scholarly journals Control of Spreading Depression with Electrical Fields

2018 ◽  
Author(s):  
Andrew J. Whalen ◽  
Ying Xiao ◽  
Herve Kadji ◽  
Markus Dahlem ◽  
Bruce J. Gluckman ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Large Scale ◽  
Spreading Depression ◽  
Brain Slices ◽  
Propagation Path ◽  
Field Polarity ◽  
Biophysical Models ◽  
Control And Prevention ◽  
Cellular Swelling

AbstractSpreading depression or depolarization is a large-scale pathological brain phenomenon related to migraine, stroke, hemorrhage and traumatic brain injury. Once initiated, spreading depression propagates across gray matter extruding potassium and other active molecules, collapsing the resting membrane electro-chemical gradient of cells leading to spike inactivation and cellular swelling, and propagates independently of synaptic transmission. We demonstrate the modulation, suppression and prevention of spreading depression utilizing applied transcortical DC electric fields in brain slices, measured with intrinsic optical imaging and potassium dye epifluorescence. We experimentally observe a surface-positive electric field induced forcing of spreading depression propagation to locations in cortex deeper than the unmodulated propagation path, whereby further propagation is confined and arrested even after field termination. The opposite surface-negative electric field polarity produces an increase in propagation velocity and a confinement of the wave to more superficial layers of cortex than the unmodulated propagation path. These field polarities are of opposite sign to the polarity that blocks neuronal spiking and seizures, and are consistent with biophysical models of spreading depression. The results demonstrate the potential feasibility of electrical control and prevention of spreading depression.

scholarly journals The genomic basis of electrotaxis in Dictyostelium discoideum: Electric field sensitive amino acids are dynamically encoded en masse for the streaming-stage proteome

2015 ◽  
Author(s):  
Albert J Erives
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Electric Field ◽  
Electric Fields ◽  
Large Scale ◽  
Genetic Model ◽  
Critical Role ◽  
Axon Growth ◽  
Amino Acid Residues ◽  
Signaling Systems

Electrotaxis plays a critical role in developmental cell migration, axon growth cone guidance, epithelial wound healing, tissue regeneration, and the degree of invasiveness characterizing different cancer cell lines. During electrotaxis in a direct current electric field (EF), a cell migrates preferentially either towards the anode or cathode depending on the cell-type. However, the types and ranges of mechanisms coupling trans-cellular electric fields to cellular EF-sensitive signaling systems are largely unknown. To address this cell biological phenomenon, I use transcriptomic data from a developmental genetic model in which multicellular social aggregation is induced by starvation of amoeboid cells. I find that the developmental proteome expressed during the streaming aggregation stage is measurably and substantially enriched in charged and highly polar amino acids relative to the proteomes of either the unicellular amoeboid or the multicellular fruiting body. This large-scale coding augmentation of EF-sensitive amino acid residues in thousands of streaming-specific proteins is accompanied by a proportional coding decrease in the number of small, uncharged amino acid residues. I also confirm an expected coding increase of biosynthetically costly amino acids in the proteome of the satiated feeding-stage amoeboid. These findings suggest that electrotactic capability is encoded broadly in the genetically regulated deployment of a developmental proteome with augmented EF-sensitivity. These results signify that extreme, nonuniform, evolutionary constraints can be exerted on the amino acid composition of an organism’s proteome.

scholarly journals Observations of the generation of eastward equatorial electric fields near dawn

2014 ◽  
Vol 32 (9) ◽  
pp. 1169-1175 ◽  
Author(s):  
M. C. Kelley ◽  
F. S. Rodrigues ◽  
R. F. Pfaff ◽  
J. Klenzing
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Plasma Density ◽  
Large Scale ◽  
Field Measurements ◽  
Equatorial Ionosphere ◽  
Winter Solstice ◽  
The Pacific ◽  
Density Perturbations ◽  
Forecasting System

Abstract. We report and discuss interesting observations of the variability of electric fields and ionospheric densities near sunrise in the equatorial ionosphere made by instruments onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite over six consecutive orbits. Electric field measurements were made by the Vector Electric Field Instrument (VEFI), and ionospheric plasma densities were measured by Planar Langmuir Probe (PLP). The data were obtained on 17 June 2008, a period of solar minimum conditions. Deep depletions in the equatorial plasma density were observed just before sunrise on three orbits, for which one of these depletions was accompanied by a very large eastward electric field associated with the density depletion, as previously described by de La Beaujardière et al. (2009), Su et al. (2009) and Burke et al. (2009). The origin of this large eastward field (positive upward/meridional drift), which occurred when that component of the field is usually small and westward, is thought to be due to a large-scale Rayleigh–Taylor process. On three subsequent orbits, however, a distinctly different, second type of relationship between the electric field and plasma density near dawn was observed. Enhancements of the eastward electric field were also detected, one of them peaking around 3 mV m−1, but they were found to the east (later local time) of pre-dawn density perturbations. These observations represent sunrise enhancements of vertical drifts accompanied by eastward drifts such as those observed by the San Marco satellite (Aggson et al., 1995). Like the San Marco measurements, the enhancements occurred during winter solstice and low solar flux conditions in the Pacific longitude sector. While the evening equatorial ionosphere is believed to present the most dramatic examples of variability, our observations exemplify that the dawn sector can be highly variable as well.

scholarly journals Astrid-2 and ground-based observations of the auroral bulge in the middle of the nightside convection throat

2001 ◽  
Vol 19 (6) ◽  
pp. 633-641 ◽  
Author(s):  
G. T. Marklund ◽  
T. Karlsson ◽  
P. Eglitis ◽  
H. Opgenoorth
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Large Scale ◽  
Current Model ◽  
Energetic Electron ◽  
Auroral Oval ◽  
Plasma Convection ◽  
Magnetometer Data ◽  
Electric Fields And Currents ◽  
Good Agreement

Abstract. Results concerning the electrodynamics of the nightside auroral bulge are presented based on simultaneous satellite and ground-based observations. The satellite data include Astrid-2 measurements of electric fields, currents and particles from a midnight auroral oval crossing and Polar UVI images of the large-scale auroral distribution. The ground-based observations include STARE and SuperDARN electric fields and magnetic records from the Greenland and MIRACLE magnetometer network, the latter including stations from northern Scandinavia north to Svalbard. At the time of the Astrid-2 crossing the ground-based data reveal intense electrojet activity, both to the east and west of the Astrid-2 trajectory, related to the Polar observations of the auroral bulge but not necessarily to a typical substorm. The energetic electron fluxes measured by Astrid-2 across the auroral oval were generally weak being consistent with a gap observed in the auroral luminosity distribution. The electric field across the oval was directed westward, intensifying close to the poleward boundary followed by a decrease in the polar cap. The combined observations suggests that Astrid-2 was moving close to the separatrix between the dusk and dawn convection cells in a region of low conductivity. The constant westward direction of the electric field across the oval indicates that current continuity was maintained, not by polarisation electric fields (as in a Cowling channel), but solely by localized up- and downward field-aligned currents in good agreement with the Astrid-2 magnetometer data. The absence of a polarisation electric field and thus of an intense westward closure current between the dawn and dusk convection cells is consistent with the relatively weak precipitation and low conductivity in the convection throat. Thus, the Cowling current model is not adequate for describing the electrodynamics of the nightside auroral bulge treated here.Key words. Ionosphere (auroral ionosphere; electric fields and currents; plasma convection)

scholarly journals Some aspects of double layer formation in a plasma constrained by a magnetic mirror

1987 ◽  
Vol 5 (2) ◽  
pp. 315-324 ◽  
Author(s):  
W. Lennartsson
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Double Layer ◽  
Large Scale ◽  
Scale Effects ◽  
Distribution Functions ◽  
Electrons And Ions ◽  
Auroral Electrons ◽  
Complex Electric Field ◽  
Necessary And Sufficient

The discussion of parallel electric fields in the earth's magnetosphere has undergone a notable shift of emphasis in recent years, away from wave-generated anomalous resistivity towards the more large-scale effects of magnetic confinement of current carrying plasmas. This shift has been inspired in large part by the more extensive data on auroral particle distribution functions that have been made available, data that may often seem consistent with a dissipation-free acceleration of auroral electrons over an extended altitude range.Efforts to interpret these data have brought new vigor to the concept that a smooth and static electric field can be self-consistently generated by suitable pitch-angle anisotropies among the high-altitude particle populations, different for electrons and ions, and that such an electric field is both necessary and sufficient to maintain the plasma in a quasi-neutral steady state. This paper reviews and criticizes certain aspects of this concept, both from a general theoretical standpoint and from the standpoint of what we know about the magnetospheric environment. It is argued that this concept has flaws and that the actual physical problem is considerably more complicated, requiring a more complex electric field, possibly including double layer structures.

scholarly journals Equatorial electrojet as part of the global circuit: a case-study from the IEEY

1998 ◽  
Vol 16 (6) ◽  
pp. 698-710 ◽  
Author(s):  
A. T. Kobea ◽  
C. Amory-Mazaudier ◽  
J. M. Do ◽  
H. Lühr ◽  
E. Houngninou ◽  
...  
Keyword(s):  
Electric Field ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
High Latitude ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Doppler Frequency ◽  
Time Interval ◽  
Ground Field ◽  
Equatorial Latitude

Abstract. Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400-0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800-0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ∆H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.Keywords. Equatorial electrojet · Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral ionosphere · Ionospheric disturbances

scholarly journals Field-aligned currents and ionospheric parameters deduced from EISCAT radar measurements in the post-midnight sector

2002 ◽  
Vol 20 (9) ◽  
pp. 1335-1348 ◽  
Author(s):  
M. Sugino ◽  
R. Fujii ◽  
S. Nozawa ◽  
T. Nagatsuma ◽  
S. C. Buchert ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Large Scale ◽  
Radar Data ◽  
Temporal Variations ◽  
Dark Spot ◽  
Ionospheric Conductivity ◽  
Eiscat Radar ◽  
Transmitting Antenna

Abstract. Attempting to derive the field-aligned current (FAC) density using the EISCAT radar and to understand the role of the ionosphere on closing FACs, we conducted special radar experiments with the EISCAT radar on 9 October 1999. In order to derive the gradient of the ionospheric conductivity (grad S) and the divergence of the electric field (div E) nearly simultaneously, a special experiment employed an EISCAT radar mode which let the transmitting antenna sequentially point to four directions within 10 min; two pairs of the four directions formed two orthogonal diagonals of a square.  Our analysis of the EISCAT radar data disclosed that SP div E and E · grad SP produced FACs with the same direction inside a stable broad arc around 05:00 MLT, when the EISCAT radar presumably crossed the boundary between the large-scale upward and downward current regions. In the most successfully observed case, in which the conductances and the electric field were spatially varying with little temporal variations, the contribution of SP div E was nearly twice as large as that of E · grad SP . On the other hand, the contribution of (b × E) · grad SH was small and not effective in closing FACs. The present EISCAT radar mode along with auroral images also enables us to focus on the temporal or spatial variation of high electric fields associated with auroral arcs. In the present experiment, the electric field associated with a stable arc was confined in a spatially restricted region, within ~ 100 km from the arc, with no distinct depletion of electron density. We also detected a region of the high arc-associated electric field, accompanied by the depletion of electron density above 110 km. Using auroral images, this region was identified as a dark spot with a spatial scale of over 150 × 150 km. The dark spot and the electron depletion were likely in existence for a limited time of a few minutes.Key words. Ionosphere (auroral ionosphere; electric fields and currents; particle precipitation)

scholarly journals Electric field and air ion exposures near high voltage overhead power lines and adult cancers: a case control study across England and Wales

2020 ◽  
Vol 49 (Supplement_1) ◽  
pp. i57-i66 ◽  
Author(s):  
Mireille B Toledano ◽  
Gavin Shaddick ◽  
Kees de Hoogh ◽  
Daniela Fecht ◽  
Anna Freni Sterrantino ◽  
...  
Keyword(s):  
Cancer Risk ◽  
Electric Field ◽  
Electric Fields ◽  
High Voltage ◽  
Large Scale ◽  
Power Lines ◽  
Ion Density ◽  
England And Wales ◽  
Overhead Power Lines ◽  
Charged Ions

Abstract Background Various mechanisms have been postulated to explain how electric fields emitted by high voltage overhead power lines, and the charged ions they produce, might be associated with possible adult cancer risk, but this has not previously been systematically explored in large scale epidemiological research. Methods We investigated risks of adult cancers in relation to modelled air ion density (per cm3) within 600 m (focusing analysis on mouth, lung, respiratory), and calculated electric field within 25 m (focusing analysis on non-melanoma skin), of high voltage overhead power lines in England and Wales, 1974–2008. Results With adjustment for age, sex, deprivation and rurality, odds ratios (OR) in the highest fifth of net air ion density (0.504–1) compared with the lowest (0–0.1879) ranged from 0.94 [95% confidence interval (CI) 0.82–1.08] for mouth cancers to 1.03 (95% CI 0.97–1.09) for respiratory system cancers, with no trends in risk. The pattern of cancer risk was similar using corona ion estimates from an alternative model proposed by others. For keratinocyte carcinoma, adjusted OR in the highest (1.06–4.11 kV/m) compared with the lowest (<0.70 kV/m) thirds of electric field strength was 1.23 (95% CI 0.65–2.34), with no trend in risk. Conclusions Our results do not provide evidence to support hypotheses that air ion density or electric fields in the vicinity of power lines are associated with cancer risk in adults.

scholarly journals Temporal and spatial evolution of discrete auroral arcs as seen by Cluster

2005 ◽  
Vol 23 (7) ◽  
pp. 2531-2557 ◽  
Author(s):  
S. Figueiredo ◽  
G. T. Marklund ◽  
T. Karlsson ◽  
T. Johansson ◽  
Y. Ebihara ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Plasma Sheet ◽  
Large Scale ◽  
Potential Drop ◽  
Recovery Phase ◽  
Auroral Oval ◽  
Expansion Phase ◽  
Electric Fields And Currents ◽  
Auroral Arcs

Abstract. Two event studies are presented in this paper where intense convergent electric fields, with mapped intensities up to 1350 mV/m, are measured in the auroral upward current region by the Cluster spacecraft, at altitudes between 3 and 5 Earth radii. Both events are from May 2003, Southern Hemisphere, with equatorward crossings by the Cluster spacecraft of the pre-midnight auroral oval. Event 1 occurs during the end of the recovery phase of a strong substorm. A system of auroral arcs associated with convergent electric field structures, with a maximum perpendicular potential drop of about ~10 kV, and upflowing field-aligned currents with densities of 3 µA/m2 (mapped to the ionosphere), was detected at the boundary between the Plasma Sheet Boundary Layer (PSBL) and the Plasma Sheet (PS). The auroral arc structures evolve in shape and in magnitude on a timescale of tens of minutes, merging, broadening and intensifying, until finally fading away after about 50 min. Throughout this time, both the PS region and the auroral arc structure in its poleward part remain relatively fixed in space, reflecting the rather quiet auroral conditions during the end of the substorm. The auroral upward acceleration region is shown for this event to extend beyond 3.9 Earth radii altitude. Event 2 occurs during a more active period associated with the expansion phase of a moderate substorm. Images from the Defense Meteorological Satellite Program (DMSP) F13 spacecraft show that the Cluster spacecraft crossed the horn region of a surge-type aurora. Conjugated with the Cluster spacecraft crossing above the surge horn, the South Pole All Sky Imager recorded the motion and the temporal evolution of an east-west aligned auroral arc, 30 to 50 km wide. Intense electric field variations are measured by the Cluster spacecraft when crossing above the auroral arc structure, collocated with the density gradient at the PS poleward boundary, and coupled to intense upflowing field-aligned currents with mapped densities of up to 20 µA/m2. The surge horn consists of multiple arc structures which later merge into one structure and intensify at the PS poleward boundary. The surge horn and the associated PS region moved poleward with a velocity at the ionospheric level of 0.5 km/s, following the large-scale poleward expansion of the auroral oval associated with the substorm expansion phase. Keywords. Ionosphere (Ionosphere-magnetosphere interacctions; Electric fields and currents; Particle acceleration)

scholarly journals Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1471-1481 ◽  
Author(s):  
M. André ◽  
R. Behlke ◽  
J.-E. Wahlund ◽  
A. Vaivads ◽  
A.-I. Eriksson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Electric Field ◽  
Electric Fields ◽  
Large Scale ◽  
Small Scale ◽  
Lower Hybrid ◽  
Hybrid Frequency ◽  
Broadband Waves ◽  
Depression Wave ◽  
Magnetic Oscillations

Abstract. Broadband waves around the lower hybrid frequency (around 10 Hz) near the magnetopause are studied, using the four Cluster satellites. These waves are common at the Earthward edge of the boundary layer, consistent with earlier observations, and can have amplitudes at least up to 5 mV/m. These waves are similar on all four Cluster satellites, i.e. they are likely to be distributed over large areas of the boundary. The strongest electric fields occur during a few seconds, i.e. over distances of a few hundred km in the frame of the moving magnetopause, a scale length comparable to the ion gyroradius. The strongest magnetic oscillations in the same frequency range are typically found in the boundary layer, and across the magnetopause. During an event studied in detail, the magnetopause velocity is consistent with a large-scale depression wave, i.e. an inward bulge of magnetosheath plasma, moving tailward along the nominal magnetopause boundary. Preliminary investigations indicate that a rather flat front side of the large-scale wave is associated with a rather static small-scale electric field, while a more turbulent backside of the large-scale wave is associated with small-scale time varying electric field wave packets.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers) – Space plasma physics (waves and in-stabilities)

The generation of electric charges and fields in thuderstorms

1988 ◽  
Vol 415 (1849) ◽  
pp. 303-315 ◽  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cross Sections ◽  
Large Scale ◽  
Breakdown Strength ◽  
Grazing Incidence ◽  
Precipitation Intensity ◽  
Cloud Droplets ◽  
Storm Cells ◽  
Impact Angles

The generation and separation of electric charge and the growth of electric fields in thunderstorms are accounted for by the rebound of a small fraction of the cloud droplets impacting on the undersides of small pellets of soft hail, thereby carrying away some of the polarized charge induced by the prevailing vertical electric field. It is shown that just those droplets making grazing incidence with the millimetre-sized hail pellets are able to separate sufficient charge to create large-scale fields of 4000 V cm -1 within 10 min if, during this time, the precipitation intensity builds up from zero to 20 mm h -1 to produce a total precipitation of about 2 mm. The growth rate of the electric field is determined largely by the precipitation intensity, which is related to the size, density and hence the falling speed of the hail pellets. The field, starting from the initial fine-weather value, grows exponentially but slowly at first, then more rapidly as the hail pellets grow and because the mechanism is self-accelerating, but eventually slows down as the electrical forces on the charged hail pellets and rebounding droplets counteract the gravitational forces and slow down their rate of separation. Calculation of the trajectories of the droplets that make grazing contact with the hail pellets of different sizes and densities, ρ i , allow the collision cross sections and impact angles, θ , to be determined. Charge separation is proportional to cos θ and is most effective when 0.1 < ρ i ≤ 0.5 g cm -3 . Very light hail pellets with ρ i < 0.1 g cm -3 become ‘suspended’ in the electric field before this reaches breakdown strength, whereas the faster-falling particles of ρ i > 0.5 g m -3 force the droplets to rebound very close to the electrical equator of the hail pellet where they carry away little charge. It is shown that thunderstorm cells of radius 2 km would be able to produce a succession of lightning flashes at intervals of about 30 s as long as the updraught and precipitation rate are maintained. Very intense lightning activity, with flashes at intervals of less than 10 s, would require storm cells exceeding 5 km in radius, but is more likely to be produced by large multicellular storms.

Sign in / Sign up

Export Citation Format

Share Document