Shunt Conductance Research Articles

Resting membrane potential of rat ventroposteriomedial thalamic neurons during postnatal development

Resting membrane potential is a critical parameter determining tonic or bursting mode of the thalamic neurons. Previous studies using whole-cell recordings showed that immature ventroposteriomedial (VPM) and lateral geniculate thalamic neurons are strongly depolarized and have resting membrane potential near −50 mV. Yet, whole-cell recordings are associated with an introduction of the shunting conductance via the gigaseal that may lead to membrane depolarization in small neurons with high, in the gigaohm range, membrane resistance. Therefore, we have performed measurements of resting potential of VPM neurons in slices obtained from neonatal rats of postnatal days P2-P7 using cell-attached recordings of NMDA channels as voltage sensors. Because currents through the NMDA channels reverse near 0 mV, we assumed that the resting potential should equal the reversal potential of currents through NMDA channels in cell-attached recordings. Analysis of the current-voltage relationships of NMDA currents revealed that the resting potential in the immature VPM neurons is around −74 mV and that it does not change during the first postnatal week. This suggests that VPM neurons may operate in the bursting mode during the early postnatal period and support the oscillatory activity (spindle-like bursts) in the developing thalamocortical networks.

Diagnosis of inhomogeneous insulation degradation in electric cables by distributed shunt conductance estimation

For the diagnosis of inhomogeneous insulation degradation in electric cables, the estimation of distributed shunt conductance is studied in this paper. Gradual growth of the shunt conductance is a consequence of degradation of the dielectric properties of the insulator. The proposed estimation method is based on voltage and current measurements at a single end of the cable. After the linearization of the bilinear term of the telegrapher's equations through a perturbation approach, the Kalman filter is applied to transform the problem of dynamic system parameter estimation to a simple linear regression problem. Results of numerical simulations are presented to demonstrate the feasibility of the proposed method. In particular, it is shown that the weak sensitivity of the available measurements to the shunt conductance can be compensated by long time data samples.

An experimental analysis of illumination intensity and temperature dependency of photovoltaic cell parameters

It is well known that accurate knowledge of photovoltaic cell parameters from the measured current–voltage characteristics is of vital importance for the quality control and the performance assessment of photovoltaic cells/modules. Although many attempts have been made so far for a thorough analysis of cell parameters, there are still significant discrepancies between the previously published results. In this regard, a detailed investigation of cell parameters through a comprehensive experimental and statistical work is important to elucidate the aforementioned contradictions. Therefore in the present work, effects of two main environmental factors on performance parameters of mono-crystalline and poly-crystalline silicon photovoltaic modules have been experimentally investigated. The experiments have been carried out under a calibrated solar simulator for various intensity levels and cell temperatures in the range 200–500W/m2 and 15–60°C, respectively. The results indicated that light intensity has a dominant effect on current parameters. Photocurrent, short circuit current and maximum current increase linearly with increasing intensity level. A new term, solar intensity coefficient, has been defined first time to characterize the solar radiation dependency of current parameters. On the other hand, it has been observed that cell temperature has a dramatic effect on voltage parameters. Open circuit voltage and maximum voltage considerably decrease with increasing cell temperature. Temperature coefficients of voltage parameters have been calculated for each case. Shunt resistance has also been found to be rather sensitive to the variations in cell temperature. Shunt conductance of photovoltaic modules has almost remained constant as light intensity level changed. A linear decrease of series resistance has been observed with increasing cell temperature. Thermodynamic performance assessment of photovoltaic modules has also been done in the study.

A biogenic amine and a neuropeptide act identically: tyramine signals through calcium inDrosophilatubule stellate cells

Insect osmoregulation is subject to highly sophisticated endocrine control. In Drosophila, both Drosophila kinin and tyramine act on the Malpighian (renal) tubule stellate cell to activate chloride shunt conductance, and so increase the fluid production rate. Drosophila kinin is known to act through intracellular calcium, but the mode of action of tyramine is not known. Here, we used a transgenically encoded GFP::apoaequorin translational fusion, targeted to either principal or stellate cells under GAL4/UAS control, to demonstrate that tyramine indeed acts to raise calcium in stellate, but not principal cells. Furthermore, the EC(50) tyramine concentration for half-maximal activation of the intracellular calcium signal is the same as that calculated from previously published data on tyramine-induced increase in chloride flux. In addition, tyramine signalling to calcium is markedly reduced in mutants of NorpA (a phospholipase C) and itpr, the inositol trisphosphate receptor gene, which we have previously shown to be necessary for Drosophila kinin signalling. Therefore, tyramine and Drosophila kinin signals converge on phospholipase C, and thence on intracellular calcium; and both act to increase chloride shunt conductance by signalling through itpr. To test this model, we co-applied tyramine and Drosophila kinin, and showed that the calcium signals were neither additive nor synergistic. The two signalling pathways thus represent parallel, independent mechanisms for distinct tissues (nervous and epithelial) to control the same aspect of renal function.

In situ characterization of fouling in reverse osmosis membranes using electrical impedance spectroscopy

Analytical solutions of the Nernst-Planck, Poisson and continuity equations for a membrane undergoing reverse osmosis in a cross-flow system reveal that the flow of alternating ionic charge induced in the membrane during impedance measurements is actively assisted by the flow of water. The actively driven current manifested "inductive" responses in impedance measurements of a Filmtec BW30 reverse osmosis membrane mounted in an Inphaze flat-bed cross-flow module after 16 hours of filtering a mineral salt solution seeded with CaCl2 and NaHCO3 at pressure of 900 kPa. Fitted transfer functions resolved conduction and capacitive properties of four membrane layers, diffusion/concentration phenomenon and a pseudo "inductor" shunted by a conductor. A 10-fold decrease in the shunt conductance correlated with smaller increases in the conductance values for the filtrate and membranous layers, and the onset of fouling diagnosed by a rapid increase in flux decline.

Electrical characterization of all-layers-sprayed solar cell based on ZnO nanorods and extremely thin CIS absorber

Nanostructured ZnO/In2S3/CuInS2 superstrate solar cell with all component layers deposited by a low cost chemical spray pyrolysis (CSP) method is characterized. The characteristics of a cell based on a nano-columnar ZnO window layer and a thin film reference prepared by spray are compared. The aim is to determine the dominating non-ideality and the recombination mechanism of these cells in both dark and illuminated conditions and relate the findings to the imperfections in the cell materials. We performed J–V–T (current–voltage–temperature) measurements in dark and under 0.5–100mW/cm2 illumination intensities, and admittance spectroscopy, in the temperature range of 100–360K. We further measured EQE (external quantum efficiency) at room temperature. The solar cell outputs at AM1.5 of the flat reference cell are: Voc=497mV, Jsc=6.4mA/cm2, FF=62%, η=2%. The use of a nanostructured instead of a flat window layer resulted in short-circuit current density Jsc=12.2mA/cm2 and efficiency of η=3% at the expense of slightly reduced open-circuit voltage Voc=430mV and fill factor FF=58%. Interestingly, the nanostructured cell performs worse than the flat reference at low illumination intensity, as also indicated by illumination dependent shunt conductance. The diode ideality factor of both cells has a significant temperature and illumination dependence. The absorber bandgaps deduced from EQE are 1.5eV for the flat cell and 1.3eV for the structured cell. The nanostructured cell shows an increase of light scattering ability accompanied by a less effective charge carrier separation, compared to those of the flat reference cell. The extrapolation of Voc(T) to 0K yields 740–830meV and 950–990meV at varied illumination intensity, for the structured and the flat reference cell respectively, pointing to a non-midgap defect recombination. C–f–T (capacitance – ac frequency – temperature) analysis indicates that the structured cell has a higher concentration of defects and an additional band of defects. This further explains the limited performance enhancement of the structured cell over the flat cell. The illumination dependent cell parameters reveal that copper diffusion from absorber to buffer layer is likely. To eliminate problems associated with Cu diffusion, binary compounds like Sb2S3 or SnS for use as absorber material are considered to further develop the low-cost superstrate type solar cell deposited by the CSP method.

Diagnosis of inhomogeneous insulation degradation in electric cables by distributed shunt conductance estimation

For the diagnosis of inhomogeneous insulation degradation in electrical cables, the estimation of the distributed shunt conductance is studied in this paper. Gradual growth of the shunt conductance is a consequence of degradation of the dielectric properties of the insulator. The proposed estimation method is based on voltage and current measurements at a single end of the cable. After the linearization of the bilinear term of the telegrapher's equations through a perturbation approach, the Kalman filter is applied to transform the problem of dynamic system parameter estimation to a simple linear regression problem. Results of numerical simulations are presented to demonstrate the feasibility of the proposed method. In particular, it is shown that the weak sensitivity of the available measurements to the shunt conductance can be compensated by long time data samples.

Influence of shunt conduction on determining the dominant recombination processes in CIGS thin-film solar cells

We investigated the transport and photovoltaic properties of Cu(In1-xGax)Se2 (CIGS) thin-film solar cells. The shunt-current-eliminated diode current could be obtained from the current–voltage characteristics by subtracting the parasitic shunt leakage current from the total current. The temperature dependence of the open-circuit voltage, extracted from the shunt-eliminated (total) current, suggested that the recombination activation energy is comparable to (much less than) the CIGS bandgap. The low-temperature characteristics of the diode ideality factor supported bulk-dominated recombination in the same cell. This suggests that shunt-current subtraction can provide the proper diode parameters of CIGS solar cells.

Mathematical Model for the Determination of Voltage and Current on Lossy Power Transmission Lines

Energy is a basic necessity for the economic development of a nation. There are different forms of energy, but the most important form is the electrical energy. A modern and civilized society is so much dependent on the use of electrical energy. Electrical energy is transmitted by means of transmission lines which deliver bulk power from generating stations to load centers. The industrial development of any nation depends majorly upon the reliability of its interconnected electric power system. Availability of electric energy has been the most powerful vehicle for facilitating economic, industrial and social developments of any nation. When an electric power is generated in sufficient quantities, it needs to be transmitted in bulk to load centers and then distributed to individual consumers in proper form and quality at the lowest possible ecological and economic price. This electric power is transmitted by means of transmission lines. In this paper, we developed mathematical models for the determination of voltage and current on lossy electric power transmission lines. We derived relations which the voltage and current must satisfy on a uniform transmission line. The models contain the primary constants or parameters of the transmission line which include the series resistance (R), the shunt conductance (G), the inductance (L) and the capacitance (C). Values of these constants are specified per unit length.

Solar Cells Parameters Evaluation from Dark I-V Characteristics

In this paper, a comparative analysis of three methods to determine the four solar cells parameters (the saturation current (Is), the series resistance (Rs), the ideality factor (n), and the shunt conductance (Gsh)) of the single diode lumped model from its dark curve is presented. These methods are based on Gromov, Werner, and Mikhelashviliet al. methods that were used to extract the Schottky diode parameters. These techniques have been adequately modified, extended to cover the case of solar cells and used to extract the parameters of interest from experimental I-V characteristic of a Poly-Si solar cell under dark condition.

A novel model of photovoltaic modules for parameter estimation and thermodynamic assessment

This paper presents a novel model to evaluate the electrical performance of a silicon photovoltaic (PV) module with respect to changes in main environmental parameters such as temperature and illumination intensity. A simple one-diode model is proposed to estimate the electrical parameters of PV module considering the series resistance and shunt conductance. Effects of PV module parameters on current–voltage characteristic curve are investigated. The proposed model also makes a thermodynamic assessment concerning the effects of environmental and electrical parameters on efficiency and maximum power output of the PV module. Kyocera KD205GH-2P 205-W high-efficiency multi-crystal PV module is used for model evaluation. Model results are compared with the manufacturer's data report and an excellent agreement is observed.

Electrical properties of BaTiO3 based ferroelectric capacitors grown on oxide sacrificial layers for micro-cantilevers applications

An investigation of all oxide ferroelectric capacitors based on SrRuO3/BaTiO3/SrRuO3 multi-layers grown on sacrificial oxide layers of YBa2Cu3O7 and MgO for Micro-Electro-Mechanical systems applications is reported. By insertion of additional MgO or SrTiO3 buffer layers the orientation of the BaTiO3 film can be controlled allowing the fabrication of suspended cantilevers using the 31 and the 33 piezoelectric modes. The electrical properties of SrRuO3/BaTiO3/SrRuO3 capacitors are changed compared with those grown directly on a single crystal substrate by the introduction of sacrificial layers. Circuit modeling of the electrical characteristics of these devices shows that a reduction of the deposition pressure for BaTiO3 produces a decrease of the parasitic shunting conductance (modeled with a resistor in parallel to the capacitance of the device) which reduces the resistive losses present in the BaTiO3 film. However for extremely low deposition pressure the quality of the polarization hysteresis loops is compromised.Particulates present on the surface of the YBa2Cu3O7 increase the parasitic conductance at low frequency in the capacitive structure grown on this sacrificial layer. Good electrical properties are obtained for the capacitive structures grown on top of the MgO sacrificial layers at pressures equal or lower than 8Pa.

Physics and Statistics of Non-Ohmic Shunt Conduction and Metastability in Amorphous Silicon p–i–n Solar Cells

In this paper, we present a physical model of the non-Ohmic shunt current ISH in amorphous silicon (a-Si:H) p-i-n solar cells and validate it with detailed measurements. This model is based on space-charge-limited (SCL) transport through localized p-i-p shunt paths. These paths can arise from n-contact metal incorporation in the a-Si:H layer, causing the (n)a-Si:H to be counterdoped to p-type. The model not only explains all the electrical characteristics of preexisting shunts but also provides insight into the metastable switching that is observed in the shunt-dominated region of dark current as well. We first verify the SCL model using simulations and statistically robust measurements, and then use it to analyze our systematic observations of nonvolatile switching of the low-bias dark characteristics. This study interprets broad experimental observations regarding shunt behavior, and suggests possible techniques for alleviating shunt-induced performance and reliability issues.

Nanocrystalline silicon thickness dependence of transmission characteristics of CPWs on surface-passivated high-resistivity silicon substrates

A nanocrystalline silicon (nc-Si) layer was used as a surface-passivation layer (SPL) on a high-resistivity silicon (HR-Si) substrate. The transmission loss (αTL) of coplanar waveguide (CPW) lines on oxide/SPL/HR-Si substrates with an nc-Si SPL of 100, 200, and 400 nm was measured and analysed. The experimental results demonstrate that the thicker nc-Si SPL provides better passivation effect and the αTL can be down to 0.69 dB/cm. The equivalent series resistance and shunt conductance were extracted to investigate the dependence of αTL on the SPL thickness. The cross-talk effect of CPWs on oxide/SPL/HR-Si substrates was also studied.

Modelling and design of resonant one-dimensional metamaterial-based transmission lines for antenna applications

Various methods of extracting circuit parameters related to radiation effects and closed-form design equations based on them are provided for a one-dimensional (1D) resonant right-/left-handed transmission line (RLH-TL) with open and short terminations. The radiation properties of the RLH-TL have been characterised by simple parameters such as series resistance and shunt conductance in a unit cell using transmission line theory. In order to demonstrate the effectiveness of the modelling and to validate the design equations, two types of zeroth-order antennas based on low- and high-radiation structures have been designed, fabricated and measured. The low-radiation zeroth-order resonant (ZOR) antenna structure at 2 GHz is shown to have a very compact size (0.05λ 0 ×0.1λ 0 ×0.01λ 0 ) with a limited bandwidth, whereas the high-radiation ZOR antenna structure at 10 GHz is shown to have a much wider bandwidth of about 25 , as compared with any reported ZOR antennas in currently available research publications. The modelling of the 1D resonant RLH-TL, in consideration of the radiation effects, considerably narrowed the gap between the RLH-TL characteristics based on circuit simulations and those based on electromagnetic simulations and measurements.

New Analysis to Measure the Capacitance and Conductance of MOS Structure toward Small Size of VLSI Circuits

In this research thin film layers have been prepared at alternate layers of resistive and dielectric deposited on appropriate substrates to form four – terminal R-Y-NR network. If the gate of the MOS structures deposited as a strip of resistor film like NiCr, the MOS structure can be analyzed as R-Y-NR network. A method of analysis has been proposed to measure the shunt capacitance and the shunt conductance of certain MOS samples. Mat lab program has been used to compute shunt capacitance and shunt conductance at different frequencies. The results computed by this method have been compared with the results obtained by LCR meter method and showed perfect coincident with each other.

Reduced leakage current in Josephson tunnel junctions with codeposited barriers

Josephson junctions were fabricated using two different methods of barrier formation. The trilayers employed were Nb/Al–AlOx/Nb on sapphire, where the first two layers were epitaxial. The oxide barrier was formed either by exposing the Al surface to O2 or by codepositing Al in an O2 background. The codeposition process yielded tunnel junctions that showed the theoretically predicted subgap current and no measurable shunt conductance. In contrast, devices with barriers formed by thermal oxidation showed a small shunt conductance in addition to the predicted subgap current.

Reduced P2x2 receptor-mediated regulation of endocochlear potential in the ageing mouse cochlea

Extracellular adenosine triphosphate (ATP) has profound effects on the cochlea, including an effect on the regulation of the endocochlear potential (EP). Noise-induced release of ATP into the endolymph activates a shunt conductance mediated by P2X(2) receptors in tissues lining the endolymphatic compartment, which reduces the EP and, consequentially, hearing sensitivity. This may be a mechanism of adaptation or protection from high sound levels. As inaction of such a process could contribute to hearing loss, this study examined whether the action of ATP on EP changes with age and noise exposure in the mouse. The EP and the endolymphatic compartment resistance (CoPR) were measured in mice (CBA/CaJ) aged between 3 and 15 months. The EP and CoPR declined slightly with age with an associated small, but significant, reduction in auditory brainstem response thresholds. ATP (100-1,000 muM) microinjected into the endolymphatic compartment caused a dose-dependent decline in EP correlated to a similar decrease in CoPR. This was blocked by pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate, consistent with a P2X(2) receptor-mediated shunt conductance. There was no substantial difference in the ATP response with age. Noise exposure (octave-band noise 80-100 decibels sound pressure level (dBSPL), 48 h) in young animals induced an upregulation of the P2X(2) receptor expression in the organ of Corti and spiral limbus, most noticeably with the 90-dB exposure. This did not occur in the aged animals except following exposure at 90 dBSPL. The EP response to ATP was muted in the noise-exposed aged animals except following the 90-dB exposure. These findings provide some evidence that the adaptive response of the cochlea to noise may be reduced in older animals, and it is speculated that this could increase their susceptibility to noise-induced injury.

Screen printing metallization of boron emitters

AbstractThis paper analyzes the influence of the composition of screen printing metal pastes on contacting boron emitters for crystalline silicon solar cells, optimized on the basis of commercial Ag‐paste Ferro 3347 by adding silicon and aluminum. Aluminum provides a lower contact resistance, while silicon prevents the spiking and alloying of aluminum with the silicon of the substrate. The best pastes have turned out to be high Si‐concentrated, which have provided a final specific contact resistance of 3–4 mΩ cm2 on screen printed boron emitters diffused at 1000°C for 8 min, with shunt conductance lower than 0.6 mS/cm2. The final fill factors have been better than 77.5% and open circuit voltages have exceeded 605 mV on Czochralski (Cz) n type 0.7 Ω cm solar cells. These results have proven the feasibility of our screen printing process for p+nn+ structures. Copyright © 2009 John Wiley & Sons, Ltd.

전송 이론을 이용한 공진 MTM-TL 특성 분석 및 응용

본 논문에서는 공진 MTM-TL(Metamaterial Transmission Line) 등가 회로를 이용하여 방사 및 회로 파라미터의 추출 식을 제시하였다. 특히 개방 또는 단락 상태에서 방사 소자인 직렬 <TEX>$R_0$</TEX>와 병렬 <TEX>$G_0$</TEX>를 EM 시뮬레이션 또는 측정을 통해 얻은 S-parameterd(|<TEX>$S_{11}$</TEX>|)를 이용하여 추출한다, EM 시뮬레이션의 결과, 추출한 파라미터를 이용한 회로 시뮬레이션의 결과 그리고 측정 결과가 매우 일치함을 확인하였다. Some closed-form expressions for circuit parameters are derived based on the equivalent circuits for the resonant MTM-TL(open and short). The lumped series resistance and shunt conductance, which explain radiation effects of a unit cell may be found by |<TEX>$S_{11}$</TEX>|(simulated or measured) with open and short terminations, respectively. The EM-simulated results, circuit-simulated results(obtained using extracted circuit parameters) and measurement results are shown to be in good agreement.