracturing could be detected; the signal intensity decreased as the distance between the indent and electrode increased. Possible mechanisms for fracture-induced charge generation and their propagation through rock media are discussed.

Enomoto, Y.; Hashimoto, H.

1992-09-01

231

AC Electric Field Activated Shape Memory Polymer Composite  

NASA Technical Reports Server (NTRS)

Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

2011-01-01

232

An Intense and Short-Lasting Burst of Neutrophil Activation Differentiates Early Acute Myocardial Infarction from Systemic Inflammatory Syndromes  

PubMed Central

Background Neutrophils are involved in thrombus formation. We investigated whether specific features of neutrophil activation characterize patients with acute coronary syndromes (ACS) compared to stable angina and to systemic inflammatory diseases. Methods and Findings The myeloperoxidase (MPO) content of circulating neutrophils was determined by flow cytometry in 330 subjects: 69 consecutive patients with acute coronary syndromes (ACS), 69 with chronic stable angina (CSA), 50 with inflammation due to either non-infectious (acute bone fracture), infectious (sepsis) or autoimmune diseases (small and large vessel systemic vasculitis, rheumatoid arthritis). Four patients have also been studied before and after sterile acute injury of the myocardium (septal alcoholization). One hundred thirty-eight healthy donors were studied in parallel. Neutrophils with normal MPO content were 96% in controls, >92% in patients undergoing septal alcoholization, 91% in CSA patients, but only 35 and 30% in unstable angina and AMI (STEMI and NSTEMI) patients, compared to 80%, 75% and 2% of patients with giant cell arteritis, acute bone fracture and severe sepsis. In addition, in 32/33 STEMI and 9/21 NSTEMI patients respectively, 20% and 12% of neutrophils had complete MPO depletion during the first 4 hours after the onset of symptoms, a feature not observed in any other group of patients. MPO depletion was associated with platelet activation, indicated by P-selectin expression, activation and transactivation of leukocyte ?2-integrins and formation of platelet neutrophil and -monocyte aggregates. The injection of activated platelets in mice produced transient, P-selectin dependent, complete MPO depletion in about 50% of neutrophils. Conclusions ACS are characterized by intense neutrophil activation, like other systemic inflammatory syndromes. In the very early phase of acute myocardial infarction only a subpopulation of neutrophils is massively activated, possibly via platelet-P selectin interactions. This paroxysmal activation could contribute to occlusive thrombosis.

Maugeri, Norma; Rovere-Querini, Patrizia; Evangelista, Virgilio; Godino, Cosmo; Demetrio, Monica; Baldini, Mattia; Figini, Filippo; Coppi, Giovanni; Slavich, Massimo; Camera, Marina; Bartorelli, Antonio; Marenzi, Giancarlo; Campana, Lara; Baldissera, Elena; Sabbadini, Maria Grazia; Cianflone, Domenico; Tremoli, Elena; D'Angelo, Armando; Manfredi, Angelo A.; Maseri, Attilio

2012-01-01

233

Assessment of antibody-dependent respiratory burst activity from mouse neutrophils on Plasmodium yoelii malaria challenge outcome.  

PubMed

New tools are required to expedite the development of an effective vaccine against the blood-stage infection with the human malaria parasite Plasmodium falciparum. This work describes the assessment of the ADRB assay in a mouse model, characterizing the functional interaction between antimalarial serum antibodies and FcRs upon neutrophils. We describe a reproducible, antigen-specific assay, dependent on functional FcR signaling, and show that ADRB activity is induced equally by IgG1 and IgG2a isotypes and is modulated by blocking FcR function. However, following immunization of mice with the blood-stage vaccine candidate antigen MSP142, no measurable ADRB activity was induced against PEMS and neither was vaccine efficacy modulated against Plasmodium yoelii blood-stage challenge in ?(-/-) mice compared with WT mice. In contrast, following a primary, nonlethal P. yoelii parasite challenge, serum from vaccinated mice and nonimmunized controls showed anti-PEMS ADRB activity. Upon secondary challenge, nonimmunized ?(-/-) mice showed a reduced ability to control blood-stage parasitemia compared with immunized ?(-/-) mice; however, WT mice, depleted of their neutrophils, did not lose their ability to control infection. Thus, whereas neutrophil-induced ADRB against PEMS does not appear to play a role in protection against P. yoelii rodent malaria, induction of ADRB activity after challenge suggests that antigen targets of anti-PEMS ADRB activity remain to be established, as well as further supporting the observation that ADRB activity to P. falciparum arises following repeated natural exposure. PMID:24163420

Llewellyn, David; de Cassan, Simone C; Williams, Andrew R; Douglas, Alexander D; Forbes, Emily K; Adame-Gallegos, Jaime R; Shi, Jianguo; Pleass, Richard J; Draper, Simon J

2014-02-01

234

Hybrid Electric and Plug-in Hybrid Electric Vehicle Testing Activities  

SciTech Connect

The Advanced Vehicle Testing Activity (AVTA) conducts hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV) testing in order to provide benchmark data for technology modeling and research and development programs, and to be an independent source of test data for fleet managers and other early adaptors of advanced-technology vehicles. To date, the AVTA has completed baseline performance testing on 12 HEV models and accumulated 2.7 million fleet testing miles on 35 HEVs. The HEV baseline performance testing includes dynamometer and closed-track testing to document HEV performance in a controlled environment. During fleet testing, two of each HEV model accumulate 160,000 test miles within 36 months, during which maintenance and repair events and fuel use were recorded. Three models of PHEVs, from vehicle converters Energy CS and Hymotion and the original equipment manufacturer Renault, are currently in testing. The PHEV baseline performance testing includes 5 days of dynamometer testing with a minimum of 26 test drive cycles, including the Urban Dynamometer Driving Schedule, the Highway Fuel Economy Driving Schedule, and the US06 test cycle, in charge-depleting and charge-sustaining modes. The PHEV accelerated testing is conducted with dedicated drivers for 4,240 miles, over a series of 132 driving loops that range from 10 to 200 miles over various combinations of defined 10-mile urban and 10-mile highway loops, with 984 hours of vehicle charging. The AVTA is part of the U.S. Department of Energy’s FreedomCAR and Vehicle Technologies Program. These AVTA testing activities were conducted by the Idaho National Laboratory and Electric Transportation Applications, with dynamometer testing conducted at Argonne National Laboratory. This paper discusses the testing methods and results.

Donald Karner

2007-12-01

235

Characterizing Oscillatory Bursts in Single-Trial EEG Data  

NASA Technical Reports Server (NTRS)

Oscillatory bursts in numerous bands ranging from low (theta) to high frequencies (e.g., gamma) undoubtedly play an important role in cortical dynamics. Largely because of the inadequacy of existing analytic techniques. however, oscillatory bursts and their role in cortical processing remains poorly understood. To study oscillatory bursts effectively one must be able to isolate them and characterize them in the single trial. We describe a series of straightforward analysis techniques that produce useful indices of burst characteristics. First, stimulus-evoked responses are estimated using Differentially Variable Component Analysis (dVCA), and are subtracted from the single-trial. The single-trial characteristics of the evoked responses are stored to identify possible correlations with burst activity. Time-frequency (T-F), or wavelet, analyses are then applied to the single trial residuals. While T-F plots have been used in recent studies to identify and isolate bursts, we go further by fitting each burst in the T-F plot with a two-dimensional Gaussian. This provides a set of burst characteristics, such as, center time. burst duration, center frequency. frequency dispersion. and amplitude, all of which contribute to the accurate characterization of the individual burst. The burst phase can also be estimated. Burst characteristics can be quantified with several standard techniques (e.g.. histogramming and clustering), as well as Bayesian techniques (e.g., blocking) to allow a more parametric description analysis of the characteristics of oscillatory bursts, and the relationships of specific parameters to cortical excitability and stimulus integration.

Knuth, K. H.; Shah, A. S.; Lakatos, P.; Schroeder, C. E.

2004-01-01

236

Anoxic persistence of lumbar respiratory bursts and block of lumbar locomotion in newborn rat brainstem spinal cords.  

PubMed

The tolerance of breathing in neonates to oxygen depletion is reflected by persistence of inspiratory-related motor output during sustained anoxia in newborn rat brainstem preparations. It is not known whether lumbar motor networks innervating expiratory abdominal muscles are, in contrast, inhibited by anoxia similar to locomotor networks in neonatal mouse lumbar cords. To test this, we recorded inspiratory-related cervical/hypoglossal plus pre/postinspiratory lumbar/facial nerve activities and, sometimes simultaneously, locomotor rhythms in newborn rat brainstem-spinal cords. Chemical anoxia slowed 1 : 1-coupled cervical and lumbar respiratory rhythms and induced cervical burst doublets associated with depressed preinspiratory and augmented postinspiratory lumbar activities. Similarly, anoxia evoked repetitive hypoglossal bursts and shifted facial activity toward augmented postinspiratory bursting in medullas without spinal cord. Selective lumbar anoxia augmented pre/postinspiratory lumbar bursting without slowing the rhythm. This suggests a medullary origin of both anoxic inspiratory double bursts and preinspiratory depression, but a mixed medullary/lumbar origin of boosted postinspiratory lumbar activity. Lumbar respiratory rhythm is likely to be generated by the parafacial respiratory group expiratory centre as indicated by lack of normoxic and anoxic bursting following brainstem transection between the facial motonucleus and the more caudal pre-Bötzinger complex inspiratory centre. Opposed to sustained respiratory activities, anoxia reversibly abolished non-rhythmic spinal discharges and electrically or chemically evoked lumbar locomotor activities, followed by pronounced postanoxic spinal hyperexcitability. We hypothesize that (i) the anoxia tolerance of neonatal breathing includes pFRG-driven lumbar expiratory networks, (ii) the anoxic respiratory pattern transformation is due to disturbed inspiratory-expiratory centre interactions, and (iii) postanoxic lumbar hyperexcitability contributes to spasticity in cerebral palsy. PMID:17932145

Taccola, Giuliano; Secchia, Lucia; Ballanyi, Klaus

2007-12-01

237

An active approach for charge balancing in functional electrical stimulation.  

PubMed

Charge balancing is a major concern in functional electrical stimulation, since any excess charge accumulation over time leads to electrolysis with electrode dissolution and tissue destruction. This paper presents a new active approach for charge balancing using long-term offset regulation. Therefore, the electrode voltage is briefly monitored after each stimulation cycle and checked if it remains within a predefined voltage range. If not, an offset current is adjusted in order to track the biphasic current mismatch in upcoming stimulations. This technique is compared to a previously introduced active charge balancer as well as commonly used passive balancing techniques. Subsequently, the techniques are verified through experiments on a platinum black electrode in 0.9% saline solution. PMID:23853340

Sooksood, Kriangkrai; Stieglitz, Thomas; Ortmanns, Maurits

2010-06-01

238

[Electric activity of vagus nerve in rats according to satiety].  

PubMed

Vagus nerve as a part of brain-gut axis transmits peripheral information to the brain via vagovagal reflexes. Electric properties of the vagus are not exactly known. Analysis of electric changes in vagal nerves evoked by physiologic impulse such as stomach distention by food would facilitate applying better documented and therefore safer vagal neuromodulation. The aim of our study was analysis and interpretation of electric properties of the left vagus in vivo in fasted and satiated Wistar rats. Silver measuring electrodes connected to analog amplifier (A-M Systems 3000) were attached to the nerve in the neck region. The signal was filtered and probing by computer recording system (ADInstruments Power Lab) and additional analyses were performed using GNU Octave programme. Our resuts have shown that the higher amplitude the smaller number of counted impulses in the vagus was detected. This relationship was true only till the maximum level typical for each recording (about 15-20 dB). We note that observed inter spike interval can be approximated with log-normal distribution, and that its mu parameter is enough to characterize a particular recording. Satiated rats were characterized by higher number of spikes per second in the nerve than fasted ones (0.9 vs 0.26) indicating that food intake increased nervous activity 3-4 times comparing to fasted state. The outcomes encourage us to state that good quality characteristic of the left vagus nerve activity provides an effective tool for detection of peripheral signals which are transmitting via vagal afferents to the higher centres. Target vagal neuromodulation to obtain certain terapeutic effects may be possible. PMID:22891533

Zaraska, Krzysztof; Ziomber, Agata; Ciesielczyk, Katarzyna; Bugajski, Andrzej; Wi?niewska, Olga; Skowron, Beata; Juszczak, Kajetan; Zaraska, Wies?aw; Thor, Piotr J

2011-01-01

239

Controlling Bursting in Cortical Cultures with Closed-Loop Multi-Electrode Stimulation  

Microsoft Academic Search

One of the major modes of activity of high-density cultures of dissociated neurons is globally synchro- nized bursting. Unlike in vivo, neuronal ensembles in culture maintain activity patterns dominated by global bursts for the lifetime of the culture (up to two years). We hypothesize that persistence of bursting is due to a lack of input from other brain areas. To

Daniel A. Wagenaar; Radhika Madhavan; Jerome Pine; Steve M. Potter

2005-01-01

240

Electrically activated artificial muscles made with liquid crystal elastomers  

NASA Astrophysics Data System (ADS)

Composites of monodomain nematic liquid crystal elastomers and a conducting material distributed within their network are shown to exhibit large deformations, i.e. contraction, expansion, bending with strains of over 200 percent and appreciable force, by Joule heating through electrical activation. The electrical activation of the conducting material induces a rapid Joule heating in the sample leading to a nematic to isotropic phase transition where the elastomer of dimensions 32 mm X 7 mm X 0.4 mm contracted in less than a second. The cooling process, isotropic to nematic transition where the elastomer expands back to its original length, was slow and took 8 seconds. The material studied here is a highly novel liquid crystalline co-elastomer, invented and developed by Heino Finkelmann and co-workers at Albert-Ludwigs-Universitaet in Freiburg, Germany. The material is such that in which the mesogenic units are in both the side chains and the main chains of the elastomer. This co-elastomer was then mechanically loaded to induce a uniaxial network anisotropy before the cross-linking reaction was completed. These samples were then made into a composite with a conducting material such as dispersed silver particles or graphite fibers. The final samples was capable of undergoing more than 200 percent reversible strain in a few seconds.

Shahinpoor, Mohsen

2000-06-01

241

Topography of brain electrical activity: a bioengineering approach.  

PubMed

The aim of this work is to describe a system for the mono- and bi-dimensional analysis of brain electrical activity. The analysis was carried on either by visual inspection of mono- and bi-dimensional data, or by automatic feature extraction from the bidimensional data. Because of the importance of visual inspection for the analysis of experimental data, particular care was devoted to optimize the displayed data perceptually. For automatic screening of large amounts of data (and to allow long term studies of clinical records), statistical facilities were also provided. One purpose of the system was to develop image processing algorithms oriented toward biomedical images, that could be easily implemented on special purpose, low cost hardware, like VLSI or microcomputer arrays. This was possible because of the modularity of the larger part of bidimensional processing, such as interpolation and statistical analysis. Results of an experiment on Visual Evoked Response are presented, showing that through abidimensional analysis of the recorded data the resolution achievable in the localization of brain electrical activity can be increased to less than 1 cm. PMID:6669147

Sandini, G; Romano, P; Scotto, A; Traverso, G

1983-01-01

242

Magnetotail flow bursts: association to global magnetospheric circulation, relationship to ionospheric activity and direct evidence for localization  

Microsoft Academic Search

A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the UVI instrument on POLAR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between BBFs and ionospheric activity observed by UVI even when ground

V. Angelopoulos; T. D. Phan; D. E. Larson; F. S. Mozer; R. P. Lin; K. Tsuruda; H. Hayakawa; T. Mukai; S. Kokubun; T. Yamamoto; D. J. Williams; R. W. McEntire; R. P. Lepping; G. K. Parks; M. Brittnacher; G. Germany; J. Spann; H. J. Singer; K. Yumoto

1997-01-01

243

Antioxidant Activity of Calendula officinalis Extract: Inhibitory Effects on Chemiluminescence of Human Neutrophil Bursts and Electron Paramagnetic Resonance Spectroscopy  

Microsoft Academic Search

There is growing interest in natural chemical compounds from aromatic, spicy, medicinal and other plants with antioxidant properties in order to find new sources of compounds inactivating free radicals generated by metabolic pathways within body tissue and cells, mainly polymorphonuclear leukocytes (PMNs) whose overregulated recruitment and activation generate a large amount of reactive oxygen species (ROS) and reactive nitrogen species

Pier Carlo Braga; Monica Dal Sasso; Maria Culici; Alessandra Spallino; Mario Falchi; Aldo Bertelli; Roberto Morelli; Roberto Lo Scalzo

2009-01-01

244

An Assessment of the Respiratory Burst and Bactericidal Activity of Alveolar Macrophages From Adult and Senescent Mice  

Microsoft Academic Search

To assess the effects of advanced age on the nonspecific antimicrobial activity of resident alveolar macrophages (AM), superoxide anion (02) release and the phagocytic and bactericidal capacIty of cells from three genetically distinct murine strains were evaluated. In Initial experiments, resident AM, obtained by bronchoalveolar lavage of pathogen-free adult female CD-i mice and studied in suspension, were found to produce

Anthony L. Esposito; Carolyn A. Clark; William J. Poirier

245

Observed Contemporaneous Electric-Field Pulses and X-ray Bursts in a Thunderstorm in Relation to Charge Distribution, Lightning Channels, and CG Flash Occurrence  

Microsoft Academic Search

We present data from contemporaneous observations of X-rays and electric-field changes made by means of balloon-borne instruments deployed in a thunderstorm on June 17, 2004 as part of the TELEX 2004 field program in central Oklahoma. The purpose of our observations was to provide data suitable for tests of hypotheses for runaway electron processes in thunderstorms. Our measurements show X-ray

W. H. Beasley; K. B. Eack; R. A. Roussel-Dupre; E. C. Bruning; W. D. Rust; D. R. Macgorman

2004-01-01

246

Recent Electric Propulsion Development Activities for NASA Science Missions  

NASA Technical Reports Server (NTRS)

(The primary source of electric propulsion development throughout NASA is managed by the In-Space Propulsion Technology Project at the NASA Glenn Research Center for the Science Mission Directorate. The objective of the Electric Propulsion project area is to develop near-term electric propulsion technology to enhance or enable science missions while minimizing risk and cost to the end user. Major hardware tasks include developing NASA s Evolutionary Xenon Thruster (NEXT), developing a long-life High Voltage Hall Accelerator (HIVHAC), developing an advanced feed system, and developing cross-platform components. The objective of the NEXT task is to advance next generation ion propulsion technology readiness. The baseline NEXT system consists of a high-performance, 7-kW ion thruster; a high-efficiency, 7-kW power processor unit (PPU); a highly flexible advanced xenon propellant management system (PMS); a lightweight engine gimbal; and key elements of a digital control interface unit (DCIU) including software algorithms. This design approach was selected to provide future NASA science missions with the greatest value in mission performance benefit at a low total development cost. The objective of the HIVHAC task is to advance the Hall thruster technology readiness for science mission applications. The task seeks to increase specific impulse, throttle-ability and lifetime to make Hall propulsion systems applicable to deep space science missions. The primary application focus for the resulting Hall propulsion system would be cost-capped missions, such as competitively selected, Discovery-class missions. The objective of the advanced xenon feed system task is to demonstrate novel manufacturing techniques that will significantly reduce mass, volume, and footprint size of xenon feed systems over conventional feed systems. This task has focused on the development of a flow control module, which consists of a three-channel flow system based on a piezo-electrically actuated valve concept, as well as a pressure control module, which will regulate pressure from the propellant tank. Cross-platform component standardization and simplification are being investigated through the Standard Architecture task to reduce first user costs for implementing electric propulsion systems. Progress on current hardware development, recent test activities and future plans are discussed.

Pencil, Eric J.

2009-01-01

247

Paraventricular and supraoptic bursting oxytocin cells in rat are locally regulated by oxytocin and functionally related.  

PubMed Central

1. Oxytocin was pressure injected through a glass micropipette into a supraoptic (SON) or paraventricular nucleus (PVN) while recording the electrical activities of oxytocin cells in a contralateral nucleus, to see whether oxytocin acts locally in the magnocellular nuclei to control their bursting activity and whether the oxytocin cells of the four magnocellular nuclei were functionally interconnected during suckling. To test the rapidity of these relations, similar intranuclear injections were realized with acetylcholine, known to rapidly increase the background activity of oxytocin cells. The effects of intranuclear injections of oxytocin and acetylcholine were tested before and after interhemisphere sections of various dimensions. 2. Injecting oxytocin (1 ng in 100 nl) into a magnocellular nucleus (5 times into the PVN and 15 times into the SON) facilitated the occurrence and increased the amplitude of bursts of the oxytocin cells in both the contralateral PVN and SON. This facilitatory effect was similar to that induced by intraventricular injection of the same dose of oxytocin, though slightly delayed and lower. 3. Injecting acetylcholine (0.6 microgram in 100 nl) into the SON (7 times) induced a rapid and sustained increase in the background activity of oxytocin cells in both the contralateral PVN (2 times) and SON (5 times) within the same delay (less than 15 s). This excitatory effect was similar to that induced by an intraventricular injection of 5 micrograms acetylcholine. The effects on bursting activity were not considered in this study. 4. Neither the injections of oxytocin or acetylcholine outside but near the magnocellular nuclei (200-500 microns), nor the intranuclear injection of 100-200 nl of cerebrospinal fluid-like medium, modified the background activity, the frequency and amplitude of bursts of the oxytocin cells in the nucleus contralateral to the injection site. 5. After interhemisphere sections most oxytocin cells were silent, bursts occurred in an erratic manner, and their amplitude was attenuated and irregular (more than the 20% variation normally recorded in non-operated rats). Moreover, the amplitudes of successive bursts of pair-recorded supraoptic-supraoptic (SO-SO) oxytocin cells, highly related in control conditions (correlation coefficient, r = 0.68 to 0.98) were no longer correlated after interhemisphere section (r = 0.24 to -0.61), but all bursts remained synchronized.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 1

Moos, F; Richard, P

1989-01-01

248

Chandra Observations of the Bursting X-Ray Transient SAX J1747.0-2853 during Low-Level Accretion Activity  

NASA Astrophysics Data System (ADS)

We present Chandra/ACIS observations of the bursting X-ray transient SAX J1747.0-2853 performed on 2001 July 18. We detected a bright source at the position of R.A. = 17h47m02.60s and decl. = -28°52'58.9" (J2000.0, with a 1 ? error of ~0.7"), consistent with the BeppoSAX and ASCA positions of SAX J1747.0-2853 and with the Ariel V position of the transient GX +0.2-0.2, which was active during the 1970s. The 0.5-10 keV luminosity of the source during our observations was ~3×1035 ergs s-1 (assuming a distance of 9 kpc), demonstrating that the source was in a low-level accretion state. We also report on the long-term light curve of the source as observed with the all-sky monitor on board the Rossi X-Ray Timing Explorer. After the initial 1998 outburst, two more outbursts (in 2000 and 2001) were detected with peak luminosities about 2 orders of magnitude larger than our Chandra luminosity. Our Chandra observation falls between those two outbursts, making the outburst history for SAX J1747.0-2853 complex. Those bright 2000 and 2001 outbursts, combined with the likely extended period of low-level activity between those outbursts, strongly suggest that the classification of SAX J1747.0-2853 as a faint X-ray transient was premature. It might be possible that the other faint X-ray transients can also exhibit bright, extended outbursts that would eliminate the need for a separate subclass of X-ray transients. We discuss our results also in the context of the behavior of X-ray binaries accreting at low levels with luminosities around 1035 ergs s-1, a poorly studied accretion rate regime.

Wijnands, Rudy; Miller, Jon M.; Wang, Q. Daniel

2002-11-01

249

Electrical impedance tomography system based on active electrodes.  

PubMed

Electrical impedance tomography (EIT) can image the distribution of ventilated lung tissue, and is thus a promising technology to help monitor patient breathing to help selection of mechanical ventilation parameters. Two key difficulties in EIT instrumentation make such monitoring difficult: (1) EIT data quality depends on good electrode contact and is sensitive to changes in contact quality, and (2) EIT electrodes are difficult and time consuming to place on patients. This paper presents the design and initial tests of an active electrode-based system to address these difficulties. Our active electrode EIT system incorporates an active electrode belt, a central voltage-driven current source, central analog to digital converters and digital to analog converters, a central FPGA-based demodulator and controller. The electrode belt is designed incorporating 32 active electrodes, each of which contains the electronic amplifiers, switches and associated logic. Tests show stable device performance with a convenient ease of use and good imaging ability in volunteer tests. PMID:22531225

Gaggero, Pascal Olivier; Adler, Andy; Brunner, Josef; Seitz, Peter

2012-05-01

250

Study On Burst Location Technology under Steady-state in Water Distribution System  

NASA Astrophysics Data System (ADS)

According to the characteristics of hydraulic information under the state of burst in water distribution system, to get the correlation of monitoring values and burst location and locate the position of burst on time by mathematical fitting. This method can effectively make use of the information of SCADA in water distribution system to active locating burst position. A new idea of burst location in water distribution systems to shorten the burst time, reduce the impact on urban water supply, economic losses and waste of water resources.

Liu, Xianpin; Li, Shuping; Wang, Shaowei; He, Fang; He, Zhixun; Cao, Guodong

2010-11-01

251

A Burst to See  

NASA Astrophysics Data System (ADS)

On 19 March, Nature was particularly generous and provided astronomers with the wealth of four gamma-ray bursts on the same day. But that was not all: one of them is the most luminous object ever observed in the Universe. Despite being located in a distant galaxy, billions of light years away, it was so bright that it could have been seen, for a brief while, with the unaided eye. ESO PR Photo 08a/08 ESO PR Photo 08a/08 The REM Telescope and TORTORA Camera Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous quantity of energy in this short time making them the most powerful events since the Big Bang. It is now widely accepted that the majority of the gamma-ray bursts signal the explosion of very massive, highly evolved stars that collapse into black holes. Gamma-ray bursts, which are invisible to our eyes, are discovered by telescopes in space. After releasing their intense burst of high-energy radiation, they become detectable for a short while in the optical and in the near-infrared. This 'afterglow' fades very rapidly, making detailed analysis possible for only a few hours after the gamma-ray detection. This analysis is important in particular in order to determine the GRB's distance and, hence, intrinsic brightness. The gamma-ray burst GRB 080319B was detected by the NASA/STFC/ASI Swift satellite. "It was so bright that it almost blinded the Swift instruments for a while," says Guido Chincarini, Italian principal investigator of the mission. A bright optical counterpart was soon identified in the Boötes Constellation (the "Bear Driver" or "Herdsman"). A host of ground-based telescopes reacted promptly to study this new object in the sky. In particular, the optical emission was detected by a few wide-field cameras on telescopes that constantly monitor a large fraction of the sky, including the TORTORA camera in symbiosis with the 0.6-m REM telescope located at La Silla, able to record the event with unprecedented temporal resolution.. "These very early detections (just seconds after the beginning of the burst) showed the object to be so bright that it would have been visible just with the unaided eye," says Stefano Covino, from the REM team. "It was astonishing to see how rapidly the source varied during the observations," adds Sergey Karpov, of the TORTORA team. Astronomers use the so-called magnitude scale, an inverse scale where fainter objects have larger magnitudes. In dark sites, the most acute of human eyes can distinguish sources as faint as magnitude 6. GRB 080319B was slightly brighter than this limit, although for just less than a minute. The 8.2-metre ESO Very Large Telescope also reacted to the gamma-ray burst, thanks to a special procedure known as the rapid-response mode (see ESO 17/07), which allows automatic observations with no human intervention. The high-resolution spectrograph UVES could collect exquisite data starting only 10 minutes after the burst, following requests by Fabrizio Fiore and his team. Another team then used also UVES to determine the distance of the burst. "Despite its stunning brightness, the burst exploded in a galaxy 7.5 billion light years away," says Paul Vreeswijk, who led the second team. "It was therefore not only apparently bright, but also intrinsically very luminous. Indeed, it reached the brightest optical luminosity ever recorded for any astronomical object. For comparison, should the burst have exploded in our Galaxy, it would have lit up the night sky for several minutes as if it were daytime."

2008-04-01

252

Theta-burst stimulation of hippocampal slices induces network-level calcium oscillations and activates analogous gene transcription to spatial learning.  

PubMed

Over four decades ago, it was discovered that high-frequency stimulation of the dentate gyrus induces long-term potentiation (LTP) of synaptic transmission. LTP is believed to underlie how we process and code external stimuli before converting it to salient information that we store as 'memories'. It has been shown that rats performing spatial learning tasks display theta-frequency (3-12 Hz) hippocampal neural activity. Moreover, administering theta-burst stimulation (TBS) to hippocampal slices can induce LTP. TBS triggers a sustained rise in intracellular calcium [Ca2+]i in neurons leading to new protein synthesis important for LTP maintenance. In this study, we measured TBS-induced [Ca2+]i oscillations in thousands of cells at increasing distances from the source of stimulation. Following TBS, a calcium wave propagates radially with an average speed of 5.2 µm/s and triggers multiple and regular [Ca2+]i oscillations in the hippocampus. Interestingly, the number and frequency of [Ca2+]i fluctuations post-TBS increased with respect to distance from the electrode. During the post-tetanic phase, 18% of cells exhibited 3 peaks in [Ca2+]i with a frequency of 17 mHz, whereas 2.3% of cells distributed further from the electrode displayed 8 [Ca2+]i oscillations at 33 mHz. We suggest that these observed [Ca2+]i oscillations could lead to activation of transcription factors involved in synaptic plasticity. In particular, the transcription factor, NF-?B, has been implicated in memory formation and is up-regulated after LTP induction. We measured increased activation of NF-?B 30 min post-TBS in CA1 pyramidal cells and also observed similar temporal up-regulation of NF-?B levels in CA1 neurons following water maze training in rats. Therefore, TBS of hippocampal slice cultures in vitro can mimic the cell type-specific up-regulations in activated NF-?B following spatial learning in vivo. This indicates that TBS may induce similar transcriptional changes to spatial learning and that TBS-triggered [Ca2+]i oscillations could activate memory-associated gene expression. PMID:24950243

Sheridan, Graham K; Moeendarbary, Emad; Pickering, Mark; O'Connor, John J; Murphy, Keith J

2014-01-01

253

Theta-Burst Stimulation of Hippocampal Slices Induces Network-Level Calcium Oscillations and Activates Analogous Gene Transcription to Spatial Learning  

PubMed Central

Over four decades ago, it was discovered that high-frequency stimulation of the dentate gyrus induces long-term potentiation (LTP) of synaptic transmission. LTP is believed to underlie how we process and code external stimuli before converting it to salient information that we store as 'memories'. It has been shown that rats performing spatial learning tasks display theta-frequency (3–12 Hz) hippocampal neural activity. Moreover, administering theta-burst stimulation (TBS) to hippocampal slices can induce LTP. TBS triggers a sustained rise in intracellular calcium [Ca2+]i in neurons leading to new protein synthesis important for LTP maintenance. In this study, we measured TBS-induced [Ca2+]i oscillations in thousands of cells at increasing distances from the source of stimulation. Following TBS, a calcium wave propagates radially with an average speed of 5.2 µm/s and triggers multiple and regular [Ca2+]i oscillations in the hippocampus. Interestingly, the number and frequency of [Ca2+]i fluctuations post-TBS increased with respect to distance from the electrode. During the post-tetanic phase, 18% of cells exhibited 3 peaks in [Ca2+]i with a frequency of 17 mHz, whereas 2.3% of cells distributed further from the electrode displayed 8 [Ca2+]i oscillations at 33 mHz. We suggest that these observed [Ca2+]i oscillations could lead to activation of transcription factors involved in synaptic plasticity. In particular, the transcription factor, NF-?B, has been implicated in memory formation and is up-regulated after LTP induction. We measured increased activation of NF-?B 30 min post-TBS in CA1 pyramidal cells and also observed similar temporal up-regulation of NF-?B levels in CA1 neurons following water maze training in rats. Therefore, TBS of hippocampal slice cultures in vitro can mimic the cell type-specific up-regulations in activated NF-?B following spatial learning in vivo. This indicates that TBS may induce similar transcriptional changes to spatial learning and that TBS-triggered [Ca2+]i oscillations could activate memory-associated gene expression.

O'Connor, John J.; Murphy, Keith J.

2014-01-01

254

A closed-loop anesthetic delivery system for real-time control of burst suppression  

NASA Astrophysics Data System (ADS)

Objective. There is growing interest in using closed-loop anesthetic delivery (CLAD) systems to automate control of brain states (sedation, unconsciousness and antinociception) in patients receiving anesthesia care. The accuracy and reliability of these systems can be improved by using as control signals electroencephalogram (EEG) markers for which the neurophysiological links to the anesthetic-induced brain states are well established. Burst suppression, in which bursts of electrical activity alternate with periods of quiescence or suppression, is a well-known, readily discernible EEG marker of profound brain inactivation and unconsciousness. This pattern is commonly maintained when anesthetics are administered to produce a medically-induced coma for cerebral protection in patients suffering from brain injuries or to arrest brain activity in patients having uncontrollable seizures. Although the coma may be required for several hours or days, drug infusion rates are managed inefficiently by manual adjustment. Our objective is to design a CLAD system for burst suppression control to automate management of medically-induced coma. Approach. We establish a CLAD system to control burst suppression consisting of: a two-dimensional linear system model relating the anesthetic brain level to the EEG dynamics; a new control signal, the burst suppression probability (BSP) defining the instantaneous probability of suppression; the BSP filter, a state-space algorithm to estimate the BSP from EEG recordings; a proportional-integral controller; and a system identification procedure to estimate the model and controller parameters. Main results. We demonstrate reliable performance of our system in simulation studies of burst suppression control using both propofol and etomidate in rodent experiments based on Vijn and Sneyd, and in human experiments based on the Schnider pharmacokinetic model for propofol. Using propofol, we further demonstrate that our control system reliably tracks changing target levels of burst suppression in simulated human subjects across different epidemiological profiles. Significance. Our results give new insights into CLAD system design and suggest a control-theory framework to automate second-to-second control of burst suppression for management of medically-induced coma.

Liberman, Max Y.; Ching, ShiNung; Chemali, Jessica; Brown, Emery N.

2013-08-01

255

Dynamin phosphorylation controls optimization of endocytosis for brief action potential bursts  

PubMed Central

Modulation of synaptic vesicle retrieval is considered to be potentially important in steady-state synaptic performance. Here we show that at physiological temperature endocytosis kinetics at hippocampal and cortical nerve terminals show a bi-phasic dependence on electrical activity. Endocytosis accelerates for the first 15–25 APs during bursts of action potential firing, after which it slows with increasing burst length creating an optimum stimulus for this kinetic parameter. We show that activity-dependent acceleration is only prominent at physiological temperature and that the mechanism of this modulation is based on the dephosphorylation of dynamin 1. Nerve terminals in which dynamin 1 and 3 have been replaced with dynamin 1 harboring dephospho- or phospho-mimetic mutations in the proline-rich domain eliminate the acceleration phase by either setting endocytosis at an accelerated state or a decelerated state, respectively. DOI: http://dx.doi.org/10.7554/eLife.00845.001

Armbruster, Moritz; Messa, Mirko; Ferguson, Shawn M; De Camilli, Pietro; Ryan, Timothy A

2013-01-01

256

The Glast Burst Monitor  

NASA Technical Reports Server (NTRS)

The Gamma-Ray Large Area Space Telescope (GLAST) will include a secondary instrument to augment the observatory's capabilities for GRB studies. The GLAST Burst Monitor (GBK is a collaboration between Marshall Space Flight Center, the University of Huntsville, Alabama, and the Max Plank Institute for Extraterrestrial Physics. The purpose of the GBM is to extend energy coverage below the main instrument's lower limit of about 20 MeV, and to provide an on-board burst trigger and approximate location. The instrument consists of twelve NaI detectors and two BGO detectors. This combination provides energy coverage from a few keV up to about 30 MeV.

Meegan, Charles

2000-01-01

257

Modeling the electrical field created by mass neural activity.  

PubMed

Gamma oscillations of large scale electrical activity are used in electrophysiological studies as markers for neural activity and functional processes in the cortex, yet the nature of this mass neural phenomenon and its relation to the evoked response potentials (ERP) are still not well understood. Many studies associated the gamma oscillations with oscillators around the 40 Hz frequency, yet recent studies have shown that gamma frequencies may be part of a broadband phenomenon ranging from 30 Hz up to 250 Hz. In this study we have examined the possibility that a simple model, based on available neurophysiological parameters, involving an increase in asynchronous (Poisson distributed) neural firing may be sufficient to generate the observed gamma power increases. Our simulation shows a roughly linear increase in gamma power as a function of the aggregated firing rate of the neural population, while the influence of the synchronization level within the neurons on the gamma power is limited. Our model supports the viewpoint that the broadband gamma response is mainly driven by the summed, asynchronous, activity of the neural population. We show that the time frequency spectrogram of the stimulus response can be reconstructed by combining two different phenomena-the broadband gamma power increase due to local processing and the more spatially distributed event related desynchronization (ERD). Our model thus raises the possibility that the broadband gamma response is closely linked to the aggregate population firing rate of the recorded neurons. PMID:23391515

Privman, Eran; Malach, Rafael; Yeshurun, Yehezkel

2013-04-01

258

Critical role of the carboxyl terminus of proline-rich tyrosine kinase (Pyk2) in the activation of human neutrophils by tumor necrosis factor: separation of signals for the respiratory burst and degranulation.  

PubMed

Transduction of Tat-tagged fusion proteins confirmed a hypothesis based on pharmacologic inhibitors (Fuortes, M., M. Melchior, H. Han, G.J. Lyon, and C. Nathan. 1999. J. Clin. Invest. 104:327-335) that proline-rich tyrosine kinase (Pyk2) plays a critical role in the activation of adherent human neutrophils, and allowed an analysis of individual Pyk2 domains not possible with chemical inhibitors. Acting as a dominant negative, the COOH terminus of Pyk2 fused to a Tat peptide (Tat-CT), but not other regions of Pyk2, specifically inhibited the respiratory burst of cells responding to tumor necrosis factor (TNF), Salmonella, or Listeria, while sparing responses induced by phorbol ester. Tat-CT suppressed TNF-triggered cell spreading and the phosphorylation of endogenous Pyk2 and the associated tyrosine kinase Syk without blocking the ability of neutrophils to degranulate and kill bacteria. Thus, separate signals control the respiratory burst and degranulation, and a normal rate of killing of some bacteria can be sustained by granule products in conjunction with a minimal residual respiratory burst. Inhibition of select inflammatory functions without impairment of antibacterial activity may commend the Pyk2 pathway as a potential target for antiinflammatory therapy. PMID:12515814

Han, Hyunsil; Fuortes, Michele; Nathan, Carl

2003-01-01

259

Sodium flux and electrical activity of arterial smooth muscle  

PubMed Central

1. The intracellular concentration and transmembrane flux of Na in smooth muscle cells of sheep carotid arteries were measured by identifying a fraction of tissue Na whose efflux was markedly sensitive to removal of external Ca. This allowed intracellular Na to be distinguished from extracellular bound Na exchanging with a similar time constant. 2. When the arteries were in solution containing Na 148 mM and Ca 2·5 mM the mean intracellular Na concentration was 7·3 m-mole/kg cell water and the mean transmembrane flux of Na was 0·18 p-mole cm-2 sec-1, both values being much lower than reported values for intestinal smooth muscle. 3. During electrical activity induced by Ca deprivation the influx of Na increased to 3·2 p-mole cm-2 sec-1; a 50% reduction in Na concentration stopped electrical activity and reduced influx by more than 50%, and the excess Na influx per action potential was calculated to be at least 1·0-1·5 p-mole cm-2. 4. Arteries in physiological saline (Ca 2·5 mM) contained 3·48 ?mole Ca/g, much of which was bound extracellularly; in Ca-free saline 1·39 ?mole Ca/g left the tissue within 3 min, showing that extracellular dissolved Ca diffused freely out of the tissue. 5. The results provide further evidence that Na is the principal ion carrying the depolarizing current of action potentials in this smooth muscle.

Keatinge, W. R.

1968-01-01

260

MID-INFRARED PROPERTIES OF THE SWIFT BURST ALERT TELESCOPE ACTIVE GALACTIC NUCLEI SAMPLE OF THE LOCAL UNIVERSE. I. EMISSION-LINE DIAGNOSTICS  

SciTech Connect

We compare mid-infrared emission-line properties from high-resolution Spitzer spectra of a hard X-ray (14-195 keV) selected sample of nearby (z < 0.05) active galactic nuclei (AGNs) detected by the Burst Alert Telescope (BAT) aboard Swift. The luminosity distribution for the mid-infrared emission lines, [O IV] 25.89 {mu}m, [Ne II] 12.81 {mu}m, [Ne III] 15.56 {mu}m, and [Ne V] 14.32/24.32 {mu}m, and hard X-ray continuum show no differences between Seyfert 1 and Seyfert 2 populations; however, six newly discovered BAT AGNs are under-luminous in [O IV], most likely the result of dust extinction in the host galaxy. The overall tightness of the mid-infrared correlations and BAT fluxes and luminosities suggests that the emission lines primarily arise in gas ionized by the AGNs. We also compare the mid-infrared emission lines in the BAT AGNs with those from published studies of ULIRGs, Palomar-Green quasars, star-forming galaxies, and LINERs. We find that the BAT AGN sample falls into a distinctive region when comparing the [Ne III]/[Ne II] and the [O IV]/[Ne III] ratios. These line ratios are lower in sources that have been previously classified in the mid-infrared/optical as AGNs than those found for the BAT AGNs, suggesting that, in our X-ray selected sample, the AGNs represent the main contribution to the observed line emission. These ratios represent a new emission line diagnostic for distinguishing between AGNs and star-forming galaxies.

Weaver, K. A.; Melendez, M.; Mushotzky, R. F.; Kraemer, S.; Engle, K.; Malumuth, E.; Tueller, J.; Markwardt, C. [NASA Goddard Space Flight Center, Greenbelt, MD, 20771 (United States); Berghea, C. T.; Dudik, R. P. [U.S. Naval Observatory, Washington, DC 20392 (United States); Winter, L. M. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0440 (United States); Armus, L. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)

2010-06-20

261

RADIATION MECHANISM AND JET COMPOSITION OF GAMMA-RAY BURSTS AND GeV-TeV-SELECTED RADIO-LOUD ACTIVE GALACTIC NUCLEI  

SciTech Connect

Gamma-ray bursts (GRBs) and GeV-TeV-selected radio-loud active galactic nuclei (AGNs) are compared based on our systematic modeling of the observed spectral energy distributions of a sample of AGNs with a single-zone leptonic model. We show that the correlation between the jet power (P{sub jet}) and the prompt gamma-ray luminosity (L{sub jet}) of GRBs is consistent, within the uncertainties, with the correlation between jet power and the synchrotron peak luminosity (L{sub s,jet}) of flat spectrum radio quasars (FSRQs). Their radiation efficiencies ({epsilon}) are also comparable (>10% for most sources), which increase with the bolometric jet luminosity (L{sub bol,jet}) for FSRQs and with the L{sub jet} for GRBs with similar power-law indices. BL Lac objects (BL Lacs) do not follow the P{sub jet}-L{sub s,jet} relation of FSRQs. They have lower {epsilon} and L{sub bol,jet} values than FSRQs, and a tentative L{sub bol,jet}-{epsilon} relation is also found, with a power-law index different from that of the FSRQs. The magnetization parameters ({sigma}) of FSRQs are on average larger than that of BL Lacs. They are anti-correlated with {epsilon} for the FSRQs, but positively correlated with {epsilon} for the BL Lacs. GeV narrow-line Seyfert 1 galaxies potentially share similar properties with FSRQs. Based on the analogy between GRBs and FSRQs, we suggest that the prompt gamma-ray emission of GRBs is likely produced by the synchrotron process in a magnetized jet with high radiation efficiency, similar to FSRQs. The jets of BL Lacs, on the other hand, are less efficient and are likely more matter-dominated.

Zhang Jin; Lu Ye; Zhang Shuangnan [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Liang Enwei; Sun Xiaona [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China); Zhang Bing, E-mail: lew@gxu.edu.cn [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

2013-09-01

262

Electricity  

NSDL National Science Digital Library

William J. Beaty, an Electrical Engineer at the University of Washington, has posted this website about electricity. He offers a simple answer to the question, What Is "Electricity?," identifies twenty misconceptions he has found to be barriers to understanding electricity, and then proceeds to explain various aspects of electricity. Beaty's debunking articles address common misconceptions about circuitry, doorknob sparks, voltage, and more.

Beaty, William J.

263

The effects of high-frequency oscillations in hippocampal electrical activities on the classification of epileptiform events using artificial neural networks.  

PubMed

The existence of hippocampal high-frequency electrical activities (greater than 100 Hz) during the progression of seizure episodes in both human and animal experimental models of epilepsy has been well documented (Bragin A, Engel J, Wilson C L, Fried I and Buzsáki G 1999 Hippocampus 9 137-42; Khosravani H, Pinnegar C R, Mitchell J R, Bardakjian B L, Federico P and Carlen P L 2005 Epilepsia 46 1-10). However, this information has not been studied between successive seizure episodes or utilized in the application of seizure classification. In this study, we examine the dynamical changes of an in vitro low Mg2+ rat hippocampal slice model of epilepsy at different frequency bands using wavelet transforms and artificial neural networks. By dividing the time-frequency spectrum of each seizure-like event (SLE) into frequency bins, we can analyze their burst-to-burst variations within individual SLEs as well as between successive SLE episodes. Wavelet energy and wavelet entropy are estimated for intracellular and extracellular electrical recordings using sufficiently high sampling rates (10 kHz). We demonstrate that the activities of high-frequency oscillations in the 100-400 Hz range increase as the slice approaches SLE onsets and in later episodes of SLEs. Utilizing the time-dependent relationship between different frequency bands, we can achieve frequency-dependent state classification. We demonstrate that activities in the frequency range 100-400 Hz are critical for the accurate classification of the different states of electrographic seizure-like episodes (containing interictal, preictal and ictal states) in brain slices undergoing recurrent spontaneous SLEs. While preictal activities can be classified with an average accuracy of 77.4 +/- 6.7% utilizing the frequency spectrum in the range 0-400 Hz, we can also achieve a similar level of accuracy by using a nonlinear relationship between 100-400 Hz and <4 Hz frequency bands only. PMID:16510938

Chiu, Alan W L; Jahromi, Shokrollah S; Khosravani, Houman; Carlen, Peter L; Bardakjian, Berj L

2006-03-01

264

The effects of high-frequency oscillations in hippocampal electrical activities on the classification of epileptiform events using artificial neural networks  

NASA Astrophysics Data System (ADS)

The existence of hippocampal high-frequency electrical activities (greater than 100 Hz) during the progression of seizure episodes in both human and animal experimental models of epilepsy has been well documented (Bragin A, Engel J, Wilson C L, Fried I and Buzsáki G 1999 Hippocampus 9 137-42 Khosravani H, Pinnegar C R, Mitchell J R, Bardakjian B L, Federico P and Carlen P L 2005 Epilepsia 46 1-10). However, this information has not been studied between successive seizure episodes or utilized in the application of seizure classification. In this study, we examine the dynamical changes of an in vitro low Mg2+ rat hippocampal slice model of epilepsy at different frequency bands using wavelet transforms and artificial neural networks. By dividing the time-frequency spectrum of each seizure-like event (SLE) into frequency bins, we can analyze their burst-to-burst variations within individual SLEs as well as between successive SLE episodes. Wavelet energy and wavelet entropy are estimated for intracellular and extracellular electrical recordings using sufficiently high sampling rates (10 kHz). We demonstrate that the activities of high-frequency oscillations in the 100-400 Hz range increase as the slice approaches SLE onsets and in later episodes of SLEs. Utilizing the time-dependent relationship between different frequency bands, we can achieve frequency-dependent state classification. We demonstrate that activities in the frequency range 100-400 Hz are critical for the accurate classification of the different states of electrographic seizure-like episodes (containing interictal, preictal and ictal states) in brain slices undergoing recurrent spontaneous SLEs. While preictal activities can be classified with an average accuracy of 77.4 ± 6.7% utilizing the frequency spectrum in the range 0-400 Hz, we can also achieve a similar level of accuracy by using a nonlinear relationship between 100-400 Hz and <4 Hz frequency bands only.

Chiu, Alan W. L.; Jahromi, Shokrollah S.; Khosravani, Houman; Carlen, Peter L.; Bardakjian, Berj L.

2006-03-01

265

Electrical basis of excitation and inhibition of human colonic smooth muscle.  

PubMed

Excitation and inhibition of electrical activities of the musculature of the human colon and the consequent changes in motor activities were studied in vitro. The mechanisms of excitation and inhibition were very different from those of the small intestine and colons from animal models. Carbachol increased spiking activity and the frequency of bursts of electrical oscillations in longitudinal muscle. Each longitudinal muscle contraction was related to a burst of electrical oscillations. Carbachol induced one of three patterns of activity in circular muscle: (a) continuous electrical oscillatory activity (14-24 cpm) with spikes, associated with tonic contraction; (b) bursts of such electrical activity, associated with broad phasic contractions; or (c) prolonged membrane potential depolarizations (frequency 1-3 cpm) with superimposed intense spiking activity, associated with phasic contractions. Isoproterenol inhibited all electrical and mechanical activities in both muscle layers. These results may provide a better understanding of (a) the origins of the variable patterns of electrical and motor activities and (b) the relationship between electrical and mechanical activities of the human colon musculature. PMID:3956938

Huizinga, J D; Stern, H S; Chow, E; Diamant, N E; el-Sharkawy, T Y

1986-05-01

266

Electrical potentials associated with Microbial Activity in a Winogradsky Column  

NASA Astrophysics Data System (ADS)

: Electrical Potential (EP) measurements using Ag-AgCl electrodes have been conducted in a 1-D column containing a complex of sulphate-reducing microbial communities. The Winogradksky column design, typically used to study the microbial diversity of photoautotrophic anaerobes, represents in the laboratory a model biogeochemical soil-water interface. Once the bacterial communities in the column begin to grow dissolved oxygen content decreases downwards; an H2S gradient, produced by Sulphate Reducing Bacteria (SRB) develops in the anaerobic sediment at the base of the column, increases. These two gradients, acting in opposite directions, then create a range of habitats for a variety of microorganisms. The results presented here show EP data monitored over a period of 10 months at several points in the column during the establishment and evolution of the microbial niches, along with certain dissolved gases (O2, CO2, and H2S). The interpretation of EP data and analysis of gases produced in the column due biogeochemical activities show that it is possible to monitor and identify several states of microbial activity that could be inferred as a series of microbially mediated electron acceptors. Thus, overall, the EP observations show that Ag-AgCl electrodes have potential to be used to monitor the activities of biofilm growth in complex environments. Although the EP response may not reflect necessarily the 'true' geophysical response of microbial activity but a galvanic reaction mediated by microbes or caused by the by-products produced during biofilm growth, nevertheless EP still has its uses in the non-invasive monitoring of environmental and microbial systems coupled with other geophysical techniques.

Singh, K.; Doherty, R.; Ntarlagiannis, D.; Elliot, T.

2007-12-01

267

Various Seizure Activities Following gamma-Hydroxybutyrate.  

National Technical Information Service (NTIS)

The studies demonstrate that 0.7-1.0 gm/kg of gamma-hydroxybutyrate (GHB) induces 2 1/2 c/s electrical epileptiform activity which progresses to spiking with short polyphasic bursts followed by electrical silence. Spontaneous and induced myoclonic jerks a...

W. D. Winters C. E. Spooner

1965-01-01

268

Gamma Ray Bursts.  

National Technical Information Service (NTIS)

Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day, last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pion...

N. Gehrels P. Meszaros

2012-01-01

269

The Subthalamic Nucleus becomes a Generator of Bursts in the Dopamine-Depleted State. Its High Frequency Stimulation Dramatically Weakens Transmission to the Globus Pallidus  

PubMed Central

Excessive burst firing in the dopamine-depleted basal ganglia correlates with severe motor symptoms of Parkinson's disease that are attenuated by high frequency electrical stimulation of the subthalamic nucleus (STN). Here we test the hypothesis that pathological bursts in dopamine-deprived basal ganglia are generated within the STN and transmitted to globus pallidus neurons. To answer this question we recorded excitatory synaptic currents and potentials from subthalamic and pallidal neurons in the basal ganglia slice (BGS) from dopamine-depleted mice while continuously blocking GABAA receptors. In control mice, a single electrical stimulus delivered to the internal capsule or the rostral pole of the STN evoked a short duration, small amplitude, monosynaptic EPSC in subthalamic neurons. In contrast, in the dopamine-depleted BGS, this monosynaptic EPSC was amplified and followed by a burst of polysynaptic EPSCs that eventually reverberated three to seven times, providing a long lasting response that gave rise to bursts of EPSCs and spikes in GP neurons. Repetitive (10–120 Hz) stimulation delivered to the STN in the dopamine-depleted BGS attenuated STN-evoked bursts of EPSCs in pallidal neurons after several minutes of stimulation but only high frequency (90–120 Hz) stimulation replaced them with small amplitude EPSCs at 20 Hz. We propose that the polysynaptic pathway within the STN amplifies subthalamic responses to incoming excitation in the dopamine-depleted basal ganglia, thereby transforming the STN into a burst generator and entraining pallidal neurons in pathogenic bursting activities. High frequency stimulation of the STN prevents the transmission of this pathological activity to globus pallidus and imposes a new glutamatergic synaptic noise on pallidal neurons.

Ammari, Rachida; Bioulac, Bernard; Garcia, Liliana; Hammond, Constance

2011-01-01

270

Is the Rate of ?-Ray Bursts Constant?  

NASA Astrophysics Data System (ADS)

The origin of ?-ray bursts remains one of the most intriguing mysteries in astrophysics today. Observations still allow a wide range of distance scales for the sources from cosmological to heliospheric. The SMM ?-ray spectrometer detected 132 bursts >300 keV from 1980 to 1989 using a standard computer algorithm. We divided this observing period into 12 intervals each of 283 days, corrected for relative exposure. Assuming the rates to be constant yields an acceptable fit (\\chi^2 = 13.3 for 11 dof). However, there is weak evidence (95% confidence) for a correlation of the bursts with solar activity. (Share et al., Astron. Astrophys. Suppl. 97, 341 (1993).) There are three contiguous time intervals from about 1986 January to about 1988 April, corresponding to the latter half of solar minimum, which are responsible for this effect. The average rate in these intervals is 6.0 ± 1.4/interval compared with a rate of 12.1 ± 1.7/ interval for the remaining nine intervals. If this difference is physical in origin, it would imply that at least some of the ?-ray bursts are associated with the heliosphere and the solar cycle. If this is true, we would expect the BATSE experiment on the Compton Gamma Ray Observatory to observe a decrease in the burst rate for 2--3 yr beginning mid/late 1996 or early 1997.

Share, Gerald; Messina, Daniel

1997-04-01

271

Recent electric propulsion development activities for NASA science missions  

Microsoft Academic Search

The primary source of electric propulsion development throughout NASA is managed by the In-Space Propulsion Technology Project at the NASA Glenn Research Center for the Science Mission Directorate. The objective of the Electric Propulsion project area is to develop near-term electric propulsion technology to enhance or enable science missions while minimizing risk and cost to the end user. Major hardware

E. J. Pencil

2009-01-01

272

Statistical Properties of SGR J1550-5418 Bursts  

NASA Technical Reports Server (NTRS)

Magnetars are slowly rotating neutron stars with extreme magnetic fields, over 10(exp 15) Gauss. Only few have been discovered in the last 30 years. These sources are dormant most of their lifetimes and become randomly active emitting multiple soft gamma-ray bursts. We present here our results on the temporal analysis of 300 bursts from Soft Gamma Repeater SGR J1550-5418 recorded with the Gamma-ray Burst Monitor (GBM) onboard the Fermi Observatory during its activation on January 22-29, 2009. We employed an un-triggered burst search in the energy range 8-100keV to collect all events from the source, besides the ones that triggered GBM. For the entire sample of bursts we determined their durations, rise and decay times. We study here the statistical properties of these characteristics and discuss how these may help us better understand the physical characteristics of the magnetar model.

Gorgone, Nicholas M.

2010-01-01

273

A Meshfree Method for Simulating Myocardial Electrical Activity  

PubMed Central

An element-free Galerkin method (EFGM) is proposed to simulate the propagation of myocardial electrical activation without explicit mesh constraints using a monodomain model. In our framework the geometry of myocardium is first defined by a meshfree particle representation that is, a sufficient number of sample nodes without explicit connectivities are placed in and inside the surface of myocardium. Fiber orientations and other material properties of myocardium are then attached to sample nodes according to their geometrical locations, and over the meshfree particle representation spatial variation of these properties is approximated using the shape function of EFGM. After the monodomain equations are converted to their Galerkin weak form and solved using EFGM, the propagation of myocardial activation can be simulated over the meshfree particle representation. The derivation of this solution technique is presented along a series of numerical experiments and a solution of monodomain model using a FitzHugh-Nagumo (FHN) membrane model in a canine ventricular model and a human-heart model which is constructed from digitized virtual Chinese dataset.

Zhang, Heye; Ye, Huajun; Huang, Wenhua

2012-01-01

274

Electrically active sodium-related defect centres in silicon  

NASA Astrophysics Data System (ADS)

Electrically active defect centres related to sodium in silicon have been examined with deep level transient spectroscopy, and their recombination potential analysed with the microwave photoconductive decay technique. In order to investigate the entire silicon band gap for defect centres, both p-type (B-doped) and n-type (P-doped) float zone monocrystalline silicon samples were ion implanted with sodium. Three Na-related levels were identified in the upper half of the band gap at EC - 0.094 eV, EC - 0.119 eV and EC - 0.139 eV in implanted n-type silicon. In implanted p-type silicon three Na-related levels were identified at EV + 0.088, EV + 0.270 eV and EV + 0.139 eV. The capture cross sections of all levels were in the range 2-5 × 10-15 cm2, with an exception for the level at EV + 0.270 eV that was found to have a capture cross section of 4 × 10-14 cm2. Implantations of sodium lead to a significant drop in minority carrier lifetime of both n-type and p-type silicon. This degradation was substantially higher in p-type silicon. The observed recombination activity can be compared to that of nickel and manganese.

Hvidsten Dahl, E.; Madsbøll, J.; Søiland, A.-K.; Odden, J.-O.; Tronstad, R.; Nylandsted Larsen, A.

2013-10-01

275

Chandra Observations of the Bursting X-Ray Transient SAX J1747.0-2853 during Low-Level Accretion Activity  

Microsoft Academic Search

We present Chandra\\/ACIS observations of the bursting X-ray transient SAX J1747.0-2853 performed on 2001 July 18. We detected a bright source at the position of R.A. = 17h47m02.60s and decl. = -28°52'58.9\\

Rudy Wijnands; Jon M. Miller; Q. Daniel Wang

2002-01-01

276

Observing a Burst with Sunglasses  

NASA Astrophysics Data System (ADS)

Unique Five-Week VLT Study of the Polarisation of a Gamma-Ray Burst Afterglow "Gamma-ray bursts (GRBs)" are certainly amongst the most dramatic events known in astrophysics. These short flashes of energetic gamma-rays, first detected in the late 1960's by military satellites, last from less than one second to several minutes. GRBs have been found to be situated at extremely large ("cosmological") distances. The energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00. During the past years circumstantial evidence has mounted that GRBs signal the collapse of extremely massive stars, the so-called hypernovae. This was finally demonstrated some months ago when astronomers, using the FORS instrument on ESO's Very Large Telescope (VLT), documented in unprecedented detail the changes in the spectrum of the light source ("the optical afterglow") of the gamma-ray burst GRB 030329 (cf. ESO PR 16/03). A conclusive and direct link between cosmological gamma-ray bursts and explosions of very massive stars was provided on this occasion. Gamma-Ray Burst GRB 030329 was discovered on March 29, 2003 by NASA's High Energy Transient Explorer spacecraft. Follow-up observations with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the Paranal Observatory (Chile) showed the burst to have a redshift of 0.1685 [1]. This corresponds to a distance of about 2,650 million light-years, making GRB 030329 the second-nearest long-duration GRB ever detected. The proximity of GRB 030329 resulted in very bright afterglow emission, permitting the most extensive follow-up observations of any afterglow to date. A team of astronomers [2] led by Jochen Greiner of the Max-Planck-Institut für extraterrestrische Physik (Germany) decided to make use of this unique opportunity to study the polarisation properties of the afterglow of GRB 030329 as it developed after the explosion. Hypernovae, the source of GRBs, are indeed so far away that they can only be seen as unresolved points of light. To probe their spatial structure, astronomers have thus to rely on a trick: polarimetry (see ESO PR 23/03). Polarimetry works as follows: light is composed of electromagnetic waves which oscillate in certain directions (planes). Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflecting off a pond. The radiation in a gamma-ray burst is generated in an ordered magnetic field, as so-called synchrotron radiation [3]. If the hypernova is spherically symmetric, all orientations of the electromagnetic waves will be present equally and will average out, so there will be no net polarisation. If, however, the gas is not ejected symmetrically, but into a jet, a slight net polarisation will be imprinted on the light. This net polarisation will change with time since the opening angle of the jet widens with time, and we see a different fraction of the emission cone. Studying the polarisation properties of the afterglow of a gamma-ray burst thus allows to gain knowledge about the underlying spatial structures and the strength and orientation of the magnetic field in the region where the radiation is generated. " And doing this over a long period of time, as the afterglow fades and evolves, provides us with a unique diagnostic tool for gamma-ray burst studies ", says Jochen Greiner . Although previous single measurements of the polarisation of GRB's optical afterglow exist, no detailed study has ever been done of the evolution of polarisation with time. This is indeed a very demanding task, only possible with an extremely stable instrument on the largest telescope... and a sufficient bright optical afterglow. As soon as GRB 030329 was detected, the team of astronomers therefore turned to the powerful mu

2003-11-01

277

Spiking patterns of a hippocampus model in electric fields  

NASA Astrophysics Data System (ADS)

We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.

Men, Cong; Wang, Jiang; Qin, Ying-Mei; Wei, Xi-Le; Che, Yan-Qiu; Deng, Bin

2011-12-01

278

Burst Populations and Detector Sensitivity  

NASA Technical Reports Server (NTRS)

The F(sub T) (peak bolometric photon flux) vs. E(sub p) (peak energy) plane is a powerful tool to compare the burst populations detected by different detectors. Detector sensitivity curves in this plane demonstrate which burst populations the detectors will detect. For example, future CZT-based detectors will show the largest increase in sensitivity for soft bursts, and will be particularly well- suited to study X-ray rich bursts and X-ray Flashes. Identical bursts at different redshifts describe a track in the F(sub T)-E(sub p) plane.

Band, David L.

2003-01-01

279

Electrical activity of grain boundaries in silicon bicrystals and its modification by hydrogen plasma treatment  

Microsoft Academic Search

Electrical activity of grain boundaries (GBs) and its transformation under the influence of low-energy hydrogen plasma treatment in p-type silicon bicrystalline samples cut from EFG silicon polycrystals were investigated. Comprehensive studies have enabled one to investigate the electrical activity of GBs relative to the minority (MIC) and majority (MAC) carriers and to demonstrate the possibility of controlling this activity by

A. Fedotov; A. Mazanik; A. Ulyashin

2002-01-01

280

The Double Firing Burst  

NASA Astrophysics Data System (ADS)

Astronomers from around the world combined data from ground- and space-based telescopes to paint a detailed portrait of the brightest explosion ever seen. The observations reveal that the jets of the gamma-ray burst called GRB 080319B were aimed almost directly at the Earth. Uncovering the disc ESO PR Photo 28/08 A Gamma-Ray Burst with Two Jets Read more on this illuminating blast in the additional story. GRB 080319B was so intense that, despite happening halfway across the Universe, it could have been seen briefly with the unaided eye (ESO 08/08). In a paper to appear in the 11 September issue of Nature, Judith Racusin of Penn State University, Pennsylvania (USA), and a team of 92 co-authors report observations across the electromagnetic spectrum that began 30 minutes before the explosion and followed it for months afterwards. "We conclude that the burst's extraordinary brightness arose from a jet that shot material almost directly towards Earth at almost the speed of light - the difference is only 1 part in 20 000," says Guido Chincarini, a member of the team. Gamma-ray bursts are the Universe's most luminous explosions. Most occur when massive stars run out of fuel. As a star collapses, it creates a black hole or neutron star that, through processes not fully understood, drives powerful gas jets outward. As the jets shoot into space, they strike gas previously shed by the star and heat it, thereby generating bright afterglows. The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 degrees across (this is slightly smaller than the apparent size of the Full Moon). This jet is contained within another slightly less energetic jet about 20 times wider. The broad component is more typical of other bursts. "Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time," says team member Stefano Covino. "We happened to view this monster down the barrel of the very narrow and energetic jet, and the chance for this nearly head-on alignment to occur is only about once a decade," added his colleague Cristiano Guidorzi. GRB 080319B was detected by the NASA/STFC/ASI Swift satellite towards the constellation of Boötes, the "Herdsman". A host of ground-based telescopes reacted promptly to study this new object in the sky, including ESO's Very Large Telescope, which was the first to provide the distance of the object, 7.5 billion light-years. The visible light from the burst was detected by a handful of wide-field cameras worldwide that are mounted on telescopes constantly monitoring a large fraction of the sky. One of these was the TORTORA camera mounted on the 0.6-m REM telescope at ESO's La Silla Observatory (ESO 26/07). TORTORA's rapid imaging provides the most detailed look yet at the visible light associated with the initial blast of a gamma-ray burst. "We've been waiting a long time for this one," says TORTORA senior scientist Grigory Beskin of Russia's Special Astrophysical Observatory. The data collected simultaneously by TORTORA and the Swift satellite allowed astronomers to explain the properties of this burst.

2008-09-01

281

On the Modeling of Electrical Effects Experienced by Space Explorers During Extra Vehicular Activities: Intracorporal Currents, Resistances, and Electric Fields  

NASA Technical Reports Server (NTRS)

Recent research has shown that space explorers engaged in Extra Vehicular Activities (EVAs) may be exposed, under certain conditions, to undesired electrical currents. This work focuses on determining whether these undesired induced electrical currents could be responsible for involuntary neuromuscular activity in the subjects, possibly caused by either large diameter peripheral nerve activation or reflex activity from cutaneous afferent stimulation. An efficient multiresolution variant of the admittance method along with a millimeter-resolution model of a male human body were used to calculate induced electric fields, resistance between contact electrodes used to simulate the potential exposure condition, and currents induced in the human body model. Results show that, under realistic exposure conditions using a 15V source, current density magnitudes and total current injected are well above previously reported startle reaction thresholds. This indicates that, under the considered conditions, the subjects could experience involuntary motor response.

Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.

2011-01-01

282

Jovian type III radio bursts  

NASA Technical Reports Server (NTRS)

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

1989-01-01

283

Jovian type III radio bursts  

SciTech Connect

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

Kurth, W.S.; Gurnett, D.A. (Univ. of Iowa, Iowa City (USA)); Scarf, F.L. (TRW Space and Technology Group, Redondo Beach, CA (USA))

1989-06-01

284

Computation of induced electric field for the sacral nerve activation.  

PubMed

The induced electric field/current in the sacral nerve by stimulation devices for the treatment of bladder overactivity is investigated. Implanted and transcutaneous electrode configurations are considered. The electric field induced in the sacral nerve by the implanted electrode is largely affected by its surrounding tissues, which is attributable to the variation in the input impedance of the electrode. In contrast, the electric field induced by the transcutaneous electrode is affected by the tissue conductivity and anatomical composition of the body. In addition, the electric field induced in the subcutaneous fat in close proximity of the electrode is comparable with the estimated threshold electric field for pain. These computational findings explain the clinically observed weakness and side effect of each configuration. For the transcutaneous stimulator, we suggest that the electrode contact area be increased to reduce the induced electric field in the subcutaneous fat. PMID:24140875

Hirata, Akimasa; Hattori, Junya; Laakso, Ilkka; Takagi, Airi; Shimada, Takuo

2013-11-01

285

l-Tyrosine-loaded nanoparticles increase the antitumoral activity of direct electric current in a metastatic melanoma cell model  

PubMed Central

Inhibition of tumor growth induced by treatment with direct electric current (DC) has been reported in several models. One of the mechanisms responsible for the antitumoral activity of DC is the generation of oxidative species, known as chloramines. With the aim of increasing chloramine production in the electrolytic medium and optimizing the antitumoral effects of DC, poly(?-caprolactone) (PCL) nanoparticles (NPs) loaded with the amino acid tyrosine were obtained. The physical–chemical characterization showed that the NPs presented size in nanometric range and monomodal distribution. A slightly negative electrokinetic potential was also found in both blank NPs and l-tyrosine-loaded PCL NPs. The yield of the loading process was approximately 50%. Within 3 h of dissolution assay, a burst release of about 80% l-tyrosine was obtained. The in vitro cytotoxicity of DC was significantly increased when associated with l-tyrosine-loaded NPs, using a murine multidrug-resistant melanoma cell line model. This study showed that the use of the combination of nanotechnology and DC has a promising antineoplastic potential and opens a new perspective in cancer therapy.

de Campos, Vania Emerich Bucco; Teixeira, Cesar Augusto Antunes; da Veiga, Venicio Feo; Junior, Eduardo Ricci; Holandino, Carla

2010-01-01

286

Full System Bifurcation Analysis of Endocrine Bursting Models  

PubMed Central

Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. We investigate so-called square-wave and pseudo-plateau bursting patterns found in endocrine cell models that are characterized by a super- or subcritical Hopf bifurcation in the fast subsystem, respectively. By using the polynomial model of Hindmarsh and Rose (Proceedings of the Royal Society of London B 221(1222), 87–102), which preserves the main properties of the biophysical class of models that we consider, we perform a detailed bifurcation analysis of the full fast-slow system for both bursting patterns. We find that both cases lead to the same possibility of two routes to bursting, that is, the criticality of the Hopf bifurcation is not relevant for characterizing the route to bursting. The actual route depends on the relative location of the full-system’s fixed point with respect to a homoclinic bifurcation of the fast subsystem. Our full-system bifurcation analysis reveals properties of endocrine bursting that are not captured by the standard fast-slow analysis.

Tsaneva-Atanasova, Krasimira; Osinga, Hinke M.; Rie?, Thorsten; Sherman, Arthur

2010-01-01

287

Meteor burst communication system  

NASA Astrophysics Data System (ADS)

A meteor burst communication network is disclosed that consists of a plurality of meteor burst communication stations that relay radio messages off of meteor burst trails from one station to another. Each station includes an antenna operably coupled to a receiver and transmitter, a display, a message input device, a computer operably connected to the aforementioned equipment, and a clock that provides a time base to the computer. The computer provides instructions to the transmitter and outputs to a display. The program determines if a message has been received by the receiver. If a message has been received, it is stored in the computer memory. The computer then instructs the transmitter to transmit a probing message for a predetermined period of time. If a response to the probing message has been detected by the receiver, the computer directs the transmitter to cease transmitting the probing message, transmit the message, and purge the message from memory after an acknowledgement message is received that the message was received. In cases where the probing message has been transmitted for a period in excess of the predetermined period, the computer directs the transmitter to cease transmitting and purge the message from memory. Messages may also be input into the station through the message input device.

Bickel, John E.

1992-06-01

288

Periodic bursts of Jovian non-Io decametric radio emission  

PubMed Central

During the years 2000–2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ?1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ?25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

Panchenko, M.; Rucker, H.O.; Farrell, W.M.

2013-01-01

289

Periodic bursts of Jovian non-Io decametric radio emission.  

PubMed

During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period [Formula: see text] longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every [Formula: see text] days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

Panchenko, M; Rucker, H O; Farrell, W M

2013-03-01

290

Low-Frequency Type III Bursts and Solar Energetic Particle Events  

NASA Technical Reports Server (NTRS)

We analyzed the coronal mass ejections (CMEs), flares, and type 11 radio bursts associated with a set of six low frequency (<14 MHz) extended type III bursts from active region 10588. The durations were measured at 1 and 14 MHz using high resolution data from Wind/WAVES and were within the range (>15 min) normally used to define these bursts. All but one of the type III bursts was not associated with a type 11 burst in the metric or longer wavelength domains. The burst without type 11 burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 min) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. The CMEs were of similar speeds and the flares are also of similar size and duration. This study suggests that the type III burst duration may not be a good indicator of an SEP event.

Gopalswamy, Nat; Makela, Pertti

2010-01-01

291

Inhibition and recovery of continuous electric field application on the activity of anammox biomass.  

PubMed

In this study, the effects of electric field on the activity of anammox biomass were investigated. In batch mode, experimental results demonstrated that the nitrogen removal rate enhanced by 25.6 % compared with the control experiment at the electric field of 2 V/cm with application time of 20 min. However, continuous application (24 h) of electric field impacted a mal-effect on anammox biomass during the intensity between 1 and 4 V/cm. After the electric field was removed, the activity of anammox biomass could recover within 2 weeks. This implied that the mal-effect of electric field on anammox biomass was reversible. The decrease of heme c contents and crude enzyme activity demonstrated to be the main reason for the depress of the anammox biomass activity. Transmission electron microscope observation also proved the morphological change of anammox biomass under electric field. PMID:24258098

Qiao, Sen; Yin, Xin; Zhou, Jiti; Furukawa, Kenji

2014-07-01

292

Final report on electric vehicle activities, September 1991--October 1994  

SciTech Connect

The data and information collected for the Public Service Electric and Gas Company`s (PSE&G) electric vehicle demonstration program were intended to support and enhance DOE`s Electric and Hybrid Vehicle Site Operator Program. The DOE Site Operator Program is focused on the life cycle and reliability of Electric Vehicles (EVs). Of particular interest are vehicles currently available with features that are likely to be put into production or demonstrate new technology. PSE&G acquired eight GMC Electric G-Vans in 1991, and three TEVans in 1993, and conducted a program plan to test and assess the overall performance of these electric vehicles. To accomplish the objectives of DOE`s Site Operator`s test program, a manual data collection system was implemented. The manual data collection system has provided energy use and mileage data. From September 1991 to October 1994 PSE&G logged 69,368 miles on eleven test vehicles. PSE&G also demonstrated the EVs to diverse groups and associations at fifty seven various events. Included in the report are lessons learned concerning maintenance, operation, public reactions, and driver`s acceptance of the electric vehicles.

Del Monaco, J.L.; Pandya, D.A.

1995-02-01

293

Electricity  

NSDL National Science Digital Library

Electricity is very important to our lives. This reading, part of a series about the future of energy, introduces students to the need and uses for electricity. Students review sources of electricity generation and investigate the evaluation of energy production resources. Here students review information on the generation of electric power and the infrastructure needed to transmit and distribute electricity. Thought-provoking questions afford students chances to reflect on what they've read. Web links to two PBS NewsHour energy-related articles are provided, along with a link to information on the benefits of small-scale wind projects. Copyright 2005 Eisenhower National Clearinghouse

Project, Iowa P.

2004-01-01

294

Activity Based Physics Alternative Homework Assignment: Electrical Safety 1  

NSDL National Science Digital Library

This homework assignment is a realistic problem based on household electrical circuits. The user must make estimations of physical parameters from the properties, sizes, and shapes of common objects. Topics covered include Ohm's Law, resistivity, capacitance, alternating current, and circuits.

Redish, Edward F.; Cooney, Patrick

2009-03-19

295

Review of ESA Experimental Research Activities for Electric Propulsion.  

National Technical Information Service (NTIS)

In the commercial telecommunication space arena, the strong competition among satellite manufacturers is a major driver for advancements in the area of Electric Propulsion (EP), where increasing better performance together with low prices are required. Th...

J. A. Gonzalez del Amo

2011-01-01

296

Unilateral electrical stimulation of rat locus coeruleus elicits bilateral response of norepinephrine neurons and sustained activation of medial prefrontal cortex.  

PubMed

The brain stem nucleus locus coeruleus (LC) is thought to modulate cortical excitability by norepinephrine (NE) release in LC forebrain targets. The effects of LC burst discharge, typically evoked by a strong excitatory input, on cortical ongoing activity are poorly understood. To address this question, we combined direct electrical stimulation of LC (LC-DES) with extracellular recording in LC and medial prefrontal cortex (mPFC), an important cortical target of LC. LC-DES consisting of single pulses (0.1-0.5 ms, 0.01-0.05 mA) or pulse trains (20-50 Hz, 50-200 ms) evoked short-latency excitatory and inhibitory LC responses bilaterally as well as a delayed rebound excitation occurring ?100 ms after stimulation offset. The pulse trains, but not single pulses, reliably elicited mPFC activity change, which was proportional to the stimulation strength. The firing rate of ?50% of mPFC units was significantly modulated by the strongest LC-DES. Responses of mPFC putative pyramidal neurons included fast (?100 ms), transient (?100-200 ms) inhibition (10% of units) or excitation (13%) and delayed (?500 ms), sustained (?1 s) excitation (26%). The sustained spiking resembled NE-dependent mPFC activity during the delay period of working memory tasks. Concurrently, the low-frequency (0.1-8 Hz) power of the local field potential (LFP) decreased and high-frequency (>20 Hz) power increased. Overall, the DES-induced LC firing pattern resembled the naturalistic biphasic response of LC-NE neurons to alerting stimuli and was associated with a shift in cortical state that may optimize processing of behaviorally relevant events. PMID:24671530

Marzo, Aude; Totah, Nelson K; Neves, Ricardo M; Logothetis, Nikos K; Eschenko, Oxana

2014-06-15

297

Accreting, Mixing, and X-ray Bursting  

NASA Astrophysics Data System (ADS)

During accretion, a neutron star (NS) is spun up as angular momentum is transported through its liquid surface layers. We study the resulting differentially rotating profile, focusing on the impact this has for type I X-ray bursts. The viscous heating is found to be negligible, but turbulent mixing can be activated. Mixing has the greatest impact when the buoyancy at the compositional discontinuity between accreted matter and ashes is overcome. This occurs preferentially at high accretion rates or low spin frequencies and may depend on the ash composition from the previous burst. We then find two new regimes of burning. The first is ignition in a layer containing a mixture of heavier elements with recurrence times as short as ~5-30 minutes, similar to short recurrence time bursts. When mixing is sufficiently strong, a second regime is found where accreted helium mixes deep enough to burn stably, quenching X-ray bursts altogether. The carbon-rich material produced by stable helium burning would be important for triggering and fueling superbursts.

Piro, Anthony L.; Bildsten, Lars

2008-05-01

298

Dust formation by bubble-burst phenomenon at the surface of a liquid steel bath  

Microsoft Academic Search

We have developed an experimental device for studying the main mechanism of dust formation in electric arc furnace steelmaking: the burst of gas bubbles at the liquid steel surface. As in the case of the air-water system, the bubble-burst process takes place in three steps: breaking of the film cap, projection of film drops, and projection of jet drops. The

Anne-Gwénaëlle Guézennec; Jean-Christophe Huber; Fabrice Patisson; Philippe Sessiecq; Jean-Pierre Birat; Denis Ablitzer

2007-01-01

299

On the Dynamics of the Spontaneous Activity in Neuronal Networks  

PubMed Central

Most neuronal networks, even in the absence of external stimuli, produce spontaneous bursts of spikes separated by periods of reduced activity. The origin and functional role of these neuronal events are still unclear. The present work shows that the spontaneous activity of two very different networks, intact leech ganglia and dissociated cultures of rat hippocampal neurons, share several features. Indeed, in both networks: i) the inter-spike intervals distribution of the spontaneous firing of single neurons is either regular or periodic or bursting, with the fraction of bursting neurons depending on the network activity; ii) bursts of spontaneous spikes have the same broad distributions of size and duration; iii) the degree of correlated activity increases with the bin width, and the power spectrum of the network firing rate has a 1/f behavior at low frequencies, indicating the existence of long-range temporal correlations; iv) the activity of excitatory synaptic pathways mediated by NMDA receptors is necessary for the onset of the long-range correlations and for the presence of large bursts; v) blockage of inhibitory synaptic pathways mediated by GABAA receptors causes instead an increase in the correlation among neurons and leads to a burst distribution composed only of very small and very large bursts. These results suggest that the spontaneous electrical activity in neuronal networks with different architectures and functions can have very similar properties and common dynamics.

Bonifazi, Paolo; Ruaro, Maria Elisabetta; Torre, Vincent

2007-01-01

300

Fast Burst Reactor burst rod adaptor failure analysis  

Microsoft Academic Search

Failure of a 440C stainless steel burst rod adaptor from the White Sands Missile Range Fast Burst Reactor is analyzed. The operational history of the adaptor, including nature of loading, radiation accumulation, and thermal environment, was examined. Problems associated with handling radioactive materials were overcome through careful monitoring and disposal. The chemical composition of the adaptor material was checked by

W. C. Hull; D. L. Welch

1977-01-01

301

Chandra observations of the bursting X-ray transient SAX J1747.0-2853 during low-level accretion activity  

Microsoft Academic Search

We present Chandra\\/ACIS observations of the bursting X-ray transient SAX\\u000aJ1747.0-2853 performed on 18 July 2001. We detected a bright source at the\\u000aposition of R.A = 17^h 47^m 02.60^s and Dec. = -28 52' 58.9'' (J2000.0; with a\\u000a1 sigma error of ~0.7 arcseconds), consistent with the BeppoSAX and ASCA\\u000apositions of SAX J1747.0-2853 and with the Ariel V

Rudy Wijnands; Jon M. Miller; Q. Daniel Wang

2002-01-01

302

Electrospun nanofiber membranes for electrically activated shape memory nanocomposites  

NASA Astrophysics Data System (ADS)

A novel shape memory nanocomposite system, consisting of a thermoplastic Nafion polymer and ultrathin electrospun polyacrylonitrile (PAN)-based carbonization nanofiber membranes, is successfully synthesized. PAN-based carbonization nanofiber networks that offer responses to deformations are considered to be an excellent actuation source. Significant improvement in the electrical conductivity of carbon nanofiber membranes is found by adjusting the applied voltage power in the electrospinning PAN process varying from 7.85 to 12.30 S cm?1. The porous structure of the carbon nanofiber membranes provides a large specific surface area and interfacial contact area when combined with the polymer matrix. Shape memory Nafion nanocomposites filled with interpenetrating non-woven electrospun PAN carbonization membranes can be actuated by applying 14 V electrical voltage within 5 s. The results, as demonstrated through morphology, electrical and thermal measurements and a shape recovery test, suggest a valuable route to producing soft nanocomposites.

Zhang, Fenghua; Zhang, Zhichun; Liu, Yanju; Leng, Jinsong

2014-06-01

303

Bursting as a source of non-linear determinism in the firing patterns of nigral dopamine neurons  

PubMed Central

Nigral dopamine (DA) neurons in vivo exhibit complex firing patterns consisting of tonic single-spikes and phasic bursts that encode information for certain types of reward-related learning and behavior. Non-linear dynamical analysis has previously demonstrated the presence of a non-linear deterministic structure in complex firing patterns of DA neurons, yet the origin of this non-linear determinism remains unknown. In this study, we hypothesized that bursting activity is the primary source of non-linear determinism in the firing patterns of DA neurons. To test this hypothesis, we investigated the dimension complexity of inter-spike interval data recorded in vivo from bursting and non-bursting DA neurons in the chloral hydrate-anesthetized rat substantia nigra. We found that bursting DA neurons exhibited non-linear determinism in their firing patterns, whereas non-bursting DA neurons showed truly stochastic firing patterns. Determinism was also detected in the isolated burst and inter-burst interval data extracted from firing patterns of bursting neurons. Moreover, less bursting DA neurons in halothane-anesthetized rats exhibited higher dimensional spiking dynamics than do more bursting DA neurons in chloral hydrate-anesthetized rats. These results strongly indicate that bursting activity is the main source of low-dimensional, non-linear determinism in the firing patterns of DA neurons. This finding furthermore suggests that bursts are the likely carriers of meaningful information in the firing activities of DA neurons.

Jeong, Jaeseung; Shi, Wei-Xing; Hoffman, Ralph; Oh, Jihoon; Gore, John C.; Bunney, Benjamin S.; Peterson, Bradley S.

2012-01-01

304

A Different Cone: Bursting Drops in Solids  

NASA Astrophysics Data System (ADS)

Drops in fluids tend to be spheres---a shape that minimizes surface energy. In thunderstorm clouds, drops can become unstable and emit thin jets when charged beyond certain limits. The instability of electrified drops in gases and liquids has been widely studied and used in applications including ink-jet printing, electrospinning nano-fibers, microfluidics and electrospray ionization. Here we report a different scenario: drops in solids become unstable and burst under sufficiently high electric fields. We find the instability of drops in solids morphologically resembles that in liquids, but the critical electric field for the instability follows a different scaling due to elasticity of solids. Our observations and theoretical models not only advance the fundamental understanding of electrified drops but also suggest a new failure mechanism of high-energy-density dielectric polymers, which have diverse applications ranging from capacitors for power grids and electric vehicles to muscle-like transducers for soft robots and energy harvesting.

Zhao, Xuanhe

2013-03-01

305

The Swift Burst Alert Telescope  

Microsoft Academic Search

The Swift Gamma Ray Burst MIDEX is a multiwavelength observatory scheduled to be launched in September 2003 to study gamma-ray bursts (GRBs) and their x-ray and optical afterglow emission. Swift will exploit these newly discovered GRB afterglow characteristics to make a comprehensive study of ~ 1000 GRBs and use the afterglow phenomenon as a tool for probing their source and

A. Parsons; S. Barthelmy; L. Barbier; N. Gehrels; D. Palmer; J. Tueller; E. Fenimore

2000-01-01

306

Transcription Factors Modulate c-Fos Transcriptional Bursts.  

PubMed

Transcription is a stochastic process occurring mostly in episodic bursts. Although the local chromatin environment is known to influence the bursting behavior on long timescales, the impact of transcription factors (TFs)-especially in rapidly inducible systems-is largely unknown. Using fluorescence in situ hybridization and computational models, we quantified the transcriptional activity of the proto-oncogene c-Fos with single mRNA accuracy at individual endogenous alleles. We showed that, during MAPK induction, the TF concentration modulates the burst frequency of c-Fos, whereas other bursting parameters remain mostly unchanged. By using synthetic TFs with TALE DNA-binding domains, we systematically altered different aspects of these bursts. Specifically, we linked the polymerase initiation frequency to the strength of the transactivation domain and the burst duration to the TF lifetime on the promoter. Our results show how TFs and promoter binding domains collectively act to regulate different bursting parameters, offering a vast, evolutionarily tunable regulatory range for individual genes. PMID:24981864

Senecal, Adrien; Munsky, Brian; Proux, Florence; Ly, Nathalie; Braye, Floriane E; Zimmer, Christophe; Mueller, Florian; Darzacq, Xavier

2014-07-10

307

Burst Detector Sensitivity: Past, Present and Future  

NASA Technical Reports Server (NTRS)

I compare the burst detection sensitivity of CGRO's BATSE, Swift's BAT, the GLAST Burst Monitor (GBM) and EXIST as a function of a burst s spectrum and duration. A detector's overall burst sensitivity depends on its energy sensitivity and set of accumulations times (Delta)t; these two factors shape the detected burst population. For example, relative to BATSE, the BAT s softer energy band decreases the detection rate of short, hard bursts, while the BAT s longer accumulation times increase the detection rate of long, soft bursts. Consequently, Swift is detecting long, low fluence bursts (2-3 x fainter than BATSE).

Band, David L.

2005-01-01

308

Development of a Remote Monitoring System Using Meteor Burst Technology  

SciTech Connect

Monitoring the cleanup and closure of contaminated sites requires extensive data acquisition, processing, and storage. At remote sites, the task of monitoring often becomes problematical due to the lack of site infrastructure (i.e., electrical power lines, telephone lines, etc.). MSE Technology Applications, Inc. (MSE) has designed an economical and efficient remote monitoring system that will handle large amounts of data; process the data, if necessary; and transmit this data over long distances. Design criteria MSE considered during the development of the remote monitoring system included: the ability to handle multiple, remote sampling points with independent sampling frequencies; robust (i.e., less susceptible to moisture, heat, and cold extremes); independent of infrastructure; user friendly; economical; and easy to expand system capabilities. MSE installed and tested a prototype system at the Mike Mansfield Advanced Technology Center (MMATC), Butte, Montana, in June 2005. The system MSE designed and installed consisted of a 'master' control station and two remote 'slave' stations. Data acquired at the two slave stations were transmitted to the master control station, which then transmits a complete data package to a ground station using meteor burst technology. The meteor burst technology has no need for hardwired land-lines or man-made satellites. Instead, it uses ionized particles in the Earth's atmosphere to propagate a radio signal. One major advantage of the system is that it can be configured to accept data from virtually any type of device, so long as the signal from the device can be read and recorded by a standard data-logger. In fact, MSE has designed and built an electrical resistivity monitoring system that will be powered and controlled by the meteor burst system components. As sites move through the process of remediation and eventual closure, monitoring provides data vital to the successful long term management of the site. The remote monitoring system developed by MSE is cost effective, robust, and can easily be integrated into a site monitoring plan yet remains independent of other site activities/infrastructure and is expandable to meet future site monitoring requirements. (authors)

Ewanic, M.A.; Dunstan, M.T.; Reichhardt, D.K. [MSE Technology Applications, Inc., 200 Technology Way, Butte, MT 59701 (United States)

2006-07-01

309

Quantum key based burst confidentiality in optical burst switched networks.  

PubMed

The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks. PMID:24578663

Balamurugan, A M; Sivasubramanian, A

2014-01-01

310

ELF Q-bursts from African Squall Lines  

NASA Astrophysics Data System (ADS)

A number of large amplitude ELF transient signals (Q-bursts) are documented at multiple sites around the world (Japan, Hungary, Israel and USA) in association with westward moving mesoscale convective systems (MCSs) in West Africa during the African Monsoon and Multidisciplinary Analysis campaign in 2006. Some of these bursts are associated with red sprites first observed from ground-based measurement in Africa. Using MIT Doppler radar and electric field measurements locally installed in Niamey, we investigate quantitatively the meteorological conditions responsible for generating these exceptionally large Q-bursts. Detailed meteorological information is provided from radar such as the spatio-temporal evolution of radar echo, while the electrical properties oflarge Q-bursts (e.g. charge moment charge (CMC)) are experimentally derived by using the remote-sensing method taking into account the theory for the earth-ionoshere wave guide. Furthermore, detailed propagation characteristics of Q-bursts and their effect on the location and remotely derived accuracy of the CMC will be discussed by comparing the results from multi ELF stations under different ionospheric conditions such as day-night asymmetry and the ionospheric terminator lines. Preliminary results from similar campaign in 2007 in Niger will also be presented to be compared with those in 2006.

Hobara, Y.; Williams, E.; Mushtak, V.; Boldi, R.; Hayakawa, M.; Yamashita, K.; Lyons, W.; Russell, B.; Satori, G.; Bor, J.; Price, C.; Greenberg, E.; Holzworth, R.

2007-12-01

311

Modeling electrical activities of a growing breast cancerous cell based on a semiconductor approach  

Microsoft Academic Search

A two dimensional diffusion-drift model is developed to simulate the electrical activities of a breast cancerous cell during the hyperpolarization which occurs at the G1\\/S transition. The model focuses on calculating the temporal and the spatial patterns of the electric current densities and biopotentials generated at the cell boundary and its surroundings. Different durations for the hyperpolarization phase were studied.

Ahmed Hassan; Magda El-Shenawee

2009-01-01

312

Effect of Instruction Based on Conceptual Change Activities on Students' Understanding of Static Electricity Concepts  

ERIC Educational Resources Information Center

This study was conducted to investigate the effectiveness of learning activities based on conceptual change conditions and traditionally designed physics instruction on tenth-grade students' understanding of static electricity concepts and their attitudes toward physics as a school subject. Misconceptions related to static electricity concepts…

Baser, Mustafa; Geban, Omer

2007-01-01

313

Pain reactivity in Alzheimer patients with different degrees of cognitive impairment and brain electrical activity deterioration  

Microsoft Academic Search

Pain perception and autonomic responses to pain are known to be altered in dementia, although the mechanisms are poorly understood. We studied patients with Alzheimer's disease (AD) whose cognitive status was assessed through the Mini Mental State Examination test and whose brain electrical activity was measured by means of quantitative electroencephalography. After assessment of both cognitive impairment and brain electrical

Fabrizio Benedetti; Claudia Arduino; Sergio Vighetti; Giovanni Asteggiano; Luisella Tarenzi; Innocenzo Rainero

2004-01-01

314

PhET Teacher Ideas & Activities: Exploring Electric Charges  

NSDL National Science Digital Library

This is a student guide created by the PhET team specifically for use with the simulation Balloons and Static Electricity. It gives step-by-step directions for simulation set-up and offers open-ended questions to help students explore the interactions between charged objects and charged/neutral objects. It is appropriate for middle school and 9th grade physical science courses. Editor's Note: We suggest letting students play with this simulation prior to doing a static electricity experiment. Its design should help students build concepts in a way that helps prevent misconception about charge interaction. This item is part of a larger collection of simulations developed by the Physics Education Technology project (PhET). The simulations are animated, interactive, and game-like environments.

Kosztin, Dorina

2011-01-23

315

Electrical standards development activities for nuclear power plant maintenance  

SciTech Connect

This paper presents information describing the concern for nuclear power plant electrical equipment maintenance and the IEEE Nuclear Power Engineering Committee's method to address that concern. That method includes the creation of Working Group 3.3, ''Maintenance Good Practices'' which is developing specific maintenance good practice documents, supporting technical information exchange, and providing a vehicle to promote practices which can reduce cost and enhance plant safety.

Gradin, L.P.; Sorenson, R.M.

1986-02-01

316

Museum of Science: Activities to Explore Static Electricity  

NSDL National Science Digital Library

This page links to five lesson plans in static electricity for beginning learners, plus reference material on the topic of electrostatics. Each lesson incorporates common household items and can be set up quickly for either classroom or home use. The lessons are designed to help beginners understand charge, electrostatic induction, and how transfer of electrons occurs. It is part of a larger collection created by the Boston Museum of Science.

Science, Boston M.

2006-11-10

317

Electric-utility solar-energy activities: 1982 survey update  

NASA Astrophysics Data System (ADS)

The scope of electric utility participation in solar energy projects in the United States was determined. The projects for 1982 are described and significant changes from 1981 in ongoing projects are summarized. A total of 930 projects were reported by 235 utility companies. An index of projects by category, a statistical summary, a list of participating utilities with information contacts and addresses, a list of utilities organized by state, and a list of new reports on utility sponsored projects are included.

Spelman, J. R.

1982-12-01

318

The Electrical Activity of a Denervated Ear 1  

PubMed Central

The electrical response from the cochlea of a cat which had previously been denervated by intracranial crushing of the auditory nerve was submitted to a lengthy study, the results of which may be summarized as follows:- The responses to acoustical stimulation derived from electrodes placed on the round window margin and in the chin muscles were studied by means of an amplifier and cathode ray oscillograph, in the usual way. Transient stimuli whose polarity could be reversed were employed to demonstrate the absence of any electrical component of neural origin such as is invariably present in a normal ear. In all other respects, however, the responses were unaffected, and both threshold contours (the so-called “electrical audiogram”) and equal response contours for approximately pure-tone stimuli demonstrated close comparability with those for normal ears. Harmonic analysis of the cochlear response yielded results departing from the normal only in such respects as would be expected in view of the complete absence of nervous component in the analysed wave. From these data, it is argued that this animal presented a case in which normal electrical responses were obtained from the peripheral organ, despite virtually complete degeneration of the auditory nerve, and, it follows, complete unilateral deafness. Subsequent histological examination confirmed these observations, and it is urged, therefore, that the validity of the view that the cochlear response provides an index of the hearing ability of an animal, as is sometimes stated, is open to question. Additionally, this experiment finally discredits the hypothesis that the cochlear response itself is, in any sense, neural in origin; it further indicates the necessity for caution in the interpretation of results obtained from normal ears, where the cochlear response, however derived, is in some degree adulterated by the simultaneous presence of an action potential component. ImagesFig. 8

Rawdon-Smith, A. F.; Hawkins, J. E.

1939-01-01

319

Electrical Activity Modulates Growth Cone Guidance by Diffusible Factors  

Microsoft Academic Search

Brief periods of electrical stimulation of cultured Xenopus spinal neurons resulted in a marked alteration in the turning responses of the growth cone induced by gradients of attractive or repulsive guidance cues. Netrin-1-induced attraction was enhanced, and the repulsion induced by myelin-associated glycoprotein (MAG) or myelin membrane fragments was converted to attraction. The effect required the presence of extracellular Ca2+

Guo-li Ming; John Henley; Marc Tessier-Lavigne; Hong-jun Song; Mu-ming Poo

2001-01-01

320

Active management of a heterogeneous energy store for electric vehicles  

Microsoft Academic Search

The successful introduction of electric vehicles continues to be stifled by the high cost and limited perfor- mance life of battery technology. We assert that a disruptive improvement in systems-level cost-of-performance is possible by employing a rate-heterogeneous energy storage system, combining low-rate batteries and high-rate supercapacitors, that is mated to a predictive control system that optimizes power management by exploiting

Alexander Styler; Gregg Podnar; Paul Dille; Matthew Duescher; Christopher Bartley; Illah Nourbakhsh

2011-01-01

321

Deterministic and Stochastic Neuronal Contributions to Distinct Synchronous CA3 Network Bursts  

PubMed Central

Computational studies have suggested that stochastic, deterministic, and mixed processes all could be possible determinants of spontaneous, synchronous network bursts. In the present study, utilizing multicellular calcium imaging coupled with fast confocal microscopy, we describe neuronal behavior underlying spontaneous network bursts in developing rat and mouse hippocampal area CA3 networks. Two primary burst types were studied: giant depolarizing potentials (GDPs) and spontaneous interictal bursts recorded in bicuculline, a GABAA receptor antagonist. Analysis of the simultaneous behavior of multiple CA3 neurons during synchronous GDPs revealed a repeatable activation order from burst to burst. This was validated using several statistical methods, including high Kendall’s W values for firing order during GDPs, high Pearson’s correlations of cellular activation times between burst pairs, and latent class analysis, which revealed a population of 5-6% of CA3 neurons reliably firing very early during GDPs. In contrast, neuronal firing order during interictal bursts appeared homogenous, with no particular cells repeatedly leading or lagging during these synchronous events. We conclude that GDPs activate via a deterministic mechanism, with distinct, repeatable roles for subsets of neurons during burst generation, while interictal bursts appear to be stochastic events with cells assuming interchangeable roles in the generation of these events.

Takano, Hajime; McCartney, Melissa; Ortinski, Pavel I.; Putt, Mary E.; Coulter, Douglas A.

2012-01-01

322

Morphological study of short gamma ray bursts  

NASA Astrophysics Data System (ADS)

Gamma Ray Bursts (GRB) of duration less than about 2 s, detected by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory have been selected for temporal analysis. These bursts constitute nearly 25% of the total and presumably form a separate class. Several parameters to describe the complexity and rapidity based on the burst temporal structure are derived and their dependence on other temporal and spectral properties are explored. A parameter is derived for each burst to characterize its spectral evolution based on its light curves in 4 energy channels. Bursts detected during April 1991 and March 1993 have been analysed yielding a sample size of 51 bursts. It has been found that the burst complexity is independent of its spectral content. The spectral evolution of short bursts is same as that of longer bursts. Also a systematic search for a coherent emission of ?-rays in short bursts yielded a negative result.

Bhat, P. N.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.

1996-08-01

323

Open-loop simulations of the primate saccadic system using burst cell discharge from the superior colliculus  

Microsoft Academic Search

Saccade-related burst neurons (SRBNs) in the monkey superior colliculus (SC) have been hypothesized to provide the brainstem saccadic burst generator with the dynamic error signal and the movement initiating trigger signal. To test this claim, we performed two sets of open-loop simulations on a burst generator model with the local feedback disconnected using experimentally obtained SRBN activity as both the

S. Das; N. J. Gandhi; E. L. Keller

1995-01-01

324

The use of dendrograms to describe the electrical activity of motoneurons underlying behaviors in leeches  

PubMed Central

The present manuscript aims at identifying patterns of electrical activity recorded from neurons of the leech nervous system, characterizing specific behaviors. When leeches are at rest, the electrical activity of neurons and motoneurons is poorly correlated. When leeches move their head and/or tail, in contrast, action potential (AP) firing becomes highly correlated. When the head or tail suckers detach, specific patterns of electrical activity are detected. During elongation and contraction the electrical activity of motoneurons in the Medial Anterior and Dorsal Posterior nerves increase, respectively, and several motoneurons are activated both during elongation and contraction. During crawling, swimming, and pseudo-swimming patterns of electrical activity are better described by the dendrograms of cross-correlations of motoneurons pairs. Dendrograms obtained from different animals exhibiting the same behavior are similar and by averaging these dendrograms we obtained a template underlying a given behavior. By using this template, the corresponding behavior is reliably identified from the recorded electrical activity. The analysis of dendrograms during different leech behavior reveals the fine orchestration of motoneurons firing specific to each stereotyped behavior. Therefore, dendrograms capture the subtle changes in the correlation pattern of neuronal networks when they become involved in different tasks or functions.

Juarez-Hernandez, Leon J.; Bisson, Giacomo; Torre, Vincent

2013-01-01

325

Electric Current Activated Combustion Synthesis and Chemical Ovens Under Terrestrial and Reduced Gravity Conditions.  

National Technical Information Service (NTIS)

Combustion synthesis (CS) generally involves mixing reactants together (e.g., metal powders) and igniting the mixture. Typically, a reaction wave will pass through the sample. In field activated combustion synthesis (FACS), the addition of an electric fie...

C. Unuvar D. Fredrick U. Anselmi-Tamburini A. Manerbino J. Y. Guigne Z. A. Munir B. D. Shaw

2004-01-01

326

Dendritic initiation and propagation of spikes and spike bursts in a multimodal sensory interneuron: the crustacean parasol cell.  

PubMed

Invasion of dendrites by spikes and spike bursts can play a critical role in regulating the output of central neurons by modifying their dynamic input-output relationships. Back-propagating bursts can modulate voltage-gated channels in the short term and can also modify long-term responses to synaptic input. Determining the morphological site of spike initiation and the mode of propagation through the dendritic arbor is therefore crucial to an understanding of a neuron's functional properties. I used electrophysiological methods to study parasol cells in isolated, perfused head preparations of the freshwater crayfish Procambarus clarkii to determine the compartment of origin of orthodromically activated action potentials and bursts that propagate within the dendritic arbor and to examine the identity of low-amplitude, electrotonically recorded spike events that are present in more than one-half of the intracellular recordings obtained from dendrites in these neurons. Experiments using antidromic activation of parasol cell axons indicated that electrotonically recorded spikes probably are generated in neighboring parasol cells, to which the impaled neurons are electrically coupled. Both paired intracellular recordings and extracellular field potential measurements were used to compare arrival times of antidromic and orthodromic spikes at loci in the vicinity of the trunk and the basal branch compartments of parasol cell dendrites. These methods provided consistent results, indicating that synaptically evoked action potentials are initiated at a site on the trunk, from which point they back-propagate into the basal branches within the hemiellipsoid body, and presumably, also orthodromically to the axon. Data are presented suggesting that bursts also arise at a trunk locus, but one that is different from the initiation point of single spikes evoked by excitatory postsynaptic potentials (EPSPs). Morphological specializations between the dendritic trunk and basal branches may facilitate back-propagation of spikes and spike bursts into the basal branches. PMID:12789014

Mellon, DeForest

2003-10-01

327

Gamma-ray burst populations  

NASA Astrophysics Data System (ADS)

Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists alike wondering about some of the basic questions surrounding these phenomena. Additionally, these events show remarkable individuality and extrema, ranging in redshift throughout the observable universe and over ten orders of magnitude in energy. This work focuses on analyzing groups of bursts that are different from the general trend and trying to understand whether these bursts are from different intrinsic populations and if so, what can be said about their progenitors. This is achieved through numerical Monte Carlo simulations and statistical inference in conjunction with current GRB observations. Chapter 1 gives a general introduction of gamma-ray burst theory and observations in a semi-historical context. Chapter 2 provides an introduction to the theory and practical issues surrounding the numerical simulations and statistics. Chapters 3--5 are each dedicated to a specific problem relating to a different type of GRB population: high-luminosity v. low-luminosity bursts, constraints from high-redshift bursts, and Type I v. Type II bursts. Chapter 6 follows with concluding remarks.

Virgili, Francisco Javier

328

Cosmological gamma-ray bursts  

NASA Technical Reports Server (NTRS)

The distribution in angle and flux of gamma-ray bursts indicates that the majority of gamma-ray bursters are at cosmological distances, i.e., at z of about 1. The rate is then about 10 exp -8/yr in a galaxy like the Milky Way, i.e., orders of magnitude lower than the estimated rate for collisions between neutron stars in close binary systems. The energy per burst is about 10 exp 51 ergs, assuming isotropic emission. The events appear to be less energetic and more frequent if their emission is strongly beamed. Some tests for the distance scale are discussed: a correlation between the burst's strength and its spectrum; the absorption by the Galactic gas below about 2 keV; the X-ray tails caused by forward scattering by the Galactic dust; about 1 month recurrence of some bursts caused by gravitational lensing by foreground galaxies; and a search for gamma-ray bursts in M31. The bursts appear to be a manifestation of something exotic, but conventional compact objects can provide an explanation. The best possibility is offered by a decay of a bindary composed of a spinning-stellar-mass black-hole primary and a neutron or a strange-quark star secondary. In the final phase the secondary is tidally disrupted, forms an accretion disk, and up to 10 exp 54 ergs are released. A very small fraction of this energy powers the gamma-ray burst.

Paczynski, Bohdan

1991-01-01

329

Electrical activities associated with inclined-plane tracking and erosion test  

Microsoft Academic Search

A leakage current monitoring system was installed to measure the electrical activities including peak leakage current, average leakage current, cumulative charge, and number of leakage current pulses in four ranges: 1-5 mA, 5-15 mA, 15-50 mA and 50-200 mA during the inclined-plane test (ASTM D2303). The electrical activities were measured for two materials-a silicone without aluminum trihydrate (ATH) and an

R. J. Chang; L. Mazeika

1996-01-01

330

Active electrical and optical tuning of silicon photonic devices with liquid crystals  

NASA Astrophysics Data System (ADS)

Silicon photonics is a rapidly evolving field allowing for optical devices to be made cost effectively using standard semiconductor fabrication techniques and integrated with microelectronic chips. Active tuning of silicon photonic devices has been demonstrated using thermal, electrical and optical means in the form of injection of free carriers through two-photon absorption. This work explores active electrical and optical tuning of silicon photonic devices using silicon strip waveguides combined with nematic liquid crystal (NLC) claddings. Simulation and experimental studies are presented.

Ptasinski, Joanna N.; Kim, Sung W.; Pang, Lin; Khoo, Iam-Choon; Fainman, Yeshaiahu

2013-09-01

331

Electric-utility solar-energy activities: 1981 survey  

NASA Astrophysics Data System (ADS)

Presented are the results of a survey to determine the scope of electric participation in solar energy projects in the United States. Brief descriptions are given of 943 projects being conducted by 236 utility companies. An index of projects by category, a statistical summary, a list of participating utilities with information contacts and addresses, a list of utilities with projects organized by technology, a list of utilities organized by state, a list of available reports on utility-sponsored projects, and a list of projects having multiple utility participants are included.

Baccelli, E.; Gordon, K.

1982-07-01

332

Origin of wide-band IP type II bursts  

NASA Astrophysics Data System (ADS)

Context. Different types of interplanetary (IP) type II bursts have been observed, where the more usual ones show narrow-band and patchy emissions, sometimes with harmonics, and which at intervals may disappear completely from the dynamic spectrum. The more unusual bursts are wide-band and diffuse, show no patches or breaks or harmonic emission, and often have long durations. Type II bursts are thought to be plasma emission, caused by propagating shock waves, but a synchrotron-emitting source has also been proposed as the origin for the wide-band type IIs. Aims: Our aim is to find out where the wide-band IP type II bursts originate and what is their connection to particle acceleration. Methods: We analyzed in detail 25 solar events that produced well-separated, wide-band IP type II bursts in 2001-2011. Their associations to flares, coronal mass ejections (CMEs), and solar energetic particle events (SEPs) were investigated. Results: Of the 25 bursts, 18 were estimated to have heights corresponding to the CME leading fronts, suggesting that they were created by bow shocks ahead of the CMEs. However, seven events were found in which the burst heights were significantly lower and which showed a different type of height-time evolution. Almost all the analyzed wide-band type II bursts were associated with very high-speed CMEs, originating from different parts of the solar hemisphere. In terms of SEP associations, many of the SEP events were weak, had poor connectivity due to the eastern limb source location, or were masked by previous events. Some of the events had precursors in specific energy ranges. These properties and conditions affected the intensity-time profiles and made the injection-time-based associations with the type II bursts difficult to interpret. In several cases where the SEP injection times could be determined, the radio dynamic spectra showed other features (in addition to the wide-band type II bursts) that could be signatures of shock fronts. Conclusions: We conclude that in most cases (in 18 out of 25 events) the wide-band IP type II bursts can be plasma emission, formed at or just above the CME leading edge. The results for the remaining seven events might suggest the possibility of a synchrotron source. These events, however, occurred during periods of high solar activity, and coronal conditions affecting the results of the burst height calculations cannot be ruled out. The observed wide and diffuse emission bands may also indicate specific CME leading edge structures and special shock conditions. Figures 2-26 and Table 4 are available in electronic form at http://www.aanda.org

Pohjolainen, S.; Allawi, H.; Valtonen, E.

2013-10-01

333

Application of proteins in burst delivery systems  

NASA Astrophysics Data System (ADS)

Biological proteins embedded in either a biological or an engineered membrane will actively maintain electrochemical balance across that membrane. In this study two applications will be examined. First a system of governing equations will be calibrated for a biological endosome. The endocytosis predictions presented then serve to validate the model. In addition, these predictions introduce new insights into endosome burst, which is of interest for advancing DNA vaccine delivery. The calibrated model is subsequently adapted to an analogous engineering scenario for targeted payload delivery. In the presence of a specific external stimulus, burst release of an arbitrary payload encased in a vesicle akin to an endosome is explored. Control of the process through manipulation of vesicle size, stimulus, and transporters is presented. A case is made for application of proteins as building blocks in the design of targeted response materials.

Freeman, E.; Weiland, L. M.; Meng, W. S.

2010-09-01

334

Radio bursts from superconducting strings  

NASA Astrophysics Data System (ADS)

We show that radio bursts from cusps on superconducting strings are linearly polarized, thus providing a signature that can be used to distinguish them from astrophysical sources. We write the event rate of string-generated radio transients in terms of observational variables, namely, the event duration and flux. Assuming a canonical set of observational parameters, we find that the burst event rate can be quite reasonable, e.g., order ten a year for grand unified strings with 100 TeV currents, and a lack of observed radio bursts can potentially place strong constraints on particle physics models.

Cai, Yi-Fu; Sabancilar, Eray; Vachaspati, Tanmay

2012-01-01

335

The Korean Solar Radio Burst Locator (KSRBL)  

NASA Astrophysics Data System (ADS)

This paper describes the design and operation of the Korean Solar Radio Burst Locator (KSRBL). The KSRBL is a radio spectrometer designed to observe solar decimeter and microwave bursts over a wide band (0.245-18 GHz) as well as to detect the burst locations without interferometry or mechanical sweeping. As a prototype, it is temporarily observing at the Owens Valley Radio Observatory (OVRO), California, USA, and after commissioning will be operated at the Korea Astronomy and Space Science Institute (KASI), Daejeon, Republic of Korea. The control system can agilely choose four 500 MHz intermediate frequency (IF) bands (2 GHz instantaneous bandwidth) from the entire 0.245-18 GHz band, with a standard time resolution of 100 ms, although higher time resolution is possible subject to data-rate constraints. To cover the entire band requires 10 tunings, which are therefore completed in 1 s. Each 500 MHz band is sampled at a 1 GS s (gigasample per second) rate, and 4096 time samples are Fast Fourier transformed (FFT) to 2048 subchannels for a frequency resolution of 0.24 MHz. To cover the entire range also requires two different feeds, a dual-frequency Yagi centered at 245 and 410 MHz, and a broadband spiral feed covering 0.5-18 GHz. The dynamic range is 35 dB over the 0.5-18 GHz band, and 55 dB in the 245 and 410 MHz bands, set by using switchable attenuators in steps of 5 dB. Each 500 MHz IF has a further 63 dB of settable analog attenuation. The characteristics of the spiral feed provide the ability to locate flaring sources on the Sun to typically 2'. The KSRBL will provide a broadband view of solar bursts for the purposes of studying solar activity for basic research, and for monitoring solar activity as the source of Space Weather and solar-terrestrial effects.

Dou, Yujiang; Gary, Dale E.; Liu, Zhiwei; Nita, Gelu M.; Bong, Su-Chan; Cho, Kyung-Suk; Park, Young-Deuk; Moon, Yong-Jae

2009-05-01

336

Contention Problem in Optical Burst Switching Network  

Microsoft Academic Search

Optical burst switching (OBS) is a promising switching technology for next-generation Internet backbone networks. One of the key problems hindering the realization of optical burst switching (OBS) technology in the core networks is the losses due to contention among the bursts at the core nodes. Wavelength Conversion is an effective contention resolution technique used to reduce the number of bursts

M. S. Reza; Maruf Hossain; Satya Prasad Majumder

2010-01-01

337

Nonrelativistic phase in -ray burst afterglows 1  

Microsoft Academic Search

The discovery of multiband afterglows definitely shows that most ?-ray bursts are of cosmological origin. ?-ray bursts are found to be one of the most violent explosive phenomena in the Universe, in which astonishing ultra-relativistic motions are involved. In this article, the multiband observational characteristics of ?-ray bursts and their afterglows are briefly reviewed. The standard model of ?-ray bursts,

HUANG Yongfeng

338

Intraphagosomal measurement of the magnitude and duration of the oxidative burst  

PubMed Central

Generation of an oxidative burst within the phagosomes of neutrophils, dendritic cells, and macrophages is an essential component of the innate immune system. To examine the kinetics of the oxidative burst in the macrophage phagosome, we developed two new assays using beads coated with oxidation sensitive fluorochromes. These assays permitted quantification and temporal resolution of the oxidative burst within the phagosome. The macrophage phagosomal oxidative burst is short-lived, with oxidation of bead-associated substrates reaching maximal activity within 30 min following phagocytosis. Additionally, the extent and rate of macrophage phagosomal substrate oxidation was subject to immuno-modulation by activation with LPS and/or IFN-?.

VanderVen, Brian C.; Yates, Robin M.; Russell, David G.

2009-01-01

339

Effect of Burst Temperature on Coolant Channel Restriction in Multirods Burst Tests  

Microsoft Academic Search

In order to study the effect of burst temperature on the coolant flow channel restriction, burst tests of fuel bundles were performed. Each bundle consisted of 49 rods (7×7 rods), and bursts were conducted in flowing steam. Burst temperature was changed by changing the internal gas pressure in rods. After the burst, the ballooning behavior of each rod and the

Satoru KAWASAKI; Masao HASHIMOTO; Takashi OTOMO; Teruo FURUTA; Hiroshi UETSUKA

1983-01-01

340

Burst interference in TDMA radio systems  

NASA Astrophysics Data System (ADS)

Burst interference is inherent in TDMA subscriber radio and satellite communications systems. Spectral and interference properties of burst modulated signals are investigated. Owing to the burst mode operation of the TDMA system its spectrum spreads; this spread increases with the increase of burst gating rate and the decrease of the burst length. A theoretical derivation of the Pe = f(Eb/N0; I) performance, computer simulation and experimental results of IJF-OQPSK and conventional QPSK burst operated systems are presented. The performance of these systems in the presence of burst mode TDMA co-channel and adjacent channel interference (I) is evaluated.

Lei, Z.; Chen, M.-X.; Feher, K.

1985-12-01

341

Electrical activity of chalcogen-hydrogen defects in silicon  

NASA Astrophysics Data System (ADS)

The interaction of hydrogen with substitutional chalcogen impurities (S, Se, or Te) is investigated by ab initio modeling. In Se-Hn and Te-Hn complexes (n=1,2), protons are located at sites antibonding to nearest-neighbor silicon atoms. For sulfur, two competitive sites for S-H are found, resulting in two nearly degenerate structures. All the singly hydrogenated complexes are predicted to be shallow donors with levels lying above those of the substitutional S, Se, and Te double donors. In contrast, doubly hydrogenated chalcogen impurities are predicted to be electrically inert. A comparison of our results with experimental data suggests that the NL60 and NL61 electron-paramagnetic-resonance centers can be identified with two Se-H defects, where H is antibonded to a Si neighbor of Se.

Coutinho, J.; Torres, V. J.; Jones, R.; Briddon, P. R.

2003-01-01

342

Ion chamber gamma burst detector  

SciTech Connect

A gamma ray burst detector of x-ray photons 2 to 10 keV is designed to maximize area, 100 m/sup 2/, and sensitivity, 10/sup -10/ ergs cm/sup -2/ s/sup 1/2/ modest directionality, 2 x 10/sup -4/ sr, and minimize thickness, 3 mg cm/sup -2/, as a plastic space balloon ion chamber. If the log N - log S curve for gamma bursts extends as the -3/2 power, the sensitivity is limited by gamma-burst peak overlap in time so that the question of the size spectrum and isotropy is maximally tested. Supernova type I prompt x-ray bursts of congruent to 3-ms duration should be detected at a rate of several per day from supernova at a distance greater than 100 Mpc.

Colgate, S.A.

1981-08-25

343

New Views of Thermonuclear Bursts  

Microsoft Academic Search

Since the advent of powerful new X-ray observatories, NASA's Rossi X-ray Timing Explorer (RXTE), the Italian - Dutch BeppoSAX mission, XMM-Newton and Chandra, a number of entirely new phenomena associated with thermonuclear burning on neutron stars have been discovered. These include: (i) the discovery of millisecond (300 - 600 Hz) oscillations during bursts, so called ``burst oscillations'', (ii) a new

Tod Strohmayer; Lars Bildsten

2003-01-01

344

X-ray bursts: Observation versus theory  

NASA Technical Reports Server (NTRS)

Results of various observations of common type I X-ray bursts are discussed with respect to the theory of thermonuclear flashes in the surface layers of accreting neutron stars. Topics covered include burst profiles; irregular burst intervals; rise and decay times and the role of hydrogen; the accuracy of source distances; accuracy in radii determination; radius increase early in the burst; the super Eddington limit; temperatures at burst maximum; and the role of the magnetic field.

Lewin, W. H. G.

1981-01-01

345

Swift Burst Alert Telescope (BAT) Spectral Response  

Microsoft Academic Search

The Burst Alert Telescope (BAT) is one of three telescopes aboard the Swift Gamma-Ray Burst Explorer that was launched on November 20, 2004. Swift's primary purpose is to identify and localize astronomical gamma-ray bursts and study their X-ray, UV and optical afterglow emission within seconds of the burst trigger. BAT provides the initial burst positions, as well as gamma-ray light

Ann Parsons

2005-01-01

346

X-ray bursts: observation versus theory  

SciTech Connect

Results of various observations of common type I X-ray bursts are discussed with respect to the theory of thermonuclear flashes in the surface layers of accreting neutron stars. Topics covered include burst profiles; irregular burst intervals; rise and decay times and the role of hydrogen; the accuracy of source distances; accuracy in radii determination; radius increase early in the burst; the super Eddington limit; temperatures at burst maximum; and the role of the magnetic field.

Lewin, W.H.G.

1981-01-01

347

Detailed Measurements of Gastric Electrical Activity and Their Implications on Inverse Solutions  

PubMed Central

Significant research effort has been expended on investigating methods to non-invasively characterize gastrointestinal electrical activity. Despite the clinical success of the 12-lead electrocardiograms (ECG) and the emerging success of inverse methods for characterizing electrical activity of the heart and brain, similar methods have not been successfully transferred to the gastrointestinal field. The normal human stomach generates rhythmic electrical impulses, known as slow waves, that propagate within the stomach at a frequency of 3 cycles per minute. Disturbances in this activity are known to result in disorders in the motility patterns of the stomach. However, there is still limited understanding regarding the basic characteristics of the electrical propagation in the stomach. Contrary to existing beliefs, recent results from high resolution recordings of gastric electrical activity have shown that multiple waves, complete with depolarization and repolarization fronts, can be simultaneously present at any given time in the human stomach. In addition, it has been shown that there are marked variations in the amplitude and velocities in different regions in the stomach. In human recordings, the antrum had slow waves with significantly higher amplitudes and velocities than the corpus. Due to the presence of multiple slow wave events, single and multiple dipole-type inverse methods are not appropriate and distributed source models must therefore be considered. Furthermore, gastric electrical waves move significantly slower than electrical waves in the heart, and it is currently difficult to obtain structural images of the stomach at the same time as surface electrical or magnetic gastric recordings are made. This further complicates the application of inverse procedures for gastric electrical imaging.

Cheng, Leo K.; O'Grady, Greg; Du, Peng; Egbuji, John U.; Windsor, John A.; Pullan, Andrew J.

2014-01-01

348

Symmetric bursting behaviors in the generalized FitzHugh-Nagumo model.  

PubMed

In the current paper, we have investigated the generalized FitzHugh-Nagumo model. We have shown that symmetric bursting behaviors of different types could be observed in this model with an appropriate recovery term. A modified version of this system is used to construct bursting activities. Furthermore, we have shown some numerical examples of delayed Hopf bifurcation and canard phenomenon in the symmetric bursting of super-Hopf/homoclinic type near its super-Hopf and homoclinic bifurcations, respectively. PMID:23801268

Abbasian, A H; Fallah, H; Razvan, M R

2013-08-01

349

Storms of U-bursts and the stability of coronal loops  

Microsoft Academic Search

U-burst activity as observed in the frequency range of 25-75 MHz with the large array and sweep frequency spectrograph of Nancay, is analyzed by using five years of observations. In this frequency range, U-bursts sometimes occur isolated but most often in groups and in storms; in this case U-bursts are generally inverted J or L-shaped. Evidence is shown for a

Y. Leblanc; M. Hoyos

1985-01-01

350

Observations of Solar Radio Bursts with NRL LWA Antenna Prototypes  

NASA Astrophysics Data System (ADS)

We present spectra of solar bursts observed with active antenna prototypes. Combining active antenna systems developed for the NLTA (NRL Long-wavelength Test Array) and experience gained from BIRS (Bruny Island Radio Spectrometer) we have developed the GDRT (Goddard Decametric Radio Telescope). The GDRT and Green Bank Solar Radio Burst Spectrometer (GB/SRBS) serve as the northern hemisphere companions to BIRS, which operates in Tasmania. These instruments continuously scan from <12 MHz to >100 MHz while simultaneously applying RFI mitigation algorithms to produce a continuous record of solar activity. This space weather initiative demonstrates one application of hardware developed for the LWA (Long Wavelength Array).

Stewart, K. P.; Hicks, B. C.; Crane, P. C.; Kassim, N. E.; MacDowall, R. J.; Bradley, R.; Erickson, W. C.

2005-12-01

351

Workshop Physics Activity Guide, Electricity and Magnetism, Module 4  

NSDL National Science Digital Library

This student workbook is part of a set of workbooks designed to serve as the foundation for a two-semester calculus-based introductory physics course consisting of 28 units that interweave text materials with activities that include prediction, qualitative observation, explanation, equation derivation, mathematical modeling, quantitative experiments, and problem solving. This workbook covers electrostatics, DC circuits, electronics, and magnetism.

Laws, Priscilla W.

2006-07-22

352

Inferred flows of electric currents in solar active regions  

NASA Technical Reports Server (NTRS)

Techniques to identify sources of major current systems in active regions and their channels of flow are explored. Measured photospheric vector magnetic fields together with high resolution white light and H-alpha photographs provide the data base to derive the current systems in the photosphere and chromosphere of a solar active region. Simple mathematical constructions of active region fields and currents are used to interpret these data under the assumptions that the fields in the lower atmosphere (below 200 km) may not be force free but those in the chromosphere and higher are. The results obtained for the complex active region AR 2372 are: (1) Spots exhibiting significant spiral structure in the penumbral filaments were the source of vertical currents at the photospheric surface; (2) Magnetic neutral lines where the transverse magnetic field was strongly sheared were channels along which a strong current system flowed; (3) The inferred current systems produced a neutral sheet and oppositely-flowing currents in the area of the magnetic delta configuration that was the site of flaring.

Ding, Y. J.; Hong, Q. F.; Hagyard, M. J.; Deloach, A. C.

1985-01-01

353

Characterization and Origin of Silicon Defect Electrical Activity Through Electron-Beam Current(ebic) Microscopy.  

NASA Astrophysics Data System (ADS)

This thesis is concerned with characterizing, observing, and exploring the origins of a silicon crystalline defect's electrical properties. These goals are accomplished by unique applications of the electron-beam-induced current (EBIC) technique. To begin, bulk silicon solar cell properties are correlated with EBIC at low accelerating voltage (LAV-EBIC) and high accelerating voltage (HAV-EBIC). HAV-EBIC currents were related linearly to the short circuit current density, conversion efficiency, and dislocation density, but LAV -EBIC currents were found to be independent of the same properties. The difference in probing depth was used to explain the discrepancy. The next section combines EBIC and transmission electron microscopy (TEM), into one scanning transmission electron microscope (STEM), to unambiguously correlate electrical activity with defect structure. This technique is successfully applied to defects in polycrystalline silicon, but the complexity and variety of general silicon defects made this approach unsuitable for uncovering the origins of a defect's electrical activity. The origins of electrical activity were investigated by welding together two float-zone silicon wafers to form twist boundaries. These boundaries are composed of a square array of screw dislocations of sufficient number and purity to separate impurity effects from the intrinsic electrical activity. Applying the Kittler and Seifert model, the silicon screw dislocations were estimated to have between 0.3 and 0.5 recombination sites per Burgers vector. It was subsequently concluded that kinks and jogs were responsible for screw dislocation electrical recombination.

Perreault, George Charles

354

Magnetic Activity and Stability of the UCLA Electric Tokamak.  

NASA Astrophysics Data System (ADS)

The Electric Tokamak (ET) is now operating at .25 Tesla with 60 kA of plasma current and with a 1.5 sec pulse length. The current as well as the radial and vertical positions are controlled in real-time, giving a stable target for ICRH at the 2^nd harmonic. With about 50 kW of RF heating, the loop voltage decreases by 30indicating a broadening of the current profile. We are in the process of increasing the RF input power to the 1/2 MW level in order to go beyond the Troyon limit. High field side and low field side injection will take place. Elongation of the plasma will improve the antennas' coupling. We are also preparing ion cyclotron current drive for long pulse operation (30 sec) and for shaping the current profile to peak near the outer edge. This profile will help avoid low n,m internal kink modes. The long pulses will allow the current to diffuse to its steady state profile. Discharge cleaning and Titanium gettering of the walls are routinely performed to insure excellent wall conditions and Z_eff < 1.1. VL of .6 Volt is achieved in ohmic conditions. Without Ti deposition, VL > 1 Volt and minor disruptions caused by internal kink modes become frequent.

Gauvreau, J.-L.; Gourdain, P.-A.; Lafonteese, D. J.; Schmitz, L. W.; Taylor, R. J.

2001-10-01

355

ELECTRICAL ACTIVITY IN THE CHEMORECEPTORS OF THE BLOWFLY  

PubMed Central

The electrical responses of the neurons associated with the various types of chemosensory hairs of the blowfly, Phormia regina Meigen, following stimulation by chemical and mechanical means have been studied. The singly innervated chemosensory hairs on the ovipositor, maxillary palpi, and antennae respond vigorously to chemical stimulation, but not to mechanical stimulation. The triply innervated chemosensory hairs on the labellum, tarsus, and wing have two neurons which respond only to chemical stimuli. The third neuron responds only to mechanical stimulation. The differential responses of the two chemosensory neurons to various chemical stimuli following the removal of the tip of the hair suggest that the structures responsible for chemoreception are located throughout the distal processes of these neurons. The response of the third neuron to mechanical stimulation is similar to the response recorded from the neuron associated with one type of tactile hair which responds to motion and not to steady deformation. Recordings have been made from the neurons associated with purely tactile hairs using the cut hair as an extension of the micropipette. The mechanosensory neuron of the wing chemosensory hair is capable of responding at the rate of at least 600 impulses per sec. and may serve to indicate changes in air flow over the wing surfaces during flight to enable the fly to correct the wing camber and attack angle.

Wolbarsht, M. L.; Dethier, V. G.

1958-01-01

356

Emission Patterns of Solar Type III Radio Bursts: Stereoscopic Observations  

NASA Astrophysics Data System (ADS)

Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft Rj = Ij /?Ij (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of ~2° and (2) bursts emitting into a wider cone with angular width spanning from ~ - 100° to ~100°. The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

Thejappa, G.; MacDowall, R. J.; Bergamo, M.

2012-02-01

357

Emission Patterns of Solar Type III Radio Bursts: Stereoscopic Observations  

NASA Technical Reports Server (NTRS)

Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft Rj = Ij /[Sigma]Ij (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of approximately 2 deg and (2) bursts emitting into a wider cone with angular width spanning from [approx] -100 deg to approximately 100 deg. The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

Thejappa, G.; MacDowall, R.; Bergamo, M.

2012-01-01

358

Analysis of electrical activity associated with inclined-plane tracking and erosion of insulating materials  

Microsoft Academic Search

Surface electrical activity and physical changes were measured and compared for several types of outdoor insulation materials, using a standard test method. The leakage current activities during the inclined-plane test (ASTM D2303) were measured by using four representative materials: a silicone with high (>70% by weight) loading of alumina trihydrate (ATH), a silicone with no ATH, a poly ethylene vinyl

R. J. Chang; L. Mazeika

2000-01-01

359

Electric arc furnace power quality improvement using shunt active filter and series inductor  

Microsoft Academic Search

This paper presents an investigation of power quality problems arising from electric arc furnace (EAF) operation, and the required compensating system capabilities. It also proposes a compensation system using a shunt active filter and a series inductor. A shunt active filter compensates for the reactive power and the current harmonics of the highly varying load. Reference signals for the compensation

Ahmad Esfandiari; Mostafa Parniani

2004-01-01

360

Correlation between cognitive brain function and electrical brain activity in dementia of Alzheimer type  

Microsoft Academic Search

Summary Psychometric tests which assess cognitive brain function in dementia disorders are partly prone to artifacts, e.g., the experience of the investigator and the cooperation of the patient influences the results. An objective way to assess the degree of cognitive disturbance could be to measure neuronal activity represented by the electrical brain activity. The aim of the present study was

T. Dierks; L. Frölich; R. Ihl; K. Maurer

1995-01-01

361

IPMSM sensorless control based on fuzzy active-disturbance rejection controller for electric vehicle  

Microsoft Academic Search

In the interior permanent magnet synchronous motor (IPMSM) sensorless control system for electric vehicle (EV), in order to improve system robustness and adaptive ability, a novel active-disturbance rejection controller (ADRC) is presented in this paper. In practice, the ADRC parameters are difficult to operate and adjust, so we introduce the fuzzy control, combined with their own characteristics, a self-adapted active

Shoudao Huang; Jiangchuan Kuang; Qing Huang; Keyuan Huang; Jian Gao; Ting Liu

2011-01-01

362

Fostering Elementary School Students' Understanding of Simple Electricity by Combining Simulation and Laboratory Activities  

ERIC Educational Resources Information Center

Computer simulations and laboratory activities have been traditionally treated as substitute or competing methods in science teaching. The aim of this experimental study was to investigate if it would be more beneficial to combine simulation and laboratory activities than to use them separately in teaching the concepts of simple electricity. Based…

Jaakkola, T.; Nurmi, S.

2008-01-01

363

The use of research activities as learning instrument in electrical engineering and computer science graduations  

Microsoft Academic Search

In this paper we analyze the use of research activities as learning instrument in electrical engineering and computer science. This pedagogic approach was applied in undergraduate disciplines, undergraduate teaching assistance and undergraduate research projects. Our main goals are optimize the learning process using research and motivate the use of research activities as learning instrument.

Carlos A. P. S. Martins; Milene B. Carvalho; Christiane V. Pousa; Dulcinéia O. Penha

2003-01-01

364

Investigation of a Bubble Detector based on Active Electrolocation of Weakly Electric Fish  

NASA Astrophysics Data System (ADS)

Weakly electric fish employ active electrolocation for navigation and object detection. They emit an electric signal with their electric organ in the tail and sense the electric field with electroreceptors that are distributed over their skin. We adopted this principle to design a bubble detector that can detect gas bubbles in a fluid or, in principle, objects with different electric conductivity than the surrounding fluid. The evaluation of the influence of electrode diameter on detecting a given bubble size showed that the signal increases with electrode diameter. Therefore it appears that this detector will be more appropriate for large sized applications such as bubble columns than small sized applications such as bubble detectors in dialysis.

Mohan, M.; Mayekar, K.; Zhou, R.; von der Emde, G.; Bousack, H.

2013-04-01

365

Separating burst from background spikes in multichannel neuronal recordings using return map analysis.  

PubMed

We propose a preprocessing method to separate coherent neuronal network activity, referred to as “bursts”, from background spikes. High background activity in neuronal recordings reduces the effectiveness of currently available burst detection methods. For long-term, stationary recordings, burst and background spikes have a bimodal ISI distribution which makes it easy to select the threshold to separate burst and background spikes. Finite, nonstationary recordings lead to noisy ISIs for which the bimodality is not that clear. We introduce a preprocessing method to separate burst from background spikes to improve burst detection reliability because it efficiently uses both single and multichannel activity. The method is tested using a stochastic model constrained by data available in the literature and recordings from primary cortical neurons cultured on multielectrode arrays. The separation between burst and background spikes is obtained using the interspike interval return map. The cutoff threshold is the key parameter to separate the burst and background spikes. We compare two methods for selecting the threshold. The 2-step method, in which threshold selection is based on fixed heuristics. The iterative method, in which the optimal cutoff threshold is directly estimated from the data. The proposed preprocessing method significantly increases the reliability of several established burst detection algorithms, both for simulated and real recordings. The preprocessing method makes it possible to study the effects of diseases or pharmacological manipulations, because it can deal efficiently with nonstationarity in the data. PMID:24812717

Martens, M B; Chiappalone, M; Schubert, D; Tiesinga, P H E

2014-06-01

366

A Search for Nontriggered Gamma-Ray Bursts in the BATSE Database  

NASA Technical Reports Server (NTRS)

We describe a search of archival data from the Burst and Transient Source Experiment (BATSE). The purpose of the search is to find astronomically interesting transients that did not activate the burst-detection (or "trigger") system on board the spacecraft. Our search is sensitive to events with peak fluxes (on the 1.024 s timescale) that are lower by a factor of approximately 2 than can be detected with the on-board burst trigger. In a search of 345 days of archival data, we detected 91 events in the 50-300 keV range that resemble classical gamma-ray bursts but that did not activate the on-board burst trigger. We also detected 110 low-energy (25-50 keV) events of unknown origin that may include activity from' soft gamma repeater (SGR) 1806-20 and bursts and flares from X-ray binaries. This paper gives the occurrence times, estimated source directions, durations, peak fluxes, and fluences for the 91 gamma-ray burst candidates. The direction and intensity distributions of these bursts imply that the biases inherent in the on-board trigger mechanism have not significantly affected the completeness of the published BATSE gamma-ray burst catalogs.

Kommers, Jefferson M.; Lewin, Walter H. G.; Kouveliotou, Chryssa; VanParadus, Jan; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.

1997-01-01

367

Efficacy of prefrontal theta-burst stimulation in refractory depression: a randomized sham-controlled study.  

PubMed

Theta-burst transcranial magnetic stimulation could modulate cortical excitability and has the potential to treat refractory depression. However, there has been a lack of large randomized studies of the antidepressant efficacy of different forms of theta-burst stimulation, such as intermittent and continuous theta-burst stimulation. A randomized sham-controlled study was conducted to investigate antidepressant efficacy of theta-burst stimulation and to compare efficacy among left-prefrontal intermittent theta-burst stimulation, right-prefrontal continuous theta-burst stimulation and a combination of them in patients showing different levels of antidepressant refractoriness. A group of 60 treatment-refractory patients with recurrent major depressive disorder were recruited and randomized to four groups (Group A: continuous theta-burst stimulation; Group B: intermittent theta-burst stimulation; Group C: a combination of continuous and intermittent theta-burst stimulation; and Group D: sham theta-burst stimulation; 15 patients were included in each group). After 2 weeks of theta-burst stimulation treatment, depression improved in all groups. Groups B and C had better antidepressant responses (as reflected by % decreases in depression score) than Groups A and D (P = 0.001, post hoc analysis: B > A, B > D, C > A, and C > D), even after controlling for age and refractoriness scores. The mean antidepressant effect was highest in Group C and followed by that in Group B. Additionally, a significant placebo effect was found in patients with low refractoriness; this disappeared in patients with moderate-to-high refractoriness. A significant correlation existed between refractoriness scores and treatment responses. Treatment refractoriness was a significant factor negatively predicting efficacy of theta-burst stimulation (P = 0.039). This randomized sham-controlled study demonstrated that active theta-burst stimulation is a well-tolerated form of repetitive transcranial magnetic stimulation and has good antidepressant efficacy, particularly in depressed subjects within a certain range of treatment refractoriness. PMID:24817188

Li, Cheng-Ta; Chen, Mu-Hong; Juan, Chi-Hung; Huang, Hsiang-Hsuan; Chen, Li-Fen; Hsieh, Jen-Chuen; Tu, Pei-Chi; Bai, Ya-Mei; Tsai, Shin-Jen; Lee, Ying-Chiao; Su, Tung-Ping

2014-07-01

368

Complex evolution of spike patterns during burst propagation through feed-forward networks.  

PubMed

Stable signal transmission is crucial for information processing by the brain. Synfire-chains, defined as feed-forward networks of spiking neurons, are a well-studied class of circuit structure that can propagate a packet of single spikes while maintaining a fixed packet profile. Here, we studied the stable propagation of spike bursts, rather than single spike activities, in a feed-forward network of a general class of excitable bursting neurons. In contrast to single spikes, bursts can propagate stably without converging to any fixed profiles. Spike timings of bursts continue to change cyclically or irregularly during propagation depending on intrinsic properties of the neurons and the coupling strength of the network. To find the conditions under which bursts lose fixed profiles, we propose an analysis based on timing shifts of burst spikes similar to the phase response analysis of limit-cycle oscillators. PMID:18685860

Teramae, Jun-nosuke; Fukai, Tomoki

2008-08-01

369

Roles of phospholipase D in phorbol myristate acetate-stimulated neutrophil respiratory burst.  

PubMed

The phorbol myristate acetate (PMA) stimulated nutrophil respiratory burst has been considered to simply involve the activation of protein kinase C (PKC). However, the PLD activity was also increased by 10-fold in human neutrophils stimulated with 100 nM PMA. Unexpectedly, U73122, an inhibitor of phospholipase C, was found to significantly inhibit PMA-stimulated respiratory burst in human neutrophils. U73122 at the concentrations, which were sufficient to inhibit the respiratory burst completely, caused partial inhibition of the PLD activity but no inhibition on PKC translocation and activation, suggesting that PLD activity is also required in PMA-stimulated respiratory burst. Using 1-butanol, a PLD substrate, to block phosphatidic acid (PA) generation, the PMA-stimulated neutrophil respiratory burst was also partially inhibited, further indicating that PLD activation, possibly its hydrolytic product PA and diacylglycerol (DAG), is involved in PMA-stimulated respiratory burst. Since GF109203X, an inhibitor of PKC that could completely inhibit the respiratory burst in PMA-stimulated neutrophils, also caused certain suppression of PLD activation, it may suggest that PLD activation in PMA-stimulated neutrophils might be, to some extent, PKC dependent. To further study whether PLD contributes to the PMA stimulated respiratory burst through itself or its hydrolytic product, 1,2-dioctanoyl-sn-glycerol, an analogue of DAG , was used to prime cells at low concentration, and it reversed the inhibition of PMA-stimulated respiratory burst by U73122. The results indicate that U73122 may act as an inhibitor of PLD, and PLD activation is required in PMA-stimulated respiratory burst. PMID:20158570

Hu, Tianhui; Liu, Zhaoxia; Shen, Xun

2011-03-01

370

Active RF Pulse Compression Using Electrically Controlled Semiconductor Switches  

SciTech Connect

In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer and has achieved a switching time of 300ns. The wafer is inserted into a cylindrical waveguide operating in the TE01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. The RF energy is stored in a room-temperature, high-Q 375 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 8, which is the ratio between output and input power.

Guo, J.; Tantawi, S.; /SLAC

2007-03-21

371

Active RF Pulse Compression using Electrically Controlled Semiconductor Switches  

SciTech Connect

In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer and has achieved a switching time of 300ns. The wafer is inserted into a cylindrical waveguide operating in the TE01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. The RF energy is stored in a room-temperature, high-Q 375 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 8, which is the ratio between output and input power.

Guo Jiquan; Tantawi, Sami [Stanford Linear Accelerator Center, 2575 Sand Hill Rd, Menlo Park, CA 94025 (United States)

2006-11-27

372

On the haptic nature of the active electric sense of fish.  

PubMed

Electroreception is a sensory modality present in chondrichthyes, actinopterygii, amphibians, and mammalian monotremes. The study of this non-intuitive sensory modality has provided insights for better understanding of sensory systems in general and inspired the development of innovative artificial devices. Here we review evidence obtained from the analysis of electrosensory images, neurophysiological data from the recording of unitary activity in the electrosensory lobe, and psychophysical data from analysis of novelty responses provoked in well-defined stimulus conditions, which all confirm that active electroreception has a short range, and that the influence of exploratory movements on object identification is strong. In active electric images two components can be identified: a "global" image profile depending on the volume, shape and global impedance of an object and a "texture" component depending on its surface attributes. There is a short range of the active electric sense and the progressive "blurring" of object image with distance. Consequently, the lack of precision regarding object location, considered together, challenge the current view of this sense as serving long range electrolocation and the commonly used metaphor of "electric vision". In fact, the active electric sense shares more commonalities with human active touch than with teleceptive senses as vision or audition. Taking into account that other skin exteroceptors and proprioception may be congruently stimulated during fish exploratory movements we propose that electric, mechanoceptive and proprioceptive sensory modalities found in electric fish could be considered together as a single haptic sensory system. This article is part of a Special Issue entitled Neural Coding 2012. PMID:23727613

Caputi, Angel A; Aguilera, Pedro A; Carolina Pereira, Ana; Rodríguez-Cattáneo, Alejo

2013-11-01

373

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, W. S.; Pendleton, G. N.; Kouveliotou, C.

1991-09-01

374

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, Gerald J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, William S.; Pendleton, G. N.; Kouveliotou, C.

375

U.S. Department of Energy -- Advanced Vehicle Testing Activity: Plug-in Hybrid Electric Vehicle Testing and Demonstration Activities  

Microsoft Academic Search

The U.S. Department of Energys (DOE) Advanced Vehicle Testing Activity (AVTA) tests plug-in hybrid electric vehicles (PHEV) in closed track, dynamometer and onroad testing environments. The onroad testing includes the use of dedicated drivers on repeated urban and highway driving cycles that range from 10 to 200 miles, with recharging between each loop. Fleet demonstrations with onboard data collectors are

James E. Francfort; Donald Karner; John G. Smart

2009-01-01

376

Intracellular electrical activity of canine and human gastric smooth muscle.  

PubMed Central

1. Intracellular recordings were obtained from circular smooth muscle fibres of the canine fundus, corpus, antrum and pylorus as well as from the human corpus and antrum. 2. In the canine stomach, all regions of the stomach except the fundus exhibited spontaneous action potentials. 3. The spontaneous action potential consisted of an upstroke potential and a plateau potential. 4. There were regional differences in the configuration of the plateau potential. Corporal and antral smooth muscle did not normally spike during the plateau potential whereas terminal antral and pyloric muscle usually showed spikes on top of the plateau potential. Near the intermediate sphincter, there was a zone of transition in which oscillations in potential of variable amplitude were superimposed on the plateau potential. 5. The configuration of the action potential of the human stomach was similar to the configuration of the canine action potential when the same region of the stomach was compared. 6. The ionic dependence of the plateau potential was studied in canine stomach in an area where neither oscillations nor spikes occurred. 7. In clacium-free solution, all spontaneous activity stopped. D600 selectively suppressed the size of the plateau potential. 8. Sodium-deficient solution reduced the size of the plateau potential. 9. These results suggest that both calcium and sodium may be involved as current carriers in the generation of the plateau potential. Images Fig. 1

el-Sharkawy, T Y; Morgan, K G; Szurszewski, J H

1978-01-01

377

Bursting and calcium oscillations in pancreatic ?-cells: specific pacemakers for specific mechanisms  

PubMed Central

Oscillatory phenomenon in electrical activity and cytoplasmic calcium concentration in response to glucose are intimately connected to multiple key aspects of pancreatic ?-cell physiology. However, there is no single model for oscillatory mechanisms in these cells. We set out to identify possible pacemaker candidates for burst activity and cytoplasmic Ca2+ oscillations in these cells by analyzing published hypotheses, their corresponding mathematical models, and relevant experimental data. We found that although no single pacemaker can account for the variety of oscillatory phenomena in ?-cells, at least several separate mechanisms can underlie specific kinds of oscillations. According to our analysis, slowly activating Ca2+-sensitive K+ channels can be responsible for very fast Ca2+ oscillations; changes in the ATP/ADP ratio and in the endoplasmic reticulum calcium concentration can be pacemakers for both fast bursts and cytoplasmic calcium oscillations, and cyclical cytoplasmic Na+ changes may underlie patterning of slow calcium oscillations. However, these mechanisms still lack direct confirmation, and their potential interactions raises new issues. Further studies supported by improved mathematical models are necessary to understand oscillatory phenomena in ?-cell physiology.

Tamarina, N.; Philipson, L. H.

2010-01-01

378

Global synchronization of N neurons in external electrical stimulation via active control.  

PubMed

In this paper, active control law is derived and applied to control and synchronize N(N >or= 3) unidirectional coupled Fitzhugh-Nagumo neurons in external electrical stimulation. Firstly, the dynamical behavior of the nonlinear Fitzhugh-Nagumo model responding to various external electrical stimulations is studied. Then, using the results of the analysis, the active control strategy is designed for global synchronization of the N(N >or= 3) unidirectional coupled neurons and stabilizing the chaotic trajectory of the slave system to desired periodic orbit of the master system. Numerical simulations demonstrate the validity and feasibility of the proposed method. PMID:19163207

Li, Huiyan; Zhang, Ronghua; Wang, Jiang; Deng, Bin; Dong, Feng

2008-01-01

379

Modeling gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. This shell model code can be used to constrain broadband observations of GRB 090926A, which showed two flares in both the Swift UVOT and XRT bands. Using the prompt emission fluence to constrain the total energy contained in the blastwave, the internal shock model requires that Lorentz factors of the shells causing flares must be less than the Lorentz factor of the blastwave when the shells are ejected. Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from an external shock. We analyze four GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM), which have high quality lightcurves in both instrument energy bands. Using the MeV prompt emission (GBM) data, we can record the energy output from the central engine as a function of time. Assuming a constant radiative efficiency, we are able to track energy accumulation in the external shock using our internal/external shell model code and show that the late time lightcurves fit well within the external shock model, but the early time lightcurves are dominated by the internal shock component which has a shallow decay phase due to the initial pile-up of shells onto the blast wave.

Maxham, Amanda

380

GABA-A receptor antagonists increase firing, bursting and synchrony of spontaneous activity in neuronal networks grown on microelectrode arrays: a step towards chemical "fingerprinting"  

EPA Science Inventory

Assessment of effects on spontaneous network activity in neurons grown on MEAs is a proposed method to screen chemicals for potential neurotoxicity. In addition, differential effects on network activity (chemical "fingerprints") could be used to classify chemical modes of action....

381

Motion of the dipolarization front during a flow burst event observed by Cluster  

Microsoft Academic Search

In this paper we study a flow burst event which took place during enhanced geomagnetic activity on July 22, 2001, when Cluster was located in the postmidnight magnetotail. The flow burst was associated with a clear dipolarization ahead of the high-speed part of the predominantly Earthward directed flow. Based on the analysis of the four spacecraft data, we found that

R. Nakamura; W. Baumjohann; B. Klecker; Y. Bogdanova; A. Balogh; R. Nakamura; J. M. Bosqued; I. Dandouras; J. A. Sauvaud; K.-H. Glassmeier; L. Kistler; C. Mouikis; T. L. Zhang; H. Eichelberger; A. Runov

2002-01-01

382

Localization of self-potential sources in volcano-electric effect with complex continuous wavelet transform and electrical tomography methods for an active volcano  

Microsoft Academic Search

This study concerns the fluid flow circulation associated with magmatic intrusion during volcanic eruptions from electrical tomography studies. The objective is to localize and characterize the sources responsible for electrical disturbances during a time evolution survey between 1993 and 1999 of an active volcano, the Piton de la Fournaise. We have applied a dipolar probability tomography and a multi-scale analysis

Ginette Saracco; Philippe Labazuy; Frédérique Moreau

2004-01-01

383

In-vitro suppression of metabolic activity in malignant human glioblastomas due to pulsed - low frequency electric potential exposures  

NASA Astrophysics Data System (ADS)

The role of pulsed - low repetition frequency electric potential was investigated in suppressing the metabolic activities of aggressive human brain cancer cells. Twenty four hours post exposure the glioblastomas were found to be significantly inhibited in their metabolic activity. The findings herein reveal a near complete inhibition of glioblastoma's metabolic activity through selective applications of low frequency pulsed electric potentials.

Schlichting, Abby; Waynant, Ronald W.; Tata, Darrell B.

2010-02-01

384

First experimental observations of neutron bursts under thunderstorm clouds near sea level  

NASA Astrophysics Data System (ADS)

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009-2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1-3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10-3 cm-2 s-1. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of -16 kV/m.

Starodubtsev, S. A.; Kozlov, V. I.; Toropov, A. A.; Mullayarov, V. A.; Grigor'ev, V. G.; Moiseev, A. V.

2012-10-01

385

Fermi/GBM Observations of SGRJ0501 + 4516 Bursts  

NASA Technical Reports Server (NTRS)

We present our temporal and spectral analyses of 29 bursts from SGRJ0501+4516, detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope during the 13 days of the source activation in 2008 (August 22 to September 3). We find that the T(sub 90) durations of the bursts can be fit with a log-normal distribution with a mean value of approx. 123 ms. We also estimate for the first time event durations of Soft Gamma Repeater (SGR) bursts in photon space (i.e., using their deconvolved spectra) and find that these are very similar to the T(sub 90)s estimated in count space (following a log-normal distribution with a mean value of approx. 124 ms). We fit the time-integrated spectra for each burst and the time-resolved spectra of the five brightest bursts with several models. We find that a single power law with an exponential cutoff model fits all 29 bursts well, while 18 of the events can also be fit with two black body functions. We expand on the physical interpretation of these two models and we compare their parameters and discuss their evolution. We show that the time-integrated and time-resolved spectra reveal that E(sub peak) decreases with energy flux (and fluence) to a minimum of approx. 30 keV at F = 8.7 x 10(exp -6)erg/sq cm/s, increasing steadily afterwards. Two more sources exhibit a similar trend: SGRs J1550 - 5418 and 1806 - 20. The isotropic luminosity, L(sub iso), corresponding to these flux values is roughly similar for all sources (0.4 - l.5 x 10(exp 40) erg/s.

Lin, Lin; Kouveliotou, Chryssa; Baring, Matthew G.; van der Horst, Alexander J.; Guiriec, Sylvain; Woods, Peter M.; Goegues, Ersin; Kaneko, Yuki; Scargle, Jeffrey; Granot, Jonathan; Preece, Robert; von Kienlin, Andreas; Chaplin, Vandiver; Watts, Anna L.; Wijers, Ralph A. M. J.; Zhang, Shuang Nan; Bhat, Narayan; Finger, Mark H.; Gehrels. Neil; Harding, Alice; Kaper, Lex; Kaspi, Victoria; Mcenery, Julie; Meegan, Charles A.; Wilson-Hodge, Colleen

2011-01-01

386

Physical mechanism of the vertical electric field generation over active tectonic faults  

NASA Astrophysics Data System (ADS)

The concept of the Global Electric Circuit (GEC) provides an explanation of the existence of a vertical atmospheric electric field and coupling between the ground and ionosphere. Presently, ionospheric physics pays more attention to electric fields and coupling processes in the polar and auroral regions, whereas in other areas the potential difference between the ground and ionosphere usually is not taken into account. Regional processes exist, however, that are able to significantly affect the GEC parameters and through modification of the ionospheric potential to create plasma density irregularities of different scales within the ionosphere. One such source of ionosphere modification is air ionization in the vicinity of active tectonic faults, which takes place due to increased radon emanation. This paper considers the process of local modification of the GEC and corresponding ionospheric variability due to tectonic activity.

Pulinets, S. A.

2009-09-01

387

A novel application of pulsed electric field (PEF) processing for improving glutathione (GSH) antioxidant activity.  

PubMed

Glutathione (GSH) was treated by pulsed electric field (PEF) processing to investigate its effect on antioxidant activity. The antioxidant activity of GSH was evaluated using 2,2-diphenyl-1-picrylhydrazy (DPPH) radical inhibition. A Box-Behnken design (BBD) with three independent variables, which were concentration, electric field intensity and pulse frequency was used to establish the regression equation of second-order response surface. Optimal conditions were as follows: GSH concentration 8.86mg/mL, electric field intensity 9.74kV/cm and pulse frequency 2549.08Hz. The DPPH radical inhibition increased from 81.83% to 97.40%. Near-infrared spectroscopy (NIR) and mid-infrared spectroscopy (MIR) were used to analyse the change of structure and functional groups of GSH. PMID:24837963

Wang, Jia; Wang, Ke; Wang, Ying; Lin, Songyi; Zhao, Ping; Jones, Gregory

2014-10-15

388

[The changes of basal brain electric activity in patients with epilepsy after callosotomy].  

PubMed

Short-term and long-term outcomes of basal brain activity were estimated in 20 epileptic patients with a medical history of callosotomy. Patients with malignant courses selected for callosotomy retained the high capacity of cerebral electric activity after surgery. In spite of limitations of bilateral synchronized irradiation of electric discharges in the brain, patients had the high power of cerebral electric genesis. A clinical study revealed the decrease of the number of seizures and their severity in patients who underwent the surgery. Thus, callosotomy plays only a palliative role in epileptic processes. Of primary importance is individual selection of anti-epileptic drugs to support cell mechanisms of epilepsy and improvement of treatment outcomes. PMID:19621488

Be?n, B N; Dravert, N E; Tatarenko, S A

2008-01-01

389

Cellular mechanisms of burst firing-mediated long-term depression in rat neocortical pyramidal cells  

PubMed Central

During wakefulness and sleep, neurons in the neocortex emit action potentials tonically or in rhythmic bursts, respectively. However, the role of synchronized discharge patterns is largely unknown. We have recently shown that pairings of excitatory postsynaptic potentials (EPSPs) and action potential bursts or single spikes lead to long-term depression (burst-LTD) or long-term potentiation, respectively. In this study, we elucidate the cellular mechanisms of burst-LTD and characterize its functional properties. Whole-cell patch-clamp recordings were obtained from layer V pyramidal cells in somatosensory cortex of juvenile rats in vitro and composite EPSPs and EPSCs were evoked extracellularly in layers II/III. Repetitive burst-pairings led to a long-lasting depression of EPSPs and EPSCs that was blocked by inhibitors of metabotropic glutamate group 1 receptors, phospholipase C, protein kinase C (PKC) and calcium release from the endoplasmic reticulum, and that required an intact machinery for endocytosis. Thus, burst-LTD is induced via a Ca2+- and phosphatidylinositol-dependent activation of PKC and expressed through phosphorylation-triggered endocytosis of AMPA receptors. Functionally, burst-LTD is inversely related to EPSP size and bursts dominate single spikes in determining the sign of synaptic plasticity. Thus burst-firing constitutes a signal by which coincident synaptic inputs are proportionally downsized. Overall, our data thus suggest a mechanism by which synaptic weights can be reconfigured during non-rapid eye movement sleep.

Czarnecki, Antonny; Birtoli, Barbara; Ulrich, Daniel

2007-01-01

390

Low Temperature Geothermal Electricity Generation: Google Earth Virtual Field Trip Activity  

NSDL National Science Digital Library

This exploration takes students to Chena Hot Springs Resort in Alaska where they will learn how to produce low temperature geothermal electricity. Teacher's guide, activity sheet and PowerPoint presenation included. The 2008 ATEEC Fellows Institute brought 18 environmental science community college and high school instructors to Alaska. They created virtual field trips using Google Earth. In the activity, explore Chena Hot Springs Resort in Alaska to learn about low temperature geothermal electricity generation. Chena Hot Springs runs their entire facility on renewable energy. Learn how they do it why they do it and the engineering challenges along the way. This activity includes numerous turnkey teaching resources such as a PowerPoint presentation explaining the geothermal heat exchanging process, video interviews with environmental engineers, a teacher's guide and student activity. Users must create a free login to access this resource.

2013-06-06

391

Second SWIFT Burst Alert Telescope (BAT) Gamma-Ray Burst Catalog.  

National Technical Information Service (NTIS)

We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts. (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog) presents burst trigger time...

A. M. Parsons B. Zhang C. B. Markwardt D. M. Palmer E. E. Fenimore G. Sato H. A. Krimm J. Tueller J. R. Cummings M. Stamatikos N. Gehrels S. D. Barthelmy T. Sakamoto T. N. Ukwatta W. H. Baumgartner

2012-01-01

392

Swift Burst Alert Telescope (BAT) Instrument Response  

Microsoft Academic Search

The Burst Alert Telescope (BAT), a large coded aperture instrument with a wide field-of-view (FOV), provides the gamma-ray burst triggers and locations for the Swift Gamma-Ray Burst Explorer. In addition to providing this imaging information, BAT will perform a 15 keV - 150 keV all-sky hard x-ray survey based on the serendipitous pointings resulting from the study of gamma-ray bursts,

A. Parsons; S. Barthelmy; J. Cummings; N. Gehrels; D. Hullinger; H. Krimm; C. Markwardt; J. Tueller; E. Fenimore; D. Palmer; G. Sato; T. Takahashi; K. Nakazawa; Y. Okada; H. Takahashi; M. Suzuki; M. Tashiro

2004-01-01

393

Active building envelope system (ABE): Wind and solar-driven ventilation, electricity and heat pump  

Microsoft Academic Search

This study takes the ventilation into consideration, making the active building envelope (ABE) system more close to the realistic application conditions. The ABE system is comprised of a photovoltaic unit (PV unit) and a thermoelectric heat pump unit (TE unit). The PV unit consists of photovoltaic cells, which convert solar radiation energy into electrical energy. The TE unit consists of