Home About us Contact
|
Home About us Contact | ||
|
|
||
Voltage Responses (voltage + response)
Selected AbstractsElectrothermal Model Evaluation of Grain Size and Disorder Effects on Pulsed Voltage Response of Microstructured ZnO VaristorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008Guogang Zhao Time-dependent, two-dimensional, electrothermal simulations based on random Voronoi networks have been developed to study the internal heating, current distributions and breakdown effects in ZnO varistors in response to high-voltage pulsing. The simulations allow for dynamic predictions of internal failures and to track the progression of hot-spots and thermal stresses. The focus is on internal grain-size variations and relative disorder including micropores. Our results predict that parameters such as the hold-off voltage, internal temperature, and average dissipated energy density would be higher with more uniform grains. This uniformity is also predicted to produce lower thermal stresses and to allow for the application of longer duration pulses. It is shown that the principal failure mechanism arises from internal localized melting, while thermal stresses are well below the thresholds for cracking. Finally, detrimental effects of micropores have been quantified and shown to be in agreement with experimental trends. [source] Efficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series ResistanceADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Jonathan D. Servaites Abstract Here, means to enhance power conversion efficiency (PCE or ,) in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells by optimizing the series resistance (Rs),also known as the cell internal resistance,are studied. It is shown that current state-of-the-art BHJ OPVs are approaching the limit for which efficiency can be improved via Rs reduction alone. This evaluation addresses OPVs based on a poly(3-hexylthiophene):6,6-phenyl C61 -butyric acid methyl ester (P3HT:PCBM) active layer, as well as future high-efficiency OPVs (,,>,10%). A diode-based modeling approach is used to assess changes in Rs. Given that typical published P3HT:PCBM test cells have relatively small areas (,0.1,cm2), the analysis is extended to consider efficiency losses for larger area cells and shows that the transparent anode conductivity is then the dominant materials parameter affecting Rs efficiency losses. A model is developed that uses cell sizes and anode conductivities to predict current,voltage response as a function of resistive losses. The results show that the losses due to Rs remain minimal until relatively large cell areas (>0.1,cm2) are employed. Finally, Rs effects on a projected high-efficiency OPV scenario are assessed, based on the goal of cell efficiencies >10%. Here, Rs optimization effects remain modest; however, there are now more pronounced losses due to cell size, and it is shown how these losses can be mitigated by using higher conductivity anodes. [source] Carbon nanotube , molecular resonant tunneling diodePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2006Rajeev R. Pandey Abstract Carbon nanotube (CNT) molecular resonant tunnel diodes (RTDs) are proposed to complement bio-assembled CNT field effect transistors (CNTFETs). A model CNT,pseudopeptide,CNT device is shown to exhibit the current,voltage response of an RTD. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantitative analyses of anatomical and electrotonic structures of local spiking interneurons by three-dimensional morphometry in crayfishTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2001Ryou Hikosaka Abstract We quantitatively investigated the three-dimensional structure of the dendrites of local spiking interneurons using a confocal laser scanning microscope in the terminal abdominal ganglion of crayfish. We also studied their passive membrane properties electrophysiologically using the single-electrode current clamp techniques to analyze their electrotonic structure. All of the local spiking interneurons examined in this study lacked distinctive axonal structure and had a monopolar cell body that was connected with a fine primary process to a thick main segment. Numerous fine secondary processes projected from the main segment in the ganglionic neuropile. The average anatomical length of a secondary process from the main segment to its terminal was 261.9 ± 15.2 ,m. The average input resistance and membrane time constant of local spiking interneurons, obtained from their voltage responses to intracellular injection of step current pulses in the main segment, were 15.2 ± 1.6 M, and 13.9 ± 1.9 msec, respectively. Calculation of the electrotonic length of dendritic processes based on morphological and physiological data obtained in this study revealed that the average electrotonic length of secondary processes in local spiking interneurons was significantly longer than in local nonspiking interneurons, although both types of local interneurons showed apparently similar anaxonic structure. The steady-state voltage attenuation factors for the secondary processes of local spiking interneurons were significantly greater than those of local nonspiking interneurons in both centrifugal and centripetal directions. The larger electrotonic structure of local spiking interneurons compared to that of nonspiking interneurons appears to be compensated for by their excitable dendritic membrane. J. Comp. Neurol. 432:269,284, 2001. © 2001 Wiley-Liss, Inc. [source] Extracellular ATP inhibits chloride channels in mature mammalian skeletal muscle by activating P2Y1 receptorsTHE JOURNAL OF PHYSIOLOGY, Issue 23 2009Andrew A. VossArticle first published online: 30 NOV 200 ATP is released from skeletal muscle during exercise, a discovery dating back to 1969. Surprisingly, few studies have examined the effects of extracellular ATP on mature mammalian skeletal muscle. This electrophysiological study examined the effects of extracellular ATP on fully innervated rat levator auris longus using two intracellular microelectrodes. The effects of ATP were determined by measuring the relative changes of miniature endplate potentials (mEPPs) and voltage responses to step current pulses in individual muscle fibres. Exposure to ATP (20 ,m) prolonged the mEPP falling phase by 31 ± 7.5% (values ±s.d., n= 3 fibres). Concurrently, the input resistance increased by 31 ± 2.0% and the time course of the voltage responses increased by 59 ± 3.0%. Analogous effects were observed using 2 and 5 ,mATP, and on regions distal from the neuromuscular junction, indicating that physiologically relevant levels of ATP enhanced electrical signalling over the entire muscle fibre. The effects of extracellular ATP were blocked by 200 ,manthracene-9-carboxylic acid, a chloride channel inhibitor, and reduced concentrations of extracellular chloride, indicating that ATP inhibited chloride channels. A high affinity agonist for P2Y receptors, 2-methylthioadenosine-5,- O -diphosphate (2MeSADP), induced similar effects to ATP with an EC50 of 160 ± 30 nm. The effects of 250 nm2MeSADP were blocked by 500 nmMRS2179, a specific P2Y1 receptor inhibitor, suggesting that ATP acts on P2Y1 receptors to inhibit chloride channels. The inhibition of chloride channels by extracellular ATP has implications for muscle excitability and fatigue, and the pathophysiology of myotonias. [source] Physiological properties of rod photoreceptor electrical coupling in the tiger salamander retinaTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Jian Zhang Using dual whole-cell voltage and current clamp recording techniques, we investigated the gap junctional conductance and the coupling coefficient between neighbouring rods in live salamander retinal slices. The application of sinusoidal stimuli over a wide range of temporal frequencies allowed us to characterize the band-pass filtering properties of the rod network. We found that the electrical coupling of all neighbouring rods exhibited reciprocal and symmetrical conductivities. On average, the junctional conductance between paired rods was 500 pS and the coupling coefficient (the ratio of voltage responses of the follower cell to those of the driver cell), or K -value, was 0.07. Our experimental results also demonstrated that the rod network behaved like a band-pass filter with a peak frequency of about 2,5 Hz. However, the gap junctions between adjacent rods exhibited linearity and voltage independency within the physiological range of rods. These gap junctions did not contribute to the filtering mechanisms of the rod network. Combined with the computational modelling, our data suggest that the filtering of higher frequency rod signals by the network is largely mediated by the passive resistive and capacitive (RC) properties of rod plasma membranes. Furthermore, we found several attributes of rod electrical coupling resembling the physiological properties of gene-encoded Cx35/36 gap junctions examined in other in vitro studies. This indicates that the previously found Cx35/36 expression in the salamander rod network may be functionally involved in rod,rod electrical coupling. [source] | |||||||||||||