scholarly journals Anomalous diurnal variation of atmospheric potential gradient and air‐Earth current density observed at Maitri, Antarctica

2016 ◽  
Vol 121 (21) ◽  
pp. 12,593-12,611 ◽  
Author(s):  
K. Jeeva ◽  
S. Gurubaran ◽  
E. R. Williams ◽  
A. K. Kamra ◽  
A. K. Sinha ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Current Density ◽  
Potential Gradient

Measuring surface potential components necessary for transmembrane current computation using microfabricated arrays

2005 ◽  
Vol 289 (6) ◽  
pp. H2468-H2477 ◽  
Author(s):  
J. James Wiley ◽  
Raymond E. Ideker ◽  
William M. Smith ◽  
Andrew E. Pollard
Keyword(s):  
Spatial Resolution ◽  
Current Density ◽  
Potential Gradient ◽  
Electrode Spacing ◽  
Back Side ◽  
Transmembrane Current ◽  
Fine Wire ◽  
Microfabricated Arrays ◽  
Potential Gradients ◽  
Unipolar Electrograms

This study was designed to test the feasibility of using microfabricated electrodes to record surface potentials with sufficiently fine spatial resolution to measure the potential gradients necessary for improved computation of transmembrane current density. To assess that feasibility, we recorded unipolar electrograms from perfused rabbit right ventricular free wall epicardium ( n = 6) using electrode arrays that included 25-μm sensors fabricated onto a flexible substrate with 75-μm interelectrode spacing. Electrode spacing was therefore on the size scale of an individual myocyte. Signal conditioning adjacent to the sensors to control lead noise was achieved by routing traces from the electrodes to the back side of the substrate where buffer amplifiers were located. For comparison, recordings were also made using arrays built from chloridized silver wire electrodes of either 50-μm (fine wire) or 250-μm (coarse wire) diameters. Electrode separations were necessarily wider than with microfabricated arrays. Comparable signal-to-noise ratios (SNRs) of 21.2 ± 2.2, 32.5 ± 4.1, and 22.9 ± 0.7 for electrograms recorded using microfabricated sensors ( n = 78), fine wires ( n = 78), and coarse wires ( n = 78), respectively, were found. High SNRs were maintained in bipolar electrograms assembled using spatial combinations of the unipolar electrograms necessary for the potential gradient measurements and in second-difference electrograms assembled using spatial combinations of the bipolar electrograms necessary for surface Laplacian (SL) measurements. Simulations incorporating a bidomain representation of tissue structure and a two-dimensional network of guinea pig myocytes prescribed following the Luo and Rudy dynamic membrane equations were completed using 12.5-μm spatial resolution to assess contributions of electrode spacing to the potential gradient and SL measurements. In those simulations, increases in electrode separation from 12.5 to 75.0, 237.5, and 875.0 μm, which were separations comparable to the finest available with our microfabricated, fine wire, and coarse wire arrays, led to 10%, 42%, and 81% reductions in maximum potential gradients and 33%, 76%, and 96% reductions in peak-to-peak SLs. Maintenance of comparable SNRs for source electrograms was therefore important because microfabrication provides a highly attractive methods to achieve spatial resolutions necessary for improved computation of transmembrane current density.

THE ATMOSPHERIC POTENTIAL GRADIENT AT OTTAWA, CANADA

1937 ◽  
Vol 15a (8) ◽  
pp. 119-148 ◽  
Author(s):  
D. C. Rose
Keyword(s):  
Diurnal Variation ◽  
Potential Gradient ◽  
Meteorological Conditions ◽  
Fine Weather ◽  
Points Of View ◽  
Set Up ◽  
A Site

The atmospheric potential gradient was observed continuously at the National Research Laboratories at Ottawa for a year ending December 1, 1935, and at a country station about nine miles northwest of Ottawa, for four months ending November 1, 1936. The country station was set up on a site as free as possible from man-made pollution of the atmosphere. The records were studied from two points of view, the diurnal variation and disturbances in the normal fine weather value of the potential gradient. The results indicate that the diurnal variation is similar to that of other similarly situated stations. The study of disturbances in the potential gradient shows that all disturbances can be correlated with local meteorological conditions. The disturbances were for the most part associated with the stormy conditions usual at the passage of a front. The effect of city pollution on potential gradient records is clearly shown.

scholarly journals V. Atmospheric electricity potential gradient at Kew Observatory, 1898 to 1912

1915 ◽  
Vol 215 (523-537) ◽  
pp. 133-159 ◽  
Keyword(s):  
Diurnal Variation ◽  
Atmospheric Electricity ◽  
Potential Gradient ◽  
Barometric Pressure ◽  
One Year ◽  
Meteorological Elements

In a previous paper, called E 1 for brevity, I discussed the results obtained for the diurnal variation of the potential gradient of atmospheric electricity at Kew Observatory from 1898 to 1904. The present paper deals with the same subject, but employs data from the fifteen years 1898 to 1912. The earlier period of seven years, though longer than that available at most observatories, was too short to give a satisfactorily representative presentation of some of the phenomena. To obtain results fairly characteristic of the locality many years data are required of some of the meteorological elements, especially barometric pressure and rainfall. For the latter element, in fact, a considerably longer period is desirable than that available even now for potential gradient at Kew. The same may be true of potential gradient itself, but various reasons exist for not waiting longer. Owing to building operations, the electrograph results for 1913 were exposed to special uncertainties. Also the transfer of the electrograph from the position it has occupied since 1898 is now in contemplation. Thus 1912 may be regarded as ending an epoch. Another reason requires fuller explanation. The Kew water-dropper—the earliest it is believed in regular operation—was erected in 1861 under Lord Kelvin’s personal supervision. The original electrometer and batteries as they decayed were replaced by others, but the instrument remained essentially unchanged in its original site until 1896. Of the records obtained prior to that date those of only three years had been discussed, two years, 1862 to 1864, by Prof. J. D. Everett, and one year, 1880, by Mr. G. M Whipple. In both cases the results were expressed in what were really arbitrary units. The relation between the voltage shown by the instrument and the true potential gradient in the open was altogether unknown.

Failure of Flip-Chip Circuit Interconnects under High Current Density

2010 ◽  
Vol 118-120 ◽  
pp. 449-453
Author(s):  
Yu Dong Lu ◽  
Xiao Qi He ◽  
Yun Fei En ◽  
Xin Wang ◽  
Zhi Qiang Zhuang
Keyword(s):  
Current Density ◽  
Flip Chip ◽  
Chemical Potential ◽  
High Current Density ◽  
Potential Gradient ◽  
High Current ◽  
Wind Force ◽  
Chemical Potential Gradient ◽  
Solder Bumps ◽  
Electron Wind

Both Al interconnects and flip-chip solder bumps were sensitive to high current. The failure mechanism of circuits interconnects would be more complicated if the current density in circuits was exceed the critical magnitudes of electromigration in both Al interconnects and solder bumps. The failure of circuit interconnects under different magnitudes of current density was studied and the interaction of electromigration in solder bumps and Al interconnects was discussed. The circuit interconnects of flip chip show three failure phenomena under high current density: voids in Al final metal, inter-diffusion of Al and SnPb, and melting of solder bumps. The voids in Al metal show the directional diffusion of Al atoms was mainly controlled by the electron wind fore. However the inter-diffusion of Al and SnPb demonstrated the electron wind force to Sn and Pb atoms would be ignored in contrast with chemical potential gradient or intrinsic stress. The flow of Sn and Pb atoms under high current density was in opposite direction with electron wind force and uniform with chemical potential gradient.

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