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1

Perturbation techniques for models of bursting electrical activity in pancreatic (beta)-cells.  

National Technical Information Service (NTIS)

Pancreatic (beta)-cells exhibit periodic bursting electrical activity consisting of active and silent phases. Experimentally, the ratio, (rho)(sub f), of the active phase duration to the overall period is correlated to the insulin response of these cells ...

M. Pernarowski R. M. Muira J. Kevorkian

1991-01-01

2

Spiking signatures of spontaneous activity bursts in hippocampal cultures.  

PubMed

Dense dissociated hippocampal cultures are known to generate spontaneous bursting electrical activity which can be recorded by multielectrode arrays. We have analyzed spatio-temporal profiles of the distribution of spikes in the bursts recorded after 2?weeks in vitro. We have found a statistically significant similarity between the spiking patterns in sequential bursting events, we refer to these spiking patterns as spiking signatures. Such spiking signatures may appear in different parts of the bursts, including the activation patterns - the first spike times in the bursts, and deactivation patterns - the last spike times in the bursts. Moreover, these patterns may display apparent time scaling, e.g., they may be replayed in the subsequent bursts at different speeds, while preserving the spiking order. We discuss how such properties of the bursts may be associated with the formation of repeatable signaling pathways in cultured networks in vitro. PMID:22087091

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

2011-11-11

3

Shaping bursting by electrical coupling and noise.  

PubMed

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

Medvedev, Georgi S; Zhuravytska, Svitlana

2012-03-27

4

Observations of energitic radiation bursts from thunder activities  

NASA Astrophysics Data System (ADS)

Energetic radiation bursts have been observed during strong thunderstorms by ground-based detectors as well as high-mountain ones. Those radiation bursts are thought to result from runaway electrons originating from electrons accelerated by strong electric field in lightning discharges and thunderclouds, and hence provide a valuable key to understand particle acceleration in thunder activity. Interestingly, they can be categorized into two bursts by their duration. One consists of short bursts lasting for milli-seconds or less. The other comprises long bursts having duration of a few seconds. In order to better understand both short and long bursts, we have conducted experiments at coastal area of the Japan Sea and a 2770-m altitude observatory. In this talk, we will report on those experiments, showing the two experiments has successfully observed both short and long bursts. Especially, we will focus on high-energy radiations extending over MeV energies, and then discuss a plausible model to explain how those high-energy radiations are produced in thunder activity.

Tsuchiya, H.; Enoto, T.; Torii, T.; Yuasa, T.; Yamada, S.; Kitacuhi, T.; Nakazawa, K.; Kato, H.; Okano, M.; Makishima, K.

2009-04-01

5

Regulation of electrical bursting in a spatiotemporal model of a GnRH neuron.  

PubMed

Gonadotropin-releasing hormone (GnRH) neurons are hypothalamic neurons that control the pulsatile release of GnRH that governs fertility and reproduction in mammals. The mechanisms underlying the pulsatile release of GnRH are not well understood. Some mathematical models have been developed previously to explain different aspects of these activities, such as the properties of burst action potential firing and their associated Ca(2+) transients. These previous studies were based on experimental recordings taken from the soma of GnRH neurons. However, some research groups have shown that the dendrites of GnRH neurons play very important roles. In particular, it is now known that the site of action potential initiation in these neurons is often in the dendrite, over 100 ?m from the soma. This raises an important question. Since some of the mechanisms for controlling the burst length and interburst interval are located in the soma, how can electrical bursting be controlled when initiated at a site located some distance from these controlling mechanisms? In order to answer this question, we construct a spatio-temporal mathematical model that includes both the soma and the dendrite. Our model shows that the diffusion coefficient for the spread of electrical potentials in the dendrite is large enough to coordinate burst firing of action potentials when the initiation site is located at some distance from the soma. PMID:23943344

Chen, Xingjiang; Iremonger, Karl; Herbison, Allan; Kirk, Vivien; Sneyd, James

2013-08-13

6

Fast activating voltage- and calcium-dependent potassium (BK) conductance promotes bursting in pituitary cells: a dynamic clamp study  

PubMed Central

The electrical activity pattern of endocrine pituitary cells regulates their basal secretion level. Rat somatotrophs and lactotrophs exhibit spontaneous bursting and have high basal levels of hormone secretion, while gonadotrophs exhibit spontaneous spiking and have low basal hormone secretion. It has been proposed that the difference in electrical activity between bursting somatotrophs and spiking gonadotrophs is due to the presence of large conductance potassium (BK) channels on somatotrophs but not on gonadotrophs. This is one example where the role of an ion channel type may be clearly established. We demonstrate here that BK channels indeed promote bursting activity in pituitary cells. Blocking BK channels in bursting lacto-somatotroph GH4C1 cells changes their firing activity to spiking, while further adding an artificial BK conductance via dynamic clamp restores bursting. Importantly, this burst-promoting effect requires a relatively fast BK activation/deactivation, as predicted by computational models. We also show that adding a fast activating BK conductance to spiking gonadotrophs converts the activity of these cells to bursting. Together, our results suggest that differences in BK channel expression may underlie the differences in electrical activity and basal hormone secretion levels among pituitary cell types and that the rapid rate of BK channel activation is key to its role in burst promotion.

Tabak, Joel; Tomaiuolo, Maurizio; Gonzalez-Iglesias, Arturo E.; Milescu, Lorin S.; Bertram, Richard

2011-01-01

7

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.

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

8

Analysis of burst dynamics bound by potential with active areas  

NASA Astrophysics Data System (ADS)

Burst firing dynamics that are observed in many neuron models including the Hodgkin-Huxley model, are explained in terms of a motion of a quasi particle bound by potential. We are able to foresee the solution landscape with the curvature of the potential, and can design the wave form of the output to properly set active areas on the potential. In this paper, we apply this concept for a single Hindmarsh-Rose model and a coupled van der Pol oscillators. Therefore, we provide an understanding of the burst firings with spatiotemporal constructions of the potential and the active areas, and claim that the active areas cause the eigen-oscillations individually. Hence, we dispose the active areas on the potential properly and design the intended wave forms. Then, the global curvature of the potential function ensures that these oscillations do not diverge.

Kurose, Koji; Hayakawa, Yoshihiro; Sato, Shigeo; Nakajima, Koji

9

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

PubMed

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

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

2013-08-06

10

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

11

Spontaneous Electrical Activity and Behavior in the Leech Hirudo Medicinalis  

PubMed Central

In the absence of external stimuli, animals explore the environment by performing irregular movements, but the neuronal mechanisms underlying this arrhythmic motion are largely unknown. In this paper, we studied the relationship between the spontaneous neuronal activity in the leech (Hirudo medicinalis) and its behavior. We analyzed the electrical activity of isolated ganglia, chains of two connected ganglia, and semi-intact preparations. The spontaneous electrical activity in ganglia was characterized by the occurrence of irregular bursts of spikes with variable duration and size. Properties of these bursts were modified by synaptic inputs arriving from the neighboring ganglia and from the two primitive brains located in the head and tail. In fact, in semi-intact preparations, unusually large bursts of spikes occurring spontaneously were recorded and caused the leech to move even in the absence of any external sensory stimulation. These large bursts appear to act as internal triggers controlling the spontaneous leech behavior and determining the duration of stereotypical motor patterns.

Garcia-Perez, Elizabeth; Mazzoni, Alberto; Torre, Vincent

2007-01-01

12

Effects of extracellular calcium on electrical bursting and intracellular and luminal calcium oscillations in insulin secreting pancreatic beta-cells.  

PubMed Central

The extracellular calcium concentration has interesting effects on bursting of pancreatic beta-cells. The mechanism underlying the extracellular Ca2+ effect is not well understood. By incorporating a low-threshold transient inward current to the store-operated bursting model of Chay, this paper elucidates the role of the extracellular Ca2+ concentration in influencing electrical activity, intracellular Ca2+ concentration, and the luminal Ca2+ concentration in the intracellular Ca2+ store. The possibility that this inward current is a carbachol-sensitive and TTX-insensitive Na+ current discovered by others is discussed. In addition, this paper explains how these three variables respond when various pharmacological agents are applied to the store-operated model. Images FIGURE 2 FIGURE 5 FIGURE 9 FIGURE 10

Chay, T R

1997-01-01

13

Oxidative burst and anticancer activities of rat neutrophils.  

PubMed

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

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

2005-01-01

14

Electrical Conduction Activity  

NSDL National Science Digital Library

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

2012-10-02

15

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

PubMed

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

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

2013-01-04

16

Reliability of burst superimposed technique to assess central activation failure during fatiguing contraction.  

PubMed

Recording a superimposed electrically-induced contraction at the limit of endurance during voluntary contraction is used as an indicator of failure of muscle activation by the central nervous system and discards the existence of peripheral muscle fatigue. We questioned on the reliability of this method by using other means to explore peripheral muscle failure. Fifteen normal subjects sustained handgrip at 60% of maximal voluntary contraction (MVC) until exhaustion. During sustained contraction, the power spectrum analysis of the flexor digitorum surface electromyogram allowed us to calculate the leftward shift of median frequency (MF). A superimposed 60 Hz 3 s pulse train (burst superimposition) was delivered to the muscle when force levelled off close to the preset value. Immediately after the fatigue trial had ended, the subject was asked to perform a 5 s 60% MVC and we measured the peak contractile response to a 60 Hz 3 s burst stimulation. Recordings of the compound evoked muscle action potential (M-wave) allowed us to explore an impairment of neuromuscular propagation. A superimposed contraction was measured in 7 subjects in their two forearms, whereas it was absent in the 8 others. Despite these discrepancies, all subjects were able to reproduce a 3 s 60% MVC immediately after the fatigue trial ended and there was no post-fatigue decrease of contraction elicited by the 60 Hz 3 s burst stimulation, as well as no M-wave decrease in amplitude and conduction time. Thus, there was no indication of peripheral muscle fatigue. MF decrease was present in all individuals throughout the fatiguing contraction and it was not correlated with the magnitude of superimposed force. These observations indicate that an absence of superimposed electrically-induced muscle contraction does not allow us to conclude the existence of a sole peripheral muscle fatigue in these circumstances. PMID:12586516

Dousset, Erick; Jammes, Yves

2003-04-01

17

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

PubMed

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

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

2013-05-01

18

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

PubMed Central

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

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

2013-01-01

19

Age-related increase in electromyography burst activity in males and females.  

PubMed

The rapid advancement of electromyography (EMG) technology facilitates measurement of muscle activity outside the laboratory during daily life. The purpose of this study was to determine whether bursts in EMG recorded over a typical 8-hour day differed between young and old males and females. Muscle activity was recorded from biceps brachii, triceps brachii, vastus lateralis, and biceps femoris of 16 young and 15 old adults using portable surface EMG. Old muscles were active 16-27% of the time compared to 5-9% in young muscles. The number of bursts was greater in old than young adults and in females compared to males. Burst percentage and mean amplitude were greater in the flexor muscles compared with the extensor muscles. The greater burst activity in old adults coupled with the unique activity patterns across muscles in males and females provides further understanding of how changes in neuromuscular activity effects age-related functional decline between the sexes. PMID:23984069

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

2013-07-31

20

Observations of burst-like VLF sferic activity in association with sprites  

NASA Astrophysics Data System (ADS)

Recent observations have revealed the occurrence of burst-like VLF activity, sometimes lasting several hundred ms, near the onset of many sprites. These "sferic bursts" are thought to be due to intra-cloud lightning activity, since they have been observed to only propagate short distances (a few hundred km) in the Earth- ionosphere waveguide and are generally not reported by the National Lightning Detection Network (NLDN). Similar types of sferic bursts have also been previously observed in association with Early/fast VLF events. The possible involvement of intra-cloud lightning in sprite production has been previously suggested based on the observed long delays between causative CG discharges and sprite events. In this work, we investigate the correlation between sprites and sferic bursts using VLF and optical data from the past decade of sprite observations. In particular, a wideband (10 Hz - 20 kHz) VLF receiver was deployed in the summers of 1995 - 2000 at Yucca Ridge Field Station in Fort Collins, CO, while sprite observations were made from the same location. With VLF data available for thousands of sprite observations through many different dates and storms, we compare the occurrence of sferic bursts in association with sprites. Preliminary results idicate that most sprites, but not all, are found in association with bursts of sferic activity. The data set in hand also allows comparative correlations with such metrics as VLF burst intensity and energy content; and sprite type, size and intensity.

Marshall, R. A.; Inan, U. S.

2006-12-01

21

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

PubMed Central

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

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

2012-01-01

22

Gamma-ray bursts, QSOs and active galaxies.  

PubMed

The similarity of the absorption spectra of gamma-ray burst (GRB) sources or afterglows with the absorption spectra of quasars (QSOs) suggests that QSOs and GRB sources are very closely related. Since most people believe that the redshifts of QSOs are of cosmological origin, it is natural to assume that GRBs or their afterglows also have cosmological redshifts. For some years a few of us have argued that there is much optical evidence suggesting a very different model for QSOs, in which their redshifts have a non-cosmological origin, and are ejected from low-redshift active galaxies. In this paper I extend these ideas to GRBs. In 2003, Burbidge (Burbidge 2003 Astrophys. J. 183, 112-120) showed that the redshift periodicity in the spectra of QSOs appears in the redshift of GRBs. This in turn means that both the QSOs and the GRB sources are similar objects ejected from comparatively low-redshift active galaxies. It is now clear that many of the GRBs of low redshift do appear in, or very near, active galaxies.A new and powerful result supporting this hypothesis has been produced by Prochter et al. (Prochter et al. 2006 Astrophys. J. Lett. 648, L93-L96). They show that in a survey for strong MgII absorption systems along the sightlines to long-duration GRBs, nearly every sightline shows at least one absorber. If the absorbers are intervening clouds or galaxies, only a small fraction should show absorption of this kind. The number found by Prochter et al. is four times higher than that normally found for the MgII absorption spectra of QSOs. They believe that this result is inconsistent with the intervening hypothesis and would require a statistical fluctuation greater than 99.1% probability. This is what we expect if the absorption is intrinsic to the GRBs and the redshifts are not associated with their distances. In this case, the absorption must be associated with gas ejected from the QSO. This in turn implies that the GRBs actually originate in comparatively low-redshift active galaxies and are ejected in the same way as are the QSOs. This relates these phenomena to a supernova origin for the GRBs. The current situation based on the latest observational data will be discussed. PMID:17301024

Burbidge, Geoffrey

2007-05-15

23

The dynamics underlying pseudo-plateau bursting in a pituitary cell model  

PubMed Central

Pituitary cells of the anterior pituitary gland secrete hormones in response to patterns of electrical activity. Several types of pituitary cells produce short bursts of electrical activity which are more effective than single spikes in evoking hormone release. These bursts, called pseudo-plateau bursts, are unlike bursts studied mathematically in neurons (plateau bursting) and the standard fast-slow analysis used for plateau bursting is of limited use. Using an alternative fast-slow analysis, with one fast and two slow variables, we show that pseudo-plateau bursting is a canard-induced mixed mode oscillation. Using this technique, it is possible to determine the region of parameter space where bursting occurs as well as salient properties of the burst such as the number of spikes in the burst. The information gained from this one-fast/two-slow decomposition complements the information obtained from a two-fast/one-slow decomposition.

2011-01-01

24

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

PubMed Central

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

Shen, Ke-Zhong; Johnson, Steven W.

2011-01-01

25

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

26

Functional implications of burst firing and single spike activity in lateral geniculate relay neurons.  

PubMed

Guinea-pig thalamocortical relay neurons can intrinsically generate action potentials in two distinct patterns: as high frequency bursts or as relatively independent single spikes. The burst firing mode is due to the presence of a low threshold Ca2+ current and imposes a marked non-linear transformation on depolarizing or hyperpolarizing inputs. In the burst firing mode, thalamic neurons respond to increasing frequencies of depolarizing inputs with progressively fewer action potentials such that they fail to respond to inputs arriving at rates greater than approximately 15 Hz. In this manner, the amplitude of the burst discharge relays little information concerning the characteristics of phasic excitatory postsynaptic potentials which may trigger them, but rather is determined by the membrane potential preceding the burst and the time interval since the last burst. In contrast to the behavior of neurons in the burst firing mode, the pattern of action potentials generated after depolarization into the single spike mode is a more faithful representation of the characteristics of incoming excitatory postsynaptic potentials or depolarizing inputs. The pattern of action potentials generated in the single spike mode is determined by the intensity, duration, and frequency of incoming excitatory inputs even when they arrive at rates in excess of 100 Hz. These, and other properties, allow thalamic neurons to possess two distinct states of neuronal activity: an oscillatory mode in which rhythmic bursts of action potentials are generated and in which responsiveness to stimulation of peripheral receptive fields is greatly reduced, and a transfer mode in which action potentials are generated in relative independence of one another and in which the ability to respond to barrages of phasic excitatory inputs is greatly enhanced. The presence of the rhythmic burst firing mode may therefore facilitate the filtering of sensory information during periods of drowsiness, inattentiveness, and slow wave sleep. PMID:2089273

McCormick, D A; Feeser, H R

1990-01-01

27

Is burst activity in cortical slices a representative model for epilepsy?  

Microsoft Academic Search

Neocortical slices including sensory cortex of mouse were used to study cellular and network activity during bicuculline evoked seizure-like activity. The relationship between the activities of single cells and the network was quantified using entropy measures of spike trains. The network shows a large increase in synchronous burst activity during the seizure-like phase. Surprisingly, the individual cells do not seem

Wim van Drongelen; Henner Koch; Charles Marcuccilli; Kurt Hecox; Jan-Marino Ramirez

2003-01-01

28

Studies on bursting pacemaker potential activity in molluscan neurons. III. Effects of hormones.  

PubMed

Vertebrate peptides and hormones have been appled to a number of identified neurosecretory and ono-neurosecretory cells in two molluscan preparations. Active peptide hormones included vasopressin and analogues. Active steriod hormones included aldosterone and hydrocortisone. Peptide effects were present at 10-9 M concentration of peptide, were confined to two neurosecrotory cells and consisted of long lasting changes in the membrane properties of these cells (characterized either by the initiation or potentiation of bursting pacemaker potential activity in these cells). The regulatory changes in membrane properties induced by the peptides were unlike the transient conductance changes produced by conventional neurotransmitters. Steroid effects were observed at 10-6M concentration of steroid and consisted of an increase in membrane potential and conductance which was dependent on the species of divalent cations present. The net effect of peptide activation would be to increase the release of neurosecretory material form the cell terminals, while the net effect of the steroids would be to decrease the release of this material. The results obtained with these invertebrate preparations may serve to describe new forms of cellular communication in the nervous system whereby peptides and steroids modulate electrical activity. PMID:1122383

Barker, J L; Ifshin, M S; Gainer, N

1975-02-14

29

Transitions to Synchrony in Coupled Bursting Neurons  

NASA Astrophysics Data System (ADS)

Certain cells in the brain, for example, thalamic neurons during sleep, show spike-burst activity. We study such spike-burst neural activity and the transitions to a synchronized state using a model of coupled bursting neurons. In an electrically coupled network, we show that the increase of coupling strength increases incoherence first and then induces two different transitions to synchronized states, one associated with bursts and the other with spikes. These sequential transitions to synchronized states are determined by the zero crossings of the maximum transverse Lyapunov exponents. These results suggest that synchronization of spike-burst activity is a multi-time-scale phenomenon and burst synchrony is a precursor to spike synchrony.

Dhamala, Mukeshwar; Jirsa, Viktor K.; Ding, Mingzhou

2004-01-01

30

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

SciTech Connect

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

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

2011-10-10

31

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

PubMed Central

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

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

2013-01-01

32

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

PubMed

Objective. Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily identify burst suppression periods, analysis algorithms require long intervals of data to characterize burst suppression at a given time and provide no framework for statistical inference. Approach. We introduce the concept of the burst suppression probability (BSP) to define the brain's instantaneous propensity of being in the suppressed state. To conduct dynamic analyses of burst suppression we propose a state-space model in which the observation process is a binomial model and the state equation is a Gaussian random walk. We estimate the model using an approximate expectation maximization algorithm and illustrate its application in the analysis of rodent burst suppression recordings under general anesthesia and a patient during induction of controlled hypothermia. Main result. The BSP algorithms track burst suppression on a second-to-second time scale, and make possible formal statistical comparisons of burst suppression at different times. Significance. The state-space approach suggests a principled and informative way to analyze burst suppression that can be used to monitor, and eventually to control, the brain states of patients in the operating room and in the intensive care unit. PMID:24018288

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

2013-09-10

33

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

34

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

PubMed

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

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

2013-07-05

35

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

36

Effect of dietary administration of Porphyridium cruentum on the respiratory burst activity of sole, Solea senegalensis (Kaup), phagocytes.  

PubMed

The stimulatory effect of the red microalga Porphyridium cruentum on respiratory burst activity of sole phagocytes was evaluated in vivo. Oral administration of a diet supplemented with lyophilized P. cruentum cells (10 g kg(-1)) stimulated respiratory burst activity after 4 weeks feeding in sole vaccinated with Photobacterium damselae subsp. piscicida bacterin. PMID:18577098

Díaz-Rosales, P; Chabrillón, M; Abdala, R T; Figueroa, F L; Balebona, M C; Moriñigo, M A

2008-07-01

37

A self-adapting approach for the detection of bursts and network bursts in neuronal cultures.  

PubMed

Dissociated networks of neurons typically exhibit bursting behavior, whose features are strongly influenced by the age of the culture, by chemical/electrical stimulation or by environmental conditions. To help the experimenter in identifying the changes possibly induced by specific protocols, we developed a self-adapting method for detecting both bursts and network bursts from electrophysiological activity recorded by means of micro-electrode arrays. The algorithm is based on the computation of the logarithmic inter-spike interval histogram and automatically detects the best threshold to distinguish between inter- and intra-burst inter-spike intervals for each recording channel of the array. An analogous procedure is followed for the detection of network bursts, looking for sequences of closely spaced single-channel bursts. We tested our algorithm on recordings of spontaneous as well as chemically stimulated activity, comparing its performance to other methods available in the literature. PMID:19669401

Pasquale, Valentina; Martinoia, Sergio; Chiappalone, Michela

2009-08-08

38

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

39

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

40

Heterogeneity in spontaneous and tetraethylammonium induced intracellular electrical activity in colonic circular muscle  

Microsoft Academic Search

Marked differences were observed in the intracellular electrical activities (spontaneous and TEA-induced) comparing the submucosal and myenteric plexus surfaces of the circular muscle of the dog colon. Distinct characteristics of the cells at the myenteric plexus surface were: a less (10 mV) polarized membrane, a lower amplitude slow wave, and the occurrence of burst type spiking activity. However, slow waves

Carlos Barajas-López; Jan D. Huizinga

1988-01-01

41

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

NASA Astrophysics Data System (ADS)

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

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

42

Mode of activation of the metabolic burst in polymorphonuclear leukocytes by calcium oxalate crystals.  

PubMed

Microcrystals of calcium oxalate cause an activation of the metabolic burst in polymorphonuclear leukocytes, measured as NBT reduction. Crystal-induced NBT reduction, which was mainly due to superoxide release, was accompanied by enzyme release. Modulation of calcium oxalate-induced activation by several agents resembles the effect of these agents on activation by opsonized zymosan and by phorbol myristate acetate. Both the activation of the metabolic burst and concomitant enzyme release could be counteracted by certain anions, such as oxalate, pyruvate and citrate, indicating that positive charges on the crystals play an important role in crystal-cell interaction. Removal of the negatively charged sialic acid from the cell surface by neuraminidase did not affect the the action of the crystals. The mechanism, by which calcium oxalate activates polymorphonuclear leukocytes, is discussed. PMID:3445822

Elferink, J G

1987-12-01

43

DIFFERENTIAL EFFECTS OF HUMAN ERYTHROID BURST STIMULATING ACTIVITY (HuEBSA) ON HUMAN CORD BLOOD BURST FORMING UNITS-ERYTHROID (BFU-Es) AS A FUNCTION OF THEIR DIFFERENTIATION STATE  

Microsoft Academic Search

An erythroid stimulating activity which promotes the growth of small bursts probably arising from mature burst forming units-erythroid (BFU-Es) of adult human bone marrow cells and called human erythroid burst stimulating activity (HuEBSA), was previously found in media conditioned by a fetal human kidney cell line. In the present work we report that adding HuEBSA to cultures did not increase

Marie-Hélène Rodriguez; Sylvie Arnaud; Marie-France Grasset; Guy Mouchiroud; Jean Paul Blanchet

1999-01-01

44

Dendritic calcium activity precedes inspiratory bursts in preBotzinger complex neurons.  

PubMed

Medullary interneurons of the preBötzinger complex 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 Ca(2+) accumulation postsynaptically to evoke a Ca(2+)-activated inward current that contributes to inspiratory burst generation. We measured Ca(2+) transients by two-photon imaging dendrites while recording neuronal somata electrophysiologically. Dendritic Ca(2+) accumulation frequently precedes inspiratory bursts, particularly at recording sites 50-300 ?m distal from the soma. Preinspiratory Ca(2+) transients occur in hotspots, not ubiquitously, in dendrites. Ca(2+) 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 Ca(2+) activates an inward current to electrotonically depolarize the soma, rather than propagate as a regenerative Ca(2+) 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

2011-01-19

45

Very Large Array observations of solar active regions. IV Structure and evolution of radio bursts from 20 centimeter loops  

NASA Astrophysics Data System (ADS)

It is pointed out that centimeter wavelength (2 or 6 cm) observations with the Very Large Array (VLA) at high angular resolution and moderate time resolution have provided new insights into the physics of solar radio bursts. However, there have been comparatively few VLA observations of solar bursts at the longer 20 cm wavelength. The present investigation is concerned with a VLA analysis of six bursts from 20 cm loops. The Very Large Array was used to observe the active region AR 3804 on July 12-20, 1982 at 1380 MHz, 1540 MHz, or 1705 MHz. Attention is given to time profiles and 10 s snapshot maps which describe the evolution of the 20 cm bursts, preburst heating, and changes in magnetic structure before and during the bursts. The observations presented provide new insight into the evolution of solar microwave bursts and the physical processes which may trigger them. In one case, the intense components of multiple bursts originated in different sources, suggesting that a number of loops may have become successively activated like some complex X-ray bursts.

Willson, R. F.; Lang, K. R.

1984-04-01

46

Modeling of an active burst illumination imaging system: comparison between experimental and modelled 3D scene  

NASA Astrophysics Data System (ADS)

Onera, The French Aerospace Lab, has developed an active burst illumination imaging system with a short time gating. This imaging device is used to obtain a passive or an active image of a small volume of the illuminated scene. To better understand and evaluate the relevant physical phenomena (scintillation, speckle...) impacting on the performance on burst illumination imaging system, Onera has implemented a code (PIAF). The aim of this paper is to describe the model and to present some results. Efforts have done on 3D target geometries and surface properties. We analyze each contribution like the incoherent solar field or the incident laser field. We adapt classical and physical models for light reflection. Speckle contributions are also treated using data bases generated by an Onera tool.

Rivière, N.; Anna, G.; Hespel, L.; Tanguy, B.; Velluet, M.-T.; Frédéric, Y.-M.

2010-10-01

47

[Variability of the electrical activity of Helix pomatia neuron PPa1].  

PubMed

Transitions of electrical activity were investigated in the PPa1 bursting neuron of the snail Helix pomatia. This neuron was found to exhibit the following modes of the activity: silent, beating, low amplitude and high amplitude bursting ones. The transitions between different modes of electrical activity occur within several hundreds of seconds. Such transitions were demonstrated to be simultaneous with changes in the membrane potential of other neurons. Application of a water-soluble fraction of the snail brain to the neuron evoked transitions of electrical activity similar to those occurring spontaneously. The analysis of the data obtained leads to the hypothesis that the activity of the PPa1 neuron is not of endogenous nature but is due to the action of substances released by other neurons. PMID:6913792

Kononenko, N I

1981-01-01

48

Analysis of the electrosensory pyramidal cell bursting model for weakly electric fish: model prediction under low levels of dendritic potassium conductance.  

PubMed

Pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish produce burst discharge. A Hodgkin-Huxley-type model, called ghostburster, consisting of two compartments (soma and dendrite) reproduces ELL pyramidal cell bursting observed in vitro. A previous study analyzed the ghostburster by treating Is and gDr,d as bifurcation parameters (Is: current injected into the somatic compartment and gDr,d: maximal conductance of the delayed rectifying potassium current in the dendritic compartment) and indicated that when both Is and gDr,d are set at particular values, the ghostburster shows a codimension-two bifurcation at which both saddle-node bifurcation of fixed points and saddle-node bifurcation of limit cycles occur simultaneously. In the present study, the ghostburster was investigated to clarify the bursting that occurred at gDr,d values smaller than that at the codimension-two bifurcation. Based on the number of spikes per burst, various burst patterns were observed depending on the (Is, gDr,d) values. Depending on the (Is, gDr,d) values, the burst trajectory in a phase space of the ghostburster showed either a high or a low degree of periodicity. Compared to the previous study, the present findings contribute to a more detailed understanding of ghostburster bursting. PMID:22963912

Shirahata, T

2012-09-01

49

Modeling Electrically Active Viscoelastic Membranes  

PubMed Central

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

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

2012-01-01

50

Nicotinamide effects oxidative burst activity of neutrophils in patients with poorly controlled type 2 diabetes mellitus.  

PubMed

Neutrophil functions are impaired in patients with diabetes mellitus. Bacterial phagocytosis and oxidative burst activity are reduced at high glucose concentrations in diabetic patients. Defects in neutrophil oxidative burst capacity are of multifactorial origin in diabetes mellitus and correlate with glucose levels. It has been reported that neutrophil NADPH oxidase activity is impaired and superoxide production is reduced in diabetic patients with or without any infections. Nicotinamide is a vitamin B3 derivative and a NAD precursor with immunomodulatory effects. In vitro studies demonstrated that nicotinamide increases NAD and NADH content of beta cells. The authors hypothesized that nicotinamide may restore the impaired oxidative burst capacity of neutrophils in diabetic patients by increasing the NADH content as an electron donor and possibly through NADPH oxidase activity of the cell. In order to test the hypothesis, this placebo-controlled and open study was designed to evaluate neutrophil functions in infection-free poorly controlled type 2 diabetic patients as compared to healthy subjects and assess the effects of nicotinamide on neutrophil phagocytosis as well as oxidative burst activity. Thirty patients with type 2 diabetes mellitus were enrolled in the study. Sixteen were females and 14 were males, with a mean age 58 +/- 10. All patients were on sulphonylurea treatment and their hemoglobin A(1c) (HbA(1c)) levels were above 7.5%. The control group consisted of 10 voluntary healthy subjects. Diabetic and control subjects were not significantly different in terms of age, body mass index (BMI), leucocyte and neutrophil counts, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR), but HbA(1c) and fasting glucose levels were significantly higher in patients with diabetes mellitus. Phagocytic activity and respiratory burst indexes were measured by flow cytometric analyses as previously described by Rothe and Valet (Methods Enzyml., 233, 539-548, 1994) and compared in diabetic subjects and healthy controls. Diabetic patients were grouped to receive either 50 mg/kg oral nicotinamide (n = 15) or placebo (n = 15) for a period of 1 month. The 2 groups did not differ in terms of treatment, frequency of hypertension, BMI, diabetes duration, age, fasting plasma glucose (FPG), HbA(1c), CRP, ESR, polymorphonuclear leukocyte (PNL) and neutrophil counts. Neutrophil functions were reassessed after the treatment period. Phagocytic activity represented as indexes were lower in diabetic patients when compared to healthy subjects, but the differences were not statistically significant (P >.05). Patients with diabetes mellitus had significantly lower oxidative burst indexes when compared to healthy controls (P values <.05). In diabetic patients, a negative correlation between neutrophil functions and HbA(1c) was found which was not statistically significant (P values >.05). Phagocytic indexes were similar in nicotinamide and placebo groups after treatment period (P >.05). But oxidative burst activity in patients receiving nicotinamide was greater when compared with placebo and the difference was statistically significant at 30 and 45 minutes (P values.04 and.03). This effect of nicotinamide may be due to increased NADH content and NADPH oxidase activity of the cell, which needs to be further studied. Impaired neutrophil functions may aggravate various infections in patients with diabetes mellitus and blood glucose regulation is an important target of treatment to improve neutrophil functions. But nicotinamide treatment may help to improve prognosis in diabetic patients with severe infections. PMID:15203886

Osar, Zeynep; Samanci, Tülay; Demirel, Gülderen Yanikkaya; Damci, Taner; Ilkova, Hasan

51

Nicotinamide Effects Oxidative Burst Activity of Neutrophils in Patients with Poorly Controlled Type 2 Diabetes Mellitus  

PubMed Central

Neutrophil functions are impaired in patients with diabetes mellitus. Bacterial phagocytosis and oxidative burst activity are reduced at high glucose concentrations in diabetic patients. Defects in neutrophil oxidative burst capacity are of multifactorial origin in diabetes mellitus and correlate with glucose levels. It has been reported that neutrophil NADPH oxidase activity is impaired and superoxide production is reduced in diabetic patients with or without any infections. Nicotinamide is a vitamin B3 derivative and a NAD precursor with immunomodulatory effects. In vitro studies demonstrated that nicotinamide increases NAD and NADH content of beta cells. The authors hypothesized that nicotinamide may restore the impaired oxidative burst capacity of neutrophils in diabetic patients by increasing the NADH content as an electron donor and possibly through NADPH oxidase activity of the cell. In order to test the hypothesis, this placebo-controlled and open study was designed to evaluate neutrophil functions in infection-free poorly controlled type 2 diabetic patients as compared to healthy subjects and assess the effects of nicotinamide on neutrophil phagocytosis as well as oxidative burst activity. Thirty patients with type 2 diabetes mellitus were enrolled in the study. Sixteen were females and 14 were males, with a mean age 58 ± 10. All patients were on sulphonylurea treatment and their hemoglobin A1c (HbA1c) levels were above 7.5%. The control group consisted of 10 voluntary healthy subjects. Diabetic and control subjects were not significantly different in terms of age, body mass index (BMI), leucocyte and neutrophil counts, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR), but HbA1c and fasting glucose levels were significantly higher in patients with diabetes mellitus. Phagocytic activity and respiratory burst indexes were measured by flow cytometric analyses as previously described by Rothe and Valet (Methods Enzyml., 233, 539–548, 1994) and compared in diabetic subjects and healthy controls. Diabetic patients were grouped to receive either 50 mg/kg oral nicotinamide (n = 15) or placebo (n = 15) for a period of 1 month. The 2 groups did not differ in terms of treatment, frequency of hypertension, BMI, diabetes duration, age, fasting plasma glucose (FPG), HbA1c, CRP, ESR, polymorphonuclear leukocyte (PNL) and neutrophil counts. Neutrophil functions were reassessed after the treatment period. Phagocytic activity represented as indexes were lower in diabetic patients when compared to healthy subjects, but the differences were not statistically significant (P > .05). Patients with diabetes mellitus had significantly lower oxidative burst indexes when compared to healthy controls (P values < .05). In diabetic patients, a negative correlation between neutrophil functions and HbA1c was found which was not statistically significant (P values > .05). Phagocytic indexes were similar in nicotinamide and placebo groups after treatment period (P > .05). But oxidative burst activity in patients receiving nicotinamide was greater when compared with placebo and the difference was statistically significant at 30 and 45 minutes (P values .04 and .03). This effect of nicotinamide may be due to increased NADH content and NADPH oxidase activity of the cell, which needs to be further studied. Impaired neutrophil functions may aggravate various infections in patients with diabetes mellitus and blood glucose regulation is an important target of treatment to improve neutrophil functions. But nicotinamide treatment may help to improve prognosis in diabetic patients with severe infections.

Samanci, Tulay; Demirel, Gulderen Yanikkaya; Damci, Taner; Ilkova, Hasan

2004-01-01

52

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

PubMed Central

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

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

2013-01-01

53

A burst-based "Hebbian" learning rule at retinogeniculate synapses links retinal waves to activity-dependent refinement.  

PubMed

Patterned spontaneous activity in the developing retina is necessary to drive synaptic refinement in the lateral geniculate nucleus (LGN). Using perforated patch recordings from neurons in LGN slices during the period of eye segregation, we examine how such burst-based activity can instruct this refinement. Retinogeniculate synapses have a novel learning rule that depends on the latencies between pre- and postsynaptic bursts on the order of one second: coincident bursts produce long-lasting synaptic enhancement, whereas non-overlapping bursts produce mild synaptic weakening. It is consistent with "Hebbian" development thought to exist at this synapse, and we demonstrate computationally that such a rule can robustly use retinal waves to drive eye segregation and retinotopic refinement. Thus, by measuring plasticity induced by natural activity patterns, synaptic learning rules can be linked directly to their larger role in instructing the patterning of neural connectivity. PMID:17341130

Butts, Daniel A; Kanold, Patrick O; Shatz, Carla J

2007-03-01

54

Activation of Postsynaptic GABAB Receptors Modulates the Bursting Pattern and Synaptic Activity of Olfactory Bulb Juxtaglomerular Neurons  

PubMed Central

Olfactory bulb glomeruli are formed by a network of three major types of neurons collectively called juxtaglomerular (JG) cells, which include external tufted (ET), periglomerular (PG), and short axon (SA) cells. There is solid evidence that ?-aminobutyric acid (GABA) released from PG neurons presynaptically inhibits glutamate release from olfactory nerve terminals via activation of GABAB receptors (GABAB-Rs). However, it is still unclear whether ET cells have GABAB-Rs. We have investigated whether ET cells have functional postsynaptic GABAB-Rs using extracellular and whole cell recordings in olfactory bulb slices. In the presence of fast synaptic blockers (CNQX, APV, and gabazine), the GABAB-R agonist baclofen either completely inhibited the bursting or reduced the bursting frequency and increased the burst duration and the number of spikes/burst in ET cells. In the presence of fast synaptic blockers and tetrodotoxin, baclofen induced an outward current in ET cells, suggesting a direct postsynaptic effect. Baclofen reduced the frequency and amplitude of spontaneous EPSCs in PG and SA cells. In the presence of sodium and potassium channel blockers, baclofen reduced the frequency of miniature EPSCs, which were inhibited by the calcium channel blocker cadmium. All baclofen effects were reversed by application of the GABAB-R antagonist CGP55845. We suggest that activation of GABAB-Rs directly inhibits ET cell bursting and decreases excitatory dendrodendritic transmission from ET to PG and SA cells. Thus the postsynaptic GABAB-Rs on ET cells may play an important role in shaping the activation pattern of the glomeruli during olfactory coding.

Karpuk, Nikolay; Hayar, Abdallah

2008-01-01

55

Role for membrane fusion in the activation of the respiratory burst in human neutrophils  

SciTech Connect

Components of the respiratory burst oxidase reside in intracellular membranes of the tertiary granules in resting cells, yet oxidase activity in the activated cells occurs at the neutrophil surface. The role of degranulation in activation of the neutrophil respiratory burst was therefore investigated. Surface labeling experiments were carried out on resting and activated neutrophils using three impermeant labeling methods. Activated neutrophils labeled with (/sup 35/S) diazobenzene sulfonic acid showed a fourfold higher specific radioactivity than resting neutrophils. Similar results were obtained with the pyridoxal phosphate/borotritide labeling method. On the other hand, little difference in labeling was seen using the periodate/borotritide method which detects the carbohydrate of glycoproteins. These results suggest that either a large amount of protein, or a highly reactive protein becomes exposed upon activation. Resting, activated, and enucleated cells were labeled using the (/sup 125/I) lactoperoxidase method, then subjected to polyacrylamide gel electrophoresis. Autoradiograms of these gels showed that two proteins of about 75 and 45 kD, are labeled at the external surface of enucleated and activated cells but not resting cells.

Manara-Shediac, F.S.

1986-01-01

56

Inhibition of the neutrophil oxidative burst by sphingoid long-chain bases: role of protein kinase C in the activation of the burst  

SciTech Connect

The neutrophil oxidative burst is triggered by a variety of both particulate (opsonized zymosan) and soluble agonists (formylmethionylleucylphenylalanine (FMLP), arachidonate, short-chained diacylglycerols (DAG) and phorbol myristate acetate (PMA)). The authors show that the long-chain lipid bases sphinganine and sphingosine block activation of the burst in human neutrophils. Inhibition is reversible, does not alter cell viability, and does not affect phagocytosis. The inhibition affects the activation mechanism rather than the NADPH-oxidase enzyme. The structural requirements for inhibition include a hydrophobic carbon chain and an amino-containing headgroup, and the naturally occurring erythro sphinganine was more potent than the threo isomer. Activation of the oxidative burst by a variety of agonists was blocked by the same concentration of sphinganine indicating a common inhibited step. The authors suggest that the common step is protein kinase C, as evidenced by the following: 1) long-chain bases inhibit PKC in a micelle reconstituted system, 2) PMA-induced phophorylation is inhibited by sphinganine, and 3) sphinganine competes with (/sup 3/H)-phorbol dibutyrate for its cytosolic receptor (i.e. protein kinase C). The authors suggest that sphingoid long-chain bases play a role in the cellular regulations.

Wilson, E.; Olcott, M.C.; Bell, R.M.; Merrill, A.H.; Lambeth, J.D.

1986-05-01

57

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

PubMed Central

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

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

2012-01-01

58

Spontaneous electrical activity in the human fetal cortex in vitro.  

PubMed

Our knowledge about the developing human cerebral cortex is based on the analysis of fixed postmortem material. Here we use electrical recordings from unfixed human postmortem tissue to characterize the synaptic physiology and spontaneous network activity of pioneer cortical neurons ("subplate neurons"). Our electrophysiological experiments show that functional glutamate or GABA ionotropic receptors are expressed on human subplate (SP) neurons as early as 20 gestational weeks. Extracellular (synaptic) stimulations evoked postsynaptic potentials in a very small fraction of SP neurons, suggesting that functional synaptic contacts are rare at midgestation. Although synaptic inputs were scarce, we regularly observed spontaneous (unprovoked) electrical activity among human SP neurons, comprised of sustained plateau depolarizations and bursts of action potential firing, which resembled cortical UP and DOWN states in the adult neocortex. Plateau depolarizations and bursts of action potential firing are thought to depend on the mature morphology and physiology of adult cortical network. However, our current data reveal that similar cortical rhythm is generated by a very immature ensemble of human fetal neurons. In the relative absence of sensory inputs, as in development in utero, or in slow-wave sleep (i.e., throughout the entire lifespan), the spontaneous slow oscillatory pattern (UP and DOWN states) is a fundamental aspect of human cortical physiology. PMID:21325506

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

2011-02-16

59

New Method to Model the Equivalent Circuit of the Pulse Generator in Electrical Fast Transient/Burst Test  

NASA Astrophysics Data System (ADS)

This paper presents an accurate and systematic method to model the equivalent circuit of pulse generator in the electrical fast transients/burst test (EFT/B). Firstly, a new analytical expression is presented to express the generator's charging and discharging process under open-condition (1000-?), which all its coefficients are determined according to the output waveform specified by the manufacturer. And then, with adoption of the step source, the transfer function of the pulse forming network in Laplace domain is deduced, which is ready for the network synthesis. Based on above discussion, the parameterized method and the technique of constant-resistance are adopted for the network synthesis. Finally, the equivalent circuit is renormalized and improved to meet the specification under matching-condition (50-?). In this way, the equivalent circuit of EFT/B generator is obtained and can be adjusted conveniently to satisfy the different manufacturers. The PSPICE simulation with a certain load is validated by measurement.

Zhai, Xiaoshe; Geng, Yingsan; Wang, Jianhua; Song, Zhengxiang; Chen, Degui

60

Electrical activity in the rectum of anaesthetized dogs.  

PubMed

There is limited data available on the electrical activity of the rectum. An in vivo canine model was developed to record 240 extracellular electrograms simultaneously from the serosal surface of the rectum thereby enabling an off-line reconstruction of the behaviour of the electrical signals. Serosal rectal electrical activity is characterized by brief bursts of action potentials (=spikes) with a frequency of 22 cycles min(-1). High-resolution mapping of these signals revealed predominant propagation of these spikes in the longitudinal direction, originating from any site and conducted for a limited time and length before stopping spontaneously, thereby describing a patch of activity. The dimension of the patches in the longitudinal direction was significantly longer than the transversal width (13.6 vs 2.4 mm; P < 0.001). Spike propagation could occur in the aboral (46% of cases), in the oral (34%) or in both directions (20%). A bolus of betanechol (i.v., 0.5 mg kg(-1)) increased the frequency of the spikes without affecting size, shape or orientation of the patches. As in other parts of the gastrointestinal system, individual spike propagation in the rectum is limited to small areas or patches. The contractile activity of the organ could possibly reflect this underlying pattern of electrical behaviour. PMID:16771772

Lammers, W J E P; Abazer, F A; Ver Donck, L; Smets, D; Schuurkes, J A J; Coulie, B

2006-07-01

61

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

62

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

PubMed

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

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

2013-04-10

63

The Sources of Gamma-Ray Bursts and Their Connections with QSOs and Active Galaxies  

NASA Astrophysics Data System (ADS)

It is shown that the redshifts zo of ?-ray burst (GRB) sources, where they have been measured, together with the redshifts for seven quasars (QSOs) that lie very close to the positions of the unidentified sources GRB 990625, 000210, 001105 (two QSOs), 940720, 991217, and 990506, show a remarkable tendency to cluster about several of the periodic redshift peaks previously established for QSOs at z=0.061, 0.30, 0.60, 0.96, 1.41, 1.96, 2.63, 3.44, and 4.45. In 1971, Karlsson showed that these peaks lie in a series with ?log(1+z)=0.089. Out of a total of 32 currently known redshifts of GRBs, afterglows, or QSOs very close to burst positions, two are very close to 0.30, three are close to 0.60, nine are equal to or very close to 0.96, three are very close to 1.41, six are close to 1.96, two are close to 3.44, and one is very close to 4.45. Statistical tests by W. Napier show that the observed redshifts zo showed periodicity at the 98% confidence level. In addition, very close to the positions of two bursts GRB 990625 and GRB 001105, many QSOs with redshifts close to the peak values have been found. Since zo=[(1+zc)(1+zD)(1+zi)-1], where zc, zD, and zi are the cosmological, Doppler, and intrinsic components of the observed redshift zo, the existence of these peaks suggests that zo~=zi, so that both zc and zD are very much less than zo. However, while the observed values of zo are very close to the corresponding values of zi, in most cases zo>zi, suggesting that in most cases zc is greater than it was found to be in earlier samples of X-ray QSOs that appear to be ejected from bright galaxies. It appears likely, therefore, that the GRB sources, like the QSOs, are ejected from active galaxies, most of which have comparatively small cosmological redshifts 0.02<=zc<=0.1, thus suggesting that the distances of most of the GRB sources are <=500 Mpc. A possible example of an active galaxy that has given rise to such phenomena is UGC 12348 (zi=0.03). This galaxy has two GRB sources and three QSOs with measured redshifts zo that lie very close to intrinsic redshift peaks all lying within 1° of it. Among these five objects, the QSO at z=3.7 lies inside the error box for the unidentified burst GRB 991217.

Burbidge, G. R.

2003-03-01

64

Slow Variable Dominance and Phase Resetting in Phantom Bursting  

PubMed Central

Bursting oscillations are common in neurons and endocrine cells. One type of bursting model with two slow variables has been called ‘phantom bursting’ since the burst period is a blend of the time constants of the slow variables. A phantom bursting model can produce bursting with a wide range of periods: fast (short period), medium, and slow (long period). We describe a measure, which we call the ‘dominance factor’, of the relative contributions of the two slow variables to the bursting produced by a simple phantom bursting model. Using this tool, we demonstrate how the control of different phases of the burst can be shifted from one slow variable to another by changing a model parameter. We then show that the dominance curves obtained as a parameter is varied can be useful in making predictions about the resetting properties of the model cells. Finally, we demonstrate two mechanisms by which phase-independent resetting of a burst can be achieved, as has been shown to occur in the electrical activity of pancreatic islets.

Watts, Margaret; Tabak, Joel; Zimliki, Charles; Sherman, Arthur; Bertram, Richard

2011-01-01

65

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

66

Government Activities to Protect the Electric Grid.  

National Technical Information Service (NTIS)

The electric utility system is vulnerable to outages caused by a range of activities, including system operator errors, weather-related damage, and terrorist attacks. The main risk from a successful terrorist attack against the electric power industry wou...

A. Abel

2005-01-01

67

Elselskabernes sideordnede aktiviteter. (Electricity companies' extraordinary activities).  

National Technical Information Service (NTIS)

An investigation of the extent of activities related to thermal electric power stations, which did not have any direct connection to the production, distribution and transmission of electricity, was carried out. The aim was to discover the economic conseq...

1992-01-01

68

Simultaneous flow cytometric measurement of phagocytotic and oxidative burst activity of polymorphonuclear leukocytes in whole bovine blood  

Microsoft Academic Search

Polymorphonuclear neutrophils (PMN) are important in host defence against bacterial infection in the bovine mammary gland and techniques are needed to evaluate their functional activities. A rapid and sensitive two-color flow cytometric method for simultaneous measurement of phagocytosis arte and oxidative burst activity of bovine PMN in small blood samples is described. The method utilizes the oxidation of intracellular dihydrorhodamine

E. Smits; C. Burvenich; R. Heyneman

1997-01-01

69

Regulation of Erythropoietin and Burst-Promoting Activity Production in Patients with Aplastic Anemia and Iron Deficiency Anemia  

Microsoft Academic Search

To clarify the control mechanism of production of erythropoietic growth factors in anemic states, we compared erythropoietin (Epo) and burst-promoting activity (BPA) in patients with aplastic anemia and iron deficiency anemia, using in vitro erythroid progenitor assays. Although serum levels of Epo activity increased in the presence of anemia, the rise was more marked in patients with aplastic anemia. BPA

Naohisa Takeichi; Tsukuru Umemura; Junji Nishimura; Seiji Motomura; Mitsuo Kozuru; Hiroshi Ibayashi

1988-01-01

70

[Monosynaptic pathway responsible for generation of burst activity in neuron PPa1 of Helix pomatia].  

PubMed

The connections between an interneuron in the visceral ganglion initiating the pacemaker activity in RPa1 neuron and RPa1 neuron itself have been analyzed in snail. The interneuron stimulation led to initiation of the bursting activity in the RPa1 neuron. Replacement of extracellular Ca2+ by Mg2+ ions, as well as addition of CdCl2 to the external solution reversibly inhibited the effect of the interneuronal stimulation on the RPa1 neuron. An increase of extracellular Ca2+ ions concentration to 70 mM did not prevent the effect. Intracellular Cs+ and TEA injection in the interneuron increasing the action potential duration in the interneuron increased also the effectiveness of connection between the neurons. It is concluded that the connection between the neurons under investigation is monosynaptic and peptidergic. PMID:2437466

Kononenko, N I; Osipenko, O N

1987-01-01

71

Activation of the lipoxygenase pathway in the methionine enkephalin induced respiratory burst in human polymorphonuclear leukocytes  

SciTech Connect

In comparative studies of f-met-Leu-Phe (FMLP) and methionine enkephalin (ME) induced polymorphonuclear leukocyte (PMNL) stimulation the following results were obtained: (i) both FMLP and ME increased the intracellular killing (IK) capability of human PMNLs probably through NADPH oxidase activation, (ii) the ME-induced respiratory burst (RB) differed from the chemotactic peptide FMLP-triggered superoxide generation because the former was not accompanied by the activation of the glutathione system and the duration of the superoxide production was prolonged. The reaction was dependent on lipoxygenation, was potentiated by indomethacin (IM) and was inhibited by nordihidro-guairetic acid (NDGA), (iii) both /sup 14/C-arachidonic acid release and leukotriene B/sub 4/ (LTB/sub 4/) synthesis of ME-treated PMNLs were elevated as compared to those of FMLP triggered cells. Their results suggest that lipoxygenation and even an increased LTB/sub 4/ synthesis are involved in the ME-induced RB of leukocytes.

Nagy, J.T.; Foris, G.; Fulop, T. Jr.; Paragh, G.; Plotnikoff, N.P.

1988-01-01

72

Bursting into the Nucleus  

NSDL National Science Digital Library

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

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

2008-12-23

73

[Induction of slow membrane potential oscillations and burst activity in neuron PPa1 of Helix pomatia by a calcium ionophore and serotonin].  

PubMed

The nonbursting pattern of activity of the neuron RPa1 in preparations from dormant snails Helix lucorum was reversibly transformed into the bursting one by addition of Ca-ionophore A23187 (10(-6)-10(-5) M) or serotonin (10(-5)-10(-4) M) into the saline. The slow waves underlying bursts disappeared in presence of quinine (10(-4) M) thus suggesting involvement of Ca-dependent K-conductance in the mechanism of burst generation. PMID:3919320

D'iakonova, T L; Sakharov, D A

1985-01-01

74

From Plateau to Pseudo-Plateau Bursting: Making the Transition  

PubMed Central

Bursting electrical activity is ubiquitous in excitable cells such as neurons and many endocrine cells. The technique of fast/slow analysis, which takes advantage of time scale differences, is typically used to analyze the dynamics of bursting in mathematical models. Two classes of bursting oscillations that have been identified with this technique, plateau and pseudo- plateau bursting, are often observed in neurons and endocrine cells, respectively. These two types of bursting have very different properties and likely serve different functions. This latter point is supported by the divergent expression of the bursting patterns into different cell types, and raises the question of whether it is even possible for a model for one type of cell to produce bursting of the type seen in the other type without large changes to the model. Using fast/slow analysis, we show here that this is possible, and we provide a procedure for achieving this transition. This suggests that the design principles for bursting in endocrine cells are just quantitative variations of those for bursting in neurons.

Teka, Wondimu; Tsaneva-Atanasova, Krasimira; Bertram, Richard; Tabak, Joel

2011-01-01

75

Bursts of calving activity and controls on the terminus position of Yahtse Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The tidewater glacier terminus is the interface that links oceanic and glaciological processes. Tidewater glaciers contribute large amounts of cold, fresh water to their fjords. Ocean heat exerts a significant control on glacier mass balance. On the Gulf of Alaska, the terminus of tidewater Yahtse Glacier has advanced slowly since its 1990 post-Little Ice Age minimum. At Yahtse's terminus, ice flowing at 18 m/d encounters water with temperatures of up to 10.5°C (measured 1.5 km from the terminus). Profiles of temperature and salinity in Icy Bay, in which Yahtse Glacier terminates, have revealed a strongly stratified, single-cell circulation pattern. Fresh, glacier outflow exits the bay atop warm, saline Gulf of Alaska water. The Alaska Coastal Current, a major source of Icy Bay water, has warmed by 1°C over the last 40 years. These observations prompt the question of how a tidewater advance may be sustained in spite of warming ocean and atmosphere temperatures. Superimposed on Yahtse Glacier's longer-term advance have been smaller-scale summer retreats and winter-spring re-advances. These smaller fluctuations indicate that factors that change on short timescales, such as ocean conditions and weather, also have an important control on terminus position. Observed bursts in calving frequency are a further reflection of the unsteady conditions at the glacier terminus. In the present study, we use seismograms recorded on bedrock within 500 m of the glacier terminus as a calving counter. The epicenters of a significant majority of glacier-generated seismic events within the St. Elias Mountains have been located to within 15 km of the terminus of Yahtse Glacier. Previous study at Yahtse Glacier has revealed that at least 75% of these seismic events originate from calving processes, most notably through the interactions between iceberg and water. Calving frequency is characterized by a relatively steady rate of background events, punctuated by bursts of calving activity. These bursts are correlated with rain-associated speed-ups that are present along at least 75% of the glacier length. Our analysis of these results considers the relative importance of three potential calving-related processes: along-glacier coupling in glacier flow that forces ice off the end of a submarine terminal moraine, submarine melt and undercutting of the terminus, and enhanced subaerial melt of serac pillars by rainwater that weakens the foundations of these pillars.

Bartholomaus, T. C.; Larsen, C. F.; West, M. E.; Oneel, S.

2011-12-01

76

Simultaneous Estimation of Electrical and Thermal Properties of 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 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

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

2010-01-01

77

Patterns of electric organ discharge activity in the weakly electric fish Brienomyrus niger L. (Mormyridae).  

PubMed

In this study we investigated the electric organ discharge (EOD) activity of the mormyrid fish Brienomyrus niger when they were not affected by conspecific EODs. The fish emitted two types of EOD patterns: phasic and tonic sequences of pulse intervals (SPIs). The phasic SPI occurred in the form of stereotyped, individual-specific bursts in EOD activity which we called scallop. Tonic SPIs varied in mean EOD repetition rate and pulse interval stability, and consisted of either regular activity with mean frequencies exceeding 10 Hz and a coefficient of variation (cv) below 15%, or variable activity with mean rates below 10 Hz and cv's of 15% and above. Individual fish predominantly generated one of the three patterns: "variable", "regular", or "scallop". Most fish emitted "variable" activity, but "regular" activity was typical of females and "scallop" of males. We suggest that these SPIs may facilitate individual recognition. The dynamics of the electromotor command system, as reflected by the fish's EOD activity, is compared with that of the well-studied mammalian inferior olive, and mechanisms for a possible self-regulatory central pattern generator are discussed. PMID:2620705

Serrier, J; Moller, P

1989-01-01

78

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

Microsoft Academic Search

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

R Wong; C. J. Shatz

1993-01-01

79

Vortex Bursting.  

National Technical Information Service (NTIS)

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...

H. Werle

1984-01-01

80

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

NASA Astrophysics Data System (ADS)

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 (?), thermal conductivity (k), density (?), and specific heat (Cp) 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

2010-02-01

81

Theoretical studies on the electrical activity of pancreatic beta-cells as a function of glucose.  

PubMed Central

The electrical activity of pancreatic beta-cells, which has been closely correlated both with intracellular Ca2+ concentration and insulin release, is characterized by a biphasic response to glucose and bursts of spiking action potentials. Recent voltage clamp and single channel patch clamp experiments have identified several transmembrane ionic channels that may play key roles in the electrophysiological behavior of beta-cells. There is a hypothesis that Ca2+-activated K+ channels are responsible for both the resting potential during low glucose concentration and the silent phase during bursting. The discovery of the ATP-inactivated K+ channel raises the possibility that the current for this latter K+ channel may dominate the resting potential, while the Ca2+-activated K+ current dominates the silent phase potential between bursts. The recent discovery that Ca2+-activated K+ channels are pH sensitive raises an interesting possibility for the biphasic electrical response. In this paper, numerical methods are presented for evaluating these hypotheses against experimental evidence.

Himmel, D M; Chay, T R

1987-01-01

82

Arsenic stress elicits cytosolic Ca(2+) bursts and Crz1 activation in Saccharomyces cerevisiae.  

PubMed

Although arsenic is notoriously poisonous to life, its utilization in therapeutics brings many benefits to human health, so it is therefore essential to discover the molecular mechanisms underlying arsenic stress responses in eukaryotic cells. Aiming to determine the contribution of Ca(2+) signalling pathways to arsenic stress responses, we took advantage of the use of Saccharomyces cerevisiae as a model organism. Here we show that Ca(2+) enhances the tolerance of the wild-type and arsenic-sensitive yap1 strains to arsenic stress in a Crz1-dependent manner, thus providing the first evidence that Ca(2+) signalling cascades are involved in arsenic stress responses. Moreover, our results indicate that arsenic shock elicits a cytosolic Ca(2+) burst in these strains, without the addition of exogenous Ca(2+) sources, strongly supporting the notion that Ca(2+) homeostasis is disrupted by arsenic stress. In response to an arsenite-induced increase of Ca(2+) in the cytosol, Crz1 is dephosphorylated and translocated to the nucleus, and stimulates CDRE-driven expression of the lacZ reporter gene in a Cnb1-dependent manner. The activation of Crz1 by arsenite culminates in the induction of the endogenous genes PMR1, PMC1 and GSC2. Taken together, these data establish that activation of Ca(2+) signalling pathways and the downstream activation of the Crz1 transcription factor contribute to arsenic tolerance in the eukaryotic model organism S. cerevisiae. PMID:22745270

Ferreira, Rita T; Silva, Ana R Courelas; Pimentel, Catarina; Batista-Nascimento, Liliana; Rodrigues-Pousada, Claudina; Menezes, Regina A

2012-06-28

83

Gamma-Ray Burst Wallsheet  

NSDL National Science Digital Library

The Gamma-ray Burst Wallsheet was developed to illustrate the properties of light emanating from a gamma-ray burst as seen by three distant satellites, including NASA's Swift. The back of the wallsheet has one of the three activities in the accompanying educator guide (Angling for Gamma-ray Bursts).

2005-01-01

84

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

85

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

PubMed

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

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

2013-06-27

86

Influence of age and sex on the pressor response following a spontaneous burst of muscle sympathetic nerve activity  

PubMed Central

The sympathetic nervous system is critical for the beat-to-beat regulation of arterial blood pressure (BP). Although studies have examined age- and sex-related effects on BP control, findings are inconsistent and limited data are available in postmenopausal women. In addition, the majority of studies have focused on time-averaged responses without consideration for potential beat-to-beat alterations. Thus we examined whether the ability of muscle sympathetic nerve activity (MSNA) to modulate BP on a beat-to-beat basis is affected by age or sex. BP and MSNA were measured during supine rest in 40 young (20 men) and 40 older (20 men) healthy subjects. Beat-to-beat fluctuations in mean arterial pressure (MAP) were characterized for 15 cardiac cycles after each MSNA burst using signal averaging. The rise in MAP following an MSNA burst was similar between young men and women (+2.64 ± 0.3 vs. +2.57 ± 0.3 mmHg, respectively). However, the magnitude of the increase in MAP after an MSNA burst was reduced in older compared with young subjects (P < 0.05). Moreover, the attenuation of the pressor response was greater in older women (+1.20 ± 0.1 mmHg) compared with older men (+1.72 ± 0.2 mmHg; P < 0.05). Interestingly, in all groups, MAP consistently decreased after cardiac cycles without MSNA bursts (nonbursts) with the magnitude of fall greatest in older men. In summary, healthy aging is associated with an attenuated beat-to-beat increase in BP after a spontaneous MSNA burst, and this attenuation is more pronounced in postmenopausal women. Furthermore, our nonburst findings highlight the importance of sympathetic vasoconstrictor activity to maintain beat-to-beat BP, particularly in older men.

Vianna, Lauro C.; Hart, Emma C.; Fairfax, Seth T.; Charkoudian, Nisha; Joyner, Michael J.

2012-01-01

87

Gold complexes and activation of human polymorphonuclear leukocytes. Dissociation of changes in membrane potential and oxidative burst.  

PubMed

The effects of the gold compounds on the alteration of membrane potential of polymorphonuclear leukocytes (PMN) in response to various stimulants have been compared with their effects on the oxidative burst. The present studies have shown that gold complexes [auranofin (AF), aurothiomalate (Autm), aurocyanide (Au(CN)2-)] have contrasting effects on the membrane potential of 3,3'-dipentyloxacarbocyanine [di-O-C5(3)] loaded PMN. Au(CN)2- at concentrations which inhibit the oxidative burst of PMN did not affect the membrane depolarization after activation of PMN by phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl phenylalanine (FMLP); Autm slightly stimulated the oxidative burst but had no effect on the depolarization of PMN. In contrast, AF inhibited the depolarization of stimulated PMN to an extent depending upon the concentration of AF, the time of preincubation and the stimulus. The membrane depolarization of PMN caused by PMA, FMLP and concanavalin A (ConA) was inhibited by AF (5 microM) but the depolarization induced by calcium ionophore (A23187) was not affected. AF at the same conditions inhibits the oxidative burst of PMN induced by all these single stimuli including the calcium ionophore. Dissociation of membrane depolarization and superoxide generation caused by AF was also seen in PMN activated by two stimuli. AF (5 microM) had little initial inhibitory effect on the oxidative burst of PMN stimulated by combinations of PMA and ConA or PMA and FMLP whereas it almost totally blocked the depolarization caused by these combinations. Preincubation of cells with 5 microM AF for less than 5 min prior to the addition of PMA allowed membrane depolarization which was followed rapidly by repolarization. None of the gold complexes studied had any effect on the resting membrane potential of PMN. PMID:1417933

Rudkowski, R; Ziegler, J B; Graham, G G; Joulianos, G

1992-09-25

88

Overview of Electric Propulsion Activities at NASA.  

National Technical Information Service (NTIS)

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 tech...

J. W. Dunning J. A. Hamley R. S. Jankovsky S. R. Oleson

2004-01-01

89

Reliability of burst superimposed technique to assess central activation failure during fatiguing contraction  

Microsoft Academic Search

Recording a superimposed electrically-induced contraction at the limit of endurance during voluntary contraction is used as an indicator of failure of muscle activation by the central nervous system and discards the existence of peripheral muscle fatigue. We questioned on the reliability of this method by using other means to explore peripheral muscle failure. Fifteen normal subjects sustained handgrip at 60%

Erick Dousset; Yves Jammes

2003-01-01

90

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

SciTech Connect

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

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

1989-08-01

91

Brain Electrical Activity Mapping (BEAM) Interim Guidelines.  

National Technical Information Service (NTIS)

The BEAM equipment is a neurophysiological diagnostic device which converts the output of a 20-channel electroencephalograph (EEG) into a color contour map of the electrical activity at the surface of the brain. Preliminary data on clinical efficacy indic...

J. Murphy

1983-01-01

92

[Postsynaptic mechanisms of the initiation of burst activity in neuron PPa1 of Helix pomatia in response to an interneuron].  

PubMed

Postsynaptic mechanisms of the connection between an interneuron initiating the bursting activity in neurons RPa1 and V7 and the neurons themselves were examined. Under voltage clamp conditions a slow inward current could be recorded in these neurons after stimulation of the interneuron. A decrease of temperature reduced the speed of rise and fall of this current with a temperature coefficient about 10. The current-voltage characteristic of the slow inward current had a maximum near -65 mV. The decrease in external concentration of Na+ ions led to a decrease of its amplitude. At the maximum of this current short hyperpolarizing pulses induced outward currents instead of inward ones. It is concluded that interneuronal stimulation activate at least two types of ionic channels in the bursting neurons soma. This process, perhaps, is mediated via a chain of cytoplasmic biochemical reactions. PMID:2437467

Kononenko, N I; Osipenko, O N

1987-01-01

93

Monocytes Constitute the Only Peripheral Blood Cell Population Showing an Increased Burst Activity in Multiple Sclerosis Patients  

Microsoft Academic Search

We examined peripheral mononuclear cells (PMNC), peripheral polymorphonuclear cells (PPNC), adherent mononuclear cells, non-adherent mononuclear cells, non-phagocytic mononuclear cells and non-phagocytic Percoll-fractionated mononuclear cells of multiple sclerosis (MS) patients for their spontaneous burst activity (B A). According to previous results PMNC of MS patients showed a markedly increased BA (p = 0.0002); PPNC, however, did not show significantly elevated values

Klaus P. Hammann; Hanns C. Hopf

1986-01-01

94

Effect of Hydrocortisone on BFU-E Growth and on Burst-Promoting Activity of T Lymphocytes in Man  

Microsoft Academic Search

Glucocorticosteroid hormones have been reported either to stimulate or to inhibit human erythropoiesis. We have studied the in vitro effect of hydrocortisone, 10-6 mol\\/l, on human BFU-E when stimulated by preconstituted burst-promoting activity (BPA) in a medium conditioned by T lymphocytes. Hydrocortisone was found to stimulate BFU-E growth, even at largely suboptimal concentrations of BPA, through hormone receptors, as the

L. Morra; A. Ponassi; F. Moccia; G. S. Mela; I. Ponassi; G. Bessone

1989-01-01

95

Ortho-Substituted Polychlorinated Biphenyls Activate Respiratory Burst Measured as Luminol-Amplified Chemoluminescence in Human Granulocytes  

Microsoft Academic Search

The effect of polychlorinated biphenyls (PCBs) on the activation of respiratory burst measured as luminol-amplified chemoluminescence in human granulocytes is elucidated here. Chemoluminescence was stimulated in a concentration-dependent manner (ED50? 10 ?M) byortho-substituted PCB congeners, whilemeta- andpara-substituted congeners had no significant effect. Twoortho-substituted PCB congeners were chosen for the mechanistic studies, namely 2,2?,4,4?-TeCB and 2,2?-DCB, since they have been used

Ø. A. Voie; P. Wiik; F. Fonnum

1998-01-01

96

Priming effect of fibronectin on respiratory burst of human neutrophils induced by formyl peptides and platelet-activating factor  

Microsoft Academic Search

Fibronectin (FN), a glycoprotein present in the plasma and the extracellular matrix, has been shown to enhance adherence-related functions of polymorphonuclear leukocytes (PMNs). In this study we investigated the effects of FN on the activation of human PMNs in suspension by soluble stimuli, as determined by the generation of Superoxide radicals (respiratory burst). FN (up to 100?g\\/ml) did not directly

Lena Stanislawski; Trung Pham Huu; Axel Perianin

1990-01-01

97

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

PubMed

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

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

2012-08-02

98

The Sources of Gamma-Ray Bursts and Their Connections with QSOs and Active Galaxies  

Microsoft Academic Search

It is shown that the redshifts zo of gamma-ray burst (GRB) sources, where they have been measured, together with the redshifts for seven quasars (QSOs) that lie very close to the positions of the unidentified sources GRB 990625, 000210, 001105 (two QSOs), 940720, 991217, and 990506, show a remarkable tendency to cluster about several of the periodic redshift peaks previously

G. R. Burbidge

2003-01-01

99

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

PubMed Central

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

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

1989-01-01

100

How Noise and Coupling Induce Bursting Action Potentials in Pancreatic ?-Cells  

PubMed Central

Unlike isolated ?-cells, which usually produce continuous spikes or fast and irregular bursts, electrically coupled ?-cells are apt to exhibit robust bursting action potentials. We consider the noise induced by thermal fluctuations as well as that by channel-gating stochasticity and examine its effects on the action potential behavior of the ?-cell model. It is observed numerically that such noise in general helps single cells to produce a variety of electrical activities. In addition, we also probe coupling via gap junctions between neighboring cells, with heterogeneity induced by noise, to find that it enhances regular bursts.

Jo, Junghyo; Kang, Hyuk; Choi, Moo Young; Koh, Duk-Su

2005-01-01

101

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

102

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.

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

2009-01-01

103

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

NASA Astrophysics Data System (ADS)

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

Duarte, Jorge; Januário, Cristina; Martins, Nuno

2009-11-01

104

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

PubMed Central

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

Coles, J A; Poulain, D A

1991-01-01

105

Regulation by glucose of oscillatory electrical activity and 5-HT/insulin release from single mouse pancreatic islets in absence of functional K(ATP) channels.  

PubMed

The glucose sensitivity of bursting electrical activity and pulsatile insulin release from pancreatic islets was determined in absence of functional K(ATP) channels. Membrane potential, [Ca(2+)](i) and 5-HT/insulin release were measured by intracellular recording, fura-2 fluorescence and 5-HT amperometry, respectively. Single mouse islets, bathed in tolbutamide or glibenclamide and high extracellular Ca(2+) (Ca(2+)(o)), displayed bursting activity and concomitant fast [Ca(2+)](i) and 5-HT/insulin oscillations. Sulphonylurea block of K(ATP) channel current was unaffected by raising Ca(2+)(o). Raising glucose or alpha-ketoisocaproic acid (KIC) concentration from 3 to 30 mM increased spiking activity and burst plateau duration. Staurosporine did not impair glucose potentiation of electrical activity, ruling out the involvement of serine/threonine kinases. Glucose enhanced both [Ca(2+)](i) and 5-HT/insulin oscillatory activity, causing a approximately 3-fold increase in overall 5-HT release rate. Cells lacking bursting activity in high Ca(2+)(o) and low glucose (or KIC) developed a pattern of intensified spiking in response to 11 mM glucose. It is concluded that beta-cells exhibit graded oscillatory electrical and secretory responses to glucose in absence of functional K(ATP) channels. This suggests that, under physiological conditions, early glucose sensing may involve other channels besides the K(ATP) channel. PMID:18493109

Rosário, Luís M; Barbosa, Rui M; Antunes, Célia M; Baldeiras, Inês E; Silva, Amélia M; Tomé, Angelo R; Santos, Rosa M

2008-05-21

106

Effect of Burst-Promoting Activity (BPA) and Erythropoietin on Hemoglobin Biosynthesis in Culture  

Microsoft Academic Search

relationship between the concentration and the relative rate of HbF biosynthesis by circulating erythropoietic precursors was clearly observed. In contrast. increasing the concentration of purified Ep enhanced the synthesis of HbF and HbA equally. BPA from bone marrow conditioned media and T-cell conditioned media enhanced the relative rate of HbF biosynthesis and burst number at limiting serum concentrations (1 0%-i

Takashi Terasawa; Makio Ogawa; Pamela N. Porter; David W. Golde; Eugene Goldwasser

1980-01-01

107

Repetitive firing and oscillatory activity of pyramidal-like bursting neurons in the rat subiculum  

Microsoft Academic Search

Electrophysiological characterization of neurons within the rat subiculum was carried out with intracellular recordings in\\u000a an in vitro slice preparation. Subicular neurons responded to threshold pulses of depolarizing current delivered at a resting\\u000a membrane potential (RMP) of –65.7±5.8 mV (mean±SD, n=85) with an initial burst of three to five fast action potentials that rode on a depolarizing envelope and was

D. Mattia; Hiroto Kawasaki; Massimo Avoli

1997-01-01

108

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

109

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

PubMed

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

Masurkar, Arjun V; Chen, Wei R

2012-01-25

110

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.

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

1991-01-01

111

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

2013-06-10

112

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

2012-04-12

113

Electrical and contractile activities of the human rectosigmoid  

Microsoft Academic Search

Electrical and mechanical activities were recorded from the rectosigmoid of normal subjects using an intraluminal recording tube with two sets of bipolar electrodes and strain gauges. Four distinct types of electrical activities were recorded. (1) Electrical control activity (ECA). This activity varied in amplitude and frequency over time and the control waves were not phase-locked. The means of dominant frequency

S Sarna; P Latimer; D Campbell; W E Waterfall

1982-01-01

114

Burst analysis tool for developing neuronal networks exhibiting highly varying action potential dynamics  

PubMed Central

In this paper we propose a firing statistics based neuronal network burst detection algorithm for neuronal networks exhibiting highly variable action potential dynamics. Electrical activity of neuronal networks is generally analyzed by the occurrences of spikes and bursts both in time and space. Commonly accepted analysis tools employ burst detection algorithms based on predefined criteria. However, maturing neuronal networks, such as those originating from human embryonic stem cells (hESCs), exhibit highly variable network structure and time-varying dynamics. To explore the developing burst/spike activities of such networks, we propose a burst detection algorithm which utilizes the firing statistics based on interspike interval (ISI) histograms. Moreover, the algorithm calculates ISI thresholds for burst spikes as well as for pre-burst spikes and burst tails by evaluating the cumulative moving average (CMA) and skewness of the ISI histogram. Because of the adaptive nature of the proposed algorithm, its analysis power is not limited by the type of neuronal cell network at hand. We demonstrate the functionality of our algorithm with two different types of microelectrode array (MEA) data recorded from spontaneously active hESC-derived neuronal cell networks. The same data was also analyzed by two commonly employed burst detection algorithms and the differences in burst detection results are illustrated. The results demonstrate that our method is both adaptive to the firing statistics of the network and yields successful burst detection from the data. In conclusion, the proposed method is a potential tool for analyzing of hESC-derived neuronal cell networks and thus can be utilized in studies aiming to understand the development and functioning of human neuronal networks and as an analysis tool for in vitro drug screening and neurotoxicity assays.

Kapucu, Fikret E.; Tanskanen, Jarno M. A.; Mikkonen, Jarno E.; Yla-Outinen, Laura; Narkilahti, Susanna; Hyttinen, Jari A. K.

2012-01-01

115

THE CORPUS CALLOSUM MODULATES SPINDLE-BURST ACTIVITY WITHIN HOMOTOPIC REGIONS OF SOMATOSENSORY CORTEX IN NEWBORN RATS  

PubMed Central

The corpus callosum, a major interhemispheric fiber tract, mediates communication between homotopic regions within somatosensory cortex (S1). Recently, in 1-6-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 1–6-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 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 neocortex.

Jo Marcano-Reik, Amy; Blumberg, Mark S.

2008-01-01

116

C3a activates the respiratory burst in human polymorphonuclear neutrophilic leukocytes via pertussis toxin-sensitive G-proteins.  

PubMed

In contrast to C5a, which represents a well-established potent activator of the respiratory burst in polymorphonuclear neutrophilic granulocytes (PMN), the functional role of C3a in the activation of PMN is, so far, poorly understood. Herein, the potential role of human C3a in the activation of the respiratory burst in human PMN was investigated. The release of reactive oxygen species (ROS) of PMN from healthy donors was measured by lucigenin-dependent chemiluminescence. C3a dose-dependently induced the production of ROS in human PMN in the range between 10 ng/mL and 1,000 ng/mL, whereas C3a-desArg was inactive. Flow cytometric measurement of H2O2 by dihydrorhodamine-123 labeling of anti-CD16-stained PMN showed that predominantly neutrophilic PMN are responsible for the C3a-induced activation of the respiratory burst. To exclude that C3a stimulation was caused by contamination with C5a, the specificity of C3a-induced activation of PMN was shown using monoclonal antibodies (MoAbs). Accordingly, the effect of C3a was completely abolished in the presence of Fab fragments of a blocking anti-C3a MoAb. In addition, blockade of the C5a receptor by the anti-C5a receptor (anti-C5aR) MoAb, S5/1, totally inhibited the C5a-induced production of ROS, whereas the C3a response in the presence of the anti-C5aR MoAb was unaffected. The specificity of the response was further confirmed by homologous desensitization after restimulation with C3a. In contrast, no cross-desensitization was observed upon stimulation with C5a. The C3a-induced ROS production by PMN was inhibited by pertussis toxin, indicating the involvement of guanine nucleotide-binding proteins (Gi proteins) in the signal transduction process initiated by C3a. In addition, stimulation of PMN by C3a resulted in a transient increase in the cytosolic free calcium concentration ([Ca2+]i) in a dose-dependent manner. In contrast to C3a-induced ROS production, C3a did not induce a chemotactic response in PMN, indicating functional qualitative differences as compared with C5a. In summary, these results show that C3a is a potent activator of the respiratory burst in human PMN. Therefore, these findings point to a novel role of C3a in the pathogenesis of inflammatory diseases associated with increased C3a levels and PMN activation. PMID:8193368

Elsner, J; Oppermann, M; Czech, W; Kapp, A

1994-06-01

117

EMG Hand Burst Activity Detection Study Based on Hard and Soft Thresholding  

Microsoft Academic Search

Electric signal analysis from live organism is an old area that was documented by Francesco Redi dated from 1666, Walsh 1773,\\u000a and Galvani 1792 [1]. Contraction of muscular fibers by electric impulses was recorded by Debois-Raymmod 1849 [1]. Electric\\u000a impulses known as myolectric signal and their recording are named electromyographic signals or EMG [2-8]. The first clinical\\u000a use of EMG

Mario Ignacio Chacon Murguia; Leonardo Valencia Olvera; Alfonso Delgado Reyes

2009-01-01

118

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

PubMed

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

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

2013-07-24

119

Complex networks in brain electrical activity  

NASA Astrophysics Data System (ADS)

This letter reports a method to extract a functional network of the human brain from electroencephalogram measurements. A network analysis was performed on the resultant network and the statistics of the cluster coefficient, node degree, path length, and physical distance of the links, were studied. Even given the low electrode count of the experimental data the method was able to extract networks with network parameters that clearly depend on the type of stimulus presented to the subject. This type of analysis opens a door to studying the cerebral networks underlying brain electrical activity, and links the fields of complex networks and cognitive neuroscience.

Ray, C.; Ruffini, G.; Marco-Pallarés, J.; Fuentemilla, L.; Grau, C.

2007-08-01

120

Burst regimes of long-period irregular pulsations at frequencies of 2.0-6.0 mHz and substorm activity in the nightside magnetosphere  

NASA Astrophysics Data System (ADS)

The results of studying the simultaneous observations of burst regimes of long-period irregular pulsations at frequencies of 2.0-6.0 mHz (the series of ipcl bursts) in the region of the dayside polar cusp and magnetic field disturbances in the nightside auroral oval are presented. The data on the magnetic field at Mirny (MIR, ? = 76.93°; ? = 122.92°) and Yellowknife (YKC, ? = 69.94°; ? = 294.38°) antipodal observatories as well as the AE index values ( http://www.cetp.ipsl.fr/~isgi/homepag1.htm ) have been used in an analysis. It has been found out that 87% (group I) and 13% (group II) of events were registered against a back-ground of substorm activity and a quiet nightside magnetosphere, respectively. It has been revealed that several morphological characteristics of the group-I and -II ipcl bursts differ depending on the conditions in the nightside magnetosphere. It has been indicated that the intervals between peaks and the amplitudes of ipcl bursts of both types are distributed according to the exponential and power laws. The results indicate that magnetospheric plasma turbulence develops in the region where burst regimes are formed. It is assumed that the substorm processes in the magnetotail manifest themselves in plasma turbulence in the dayside cusp.

Kurazhkovskaya, N. A.; Klain, B. I.

2009-08-01

121

A low-pressure encapsulated deep reactive ion etched resonant pressure sensor electrically excited and detected using `burst' technology  

NASA Astrophysics Data System (ADS)

A purely silicon resonant pressure sensor fabricated using deep reactive ion etching (DRIE) and encapsulated at low pressure by two glass lids is presented. The sensor consists of a vibrating dual-diaphragm capsule suspended at four points in a fixed frame. The support beams are hollow and act as pressure inlet ports. As the ambient gas pressure changes, the resonator shape changes, thereby changing its resonance frequency. The sensor integrates corner holes and is encapsulated at low pressure to reduce squeezed-film damping effects between the resonating structure and the glass lid. The sensor is electrostatically excited into a balanced mode of oscillation and capacitively detected using a novel `burst' technology. This technique is based on independently exciting the structure and detecting the resulting output frequency at separate periods in time. Several sizes and design variations of the sensor have been fabricated and evaluated. Measurements show the smallest structure (5 mm membrane diameter width) to have a Q factor of 14 000 after low-pressure encapsulation, pressure sensitivity of 15 ppm/mbar-1 over the range 0.1-1500 mbar, and expected temperature sensitivity of -34 ppm °C-1. The structure had a resonance frequency of 35 078 Hz in atmospheric air pressure. If higher sensitivity is desired, a larger sensor can be chosen (140 ppm/mbar-1 for a sensor with a 10 mm wide membrane), however, at the expense of a lower Q factor.

Melin, Jessica; Enoksson, Peter; Corman, Thierry; Stemme, Göran

2000-06-01

122

Multiplicative optical tomography of cardiac electrical activity  

NASA Astrophysics Data System (ADS)

Cardiac electrical activity can be mapped today through the response of voltage-sensitive dyes; but poor transparency of muscle tissue has enforced shallow-depth imaging. We present a three-dimensional (3D) reconstruction method for electrical activity deep inside the myocardial wall. Our approach is nonlinear and differs substantially from standard diffusive optical tomography. It does not require matrix inversion, data regularization or a priori information concerning the original object. Opposite sides of a slab-shaped preparation are scanned in parallel by detection and illumination points with a constant vector offset between illumination and detection axes (biaxial scanning). Scanning is performed in two perpendicular directions. In each direction, a pair of 2D images is obtained under offsets of opposite signs. These two pairs are the input for a multiplicative reconstruction algorithm, whose output is a 3D image. The overall procedure was successfully tested on computer-generated sources that include points, lines and hemispheres, patterned after actual electrophysiological excitations. The algorithm is computationally efficient and stable with respect to varying noise levels in the raw data.

Wellner, Marcel; Bernus, Olivier; Mironov, Sergey F.; Pertsov, Arkady M.

2006-09-01

123

Early events in the perception of lipopolysaccharides in the brown alga Laminaria digitata include an oxidative burst and activation of fatty acid oxidation cascades  

Microsoft Academic Search

This study provides evidence that bacterial lipopoly- saccharides can be strong triggers of early events of defence reactions in the brown algal kelp Laminaria digitata, constituting the first report of a biological activity of this class of macromolecules in a marine alga. The early events include an oxidative burst, re- lease of free saturated and unsaturated fatty acids (FFAs) and

Frithjof C. Kupper; Emmanuel Gaquerel; Eva-Maria Boneberg; Siegfried Morath; Jean-Pierre Salaun; Philippe Potin

2006-01-01

124

Role of Electrical Activity in Promoting Neural Repair  

PubMed Central

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

Goldberg, Jeffrey L.

2012-01-01

125

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

PubMed

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

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

2007-01-08

126

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

PubMed

Auditory information transfer to afferent neurons relies on precise triggering of neurotransmitter release at the inner hair cell (IHC) ribbon synapses by Ca²? entry through CaV1.3 Ca²? channels. Despite the crucial role of CaV1.3 Ca²? channels in governing synaptic vesicle fusion, their elementary properties in adult mammals remain unknown. Using near-physiological recording conditions we investigated Ca²? channel activity in adult gerbil IHCs. We found that Ca²? channels are partially active at the IHC resting membrane potential (-60 mV). At -20 mV, the large majority (>70%) of Ca²? channel first openings occurred with an estimated delay of about 50 ?s in physiological conditions, with a mean open time of 0.5 ms. Similar to other ribbon synapses, Ca²? channels in IHCs showed a low mean open probability (0.21 at -20 mV), but this increased significantly (up to 0.91) when Ca²? channel activity switched to a bursting modality. We propose that IHC Ca²? channels are sufficiently rapid to transmit fast signals of sound onset and support phase-locking. Short-latency Ca²? channel opening coupled to multivesicular release would ensure precise and reliable signal transmission at the IHC ribbon synapse. PMID:23713031

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

2013-05-27

127

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

PubMed Central

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

Bolton, T. B.

1968-01-01

128

Electrical Fluctuations Associated with Active Transport  

PubMed Central

Measurements were made of the spectrum of the voltage fluctuations developed in the 0.025-10 Hz band during active transport by frog abdominal skin with Ringer's solution on both sides. Decreasing the potential across the skin by an external supply of current diminishes the voltage fluctuations, but they do not disappear, reaching a minimum finite value. Thus, fluctuations in both the resistance of the skin and the electric current attendant to the active transport of sodium contribute to the voltage fluctuations. Ouabain eliminates the current fluctuations but not those of the resistance. At 20°C, the spectral intensities of the resistance and current fluctuations are nearly identical, varying as 1/fa, where f is frequency and a = 1.6-2.0. At 32°C, the spectrum of the voltage fluctuations is sigmoid shaped, evidencing a relaxation process with a time constant of 0.6 sec. The fluctuations can be accounted for by stochastic variations in the concentration of a complex formed between a carrier molecule, fixed or mobile, and the actively transported species, sodium.

Segal, John R.

1972-01-01

129

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

130

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

SciTech Connect

Gene expression occurs either as an episodic process, characterized by pulsatile bursts or as a constitutive, Poisson-like accumulation of gene products. It is not clear which mode of gene expression (constitutive versus bursty) predominates across a genome or how transcriptional dynamics are influenced by genomic position and promoter sequence. Here, we use time-lapse fluorescence microscopy, building off of theoretical studies that exploit the time-resolved structure of stochastic fluctuations in gene expression, to develop a three-dimensional method for mapping underlying gene-regulatory mechanisms. Over 8,000 individual human genomic loci were analyzed, and at virtually all loci, episodic bursting as opposed to constitutive expression was found to be the predominant mode of expression. Quantitative analysis of the expression dynamics at these 8,000 loci indicates that both frequency and size of transcriptional bursts vary equally across the human genome independent of promoter sequence. Strikingly, weaker expression loci modulate burst frequency to increase activity, while stronger expression loci modulate burst size to increase activity. Transcriptional activators, such as TNF, generate similar patterns of change in burst frequency and burst size. In summary, transcriptional bursting dominates across the human genome, both burst frequency and burst size vary by chromosomal location, and transcriptional activators alter burst frequency and burst size, depending on the expression level of the locus.

Dar, Roy D. [University of Tennessee, Knoxville (UTK); Simpson, Michael L [ORNL; Weinberger, Leor S. [University of California, San Diego; Razooky, B [University of California, San Diego; Cox, Chris D. [University of Tennessee, Knoxville (UTK); McCollum, James M. [Miami University; Trimeloni, Tom [Virginia Commonwealth University, Richland; Singh, A [University of California, San Diego

2012-01-01

131

Electrical activation induces reactive oxygen species in porcine embryos  

Microsoft Academic Search

The objectives were to determine factors affecting generation of reactive oxygen species (ROS) in porcine embryos after electrical activation of oocytes, and the effects of an antioxidant and chemical agent on ROS generation. Greater ROS were induced by electrical activation compared to IVF (mean±S.E.M., 14.6±0.8 vs. 9.2±0.4, P<0.05). Furthermore, ROS generation in embryos after electrical activation was significantly increased by

O. J. Koo; G. Jang; D. K. Kwon; J. T. Kang; O. S. Kwon; H. J. Park; S. K. Kang; B. C. Lee

2008-01-01

132

A processing scheme for time-variant phase analysis in EEG burst activity of premature and full-term newborns in quiet sleep: a methodological study.  

PubMed

A processing scheme for the investigation of neonatal electroencephalographic burst oscillations that is composed of time-variant methods for linear and nonlinear phase analysis is introduced. Starting from a time-frequency analysis of oscillations' amplitudes, time-variant approaches for quantification of phase locking, n:m phase synchronization, and quadratic phase coupling are applied. Tracé discontinue patterns from premature newborns and tracé alternant patterns from full-term newborns were investigated using bipolar EEG recordings. Maturation-related differences between the burst generation mechanisms can be shown, which are reflected in group-specific patterns of augmentation, timing, and grouping of time-varying phase characteristics of the EEG burst oscillations. We demonstrate for both groups (premature and full-term newborns) that phase-locked low-frequency oscillations are pronounced in the frequency range of 0.5-1.5 Hz. Phase-locked oscillations also occur in a frequency range of >3 Hz. The amplitude of a phase-locked 2-Hz oscillation is higher in full-term than in premature newborns. After onset, n:m synchronization and an increase in bicoherence occur earlier in the premature group (between 0.5-1.5 Hz and 3.0-6.0 Hz). It can be suggested that during the maturation process, the driving force of thalamic structures decreases and that cortical activity plays an increasingly important role in the process of burst generation. PMID:23183723

Wacker, Matthias; Schiecke, Karin; Putsche, Peter; Eiselt, Michael; Witte, Herbert

2012-12-01

133

On Gamma-Ray Bursts  

Microsoft Academic Search

We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high

Remo Ruffini; M. G. Bernardini; C. L. Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; M. G. Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; J. A. Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

2008-01-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

135

RADIAL ANGULAR MOMENTUM TRANSFER AND MAGNETIC BARRIER FOR SHORT-TYPE GAMMA-RAY-BURST CENTRAL ENGINE ACTIVITY  

SciTech Connect

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

Liu Tong; Gu Weimin; Hou Shujin [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China); Liang Enwei [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning, Guangxi 530004 (China); Lei Weihua [School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Lin Lin; Zhang Shuangnan [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Dai Zigao, E-mail: lew@gxu.edu.cn [Department of Astronomy, Nanjing University, Nanjing, Jiangsu 210093 (China)

2012-11-20

136

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

PubMed

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

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

2013-05-13

137

The activation of gold complexes by cyanide produced by polymorphonuclear leukocytes--I. The effects of aurocyanide on the oxidative burst of polymorphonuclear leukocytes.  

PubMed

It has been suggested that the antiarthritic gold complex, aurothiomalate (Autm), is activated by its conversion to aurocyanide by polymorphonuclear leukocytes (PMN) which generate cyanide from thiocyanate. In an examination of this hypothesis, a study has been conducted on the effects of aurocyanide on the oxidative burst of polymorphonuclear leukocytes (PMN) and monocytes activated by phorbol myristate acetate (PMA). Aurocyanide produced delayed inhibition of the oxidative burst as shown by its effect on both lucigenin and luminol-dependent chemiluminescence and on the production of superoxide. It was a more potent inhibitor of luminol-dependent chemiluminescence than free thiomalate and other by-products of the reaction between Autm and cyanide. Aurocyanide had a biphasic effect on the PMA-stimulated hexose monophosphate shunt of PMN, with enhancement at 0.1 microM and inhibition at 10 and 100 microM. The activity of aurocyanide was also compared with that of auranofin, an orally active gold complex, which inhibits a variety of functions of PMN and monocytes. At low concentrations, auranofin produced delayed inhibition of chemiluminescence in a similar fashion to aurocyanide but at high concentrations was an immediate inhibitor of the oxidative burst. PMID:2160817

Rudkowski, R; Graham, G G; Champion, G D; Ziegler, J B

1990-06-01

138

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

PubMed Central

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

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

2012-01-01

139

Effects of two closely related probiotics on respiratory burst activity of Senegalese sole ( Solea senegalensis, Kaup) phagocytes, and protection against Photobacterium damselae subsp. piscicida  

Microsoft Academic Search

The effects of dietary administration of two probiotics, Shewanellaputrefaciens Pdp11 and Shewanellabaltica Pdp13, on growth, respiratory burst activity of phagocytes of Senegalese sole (Soleasenegalensis), and survival of fish challenged with Photobacteriumdamselae subsp. piscicida have been studied. Fish were fed for 60 days with three different diets: one control, and two diets supplemented with 109 cfu g?1of probiotics Pdp11 (Pdp11 diet) and Pdp13

P. Díaz-Rosales; S. Arijo; M. Chabrillón; F. J. Alarcón; S. T. Tapia-Paniagua; E. Martínez-Manzanares; M. C. Balebona; M. A. Moriñigo

2009-01-01

140

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

PubMed

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

Dorokhov, V B

141

Design and Development of Electric Active Stabilizer Suspension System  

NASA Astrophysics Data System (ADS)

An electric active stabilizer suspension system has been developed as a technology for controlling vehicle roll. The system includes various sensors that detect the vehicle's running state, and active stabilizer actuators that use electric motors and reduction gears to control roll. The electric stabilizer suspension system was compared with hydraulic stabilizer systems, and an investigation demonstrated the superiority of the developed system, which offers outstanding vehicle behavior, improved responsiveness and reduced energy consumption (including energy regeneration).

Buma, Shuuichi; Ookuma, Yasuhiro; Taneda, Akiya; Suzuki, Katsumi; Cho, Jae-Sung; Kobayashi, Masaru

142

Electrical activation induces reactive oxygen species in porcine embryos.  

PubMed

The objectives were to determine factors affecting generation of reactive oxygen species (ROS) in porcine embryos after electrical activation of oocytes, and the effects of an antioxidant and chemical agent on ROS generation. Greater ROS were induced by electrical activation compared to IVF (mean+/-S.E.M., 14.6+/-0.8 vs. 9.2+/-0.4, P<0.05). Furthermore, ROS generation in embryos after electrical activation was significantly increased by higher intensity and longer duration electrical pulses and by higher exogenous Ca(2+) concentrations. Cleavage rate and blastocyst formation rate were not directly related to the level of ROS. Supplementation of the IVC medium with 0.5mM glutathione (GSH) reduced ROS (9.2+/-0.4 vs. 14.7+/-0.9, P<0.05). Treatment with the chemical activation agent, 6-dimethylaminopurine (6-DMAP) for 3h did not induce further ROS generation in combination with electrical activation, but it improved blastocyst formation rate (53.8+/-1.1 vs. 23.7+/-3.5, P<0.05). We concluded that generation of ROS should be considered for optimizing electrical activation and that supplementing an antioxidant or combining electrical and chemical activation induced lower ROS generation in electrically activated porcine embryos. PMID:18675447

Koo, O J; Jang, G; Kwon, D K; Kang, J T; Kwon, O S; Park, H J; Kang, S K; Lee, B C

2008-10-15

143

Comparative evaluation of assays for the measurement of bovine neutrophil oxidative burst activity  

Technology Transfer Automated Retrieval System (TEKTRAN)

During mastitis and other bacterial-mediated diseases of cattle, neutrophils play a critical role in the host innate immune response to infection. The bactericidal activity of neutrophils is mediated, in part, through the generation of reactive oxygen species (ROS). The objectives of the current stu...

144

Mixed Mode Oscillations as a Mechanism for Pseudo-Plateau Bursting  

PubMed Central

We combine bifurcation analysis with the theory of canard-induced mixed mode oscillations to investigate the dynamics of a novel form of bursting. This bursting oscillation, which arises from a model of the electrical activity of a pituitary cell, is characterized by small impulses or spikes riding on top of an elevated voltage plateau. Oscillations with these characteristics have been called “pseudo-plateau bursting”. Unlike standard bursting, the subsystem of fast variables does not posses a stable branch of periodic spiking solutions, and in the case studied here the standard fast/slow analysis provides little information about the underlying dynamics. We demonstrate that the bursting is actually a canard-induced mixed mode oscillation, and use canard theory to characterize the dynamics of the oscillation. We also use bifurcation analysis of the full system of equations to extend the results of the singular analysis to the physiological regime. This demonstrates that the combination of these two analysis techniques can be a powerful tool for understanding the pseudo-plateau bursting oscillations that arise in electrically excitable pituitary cells and isolated pancreatic ?-cells.

Vo, Theodore; Bertram, Richard; Tabak, Joel; Wechselberger, Martin

2011-01-01

145

Electrostatic Charging of Electrically Active Spacecraft.  

National Technical Information Service (NTIS)

A model is presented which predicts the temporal behavior of the ionospheric charging of spacecraft which eject energetic positive ions. The dynamic interaction of the spacecraft with the space-plasma environment is modelled as an equivalent electrical ci...

J. N. Matossian J. R. Beattie

1986-01-01

146

Diffusion of extracellular K+ can synchronize bursting oscillations in a model islet of Langerhans.  

PubMed Central

Electrical bursting oscillations of mammalian pancreatic beta-cells are synchronous among cells within an islet. While electrical coupling among cells via gap junctions has been demonstrated, its extent and topology are unclear. The beta-cells also share an extracellular compartment in which oscillations of K+ concentration have been measured (Perez-Armendariz and Atwater, 1985). These oscillations (1-2 mM) are synchronous with the burst pattern, and apparently are caused by the oscillating voltage-dependent membrane currents: Extracellular K+ concentration (Ke) rises during the depolarized active (spiking) phase and falls during the hyperpolarized silent phase. Because raising Ke depolarizes the cell membrane by increasing the potassium reversal potential (VK), any cell in the active phase should recruit nonspiking cells into the active phase. The opposite is predicted for the silent phase. This positive feedback system might couple the cells' electrical activity and synchronize bursting. We have explored this possibility using a theoretical model for bursting of beta-cells (Sherman et al., 1988) and K+ diffusion in the extracellular space of an islet. Computer simulations demonstrate that the bursts synchronize very quickly (within one burst) without gap junctional coupling among the cells. The shape and amplitude of computed Ke oscillations resemble those seen in experiments for certain parameter ranges. The model cells synchronize with exterior cells leading, though incorporating heterogeneous cell properties can allow interior cells to lead. The model islet can also be forced to oscillate at both faster and slower frequencies using periodic pulses of higher K+ in the medium surrounding the islet. Phase plane analysis was used to understand the synchronization mechanism. The results of our model suggest that diffusion of extracellular K+ may contribute to coupling and synchronization of electrical oscillations in beta-cells within an islet. Images FIGURE 1

Stokes, C L; Rinzel, J

1993-01-01

147

Silent plateau potentials, rhythmic bursts, and pacemaker firing: Three patterns of activity that coexist in quadristable subthalamic neurons  

PubMed Central

Subthalamic neurons display uncommon intrinsic behaviors that are likely to contribute to the motor and cognitive functions of the basal ganglia and to many of its disorders. Here, we report silent plateau potentials in these cells. These plateau responses start with a transient burst of action potentials that quickly diminish in amplitude because of spike inactivation and current shunt. The resulting interruption of spiking reveals a stable depolarization (up state) that clamps the cell membrane potential near –40 mV for several seconds. These plateau potentials coexist in single subthalamic neurons with more familiar patterns of burst and pacemaker firing. Within a narrow range of baseline membrane potentials (–67 to –60 mV), depolarization abruptly switches single cells from bistable to rhythmic bursts or tonic firing modes, thus selecting entirely distinct algorithms for integrating cortical and pallidal synaptic inputs.

Kass, Jason I.; Mintz, Isabelle M.

2006-01-01

148

Analysis of Q burst waveforms  

NASA Astrophysics Data System (ADS)

The electric field changes in ELF to VLF were observed with a ball antenna in fair weather at Kochi (latitude 33.3°N, longitude 133.4°E) during 2003-2004. Some 376 Q bursts were obtained, seven examples of which are analyzed in the present study. The continuous frequency spectra of the Q bursts and the background noises from 1.0 Hz to 11 kHz are compared, and it was found that the Q bursts prevail over the background in the frequency range from 1 to 300 Hz. The surplus is 20 dB (in amplitude) near the fundamental mode frequency. The "W"-type changes found in the initial portion of the Q burst waveforms are interpreted as the combined electromagnetic waveform of direct and antipodal waves from the causative lightning strokes. From the time intervals between the two waves, the source-receiver distances are estimated as far as 19 Mm. The pulses to excite the Schumann resonances in the Q bursts are clearly identified.

Ogawa, Toshio; Komatsu, Masayuki

2007-04-01

149

Jovian Radio Burst Remote Sensing of Solar Wind Triggered Jovian Magnetospheric Activity: Ulysses Observations  

NASA Astrophysics Data System (ADS)

In 2003 and early 2004, the Ulysses spacecraft descended from high heliographic latitudes towards perihelion, bringing it relatively close to Jupiter. The geometry of this distant flyby (0.8 AU closest approach) caused Ulysses to spend more than 6 months above a jovicentric latitude of 50 deg at a range of less than 2 AU, while the spacecraft traversed a considerable range of Jovian local time (9 hrs to 17 hrs). During much of this time interval, Jupiter was intercepted each solar rotation by two corotating high density structures and sector boundaries. From the perspective of Ulysses, the radio response of the magnetosphere to a given corotating structure was the intensification of either Jovian broad-band kilometric (bKOM) emission or of a combination of emissions, including bKOM and Jovian narrow-band kilometric (nKOM) emission. Such enhancements have been studied previously with Voyager, Ulysses, Galileo, and Cassini radio data. For Ulysses observations in 1991 and 1992, in particular, the typical scenario was brightening in the Jovian bKOM emission, followed by a sudden cessation of the bKOM emission and an onset of an nKOM "event" that lasted for some 120 hours (Reiner et al., 2000). For the sequences of events in 2003-2004, the two episodes per solar rotation; driven by high speed streams and/or current sheet crossing, clearly have different morphologies. In this presentation, variations in solar wind kinetic pressure and magnetic field direction (measured by Ulysses) are analyzed as triggers of Jovian magnetospheric activity, indicated by the intense radio emissions. Several intervals when magnetic clouds intercept Jupiter and produce Jovian radio events are also examined.

MacDowall, R. J.; Desch, M. D.; Kaiser, M. L.; Reiner, M. J.; Forsyth, R. J.; McComas, D. J.

2004-12-01

150

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

PubMed

The brainstem nucleus hypoglossus contains motoneurons that provide the exclusive motor nerve supply to the tongue. In addition to voluntary tongue movements, tongue muscles rhythmically contract during a wide range of physiological activities, such as respiration, swallowing, chewing and sucking. Hypoglossal motoneurons are destroyed early in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease often associated with a deficit in the transport system of the neurotransmitter glutamate. The present study shows how periodic electrical discharges of motoneurons are mainly produced by a neuronal network that drives them into bursting mode via glutamatergic excitatory synapses. Burst activity is, however, modulated by the intrinsic properties of motoneurons that collectively synchronize their discharges via gap junctions to create 'group bursters'. When glial uptake of glutamate is blocked, a distinct form of pathological bursting spontaneously emerges and leads to motoneuron death. Conversely, H(2)O(2)-induced oxidative stress strongly increases motoneuron excitability without eliciting bursting. Riluzole (the only drug currently licensed for the treatment of ALS) suppresses bursting of hypoglossal motoneurons caused by blockage of glutamate uptake and limits motoneuron death. These findings highlight how different patterns of electrical oscillations of brainstem motoneurons underpin not only certain physiological activities, but also motoneuron death induced by glutamate transporter impairment. PMID:19651651

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

2009-09-12

151

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

PubMed Central

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

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

2009-01-01

152

Detecting electrical activity from Martian dust storms  

Microsoft Academic Search

We present a model addressing the possible electrification of Martian dust storms based on the effective electrical charging of an individual dust grain. An upper charge bound on a grain can be determined based on the grain capacitance in the low- pressure Martian atmosphere. It is assumed that treiboelectric and inductive processes, like that presumed operating in terrestrial dust storms,

W. M. Farrell; M. L. Kaiser; M. D. Desch; J. G. Houser; S. A. Cummer; D. M. Wilt; G. A. Landis

1999-01-01

153

Problems in Identifying 'Bursts' of Periodontal Attachment Loss.  

National Technical Information Service (NTIS)

A theory of periodontal attachment loss which postulates discrete bursts of activity has recently been proposed. This paper identifies several problems in the interpretation of the experimental data that have been used to support the burst model. Major ob...

S. A. Ralls M. E. Cohen

1986-01-01

154

Mitogen-activated protein kinases mediate the oxidative burst and saponin synthesis induced by chitosan in cell cultures of Panax ginseng.  

PubMed

Chitosan (CHN) specially induced the activities of 39 kD and 42 kD protein kinases in ginseng cells, which could be suppressed by an inhibitor of mitogen-activated protein kinase (MAPK) pathway, PD98059. The immunoprecipitation (IP) using MAPK antibody or kinase assay in vitro also showed that CHN-induced 42 kD and 39 kD protein kinases belonged to the MAPK family. PD98059 suppressed CHN-induced transcriptions of ginseng squalene synthase and ginseng squalene epoxidase genes (gss and gse), CHN-induced accumulation of beta-Amyrin synthase (beta-AS) and synthesis of saponin. These results showed that CHN-induced activities of MAPKs were necessary for the CHN-induced saponin synthesis. EGTA and LaCl3 suppressed CHN-induced 39 kD and 42 kD MAPK activities. Ruthenium red (RR) could suppress CHN-induced 39 kD activity. All of them suppressed CHN-induced saponin synthesis. These results indicated that CHN-induced increment of cytosolic calcium was necessary for CHN-induced saponin synthesis. PD98059 also suppressed CHN-induced oxidative burst (including the increment of activity of plasma membrane NADPH oxidase and production of H2O2), but diphenylene iodonium (DPI), dimethylthiourea (DMTU) and 2,5-dihydroxycinnamic acid methyl ester (DHC) could not suppress CHN-induced MAPK activities, which indicated that MAPK was possibly function upstream of CHN-induced oxidative burst. PMID:15493471

Hu, Xiangyang; Neill, Steven J; Fang, Jianying; Cai, Weiming; Tang, Zhangcheng

2004-08-01

155

Optimization of encapsulation of a synthetic long peptide in PLGA nanoparticles: low-burst release is crucial for efficient CD8(+) T cell activation.  

PubMed

Overlapping synthetic long peptides (SLPs) hold great promise for immunotherapy of cancer. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) are being developed as delivery systems to improve the potency of peptide-based therapeutic cancer vaccines. Our aim was to optimize PLGA NP for SLP delivery with respect to encapsulation and release, using OVA24, a 24-residue long synthetic antigenic peptide covering a CTL epitope of ovalbumin (SIINFEKL), as a model antigen. Peptide-loaded PLGA NPs were prepared by a double emulsion/solvent evaporation technique. Using standard conditions (acidic inner aqueous phase), we observed that either encapsulation was very low (1-30%), or burst release extremely high (>70%) upon resuspension of NP in physiological buffers. By adjusting formulation and process parameters, we uncovered that the pH of the first emulsion was critical to efficient encapsulation and controlled release. In particular, an alkaline inner aqueous phase resulted in circa 330 nm sized NP with approximately 40% encapsulation efficiency and low (<10%) burst release. These NP showed enhanced MHC class I restricted T cell activation in vitro when compared to high-burst releasing NP and soluble OVA24, proving that efficient entrapment of the antigen is crucial to induce a potent cellular immune response. PMID:23201055

Silva, A L; Rosalia, R A; Sazak, A; Carstens, M G; Ossendorp, F; Oostendorp, J; Jiskoot, W

2012-11-29

156

Network mechanisms of spindle-burst oscillations in the neonatal rat barrel cortex in vivo.  

PubMed

Early in development, cortical networks generate particular patterns of activity that participate in cortical development. The dominant pattern of electrical activity in the neonatal rat neocortex in vivo is a spatially confined spindle-burst. Here, we studied network mechanisms of generation of spindle-bursts in the barrel cortex of neonatal rats using a superfused cortex preparation in vivo. Both spontaneous and sensory-evoked spindle-bursts were present in the superfused barrel cortex. Pharmacological analysis revealed that spindle-bursts are driven by glutamatergic synapses with a major contribution of AMPA/kainate receptors, but slight participation of NMDA receptors and gap junctions. Although GABAergic synapses contributed minimally to the pacing the rhythm of spindle-burst oscillations, surround GABAergic inhibition appeared to be crucial for their compartmentalization. We propose that local spindle-burst oscillations, driven by glutamatergic synapses and spatially confined by GABAergic synapses, contribute to the development of barrel cortex during the critical period of developmental plasticity. PMID:17093125

Minlebaev, Marat; Ben-Ari, Yehezkel; Khazipov, Rustem

2006-11-08

157

Inhibitory effect of lactone fractions and individual components from three species of the Achillea millefolium complex of Bulgarian origin on the human neutrophils respiratory burst activity.  

PubMed

Achillea species are widely used in folk medicine for treatment of inflammatory diseases. The inhibitory effect on the human neutrophils respiratory burst activity of total extracts, their fractions and some main constituents of the flower heads from Achillea asplenifolia, A. collina and A. distans belonging to A. millefolium complex of Bulgarian origin, were tested by the modified method of Tan and Berridge. Seven from the investigated fractions showed activity similar or higher than that of indomethacine and might be evaluated as nonsteroidal anti-inflammatory agents. PMID:17691054

Choudhary, Muhammad Iqbal; Jalil, Saima; Todorova, M; Trendafilova, A; Mikhova, B; Duddeck, H; Atta-ur-Rahman

2007-09-01

158

Pacific Gas and Electric Company - Biomass energy activities  

Microsoft Academic Search

Pacific Gas and Electric activities in utilizing biomass for the production of gas and electricity are reviewed. Research is centering on quantifying the available resource, identifying viable conversion systems, determining the economics, and defining limiting factors such as balances between competing alternatives and institutional restraints. A feasibility study for a pyrolysis plant for producing syngas from San Francisco solid waste

M. J. Blanchet; B. M. Jenkins; J. G. Meyer; P. Maciel; R. F. Goldstein

1980-01-01

159

Burst of activity  

NASA Astrophysics Data System (ADS)

In the 17years since the Voyager spacecraft flew by, the volcano Ra Patera on Jupiter's moon Io has been quite busy. This summer, the Galileo orbiter caught Ra Patera in action on June 28 as it spit a blue-tinted plume 100 km into space (see plume at 9 o'clock on photo and inset at the lower left). The plume is believed to be sulfur dioxide gas that condenses as snow as it expands and cools in the magnetosphere. Other images gathered by Galileo reveal that the plume glows in the dark, perhaps due to fluorescence in oxygen and sulfur ions as the sulfur dioxide breaks apart.

160

Development of an Electrically-Activated Artificial Muscle System.  

National Technical Information Service (NTIS)

An electrically-activated artificial muscle system is described which uses weakly acidic contractile polymers sensitive to pH changes. pH changes are produced through electrodialysis of a solution compartment containing the muscle membrane. Mathematical e...

A. Fragala A. LaConti J. Boyack J. Enos

1970-01-01

161

Activity Rhythm of an Electric Fish, Gymnorhamphichthys Hypostomus, Ellis.  

National Technical Information Service (NTIS)

The gymnotid, Gymnorhamphichthys hypostomus, (sandfish) exhibits in nature well marked activity cycles which are accompanied by substantial changes in the frequency of discharges from its electric organ. During the day the sandfish is buried in the sand a...

H. W. Lissmann H. O. Schwassmann

1965-01-01

162

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

163

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

164

Electrical Activity of the Amygdala and Hippocampus during Biting.  

National Technical Information Service (NTIS)

Restraint-produced biting showed a consistent correlation with certain changes in electrical activity of brain structures previously linked with the mediation of aggression. Biting of food, on the other hand, showed no such correlation. The differences ma...

J. DeFrance R. R. Hutchinson

1970-01-01

165

Influence of pulsed electric field on various enzyme activities  

Microsoft Academic Search

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

Takayuki Ohshima; Tsuruki Tamura; Masayuki Sato

2007-01-01

166

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.

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

2010-01-01

167

BURST SWIMMING PERFORMANCEOF NORTHERN ANCHOVY, ENGRAULISMORDAX, LARVAE  

Microsoft Academic Search

Burst swimming performance was measured for northern anchovy larvae from 0.23 to 1.33 cm total length at a temperature of17° C. Fast starts and burst swimming were initiated using a 3 V\\/cm direct current electric shock. Performance was measured from movie film recorded at 250 frames\\/so Percent­ ages of larvae responding to the stimulus increased from 9% 40 hours after

P. W. WEBBI; R. T. COROLLA

168

Feed-forward and feed-back activation of the dentate gyrus in vivo during dentate spikes and sharp wave bursts.  

PubMed

Intermittently occurring field events, dentate spikes (DS), and sharp waves (SPW) in the hippocampus reflect population synchrony of principal cells and interneurons along the entorhinal cortex-hippocampus axis. We have investigated the cellular-synaptic generation of DSs and SPWs by intracellular recording from granule cells, pyramidal cells, and interneurons in anesthetized rats. The recorded neurons were anatomically identified by intracellular injection of biocytin. Extracellular recording electrodes were placed in the hilus to record field DSs and multiple units and in the CA1 pyramidal cell layer to monitor SPW-associated fast field oscillations (ripples) and unit activity. DSs were associated with large depolarizing potentials in granule cells, but they rarely discharged action potentials. When they were depolarized slightly with intracellular current injection, bursts of action potentials occurred concurrently with extracellularly recorded DSs. Two interneurons in the hilar region were also found to discharge preferentially with DSs. In contrast, CA1 pyramidal cells, recorded extracellularly and intracellularly, were suppressed during DSs. In association with field SPWs, extracellular recordings from the CA1 pyramidal layer and the hilar region revealed synchronous bursting of these cell populations. Intracellular recordings from CA3 and CA1 pyramidal cells, granule cells, and from a single CA3 region interneuron revealed SPW-concurrent depolarizing potentials and action potentials. These findings suggest that granule cells may be discharged anterogradely by entorhinal input or retrogradely by the CA3-mossy cell feedback pathway during DSs and SPWs, respectively. Although both of these intermittent population patterns can activate granule cells, the impact of DSs and SPWs is diametrically opposite on the rest of the hippocampal circuitry. Entorhinal cortex activation of the granule cells during DSs induces a transient decrease in the hippocampal output, whereas during SPW bursts every principal cell population of the hippocampal formation may be recruited into the population event. PMID:9287083

Penttonen, M; Kamondi, A; Sik, A; Acsády, L; Buzsáki, G

1997-01-01

169

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

PubMed

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

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

2012-04-26

170

Phagocytic activity, respiratory burst, cytoplasmic free-Ca 2+ concentration and apoptotic cell ratio of haemocytes from the black tiger shrimp, Penaeus monodon under acute copper stress  

Microsoft Academic Search

The aim of this study was to investigate the cellular toxicity of copper-induced injury to the black tiger shrimp Penaeus monodon. The 24h, 48h, 72h and 96h LC50 (median lethal concentration) of Cu2+ on P. monodon (11.63±1.14g) were found to be 3.49, 1.54, 0.73 and 0.40mgL?1, respectively. Total haemocyte count (THC), phagocytic activity, respiratory burst (RB), cytoplasmic free-Ca2+ (cf-Ca2+) concentration

Jian-An Xian; An-Li Wang; Chao-Xia Ye; Xiao-Dan Chen; Wei-Na Wang

2010-01-01

171

Impulse Trains Generated by Populations of Cortical Neurons of Rabbits Exposed to Low-Intensity Extrahigh-Frequency Electromagnetic Radiation: Bursting Activity  

Microsoft Academic Search

In experiments on rabbits, we studied patterns of impulse trains generated by limited populations of neurons in the sensorimotor\\u000a cortex (recording by a relatively thick microelectrode) prior to, in the course of, and after 1-min-long extrahigh-frequency\\u000a (EHF) electromagnetic irradiation (wavelength 37.5 cm, power rate density 0.2 to 0.3 mW\\/cm2). It was demonstrated that irradiation resulted in appreciable rearrangements of the bursting activity.

R. A. Chizhenkova

2008-01-01

172

A Hodgkin-Huxley model exhibiting bursting oscillations  

Microsoft Academic Search

We investigate bursting behaviour generated in an electrophysiological model of pituitary corticotrophs. The active and silent\\u000a phases of this mode of bursting are generated by moving between two stable oscillatory solutions. The bursting is indirectly\\u000a driven by slow modulation of the endoplasmic reticulum Ca2+ concentration. The model exhibits different modes of bursting, and we investigate mode transitions and similar modes

Paul R. Shorten; David J. N. Wall

2000-01-01

173

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

PubMed

Thermally sensitive neurons present bursting activity for certain temperature ranges, characterized by fast repetitive spiking of action potential followed by a short quiescent period. Synchronization of bursting activity is possible in networks of coupled neurons, and it is sometimes an undesirable feature. Control procedures can suppress totally or partially this collective behavior, with potential applications in deep-brain stimulation techniques. We investigate the control of bursting synchronization in small-world networks of Hodgkin-Huxley-type thermally sensitive neurons with chemical synapses through two different strategies. One is the application of an external time-periodic electrical signal and another consists of a time-delayed feedback signal. We consider the effectiveness of both strategies in terms of protocols of applications suitable to be applied by pacemakers. PMID:23679455

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

2013-04-16

174

A novel post-translational incorporation of tyrosine into multiple proteins in activated human neutrophils. Correlation with phagocytosis and activation of the NADPH oxidase-mediated respiratory burst.  

PubMed

Activation of human neutrophils by PMA causes a post-translational incorporation of 14C-labeled tyrosine into multiple neutrophil (PMN) proteins, that is distinctly different from the enzymatic tyrosinolation of tubulin in FMLP-stimulated PMN. Post-translational incorporation of other radiolabeled amino acids, including the structurally similar amino acid phenylalanine, does not occur under identical conditions of neutrophil activation, suggesting an involvement of the phenolic hydroxyl group of tyrosine in the PMA-mediated reaction. Similar to the stimulation of PMN tubulin tyrosinolation by FMLP, the PMA-induced incorporation of tyrosine into multiple PMN proteins is closely associated with activation of the NADPH oxidase-mediated respiratory burst in stimulated PMN and can be inhibited by a variety of reducing agents, inhibitors of peroxidase-mediated reactions, and intracellular scavengers of oxygen radicals. Moreover, the PMA-induced post-translational incorporation of tyrosine does not occur in PMN from patients with chronic granulomatous disease and is significantly reduced (50%) in PMN of an individual with myeloperoxidase deficiency. A similar stimulus-induced incorporation of tyrosine into multiple PMN proteins is also observed in PMN exposed to various phagocytic stimuli, and the incorporated radioactivity in cells undergoing phagocytosis is substantially enriched (40- to 50-fold) in isolated PMN phagolysosomes. Consistent with this latter observation, HPLC fractionation of stimulated PMN proteins and analysis of the incorporated radioactivity reveal that the 14C label is primarily associated with PMN membrane proteins. Furthermore, this post-translational incorporation of tyrosine, like that associated with PMA stimulation, is associated with production of oxygen radicals and the generation of protein carbonyl derivatives, which are indicative of oxidative protein modifications via mixed function oxidases. Our findings indicate that tyrosine incorporation into membrane proteins of stimulated PMN is functionally relevant to the physiologic host-defense responses of human neutrophils undergoing phagocytosis. PMID:1331234

Nath, J; Ohno, Y; Gallin, J I; Wright, D G

1992-11-15

175

Cytoskeletal modulation of electrical and mechanical activity in cardiac myocytes  

Microsoft Academic Search

The cardiac myocyte has an intracellular scaffold, the cytoskeleton, which has been implicated in several cardiac pathologies including hypertrophy and failure. In this review we describe the role that the cytoskeleton plays in modulating both the electrical activity (through ion channels and exchangers) and mechanical (or contractile) activity of the adult heart. We focus on the 3 components of the

S. C. Calaghan; J.-Y. Le Guennec; E. White

2004-01-01

176

New Results on the Spectral Evolution of Magnetar Bright Bursts  

NASA Astrophysics Data System (ADS)

Magnetars are isolated neutron stars characterized by long spin periods (2-12 s) and large spin down rates, implying a very strong magnetic field, B>10E14 G. Magnetars exhibit short bursts of hard X-/soft gamma-rays with luminosities ranging from 10E37 to 10E41 erg/s. The magnetar SGR J1550-5418 entered an extremely active bursting episode, starting on 2008 October 03 until 2009 April 17, during which Fermi Gamma-ray Burst Monitor (GBM) observed several hundred bursts from this source. Such wealth of bursts resulted in the largest catalog of detailed temporal and spectral results for SGR J1550-5418. Here, we discuss new results from time-resolved spectral analysis of the brightest bursts from this source. Our analysis, together with the comparison of our results with other magnetar bursts, enabled us to put strong constraints on the theories underlying the magnetar bursts emission mechanism.

Younes, George A.; Kouveliotou, C.; van der Horst, A.; GBM Magnetar Team

2013-04-01

177

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

178

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

PubMed

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(2+), we found that the PMA-induced respiratory burst of human neutrophils is inhibited when assessed as extracellular production of O2(-) and H2O2, in accordance with literature studies, but, surprisingly, unaffected when measured as oxygen consumption or total (extracellular plus intracellular) H2O2 production. Furthermore, we show that inhibiting Hv1 with Zn(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 H2O2. Zinc caused an increase in the rate but not in the extent of depolarization and cytosolic acidification indicating that mechanisms other than proton efflux take part in charge compensation. Our results suggest a hitherto unpredicted mechanism of charge compensation whereby, in the absence of proton efflux, part of O2(-) generated within gp91(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. PMID:23578765

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

2013-04-08

179

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

PubMed Central

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

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

2013-01-01

180

Ensemble Recording of Electrical Activity in Neurons Derived from P19 Embryonal Carcinoma Cells  

NASA Astrophysics Data System (ADS)

Regeneration of the central nervous system (CNS) is one of the most important research themes in neuroscience and neuroengineering. It is essential to replenish the lost neurons and to establish appropriate functional neuronal networks using pluripotent stem cells. Little is known, however, about the properties of stem cell-derived neuronal networks, particularly under the differentiation and development processes. In this work, we cultured P19 embryonal carcinoma cells on micro-electrode arrays (MEAs). P19 cells were differentiated into neurons by retinoic acid application and formed densely connected networks. Spontaneous electrical activity was extracellulary recorded through substrate electrodes and analyzed. Synchronized periodic bursts, which were the characteristic features in primary cultured CNS neurons, were observed. Pharmacological studies demonstrated that the glutamatergic excitatory synapses and the GABAergic inhibitory synapses were active in these P19-derived neuronal networks. The results suggested that MEA-based recording was useful for monitoring differentiation processes of stem cells. P19-derived neuronal networks had quite similar network properties to those of primary cultured neurons, and thus provide a novel model system to investigate stem cell-based neuronal regeneration.

Takayama, Yuzo; Saito, Atushi; Moriguchi, Hiroyuki; Kotani, Kiyoshi; Jimbo, Yasuhiko

181

Burst switching between incoherence and synchrony  

NASA Astrophysics Data System (ADS)

Studies of coupled oscillators often use diffusive connections to ensure that the coupled quantity is conserved. Signals between neurons, however, are not diffusive and may propagate unattenuated throughout a network. We compare diffusive and synapse-like coupling of Hindmarsh-Rose (HMR) oscillators through numerical simulations. HMR parameters are tuned to either oscillate continuously or alternate bursts of oscillations and periods of quiescence. In diffusive coupling, two HMR units synchronize bursts and individual oscillations within a burst at nearly the same coupling strength. Synapse-like coupling, however, shows a new behavior, called burst switching, between incoherence and synchrony. For example, a bursting unit can entrain an oscillating unit of a different frequency during the burst but then force the oscillator into quiescence. Burst switching in various network topologies synchronizes inhomogeneous units for the duration of the burst, followed by a period of network quiescence and a return to incoherence. The summed activity resembles the progression of an epileptic seizure including the ``spike and wave'' at the transition from synchrony to quiescence.

Crosby, Nathan; Tranquillo, Joseph

2009-03-01

182

Q-Burst Origins in Africa  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

183

Fast optical response to electrical activation in peripheral nerves  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

184

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

Microsoft Academic Search

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

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

1975-01-01

185

Endogenous Electric Fields May Guide Neocortical Network Activity  

PubMed Central

Local field potentials and the underlying endogenous electric fields (EFs) are traditionally considered to be epiphenomena of structured neuronal network activity. Recently, however, externally applied EFs have been shown to modulate pharmacologically evoked network activity in rodent hippocampus. In contrast, very little is known about the role of endogenous EFs during physiological activity states in neocortex. Here we used the neocortical slow oscillation in vitro as a model system to show that weak sinusoidal and naturalistic EFs enhance and entrain physiological neocortical network activity with an amplitude threshold within the range of in vivo endogenous field strengths. Modulation of network activity by positive and negative feedback fields based on the network activity in real-time provide direct evidence for a feedback loop between neuronal activity and endogenous EF. This significant susceptibility of active networks to EFs that only cause small changes in membrane potential in individual neurons suggests that endogenous EFs could guide neocortical network activity.

Frohlich, Flavio; McCormick, David A.

2011-01-01

186

The electrical and motor actions of gastrointestinal hormones on the duodenum in man  

Microsoft Academic Search

The electrical and motor activity was recorded from the duodenum in 16 conscious human subjects in resting conditions. The main electrical wave form variously known as the pace-setter potential or slow wave was constantly present and periodically accompanied by a second electrical trace consisting of rapid bursts of fast waves or action potentials which were related to motor waves. Secretin

W. E. Waterfall; H. L. Duthie; B. H. Brown

1973-01-01

187

Mandibular rest position and electrical activity of the masticatory muscles  

Microsoft Academic Search

Statement of problem. The determination of a correct vertical dimension of occlusion is a critical procedure in clinical dentistry.Purpose. The objectives of this study were to analyze the relation between mandibular rest position and electrical activity of masticatory muscles and to compare clinical and electromyographic rest position in subjects with different vertical facial morphologic features.Material and methods. Clinical rest position

Ambra Michelotti; Mauro Farella; Stefano Vollaro; Roberto Martina

1997-01-01

188

Biometrics from Brain Electrical Activity: A Machine Learning Approach  

Microsoft Academic Search

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

Ramaswamy Palaniappan; Danilo P. Mandic

2007-01-01

189

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

190

Electrical Breakdown Studies on Electro-active Paper  

Microsoft Academic Search

The concept of using cellulose as a smart material for preparing electro-active paper (EAPap) has been a land mark discovery, since it exhibits an impressive magnitude of actuation at relatively modest voltages. Considering the small thickness of cellulose samples (35 mum) and smaller depth of electrodes (100 nm), even at relatively low operating voltages (7 V), high electrical stresses can

Prathap Basappa; Sangdong Jang; Jaehwan Kim

2007-01-01

191

Capturing Users' Buying Activity at Akihabara Electric Town from Twitter  

Microsoft Academic Search

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

Takahiro Kawamura; Yasuyuki Tahara; Akihiko Ohsuga

2010-01-01

192

Physicochemical and electrical properties of activated carbon cloths  

Microsoft Academic Search

Five different cellulose-based fabrics were used to prepare activated carbon cloths (ACCs) by phosphoric acid activation at pre-established experimental conditions, in an attempt to explore the effect of the precursor's nature on properties of the resulting ACCs. Characterization by elemental analysis, nitrogen (77K) adsorption, and scanning electron microscopy was carried out. Electrical properties of the developed ACCs were investigated to

María E. Ramos; Pablo R. Bonelli; Ana L. Cukierman

2008-01-01

193

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

PubMed

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

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

2012-12-01

194

Remote monitoring of biodynamic activity using electric potential sensors  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

195

Gestational maturation of electrical activity of the stomach.  

PubMed

Gestational maturation of gastrointestinal motility is a key factor in readiness of the preterm neonates for enteral nutrition. Since gastric motility mainly depends on the electrical activity of the smooth muscle cells, it was of interest to investigate the developmental aspects of electrical activity of the stomach. The latter was recorded weekly through cutaneous electrogastrography in 27 preterm infants (aged 29-34 weeks of gestation). Recordings were done for 1 hr before and 1 hr after meal. The electrogastrographic variables measured were: percentage of normal gastric rhythm, ie, 2-4 cpm; percentage of tachygastria (>4 cpm); the fed-to-fasting ratio of the dominant electrogastrographic power; and the instability coefficient of the dominant frequency. Data were compared with those measured in 10 full-term infants. Peaks of normal electrical activity (2-4 cpm) were present in most of the recordings at all the gestational ages; however, percentages of both normal electrical rhythm and tachygastria in preterm infants were similar to those measured in full-term infants (mean +/- SD) (normal rhythm; fasting: 70.2 +/- 3.8, fed: 72.2 +/- 5.0; tachygastria: fasting: 24.6 +/- 4.0, fed: 19.1 +/- 3.5) by 35 weeks of gestation (normal rhythm; fasting: 67.5 +/- 2.0, fed: 69.6 +/- 4.4; tachygastria: fasting: 27.1 +/- 4.0, fed: 25.6 +/- 4.1). The coefficient of instability of the dominant frequency in preterm infants was also similar to the value measured in full-term infants by 35 weeks of gestation, whereas the EGG power showed a significant increase in the postprandial state at all the gestational ages. We conclude that a maturation pattern of the electrical activity of the stomach can be detected by means of a noninvasive tool such as cutaneous electrogastrography: a normal electrical rhythm can be detected at very early gestational ages; however, this activity becomes dominant at around the 35 weeks of gestational age. In preterm infants developmental changes of gastric electrical activity are a function of advancing postnatal age. PMID:10548351

Cucchiara, S; Salvia, G; Scarcella, A; Rapagiolo, S; Borrelli, O; Boccia, G; Riezzo, G; Ciccimarra, F

1999-10-01

196

Burst synchronization transitions in a neuronal network of subnetworks  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

197

Wireless integrated microsystems for monitoring brain chemical and electrical activity  

NASA Astrophysics Data System (ADS)

A 16-channel chip for wireless in vivo recording of chemical and electrical neural activity is described. The 7.83-mm2 IC is fabricated using a 0.5-?m CMOS process and incorporates a 71-?W, 3rd-order, reconfigurable, ?? modulator per channel, achieving an input-referred noise of 4.69 ?Vrms in 4-kHz BW and 94.1 pArms in 5-kHz BW for electrical and fast-scan voltammetric chemical neurosensing, respectively. The chip has been externally interfaced with carbon-fiber microelectrodes implanted acutely in the caudate-putamen of an anesthetized rat, and, for the first time, extracellular levels of dopamine elicited by electrical stimulation of the medial forebrain bundle have been successfully recorded wirelessly across multiple channels using 300-V/s fast-scan cyclic voltammetry.

Roham, Masoud; Garris, Paul A.; Mohseni, Pedram

2008-08-01

198

Subthalamic Nucleus Electrical Stimulation Modulates Calcium Activity of Nigral Astrocytes  

PubMed Central

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

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

2012-01-01

199

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

200

Oxidative burst and cognate redox signalling reported by luciferase imaging: identification of a signal network that functions independently of ethylene, SA and Me-JA but is dependent on MAPKK activity  

Microsoft Academic Search

Summary Recognition of avirulent microbial pathogens activates an oxidative burst leading to the accumulation of reactive oxygen intermediates (ROIs), which are thought to integrate a diverse set of defence mechanisms resulting in the establishment of plant disease resistance. A novel transgenic Arabidopsis line containing a gst1::luc transgene was developed and employed to report the temporal and spatial dynamics of ROI

John J. Grant; Byung-Wook Yun; Gary J. Loake

2000-01-01

201

SHEBA prompt burst dynamics  

SciTech Connect

The Solution High-Energy Burst Assembly (SHEBA), located at the Los Alamos Critical Experiments Facility, is a homogeneous liquid-fueled reactor that is being prepared for prompt burst operation. As part of the preparations, a reactor safety study was performed in support of the new SHEBA experiment plan. This study looked at the maximum power, total energy yield, and maximum transient pressures that may occur in the reactor during prompt burst operation. The goal of this study is to analyze the neutronic and hydrodynamic behavior of the reactor during burst operation, and to ensure that prompt burst operation does not damage the reactor or exceed the safety envelope of the facility`s Safety Analysis Report (SAR).

Kimpland, R.

1997-12-31

202

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

203

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

DOEpatents

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

Wilcox, R.B.

1991-09-10

204

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

DOEpatents

A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch. 9 figs.

Wilcox, R.B.

1990-02-02

205

Electrical activity during the 2006 Mount St. Augustine volcanic eruptions.  

PubMed

By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms. PMID:17322054

Thomas, R J; Krehbiel, P R; Rison, W; Edens, H E; Aulich, G D; Winn, W P; McNutt, S R; Tytgat, G; Clark, E

2007-02-23

206

Earthward flow bursts in the inner magnetotail and their relation to auroral brightenings, AKR intensifications, geosynchronous particle injections and magnetic activity  

Microsoft Academic Search

High-velocity magnetotail flow bursts measured by the Geotail Low Energy Plasma experiment in the premidnight equatorial region between 10 and 15 RE have been compared with other magnetospheric phenomena. These bursts, typically characterized by earthward velocities approaching 1000 km\\/s and lasting for times of the order of 1 min, are associated with magnetotail dipolarizations and large magnetic field fluctuations. Using

D. H. Fairfield; T. Mukai; M. Brittnacher; G. D. Reeves; S. Kokubun; G. K. Parks; T. Nagai; H. Matsumoto; K. Hashimoto; D. A. Gurnett; T. Yamamoto

1999-01-01

207

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...

208

Protein kinase B (AKT) mediates phospholipase D activation via ERK1/2 and promotes respiratory burst parameters in formylpeptide-stimulated neutrophil-like HL-60 cells.  

PubMed

Phospholipase D (PLD), a major source of lipid second messengers (phosphatidic acid, diglycerides) in many cell types, is tightly regulated by protein kinases, but only a few of them have been identified. We show here that protein kinase B (AKT) is a novel major signaling effector of PLD activity induced by the formylpeptide f-Met-Leu-Phe (fMLP) in human neutrophil-like HL-60 cells (dHL-60 cells). AKT inhibition with the selective antagonist AKTib1/2 almost completely prevented fMLP-mediated activity of PLD, its upstream effector ERK1/2, but not p38 MAPK. Immunoprecipitation studies show that phosphorylated AKT, ERK, and PLD2 form a complex induced by fMLP, which can be prevented by AKTib1/2. In cell-free systems, AKT1 stimulated PLD activity via activation of ERK. AKT1 actually phosphorylated ERK2 as a substrate (K(m) 1 ?m). Blocking AKT activation with AKTib1/2 also prevented fMLP- but not phorbol 12-myristate 13-acetate-mediated NADPH oxidase activation (respiratory burst, RB) of dHL-60 cells. Impaired RB was associated with defective membrane translocation of NADPH oxidase components p67(phox) and p47(phox), ERK, AKT1, AKT2, but not AKT3. Depletion of AKT1 or AKT2 with antisense oligonucleotides further indicates a partial contribution of both isoforms in fMLP-induced activation of ERK, PLD, and RB, with a predominant role of AKT1. Thus, formylpeptides induce sequential activation of AKT, ERK1/2, and PLD, which represents a novel signaling pathway. A major primarily role of this AKT signaling pathway also emerges in membrane recruitment of NOX2 components p47(phox), p67(phox), and ERK, which may contribute to assembly and activation of the RB motor system, NADPH oxidase. PMID:20693286

Patel, Satyananda; Djerdjouri, Bahia; Raoul-Des-Essarts, Yannick; Dang, Pham My-Chan; El-Benna, Jamel; Périanin, Axel

2010-08-06

209

External Resource: Anglin for Gamma-Ray Bursts: Gama Ray Burst Educational Unit  

NSDL National Science Digital Library

This Gamma Ray Burst educator's guide contains science and mathematics activities that address the following topics: electromagnetic spectrum, low-energy radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and extremely high

1900-01-01

210

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

211

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

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

Bunshah, R.; Nath, P.

1982-06-22

212

Jovian S burst sources  

SciTech Connect

By using the high resolution observation of Nancay observatory, we have been able to identify the S burst emission on the planetary radio astronomy (PRA) records of Voyager. It is shown that the S bursts occur in two regions of the Phi/sub 10/-CML plane (S-IoB and S-IoA'C regions). In these regions the S burst emission is arranged into a pattern of repetitive features, drifting negatively. These features could be incomplete vertex late arcs. We show that the S burst pattern is distinct from the pattern of the Io-controlled emission. These results are discussed in the frame of Goldstein and Thieman's arc model.

Leblanc, Y.; Genova, F.

1981-09-30

213

Extragalactic Radio Bursts  

NASA Astrophysics Data System (ADS)

We propose a sky monitoring survey that will piggy-back multibeam observations of other scientific programmes; the intent of our search is to intercept and analyse millisecond-duration, single, impulsive bursts from transient events in the extragalactic sky.

Bailes, Matthew; Johnston, Simon; Bhat, Ramesh; Burke-Spolaor, Sarah; Barnes, David; van Straten, Willem

2008-04-01

214

Extragalactic Radio Bursts  

NASA Astrophysics Data System (ADS)

We propose a sky monitoring survey that will piggy-back multibeam observations of other scientific programmes; the intent of our search is to intercept and analyse millisecond-duration, single, impulsive bursts from transient events in the extragalactic sky.

Bailes, Matthew; Johnston, Simon; Bhat, Ramesh; Burke-Spolaor, Sarah; Barnes, David; van Straten, Willem

2007-10-01

215

Extragalactic Radio Bursts  

NASA Astrophysics Data System (ADS)

We propose a sky monitoring survey that will piggy-back multibeam observations of other scientific programmes; the intent of our search is to intercept and analyse millisecond-duration, single, impulsive bursts from transient events in the extragalactic sky.

Burke-Spolaor, Sarah; Johnston, Simon; Bailes, Matthew; Bhat, Ramesh; Barnes, David; van Straten, Willem

2008-10-01

216

Effect of IgA on Respiratory Burst and Cytokine Release by Human Alveolar Macrophages Role of ERK1\\/2 Mitogen-Activated Protein Kinases and NF ? B  

Microsoft Academic Search

Human alveolar macrophages (HAM) express FcR receptors for immunoglobulin (Ig)A which could link humoral and cellu- lar branches of lung immunity. Here, we investigate the ef- fects of polymeric (p-IgA) and secretory (S-IgA) IgA interaction with FcR on lipopolysaccharide (LPS)- and phorbol myristate acetate (PMA)-activated respiratory burst and TNF- ? release by HAM. Activation of HAM with LPS and PMA

Youssef Ouadrhiri; Charles Pilette; Renato C. Monteiro; Jean-Pierre Vaerman; Yves Sibille

217

Statistical Properties of SGR 1900+14 Bursts.  

PubMed

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. PMID:10550286

Göğüş; Woods; Kouveliotou; van Paradijs J; Briggs; Duncan; Thompson

1999-12-01

218

Study of the Electrical and Mechanical Activity of the Rectum: An Experimental Study  

Microsoft Academic Search

The electrical activity of the rectal detrusor was studied in 13 dogs. 10 electrodes were sutured serially to the rectal and lower sigmoid colon serosa. Electrical activity was recorded for 30 min\\/day for 10 days. Simultaneous electric and mechanical activity (recorded by a 6-French catheter connected to a pressure transducer) was also recorded with and without rectal distension by a

A. Shafik

1994-01-01

219

Toward a multiscale model of the uterine electrical activity.  

PubMed

A comprehensive multiscale model of the uterine muscle electrical activity would permit understanding the important link between the genesis and evolution of the action potential at the cell level and the process leading to labor. Understanding this link can open the way to more effective tools for the prediction of labor and prevention of preterm delivery. A first step toward the realization of such a model is presented here. By using as starting point a previously published model of the generation of the uterine muscle action potential at the cell level, a significant reduction of the model complexity is here achieved in order to simulate 2-D propagation of the cellular activity at the uterine tissue level, for tissue strips of arbitrary dimension. From the obtained dynamic behavior of the electrical activity simulated at the tissue level, the use of a previously validated volume conductor model at the organ level permits us to simulate the electrohysterogram as recorded on the abdominal surface by an electrode array. Qualitative evaluation of the model at the cell level and at the organ level confirms the potential of the proposed multiscale approach for further refinement and extension aiming at clinical application. PMID:21968708

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

2011-10-03

220

Pulseless electrical activity during electroconvulsive therapy: a case report  

PubMed Central

Background Arrhythmias resulting in cardiac arrest during electroconvulsive therapy have been reported. Most reported cases of cardiac arrest had asystole as the initial rhythm. Pulseless electrical activity as an initial rhythm of cardiac arrest during electroconvulsive therapy has never been reported. Also, thromboembolism after inflation of pneumatic tourniquet during lower limb surgery has been reported but never following tourniquet inflation during an electroconvulsive therapy. Case presentation We report a case involving an 81- year- old female who presented to us for an electroconvulsive therapy for severe depression and developed pulseless electrical activity immediately after electroconvulsive therapy. She was successfully resuscitated and was later found to have bilateral pulmonary emboli with a complete occlusion of the right lower lobe pulmonary artery. The source of embolus was from her left lower extremity deep venous thrombus, which we believe, got dislodged intraoperatively after inflation of pneumatic tourniquet. Our patient not only survived the massive pulmonary embolus, but also showed significant improvement in her mental status compared to her pre-admission level at the time of discharge to a sub-acute rehabilitation centre. Conclusion We recommend that patients who are elderly and at high risk of thromboembolism should selectively undergo a preoperative doppler ultrasound for deep venous thrombosis. Also, selective application of tourniquet in the upper limb, to monitor for seizure activity, would reduce the incidence of pulmonary thrombo-embolism as embolic events are significantly less from deep venous thromboses of upper extremities when compared to lower extremities.

2012-01-01

221

Therapeutic hypothermia after prolonged cardiopulmonary resuscitation for pulseless electrical activity.  

PubMed

We report an 18-year-old female patient with cardiac arrest due to pulseless electrical activity caused by a massive pulmonary embolism. Cardiopulmonary resuscitation was continued for more than one hour. Although the initial clinical signs and symptoms suggested poor outcome, immediate intravenous thrombolysis was instituted. After return of spontaneous circulation (75 minutes) the patient was still comatose and mild therapeutic hypothermia (32.5 degrees C) was instituted for brain protection during the first 24 hours. She recovered uneventfully without neurological deficit. Therapeutic hypothermia may be effective for neuroprotection in non-VFcardiac arrest. PMID:17293639

Bartels, M; Tjan, D H T; Reussen, E M; van Zanten, A R H

2007-01-01

222

Vasoactive intestinal peptide and electrical activity influence neuronal survival  

SciTech Connect

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

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

1986-02-01

223

On the Likelihood of Electrical Activity in Titan's Tropospheric Clouds  

NASA Astrophysics Data System (ADS)

An opportunity to search for lightning in Titan occurred during the Voyager 1 encounter with Saturn. Optically thick cloud and haze layers in the stratosphere prevented lightning detection at optical wavelengths. A search for lightning-radiated signals at radio wavelengths yielded negative results. The lack of terrestrial-like lightning does not dismiss, however, the possibility of other types of unusual lightning discharges in Titan. Titan's atmosphere appears to contain no polarizable gas that could lead to generation of a gross electrical structure of clouds by precipitation mechanisms. Instead the electrical dipole within Titan's clouds could result by convective motions to bring externally derived ions into the cloud, where they are attached to cloud particles. These ions and precipitating particles are continuously being generated by cosmic ray and Saturnian magnetospheric interactions with Titan's atmosphere. The net dipole within the cloud would result from updrafts transporting the positively charged particles to its upper portions while the downdrafts deliver negative charged aerosols from above the cloud top to the base. It is expected that weak electric fields would be developed within Titan's clouds that would result in corona discharge and weak intracloud lightning activity.

Navarro-Gonzalez, R.

1997-07-01

224

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

PubMed Central

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

Taccola, Giuliano; Secchia, Lucia; Ballanyi, Klaus

2007-01-01

225

Hybrid Electric and Plug-in Hybrid Electric Vehicle Testing Activities  

SciTech Connect

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

Donald Karner

2007-12-01

226

Quantum Electrical Metrology Division Programs, Activities, and Accomplishments.  

National Technical Information Service (NTIS)

The Quantum Electrical Metrology Division was created in November, 2003, with the merger of the Electricity Division in Gaithersburg, Maryland, and the Electromagnetic Technology Division in Boulder, Colorado. The Electricity Division brings a proud 100-y...

2005-01-01

227

Criteria for local myocardial electrical activation: effects of electrogram characteristics.  

PubMed

Detection of local electrical myocardial activation by means of extracellular recordings is often difficult in the presence of polyphasic electrograms. The purpose of this investigation was to compare the ability of several variables to distinguish unipolar deflections due to local activation from those due to nonlocal activity. A model of polyphasic deflections based on atrial recordings during reentrant tachycardia was used to facilitate distinction of local and distant activity by methods independent of the test variables. The performance of variables were assessed by comparing areas under receiver operating characteristic curves. Optimal thresholds of test variables were identified by maximizing statistics which corrected for the pretest probability of local activation. We found that the greatest negative first derivative of the unipolar potential discriminated between local and distant ventricular signals, but performed less well than the ratio of the first derivative to the potential for distinguishing between local atrial signals and distant ventricular signals. A linear combination of the potential and the ratio of the first derivative and the potential performed well for all groups of signals studied. We conclude that optimal criteria for detecting local activation depends on the characteristics of the population of signals and that a statistical approach can be used to identify optimal criteria for a given population. PMID:8319968

Anderson, K P; Walker, R; Fuller, M; Dustman, T; Ershler, P R; Lux, R L

1993-02-01

228

Synchronous and asynchronous electrically evoked motor activities during wind-up stimulation are differentially modulated following an acute spinal transection.  

PubMed

In this study, we used a novel technique to study reflex wind-up when the spinal cord is intact and following an acute spinal transection. Specifically, we evaluated reflex responses evoked by a series of 10 electrical pulses to the tibial or superficial peroneal nerves in 9 decerebrate adult cats, before and after an acute spinal transection. Electromyograms were recorded in four hindlimb muscles (lateral gastrocnemius, tibialis anterior, semitendinosus, and sartorius) to evaluate reflex amplitude, duration, and the temporal summation of reflex responses, so-called wind-up. We identified two distinct reflex responses evoked by electrical stimulation of the tibial or superficial peroneal nerves on the basis of their pattern of change following acute spinal transection, a short-latency (?10 ms) compound action potential (CAP) that was followed by a burst of sustained activity (SA). Wind-up of CAP and SA amplitudes was clearly present when the spinal cord was intact but was drastically reduced after acute spinalization in some muscles. Moreover, CAP and SA reflex responses were differentially modified by the acute spinalization. When the effects of acute spinal transection were significant, CAP responses were increased after acute spinalization, whereas SA responses were reduced, suggesting that the two signals are regulated by different neuronal mechanisms. The present results provide the first assessment of reflex wind-up before and after an acute spinal transection in the same animals and indicate that different reflex components must be considered separately when evaluating changes in neuronal excitability following SCI. PMID:22993264

Frigon, Alain; Hurteau, Marie-France; Johnson, Michael D; Heckman, C J; Telonio, Alessandro; Thibaudier, Yann

2012-09-19

229

An Intrinsic Neuronal Oscillator Underlies Dopaminergic Neuron Bursting  

PubMed Central

Dopaminergic neurons of the ventral midbrain fire high frequency bursts when animals are presented with unexpected rewards, or stimuli that predict reward. To identify the afferents that can initiate bursting and establish therapeutic strategies for diseases affected by altered bursting, a mechanistic understanding of bursting is essential. Our results show that bursting is initiated by a specific interaction between the voltage sensitivity of NMDA receptors and voltage-gated ion channels, which result in the activation of an intrinsic, action potential-independent, high-frequency membrane potential oscillation. We further show that the NMDA receptor is uniquely suited for this because of the rapid kinetics and voltage dependence imparted to it by Mg2+ ion block and unblock. This mechanism explains the discrete nature of bursting in dopaminergic cells, and demonstrates how synaptic signals may be reshaped by local intrinsic properties of a neuron before influencing action potential generation.

Deister, Christopher A.; Teagarden, Mark A.; Wilson, Charles J.; Paladini, Carlos A.

2010-01-01

230

Differential activation of signal transduction pathways mediating phagocytosis, oxidative burst, and degranulation by chicken heterophils in response to stimulation with opsonized Salmonella enteritidis.  

PubMed

The activation of signal transduction pathways is required for the expression of functional enhancement of cellular activities. In the present studies, initial attempts were made to identify the signal transduction factors involved in activating phagocytosis, generation of an oxidative burst, and degranulation by heterophils isolated from neonatal chickens in response to opsonized Salmonella enteritidis (opsonized SE). Peripheral blood heterophils were isolated and exposed to known inhibitors of signal transduction pathways for either 20 min (staurosporin, genistein, or verapamil) or 120 min (pertussis toxin) at 39 degrees C. The cells were then stimulated for 30 min at 39 degrees C with opsonized SE. Phagocytosis, luminol-dependent chemoluminescence (LDCL), and beta-D glucuronidase release were then evaluated in vitro. The G-protein inhibitor pertussin toxin markedly inhibited (>80%) phagocytosis of opsonized SE. Both the protein kinase inhibitor (staurosporin) and calcium channel inhibitor (verapamil) reduced phagocytosis in a dose response manner. Genistein, a tyrosine kinase inhibitor, had no effect on phagocytosis. Staurosporin had a marked inhibitory effect on LDCL (>90%) while genistein had a dose responsive inhibition on LDCL. Both verapamil (40-45%) and pertussin toxin (50-55%) had a statistically significant, but less biologically significant effect on LDCL. Genistein significantly reduced the degranulation (78-81%) of heterophils by opsonized SE. Staurosporin also reduced degranulation by 43-50%, but neither verapamil nor pertussis toxin had a significant effect on degranulation. These findings demonstrate that distinct signal transduction pathways differentially regulate the stimulation of the functional activities of avian heterophils. Pertussin toxin-sensitive, Ca++-dependent G-proteins appear to regulate phagocytosis of opsonized SE, protein kinase C-dependent, tyrosine kinase-dependent protein phosphorylation plays a major role in LDCL, and tyrosine kinase(s)-dependent phosphorylation regulates primary granule release. PMID:11293667

Kogut, M H; Genovese, K J; Lowry, V K

2001-02-01

231

Avalanches and bursts in low-pressure helium gas below the breakdown voltage  

Microsoft Academic Search

External ionizing particles may induce electron avalanches and bursts (sequences of avalanches) in a gas subjected to an electric field. The properties of these avalanches and bursts at a given pressure depend on the strength of the electric field, which in our case is considered to be homogeneous between two plane-parallel metal electrodes. With increasing voltage (V) applied to the

Z. Donkó

1995-01-01

232

Modeling cardiac electrical activity at the cell and tissue levels.  

PubMed

Significant tissue structures exist in cardiac ventricular tissue, which are of supracellular dimension. It is hypothesized that these tissue structures contribute to the discontinuous spread of electrical activation, may contribute to arrhythmogenesis, and also provide a substrate for effective cardioversion. However, the influences of these mesoscale tissue structures in intact ventricular tissue are difficult to understand solely on the basis of experimental measurement. Current measurement technology is able to record at both the macroscale tissue level and the microscale cellular or subcellular level, but to date it has not been possible to obtain large volume, direct measurements at the mesoscales. To bridge this scale gap in experimental measurements, we use tissue-specific structure and mathematical modeling. Our models, which can incorporate ion channel models at the cell level into the reaction-diffusion equations at the tissue level, have enabled us to consider key hypotheses regarding discontinuous activation. PMID:17132793

Austin, Travis M; Hooks, Darren A; Hunter, Peter J; Nickerson, David P; Pullan, Andrew J; Sands, Gregory B; Smaill, Bruce H; Trew, Mark L

2006-10-01

233

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.

234

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

PubMed Central

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

Keizer, J; Magnus, G

1989-01-01

235

Design and testing of a NITPC X-ray polarimeter with applications for the measurement of SGR burst polarization  

NASA Astrophysics Data System (ADS)

Soft gamma repeaters (SGRs) are neutron stars with ultra-strong magnetic fields, on the order of 1014 G. As the source of the strongest magnetic fields in the universe, they are ideal objects to study the behavior of matter and light in this extreme environment. SGRs emit recurrent short duration, 0.1s, bursts of soft gamma-rays/hard X-rays that are expected to be highly polarized in the 2-10 keV energy range. By measuring the polarization of these bursts we can learn about the strength and configuration of the magnetic fields, the geometry of the emission region and the mass/radius relationship of the neutron star. Using the archival RXTE/PCA data we analyzed ˜3 Ms of observations for SGR1806-20 and SGR1900+14. Over 5000 bursts were detected from the sources and each distribution of burst fluence was found to be well fit by a power law with an exponent of 1.60+/-0.02 for SGR1806-20 and 1.64+/-0.03 for SGR1900+14. The power law form holds over 4 magnitudes of fluence and the exponents were found to be independent of the level of burst activity. The exponent values suggest that SGR bursts are associated with a self-organized critical system, similar to earthquakes. To measure the polarization of SGR bursts a wide-field-of-view, large area detector is needed. To accomplish this we designed and tested a negative ion time projection chamber (NITPC) X-ray polarimeter which uses nitromethane (CH3NO2) as an electronegative gas additive. Utilizing a double gas electron multiplier (GEM) NITPC with CO2+CH3 NO2 as a gas mixture we successfully measured gas gains, imaged photoelectron tracks and measured distributions of their length, measured drift velocity of negative ions in various electric fields, and measured modulation from polarized and unpolarized X-ray sources between 3 and 8 keV. Based on the lab instrument results and our SGR burst fluence analysis we propose an instrument appropriately sized for a NASA Small Mission Explorer Mission (SMEX) that would be capable of measuring the polarization of hundreds of bursts from an SGR in a state of high burst activity.

Prieskorn, Zachary Ryan

236

Gamma-ray Burst Educator Guide  

NSDL National Science Digital Library

This guide accompanies an educational wallsheet that uses Gamma-ray Bursts as an engagement to teach selected topics in physical science and mathematics. It features four curriculum enhancement activities, background information, assessment information, student worksheets, extension and transfer activities, and detailed information about the physical science and mathematics content standards for grades 9-12.

2004-01-01

237

Infrared optical activity: electric field approaches in time domain.  

PubMed

Vibrational circular dichroism (VCD) spectroscopy provides detailed information about the absolute configurations of chiral molecules including biomolecules and synthetic drugs. This method is the infrared (IR) analogue of the more popular electronic CD spectroscopy that uses the ultraviolet and visible ranges of the electromagnetic spectrum. Because conventional electronic CD spectroscopy measures the difference in signal intensity, problems such as weak signal and low time-resolution can limit its utility. To overcome the difficulties associated with that approach, we have recently developed femtosecond IR optical activity (IOA) spectrometry, which directly measures the IOA free-induction-decay (FID), the impulsive chiroptical IR response that occurs over time. In this Account, we review the time-domain electric field measurement and calculation methods used to simultaneously characterize VCD and related vibrational optical rotatory dispersion (VORD) spectra. Although conventional methods measure the electric field intensity, this vibrational technique is based on a direct phase-and-amplitude measurement of the electric field of the chiroptical signal over time. This method uses a cross-polarization analyzer to carry out heterodyned spectral interferometry. The cross-polarization scheme enables us to selectively remove the achiral background signal, which is the dominant noise component present in differential intensity measurement techniques. Because we can detect the IOA FID signal in a phase-amplitude-sensitive manner, we can directly characterize the time-dependent electric dipole/magnetic dipole response function and the complex chiral susceptibility that contain information about the angular oscillations of charged particles. These parameters yield information about the VCD and VORD spectra. In parallel with such experimental developments, we have also calculated the IOA FID signal and the resulting VCD spectrum. These simulations use a quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) method and calculate the electric dipole/magnetic dipole cross-correlation function in the time domain. Although many quantum chemistry calculation approaches can only consider a limited number of geometry-optimized conformations of chiral molecules in a gas phase, this computational method includes the solute-solvent interactions and the inhomogeneous distributions of solute conformers in condensed phases. A subsequent Fourier transformation of the chiral response function produced a theoretical VCD spectrum in the entire mid-IR frequency range. Directly comparing theory and experiment, we demonstrate quantitative agreement between frequency-tunable femtosecond IOA measurements and QM/MM MD simulations of (1S)-?-pinene in CCl(4) solution. We anticipate that these direct IOA measurement and calculation methods will be applied to the studies of equilibrium chiroptical properties and structure determinations. These methods provide tools to investigate ultrafast structural dynamics of chiral systems with unprecedented time resolution. PMID:20931956

Rhee, Hanju; Choi, Jun-Ho; Cho, Minhaeng

2010-10-08

238

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

239

Local cortical dynamics of burst suppression in the anaesthetized brain  

PubMed Central

Burst suppression is an electroencephalogram pattern that consists of a quasi-periodic alternation between isoelectric ‘suppressions’ lasting seconds or minutes, and high-voltage ‘bursts’. It is characteristic of a profoundly inactivated brain, occurring in conditions including hypothermia, deep general anaesthesia, infant encephalopathy and coma. It is also used in neurology as an electrophysiological endpoint in pharmacologically induced coma for brain protection after traumatic injury and during status epilepticus. Classically, burst suppression has been regarded as a ‘global’ state with synchronous activity throughout cortex. This assumption has influenced the clinical use of burst suppression as a way to broadly reduce neural activity. However, the extent of spatial homogeneity has not been fully explored due to the challenges in recording from multiple cortical sites simultaneously. The neurophysiological dynamics of large-scale cortical circuits during burst suppression are therefore not well understood. To address this question, we recorded intracranial electrocorticograms from patients who entered burst suppression while receiving propofol general anaesthesia. The electrodes were broadly distributed across cortex, enabling us to examine both the dynamics of burst suppression within local cortical regions and larger-scale network interactions. We found that in contrast to previous characterizations, bursts could be substantially asynchronous across the cortex. Furthermore, the state of burst suppression itself could occur in a limited cortical region while other areas exhibited ongoing continuous activity. In addition, we found a complex temporal structure within bursts, which recapitulated the spectral dynamics of the state preceding burst suppression, and evolved throughout the course of a single burst. Our observations imply that local cortical dynamics are not homogeneous, even during significant brain inactivation. Instead, cortical and, implicitly, subcortical circuits express seemingly different sensitivities to high doses of anaesthetics that suggest a hierarchy governing how the brain enters burst suppression, and emphasize the role of local dynamics in what has previously been regarded as a global state. These findings suggest a conceptual shift in how neurologists could assess the brain function of patients undergoing burst suppression. First, analysing spatial variation in burst suppression could provide insight into the circuit dysfunction underlying a given pathology, and could improve monitoring of medically-induced coma. Second, analysing the temporal dynamics within a burst could help assess the underlying brain state. This approach could be explored as a prognostic tool for recovery from coma, and for guiding treatment of status epilepticus. Overall, these results suggest new research directions and methods that could improve patient monitoring in clinical practice.

Weiner, Veronica S.; Peterfreund, Robert A.; Eskandar, Emad N.; Cash, Sydney S.; Brown, Emery N.; Purdon, Patrick L.

2013-01-01

240

Thermonuclear Burst Oscillations  

NASA Astrophysics Data System (ADS)

Burst oscillations, a phenomenon observed in a significant fraction of Type I (thermonuclear) X-ray bursts, involve the development of highly asymmetric brightness patches in the burning surface layers of accreting neutron stars. Intrinsically interesting as nuclear phenomena, they are also important as probes of dense matter physics and the strong gravity, high magnetic field environment of the neutron star surface. Burst oscillation frequency is also used to measure stellar spin, and doubles the sample of rapidly rotating (above 10 Hz) accreting neutron stars with known spins. Although the mechanism remains mysterious, burst oscillation models must take into account thermonuclear flame spread, nuclear processes, rapid rotation, and the dynamical role of the magnetic field. This review provides a comprehensive summary of the observational properties of burst oscillations, an assessment of the status of the theoretical models that are being developed to explain them, and an overview of how they can be used to constrain neutron star properties such as spin, mass, and radius.

Watts, Anna L.

2012-09-01

241

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

PubMed Central

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

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

2012-01-01

242

Bradykinin enhances membrane electrical activity of pancreatic beta cells in the presence of low glucose concentrations.  

PubMed

In most of cells bradykinin (BK) induces intracellular calcium mobilization. In pancreatic beta cells intracellular calcium is a major signal for insulin secretion. In these cells, glucose metabolism yields intracellular ATP which blocks membrane potassium channels. The membrane depolarizes, voltage-dependent Ca2+ channels are activated and the intracellular calcium load allows insulin secretion. Repolarization occurs due to activation of the Ca2+-dependent K+ channel. The insulin secretion depends on the integrity of this oscillatory process (bursts). Therefore, we decided to determine whether BK (100 nM) induces bursts in the presence of a non-stimulatory glucose concentration (5.6 mM). During continuous membrane voltage recording, our results showed that bursts were obtained with 11 mM glucose, blocked with 5.6 mM glucose and recovered with 5.6 mM glucose plus 100 nM BK. Thus, the stimulatory process obtained in the presence of BK and of a non-stimulatory concentration of glucose in the present study suggests that BK may facilitate the action of glucose on beta cell secretion. PMID:10973143

Moura, A S

2000-09-01

243

Electrical impedance tomography system based on active electrodes.  

PubMed

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

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

2012-04-24

244

Detailed measurements of gastric electrical activity and their implications on inverse solutions  

Microsoft Academic Search

Significant research effort has been expended on investigating methods to non-invasively characterize gastrointestinal electrical activity. Despite the clinical success of the 12-lead electrocardiograms (ECG) and the emerging success of inverse methods for characterizing electrical activity of the heart and brain, similar methods have not been successfully transferred to the gastrointestinal field. The normal human stomach generates rhythmic electrical impulses, known

Leo K. Cheng; G. O'Grady; Peng Du; J. U. Egbuji; J. A. Windsor; A. J. Pullan

2009-01-01

245

Third plasma harmonic radiation in type II bursts  

Microsoft Academic Search

We present observational evidence for simultaneous fundamental, second and third harmonic radio emission during an excessively strong type II burst on February 16, 1984. This burst was emitted from an active region behind the limb allowing for fair resolution of the wave bands. If interpreted as a triple harmonic system, three different, nearly equally probable mechanisms for higher harmonic emission

B. Kliem; A. Krueger; R. A. Treumann

1992-01-01

246

Gamma ray bursts as probes of the first stars  

Microsoft Academic Search

The redshift where the first stars formed is an important and unknown milestone in cosmological structure formation. The evidence linking gamma ray bursts (GRBs) with star formation activity implies that the first GRBs occurred shortly after the first stars formed. Gamma ray bursts and their afterglows may thus offer a unique probe of this epoch, because they are bright from

James E. Rhoads

2001-01-01

247

Project BudBurst: Citizen Science for All Seasons  

Microsoft Academic Search

Project BudBurst is a national citizen science initiative designed to engage the public in observations of phenological (plant life cycle) events that raise awareness of climate change, and create a cadre of informed citizen scientists. Citizen science programs such as Project BudBurst provide the opportunity for students and interested laypersons to actively participate in scientific research. Such programs are important

S. Henderson; C. Brewer; K. Havens; K. Meymaris

2007-01-01

248

Neutron bursts associated with lightning cloud-to-ground discharges  

NASA Astrophysics Data System (ADS)

We consider bursts in the neutrons registered by the Yakut spectrograph of cosmic rays and the electrostatic fluxmeter (± 50 kV/m). Bursts were observed during a significant change in the field, which changes abruptly from - 16 kV/m to 18 kV/m during negative lightning. It was found that during the positive lightning have not been observed bursts of neutrons, despite that the electric field changes abruptly from 10 kV/m up to -30 kV/m during the lightning discharge.

Kozlov, V. I.; Mullayarov, V. A.; Starodubtsev, S. A.; Toropov, A. A.

2013-02-01

249

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

Microsoft Academic Search

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

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

2009-01-01

250

Effect of organic compounds on cloud condensation nuclei (CCN) activity of sea spray aerosol produced by bubble bursting  

NASA Astrophysics Data System (ADS)

The ocean comprises over 70% of the surface of the earth and thus sea spray aerosols generated by wave processes represent a critical component of our climate system. The manner in which different complex oceanic mixtures of organic species and inorganic salts are distributed between individual particles in sea spray directly determines which particles will effectively form cloud nuclei. Controlled laboratory experiments were undertaken to better understand the full range of particle properties produced by bubbling solutions composed of simplistic model organic species, oleic acid and sodium dodecyl sulfate (SDS), mixed with NaCl to more complex artificial seawater mixed with complex organic mixtures produced by common oceanic microorganisms. Simple mixtures of NaCl and oleic acid or SDS had a significant effect on CCN activity, even in relatively small amounts. However, an artificial seawater (ASW) solution containing microorganisms, the common cyanobacteria ( Synechococcus ) and DMS-producing green algae ( Ostreococcus ), produced particles containing ˜34 times more carbon than the particles produced from pure ASW, yet no significant change was observed in the overall CCN activity. We hypothesize that these microorganisms produce diverse mixtures of organic species with a wide range of properties that produced offsetting effects, leading to no net change in the overall average measured hygroscopicity of the collection of sea spray particles. Based on these observations, changes in CCN activity due to "bloom" conditions would be predicted to lead to small changes in the average CCN activity, and thus have a negligible impact on cloud formation. However, each sea spray particle will contain a broad spectrum of different species, and thus further studies are needed of the CCN activity of individual sea spray particles and biological processes under a wide range of controllable conditions.

Moore, Meagan J. K.; Furutani, Hiroshi; Roberts, Gregory C.; Moffet, Ryan C.; Gilles, Mary K.; Palenik, Brian; Prather, Kimberly A.

2011-12-01

251

Type III Radio Bursts at Long Wavelengths: Statistics from STEREO/Waves 2007-2010  

NASA Astrophysics Data System (ADS)

During increased solar activity type III radio bursts are frequently observed by the S/Waves instrument on-board both STEREO spacecraft. These radio bursts are generated by a non-linear conversion of the Langmuir waves which have been excited by beams of fast electrons connected with solar flares and/or CME driven shocks. The High Frequency Receiver (HFR; a part of S/Waves) records fluctuations of the electric field from 125 kHz up to 1975 kHz with goniopolarimetric (GP) capabilities that allows us to perform propagation analysis of an incident wave. We present extensive statistics of more than 100 intense events observed between March 2007 and July 2010. We have found that type III radio bursts generally propagate in the solar equatorial plane. For larger frequencies dispersion of the central directions toward the sources distribution decreases suggesting that scattering of the primary beam pattern plays a key role in propagation comparing to refraction. Our results indicate that type III radio bursts have the apparent source 23 size half-width of 25 - 30 degrees.

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

2010-12-01

252

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

PubMed Central

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

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

2011-01-01

253

Electrically Conductive and Optically Active Porous Silicon Nanowires  

PubMed Central

We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, and entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer, and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for the novel optoelectronic devices for energy harvesting, conversion and biosensing.

Qu, Yongquan; Liao, Lei; Li, Yujing; Zhang, Hua; Huang, Yu; Duan, Xiangfeng

2009-01-01

254

The high-resolution optical mapping of cardiac electrical activity  

NASA Astrophysics Data System (ADS)

High-resolution optical mapping based on voltage-sensitive dyes is a relatively new technology that is used to "image" electrical activity in a wide range, from the level of cellular to the whole heart. By using optical recording it is possible to overcome several limitations of other conventional mapping techniques and to depict complex propagation patterns of cardiac transmembrane potentials while it has been proven to be very useful for illuminating basic electrophysiological development. Strategies for maximizing signal-to-noise ratios and removing motion artifacts are the research emphases. Currently, two types of devices dominate in this field, Charge Coupled Devices (CCD) and Photo Diode Arrays (PDA), and some algorithms correcting motion artifacts are used in data processing. In this article, we have attempted to conduct and present a comprehensive review and a perspective of this rapidly developing novel field.

Xu, Zhenghong; Zhang, Zhenxi; Wang, Jing; Huang, Ye-cho

2003-12-01

255

Federal Electricity Subsidies: Information on Research Funding, Tax Expenditures, and Other Activities That Support Electricity Production.  

National Technical Information Service (NTIS)

Electricity is vital to our daily lives, powering homes, businesses, and industries. Presently, electricity is generated largely by coal and other fossil fuels and nuclear power, with hydropower, and, to a lesser extent, renewable energy sources, such as ...

2007-01-01

256

Mutual passivation of electrically active and isovalent impurities.  

PubMed

The alloy GaN(x) As(1-x) (with x typically less than 0.05) is a novel semiconductor that has many interesting electronic properties because of the nitrogen-induced dramatic modifications of the conduction band structure of the host material (GaAs). Here we demonstrate the existence of an entirely new effect in the GaN(x) As(1-x) alloy system in which the Si donor in the substitututional Ga site (Si(Ga)) and the isovalent atom N in the As sublattice (N(As)) passivate each other's electronic activity. This mutual passivation occurs in Si-doped GaN(x) As(1-x) through the formation of nearest-neighbour Si(Ga) -N(As) pairs and is thermally stable up to 950 degrees C. Consequently, Si doping in GaN(x) As(1-x) under equilibrium conditions results in a highly resistive GaN(x) As(1-x) layer with the fundamental bandgap governed by a net 'active' N, roughly equal to the total N content minus the Si concentration. Such mutual passivation is expected to be a general phenomenon for electrically active dopants and localized state impurities that can form nearest-neighbour pairs. PMID:12618808

Yu, K M; Walukiewicz, W; Wu, J; Mars, D E; Chamberlin, D R; Scarpulla, M A; Dubon, O D; Geisz, J F

2002-11-01

257

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

258

Quantum Electrical Metrology Division Programs, Activities, and Accomplishments, January 2007.  

National Technical Information Service (NTIS)

The Quantum Electrical Metrology Division unites fundamental electrical metrology and leading-edge quantum-based metrology research to create a dynamic organization poised to lead quantum metrology into the future. The Division consists of three groups: F...

2007-01-01

259

Changing excitation and inhibition in simulated neural networks: effects on induced bursting behavior  

Microsoft Academic Search

The development of synchronous bursting in neu- ronal ensembles represents an important change in network behavior. To determine the influences on development of such synchronous bursting behavior we study the dynamics of small networks of sparsely connected excitatory and inhibitory neu- rons using numerical simulations. The synchronized bursting activities in networks evoked by background spikes are in- vestigated. Specifically, patterns

Pawel Kudela; Piotr J. Franaszczuk; Gregory K. Bergey

2003-01-01

260

Gamma-ray bursts  

Microsoft Academic Search

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models

P. Mészáros

2006-01-01

261

Terabit burst switching  

Microsoft Academic Search

Demand for network bandwidth is growing at unprecedented rates, placing growing demands on switching and transmission technologies. Wavelength division multiplexing will soon make it possible to combine hundreds of gigabit channels on a single fiber. This paper presents an architecture for Burst Switching Systems designed to switch data among WDM links, treating each link as a shared resource rather than

Jonathan S. Turner

1999-01-01

262

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

SciTech Connect

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

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

2010-06-20

263

Radiation Mechanism and Jet Composition of Gamma-Ray Bursts and GeV-TeV-selected Radio-loud Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

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

Zhang, Jin; Liang, En-Wei; Sun, Xiao-Na; Zhang, Bing; Lu, Ye; Zhang, Shuang-Nan

2013-09-01

264

Electrically active sodium-related defect centres in silicon  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

265

A Meshfree Method for Simulating Myocardial Electrical Activity  

PubMed Central

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

Zhang, Heye; Ye, Huajun; Huang, Wenhua

2012-01-01

266

Efficient elastic burst detection in data streams  

Microsoft Academic Search

Burst detection is the activity of finding abnormal aggregates in data streams. Such aggregates are based on sliding windows over data streams. In some applications, we want to monitor many sliding window sizes simultaneously and to report those windows with aggregates significantly different from other periods. We will present a general data structure for detecting interesting aggregates over such elastic

Yunyue Zhu; Dennis Shasha

2003-01-01

267

Electricity  

SciTech Connect

Historical aspects of electricity are reviewed with individual articles on hydroelectric dams, coal-burning power plants, nuclear power plants, electricity distribution, and the energy future. A glossary is included. (PSB)

Sims, B. (ed.)

1983-01-01

268

The effects of steroid hormones on electrical activity of excitable cells  

Microsoft Academic Search

Steroid hormones influence the electrical activity of many neurons and effectors by regulating the transcription of their ion channels and neurotransmitter receptors, or by modulating the activity of their channels and receptors through second messenger-coupled membrane receptors, or both. In this article, four cell types with known functions and distinct electrical activities are focused on to illustrate how different steroids

Harold H. Zakon

1998-01-01

269

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

Microsoft Academic Search

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

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

2004-01-01

270

Action potential bursts enhance transmitter release at a giant central synapse  

PubMed Central

Abstract Patterns of action potentials (APs), often in the form of bursts, are critical for coding and processing information in the brain. However, how AP bursts modulate secretion at synapses remains elusive. Here, using the calyx of Held synapse as a model we compared synaptic release evoked by AP patterns with a different number of bursts while the total number of APs and frequency were fixed. The ratio of total release produced by multiple bursts to that by a single burst was defined as ‘burst-effect’. We found that four bursts of 25 stimuli at 100 Hz increased the total charge of EPSCs to 1.47 ± 0.04 times that by a single burst of 100 stimuli at the same frequency. Blocking AMPA receptor desensitization and saturation did not alter the burst-effect, indicating that it was mainly determined by presynaptic mechanisms. Simultaneous dual recordings of presynaptic membrane capacitance (Cm) and EPSCs revealed a similar burst-effect, being 1.58 ± 0.13 by Cm and 1.49 ± 0.05 by EPSCs. Reducing presynaptic Ca2+ influx by lowering extracellular Ca2+ concentration or buffering residual intracellular Ca2+ with EGTA inhibited the burst-effect. We further developed a computational model largely recapitulating the burst-effect and demonstrated that this effect is highly sensitive to dynamic change in availability of the releasable pool of synaptic vesicles during various patterns of activities. Taken together, we conclude that AP bursts modulate synaptic output mainly through intricate interaction between depletion and replenishment of the large releasable pool. This burst-effect differs from the somatic burst-effect previously described from adrenal chromaffin cells, which substantially depends on activity-induced accumulation of Ca2+ to facilitate release of a limited number of vesicles in the releasable pool. Hence, AP bursts may play an important role in dynamically regulating synaptic strength and fidelity during intense neuronal activity at central synapses.

Zhang, Bo; Sun, Liang; Yang, Yi-Mei; Huang, Hong-Ping; Zhu, Fei-Peng; Wang, Li; Zhang, Xiao-Yu; Guo, Shu; Zuo, Pan-Li; Zhang, Claire X; Ding, Jiu-Ping; Wang, Lu-Yang; Zhou, Zhuan

2011-01-01

271

Phagocytic activity, respiratory burst, cytoplasmic free-Ca(2+) concentration and apoptotic cell ratio of haemocytes from the black tiger shrimp, Penaeus monodon under acute copper stress.  

PubMed

The aim of this study was to investigate the cellular toxicity of copper-induced injury to the black tiger shrimp Penaeus monodon. The 24h, 48h, 72h and 96h LC(50) (median lethal concentration) of Cu(2+) on P. monodon (11.63+/-1.14g) were found to be 3.49, 1.54, 0.73 and 0.40mgL(-1), respectively. Total haemocyte count (THC), phagocytic activity, respiratory burst (RB), cytoplasmic free-Ca(2+) (cf-Ca(2+)) concentration and apoptotic cell ratio of shrimp were determined after exposure to different concentrations of Cu(2+) (0, 0.05, 0.5, 1.5 and 3.5mgL(-1)) for 0, 6, 12, 24 and 48h. There was no significant effect on the analytic indicator of shrimp exposed to 0.05mgL(-1) Cu(2+). THC decreased after Cu-exposure to 0.5mgL(-1) for 48h, 1.5mgL(-1) for 24h and 3.5mgL(-1) for 12h. Phagocytic activity decreased in P. monodon following 48h exposure to 3.5mgL(-1) Cu(2+). RB was induced after 6h exposure to 0.5, 1.5 and 3.5mgL(-1) Cu(2+). cf-Ca(2+) concentration increased after 48h exposure to 0.5mgL(-1) Cu(2+), and 12h exposure to 1.5 and 3.5mgL(-1) Cu(2+). The percentage of apoptotic cells increased to 9.5%, 16.3% and 18.6% respectively following 48h exposure to 0.5, 1.5 and 3.5mgL(-1) Cu(2+). These results indicate that Cu can induce oxidative stress, elevation of cf-Ca(2+) and cell apoptosis, and inhibit phagocytic activity in the shrimp P. monodon, and the lethal injury of Cu(2+) to P. monodon may be mainly due to the sharp reduction of THC caused by ROS-induced apoptosis. PMID:20398793

Xian, Jian-An; Wang, An-Li; Ye, Chao-Xia; Chen, Xiao-Dan; Wang, Wei-Na

2010-04-14

272

Jovian type III radio bursts  

NASA Astrophysics Data System (ADS)

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.

1989-06-01

273

Endogenous GABA and Glutamate Finely Tune the Bursting of Olfactory Bulb External Tufted Cells  

PubMed Central

In rat olfactory bulb slices, external tufted (ET) cells spontaneously generate spike bursts. Although ET cell bursting is intrinsically generated, its strength and precise timing may be regulated by synaptic input. We tested this hypothesis by analyzing whether the burst properties are modulated by activation of ionotropic ?-aminobutyric acid (GABA) and glutamate receptors. Blocking GABAA receptors increased—whereas blocking ionotropic glutamate receptors decreased—the number of spikes/burst without changing the interburst frequency. The GABAA agonist (isoguvacine, 10 ?M) completely inhibited bursting or reduced the number of spikes/burst, suggesting a shunting effect. These findings indicate that the properties of ET cell spontaneous bursting are differentially controlled by GABAergic and glutamatergic fast synaptic transmission. We suggest that ET cell excitatory and inhibitory inputs may be encoded as a change in the pattern of spike bursting in ET cells, which together with mitral/tufted cells constitute the output circuit of the olfactory bulb.

Hayar, Abdallah; Ennis, Matthew

2008-01-01

274

Electrical activity of the intestine of mice with hereditary megacolon and absence of enteric ganglion cells  

Microsoft Academic Search

Mice with a recessive gene which reduces the number of ganglion cells of the large intestine and produces megacolon similar to Hirschsprung's disease were studied. Electrical activity of the small bowel consisted of electrical slow waves and action potentials and showed no difference between the mice with megacolon and their normal siblings. Electrical slow waves and action potentials occurred in

J. D. Wood

1973-01-01

275

Full System Bifurcation Analysis of Endocrine Bursting Models  

PubMed Central

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

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

2010-01-01

276

Computation of induced electric field for the sacral nerve activation.  

PubMed

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

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

2013-10-18

277

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

278

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

279

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

PubMed Central

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

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

2010-01-01

280

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

281

Characteristics of hippocampal primed burst potentiation in vitro and in the awake rat.  

PubMed

A pattern of electrical stimulation based on 2 prominent physiological features of the hippocampus, complex spike discharge and theta rhythm, was used to induce lasting increases in responses recorded in area CA1 of hippocampal slices maintained in vitro and from the hippocampus of behaving rats. This effect, termed primed burst (PB) potentiation, was elicited by as few as 3 stimuli delivered to the commissural/associational afferents to CA1. The patterns of stimulus presentation consisted of a single priming pulse followed either 140 or 170 msec later by a high-frequency burst of 2-10 pulses; control stimulation composed of unprimed high-frequency trains of up to 10 pulses had no enduring effect. Of all intervals tested, only 140 and 170 msec delays between the priming and burst stimuli were effective. PB potentiation could be induced both homo- and heterosynaptically. In the latter case, the priming pulse and burst stimuli were delivered to different dendritic fields; under these conditions, the PB effect was confined to the "burst" pathway. PB potentiation is not dependent on somal spiking; dendritic activation appears to be both necessary and sufficient for lasting changes to occur. Two findings indicate that PB potentiation and LTP have common mechanisms: (1) The effects of PB stimulation and LTP were not additive, in that saturation of the enhancement by PB stimulation eliminated any further increases in response with LTP stimulation; and (2) both PB potentiation and LTP were prevented if the N-methyl-D-aspartate antagonists 2-amino-5-phosphonovaleric acid or phencyclidine were added to the in vitro perfusion medium. Recordings from the hippocampus of awake rats demonstrated that PB potentiation of the CA1 population spike and slope of the EPSP are reliably induced under physiological conditions. This extensive characterization of PB stimulation provides novel information regarding the physiological and pharmacological basis of a possible role of endogenous rhythms in the processing and storage of information. PMID:3183713

Diamond, D M; Dunwiddie, T V; Rose, G M

1988-11-01

282

Periodic bursts of Jovian non-Io decametric radio emission  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

283

Periodic bursts of Jovian non-Io decametric radio emission.  

PubMed

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

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

2013-03-01

284

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

285

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

286

Bubble bursting mediated aerosols  

NASA Astrophysics Data System (ADS)

Wave breaking over the ocean in the surf zone is responsible for a substantial amount of atmospheric aerosols production. The objects mediating their formation are bubbles entrained below breaking waves, and bursting at the sea surface. We describe the mechanisms by which the liquid shell constitutive of a bubble ultimately results into small drops, also called film drops. A bubble bursts when a hole nucleates through the liquid shell. The hole grows at the Culick velocity balancing inertia with surface tension and is bordered by a rim collecting the shell liquid. This initially smooth toroidal rim corrugates when the centripetal acceleration caused by the recession motion is strong enough to trigger a Rayleigh-Taylor destabilization. Ligaments then emerge from corrugations crests and resolve by a Plateau-Rayleigh mechanism into droplets. The final myst properties are thus solely determined by the shell geometry at the bursting onset. It depends on the ratio of the bubble radius to the capillary length, and on the slow gravity drainage of the liquid on which are superimposed rearrangements due to the marginal regeneration at the bubble foot. Our findings will be discussed in connexion with know facts in that context.

Lhuissier, Henri; Villermaux, Emmanuel

2009-11-01

287

Interactions Among Hippocampal Neurons and Synchronization Leading to Epileptiform Bursts,  

National Technical Information Service (NTIS)

A fundamental component of epileptiform activity is synchronous bursting within a population of cortical neurons. In vitro preparations of mammaliam nervous tissue (in particular, slices of hippocampus) have provided direct evidence for and detailed analy...

F. E. Dudek E. P. Christian

1987-01-01

288

Automatic recognition of type III solar radio bursts: Automated Radio Burst Identification System method and first observations  

NASA Astrophysics Data System (ADS)

Because of the rapidly increasing role of technology, including complicated electronic systems, spacecraft, etc., modern society has become more vulnerable to a set of extraterrestrial influences (space weather) and requires continuous observation and forecasts of space weather. The major space weather events like solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can be used for a real-time space weather forecast. Coronal type III radio bursts are produced near the local electron plasma frequency and near its harmonic by fast electrons ejected from the solar active regions and moving through the corona and solar wind. These bursts have dynamic spectra with frequency rapidly falling with time, the typical duration of the coronal burst being about 1-3 s. This paper presents a new method developed to detect coronal type III bursts automatically and its implementation in a new Automated Radio Burst Identification System. The central idea of the implementation is to use the Radon transform for more objective detection of the bursts as approximately straight lines in dynamic spectra. Preliminary tests of the method with the use of the spectra obtained during 13 days show that the performance of the current implementation is quite high, ˜84%, while no false positives are observed and 23 events not listed previously are found. Prospects for improvements are discussed. The first automatically detected coronal type III radio bursts are presented.

Lobzin, Vasili V.; Cairns, Iver H.; Robinson, Peter A.; Steward, Graham; Patterson, Garth

2009-04-01

289

Radio bursts with rapid frequency variations - Lace bursts  

Microsoft Academic Search

The Ondrejov radiospectrograph operating in the 0.8-2.0 GHz frequency range recorded in recent years (1998-2000), three (August 10, 1998; August 17, 1999; June 27, 2000) unique bursts with rapid frequency variations (lace bursts) lasting for several minutes. On August 17, 1999, the same burst was recorded simultaneously by the Brazilian Solar Spectroscope in the 1.0-2.5 GHz frequency range. The frequency

M. Karlický; M. Bárta; K. Jiricka; H. Mészárosová; H. S. Sawant; F. C. R. Fernandes; J. R. Cecatto

2001-01-01

290

Single potential analysis of cavernous electric activity —a possible diagnosis of autonomic impotence?  

Microsoft Academic Search

Summary The aim of our study was to examine the cavernous smooth-muscle electric activity in normal and impotent patients as well as in those with (presumably) well-defined neurologic lesions. Single potential analysis of cavernous electric activity (SPACE) was done in 12 consecutive impotent patients, 34 normal patients, and 19 patients referred especially for SPACE. In the normal patients, similar potentials

C. G. Stief; M. Djamilian; F. Schaebsdau; M. C. Truss; R. W. Schlick; J. H. Abicht; E. P. Allhoff; U. Jonas

1990-01-01

291

Role of functional groups on the microwave attenuation and electric resistivity of activated carbon fiber cloth  

Microsoft Academic Search

Virgin activated carbon fiber cloth (ACFC) samples with select degrees of activation\\/porosity were treated with nitric and sulfuric acids or with hydrogen. Composition, microwave attenuation constant and electric resistivity results for these samples are provided. On average, acid treatment resulted in a 677% increase in oxygen content, 89% decrease in microwave attenuation constant, and 3200% increase in electrical resistivity when

Zaher Hashisho; Mark J. Rood; Suhail Barot; Jennifer Bernhard

2009-01-01

292

Lightning and the evolution of electrical activity during the explosions of Mt. Redoubt  

Microsoft Academic Search

In January 2009 a 4-station VHF Lightning Mapping Array (LMA) was deployed along the west coast of the Kenai Peninsula, with hopes of capturing electrical activity from an eruption of Mt. Redoubt. For the first time, we were able to record the electrical activity from an entire eruptive sequence. The 4-station LMA data has enabled us to locate the plan-position

S. A. Behnke; R. J. Thomas; P. R. Krehbiel; W. Rison; H. E. Edens; S. R. McNutt

2009-01-01

293

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.

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

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

Microsoft Academic Search

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

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

2007-01-01

296

Activity-dependent neuronal cell migration induced by electrical stimulation  

Microsoft Academic Search

Recently, we found that electrical stimulation can induce neuronal migration in neural networks cultured for more than 3 weeks\\u000a on microelectrode arrays. Immunocytochemistry data showed that the aggregation of neurons was related to the emergence of\\u000a astrocytes in culture. In this study, when neurons were cocultured with astrocytes, electrical stimulation could induce the\\u000a migration of neuronal cell bodies after only 1 week

Se Hoon Jeong; Sang Beom Jun; Jong Keun Song; Sung June Kim

2009-01-01

297

Swift: Gamma-Ray Bursts  

NSDL National Science Digital Library

In the late 1960s, scientists accidentally discovered gamma-ray bursts, intense flashes of energy that typically last no more than a few seconds or minutes. For decades after the discovery of these powerful bursts, they remained one of the greatest mysteries in astronomy. This video segment discusses the Swift satellite mission, launched in 2004 to investigate gamma-ray bursts, and presents some theories as to their origins. The segment is four minutes fourteen seconds in length.

298

UWB dual burst transmit driver  

SciTech Connect

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

299

Sympathetic control of antral and pyloric electrical activity in the rabbit.  

PubMed

The effects of section and stimulation of the sympathetic nerve trunk on gastric motility were investigated in conscious and decorticate rabbits. In conscious animals after section of the abdominal splanchnic nerve, rhythm of antral and pyloric bursts was enhanced, becoming more regular, and the period of arrest of the rhythmic bursts, which was usually observed at the end of inflation of the antrum in intact rabbits, was shortened to 33.6 +/- 4.0 s from 112.2 +/- 14.6 s observed before the sympathetic nerve transection. Adrenergic agonists, phenylephrine (100 micrograms/kg), clonidine (5 micrograms/kg) and salbutamol (1 mg/kg) inhibited antral and pyloric activity. In decorticate rabbits the major effect of stimulation of the peripheral or the central end of the thoracic sympathetic trunk was inhibition; this was seen both with the spontaneous and vagally induced e.m.g. activity of the antrum and pylorus. Inhibition induced by stimulation of sympathetic efferents was abolished by beta-blocking agents and that induced by stimulation of the sympathetic afferents disappeared after alpha-adrenergic block. Significance of a dual control of the gastric motility by the sympathetic nerve was discussed. PMID:3351191

Deloof, S

1988-02-01

300

On the Dynamics of the Spontaneous Activity in Neuronal Networks  

PubMed Central

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

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

2007-01-01

301

Prioritized burst segmentation and composite burst-assembly techniques for QoS support in optical burst-switched networks  

Microsoft Academic Search

We address the issue of providing quality-of-service (QoS) in an optical burst-switched network. QoS is provided by introducing prioritized contention resolution policies in the network core and a composite burst-assembly technique at the network edge. In the core, contention is resolved through prioritized burst segmentation and prioritized deflection. The burst segmentation scheme allows high-priority bursts to preempt low-priority bursts and

Vinod M. Vokkarane; Jason P. Jue

2003-01-01

302

Comets, X-ray bursts, and gamma-ray bursts  

Microsoft Academic Search

The proposal, revived by Tremaine and Zytkow (1985), that accretion of comets by neutron stars may be the origin of gamma-ray bursts is considered. This mechanism has difficulty accounting for the observed gamma-ray spectrum and optical counterparts of the bursts. The survival of comets near supernovae is investigated. Ablation rates and the thermal structure of an ablating surface layer are

J. I. Katz

1986-01-01

303

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

PubMed Central

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

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

2011-01-01

304

Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are the brightest transient sources in the gamma-ray sky. Since their discovery in the late 1960s, the investigation of the astrophysical sys- tems in which these phenomena take place, and the physical mechanisms that drive them, has become a vast and prolific area of modern astrophysics. In this work I will briefly describe the most relevant observations of these sources, and the models that describe their nature, emphasizing on the in- vestigations about the progenitor astrophysical systems. FULL TEXT IN SPANISH

Pellizza, L. J.

305

Gamma-ray bursts.  

PubMed

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

Gehrels, Neil; Mészáros, Péter

2012-08-24

306

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

PubMed

Nigral dopamine (DA) neurons in vivo exhibit complex firing patterns consisting of tonic single-spikes and phasic bursts that encode information for certain types of reward-related learning and behavior. Non-linear dynamical analysis has previously demonstrated the presence of a non-linear deterministic structure in complex firing patterns of DA neurons, yet the origin of this non-linear determinism remains unknown. In this study, we hypothesized that bursting activity is the primary source of non-linear determinism in the firing patterns of DA neurons. To test this hypothesis, we investigated the dimension complexity of inter-spike interval data recorded in vivo from bursting and non-bursting DA neurons in the chloral hydrate-anesthetized rat substantia nigra. We found that bursting DA neurons exhibited non-linear determinism in their firing patterns, whereas non-bursting DA neurons showed truly stochastic firing patterns. Determinism was also detected in the isolated burst and inter-burst interval data extracted from firing patterns of bursting neurons. Moreover, less bursting DA neurons in halothane-anesthetized rats exhibited higher dimensional spiking dynamics than do more bursting DA neurons in chloral hydrate-anesthetized rats. These results strongly indicate that bursting activity is the main source of low-dimensional, non-linear determinism in the firing patterns of DA neurons. This finding furthermore suggests that bursts are the likely carriers of meaningful information in the firing activities of DA neurons. PMID:22831464

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

2012-07-25

307

Do Gamma-ray Burst Sources Repeat.  

National Technical Information Service (NTIS)

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analy...

C. A. Meegan D. H. Hartmann J. J. Brainerd M. Briggs W. S. Paciesas

1994-01-01

308

General Electric ATS Program technical review Phase 2 activities  

SciTech Connect

The Advanced Turbine Systems (ATS) Program Phase 2 objectives are to select a cycle, and to identify and resolve technical issues required to realize the ATS Program goals of 60% net combined cycle efficiency, single digit NOx, and a 10% electric power cost reduction, compared to current technology. The Phase 2 efforts have showns that the ATS Program goals are achievable. The GE Power Generation advanced gas turbine will use closed-loop steam cooling in the first two turbine stages and advanced coatings, seals and cooling designs to meet ATS performance and cost of electricity goals.

Chance, T. [General Electric Co., Schenectady, NY (United States). Power Generation Div.; Smith, D. [General Electric Co., Schenectady, NY (United States). Corporate Research and Development Center

1995-12-31

309

The electrical activity of the atmosphere of Venus  

Microsoft Academic Search

Electrical discharges in the atmosphere of Venus produce electromagnetic radiation which can be detected by remote sensors. The lowest-frequency wave components (f <= 300 Hz) propagate through the ionosphere in the whistler mode when the magnetic field strength is high and the field points toward the planet; the signals are detected on the Pioneer Venus orbiter. More complete information on

L. V. Ksanfomaliti; F. L. Scarf; W. W. L. Taylor

1983-01-01

310

Performance of an active electric bearing for rotary micromotors  

NASA Astrophysics Data System (ADS)

An electric bearing used to support a micromachined rotor of variable-capacitance motors was designed and tested in order to study the characteristics of this frictionless bearing. Electrostatic suspension of a ring-shaped rotor in five degrees of freedom is required to eliminate the mechanical bearing and thus the friction and wear between the rotor and the substrate. Bulk microfabrication-based glass/silicon/glass bonding is chosen for this device, allowing the fabrication of large area sense capacitors and rotor, which make the device potentially suitable for the development of an electrostatically suspended micromachined gyroscope. The device and its basic operating principle are described, as well as the dynamics of the rotor and basic design considerations of the electric bearing system. A theoretical relationship to relate the characteristics of a classical lag-lead compensator to the stiffness properties of the electric bearing is developed to explain the experimental bearing measurements. The experimental results of closed-loop frequency response, suspension stiffness and drive voltage effects are presented and discussed for the bearing operated initially in the atmospheric environment. The performance of a tri-axial electrostatic accelerometer has also been experimentally investigated on the prototype of the electric bearing system.

Han, F. T.; Wang, L.; Wu, Q. P.; Liu, Y. F.

2011-08-01

311

Cosmic gamma-ray bursts  

Microsoft Academic Search

The results of the observation of cosmic gamma-ray bursts are discussed and available theoretical models are presented. Emphasis is placed on a cosmological model in which a gamma burst results from a powerful (? 1051–1053 erg) and very short ( ?10 –100 s) energy release which occurs in a compact ( ? 106–107 cm) region and gives rise to a

Konstantin A Postnov

1999-01-01

312

Ionic and neuromodulatory regulation of burst discharge controls frequency tuning  

Microsoft Academic Search

Sensory neurons encode natural stimuli by changes in firing rate or by generating specific firing patterns, such as bursts. Many neural computations rely on the fact that neurons can be tuned to specific stimulus frequencies. It is thus important to understand the mechanisms underlying frequency tuning. In the electrosensory system of the weakly electric fish, Apteronotus leptorhynchus, the primary processing

W. Hamish Mehaffey; Lee D. Ellis; Rüdiger Krahe; Robert J. Dunn; Maurice J. Chacron

2008-01-01

313

Critical Heat Flux Tests of a Simulated Power Burst Facility Rod Bundle.  

National Technical Information Service (NTIS)

Critical heat flux (CHF) tests were performed at low pressure in a close-packed rod bundle. The test bundle was electrically heated with geometrical configurations the same as the Power Burst Facility nuclear core. Existing low pressure CHF correlations, ...

R. G. Ambrosek R. P. Wadkins M. W. Young

1978-01-01

314

Significance of changes in cerebral electrical activity at onset of cardiopulmonary bypass.  

PubMed Central

A study of 100 patients requiring open-heart surgery has been undertaken to ascertain whether prophylactic measures designed to minimise cerebral damage have influenced the incidence or severity of changes in cerebral electrical activity recorded at the onset of cardiopulmonary bypass. The incidence of change in cerebral electrical activity remains high but the severity of the disturbances has diminished as compared with a series investigated before prophylactic measures were introduced. Changes suggestive of cerebral depression were particularly notable in children under 10 years of age. The significance of these findings is discussed in the context of factors which might influence cerebral electrical activity at the onset of bypass. Images

Kritikou, P E; Branthwaite, M A

1977-01-01

315

Lockin and burst-phase induction thermography for NDE  

Microsoft Academic Search

Eddy current activated thermography uses resistive losses inside the sample for heating. This heating is done in a modulated way (Induction-Lockin-Thermography: ILT) or as a burst with a subsequent Fourier transformation of the temperature image sequence (Induction-Burst-Phase thermography: IBP). The phase evaluation of ILT and IBP has significant advantages as compared to inductive heating with visual inspection of the thermographic

Gernot Rieger

2006-01-01

316

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

317

Inhibition of Human Peripheral Blood Neutrophil Respiratory Burst by Alcohol-Based Venipuncture Site Disinfection  

PubMed Central

Ethanol inhibits the respiratory burst of neutrophils. Therefore, the effects of alcohol-based skin disinfection on oxygen metabolism in neutrophils were tested using 70% ethanol or an ethanol–isopropanol–n-propanol mixture. Neutrophil respiratory burst activity as assessed fluorometrically by oxidation of 2?,7?-dichlorofluorescein diacetate increased at 10 min after disinfection with 70% ethanol compared to the activity at 30 s. The increase was significant for triggering oxidative burst with formylpeptide but not with phorbol myristate acetate.

Reinisch, Norbert; Wiedermann, Christian J.; Ricevuti, Giovanni

2000-01-01

318

Gamma-Ray Bursts from Minijets  

Microsoft Academic Search

Striking similarities exist between high-energy gamma-ray emission from active galactic nuclei (AGNs) and gamma-ray bursts (GRBs). They suggest that GRBs are generated by inverse Compton scattering from highly relativistic electrons in transient jets. Such jets may be produced along the axis of an accretion disk formed around stellar black holes (BHs) or neutron stars (NSs) in BH-NS and NS-NS mergers

Nir J. Shaviv; Arnon Dar

1995-01-01

319

Direct electrical stimulation of specific human brain structures and bilateral electrodermal activity  

Microsoft Academic Search

We are presenting data of research conducted for the first time with human subjects in whom specific intracerebral sites were electrically stimulated through intracerebral electrodes with the concomitant recording of bilateral electrodermal activity. Direct electrical stimulation of specific intracerebral structures for which electrodermal responses were analyzed were the amygdalae, the anterior and posterior hippocampi, the anterior cingulate gyri, the frontal

Constantine A. Mangina; J. Helen Beuzeron-Mangina

1996-01-01

320

Detection of fatigue in the isometric electrical activation of paralyzed hand muscles of persons with tetraplegia  

Microsoft Academic Search

Paralyzed muscle fatigue is the eventual depression of force due to either prolonged or repetitive electrical stimulation of motor units. The robustness and safety of future functional electrical stimulation (FES) systems will rely on their ability to detect the onset of muscle fatigue. The relative degree of muscle activation can be estimated by monitoring the M-wave. The aim of this

John M. Heasman; Timothy R. D. Scott; Veronica A. Vare; Ruth Y. Flynn; Claudia R. Gschwind; James W. Middleton; S. B. Butkowski

2000-01-01

321

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

322

Effect of Eccentric and Concentric Muscle Conditioning on Tension and Electrical Activity of Human Muscle  

Microsoft Academic Search

The effects of seven weeks of eccentric or concentric muscle conditioning on muscle tension and. integrated electrical activity (IEMG) were investigated on human subjects by using a special electrical dynamometer as a testing and training apparatus. The eccentric conditioning caused, on the average, a greater improvement in muscle tension than did the concentric conditioning. In early conditioning those in the

P. V. KOMI; E. R. BUSKIRK

1972-01-01

323

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

324

Electrical activity of the Venus atmosphere. II - Measurements by Venus satellites  

Microsoft Academic Search

Probe studies of the electrical activity of the Venus atmosphere are examined with particular attention given to the Pioneer-Venus OEFD experiment. Electromagnetic-radiation measurements demonstrate the presence of numerous electric discharges in the atmosphere, the pulse succession frequency from a single source being 20 and more per second. Owing to the presence of trapped magnetic fields in layers of the nocturnal

L. V. Ksanfomaliti

1983-01-01

325

Kinetics of the direct electric heating of a stationary bed of activated charcoal  

Microsoft Academic Search

Direct electric heating by passing an electrical current directly through a bed of adsorbent may prove to be an efficient means of regenerating activated charcoal in continuous and batch adsorption processes. Obvious advantages of this type of regeneration are its almost complete lack of inertia, which makes it possible to reduce the number and dimensions of the adsorbers, and its

M. N. Marfin; Yu. I. Shumyatskii

1987-01-01

326

Electrostatic precipitator electrode cleaning system. [Patent: electrically-activated shaking devices  

Microsoft Academic Search

Electrically-activated shaking devices are arranged in modules to shake the electrodes of an electrostatic precipitator, each module corresponding to a different section of the precipitator. An operating system for the shaking devices includes a main distributor circuit that sends electrical signals to individual control circuits at each of the modules in sequence and at a relatively fast rate. Each control

P. C. Gelfand; R. A. Carpenter; J. F. Shoup

1977-01-01

327

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

328

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

PubMed

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

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

2012-04-01

329

PhET Teacher Ideas & Activities: Exploring Electric Charges  

NSDL National Science Digital Library

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

Kosztin, Dorina

2011-01-23

330

Efficiency crisis of swift gamma-ray bursts with shallow X-ray afterglows: prior activity or time-dependent microphysics?  

NASA Astrophysics Data System (ADS)

Context: .Most X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase proptot-1/2 in the first few hours. Aims: .This is not predicted by the standard afterglow model and needs an explanation. Methods: .We discuss that the shallow decay requires an unreasonably high gamma-ray efficiency, ?75-90%, within current models, which is difficult to produce by internal shocks. Such a crisis may be avoided if a weak relativistic explosion occurs 10^3-106 s prior to the main burst or if the microphysical parameter of the electron energy increases during the shallow decay, ?e propto t1/2. The former explanation predicts a very long precursor, while both prefer dim optical flashes from the reverse shock, as was recently reported. We also calculate the multi-wavelength afterglows and compare them with observations. Results: .No optical break at the end of the shallow X-ray decay indicates a preference for the time-dependent microphysics model with additionally decaying magnetic fields, ?B propto t-0.6.

Ioka, K.; Toma, K.; Yamazaki, R.; Nakamura, T.

2006-10-01

331

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

332

Hodgkin-Huxley type electronic modelling of gastrointestinal electrical activity  

Microsoft Academic Search

An electronic model comprising a number of coupled Hodgkin-Huxley type nonlinear oscillators is described. The individual\\u000a oscillator units are based on a simplified version of an analogue of the Hodgkin-Huxley squid axon membrane due to Roy (1972).\\u000a The electronic model is capable of reproducing physiological phenomena such as ‘waxing and waning’ and frequency entrainment\\u000a which have been observed in electrical

R. J. Patton; D. A. Linkens

1978-01-01

333

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

PubMed

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

Mellon, DeForest

2003-06-04

334

Comets, X-ray bursts, and gamma-ray bursts  

NASA Astrophysics Data System (ADS)

The proposal, revived by Tremaine and Zytkow (1985), that accretion of comets by neutron stars may be the origin of gamma-ray bursts is considered. This mechanism has difficulty accounting for the observed gamma-ray spectrum and optical counterparts of the bursts. The survival of comets near supernovae is investigated. Ablation rates and the thermal structure of an ablating surface layer are calculated. In some circumstances, mechanical disruption will erode a comet more rapidly than evaporation. The accretion of comets by neutron stars may produce a class of X-ray burst sources with novel properties.

Katz, J. I.

1986-10-01

335

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

PubMed Central

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

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

2013-01-01

336

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

PubMed

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

2013-09-27

337

Long-term cortical plasticity evoked by electric stimulation and acetylcholine applied to the auditory cortex  

Microsoft Academic Search

Auditory fear conditioning with tone bursts followed by electric leg stimulation activates neurons not only in the auditory and somatosensory systems but also in many other regions of the brain and elicits shifts in the best frequencies (BFs) of collicular and cortical neurons, i.e., reorganization of the frequency (co-chleotopic) maps in the inferior colliculus and auditory cortex (AC). What are

Xiaofeng Ma; Nobuo Suga

2005-01-01

338

An active learning organisation: teaching projects in electrical engineering education  

Microsoft Academic Search

The introduction of active learning in engineering education is often started by enthusiastic teachers or change agents. They usually encounter resistance from stakeholders such as colleagues, department boards or students. For a successful introduction these stakeholders all have to learn what active learning involves for them. This means that active learning has to take place on three levels: the students,

Henk Vos; H.-P. Christensen; Graaff de E; B. Lemoult

2004-01-01

339

Electrical and Mechanical Activity of Isolated Vascular Smooth Muscle of the Rat  

Microsoft Academic Search

SPONTANEOUS electrical and mechanical activity of smooth muscle from the portal vein of the rat were recorded simultaneously for the purpose of determining the relationship of membrane potential to tension development.

S. Funaki; DAVID F. BOHR

1964-01-01

340

Theoretical model of DC electric field formation in the ionosphere stimulated by seismic activity  

NASA Astrophysics Data System (ADS)

Seismic activity is accompanied by emanation of soil gases into the atmosphere. These gases transfer positive and negative charged aerosols. Atmospheric convection of charged aerosols forms external electric current, which works as a source of perturbation in the atmosphere ionosphere electric circuit. It is shown that DC electric field generated in the ionosphere by this current reaches up to 10 mV/m, while the long-term vertical electric field disturbances near the Earth's surface do not exceed 100 V/m. Such a limitation of the near-ground field is caused by the formation of potential barrier for charged particles at the Earth's surface in a process of their transport from soil to atmosphere. This paper presents the method for calculation of the electric field in the atmosphere and the ionosphere generated by given distribution of external electric current in the atmosphere.

Sorokin, V. M.; Chmyrev, V. M.; Yaschenko, A. K.

2005-09-01

341

Changes in spectral measures of brain electrical activity in rats after transection of the sciatic nerve  

Microsoft Academic Search

Electrophysiological measures of brain electrical activity were studied in rats during the development of neurogenic pain\\u000a syndrome induced by transection of the sciatic nerve. At the peak of development of pain syndrome, three weeks after deafferentation,\\u000a rearrangements in the spectra of electrical activity were seen in the limbic structures of the brain (hippocampus, amygdala,\\u000a nucleus accumbens), in the frontal areas

N. B. Pankova

2009-01-01

342

Fast-drift kilometric bursts and solar-proton events  

SciTech Connect

Initial results are presented of a comparative study of major fast-drift kilometric bursts and solar-proton events from Sep 1978-Feb 1983. It was found that only about half of all intense, long duration (> 40 min above 500 sfu) 1-MHz bursts can be associated with E > 20-MeV proton events. However, for the subset of such fast-drift bursts accompanied by metric Type II and or IV activity (about 40% of the total), the degree of association with > 20 MeV events is 80%. For the reverse association, it was found that proton events with J (> 20 MeV)>.01 pr/sq cm/s/sr/MeV were typically (about 80% of the time) preceded by intense 1-MHz bursts that exceeded the 500 sfu level for times > 20 min (median duration about 35 min).

Cliver, E.W.; Kahler, S.W.; Cane, H.V.; McGuire, R.E.; von Rosenvinge, T.T.

1985-01-01

343

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

344

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

ERIC Educational Resources Information Center

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

DeBruin, Jerry

345

Influence of physical properties of activated carbons on characteristics of electric double-layer capacitors  

Microsoft Academic Search

Electrochemical characterization has been carried out for several activated carbons used as polarizable electrodes of electric double-layer capacitors in an aqueous electrolytic solution. The rest potential of the activated carbon was proportional to the logarithm of the oxygen content or to the concentration of the acidic surface functional groups of the activated carbon. The result of triangular voltage-sweep cyclic voltammetry

Mitsuhiro Nakamura; Masanori Nakanishi; Kohei Yamamoto

1996-01-01

346

LONG-DURATION LOW-FREQUENCY TYPE III BURSTS AND SOLAR ENERGETIC PARTICLE EVENTS  

SciTech Connect

We analyzed the coronal mass ejections (CMEs), flares, and type II radio bursts associated with a set of three complex, long-duration, low-frequency (<14 MHz) type III bursts from active region 10588 in 2004 April. The durations were measured at 1 and 14 MHz using data from Wind/WAVES and were well above the threshold value (>15 minutes) normally used to define these bursts. One of the three type III bursts was not associated with a type II burst, which also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1 MHz duration of the type III burst (28 minutes) for this event was near the median value of type III durations found for gradual SEP events and ground level enhancement events. Yet, there was no sign of an SEP event. On the other hand, the other two type III bursts from the same active region had similar duration but were accompanied by WAVES type II bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. The CMEs for the three events had similar speeds, and the flares also had similar size and duration. This study suggests that the occurrence of a complex, long-duration, low-frequency type III burst is not a good indicator of an SEP event.

Gopalswamy, Nat; Maekelae, Pertti [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2010-09-20

347

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

348

Plasma Instabilities in Gamma-Ray Bursts  

SciTech Connect

Magnetic fields are important in a variety of astrophysical scenarios, ranging from possible creation mechanisms of cosmological magnetic fields through relativistic jets such as that from Active Galactic Nuclei and gamma-ray bursts to local phenomena in the solar system. Here, the outstanding importance of plasma instabilities to astrophysics is illustrated by applying the so-called neutral point method to gamma-ray bursts (GRBs), which are assumed to have a homogeneous background magnetic field. It is shown how magnetic turbulence, which is a prerequisite for the creation of dissipation and, subsequently, radiation, is created by the highly relativistic particles in the GRB jet. Using the fact that different particle compositions lead to different instability conditions, conclusions can be drawn about the particle composition of the jet, showing that it is more likely of baryonic nature.

Tautz, Robert C. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2008-12-24

349

Changes in electrical properties of rat myometrium during gestation and following hormonal treatments.  

PubMed

1. The membrane properties of the rat myometrium, during gestation and following ovarian hormone treatment, have been investigated with the micro-electrode technique. 2. Spontaneously generated bursts of electrical activity alternating with silent periods were recorded from non-pregnant, pregnant and post-partum myometria. The membrane potential was highest during the middle stage of gestation, but the spike amplitude within a burst was not uniform. In the final stage of gestation and during parturition, the membrane potential was low and the spikes within a burst were of low frequency and uniform amplitude. 3. During parturition and post-partum, a gradual depolarization of the membrane, accompanied by an increase in membrane resistance, occurred before the generation of a burst. 4. Excitability of the membrane fluctuated from a peak just before the generation of a burst to a low after the cessation of a burst. 5. Displacement of the membrane potential by electrical current or by lowering the temperature modified the slope spontaneous depolarization, but the fluctuations of excitability persisted. The Q10 value for the frequency of spontaneous bursts, measured between 36 and 30 degrees C, was 3-8. 6. Hyperpolarization of the membrane increased the maximum rate of rise of the spike, but beyond -70 mV, the rate of rise was reduced. Half-inactivation of spike generation of spike generation occurred at a membrane potential less negative than the interburst potential, indicating that the current carrying system was not fully activated during parturition. 7. In both normal and spayed rats, oestradiol hyperpolarized the membrane and the burst of spikes was generated hyperpolarized the membrane and the burst of spikes was generated on a sustained depolarization. Progesterone slightly hyperpolarized the membrane and burst discharges occurred without a sustained depolarization. Simultaneous treatment with progesterone and oestradiol produced a plateau potential of long duration during burst discharges. 8. The thickness of the muscle layer, length constant of the tissue and time constant of the membrane were measured during gestation and from spayed rats under various hormonal conditions. The length constant of the tissue was increased by oestradiol and was further increased by simultaneous treatment withoestradiol and progesterone. The increase in tissue thickness appeared to have the most marked influence on the length constant. 9. The resting and active membrane properties of the progresterone treated myometrium were similar to those observed during the middle stages of gestation. The oestradiol-treated myometrium did not resemble that during the last stages of gestation and parturition, which was simulated by combination of the two hormones, oestradiol preceding progesterone. PMID:978524

Kuriyama, H; Suzuki, H

1976-09-01

350

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

351

AUTOMATIC RECOGNITION OF CORONAL TYPE II RADIO BURSTS: THE AUTOMATED RADIO BURST IDENTIFICATION SYSTEM METHOD AND FIRST OBSERVATIONS  

SciTech Connect

Major space weather events such as solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can potentially be used for real-time space weather forecasts. Type II radio bursts are produced near the local plasma frequency and its harmonic by fast electrons accelerated by a shock wave moving through the corona and solar wind with a typical speed of {approx}1000 km s{sup -1}. The coronal bursts have dynamic spectra with frequency gradually falling with time and durations of several minutes. This Letter presents a new method developed to detect type II coronal radio bursts automatically and describes its implementation in an extended Automated Radio Burst Identification System (ARBIS 2). Preliminary tests of the method with spectra obtained in 2002 show that the performance of the current implementation is quite high, {approx}80%, while the probability of false positives is reasonably low, with one false positive per 100-200 hr for high solar activity and less than one false event per 10000 hr for low solar activity periods. The first automatically detected coronal type II radio burst is also presented.

Lobzin, Vasili V.; Cairns, Iver H.; Robinson, Peter A. [School of Physics, University of Sydney, New South Wales (Australia); Steward, Graham; Patterson, Garth [Ionospheric Prediction Service, Bureau of Meteorology, Sydney, New South Wales (Australia)

2010-02-10

352

Automatic Recognition of Coronal Type II Radio Bursts: The Automated Radio Burst Identification System Method and First Observations  

NASA Astrophysics Data System (ADS)

Major space weather events such as solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can potentially be used for real-time space weather forecasts. Type II radio bursts are produced near the local plasma frequency and its harmonic by fast electrons accelerated by a shock wave moving through the corona and solar wind with a typical speed of ~1000 km s-1. The coronal bursts have dynamic spectra with frequency gradually falling with time and durations of several minutes. This Letter presents a new method developed to detect type II coronal radio bursts automatically and describes its implementation in an extended Automated Radio Burst Identification System (ARBIS 2). Preliminary tests of the method with spectra obtained in 2002 show that the performance of the current implementation is quite high, ~80%, while the probability of false positives is reasonably low, with one false positive per 100-200 hr for high solar activity and less than one false event per 10000 hr for low solar activity periods. The first automatically detected coronal type II radio burst is also presented.

Lobzin, Vasili V.; Cairns, Iver H.; Robinson, Peter A.; Steward, Graham; Patterson, Garth

2010-02-01

353

Delay-induced synchronization transitions in small-world neuronal networks with hybrid electrical and chemical synapses  

NASA Astrophysics Data System (ADS)

We study the dependence of synchronization transitions in small-world networks of bursting neurons with hybrid electrical-chemical synapses on the information transmission delay, the probability of electrical synapses, and the rewiring probability. It is shown that, irrespective of the probability of electrical synapses, the information transmission delay can always induce synchronization transitions in small-world neuronal networks, i.e., regions of synchronization and nonsynchronization appear intermittently as the delay increases. In particular, all these transitions to burst synchronization occur approximately at integer multiples of the bursting period of individual neurons. In addition, for larger probability of electrical synapses, the intermittent synchronization transition is more profound, due to the stronger synchronization ability of electrical synapses compared with chemical ones. More importantly, chemical and electrical synapses can perform complementary roles in the synchronization of hybrid small-world neuronal networks: the larger the electrical synapse strength is, the smaller the chemical synapse strength needed to achieve burst synchronization. Furthermore, the small-world topology has a significant effect on the synchronization transition in hybrid neuronal networks. It is found that increasing the rewiring probability can always enhance the synchronization of neuronal activity. The results obtained are instructive for understanding the synchronous behavior of neural systems.

Yu, Haitao; Wang, Jiang; Liu, Chen; Deng, Bin; Wei, Xile

2013-11-01

354

Direct inhibitory synaptic linkage of pontomedullary reticular burst neurons with abducens motoneurons in the cat  

Microsoft Academic Search

1.Unit spikes of burst neurons were extracellularly recorded in the pontomedullary reticular formation of the cat. These neurons were identified by their burst activity coincident with the quick inhibitory phase of the contralateral abducens nerve during vestibular nystagmus and their antidromic activation from the contralateral abducens nucleus.2.When the extracellular field potentials in and near the abducens nucleus were triggered by

O. Hikosaka; Y. Igusa; S. Nakao; H. Shimazu

1978-01-01

355

Ion chamber gamma burst detector  

SciTech Connect

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

Colgate, S.A.

1981-08-25

356

Swift's 500th Gamma Ray Burst  

NASA Video Gallery

On April 13, 2010, NASA's Swift Gamma-ray Burst Explorer satellite discovered its 500th burst. Swift's main job is to quickly localize each gamma-ray burst (GRB), report its position so that others can immediately conduct follow-up observations, and then study the burst using its X-ray and Ultraviolet/Optical telescopes. Some notable bursts are identified in the video.

Katherine Lewis

2010-04-19

357

Optical observations of Gamma-Ray Bursts  

Microsoft Academic Search

We briefly review the status and recent progress in the field of optical observations of gamma-ray burst afterglows. We will focus on the fundamental observational evidence for the relationship between gamma-ray bursts and the final evolutionary phases of massive stars. In particular, we will address (i) gamma-ray burst host galaxies, (ii) optically dark gamma-ray burst afterglows, (iii) the gamma-ray burst–supernova

J. Hjorth; E. Pian; J. P. U. Fynbo

2004-01-01

358

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

359

Properties of Swift's intermediate bursts  

Microsoft Academic Search

Gamma-ray bursts are usually classified through their high-energy emission into short-duration and long-duration bursts. A third intermediate group has been identified on statistical grounds but its individual properties have not yet been studied in detail. Using the large sample of follow-up observations of GRBs produced during the Swift era we analyze the individual characteristics of this group. We find that

A. de Ugarte Postigo; I. Horváth; P. Veres; Z. Bagoly; D. A. Kann; C. C. Thöne; L. G. Balazs; P. D'Avanzo; M. A. Aloy; S. Foley; S. Campana; J. Mao; P. Jakobsson; S. Covino; J. P. U. Fynbo; J. Gorosabel; A. J. Castro-Tirado; L. Amati; M. Nardini

2010-01-01

360

Gamma-ray burst afterglows  

Microsoft Academic Search

The discovery of counterparts in X-ray and optical to radio wavelengths has revolutionized the study of gamma-ray bursts, until recently the most enigmatic of astrophysical phenomena. We now know that gamma-ray bursts are the biggest explosions in nature, caused by the ejection of ultrarelativistic matter from a powerful energy source and its subsequent collision with its environment. We have just

Paradijs van J. A; Chryssa Kouveliotou; Ralph A. M. J. Wijers

2000-01-01

361

Supernovae and Gamma Ray Bursts  

Microsoft Academic Search

We review the observational status of the Supernova\\/Gamma-Ray Burst connection. Recent (and less recent) observations of long duration Gamma-ray bursts suggest that a significant fraction of them (but not all) are associated with bright SNe of type Ib\\/c. Current estimates of the SN and GRB rates yield a ratio GRB\\/SNe-Ibc in the range ~ 0.4% - 3%. An analysis of

M. Della Valle

2007-01-01

362

EMISSION PATTERNS OF SOLAR TYPE III RADIO BURSTS: STEREOSCOPIC OBSERVATIONS  

SciTech Connect

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 R{sub j} = I{sub j} /{Sigma}I{sub j} (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 {approx}2 Degree-Sign and (2) bursts emitting into a wider cone with angular width spanning from {approx} - 100 Degree-Sign to {approx}100 Degree-Sign . 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.; Bergamo, M. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); MacDowall, R. J., E-mail: thejappa.golla@nasa.gov, E-mail: mbergamo@umd.edu, E-mail: Robert.MacDowall@nasa.gov [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-02-01

363

Broadband spectral investigations of SGR J1550-5418 bursts  

NASA Astrophysics Data System (ADS)

We present the results of our broadband (0.5 - 200 keV) 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. We find 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. We also studied the spin phase of the XRT burst emission, which 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 and the surface magnetic field of SGR J1550-5418 is likely non-uniform over the emission zone.

Lin, Lin; Gö?ü?, Ersin

2013-03-01

364

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

365

Gamma-ray burst models.  

PubMed

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts. PMID:17293332

King, Andrew

2007-05-15

366

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.

Lillie, Ralph S.

1935-01-01

367

Electric-field control of the activity of the graphene-based catalyst  

NASA Astrophysics Data System (ADS)

Effects of an electric field on CO oxidation of Au-embedded graphene are investigated using first-principles method. Results of our calculations show that the initial step of the reaction is more likely to proceed via the Langmuir-Hinshelwood mechanism in the presence of the field, and the reaction barrier can be tuned continuously by the electric field. However, the applied electric field makes it more difficult for the product of the reaction, CO2, to desorb from the reaction site. These two competing effects make an electric field not entirely advantageous in controlling the activity of Au-embedded graphene for CO oxidation reaction. Nevertheless, the findings of our study provide a basis for further investigation on control of chemical reactions by electric fields.

Lu, Yunhao; Feng, Yuanping

2011-05-01

368

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

369

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

370

Spotless flares and type II radio bursts  

NASA Astrophysics Data System (ADS)

Flares accompanied by type II meter radio bursts that occurred in plages with no visible spots are examined in this paper. There have been found 12 such 'spotless' flares observed in the period of January 1981-August, 1990. Six out of all the flares may be said to have not been associated with any filament activation or disruption. A few of these flares have shown features of major events. The study suggests that a filament activation seems not to be the crucial factor for the occurrence of major flares in regions with no visible spots.

Sersen, Michal; Valnicek, Boris

1993-06-01

371

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

ERIC Educational Resources Information Center

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

Morasch, Katherine C.; Bell, Martha Ann

2009-01-01

372

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

373

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

Microsoft Academic Search

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

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

1995-01-01

374

The effects of high-voltage pulse electric discharges on ion adsorption on activated carbons  

NASA Astrophysics Data System (ADS)

The effects of high-voltage pulse electric discharges (HPED) on sorption of boron and sulfate ions on activated carbons of different kinds (KM-2, BAU, DAK) were investigated. The effect of HPED activation on the sorption characteristics of the systems was found to be similar to the temperature effect.

Gafurov, M. M.; Sveshnikova, D. A.; Larin, S. V.; Rabadanov, K. Sh.; Shabanova, Z. E.; Yusupova, A. A.; Ramazanov, A. Sh.

2008-07-01

375

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.…

Jaakkola, T.; Nurmi, S.

2008-01-01

376

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

377

Heterogeneity in Short Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales—durations, pulse structure widths, and peak intervals—for EE bursts are factors of ~2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts—the anti-correlation of pulse intensity and width—continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts (~6×10-10 erg cm-2 s-1) is gsim20× brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (~60,000 s) is ~30× longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Norris, Jay P.; Gehrels, Neil; Scargle, Jeffrey D.

2011-07-01

378

HETEROGENEITY IN SHORT GAMMA-RAY BURSTS  

SciTech Connect

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales-durations, pulse structure widths, and peak intervals-for EE bursts are factors of {approx}2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts-the anti-correlation of pulse intensity and width-continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts ({approx}6x10{sup -10} erg cm{sup -2} s{sup -1}) is {approx}>20x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts ({approx}60,000 s) is {approx}30x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Norris, Jay P. [Physics and Astronomy Department, University of Denver, Denver, CO 80208 (United States); Gehrels, Neil [Astroparticle Physics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Scargle, Jeffrey D. [Space Science and Astrobiology Division, NASA/Ames Research Center, Moffett Field, CA 94035-1000 (United States)

2011-07-01

379

Experiment-specific models of ventricular electrical activation: construction and application.  

PubMed

Experimental intramural recordings of electrical activity at high resolution have been made in the in-vivo pig LV free wall. To analyze features of these recordings experiment-specific 3D computer models of tissue structures and electrical behavior around the recording sites were constructed. The construction of the models used novel tissue image registration, correction and feature extraction methods. Appropriate model conductivity parameters were deduced from measurements and used to replicate features of experimental recordings. PMID:19162612

Trew, Mark L; Caldwell, Bryan J; Barbarenda Gamage, Thiranja P; Sands, Gregory B; Smaill, Bruce H

2008-01-01

380

Electric field profile in the presence of sawtooth activity in a tokamak  

SciTech Connect

The two coupled diffusive equations for the perturbed electron temperature and poloidal magnetic field have been solved in the framework of the Kadomtsev model for the sawtooth activity. It is found that the time averaged toroidal electric field profile is radially nonuniform. A simple formula that describes the radial behavior of the toroidal electric field is proposed, and the effect on the power balance is presented.

Alladio, F.; Vlad, G.

1988-03-01

381

Alterations of Cortical Electrical Activity in Patients with Sacral Neuromodulator  

Microsoft Academic Search

Objectives: Sacral neuromodulation represents chronic stimulation of the sacral (S3) nerve. So far, the mode of action and neuro-anatomical basis is unclear. Sacral reflex mechanisms as well as pontine or cortical centers of modulation have been postulated. Our aim was to evaluate possible alterations in electroencephalogram (EEG) activity as an indicator of a supraspinally mediated mechanism of sacral neuromodulation.Materials and

P. M. Braun; H. Baezner; C. Seif; G. Boehler; S. Bross; C. C. Eschenfelder; P. Alken; M. Hennerici; P. Juenemann

2002-01-01

382

Performance and brain electrical activity during prolonged confinement.  

PubMed

A subset of the AGARD-STRES battery including memory search, unstable tracking, and a combination of both tasks (dual-task), was applied repeatedly to the four chamber crew members before, during, and after the 60-day isolation period of EXEMSI. Five ground control group members served as a control group. A subjective state questionnaire was also included. The results were subjected to a quantitative single-subject analysis. Electroencephalograms (EEG) were recorded to permit correlation of changes in task performance with changes in the physiological state. Evaluation of the EEG focused on spectral parameters of spontaneous EEG waves. No physiological data were collected from the control group. Significant decrements in tracking ability were observed in the chamber crew. The time course of these effects followed a triphasic pattern with initial deterioration, intermediate recovery to pre-isolation baseline scores after the first half of the isolation period, and a second deterioration towards the end. None of the control group subjects displayed such an effect. Memory search (speed and accuracy) was only occasionally impaired during isolation, but the control group displayed a similar pattern of changes. It is suggested that a state of decreased alertness causes tracking deterioration, which leads to a reduced efficiency of sustained cue utilization. The assumption of low alertness was further substantiated by higher fatigue ratings by the chamber crew compared to those of the control group. Analysis of the continuous EEG recordings revealed that only two subjects produced reliable alpha wave activity (8-12 Hz) over Pz and, to a much smaller extent, Fz-theta wave activity (5-7 Hz) during task performance. In both subjects Pz-alpha power decreased consistently under task conditions involving single-task and dual-task tracking. Fz-theta activity was increased more by single-task and dual-task memory search than by single-task tracking. The alpha attenuation appears to be associated with an increasing demand on perceptual cue utilization required by the tracking performance. In one subject marked attenuation of alpha power occurred during the first half of the confinement period, where he also scored the highest fatigue ratings. A striking increase in fronto-central theta activity was observed in the same subject after six weeks of isolation. The change was associated with an efficient rather than a degraded task performance, and a high rating of the item "concentrated" and a low rating of the item "fatigued." This finding supports the hypothesis that the activation state associated with increased fronto-central theta activity accompanies efficient performance of demanding mental tasks. The usefulness of standardized laboratory tasks as monitoring instruments is demonstrated by the direct comparability with results of studies obtained from other relevant research applications using the same tasks. The feasibility of a self-administered integrated psychophysiological assessment of the individual state was illustrated by the nearly complete collection of data. The large number of individual data collected over the entire period permitted application of quantitative single-subject analysis, allowing reliable determination of changes in the individual state in the course of time. It thus appears that this assessment technique can be adapted for in-flight monitoring of astronauts during prolonged spaceflights. Parallel EEG recording can provide relevant supplementary information for diagnosing the individual activation state associated with task performance. The existence of large individual differences in the generation of task-sensitive EEG rhythms forms an important issue for further studies. PMID:8814797

Lorenz, B; Lorenz, J; Manzey, D

1996-01-01

383

Study of the electrical and mechanical activity of the rectum: an experimental study.  

PubMed

The electrical activity of the rectal detrusor was studied in 13 dogs. 10 electrodes were sutured serially to the rectal and lower sigmoid colon serosa. Electrical activity was recorded for 30 min/day for 10 days. Simultaneous electric and mechanical activity (recorded by a 6-French catheter connected to a pressure transducer) was also recorded with and without rectal distension by a condom balloon. Electrical activity was further determined after annular myotomy performed at different levels in the rectum and lower sigmoid colon. Pacesetter potentials (PP) were recorded from electrodes 3-10. They were triphasic, propagated caudally and had the same frequency and regular rhythm by all electrodes distal to the 3rd one. Frequency was constant in each dog from day to day. PP were accompanied by action potentials (AP) which had inconsistent frequencies and were accompanied by increased rectal pressure. Rectal distension led to an increase in both the frequency and amplitude of PP and AP. Rectal myotomy below the 3rd electrode resulted in PP and AP disappearing distal but not proximal to the cut, excluding the 1st and 2nd electrodes, which did not show activity. The results suggest that PP start at the 3rd electrode, which corresponds anatomically to the rectosigmoid junction (RSJ). AP cause contractile activity along the rectum. It seems that the RSJ is the site of a pacemaker triggering the PP that pace the AP which initiate the rectal contractile activity. PMID:8005171

Shafik, A

1994-01-01

384

Auditory Evoked Bursts in Mouse Visual Cortex during Isoflurane Anesthesia  

PubMed Central

General anesthesia is not a uniform state of the brain. Ongoing activity differs between light and deep anesthesia and cortical response properties are modulated in dependence of anesthetic dosage. We investigated how anesthesia level affects cross-modal interactions in primary sensory cortex. To examine this, we continuously measured the effects of visual and auditory stimulation during increasing and decreasing isoflurane level in the mouse visual cortex and the subiculum (from baseline at 0.7 to 2.5 vol % and reverse). Auditory evoked burst activity occurred in visual cortex after a transition during increase of anesthesia level. At the same time, auditory and visual evoked bursts occurred in the subiculum, even though the subiculum was unresponsive to both stimuli previous to the transition. This altered sensory excitability was linked to the presence of burst suppression activity in cortex, and to a regular slow burst suppression rhythm (?0.2 Hz) in the subiculum. The effect disappeared during return to light anesthesia. The results show that pseudo-heteromodal sensory burst responses can appear in brain structures as an effect of an anesthesia induced state change.

Land, Rudiger; Engler, Gerhard

2012-01-01

385

Computing Electric Currents in Solar Active Regions with HMI Vector Magnetograms  

NASA Astrophysics Data System (ADS)

Electric currents in the photosphere may be good indicators of future solar activity. We investigate the time evolution of electric current patterns in a few active regions observed by the Helioseismic and Magnetic Imager (HMI). The electric currents are calculated by taking the curl of the HMI vector magnetograms. Using data from HMI has two main benefits. Since HMI continuously surveys the full solar disk with good resolution, no targeting is necessary; we are able to determine the currents before the active region forms, as well as during its emergence, rise, and decay. Also, since HMI is a space telescope, it provides frequent and consistent observations with which the time evolution of the current can be followed.

Lo, L.; Hoeksema, J. T.; Schuck, P. W.; Sun, X.

2010-12-01

386

Periodicity analysis of Jovian quasi-periodic radio bursts based on Lomb-Scargle periodograms  

NASA Astrophysics Data System (ADS)

The Jovian polar magnetosphere has relativistic particle accelerations with quasi-periodicity (hereafter QP accelerations) that are accompanied by periodic auroral emissions and low-frequency radio bursts called quasi-periodic (QP) bursts. Some previous observations suggested a possible physical relationship between the QP accelerations and QP radio bursts. However, the cause of the QP accelerations has not been revealed yet. This study investigated the generation process of QP radio bursts that constrain the QP acceleration process. The statistical features of QP bursts' periodicity were investigated by applying Lomb-Scargle periodogram analysis to the variations of the QP bursts' spectral densities observed by the Galileo and Ulysses spacecraft. The Lomb-Scargle analysis revealed remarkable characteristics: QP bursts have statistically large amplitudes with periods of 30-50 min at all latitudes. This result suggests that 30-50 min is an "eigenfrequency" of the QP accelerations which is close to the 45 min periodicity of the pulsating X-ray hot spot in the polar cap region. In addition, it was also revealed that successive pulses sometimes exhibit periodicity transition. We discussed one possible scenario which links Jovian periodic accelerations to those in the terrestrial magnetosphere. The scenario is that particles are energized within the period of the dispersive Alfvén waves with field-aligned electric fields that obliquely propagate between the northern and southern ionospheres. The observed eigenfrequency and periodicity transition of QP bursts are consistent with the Alfvénic acceleration scenario.

Kimura, Tomoki; Tsuchiya, Fuminori; Misawa, Hiroaki; Morioka, Akira; Nozawa, Hiromasa; Fujimoto, Masaki

2011-03-01

387

Incorporation and electrical activity of Fe in LEC InP  

NASA Astrophysics Data System (ADS)

InP crystals grown by the liquid encapsulated Czochralski method under different parameters are investigated by Hall effect, IR absorption, atomic absorption spectroscopy and glow discharge mass spectroscopy. The concentrations of total and electrically active Fe atoms (substitutional for In) in ingots pulled under different growth conditions are independently determined. The results prove that the pulling rate can affect the effective Fe distribution coefficient. Quite surprisingly, we found that the electrical activity of the incorporated iron (expressed as ratio 0268-1242/13/5/012/img7) changes dramatically between the top and tail of the LEC crystals.

Fornari, R.; Zappettini, A.; Bagnoli, G.; Taddia, M.; Battagliarin, M.

1998-05-01

388

Electrical activity as a developmental regulator in the formation of spinal cord circuits  

PubMed Central

Spinal cord development is a complex process involving generation of the appropriate number of cells, acquisition of distinctive phenotypes and establishment of functional connections that enable execution of critical functions such as sensation and locomotion. Here we review the basic cellular events occurring during spinal cord development, highlighting studies that demonstrate the roles of electrical activity in this process. We conclude that the participation of different forms of electrical activity is evident from the beginning of spinal cord development and intermingles with other developmental cues and programs to implement dynamic and integrated control of spinal cord function.

Borodinsky, Laura N.; Belgacem, Yesser Hadj; Swapna, Immani

2012-01-01

389

Work in progress report - Cardiac general Short-term transcutaneous electrical nerve stimulation after cardiac surgery: effect on pain, pulmonary function and electrical muscle activity  

Microsoft Academic Search

This study aimed to evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) for treatment of postoperative pain in patients who underwent cardiac surgery. In addition, we sought to determine whether TENS would be related to improved pulmonary function and muscle electrical activity in this patient population. Forty-five patients, 32 males and 13 females, aged 41-74 years were randomly allocated

Gerson Cipriano Jr; Antonio Carlos de Camargo; Graziella Franca Bernardelli; Paulo Alberto Tayar Peresb; Tayar Peres

2010-01-01

390

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

Microsoft Academic Search

The U.S. Department of Energys (DOE) Advanced Vehicle Testing Activity (AVTA) tests plug-in hybrid electric vehicles (PHEV) in closed track, dynamometer and onroad testing environments. The onroad testing includes the use of dedicated drivers on repeated urban and highway driving cycles that range from 10 to 200 miles, with recharging between each loop. Fleet demonstrations with onboard data collectors are

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

2009-01-01

391

Emergent bursting and synchrony in computer simulations of neuronal cultures.  

PubMed

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

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

2012-04-03

392

ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY.  

PubMed

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, K S; Curtis, H J

1939-05-20

393

Nuclear Weapon Burst Parameters Governing Urban Fire Vulnerability.  

National Technical Information Service (NTIS)

The weapon burst parameters governing thermal effects from nuclear weapon explosions are reviewed as part of the OCD program for assessing urban vulnerability to fire from nuclear bursts. The most important burst parameters are weapon yield, burst height,...

R. E. Jones S. B. Martin R. H. Renner

1967-01-01

394

In-vitro suppression of metabolic activity in malignant human glioblastomas due to pulsed - low frequency electric potential exposures  

NASA Astrophysics Data System (ADS)

The role of pulsed - low repetition frequency electric potential was investigated in suppressing the metabolic activities of aggressive human brain cancer cells. Twenty four hours post exposure the glioblastomas were found to be significantly inhibited in their metabolic activity. The findings herein reveal a near complete inhibition of glioblastoma's metabolic activity through selective applications of low frequency pulsed electric potentials.

Schlichting, Abby; Waynant, Ronald W.; Tata, Darrell B.

2010-02-01

395

Dendritic glutamate-induced bursting in the prefrontal cortex: further characterization and effects of phencyclidine.  

PubMed

To understand the role of N-methyl-d-aspartate (NMDA) receptors in the prefrontal cortex (PFC) and to investigate how the psychotomimetic drug phencyclidine (PCP) may alter PFC function, we made whole-cell recordings from PFC neurons in rat brain slices. Our result showed that most deep layer pyramidal neurons in the PFC were regular spiking cells. They could fire repetitive bursts, however, when activated by glutamate focally applied to the apical dendrite. Application of NMDA to the same dendritic spot also induced bursting, whereas application of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) evoked single spikes only. Coapplication of AMPA with NMDA evoked more single spikes and decreased NMDA-induced bursting. Experiments with NMDA and AMPA antagonists further showed that dendritic glutamate (dGlu)-induced bursting required NMDA receptor activation and was enhanced when AMPA receptors were blocked. At subanesthetic concentrations, PCP decreased dGlu-induced bursting and altered the temporal characteristics of the bursts by decreasing spikes per burst and increasing interspike intervals within bursts. The latter two changes were not observed when AMPA receptors were blocked, suggesting that they are secondary to the increased AMPA receptor contribution to glutamate responses evoked in the presence of PCP. These results suggest that NMDA receptors are essential for PFC pyramidal cells to fire in bursts in response to dGlu input and that PCP suppresses dGlu-induced bursting. Since bursting is necessary for pyramidal cells to activate GABA interneurons, the suppression effect of PCP may further lead to a weakening of the connections from pyramidal cells and GABA interneurons, thereby contributing to PCP's psychotomimetic effects. PMID:12606677

Shi, Wei-Xing; Zhang, Xue-Xiang

2003-01-24

396

Periodic bursts observed in Jovian decametric radio emission  

NASA Astrophysics Data System (ADS)

Dynamic radio spectra of Jovian decametric radio emission (DAM) acquired by STEREO/ WAVES, Wind/WAVES and Cassini/RPWS instruments have been analyzed in a frequency range from few MHz up to ˜16 MHz during the time interval between the years 2002-2008. The non-Io component of the DAM, which is the subject of our study, appears mainly in a form of arcs in time-frequency coordinates and is generally modulated by the Jovian ˜9.925 - hour rotation period (System III). Nevertheless, we have found several unusual episodes when non-Io related bursts recurred with a period of ˜10.07 hour which is ˜1.5% longer than the System III and shorter than the period of System IV (System III + 3%). The bursts were observed in a frequency range from ˜4-5 MHz to ˜12-16 MHz. Typically, the bursts recurred very periodically during several Jovian days with decreasing intensity and displayed negative drift in time-frequency domain. All bursts were detected within the same sector of Jovian Central Meridian Longitude (III), between 300° and 60° (via 360°) of CML (III), close to the region of non-Io-C source. The absence of any correlation with the position of Io has been found. Since the bursts were observed sequentially by STEREO-A and STEREO-B, as well as by Wind and Cassini during several Jovian rotations with proper time delay we can conclude that the source of the periodic bursts sub-corotates with Jupiter and it may be active during longer periods of time. The possible relation between the Io plasma torus and ˜10.07-hour periodic bursts of the DAM is discussed.

Panchenko, M.; Rucker, H. O.; Kaiser, M. L.; Bougeret, J. L.; Gurnett, D. A.

2009-12-01

397

A Comprehensive Study of GBM Bursts of SGR J1550-5418  

NASA Astrophysics Data System (ADS)

Starting in October of 2008 and continuing through April of 2009, the Fermi Gamma-ray Burst Monitor (GBM) observed three periods of activity from SGR J1550-5418. Over the course of these outburst periods, GBM observed several hundred bursts from this source. We have performed analysis on all the bursts, and identified significant spectral evolution between the first and the other two periods. While a single blackbody function best describes the bursts of the first period, a two black body model best describes those of the second; more than one model fits the bursts of the third period equally well (OTTB, BB+BB, Comptonized model). These results show an evolution in the burst emission mechanism of the source. We have analyzed a sample of ~66 bursts within the tail of the second period to identify the onset of spectral changes, without success. Finally, we present a comprehensive review of all temporal and time-integrated spectral analyses of the entire set of GBM bursts 384 bursts) from this source.

Collazzi, Andrew C.; GRB Magnetar Team

2013-04-01

398

Modeling gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. This shell model code can be used to constrain broadband observations of GRB 090926A, which showed two flares in both the Swift UVOT and XRT bands. Using the prompt emission fluence to constrain the total energy contained in the blastwave, the internal shock model requires that Lorentz factors of the shells causing flares must be less than the Lorentz factor of the blastwave when the shells are ejected. Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from an external shock. We analyze four GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM), which have high quality lightcurves in both instrument energy bands. Using the MeV prompt emission (GBM) data, we can record the energy output from the central engine as a function of time. Assuming a constant radiative efficiency, we are able to track energy accumulation in the external shock using our internal/external shell model code and show that the late time lightcurves fit well within the external shock model, but the early time lightcurves are dominated by the internal shock component which has a shallow decay phase due to the initial pile-up of shells onto the blast wave.

Maxham, Amanda

399

Effect of theta burst stimulation on sensorimotor cortex in humans  

Microsoft Academic Search

Objective: To study the after-effect of theta burst transcranial magnetic stimulation (TBS) on sensorimotor cortex excitability as well as cortico-muscular synchronization in humans. Methods: We used a continuous TBS (cTBS) paradigm for 40 sec (600 pulses) (Huang et al., 2005). Somatosensory evoked potentials (SEPs) following electrical stimulation of right or left median nerve and motor evoked potentials (MEPs) in the

Kaoru Matsunaga; M. Saglam; N. Murayama; Y. Hayashida; R. Nakanishi

2009-01-01

400

Value assessment of energy storage concepts in burst power systems  

NASA Astrophysics Data System (ADS)

Due to the pulsed nature of burst power demands, energy storage can be considered to effect reductions in overall system mass and reduce the area requirements for radiators. Incorporation of energy storage allows subsystems to be sized for orbital average duty. Without storage these systems must be sized to meet peak demands. Storage technologies include thermal (TES) and regenerable electrical energy (RES) storage. Technologies targeted for RES include flywheels, fuel cells and batteries.

Siman-Tov, Moshe; Olszewski, Mitchell; Klett, David E.

401

Effects of nanosecond pulsed electric fields on the activity of a Hodgkin and Huxley neuron model.  

PubMed

The cell membrane poration is one of the main assessed biological effects of nanosecond pulsed electric fields (nsPEF). This structural change of the cell membrane appears soon after the pulse delivery and lasts for a time period long enough to modify the electrical activity of excitable membranes in neurons. Inserting such a phenomenon in a Hodgkin and Huxley neuron model by means of an enhanced time varying conductance resulted in the temporary inhibition of the action potential generation. The inhibition time is a function of the level of poration, the pore resealing time and the background stimulation level of the neuron. Such results suggest that the neuronal activity may be efficiently modulated by the delivery of repeated pulses. This opens the way to the use of nsPEFs as a stimulation technique alternative to the conventional direct electric stimulation for medical applications such as chronic pain treatment. PMID:23366449

Camera, F; Paffi, A; Merla, C; Denzi, A; Apollonio, F; Marracino, P; d'Inzeo, G; Liberti, M

2012-01-01

402