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1
Azizov, �. �., V. G. Babaev, and V. A. Mashtakova. "Voltage-current curves for a planar symmetrical diode with reverse bias." Radiophysics and Quantum Electronics 31, no. 1 (January 1988): 83–89. http://dx.doi.org/10.1007/bf01034576.
Повний текст джерела
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Su, Xuebing, Yang Wang, Xiangliang Jin, and Hongjiao Yang. "Design of high voltage electrostatic protection device for CAN bus." Journal of Physics: Conference Series 2221, no. 1 (May 1, 2022): 012014. http://dx.doi.org/10.1088/1742-6596/2221/1/012014.
Повний текст джерелаАнотація:
Abstract The Dual-Direction Silicon Controlled Rectifier (DDSCR) device has dual-direction electrostatic protection function and strong current discharging ability, which is widely used in ESD on-chip protection. In this paper, a high performance symmetric high voltage Dual-Direction Silicon Controlled Rectifier with floating P+ (HVDDSCR_FP+) is designed for CAN bus under 0.18 μm BCD process. In order to predict and verify the ESD performance of the device, TCAD two-dimensional device simulation and Transmission Line Pulse (TLP) test system were used. The experimental results show that the HVDDSCR_FP + structure has not only symmetrical positive and reverse I-V curves, but also the characteristics of high holding voltage and high failure current. Compared with the traditional HVDDSCR, HVDDSCR_FP+, at 25V forward and reverse trigger voltages (Vt), has increased its holding voltage (Vh) from 12V to 20V, failure current (It2) from 5A to 35A. In the actual tape-out process, it is found that the width of the N-well has a great influence on the performance of the device. After analyzing the reason and improving it, the leakage current of the device is reduced from μA level to nA level.
3
Guo, Bin, Dazheng Wang, Xu Zhou, Weichao Shi, and Fengmei Jing. "Performance Evaluation of a Tidal Current Turbine with Bidirectional Symmetrical Foils." Water 12, no. 1 (December 19, 2019): 22. http://dx.doi.org/10.3390/w12010022.
Повний текст джерелаАнотація:
As one might expect, tidal currents in terms of ebb and flood tides are approximately bidirectional. A Horizontal Axial Tidal Turbine (HATT) with unidirectional foils has to be able to face the current directions in order to maximize current energy harvesting. There are two regular solutions to keep a HATT always facing the direction of the flow, which are transferred from wind turbine applications. One is to yaw the turbine around the supporting structure with a yaw mechanism. The other is to reverse the blade pitch angle through 180° with a pitch-adjusting mechanism. The above solutions are not cost-effective in marine applications due to the harsh marine environment and high cost of installation and maintenance. In order to avoid the above disadvantages, a turbine with bidirectional foils is presented in this paper. A bare turbine with bidirectional foils is characterized in that it has nearly the same energy conversion capability in both tidal current directions without using the yaw or pitch mechanism. Considering the working conditions of the bidirectional turbine in which the turbine is installed on a mono-pile, the effect of the mono-pile on the turbine’s performance is evaluated in this paper, especially when the turbine is downstream of the mono-pile. The paper was focused on the evaluation of the hydrodynamic performance of the bidirectional turbine. The hydrodynamic performance of the bare bidirectional turbine without any supporting structure was evaluated based on a steady-state computational fluid dynamics (CFD) model and model tests. Performance comparison has been made between the turbine with bidirectional foils and the turbine with NACA foils. The effect of the mono-pile on the performance of the bidirectional turbine was studied by using the steady-state and the transient CFD model. The steady-state CFD model was used to evaluate the effect of the mono-pile clearance, which is the distance between the mono-pile and the turbine on the performance of the turbine. The transient CFD model was used to determine the time-dependent characteristics of the turbine, such as time-dependent power and drag coefficients. The results show that the bare bidirectional turbine has nearly the same energy conversion capability in both tidal current directions. The performance of the bidirectional turbine is inferior to the turbine with NACA foils. At the designed tip speed ratio, the power coefficient of the turbine with NACA foils is 0.4498, which increases by 1.6% compared to the 0.4338 of the bidirectional turbine. The turbine’s performance decreases due to the introduction of the mono-pile, and the closer the turbine is to the mono-pile, the greater effect on the turbine’s performance the mono-pile has. At the designed clearance of 1.5 DS, the presence of a mono-pile decreases the peak Cp value by 1.82% and 3.17% to a value of 0.4156 and 0.4004 for the turbine located in the mono-pile upstream and downstream, respectively. The mono-pile can result in the fluctuation of the turbine’s performance. This fluctuation will detrimentally harm the life of the turbine as it will lead to increased wear and fatigue issues.
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Iioka, Daisuke, Takahiro Fujii, Toshio Tanaka, Tsuyoshi Harimoto, Junpei Motoyama, and Daisuke Nagae. "Improvement of Voltage Unbalance by Current Injection Based on Unbalanced Line Impedance in Distribution Network with PV System." Energies 14, no. 23 (December 3, 2021): 8126. http://dx.doi.org/10.3390/en14238126.
Повний текст джерелаАнотація:
In this study, we have proposed a novel current injection determination method that improves the voltage unbalance based on the unbalanced line impedance in a distribution network with a large-capacity PV system. An increase in the unbalance of the distribution line voltage was observed owing to a large-scale reverse power flow. To visualize this phenomenon, the P-V curves were derived for each phase to indicate the increase in the voltage unbalance with respect to the reverse power flow. Based on the derived P-V curves, the effect of a current unbalance on the voltage unbalance was investigated. It was clarified that there is a current unbalance that can improve the voltage unbalance even if the line impedance is unbalanced. In other words, the current unbalance that can theoretically make the voltage unbalance zero could be expressed in terms of the symmetrical components of unbalanced line impedance. As an application of the proposed method, the effect of the mitigation of voltage unbalance was demonstrated by controlling single-phase reactors, whose numbers were determined by using the relationship between the unbalanced line current and unbalanced line impedance.
5
Lef, M. R., K. F. Yarn, C. C. Chen, and W. R. Chang. "GaAs Triac-like Triangular Barrier Switch Prepared by Molecular Beam Epitaxy." Active and Passive Electronic Components 24, no. 1 (2001): 1–11. http://dx.doi.org/10.1155/2001/29392.
Повний текст джерелаАнотація:
A new S-shaped negative differential resistance (NDR) switching device, prepared by molecular beam epitaxy (MBE), has been successfully developed in a GaAs double triangular barrier structure. Symmetrical bidirectional S-shaped NDR characteristics are observed experimentally. The bidirectional current-voltage (I–V) characteristics exhibit a new type of NDR caused by an avalanche multiplication process in reverse biased base-collector region and barrier redistribution. Under a base current injection with respect to the cathode, the device exhibits a conventional transistor with a current gain of 1.2 at room temperature. The experimentally electrical results can be easily understood by an equivalent circuit. In addition, a new optoelectronic switching device is also proposed which may have the potential for bidirectional wave length emission.
6
Overholt, J. L., A. Saulino, M. L. Drumm, and R. D. Harvey. "Rectification of whole cell cystic fibrosis transmembrane conductance regulator chloride current." American Journal of Physiology-Cell Physiology 268, no. 3 (March 1, 1995): C636—C646. http://dx.doi.org/10.1152/ajpcell.1995.268.3.c636.
Повний текст джерелаАнотація:
Whole cell epithelial cystic fibrosis transmembrane conductance regulator (CFTR) Cl- currents exhibited a linear current-voltage (I-V) relationship with high symmetrical transmembrane Cl- concentrations. However, when intracellular Cl- (Cli-) was reduced by replacement with glutamate, I-V relationships were outwardly rectifying. Rectification was not affected by reducing extracellular Cl- to eliminate or reverse the gradient, indicating that rectification is not a function of the Cl- gradient. Rectification was affected by Cli- in a concentration-dependent manner, and it was weaker when Cli- was reduced by replacement with sucrose. These characteristics are identical to those of the cardiac isoform of CFTR, and the experimental data could be simulated by an Eyring rate theory model assuming that permeating anions interact at a single binding site within the channel pore. No evidence was found for multiple binding sites. These results indicate that rectification is a function of the concentration and permeability of the anions inside the cell. It is concluded that rectification of CFTR Cl- current is a property of ion channel permeation that would occur under physiological conditions and that permeation of the epithelial and cardiac isoforms of CFTR is identical.
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Brzezinska, Anna K., Nicole Lohr, and William M. Chilian. "Electrophysiological effects of O2−· on the plasma membrane in vascular endothelial cells." American Journal of Physiology-Heart and Circulatory Physiology 289, no. 6 (December 2005): H2379—H2386. http://dx.doi.org/10.1152/ajpheart.00132.2005.
Повний текст джерелаАнотація:
Vascular dysfunction is a hallmark of many diseases, including coronary heart disease, stroke, and diabetes. The underlying mechanisms of these disorders are intimately associated with an increase in oxidative stress and excess generation of reactive oxygen species. Here, we report that the anionic free radical, superoxide (O2−·), directly affects the function of ion channels in vascular endothelial cells. Vascular endothelial cells were exposed to O2−· under physiological, symmetrical chloride and chloride-free conditions. Superoxide was generated from the reaction of xanthine (0.2 mM) and xanthine oxidase (0.1, 1, and 10 mU/ml) while its effects were determined with the whole cell mode of the patch-clamp technique. Inhibitors of K+ and Cl− channels were used to determine the role of these ion channels in mediating the electrophysiological effects of superoxide. The addition of O2−· caused a dose-dependent depolarization of endothelial cells and activation of the whole cell current. Activation of superoxide-dependent current was observed in the presence of inhibitors of K+ channels, Ba2+ (100 μM) or iberiotoxin (100 nM), and was not affected by inhibitors of nonselective cation channels, La3+, or by inhibition of the Cl−/HCO3− transporter by bumetanide. The inhibitors of the Cl− channel, NPPB (0.1 mM) or DIDS (100 μM), partially prevented activation of superoxide-dependent current but were unable to reverse it. The effects of superoxide on the amplitude of whole cell current were prevented and reversed by superoxide dismutase. Taken together, these results suggest that superoxide directly affects the function of ion channels in vascular endothelium but the mechanisms of its modulatory effects remain unresolved.
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Ding, Meng, Fan Yang, Qingquan Lv, and Qiongfang Liu. "Two coordination polymers: Crystal structures, prevention and nursing values on postoperative infection." Progress in Reaction Kinetics and Mechanism 47 (January 2022): 146867832210903. http://dx.doi.org/10.1177/14686783221090376.
Повний текст джерелаАнотація:
In this current work, two fresh transition metal coordination polymers (CPs) have been created with the reaction between terphenyl-3,3″,5,5″-tetracarboxylic acid (H4L), the symmetrical rigid carboxylic acid ligand and the relevant metal salts under the reaction conditions of solvothermal, and the chemical compositions of the compounds respectively are {[Cu2(TPTC) (DMF)2(H2O)]·2DMF·2H2O} (2) and {[Zn (TPTC) (1,2-bimb)2]·4(H2O)}n (1, bimb = 1,2-bis((1H-imidazol-1-yl)methyl)benzene). Moreover, the prevention and nursing values of the compound on postoperative infection was explored and their corresponding mechanism also was investigated. Firstly, enzyme linked immunosorbent assay kit (ELISA) was employed to detect the release of inflammatory cytokines into plasma. Additionally, the expression of the bacterial survival genes was determined via exploiting the real time reverse transcription-polymerase chain reaction (RT-PCR) after treated with the compound.
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Dero, Dr Sumera, Ghulam Hyder Talpur, Abbas Ali Ghoto, and Shokat Ali. "Mathematical Analysis of Magnetized Rotating Nanofluid Flow Over nonlinear shrinking surface: Duality and Stability." Sukkur IBA Journal of Computing and Mathematical Sciences 5, no. 2 (December 28, 2021): 1–13. http://dx.doi.org/10.30537/sjcms.v5i2.880.
Повний текст джерелаАнотація:
In this study, the MHD effect on boundary layer rotating flow of a nanofluid is investigated for the multiple branches case. The main focus of current research is to examine flow characteristics on a nonlinear permeable shrinking sheet. Moreover, the governing partial differential equations (PDEs) of the problem considered are reduced into coupled nonlinear ordinary differential equations (ODEs) with the appropriate similarity transformation. Numerical results based on the plotted graphs are gotten by solving ODEs with help of the three-stage Labatto IIIA method in bvp4c solver in MATLAB. To confirm numerical outcomes, current results are compared with previously available outcomes and found in good agreement. Skin friction coefficients, Nusselt and Sherwood numbers, velocity profiles, temperature profiles, and concentration profiles are examined. The results show that dual (no) branches exist in certain ranges of the suction parameter i.e., SSc (SSc). Further, profiles of velocity decrease for rising values of Hartmann number in the upper branch, while reverse trend has been noticed in a lower branch. Profiles of temperature and concentration enhance for the increasing values of thermophoresis in both branches. stability analysis of the branches is also done and noticed that upper branch is a stable branch from both branches. Finally, it is noted that the stable branch has symmetrical behavior with regard to the parameter of rotation.
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Freudenberg, J., H. Boriss, and D. Hasenclever. "Comparison of Preprocessing Procedures for Oligo-nucleotide Micro-arrays by Parametric Bootstrap Simulation of Spike-in Experiments." Methods of Information in Medicine 43, no. 05 (2004): 434–38. http://dx.doi.org/10.1055/s-0038-1633893.
Повний текст джерелаАнотація:
Summary Objective: Due to scarcity of calibration data for micro-array experiments, simulation methods are employed to assess preprocessing procedures. Here we analyze several procedures’ robustness against increasing numbers of differentially expressed genes and varying proportions of up-regulation. Methods: Raw probe data from oligo-nucleotide micro-arrays are assumed to be approximately multivariate normally distributed on the log scale. Chips can be simulated from a multivariate normal distribution with mean and variance-covariance matrix estimated from a real raw data set.A chip effect induces strong positive correlations. In reverse, sampling from a normal distribution with strong correlation variance-covariance matrix generates data exhibiting a chip effect. No explicit model of chip-effect is needed. Differences can be artificially spiked-in according to a given distribution of effect sizes.Thirty preprocessing procedures combining background correction, normalization, perfect match correction and summarization methods available from the BioConductor project were compared. Results: In the symmetrical setting “50% differentially expressed genes, 50% of which up-regulated” background correction reduces bias, but inflates low intensity probe variance as well as the mean squared error of the estimates. Any normalization reduces variance and increases sensitivity with no clear winner. Asymmetry between up and down regulation causes bias in the effect-size estimate of non-differentially expressed genes. This markedly inflates the false positive discovery rates. Variance stabilizing normalization (VSN) behaved best. Conclusion: A simple parametric bootstrap was used to simulate oligo-nucleotide micro-array raw data. Current normalization methods inflate the false positive rate when many genes show an effect in the same direction.
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Devor, Daniel C., та Joseph M. Pilewski. "UTP inhibits Na+ absorption in wild-type and ΔF508 CFTR-expressing human bronchial epithelia". American Journal of Physiology-Cell Physiology 276, № 4 (1 квітня 1999): C827—C837. http://dx.doi.org/10.1152/ajpcell.1999.276.4.c827.
Повний текст джерелаАнотація:
Ca2+-mediated agonists, including UTP, are being developed for therapeutic use in cystic fibrosis (CF) based on their ability to modulate alternative Cl− conductances. As CF is also characterized by hyperabsorption of Na+, we determined the effect of mucosal UTP on transepithelial Na+transport in primary cultures of human bronchial epithelia (HBE). In symmetrical NaCl, UTP induced an initial increase in short-circuit current ( I sc) followed by a sustained inhibition. To differentiate between effects on Na+ absorption and Cl− secretion, I sc was measured in the absence of mucosal and serosal Cl−( I Na). Again, mucosal UTP induced an initial increase and then a sustained decrease that reduced amiloride-sensitive I Na by 73%. The Ca2+-dependent agonists histamine, bradykinin, serosal UTP, and thapsigargin similarly induced sustained inhibition (62–84%) of I Na. Mucosal UTP induced similar sustained inhibition (half-maximal inhibitory concentration 296 nM) of I Na in primary cultures of human CF airway homozygous for the ΔF508 mutation. BAPTA-AM blunted UTP-dependent inhibition of I Na, but inhibitors of protein kinase C (PKC) and phospholipase A2 had no effect. Indeed, direct activation of PKC by phorbol 12-myristate 13-acetate failed to inhibit Na+ absorption. Apyrase, a tri- and diphosphatase, did not reverse inhibitory effects of UTP on I Na, suggesting a long-term inhibitory effect of UTP that is independent of receptor occupancy. After establishment of a mucosa-to-serosa K+ concentration gradient and permeabilization of the mucosal membrane with nystatin, mucosal UTP induced an initial increase in K+current followed by a sustained inhibition. We conclude that increasing cellular Ca2+ induces a long-term inhibition of transepithelial Na+transport across normal and CF HBE at least partly due to downregulation of a basolateral membrane K+ conductance. Thus UTP may have a dual therapeutic effect in CF airway: 1) stimulation of a Cl− secretory response and 2) inhibition of Na+ transport.
12
Korovin, Aleksandr V., and Ivan V. Aleksandrov. "COORDINATE TRANSFORMATIONS OF THREE-PHASE VARIABLES USING QUATERNIONS." Vestnik Chuvashskogo universiteta, no. 1 (March 30, 2022): 65–72. http://dx.doi.org/10.47026/1810-1909-2022-1-65-72.
Повний текст джерелаАнотація:
Among the variety of modern approaches to the mathematical description of the power quality indicators during the processes of transmission, distribution, conversion and calculation of the ac electric power, the representation of three-phase models in the form of a purely imaginary quaternion located in a separate subspace of the four-dimensional hypercomplex space allows, in relation to the generally accepted method of analyzing linear circuits, for example, symmetrical components with the selection of a direct, reverse and zero phase sequence for the fundamental harmonic, to take into a more complete account the features of energy consumption, especially in the presence of distortion in the modified forms of harmonic signals. In addition, the division of the quaternion into scalar (real) and partial (imaginary) makes it possible to significantly simplify the subsequent analytical processing of synthesis of a power converters control signals for active filtering and power supply of autonomous loads of an arbitrary type, including a single-phase configuration, by extracting from its composition individual components responsible for both the amplitude-phase asymmetry and the nonlinearity of the characteristics.
The main algorithmic principles of organizing control structures as part of three-phase systems of various functional purposes, as a rule, are based on the conversion of reference signals and current values of measured currents and voltages into state coordinates obtained by rotating the three-dimensional space plane by a given angle. At the same time, the calculated ratios for the numerical determination of the initial variables transformed by rotation in the quaternion basis are a function of only four kinematic parameters, which, other things being equal, leads to a simplification of the control law in relation to the traditional vector-matrix approach using nine direction cosines with six connection equations. In this regard, this paper is devoted to the applied problems of implementing linear transformations by E. Clarke and R.H. Park in terms of four-dimensional hypercomplex numbers, in compliance with the additional requirement of the invariance of scalar quantities after the transition.
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Cao, Chunhua, Whaseon Lee-Kwon, Erik P. Silldorff, and Thomas L. Pallone. "KATP channel conductance of descending vasa recta pericytes." American Journal of Physiology-Renal Physiology 289, no. 6 (December 2005): F1235—F1245. http://dx.doi.org/10.1152/ajprenal.00111.2005.
Повний текст джерелаАнотація:
Using nystatin-perforated patch-clamp and whole cell recording, we tested the hypothesis that KATP channels contribute to resting conductance of rat descending vasa recta (DVR) pericytes and are modulated by vasoconstrictors. The KATP blocker glybenclamide (Glb; 10 μM) depolarized pericytes and inhibited outward currents of cells held at −40 mV. KATP openers pinacidil (Pnc; 10 μM) and P-1075 (1 μM) hyperpolarized pericytes and transiently augmented outward currents. All effects of Pnc and P-1075 were fully reversed by Glb. Inward currents of pericytes held at −60 mV in symmetrical 140 mM K+ were markedly augmented by Pnc and fully reversed by Glb. Ramp depolarizations in symmetrical K+, performed in Pnc and Pnc + Glb, yielded a Pnc-induced, Glb-sensitive KATP difference current that lacked rectification and reversed at 0 mV. Immunostaining identified both KIR6.1, KIR6.2 inward rectifier subunits and sulfonurea receptor subtype 2B. ANG II (1 and 10 nM) and endothelin-1 (10 nM) but not vasopressin (100 nM) significantly lowered holding current at −40 mV and abolished Pnc-stimulated outward currents. We conclude that DVR pericytes express KATP channels that make a significant contribution to basal K+ conductance and are inhibited by ANG II and endothelin-1.
14
Toland, H. M., K. D. McCloskey, K. D. Thornbury, N. G. McHale, and M. A. Hollywood. "Ca2+-activated Cl− current in sheep lymphatic smooth muscle." American Journal of Physiology-Cell Physiology 279, no. 5 (November 1, 2000): C1327—C1335. http://dx.doi.org/10.1152/ajpcell.2000.279.5.c1327.
Повний текст джерелаАнотація:
Freshly dispersed sheep mesenteric lymphatic smooth muscle cells were studied at 37°C using the perforated patch-clamp technique with Cs+- and K+-filled pipettes. Depolarizing steps evoked currents that consisted ofl-type Ca2+ [ I Ca(L)] current and a slowly developing current. The slow current reversed at 1 ± 1.5 mV with symmetrical Cl− concentrations compared with 23.2 ± 1.2 mV ( n = 5) and −34.3 ± 3.5 mV ( n = 4) when external Cl− was substituted with either glutamate (86 mM) or I− (125 mM). Nifedipine (1 μM) blocked and BAY K 8644 enhanced I Ca(L), the slow-developing sustained current, and the tail current. The Cl− channel blocker anthracene-9-carboxylic acid (9-AC) reduced only the slowly developing inward and tail currents. Application of caffeine (10 mM) to voltage-clamped cells evoked currents that reversed close to the Cl− equilibrium potential and were sensitive to 9-AC. Small spontaneous transient depolarizations and larger action potentials were observed in current clamp, and these were blocked by 9-AC. Evoked action potentials were triphasic and had a prominent plateau phase that was selectively blocked by 9-AC. Similarly, fluid output was reduced by 9-AC in doubly cannulated segments of spontaneously pumping sheep lymphatics, suggesting that the Ca2+-activated Cl− current plays an important role in the electrical activity underlying spontaneous activity in this tissue.
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Whitney, Michael M., and J. S. Allen. "Coastal Wind-Driven Circulation in the Vicinity of a Bank. Part II: Modeling Flow over the Heceta Bank Complex on the Oregon Coast." Journal of Physical Oceanography 39, no. 6 (June 1, 2009): 1298–316. http://dx.doi.org/10.1175/2008jpo3967.1.
Повний текст джерелаАнотація:
Abstract This study investigates wind-driven circulation in the vicinity of the Heceta Bank complex along the Oregon shelf. Numerical experiments forced with steady winds (0.1 Pa) are conducted; upwelling and downwelling cases are compared. The asymmetric bank bathymetry is the only configurational difference from the symmetric bank runs analyzed in Part I (Whitney and Allen). Upwelling-favorable winds generate an upwelling front and southward baroclinic jet. Model results indicate the upwelling jet is centered on the 100-m isobath along the straight shelf. The jet follows this isobath offshore around the northern part of the bank but separates from sharply turning isobaths in the southern half and flows over deeper waters. The jet turns back toward the coast farther downstream. Inshore of the main jet, currents reverse and flow back onto the bank. These reversed currents turn southward again (at the bank center) and join a secondary southward coastal upwelling jet. This secondary coastal jet converges with the stronger main jet farther downstream. Upwelling is intense at the northern bank edge near the coast, where a dense water tongue is advected over the bank. Upwelling also is strong on the southern bank half where the flow turns and reverses. Other areas of the bank have reduced upwelling or even downwelling during upwelling-favorable winds. Downwelling-favorable winds drive a near-bottom density front and a northward jet. The slower downwelling jet flows along the 130-m isobath over the straight shelf. The jet departs from isobaths over the southern bank half and follows a straighter path over shallower waters. There are no reversed currents over the bank. The bank is an area of reduced downwelling. Some of the differences in the evolution of the current and density fields are linked to fundamental differences between the upwelling and downwelling regimes; these are anticipated by the symmetric bank results of Part I. Other differences arise because of the bank asymmetry and opposite flow directions over the bank. The lowest-order depth-averaged across-stream momentum balance remains geostrophic over the bank. Advection, ageostrophic pressure gradients, wind stress, and bottom stress all are important in the depth-averaged alongstream momentum balance over the Heceta Bank complex. Both across-shelf and alongshelf density advection are important. Barotropic potential vorticity is not conserved over the bank, but the tendency for relative vorticity changes and depth changes to partially counter each other influences the different paths of the upwelling and downwelling jets. There are several regions of active upwelling and downwelling over the bank. In these areas, vertical velocities at the top of the bottom boundary layer are linked to topographic upwelling and downwelling and Ekman pumping. There is considerable spatial variability in the currents, densities, and dynamics over the Heceta Bank complex.
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Li, Ji-Hong, Min-Gyu Kim, Hyungjoo Kang, Mun-Jik Lee, and Gun Cho. "UUV Simulation Modeling and its Control Method: Simulation and Experimental Studies." Journal of Marine Science and Engineering 7, no. 4 (March 28, 2019): 89. http://dx.doi.org/10.3390/jmse7040089.
Повний текст джерелаАнотація:
This paper presents the development of an unmanned underwater vehicle (UUV) platform, especially the derivation of the vehicle’s simulation model and its control method to overcome strong sea current. The platform is designed to have a flattened ellipsoidal exterior so as to minimize the hydrodynamic damping on the horizontal plane. Four horizontal thrusters with the identical specifications are symmetrically mounted on the horizontal plane, and each of them has the same thrust dynamics in both forward and reverse directions. In addition, there are three vertical thrusters used to handle the vehicle’s roll, pitch and heave motions. Control strategy proposed in this paper to overcome strong current is that: maximizing the vectored horizontal thrust force against the sea current without or with the least of the vehicle’s rotation on the horizontal plane. For the vehicle model, due to it being symmetric in all of three axes, the vehicle dynamics can be simplified and all of hydrodynamic coefficients are calculated through both of theoretical and empirically-derived formulas. Numerical simulations and experimental studies in both of the water tank and the circulating water channel are carried out to demonstrate the vehicle’s capability of overcoming strong current.
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Melrose, D. B., Jennifer Nicholls, and N. G. Broderick. "Surface currents on models of force-free solar magnetic flux tubes." Journal of Plasma Physics 51, no. 1 (February 1994): 163–76. http://dx.doi.org/10.1017/s0022377800017451.
Повний текст джерелаАнотація:
A model of a cylindrically symmetric, force-free magnetic field consisting of a sequence of concentric layers with piecewise-constant α is used to construct models of the surface currents on isolated, force-free magnetic flux tubes. Two boundary conditions are considered: a current-neutralized flux tube (Bφ = 0, Bz φ 0, Bz ≠ O at r > r0), and an isolated current-carrying flux tube (Bφ ≠ 0, Bz = 0 at r > r0). A single-a model that is current-neutralized is a reverse-field pinch, and is unacceptable as a model for a solar flux tube. Examples of two-α models for a current-neutralized flux tube are presented. The models of the surface currents satisfying either boundary condition are shown to simplify considerably when the surface layer is thin. A model consisting of several layers, with piecewise-constant α, may be used to find an approximate solution for a force-free flux tube with an arbitrarily specified current profile.
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DAN, DEBASIS, A. M. JAYANNAVAR, and MANGAL C. MAHATO. "EFFICIENCY AND CURRENT REVERSALS IN SPATIALLY INHOMOGENEOUS RATCHETS." International Journal of Modern Physics B 14, no. 15 (June 20, 2000): 1585–91. http://dx.doi.org/10.1142/s0217979200001291.
Повний текст джерелаАнотація:
Efficiency of generation of net unidirectional current in an adiabatically driven symmetric periodic potential system is studied. The efficiency shows a maximum, in the case of an inhomogeneous system with spatially varying periodic friction coefficient, as a function of temperature. The ratchet is not most efficient when it gives maximum current. The direction of current may also be reversed as a function of noise strength when, instead, an asymmetric periodic potential is considered.
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Kim, Min-Gyu, Hyungjoo Kang, Mun-Jik Lee, Gun Rae Cho, Ji-Hong Li, and Cheol Kim. "UUV Platform Optimal Design for Overcoming Strong Current." Journal of Ocean Engineering and Technology 35, no. 6 (December 31, 2021): 434–45. http://dx.doi.org/10.26748/ksoe.2021.069.
Повний текст джерелаАнотація:
This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle’s horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle’s rotation and maintaining its heading. However, for the numerical simulations, the vehicle’s hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle’s various final performances, including its ability to overcome strong current.
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McCann, J. D., M. Li, and M. J. Welsh. "Identification and regulation of whole-cell chloride currents in airway epithelium." Journal of General Physiology 94, no. 6 (December 1, 1989): 1015–36. http://dx.doi.org/10.1085/jgp.94.6.1015.
Повний текст джерелаАнотація:
We used the whole-cell patch-clamp technique to study membrane currents in human airway epithelial cells. The conductive properties, as described by the instantaneous current-voltage relationship, rectified in the outward direction when bathed in symmetrical CsCl solutions. In the presence of Cl concentration gradients, currents reversed near ECl and were not altered significantly by cations. Agents that inhibit the apical membrane Cl conductance inhibited Cl currents. These conductive properties are similar to the conductive properties of the apical membrane Cl channel studied with the single-channel patch-clamp technique. The results suggest that the outwardly rectifying Cl channel is the predominant Cl-conductive pathway in the cell membrane. The steady-state and non-steady-state kinetics indicate that current flows through ion channels that are open at hyperpolarizing voltages and close with depolarization. These Cl currents were regulated by the cAMP-dependent protein kinase: when the catalytic subunit of cAMP-dependent protein kinase was included in the pipette solution, Cl channel current more than doubled. We also found that reducing extracellular osmolarity by 30% increased Cl current, suggesting that cell-swelling stimulated Cl current. Studies of transepithelial Cl transport in cell monolayers suggest that a reduction in solution osmolarity activates the apical Cl channel: reducing extracellular osmolarity stimulated a short-circuit current that was inhibited by Cl-free solution, by mucosal addition of a Cl channel antagonist, and by submucosal addition of a loop diuretic. These results suggest that apical membrane Cl channels may be regulated by cell volume and by the cAMP-dependent protein kinase.
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Araki, I. "Inhibitory postsynaptic currents and the effects of GABA on visually identified sacral parasympathetic preganglionic neurons in neonatal rats." Journal of Neurophysiology 72, no. 6 (December 1, 1994): 2903–10. http://dx.doi.org/10.1152/jn.1994.72.6.2903.
Повний текст джерелаАнотація:
1. The actions of gamma-aminobutyric acid (GABA) on sacral parasympathetic preganglionic (SPP) neurons were examined in slice preparations using the whole cell patch-clamp technique. 2. Inhibitory postsynaptic currents (IPSCs), which were evoked by focal electrical stimulation, were recorded from SPP neurons in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a glutamate receptor antagonist. The IPSCs were substantially reduced by strychnine (1 microM), a glycine receptor antagonist. The remaining IPSCs were completely blocked by bicuculline (20 microM), a GABAA receptor antagonist. The mean peak amplitude of bicuculline-sensitive, GABAergic currents recorded at -60 mV was 53.6 +/- 10.9%, mean +/- SD (n = 8), of that of the total IPSCs. The GABAergic currents were reversed in polarity at about -30 mV, near the Cl- equilibrium potential. 3. GABA (5-50 microM) induced inward currents in SPP neurons with symmetrical internal and external Cl- concentrations. This response was completely blocked by 100 microM bicuculline. Muscimol (2-8 microM), a GABAA agonist, mimicked the GABA-induced responses, whereas a GABAB receptor agonist, baclofen (20-200 microM), produced responses in only a few cells. The GABA-induced currents reversed their polarity at approximately 0 mV, near the Cl- equilibrium potential. When the internal Cl- concentration was reduced, the reversal potential was shifted according to the Nernst equation for Cl-. 4. GABA-induced currents exhibited an outward "hump" between -35 and 15 mV. This voltage range coincided with that at which a depolarization-induced inward whole cell current was elicited.(ABSTRACT TRUNCATED AT 250 WORDS)
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Cittanti, Davide, Cristoph Gammeter, Jonas Huber, Radu Bojoi, and Johann W. Kolar. "A Simplified Hard-Switching Loss Model for Fast-Switching Three-Level T-Type SiC Bridge-Legs." Electronics 11, no. 11 (May 25, 2022): 1686. http://dx.doi.org/10.3390/electronics11111686.
Повний текст джерелаАнотація:
Hard-switching losses in three-level T-type (3LTT) bridge-legs cannot be directly estimated from datasheet energy loss curves, which are given for symmetric two-level half-bridge configurations only. The commutations in a 3LTT bridge-leg occur between semiconductors with different blocking voltages and/or current ratings, and involve a third semiconductor device in the switching transition, which contributes additional capacitive losses. This paper, therefore, describes a simplifed approach to estimate a lower bound for the hard-switching losses of 3LTT bridge-legs (note that the approach is applicable to other three-level topolgies as well). In view of the very fast switching speeds of wide-bandgap semiconductors, the model neglects voltage/current overlap losses and considers only the dominating charge-related loss contributions (semiconductor output capacitances, body diode reverse-recovery charge), thus requiring minimal information from datasheets. A direct experimental verification with an 800 V DC-link 3LTT bridge-leg (1200 V and 650 V SiC MOSFETs) operating with output currents up to 25 A confirms the good accuracy of the simplified switching-loss model.
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Ren, Zuojun, and Clive M. Baumgarten. "Antagonistic regulation of swelling-activated Cl− current in rabbit ventricle by Src and EGFR protein tyrosine kinases." American Journal of Physiology-Heart and Circulatory Physiology 288, no. 6 (June 2005): H2628—H2636. http://dx.doi.org/10.1152/ajpheart.00992.2004.
Повний текст джерелаАнотація:
Regulation of swelling-activated Cl− current ( ICl,swell) is complex, and multiple signaling cascades are implicated. To determine whether protein tyrosine kinase (PTK) modulates ICl,swell and to identify the PTK involved, we studied the effects of a broad-spectrum PTK inhibitor (genistein), selective inhibitors of Src (PP2, a pyrazolopyrimidine) and epidermal growth factor receptor (EGFR) kinase (PD-153035), and a protein tyrosine phosphatase (PTP) inhibitor (orthovanadate). ICl,swell evoked by hyposmotic swelling was increased 181 ± 17% by 100 μM genistein, and the genistein-induced current was blocked by the selective ICl,swell blocker tamoxifen (10 μM). Block of Src with PP2 (10 μM) stimulated tamoxifen-sensitive ICl,swell by 234 ± 27%, mimicking genistein, whereas the inactive analog of PP2, PP3 (10 μM), had no effect. Moreover, block of PTP by orthovanadate (1 mM) inhibited ICl,swell and prevented its stimulation by PP2. In contrast with block of Src, block of EGFR kinase with PD-153035 (20 nM) inhibited ICl,swell. Several lines of evidence argue that the PP2-stimulated current was ICl,swell: 1) the stimulation was volume dependent, 2) the current was blocked by tamoxifen, 3) the current outwardly rectified with both symmetrical and physiological Cl− gradients, and 4) the current reversed near the Cl− equilibrium potential. To rule out contributions of other currents, Cd2+ (0.2 mM) and Ba2+ (1 mM) were added to the bath. Surprisingly, Cd2+ suppressed the decay of ICl,swell, and Cd2+ plus Ba2+ eliminated time-dependent currents between −100 and +100 mV. Nevertheless, these divalent ions did not eliminate ICl,swell or prevent its stimulation by PP2. The results indicate that tyrosine phosphorylation controls ICl,swell, and regulation of ICl,swell by the Src and EGFR kinase families of PTK is antagonistic.
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Cao, Chunhua, Jae Hwan Goo, Whaseon Lee-Kwon, and Thomas L. Pallone. "Vasa recta pericytes express a strong inward rectifier K+ conductance." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290, no. 6 (June 2006): R1601—R1607. http://dx.doi.org/10.1152/ajpregu.00877.2005.
Повний текст джерелаАнотація:
Strong inward rectifier potassium channels are expressed by some vascular smooth muscle cells and facilitate K+-induced hyperpolarization. Using whole cell patch clamp of isolated descending vasa recta (DVR), we tested whether strong inward rectifier K+ currents are present in smooth muscle and pericytes. Increasing extracellular K+ from 5 to 50 and 140 mmol/l induced inward rectifying currents. Those currents were Ba2+ sensitive and reversed at the K+ equilibrium potential imposed by the electrode and extracellular buffers. Ba2+ binding constants in symmetrical K+ varied between 0.24 and 24 μmol/l at −150 and −20 mV, respectively. Ba2+ blockade was time and voltage dependent. Extracellular Cs+ also blocked the inward currents with binding constants between 268 and 4,938 μmol/l at −150 and −50 mV, respectively. Ba2+ (30 μmol/l) and ouabain (1 mmol/l) depolarized pericytes by an average of 11 and 24 mV, respectively. Elevation of extracellular K+ from 5 to 10 mmol/l hyperpolarized pericytes by 6 mV. That hyperpolarization was reversed by Ba2+ (30 μmol/l). We conclude that strong inward rectifier K+ channels and Na+-K+-ATPase contribute to resting potential and that KIR channels can mediate K+-induced hyperpolarization of DVR pericytes.
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Reimchen, T. E., and P. Nosil. "Dietary differences between phenotypes with symmetrical and asymmetrical pelvis in the stickleback Gasterosteus aculeatus." Canadian Journal of Zoology 79, no. 3 (March 1, 2001): 533–39. http://dx.doi.org/10.1139/z01-006.
Повний текст джерелаАнотація:
Differential parasitism among phenotypes within populations can result from intrinsic factors such as immunocompetence or extrinsic factors such as ecological overlap with pathogens. In a recent study of a population of sticklebacks (Gasterosteus aculeatus) from Boulton Lake, British Columbia, relative cestode infections were related to pelvic-girdle symmetry. Adult sticklebacks with an asymmetrical pelvis had a higher incidence of infections than fish with a symmetrical pelvis, yet the pattern was reversed among yearlings. In the current study we test whether this unexpected result for yearlings, which is inconsistent with general theory coupling asymmetry with reduced immuno competence, might be due to ecological factors rather than to differences in immunocompetence. We analyze the diet of 9089 uninfected sticklebacks collected during a 15-year study and show that male and female yearling sticklebacks with an asymmetrical pelvis are more benthic than symmetrical phenotypes. This could reduce the probability of exposure to pelagic copepods, the primary hosts of the cestode Schistocephalus solidus, and thereby lead to lower infection rates relative to pelagic fish. This finding would account for the unusual reversal in relative parasitism in this population and raises the possibility of finding further diet-induced causes of differential parasitism in studies of asymmetry.
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Huang, Yaren, Benedikt Lechner, and Gerhard Wachutka. "Comparative Numerical Analysis of the Robustness of Si and SiC PiN Diodes Against Cosmic Radiation-Induced Failure." Materials Science Forum 1004 (July 2020): 1088–96. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.1088.
Повний текст джерелаАнотація:
This work aims at extending the predictive simulation technique for cosmic ray-induced failure analysis from Si PiN diodes [1] to SiC PiN diodes. Accurate 3D cylindrical-symmetric transient simulations were performed with a minimum mesh size of 20nm at the center track of the impinging ion and a maximum time step of 0.1ps during the development of the ion-induced transient current. We made a comparative study between a SiC PiN diode and a Si PiN diode with the same blocking voltage of 1.5kV, using the same heavy ion transportation models. In the simulation, we observed different ion-induced current transients, differing not only in the peak value of the current, but also in its duration. Due to different physical mechanisms, the dependence of the ion-induced current on the reverse pre-bias voltage and the numerical mesh adaptations are also different. Eventually, we brieflydiscuss electro-thermal simulations, which indicate once more that the ion-induced transient current in the SiC PiN diodes under consideration is primarily drift current and involves only negligible impact ionization.
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Watterson, Peter A. "Infinite contraction in force-free magnetic field evolution in cylindrical geometry." Journal of Plasma Physics 35, no. 2 (April 1986): 273–93. http://dx.doi.org/10.1017/s0022377800011338.
Повний текст джерелаАнотація:
This paper provides a new formulation of the resistive force-free evolution of cylindrically symmetric magnetic fields subject to purely radial motions. It is shown analytically that the evolution bounded by a perfect conductor ceases to exist after a finite time if the initial field has total axial flux of opposite sign to the field on the axis of symmetry. A numerical solution indicates that the evolution ceases to exist owing to the unlimited contraction of the field profile producing a line of infinite current density. The asymptotic form of this ‘blow-up’ is identified as the particular self-similar contraction for which the field direction is exactly reversed in the limit of large radius. Possible applications to solar flares and the reversed-field pinch are discussed.
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Poklonski, N. A., A. I. Kovalev, N. I. Gorbachuk та S. V. Shpakovski. "CALCULATION OF STATIC PARAMETERS OF SILICON DIODE CONTAINING δ-LAYER OF TRIPLE-CHARGED POINT DEFECTS IN SYMMETRIC p–n-JUNCTION". Devices and Methods of Measurements 9, № 2 (15 червня 2018): 130–41. http://dx.doi.org/10.21122/2220-9506-2018-9-2-130-141.
Повний текст джерелаАнотація:
The study of semiconductor materials and devices containing a narrow layer of impurity atoms and/or intrinsic point defects of the crystal lattice is of fundamental and practical interest. The aim of the study is to calculate the electric parameters of a symmetric silicon diode, in the flat p–n-junction of which a δ-layer of point triple-charged t-defects is formed. Such a diode is called p–t–n-diode, similarly to p–i–n-diode.Each t-defect can be in one of the three charge states (−1, 0, and +1; in the units of the elementary charge). It is assumed that at room temperature all hydrogen-like acceptors in p-region and hydrogen-like donors in n-region are ionized. It was assumed that the cross-section for v-band hole capture on t-defects is greater than the cross-section for c-band electron capture on t-defects.The system of stationary nonlinear differential equations, which describe in the drift-diffusion approximation a migration of electrons and holes in semiconductors, is solved numerically. The static capacityvoltage and current-voltage characteristics of the silicon diode with nondegenerate regions of pand n-type of electrical conductivity are calculated for forward and reverse electric bias voltage.It is shown by calculation that in the p–t–n-diode containing the δ-layer of t-defects, at the forward bias a region of current density stabilization occurs. At the reverse bias the current density in such a diode is much greater than the one in a p–n-diode without t-defects. With the reverse bias the capacitance of the p–t–n-diode, in contrast to the p–n-diode, increases at first and then decreases.
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Salahuddin, Shairfe Muhammad, and Volkan Kursun. "Write Assist SRAM Cell with Asymmetrical Bitline Access Transistors for Enhanced Data Stability and Write Ability." Journal of Circuits, Systems and Computers 25, no. 01 (November 15, 2015): 1640009. http://dx.doi.org/10.1142/s0218126616400090.
Повний текст джерелаАнотація:
A novel six-transistor static random-access memory (6T SRAM) cell is proposed in this paper for enhancing the data stability and write ability as compared to the conventional memory circuits. Asymmetrically gate overlapped / underlapped FinFETs are employed as bitline access transistors in the proposed SRAM cell. The strength of the asymmetrical bitline access transistors are weakened during read operations. Furthermore, voltage transfer characteristics (VTCs) of cross-coupled inverters have narrower transition regions in the new SRAM cell as compared to the conventional SRAM cells. The proposed SRAM cell thereby provides stronger read data stability as compared to the conventional symmetrical SRAM cells. The strength of bitline access transistors are enhanced during write operations as the direction of current flow is reversed in the new asymmetrical SRAM cell. The power supply voltage of a selected word floats during write operations. The write voltage margin is thereby significantly increased with the proposed SRAM cell as compared to the conventional SRAM cells. The read data stability and write ability are both enhanced by up to 51.7% and 65.5%, respectively, with the proposed SRAM cell as compared to the conventional symmetrical six-FinFET SRAM cells in a 15[Formula: see text]nm FinFET technology.
30
Devor, D. C., S. M. Simasko, and M. E. Duffey. "Carbachol induces oscillations of membrane potassium conductance in a colonic cell line, T84." American Journal of Physiology-Cell Physiology 258, no. 2 (February 1, 1990): C318—C326. http://dx.doi.org/10.1152/ajpcell.1990.258.2.c318.
Повний текст джерелаАнотація:
Effects of carbachol on membrane potential and current in T84 cells were determined using whole cell patch-clamp techniques. When the pipettes contained a standard KCl solution and the bath contained a standard NaCl solution, carbachol (100 microM) caused a rapid hyperpolarization to the K+ equilibrium potential (EK+), followed by potential oscillations. When membrane potential was clamped to 0 mV, carbachol induced an outwardly directed K+ current in 31 of 37 cells, with a peak value of 618 +/- 51 (SE) pA. In 77% of these cells the current oscillated and gradually declined to base line. Atropine (20 microM) blocked this response. In symmetric KCl solutions the carbachol-induced current reversed at 0 mV with no rectification. Ba2+ or Cs+ did not block the current, but tetraethylammonium ion (TEA) reduced the number of responding cells. Although a Cl- conductance was found in resting cells, carbachol did not cause an increase in Cl- current when the cells were voltage-clamped to EK+, or when voltage-clamped to +/- 60 mV while bathed in symmetric NaCl solutions. When the Ca2(+)-buffering capacity of the pipette solution was increased, 80% of the cells responded to carbachol, but only 10% oscillated; however, no K+ current was induced by carbachol when the pipette was made nominally Ca2+ free. The current was not affected by removal of Ca2+ from the bath. These results show that carbachol induces an oscillating Ca2(+)-activated K+ conductance in T84 cells, but no Cl- conductance. This K+ conductance is dependent on the mechanisms that regulate intracellular Ca2+.
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García-Díaz, J. F. "Whole-cell and single channel K+ and Cl- currents in epithelial cells of frog skin." Journal of General Physiology 98, no. 1 (July 1, 1991): 131–61. http://dx.doi.org/10.1085/jgp.98.1.131.
Повний текст джерелаАнотація:
Whole-cell and single channel currents were studied in cells from frog (R. pipiens and R. catesbiana) skin epithelium, isolated by collagenase and trypsin treatment, and kept in primary cultures up to three days. Whole-cell currents did not exhibit any significant time-dependent kinetics under any ionic conditions used. With an external K gluconate Ringer solution the currents showed slight inward rectification with a reversal potential near zero and an average conductance of 5 nS at reversal. Ionic substitution of the external medium showed that most of the cell conductance was due to K and that very little, if any, Na conductance was present. This confirmed that most cells originate from inner epithelial layers and contain membranes with basolateral properties. At voltages more positive than 20 mV outward currents were larger with K in the medium than with Na or N-methyl-D-glucamine. Such behavior is indicative of a multi-ion transport mechanism. Whole-cell K current was inhibited by external Ba and quinidine. Blockade by Ba was strongly voltage dependent, while that by quinidine was not. In the presence of high external Cl, a component of outward current that was inhibited by the anion channel blocker diphenylamine-2-carboxylate (DPC) appeared in 70% of the cells. This component was strongly outwardly rectifying and reversed at a potential expected for a Cl current. At the single channel level the event most frequently observed in the cell-attached configuration was a K channel with the following characteristics: inward-rectifying I-V relation with a conductance (with 112.5 mM K in the pipette) of 44 pS at the reversal potential, one open and at least two closed states, and open probability that increased with depolarization. Quinidine blocked by binding in the open state and decreasing mean open time. Several observations suggest that this channel is responsible for most of the whole-cell current observed in high external K, and for the K conductance of the basolateral membrane of the intact epithelium. On a few occasions a Cl channel was observed that activated upon excision and brief strong depolarization. The I-V relation exhibited strong outward rectification with a single channel conductance of 48 pS at 0 mV in symmetrical 112 mM Cl solutions. Kinetic analysis showed the presence of two open and at least two closed states. Open time constants and open probability increased markedly with depolarization.(ABSTRACT TRUNCATED AT 400 WORDS)
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Kuiroukidis, AP, and G. N. Throumoulopoulos. "Two-dimensional nonlinear cylindrical equilibria with reversed magnetic shear and sheared flow." Journal of Plasma Physics 80, no. 1 (November 12, 2013): 27–41. http://dx.doi.org/10.1017/s0022377813000883.
Повний текст джерелаАнотація:
Nonlinear translational symmetric equilibria with up to quartic flux terms in free functions, reversed magnetic shear, and sheared flow are constructed in two ways: (i) quasi-analytically by an ansatz, which reduces the pertinent generalized Grad–Shafranov equation to a set of ordinary differential equations and algebraic constraints which is then solved numerically, and (ii) completely numerically by prescribing analytically a boundary having an X-point. This latter case presented in Sec. 4 is relevant to the International Thermonuclear Experimental Reactor project. The equilibrium characteristics are then examined by means of pressure, safety factor, current density, and electric field. For flows parallel to the magnetic field, the stability of the equilibria constructed is also examined by applying a sufficient condition. It turns out that the equilibrium nonlinearity has a stabilizing impact, which is slightly enhanced by the sheared flow. In addition, the results indicate that the stability is affected by the up-down asymmetry.
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Yao, Shengjie, Long Chen, Guannan Chu, Hongyun Zhao, Lei Feng, and Guodong Wang. "Microstructure Characterization of Reversed Transformation in Cryogenically Rolled 22MnB5." Materials 13, no. 7 (April 8, 2020): 1741. http://dx.doi.org/10.3390/ma13071741.
Повний текст джерелаАнотація:
Hot stamping is a well-known process to produce structural automotive parts with an excellent strength-to-weight ratio. However, this process is more expensive due to the lower energy efficiency and operating cost of the traditional roller-hearth furnace. Additionally, lower ductility and toughness are commonly recognized as the main disadvantages of the current hot stamped ultra-high-strength parts. Refinement of austenite grains could be a profitable way to improve the strength of hot stamped parts. In this work, the evolution of reversed transformation in asymmetrically cryogenically rolled samples was studied in order to control the austenite. Thermomechanical simulation and heat treatment in the salt bath were used to investigate the reversed transformation process, and the typical microstructures were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Compared with symmetric prerolling, ferrite recrystallization could be remarkably inhibited by asymmetric rolling at the liquid nitrogen temperature (LNT) during the reheating process. Additionally, the nucleation of the austenite inner grains can also be promoted and the dynamics of the reversed transformation accelerated by asymmetric prerolling. Such phenomena might be very useful to refine the parent austenite grains before press hardening and enhance the new hot stamping strategy by partial fast reheating.
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O'Leary, M. E., R. G. Kallen, and R. Horn. "Evidence for a direct interaction between internal tetra-alkylammonium cations and the inactivation gate of cardiac sodium channels." Journal of General Physiology 104, no. 3 (September 1, 1994): 523–39. http://dx.doi.org/10.1085/jgp.104.3.523.
Повний текст джерелаАнотація:
The effects of internal tetrabutylammonium (TBA) and tetrapentylammonium (TPeA) were studied on human cardiac sodium channels (hH1) expressed in a mammalian tsA201 cell line. Outward currents were measured at positive voltages using a reversed Na gradient. TBA and TPeA cause a concentration-dependent increase in the apparent rate of macroscopic Na current inactivation in response to step depolarizations. At TPeA concentrations < 50 microM the current decay is well fit by a single exponential over a wide voltage range. At higher concentrations a second exponential component is observed, with the fast component being dominant. The blocking and unblocking rate constants of TPeA were estimated from these data, using a three-state kinetic model, and were found to be voltage dependent. The apparent inhibition constant at 0 mV is 9.8 microM, and the blocking site is located 41 +/- 3% of the way into the membrane field from the cytoplasmic side of the channel. Raising the external Na concentration from 10 to 100 mM reduces the TPeA-modified inactivation rates, consistent with a mechanism in which external Na ions displace TPeA from its binding site within the pore. TBA (500 microM) and TPeA (20 microM) induce a use-dependent block of Na channels characterized by a progressive, reversible, decrease in current amplitude in response to trains of depolarizing pulses delivered at 1-s intervals. Tetrapropylammonium (TPrA), a related symmetrical tetra-alkylammonium (TAA), blocks Na currents but does not alter inactivation (O'Leary, M. E., and R. Horn. 1994. Journal of General Physiology. 104:507-522.) or show use dependence. Internal TPrA antagonizes both the TPeA-induced increase in the apparent inactivation rate and the use dependence, suggesting that all TAA compounds share a common binding site in the pore. A channel blocked by TBA or TPeA inactivates at nearly the normal rate, but recovers slowly from inactivation, suggesting that TBA or TPeA in the blocking site can interact directly with a cytoplasmic inactivation gate.
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Chang, Wen-Teng, Ming-Chih Cheng, Tsung-Ying Chuang, and Ming-Yen Tsai. "Field Emission Air-Channel Devices as a Voltage Adder." Nanomaterials 10, no. 12 (November 29, 2020): 2378. http://dx.doi.org/10.3390/nano10122378.
Повний текст джерелаАнотація:
Field emission air-channel (FEAC) devices can work under atmospheric pressure with a low operation voltage when the electron channel is far less than the mean free path (MFP) in the air, thereby making them a practical component in circuits. Forward and reverse electron emissions of the current FEAC devices demonstrated symmetric Fowler–Nordheim (F–N) plots owing to the symmetric cathode and anode electrodes. This research aimed to demonstrate the arithmetic application of the FEAC devices, their substrate effect, and reliability. A voltage adder was composed of two FEAC devices whose two inputs were connected to two separate function generators, and one output was wire-connected to an oscilloscope. The devices were on a thin dielectric film and low-resistivity silicon substrate to evaluate the parasitic components and substrate effect, resulting in frequency-dependent impedance. The results show that the FEAC devices possessed arithmetic function, but the output voltage decreased. The FEAC devices were still capable of serving as a voltage adder after the reliability test, but electric current leakage increased. Finite element analysis indicated that the highest electrical fields and electron trajectories occur at the apices where the electrons travel with the shortest route less than the MFP in the air, thereby meeting the FEAC devices’ design. The modeling also showed that a sharp apex would generate a high electric field at the tip-gap-tip, enhancing the tunneling current.
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Gonzales, Albert L., Gregory C. Amberg, and Scott Earley. "Ca2+ release from the sarcoplasmic reticulum is required for sustained TRPM4 activity in cerebral artery smooth muscle cells." American Journal of Physiology-Cell Physiology 299, no. 2 (August 2010): C279—C288. http://dx.doi.org/10.1152/ajpcell.00550.2009.
Повний текст джерелаАнотація:
The melastatin transient receptor potential (TRP) channel TRPM4 is a critical regulator of vascular smooth muscle cell membrane potential and contractility. Activation of the channel is Ca2+-dependent, but prolonged exposure to high (>1 μM) levels of intracellular Ca2+ causes rapid (within ∼2 min) desensitization of TRPM4 currents under conventional whole cell and inside-out patch-clamp conditions. The goal of the present study was to establish a novel method to record sustained TRPM4 currents in smooth muscle cells under near-physiological conditions. Using the amphotericin B-perforated patch-clamp technique, we recorded and characterized sustained (up to 30 min) transient inward cation currents (TICCs) in freshly isolated cerebral artery myocytes. In symmetrical cation solutions, TICCs reversed at 0 mV and had an apparent unitary conductance of 25 pS. Replacement of extracellular Na+ with the nonpermeable cation N-methyl-d-glucamine abolished the current. TICC activity was attenuated by the TRPM4 blockers fluflenamic acid and 9-phenanthrol. Selective silencing of TRPM4 expression using small interfering RNA diminished TICC activity, suggesting that the molecular identity of the responsible ion channel is TRPM4. We used the perforated patch-clamp method to test the hypothesis that TRPM4 is activated by intracellular Ca2+ signaling events. We found that TICC activity is independent of Ca2+ influx and ryanodine receptor activity but is attenuated by sarco(endo)plasmic reticulum Ca2+-ATPase inhibition and blockade of inositol 1,4,5-trisphosphate receptor-mediated Ca2+ release from the sarcoplasmic reticulum. Our findings suggest that TRPM4 channels in cerebral artery myocytes are regulated by Ca2+ release from inositol 1,4,5-trisphosphate receptor on the sarcoplasmic reticulum.
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Mathers, David A. "Spontaneous and GABA-induced single channel currents in cultured murine spinal cord neurons." Canadian Journal of Physiology and Pharmacology 63, no. 10 (October 1, 1985): 1228–33. http://dx.doi.org/10.1139/y85-203.
Повний текст джерелаАнотація:
Intracellular and patch clamp recordings were made from embryonic mouse spinal cord neurons growing in primary cell culture. Outside-out membrane patches obtained from these cells usually showed spontaneous single channel currents when studied at the resting potential (−56 ± 1.5 mV). In 18 out of 30 patches tested, spontaneous single channel activity was abolished by making Tris+ the major cation on both sides of the membrane. The remaining patches continued to display spontaneous single channel currents under these conditions. These events reversed polarity at a patch potential of 0 mV and displayed a mean single channel conductance of 24 ± 1.2 pS. Application of the putative inhibitory transmitter γ-aminobutyric acid (0.5–10 μM) to outside-out patches of spinal cord cell membrane induced single channel currents in 10 out of 15 patches tested. These channels had a primary conductance of 29 ± 2.8 pS in symmetrical 145 mM Cl solutions. Frequency distributions for the open times of these channels were well fit by the sum of a fast exponential term ("of") with a time constant τof = 4 ± 1.3 ms and a slow exponential term ("os") with a time constant τos = 24 ± 8.1 ms. Frequency distributions for channel closed times were also well fit by a double exponential equation, with time constants τcf = 2 ± 0.2 ms and τcs = 62 ± 20.9 ms.
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Deng, Nan, and Qin Zhang. "The Application of Dynamic Uncertain Causality Graph Based Diagnosis and Treatment Unification Model in the Intelligent Diagnosis and Treatment of Hepatitis B." Symmetry 13, no. 7 (June 30, 2021): 1185. http://dx.doi.org/10.3390/sym13071185.
Повний текст джерелаАнотація:
Although hepatitis B is widespread, it is hard to cure. This paper presents a new and more accurate model for the diagnosis and treatment of hepatitis B. Based on previous research, the diagnosis and treatment modes were combined into one. By adding more influencing factors and risk factors, the overall diagnosis and treatment model will be further expanded, and a richer and more detailed overall diagnosis and treatment model will be constructed. Reverse logic gates are used in the model to improve the accuracy of the treatment planning. The new unified model is more accurate in subdividing diagnosis results, and it is more flexible and accurate in providing dynamic treatment plans. The prediction process and the static diagnosis process of the model are symmetric, and the related sub-graph is symmetric in structure. In addition, an algorithm for predicting the response probability of treatment scheme is developed, so as to predict the subsequent treatment effects of the current treatment scheme, such as the probability of drug resistance. The results show that this method is more accurate than other available systems, and it has encouraging diagnostic accuracy and effectiveness, which provides a promising help for doctors in diagnosing hepatitis B.
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Zhou, Fu-Ming, and John J. Hablitz. "Metabotropic Glutamate Receptor Enhancement of Spontaneous IPSCs in Neocortical Interneurons." Journal of Neurophysiology 78, no. 5 (November 1, 1997): 2287–95. http://dx.doi.org/10.1152/jn.1997.78.5.2287.
Повний текст джерелаАнотація:
Zhou, Fu-Ming and John J. Hablitz. Metabotropic glutamate receptor enhancement of spontaneous IPSCs in neocortical interneurons. J. Neurophysiol. 78: 2287–2295, 1997. Using neocortical layer I neurons as a model for GABAergic interneurons, we have studied γ-aminobutyric acid-A (GABAA) receptor-mediated spontaneous inhibitory postsynaptic currents (IPSCs) and modulation by metabotropic glutamate receptors (mGluRs). In the presence of 0.5 μM tetrodotoxin (TTX) and ionotropic glutamate receptor antagonists and under symmetrical Cl− conditions, the mean amplitude of miniature IPSCs (mIPSCs) was ∼50 pA at a holding potential of −70 mV with individual events ranging from 10 to 400 pA. Averaged mIPSCs had a 10–90% rise time of ∼0.6 ms. The decay was double exponential. The fast component had a time constant of ∼4 ms and comprised ∼40% of the total amplitude. The slow component had a time constant of ∼22 ms. The frequency of spontaneous IPSCs (sIPSCs), recorded in the absence of TTX, was increased by bath application of the mGluR agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 10–100 μM) or the group I mGluR selective agonist quisqualic acid (Quis; 0.5–1 μM). Under identical conditions, mIPSCs were not affected. The kinetics of sIPSCs and mIPSCs were not altered by ACPD or Quis. Quis (1 μM) induced an inward current of ∼70 pA at a holding potential of −70 mV, whereas ACPD (40–200 μM) induced a smaller inward current. This current was linear over the voltage range −70 to +30 mV and reversed polarity near 0 mV. In current-clamp recordings, both Quis and ACPD induced a depolarization and action potential firing in layer I and deeper layer interneurons. We conclude that neocortical layer I neurons receive GABAA receptor-mediated inhibitory synaptic inputs. Activation of mGluRs, possibly mGluR1 and/or mGluR5, causes an enhancement of inhibitory synaptic transmission by directly depolarizing corticalGABAergic interneurons through the opening of nonselective cation channels.
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URCIUOLI, D. P., and VICTOR VELIADIS. "BI-DIRECTIONAL SCALABLE SOLID-STATE CIRCUIT BREAKERS FOR HYBRID-ELECTRIC VEHICLES." International Journal of High Speed Electronics and Systems 19, no. 01 (March 2009): 183–92. http://dx.doi.org/10.1142/s0129156409006242.
Повний текст джерелаАнотація:
Power electronics in hybrid-electric military ground vehicles require fast fault isolation, and benefit additionally from bi-directional fault isolation. To prevent system damage or failure, maximum fault current interrupt speeds in tens to hundreds of microseconds are necessary. While inherently providing bi-directional fault isolation, mechanical contactors and circuit breakers do not provide adequate actuation speeds, and suffer severe degradation during repeated fault isolation. Instead, it is desired to use a scalable array of solid-state devices as a solid-state circuit breaker (SSCB) having a collectively low conduction loss to provide large current handling capability and fast transition speed for current interruption. Although, both silicon-carbide (SiC) JFET and SiC MOSFET devices having high breakdown voltages and low drain-to-source resistances have been developed, neither device structure alone is capable of reverse blocking at full voltage. Limitations exist for using a dual common-source structure for either device type. Small-scale SSCB experiments were conducted using 0.03 cm2 normally-on SiC VJFETs. Based on results of these tests, a normally-on VJFET device modification is made, and a proposed symmetric SiC JFET is considered for this application.
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Cherepanov, Aleksandr, Vasily Zakaryukin, and Andrey Kryukov. "Modeling of traction power supply systems for movement of high-speed trains." MATEC Web of Conferences 216 (2018): 02006. http://dx.doi.org/10.1051/matecconf/201821602006.
Повний текст джерелаАнотація:
Upgrading of traction power supply systems will be required to transfer electrified railway lines to high-speed traffic. Coaxial cables and balancing transformers can be used as technical upgrading means. The article presents the results of computer simulation in the Fazonord software complex of the traditional 2x25 kV traction system, as well as systems with coaxial cables and Woodbridge symmetric transformers. Simulation results showed that the use of cables contributes to a significant increase in the level of voltage on current collectors of electric rolling stock. Use of modified Woodbridge transformers makes it possible to reduce the imbalance coefficient by the reverse sequence on high voltage buses of traction substations. However, the reduction is insignificant and depends on the modes of movement of trains in adjacent inter-station zones. The biggest positive effects occur in the integrated application of balancing transformers and coaxial cables.
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Overholt, J. L., M. E. Hobert, and R. D. Harvey. "On the mechanism of rectification of the isoproterenol-activated chloride current in guinea-pig ventricular myocytes." Journal of General Physiology 102, no. 5 (November 1, 1993): 871–95. http://dx.doi.org/10.1085/jgp.102.5.871.
Повний текст джерелаАнотація:
The whole cell configuration of the patch clamp technique was used to investigate the mechanism underlying rectification of the isoproterenol-activated chloride (Cl-) current in isolated guinea pig ventricular myocytes. When extracellular Cl- was replaced with either bromide (Br-), glutamate (Glut), iodide (I-), isethionate (Iseth), or nitrate (NO3-), the magnitude of the shift in reversal potential of the macroscopic current suggested the following selectivity sequence: NO3- > Br- > or = Cl- > or = I- > Iseth > or = Glut. This information was used to investigate the role of permeant ions in rectification of this current. Consistent with previous observations, when the concentration of intracellular Cl- (Cli-) was less than the concentration of extracellular Cl- (Clo-) (40 mM Cli-/150 mM Clo-) the current exhibited outward rectification, but when Cli- was increased to equal that outside (150 Cli-/150 Clo-), the current no longer rectified. Rectification in the presence of asymmetrical concentrations of permeant ions on either side of the membrane is predicted by constant field theory, as described by the Goldman-Hodgkin-Katz current equation. However, when the Cl- gradient was reversed (150 Cli-/40 Clo-) the current did not rectify in the opposite direction, and in the presence of lower symmetrical concentrations of Cl- inside and out (40 Cli-/40 Clo-), outward rectification did not disappear. Reducing Cli- by equimolar replacement with glutamate caused a concentration dependent increase in the degree of rectification. However, when Cli- was replaced with more permeant anions (NO3- and Br-), rectification was not observed. These results can be explained by a single binding site model based on Eyring rate theory, indicating that rectification is a function of the concentration and the permeability of the anions in the intracellular solution.
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MacGregor, G. G., R. E. Olver, and P. J. Kemp. "Amiloride-sensitive Na+ channels in fetal type II pneumocytes are regulated by G proteins." American Journal of Physiology-Lung Cellular and Molecular Physiology 267, no. 1 (July 1, 1994): L1—L8. http://dx.doi.org/10.1152/ajplung.1994.267.1.l1.
Повний текст джерелаАнотація:
We have used the patch-clamp technique to record single channels in excised membrane patches from type II pneumocytes freshly isolated from fetal guinea pig lung by elastase digestion and differential filtration. The 10/56 patches exhibited spontaneous channel activity with a mean open-state probability (NPo) of 0.5 +/- 0.1. In symmetrical Na(+)-rich solutions, the channels had a unitary conductance of 11.1 +/- 0.5 pS and showed current reversal at approximately 0 mV. Superfusing the inner membrane leaflet of the patch with a K(+)-rich solution resulted in single-channel current activity with a conductance of 5.6 +/- 0.2 pS being resolved. Current reversed at +22.1 +/- 1.9 mV, which is compatible with a PNa+/PK+ of 1.8 +/- 0.1. The addition of 0.1 mM guanosine 5'-O-(3-thiotriphosphate) to the cytoplasmic face of the patch elicited channel activity in 12/31 previously quiescent patches, whereas, in spontaneously active patches, channel NPo was increased. Amiloride, in the concentration range 0.4-4 microM, reduced the frequency of observed spontaneous (or activatable) channel activity, reduced NPo, and induced flickery channel behavior. No activity was seen in the presence of 10 microM amiloride in the pipette. This is the first direct observation of a G protein regulated Na(+)-conductive pathway in alveolar epithelium, and it may represent one route by which the alveolar epithelium of the fetus can regulate the Na(+)-driven fluid reabsorption necessary for the adaptation of the newborn lung to air breathing at birth.
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Akbar, Jehan, Muhammad Hanif, Muhammad Azhar Naeem, and Kamran Abid. "AlGaInAs/InP Based Five & Three Quantum Wells Mode Locked Laser Diodes: A Comparative Study." Elektronika ir Elektrotechnika 26, no. 5 (October 27, 2020): 22–27. http://dx.doi.org/10.5755/j01.eie.26.5.26002.
Повний текст джерелаАнотація:
Comparison of performance of semiconductor mode-locked laser diodes fabricated using AlGaInAs/InP material containing 5 and 3 quantum wells (QWs) inside the active region is reported. The simulations and experimental results show that lasers containing five QWs materials produce larger beam divergence and temporally broader optical pulses. For improvement in the mode-locking of lasers and reducing the far-field pattern, the number of QWs inside the active region was decreased from five to three and a far-field decreasing layer along with a thick spacer layer were introduced in the n-cladding region of epitaxial material. Before growing the material, simulations were carried out to optimise the design. The lower optical confinement factor and higher gain saturation energy of three QWs based mode-locked lasers provide higher average and peak output power, reduced and symmetric far-field pattern, better radio frequency (RF) spectra, shorter optical pulses, and stable optimal mode-locking for a wide range of gain current and saturable absorber reverse voltage.
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Cao, Chunhua, Whaseon Lee-Kwon, Kristie Payne, Aurélie Edwards, and Thomas L. Pallone. "Descending vasa recta endothelia express inward rectifier potassium channels." American Journal of Physiology-Renal Physiology 293, no. 4 (October 2007): F1248—F1255. http://dx.doi.org/10.1152/ajprenal.00278.2007.
Повний текст джерелаАнотація:
Descending vasa recta (DVR) are capillary-sized microvessels that supply blood flow to the renal medulla. They are composed of contractile pericytes and endothelial cells. In this study, we used the whole cell patch-clamp method to determine whether inward rectifier potassium channels (KIR) exist in the endothelia, affect membrane potential, and modulate intracellular Ca2+ concentration ([Ca2+]cyt). The endothelium was accessed for electrophysiology by removing abluminal pericytes from collagenase-digested vessels. KIR currents were recorded using symmetrical 140 mM K+ solutions that served to maximize currents and eliminate cell-to-cell coupling by closing gap junctions. Large, inwardly rectifying currents were observed at membrane potentials below the equilibrium potential for K+. Ba2+ potently inhibited those currents in a voltage-dependent manner, with affinity k = 0.18, 0.33, 0.60, and 1.20 μM at −160, −120, −80, and −40 mV, respectively. Cs+ also blocked those currents with k = 20, 48, 253, and 1,856 μM at −160, −120, −80, and −40 mV, respectively. In the presence of 1 mM ouabain, increasing extracellular K+ concentration from 5 to 10 mM hyperpolarized endothelial membrane potential by 15 mV and raised endothelial [Ca2+]cyt. Both the K+-induced membrane hyperpolarization and the [Ca2+]cyt elevation were reversed by Ba2+. Immunochemical staining verified that both pericytes and endothelial cells of DVR express KIR2.1, KIR2.2, and KIR2.3 subunits. We conclude that strong, inwardly rectifying KIR2.x isoforms are expressed in DVR and mediate K+-induced hyperpolarization of the endothelium.
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Liu, Yong-Tang, Liang Sheng, Yang Li, Jin-Hai Zhang, and Xiao-Ping Ouyang. "Current channel in plasma of inverse exploding planar foils." Acta Physica Sinica 71, no. 3 (2022): 035205. http://dx.doi.org/10.7498/aps.71.20211495.
Повний текст джерелаАнотація:
In the research of <i>Z</i>-pinch, the initial establishment of current in load, current density distribution mode and current evolution characteristics in different stages are of great significance in studying the development of plasma dynamics, analyzing plasma instability mode, and carrying out the MHD numerical simulation. Thin planar foil is an ideal configuration with continuous two-dimensional structure to study the problem. Based on an ideal model that consists of foil-backpost configuration under the assumption of infinite length in reverse exploding condition, the establishment, distribution and evolution of the current channel, magnetic field distribution characteristics and the force state of foil plasma by the inductive mode are calculated and analyzed theoretically. Relevant experiments are carried out on the QG-1 facility with about 1.4 MA peak current and 100 ns rise time to verify the calculated results. The self-emission graphs of exploding foils are recorded by visible-light frame cameras from side-on view and end-on view. Different load configurations are utilized including symmetric and asymmetric condition both assembled with two 20-μm-thick aluminum foils. The results show that the establishment of the initial current in foil (0–70 ns) accord with the expectation of the inductance model. The inductance feature determines the distribution of the current in this stage, which causes the current to aggregate in foil edges and then the edges will suffer much higher magnetic field and <i> <b>J</b> </i> × <i> <b>B</b> </i> force than the center. This results in the formation of a clamp plasma morphology. The later images (70–120 ns) show that the intense emission region will transfer from the foil edges to the center, which proves a transfer of current channel. So the magnetic field and <i> <b>J</b> </i> × <i> <b>B</b> </i> force in the foil center increase and a peak convex plasma morphology forms then. It shows that the current distribution will be affected by the plasma evolution process. The convergence process of ablated plasma with current finally leads to rapidly switch the current channel (in 60–80 ns).
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McVeigh, P. A., and T. N. Farris. "Finite Element Analysis of Fretting Stresses." Journal of Tribology 119, no. 4 (October 1, 1997): 797–801. http://dx.doi.org/10.1115/1.2833887.
Повний текст джерелаАнотація:
Clamped contacts subjected to vibratory loading undergo cyclic relative tangential motion or micro-slip near the edges of contact. This cyclic micro-slip, known as fretting, leads to removal of material through a mechanism known as fretting wear and formation and growth of cracks through a mechanism known as fretting fatigue. In aircraft, fretting fatigue occurs at the rivet/hole interface leading to multisite damage which is a potential failure mechanism for aging aircraft. A finite element model of a current fretting fatigue experiment aimed at characterizing fretting in riveted joints is detailed. A non-symmetric bulk tension is applied to the specimen in addition to the loads transferred from the fretting pad. The model is verified through comparison to the Mindlin solution for a reduced loading configuration, in which the bulk tension is not applied. Results from the model with the bulk tension show that the distribution of micro-slip in the contact is not symmetric and that for some loads reversed micro-slip occurs. Finite element results are given for the effects that four different sets of loading parameters have on the maximum tensile stress induced by fretting at the trailing edge of contact. It can be shown using multiaxial fatigue theory that this stress controls fretting fatigue crack formation. This maximum tensile stress is compared to that of the Mindlin solution for a symmetric distribution of micro-slip. This stress is also compared to that of a variation based on the Mindlin solution for the cases with a non-symmetric distribution of micro-slip. It is concluded that the solution based on the Mindlin variation and the full finite element solution lead to similar predictions of the maximum tensile stress, even when the shear traction solutions differ significantly.
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Xing, Zhi-zhong. "A translational flavor symmetry in the mass terms of Dirac and Majorana fermions." Journal of Physics G: Nuclear and Particle Physics 49, no. 2 (January 4, 2022): 025003. http://dx.doi.org/10.1088/1361-6471/ac421e.
Повний текст джерелаАнотація:
Abstract Requiring the effective mass term for a category of fundamental Dirac or Majorana fermions of the same electric charge to be invariant under the translational transformations ψ αL(R) → ψ αL(R) + n α z ψL(R) in the flavor space, where n α and z ψL(R) stand respectively for the flavor-dependent complex numbers and a constant spinor field anticommuting with the fermion fields, we show that n α can be identified as the elements U αi in the ith column of the unitary matrix U used to diagonalize the corresponding Hermitian or symmetric fermion mass matrix M ψ , and m i = 0 holds accordingly. We find that the reverse is also true. Now that the mass spectra of charged leptons, up- and down-type quarks are all strongly hierarchical and current experimental data allow the lightest neutrino to be massless, we argue that the zero mass limit for the first-family fermions and the translational flavor symmetry behind it should be a natural starting point for building viable fermion mass models.
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Puopolo, Michelino, and Ottorino Belluzzi. "Inhibitory Synapses Among Interneurons in the Glomerular Layer of Rat and Frog Olfactory Bulbs." Journal of Neurophysiology 80, no. 1 (July 1, 1998): 344–49. http://dx.doi.org/10.1152/jn.1998.80.1.344.
Повний текст джерелаАнотація:
Puopolo, Michelino and Ottorino Belluzzi. Inhibitory synapses among interneurons in the glomerular layer of rat and frog olfactory bulbs. J. Neurophysiol. 80: 344–349, 1998. The patch-clamp technique was applied to periglomerular (PG) cells from slices of frog and rat olfactory bulbs to characterize whole cell and single-channel properties of inhibitory synaptic currents. Spontaneous and electrically driven bicuculline-sensitive synaptic events were recorded under ionic conditions that excluded any possible interference of excitatory synapses. The peak amplitude distribution of spontaneous events could be fitted by several Gaussians having the same interpeak distance. Spontaneous currents reversed polarity at the chloride equilibrium potential and were suppressed by 2 mM Co2+; the decay phase could be fitted with a single exponential having a time constant of ∼10 ms at 0 mV. Bicuculline-sensitive monosynaptic responses could be evoked in PG cells by electrical stimulations delivered at the distance of several glomeruli within the glomerular layer. Finally, in excised outside-out patches, single-channel analysis revealed the presence of typical γ-aminobutyric acid-A receptor channels, with a single-channel conductance of 28 pS in symmetrical chloride and mean open times of 3–4 ms. The simplest explanation of these data, effectively supported by pristine anatomic findings, is that there could be inhibitory contacts among interneurons in the glomerular layer.
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Torrell, M., S. García-Rodríguez, A. Morata, G. Penelas, and A. Tarancón. "Co-electrolysis of steam and CO2 in full-ceramic symmetrical SOECs: a strategy for avoiding the use of hydrogen as a safe gas." Faraday Discussions 182 (2015): 241–55. http://dx.doi.org/10.1039/c5fd00018a.
Повний текст джерелаАнотація:
The use of cermets as fuel electrodes for solid oxide electrolysis cells requires permanent circulation of reducing gas, e.g. H2 or CO, so called safe gas, in order to avoid oxidation of the metallic phase. Replacing metallic based electrodes by pure oxides is therefore proposed as an advantage for the industrial application of solid oxide electrolyzers. In this work, full-ceramic symmetrical solid oxide electrolysis cells have been investigated for steam/CO2 co-electrolysis. Electrolyte supported cells with La0.75Sr0.25Cr0.5Mn0.5O3−δ reversible electrodes have been fabricated and tested in co-electrolysis mode using different fuel compositions, from pure H2O to pure CO2, at temperatures between 850–900 °C. Electrochemical impedance spectroscopy and galvanostatic measurements have been carried out for the mechanistic understanding of the symmetrical cell performance. The content of H2 and CO in the product gas has been measured by in-line gas micro-chromatography. The effect of employing H2 as a safe gas has also been investigated. Maximum density currents of 750 mA cm−2 and 620 mA cm−2 have been applied at 1.7 V for pure H2O and for H2O : CO2 ratios of 1 : 1, respectively. Remarkable results were obtained for hydrogen-free fuel compositions, which confirmed the interest of using ceramic oxides as a fuel electrode candidate to reduce or completely avoid the use of safe gas in operation minimizing the contribution of the reverse water shift reaction (RWSR) in the process. H2 : CO ratios close to two were obtained for hydrogen-free tests fulfilling the basic requirements for synthetic fuel production. An important increase in the operation voltage was detected under continuous operation leading to a dramatic failure by delaminating of the oxygen electrode.