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1

Calcium bursts induced by nanosecond electric pulses.  

PubMed

We report here real-time imaging of calcium bursts in human lymphocytes exposed to nanosecond, megavolt-per-meter pulsed electric fields. Ultra-short (less than 30 ns), high-field (greater than 1 MV/m), electric pulses induce increases in cytosolic calcium concentration and translocation of phosphatidylserine (PS) to the outer layer of the plasma membrane in Jurkat T lymphoblasts. Pulse-induced calcium bursts occur within milliseconds and PS externalization within minutes. Caspase activation and other indicators of apoptosis follow these initial symptoms of nanosecond pulse exposure. Pulse-induced PS translocation is observed even in the presence of caspase inhibitors. Ultra-short, high-field, electroperturbative pulse effects differ substantially from those associated with electroporation, where pulses of a few tens of kilovolts-per-meter lasting a few tens of microseconds open pores in the cytoplasmic membrane. Nanosecond pulsed electric fields, because their duration is less than the plasma membrane charging time, develop voltages across intracellular structures without porating the cell. PMID:14521908

Vernier, P Thomas; Sun, Yinghua; Marcu, Laura; Salemi, Sarah; Craft, Cheryl M; Gundersen, Martin A

2003-10-17

2

Changes during the moult cycle in the bursting firing pattern of the electrical activity recorded extracellularly from the sinus gland of the terrestrial isopod, Oniscus asellus.  

PubMed

Ongoing electrical activity of the sinus gland (SG) of the terrestrial isopod, Oniscus asellus, was recorded extracellularly from almost intact breeding or non-breeding females to delineate the major times of neurohormone release during the moult cycle. In intermoult, SGs discharged in long bursts (10-50 s) at high frequency (10-45 Hz), and their activity ratios (total burst duration divided by total time the SG was monitored) ranged from 0.22 to 0.73. At premoult initiation when release of moult-inhibiting hormone is expected to decline, a decrease in SG activity occurred. It rose again in early premoult in parallel with increases in ecdysteroid titre; declined again in late premoult during peak ecdysteroid titres; increased again just prior to posterior ecdysis, and was very low during posterior ecdysis itself. Activity increased immediately after posterior and anterior ecdysis suggesting the release of neurohormones involved in calcification of the new cuticle. Burst duration was ca. two-fold longer in breeding compared to non-breeding females during early premoult suggesting the release of neurohormones involved in vitellogenesis, and before anterior ecdysis suggesting release of neurohormones involved in egg deposition. Thus, the release of neurohormones occurred during 4 major periods in each moult cycle, clearly demonstrating a relationship between SG activity in situ, and the physiological events dependent on SG hormones. PMID:3828788

Chiang, R G; Steel, C G

1987-01-27

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

2012-02-01

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

Identifying Crucial Parameter Correlations Maintaining Bursting Activity  

PubMed Central

Recent experimental and computational studies suggest that linearly correlated sets of parameters (intrinsic and synaptic properties of neurons) allow central pattern-generating networks to produce and maintain their rhythmic activity regardless of changing internal and external conditions. To determine the role of correlated conductances in the robust maintenance of functional bursting activity, we used our existing database of half-center oscillator (HCO) model instances of the leech heartbeat CPG. From the database, we identified functional activity groups of burster (isolated neuron) and half-center oscillator model instances and realistic subgroups of each that showed burst characteristics (principally period and spike frequency) similar to the animal. To find linear correlations among the conductance parameters maintaining functional leech bursting activity, we applied Principal Component Analysis (PCA) to each of these four groups. PCA identified a set of three maximal conductances (leak current, Leak; a persistent K current, K2; and of a persistent Na+ current, P) that correlate linearly for the two groups of burster instances but not for the HCO groups. Visualizations of HCO instances in a reduced space suggested that there might be non-linear relationships between these parameters for these instances. Experimental studies have shown that period is a key attribute influenced by modulatory inputs and temperature variations in heart interneurons. Thus, we explored the sensitivity of period to changes in maximal conductances of Leak, K2, and P, and we found that for our realistic bursters the effect of these parameters on period could not be assessed because when varied individually bursting activity was not maintained. PMID:24945358

Doloc-Mihu, Anca; Calabrese, Ronald L.

2014-01-01

6

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

PubMed

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. PMID:22090511

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

2011-11-16

7

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. PMID:22090511

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

2011-01-01

8

Calcium and Glycolysis Mediate Multiple Bursting Modes in Pancreatic Islets  

Microsoft Academic Search

Pancreatic islets of Langerhans produce bursts of electrical activity when exposed to stimulatory glucose levels. These bursts often have a regular repeating pattern, with a period of 10–60s. In some cases, however, the bursts are episodic, clustered into bursts of bursts, which we call compound bursting. Consistent with this are recordings of free Ca2+ concentration, oxygen consumption, mitochondrial membrane potential,

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

2004-01-01

9

Simulated microgravity impairs respiratory burst activity in human promyelocytic cells.  

PubMed

The concept of microgravity (free-fall) influencing cellular functions in nonadherent cells has not been a part of mainstream scientific thought. Utilizing rotating wall vessels (RWVs) to generate simulated microgravity conditions, we found that respiratory burst activity was significantly altered in nonadherent promyelocytic (HL-60) cells. Specifically, HL-60 cells in simulated microgravity for 6, 19, 42, 47, and 49 d had 3.8-fold fewer cells that were able to participate in respiratory burst activity than cells from 1 x g cultures (P = 0.0011, N = 5). The quantity of respiratory burst products from the cells in simulated microgravity was also significantly reduced. The fold increase over controls in mean fluorescence intensities for oxidative products from cells in microgravity was 1.1+/-0.1 versus 1.8+/-0.3 for cells at 1 x g (P = 0.013, N = 4). Furthermore, the kinetic response for phorbol ester-stimulated burst activity was affected by simulated microgravity. These results demonstrate that simulated microgravity alters an innate cellular function (burst activity). If respiratory burst activity is impaired by true microgravity, then recovery from infections during spaceflight could be delayed. Finally, RWVs provide an excellent model for investigating the mechanisms associated with microgravity-induced changes in nonadherent cells. PMID:11409685

Hughes, J H; Long, J P

2001-04-01

10

An integrated model of electrical spiking, bursting, and calcium oscillations in GnRH neurons.  

PubMed

The plasma membrane electrical activities of neurons that secrete gonadotropin-releasing hormone (GnRH) have been studied extensively. A couple of mathematical models have been developed previously to explain different aspects of these activities. The goal of this article is to develop a single model that accounts for the previously modeled experimental results and some more recent results that have not been accounted for. The latter includes two types of membrane potential bursting mechanisms and their associated cytosolic calcium oscillations. One bursting mechanism has not been reported in experiments and is thus regarded as a model prediction. Although the model is mainly based on data collected in immortalized GnRH cell lines, it is capable of explaining some properties of GnRH neurons observed in several other preparations including mature GnRH neurons in hypothalamic slices. We present a spatial model that incorporates a detailed description of calcium dynamics in a three-dimensional cell body with the ion channels evenly distributed on the cell surface. A phenomenological reduction of the spatial model into a simplified form is also presented. The simplified model will facilitate the study of the roles of plasma membrane electrical activities in the pulsatile release of GnRH. PMID:19486674

Fletcher, Patrick A; Li, Yue-Xian

2009-06-01

11

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. Although a preview of the activity is available, instructors and students are encouraged to sign up with the Electron Technologies site before starting to use these materials.

12

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

E-print Network

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 ...

Chemali, Jessica

13

Gamma-Ray Burst Precursor Activity as Observed with BATSE  

NASA Technical Reports Server (NTRS)

Gamma-ray burst time histories often consist of multiple episodes of emission with the count rate dropping to the background level between adjacent episodes. We define precursor activity as any case in which the first episode (referred to as the precursor episode) has a lower peak intensity than that of the remaining emission (referred to as the main episode) and is separated from the remaining burst emission by a background interval that is at least as long as the remaining emission. We find that approx. 3% of the bursts observed with the Burst and Transient Source Experiment (BATSE) on Compton Gamma Ray Observatory (CGRO) satisfy this definition. We present the results of a study of the properties of these events. The spatial distribution of these sources is consistent with that of the larger set of all BATSE gamma-ray bursts: inhomogeneous and isotropic. A correlation between the duration of the precursor emission and the duration of the main episode emission is observed at about the 3 sigma confidence level. We find no meaningful significant correlations between or among any of the other characteristics of the precursor or main episode emission. It appears that the characteristics of the main episode emission are independent of the existence of the precursor emission.

Koshut, Thomas M.; Kouveliotou, Chryssa; Paciesas, William S.; vanParadijs, Jan; Pendleton, Geoffrey N.; Briggs, Michael S.; Fishman, Gerald J.; Meegan, Charles A.

1995-01-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

15

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

PubMed Central

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

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

2013-01-01

16

Quantifying bursting neuron activity from calcium signals using blind deconvolution  

PubMed Central

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

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

2013-01-01

17

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 PMID:9284334

Chay, T R

1997-01-01

18

The Effects of Burst Activity on Soft Gamma Repeater Pulse Properties and Persistent Emission  

E-print Network

Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and persistent emission during episodes of intense burst activity. SGR 1900+14 has undergone large flux increases following recent burst activity. Both SGR 1900+14 and SGR 1806-20 have shown significant changes in their pulse profile and spin-down rates during the last several years. The pulse profile changes are linked with the burst activity whereas the torque variations are not directly correlated with the bursts. Here, we review the observed dynamics of the pulsed and persistent emission of SGR 1900+14 and SGR 1806-20 during burst active episodes and discuss what implications these results have for the burst emission mechanism, the magnetic field dynamics of magnetars, the nature of the torque variability, and SGRs in general.

Peter M. Woods

2002-04-22

19

Colloidal polyaniline dispersions: antibacterial activity, cytotoxicity and neutrophil oxidative burst.  

PubMed

Polyaniline colloids rank among promising application forms of this conducting polymer. Cytotoxicity, antibacterial activity, and neutrophil oxidative burst tests were performed on cells treated with colloidal polyaniline dispersions. The antibacterial effect of colloidal polyaniline against gram-positive and gram-negative bacteria was most pronounced for Bacillus cereus and Escherichia coli, with a minimum inhibitory concentration of 3,500 ?g mL(-1). The data recorded on human keratinocyte (HaCaT) and a mouse embryonic fibroblast (NIH/3T3) cell lines using an MTT assay and flow cytometry indicated a concentration-dependent cytotoxicity of colloid, with the absence of cytotoxic effect at around 150 ?g mL(-1). The neutrophil oxidative burst test then showed that colloidal polyaniline, in concentrations <150 ?g mL(-1), was not able to stimulate the production of reactive oxygen species in neutrophils and whole human blood. However, it worked efficiently as a scavenger of those already formed. PMID:24534430

Kucekova, Zdenka; Humpolicek, Petr; Kasparkova, Vera; Perecko, Tomas; Lehocký, Marián; Hauerlandová, Iva; Sáha, Petr; Stejskal, Jaroslav

2014-04-01

20

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

PubMed

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

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

2014-06-01

21

Magnetar Bursts  

NASA Technical Reports Server (NTRS)

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

Kouveliotou, Chryssa

2014-01-01

22

Emergence of spatially heterogeneous burst suppression in a neural field model of electrocortical activity.  

PubMed

Burst suppression in the electroencephalogram (EEG) is a well-described phenomenon that occurs during deep anesthesia, as well as in a variety of congenital and acquired brain insults. Classically it is thought of as spatially synchronous, quasi-periodic bursts of high amplitude EEG separated by low amplitude activity. However, its characterization as a "global brain state" has been challenged by recent results obtained with intracranial electrocortigraphy. Not only does it appear that burst suppression activity is highly asynchronous across cortex, but also that it may occur in isolated regions of circumscribed spatial extent. Here we outline a realistic neural field model for burst suppression by adding a slow process of synaptic resource depletion and recovery, which is able to reproduce qualitatively the empirically observed features during general anesthesia at the whole cortex level. Simulations reveal heterogeneous bursting over the model cortex and complex spatiotemporal dynamics during simulated anesthetic action, and provide forward predictions of neuroimaging signals for subsequent empirical comparisons and more detailed characterization. Because burst suppression corresponds to a dynamical end-point of brain activity, theoretically accounting for its spatiotemporal emergence will vitally contribute to efforts aimed at clarifying whether a common physiological trajectory is induced by the actions of general anesthetic agents. We have taken a first step in this direction by showing that a neural field model can qualitatively match recent experimental data that indicate spatial differentiation of burst suppression activity across cortex. PMID:25767438

Bojak, Ingo; Stoyanov, Zhivko V; Liley, David T J

2015-01-01

23

Emergence of spatially heterogeneous burst suppression in a neural field model of electrocortical activity  

PubMed Central

Burst suppression in the electroencephalogram (EEG) is a well-described phenomenon that occurs during deep anesthesia, as well as in a variety of congenital and acquired brain insults. Classically it is thought of as spatially synchronous, quasi-periodic bursts of high amplitude EEG separated by low amplitude activity. However, its characterization as a “global brain state” has been challenged by recent results obtained with intracranial electrocortigraphy. Not only does it appear that burst suppression activity is highly asynchronous across cortex, but also that it may occur in isolated regions of circumscribed spatial extent. Here we outline a realistic neural field model for burst suppression by adding a slow process of synaptic resource depletion and recovery, which is able to reproduce qualitatively the empirically observed features during general anesthesia at the whole cortex level. Simulations reveal heterogeneous bursting over the model cortex and complex spatiotemporal dynamics during simulated anesthetic action, and provide forward predictions of neuroimaging signals for subsequent empirical comparisons and more detailed characterization. Because burst suppression corresponds to a dynamical end-point of brain activity, theoretically accounting for its spatiotemporal emergence will vitally contribute to efforts aimed at clarifying whether a common physiological trajectory is induced by the actions of general anesthetic agents. We have taken a first step in this direction by showing that a neural field model can qualitatively match recent experimental data that indicate spatial differentiation of burst suppression activity across cortex.

Bojak, Ingo; Stoyanov, Zhivko V.; Liley, David T. J.

2015-01-01

24

Growth dynamics explain the development of spatiotemporal burst activity of young cultured neuronal networks in detail.  

PubMed

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

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

2012-01-01

25

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

PubMed Central

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

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

2012-01-01

26

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

27

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. PMID:22268000

2011-01-01

28

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

29

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

30

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

PubMed Central

Emergence of persistent activity in networks can be controlled by intracellular signalling pathways but the mechanisms involved and their role are not yet fully explored. Using calcium imaging and patch-clamp we examined the rhythmic activity in the preBötzinger complex (preBötC) in the lower brainstem that generates the respiratory motor output. In functionally intact acute slices brief hypoxia, electrical stimulation and activation of AMPA receptors transiently depressed bursting activity which then recovered with augmentation. The effects were abrogated after chelation of intracellular calcium, blockade of l-type calcium channels and inhibition of calmodulin (CaM) and CaM kinase (CaMKII). Rhythmic calcium transients and synaptic drive currents in preBötC neurons in the organotypic slices showed similar CaM- and CaMKII-dependent responses. The stimuli increased the amplitude of spontaneous and miniature excitatory synaptic currents indicating postsynaptic changes at glutamatergic synapses. In the acute and organotypic slices, CaM stimulated and ADP inhibited calcium-dependent TRPM4 channels and CaMKII augmented synaptic drive currents. Experimental data and simulations show the role of ADP and CaMKII in the control of bursting activity and its relation to intracellular signalling. I propose that CaMKII-mediated facilitation of glutamatergic transmission strengthens emergent synchronous activity within preBötC that is then maintained by periodic surges of calcium during the bursts. This may find implications in restoration and consolidation of autonomous activity in the respiratory disorders. PMID:23207595

Mironov, S L

2013-01-01

31

Calmodulin and calmodulin kinase II mediate emergent bursting activity in the brainstem respiratory network (preBötzinger complex).  

PubMed

Emergence of persistent activity in networks can be controlled by intracellular signalling pathways but the mechanisms involved and their role are not yet fully explored. Using calcium imaging and patch-clamp we examined the rhythmic activity in the preBötzinger complex (preBötC) in the lower brainstem that generates the respiratory motor output. In functionally intact acute slices brief hypoxia, electrical stimulation and activation of AMPA receptors transiently depressed bursting activity which then recovered with augmentation. The effects were abrogated after chelation of intracellular calcium, blockade of L-type calcium channels and inhibition of calmodulin (CaM) and CaM kinase (CaMKII). Rhythmic calcium transients and synaptic drive currents in preBötC neurons in the organotypic slices showed similar CaM- and CaMKII-dependent responses. The stimuli increased the amplitude of spontaneous and miniature excitatory synaptic currents indicating postsynaptic changes at glutamatergic synapses. In the acute and organotypic slices, CaM stimulated and ADP inhibited calcium-dependent TRPM4 channels and CaMKII augmented synaptic drive currents. Experimental data and simulations show the role of ADP and CaMKII in the control of bursting activity and its relation to intracellular signalling. I propose that CaMKII-mediated facilitation of glutamatergic transmission strengthens emergent synchronous activity within preBötC that is then maintained by periodic surges of calcium during the bursts. This may find implications in restoration and consolidation of autonomous activity in the respiratory disorders. PMID:23207595

Mironov, S L

2013-04-01

32

Effect of variation in the burst and carrier frequency modes of neuromuscular electrical stimulation on pain perception of healthy subjects.  

PubMed

The purpose of this study was to explore the effect of various combinations of burst and carrier frequencies of neuromuscular electrical stimulation (NMES) on subjects' perception of pain intensity associated with induction of high intensity muscle contractions. Twenty-seven healthy volunteers completed the study. After the initial test session, all subjects were treated in three additional sessions with nine combinations of burst frequencies (50, 70, and 90 bursts per second [bps]) and carrier frequencies (2,500, 5,000, and 10,000 Hz) at an NMES amplitude that produced torque equivalent to 50% of maximal voluntary contraction of their quadriceps femoris muscle. Subjects rated each frequency combination for perceived pain intensity with a visual analog scale. The combinations of burst frequencies (50, 70, and 90 bps) and carrier frequencies (2,500 and 5,000 Hz) do not differ from each other in perceived pain intensity but do differ significantly in perceived pain from the combinations of burst frequencies at the carrier frequency of 10,000 Hz. Thus, the clinician may have to try different stimulus combinations on patients at different current training levels to obtain the least individually perceived pain. PMID:1409877

Rooney, J G; Currier, D P; Nitz, A J

1992-11-01

33

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

PubMed

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

Chaveiro, A; Moreira da Silva, F

2009-12-01

34

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

Microsoft Academic Search

Dissociated networks of neurons typically exhibit bursting behavior, whose features are strongly influenced by the age of\\u000a the culture, by chemical\\/electrical stimulation or by environmental conditions. To help the experimenter in identifying the\\u000a changes possibly induced by specific protocols, we developed a self-adapting method for detecting both bursts and network\\u000a bursts from electrophysiological activity recorded by means of micro-electrode arrays.

Valentina Pasquale; Sergio Martinoia; Michela Chiappalone

2010-01-01

35

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

NASA Technical Reports Server (NTRS)

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in >11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 8-3x10(exp 3)s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx. 2 - 6 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus three emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4)x10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. We discuss these events in the context of the magnetar model.

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

2009-01-01

36

Spontaneous Electrical Activity in the Human Fetal Cortex in vitro  

PubMed Central

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

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

2011-01-01

37

The Role of the Hyperpolarization-Activated Cationic Current Ih in the Timing of Interictal Bursts in the  

E-print Network

The Role of the Hyperpolarization-Activated Cationic Current Ih in the Timing of Interictal Bursts the hyperpolarization-activated, cationic current Ih. Augmenting Ih by elevating intracellular cAMP dramatically a burst and then relaxed exponentially to a steady-state level. The effect of blocking Ih in any given

38

Axonal conduction slowing induced by spontaneous bursting activity in cortical neurons cultured in a microtunnel device.  

PubMed

Recently, axons have been recognized as computational units in neuronal networks that can change their conduction properties along with their firing. However, little is known about the relationship between spontaneous activity and changes in the conduction velocity due to lack of a suitable method. Here, we studied changes in the conduction velocity during bursting activity using a new microfabricated device and the spike sorting method. The propagating action potentials were recorded from axons, which extended through a microtunnel in our device, comprised of a microfabricated chamber and a microelectrode array. By using waveforms recorded from a series of three electrodes along the bottom of a microtunnel, we achieved a sorting accuracy approximately 8.0% higher than that of the conventional one-electrode waveform method. We then demonstrated for the first time that conduction delays increased by 8.0% in action potentials of a mathematically isolated axon during one burst recorded at 10 days in vitro (DIV). Moreover, 79.4% of all clusters showed this conduction slowing during bursting activity at 10 DIV. Finally, we evaluated the days-in-culture dependence of the properties of bursting activity. These results suggest that our method is suitable for evaluating changes in conduction properties induced by spontaneous activity. PMID:25418582

Shimba, Kenta; Sakai, Koji; Isomura, Takuya; Kotani, Kiyoshi; Jimbo, Yasuhiko

2015-01-01

39

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

40

Active velocity tomography for assessing rock burst hazards in a kilometer deep mine  

Microsoft Academic Search

Active velocity tomography was used to determine the stress state and rock burst hazards in a deep coal mine. The deepest longwall face, number 3207 in the Xingcun colliery, was the location of the field trials. The positive correlation between stress and seismic velocity was used to link the velocity data with stratum stresses. A GeoPen SE2404NT data acquisition system

Hu He; Linming Dou; Xuwei Li; Qiuqiu Qiao; Tongjun Chen; Siyuan Gong

41

Heat stress enhances arterial baroreflex control of muscle sympathetic nerve activity via increased sensitivity of burst gating, not burst area, in humans  

PubMed Central

The relationship between muscle sympathetic nerve activity (MSNA) and diastolic blood pressure has been used to describe two sites for arterial baroreflex control of MSNA. By determining both the likelihood of occurrence for sympathetic bursts and the area of each burst for a given diastolic blood pressure, both a ‘gating’ and an ‘area’ control site has been described in normothermic humans. Assessing the effect of heat stress on these mechanisms will improve the understanding of baroreflex control of arterial blood pressure under this thermal condition. Therefore, the purpose of this study was to test the hypothesis that heat stress enhances arterial baroreflex control of burst gating and area. In 10 normotensive subjects (age, 32 ± 2 years; mean ± s.e.m), MSNA (peroneal) was assessed using standard microneurographic techniques. Five minute periods of data were examined during normothermic and whole-body heating conditions. The burst incidence (i.e. number of sympathetic bursts per 100 cardiac cycles) and the area of each burst were determined for each cardiac cycle and were placed into 3 mmHg intervals of diastolic blood pressure. During normotheric conditions, there was a moderate, negative relationship between burst incidence and diastolic blood pressure (slope = ?2.49 ± 0.38; r2 = 0.73 ± 0.06; mean ± s.e.m), while area per burst relative to diastolic blood pressure exhibited a less strong relationship (slope = ?1.13 ± 0.46; r2 = 0.45 ± 0.09). During whole-body heating there was an increase in the slope of the relationship between burst incidence and diastolic blood pressure (slope = ?4.69 ± 0.44; r2 = 0.84 ± 0.03) compared to normothermia (P < 0.05), while the relationship between area per burst and diastolic blood pressure was unchanged (slope = ?0.92 ± 0.29; r2 = 0.41 ± 0.08) (P = 0.50). The primary finding of this investigation is that, at rest, whole-body heating enhanced arterial baroreflex control of MSNA through increased sensitivity of a ‘gating’ mechanism, as indicated by an increase in the slope of the relationship between burst incidence and diastolic blood pressure. This occurrence is likely to afford protection against potential decreases in arterial blood pressure in an effort to preserve orthostatic tolerance during heat stress. PMID:16581857

Keller, D M; Cui, J; Davis, S L; Low, D A; Crandall, C G

2006-01-01

42

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

43

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

44

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

SciTech Connect

After at least six years of quiescence, anomalous X-ray pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in >11 yr of Rossi X-Ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from (0.4-1.8) x 10{sup 3} s. The first five burst spectra are well modeled by blackbodies, with temperatures kT {approx} 2-9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase, the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9 {+-} 0.4) x 10{sup -7} Hz, which recovered with a decay time of 17 {+-} 2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

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

2011-08-01

45

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

NASA Technical Reports Server (NTRS)

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 0.4 - 1.8 x 10(exp 3) s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx 2 - 9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4) x 10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate. slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

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

2011-01-01

46

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

PubMed

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

Di, Guilan; Zhang, Zhaoxia; Ke, Caihuan

2013-08-01

47

EMG burst presence probability: A joint time-frequency representation of muscle activity and its application to onset detection.  

PubMed

The purpose of this study was to quantify muscle activity in the time-frequency domain, therefore providing an alternative tool to measure muscle activity. This paper presents a novel method to measure muscle activity by utilizing EMG burst presence probability (EBPP) in the time-frequency domain. The EMG signal is grouped into several Mel-scale subbands, and the logarithmic power sequence is extracted from each subband. Each log-power sequence can be regarded as a dynamic process that transits between the states of EMG burst and non-burst. The hidden Markov model (HMM) was employed to elaborate this dynamic process since HMM is intrinsically advantageous in modeling the temporal correlation of EMG burst/non-burst presence. The EBPP was eventually yielded by HMM based on the criterion of maximum likelihood. Our approach achieved comparable performance with the Bonato method. PMID:25748222

Liu, Jie; Ying, Dongwen; Rymer, William Zev

2015-04-13

48

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

49

Suppression of acute seizures by theta burst electrical stimulation of the hippocampal commissure using a closed-loop system.  

PubMed

This study investigated the effects of electrical stimulation with theta burst stimulation (eTBS) on seizure suppression. Optimal parameters of eTBS were determined through open-loop stimulation experiments and then implemented in a close-loop seizure control system. For the experiments, 4-aminopyridine (4-AP) was injected into the right hippocampus of Sprague-Dawley rats to induce an acute seizure. eTBS was applied on the ventral hippocampal commissure and the effects of eTBS with different combinations of burst frequency and number of pulses per burst were analyzed in terms of seizure suppression. A closed-loop seizure control system was then implemented based on optimal eTBS parameters. The efficiency of the closed-loop eTBS was evaluated and compared to that of high frequency stimulation. The results show that eTBS induced global suppression in the hippocampus and this was sustained even after the application of eTBS. The optimal parameter of eTBS in the open-loop stimulation experiments was a burst frequency at 100Hz with nine pulses in a burst. The eTBS integrated with the on-off control law yielded less actions and cumulative delivered charge, but induced longer after-effects of seizure suppression compared to continuous high frequency stimulation (cHFS). To conclude, eTBS has suppressive effects on 4-AP induced seizure. A closed-loop eTBS system provides a more effective way of suppressing seizure and requires less effort compared to cHFS. eTBS may be a novel stimulation protocol for effective seizure control. PMID:25451100

Siah, Boon Hong; Chiang, Chia-Chu; Ju, Ming-Shaung; Lin, Chou-Ching K

2014-12-17

50

Effect of electric potential structures on Jovian S-burst morphology  

Microsoft Academic Search

Jupiter's radio emissions are dominated in intensity by decametric radio emissions due to the Io-Jupiter interaction. A significant part of these emissions consists of short radio bursts (so-called S-bursts) drifting in time and frequency. Previous analyses suggest that these emissions are cyclotron-maser emissions in the flux tube connecting Io or Io's wake to Jupiter. We present simulations of these electrons

S. Hess; F. Mottez; P. Zarka

2009-01-01

51

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

52

SGR J1550-5418 bursts detected with the Fermi Gamma-ray Burst Monitor during its most prolific activity  

E-print Network

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 January 2009, 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 with an exponential cutoff (Comptonized model), and two black-body functions (BB+BB). In the spectral fits with the Comptonized model we find a mean power-law index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlati...

van der Horst, A J; Gorgone, N M; Kaneko, Y; Baring, M G; Guiriec, S; Gogus, E; Granot, J; Watts, A L; Lin, L; Bhat, P N; Bissaldi, E; Chaplin, V L; Connaughton, V; Finger, M H; Gehrels, N; Gibby, M H; Giles, M M; Goldstein, A; Gruber, D; Harding, A K; Kaper, L; von Kienlin, A; van der Klis, M; McBreen, S; Mcenery, J; Meegan, C A; Paciesas, W S; Pe'er, A; Preece, R D; Ramirez-Ruiz, E; Rau, A; Wachter, S; Wilson-Hodge, C; Woods, P M; Wijers, R A M J

2012-01-01

53

Cannabinoid Receptor Activation Reverses Kainate-Induced Synchronized Population Burst Firing in Rat Hippocampus  

PubMed Central

Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA)-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10?mg kg?1, i.p.) entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate). Injection of the high-affinity cannabinoid agonist (-)-11-hydroxy-8-tetrahydrocannabinol-dimethyl-heptyl (HU210, 100??g kg?1, i.p.) following KA markedly reduced the burst frequency (% decrease in burst frequency) and reversed synchronized firing patterns back to baseline levels. Pre-treatment with the central cannabinoid receptor (CB1) antagonist N-piperidino-5-(4-clorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (rimonabant, SR141716A 3?mg kg?1, i.p.) completely prevented the actions of HU210. The present results indicate that cannabinoids exert their antiepileptic effects by impeding pathological synchronization of neuronal networks in the hippocampus. PMID:19562087

Mason, Rob; Cheer, Joseph F.

2009-01-01

54

Relative burst amplitude in human muscle sympathetic nerve activity: a sensitive indicator of altered sympathetic traffic  

Microsoft Academic Search

Microneurographically recorded sympathetic outflow to the human muscle vascular bed is traditionally quantified by identifying pulse-synchronous bursts of impulses in a mean voltage neurogram and expressing them in terms of bursts per minute (burst frequency) or bursts per 100 heart beats (burst incidence). As both these measures show large inter-individual differences in resting healthy subjects, a problem arises when comparing

Yrsa Bergmann Sverrisdóttir; Bengt Rundqvist; Mikael Elam

1998-01-01

55

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

PubMed

Central pattern generators (CPGs) produce neural-motor rhythms that often depend on specialized cellular or synaptic properties such as pacemaker neurons or alternating phases of synaptic inhibition. Motivated by experimental evidence suggesting that activity in the mammalian respiratory CPG, the preBötzinger complex, does not require either of these components, we present and analyze a mathematical model demonstrating an unconventional mechanism of rhythm generation in which glutamatergic synapses and the short-term depression of excitatory transmission play key rhythmogenic roles. Recurrent synaptic excitation triggers postsynaptic Ca(2+)-activated nonspecific cation current (I(CAN)) to initiate a network-wide burst. Robust depolarization due to I(CAN) also causes voltage-dependent spike inactivation, which diminishes recurrent excitation and thus attenuates postsynaptic Ca(2+) accumulation. Consequently, activity-dependent outward currents-produced by Na/K ATPase pumps or other ionic mechanisms-can terminate the burst and cause a transient quiescent state in the network. The recovery of sporadic spiking activity rekindles excitatory interactions and initiates a new cycle. Because synaptic inputs gate postsynaptic burst-generating conductances, this rhythm-generating mechanism represents a new paradigm that can be dubbed a 'group pacemaker' in which the basic rhythmogenic unit encompasses a fully interdependent ensemble of synaptic and intrinsic components. This conceptual framework should be considered as an alternative to traditional models when analyzing CPGs for which mechanistic details have not yet been elucidated. PMID:19196976

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

2009-02-24

56

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

NASA Technical Reports Server (NTRS)

We report on observations of SGR 1900+14 made with the Rossi X-Ray Timing Explorer (RXTE) and BeppoSAXduring the 2001 April burst activation of the source. Using these data, we measure the spin-down torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to the gamma-ray profile during the April 18 intermediate flare and show that (1) their shapes are similar and (1) the gamma-ray profile aligns closely in phase with the X-ray pulsations. The good phase alignment of the gamma-ray and X-ray profiles suggests that there was no rapid spin-down following this flare of the magnitude inferred for the August 27 giant flare. We discuss how these observations further constrain magnetic field reconfiguration models for the large flares of SGRs.

Woods, P. M.; Kouveliotou, C.; Goegues, E.; Finger, M. H.; Feroci, M.; Mereghetti, S.; Swank, J. H.; Hurley, K.; Heise, J.; Smith D.

2003-01-01

57

Bursts of Active Transport in Living Cells James Kuo,2  

E-print Network

a crowded environment in a weak force regime. The implied regulation of the speed of active cellular as molecular motors [1,2], and under- pins essential functions, including locomotion, cell cycle, signaling, and metabolism. Much is known about the molecular mechanisms of elementary steps taken by the motors [3

Granick, Steve

58

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

Microsoft Academic Search

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

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

59

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

PubMed Central

In the present study, we have isolated leucocytes from peripheral blood, head kidney and spleen from lumpsucker (Cyclopterus lumpus L.), and performed functional studies like phagocytosis and respiratory burst, as well as morphological and cytochemical analyses. Different leucocytes were identified, such as lymphocytes, monocytes/macrophages and polymorphonuclear cells with bean shaped or bilobed nuclei. In addition, cells with similar morphology as described for dendritic cells in trout were abundant among the isolated leucocytes. Flow cytometry was successfully used for measuring phagocytosis and respiratory burst activity. The phagocytic capacity and ability were very high, and cells with different morphology in all three leucocyte preparations phagocytised beads rapidly. Due to lack of available cell markers, the identity of the phagocytic cells could not be determined. The potent non-specific phagocytosis was in accordance with a high number of cells positive for myeloperoxidase, an enzyme involved in oxygen-dependent killing mechanism present in phagocytic cells. Further, high respiratory burst activity was present in the leucocytes samples, verifying a potent oxygen- dependent degradation. At present, the specific antibody immune response could not be measured, as immunoglobulin or B-cells have not yet been isolated. Therefore, analyses of the specific immune response in this fish species await further clarification. The present study presents the first analyses of lumpsucker immunity and also the first within the order Scopaeniformes. PMID:23112870

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

2012-01-01

60

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

PubMed Central

Familial dysautonomia (Riley–Day syndrome) is an hereditary sensory and autonomic neuropathy (HSAN type III), expressed at birth, that is associated with reduced pain and temperature sensibilities and absent baroreflexes, causing orthostatic hypotension as well as labile blood pressure that increases markedly during emotional excitement. Given the apparent absence of functional baroreceptor afferents, we tested the hypothesis that the normal cardiac-locked bursts of muscle sympathetic nerve activity (MSNA) are absent in patients with familial dysautonomia. Tungsten microelectrodes were inserted percutaneously into muscle or cutaneous fascicles of the common peroneal nerve in 12 patients with familial dysautonomia. Spontaneous bursts of MSNA were absent in all patients, but in five patients we found evidence of tonically firing sympathetic neurones, with no cardiac rhythmicity, that increased their spontaneous discharge during emotional arousal but not during a manoeuvre that unloads the baroreceptors. Conversely, skin sympathetic nerve activity (SSNA), recorded in four patients, appeared normal. We conclude that the loss of phasic bursts of MSNA and the loss of baroreflex modulation of muscle vasoconstrictor drive contributes to the poor control of blood pressure in familial dysautonomia, and that the increase in tonic firing of muscle vasoconstrictor neurones contributes to the increase in blood pressure during emotional excitement. PMID:23165765

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

2013-01-01

61

Emergence of Population Bursts from Simultaneous Activation of Small Subsets of preBötzinger 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. PMID:23426661

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

2013-01-01

62

Emergence of population bursts from simultaneous activation of small subsets of preBötzinger complex inspiratory neurons.  

PubMed

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 underlying respiratory rhythmogenesis. PMID:23426661

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

2013-02-20

63

Electricity/Electronics Systems. Laboratory Activities.  

ERIC Educational Resources Information Center

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

Sutherland, Barbara, Ed.

64

Extracting Information from the Electrical Activity of  

E-print Network

Institute Presentation Overview · Brief background: ­ Muscle electrical activity (EMG) · Engineering models, methods for extracting "EMG amplitude" · Applications of EMGamp: ­ Prosthesis control, gait biofeedback, EMG- torque, EMG-impedance · Surface EMG arrays ( newest stuff !!) Introduction EAC06­056 #12

Clancy, Ted

65

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

PubMed Central

The kinetics of cellulose hydrolysis have longbeen described by an initial fast hydrolysis rate, tapering rapidly off, leading to a process that takes days rather than hours to complete. This behavior has been mainly attributed to the action of cellobiohydrolases and often linked to the processive mechanism of this exo-acting group of enzymes. The initial kinetics of endo-glucanases (EGs) is far less investigated, partly due to a limited availability of quantitative assay technologies. We have used isothermal calorimetry to monitor the early time course of the hydrolysis of insoluble cellulose by the three main EGs from Trichoderma reesei (Tr): TrCel7B (formerly EG I), TrCel5A (EG II), and TrCel12A (EG III). These endo-glucanases show a distinctive initial burst with a maximal rate that is about 5-fold higher than the rate after 5 min of hydrolysis. The burst is particularly conspicuous for TrCel7B, which reaches a maximal turnover of about 20 s?1 at 30 °C and conducts about 1200 catalytic cycles per enzyme molecule in the initial fast phase. For TrCel5A and TrCel12A the extent of the burst is 2–300 cycles per enzyme molecule. The availability of continuous data on EG activity allows an analysis of the mechanisms underlying the initial kinetics, and it is suggested that the slowdown is linked to transient inactivation of enzyme on the cellulose surface. We propose, therefore, that the frequency of structures on the substrate surface that cause transient inactivation determine the extent of the burst phase. PMID:22110134

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

2012-01-01

66

Metabolic regulations of the rhythmic activity in pacemaker neurons. II. Metabolically induced conversions of beating to bursting pacemaker activity in isolated Aplysia neurons.  

PubMed

In pacemaker neurons of the sea hare Aplysia californica, isolated from their synaptic, ephaptic and humoral inputs, conversion of the regular beating to a bursting discharge pattern can be induced by certain cell metabolites. Administration of the phosphofructokinase (PFK) activator fructose-6-phosphate (F-6-P), or its nonmetabolizable analogue 1-deoxy-F-6-P, induced bursting discharges in R3, R5, R6 and R11 neurons, with spike doublets and triplets appearing transiently in the time pattern. With another PFK activitor, adenosine-5-monophosphate, only double spikes have been noted in R7, R8 and R14 neurons. Burst activity was induced also in the presence of the fructose-1,6-diphosphatase activators, citrate and 3-phosphoglycerate, in R9, R10 and R12 neurons. Cyclic 3',5'-AMP, which also activates the PFK (beside other effects on cellular metabolism), induced bursting discharges in all R3-R14 neurons. In contrast, the inhibitors of the PFK, citrate and ATP, decreased the spike activity of the bursting L3 and L6 neurons, even changing L3 neurons to the regular beating type. Among a variety of cell metabolites tested only pyruvate was able to induce a burst-like tendency in R9 neurons. The characteristic bursting patterns which appeared in the presence of the described metabolic effectors could not be duplicated by low Ca2+ and/or high K+ media nor by artificial shifts in membrane potential triggered by depolarizing and hyperpolarizing currents. PMID:179661

Chaplain, R A

1976-04-23

67

Effect of electric potential structures on Jovian S-burst morphology  

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

68

Activity-based costing for electric utilities  

Microsoft Academic Search

This EPRI report is a primer'' on Activity-Based Costing (ABC). ABC is a cost management aproach which can make an important contribution to understanding and controlling the changing costs in the electric utility industry. It is a method for attributing costs to activities, products and services by better understanding the underlying factors which drive those costs. ABC can help utility

D. R. Croyle; I. A. Schapiro; P. M. Keglevic

1992-01-01

69

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

PubMed Central

The dynamics of individual neurons are crucial for producing functional activity in neuronal networks. An open question is how temporal characteristics can be controlled in bursting activity and in transient neuronal responses to synaptic input. Bifurcation theory provides a framework to discover generic mechanisms addressing this question. We present a family of mechanisms organized around a global codimension-2 bifurcation. The cornerstone bifurcation is located at the intersection of the border between bursting and spiking and the border between bursting and silence. These borders correspond to the blue sky catastrophe bifurcation and the saddle-node bifurcation on an invariant circle (SNIC) curves, respectively. The cornerstone bifurcation satisfies the conditions for both the blue sky catastrophe and SNIC. The burst duration and interburst interval increase as the inverse of the square root of the difference between the corresponding bifurcation parameter and its bifurcation value. For a given set of burst duration and interburst interval, one can find the parameter values supporting these temporal characteristics. The cornerstone bifurcation also determines the responses of silent and spiking neurons. In a silent neuron with parameters close to the SNIC, a pulse of current triggers a single burst. In a spiking neuron with parameters close to the blue sky catastrophe, a pulse of current temporarily silences the neuron. These responses are stereotypical: the durations of the transient intervals–the duration of the burst and the duration of latency to spiking–are governed by the inverse-square-root laws. The mechanisms described here could be used to coordinate neuromuscular control in central pattern generators. As proof of principle, we construct small networks that control metachronal-wave motor pattern exhibited in locomotion. This pattern is determined by the phase relations of bursting neurons in a simple central pattern generator modeled by a chain of oscillators. PMID:24497927

Barnett, William H.; Cymbalyuk, Gennady S.

2014-01-01

70

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

PubMed

The dynamics of individual neurons are crucial for producing functional activity in neuronal networks. An open question is how temporal characteristics can be controlled in bursting activity and in transient neuronal responses to synaptic input. Bifurcation theory provides a framework to discover generic mechanisms addressing this question. We present a family of mechanisms organized around a global codimension-2 bifurcation. The cornerstone bifurcation is located at the intersection of the border between bursting and spiking and the border between bursting and silence. These borders correspond to the blue sky catastrophe bifurcation and the saddle-node bifurcation on an invariant circle (SNIC) curves, respectively. The cornerstone bifurcation satisfies the conditions for both the blue sky catastrophe and SNIC. The burst duration and interburst interval increase as the inverse of the square root of the difference between the corresponding bifurcation parameter and its bifurcation value. For a given set of burst duration and interburst interval, one can find the parameter values supporting these temporal characteristics. The cornerstone bifurcation also determines the responses of silent and spiking neurons. In a silent neuron with parameters close to the SNIC, a pulse of current triggers a single burst. In a spiking neuron with parameters close to the blue sky catastrophe, a pulse of current temporarily silences the neuron. These responses are stereotypical: the durations of the transient intervals-the duration of the burst and the duration of latency to spiking-are governed by the inverse-square-root laws. The mechanisms described here could be used to coordinate neuromuscular control in central pattern generators. As proof of principle, we construct small networks that control metachronal-wave motor pattern exhibited in locomotion. This pattern is determined by the phase relations of bursting neurons in a simple central pattern generator modeled by a chain of oscillators. PMID:24497927

Barnett, William H; Cymbalyuk, Gennady S

2014-01-01

71

Active piezo-electric damping composites  

Microsoft Academic Search

Active piezo-electric damping composites (APDC) consisting of piezoelectric rods, which are obliquely embedded across the thickness of a viscoelastic damping matrix, are presented. In this configuration, activation of the piezo-rods simultaneously enhances both the shear and compression damping characteristics of the composite. With such active\\/passive capabilities, the APDC presents a viable and effective means for controlling structural vibration and noise.

A. Baz; A. Tempia

1998-01-01

72

Stimulus information stored in lasting active and hidden network states is destroyed by network bursts  

PubMed Central

In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs) can, even in the absence of overt seizures, cause transient cognitive impairments (TCI) that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs), which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array (MEA) recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI. PMID:25755638

Dranias, Mark R.; Westover, M. Brandon; Cash, Sidney; VanDongen, Antonius M. J.

2015-01-01

73

Stimulus information stored in lasting active and hidden network states is destroyed by network bursts.  

PubMed

In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs) can, even in the absence of overt seizures, cause transient cognitive impairments (TCI) that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs), which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array (MEA) recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI. PMID:25755638

Dranias, Mark R; Westover, M Brandon; Cash, Sidney; VanDongen, Antonius M J

2015-01-01

74

Mimicking muscle activity with electrical stimulation  

NASA Astrophysics Data System (ADS)

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

Johnson, Lise A.; Fuglevand, Andrew J.

2011-02-01

75

Electric current neutralization in solar active regions  

NASA Astrophysics Data System (ADS)

There is a recurring question in solar physics of whether or not photospheric vertical electric currents are neutralized in solar active regions, i.e., whether or not the total electric current integrated over a single magnetic polarity of an active region vanishes. While different arguments have been proposed in favor of, or against, the neutralization of electric currents, both theory and observations are still not fully conclusive. Providing the answer to this question is crucial for theoretical models of solar eruptions. Indeed, if currents are neutralized in active regions, then any eruption model based on net - i.e., non-zero - electric currents, such as the torus instability, requires further consideration. We address the question of electric current neutralization in active regions using 3D zero-beta MHD simulations of line-tied, slow photospheric driving motions imposed on an initially potential magnetic field. We compare our results to a recent study of the build-up of coronal electric currents in an MHD simulation of the emergence of a current-neutralized twisted flux tube into the solar atmosphere. Our parametric study shows that, in accordance with the flux emergence simulation, photospheric motions are associated with the formation of both direct and return currents. It further shows that both processes (flux emergence and photospheric flows) can lead to the formation of strong net currents in the solar corona, and that the non-neutralization of electric currents is related to the presence of magnetic shear at the polarity inversion line. We discuss the implications of our results for the observations and for theoretical models of solar eruptions.

Dalmasse, Kévin; Aulanier, Guillaume; Török, Tibor; Démoulin, Pascal; Pariat, Etienne; Kliem, Bernhard

2015-04-01

76

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

77

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

E-print Network

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

Turner, Ray

78

Brain Electrical Activity Changes and Cognitive Development.  

ERIC Educational Resources Information Center

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

Hartley, Deborah; Thomas, David G.

79

[Multiscale modeling of cardiac electrical activity].  

PubMed

Models of cardiac electrical activity cover a wide range of spatial scales, from the genesis of the ionic currents in individual cardiomyocytes to the generation of electrocardiograms on the torso. The level of detail that is appropriate and practicable depends on the problem investigated and the scope of the computations that are required. We briefly present three examples of modelling: the dynamics of the entrainment of a single cell, the impact of fibrosis on electrical propagation in a piece of tissue and the generation of ECG in human. In each case, the methods, results and limitations are discussed. PMID:20132776

Comtois, Philippe; Potse, Mark; Vinet, Alain

2010-01-01

80

Activation of Metabotropic Glutamate 5 and NMDA Receptors Underlies the Induction of Persistent Bursting and Associated Long-Lasting Changes in CA3 Recurrent Connections  

Microsoft Academic Search

The aim of this study was to describe the induction and expression mechanisms of a persistent bursting activity in a horizontal slice preparation of the rat limbic system that includes the ventral part of the hippocampus and the entorhinal cortex. Disinhibition of this preparation by bicuculline led to interictal-like bursts in the CA3 region that triggered synchronous activity in the

Ron Stoop; Francois Conquet; Benoit Zuber; Leon L. Voronin; Etienne Pralong

2003-01-01

81

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

PubMed

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

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

2001-01-01

82

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

E-print Network

Chronic electrical stimulation homeostatically decreases spontaneous activity, but paradoxically. Chronic electrical stimulation homeo- statically decreases spontaneous activity, but paradoxically chronic electrical stimulation to increase activity in in vitro cortical circuits in a more physiological

Buonomano, Dean

83

Spatiotemporal dynamics of the electrical network activity in the root apex  

PubMed Central

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

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

2009-01-01

84

[Dynamic ion mechanism of bursting in the stomatogastric ganglion neurons of crayfish].  

PubMed

The purpose of this study is to identify the electrical activity of neuron, the existence of the transition from bursting pattern to spiking pattern and the ion mechanism of the bursting pattern. The intracellular electrical activity patterns of single neurons in the stomatogastric ganglion (STG) of crayfish were recorded when the extracellular calcium concentration ([Ca(2+)](o)) or calcium-dependent potassium channel blocker tetraethylammonium concentration ([TEA](o)) were changed, using intracellular recording method. These single neurons were also functionally isolated from the ganglion by application of atropine and picrotoxin which could block the inhibitory acetylcholine synapses and glutamatergic synapses respectively. When [Ca(2+)](o) was decreased by increasing EGTA, the membrane potential of the neuron was increased, and the electrical activity patterns were changed from the resting state with lower potential value (resting state of polarization) to the bursting pattern firstly, and then to the spiking pattern, at last to the resting state with higher potential value (resting state of depolarization). When [TEA](o) was increased, the membrane potential of the neuron was increased, and the electrical activity pattern was changed from the resting state with lower potential value (resting state of polarization) to the bursting pattern firstly, and then to the spiking pattern. The duration of the burst of the bursting pattern was increased. When [Ca(2+)](o) was increased or [TEA](o) was decreased, an inverse procedure of the electrical activity pattern was exhibited. On one hand, the results indicate that a single neuron can generate various electrical activity patterns corresponding to different physiological conditions, and the regularity of the transitions between different electrical activity patterns. On the other hand, the results identify that the initiation and termination of the burst in bursting pattern are determined by calcium-activated potassium conductance, which is adjusted by intracellular calcium concentration influenced by inward calcium current. It may be the ionic mechanism of generation of the bursting pattern in a single neuron. PMID:20717638

Zhang, Lei; Yuan, Lan; Yang, Ming-Hao; Ren, Wei; Gu, Hua-Guang

2010-08-25

85

Hypoxia Selectively Inhibits Respiratory Burst Activity and Killing of Staphylococcus aureus in Human Neutrophils  

PubMed Central

Neutrophils play a central role in the innate immune response and a critical role in bacterial killing. Most studies of neutrophil function have been conducted under conditions of ambient oxygen, but inflamed sites where neutrophils operate may be extremely hypoxic. Previous studies indicate that neutrophils sense and respond to hypoxia via the ubiquitous prolyl hydroxylase/hypoxia-inducible factor pathway and that this can signal for enhanced survival. In the current study, human neutrophils were shown to upregulate hypoxia-inducible factor (HIF)-1?–dependent gene expression under hypoxic incubation conditions (3 kPa), with a consequent substantial delay in the onset of apoptosis. Despite this, polarization and chemotactic responsiveness to IL-8 and fMLP were entirely unaffected by hypoxia. Similarly, hypoxia did not diminish the ability of neutrophils to phagocytose serum-opsonized heat-killed streptococci. Of the secretory functions examined, IL-8 generation was preserved and elastase release was enhanced by hypoxia. Hypoxia did, however, cause a major reduction in respiratory burst activity induced both by the soluble agonist fMLP and by ingestion of opsonized zymosan, without affecting expression of the NADPH oxidase subunits. Critically, this reduction in respiratory burst activity under hypoxia was associated with a significant defect in the killing of Staphylococcus aureus. In contrast, killing of Escherichia coli, which is predominantly oxidase independent, was fully preserved under hypoxia. In conclusion, these studies suggest that although the NADPH oxidase-dependent bacterial killing mechanism may be compromised by hypoxia, neutrophils overall appear extremely well adapted to operate successfully under severely hypoxic conditions. PMID:21135168

McGovern, Naomi N.; Cowburn, Andrew S.; Porter, Linsey; Walmsley, Sarah R.; Summers, Charlotte; Thompson, Alfred A. R.; Anwar, Sadia; Willcocks, Lisa C.; Whyte, Moira K. B.

2014-01-01

86

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

87

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

E-print Network

-3- Research Activities in Physics at McGill University #12;Cover image: A Star-Bursting Filament dust obscures the star-formation activity in distant galaxies. Telescopes like Herschel, however, can ..........................................................................................................The Challenge of Physics! 5

Barthelat, Francois

88

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. ...

Miss Lerdahl

2010-02-23

89

Theta bursts in the olfactory nerve paired with ?-adrenoceptor activation induce calcium elevation in mitral cells: A mechanism for odor preference learning in the neonate rat  

PubMed Central

Odor preference learning in the neonate rat follows pairing of odor input and noradrenergic activation of ?-adrenoceptors. Odor learning is hypothesized to be supported by enhanced mitral cell activation. Here a mechanism for enhanced mitral cell signaling is described. Theta bursts in the olfactory nerve (ON) produce long-term potentiation (LTP) of glomerular excitatory postsynaptic potentials (EPSPs) and of excitatory postsynaptic currents (EPSCs) in the periglomerular (PG) and external tufted (ET) cells. Theta bursts paired with ?-adrenoceptor activation significantly elevate mitral cell (MC) calcium. Juxtaglomerular inhibitory network depression by ?-adrenoceptor activation appears to increase calcium in MCs in response to theta burst stimulation. PMID:19858361

Yuan, Qi

2009-01-01

90

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

PubMed Central

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

Ennis, Matthew

2013-01-01

91

Subthalamic Nucleus Electrical Stimulation Modulates Calcium Activity of Nigral Astrocytes  

E-print Network

Subthalamic Nucleus Electrical Stimulation Modulates Calcium Activity of Nigral Astrocytes Elodie.g. in Parkinson's disease. One way to restore this pathological activity is to electrically stimulate one-nigral and subthalamo-nigral loops. Modification of the activity of the loops by STN electrical stimulation disrupted

Boyer, Edmond

92

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

PubMed

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

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

2013-10-01

93

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

PubMed Central

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

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

2013-01-01

94

Bursting into the Nucleus  

NSDL National Science Digital Library

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

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

2008-12-23

95

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

PubMed Central

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

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

2014-01-01

96

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

PubMed

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

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

2014-09-16

97

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. PMID:22427525

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

2012-01-01

98

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

PubMed Central

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

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

2014-01-01

99

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

100

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

E-print Network

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

Davide Lazzati; Rosalba Perna

2006-11-30

101

Models of Electrical Activity: Calibration and Prediction Testing on the Same Cell  

PubMed Central

Mathematical models are increasingly important in biology, and testability is becoming a critical issue. One limitation is that one model simulation tests a parameter set representing one instance of the biological counterpart, whereas biological systems are heterogeneous in their properties and behavior, and a model often is fitted to represent an ideal average. This is also true for models of a cell’s electrical activity; even within a narrowly defined population there can be considerable variation in electrophysiological phenotype. Here, we describe a computational experimental approach for parameterizing a model of the electrical activity of a cell in real time. We combine the inexpensive parallel computational power of a programmable graphics processing unit with the flexibility of the dynamic clamp method. The approach involves 1), recording a cell’s electrical activity, 2), parameterizing a model to the recording, 3), generating predictions, and 4), testing the predictions on the same cell used for the calibration. We demonstrate the experimental feasibility of our approach using a cell line (GH4C1). These cells are electrically active, and they display tonic spiking or bursting. We use our approach to predict parameter changes that can convert one pattern to the other. PMID:23199930

Tomaiuolo, Maurizio; Bertram, Richard; Leng, Gareth; Tabak, Joël

2012-01-01

102

Models of electrical activity: calibration and prediction testing on the same cell.  

PubMed

Mathematical models are increasingly important in biology, and testability is becoming a critical issue. One limitation is that one model simulation tests a parameter set representing one instance of the biological counterpart, whereas biological systems are heterogeneous in their properties and behavior, and a model often is fitted to represent an ideal average. This is also true for models of a cell's electrical activity; even within a narrowly defined population there can be considerable variation in electrophysiological phenotype. Here, we describe a computational experimental approach for parameterizing a model of the electrical activity of a cell in real time. We combine the inexpensive parallel computational power of a programmable graphics processing unit with the flexibility of the dynamic clamp method. The approach involves 1), recording a cell's electrical activity, 2), parameterizing a model to the recording, 3), generating predictions, and 4), testing the predictions on the same cell used for the calibration. We demonstrate the experimental feasibility of our approach using a cell line (GH4C1). These cells are electrically active, and they display tonic spiking or bursting. We use our approach to predict parameter changes that can convert one pattern to the other. PMID:23199930

Tomaiuolo, Maurizio; Bertram, Richard; Leng, Gareth; Tabak, Joël

2012-11-01

103

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

104

Electrical signatures of martian dust activity  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

105

Project BudBurst  

NSDL National Science Digital Library

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

2007-01-01

106

Integrated electric alternators/active filters  

NASA Astrophysics Data System (ADS)

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

Towliat Abolhassani, Mehdi

107

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

108

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

109

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

PubMed Central

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

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

1989-01-01

110

Propofol and sevoflurane induce distinct burst suppression patterns in rats  

E-print Network

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

Westover, M. Brandon

111

Metabolic activation and nucleic acid binding of acetaminophen and related arylamine substrates by the respiratory burst of human granulocytes.  

PubMed

Following stimulation with phorbol myristate acetate, human granulocytes were found to incorporate acetaminophen, p-phenetidine, p-aminophenol, and p-chloroaniline into cellular DNA and RNA. Phenacetin was not incorporated into nucleic acid or metabolized by such activated granulocytes. None of the substrates gave nucleic acid binding if the granulocyte cultures were not induced to undergo the respiratory burst. Additional studies on the binding of acetaminophen to DNA and RNA were made by use of both ring-14C-labeled and carbonyl-14C-labeled forms of this substrate. The finding that equivalent amounts of these two labeled acetaminophen substrates were bound to cellular DNA demonstrated that the intact acetaminophen molecule was incorporated into DNA. On the other hand, the finding that excess ring-14C-labeled acetaminophen was incorporated into cellular RNA implies partial hydrolysis of the acetaminophen substrate prior to RNA binding. Evidence was presented which strongly indicates that the nucleic acid binding of the substrates was covalent in nature. The inability of the respiratory burst to result in the binding of phenacetin to nucleic acid suggests that arylamides are not normally activated or metabolized by activated granulocytes. Acetaminophen is an exception to the recalcitrance of arylamides to such bioactivation processes because it also possesses the phenolic functional group, which, like the arylamine group, is oxidized by certain reactive oxygen species. Myeloperoxidase appears to be much more important in the binding of acetaminophen to DNA than it is in the DNA binding of arylamines in general. The role of the respiratory burst in causing the bioactivation of certain arylamines, which are not normally genotoxic via the more usual microsomal activation pathways, was extended to include certain amide substrates such as acetaminophen. PMID:2485128

Corbett, M D; Corbett, B R; Hannothiaux, M H; Quintana, S J

1989-01-01

112

Robotic Electrolocation: Active Underwater Target Localization with Electric Fields  

Microsoft Academic Search

We explore the capabilities of a robot designed to locate objects underwater through active movement of an electric field emitter and sensor apparatus. The robot is inspired by the biological phenomenon of active electrolocation, a sensing strategy found in two groups of freshwater fishes known to emit weak electric fields for target localization and communication. We characterize the performance of

James R. Solberg; Kevin M. Lynch; Malcolm A. Maciver

2007-01-01

113

Theta-burst LTP.  

PubMed

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

Larson, John; Munkácsy, Erin

2014-10-27

114

Correlation between spontaneous bursts of activity recorded from the dorsal roots in an isolated hamster spinal cord preparation.  

PubMed

At a temperature of 25-27 degrees C spontaneous antidromic activity has been demonstrated in lumbar and thoracic dorsal roots of an isolated spinal cord preparation taken from the golden hamster. A characteristic pattern of bursts of action potentials has been identified, which develops within 1-2 h following dissection and persists for more than 8 h. Simultaneous recordings made from pairs of dorsal roots have revealed correlations between the patterns of spontaneous activity in dorsal roots separated by up to sixteen segments longitudinally and across the cord. The strongest correlations were found between pairs of adjacent roots on the same side of the cord which produced a cross-correlation histogram having a single peak with a mode close to 0 ms. As the separation between the roots was increased the cross-correlation histogram became bimodal, with peaks equidistant on either side of 0 ms. Activity recorded in ipsilateral and contralateral pairs of roots supplying the same spinal segment also produced bimodal cross-correlation histograms. Transverse sectioning of the cord did not abolish spontaneous activity in any of the spinal roots examined, although there was a progressive reduction in the frequency of the bursts of spontaneous activity with shorter lengths of cord. These results suggest that each spinal segment is capable of generating spontaneous activity, and that there is a system by which adjacent segments are linked, allowing the activity to spread up and down the cord from the point of origin. The networks associated with the spread of dorsal root activity and primary afferent depolarization (PAD) in the spinal cord are discussed. PMID:8311947

Chen, Y; Bagust, J; Kerkut, G A; Tyler, A W

1993-11-01

115

Interactions of persistent sodium and calcium-activated nonspecific cationic currents yield dynamically distinct bursting regimes in a model of respiratory neurons.  

PubMed

The preBötzinger complex (preBötC) is a heterogeneous neuronal network within the mammalian brainstem that has been experimentally found to generate robust, synchronous bursts that drive the inspiratory phase of the respiratory rhythm. The persistent sodium (NaP) current is observed in every preBötC neuron, and significant modeling effort has characterized its contribution to square-wave bursting in the preBötC. Recent experimental work demonstrated that neurons within the preBötC are endowed with a calcium-activated nonspecific cationic (CAN) current that is activated by a signaling cascade initiated by glutamate. In a preBötC model, the CAN current was shown to promote robust bursts that experience depolarization block (DB bursts). We consider a self-coupled model neuron, which we represent as a single compartment based on our experimental finding of electrotonic compactness, under variation of g (NaP), the conductance of the NaP current, and g (CAN), the conductance of the CAN current. Varying these two conductances yields a spectrum of activity patterns, including quiescence, tonic activity, square-wave bursting, DB bursting, and a novel mixture of square-wave and DB bursts, which match well with activity that we observe in experimental preparations. We elucidate the mechanisms underlying these dynamics, as well as the transitions between these regimes and the occurrence of bistability, by applying the mathematical tools of bifurcation analysis and slow-fast decomposition. Based on the prevalence of NaP and CAN currents, we expect that the generalizable framework for modeling their interactions that we present may be relevant to the rhythmicity of other brain areas beyond the preBötC as well. PMID:21234794

Dunmyre, Justin R; Del Negro, Christopher A; Rubin, Jonathan E

2011-10-01

116

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

PubMed Central

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

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

2012-01-01

117

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

PubMed

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

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

2012-01-01

118

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

PubMed

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

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

2014-05-01

119

Activation of the respiratory burst oxidase in neutrophils: On the role of membrane-derived second messengers, Ca ++ , and protein kinase C  

Microsoft Academic Search

A major bactericidal mechanism of neutrophils involves activation of the respiratory burst oxidase to generate superoxide (O2-). The oxidase is activated rapidly, often within a minute, in response to extracellular signals such as chemoattractants, inflammatory mediators, and invading microorganisms. Increasing evidence indicates that lipases also respond rapidly, releasting potent regulatory molecules from progenitor lipids. Released molecules include potential regulators of

J. David Lambeth

1988-01-01

120

Direct magnetic resonance detection of neuronal electrical activity  

PubMed Central

Present noninvasive neuroimaging methods measure neuronal activity indirectly, via either cerebrovascular changes or extracranial measurements of electrical/magnetic signals. Recent studies have shown evidence that MRI may be used to directly and noninvasively map electrical activity associated with human brain activation, but results are inconclusive. Here, we show that MRI can detect cortical electrical activity directly. We use organotypic rat-brain cultures in vitro that are spontaneously active in the absence of a cerebrovascular system. Single-voxel magnetic resonance (MR) measurements obtained at 7 T were highly correlated with multisite extracellular local field potential recordings of the same cultures before and after blockade of neuronal activity with tetrodotoxin. Similarly, for MR images obtained at 3 T, the MR signal changed solely in voxels containing the culture, thus allowing the spatial localization of the active neuronal tissue. PMID:17038505

Petridou, Natalia; Plenz, Dietmar; Silva, Afonso C.; Loew, Murray; Bodurka, Jerzy; Bandettini, Peter A.

2006-01-01

121

Unusual Central Engine Activity in the Double Burst GRB 110709B  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

122

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

E-print Network

Houston TX MENG Citigroup Technology Analyst, Citi New York City NY MENG General Electric Edison Engineer Postdoctoral Fellow New York City NY PhD Epowersoft Engineer San Jose CA PhD IBM Consultant Almaden CA PhD Icad2011 Electrical and Computer Engineering - Graduate Post Graduate Activities Detail & History

Lipson, Michal

123

Lighting and Electrical Plan Class Activity  

NSDL National Science Digital Library

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

Wolf, Arlynne

124

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

PubMed Central

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

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

2011-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

126

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

PubMed Central

The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in ?-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca2+ oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse ?-cells or RINm5F ?-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 ?-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in ?-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy. PMID:25025956

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

2014-01-01

127

An electrically active microneedle array for electroporation  

PubMed Central

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

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

2010-01-01

128

Burst tumulus  

USGS Multimedia Gallery

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

129

Electric-propulsion activities in Europe  

NASA Astrophysics Data System (ADS)

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

Bartoli, C.; Saccoccia, G.

1992-05-01

130

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

PubMed Central

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

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

2013-01-01

131

Overview on NASA's Advanced Electric Propulsion Concepts Activities  

NASA Technical Reports Server (NTRS)

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

Frisbee, Robert H.

1999-01-01

132

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

PubMed

Neurons of the preBötzinger complex (preBötC) form local excitatory networks and synchronously discharge bursts of action potentials during the inspiratory phase of respiratory network activity. Synaptic input periodically evokes a Ca(2+)-activated non-specific cation current (I(CAN)) postsynaptically to generate 10-30 mV transient depolarizations, dubbed inspiratory drive potentials, which underlie inspiratory bursts. The molecular identity of I(CAN) and its regulation by intracellular signalling mechanisms during inspiratory drive potential generation remains unknown. Here we show that mRNAs coding for two members of the transient receptor potential (TRP) family of ion channels, namely TRPM4 and TRPM5, are expressed within the preBötC region of neonatal mice. Hypothesizing that the phosphoinositides maintaining TRPM4 and TRPM5 channel sensitivity to Ca(2+) may similarly influence I(CAN) and thus regulate inspiratory drive potentials, we manipulated intracellular phosphatidylinositol 4,5-bisphosphate (PIP(2)) and measured its effect on preBötC neurons in the context of ongoing respiratory-related rhythms in slice preparations. Consistent with the involvement of TRPM4 and TRPM5, excess PIP(2) augmented the inspiratory drive potential and diminution of PIP(2) reduced it; sensitivity to flufenamic acid (FFA) suggested that these effects of PIP(2) were I(CAN) mediated. Inositol 1,4,5-trisphosphate (IP(3)), the product of PIP(2) hydrolysis, ordinarily causes IP(3) receptor-mediated I(CAN) activation. Simultaneously increasing PIP(2) while blocking IP(3) receptors intracellularly counteracted the reduction in the inspiratory drive potential that normally resulted from IP(3) receptor blockade. We propose that PIP(2) protects I(CAN) from rundown by interacting directly with underlying ion channels and preventing desensitization, which may enhance the robustness of respiratory rhythm. PMID:17599963

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

2007-08-01

133

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

PubMed Central

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

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

2014-01-01

134

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

PubMed Central

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 Ca2+ 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 Ca2+ 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 Ca2+ chelator, intracellularly, or flufenamic acid, a Ca2+-activated nonspecific cationic channel (ICAN) antagonist, extracellularly to the bath, suppressed rhythmical bursting and the postspike ADP. Application of drugs to alter Ca2+ release from endoplasmic reticulum also suppressed bursting. Finally, voltage-clamp methods demonstrated that nominal Ca2+ 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 Ca2+ is mediated by enhancement of INaP and onset of ICAN, which are dependent on intracellular Ca2+. PMID:23883859

Tsuruyama, Kentaro; Hsiao, Chie-Fang

2013-01-01

135

Modeling active electrolocation in weakly electric fish  

E-print Network

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

Habib Ammari; Thomas Boulier; Josselin Garnier

2013-03-06

136

Estimating electric current densities in solar active regions  

E-print Network

Electric currents in solar active regions are thought to provide the energy released via magnetic reconnection in solar flares. Vertical electric current densities $J_z$ at the photosphere may be estimated from vector magnetogram data, subject to substantial uncertainties. The values provide boundary conditions for nonlinear force- free modelling of active region magnetic fields. A method is presented for estimating values of $J_z$ taking into account uncertainties in vector magnetogram field values, and minimizing $J_z^2$ across the active region. The method is demonstrated using the boundary values of the field for a force-free twisted bipole, with the addition of noise at randomly chosen locations.

Wheatland, M S

2015-01-01

137

Estimating Electric Current Densities in Solar Active Regions  

NASA Astrophysics Data System (ADS)

Electric currents in solar active regions are thought to provide the energy released via magnetic reconnection in solar flares. Vertical electric current densities J z at the photosphere may be estimated from vector magnetogram data, subject to substantial uncertainties. The values provide boundary conditions for nonlinear force-free modelling of active region magnetic fields. A method is presented for estimating values of J z taking into account uncertainties in vector magnetogram field values, and minimising Jz2 across the active region. The method is demonstrated using the boundary values of the field for a force-free twisted bipole, with the addition of noise at randomly chosen locations.

Wheatland, M. S.

2015-04-01

138

Mathematical Approach for Modeling the Uterine Electrical Activity  

NASA Astrophysics Data System (ADS)

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

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

139

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

E-print Network

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

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

2014-01-01

140

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

NASA Astrophysics Data System (ADS)

We have observed bursting variability of the 6.7 GHz methanol maser of G33.641-0.228. Five bursts were detected in the observation period of 294 days from 2009 to 2012. The typical burst is a large flux density rise in about one day followed by a slow fall. A non-typical burst observed in 2010 showed a large and rapid flux density enhancement from the stable state, but the rise and fall of the flux density were temporally symmetric and a fast fluctuation continued for 12 days. On average, the bursts occurred once every 59 days, although bursting was not periodic. Since the average power required for causing a burst of order of 1021 J s-1 is far smaller than the luminosity of G33.641-0.228, a very small fraction of the source's power would be sufficient to cause the burst occasionally. The burst can be explained as a solar-flare-like event in which the energy is accumulated in the magnetic field of the circumstellar disk, and is released for a short time. However, the mechanism of the energy release and the dust heating process are still unknown.

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

2014-12-01

141

School of Electrical & Computer Engineering -Undergraduate Post Graduate Activities Detail & History  

E-print Network

San Jose CA #12;Electrical & Computer Engineering - Undergraduate (continued) 2009 Employment Employer Atlanta GA General Electric General Electric EEDP Classic Lynn MA Intel Component Design Engineer Hudson2009 School of Electrical & Computer Engineering - Undergraduate Post Graduate Activities Detail

Lipson, Michal

142

Ghostbursting: A Novel Neuronal Burst Mechanism Brent Doiron*  

E-print Network

) of weakly electric fish have been observed to produce high frequency burst discharge with constant burst at low frequencies (., 1995). However, recent work in numerous systems has now identified the existence of "chattering" cells

Laing, Carlo R.

143

NMDA receptor activation strengthens weak electrical coupling in mammalian brain.  

PubMed

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

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

2014-03-19

144

NMDA RECEPTOR ACTIVATION STRENGTHENS WEAK ELECTRICAL COUPLING IN MAMMALIAN BRAIN  

PubMed Central

SUMMARY Electrical synapses are formed by gap junctions and permit electrical coupling that shapes the synchrony of neuronal ensembles. Here, we provide the first direct demonstration of receptormediated strengthening of electrical coupling in mammalian brain. Electrical coupling in the inferior olive of rats was strengthened by activation of NMDA-type glutamate-receptors (NMDARs), which were found at synaptic loci and at extrasynaptic loci 20–100 nm proximal to gap junctions. Electrical coupling was strengthened by pharmacological and synaptic activation of NMDARs, while co-stimulation of ionotropic non-NMDAR glutamate-receptors transiently antagonized the effect of NMDAR activation. NMDAR-dependent strengthening (i) occurred despite increased input conductance, (ii) induced Ca2+-influx microdomains near dendritic spines, (iii) required activation of the Ca2+/calmodulin-dependent protein-kinase II, (iv) was restricted to neurons that were weakly coupled, and thus, (v) strengthened coupling mainly between non-adjacent neurons. This provided a mechanism to expand the synchronization of rhythmic membrane potential oscillations by chemical neurotransmitter input. PMID:24656255

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

2014-01-01

145

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

E-print Network

The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission design concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to register hard X-rays in the energy region from 10 keV to 600 keV. A partially active or fully active anti-coincidence shield/collimator with a total area of between 15 and 35 square meters will be used to define the field of view of the CZT detectors and to suppress the background of cosmic-ray-induced events. In this paper, we describe the use of a sodium activated cesium iodide shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT4 to simulate the interactions of photons and cosmic rays with the spacecraft and instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield collimator achieves a nu-F-nu sensitivity of 3 x 10^(-9) erg cm^(-2) s^(-1) and 2 x 10^(-8) erg cm^(-2) s^(-1) at 100 keV and 600 keV, re...

Krawczynski, H; Fishman, G J; Wilson, C A

2006-01-01

146

Enormous enhancement of electric field in active gold nanoshells  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

147

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

PubMed

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

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

2013-08-01

148

Modeling slowly bursting neurons via calcium store and voltage-independent calcium current.  

PubMed

Recent experiments indicate that the calcium store (e.g., endoplasmic reticulum) is involved in electrical bursting and [Ca2+]i oscillation in bursting neuronal cells. In this paper, we formulate a mathematical model for bursting neurons, which includes Ca2+ in the intracellular Ca2+ stores and a voltage-independent calcium channel (VICC). This VICC is activated by a depletion of Ca2+ concentration in the store, [Ca2+]cs. In this model, [Ca2+]cs oscillates slowly, and this slow dynamic in turn gives rise to electrical bursting. The newly formulated model thus is radically different from existing models of bursting excitable cells, whose mechanism owes its origin to the ion channels in the plasma membrane and the [Ca2+]i dynamics. In addition, this model is capable of providing answers to some puzzling phenomena, which the previous models could not (e.g., why cAMP, glucagon, and caffeine have ability to change the burst periodicity). Using mag-fura-2 fluorescent dyes, it would be interesting to verify the prediction of the model that (1) [Ca2+]cs oscillates in bursting neurons such as Aplysia neuron and (2) the neurotransmitters and hormones that affect the adenylate cyclase pathway can influence this oscillation. PMID:8697230

Chay, T R

1996-07-01

149

Different patterns of electrical activity lead to long-term potentiation by activating different intracellular pathways.  

PubMed

Deciphering and storing information coded in different firing patterns are important properties of neuronal networks, as they allow organisms to respond and adapt to external and internal events. Here we report that hippocampal CA1 pyramidal neurons respond to brief bursts of high-frequency stimulation (HFS) and ? burst stimulation (TBS) with long-lasting enhanced responses (long-term potentiation [LTP]), albeit by engaging different signaling pathways. TBS induces LTP through calpain-1-mediated suprachiasmatic nucleus circadian oscillatory protein degradation, ERK activation, and actin polymerization, whereas HFS requires adenosine A2 receptors, PKA, and actin polymerization. TBS- but not HFS-induced LTP is impaired in calpain-1 knock-out mice. However, TBS-induced LTP and learning impairment in knock-out mice are restored by activating the HFS pathway. Thus, different patterns of rhythmic activities trigger potentiation by activating different pathways, and cross talks between these can be used to restore LTP and learning when elements of the pathways are impaired. PMID:25589756

Zhu, Guoqi; Liu, Yan; Wang, Yubin; Bi, Xiaoning; Baudry, Michel

2015-01-14

150

Effect of Na\\/Ca Exchange on Plateau Fraction and [Ca] i in Models for Bursting in Pancreatic ?-Cells  

Microsoft Academic Search

In the presence of an insulinotropic glucose concentration, ?-cells, in intact pancreatic islets, exhibit periodic bursting electrical activity consisting of an alternation of active and silent phases. The fraction of time spent in the active phase over a period is called the plateau fraction and is correlated with the rate of insulin release. However, the mechanisms that regulate the plateau

David Gall; Isabella Susa

1999-01-01

151

Propofol and sevoflurane induce distinct burst suppression patterns in rats  

PubMed Central

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

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

2014-01-01

152

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

153

Neuroscience The electrical activity in neural networks can be  

E-print Network

Neuroscience The electrical activity in neural networks can be analysed using microelectrodes Taught degree MSc in Cellular and Molecular Neuroscience Research degrees MPhil, PhD in Neuroscience Related degree MSc in Cognitive Neuroscience (p140) Admissions requirements For information on overseas

Sussex, University of

154

Gastric Electrical Activity and Gastrointestinal Hormones in Dyspeptic Patients  

Microsoft Academic Search

Aims: To explore the patterns of gastric electrical activity, gastric emptying and gastrointestinal hormones in dyspeptic patients and relate them to Helicobacter pylori status. Methods: Twenty-two patients with functional dyspepsia and 29 healthy volunteers underwent cutaneous electrogastrography and dynamic ultrasound before and after a test meal. All dyspeptic patients underwent endoscopy and biopsy; all subjects were examined for the presence

Giuseppe Riezzo; Marisa Chiloiro; Francesco Russo; Caterina Clemente; Giovanni Di Matteo; Vito Guerra; Alfredo Di Leo

2001-01-01

155

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

156

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

PubMed

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

Chaveiro, A; Moreira da Silva, F

2010-10-01

157

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

E-print Network

The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission design concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to register hard X-rays in the energy region from 10 keV to 600 keV. A partially active or fully active anti-coincidence shield/collimator with a total area of between 15 and 35 square meters will be used to define the field of view of the CZT detectors and to suppress the background of cosmic-ray-induced events. In this paper, we describe the use of a sodium activated cesium iodide shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT4 to simulate the interactions of photons and cosmic rays with the spacecraft and instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield collimator achieves a nu-F-nu sensitivity of 3 x 10^(-9) erg cm^(-2) s^(-1) and 2 x 10^(-8) erg cm^(-2) s^(-1) at 100 keV and 600 keV, respectively. The sensitivity is well matched to that of the coded mask telescope. The broad energy coverage of an EXIST-type mission with active shields will constrain the peak of the spectral energy distribution (SED) for a large number of GRBs. The measurement of the SED peak may be key for determining photometric GRB redshifts and for using GRBs as cosmological probes.

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

2006-06-05

158

An Overview of Electric Propulsion Activities at NASA  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

159

Activation of NF-?B and respiratory burst following Aspergillus fumigatus stimulation of macrophages.  

PubMed

Dectin-2, a C-type lectin receptor (CLR), plays an essential role in mediating nuclear factor-kappa B (NF-?B) activation and anti-fungal immunity in response to Candida albicans infection. However, the molecular mechanisms and function of Dectin-2 signaling in response to infection by the pathogenic fungus Aspergillus fumigatus have not been characterized. In order to characterize Dectin-2 signaling in response to A. fumigatus infection, activation of Dectin-2 was analyzed at both transcriptional and translational levels. Spleen tyrosine kinase (Syk) phosphorylation, NF-?B activation and cytokine production downstream of Dectin-2 activation were also investigated. In addition, Dectin-2-Syk function and its ability to mediate reactive oxygen species (ROS) production and elimination of A. fumigatus conidia was examined. We demonstrate that Syk is involved in Dectin-2-induced I?B? (inhibitor of kappa B protein) phosphorylation and NF-?B activation following A. fumigatus stimulation in a time dependent manner. Silencing of Dectin-2 and Syk as well as Syk inhibition blocks NF-?B activation and cytokine secretion. Furthermore, the killing of A. fumigatus conidia and ROS production are significantly affected by Dectin-2 or Syk silencing as well as Syk inhibition. Swelling and germination of the fungus followed by hyphae formation and not the resting and heat-inactivated form of A. fumigatus mediate the activation of Dectin-2 signaling. In conclusion, Syk plays an essential role in I?B? kinase phosphorylation, NF-?B activation, and ROS production mediated by Dectin-2 activation in response to A. fumigatus infection. PMID:23886693

Sun, He; Xu, Xiao-yong; Tian, Xiao-li; Shao, Hong-tao; Wu, Xiao-dong; Wang, Quan; Su, Xin; Shi, Yi

2014-01-01

160

Platelet-derived growth factor stimulates phagocytosis and blocks agonist-induced activation of the neutrophil oxidative burst: a possible cellular mechanism to protect against oxygen radical damage.  

PubMed Central

The effect of platelet-derived growth factor (PDGF) on agonist-induced activation of the superoxide-generating oxidative burst in human neutrophils was tested. PDGF had no effect on the resting level of superoxide generation but inhibited both the rate and the extent of fMet-Leu-Phe-stimulated superoxide production in a dose-dependent manner. The concentration required to inhibit the response by 50% was 95 +/- 26 pM (n = 10). PDGF also blocked activation by other receptor-mediated agonists such as the complement protein C5a and opsonized zymosan, but not by phorbol myristate acetate or arachidonate, both of which may act at postreceptor sites. The growth factor, however, had no effect on the binding of fMet-Leu-Phe to its receptor. PDGF in concentrations that blocked the oxidative burst stimulated phagocytosis of opsonized latex particles. Thus, PDGF functions as a heterologous "down-regulator" of receptor-mediated activation of the neutrophil oxidative burst and an activator of phagocytosis. A model for a feedback regulatory loop between platelets and neutrophils is proposed. PMID:3031672

Wilson, E; Laster, S M; Gooding, L R; Lambeth, J D

1987-01-01

161

Designing an Active House deployment architecture for residential electricity customers' active interaction with the smart grid  

Microsoft Academic Search

The increased focus on reduction of greenhouse gas emissions can be achieved in part by interactively integrating residential electricity production from renewable resources while giving customers incentives to shift and reduce electricity consumption during times of production with high CO2 emissions. In this paper we present the Active House deployment architecture in the smart grid, which has been designed based

Judith E. Y. Rossebo; Pia Stoll; Gargi Bag; Larisa Rizvanovic; Mikael Akerholm

2011-01-01

162

Carbon monoxide affects electrical and contractile activity of rat myocardium  

PubMed Central

Background Carbon monoxide (CO) is a toxic gas, which also acts in the organism as a neurotransmitter. It is generated as a by-product of heme breakdown catalyzed by heme oxygenase. We have investigated changes in electrical and contractile activity of isolated rat atrial and ventricular myocardium preparations under the influence of CO. Methods Standard microelectrode technique was used for intracellular registration of electrical activity in isolated preparations of atrial and ventricular myocardium. Contractions of atrial myocardial stripes were registered via force transducer. Results CO (10-4 - 10-3 M) caused prominent decrease of action potential duration (APD) in working atrial myocardium as well as significant acceleration of sinus rhythm. In addition CO reduced force of contractions and other parameters of contractile activity. Inhibitor of heme oxygenase zinc protoporphyrin IX exerts opposite effects: prolongation of action potential, reduction of sinus rhythm rate and enhancement of contractile function. Therefore, endogenous CO, which may be generated in the heart due to the presence of active heme oxygenase, is likely to exert the same effects as exogenous CO applied to the perfusing medium. In ventricular myocardium preparations exogenous CO also induced shortening of action potential, while zinc protoporphyrin IX produced the opposite effect. Conclusions Thus, endogenous or exogenous carbon monoxide may act as an important regulator of electrical and contractile cardiac activity. PMID:21676214

2011-01-01

163

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.

164

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

165

Nanoelectropulse Intracellular Perturbation and Electropermeabilization Technology: Phospholipid Translocation, Calcium Bursts, Chromatin Rearrangement, Cardiomyocyte Activation, and Tumor Cell Sensitivity  

Microsoft Academic Search

Nanosecond, megavolt-per-meter pulsed electric fields scramble the asymmetric arrangement of phospholipids in the plasma membrane, release intracellular calcium, trigger cardiomyocyte activity, and induce apoptosis in mammalian cancer cells, without the permeabilizing effects associated with longer, lower-field pulses. Dose dependencies with respect to pulse width, amplitude, and repetition rate, and total pulse count are observed for all of these phenomena. Sensitivities

P. Thomas Vernier; Yinghua Sun; Jingjing Wang; Mya Mya Thu; Edward Garon; Miguel Valderrabano; Laura Marcu; H. Phillip Koeffler; Martin A. Gundersen

2005-01-01

166

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

Microsoft Academic Search

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

J. I. Katz

2006-01-01

167

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...

168

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

DOEpatents

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

Wilcox, Russell B. (Oakland, CA)

1991-01-01

169

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

170

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

PubMed

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

Reynolds, Edward H

2004-09-01

171

Network bursts in cortical neuronal cultures ‘Noise versus pacemaker’- driven neural network simulations  

Microsoft Academic Search

Dissociated neuronal cultures provide a useful platform to study behavior and development of biological neural networks. Isolated from external inputs neural cultures generate electrical activity of their own, showing several features. The most striking feature is the phenomenon of, more or less regular, network bursts, i.e. simultaneous firing of many neurons in a relatively short time window. In this paper

T. Gritsun; J. Stegenga; J. le Feber; W. L. C. Rutten

2009-01-01

172

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

173

Electrical activity and calcium channels in neuroendocrine cells.  

PubMed

Similar to neuronal cells, neuroendocrine cells express voltage-dependent ion channels and fire action potentials. Ca2+ influx through voltage-dependent Ca2+ channels couples changes in membrane potential to Ca(2+)-dependent cellular processes, such as hormone release. Using the patch-clamp technique, we studied the spontaneous electrical activity as well as voltage-dependent Ca2+ channels in cholecystokinin-producing pancreatic cells (RIN 1056E cell line), in prolactin-secreting pituitary cells (GH3 cell line), and in calcitonin-secreting cells of the thyroid (rMTC 44-2 cell line). All three cell types displayed spontaneous electrical activity, that is, they spontaneously produced action potentials. RIN 1056E cells, GH3 cells, and rMTC cells exhibited (various types of) voltage-dependent Ca2+ channels that were regulated by various neurotransmitters and hormones, such as somatostatin. PMID:7978883

Scherübl, H; Hescheler, J; Bychkov, R; Cuber, J C; John, M; Riecken, E O; Wiedenmann, B

1994-09-15

174

Activity rhythm of an electric fish, Gymnorhamphichthys hypostomus , ellis  

Microsoft Academic Search

1.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.2.During the day the sandfish is buried in the sand and the discharge frequency is low (10 to 15\\/sec): at night the fish is freely swimming and the frequency is high (65 to 100\\/sec).3.The

Hans W. Lissmann; Horst O. Schwassmann

1965-01-01

175

Nanoelectropulse intracellular perturbation and electropermeabilization technology: phospholipid translocation, calcium bursts, chromatin rearrangement, cardiomyocyte activation, and tumor cell sensitivity.  

PubMed

Nanosecond, megavolt-per-meter pulsed electric fields scramble the asymmetric arrangement of phospholipids in the plasma membrane, release intracellular calcium, trigger cardiomyocyte activity, and induce apoptosis in mammalian cancer cells, without the permeabilizing effects associated with longer, lower-field pulses. Dose dependencies with respect to pulse width, amplitude, and repetition rate, and total pulse count are observed for all of these phenomena. Sensitivities vary among cell types; cells of lymphoid origin growing in suspension are more susceptible to nanoelectropulse exposure than solid tumor lines. Simple electrical models of the cell are useful for first-order explanations, but more sophisticated treatments will be required for analysis and prediction at both biomolecular and tissue levels. PMID:17281590

Vernier, P Thomas; Sun, Yinghua; Wang, Jingjing; Thu, Mya Mya; Garon, Edward; Valderrabano, Miguel; Marcu, Laura; Koeffler, H Phillip; Gundersen, Martin A

2005-01-01

176

An adaptive brain-machine interface algorithm for control of burst suppression in medical coma.  

PubMed

Burst suppression is an electroencephalogram (EEG) indicator of profound brain inactivation in which bursts of electrical activity alternate with periods of isoelectricity termed suppression. Specified time-varying levels of burst suppression are targeted in medical coma, a drug-induced brain state used for example to treat uncontrollable seizures. A brain-machine interface (BMI) that observes the EEG could automate the control of drug infusion rate to track a desired target burst suppression trajectory. Such a BMI needs to use models of drug dynamics and burst suppression observations, whose parameters could change with the burst suppression level and the environment over time. Currently, these parameters are fit prior to real-time control, requiring a separate system identification session. Moreover, this approach cannot track parameter variations over time. In addition, small variations in drug infusion rate may be desired at steady state. Here we develop a novel adaptive algorithm for robust control of medical coma in face of unknown and time-varying system parameters. We design an adaptive recursive Bayesian estimator to jointly estimate drug concentrations and system parameters in real time. We construct a controller using the linear-quadratic-regulator strategy that explicitly penalizes large infusion rate variations at steady state and uses the estimates as feedback to generate robust control. Using simulations, we show that the adaptive algorithm achieves precise control of time-varying target levels of burst suppression even when model parameters are initialized randomly, and reduces the infusion rate variation at steady state. PMID:25570287

Yuxiao Yang; Shanechi, Maryam M

2014-08-01

177

Optical Spectral Properties of Swift Burst Alert Telescope Hard X-Ray-Selected Active Galactic Nuclei Sources  

NASA Astrophysics Data System (ADS)

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

Winter, Lisa M.; Lewis, Karen T.; Koss, Michael; Veilleux, Sylvain; Keeney, Brian; Mushotzky, Richard F.

2010-02-01

178

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

179

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

SciTech Connect

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

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

2010-02-10

180

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

SciTech Connect

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

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

2012-04-10

181

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

182

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

183

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

184

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

185

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. PMID:23064634

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

186

Differential induction of nitric oxide, degranulation, and oxidative burst activities in response to microbial agonist stimulations in monocytes and heterophils from young commercial turkeys.  

PubMed

The toll-like receptors (TLRs) recognize microbial pathogens and pathogen-associated molecular patterns and trigger inflammatory immune responses to control the infection. Here, we examined functional innate immune responses to Salmonella enteritidis (SE, live or formalin-killed) and various TLR agonists including lipoteichoic acid (LTA) and peptidoglycan (PGN) from Staphylococcus aureus and synthetic lipoprotein Pam3CSK4 (PAM), poly I:C (synthetic double-stranded RNA analog), lipopolysaccharide (LPS) from S. enteritidis, flagellin (FGN) from S. typhimurium, loxoribine (LOX) and R837 (synthetic anti-viral compounds), and CpG oligodeoxydinucleotide (CpG ODN)by measuring antimicrobial activities including oxidative burst and degranulation in heterophils and nitric oxide production in peripheral blood monocytes. Our results demonstrate differential nitric oxide responses to TLR agonists in turkey monocytes. LTA and CpG ODN were the most potent stimuli for nitric oxide induction followed by PAM, poly I:C, and LPS, whereas FGN, PGN, LOX, R837, and control ODN stimulated little or no nitric oxide production. Live SE stimulated significantly less NO production than formalin-killed SE (FKSE). Although FKSE induced significant degranulation and oxidative burst, most TLR agonists stimulate little oxidative burst and degranulation responses in turkey heterophils. PMID:18304649

He, Haiqi; Genovese, Kenneth J; Swaggerty, Christina L; Nisbet, David J; Kogut, Michael H

2008-06-15

187

[Afobazole effect on the electrical activity of neurons].  

PubMed

Changes in the membrane rest potential (RP), action potential (AP) and impulse activity (IA) in neurons of isolated central nervous system of Lymnaea stagnalis and Planorbarius corneus under the action of anxiolytic afobazole (2-mercaptobenzimidazole derivative) in 1, 10, 100 and 1000 microM concentrations have been studied using a microelectrode technique. It is established that afobazole produces a two-phase, dose-dependent and reversible effect on the electrical activity of neurons. Hyperpolarization by 5-8 mV in the first phase (1-100 microM) and depolarization by 8-10 mV in the second phase (1000 microM) have been observed. The corresponding changes in AP and IA parameters were due to the RP level changes related to their potential dependence and resulted from the direct activation-suppression action of afobazole on the neuron ionic currents. PMID:22891434

Vislobokov, A I; Ignatov, Iu D; Seredenin, S B

2012-01-01

188

Optical Mapping of Electrical Activation in the Developing Heart  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

189

AC Electric Field Activated Shape Memory Polymer Composite  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

190

The effects of caffeine and ryanodine on the electrical activity of the canine coronary sinus.  

PubMed

Cells of the coronary sinus of the canine heart can exhibit triggered activity which each action potential arises from a depolarizing after-potential that follows the previous action potential; an early after-hyperpolarization commonly precedes the delayed after-depolarization and both are increased in amplitude by the addition of noradrenaline. The delayed after-depolarization is thought to be caused by an inward current activated by a rise in intracellular Ca2+ that is, in turn, caused by Ca2+-induced release of Ca2+ from the sarcoplasmic reticulum (s.r.). The effects of caffeine and of ryanodine on the electrical activity of the coronary sinus were investigated because each of those agents is thought to affect the handling of intracellular Ca2+ by the s.r. The steady-state effect of exposure to 5 mM-caffeine is to cause the delayed after-depolarization to move much earlier in the cycle, and become too small to give rise to an action potential so that preparations cannot show triggered activity; moreover, if a burst of activity is in progress it is terminated by exposure to 5 mM-caffeine. Exposure to 0.5 mM-caffeine causes the delayed after-depolarization to move earlier in the cycle but to become larger so that triggered activity is more easily induced and longer lasting than in the absence of caffeine. Shortly after the addition (or wash-out) of 5 mM-caffeine the after-depolarization transiently resembles that seen in the presence of 0.5 mM-caffeine so that bursts of triggered activity may occur just after the addition or removal of 5 mM-caffeine. Exposure to 5 mM-caffeine abolishes early rapid repolarization (phase 1), shifts the plateau to a more positive level and retards the completion of repolarization. The effect on phase 1 is mimicked by exposure to solutions low in Cl-; the effect on the plateau is mimicked by exposure to 20 mM-tetraethylammonium (TEA); fibres exposed to solutions containing 20 mM-TEA and 21 mM-Cl- show action potentials very like those of fibres exposed to 5 mM-caffeine. If a fibre already exposed to a low Cl-, TEA-containing solution is then exposed to 5 mM-caffeine, no further change occurs in the action potential but the characteristic effects of caffeine on the after-depolarization appear. Exposure to ryanodine prevents the appearance of the delayed after-depolarization but leads to the appearance of an exceptionally long depolarizing after-potential that begins very early in diastole and, though waning, persists almost throughout diastole.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:4078750

Aronson, R S; Cranefield, P F; Wit, A L

1985-11-01

191

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

PubMed

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

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

2012-07-01

192

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

SciTech Connect

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

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

1990-02-15

193

A state-space model of the burst suppression ratio  

E-print Network

Burst suppression is an electroencephalogram pattern observed in states of severely reduced brain activity, such as general anesthesia, hypothermia and anoxic brain injuries. The burst suppression ratio (BSR), defined as ...

Solt, Ken

194

Active Bending Electric Endoscope Using Shape Memory Alloy Coil Actuators  

NASA Astrophysics Data System (ADS)

Bending motions of the tip of a conventional endoscope are controlled from outside the body by wire traction. A shaft of an endoscope should be relatively hard to avoid buckling by wire traction. Therefore, precise operation of the endoscope is difficult in complex shape areas such as the intestine. Furthermore, patients suffer pain during a procedure with an endoscope. An active bending electric endoscope using shape memory alloy (SMA) actuators has been developed. A CCD camera (410,000 pixels) is mounted at the end of the endoscope and the tip has an omni-directional bending mechanism using three SMA coil actuators. The SMA coil actuators contract by supplying electrical current and bend the endoscope. The external diameter of the fabricated endoscope is 5.5 mm. The maximum bending angle of the fabricated endoscope is 90° (Curvature radius: 29 mm). The observation of the inside of a blood vessel model by the CCD imager of a fabricated endoscope was confirmed. The active bending shaft of the fabricated endoscope, which is realized using SMA coil actuators instead of wire traction, is soft. Therefore, using this endoscope, it may be possible to perform precise observations and treatment of deep areas of the human body.

Makishi, Wataru; Matsunaga, Tadao; Esashi, Masayoshi; Haga, Yoichi

195

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

196

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

Microsoft Academic Search

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

Anthony G. Moss; Sidney L. Tamm

1993-01-01

197

Recent Electric Propulsion Development Activities for NASA Science Missions  

NASA Technical Reports Server (NTRS)

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

Pencil, Eric J.

2009-01-01

198

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

199

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

200

A Burst of Electromagnetic Radiation from a Collapsing Magnetized Star  

E-print Network

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

Galina V. Lipunova

1997-03-01

201

Routes to chaos in a model of a bursting neuron.  

PubMed Central

Chaotic regimens have been observed experimentally in neurons as well as in deterministic neuronal models. The R15 bursting cell in the abdominal ganglion of Aplysia has been the subject of extensive mathematical modeling. Previously, the model of Plant and Kim has been shown to exhibit both bursting and beating modes of electrical activity. In this report, we demonstrate (a) that a chaotic regime exists between the bursting and beating modes of the model, and (b) that the model approaches chaos from both modes by a period doubling cascade. The bifurcation parameter employed is the external stimulus current. In addition to the period doubling observed in the model-generated trajectories, a period three "window" was observed, power spectra that demonstrate the approaches to chaos were generated, and the Lyaponov exponents and the fractal dimension of the chaotic attractors were calculated. Chaotic regimes have been observed in several similar models, which suggests that they are a general characteristic of cells that exhibit both bursting and beating modes. PMID:1697484

Canavier, C C; Clark, J W; Byrne, J H

1990-01-01

202

Convolutional Virtual Electric Field for Image Segmentation Using Active Contours  

PubMed Central

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

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

2014-01-01

203

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

2012-12-01

204

T & I--Electric Motors. Kit No. 621. Instructor's Manual and Student Learning Activity Guide.  

ERIC Educational Resources Information Center

This instructor's manual and student learning activity guide comprise a kit for trade and industrial education (T & I) activities on electric motors. Purpose stated for the activities is to teach the student the four basic types of electric motors, the advantages and disadvantages of each, the types of jobs each can perform, and how to disassemble…

Bomar, William

205

A Meshfree Method for Simulating Myocardial Electrical Activity  

PubMed Central

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

Zhang, Heye; Ye, Huajun; Huang, Wenhua

2012-01-01

206

Determination of local myocardial electrical activation for activation sequence mapping. A statistical approach.  

PubMed

Electrical activation sequence mapping requires accurate identification of local activation, but because extracellular recordings do not exclusively reflect local events, complex electrograms may be difficult to interpret. In such cases, the assignment of local activation is subject to error that could affect interpretation of the resulting activation maps. The purpose of this investigation was to develop an approach that would provide quantitative indexes of error in the determination of local activation. An electrode array with 64 closely spaced unipolar electrodes was used to record from the left ventricular surface during open heart surgery. Electrograms with multiple deflections were recorded from four patients with scarred myocardium; two other patients with normal myocardial function served as controls. Each of 784 deflections was scored on the basis of three features: evidence for propagation, the configuration of the bipolar signal, and the effect of changing from the chest to an average reference. Local activation was considered probable if evidence for all three features was present and improbable if none of the three features was present. Deflections that were ambiguous with respect to this standard were excluded. Of over 30 test variables analyzed, the three with the greatest power to discriminate signals due to local activation from those due to distant activity were 1) a linear combination of the extracellular potential plus the ratio of the second derivative and the extracellular potential, 2) the second derivative, and 3) the minimum (greatest negative) first derivative. For each of these variables, the threshold value providing the greatest performance was identified by the maximum quality of efficiency, an index of agreement. This statistical approach provides an objective basis for determining local activation and provides a quantitative assessment of error that could enhance interpretation of electrical activation sequence maps. PMID:1934344

Anderson, K P; Walker, R; Ershler, P R; Fuller, M; Dustman, T; Menlove, R; Karwandee, S V; Lux, R L

1991-10-01

207

Knockdown of sodium channel NaV1.6 blocks mechanical pain and abnormal bursting activity of afferent neurons in inflamed sensory ganglia  

PubMed Central

Inflammatory processes in the sensory ganglia contribute to many forms of chronic pain. We previously showed that local inflammation of the lumbar sensory ganglia rapidly leads to prolonged mechanical pain behaviors and high levels of spontaneous bursting activity in myelinated cells. Abnormal spontaneous activity of sensory neurons occurs early in many preclinical pain models, and initiates many other pathological changes, but its molecular basis is not well understood. The sodium channel isoform NaV1.6 can underlie repetitive firing and excitatory persistent and resurgent currents. We used in vivo knockdown of this channel via local injection of siRNA to examine its role in chronic pain following local inflammation of the rat lumbar sensory ganglia. In normal DRG, quantitative PCR showed that cells capable of firing repetitively had significantly higher relative expression of NaV1.6. In inflamed DRG, spontaneously active bursting cells expressed high levels of NaV1.6? immunoreactivity. In vivo knockdown of NaV1.6 locally in the lumbar DRG at the time of DRG inflammation completely blocked development of pain behaviors and abnormal spontaneous activity, while having only minor effects on unmyelinated C-cells. Current research on isoform-specific sodium channel blockers for chronic pain is largely focused on NaV1.8, because it is present primarily in unmyelinated C fiber nociceptors, or on NaV1.7, because lack of this channel causes congenital indifference to pain. However, the results suggest that NaV1.6 may be a useful therapeutic target for chronic pain, and that some pain conditions may be primarily mediated by myelinated A-fiber sensory neurons. PMID:23622763

Xie, Wenrui; Strong, Judith A.; Ye, Ling; Mao, Ju-Xian; Zhang, Jun-Ming

2013-01-01

208

Recent electric propulsion development activities for NASA science missions  

Microsoft Academic Search

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

E. J. Pencil

2009-01-01

209

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.

210

Multiple Bifurcations in a Polynomial Model of Bursting Oscillations  

NASA Astrophysics Data System (ADS)

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

de Vries, G.

1998-06-01

211

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

212

Computation of induced electric field for the sacral nerve activation  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

213

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

214

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

SciTech Connect

Proton efflux via voltage-gated proton channels (Hv1) is considered to mediate the charge compensation necessary to preserve NADPH oxidase activity during the respiratory burst. Using the Hv1 inhibitor Zn{sup 2+}, we found that the PMA-induced respiratory burst of human neutrophils is inhibited when assessed as extracellular production of O{sub 2}{sup ?} and H{sub 2}O{sub 2}, in accordance with literature studies, but, surprisingly, unaffected when measured as oxygen consumption or total (extracellular plus intracellular) H{sub 2}O{sub 2} production. Furthermore, we show that inhibiting Hv1 with Zn{sup 2+} results in an increased production of intracellular ROS. Similar results, i.e. decreased extracellular and increased intracellular ROS production, were obtained using a human granulocyte-like cell line with severely impaired Hv1 expression. Acidic extracellular pH, which dampens proton efflux, also augmented intracellular production of H{sub 2}O{sub 2}. Zinc caused an increase in the rate but not in the extent of depolarization and cytosolic acidification indicating that mechanisms other than proton efflux take part in charge compensation. Our results suggest a hitherto unpredicted mechanism of charge compensation whereby, in the absence of proton efflux, part of O{sub 2}{sup ?} generated within gp91{sup phox} in the plasma membrane is shunted intracellularly down electrochemical gradient to dampen excessive depolarization. This would preserve NADPH oxidase activity under conditions such as the inflammatory exudate in which the acidic pH hinders charge compensation by proton efflux. Highlights: • Neutrophils’ respiratory burst is not inhibited by the H{sup +} channel inhibitor Zn{sup 2+}. • Intracellular production of O{sub 2}{sup ?} and H{sub 2}O{sub 2} is increased in the presence of Zn{sup 2+}. • Intracellular H{sub 2}O{sub 2} production is increased in H{sup +} channels knock-down cells. • Zn{sup 2+} increases the rate but not the extent of depolarization and pH{sub i} decrease. • Intracellular shunting of O{sub 2}{sup ?} contributes to charge compensation in neutrophils.

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

2013-07-15

215

Discovery and Monitoring of the likely IR Counterpart of SGR 1806-20 during the 2004 gamma-ray burst-active state  

E-print Network

The sky region including the Chandra position of SGR 1806-20 was monitored in the IR band during 2004, following its increased high energy bursting activity. Observations were performed using NAOS-CONICA, the adaptive optics IR camera mounted on Yepun VLT, which provided images of unprecedented quality (FWHM better than 0.1"). After the 2004 December 27th giant flare, the source position has been nailed by VLA observations of its radio counterpart, reducing the positional uncertainty to 0.04". Using IR data from our monitoring campaign, we discovered the likely IR counterpart to SGR 1806-20 based on positional coincidence with the Chandra and VLA uncertainty regions and flux variability of a factor of about 2 correlated with that at higher energies. We compare our findings with other isolated neutron star classes thought to be related, at some level, with SGRs.

GianLuca Israel; Stefano Covino; Roberto Mignani; Luigi Stella; Gianni Marconi; Vincenzo Testa; Sandro Mereghetti; Sergio Campana; Nanda Rea; Diego Gotz; Rosalba Perna; Gaspare Lo Curto

2005-06-04

216

Using image registration to reconstruct spatiotemporal electrical activity in cardiac optical mapping studies  

Microsoft Academic Search

Optical mapping using membrane potential-sensitive fluorescent dyes provides a means of recording electrical activation on the heart surface with high spatial resolution. However, in order to interpret these data, it is necessary to correct for artifact introduced by heart wall motion. This paper describes a novel image registration technique that enables electrical activity on the heart surface to be reconstructed

M. Svrcek; S. Rutherford; A. Y. H. Chen; I. Provaznik; B. H. Smaill

2009-01-01

217

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

E-print Network

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

Paris-Sud XI, Université de

218

Line Length as a Robust Method to Detect High-Activity Events Automated Burst Detection in Premature EEG Recordings  

E-print Network

all" & Methods in neurocognitive Psychology, University of Oldenburg, Oldenburg, Germany 5 Neonatal. Corresponding author: Ninah Koolen From the Department of Electrical Engineering (ESAT) ­ STADIUS , Centre and cognitive problems (Institute of Medicine, 2007). These disabilities excert pressure and raise cost

219

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

SciTech Connect

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

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

1995-02-01

220

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts originate from cosmological distances and represent the largest known explosions in the Universe. The observed temporal and spectral characteristics of bursts in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory, will be described. The talk will concentrate on recent studies of burst properties, correlations of GRB parameters and other statistical studies that have recently come to light. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various models for the energy source of gamma-ray bursts will be described.

Fishman, Gearld J.

2003-01-01

221

Active current gating in electrically biased conical nanopores.  

PubMed

We observed that the ionic current through a gold/silicon nitride (Si3N4) nanopore could be modulated and gated by electrically biasing the gold layer. Rather than employing chemical modification to alter device behavior, we achieved control of conductance directly by electrically biasing the gold portion of the nanopore. By stepping through a range of bias potentials under a constant trans-pore electric field, we observed a gating phenomenon in the trans-pore current response in a variety of solutions including potassium chloride (KCl), sodium chloride (NaCl), and potassium iodide (KI). A computational model with a conical nanopore was developed to examine the effect of the Gouy-Chapman-Stern electrical double layer along with nanopore geometry, work function potentials, and applied electrical bias on the ionic current. The numerical results indicated that the observed modulation and gating behavior was due to dynamic reorganization of the electrical double layer in response to changes in the electrical bias. Specifically, in the conducting state, the nanopore conductance (both numerical and experimental) is linearly proportional to the applied bias due to accumulation of charge in the diffuse layer. The gating effect occurs due to the asymmetric charge distribution in the fluid induced by the distribution of potentials at the nanopore surface. Time dependent changes in current due to restructuring of the electrical double layer occur when the electrostatic bias is instantaneously changed. The nanopore device demonstrates direct external control over nanopore behavior via modulation of the electrical double layer by electrostatic biasing. PMID:25865738

Bearden, Samuel; Simpanen, Erik; Zhang, Guigen

2015-05-01

222

Spiking patterns of a hippocampus model in electric fields  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

223

Active RF Pulse Compression using Electrically Controlled Semiconductor Switches  

SciTech Connect

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

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

2008-01-30

224

Todd, Faraday and the electrical basis of brain activity  

Microsoft Academic Search

The origins of our understanding of brain electricity and electrical discharges in epilepsy can be traced to Robert Bentley Todd (1809–60). Todd was influenced by his contemporary in London, Michael Faraday (1791–1867), who in the 1830s and 1840s was laying the foundations of our modern understanding of electromagnetism. Todd’s concept of nervous polarity, generated in nerve vesicles and transmitted in

Edward Reynolds

2007-01-01

225

Selective interference with pacemaker activity by electrical dental devices  

Microsoft Academic Search

Objective. We sought to determine whether electromagnetic interference with cardiac pacemakers occurs during the operation of contemporary electrical dental equipment.Study Design. Fourteen electrical dental devices were tested in vitro for their ability to interfere with the function of two Medtronics cardiac pacemakers (one a dual-chamber, bipolar Thera 7942 pacemaker, the other a single-chamber, unipolar Minix 8340 pacemaker). Atrial and ventricular

Craig S Miller; Fabio M Leonelli; Emma Latham

1998-01-01

226

Cytoplasts made from human blood polymorphonuclear leukocytes with or without heat: preservation of both motile function and respiratory burst oxidase activity.  

PubMed Central

Anucleate fragments (cytoplasts) from polymorphonuclear leukocytes (PMN) are simplified systems that can be used to elucidate specific pathways by which cell function is altered. PMN cytoplasts in current use are defective either in activatable respiratory burst oxidase activity or in motile function. By centrifugation of PMN on discontinuous gradients of Ficoll without cytochalasin B, we have created granule-poor cytoplasts in which both these capacities are preserved. Specifically, they generate superoxide anion (O2-.) and reduce nitroblue tetrazolium dye on appropriate stimulation; they respond chemotactically to erythrocytes destroyed by laser microirradiation or to the specific chemoattractants fMet-Leu-Phe (10 nM) and C5a (zymosan-activated serum); and they ingest and kill staphylococci. We can improve the yield of these fragments progressively by preheating (45 degrees C) the cells in suspension for increasing periods of time, but those treatments are attended by a decreasing percentage of cytoplasts with activatable oxidase activity, and a progressive inability of the cytoplasts to ingest and to kill staphylococci. These easily made and multipotent cytoplasts readily lend themselves to studies of PMN physiology. Images PMID:3025874

Malawista, S E; Van Blaricom, G

1987-01-01

227

DIFFERENTIAL ACTIVATION OF SIGNAL TRANSDUCTION PATHWAYS MEDIATING OXIDATIVE BURST BY CHICKEN HETEROPHILS IN RESPONSE TO STIMULATION WITH LIPOPOLYSACCHARIDE AND 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 begin to map the molecular pathways that regulate TLR-mediated oxidative burst. Peripheral blood heterophils from neonatal chicks were isolated and exposed to known ...

228

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...

229

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

230

Intensive X-ray emission bursts during thunderstorms  

NASA Astrophysics Data System (ADS)

The intensive X-ray emission during thunderstorms was studied at a height of 3340 m above sea level. For the first time, short-time (1-5 min) bursts of X-ray emission were observed. The bursts are highly correlated over a wide space region (about 0.5 km). The main component of X-ray emission in bursts has energies between 50-80 keV. The observed bursts could be attributed to the bremsstrahlung determined by the runaway breakdown (RB) effect in the thundercloud's electric field. Ground-based observations of RB open a wide range of opportunities for the studies of fundamental processes in thunderstorms.

Chubenko, A. P.; Antonova, V. P.; Kryukov, S. Yu.; Piskal, V. V.; Ptitsyn, M. O.; Shepetov, A. L.; Vildanova, L. I.; Zybin, K. P.; Gurevich, A. V.

2000-10-01

231

Burst-by-burst laser frequency monitor  

NASA Technical Reports Server (NTRS)

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

Esproles, Carlos (inventor)

1994-01-01

232

Electrically controlled transfer of spin angular momentum of light in an optically active medium  

NASA Astrophysics Data System (ADS)

Spin is an intrinsic property of the photon. A method for using an externally applied dc electric field to manipulate the transfer of spin angular momentum of light in an optically active medium is presented. To discuss this, we first develop a wave coupling theory of the mutual action of natural optical activity and the linear electro-optic effect. Besides being used for analyzing the electrically controlled transfer of spin angular momentum of light, the theory can also be used to describe the propagation of light traveling along an arbitrary direction in any optically active medium with an external dc electric field along an arbitrary direction.

Chen, Lixiang; Zheng, Guoliang; Xu, Jie; Zhang, Bingzhi; She, Weilong

2006-12-01

233

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

Iowa Public Television. Explore More Project

2004-01-01

234

A Comparison of Integrated Electric Field with Substorm Activity  

NASA Astrophysics Data System (ADS)

When the interplanetary magnetic field (IMF) in the solar wind suddenly turns northward after pointing southward for ˜1-2 hours, a substorm is usually triggered. A study was undertaken to compare strength and duration of substorms to electric field input prior to the onset into the Earth's magnetosphere. Periods for which the IMF pointed southward for 1-2 hours and then rapidly turned northward (i.e., when the Bz component of the solar wind is negative and turns positive) were found using the ACE satellite data available through CDAWeb. Using Ey=VxBz, the electric field data was integrated to determine an estimate of the solar wind input during these periods. The integrated electric field will be compared directly to substorm data to check for correlations between solar wind input and magnetospheric output.

Kissinger, Jennifer; Cullens, Tamara; Moss, Alicia; Bruntz, Robert; Lopez, Ramon

2007-04-01

235

Electrospun nanofiber membranes for electrically activated shape memory nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

236

Diagnostic Thresholds for Quantitative REM Sleep Phasic Burst Duration, Phasic and Tonic Muscle Activity, and REM Atonia Index in REM Sleep Behavior Disorder with and without Comorbid Obstructive Sleep Apnea  

PubMed Central

Objectives: We aimed to determine whether phasic burst duration and conventional REM sleep without atonia (RSWA) methods could accurately diagnose REM sleep behavior disorder (RBD) patients with comorbid OSA. Design: We visually analyzed RSWA phasic burst durations, phasic, “any,” and tonic muscle activity by 3-s mini-epochs, phasic activity by 30-s (AASM rules) epochs, and conducted automated REM atonia index (RAI) analysis. Group RSWA metrics were analyzed and regression models fit, with receiver operating characteristic (ROC) curves determining the best diagnostic cutoff thresholds for RBD. Both split-night and full-night polysomnographic studies were analyzed. Setting: N/A. Participants: Parkinson disease (PD)-RBD (n = 20) and matched controls with (n = 20) and without (n = 20) OSA. Interventions: N/A. Measurements and Results: All mean RSWA phasic burst durations and muscle activities were higher in PD-RBD patients than controls (P < 0.0001), and RSWA associations with PD-RBD remained significant when adjusting for age, gender, and REM AHI (P < 0.0001). RSWA muscle activity (phasic, “any”) cutoffs for 3-s mini-epoch scorings were submentalis (SM) (15.5%, 21.6%), anterior tibialis (AT) (30.2%, 30.2%), and combined SM/AT (37.9%, 43.4%). Diagnostic cutoffs for 30-s epochs (AASM criteria) were SM 2.8%, AT 11.3%, and combined SM/AT 34.7%. Tonic muscle activity cutoff of 1.2% was 100% sensitive and specific, while RAI (SM) cutoff was 0.88. Phasic muscle burst duration cutoffs were: SM (0.65) and AT (0.79) seconds. Combining phasic burst durations with RSWA muscle activity improved sensitivity and specificity of RBD diagnosis. Conclusions: This study provides evidence for REM sleep without atonia diagnostic thresholds applicable in Parkinson disease-REM sleep behavior disorder (PD-RBD) patient populations with comorbid OSA that may be useful toward distinguishing PD-RBD in typical outpatient populations. Citation: McCarter SJ, St. Louis EK, Duwell EJ, Timm PC, Sandness DJ, Boeve BF, Silber MH. Diagnostic thresholds for quantitative REM sleep phasic burst duration, phasic and tonic muscle activity, and REM atonia index in REM sleep behavior disorder with and without comorbid obstructive sleep apnea. SLEEP 2014;37(10):1649-1662. PMID:25197816

McCarter, Stuart J.; St. Louis, Erik K.; Duwell, Ethan J.; Timm, Paul C.; Sandness, David J.; Boeve, Bradley F.; Silber, Michael H.

2014-01-01

237

Application of subharmonics for active sound design of electric vehicles.  

PubMed

The powertrain of electric vehicles generates an unfamiliar acoustical environment for customers. This paper seeks optimal interior sound for electric vehicles based on psychoacoustic knowledge and musical harmonic theory. The concept of inserting a virtual sound, which consists of the subharmonics of an existing high-frequency component, is suggested to improve sound quality. Subjective evaluation results indicate that the impression of interior sound can be enhanced in this manner. Increased appeal is achieved through two designed stimuli, which proves the effectiveness of the method proposed. PMID:25480088

Gwak, Doo Young; Yoon, Kiseop; Seong, Yeolwan; Lee, Soogab

2014-12-01

238

Electrical multisite stimulation of the isolated chicken retina  

Microsoft Academic Search

Visual prostheses such as subretinal implants are intended for electrical multisite excitation of the retinal network. To investigate relevant issues like spatial resolution and operational range, we have developed an in vitro method using microelectrode arrays to stimulate isolated retinae. Ganglion cell activity in the chicken retina evoked by distally applied spatial voltage patterns consisted of fast bursts, transient inhibition

Alfred Stett; Wolfgang Barth; Stefan Weiss; Hugo Haemmerle; Eberhart Zrenner

2000-01-01

239

Parameters Affecting the Loading Behavior and Degradation of Electrically Active Filter Materials  

Microsoft Academic Search

Electrically active fibrous filters, that is fibrous filters whose fibers carry a permanent electric charge, are a popular alternative to conventional fibrous filters in applications where low pressure drop and high collection efficiencies are critical. The advantage of these materials is the additional collection efficiency, due to electrostatic mechanisms, that can be achieved without pressure drop increase. Although the efficiency

D. C. Walsh; J. I. T. Stenhouse

1998-01-01

240

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

241

An Overview of Electric and Advanced Propulsion Activities in Japan  

Microsoft Academic Search

This paper describes the current status of electric propulsion technology development and related studies in Japan. Ion engine systems (IES) onboard the Engineering Test Satellite VI (ETS-VI) and the Communications and Broadcasting Engineering Test Satellite (COMETS), and a quasisteady MPD thruster onboard the Space Flyer Unit (SFU) were successfully demonstrated. The National Space Development Agency of Japan (NASDA) is to

Kimiya Komurasaki; Yoshihiro Arakawa; Haruki Takegahara

2000-01-01

242

ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY  

Microsoft Academic Search

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

KENNETH S. COLE; HOWARD J. CURTIS

1939-01-01

243

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

PubMed Central

The present manuscript aims at identifying patterns of electrical activity recorded from neurons of the leech nervous system, characterizing specific behaviors. When leeches are at rest, the electrical activity of neurons and motoneurons is poorly correlated. When leeches move their head and/or tail, in contrast, action potential (AP) firing becomes highly correlated. When the head or tail suckers detach, specific patterns of electrical activity are detected. During elongation and contraction the electrical activity of motoneurons in the Medial Anterior and Dorsal Posterior nerves increase, respectively, and several motoneurons are activated both during elongation and contraction. During crawling, swimming, and pseudo-swimming patterns of electrical activity are better described by the dendrograms of cross-correlations of motoneurons pairs. Dendrograms obtained from different animals exhibiting the same behavior are similar and by averaging these dendrograms we obtained a template underlying a given behavior. By using this template, the corresponding behavior is reliably identified from the recorded electrical activity. The analysis of dendrograms during different leech behavior reveals the fine orchestration of motoneurons firing specific to each stereotyped behavior. Therefore, dendrograms capture the subtle changes in the correlation pattern of neuronal networks when they become involved in different tasks or functions. PMID:24098274

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

2013-01-01

244

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

E-print Network

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

Karameh, Fadi Nabih

2002-01-01

245

Numerical modelling of the electrical activity of the atria and the pulmonary veins.  

E-print Network

Numerical modelling of the electrical activity of the atria and the pulmonary veins. SIMON LABARTHE FIBROSIS AND ABLATION. VPIG cercle obstacle spots VPID SC OD ­ Transmural fibrosis Stabilization effect

Boyer, Edmond

246

An Improved Ivermectin-activated Chloride Channel Receptor for Inhibiting Electrical Activity in Defined Neuronal Populations*  

PubMed Central

The ability to silence the electrical activity of defined neuronal populations in vivo is dramatically advancing our understanding of brain function. This technology may eventually be useful clinically for treating a variety of neuropathological disorders caused by excessive neuronal activity. Several neuronal silencing methods have been developed, with the bacterial light-activated halorhodopsin and the invertebrate allatostatin-activated G protein-coupled receptor proving the most successful to date. However, both techniques may be difficult to implement clinically due to their requirement for surgically implanted stimulus delivery methods and their use of nonhuman receptors. A third silencing method, an invertebrate glutamate-gated chloride channel receptor (GluClR) activated by ivermectin, solves the stimulus delivery problem as ivermectin is a safe, well tolerated drug that reaches the brain following systemic administration. However, the limitations of this method include poor functional expression, possibly due to the requirement to coexpress two different subunits in individual neurons, and the nonhuman origin of GluClR. Here, we describe the development of a modified human ?1 glycine receptor as an improved ivermectin-gated silencing receptor. The crucial development was the identification of a mutation, A288G, which increased ivermectin sensitivity almost 100-fold, rendering it similar to that of GluClR. Glycine sensitivity was eliminated via the F207A mutation. Its large unitary conductance, homomeric expression, and human origin may render the F207A/A288G ?1 glycine receptor an improved silencing receptor for neuroscientific and clinical purposes. As all known highly ivermectin-sensitive GluClRs contain an endogenous glycine residue at the corresponding location, this residue appears essential for exquisite ivermectin sensitivity. PMID:20308070

Lynagh, Timothy; Lynch, Joseph W.

2010-01-01

247

The GLAST Burst Monitor  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

248

Inhibition of Electrical Activity by Retroviral Infection with Kir2.1 Transgenes Disrupts Electrical Differentiation of Motoneurons  

PubMed Central

Network-driven spontaneous electrical activity in the chicken spinal cord regulates a variety of developmental processes including neuronal differentiation and formation of neuromuscular structures. In this study we have examined the effect of chronic inhibition of spinal cord activity on motoneuron survival and differentiation. Early spinal cord activity in chick embryos was blocked using an avian replication-competent retroviral vector RCASBP (B) carrying the inward rectifier potassium channel Kir2.1. Chicken embryos were infected with one of the following constructs: RCASBP(B), RCASBP(B)-Kir2.1, or RCASBP(B)-GFP. Infection of chicken embryos at E2 resulted in widespread expression of the viral protein marker p27 gag throughout the spinal cord. Electrophysiological recordings revealed the presence of functional Kir2.1 channels in RCASBP(B)-Kir2.1 but not in RCASBP(B)-infected embryos. Kir2.1 expression significantly reduced the generation of spontaneous motor movements in chicken embryos developing in ovo. Suppression of spontaneous electrical activity was not due to a reduction in the number of surviving motoneurons or the number of synapses in hindlimb muscle tissue. Disruption of the normal pattern of activity in chicken embryos resulted in a significant downregulation in the functional expression of large-conductance Ca2+-dependent K+ channels. Reduction of spinal cord activity also generates a significant acceleration in the inactivation rate of A-type K+ currents without any significant change in current density. Kir2.1 expression did not affect the expression of voltage-gated Na+ channels or cell capacitance. These experiments demonstrate that chronic inhibition of chicken spinal cord activity causes a significant change in the electrical properties of developing motoneurons. PMID:18698433

Yoon, Yone Jung; Kominami, Hisashi; Trimarchi, Thomas; Martin-Caraballo, Miguel

2008-01-01

249

Neural sensing of electrical activity with stretchable microelectrode arrays  

Microsoft Academic Search

Sensing neural activity within mechanically active tissues poses particular hurdles because most electrodes are much stiffer than biological tissues. As the tissue deforms, the rigid electrodes may damage the surrounding tissue. The problem is exacerbated when sensing neural activity in experimental models of traumatic brain injury (TBI) which is caused by the rapid and large deformation of brain tissue. We

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

2009-01-01

250

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

251

Todd, Faraday and the electrical basis of brain activity.  

PubMed

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

Reynolds, Edward

2007-10-01

252

A brief review of JPL's electric propulsion technology activities  

Microsoft Academic Search

Near-term objectives and recent technological progress of JPL's electric propulsion program are discussed. Particular attention is given to accomplishments for ion, magnetoplasmadynamic (MPD), electron-cyclotron resonance (ECR), and arcjet thrusters. Xenon ion thruster erosion tests indicate a 15-fold reduction in tantalum baffle erosion when nitrogen is added to the xenon propellant and steady-state cylindrical MPD thruster tests at powers up to

J. W. Barnett; A. Chopra; W. D. Deininger; C. E. Garner; T. J. Pivirotto; J. C. Sercel

1989-01-01

253

The Electrical Activity of a Denervated Ear 1  

PubMed Central

The electrical response from the cochlea of a cat which had previously been denervated by intracranial crushing of the auditory nerve was submitted to a lengthy study, the results of which may be summarized as follows:- The responses to acoustical stimulation derived from electrodes placed on the round window margin and in the chin muscles were studied by means of an amplifier and cathode ray oscillograph, in the usual way. Transient stimuli whose polarity could be reversed were employed to demonstrate the absence of any electrical component of neural origin such as is invariably present in a normal ear. In all other respects, however, the responses were unaffected, and both threshold contours (the so-called “electrical audiogram”) and equal response contours for approximately pure-tone stimuli demonstrated close comparability with those for normal ears. Harmonic analysis of the cochlear response yielded results departing from the normal only in such respects as would be expected in view of the complete absence of nervous component in the analysed wave. From these data, it is argued that this animal presented a case in which normal electrical responses were obtained from the peripheral organ, despite virtually complete degeneration of the auditory nerve, and, it follows, complete unilateral deafness. Subsequent histological examination confirmed these observations, and it is urged, therefore, that the validity of the view that the cochlear response provides an index of the hearing ability of an animal, as is sometimes stated, is open to question. Additionally, this experiment finally discredits the hypothesis that the cochlear response itself is, in any sense, neural in origin; it further indicates the necessity for caution in the interpretation of results obtained from normal ears, where the cochlear response, however derived, is in some degree adulterated by the simultaneous presence of an action potential component. ImagesFig. 8 PMID:19991849

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

1939-01-01

254

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

E-print Network

. Maximum locomotor performance of ectothermic vertebrates, for example, is highly sensitive (reviewed in Bennett 1990). In adult ectotherms, acclimation to different temperatures (usually kinetics, myofibrillar structure, and myofibrillar ATPase activity. Locomotor performance of ectotherms can

Ahmad, Sajjad

255

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

E-print Network

I consider how physical processes scale over eight orders of magnitude in black hole mass, from stellar masses in gamma-ray bursts (GRB) and black-hole X-ray binaries (BHXRB) to supermassive active galactic nuclei (AGN). Accretion rates onto stellar mass black holes range over more than sixteen orders of magnitude, from the lower luminosity BHXRB to GRB. These enormous parameter ranges correspond to qualitative as well as quantitative differences in behavior. The fundamental questions involve the balance between nonequilibrium and thermalized plasmas. When energy fluxes exceed a critical value $\\sim 10^{29}$ erg/cm$^2$s, as in GRB, a black-body equilibrium pair plasma forms. At the lower fluxes found in AGN, BHXRB and microquasars, accretion power electrodynamically accelerates a small number of very energetic particles, explaining their non-thermal spectra and the high energy gamma-ray emission of blazars. Ultra-high energy cosmic rays may be accelerated by massive black holes, otherwise undetectable, with very low thermal luminosities. New-born fast high-field pulsars may be in the black-body equilibrium regime, resembling SGR in permanent outburst. I also consider the question, significant for the acceleration of nonthermal particles in GRB outflows, of whether collisionless plasmas interpenetrate rather than forming hydrodynamic shocks, and propose this as an alternative to internal shock models of GRB.

J. I. Katz

2009-04-23

256

Transitions to Synchrony in Coupled Bursting Neurons Mukeshwar Dhamala,1  

E-print Network

in the brain, for example, thalamic neurons during sleep, show spike-burst activity. We study such spike during periods of drowsiness, inattentiveness, and sleep, are known to exhibit spike-burst activity [1, Florida 33431, USA 2 Department of Physics, Florida Atlantic University, Boca Raton, Florida 33431, USA 3

Dhamala, Mukesh

257

Neuronal networks and energy bursts in epilepsy.  

PubMed

Epilepsy can be defined as the abnormal activities of neurons. The occurrence, propagation and termination of epileptic seizures rely on the networks of neuronal cells that are connected through both synaptic- and non-synaptic interactions. These complicated interactions contain the modified functions of normal neurons and glias as well as the mediation of excitatory and inhibitory mechanisms with feedback homeostasis. Numerous spread patterns are detected in disparate networks of ictal activities. The cortical-thalamic-cortical loop is present during a general spike wave seizure. The thalamic reticular nucleus (nRT) is the major inhibitory input traversing the region, and the dentate gyrus (DG) controls CA3 excitability. The imbalance between ?-aminobutyric acid (GABA)-ergic inhibition and glutamatergic excitation is the main disorder in epilepsy. Adjustable negative feedback that mediates both inhibitory and excitatory components affects neuronal networks through neurotransmission fluctuation, receptor and transmitter signaling, and through concomitant influences on ion concentrations and field effects. Within a limited dynamic range, neurons slowly adapt to input levels and have a high sensitivity to synaptic changes. The stability of the adapting network depends on the ratio of the adaptation rates of both the excitatory and inhibitory populations. Thus, therapeutic strategies with multiple effects on seizures are required for the treatment of epilepsy, and the therapeutic functions on networks are reviewed here. Based on the high-energy burst theory of epileptic activity, we propose a potential antiepileptic therapeutic strategy to transfer the high energy and extra electricity out of the foci. PMID:24993475

Wu, Y; Liu, D; Song, Z

2015-02-26

258

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

NASA Astrophysics Data System (ADS)

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

Gwal, A. K.; Shrivastava, A.

2006-11-01

259

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

PubMed

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

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

2014-09-23

260

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

PubMed Central

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

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

2014-01-01

261

INMED/TINS special issue Early patterns of electrical activity  

E-print Network

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

Cossart, Rosa

262

A brief review of JPL's electric propulsion technology activities  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

263

Section of burst tumulus  

USGS Multimedia Gallery

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

264

Section of Burst Tumulus  

USGS Multimedia Gallery

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

265

Meteor burst communications  

Microsoft Academic Search

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

Davras Yavuz

1990-01-01

266

Gamma Ray Bursts - Observations  

NASA Technical Reports Server (NTRS)

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

Gehrels, N.; Cannizzo, J. K.

2010-01-01

267

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

PubMed Central

1. Oxytocin was pressure injected through a glass micropipette into a supraoptic (SON) or paraventricular nucleus (PVN) while recording the electrical activities of oxytocin cells in a contralateral nucleus, to see whether oxytocin acts locally in the magnocellular nuclei to control their bursting activity and whether the oxytocin cells of the four magnocellular nuclei were functionally interconnected during suckling. To test the rapidity of these relations, similar intranuclear injections were realized with acetylcholine, known to rapidly increase the background activity of oxytocin cells. The effects of intranuclear injections of oxytocin and acetylcholine were tested before and after interhemisphere sections of various dimensions. 2. Injecting oxytocin (1 ng in 100 nl) into a magnocellular nucleus (5 times into the PVN and 15 times into the SON) facilitated the occurrence and increased the amplitude of bursts of the oxytocin cells in both the contralateral PVN and SON. This facilitatory effect was similar to that induced by intraventricular injection of the same dose of oxytocin, though slightly delayed and lower. 3. Injecting acetylcholine (0.6 microgram in 100 nl) into the SON (7 times) induced a rapid and sustained increase in the background activity of oxytocin cells in both the contralateral PVN (2 times) and SON (5 times) within the same delay (less than 15 s). This excitatory effect was similar to that induced by an intraventricular injection of 5 micrograms acetylcholine. The effects on bursting activity were not considered in this study. 4. Neither the injections of oxytocin or acetylcholine outside but near the magnocellular nuclei (200-500 microns), nor the intranuclear injection of 100-200 nl of cerebrospinal fluid-like medium, modified the background activity, the frequency and amplitude of bursts of the oxytocin cells in the nucleus contralateral to the injection site. 5. After interhemisphere sections most oxytocin cells were silent, bursts occurred in an erratic manner, and their amplitude was attenuated and irregular (more than the 20% variation normally recorded in non-operated rats). Moreover, the amplitudes of successive bursts of pair-recorded supraoptic-supraoptic (SO-SO) oxytocin cells, highly related in control conditions (correlation coefficient, r = 0.68 to 0.98) were no longer correlated after interhemisphere section (r = 0.24 to -0.61), but all bursts remained synchronized.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 1 PMID:2778722

Moos, F; Richard, P

1989-01-01

268

Comparison of chemical, electrical, and combined activation methods for in vitro matured porcine oocytes.  

PubMed

Factors influencing porcine oocyte activation were systematically studied. This study included (1) the effect of ionomycin plus various chemical agents on activation, (2) comparison of different electrical activation parameters, (3) optimization of combined activation, and (4) evaluation of the optimized protocols. The results showed that (1) blastocyst rates of ionomycin (Ion) + 6-dimethylaminopurine (6-DMAP) (29.7?±?1.1%), Ion + cytochalasin B (CB) + cycloheximide (CHX) (29.8?±?1.2%), Ion + CB + 6-DMAP (30.4?±?1.6%), and Ion + CB + CHX + 6-DMAP (30.2?±?2.7%) were significantly higher than Ion + CHX (15.8?±?1.5%, p?electrical activation was optimal when oocytes were activated by three direct current (DC) pulses of 1.00 kV cm(-1) for 80 ?s (39.5?±?1.1%); (3) blastocyst rates of DC + CB + CHX (55.4?±?1.2%) and DC + CB + 6-DMAP (50.4?±?2.9%) were significantly higher than DC + 6-DMAP, DC + CB + CHX + 6-DMAP, electrical activation, and chemical activation alone (p?electrical activation blastocysts (40%). Using the optimized electrical and combined activation protocol, high blastocyst rates were generated by intracytoplasmic sperm injection (ICSI) (34.6?±?1.1%), cytoplasmic microinjection (CI) (52.3?±?2.2%), and handmade cloning (HMC) (31.2?±?1.0%), respectively. This study concludes that the optimal activation protocol of in vitro matured porcine oocytes was combined activation with parameter as three DC pulses of 1.00 kV cm(-1) for 80 ?s plus CB and CHX treatment. PMID:25424832

Liu, Shuai; Cui, Kuiqing; Li, Hong Li; Sun, Jun Ming; Lu, Xing Rong; Shen, Kai Yuan; Liu, Qing You; Shi, De Shun

2015-02-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

270

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

PubMed Central

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

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

2014-01-01

271

Electrically silent divalent cation entries in resting and active voltage-controlled muscle fibers  

E-print Network

1 Electrically silent divalent cation entries in resting and active voltage-controlled muscle 1, CNRS UMR 5123, Villeurbanne, France Running title: Mn2+ entry and current in muscle cells to enter skeletal muscle at rest and during activity. Except for the well characterized Ca2+ entry through

Paris-Sud XI, Université de

272

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

273

Electron microscopic localization of choline acetyl transferase activity in the electric organ of Torpedo marmorata  

Microsoft Academic Search

The light microscopic method for demonstration of choline acetyltransferase (CAT) activity based on the formation of a lead mercaptide of free SH-acetyl Coenzyme A was adapted for electron microscopy. In samples of electric organ of Torpedo marmorata CAT activity was found to be restricted to synaptic vesicles and cysternae. The precipitate formed was mostly fine grained and distributed more or

K. Munz; U. Mfiller; P. G. Waser

1983-01-01

274

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

275

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

276

Statistical Properties of SGR 1900+14 Bursts  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

277

Statistical Properties of SGR 1900+14 Bursts  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

278

Activation energies and temperature effects from electrical spectra of soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

Apparent permittivity often has soil-specific temperature responses as well as soil water responses. Variations of permittivity as a function of frequency and temperature can be used to calculate activation energies. The purpose of this study was to examine permittivity-temperature responses for six...

279

Measurement of brain activity using optical and electrical method  

Microsoft Academic Search

There are patients that cannot produce bioelectric signals such as patients with advanced stages of Amyotrophic Lateral Sclerosis or that have suffered severe spinal cord injury, are unable to use assistive devices such as the exoskeleton HAL. This paper proposes a non-invasive brain activity scanning method for collecting the patient's movement intentions by developing a hybrid sensor that can measure

Atsushi Saito; Alexsandr Ianov; Yoshiyuki Sankai

2009-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

281

Electrical cortical activity associated with joint torque direction in the human arm.  

PubMed

The objective of this study is to determine whether electrical brain activity differs for static joint torques generated in the elbow flexion/extension and shoulder abduction/adduction directions in humans. Electrical brain activity was quantified using a technique that incorporates a realistic, subject-specific electromagnetic head model to create a three-dimensional spatial resultant vector representation of the cortical region of activation. The findings demonstrate that generation of torque in each of the four directions produced significantly different locations of centers of cortical activation. These differences in location were maintained from preparatory to the early execution phases of the task. The organization of the centers of cortical activity during the generation of elbow/shoulder torques resulted in centers associated with the generation of elbow torques that were more lateral than centers accompanying shoulder torques in all five subjects tested. The authors conclude that electrical brain activity is spatially organized during the generation of joint torques in opposing directions at the elbow and shoulder joints. In addition, the results indicate that the center of the electrical brain activity associated with these static tasks is localized over the primary motor cortex as opposed to secondary sensorimotor cortices. PMID:15375349

Ricamato, Anthony L; Dhaher, Yasin Y

2004-01-01

282

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.

283

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

284

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

SciTech Connect

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

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

2013-09-01

285

Characterizing Oscillatory Bursts in Single-Trial EEG Data  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

286

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

287

Direct magnetic resonance detection of neuronal electrical activity Natalia Petridou, Dietmar Plenz, Afonso C. Silva, Murray Loew, Jerzy Bodurka, and Peter A.  

E-print Network

Direct magnetic resonance detection of neuronal electrical activity Bandettini Natalia Petridou, see: Notes: #12;Direct magnetic resonance detection of neuronal electrical activity Natalia Petridou either cerebrovascular changes or extracra- nial measurements of electrical magnetic signals. Recent

Baker, Chris I.

288

Noninvasive functional imaging of volumetric cardiac electrical activity: a human study on myocardial infarction.  

PubMed

Identification of infarct substrates provides necessary guidance to the prevention and treatment of cardiac arrhythmias. Compared to diagnostic criteria of body surface potentials (BSP) or electrophysiological information on heart surfaces, the underlying volumetric cardiac electrical activity is of more direct clinical relevance in exhibiting patient-specific arrhythmic dynamics and arrhythmogenic substrates. We have developed a paradigm for noninvasive imaging of volumetric myocardial transmembrane potential from BSPs. In this paper, we present a human study for a patient with acute myocardial infarction. Using patient MRI and BSP data, the framework is able to reconstruct details of the complete arrhythmic electrical activity on the 3D myocardium of the patient. Exploring a subset of the results, the extent, centroid and affected segments of the infarct is correctly evaluated, with comparable performance to existent best results. This human study demonstrates the potential of the presented paradigm as a noninvasive functional imaging technique for patient-specific volumetric cardiac electrical activity in practice. PMID:18979848

Wang, Linwei; Wong, Ken C L; Zhang, Heye; Shi, Pengcheng

2008-01-01

289

Reciprocal inhibitory coupling: Measure and control of chaos on a biophysically motivated model of bursting  

NASA Astrophysics Data System (ADS)

Bursting activity is an interesting feature of the temporal organization in many cell firing patterns. This complex behavior is characterized by clusters of spikes (action potentials) interspersed with phases of quiescence. As shown in experimental recordings, concerning the electrical activity of real neurons, the analysis of bursting models reveals not only patterned periodic activity but also irregular behavior 1,2]. The interpretation of experimental results, particularly the study of the influence of coupling on chaotic bursting oscillations, is of great interest from physiological and physical perspectives. The inability to predict the behavior of dynamical systems in presence of chaos suggests the application of chaos control methods, when we are more interested in obtaining regular behavior. In the present article, we focus our attention on a specific class of biophysically motivated maps, proposed in the literature to describe the chaotic activity of spiking-bursting cells [Cazelles B, Courbage M, Rabinovich M. Anti-phase regularization of coupled chaotic maps modelling bursting neurons. Europhys Lett 2001;56:504-9]. More precisely, we study a map that reproduces the behavior of a single cell and a map used to examine the role of reciprocal inhibitory coupling, specially on two symmetrically coupled bursting neurons. Firstly, using results of symbolic dynamics, we characterize the topological entropy associated to the maps, which allows us to quantify and to distinguish different chaotic regimes. In particular, we exhibit numerical results about the effect of the coupling strength on the variation of the topological entropy. Finally, we show that complicated behavior arising from the chaotic coupled maps can be controlled, without changing of its original properties, and turned into a desired attracting time periodic motion (a regular cycle). The control is illustrated by an application of a feedback control technique developed by Romeiras et al. [Romeiras FJ, Grebogi C, Ott E, Dayawansa WP. Controlling chaotic dynamical systems. Physica D 1992;58:165-92]. This work provides an illustration of how our understanding of chaotic bursting models can be enhanced by the theory of dynamical systems.

Duarte, Jorge; Januário, Cristina; Martins, Nuno

2009-06-01

290

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

291

Gamma Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. There has been tremendous recent progress in our understanding of bursts with the new data from the Swift mission. Swift was launched in November 2004 and is a multiwave length observatory designed to determine the origin of bursts and use them to probe the early Universe. It was developed and is being operated by an international team of scientists from the US, UK and Italian. The first year of findings from the mission will be presented. A large step forward has been made in our understanding of the mysterious short GRBs. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gehrels, Neil

2006-01-01

292

INTEGRAL burst alert service  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

293

Dynamics of event-related causality in brain electrical activity.  

PubMed

A new method (Event-Related Causality, ERC) is proposed for the investigation of functional interactions between brain regions during cognitive processing. ERC estimates the direction, intensity, spectral content, and temporal course of brain activity propagation within a cortical network. ERC is based upon the short-time directed transfer function (SDTF), which is measured in short EEG epochs during multiple trials of a cognitive task, as well as the direct directed transfer function (dDTF), which distinguishes direct interactions between brain regions from indirect interactions via brain regions. ERC uses new statistical methods for comparing estimates of causal interactions during prestimulus "baseline" epochs and during poststimulus "activated" epochs in order to estimate event-related increases and decreases in the functional interactions between cortical network components during cognitive tasks. The utility of the ERC approach is demonstrated through its application to human electrocorticographic recordings (ECoG) of a simple language task. ERC analyses of these ECoG recordings reveal frequency-dependent interactions, particularly in high gamma (>60 Hz) frequencies, between brain regions known to participate in the recorded language task, and the temporal evolution of these interactions is consistent with the putative processing stages of this task. The method may be a useful tool for investigating the dynamics of causal interactions between various brain regions during cognitive task performance. PMID:17712784

Korzeniewska, Anna; Crainiceanu, Ciprian M; Ku?, Rafa?; Franaszczuk, Piotr J; Crone, Nathan E

2008-10-01

294

Active and passive electrical properties of single bullfrog atrial cells  

PubMed Central

Single cells from the bullfrog (Rana catesbeiana) atrium have been prepared by using a modification of the enzymatic dispersion procedure described by Bagby et al. (1971. Nature [Long.]. 234:351--352) and Fay and Delise (1973. Proc. Natl. Acad. Sci. U.S.A. 70:641--645). Visualization of relaxed cells via phase-contrast or Nomarski optics (magnification, 400--600) indicates that cells range between 150 and 350 micrometers in length and 4 and 7 micrometers in diameter. The mean sarcomere length in relaxed, quiescent atrial cells in 2.05 micrometer. Conventional electrophysiological measurements have been made. In normal Ringer's solution (2.5 mM K+, 2.5 mM Ca++) acceptable cells have stable resting potentials of about -88 mV, and large (125 mV) long- duration (approximately 720 ms) action potentials can be elicited. The Vm vs. log[K+]0 relation obtained from isolated cells is similar to that of the intact atrium. The depolarizing phase of the action potential of isolated atrial myocytes exhibits two pharmacologically separable components: tetrodotoxin (10(-6) g/ml) markedly suppresses the initial regenerative depolarization, whereas verapamil (3 x 10(-6) M) inhibits the secondary depolarization and reduce the plateau height. A bridge circuit was used to estimate the input resistance (220 +/- 7 M omega) and time constant 20 +/- 7 ms) of these cells. Two- microelectrode experiments have revealed small differences in the electrotonic potentials recorded simultaneously at two different sites within a single cell. The equations for a linear, short cable were used to calculate the electrical constants of relaxed, single atrial cells: lambda = 921.3 +/- 29.5 micrometers; Ri = 118.1 +/- 24.5 omega cm; Rm = 7.9 +/- 1.2 x 10(3) omega cm2; Cm = 2.2 +/- 0.3 mu Fcm-2. These results and the atrial cell morphology suggest that this preparation may be particularly suitable for voltage-clamp studies. PMID:6973007

1981-01-01

295

Mathematical models of electrical activity of the pancreatic ?-cell: a physiological review.  

PubMed

Mathematical modeling of the electrical activity of the pancreatic ?-cell has been extremely important for understanding the cellular mechanisms involved in glucose-stimulated insulin secretion. Several models have been proposed over the last 30 y, growing in complexity as experimental evidence of the cellular mechanisms involved has become available. Almost all the models have been developed based on experimental data from rodents. However, given the many important differences between species, models of human ?-cells have recently been developed. This review summarizes how modeling of ?-cells has evolved, highlighting the proposed physiological mechanisms underlying ?-cell electrical activity. PMID:25322829

Félix-Martínez, Gerardo J; Godínez-Fernández, J Rafael

2014-01-01

296

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

PubMed Central

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

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

2014-01-01

297

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

PubMed

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

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

2014-09-01

298

Active RF Pulse Compression Using Electrically Controlled Semiconductor Switches  

SciTech Connect

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

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

2007-03-21

299

Observations of the bursting pulsar and magnetars  

NASA Astrophysics Data System (ADS)

Following the discovery that some (and possibly all) gamma-ray bursts (GRBs) come from cosmological distances, it is now apparent that active Galactic sources of high- energy (>25 keV) bursts are rare. The rarity of these sources warrants a detailed study of their observed properties in order to better understand their nature. Observations of two different types of magnetized neutron stars which produce super-Eddington bursts are presented in this dissertation. The Bursting Pulsar (GRO J1744-28) is a transient low- mass X-ray binary (LMXB) near the Galactic center that emits both Type II bursts and periodic pulsations. It is unique in that it is the only known binary to exhibit this behavior. GRO J1744-28 has gone into outburst twice since its discovery and we show the second outburst is nearly identical to the first with the exception of a decrease in intensity by a factor ~1.7 of both the burst and persistent emission. During the bursts of the first outburst, the pulsations are observed to lag behind their expected arrival times based upon the persistent emission pulsar ephemeris. The magnitude of the pulse time lags during and after bursts are quantified with greater precision than before for a large subset of events from the first and second outbursts. The pulse time delay during bursts of the first outburst is found to be correlated with the peak intensity of the bursts. Soft gamma repeaters (SGIRs) are transient sources of brief, intense hard X-rays and low-energy ?-rays, very likely neutron stars with superstrong magnetic fields of order 1014-1015 G, i.e., magnetars. This dissertation presents the discovery of one of the four known SGRs, 1627-41. We have discovered the probable persistent X-ray counterpart to this SGR whose characteristics are consistent with the other SGR counterparts. Observations of the persistent X-ray emission from SGR 1900+14 show that the spectrum is best fit with a two-component model (blackbody + power law) during quiescence. This two-component model is a common trait of anomalous X-ray pulsars, a group of isolated X- ray sources (i.e., no companion) that also show strong evidence for a magnetar origin. The persistent flux is found to increase during a burst active interval for this source, and we find this increase lies exclusively in the non-thermal component of the spectrum. Next, we study the spin history of SGR 1900+14 over 2.5 yrs and find significant deviations from a constant spin down both during quiescence and a burst active interval. We find circumstantial evidence for a discrete spin-down event, i.e., a `braking' glitch, possibly associated with a giant flare recorded on 27 August 1998. Finally, we report the detection of two unusually hard bursts from SGR 1900+14. These events are distinctly different from typical bursts both temporally and spectrally. In fact, aside from their spectral evolution, they more closely resemble GRBs.

Woods, Peter Matthew

2000-10-01

300

The Role of Cellular Coupling in the Spontaneous Generation of Electrical Activity in Uterine Tissue  

PubMed Central

The spontaneous emergence of contraction-inducing electrical activity in the uterus at the beginning of labor remains poorly understood, partly due to the seemingly contradictory observation that isolated uterine cells are not spontaneously active. It is known, however, that the expression of gap junctions increases dramatically in the approach to parturition, by more than one order of magnitude, which results in a significant increase in inter-cellular electrical coupling. In this paper, we build upon previous studies of the activity of electrically excitable smooth muscle cells (myocytes) and investigate the mechanism through which the coupling of these cells to electrically passive cells results in the generation of spontaneous activity in the uterus. Using a recently developed, realistic model of uterine muscle cell dynamics, we investigate a system consisting of a myocyte coupled to passive cells. We then extend our analysis to a simple two-dimensional lattice model of the tissue, with each myocyte being coupled to its neighbors, as well as to a random number of passive cells. We observe that different dynamical regimes can be observed over a range of gap junction conductances: at low coupling strength, corresponding to values measured long before delivery, the activity is confined to cell clusters, while the activity for high coupling, compatible with values measured shortly before delivery, may spread across the entire tissue. Additionally, we find that the system supports the spontaneous generation of spiral wave activity. Our results are both qualitatively and quantitatively consistent with observations from in vitro experiments. In particular, we demonstrate that the increase in inter-cellular electrical coupling observed experimentally strongly facilitates the appearance of spontaneous action potentials that may eventually lead to parturition. PMID:25793276

Xu, Jinshan; Menon, Shakti N.; Singh, Rajeev; Garnier, Nicolas B.; Sinha, Sitabhra; Pumir, Alain

2015-01-01

301

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

PubMed

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

Newman, Johanna

2013-12-01

302

A novel application of pulsed electric field (PEF) processing for improving glutathione (GSH) antioxidant activity.  

PubMed

Glutathione (GSH) was treated by pulsed electric field (PEF) processing to investigate its effect on antioxidant activity. The antioxidant activity of GSH was evaluated using 2,2-diphenyl-1-picrylhydrazy (DPPH) radical inhibition. A Box-Behnken design (BBD) with three independent variables, which were concentration, electric field intensity and pulse frequency was used to establish the regression equation of second-order response surface. Optimal conditions were as follows: GSH concentration 8.86mg/mL, electric field intensity 9.74kV/cm and pulse frequency 2549.08Hz. The DPPH radical inhibition increased from 81.83% to 97.40%. Near-infrared spectroscopy (NIR) and mid-infrared spectroscopy (MIR) were used to analyse the change of structure and functional groups of GSH. PMID:24837963

Wang, Jia; Wang, Ke; Wang, Ying; Lin, Songyi; Zhao, Ping; Jones, Gregory

2014-10-15

303

Simultaneous Manipulation of Electric and Thermal Fields via Combination of Passive and Active Schemes  

E-print Network

Increasing attention has been focused on the invisibility cloak due to its novel concept for manipulation of physical field. However, it is usually realized by single scheme (namely passive or active scheme) and limited in a single field. Here, we proposed a general method to achieve simultaneous manipulation of multi-physics field via combination of passive and active schemes. Experimentally, this method was demonstrated by simultaneous manipulation of electric field and thermal field. Firstly, a device was designed to simultaneously behave as electric and thermal invisibility cloak. Secondly, another device was demonstrated to simultaneously behave as electric invisibility cloak and thermal concentrator. The experimental results agree well with the simulated ones, thus confirming the feasibility of our method. Our method can also be extended to the other multi-physics fields, which would create much more freedom to design of new system and might enable new potential application in broad areas.

Lan, Chuwen; Zhou, Ji

2015-01-01

304

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

PubMed

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

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

2014-12-19

305

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

NSDL National Science Digital Library

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

306

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

E-print Network

162 Electrical and Computer Engineering 163 · Courses and projects that actively involve them · A broad education outside of engineering and science that emphasizes the role of electrical and computer of technology Graduate and undergraduate programs in electrical and computer engineering offer concentrations

Richards-Kortum, Rebecca

307

Hybrid and plug-in hybrid electric vehicle performance testing by the US Department of Energy Advanced Vehicle Testing Activity  

Microsoft Academic Search

The Advanced Vehicle Testing Activity (AVTA), part of the U.S. Department of Energy's FreedomCAR and Vehicle Technologies Program, has conducted testing of advanced technology vehicles since August 1995 in support of the AVTA goal to provide benchmark data for technology modeling, and vehicle development programs. The AVTA has tested full size electric vehicles, urban electric vehicles, neighborhood electric vehicles, and

Donald Karner; James Francfort

2007-01-01

308

Real-time electrical impedance detection of cellular activities of oral cancer cells  

Microsoft Academic Search

In this study, the electric cell-substrate impedance sensing (ECIS) system was used to study the cellular activities of oral squamous cell carcinoma (OSCC) cells in a real-time and label-free manner. Various cellular activities, including cell adhesion, spreading, proliferation, and drug-induced apoptosis and inhibition of apoptosis, were monitored. A linear relationship was found between the impedance-based cell index and the cell

L. Renea Arias; Carla A. Perry; Liju Yang

2010-01-01

309

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

SciTech Connect

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

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

1993-12-10

310

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

EPA Science Inventory

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

311

Distributed Measurement Unit for Closed-Loop Functional Electrical Stimulation: Prototype for Muscular Activity Detection  

E-print Network

centralized Functional Electrical Stimulation (FES) architecture limitations is to distribute elec- tronicsMyoGramm (EMG) activity reading. The paper exposes the embedded digital architecture as well as results of EMG electronics and software close to the sensors / electrodes. It induces a network architecture and distributed

Paris-Sud XI, Université de

312

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

NASA Technical Reports Server (NTRS)

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

Cubley, H. D.

1972-01-01

313

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

PubMed

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

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

2015-01-01

314

Relationship between neural activation and electric field distribution during deep brain stimulation.  

PubMed

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

Åström, Mattias; Diczfalusy, Elin; Martens, Hubert; Wårdell, Karin

2015-02-01

315

Ultrashort pulse electroporation: applications of high pulsed electric fields to induced caspase activation of human lymphocytes  

Microsoft Academic Search

Presents evidence for apoptosis, or programmed cell death, and up-regulation of a subset of important genes induced by intense electric fields of short duration (10's nsec). The fields are observed to perturb mitochondrial membranes and the compartmentalized intracellular environment of Jurkat T lymphocytes, and within hours caspase activation occurs. Intense, but low energy, fields can penetrate a biological cell and

Martin Gundersen; P. T. Vernier; L. Marcu; Aimin Li; Xhumei Zhu; A. Z. Gallam; T. Katsouleas; C. Young; M. Behrend; C. M. Craft

2002-01-01

316

Research activities Effect of an External Electric Field on Grain Boundary Evolution in  

E-print Network

of Nano-Ceramic Sintering PI: Dr. Shmuel Hayun, Department of Materials Engineering. ConsolidationResearch activities Effect of an External Electric Field on Grain Boundary Evolution in the Course-vapor interfacial energy to the solid-solid interfacial (i.e., grain boundary) energy of the material. We propose

Vardi, Amichay

317

Suppression and control of epileptiform activity by electrical stimulation: a review  

Microsoft Academic Search

Epilepsy is a devastating disease affecting ~1% of the world's population. Although drug therapy is effective in many patients, 25% are not responsive to anticonvulsants. In addition, up to 50% of those receiving regular mediation suffer major side effects. Surgical resection is another treatment also associated with serious complications. An alternative method to control seizure activity is electrical stimulation. Several

DOMINIQUE M. DURAND; MAROM BIKSON

2001-01-01

318

ter, electrical conductivity, activity of sac-charase, amount of proline and sugar spectra.  

E-print Network

ter, electrical conductivity, activity of sac- charase, amount of proline and sugar spectra. A short time after intake of sugar solu- tions there are changes of sugar spectra, which can be explained by the effect of the enzyme invertase/saccharase. But, in addi- tion, there are sugar types in the honey sac

Boyer, Edmond

319

Intracellular pH changes induced by calcium influx during electrical activity in molluscan neurons  

Microsoft Academic Search

A B S W R A C T Simultaneous measurements of electrical activity and light absorb- ance have been made on nerve cell bodies from Archidoris montoyensis injected with indicator dyes. pH indicators, phenol red and bromocresol purple, and arsenazo III, which under normal conditions is primarily a calcium indicator, have been employed. Voltage clamp pulses which induced calcium influx

Z. Ahmed

1980-01-01

320

Ajmaline-Induced Changes in Mechanical and Electrical Activity of Vascular Smooth Muscle  

Microsoft Academic Search

The effects of ajmaline on vascular smooth muscle were studied using helical aortic strips and portal veins of male rats. This report is based on the results of 104 mechanical experiments. In 30 additional experiments electrical activity was recorded simultaneously at different points of the preparation using extracellular methods (liquid paraffine or pressure electrodes technique). Ajmaline induces relaxation of aortic

Giancarlo Biamino; Hans-Joachim Wessel; Jutta Nöring

1975-01-01

321

Agriculture--Agricultural Mechanics, Electric Motors. Kit No. 56. Instructor's Manual [and] Student Learning Activity Guide.  

ERIC Educational Resources Information Center

An instructor's manual and student activity guide on agricultural mechanics (electric motors) are provided in this set of prevocational education materials which focuses on the vocational area of agriculture. (This set of materials is one of ninety-two prevocational education sets arranged around a cluster of seven vocational offerings:…

Bomar, William

322

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

ERIC Educational Resources Information Center

Individual variation in the experience and expression of pleasure may relate to differential patterns of lateral frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral frontal cortex in positive emotion, but the excellent time resolution of these measures has not been used to capture…

Light, Sharee N.; Coan, James A.; Frye, Corrina; Goldsmith, H. Hill; Davidson, Richard J.

2009-01-01

323

The incidence of pulmonary embolism in unexplained sudden cardiac arrest with pulseless electrical activity?  

Microsoft Academic Search

PURPOSE: The cause of many cases of sudden cardiac arrest from pulseless electrical activity is unknown. We hypothesized that pulmonary embolism was responsible for a substantial proportion of these cases and used transesophageal echocardiography to identify pulmonary embolism among patients with sudden cardiac arrest.SUBJECTS AND METHODS: We performed a prospective study at a tertiary care, university-operated county hospital, with a

Keith A Comess; Frances A DeRook; Margaret L Russell; Terese A Tognazzi-Evans; Kirk W Beach

2000-01-01

324

Effects of Hypoxic Hypoxia on the Spontaneous Electrical Activity of the Human Brain  

Microsoft Academic Search

An attempt was made to reveal the mechanisms of adaptation of the human brain to fractional hypoxic load. With this in mind, the dynamics of spontaneous EEG was studied in a 10% hypoxic test performed before and after a course of normobaric hypoxic training. It was shown that under acute hypoxic conditions, the electrical activity of the brain is switched

M. V. Aleksandrov; A. O. Ivanov; N. I. Kosenkov; M. A. Lutsyk

2001-01-01

325

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

ERIC Educational Resources Information Center

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

Bell, Martha Ann; Fox, Nathan A.

1992-01-01

326

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

E-print Network

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

327

Bistability with hysteresis in the activity of vasopressin cells.  

PubMed

Magnocellular vasopressin neurones generate distinctive 'phasic' patterns of electrical activity during which periods of spiking activity (bursts) alternate with periods of no spikes or occasional spikes. The mechanisms of burst termination in vivo are still not clearly understood. We recorded from single phasic vasopressin cells in vivo and here we show that burst terminations in some phasic cells is preceded by transient increases in activity, consistent with bursts ending as a result of activity-dependent inhibition. We show that extrinsically imposed increases in activity, evoked by brief stimulation of the organum vasculosum of the lamina terminalis, can either trigger bursts if given when a cell is silent, or stop bursts if given when a cell is active. Thus, the magnocellular vasopressin system is a population of independent bistable oscillators. The population as a whole is insensitive to transient changes in input level, whether these are excitatory or inhibitory. The vasopressin cell population thus acts like a 'low-pass filter'; although brief large changes in input rate have little overall effect, the population responds very effectively to small, sustained changes in input rate by evolving a pattern of discharge activity that efficiently maintains secretion. We note that these filtering characteristics are the opposite of the filtering characteristics that are typically associated with neurones. PMID:17214871

Sabatier, N; Leng, G

2007-02-01

328

Gamma-ray bursts: Restarting the Engine  

E-print Network

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

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

2005-08-04

329

Gamma-Ray Burst Early Afterglows  

E-print Network

The successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore the unknown physical composition of GRB jets, the link between the prompt gamma-ray emission and the afterglow emission, the GRB central engine activity, as well as the immediate GRB environment. Here I review some of the recent theoretical efforts to address these problems and describe how the latest Swift data give answers to these outstanding questions.

Bing Zhang

2005-09-19

330

Large plasmaspheric electric fields at L approximately 2 measured by the S3-3 satellite during strong geomagnetic activity  

NASA Technical Reports Server (NTRS)

Large plasmaspheric electric fields at L is approximately 2 measured by the S3-3 satellite during strong geomagnetic activity are reported. Since these measurements have amplitudes comparable to those of the local corotation electric field, during such events the plasmasphere is expected to get strongly altered event at such low L-values. Furthermore, those measurements could contribute to the understanding of the physics of the convection/electric field penetration to the low latitude plasmaphere as well as the disturbed dynamo, during strong geomagnetic activity. For this purpose, critical parameters related to geomagnetic activity are also presented for the reported electric field events.

Gonzalez, W. D.; Pinto, O., Jr.; Mendes, O., Jr.; Mozer, F. S.

1986-01-01

331

Vortex shedding as a precursor of turbulent electrical activity in cardiac muscle.  

PubMed Central

In cardiac tissue, during partial blockade of the membrane sodium channels, or at high frequencies of excitation, inexcitable obstacles with sharp edges may destabilize the propagation of electrical excitation waves, causing the formation of self-sustained vortices and turbulent cardiac electrical activity. The formation of such vortices, which visually resembles vortex shedding in hydrodynamic turbulent flows, was observed in sheep epicardial tissue using voltage-sensitive dyes in combination with video-imaging techniques. Vortex shedding is a potential mechanism leading to the spontaneous initiation of uncontrolled high-frequency excitation of the heart. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 PMID:8785270

Cabo, C; Pertsov, A M; Davidenko, J M; Baxter, W T; Gray, R A; Jalife, J

1996-01-01

332

Study of electrically active lattice defects in Cf-252 and proton irradiated silicon diodes  

NASA Astrophysics Data System (ADS)

The results of a comparative study of electrically active damage introduced in silicon diodes by irradiation with the fission products of a Cf-252 source and with high-energy protons are presented. The influence of substrate doping, oxygen content, and thermal pretreatments on the damage formation is investigated using electrical evaluation of the diode characteristics correlated with deep level transient spectroscopy investigations. Both types of irradiation create the same dominant defect types but with different efficiencies and relative densities. A radiation hardening effect by interstitial oxygen is observed. Both the leakage current and the deep level density show a linear dependence on the irradiating particle fluence.

Trauwaert, M.-A.; Vanhellemont, J.; Simoen, E.; Claeys, C.; Johlander, B.; Adams, L.; Clauws, P.

1992-12-01

333

Changes of electric cochlea activity of guinea pigs during argon laser stapedotomy  

NASA Astrophysics Data System (ADS)

Small electric signals appear on surface of a cochlea when the ear is stimulated by sound. A level of the signals can be measured of the electric activity of cochlea. The aim of the experiments was recording of changes of the cochlear potentials during argon laser stapedotomy. On the base of the recording the limits of the safe argon laser stapedotomy have been preliminary estimated. The series of argon laser pulses lasting 0.2-0.5 s and of 16 s interval between the pulses are preferable for safety of argon laser stapedotomy. The pulse peak power should be below 1 W.

Michalski, Wojciech; Pres, Krzysztof; Dziewiszek, Wojciech; Pospiech, Lucyna

2000-11-01

334

Efficiency Crisis of Swift Gamma-Ray Bursts with Shallow X-ray Afterglows: Prior Activity or Time-Dependent Microphysics?  

E-print Network

Most X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase t^{-1/2} in the first thousands of seconds. We discuss that the shallow decay requires an unreasonably high gamma-ray efficiency, > 75-90%, within current models, which is difficult to be produced by internal shocks. Such a crisis may be avoided if a weak relativistic explosion occurs ~ 10^3-10^6 s prior to the main burst or if the energy fraction that goes into electrons increases during the shallow decay, \\epsilon_e ~ t^{1/2}. The former model predicts a very long precursor while either model would prefer dim optical flashes from the reverse shock as recently reported.

Ioka, K; Yamazaki, R; Nakamura, T; Ioka, Kunihito; Toma, Kenji; Yamazaki, Ryo; Nakamura, Takashi

2005-01-01

335

Gamma Ray Bursts from Binary Black Holes  

NASA Astrophysics Data System (ADS)

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

Janiuk, A.; Bejger, M.; Charzynski, S.

2014-07-01

336

Activation of the respiratory burst in murine phagocytes by certain guanine ribonucleosides modified at the 7 and 8 positions: possible involvement of a pertussis toxin-sensitive G-protein.  

PubMed

The capacity of certain guanine ribonucleosides (modified at the 7 and/or 8 positions) to enhance the respiratory burst of murine peritoneal phagocytes was evaluated. The results show that 8-mercaptoguanosine, 8-bromoguanosine, 7-methyl-8-oxoguanosine and 7-thia-8-oxoguanosine, when injected intraperitoneally into mice, induced peritoneal phagocytes to generate reactive oxygen species as early as 1 h after injection. In vivo administration of the nucleosides induced higher levels of phagocyte activation than in vitro treatment with the same nucleosides. However, the addition of interferon alpha/beta in vitro significantly increased the magnitude of phagocyte activation by the nucleosides, suggesting an important role for cytokines/lymphokines in the nucleoside-induced phagocyte activation in vivo. Furthermore, pre-treatment of phagocytes in vitro with Bordetella pertussis toxin, before treatment with the guanosines, inhibited their capacity to induce the respiratory burst. These observations establish these low-molecular-weight compounds as interesting probes for the study of stimulus-response coupling in phagocytes. PMID:2106487

Ojo-Amaize, E A; Rubalcava, B; Avery, T L; Cottam, H B; Matsumoto, S S; Jolley, W B; Robins, R K

1990-01-01

337

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

PubMed

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

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

2015-02-01

338

System and method for coproduction of activated carbon and steam/electricity  

DOEpatents

A system and method for producing activated carbon comprising carbonizing a solid carbonaceous material in a carbonization zone of an activated carbon production apparatus (ACPA) to yield a carbonized product and carbonization product gases, the carbonization zone comprising carbonaceous material inlet, char outlet and carbonization gas outlet; activating the carbonized product via activation with steam in an activation zone of the ACPA to yield activated carbon and activation product gases, the activation zone comprising activated carbon outlet, activation gas outlet, and activation steam inlet; and utilizing process gas comprising at least a portion of the carbonization product gases or a combustion product thereof; at least a portion of the activation product gases or a combustion product thereof; or a combination thereof in a solid fuel boiler system that burns a solid fuel boiler feed with air to produce boiler-produced steam and flue gas, the boiler upstream of an air heater within a steam/electricity generation plant, said boiler comprising a combustion zone, a boiler-produced steam outlet and at least one flue gas outlet.

Srinivasachar, Srivats (Sturbridge, MA); Benson, Steven (Grand Forks, ND); Crocker, Charlene (Newfolden, MN); Mackenzie, Jill (Carmel, IN)

2011-07-19

339

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

SciTech Connect

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

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

1997-12-01

340

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

341

Observing a Burst with Sunglasses  

NASA Astrophysics Data System (ADS)

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

2003-11-01

342

Initial Observations of Lightning and Electrical Activity from the 2008 Chaiten Eruption.  

NASA Astrophysics Data System (ADS)

Spectacular photos of lightning during Chaiten's original paroxysm inspired us to install a local ground-based electrical monitoring array. Geography was especially well-suited to lightning detection from the island of Chiloe, where four stations were safely situated 70-110 km from the erupting volcano. All sites possessed line-of-sight view to the erupting vent and used precise signal arrival times to locate sources. At these distances we map electrical discharge with a horizontal resolution of tens to hundreds of meters and a vertical resolution of several kilometers. It provides a picture of electrical discharges from the charged particles (e.g., ash and volatiles) produced during the eruption. Our array is capable of providing continuous monitoring of electrical activity, and will be analyzed in conjunction with other monitoring tools (i.e., seismic and infrasound) to develop remote electrical activity monitoring as a proxy tool for monitoring eruption intensity. In addition to a time lapse camera, seismic, infrasound, and an electric field change detector were deployed and logged to IRIS PASSCAL dataloggers at our closest array site. Analysis of data from May 24 to July 3 shows discharges close to the volcanic vent lasting from a few to 20 ms. 3-D inversions were possible for about 55 hours of data and show horizontal lightning channels up to 8 km in length occasionally with branches. These flashes are much shorter then typical thunderstorm lightning, but form at a similar velocity, about 105 m/s. During these measurements the plume heights were about 4 km.

Thomas, R. J.; Rison, W.; Johnson, J. B.; Behnke, S. A.; Krehbiel, P. R.; McNutt, S. R.

2008-12-01

343

Dopamine affects the change of pain-related electrical activity induced by morphine dependence.  

PubMed

Morphine is among the most effective analgesics. However, many evidences suggest that, besides the well-know analgesic activity, repeated opioids treatment can induce some side effects such as dependence, hyperalgesia and tolerance. The mechanism of noxious information transmission in the central nervous system after dependence is not clear. An important neurotransmitter, dopamine (DA) participates not only in the process of opioid dependence but also in pain modulation in the central nervous system. In the present study we observed changes of electrical activities of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the caudate nucleus (Cd) following the development of morphine dependence. We also observed the role of DA on these changes. Our results revealed that both the latency of PEN discharges and the inhibitory duration of PIN discharges decreased, and the net increased values of PEN and PIN discharges increased in the Cd of morphine dependent rats. Those demonstrated that electrical activities of both PENs and PINs increased in morphine dependent rats. DA inhibited the electrical activities of PENs and enhanced those of PINs in morphine dependent rats. PMID:22240902

Zhang, Ying; Zhang, Fengmin; Yang, Chunxiao; Jin, Hongbo; Yang, Yongbin; Xu, Manying

2012-05-01

344

Light scattering and birefringence changes during activity in the electric organ of Electrophorus electricus  

PubMed Central

1. In an attempt to obtain information about structural changes related to electrical activity in Electrophorus electroplates, we have determined the size and time course of the changes in light scattering and in bire-fringence that occur during and after the discharge of the electric organ. 2. The changes in light intensity detected with a photomultiplier were never greater than 0·2% for a single discharge, and were often much smaller than this, but records with an acceptable ratio of signal to noise could be obtained by signal-averaging techniques. 3. A single stimulus led to a decrease, then an increase, and finally another decrease in the light scattered by slices of the main electric organ. These three phases were designated E1, E2 and E3. 4. E1 started at the beginning of the action potential, and its peak was reached at the same time as the completion of repolarization, even when the repolarization was delayed by cooling or hastened by drawing larger currents from the tissue. 5. E2 was proportional to the integral of the current flowing through the slice of electric organ, and may arise from the swelling and shrinking of the tubules that stud the faces of the electroplates. It developed within a millisecond or two of the start of an applied current, and lasted for about 100 msec. 6. E3 was a variable decrease in scattering that lasted for some seconds. 7. A stimulus also led to a transient increase in the birefringence of the electric organ. The optical change followed the change in electrical potential across the innervated faces of the electroplates with a delay of somewhat under 50 ?sec. 8. This voltage-dependent change in birefringence may arise from a Kerr effect (electric birefringence) in the membrane or from compression of the membrane. PMID:5796473

Cohen, L. B.; Hille, B.; Keynes, R. D.

1969-01-01

345

An optical burst reordering model for a time-based burst assembly scheme  

Microsoft Academic Search

In optical burst switching networks, contention resolution schemes as well as contention avoidance schemes reduce the burst loss probability. These schemes delay the burst delivery and may change the burst arrival sequence. In this paper we present an analytic burst reordering model and derive analytically the impact of a time-based burst assembly scheme on the burst reordering pattern. Our results

Sebastian Gunreben

2008-01-01

346

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

347

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

PubMed Central

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

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

2014-01-01

348

A miniature voltmeter for monitoring small amplitude electrical activity in the hypothermic arrested myocardium.  

PubMed

A measurement system which is capable of detecting microfibrillation in the hypothermic, arrested heart has been developed. It is shown that this system can reliably measure microfibrillation signals as low as 10 microV in amplitude. Using this system, it has been shown that even after the heart has been rendered visibly arrested using cold potassium, it may still be producing a low level of electrical activity. It has also been shown that the presence of this microfibrillation during the period of the cold potassium administration and visible arrest, is very highly correlated with the decrease in high energy phosphates (ATP), mitochondrial injury, and a decreased cardiac function post-operatively. Using the information obtained from this first measurement system, a miniature, battery powered voltmeter has been designed and fabricated. This voltmeter has been tested using the initial measurement system as reference and produces the same information concerning the small signal electrical activity (i.e.: same waveform and RMS value). Because this voltmeter is battery powered and is, therefore, completely isolated from all electrical equipment in the operating theatre, it can be used to monitor the presence, or absence, of microfibrillation in the human heart. Of greatest importance, however, is the fact that the voltmeter can serve as a monitoring device which will indicate when the potassium should be administered in order to render the heart both mechanically and electrically arrested. PMID:2138695

Marble, A E; Landymore, R W; Church, D W

1990-05-01

349

Microstructural and electrical changes in nickel manganite powder induced by mechanical activation  

SciTech Connect

Highlights: {yields} The influence of mechanical activation on microstructure evolution in the nickel manganite powder was investigated as well as electrical properties of the sintered samples. {yields} Structural refinement obtained by Topas-Academic software based on Rietveld analysis showed that the milling process remarkably changed the powder morphology and microstructure. {yields} SEM studies of sintered samples also revealed the strong influence of milling time on ceramics density (increases with milling time). {yields} The electrical properties of ceramic samples are clearly conditioned by terms of synthesis, in our case the time of mechanical activation. {yields} The highest density and higher values of dielectric constant were achieved at the sample activated for 45 min. -- Abstract: Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn{sub 2}O{sub 4} phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 {sup o}C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 {sup o}C, 50 {sup o}C and 80 {sup o}C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions.

Savic, S.M., E-mail: slavicas@cms.bg.ac.rs [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia); Mancic, L. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia)] [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Vojisavljevic, K. [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia)] [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia); Stojanovic, G. [Faculty of Technical Sciences University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad (Serbia)] [Faculty of Technical Sciences University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad (Serbia); Brankovic, Z.; Aleksic, O.S.; Brankovic, G. [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia)] [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia)

2011-07-15

350

Computationally efficient simulation of electrical activity at cell membranes interacting with self-generated and externally imposed electric fields  

NASA Astrophysics Data System (ADS)

Objective. We present a computational method that implements a reduced set of Maxwell's equations to allow simulation of cells under realistic conditions: sub-micron cell morphology, a conductive non-homogeneous space and various ion channel properties and distributions. Approach. While a reduced set of Maxwell's equations can be used to couple membrane currents to extra- and intracellular potentials, this approach is rarely taken, most likely because adequate computational tools are missing. By using these equations, and introducing an implicit solver, numerical stability is attained even with large time steps. The time steps are limited only by the time development of the membrane potentials. Main results. This method allows simulation times of tens of minutes instead of weeks, even for complex problems. The extracellular fields are accurately represented, including secondary fields, which originate at inhomogeneities of the extracellular space and can reach several millivolts. We present a set of instructive examples that show how this method can be used to obtain reference solutions for problems, which might not be accurately captured by the traditional approaches. This includes the simulation of realistic magnitudes of extracellular action potential signals in restricted extracellular space. Significance. The electric activity of neurons creates extracellular potentials. Recent findings show that these endogenous fields act back onto the neurons, contributing to the synchronization of population activity. The influence of endogenous fields is also relevant for understanding therapeutic approaches such as transcranial direct current, transcranial magnetic and deep brain stimulation. The mutual interaction between fields and membrane currents is not captured by today's concepts of cellular electrophysiology, including the commonly used activation function, as those concepts are based on isolated membranes in an infinite, isopotential extracellular space. The presented tool makes simulations with detailed morphology and implicit interactions of currents and fields available to the electrophysiology community.

Agudelo-Toro, Andres; Neef, Andreas

2013-04-01

351

Empathy is associated with dynamic change in prefrontal brain electrical activity during positive emotion in children  

PubMed Central

Empathy is the combined ability to interpret the emotional states of others and experience resultant, related emotions. The relation between prefrontal electroencephalographic asymmetry and emotion in infants and children is well known. The relationship between positive emotion (assessed via parent-report), empathy (measured via observation) and second-by-second brain electrical activity (recorded during a pleasurable task) was investigated using a sample of 128 six to ten year olds. Contentment predicted increasing left-sided frontopolar activation (p<.05). Empathic concern and one form of positive empathy predicted increasing right-sided frontopolar activation (ps<.05). A second form of positive empathy predicted increasing left-sided dorsolateral activation (p<.05). This suggests that positive emotion and (negative and positive) empathy predict changes in prefrontal activity in children during a pleasurable task. PMID:19630903

Light, Sharee N.; Coan, James A.; Zahn-Waxler, Carolyn; Frye, Corrina; Goldsmith, H. Hill; Davidson, Richard J.

2009-01-01

352

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

353

Gamma Ray Bursts  

E-print Network

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

Peter Mészáros

2012-04-12

354

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

355

Inversion of Sonic hedgehog action on its canonical pathway by electrical activity  

PubMed Central

Sonic hedgehog (Shh) is a morphogenic protein that operates through the Gli transcription factor-dependent canonical pathway to orchestrate normal development of many tissues. Because aberrant levels of Gli activity lead to a wide spectrum of diseases ranging from neurodevelopmental defects to cancer, understanding the regulatory mechanisms of Shh canonical pathway is paramount. During early stages of spinal cord development, Shh specifies neural progenitors through the canonical signaling. Despite persistence of Shh as spinal cord development progresses, Gli activity is switched off by unknown mechanisms. In this study we find that Shh inverts its action on Gli during development. Strikingly, Shh decreases Gli signaling in the embryonic spinal cord by an electrical activity- and cAMP-dependent protein kinase-mediated pathway. The inhibition of Gli activity by Shh operates at multiple levels. Shh promotes cytosolic over nuclear localization of Gli2, induces Gli2 and Gli3 processing into repressor forms, and activates cAMP-responsive element binding protein that in turn represses gli1 transcription. The regulatory mechanisms identified in this study likely operate with different spatiotemporal resolution and ensure effective down-regulation of the canonical Shh signaling as spinal cord development progresses. The developmentally regulated intercalation of electrical activity in the Shh pathway may represent a paradigm for switching from canonical to noncanonical roles of developmental cues during neuronal differentiation and maturation. PMID:25829542

Belgacem, Yesser H.; Borodinsky, Laura N.

2015-01-01

356

Periodic bursts of Jovian non-Io decametric radio emission  

PubMed Central

During the years 2000–2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ?1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ?25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

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

2013-01-01

357

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

358

Periodic Bursts of Jovian Non-Io Decametric Radio Emission  

NASA Technical Reports Server (NTRS)

During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have Recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period approx. = 1:5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300 deg. and 60 deg. (via 360 deg.). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every approx. 25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

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

2013-01-01

359

Electrical activation and spin coherence of ultra low doseantimony implants in silicon  

SciTech Connect

We implanted ultra low doses (0.2 to 2 x 10{sup 11} cm{sup -2}) of Sb ions into isotopically enriched {sup 28}Si, and probed electrical activation and electron spin relaxation after rapid thermal annealing. Strong segregation of dopants towards both Si{sub 3}N{sub 4} and SiO{sub 2} interfaces limits electrical activation. Pulsed Electron Spin Resonance shows that spin echo decay is sensitive to the dopant profiles, and the interface quality. A spin decoherence time, T{sub 2}, of 1.5 ms is found for profiles peaking 25 nm below a Si/SiO{sub 2} interface, increasing to 2.1 ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins.

Schenkel, T.; Tyryshkin, A.M.; de Sousa, R.; Whaley, K.B.; Bokor,J.; Liddle, J.A.; Persaud, A.; Shangkuan, J.; Chakarov, I.; Lyon, S.A.

2005-07-13

360

LASERS, ACTIVE MEDIA: Emission spectrum of an electric-discharge ClF laser  

NASA Astrophysics Data System (ADS)

Experiments revealed a complex structure of the emission spectrum of an electric-discharge ClF laser, corresponding to the D'—A' transitions with a maximum near 285 nm. The vibrational bands in the emission spectrum overlapped at the base in the range 282-286 nm because of a high pressure in the gaseous active medium. Theoretical calculations were made and an interpretation was provided of the vibrational structure of the emission spectrum of the ClF molecules. The emission spectrum of the electric-discharge ClF laser was shown to consist of the 0-4, 0-5, 0-6, 1-6, 1-7, and 2-8 bands of the D'—A' transition. A total efficiency of 0.1% was achieved for the first time for the ClF laser and lasing was observed in a gaseous He — F2—BCl3 active medium.

Deryugin, A. A.; Kochetov, Igor'V.; Razhev, A. M.

1998-06-01

361

Dysaesthesiae induced by physiological and electrical activation of posterior column afferents after stroke.  

PubMed Central

Six of 48 stroke patients had functionally limiting dysaesthesiae induced by repetitive light touch, joint movement, or neuromuscular electrical stimulation (NMS). Only one of these six patients had a thalamic lesion. Quantitative sensory testing showed substantial impairment of pain and temperature sensation in all six patients, whereas light touch, vibration and position sense, and graphaesthesia were normal (three patients) or relatively spared (three patients). By contrast, none of 15 stroke patients in whom NMS did not evoke dysaesthesiae had clinical evidence of dissociated sensory loss. Conscious perception of joint movement and light touch is mediated mainly by the same population of large myelinated fibres activated preferentially by low intensity electrical stimulation. It is suggested that activation of these non-nociceptive, presumably dorsal column, afferents may contribute to dysaesthesiae in some patients with sensory loss after stroke. PMID:8089673

Triggs, W J; Beri?, A

1994-01-01

362

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

PubMed

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

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

2015-01-01

363

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

364

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

PubMed Central

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

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

2015-01-01

365

Thermodynamic and Statistical-Mechanical Measures for Characterization of the Burst and Spike Synchronizations of Bursting Neurons  

E-print Network

By varying the noise intensity, we investigate the population synchronization in an inhibitory population of bursting Hindmarsh-Rose neurons. Unlike spiking neurons, bursting neurons show firing patterns with two timescales: a fast spiking timescale and a slow bursting timescale that modulates the spiking activity. Through separation of the fast and slow timescales, we characterize the burst and spike synchronization transitions by using ``thermodynamic'' order parameters, and quantitatively measure the degree of the burst and spike synchronizations by employing ``statistical-mechanical'' measures. Population synchronization may be well visualized in the raster plot of neural spikes which can be obtained in experiments. Instantaneous population firing rate, $R(t)$, which is directly obtained from the raster plot of spikes, is a realistic population quantity showing collective behaviors with both the slow and fast timescales. Through frequency filtering, we separate $R(t)$ into $R_b(t)$ (the instantaneous popu...

Kim, Sang-Yoon

2014-01-01

366

Changes in spontaneous brain bioelectrical activity during transcranial electrical and electromagnetic stimulation  

Microsoft Academic Search

The systems responses of the brain to therapeutic transcranial electrical and electromagnetic stimulation were studied and\\u000a the neurophysiological criteria for assessing the efficacy of this treatment were identified using comparative clinical and\\u000a experimental studies with analysis of spontaneous bioelectrical activity, along with assessment of behavioral and clinical\\u000a measures. Study groups consisted of six patients with chronic post-traumatic unconscious states during

E. V. Sharova; A. V. Mel’nikov; M. R. Novikova; M. A. Kulikov; T. N. Grechenko; E. D. Shekhter; A. Yu. Zaslavskii

2007-01-01

367

Erbb2 Is Required for Cardiac Atrial Electrical Activity during Development  

PubMed Central

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

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

2014-01-01

368

Optical mapping study of blebbistatin-induced chaotic electrical activities in isolated rat atrium preparations  

Microsoft Academic Search

We have studied the spatiotemporal pattern of blebbistatin-induced anomalous electrical activities in isolated rat atrial\\u000a preparations using the optical mapping of excitation spread. Atrial preparations including the right or left auricle were\\u000a dissected from adult rat hearts. Each preparation was then stained with a fast merocyanine–rhodanine voltage-sensitive dye\\u000a (NK2761). Using a multi-element (16 × 16) photodiode array, we assessed the spread of

Natnicha Kanlop; Tetsuro Sakai

2010-01-01

369

Effects of prenatal protein malnutrition on the electrical cerebral activity during development.  

PubMed

Early protein restriction during the prenatal period has significant repercussions on the ontogeny and development of the central nervous system. The present study investigates whether early prenatal protein malnutrition could alter the electrical cerebral activity of the progeny. We used Sprague-Dawley female rats of 200 g randomly divided into three groups: a control group that received a diet with 25% of the protein content (lactalbumin), the experimental group, that received a diet with 6% of the protein content and the rehabilitated group that initially received a diet with 6% of the protein content, then switched to a diet with 25% of the protein content after the weaning period (P20D) up to 60 days of life (P60D). Reduction of the protein content from 25% to 6% of lactalbumin in the diet of pregnant rats produces impairment in the electrical cerebral activity in the progeny at P20D and at P60D. The power spectral analysis for each one of the electroencephalograms revealed that prenatal protein malnutrition in rats produced a significant reduction of the alpha (8-13 Hz) and the beta bands (13-30 Hz) and a significant increase of the theta (4-8 Hz), and delta bands (1-4 Hz), at two different stages of life (P20D and P60D). Similar results were obtained for the rehabilitated group. These results indicate that early malnutrition in life affects the ontogeny of the electrical cerebral activity. This insult probably disrupts the establishment of cortical neural circuits during the critical period of brain development. The rehabilitation period did not revert the impairment in the electrical cerebral activity produced by malnutrition. We used one-way ANOVA analysis, followed by Tukey test (*p<0.001). PMID:20654694

De Frías, V; Varela, O; Oropeza, J J; Bisiacchi, B; Alvarez, A

2010-10-01

370

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

Microsoft Academic Search

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

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

2007-01-01

371

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

E-print Network

, which started the deregulation process in the US power industry. Thus, competition in the downstream generation sector adversely affected the innovation behavior of electric equipment manufacturers. They identify two channels through which the effects... , customer-oriented product and organisational innovations. At the sector level, liberalisation can be a driver for the overall level of innovation activity as competition represents a significant challenge for incumbent utilities and potential entrants...

Jamasb, Tooraj; Pollitt, Michael G.

372

New solutions of the Zakharov's equation system for quantum plasmas in form of nonlinear bursts lattice  

SciTech Connect

New multiplicative solutions of the Zakharov's quantum system of equations using the separation of variables method are found. The found solutions are interpreted as spatial-periodical lattices of non-linear plasma bursts. It is shown that the bursts could be both symmetrical and asymmetrical by an electric field.

Dubinov, Alexander E.; Kitayev, Ilya N. [Russian Federal Nuclear Center-VNIIEF, Sarov, Nizhny Novgorod Region 607188 (Russian Federation)] [Russian Federal Nuclear Center-VNIIEF, Sarov, Nizhny Novgorod Region 607188 (Russian Federation)

2014-02-15

373

Modeling cancellation of periodic inputs with burst-STDP and feedback  

E-print Network

-like structure in wave-type electric fish. Our biologi- cally plausible mechanism is motivated by experimental-dependent learning rule, which in turn affects the feedback input and thus the burst rate. We show how the mean strength is also derived. Our results shed light on why bursts rather than single spikes can drive learning

Mejías, Jorge F.

374

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

PubMed Central

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

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

2013-01-01

375

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

376

Voltage Bursting Drops in Solids  

NASA Astrophysics Data System (ADS)

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

Wang, Qiming; Suo, Zhigang; Zhao, Xuanhe

2012-02-01

377

External modulators for TeraHertz Quantum Cascade Lasers based on electrically-driven active metamaterials  

NASA Astrophysics Data System (ADS)

We have designed, fabricated and measured electrically-driven active metamaterials which operate as external modulators for TeraHertz Quantum Cascade Lasers. The modulation is achieved by applying a voltage to the metamaterial layer which actively displaces carriers from the n-doped layer causing changes in damping and frequency location of the lowest metamaterial response. We demonstrate their operation at 2.4 and 2.8 TeraHertz and obtain a maximum modulation depth of ˜60% with a large degree of modulation linearity.

Peralta, X. G.; Brener, I.; Padilla, W. J.; Young, E. W.; Hoffman, A. J.; Cich, M. J.; Averitt, R. D.; Wanke, M. C.; Wright, J. B.; Chen, H.-T.; O'Hara, J. F.; Taylor, A. J.; Waldman, J.; Goodhue, W. D.; Li, J.; Reno, J.

2010-08-01

378

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

NASA Astrophysics Data System (ADS)

The authors demonstrate the direct, noninvasive and time resolved imaging of functional frog auricular fibers by ionic contrast terahertz (ICT) near field microscopy. This technique provides quantitative, time-dependent measurement of ionic flow during auricular muscle electrical activity, and opens the way of direct noninvasive imaging of cardiac activity under stimulation. ICT microscopy technique was associated with full three-dimensional simulation enabling to measure precisely the fiber sizes. This technique coupled to waveguide technology should provide the grounds to development of advanced in vivo ion flux measurement in mammalian hearts, allowing the prediction of heart attack from change in K+ fluxes.

Masson, Jean-Baptiste; Sauviat, Martin-Pierre; Gallot, Guilhem

2006-10-01

379

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

PubMed Central

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

Stasiuk, Maria; Janiszewska, Alicja; Kozubek, Arkadiusz

2014-01-01

380

The Double Firing Burst  

NASA Astrophysics Data System (ADS)

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

2008-09-01

381

Phase of the electrical activity rhythm in the SCN in vitro not influenced by preparation time.  

PubMed

The mammalian circadian clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus, drives daily rhythms in behavioral, physiological, and endocrine functions. The SCN has a genetic basis for rhythm generation and remains rhythmic when it is isolated and kept in constant conditions. This allows for an in vitro analysis of circadian attributes, which is a powerful approach in the study of SCN cellular mechanisms. For studying the phase of the SCN rhythm in vitro, it is important to assess whether preparation of the tissue itself introduces phase shifts. In the present study, we investigated whether preparation of hypothalamic brain slices affects the phase and waveform of the rhythm in electrical impulse frequency of the mouse SCN. Mice were kept under a 12:12 h light-dark cycle, and slices were prepared at six timepoints distributed over the 24 h cycle. We used the peak time and the time of the half-maximum levels in electrical activity as markers for circadian phase. The peak time in electrical activity was observed during the mid-subjective day, irrespective of the time of preparation, at a mean ZT of 5.18+/-0.20 h (n = 39). After preparation in red light at the end of the subjective night, the circadian phase appeared slightly advanced. When slices were prepared in the dark, using infrared illumination, the ANOVA showed no significant differences in peak times and time of half-maximum values between preparation times. The results affirm the value of the slice preparation for studying the phase of the SCN in vitro. We conclude that the phase and waveform of the electrical activity in the SCN in vitro is unaffected by the time of slice preparation but may be influenced by short light presentation when preparation is performed during the subjective night. PMID:19731107

vanderLeest, Henk Tjebbe; Vansteensel, Mariska J; Duindam, Hans; Michel, Stephan; Meijer, Johanna H

2009-08-01

382

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

383

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

NASA Technical Reports Server (NTRS)

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

Hann, Raiford E.

1991-01-01

384

Inspecting the microstructure of electrically active defects at the Ge/GeOx interface  

NASA Astrophysics Data System (ADS)

High mobility substrates are important key elements in the development of advanced devices targeting a vast range of functionalities. Among them, Ge showed promising properties promoting it as valid candidate to replace Si in CMOS technology. However, the electrical quality of the Ge/oxide interface is still a problematic issue, in particular for the observed inversion of the n-type Ge surface, attributed to the presence of dangling bonds inducing a severe band bending [1]. In this scenario, the identification of electrically active defects present at the Ge/oxide interface and the capability to passivate or anneal them becomes a mandatory issue aiming at an electrically optimized interface. We report on the application of highly sensitive electrically detected magnetic resonance (EDMR) techniques in the investigation of defects at the interface between Ge and GeO2 (or GeOx), including Ge dangling bonds and defects in the oxide [2]. In particular we will investigate how different surface orientations, e.g. the (001) against the (111) Ge surface, impacts the microstructure of the interface defects. [1] P. Tsipas and A. Dimoulas, Appl. Phys. Lett. 94, 012114 (2009) [2] S. Baldovino, A. Molle, and M. Fanciulli, Appl. Phys. Lett. 96, 222110 (2010)

Fanciulli, Marco; Baldovino, Silvia; Molle, Alessandro

2012-02-01

385

S. cerevisiae fermentation activity after moderate pulsed electric field pre-treatments.  

PubMed

The batch fermentation process, inoculated by Pulsed Electric Field (PEF) treated wine yeasts (Saccharomyces cerevisiae Actiflore F33), was studied. PEF treatment was applied to the aqueous yeast suspensions ([Y]=0.012g/L) at the electric field strengths of E=100 and 6000V/cm using the same treatment protocol (number of pulses n=1000, pulse duration ti=100?s, and pulse repetition time ?t=100ms). Electrical conductivity was increasing during and after the PEF treatment, which reflected cell electroporation. Then, fermentation was run for 150h in an incubator (30°C) with synchronic agitation. Electro-stimulation was revealing itself by the improvement of fermentation characteristics, and thus increased yeast metabolism. At the end of the lag phase (t=40h), fructose consumption in samples with electrically activated inoculum exceeded that of the control samples by ?2.33 times for E=100V/cm and by ?3.98 for E=6000V/cm. At the end of the log phase (120h of fermentation), ?30% mass reduction was reached in samples with PEF-treated inocula (E=6000V/cm), whereas the same mass reduction of the control sample required approximately 20 extra hours of fermentation. PMID:25204702

Mattar, Jessy R; Turk, Mohammad F; Nonus, Maurice; Lebovka, Nikolai I; El Zakhem, Henri; Vorobiev, Eugene

2015-06-01

386

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

NASA Astrophysics Data System (ADS)

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

Singh, Vandana

2010-05-01

387

Electro-active device using radial electric field piezo-diaphragm for sonic applications  

NASA Technical Reports Server (NTRS)

An electro-active transducer for sonic applications includes a ferroelectric material sandwiched by first and second electrode patterns to form a piezo-diaphragm coupled to a mounting frame. When the device is used as a sonic actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sonic sensor, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns, and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the plane of the ferroelectric material. The mounting frame perimetrically surrounds the peizo-diaphragm and enables attachment of the piezo-diaphragm to a housing.

Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

2005-01-01

388

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

NASA Astrophysics Data System (ADS)

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

Petrov, Yury

2012-07-01

389

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

390

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

2012-11-01

391

Electric Highway  

NSDL National Science Digital Library

In this design challenge activity, learners design and build a circuit: an "electric highway" that connects a battery and buzzer at least three feet apart using four types of materials. This is a simple exploratory activity about electricity and conductivity.

WGBH

2010-01-01

392

Static Electricity  

NSDL National Science Digital Library

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

Carlyn Little

1997-01-01

393

Effects of electric stimulation of the hunger center in the lateral hypothalamus on slow electric activity and spike activity of fundal and antral stomach muscles in rabbits under conditions of hunger and satiation.  

PubMed

In chronic experiments on rabbits, the effect of electric stimulation of the hunger center in the lateral hypothalamus on myoelectric activity of the fundal and antral parts of the stomach was studied under conditions of hunger and satiation in the absence of food. Stimulation of the lateral hypothalamus in rabbits subjected to 24-h food deprivation and in previously fed rabbits produced incessant seeking behavior, which was followed by reorganization of the structure of temporal organization of slow wave electric activity of muscles of the stomach body and antrum specific for hungry and satiated animals. Increased hunger motivation during electric stimulation of the lateral hypothalamus manifested in the structure of temporal organization of slow wave electric activity of the stomach body and antrum muscles in rabbits subjected to 24-h food deprivation in the replacement of bimodal distribution of slow wave periods to a trimodal type typical of 2-day deprivation, while transition from satiation to hunger caused by electric stimulation of the lateral hypothalamus was associated with a shift from monomodal distributions of slow wave periods to a bimodal type typical of 24-h deprivation. Reorganization of the structure of temporal organization of slow wave electric activity of the stomach body and antrum muscles during electric stimulation of the lateral hypothalamus was determined by descending inhibitory influences of food motivational excitation on activity of the myogenic pacemaker of the lesser curvature of the stomach. PMID:24288716

Kromin, A A; Zenina, O Yu

2013-09-01

394

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

395

Brain electrical activities of dancers and fast ball sports athletes are different.  

PubMed

Exercise training has been shown not only to influence physical fitness positively but also cognition in healthy and impaired populations. However, some particular exercise types, even though comparable based on physical efforts, have distinct cognitive and sensorimotor features. In this study, the effects of different types of exercise, such as fast ball sports and dance training, on brain electrical activity were investigated. Electroencephalography (EEG) scans were recorded in professional dancer, professional fast ball sports athlete (FBSA) and healthy control volunteer groups consisting of twelve subjects each. In FBSA, power of delta and theta frequency activities of EEG was significantly higher than those of the dancers and the controls. Conversely, dancers had significantly higher amplitudes in alpha and beta bands compared to FBSA and significantly higher amplitudes in the alpha band in comparison with controls. The results suggest that cognitive features of physical training can be reflected in resting brain electrical oscillations. The differences in resting brain electrical oscillations between the dancers and the FBSA can be the result of innate network differences determining the talents and/or plastic changes induced by physical training. PMID:25834650

Ermutlu, Numan; Yücesir, Ilker; Eskikurt, Gökçer; Temel, Tan; ??o?lu-Alkaç, Ümmühan

2015-04-01

396

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

PubMed Central

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

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

2013-01-01

397

An interacting loop model of solar flare bursts  

NASA Technical Reports Server (NTRS)

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

Emslie, A. G.

1981-01-01

398

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

NASA Astrophysics Data System (ADS)

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

Bock, Mark Joseph

399

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

PubMed

The activation procedure used in nuclear transfer (NT) is one of the critical factors affecting the efficiency of animal cloning. The purpose of this study was to compare the effect of two electrical field strengths (EFS) for activation on the developmental competence of caprine NT embryos reconstructed from ear skin fibroblasts of adult Alpine does. The NT embryos were obtained by transfer of the quiescent fibroblasts at the fourth passage into the enucleated metaphase II (M II) oocytes. Four to five hours after electrical fusion, the NT-embryos were activated by EFS either at 1.67 or at 2.33 kV/cm and immediately incubated in 6-DMAP (2 mM) for 4 h. The cleavage rate of the NT-embryos activated with 2.33 kV/cm was greater than that activated with 1.67 kV/cm after in vitro culture for 18 h (65.6% versus 19.6%, p < 0.001). No pregnancy was found in 14 recipient does after transferring 51 NT embryos at 1-2 cell stages activated with 1.67 kV/cm. In contrast, two of the seven recipients were pregnant and gave birth to three kids after transferring 61 NT embryos at 1-2 cell stages activated by 2.33 kV/cm. The birth weights of three cloned kids were within the normal range of Alpine goats. However, one kid died 1h after birth while the remaining two are still healthy. DNA analysis by polymerase chain reaction (single-strand conformation polymorphism, SSCP) confirmed that the three kids were genetically identical to the nuclear donor. PMID:16159700

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

2006-05-01

400

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

PubMed

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

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

2015-01-01

401

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

E-print Network

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

Lee, Hyang-Won

402

Development of a Remote Monitoring System Using Meteor Burst Technology  

SciTech Connect

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

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

2006-07-01

403

Analysis of multisite activity in organotypic hippocampal slices evoked by electrical stimulation using a Microelectrode-Array  

E-print Network

Analysis of multisite activity in organotypic hippocampal slices evoked by electrical stimulation by electrical stimulation. Hippocampal slices of 6 to 7 day old Wistar rats were cultured on a Microelectrod e and a diameter of 10µm. Slices were used for experiments after 8-10days in vitro. Stimulation and recording

Egert, Ulrich

404

Integrated Doubly Fed Electric Alternator\\/Active Filter (IDEA), a Viable Power Quality Solution, for Wind Energy Conversion Systems  

Microsoft Academic Search

In response to electric energy crisis and power quality concerns, a simple and low-cost variable speed integrated doubly fed electric alternator\\/active filter (IDEA) for wind energy conversion systems is proposed. The proposed IDEA is capable of simultaneously capturing maximum power of wind energy with fluctuating wind speed and improving power quality, which are achieved by canceling the most significant and

Mehdi T. Abolhassani; Prasad Enjeti; Hamid Toliyat

2008-01-01

405

A method to predict electric field spectra from empirically modeled geomagnetic ULF activity  

NASA Astrophysics Data System (ADS)

A model for prediction of the Earth background electromagnetic field spectra in the ULF range (1 mHz to 10 Hz) is developed. The possibility to model the hourly integrated magnetic wave power spectra with two different mathematical models, a power law or a fourth?order polynomial, is investigated. Spectral properties of 3 months of ground magnetic data show that the temporal evolution of the power law parameters can be modeled based on the hourly planetary magnetic activity, the Kp index. Furthermore, the parameters of the polynomial model are related to the magnetic wave power in two spectral bands within the Pc3 and Pc1 pulsation bands. Empirical models of the magnetic wave power in these bands are developed based on the diurnal variation and the correlation with solar wind velocity of geomagnetic pulsations. Comparison with observations shows that the power law model represents the spectra well for low frequencies. However, the polynomial model based on solar wind velocity provides a better representation for the bulk of the ULF domain with mean errors between 2 and 7 dB, increasing with decreasing frequency. The modeled magnetic wave spectrum and knowledge of the underlying electrical conductivity profile can be used to predict the induced ground electric field spectra. An apparent electric conductivity profile was found via model?based inversion, and the predicted electric wave power is compared to observations from an electrode systems offshore of the test site. The mean error between the observed and predicted electric field amplitudes is 2-7 dB and is consistently lower than the 95% central range of the data set.

Rosenqvist, L.

2013-08-01

406

Comparison and Analysis of Inter-Subject Variability of Simulated Magnetic Activity Generated from Gastric Electrical Activity  

PubMed Central

Electrogastrograms (EGGs) produced from gastric electrical activity (GEA) are used as a non-invasive method to aid in the assessment of a subject’s gastric condition. It has been documented that recordings of the magnetic activity generated from GEA are more reliable. Typically, with magnetic measurements of GEA, only activity perpendicular to the body is recorded. Also, external anatomical landmarks are used to position the magnetic recording devices, SQUIDs, (Superconducting Quantum Interference Devices) over the stomach with no allowance made for body habitus. In the work presented here, GEA and its corresponding magnetic activity are simulated. Using these data, we investigate the effects of using a standard SQUID location as well as a customized SQUID position and the contribution the magnetic component perpendicular to the body makes to the magnetic field. We also explore the effects of the stomach wall thickness on the resultant magnetic fields. The simulated results show that the thicker the wall, the larger the magnitude of the magnetic field holding the same signal patterns. We conclude that most of the magnetic activity arising from GEA occurs in a plane parallel to the anterior body. We also conclude that using a standard SQUID position can be suboptimal. PMID:18330701

Komuro, Rie; Cheng, Leo K.; Pullan, Andrew J.

2014-01-01