Reduction Of Short Circuit Current Research Articles

The effect of electrolyte filling method on the performance of dye-sensitized solar cells

The effect of electrolyte filling method on the performance of the dye-sensitized solar cells is investigated with the segmented cell method, a recent technique which is very simple but effective as it can be used to examine all the photovoltaic characteristics. The electrolyte filling techniques compared were single injection, which is typically used in small laboratory cells, and pumping the electrolyte through the cell several times, which is often used for larger cells and modules. Significant photovoltage and photocurrent variations occur with the repeated pumping of the electrolyte in the cell preparation. Transient and charge extraction measurements confirmed that the differences in open circuit voltage were due to the shifts of the TiO2 conduction band and time correlated single photon counting confirmed that the reduction of short circuit current was largely due to reduced electron injection correlated with the increasing conduction band edge in the studied cases. This was interpreted as an effect of molecular filtering by the TiO2 causing an accumulation of electrolyte additives (4-tert-butylpyridine and benzimidazole) near the electrolyte filling hole, the concentration of which increased with repeated pumping of the electrolyte. Interestingly, spatial variations were seen not only in the relative TiO2 conduction band energy but also in the density of trap states. In this contribution it is demonstrated how the changes in the conduction band can be separated from the changes in the density of trap states which is an essential for the correct interpretation of the data.

The effect of Helicobacter typhlonius infection on colonic ion transport in the IL10 knockout mice

Helicobacter infection causes severe colitis in immunocompromised mice, but little is know of its effects on the properties of the colonic epithelium. We compared the effects of H. typhlonius infection on the functional properties of the proximal (PC) and distal colon (DC) of wildtype (WT) and IL10 knockout (IL10−/−) mice. WT mice showed no clinical effects of infection, colonic inflammation or changes in functional properties of the colon. Other than a slight increase in water content of the stool, IL10−/− mice also showed no clinical effects of infection. Despite this the PC was severely inflamed, with a milder inflammation in the DC. There was no increase in TNFα or INFγ associated with the inflammation, but IL12p40 levels were increased. Unexpectedly, the conductance (GT) of the PC was decreased, as was the permeability. No change in GT of the DC occurred. Associated with infection was a reduction in the spontaneous short circuit current (Isc) in the PC but not the DC. Also, in the PC of infected animals the forskolin‐stimulated Isc was only ≈5% of that of non‐infected controls, whereas the response of the DC was ≈50% of that of controls. In contrast, in infected animals the carbachol‐stimulated Isc was essentially eliminated in both the PC and DC. As seen in other inflammatory models colonic inflammation associated with H. typhlonius infection of IL10−/− mice markedly alters the transport properties of the colon, however this does not result in diarrhea. This may be a consequence of the absence of a change in colonic permeability or distal sparing due to the limited inflammation in the distal colon. Supported by the University of Otago.

Reduction of short circuit current in static CMOS inverters using novel smart delay generator circuits

CMOS inverters have the advantage of zero static power consumption. However, they suffer from dynamic power consumption and short circuit power consumption. Dynamic power consumption results from charging the output capacitance then discharging it again. Whereas short circuit power consumption happens during the switching of the inverter between logic '1' and logic '0' due to the direct current path that opens between V DD and Ground for the duration of the inverter switching. The problem of short circuit current is not only the amount of power consumption but also its contribution to the noise in the supply by adding unnecessary rebels to the supply current. This paper introduces two different novel and simple smart delay generator circuits that will reduce the amount of short circuit current in CMOS inverters by more than 50%.

Reversible and irreversible degradation of organic solar cell performance by oxygen

Abstract The effect of oxygen on the degradation of inverted bulk heterojunction solar cells based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blends has been investigated by monitoring current–voltage (jV)-curves, impedance spectra and charge extraction by linearly increasing voltage (CELIV) traces during the degradation process. The use of gas permeable top electrodes allows monitoring the kinetics of degradation without being limited by the diffusion through a compact metal electrode. A computational model is used to provide a phenomenological explanation of the experimental results. The charge distribution inside the device is modeled by solving the fully coupled set of nonlinear differential equations for the quasi-one-dimensional transport of electrons and holes. Degradation of the cells in the presence of oxygen results mainly in the reduction of short circuit current (jsc), while the concomitant loss in light absorption is negligible. The rate of degradation is enhanced significantly by illumination. A significant part of the loss in jsc is reversible upon annealing under nitrogen or in vacuum. The irreversible part of the degradation is assigned to the photochemical formation of carbonyl and carboxylic groups, which act as traps for electrons. The reversible component of degradation is due to p-doping of the photoactive layer by oxygen, which results in the formation of mobile holes and immobile superoxide anions. This leads to the formation of a space charge region in front of the electron extracting electrode whose width depends on the doping level as well as on the applied bias. The space charge region shields the electric field inside the photoactive layer and hence hampers charge carrier extraction, which leads to the observed loss in short circuit current.

Effects of Ti-incorporation in CuInS 2 solar cells

Titanium has been incorporated in CuInS 2 thin films and devices by diffusion of Ti from the substrate during the CuInS 2 co-evaporation growth process. The CuInS 2 crystal structure is unaffected but the grain size is reduced compared to Ti-free reference samples. X-ray photoelectron spectroscopy shows the presence of TiO 2 at the front of the absorber layer, which appears at the heterojunction interface of the completed CuInS 2/TiO 2/CdS/ZnO solar cells. Low temperature photoluminescence spectra show no additional transitions that could be assigned to Ti-based impurity defect levels. Ti-containing cells show conversion efficiencies higher than the Ti-free reference cells due to higher open-circuit voltage (efficiency 11%, V OC =731 mV). No reduction in short circuit current is detected, indicating that the titanium does not introduce additional bulk recombination. Temperature-dependent current-voltage measurements indicate a reduced interface recombination for cells containing Ti, which is attributed to the TiO 2 interlayer detected by X-ray photoelectron spectroscopy.

Functional Regulation of the Epithelial Na+ Channel by IκB Kinase-β Occurs via Phosphorylation of the Ubiquitin Ligase Nedd4-2

We have previously shown that IkappaB kinase-beta (IKKbeta) interacts with the epithelial Na+ channel (ENaC) beta-subunit and enhances ENaC activity by increasing its surface expression in Xenopus oocytes. Here, we show that the IKKbeta-ENaC interaction is physiologically relevant in mouse polarized kidney cortical collecting duct (mpkCCDc14) cells, as RNA interference-mediated knockdown of endogenous IKKbeta in these cells by approximately 50% resulted in a similar reduction in transepithelial ENaC-dependent equivalent short circuit current. Although IKKbeta binds to ENaC, there was no detectable phosphorylation of ENaC subunits by IKKbeta in vitro. Because IKKbeta stimulation of ENaC activity occurs through enhanced channel surface expression and the ubiquitin-protein ligase Nedd4-2 has emerged as a central locus for ENaC regulation at the plasma membrane, we tested the role of Nedd4-2 in this regulation. IKKbeta-dependent phosphorylation of Xenopus Nedd4-2 expressed in HEK-293 cells occurred both in vitro and in vivo, suggesting a potential mechanism for regulation of Nedd4-2 and thus ENaC activity. 32P labeling studies utilizing wild-type or mutant forms of Xenopus Nedd4-2 demonstrated that Ser-444, a key SGK1 and protein kinase A-phosphorylated residue, is also an important IKKbeta phosphorylation target. ENaC stimulation by IKKbeta was preserved in oocytes expressing wild-type Nedd4-2 but blocked in oocytes expressing either a dominant-negative (C938S) or phospho-deficient (S444A) Nedd4-2 mutant, suggesting that Nedd4-2 function and phosphorylation by IKKbeta are required for IKKbeta regulation of ENaC. In summary, these results suggest a novel mode of ENaC regulation that occurs through IKKbeta-dependent Nedd4-2 phosphorylation at a recognized SGK1 and protein kinase A target site.

A new correlation between photovoltaic panel's efficiency and amount of sand dust accumulated on their surface

The accumulation of dust particles on the surface of photovoltaic (PV) panel greatly affects its performance especially in the dusty areas. In the present work, an experimental and theoretical study has been carried out to investigate the effect of sand dust concentration on the efficiency of PV panels. A stand-alone PV system is designed to carry out this work. The I–V characteristics have been measured simultaneously for both clean and dusty modules. It has been found that the short circuit current and the maximum output power decrease significantly as dust particles start to accumulate on the panel surface up to a concentration of 1 g/m2, but the rate of decrease is slower for concentrations beyond that value. The reduction in short circuit current in one sample of study is found to be ∼40%, whereas it is ∼34% in the maximum output power. In contrast, it is stated that the open circuit voltage is not sensitive to sand dust accumulation. A significant degradation in the efficiency of PV modules is observed for sand dust accumulation up to 1 g/m2. A linear relation has been proposed to correlate the degradation in efficiency to the amount of sand dust accumulated on the module surface. This relation can help PV system designers to reliably predict the effect of sand dust accumulation on PV module efficiency under real environmental conditions.

Simplified edge isolation of buried contact solar cells

Abstract The aim of this work is to implement simple edge isolation techniques in buried contact solar cell (BCSC) process by preserving the active cell area. Here we present results of two simplified edge isolation techniques for BCSC and they are compared with the standard process incorporating mechanical edge isolation using a dicing saw. The first technique is chemical wet etching of the solar cell's rear side in an inline system recently developed by University of Konstanz and Rena. The second technique is edge removal carried out in a fluoride/oxide radicals environment of a Asyntis plasma etcher. While the shunt resistance R sh obtained with wet etching is between 1500 and 7000 Ω cm 2 , the standard process shows R sh values ranging from 2100–6300 Ω cm 2 . The R sh after plasma processing is between 1000 and 3600 Ω cm 2 . These cell results show that both wet and plasma etching achieve results close to mechanical edge isolation. However, a slight reduction of short circuit current is observed for the cells undergone standard as well as plasma processing. This is due to the presence of floating volume shunts formed at the rear n–p + junction, which are not removed by either the standard or plasma process. These shunts do not influence the IV -curve of the solar cells and are nearly invisible with conventional thermography, as they are not connected to the front side emitter grid. Hence, light-modulated lock-in thermography measurements were carried out to analyse these shunts.

Tauroursodeoxycholic Acid Reduces Damaging Effects of Taurodeoxycholic Acid on Fundus Gastric Mucosa

We investigated the effects of tauroursodeoxycholic acid (TUDCA) to assess whether this acid may also have ‘protective’ effects similar to those found with ursodeoxycholic acid (UDCA). We used a well-known amphibian model of gastric mucosa, and studied the effects of taurodeoxycholic acid (TDCA) on electrical transepithelial parameters, acid secretion and histology in absence or in presence of TUDCA. Mucosal exposure to TDCA, after stimulation with histamine, caused a reduction in transepithelial potential difference (V t) and transepithelial resistance (R t) and a decrease in acid secretion while mucosal exposure to TUDCA did not cause a significant change in the electrical parameters. Moreover, TDCA primarily affected the neck cells, while TUDCA affected only oxyntic cells, causing a similar degree of injury to that observed in controls. Mucosal exposure to TUDCA plus TDCA caused a reduction in short circuit current (I sc) and R t, whereas acid secretion did not change. These results suggest that: (1) TUDCA reduces the damaging effects of TDCA on fundus gastric mucosa; (2) TUDCA may play an important role in the treatment of gastritis associated with bile reflux.

Neural control of intestinal ion transport and paracellular permeability is altered by nutritional status.

This study examined the effect of fasting on the neural control of ion transport and paracellular permeability in piglet jejunum. Muscle-stripped tissues from fed or 48-h fasted piglets were mounted in Ussing chambers. Neural blockade with tetrodotoxin (TTX) or antagonists of muscarinic or nicotinic receptors caused reductions in basal short-circuit current that were approximately threefold greater in fasted piglets. The TTX-induced reduction in short-circuit current in fasted piglets was due to a decrease in residual ion flux and was abolished in the absence of HCO(-)(3). Intestinal paracellular permeability, as indicated by tissue conductance (G(t)) and fluxes of inulin and mannitol, was significantly increased by fasting. TTX increased inulin flux and G(t) in fed but not fasted piglets. In fasted piglets, carbachol reduced G(t) by 29% and mannitol flux by 27% but had no effect on these parameters in the fed state. We conclude that fasting enhances enteric neural control of basal ion transport and increases paracellular permeability in piglet jejunum. Tonic release of enteric neurotransmitters regulates paracellular permeability in the fed state, and cholinergic stimulation restores fasting-induced elevations in paracellular permeability to fed levels.

97/02859 Comparative assessment of the effect of dynamic load models on voltage stability

This paper characterizes the operation of a thyristor controlled reactor (TCR) which consists of an inductance and a bi-directional thyristor switch connected in parallel. Firing angle control of the thyristor switches regulates the time for which the inductance is included in the circuit. This controls the average value of the inductance. The continuously regulated inductance can be used for line flow regulation and short circuit current reduction. It can also be used for series compensation when the TCR is connected in series with a fixed capacitor and when the combination is inserted in series with transmission lines. This paper analysis the operation of the TCR using equations and EMTP simulations.The analysis shows that a series compensator using TCR regulates the level of compensation from inductive to capacitive and the system response is faster than the recently commercialized ‘Advanced Series Compensation’ (ASC) scheme. Also, the problems of resonance and harmonic instability associated with the ASC are eliminated. The TCR can control short circuit current within half cycle.

97/02868 Focus on motors and drives

This paper characterizes the operation of a thyristor controlled reactor (TCR) which consists of an inductance and a bi-directional thyristor switch connected in parallel. Firing angle control of the thyristor switches regulates the time for which the inductance is included in the circuit. This controls the average value of the inductance. The continuously regulated inductance can be used for line flow regulation and short circuit current reduction. It can also be used for series compensation when the TCR is connected in series with a fixed capacitor and when the combination is inserted in series with transmission lines. This paper analysis the operation of the TCR using equations and EMTP simulations.The analysis shows that a series compensator using TCR regulates the level of compensation from inductive to capacitive and the system response is faster than the recently commercialized ‘Advanced Series Compensation’ (ASC) scheme. Also, the problems of resonance and harmonic instability associated with the ASC are eliminated. The TCR can control short circuit current within half cycle.

Characterization of a thyristor controlled reactor

This paper characterizes the operation of a thyristor controlled reactor (TCR) which consists of an inductance and a bi-directional thyristor switch connected in parallel. Firing angle control of the thyristor switches regulates the time for which the inductance is included in the circuit. This controls the average value of the inductance. The continuously regulated inductance can be used for line flow regulation and short circuit current reduction. It can also be used for series compensation when the TCR is connected in series with a fixed capacitor and when the combination is inserted in series with transmission lines. This paper analysis the operation of the TCR using equations and EMTP simulations. The analysis shows that a series compensator using TCR regulates the level of compensation from inductive to capacitive and the system response is faster than the recently commercialized ‘Advanced Series Compensation’ (ASC) scheme. Also, the problems of resonance and harmonic instability associated with the ASC are eliminated. The TCR can control short circuit current within half cycle.

Growth of a-Si:H on transparent conductive oxides for solar cell applications

Different concepts for optimizing the transparent conductive oxide (TCO)/p-interface in hydrogenated amorphous silicon (a-Si:H) based solar cells have been studied in order to avoid the segregation of metal layers, and hence considerable reductions in short circuit current. We analysed structural and chemical changes which occur at the surface of transparent conductive oxides — TCOs (SnO 2, ZnO, and Indium Tin Oxide — ITO) in silane, hydrogen and C0 2 plasmas. We also used a-SiO:H instead of a-SiC:H in the p-doped layer. In-situ ellipsometry and SIMS/XPS depth profiling show that room temperature as well as fast deposition easily overcome all detrimental effects. TCO deterioration by ion and radical bombardement at high deposition rates is more than compensated if the surface is protected by a rapidly growing a-Si:H film. Using ZnO as a TCO, or as a 20 nm buffer layer only, completely suppresses metal formation. In-situ ellipsometry in conjunction with atomic force microscopy reveals significant changes in surface morphology, namely filling of the TCO-texture during deposition, which is of crucial importance for light trapping in solar cells.

An immortal cell line to study the role of endogenous CFTR in electrolyte absorption.

The intact human reabsorptive sweat duct (RD) has been a reliable model for investigations of the functional role of "endogenous" CFTR (cystic fibrosis transmembrane conductance regulator) in normal and abnormal electrolyte absorptive function. But to overcome the limitations imposed by the use of fresh, intact tissue, we transformed cultured RD cells using the chimeric virus Ad5/SV40 1613 ori-. The resultant cell line, RD2(NL), has remained differentiated forming a polarized epithelium that expressed two fundamental components of absorption, a cAMP activated Cl- conductance (GCl) and an amiloride-sensitive Na+ conductance (GNa). In the unstimulated state, there was a low level of transport activity; however, addition of forskolin (10(-5) M) significantly increased the Cl- diffusion potential (Vt) generated by a luminally directed Cl- gradient from -15.3 +/- 0.7 mV to -23.9 +/- 1.1 mV, n = 39; and decreased the transepithelial resistance (Rt) from 814.8 +/- 56.3 omega.cm2 to 750.5 +/- 47.5 omega.cm2, n = 39, (n = number of cultures). cAMP activation, anion selectivity (Cl- > I- > gluconate), and a dependence upon metabolic energy (metabolic poisoning inhibited GCl), all indicate that the GCl expressed in RD2(NL) is in fact CFTR-GCl. The presence of an apical amiloride-sensitive GNa was shown by the amiloride (10(-5) M) inhibition of GNa as indicated by a reduction of Vt and equivalent short circuit current by 78.0 +/- 3.1% and 77.9 +/- 2.6%, respectively, and an increase in Rt by 7.2 +/- 0.8%, n = 36. In conclusion, the RD2(NL) cell line presents the first model system in which CFTR-GCl is expressed in a purely absorptive tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Fault-current limiter with thyristor-controlled impedance

A new fault current limiter with thyristor-controlled impedance (FCL-TCI) is proposed. The FCL-TCI helps in improving the steady-state stability limit, while providing an effective reduction of short circuit current during the fault. Analytical, experimental and computer simulation studies on a working model are conducted. The effects on improvement of stability limits and reduction of the short-circuit current are shown using the experimental model. The economical benefits of the FCL-TCI are due to the extension of the useful life of the existing circuit breakers and power transformers, and to the improvement in the performance of the transmission line. >

Effects of purified Pseudomonas rhamnolipids on bioelectric properties of sheep tracheal epithelium.

The effects of purified rhamnolipids from Pseudomonas aeruginosa on short circuit current in respiratory epithelium have been studied in sheep tracheal epithelium mounted in Ussing chambers under short circuit conditions. In low concentrations (100 microM) mucosal addition of rhamnolipids produces a decrease in short circuit current of 22% and in conductance of 4%. At higher concentrations (> 100 microM), large increases in tissue conductance accompany a greater reduction in short circuit current, suggesting disruption of the intercellular junctions. Serosal addition of rhamnolipids has no effect on ion transport. Pretreatment of the tissues with the sodium channel blocker amiloride (100 microM) or bathing the mucosal surface with sodium-free solution significantly decreased the rhamnolipid-induced fall in short circuit current but did not prevent it completely. Inhibition of chloride transport, sodium-glucose cotransport, and bicarbonate secretion with bumetanide, phloridzin, and acetazolamide, respectively, did not significantly alter the rhamnolipid effect. This suggests that the effect of rhamnolipids on short circuit current is mediated predominantly but not exclusively by an effect on sodium transport. The effects of rhamnolipids on ion transport occur at concentrations within the range occurring in the sputum of patients with cystic fibrosis. The changes in ion transport may explain some of the known effects of rhamnolipid on mucociliary clearance.

Aldosterone alters the open probability of amiloride-blockable sodium channels in A6 epithelia.

We used patch-clamp methods to examine the effects of depletion and readdition of aldosterone on single, highly selective, amiloride-blockable sodium channels in the A6 cell line. Single-channel characteristics changed little before 24 h of continuous aldosterone depletion, although there was some reduction in short-circuit current. Thereafter, apical sodium permeability, measured as product of channel number per patch and individual channel open probability (NPo), was reduced between five- and sevenfold, primarily due to a large decrease in channel mean open time. With about the same time course, short-circuit current also decreased approximately fivefold. Readdition of aldosterone to depleted cells produced an increase in NPo within 2 h, primarily through an increase in mean open time. After readdition, channel number per patch increased twofold compared with cells not hormone deprived, with a return to control levels between 24 and 48 h after continuous exposure. The increase in short-circuit current followed a similar time course. The primary effect of aldosterone appears to be modulation of the open time of channels continuously present in the apical membrane, rather than promotion of the appearance or disappearance of channels from the membrane. In particular, it cannot be demonstrated statistically that aldosterone removal reduces the number of channels per patch, and there may actually be up to a twofold increase after a long period of aldosterone depletion.

Acetylcholine release from colonic submucous neurons associated with chloride secretion in the guinea pig

Electrical field stimulation of submucous neurons in the guinea pig distal colon evokes an increase in chloride secretion sensitive to cholinergic blockade. This study was undertaken in the guinea pig to determine the feasibility of measuring acetylcholine (ACh) release simultaneously with ion transport in sheets of colonic submucosa/mucosa set up in flux chambers modified for perfusion of the submucosal surface. Release of [3H]ACh was determined in the absence of cholinesterase inhibitors as the stimulus-evoked outflow of 3H from preparations preloaded with [3H]choline. [3H]ACh released in response to electrical stimulation correlated with short-circuit current at frequencies from 0.5 to 10 Hz. At 5 and 10 Hz, the stimulus-evoked release of [3H]ACh decreased during subsequent stimulation periods. The stimulus-evoked increase in [3H]ACh was attenuated by tetrodotoxin. [3H]ACh release evoked at stimulus frequencies of 0.5-10 Hz was not altered by atropine despite a reduction in short-circuit current. This study illustrates the feasibility of measuring ACh release simultaneously with ion transport in flux chambers. The results provide new information on the response characteristics of colonic submucous neurons and provide direct evidence for regulation of chloride secretion by ACh.

Effects of cell volume changes on membrane ionic permeabilities and sodium transport in frog skin (Rana ridibunda).

1. Membrane potential and conductances and short-circuit current were continuously measured with microelectrodes and conventional electrophysiological techniques in a stripped preparation of frog skin epithelium. The effects of the removal of chloride or sodium ions and the concentration or dilution of the serosal (inner) bathing solution were studied. 2. Chloride- or sodium-free solutions produced a cell depolarization of about 30 mV in parallel with a fall in the short-circuit current. Mucosal and serosal membrane conductances both decreased and the sodium permeability of the mucosal barrier was calculated to fall to about one-half its value in standard Ringer solution. The observed decrease in the short-circuit current is probably related to the combined effect of the decrease in sodium permeability and the decrease in the driving force across the mucosal membrane. 3. The removal of chloride or sodium ions reduced the depolarization caused by serosal perfusion with high-potassium solutions (50 mM-KCl). The ratio of the change in cell membrane potential under short-circuit conditions to the change in the potassium equilibrium potential (delta Ec(s.c.)/delta EK), was 0.59 in standard Ringer solution and 0.26 and 0.24 after the removal of chloride or sodium respectively. The depolarizing effect of barium-containing solutions (2 mM-BaCl2) was also markedly reduced in chloride- or sodium-free solutions, suggesting a decrease of the potassium selectivity of the serosal membrane in these conditions. 4. Increasing the osmolality of the serosal bathing solution produced similar effects, i.e. cell depolarization, fall in the short-circuit current and membrane conductances and reduction of the depolarizing effect of high-potassium and barium solutions. On the contrary, dilution of the serosal bath produced the opposite effects, consistent with an increase in the serosal permeability to potassium. 5. The effects of chloride- or sodium-free solutions were reversed by the dilution of the serosal bath. Cells repolarized when exposed to low-osmolality solutions after being in the absence of serosal chloride or sodium. The repolarization ran in parallel with the restoration of the short-circuit current and the potassium selectivity of the serosal membrane. 6. The results show that the effects produced by the removal of sodium or chloride ions from the serosal bathing solution are most probably mediated by a reduction in cell volume. Cell volume changes would lead to changes in the serosal membrane selectivity to potassium and thus to changes in cell membrane potential and sodium transport.(ABSTRACT TRUNCATED AT 400 WORDS)