Electrokinetic Energy Conversion by Microchannel Array: Electrical Analogy, Experiments, and Electrode Polarization

To determine how rapidly pulmonary capillaries recruit after sudden changes in blood flow, we used an isolated canine lung lobe perfused by two pumps running in parallel. When one pump was turned off, flow was rapidly halved; when it was turned on again, flow immediately doubled. We recorded pulmonary capillary recruitment in subpleural alveoli using videomicroscopy to measure how rapidly the capillaries reached a new steady state after these step changes in blood flow. When flow was doubled, capillary recruitment reached steady state in <4 s. When flow was halved, steady state was reached in approximately 8 s. We conclude that the pulmonary microcirculation responds rapidly to step changes in flow, even in the capillaries that are most distant from the hilum.

This paper describes a new type of MCA (micro channel array) for simultaneous multipoint measurement of cellular network. Presented MCA is designed for advanced neural network analysis which has been studied by co-authors using 64 ch MEA (micro electrode arrays) system. First of all, sucking and clamping of cells through channels of developed MCA is expected to improve electrophysiological signal detections. Electrophysiological sensing electrodes integrated around individual channels of MCA are electrically isolated for simultaneous multipoint measurement.

The effects of norepinephrine (NE), an inhibitor of insulin secretion, were examined on membrane potential and the ATP-sensitive K+ channel (K ATP) in INS 832/13 cells. Membrane potential was monitored under the whole cell current clamp mode. NE hyperpolarized the cell membrane, an effect that was abolished by tolbutamide. The effect of NE on K ATP channels was investigated in parallel using outside-out single channel recording. This revealed that NE enhanced the open activities of the K ATP channels approximately 2-fold without changing the single channel conductance, demonstrating that NE-induced hyperpolarization was mediated by activation of the K ATP channels. The NE effect was abolished in cells preincubated with pertussis toxin, indicating coupling to heterotrimeric G i/G o proteins. To identify the G proteins involved, antisera raised against alpha and beta subunits (anti-G alpha common, anti-G beta, anti-G alpha i1/2/3, and anti-G alpha o) were used. Anti-G alpha common totally blocked the effects of NE on membrane potential and K ATP channels. Individually, anti-G alpha i1/2/3 and anti-G alpha o only partially inhibited the action of NE on K ATP channels. However, the combination of both completely eliminated the action. Antibodies against G beta had no effects. To confirm these results and to further identify the G protein subunits involved, the blocking effects of peptides containing the sequence of 11 amino acids at the C termini of the alpha subunits were used. The data obtained were similar to those derived from the antibody work with the additional information that G alpha i3 and G alpha o1 were not involved. In conclusion, both G i and G o proteins are required for the full effect of norepinephrine to activate the K ATP channel.

Current evolution in Datacoms and Gigabit Ethernet have made 850nm Vertical Cavity Surface Emitting Lasers (VCSEL) the most important and promising emitter. Numerous different structures have been growth, to obtain best current confinement and then to control the emitted light modal behavior. We have developed a small signal equivalent electrical model of VCSEL including Bragg reflectors, active area, chip connection and noise behavior. Easy to integrate with classical software for circuit studies, this model which is widely adaptable for different structures takes into account the complete electrical environment of the chip. An experimental validation for RF modulation up to 10 GHz has been realized on oxide confined VCSEL, demonstrating that the model could be used to get realistic values for the VCSEL intrinsic parameters. Including Langevin noise sources into the rate equations and using the same electrical analogy, noise current and voltage sources can be added to the model. It allows good prediction for the RIN function shape up to 10GHz for monomodal emitter.

Current-Voltage (I-V) curve tracers are useful implements for solar Photovoltaic (PV) research and manufacturing, particularly when wishing to ascertain module yield viz-a-viz solar irradiation falling on the module in different climatic conditions. This paper presents a simple affordable and easy to fabricate instrument for tracing I-V characteristics of a PV module. It comprises of rapidly varying resistive loads centred on power resistors connected to relays and controlled by an electronic circuitry. The circuit consists of a 555 astable oscillator that is used to send clock pulses to the clock terminal of a 4017 decade counter which in turn produces a sequence of pulses. Each progression of pulse advances by one bit to sequentially turn on individual relays via driver transistors. The speed of the count is made variable from the frequency determining network of the 555 oscillator. The I-V characteristics of the module are thus measured by the sequential selection of the relays which are each connected to a selected load resistor to determine the operating point on the I-V curve. The currents and voltages are then recorded simultaneously with irradiance from a pyranometer, by a datalogger to which the instruments are connected. The circuit was tested on two monocrystalline modules to compare the effect of Harmattan dust on PV output yield.

Using the geometry of the spin field-effect transistor, we investigate the spin transport of in-plane spins in an array of narrow channels formed in a two-dimensional electron gas confined in an $(\mathrm{In},\mathrm{Ga})\mathrm{As}$ quantum well. We demonstrate a clear enhancement of the spin-diffusion length with decreasing channel width, yielding up to 10 \textmu{}m for the narrowest channels. We discuss the observed enhancement in terms of the suppression of the Dyakonov-Perel mechanism of spin relaxation, which has been invoked in previous studies in the case of diffusion of out-of-plane oriented spins. We also show that the spin signal is significantly higher when injecting into an array of narrow channels, compared with injecting into a single narrow channel.

This paper proposes a unified phase shift control strategy for optimized transient current response of dual active bridge (DAB) dc-dc converters. Conventional phase shift control for DAB converters may cause dc offset in the high-frequency-link inductor current during transients, which may lead to magnetic flux saturation and excessive current stress on the switching devices. The proposed phase shift method can eliminate the transient current offset during both unidirectional and bidirectional power flow changes in a unified form. Experimental results are provided to verify the theoretical analysis.

Mental fatigue is closely related to our daily life and work, a considerable number of studies have achieved good results in quantifying and predicting them. Although some studies have achieved a high accuracy by using only a single channel, and a few have explored the optimal solution for feature and channel selection. However, detailed research of optimally setting the electrodes position and determining the number channels are rarely seen. In this study, by designing a novel genetic operator and applying the GA-SVM model, we compared the maximum number of optimal channels and their distributions. The result suggests that the classification accuracy almost reaches its optimum (94.0±5.3 %) when the maximum number of channels reaches 5, and is not affected by the epoch length. The whole brain optimal channels topographic map analysis shows that the optimal channels are mainly distributed in the prefrontal, occipital and temporal lobes, while hardly any is located in the parietal lobe, which indicates that the mental fatigue induced by visual search task characterized similarly among different individuals and highly task-related.

Minimal mathematical models were developed to describe the electrophysiological properties of human δ-cells. Markov models of single channels were first developed based on the analysis of electrophysiological data. Monte Carlo simulations of voltage-clamp experiments were performed in an iteratively optimization procedure to estimate the number of channels required to reproduce the main characteristics of the macroscopic currents recorded experimentally. A membrane model of the firing of action potentials was then developed based on the kinetic schemes of single channels and the number of channels estimated. We showed that macroscopic currents of human δ-cells can be reproduced by minimal models of single channels when the appropriate number of channels is considered. In addition, our simulations suggest that human δ-cells are capable of generating action potentials through the interaction of the ionic currents involved. Finally, we determined the relative contribution of the currents underlying the firing of action potentials in human pancreatic δ-cells, which allowed us to propose a qualitative model of an action potential in terms of the underlying ionic currents.

In this work, we use time-resolved photoluminescence (PL) spectroscopy, microscopy, and current measurements to characterize the slow transient responses of methylammonium lead triiodide (MAPbI3) on a lateral interdigitated electrode device. By systematically varying the applied bias magnitude and electrode polarity, we observed distinct reversible and irreversible PL transient responses in the form of spectrally and spatially resolved PL quenching occurring over a range of 0.5–100 s. When the simultaneous current and the PL measurements were correlated, the reversible responses, present under all electric fields, were attributed to charge trapping, whereas the irreversible response, occurring above a nominal electric field between 1 and 5 kV cm–1, was attributed to ion migration. Thus, these results indicate that the slow transient response, and therefore hysteretic behavior, in MAPbI3 devices is a complex response with contributions from both charge trapping and ion migration.

1. The nature of the membrane channels underlying the membrane conductance changes induced by the nitric oxide (NO) donors, S-nitroso-L-cysteine (NOCys) and sodium nitroprusside (SNP) were investigated in single myocytes isolated from the circular muscle layer of the guinea-pig proximal colon, by use of standard whole-cell and single channel recording techniques. 2. Under voltage clamp, depolarizing steps from -60 mV elicited a rapidly-developing, little-inactivating outward K+ current (IK) at potentials positive to -40 mV (at 20-25 degrees C). The steady-state level (ISS) of this K current increased in amplitude as the step potential was made to more positive potentials. If the depolarizing steps were made from a holding potential of -80 mV an additional rapidly activating and inactivating outward K+ current was also elicited, superimposed on IK. 3. At 20-25 degrees C, NOCys (2.5 microM), SNP (100 microM) and 8-bromo-cyclic GMP (500 microM) increased the amplitude of ISS of IK elicited from a holding potential of -60 mV. In contrast, NOCys (2-5 microM) had little effect on ISS at 35 degrees C. Higher concentrations (> or = 5 microM at 20-25 degrees C and > or = 10 microM at 35 degrees C) of NOCys decreased the peak amplitude (I[Peak]) and ISS of IK in a concentration-dependent manner. This blockade of IK with NOCys was always associated with an increase of the holding current (IHold), due to the activation of a membrane conductance with a reversal potential between 0 and + 30 mV and which was reduced approximately 50% upon the addition of Cd2+ (1 mM). 4. NOCys (2.5 to 10 microM) or SNP (100 microM) increased the activity of large conductance Ca2+-activated (BK) K' channels in both cell-attached and excised inside-out patches, bathed in either a symmetrical high K+ (130 mM) or an asymmetrically K+ (6 mMout: 130 mMin) physiological saline. Increases in BK channel activity in NOCys (10 microM) or SNP (100 microM) were associated with an increase in the probability of BK channel opening (N.Po), and with a negative shift of the plots of ln(N.Po) against the patch potential, with little change in the slopes of these plots. In cell-attached patches, the increase in N.Po with NOCys was often associated with a decrease in the BK single channel conductance. 5. In both cell-attached and excised patches, NOCys (2.5 to 10 microM) also activated an additional population of channels which allowed inward current flow at potentials positive to EK. In excised inside-out patches bathed in asymmetrical K+ physiological saline, these single channel currents were 2-3 pA in amplitude at -30 mV and reversed in direction near + 10 mV, even if the NaCl (126 mM) concentration in the pipette solution had been replaced with an equimolar concentration of Na gluconate. 6. Under current clamp, NOCys (2.5 microM) and SNP (100 microM) had variable effects on the membrane potential of colonic myocytes, inducing either a small membrane hyperpolarization of <5 mV, or a slowly-developing membrane depolarization of about 5 mV. In contrast, NOCys (5 microM) produced a transient membrane hyperpolarization which was followed by a large depolarization of the membrane potential to positive potentials. The electrotonic potentials elicited in response to an injection of constant hyperpolarizing current (10 pA for 400 ms) were little changed during the NOCys (5 PM)-induced membrane hyperpolarization, but significantly reduced (to 61% of control) during the periods of membrane depolarization. 7. It was concluded that NOCys and SNP, directly increased the number of active BK channels in the membrane of colonic myocytes which leads to a small rapidly oscillating membrane hyperpolarization. The following rebound depolarization in NOCys arises from both the direct opening of a population of cationic channels and the blockade of voltage- and Ca-activated K+ conductances. Finally, the apamin-sensitive K+channels underlying the initial transient hyperpolarization recorded in the intact proximal colon, in response to nerve-released or directly-applied NO, have yet to be identified at the single channel or whole-cell current level.

The activity of the epithelial Na(+) channel (ENaC) is modulated by Na(+) self-inhibition, a down-regulation of the open probability of ENaC by extracellular Na(+). A His residue within the extracellular domain of gammaENaC (gammaHis(239)) was found to have a critical role in Na(+) self-inhibition. We investigated the functional roles of residues in the vicinity of this His by mutagenesis and analyses of Na(+) self-inhibition responses in Xenopus oocytes. Significant changes in the speed and magnitude of Na(+) self-inhibition were observed in 16 of the 47 mutants analyzed. These 16 mutants were distributed within a 22-residue tract. We further characterized this scanned region by examining the accessibility of introduced Cys residues to the sulfhydryl reagent MTSET. External MTSET irreversibly increased or decreased currents in 13 of 47 mutants. The distribution patterns of the residues where substitutions significantly altered Na(+) self-inhibition or/and conferred sensitivity to MTSET were consistent with the existence of two helices within this region. In addition, single channel recordings of the gammaH239F mutant showed that, in the absence of Na(+) self-inhibition and with an increased open probability, ENaCs still undergo transitions between open and closed states. We conclude that gammaHis(239) functions within an extracellular allosteric regulatory subdomain of the gamma subunit that has an important role in conferring the response of the channel to external Na(+).

The aim of this randomized controlled crossover study was to investigate the effect of a bout of unaccustomed eccentric exercise (ECC) followed by a consecutive bout of the same intensity on local muscle blood flow, amplitude, and frequency of the electromyographic (EMG) signal from the exercised tibialis anterior muscle. Sixteen healthy male participants (age, 25.7 (0.6) years; body mass index 24.8 (1) kg·m(-2) participated in this study. Two identical bouts of high-intensity ECC were performed on the tibialis anterior muscle 7 days apart. Control sessions involving no exercise were performed 4 weeks either before or after the exercise sessions. Changes in local total blood flow [ΔtHb], EMG root mean square, and median power frequency were recorded during isometric maximum voluntary contraction of ankle dorsiflexion. Measurements were performed before, immediately after, and the day after both ECCs (ECC1 and ECC2). The participants rested quietly in a chair in the control session. Eccentric exercise 1 led to a significant decrease in [ΔtHb] on the day after (p ≤ 0.05), whereas ECC2 did not. Median power frequency decreased significantly in ECC2 compared with ECC1 (p < 0.01). Root mean square was unchanged in all the instants. The present study showed that adaptation is depicted in the local muscle blood flow and the frequency contents of the EMG after an unaccustomed ECC inducing muscle soreness. These alterations provide a potential mechanism for a rapid adaptation, which decreases susceptibility of the muscle to develop further soreness in the subsequent ECC bout.

This article focuses on developing electrical models to investigate the conversion of solar radiation into both electrical and thermal energy. Our findings indicate that semiconductor converters are unable to harness the entire electromagnetic spectrum emitted by the sun. A substantial portion of solar radiation is transformed into heat. To achieve these results, we employed a corpuscular model to represent the solar radiation flow and a quantum mechanical framework to describe the energy associated with electromagnetic radiation and thermal processes within the crystal. To derive electrical modeling parameters, this study leveraged the principle of electrical and electrothermal analogies. We established a direct equivalence between the flow of solar photons and the flow of charge carriers represented by the electric current. Additionally, we demonstrated that the energy carried by photons is analogous to the voltage generated across the photovoltaic device. When modeling thermal energy using electrical circuits, we found that the electric current can be used to represent the flow of phonons, quasiparticles associated with thermal vibrations in the crystal, while the voltage corresponds to the energy of phonons. This study developed electrical models to simulate the conversion of solar radiation into both electrical and thermal energy. Current and voltage sources were employed to represent the energy conversion processes. It is shown that the internal resistances of energy sources in electrical models simulate the losses during the generation of electrical and thermal energy. It is noted that the proposed electrical model of a photovoltaic power source corresponds to the traditional equivalent circuit with a diode. The paper concludes by discussing the potential applications of the proposed modeling framework.

We have studied experimentally the electro-optics properties of the slab waveguide induced by the electric poling. The thin film waveguide is made by a commercial polymer PA-11 and was poled by applying voltage between the botttom electrode and the top electrode. The poling voltage dominates the magnitude of E-O effect. In this work, I-V curves and electro-optic characteristics of the PA-11 films were in-situ measured during poling. In order to evaluate the molecular dipole alignment under the poling field, absorption spectra of this film was observed by the FTIR. Moreover, the static field analysis of the poling electrodes is performed to determine the optimum electrode geometry. Numerical evidence demonstrated that the distribution of poling field is function of electrode spacing and width. Thus these numerical results should be useful to establish a novel guideline for designing the poling electrode of poled polymer waveguide devices.