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1

Mathematical Analysis of BurstingMathematical Analysis of Bursting Electrical Activity in Nerve andElectrical Activity in Nerve and  

E-print Network

CER = free calcium concentration in the Endoplasmic Reticulum (ER) Cytosolic calcium feeds back ontoPituitary Cells Also Burst Bursting in isolated cells (Van Goor et al, J. Biol. Chem., 276:33840, 2001) #12;What

Bertram, Richard

2

The mathematical analysis of bursting electrical activity in pancreatic beta cells  

SciTech Connect

Pancreatic {beta}-cells exhibit periodic bursting electrical activity (BEA) consisting of active and silent phases. Experimentally, the ratio of the active phase duration to the overall period, {rho}{sub f}, has been correlated to the insulin-glucose response of these cells. Many different mathematical models of the {beta}-cell have been developed to describe changes in the intracellular ionic concentrations and the ionic flow through the cellular membrane. The membrane potential in these models exhibit the same active and silent phase bursting patterns as those observed experimentally and therefore can be used to predict the value of the plateau fraction, {rho}{sub f}. The Sherman-Rinzel-Keizer (SRK) mathematical model of this phenomenon consists of three coupled first-order nonlinear differential equations which describe the dynamics of the membrane potential, the activation parameter for the voltage-gated potassium channel, and the intracellular calcium concentration. These equations are transformed into a Lienard differential equation coupled to a single first-order differential equation for the slowly changing nondimensional calcium cocentration. Leading-order perturbation problems for the silent phase and the transition regions are reduced to quadrature. The solution of the leading-order active phase problem is a limit cycle which depends on the value of the intracellular calcium concentration. Since the active phase equations exhibit weak damping, Melnikov's method can be applied to determine the bifurcation point of these equations. Thus, an explicit expression for the active phase duration is obtained. Together with the silent phase analysis, an approximation of the plateau fraction, {rho}{sub f}, is derived and its value compared to the plateau fraction numerically obtained from the SRK model. 47 figs., 11 tabs.

Pernarowski, M.

1990-07-01

3

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. PMID:24945358

Doloc-Mihu, Anca; Calabrese, Ronald L.

2014-01-01

4

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

5

Brief Communications Dendritic Calcium Activity Precedes Inspiratory Bursts in  

E-print Network

evidence that respiratory rhythmogenesis may depend on den- dritic burst-generating conductances activated of respiratory rhythm show that ICAN is one important charge carrier underlying inspiratory bursts (Thoby locations, using acute slices that retain respiratory function in vitro. We show that endogenous synaptic

Del Negro, Christopher A.

6

Adaptation-dependent synchronization transitions and burst generations in electrically coupled neural networks.  

PubMed

A typical feature of neurons is their ability to encode neural information dynamically through spike frequency adaptation (SFA). Previous studies of SFA on neuronal synchronization were mainly concentrated on the correlated firing between neuron pairs, while the synchronization of neuron populations in the presence of SFA is still unclear. In this study, the influence of SFA on the population synchronization of neurons was numerically explored in electrically coupled networks, with regular, small-world, and random connectivity, respectively. The simulation results indicate that cross-correlation indices decrease significantly when the neurons have adaptation compared with those of nonadapting neurons, similar to previous experimental observations. However, the synchronous activity of population neurons exhibits a rather complex adaptation-dependent manner. Specifically, synchronization strength of neuron populations changes nonmonotonically, depending on the degree of adaptation. In addition, single neurons in the networks can switch from regular spiking to bursting with the increase of adaptation degree. Furthermore, the connection probability among neurons exhibits significant influence on the population synchronous activity, but has little effect on the burst generation of single neurons. Accordingly, the results may suggest that synchronous activity and burst firing of population neurons are both adaptation-dependent. PMID:25406642

Wang, Lei; Liang, Pei-Ji; Zhang, Pu-Ming; Qiu, Yi-Hong

2014-12-01

7

SGR J1550-5418 BURSTS DETECTED WITH THE FERMI GAMMA-RAY BURST MONITOR DURING ITS MOST PROLIFIC ACTIVITY  

SciTech Connect

We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties. We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized E{sub peak} and the burst fluence and average flux. For the BB+BB fits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high-temperature BB has a much smaller area and shows an anti-correlation between emission area and temperature. We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.

Van der Horst, A. J.; Finger, M. H. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Kouveliotou, C. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gorgone, N. M. [Connecticut College, New London, CT 06320 (United States); Kaneko, Y.; Goegues, E.; Lin, L. [Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I -Tuzla, Istanbul 34956 (Turkey); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Guiriec, S.; Bhat, P. N.; Chaplin, V. L.; Goldstein, A. [University of Alabama, Huntsville, CSPAR, Huntsville, AL 35805 (United States); Granot, J. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Watts, A. L. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Bissaldi, E.; Gruber, D. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, 85748 Garching (Germany); Gehrels, N.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gibby, M. H.; Giles, M. M., E-mail: A.J.VanDerHorst@uva.nl [Jacobs Technology, Inc., Huntsville, AL (United States); and others

2012-04-20

8

Thermal electron acceleration by localized bursts of electric field in the radiation belts  

NASA Astrophysics Data System (ADS)

In this paper we investigate the resonant interaction of thermal ˜10-100 eV electrons with a burst of electrostatic field that results in electron acceleration to kilovolt energies. This single burst contains a large parallel electric field of one sign and a much smaller, longer-lasting parallel field of the opposite sign. The Van Allen Probe spacecraft often observes clusters of spatially localized bursts in the Earth's outer radiation belts. These structures propagate mostly away from the geomagnetic equator and share properties of soliton-like nonlinear electron acoustic waves: a velocity of propagation is about the thermal velocity of cold electrons (˜3000-10,000 km/s), and a spatial scale of electric field localization along the field lines is about the Debye radius of hot electrons (˜5-30 km). We model the nonlinear resonant interaction of these electric field structures and cold background electrons.

Artemyev, A. V.; Agapitov, O. V.; Mozer, F.; Krasnoselskikh, V.

2014-08-01

9

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

10

Slow oscillations of KATP conductance in mouse pancreatic islets provide support for electrical bursting driven by metabolic oscillations  

PubMed Central

We used the patch clamp technique in situ to test the hypothesis that slow oscillations in metabolism mediate slow electrical oscillations in mouse pancreatic islets by causing oscillations in KATP channel activity. Total conductance was measured over the course of slow bursting oscillations in surface ?-cells of islets exposed to 11.1 mM glucose by either switching from current clamp to voltage clamp at different phases of the bursting cycle or by clamping the cells to ?60 mV and running two-second voltage ramps from ?120 to ?50 mV every 20 s. The membrane conductance, calculated from the slopes of the ramp current-voltage curves, oscillated and was larger during the silent phase than during the active phase of the burst. The ramp conductance was sensitive to diazoxide, and the oscillatory component was reduced by sulfonylureas or by lowering extracellular glucose to 2.8 mM, suggesting that the oscillatory total conductance is due to oscillatory KATP channel conductance. We demonstrate that these results are consistent with the Dual Oscillator model, in which glycolytic oscillations drive slow electrical bursting, but not with other models in which metabolic oscillations are secondary to calcium oscillations. The simulations also confirm that oscillations in membrane conductance can be well estimated from measurements of slope conductance and distinguished from gap junction conductance. Furthermore, the oscillatory conductance was blocked by tolbutamide in isolated ?-cells. The data, combined with insights from mathematical models, support a mechanism of slow (?5 min) bursting driven by oscillations in metabolism, rather than by oscillations in the intracellular free calcium concentration. PMID:23921138

Ren, Jianhua; Sherman, Arthur; Bertram, Richard; Goforth, Paulette B.; Nunemaker, Craig S.; Waters, Christopher D.

2013-01-01

11

Emergence of bursting activity in connected neuronal sub-populations.  

PubMed

Uniform and modular primary hippocampal cultures from embryonic rats were grown on commercially available micro-electrode arrays to investigate network activity with respect to development and integration of different neuronal populations. Modular networks consisting of two confined active and inter-connected sub-populations of neurons were realized by means of bi-compartmental polydimethylsiloxane structures. Spontaneous activity in both uniform and modular cultures was periodically monitored, from three up to eight weeks after plating. Compared to uniform cultures and despite lower cellular density, modular networks interestingly showed higher firing rates at earlier developmental stages, and network-wide firing and bursting statistics were less variable over time. Although globally less correlated than uniform cultures, modular networks exhibited also higher intra-cluster than inter-cluster correlations, thus demonstrating that segregation and integration of activity coexisted in this simple yet powerful in vitro model. Finally, the peculiar synchronized bursting activity shown by confined modular networks preferentially propagated within one of the two compartments ('dominant'), even in cases of perfect balance of firing rate between the two sub-populations. This dominance was generally maintained during the entire monitored developmental frame, thus suggesting that the implementation of this hierarchy arose from early network development. PMID:25250616

Bisio, Marta; Bosca, Alessandro; Pasquale, Valentina; Berdondini, Luca; Chiappalone, Michela

2014-01-01

12

Emergence of Bursting Activity in Connected Neuronal Sub-Populations  

PubMed Central

Uniform and modular primary hippocampal cultures from embryonic rats were grown on commercially available micro-electrode arrays to investigate network activity with respect to development and integration of different neuronal populations. Modular networks consisting of two confined active and inter-connected sub-populations of neurons were realized by means of bi-compartmental polydimethylsiloxane structures. Spontaneous activity in both uniform and modular cultures was periodically monitored, from three up to eight weeks after plating. Compared to uniform cultures and despite lower cellular density, modular networks interestingly showed higher firing rates at earlier developmental stages, and network-wide firing and bursting statistics were less variable over time. Although globally less correlated than uniform cultures, modular networks exhibited also higher intra-cluster than inter-cluster correlations, thus demonstrating that segregation and integration of activity coexisted in this simple yet powerful in vitro model. Finally, the peculiar synchronized bursting activity shown by confined modular networks preferentially propagated within one of the two compartments (‘dominant’), even in cases of perfect balance of firing rate between the two sub-populations. This dominance was generally maintained during the entire monitored developmental frame, thus suggesting that the implementation of this hierarchy arose from early network development. PMID:25250616

Pasquale, Valentina; Berdondini, Luca; Chiappalone, Michela

2014-01-01

13

Oxidative burst and anticancer activities of rat neutrophils.  

PubMed

It is assumed that oxidative damage caused by reactive oxygen species (ROS) from activated neutrophil granulocytes may contribute to pathology of tumors. ROS are crucial in neutrophil-mediated tumor cell lysis. The present study is focused on the oxidative burst and antitumorous activities of neutrophils when challenged with Walker carcinoma W256. Survival and tumor growth dynamics were monitored in vivo, while tumor cell proliferation when mixed with neutrophils was studied in vitro together with the generation/release of neutrophil respiratory burst products, primarily 1O2. Neutrophils were collected upon Sephadex injection. The survival of Sephadex injected animals was slightly improved, while their tumors grew less than in controls. The presence of tumor cells in vitro activated neutrophils to produce singlet oxygen similar to phorbol ester. Neutrophils from Sephadex-bearing animals diminished tumor cell proliferation in vitro (measured by 3H-TdR incorporation), while neutrophils from Sephadex and the tumor-bearing animals did not show such activity in vitro. Our results confirm that in the case of rapidly growing tumors such as murine W256 carcinoma neutrophils have antitumorous effects in the early phase of tumor development. PMID:16403992

Zivkovic, Morana; Poljak-Blazi, Marija; Egger, Gerd; Sunjic, Suzana Borovic; Schaur, Rudolf Jörg; Zarkovic, Neven

2005-01-01

14

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. PMID:23292718

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

2013-01-01

15

The role of large-conductance Calcium-activated K + (BK) channels in shaping bursting oscillations of a somatotroph cell model  

Microsoft Academic Search

We study a recently proposed somatotroph model that exhibits plateau bursting, a form of electrical activity that is typical for this cell type. We focus on the influence of the large conductance (BK-type) Ca2+-activated K+ current on the oscillations and duration of the active phase. The model involves two different time scales, but a standard bifurcation analysis of the fast

Jakub Nowacki; Siti Mazlan; Hinke M. Osinga; Krasimira Tsaneva-Atanasova

2010-01-01

16

Enhanced oxidative burst in immunologically activated but not elicited polymorphonuclear leukocytes correlates with fungicidal activity.  

PubMed

Polymorphonuclear neutrophils (PMN) induced locally in immune mice by intraperitoneal injection of antigen exhibit enhanced fungicidal activity compared with PMN elicited with thioglycolate. The mechanism of the differences in these PMN populations was studied. Sublethal infection was used to produce immunity to Blastomyces dermatitidis. A correlation was sought between the ability of PMN to kill, or not kill, B. dermatitidis and the production of the oxidative burst, as measured by luminol-enhanced chemiluminescence (CL). Although elicited PMN cocultured with Candida albicans produced a burst of CL and were candidacidal, killing did not occur when PMN were cocultured with B. dermatitidis. Lack of killing of B. dermatitidis by elicited PMN correlated with lack of stimulation of a brisk oxidative burst. In contrast to elicited PMN, PMN induced by B. dermatitidis antigen responded to this fungus with a burst of CL and a significant reduction of inoculum CFU (80%). Furthermore, these PMN when cocultured with C. albicans produced an enhanced burst of CL, and killing was enhanced compared with that by elicited PMN, e.g., 86 versus 58%. The CL burst and killing of B. dermatitidis by antigen-induced PMN was abrogated in the presence of catalase, implying a critical role for hydrogen peroxide. Partial but significant depression of CL and killing in the presence of dimethyl sulfoxide, a hydroxyl radical scavenger, identified hydroxyl radical, or its metabolites, as a toxic product(s) responsible for a significant fraction of fungicidal activity. These results indicate that the metabolic activity and microbicidal activity of PMN can be altered (enhanced) at the site of an immunological reaction and thus could constitute an important factor in resistance. PMID:3894234

Brummer, E; Sugar, A M; Stevens, D A

1985-08-01

17

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

18

The spontaneous electrical activity of neurons in leech ganglia.  

PubMed

Using the newly developed voltage-sensitive dye VF2.1.Cl, we monitored simultaneously the spontaneous electrical activity of ?80 neurons in a leech ganglion, representing around 20% of the entire neuronal population. Neurons imaged on the ventral surface of the ganglion either fired spikes regularly at a rate of 1-5 Hz or fired sparse spikes irregularly. In contrast, neurons imaged on the dorsal surface, fired spikes in bursts involving several neurons. The overall degree of correlated electrical activity among leech neurons was limited in control conditions but increased in the presence of the neuromodulator serotonin. The spontaneous electrical activity in a leech ganglion is segregated in three main groups: neurons comprising Retzius cells, Anterior Pagoda, and Annulus Erector motoneurons firing almost periodically, a group of neurons firing sparsely and randomly, and a group of neurons firing bursts of spikes of varying durations. These three groups interact and influence each other only weakly. PMID:24303164

Moshtagh-Khorasani, Majid; Miller, Evan W; Torre, Vincent

2013-10-01

19

Anandamide activation of CB1 receptors increases spontaneous bursting and oscillatory activity in the thalamus.  

PubMed

The endocannabinoid system is a modulatory system that has been strongly associated with the regulation of functions as learning and memory, pain perception and sensory physiology in many areas of the central nervous system. However, although a role in sensory processing has been demonstrated at the level of the thalamus, the influence of the endocannabinoid system on thalamic rhythms and oscillations has been less studied, despite the fact that such activities are significant characteristics of the thalamic state. The present work aimed to characterize the role of anandamide (AEA) - one of the endogenous CB1 receptor agonists - and AM251 - a CB1 antagonist - in the modulation of burst firing and oscillatory activity present in the dLGN of the anesthetized rat. Administration of AEA (0.5mg/kg iv) increased the number of bursts in the majority of the cells tested and induced the appearance of a slow delta-like (1.5Hz) oscillatory activity. These effects were CB1-mediated, as demonstrated by the complete antagonism during the co-application of AM251 (0.5mg/kg iv). Thus, by demonstrating that the AEA-mediated activation of CB1 receptors increases spontaneous bursting and oscillatory activity in the thalamus our study infers that endocannabinoids could have a role in processes controlling the sleep-wake cycle and level of arousal. PMID:24508153

Dasilva, M; Grieve, K L; Cudeiro, J; Rivadulla, C

2014-04-18

20

Growth Dynamics Explain the Development of Spatiotemporal Burst Activity of Young Cultured Neuronal Networks in Detail  

PubMed Central

A typical property of isolated cultured neuronal networks of dissociated rat cortical cells is synchronized spiking, called bursting, starting about one week after plating, when the dissociated cells have sufficiently sent out their neurites and formed enough synaptic connections. This paper is the third in a series of three on simulation models of cultured networks. Our two previous studies [26], [27] have shown that random recurrent network activity models generate intra- and inter-bursting patterns similar to experimental data. The networks were noise or pacemaker-driven and had Izhikevich-neuronal elements with only short-term plastic (STP) synapses (so, no long-term potentiation, LTP, or depression, LTD, was included). However, elevated pre-phases (burst leaders) and after-phases of burst main shapes, that usually arise during the development of the network, were not yet simulated in sufficient detail. This lack of detail may be due to the fact that the random models completely missed network topology .and a growth model. Therefore, the present paper adds, for the first time, a growth model to the activity model, to give the network a time dependent topology and to explain burst shapes in more detail. Again, without LTP or LTD mechanisms. The integrated growth-activity model yielded realistic bursting patterns. The automatic adjustment of various mutually interdependent network parameters is one of the major advantages of our current approach. Spatio-temporal bursting activity was validated against experiment. Depending on network size, wave reverberation mechanisms were seen along the network boundaries, which may explain the generation of phases of elevated firing before and after the main phase of the burst shape.In summary, the results show that adding topology and growth explain burst shapes in great detail and suggest that young networks still lack/do not need LTP or LTD mechanisms. PMID:23028450

Gritsun, Taras A.; le Feber, Joost; Rutten, Wim L. C.

2012-01-01

21

GABAB receptor activation suppresses stimulus-evoked burst firing in rat substantia nigra reticulata neurons  

PubMed Central

Previous whole-cell patch-pipette studies showed that focal electrical stimulation of the subthalamic nucleus (STN) evokes a long-lasting complex EPSC and synaptically-evoked bursts of action potentials in substantia nigra pars reticulata (SNR) neurons. Although synaptically-evoked bursting may play a role in normal physiology, excessive burst firing correlates with symptoms of Parkinson’s disease. We used patch-pipette recordings in rat brain slices to study the effects of baclofen on complex EPSCs and STN-induced burst firing in SNR neurons. Baclofen (1 ?M) caused a reversible, 73% reduction in complex EPSCs, and this effect was blocked by the GABAB antagonist CGP35348 (100 ?M). Using the loose-patch method to record extracellular potentials, a lower concentration of baclofen (100 nM) inhibited STN-evoked bursts while leaving spontaneous firing of action potentials less affected. We suggest that strategies that selectively inhibit burst firing in the SNR might have therapeutic potential in the treatment of Parkinson’s disease. PMID:22127013

Shen, Ke-Zhong; Johnson, Steven W.

2011-01-01

22

Tracking Triadic Cardinality Distributions for Burst Detection in Social Activity Streams  

E-print Network

In online social networks (OSNs), we often observe abnormally frequent interactions among people before or during some important day, e.g., we receive/send more greetings from/to friends on Christmas Day than usual. We also often observe some viral videos suddenly become worldwide popular through one night diffusion in OSNs. Do these seemingly different phenomena share common structure? All these phenomena are related to sudden surges of user activities in OSNs, and are referred to as bursts in this work. We find that the emergence of a burst is accompanied with the formation of new triangles in networks. This finding provokes a new method for detecting bursts in OSNs. We first introduce a new measure, named triadic cardinality distribution, which measures the fraction of nodes with certain number of triangles, i.e., triadic cardinality, in a network. The distribution will change when burst occurs, and is congenitally immunized against spamming social bots. Hence, by tracking triadic cardinality distributions...

Zhao, Junzhou; Towsley, Don; Wang, Pinghui; Guan, Xiaohong

2014-01-01

23

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

24

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

25

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

NASA Technical Reports Server (NTRS)

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 seen from this AXP in >11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 8-3x10(exp 3)s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx. 2 - 6 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus three emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4)x10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. We discuss these events in the context of the magnetar model.

Gavril, Fotis P.; Dib, Rim; Kaspi, Victoria M.

2009-01-01

26

Characteristics of the Extended Burst Tails from SGR 1806-20 During the 2004 Active Episode  

NASA Technical Reports Server (NTRS)

In 2004, SGR 1806-20 underwent an episode of extreme activities, exhibiting thousands of recurrent bursts and finally the 27 December giant flare, which was the most energetic extra-solar event ever detected near Earth. During this active episode, we routinely monitored the source with Rossi X-ray Timing Explorer and occasionally with Chandra. We identified two relatively strong event that were followed by extended (few hundreds-thousands seconds long) tail emission. Here, we present detailed spectral investigations of these two strong SGR 1806-20 events with extended tail observed about 6 and 1.5 months prior to the 27 December 2004 giant flare. We find that both extended burst tail spectra exhibit thermal behavior. Similar thermal spectral trend was also seen in two SGR 1900+14 bursts with extended tails, therefore, it may be a general characteristic of extended SGR events.

Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Finger, Mark H.; Lenter, Geoffrey; Patel, Sandeep K.; Frederiks, Dmitry; Golenetskii, Sergey

2006-01-01

27

THE 2006-2007 ACTIVE PHASE OF ANOMALOUS X-RAY PULSAR 4U 0142+61: RADIATIVE AND TIMING CHANGES, BURSTS, AND BURST SPECTRAL FEATURES  

SciTech Connect

After at least six 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 seen from this AXP in >11 yr of Rossi X-Ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from (0.4-1.8) x 10{sup 3} s. The first five burst spectra are well modeled by blackbodies, with temperatures kT {approx} 2-9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase, the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9 {+-} 0.4) x 10{sup -7} Hz, which recovered with a decay time of 17 {+-} 2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

Gavriil, Fotis P. [NASA Goddard Space Flight Center, Astrophysics Science Division, Code 662, Greenbelt, MD 20771 (United States); Dib, Rim; Kaspi, Victoria M. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada)

2011-08-01

28

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

NASA Technical Reports Server (NTRS)

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 seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 0.4 - 1.8 x 10(exp 3) s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx 2 - 9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4) x 10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate. slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

Gavriil, Fotis P.; Dib, Rim; Kaspi, Victoria M.

2011-01-01

29

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. PMID:24018288

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

2013-01-01

30

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

NASA Astrophysics Data System (ADS)

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.

2013-10-01

31

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

32

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

NASA Technical Reports Server (NTRS)

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 persistent X-ray emission of the source. The T90 durations of the bursts range between 18 - 140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8-25) x 1038 erg, which is in the low side of SGR 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 IE 1841-045 might not involve large scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.

Lin, Lin; Kouveliotou, Chryssa; Gogus, Ersin; van der Horst, Alexander J.; Watts, Anna L.; Baring, Matthew G.; Kaneko, Yuki; Wijers, Ralph A. M. J.; Woods, Peter M.; Barthelmy, Scott; Burgess, J. Michael; Chaplin, Vandiver; Gehrels, Neil; Goldstein, Adam; Granot, Jonathan; Guiriec, Sylvain; Mcenery, Julie; Preece, Robert D.; Tierney, David; van der Klis, Michiel; von Kienlin, Andreas; Zhang, Shuang Nan

2011-01-01

33

On-off control of burst high frequency electrical stimulation to suppress 4-AP induced seizures  

NASA Astrophysics Data System (ADS)

Objective. The goal of this study was to investigate, using model simulations and animal experiments, the efficiency and the side effects of burst high frequency stimulation combined with on-off control in seizure suppression. Approach. A modified mathematical hippocampal seizure model was created to provide evidence of the eligibility of this approach. In the experimental setup, two recording electrodes were inserted into bilateral septal CA1 of the hippocampus, and a stimulation electrode was placed on the ventral hippocampal commissure of a rat. After seizures had been induced by 4-aminopyridine treatment, on-off control stimulation was used to suppress the seizures at 20 s intervals. The stimulation time, cumulative charge and post-stimulation suppression were used to assess the effects of burst duration. Main results. The results showed that burst stimulation could suppress the seizures during the control period and burst stimulation of a shorter duration could keep the seizure suppressed with less effort. By decreasing the burst duration, the cumulative stimulation time became shorter, the delivered cumulative charge became lower, and the cumulative time of post-stimulation suppression became longer. Significance. The on-off control stimulation not only prolonged the duration of suppression but also avoided the side effects of the conversion of seizure patterns. In particular, decreasing the specified burst duration increased the efficiency of the burst stimulation.

Chiang, Chia-Chu; Lin, Chou-Ching K.; Ju, Ming-Shaung

2013-06-01

34

Oxytocin-induced postinhibitory rebound firing facilitates bursting activity in oxytocin neurons  

PubMed Central

During parturition and lactation, neurosecretory oxytocin (OT) neurons in the hypothalamus achieve pulsatile hormone secretion by coordinated bursts of firing that occur throughout the neuronal population. This activity is partly controlled by somatodendritic release of OT which facilitates the onset and recurrence of synchronized bursting. To further investigate the cellular mechanisms underlying the control exerted by OT on the activity of its own neurons, we studied the effects of the peptide on membrane potential and synaptic activity in OT neurons in hypothalamic organotypic slice cultures. Bath application of low concentrations of OT (<100 nM) facilitated GABA-A receptor-mediated inhibitory transmission through a presynaptic mechanism without affecting membrane potential and excitatory glutamatergic synaptic activity. The facilitatory action of OT on GABAergic transmission was dose-dependent, starting at 25 nM and disappearing at concentrations above 100 nM. As previously shown, higher concentrations of OT (>500 nM) had the opposite effect, inhibiting GABA-A receptors via a postsynaptic mechanism. Surprisingly, OT-mediated facilitation of GABAergic transmission promoted action potential firing in 40% of the neurons. Each action potential occurred at the end of the repolarizing phase of an inhibitory potential. Pharmacological dissection revealed that this firing involved the activation of low-threshold activated calcium channels. Detailed statistical analysis showed that OT-mediated firing up-regulated bursting activity in OT neurons. It is thus likely to optimize OT secretion and, as a consequence, facilitate delivery and milk ejection in mammals. PMID:18184781

Israel, Jean-Marc; Poulain, Dominique A.; Oliet, Stéphane H.R.

2008-01-01

35

Group I metabotropic glutamate receptors activate burst firing in rat midbrain dopaminergic neurons  

Microsoft Academic Search

We have investigated the changes in the spontaneous firing pattern induced by DHPG ((S)-3,5-dihydroxyphenylglycine) and NMDA (N-methyl-d-aspartic acid) on rat dopaminergic neurons in substantia nigra pars compacta (SNc) using sharp microelectrode recordings in in vitro conditions. Twenty-five out of 33 cells modified the regular single-pacemaker activity in burst firing when exposed to the Group I metabotropic glutamate receptor (mGluR) agonist

Simonetta Prisco; Silvia Natoli; Giorgio Bernardi; Nicola B. Mercuri

2002-01-01

36

Granule exocytosis contributes to priming and activation of the human neutrophil respiratory burst.  

PubMed

The role of exocytosis in the human neutrophil respiratory burst was determined using a fusion protein (TAT-SNAP-23) containing the HIV transactivator of transcription (TAT) cell-penetrating sequence and the N-terminal SNARE domain of synaptosome-associated protein-23 (SNAP-23). This agent inhibited stimulated exocytosis of secretory vesicles and gelatinase and specific granules but not azurophil granules. GST pulldown showed that TAT-SNAP-23 bound to the combination of vesicle-associated membrane protein-2 and syntaxin-4 but not to either individually. TAT-SNAP-23 reduced phagocytosis-stimulated hydrogen peroxide production by 60% without affecting phagocytosis or generation of HOCl within phagosomes. TAT-SNAP-23 had no effect on fMLF-stimulated superoxide release but significantly inhibited priming of this response by TNF-? and platelet-activating factor. Pretreatment with TAT-SNAP-23 inhibited the increase in plasma membrane expression of gp91(phox) in TNF-?-primed neutrophils, whereas TNF-? activation of ERK1/2 and p38 MAPK was not affected. The data demonstrate that neutrophil granule exocytosis contributes to phagocytosis-induced respiratory burst activity and plays a critical role in priming of the respiratory burst by increasing expression of membrane components of the NADPH oxidase. PMID:21642540

Uriarte, Silvia M; Rane, Madhavi J; Luerman, Gregory C; Barati, Michelle T; Ward, Richard A; Nauseef, William M; McLeish, Kenneth R

2011-07-01

37

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. PMID:23112870

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

2012-01-01

38

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. PMID:23165765

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

2013-01-01

39

Bursts of Vertex Activation and Epidemics in Evolving Networks  

PubMed Central

The dynamic nature of contact patterns creates diverse temporal structures. In particular, empirical studies have shown that contact patterns follow heterogeneous inter-event time intervals, meaning that periods of high activity are followed by long periods of inactivity. To investigate the impact of these heterogeneities in the spread of infection from a theoretical perspective, we propose a stochastic model to generate temporal networks where vertices make instantaneous contacts following heterogeneous inter-event intervals, and may leave and enter the system. We study how these properties affect the prevalence of an infection and estimate , the number of secondary infections of an infectious individual in a completely susceptible population, by modeling simulated infections (SI and SIR) that co-evolve with the network structure. We find that heterogeneous contact patterns cause earlier and larger epidemics in the SIR model in comparison to homogeneous scenarios for a vast range of parameter values, while smaller epidemics may happen in some combinations of parameters. In the case of SI and heterogeneous patterns, the epidemics develop faster in the earlier stages followed by a slowdown in the asymptotic limit. For increasing vertex turnover rates, heterogeneous patterns generally cause higher prevalence in comparison to homogeneous scenarios with the same average inter-event interval. We find that is generally higher for heterogeneous patterns, except for sufficiently large infection duration and transmission probability. PMID:23555211

Rocha, Luis E. C.; Blondel, Vincent D.

2013-01-01

40

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. PMID:19776280

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

2013-01-01

41

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. PMID:22110134

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

42

Effect of electric potential structures on Jovian S-burst morphology  

NASA Astrophysics Data System (ADS)

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. A significant part of these emissions consists of short radio bursts (so-called S-bursts) drifting in time and frequency. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tube connecting Io or Io's wake to Jupiter. We present simulations of these electrons under the assumption of acceleration by Alfvén waves in the Io flux tube. Near Jupiter, a loss cone and a ring distribution appear in the magnetically mirrored electron population, which can then amplify extraordinary (X) mode radio waves. The X-mode growth rate is computed, which allows us to build theoretical dynamic spectra of the resulting Jovian radio emissions. Additional potential structures are assumed in the Jovian auroral region. We reconstruct their impact on the morphology of the emission. They match some of the time-frequency patterns observed with Jovian S-bursts. This provides the first evidence of bipolar electrostatic structures in the Jovian auroral region.

Hess, S.; Mottez, F.; Zarka, P.

2009-07-01

43

Analysis of the visual artifact in range-gated active imaging, especially in burst mode.  

PubMed

After the demonstration of the occurrence of visual artifacts with an active imaging system in burst mode in a previous paper, the analysis of this phenomenon was realized. A visual artifact resulting from a remote zone in the scene can appear in the image of the real visualized zone when the duty cycle of laser pulses is close to 50%, as in the burst mode. Therefore, the elements of this remote zone will create confusion in the image, with erroneous estimated distances. These misinterpretations can be very embarrassing to those attempting to determine the distance of a target in the scene. From the modeling realized and validated in the previous paper, the behavior of the visual artifact was analyzed with two types of burst mode used in active imaging, the duration of the laser pulse being identical to the duration of the temporal aperture of the imager. In the first mode, the width of the visualized zone is set, depending on the distance. The second mode increases the width of the visualized zone so that the foreground of the zone is constantly visible. The results showed that the distance of the visual artifacts in variable mode increased much more quickly than the distance in fixed mode. In both modes, the most intense visual artifacts appear when the range of the visualized zone remains within the first kilometer. When this range is very short, the illuminance of the visual artifact in fixed mode is much more intense than the illuminance in variable mode. On the other hand, for long distances, the illuminance of the visual artifact in variable mode is greater than the illuminance in fixed mode, but decreases quickly beyond a certain distance, making it insignificant. PMID:25322113

Matwyschuk, Alexis

2014-09-20

44

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. PMID:24497927

Barnett, William H.; Cymbalyuk, Gennady S.

2014-01-01

45

A codimension-2 bifurcation controlling endogenous bursting activity and pulse-triggered responses of a neuron model.  

PubMed

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. PMID:24497927

Barnett, William H; Cymbalyuk, Gennady S

2014-01-01

46

The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque  

NASA Technical Reports Server (NTRS)

We report on observations of SGR 1900+14 made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX during the April 2001 burst activation of the source. Using these data, we measure the spindown torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to the gamma-ray profile during the April 18 intermediate flare and show that (i) their shapes are similar and (ii) the gamma-ray profile aligns closely in phase with the X-ray pulsations. The good phase alignment of the gamma-ray and X-ray profiles suggests that there was no rapid spindown following this flare, in contrast to the August 27 giant flare. The absence of rapid spindown in the hours following the April 18 flare suggests that there was no significant outflow of material as was believed to be present following the August 27 flare. Finally, we discuss how these observations further constrain magnetic field reconfiguration models for the large flares of SGRs.

Woods, P. M.; Kouveliotou, C.; Goegues, E.; Finger, M. H.; Feroci, M.; Mereghetti, S.; Swank, J. H.; Hurley, K.; Heise, J.; Smith, D.; Six, N. Frank (Technical Monitor)

2002-01-01

47

Research Activities in Physics at McGill University Cover image: A Star-Bursting Filament (from the group of Prof. Tracy Webb). The Herschel Space Observatory has  

E-print Network

........................................................................................................................Medical Physics! 59-3- Research Activities in Physics at McGill University #12;Cover image: A Star-Bursting Filament ..........................................................................................................The Challenge of Physics! 5

Barthelat, Francois

48

A Dynamic Dendritic Refractory Period Regulates Burst Discharge in the Electrosensory Lobe of Weakly Electric Fish  

E-print Network

of Weakly Electric Fish Liza Noonan,1* Brent Doiron,2* Carlo Laing,2* Andre Longtin,2 and Ray W. Turner1 1 other voltage-dependent currents (Yuste et al., 1994; Golding et al., 1999; Magee and Car- ruth, 1999 lateral line lobe (ELL) of weakly electr

Turner, Ray

49

Simulation of the Electrical Activity of the Pancreatic Cells Induced by Ingesting of Glucose During an Oral Glucose Tolerance Test  

Microsoft Academic Search

of the increase on ATPi before an extracellular glucose load. In this work, we described the simulation of the electrical activity of the -cells induced during an oral glucose tolerance test in normal subjects. The model describes the glucose level in blood, the increase of associated ATPi, the burst of action potentials and the pulsating elevation of Ca++ i indispensable

R. Avila-Pozos; H. M. Trujillo; J. R. Godinez

50

Bursting into the Nucleus  

NSDL National Science Digital Library

An increase in extracellular Ca2+ induces the nuclear localization of the Crz1 transcription factor and the activation of target genes in yeast. A recent study indicates that nuclear entry occurs in short stochastic bursts that are unsynchronized within the population of cells. The frequency but not the amplitude of the bursts is controlled by Ca2+. Modulation of the frequency of the burst coordinates aspects of expression of Crz target genes.

Gerald R. Crabtree (Stanford University Medical School; REV); Isabella A. Graef (Stanford University Medical School; REV)

2008-12-23

51

Comparative Corrosion and Current Burst Testing of Copper and Aluminum Electrical Power Connectors  

Microsoft Academic Search

Crimped and mechanically bolted aluminum and copper connectors are commonly used for terminating industrial electrical power cables with ratings up to 600 V. Aluminum connectors are available for use with aluminum and copper conductors, and copper connectors are available for use with copper conductor only. The performance of copper and aluminum connectors was compared by conducting accelerated aging under corrosive

Ronald F. Frank; Christopher P. Morton

2007-01-01

52

Comparative corrosion and current burst testing of copper and aluminum electrical power connectors  

Microsoft Academic Search

Crimped and mechanically bolted aluminum and copper connectors are commonly used for terminating industrial electrical power cables with ratings up to 600 V. Aluminum connectors are available for use with aluminum or copper conductor, and copper connectors are available for use with copper conductor only. The performance of copper and aluminum connectors was compared by conducting accelerated aging under corrosive

Ron Frank; C. Morton

2005-01-01

53

Corrosion and Current Burst Testing of Copper and Aluminum Electrical Power Connectors  

Microsoft Academic Search

Crimped and mechanically bolted aluminum and copper connectors are commonly used for terminating industrial electrical power cables of ratings up to 600 V. Aluminum connectors are available for use with aluminum or copper conductor, and copper connectors are available for use with copper conductor only. The performance of copper and aluminum connectors was compared by accelerated aging under corrosive environmental

V. Buccholz; Ron Frank; Chris Morton

2006-01-01

54

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

55

The Correlation of $\\gamma$-Ray Bursts with Active Galactic Nuclei  

E-print Network

We search for angular correlation of gamma-ray bursts with cataloged quasars, BL Lac objects, and AGN using a large sample of relatively well-localized bursts detected by WATCH on board GRANAT and EURECA, IPN, and BATSE (327 bursts total). A statistically significant (99.99% confidence) correlation between GRB and M_B<-21 AGN in the redshift range 0.1bursts with peak fluxes in the range 3-30x10**-6 erg/s/cm^2 in the 100-500 keV band are physically related to AGN. The established distance scale corresponds to the energy release of order 10**52 ergs per burst.

Burenin, R A; Terekhov, O V; Sazonov, S Y

1998-01-01

56

The Correlation of Gamma-Ray Bursts with Active Galactic Nuclei  

E-print Network

We search for angular correlation of gamma-ray bursts with cataloged quasars, BL Lac objects, and AGN using a large sample of relatively well-localized bursts detected by WATCH on board GRANAT and EURECA, IPN, and BATSE (327 bursts total). A statistically significant (99.99% confidence) correlation between GRB and M_B<-21 AGN in the redshift range 0.1bursts with peak fluxes in the range 3-30x10**-6 erg/s/cm^2 in the 100-500 keV band are physically related to AGN. The established distance scale corresponds to the energy release of order 10**52 ergs per burst.

R. A. Burenin; A. A. Vikhlinin; O. V. Terekhov; S. Yu. Sazonov

1998-04-27

57

Myocardial electrical activity does not affect myocardial electrical impedance measurements  

Microsoft Academic Search

Objective  Myocardial electrical impedance (MEI) has shown to be an effective indicator of myocardial ischemia. We have previously developed\\u000a a novel monitor for measuring MEI in near-real time. The object of this study was to test whether drug-induced changes in\\u000a the frequency of the periodic myocardial electrical activity, as measured by the heart rate (HR), affect MEI measurements\\u000a made with our

Roger Dzwonczyk; Carlos del Rio; Thomas D. McSweeney; Xiaoli Zhang; Michael B. Howie

2009-01-01

58

Variable Spin-Down in the Soft Gamma Repeater SGR 1900+14 and Correlations with Burst Activity  

NASA Technical Reports Server (NTRS)

We have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+ 14 during 1996 September, 1998 June-October, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 yr. We find significant deviations from a steady spin-down trend during quiescence and the burst active interval. Burst and Transient Source Experiment observations of the burst emission are presented and correlations between the burst activity and spin-down rate of SGR 1900+14 are discussed. We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor approximately 2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or "braking glitch" at the time of the giant flare on 1998 August 27. Furthermore, we find a large discrepancy between the pulsar period and average spin-down rate in X-rays as compared to radio observations for 1998 December and 1999 January.

Woods, Peter M.; Kouveliotou, Chryssa; VanParadijs, Jan; Finger, Mark H.; Thompson, Christopher; Duncan, Robert C.; Hurley, Kevin; Strohmayer, Tod; Swank, Jean; Murakami, Toshio

1999-01-01

59

Variable Spin-Down in the Soft Gamma Repeater SGR 1900+14 and Correlations with Burst Activity  

NASA Technical Reports Server (NTRS)

We have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observation of the pulsed emission from SGR 1900+14 during September 1996, June-October 1998, and early 1999. Using these measurements and results reported elsewhere. we construct a period history of this source for 2.5 years. We find significant deviations from a steady spin-down trend during quiescence and the burst active interval. Burst And Transient Source Experiment (BATSE) observations of the burst emission are presented and correlations between the burst activity and spin-down rate of SGR 1900 + 14 are discussed. We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor of about 2.3. This enhanced spin-down may, be the result of a discontinuous spin-down event or "braking glitch" at the time of the giant flare on 27 August 1998. Furthermore find a large discrepancy between the pulsar period and average spin-down rate in X-rays as compared to radio observation for December 1998 and January 1999.

Woods, Peter M.; Kouveliotou, Chryssa; vanParadijs, Jan; Finger, Mark H.; Thompson, Christopher; Duncan, Robert C.; Hurley, Kevin; Swank, Jean; Murakami, Toshio

1999-01-01

60

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

61

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

62

Diacylglycerol kinases terminate diacylglycerol signaling during the respiratory burst leading to heterogeneous phagosomal NADPH oxidase activation.  

PubMed

It is commonly assumed that all phagosomes have identical molecular composition. This assumption has remained largely unchallenged due to a paucity of methods to distinguish individual phagosomes. We devised an assay that extends the utility of nitro blue tetrazolium for detection and quantification of NAPDH oxidase (NOX) activity in individual phagosomes. Implementation of this assay revealed that in murine macrophages there is heterogeneity in the ability of individual phagosomes to generate superoxide, both between and within cells. To elucidate the molecular basis of the variability in NOX activation, we employed genetically encoded fluorescent biosensors to evaluate the uniformity in the distribution of phospholipid mediators of the oxidative response. Despite variability in superoxide generation, the distribution of phosphatidylinositol 3,4,5-trisphosphate, phosphatidylinositol 3-phosphate, and phosphatidic acid was nearly identical in all phagosomes. In contrast, diacylglycerol (DAG) was not generated uniformly across the phagosomal population, varying in a manner that directly mirrored superoxide production. Modulation of DAG levels suggested that NOX activation is precluded when phagosomes fail to reach a critical DAG concentration. In particular, forced expression of diacylglycerol kinase ? abrogated DAG accumulation at the phagosome, leading to impaired respiratory burst. Conversely, pharmacological inhibition of DAG kinases or expression of an inactive diacylglycerol kinase ? mutant increased the proportion of DAG-positive phagosomes, concomitantly potentiating phagosomal NOX activity. Our data suggest that diacylglycerol kinases limit the extent of NADPH oxidase activation, curtailing the production of potentially harmful reactive oxygen species. The resulting heterogeneity in phagosome responsiveness could enable the survival of a fraction of invading microorganisms. PMID:23814057

Schlam, Daniel; Bohdanowicz, Michal; Chatgilialoglu, Alexandros; Chatilialoglu, Alexandros; Steinberg, Benjamin E; Ueyama, Takehiko; Du, Guangwei; Grinstein, Sergio; Fairn, Gregory D

2013-08-01

63

A model of abnormal gastric electrical activity  

Microsoft Academic Search

A mathematical model of abnormal gastric electrical activity is presented and used to investigate the accuracy of surface EGGs in the detection of gastric electrical abnormalities. The results show that current surface electrode configurations, cannot detect abnormalities that are not widespread. Substantial improvements can be obtained by using electrode arrays. Surface maps of the slow waves and the signal-to-noise ratio

B. O. Familoni; T. L. Abell; R. Praturu; S. Katragadda; P. Sabourin

1989-01-01

64

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.

65

Utility of intracerebral theta burst electrical stimulation to attenuate interhemispheric inhibition and to promote motor recovery after cortical injury in an animal model.  

PubMed

Following a cerebral cortex injury such as stroke, excessive inhibition around the core of the injury is thought to reduce the potential for new motor learning. In part, this may be caused by an imbalance of interhemispheric inhibition (IHI); therefore, treatments that relieve the inhibitory drive from the healthy hemisphere to the peri-lesional area may enhance motor recovery. Theta burst stimulation delivered by transcranial magnetic stimulation has been tested as a means of normalizing IHI, but clinical results have been variable. Here we use a new rat model of synaptic IHI to demonstrate that electrical intracranial theta burst stimulation causes long-lasting changes in motor cortex excitability. Further, we show that contralateral intermittent theta burst stimulation (iTBS) blocks IHI via a mechanism involving cannabinoid receptors. Finally, we show that contralesional iTBS applied during recovery from cortical injury in rats improves the recovery of motor function. These findings suggest that theta burst stimulation delivered through implanted electrodes may be a promising avenue to explore for augmenting rehabilitation from brain injury. PMID:24905955

Barry, Melissa D; Boddington, Laura J; Igelström, Kajsa M; Gray, Jason P; Shemmell, Jon; Tseng, Kuei Y; Oorschot, Dorothy E; Reynolds, John N J

2014-11-01

66

Characteristics of short-duration electron precipitation bursts and their relationship with VLF wave activity  

SciTech Connect

Energetic ({gt}6 keV) electron data from the SEEP payload on the low altitude ({similar to}200 km) polar orbiting S81-1 satellite indicate a high rate of occurrence of short duration ({lt}0.6 s) electron precipitation bursts. Characteristics of events observed at night (2230 MLT) versus daytime (1030 MLT) and at midlatitudes (2{lt}{ital L}{lt}3) versus higher latitudes ({ital L}{gt}3) were distinctly different in several ways. For 2{lt}{ital L}{lt}3 the day time bursts occurred approximately uniformly in longitude and were equally distributed between the northern and southern hemispheres. The nighttime bursts in the same {ital L} shell range occurred approximately twice as often on a worldwide basis and were observed predominantly in the northern hemisphere and at longitudes of 260 {degree}E to 320 {degree}E. In a significant number of the nighttime events at 2{lt}{ital L}{lt}3 the median electron energy increased with time during the burst, but most of the other spectra showed no well-defined trend. During some of the nighttime bursts broad peaks were observed in the energy spectra, but these peaks were not so evident in the daytime bursts.

Imhof, W.L.; Voss, H.D.; Mobilia, J.; Walt, M. (Lockheed Palo Alto Research Laboratory, Palo Alto, California (US)); Inan, U.S. (Lockheed Palo Alto Research Laboratory, Palo Alto, California (US)); Carpenter, D.L. (STAR Laboratory, Stanford University, Stanford, California)

1989-08-01

67

Control of VLF burst activity in the nightside ionosphere of Venus by the magnetic field orientation  

NASA Technical Reports Server (NTRS)

A burst identificaton method developed by Ho et al. (1991) is used to analyze data on the nightside ionosphere of Venus in order to determine whether VLF bursts observed there are better interpreted as whistler mode waves or ion acoustic waves. The correlation between burst occurrence and the angle between the magnetic field and the radial direction, as well as the spacecraft flight direction are examined. Narrow-band 100-Hz bursts are found to be more frequently associated with radial magnetic fields while wideband signals are more frequently associated with horizontal fields. Under the assumption of vertical propagation, the normalized 100-Hz burst rate inside the resonance cone is larger than that outside. The burst rate inside the resonance cone dominates the altitude distribution. By assuming vertical propagation, the 100-Hz signals clearly divide into two populations. One is whistler mode propagating inside the resonance cone. The other is a nonpropagating mode outside the resonance cone which decreases quickly with altitude with a scale height of about 20 km.

Ho, C.-M.; Strangeway, R. J.; Russell, C. T.

1992-01-01

68

X-ray flares and the duration of engine activity in gamma-ray bursts  

E-print Network

The detection of bright X-ray flares superimposed on the regular afterglow decay in Swift gamma-ray bursts has triggered theoretical speculations on their origin. We study the temporal properties of flares due to internal dissipation and external shock mechanisms. We first show that at least a sizable fraction of the flares cannot be related to external shock mechanisms, since external shock flares evolve on much longer time scales than observed. We then study flares from internal dissipation, showing that the temporal properties allow us to distinguish the emission of slow early shells from that of late faster shells. We show that, due to the rapid evolution of the detected flares, it is most likely that the flares are produced by relatively fast shells ejected by the central engine shortly before they are observed. This implies that the central engine must be active for, in some cases, as long as one day. We finally discuss the constraints and implications that this observation has on the properties and physics of the inner engine, and we elaborate on possible future observational tests on the flare sample to further understand their origin and physics.

Davide Lazzati; Rosalba Perna

2006-10-24

69

Benchmark of the SixTrack-Fluka Active Coupling Against the SPS Scrapers Burst Test  

E-print Network

The SPS scrapers are a key ingredient for the clean injection into the LHC: they cut off halo particles quite close to the beam core (e.g.~3.5 sigma) just before extraction, to minimise the risk for quenches. The improved beam parameters as envisaged by the LHC Injectors Upgrade (LIU) Project required a revision of the present system, to assess its suitability and robustness. In particular, a burst (i.e. endurance) test of the scraper blades has been carried out, with the whole bunch train being scraped at the centre (worst working conditions). In order to take into account the effect of betatron and longitudinal beam dynamics on energy deposition patterns, and nuclear and Coulomb scattering in the absorbing medium onto loss patterns, the SixTrack and Fluka codes have been coupled, profiting from the best of the refined physical models they respectively embed. The coupling envisages an active exchange of tracked particles between the two codes at each turn, and an on-line aperture check in SixTrack, in order ...

Mereghetti, A; Cerutti, F

2014-01-01

70

Sensory-evoked and spontaneous gamma and spindle bursts in neonatal rat motor cortex.  

PubMed

Self-generated neuronal activity originating from subcortical regions drives early spontaneous motor activity, which is a hallmark of the developing sensorimotor system. However, the neural activity patterns and role of primary motor cortex (M1) in these early movements are still unknown. Combining voltage-sensitive dye imaging (VSDI) with simultaneous extracellular multielectrode recordings in postnatal day 3 (P3)-P5 rat primary somatosensory cortex (S1) and M1 in vivo, we observed that tactile forepaw stimulation induced spindle bursts in S1 and gamma and spindle bursts in M1. Approximately 40% of the spontaneous gamma and spindle bursts in M1 were driven by early motor activity, whereas 23.7% of the M1 bursts triggered forepaw movements. Approximately 35% of the M1 bursts were uncorrelated to movements and these bursts had significantly fewer spikes and shorter burst duration. Focal electrical stimulation of layer V neurons in M1 mimicking physiologically relevant 40 Hz gamma or 10 Hz spindle burst activity reliably elicited forepaw movements. We conclude that M1 is already involved in somatosensory information processing during early development. M1 is mainly activated by tactile stimuli triggered by preceding spontaneous movements, which reach M1 via S1. Only a fraction of M1 activity transients trigger motor responses directly. We suggest that both spontaneously occurring and sensory-evoked gamma and spindle bursts in M1 contribute to the maturation of corticospinal and sensorimotor networks required for the refinement of sensorimotor coordination. PMID:25122889

An, Shuming; Kilb, Werner; Luhmann, Heiko J

2014-08-13

71

The effect of ex vivo refrigerated storage and cell preservation solution (Cyto-Chex II™) on CD11b expression and oxidative burst activity of dog neutrophils  

Microsoft Academic Search

The expression of CD11b and oxidative burst activity of dog neutrophils undergoing ex vivo refrigerated storage was studied using flow-cytometry. Additionally, the effect of a proprietary cell stabilization reagent (Cyto-Chex™) on the expression of CD11b and oxidative burst activity was studied. Expression of CD11b was very high (>90% positive) on dog neutrophils isolated from peripheral blood. Dog neutrophils showed a

Craig G Ruaux; David A Williams

2000-01-01

72

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. PMID:23363774

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

2013-01-01

73

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

74

Ulysses observations of wave activity at interplanetary shocks and implications for type II radio bursts  

SciTech Connect

We present the first quantitative investigation of interplanetary type II radio emission in which in situ waves measured at interplanetary shocks are used to compute radio wave intensities for comparison with type II observations. This study is based on in situ measurements of 42 in-ecliptic forward shocks as well as 10 intervals of type II emission observed by the Ulysses spacecraft between 1 AU and 5 AU. The analysis involves comparisons of statistical properties of type II bursts and in situ waves. Most of the 42 shocks are associated with the occurrence of electrostatic waves near the time of shock passage at Ulysses. These waves, which are identified as electron plasma waves and ion acoustic-like waves, are typically most intense several minutes before shock passage. This suggests that wave-wave interactions might be of importance in electromagnetic wave generation and that type II source regions are located immediately upstream of the shocks. We use the in situ wave measurements to compute type II brightness temperatures, assuming that emission at the fundamental of the electron plasma frequency is generated by the merging of electron plasma waves and ion acoustic waves or the decay of electron plasma waves into ion acoustic and transverse waves. Second harmonic emission is assumed to be produced by the merging of electron plasma waves. The latter mechanism requires that a portion of the electron plasma wave distribution is backscattered, presumably by density inhomogeneities in regions of observed ion acoustic wave activity. The computed type II brightness temperatures are found to be consistent with observed values for both fundamental and second harmonic emission, assuming that strong ({approx_equal}10{sup {minus}4}V/m) electron plasma waves and ion acoustic waves are coincident and that the electron plasma waves have phase velocities less than about 10 times the electron thermal velocity. (Abstract Truncated)

Lengyel-Frey, D. [Department of Astronomy, University of Maryland, College Park, Maryland (United States)] [Department of Astronomy, University of Maryland, College Park, Maryland (United States); [Computer Sciences Corporation, Suitland, Maryland (United States); Thejappa, G. [Department of Astronomy, University of Maryland, College Park, Maryland (United States)] [Department of Astronomy, University of Maryland, College Park, Maryland (United States); MacDowall, R.J.; Stone, R.G. [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)] [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Phillips, J.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); [NASA Johnson Space Flight Center, Houston, Texas (United States)

1997-02-01

75

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

76

FAST AND SLOW SUBSYSTEMS FOR A CONTINUUM MODEL OF BURSTING ACTIVITY IN THE PANCREATIC ISLET \\Lambda  

E-print Network

of calcium in the endoplasmic reticulum and ADP. Specific forms of the functions defining (1)­(3) depend],[7],[16],[24]). At elevated temperatures (30 ffi C), bursting was observed in fi­cells which were isolated from the islet [30]. In other experiments at room temperature using different measuring techniques, isolated fi­cells exhibit

Pernarowski, Mark

77

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

78

The effects of 3-methylcholanthrene on macrophage respiratory burst and biotransformation activities in the common carp (Cyprinus carpio L.).  

PubMed

The sensitivity of phagocytic cell function as a bioindicator of pollution stress by polycyclic aromatic hydrocarbons was evaluated in the common carp (Cyprinus carpio L). The time course response of the head-kidney macrophage respiratory burst was measured 1, 2, 3, 5 and 7 days after intraperitoneal injection of a prototypical Cyp 1A inducer (3-methylcholanthrene). This immune activity was compared to the rate of induction of total cytochrome P450, ethoxyresorufin O-deethylase activity (EROD) and glutathione S-transferase activity (GST) in the liver and head-kidney. 3-methylcholanthrene (40 mg kg(-1)) caused a rapid increase in the macrophage respiratory burst. This response was maximal at day 3 post exposure and coincided with maximum induction of cytochrome P450 and EROD activity in liver and head-kidney. Moreover, alpha-naphtoflavone, which functions as both an Ah receptor antagonist and an inhibitor of cytochrome P450 1A activity, reversed the 3-methylcholanthrene induction of immune and enzymatic parameters measured, suggesting metabolic processes. Taken together these results suggest that the induction of macrophage oxidative function may be an equally sensitive marker of exposure to polycyclic aromatic hydrocarbon as the induction of biotransformation activities and confirm that responses mediated by the Ah receptor are similar, if not identical, to those of mammals. PMID:11866128

Reynaud, S; Marionnet, D; Taysse, L; Duchiron, C; Deschaux, P

2002-01-01

79

Electrical activity of the normal human stomach  

Microsoft Academic Search

Using monopolar electrodes, the gastric electrical activity was recorded in waking human beings from both the mucosal and the serosal sides of the gastric wall. For each electrode location in a given subject, a mean curve of the regular fluctuations in potential (pacesetter potential) was obtained by an iteration process allowing measurement of characteristic amplitudes. A detailed study of the

D. Couturier; C. Rozé; J. Paolaggi; C. Debray

1972-01-01

80

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.

81

Ulysses observations of wave activity at interplanetary shocks and implications for type II radio bursts  

NASA Astrophysics Data System (ADS)

We present the first quantitative investigation of interplanetary type II radio emission in which in situ waves measured at interplanetary shocks are used to compute radio wave intensities for comparison with type II observations. This study is based on in situ measurements of 42 in-ecliptic forward shocks as well as 10 intervals of type II emission observed by the Ulysses spacecraft between 1 AU and 5 AU. The analysis involves comparisons of statistical properties of type II bursts and in situ waves, since the type II events are not related to particular shock passages at Ulysses. Most of the 42 shocks are associated with the occurrence of electrostatic waves near the time of shock passage at Ulysses. These waves, which are identified as electron plasma waves and ion acoustic-like waves, are typically most intense several minutes before shock passage. This suggests that wave-wave interactions might be of importance in electromagnetic wave generation and that type II source regions are located immediately upstream of the shocks. We use the in situ wave measurements to compute type II brightness temperatures, assuming that emission at the fundamental of the electron plasma frequency is generated by the merging of electron plasma waves and ion acoustic waves or the decay of electron plasma waves into ion acoustic and transverse waves. Second harmonic emission is assumed to be produced by the merging of electron plasma waves. The latter mechanism requires that a portion of the electron plasma wave distribution is backscattered, presumably by density inhomogeneities in regions of observed ion acoustic wave activity. The computed type II brightness temperatures are found to be consistent with observed values for both fundamental and second harmonic emission, assuming that strong (~=10-4V/m) electron plasma waves and ion acoustic waves are coincident and that the electron plasma waves have phase velocities less than about 10 times the electron thermal velocity. Thus a single conversion mechanism provides a plausible scenario for generation of both fundamental and harmonic interplanetary type II emission.

Lengyel-Frey, D.; Thejappa, G.; MacDowall, R. J.; Stone, R. G.; Phillips, J. L.

1997-02-01

82

Impairment of human neutrophil oxidative burst by polychlorinated biphenyls: inhibition of superoxide dismutase activity  

Microsoft Academic Search

We report evidence of a novel mecha- nism by which polychlorinated biphenyls might act as potent inducers of inflammation. Aroclor 1242 (A1242), a polychlorinated biphenyl mixture, and 2,2',4,4'-tetrachlorobiphenyl (PCB47), a constitu- ent of A1242 that produces the same patterns of effects, impaired the oxidative burst of human neutrophils by inhibiting the antioxidant enzyme superoxide dismutase, which converts O22 to H2O2.

P. K. Narayanan; W. O. Carter; P. E. Ganey; R. A. Roth; S. L. Voytik-Harbin; J. P. Robinson

83

Spatiotemporal dynamics of the electrical network activity in the root apex  

PubMed Central

The study of electrical network systems, integrated with chemical signaling networks, is becoming a common trend in contemporary biology. Classical techniques are limited to the assessment of signals from doublets or triplets of cells at a fixed temporal bin width. At present, full characteristics of the electrical network distribution and dynamics in plant cells and tissues has not been established. Here, a 60-channels multielectrode array (MEA) is applied to study spatiotemporal characteristics of the electrical network activity of the root apex. Both intense spontaneous electrical activities and stimulation-elicited bursts of locally propagating electrical signals have been observed. Propagation of the spikes indicates the existence of excitable traveling waves in plants, similar to those observed in non-nerve electrogenic tissues of animals. Obtained data reveal synchronous electric activities of root cells emerging in a specific root apex region. The dynamic electrochemical activity of root apex cells is proposed to continuously integrate internal and external signaling for developmental adaptations in a changing environment. PMID:19234119

Masi, E.; Ciszak, M.; Stefano, G.; Renna, L.; Azzarello, E.; Pandolfi, C.; Mugnai, S.; Baluska, F.; Arecchi, F. T.; Mancuso, S.

2009-01-01

84

SIMULTANEOUS ESTIMATION OF ELECTRICAL AND THERMAL PROPERTIES OF MATERIAL FROM THE TONE-BURST EDDY CURRENT THERMOGRAPHY (TBET) TIME-TEMPERATURE DATA  

SciTech Connect

In this paper, an inversion method is proposed to determine simultaneously the electrical and thermal properties of a given isotropic material from the time-temperature data obtained from the Tone-Burst Eddy current Thermography (TBET). A multi-physics forward model for computing the surface temperature data was used in a Genetic Algorithm (GA) based inversion technique to determine the material properties such as electrical conductivity (sigma), thermal conductivity (k), density (rho), and specific heat (C{sub p}) simultaneously. Different trials were carried out initially with simulated temperature data (with and without noise). A typical case of inversion of anisotropic material properties using a 2D finite element model is also discussed.

Biju, N.; Ganesan, N.; Krishnamurthy, C. V.; Balasubramaniam, Krishnan [Centre for Nondestructive Evaluation, Department of Mechanical Engineering, Indian Institute of Technology Madras (India)

2010-02-22

85

Electrically driven plasmon chip: Active plasmon filter  

NASA Astrophysics Data System (ADS)

We have developed an electrically driven plasmon chip, i.e., an active plasmon filter, consisting of a metallic subwavelength grating modulated by a nano-electro-mechanical system (NEMS) type actuator. The device shifts the plasmon resonance wavelength and the transmittance when an electrical signal is applied. The fabricated filter shows resonance wavelength shifts of 60 nm with a bias voltage of less than 10 V. A rigorous numerical calculation confirms the origin of the surface plasmon resonance and qualitatively explains the effect. Such NEMS optical devices offer rapid voltage-controlled plasmonic tuning of 20 MHz, opening up applications in agile sensing and nanoscale object trapping using actively tailored optical hot spots.

Yamaguchi, Kenzo; Fujii, Masamitsu; Okamoto, Toshihiro; Haraguchi, Masanobu

2014-01-01

86

Alterations in the intrinsic burst activity of Purkinje neurons in offspring maternally exposed to the CB1 cannabinoid agonist WIN 55212-2.  

PubMed

Burst firing plays an important role in normal neuronal function and dysfunction. In Purkinje neurons, where the firing rate and discharge pattern encode the timing signals necessary for motor function, any alteration in firing properties, including burst activity, may affect the motor output. Therefore, we examined whether maternal exposure to the cannabinoid receptor agonist WIN 55212-2 (WIN) may affect the burst firing properties of cerebellar Purkinje cells in offspring. Whole-cell somatic patch-clamp recordings were made from cerebellar slices of adult male rats that were exposed to WIN prenatally. WIN exposure during pregnancy induced long-term alterations in the burst firing behavior of Purkinje neurons in rat offspring as evidenced by a significant increase in the mean number of spikes per burst (p < 0.05) and the prolongation of burst firing activity (p < 0.01). The postburst afterhyperpolarization potential (p < 0.001), the mean intraburst interspike intervals (p < 0.001) and the mean intraburst firing frequency (p < 0.001) were also significantly increased in the WIN-treated group. Prenatal exposure to WIN enhanced the firing irregularity as reflected by a significant decrease in the coefficient of variation of the intraburst interspike interval (p < 0.05). Furthermore, whole-cell voltage-clamp recordings revealed that prenatal WIN exposure significantly enhanced Ca(2+) channel current amplitude in offspring Purkinje neurons compared to control cells. Overall, the data presented here strongly suggest that maternal exposure to cannabinoids can induce long-term changes in complex spike burst activity, which in turn may lead to alterations in neuronal output. PMID:24218023

Shabani, Mohammad; Mahnam, Amin; Sheibani, Vahid; Janahmadi, Mahyar

2014-01-01

87

Induced immunity against belowground insect herbivores- activation of defenses in the absence of a jasmonate burst.  

PubMed

Roots respond dynamically to belowground herbivore attack. Yet, little is known about the mechanisms and ecological consequences of these responses. Do roots behave the same way as leaves, or do the paradigms derived from aboveground research need to be rewritten? This is the central question that we tackle in this article. To this end, we review the current literature on induced root defenses and present a number of experiments on the interaction between the root herbivore Diabrotica virgifera and its natural host, maize. Currently, the literature provides no clear evidence that plants can recognize root herbivores specifically. In maize, mild mechanical damage is sufficient to trigger a root volatile response comparable to D. virgifera induction. Interestingly, the jasmonate (JA) burst, a highly conserved signaling event following leaf attack, is consistently attenuated in the roots across plant species, from wild tobacco to Arabidopsis. In accordance, we found only a weak JA response in D. virgifera attacked maize roots. Despite this reduction in JA-signaling, roots of many plants start producing a distinct suite of secondary metabolites upon attack and reconfigure their primary metabolism. We, therefore, postulate the existence of additional, unknown signals that govern induced root responses in the absence of a jasmonate burst. Surprisingly, despite the high phenotypic plasticity of plant roots, evidence for herbivore-induced resistance below ground is virtually absent from the literature. We propose that other defensive mechanisms, including resource reallocation and compensatory growth, may be more important to improve plant immunity below ground. PMID:22527052

Erb, Matthias; Glauser, Gaetan; Robert, Christelle A M

2012-06-01

88

Short intense bursts in magmatic activity in the south of Siberian Platform (Angara-Taseeva depression): the paleomagnetic evidence  

NASA Astrophysics Data System (ADS)

Based on the paleomagnetic study of intrusive and explosive Permian-Triassic traps in the Angara River basin, Siberian Platform, it is established that the formation of the traps was marked by three short and highly intense bursts in magmatic activity, which resulted in the intrusion of three large dolerite sills (Tolstomysovsky, Padunsky and Tulunsky) and the deposition of the tuffs of the Kapaevsky Formation. These magmatic bursts occurred against the long-lived less intense background magmatism, which caused the formation of small intrusive bodies and tuff sequences. The geochronological data and correlation of the Angara traps to the effusive trap sequences in the north of the Siberian Platform (Norilsk and Maymecha-Kotuy regions) indicate that intrusion of the Tolstomysovsky sill and eruption of its comagmatic tuffs of the Kapaevsky Formation occurred in the Early Triassic. The obtained paleomagnetic data contradict the existing idea that the Padunsky and Tulunsky sills are coeval. Moreover, these data show that the magmatic bodies of different ages were mistakenly referred to the same sill.

Latyshev, A. V.; Veselovskiy, R. V.; Ivanov, A. V.; Fetisova, A. M.; Pavlov, V. E.

2013-11-01

89

Change and Stability in Active and Passive Social Influence Dynamics during Natural Drinking Events: A Longitudinal Measurement-Burst Study  

PubMed Central

We examined the link between social norms and active social influences occurring during natural social drinking contexts. Across 4 yearly measurement-bursts, college students (N = 523) reported daily for 30-day periods on drinking norms, drinking offers, how many drinks they accepted, and personal drinking levels during social drinking events. In contexts where drinking norms were higher, students were more likely to both receive and comply with drinking offers. These acute social influences were highly stable throughout college, but affected men and women differently across time: Women received more drinking offers than men, especially at the beginning of college and when norms were higher, but men complied with more drinking offers per occasion. These effects were not attributable to between-person differences in social drinking motives or drinking levels, nor to within-person patterns of situation-selection. The present work suggests that context-specific drinking norms catalyze active social influence attempts, and further promote compliance drinking. PMID:22661826

Cullum, Jerry; O'Grady, Megan; Armeli, Stephen; Tennen, Howard

2011-01-01

90

Proton secretion by stimulated neutrophils. Significance of hexose monophosphate shunt activity as source of electrons and protons for the respiratory burst.  

PubMed Central

Phagocytosis by neutrophils is accompanied by a burst in O2 consumption and activation of the hexose monophosphate shunt (HMPS). Proton secretion equal to the amount of O2 consumed is an additional feature of the respiratory burst, but its source has not been identified, nor has the source of all electrons donated to O2 in the respiratory burst. We chemically quantitated total CO2 generation in human neutrophils and found that proton secretion elicited by phagocytosis was accompanied by a stoichiometric increase in CO2 generation. Addition of carbonic anhydrase and its inhibitors had no effect on either the quantities of CO2 measured or the quantities of protons secreted. Therefore, the CO2 generated in the respiratory burst of stimulated neutrophils is hydrated to form H2CO3, which then dissociates, accounting for the observed proton secretion. Furthermore, the CO2 generated corresponds to the O2 consumed with a respiratory quotient of nearly 1. We conclude on the basis of this and previous studies that the HMPS activity is the source of both the electrons for the NADPH oxidase and of protons secreted in association with the respiratory burst. PMID:6430961

Borregaard, N; Schwartz, J H; Tauber, A I

1984-01-01

91

Phosphatidylinositol 4,5-bisphosphate regulates inspiratory burst activity in the neonatal mouse preBötzinger 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. PMID:17599963

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

2007-01-01

92

Observations of the Bursting Activity of the 6.7GHz Methanol Maser in G33.641-0.228  

E-print Network

We have observed bursting variability of the 6.7 GHz methanol maser of G33.641-0.228. Five bursts were detected in the observation period of 294 days from 2009 to 2012. The typical burst is a large flux density rise in about one day followed by a slow fall. A non-typical burst observed in 2010 showed a large and rapid flux density enhancement from the stable state, but the rise and fall of the flux density were temporally symmetric and a fast fluctuation continued 12 days. On average, the bursts occurred once every 59 days, although bursting was not periodic. Since the average power required for causing the burst of order of 10^21 Js^-1 is far smaller than the luminosity of G33.641-0.228, a very small fraction of the source's power would be sufficient to cause the burst occasionally. The burst can be explained as a solar-flare like event in which the energy is accumulated in the magnetic field of the circumstellar disk, and is released for a short time. However, the mechanism of the energy release and the dus...

Fujisawa, Kenta; Nagadomi, Yoshito; Kimura, Saki; Shimomura, Tadashi; Takase, Genta; Sugiyama, Koichiro; Motogi, Kazuhito; Niinuma, Kotaro; Hirota, Tomoya; Yonekura, Yoshinori

2014-01-01

93

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

94

Short burst oxygen therapy after activities of daily living in the home in chronic obstructive pulmonary disease  

PubMed Central

Background Short burst oxygen therapy (SBOT) is widely prescribed in the UK with little evidence of benefit. A study was performed to examine whether SBOT benefits patients when undertaking normal activities at home among those who already use it. Methods Twenty?two patients with chronic obstructive pulmonary disease (COPD) were included in the study. All regularly used SBOT at home and claimed that it helps them. Each patient chose two daily living activities for which they used SBOT for relief of breathlessness. Patients were then randomised to use either an air or oxygen gas cylinder. At least 15?min later the same activity was performed using the other gas cylinder. The same process was then repeated for the second chosen activity. The main endpoints were subjective and objective times to recovery, analysed for each activity separately or taking the average over the two activities. A paired statistical analysis was performed. Results All patients used SBOT with nasal prongs after exercise. Using the average recovery time over two activities for each patient, the mean objective recovery time was 38?s lower (95% CI ?81 to +5) using oxygen and the mean subjective recovery time was 34?s lower (95% CI ?69 to +2). Five patients were correctly able to distinguish oxygen from air after both activities and there was a suggestion that their recovery times were shorter than those who did not correctly identify the gases (91?s vs 20?s using objective recovery times, and 80?s vs 22?s using subjective recovery times), although this was a subgroup analysis based on only five patients with non?significant results. Conclusions There is some evidence that SBOT shortens recovery time after activities of daily living in a selected group of patients with COPD, but the effect is small. There appears to be a subgroup of patients who may benefit to a much greater degree. PMID:17311844

Quantrill, S J; White, R; Crawford, A; Barry, J S; Batra, S; Whyte, P; Roberts, C M

2007-01-01

95

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

96

Ionic mechanisms of intestinal electrical control activity.  

PubMed

The effects of inhibition and stimulation of the electrogenic Na pump and of altering the ionic environment on the electrical control activity (ECA) were studied in rabbit jejunal smooth muscle. Pump inhibition abolished the ECA at a time when the membrane potential was more negative than the peak depolarization of the control potential (CP). Pump stimulation hyperpolarized the membrane and CP's appeared. Their amplitude was initially small and progressively increased as the hyperpolarization subsided. Lowering external Na to 20 mM or Ca withdrawal, but not addition of verapamil, reversibly abolished the ECA. Chloride replacement by propionate, isethionate, or benzene-sulphonate caused a transient augmentation, followed by suppression of the secondary depolarization of the CP's and decreased their frequency. The initial depolarization of the CP was little affected. Nitrate substitution increased CP frequency and spiking activity but had no observable effects on the CP configuration. These results suggest that the intestinal control potential may result from conductance changes initially to Na and later to C1 rather than fron an oscillatory electrogenic pump. PMID:1200148

El-Sharkaway, T Y; Daniel, E E

1975-11-01

97

Image-based cytometry reveals three distinct subsets of activated granulocytes based on phagocytosis and oxidative burst.  

PubMed

Granulocytes play a key role in innate immunity and the most common functional assays are phagocytosis and oxidative burst. The purpose of this technical note is to use image-based flow cytometry to divide activated granulocytes into unique subsets based on their degree of phagocytosis and oxidative burst in response to different experimental incubations. Prior to the experiments, all reagents were titered to determine the lowest dose that resulted in an acceptable signal to noise ratio. Heparinized, whole blood (100 µl) was mixed with one of two bioparticles (E. coli and S. aureus) and DHE (10 µg/ml) and incubated for 5, 10, 20, 40, 60, 80, 100, 120, and 140 min in a 37°C water bath. An additional tube kept on ice was used as a negative control. All subsequent processing steps were completed on ice in the dark to minimize additional activation of cells. After the 37°C incubation, N-ethylmaleimide (15 mM) was added to halt phagocytosis, preventing the uptake of additional microparticles. Suspensions were labeled with CD66b-APC and CD45-APCeFluor780 for 60 min and a fix/lyse solution was added. Prior to acquisition, 7AAD was added to stain nuclear DNA. A minimum of 5,000 granulocyte (CD66b+) events were acquired using a Millipore-Amnis FlowSight equipped with blue (488 nm, 60 mW), red (642 nm, 100 mW), and side scatter (785 nm, 12 mW) lasers. Samples were compensated and analyzed using Amnis IDEAS software (v.5.0.983.0). Image-based analysis allowed us to divide activated granulocytes into three distinct subsets, whose relative abundance changed as a function of both bioparticle type and incubation length. The method described in this technical note represents a potential novel adaptation to common methods of assessing granulocyte function. More research is needed to test and validate our image-based method in clinical conditions that impair granulocyte function. PMID:23839911

McFarlin, Brian K; Williams, Randall R; Venable, Adam S; Dwyer, Karen C; Haviland, David L

2013-08-01

98

Occurrence characteristics of VLF bursts in the nightside ionosphere of Venus  

NASA Technical Reports Server (NTRS)

Many of the impulsive VLF signals observed by the Pioneer Venus orbiter electric field detector (OEFD) in the nightside ionosphere have been interpreted as arising from lightning in the Venus atmosphere. In order to determine the characteristics of the source, and to compare with terrestrial lightning, the normalized occurrence rate for individual bursts at Venus are determined, as opposed to previous studies of activity in 30-s intervals. Burst identification criteria are determined which take into account the decay constant of the instrument to calculate the burst rate. Under the assumption that all OEFD observations in the nightside ionosphere are due to impulsive signals, it is found that the 100-Hz channel has the highest burst rate, about 0.20/s in the altitude range 150-180 km and in the postmidnight local time sector. The burst occurrence rates for all four frequency channels decrease with increasing altitude. Burst rates at frequencies above 100 Hz are greater in the premidnight hours while 100-Hz signals peak after midnight; however, these burst rates vary from orbit to orbit. The 100-Hz low-frequency burst rate has a stronger dependence on the magnetic field strength than the higher-frequency rates. Most 100-Hz bursts are closely spaced and occur independently of signals at higher frequencies. These dependences suggest that the low- and high-frequency signals have different propagation mechanisms. The properties of the bursts are generally consistent with a lightning source, and the planet-wide burst rate at Venus may be comparable to or larger than the terrestrial lightning rate.

Ho, C.-M.; Strangeway, R. J.; Russell, C. T.

1991-01-01

99

http://www.pdl.cs.cmu.edu/Active Thesis Defense Electrical and Computer Engineering Active Disks  

E-print Network

http://www.pdl.cs.cmu.edu/Active Thesis Defense Electrical and Computer Engineering Active Disks Electrical and Computer Engineering Prof. David Nagle, ECE Prof. Christos Faloutsos, SCS Prof. Garth Gibson://www.pdl.cs.cmu.edu/Active Thesis Defense Electrical and Computer Engineering Active Disks Carnegie Mellon Thesis Statement A number

100

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

101

Using the Active Collimator and Shield Assembly of an EXIST-Type Mission as a Gamma-Ray Burst Spectrometer  

E-print Network

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 and 35 square meters 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 GEANT4 to simulate the interactions of photons and cosmic rays with the spacecraft and instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield collimator achieves a nu-F-nu sensitivity of 3 x 10^(-9) erg cm^(-2) s^(-1) and 2 x 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.

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

2006-06-05

102

DEMETER Satellite Observations of Particle Burst Prior to Chile Earthquake  

E-print Network

The lithosphere activity during seismogenic or occurrence of one earthquake may emit electromagnetic wave which propagate to ionosphere and radiation belt, then induce disturbance of electric and magnetic field and the precipitation of high energy charged particles. This paper, based on the data detected by DEMETER satellite, present the high energy charged particle burst(PB) with 4 to 6 times enhancement over the average value observed about ten days days before Chile earthquake. The obvious particle burst was also observed in the northern hemisphere mirror points conjugate of epicenter and no PB events in different years over the same epicenter region was found. The energy spectra of the PBs are different from the one averaged within the first three months in 2010. At the same time, the disturbance of the VLF electric spectrum in ionosphere over the epicenter detected by the DEMETER satellite are also observed in the same two orbits. Those observations from energetic PB and VLF electric spectrum disturbance...

Zhang, Zhenxia; Shen, Xuhui; Ma, Yuqian; Chen, Huaran; You, Xinzhao; Yuan, Yahong

2010-01-01

103

Radial Angular Momentum Transfer and Magnetic Barrier for Short-type Gamma-Ray-burst Central Engine Activity  

NASA Astrophysics Data System (ADS)

Soft extended emission (EE) following initial hard spikes up to 100 s was observed with Swift/BAT for about half of known short-type gamma-ray bursts (SGRBs). This challenges the conversional central engine models of SGRBs, i.e., compact star merger models. In the framework of black-hole-neutron-star merger models, we study the roles of radial angular momentum transfer in the disk and the magnetic barrier around the black hole in the activity of SGRB central engines. We show that radial angular momentum transfer may significantly prolong the lifetime of the accretion process, which may be divided into multiple episodes by the magnetic barrier. Our numerical calculations based on models of neutrino-dominated accretion flows suggest that disk mass is critical for producing the observed EE. In the case of the mass being ~0.8 M ?, our model can reproduce the observed timescale and luminosity of both the main and the EE episodes in a reasonable parameter set. The predicted luminosity of the EE component is lower than the observed EE within about one order of magnitude and the timescale is shorter than 20 s if the disk mass is ~0.2 M ?. Swift/BAT-like instruments may be not sensitive enough to detect the EE component in this case. We argue that the EE component could be a probe for the merger process and disk formation for compact star mergers.

Liu, Tong; Liang, En-Wei; Gu, Wei-Min; Hou, Shu-Jin; Lei, Wei-Hua; Lin, Lin; Dai, Zi-Gao; Zhang, Shuang-Nan

2012-11-01

104

Effects of RNA interference-mediated knock-down of hypoxia-inducible factor-? on respiratory burst activity of the Pacific oyster Crassostrea gigas hemocytes.  

PubMed

In mammals, hypoxia-inducible factor-1 ? (HIF-1?) is known to play important roles not only in oxygen homeostasis but also in innate immune responses. In this study, to assess the functional role of HIF-? in respiratory burst activity of Crassostrea gigas hemocytes, oysters were injected with HIF-?- or green fluorescent protein (GFP)-targeted-long double-stranded RNAs (dsRNAs), and at 1, 3, and 7 days post-injection, knock-down of C. gigas HIF-? expression and production of reactive oxygen species (ROS) were analyzed. Expression of HIF-? in mantle, gill, and hemocytes of C. gigas was clearly down-regulated by injection of the HIF-?-targeted-long dsRNA, but was not inhibited by the GFP-targeted-long dsRNA, indicating that HIF-? expression was suppressed through sequence-specific and systemic RNA interference (RNAi). Respiratory burst activity of hemocytes was significantly increased by administration of GFP-targeted-long dsRNA. However, knock-down of HIF-? expression led to significant decrease of chemiluminescence (CL) response of C. gigas hemocytes at 3 and 7 days post-administration of HIF-?-targeted-long dsRNA, indicating the critical role of HIF-? in activation of respiratory burst activity of oyster hemocytes. PMID:23680843

Choi, Seung Hyuk; Jee, Bo Young; Lee, Su Jin; Cho, Mi Young; Lee, Soon Jeong; Kim, Jin Woo; Jeong, Hyun Do; Kim, Ki Hong

2013-08-01

105

The structure of a late-spring moisture burst  

E-print Network

that hurst occurrence in the spring remains near winter levels in the 'normal year' climatology. After the El Nino episode of 1982-1983. burst activity increased greatly in the spring after a lull in wuiter burst activity. A useful framev... mechanism or as a late development stage. In the latter case, the association usually became active after the source region became inactive. In the El Nino years, burst activity decreased to an average of six per month, with burst activity occurring only...

Stockton, Jay Richard

2012-06-07

106

The inward rectifier in a model of corticotroph electrical activity  

E-print Network

The inward rectifier in a model of corticotroph electrical activity Paul R. Shorten , A. Bruce, Canterbury, New Zealand. #12;#12;The inward rectifier in a model of corticotroph electrical activity Paul R an inwardly rectifying K+ current. In this paper we investigate a role of the inwardly rectifying K+ current

Reale, Marco

107

Solar microwave bursts - A review  

NASA Technical Reports Server (NTRS)

Observational and theoretical results on the physics of microwave bursts that occur in the solar atmosphere are reviewed. Special attention is given to the advances made in burst physics over the last few years with the great improvement in spatial and time resolution, especially with instruments like the NRAO three-element interferometer, the Westerbork Synthesis Radio Telescope, and more recently the Very Large Array. Observations made on the preflare build-up of an active region at centimeter wavelengths are reviewed. Three distinct phases in the evolution of cm bursts, namely the impulsive phase, the post-burst phase, and the gradual rise and fall, are discussed. Attention is also given to the flux density spectra of centimeter bursts. Descriptions are given of observations of fine structures with temporal resolution of 10-100 ms in the intensity profiles of cm-wavelength bursts. High spatial resolution observations are analyzed, with special reference to the one- and two-dimensional maps of cm burst sources.

Kundu, M. R.; Vlahos, L.

1982-01-01

108

Multiple Bifurcations in a Polynomial Model of Bursting Oscillations  

Microsoft Academic Search

Bursting oscillations are commonly seen to be the primary mode of electrical behaviour in a variety of nerve and endocrine cells, and have also been observed in some biochemical and chemical systems. There are many models of bursting. This paper addresses the issue of being able to predict the type of bursting oscillation that can be produced by a model.

G. de Vries

1998-01-01

109

From static electric images to electric flow: Towards dynamic perceptual cues in active electroreception.  

PubMed

Active electroreception is an ancestral trait found in many aquatic vertebrates and has evolved independently in two teleost lineages, the Gymnotiformes and the Mormyriformes. Unique to these so-called weakly electric fish is their ability to actively generate electrical currents in the water and sense the electrical properties of the environment. How natural behavior contributes to this sensory system has been of interest to neuroethologists since the pioneering works of Lissmann. Here we report on a mutual modeling and experimental study of the stimuli available during active electrolocation of Gnathonemus petersii (Mormyridae). We show the validity of the model (I) by demonstrating that localized spatial patterns of object induced modulations in the electric field (electric images) are comparable to experimentally mapped 2-dimensional electric images and (II) by replicating earlier key findings showing that a normalized metric of electric image width provides an unambiguous cue for distance estimation. We then show that electric images and the distance metric vary systematically when an object is moved along the trunk. These potential ambiguities with regard to localization lead us to a spatiotemporal analysis of electric images. We introduce a new temporal metric for distance estimation that is based on the normalized spatial properties of electrical images. Finally, based on a survey of exploratory behavior, we show how objects situated at the tail, a region previously neglected, cast global electric images that extend over the whole sensory epithelium of the animals. PMID:22781955

Hofmann, Volker; Sanguinetti-Scheck, Juan I; Gómez-Sena, Leonel; Engelmann, Jacob

2013-01-01

110

Augmentation of bursting pacemaker activity by serotonin in an identified Achatina fulica neurone: an increase in sodium- and calcium-activated negative slope resistance via cyclic-AMP-dependent protein phosphorylation.  

PubMed

The mechanism of serotonin (5-HT) action on bursting activity was examined in a bursting pacemaker neurone of the snail Achatina fulica. 5-HT augmented both the depolarizing and post-burst-hyperpolarizing phases of the bursting cycle in a dose-dependent manner. This biogenic amine also enhanced the negative slope resistance (NSR), which was normally detectable at membrane potentials between -40 and -20 mV, and produced another NSR at voltages between -20 and 0 mV. The former NSR disappeared in Na(+)-free saline and the latter was abolished by replacement with Co(2+)-substituted Ca(2+)-free saline. Both isobutylmethylxanthine, extracellular applied, and intracellularly applied cyclic AMP simulated a 5-HT effect on the current-voltage relationships. In contrast, the 5-HT effect was suppressed in a dose-dependent manner by prior treatment with a cyclic-AMP-dependent protein kinase inhibitor, isoquinoline sulphonamide. Similar suppression was observed after intracellular injection of a cyclic-AMP-dependent protein kinase inhibitor isolated from bovine muscle. These results suggest that 5-HT may augment the bursting pacemaker activity by its stimulatory effect on both the slow Na+ channels and the Ca2+ channels through cyclic-AMP-dependent protein phosphorylation. PMID:8382731

Funase, K; Watanabe, K; Onozuka, M

1993-02-01

111

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

112

Evaluation of pozzolanic activity by the electric resistance measurement method  

SciTech Connect

Measurements of electric resistance and amount of consumption of portlandite were carried out in accelerated curing conditions by preparing pastes of Fine Ceraments, fly ash, silica fume, kaolin, acid clay, zeolite and quartz activated with portlandite. Electric resistances of reactive pozzolans showed sharp rises except that of kaolin, whereas that of inactive material, quartz, showed no sharp rise. Electric resistances are proportional to the consumptions of portlandite except for fly ashes. The electric resistance measurement method combined with portlandite consumption measurement is useful to the rapid evaluation of pozzolanic activity.

Tashiro, Chuichi; Ikeda, Ko (Yamaguchi Univ., Ube (Japan). Dept. of Advanced Materials Science and Engineering); Inoue, Yoshihiro (Fuji Denki Kagaku Co., Ltd., Kosai (Japan))

1994-01-01

113

Nanomolar Oxytocin Synergizes with Weak Electrical Afferent Stimulation to Activate the Locomotor CPG of the Rat Spinal Cord In Vitro  

PubMed Central

Synergizing the effect of afferent fibre stimulation with pharmacological interventions is a desirable goal to trigger spinal locomotor activity, especially after injury. Thus, to better understand the mechanisms to optimize this process, we studied the role of the neuropeptide oxytocin (previously shown to stimulate locomotor networks) on network and motoneuron properties using the isolated neonatal rat spinal cord. On motoneurons oxytocin (1 nM–1 ?M) generated sporadic bursts with superimposed firing and dose-dependent depolarization. No desensitization was observed despite repeated applications. Tetrodotoxin completely blocked the effects of oxytocin, demonstrating the network origin of the responses. Recording motoneuron pool activity from lumbar ventral roots showed oxytocin mediated depolarization with synchronous bursts, and depression of reflex responses in a stimulus and peptide-concentration dependent fashion. Disinhibited bursting caused by strychnine and bicuculline was accelerated by oxytocin whose action was blocked by the oxytocin antagonist atosiban. Fictive locomotion appeared when subthreshold concentrations of NMDA plus 5HT were coapplied with oxytocin, an effect prevented after 24 h incubation with the inhibitor of 5HT synthesis, PCPA. When fictive locomotion was fully manifested, oxytocin did not change periodicity, although cycle amplitude became smaller. A novel protocol of electrical stimulation based on noisy waveforms and applied to one dorsal root evoked stereotypic fictive locomotion. Whenever the stimulus intensity was subthreshold, low doses of oxytocin triggered fictive locomotion although oxytocin per se did not affect primary afferent depolarization evoked by dorsal root pulses. Among the several functional targets for the action of oxytocin at lumbar spinal cord level, the present results highlight how small concentrations of this peptide could bring spinal networks to threshold for fictive locomotion in combination with other protocols, and delineate the use of oxytocin to strengthen the efficiency of electrical stimulation to activate locomotor circuits. PMID:24658101

Dose, Francesco; Zanon, Patrizia; Coslovich, Tamara; Taccola, Giuliano

2014-01-01

114

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

115

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

116

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

117

Electric-propulsion activities in Europe  

Microsoft Academic Search

Electric-propulsion systems developed or under development in the USA, Europe, Japan, and Russia are reviewed, including those involving electrostatic, electrothermal, and electromagnetic propulsion. The paper describes the principles of operation of each of these types of thrusters and examines the technology applied in developing particular applications. Nonpropulsive applications of the information gained in the course of research and development of

C. Bartoli; G. Saccoccia

1992-01-01

118

Electric utility solar energy activities: 1979survey  

Microsoft Academic Search

The results of surveys to determine the scope of solar energy projects sponsored by electric utilities in the United States are presented. It contains brief descriptions of 735 projects being conducted by 180 utility companies. Also included are an index of projects by category, a statistical summary, a list of participating utilities with information contacts and addresses, a list of

R. Furness

1979-01-01

119

Electric utility solar energy activities: 1983 survey  

Microsoft Academic Search

This report presents the results of a survey to determine the scope of electric utility participation in solar energy projects in the United States. This ninth edition contains brief descriptions of 870 projects conducted by 184 utility companies. The report also includes an index of projects by category, a statistical summary, a list of new reports on utility-sponsored projects, a

1984-01-01

120

Electric utility solar energy activities: 1979 survey  

Microsoft Academic Search

The results of a survey to determine the scope of solar energy projects sponsored by electric utilities in the United States are presented. It contains brief descriptions of 735 projects being conducted by 180 utility companies. Also included are an index of projects by category, a statistical summary, a list of participating utilities with information contacts and addresses, a list

Furness

1979-01-01

121

Lighting and Electrical Plan Class Activity  

NSDL National Science Digital Library

This class exercise asks students to complete a lighting and electrical plan for a building in the most energy efficient approach possible. They will be given a floor plan to work with, and will then determine which outlets, types of lighting and switches to use. This document may be downloaded in Microsoft Word Doc file format.

Wolf, Arlynne

2011-12-06

122

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

123

Propeller tone bursts  

Microsoft Academic Search

Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts

G. P. Succi; D. H. Munro; K. U. Ingard

1983-01-01

124

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

125

Electrical and Computer Engineering -Graduate Post Graduate Activities Detail & History  

E-print Network

2010 Electrical and Computer Engineering - Graduate Post Graduate Activities Detail & History Google Software Engineer New York City NY MENG Intel Analog Engineer Sacramento CA MENG Intel Component Design Engineer Santa Clara CA MENG Intel Research Engineer Phoenix AZ www

Lipson, Michal

126

Electrical and Computer Engineering -Graduate Post Graduate Activities Detail & History  

E-print Network

2008 Electrical and Computer Engineering - Graduate Post Graduate Activities Detail & History Concepts, Inc. Software Test Engineer Baltimore MD MENG Intel Corporation Component Design Engineer San Francisco CA MENG Intel Corporation Intel Rotational Engineer Portland OR MENG Jacobs Engineering Group

Lipson, Michal

127

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

128

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

129

Influence of pulsed electric field on various enzyme activities  

Microsoft Academic Search

Effects of high-voltage pulsed electric field (PEF) on native or thermal denatured enzyme activities were studied. When PEF was applied to various native enzymes, 105–120% of initial enzyme activities were observed after PEF treatment. It was suggested that an activation of enzyme would be possible by PEF treatment. We attempted a refolding of thermal denatured enzyme by using PEF. When

Takayuki Ohshima; Tsuruki Tamura; Masayuki Sato

2007-01-01

130

Computer analysis of mechanical and electrical uterine activity  

Microsoft Academic Search

To facilitate the study of myometrial activity two algorithms were developed for continuous analysis of both electrical and\\u000a mechanical (intrauterine pressure) activity. A combination of maxima- and level detection was used to define cycles in the\\u000a intrauterine pressure signal, in which frequency, period time, area of the cycle, amplitude, overall- and maximum rate of\\u000a rise were calculated. The electrical signal

J. Ramondt; C. van Kooten; A. Verhoeff; H. C. S. Wallenburg

1986-01-01

131

Heterogeneity in the properties of burst-forming units of erythroid lineage in sickle cell anemia: DNA synthesis and burst-promoting activity production is related to peripheral hemoglobin F levels  

SciTech Connect

Circulating 14-day erythroid progenitors (BFU-E) from 28 sickle cell anemia (SS) patients with hemoglobin F (HbF) levels ranging from 2% to 16% were studied to determine their sensitivity to ({sup 3}H) thymidine kill and burst-promoting activity (BPA)-like factor production. We find that the proportion of BFU-E sensitive to 3H-dT kill, and hence active in DNA synthesis, was inversely correlated with the percent of peripheral HbF when light density (LD) mononuclear cells were used for plating. Regression analysis showed that the correlation between HbF level and BFU-E kill was highly significant (r = .88; P less than .00003). We confirmed the BPA-like factor(s) production by LD mononuclear cells of SS patients, and found, in addition, that this phenomenon is restricted to the population of SS patients with HbF levels lower than 9%. Circulating BFU-E of patients with high HbF levels are not sensitive to 3H-dT, and their mononuclear cells do not release BPA-like factor. In summary, SS patients exhibit differences in the capacity of their mononuclear cells to produce BPA activity according to their peripheral HbF level, as well as to the DNA synthesis-state of their circulating BFU-E. We conclude that erythroid progenitors differ among SS patients in relation to their peripheral HbF level.

Croizat, H.; Billett, H.H.; Nagel, R.L. (Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, NY (USA))

1990-02-15

132

Overview on NASA's Advanced Electric Propulsion Concepts Activities  

NASA Technical Reports Server (NTRS)

Advanced electric propulsion research activities are currently underway that seek to addresses feasibility issues of a wide range of advanced concepts, and may result in the development of technologies that will enable exciting new missions within our solar system and beyond. Each research activity is described in terms of the present focus and potential future applications. Topics include micro-electric thrusters, electrodynamic tethers, high power plasma thrusters and related applications in materials processing, variable specific impulse plasma thrusters, pulsed inductive thrusters, computational techniques for thruster modeling, and advanced electric propulsion missions and systems studies.

Frisbee, Robert H.

1999-01-01

133

A repertoire of rhythmic bursting produced by hypoglossal motoneurons in physiological and pathological conditions  

PubMed Central

The brainstem nucleus hypoglossus contains motoneurons that provide the exclusive motor nerve supply to the tongue. In addition to voluntary tongue movements, tongue muscles rhythmically contract during a wide range of physiological activities, such as respiration, swallowing, chewing and sucking. Hypoglossal motoneurons are destroyed early in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease often associated with a deficit in the transport system of the neurotransmitter glutamate. The present study shows how periodic electrical discharges of motoneurons are mainly produced by a neuronal network that drives them into bursting mode via glutamatergic excitatory synapses. Burst activity is, however, modulated by the intrinsic properties of motoneurons that collectively synchronize their discharges via gap junctions to create ‘group bursters’. When glial uptake of glutamate is blocked, a distinct form of pathological bursting spontaneously emerges and leads to motoneuron death. Conversely, H2O2-induced oxidative stress strongly increases motoneuron excitability without eliciting bursting. Riluzole (the only drug currently licensed for the treatment of ALS) suppresses bursting of hypoglossal motoneurons caused by blockage of glutamate uptake and limits motoneuron death. These findings highlight how different patterns of electrical oscillations of brainstem motoneurons underpin not only certain physiological activities, but also motoneuron death induced by glutamate transporter impairment. PMID:19651651

Cifra, Alessandra; Nani, Francesca; Sharifullina, Elina; Nistri, Andrea

2009-01-01

134

Analysis of the effects of modulatory agents on a modeled bursting neuron: Dynamic interactions between voltage and calcium dependent systems  

Microsoft Academic Search

In a computational model of the bursting neuron R15, we have implemented proposed mechanisms for the modulation of two ionic currents (IR andISI) that play key roles in regulating its spontaneous electrical activity. The model was sufficient to simulate a wide range of endogenous activity in the presence of various concentrations of serotonin (5-HT) or dopamine (DA). The model was

C. C. Canavier; D. A. Baxter; J. H. Byrne

1995-01-01

135

Nanoparticles Induce Changes of the Electrical Activity of Neuronal Networks on Microelectrode Array Neurochips  

PubMed Central

Background Nanomaterials are extensively used in industry and daily life, but little is known about possible health effects. An intensified research regarding toxicity of nanomaterials is urgently needed. Several studies have demonstrated that nanoparticles (NPs; diameter < 100 nm) can be transported to the central nervous system; however, interference of NPs with the electrical activity of neurons has not yet been shown. Objectives/methods We investigated the acute electrophysiological effects of carbon black (CB), hematite (Fe2O3), and titanium dioxide (TiO2) NPs in primary murine cortical networks on microelectrode array (MEA) neurochips. Uptake of NPs was studied by transmission electron microscopy (TEM), and intracellular formation of reactive oxygen species (ROS) was studied by flow cytometry. Results The multiparametric assessment of electrical activity changes caused by the NPs revealed an NP-specific and concentration-dependent inhibition of the firing patterns. The number of action potentials and the frequency of their patterns (spike and burst rates) showed a significant particle-dependent decrease and significant differences in potency. Further, we detected the uptake of CB, Fe2O3, and TiO2 into glial cells and neurons by TEM. Additionally, 24 hr exposure to TiO2 NPs caused intracellular formation of ROS in neuronal and glial cells, whereas exposure to CB and Fe2O3 NPs up to a concentration of 10 ?g/cm2 did not induce significant changes in free radical levels. Conclusion NPs at low particle concentrations are able to exhibit a neurotoxic effect by disturbing the electrical activity of neuronal networks, but the underlying mechanisms depend on the particle type. PMID:20457553

Gramowski, Alexandra; Flossdorf, Juliane; Bhattacharya, Kunal; Jonas, Ludwig; Lantow, Margareta; Rahman, Qamar; Schiffmann, Dietmar; Weiss, Dieter G.; Dopp, Elke

2010-01-01

136

Mechanism of vanadate-induced activation of tyrosine phosphorylation and of the respiratory burst in HL60 cells. Role of reduced oxygen metabolites.  

PubMed Central

Vanadate induces phosphotyrosine accumulation and activates O2 consumption in permeabilized differentiated HL60 cells. NADPH, the substrate of the respiratory burst oxidase, was found to be necessary not only for the increased O2 consumption, but also for tyrosine phosphorylation. The effect of NADPH was not due to reduction of vanadate to vanadyl. Instead, NADPH was required for the synthesis of superoxide, which triggered the formation of peroxovanadyl [V(4+)-OO] and vanadyl hydroperoxide [V(4+)-OOH]. One or both of these species, rather than vanadate itself, appears to be responsible for phosphotyrosine accumulation and activation of the respiratory burst. Accordingly, the stimulatory effects of vanadate and NADPH were abrogated by superoxide dismutase. Moreover, phosphorylation was activated in the absence of NADPH by treatment with V(4+)-OO and/or V(4+)-OOH, generated by treatment of orthovanadate with KO2 or H2O2 respectively. The main source of the superoxide involved in the formation of V(4+)-OO and V(4+)-OOH is the NADPH oxidase. This was shown by the inhibitory effects of diphenylene iodonium and by the failure of undifferentiated cells, which lack oxidase activity, to undergo tyrosine phosphorylation when treated with vanadate and NADPH. By contrast, exogenously generated V(4+)-OO induced marked phosphorylation in the undifferentiated cells, demonstrating the presence of the appropriate tyrosine kinases and phosphatases. A good correlation was found to exist between induction of tyrosine phosphorylation and activation of the respiratory burst, suggesting a causal relationship. Therefore an amplification cycle appears to exist in cells treated with vanadate, whereby trace amounts of superoxide initiate the formation of V(4+)-OO and/or V(4+)-OOH. These peroxides promote phosphotyrosine formation, most likely by inhibition of tyrosine phosphatases. Accumulation of critical tyrosine-phosphorylated proteins then initiates a respiratory burst, with abundant production of superoxide. The newly formed superoxide catalyses the formation of additional V(4+)-OO and/or V(4+)-OOH, thereby magnifying the response. Since vanadium derivatives are ubiquitous in animal tissues, V(4+)-OO and/or V(4+)-OOH could be formed in vivo by reduced O2 metabolites, becoming potential endogenous tyrosine phosphatase inhibitors. Because of their potency, peroxides of vanadate may be useful as probes for the study of protein phosphotyrosine turnover. Images Fig. 1. Fig. 2. Fig. 3. Fig. 5. PMID:1712198

Trudel, S; Paquet, M R; Grinstein, S

1991-01-01

137

Modeling active electrolocation in weakly electric fish  

E-print Network

In this paper, we provide a mathematical model for the electrolocation in weakly electric fishes. We first investigate the forward complex conductivity problem and derive the approximate boundary conditions on the skin of the fish. Then we provide a dipole approximation for small targets away from the fish. Based on this approximation, we obtain a non-iterative location search algorithm using multi-frequency measurements. We present numerical experiments to illustrate the performance and the stability of the proposed multi-frequency location search algorithm. Finally, in the case of disk- and ellipse-shaped targets, we provide a method to reconstruct separately the conductivity, the permittivity, and the size of the targets from multi-frequency measurements.

Habib Ammari; Thomas Boulier; Josselin Garnier

2012-03-05

138

Electrically active magnetic excitations in antiferromagnets (Review Article)  

NASA Astrophysics Data System (ADS)

Operating magnetic resonance by an electric field is a highly nontrivial concept, but is the most demanding function in the future of spin-electronics. Recent observations in a variety of multiferroic materials, named `collective electrically active magnetic excitations' and frequently referred to as "electromagnons," reveal a possibility of implementing such a function. Experimental advances in terahertz spectroscopy of electromagnons in multiferroics, as well as related theoretical models, are reviewed. Earlier theoretical works, where the existence of electric-dipole-active magnetic excitations in antiferro- and ferrimagnets with collinear spin structure has been predicted, are also discussed. Multi-sublattice magnets with electrically active magnetic excitations at room temperature provide a direct opportunity to transform one type of excitation into another in a terahertz time-domain. This is of crucial importance for magnon-based spintronics, since only short-wavelength exchange magnons allow signal processing at nanoscale distances.

Krivoruchko, V. N.

2012-09-01

139

Ouabain modulation of snail Br neuron bursting activity after the exposure to 10 mT static magnetic field revealed by Higuchi fractal dimension.  

PubMed

Aim of this study was to investigate the application of normalized mean of the empirical Higuchi fractal dimension (FD) distributions, as a new approach to analyze the spontaneous bioelectrical activity of garden snail (Helix pomatia) Br neuron. The effect of ouabain on modulation of Br neuron bursting activity before and after the exposure to 10 mT static magnetic field (SMF) was observed by analyzing the following parameters: action potential (AP), interspike interval (ISI) and interbursting interval (IBI) components. Normalized mean of the empirical FD distributions were formed for the following experimental conditions: Control 1, Ouabain 1, Control 2, SMF 2, ASMF 2, Control 3, SMF 3 and Ouabain ASMF 3. Our main results have shown that ouabain without SMF induced increase in participation of AP and a decrease in participation of IBI components compared to the first control condition. However, in the presence of 10 mT SMF, ouabain-induced changes of measured parameters of Br neuron activity were less pronounced compared to the third control condition. We have shown that normalized mean of the empirical FD distributions is a useful method for detecting the changes in AP, ISI, and IBI components of complex bursting activity in altered physiological states. PMID:24968407

Kesi?, Srdjan; Nikoli?, Ljiljana; Savi?, Aleksandar G; Petkovi?, Branka; Spasi?, Sladjana Z

2014-01-01

140

Involvement of Na+/K+ pump in fine modulation of bursting activity of the snail Br neuron by 10 mT static magnetic field.  

PubMed

The spontaneously active Br neuron from the brain-subesophageal ganglion complex of the garden snail Helix pomatia rhythmically generates regular bursts of action potentials with quiescent intervals accompanied by slow oscillations of membrane potential. We examined the involvement of the Na(+)/K(+) pump in modulating its bursting activity by applying a static magnetic field. Whole snail brains and Br neuron were exposed to the 10-mT static magnetic field for 15 min. Biochemical data showed that Na(+)/K(+)-ATPase activity increased almost twofold after exposure of snail brains to the static magnetic field. Similarly, (31)P NMR data revealed a trend of increasing ATP consumption and increase in intracellular pH mediated by the Na(+)/H(+) exchanger in snail brains exposed to the static magnetic field. Importantly, current clamp recordings from the Br neuron confirmed the increase in activity of the Na(+)/K(+) pump after exposure to the static magnetic field, as the magnitude of ouabain's effect measured on the membrane resting potential, action potential, and interspike interval duration was higher in neurons exposed to the magnetic field. Metabolic pathways through which the magnetic field influenced the Na(+)/K(+) pump could involve phosphorylation and dephosphorylation, as blocking these processes abolished the effect of the static magnetic field. PMID:22534773

Nikoli?, Ljiljana; Todorovi?, Nataša; Zakrzewska, Joanna; Stani?, Marina; Rauš, Snežana; Kalauzi, Aleksandar; Jana?, Branka

2012-07-01

141

The effect of ex vivo refrigerated storage and cell preservation solution (Cyto-Chex II) on CD11b expression and oxidative burst activity of dog neutrophils.  

PubMed

The expression of CD11b and oxidative burst activity of dog neutrophils undergoing ex vivo refrigerated storage was studied using flow-cytometry . Additionally, the effect of a proprietary cell stabilization reagent (Cyto-Chex) on the expression of CD11b and oxidative burst activity was studied. Expression of CD11b was very high (>90% positive) on dog neutr ophils isolated from peripheral blood. Dog neutrophils showed a rapid and sustained increase in CD11b antigen density (P<0.01) during refrigerated storage, this increase was prevented by treatment with Cyto-Chex but was not completely blocked on the first day. There were no significant differences in mean antigen density between any days in the non-preserved group or between Days 1 to 4 in the Cyto-Chex treated group. The non-treated group showed significantly greater mean antigen density at all time points when compared to the preservative treated group (P<0.0001). Treatment with Cyto-Chex did not interfere with measurement of oxidative burst function on the first 2 days. Alterations of both resting oxidative activity and stimulated response were observed over time in both treated and untreated blood samples. Cyto-Chex treated samples showed a dramatic, significant decline in stimulated response after the third day of storage (P<0.001), while non-treated cells showed steadily increasing, but non-significant differences in stimulated response. Cyto-Chex was demonstrated to be a useful reagent for stabilization of dog neutrophil membrane antigens during storage, however this reagent is not recommended for preservation of cells for functional assays. PMID:10760390

Ruaux, C G; Williams, D A

2000-04-19

142

Dendritic Ca2 -Activated K Conductances Regulate Electrical  

E-print Network

Dendritic Ca2 -Activated K Conductances Regulate Electrical Signal Propagation in an Invertebrate the intracellular concentration of free Ca2 was reduced by a high-affinity Ca2 buffer. Ca2 released in the neurite signal propagation. Key words: calcium; dendrite; calcium-activated potassium conductance

Wessel, Ralf

143

A Burst of Electromagnetic Radiation from a Collapsing Magnetized Star  

E-print Network

The pattern of variations in the intensity of magnetodipole losses is studied with the relativistic effect of magnetic-field dissipation during collapse into a black hole taken into account. A burst-type solution can be obtained both for a direct collapse and for the formation of a rapidly-rotating, self-gravitating object - a spinar - using a simple model. Analytical dependences on radius describing an electromagnetic burst are derived. The time dependence of the burst shape for an infinitely distant observer and the maximum energy of relativistic particles accelerated by an electric field are numerically calculated. The objects under consideration are of particular interest because particles in their vicinity can be accelerated up to the Planck energies. Possible astrophysical applications to the theory of active galactic nuclei (AGNs) and QSOs are briefly discussed. It is shown for the first time that a spinar can be produced by a merger of neutron stars; this possibility is considered in and without connection with the formation of gamma-ray bursts.

Galina V. Lipunova

1997-03-01

144

NMDA receptor activation strengthens weak electrical coupling in mammalian brain.  

PubMed

Electrical synapses are formed by gap junctions and permit electrical coupling, which shapes the synchrony of neuronal ensembles. Here, we provide a direct demonstration of receptor-mediated strengthening of electrical coupling in mammalian brain. Electrical coupling in the inferior olive of rats was strengthened by activation of NMDA-type glutamate receptors (NMDARs), which were found at synaptic loci and at extrasynaptic loci 20-100 nm proximal to gap junctions. Electrical coupling was strengthened by pharmacological and synaptic activation of NMDARs, whereas costimulation of ionotropic non-NMDAR glutamate receptors transiently antagonized the effect of NMDAR activation. NMDAR-dependent strengthening (1) occurred despite increased input conductance, (2) induced Ca(2+)-influx microdomains near dendritic spines, (3) required activation of the Ca(2+)/calmodulin-dependent protein-kinase II, (4) was restricted to neurons that were weakly coupled, and (5) thus strengthened coupling, mainly between nonadjacent neurons. This provided a mechanism to expand the synchronization of rhythmic membrane potential oscillations by chemical neurotransmitter input. PMID:24656255

Turecek, Josef; Yuen, Genevieve S; Han, Victor Z; Zeng, Xiao-Hui; Bayer, K Ulrich; Welsh, John P

2014-03-19

145

ANL's electric vehicle battery activities for USABC  

NASA Astrophysics Data System (ADS)

The Electrochemical Technology Program at Argonne National Laboratory (ANL) provides advanced battery R&D technology transfer to industry; technical analyses, assessments, modeling, and databases; and independent testing and post-test analyses of advanced batteries. These capabilities and services are being offered to the US Advanced Battery Consortium (USABC) and Cooperative Research and Development Agreements (CRADA) are being negotiated for USABC-sponsored work at ANL. A small portion of DOE's cost share for USABC projects has been provided to ANL to continue R&D and testing activities on key technologies that were previously supported directly by DOE. This report summarizes progress on these USABC projects during the period of April 1 through September 30, 1992. In this report, the objective, background, technical progress, and status are described for each task. The work is organized into the following task areas: 1.0 Lithium/Sulfide Batteries; 2.0 Nickel/Metal Hydride Support 3.0 EV Battery Performance; and Life Evaluation.

146

Multiple Bifurcations in a Polynomial Model of Bursting Oscillations  

NASA Astrophysics Data System (ADS)

Bursting oscillations are commonly seen to be the primary mode of electrical behaviour in a variety of nerve and endocrine cells, and have also been observed in some biochemical and chemical systems. There are many models of bursting. This paper addresses the issue of being able to predict the type of bursting oscillation that can be produced by a model. A simplified model capable of exhibiting a wide variety of bursting oscillations is examined. By considering the codimension-2 bifurcations associated with Hopf, homoclinic, and saddle-node of periodics bifurcations, a bifurcation map in two-dimensional parameter space is created. Each region on the map is characterized by a qualitatively distinct bifurcation diagram and, hence, represents one type of bursting oscillation. The map elucidates the relationship between the various types of bursting oscillations. In addition, the map provides a different and broader view of the current classification scheme of bursting oscillations.

de Vries, G.

1998-06-01

147

Electrically rechargeable anionically active reduction-oxidation electrical storage-supply system  

SciTech Connect

An electrically rechargeable anionically active reduction-oxidation electric storage-supply system and process is disclosed using a sodium or potassium sulfidepolysulfide anolyte reaction and an iodide-polyiodide, chloride-chlorine or bromide-bromine species catholyte reaction. The catholyte and anolyte are separated by an ion selective membrane permeable to positive sodium and potassium ions and substantially impermeable to negative bromide, chloride, iodide, sulfide and polysulfide ions. A flowing electrolyte system is disclosed with external electrolyte storage vessels. The apparatus and process provide an electrically rechargeable anionically active reduction-oxidation system in which the electrolytes may be maintained at near neutral or slightly basic pH, with virtually no parasitic side reactions upon charging, such as hydrogen or oxygen evolution, and the disclosed storage and supply system provides higher energy densities than referenced prior art systems.

Remick, R.J.; Ang, P.G.P.

1984-11-27

148

Electrical and Computer Engineering -Graduate Post Graduate Activities Detail & History  

E-print Network

2009 Electrical and Computer Engineering - Graduate Post Graduate Activities Detail & History TAIWAN MENG Garmin Software Engineer Taipei TAIWAN MENG Intel Design Engineer Hudson MA MENG Intel PhD EMC Sr. Hardware Engineer Hopkinton MA PhD Intel Test Engineer Hillsboro MA PhD Marconi Institute

Lipson, Michal

149

Electrical and Computer Engineering -Graduate Post Graduate Activities Detail & History  

E-print Network

2011 Electrical and Computer Engineering - Graduate Post Graduate Activities Detail & History Application Engineer Essex Junction VT MENG IBM Staff Engineer Essex Junction VT MENG Intel Corporation Analog-career@cornell.edu 2011 Employment Employer Title City State/Country MENG Intel Corporation Component Hardware Design

Lipson, Michal

150

Analysing the dynamics of pulseless electrical activity during cardiopulmonary resuscitation  

Microsoft Academic Search

Possible clinical states of a cardiac arrest patient are ventricular fibrillation\\/tachycardia (VF\\/VT), asystole (ASY) or pulseless electrical activity (PEA), and the treatment goals are return of spontaneous circulation (ROSC) and neurologic ally intact survival. Waveform analysis has been used in VF to predict treatment outcomes and we hypothesised that similar analysis in PEA could predict transformation to ROSC. We analysed

I. Dragsund; K. Gundersen; M. Risdal; J. Kramer-Johansen; B. Abella; D. Edelson; F. Sterz; T. Eftestol

2006-01-01

151

Toward a Multiscale Model of the Uterine Electrical Activity  

Microsoft Academic Search

A comprehensive multiscale model of the uterine mus- cle electrical activity would permit understanding the important link between the genesis and evolution of the action potential at the cell level and the process leading to labor. Understanding this link can open the way to more effective tools for the prediction of labor and prevention of preterm delivery. A first step

Jeremy Laforet; Chiara Rabotti; Jeremy Terrien; Massimo Mischi; Catherine Marque

2011-01-01

152

Biometrics from Brain Electrical Activity: A Machine Learning Approach  

Microsoft Academic Search

The potential of brain electrical activity generated as a response to a visual stimulus is examined in the context of the identification of individuals. Specifically, a framework for the Visual Evoked Potential (VEP)-based biometrics is established, whereby energy features of the gamma band within VEP signals were of particular interest. A rigorous analysis is conducted which unifies and extends results

Ramaswamy Palaniappan; Danilo P. Mandic

2007-01-01

153

Biomems Microprobe for Electrical Activity Recording of Living Cells  

Microsoft Academic Search

An implantable probe fabricated on a silicon substrate for electrical activity monitoring of living tissues was developed and fabricated. In order to improve the mechanical resistance and biocompatibility of the device, the technology of thermionic vacuum arc (IVA) deposition was used for coating the implantable parts with diamond like carbon (DLC) with zero stress (OSC), at the end of silicon

C. Moldovan; R. Iosub; C. P. Lungu; A. M. Lungu; B. Firtat; C. Roman; R. Albulescu

2007-01-01

154

Capturing Users' Buying Activity at Akihabara Electric Town from Twitter  

Microsoft Academic Search

\\u000a The goal of this paper is to describe a method to automatically capture users’ buying activity at Akihabara electric town\\u000a in each sentence retrieved from twitter. Sentences retrieved from twitter are often diversified, complex, syntactically wrong,\\u000a have emoticons and new words. There are some works that have tried to extract users’ activities in sentences retrieved from\\u000a weblogs and twitter. However,

Takahiro Kawamura; Yasuyuki Tahara; Akihiko Ohsuga

2010-01-01

155

Unihemispheric Burst Suppression  

PubMed Central

Burst suppression (BS) consists of bursts of high-voltage slow and sharp wave activity alternating with periods of background suppression in the electroencephalogram (EEG). When induced by deep anesthesia or encephalopathy, BS is bihemispheric and is often viewed as a non-epileptic phenomenon. In contrast, unihemispheric BS is rare and its clinical significance is poorly understood. We describe here two cases of unihemispheric BS. The first patient is a 56-year-old woman with a left temporoparietal tumor who presented in convulsive status epilepticus. EEG showed left hemispheric BS after clinical seizure termination with lorazepam and propofol. The second patient is a 39-year-old woman with multiple medical problems and a vague history of seizures. After abdominal surgery, she experienced a convulsive seizure prompting treatment with propofol. Her EEG also showed left hemispheric BS. In both cases, increasing the propofol infusion rate resulted in disappearance of unihemispheric BS and clinical improvement. The prevailing view that typical bihemispheric BS is non-epileptic should not be extrapolated automatically to unihemispheric BS. The fact that unihemispheric BS was associated with clinical seizure and resolved with propofol suggests that, in both cases, an epileptic mechanism was responsible for unihemispheric BS. PMID:25309713

Villemarette-Pittman, Nicole R.; Rogers, Cornel T.; Torres-Delgado, Frank; Olejniczak, Piotr W.; England, John D.

2014-01-01

156

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

157

Burst-by-burst laser frequency monitor  

NASA Astrophysics Data System (ADS)

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

1993-02-01

158

Burst-by-burst laser frequency monitor  

NASA Astrophysics Data System (ADS)

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

1994-09-01

159

Multiple Bifurcations in a Polynomial Model of Bursting Oscillations  

Microsoft Academic Search

Summary.    Bursting oscillations are commonly seen to be the primary mode of electrical behaviour in a variety of nerve and endocrine\\u000a cells, and have also been observed in some biochemical and chemical systems. There are many models of bursting. This paper\\u000a addresses the issue of being able to predict the type of bursting oscillation that can be produced by

G. de Vries

1998-01-01

160

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. PMID:14587606

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

2008-01-01

161

Bacterial inhibition by electrical activation of percutaneous silver implants.  

PubMed

Percutaneous silver wire implants were looped through the dorsal skin of rats and inoculated with Staphylococcus aureus to test the effect on bacteria in the tract. The silver was activated with four brief daily applications of anodic microcurrent. Contralateral 316L stainless steel implants, identically inoculated, served as controls. Cultures from the silver tracts showed a marked reduction or elimination of bacteria, which persisted for the 3-week study period. In tracts with colonization established for 1 week, subsequent electrical activation of the silver also suppressed the bacteria. Inflammatory reactions at 3 weeks were mild at both the silver and stainless implants and no giant cells or toxicity were seen. This suggests that electrically activated silver may be useful in preventing or treating infection at percutaneous devices. PMID:3711134

Spadaro, J A; Chase, S E; Webster, D A

1986-01-01

162

Subthalamic Nucleus Electrical Stimulation Modulates Calcium Activity of Nigral Astrocytes  

PubMed Central

Background The substantia nigra pars reticulata (SNr) is a major output nucleus of the basal ganglia, delivering inhibitory efferents to the relay nuclei of the thalamus. Pathological hyperactivity of SNr neurons is known to be responsible for some motor disorders e.g. in Parkinson's disease. One way to restore this pathological activity is to electrically stimulate one of the SNr input, the excitatory subthalamic nucleus (STN), which has emerged as an effective treatment for parkinsonian patients. The neuronal network and signal processing of the basal ganglia are well known but, paradoxically, the role of astrocytes in the regulation of SNr activity has never been studied. Principal Findings In this work, we developed a rat brain slice model to study the influence of spontaneous and induced excitability of afferent nuclei on SNr astrocytes calcium activity. Astrocytes represent the main cellular population in the SNr and display spontaneous calcium activities in basal conditions. Half of this activity is autonomous (i.e. independent of synaptic activity) while the other half is dependent on spontaneous glutamate and GABA release, probably controlled by the pace-maker activity of the pallido-nigral and subthalamo-nigral loops. Modification of the activity of the loops by STN electrical stimulation disrupted this astrocytic calcium excitability through an increase of glutamate and GABA releases. Astrocytic AMPA, mGlu and GABAA receptors were involved in this effect. Significance Astrocytes are now viewed as active components of neural networks but their role depends on the brain structure concerned. In the SNr, evoked activity prevails and autonomous calcium activity is lower than in the cortex or hippocampus. Our data therefore reflect a specific role of SNr astrocytes in sensing the STN-GPe-SNr loops activity and suggest that SNr astrocytes could potentially feedback on SNr neuronal activity. These findings have major implications given the position of SNr in the basal ganglia network. PMID:22848608

Barat, Elodie; Boisseau, Sylvie; Bouyssieres, Celine; Appaix, Florence; Savasta, Marc; Albrieux, Mireille

2012-01-01

163

Intracellular shunting of O{sub 2}{sup ?} contributes to charge compensation and preservation of neutrophil respiratory burst in the absence of voltage-gated proton channel activity  

SciTech Connect

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 Zn{sup 2+}, we found that the PMA-induced respiratory burst of human neutrophils is inhibited when assessed as extracellular production of O{sub 2}{sup ?} and H{sub 2}O{sub 2}, in accordance with literature studies, but, surprisingly, unaffected when measured as oxygen consumption or total (extracellular plus intracellular) H{sub 2}O{sub 2} production. Furthermore, we show that inhibiting Hv1 with Zn{sup 2+} 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 H{sub 2}O{sub 2}. 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 O{sub 2}{sup ?} generated within gp91{sup phox} 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. Highlights: • Neutrophils’ respiratory burst is not inhibited by the H{sup +} channel inhibitor Zn{sup 2+}. • Intracellular production of O{sub 2}{sup ?} and H{sub 2}O{sub 2} is increased in the presence of Zn{sup 2+}. • Intracellular H{sub 2}O{sub 2} production is increased in H{sup +} channels knock-down cells. • Zn{sup 2+} increases the rate but not the extent of depolarization and pH{sub i} decrease. • Intracellular shunting of O{sub 2}{sup ?} contributes to charge compensation in neutrophils.

Decleva, Eva [Department of Life Sciences, University of Trieste, Trieste (Italy); Menegazzi, Renzo, E-mail: menegazz@units.it [Department of Life Sciences, University of Trieste, Trieste (Italy); Fasolo, Alba [Department of Life Sciences, University of Trieste, Trieste (Italy); Defendi, Federica [Université Joseph Fourier, GREPI/AGIM CNRS FRE 3405, Grenoble (France); Sebastianutto, Michele; Dri, Pietro [Department of Life Sciences, University of Trieste, Trieste (Italy)

2013-07-15

164

Todd, Faraday, and the electrical basis of brain activity.  

PubMed

Robert Bentley Todd (1809-60) was the UK's first eminent neurologist and neuroscientist. An anatomist, physiologist, and clinical scientist with an interest in the nervous system, he was the first to confirm the electrical basis of brain activity in the 1840s. He was influenced by his contemporary, Michael Faraday at the Royal Institution, and by two colleagues at King's College, John Daniell and Charles Wheatstone, who were also working at the cutting edge of electrical science. Todd conceived of nervous polarity (force) generated in nervous centres and compared this with the polar force of voltaic electricity developed in the galvanic battery. He brilliantly foresaw each nerve vesicle (cell) and its related fibres (ie, neuron) as a distinct apparatus for the development and transmission of nervous polarity. Epilepsy was the result of periodic unnatural development of nervous force leading to the "disruptive discharge" described by Faraday. Faraday, who studied animal electricity in the Gymnotus (electric eel), and Todd saw nervous polarity as a higher form of interchangeable energy. PMID:15324724

Reynolds, Edward H

2004-09-01

165

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

166

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.

Wilcox, Russell B. (Oakland, CA)

1991-01-01

167

Propeller tone bursts  

NASA Technical Reports Server (NTRS)

Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts is a periodic flow oscillation on the suction surface of the propeller blade tips which may be due to the interaction between an oscillating shock wave and a laminar boundary layer.

Succi, G. P.; Munro, D. H.; Ingard, K. U.

1983-01-01

168

Propeller tone bursts  

NASA Astrophysics Data System (ADS)

Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts is a periodic flow oscillation on the suction surface of the propeller blade tips which may be due to the interaction between an oscillating shock wave and a laminar boundary layer.

Succi, G. P.; Munro, D. H.; Ingard, K. U.

1983-07-01

169

The GLAST Burst Monitor  

NASA Technical Reports Server (NTRS)

The GLAST Burst Monitor (GBM) comprises an array of NaI and BGO scintillation detectors designed to enhance the scientific return from GLAST in the study of gamma-ray bursts (GRBs). By observing in the 10 keV to 30 MeV energy range, GBM extends the spectral coverage of GRBs more than 3 decades below the LAT energy threshold. GBM computes burst locations on-board, allowing repointing of the GLAST Observatory to place strong bursts within the LAT field-of-view to observe delayed high-energy emission.

Meegan, Charles; Bhat, Narayana; Connaughton, Valerie; Briggs, Michael; Diehl, Roland; Fishman, Gerald; Greiner, Jochen; Kippen, R. Marc; vonKienlin, Andreas; Kouveliotou, Chryssa; Lichti, Giselher; Paciesas, William; Preece, Robert; Steinle, Helmut; Wilson-Hodge, Colleen

2007-01-01

170

Network Based Statistical Analysis Detects Changes Induced by Continuous Theta-Burst Stimulation on Brain Activity at Rest  

PubMed Central

We combined continuous theta-burst stimulation (cTBS) and resting state (RS)-fMRI approaches to investigate changes in functional connectivity (FC) induced by right dorsolateral prefrontal cortex (DLPFC)–cTBS at rest in a group of healthy subjects. Seed-based fMRI analysis revealed a specific pattern of correlation between the right prefrontal cortex and several brain regions: based on these results, we defined a 29-node network to assess changes in each network connection before and after, respectively, DLPFC–cTBS and sham sessions. A decrease of correlation between the right prefrontal cortex and right parietal cortex (Brodmann areas 46 and 40, respectively) was detected after cTBS, while no significant result was found when analyzing sham-session data. To our knowledge, this is the first study that demonstrates within-subject changes in FC induced by cTBS applied on prefrontal area. The possibility to induce selective changes in a specific region without interfering with functionally correlated area could have several implications for the study of functional properties of the brain, and for the emerging therapeutic strategies based on transcranial stimulation. PMID:25140158

Mastropasqua, Chiara; Bozzali, Marco; Ponzo, Viviana; Giulietti, Giovanni; Caltagirone, Carlo; Cercignani, Mara; Koch, Giacomo

2014-01-01

171

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. PMID:21876730

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

2011-01-01

172

Distribution of Electric Currents in Solar Active Regions  

NASA Astrophysics Data System (ADS)

There has been a long-standing debate on the question of whether or not electric currents in solar active regions are neutralized. That is, whether or not the main (or direct) coronal currents connecting the active region polarities are surrounded by shielding (or return) currents of equal total value and opposite direction. Both theory and observations are not yet fully conclusive regarding this question, and numerical simulations have, surprisingly, barely been used to address it. Here we quantify the evolution of electric currents during the formation of a bipolar active region by considering a three-dimensional magnetohydrodynamic simulation of the emergence of a sub-photospheric, current-neutralized magnetic flux rope into the solar atmosphere. We find that a strong deviation from current neutralization develops simultaneously with the onset of significant flux emergence into the corona, accompanied by the development of substantial magnetic shear along the active region's polarity inversion line. After the region has formed and flux emergence has ceased, the strong magnetic fields in the region's center are connected solely by direct currents, and the total direct current is several times larger than the total return current. These results suggest that active regions, the main sources of coronal mass ejections and flares, are born with substantial net currents, in agreement with recent observations. Furthermore, they support eruption models that employ pre-eruption magnetic fields containing such currents.

Török, T.; Leake, J. E.; Titov, V. S.; Archontis, V.; Miki?, Z.; Linton, M. G.; Dalmasse, K.; Aulanier, G.; Kliem, B.

2014-02-01

173

Burst synchronization transitions in a neuronal network of subnetworks  

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

174

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

175

Oligochitosan stimulated phagocytic activity of macrophages from blunt snout bream (Megalobrama amblycephala) associated with respiratory burst coupled with nitric oxide production.  

PubMed

The immunostimulating effects of oligochitosan have been proven in several fish, however, the mechanisms underlying the stimulation are not characterized. In the present study, the effects of oligochitosan were investigated using macrophages isolated from blunt snout bream (Megalobrama amblycephala). The results showed that the phagocytic activity of the macrophages was enhanced by the addition of oligochitosan in vitro and in vivo. The two of the most important antimicrobial pathways of macrophages, NADPH oxidase and iNOS pathways were included for further studies. The amounts of superoxide anion and the mRNAs of the five subunits of NADPH oxidase genes were significantly enhanced in the oligochitosan-treated macrophages and macrophages isolated from fish fed with feed containing oligochitosan. In addition, the NO production, iNOS activity and iNOS gene expression were all significantly increased in the presence of oligochitosan. Furthermore, the mRNA levels of the TNF-? and IL-1? were also significantly increased in the macrophages derived from fish fed with oligochitosan. In conclusion, the stimulation effects of oligochitosan on the phagocytic activity of the fish macrophages were associated with respiratory burst coupled with nitric oxide production. PMID:24968077

Liu, Lichun; Zhou, Yang; Zhao, Xiaoheng; Wang, Hong; Wang, Li; Yuan, Gailing; Asim, Muhammad; Wang, Weimin; Zeng, Lingbing; Liu, Xiaoling; Lin, Li

2014-11-01

176

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

177

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

178

A Nontriggered 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 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; vanParadijs, Jan; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.

2001-01-01

179

The Effects of Acute and Developmental Temperature on Burst Swimming Speed and Myofibrillar ATPase Activity in Tadpoles  

E-print Network

temperature ( ). Like swimming speed,P ! 0.001 enzyme activity was greater in the cool-reared tadpoles than ATPase Activity in Tadpoles of the Pacific Tree Frog, Hyla regilla Timothy B. Watkins* Department, and myofibrillar ATP- ase activity were assessed in tadpoles of the Pacific tree frog, Hyla regilla. Tadpoles from

Ahmad, Sajjad

180

Optimizing electrical activation of porcine oocytes by adjusting pre- and post-activation mannitol exposure times.  

PubMed

Modifying electrical activation conditions have been used to improve in vitro embryo production and development in pigs. However, there is insufficient information about correlations of porcine embryo development with oocyte pre- and post-activation conditions. The purpose of this study was to compare the developmental rates of porcine oocytes subjected to different mannitol exposure times, either pre- or post-electrical activation, and to elucidate the reason for the optimal mannitol exposure time. Mannitol exposure times around activation were adjusted as 0, 1, 2 or 3 min. Blastocyst development were checked on day 7. Exposure of oocytes to mannitol for 1 or 2 min before electrical activation produced significantly higher blastocyst rates than exposure for 0 or 3 min. There was no significant difference in blastocyst rates when activated oocytes were exposed to mannitol for 0, 1, 2 or 3 min after electrical activation. While exposure of oocytes to mannitol for 1 min pre- and 3 min post-activation showed significantly higher blastocyst development than 0 min pre- and 0 min post-activation. It also showed higher maintenance of normal oocyte morphology than exposure for 0 min pre- and 0 min post-activation. In conclusion, exposure of oocytes to mannitol for 1 min pre- and 3 min post-activation seems to be optimal for producing higher in vitro blastocyst development of porcine parthenogenetic embryos. The higher blastocyst development is correlated with higher maintenance of normal morphology in oocytes exposed to mannitol for 1 min pre- and 3 min post-activation. PMID:25256295

Kwon, D; Saadeldin, Im; Kim, Sj; Park, Sj; Kang, Jt; Park, Hj; Moon, Jh; Koo, Oj; Jang, G; Lee, Bc

2014-12-01

181

Optical Mapping of Electrical Activation in the Developing Heart  

NASA Astrophysics Data System (ADS)

Specialized conduction tissues mediate coordinated propagation of electrical activity through the adult vertebrate heart. Following activation of the atria, the activation wave is slowed down in the atrioventricular canal or node, after which it spreads rapidly into the left and right ventricles via the His-Purkinje system (HPS). This results in the ventricles being activated from the apex toward the base, which is a hallmark of HPS function. The development of mature HPS function follows significant phases of cardiac morphogenesis. Initially, the cardiac impulse propagates in a slow, linear, and isotropic fashion from the sinus venosus at the most caudal portion of the tubular heart. Although the speed of impulse propagation gradually increases as it travels toward the anterior regions of the heart tube, the actual sequence of ventricular activation in the looped heart proceeds in the same direction as blood flow. Eventually, the immature base-to-apex sequence of ventricular activation undergoes an apparent reversal, changing to the mature apex-to-base pattern. Using an optical mapping approach, we demonstrate that the timing of this last transition shows striking dependence on hemodynamic loading of the ventricle, being accelerated by pressure overload and delayed in left ventricular hypoplasia. Comparison of chick and mammalian hearts revealed some striking similarities as well as key differences in the timing of such events during cardiac organogenesis.

Sedmera, David; Reckova, Maria; Rosengarten, Carlin; Torres, Maria I.; Gourdie, Robert G.; Thompson, Robert P.

2005-06-01

182

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

183

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

184

Dislocation Electrical Activity in III-nitride Films  

NASA Astrophysics Data System (ADS)

The effect of dislocation type and MBE growth stoichiometry on the excess reverse bias gate leakage in GaN Schottky diodes will be discussed. By comparing high quality GaN films grown by MBE on either HVPE or MOCVD templates, we show definitive evidence that pure screw threading dislocations are the primary source of reverse bias gate leakage. This conclusion was reached by correlating the scanning current image taken at fixed reverse biases with simultaneously acquired topographic images, and by comparing the density of leakage spots to total dislocation density and distributions of different dislocation types obtained from cross sectional TEM measurements. While dislocation type is the primary factor in determining gate leakage, growth stoichiometry also has a large effect. The leakage current is 2 to 3 orders of magnitude higher for samples grown under Ga-rich conditions. TEM results indicate that excess Ga induced changes in dislocation core structure. This in terms causes the different electrical activity associated with screw/mixed dislocations in samples grown under different conditions. We will present arguments on how core structural differences between screw and edge dislocations in the template could lead to the drastically different electrical activity.

Hsu, Julia W. P.

2002-03-01

185

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

186

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

187

Herschel Far-Infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. PACS Observations  

E-print Network

Far-Infrared (FIR) photometry from the the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory is presented for 313 nearby, hard X-ray selected galaxies from the 58-month Swift Burst Alert Telescope (BAT) Active Galactic catalog. The present data do not distinguish between the FIR luminosity distributions at 70 and 160um for Seyfert 1 and Seyfert 2 galaxies. This result suggests that if the FIR emission is from the nuclear obscuring material surrounding the accretion disk, then it emits isotropically, independent of orientation. Alternatively, a significant fraction of the 70 and 160um could be from star formation, independent of AGN type. Using a non-parametric test for partial correlation with censored data, we find a statistically significant correlation between the AGN intrinsic power (in the 14-195 keV band ) and the FIR emission at 70 and 160um for Seyfert 1 galaxies. We find no correlation between the 14-195 keV and FIR luminosities in Seyfert 2 galaxies. The observed c...

Meléndez, M; Shimizu, T T; Barger, A J; Cowie, L L

2014-01-01

188

Probabilistic word pre-activation during language comprehension inferred from electrical brain activity  

E-print Network

words in a graded fashion to a degree that can be estimated from the probability that each word is given in a sentence (as cues to their world knowledge) to estimate relative likelihoods for upcoming words. DespiteProbabilistic word pre-activation during language comprehension inferred from electrical brain

Kutas, Marta

189

Monocular and binocular neuronal activity in human visual cortex revealed by electrical brain activity mapping  

Microsoft Academic Search

In the present study, we investigated topographical differences between monocularly and binocularly evoked potential fields related to the retinal location and spatial frequency of grating stimuli. Electrical brain activity was recorded in 18 healthy adults using an array of 21 electrodes over the occipital areas. Vertical black-and-white grating patterns of different spatial frequencies were presented with central fixation or lateralized

Wolfgang Skrandies

1993-01-01

190

Convolutional virtual electric field for image segmentation using active contours.  

PubMed

Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586

Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden

2014-01-01

191

Convolutional Virtual Electric Field for Image Segmentation Using Active Contours  

PubMed Central

Gradient vector flow (GVF) is an effective external force for active contours; however, it suffers from heavy computation load. The virtual electric field (VEF) model, which can be implemented in real time using fast Fourier transform (FFT), has been proposed later as a remedy for the GVF model. In this work, we present an extension of the VEF model, which is referred to as CONvolutional Virtual Electric Field, CONVEF for short. This proposed CONVEF model takes the VEF model as a convolution operation and employs a modified distance in the convolution kernel. The CONVEF model is also closely related to the vector field convolution (VFC) model. Compared with the GVF, VEF and VFC models, the CONVEF model possesses not only some desirable properties of these models, such as enlarged capture range, u-shape concavity convergence, subject contour convergence and initialization insensitivity, but also some other interesting properties such as G-shape concavity convergence, neighboring objects separation, and noise suppression and simultaneously weak edge preserving. Meanwhile, the CONVEF model can also be implemented in real-time by using FFT. Experimental results illustrate these advantages of the CONVEF model on both synthetic and natural images. PMID:25360586

Wang, Yuanquan; Zhu, Ce; Zhang, Jiawan; Jian, Yuden

2014-01-01

192

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

193

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. PMID:5639767

Keatinge, W. R.

1968-01-01

194

Herschel Far-infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. PACS Observations  

NASA Astrophysics Data System (ADS)

Far-Infrared (FIR) photometry from the Photodetector Array Camera and Spectrometer on the Herschel Space Observatory is presented for 313 nearby, hard X-ray selected galaxies from the 58 month Swift Burst Alert Telescope (BAT) Active Galactic Nuclei catalog. The present data do not distinguish between the FIR luminosity distributions at 70 and 160 ?m for Seyfert 1 and Seyfert 2 galaxies. This result suggests that if the FIR emission is from the nuclear obscuring material surrounding the accretion disk, then it emits isotropically, independent of orientation. Alternatively, a significant fraction of the 70 and 160 ?m luminosity could be from star formation, independent of active galactic nucleus (AGN) type. Using a non-parametric test for partial correlation with censored data, we find a statistically significant correlation between the AGN intrinsic power (in the 14-195 keV band) and the FIR emission at 70 and 160 ?m for Seyfert 1 galaxies. We find no correlation between the 14-195 keV and FIR luminosities in Seyfert 2 galaxies. The observed correlations suggest two possible scenarios: (1) if we assume that the FIR luminosity is a good tracer of star formation, then there is a connection between star formation and the AGN at sub-kiloparsec scales, or (2) dust heated by the AGN has a statistically significant contribution to the FIR emission. Using a Spearman rank-order analysis, the 14-195 keV luminosities for the Seyfert 1 and 2 galaxies are weakly statistically correlated with the F 70/F 160 ratios. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Meléndez, M.; Mushotzky, R. F.; Shimizu, T. T.; Barger, A. J.; Cowie, L. L.

2014-10-01

195

Spontaneous generation and disappearance of burst firing in cultured neuronal network  

NASA Astrophysics Data System (ADS)

Burst as a unit of information coding is widely investigated in the developing central nervous system. However the mechanism underling the bursts generate and disappear is unclear at present. Neurons cultured on the multi-electrode arrays, are spontaneously active, and show complex pattern with random spikes and bursts firing. With long-term recording, the course of bursts generation and disappearance was detected. The results showed that the firing pattern could transform from random spikes to bursts firing. In the beginning, the random spikes rate decreased, accompanied with bursts occurred once in a while. It appeared both single spikes and bursts at the same time. After that, the random spikes disappeared. Spontaneous activity displayed a regular occurrence of bursts with shorter interspike interval. During such bursts the firing rate at the active sites was increased dramatically. After several seconds, firing rate decreased, interburst interval extended, accompanied with the occurrence of random spikes, opposite to the beginning. At last, bursts disappeared and the networks just fired in random spikes. The observation showed that the complex electrophysiological activities of the cultured neuronal networks could implicate the spontaneous generation of burst firing. Understanding how bursts generate and disappear might be significant for deeply investigating the function and mechanism of bursts information coding.

Liu, Man; Zhou, Wei; Li, Xiangning; Luo, Qingming

2007-05-01

196

ATP-sensitive potassium channel and bursting in the pancreatic beta cell. A theoretical study.  

PubMed Central

Based on the existence of ATP-sensitive potassium channels in the plasma membrane of pancreatic beta cells, we develop a quantitative explanation of the electrical activity observed in pancreatic islets. The proposed mechanism involves the voltage-dependent inward calcium and outward potassium currents described by Rorsman and Trube (1986), which are voltage-activated when an increase in the cytoplasmic ATP/ADP ratio decreases the conductance of the ATP-sensitive potassium channels. It is proposed that modulation of the ATP/ADP ratio occurs through calcium inhibition of oxidative phosphorylation. In this picture the mitochondria serve as a transducer of metabolic activity whose sensitivity is modulated by cytosolic calcium. Solution of the differential equations that describe this mechanism gives rise to both bursting and continuous spiking electrical activity similar to that observed experimentally. While the mechanism for bursting in this model involves the ATP/ADP ratio, the feedback is still provided by calcium, as originally proposed by Chay and Keizer (1983) using a Ca2+-activated potassium conductance. A mixed-model, which includes both ATP-sensitive and Ca2+-activated potassium conductances, also reproduces the experimentally observed electrical activity and may correspond more closely to the actual situation in vivo. PMID:2673420

Keizer, J; Magnus, G

1989-01-01

197

Computational model of electrically coupled, intrinsically distinct pacemaker neurons.  

PubMed

Electrical coupling between neurons with similar properties is often studied. Nonetheless, the role of electrical coupling between neurons with widely different intrinsic properties also occurs, but is less well understood. Inspired by the pacemaker group of the crustacean pyloric network, we developed a multicompartment, conductance-based model of a small network of intrinsically distinct, electrically coupled neurons. In the pyloric network, a small intrinsically bursting neuron, through gap junctions, drives 2 larger, tonically spiking neurons to reliably burst in-phase with it. Each model neuron has 2 compartments, one responsible for spike generation and the other for producing a slow, large-amplitude oscillation. We illustrate how these compartments interact and determine the dynamics of the model neurons. Our model captures the dynamic oscillation range measured from the isolated and coupled biological neurons. At the network level, we explore the range of coupling strengths for which synchronous bursting oscillations are possible. The spatial segregation of ionic currents significantly enhances the ability of the 2 neurons to burst synchronously, and the oscillation range of the model pacemaker network depends not only on the strength of the electrical synapse but also on the identity of the neuron receiving inputs. We also compare the activity of the electrically coupled, distinct neurons with that of a network of coupled identical bursting neurons. For small to moderate coupling strengths, the network of identical elements, when receiving asymmetrical inputs, can have a smaller dynamic range of oscillation than that of its constituent neurons in isolation. PMID:15728775

Soto-Treviño, Cristina; Rabbah, Pascale; Marder, Eve; Nadim, Farzan

2005-07-01

198

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

199

Addressable Floating Light Activated Micro-Electrical Stimulators for Wireless Neurostimulation  

E-print Network

Addressable Floating Light Activated Micro-Electrical Stimulators for Wireless Neurostimulation activate photodiodes in an array. Additionally, gene therapy technologies have enabled photonic neurostimulation in neurons that have algal proteins [10], [11]. Floating Light Activated Microelectrical

200

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

201

A Closed-Loop Anesthetic Delivery System for Real-Time Control of Burst Suppression  

PubMed Central

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. PMID:23744607

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

2013-01-01

202

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

203

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.

204

Activation of 5?HT2A receptors by TCB?2 induces recurrent oscillatory burst discharge in layer 5 pyramidal neurons of the mPFC in vitro  

PubMed Central

Abstract The medial prefrontal cortex (mPFC) is a region of neocortex that plays an integral role in several cognitive processes which are abnormal in schizophrenic patients. As with other cortical regions, large?bodied layer 5 pyramidal neurons serve as the principle subcortical output of microcircuits of the mPFC. The coexpression of both inhibitory serotonin 5?HT1A receptors on the axon initial segments, and excitatory 5?HT2A receptors throughout the somatodendritic compartments, by layer 5 pyramidal neurons allows serotonin to provide potent top–down regulation of input–output relationships within cortical microcircuits. Application of 5?HT2A agonists has previously been shown to enhance synaptic input to layer 5 pyramidal neurons, as well as increase the gain in neuronal firing rate in response to increasing depolarizing current steps. Using whole?cell patch?clamp recordings obtained from layer 5 pyramidal neurons of the mPFC of C57/bl6 mice, the aim of our present study was to investigate the modulation of long?term spike trains by the selective 5?HT2A agonist TCB?2. We found that in the presence of synaptic blockers, TCB?2 induced recurrent oscillatory bursting (ROB) after 15–20 sec of tonic spiking in 7 of the 14 cells. In those seven cells, ROB discharge was accurately predicted by the presence of a voltage sag in response to a hyperpolarizing current injection. This effect was reversed by 5–10 min of drug washout and ROB discharge was inhibited by both synaptic activity and coapplication of the 5?HT2A/2C antagonist ketanserin. While the full implications of this work are not yet understood, it may provide important insight into serotonergic modulation of cortical networks. PMID:24844635

Spindle, Michael S.; Thomas, Mark P.

2014-01-01

205

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

206

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

NASA Astrophysics Data System (ADS)

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 ?m, [Ne II] 12.81 ?m, [Ne III] 15.56 ?m, and [Ne V] 14.32/24.32 ?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.; Meléndez, M.; Mushotzky, R. F.; Kraemer, S.; Engle, K.; Malumuth, E.; Tueller, J.; Markwardt, C.; Berghea, C. T.; Dudik, R. P.; Winter, L. M.; Armus, L.

2010-06-01

207

Functional coupling of simultaneous electrical and metabolic activity in the human brain  

Microsoft Academic Search

The relationships between brain electrical and metabolic activity are being uncovered currently in animal models using invasive methods; however, in the human brain this relationship remains not well understood. In particular, the relationship between noninvasive measurements of electrical activity and metabolism remains largely undefined. To understand better these relations, cerebral activity was measured simultaneously with electroencephalography (EEG) and positron emission

Terrence R. Oakes; Diego A. Pizzagalli; Andrew M. Hendrick; Katherine A. Horras; Christine L. Larson; Heather C. Abercrombie; Stacey M. Schaefer; John V. Koger; Richard J. Davidson

2004-01-01

208

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

209

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

210

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

211

Ion chamber gamma burst detector  

Microsoft Academic Search

The sensitivity of burst detection is examined with respect to the space distribution of gamma-ray bursts and to early X-ray bursts from Type I supernovae. An ion-chamber burst detector for the 2-10 keV energy range is proposed in the form of a system of three mutually orthogonal gas-filled Mylar space balloons. The proposed balloon detector has an area of 100

S. A. Colgate

1982-01-01

212

Computation of induced electric field for the sacral nerve activation  

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

213

Investigation of Optical-Burst-Transmission Induced Impairment in Gain-Clamped Amplifiers  

Microsoft Academic Search

In this paper we review our recent research activities on optical burst amplification. In a gain-stabilized amplifier the optical burst transmission may generate complex dynamics. Here a thoroughly investigation of this phenomenon is carried out based on theoretical and experiment data. The impact on optical burst switching network is discussed.

K. Ennser; G. Della Valle; S. Taccheo; J. Aracil

2007-01-01

214

Statistical Analysis of Solar Electron Bursts at Energies Below 1.4 keV  

Microsoft Academic Search

The SWEPAM experiment aboard the ACE spacecraft has observed approximately 300 solar electron bursts below 1.4 keV. These low energy solar electron bursts are detected on interplanetary field lines connected to, or surrounding, solar active regions and are usually associated with solar type III radio bursts. Detailed statistical analysis can aid in understanding the physical mechanisms governing the acceleration and

C. A. de Koning; J. T. Gosling; R. M. Skoug; J. T. Steinberg

2003-01-01

215

Gamma Ray Bursts  

E-print Network

Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed to explain them, with a view towards implications for C.T.A.

Peter Mészáros

2012-04-09

216

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

217

Gamma-ray bursts: Restarting the Engine  

E-print Network

Recent gamma-ray burst observations have revealed late-time, highly energetic events which deviate from the simplest expectations of the standard fireball picture. Instead they may indicate that the central engine is active or restarted at late times. We suggest that fragmentation and subsequent accretion during the collapse of a rapidly rotating stellar core offers a natural mechanism for this.

Andrew King; Paul T. O'Brien; Michael R. Goad; Julian Osborne; Emma Olsson; Kim Page

2005-08-04

218

Short-term transcutaneous electrical nerve stimulation after cardiac surgery: effect on pain, pulmonary function and electrical muscle activity.  

PubMed

This study aimed to evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) for treatment of postoperative pain in patients who underwent cardiac surgery. In addition, we sought to determine whether TENS would be related to improved pulmonary function and muscle electrical activity in this patient population. Forty-five patients, 32 males and 13 females, aged 41-74 years were randomly allocated to receive TENS (n=23) or sham treatment (n=22) during 4 h on the third postoperative day. A 0-10 visual analogic scale was used to assess pain; lung function was evaluated by spirometry and surface electromyography (n=10 in each group) was used to quantify electrically-induced muscle activity (trapezius and pectoralis major). TENS was associated with significant reductions on spontaneous and cough-induced postoperative pain as compared to sham (P<0.05). There was also improvement in chest wall-pulmonary mechanics after TENS with proportional increases in tidal volume and vital capacity (P<0.05). In addition, electrical activity of both muscle groups was enhanced after TENS, but not post sham (P<0.05). TENS is a valuable strategy to alleviate postoperative pain following cardiac surgery with positive effects on pulmonary ventilatory function and electrical activity of thoracic and girdle muscles. PMID:18417519

Cipriano, Gerson; de Camargo Carvalho, Antonio Carlosde; Bernardelli, Graziella França; Tayar Peres, Paulo Alberto

2008-08-01

219

Burst Populations and Detector Sensitivity  

E-print Network

The F_T (peak bolometric photon flux) vs. E_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_T-E_p plane.

David L. Band

2003-12-12

220

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

221

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

222

Ionic contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity  

E-print Network

Ionic contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity Jean of functional frog auricular fibers by ionic contrast terahertz ICT near field microscopy. This technique

Paris-Sud XI, Université de

223

Neurotensin-Induced Bursting of Cholinergic Basal Forebrain Neurons Promotes g and u Cortical Activity Together with Waking and Paradoxical Sleep  

Microsoft Academic Search

cal sleep (PS) and transitional PS (tPS), despite the virtual ab- sence of SWS. The effects were attributed to direct action on cholinergic neurons as evidenced by selective internalization of a fluorescent ligand, Fluo-NT, in choline acetyltransferase (ChAT)- immunoreactive cells and stimulation by NT of bursting dis- charge in juxtacellularly recorded, Neurobiotin-labeled, ChAT- immunoreactive neurons. We conclude that NT-induced rhythmic

Edmund G. Cape; Ian D. Manns; Angel Alonso; Alain Beaudet; Barbara E. Jones

2000-01-01

224

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. PMID:23585696

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

2013-01-01

225

Periodic Bursts of Jovian Non-Io Decametric Radio Emission  

NASA Technical Reports Server (NTRS)

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 approx. = 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 deg. and 60 deg. (via 360 deg.). 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 approx. 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

226

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

227

Gamma-ray Bursts  

Microsoft Academic Search

Since their discovery in 1967, Gamma-ray bursts (GRBs) have been puzzling to astrophysicists. With the advent of a new generation\\u000a of X-ray satellites in the late 90’s, it was possible to carry out deep multi-wavelength observations of the counterparts\\u000a associated with the long duration GRBs class just within a few hours of occurrence, thanks to the observation of the fading

Alberto J. Castro-Tirado

228

A mechanism for elliptic-like bursting and synchronization of bursts in a map-based neuron network.  

PubMed

A system consisting of two Rulkov map-based neurons coupled through reciprocal electrical synapses as a simple phenomenological example is discussed. When the electrical coupling is excitatory, the square-wave bursting can be well predicted by the bifurcation analysis of a comparatively simple low-dimensional subsystem embedded in the invariant manifold. While, when the synapses are inhibitory due to the artificial electrical coupling, a fast-slow analysis is carried out by treating the two slow variables as two different bifurcation parameters. The main result of this paper is to present a mechanism for the occurrence of a kind of special elliptic bursting. The mechanism for this kind of elliptic-like bursting is due to the interaction between two chaotic oscillations with different amplitudes. Moreover, the generation of antiphase synchronization of networks lies in the different switching orders between two pairs of different chaotic oscillations corresponding to the first neuron and the second neuron, respectively. PMID:18668272

Cao, Hongjun; Sanjuán, Miguel A F

2009-02-01

229

Fermi/GAMMA-RAY BURST MONITOR OBSERVATIONS OF SGR J0501+4516 BURSTS  

SciTech Connect

We present our temporal and spectral analyses of 29 bursts from SGR J0501+4516, detected with the gamma-ray burst monitor on board the Fermi Gamma-ray Space Telescope during 13 days of the source's activation in 2008 (August 22- 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} values 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 blackbody 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{sup -6} erg cm{sup -2} s{sup -1}, increasing steadily afterward. 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 (0.4-1.5 x 10{sup 40} erg s{sup -1}).

Lin Lin; Zhang Shuangnan [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); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, Houston, TX 77251 (United States); Van der Horst, Alexander J.; Finger, Mark H. [NSSTC, Universities Space Research Association, Huntsville, AL 35805 (United States); Guiriec, Sylvain; Preece, Robert; Chaplin, Vandiver; Bhat, Narayan [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Woods, Peter M. [Corvid Technologies, Huntsville, AL 35806 (United States); Goegues, Ersin; Kaneko, Yuki [Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli- Tuzla, Istanbul 34956 (Turkey); Scargle, Jeffrey [Space Science and Astrobiology Division, NASA/Ames Research Center, Moffett Field, CA 94035-1000 (United States); Granot, Jonathan [Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts, AL10 9AB (United Kingdom); Von Kienlin, Andreas [Max Planck Institute for extraterrestrial Physics, 85748 Garching (Germany); Watts, Anna L.; Wijers, Ralph A. M. J. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Gehrels, Neil; Harding, Alice, E-mail: lin.lin@uah.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2011-10-01

230

A Joint Design of Congestion Control and Burst Contention Resolution for Optical Burst Switching Networks  

E-print Network

This paper revisits burst contention resolution problems in optical burst switching (OBS) networks from the viewpoint of network utility maximization. Burst collision occurs when two or more bursts access the same wavelength ...

Lee, Hyang-Won

231

Robotic Electrolocation: Active Underwater Target Localization with Electric Fields  

E-print Network

Iver (maciver@northwestern.edu) is with the Department of Mechanical Engineering, Department of Biomedical by one species of weakly electric fish to guide a strike at small prey (2 mm) at distances of up to 30 mm electrolocation [14], [16], [11]. We expect this will yield helpful new avenues of research and experimentation

Hartmann, Mitra J. Z.

232

Electric-utility solar-energy activities: 1982 survey update  

Microsoft Academic Search

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

J. R. Spelman

1982-01-01

233

Electric-utility solar-energy activities: 1981 survey  

Microsoft Academic Search

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

E. Baccelli; K. Gordon

1982-01-01

234

[The effect of anesthetic concentration on burst-suppression of the EEG in rats].  

PubMed

The term "burst-suppression" is used to describe the electroencephalogram (EEG) pattern characterized by theta or delta waves, at times intermixed with faster waves, and intervening periods of relative quiescence. Burst-suppression pattern can reflect the seriously suppressed brain activity under deep anesthesia. To investigate the relationship between burst-suppression features and anesthetic concentration, we adopted four straightforward indexes, i. e., burst-suppression ratio (BSR), burst frequency, burst amplitude and suppression amplitude, and used them to analyze the EEG recordings in ten isoflurane-anesthetized rats. It was found that all the four burst-suppression indexes changed along with anesthetic concentration, that BSR and burst amplitude increased with higher concentration of isoflurane while burst frequency and suppression amplitude decreased, and that BSR was the most sensitive and consistent measurement to indicate isoflurane concentration so it constituted a valuable tool for timely evaluation of burst-suppression feature under deep anesthesia. The result also showed that the composition of carrier gas (i. e. pure oxygen vs. mixed oxygen) did not influence the effect of anesthesia significantly; and the four indexes of burst-suppression features could keep relatively stable within 60 min under the isoflurane concentration of 2%. The present study provides quantitative information of burst-suppression features under different anesthetic depth and may help to develop a clinically satisfied system that could quantify the characteristics of EEG and rigorously evaluate the cerebral state of patients. PMID:22616162

Zhang, Dandan; Jia, Xiaofeng; Ding, Haiyan

2012-04-01

235

Bright X-ray Flares in Gamma-Ray Burst Afterglows  

NASA Astrophysics Data System (ADS)

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

Burrows, D. N.; Romano, P.; Falcone, A.; Kobayashi, S.; Zhang, B.; Moretti, A.; O'Brien, P. T.; Goad, M. R.; Campana, S.; Page, K. L.; Angelini, L.; Barthelmy, S.; Beardmore, A. P.; Capalbi, M.; Chincarini, G.; Cummings, J.; Cusumano, G.; Fox, D.; Giommi, P.; Hill, J. E.; Kennea, J. A.; Krimm, H.; Mangano, V.; Marshall, F.; Mészáros, P.; Morris, D. C.; Nousek, J. A.; Osborne, J. P.; Pagani, C.; Perri, M.; Tagliaferri, G.; Wells, A. A.; Woosley, S.; Gehrels, N.

2005-09-01

236

Nanosecond pulsed electric fields activate AMP-activated protein kinase: implications for calcium-mediated activation of cellular signaling.  

PubMed

Nanosecond pulsed electric fields (nsPEFs) are increasingly being recognized as a potential tool for use in the life sciences. Exposure of human cells to nsPEFs elicits the formation of small membrane pores, intracellular Ca(2+) mobilization, signaling pathway activation, and apoptosis. Here we report the activation of AMP-activated protein kinase (AMPK) by nsPEFs. AMPK activation is generally achieved by the phosphorylation of AMPK in response to changes in cellular energy status and is mediated by two protein kinases, LKB1 and CaMKK. Exposure to nsPEFs rapidly induced phosphorylation of AMPK and its downstream target ACC in both LKB1-proficient and LKB1-deficient cells. In LKB1-deficient cells, AMPK activation by nsPEFs was mediated by CaMKK and required extracellular Ca(2+), which suggested the occurrence of Ca(2+) mobilization and its participation in AMPK activation by nsPEFs. Our results provide experimental evidence for a direct link between activated cellular signaling and Ca(2+) mobilization in nsPEF-exposed cells. PMID:23103546

Morotomi-Yano, Keiko; Akiyama, Hidenori; Yano, Ken-ichi

2012-11-23

237

An interacting loop model of solar flare bursts  

NASA Technical Reports Server (NTRS)

As a result of the strong heating produced at chromospheric levels during a solar flare burst, the local gas pressure can transiently attain very large values in certain regions. The effectiveness of the surrounding magnetic field at confining this high pressure plasma is therefore reduced and the flaring loop becomes free to expand laterally. In so doing it may drive magnetic field lines into neighboring, nonflaring, loops in the same active region, causing magnetic reconnection to take place and triggering another flare burst. The features of this interacting loop model are found to be in good agreement with the energetics and time structure of flare associated solar hard X-ray bursts.

Emslie, A. G.

1981-01-01

238

Voltage interval mappings for an elliptic bursting model  

E-print Network

We employed Poincar\\'e return mappings for a parameter interval to an exemplary elliptic bursting model, the FitzHugh-Nagumo-Rinzel model. Using the interval mappings, we were able to examine in detail the bifurcations that underlie the complex activity transitions between: tonic spiking and bursting, bursting and mixed-mode oscillations, and finally, mixed-mode oscillations and quiescence in the FitzHugh-Nagumo-Rinzel model. We illustrate the wealth of information, qualitative and quantitative, that was derived from the Poincar\\'e mappings, for the neuronal models and for similar (electro)chemical systems.

Jeremy Wojcik; Andrey Shilnikov

2013-10-19

239

Todd, Faraday and the electrical basis of brain activity.  

PubMed

The origins of our understanding of brain electricity and electrical discharges in epilepsy can be traced to Robert Bentley Todd (1809-60). Todd was influenced by his contemporary in London, Michael Faraday (1791-1867), who in the 1830 s and 1840 s was laying the foundations of our modern understanding of electromagnetism. Todd's concept of nervous polarity, generated in nerve vesicles and transmitted in nerve fibres (neurons in later terminology), was confirmed a century later by the Nobel Prize-winning work of Hodgkin and Huxley, who demonstrated the ionic basis of neuro-transmission, involving the same ions which had had been discovered by Faraday's mentor, Sir Humphry Davy (1778-1829). PMID:17885273

Reynolds, Edward

2007-10-01

240

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 PMID:19991849

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

1939-01-01

241

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray burst (GRB) have been an unsolved mystery in high-energy astrophysics for the last 30 years. Immediately after GRB were discovered, scientists tried to understand the mechanism that causes these events and where they come from. Since than, many theories have been suggested to explain GRB which have durations spanning five orders of magnitude (ranging between a few milliseconds and minutes) and spectrals that peak generally in the range of 0.1 to 1 MeV. Given this numbers, most theorists would think of processes occurring near neutron stars in our galaxy, many of which are known sources of rapidly varying, high-energy photon emission.

Kouveliotou, Chryssa

1997-01-01

242

Gamma-ray bursts.  

PubMed

Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow. PMID:22923573

Gehrels, Neil; Mészáros, Péter

2012-08-24

243

Gamma Ray Bursts  

NASA Technical Reports Server (NTRS)

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 pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

Gehrels, Neil; Meszaros, Peter

2012-01-01

244

Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active  

E-print Network

28/04/14 1 Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated computers, tablets, internet... · Mobile devices: iPhones, mp3 players... · Solar cells, led displays

Ã?nay, Devrim

245

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

246

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. PMID:24098274

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

2013-01-01

247

Swift's 500th Gamma Ray Burst  

NASA Video Gallery

On April 13, 2010, NASA's Swift Gamma-ray Burst Explorer satellite discovered its 500th burst. Swift's main job is to quickly localize each gamma-ray burst (GRB), report its position so that others...

248

Astrophysics: A burst of new ideas  

E-print Network

Gigantic cosmological gamma-ray bursts have fallen into a dichotomy of long and short bursts, each with a very different origin. The discovery of an oddball burst calls for a rethink of that classification.

Bing Zhang

2006-12-21

249

Responses of a bursting pacemaker to excitation reveal spatial segregation between bursting and spiking mechanisms  

PubMed Central

Central pattern generators (CPGs) frequently include bursting neurons that serve as pacemakers for rhythm generation. Phase resetting curves (PRCs) can provide insight into mechanisms underlying phase locking in such circuits. PRCs were constructed for a pacemaker bursting complex in the pyloric circuit in the stomatogastric ganglion of the lobster and crab. This complex is comprised of the Anterior Burster (AB) neuron and two Pyloric Dilator (PD) neurons that are all electrically coupled. Artificial excitatory synaptic conductance pulses of different strengths and durations were injected into one of the AB or PD somata using the Dynamic Clamp. Previously, we characterized the inhibitory PRCs by assuming a single slow process that enabled synaptic inputs to trigger switches between an up state in which spiking occurs and a down state in which it does not. Excitation produced five different PRC shapes, which could not be explained with such a simple model. A separate dendritic compartment was required to separate the mechanism that generates the up and down phases of the bursting envelope (1) from synaptic inputs applied at the soma, (2) from axonal spike generation and (3) from a slow process with a slower time scale than burst generation. This study reveals that due to the nonlinear properties and compartmentalization of ionic channels, the response to excitation is more complex than inhibition. PMID:21360137

Maran, Selva K; Sieling, Fred H; Demla, Kavita; Prinz, Astrid A; Canavier, Carmen C

2011-01-01

250

A model for cerebral cortical neuron group electric activity and its implications for cerebral function  

E-print Network

The electroencephalogram, or EEG, is a recording of the field potential generated by the electric activity of neuronal populations of the brain. Its utility has long been recognized as a monitor which reflects the vigilance ...

Karameh, Fadi Nabih

2002-01-01

251

Young Scientists Explore Electricity & Magnetism. Book 7--Intermediate Level. A Good Apple Activity Book.  

ERIC Educational Resources Information Center

Designed to develop creativity in young learners, this book contains interdisciplinary activities which focus on the theme of electricity and magnetism. Activity pages are provided that can serve as front and back covers of a student booklet and the suggested activities can be duplicated for insertion between the covers resulting in a booklet for…

DeBruin, Jerry

252

A brief review of JPL's electric propulsion technology activities  

NASA Technical Reports Server (NTRS)

Near-term objectives and recent technological progress of JPL's electric propulsion program are discussed. Particular attention is given to accomplishments for ion, magnetoplasmadynamic (MPD), electron-cyclotron resonance (ECR), and arcjet thrusters. Xenon ion thruster erosion tests indicate a 15-fold reduction in tantalum baffle erosion when nitrogen is added to the xenon propellant and steady-state cylindrical MPD thruster tests at powers up to 72 kW show distinct self-constricted and diffuse discharge modes. An ECR thruster was operated at up to 7 kW with plasma acceleration at energies up to 7 kW; there was plasma acceleration at energies approaching 100 electron volts.

Barnett, John W.; Chopra, Ann; Deininger, William D.; Garner, Charles E.; Pivirotto, Thomas J.; Sercel, Joel C.

1989-01-01

253

Impulsive EUV bursts observed in C IV with OSO-8. [UV solar spectra  

NASA Technical Reports Server (NTRS)

Time sequences of profiles of the 1548 A line of C IV containing 51 EUV bursts observed in or near active regions are analyzed to determine the brightness, Doppler shift and line broadening characteristics of the bursts. The bursts have mean lifetimes of approximately 150 s, and mean increases in brightness at burst maximum of four-fold as observed with a field of view of 2 x 20 arc sec. Mean burst diameters are estimated to be 3 arc sec, or smaller. All but three of the bursts show Doppler shifts with velocities sometimes exceeding 75 km/s; 31 are dominated by red shifts and 17 are dominated by blue shifts. Approximately half of the latter group have red-shifted precursors. The bursts are interpreted as prominence material, such as surges and coronal rain, moving through the field of view of the spectrometer.

Athay, R. G.; White, O. R.; Lites, B. W.; Bruner, E. C., Jr.

1980-01-01

254

Workshop Physics Activity Guide, Module 4: Electricity and Magnetism  

Microsoft Academic Search

The Workshop Physics Activity Guide is a set of student workbooks designed to serve as the foundation for a two-semester calculus-based introductory physics course. It consists of 28 units that interweave text materials with activities that include prediction, qualitative observation, explanation, equation derivation, mathematical modeling, quantitative experiments, and problem solving. Students use a powerful set of computer tools to record,

Priscilla W. Laws

2004-01-01

255

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

256

Ion chamber gamma burst detector  

NASA Astrophysics Data System (ADS)

The sensitivity of burst detection is examined with respect to the space distribution of gamma-ray bursts and to early X-ray bursts from Type I supernovae. An ion-chamber burst detector for the 2-10 keV energy range is proposed in the form of a system of three mutually orthogonal gas-filled Mylar space balloons. The proposed balloon detector has an area of 100 sq m, a sensitivity of 2 x 10 to the -10th erg/sq cm, a directionality of 0.0001 sr, and a Mylar thickness of 3 mg/sq cm. It is shown that the detector can extend the gamma-burst log N - log S curve down to a presumed temporal-confusion limit and can detect expected prompt Type I supernovae in galaxies at 100 Mpc at a rate of at least one per day.

Colgate, S. A.

257

New Views of Thermonuclear Bursts  

E-print Network

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 regime of nuclear burning on neutron stars which manifests itself through the generation of hours long flares about once a decade, now referred to as ``superbursts'',(iii) discoveries of bursts from low accretion rate neutron stars, and (iv) new evidence for discrete spectral features from bursting neutron stars. In this article we review our current understanding of thermonuclear bursts on neutron stars, with a focus on these new phenomena.

Tod Strohmayer; Lars Bildsten

2003-01-28

258

On Gamma-Ray Bursts  

E-print Network

(Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the process of gravitational collapse, leading to the creation of an electron-positron-photon plasma: the basic self-accelerating system explaining both the energetics and the high energy Lorentz factor observed in GRBs. We then turn to recall the two basic interpretational paradigms of our GRB model. [...] We then turn to the special role of the baryon loading in discriminating between "genuine" short and long or "fake" short GRBs [...] We finally turn to the GRB-Supernova Time Sequence (GSTS) paradigm: the concept of induced gravitational collapse. [...] We then present some general conclusions.

Remo Ruffini; Maria Grazia Bernardini; Carlo Luciano Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; Maria Giovanna Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; Jorge Armando Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

2008-04-17

259

Electrical Excitation of the Acoustically Sensitive Auditory Nerve: Single-Fiber Responses to Electric Pulse Trains  

PubMed Central

Nearly all studies on auditory-nerve responses to electric stimuli have been conducted using chemically deafened animals so as to more realistically model the implanted human ear that has typically been profoundly deaf. However, clinical criteria for implantation have recently been relaxed. Ears with “residual” acoustic sensitivity are now being implanted, calling for the systematic evaluation of auditory-nerve responses to electric stimuli as well as combined electric and acoustic stimuli in acoustically sensitive ears. This article presents a systematic investigation of single-fiber responses to electric stimuli in acoustically sensitive ears. Responses to 250 pulse/s electric pulse trains were collected from 18 cats. Properties such as threshold, dynamic range, and jitter were found to differ from those of deaf ears. Other types of fiber activity observed in acoustically sensitive ears (i.e., spontaneous activity and electrophonic responses) were found to alter the temporal coding of electric stimuli. The electrophonic response, which was shown to greatly change the information encoded by spike intervals, also exhibited fast adaptation relative to that observed in the “direct” response to electric stimuli. More complex responses, such as “buildup” (increased responsiveness to successive pulses) and “bursting” (alternating periods of responsiveness and unresponsiveness) were observed. Our findings suggest that bursting is a response unique to sustained electric stimulation in ears with functional hair cells. PMID:16708257

Abbas, Paul J.; Robinson, Barbara K.; Nourski, Kirill V.; Zhang, Fawen; Jeng, Fuh-Cherng

2006-01-01

260

Magnetic Flux Transport and Pressure Variations at Magnetotail Plasma Flow Bursts during Geomagnetically Quiet Times  

NASA Astrophysics Data System (ADS)

The fast plasma flows in the geomagnetotail are observed during both geomagnetically active and quiet times. However, it has been unclear about the fundamental difference in the plasma fast flows between at two different geomagnetic conditions, that is, the generation mechanism of, and pictures of the energy transport and balance at the fast plasma flows. Magnetic reconnection in the magnetotail has been believed as one of the most possible mechanisms to generate the fast plasma flows regardless of the geomagnetic conditions. Recently, Nowada et al. [2012], however, demonstrated that the magnetotail magnetic reconnection does not always contribute to the generation of the fast plasma flows at geomagnetically quiet times based on the THEMIS measurements. It is very important to reveal how the energy transport and balance in the magnetotail in association with these plasma fast flows are on obtaining a clue to elucidate an essential difference in the plasma fast flows between during active and quiet geomagnetic conditions. Based on three events of the magnetotail plasma flow bursts, which are transient fast plasma flows with the durations between 1 and 2 minutes, during geomagnetically quiet times, observed by THEMIS, we examined detailed variations of the electric field as a proxy of the flux transport aspect, and associated pressure. The main characteristics of these events are shown as follows; 1) the GSM-X component of the plasma velocity (Vx) was higher than 300 km/s 2) associated parallel (V//) and perpendicular (V?) velocities to the local magnetic field line were higher than 200 km/s 3) the flow bursts were observed during which AL and AU indices were lower than 40 nT, and simultaneous Kp index range was between -1 and 1. For almost events, the parallel (E//) and perpendicular (E?) components of the electric field to the local magnetic field line were much stronger than the dawn-dusk electric field component (Ey). This result implies that a larger amount of the magnetic flux was transported into the parallel and perpendicular directions to the local magnetic field line than the dawn-dusk direction at the flow bursts. However, in the Ey component, the contribution from the dawn-to-dusk electric field (VxBz) was much greater than that from the dusk-to-dawn component (VzBx). Furthermore, for two events, significant reduction of the plasma pressure, and enhancement of the north-south magnetic field component (Bz) were observed at/near the flow bursts. Simultaneous total pressure was well-balanced, indicating that the magnetotail during the plasma flow bursts was in the state of equilibrium. Based on these results, "bubble" might play a crucial role for generating the plasma flow bursts at geomagnetically quiet times. Reference: Nowada, M., S. -Y. Fu, G. K. Parks, Z. -Y. Pu, V. Angelopoulos, C. W. Carlson, H. -U. Auster (2012), Plasma flow bursts in the magnetotail during geomagnetically quiet times 2: Relation to the magnetic reconnection and substorm process, to be submitted to Journal of Geophysical Research -Space Physics-. Corresponding Author : Motoharu Nowada nowada@pku.edu.cn

Nowada, M.; Fu, S.-Y.; Parks, G. K.; Pu, Z.-Y.; Angelopoulos, V.; Carlson, C. W.; Auster, H.-U.

2012-04-01

261

Deterministic and stochastic neuronal contributions to distinct synchronous CA3 network bursts.  

PubMed

Computational studies have suggested that stochastic, deterministic, and mixed processes all could be possible determinants of spontaneous, synchronous network bursts. In the present study, using 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 GABA(A) 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 coefficient of concordance 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 homogeneous, 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. PMID:22492030

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

2012-04-01

262

BROADBAND SPECTRAL INVESTIGATIONS OF SGR J1550-5418 BURSTS  

SciTech Connect

We present the results of our broadband spectral analysis of 42 SGR J1550-5418 bursts simultaneously detected with the Swift/X-ray Telescope (XRT) and the Fermi/Gamma-ray Burst Monitor (GBM), during the 2009 January active episode of the source. The unique spectral and temporal capabilities of the XRT windowed timing mode have allowed us to extend the GBM spectral coverage for these events down to the X-ray domain (0.5-10 keV). Our earlier analysis of the GBM data found that the SGR J1550-5418 burst spectra were described equally well with either a Comptonized model or with two blackbody functions; the two models were statistically indistinguishable. Our new broadband (0.5-200 keV) spectral fits show that, on average, the burst spectra are better described with two blackbody functions than with the Comptonized model. Thus, our joint XRT-GBM analysis clearly shows for the first time that the SGR J1550-5418 burst spectra might naturally be expected to exhibit a more truly thermalized character, such as a two-blackbody or even a multi-blackbody signal. Using the Swift and RXTE timing ephemeris for SGR J1550-5418 we construct the distribution of the XRT burst counts with spin phase and find that it is not correlated with the persistent X-ray emission pulse phase from SGR J1550-5418. These results indicate that the burst emitting sites on the neutron star need not to be co-located with hot spots emitting the bulk of the persistent X-ray emission. Finally, we show that there is a significant pulse phase dependence of the XRT burst counts, likely demonstrating that the surface magnetic field of SGR J1550-5418 is not uniform over the emission zones, since it is anticipated that regions with stronger surface magnetic field could trigger bursts more efficiently.

Lin Lin; Goegues, Ersin; Kaneko, Yuki [Faculty of Engineering and Natural Sciences, Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I Tuzla, Istanbul 34956 (Turkey); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Granot, Jonathan [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, Alexander; Watts, Anna L. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Gruber, David; Von Kienlin, Andreas [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85748 Garching bei Mnchen (Germany); Younes, George [USRA, National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Gehrels, Neil, E-mail: linlin@sabanciuniv.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-09-01

263

Broadband Spectral Investigations of SGR J1550-5418 Bursts  

NASA Astrophysics Data System (ADS)

We present the results of our broadband spectral analysis of 42 SGR J1550-5418 bursts simultaneously detected with the Swift/X-ray Telescope (XRT) and the Fermi/Gamma-ray Burst Monitor (GBM), during the 2009 January active episode of the source. The unique spectral and temporal capabilities of the XRT windowed timing mode have allowed us to extend the GBM spectral coverage for these events down to the X-ray domain (0.5-10 keV). Our earlier analysis of the GBM data found that the SGR J1550-5418 burst spectra were described equally well with either a Comptonized model or with two blackbody functions; the two models were statistically indistinguishable. Our new broadband (0.5-200 keV) spectral fits show that, on average, the burst spectra are better described with two blackbody functions than with the Comptonized model. Thus, our joint XRT-GBM analysis clearly shows for the first time that the SGR J1550-5418 burst spectra might naturally be expected to exhibit a more truly thermalized character, such as a two-blackbody or even a multi-blackbody signal. Using the Swift and RXTE timing ephemeris for SGR J1550-5418 we construct the distribution of the XRT burst counts with spin phase and find that it is not correlated with the persistent X-ray emission pulse phase from SGR J1550-5418. These results indicate that the burst emitting sites on the neutron star need not to be co-located with hot spots emitting the bulk of the persistent X-ray emission. Finally, we show that there is a significant pulse phase dependence of the XRT burst counts, likely demonstrating that the surface magnetic field of SGR J1550-5418 is not uniform over the emission zones, since it is anticipated that regions with stronger surface magnetic field could trigger bursts more efficiently.

Lin, Lin; Gö?ü?, Ersin; Baring, Matthew G.; Granot, Jonathan; Kouveliotou, Chryssa; Kaneko, Yuki; van der Horst, Alexander; Gruber, David; von Kienlin, Andreas; Younes, George; Watts, Anna L.; Gehrels, Neil

2012-09-01

264

Self-organization on social media: endo-exo bursts and baseline fluctuations  

E-print Network

A salient dynamic property of social media is bursting behavior. In this paper, we study bursting behavior in terms of the temporal relation between a preceding baseline fluctuation and the successive burst response using a frequency time series of 3,000 keywords on Twitter. We found that there is a fluctuation threshold up to which the burst size increases as the fluctuation increases and that above the threshold, there appears a variety of burst sizes. We call this threshold the critical threshold. Investigating this threshold in relation to endogenous bursts and exogenous bursts based on peak ratio and burst size reveals that the bursts below this threshold are endogenously caused and above this threshold, exogenous bursts emerge. Analysis of the 3,000 keywords shows that all the nouns have both endogenous and exogenous origins of bursts and that each keyword has a critical threshold in the baseline fluctuation value to distinguish between the two. Having a threshold for an input value for activating the s...

Oka, Mizuki; Ikegami, Takashi

2014-01-01

265

Self-Organization on Social Media: Endo-Exo Bursts and Baseline Fluctuations  

PubMed Central

A salient dynamic property of social media is bursting behavior. In this paper, we study bursting behavior in terms of the temporal relation between a preceding baseline fluctuation and the successive burst response using a frequency time series of 3,000 keywords on Twitter. We found that there is a fluctuation threshold up to which the burst size increases as the fluctuation increases and that above the threshold, there appears a variety of burst sizes. We call this threshold the critical threshold. Investigating this threshold in relation to endogenous bursts and exogenous bursts based on peak ratio and burst size reveals that the bursts below this threshold are endogenously caused and above this threshold, exogenous bursts emerge. Analysis of the 3,000 keywords shows that all the nouns have both endogenous and exogenous origins of bursts and that each keyword has a critical threshold in the baseline fluctuation value to distinguish between the two. Having a threshold for an input value for activating the system implies that Twitter is an excitable medium. These findings are useful for characterizing how excitable a keyword is on Twitter and could be used, for example, to predict the response to particular information on social media. PMID:25329610

Oka, Mizuki; Hashimoto, Yasuhiro; Ikegami, Takashi

2014-01-01

266

Self-organization on social media: endo-exo bursts and baseline fluctuations.  

PubMed

A salient dynamic property of social media is bursting behavior. In this paper, we study bursting behavior in terms of the temporal relation between a preceding baseline fluctuation and the successive burst response using a frequency time series of 3,000 keywords on Twitter. We found that there is a fluctuation threshold up to which the burst size increases as the fluctuation increases and that above the threshold, there appears a variety of burst sizes. We call this threshold the critical threshold. Investigating this threshold in relation to endogenous bursts and exogenous bursts based on peak ratio and burst size reveals that the bursts below this threshold are endogenously caused and above this threshold, exogenous bursts emerge. Analysis of the 3,000 keywords shows that all the nouns have both endogenous and exogenous origins of bursts and that each keyword has a critical threshold in the baseline fluctuation value to distinguish between the two. Having a threshold for an input value for activating the system implies that Twitter is an excitable medium. These findings are useful for characterizing how excitable a keyword is on Twitter and could be used, for example, to predict the response to particular information on social media. PMID:25329610

Oka, Mizuki; Hashimoto, Yasuhiro; Ikegami, Takashi

2014-01-01

267

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

268

Neural sensing of electrical activity with stretchable microelectrode arrays.  

PubMed

Sensing neural activity within mechanically active tissues poses particular hurdles because most electrodes are much stiffer than biological tissues. As the tissue deforms, the rigid electrodes may damage the surrounding tissue. The problem is exacerbated when sensing neural activity in experimental models of traumatic brain injury (TBI) which is caused by the rapid and large deformation of brain tissue. We have developed a stretchable microelectrode array (SMEA) that can withstand large elastic deformations (>5% biaxial strain) while continuing to function. The SMEA were fabricated from thin metal conductors patterned on polydimethylsiloxane (PDMS) and encapsulated with a photo-patternable silicone. SMEA were used to record spontaneous activity from brain slice cultures, as well as evoked activity after stimulating through SMEA electrodes. Slices of brain tissue were grown on SMEA in long-term culture and then mechanically injured with our well-characterized in vitro injury model by stretching the SMEA and the adherent culture, which was confirmed by image analysis. Because brain tissue was grown on the substrate-integrated SMEA, post-injury changes in electrophysiological function were normalized to pre-injury function since the SMEA deformed with the tissue and remained in place during mechanical stimulation. The combination of our injury model and SMEA could help elucidate mechanisms responsible for post-traumatic neuronal dysfunction in the quest for TBI therapies. The SMEA may have additional sensing applications in other mechanically active tissues such as peripheral nerve and heart. PMID:19964344

Yu, Zhe; Graudejus, Oliver; Lacour, Stéphanie P; Wagner, Sigurd; Morrison, Barclay

2009-01-01

269

Chemical Events in Conducting and Synaptic Membrances during Electrical Activity  

PubMed Central

Evidence has accumulated in recent years for the central role of proteins and enzymes in the function of cell membranes. In the chemical theory proposed for the generation of bioelectricity, i.e., for the control of the ion permeability changes of excitable membranes, the protein assembly associated with the action of acetylcholine plays an essential role. Support of the theory by recent protein studies in which the excitable membranes of the highly specialized electric tissue were used will be discussed. A scheme is presented indicating the possible sequence of chemical reactions that change ion permeability after excitation. A sequence of chemical events within the excitable membranes of the synaptic junctions, i.e., within the pre- and postsynaptic membranes, similar to that proposed for the conducting membranes, is presented in a second scheme as an alternative to the hypothesis of the role of acetylcholine as a transmitter between two cells. Images PMID:4332011

Nachmansohn, David

1971-01-01

270

Effective electrode length enhances electrical activation of nanowire networks: experiment and simulation.  

PubMed

Networks comprised of randomly oriented overlapping nanowires offer the possibility of simple fabrication on a variety of substrates, in contrast with the precise placement required for devices with single or aligned nanowires. Metal nanowires typically have a coating of surfactant or oxide that prevents aggregation, but also prevents electrical connection. Prohibitively high voltages can be required to electrically activate nanowire networks, and even after activation many nanowire junctions remain nonconducting. Nonelectrical activation methods can enhance conductivity but destroy the memristive behavior of the junctions that comprise the network. We show through both simulation and experiment that electrical stimulation, microstructured electrode geometry, and feature scaling can all be used to manipulate the connectivity and thus electrical conductivity of networks of silver nanowires with a nonconducting polymer coating. More generally, these results describe a strategy to integrate nanomaterials into controllable, adaptive macroscale materials. PMID:25153920

Fairfield, Jessamyn A; Ritter, Carlos; Bellew, Allen T; McCarthy, Eoin K; Ferreira, Mauro S; Boland, John J

2014-09-23

271

Workshop Physics Activity Guide, Module 4: Electricity and Magnetism  

NASA Astrophysics Data System (ADS)

The Workshop Physics Activity Guide is a set of student workbooks designed to serve as the foundation for a two-semester calculus-based introductory physics course. It consists of 28 units that interweave text materials with activities that include prediction, qualitative observation, explanation, equation derivation, mathematical modeling, quantitative experiments, and problem solving. Students use a powerful set of computer tools to record, display, and analyze data, as well as to develop mathematical models of physical phenomena. The design of many of the activities is based on the outcomes of physics education research. The Workshop Physics Activity Guide is supported by an Instructor's Website that: (1) describes the history and philosophy of the Workshop Physics Project; (2) provides advice on how to integrate the Guide into a variety of educational settings; (3) provides information on computer tools (hardware and software) and apparatus; and (4) includes suggested homework assignments for each unit. Log on to the Workshop Physics Project website at http://physics.dickinson.edu/ Workshop Physics is a component of the Physics Suite--a collection of materials created by a group of educational reformers known as the Activity Based Physics Group. The Physics Suite contains a broad array of curricular materials that are based on physics education research, including:

    Understanding Physics, by Cummings, Laws, Redish and Cooney (an introductory textbook based on the best-selling text by Halliday/Resnick/Walker) RealTime Physics Laboratory Modules Physics by Inquiry (intended for use in a workshop setting) Interactive Lecture Demonstration Tutorials in Introductory Physics Activity Based Tutorials (designed primarily for use in recitations)

    Laws, Priscilla W.

    2004-05-01

272

An interacting loop model for solar flare bursts  

NASA Technical Reports Server (NTRS)

A schematic model is presented which attempts to explain the quasi-periodic behavior (on a timescale of less than or approximately equal to 10 s) frequency observed in solar hard X-ray bursts. It is shown how, as a result of the strong heating produced during a solar flare burst, the local gas pressure can transiently attain very large values in regions corresponding to the upper preflare chromosphere. The effectiveness of the surrounding magnetic field at confining this high pressure plasma is therefore reduced and the flaring loop becomes free to expand laterally. In so doing it may drive magnetic field lines into neighboring, non-flaring, loops in the same active region, causing magnetic reconnection to take place and triggering another flare burst. The features of this interacting loop model are found to be in good agreement with the energetics and time structure of flare-associated solar hard X-ray bursts.

Emslie, A. G.

1981-01-01

273

Quark Stars as inner engines for Gamma Ray Bursts?  

E-print Network

A model for Gamma ray bursts inner engine based on quark stars (speculated to exist in nature) is presented. We describe how and why these objects might constitute new candidates for GRB inner engines. At the heart of the model is the onset of exotic phases of quark matter at the surface of such stars, in particular the 2-flavor color superconductivity. A novel feature of such a phase is the generation of particles which are unstable to photon decay providing a natural mechanism for a fireball generation; an approach which is fundamentally different from models where the fireball is generated during collapse or conversion of neutron star to quark star processes. The model is capable of reproducing crucial features of Gamma ray bursts, such as the episodic activity of the engine (multiple and random shell emission) and the two distinct categories of the bursts (two regimes are isolated in the model with \\sim 2 s and \\sim 81 s burst total duration).

R. Ouyed; F. Sannino

2001-03-01

274

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

275

Ionic factors governing rebound burst phenotype in rat deep cerebellar neurons.  

PubMed

Large diameter cells in rat deep cerebellar nuclei (DCN) can be distinguished according to the generation of a transient or weak rebound burst and the expression of T-type Ca(2+) channel isoforms. We studied the ionic basis for the distinction in burst phenotypes in rat DCN cells in vitro. Following a hyperpolarization, transient burst cells generated a high-frequency spike burst of < or = 450 Hz, whereas weak burst cells generated a lower-frequency increase (<140 Hz). Both cell types expressed a low voltage-activated (LVA) Ca(2+) current near threshold for rebound burst discharge (-50 mV) that was consistent with T-type Ca(2+) current, but on average 7 times more current was recorded in transient burst cells. The number and frequency of spikes in rebound bursts was tightly correlated with the peak Ca(2+) current at -50 mV, showing a direct relationship between the availability of LVA Ca(2+) current and spike output. Transient burst cells exhibited a larger spike depolarizing afterpotential that was insensitive to blockers of voltage-gated Na(+) or Ca(2+) channels. In comparison, weak burst cells exhibited larger afterhyperpolarizations (AHPs) that reduced cell excitability and rebound spike output. The sensitivity of AHPs to Ca(2+) channel blockers suggests that both LVA and high voltage-activated (HVA) Ca(2+) channels trigger AHPs in weak burst compared with only HVA Ca(2+) channels in transient burst cells. The two burst phenotypes in rat DCN cells thus derive in part from a difference in the availability of LVA Ca(2+) current following a hyperpolarization and a differential activation of AHPs that establish distinct levels of membrane excitability. PMID:18768644

Molineux, Michael L; Mehaffey, W Hamish; Tadayonnejad, Reza; Anderson, Dustin; Tennent, Adrien F; Turner, Ray W

2008-11-01

276

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

277

The effect of electrical field strength on activation and development of cloned caprine embryos  

Microsoft Academic Search

The activation procedure used in nuclear transfer (NT) is one of the critical factors affecting the efficiency of animal cloning. The purpose of this study was to compare the effect of two electrical field strengths (EFS) for activation on the developmental competence of caprine NT embryos reconstructed from ear skin fibroblasts of adult Alpine does. The NT embryos were obtained

P. C. Shen; S. N. Lee; J. S. Wu; J. C. Huang; F. H. Chu; C. C. Chang; J. C. Kung; H. H. Lin; L. R. Chen; J. W. Shiau; N. T. Yen; W. T. K. Cheng

2006-01-01

278

Dynamic Variation in Pleasure in Children Predicts Nonlinear Change in Lateral Frontal Brain Electrical Activity  

E-print Network

Dynamic Variation in Pleasure in Children Predicts Nonlinear Change in Lateral Frontal Brain frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral in a sample of 128 children ages 6­10 years. Electroencephalographic activity was recorded during "pop-out toy

Wisconsin at Madison, University of

279

Patterns of Brain-Electrical Activity during Declarative Memory Performance in 10-Month-Old Infants  

ERIC Educational Resources Information Center

This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation…

Morasch, Katherine C.; Bell, Martha Ann

2009-01-01

280

ON THE COOLING TAILS OF THERMONUCLEAR X-RAY BURSTS: THE IGR J17480-2446 LINK  

SciTech Connect

The neutron star transient and 11 Hz X-ray pulsar IGR J17480-2446, recently discovered in the globular cluster Terzan 5, showed unprecedented bursting activity during its 2010 October-November outburst. We analyzed all X-ray bursts detected with the Rossi X-ray Timing Explorer and find strong evidence that they all have a thermonuclear origin, despite the fact that many do not show the canonical spectral softening along the decay imprinted on type I X-ray bursts by the cooling of the neutron star photosphere. We show that the persistent-to-burst power ratio is fully consistent with the accretion-to-thermonuclear efficiency ratio along the whole outburst, as is typical for type I X-ray bursts. The burst energy, peak luminosity, and daily-averaged spectral profiles all evolve smoothly throughout the outburst, in parallel with the persistent (non-burst) luminosity. We also find that the peak-burst to persistent luminosity ratio determines whether or not cooling is present in the bursts from IGR J17480-2446, and argue that the apparent lack of cooling is due to the 'non-cooling' bursts having both a lower peak temperature and a higher non-burst (persistent) emission. We conclude that the detection of cooling along the decay is a sufficient, but not a necessary condition to identify an X-ray burst as thermonuclear. Finally, we compare these findings with X-ray bursts from other rapidly accreting neutron stars.

Linares, M.; Chakrabarty, D. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 (United States); Van der Klis, M. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam and Center for High-Energy Astrophysics, P.O. Box 94249, 1090 GE Amsterdam (Netherlands)

2011-06-01

281

The Burst of the Century  

NASA Astrophysics Data System (ADS)

The extraordinarily bright GRB 130427A has provided a multiwavelength data set unprecedented in the history of the field. However the light curve of this burst, like that of the large majority of LAT bursts, shows a puzzling lack of a jet break (the hallmark of a collimated outflow). We propose to continue our long-term monitoring of this GRB through to the end of 2015. A detection of a jet break will give us a direct measure of the absolute energy of the burst; its absence will effectively rule out a rotating neutron star as the central engine of the GRB.

Fruchter, Andrew

2014-09-01

282

Neutrinos from Gamma Ray Bursts  

E-print Network

We show that the detection of neutrinos from a typical gamma ray burst requires a kilometer-scale detector. We argue that large bursts should be visible with the neutrino telescopes under construction. We emphasize the 3 techniques by which neutrino telescopes can perform this search: by triggering on i) bursts of muons from muon neutrinos, ii) muons from air cascades initiated by high energy gamma rays and iii) showers made by relatively low energy ($\\simeq 100\\,\\mev$) electron neutrinos. Timing of neutrino-photon coincidences may yield a measurement of the neutrino mass to order $10^{-5}$~eV, an interesting range in light of the solar neutrino anomaly.

F. Halzen; G. Jaczko

1996-02-07

283

Store-operated Ca²? entry and depolarization explain the anomalous behaviour of myometrial SR: effects of SERCA inhibition on electrical activity, Ca²? and force.  

PubMed

In the myometrium SR Ca(2+) depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca(2+) sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca(2+)-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca(2+) transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20 ?M), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca(2+)]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca(2+) spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca(2+) and depolarization continued a point was reached when electrical and Ca(2+) spikes and phasic contractions ceased, and a maintained, tonic force and Ca(2+) was produced. Lanthanum, a non-selective blocker of store-operated Ca(2+) entry, but not the L-type Ca(2+) channel blocker nifedipine (1-10 ?M), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca(2+) depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca(2+) release is coupled to marked Ca(2+) entry, via store operated Ca(2+) channels, leading to depolarization and enhanced electrical and mechanical activity. PMID:25084623

Noble, Debbie; Borysova, Lyudmyla; Wray, Susan; Burdyga, Theodor

2014-09-01

284

Store-operated Ca2+ entry and depolarization explain the anomalous behaviour of myometrial SR: Effects of SERCA inhibition on electrical activity, Ca2+ and force  

PubMed Central

In the myometrium SR Ca2+ depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca2+ sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca2+-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca2+ transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20 ?M), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca2+]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca2+ spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca2+ and depolarization continued a point was reached when electrical and Ca2+ spikes and phasic contractions ceased, and a maintained, tonic force and Ca2+ was produced. Lanthanum, a non-selective blocker of store-operated Ca2+ entry, but not the L-type Ca2+ channel blocker nifedipine (1–10 ?M), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca2+ depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca2+ release is coupled to marked Ca2+ entry, via store operated Ca2+ channels, leading to depolarization and enhanced electrical and mechanical activity. PMID:25084623

Noble, Debbie; Borysova, Lyudmyla; Wray, Susan; Burdyga, Theodor

2014-01-01

285

Removal of impulse bursts in satellite images  

Microsoft Academic Search

Characteristics of impulse bursts in satellite images are analyzed and methods for burst removal are considered. Artificial compact burst model is proposed and test images are created. An advanced multipass algorithm for the detection and removal of compact bursts in the presence of both additive and multiplicative noise is proposed. The efficiency of the algorithm is evaluated quantitatively using the

O. V. Tsymbal; V. V. Lukin; P. T. Koivisto; V. P. Melnik

2003-01-01

286

Gamma ray bursts ROBERT S MACKAY  

E-print Network

Gamma ray bursts ROBERT S MACKAY COLIN ROURKE We propose that a gamma ray burst is a kinematic Gamma ray bursts are intense flashes of electromagnetic radiation of cosmic origin lasting from ten accepted mechanism. We propose that a gamma ray burst is simply a kinematic effect, namely the effect

Rourke, Colin

287

An Analysis of Burst Disc Pressure Instability  

SciTech Connect

During the development stage of the 1X Acorn burst disc, burst pressure test results exhibited an unexpected increase of 8 to 14% over times of 90--100 days from initial fabrication. This increase is a concern where design constraints require stability. The disc material, 316L stainless steel sheet, is formed to a dome-like geometry and scored to produce a thin-walled, high-strength ligament. The fracture events controlling burst occur in that ligament. Thus it has been characterized both for tensile properties and microstructure through nanoindentation, magnetic measurements, optical and transmission electron microscopy. These results compare favorably with finite element simulation of the properties of the ligament. The ligament exhibits a highly heterogeneous microstructure; its small volume and microstructural heterogeneity make it difficult to identify which microstructural feature controls fracture and hence burst pressure. Bulk mechanical test specimens were fabricated to emulate mid-ligament properties, and aged at both room and elevated temperatures to characterize and accelerate the temporal behavior of the burst disc. Property changes included yield and ultimate tensile strength increases, and fracture strain decreases with aging. Specimens were subjected to a reversion anneal identical to that given the burst disc to eliminate the martensite phase formed during rolling. Reversion-annealed samples exhibited no change in properties in room temperature or accelerated aging, showing that the reversion-anneal eliminated the aging phenomenon. Aging was analyzed in terms of diffusion controlled precipitate growth kinetics, showing that carbon migration to dislocations is consistent with the strength increases. A vacancy-assisted diffusion mechanism for carbon transport is proposed, giving rise to rapid aging, which replaces interstitial carbon diffusion until excess vacancies from deformation are consumed. Mechanical activation parameters in stress relaxation were measured, indicating that the deformation structures formed at high strains typical of the score ligament are resistant to annealing, and mimic the behavior of a thermal obstacles. This model also qualitatively explains the different rates of aging resulting from a range of levels of cold work.

S. L. Robinson; B. C. Odegard, Jr.; N. r. Moody; S. H. Goods

2000-06-01

288

Do gamma-ray burst sources repeat?  

NASA Technical Reports Server (NTRS)

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al. 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic ad the two-point angular correlation function. We find the data to be consistent with the hypothesis that burst sources do not repeat; however, a repeater fraction of up to about 20% of the bursts cannot be excluded.

Meegan, C. A.; Hartmann, D. H.; Brainerd, J. J.; Briggs, M.; Paciesas, W. S.; Pendleton, G.; Kouveliotou, C.; Fishman, G.; Blumenthal, G.; Brock, M.

1994-01-01

289

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

290

High-energy charged particle bursts in the near-Earth space as earthquake precursors  

Microsoft Academic Search

The experimental data on high-energy charged particle fluxes, obtained in various near-Earth space experiments (MIR orbital station, METEOR-3, GAMMA and SAMPEX satellites) were processed and analyzed with the goal to search for particle bursts. Particle bursts have been selected in every experiment considered. It was shown that the significant part of high-energy charged particle bursts correlates with seismic activity. Moreover,

S. Yu. Aleksandrin; A. M. Galper; L. A. Grishantzeva; S. V. Koldashov; L. V. Maslennikov; A. M. Murashov; P. Picozza; V. Sgrigna; S. A. Voronov

2003-01-01

291

Bursting in the near-surface boundary layer: Comparisons between realistic models and observations  

SciTech Connect

In this paper, the authors examine the stable, nocturnal boundary layer, bursting phenomena. Bursting (or intermittent breakdowns from turbulent to laminar flow) can occur if the critical Richardson number, Ri{sub c}, is exceeded. During the bursting process, which occurs at irregular, chaotic intervals, periods of active turbulence (large sudden changes in u*) are followed by calm periods when the air temperatures near the ground can drop rapidly. During the turbulent periods, air temperatures can also rise considerably.

ReVelle, D.O.; Coulter, R.C.

1995-12-31

292

fMRI analysis of active, passive and electrically stimulated ankle dorsiflexion  

Microsoft Academic Search

Ankle dorsiflexion (ADF) is an integral component in gait. The objective of this study was to define, using functional magnetic resonance imaging (fMRI) in healthy volunteers (n=12), the brain regions that are activated during Electrical Stimulation (ES)-induced ADF movements, and compare this to the pattern of activation occurring during active and passive ADF. Concurrent electromyography (EMG) was used to monitor

Susan Francis; Xia Lin; Samia Aboushoushah; Thomas P. White; Margaret Phillips; Richard Bowtell; Cris S. Constantinescu

2009-01-01

293

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

294

Understanding the Continuum Spectra of Short Soft Gamma Repeater Bursts  

NASA Technical Reports Server (NTRS)

The spectra of short soft gamma repeater (SGR) bursts at photon energies above -15 keV are often well described by an optically thin thermal bremsstrahlung model (i.e., F(E) - E^-1 * exp(-E/kT) ) with kT=20-40 keV. However, the spectral shape burst continuum at lower photon energies (down to -2 keV) is not well established. It is important to better understand the SGR burst spectral properties at lower energies since inadequate description of the burst spectral continuum could lead to incorrect conclusions, such as existence of spectral lines. Here, we present detailed spectral investigations (in 2-200 keV) of 163 bursts from SGR 1806-20, all detected with Rossi X-ray Timing Explorer during the 2004 active episode that included the giant flare on 27 December 2004. We find that the great majority of burst spectra are well represented by the combination of a blackbody plus a OTTB models.

Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Finger, Mark H.; Lenter, Geoffrey; Patel, Sandeep K.; Swank, Jean

2006-01-01

295

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

296

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

297

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

298

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

299

On the Real-time Prediction Problems of Bursting Hashtags in Twitter  

E-print Network

Hundreds of thousands of hashtags are generated every day on Twitter. Only a few become bursting topics. Among the few, only some can be predicted in real-time. In this paper, we take the initiative to conduct a systematic study of a series of challenging real-time prediction problems of bursting hashtags. Which hashtags will become bursting? If they do, when will the burst happen? How long will they remain active? And how soon will they fade away? Based on empirical analysis of real data from Twitter, we provide insightful statistics to answer these questions, which span over the entire lifecycles of hashtags.

Kong, Shoubin; Feng, Ling; Zhao, Zhe; Ye, Fei

2014-01-01

300

Linking Burst-Only X-Ray Binary Sources to Faint X-Ray Transients  

NASA Astrophysics Data System (ADS)

Burst-only sources are X-ray sources discovered thanks to their bursting activity with no associated emission (at least with the monitoring instrument that led to their discovery). This bursting activity consists in one single short (tens of seconds to minutes) burst of X-ray emission, with spectral and timing properties consistent with thermonuclear (type I) bursts usually occurring on the surface of a neutron star. This likely provides a tight link between burst-only sources and neutron star X-ray binary transients. We carried out a series of snapshot observations of the entire sample of burst-only sources with the Swift satellite. We found a few sources in outburst and detected faint candidates, likely representing their quiescent counterparts. To provide a more comprehensive view, we analyzed data for three quasi-persistent faint X-ray binary transients, another sub-class closely related to burst-only sources. We discuss burst-only sources and quasi-persistent sources in the framework of neutron star transients, providing clues on their nature.

Campana, S.

2009-07-01

301

Evaporation causes flare-related radio burst continuum depressions  

NASA Astrophysics Data System (ADS)

We study the active region NOAA 6718 and the development of a (2N, M3.6) flare in radio and H-alpha. Due to our knowledge of the magnetic field structure in the active region, we are able to associate the different radio flare burst components with the stages in the H-alpha flare evolution. A discussion of the data in terms of chromospheric flare kernel heating reveals that in the present case the observed flare-related radio burst continuum switch-off is caused by the penetration of hot, ablated gas into the coronal radio source.

Aurass, H.; Hofmann, A.; Magun, A.; Soru-Escaut, I.; Zlobec, P.

1993-05-01

302

Comparison of Gastric Electrical Activity and Gastric Emptying in Healthy and Dyspeptic Children  

Microsoft Academic Search

To assess and compare gastric electrical activity and gastric emptying recorded from dyspeptic and healthy children, cutaneous electrogastrography and ultrasound examination of the gastric emptying were simultaneously performed in 52 children with nonulcer dyspepsia and 114 healthy children. Symptoms were scored from 0 (none) to 6 (severe). A higher percentage of tachygastria, a higher instability of gastric power, and a

Giuseppe Riezzo; Marisa Chiloiro; Vito Guerra; Osvaldo Borrelli; Gennaro Salvia; Salvatore Cucchiara

2000-01-01

303

Buckling of dielectric elastomeric plates for soft, electrically active microfluidic pumps  

E-print Network

channels. These structures consist of a dielectric elastomer conned between two compliant electrodes dielectric elastomer (DE) is sandwiched between two electrode lms, creating a composite plate (Fig. 1a of the electrically active microfluidic pump: a thin composite plate consists of a prestrained dielectric elastomer

Aksay, Ilhan A.

304

Spatio-temporal analysis of brain electrical activity in epilepsy based on cellular nonlinear networks  

Microsoft Academic Search

Epilepsy is the most common chronic disorder of the nervous system. Generally, epileptic seizures appear without foregoing sign or warning. The problem of detecting a possible pre-seizure state in epilepsy from EEG signals has been addressed by many authors over the past decades. Different approaches of time series analysis of brain electrical activity already are providing valuable insights into the

Frank Gollas; Ronald Tetzlaff

2009-01-01

305

Active and Collaborative Learning in an Introductory Electrical and Computer Engineering Course  

ERIC Educational Resources Information Center

Active and collaborative learning instruments were introduced into an introductory electrical and computer engineering course. These instruments were designed to assess specific learning objectives and program outcomes. Results show that students developed an understanding comparable to that of more advanced students assessed later in the…

Kotru, Sushma; Burkett, Susan L.; Jackson, David Jeff

2010-01-01

306

ALTERATION OF CARDIAC ELECTRICAL ACTIVITY BY WATER-LEACHABLE COMPONENTS OF RESIDUAL OIL FLY ASH (ROFA)  

EPA Science Inventory

Alteration of cardiac electrical activity by water-leachable components of residual oil fly ash (ROFA) Desuo Wang, Yuh-Chin T. Huang*, An Xie, Ting Wang *Human Studies Division, NHEERL, US EPA 104 Mason Farm Road, Chapel Hill, NC 27599 Department of Basic ...

307

Development of electrical activity in cardiac myocyte aggregates derived from mouse embryonic stem cells  

E-print Network

. Development of electrical activity in cardiac myo- cyte aggregates derived from mouse embryonic stem cells. Am.1152/ajpheart. 01106.2001.--Embryonic stem cells differentiate into cardiac myocytes, repeating in vitro; connexin43; mouse embryonic stem cells EMBRYONIC STEM (ES) cells differentiate in vitro into various cell

308

Engineering support activities for the Apollo 17 Surface Electrical Properties Experiment.  

NASA Technical Reports Server (NTRS)

Description of the engineering support activities which were required to ensure fulfillment of objectives specified for the Apollo 17 SEP (Surface Electrical Properties) Experiment. Attention is given to procedural steps involving verification of hardware acceptability to the astronauts, computer simulation of the experiment hardware, field trials, receiver antenna pattern measurements, and the qualification test program.

Cubley, H. D.

1972-01-01

309

Electrical relaxation in double doped calcium fluoride and activation volume for the RI relaxation  

E-print Network

Electrical relaxation in double doped calcium fluoride and activation volume for the RI relaxation over a temperature range 150-250 K for various samples of calcium fluoride doped with two different). In addition, the complex dielectric constant for calcium fluoride doped with either erbium or terbium has been

Paris-Sud XI, Université de

310

Brain electrical activity changes in treatment refractory schizophrenics after olanzapine treatment  

Microsoft Academic Search

The aim of the present study was to identify brain electrical activity changes generated by olanzapine (OLZ) in treatment refractory schizophrenics (TRS). 14 paranoid TRS (31.5±8.39 years old) were evaluated before and after 8 weeks of OLZ treatment. Psychopathology was evaluated by means of total BPRS and PANSS scores. Resting EEG was recorded in the pre (under typical neuroleptics) and

Luis F. Cerdán; Miguel A. Guevara; Araceli Sanz; Claudia Amezcua; Julieta Ramos-Loyo

2005-01-01

311

DLC based BioMEMS probe for electrical activity recording of tissues and cells  

Microsoft Academic Search

An implantable probe for electrical activity monitoring of living tissues was engineered and fabricated on a silicon chip at IMT-Bucharest, Romania. In order to improve the mechanical resistance and biocompatibility of the device, the technology of Thermionic Vacuum Arc (TVA) deposition was used for coating the implantable parts with diamond like carbon (DLC) with zero stress (0SC). The paper presents

C. Moldovan; R. Iosub; C. P. Lungu; A. M. Lungu; B. Firtat; C. Roman; R. Albulescu

312

Transition to Bursting via Deterministic Chaos  

NASA Astrophysics Data System (ADS)

We study statistical properties of the irregular bursting arising in a class of neuronal models close to the transition from spiking to bursting. Prior to the transition to bursting, the systems in this class develop chaotic attractors, which generate irregular spiking. The chaotic spiking gives rise to irregular bursting. The duration of bursts near the transition can be very long. We describe the statistics of the number of spikes and the interspike interval distributions within one burst as functions of the distance from criticality.

Medvedev, Georgi S.

2006-07-01

313

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....

314

162 Electrical and Computer Engineering 163 Courses and projects that actively involve them in their own education and  

E-print Network

162 Electrical and Computer Engineering 163 · Courses and projects that actively involve them of technology Graduate and undergraduate programs in electrical and computer engineering offer concentrations in electrical and computer engineering that the student can build upon to construct a custom program. Because

Richards-Kortum, Rebecca

315

MBE growth of active regions for electrically pumped, cw-operating GaSb-based VCSELs  

NASA Astrophysics Data System (ADS)

Electrically pumped, cw-operating, single-mode GaSb-based VCSELs are attractive light sources for trace-gas sensing systems using tunable diode laser absorption spectroscopy (TDLAS) [A. Vicet, D.A. Yarekha, A. Pérona, Y. Rouillard, S. Gaillard, Spectrochimica Acta Part A 58 (2002) 2405-2412]. Only recently, the first electrically pumped (EP) devices emitting at 2.325 ?m in cw-mode at room temperature have been reported [A. Bachmann, T. Lim, K. Kashani-Shirazi, O. Dier, C. Lauer, M.-C. Amann, Electronics Letters 44(3) (2008) 202-203]. The fabrication of these devices employs the molecular beam epitaxy (MBE) growth of GaSb/AlAsSb-distributed Bragg mirrors, a multi-quantum-well active region made of AlGaAsSb/InGaAsSb and an InAsSb/GaSb-buried-tunnel junction. As VCSELs are usually driven under high injection rates, an optimum electrical design of active regions is essential for high-performance devices. In this paper we present an enhanced simulation of current flow in the active region under operation conditions. The calculation includes carrier transport by drift, diffusion and tunneling. We discuss different design criteria and material compositions for active regions. Active regions with various barrier materials were incorporated into edge emitter samples to evaluate their performance. Aluminum-containing barriers show better internal efficiency compared to active regions with GaSb as the barrier material.

Kashani-Shirazi, K.; Bachmann, A.; Boehm, G.; Ziegler, S.; Amann, M.-C.

2009-03-01

316

Emergent bursting and synchrony in computer simulations of neuronal cultures  

PubMed Central

Experimental studies of neuronal cultures have revealed a wide variety of spiking network activity ranging from sparse, asynchronous firing to distinct, network-wide synchronous bursting. However, the functional mechanisms driving these observed firing patterns are not well understood. In this work, we develop an in silico network of cortical neurons based on known features of similar in vitro networks. The activity from these simulations is found to closely mimic experimental data. Furthermore, the strength or degree of network bursting is found to depend on a few parameters: the density of the culture, the type of synaptic connections, and the ratio of excitatory to inhibitory connections. Network bursting gradually becomes more prominent as either the density, the fraction of long range connections, or the fraction of excitatory neurons is increased. Interestingly, biologically prevalent values of parameters result in networks that are at the transition between strong bursting and sparse firing. Using principal components analysis, we show that a large fraction of the variance in firing rates is captured by the first component for bursting networks. These results have implications for understanding how information is encoded at the population level as well as for why certain network parameters are ubiquitous in cortical tissue. PMID:22514531

Maheswaranathan, Niru; Ferrari, Silvia; VanDongen, Antonius M. J.; Henriquez, Craig S.

2012-01-01

317

Direct activation of sparse, distributed populations of cortical neurons by electrical microstimulation  

PubMed Central

Summary For over a century, electrical microstimulation has been the most direct method for causally linking brain function with behavior. Despite this long history, it is still unclear how the activity of neural populations is affected by stimulation. For example, there is still no consensus on where activated cells lie, or on the extent to which neural processes such as passing axons near the electrode are also activated. Past studies of this question have proven difficult because microstimulation interferes with electrophysiological recordings, which in any case provide only coarse information about the location of activated cells. We used two-photon calcium imaging, an optical method, to circumvent these hurdles. We found that microstimulation sparsely activates neurons around the electrode, sometimes as far as millimeters away, even at low currents. The pattern of activated neurons likely arises from the direct activation of axons in a volume with a diameter of tens of microns. PMID:19709632

Histed, Mark H.; Bonin, Vincent; Reid, R. Clay

2010-01-01

318

Silicon neurons that burst when primed Kai M Hynna, Kwabena Boahen  

E-print Network

activity within the cortex [1]. The thalamus is ideally situated to mediate bursting, as (most) sensory could be primed to burst by feedback axons from the cortex to the thalamus, which pass through a thin layer of cells surrounding the thalamus called the reticular nucleus. These reticular cells

Boahen, Kwabena

319

Gamma-Ray Burst Lines  

E-print Network

The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980's, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features around 400 keV. During the 1990's the situation has become much less clear. A small fraction of bursts observed with BATSE have statistically significant low-energy features, but the reality of the features is suspect because in several cases the data of the BATSE detectors appear to be inconsistent. Furthermore, most of the possible features appear in emission rather than the expected absorption. Analysis of data from other instruments has either not been finalized or has not detected lines.

Michael S. Briggs

1999-10-20

320

The INTEGRAL Burst Alert System  

E-print Network

We describe the INTEGRAL Burst Alert System (IBAS): the automatic software developed at the INTEGRAL Science Data Center to allow the rapid distribution of the coordinates of the Gamma-Ray Bursts detected by INTEGRAL. IBAS is implemented as a ground based system, working on the near-real time telemetry stream. It is expected that the system will detect more than one GRB per month in the field of view of the main instruments. Positions with an accuracy of a few arcminutes will be distributed to the community for follow-up observations within a few tens of seconds of the event. The system will also upload commands to optimize the possible detection of bursts in the visible band with the INTEGRAL Optical Monitor Camera.

S. Mereghetti; D. I. Cremonesi; J. Borkowski

2001-01-08

321

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

322

Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region  

E-print Network

The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

Kachakhidze, M K; Kachakhidze, N K

2012-01-01

323

University of Virginia Physical Science SOL Activities: Introduction to Static Electricity  

NSDL National Science Digital Library

This lesson plan features a creative update of the "Kissing Balloon", plus three additional activities designed to enhance student understanding of electric charge, electron transfer, and polarization. Estimated set-up time is about 15 minutes. Conceptual questions are posed and answered by the authors. Included are printable student data sheets, background information on static electricity, and modifications for students with disabilities. This lesson is part of a larger collection generated by the University of Virginia Department of Physics outreach program. See Related Materials for a link to the full collection.

2006-11-13

324

Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region  

NASA Astrophysics Data System (ADS)

The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

Kachakhidze, M. K.; Kereselidze, Z. A.; Kachakhidze, N. K.

2013-01-01

325

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

326

UHF and S-band radar observations of electrically active storm cells  

NASA Technical Reports Server (NTRS)

The UHF-band and S-band research radars of NASA Goddard's atmospheric sciences research facility at Wallop's Island, Virginia are used to study the correlation between the location of radar-detected electrical activity in a storm cell and its precipitation reflectivity structure. The technique used to make the measurements is discussed and some typical results are presented. The existence of a bimodal distribution of lightning activity as a function of altitude is reported and supported by the data. The vertical structure of the electrical activity may be evidence of K and/or J processes. The technique used is very valuable, and provides high-resolution radar data of both reflectivities and flash density.

Gerlach, J. C.; Mazur, V.

1983-01-01

327

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

328

Unloaded Shortening Velocity of Voluntarily and Electrically Activated Human Dorsiflexor Muscles In Vivo  

PubMed Central

We have previously shown that unloaded shortening velocity (V0) of human plantar flexors can be determined in vivo, by applying the “slack test” to submaximal voluntary contractions (J Physiol 567:1047–1056, 2005). In the present study, to investigate the effect of motor unit recruitment pattern on V0 of human muscle, we modified the slack test and applied this method to both voluntary and electrically elicited contractions of dorsiflexors. A series of quick releases (i.e., rapid ankle joint rotation driven by an electrical dynamometer) was applied to voluntarily activated dorsiflexor muscles at three different contraction intensities (15, 50, and 85% of maximal voluntary contraction; MVC). The quick-release trials were also performed on electrically activated dorsiflexor muscles, in which three stimulus conditions were used: submaximal (equal to 15%MVC) 50-Hz stimulation, supramaximal 50-Hz stimulation, and supramaximal 20-Hz stimulation. Modification of the slack test in vivo resulted in good reproducibility of V0, with an intraclass correlation coefficient of 0.87 (95% confidence interval: 0.68–0.95). Regression analysis showed that V0 of voluntarily activated dorsiflexor muscles significantly increased with increasing contraction intensity (R2?=?0.52, P<0.001). By contrast, V0 of electrically activated dorsiflexor muscles remained unchanged (R2<0.001, P?=?0.98) among three different stimulus conditions showing a large variation of tetanic torque. These results suggest that the recruitment pattern of motor units, which is quite different between voluntary and electrically elicited contractions, plays an important role in determining shortening velocity of human skeletal muscle in vivo. PMID:20885951

Sasaki, Kazushige; Ishii, Naokata

2010-01-01

329

Gamma-Ray Burst Smashes a Record  

NSF Publications Database

... death of a massive star as it collapsed into a black hole, was detected on Sept. 4. The burst comes ... this burst comes from a single star. Scientists find it puzzling how a single star could generate ...

330

A novel network of multipolar bursting interneurons generates theta frequency oscillations in neocortex.  

PubMed

GABAergic interneurons can phase the output of principal cells, giving rise to oscillatory activity in different frequency bands. Here we describe a new subtype of GABAergic interneuron, the multipolar bursting (MB) cell in the mouse neocortex. MB cells are parvalbumin positive but differ from fast-spiking multipolar (FS) cells in their morphological, neurochemical, and physiological properties. MB cells are reciprocally connected with layer 2/3 pyramidal cells and are coupled with each other by chemical and electrical synapses. MB cells innervate FS cells but not vice versa. MB to MB cell as well as MB to pyramidal cell synapses exhibit paired-pulse facilitation. Carbachol selectively induced synchronized theta frequency oscillations in MB cells. Synchrony required both gap junction coupling and GABAergic chemical transmission, but not excitatory glutamatergic input. Hence, MB cells form a distinct inhibitory network, which upon cholinergic drive can generate rhythmic and synchronous theta frequency activity, providing temporal coordination of pyramidal cell output. PMID:12797964

Blatow, Maria; Rozov, Andrei; Katona, Istvan; Hormuzdi, Sheriar G; Meyer, Axel H; Whittington, Miles A; Caputi, Antonio; Monyer, Hannah

2003-06-01

331

Search for electric dipole moment in 129Xe atom using active nuclear spin maser  

NASA Astrophysics Data System (ADS)

An experimental search for an electric dipole moment in the diamagnetic atom 129Xe is in progress through the precision measurement of spin precession frequency using an active nuclear spin maser. A 3He comagnetometer has been incorporated into the active spin maser system in order to cancel out the long-term drifts in the external magnetic field. Also, a double-cell geometry has been adopted in order to suppress the frequency shifts due to interaction with polarized Rb atoms. The first EDM measurement with the 129Xe active spin maser and the 3He comagnetometer has been conducted.

Ichikawa, Y.; Chikamori, M.; Ohtomo, Y.; Hikota, E.; Sakamoto, Y.; Suzuki, T.; Bidinosti, C. P.; Inoue, T.; Furukawa, T.; Yoshimi, A.; Suzuki, K.; Nanao, T.; Miyatake, H.; Tsuchiya, M.; Yoshida, N.; Shirai, H.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.

2014-03-01

332

The Most Remote Gamma-Ray Burst  

NASA Astrophysics Data System (ADS)

ESO Telescopes Observe "Lightning" in the Young Universe Summary Observations with telescopes at the ESO La Silla and Paranal observatories (Chile) have enabled an international team of astronomers [1] to measure the distance of a "gamma-ray burst", an extremely violent, cosmic explosion of still unknown physical origin. It turns out to be the most remote gamma-ray burst ever observed . The exceedingly powerful flash of light from this event was emitted when the Universe was very young, less than about 1,500 million years old, or only 10% of its present age. Travelling with the speed of light (300,000 km/sec) during 11,000 million years or more, the signal finally reached the Earth on January 31, 2000. The brightness of the exploding object was enormous, at least 1,000,000,000,000 times that of our Sun, or thousands of times that of the explosion of a single, heavy star (a "supernova"). The ESO Very Large Telescope (VLT) was also involved in trail-blazing observations of another gamma-ray burst in May 1999, cf. ESO PR 08/99. PR Photo 28a/00 : Sky field near GRB 000131 . PR Photo 28b/00 : The fading optical counterpart of GRB 000131 . PR Photo 28c/00 : VLT spectrum of GRB 000131 . What are Gamma-Ray Bursts? One of the currently most active fields of astrophysics is the study of the mysterious events known as "gamma-ray bursts" . They were first detected in the late 1960's by instruments on orbiting satellites. These short flashes of energetic gamma-rays last from less than a second to several minutes. Despite much effort, it is only within the last few years that it has become possible to locate the sites of some of these events (e.g. with the Beppo-Sax satellite ). Since the beginning of 1997, astronomers have identified about twenty optical sources in the sky that are associated with gamma-ray bursts. They have been found to be situated at extremely large (i.e., "cosmological") distances. This implies that the energy release during a gamma-ray burst within a few seconds is larger than that of the Sun during its entire life time (about 10,000 million years). "Gamma-ray bursts" are in fact by far the most powerful events since the Big Bang that are known in the Universe. While there are indications that gamma-ray bursts originate in star-forming regions within distant galaxies, the nature of such explosions remains a puzzle. Recent observations with large telescopes, e.g. the measurement of the degree of polarization of light from a gamma-ray burst in May 1999 with the VLT ( ESO PR 08/99), are now beginning to cast some light on this long-standing mystery. The afterglow of GRB 000131 ESO PR Photo 28a/00 ESO PR Photo 28a/00 [Preview - JPEG: 400 x 475 pix - 41k] [Normal - JPEG: 800 x 949 pix - 232k] [Full-Res - JPEG: 1200 x 1424 pix - 1.2Mb] ESO PR Photo 28b/00 ESO PR Photo 28b/00 [Preview - JPEG: 400 x 480 pix - 67k] [Normal - JPEG: 800 x 959 pix - 288k] [Full-Res - JPEG: 1200 x 1439 pix - 856k] Caption : PR Photo 28a/00 is a colour composite image of the sky field around the position of the gamma-ray burst GRB 000131 that was detected on January 31, 2000. It is based on images obtained with the ESO Very Large Telescope at Paranal. The object is indicated with an arrow, near a rather bright star (magnitude 9, i.e., over 1 million times brighter than the faintest objects visible on this photo). This and other bright objects in the field are responsible for various unavoidable imaging effects, caused by optical reflections (ring-shaped "ghost images", e.g. to the left of the brightest star) and detector saturation effects (horizontal and vertical straight lines and coloured "coronae" at the bright objects, and areas of "bleeding", e.g. below the bright star). PR Photo 28b/00 shows the rapid fading of the optical counterpart of GRB 000131 (slightly left of the centre), by means of exposures with the VLT on February 4 (upper left), 6 (upper right), 8 (lower left) and March 5 (lower right). It is no longer visible on the last photo. Techni

2000-10-01

333

Jovian S burst generation by Alfvén waves  

NASA Astrophysics Data System (ADS)

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tubes connecting Io or Io's wake to Jupiter. Electrons responsible for the emission are thought to be accelerated from Io to Jupiter. We present simulations of this hot electron population under the assumption of acceleration by Alfvén waves in the Io flux tube. Outside of limited acceleration regions where a parallel electric field associated with Alfvén waves exists, the electrons are supposed to have an adiabatic motion along the magnetic field lines. Near Jupiter a loss cone appears in the magnetically mirrored electron population, which is able to amplify extraordinary (X) mode radio waves. The X-mode growth rate is computed, which allows us to build theoretical dynamic spectra of the resulting Jovian radio emissions, whose characteristics match those observed for Jovian S bursts.

Hess, S.; Mottez, F.; Zarka, P.

2007-11-01

334

Active control of thermoacoustic amplification in a thermo-acousto-electric engine  

NASA Astrophysics Data System (ADS)

In this paper, a new approach is proposed to control the operation of a thermoacoustic Stirling electricity generator. This control basically consists in adding an additional acoustic source to the device, connected through a feedback loop to a reference microphone, a phase-shifter, and an audio amplifier. Experiments are performed to characterize the impact of the feedback loop (and especially that of the controlled phase-shift) on the overall efficiency of the thermal to electric energy conversion performed by the engine. It is demonstrated that this external forcing of thermoacoustic self-sustained oscillations strongly impacts the performance of the engine, and that it is possible under some circumstances to improve the efficiency of the thermo-electric transduction, compared to the one reached without active control. Applicability and further directions of investigation are also discussed.

Olivier, Come; Penelet, Guillaume; Poignand, Gaelle; Lotton, Pierrick

2014-05-01

335

Electro-Active Device Using Radial Electric Field Piezo-Diaphragm for Control of Fluid Movement  

NASA Technical Reports Server (NTRS)

A fluid-control electro-active device includes a piezo-diaphragm made from a ferroelectric material sandwiched by first and second electrode patterns configured to introduce an electric field into the ferroelectric material when voltage is applied thereto. The electric field originates at a region of the ferroelectric material between the first and second electrode patterns, and extends radially outward from this region of the ferroelectric material and substantially parallel to the plane of the ferroelectric material. The piezo-diaphragm deflects symmetrically about this region in a direction substantially perpendicular to the electric field. An annular region coupled to and extending radially outward from the piezo-diaphragm perimetrically borders the piezo-diaphragm, A housing is connected to the region and at least one fluid flow path with piezo-diaphragm disposed therein.

Bryant, Robert G. (Inventor); Working, Dennis C. (Inventor)

2005-01-01

336

Properties of the electromagnetic field associated with the electrical activity of severe storms  

NASA Astrophysics Data System (ADS)

Quantitative relations are established among the components of the natural electromagnetic field, to yield values for vertical components of electricity and magnetism, magnetic vertical and horizontal components, and vertical electrical and magnetic horizontal components. It is also noted that, under calm conditions, the horizontal magnetic component has the same intensity in north-south orientation as in the east-west, allowing this component to be used in indicating the direction toward severe storm conditions. Attention given to the intensity of the vertical magnetic component under both tranquil and perturbed conditions indicates that this component can be used in preliminary form to serve as a quantitative index that indicates the presence of severe storms with associated electrical activity.

Pascual Garcia, A.

337

Application of electrical methods to measure microbial activity in soils: Preliminary microcosm results  

SciTech Connect

The application of the geophysical technique known as self-potential to the measurement of microbial activity was tested on laboratory microcosms containing ferric iron and iron-reducing bacteria Shewanella alga BrY. Measurements of the electrical response of silver-coated copper electrodes distributed along a Teflon probe inserted into sterile and inoculated layers containing either ferric chloride, ferric citrate, or ferric oxide rich soil were recorded over hours or days. Strong electrical signals reached values more negative than {minus}400 mV for all types of inoculated ferric iron layers. Electric signals in sterile control layers, by contrast, rarely reached values more negative than {minus}150 mV. These preliminary experiments indicate that it may be possible to apply the self-potential geophysical method to monitor bioremediation in the field.

Cox, B.L. Sweet, A.; Majer, E.

1997-12-01

338

Relative clock verifies endogenous bursts of human dynamics  

NASA Astrophysics Data System (ADS)

Temporal bursts are widely observed in many human-activated systems, which may result from both endogenous mechanisms like the highest-priority-first protocol and exogenous factors like the seasonality of activities. To distinguish the effects from different mechanisms is thus of theoretical significance. This letter reports a new timing method by using a relative clock, namely the time length between two consecutive events of an agent is counted as the number of other agents' events appeared during this interval. We propose a model, in which agents act either in a constant rate or with a power-law inter-event time distribution, and the global activity either keeps unchanged or varies periodically vs. time. Our analysis shows that the bursts caused by the heterogeneity of global activity can be eliminated by setting the relative clock, yet the bursts from real individual behaviors still exist. We perform extensive experiments on four large-scale systems, the search engine by AOL, a social bookmarking system —Delicious, a short-message communication network, and a microblogging system —Twitter. Seasonality of global activity is observed, yet the bursts cannot be eliminated by using the relative clock.

Zhou, Tao; Zhao, Zhi-Dan; Yang, Zimo; Zhou, Changsong

2012-01-01

339

Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift  

E-print Network

Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift to GLASTto GLAST Bing ZhangBing ZhangGehrels, et al), et al) #12;Gamma-ray bursts: the mostGamma-ray bursts: the most violent explosions fireball central photosphere internal external shocks engine (shocks) (reverse) (forward) gamma-ray UV

California at Santa Cruz, University of

340

Light Curves of Swift Gamma Ray Bursts  

E-print Network

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short - long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars.

Paolo Cea

2006-06-05

341

Endogenous burst capability in a neuron of the gastric mill pattern generator of the spiny lobster Panulirus interruptus.  

PubMed

The gastric system of the lobster stomatogastric ganglion has previously been thought to include no neurons capable of endogenous bursting. We describe conditions under which one of the motorneurons, the CP cell, can burst endogenously in a free-running manner in the absence of other phasic network activity. Isolated preparations of the foregut nervous system were used, and the CP bursting was either spontaneous or was activated by continuous stimulation of an input nerve. Three criteria were applied to establish the endogenous nature of such burst generation in CP: absence of phasic input, reset of the bursting pattern by pulses of current in a characteristic phase-dependent manner, and modulation of burst rate by sustained injected current. (1) The firing of other cells which are known to be related synaptically to CP was monitored in nerve records. These other cells were either silent or fired only tonically. Cross-correlograms showed that CP bursting was not ascribable to phasic activity in these other network cells. (2) A depolarizing current pulse of sufficient strength injected intracellularly between bursts triggered a burst prematurely and reset the subsequent rhythm. A hyperpolarizing pulse during a burst terminated it and reset the subsequent rhythm. Reset behavior was similar to that described for other endogenous bursters. (3) Application of a positive-going ramp current initially caused an increase in burst rate, as described for other endogenous bursters. However, further depolarization caused a slower burst rate due to lengthening of the individual bursts, although mean firing frequency continued to increase throughout the range tested. Such free-running endogenous repetitive bursting appeared to result from the CP's ability to produce slow regenerative depolarizations ("plateau potentials"). When bursting was present, so was the plateau property, as determined by I-V analysis and by the ability of brief current pulses to trigger and terminate bursts. The previous inability to observe endogenous bursting in preparations with central input removed may be due to the usual absence of the plateau property in such preparations. CP bursting during normal gastric mill rhythms, while underlain by plateau potentials, is strongly controlled by network interactions. CP appears not to be well placed in the network to be considered a source of normal gastric rhythmicity. Nevertheless, endogenous bursting in CP may explain some of the partial gastric rhythms seen in behavioral studies, and illustrates one way that cellular properties might contribute to rhythmic behaviors. PMID:6502157

Hartline, D K; Russell, D F

1984-09-01

342

Electrically Active Magnetic Nanoparticles for Concentrating and Detecting Bacillus anthracis Spores in a Direct-Charge Transfer Biosensor  

Microsoft Academic Search

Bacillus anthracis, the causative agent of anthrax, is considered as one of the most important pathogens in the list of bioterrorism threats. This paper describes the synthesis of electrically active magnetic (EAM) nanoparticles and their application in a direct-charge transfer biosensor for detecting B. anthracis Sterne endospores. These EAM nanoparticles were synthesized from aniline monomer made electrically active by acid

Sudeshna Pal; Emma B. Setterington; Evangelyn C. Alocilja

2008-01-01

343

An investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere  

NASA Technical Reports Server (NTRS)

Several related topics are briefly discussed. Reviewed here is work on an investigation of plasma wave phenomena associated with the question of lightning on Venus. The work supported the contention that lightning is at least a candidate explanation for many of the 100 Hz-only Pioneer Venus orbital electric field detector (OEFD) signals. A review of the work on the investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere is given. A summary is given of our analysis of data from 23 OEFD observing periods as well as a discussion of the properties of specifically multifrequency events. Our opportunity to work on this topic was not sufficient to draw any firm conclusions about the origins of the multifrequency bursts, but we call attention to what we consider to be several candidate sources. Also discussed are case studies to test for evidence of whistler mode propagation from subionospheric sources, results of a search for dispersive effects in the OEFD data, the results for a search for simultaneous 100 Hz and 730 Hz observations at altitudes below 150 km, changes with altitude in dispersive broadening effects in the time signatures of 100 Hz bursts, and a survey of activity at altitudes above 1000 km.

Carpenter, D. L.

1992-01-01

344

WDM burst switching for petabit capacity routers  

Microsoft Academic Search

WDM burst switching is an approach to building very high capacity routing switches based on optical data paths and electronic control. Burst switches assign user data bursts to channels in WDM links on-the-fly in order to provide efficient statistical multiplexing of high rate data channels. The overall system architecture is designed to facilitate the introduction of optical switching components as

Yuhua Chen; Jonathan S. Turner

1999-01-01

345

30 CFR 57.3461 - Rock bursts.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Rock bursts. 57.3461 Section 57.3461...Precautions-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty...

2011-07-01

346

30 CFR 57.3461 - Rock bursts.  

...2014-07-01 2014-07-01 false Rock bursts. 57.3461 Section 57.3461...Precautions-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty...

2014-07-01

347

30 CFR 57.3461 - Rock bursts.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Rock bursts. 57.3461 Section 57.3461...Precautions-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty...

2010-07-01

348

30 CFR 57.3461 - Rock bursts.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Rock bursts. 57.3461 Section 57.3461...Precautions-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty...

2012-07-01

349

30 CFR 57.3461 - Rock bursts.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Rock bursts. 57.3461 Section 57.3461...Precautions-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty...

2013-07-01

350

Adaptive Optical Burst Switching Thomas Bonald  

E-print Network

Adaptive Optical Burst Switching Thomas Bonald Telecom ParisTech Paris, France thomas.indre,sara.oueslati}@orange-ftgroup.com Abstract--We propose a modified version of Optical Burst Switching (OBS) that adapts the size of switched refer to this technique as Adaptive Optical Burst Switching. We prove that the proposed scheme

Bonald, Thomas

351

Association of Energetic Neutral Atom Bursts and Magnetospheric Substorms  

NASA Technical Reports Server (NTRS)

In this paper we present evidence that short-lived bursts of energetic neutral atoms (ENAs) observed with the Comprehensive Energetic Particle and Pitch Angle Distribution/Imaging Proton Spectrometer (CEPPAD/IPS) instrument on the Polar spacecraft are signatures of substorms. The IPS was designed primarily to measure ions in situ, with energies between 17.5 and 1500 keV. However, it has also proven to be a very capable ENA imager in the range 17.5 keV to a couple hundred keV. It was expected that some ENA signatures of the storm time ring current would be observed. Interestingly, IPS also routinely measures weaker, shorter-lived, and more spatially confined bursts of ENAs with duration from a few tens of minutes to a few hours and appearing once or twice a day. One of these bursts was quickly associated with magnetospheric and auroral substorm activity and has been reported in the literature [Henderson et al., 19971. In this paper we characterize ENA bursts observed from Polar and establish statistically their association with classic substorm signatures (global auroral onsets, electron and ion injections, AL drops, and Pi2 onsets). We conclude that -90% of the observed ENA bursts are associated with classic substorms and thus represent a new type of substorm signature.

Jorgensen, A. M.; Kepko, L.; Henderson, M. G.; Spence, H. E.; Reeves, G. D.; Sigwarth, J. B.; Frank, L. A.

2000-01-01

352

Broadband Spectral Investigations of SGR J1550-5418 Bursts  

E-print Network

We present the results of our broadband spectral analysis of 42 SGR J1550-5418 bursts simultaneously detected with the Swift/X-ray Telescope (XRT) and the Fermi/Gamma-ray Burst Monitor (GBM), during the 2009 January active episode of the source. The unique spectral and temporal capabilities of the XRT Windowed Timing mode have allowed us to extend the GBM spectral coverage for these events down to the X-ray domain (0.5-10 keV). Our earlier analysis of the GBM data found that the SGR J1550-5418 burst spectra were described equally well with a Comptonized model or with two blackbody functions; the two models were statistically indistinguishable. Our new broadband (0.5 - 200 keV) spectral fits show that, on average, the burst spectra are better described with two blackbody functions than with the Comptonized model. Thus, our joint XRT/GBM analysis clearly shows for the first time that the SGR J1550-5418 burst spectra might naturally be expected to exhibit a more truly thermalized character, such as a two-blackbo...

Lin, Lin; Baring, Matthew G; Granot, Jonathan; Kouveliotou, Chryssa; Kaneko, Yuki; van der Horst, Alexander; Gruber, David; von Kienlin, Andreas; Younes, George; Watts, Anna L; Gehrels, Neil

2012-01-01

353

Signal role for activation of caspase-3-like protease and burst of superoxide anions during Ce 4+ -induced apoptosis of cultured Taxus cuspidata cells  

Microsoft Academic Search

The signal events of 1 mM Ce4+ (Ce(NH4)2(NO3)6)-induced apoptosis of cultured Taxus cuspidata cells were investigated. The percentage of apoptotic cells increased from 0.82% to 51.32% within 6 days. Caspase-3-like protease activity became notable during the second day of Ce4+-treatment, and the maximum activity was 5-fold higher than that of control cells at the fourth day. When the experiment system was

Zhi-Qiang Ge; Song Yang; Jing-Sheng Cheng; Ying-Jin Yuan

2005-01-01

354

Defects in T-tubular electrical activity underlie local alterations of calcium release in heart failure  

PubMed Central

Action potentials (APs), via the transverse axial tubular system (TATS), synchronously trigger uniform Ca2+ release throughout the cardiomyocyte. In heart failure (HF), TATS structural remodeling occurs, leading to asynchronous Ca2+ release across the myocyte and contributing to contractile dysfunction. In cardiomyocytes from failing rat hearts, we previously documented the presence of TATS elements which failed to propagate AP and displayed spontaneous electrical activity; the consequence for Ca2+ release remained, however, unsolved. Here, we develop an imaging method to simultaneously assess TATS electrical activity and local Ca2+ release. In HF cardiomyocytes, sites where T-tubules fail to conduct AP show a slower and reduced local Ca2+ transient compared with regions with electrically coupled elements. It is concluded that TATS electrical remodeling is a major determinant of altered kinetics, amplitude, and homogeneity of Ca2+ release in HF. Moreover, spontaneous depolarization events occurring in failing T-tubules can trigger local Ca2+ release, resulting in Ca2+ sparks. The occurrence of tubule-driven depolarizations and Ca2+ sparks may contribute to the arrhythmic burden in heart failure. PMID:25288764

Crocini, Claudia; Coppini, Raffaele; Ferrantini, Cecilia; Yan, Ping; Loew, Leslie M.; Tesi, Chiara; Cerbai, Elisabetta; Poggesi, Corrado; Pavone, Francesco S.; Sacconi, Leonardo

2014-01-01

355

Sensory flow shaped by active sensing: sensorimotor strategies in electric fish.  

PubMed

Goal-directed behavior in most cases is composed of a sequential order of elementary motor patterns shaped by sensorimotor contingencies. The sensory information acquired thus is structured in both space and time. Here we review the role of motion during the generation of sensory flow focusing on how animals actively shape information by behavioral strategies. We use the well-studied examples of vision in insects and echolocation in bats to describe commonalities of sensory-related behavioral strategies across sensory systems, and evaluate what is currently known about comparable active sensing strategies in electroreception of electric fish. In this sensory system the sensors are dispersed across the animal's body and the carrier source emitting energy used for sensing, the electric organ, is moved while the animal moves. Thus ego-motions strongly influence sensory dynamics. We present, for the first time, data of electric flow during natural probing behavior in Gnathonemus petersii (Mormyridae), which provide evidence for this influence. These data reveal a complex interdependency between the physical input to the receptors and the animal's movements, posture and objects in its environment. Although research on spatiotemporal dynamics in electrolocation is still in its infancy, the emerging field of dynamical sensory systems analysis in electric fish is a promising approach to the study of the link between movement and acquisition of sensory information. PMID:23761474

Hofmann, Volker; Sanguinetti-Scheck, Juan I; Künzel, Silke; Geurten, Bart; Gómez-Sena, Leonel; Engelmann, Jacob

2013-07-01

356

Defects in T-tubular electrical activity underlie local alterations of calcium release in heart failure.  

PubMed

Action potentials (APs), via the transverse axial tubular system (TATS), synchronously trigger uniform Ca(2+) release throughout the cardiomyocyte. In heart failure (HF), TATS structural remodeling occurs, leading to asynchronous Ca(2+) release across the myocyte and contributing to contractile dysfunction. In cardiomyocytes from failing rat hearts, we previously documented the presence of TATS elements which failed to propagate AP and displayed spontaneous electrical activity; the consequence for Ca(2+) release remained, however, unsolved. Here, we develop an imaging method to simultaneously assess TATS electrical activity and local Ca(2+) release. In HF cardiomyocytes, sites where T-tubules fail to conduct AP show a slower and reduced local Ca(2+) transient compared with regions with electrically coupled elements. It is concluded that TATS electrical remodeling is a major determinant of altered kinetics, amplitude, and homogeneity of Ca(2+) release in HF. Moreover, spontaneous depolarization events occurring in failing T-tubules can trigger local Ca(2+) release, resulting in Ca(2+) sparks. The occurrence of tubule-driven depolarizations and Ca(2+) sparks may contribute to the arrhythmic burden in heart failure. PMID:25288764

Crocini, Claudia; Coppini, Raffaele; Ferrantini, Cecilia; Yan, Ping; Loew, Leslie M; Tesi, Chiara; Cerbai, Elisabetta; Poggesi, Corrado; Pavone, Francesco S; Sacconi, Leonardo

2014-10-21

357

Bursting transition in a linear self-exciting point process  

NASA Astrophysics Data System (ADS)

Self-exciting point processes describe the manner in which every event facilitates the occurrence of succeeding events, as in the case of epidemics or human activity. By increasing excitability, the event occurrences start to exhibit bursts even in the absence of external stimuli. We revealed that the transition is uniquely determined by the average number of events added by a single event, 1-1/?2 ?0.2929, independently of the temporal excitation profile. We further extended the theory to multidimensional processes, to be able to incite or inhibit bursting in networks of agents by altering their connections.

Onaga, Tomokatsu; Shinomoto, Shigeru

2014-04-01

358

Gamma-ray burst observations  

Microsoft Academic Search

Gamma-ray bursts (GRBs) are the most luminous known objects in the Universe. Their brief, random appearance in the gamma-ray region had made their study difficult since their discovery, over thirty years ago. There is a rich diversity in the duration and morphology of GRB time profiles. The spectra are characterized by a smooth continuum, usually peaking in the range from

Gerald J. Fishman

2000-01-01

359

Long gamma ray bursts from binary black holes  

NASA Astrophysics Data System (ADS)

Aims: We consider a scenario for the longest duration gamma ray bursts, resulting from the collapse of a massive rotating star in a close binary system with a companion black hole (BH). Methods: The primary BH born during the core collapse is first being spun up and increases its mass during the fallback of the stellar envelope just after its birth. As the companion BH enters the outer envelope, it provides an additional angular momentum to the gas. After the infall and spiral-in toward the primary, the two BHs merge inside the circumbinary disk. Results: The second episode of mass accretion and high final spin of the postmerger BH prolongs the gamma ray burst central engine activity. The observed events should have two distinct peaks in the electromagnetic signal, separated by the gravitational wave emission. The gravitational recoil of the burst engine is also possible.

Janiuk, Agnieszka; Charzy?ski, Szymon; Bejger, Micha?

2013-12-01

360

mPing: The bursting transposon  

PubMed Central

Though transposable elements (TEs) have been considered as an efficient source of evolution, it has never been possible to test this hypothesis because most of TE insertions had occurred millions of years ago, or because currently active TEs have very few copies in a host genome. However, mPing, the first active DNA transposon in rice, was revealed to hold a key to answer this question. mPing has attained high copy numbers and still retained very high activity in a traditional rice strain, which enabled direct observation of behavior and impact of a bursting TE. A comprehensive analysis of mPing insertion sites has revealed it avoids exons but prefers promoter regions and thus moderately affects transcription of neighboring genes. Some of the mPing insertions have introduced possibly useful expression profile to adjacent genes that indicated TE’s potential in de novo formation of gene regulatory network. PMID:25053919

Naito, Ken; Monden, Yuki; Yasuda, Kanako; Saito, Hiroki; Okumoto, Yutaka

2014-01-01

361

Burst of ethylene upon horizontal placement of tomato seedlings  

NASA Technical Reports Server (NTRS)

Seedlings of Lycopersicon esculentum Mill. cv Rutgers emit a pulse of ethylene during the first 2 to 4 minutes following horizontal placement. Because this burst appears too rapid and brief to be mediated by increase in net activity of 1-aminocyclopropane-1-carboxylic acid synthase, it might result form accelerated transformation of vacuolar 1-aminocyclopropane-1-carboxylic acid to ethylene.

Harrison, M.; Pickard, B. G.

1984-01-01

362

Electrical activities of stacking faults and partial dislocations in 4H-SiC homoepitaxial films  

NASA Astrophysics Data System (ADS)

The electrical activities of stacking faults (SFs) and partial dislocations in 4H-SiC homoepitaxial films were investigated by using the electron-beam-induced current (EBIC) technique. The basal plane dislocation was dissociated into Si ( g) 30 ? and C ( g) 30 ? partials under electron-beam irradiation, with a SF formed in between. The SF shows bright contrast at RT and dark contrast at 50 K in EBIC images. The reasons were discussed according to the quantum-well state of SF. C ( g) 30 ? partial is always more electrically active than Si ( g) 30 ? partial at each specific accelerating voltage. The EBIC contrasts of those two partials were discussed with the number of recombination centers.

Chen, Bin; Chen, Jun; Sekiguchi, Takashi; Ohyanagi, Takasumi; Matsuhata, Hirofumi; Kinoshita, Akimasa; Okumura, Hajime; Fabbri, Filippo

2009-04-01

363

Io Jupiter interaction, millisecond bursts and field-aligned potentials  

NASA Astrophysics Data System (ADS)

Jovian millisecond (or S-) bursts are intense impulsive decametric radio bursts drifting in frequency in tens of milliseconds. Most of the theories about their origin comprise an interpretation of their frequency drift. Previous analyses suggest that S-bursts are cyclotron-maser emission in the flux tubes connecting Io or Io's wake to Jupiter. Electrons are thought to be accelerated from Io to Jupiter. Near Jupiter, a loss cone appears in the magnetically mirrored electron population, which is able to amplify extraordinary (X) mode radio waves. Here, we perform an automated analysis of 230 high-resolution dynamic spectra of S-bursts, providing 5×106 frequency drift measurements. Our data are consistent with the above scenario. In addition, we confirm over a large number of measurements that the frequency drift df/dt(f) is in average negative and decreases (in absolute value) at high frequencies, as predicted by the adiabatic theory. We find a typical energy of 4 keV for the emitting electrons. In 15% of the cases (out of 230), we find for the first time evidence of localized ˜1keV electric potential jumps at high latitudes along the field lines connecting Io or Io's wake to Jupiter. These potential jumps appear stable over tens of minutes. Finally, a statistical analysis suggests the existence of a distributed parallel acceleration of the emitting electrons along the same field lines.

Hess, S.; Zarka, P.; Mottez, F.

2007-01-01

364

High-Performance Electric Vehicle Battery with Lithium Iron Phosphate for Positive Active Material  

Microsoft Academic Search

LiFePO4 is very attractive positive active material because of its features such as environmentally-friendly chemicals and high thermal stability. New prototype carbon-loaded LiFePO4\\/graphite lithium-ion cells with large capacity of 25 Ah have been developed for electric vehicles (EVs) applications. The developed cells show remarkably high discharge performance with a flat voltage profile and high-rate capacity retention of 99% even at

Isao Suzuki; Tomotada Mochizuki; Takeshi Nakamoto; Yasushi Uebo; Koichi Nishiyama

365

Erbb2 Is Required for Cardiac Atrial Electrical Activity during Development  

PubMed Central

The heart is the first organ required to function during embryonic development and is absolutely necessary for embryo survival. Cardiac activity is dependent on both the sinoatrial node (SAN), which is the pacemaker of heart's electrical activity, and the cardiac conduction system which transduces the electrical signal though the heart tissue, leading to heart muscle contractions. Defects in the development of cardiac electrical function may lead to severe heart disorders. The Erbb2 (Epidermal Growth Factor Receptor 2) gene encodes a member of the EGF receptor family of receptor tyrosine kinases. The Erbb2 receptor lacks ligand-binding activity but forms heterodimers with other EGF receptors, stabilising their ligand binding and enhancing kinase-mediated activation of downstream signalling pathways. Erbb2 is absolutely necessary in normal embryonic development and homozygous mouse knock-out Erbb2 embryos die at embryonic day (E)10.5 due to severe cardiac defects. We have isolated a mouse line, l11Jus8, from a random chemical mutagenesis screen, which carries a hypomorphic missense mutation in the Erbb2 gene. Homozygous mutant embryos exhibit embryonic lethality by E12.5-13. The l11Jus8 mutants display cardiac haemorrhage and a failure of atrial function due to defects in atrial electrical signal propagation, leading to an atrial-specific conduction block, which does not affect ventricular conduction. The l11Jus8 mutant phenotype is distinct from those reported for Erbb2 knockout mouse mutants. Thus, the l11Jus8 mouse reveals a novel function of Erbb2 during atrial conduction system development, which when disrupted causes death at mid-gestation. PMID:25269082

Tenin, Gennadiy; Clowes, Christopher; Wolton, Kathryn; Krejci, Eliska; Wright, Jayne A.; Lovell, Simon C.; Sedmera, David; Hentges, Kathryn E.

2014-01-01

366

Optimal Intrinsic Dynamics for Bursting in a Three-Cell Network  

NASA Astrophysics Data System (ADS)

Previous numerical and analytical work has shown that synaptic coupling can allow a network of model neurons to synchronize despite heterogeneity in intrinsic parameter values. In particular, synchronous bursting oscillations can arise in a network with excitatory synaptic coupling, even in the absence of intrinsically bursting neurons. In this work, we explore how the intrinsic dynamics of neurons within a reduced three-cell network influence its ability to exhibit synchronous bursting and the frequency range over which such activity can occur. We establish necessary and sufficient conditions for the existence of synchronous bursting solutions and perform related numerical experiments in three-cell networks that include a quiescent cell, a tonically active cell, and a third added cell. Our results show that, in most cases, the addition of a quiescent cell is optimal for synchronous network bursting, in a variety of ways, and that intrinsically bursting cells can be detrimental to synchronous bursting, and we explain the mechanisms underlying these effects. These findings may help explain how robust synchronous oscillations arise in neuronal central pattern generators, such as the mammalian inspiratory network, despite the presence of significant cellular heterogeneity. They also support the idea that intrinsic burst capabilities of individual cells need not be central to these networks' rhythms.

Dunmyre, Justin R.; Rubin, Jonathan E.

2010-01-01

367

Mathematical model of the glucose-insulin regulatory system: From the bursting electrical activity in pancreatic ?-cells to the glucose dynamics in the whole body  

NASA Astrophysics Data System (ADS)

A theoretical approach to the glucose-insulin regulatory system is presented. By means of integrated mathematical modeling and extensive numerical simulations, we probe the cell-level dynamics of the membrane potential, intracellular Ca2+ concentration, and insulin secretion in pancreatic ?-cells, together with the whole-body level glucose-insulin dynamics in the liver, brain, muscle, and adipose tissues. In particular, the three oscillatory modes of insulin secretion are reproduced successfully. Such comprehensive mathematical modeling may provide a theoretical basis for the simultaneous assessment of the ?-cell function and insulin resistance in clinical examination.

Han, Kyungreem; Kang, Hyuk; Choi, M. Y.; Kim, Jinwoong; Lee, Myung-Shik

2012-10-01

368

Improved detection of electrical activity with a voltage probe based on a voltage-sensing phosphatase  

PubMed Central

One of the most awaited techniques in modern physiology is the sensitive detection of spatiotemporal electrical activity in a complex network of excitable cells. The use of genetically encoded voltage probes has been expected to enable such analysis. However, in spite of recent progress, existing probes still suffer from low signal amplitude and/or kinetics too slow to detect fast electrical activity. Here, we have developed an improved voltage probe named Mermaid2, which is based on the voltage-sensor domain of the voltage-sensing phosphatase from Ciona intestinalis and Förster energy transfer between a pair of fluorescent proteins. In mammalian cells, Mermaid2 permits ratiometric readouts of fractional changes of more than 50% over a physiologically relevant voltage range with fast kinetics, and it was used to follow a train of action potentials at frequencies of up to 150 Hz. Mermaid2 was also able to detect single action potentials and subthreshold voltage responses in hippocampal neurons in vitro, in addition to cortical electrical activity evoked by sound stimuli in single trials in living mice. PMID:23836686

Tsutsui, Hidekazu; Jinno, Yuka; Tomita, Akiko; Niino, Yusuke; Yamada, Yoshiyuki; Mikoshiba, Katsuhiko; Miyawaki, Atsushi; Okamura, Yasushi

2013-01-01

369

Relation Between Lightning Activity of Summer and Winter Thunderclouds and Surface Electric Field Variation, Japan  

NASA Technical Reports Server (NTRS)

In winter, active convective clouds frequently form along the coastline of the Hokuriku district, in association with strong advection of Siberian air masses over the Sea of Japan. On the other hand, in summer, many thunderclouds form in the Kanto region in the afternoon every day. Summer and winter thunderclouds were investigated by field works, operation of the C- and X-band weather radars and a car-borne fieldmill. The investigation found a very close relation between the temporal variation of 3-dimensional radar echo and surface electric field magnitude detected by a car-borne fieldmill in the case of summer thunderclouds and winter convective clouds or thunderclouds. The study probed the close relation among radar echoes, quantity of thunderclouds and surface electric field magnitude in the summer and winter seasons. We think that summer thundercloud activity can basically be equated with winter thundercloud lightning activity, except that the magnitude of surface electric field under summer thunderclouds in the case of the Kanto region cannot be equated with that under winter thunderclouds in the case of the Hokuriku district in winter.

Michimoto, K.; Shimura, T.; Suzuki, T.

1999-01-01

370

Neutrino Event Rates from Gamma Ray Bursts  

E-print Network

We recalculate the diffuse flux of high energy neutrinos produced by Gamma Ray Bursts (GRB) in the relativistic fireball model. Although we confirm that the average single burst produces only ~10^{-2} high energy neutrino events in a detector with 1 km^2 effective area, i.e. about 10 events per year, we show that the observed rate is dominated by burst-to-burst fluctuations which are very large. We find event rates that are expected to be larger by one order of magnitude, likely more, which are dominated by a few very bright bursts. This greatly simplifies their detection.

F. Halzen; D. W. Hooper

1999-08-12

371

Noise-induced transition to bursting in responses of paddlefish electroreceptor afferents.  

PubMed

The response properties of ampullary electroreceptors of paddlefish, Polyodon spathula, were studied in vivo, as single-unit afferent responses to external electrical stimulation with varied intensities of several types of noise waveforms, all Gaussian and zero-mean. They included broadband white noise, Ornstein-Uhlenbeck noise, low- or high-frequency band-limited noise, or natural noise recorded from swarms of Daphnia zooplankton prey, or from individual prey. Normally the afferents fire spontaneously in a tonic manner, which is actually quasiperiodic due to embedded oscillators. 1) Weak noise stimuli increased the variability of afferent firing, but it remained tonic. 2) In contrast, stimulation with less-weak broadband noise led to a qualitative change of the firing patterns, to parabolic bursting, even though the mean firing rate was scarcely affected. 3) The transition to afferent bursting was marked by the development of two well-separated timescales: the fast frequency of spiking inside bursts at burst occurrences at about 9 (range 5-13) bursts/s. These two timescales were manifested as two regimes in afferent power spectra, bimodal interspike interval histograms, return maps, and autocorrelation functions of afferent spike trains. 4) The stochastic approximately 9-Hz bursts were not simply driven by similar-frequency components of noise stimuli because bursts could be dissociated from stimulus waveforms using high-pass filtered noise, or a 0.1-Hz sine-wave stimulus. 5) Arrhenius plots showed that the threshold noise intensity required to elicit bursting depended on the frequency content of a noise stimulus, being lowest, about 1.2 microV/cm, for stimuli matching the 1- to 20-Hz best response band of these cathodally excited ampullary electroreceptors. This is only slightly higher than previous behavioral estimates of the electrosensory threshold as 0.5 microV/cm. 6) Comparable threshold values for bursting came from an alternate analytical approach, based on correlation times of spike trains. 7) Simultaneous recordings from pairs of afferents showed that their bursting frequencies (bursts/s) always converged as the amplitude of a noise stimulus was raised. Thus the slow timescale of bursting is similar for different electroreceptors, even though their mean spiking rates can differ. In conclusion, the ampullary electroreceptors of paddlefish have two distinct modes of operation: their spontaneous tonic firing is modulated by the weakest stimuli, but they switch to bursting output for less-weak stimuli. We propose that afferent bursting may mediate close-range tracking of planktonic prey. PMID:17855580

Neiman, Alexander B; Yakusheva, Tatyana A; Russell, David F

2007-11-01

372

[Dynamics of the respiratory center activity during electrical stimulation of the diaphragmatic nerve].  

PubMed

The adoption of artificial rhythm of electrical stimulation of diaphragmatic nerve was found to be determined by the force and rate of artificial contractions of the diaphragm, by the concentration of barbiturates in the blood and by gaseous composition of inspired air in anesthetized dogs. The time interval between the onset of artificial contraction and onset of natural one seems to characterize functional activity of respiratory center and to result from inhibitory afferent effect of the lungs' mechanoreceptors, on the one hand, and from activating effects of central and peripheral chemoreceptors, on the other hand. PMID:2612648

Ul'kin, S V; Nasledkov, V N

1989-10-01

373

Phenolic Lipids Affect the Activity and Conformation of Acetylcholinesterase from Electrophorus electricus (Electric eel)  

PubMed Central

Phenolic lipids were isolated from rye grains, cashew nutshell liquid (CNSL) from Anacardium occidentale, and fruit bodies of Merrulius tremellosus, and their effects on the electric eel acetylcholinesterase activity and conformation were studied. The observed effect distinctly depended on the chemical structure of the phenolic lipids that were available for interaction with the enzyme. All of the tested compounds reduced the activity of acetylcholinesterase. The degree of inhibition varied, showing a correlation with changes in the conformation of the enzyme tested by the intrinsic fluorescence of the Trp residues of the protein. PMID:24787269

Stasiuk, Maria; Janiszewska, Alicja; Kozubek, Arkadiusz

2014-01-01

374

Quantification of direct current in electrically active implants using MRI methods.  

PubMed

The aim of this study was to evaluate a variety of phase- and magnitude-based MRI methods at 1.5 T and 3 T regarding their sensitivity and accuracy with respect to the quantification of electrical direct current via the induced magnetic field inhomogeneity. For this, a phantom was constructed which was specially designed to reduce RF effects and which provided a one-dimensional electrical direct current in a thin copper conductor perpendicular to the static magnetic field of the scanner. The current was varied between 4 mA and 472 mA. The analysis of FLASH phase images as well as trueFISP and MAGSUS images revealed that the accuracy of the MR current measurement depended on the method and the field strength: the mean of the absolute deviations of the measured current values from the adjusted current values varied between 9% and 21%. The phase measurement with a FLASH sequence was found to be more sensitive than the trueFISP and MAGSUS measurements. In FLASH magnitude images as well as in images of spin echo sequences with on- and off-resonant frequency selective saturation pulses the extension of the artifact increased with the electrical current. MRI methods for the quantification of electrical direct current might e.g. play a role in functional testing of electrically active devices in the human body in terms of measuring the present current. One-dimensional electrical direct current in a thin, straight conductor could also be applied to the visualization of instruments in interventional MRI procedures. Currents below 100 mA would be sufficient to create distinct artifacts, at least under simplified conditions (homogeneous background etc.). PMID:21277177

Wojtczyk, Hanne; Graf, Hansjörg; Martirosian, Petros; Ballweg, Verena; Kraiger, Markus; Pintaske, Jörg; Schick, Fritz

2011-05-01

375

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Some basic observed properties of gamma-ray bursts are reviewed. Although some properties were known 25 years ago, new and more detailed observations have been made by the Compton Observatory in the past three years. The new observation with the greatest impact has been the observed isotropic distribution of bursts along with a deficiency of weak bursts which would be expected from a homogeneous burst distribution. This is not compatible with any known Galactic population of objects. Gamma-ray bursts show an enormous variety of burst morphologies and a wide spread in burst durations. The spectra of gamma-ray bursts are characterized by rapid variations and peak power which is almost entirely in the gamma-ray energy range. Delayed gamma-ray burst photons extending to GeV energies have been detected for the first time. A time dilation effect has also been reported to be observed in gamma-ray, bursts. The observation of a gamma-ray burst counterpart in another wavelength region has yet to be made.

Fishman, G. J.

1995-01-01

376

Solar Radio Bursts and Space Weather  

NASA Technical Reports Server (NTRS)

Radio bursts from the Sun are produced by electron accelerated to relativistic energies by physical processes on the Sun such as solar flares and coronal mass ejections (CMEs). The radio bursts are thus good indicators of solar eruptions. Three types of nonthermal radio bursts are generally associated with CMEs. Type III bursts due to accelerated electrons propagating along open magnetic field lines. The electrons are thought to be accelerated at the reconnection region beneath the erupting CME, although there is another view that the electrons may be accelerated at the CME-driven shock. Type II bursts are due to electrons accelerated at the shock front. Type II bursts are also excellent indicators of solar energetic particle (SEP) events because the same shock is supposed accelerate electrons and ions. There is a hierarchical relationship between the wavelength range of type /I bursts and the CME kinetic energy. Finally, Type IV bursts are due to electrons trapped in moving or stationary structures. The low frequency stationary type IV bursts are observed occasionally in association with very fast CMEs. These bursts originate from flare loops behind the erupting CME and hence indicate tall loops. This paper presents a summary of radio bursts and their relation to CMEs and how they can be useful for space weather predictions.

Gopalswamy, Natchimuthuk,

2012-01-01

377

Effects of Cardiac Glycosides on Electrical Activity in the Isolated Retina of the Frog  

PubMed Central

Ouabain added to physiological salt solutions bathing the isolated frog retina irreversibly abolishes the electrical response to light (the electroretinogram or ERG). The time course of abolition depends on the concentration of ouabain in the medium and the surface of the retina to which it is applied. When the glycoside is placed on the receptor surface, in 7 min the ERG is completely eliminated by 10-4 M ouabain and more than 90% inhibited by 3 x 10-5 M ouabain. The effect is slower at lower concentrations and when the solution is applied to the vitreous surface of the retina. The evidence suggests that abolition of the ERG by ouabain is due principally to inhibition of the active transport of sodium: (a) Structurally modified glycosides which are considerably less potent inhibitors of alkali cation-activated ATPase activity in preparations of frog retinal outer segments are also poorer inhibitors of electrical activity in isolated retinas. (b) Replacing much of the sodium in the medium bathing the retina by choline, Tris, or sucrose significantly protects the retina from ouabain. It is suggested that in a standard sodium environment essentially constant activity of the sodium pump is required to prevent rapid and irreversible change. The cellular sites most critically dependent on the sodium pump have not been identified. PMID:6034759

Frank, Robert N.; Goldsmith, Timothy H.

1967-01-01

378

Do gamma-ray burst sources repeat?  

NASA Technical Reports Server (NTRS)

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports (Quashnock and Lamb, 1993; Wang and Lingenfelter, 1993) of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al., 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic and the two-point angular correlation function. We find the data to be consistent with the hypothesis that burst sources do not repeat; however, a repeater fraction of up to about 20% of the observed bursts cannot be excluded.

Meegan, Charles A.; Hartmann, Dieter H.; Brainerd, J. J.; Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey; Kouveliotou, Chryssa; Fishman, Gerald; Blumenthal, George; Brock, Martin

1995-01-01

379

Intensity distributions of gamma-ray bursts  

SciTech Connect

Observations of individual bursts chosen by the vagaries of telescope availability demonstrated that bursts are not standard candles and that their apparent energy can be as great as 10{sup 54} erg. However, determining the distribution of their apparent energy (and of other burst properties) requires the statistical analysis of a well-defined burst sample; the sample definition includes the threshold for including a burst in the sample. Thus optical groups need to the criteria behind the decision to search for a spectroscopic redshift. Currently the burst samples are insufficient to choose between lognormal and power law functional forms of the distribution, and the parameter values for these functional forms differ between burst samples. Similarly, the actual intensity distribution may be broader than observed, with a low energy tail extending below the detection threshold.

Band, D. L. (David L.)

2001-01-01

380

Locomotor activities in the decerebrate bird without phasic afferent input.  

PubMed

We examined whether forelimb and hindlimb phasic afferent input is a prerequisite for the production of avian locomotor patterns. We eliminated phasic afferent feedback through paralysis of a decerebrate animal. The term "fictive" has been used to describe the neural activity associated with spontaneous or evoked motor output during neuromuscular paralysis. We observed that a paralysed decerebrate bird is capable of producing similar locomotor activity patterns as an unparalysed preparation, regardless of whether the "fictive" locomotion is generated spontaneously, or in response to focal electrical and/or neurochemical stimulation of discrete brainstem locomotor regions. Not all aspects of "fictive" locomotor patterns were identical to the locomotion elicited prior to paralysis. The stimulus current threshold necessary to evoke hindlimb locomotion increased from 69 +/- 22 mu A (mean +/- S.D.) prior to paralysis to 185 +/- 87 mu A for "fictive" stepping. For wing activity, the threshold increased from 84 +/- 46 mu A during wing flapping to 228 +/- 148 mu A for "fictive" flight. In addition, the frequency of "fictive" efferent locomotor activity from the leg nerve (1.04 +/- 0.44 Hz) decreased relative to the frequency of leg activity prior to paralysis (1.55 +/- 0.70 Hz). Similarly, the frequency of wing activity decreased from 2.73 +/- 0.73 Hz before paralysis to 1.8 +/- 0.69 Hz after paralysis. Finally flexor burst duration remained constant during treadmill and "fictive" walking while the extensor burst duration was markedly increased during "fictive" walking. Thus, the relative contributions of leg flexor activity to the overall step cycle (burst proportion = burst duration/cycle duration) decreased during evoked "fictive" stepping, while the burst proportion of the leg extensor increased. Afferent feedback therefore appears to modulate leg extensor burst duration more than leg flexor duration. For the wings, the burst proportion of the major wing depressors remained constant before and after paralysis. PMID:2052153

Sholomenko, G N; Funk, G D; Steeves, J D

1991-01-01

381

The Electron Runaround: Understanding Electric Circuit Basics Through a Classroom Activity  

NASA Astrophysics Data System (ADS)

Several misconceptions abound among college students taking their first general physics course, and to some extent pre-engineering physics students, regarding the physics and applications of electric circuits. Analogies used in textbooks, such as those that liken an electric circuit to a piped closed loop of water driven by a water pump, do not completely resolve these misconceptions. Mazur and Knight,2 in particular, separately note that such misconceptions include the notion that electric current on either side of a light bulb in a circuit can be different. Other difficulties and confusions involve understanding why the current in a parallel circuit exceeds the current in a series circuit with the same components, and include the role of the battery (where students may assume wrongly that a dry cell battery is a fixed-current rather than a fixed-voltage device). A simple classroom activity that students can play as a game can resolve these misconceptions, providing an intellectual as well as a hands-on understanding. This paper describes the "Electron Runaround," first developed by the author to teach extremely bright 8-year-old home-schooled children the basics of electric circuits and subsequently altered (according to the required level of instruction) and used for various college physics courses.

Singh, Vandana

2010-05-01

382

Bursting thalamic responses in awake monkey contribute to visual detection and are modulated by corticofugal feedback  

PubMed Central

The lateral geniculate nucleus is the gateway for visual information en route to the visual cortex. Neural activity is characterized by the existence of two firing modes: burst and tonic. Originally associated with sleep, bursts have now been postulated to be a part of the normal visual response, structured to increase the probability of cortical activation, able to act as a “wake-up” call to the cortex. We investigated a potential role for burst in the detection of novel stimuli by recording neuronal activity in the lateral geniculate nucleus (LGN) of behaving monkeys during a visual detection task. Our results show that bursts are often the neuron’s first response, and are more numerous in the response to attended target stimuli than to unattended distractor stimuli. Bursts are indicators of the task novelty, as repetition decreased bursting. Because the primary visual cortex is the major modulatory input to the LGN, we compared the results obtained in control conditions with those observed when cortical activity was reduced by TMS. This cortical deactivation reduced visual response related bursting by 90%. These results highlight a novel role for the thalamus, able to code higher order image attributes as important as novelty early in the thalamo-cortical conversation. PMID:24910601

Ortuño, Tania; Grieve, Kenneth L.; Cao, Ricardo; Cudeiro, Javier; Rivadulla, Casto

2014-01-01

383

The influence of premolding load on the electrical behavior in the initial stage of electric current activated sintering of carbonyl iron powders  

NASA Astrophysics Data System (ADS)

This paper reports the premolding load effect on the electrical behavior in the initial stage of electric current activated sintering of carbonyl iron powders. An electrical network model is put forward to estimate the uniformity of electric current in a powder compact subjected to different premolding loads in the initial stage. The improvement in current uniformity can be reflected from a simultaneous increase in the number N and the mass fraction ? of conductive particle chains in the compact. Both N and ? are found to follow a power law with the premolding load F for different exponent values. When ? is equal to 1, a critical load is reached, at which point the current flows through all particles during sintering. Using the results of the model and the electrical contact theory, it is also found that only an increased temperature of less than 20 K across the particle contacts. The distribution of temperature is uniform in particles. This is clearly different from the general acceptance that local high temperature is created at contact during electric current activated sintering. The neck formation and growth are thought to be mainly due to heat bonding and electromigration, of which effects on mass transport are pronouncedly enhanced by increasing the bulk temperature. Because of the poor current uniformity and relatively large power dissipation, a soft thermal breakdown is observed in the sample with high initial resistance. A reduction in premolding load may cause an increase in the initial electrical resistance of the compact. Owing to the unique voltage-current characteristic of electric current activated sintering, a higher initial resistance of compact means more thermal energy is involved, consequently producing a higher bulk temperature and getting a better quality of sintering. This also provides theoretical explanation for the experimental results from Inoue and Istomina.

Ye, Yongquan; Li, Xiaoqiang; Hu, Ke; Lai, Yangen; Li, Yuanyuan

2013-06-01

384

Gamma-ray bursts as cosmological probes  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts (GRBs) are short, intense burstsof gamma-rays which during seconds to minutes outshine all other sources of gamma-ray emission in the sky.Following the prompt gamma-ray emission, an `afterglow' of emission from the X-ray range to radio wavelengthspersists up to months after the initial burst. The association of the class of long GRBs with the explosion of broad-line type Ic SNe GRBs allow galaxies to be selected independently oftheir emission properties (independently of dust obscuration and, uniquely, independently of their brightnesses atany wavelength) and they also permit the study of the gas in the interstellar medium (ISM) systematically and at anyredshift by the absorption lines present in the afterglow spectra. Moreover, the fading nature of GRBs and theprecise localization of the afterglow allow a detailed investigation of the emission properties of the GRB hostgalaxy once the afterglow has vanished. GRBs therefore constitute a unique tool to understand the link between theproperties of the ISM in the galaxy and the star formation activity, and this at any redshift. This is a unique wayto reveal the physical processes that trigger galaxy formation. The SVOM space mission project is designed to improve the use GRBs as cosmological probes.

Vergani, S. D.

2013-11-01

385

Chronic electrical stimulation homeostatically decreases spontaneous activity, but paradoxically increases evoked network activity  

E-print Network

functional dynamic regimes, and the degree to which these regimes are themselves plastic, are not known. In this study we examined plasticity of network dynamics in cortical orga- notypic slices in response to chronic. Paradoxically, however, whereas bicu- culline decreased evoked network activity, chronic stimulation actu- ally

Buonomano, Dean

386

Metabolic syndrome remodels electrical activity of the sinoatrial node and produces arrhythmias in rats.  

PubMed

In the last ten years, the incidences of metabolic syndrome and supraventricular arrhythmias have greatly increased. The metabolic syndrome is a cluster of alterations, which include obesity, hypertension, hypertriglyceridemia, glucose intolerance and insulin resistance, that increase the risk of developing, among others, atrial and nodal arrhythmias. The aim of this study is to demonstrate that metabolic syndrome induces electrical remodeling of the sinus node and produces arrhythmias. We induced metabolic syndrome in 2-month-old male Wistar rats by administering 20% sucrose in the drinking water. Eight weeks later, the rats were anesthetized and the electrocardiogram was recorded, revealing the presence of arrhythmias only in treated rats. Using conventional microelectrode and voltage clamp techniques, we analyzed the electrical activity of the sinoatrial node. We observed that in the sinoatrial node of "metabolic syndrome rats", compared to controls, the spontaneous firing of all cells decreased, while the slope of the diastolic depolarization increased only in latent pacemaker cells. Accordingly, the pacemaker currents If and Ist increased. Furthermore, histological analysis showed a large amount of fat surrounding nodal cardiomyocytes and a rise in the sympathetic innervation. Finally, Poincaré plot denoted irregularity in the R-R and P-P ECG intervals, in agreement with the variability of nodal firing potential recorded in metabolic syndrome rats. We conclude that metabolic syndrome produces a dysfunction SA node by disrupting normal architecture and the electrical activity, which could explain the onset of arrhythmias in rats. PMID:24250786

Albarado-Ibañez, Alondra; Avelino-Cruz, José Everardo; Velasco, Myrian; Torres-Jácome, Julián; Hiriart, Marcia

2013-01-01

387

Metabolic Syndrome Remodels Electrical Activity of the Sinoatrial Node and Produces Arrhythmias in Rats  

PubMed Central

In the last ten years, the incidences of metabolic syndrome and supraventricular arrhythmias have greatly increased. The metabolic syndrome is a cluster of alterations, which include obesity, hypertension, hypertriglyceridemia, glucose intolerance and insulin resistance, that increase the risk of developing, among others, atrial and nodal arrhythmias. The aim of this study is to demonstrate that metabolic syndrome induces electrical remodeling of the sinus node and produces arrhythmias. We induced metabolic syndrome in 2-month-old male Wistar rats by administering 20% sucrose in the drinking water. Eight weeks later, the rats were anesthetized and the electrocardiogram was recorded, revealing the presence of arrhythmias only in treated rats. Using conventional microelectrode and voltage clamp techniques, we analyzed the electrical activity of the sinoatrial node. We observed that in the sinoatrial node of “metabolic syndrome rats”, compared to controls, the spontaneous firing of all cells decreased, while the slope of the diastolic depolarization increased only in latent pacemaker cells. Accordingly, the pacemaker currents If and Ist increased. Furthermore, histological analysis showed a large amount of fat surrounding nodal cardiomyocytes and a rise in the sympathetic innervation. Finally, Poincaré plot denoted irregularity in the R-R and P-P ECG intervals, in agreement with the variability of nodal firing potential recorded in metabolic syndrome rats. We conclude that metabolic syndrome produces a dysfunction SA node by disrupting normal architecture and the electrical activity, which could explain the onset of arrhythmias in rats. PMID:24250786

Albarado-Ibanez, Alondra; Avelino-Cruz, Jose Everardo; Velasco, Myrian; Torres-Jacome, Julian; Hiriart, Marcia

2013-01-01

388

Gamma Ray Burst engine activity within the quark nova scenario: Prompt emission, X-ray Plateau, and sharp drop-off  

E-print Network

We present a three-stage model for a long GRB inner engine to explain the prompt gamma ray emission, and interpret recent Swift satellite observations of early X-ray afterglow plateaus followed by a sharp drop off or a shallow power law decay. The three stages involves a neutron star phase, a quark star (QS) and a black hole phase as described in Staff et al. (2007). We find that the QS stage allows for more energy to be extracted from neutron star to QS conversion as well as from ensuing accretion onto the QS. The QS accretion phase naturally extends the engine activity and can account for both the prompt emission and irregular early X-ray afterglow activity. Following the accretion phase, the QS can spin-down by emission of a baryon-free outflow. The magnetar-like magnetic field strengths resulting from the NS to QS transition provide enough spin-down energy, for the correct amount of time, to account for the plateau in the X-ray afterglow. In our model, a sharp drop-off following the plateau occurs when the QS collapses to a BH during the spin-down, thus shutting-off the secondary outflow. We applied our model to GRB 070110 and GRB 060607A and found that we can consistently account for the energetics and duration during the prompt and plateau phases.

Jan Staff; Brian Niebergal; Rachid Ouyed

2007-11-19

389

Inspiratory bursts in the preBötzinger complex depend on a calcium-activated non-specific cation current linked to glutamate receptors in neonatal mice  

PubMed Central

Inspiratory neurons of the preBötzinger complex (preBötC) form local excitatory networks and display 10–30 mV transient depolarizations, dubbed inspiratory drive potentials, with superimposed spiking. AMPA receptors are critical for rhythmogenesis under normal conditions in vitro but whether other postsynaptic mechanisms contribute to drive potential generation remains unknown. We examined synaptic and intrinsic membrane properties that generate inspiratory drive potentials in preBötC neurons using neonatal mouse medullary slice preparations that generate respiratory rhythm. We found that NMDA receptors, group I metabotropic glutamate receptors (mGluRs), but not group II mGluRs, contributed to inspiratory drive potentials. Subtype 1 of the group I mGluR family (mGluR1) probably regulates a K+ channel, whereas mGluR5 operates via an inositol 1,4,5-trisphosphate (IP3) receptor-dependent mechanism to augment drive potential generation. We tested for and verified the presence of a Ca2+-activated non-specific cation current (ICAN) in preBötC neurons. We also found that high concentrations of intracellular BAPTA, a high-affinity Ca2+ chelator, and the ICAN antagonist flufenamic acid (FFA) decreased the magnitude of drive potentials. We conclude that ICAN underlies robust inspiratory drive potentials in preBötC neurons, and is only fully evoked by ionotropic and metabotropic glutamatergic synaptic inputs, i.e. by network activity. PMID:17446214

Pace, Ryland W; Mackay, Devin D; Feldman, Jack L; Del Negro, Christopher A

2007-01-01

390

Inspiratory bursts in the preBötzinger complex depend on a calcium-activated non-specific cation current linked to glutamate receptors in neonatal mice.  

PubMed

Inspiratory neurons of the preBötzinger complex (preBötC) form local excitatory networks and display 10-30 mV transient depolarizations, dubbed inspiratory drive potentials, with superimposed spiking. AMPA receptors are critical for rhythmogenesis under normal conditions in vitro but whether other postsynaptic mechanisms contribute to drive potential generation remains unknown. We examined synaptic and intrinsic membrane properties that generate inspiratory drive potentials in preBötC neurons using neonatal mouse medullary slice preparations that generate respiratory rhythm. We found that NMDA receptors, group I metabotropic glutamate receptors (mGluRs), but not group II mGluRs, contributed to inspiratory drive potentials. Subtype 1 of the group I mGluR family (mGluR1) probably regulates a K+ channel, whereas mGluR5 operates via an inositol 1,4,5-trisphosphate (IP3) receptor-dependent mechanism to augment drive potential generation. We tested for and verified the presence of a Ca2+-activated non-specific cation current (I(CAN)) in preBötC neurons. We also found that high concentrations of intracellular BAPTA, a high-affinity Ca2+ chelator, and the I(CAN) antagonist flufenamic acid (FFA) decreased the magnitude of drive potentials. We conclude that I(CAN) underlies robust inspiratory drive potentials in preBötC neurons, and is only fully evoked by ionotropic and metabotropic glutamatergic synaptic inputs, i.e. by network activity. PMID:17446214

Pace, Ryland W; Mackay, Devin D; Feldman, Jack L; Del Negro, Christopher A

2007-07-01

391

Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM  

NASA Astrophysics Data System (ADS)

We present a project devoted to the scientific exploitation of SWARM multi-point measurements of the magnetic and electric field, of the electron temperature and density in the ionosphere. These data provide unique opportunities to study in-situ and remotely the electromagnetic and plasma variability due to ionospheric forcing from above and below. The project "Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM (EMISSARS)" focus on coordinated studies between SWARM and ground based observatories to survey electromagnetic and ionospheric variability at medium latitudes and look for possible correlations with the seismic activity in central Europe. The project is coordinated by the Institute for Space Sciences (INFLPR-ISS) and the National Institute for Earth Physics (INFP) in Bucharest, Romania. In addition to SWARM data the project benefits from support of dedicated ground based measurements provided by the MEMFIS network coordinated by INFP, the MM100 network of magnetic observatories coordinated by the Geological and Geophysical Institute of Hungary (MFGI) in Budapest. Seismic data are provided by INFP and the European Mediterranean Seismological Center. The mission of the project is to monitor from space and from ground the ionospheric and electromagnetic variability during time intervals prior, during and after seismic activity in (i) the seismic active regions of the central Europe and (ii) in regions unaffected by the seismic activity. The latter will provide reference measurements, free from possible seismogenic signals. The scientific objectives of the project are: (1) Observation of electric, magnetic and ionospheric (electron temperature, density) variability in the ionosphere above or in the close vicinity of seismic active regions, in conjunction with ground based observations from dedicated networks; (2) Investigation of the coupling between the litosphere - atmosphere - ionosphere, during Earthquakes; (3) Quantitative nonlinear analysis of anomalous magnetic events detected on ground and in space before, during and after Earthquakes. The methodology includes methods of analysis like : (i) the Power Spectral Density (PSD) of electric, magnetic, lithospheric signal, (ii) the Probability Distribution Functions (PDFs) at various scales from multi-spacecraft statistical ensembles, (iii) the auto and cross-correlation analysis of magnetic field and ionospheric variables for search of coherent structures, (iv) numerical modelling of the litosphere-atmosphere-ionosphere coupling based on the current continuity.

Echim, Marius M.; Moldovan, Iren; Voiculescu, Mirela; Balasis, George; Lichtenberger, Janos; Heilig, Balazs; Kovacs, Peter

2014-05-01

392

An analysis of the factors influencing demand-side management activity in the electric utility industry  

NASA Astrophysics Data System (ADS)

Demand-side management (DSM), defined as the "planning, implementation, and monitoring of utility activities designed to encourage consumers to modify their pattern of electricity usage, including the timing and level of electricity demand," is a relatively new concept in the U.S. electric power industry. Nevertheless, in twenty years since it was first introduced, utility expenditures on DSM programs, as well as the number of such programs, have grown rapidly. At first glance, it may seem peculiar that a firm would actively attempt to reduce demand for its primary product. There are two primary explanations as to why a utility might pursue DSM: regulatory mandate, and self-interest. The purpose of this dissertation is to determine the impact these influences have on the amount of DSM undertaken by utilities. This research is important for two reasons. First, it provides insight into whether DSM will continue to exist as competition becomes more prevalent in the industry. Secondly, it is important because no one has taken a comprehensive look at firm-level DSM activity on an industry-wide basis. The primary data set used in this dissertation is the U.S. Department of Energy's Annual Electric Utility Report, Form EIA-861, which represents the most comprehensive data set available for analyzing DSM activity in the U.S. There are four measures of DSM activity in this data set: (1) utility expenditures on DSM programs; (2) energy savings by DSM program participants; and (3) the actual and (4) the potential reductions in peak load resulting from utility DSM measures. Each is used as the dependent variable in an econometric analysis where independent variables include various utility characteristics, regulatory characteristics, and service territory and customer characteristics. In general, the results from the econometric analysis suggest that in 1993, DSM activity was primarily the result of regulatory pressure. All of the evidence suggests that if DSM continues to exist in a deregulated environment, it will be at a greatly reduced level. This conclusion holds unless utilities see advantages to DSM as a marketing tool to increase customer satisfaction and loyalty.

Bock, Mark Joseph

393

[Changes in the high-frequency electrical brain activity in the animal hypnosis state in rabbits].  

PubMed

The EEG spectral analysis applied to electrical brain activity of rabbits in the state of animal hypnosis revealed a 2-4-fold increase in the power of the sigma frequency band (12-17 Hz) and a 1.5-2-fold decrease in the gamma frequency (especially 40-70 Hz) in addition to well-known growth of delta (0.3-3 Hz) and reduction of theta activity (4-8 Hz). The changes were more prominent in the frontal cortex areas. The influence of hypnotic state on cortical gamma activity pharmacologically augmented by ketamine injection was analyzed. Administration of subanesthetic ketamine doses led to behavioral locomotor excitation of an animal accompanied by a long-lasting (up to 2 h) increase in the gamma electrical activity. If the animal hypnosis was induced after the ketamine injection, it resulted in an almost instant reorganization of the spectral power. The slow-wave power increased and the gamma-power decreased to the baseline levels. Thus, the animal hypnosis eliminated the reorganization of cortical rhythmicity produced by ketamine, which suggests a stabilizing and, to a certain extent, protective function of this kind of hypnosis in the states of behavioral locomotion and stress. PMID:20737897

Roshchina, G Ia; Koroleva, V I; Davydov, V I

2010-01-01

394

Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation.  

PubMed

Active myofascial trigger points are one of the major peripheral pain generators for regional and generalized musculoskeletal pain conditions. Myofascial trigger points are also the targets for acupuncture and/or dry needling therapies. Recent evidence in the understanding of the pathophysiology of myofascial trigger points supports The Integrated Hypothesis for the trigger point formation; however unanswered questions remain. Current evidence shows that spontaneous electrical activity at myofascial trigger point originates from the extrafusal motor endplate. The spontaneous electrical activity represents focal muscle fiber contraction and/or muscle cramp potentials depending on trigger point sensitivity. Local pain and tenderness at myofascial trigger points are largely due to nociceptor sensitization with a lesser contribution from non-nociceptor sensitization. Nociceptor and non-nociceptor sensitization at myofascial trigger points may be part of the process of muscle ischemia associated with sustained focal muscle contraction and/or muscle cramps. Referred pain is dependent on the sensitivity of myofascial trigger points. Active myofascial trigger points may play an important role in the transition from localized pain to generalized pain conditions via the enhanced central sensitization, decreased descending inhibition and dysfunctional motor control strategy. PMID:21439050

Ge, Hong-You; Fernández-de-Las-Peñas, César; Yue, Shou-Wei

2011-01-01

395

A model for the scattering of high-frequency electromagnetic fields from dielectrics exhibiting thermally-activated electrical losses  

NASA Technical Reports Server (NTRS)

An equivalent circuit model (ECM) approach is used to predict the scattering behavior of temperature-activated, electrically lossy dielectric layers. The total electrical response of the dielectric (relaxation + conductive) is given by the ECM and used in combination with transmission line theory to compute reflectance spectra for a Dallenbach layer configuration. The effects of thermally-activated relaxation processes on the scattering properties is discussed. Also, the effect of relaxation and conduction activation energy on the electrical properties of the dielectric is described.

Hann, Raiford E.

1991-01-01

396

Geometric analysis of transient bursts  

NASA Astrophysics Data System (ADS)

We consider the effect of a brief stimulation from the rest state of a minimal neuronal model with multiple time scales. Such transient dynamics brings out the intrinsic bursting capabilities of the system. Our main goal is to show that a minimum of three dimensions is enough to generate spike-adding phenomena in transient responses, and that the onset of a new spike can be tracked using existing continuation packages. We take a geometric approach to illustrate how the underlying fast subsystem organises the spike adding in much the same way as for spike adding in periodic bursts, but the bifurcation analysis for spike onset is entirely different. By using a generic model, we further strengthen claims made in our earlier work that our numerical method for spike onset can be used for a broad class of systems.

Osinga, Hinke M.; Tsaneva-Atanasova, Krasimira T.

2013-12-01

397

BART - Burst Alert Robotic Telescope  

NASA Astrophysics Data System (ADS)

BART is a small intelligent robotic CCD telescope, devoted to rapid observation of prompt gamma ray burst transients. During its operation since early 2001, it had several prompt observations with world-competitive response time. The constraints to object magnitude were estimated and published in GCN circulars. Telescope is located in Astronomical Institute of the Czech Academy of Sciences in Ond?ejov. This paper describes also its new control system, named RTS2, which is in service since February 2003.

Jelínek, M.; Kubánek, P.; Hudec, R.; Nekola, M.; Topinka, M.; Štrobl, J.

2005-08-01