These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Bursts of active transport in living cells  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

2

Bursts of Active Transport in Living Cells  

NASA Astrophysics Data System (ADS)

We show, using a large new data set, that the temporally resolved speed of active cargo transport in living cells follows a scaling law over several decades of time and length. The statistical regularities display a time-averaged shape that we interpret to reflect stress buildup, followed by rapid release. The scaling power law agrees quantitatively with those reported in inanimate systems (jammed colloids and granular media, and magnetic Barkhausen noise), suggesting a common origin in pushing through a crowded environment in a weak force regime. The implied regulation of the speed of active cellular transport due to environmental obstruction results in bursts of speed and acceleration. These findings extend the classical notion of molecular crowding.

Wang, Bo; Kuo, James; Granick, Steve

2013-11-01

3

Olivary subthreshold oscillations and burst activity revisited  

PubMed Central

The inferior olive (IO) forms one of the major gateways for information that travels to the cerebellar cortex. Olivary neurons process sensory and motor signals that are subsequently relayed to Purkinje cells. The intrinsic subthreshold membrane potential oscillations of the olivary neurons are thought to be important for gating this flow of information. In vitro studies have revealed that the phase of the subthreshold oscillation determines the size of the olivary burst and may gate the information flow or encode the temporal state of the olivary network. Here, we investigated whether the same phenomenon occurred in murine olivary cells in an intact olivocerebellar system using the in vivo whole-cell recording technique. Our in vivo findings revealed that the number of wavelets within the olivary burst did not encode the timing of the spike relative to the phase of the oscillation but was related to the amplitude of the oscillation. Manipulating the oscillation amplitude by applying Harmaline confirmed the inverse relationship between the amplitude of oscillation and the number of wavelets within the olivary burst. Furthermore, we demonstrated that electrotonic coupling between olivary neurons affect this modulation of the olivary burst size. Based on these results, we suggest that the olivary burst size might reflect the “expectancy” of a spike to occur rather than the spike timing, and that this process requires the presence of gap junction coupling. PMID:23189043

Bazzigaluppi, Paolo; De Gruijl, Jornt R.; van der Giessen, Ruben S.; Khosrovani, Sara; De Zeeuw, Chris I.; de Jeu, Marcel T. G.

2012-01-01

4

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

5

Hemicholinium-3 selectively alters the rhythmically bursting activity of septo-hippocampal neurons in the rat.  

PubMed

The medial septal area contains neurons which project to the hippocampal formation. A sizeable proportion of these septo-hippocampal neurons (SHNs) are cholinergic. About 40% of them also display a characteristic discharge pattern in rhythmic bursts. We hypothesized that SHNs with a rhythmically bursting activity (RBA) are the cholinergic ones. To test this hypothesis we studied the effects of acetylcholine synthesis blockade by hemicholinium-3 (HC-3) on the properties of the SHNs. HC-3 (16, 32 or 64 micrograms total dose) or saline were injected in the lateral ventricles of adult male Sprague-Dawley rats anesthetized with urethane. Extracellular recordings from SHNs in the medial septal area were obtained within hours after HC-3 injections (n = 24 animals). SHNs were identified by their antidromic response following electrical stimulation of the fimbria-fornix. The pharmacological properties of SHNs were studied in some animals using microiontophoretic applications from multibarreled electrodes filled with various neurotransmitters. The hippocampal rhythmic slow activity (RSA or theta) was abolished even after the lowest dose of HC-3 tested (16 micrograms). No significant change in SHNs conduction velocity or spontaneous activity was observed at any dose of HC-3. The percentage of SHNs with RBA was unchanged. In contrast the mean frequency of the RBA was decreased by HC-3 in a dose-dependent fashion. The mean frequency was lowest within the first 3 h after injection. Although the mean spontaneous activity was unchanged SHNs tended to have more spikes per burst. The effects of various neurotransmitters on SHNs were qualitatively unchanged after HC-3 injection. These results suggest that acetylcholine synthesis blockade by HC-3 leads not only to the disappearance of the hippocampal RSA in urethane-anesthetized animals, but also to a decrease in the frequency of the rhythmically bursting activity of the SHNs. Since the 4-Hz hippocampal theta is atropine-sensitive, the results provide indirect evidence that the SHNs with rhythmically bursting activity are the cholinergic SHNs. PMID:2702465

Jobert, A; Bassant, M H; Lamour, Y

1989-01-01

6

The 2008 May burst activation of SGR 1627-41  

E-print Network

In May 2008 the soft gamma-ray repeater SGR 1627-41 resumed its bursting activity after nearly a decade of quiescence. After detection of a bright burst, Swift pointed its X-ray telescope in the direction of the source in less than five hours and followed it for over five weeks. In this paper we present an analysis of the data from these Swift observations and an XMM-Newton one performed when SGR 1627-41 was still in a quiescent state. The analysis of the bursts detected with Swift/BAT shows that their temporal and spectral properties are similar to those found in previous observations of SGR 1627-41 and other soft gamma-ray repeaters. The maximum peak luminosity of the bursts was about 2E+41 erg/s. Our data show that the outburst was accompanied by a fast flux enhancement and by a hardening of the spectrum with respect to the persistent emission.

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

2008-07-10

7

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

8

Quantifying bursting neuron activity from calcium signals using blind deconvolution  

PubMed Central

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.

2013-01-01

9

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

10

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

11

Size scaling and bursting activity due to thermally induced cracking  

NASA Astrophysics Data System (ADS)

Sub-critical rupture, occurring under a constant load below the fracture strength of materials, is of fundamental importance in a wide range of physical, biological, and geological systems. During the last decade major progress has been achieved in the understanding of the role of quenched disorder in the size scaling of materials strength. However, under sub-critical loads, the interplay of annealed disorder (thermal noise) and of the inhomogeneous stress field in the rupture process still remained an open fundamental problem. We study sub-critical fracture driven by thermally activated crack nucleation in the framework of fiber bundle models. Based on analytic calculations and computer simulations we show that in the presence of stress inhomogeneities, thermally activated cracking results in an anomalous size effect, i.e. the average lifetime of the system decreases as a power law of the system size, where the exponent depends on the external load and on the temperature. We propose a modified form of the Arrhenius law which provides a comprehensive description of thermally activated breakdown. On the microlevel, thermal fluctuations trigger bursts of breakings which proved to have a power law size distribution. We compare analytic results obtained in the mean field limit to the computer simulations of localized load redistribution to reveal the effect of the range of interaction on the time evolution. Focusing on the waiting times between consecutive bursts we show that the time evolution has two distinct forms: at high load values the breaking process continuously accelerates towards macroscopic failure, however, for low loads and high enough temperatures the acceleration is preceded by a slow-down. Analyzing the structural entropy and the location of consecutive bursts we show that in the presence of stress concentration the early acceleration is the consequence of damage localization. The distribution of waiting times has a power law form with an exponent switching between 1 and 2 as the load and temperature are varied.

Kun, F.; Yoshioka, N.; Ito, N.

2012-04-01

12

The spontaneous electrical activity of neurons in leech ganglia  

PubMed Central

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

2013-01-01

13

Type II and IV radio bursts in the active period October-November 2003  

NASA Astrophysics Data System (ADS)

In this report we present the Type II and IV radio bursts observed and analyzed by the radio spectrograph ARTEMIS IV1, in the 650-20MHz frequency range, during the active period October-November 2003. These bursts exhibit very rich fine structures such fibers, pulsations and zebra patterns which is associated with certain characteristics of the associated solar flares and CMEs.

Petoussis, V.; Tsitsipis, P.; Kontogeorgos, A.; Moussas, X.; Preka-Papadema, P.; Hillaris, A.; Caroubalos, C.; Alissandrakis, C. E.; Bougeret, J.-L.; Dumas, G.

2006-08-01

14

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

E-print Network

of plasma insulin in humans, mice, rats and dogs (28, 33, 36, 42). Mouse islets display diverse oscillatorySlow oscillations of KATP conductance in mouse pancreatic islets provide support for electrical of KATP conductance in mouse pancreatic islets provide support for electrical bursting driven by metabolic

Bertram, Richard

15

Magnetar Bursts  

NASA Technical Reports Server (NTRS)

The Fermi/Gamma-ray Burst Monitor (GBM) was launched in June 2008. During the last five years the instrument has observed several hundreds of bursts from 8 confirmed magnetars and 19 events from unconfirmed sources. I will discuss the results of the GBM magnetar burst catalog, expand on the different properties of their diverse source population, and compare these results with the bursting activity of past sources. I will then conclude with thoughts of how these properties fit the magnetar theoretical models.

Kouveliotou, Chryssa

2014-01-01

16

Hamstrings Activity During Knee Extensor Strength Testing: Effects of Burst Superimposition  

PubMed Central

Quadriceps muscle strength is often used as a criterion for functional progression and return to activity after knee joint injury or surgery. Previous research has demonstrated that noteworthy antagonist activity is present during knee strength testing. the countermoment associated with this antagonist muscle activity may lead to an underestimation of knee strength. the burst superimposition method of strength testing is considered by some to be the current gold standard. the effect of burst super-imposition on antagonist activity is unknown. the purpose of this study was to test the hypothesis that burst superimposition diminishes antagonistic hamstrings activity during knee extensor strength testing. Isometric knee strength testing was performed in 22 (11 males, 11 females) active young people with no history of serious lower extremity injuries using the burst superimposition method. the magnitude of hamstrings muscle activity was assessed just before and after burst superimposition. contrary to our hypothesis, a small, but statistically significant increase in antagonistic medial hamstrings activity was observed with burst superimposition (7.23 vs. 9.62; P < 0.001). Higher lateral hamstrings activity was also observed, but this did not reach statistical significance (15.03 vs. 13.50; P = 0.087). though statistically significant, the small increase in hamstrings activity is unlikely to be clinically meaningful. PMID:19223946

Krishnan, Chandramouli; Williams, Glenn N.

2008-01-01

17

Tamoxifen does not inhibit the swell activated chloride channel in human neutrophils during the respiratory burst  

SciTech Connect

Effective functioning of neutrophils relies upon electron translocation through the NADPH oxidase (NOX). The electron current generated (I{sub e}) by the neutrophil NADPH oxidase is electrogenic and rapidly depolarises the membrane potential in activated human neutrophils. Swelling activated chloride channels have been demonstrated in part to counteract the depolarisation generated by the NADPH oxidase I{sub e}. In the present study, the effects of inhibitors of swell activated chloride channels on ROS production and on the swelling activated chloride conductance was investigated in activated human neutrophils. Tamoxifen (10 {mu}M), a specific inhibitor for swell activated chloride channels in neutrophils, completely inhibited both the PMA and FMLP stimulated respiratory burst. This inhibition of the neutrophil respiratory burst was not due to the blocking effect of tamoxifen on the swelling activated chloride conductance in these cells. These results demonstrate that a tamoxifen insensitive swell activated chloride channel has important significance during the neutrophil respiratory burst.

Ahluwalia, Jatinder [Leukocyte and Ion Channel Research Laboratory, School of Health and Biosciences, University of East London, Stratford Campus, London E15 4LZ (United Kingdom)], E-mail: j.ahluwalia@uel.ac.uk

2008-10-31

18

Bursts and Oscillations as Independent Properties of Neural Activity in the Parkinsonian Globus Pallidus internus  

PubMed Central

Bursts and oscillatory modulations in firing rate are hallmark features of abnormal neuronal activity in the parkinsonian Globus Pallidus internus (GPi). Although often implicated together in the pathophysiology of parkinsonian signs, little is known about how burst discharges and oscillatory firing (OF) relate to each other. To investigate this question, extracellular single-unit neuronal activity was recorded from 132 GPi cells in 14 Parkinson’s disease patients. We found that burst firing was equally prevalent in OF and non-oscillatory firing (NOF) cells (p>0.5). More than half of the cells were characterized by either aperiodic bursty activity or OF, but not both. OF and NOF cells had statistically-indistinguishable levels of mean burstiness (p=0.8). Even when bursting and OF co-existed in individual cells, levels of burstiness and oscillatory power were seldom correlated across time. Interestingly, however, the few OF cells with spectral peaks between 8–13-Hz (?-range) were substantially burstier than other cells (p<0.01) and showed an unique burst morphology and stronger temporal correlations between oscillatory power and burstiness. We conclude that independent mechanisms may underlie the burst discharges and OF typical of most neurons in the parkinsonian GPi. PMID:20727974

Chan, Vanessa; Starr, Philip A; Turner, Robert S.

2010-01-01

19

Modeling Electrically Active Viscoelastic Membranes  

PubMed Central

The membrane protein prestin is native to the cochlear outer hair cell that is crucial to the ear's amplification and frequency selectivity throughout the whole acoustic frequency range. The outer hair cell exhibits interrelated dimensional changes, force generation, and electric charge transfer. Cells transfected with prestin acquire unique active properties similar to those in the native cell that have also been useful in understanding the process. Here we propose a model describing the major electromechanical features of such active membranes. The model derived from thermodynamic principles is in the form of integral relationships between the history of voltage and membrane resultants as independent variables and the charge density and strains as dependent variables. The proposed model is applied to the analysis of an active force produced by the outer hair cell in response to a harmonic electric field. Our analysis reveals the mechanism of the outer hair cell active (isometric) force having an almost constant amplitude and phase up to 80 kHz. We found that the frequency-invariance of the force is a result of interplay between the electrical filtering associated with prestin and power law viscoelasticity of the surrounding membrane. Paradoxically, the membrane viscoelasticity boosts the force balancing the electrical filtering effect. We also consider various modes of electromechanical coupling in membrane with prestin associated with mechanical perturbations in the cell. We consider pressure or strains applied step-wise or at a constant rate and compute the time course of the resulting electric charge. The results obtained here are important for the analysis of electromechanical properties of membranes, cells, and biological materials as well as for a better understanding of the mechanism of hearing and the role of the protein prestin in this mechanism. PMID:22701528

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

2012-01-01

20

Age-related changes in rhythmically bursting activity in the medial septum of rats.  

PubMed

The effects of aging on the firing of septohippocampal neurons were estimated in unanesthetized, restrained young, old and very old rats (respectively 3, 23 and 30 months). Extracellular recordings were obtained during various states of arousal. The mean spontaneous activity for the overall neuronal population was not modified by aging. In contrast, the percentage of rhythmically bursting neurons was significantly lower in aged rats. During wakefulness, decrease of bursting activity was observed in old and very old rats (P<0.01 and P<0.001) whereas during rapid eye movement sleep it appeared only in the oldest group (P<0.01). The frequency of the bursts decreased in 30-month-old rats during wakefulness while it remained unchanged in both aged groups during rapid eye movement sleep. In old rats, at a time when the cholinergic septal neurons already deteriorated, a third of neurons recorded during rapid eye movement sleep exhibited a pattern of activity composed of long duration bursts with higher intraburst frequency than in young or very old rats. Our study shows that rhythmically bursting septal activity is impaired in aged rats and that the amplitude of the changes depends on advancing age and on states of arousal. Our findings suggest that age-induced loss and atrophy of cholinergic septal neurons contribute to the disorganization of the rhythmic activity but that functional alterations, influenced by the states of arousal, may also be considered. PMID:10973591

Apartis, E; Poindessous-Jazat, F; Epelbaum, J; Bassant, M H

2000-09-01

21

Electrical Activity in the Spinal Cord of the Chick Embryo, in situ*  

PubMed Central

Unit electrical activity was recorded from single neurons in the lumbo-sacral spinal cord of 15-, 17-, and 19-day chick embryos, in situ. The dorsal columns showed relatively continuous single-unit activity. Below this lies an area of relative quiet 100-200? deep. The ventral two thirds of the cord was the most active region, being characterized by polyneuronal bursts and intermittently active single units. PMID:5267135

Provine, R. R.; Sharma, S. C.; Sandel, T. T.; Hamburger, V.

1970-01-01

22

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

23

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

24

SOLAR CYCLE VARIATIONS OF THE OCCURRENCE OF CORONAL TYPE III RADIO BURSTS AND A NEW SOLAR ACTIVITY INDEX  

SciTech Connect

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

Lobzin, Vasili; Cairns, Iver H.; Robinson, Peter A. [School of Physics, University of Sydney, New South Wales (Australia)

2011-07-20

25

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

26

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

27

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

28

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

PubMed Central

The ability of living cells to maintain an inheritable memory of their gene-expression state is key to cellular differentiation. Bacterial lysogeny serves as a simple paradigm for long-term cellular memory. In this study, we address the following question: in the absence of external perturbation, how long will a cell stay in the lysogenic state before spontaneously switching away from that state? We show by direct measurement that lysogen stability exhibits a simple exponential dependence on the frequency of activity bursts from the fate-determining gene, cI. We quantify these gene-activity bursts using single-molecule-resolution mRNA measurements in individual cells, analyzed using a stochastic mathematical model of the gene-network kinetics. The quantitative relation between stability and gene activity is independent of the fine details of gene regulation, suggesting that a quantitative prediction of cell-state stability may also be possible in more complex systems. PMID:21119634

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

2010-01-01

29

Dendritic calcium activity precedes inspiratory bursts in preBötzinger Complex neurons  

PubMed Central

Medullary interneurons of the preBötzinger Complex (preBötC) assemble excitatory networks that produce inspiratory related neural rhythms, but the importance of somatodendritic conductances in rhythm generation is still incompletely understood. Synaptic input may cause Ca2+ accumulation post-synaptically to evoke a Ca2+-activated inward current that contributes to inspiratory burst generation. We measured Ca2+ transients by two-photon imaging dendrites while recording neuronal somata electrophysiologically. Dendritic Ca2+ accumulation frequently precedes inspiratory bursts, particularly at recording sites 50–300 ?m distal from the soma. Pre-inspiratory Ca2+ transients occur in ‘hotspots’, not ubiquitously, in dendrites. Ca2+ activity propagates orthodromically toward the soma (and antidromically to more distal regions of the dendrite), at rapid rates (300–700 ?m/s). These high propagation rates suggest that dendritic Ca2+ activates an inward current to electrotonically depolarize the soma, rather than propagate as a regenerative Ca2+ wave. These data provide new evidence that respiratory rhythmogenesis may depend on dendritic burst-generating conductances activated in the context of network activity. PMID:21248126

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

2010-01-01

30

Metric type III bursts from a flaring X-ray bright point near an active region  

NASA Technical Reports Server (NTRS)

X-ray bright points (XBPs) are known to show variability on a number of timescales, including impulsive X-ray brightenings. The relationship between these XBP 'flares' and normal flares is poorly known. A fundamental question is whether nonthermal acceleration of particles takes place in XBP flares. We address this issue by seravhing for nonthermal radio emission at metric wavelengths from flaring XBPs identified in Yohkoh/SXT data. Unequivocal evidence for type III-like radio bursts usually attributed to beams of nonthermal electrons on open field lines was found recently by Kundu et al. This suggests that XBP flares are similar to normal flares and can indeed accelerate nonthermal populations of energetic particles. Here we provide further evidence of metric type III bursts from flaring XBPs located near active regions.

Kundu, M. R.; Raulin, J. P.; Pick, M.; Strong, K. T.

1995-01-01

31

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

32

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, Søren Nymand; Borch, Kim; Lassen, Søren Flensted; Sweeney, Matt; Tatsumi, Hirosuke; Westh, Peter

2012-01-01

33

[Sporting activity after burst fractures of the thoracic and lumbar spine A retrospective clinical trial].  

PubMed

Reviewing the international literature, there are only a few papers dealing with the problem of sporting ability after spinal surgery, except some individual case reports. A retrospective clinical trial was initiated to analyze sporting activity and performance after surgical treatment of spinal fractures. The study was designed as a retrospective clinical trial. The patients were followed-up clinically or they were interviewed on phone. Sporting activity and performance level were measured by a self-developed score adapted to the Seto classification. The results in the group of burst fracture patients are presented. 35 out of 104 surgically treated patients fulfilled all criteria of the study, 29 of them could be followed-up. After scoring the sporting activity and the performance level, the results showed that sports like table tennis, jogging, soccer, handball and volleyball are often stopped after the surgical treatment. Downhill skiing, swimming, biking and athletics can be continued, even on a higher performance level than before surgery. Sporting activity is an important part of quality of life in the age group from 20 to 40 years. The data of the study show, that a stable spine after a severe burst fracture allows sporting activity on an equal or even higher level than before. PMID:24193445

Stiletto, R; Hessmann, M; Gotzen, L; Stiletto, H

1995-12-01

34

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

35

NMDA receptor-mediated rhythmic bursting activity in rat supraoptic nucleus neurones in vitro.  

PubMed Central

1. Intracellular recordings were obtained from 112 supraoptic nucleus magnocellular neurosecretory cells (MNCs) in superfused explants of rat hypothalamus maintained in vitro. The effects of glutamate receptor agonists and antagonists were examined at 32-34 degrees C. 2. In control solutions, spontaneously active (> 5 Hz) phasic or continuous neurones showed interspike interval distributions slightly skewed toward short intervals, but did not feature pauses in the 0.4-2 s range. Current injection to alter the rate of cell discharge shifted the histograms according to the mean firing rate, but failed to induce intermittent pauses in the 0.4-2 s range. 3. Application of N-methyl-D-aspartate (NMDA) induced a mode of firing in which bimodal interspike interval distributions reflected a high incidence of clusters of short interspike intervals (0.5-1.5 s) recurring every 1-3 s. In contrast, firing evoked by application of D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid (AMPA) was not associated with a clustering of impulse discharge. 4. The putative endogenous excitatory amino acid transmitters L-glutamate, L-aspartate and quinolinate all mimicked the effects of NMDA. Clustered spiking responses to these agents were reversibly blocked by D,L-2-amino-5-phosphono-valerate (APV), but not by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In contrast, the non-NMDA receptor ligands kainate and quisqualate caused CNQX-sensitive increases in firing rate, but these responses were not associated with the appearance of clustered activity. 5. When applied to cells showing negative resting potentials (< -70 mV), or to neurones hyperpolarized by current injection, responses to NMDA consisted of rhythmic (approximately 1 Hz) voltage oscillations associated with bursts of spike discharge. In the presence of TTX, NMDA could induce subthreshold voltage oscillations in the absence of action potentials. 6. Application of a voltage clamp to potentials between -75 and -55 mV during rhythmic bursting responses failed to reveal any rhythmic oscillation of the membrane current. In all cases, rhythmic bursting activity resumed upon returning to the current-clamp mode. 7. Rhythmic bursting responses to NMDA application were abolished in Mg(2+)-free solutions, suggesting that the voltage dependence of NMDA channels served to promote regenerative voltage changes throughout the cycle. The NMDA-induced current itself, however, did not appear to decrease with time, suggesting that a distinct, outward current, was necessary to initiate the repolarizing phase of each cycle.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1302282

Hu, B; Bourque, C W

1992-01-01

36

Simultaneous Estimation of Electrical and Thermal Properties of Isotropic Material from the Tone-Burst Eddy Current Thermography (TBET) Time–Temperature Data  

Microsoft Academic Search

In this paper, an inversion method is proposed to determine simultaneously the electrical and the thermal properties of a given isotropic material from the time–temperature data obtained from tone-burst eddy current thermography (TBET). A multiphysics 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

N. Biju; N. Ganesan; C. V. Krishnamurthy; Krishnan Balasubramaniam

2011-01-01

37

Type III Radio Bursts Observed with Radio Spectrograph ARTEMIS IV within the Intense Active Period of October-November 2003  

NASA Astrophysics Data System (ADS)

We investigate the relationship of metric type III radio bursts obtained with radio spectrograph ARTEMIS IV (20-650 MHz) in Thermopylae, to GOES SXR/Ha and SOHO/LASCO CMEs within the period of intense activity 20 October to 5 November 2003. Our sample consists of 123 type III radio bursts, 115 SXR Flares (mostly C-type) and 12 CMEs. 69% of type III bursts are coincident in time with SXR Flares, while the rest 31% were detected between successive SXR flux maxima and though not always in the same active region as the SXR Flare, thereby labeled as SXR Less. The lack of SXR enhancement in SXR less type III bursts was probably the result of increased SXR background which prevented detection. It is found also, that 62% of the Flares are associated with type III radio bursts. Furthermore, we study the characteristic type III parameters i.e. start frequency, frequency band and duration as well as the SXR Flare parameters i.e. Flux, Duration, Apparent Area, rise time, decay time and their ratio. Finally, we tried to investigate any characteristic variation occurred because of the different morphology of the three major active regions, 484, 486 and 488 of that period.

Thanasa, M.; Preka-Papadima, P.; Moussas, X.; Tsitsipis, P.; Kontogeorgos, A.

2010-01-01

38

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

39

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.

40

Spatiotemporal dynamics of the electrical network activity in the root apex.  

PubMed

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

2009-03-10

41

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.; Baluška, F.; Arecchi, F. T.; Mancuso, S.

2009-01-01

42

Activation of group I metabotropic glutamate receptors enhances persistent sodium current and rhythmic bursting in main olfactory bulb external tufted cells  

PubMed Central

Rhythmically bursting olfactory bulb external tufted (ET) cells are thought to play a key role in synchronizing glomerular network activity to respiratory-driven sensory input. Whereas spontaneous bursting in these cells is intrinsically generated by interplay of several voltage-dependent currents, bursting strength and frequency can be modified by local intrinsic and centrifugal synaptic input. Activation of metabotropic glutamate receptors (mGluRs) engages a calcium-dependent cation current (ICAN) that increases rhythmic bursting, but mGluRs may also modulate intrinsic mechanisms involved in bursting. Here, we used patch-clamp electrophysiology in rat olfactory bulb slices to investigate whether mGluRs modulate two key intrinsic currents involved in ET cell burst initiation: persistent sodium (INaP) and hyperpolarization-activated cation (Ih) currents. Using a BAPTA-based internal solution to block ICAN, we found that the mGluR1/5 agonist DHPG enhanced INaP but did not alter Ih. INaP enhancement consisted of increased current at membrane potentials between ?60 and ?50 mV and a hyperpolarizing shift in activation threshold. Both effects would be predicted to shorten the interburst interval. In agreement, DHPG modestly depolarized (?3.5 mV) ET cells and increased burst frequency without effect on other major burst parameters. This increase was inversely proportional to the basal burst rate such that slower ET cells exhibited the largest increases. This may enable ET cells with slow intrinsic burst rates to pace with faster sniff rates. Taken with other findings, these results indicate that multiple neurotransmitter mechanisms are engaged to fine-tune rhythmic ET cell bursting to context- and state-dependent changes in sniffing frequency. PMID:24225539

Ennis, Matthew

2013-01-01

43

The atmospheric electric global circuit. [thunderstorm activity  

NASA Technical Reports Server (NTRS)

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

Kasemir, H. W.

1979-01-01

44

Early detectors of the heart's electrical activity.  

PubMed

It was in Matteucci's rheoscopic frog in Pisa that evidence was first found for the electrical activity of the heart in 1844, and his results were confirmed and expanded 12 years later at Würzburg. The capillary electrometer gave a continuous record that could be photographed, and was used initially by Einthoven who, to obviate the onerous mathematical conversion of the electrometer record, developed the string galvanometer by the close of the century, and showed its clinical value in 1906. PMID:16650272

Breathnach, Caoimhghín S; Westphal, Wolfgang

2006-04-01

45

The Effects of Acute and Developmental Temperature on Burst Swimming Speed and Myofibrillar ATPase Activity in Tadpoles of the Pacific Tree Frog, [ITAL]Hyla regilla[\\/ITAL  

Microsoft Academic Search

The effects of acute and developmental temperature on max- imum burst swimming speed, body size, and myofibrillar ATP- ase activity were assessed in tadpoles of the Pacific tree frog, Hyla regilla. Tadpoles from field-collected egg masses were reared in the laboratory at 157 (cool) and 257C (warm). Body size, maximum burst swimming speed from 57 to 357C, and tail myofibrillar

Timothy B. Watkins

2000-01-01

46

How Long does a Burst Burst?  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

47

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)

2008-12-23

48

Diacylglycerol Kinases Terminate Diacylglycerol Signaling during the Respiratory Burst Leading to Heterogeneous Phagosomal NADPH Oxidase Activation*  

PubMed Central

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; Chatilialoglu, Alexandros; Steinberg, Benjamin E.; Ueyama, Takehiko; Du, Guangwei; Grinstein, Sergio; Fairn, Gregory D.

2013-01-01

49

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

50

The Activated SA and JA Signaling Pathways Have an Influence on flg22-Triggered Oxidative Burst and Callose Deposition  

PubMed Central

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

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

2014-01-01

51

Electricity  

NSDL National Science Digital Library

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

Lerdahl, Miss

2010-02-23

52

Connexin hemichannels contribute to spontaneous electrical activity in the human fetal cortex.  

PubMed

Before the human cortex is able to process sensory information, young postmitotic neurons must maintain occasional bursts of action-potential firing to attract and keep synaptic contacts, to drive gene expression, and to transition to mature membrane properties. Before birth, human subplate (SP) neurons are spontaneously active, displaying bursts of electrical activity (plateau depolarizations with action potentials). Using whole-cell recordings in acute cortical slices, we investigated the source of this early activity. The spontaneous depolarizations in human SP neurons at midgestation (17-23 gestational weeks) were not completely eliminated by tetrodotoxin--a drug that blocks action potential firing and network activity--or by antagonists of glutamatergic, GABAergic, or glycinergic synaptic transmission. We then turned our focus away from standard chemical synapses to connexin-based gap junctions and hemichannels. PCR and immunohistochemical analysis identified the presence of connexins (Cx26/Cx32/Cx36) in the human fetal cortex. However, the connexin-positive cells were not found in clusters but, rather, were dispersed in the SP zone. Also, gap junction-permeable dyes did not diffuse to neighboring cells, suggesting that SP neurons were not strongly coupled to other cells at this age. Application of the gap junction and hemichannel inhibitors octanol, flufenamic acid, and carbenoxolone significantly blocked spontaneous activity. The putative hemichannel antagonist lanthanum alone was a potent inhibitor of the spontaneous activity. Together, these data suggest that connexin hemichannels contribute to spontaneous depolarizations in the human fetal cortex during the second trimester of gestation. PMID:25197082

Moore, Anna R; Zhou, Wen-Liang; Sirois, Carissa L; Belinsky, Glenn S; Zecevic, Nada; Antic, Srdjan D

2014-09-16

53

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

2006-11-30

54

Three dimensional representation of brain electrical activity.  

PubMed

Brain topography mapping is a useful technique for the representation of electrical activity recorded on the scalp. It clarifies spatial and temporal relationships between different cortical areas. In this work we propose a system which includes several enhancements over those previously proposed, such as an optimised interpolation method and a three dimensional reconstruction of maps. This system is available in a personal computer environment. Results clearly show a superiority of the 3D representation over 2D maps obtained with different projections. The performance of this system in terms of speed and precision is comparable to that of dedicated image processing and image synthesis workstations proposed for brain mapping. PMID:7803200

Medina, V; Hassainia, F; Langevin, F; Gaillard, P

1994-01-01

55

Electric current-induced lymphatic activation.  

PubMed

The lymphatic system in skin plays important roles in drainage of wastes and in the afferent phase of immune response. We previously showed that activation of vascular endothelial growth factor receptor (VEGFR), specifically the VEGFC/VEGFR-3 pathway, attenuates oedema and inflammation by promoting lymphangiogenesis, suggesting a protective role of lymphatic vessels against skin inflammation. However, it remains unknown how physical stimuli promote lymphatic function. Here, we show that lymphatic endothelial cells (LECs) are activated by direct-current (DC) electrical stimulation, which induced extension of actin filaments of LECs, increased calcium influx into LECs, and increased phosphorylation of p38 mitogen-activated protein kinase (MAPK). An inhibitor of focal adhesion kinase, which plays a role in cellular adhesion and motility, diminished the DC-induced extension of F-actin and abrogated p38 phosphorylation. Time-lapse imaging revealed that pulsed-DC stimulation promoted proliferation and migration of LECs. Overall, these results indicate that electro-stimulation activates lymphatic function by activating p38 MAPK. PMID:25308203

Kajiya, Kentaro; Matsumoto-Okazaki, Yuko; Sawane, Mika; Fukada, Kaedeko; Takasugi, Yuya; Akai, Tomonori; Saito, Naoki; Mori, Yuichiro

2014-12-01

56

Role of Electrical Activity in Promoting Neural Repair  

PubMed Central

The nervous system communicates in a language of electrical activities. The motivation to replace function lost through injury or disease through electrical prostheses has gained traction through steady advances in basic and translational science addressing the interface between electrical prostheses and the nervous system. Recent experiments suggest that electrical activity, signaling through specific molecular pathways, promotes neuronal survival and regeneration. Such data suggests that electrical prostheses, in addition to replacing lost function, may slow underlying degenerative disease or induce regenerative response. Here we review these data with a focus on retinal neurons, and discuss current efforts to translate this effect of electrical activity into clinically applicable treatments. PMID:22342908

Goldberg, Jeffrey L.

2012-01-01

57

Role of Ca(2+)-activated K+ channels in electrical activity of longitudinal and circular muscle layers of canine colon.  

PubMed

The role of Ca(2+)-activated K+ channels (BK channels) in the canine colon was evaluated by testing the effects of charybdotoxin (ChTX) and tetraethylammonium on K+ currents of isolated myocytes and on electrical and mechanical activity of tissue strips. ChTX blocked Ca(2+)-activated outward current [IK(Ca)] in a dose- and voltage-dependent manner. No significant differences in IK(Ca) density, ChTX block, or Ca2+ sensitivity of BK channels were observed between circular and longitudinal myocytes. ChTX (100 nM) blocked 60% of current at +80 mV. Delayed rectifier current was not inhibited by 100 nM ChTX. In the absence of agonists, ChTX did not affect electrical or mechanical activity of circular muscle strips. In the presence of 10(-6) M BAY K 8644 or 10(-6) M acetylcholine, ChTX increased slow-wave duration and amplitude, induced membrane potential oscillations, and potentiated contraction. In unstimulated longitudinal muscle strips, ChTX depolarized the tissue, increased burst duration and spiking frequency, and resulted in an increase in contractions. These results indicate that BK channels are important regulators of colonic motility. In the longitudinal layer, BK channels are involved in setting membrane potential and determine excitability. In the circular layer, ChTX-sensitive channels do not participate in the in vitro basal electrical activity but limit the responses to excitatory agonists. PMID:7534981

Carl, A; Bayguinov, O; Shuttleworth, C W; Ward, S M; Sanders, K M

1995-03-01

58

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

59

Complicated Electrical Activities in Cardiac Tissue  

NASA Astrophysics Data System (ADS)

It has become widely accepted that ventricular fibrillation, the most dangerous cardiac arrhythmias, is a major cause of death in the industrialized world. Alternans and conduction block have recently been related to the progression from ventricular tachycardia to ventricular fibrillation. From the point of view in cellular electrophysiology, ventricular tachycardia is the formation of reentrant wave in cardiac tissue. And ventricular fibrillation arises from subsequent breakdown of reentrant wave into multiple drifting and meandering spiral waves. In this paper, we numerically study pulse and vortex dynamics in cardiac tissue. Our numerical results include 1:1 normal sinus rhythm, 2:1 conduction block, complete conduction block, spiral wave, and spiral breakup. All of our numerical findings can be corresponding to clinical measurements in electrocardiogram. Various electrical activities in cardiac tissue will be discussed in detail in the present manuscript.

Shiau, Yuo-Hsien; Hsueh, Ming-Pin; Hseu, Shu-Shya; Yien, Huey-Wen

60

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

61

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

PubMed Central

Macrophages isolated from normal mucosa (greater than 5 cm from tumour) and inflamed mucosa (from patients with inflammatory bowel disease) of colon and ileum were studied for their ability to undergo a respiratory burst as assessed by reduction of nitroblue tetrazolium to formazan. Using phorbol myristate acetate (PMA) and opsonised zymosan as triggers, only a minority (median: 8% for zymosan and 9% for PMA) of macrophages isolated from normal colonic mucosa demonstrated release of oxygen radicals. In contrast, a significantly greater (median: 17% for zymosan and 45% for PMA) proportion of macrophages isolated from inflamed colonic mucosa were able to undergo respiratory burst. Studies with normal and inflamed ileum showed similar results. Stimulation of macrophages isolated from normal colon with interferon-gamma produced only a small increase in the proportion of cells showing release of oxygen radicals. We conclude that the respiratory burst capacity of majority of macrophages isolated from normal colon and ileum is downregulated and a greater proportion of macrophages isolated from inflamed colon and ileum are able to undergo a respiratory burst. Images Fig. 2 PMID:2511088

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

1989-01-01

62

Propofol and sevoflurane induce distinct burst suppression patterns in rats  

E-print Network

Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological ...

Westover, M. Brandon

63

Electrically evoked locomotor activity in the turtle spinal cord hemi-enlargement preparation.  

PubMed

We assessed the locomotor capacity of the left half of the spinal cord hindlimb enlargement in low-spinal turtles. Forward swimming was evoked in the left hindlimb by electrical stimulation of the right dorsolateral funiculus (DLF) at the anterior end of the third postcervical spinal segment (D3). Animals were held by a band-clamp in a water-filled tank so that hindlimb movements could be recorded from below with a digital video camera. Left hindlimb hip and knee movements were tracked while electromyograms (EMGs) were recorded from left hip and knee muscles. In turtles with intact spinal cords, electrical stimulation of the right D3 DLF evoked robust forward swimming movements of the left hindlimb, characterized by rhythmic alternation between hip flexor (HF) and hip extensor (HE) EMG discharge, with knee extensor (KE) bursts occurring during the latter part of each HE-off phase. After removing the right spinal hemi-enlargement (D8-S2), DLF stimulation still evoked rhythmic locomotor movements and EMG bursts in the left hindlimb that included HF-HE alternation and KE discharge. However, post-surgical movements and EMG bursts had longer cycle periods, and movements showed lower amplitudes compared to controls. These results show that (1) sufficient locomotor CPG circuitry resides within the turtle spinal hemi-enlargement to drive major components of the forward swim motor pattern, (2) contralateral circuitry contributes to the excitation of the locomotor CPG for a given limb, and (3) a sufficient portion of the descending DLF pathway crosses over to the contralateral cord anterior to the hindlimb enlargement to activate swimming. PMID:18597937

Samara, Ramsey F; Currie, Scott N

2008-08-15

64

Evidence That Calcium Release-activated Current Mediates the Biphasic Electrical Activity of Mouse Pancreatic ?-Cells  

Microsoft Academic Search

.   The electrical response of pancreatic ?-cells to step increases in glucose concentration is biphasic, consisting of a prolonged\\u000a depolarization with action potentials (Phase 1) followed by membrane potential oscillations known as bursts. We have proposed\\u000a that the Phase 1 response results from the combined depolarizing influences of potassium channel closure and an inward, nonselective\\u000a cation current (I\\u000a \\u000a CRAN) that

D. Mears; I. Atwater; E. Rojas; R. Bertram; A. Sherman

1997-01-01

65

Magnetism and Electricity Activity "Attracts" Student Interest  

ERIC Educational Resources Information Center

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

Roman, Harry T.

2010-01-01

66

Theta-burst LTP.  

PubMed

This review covers the spatial and temporal rules governing induction of hippocampal long-term potentiation (LTP) by theta-burst stimulation. Induction of LTP in field CA1 by high frequency stimulation bursts that resemble the burst discharges (complex-spikes) of hippocampal pyramidal neurons involves a multiple-step mechanism. A single burst is insufficient for LTP induction because it evokes both excitatory and inhibitory currents that partially cancel and limit postsynaptic depolarization. Bursts repeated at the frequency (~5Hz) of the endogenous theta rhythm induce maximal LTP, primarily because this frequency disables feed-forward inhibition and allows sufficient postsynaptic depolarization to activate voltage-sensitive NMDA receptors. The disinhibitory process, referred to as "priming", involves presynaptic GABA autoreceptors that inhibit GABA release. Activation of NMDA receptors allows a calcium flux into dendritic spines that serves as the proximal trigger for LTP. We include new data showing that theta-burst stimulation is more efficient than other forms of stimulation for LTP induction. In addition, we demonstrate that associative interactions between synapses activated during theta-bursts are limited to major dendritic domains since such interactions occur within apical or basal dendritic trees but not between them. We review evidence that recordings of electrophysiological responses during theta burst stimulation can help to determine if experimental manipulations that affect LTP do so by affecting events antecedent to the induction process, such as NMDA receptor activation, or downstream signaling cascades that result from postsynaptic calcium fluxes. Finally, we argue that theta-burst LTP represents a minimal model for stable, non-decremental LTP that is more sensitive to a variety of experimental manipulations than is LTP induced by other stimulation paradigms. This article is part of a Special Issue entitled SI: Brain and Memory. PMID:25452022

Larson, John; Munkácsy, Erin

2014-10-27

67

U-Shape Suppressive Effect of Phenol Red on the Epileptiform Burst Activity via Activation of Estrogen Receptors in Primary Hippocampal Culture  

PubMed Central

Phenol red is widely used in cell culture as a pH indicator. Recently, it also has been reported to have estrogen-like bioactivity and be capable of promoting cell proliferation in different cell lines. However, the effect of phenol red on primary neuronal culture has never been investigated. By using patch clamp technique, we demonstrated that hippocampal pyramidal neurons cultured in neurobasal medium containing no phenol red had large depolarization-associated epileptiform bursting activities, which were rarely seen in neurons cultured in phenol red-containing medium. Further experiment data indicate that the suppressive effect of the phenol red on the abnormal epileptiform burst neuronal activities was U-shape dose related, with the most effective concentration at 28 µM. In addition, this concentration related inhibitory effect of phenol red on the epileptiform neuronal discharges was mimicked by 17-?-estradiol, an estrogen receptor agonist, and inhibited by ICI-182,780, an estrogen receptor antagonist. Our results suggest that estrogen receptor activation by phenol red in the culture medium prevents formation of abnormal, epileptiform burst activity. These studies highlight the importance of phenol red as estrogen receptor stimulator and cautions of careful use of phenol red in cell culture media. PMID:23560076

Liu, Xu; Chen, Ben; Chen, Lulan; Ren, Wan-Ting; Liu, Juan; Wang, Guoxiang; Fan, Wei; Wang, Xin; Wang, Yun

2013-01-01

68

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

69

Ghostbursting: A Novel Neuronal Burst Mechanism  

Microsoft Academic Search

Pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish have been observed to produce high-frequency burst discharge with constant depolarizing current (Turner et al., 1994). We present a two-compartment model of an ELL pyramidal cell that produces burst discharges similar to those seen in experiments. The burst mechanism involves a slowly changing interaction between the somatic

Brent Doiron; Carlo Laing; André Longtin; Leonard Maler

2002-01-01

70

Ghostbursting: A Novel Neuronal Burst Mechanism  

Microsoft Academic Search

Pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish have been observed to produce high-frequency burst discharge with constant depolarizing current (Turner et al., 1994). We present a two- compartment model of an ELL pyramidal cell that produces burst discharges similar to those seen in experiments. The burst mechanism involves a slowly changing interaction between the

Brent Doiron; Carlo R. Laing; André Longtin; Leonard Maler

2002-01-01

71

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

PubMed

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

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

2014-05-01

72

Role of disulphide bonds in burst-like activity of nicotinic acetylcholine receptor channels in rat sympathetic neurones.  

PubMed Central

1. The effects of reduction of disulphide bonds in nicotinic acetylcholine receptors (nicotinic AChRs) with dithiothreitol (DTT) were studied in rat superior cervical ganglion neurones using the patch-clamp method in whole-cell and cell-attached recording modes. 2. Dithiothreitol (1 mM) markedly reduced the ACh-induced membrane current, while the action of ACh remained reversible. Conversely, bromoacetylcholine (BrACh), if applied after the treatment with DTT, caused irreversible activation of nicotinic AChRs manifested in the appearance of a non-declined steady-state component in BrACh-induced currents accompanied by increased membrane current fluctuations. The successive reoxidation of sulphydryl groups by potassium ferricyanide (1 mM-ferricyanide) restored the response to ACh. Ferricyanide itself had a weaker inhibitory effect on the ACh-induced current, compared to the effect of DTT. 3. As a result of the action of DTT (1 mM), the spectrum of BrACh-induced current noise shifted to a higher frequency range. 4. The distributions of durations of the gaps (closed states) and the bursts (the states identified as open states after the shortest gaps were ignored) in single-channel activity of native (non-treated with DTT) nicotinic AChRs caused by ACh (30 microM) and BrACh (30 microM) were similar and both revealed four to five and two to three components for gap intervals and burst durations respectively. 5. Single-channel behaviour of reduced nicotinic AChRs was similar for both ACh and BrACh as agonists, but significantly differed from that in the native one. The first difference was the marked increase in the frequency of the appearance of long closed states of the channel that was presumably due to enhanced receptor desensitization. The second difference was an almost complete disappearance of long bursts associated with disappearance of the fastest component in gap interval distribution. 6. Mean conductance of single nicotinic AChR channels decreased by approximately 20% in the reduced receptor compared with that in the native one, for both agonists. 7. The results suggest a critical role of disulphide bonds for the functioning of native neuronal nicotinic AChRs: the disruption of disulphide bonds leads to the loss of burst-like kinetics of the nicotinic AChR ionic channel. PMID:1725180

Derkach, V A; Kurenny, D E; Melishchuk, A I; Selyanko, A A; Skok, V I

1991-01-01

73

Francisella noatunensis subsp. noatunensis replicates within Atlantic cod (Gadus morhua L.) leucocytes and inhibits respiratory burst activity.  

PubMed

Francisella noatunensis subsp. noatunensis, causing granulomatosis in cod, has been shown to reside within cod immune cells, mainly within monocytes and macrophages. In the present study, we analysed the ability of the bacterium to replicate within adherent cells isolated from head kidney by in vitro infection of leucocytes. Two different technical approaches for flow cytometry analyses were performed for detection of intracellular bacteria. The presence of the wild type was assessed after identification by intracellular binding of specific antibodies to the pathogen. The other way was to use green fluorescent protein (GFP) transformed bacterium for infection studies allowing direct measurements of fluorescence from infected cells. By both methods we found an increase in fluorescence in infected cells, verifying bacterial replication, both after 4 and 28 h post infection in leucocytes isolated from head kidney (HKL). The GFP transformed bacterium was similar to the wild type in growth and infectivity pattern, showing that it can be a valuable tool for further studies of infection routes and pathology. Further, F. noatunensis subsp. noatunensis was found to inhibit respiratory burst activity, a potent pathogen killing mechanism, in cod leucocytes, but not in such cells from salmon. Our findings may indicate that inhibition of respiratory burst during Francisella infection is a key to its intracellular existence. This strategy seems to be conserved through evolution as it is also observed during infections in higher vertebrates caused by bacteria within the Francisella genus. The results presented here, showing the intracellular existence of Francisella, its replication within leucocytes and the inhibitory effect on respiratory burst, strongly support that these factors contribute to disease and pathology in infected cod. The intracellular replication shown in the present study might contribute to explain the problems of obtaining protective vaccines against Francisella and effective antibiotic treatment of infected fish. PMID:23765119

Vestvik, Nils; Rønneseth, Anita; Kalgraff, Cathrine A K; Winther-Larsen, Hanne C; Wergeland, Heidrun I; Haugland, Gyri T

2013-09-01

74

Status of State Electric Industry Restructuring Activity  

NSDL National Science Digital Library

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

75

Recurrent burst activity from the soft gamma-ray repeater SGR 1900 + 14  

NASA Technical Reports Server (NTRS)

Three short very soft gamma-ray (SGR) transient events from a location consistent with that of the SGR 1900 + 14, first described by Mazets et al. (1979), were detected by the Burst and Transient Source Experiment. The results of observations of the temporal and spectral properties of the SGR 1900 + 14 suggest that the SGR phase lasts at least 13 years, lending support to the suggestion by Kouveliotou et al. (1987) and Fishman et al. (1989) that SGRs are related to galactic (possibly population I) objects, perhaps neutron stars.

Kouveliotou, C.; Fishman, G. J.; Meegan, C. A.; Paciesas, W. S.; Wilson, R. B.; Van Paradijs, J.; Preece, R. D.; Briggs, M. S.; Pendleton, G. N.; Brock, M. N.

1993-01-01

76

Unusual Central Engine Activity in the Double Burst GRB 110709B  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

77

Modification of activation and evaluation properties of narratives by weak complex magnetic field patterns that simulate limbic burst firing.  

PubMed

In two separate experiments a total of 71 volunteers were asked to generate spontaneous narratives that were scored automatically by the Whissell Dictionary of Affect. During the narratives, weak (1 microT; 10 mG) magnetic fields were applied briefly through the temporal planes. In Experiment I, subjects who were exposed to simple sine wave or pulsed fields generated more scorable words that indicated lower activation and evaluation than sham-field conditions. In Experiment II subjects exposed to a computer-generated wave form, designed to simulate neuronal burst firing, generated narratives dominated by more pleasantness and less activation than a reference group. The possibility that this approach could be utilized to study the affective dimension of language selection was indicated. PMID:8407157

Richards, P M; Persinger, M A; Koren, S A

1993-01-01

78

Burst tumulus  

USGS Multimedia Gallery

A burst tumulus near Kamokuna, which is a lava delta where Pu?u ???? flows enter the Pacific Ocean. Tumuli can burst when the influx of lava is rapid compared to the rate at which the crust is thickening by cooling. In these cases the pressure driving the lava is significant...

79

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

80

Energetic electron bursts at high magnetic latitudes: Correlation with magnetospheric activity  

NASA Astrophysics Data System (ADS)

Recently, energetic electron bursts have been reported by the GPS satellites at high magnetic latitudes on field lines that are nominally open, and correlated with sub- storm injections observed on geosynchronous satellites*. These bursts, around 200 KeV in energy (up to ~500 keV), would appear to be magnetospheric in origin, yet they are seen in the polar cap (at model L-values > 10). A list of 397 such events that occurred from February 26, 2001 to November 1, 2001 has been compiled*. In this study we are correlating these events with geophysical indices such AE and Dst (both provisional). We are also correlating the events with solar wind conditions and direct observations of particle precipitating in the polar cap from DMSP observations. Using these correlative observations, we hope to shed light on the nature and origin of the events seen by the GPS spacecraft. * J. C. Ingraham, T. E. Cayton, R. H. W. Friedel, M. G. Henderson and M. G. Tuszewski, Energetic electron injection signatures observed by GPS at high magnetic latitudes, Eos Trans. AGU, 82 (47), Fall Meet. Suppl., Abstract SM31B-0789, 2001.

Lugo-Solis, A.; Lopez, R.; Turner, N.; Friedel, R.; Ingrahm, J.

81

The corpus callosum modulates spindle-burst activity within homotopic regions of somatosensory cortex in newborn rats.  

PubMed

The corpus callosum, a major interhemispheric fiber tract, mediates communication between homotopic regions within the primary somatosensory cortex (S1). Recently, in 1- to 6-day-old rats, brief bursts of oscillatory activity - called spindle-bursts (SBs) - were described in cortical somatosensory areas following sensory feedback from sleep-related myoclonic twitches or specific peripheral stimulation. To determine whether interhemispheric communication via the corpus callosum modulates the expression of SBs during this early period of development, we investigated the spontaneous expression of SBs in unanesthetized 1- to 6-day-old rats as well as SBs evoked by plantar surface stimulation of the forepaw. We hypothesized that surgically disrupting transcallosal communication (i.e. with callosotomy) or unilateral pharmacological manipulation of S1 activity (e.g. by blocking muscarinic receptors) would alter S1 activity in one or both hemispheres. First, callosotomy doubled the rate of spontaneous, twitch-related SBs in left and right S1s by reducing the interval between successive SBs. Second, unilateral infusion into the left S1 of the muscarinic receptor antagonist, scopolamine, inhibited SBs in response to right forepaw stimulation; importantly, SBs were now disinhibited in the right S1 to right forepaw stimulation, thus 'unmasking' an ipsilateral representation. Subsequent callosotomy reinstated contralateral SB responses in the left S1. Finally, tactile and proprioceptive stimulation produced dissociable neurophysiological S1 responses; specifically, SBs were produced in response to proprioceptive, but not tactile, stimulation. We conclude that the corpus callosum modulates functionally inhibitory interactions between homotopic regions in left and right S1s during the early developmental period when organized neurophysiological activity is first detected in the neocortex. PMID:18973571

Marcano-Reik, Amy Jo; Blumberg, Mark S

2008-10-01

82

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

83

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

84

Methylxanthines do not affect rhythmogenic preBötC inspiratory network activity but impair bursting of preBötC-driven motoneurons.  

PubMed

Clinical stimulation of preterm infant breathing with methylxanthines like caffeine and theophylline can evoke seizures. It is unknown whether underlying neuronal hyperexcitability involves the rhythmogenic inspiratory active pre-Bötzinger complex (preBötC) in the brainstem or preBötC-driven motor networks. Inspiratory-related preBötC interneuronal plus spinal (cervical/phrenic) or cranial hypoglossal (XII) motoneuronal bursting was studied in newborn rat en bloc brainstem-spinal cords and brainstem slices, respectively. Non-respiratory bursting perturbed inspiratory cervical nerve activity in en bloc models at >0.25mM theophylline or caffeine. Rhythm in the exposed preBötC of transected en bloc preparations was less perturbed by 10mM theophylline than cervical root bursting which was more affected than phrenic nerve activity. In the preBötC of slices, even 10mM methylxanthine did not evoke seizure-like bursting whereas >1mM masked XII rhythm via large amplitude 1-10Hz oscillations. Blocking A-type ?-aminobutyric (GABAA) receptors evoked seizure-like cervical activity whereas in slices neither XII nor preBötC rhythm was disrupted. Methylxanthines (2.5-10mM), but not blockade of adenosine receptors, phosphodiesterase-4 or the sarcoplasmatic/endoplasmatic reticulum ATPase countered inspiratory depression by muscimol-evoked GABAA receptor activation that was associated with a hyperpolarization and input resistance decrease silencing preBötC neurons in slices. The latter blockers did neither affect preBötC or cranial/spinal motor network bursting nor evoke seizure-like activity or mask corresponding methylxanthine-evoked discharges. Our findings show that methylxanthine-evoked hyperexcitability originates from motor networks, leaving preBötC activity largely unaffected, and suggest that GABAA receptors contribute to methylxanthine-evoked seizure-like perturbation of spinal motoneurons whereas non-respiratory XII motoneuron oscillations are of different origin. PMID:24120555

Panaitescu, B; Kuribayashi, J; Ruangkittisakul, A; Leung, V; Iizuka, M; Ballanyi, K

2013-01-01

85

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

PubMed Central

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

86

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

87

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

88

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

89

Observations of the bursting activity of the 6.7 GHz methanol maser in G33.641-0.228  

NASA Astrophysics Data System (ADS)

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 for 12 days. On average, the bursts occurred once every 59 days, although bursting was not periodic. Since the average power required for causing a burst of order of 1021 J s-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 dust heating process are still unknown.

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

2014-12-01

90

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

91

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

92

Mathematical Approach for Modeling the Uterine Electrical Activity  

NASA Astrophysics Data System (ADS)

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

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

93

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

94

Phase singularities in cardiac electrical activity  

NASA Astrophysics Data System (ADS)

theory of topological spaces has its analogy in biological systems, one of which is the heart. The heart is an excitable medium that can be represented as a set of excitable elements (cardiomyocytes) that behave similarly to hourglasses. Excitable element needs external stimuli to be excited and after finite time goes back to its initial state, so its natural topological space is a ring. Topological space set (phases) can be simple set as ``rest,'' ``excited,'' ``refractory,'' ``relatively refractory'', but it can be as continuous as a set of angles on a 2? circle. In topological spaces topological charge is defined by: [ W=12?ld? (l) ] where l is the integration path and d? is the change in phase. Non zero topological charge is called phase singularity of mapping. Practical application of topological charge analysis is a powerful method to quantify electrical dynamics during ventricular fibrillation (VF). Particularly by means of phase singularity detection it is possible to track wave breaks which relate to anatomical and electrophysiological heterogeneities.

Uzelac, Ilija; Sidorov, Veniamin; Wikswo, John

2010-03-01

95

[Effects of dachengqi decoction and rhubarb on cellular electrical activities in smooth muscle of the guinea-pig taenia coli].  

PubMed

The effects of Dachengqi decoction (DCQ) and Rhubarb (Rb) on spontaneous cellular electrical activities of guinea-pig's taenia coli has been studied by intracellular microelectrode technique. DCQ and Rb could both improve depolarization of cell membrane, speed up the burst of slow wave potential (when drug concentration was 1%, P > 0.05; 10% or 20%, P < 0.05), which was dose dependent. At the same concentration, the effects of Rb were more significant than that of DCQ. These results suggested that DCQ and Rb enhanced directly the cellular electrical excitability so as to strengthen the contraction of colon, is one of the mechanisms of these drugs in cellular level on diarrhea action. The ionic basis of the effects might be that DCQ and Rb reduced the K+conductance of cell membrane in rest state. PMID:8499733

Yang, W X; Jin, Z G; Tian, Z S

1993-01-01

96

Electrically tunable porous silicon active mirrors  

NASA Astrophysics Data System (ADS)

We demonstrate tunable mirrors that consist of a porous silicon microcavity infiltrated with liquid crystal molecules. We show theoretically that by utilizing the electro-optic properties of liquid crystals and the sensitivity of the microcavity resonance position to small changes in optical thickness, the porous silicon active mirror can be switched on (high reflectance) and off (low reflectance) by simply applying a voltage. We discuss the issues of obtaining uniform infiltration of liquid crystal molecules in the constricted geometry of the porous silicon microcavity and determining the necessary change in the liquid crystal orientation to achieve a high reflectance contrast. We also present preliminary experimental results showing a greater than 40% change in the reflectance of our active mirror with the application of voltage.

Weiss, Sharon M.; Fauchet, Philippe M.

2003-05-01

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

Electrically active defects in irradiated 4H-SiC  

Microsoft Academic Search

4H-SiC epilayers were irradiated with either protons or electrons and electrically active defects were studied by means of deep level transient spectroscopy. Motion of defects has been found to occur at temperature as low as 350-400 K. Indeed, the application of an electric field has been found to enhance modifications in defect concentrations that can also occur during long time

M. L. David; G. Alfieri; E. M. Monakhov; A. Hallén; C. Blanchard; B. G. Svensson; J. F. Barbot

2004-01-01

99

Electrically active defects in irradiated 4H-SiC  

Microsoft Academic Search

4H-SiC epilayers were irradiated with either protons or electrons and electrically active defects were studied by means of deep level transient spectroscopy. Motion of defects has been found to occur at temperature as low as 350–400 K. Indeed, the application of an electric field has been found to enhance modifications in defect concentrations that can also occur during long time

M. L. David; G. Alfieri; E. M. Monakhov; A. Halle´n; C. Blanchard; B. G. Svensson; J. F. Barbot

2004-01-01

100

Propofol and sevoflurane induce distinct burst suppression patterns in rats  

PubMed Central

Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Finally, we report the results of our new study showing clear electrophysiological differences in burst suppression patterns induced by two common general anesthetics, sevoflurane and propofol. Our data suggest that the circuit mechanisms that generate burst suppression activity may differ among general anesthetics. PMID:25565990

Kenny, Jonathan D.; Westover, M. Brandon; Ching, ShiNung; Brown, Emery N.; Solt, Ken

2014-01-01

101

The effects of oral consumption of selenium nanoparticles on chemotactic and respiratory burst activities of neutrophils in comparison with sodium selenite in sheep.  

PubMed

The present study was designed to compare the effects of nano-selenium and of sodium selenite on the chemotactic and respiratory burst activities of neutrophils in sheep. Fifteen sheep were randomly divided into three groups. Groups 1 and 2 received selenium nanoparticles (1 mg/kg) or sodium selenite (1 mg/kg) orally, respectively, for ten consecutive days, and the third group was considered as the control. To determine the chemotactic and respiratory burst activities of the neutrophils, the leading front assay and the NBT test were used on heparinized blood samples that were collected at different intervals (days 0, 10th, 20th, and 30th). The results obtained showed that the chemotactic activities in groups 1 and 2 increased significantly on the 10th, 20th, and 30th day, compared to day 0, and on the 20th day in comparison with the 10th day, while in group 2, there was a significant decrease on the 30th day compared to the 20th day. The chemotactic activities in group 1 were significantly higher than in group 2 on the 10th day and in the control group on the 10th, 20th, and 30th day, but the chemotactic activities in group 2 were significantly higher than those in the control group only on the 20th day. On the 30th day into the experiment, the respiratory bursts in groups 1 and 2 were significantly stronger in comparison with those at day 0. Overall, nano-selenium increased the chemotactic and respiratory burst activities more significantly than sodium selenite, which is suggestive of a stronger stimulatory effect of the Se nanoparticles on intracellular activities. PMID:22105658

Kojouri, Gholam Ali; Sadeghian, Sirous; Mohebbi, Abdonnaser; Mokhber Dezfouli, Mohammad Reza

2012-05-01

102

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

PubMed

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

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

2000-08-01

103

Bursting activity in myelinated sensory neurons plays a key role in pain behavior induced by localized inflammation of the rat sensory anglion  

PubMed Central

Abnormal spontaneous activity of sensory neurons is observed in many different preclinical pain models, but its basis is not well understood. In this study mechanical and cold hypersensitivity were induced in rats after inflammation of the L5 dorsal root ganglion (DRG), initiated by local application of the immune stimulator zymosan in incomplete Freund’s adjuvant. Mechanical hypersensitivity was evident by day 1 and maintained for two months. The model also showed reduction of rearing behavior in a novel environment. Microelectrode recordings made in isolated whole DRG on day 3 after inflammation showed a marked increase of spontaneous activity, predominantly with a bursting pattern. The incidence was especially high (44%) in A?? cells. Spontaneous activity and subthreshold membrane potential oscillations were completely blocked by tetrodotoxin (500 nM) and by riluzole (10 ?M), a blocker of persistent sodium currents. In vivo, local perfusion of the inflamed DRG for the first 7 days with riluzole gave long-lasting, dose-dependent reduction in mechanical pain behaviors. Riluzole perfusion did not affect mechanical sensitivity in normal animals. Unmyelinated C cells had a very low incidence of spontaneous activity and were much less affected by riluzole in vitro. Taken together these results suggest that high-frequency and/or bursting spontaneous bursting activity in A?? sensory neurons may play important roles in initiating pain behaviors resulting from inflammatory irritation of the DRG. PMID:22265726

Xie, Wenrui; Strong, Judith A.; Kim, Daniel; Shahrestani, Sameam; Zhang, Jun-Ming

2012-01-01

104

Electrical Impedance Tomography System Based on Active Pascal Olivier Gaggero1,5  

E-print Network

Electrical Impedance Tomography System Based on Active Electrodes Pascal Olivier Gaggero1,5 , Andy in volunteer tests. Keywords: electrical impedance tomography, hardware, EIT, active electrode, electrode belt Based EIT System 1. Introduction Electrical Impedance Tomography (EIT) produces images

Adler, Andy

105

Fast optical response to electrical activation in peripheral nerves  

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

106

Cholecystokinin8 induces edematous pancreatitis in dogs associated with short burst of trypsinogen activation  

Microsoft Academic Search

To study the early pathogenesis of acute edematous pancreatitis in dogs, we examined the relationship of pancreatic hyperstimulation with cholecystokinin-8 (10 ?g\\/kg\\/hr intravenously for 6 hr) to alterations in circulating pancreatic enzymes and pancreatic morphology with special reference to trypsinogen activation. Cholecystokinin-8 infusion was associated with increases in plasma amylase, lipase, trypsin-like immunoreactivity, and plasma and urine trypsinogen activation peptide.

K. W. Simpson; N. Beechey-Newman; C. R. Lamb; J. B. A. Smyth; G. Hughes; K. Coombe; N. Sumar; J. Hermon-Taylor

1995-01-01

107

Antioxidant activity of hyaluronic acid investigated by means of chemiluminescence of equine neutrophil bursts and electron paramagnetic resonance spectroscopy.  

PubMed

Activated neutrophils (PMNs), the ROS/RNS released by PMNs and the derived inflammatory processes are involved in the pathogenesis and progression of human inflammatory airway diseases. Similar diseases are also present in horses which suffer from recurrent airway obstruction (RAO), exercise-induced pulmonary haemorrhage (EIPH) and inflammatory airway diseases (IAD). Hyaluronic acid (HA) plays numerous roles in modulating inflammatory processes. The aim of this study was to examine whether a preparation of HA (MW 900 000 Da) interferes with ROS/RNS during the course of equine PMN respiratory bursts, and to establish the lowest concentration at which it still has antioxidant activity by means of luminol-amplified chemiluminescence (LACL). Electron paramagnetic resonance (EPR) spectroscopy was also used to investigate the direct antiradical activity of HA. The hydroxyl radical was significantly scavenged in a concentration-dependent manner at HA concentrations ranging from 2.5 to 0.16 mg/mL. Superoxide anion, Tempol radical and the ABTS(•+) were significantly inhibited at concentrations ranging from 2.5 to 0.62 mg/mL. The LACL of stimulated equine neutrophils showed that HA induced a statistically significant concentration-effect reduction from 5 mg/mL to 1.25 mg/mL. These findings were confirmed also when l-Arg was added to investigate the inhibition of the resulting peroxynitrite anion. Our findings indicate that, in addition to the human use, HA can also be used to antagonize the oxidative stress generated by free radicals in horses peripheral blood mononuclear cells (PBMCs). In order to achieve therapeutic concentrations, a direct aerosol administration to horses with horse respiratory diseases can be considered, as this route of application is also recommended in human medicine. PMID:25066541

Braga, P C; Dal Sasso, M; Lattuada, N; Greco, V; Sibilia, V; Zucca, E; Stucchi, L; Ferro, E; Ferrucci, F

2015-02-01

108

PERSPECTIVE: Electrical activity enhances neuronal survival and regeneration  

NASA Astrophysics Data System (ADS)

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

Corredor, Raul G.; Goldberg, Jeffrey L.

2009-10-01

109

Dislocation Electrical Activity in III-nitride Films  

Microsoft Academic Search

While it has been postulated that dislocations degrade the performance of III-nitride lasers and electronic devices, the electrical activity of dislocations is not completely understood. Due to their high densities, spatially resolved techniques are necessary to separate out the dislocation contribution. In scanning current-voltage microscopy (SIVM), a conducting tip makes a microscopic size Schottky contact with the sample. Rastering the

J. W. P. Hsu; D. V. Lang; M. J. Manfra; S. Richter; S. N. G. Chu; A. M. Sergent; R. N. Kleiman; L. N. Pfeiffer; R. J. Molnar

2001-01-01

110

dc side active power filters for aircraft electric power systems  

Microsoft Academic Search

A dc side active filter for a 400 Hz aircraft electric power system is proposed. The filter provides continuous adjustable reactive power, has fast response and high efficiency, and does not necessitate excess capacitive kVA required to supply highly unbalanced or nonlinear loads.

P. Enjeti; S. Kim

1992-01-01

111

Monitoring of Tunneling Activities with Electrical Resistivity Imaging Methods  

Microsoft Academic Search

We demonstrate the effectiveness of electrical resistivity imaging methods for monitoring of tunneling activities with numerical modeling. The sharp resistivity contrast between an air-filled tunnel and surrounding materials presents an excellent opportunity for resistivity imaging methods to locate a tunnel. However, the subsurface inhomogeneity and varying moisture conditions produce strong resistivity anomalies that sometimes overwhelm the tunnel signature. Therefore, tunnel

X. Yang; B. Carr; M. B. Lagmanson

2006-01-01

112

Electric Magnetic Circuit Active Elements Based on Magnetorheological Elastomers  

Microsoft Academic Search

The circuit magnetic active element presented in the paper is based on electroconductive magnetorheological elastomer. This element and the experimental set-up for studies in magnetic field are presented in some detail. It is shown that the voltage U at the outlet of the electric circuit depends on the intensity H of the magnetic field and is considerably influenced by the

G. Catana; B. Vatzulik; O. E. Andrei; L. Chirigiu; I. Bica

2010-01-01

113

Three-Dimensional Electrical Impedance Tomography of Human Brain Activity  

Microsoft Academic Search

Regional cerebral blood flow and blood volume changes that occur during human brain activity will change the local impedance of that cortical area, as blood has a lower impedance than that of brain. Theoretically, such impedance changes could be measured from scalp electrodes and reconstructed into images of the internal impedance of the head. Electrical Impedance Tomography (EIT) is a

Tom Tidswell; Adam Gibson; Richard H. Bayford; David S. Holder

2001-01-01

114

Products of Submarine Fountains and Bubble-burst Eruptive Activity at 1200 m on West Mata Volcano, Lau Basin  

NASA Astrophysics Data System (ADS)

An eruption was observed and sampled at West Mata Volcano using ROV JASON II for 5 days in May 2009 during the NSF-NOAA eruption response cruise to this region of suspected volcanic activity. Activity was focused near the summit at the Prometheus and Hades vents. Prometheus erupted almost exclusively as low-level fountains. Activity at Hades cycled between vigorous degassing, low fountains, and bubble-bursts, building up and partially collapsing a small spatter/scoria cone and feeding short sheet-like and pillow flows. Fire fountains at Prometheus produced mostly small primary pyroclasts that include Pele's hair and fluidal fragments of highly vesicular volcanic glass. These fragments have mostly shattered and broken surfaces, although smooth spatter-like surfaces also occur. As activity wanes, glow in the vent fades, and denser, sometimes altered volcanic clasts are incorporated into the eruption. The latter are likely from the conduit walls and/or vent-rim ejecta, drawn back into the vent by inrushing seawater that replaces water entrained in the rising volcanic plume. Repeated recycling of previously erupted materials eventually produces rounded clasts resembling beach cobbles and pitted surfaces on broken phenocrysts of pyroxene and olivine. We estimate that roughly 33% of near vent ejecta are recycled. Our best sample of this ejecta type was deposited in the drawer of the JASON II ROV during a particularly large explosion that occurred during plume sampling immediately above the vent. Elemental sulfur spherules up to 5 mm in diameter are common in ejecta from both vents and occur inside some of the lava fragments Hades activity included dramatic bubble-bursts unlike anything previously observed under water. The lava bubbles, sometimes occurring in rapid-fire sequence, collapsed in the water-column, producing fragments that are quenched in less than a second to form Pele's hair, limu o Pele, spatter-like lava blobs, and scoria. All are highly vesicular, including the hairs and limu, unlike similar fragments from Loihi Seamount, Axial Seamount, and mid-ocean ridges that have <10% vesicles. The lava bubbles were observed to reach about 1 m in diameter, sometimes appearing to separate from the lava surface, suggesting that they are fed by gasses rising directly from the conduit. Slow-motion video analysis shows that the lava skin stretches to form thin regions that then separate, exposing still incandescent gas within. Bubbles collapse as the lava skin disrupts (usually at the top of the bubble), producing a shower of convex spatter-like lava fragments. Sheet-like lava flows are associated with collapse of the spatter cone and change to pillow lobe extrusion about 5 m from the vent orifice. One pillow lobe sample collected molten contains ~60% vesicles. We suggest that the erupting melt contains large coalesced slugs of magmatic gas and abundant small expanding vesicles that have yet to be incorporated into the large gas slugs. The contrast with Prometheus suggests highly localized conditions of magma devolatilization at W. Mata.

Clague, D. A.; Rubin, K. H.; Keller, N. S.

2009-12-01

115

Factors affecting uterine electrical activity during the active phase of labor prior to rupture of membranes.  

PubMed

Abstract Objective: Limited data exist regarding uterine contraction intensity prior to membrane rupture. Using a novel technique of electrical uterine myography (EUM) we aimed to determine which factors affect myometrial activity during active phase of labor. Methods: EUM was prospectively measured in 37 women with singleton pregnancy at term during the active phase of labor until membranes' rupture. EUM was measured using non-invasive nine channels recorder with an EMG amplifier and three-dimensional position sensor. Uterine electrical activity was quantified with the EUM-index, defined as the mean electrical activity of the uterine muscle over a period of 10?min and measured in units of micro-Joule (microwatt per second [mW/s]). Results: The mean EUM-index at the first 10?min of the measurement was 3.3?±?0.6?mW/s. In a stepwise linear regression model accounting potential confounders EUM was significantly affected by cervical dilatation (p?=?0.005), maternal age (p?=?0.04) and previous cesarean delivery status (p?=?0.02). In a repeated measurement assessment of non-parametric Fridman's test for all subjects who had at least 10 continuouss EUM measurements, there was a significant increase in electrical uterine activity as labor progressed (p?=?0.01). Conclusion: Electrical uterine activity during the active phase of labor prior to rupture of membranes is affected by maternal age, previous cesarean delivery status and cervical dilatation. Moreover, electrical uterine activity is enhanced throughout labor. PMID:25212973

Hiersch, Liran; Salzer, Liat; Aviram, Amir; Ben-Haroush, Avi; Ashwal, Eran; Yogev, Yariv

2014-09-29

116

Scaling of Black Hole Accretion Discs from Gamma-Ray Bursts and Black Hole X-Ray Binaries to Active Galactic Nuclei  

Microsoft Academic Search

I consider how physical processes scale over eight orders of magnitude in black hole mass, from stellar masses in gamma-ray bursts (GRB) and black-hole X-ray binaries (BHXRB) to supermassive active galactic nuclei (AGN). Accretion rates onto stellar mass black holes range over more than sixteen orders of magnitude, from the lower luminosity BHXRB to GRB. These enormous parameter ranges correspond

J. I. Katz

2006-01-01

117

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

118

Electricity  

NSDL National Science Digital Library

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

Brieske, Joel A.

2002-01-01

119

Electrical activation of PAN-Pt artificial muscles  

NASA Astrophysics Data System (ADS)

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

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

1999-05-01

120

Active RF Pulse Compression Using An Electrically Controlled Semiconductor Switch  

SciTech Connect

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

Guo, Jiquan; Tantawi, Sami; /SLAC

2007-01-10

121

Persistent Na+ current modifies burst discharge by regulating conditional backpropagation of dendritic spikes.  

PubMed

The estimation and detection of stimuli by sensory neurons is affected by factors that govern a transition from tonic to burst mode and the frequency characteristics of burst output. Pyramidal cells in the electrosensory lobe of weakly electric fish generate spike bursts for the purpose of stimulus detection. Spike bursts are generated during repetitive discharge when a frequency-dependent broadening of dendritic spikes increases current flow from dendrite to soma to potentiate a somatic depolarizing afterpotential (DAP). The DAP eventually triggers a somatic spike doublet with an interspike interval that falls inside the dendritic refractory period, blocking spike backpropagiation and the DAP. Repetition of this process gives rise to a rhythmic dendritic spike failure, termed conditional backpropagation, that converts cell output from tonic to burst discharge. Through in vitro recordings and compartmental modeling we show that burst frequency is regulated by the rate of DAP potentiation during a burst, which determines the time required to discharge the spike doublet that blocks backpropagation. DAP potentiation is magnified through a positive feedback process when an increase in dendritic spike duration activates persistent sodium current (I(NaP)). I(NaP) further promotes a slow depolarization that induces a shift from tonic to burst discharge over time. The results are consistent with a dynamical systems analysis that shows that the threshold separating tonic and burst discharge can be represented as a saddle-node bifurcation. The interaction between dendritic K(+) current and I(NaP) provides a physiological explanation for a variable time scale of bursting dynamics characteristic of such a bifurcation. PMID:12522183

Doiron, Brent; Noonan, Liza; Lemon, Neal; Turner, Ray W

2003-01-01

122

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

123

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

NASA Technical Reports Server (NTRS)

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(+4.1/-2.9)× 10(exp -5)/cubic Mpc for objects with a de-absorbed luminosity larger than 2 × 10(exp 42) erg / s. 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 (much < 85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions..

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

2014-01-01

124

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

125

Thermonuclear Burst Studies With Large Burst Samples  

NASA Astrophysics Data System (ADS)

Some types of thermonuclear burst behavior are not amenable to study via observations of individual sources, typically because they occur rarely and/or unpredictably. A more promising approach lies in combining data from multiple sources. To date, many thousands of bursts have been detected by various instruments, and new observations are continually adding to the available data. I will describe the results from one such study, involving all the public observations to date made by the Rossi X-ray Timing Explorer (RXTE), presently totalling 1185 bursts from 48 sources. The capabilities of the Proportional Counter Array onboard RXTE enable detailed studies of photospheric radius-expansion, weak bursts (including short recurrence time bursts) and burst oscillations. The two most prolific bursters in the sample exhibit distinctly different bursting properties, suggesting different accreted compositions in the accreted fuel, and highlighting the diversity in burst behaviour which must be considered when combining burst samples. Large burst samples can also be used to measure the global variation of burst properties as a function of accretion rate, to compare with theoretical models. I will also describe a successor project, the Multi-Instrument Burst ARchive (MINBAR), which aims to collate all bursts observed by modern instruments to enable comprehensive future studies of rare events and broad-scale behavior.

Galloway, Duncan; Muno, M. P.; in't Zand, J. J. M.; Chakrabarty, D.; Chenevez, J.; Psaltis, D.; Hartman, J. M.; Keek, L.

2008-03-01

126

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; Pâquet, M R; Grinstein, S

1991-01-01

127

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

128

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

129

SK channels gate information processing in vivo by regulating an intrinsic bursting mechanism seen in vitro.  

PubMed

Understanding the mechanistic substrates of neural computations that lead to behavior remains a fundamental problem in neuroscience. In particular, the contributions of intrinsic neural properties such as burst firing and dendritic morphology to the processing of behaviorally relevant sensory input have received much interest recently. Pyramidal cells within the electrosensory lateral line lobe of weakly electric fish display an intrinsic bursting mechanism that relies on somato-dendritic interactions when recorded in vitro: backpropagating somatic action potentials trigger dendritic action potentials that lead to a depolarizing afterpotential (DAP) at the soma. We recorded intracellularly from these neurons in vivo and found firing patterns that were quite different from those seen in vitro: we found no evidence for DAPs as each somatic action potential was followed by a pronounced afterhyperpolarization (AHP). Calcium chelators injected in vivo reduced the AHP, thereby unmasking the DAP and inducing in vitro-like bursting in pyramidal cells. These bursting dynamics significantly reduced the cell's ability to encode the detailed time course of sensory input. We performed additional in vivo pharmacological manipulations and mathematical modeling to show that calcium influx through N-methyl-d-aspartate (NMDA) receptors activate dendritic small conductance (SK) calcium-activated potassium channels, which causes an AHP that counteracts the DAP and leads to early termination of the burst. Our results show that ion channels located in dendrites can have a profound influence on the processing of sensory input by neurons in vivo through the modulation of an intrinsic bursting mechanism. PMID:19675292

Toporikova, Natalia; Chacron, Maurice J

2009-10-01

130

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, I M; Kim, S J; Park, S J; Kang, J T; Park, H J; Moon, J H; Koo, O J; Jang, G; Lee, B C

2014-12-01

131

Nanomolar oxytocin synergizes with weak electrical afferent stimulation to activate the locomotor CpG of the rat spinal cord in vitro.  

PubMed

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

132

AC Electric Field Activated Shape Memory Polymer Composite  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

133

DEMETER observations of bursty MF emissions and their relation to ground-level auroral MF burst  

NASA Astrophysics Data System (ADS)

A survey of medium frequency (MF) electric field data from selected orbits of the Detection of Electro-Magnetic Emissions Transmitted from Earthquakes (DEMETER) spacecraft reveals 68 examples of a new type of bursty MF emissions occurring at high latitudes associated with auroral phenomena. These resemble auroral MF burst, a natural radio emission observed at ground level near local substorm onsets. Similar to MF burst, the bursty MF waves observed by DEMETER have broadband, impulsive frequency structure covering 1.5-3.0 MHz, amplitudes of 50-100 ?V/m, an overall occurrence rate of ˜0.76% with higher occurrence during active times, and strong correlation with auroral hiss. The magnetic local time distribution of the MF waves observed by DEMETER shows peak occurrence rate near 18 MLT, somewhat earlier than the equivalent peak in the occurrence rate of ground level MF burst, though propagation effects and differences in the latitudes sampled by the two techniques may explain this discrepancy. Analysis of solar wind and SuperMAG data suggests that while the bursty MF waves observed by DEMETER are associated with enhanced auroral activity, their coincidence with substorm onset may not be as exact as that of ground level MF burst. One conjunction occurs in which MF burst is observed at Churchill, Manitoba, within 8 min of MF emissions detected by DEMETER on field lines approximately 1000 km southeast of Churchill. These observations may plausibly be associated with the same auroral event detected by ground level magnetometers at several Canadian observatories. Although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground level MF burst. Hence, theories of MF burst generation in the ionosphere, such as beam-generated Langmuir waves excited over a range of altitudes or strong Langmuir turbulence generating a range of frequencies within a narrow altitude range, need to be revisited to see whether they predict in situ detection of MF burst.

Broughton, M. C.; LaBelle, J.; Parrot, M.

2014-12-01

134

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

135

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

136

[Neuron contractile and electrical activities as affected by colchicine].  

PubMed

The purpose of this investigation was to analyze the contractile activity of traumatized nerve cell processes and to try to inhibit their retraction by colchicine solution. Isolated living neurons of mollusks (Lymnaea stagnalis and Planorbis comeus vulgaris) were studied using phase contrast and time-lapse microvideorecording. In the control group, contractile activity of nerve cell processes in Ringers solution was detected in 92% of cases. Application of colchicine resulted in the inhibition of retraction of nerve fibers in 86% of neurons. In the experiments designed to study neuron electrical activity, leech Retzius neurons were used. It was found that ganglion incubation in colchicine solution of increased the frequency of spontaneous pulse activity from 0.22 to 0.75 imp/s. The amplitude of spontaneous potentials decreased from 46.9 to 37 mV, the threshold was reduced by 18%, spontaneous spike duration increased from 4.3 ms to 7.1 ms, while the latent period of the response to irritating stimulus increased from 25.0 to 37.9 ms. During the irritation with a frequency of 7-10 Hz, neuron generated higher frequency of pulse activity, than in norm. Thus, it was possible to show, that cochicine can inhibit the contractive activity of the traumatized nerve cell processes, preserving an electroexcitable membrane in a satisfactory state. These results suggest that it is possible to partially inhibit the nerve fiber retraction in vivo, thus preventing the diastasis increase in the nerves that impedes their contact surgical approximation and promotes the development of a massive scar in severed area. PMID:23659035

Sergeeva, S S; Vasyagina, N Yu; Sotnikov, O S; Krasnova, T V; Gendina, Ye A

2012-01-01

137

Patterns of Electrical Activity in Comb Plates of Feeding Pleurobrachia (Ctenophora)  

Microsoft Academic Search

The electromotor behaviour of ciliary comb plates was studied during prey-stimulated and electrically stimulated feeding by intact Pleurobrachia pileus (Muller). Comb plate electrical activity was recorded by extracellular electrodes attached directly to the cilia; comb plate motility was recorded by high-speed video microscopy. Comb plate electrical activity fell into two distinct classes, identified by waveform and amplitude: (i) excitatory postsynaptic

Anthony G. Moss; Sidney L. Tamm

1993-01-01

138

Effects of low intensity radiofrequency electromagnetic fields on electrical activity in rat hippocampal slices.  

PubMed

Slices of rat hippocampus were exposed to 700 MHz continuous wave radiofrequency (RF) fields (25.2-71.0 V m(-1), 5-15 min exposure) in a stripline waveguide. At low field intensities, the predominant effect on the electrically evoked field potential in CA1 was a potentiation of the amplitude of the population spike by up to 20%, but higher intensity fields could produce either increases or decreases of up to 120 and 80%, respectively, in the amplitude of the population spike. To eliminate the possibility of RF-induced artefacts due to the metal stimulating electrode, the effect of RF exposure on spontaneous epileptiform activity induced in CA3 by 4-aminopyridine (50-100 microM) was investigated. Exposure to RF fields (50.0 V m(-1)) reduced or abolished epileptiform bursting in 36% of slices tested. The maximum field intensity used in these experiments, 71.0 V m(-1), was calculated to produce a specific absorption rate (SAR) of between 0.0016 and 0.0044 W kg(-1) in the slices. Measurements with a Luxtron fibreoptic probe confirmed that there was no detectable temperature change (+/- 0.1 degrees C) during a 15 min exposure to this field intensity. Furthermore, imposed temperature changes of up to 1 degrees C failed to mimic the effects of RF exposure. These results suggest that low-intensity RF fields can modulate the excitability of hippocampal tissue in vitro in the absence of gross thermal effects. The changes in excitability may be consistent with reported behavioural effects of RF fields. PMID:11516410

Tattersall, J E; Scott, I R; Wood, S J; Nettell, J J; Bevir, M K; Wang, Z; Somasiri, N P; Chen, X

2001-06-15

139

On the conversion of blast wave energy into radiation in active galactic nuclei and gamma-ray bursts  

E-print Network

It has been suggested that relativistic blast waves may power the jets of AGN and gamma-ray bursts (GRB). We address the important issue how the kinetic energy of collimated blast waves is converted into radiation. It is shown that swept-up ambient matter is quickly isotropised in the blast wave frame by a relativistic two-stream instability, which provides relativistic particles in the jet without invoking any acceleration process. The fate of the blast wave and the spectral evolution of the emission of the energetic particles is therefore solely determined by the initial conditions. We compare our model with existing multiwavelength data of AGN and find remarkable agreement.

Martin Pohl; Reinhard Schlickeiser

1999-11-24

140

Electrical activity of caudal neurosecretory neurons in seawater- and freshwater-adapted flounder: responses to cholinergic agonists.  

PubMed

The caudal neurosecretory system (CNSS) of the euryhaline flounder is involved in osmoregulatory responses underlying adaptation to seawater and freshwater. This study compared electrophysiological activity and responses to cholinergic agonists in the neuroendocrine Dahlgren cells in an in vitro preparation taken from fully seawater- (SWA) or freshwater-adapted (FWA) fish. Resting membrane and action potential parameters showed few differences between SWA and FWA cells. The hyperpolarisation-activated sag potential and depolarising afterpotential were present under both conditions; however, amplitude of the latter was significantly greater in SWA cells. The proportions of cells within the population exhibiting different firing patterns were similar in both adaptation states. However, bursting parameters were more variable in FWA cells, suggesting that bursting activity was less robust. The muscarinic agonist, oxotremorine, was largely inhibitory in Dahlgren cells, but increased activity in a non-Dahlgren cell population, alpha neurons. Nicotine promoted bursting activity in SWA Dahlgren cells, whereas it inhibited over half of FWA cells. PMID:14555741

Brierley, M J; Ashworth, A J; Craven, T P; Woodburn, M; Banks, J R; Lu, W; Riccardi, D; Balment, R J; McCrohan, C R

2003-11-01

141

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

142

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

143

Diclofenac-Choline Antioxidant Activity Investigated by means of Luminol Amplified Chemiluminescence of Human Neutrophil Bursts and Electron Paramagnetic Resonance Spectroscopy.  

PubMed

A new diclofenac salt called diclofenac-choline (DC) has recently been proposed for the symptomatic treatment of oropharyngeal inflammatory processes and pain because its greater water solubility allows the use of high concentrations, which are useful when the contact time between the drug and the oropharyngeal mucosa is brief, as in the case of mouthwashes or spray formulations. The antioxidant activity of DC has not yet been investigated, and so the aim was to use luminol-amplified-chemiluminescence (LACL) to verify whether various concentrations of DC (1.48, 0.74 and 0.37?mg/mL for incubation times of 2, 4 and 8?min) interfere with oxygen and nitrogen radicals during the course of human neutrophils respiratory bursts; electron paramagnetic resonance (EPR) spectroscopy was used to investigate its direct antiradical (scavenger) activity. The EPR findings showed that DC has concentration-dependent scavenging activity against the ABTS, the DPPH, and the hydroxyl radicals, but no activity on superoxide anion, as has been previously reported in the case of other NSAIDs. LACL revealed an inhibitory effect that was statistically significant after only 2?min of incubation, and similar after 4 and 8?min. The effects on the peroxynitrite radical paralleled those observed in the previous test. High concentrations and short incubation times showed that there is no interference on PMN viability, and so the inhibitory findings must be attributed to the effect of the drug. The anti-inflammatory effects of DC cannot be attributed solely to the inhibition of prostaglandin synthesis, but its effects on free radicals and neutrophil bursts suggest that they may contribute to its final therapeutic effect. PMID:24918344

Braga, P C; Lattuada, N; Greco, V; Sibilia, V; Falchi, M; Bianchi, T; Dal Sasso, M

2014-06-11

144

Fermi\\/Gamma-Ray Burst Monitor Observations of SGR J0501+4516 Bursts  

Microsoft Academic Search

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 90 durations of the bursts can be fit with a log-normal distribution with a mean value

Lin Lin; Chryssa Kouveliotou; Matthew G. Baring; Alexander J. van der Horst; Sylvain Guiriec; Peter M. Woods; Ersin Gögüs; Yuki Kaneko; Jeffrey Scargle; Jonathan Granot; Robert Preece; Andreas von Kienlin; Vandiver Chaplin; Anna L. Watts; Ralph A. M. J. Wijers; Shuang Nan Zhang; Narayan Bhat; Mark H. Finger; Neil Gehrels; Alice Harding; Lex Kaper; Victoria Kaspi; Julie Mcenery; Charles A. Meegan; William S. Paciesas; Asaf Pe'er; Enrico Ramirez-Ruiz; Michiel van der Klis; Stefanie Wachter; Colleen Wilson-Hodge

2011-01-01

145

Does artificial rupturing of membranes in the active phase of labor enhance myometrial electrical activity?  

PubMed

Abstract Objective: To determine whether artificial rupture of membranes (AROM) during active phase of labor augments uterine contractility using Electrical Uterine Myography (EUM). Study design: A prospective study of 31 women with term singleton pregnancy during active phase of labor. Using a non-invasive EUM technique, electrical uterine activity was recorded in the 30?min preceding AROM and in the immediate 30?min thereafter. Augmentation was defined as >5% increase in EUM index between the basal and post-AROM states, representing the mean EUM increase of the entire cohort. Low basal uterine contraction was defined as EUM index of less than the entire cohort median result prior AROM (3.5 micro-Watt-Second (mWS)). Results: Mean dilatation in which AROM was preformed was 5.5?±?1.8?cm. There was a significant increase in mean EUM measurement in the post-AROM compared to the basal state (3.59?±?0.39 versus 3.42?±?0.47?mWS, p?electrical activity was significantly enhanced following AROM. Augmentation was mostly pronounced in patients with lower BMI and initial lower basal uterine contraction. PMID:24863634

Hiersch, Liran; Rosen, Hadar; Salzer, Liat; Aviram, Amir; Ben-Haroush, Avi; Yogev, Yariv

2014-06-18

146

A Meshfree Method for Simulating Myocardial Electrical Activity  

PubMed Central

An element-free Galerkin method (EFGM) is proposed to simulate the propagation of myocardial electrical activation without explicit mesh constraints using a monodomain model. In our framework the geometry of myocardium is first defined by a meshfree particle representation that is, a sufficient number of sample nodes without explicit connectivities are placed in and inside the surface of myocardium. Fiber orientations and other material properties of myocardium are then attached to sample nodes according to their geometrical locations, and over the meshfree particle representation spatial variation of these properties is approximated using the shape function of EFGM. After the monodomain equations are converted to their Galerkin weak form and solved using EFGM, the propagation of myocardial activation can be simulated over the meshfree particle representation. The derivation of this solution technique is presented along a series of numerical experiments and a solution of monodomain model using a FitzHugh-Nagumo (FHN) membrane model in a canine ventricular model and a human-heart model which is constructed from digitized virtual Chinese dataset. PMID:22997540

Zhang, Heye; Ye, Huajun; Huang, Wenhua

2012-01-01

147

On the effect of the intracellular calcium-sensitive K+ channel in the bursting pancreatic beta-cell.  

PubMed Central

Based on the observation that the calcium-activated K+ channel in the pancreatic islet cells can also be activated by the membrane potential, we have formulated a mathematical model for the electrical activity in the pancreatic beta-cell. Our model contains two types of ionic channels, which are active above the subthreshold glucose concentration in the limit-cycle region: a Ca2+-activated, voltage-gated K+ channel and voltage-gated Ca2+ channel. Numerical simulation of the model generates bursts of electrical activity in response to a variation of kCa, the rate constant for sequestration of intracellular calcium ions. The period and duration of the bursts in response to kCa are in good agreement with experiment. The model predicts that a combined spike and burst pattern can be created using only single species of inward and outward currents, the inactivation kinetics (i.e., h) in the inward current is not a necessary condition for the generation of the pattern, and a given pattern or intensity of electrical activity may produce different levels of intracellular Ca2+ depending on the set of certain electrical parameters. PMID:2431725

Chay, T R

1986-01-01

148

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

149

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.

150

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

151

Pulse-driven magnetoimpedance sensor detection of biomagnetic fields in musculatures with spontaneous electric activity.  

PubMed

We measured biomagnetic fields in musculatures with spontaneous electric activity using a pulse-driven magnetoimpedance (PMI) sensor with the sensitivity improved toward a pico-Tesla (pT) level. Due to the sufficiently short operation interval of 1 ?s, this magnetic sensor enabled quasi-real time recordings of the magnetic field for biological electric activity. Isolated small musculatures from the guinea-pig stomach, taenia caeci, portal vein and urinary bladder were incubated in an organ bath at a body temperature. The improved PMI sensor mounted approximately 1mm below the preparations detected oscillatory magnetic fields reflecting spontaneous electric activities of musculature preparations. In the taenia caeci, application of tetraethyl ammonium (TEA), a K(+) channel blocker, significantly enhanced the magnetic activity estimated by histogram analysis. Also, in some musculature preparations, simultaneous measurements with electric activity revealed that the observed magnetic activities were attributed to biological electric activity. PMI technology is promising for applications in biology and medicine. PMID:21741817

Nakayama, Shinsuke; Atsuta, Satoshi; Shinmi, Takao; Uchiyama, Tsuyoshi

2011-09-15

152

Insulin modulates the electrical activity of subfornical organ neurons.  

PubMed

Insulin plays a crucial role in the regulation of energy balance. Within the central nervous system, hypothalamic nuclei such as the arcuate and ventromedial nuclei are targets of insulin; however, insulin may only access these nuclei after transport across the blood-brain barrier. Neurons of the subfornical organ are not protected by the blood-brain barrier and can rapidly detect and respond to circulating hormones such as leptin and ghrelin. Moreover, subfornical organ neurons form synaptic connections with hypothalamic control centers that regulate energy balance, including the arcuate and dorsomedial nuclei. However, it is unknown whether subfornical organ neurons respond to insulin. Using whole-cell current clamp, we examined the electrophysiological effects of insulin on rat subfornical organ neurons. Upon insulin application, 70% of neurons tested were responsive, with 33% of neurons tested (9/27) exhibiting hyperpolarization of membrane potential (-8.7 ± 1.7 mV) and 37% (10/27) exhibiting depolarization (10.5 ± 2.8 mV). Using pharmacological blockade, our data further indicate that the hyperpolarization was mediated by opening of KATP channels, whereas depolarization resulted from opening of Ih channels. These data are the first to show that insulin exerts a direct effect on the electrical activity of subfornical organ neurons and support the notion that the subfornical organ may act to communicate information on circulating satiety signals to homeostatic control centers. PMID:23481267

Lakhi, Suman; Snow, Wanda; Fry, Mark

2013-04-17

153

Tetrodotoxin-resistant electric activity in presynaptic terminals  

PubMed Central

1. The electric properties of the giant synapse in the stellate ganglion of the squid have been further investigated. 2. During tetrodotoxin (TTX) paralysis, a local response can be elicited from the terminal parts of the presynaptic axons after intracellular injection of tetraethyl ammonium ions (TEA). 3. The response is characterized by an action potential of variable size and duration, whose fall is often preceded by a prolonged plateau. The response, especially the duration of the plateau, is subject to `fatigue' during repetitive stimulation. 4. The TTX-resistant form of activity is localized in the region of the synaptic contacts, and shows a marked electrotonic decrement even within less than 1 mm from the synapse. It is found only on the afferent, not on the efferent, side of the synapse. 5. During the plateau of the response, the membrane resistance is greatly reduced below its resting value. 6. The response depends on presence of external calcium and increases in size and duration with the calcium concentration. Strontium and barium substitute effectively for calcium. Manganese and, to a lesser extent, magnesium, counteract calcium and reduce the response. The response also declines, and ultimately disappears, if sodium is withdrawn for long periods. 7. The relation of the local TTX-resistant response to the influx of calcium ions and to the release of the synaptic transmitter is discussed. PMID:4307710

Katz, B.; Miledi, R.

1969-01-01

154

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

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

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

157

The global atmospheric electric circuit, solar activity and climate change  

Microsoft Academic Search

The study of the global atmospheric electric circuit has advanced dramatically in the past 50 years. Large advances have been made in the areas of lightning and thunderstorm research, as related to the global circuit. We now have satellites looking down on the Earth continuously, supplying information on the temporal and spatial variability of lightning and thunderstorms. Thunderstorms are electric

M. J Rycroft; S. Israelsson; C. Price

2000-01-01

158

Electrical activation in silicon-on-insulator after low energy boron implantation  

E-print Network

Electrical activation in silicon-on-insulator after low energy boron implantation Antonio F 18 May 2004) We have investigated the electrical activation of implanted boron in silicon-on-insulator (SOI) material using Hall effect, four-point probe, and secondary ion mass spectrometry. Boron

Florida, University of

159

A hybrid approach to measuring electrical activity in genetically specified neurons  

Microsoft Academic Search

The development of genetically encoded fluorescent voltage probes is essential to image electrical activity from neuronal populations. Previous green fluorescent protein (GFP)-based probes have had limited success in recording electrical activity of neurons because of their low sensitivity and poor temporal resolution. Here we describe a hybrid approach that combines a genetically encoded fluorescent probe (membrane-anchored enhanced GFP) with dipicrylamine,

Baron Chanda; Rikard Blunck; Leonardo C Faria; Felix E Schweizer; Istvan Mody; Francisco Bezanilla

2005-01-01

160

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

161

Learning Activity Packets for Auto Mechanics II. Section B--Electrical Systems.  

ERIC Educational Resources Information Center

Six learning activity packets (LAPs) are provided for the instructional area of electrical systems in the auto mechanics II program. They accompany an instructor's guide available separately. The LAPs outline the study activities and performance tasks for these six units: (1) basic electrical theory, (2) battery service, (3) starting system, (4)…

Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

162

Burst generation mediated by cholinergic input in terminal nerve-gonadotrophin releasing hormone neurones of the goldfish  

PubMed Central

Peptidergic neurones play a pivotal role in the neuromodulation of widespread areas in the nervous system. Generally, it has been accepted that the peptide release from these neurones is regulated by their firing activities. The terminal nerve (TN)-gonadotrophin releasing hormone (GnRH) neurones, which are one of the well-studied peptidergic neurones in vertebrate brains, are characterised by their spontaneous regular pacemaker activities, and GnRH has been suggested to modulate the sensory responsiveness of animals. Although many peptidergic neurones are known to exhibit burst firing activities when they release the peptides, TN-GnRH neurones show spontaneous burst firing activities only infrequently. Thus, it remains to be elucidated whether the TN-GnRH neurones show burst activities and, if so, how the mode switching between the regular pacemaking and bursting modes is regulated in these neurones. In this study, we found that only a single pulse electrical stimulation of the neuropil surrounding the TN-GnRH neurones reproducibly induces transient burst activities in TN-GnRH neurones. Our combined physiological and morphological data suggest that this phenomenon occurs following slow inhibitory postsynaptic potentials mediated by cholinergic terminals surrounding the TN-GnRH neurones. We also found that the activation of muscarinic acetylcholine receptors induces persistent opening of potassium channels, resulting in a long-lasting hyperpolarisation. This long hyperpolarisation induces sustained rebound depolarisation that has been suggested to be generated by a combination of persistent voltage-gated Na+ channels and low-voltage-activated Ca2+ channels. These new findings suggest a novel type of cholinergic regulation of burst activities in peptidergic neurones, which should contribute to the release of neuropeptides. PMID:23959678

Kawai, Takafumi; Abe, Hideki; Oka, Yoshitaka

2013-01-01

163

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

164

DIFFERENTIAL ACTIVATION OF SIGNAL TRANSDUCTION PATHWAYS MEDIATING OXIDATIVE BURST BY CHICKEN HETEROPHILS IN RESPONSE TO STIMULATION WITH SALMONELLA ENTERITIDIS LIPOPOLYSACCHARIDE AND STAPHYLOCOCCUS AUREUS LIPOTEICHOIC ACID  

Technology Transfer Automated Retrieval System (TEKTRAN)

Toll-like receptors (TLRs) have been previously shown to mediate oxidative burst in chicken heterophils. This study was conducted to determine which molecular pathways are involved in TLR mediated oxidative burst. Peripheral blood heterophils from neonatal chicks were isolated and exposed to known...

165

Solar Radio Bursts on 16 February 1999  

NASA Astrophysics Data System (ADS)

The 2.60-3.80 GHz spectrometer at the Beijing Astronomical Observatory (BAO) recorded a `decimetric pulsation' event (DCIM) around the time 1999 0216 0300. At the beginning and end of this DCIM, two groups of reverse slope type III bursts (RS-III) are also detected; meanwhile, metric type II bursts are recorded by CULG and HIRA during the same time. These solar radio bursts on that day might be caused by the same active region 8458 and a same flare. We present a plausible qualitative model for all of them.

Ning, Zongjun; Fu, Qijun; Yan, Yihua; Liu, Yuying; Lu, Quankang

2001-09-01

166

Frequency chirping during a fishbone burst  

NASA Astrophysics Data System (ADS)

It is shown that frequency chirping during fishbone activity can be attributed to the reactive torque exerted on the plasma during the instability burst, which slows down plasma rotation inside the q = 1 surface and reduces the mode frequency in the lab frame. Estimates show that the peak value of this torque can exceed the neutral beam torque in modern tokamaks. The simple line-broadened quasilinear burst model (Berk et al 1995 Nucl. Fusion 35 1661), properly adapted for the fishbone case, is capable of reproducing the key features of the bursting mode.

Marchenko, V. S.; Reznik, S. N.

2011-12-01

167

Magnetar Twists: Fermi\\/Gamma-Ray Burst Monitor Detection of SGR J1550-5418  

Microsoft Academic Search

SGR J1550-5418 (previously known as AXP 1E 1547.0-5408 or PSR J1550-5418) went into three active bursting episodes in 2008 October and in 2009 January and March, emitting hundreds of typical soft gamma repeater bursts in soft gamma rays. The second episode was especially intense, and our untriggered burst search on Fermi\\/Gamma-ray Burst Monitor (GBM) data (8-1000 keV) revealed ~450 bursts

Yuki Kaneko; Ersin Goegues; Chryssa Kouveliotou; Jonathan Granot; Enrico Ramirez-Ruiz; Alexander J. van der Horst; Anna L. Watts; Mark H. Finger; Neil Gehrels; Asaf Pe'er; Michiels van der Klis; Andreas von Kienlin; Stefanie Wachter; Colleen A. Wilson-Hodge; Peter M. Woods

2010-01-01

168

Active RF Pulse Compression using Electrically Controlled Semiconductor Switches  

SciTech Connect

In this paper, we will present our recent results on the research of the ultra-fast high power RF switches based on silicon. We have developed a switch module at X-band which can use a silicon window as the switch. The switching is realized by generation of carriers in the bulk silicon. The carriers can be generated electrically or/and optically. The electrically controlled switches use PIN diodes to inject carrier. We have built the PIN diode switches at X-band, with <300ns switching time. The optically controlled switches use powerful lasers to excite carriers. By combining the laser excitation and electrical carrier generation, significant reduction in the required power of both the laser and the electrical driver is expected. High power test is under going.

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

2008-01-30

169

Todd, Faraday and the electrical basis of brain activity  

Microsoft Academic Search

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 1830s and 1840s was laying the foundations of our modern understanding of electromagnetism. Todd’s concept of nervous polarity, generated in nerve vesicles and transmitted in

Edward Reynolds

2007-01-01

170

Variation of middle atmospheric electrical conductivity with solar activity  

Microsoft Academic Search

The electrical conductivity is an important parameter of stratosphere and mesosphere. It plays a vital role in global electric circuit. The stratospheric conductivity is mainly due to cosmic rays produced ionisation while in mesosphere the solar U.V. radiation, 1216Å produces ionisation. It is well known that both cosmic rays and solar U.V. radiation intensity show solar cycle effect. In order

S. P. Gupta

2004-01-01

171

Classification of rock bursts  

SciTech Connect

The authors provide classification criteria for rock bursts based primarily on three features: the location of the focal zone of a rock burst relative to the mine; the reciprocal interaction of a rock burst and the existing tectonic structure in the part of the bed experiencing the rock burst; and the distribution of rock bursts according to the energy released by the dynamic event, including the results of the event over the area and in the volume of the surrounding rocks. Their mathematical formulations for different classes of rock bursts take into account the effects of small earthquakes, the configuration of the stope and support pillars, and the stress and deformation behavior of the coal along with other considerations.

Shemyakin, E.I.; Kurlenya, M.V.; Kulakov, G.I.

1987-07-01

172

Electricity Sector Liberalisation and Innovation: An Analysis of the UK Patenting Activities  

E-print Network

www.electricitypolicy.org.uk E P R G W O R K IN G P A P E R Abstract Electricity Sector Liberalisation and Innovation: An Analysis of the UK Patenting Activities EPRG Working Paper 0901 Cambridge Working Paper in Economics 0902... Tooraj Jamasb and Michael Pollitt Liberalisation has had a marked effect on innovative activities in the electricity industry. R&D and patenting activities are generally regarded respectively as innovative inputs to and outputs from technological...

Jamasb, Tooraj; Pollitt, Michael G.

173

The GLAST Burst Monitor  

SciTech Connect

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; Fishman, Gerald; Kouveliotou, Chryssa; Wilson-Hodge, Colleen [Marshall Space Flight Center, VP62, Huntsville, AL 35812 (United States); Bhat, Narayana; Connaughton, Valerie; Briggs, Michael; Paciesas, William; Preece, Robert [University of Alabama, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Diehl, Roland; Greiner, Jochen; Kienlin, Andreas von; Lichti, Giselher; Steinle, Helmut [Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 85748 Garching (Germany); Kippen, R. Marc [Los Alamos National Laboratory, ISR-1, MS B244, Los Alamos, NM 87545 (United States)

2007-07-12

174

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

175

Electricity  

NSDL National Science Digital Library

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

Project, Iowa P.

2004-01-01

176

Electrospun nanofiber membranes for electrically activated shape memory nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

177

Neutrino bursts from gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

Paczynski, Bohdan; Xu, Guohong

1994-01-01

178

[The cortico-hypothalamic relations of the electrical activity in a motor polarization dominant].  

PubMed

By means of spectral-correlation analysis was studied the dynamics of the structural changes of coherent relations of the electrical activity of the sensorimotor cortex and the medical hypothalamus (MH) of the rabbit under motor polarization dominant created by the action of DC anode on the sensorimotor cortex area. During the motor dominant the spectral power of MH activity was shown to increase in the delta-band. The structural changes of coherent relations of the electrical activity of the sensorimotor cortex and the MH were manifested by a decrease of coherence in the delta- and alpha-frequency bands. Electrical stimulation of the MH inhibited the motor dominant reactions. PMID:8212865

Rusinova, E V

1993-01-01

179

Sources of electric brain activity: intracortical current dipoles  

Microsoft Academic Search

Intracortical evoked potentials after electrical stimulation of the optic nerve were simultaneously recorded from the different layers of the rabbit's visual cortex. The averaged potentials were subjected to current source density analyses. The results show that the first event after the stimulus is a current sink in layer VI according to the excitatory terminations of the specific afferent fibres of

P Rappelsberger; H Pockberger; H Petsche

1993-01-01

180

Electrical activity and behavior in the pharynx of caenorhabditis elegans  

Microsoft Academic Search

Summary The pharynx of C. elegans, a model system for neural networks and for membrane excitability, has been chiefly studied by observing its behavior in normal worms, in mutant worms, and in worms lacking pharyn- geal neurons. To complement this behavioral approach, we devised a method for recording currents produced by changes in pharyngeal muscle membrane potential. The electrical records,

David M. Raizen; Leon Avery

1994-01-01

181

ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY  

Microsoft Academic Search

The permeability of a membrane to a penetrating substance is given quantitatively by the amount of the substance which crosses a unit area of the membrane in unit time under the action of a unit force. In simple cases of ionized substances both the amount of substance and the force acting may be expressed in electrical terms. Then the permeability

KENNETH S. COLE; HOWARD J. CURTIS

1939-01-01

182

Bursts of Gravitational Waves Emitted During Ejection of Jet Superluminal Components in Active Galactic Nuclei Dynamically Dominated by Bardeen-Petterson Effect  

NASA Astrophysics Data System (ADS)

Superluminal jet components are recurrently ejected from the core of active galactic nuclei (AGNs). The mechanism driving this powerful phenomenon is not properly understood yet. Here we suggest that the components ejection from AGNs may be related to the astrophysical process known as Bardeen-Petterson (B-P) effect, a general relativistic effect which forces a tilt (precessing) accretion disk orbiting a Kerr black hole (KBH) to break apart at the B-P radius. This transition region hereby builds up a magneto-centrifugal barrier which precludes incoming matter to penetrate the AGN inner disk or torus, and creates a sort of force-free bridge or Lagrange internal point in a force-free magnetosphere. (Inwardly pointing forces are counterbalanced by outwardly pointing forces). The material trapped in such a region will eventually find a condition of orbital resonance (beating) with the warps traveling along the torus due to its differential rotation. At resonance the mass blobs can be expelled from the B-P radius in virtue of either the vertical (to the disk) linear momentum carried by the torus warps, or the Aschenbach effect in a nearly maximal KBH, or some other orbital resonances like the well known resonance 3:1. The launching of such superluminal components should produce powerful gravitational wave (GW) bursts during its early acceleration phase. These are GW signals that the LISA space-borne GW observatory can detect for distances upto nearly the Hubble radius.

Mosquera Cuesta, Herman J.; Caproni, Anderson; Abraham, Zulema

2009-09-01

183

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

PubMed Central

Background Neutrophils are involved in thrombus formation. We investigated whether specific features of neutrophil activation characterize patients with acute coronary syndromes (ACS) compared to stable angina and to systemic inflammatory diseases. Methods and Findings The myeloperoxidase (MPO) content of circulating neutrophils was determined by flow cytometry in 330 subjects: 69 consecutive patients with acute coronary syndromes (ACS), 69 with chronic stable angina (CSA), 50 with inflammation due to either non-infectious (acute bone fracture), infectious (sepsis) or autoimmune diseases (small and large vessel systemic vasculitis, rheumatoid arthritis). Four patients have also been studied before and after sterile acute injury of the myocardium (septal alcoholization). One hundred thirty-eight healthy donors were studied in parallel. Neutrophils with normal MPO content were 96% in controls, >92% in patients undergoing septal alcoholization, 91% in CSA patients, but only 35 and 30% in unstable angina and AMI (STEMI and NSTEMI) patients, compared to 80%, 75% and 2% of patients with giant cell arteritis, acute bone fracture and severe sepsis. In addition, in 32/33 STEMI and 9/21 NSTEMI patients respectively, 20% and 12% of neutrophils had complete MPO depletion during the first 4 hours after the onset of symptoms, a feature not observed in any other group of patients. MPO depletion was associated with platelet activation, indicated by P-selectin expression, activation and transactivation of leukocyte ?2-integrins and formation of platelet neutrophil and -monocyte aggregates. The injection of activated platelets in mice produced transient, P-selectin dependent, complete MPO depletion in about 50% of neutrophils. Conclusions ACS are characterized by intense neutrophil activation, like other systemic inflammatory syndromes. In the very early phase of acute myocardial infarction only a subpopulation of neutrophils is massively activated, possibly via platelet-P selectin interactions. This paroxysmal activation could contribute to occlusive thrombosis. PMID:22761804

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

2012-01-01

184

Section of burst tumulus  

USGS Multimedia Gallery

A section of burst tumulus that has fallen away from the larger structure. Tumuli can burst when the influx of lava is rapid compared to the rate at which the crust is thickening by cooling. In these cases the pressure driving the lava is significantly greater than the weight of the overlying crust....

185

Section of Burst Tumulus  

USGS Multimedia Gallery

A section of burst tumulus that has fallen away from the larger structure. Tumuli can burst when the influx of lava is rapid compared to the rate at which the crust is thickening by cooling. In these cases the pressure driving the lava is significantly greater than the weight of the overlying crust....

186

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

187

Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

188

PLUG-IN ELECTRIC VEHICLE CHARGING ONLY Must be ACTIVELY Charging  

E-print Network

PLUG-IN ELECTRIC VEHICLE CHARGING ONLY Must be ACTIVELY Charging All Others Subject to Citation. PLUG-IN ELECTRIC VEHICLE CHARGING RATES Monday­Friday, 7:30am­5pm Hours Power Parking Power+Parking 1://chargepoint.net PAYMENT IS REQUIRED FOR USE OF A CHARGING STATION The rate for charging your vehicle is $1/hour. Please

Bigelow, Stephen

189

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

ERIC Educational Resources Information Center

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

Baser, Mustafa; Geban, Omer

2007-01-01

190

Burst of ULF Electric Field Recorded by DEMETER Possibly Related to the Series of Earthquakes Occurred during the Tsunami Over the Indian Region (P19)  

NASA Astrophysics Data System (ADS)

ak_gwal@yahoo.co.in The scientists have found that the accumulation of tectonic energy is localized in certain places and is not universal. Taking into account this hypothesis the authors have studied the sequence of occurrence rate of the earthquakes (M?5) in the South-East Asian region, as the chronological data related to the occurrence of earthquakes collected in that region for last five years i.e. from 2001 to 2005 have revealed that the disastrous tsunami events which took place on 26th December, 2004 as an effect of Sumatra earthquake( M=9) have increased the occurrence of earthquake frequency for a longer period (which might be due to adjustment of tectonic plates). Observing these facts i.e. sudden enhancement in occurrence rate of earthquakes, the authors have availed this opportunity to further explore the concept of seismoelectromagnetic-ionospheric phenomena, which still needs a lot of statistical evidences, comprising tremendous amount of data to establish it. In this paper the authors have tried to analyze the chain of observations made and data collected and stored month wise w.e.f. 26th December, 2004 to 31st March, 2005 in the region, using DEMETER satellite. Further, efforts have also been made to provide the statistical analysis of the ionospheric variability caused due to detected electromagnetic burst in ULF frequency ranges in the context of natural variability in order to distinguish the variability introduced by other sources. In brief, it could be concluded that there is possibility of getting the electromagnetic precursors in the ionosphere at different frequency ranges due to excess release of tectonic energy as a result of occurrence rate of the earthquakes in the region.

Gwal, A. K.; Shrivastava, A.

2006-11-01

191

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

Juárez-Hernández, León J.; Bisson, Giacomo; Torre, Vincent

2013-01-01

192

Gamma Ray Bursts - Observations  

NASA Technical Reports Server (NTRS)

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

Gehrels, N.; Cannizzo, J. K.

2010-01-01

193

Case studies of electrical and electromagnetic methods applied to mapping active faults beneath the thick quaternary  

Microsoft Academic Search

It is of considerable importance to explore the geological structure around active faults, especially near-surface unconsolidated layers, to estimate the faults' activity. There are numerous case studies to investigate active faults using geophysical exploration methods; however, only a few cases have been verified in detail by comparison with other geological information. We have applied electric and electromagnetic methods, which can

Koichi Suzuki; Shinji Toda; Kenichiro Kusunoki; Yasuhiro Fujimitsu; Tohru Mogi; Akira Jomori

2000-01-01

194

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

PubMed Central

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

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

2014-01-01

195

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

PubMed

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

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

2014-02-01

196

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

197

Neural activity and diurnal variation of cortisol: Evidence from brain electrical tomography analysis and  

E-print Network

Neural activity and diurnal variation of cortisol: Evidence from brain electrical tomography tomography was used to compute intracerebral cur- rent density. For the control group, voxelwise analyses, Stress, Prefrontal cortex, Low resolution electro- magnetic tomography (LORETA) In recent years

Wisconsin at Madison, University of

198

Cacnb4 directly couples electrical activity to gene expression, a process defective in juvenile epilepsy  

E-print Network

mutation, responsible for a form of juvenile myoclonic epilepsy, prevents association with Ppp2r5 to juvenile myoclonic epilepsy (Escayg et a1 Cacnb4 directly couples electrical activity to gene expression, a process defective in juvenile

Paris-Sud XI, Université de

199

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

200

Museum of Science: Activities to Explore Static Electricity  

NSDL National Science Digital Library

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

Science, Boston M.

2006-11-10

201

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

Microsoft Academic Search

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

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

2005-01-01

202

INMED/TINS special issue Early patterns of electrical activity  

E-print Network

of the INMED/TINS special issue Nature and nurture in brain development and neurological disorders, based cortical circuits. The nature and functional role of these early activity patterns are of central interest. The first notion of the discontinuous nature of the early cortical activity came from studies of human

Cossart, Rosa

203

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

204

Statistical Properties of SGR 1900+14 Bursts  

NASA Technical Reports Server (NTRS)

We study the statistics of soft gamma repeater (SGR) bursts using a database of 187 events detected with BATSE and 837 events detected with the Rossi X-Ray Timing Explorer Proportional Counter Array: all events are from SGR 1900+14 during its 1998-1999 active phase. We find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66, over 4 orders of magnitude. This scale-free distribution resembles the Gutenberg-Richter law for earthquakes and gives evidence for self-organized criticality in SGRS. The distribution of time intervals between successive bursts from SGR 1900+14 is consistent with a lognormal distribution. There is no correlation between burst intensity and the waiting times till the next burst, but there is some evidence for a correlation between burst intensity and the time elapsed since the previous burst. We also find a correlation between the duration and the energy of the bursts, but with significant scatter. In all these statistical properties, SGR bursts resemble earthquakes and solar flares more closely than they resemble any known accretion-powered or nuclear-powered phenomena. Thus, our analysis lends support to the hypothesis that the energy source for SGR bursts is internal to the neutron star and plausibly magnetic.

Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; VanParadijs, Jan

1999-01-01

205

Statistical Properties of SGR 1900+14 Bursts  

NASA Technical Reports Server (NTRS)

We study the statistics of soft gamma repeater (SGR) bursts, using a data base of 187 events detected with BATSE and 837 events detected with RXTE PCA, all from SGR 1900+14 during its 1998-1999 active phase. we find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66, over 4 orders of magnitude. This scale-free distribution resembles the Gutenberg-Richter Law for earthquakes, and gives evidence for self-organized criticality in SGRS. The distribution of time intervals between successive bursts from SGR 1900+14 is consistent with a log-normal distribution. There is no correlation between burst intensity and the waiting times till the next burst, but there is some evidence for a correlation between burst intensity and the time elapsed since the previous burst. We also find a correlation between the duration and the energy of the bursts, but with significant scatter. In all these statistical properties, SGR bursts resemble earthquakes and solar flares more closely than they resemble any known accretion-powered or nuclear-powered phenomena. Thus our analysis lends support to the hypothesis that the energy source for SGR bursts is internal to the neutron star, and plausibly magnetic.

Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; vanParadijs, Jan; Briggs, Michael S.; Duncan, Robert C.; Thompson, Christopher

1999-01-01

206

Anatomically realistic multiscale models of normal and abnormal gastrointestinal electrical activity  

PubMed Central

One of the major aims of the International Union of Physiological Sciences (IUPS) Physiome Project is to develop multiscale mathematical and computer models that can be used to help understand human health. We present here a small facet of this broad plan that applies to the gastrointestinal system. Specifically, we present an anatomically and physiologically based modelling framework that is capable of simulating normal and pathological electrical activity within the stomach and small intestine. The continuum models used within this framework have been created using anatomical information derived from common medical imaging modalities and data from the Visible Human Project. These models explicitly incorporate the various smooth muscle layers and networks of interstitial cells of Cajal (ICC) that are known to exist within the walls of the stomach and small bowel. Electrical activity within individual ICCs and smooth muscle cells is simulated using a previously published simplified representation of the cell level electrical activity. This simulated cell level activity is incorporated into a bidomain representation of the tissue, allowing electrical activity of the entire stomach or intestine to be simulated in the anatomically derived models. This electrical modelling framework successfully replicates many of the qualitative features of the slow wave activity within the stomach and intestine and has also been used to investigate activity associated with functional uncoupling of the stomach. PMID:17457969

Cheng, Leo K; Komuro, Rie; Austin, Travis M; Buist, Martin L; Pullan, Andrew J

2007-01-01

207

On vortex bursting  

NASA Technical Reports Server (NTRS)

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

Werle, H.

1984-01-01

208

Dendritic Ca2 -Activated K Conductances Regulate Electrical  

E-print Network

studies revealed that backpropagating Na spikes and synaptically evoked EPSPs caused Ca2 entry through low spikes and synaptically evoked EPSPs increased in amplitude. Hence, the activity-dependent changes

Wessel, Ralf

209

VSCF aircraft electric power system performance with active power filters  

Microsoft Academic Search

A three-phase three-wire shunt active power filter (APF) is presented to regulate the load terminal voltage, eliminate harmonics, correct supply power-factor and balance the nonlinear unbalanced loads. A three-phase based current controlled voltage source inverter is used as an active power filter. The control algorithm for the APF is based on the perfect harmonic cancellation method which provides a three-phase

A. Eid; H. El-Kishky; M. Abdel-Salam; T. El-Mohandes

2010-01-01

210

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

211

Coexistence of tonic firing and bursting in cortical neurons.  

PubMed

Sustained neuronal activity can be broadly classified as either tonic firing or bursting. These two major patterns of neuronal oscillations are state dependent and may coexist. The dynamics and intracellular mechanisms of transitions between tonic firing and bursting in cortical networks remain poorly understood. Here we describe a detailed two-compartment conductance-based cortical neuron model which exhibits bistability with hysteresis between tonic firing and bursting for elevated extracellular potassium concentration. The study explains the ionic and dynamical mechanisms of burst generation and reveals the conditions underlying coexistence of two different oscillatory modes as a function of neuronal excitability. PMID:17025682

Fröhlich, Flavio; Bazhenov, Maxim

2006-09-01

212

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

213

Emergence of organized bursting in clusters of pancreatic beta-cells by channel sharing.  

PubMed Central

Pancreatic beta-cells in an intact Islet of Langerhans exhibit bursting electrical behavior. The Chay-Keizer model describes this using a calcium-activated potassium (K-Ca) channel, but cannot account for the irregular spiking of isolated beta-cells. Atwater I., L. Rosario, and E. Rojas, Cell Calcium. 4:451-461, proposed that the K-Ca channels, which are rarely open, are shared by several cells. This suggests that the chaotic behavior of isolated cells is stochastic. We have revised the Chay-Keizer model to incorporate voltage clamp data of Rorsman and Trube and extended it to include stochastic K-Ca channels. This model can describe the behavior of single cells, as well as that of clusters of cells tightly coupled by gap junctions. As the size of the clusters is increased, the electrical activity shows a transition from chaotic spiking to regular bursting. Although the model of coupling is over-simplified, the simulations lend support to the hypothesis that bursting is the result of channel sharing. PMID:2850029

Sherman, A; Rinzel, J; Keizer, J

1988-01-01

214

Rapid tissue dissolution efficiency of electrically-activated sodium hypochlorite on bovine muscle  

PubMed Central

Objective: Sodium hypochlorite (NaOCl) is a common antimicrobial and tissue-dissolving irrigant. The aim of this in vitro study is to evaluate and compare dissolution capacities of sodium hypochlorite solutions after electrically activation (E-NaOCl) on bovine muscle specimens at various time periods and concentrations. Materials and Methods: Three sodium hypochlorite solutions of 1.25%, 2.5%, and 5% were tested at 3-min. and 5-min. with and without activation by electrically. Distilled water and NaOCl solutions without electrically activation were used as controls. Pieces of bovine muscle tissue (34 ± 2 mg) were placed in 10 mL of each solution at room temperature. In the group of E-NaOCl, electrically activation was performed through the potentiostat. The tissue specimens were weighed before and after treatment, and the percentage of weight loss was calculated. Results: Weight loss of the tissue increased with the concentration of E-NaOCl and NaOCl. Higher concentration and electrically activation considerably enhanced the efficacy of sodium hypochlorite. The effect of electrically activation on tissue dissolution was much greater than that of same concentrations in the groups of NaOCl (P < 0.001). Tissue weight loss was significantly higher in 2.5% and 5% E-NaOCl at 3 min. than in 2.5% and 5% NaOCl at 5 min. (P < 0.05). There were not any significant differences between the 2.5% E-NaOCl and 5% NaOCl at 5 min. (P > 0.05). Conclusion: Electrically activation can improve the tissue-dissolving effectiveness of sodium hypochlorite. PMID:25512725

Ertugrul, Ihsan Furkan; Maden, Murat; Orhan, Ekim Onur; Ozkorucuklu, Sabriye Percin; Aglarca, Ali Vasfi

2014-01-01

215

THE ELECTRICAL ACTIVATION OF PASSIVE IRON WIRES IN NITRIC ACID  

PubMed Central

1. The relation between the E. M. F. and the minimal duration of an activating current has been determined for passive iron wires in nitric acid under varying conditions of concentration of acid, duration of recovery period, and presence of surface-action compounds. 2. The characteristic intensity-duration curves resemble those of irritable living tissues with moderate speeds of response to stimulation (with chronaxies of the order of 10 to 30?). 3. The intensity of the current required for activation, as well as its minimal effective duration for a given intensity, increases rapidly with increase in the concentration of HNO3. 4. The responsiveness of the iron wire to brief currents is low immediately after activation and returns progressively to the original level during the immediately following period, at first rapidly and then slowly, following a time curve resembling the corresponding curve of living tissues during the relative refractory period. 5. Surface-active compounds decrease reversibly, to a degree dependent on concentration, the responsiveness of iron wires to brief currents. 6. Conditions are described under which the iron wire is activated by the break of an already flowing constant current. PMID:19872905

Lillie, Ralph S.

1935-01-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

217

INTEGRAL burst alert service  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

218

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

219

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

Microsoft Academic Search

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

Ahmad Esfandiari; Mostafa Parniani

2004-01-01

220

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

ERIC Educational Resources Information Center

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

Jaakkola, T.; Nurmi, S.

2008-01-01

221

Evidence-Based Systematic Review: Effects of Neuromuscular Electrical Stimulation on Swallowing and Neural Activation  

ERIC Educational Resources Information Center

Purpose: To systematically review the literature examining the effects of neuromuscular electrical stimulation (NMES) on swallowing and neural activation. The review was conducted as part of a series examining the effects of oral motor exercises (OMEs) on speech, swallowing, and neural activation. Method: A systematic search was conducted to…

Clark, Heather; Lazarus, Cathy; Arvedson, Joan; Schooling, Tracy; Frymark, Tobi

2009-01-01

222

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

Microsoft Academic Search

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

R. J. Chang; L. Mazeika

2000-01-01

223

GLAST's GBM Burst Trigger  

NASA Technical Reports Server (NTRS)

The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

Band, D.; Briggs, M.; Connaughton, V.; Kippen, M.; Preece, R.

2003-01-01

224

GLAST's GBM Burst Trigger  

SciTech Connect

The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

Band, D. [Code 661, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Briggs, M.; Connaughton, V.; Preece, R. [National Space Science and Technology Center, Huntsville, AL 35805 (United States); Kippen, M. [NIS-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2004-09-28

225

GLAST's GBM Burst Trigger  

E-print Network

The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

D. Band; M. Briggs; V. Connaughton; M. Kippen; R. Preece

2003-12-12

226

Inferred flows of electric currents in solar active regions  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

227

Workshop Physics Activity Guide, Electricity and Magnetism, Module 4  

NSDL National Science Digital Library

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

Laws, Priscilla W.

2006-07-22

228

Parameters for burst detection  

PubMed Central

Bursts of action potentials within neurons and throughout networks are believed to serve roles in how neurons handle and store information, both in vivo and in vitro. Accurate detection of burst occurrences and durations are therefore crucial for many studies. A number of algorithms have been proposed to do so, but a standard method has not been adopted. This is due, in part, to many algorithms requiring the adjustment of multiple ad-hoc parameters and further post-hoc criteria in order to produce satisfactory results. Here, we broadly catalog existing approaches and present a new approach requiring the selection of only a single parameter: the number of spikes N comprising the smallest burst to consider. A burst was identified if N spikes occurred in less than T ms, where the threshold T was automatically determined from observing a probability distribution of inter-spike-intervals. Performance was compared vs. different classes of detectors on data gathered from in vitro neuronal networks grown over microelectrode arrays. Our approach offered a number of useful features including: a simple implementation, no need for ad-hoc or post-hoc criteria, and precise assignment of burst boundary time points. Unlike existing approaches, detection was not biased toward larger bursts, allowing identification and analysis of a greater range of neuronal and network dynamics. PMID:24567714

Bakkum, Douglas J.; Radivojevic, Milos; Frey, Urs; Franke, Felix; Hierlemann, Andreas; Takahashi, Hirokazu

2014-01-01

229

BATSE results on observational properties of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

The Burst and Transient Source Experiment (BATSE) has observed over 600 gamma-ray bursts since its activation on 1991 April 21. We present here results on the global properties of the first 542 events. Their angular distribution is consistent with isotropy; their peak intensity distribution shows a depletion at low intensities, consistent with inhomogeneity in Euclidean space.

Kouveliotou, Chryssa

1994-01-01

230

Coexistence of tonic firing and bursting in cortical neurons  

Microsoft Academic Search

Sustained neuronal activity can be broadly classified as either tonic firing or bursting. These two major patterns of neuronal oscillations are state dependent and may coexist. The dynamics and intracellular mechanisms of transitions between tonic firing and bursting in cortical networks remain poorly understood. Here we describe a detailed two-compartment conductance-based cortical neuron model which exhibits bistability with hysteresis between

Flavio Fröhlich; Maxim Bazhenov

2006-01-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

232

Propagation of electrical activity in uterine muscle during pregnancy: a review.  

PubMed

The uterine muscle (the myometrium) plays its most evident role during pregnancy, when quiescence is required for adequate nourishment and development of the foetus, and during labour, when forceful contractions are needed to expel the foetus and the other products of conception. The myometrium is composed of smooth muscle cells. Contraction is initiated by the spontaneous generation of electrical activity at the cell level in the form of action potentials. The mechanisms underlying uterine quiescence during pregnancy and electrical activation during labour remain largely unknown; as a consequence, the clinical management of preterm contractions during pregnancy and inefficient uterine contractility during labour remains suboptimal. In an effort to improve clinical management of uterine contractions, research has focused on understanding the propagation properties of the electrical activity of the uterus. Different perspectives have been undertaken, from animal and in vitro experiments up to clinical studies and dedicated methods for non-invasive parameter estimation. A comparison of the results is not straightforward due to the wide range of different approaches reported in the literature. However, previous studies unanimously reveal a unique complexity as compared to other organs in the pattern of uterine electrical activity propagation, which necessarily needs to be taken into consideration for future studies to be conclusive. The aim of this review is to structure current variegated knowledge on the properties of the uterus in terms of pacemaker position, pattern, direction and speed of the electrical activity during pregnancy and labour. PMID:25393600

Rabotti, C; Mischi, M

2015-02-01

233

[Interactions between electrical activities of the sensomotor cortex and the hippocampus during 'animal hypnosis' in rabbits].  

PubMed

The electrical activity of the left and right sensorimotor cortex and left and right dorsal hippocampus (CA3 fields) was recorded during "animal hypnosis" in rabbits. The "animal hypnosis" produced asymmetry in the spectral power of the hippocampal electrical activity due to an increase in the power of delta 1, delta 2, and theta 1 components in the left-hippocampus and decrease in the spectral power in the same ranges in the right-hippocampus. Hemispheric asymmetry in the electrical activity during the "animal hypnosis" was also expressed in the indices of coherence between the sensorimotor cortex and hippocampus. EEG coherence between the left sensorimotor cortex and left hippocampus in the delta 1, theta 1, and theta 2 ranges was higher than that between the right-side structures. PMID:10984904

Rusinova, E V; Roshchina, G Ia

2000-01-01

234

[The dynamics of modification of electrical activity of the rabbit brain during consistent "animal hypnosis" series].  

PubMed

The dynamics of modification of individual rhythms of electrical activity in both hemispheres was studied under condition of chronic experiments in rabbits during "animal hypnosis" sessions. It was shown that, after the first "animal hypnosis" session, significant changes in the spectral power of electrical activity appeared only in the right premotor cortical area. They consisted in an increase in the spectral power of the delta1 and delta2 rhythms and a decrease in the spectral power of the other rhythms. During the next "animal hypnosis" sessions, changes in the electrical activity became stronger, especially in the right hemisphere. Significant changes in the spectral power of the delta and theta rhythms appeared not at the beginning of the "animal hypnosis" session but 4-6 min later. During the third "animal hypnosis" session, the power of the alpha and beta rhythms in the premotor and sensorimotor cortical areas of both hemispheres varied in an undulatory way. PMID:19445384

Rusinova, E V; Davydov, V I

2009-01-01

235

EMG activity of finger flexor muscles and grip force following low-dose transcutaneous electrical nerve stimulation in healthy adult subjects.  

PubMed

Abstract Somatosensory stimulation modulates cortical and corticospinal excitability and consequently affects motor output. Therefore, low-amplitude transcutaneous electrical nerve stimulation (TENS) has the potential to elicit favorable motor responses. The purpose of the two presented pilot studies was to shed light on TENS parameters that are relevant for the enhancement of two desirable motor outcomes, namely, electromyographic (EMG) activity and contraction strength of the finger flexors and wrist muscles. In 5 and 10 healthy young adults (in Study I and Study II, respectively) TENS was delivered to the volar aspect of the forearm. We manipulated TENS frequency (150?Hz vs. 5?Hz), length of application (10, 20, and 60?min), and side of application (unilateral, right forearm vs. bilateral forearms). EMG amplitude and grip force were measured before (Pre), immediately after (Post), and following 15?min of no stimulation (Study I only). The results indicated that low-frequency bursts of TENS applied to the skin overlying the finger flexor muscles enhance the EMG activity of the finger flexors and grip force. The increase in EMG activity of the flexor muscles was observed after 20?min of stimulation, while grip force was increased only after 1?h. The effects of uni- and bilateral TENS were comparable. These observations allude to a modulatory effect of TENS on the tested motor responses; however, unequivocal conclusions of the findings are hampered by individual differences that affect motor outcomes, such as in level of attention. PMID:25059799

Kafri, Michal; Zaltsberg, Nir; Dickstein, Ruth

2014-07-25

236

Synchronous Bursts of Action Potentials in Ganglion Cells of the Developing Mammalian Retina  

NASA Astrophysics Data System (ADS)

The development of orderly connections in the mammalian visual system depends on action potentials in the optic nerve fibers, even before the retina receives visual input. In particular, it has been suggested that correlated firing of retinal ganglion cells in the same eye directs the segregation of their synaptic terminals into eye-specific layers within the lateral geniculate nucleus. Such correlations in electrical activity were found by simultaneous recording of the extracellular action potentials of up to 100 ganglion cells in the isolated retina of the newborn ferret and the fetal cat. These neurons fired spikes in nearly synchronous bursts lasting a few seconds and separated by 1 to 2 minutes of silence. Individual bursts consisted of a wave of excitation, several hundred micrometers wide, sweeping across the retina at about 100 micrometers per second. These concerted firing patterns have the appropriate spatial and temporal properties to guide the refinement of connections between the retina and the lateral geniculate nucleus.

Meister, Markus; Wong, Rachel O. L.; Baylor, Denis A.; Shatz, Carla J.

1991-05-01

237

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

238

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

239

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

240

Statistical Properties of SGR J1550-5418 Bursts  

NASA Technical Reports Server (NTRS)

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

Gorgone, Nicholas M.

2010-01-01

241

ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY  

PubMed Central

Alternating current impedance measurements have been made over a wide frequency range on the giant axon from the stellar nerve of the squid, Loligo pealii, during the passage of a nerve impulse. The transverse impedance was measured between narrow electrodes on either side of the axon with a Wheatstone bridge having an amplifier and cathode ray oscillograph for detector. When the bridge was balanced, the resting axon gave a narrow line on the oscillograph screen as a sweep circuit moved the spot across. As an impulse passed between impedance electrodes after the axon had been stimulated at one end, the oscillograph line first broadened into a band, indicating a bridge unbalance, and then narrowed down to balance during recovery. From measurements made during the passage of the impulse and appropriate analysis, it was found that the membrane phase angle was unchanged, the membrane capacity decreased about 2 per cent, while the membrane conductance fell from a resting value of 1000 ohm cm.2 to an average of 25 ohm cm.2 The onset of the resistance change occurs somewhat after the start of the monophasic action potential, but coincides quite closely with the point of inflection on the rising phase, where the membrane current reverses in direction, corresponding to a decrease in the membrane electromotive force. This E.M.F. and the conductance are closely associated properties of the membrane, and their sudden changes constitute, or are due to, the activity which is responsible for the all-or-none law and the initiation and propagation of the nerve impulse. These results correspond to those previously found for Nitella and lead us to expect similar phenomena in other nerve fibers. PMID:19873125

Cole, Kenneth S.; Curtis, Howard J.

1939-01-01

242

Bursting of sensitive polymersomes induced by curling  

Microsoft Academic Search

Polymersomes, which are stable and robust vesicles made of block copolymer amphiphiles, are good candidates for drug carriers or micro\\/nanoreactors. Polymer chemistry enables almost unlimited molecular design of responsive polymersomes whose degradation upon environmental changes has been used for the slow release of active species. Here, we propose a strategy to remotely trigger instantaneous polymersome bursting. We have designed asymmetric

Elyes Mabrouk; Damien Cuvelier; Françoise Brochard-Wyart; Pierre Nassoy; Min-Hui Li

2009-01-01

243

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

244

Comet Bursting Through Relaxation  

NASA Astrophysics Data System (ADS)

Comets may be excited and occupy non-principal axis (complex) rotation states for a large fraction of their lifetimes. Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Comet orbits drive these rotation states through cycles of excitation due to surface jets and relaxation due to time variable internal stresses that dissipate energy in the anelastic comet interior. Furthermore, relaxation from complex rotation can increase the loads along the symmetry axis of prolate comets. These loads stretch the body along the symmetry axis and may be the cause of the characteristic ``bowling pin’’ shape and eventually may lead to failure. This is an alternative model for comet bursting. Each cycle deposits only a small amount of energy and stress along the axis, but this process is repeated every orbit during which jets are activated. Our model for the evolution of comet nuclei includes torques due to a number of discrete jets located on the surface based on Neishtadt et al. [2002]. The model also includes internal dissipation using an approach developed by Sharma et al. [2005] and Vokrouhlicky et al. [2009]. These equations are averaged over the instantaneous spin state and the heliocentric orbit so the long-term evolution of the comet can be determined. We determine that even after the inclusion of internal dissipation there still exist non-principal axis equilibrium states for certain jet geometries. For ranges of dissipation factors and jet geometries, prolate comets are found to occupy states that have time variable internal loads over long time periods. These periodic loadings along the symmetry axis may lead to ``necking’’ as the body extends along the axis to release the stress and eventually disruption.

Jacobson, Seth A.; Scheeres, D. J.

2012-10-01

245

The GLAST Burst Monitor  

NASA Technical Reports Server (NTRS)

The Gamma Ray Large Area Space Telescope (GLAST) observatory, scheduled for launch in September 2007, comprises the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). LAT is a pair telescope that will observe many sources, including gamma-ray bursts, at energies above 20 MeV. GBM consists of twelve NaI and two BGO scintillation detectors operating in the 10 keV to 30 MeV range. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for re-orienting the spacecraft to observe delayed emission from bursts outside the LAT field of view. GBM capabilities and performance characteristics will be described. Opportunities for guest investigations will be presented.

Meegan, Charles

2006-01-01

246

Localization of self-potential sources in volcano-electric effect with complex continuous wavelet transform and electrical tomography methods for an active volcano  

Microsoft Academic Search

This study concerns the fluid flow circulation associated with magmatic intrusion during volcanic eruptions from electrical tomography studies. The objective is to localize and characterize the sources responsible for electrical disturbances during a time evolution survey between 1993 and 1999 of an active volcano, the Piton de la Fournaise. We have applied a dipolar probability tomography and a multi-scale analysis

Ginette Saracco; Philippe Labazuy; Frédérique Moreau

2004-01-01

247

Pulseless electrical activity in a pediatric patient: a case report and review of causative factors and treatment.  

PubMed

Pulseless electrical activity, an arrhythmia that leads to cardiac arrest, is defined as the presence of organized electrical activity without a palpable pulse or arterial blood pressure. When this arrhythmia presents during anesthesia, it has become routine practice to initiate advanced cardiac life support according to the American Heart Association guidelines. This arrhythmia is usually associated with a poor prognosis unless a reversible cause is investigated and treated immediately. The purpose of this article is to summarize the causative factors of pulseless electrical activity and its treatment modalities. This case report describes the successful resuscitation of a pediatric patient who presented with pulseless electrical activity during anesthesia for a rigid bronchoscopy. PMID:24597008

Newman, Johanna

2013-12-01

248

Extreme electric fields power catalysis in the active site of ketosteroid isomerase.  

PubMed

Enzymes use protein architecture to impose specific electrostatic fields onto their bound substrates, but the magnitude and catalytic effect of these electric fields have proven difficult to quantify with standard experimental approaches. Using vibrational Stark effect spectroscopy, we found that the active site of the enzyme ketosteroid isomerase (KSI) exerts an extremely large electric field onto the C=O chemical bond that undergoes a charge rearrangement in KSI's rate-determining step. Moreover, we found that the magnitude of the electric field exerted by the active site strongly correlates with the enzyme's catalytic rate enhancement, enabling us to quantify the fraction of the catalytic effect that is electrostatic in origin. The measurements described here may help explain the role of electrostatics in many other enzymes and biomolecular systems. PMID:25525245

Fried, Stephen D; Bagchi, Sayan; Boxer, Steven G

2014-12-19

249

Low Temperature Geothermal Electricity Generation: Google Earth Virtual Field Trip Activity  

NSDL National Science Digital Library

This exploration takes students to Chena Hot Springs Resort in Alaska where they will learn how to produce low temperature geothermal electricity. Teacher's guide, activity sheet and PowerPoint presenation included. The 2008 ATEEC Fellows Institute brought 18 environmental science community college and high school instructors to Alaska. They created virtual field trips using Google Earth. In the activity, explore Chena Hot Springs Resort in Alaska to learn about low temperature geothermal electricity generation. Chena Hot Springs runs their entire facility on renewable energy. Learn how they do it why they do it and the engineering challenges along the way. This activity includes numerous turnkey teaching resources such as a PowerPoint presentation explaining the geothermal heat exchanging process, video interviews with environmental engineers, a teacher's guide and student activity. Users must create a free login to access this resource.

2013-06-06

250

Torsion Field Effect and Zero-Point Energy in Electrical Discharge Systems  

Microsoft Academic Search

Highly localized nuclear activation in electrochemical systems and other electrical discharge processes have been observed by many laboratories in world. There is an attempt to explain such anomalous phenomena by using torsion field theory and axion model in this report. Anisotopic behaviours of radiation products, burst charaster, \\

Xiong-wei Wen; Li-jun Han

2004-01-01

251

Mycorrhiza-induced lower oxidative burst is related with higher antioxidant enzyme activities, net H2O 2 effluxes, and Ca (2+) influxes in trifoliate orange roots under drought stress.  

PubMed

Mechanisms of arbuscular mycorrhiza (AM)-induced lower oxidative burst of host plants under drought stress (DS) are not elucidated. A noninvasive microtest technology (NMT) was used to investigate the effects of Funneliformis mosseae on net fluxes of root hydrogen peroxide (H2O2) and calcium ions (Ca(2+)) in 5-month-old Poncirus trifoliata, in combination with catalase (CAT) and superoxide dismutase (SOD) activities as well as tissue superoxide radical (O2 (•-)) and H2O2 concentrations under DS and well-watered (WW) conditions. A 2-month DS (55 % maximum water holding capacity of growth substrates) significantly inhibited AM fungal root colonization, while AM symbiosis significantly increased plant biomass production, irrespective of water status. F. mosseae inoculation generally increased SOD and CAT activity but decreased O2 (•-) and H2O2 concentrations in leaves and roots under WW and DS. Compared with non-AM seedlings, roots of AM seedlings had significantly higher net H2O2 effluxes and net Ca(2+) influxes, especially in the meristem zone, but lower net H2O2 efflux in the elongation zone. Net Ca(2+) influxes into roots were significantly positively correlated with root net H2O2 effluxes but negatively with root H2O2 concentrations. Results from this study suggest that AM-induced lower oxidative burst is related with higher antioxidant enzyme activities, root net H2O2 effluxes, and Ca(2+) influxes under WW and DS. PMID:25085218

Zou, Ying-Ning; Huang, Yong-Ming; Wu, Qiang-Sheng; He, Xin-Hua

2015-02-01

252

Effect of electric current frequency on the activation kinetics of raw charcoal  

SciTech Connect

The effect of electric current frequency on the kinetics of raw charcoal activation with water vapor has been investigated. It was established that under the effect of alternating current the rate constant increases under otherwise equal conditions. A dependence of the reaction rate on the current frequency was found. It was discovered that under the effect of alternating current the activation energy of interaction with water vapor diminishes.

Shevchenko, A.O.; Ivakhnyuk, G.K.; Fedorov, N.F. [St. Petersburg Technological Institute (Russian Federation)

1993-12-10

253

Diffusive properties of fluid-filled grain boundaries measured electrically during active pressure solution  

Microsoft Academic Search

Diffusion through `wetted' grain boundaries is often the rate limiting process during rock deformation by intergranular pressure solution. However, the underlying processes operative within such boundaries are poorly understood. In this contribution we have studied the diffusive properties of wetted grain boundaries by measuring the electrical resistivity of single, annular halite-glass contacts undergoing active pressure solution. Optical observation shows continuous

Siese de Meer; Christopher J. Spiers; Colin J. Peach; Tohru Watanabe

2002-01-01

254

Relationship between Neural Activation and Electric Field Distribution during Deep Brain Stimulation.  

PubMed

Models and simulations are commonly used to study deep brain stimulation (DBS). Simulated stimulation fields are often defined and visualized by electric field isolevels or volumes of tissue activated (VTA). The aim of the present study was to evaluate the relationship between stimulation field strength as defined by the electric potential V, the electric field E, and the divergence of the electric field ?(2) V, and neural activation. Axon cable models were developed and coupled to finite-element DBS models in three-dimensional (3-D). Field thresholds ( VT , ET, and ?(2) VT ) were derived at the location of activation for various stimulation amplitudes (1 to 5 V), pulse widths (30 to 120 ?s), and axon diameters (2.0 to 7.5 ?m). Results showed that thresholds for VT and ?(2) VT were highly dependent on the stimulation amplitude while ET were approximately independent of the amplitude for large axons. The activation field strength thresholds presented in this study may be used in future studies to approximate the VTA during model-based investigations of DBS without the need of computational axon models. PMID:25350910

Astrom, Mattias; Diczfalusy, Elin; Martens, Hubert; Wardell, Karin

2015-02-01

255

Video: Animals; Electric Current; Force; Science Activities. Learning in Science Project. Working Papers 51-54.  

ERIC Educational Resources Information Center

Four papers to be used in conjunction with video-tapes developed by the Learning in Science Project are presented. Topic areas of the papers focus on: (1) animals; (2) electric current; (3) force; and (4) science activities. The first paper presents transcripts of class discussions focusing on the scientific meaning of the word animal. The second…

Bell, Beverley; And Others

256

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

257

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

258

Particle acceleration and radiation by direct electric fields in flaring complex solar active regions  

E-print Network

Particle acceleration and radiation by direct electric fields in flaring complex solar active-Meudon, 92195 Meudon Cedex, FRANCE Abstract The acceleration and radiation of solar energetic particles with the existing observations. 1 Introduction The approach used for particle acceleration models proposed for solar

Anastasiadis, Anastasios

259

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

260

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 ...

261

Control of a multi-level active shunt power filter for More Electric Aircraft  

Microsoft Academic Search

The proposed increase of power electronic subsystems for More Electrical Aircraft (MEA) brings severe challenges to aircraft power distribution. Current aircraft power systems work at a fundamental frequency of 400 Hz while proposed AC MEA power networks for next generation aircrafts will have a fundamental frequency which varies most probably between 360 and 900 Hz. An active shunt filter (ASF)

Milijana Odavic; Mark Sumner; Pericle Zanchetta

2009-01-01

262

Electrical activity of the orbicularis muscles before and after installation of ocular prostheses.  

PubMed

This study examined the electrical activity of the superior (SO) and inferior (IO) orbicularis oculi muscles before and after installing ocular prostheses in patients who had undergone unilateral enucleation. Twelve volunteers requiring prostheses were selected. Their electrical activity was monitored at rest and during normal opening and closing of the eyelids, rapid opening and closing of the eyelids, and squeezing. Data were recorded before and 7, 30, and 60 days after the ocular prosthesis was installed. Two-way analysis of variance was performed to verify whether there were any significant differences between the muscles and periods, and means were compared by Tukey-Kramer honestly significant difference (HSD) tests (P<0.05). Results from the initial period differed significantly from those after prosthesis installation in all clinical situations. The SO had significantly higher electrical activity levels than the IO in all clinical situations but squeezing. The authors observed the same values during the initial period for the condition of rest (SO 8.42/IO 5.93) and the highest values for the condition of squeezing after 60 days (SO 131.50/IO 117.12). Rehabilitative treatment promoted an increase in the electrical activity of the orbicularis oculi muscles, restoring part of the muscle tone and motor function to muscles of the affected area. PMID:25457831

Goiato, M C; Santos, M R; Monteiro, B C Z; Moreno, A; Bannwart, L C; Filho, A J V; Guiotti, A M; Haddad, M F; Pesqueira, A A; Dos Santos, D M

2015-01-01

263

Effects of palytoxin on the electrical activity of dog and rabbit heart.  

PubMed

Reversible effects of palytoxin, extracted from colonies of the soft coral Palythoa caribaeorum, are described. There is a decrease of both membrane resting potential and overshoot during activity. Rise time of the action potential is prolonged, while repolarization is shortened. The electrical events resemble those seen with metabolic poisons. PMID:21804

Weidmann, S

1977-11-15

264

The Relations between Frontal Brain Electrical Activity and Cognitive Development during Infancy.  

ERIC Educational Resources Information Center

Examined the relationship between changes in electroencephalograms and the development of the ability to perform cognitive tasks involving frontal lobe functioning in infants of 7 to 12 months of age. Infants who successfully found a hidden object showed changes in the power of brain electrical activity in the frontal lobe. (BC)

Bell, Martha Ann; Fox, Nathan A.

1992-01-01

265

[Analysis of changes in the electrical activity of the neocortex in dogs during the formation of the stereotype of food-procuring conditioned reflexes in them].  

PubMed

A system of food-procuring conditioned reflexes (dynamic stereotype after I.P. Pavlov) was elaborated in dogs. In the interstimuli periods, 0.6 to 0.8 sec. prior the action of the conditioned stimulus, they exhibited a "state of expectancy" characterized by an increase of frequency (up to 80 per sec.) of potential oscillations of a small amplitude (20 to 30 mcv) and their pronounced sychroneity, predominantly in the anterior parts of the neocortex. The conditioned signal acting against such background produced specific reactions in the form of a limited number of bursts (3 to 4 in 0.5 sec.) of highfrequency (up to 100 per sec.) synchronized activity (HSA) of considerable amplitude (50 to 60 mcv) which always preceded conditioned reactions, being in certain temporal relations with them. A correlation-spectral analysis has shown that in the HSA period, electrical activity became considerably more regular; in the intensity spectra the extreme frequencies of the analyzed band (5 to 7 c/s and 90 to 100 c/s) became prominent, and in most cases high values of the coherence function were due to them. HSA reactions are regarded as a major link in the trigger mechanism of conditioned food-procuring reactions. PMID:563650

Dumenko, V N

1977-01-01

266

Abstract--Efficient methods for detecting electricity fraud has been an active research area in recent years. This paper presents  

E-print Network

1 Abstract--Efficient methods for detecting electricity fraud has been an active research area for electric utilities using Genetic Algorithm (GA) and Support Vector Machine (SVM). The main motivation, genetic algorithm, electricity theft, non-technical loss, load profile. I. INTRODUCTION LECTRIC utilities

Ducatelle, Frederick

267

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 · A broad education outside of engineering and science that emphasizes the role of electrical and computer of technology Graduate and undergraduate programs in electrical and computer engineering offer concentrations

Richards-Kortum, Rebecca

268

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

269

Low-Frequency Type III Bursts and Solar Energetic Particle Events  

NASA Technical Reports Server (NTRS)

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

Gopalswamy, Nat; Makela, Pertti

2010-01-01

270

Plasticity of hypothalamic dopamine neurons during lactation results in dissociation of electrical activity and release.  

PubMed

Tuberoinfundibular dopamine (TIDA) neurons are the central regulators of prolactin (PRL) secretion. Their extensive functional plasticity allows a change from low PRL secretion in the non-pregnant state to the condition of hyperprolactinemia that characterizes lactation. To allow this rise in PRL, TIDA neurons are thought to become unresponsive to PRL at lactation and functionally silenced. Here we show that, contrary to expectations, the electrical properties of the system were not modified during lactation and that the neurons remained electrically responsive to a PRL stimulus, with PRL inducing an acute increase in their firing rate during lactation that was identical to that seen in non-pregnant mice. Furthermore, we show a long-term organization of TIDA neuron electrical activity with an harmonization of their firing rates, which remains intact during lactation. However, PRL-induced secretion of dopamine (DA) at the median eminence was strongly blunted during lactation, at least in part attributable to lack of phosphorylation of tyrosine hydroxylase, the key enzyme involved in DA synthesis. We therefore conclude that lactation, rather than involving electrical silencing of TIDA neurons, represents a condition of decoupling between electrical activity at the cell body and DA secretion at the median eminence. PMID:23467359

Romanò, Nicola; Yip, Siew H; Hodson, David J; Guillou, Anne; Parnaudeau, Sébastien; Kirk, Siobhan; Tronche, François; Bonnefont, Xavier; Le Tissier, Paul; Bunn, Stephen J; Grattan, Dave R; Mollard, Patrice; Martin, Agnès O

2013-03-01

271

Taming desynchronized bursting with delays in the Macaque cortical network  

NASA Astrophysics Data System (ADS)

Inhibitory coupled bursting Hindmarsh—Rose neurons are considered as constitutive units of the Macaque cortical network. In the absence of information transmission delay the bursting activity is desynchronized, giving rise to spatiotemporally disordered dynamics. This paper shows that the introduction of finite delays can lead to the synchronization of bursting and thus to the emergence of coherent propagating fronts of excitation in the space-time domain. Moreover, it shows that the type of synchronous bursting is uniquely determined by the delay length, with the transitions from one type to the other occurring in a step-like manner depending on the delay. Interestingly, as the delay is tuned close to the transition points, the synchronization deteriorates, which implies the coexistence of different bursting attractors. These phenomena can be observed by different but fixed coupling strengths, thus indicating a new role for information transmission delays in realistic neuronal networks.

Wang, Qing-Yun; Murks, Aleksandra; Perc, Matjaž; Lu, Qi-Shao

2011-04-01

272

The GLAST Burst Monitor  

NASA Technical Reports Server (NTRS)

The Gamma Ray Large Area Space Telescope (GLAST) observatory, scheduled for launch in 2007, comprises the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). spectral changes that are known to occur within GRBs. between the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and the Max Planck Institute for Extraterrestrial Physics. It consists of an array of NaI and BGO scintillation detectors operating in the 10 kev to 25 MeV range. The field of view includes the entire unocculted sky when the observatory is pointing close to the zenith. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for reorienting the spacecraft to observe delayed emission from bursts outside the LAT field of view. GBM is expected to trigger on about 200 bursts per year, and will provide on-board locations of strong bursts accurate to better than 10 degrees.

Meegan, Charles A.

2004-01-01

273

The Central Italy Electromagnetic Network and the 2009 L'Aquila Earthquake: Observed Electric Activity  

NASA Astrophysics Data System (ADS)

A network of low frequency electromagnetic detectors has been operating in Central Italy for more than three years, consisting of identical instruments that continuously record the electrical components of the electromagnetic field, ranging from a few Hz to tens of kHz. These signals are analyzed in real time and their power spectrum contents and time/frequency data are available online. To date, specific interest has been devoted to searching for any possible electromagnetic features which correlate with seismic activity in the same region. In this study, spectral analysis has evidenced very distinct power spectrum signatures that increased in intensity when strong seismic activity occurred near the stations of the 2009 L'Aquila earthquake. These signatures have revealed horizontally oriented electric fields, between 20 Hz to 400 Hz, lasting from several minutes to up to two hours. Their power intensities have been found to be about 1 μV/m. Moreover, a large number of man-made signals and meteorologic electric perturbations were recorded. Anthropogenic signatures have come from power line disturbances at 50 Hz and higher harmonics up to several kHz, while radio transmissions have influenced the higher kHz spectrum. Reception from low frequency transmitters is also provided in relation to seismic activity. Meteorologic signatures cover the lower frequency band through phenomena such as spherics, Schumann resonances and rain electrical perturbations. All of these phenomena are useful teaching tools for introducing students to this invisible electromagnetic world

Fidani, Cristiano

2011-12-01

274

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

275

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

276

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

277

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

278

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

279

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

280

Jovian type III radio bursts  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

281

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

282

Voltage Bursting Drops in Solids  

NASA Astrophysics Data System (ADS)

Droplets in air or liquids under electrical voltages appear in diverse processes from thunderstorm cloud formation, ink-jet printing, electrospinning nanofibers to electrospray ionization. In these processes, the electrostatic energy competes with surface energy of the drops and causes sharp tips to form on the ends of the drops. Here, we report a physically distinct scenario for droplets in solid matrices under voltages. We show that water drops in elastic polymers can form sharp tips and surprisingly burst into long tubes under applied voltages. The new phenomenon is governed by the elasticity and fracture of the solids, instead of the drops' surface energy as in previous cases. A new scaling is derived for the critical electrical field of the voltage-induced instability of drops in solids. The observations and analyses have significant practical impacts, as they illustrate the mechanism of a major failure mode, defect-induced breakdown, of dielectric polymers, which are widely used as insulating cables and polymer capacitors and transducers.

Wang, Qiming; Suo, Zhigang; Zhao, Xuanhe

2012-02-01

283

Pulsed Gas Core Reactor For Burst Power  

NASA Astrophysics Data System (ADS)

Studies are being performed on burst power mode gas core reactors that employ closed cycle disk MHD generators for energy conversion. The disk MHD generator is configured to be an integral part of the reactor. Consequently, significant fissioning occurs throughout the MHD duct and fission fragment induced ionization of the uranium bearing fuel gas/ working fluid is anticipated to yield the required nonequilibrium electrical conductivity (> 100 mho/m) despite the relatively low gas temperatures. Calculations performed to date have shown that the Burst Power Gas Core Reactor-Disk. MHD Generator system can achieve overall efficiencies of 25 percent effective radiator temperatures of 1200 K, reactor specific powers of 100 to 200 kWt/kg and system specific powers of 5 kWe/kg.

Dugan, Edward T.; Lear, William E.; Welch, Gerard E.

1988-04-01

284

Impairment of the cortical and thalamic electrical activity in scrapie-infected rats.  

PubMed

Cortical and thalamic EEG and somatosensory evoked potential (SEP) induced by stimulation of the somesthetic radiations were studied in scrapie-infected rats. Animals were inoculated intracerebrally with a rat-adapted strain (originating in the C506 M3 mouse scrapie strain). EEG and SEP were recorded from 9 to 17 months after inoculation (ti). Abnormalities (paroxysmal bursts, isolated spikes) first occurred in the cortex (parietal areas) and later in the thalamus, where they were usually less marked. Latencies of the postsynaptic components of the SEP increased at ti + 9 months. This effect became progressively more pronounced and at ti + 15 months, latencies of presynaptic components were also delayed. Nevertheless, marked alteration of the SEP occurred only at the terminal stage of the disease. These findings show that the scrapie-induced disturbances affect more especially the cortex. Decrease of inhibitory processes as well as electronic coupling between cells, resulting from the virus-induced membrane fusion, could produce paroxysmal activity of EEG and SEP impairments. PMID:2434315

Bassant, M H; Court, L; Cathala, F

1987-03-01

285

Ionospheric quasi-static electric field anomalies during seismic activity in August-September 1981  

NASA Astrophysics Data System (ADS)

The paper proposes new results, analyses and information for the plate tectonic situation in the processing of INTERCOSMOS-BULGARIA-1300 satellite data about anomalies of the quasi-static electric field in the upper ionosphere over activated earthquake source regions at different latitudes. The earthquake catalogue is made on the basis of information from the United State Geological Survey (USGS) website. The disturbances in ionospheric quasi-static electric fields are recorded by IESP-1 instrument aboard the INTERCOSMOS-BULGARIA-1300 satellite and they are compared with significant seismic events from the period 14 August-20 September 1981 in magnetically very quiet, quiet and medium quiet days. The main tectonic characteristics of the seismically activated territories are also taken in account. The main goal of the above research work is to enlarge the research of possible connections between anomalous vertical electric field penetrations into the ionosphere and the earthquake manifestations, also to propose tectonic arguments for the observed phenomena. The studies are represented in four main blocks: (i) previous studies of similar problems, (ii) selection of satellite, seismic and plate tectonic data, (iii) data processing with new specialized software and observations of the quasi-static electric field and (iiii) summary, comparison of new with previous results in our studies and conclusion. We establish the high informativity of the vertical component Ez of the quasi-static electric field in the upper ionosphere according observations by INTERCOSMOS-BULGARIA-1300 that are placed above considerably activated earthquake sources. This component shows an increase of about 2-10 mV/m above sources, situated on mobile structures of the plates. The paper discusses the observed effects. It is represented also a statistical study of ionospheric effects 5-15 days before and 5-15 days after the earthquakes with magnitude M 4.8-7.9.

Gousheva, M.; Danov, D.; Hristov, P.; Matova, M.

2009-01-01

286

Electric-field and temperature dependence of the activation energy associated with gate induced drain leakage  

NASA Astrophysics Data System (ADS)

We examined the effect of temperature and electric field on the activation energy (Ea) of gate-induced drain leakage (GIDL) of a MOSFET. The measured GIDL current shows a temperature dependence consistent with a non-tunneling mechanism. In the low-electric-field regime and for temperatures above 55 °C, Ea is about 0.4 eV and drops from 0.4 eV to 0.1 eV as the applied gate voltage goes below VFB in the accumulation direction (decreased for the n-channel MOSFET). This suggests that electron-hole-pair generation at Si/SiO2 interface traps (Dit), enhanced by the electric field (the Poole-Frenkel effect), dominates GIDL in that regime. For temperatures below 55 °C, Ea is less than 0.15 eV for both weak and strong electric fields and displays minimal temperature dependence, indicating inelastic trap-assisted tunneling or phonon-assisted tunneling from a trap. In the very strong-electric-field regime (>1 MV/cm), band-to-band tunneling is the dominant mechanism.

Alnuaimi, Aaesha; Nayfeh, Ammar; Koldyaev, Victor

2013-01-01

287

Simultaneous monitoring of electrical capacitance and water uptake activity of plant root system  

NASA Astrophysics Data System (ADS)

Pot experiments were designed to test the applicability of root electrical capacitance measurement for in situ monitoring of root water uptake activity by growing cucumber and bean cultivars in a growth chamber. Half of the plants were inoculated with Funneliformis mosseae arbuscular mycorrhizal fungi, while the other half served as non-infected controls. Root electrical capacitance and daily transpiration were monitored during the whole plant ontogeny. Phenology-dependent changes of daily transpiration (related to root water uptake) and root electrical capacitance proved to be similar as they showed upward trends from seedling emergence to the beginning of flowering stage, and thereafter decreased continuously during fruit setting. A few days after arbuscular mycorrhizal fungi-colonization, daily transpiration and root electrical capacitance of infected plants became significantly higher than those of non-infected counterparts, and the relative increment of the measured parameters was greater for the more highly mycorrhizal-dependent bean cultivar compared to that of cucumber. Arbuscular mycorrhizal fungi colonization caused 29 and 69% relative increment in shoot dry mass for cucumbers and beans, respectively. Mycorrhization resulted in 37% increase in root dry mass for beans, but no significant difference was observed for cucumbers. Results indicate the potential of root electrical capacitance measurements for monitoring the changes and differences of root water uptake rate.

Cseresnyés, Imre; Takács, Tünde; Füzy, Anna; Rajkai, Kálmán

2014-10-01

288

Nighttime observations of thunderstorm electrical activity from a high altitude airplane  

NASA Technical Reports Server (NTRS)

Nocturnal thunderstorms were observed from above and features of cloud structure and lightning which are not generally visible from the ground are discussed. Most, lightning activity seems to be associated with clouds with strong convective cauliflower tops. In both of the storms lightning channels were visible in the clear air above the cloud. It is shown that substances produced by thunderstorm electrical discharges can be introduced directly into the stratosphere. The cause and nature of the discharges above the cloud are not clear. They may be produced by accumulations of space charge in the clear air above the cloud. The discharges may arise solely because of the intense electric fields produced by charges within the cloud. In the latter case the ions introduced by these discharges will increase the electrical conductivity of the air above the cloud and increase the conduction current that flows from the cloud to the electrosphere. More quantitative data at higher resolution may show significant spectral differences between cloud to ground and intracloud strokes. It is shown that electric field change data taken with an electric field change meter mounted in an airplane provide data on lightning discharges from above that are quite similar to those obtained from the ground in the past. The optical signals from dart leaders, from return strokes, and from continuing currents are recognizable, can be used to provide information on the fine structure of lightning, and can be used to distinguish between cloud to ground and intracloud flashes.

Brook, M.; Vonnegut, B.; Orville, R. E.; Vaughan, O. H., Jr.

1984-01-01

289

Reduction, analysis, and properties of electric current systems in solar active regions  

NASA Technical Reports Server (NTRS)

The specific attraction and, in large part, the significance of solar magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 deg ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 deg ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local `preferred' direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar (beta) (gamma) (delta)-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA/sq m and have a linear decreasing distribution to a diameter of 30 Mn.

Gary, G. Allen; Demoulin, Pascal

1995-01-01

290

Reduction, Analysis, and Properties of Electric Current Systems in Solar Active Regions  

NASA Technical Reports Server (NTRS)

The specific attraction and, in large part, the significance of solar vector magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 degree ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 degree ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local "preferred" direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar beta gamma delta-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA per square meter and have a linear decreasing distribution to a diameter of 30 Mm.

Gary, G. Allen; Demoulin, Pascal

1995-01-01

291

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

292

Voltage-Sensitive Dyes And Imaging Techniques Reveal New Patterns Of Electrical Activity In Heart Cortex  

NASA Astrophysics Data System (ADS)

Voltage-sensitive dyes bind to the plasms membrane of excitable cells (ie., muscle or nerve cells) and exhibit fluorescence and/or absorption changes that vary linearly with changes in transmembrane electrical potential. These potentiometric optical probes can be used to measure local changes in transmembrane potential by monitoring optical signals from dye molecules bound to the surface membrane. Consequently, when excitable cells are stained with such a dye and are stimulated to fire an electrical impulse (ie., an action potential (AP)), the changes in dye fluorescence have the characteristic shape and time course of APs recorded with an intracellular micro-electrode. Potentiometric dyes in conjuction with imaging techniques can now be used to visualize complex patterns and propagation of electrical activity. With photodiode arrays on video imaging techniques, patterns of biological electrical activity can be obtained with high temporal and spatial resolution which could not be obtained by conventional micro-electrodes. These methods reveal new details and offer powerful approaches to study fundamental problem in cardiac electrophysiology, communication in nerve networks, and the organization of cortical neurons.

Salama, Guy

1988-04-01

293

Changes in the cardiac muscle electric activity as a result of Coronary Artery Bypass Graft operation  

NASA Astrophysics Data System (ADS)

Many bioelectric signals have a complex internal structure that can be a rich source of information on the tissue or cell processes. The structure of such signals can be analysed in detail by applying digital methods of signal processing. Therefore, of substantial use in diagnosis of the coronary arterial disease is the method of digital enhancement of increasing signal resolution ECG (NURSE-ECG), permitting detection of temporary changes in the electric potentials in the cardiac muscle in the process of depolarisation. Thanks to the application of NURSE-ECG it has become possible to detect relatively small changes in the electric activity of particular fragments of the cardiac muscle undetectable by the standard ECG method, caused by ischemia, the effect of a drug or infarct. The aim of this study was to identify and analyse changes in the electric activity of the cardiac muscle as a result of the Coronary Artery Bypass Graft (CABG) operation. In this study the method of NURSE-ECG has been applied in order to identify and analyse changes in the electric activity of the cardiac muscle as a result of the CABG operation. In the study performed in cooperation of the Institute of Physics Adam Mickiewicz University and the Strus Hospital, Cardiac Surgery Ward, 37 patients with advanced coronary arterial disease were asked to participate. The patients were examined prior to the operation, on the day after the operation and two months after the operation and a year after the operation. The ECG recordings were subjected to a numerical procedure of resolution enhancement by a NURSE-ECG program to reveal the tentative changes in the electric potential of the cardiac muscle on its depolarisation. Results of the study have shown that the NURSE ECG method can be applied to monitor changes in the electric activity of the cardiac muscle occurring as a result of CABG operation. One the second day after the operation in the majority of patients (70%) a rapid decrease of the total cardiac muscle activity was observed. The NURSE ECG seems to be a promising supplementary method in medical diagnosis. In particular it can be applied for qualification of patients for CABG operation and for verification of the operation effects.

Grajek, Magdalena; Krzyminiewski, Ryszard; Kalawski, Ryszard; Kulczak, Mariusz

2008-01-01

294

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

295

Coherent phonon optics in a chip with an electrically controlled active device  

PubMed Central

Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378?GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale. PMID:25652241

Poyser, Caroline L.; Akimov, Andrey V.; Campion, Richard P.; Kent, Anthony J.

2015-01-01

296

Coherent phonon optics in a chip with an electrically controlled active device.  

PubMed

Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378?GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale. PMID:25652241

Poyser, Caroline L; Akimov, Andrey V; Campion, Richard P; Kent, Anthony J

2015-01-01

297

A hybrid approach to measuring electrical activity in genetically specified neurons.  

PubMed

The development of genetically encoded fluorescent voltage probes is essential to image electrical activity from neuronal populations. Previous green fluorescent protein (GFP)-based probes have had limited success in recording electrical activity of neurons because of their low sensitivity and poor temporal resolution. Here we describe a hybrid approach that combines a genetically encoded fluorescent probe (membrane-anchored enhanced GFP) with dipicrylamine, a synthetic voltage-sensing molecule that partitions into the plasma membrane. The movement of the synthetic voltage sensor is translated via fluorescence resonance energy transfer (FRET) into a large fluorescence signal (up to 34% change per 100 mV) with a fast response and recovery time (0.5 ms). Using this two-component approach, we were able to optically record action potentials from neuronal cell lines and trains of action potentials from primary cultured neurons. This hybrid approach may form the basis for a new generation of protein-based voltage probes. PMID:16205716

Chanda, Baron; Blunck, Rikard; Faria, Leonardo C; Schweizer, Felix E; Mody, Istvan; Bezanilla, Francisco

2005-11-01

298

Introductory overview of research instruments for recording the electrical activity of neurons in the human brain  

NASA Astrophysics Data System (ADS)

Scientific advancement is often spurred by the development of new instruments for investigation. Over the last several decades, many new instruments have been produced to further our understanding of the physiology of the human brain. We present a partial overview of some of these instruments, paying particular attention to those which record the electrical activity of the human brain. We preface the review with a brief primer on neuroanatomy and physiology, followed by a discussion of the latest types of apparatus used to investigate various properties of the central nervous system. A special focus is on microelectrode investigations that employ both intracellular and extracellular methods of recording the electrical activity of single neurons; another is on the modern electroencephalographic, electrocorticographic, and magnetoencephalographic methods used to study the spontaneous and evoked field potentials of the brain. Some examples of clinical applications are included, where appropriate.

Garell, P. C.; Granner, M. A.; Noh, M. D.; Howard, M. A.; Volkov, I. O.; Gillies, G. T.

1998-12-01

299

Identification and Dynamics of Spontaneous Burst Initiation Zones in Unidimensional Neuronal Cultures  

Microsoft Academic Search

Spontaneous activity is typical of in-vitro neural networks, often in the form of large population bursts. The origins of this activity are attributed to intrinsically bursting neurons and to noisy backgrounds, as well as to recurrent network connections. Spontaneous activity is often observed to emanate from localized sources or initiation zones, propagating from there to excite large populations of neurons.

Ofer Feinerman; Menahem Segal; E. Moses

2007-01-01

300

The GLAST Burst Monitor  

SciTech Connect

The Gamma Ray Large Area Space Telescope (GLAST) mission is a followup to the successful EGRET experiment onboard the Compton Gamma Ray Observatory (CGRO). It will provide a high-sensitivity survey of the sky in high-energy {gamma}-rays, and will perform detailed observations of persistent and transient sources. There are two experiments onboard the GLAST - the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM).The primary mission of the GBM instrument is to support the LAT in observing {gamma}-ray bursts (GRBs) by providing low-energy measurements with high time resolution and rapid burst locations over a large field-of-view ({>=} 8 sr). The GBM will complement the LAT measurements by observing GRBs in the energy range 10 keV to 30 MeV, the region of the spectral turnover in most GRBs. An important objective of the GBM is to compute the locations of GRB sources on-board the spacecraft and quickly communicate them to the LAT and to the ground to allow rapid followup observations. This information may be used to re-point the LAT towards particularly interesting burst sources that occurred outside its field-of-view. The GBM consists of 14 uncollimated scintillation detectors coupled to phototubes to measure {gamma}-ray energies and time profiles. Two types of detectors are used to obtain spectral information over a wide energy range: 12 NaI(Tl) detectors (10 keV to 1 MeV), and 2 BGO detectors (150 keV to 30 MeV). The detectors are distributed around the GLAST spacecraft to provide a large, unobstructed field of view. The 12 NaI(Tl) detectors are mounted with different orientations for use in locating GRB sources.

Bhat, P.N.; Briggs, M.S.; Connaughton, V.; Paciesas, W.S.; Preece, R.D. [University of Alabama in Huntsville (United States); Meegan, C.A.; Fishman, G.J.; Wilson, R.B. [NASA Marshall Space Flight Center (United States); Lichti, G.G.; Diehl, R.; Greiner, J.; Schoenfelder, V.; Kienlin, A. von [Max-Planck-Institut fuer extraterrestrische Physik (Germany); Kippen, R.M. [Los Alamos National Laboratory (United States); Kouveliotou, C. [NASA Marshall Space Flight Center (United States); Universities Space Research Association (United States)

2004-09-28

301

Explorations of electric current system in solar active regions. I - Empirical inferences of the current flows  

NASA Technical Reports Server (NTRS)

Techniques to identify sources of electric current systems and their channels of flow in solar active regions are explored. Measured photospheric vector magnetic fields together with high-resolution white-light and H-alpha filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980.

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

1987-01-01

302

Electrical Characteristics of Thin-Film Transistors with Double-Active-Layer Structure  

Microsoft Academic Search

Thin-film transistors (TFTs) with a double-active-layer (DAL) structure have been proposed and found to exhibit two kinds of special electrical characteristics. One is the improvement of current drivability and transconductance as compared to the traditional structure. The other is the double-switching characteristics caused by the bi-transistor action. By means of a buried oxide separating the conduction channel into two parts,

Meng-Jin Tsai; Ping-Wei Wang; Huan-Ping Su; Huang-Chung Cheng

1995-01-01

303

The electric activity of special grain boundaries in multicrystalline silicon grown from metallurgical refined silicon  

NASA Astrophysics Data System (ADS)

The properties of special grain boundaries in multicrystalline silicon (mc-Si) grown from metallurgical refined silicon by the Bridgman-Stockbarger method have been studied. The electric activity of grain boundaries was characterized by measuring the electron-beam-induced current. Structural features of the mc-Si samples were studied by scanning electron microscopy, electron-probe microanalysis, and atomic force microscopy techniques.

Peshcherova, S. M.; Nepomnyashchikh, A. I.; Pavlova, L. A.

2014-11-01

304

Study of transcutaneous and intraluminal measurement of gastric electrical activity in humans  

Microsoft Academic Search

Several authors have reported measurements of the human electrogastrogram (EGG), both with intraluminal electrodes and with\\u000a improved noninvasive techniques. These methods provide information about the existence and frequency of gastric electrical\\u000a activity (GEA) which may aid in diagnosing tachygastria. However, none of these methods have provided information regarding\\u000a the direction and velocity of propagation of GEA. Such information could help

B. O. Familoni; Y. J. Kingma; K. L. Bowes

1987-01-01

305

Active medium gain study of electric-discharge oxygen-iodine laser  

Microsoft Academic Search

The paper reports on experimental studies of the active medium gain in supersonic electric-discharge oxygen-iodine laser (DOIL) based on traveling mw discharge. The measurements have included: absolute concentration, yield, and energy efficiency of production of SO in pure oxygen and oxygen-helium mixes at an oxygen partial pressure 3 to 15 Torr. For the gas flow to get rid of atomic

Yuriy Kolobyanin; Yuriy Adamenkov; Boris Vyskubenko; Leonid Goryachev; Sergey Ilyin; Anatoliy Kalashnik; Tatiana Rakhimova; Georgiy Rogozhnikov

2007-01-01

306

Real-time algorithms for active power measurements on PWM-based electric drives  

Microsoft Academic Search

Two real-time algorithms for active power measurements on Pulse Width Modulation (PWM) electric drives are proposed. The former is an off-line algorithm reducing truncation error through an accurate signal period estimation and a proper window. The second is an on-line algorithm based on a low-pass IIR digital filter with an optimized transient phase. Numerical results of the metrological characterization of

P. Arpaia; F. Avallone; A. Baccigalupi; C. De Capua

1996-01-01

307

Exploratory study of EEG burst characteristics in preterm infants.  

PubMed

In this paper, we study machine learning techniques and features of electroencephalography activity bursts for predicting outcome in extremely preterm infants. It was previously shown that the distribution of interburst interval durations predicts clinical outcome, but in previous work the information within the bursts has been neglected. In this paper, we perform exploratory analysis of feature extraction of burst characteristics and use machine learning techniques to show that such features could be used for outcome prediction. The results are promising, but further verification in larger datasets is needed to obtain conclusive results. PMID:24110682

Simayijiang, Zhayida; Backman, Sofia; Ulén, Johannes; Wikström, Sverre; Åstrom, Kalle

2013-01-01

308

Activated carbon fiber composite as a new material for electrical and electrochemical applications  

NASA Astrophysics Data System (ADS)

Activated carbon fiber (ACF) is a microporous material consisting of three-dimensional network of micrographitic layers. The micrographitic edges have a considerable amount of active functional groups (such as -COOH, -OH, -CO-, -O-) and dangling bonds. The huge specific surface area (up to 3000 m2/g) is another important property of ACF. Exploitation of the high surface area and the reactivity of the functional groups of ACF, through incorporating or doping ACF with transition metal salts (M) and/or binder (B), was used to enhance the electrical properties of ACF. Such treatments created new interfaces such as (ACF/M, ACF/M/B, and ACF/B/M) through which an extra charge can be localized, transferred, or stored. This process can be of great benefit in energy storage devices such as supercapacitors for computer memory backup. In this work, activated carbon fiber nonwoven fabrics have been impregnated with different concentrations of organometallic Cu and Zn salts, a carbonaceous sot binder, or mixtures of both, followed by thermal treatment over a temperature range 300°C--900°C under an inert atmosphere. The use of carbonaceous sot as a binder has used in the study, is novel. Electrical measurements, current-voltage characterization, current-time relationship, as well as the relative permittivity and impedance of ACF composites, have been conducted. The electric double-layer capacitance of the as-received and the ACF composites were also evaluated.

Nasr, Mohamed Fathy

309

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

310

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

311

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

312

A Different Cone: Bursting Drops in Solids  

NASA Astrophysics Data System (ADS)

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

Zhao, Xuanhe

2013-03-01

313

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

314

Pituitary adenylate cyclase-activating peptide enhances electrical coupling in the mouse adrenal medulla  

PubMed Central

Neuroendocrine adrenal medullary chromaffin cells receive synaptic excitation through the sympathetic splanchnic nerve to elicit catecholamine release into the circulation. Under basal sympathetic tone, splanchnic-released acetylcholine evokes chromaffin cells to fire action potentials, leading to synchronous phasic catecholamine release. Under elevated splanchnic firing, experienced under the sympathoadrenal stress response, chromaffin cells undergo desensitization to cholinergic excitation. Yet, stress evokes a persistent and elevated adrenal catecholamine release. This sustained stress-evoked release has been shown to depend on splanchnic release of a peptide transmitter, pituitary adenylate cyclase-activating peptide (PACAP). PACAP stimulates catecholamine release through a PKC-dependent pathway that is mechanistically independent of cholinergic excitation. Moreover, it has also been reported that shorter term phospho-regulation of existing gap junction channels acts to increase junctional conductance. In this study, we test if PACAP-mediated excitation upregulates cell-cell electrical coupling to enhance chromaffin cell excitability. We utilize electrophysiological recordings conducted in adrenal tissue slices to measure the effects of PACAP stimulation on cell coupling. We report that PACAP excitation increases electrical coupling and the spread of electrical excitation between adrenal chromaffin cells. Thus PACAP acts not only as a secretagogue but also evokes an electrical remodeling of the medulla, presumably to adapt to the organism's needs during acute sympathetic stress. PMID:22592408

Hill, Jacqueline; Lee, Seong-Ki; Samasilp, Prattana

2012-01-01

315

Anisotropic spherical head model and its application to imaging electric activity of the brain  

NASA Astrophysics Data System (ADS)

This study reports on a solution to Poisson's equation describing an electric potential and field generated by a dipolar current source positioned inside a set of concentric spherical shells characterized by a homogeneous anisotropic conductivity inside each shell. Formulas giving a unique continuation of potentials and fields between the shells are derived. The formulas are applied to a spherical model of the human head to show that (i) real human skulls comprising isotropic compact and cancellous bone layers can be closely approximated by a single shell with radial-tangential conductivity anisotropy ˜1:2 and radial conductivity equal to 1/30 of the brain/scalp conductivity; (ii) errors due to the spherical approximation of the head shape are of the same magnitude as errors due to poorly known electrical properties of the modeled head tissues; (iii) commonly used electroencephalography (EEG) average reference contributes 15% of the signal (on the average) and, therefore, makes EEG measurements significantly nonlocal; and (iv) the surface Laplacian of EEG measurements closely approximates electric currents at the skull-scalp interface, providing a parameter-free (up to a constant factor) deblurring and dereferencing of EEG data. These results can be useful for localization of sources underlying electric activity of the brain.

Petrov, Yury

2012-07-01

316

UWB dual burst transmit driver  

DOEpatents

A dual burst transmitter for ultra-wideband (UWB) communication systems generates a pair of precisely spaced RF bursts from a single trigger event. An input trigger pulse produces two oscillator trigger pulses, an initial pulse and a delayed pulse, in a dual trigger generator. The two oscillator trigger pulses drive a gated RF burst (power output) oscillator. A bias driver circuit gates the RF output oscillator on and off and sets the RF burst packet width. The bias driver also level shifts the drive signal to the level that is required for the RF output device.

Dallum, Gregory E. (Livermore, CA); Pratt, Garth C. (Discovery Bay, CA); Haugen, Peter C. (Livermore, CA); Zumstein, James M. (Livermore, CA); Vigars, Mark L. (Livermore, CA); Romero, Carlos E. (Livermore, CA)

2012-04-17

317

Deterministic and Stochastic Neuronal Contributions to Distinct Synchronous CA3 Network Bursts  

PubMed Central

Computational studies have suggested that stochastic, deterministic, and mixed processes all could be possible determinants of spontaneous, synchronous network bursts. In the present study, utilizing multicellular calcium imaging coupled with fast confocal microscopy, we describe neuronal behavior underlying spontaneous network bursts in developing rat and mouse hippocampal area CA3 networks. Two primary burst types were studied: giant depolarizing potentials (GDPs) and spontaneous interictal bursts recorded in bicuculline, a GABAA receptor antagonist. Analysis of the simultaneous behavior of multiple CA3 neurons during synchronous GDPs revealed a repeatable activation order from burst to burst. This was validated using several statistical methods, including high Kendall’s W values for firing order during GDPs, high Pearson’s correlations of cellular activation times between burst pairs, and latent class analysis, which revealed a population of 5-6% of CA3 neurons reliably firing very early during GDPs. In contrast, neuronal firing order during interictal bursts appeared homogenous, with no particular cells repeatedly leading or lagging during these synchronous events. We conclude that GDPs activate via a deterministic mechanism, with distinct, repeatable roles for subsets of neurons during burst generation, while interictal bursts appear to be stochastic events with cells assuming interchangeable roles in the generation of these events. PMID:22492030

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

2012-01-01

318

Static Electricity  

NSDL National Science Digital Library

In this quick activity, learners explore static electricity using a plastic comb, wool cloth, puffed rice, and a plastic bag. Use this activity to introduce learners to how static electricity is created when an object gives up or gains electrons.

Carlyn Little

1997-01-01

319

Recording of the Neural Activity Induced by the Electrical Subthalamic Stimulation Using Ca2+ Imaging  

NASA Astrophysics Data System (ADS)

The basal ganglia (BG) have important roles in some kind of motor control and learning. Parkinson's disease is one of the motor impairment disease. Recently, to recover a motor severity in patients of Parkinsonism, the stimulus electrode is implanted to the subthalamic nucleus, which is a part of the basal ganglia, and the deep brain stimulation (DBS) is often conducted. However, the effects of the DBS on the subthalamic neurons have not been elucidated. Thus, to analyze the effects of the electrical stimulation on the subthalamic neurons, we conducted the calcium imaging at the mouse subthalamic nucleus. When the single stimulus was applied to the subthalamic nucleus, the intracellular calcium ([Ca2+]i) transients were observed. In the case of application of the single electrical stimulation, the [Ca2+]i arose near the stimulus position. When 100 Hz 10-100 times tetanic stimulations were applied, the responded area and the amplitudes of [Ca2+]i transients were increased. The [Ca2+]i transients were disappeared almost completely on the action potential blockade, but blockade of the excitatory and the inhibitory synaptic transmission had little effects on the responded area and the amplitudes of the [Ca2+]i transients. These results suggested that the electrical stimulation to the subthalamic neurons led to activate the subthalamic neurons directly but not via synaptic transmissions. Thus, DBS may change the activity of the subthalamic neurons, hence, may alter the input-output relationship of the subthalamic neurons

Tamura, Atsushi; Yagi, Tetsuya; Osanai, Makoto

320

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

2013-01-01

321

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

322

Suppression of putative tinnitus-related activity by extra-cochlear electrical stimulation.  

PubMed

Studies on animals have shown that noise-induced hearing loss is followed by an increase of spontaneous firing at several stages of the central auditory system. This central hyperactivity has been suggested to underpin the perception of tinnitus. It was shown that decreasing cochlear activity can abolish the noise-induced central hyperactivity. This latter result further suggests that an approach consisting of reducing cochlear activity may provide a therapeutic avenue for tinnitus. In this context, extra-cochlear electric stimulation (ECES) may be a good candidate to modulate cochlear activity and suppress tinnitus. Indeed, it has been shown that a positive current applied at the round window reduces cochlear nerve activity and can suppress tinnitus reliably in tinnitus subjects. The present study investigates whether ECES with a positive current can abolish the noise-induced central hyperactivity, i.e., the putative tinnitus-related activity. Spontaneous and stimulus-evoked neural activity before, during and after ECES was assessed from single-unit recordings in the inferior colliculus of anesthetized guinea pigs. We found that ECES with positive current significantly decreases the spontaneous firing rate of neurons with high characteristic frequencies, whereas negative current produces the opposite effect. The effects of the ECES are absent or even reversed for neurons with low characteristic frequencies. Importantly, ECES with positive current had only a marginal effect on thresholds and tone-induced activity of collicular neurons, suggesting that the main action of positive current is to modulate the spontaneous firing. Overall, cochlear electrical stimulation may be a viable approach for suppressing some forms of (peripheral-dependent) tinnitus. PMID:25298390

Noreña, A J; Mulders, W H A M; Robertson, D

2015-01-01

323

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

324

Bond polarizability and vibronic coupling theories of Raman optical activity: The electric-dipole magnetic-dipole optical activity tensor  

NASA Astrophysics Data System (ADS)

A new formulation of the bond polarizability and vibronic coupling theories of Raman optical activity (ROA) is presented in which terms dependent upon the nuclear momentum are introduced for the first time. The new terms appear in the magnetic-dipole electric-dipole optical activity tensor and are directly analogous to the non-Born-Oppenheimer, momentum-dependent terms required in the formulation of the theory of vibrational circular dichroism. Through the use of simplifying approximations in the ROA vibronic coupling theory, a term-for-term correspondence with the bond polarizability theory is established. It is shown that the new terms are smaller than the original terms by the ratio of the vibrational transition frequency to the frequency of the incident radiation. The new terms also contribute oppositely to Stokes and anti-Stokes ROA which provides a basis for their experimental isolation.

Escribano, Juan R.; Freedman, Teresa B.; Nafie, Laurence A.

1987-09-01

325

Status of electric vehicle battery development and manufacturing activities outside of the United States  

SciTech Connect

A study was conducted to summarize and analyze current activities outside of the United States in battery technology for electric vehicles. Emphasis was placed on batteries which are either commercially available now or may be fully developed within the next ten years. The battery systems of greatest interest currently are sodium/sulfur, nickel/iron, zinc/bromine, and advanced lead/acid. The countries with the largest programs are England, Japan, and the Federal Republic of Germany. Performance and cost goals for each system do not vary significantly from one country to another, with the possible exception of the Soviet Union. The number of joint ventures and consortia that have formed in recent years has increased, and international cooperation is now an important feature of current activities in battery technology. US Executive Branch policy is now very supportive of joint ventures. For this and other reasons, organizations in the United States could benefit from increased involvement in cooperative international activities.

Swisher, J.H.

1985-12-01

326

Reticular activating system of a central pattern generator: premovement electrical potentials.  

PubMed

For the first time, here we characterize a bulbar reticular activating system (RAS) of neurons in decerebrate, deafferented and decerebellated cats producing a premovement electrical potential that we named obex slow potential (OSP). The OSP occurs about 0.8 ± 0.4 sec prior to the onset of a fictive-scratching-episode. Here, we describe two classes of bulbar neurons, off-on, which are silent but exhibit a 80 ± 56 Hz firing discharge at the beginning of (and during) the OSP, and on-off interneurons, with a 27 ± 14 Hz firing activity that stops at the beginning of (and during) the OSP. We suggest that these OSP-associated neurons belong to a descending RAS, which contributes to the activation of the spinal central pattern generators. PMID:24303193

Tapia, Jesus A; Trejo, Argelia; Linares, Pablo; Alva, J Manuel; Kristeva, Rumyana; Manjarrez, Elias

2013-10-01

327

Reticular activating system of a central pattern generator: premovement electrical potentials  

PubMed Central

For the first time, here we characterize a bulbar reticular activating system (RAS) of neurons in decerebrate, deafferented and decerebellated cats producing a premovement electrical potential that we named obex slow potential (OSP). The OSP occurs about 0.8 ± 0.4 sec prior to the onset of a fictive-scratching-episode. Here, we describe two classes of bulbar neurons, off-on, which are silent but exhibit a 80 ± 56 Hz firing discharge at the beginning of (and during) the OSP, and on-off interneurons, with a 27 ± 14 Hz firing activity that stops at the beginning of (and during) the OSP. We suggest that these OSP-associated neurons belong to a descending RAS, which contributes to the activation of the spinal central pattern generators. PMID:24303193

Tapia, Jesus A; Trejo, Argelia; Linares, Pablo; Alva, J Manuel; Kristeva, Rumyana; Manjarrez, Elias

2013-01-01

328

[Intercentral reticulo-cortical relations of brain electrical activity during "animal hypnosis" in rabbits].  

PubMed

The electrical activity of the right and left sensorimotor and premotor cortical areas and right and left medulary reticular formation was recorded during "animal hypnosis" in rabbits. In this state, the spectral power of potentials (predominantly, in the delta-range) recorded from the left reticular formation was higher than that recorded from the right side. The value of the function of coherence between the right and left reticular recordings was decreased to 0.1-0.2 in the whole frequency range. The tight-side intrahemispheric coherence between the activities recorded from the sensorimotor cortex and reticular formation was higher than respective left-side values, whereas the coherent relations between the activities recorded from the reticular formation and premotor cortex were not changed (as compared to nonhypnotic state). PMID:12125401

Rusinova, E V; Roshchina, G Ia

2002-01-01

329

Development of Active Magnetic Shielding for the Neutron Electric Dipole Moment Experiment at TRIUMF  

NASA Astrophysics Data System (ADS)

Active magnetic shielding has been proposed to provide low-frequency magnetic field stability in the neutron electric dipole moment (nEDM) experiment planned for TRIUMF. A prototype active magnetic shielding system was constructed and tested at the University of Winnipeg. The system is capable of providing RMS shielding factors > 1000 for magnetic field perturbation frequencies ? 20 mHz, and > 100 for frequencies ? 0.5 Hz, and can reduce magnetic field variations on the order of tens of muT to the level of tens of nT. The achievable shielding factor was limited by the field sampling rate limit of ~400 Hz, and by the background fi eld noise floor of the laboratory. This represents good progress towards the eventual system for nEDM experiments, where low-frequency field drifts on the order of 100 nT require active shielding to the order of 1 nT.

Lang, Michael Loren

330

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

NASA Technical Reports Server (NTRS)

Combustion synthesis (CS) generally involves mixing reactants together (e.g., metal powders) and igniting the mixture. Typically, a reaction wave will pass through the sample. In field activated combustion synthesis (FACS), the addition of an electric field has a marked effect on the dynamics of wave propagation and on the nature, composition, and homogeneity of the product as well as capillary flow, mass-transport in porous media, and Marangoni flows, which are influenced by gravity. The objective is to understand the role of an electric field in CS reactions under conditions where gravity-related effects are suppressed or altered. The systems being studied are Ti+Al and Ti+3Al. Two different ignition orientations have been used to observe effects of gravity when one of the reactants becomes molten. This consequentially influences the position and concentration of the electric current, which in turn influences the entire process. Experiments have also been performed in microgravity conditions. This process has been named Microgravity Field Activated Combustion Synthesis (MFACS). Effects of gravity have been demonstrated, where the reaction wave temperature and velocity demonstrate considerable differences besides the changes of combustion mechanisms with the different high currents applied. Also the threshold for the formation of a stable reaction wave is increased under zero gravity conditions. Electric current was also utilized with a chemical oven technique, where inserts of aluminum with minute amounts of tungsten and tantalum were used to allow observation of effects of settling of the higher density solid particles in liquid aluminum at the present temperature profile and wave velocity of the reaction.

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

2004-01-01

331

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

332

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

333

78 FR 28190 - Authorization of Production Activity; Foreign-Trade Subzone 29C; GE Appliances (Electric Water...  

Federal Register 2010, 2011, 2012, 2013

...Foreign-Trade Subzone 29C; GE Appliances (Electric Water Heaters); Louisville, Kentucky On January 7, 2013, GE Appliances, operator of Subzone 29C in Louisville, Kentucky, submitted a notification of proposed production activity...

2013-05-14

334

Burst Detector Sensitivity: Past, Present and Future  

NASA Technical Reports Server (NTRS)

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

Band, David L.

2005-01-01

335

Burst Detector Sensitivity: Past, Present and Future  

SciTech Connect

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

Band, David L. [Code 661, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); JCA, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States)

2006-05-19

336

Enhanced electricity generation by using algae biomass and activated sludge in microbial fuel cell.  

PubMed

Recently, interest is growing to explore low-cost and sustainable means of energy production. In this study, we have exploited the potential of sustainable energy production from wastes. Activated sludge and algae biomass are used as substrates in microbial fuel cell (MFC) to produce electricity. Activated sludge is used at anode as inoculum and nutrient source. Various concentrations (1-5 g/L) of dry algae biomass are tested. Among tested concentrations, 5 g/L (5000 mg COD/L) produced the highest voltage of 0.89 V and power density of 1.78 W/m(2) under 1000 ? electric resistance. Pre-treated algae biomass and activated sludge are also used at anode. They give low power output than without pre-treatment. Spent algae biomass is tested to replace whole (before oil extraction) algae biomass as a substrate, but it gives low power output. This work has proved the concept of using algae biomass in MFC for high energy output. PMID:23584037

Rashid, Naim; Cui, Yu-Feng; Saif Ur Rehman, Muhammad; Han, Jong-In

2013-07-01

337

Simplified 2D Bidomain Model of Whole Heart Electrical Activity and ECG Generation  

NASA Astrophysics Data System (ADS)

The aim of this study was the development of a geometrically simple and highly computationally-efficient two dimensional (2D) biophysical model of whole heart electrical activity, incorporating spontaneous activation of the sinoatrial node (SAN), the specialized conduction system, and realistic surface ECG morphology computed on the torso. The FitzHugh-Nagumo (FHN) equations were incorporated into a bidomain finite element model of cardiac electrical activity, which was comprised of a simplified geometry of the whole heart with the blood cavities, the lungs and the torso as an extracellular volume conductor. To model the ECG, we placed four electrodes on the surface of the torso to simulate three Einthoven leads VI, VII and VIII from the standard 12-lead system. The 2D model was able to reconstruct ECG morphology on the torso from action potentials generated at various regions of the heart, including the sinoatrial node, atria, atrioventricular node, His bundle, bundle branches, Purkinje fibers, and ventricles. Our 2D cardiac model offers a good compromise between computational load and model complexity, and can be used as a first step towards three dimensional (3D) ECG models with more complex, precise and accurate geometry of anatomical structures, to investigate the effect of various cardiac electrophysiological parameters on ECG morphology.

Sovilj, Siniša; Magjarevi?, Ratko; Abed, Amr Al; Lovell, Nigel H.; Dokos, Socrates

2014-06-01

338

Lactate dehydrogenase activity in bovine and porcine muscle as influenced by electrical stimulation, aging, freezing, thawing and heating  

E-print Network

LACTATE DEHYDROGENASE ACTIVITY IN BOVINF. AND PORCINE MUSCLE AS INFLUENCED BY ELECTRICAL STIMULATION, AGING, FREEZING, THA&v'ING AiVD HEATING A Thesis by SHAREN SUE COLLINS Submitted to the Graduate College of Texas ARM University in partial... fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1987 Major Subject: Animal Science LACTATE DEHYDROGENASE ACTIVITY IN BOVINE AND PORCINE MUSCLE AS INFLUENCED BY ELECTRICAL STIMULATION, AGING, FREEZING, THAWING AND HEATING A Thesis...

Collins, Sharen Sue

1987-01-01

339

Duration of Coherence Intervals in Electrical Brain Activity in Perceptual Organization  

PubMed Central

We investigated the relationship between visual experience and temporal intervals of synchronized brain activity. Using high-density scalp electroencephalography, we examined how synchronized activity depends on visual stimulus information and on individual observer sensitivity. In a perceptual grouping task, we varied the ambiguity of visual stimuli and estimated observer sensitivity to this variation. We found that durations of synchronized activity in the beta frequency band were associated with both stimulus ambiguity and sensitivity: the lower the stimulus ambiguity and the higher individual observer sensitivity the longer were the episodes of synchronized activity. Durations of synchronized activity intervals followed an extreme value distribution, indicating that they were limited by the slowest mechanism among the multiple neural mechanisms engaged in the perceptual task. Because the degree of stimulus ambiguity is (inversely) related to the amount of stimulus information, the durations of synchronous episodes reflect the amount of stimulus information processed in the task. We therefore interpreted our results as evidence that the alternating episodes of desynchronized and synchronized electrical brain activity reflect, respectively, the processing of information within local regions and the transfer of information across regions. PMID:19596712

Gepshtein, Sergei; Gong, Pulin; van Leeuwen, Cees

2010-01-01

340

Influence of Different Geometric Representations of the Volume Conductor on Nerve Activation during Electrical Stimulation  

PubMed Central

Volume conductor models with different geometric representations, such as the parallel layer model (PM), the cylindrical layer model (CM), or the anatomically based model (AM), have been employed during the implementation of bioelectrical models for electrical stimulation (FES). Evaluating their strengths and limitations to predict nerve activation is fundamental to achieve a good trade-off between accuracy and computation time. However, there are no studies aimed at clarifying the following questions. (1) Does the nerve activation differ between CM and PM? (2) How well do CM and PM approximate an AM? (3) What is the effect of the presence of blood vessels and nerve trunk on nerve activation prediction? Therefore, in this study, we addressed these questions by comparing nerve activation between CM, PM, and AM models by FES. The activation threshold was used to evaluate the models under different configurations of superficial electrodes (size and distance), nerve depths, and stimulation sites. Additionally, the influences of the sciatic nerve, femoral artery, and femoral vein were inspected for a human thigh. The results showed that the CM and PM had a high error rate, but the variation of the activation threshold followed the same tendency for electrode size and interelectrode distance variation as AM. PMID:25276222

Gómez-Tames, José; González, José; Yu, Wenwei

2014-01-01

341

Direct activation of the Mauthner cell by electric field pulses drives ultrarapid escape responses.  

PubMed

Rapid escape swims in fish are initiated by the Mauthner cells, giant reticulospinal neurons with unique specializations for swift responses. The Mauthner cells directly activate motoneurons and facilitate predator detection by integrating acoustic, mechanosensory, and visual stimuli. In addition, larval fish show well-coordinated escape responses when exposed to electric field pulses (EFPs). Sensitization of the Mauthner cell by genetic overexpression of the voltage-gated sodium channel SCN5 increased EFP responsiveness, whereas Mauthner ablation with an engineered variant of nitroreductase with increased activity (epNTR) eliminated the response. The reaction time to EFPs is extremely short, with many responses initiated within 2 ms of the EFP. Large neurons, such as Mauthner cells, show heightened sensitivity to extracellular voltage gradients. We therefore tested whether the rapid response to EFPs was due to direct activation of the Mauthner cells, bypassing delays imposed by stimulus detection and transmission by sensory cells. Consistent with this, calcium imaging indicated that EFPs robustly activated the Mauthner cell but only rarely fired other reticulospinal neurons. Further supporting this idea, pharmacological blockade of synaptic transmission in zebrafish did not affect Mauthner cell activity in response to EFPs. Moreover, Mauthner cells transgenically expressing a tetrodotoxin (TTX)-resistant voltage-gated sodium channel retained responses to EFPs despite TTX suppression of action potentials in the rest of the brain. We propose that EFPs directly activate Mauthner cells because of their large size, thereby driving ultrarapid escape responses in fish. PMID:24848468

Tabor, Kathryn M; Bergeron, Sadie A; Horstick, Eric J; Jordan, Diana C; Aho, Vilma; Porkka-Heiskanen, Tarja; Haspel, Gal; Burgess, Harold A

2014-08-15

342

Modelling the effects of solar activity onto the Greek national electric grid  

NASA Astrophysics Data System (ADS)

We study both the short term and long term effects of solar activity on the large transformers (150kV and 400kV) of the Greek national electric grid. We use data analysis and various analytic and statistical methods and models. Contrary to the common belief in PPC Greece, we see that there are considerable both short term (immediate) and long term effects of solar activity onto large transformers in a mid-latitude country like Greece. Our results can be summarized as follows: For the short term effects: During 1989-2010 there were 43 "stormy days" (namely days with for example Ap >= 100) and we had 19 failures occurring during a stormy day plus or minus 3 days and 51 failures occurring during a stormy day plus or minus 7 days. All these failures can be directly related to Geomagnetically Induced Currents (GIC's). Explicit cases are presented. For the long term effects we have two main results: The maximum number of transformer failures occur 3-4 years after the maximum of solar activity. There is statistical correlation between solar activity expressed using various newly defined long term solar activity indices and the annual number of transformer failures. These new long term solar activity indices were defined using both local (from geomagnetic stations in Greece) and global (planetary averages) geomagnetic data. Applying both linear and non-linear statistical regression we compute the regression equations and the corresponding coefficients of determination.

Zois, I. P.

2014-03-01

343

Application of electrical propulsion for an active debris removal system: a system engineering approach  

NASA Astrophysics Data System (ADS)

One of the main challenge in the design of an active removal system for space debris is the high ?V required both to approach space debris lying in different orbits and to de-orbit/re-orbit them. Indeed if the system does not target a number of objects during its lifetime the cost of the removal will be far too high to be considered as the basis of an economically viable business case. Using a classical chemical propulsion (CP) system, the ?V is limited by the mass of propellant that the system can carry. This limitation is greatly reduced if electrical propulsion is considered. Electrical propulsion (EP) systems are indeed characterized by low propellant mass requirements, however this comes at the cost of higher electrical power and, typically, higher complexity and mass of the power supply system. Because of this, the use of EP systems has been, therefore, primarily limited to station keeping maneuvers. However in the recent past, the success of missions using EP as primary propulsion (e.g. GOCE, SMART-1, Artemis, Deep Spcae1, Hayabusa) makes this technology a suitable candidate for providing propulsion for an active debris removal system. This study case will provide the analysis of the possible application of electrical propulsion systems in such a context, presenting a number of possible mission profiles. This paper will start with the description of possible mission concepts and the assessment of the EP technology, comparing near-term propulsion options, that best fits the mission. A more detailed analysis follows with the relevant trade-off to define the characteristics of the final system and its size in terms of mass and power required. A survey of available space qualified EP systems will be performed with the selection of the best candidates to be used and/or developed for an active debris removal system. The results of a similar analysis performed for a classical CP system are then presented and the two options are compared in terms of total cost of the mission. The output of this study case shows that the EP is a suitable solution in a very demanding ?V system such as active debris removal satellites and that the current technology is sufficiently mature to be used in the very near future.

Covello, Fabio

2012-10-01

344

Dynamics of changes in electrical activity in the rabbit cerebral cortex during sequential sessions of "animal hypnosis".  

PubMed

The dynamics of changes in individual electrical activity rhythms in the premotor, sensorimotor, and temporal-parietal areas of the cortex in both hemispheres were studied in chronic experiments in rabbits during sequential sessions of "animal hypnosis." These experiments showed that during the first session of "animal hypnosis," significant changes in electrical activity occurred only in the premotor area of the cortex of the right hemisphere, where there were increases in spectral power in the delta-1 and delta-2 ranges and decreases in spectral power in other ranges of electrical activity. Subsequent sessions of "animal hypnosis" formed increasing changes in electrical activity, which were particularly marked in cortical areas in the right hemisphere. Significant changes in spectral power in the delta and theta ranges of electrical activity in cortical areas did not arise at the beginning of the hypnotic state, but after 4-6 min. During the third session of "animal hypnosis," the course of electrical activity in the alpha and beta rhythms in the premotor and sensorimotor areas of the cortex became wave-like in nature. PMID:20490695

Rusinova, E V; Davydov, V I

2010-06-01

345

U.S. Department of Energy -- Advanced Vehicle Testing Activity: Plug-in Hybrid Electric Vehicle Testing and Demonstration Activities  

SciTech Connect

The U.S. Department of Energy’s (DOE) Advanced Vehicle Testing Activity (AVTA) tests plug-in hybrid electric vehicles (PHEV) in closed track, dynamometer and onroad testing environments. The onroad testing includes the use of dedicated drivers on repeated urban and highway driving cycles that range from 10 to 200 miles, with recharging between each loop. Fleet demonstrations with onboard data collectors are also ongoing with PHEVs operating in several dozen states and Canadian Provinces, during which trips- and miles-per-charge, charging demand and energy profiles, and miles-per-gallon and miles-per-kilowatt-hour fuel use results are all documented, allowing an understanding of fuel use when vehicles are operated in charge depleting, charge sustaining, and mixed charge modes. The intent of the PHEV testing includes documenting the petroleum reduction potential of the PHEV concept, the infrastructure requirements, and operator recharging influences and profiles. As of May 2008, the AVTA has conducted track and dynamometer testing on six PHEV conversion models and fleet testing on 70 PHEVs representing nine PHEV conversion models. A total of 150 PHEVs will be in fleet testing by the end of 2008, all with onboard data loggers. The onroad testing to date has demonstrated 100+ miles per gallon results in mostly urban applications for approximately the first 40 miles of PHEV operations. The primary goal of the AVTA is to provide advanced technology vehicle performance benchmark data for technology modelers, research and development programs, and technology goal setters. The AVTA testing results also assist fleet managers in making informed vehicle purchase, deployment and operating decisions. The AVTA is part of DOE’s Vehicle Technologies Program. These AVTA testing activities are conducted by the Idaho National Laboratory and Electric Transportation Engineering Corporation, with Argonne National Laboratory providing dynamometer testing support. The proposed paper and presentation will discuss PHEV testing activities and results. INL/CON-08-14333

James E. Francfort; Donald Karner; John G. Smart

2009-05-01

346

Intrinsic activity and positive feedback in motor circuits in organotypic spinal cord slice cultures.  

PubMed

In co-cultures of embryonic rat spinal cord slices and skeletal muscle, spinal motoneurons innervate muscle fibres and drive muscle contractions. However, multi-electrode array (MEA) recordings show that muscle contractions often appear in the absence of population activity in the spinal cord networks. Such uncorrelated muscle activity persists when the population bursts in the neuronal networks are prevented by un-coupling the network with the glutamatergic antagonists CNQX and D-APV. By contrast, the uncorrelated muscle activity is fully suppressed by the muscular nicotinic antagonist D-tubocurarine. Together, these findings confirm the previous finding that motoneurons drive muscle fibres in this preparation and suggest that they are intrinsically spiking in the absence of synaptic input. Intracellular recordings from spinal neurons support this suggestion. Analysing the correlated muscle activity, we found that in 15% of the population bursts, muscle activity appears at the beginning or before neuronal activity, suggesting that in these cases motoneurons initiate the population activity. Both the total number of population bursts and the percentage of such bursts that are initiated by muscle activity are reduced by a block of nicotinic receptors. Uncorrelated muscle and neuronal activity is reduced by the gap junction blocker carbenoxolone, suggesting that electrical coupling is involved in the generation of this activity. Together, these findings suggest that intrinsic firing of motoneurons may contribute to the activation of population bursts through cholinergic positive feedback loops in cultured spinal networks. PMID:19811528

Magloire, Vincent; Streit, Jürg

2009-10-01

347

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

348

Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping  

NASA Astrophysics Data System (ADS)

The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm2, with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells.

Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A.; Rühle, Sven; Anderson, Assaf Y.; Zaban, Arie

2014-05-01

349

Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping.  

PubMed

The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm(2), with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells. PMID:24880411

Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A; Rühle, Sven; Anderson, Assaf Y; Zaban, Arie

2014-05-01

350

Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks  

PubMed Central

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

Balamurugan, A. M.; Sivasubramanian, A.

2014-01-01

351

Application of proteins in burst delivery systems  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

352

Spatial Analysis of Slowly Oscillating Electric Activity in the Gut of Mice Using Low Impedance Arrayed Microelectrodes  

PubMed Central

Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ?1 mm2. The size of each recording electrode was 50×50 µm2, however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/Wv mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/Wv mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity. PMID:24124480

Taniguchi, Mizuki; Kajioka, Shunichi; Shozib, Habibul B.; Sawamura, Kenta; Nakayama, Shinsuke

2013-01-01

353

Electrical activity in rat tail artery during asynchronous activation of postganglionic nerve terminals by ciguatoxin-1.  

PubMed Central

1. The effects of ciguatoxin-1 (CTX-1) on the membrane potential of smooth muscle cells have been examined in rat proximal tail arteries isolated in vitro. 2. CTX-1 (> or = 10 pM) increased the frequency of spontaneous excitatory junction potentials (s.e.j.ps). At 100-400 pM, there was also a marked and maintained depolarization (19.7 +/- 1.4 mV, n = 14, at 400 pM). 3. In 20-400 pM CTX-1, perivascular stimuli evoked excitatory junction potentials (e.j.ps) which were prolonged in time course relative to control. 4. Although threshold and latency of the e.j.p. were not affected by CTX-1 (< or = 400 pM), propagated impulses were blocked at > or = 100 pM. 5. The spontaneous activity and the depolarization produced by CTX-1 were reduced in the presence of Ca2+ (0.1 mM)/Mg2+ (25 mM), omega-conotoxin (0.1 microM) or Cd2+ (50-100 microM). 6. All effects of CTX-1 were abolished by tetrodotoxin (0.3 microM). 7. Raised Ca2+ (6 mM) reduced the depolarization and spontaneous activity produced by CTX-1. 8. In 400 pM CTX-1, the membrane repolarized (17 +/- 3.2 mV, n = 4) following the addition of phentolamine (1 microM). S.e.j.ps and e.j.ps were selectively abolished by suramin (1 mM), and the membrane repolarized by 1.3 +/- 1.6 mV (n = 4). 9. We conclude that CTX-1 releases noradrenaline and ATP by initiating asynchronous discharge of postganglionic perivascular axons. In 100-400 pM CTX-1, the smooth muscle was depolarized to levels resembling those recorded in this artery during ongoing vasoconstrictor discharge in vivo. PMID:8564251

Brock, J. A.; McLachlan, E. M.; Jobling, P.; Lewis, R. J.

1995-01-01

354

Neuromagnetic source imaging of abnormal spontaneous activity in tinnitus patient modulated by electrical cortical stimulation.  

PubMed

Electrical cortical stimulation (CS) of the auditory cortices has been shown to reduce the severity of debilitating tinnitus in some patients. In this study, we performed MEG source imaging of spontaneous brain activity during concurrent CS of the left secondary auditory cortex of a volunteer suffering from right unilateral tinnitus. CS produced MEG artifacts which were successfully sorted and removed using a combination of sensor and source level signal separation and classification techniques. This contribution provides the first proof of concept reporting on analysis of MEG data with concurrent CS. Effects of CS on ongoing brain activity were revealed at the MEG sensor and source levels and indicate CS significantly reduced ongoing brain activity in the lower frequency range (<40Hz), and emphasized its higher (>40Hz), gamma range components. Further, our results show that CS increased the spectral correlation across multiple frequency bands in the low and high gamma ranges, and between the alpha and beta bands of the MEG. Finally, MEG sources localized in the auditory cortices and nearby regions exhibited abnormal spectral activity that was suppressed by CS. These results provide promising evidence in favor of the Thalamocortical Dysrhytmia (TCD) hypothesis of tinnitus, and suggest that CS may prove to be an effective treatment of tinnitus when targeted to brain regions exhibiting abnormal spontaneous activity. PMID:19964017

Ramirez, Rey Rene; Kopell, Brian Harris; Butson, Christopher R; Gaggl, Wolfgang; Friedland, David R; Baillet, Sylvain

2009-01-01

355

Effects of intermittent 60-Hz high voltage electric fields on metabolism, activity, and temperature in mice  

SciTech Connect

Transient effects of 100-kV/m extremely low frequency electric fields were studied in the white footed deermouse, Peromyscus leucopus. Gross motor activity, carbon dioxide production, oxygen consumption, and core body temperature were monitored before, during, and after intermittent field exposures (four hour-long exposures, at one-hour intervals). Thirty-four mice were exposed in cages with plastic floors floating above ground potential, and 21 mice were exposed in cages with grounded metal floor plates. The first field exposure produced an immediate, transient increase of activity and gas measures during the inactive phase of the circadian cycle. All measures returned to baseline levels before the second exposure and were not significantly changed throughout the remainder of the exposures. The rapid habituation of field-induced arousal suggests that significant metabolic changes will not be measured in experiments in which the interval between exposure and measurement is greater than two hours.

Rosenbergy, R.S; Duffy, P.H.; Sacher, G.A.

1981-01-01

356

An Overview of the Nuclear Electric Xenon Ion System (NEXIS) Activity  

NASA Technical Reports Server (NTRS)

The Nuclear Electric Xenon Ion System (NEXIS) research and development activity within NASA's Project Prometheus, was one of three proposals selected by NASA to develop thruster technologies for long life, high power, high specific impulse nuclear electric propulsion systems that would enable more robust and ambitious science exploration missions to the outer solar system. NEXIS technology represents a dramatic improvement in the state-of-the-art for ion propulsion and is designed to achieve propellant throughput capabilities >= 2000 kg and efficiencies >= 78% while increasing the thruster power to >= 20 kW and specific impulse to >= 6000 s. The NEXIS technology uses erosion resistant carbon-carbon grids, a graphite keeper, a new reservoir hollow cathode, a 65-cm diameter chamber masked to produce a 57-cm diameter ion beam, and a shared neutralizer architecture to achieve these goals. The accomplishments of the NEXIS activity so far include performance testing of a laboratory model thruster, successful completion of a proof of concept reservoir cathode 2000 hour wear test, structural and thermal analysis of a completed development model thruster design, fabrication of most of the development model piece parts, and the nearly complete vacuum facility modifications to allow long duration wear testing of high power ion thrusters.

Randolph, Thomas M.; Polk, James E., Jr.

2004-01-01

357

Electrical properties of Si/Si interfaces by using surface-activated bonding  

NASA Astrophysics Data System (ADS)

Electrical properties of n-Si/n-Si, p-Si/n-Si, and p--Si/n+-Si junctions fabricated by using surface-activated-bonding are investigated. The transmission electron microscopy/energy dispersive X-ray spectroscopy of the n-Si/n-Si interfaces reveals no evidence of oxide layers at the interfaces. From the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of the p-Si/n-Si and p--Si/n+-Si junctions, it is found that the interface states, likely to have formed due to the surface activation process using Ar plasma, have a more marked impact on the electrical properties of the p-Si/n-Si junctions. An analysis of the temperature dependence of the I-V characteristics indicates that the properties of carrier transport across the bonding interfaces for reverse-bias voltages in the p-Si/n-Si and p--Si/n+-Si junctions can be explained using the trap-assisted-tunneling and Frenkel-Poole models, respectively.

Liang, J.; Miyazaki, T.; Morimoto, M.; Nishida, S.; Shigekawa, N.

2013-11-01

358

A comparison study of different semi-active hybrid energy storage system topologies for electric vehicles  

NASA Astrophysics Data System (ADS)

In this paper, four different semi-active hybrid energy storage systems (HESSs), which use both supercapacitors (SCs) and batteries, are compared based on an electric city bus running the China Bus Driving Cycle (CBDC). The SC sizes of the different HESS topologies are optimized by using the dynamic programming (DP) approach, based on a dynamic degradation model of the LiFePO4 battery. The operation costs of different HESSs, including the electricity and the battery degradation costs over a whole CBDC, are minimized in the optimization process. Based on the DP results, near-optimal control strategies of different HESSs for on-line uses are proposed. Finally, the four HESS topologies are comprehensively compared from different aspects, including operation cost, initial cost, and DC bus voltage variation. Simulation results show that all HESS topologies have their merits and drawbacks, and can be used in different applications with different requirements. In addition, about 50% of the operation cost of the energy storage system is reduced by the semi-active HESSs when compared to the battery-only topology. Thus the effectiveness of adopting the SC in the HESS is verified.

Song, Ziyou; Hofmann, Heath; Li, Jianqiu; Han, Xuebing; Zhang, Xiaowu; Ouyang, Minggao

2015-01-01

359

High-intensity pulsed electric fields processing parameters affecting polyphenoloxidase activity of strawberry juice.  

PubMed

High-intensity pulsed electric fields (HIPEF) were applied to strawberry juice to study the feasibility of inactivating polyphenoloxidase (PPO). Response surface methodology was used to evaluate the effect of HIPEF processing, in which total treatment time (1000 to 2000 ?s), pulse frequency (50 to 250 Hz), pulse width (1.0 to 7.0 ?s), and polarity (monopolar or bipolar) were the controlled variables at a constant electric field of 35 kV/cm. The proposed 2nd-order response functions were accurate enough to fit experimental results. Strawberry juice PPO was strongly reduced within the range of assayed conditions. HIPEF treatments were more effective in bipolar than in monopolar mode in inactivating PPO. Treatments of longer duration resulted in reductions of the enzyme activity. Moreover, it was feasible to minimize residual PPO activity (down to 2.5%) by selecting bipolar treatments at frequencies higher than 229 Hz and pulse widths between 3.23 and 4.23 ?s for a constant total treatment time of 2000 ?s. PMID:21535531

Aguiló-Aguayo, Ingrid; Soliva-Fortuny, Robert; Martín-Belloso, Olga

2010-09-01

360

Mapping of Cardiac Electrical Activation with Electromechanical Wave Imaging: An in silico-in vivo Reciprocity Study  

PubMed Central

Background Electromechanical Wave Imaging (EWI) is an entirely non-invasive, ultrasound-based imaging method capable of mapping the electromechanical activation sequence of the ventricles in vivo. Given the broad accessibility of ultrasound scanners in the clinic, the application of EWI could constitute a flexible surrogate for the 3D electrical activation. Objective The purpose of this report is to reproduce the electromechanical wave (EW) using an anatomically-realistic electromechanical model, and establish the capability of EWI to map the electrical activation sequence in vivo when pacing from different locations. Methods EWI was performed in one canine during pacing from three different sites. A high-resolution dynamic model of coupled cardiac electromechanics of the canine heart was used to predict the experimentally recorded electromechanical wave. The simulated 3D electrical activation sequence was then compared with the experimental EW. Results The electrical activation sequence and the EW were highly correlated for all pacing sites. The relationship between the electrical activation and the EW onset was found to be linear with a slope of 1.01 to 1.17 for different pacing schemes and imaging angles. Conclusions The accurate reproduction of the EW in simulations indicates that the model framework is capable of accurately representing the cardiac electromechanics and thus testing new hypotheses. The one-to-one correspondence between the electrical activation sequence and the EW indicates that EWI could be used to map the cardiac electrical activity. This opens the door for further exploration of the technique in assisting in the early detection, diagnosis and treatment monitoring of rhythm dysfunction. PMID:21185403

Provost, Jean; Gurev, Viatcheslav; Trayanova, Natalia; Konofagou, Elisa E.

2011-01-01

361

77 FR 5058 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Electrical...  

Federal Register 2010, 2011, 2012, 2013

...Submission for OMB Review; Comment Request; Electrical Standards for Construction and for General...collection request (ICR) titled, ``Electrical Standards for Construction and for General...collection requirements specified by the Electrical Standards for Construction and for...

2012-02-01

362

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

363

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

364

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....

365

Radio bursts from superconducting strings  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

366

Cosmography by gamma ray bursts  

NASA Astrophysics Data System (ADS)

Aims: Relations connecting gamma ray burst quantities can be used to constrain cosmographic parameters of the Hubble law at medium-high redshifts. Methods: We consider a sample of 27 gamma ray bursts to construct the luminosity distance to redshift relation and derive the values of the parameters q_0, j_0, and s_0. The analysis is compared with other methods in the literature. Results: Gamma gay bursts, if calibrated by SNeIa, seem reliable as distance indicators and give cosmographic parameters in agreement with the ?CDM model.

Capozziello, S.; Izzo, L.

2008-10-01

367

On the electric activity of superfluid helium at the excitation of first and second sound waves  

SciTech Connect

We show that the electric activity of superfluid helium (HeII) observed in the experiments [3] during the excitation of standing second sound waves in an acoustic resonator can be described in terms of the phenomenological mechanism of the inertial polarization of atoms in a dielectric, in particular, in HeII, when the polarization field induced in the medium is proportional to the mechanical acceleration, by analogy with the Stewart-Tolman effect. The variable relative velocity w = v{sub n} - v{sub s} of the normal and superfluid HeII components that emerges in the second sound wave determines the mean group velocity of rotons, V{sub g} Almost-Equal-To w, with the density of the normal component related to their equilibrium number density in the temperature range 1.3 K {<=} T {<=} 2 K. Therefore, the acceleration of the 4He atoms involved in the formation of a roton excitation is proportional to the time derivative of the relative velocity.w. In this case, the linear local relations between the variable values of the electric induction, electric field strength, and polarization vector should be taken into account. As a result, the variable displacement current induced in the bulk of HeII and the corresponding potential difference do not depend on the anomalously low polarizability of liquid helium. This allows the ratio of the amplitudes of the temperature and potential oscillations in the second sound wave, which is almost independent of T in the above temperature range, consistent with experimental data to be obtained. At the same time, the absence of an electric response during the excitation of first sound waves in the linear regime is related to an insufficient power of the sound oscillations. Based on the experimental data on the excitation of first and second sounds, we have obtained estimates for the phenomenological coefficient of proportionality between the polarization vector and acceleration and for the drag coefficient of helium atoms by rotons in the second sound wave. We also show that the presence of a steady heat flow in HeII with nonzero longitudinal velocity and temperature gradients due to finite viscosity and thermal conductivity of the normal component leads to a change in the phase velocities of the first and second sound waves and to an exponential growth of their amplitudes with time, which should cause the amplitudes of the electric signals at the first and second sound frequencies to grow. This instability is analogous to the growth of the amplitude of long gravity waves on a shallow-water surface that propagate in the direction of decreasing basin depth.

Pashitskii, E. A., E-mail: pashitsk@iop.kiev.ua; Gurin, A. A. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)

2010-01-15

368

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

369

Loss of rhythmically bursting neurons in rat medial septum following selective lesion of septohippocampal cholinergic system.  

PubMed

The medial septum contains cholinergic and GABAergic neurons that project to the hippocampal formation. A significant proportion of the septohippocampal neurons (SHN) exhibit a rhythmically bursting (RB) activity that is involved in the generation of the hippocampal theta rhythm. The neurochemical nature of septal RB neurons is not firmly established. To address this question, the septal unit activity has been recorded in rats after selective destruction of the cholinergic septal neurons by the immunotoxin 192 IgG-saporin. Experiments have been performed in urethan-anesthetized and unanesthetized rats, 14-21 days after lesion. Acetylcholinesterase (AChE) histochemistry revealed a near-complete loss of cholinergic septal neurons and of cholinergic fibers in the hippocampus. The recorded neurons were located in the medial septum-diagonal band of Broca area. A number of these neurons were identified as projecting to the hippocampus (SHN) by their antidromic response to the electrical stimulation of the fimbria-fornix. In urethan-anesthetized lesioned rats, the percentage of RB neurons decreased significantly as compared with controls (17 vs. 41% for SHNs and 5 vs. 19% for unidentified septal neurons). The axonal conduction velocity and the burst frequency of the SHNs that retained a RB activity were higher in lesioned as compared with control rats. The number of spikes per burst was lower and the burst duration was shorter in lesioned rats as compared with controls. The urethan-resistant hippocampal theta was altered both in terms of frequency and amplitude. In unanesthetized lesioned rats, no RB septal neurons were found during arousal, as compared with 25% in controls. Their number was also markedly reduced during paradoxical sleep (9.7 vs. 38.5%). Histochemistry in 192 IgG-saporin-treated rats showed that RB neurons were found in areas devoid of AChE-positive neurons but containing parvalbumine-positive (presumably GABAergic) neurons. These data show that RB activity is considerably reduced after selective lesion of the cholinergic medial septal neurons. They suggested that the large majority of the RB septal neurons are cholinergic and that the few neurons that display RB activity in lesioned rats are GABAergic. PMID:9535934

Apartis, E; Poindessous-Jazat, F R; Lamour, Y A; Bassant, M H

1998-04-01

370

Studies of the electrical activity of the ventricles and the origin of the QRS complex.  

PubMed

Historical events in the development of cardiac electrophysiology are described briefly. Observations before 1900 showed that electrical changes accompanied activity of muscle and nerve. Other studies showed that electrical activity of the heart produced voltage changes on the human torso. In 1903 Einthoven developed the string galvanometer which made measurement of electrocardiographic potentials much easier, more accurate and more common. The bases of understanding of arrhythmias were established by Lewis in the early 1900's. Soon thereafter Wilson devised practical and theoretical approaches to the human electrocardiogram which led to many further developments. Events before 1950 established the existence and mechanism of electrical activity in excitable cells. Studies of the origin of QRS began in about 1950, with studies of depolarization of the canine ventricle. Studies of the human ventricle followed. In the 70's it appeared possible to solve the electrocardiographic forward problem, prediction of electrocardiographic potentials from a knowledge of intracardiac events. That solution appeared possible because of new approaches to the associated physical and computational problems. Attempts to solve the forward problem at that time assumed that the cardiac generator (the boundary between resting and depolarized cells) was a uniform double layer generator. (The strength of the generator is constant everywhere along the boundary). Meanwhile physiologists and anatomists had worked out the mechanism of communication between cardiac cells. The cells are longer than they are wide, and each cell can depolarize contiguous cells. The connections between cells are predominantly at the ends of the cell and the longitudinal depolarization of a cardiac mass travels three times as fast as transverse depolarization. The generator is not uniform but is strongest parallel to the long axes of the cells. Many or most of those working in the field did not recognize the importance of the connections between cardiac cells in not only the pathway of excitation, but also the potentials produced as the cells depolarized. A number of experiments indicated that the uniform double layer assumption led to both qualitative and quantitative errors in prediction of fields generated by depolarization of cardiac muscle. These are reviewed. There are now alternatives to the uniform model which recognize the non-uniformity of the cardiac generators, particularly the axial model. The forward problem is unsolved but it appears possible that these newer models will make a solution possible. PMID:8932565

Scher, A M

1995-01-01

371

Quantitative Brain Electrical Activity in the Initial Screening of Mild Traumatic Brain Injuries  

PubMed Central

Introduction: The incidence of emergency department (ED) visits for Traumatic Brain Injury (TBI) in the United States exceeds 1,000,000 cases/year with the vast majority classified as mild (mTBI). Using existing computed tomography (CT) decision rules for selecting patients to be referred for CT, such as the New Orleans Criteria (NOC), approximately 70% of those scanned are found to have a negative CT. This study investigates the use of quantified brain electrical activity to assess its possible role in the initial screening of ED mTBI patients as compared to NOC. Methods: We studied 119 patients who reported to the ED with mTBI and received a CT. Using a hand-held electroencephalogram (EEG) acquisition device, we collected data from frontal leads to determine the likelihood of a positive CT. The brain electrical activity was processed off-line to generate an index (TBI-Index, biomarker). This index was previously derived using an independent population, and the value found to be sensitive for significant brain dysfunction in TBI patients. We compared this performance of the TBI-Index to the NOC for accuracy in prediction of positive CT findings. Results: Both the brain electrical activity TBI-Index and the NOC had sensitivities, at 94.7% and 92.1% respectively. The specificity of the TBI-Index was more than twice that of NOC, 49.4% and 23.5% respectively. The positive predictive value, negative predictive value and the positive likelihood ratio were better with the TBI-Index. When either the TBI-Index or the NOC are positive (combining both indices) the sensitivity to detect a positive CT increases to 97%. Conclusion: The hand-held EEG device with a limited frontal montage is applicable to the ED environment and its performance was superior to that obtained using the New Orleans criteria. This study suggests a possible role for an index of brain function based on EEG to aid in the acute assessment of mTBI patients. PMID:23359586

O’Neil, Brian; Prichep, Leslie S.; Naunheim, Roseanne; Chabot, Robert

2012-01-01

372

The linkage between solar activity, atmospheric electricity, cloud microphysics, and climate change  

NASA Astrophysics Data System (ADS)

There are well understood links between solar activity and the global electric circuit, via cosmic rays and other energetic space particle fluxes, and the direct penetration of solar wind electric fields into the magnetic polar caps. Observations and theory show that the changing ionosphere-earth current density Jz in the global electric circuit deposits varying amounts of charge in clouds in accordance with Ohm's and Gauss's Laws. Observations and theory show that the changing space charge in clouds changes the rate of scavenging of aerosol particles, most importantly cloud condensation nuclei and ice-forming nuclei, which causes changes in precipitation and cloud cover (Tinsley, Rep. Prog. Phys., 71, 066801, 2008). Correlations and theory show changes in the intensity of winter storms are associated with such changes in the microphysics, produced by changes in Jz, mainly in the cyclogenesis regions at high geomagnetic latitudes. Also, low-latitude low-altitude cloud cover changes, as observed by Svensmark, can be explained by Jz changes. Observations and theory show changes in the general circulation over Europe are associated with increased cyclogenesis in the Icelandic Low region, and downstream anticyclonic blocking, producing advection of cold polar air to lower latitudes. More extreme changes have been inferred from reconstructions of the changed circulation over Europe during the Maunder minimum, and suggest similar cold winters would be a continuing feature of the current extended solar minimum. The complexity of the cloud microphysics and the natural and anthropogenic variability of global aerosols and the presence of dynamic feedback have made it difficult so far to put the cloud microphysical responses into quantitative cloud resolving models.

Tinsley, Brian

2010-05-01

373

Advances in recording scattered light changes in crustacean nerve with electrical activation  

SciTech Connect

We investigated optical changes associated with crustacean nerve stimulation using birefringent and large angle scattered light. Improved detection schemes disclosed high temporal structure of the optical signals and allowed further investigations of biophysical mechanisms responsible for such changes. Most studies of physiological activity in neuronal tissue use techniques that measure the electrical behavior or ionic permeability of the nerve, such as voltage or ion sensitive dyes injected into cells, or invasive electric recording apparatus. While these techniques provide high resolution, they are detrimental to tissue and do not easily lend themselves to clinical applications in humans. Electrical and chemical components of neural excitation evoke physical responses observed through changes in scattered and absorbed light. This method is suited for in-vivo applications. Intrinsic optical changes have shown themselves to be multifaceted in nature and point to several different physiological processes that occur with different time courses during neural excitation. Fast changes occur concomitantly with electrical events, and slow changes parallel metabolic events including changes in blood flow and oxygenation. Previous experiments with isolated crustacean nerves have been used to study the biophysical mechanisms of fast optical changes. However, they have been confounded by multiple superimposed action potentials which make it difficult to discriminate the temporal signatures of individual optical responses. Often many averages were needed to adequately resolve the signal. More recently, optical signals have been observed in single trials. Initially large angle scattering measurements were used to record these events with much of the signal coming from cellular swelling associated with water influx during activation. By exploiting the birefringent properties derived from the molecular stiucture of nerve membranes, signals appear larger with a greater contrast, but direct comparison of birefringent and 90{sup o} scattering signals has not been reported. New developments in computer and optical technology allow optical recording with higher temporal resolution than could be achieved previously. This has led us to undertake more detailed studies of the biophysical mechanisms underlying these transient changes. Optimization of this technology in conjunction with other technical developments presents a path to noninvasive dynamic clinical observation of optical responses. To conduct these optical recordings, we placed dissected leg, claw and ventral cord nerves from crayfish and lobster in a recording chamber constructed from black Delrin. The chamber consisted of several wells situated perpendicularly to the long axis of the nerve that could beelectrically isolated for stimulating and recording electrical activation, and a window in the center for optical measurements. To measure the birefringence from the nerve, light from a 120W halogen bulb was focused onto the nerve from below the window through a 10X microscope objective and polarized at a 45 degree angle with respect to the long axis of the nerve bundle. A second polarizer turned 90 degrees with respect to the first polarizer was placed on top of the chamber and excluded direct source illumination, passing only birefringent light from the nerve. A large area photodiode placed directly on top of the polarizer detected the magnitude of the birefringent light. To measure light scattered 90 degrees by the nerve, a short length of image conduit placed perpendicularly to the nerve directed large angle scattered light from the nerve to a second photodiode. The output of each photodiode was amplified by a first stage amplifier which produced a DC level output, and was coupled to an AC amplifier (0.3 Hz High Pass) with a gain of 1000 to optimally record changes across time.

Carter, K. M. (Kathleen M.); Rector, D. M. (David M.); Martinez, A. T. (Anne T.); Guerra, F. M. (Francisco M.); George, J. S. (John S.)

2002-01-01

374

Electric fields measured by ISEE-1 within and near the neutral sheet during quiet and active times  

NASA Technical Reports Server (NTRS)

An understanding of the physical processes occurring in the magnetotail and plasmasheet during different interplanetary magnetic field orientations and differing levels of ground magnetic activity is crucial for the development of a theory of energy transfer from the solar wind to the particles which produce auroral arcs. In the present investigation, the first observations of electric fields during neutral sheet crossings are presented, taking into account the statistical correlations of the interplanetary magnetic field direction and ground activity with the character of the electric field. The electric field data used in the study were obtained from a double probe experiment on the ISEE-1 satellite. The observations suggest that turbulent electric and magnetic fields are intimately related to plasma acceleration in the neutral sheet and to the processes which create auroral particles.

Cattell, C. A.; Mozer, F. S.

1982-01-01

375

The GLAST Burst Monitor (GBM)  

E-print Network

The selection of the GLAST burst monitor (GBM) by NASA will allow the investigation of the relation between the keV and the MeV-GeV emission from gamma-ray bursts. The GBM consists of 12 NaI and 2 BGO crystals allowing a continuous measurement of the energy spectra of gamma-ray bursts from ~5 keV to \\~30 MeV. One feature of the GBM is its high time resolution for time-resolved gamma-ray spectroscopy. Moreover the arrangement of the NaI crystals allows a rapid on-board location (<15 degrees) of a gamma-ray burst within a FoV of ~8.6 sr. This position will be communicated to the main instrument of GLAST making follow-up observations at high energies possible.

G. G. Lichti; M. S. Briggs; R. Diehl; G. Fishman; R. Georgii; R. M. Kippen; C. Kouveliotou; C. Meegan; W. Paciesas; R. Preece; V. Schoenfelder; A. von Kienlin

2001-09-10

376

In vitro studies on regulation of osteogenic activities by electrical stimulus on biodegradable electroactive polyelectrolyte multilayers.  

PubMed

In this study, a novel electroactive tetreaniline-containing degradable polyelectrolyte multilayer film (PEM) coating [(poly(l-glutamic acid)-graft-tetreaniline/poly(l-lysine)-graft-tetreaniline)n, (PGA-g-TA/PLL-g-TA)n] was designed and fabricated by layer-by-layer (LbL) assembly method. Compared with the nongrafted PEMs, the tetreaniline-grafted PEMs showed higher roughness and stiffness in micro/nanoscale structures. The special surface characteristics and the typical electroconductive properties were more beneficial for adhesion, proliferation, and differentiation of preosteoblast MC3T3-E1 cells. Moreover, the enhanced effects were observed on the modulation of MC3T3-E1 cells that differentiated into maturing osteoblasts, when the electroactive PEMs were coupled with electrical stimulus (ES), especially in the early phase of the osteoblast differentiation. The alkaline phosphatase (ALP) activity, calcium deposition, immunofluorescence staining, and RT-qPCR were evaluated on the differentiation of preosteoblast. These data indicate that the comprehensive effects through coupling electroactive scaffolds with electrical stimulus are better to develop bioelectric strategies to control cell functions for bone regeneration. PMID:24995801

Cui, Haitao; Wang, Yu; Cui, Liguo; Zhang, Peibiao; Wang, Xianhong; Wei, Yen; Chen, Xuesi

2014-08-11

377

Kinetics of positive ions and electrically neutral active particles in afterglow in neon at low pressure  

NASA Astrophysics Data System (ADS)

Kinetics of positive ions and electrically neutral active particles formed during breakdown and successive discharge in neon-filled tube at 6.6 millibars pressure had been analyzed. This analysis was performed on the basis of mean value of electrical breakdown time delay t¯d dependence on afterglow period ? (memory curve). It was shown that positive ions are present in the 1?s < ? < 30 ms interval, which is manifested through t ¯d slow increase with the increase of ?. A rapid t¯d increase in the 30 ms < ? < 3 s interval is a consequence of significant decrease of positive ions concentration and dominant role in breakdown initiation have ground state nitrogen atoms, which further release secondary electrons from the cathode by catalytic recombination process. These atoms are formed during discharge by dissociation of ground state nitrogen molecules that are present as impurities in neon. For ? > 3 s, breakdown is initiated by cosmic rays and natural radioactivity. The increase of discharge current leads to decrease of t¯d due to the increase of positive ions concentration in inter electrode gap. The increase of applied voltage also decreases t¯d for ? > 30 ms due to the increase of the probability for initial electron to initiate breakdown. The presence of UV radiation leads to the decrease of t¯d due to the increased electron yield caused by photoelectrons. The influence of photoelectrons on breakdown initiation can be noticed for ? > 0.1 ms, while they dominantly determine t¯d for ? > 30 ms.

Pejovi?, Mili? M.; Neši?, Nikola T.; Pejovi?, Mom?ilo M.

2014-04-01

378

Decameter Type III-Like Bursts  

NASA Astrophysics Data System (ADS)

Starting from 1960s Type III-like bursts (Type III bursts with high drift rates) in a wide frequency range from 300 to 950MHz have been observed. These new bursts observed at certain frequency being compared to the usual Type III bursts at the same frequency show similar behaviour but feature frequency drift 2-6 times higher than the normal bursts. In this paper we report the first observations of Type III-like bursts in decameter range, carried out during summer campaigns 2002 - 2004 at UTR-2 radio telescope. The circular polarization of the bursts was measured by the radio telescope URAN-2 in 2004. The observed bursts are analyzed and compared with usual Type III bursts in the decameter range. From the analysis of over 1100 Type III-like bursts, their main parameters have been found. Characteristic feature of the observed bursts is similar to Type III-like bursts at other frequencies, i.e. measured drift rates (5-10 MHz/s) of this bursts are few times larger than that for usual Type III bursts, and their durations (1-2 s) are few times smaller than that for usual Type III bursts in this frequency band.

Melnik, V. N.; Konovalenko, A. A.; Rutkevych, B. P.; Rucker, H. O.; Dorovskyy, V. V.; Abranin, E. P.; Lecacheux, A.; Brazhenko, A. I.; Stanislavskyy, A. A.

2007-12-01

379

Electrical Generation.  

ERIC Educational Resources Information Center

Described are two activities designed to help children investigate electrical charges, electric meters, and electromagnets. Included are background information, a list of materials, procedures, and follow-up questions. Sources of additional information are cited. (CW)

Science and Children, 1990

1990-01-01

380

Electric Gelatin  

NSDL National Science Digital Library

In this activity, learners explore static electricity and electrical charges while experimenting with an inflated balloon, unflavored gelatin powder, and a wool sweater. Challenge learners to compare what happens when they use flavored gelatin or salt.

Boston, Wgbh

2002-01-01

381

Analysis of calculated electrical activation of denervated muscle fibers in the human thigh.  

PubMed

Finite difference models of the human thigh are used to analyze the excitation process in the fibers of denervated skeletal muscles in conjunction with functional electrical stimulation (FES) via surface electrodes. The Matlab tool "FES-Analyze" was developed to simulate and analyze the super-threshold regions in a human thigh. Action potential is simulated with a muscle fiber model of the Hodgkin Huxley type and with a generalized form of the activating function. With FES-Analyze it is possible to compare the stimulation at the end of the muscle fiber and the stimulation at the central part of the muscle fiber, both in cross- and longitudinal-section, as well as to observe the effect of different impulse intensities and lengths during FES. Simulating with "Standard Values" of the pulse duration (20 ms) and the amplitude (80 V) one discovers that the main part of the activation takes place at the end of the muscle fiber. To obtain activation at the central part of the muscle fiber, higher amplitudes and longer pulse durations are needed. PMID:15926979

Martinek, Johannes; Reichel, Martin; Rattay, Frank; Mayr, Winfried

2005-06-01

382

Sensing performance of electrically conductive fabrics and dielectric electro active polymers for parachutes  

NASA Astrophysics Data System (ADS)

This paper quantifies the sensing capabilities of novel smart materials in an effort to improve the performance, better understand the physics, and enhance the safety of parachutes. Based upon a recent review of actuation technologies for parachute applications, it was surmised that the actuators reviewed could not be used to effectively alter the drag or lift (i.e. geometry, porosity, or air vent openings) of a parachute during flight. However, several materials showed potential for sensing applications within a parachute, specifically electrically conductive fabrics and dielectric electro-active polymers. This paper introduces several new conductive fabrics and provides an evaluation of the sensing performance of these smart materials based upon test results using mechanical testing and digital image correlation for comparison.

Favini, Eric; Niezrecki, Christopher; Manohar, Sanjeev K.; Willis, David; Chen, Julie; Niemi, Eugene; Desabrais, Kenneth; Charette, Christine

2011-04-01

383

Pulse-periodic chemical oxygen-iodine laser with active medium formation by volumetric electric discharge  

NASA Astrophysics Data System (ADS)

The paper describes a study of pulse-periodic operation of a chemical oxygen-iodine laser. The generator in use was of the jet type with high chlorine utilization degree (>=97%). Atomic iodine was released by dissociating methyl-iodide (CH 3I) in volumetric electric discharge. Steady lasing was achieved at a repetition rate up to 30 Hz. The emission energy attained per individual pulse in a train was 1.1 J at a pulse energy repeatability of (3÷5) % and a specific energy extraction from the active medium of 1.7 J/L. The lasing pulse duration depended on the concentration of methyl-iodide and the energy deposited into discharge. The minimal half-height duration of pulses was achieved as 10 ?m at a concentration of atomic iodine in the laser cavity ~1*10 15 cm -3.

Velikanov, S. D.; Gorelov, V. G.; Gostev, I. V.; Ireshev, Ye. V.; Kalinovsky, V. V.; Komissarov, I. A.; Konovalov, V. V.; Konovalov, I. V.; Mikhalkin, V. N.; Nikolaev, V. D.; Sevryugin, I. V.; Smirnov, A. V.; Sobolev, R. E.; Shornikov, L. N.

2007-05-01

384

[Cognitive disorders and some particularly of brain electrical activity in the use of cannabinoids].  

PubMed

In the current work we review the research on the effects of exogenous cannabinoids. Exogenous cannabinoids probably disrupt the normal functioning of cannabinoid receptors and area of the brain in which they are located, and this disruption is reflected in the change of related functions. Particular attention is drawn to the research of brain electrical activity in cannabis users. These studies can be divided into two directions--the study of acute and of long-term effects. Principal acute effects of cannabis are: reduction in the power of the theta oscillations, and the decrease in the amplitude of P300. The results of studies of long-term effects are contradictory: some studies indicate a reduction of adverse effects during disuse. Other studies give reason to believe that cognitive disorders associated with chronic use of cannabinoids are stable and long-term. PMID:25464755

Larionova, E V

2013-01-01

385

Cosmological gamma-ray bursts  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Gamma-ray bursts are brief events that dominate the emission from all other gamma-ray objects in the sky, flicker for tens of seconds, and then turn off. Their nature remains uncertain despite years of efforts to understand them. One hypothesis is that the bursts arise within our galaxy albeit in an extended halo of neutron stars. Another hypothesis uses the isotropic distribution of gamma-ray bursts to argue that they come from nearly the edge of the universe. If gamma-ray bursts originate from cosmological distances, then the expansion of the universe should cause the dimmer (and presumably further) bursts to last longer. The authors have developed methods for measuring this time stretching, related the time stretching to the distance to the bursts, determined how the detailed physics causes temporal variations, and found the amount of total energy and peak luminosity that the events must be producing.

Fenimore, E.; Epstein, R.; Ho, C.; Intzand, J.

1996-04-01

386

The effect of bradykinin on the electrical activity of rat myenteric neurons.  

PubMed

Bradykinin is a mediator involved in inflammatory processes in the gut. Here we investigated the effect of bradykinin on the electrical activity of rat myenteric neurons, the key players for regulation of gastrointestinal motility. Bradykinin (2 × 10(-8)mol/l) induced a biphasic increase in frequency of action potentials measured with microelectrode arrays. This increase was mirrored by a biphasic increase in cytosolic Ca(2+) concentration ([Ca(2+)]i), which was observed in about 40% of the myenteric neurons. The bradykinin B1 receptor agonist des-arg(9)-bradykinin as well as the bradykinin B2 receptor agonist hyp(3)-bradykinin induced a similar effect on [Ca(2+)]i. Immunocytochemical stainings confirmed the expression of both receptor types by myenteric ganglionic cells. Real time PCR showed that the inducible B1 receptor was upregulated during cell culture. The inhibition of cyclooxygenases with piroxicam reduced the effect of bradykinin on the electrical activity of myenteric neurons. The suppression of the glial growth on microelectrode arrays did not affect the bradykinin-induced change in frequency of action potentials. This suggests that prostaglandins, which probably mediate the effect of bradykinin, are not exclusively released from glial cells. The bradykinin-induced increase in [Ca(2+)]i was dependent on the presence of extracellular Ca(2+) and was inhibited by Co(2+), Cd(2+), and Ni(2+), blockers of voltage-dependent Ca(2+) channels, indicating a stimulation of the influx of extracellular Ca(2+) by the kinin. Consequently, bradykinin induces a Ca(2+) influx in myenteric neurons via Ca(2+) channels in the plasma membrane. PMID:24886885

Würner, Lisa; Pouokam, Ervice; Diener, Martin

2014-09-01

387

Floating Light-Activated Micro Electrical Stimulators Tested in the Rat Spinal Cord  

PubMed Central

Microelectrodes of neural stimulation utilize fine wires for electrical connections to driving electronics. Breakage of these wires and the neural tissue response due to their tethering forces are major problems encountered with long term implantation of microelectrodes. The lifetime of an implant for neural stimulation can be substantially improved if the wire interconnects are eliminated. Thus, we proposed a floating light-activated micro electrical stimulator (FLAMES) for wireless neural stimulation. In this paradigm, a laser beam at near infrared (NIR) wavelengths will be used as a means of energy transfer to the device. In this study, microstimulators of various sizes were fabricated, with two cascaded GaAs p-i-n photodiodes, and tested in the rat spinal cord. A train of NIR pulses (0.2 ms, 50 Hz) was sent through the tissue to wirelessly activate the devices and generate the stimulus current. The forces elicited by intraspinal stimulation were measured from the ipsilateral forelimb with a force transducer. The largest forces were around 1.08N, a significant level of force for the rat forelimb motor function. These in vivo tests suggest that the FLAMES can be used for intraspinal microstimulation even for the deepest implant locations in the rat spinal cord. The power required to generate a threshold arm movement was investigated as the laser source was moved away from the microstimulator. The results indicate that the photon density does not decrease substantially for horizontal displacements of the source that are in the same order as the beam radius. This gives confidence that the stimulation threshold may not be very sensitive to small displacement of the spinal cord relative to the spine-mounted optical power source. PMID:21914931

Abdo, Ammar; Sahin, Mesut; Freedman, David S.; Cevik, Elif; Spuhler, Philipp S.; Unlu, M. Selim

2011-01-01

388

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

389

Soluble CD40 Ligand Stimulates CD40-Dependent Activation of the ?2 Integrin Mac-1 and Protein Kinase C Zeda (PKC?) in Neutrophils: Implications for Neutrophil-Platelet Interactions and Neutrophil Oxidative Burst  

PubMed Central

Recent work has revealed an essential involvement of soluble CD40L (sCD40L) in inflammation and vascular disease. Activated platelets are the major source of sCD40L, which has been implicated in platelet and leukocyte activation, although its exact functional impact on leukocyte-platelet interactions and the underlying mechanisms remain undefined. We aimed to determine the impact and the mechanisms of sCD40L on neutrophils. We studied neutrophil interactions with activated, surface-adherent platelets as a model for leukocyte recruitment to the sites of injury. Our data show that CD40L contributes to neutrophil firm adhesion to and transmigration across activated surface-adherent platelets, possibly through two potential mechanisms. One involves the direct interaction of ligand-receptor (CD40L-CD40), i.e., platelet surface CD40L interaction with neutrophil CD40; another involves an indirect mechanism, i.e. soluble CD40L stimulates activation of the leukocyte-specific ?2 integrin Mac-1 in neutrophils and thereby further promotes neutrophil adhesion and migration. Activation of the integrin Mac-1 is known to be critical for mediating neutrophil adhesion and migration. sCD40L activated Mac-1 in neutrophils and enhanced neutrophil-platelet interactions in wild-type neutrophils, but failed to elicit such responses in CD40-deficient neutrophils. Furthermore, our data show that the protein kinase C zeta (PKC?) is critically required for sCD40L-induced Mac-1 activation and neutrophil adhesive function. sCD40L strongly stimulated the focal clustering of Mac-1 (CD11b) and the colocalization of Mac-1 with PKC? in wild-type neutrophils, but had minimal effect in CD40-deficient neutrophils. Blocking PKC? completely inhibited sCD40L-induced neutrophil firm adhesion. Moreover, sCD40L strongly stimulates neutrophil oxidative burst via CD40-dependent activation of PI3K/NF-KB, but independent of Mac-1 and PKC?. These findings may contribute to a better understanding of the underlying mechanisms by which sCD40L/CD40 pathway contributes to inflammation and vascular diseases. PMID:23785403

Zhu, Xiaolei; Wang, Cuiping; Yan, Jinchuan; Wu, Fusheng; Nanda, Anil; Granger, D. Neil; Li, Guohong

2013-01-01

390

Cloaked Gamma Ray Bursts  

E-print Network

It is suggested that many $\\gamma$-ray bursts (GRBs) are cloaked by an ultra-relativistic baryonic shell that has high optical depth when the photons are manufactured. Such a shell would not fully block photons reflected or emitted from its inner surface, because the radial velocity of the photons can be less than that of the shell. This avoids the standard problem associated with GRBs that the thermal component should be produced where the flow is still obscured by high optical depth. The radiation that escapes high optical depth obeys the Amati relation. Observational implications may include a) anomalously high ratios of afterglow to prompt emission, such as may have been the case in the recently discovered PTF 11agg, and b) ultrahigh-energy neutrino pulses that are non-coincident with detectable GRB. It is suggested that GRB 090510, a short, very hard GRB with very little afterglow, was an {\\it exposed} GRB, in contrast to those cloaked by baryonic shells. \\end{abstract}

Eichler, David

2014-01-01

391

Model of gamma frequency burst discharge generated by conditional backpropagation.  

PubMed

Pyramidal cells of the electrosensory lateral line lobe (ELL) of the weakly electric fish Apteronotus leptorhynchus have been shown to produce oscillatory burst discharge in the gamma-frequency range (20-80 Hz) in response to constant depolarizing stimuli. Previous in vitro studies have shown that these bursts arise through a recurring spike backpropagation from soma to apical dendrites that is conditional on the frequency of action potential discharge ("conditional backpropagation"). Spike bursts are characterized by a progressive decrease in inter-spike intervals (ISIs), and an increase of dendritic spike duration and the amplitude of a somatic depolarizing afterpotential (DAP). The bursts are terminated when a high-frequency somatic spike doublet exceeds the dendritic spike refractory period, preventing spike backpropagation. We present a detailed multi-compartmental model of an ELL basilar pyramidal cell to simulate somatic and dendritic spike discharge and test the conditions necessary to produce a burst output. The model ionic channels are described by modified Hodgkin-Huxley equations and distributed over both soma and dendrites under the constraint of available immunocytochemical and electrophysiological data. The currents modeled are somatic and dendritic sodium and potassium involved in action potential generation, somatic and proximal apical dendritic persistent sodium, and K(V)3.3 and fast transient A-like potassium channels distributed over the entire model cell. The core model produces realistic somatic and dendritic spikes, differential spike refractory periods, and a somatic DAP. However, the core model does not produce oscillatory spike bursts with constant depolarizing stimuli. We find that a cumulative inactivation of potassium channels underlying dendritic spike repolarization is a necessary condition for the model to produce a sustained gamma-frequency burst pattern matching experimental results. This cumulative inactivation accounts for a frequency-dependent broadening of dendritic spikes and results in a conditional failure of backpropagation when the intraburst ISI exceeds dendritic spike refractory period, terminating the burst. These findings implicate ion channels involved in repolarizing dendritic spikes as being central to the process of conditional backpropagation and oscillatory burst discharge in this principal sensory output neuron of the ELL. PMID:11600618

Doiron, B; Longtin, A; Turner, R W; Maler, L

2001-10-01

392

Conditional spike backpropagation generates burst discharge in a sensory neuron.  

PubMed

Backpropagating dendritic Na(+) spikes generate a depolarizing afterpotential (DAP) at the soma of pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish. Repetitive spike discharge is associated with a progressive depolarizing shift in somatic spike afterpotentials that eventually triggers a high-frequency spike doublet and subsequent burst afterhyperpolarization (bAHP). The rhythmic generation of a spike doublet and bAHP groups spike discharge into an oscillatory burst pattern. This study examined the soma-dendritic mechanisms controlling the depolarizing shift in somatic spike afterpotentials, and the mechanism by which spike doublets terminate spike discharge. Intracellular recordings were obtained from ELL pyramidal somata and apical dendrites in an in vitro slice preparation. The pattern of spike discharge was equivalent in somatic and dendritic regions, reflecting the backpropagation of spikes from soma to dendrites. There was a clear frequency-dependent threshold in the transition from tonic to burst discharge, with bursts initiated when interspike intervals fell between approximately 3-7 ms. Removal of all backpropagating spikes by dendritic TTX ejection revealed that the isolated somatic AHPs were entirely stable at the interspike intervals that generated burst discharge. As such, the depolarizing membrane potential shift during repetitive discharge could be attributed to a potentiation of DAP amplitude. Potentiation of the DAP was due to a frequency-dependent broadening and temporal summation of backpropagating dendritic Na(+) spikes. Spike doublets were generated with an interspike interval close to, but not within, the somatic spike refractory period. In contrast, the interspike interval of spike doublets always fell within the longer dendritic refractory period, preventing backpropagation of the second spike of the doublet. The dendritic depolarization was thus abruptly removed from one spike to the next, allowing the burst to terminate when the bAHP hyperpolarized the membrane. The transition from tonic to burst discharge was dependent on the number and frequency of spikes invoking dendritic spike summation, indicating that burst threshold depends on the immediate history of cell discharge. Spike frequency thus represents an important condition that determines the success of dendritic spike invasion, establishing an intrinsic mechanism by which backpropagating spikes can be used to generate a rhythmic burst output. PMID:10980024

Lemon, N; Turner, R W

2000-09-01

393

Photocontrol of bud burst involves gibberellin biosynthesis in Rosa sp.  

PubMed

Light is a critical determinant of plant shape by controlling branching patterns and bud burst in many species. To gain insight into how light induces bud burst, we investigated whether its inductive effect in rose was related to gibberellin (GA) biosynthesis. In axillary buds of beheaded plants subject to light, the expression of two GA biosynthesis genes (RoGA20ox and RoGA3ox) was promptly and strongly induced, while that of a GA-catabolism genes (RoGA2ox) was reduced. By contrast, lower expression levels of these two GA biosynthesis genes were found in darkness, and correlated with a total inhibition of bud burst. This effect was dependent on both light intensity and quality. In in vitro cultured buds, the inductive effect of light on the growth of preformed leaves and SAM organogenic activity was inhibited by ancymidol and paclobutrazol, two effectors of GA biosynthesis. This effect was concentration-dependent, and negated by GA(3). However, GA(3) alone could not rescue bud burst in the dark. GA biosynthesis was also required for the expression and activity of a vacuolar invertase, and therefore for light-induced sugar metabolism within buds. These findings are evidence that GA biosynthesis contributes to the light effect on bud burst and lay the foundations of a better understanding of its exact role in plant branching. PMID:22749285

Choubane, Djillali; Rabot, Amélie; Mortreau, Eric; Legourrierec, Jose; Péron, Thomas; Foucher, Fabrice; Ahcène, Youyou; Pelleschi-Travier, Sandrine; Leduc, Nathalie; Hamama, Latifa; Sakr, Soulaiman

2012-09-01

394

Gamma ray bursts from extragalactic sources  

NASA Technical Reports Server (NTRS)

The properties of gamma ray bursts of classical type are found to be explicable in terms of high speed collisions between stars. A model is proposed in which the frequency of such collisions can be calculated. The model is then applied to the nuclei of galaxies in general on the basis that galaxies, or at least some fraction of them, originate in the expulsion of stars from creation centers. Evidence that low level activity of this kind is also taking place at the center of our own Galaxy is discussed. The implications for galactic evolution are discussed and a negative view of black holes is taken.

Hoyle, Fred; Burbidge, Geoffrey

1992-01-01

395

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. III - NOAA active region 6233 (1990 August)  

NASA Technical Reports Server (NTRS)

We investigate the spatial relationship between vertical electric currents and flare phenomena in NOAA Active Region 6233, which was observed 1990, August 28-31 at Mees Solar Observatory. The two flares studied are the 1N/M1.8 flare on August 28, 22:30 UT and the 1N/M1.6 flare on August 29, 20:35 UT. Using Stokes polarimetry we make magnetograms of the region and compute the vertical current density. Using H-alpha imaging spectroscopy we identify sites of intense nonthermal electron precipitation or of high coronal pressure. The precipitation in these flares is barely strong enough to be detectable. We find that both precipitation and high pressure tend to occur near vertical currents, but that neither phenomenon is cospatial with current maxima. In contrast with the conclusion of other authors, we argue that these observations do not support a current-interruption model for flares, unless the relevant currents are primarily horizontal. The magnetic morphology and temporal evolution of these flares suggest that an erupting filament model may be relevant, but this model does not explicitly predict the relationship between precipitation, high pressure, and vertical currents.

De La Beaujardiere, J.-F.; Canfield, Richard C.; Leka, K. D.

1993-01-01

396

Lightning and Electrical Activity during the 2006 Eruption of Augustine Volcano  

USGS Publications Warehouse

Lightning and other electrical activity were measured during the 2006 eruption of Augustine Volcano. We found two phases of the activity, the explosive phase corresponding to the explosive eruptions and the plume phase. We classified the lightning into three types, vent discharges, near-vent lightning, and plume lightning. Vent discharges are small, 10 to 100 m sparks, that occur at rate as great as 10,000 s-1 at the mouth of the volcano during the energetic explosive eruptions. The vent discharges were observed six different times. Near-vent lightning appears to develop upward from the volcanic cone into the developing column during explosions. This lightning is small, in the range of 1 to 7 km, and short, 0.01 to 0.1 s. The behavior of the near-vent lightning indicates an overall positive charge in the ejecta. The plume lightning resembled intracloud thunderstorm lightning. Often it was branched, spanned more than 10 km, and lasted more than 0.5 s.

Thomas, Ronald J.; McNutt, Stephen R.; Krehbiel, Paul R.; Rison, William; Aulich, Grayden; Edens, Harald; Tytgat, Guy; Clark, Edward

2010-01-01

397

High-resolution measurement of electrically-evoked vagus nerve activity in the anesthetized dog  

NASA Astrophysics Data System (ADS)

Objective. Not fully understanding the type of axons activated during vagus nerve stimulation (VNS) is one of several factors that limit the clinical efficacy of VNS therapies. The main goal of this study was to characterize the electrical recruitment of both myelinated and unmyelinated fibers within the cervical vagus nerve. Approach. In anesthetized dogs, recording nerve cuff electrodes were implanted on the vagus nerve following surgical excision of the epineurium. Both the vagal electroneurogram (ENG) and laryngeal muscle activity were recorded in response to stimulation of the right vagus nerve. Main results. Desheathing the nerve significantly increased the signal-to-noise ratio of the ENG by 1.2 to 9.9 dB, depending on the nerve fiber type. Repeated VNS following nerve transection or neuromuscular block (1) enabled the characterization of A-fibers, two sub-types of B-fibers, and unmyelinated C-fibers, (2) confirmed the absence of stimulation-evoked reflex compound nerve action potentials in both the ipsilateral and contralateral vagus nerves, and (3) provided evidence of stimulus spillover into muscle tissue surrounding the stimulating electrode. Significance. Given the anatomical similarities between the canine and human vagus nerves, the results of this study provide a template for better understanding the nerve fiber recruitment patterns associated with VNS therapies.

Yoo, Paul B.; Lubock, Nathan B.; Hincapie, Juan G.; Ruble, Stephen B.; Hamann, Jason J.; Grill, Warren M.

2013-04-01

398

Electrical activation to the parasternal intercostal muscles during high-frequency spinal cord stimulation in dogs.  

PubMed

High-frequency spinal cord stimulation (HF-SCS) is a novel technique of inspiratory muscle activation involving stimulation of spinal cord pathways, which may have application as a method to provide inspiratory muscle pacing in ventilator-dependent patients with spinal cord injury. The purpose of the present study was to compare the spatial distribution of motor drive to the parasternal intercostal muscles during spontaneous breathing with that occurring during HF-SCS. In nine anesthetized dogs, HF-SCS was applied at the T2 spinal level. Fine-wire recording electrodes were used to assess single motor unit (SMU) pattern of activation in the medial bundles of the 2nd and 4th and lateral bundles of the 2nd interspaces during spontaneous breathing and HF-SCS following C1 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched that occurring during spontaneous breathing (protocol 1). During HF-SCS mean peak SMU firing frequency was highest in the medial bundles of the 2nd interspace (17.1 ± 0.6 Hz) and significantly lower in the lateral bundles of the 2nd interspace (13.5 ± 0.5 Hz) and medial bundles of the 4th (15.2 ± 0.7 Hz) (P < 0.05 for each comparison). Similar rostrocaudal and mediolateral gradients of activity were observed during spontaneous breathing prior to C1 section. Since rib cage movement was greater and peak discharge frequencies of the SMUs higher during HF-SCS compared with spontaneous breathing, stimulus amplitude during HF-SCS was adjusted such that rib cage movement matched that occurring during spontaneous breathing (protocol 2). Under this protocol, mean peak SMU frequencies and rostrocaudal and mediolateral gradients of activity during HF-SCS were not significantly different compared with spontaneous breathing. This study demonstrates that 1) the topographic pattern of electrical activation of the parasternal intercostal muscles during HF-SCS is similar to that occurring during spontaneous breathing, and 2) differential spatial distribution of parasternal intercostal activation does not depend upon differential descending synaptic input from supraspinal centers. PMID:25342707

DiMarco, Anthony F; Kowalski, Krzysztof E

2015-01-15

399

Accelerated electricity conservation in Juneau, Alaska: A study of household activities that reduced demand 25%  

Microsoft Academic Search

An avalanche destroyed the main hydroelectric transmission line to Juneau, Alaska in April, 2008. Diesel-generated electricity was substituted, causing electricity prices to increase 500% for 45 days. Electricity demand fell by 25% during the supply disruption. Most of the reduction occurred before the higher rates were implemented. Some conservation – about 8% of historic consumption – persisted after the transmission

Wayne Leighty; Alan Meier

2011-01-01

400

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

401

Kinetics of positive ions and electrically neutral active particles in afterglow in neon at low pressure  

SciTech Connect

Kinetics of positive ions and electrically neutral active particles formed during breakdown and successive discharge in neon-filled tube at 6.6 millibars pressure had been analyzed. This analysis was performed on the basis of mean value of electrical breakdown time delay t{sup ¯}{sub d} dependence on afterglow period ? (memory curve). It was shown that positive ions are present in the 1?s??3?s, breakdown is initiated by cosmic rays and natural radioactivity. The increase of discharge current leads to decrease of t{sup ¯}{sub d} due to the increase of positive ions concentration in inter electrode gap. The increase of applied voltage also decreases t{sup ¯}{sub d} for ??>?30?ms due to the increase of the probability for initial electron to initiate breakdown. The presence of UV radiation leads to the decrease of t{sup ¯}{sub d} due to the increased electron yield caused by photoelectrons. The influence of photoelectrons on breakdown initiation can be noticed for ??>?0.1?ms, while they dominantly determine t{sup ¯}{sub d} for ??>?30?ms.

Pejovi?, Mili? M., E-mail: milic.pejovic@elfak.ni.ac.rs; Neši?, Nikola T.; Pejovi?, Mom?ilo M. [University of Niš, Faculty of Electronic Engineering, Aleksandra Medvedeva 14, 18000 Niš (Serbia)] [University of Niš, Faculty of Electronic Engineering, Aleksandra Medvedeva 14, 18000 Niš (Serbia)

2014-04-15

402

Crop drying by indirect active hybrid solar - Electrical dryer in the eastern Algerian Septentrional Sahara  

SciTech Connect

In the present work, a new specific prototype of an indirect active hybrid solar-electrical dryer for agricultural products was constructed and investigated at LENREZA Laboratory, University of Ouargla (Algerian Sahara). In the new configuration of air drying passage; the study was done in a somewhat high range of mass flow rate between 0.04 and 0.08 kg/m{sup 2} s a range not properly investigated by most researchers. Experimental tests with and without load were performed in winter season in order to study the thermal behavior of the dryer and the effect of high air masse flow on the collector and system drying efficiency. The fraction of electrical and solar energy contribution versus air mass flow rate was investigated. Slice tomato was studied with different temperatures and velocities of drying air in order to study the influence of these parameters on the removal moisture content from the product and on the kinetics drying and also to determine their suitable values. Many different thin layer mathematical drying models were compared according to their coefficient of determination (R{sup 2}) and reduced chi square ({chi}{sup 2}) to estimate experimental drying curves. The Middli model in this condition proved to be the best for predicting drying behavior of tomato slice with (R{sup 2} = 0.9995, {chi}{sup 2} = 0.0001). Finally an economic evaluation was calculated using the criterion of payback period which is found very small 1.27 years compared to the life of the dryer 15 years. (author)

Boughali, S.; Bouchekima, B.; Mennouche, D.; Bouguettaia, H.; Bechki, D. [Laboratory of New and Renewable Energy in Aride Zones, University Kasdi Merbah, BP511 Ouargla (Algeria); Benmoussa, H. [Faculty of Science, Department of Mechanics, University Hadj Lakhdar, Batna (Algeria)

2009-12-15

403