WorldWideScience

Sample records for depolarizing voltage steps

  1. Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker.

    Science.gov (United States)

    Thouta, Samrat; Hull, Christina M; Shi, Yu Patrick; Sergeev, Valentine; Young, James; Cheng, Yen M; Claydon, Thomas W

    2017-01-24

    Slow deactivation of hERG channels is critical for preventing cardiac arrhythmia yet the mechanistic basis for the slow gating transition is unclear. Here, we characterized the temporal sequence of events leading to voltage sensor stabilization upon membrane depolarization. Progressive increase in step depolarization duration slowed voltage-sensor return in a biphasic manner (τfast = 34 ms, τslow = 2.5 s). The faster phase of voltage-sensor return slowing correlated with the kinetics of pore opening. The slower component occurred over durations that exceeded channel activation and was consistent with voltage sensor relaxation. The S4-S5 linker mutation, G546L, impeded the faster phase of voltage sensor stabilization without attenuating the slower phase, suggesting that the S4-S5 linker is important for communications between the pore gate and the voltage sensor during deactivation. These data also demonstrate that the mechanisms of pore gate-opening-induced and relaxation-induced voltage-sensor stabilization are separable. Deletion of the distal N-terminus (Δ2-135) accelerated off-gating current, but did not influence the relative contribution of either mechanism of stabilization of the voltage sensor. Lastly, we characterized mode-shift behavior in hERG channels, which results from stabilization of activated channel states. The apparent mode-shift depended greatly on recording conditions. By measuring slow activation and deactivation at steady state we found the "true" mode-shift to be ∼15 mV. Interestingly, the "true" mode-shift of gating currents was ∼40 mV, much greater than that of the pore gate. This demonstrates that voltage sensor return is less energetically favorable upon repolarization than pore gate closure. We interpret this to indicate that stabilization of the activated voltage sensor limits the return of hERG channels to rest. The data suggest that this stabilization occurs as a result of reconfiguration of the pore gate upon opening by

  2. Quantitative analysis of the cell voltage of SO{sub 2}-depolarized electrolysis in hybrid sulfur process

    Energy Technology Data Exchange (ETDEWEB)

    Lulu, Xue; Ping, Zhang, E-mail: zhangping77@mail.tsinghua.edu.cn; Songzhe, Chen; Laijun, Wang

    2016-09-15

    SO{sub 2}-depolarized electrolysis (SDE) is the pivotal reaction in hybrid sulfur process. To date, the total cell potential for an SO{sub 2}-depolarized electrolyzer has been identified to be controlled dominantly by the sulfuric acid concentration of the anolyte and electrolysis temperature. Potential loss in SDE can be separated into four components, i.e., equilibrium potential, anodic polarization overpotential, cathodic polarization overpotential, and ohmic loss. In this work, the potential individual components of SDE were measured and calculated. Results showed that the anodic polarization overpotential exhibited the highest ratio in the cell voltage of SDE reaction, and the kinetics of the anodic reaction was controlled by a distinct reaction process under different cell potentials. This study increases understanding on SDE and provides assistance to improve its performance.

  3. Voltage transients elicited by sudden step-up of auxin

    Science.gov (United States)

    Pickard, B. G.

    1984-01-01

    It is hypothesized (i) that the molecular mechanism for the reception of friction and flexure and the mechanism by which auxin enhances ethylene production have in common a release of free calcium into the cytosol, (ii) that elevated cytosolic calcium initiates vesicle exocytosis, and (iii) that the vesicles release a factor or set of factors which depolarizes the plasmalemma and promotes ethylene synthesis. One consequence of such exocytosis should be small, extracellularly observable voltage transients. Transients, ranging in size up to 600 microvolts and possessing risetimes (10-90%) of approximately 200 ms, are known to be elicited in etiolated stems of Pisum sativum L. by friction and are here shown to be elicited by sudden increase of auxin concentration and also by a Ca2+ ionophore.

  4. Automatic Functional Step-up System in High-Voltage Installation

    Institute of Scientific and Technical Information of China (English)

    陈方泉; 严一白; 宋进; 林财兴

    2004-01-01

    This article describes automatic functional step-up systems in high-voltage installation, with emphases on functional process of step-up and step-down, two-circuit control and elimination of tip burr voltage.

  5. Step voltage transient currents in poly(vinylidene fluoride)

    Science.gov (United States)

    Kaura, T.; Nath, Rabinder

    1983-10-01

    The step voltage current transient characteristics have been studied in poly(vinylidene flouride) as a function of field, temperature, and time. The current peaks have been observed in the current-time characteristics. These peaks have been attributed to the space-charge injection phenomena. Using the space-charge-limited model of current transients the mobility has been estimated to 2.2±0.2×10-9 cm2 v-1 s-1 at 301 K. The analysis of the temperature dependence of mobilities establishes that charge carrier transport in extended states involving trapping is predominant.

  6. Estradiol inhibits depolarization-evoked exocytosis in PC12 cells via N-type voltage-gated calcium channels.

    NARCIS (Netherlands)

    Adams, K.L.; Maxson, M.M.; Mellander, L.; Westerink, R.H.S.; Ewing, A.G.

    2010-01-01

    Fast neuromodulatory effects of 17-β-estradiol (E2) on cytosolic calcium concentration ([Ca(2+)](i)) have been reported in many cell types, but little is known about its direct effects on vesicular neurotransmitter secretion (exocytosis). We examined the effects of E2 on depolarization-evoked [Ca(2+

  7. Performance of a Voltage Step-Up/Step-Down Transformerless DC/DC Converter: Analytical Model

    Science.gov (United States)

    Suskis, P.; Rankis, I.

    2012-01-01

    The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software.

  8. High Output Voltage Based Multiphase Step-Up DC-DC Converter Topology with Voltage Doubler Rectifiers

    Directory of Open Access Journals (Sweden)

    Liao Xiaozhong

    2013-02-01

    Full Text Available High Output Voltage Based Multiphase Step-Up DC-DC Converter topology with voltage doubler rectifiers is presented in this paper. High output voltage is obtained due to the series combination of voltage doubler rectifiers on the secondary side of high frequency transformers. This topology is useful in the application where the output voltage is greater than the input. The two loop control strategy has been developed in order to analyze the stable and effective working of the converter topology. Therefore the working mode analysis of the converter topology has been described in detail. The multiphase step-up DC-DC converter topology is first simulated on MATLAB and then a prototype has been designed in order to verify the simulation and experimental results. Finally the simulation and experimental results are found to be satisfactory.

  9. Thevenin source resistances of the touch, transferred and step voltages of a grounding system

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Y.L.; Salama, M.M.A.; Djogo, G. [University of Waterloo, ON (Canada)

    1999-03-01

    The source resistances for surface voltages (touch, transferred and step voltage) are considered. It is proved that the source resistances of the touch and transferred voltages are the same, given by the grounding resistances between the feet of a human and the grounding system. In a practical situation, however, this resistance is very close to that of the ANSI/IEEE Standard 80 that is widely accepted. The source resistance of the step voltage is simply the resistance between the two feet, not at all perturbed by the grounding system. Proofs are derived rigorously by combining the field Galerkin's moment method and basic circuit theory. (author)

  10. Step-by-Step Design Procedure for a Grid-Connected Three-Phase PWM Voltage Source Converter,

    DEFF Research Database (Denmark)

    Liserre, Marco; Blaabjerg, Frede; Aquila, Antonio Dell’

    2004-01-01

    The voltage source active rectifier is one of the most interesting solutions to interfacing dc power systems to the grid. Many elements are responsible for the overall system behaviour, such as value of the passive elements, sensors position, analog/digital filters and ac current/dc voltage...... controllers. In this paper a step-by-step design procedure, taking into account all these elements, is proposed and validated through the tests on an experimental prototype. The reported results are particularly relevant to evaluate the influence on the grid current harmonic content of the grid sensor...... position and of the use of analog filters in the feedback signals....

  11. Fully Integrated Ultra-Low Voltage Step-up Converter with Voltage Doubling LC-Tank for Energy Harvesting Applications

    Science.gov (United States)

    Jayaweera, H. M. P. C.; Pathirana, W. P. M. R.; Muhtaroğlu, Ali

    2015-12-01

    This paper reports the design, fabrication, and validation of a novel integrated interface circuit for ultra-low voltage step up converter in 0.18 μm CMOS technology. The circuit does not use off-chip components. Fully integrated centre-tap differential inductors are introduced in the proposed LC oscillator design to achieve 38% area reduction compared to the use of four separate inductors. The efficiency of the system is hence enhanced through the elimination of clock buffer circuits traditionally utilized to drive the step-up converter. The experimental results prove that the system can self-start, and step 0.25 V up to 1.7 V to supply a 46 μW load with 15.5% efficiency. The minimum validated input voltage is 0.15 V, which is boosted up to 1.2 V under open circuit conditions.

  12. Extracellular stimulation of nerve cells with electric current spikes induced by voltage steps

    OpenAIRE

    2016-01-01

    A new stimulation paradigm is presented for the stimulation of nerve cells by extracellular electric currents. In the new paradigm stimulation is achieved with the current spike induced by a voltage step whenever the voltage step is applied to a live biological tissue. By experimental evidence and theoretical arguments, it is shown that this spike is well suited for the stimulation of nerve cells. Stimulation of the human tongue is used for proof of principle. Charge injection thresholds are ...

  13. A Study on the step response characteristics in shielded resistor divider for full lightning impulse voltage

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ik Soo; Lee, Hyeong Ho [Korea Electrotehnology Research Institute, Changwon (Korea, Republic of); Cho, Jung Soo; Park, Jung Hoo [Pusan National University, Pusan (Korea, Republic of)

    1996-02-01

    This paper presents the development technology of standard shielded resistor divider for full lightning impulse voltage. The ability of large-capacity power apparatus to withstand lighting stroke is usually evaluated by means of full lightning impulse voltage. Lightning impulse voltage test has been essential to evaluate the insulation performance of electrical power apparatus. Recently international standard (IEC 60) on high voltage measurement techniques is being revised and requests a formal traceability of high voltage measurements. Therefore, general interest for this area has grown considerably during last years, and several international intercomparisons have already completed worldwide, i.e. Europe, Japan, America etc., In this viewpoint, we have also investigated the step response of the standard shielded resistor divider, which satisfies the IEC recommendation. (author). 7 refs., 14 figs., 2 tabs.

  14. KCNE1 divides the voltage sensor movement in KCNQ1/KCNE1 channels into two steps

    Science.gov (United States)

    Barro-Soria, Rene; Rebolledo, Santiago; Liin, Sara I.; Perez, Marta E.; Sampson, Kevin J.; Kass, Robert S.; Larsson, H. Peter

    2014-04-01

    The functional properties of KCNQ1 channels are highly dependent on associated KCNE-β subunits. Mutations in KCNQ1 or KCNE subunits can cause congenital channelopathies, such as deafness, cardiac arrhythmias and epilepsy. The mechanism by which KCNE1-β subunits slow the kinetics of KCNQ1 channels is a matter of current controversy. Here we show that KCNQ1/KCNE1 channel activation occurs in two steps: first, mutually independent voltage sensor movements in the four KCNQ1 subunits generate the main gating charge movement and underlie the initial delay in the activation time course of KCNQ1/KCNE1 currents. Second, a slower and concerted conformational change of all four voltage sensors and the gate, which opens the KCNQ1/KCNE1 channel. Our data show that KCNE1 divides the voltage sensor movement into two steps with widely different voltage dependences and kinetics. The two voltage sensor steps in KCNQ1/KCNE1 channels can be pharmacologically isolated and further separated by a disease-causing mutation.

  15. Regulation of the voltage-insensitive step of HERG activation by extracellular pH.

    Science.gov (United States)

    Zhou, Qinlian; Bett, Glenna C L

    2010-06-01

    Human ether-à-go-go-related gene (HERG, Kv11.1, KCNH2) voltage-gated K(+) channels dominate cardiac action potential repolarization. In addition, HERG channels play a role in neuronal and smooth cell excitability as well as cancer pathology. Extracellular pH (pH(o)) is modified during myocardial ischemia, inflammation, and respiratory alkalosis, so understanding the response of HERG channels to changes in pH is of clinical significance. The relationship between pH(o) and HERG channel gating appears complex. Acidification has previously been reported to speed, slow, or have no effect on activation. We therefore undertook comprehensive analysis of the effect of pH(o) on HERG channel activation. HERG channels have unique and complex activation gating characteristics with both voltage-sensitive and voltage-insensitive steps in the activation pathway. Acidosis decreased the activation rate, suppressed peak current, and altered the sigmoidicity of gating near threshold potentials. At positive voltages, where the voltage-insensitive transition is rate limiting, pH(o) modified the voltage-insensitive step with a pK(a) similar to that of histidine. Hill coefficient analysis was incompatible with a coefficient of 1 but was well described by a Hill coefficient of 4. We derived a pH(o)-sensitive term for a five-state Markov model of HERG channel gating. This model demonstrates the mechanism of pH(o) sensitivity in HERG channel activation. Our experimental data and mathematical model demonstrate that the pH(o) sensitivity of HERG channel activation is dominated by the pH(o) sensitivity of the voltage-insensitive step, in a fashion that is compatible with the presence of at least one proton-binding site on each subunit of the channel tetramer.

  16. A Survey on Voltage Boosting Techniques for Step-Up DC-DC Converters

    DEFF Research Database (Denmark)

    Forouzesh, Mojtaba; Siwakoti, Yam Prasad; Gorji, Saman Asghari;

    2016-01-01

    Step-up dc-dc converters are used to boost the voltage level of the input to a higher output level. Despite of its features such as simplicity of implementation, the fundamental boost dc-dc converter has shortcomings such as low boost ability and low power density. With these limitations, researc...

  17. Spreading convulsions, spreading depolarization and epileptogenesis in human cerebral cortex

    DEFF Research Database (Denmark)

    Dreier, Jens P; Major, Sebastian; Pannek, Heinz-Wolfgang

    2012-01-01

    Spreading depolarization of cells in cerebral grey matter is characterized by massive ion translocation, neuronal swelling and large changes in direct current-coupled voltage recording. The near-complete sustained depolarization above the inactivation threshold for action potential generating...

  18. High voltage conversion ratio, switched C & L cells, step-down DC-DC converter

    DEFF Research Database (Denmark)

    Pelan, Ovidiu; Muntean, Nicolae; Cornea, Octavian;

    2013-01-01

    The paper presents a high voltage conversion ratio DC-DC step-down topology obtained from a classical buck converter associated with an input switched-capacitor cell and an output switched-inductor cell. Analytical descriptions, the voltage and current limits of the main components are synthesized...... in a comparative form, related to the classical buck structure, in order to emphasis the advantages of the proposed converter. Digital simulations and experimental results obtained with a built prototype are compared. From the first evaluation, the proposed converter is expected to be effectively used at input...

  19. Analysis of high voltage step-up nonisolated DC-DC boost converters

    Science.gov (United States)

    Alisson Alencar Freitas, Antônio; Lessa Tofoli, Fernando; Junior, Edilson Mineiro Sá; Daher, Sergio; Antunes, Fernando Luiz Marcelo

    2016-05-01

    A high voltage step-up nonisolated DC-DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC-DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.

  20. SOFT-SWITCHED HIGH STEP-UP DC-DC CONVERTER WITH HIGH VOLTAGE GAIN

    Directory of Open Access Journals (Sweden)

    J.C. PAUL IMMANUEL

    2013-04-01

    Full Text Available This paper presents a new design of soft switched high step-up dc-dc converter with high voltage gain which is suitable for high power applications such as Uninterruptible Power System (UPS, Photo Voltaic system and hybrid electric vehicles. The emergence of this front-end converter is to improve the shape of active input current given to the system. This converter proposes Soft-Switching technique to achieve ZVS turn on of active switches and ZCS turn off of diodes using Lr - Cr resonance in the auxiliary circuit. Therefore reduces the switching losses. Comparatively the voltage conversion ratio of this converter is higher when compared with the ordinary boost converter. Hence the voltage gain of this converter is also higher. A simulation platform is created using MATLAB which illustrates the ZVS and ZCS operation of the switches and diodes. Open loop and closed loop controlled converter systems are modelled and simulated.

  1. Potassium Chloride Versus Voltage Clamp Contractures in Ventricular Muscle

    Science.gov (United States)

    Morad, M.; Reeck, S.; Rao, M.

    1981-01-01

    In frog ventricle, developed tension was markedly larger in response to depolarization caused by a voltage clamp step than to depolarization induced by high concentrations of potassium chloride. Measurement of extracellular potassium activity at the surface and at the depth of muscle during the development of contractures showed that the diffusion of potassium is much slower than the spread of depolarization through the cross section of muscle. These two observations suggest that competition between the depolarizing and the negative inotropic effects of an increase in the extracellular potassium ion concentration may determine the time course and magnitude of contractile tension in heart muscle.

  2. Large voltage modulation in superconducting quantum interference devices with submicron-scale step-edge junctions

    Science.gov (United States)

    Lam, Simon K. H.

    2017-09-01

    A promising direction to improve the sensitivity of a SQUID is to increase its junction's normal resistance value, Rn, as the SQUID modulation voltage scales linearly with Rn. As a first step to develop highly sensitive single layer SQUID, submicron scale YBCO grain boundary step edge junctions and SQUIDs with large Rn were fabricated and studied. The step-edge junctions were reduced to submicron scale to increase their Rn values using focus ion beam, FIB and the measurement of transport properties were performed from 4.3 to 77 K. The FIB induced deposition layer proves to be effective to minimize the Ga ion contamination during the FIB milling process. The critical current-normal resistance value of submicron junction at 4.3 K was found to be 1-3 mV, comparable to the value of the same type of junction in micron scale. The submicron junction Rn value is in the range of 35-100 Ω, resulting a large SQUID modulation voltage in a wide temperature range. This performance promotes further investigation of cryogen-free, high field sensitivity SQUID applications at medium low temperature, e.g. at 40-60 K.

  3. dc step response of induced-charge electro-osmosis between parallel electrodes at large voltages

    Science.gov (United States)

    Sugioka, Hideyuki

    2014-07-01

    Induced-charge electro-osmosis (ICEO) is important since it can be used for realizing high performance microfluidic devices. Here, we analyze the simplest problem of ion relaxation around a circular polarizable cylinder between parallel blocking electrodes in a closed cell by using a multiphysics coupled simulation technique. This technique is based on a combination of the finite-element method and finite-volume method for the Poisson-Nernst-Planck (PNP) equations having a flow term and the Stokes equation having an electric stress term. Through this analysis, we successfully demonstrate that on application of dc voltages, quadorapolar ICEO vortex flows grow during the charging time of the cylinder for both unbounded and bounded problems and decay during the charging time of the parallel electrodes only for the bounded problem using blocking electrodes. Further, by proposing a simple model that considers the two-dimensional (2D) PNP equations analytically, we successfully explain the step response time of the ICEO flow for the both unbounded and bounded problems. Furthermore, at low applied voltages, we find analytical formulations on steady diffused-ion problems and steady ICEO-flow problems and examine that our numerical results agree well with the analytical results. Moreover, by considering an ion-conserving condition with 2D Poisson-Boltzmann equations, we explain significant decrease of the maximum slip velocity at large applied voltages fairly well. We believe that our analysis will contribute greatly to the realistic designs of prospective high-performance microfluidic devices.

  4. Derivation of linearized transfer functions for switching-mode regulations. Phase A: Current step-up and voltage step-up converters

    Science.gov (United States)

    Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

    1981-01-01

    Small-signal models are derived for the power stage of the voltage step-up (boost) and the current step-up (buck) converters. The modeling covers operation in both the continuous-mmf mode and the discontinuous-mmf mode. The power stage in the regulated current step-up converter on board the Dynamics Explorer Satellite is used as an example to illustrate the procedures in obtaining the small-signal functions characterizing a regulated converter.

  5. Novel Step-Up DC/DC Converter with No Right Half Plane Zero and Reduced Switched Voltage Stress Characteristics

    DEFF Research Database (Denmark)

    Mostaan, Ali; Alizadeh, Ebrahim; Soltani, Mohsen

    2014-01-01

    Novel step-up DC/DC converter is introduced in this paper. This converter is realized with adding the switched capacitor voltage multiplier cell to the three switch step-down DC/DC converter that has been proposed in the literature. The proposed converter is analyzed in the steady state and the v...

  6. Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (series connected step-up (1:10) transformers

    Science.gov (United States)

    Redondo, L. M.; Fernando Silva, J.; Margato, E.

    2007-03-01

    This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5kV modules, 800V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15kV/1A pulses with 5μs width, 10kHz repetition rate, with less than 1μs pulse rise time. Experimental results for resistive loads are presented and discussed.

  7. Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (series connected step-up (1:10) transformers.

    Science.gov (United States)

    Redondo, L M; Fernando Silva, J; Margato, E

    2007-03-01

    This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed.

  8. Design and Implementation of a High Efficiency, Low Component Voltage Stress, Single-Switch High Step-Up Voltage Converter for Vehicular Green Energy Systems

    Directory of Open Access Journals (Sweden)

    Yu-En Wu

    2016-09-01

    Full Text Available In this study, a novel, non-isolated, cascade-type, single-switch, high step-up DC/DC converter was developed for green energy systems. An integrated coupled inductor and voltage lift circuit were applied to simplify the converter structure and satisfy the requirements of high efficiency and high voltage gain ratios. In addition, the proposed structure is controllable with a single switch, which effectively reduces the circuit cost and simplifies the control circuit. With the leakage inductor energy recovery function and active voltage clamp characteristics being present, the circuit yields optimizable conversion efficiency and low component voltage stress. After the operating principles of the proposed structure and characteristics of a steady-state circuit were analyzed, a converter prototype with 450 W, 40 V of input voltage, 400 V of output voltage, and 95% operating efficiency was fabricated. The Renesas MCU RX62T was employed to control the circuits. Experimental results were analyzed to validate the feasibility and effectiveness of the proposed system.

  9. On the performance of voltage stepping for the simulation of adaptive, nonlinear integrate-and-fire neuronal networks.

    Science.gov (United States)

    Kaabi, Mohamed Ghaith; Tonnelier, Arnaud; Martinez, Dominique

    2011-05-01

    In traditional event-driven strategies, spike timings are analytically given or calculated with arbitrary precision (up to machine precision). Exact computation is possible only for simplified neuron models, mainly the leaky integrate-and-fire model. In a recent paper, Zheng, Tonnelier, and Martinez (2009) introduced an approximate event-driven strategy, named voltage stepping, that allows the generic simulation of nonlinear spiking neurons. Promising results were achieved in the simulation of single quadratic integrate-and-fire neurons. Here, we assess the performance of voltage stepping in network simulations by considering more complex neurons (quadratic integrate-and-fire neurons with adaptation) coupled with multiple synapses. To handle the discrete nature of synaptic interactions, we recast voltage stepping in a general framework, the discrete event system specification. The efficiency of the method is assessed through simulations and comparisons with a modified time-stepping scheme of the Runge-Kutta type. We demonstrated numerically that the original order of voltage stepping is preserved when simulating connected spiking neurons, independent of the network activity and connectivity.

  10. Step-by-Step Design Procedure for a Grid-Connected Three-Phase PWM Voltage Source Converter,

    DEFF Research Database (Denmark)

    Liserre, Marco; Blaabjerg, Frede; Aquila, Antonio Dell’

    2004-01-01

    controllers. In this paper a step-by-step design procedure, taking into account all these elements, is proposed and validated through the tests on an experimental prototype. The reported results are particularly relevant to evaluate the influence on the grid current harmonic content of the grid sensor...

  11. A Survey on Voltage Boosting Techniques for Step-Up DC-DC Converters

    DEFF Research Database (Denmark)

    Forouzesh, Mojtaba; Siwakoti, Yam Prasad; Gorji, Saman Asghari;

    2016-01-01

    , researches on new voltage boosting techniques are inevitable for various power converter applications. This can be achieved either by additional magnetic or by electric field storage elements with switching elements (switch and/or diode) in different configurations. Such combination of primary voltage...... boosting techniques and topologies are large, which at times may be confusing and difficult to follow/adapt for different applications. Considering these aspects and in order to make a clear sketch of the general law and framework of various voltage boosting techniques, this paper comprehensively reviews...... different voltage boosting techniques and categorizes them according to their circuit performance....

  12. VOLTAGE-DEPENDENT SODIUM AND POTASSIUM, BUT NO CALCIUM CONDUCTANCES IN DDT1 MF-2 SMOOTH-MUSCLE CELLS

    NARCIS (Netherlands)

    MOLLEMAN, A; NELEMANS, A; VANDENAKKER, J; DUIN, M; DENHERTOG, A

    1991-01-01

    Voltage-dependent inward and outward membrane currents were investigated in the DDT1 MF-2 smooth muscle cell line using the whole-cell patch-clamp technique. Application of a pulse protocol with subsequent depolarizing voltage steps elicited an inactivating inward current and a non-inactivating outw

  13. Effect of a Cooling Step Treatment on a High-Voltage GaN LED During ICP Dry Etching

    Science.gov (United States)

    Lin, Yen-Sheng; Hsiao, Sheng-Yu; Tseng, Chun-Lung; Shen, Ching-Hsing; Chiang, Jung-Sheng

    2016-10-01

    In this study, a lower dislocation density for a GaN surface and a reduced current path are observed at the interface of a SiO2 isolation sidewall, using high-resolution transmission electron microscopy. This is grown using a 3-min cooling step treatment during inductivity coupled plasma dry etching. The lower forward voltage is measured, the leakage current decreases from 53nA to 32nA, and the maximum output power increases from 354.8 W to 357.2 W for an input current of 30 mA. The microstructure and the optoelectronic properties of high-voltage light-emitting-diodes is proven to be affected by the cooling step treatment, which allows enough time to release the thermal energy of the SiO2 isolation well.

  14. Effect of a Cooling Step Treatment on a High-Voltage GaN LED During ICP Dry Etching

    Science.gov (United States)

    Lin, Yen-Sheng; Hsiao, Sheng-Yu; Tseng, Chun-Lung; Shen, Ching-Hsing; Chiang, Jung-Sheng

    2017-02-01

    In this study, a lower dislocation density for a GaN surface and a reduced current path are observed at the interface of a SiO2 isolation sidewall, using high-resolution transmission electron microscopy. This is grown using a 3-min cooling step treatment during inductivity coupled plasma dry etching. The lower forward voltage is measured, the leakage current decreases from 53nA to 32nA, and the maximum output power increases from 354.8 W to 357.2 W for an input current of 30 mA. The microstructure and the optoelectronic properties of high-voltage light-emitting-diodes is proven to be affected by the cooling step treatment, which allows enough time to release the thermal energy of the SiO2 isolation well.

  15. Breakdown voltage model and structure realization of a thin silicon layer with linear variable doping on a silicon on insulator high voltage device with multiple step field plates

    Institute of Scientific and Technical Information of China (English)

    Qiao Ming; Zhuang Xiang; Wu Li-Juan; Zhang Wen-Tong; Wen Heng-Juan; Zhang Bo; Li Zhao-Ji

    2012-01-01

    Based on the theoretical and experimental investigation of a thin silicon layer (TSL) with linear variable doping (LVD) and further research on the TSL LVD with a multiple step field plate (MSFP),a breakdown voltage (BV) model is proposed and experimentally verified in this paper.With the two-dimensional Poisson equation of the silicon on insulator (SOI) device,the lateral electric field in drift region of the thin silicon layer is assumed to be constant.For the SOI device with LVD in the thin silicon layer,the dependence of the BV on impurity concentration under the drain is investigated by an enhanced dielectric layer field (ENDIF),from which the reduced surface field (RESURF) condition is deduced.The drain in the centre of the device has a good self-isolation effect but the problem of the high voltage interconnection (HVI) line will become serious.The two step field plates including the source field plate and gate field plate can be adopted to shield the HVI adverse effect on the device.Based on this model,the TSL LVD SOI n-channel lateral double-diffused MOSFET (nLDMOS) with MSFP is realized.The experimental breakdown voltage (BV) and specific on-resistance (Ron,sp) of the TSL LVD SOI device are 694 V and 21.3 Ω.mm2 with a drift region length of 60 μm,buried oxide layer of 3 μm,and silicon layer of 0.15 μm,respectively.

  16. Upper drift region double step partial SOI LDMOSFET: A novel device for enhancing breakdown voltage and output characteristics

    Science.gov (United States)

    Jamali Mahabadi, S. E.

    2016-01-01

    A new LDMOSFET structure called upper drift region double step partial silicon on insulator (UDDS-PSOI) is proposed to enhance the breakdown voltage (BV) and output characteristics. The proposed structure contains two vertical steps in the top surface of the drift region. It is demonstrated that in the proposed structure, the lateral electric field distribution is modified by producing two additional electric field peaks, which decrease the common peaks near the drain and gate junctions. The electric field distribution in the drift region is modulated and that of the buried layer is enhanced by the two steps in the top surface of the drift region, thereby resulting in the enhancement of the BV. The effect of device parameters, such as the step height and length in the top surface of the drift region, the doping concentration in the drift region, and the buried oxide length and thickness, on the electric field distribution and the BV of the proposed structure is studied. Simulation results from two-dimensional ATLAS simulator show that the BV of the UDDS-PSOI structure is 120% and 220% higher than that of conventional partial SOI (C-PSOI) and conventional SOI (C-SOI) structures, respectively. Furthermore, the drain current of the UDDS-PSOI is 11% larger than the C-PSOI structure with a drain-source voltage VDS = 100 V and gate-source voltage VGS = 5 V. Simulation results show that Ron in the proposed structure is 74% and 48% of that in C-PSOI and C-SOI structures, respectively.

  17. Transient sodium current at subthreshold voltages: activation by EPSP waveforms.

    Science.gov (United States)

    Carter, Brett C; Giessel, Andrew J; Sabatini, Bernardo L; Bean, Bruce P

    2012-09-20

    Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also "persistent" sodium current, a noninactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37°C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo.

  18. Analysis and design of a high-efficiency zero-voltage-switching step-up DC–DC converter

    Indian Academy of Sciences (India)

    Jae-Won Yang; Hyun-Lark Do

    2013-08-01

    A high-efficiency zero-voltage-switching (ZVS) step-up DC–DC converter is proposed. The proposed ZVS DC–DC step-up converter has fixed switching frequency, simple control, and high efficiency. All power switches can operate with ZVS. The output diodes are under zero-current-switching (ZCS) during turn-off. Due to soft-switching operation of the power switches and output diodes, the proposed ZVS DC–DC converter shows high efficiency. Steady-state analysis of the converter is presented to determine the circuit parameters. A laboratory prototype of the proposed converter is developed, and its experimental results are presented for validation.

  19. PV Power-Generation System with a Phase-Shift PWM Technique for High Step-Up Voltage Applications

    Directory of Open Access Journals (Sweden)

    Cheng-Tao Tsai

    2012-01-01

    Full Text Available A PV power-generation system with a phase-shift pulse-width modulation (PWM technique for high step-up voltage applications is proposed. The proposed power-generation system consists of two stages. In the input stage, all power switches of the full-bridge converter with phase-shift technique can be operated with zero-current switching (ZCS at turn-on or turn-off transition. Hence, the switching losses of the power switches can be reduced. Then, in the DC output stage, a voltage-doubler circuit is used to boost a high dc-link bus voltage. To supply a utility power, a dc/ac inverter is connected to induce a sinusoidal source. In order to draw a maximum power from PV arrays source, a microcontroller is incorporated with the perturbation and observation method to implement maximum power point tracking (MPPT algorithm and power regulating scheme. In this study, a full load power of 300 W prototype has been built. Experimental results are presented to verify the performance and feasibility of the proposed PV power-generation system.

  20. Bipartite depolarizing maps

    Science.gov (United States)

    Lami, Ludovico; Huber, Marcus

    2016-09-01

    We introduce a 3-parameter class of maps (1) acting on a bipartite system which are a natural generalisation of the depolarizing channel (and include it as a special case). Then, we find the exact regions of the parameter space that alternatively determine a positive, completely positive, entanglement-breaking, or entanglement-annihilating map. This model displays a much richer behaviour than the one shown by a simple depolarizing channel, yet it stays exactly solvable. As an example of this richness, positive partial transposition but not entanglement-breaking maps is found in Theorem 2. A simple example of a positive yet indecomposable map is provided (see the Remark at the end of Section IV). The study of the entanglement-annihilating property is fully addressed by Theorem 7. Finally, we apply our results to solve the problem of the entanglement annihilation caused in a bipartite system by a tensor product of local depolarizing channels. In this context, a conjecture posed in the work of Filippov [J. Russ. Laser Res. 35, 484 (2014)] is affirmatively answered, and the gaps that the imperfect bounds of Filippov and Ziman [Phys. Rev. A 88, 032316 (2013)] left open are closed. To arrive at this result, we furthermore show how the Hadamard product between quantum states can be implemented via local operations.

  1. Development of a Micro-Step Voltage-Fed Actuator with a Novel Stepper Motor for Automobile AGS Systems

    Directory of Open Access Journals (Sweden)

    Se-Hyun Rhyu

    2014-05-01

    Full Text Available This paper presents an improved micro-step voltage-fed actuator for an automobile active grill shutter (AGS system. A novel structured stepper motor, which contains both the main and auxiliary teeth in the stator, is proposed for the actuator. In a normal permanent magnet (PM motor coils are generally wound on all the stator teeth, however, in the proposed motor, the winding is only on the main teeth. Because of the absence of coils in the auxiliary teeth, the proposed stepper motor possesses the following advantages: simple structure, lighter weight, smaller volume, and less time consumption. The unique auxiliary poles in the stepper motor supply the flux path to increase the step resolution even without any coils. The characteristics of the proposed stepper motor were investigated using finite element analysis. In particular, the effect of the magnetization distribution of the PM on the motor performance was investigated during the analysis. Cogging torque, which causes noise and vibration issues, was minimized by the tooth-shape optimization. In addition, a micro-step voltage-fed algorithm was implemented for a high-resolution position control. By employing a current close to a sine wave using space vector pulse-width modulation, a high-quality current waveform with a high resolution was obtained. Finally, the proposed prototype was fabricated, and the cogging torque, back-electromotive force, and current characteristics were measured by mounting the prototype on the AGS system. Both the analysis and experimental results validate the performance improvement from the proposed motor and its possible application for the flap control of the AGS system.

  2. An on-die ultra-low voltage DC-DC step-up converter with voltage doubling LC-tank

    Science.gov (United States)

    Jayaweera, H. M. P. C.; Pathirana, W. P. M. R.; Muhtaroğlu, Ali

    2016-12-01

    In this paper we report the design, characterization and verification of a novel on-die ultra-low voltage DC-DC converter circuit for energy harvester applications in 0.18 µm complementary metal oxide semiconductor technology. The circuit self-starts, does not use off-chip components, and is thus suitable for use in highly integrated low cost systems. The first version of the design has a five-stage charge-pump stimulated by an oscillator with two center-tap inductors. It is validated on a test chip that this converter can boost 0.25 V-1.7 V for a 60 kΩ load with 15.5% maximum efficiency. The center-tap implementation leads to a 38% area reduction compared to the conventional four planar inductors. The proposed second version of the DC-DC design has a modified LC-tank with center-tap and planar hybrid inductors, which leads to a simulated step up from 0.2 V input to 1.65 V output for a 45 kΩ load with 35% maximum efficiency. The new boost implementation is hence expected to improve both power efficiency and output power capacity significantly compared to the first design, at a cost of a 31% layout area growth. The second revision in addition provides a 15% chip area reduction compared to the conventional four planar-inductor approach.

  3. Isolated DC-DC Converter for Bidirectional Power Flow Controlling with Soft-Switching Feature and High Step-Up/Down Voltage Conversion

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2017-03-01

    Full Text Available In this paper, a novel isolated bidirectional DC-DC converter is proposed, which is able to accomplish high step-up/down voltage conversion. Therefore, it is suitable for hybrid electric vehicle, fuel cell vehicle, energy backup system, and grid-system applications. The proposed converter incorporates a coupled inductor to behave forward-and-flyback energy conversion for high voltage ratio and provide galvanic isolation. The energy stored in the leakage inductor of the coupled inductor can be recycled without the use of additional snubber mechanism or clamped circuit. No matter in step-up or step-down mode, all power switches can operate with soft switching. Moreover, there is a inherit feature that metal–oxide–semiconductor field-effect transistors (MOSFETs with smaller on-state resistance can be adopted because of lower voltage endurance at primary side. Operation principle, voltage ratio derivation, and inductor design are thoroughly described in this paper. In addition, a 1-kW prototype is implemented to validate the feasibility and correctness of the converter. Experimental results indicate that the peak efficiencies in step-up and step-down modes can be up to 95.4% and 93.6%, respectively.

  4. Design and Implementation of a Power Converter to Process Renewable Energy for Step-down Voltage Applications

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2014-04-01

    Full Text Available In this study a power converter to process renewable energy is proposed, which can not only process solar energy but deal with wind power. The proposed converter is derived from two series modified forwards to step down voltage for charger system or dc distribution application, so as called Modified-Forward Dual-Input Converter (MFDIC. The MFDIC mainly contains an upper Modified Forward (MF, a lower MF, a common output inductor and a DSP-based system controller. The upper and lower MFs can operate individually or simultaneously to accommodate the variation of atmospheric conditions. Since the MFDIC can process renewable power with interleaved operation, the ripple of output current is suppressed significantly and thus better performance is achieved. In the MFDIC only a common output inductor is needed, instead of two separated inductors, so that the volume of the converter is reduced significantly. To draw maximum power from PV panel and wind turbine, perturb-and-observe method is adopted to achieve the feature of Maximum Power Point Tracking (MPPT. The MFDIC is constructed, designed, analyzed, simulated and tested. Simulations and practical measurements have demonstrated the validity and the feasibility of the proposed dual-input converter.

  5. A NEW STRUCTURE AND ITS ANALYTICAL BREAKDOWN MODEL OF HIGH VOLTAGE SOI DEVICE WITH STEP UNMOVABLE SURFACE CHARGES OF BURIED OXIDE LAYER

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A new SOI (Silicon On Insulator) high voltage device with Step Unmovable Surface Charges(SUSC) of buried oxide layer and its analytical breakdown model are proposed in the paper. The unmovable charges are implemented into the upper surface of buried oxide layer to increase the vertical electric field and uniform the lateral one. The 2-D Poisson's equation is solved to demonstrate the modulation effect of the immobile interface charges and analyze the electric field and breakdown voltage with the various geometric parameters and step numbers. A new RESURF (REduce SURface Field) condition of the SOI device considering the interface charges and buried oxide is derived to maximize breakdown voltage. The analytical results are in good agreement with the numerical analysis obtained by the 2-D semiconductor devices simulator MEDICI. As a result, an 1200V breakdown voltage is firstly obtained in 3μm-thick top Si layer, 2μm-thick buried oxide layer and 70μm-length drift region using a linear doping profile of unmovable buried oxide charges.

  6. Six-step Voltage Control of PM Brushless AC Motors under High Speed Flux-weakening Operation for EV/HEV Applications

    Institute of Scientific and Technical Information of China (English)

    诸自强

    2008-01-01

    The torque-speed characteristics of brushless motor having an interior permanent magnet rotor and a sinusoidalback-emf waveform are compared experimentally when it is operated in brushless AC (BLAC) mode and brushless DC(BLDC) modes with both 2-phase, 120° conduction (BLDC-120) and 3-phase,180° conduction (BLDC-180).Particularemphasis is on high-speed,six-step voltage controlled,flux-weakening operation.h is shown that for EV/HEV applications,even for interior PM brushless motors which have sinusoidal back-emf waveforms,in order to achieve maximum torque perampere capability over wide operation speed range,it is advantageous to employ a hybrid operation mode-BLAC operationin the constant torque region and six-step voltage control (BLDC-180 operation, together with current phase control) inthe flux-weakening region.

  7. Muscarinic depolarization of layer II neurons of the parasubiculum.

    Directory of Open Access Journals (Sweden)

    Stephen D Glasgow

    Full Text Available The parasubiculum (PaS is a component of the hippocampal formation that sends its major output to layer II of the entorhinal cortex. The PaS receives strong cholinergic innervation from the basal forebrain that is likely to modulate neuronal excitability and contribute to theta-frequency network activity. The present study used whole cell current- and voltage-clamp recordings to determine the effects of cholinergic receptor activation on layer II PaS neurons. Bath application of carbachol (CCh; 10-50 µM resulted in a dose-dependent depolarization of morphologically-identified layer II stellate and pyramidal cells that was not prevented by blockade of excitatory and inhibitory synaptic inputs. Bath application of the M1 receptor antagonist pirenzepine (1 µM, but not the M2-preferring antagonist methoctramine (1 µM, blocked the depolarization, suggesting that it is dependent on M1 receptors. Voltage-clamp experiments using ramped voltage commands showed that CCh resulted in the gradual development of an inward current that was partially blocked by concurrent application of the selective Kv7.2/3 channel antagonist XE-991, which inhibits the muscarine-dependent K(+ current I M. The remaining inward current also reversed near EK and was inhibited by the K(+ channel blocker Ba(2+, suggesting that M1 receptor activation attenuates both I M as well as an additional K(+ current. The additional K(+ current showed rectification at depolarized voltages, similar to K(+ conductances mediated by Kir 2.3 channels. The cholinergic depolarization of layer II PaS neurons therefore appears to occur through M1-mediated effects on I M as well as an additional K(+ conductance.

  8. Muscarinic Depolarization of Layer II Neurons of the Parasubiculum

    Science.gov (United States)

    Glasgow, Stephen D.; Chapman, C. Andrew

    2013-01-01

    The parasubiculum (PaS) is a component of the hippocampal formation that sends its major output to layer II of the entorhinal cortex. The PaS receives strong cholinergic innervation from the basal forebrain that is likely to modulate neuronal excitability and contribute to theta-frequency network activity. The present study used whole cell current- and voltage-clamp recordings to determine the effects of cholinergic receptor activation on layer II PaS neurons. Bath application of carbachol (CCh; 10–50 µM) resulted in a dose-dependent depolarization of morphologically-identified layer II stellate and pyramidal cells that was not prevented by blockade of excitatory and inhibitory synaptic inputs. Bath application of the M1 receptor antagonist pirenzepine (1 µM), but not the M2-preferring antagonist methoctramine (1 µM), blocked the depolarization, suggesting that it is dependent on M1 receptors. Voltage-clamp experiments using ramped voltage commands showed that CCh resulted in the gradual development of an inward current that was partially blocked by concurrent application of the selective Kv7.2/3 channel antagonist XE-991, which inhibits the muscarine-dependent K+ current IM. The remaining inward current also reversed near EK and was inhibited by the K+ channel blocker Ba2+, suggesting that M1 receptor activation attenuates both IM as well as an additional K+ current. The additional K+ current showed rectification at depolarized voltages, similar to K+ conductances mediated by Kir 2.3 channels. The cholinergic depolarization of layer II PaS neurons therefore appears to occur through M1-mediated effects on IM as well as an additional K+ conductance. PMID:23520542

  9. The degradation and recovery properties of AlGaN/GaN high-electron mobility transistors under direct current reverse step voltage stress

    Institute of Scientific and Technical Information of China (English)

    Shi Lei; Feng Shi-Wei; Guo Chun-Sheng; Zhu Hui; Wan Ning

    2013-01-01

    Direct current (DC) reverse step voltage stress is applied on the gate of an AlGaN/GaN high-electron mobility transistor (HEMT).Experiments show that parameters degenerate under stress.Large-signal parasitic source/drain resistance (Rs/RD) and gate-source forward I-V characteristics are recoverable after breakdown of the device under test (DUT).Electrons trapped by both the AlGaN barrier trap and the surface state under stress lead to this phenomenon,and surface state recovery is the major reason for the recovery of device parameters.

  10. Differential expression of voltage-gated K+ and Ca2+ currents in bipolar cells in the zebrafish retinal slice.

    Science.gov (United States)

    Connaughton, V P; Maguire, G

    1998-04-01

    Whole-cell voltage-gated currents were recorded from bipolar cells in the zebrafish retinal slice. Two physiological populations of bipolar cells were identified. In the first, depolarizing voltage steps elicited a rapidly activating A-current that reached peak amplitude or = 10 ms after step onset and did not inactivate. IK was antagonized by internal caesium and external tetraethylammonium. Bipolar cells expressing IK also expressed a time-dependent h-current at membrane potentials calcium-dependent potassium current (IK(Ca)) were identified. Depolarizing voltage steps > -50 mV activated ICa, which reached peak amplitude between -20 and -10 mV. ICa was eliminated in Ca+2-free Ringer and blocked by cadmium and cobalt, but not tetrodotoxin. In most cells, Ica was transient, activating rapidly at -50 mV. This current was antagonized by nickel. The remaining bipolar cells expressed a nifedipine-sensitive sustained current that activated between -40 and -30 mV, with both slower kinetics and smaller amplitude than transient ICa. IK(Ca) was elicited by membrane depolarizations > -20 mV. Bipolar cells in the zebrafish retinal slice preparation express an array of voltage-gated currents which contribute to non-linear I-V characteristics. The zebrafish retinal slice preparation is well-suited to patch clamp analyses of membrane mechanisms and provides a suitable model for studying genetic defects in visual system development.

  11. The Low Voltage LED Drivers with DC/DC Step Down Converters(I)%LED低压驱动电源——DC/DC降压变换器(上)

    Institute of Scientific and Technical Information of China (English)

    陈传虞

    2011-01-01

    The low voltage LED drivers with DC/DC between output voltage, input DC voltage, the formulas typical step down converter IC and its practical circuit step down converters are analyzed in detail. The relationship used to determine the circuit parameters%详细分析了DC/DC降压变换器驱动LED电路的工作原理,并推导了输出电压与输入电压的关系和电路参数选择依据的公式;给出一种DC/DC降压变换器芯片实例及其实用电路。

  12. Delayed ischaemic neurological deficits after subarachnoid haemorrhage are associated with clusters of spreading depolarizations.

    Science.gov (United States)

    Dreier, Jens P; Woitzik, Johannes; Fabricius, Martin; Bhatia, Robin; Major, Sebastian; Drenckhahn, Chistoph; Lehmann, Thomas-Nicolas; Sarrafzadeh, Asita; Willumsen, Lisette; Hartings, Jed A; Sakowitz, Oliver W; Seemann, Jörg H; Thieme, Anja; Lauritzen, Martin; Strong, Anthony J

    2006-12-01

    Progressive ischaemic damage in animals is associated with spreading mass depolarizations of neurons and astrocytes, detected as spreading negative slow voltage variations. Speculation on whether spreading depolarizations occur in human ischaemic stroke has continued for the past 60 years. Therefore, we performed a prospective multicentre study assessing incidence and timing of spreading depolarizations and delayed ischaemic neurological deficit (DIND) in patients with major subarachnoid haemorrhage (SAH) requiring aneurysm surgery. Spreading depolarizations were recorded by electrocorticography with a subdural electrode strip placed on cerebral cortex for up to 10 days. A total of 2110 h recording time was analysed. The clinical state was monitored every 6 h. Delayed infarcts after SAH were verified by serial CT scans and/or MRI. Electrocorticography revealed 298 spreading depolarizations in 13 of the 18 patients (72%). A clinical DIND was observed in seven patients 7.8 days (7.3, 8.2) after SAH. DIND was time-locked to a sequence of recurrent spreading depolarizations in every single case (positive and negative predictive values: 86 and 100%, respectively). In four patients delayed infarcts developed in the recording area. As in the ischaemic penumbra of animals, delayed infarction was preceded by progressive prolongation of the electrocorticographic depression periods associated with spreading depolarizations to >60 min in each case. This study demonstrates that spreading depolarizations have a high incidence in major SAH and occur in ischaemic stroke. Repeated spreading depolarizations with prolonged depression periods are an early indicator of delayed ischaemic brain damage after SAH. In view of experimental evidence and the present clinical results, we suggest that spreading depolarizations with prolonged depressions are a promising target for treatment development in SAH and ischaemic stroke.

  13. Role of a T-type calcium current in supporting a depolarizing potential, damped oscillations, and phasic firing in vasopressinergic guinea pig supraoptic neurons.

    Science.gov (United States)

    Erickson, K R; Ronnekleiv, O K; Kelly, M J

    1993-05-01

    Guinea pig magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) were studied using the in vitro slice preparation. Intracellular recordings were made with biocytin-filled electrodes, permitting immunocytochemical identification of the recorded cells as arginine vasopressin- (AVP) versus oxytocin- (OT) containing. Only AVP cells displaying a depolarizing potential (DP) fired phasically. The DP was associated with a transient inward current measured in voltage clamp, which exhibited a number of properties of the T-type calcium current: activation threshold of -64 mV, time course of up to 250 ms, blockade by nickel and augmentation by barium chloride. This current has not been reported previously in SON neurons. The T-type current (IT) was always associated with a damped oscillation of the membrane following the offset from hyperpolarizing steps. In all cells tested, an apamin-sensitive afterhyperpolarization (AHP) was observed, similar to the calcium-dependent potassium current (IK, Ca) described in rat SON and other CNS regions. Therefore, as with other CNS regions displaying damped oscillations, guinea pig SON cells possess both an IT and an IK, Ca. We have previously described an Ih activating at hyperpolarized potentials in these cells, which depolarizes the membrane to a range in which the IT and IK, Ca can interactively support oscillations. In summary, the IT and associated depolarizing potential appears to be a requisite feature for phasic firing in AVP cells of guinea pig SON.

  14. Actions of a hydrogen sulfide donor (NaHS) on transient sodium, persistent sodium, and voltage-gated calcium currents in neurons of the subfornical organ.

    Science.gov (United States)

    Kuksis, Markus; Ferguson, Alastair V

    2015-09-01

    Hydrogen sulfide (H2S) is an endogenously found gasotransmitter that has been implicated in a variety of beneficial physiological functions. This study was performed to investigate the cellular mechanisms underlying actions of H2S previously observed in subfornical organ (SFO), where H2S acts to regulate blood pressure through a depolarization of the membrane and an overall increase in the excitability of SFO neurons. We used whole cell patch-clamp electrophysiology in the voltage-clamp configuration to analyze the effect of 1 mM NaHS, an H2S donor, on voltage-gated potassium, sodium, and calcium currents. We observed no effect of NaHS on potassium currents; however, both voltage-gated sodium currents (persistent and transient) and the N-type calcium current had a depolarized activation curve and an enhanced peak-induced current in response to a series of voltage-step and ramp protocols run in the control and NaHS conditions. These effects were not responsible for the previously observed depolarization of the membrane potential, as depolarizing effects of H2S were still observed following block of these conductances with tetrodotoxin (5 μM) and ω-conotoxin-GVIA (100 nM). Our studies are the first to investigate the effect of H2S on a variety of voltage-gated conductances in a single brain area, and although they do not explain mechanisms underlying the depolarizing actions of H2S on SFO neurons, they provide evidence of potential mechanisms through which this gasotransmitter influences the excitability of neurons in this important brain area as a consequence of the modulation of multiple ion channels.

  15. Mathematical analysis of depolarization block mediated by slow inactivation of fast sodium channels in midbrain dopamine neurons.

    Science.gov (United States)

    Qian, Kun; Yu, Na; Tucker, Kristal R; Levitan, Edwin S; Canavier, Carmen C

    2014-12-01

    Dopamine neurons in freely moving rats often fire behaviorally relevant high-frequency bursts, but depolarization block limits the maximum steady firing rate of dopamine neurons in vitro to ∼10 Hz. Using a reduced model that faithfully reproduces the sodium current measured in these neurons, we show that adding an additional slow component of sodium channel inactivation, recently observed in these neurons, qualitatively changes in two different ways how the model enters into depolarization block. First, the slow time course of inactivation allows multiple spikes to be elicited during a strong depolarization prior to entry into depolarization block. Second, depolarization block occurs near or below the spike threshold, which ranges from -45 to -30 mV in vitro, because the additional slow component of inactivation negates the sodium window current. In the absence of the additional slow component of inactivation, this window current produces an N-shaped steady-state current-voltage (I-V) curve that prevents depolarization block in the experimentally observed voltage range near -40 mV. The time constant of recovery from slow inactivation during the interspike interval limits the maximum steady firing rate observed prior to entry into depolarization block. These qualitative features of the entry into depolarization block can be reversed experimentally by replacing the native sodium conductance with a virtual conductance lacking the slow component of inactivation. We show that the activation of NMDA and AMPA receptors can affect bursting and depolarization block in different ways, depending upon their relative contributions to depolarization versus to the total linear/nonlinear conductance.

  16. Mechanism of blue-light-induced plasma-membrane depolarization in etiolated cucumber hypocotyls

    Science.gov (United States)

    Spalding, E. P.; Cosgrove, D. J.

    1992-01-01

    A large, transient depolarization of the plasma membrane precedes the rapid blue-light (BL)-induced growth suppression in etiolated seedlings of Cucumis sativus L. The mechanism of this voltage transient was investigated by applying inhibitors of ion channels and the plasma-membrane H(+)-ATPase, by manipulating extracellular ion concentrations, and by measuring cell input resistance and ATP levels. The depolarizing phase was not affected by Ca(2+)-channel blockers (verapamil, La3+) or by reducing extracellular free Ca2+ by treatment with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). However, these treatments did reduce the rate of repolarization, indicating an inward movement of Ca2+ is involved. No effects of the K(+)-channel blocker tetraethylammonium (TEA+) were detected. Vanadate and KCN, used to inhibit the H(+)-ATPase, reduced or completely inhibited the BL-induced depolarization. Levels of ATP increased by 11-26% after 1-2 min of BL. Input resistance of trichrome cells, measured with double-barreled microelectrodes, remained constant during the onset of the depolarization but decreased as the membrane voltage became more positive than -90 mV. The results indicate that the depolarization mechanism initially involves inactivation of the H(+)-ATPase with subsequent transient activation of one or more types of ion channels.

  17. A Depolarizing Electrogenic Pump in Frog Muscle

    Science.gov (United States)

    1975-08-01

    mw copy AFRRI SR75-20 AUGUST 1975 AFRRI SCIENTIFIC REPORT O ■ to A DEPOLARIZING ELECTROGENIC PUMP IN FROG MUSCLE D. Geduldig D. R...Academy of Sciences - National Research Council. AFRRI SR75-20 August 1975 A DEPOLARIZING ELECTROGENIC PUMP IN FROG MUSCLE D. GEDULDIG* D. R...INTRODUCTION When Na-enriched frog muscles are bathed in Na- and K-free saline, the small amount of potassium which could accumulate outside of the membrane

  18. A voltage-dependent persistent sodium current in mammalian hippocampal neurons

    OpenAIRE

    1990-01-01

    Currents generated by depolarizing voltage pulses were recorded in neurons from the pyramidal cell layer of the CA1 region of rat or guinea pig hippocampus with single electrode voltage-clamp or tight- seal whole-cell voltage-clamp techniques. In neurons in situ in slices, and in dissociated neurons, subtraction of currents generated by identical depolarizing voltage pulses before and after exposure to tetrodotoxin revealed a small, persistent current after the transient current. These curren...

  19. Dynamic Simulation Investigation of 750kV Stepped Switching Controllable High Voltage Shunt Reactor%750kV分级投切式可控高压并联电抗器的动态模拟研究

    Institute of Scientific and Technical Information of China (English)

    秦睿; 郭文科; 王惠中

    2012-01-01

    This paper describes the stepped switching controllable high voltage shunt reactors basic principle, the device can regulate the system reactive power, voltage and frequency over inhibition of arc current, with a continuous smooth power adjustable, harmonic current is small and the advantages of fast response. It analyzes the stepped switching controllable high voltage shunt reactor protection features and functionality, protection and circuit breaker protection, mainly to explain the valve protection and circuit breaker protection. According to the stepped switching controllable high voltage shunt reactors principles and technical characteristics, combined with power system dynamic simulation laboratory simulation system characteristics, stepped switching controllable high voltage shunt reactor protection system dynamic simulation experimental research, besides valve and circuit breaker protection dynamic simulation test results are necessary analysis and research.%主要分析了分级投切式可控高压并联电抗器保护的特点和功能,对阀保护和断路器保护进行了说明,并对阀保护和断路器保护动态模拟试验结果进行了必要的分析和研究.根据分级投切式可控高压并联电抗器的原理和技术特点,结合试验室电力系统动态模拟仿真系统的特点,对分级投切式可控高压并联电抗器的保护系统进行了动态模拟试验研究.

  20. GABA depolarizes immature neurons and inhibits network activity in the neonatal neocortex in vivo.

    Science.gov (United States)

    Kirmse, Knut; Kummer, Michael; Kovalchuk, Yury; Witte, Otto W; Garaschuk, Olga; Holthoff, Knut

    2015-07-16

    A large body of evidence from in vitro studies suggests that GABA is depolarizing during early postnatal development. However, the mode of GABA action in the intact developing brain is unknown. Here we examine the in vivo effects of GABA in cells of the upper cortical plate using a combination of electrophysiological and Ca(2+)-imaging techniques. We report that at postnatal days (P) 3-4, GABA depolarizes the majority of immature neurons in the occipital cortex of anaesthetized mice. At the same time, GABA does not efficiently activate voltage-gated Ca(2+) channels and fails to induce action potential firing. Blocking GABA(A) receptors disinhibits spontaneous network activity, whereas allosteric activation of GABA(A) receptors has the opposite effect. In summary, our data provide evidence that in vivo GABA acts as a depolarizing neurotransmitter imposing an inhibitory control on network activity in the neonatal (P3-4) neocortex.

  1. Proximity to Intrinsic Depolarizing Resonances with a Partial Siberian Snake

    Science.gov (United States)

    Crandell, D. A.; Alexeeva, L. V.; Anferov, V. A.; Blinov, B. B.; Chu, C. M.; Caussyn, D. D.; Courant, E. D.; Gladycheva, S. E.; Hu, S.; Krisch, A. D.; Nurushev, T. S.; Phelps, R. A.; Ratner, L. G.; Varzar, S. M.; Wong, V. K.; Derbenev, Ya. S.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E. J.; von Przewoski, B.; Baiod, R.; Russell, A. D.; Ohmori, C.; Sato, H.

    1996-05-01

    Partial Siberian snakes are effective in overcoming imperfection depolarizing resonances, but they may also change the crossing energy for intrinsic depolarizing resonances. We experimentally investigated the effect of a partial Siberian snake near intrinsic depolarizing resonances with stored 140 MeV and 160 MeV polarized proton beams. Using various partial Siberian snake strengths up to 30%, depolarization was observed; this may be due to a change in the spin precession frequency which moves the energy of nearby intrinsic depolarizing resonances.

  2. 晶体管驱动的阶跃二极管大幅度窄脉冲源%Narrow Pulse Source of High-voltag Based on Step Recovery Diode Driven by Transistor

    Institute of Scientific and Technical Information of China (English)

    杨金钢; 谢嘉; 李红英; 和先孟; 周祖国

    2012-01-01

    Current ways of generating narrow pulse is difficult to generate a high-voltage narrow-pulse or a narrow-pulse of voltage higher than working voltage. This paper presented a method to generate a high-voltage narrow-pulse by using a step recovery diode at low voltage which was driven by bipolar transistor. The basic principle of this method was to realize the generation of a high-voltage narrow-pulse by using step characteristic of step recovery diode, and the excitation source form was redesigned based on bipolar driving. Simulation results showed that the circuit's output pulse voltage was not lower than working voltage and had advantages of simple circuit,adjustable pulse width,prone to be integrated,etc. This method was suitable to generate narrow-pulse for ultra-wideband communication system and played an important role in increasing the detecting distance of ultra-wideband fuze.%目前纳秒级窄脉冲源的实现方法有很多,但很难用低电源产生大幅度窄脉冲,或是实现输出脉冲幅度大于其工作电压.提出了一种采用阶跃恢复二极管在双极型晶体管驱动下实现工作于低电压的大幅度纳秒级窄脉冲源的方法.该方法利用阶跃管的阶跃特性,同时利用晶体管的驱动,对阶跃管的激励源形式进行改进设计,实现大幅度窄脉冲.仿真和测试结果表明:该电路具有输出脉冲幅度不小于工作电压的特点,并具有电路简单、脉宽可调、易于集成等优点,适用于超宽带通信系统中窄脉冲信号的产生.

  3. Depolarization of a piezoelectric film under an alternating current field

    Science.gov (United States)

    Kwok, K. W.; Cheung, M. K.; Chan, H. L. W.; Choy, C. L.

    2007-03-01

    In this article, we demonstrate that a sol-gel-derived niobium-doped lead zirconate titanate film can be depolarized by the application of alternating current (ac) fields of diminishing amplitude and we explain the phenomenon based on the concept of the Preisach model. The amplitude of the ac fields is decreased from 20 to 2 MV/m in ten steps. The observed piezoelectric coefficient of the film decreases after each ac field step. Depending on the initial polarization and the direction of the ac fields, the piezoelectric coefficient can decrease to a very small value indicating the complete depolarization of the film. Our results reveal the existence of a distribution of the switching fields in the microdomains (Preisach dipolar units), and that because of mutual interactions the magnitudes of the switch-up and switch-down fields for each microdomain are not necessarily the same. Our results also suggest that the sputter deposition of the top electrode can induce more "down-state" microdomains, thus giving rise to an initial polarization in the film. Because of interactions with other microdomains or other effects, part of these microdomains exhibit very high switching fields.

  4. Neutron Depolarization in Submicron Ferromagnetic Materials

    NARCIS (Netherlands)

    Rekveldt, M.Th.

    1989-01-01

    The neutron depolarization technique is based on the loss of polarization of a polarized neutron beam after transmission through ferromagnetic substances. This loss, caused by Larmor precession in individual domains, determines the mean domain size, the mean square direction cosines of the domains a

  5. Depolarization of UCN stored in material traps

    CERN Document Server

    Serebrov, A; Lasakov, M; Rudnev, Y; Krasnoschekova, I A; Geltenbort, P; Butterworth, J; Bowles, T; Morris, C; Seestrom, S; Smith, D; Young, A R

    2000-01-01

    Depolarization of ultra-cold neutrons (UCN) stored in material traps was first observed. The probability of UCN spin flip per reflection depends on the trap material and varies from 7x10 sup - sup 6 (beryllium) to 10 sup - sup 4 (glass).

  6. Spreading depolarization may link migraine and stroke.

    Science.gov (United States)

    Eikermann-Haerter, Katharina

    2014-01-01

    Migraine increases the risk of stroke, particularly in young and otherwise healthy adults. Being the most frequent neurological condition, migraine prevalence is on a par with that of other common stroke risk factors, such as diabetes or hypertension. Several patterns of association have emerged: (1) migraine and stroke share a common association (eg, vasculopathies, patent foramen ovale, or pulmonary A-V malformations); (2) injury to the arterial wall such as acute arterial dissections can present as migraine aura attacks or stroke; (3) strokes rarely develop during a migraine attack, as described for "migrainous stroke." Increasing experimental evidence suggests that cerebral hyperexcitability and enhanced susceptibility to spreading depolarization, the electrophysiologic event underlying migraine, may serve as a mechanism underlying the migraine-stroke association. Mice carrying human vascular or neuronal migraine mutations exhibit an enhanced susceptibility to spreading depolarization while being particularly vulnerable to cerebral ischemia. The severe stroke phenotype in migraine mutant mice can be prevented by suppressing spreading depolarization. If confirmed in the clinical setting, inhibiting spreading depolarization might protect migraineurs at stroke risk as well as decrease attacks of migraine. © 2014 American Headache Society.

  7. Recording, analysis, and interpretation of spreading depolarizations in neurointensive care

    DEFF Research Database (Denmark)

    Dreier, Jens P; Fabricius, Martin; Ayata, Cenk

    2016-01-01

    recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy...... electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can...

  8. Resurgent Na+ current in pyramidal neurones of rat perirhinal cortex: axonal location of channels and contribution to depolarizing drive during repetitive firing

    Science.gov (United States)

    Castelli, Loretta; Biella, Gerardo; Toselli, Mauro; Magistretti, Jacopo

    2007-01-01

    The perirhinal cortex (PRC) is a supra-modal cortical area that collects and integrates information originating from uni- and multi-modal neocortical regions and directed to the hippocampus. The mechanisms that underlie the specific excitable properties of the different PRC neuronal types are still largely unknown, and their elucidation may be important in understanding the integrative functions of PRC. In this study we investigated the expression and properties of resurgent Na+ current (INaR) in pyramidal neurones of rat PRC area 35 (layer II). Patch-clamp experiments in acute PRC slices were first carried out. A measurable INaR was expressed by a large majority of neurones (31 out of 35 cells). INaR appeared as an inward, slowly decaying current elicited upon step repolarization after depolarizations sufficient to induce nearly complete inactivation of the transient Na+ current (INaT). INaR had a peak amplitude of ∼2.5% that of INaT, and showed the typical biophysical properties also observed in other neuronal types (i.e. cerebellar Purkinje and granule cells), including a bell-shaped current–voltage relationship with a peak at approximately −40 mV, and a characteristic acceleration of activation and decay speed at potentials negative to −45 mV. Current-clamp experiments were then carried out in which repetitive action-potential discharge at various frequencies was induced with depolarizing current injection. The voltage signals thus obtained were then used as command waveforms for voltage-clamp recordings. These experiments showed that a Na+ current identifiable as INaR activates in the early interspike phase even at relatively high firing frequencies (20 Hz), thereby contributing to the depolarizing drive and possibly enhancing repetitive discharge. In acutely dissociated area 35 layer II neurones, as well as in nucleated patches from the same neurones, INaR was never observed, despite the presence of typical INaTs. Since in both preparations neuronal

  9. Differential description and irreversibility of depolarizing light-matter interactions

    CERN Document Server

    Fade, Julien

    2016-01-01

    The widely-used Jones and Mueller differential polarization calculi allow non-depolarizing deterministic polarization interactions, known to be elements of the $SO^+(1,3)$ Lorentz group, to be described in an efficient way. In this Letter, a stochastic differential Jones formalism is shown to provide a clear physical insight on light depolarization, which arises from the interaction of polarized light with a random medium showing fluctuating anisotropic properties. Based on this formalism, several "intrinsic" depolarization metrics naturally arise to efficiently characterize light depolarization in a medium, and an irreversibility property of depolarizing transformations is finally established.

  10. Voltage Step Point Detection and Parameter Identification of General Dynamic Load Model%通用动态负荷模型电压阶跃检测和参数辨识方法

    Institute of Scientific and Technical Information of China (English)

    王立地; 何昕; 朴在林

    2014-01-01

    It is of significance for parameter identification of general dynamic load model to determine the position of equivalent step point in gradually-varying voltage signal and adopt reasonable signal preprocessing method. To meet the requirement of the dynamic load modeling experiment, the equivalent voltage step is adopted to take the place of gradually varied voltage signal, and the clustering analysis is led into the detection of equivalent voltage step point. Considering distribution characteristic of numerical value of voltage in a certain time interval and combining with wavelet denoising, the load signal is preprocessed;based on the platform of MATLAB and by means of development tool of graphics user interface (GUI) the parameter identification of general dynamic active load model is implemented. Experimental results show that, with the clustering method, the gradually-varying voltage step point can be effectively detected on the basis of the signal processed by average filtering and wavelet denoising;and utilizing the signal denoised by bior3.7 wavelet with the 4-th level decomposition for parameter identification, the obtained result is of the highest stability. The proposed method is suitable for load modeling with power recovery characteristic and off-line analysis under the condition of gradually-varied voltage due to manually changing the position of transformer tap and so on.%如何确定渐变电压信号等效阶跃点位置和采取合理的信号预处理方法对通用动态负荷模型参数辨识有重要影响。针对动态负荷建模试验的需要,利用等效电压阶跃来代替电压渐变信号,把聚类分析引入等效电压阶跃点检测中。在一定时间区间内考虑电压数值的分布特性,结合小波去噪进行负荷信号预处理,基于MATLAB平台,借助GUI(图形用户界面)开发手段,实现了通用动态有功负荷模型的参数辨识。实验结果表明:采用聚类分析方法,可以有效

  11. Dynamical characterization of inactivation path in voltage-gated Na(+) ion channel by non-equilibrium response spectroscopy.

    Science.gov (United States)

    Pal, Krishnendu; Gangopadhyay, Gautam

    2016-11-01

    Inactivation path of voltage gated sodium channel has been studied here under various voltage protocols as it is the main governing factor for the periodic occurrence and shape of the action potential. These voltage protocols actually serve as non-equilibrium response spectroscopic tools to study the ion channel in non-equilibrium environment. In contrast to a lot of effort in finding the crystal structure based molecular mechanism of closed-state(CSI) and open-state inactivation(OSI); here our approach is to understand the dynamical characterization of inactivation. The kinetic flux as well as energetic contribution of the closed and open- state inactivation path is compared here for voltage protocols, namely constant, pulsed and oscillating. The non-equilibrium thermodynamic quantities used in response to these voltage protocols serve as improved characterization tools for theoretical understanding which not only agrees with the previously known kinetic measurements but also predict the energetically optimum processes to sustain the auto-regulatory mechanism of action potential and the consequent inactivation steps needed. The time dependent voltage pattern governs the population of the conformational states which when couple with characteristic rate parameters, the CSI and OSI selectivity arise dynamically to control the inactivation path. Using constant, pulsed and continuous oscillating voltage protocols we have shown that during depolarization the OSI path is more favored path of inactivation however, in the hyper-polarized situation the CSI is favored. It is also shown that the re-factorisation of inactivated sodium channel to resting state occurs via CSI path. Here we have shown how the subtle energetic and entropic cost due to the change in the depolarization magnitude determines the optimum path of inactivation. It is shown that an efficient CSI and OSI dynamical profile in principle can characterize the open-state drug blocking phenomena.

  12. Spreading depolarization monitoring in neurocritical care of acute brain injury.

    Science.gov (United States)

    Hartings, Jed A

    2017-04-01

    Spreading depolarizations are unique in being discrete pathologic entities that are well characterized experimentally and also occur commonly in patients with substantial acute brain injury. Here, we review essential concepts in depolarization monitoring, highlighting its clinical significance, interpretation, and future potential. Cortical lesion development in diverse animal models is mediated by tissue waves of mass spreading depolarization that cause the toxic loss of ion homeostasis and limit energy substrate supply through associated vasoconstriction. The signatures of such deterioration are observed in electrocorticographic recordings from perilesional cortex of patients with acute stroke or brain trauma. Experimental work suggests that depolarizations are triggered by energy supply-demand mismatch in focal hotspots of the injury penumbra, and depolarizations are usually observed clinically when other monitoring variables are within recommended ranges. These results suggest that depolarizations are a sensitive measure of relative ischemia and ongoing secondary injury, and may serve as a clinical guide for personalized, mechanistically targeted therapy. Both existing and future candidate therapies offer hope to limit depolarization recurrence. Electrocorticographic monitoring of spreading depolarizations in patients with acute brain injury provides a sensitive measure of relative energy shortage in focal, vulnerable brains regions and indicates ongoing secondary damage. Depolarization monitoring holds potential for targeted clinical trial design and implementation of precision medicine approaches to acute brain injury therapy.

  13. Abnormal depolarizing patterns in three patients with filarial infection.

    Science.gov (United States)

    Crespo, S; Palacios, G; Scott, S; Lago, M; Puente, S; Martínez, M; Baquero, M; Subirats, M

    2004-05-01

    Several authors have described a particular potential of automated depolarization analysis in detecting malaria infection as part of the routine full blood count (FBC) performed by the Cell-Dyn 4000 analyzer. In these cases, abnormal depolarizing patterns are due to the presence of leukocyte-associated malaria hemozoin, a pigment which depolarizes the laser light. In this report we describe samples from three individual patients who did not have malaria infection but showed abnormal depolarizing events. Further investigation determined that these samples were from patients infected by the nematode Mansonella perstans. The observed depolarizing pattern consisted of a normal depolarizing eosinophil population and in addition an abnormal depolarizing population that showed a close "linear" relationship between "granularity" (90 degrees depolarization) and "lobularity" (90 degrees polarization). This atypical population was smaller than normal leukocytes and thus clearly different from the patterns associated with malaria infection. Abnormal depolarization patterns of M. perstans clearly do not reflect leukocyte-associated malaria hemozoin. It is possible however that the erythrocyte-lysing agent used to facilitate leukocyte analysis by the instrument may have caused microfilaria fragmentation and thus the distinctive "straight-line" features of the abnormal scatter plots

  14. 用于等离子体离子辐照的新型阶梯型脉冲高压电路研制%Novel Circuit Producing Pulsed High Voltage with Discrete Steps for Ion Bombardment in Plasma Immersion

    Institute of Scientific and Technical Information of China (English)

    石经纬; 田修波; 巩春志; 杨士勤

    2011-01-01

    为满足等离子体离子辐照和复合表面改性处理技术的发展,提出了基于Marx发生器,通过调节驱动信号延时,实现放电IGBT开关不同时导通,从而获得阶梯型脉冲高压输出的电路设计思想,并验证了其可行性.试验结果显示,该电路可输出脉冲峰值电压10 kV,峰值电流30 A,脉冲宽度3~30μs,脉冲频率20~500 Hz,最大电压阶数10阶的高压脉冲.1个原边、10个副边结构的驱动高压隔离变压器及延时驱动电路结构紧凑,抗干扰能力强.IGBT驱动反向偏置脉冲电压能够满足IGBT快速关断和过流保护的要求.等离子体负载下电路特性测试结果表明,该电路能够适应实际的工作环境,为复合处理技术的发展提供技术支持.该电路结构通过Marx单元叠加可以拓展到更高的脉冲电压输出.%A novel circuit which is capable of producing pulsed high voltage with discrete steps based on Marx generator has been developed for ion bombardment in plasma immersion, and it is realized by means of each discharge IG-BT switching on at different time by adjusting the delay time of drive signals. A compact and robust circuit is designed, using a high-voltage isolation transformer with one primary winding and ten secondary windings for control signal and designed delay drive unit, to meet the requirements of rapidity of switch off and overcurrent protection of IGBT. A pulsed high voltage with amplitude of 10kV, peak current of 30A, pulse width of 3~30 μs, frequency of 20~500 Hz and voltage steps of 10 are achieved. The developed circuit with several kinds of output voltage waveforms is applied to the plasma load with high reliability, and possesses the practicability for ion bombardment or hy-. Brid surface modification in plasma immersion mode. The higher pulse voltage may be achieved using more Marx link with the same control mode for wide application.

  15. Voltage-gated proton (H(v)1) channels, a singular voltage sensing domain.

    Science.gov (United States)

    Castillo, Karen; Pupo, Amaury; Baez-Nieto, David; Contreras, Gustavo F; Morera, Francisco J; Neely, Alan; Latorre, Ramon; Gonzalez, Carlos

    2015-11-14

    The main role of voltage-gated proton channels (Hv1) is to extrude protons from the intracellular milieu when, mediated by different cellular processes, the H(+) concentration increases. Hv1 are exquisitely selective for protons and their structure is homologous to the voltage sensing domain (VSD) of other voltage-gated ion channels like sodium, potassium, and calcium channels. In clear contrast to the classical voltage-dependent channels, Hv1 lacks a pore domain and thus permeation necessarily occurs through the voltage sensing domain. Hv1 channels are activated by depolarizing voltages, and increases in internal proton concentration. It has been proposed that local conformational changes of the transmembrane segment S4, driven by depolarization, trigger the molecular rearrangements that open Hv1. However, it is still unclear how the electromechanical coupling is achieved between the VSD and the potential pore, allowing the proton flux from the intracellular to the extracellular side. Here we provide a revised view of voltage activation in Hv1 channels, offering a comparative scenario with other voltage sensing channels domains.

  16. Evidence that heterosynaptic depolarization underlies associativity of long-term potentiation in rat hippocampus.

    Science.gov (United States)

    Clark, K A; Collingridge, G L

    1996-01-15

    1. Whole-cell patch-clamp recording has been used to study the effect of heterosynaptic depolarization on pure N-methyl-D-aspartate (NMDA) receptor-mediated synaptic transmission in the CA1 region of rat hippocampal slices. 2. In neurones voltage clamped at -60 mV, paired-pulse stimulation of one set of Schaffer collateral-commissural fibres resulted in homosynaptic paired-pulse facilitation of the NMDA receptor-mediated excitatory postsynaptic current (EPSCN). In contrast, stimulation of one set of fibres prior to stimulation of a second set of fibres (i.e. heterosynaptic paired-pulse stimulation) did not result in any heterosynaptic interactions. 3. However, under current-clamp conditions, heterosynaptic paired-pulse stimulation resulted in heterosynaptic 'paired-pulse facilitation' of the NMDA receptor-mediated excitatory postsynaptic potential (EPSPN). 4. In neurones held at -50 or -40 mV, perfusion of nominally Mg(2+)-free medium converted the response to heterosynaptic paired-pulse stimulation from 'heterosynaptic facilitation' to 'heterosynaptic depression' of EPSPN. 5. When neurones were held at potentials of between -30 and +40 mV then heterosynaptic paired-pulse stimulation, in normal Mg(2+)-containing medium, resulted in 'paired-pulse depression' of EPSPN. Under voltage-clamp conditions (tested at +40 mV) no heterosynaptic interactions were seen. 6. The time course of 'heterosynaptic facilitation' at -60 mV and of 'heterosynaptic depression' at +40 mV of EPSPN was similar to the time course of EPSCN. 7. We conclude, firstly, that the voltage clamp is able to prevent any voltage breakthrough associated with the synaptic activation of NMDA receptors from influencing neighbouring synapses. Secondly, when the neurone is not voltage clamped these same synapses are strongly influenced by the spreading depolarization generated by the synaptic activation of their neighbours. The time course and direction of this influence are compatible with the hypothesis that

  17. Dual Input High Step-up DC-DC Converters With Voltage Multiplier Cells%一种基于倍压单元的双输入高增益直流变换器

    Institute of Scientific and Technical Information of China (English)

    孙鹏菊; 李正宇; 张冀; 周雒维

    2016-01-01

    According to the problems that more than one energy source, low output voltage of the battery module and unstable output power in the distributed photovoltaic power generation system, a dual input high step-up DC-DC converter with capacitor-diode multiplier cells was proposed in this paper. The proposed topology has the following advantages: the voltage gain is high, the voltage stress of the switches is low, there are more control freedoms and the sources can deliver power to the load with flexible power management methods. Firstly, the operation mode and the performance characteristics of the converter were presented in detail. Secondly, the steady state analysis, the voltage and current stresses of the switches and the relationship between the input currents were also introduced. Finally, the correctness and feasibility of the proposed circuit topology and the theoretical analysis were fully verified by a 1000W prototype.%针对分布式光伏发电系统电池模块多、输出电压低、功率不稳定等问题,提出了一种基于电容-二极管倍压单元的双输入高增益Boost型直流变换器。该变换器具有电压调节增益高、开关器件电压应力小、控制自由度多、各输入源功率可灵活分配等优点。首先分析了双输入高增益 Boost变换器的工作原理及性能特点,给出了变换器的稳态关系式及开关管电压电流应力计算结果,最后通过一台1000W的实验样机,验证了电路拓扑和理论分析的可行性和正确性。

  18. 阶梯型脉冲电压诱导连续能量质子谱数值仿真%Numerical simulation of proton generation with continuous energy spectrum by pulse voltage with discrete steps

    Institute of Scientific and Technical Information of China (English)

    石经纬; 汪志健; 巩春志; 田修波; 杨士勤

    2011-01-01

    The performance degradation of spacecraft thermal control coatings irradiated by protons is generally investigated by using protons with the same energy in ground testing while the energy of protons is in succession in space. The irradiation e-quivalence of the two kinds of protons is still not well understood. In this paper, a method of producing protons with continuous energy by plasma sheath acceleration using pulse voltage with discrete steps is proposed for better analysis of irradiation equivalence. The dose-energy distribution on the sample is numerically investigated by particle-in-cell(PIC) method. The characteristics of dose-energy distribution and the formation mechanism of protons with continuous energy are then discussed. The results show that protons with continuous energy can be realized utilizing pulse voltage with discrete steps, as the energy of protons irradiating the sample overlaps between two adjacent 1 μs periods, and the energy of protons produced is closely related to the voltage on the sample in every 1 μs period. Moreover, the number of protons irradiating the sample may decrease if the proton energy increases.%热控涂层质子辐照的地面模拟研究中采用单一能量质子替代空间能量连续分布的质子,连续能量质子谱是其等效性研究的关键.提出了采用阶梯型脉冲负偏压鞘层加速技术在一个脉冲宽度内获得连续能量质子谱的方法,并利用质点网格法对所获得质子谱的剂量-能量关系进行了数值仿真研究,分析了连续能量质子谱的剂量-能量分布特征及连续能量质子谱的形成过程.结果表明:阶梯型脉冲负偏压鞘层加速能够产生连续能量的质子谱,连续谱是每微秒区间入射到样品的质子叠加而成的,且每个区间所产生质子的能量与该区间电压值相对应,连续谱中,随着质子能量的增加,其剂量总体上呈现下降的趋势.

  19. [Cortical spreading depolarization: a new pathophysiological mechanism in neurological diseases].

    Science.gov (United States)

    Sánchez-Porras, Renán; Robles-Cabrera, Adriana; Santos, Edgar

    2014-05-20

    Cortical spreading depolarization is a wave of almost complete depolarization of the neuronal and glial cells that occurs in different neurological diseases such as migraine with aura, subarachnoid hemorrhage, intracerebral hemorrhage, head trauma and stroke. These depolarization waves are characterized by a change in the negative potential with an amplitude between -10 and -30mV, duration of ∼1min and changes in the ion homeostasis between the intra- and extracellular space. This results in neuronal edema and dendritic distortion. Under pathologic states of hypoperfusion, cortical spreading depolarization can produce oxidative stress, worsen hypoxia and induce neuronal death. This is due to intense arterial vasoconstriction produced by an inverse response called spreading ischemia. Only in the last years there has been an electrophysiological confirmation of cortical spreading depolarization in human brains. Occurrence of cortical spreading depolarization has been associated with worse outcome in patients. Currently, increased knowledge regarding the pathophysiologic mechanisms supports the hypothetical correlation of cortical spreading depolarization with brain damage in humans. There are diverse therapeutic alternatives that promise inhibition of cortical spreading depolarization and subsequent better outcomes. Copyright © 2013 Elsevier España, S.L. All rights reserved.

  20. Depolarization Lidar Determination of Cloud-Base Microphysical Properties

    NARCIS (Netherlands)

    Donovan, D.P.; Klein Baltink, H.; Henzing, J.S.; Roode, S. de; Siebesma, A.P.

    2016-01-01

    The links between multiple-scattering induced depolarization and cloud microphysical properties (e.g. cloud particle number density, effective radius, water content) have long been recognised. Previous efforts to use depolarization information in a quantitative manner to retrieve cloud microphysical

  1. NK-3 receptor activation depolarizes and induces an after-depolarization in pyramidal neurons in gerbil cingulate cortex

    DEFF Research Database (Denmark)

    Rekling, Jens C

    2004-01-01

    The involvement of tachykinins in cortical function is poorly understood. To study the actions of neurokinin-3 (NK3) receptor activation in frontal cortex, whole cell patch clamp recordings were performed from pyramidal neurons in slices of cingulate cortex from juvenile gerbils. Senktide (500n......M), a selective NK3 receptor agonist, induced a transient increase in spontaneous EPSPs in layer V pyramidal neurons, accompanied by a small depolarization ( approximately 4 mV). EPSPs during senktide had a larger amplitude and faster 10-90% rise time than during control. Senktide induced a transient...... depolarization in layer II/III pyramidal neurons, which often reached threshold for spikes. The depolarization ( approximately 6 mV) persisted in TTX, and was accompanied by an increase in input resistance. Senktide also transiently induced a slow after-depolarization, which appeared following a depolarizing...

  2. The Position of the Fast-Inactivation Gate during Lidocaine Block of Voltage-gated Na+ Channels

    OpenAIRE

    Vedantham, Vasanth; Cannon, Stephen C.

    1999-01-01

    Lidocaine produces voltage- and use-dependent inhibition of voltage-gated Na+ channels through preferential binding to channel conformations that are normally populated at depolarized potentials and by slowing the rate of Na+ channel repriming after depolarizations. It has been proposed that the fast-inactivation mechanism plays a crucial role in these processes. However, the precise role of fast inactivation in lidocaine action has been difficult to probe because gating of drug-bound channel...

  3. Rapid State-Dependent Alteration in Kv3 Channel Availability Drives Flexible Synaptic Signaling Dependent on Somatic Subthreshold Depolarization

    Directory of Open Access Journals (Sweden)

    Matthew J.M. Rowan

    2017-02-01

    Full Text Available In many neurons, subthreshold depolarization in the soma can transiently increase action-potential (AP-evoked neurotransmission via analog-to-digital facilitation. The mechanisms underlying this form of short-term synaptic plasticity are unclear, in part, due to the relative inaccessibility of the axon to direct physiological interrogation. Using voltage imaging and patch-clamp recording from presynaptic boutons of cerebellar stellate interneurons, we observed that depolarizing somatic potentials readily spread into the axon, resulting in AP broadening, increased spike-evoked Ca2+ entry, and enhanced neurotransmission strength. Kv3 channels, which drive AP repolarization, rapidly inactivated upon incorporation of Kv3.4 subunits. This leads to fast susceptibility to depolarization-induced spike broadening and analog facilitation independent of Ca2+-dependent protein kinase C signaling. The spread of depolarization into the axon was attenuated by hyperpolarization-activated currents (Ih currents in the maturing cerebellum, precluding analog facilitation. These results suggest that analog-to-digital facilitation is tempered by development or experience in stellate cells.

  4. Rapid State-Dependent Alteration in Kv3 Channel Availability Drives Flexible Synaptic Signaling Dependent on Somatic Subthreshold Depolarization.

    Science.gov (United States)

    Rowan, Matthew J M; Christie, Jason M

    2017-02-21

    In many neurons, subthreshold depolarization in the soma can transiently increase action-potential (AP)-evoked neurotransmission via analog-to-digital facilitation. The mechanisms underlying this form of short-term synaptic plasticity are unclear, in part, due to the relative inaccessibility of the axon to direct physiological interrogation. Using voltage imaging and patch-clamp recording from presynaptic boutons of cerebellar stellate interneurons, we observed that depolarizing somatic potentials readily spread into the axon, resulting in AP broadening, increased spike-evoked Ca(2+) entry, and enhanced neurotransmission strength. Kv3 channels, which drive AP repolarization, rapidly inactivated upon incorporation of Kv3.4 subunits. This leads to fast susceptibility to depolarization-induced spike broadening and analog facilitation independent of Ca(2+)-dependent protein kinase C signaling. The spread of depolarization into the axon was attenuated by hyperpolarization-activated currents (Ih currents) in the maturing cerebellum, precluding analog facilitation. These results suggest that analog-to-digital facilitation is tempered by development or experience in stellate cells.

  5. High K+-induced contraction requires depolarization-induced Ca2+ release from internal stores in rat gut smooth muscle

    Institute of Scientific and Technical Information of China (English)

    Timo KIRSCHSTEIN; Mirko REHBERG; Rika BAJORAT; Tursonjan TOKAY; Katrin PORATH; Rudiger KOHLING

    2009-01-01

    Aim: Depolarization-induced contraction of smooth muscle is thought to be mediated by Ca2+influx through voltage-gated L-type Ca2+channels. We describe a novel contraction mechanism that is independent of Ca2+ entry.Methods: Pharmacological experiments were carried out on isolated rat gut longitudinal smooth muscle preparations, measuring iso-metric contraction strength upon high K+-induced depolarization.Results: Treatment with verapamil, which presumably leads to a conformational change in the channel, completely abolished K+-induced contraction, while residual contraction still occurred when Ca2+ entry was blocked with Cd2+. These results were further con-firmed by measuring intracellular Ca2+ transients using Fura-2. Co-application of Cd2+ and the ryanodine receptor blocker DHBP further reduced contraction, albeit incompletely. Additional blockage of either phospholipase C (U 73122) or inositol 1,4,5-trisphophate (IP3)receptors (2-APB) abolished most contractions, while sole application of these blockers and Cd2+ (without parallel ryanodine receptor manipulation) also resulted in incomplete contraction block.Conclusion: We conclude that there are parallel mechanisms of depolarization-induced smooth muscle contraction via (a) Ca2+ entry and (b) Ca2+ entry-independent, depolarization-induced Ca2+-release through ryanodine receptors and IP3, with the latter being depen-dent on phospholipase C activation.

  6. Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT.

    Science.gov (United States)

    Aguilar, Jenny I; Dunn, Matthew; Mingote, Susana; Karam, Caline S; Farino, Zachary J; Sonders, Mark S; Choi, Se Joon; Grygoruk, Anna; Zhang, Yuchao; Cela, Carolina; Choi, Ben Jiwon; Flores, Jorge; Freyberg, Robin J; McCabe, Brian D; Mosharov, Eugene V; Krantz, David E; Javitch, Jonathan A; Sulzer, David; Sames, Dalibor; Rayport, Stephen; Freyberg, Zachary

    2017-08-30

    The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. The continuum of spreading depolarizations in acute cortical lesion development

    DEFF Research Database (Denmark)

    Hartings, Jed A; Shuttleworth, C William; Kirov, Sergei A;

    2017-01-01

    A modern understanding of how cerebral cortical lesions develop after acute brain injury is based on Aristides Leão's historic discoveries of spreading depression and asphyxial/anoxic depolarization. Treated as separate entities for decades, we now appreciate that these events define a continuum...... of spreading mass depolarizations, a concept that is central to understanding their pathologic effects. Within minutes of acute severe ischemia, the onset of persistent depolarization triggers the breakdown of ion homeostasis and development of cytotoxic edema. These persistent changes are diagnosed....... The causal role of these waves in lesion development has been proven by real-time monitoring of electrophysiology, blood flow, and cytotoxic edema. The spreading depolarization continuum further applies to other models of acute cortical lesions, suggesting that it is a universal principle of cortical lesion...

  8. Scattering and Depolarization of Electromagnetic Waves--Full Wave Solutions.

    Science.gov (United States)

    1984-01-01

    Analysis," Proceedings of the International Union of Radio Science URSI Conference at Ciudad Universitaria , Madrid, August 1983, in press. . . 13...rough land and seat3 J. The full wave approach was also used to determine the scattering and depolarization of radio waves in irregular spheroidal struc...Full Wave Solutions," Radio Science, Vol. 17, No. 5, September-October 1982, pp. 1055-1066. 4. "Scattering and Depolarization by Rough Surfaces: Full

  9. Amrinone effects on electromechanical coupling and depolarization-induced automaticity in ventricular muscle of guinea pigs and ferrets.

    Science.gov (United States)

    Malécot, C O; Arlock, P; Katzung, B G

    1985-01-01

    The effects of the cardiotonic agent, amrinone (0.05-4 mM), on electrical and mechanical activities of ferret and guinea-pig papillary muscles were studied using current and voltage clamp (single sucrose gap) techniques. In current clamp studies, amrinone increased, in a dose-dependent manner, contractile force elicited by action potential in both species. Depolarization-induced automaticity was facilitated in ferret muscles at all maximum diastolic potentials between -70 and -15 mV. Facilitation of automaticity in guinea-pig muscles occurred only at potentials more negative than -35 mV and was suppressed at more positive potentials. Cimetidine (10 microM) partially reversed the effects of amrinone on automaticity in both species. In voltage clamp studies, amrinone increased the slow inward current. Steady-state outward current was increased in guinea-pig but not in ferret muscles. A dual effect of amrinone on tension was observed. Amrinone was found to increase phasic tension of ferret papillary muscles only for depolarizations lasting less than 250 to 300 msec. For longer depolarizations, amrinone decreased the phasic tension (in a dose-dependent manner), whereas the tonic tension was not modified. The decrease as well as the increase in tension was associated with an increase of the slow inward current. The results suggest that amrinone may be arrhythmogenic and may have an intracellular action at the sarcoplasmic reticulum level (partial inhibition) in addition to its action on the calcium current.

  10. On The Depolarization Asymmetry Seen in Giant Radio Lobes

    CERN Document Server

    Bell, M B

    2012-01-01

    The depolarization asymmetry seen in double-lobed radio sources, referred to as the Laing-Garrington (L-G) effect where more rapid depolarization is seen in the lobe with no visible jet as the wavelength increases, can be explained either by internal differences between the two lobes, or by an external Faraday screen that lies in front of only the depolarized lobe. If the jet one-sidedness is due to relativistic beaming the depolarization asymmetry must be due to an intervening Faraday screen. If it is intrinsic the depolarization asymmetry must be related to internal differences in the lobes. We assume in this paper that the speed in the outer jet of several Fanaroff-Riley Class 1 (FRI) sources exhibiting the L-G effect is close to the 0.1c reported by several other investigators. For these sources we find that the jet one-sidedness cannot be explained by beaming and therefore must be intrinsic. In these FRI sources the L-G effect must be due to differences that originate inside the lobes themselves. Althoug...

  11. Analysis of Antimicrobial-Triggered Membrane Depolarization Using Voltage Sensitive Dyes

    NARCIS (Netherlands)

    Derk te Winkel, J.; Gray, D.A.; Seistrup, K.H.; Hamoen, L.W.; Strahl, H.

    2016-01-01

    The bacterial cytoplasmic membrane is a major inhibitory target for antimicrobial compounds. Commonly, although not exclusively, these compounds unfold their antimicrobial activity by disrupting the essential barrier function of the cell membrane. As a consequence, membrane permeability assays are

  12. Slow Bursting Neurons of Mouse Cortical Layer 6b Are Depolarized by Hypocretin/Orexin and Major Transmitters of Arousal

    Science.gov (United States)

    Wenger Combremont, Anne-Laure; Bayer, Laurence; Dupré, Anouk; Mühlethaler, Michel; Serafin, Mauro

    2016-01-01

    Neurons firing spontaneously in bursts in the absence of synaptic transmission have been previously recorded in different layers of cortical brain slices. It has been suggested that such neurons could contribute to the generation of alternating UP and DOWN states, a pattern of activity seen during slow-wave sleep. Here, we show that in layer 6b (L6b), known from our previous studies to contain neurons highly responsive to the wake-promoting transmitter hypocretin/orexin (hcrt/orx), there is a set of neurons, endowed with distinct intrinsic properties, which displayed a strong propensity to fire spontaneously in rhythmic bursts. In response to small depolarizing steps, they responded with a delayed firing of action potentials which, upon higher depolarizing steps, invariably inactivated and were followed by a depolarized plateau potential and a depolarizing afterpotential. These cells also displayed a strong hyperpolarization-activated rectification compatible with the presence of an Ih current. Most L6b neurons with such properties were able to fire spontaneously in bursts. Their bursting activity was of intrinsic origin as it persisted not only in presence of blockers of ionotropic glutamatergic and GABAergic receptors but also in a condition of complete synaptic blockade. However, a small number of these neurons displayed a mix of intrinsic bursting and synaptically driven recurrent UP and DOWN states. Most of the bursting L6b neurons were depolarized and excited by hcrt/orx through a direct postsynaptic mechanism that led to tonic firing and eventually inactivation. Similarly, they were directly excited by noradrenaline, histamine, dopamine, and neurotensin. Finally, the intracellular injection of these cells with dye and their subsequent Neurolucida reconstruction indicated that they were spiny non-pyramidal neurons. These results lead us to suggest that the propensity for slow rhythmic bursting of this set of L6b neurons could be directly impeded by hcrt

  13. Spreading depolarizations in patients with spontaneous intracerebral hemorrhage

    DEFF Research Database (Denmark)

    Helbok, Raimund; Schiefecker, Alois Josef; Friberg, Christian;

    2017-01-01

    Pathophysiologic mechanisms of secondary brain injury after intracerebral hemorrhage and in particular mechanisms of perihematomal-edema progression remain incompletely understood. Recently, the role of spreading depolarizations in secondary brain injury was established in ischemic stroke......, subarachnoid hemorrhage and traumatic brain injury patients. Its role in intracerebral hemorrhage patients and in particular the association with perihematomal-edema is not known. A total of 27 comatose intracerebral hemorrhage patients in whom hematoma evacuation and subdural electrocorticography...... patients (67%), a total of 650 spreading depolarizations were observed. Spreading depolarizations were more common in the initial days with a peak incidence on day 2. Median electrocorticography depression time was longer than previously reported (14.7 min, IQR, 9-22 min). Postoperative perihematomal-edema...

  14. Depolarization and attenuation effects of radomes at 20 GHz

    Science.gov (United States)

    Hendrix, Charles E.; McNally, James E.; Monzingo, Robert A.

    1989-03-01

    The problem of describing the attenuation and depolarization effects of a wet radome on a transmitted signal is considered by experiments carried out with two commonly used radome materials, ESSCOLAM-6 and ESSCOLAM-8. The results suggest that a two-component model of depolarization is required to account for the observed results. Predictions for the behavior of a complete radome are obtained, but full-scale testing with an operating radome to compare predicted and actual results remains to be done. An important conclusion is that, while highly water-repellent radome materials are desirable from the point of view of attenuation, they are not so desirable in terms of the degree of depolarization introduced between orthogonally polarized signal components in frequency-reuse systems.

  15. A Novel Voltage Sensor in the Orthosteric Binding Site of the M2 Muscarinic Receptor.

    Science.gov (United States)

    Barchad-Avitzur, Ofra; Priest, Michael F; Dekel, Noa; Bezanilla, Francisco; Parnas, Hanna; Ben-Chaim, Yair

    2016-10-04

    G protein-coupled receptors (GPCRs) mediate many signal transduction processes in the body. The discovery that these receptors are voltage-sensitive has changed our understanding of their behavior. The M2 muscarinic acetylcholine receptor (M2R) was found to exhibit depolarization-induced charge movement-associated currents, implying that this prototypical GPCR possesses a voltage sensor. However, the typical domain that serves as a voltage sensor in voltage-gated channels is not present in GPCRs, making the search for the voltage sensor in the latter challenging. Here, we examine the M2R and describe a voltage sensor that is comprised of tyrosine residues. This voltage sensor is crucial for the voltage dependence of agonist binding to the receptor. The tyrosine-based voltage sensor discovered here constitutes a noncanonical by which membrane proteins may sense voltage.

  16. Voltage-dependent potassium currents during fast spikes of rat cerebellar Purkinje neurons: inhibition by BDS-I toxin.

    Science.gov (United States)

    Martina, Marco; Metz, Alexia E; Bean, Bruce P

    2007-01-01

    We characterized the kinetics and pharmacological properties of voltage-activated potassium currents in rat cerebellar Purkinje neurons using recordings from nucleated patches, which allowed high resolution of activation and deactivation kinetics. Activation was exceptionally rapid, with 10-90% activation in about 400 mus at +30 mV, near the peak of the spike. Deactivation was also extremely rapid, with a decay time constant of about 300 mus near -80 mV. These rapid activation and deactivation kinetics are consistent with mediation by Kv3-family channels but are even faster than reported for Kv3-family channels in other neurons. The peptide toxin BDS-I had very little blocking effect on potassium currents elicited by 100-ms depolarizing steps, but the potassium current evoked by action potential waveforms was inhibited nearly completely. The mechanism of inhibition by BDS-I involves slowing of activation rather than total channel block, consistent with the effects described in cloned Kv3-family channels and this explains the dramatically different effects on currents evoked by short spikes versus voltage steps. As predicted from this mechanism, the effects of toxin on spike width were relatively modest (broadening by roughly 25%). These results show that BDS-I-sensitive channels with ultrafast activation and deactivation kinetics carry virtually all of the voltage-dependent potassium current underlying repolarization during normal Purkinje cell spikes.

  17. Hydrogen depolarized carbon dioxide concentrator performance improvements and cell pair structural tests. [for manned space station

    Science.gov (United States)

    Huddleston, J. D.; Aylward, J. R.

    1973-01-01

    The investigations and testing associated with the CO2 removal efficiency and voltage degradation of a hydrogen depolarized carbon oxide concentrator are reported. Also discussed is the vibration testing of a water vapor electrolysis cell pair. Performance testing of various HDC cell pairs with Cs2CO3 electrolyte provided sufficient parametric and endurance data to size a six man space station prototype CO2 removal system as having 36 HDC cell pairs, and to verify a life capability exceeding six moths. Testing also demonstrated that tetramethylammonium carbonate is an acceptable HDC electrolyte for operating over the relative humidity range of 30 to 90 percent and over a temperature range of 50 to 80 F.

  18. Functional reconstitution of the voltage-regulated sodium channel purified from electroplax of Electrophorus electricus

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, R.L.

    1985-01-01

    The voltage-regulated NA channel is responsible for the depolarization of the excitable cell membrane during the normal action potential. This research has focused on the functional properties of the Na channel, purified from detergent extracts of electroplax membranes of the electric eel, and reconstituted into vesicles of defined phospholipid. These properties were assessed by measuring neurotoxin-modulated ion flux into the reconstituted membrane vesicles and by recording the single-channel currents of the purified channel by the patch-clamp method. The binding of tritiated tetrodotoxin (TTX) was employed as a marker for the purification of the channel. Two high-resolution fractionation steps, based on molecular charge and protein size, were used to obtain a preparation that is 80% homogeneous for a large peptide of 270,000 daltons. Radiotracer /sup 22/Na/sup +/ influx into the vesicles was stimulated by veratridine and by batrachotoxin (BTX) at concentrations of 100 ..mu..M and 5 ..mu..M, respectively. The stimulation by BTX was greater than that by veratridine, and can be as much as 16-fold over control influx levels. The stimulated influx is blocked by TTX with a K/sub i/ of 35 nM, and by local anesthetics in the normal pharmacological range. Large multilamellar vesicles prepared with a freeze-thaw step are suitable for single-channel recording techniques. When excised patches of the reconstituted membranes were voltage-clamped in the absence of activating neurotoxins, voltage-dependent single-channel currents were recorded. These displayed properties similar to those from native membranes of nerve and muscle. These results indicate that the protein purified on the basis of TTX binding is a functional Na channel possessing these functional domains: the ion-selective channel, the voltage sensors controlling activation and inactivation, and the sites of action of TTX, alkaloid neurotoxins, and local anesthetics.

  19. Enhanced Spin Depolarization and Storage Time in a Rb Vapor

    Institute of Scientific and Technical Information of China (English)

    QI Yue-Rong; GAO Hong; ZHANG Shou-Gang

    2009-01-01

    The experiment of measuring the spin depolarized time and light storage time in a Rb vapor under different conditions is performed. Typically, these measurements are accomplished in three different containers: atoms in a bare glass ceil, atoms in a buffer gas cell, and atoms in a tetracontane (C40H82) coating cell. The increasing depolarization and storage times are observed in both the buffer gas ceil and the tetracontane coating cell. In the latter case, a storage time greater than 400 μs is obtained.

  20. Nonspherical nanoparticles characterization by partially depolarized dynamic light scattering

    Science.gov (United States)

    Levin, Alexander D.; Shmytkova, Ekaterina A.

    2015-06-01

    The realization of improved depolarized dynamic light scattering method is presented. This technique supports measurement of non-spherical nanoparticals dimensions in liquids. The relations between translational and rotational diffusion coefficients and autocorrelation function of scattered light with polarized and depolarized components in various proportions are derived. Thus measurement of very weak cross-polarized component can be avoided. This improvement permits to reduce measurement time, to improve signal to noise ratio and results precision. The technique was applied for sizing of gold nanorods and multiwalled carbon nanotubes in liquids.

  1. Observation of wide rf induced synchrotron sideband depolarizing resonances.

    Science.gov (United States)

    Bychkov, M. A.; Anferov, V. A.; Blinov, B. B.; Courant, E. D.; Crandell, D. A.; Derbenev, Ya. S.; Kaufman, W. A.; Krisch, A. D.; Lorenzon, W.; Nurushev, T. S.; Phelps, R. A.; Wong, V. K.; Caussyn, D. D.; Chu, C. M.; Ellison, T. J. P.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E. J.; von Przewoski, B.; Ohmori, C.; Minty, M. G.; Russell, A. D.

    1997-04-01

    In a recent experiment with a stored 104.1 MeV vertically polarized proton beam at the IUCF Cooler Ring, we depolarized the beam using an rf solenoid with a magnetic field of about 1.3\\cdot10-3T\\cdotm. We observed the two expected rf depolarizing resonances centered around the protons' 1.5 MHz circulation frequency as in previous experiments. Near each of these resonances, we also found synchrotron sidebands which are caused by the proton's energy oscillations. The strengths and widths of the synchrotron resonances were quite different for the sidebands above and below the circulation frequency.

  2. CHARACTERIZATION TESTING AND ANALYSIS OF SINGLE CELL SO2 DEPOLARIZED ELECTROLYZER

    Energy Technology Data Exchange (ETDEWEB)

    Steimke, J; Timothy Steeper, T

    2006-09-15

    This document reports work performed at the Savannah River National Laboratory (SRNL) that further develops the use of a proton exchange membrane or PEM-type electrochemical cell to produce hydrogen via SO{sub 2}-depolarized water electrolysis. This work was begun at SRNL in 2005. This research is valuable in achieving the ultimate goal of an economical hydrogen production process based on the Hybrid Sulfur (HyS) Cycle. The HyS Process is a hybrid thermochemical cycle that may be used in conjunction with advanced nuclear reactors or centralized solar receivers to produce hydrogen by water-splitting. Like all other sulfur-based cycles, HyS utilizes the high temperature thermal decomposition of sulfuric acid to produce oxygen. The unique aspect of HyS is the generation of hydrogen in a water electrolyzer that is operated under conditions where dissolved sulfur dioxide depolarizes the anodic reaction, resulting in substantial voltage reduction. Sulfur dioxide is oxidized at the anode, producing sulfuric acid that is sent to the acid decomposition portion of the cycle. The focus of this work was to conduct single cell electrolyzer tests in order to prove the concept of SO{sub 2}-depolarization and to determine how the results can be used to evaluate the performance of key components of the HyS Process. A test facility for conducting SO{sub 2}-depolarized electrolyzer (SDE) testing was designed, constructed and commissioned. The maximum cell current is 50 amperes, which is equivalent to a hydrogen production rate of approximately 20 liters per hour. Feed to the anode of the electrolyzer is sulfuric acid solutions containing dissolved sulfur dioxide. The partial pressure of sulfur dioxide may be varied in the range of 1 to 6 atm (15 to 90 psia). Temperatures may be controlled in the range from ambient to 80 C. Hydrogen generated at the cathode of the cell is collected for the purpose of flow measurement and composition analysis. The test facility proved to be easy to

  3. CHARACTERIZATION TESTING AND ANALYSIS OF SINGLE CELL SO2 DEPOLARIZED ELECTROLYZER

    Energy Technology Data Exchange (ETDEWEB)

    Steimke, J; Timothy Steeper, T

    2006-09-15

    This document reports work performed at the Savannah River National Laboratory (SRNL) that further develops the use of a proton exchange membrane or PEM-type electrochemical cell to produce hydrogen via SO{sub 2}-depolarized water electrolysis. This work was begun at SRNL in 2005. This research is valuable in achieving the ultimate goal of an economical hydrogen production process based on the Hybrid Sulfur (HyS) Cycle. The HyS Process is a hybrid thermochemical cycle that may be used in conjunction with advanced nuclear reactors or centralized solar receivers to produce hydrogen by water-splitting. Like all other sulfur-based cycles, HyS utilizes the high temperature thermal decomposition of sulfuric acid to produce oxygen. The unique aspect of HyS is the generation of hydrogen in a water electrolyzer that is operated under conditions where dissolved sulfur dioxide depolarizes the anodic reaction, resulting in substantial voltage reduction. Sulfur dioxide is oxidized at the anode, producing sulfuric acid that is sent to the acid decomposition portion of the cycle. The focus of this work was to conduct single cell electrolyzer tests in order to prove the concept of SO{sub 2}-depolarization and to determine how the results can be used to evaluate the performance of key components of the HyS Process. A test facility for conducting SO{sub 2}-depolarized electrolyzer (SDE) testing was designed, constructed and commissioned. The maximum cell current is 50 amperes, which is equivalent to a hydrogen production rate of approximately 20 liters per hour. Feed to the anode of the electrolyzer is sulfuric acid solutions containing dissolved sulfur dioxide. The partial pressure of sulfur dioxide may be varied in the range of 1 to 6 atm (15 to 90 psia). Temperatures may be controlled in the range from ambient to 80 C. Hydrogen generated at the cathode of the cell is collected for the purpose of flow measurement and composition analysis. The test facility proved to be easy to

  4. Determining the Number of Parallel RC Branches in Polarization / Depolarization Current Modeling for XLPE Cable Insulation

    Directory of Open Access Journals (Sweden)

    S. Sulaiman

    2017-06-01

    Full Text Available An important element in the electric power distribution system is the underground cable. However continuous applications of high voltages unto the cable, may lead to insulation degradations and subsequent cable failure. Since any disruption to the electricity supply may lead to economic losses as well as lowering customer satisfaction, the maintenance of cables is very important to an electrical utility company. Thus, a reliable diagnostic technique that is able to accurately assess the condition of cable insulation operating is critical, in order for cable replacement exercise to be done. One such diagnostic technique to assess the level of degradation within the cable insulation is the Polarization / Depolarization Current (PDC analysis. This research work attempts to investigate PDC behaviour for medium voltage (MV cross-linked polyethylene (XLPE insulated cables, via baseline PDC measurements and utilizing the measured data to simulate for PDC analysis. Once PDC simulations have been achieved, the values of conductivity of XLPE cable insulations can be approximated. Cable conductivity serves as an indicator to the level of degradation within XLPE cable insulation. It was found that for new and unused XLPE cables, the polarization and depolarization currents have almost overlapping trendlines, as the cable insulation’s conduction current is negligible. Using a linear dielectric circuit equivalence model as the XLPE cable insulation and its corresponding governing equations, it is possible to optimize the number of parallel RC branches to simulate PDC analysis, with a very high degree of accuracy. The PDC simulation model has been validated against the baseline PDC measurements.

  5. Note: Galvanic isolated voltage source using a single photodiode.

    Science.gov (United States)

    Stoican, O S

    2010-04-01

    A galvanic isolated voltage source able to provide several volts by using a single photodiode is described. A pulse-modulated laser beam is sent to a photodiode. By using a step-up transformer the amplitude of the variable voltage generated by the photodiode is increased. Adding a rectifier cell the variable voltage is converted back into a dc voltage.

  6. Canals beyond Mars: Beam depolarization in radio continuum maps of the warm ISM

    CERN Document Server

    Haverkorn, M

    2004-01-01

    Multi-frequency radio polarimetric observations of the diffuse Galactic synchrotron background enable us to study the structure of the diffuse ionized gas via rotation measure maps. However, depolarization will introduce artifacts in the resulting rotation measure, most notably in the form of narrow, elongated ``depolarization canals''. We use numerical models of a non-emitting Faraday rotating medium to study the RM distribution needed to create depolarization canals by depolarization due to a finite beam width, and to estimate the influence of this depolarization mechanism on the determination of RM. We argue that the depolarization canals indeed can be caused by beam depolarization, which in turn is a natural consequence when observing a turbulent medium with limited resolution. Furthermore, we estimate that beam depolarization can induce an additional error of about 20% in RM determinations, and considerably less in regions that are not affected by depolarization canals.

  7. Electric field enhancement of depolarization of excited states

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Hillard, G.B.; Glab, W.L.

    1985-12-01

    Our calculations show that an external dc electric field can enhance by many orders of magnitude the depolarization cross section of highly excited atoms by charged particles. The enhancement is due to the fact that the electric field extends and shifts the electronic charge distribution along its direction, thus effectively creating a giant electric dipole in the atom.

  8. Primary afferent depolarization evoked by a painful stimulus.

    Science.gov (United States)

    Vyklický, L; Rudomin, P; Zajac, F E; Burke, R E

    1969-07-11

    Pulses of intense radiant heat applied to the plantar pad of unanesthetized spinal cats produced negative dorsal root potentials, increased excitability of cutaneous A fibers, and marked activation of ipsilateral flexor motoneurons. The same effects were obtained during cold block of A fiber conduction in the appropriate peripheral nerve. We conclude that adequate noxious activation of cutaneous C fibers depolarizes cutaneous A fibers.

  9. Decavanadate induces mitochondrial membrane depolarization and inhibits oxygen consumption.

    Science.gov (United States)

    Soares, S S; Gutiérrez-Merino, C; Aureliano, M

    2007-05-01

    Decavanadate induced rat liver mitochondrial depolarization at very low concentrations, half-depolarization with 39 nM decavanadate, while it was needed a 130-fold higher concentration of monomeric vanadate (5 microM) to induce the same effect. Decavanadate also inhibits mitochondrial repolarization induced by reduced glutathione in vitro, with an inhibition constant of 1 microM, whereas no effect was observed up to 100 microM of monomeric vanadate. The oxygen consumption by mitochondria is also inhibited by lower decavanadate than monomeric vanadate concentrations, i.e. 50% inhibition is attained with 99 M decavanadate and 10 microM monomeric vanadate. Thus, decavanadate is stronger as mitochondrial depolarization agent than as inhibitor of mitochondrial oxygen consumption. Up to 5 microM, decavanadate does not alter mitochondrial NADH levels nor inhibit neither F(O)F(1)-ATPase nor cytochrome c oxidase activity, but it induces changes in the redox steady-state of mitochondrial b-type cytochromes (complex III). NMR spectra showed that decameric vanadate is the predominant vanadate species in decavanadate solutions. It is concluded that decavanadate is much more potent mitochondrial depolarization agent and a more potent inhibitor of mitochondrial oxygen consumption than monomeric vanadate, pointing out the importance to take into account the contribution of higher oligomeric species of vanadium for the biological effects of vanadate solutions.

  10. Magnetic correlations in oxides: Neutron diffraction and neutron depolarization study

    Indian Academy of Sciences (India)

    S M Yusuf

    2008-10-01

    We have studied magnetic correlations in several oxide materials that belong to colossal magnetoresistive, naturally occurring layered oxide showing low-dimensional magnetic ordering, solid oxide fuel cell interconnect materials, and magnetic nanoparticles using neutron diffraction and neutron depolarization techniques. In this paper, an overview of some of these results is given.

  11. Migraine prophylaxis, ischemic depolarizations, and stroke outcomes in mice.

    Science.gov (United States)

    Eikermann-Haerter, Katharina; Lee, Jeong Hyun; Yalcin, Nilufer; Yu, Esther S; Daneshmand, Ali; Wei, Ying; Zheng, Yi; Can, Anil; Sengul, Buse; Ferrari, Michel D; van den Maagdenberg, Arn M J M; Ayata, Cenk

    2015-01-01

    Migraine with aura is an established stroke risk factor, and excitatory mechanisms such as spreading depression (SD) are implicated in the pathogenesis of both migraine and stroke. Spontaneous SD waves originate within the peri-infarct tissue and exacerbate the metabolic mismatch during focal cerebral ischemia. Genetically enhanced SD susceptibility facilitates anoxic depolarizations and peri-infarct SDs and accelerates infarct growth, suggesting that susceptibility to SD is a critical determinant of vulnerability to ischemic injury. Because chronic treatment with migraine prophylactic drugs suppresses SD susceptibility, we tested whether migraine prophylaxis can also suppress ischemic depolarizations and improve stroke outcome. We measured the cortical susceptibility to SD and ischemic depolarizations, and determined tissue and neurological outcomes after middle cerebral artery occlusion in wild-type and familial hemiplegic migraine type 1 knock-in mice treated with vehicle, topiramate or lamotrigine daily for 7 weeks or as a single dose shortly before testing. Chronic treatment with topiramate or lamotrigine reduced the susceptibility to KCl-induced or electric stimulation-induced SDs as well as ischemic depolarizations in both wild-type and familial hemiplegic migraine type 1 mutant mice. Consequently, both tissue and neurological outcomes were improved. Notably, treatment with a single dose of either drug was ineffective. These data underscore the importance of hyperexcitability as a mechanism for increased stroke risk in migraineurs, and suggest that migraine prophylaxis may not only prevent migraine attacks but also protect migraineurs against ischemic injury. © 2014 American Heart Association, Inc.

  12. Accurate Switched-Voltage voltage averaging circuit

    OpenAIRE

    金光, 一幸; 松本, 寛樹

    2006-01-01

    Abstract ###This paper proposes an accurate Switched-Voltage (SV) voltage averaging circuit. It is presented ###to compensated for NMOS missmatch error at MOS differential type voltage averaging circuit. ###The proposed circuit consists of a voltage averaging and a SV sample/hold (S/H) circuit. It can ###operate using nonoverlapping three phase clocks. Performance of this circuit is verified by PSpice ###simulations.

  13. Temporal coding at the immature depolarizing GABAergic synapse

    Directory of Open Access Journals (Sweden)

    Guzel Valeeva

    2010-07-01

    Full Text Available In the developing hippocampus, GABA exerts depolarizing and excitatory actions and contributes to the generation of neuronal network driven Giant Depolarizing Potentials (GDPs. Here, we studied spike time coding at immature GABAergic synapses and its impact on synchronization of the neuronal network during GDPs in the neonatal (postnatal days P2-6 rat hippocampal slices. Using extracellular recordings, we found that the delays of action potentials (APs evoked by synaptic activation of GABA(A receptors are long (mean, 65 ms and variable (within a time window of 10-200 ms. During patch-clamp recordings, depolarizing GABAergic responses were mainly subthreshold and their amplification by persistent sodium conductance was required to trigger APs. AP delays at GABAergic synapses shortened and their variability reduced with an increase in intracellular chloride concentration during whole-cell recordings. Negative shift of the GABA reversal potential (EGABA with low concentrations of bumetanide, or potentiation of GABA(A receptors with diazepam reduced GDPs amplitude, desynchronized neuronal firing during GDPs and slowed down GDPs propagation. Partial blockade of GABA(A receptors with bicuculline increased neuronal synchronization and accelerated GDPs propagation. We propose that spike-timing at depolarizing GABA synapses is determined by intracellular chloride concentration. At physiological levels of intracellular chloride GABAergic depolarization does not reach the action potential threshold and amplification of GABAergic responses by non-inactivating sodium conductance is required for postsynaptic AP initiation. Slow and variable excitation at GABAergic synapse determines the level of neuronal synchrony and the rate of GDPs propagation in the developing hippocampus.

  14. Temporal coding at the immature depolarizing GABAergic synapse.

    Science.gov (United States)

    Valeeva, Guzel; Abdullin, Azat; Tyzio, Roman; Skorinkin, Andrei; Nikolski, Evgeny; Ben-Ari, Yehezkiel; Khazipov, Rustem

    2010-01-01

    In the developing hippocampus, GABA exerts depolarizing and excitatory actions and contributes to the generation of neuronal network driven giant depolarizing potentials (GDPs). Here, we studied spike time coding at immature GABAergic synapses and its impact on synchronization of the neuronal network during GDPs in the neonatal (postnatal days P2-6) rat hippocampal slices. Using extracellular recordings, we found that the delays of action potentials (APs) evoked by synaptic activation of GABA(A) receptors are long (mean, 65 ms) and variable (within a time window of 10-200 ms). During patch-clamp recordings, depolarizing GABAergic responses were mainly subthreshold and their amplification by persistent sodium conductance was required to trigger APs. AP delays at GABAergic synapses shortened and their variability reduced with an increase in intracellular chloride concentration during whole-cell recordings. Negative shift of the GABA reversal potential (E(GABA)) with low concentrations of bumetanide, or potentiation of GABA(A) receptors with diazepam reduced GDPs amplitude, desynchronized neuronal firing during GDPs and slowed down GDPs propagation. Partial blockade of GABA(A) receptors with bicuculline increased neuronal synchronization and accelerated GDPs propagation. We propose that spike timing at depolarizing GABA synapses is determined by intracellular chloride concentration. At physiological levels of intracellular chloride GABAergic depolarization does not reach the action potential threshold and amplification of GABAergic responses by non-inactivating sodium conductance is required for postsynaptic AP initiation. Slow and variable excitation at GABAergic synapse determines the level of neuronal synchrony and the rate of GDPs propagation in the developing hippocampus.

  15. Hexabromocyclododecane inhibits depolarization-induced increase in intracellular calcium levels and neurotransmitter release in PC12 cells.

    Science.gov (United States)

    Dingemans, Milou M L; Heusinkveld, Harm J; de Groot, Aart; Bergman, Ake; van den Berg, Martin; Westerink, Remco H S

    2009-02-01

    Environmental levels of the brominated flame retardant (BFR) hexabromocyclododecane (HBCD) have been increasing. HBCD has been shown to cause adverse effects on learning and behavior in mice, as well as on dopamine uptake in rat synaptosomes and synaptic vesicles. For other BFRs, alterations in the intracellular Ca(2+) homeostasis have been observed. Therefore, the aim of this study was to investigate whether the technical HBCD mixture and individual stereoisomers affect the intracellular Ca(2+) concentration ([Ca(2+)](i)) in a neuroendocrine in vitro model (PC12 cells). [Ca(2+)](i) and vesicular catecholamine release were measured using respectively single-cell Fura-2 imaging and amperometry. Exposure of PC12 cells to the technical HBCD mixture or individual stereoisomers did neither affect basal [Ca(2+)](i), nor the frequency of basal neurotransmitter release. However, exposure to HBCD (0-20 microM) did cause a dose-dependent reduction of a subsequent depolarization-evoked increase in [Ca(2+)](i). This effect was apparent only when HBCD was applied at least 5 min before depolarization (maximum effect after 20 min exposure). The effects of alpha- and beta-HBCD were comparable to that of the technical mixture, whereas the inhibitory effect of gamma-HBCD was larger. Using specific blockers of L-, N- or P/Q-type voltage-gated Ca(2+) channels (VGCCs) it was shown that the inhibitory effect of HBCD is not VGCC-specific. Additionally, the number of cells showing depolarization-evoked neurotransmitter release was markedly reduced following HBCD exposure. Summarizing, HBCD inhibits depolarization-evoked [Ca(2+)](i) and neurotransmitter release. As increasing HBCD levels should be anticipated, these findings justify additional efforts to establish an adequate exposure, hazard and risk assessment.

  16. Spreading depolarizations increase delayed brain injury in a rat model of subarachnoid hemorrhage

    NARCIS (Netherlands)

    Hamming, Arend M.; Wermer, Marieke J H; Umesh Rudrapatna, S.; Lanier, Christian; Van Os, Hine J A; Van Den Bergh, Walter M.; Ferrari, Michel D.; van der Toorn, A; Van Den Maagdenberg, Arn M J M; Stowe, Ann M.; Dijkhuizen, Rick M.

    2016-01-01

    Spreading depolarizations may contribute to delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage, but the effect of spreading depolarizations on brain lesion progression after subarachnoid hemorrhage has not yet been assessed directly. Therefore, we tested the hypothesis that

  17. Spreading depolarizations increase delayed brain injury in a rat model of subarachnoid hemorrhage

    NARCIS (Netherlands)

    Hamming, Arend M.; Wermer, Marieke J. H.; Rudrapatna, S. Umesh; Lanier, Christian; van Os, Hine J. A.; van den Bergh, Walter M.; Ferrari, Michel D.; van der Toorn, Annette; van den Maagdenberg, Arn M. J. M.; Stowe, Ann M.; Dijkhuizen, Rick M.

    Spreading depolarizations may contribute to delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage, but the effect of spreading depolarizations on brain lesion progression after subarachnoid hemorrhage has not yet been assessed directly. Therefore, we tested the hypothesis that

  18. Voltage-sensor mutations in channelopathies of skeletal muscle

    Science.gov (United States)

    Cannon, Stephen C

    2010-01-01

    Mutations of voltage-gated ion channels cause several channelopathies of skeletal muscle, which present clinically with myotonia, periodic paralysis, or a combination of both. Expression studies have revealed both loss-of-function and gain-of-function defects for the currents passed by mutant channels. In many cases, these functional changes could be mechanistically linked to the defects of fibre excitability underlying myotonia or periodic paralysis. One remaining enigma was the basis for depolarization-induced weakness in hypokalaemic periodic paralysis (HypoPP) arising from mutations in either sodium or calcium channels. Curiously, 14 of 15 HypoPP mutations are at arginines in S4 voltage sensors, and recent observations show that these substitutions support an alternative pathway for ion conduction, the gating pore, that may be the source of the aberrant depolarization during an attack of paralysis. PMID:20156847

  19. Involvement of inositol 1,4,5-trisphosphate formation in the voltage-dependent regulation of the Ca(2+) concentration in porcine coronary arterial smooth muscle cells.

    Science.gov (United States)

    Yamamura, Hisao; Ohya, Susumu; Muraki, Katsuhiko; Imaizumi, Yuji

    2012-08-01

    The involvement of inositol 1,4,5-trisphosphate (IP(3)) formation in the voltage-dependent regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) was examined in smooth muscle cells of the porcine coronary artery. Slow ramp depolarization from -90 to 0 mV induced progressive [Ca(2+)](i) increase. The slope was reduced or increased in the presence of Cd(2+) or (±)-1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-[trifluoromethyl]-phenyl)pyridine-3-carboxlic acid methyl ester (Bay K 8644), respectively. The decrease in [Ca(2+)](i) via the membrane hyperpolarization induced by K(+) channel openers (levcromakalim and Evans blue) under current clamp was identical to that under voltage clamp. The step hyperpolarization from -40 to -80 mV reduced [Ca(2+)](i) uniformly over the whole-cell area with a time constant of ∼10 s. The [Ca(2+)](i) at either potential was unaffected by heparin, an inhibitor of IP(3) receptors. Alternatively, [Ca(2+)](i) rapidly increased in the peripheral regions by depolarization from -80 to 0 mV and stayed at that level (∼400 nM) during a 60-s pulse. When the pipette solution contained IP(3) pathway blockers [heparin, 2-aminoethoxydiphenylborate, xestospongin C, or 1-[6-[((17β)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione (U73122)], the peak [Ca(2+)](i) was unchanged, but the sustained [Ca(2+)](i) was gradually reduced by ∼250 nM within 30 s. In the presence of Cd(2+), a long depolarization period slightly increased the [Ca(2+)](i), which was lower than that in the presence of heparin alone. In coronary arterial myocytes, the sustained increase in the [Ca(2+)](i) during depolarization was partly caused by the Ca(2+) release mediated by the enhanced formation of IP(3). The initial [Ca(2+)](i) elevation triggered by the Ca(2+) influx though voltage-dependent Ca(2+) channels may be predominantly responsible for the activation of phospholipase C for IP(3) formation.

  20. Depolarization effect in rare-earth doped Y{sub 2}O{sub 3} films in blue and UV spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Gasimov, Naghi; Mammadov, Eldar; Babayev, Sardar; Mamedova, Irada; Mamedov, Nazim [Department of Ellipsometry, Institute of Physics, Azerbaijan National Academy of Sciences, H. Javid ave. 33, Baku-1143 (Azerbaijan); Joudrier, Anne L.; Andriamiadamanana, Christian; Naghavi, Negar; Guillemoles, Jean F. [Institute for Research and Development of Photovoltaic Energy, 6 Quai Watier, 78401 Chatou, Paris (France)

    2015-06-15

    The 200 to 300 nm thick, Er and Er,Yb doped Y{sub 2}O{sub 3} films deposited onto silicon substrate by spin coating have been studied by spectroscopic ellipsometry over the 192-1680 nm spectral range at room temperature. All samples have been found to be strongly depolarizing in the blue and UV part of the spectrum. Complimentary examination of the sample surfaces, using confocal photoluminescence microscopy has disclosed the non-uniform distribution of the rare-earth dopants. The depolarization effects have then been modeled and found to be best reproduced by taking the thickness non-uniformity as the main source of depolarization. The optical constants of the studied films have been determined after four-step modeling with sequential decrease of the mean square error. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Overcoming Depolarizing Resonances with Dual Helical Partial Siberian Snakes

    Science.gov (United States)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K.; Courant, E. D.; Gardner, C.; Glenn, J. W.; Lin, F.; Luccio, A. U.; Mackay, W. W.; Okamura, M.; Ptitsyn, V.; Roser, T.; Takano, J.; Tepikian, S.; Tsoupas, N.; Zelenski, A.; Zeno, K.

    2007-10-01

    Acceleration of polarized protons in the energy range of 5 to 25 GeV is challenging. In a medium energy accelerator, the depolarizing spin resonances are strong enough to cause significant polarization loss but full Siberian snakes cause intolerably large orbit excursions and are also not feasible since straight sections usually are too short. Recently, two helical partial Siberian snakes with double pitch design have been installed in the Brookhaven Alternating Gradient Synchrotron (AGS). With a careful setup of optics at injection and along the energy ramp, this combination can eliminate the intrinsic and imperfection depolarizing resonances otherwise encountered during acceleration to maintain a high intensity polarized beam in medium energy synchrotrons. The observation of partial snake resonances of higher than second order will also be described.

  2. Unexpectedly wide rf-induced synchrotron sideband depolarizing resonances

    Science.gov (United States)

    Chu, C. M.; Ellison, T. J.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; von Przewoski, B.; Anferov, V. A.; Blinov, B. B.; Bychkov, M. A.; Caussyn, D. D.; Courant, E. D.; Crandell, D. A.; Derbenev, Ya. S.; Kaufman, W. A.; Krisch, A. D.; Lorenzon, W.; Nurushev, T. S.; Phelps, R. A.; Ratner, L. G.; Wong, V. K.; Ohmori, C.; Minty, M. G.; Martin, P. S.; Russell, A. D.; Sivers, D. W.

    1998-10-01

    Using an rf solenoid magnet, we studied the depolarization of a stored 104.1 MeV vertically polarized proton beam. The two primary rf depolarizing resonances were properly centered around the protons' circulation frequency fc, at fc(3-νs) and fc(νs-1), where νs is the spin tune; moreover, each resonance was roughly consistent with the expected width of about 720 Hz. Each primary rf resonance had two synchrotron sideband resonances at the expected frequencies. The two νs-1 sidebands were deep dips while the two 3-νs sidebands were very shallow; this was not expected. Moreover, all four sideband resonances were unexpectedly wider than the two primary resonances.

  3. Overcoming depolarizing resonances with dual helical partial Siberian snakes.

    Science.gov (United States)

    Huang, H; Ahrens, L A; Bai, M; Brown, K; Courant, E D; Gardner, C; Glenn, J W; Lin, F; Luccio, A U; Mackay, W W; Okamura, M; Ptitsyn, V; Roser, T; Takano, J; Tepikian, S; Tsoupas, N; Zelenski, A; Zeno, K

    2007-10-12

    Acceleration of polarized protons in the energy range of 5 to 25 GeV is challenging. In a medium energy accelerator, the depolarizing spin resonances are strong enough to cause significant polarization loss but full Siberian snakes cause intolerably large orbit excursions and are also not feasible since straight sections usually are too short. Recently, two helical partial Siberian snakes with double pitch design have been installed in the Brookhaven Alternating Gradient Synchrotron (AGS). With a careful setup of optics at injection and along the energy ramp, this combination can eliminate the intrinsic and imperfection depolarizing resonances otherwise encountered during acceleration to maintain a high intensity polarized beam in medium energy synchrotrons. The observation of partial snake resonances of higher than second order will also be described.

  4. Spreading Depolarizations Have Prolonged Direct Current Shifts and Are Associated with Poor Outcome in Brain Trauma

    Science.gov (United States)

    2011-01-01

    prognosis . Keywords: cortical spreading depression; electroencephalography; craniotomy; signal processing; acute brain injury Introduction Cortical...GCS =Glasgow coma scale. differed from normality and Kruskai-Wallis tests were used for non-parametric analysis of variance. Data are reported as...graded prognosis corresponding to 100% (isoelectric depolarizations), 60% (depolarizations with de- pression periods) and 23% (no depolarizations) of

  5. Susceptibility of Primary Sensory Cortex to Spreading Depolarizations

    OpenAIRE

    Bogdanov, VB; Middleton, NA; Theriot, JJ; Parker, PD; Abdullah, OM; Ju, YS; Hartings, JA; Brennan, KC

    2016-01-01

    Spreading depolarizations (SDs) are recognized as actors in neurological disorders as diverse as migraine and traumatic brain injury (TBI). Migraine aura involves sensory percepts, suggesting that sensory cortices might be intrinsically susceptible to SDs. We used optical imaging, MRI, and field potential and potassium electrode recordings in mice and electrocorticographic recordings in humans to determine the susceptibility of different brain regions to SDs. Optical imaging experiments in mi...

  6. Transparent Depolarizing Organic and Inorganic Films for Optics and Sensors.

    Science.gov (United States)

    Hiratani, Takayuki; Hamad, Wadood Y; MacLachlan, Mark J

    2017-04-01

    Fabrication of novel organic and inorganic depolarizing films derived from quasinematic cellulose nanocrystal (CNC) organization is demonstrated. These films convert linearly polarized and circularly polarized light into unpolarized light over the entire visible region. Patterning of the quasinematic CNCs on top of a chiral nematic film gives latent images that are revealed only upon observation through the circularly polarizing filters. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Depolarization properties of the femtosecond supercontinuum generated in condensed media

    Science.gov (United States)

    Kumar, R. Sai Santosh; Deepak, K. L. N.; Rao, D. Narayana

    2008-10-01

    In this paper, we present a study of depolarization of a supercontinuum across its spectral range as a function of the femtosecond laser pump intensity for an anisotropic crystalline condensed medium, potassium-dihydrogen-phosphate (KDP) crystal, and compare our results with commonly used supercontinuum generation (SCG) materials, namely borosilicate glass Schott (BK-7) glass (representing isotropic amorphous condensed media) and BaF2 (isotropic crystalline condensed media). Our results show that at higher input powers, depolarization in the continuum increases for BK-7, BaF2 , and along the direction of the optic axis of the KDP crystal. However, in the case of KDP crystal, we observe that the depolarization properties are strongly dependent on (i) the plane of polarization of incident light and (ii) the orientation of the crystal with respect to the incident light. Our studies also confirm that one can achieve SCG in a KDP crystal that maintains the same state of input polarization even at high input intensities when proper orientation of the crystal is used.

  8. Cellular contraction precedes membrane depolarization in Vorticella convallaria

    Science.gov (United States)

    Shiono; Naitoh

    1997-01-01

    Application of a mechanical stimulus to the cell body of the peritrich ciliate Vorticella convallaria evoked an all-or-nothing membrane depolarization, the large pulse. This was always accompanied by an all-or-nothing cellular contraction, and simultaneous recordings of the two events revealed that the large pulse was always preceded by the cellular contraction. A smaller graded membrane depolarization (the medium pulse) was sometimes produced in response to a weaker mechanical stimulus. The medium pulse was accompanied by a small, graded, localized contraction of the cell body and was occasionally followed by a large pulse. When a large pulse occurred during a medium pulse, it reached the same peak level as that of a large pulse evoked without a preceding medium pulse. When a medium pulse occurred during a medium pulse, summation of the two pulses was observed. Sustained contraction causes V. convallaria to become rounded, and in this state a mechanical stimulus stronger than that used to evoke the large pulse evoked a graded depolarizing mechanoreceptor potential in the cell. We conclude that both the large and medium pulses are caused by an inward receptor current that is activated mechanically following contraction of the cell body. A localized contraction evokes a small mechanoreceptor current, causing a medium pulse. An all-or-nothing contraction evokes a saturated, all-or-nothing mechanoreceptor current, causing a large pulse.

  9. Elastodynamic metasurface: Depolarization of mechanical waves and time effects

    Energy Technology Data Exchange (ETDEWEB)

    Boutin, Claude, E-mail: claude.boutin@entpe.fr [Ecole Nationale des Travaux Publics de l' Etat, Université de Lyon, LGCB, UMR CNRS 5513, Vaulx-en-Velin (France); Schwan, Logan [Acoustics Research Center, University of Salford, Newton Building, Salford M5 4WT (United Kingdom); Dietz, Matthew S. [Department of Civil Engineering, University of Bristol, Queen' s Building, Bristol BS8 1TR (United Kingdom)

    2015-02-14

    We report the concept of microstructured surfaces with inner resonance in the field of elastodynamics, so-called elastodynamic metasurfaces. Such metasurfaces allow for wavefield manipulation of mechanical waves by tuning the boundary conditions at specific frequencies. In particular, they can be used to depolarize elastic waves without introducing heterogeneities in the medium itself; the physical means to do so in homogeneous elastic media used to remain, surprisingly, an open question while depolarization is commonplace in electromagnetism. The principle relies on the anisotropic behaviour of a subwavelength array of resonators: Their subwavelength configuration confines the Bragg interferences scattered by resonators into a boundary layer. The effective behaviour of the resonating array is expressed with homogenization as an unconventional impedance, the frequency-dependence, and anisotropy of which lead to depolarization and time effects. The concept of the elastodynamic metasurface is tested experimentally and results bear testament to its efficacy and robustness. Elastodynamic metasurfaces are easily realized and analytically predictable, opening new possibilities in tomography techniques, ultrasonics, geophysics, vibration control, materials and structure design.

  10. Hydrogen sulfide depolarizes neurons in the nucleus of the solitary tract of the rat.

    Science.gov (United States)

    Malik, Rishi; Ferguson, Alastair V

    2016-02-15

    Hydrogen sulfide (H2S) is a gasotransmitter that has been described to affect the membrane potential of neurons in a number of brain areas. Using whole cell patch-clamp electrophysiological techniques, we investigated the effects of H2S on the membrane potential of neurons in the nucleus of the solitary tract (NTS). Whole cell patch clamp recordings were obtained from 300 µm coronal NTS brain slices and bath application of the H2S donor, sodium hydrosulfide (NaHS)(1mM, 5mM and 10mM) was shown to have clear concentration-dependent, reversible, depolarizing effects on the membrane potential of 95% of neurons tested (72/76), an effect which in 64% (46/72) of these responding neurons was followed by a hyperpolarization. In the presence of the voltage-gated sodium channel blocker tetrodotoxin (TTX) and the glutamate receptor antagonist kynurenic acid (KA), these depolarizing effects of 5 mM NaHS (5.0 ± 2.2 mV (n=7)) were still observed, although they were significantly reduced compared to regular aCSF (7.7 ± 2.0 mV (n=7), p*<0.05, paired t-test). We also demonstrated that hyperpolarizations in response to 5mM NaHS resulted from modulation of the KATP channel with recordings showing that following KATP channel block with glibenclamide these hyperpolarizing effects were abolished (Control -7.9 ± 1.2 mV, Glibenclamide -1.9 ± 0.9 mV (n=8) p<0.05, paired t-test). This study has for the first time described post-synaptic effects of this gasotransmitter on the membrane potential of NTS neurons and thus implicates this transmitter in regulating the diverse autonomic systems controlled by the NTS.

  11. FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells.

    Science.gov (United States)

    Park, Kyu-Sang; Jo, Inho; Pak, Kim; Bae, Sung-Won; Rhim, Hyewhon; Suh, Suk-Hyo; Park, Jin; Zhu, Hong; So, Insuk; Kim, Ki Whan

    2002-01-01

    We investigated the effects of carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore and uncoupler of mitochondrial oxidative phosphorylation in mitochondria, on plasma membrane potential and ionic currents in bovine aortic endothelial cells (BAECs). The membrane potential and ionic currents of BAECs were recorded using the patch-clamp technique in current-clamp and voltage-clamp modes, respectively. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase. FCCP-induced currents were significantly influenced by the changes in extracellular or intracellular pH; the increased proton gradient produced by lowering the extracellular pH or intracellular alkalinization augmented the changes in membrane potential and ionic currents caused by FCCP. FCCP-induced currents were significantly reduced under extracellular Na+-free conditions. The reversal potentials of FCCP-induced currents under Na+-free conditions were well fitted to the calculated equilibrium potential for protons. Interestingly, FCCP-induced Na+ transport (subtracted currents, I(control)- I(Na+-free) was closely dependent on extracellular pH, whereas FCCP-induced H+transport was not significantly affected by the absence of Na+. These results suggest that the FCCP-induced ionic currents and depolarization, which are strongly dependent on the plasmalemmal proton gradient, are likely to be mediated by both H+ and Na+ currents across the plasma membrane. The relationship between H+ and Na+ transport still needs to be determined.

  12. Effects of in vitro and in vivo lead exposure on voltage-dependent calcium channels in central neurons of Lymnaea stagnalis.

    Science.gov (United States)

    Audesirk, G

    1987-01-01

    Currents through calcium channels of members of an identified cluster of neurons (B cells) in the pond snail Lymnaea stagnalis were studied under voltage clamp. The normal physiological saline was modified to maximize the visibility of voltage-dependent calcium currents and minimize contamination by other currents. Barium was used as the charge carrier for the calcium channels. Depolarizing voltage steps induce an inward current, the magnitude of which varies with the barium concentration. In brains taken from animals not exposed in vivo to lead, in vitro addition of lead acetate to the recording medium (0.25 to 14 microM) inhibits the barium current by 59 +/- 14% (mean +/- s.d.), in a manner that is independent of the lead concentration. The magnitude of the residual current still varies with the barium concentration. The voltage dependence of the current appears to be unaffected by lead. In contrast to some other calcium-channel blockers, such as cobalt, the inhibition of barium currents by in vitro lead exposure is irreversible, at least in short-term experiments. Contrary to expectations based on these in vitro results, barium currents in B cells of animals exposed to 5 microM lead for 6 to 12 weeks in vivo were approximately twice as large as barium currents in B cells from unexposed controls, when both were recorded in lead-free saline. It is possible that chronic in vivo lead exposure causes an increase in the number of calcium channels in these neurons.

  13. Energy and Beam-Offset dependence of the Luminosity weighted depolarization for CLIC

    CERN Document Server

    Esberg, Jakob; Uggerhoj, Ulrik; Dalena, Barbara

    2011-01-01

    We report on simulations of e+e- depolarization due to beam-beam effects. These effects are studied for CLIC at 3 TeV, using GUINEA PIG++. We find a strong energy dependence of the luminosity weighted depolarization. In the luminosity peak at CLIC the total luminosity weighted depolarization remains below the one per-mil level. The effect of a vertical offset on the energy dependent depolarization is investigated. The depolarization in the luminosity peak remains below per-cent level even for 5sy offsets.

  14. A Bidirectional Multi-Port DC-DC Converter Integrating Voltage Equalizer

    DEFF Research Database (Denmark)

    Chen, Jianfei; Hou, Shiying; Deng, Fujin

    2015-01-01

    with a uniform voltage level while eliminating the voltage imbalance. In addition, high step-down and step-up ratios with low component voltage stress can be achieved in the proposed converter. A bidirectional four-port dc-dc converter is presented to do theoretical analysis for the voltage equalization of three...

  15. Next Step for STEP

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Claire [CTSI; Bremner, Brenda [CTSI

    2013-08-09

    The Siletz Tribal Energy Program (STEP), housed in the Tribe’s Planning Department, will hire a data entry coordinator to collect, enter, analyze and store all the current and future energy efficiency and renewable energy data pertaining to administrative structures the tribe owns and operates and for homes in which tribal members live. The proposed data entry coordinator will conduct an energy options analysis in collaboration with the rest of the Siletz Tribal Energy Program and Planning Department staff. An energy options analysis will result in a thorough understanding of tribal energy resources and consumption, if energy efficiency and conservation measures being implemented are having the desired effect, analysis of tribal energy loads (current and future energy consumption), and evaluation of local and commercial energy supply options. A literature search will also be conducted. In order to educate additional tribal members about renewable energy, we will send four tribal members to be trained to install and maintain solar panels, solar hot water heaters, wind turbines and/or micro-hydro.

  16. Next Step for STEP

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Claire [CTSI; Bremner, Brenda [CTSI

    2013-08-09

    The Siletz Tribal Energy Program (STEP), housed in the Tribe’s Planning Department, will hire a data entry coordinator to collect, enter, analyze and store all the current and future energy efficiency and renewable energy data pertaining to administrative structures the tribe owns and operates and for homes in which tribal members live. The proposed data entry coordinator will conduct an energy options analysis in collaboration with the rest of the Siletz Tribal Energy Program and Planning Department staff. An energy options analysis will result in a thorough understanding of tribal energy resources and consumption, if energy efficiency and conservation measures being implemented are having the desired effect, analysis of tribal energy loads (current and future energy consumption), and evaluation of local and commercial energy supply options. A literature search will also be conducted. In order to educate additional tribal members about renewable energy, we will send four tribal members to be trained to install and maintain solar panels, solar hot water heaters, wind turbines and/or micro-hydro.

  17. Miniature 100-kV Explosively Driven Prime Power Sources Based on Transverse Shock-Wave Depolarization of Pb(Zr0.95Ti0.05)O3 Ferroelectric Ceramics

    Science.gov (United States)

    2011-06-01

    MINIATURE 100-kV EXPLOSIVELY DRIVEN PRIME POWER SOURCES BASED ON TRANSVERSE SHOCK-WAVE DEPOLARIZATION OF Pb(Zr0.95Ti0.05)O3 FERROELECTRIC CERAMICS...1,8,9]. Earlier [2-5] we reported on the development of compact prime power sources utilizing quasi-planar-shock-wave depolarization of Pb...engineering projects it is important to develop miniature prime power sources that reliably generate ultrahigh (up to 100 kV) output voltages. We work on

  18. Mechanisms of depolarizing inhibition at the crayfish giant motor synapse. II. Quantitative reconstruction.

    Science.gov (United States)

    Edwards, D H

    1990-08-01

    1. The relative strengths of four mechanisms of depolarizing synaptic inhibition described in the previous paper were evaluated with an electrical model of the giant motor synapse (GMS) and postsynaptic region of the motor giant motoneuron (MoG). 2. The model consists of one compartment that represents the presynaptic region of the medial giant (MG) interneuron and three compartments that represent the postsynaptic region and proximal axon of the MoG. The presynaptic MG compartment is linked to a postsynaptic MoG compartment by a rectifying conductance that represents the GMS. Each compartment consists of parallel paths to ground for active and/or passive membrane currents. 3. Parameter values of the model were set so the MG compartment would replicate an MG impulse and the MoG compartments would replicate the current-clamp, voltage-clamp, and synaptic responses of a single MoG neuron described in the previous paper. The Hodgkin-Huxley equations described voltage-sensitive sodium and potassium currents. 4. Comparison of the MoG compartment currents that mediate an inhibited excitatory postsynaptic potential (EPSP) [triggered during a depolarizing inhibitory postsynaptic potential (d-IPSP)] with those of an uninhibited EPSP indicate that all four mechanisms have significant inhibitory effects. Reverse bias of the GMS by the d-IPSP reduced the GMS current by 65 nA (12%). The remaining inward current was further reduced by a 243-nA outward current through the inhibitory postsynaptic conductance. The d-IPSP inactivated sodium conductance so the inward sodium current evoked by the EPSP was reduced by 319 nA (-68%). The d-IPSP reduced the latency for potassium activation by the EPSP so that the outward potassium current coincided with the inward sodium current and reduced the net inward current by 100 nA. Together, these mechanisms reduced the EPSP amplitude by 69%. 5. The resting potential of MoG is normally 15 mV more positive than MG rest potential, but in some

  19. Spreading depolarizations and late secondary insults after traumatic brain injury

    DEFF Research Database (Denmark)

    Hartings, Jed A; Strong, Anthony J; Fabricius, Martin

    2009-01-01

    -contusional cortex in 32 patients who underwent surgical treatment for TBI. Prospective electrocorticography was performed during neurointensive care with retrospective analysis of hourly nursing chart data. Recordings were 84 hr (median) per patient and 2,503 hr in total. In 17 patients (53%), 280 spreading...... temperatures suggests that the labile balance of energy supply and demand is an important determinant of their occurrence. Monitoring of depolarizations might serve as a functional measure to guide therapeutic efforts and their blockade may provide an additional line of defense against the effects of secondary...

  20. Integral decomposition and polarization properties of depolarizing Mueller matrices.

    Science.gov (United States)

    Ossikovski, Razvigor; Arteaga, Oriol

    2015-03-15

    We show that, by suitably defining the integral decomposition of a depolarizing Mueller matrix, it becomes possible to fully interpret the polarization response of the medium or structure under study in terms of mean values and variances-covariances of a set of six integral polarization properties. The latter appear as natural counterparts of the elementary (differential) polarization properties stemming from the differential decomposition of the Mueller matrix. However, unlike the differential decomposition, the integral one is always mathematically and physically realizable and is furthermore unambiguously defined inasmuch as a nondepolarizing estimate of the initial Mueller matrix is secured. The theoretical results are illustrated on an experimental example.

  1. Faraday ghosts depolarization canals in the Galactic radio emission

    CERN Document Server

    Shukurov, A M; Shukurov, Anvar; Berkhuijsen, Elly M.

    2003-01-01

    Narrow, elongated regions of very low polarized intensity -- so-called canals -- have recently been observed by several authors at decimeter wavelengths in various directions in the Milky Way, but their origin remains enigmatic. We show that the canals arise from depolarization by differential Faraday rotation in the interstellar medium and that they represent level lines of Faraday rotation measure RM, a random function of position in the sky. Statistical properties of the separation of canals depend on the autocorrelation function of RM, and so provide a useful tool for studies of interstellar turbulence.

  2. Characterizing the Depolarizing Quantum Channel in Terms of Riemannian Geometry

    CERN Document Server

    Cafaro, Carlo

    2011-01-01

    We explore the conceptual usefulness of Riemannian geometric tools induced by the statistical concept of distinguishability in quantifying the effect of a depolarizing channel on quantum states. Specifically, we compare the geometries of the interior of undeformed and deformed Bloch spheres related to density operators on a two-dimensional Hilbert space. We show that randomization emerges geometrically through a smaller infinitesimal quantum line element on the deformed Bloch sphere while the uniform contraction manifests itself via a deformed set of geodesics where the spacial components of the deformed four-Bloch vector are simply the contracted versions of the undeformed Bloch vector components.

  3. Measurement of a power system nominal voltage, frequency and voltage flicker parameters

    Energy Technology Data Exchange (ETDEWEB)

    Alkandari, A.M. [College of Technological Studies, Electrical Engineering Technology Department, Shwiekh (Kuwait); Soliman, S.A. [Electrical Power and Machines Department, Misr University for Science and Technology, Cairo (Egypt)

    2009-09-15

    We present, in this paper, an approach for identifying the frequency and amplitude of voltage flicker signal that imposed on the nominal voltage signal, as well as the amplitude and frequency of the nominal signal itself. The proposed algorithm performs the estimation in two steps; in the first step the original voltage signal is shifted forward and backward by an integer number of sample, one sample in this paper. The new generated signals from such a shift together with the original one is used to estimate the amplitude of the original signal voltage that composed of the nominal voltage and flicker voltage. The average of this amplitude gives the amplitude of the nominal voltage; this amplitude is subtracted from the original identified signal amplitude to obtain the samples of the flicker voltage. In the second step, the argument of the signal is calculated by simply dividing the magnitude of signal sample with the estimated amplitude in the first step. Calculating the arccosine of the argument, the frequency of the nominal signal as well as the phase angle can be computing using the least error square estimation algorithm. Simulation examples are given within the text to show the features of the proposed approach. (author)

  4. Molecular mechanism of voltage sensing in voltage-gated proton channels

    Science.gov (United States)

    Rebolledo, Santiago; Perez, Marta E.

    2013-01-01

    Voltage-gated proton (Hv) channels play an essential role in phagocytic cells by generating a hyperpolarizing proton current that electrically compensates for the depolarizing current generated by the NADPH oxidase during the respiratory burst, thereby ensuring a sustained production of reactive oxygen species by the NADPH oxidase in phagocytes to neutralize engulfed bacteria. Despite the importance of the voltage-dependent Hv current, it is at present unclear which residues in Hv channels are responsible for the voltage activation. Here we show that individual neutralizations of three charged residues in the fourth transmembrane domain, S4, all reduce the voltage dependence of activation. In addition, we show that the middle S4 charged residue moves from a position accessible from the cytosolic solution to a position accessible from the extracellular solution, suggesting that this residue moves across most of the membrane electric field during voltage activation of Hv channels. Our results show for the first time that the charge movement of these three S4 charges accounts for almost all of the measured gating charge in Hv channels. PMID:23401575

  5. Depolarizing actions of hydrogen sulfide on hypothalamic paraventricular nucleus neurons.

    Directory of Open Access Journals (Sweden)

    C Sahara Khademullah

    Full Text Available Hydrogen sulfide (H2S is a novel neurotransmitter that has been shown to influence cardiovascular functions as well and corticotrophin hormone (CRH secretion. Since the paraventricular nucleus of the hypothalamus (PVN is a central relay center for autonomic and endocrine functions, we sought to investigate the effects of H2S on the neuronal population of the PVN. Whole cell current clamp recordings were acquired from the PVN neurons and sodium hydrosulfide hydrate (NaHS was bath applied at various concentrations (0.1, 1, 10, and 50 mM. NaHS (1, 10, and 50 mM elicited a concentration-response relationship from the majority of recorded neurons, with almost exclusively depolarizing effects following administration. Cells responded and recovered from NaHS administration quickly and the effects were repeatable. Input differences from baseline and during the NaHS-induced depolarization uncovered a biphasic response, implicating both a potassium and non-selective cation conductance. The results from the neuronal population of the PVN shed light on the possible physiological role that H2S has in autonomic and endocrine function.

  6. Overcoming horizontal depolarizing resonances with multiple tune jumps

    Science.gov (United States)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K. A.; Dutheil, Y.; Gardner, C.; Glenn, J. W.; Lin, F.; MacKay, W. W.; Meot, F.; Poblaguev, A.; Ranjbar, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Tsoupas, N.; Yip, K.; Zelenski, A.; Zeno, K.

    2014-08-01

    In a medium energy proton synchrotron, strong enough partial Siberian snakes can be used to avoid both imperfection and vertical intrinsic depolarizing resonances. However, partial snakes tilt the stable spin direction away from vertical, which generates depolarizing resonances associated with horizontal tune. The relatively weak but numerous horizontal intrinsic resonances are the main source of the residual polarization losses. A pair of horizontal tune jump quads have been used in the Brookhaven Alternating Gradient Synchrotron to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at the Alternating Gradient Synchrotron injection, polarized proton beam had reached 1.5×1011 proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2×1011 protons per bunch has been achieved. The polarization transport efficiency is close to 90%.

  7. Overcoming horizontal depolarizing resonances with multiple tune jumps

    Directory of Open Access Journals (Sweden)

    H. Huang

    2014-08-01

    Full Text Available In a medium energy proton synchrotron, strong enough partial Siberian snakes can be used to avoid both imperfection and vertical intrinsic depolarizing resonances. However, partial snakes tilt the stable spin direction away from vertical, which generates depolarizing resonances associated with horizontal tune. The relatively weak but numerous horizontal intrinsic resonances are the main source of the residual polarization losses. A pair of horizontal tune jump quads have been used in the Brookhaven Alternating Gradient Synchrotron to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at the Alternating Gradient Synchrotron injection, polarized proton beam had reached 1.5×10^{11} proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2×10^{11} protons per bunch has been achieved. The polarization transport efficiency is close to 90%.

  8. Storage ring lattice calibration using resonant spin depolarization

    Directory of Open Access Journals (Sweden)

    K. P. Wootton

    2013-07-01

    Full Text Available This paper presents measurements of the GeV-scale electron beam energy for the storage rings at the synchrotron light source facilities Australian Synchrotron (AS and SPEAR3 at SLAC. Resonant spin depolarization was employed in the beam energy measurement, since it is presently the highest precision technique and an uncertainty of order 10^{-6} was achieved at SPEAR3 and AS. Using the resonant depolarization technique, the beam energy was measured at various rf frequencies to measure the linear momentum compaction factor. This measured linear momentum compaction factor was used to evaluate models of the beam trajectory through combined-function bending magnets. The main bending magnets of both lattices are rectangular, horizontally defocusing gradient bending magnets. Four modeling approaches are compared for the beam trajectory through the bending magnet: a circular trajectory, linear and nonlinear hyperbolic cosine trajectories, and numerical evaluation of the trajectory through the measured magnetic field map. Within the uncertainty of the measurement the momentum compaction factor is shown to agree with the numerical model of the trajectory within the bending magnet, and disagree with the hyperbolic cosine approximation.

  9. Programmable high voltage power supply with regulation confined to the high voltage section

    Science.gov (United States)

    Castell, Karen D. (Inventor); Ruitberg, Arthur P. (Inventor)

    1994-01-01

    A high voltage power supply in a dc-dc converter configuration includes a pre-regulator which filters and regulates the dc input and drives an oscillator which applies, in turn, a low voltage ac signal to the low side of a step-up high voltage transformer. The high voltage side of the transformer drives a voltage multiplier which provides a stepped up dc voltage to an output filter. The output voltage is sensed by a feedback network which then controls a regulator. Both the input and output of the regulator are on the high voltage side, avoiding isolation problems. The regulator furnishes a portion of the drive to the voltage multiplier, avoiding having a regulator in series with the load with its attendant, relatively high power losses. This power supply is highly regulated, has low power consumption, a low parts count and may be manufactured at low cost. The power supply has a programmability feature that allows for the selection of a large range of output voltages.

  10. Pacemaker rate and depolarization block in nigral dopamine neurons: a somatic sodium channel balancing act

    Science.gov (United States)

    Tucker, Kristal R.; Huertas, Marco A.; Horn, John P.; Canavier, Carmen C.; Levitan, Edwin S.

    2012-01-01

    Midbrain dopamine (DA) neurons are slow intrinsic pacemakers that undergo depolarization (DP) block upon moderate stimulation. Understanding DP block is important because it has been correlated with the clinical efficacy of chronic antipsychotic drug treatment. Here we describe how voltage-gated sodium (NaV) channels regulate DP block and pacemaker activity in DA neurons of the substantia nigra using rat brain slices. The distribution, density and gating of NaV currents were manipulated by blocking native channels with tetrodotoxin and by creating virtual channels and anti-channels with dynamic clamp. Although action potentials initiate in the axon initial segment (AIS) and NaV channels are distributed in multiple dendrites, selective reduction of NaV channel activity in the soma was sufficient to decrease pacemaker frequency and increase susceptibility to DP block. Conversely, increasing somatic NaV current density raised pacemaker frequency and lowered susceptibility to DP block. Finally, when NaV currents were restricted to the soma, pacemaker activity occurred at abnormally high rates due to excessive local subthreshold NaV current. Together with computational simulations, these data show that both the slow pacemaker rate and the sensitivity to DP block that characterizes DA neurons result from the low density of somatic NaV channels. More generally, we conclude that the somatodendritic distribution of NaV channels is a major determinant of repetitive spiking frequency. PMID:23077037

  11. 基于耦合电感单级升压逆变器的光伏并网发电系统%A Grid-Connected Photovoltaic Generation System Based on Single-Stage Voltage Step-Up Inverter With Coupled Inductor

    Institute of Scientific and Technical Information of China (English)

    周玉斐; 黄文新; 赵萍; 赵健伍

    2013-01-01

      提出了基于耦合电感单级升压逆变器的光伏并网发电系统,其可在一级变换器中实现升压、逆变、单位功率因数并网和最大功率跟踪(maximum power point tracking,MPPT)的功能。该拓扑在电压源和三相逆变桥间加入包含耦合电感的无源网络,通过调节桥臂的直通占空比和耦合电感的匝比,实现母线电压的提升。由于桥臂直通成为一种正常工作方式,系统的可靠性得到了提高。此外,采用单级逆变器和通过采样输出电流实现 MPPT 的方式简化了系统,降低了成本且易于实现。算例结果验证了该方法的可行性。%  A grid-connected photovoltaic (PV) generation system based on single-stage voltage step-up inverter with coupled inductor, which can implement the functions of voltage step-up, DC-to-AC inversion, grid-connection under unity power factor and maximum power point tracking (MPPT) by a single-stage inverter, is proposed. A passive network containing coupled inductor is added-in between voltage-source and three-phase inverter bridge and by means of adjusting duty ratio of shoot-through zero vector and turns ratio of inductor, the bus voltage step-up can be implemented. Because the shoot-through of bridge arm becomes a normal operation mode, the reliability of PV generation system can be improved, in addition, the PV generation system is simplified as a result of utilizing singe-stage inverter and MPPT is implemented by sampling output current, thus the PV generation system is easily realized and its cost is reduced. The feasibility of the proposed method is verified by results of experimental test.

  12. Depolarization of synchrotron radiation in a multilayer magneto-ionic medium

    CERN Document Server

    Shneider, Carl; Fletcher, Andrew; Shukurov, Anvar

    2014-01-01

    Depolarization of diffuse radio synchrotron emission is classified in terms of wavelength-independent and wavelength-dependent depolarization in the context of regular magnetic fields and of both isotropic and anisotropic turbulent magnetic fields. Previous analytical formulas for depolarization due to differential Faraday rotation are extended to include internal Faraday dispersion concomitantly, for a multilayer synchrotron emitting and Faraday rotating magneto-ionic medium. In particular, depolarization equations for a two- and three-layer system (disk-halo, halo-disk-halo) are explicitly derived. To both serve as a `user's guide' to the theoretical machinery and as an approach for disentangling line-of-sight depolarization contributions in face-on galaxies, the analytical framework is applied to data from a small region in the face-on grand-design spiral galaxy M51. The effectiveness of the multiwavelength observations in constraining the pool of physical depolarization scenarios is illustrated for a two-...

  13. Magnesium sulfate enhances non-depolarizing muscle relaxant vecuronium action at adult muscle-type nicotinic acetylcholine receptor in vitro

    Institute of Scientific and Technical Information of China (English)

    Hong WANG; Qi-sheng LIANG; Lan-ren CHENG; Xiao-hong LI; Wei FU; Wen-tao DAI; Shi-tong LI

    2011-01-01

    To investigate the effect of magnesium sulfate and its interaction with the non-depolarizing muscle relaxant vecuronium at adult muscle-type acetylcholine receptors in vitro.Methods:Adult muscle-type acetylcholine receptors were expressed in HEK293 cells.Drug-containing solution was applied via a gravity-driven perfusion system.The inward currents were activated by brief application of acetylcholine (ACh),and recorded using whole-cell voltage-clamp technique.Results:Magnesium sulfate (1-100 mmol/L) inhibited the inward currents induced ACh (10 μmol/L) in a concentration-dependent manner (IC5o=29.2 mmol/L).The inhibition of magnesium sulfate was non-competitive.In contrast,vecuronium produced a potent inhibition on the adult muscle-type acetylcholine receptor (IC50=8.7 nmol/L) by competitive antagonism.Magnesium sulfate at the concentrations of 1,3,and 6 mmol/L markedly enhanced the inhibition of vecuronium (10 nmol/L) on adult muscle-type acetylcholine receptors.Conclusion:Clinical enhancement of vecuronium-induced muscle relaxation by magnesium sulfate can be attributed partly to synergism between magnesium sulfate and non-depolarizing muscle relaxants at adult muscle-type acetylcholine receptors.

  14. Transient Voltage Recorder

    Science.gov (United States)

    Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

    2002-01-01

    A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

  15. Sympathetic interaction among 13.2/400 kV step up voltage transformers of the Macagua EDELCA hydroelectric complex; Interaccion simpatica entre transformadores elevadores de 13,2/400 kV del Complejo Hidroelectrico Macagua de EDELCA

    Energy Technology Data Exchange (ETDEWEB)

    Villa R, Alessandro [C.V.G. Electrification del Caroni, C.A. (EDELCA), Caracas (Venezuela). Div. de Ingenieria de Sistemas Electricos]. E-mail: avilla@edelca.com.ve

    2001-07-01

    This work analyses the sympathetic interaction phenomenon among the 13.2/400 kV step-up transformers of the Machine House 2 of the Macagua Hydroelectric Complex. The analysis determined, through simulations with ATP, the magnitudes of the energization currents, the harmonic contents and the effect of using pre insertion resistances at the 400 kV switches for the diminishing of the magnitudes and their decay time. The obtained results indicated that the sympathetic interactions among the step-up transformers influenced on the magnitude, duration and harmonic contents of the energization currents besides the using of pre insertion resistances affects the initial magnitude and duration of the mentioned currents, presenting however a lesser impact in the harmonic content.

  16. Voltage-Activated Calcium Channels as Functional Markers of Mature Neurons in Human Olfactory Neuroepithelial Cells: Implications for the Study of Neurodevelopment in Neuropsychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Héctor Solís-Chagoyán

    2016-06-01

    Full Text Available In adulthood, differentiation of precursor cells into neurons continues in several brain structures as well as in the olfactory neuroepithelium. Isolated precursors allow the study of the neurodevelopmental process in vitro. The aim of this work was to determine whether the expression of functional Voltage-Activated Ca2+ Channels (VACC is dependent on the neurodevelopmental stage in neuronal cells obtained from the human olfactory epithelium of a single healthy donor. The presence of channel-forming proteins in Olfactory Sensory Neurons (OSN was demonstrated by immunofluorescent labeling, and VACC functioning was assessed by microfluorometry and the patch-clamp technique. VACC were immunodetected only in OSN. Mature neurons responded to forskolin with a five-fold increase in Ca2+. By contrast, in precursor cells, a subtle response was observed. The involvement of VACC in the precursors’ response was discarded for the absence of transmembrane inward Ca2+ movement evoked by step depolarizations. Data suggest differential expression of VACC in neuronal cells depending on their developmental stage and also that the expression of these channels is acquired by OSN during maturation, to enable specialized functions such as ion movement triggered by membrane depolarization. The results support that VACC in OSN could be considered as a functional marker to study neurodevelopment.

  17. Voltage dependence of the Na-K pump.

    Science.gov (United States)

    De Weer, P; Gadsby, D C; Rakowski, R F

    1988-01-01

    Present evidence demonstrates that the Na-K pump rate is voltage dependent, whereas early work was largely inconclusive. The I-V relationship has a positive slope over a wide voltage range, and the existence of a negative slope region is now doubtful. Monotonic voltage dependence is consistent with the reaction cycle containing a single voltage-dependent step. Recent measurements suggest that this voltage-dependent step occurs during Na translocation and may be deocclusion of Na+. In addition, two results suggest that K translocation is voltage insensitive: (a) large positive potentials appear to have no influence on Rb-Rb exchange or associated conformational transitions; and (b) transient currents associated with Na translocation appear to involve movement of a single charge, which is sufficient for a 3Na-2K cycle. The simplest interpretation is that the pump's cation binding sites supply two negative charges. Pre-steady-state measurements demonstrate that Na translocation precedes the pump cycle's rate-limiting step, presumably K translocation. But, because K translocation seems voltage insensitive, the voltage dependence of the steady-state pump rate probably reflects that of the concentration of the intermediate entering this slow step. Further pump current and flux data (both transient and steady-state), carefully determined over a range of conditions, should increase our understanding of the voltage-dependent step(s) in the Na-K pump cycle.

  18. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L;

    2011-01-01

    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriolar...... tone. We used microdissected perfused mouse efferent arterioles and found a transient vasoconstriction in response to depolarization with potassium; an effect abolished by removal of extracellular calcium. The T-type voltage-gated calcium channel antagonists mibefradil and nickel blocked this potassium....... Low concentrations of nickel, an agent that blocks Ca(v)3.2, had a similar effect. Thus, T-type voltage-gated calcium channels are functionally important for depolarization-induced vasoconstriction and subsequent dilatation in mouse cortical efferent arterioles.Kidney International advance online...

  19. Mechanism of electromechanical coupling in voltage-gated potassium channels

    Directory of Open Access Journals (Sweden)

    Rikard eBlunck

    2012-09-01

    Full Text Available Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion – sodium, calcium or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt and vertical displacement in order to bring 3-4 e+ each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy and molecular dynamics simulations. Evidently, the S4-S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii insight as to how the voltage sensor and pore domain influence one another; and (iii theoretical predictions on the movement of the cytosolic face of the KV channels

  20. Effect of nifedipine on depolarization-induced force responses in skinned skeletal muscle fibres of rat and toad.

    Science.gov (United States)

    Posterino, G S; Lamb, G D

    1998-01-01

    The effect of the dihydropyridine, nifedipine, on excitation-contraction coupling was compared in toad and rat skeletal muscle, using the mechanically skinned fibre technique, in order to understand better the apparently disparate results of previous studies and to examine recent proposals on the importance of certain intracellular factors in determining the efficacy of dihydropyridines. In twitch fibres from the iliofibularis muscle of the toad, 10 microM nifedipine completely inhibited depolarization-induced force responses within 30 s, without interfering with direct activation of the Ca(2+)-release channels by caffeine application or reduction of myoplasmic [Mg2+]. At low concentrations of nifedipine, inhibition was considerably augmented by repeated depolarizations, with half-maximal inhibition occurring at < 0.1 microM nifedipine. In contrast, in rat extensor digitorum longus (EDL) fibres 1 microM nifedipine had virtually no effect on depolarization-induced force responses, and 10 microM nifedipine caused only approximately 25% reduction in the responses, even upon repeated depolarizations. In rat fibres, 10 microM nifedipine shifted the steady-state force inactivation curve to more negative potentials by < 11 mV, whereas in toad fibres the potent inhibitory effect of nifedipine indicated a much larger shift. The inhibitory effect of nifedipine in rat fibres was little, if at all, increased by the absence of Ca2+ in the transverse tubular (t-) system, provided that the Ca2+ was replaced with sufficient Mg2+. The presence of the reducing agents dithiothreitol (10 mM) or glutathione (10 mM) in the solution bathing a toad skinned fibre did not reduce the inhibitory effect of nifedipine, suggesting that the potency of nifedipine in toad skinned fibres was not due to the washout of intracellular reducing agents. The results are considered in terms of a model that can account for the markedly different effects of nifedipine on the two putative functions of the

  1. Postsynaptic GABA(B) Receptors Contribute to the Termination of Giant Depolarizing Potentials in CA3 Neonatal Rat Hippocampus

    Science.gov (United States)

    Khalilov, Ilgam; Minlebaev, Marat; Mukhtarov, Marat; Juzekaeva, Elvira; Khazipov, Roustem

    2017-01-01

    During development, hippocampal CA3 network generates recurrent population bursts, so-called Giant Depolarizing Potentials (GDPs). GDPs are characterized by synchronous depolarization and firing of CA3 pyramidal cells followed by afterhyperpolarization (GDP-AHP). Here, we explored the properties of GDP-AHP in CA3 pyramidal cells using gramicidin perforated patch clamp recordings from neonatal rat hippocampal slices. We found that GDP-AHP occurs independently of whether CA3 pyramidal cells fire action potentials (APs) or remain silent during GDPs. However, the amplitude of GDP-AHP increased with the number of APs the cells fired during GDPs. The reversal potential of the GDP-AHP was close to the potassium equilibrium potential. During voltage-clamp recordings, current-voltage relationships of the postsynaptic currents activated during GDP-AHP were characterized by reversal near the potassium equilibrium potential and inward rectification, similar to the responses evoked by the GABA(B) receptor agonists. Finally, the GABA(B) receptor antagonist CGP55845 strongly reduced GDP-AHP and prolonged GDPs, eventually transforming them to the interictal and ictal-like discharges. Together, our findings suggest that the GDP-AHP involves two mechanisms: (i) postsynaptic GABA(B) receptor activated potassium currents, which are activated independently on whether the cell fires or not during GDPs; and (ii) activity-dependent, likely calcium activated potassium currents, whose contribution to the GDP-AHP is dependent on the amount of firing during GDPs. We propose that these two complementary inhibitory postsynaptic mechanisms cooperate in the termination of GDP. PMID:28701925

  2. Neutron depolarization measurements of magnetite in chiton teeth

    Science.gov (United States)

    Seifert, M.; Schulz, M.; Benka, G.; Pfleiderer, C.; Gilder, S.

    2017-06-01

    Magnetite constitutes one of the most abundant magnetic minerals in the Earth's crust. In the single domain state, magnetite often carries the magnetic remanence in rocks due to its stable and strong magnetic remanence. Hence it is of keen interest to paleomagnetists who study the ancient magnetic field preserved in the rock record. The extremely small size range and vulnerability to oxidation of single domain magnetite makes synthetization and preservation virtually impossible. Consequently, most experimental work on magnetite under pressure is carried out on multidomain magnetite. The radula of the marine mollusc chiton (Polyplacophora) is one of the few natural sources of single domain magnetite. We have performed a comparative study on samples of chiton radula in a vibrating sample magnetometer (VSM) and with the newly evolving neutron depolarization imaging (NDI) technique. Despite a constant offset between the VSM and NDI data in the coercivity we find a good agreement between the two techniques.

  3. Experimental verification of depolarization effects in bioelectrical impedance measurement.

    Science.gov (United States)

    Chen, Xiaoyan; Lv, Xinqiang; Du, Meng

    2014-01-01

    The electrode polarization effects on bioelectrical impedance measurement at low-frequency cannot be ignored. In this paper, the bioelectrical data of mice livers are measured to specify the polarization effects on the bio-impedance measurement data. We firstly introduce the measurement system and methodology. Using the depolarization method, the corrected results are obtained. Besides, the specific effects of electrode polarization on bio-impedance measurement results are investigated using comparative analysis of the previous and posterior correction results from dielectric spectroscopy, Cole-Cole plot, conductivity and spectroscopy of dissipation tangent. Experimental results show that electrode polarization has a significant influence on the characteristic parameters of mouse liver tissues. To be specific, we see a low-frequency limit resistance R0 increase by 19.29%, a reactance peak XP increase by 8.50%, a low-frequency limit conductivity Kl decrease by 17.65% and a dissipation peak tangent decrease by 160%.

  4. Inflections in threshold electrotonus to depolarizing currents in sensory axons.

    Science.gov (United States)

    Burke, David; Howells, James; Trevillion, Louise; Kiernan, Matthew C; Bostock, Hugh

    2007-12-01

    Threshold electrotonus involves tracking the changes in axonal excitability produced by subthreshold polarizing currents and is the only technique that allows insight into the function of internodal conductances in human subjects in vivo. There is often an abrupt transient reversal of the threshold change as excitability increases in response to conditioning depolarizing currents (S1 phase). In recordings from motor axons, it has been recently demonstrated that this notch or inflection is due to activation of low-threshold axons. We report that a notch is frequently seen in sensory recordings (in 33 of 50 healthy subjects) using the standard threshold electrotonus protocol. When large, the notch can distort subsequent phases of threshold electrotonus and could complicate quantitative measurements and modeling studies.

  5. Multiple Tune Jumps to Overcome Horizontal Depolarizing Resonances

    Science.gov (United States)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K. A.; Dutheil, Y.; Gardner, C.; Glenn, J. W.; Lin, F.; Mackay, W. W.; Meot, F.; Poblaguev, A.; Ranjbar, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Tsoupas, N.; Yip, K.; Zelenski, A.; Zeno, K.

    2016-02-01

    Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternative Gradient Synchrotron(AGS). The relatively weak but numerous horizontal resonances are the main source of polarization loss in the AGS. A pair of horizontal tune jump quads have been used to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at AGS injection, polarized proton beam had reached 1.5 × 1011 proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2 × 1011 protons per bunch has been achieved.

  6. Depolarization in the ILC Linac-to-Ring Positron Beamline

    CERN Document Server

    Riemann, Sabine

    2012-01-01

    To achieve the physics goals of future Linear Colliders, it is important that electron and positron beams are polarized. The positron source planned for the International Linear Collider (ILC) is based on a helical undulator system and can deliver a polarised beam with positron polarization of 60%. To ensure that no significant polarization is lost during the transport of the electron and positron beams from the source to the interaction region, spin tracking has to be included in all transport elements which can contribute to a loss of polarization. These are the positron source, the damping ring, the spin rotators, the main linac and the beam delivery system. In particular, the dynamics of the polarized positron beam is required to be investigated. The results of positron spin tracking and depolarization study at the Positron-Linac-To-Ring (PLTR) beamline are presented.

  7. Chloride regulates afferent arteriolar contraction in response to depolarization

    DEFF Research Database (Denmark)

    Hansen, P B; Jensen, B L; Skott, O

    1998-01-01

    . The results show that K+-induced contraction of smooth muscle cells in the afferent arteriole is highly sensitive to chloride, whereas neurotransmitter release and ensuing contraction is not dependent on chloride. Thus, there are different activation pathways for depolarizing vasoconstrictors......-Renal vascular reactivity is influenced by the level of dietary salt intake. Recent in vitro data suggest that afferent arteriolar contractility is modulated by extracellular chloride. In the present study, we assessed the influence of chloride on K+-induced contraction in isolated perfused rabbit...... afferent arterioles. In 70% of vessels examined, K+-induced contraction was abolished by acute substitution of bath chloride. Consecutive addition of Cl- (30, 60, 80, 100, 110, and 117 mmol/L) restored the sensitivity to K+, and half-maximal response was observed at 82 mmol/L chloride. The calcium channel...

  8. Modeling of PZT Ferroelectric Ceramic Depolarization Driven by Shock Stress

    Institute of Scientific and Technical Information of China (English)

    LAN Chao-Hui; PENG Yu-Fei; LONG Ji-Dong; WANG Qiang; WANG Wen-Dou

    2011-01-01

    @@ Shock-induced phase transition of ferroelectric ceramic PZT 95/5 causes elastic stiffening and depolarization,releasing stored electrostatic energy into the load circuit.We develop a model to describe the response of the PZT ferroelectric ceramic and implement it into simulation codes.The model is based on the phenomenological theory of phase transition dyynamics and takes into account the effects of the self-generated intensive electrical field and stress.Connected with the discharge model and external circuit, the whole transient process of PZT ceramic depoling can be investigated.The results show the finite transition velocity of the ferroelectric phase and the double wave structure caused by phase transition.Simulated currents are compared with the results from experiments with shock pressures varying from 0.4 to 2.8GPa.

  9. Voltage-Gated Channels as Causative Agents for Epilepsies

    Directory of Open Access Journals (Sweden)

    Mutasem Abuhamed

    2008-01-01

    Full Text Available Problem statement: Epilepsy is a common neurological disorder that afflicts 1-2% of the general population worldwide. It encompasses a variety of disorders with seizures. Approach: Idiopathic epilepsies were defined as a heterogeneous group of seizure disorders that show no underlying cause .Voltage-gated ion channels defect were recognized etiology of epilepsy in the central nervous system. The aim of this article was to provide an update on voltage-gated channels and their mutation as causative agents for epilepsies. We described the structures of the voltage-gated channels, discuss their current genetic studies, and then review the effects of voltage-gated channels as causative agents for epilepsies. Results: Channels control the flow of ions in and out of the cell causing depolarization and hyper polarization of the cell. Voltage-gated channels were classified into four types: Sodium, potassium calcium ands chloride. Voltage-gated channels were macromolecular protein complexes within the lipid membrane. They were divided into subunits. Each subunit had a specific function and was encoded by more than one gen. Conclusion: Current genetic studies of idiopathic epilepsies show the importance of genetic influence on Voltage-gated channels. Different genes may regulate a function in a channel; the channel defect was directly responsible for neuronal hyper excitability and seizures.

  10. Automatic voltage imbalance detector

    Science.gov (United States)

    Bobbett, Ronald E.; McCormick, J. Byron; Kerwin, William J.

    1984-01-01

    A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

  11. Mixed voltage VLSI design

    Science.gov (United States)

    Panwar, Ramesh; Rennels, David; Alkalaj, Leon

    1993-01-01

    A technique for minimizing the power dissipated in a Very Large Scale Integration (VLSI) chip by lowering the operating voltage without any significant penalty in the chip throughput even though low voltage operation results in slower circuits. Since the overall throughput of a VLSI chip depends on the speed of the critical path(s) in the chip, it may be possible to sustain the throughput rates attained at higher voltages by operating the circuits in the critical path(s) with a high voltage while operating the other circuits with a lower voltage to minimize the power dissipation. The interface between the gates which operate at different voltages is crucial for low power dissipation since the interface may possibly have high static current dissipation thus negating the gains of the low voltage operation. The design of a voltage level translator which does the interface between the low voltage and high voltage circuits without any significant static dissipation is presented. Then, the results of the mixed voltage design using a greedy algorithm on three chips for various operating voltages are presented.

  12. Cortical spreading depolarization increases adult neurogenesis, and alters behavior and hippocampus-dependent memory in mice.

    Science.gov (United States)

    Urbach, Anja; Baum, Eileen; Braun, Falko; Witte, Otto W

    2017-05-01

    Cortical spreading depolarizations are an epiphenomenon of human brain pathologies and associated with extensive but transient changes in ion homeostasis, metabolism, and blood flow. Previously, we have shown that cortical spreading depolarization have long-lasting consequences on the brains transcriptome and structure. In particular, we found that cortical spreading depolarization stimulate hippocampal cell proliferation resulting in a sustained increase in adult neurogenesis. Since the hippocampus is responsible for explicit memory and adult-born dentate granule neurons contribute to this function, cortical spreading depolarization might influence hippocampus-dependent cognition. To address this question, we induced cortical spreading depolarization in C57Bl/6 J mice by epidural application of 1.5 mol/L KCl and evaluated neurogenesis and behavior at two, four, or six weeks thereafter. Congruent with our previous findings in rats, we found that cortical spreading depolarization increases numbers of newborn dentate granule neurons. Moreover, exploratory behavior and object location memory were consistently enhanced. Reference memory in the water maze was virtually unaffected, whereas memory formation in the Barnes maze was impaired with a delay of two weeks and facilitated after four weeks. These data show that cortical spreading depolarization produces lasting changes in psychomotor behavior and complex, delay- and task-dependent changes in spatial memory, and suggest that cortical spreading depolarization-like events affect the emotional and cognitive outcomes of associated brain pathologies.

  13. A rotational diffusion coefficient of the 70s ribosome determined by depolarized laser light scattering

    NARCIS (Netherlands)

    Bruining, J.; Fijnaut, H.M.

    We have obtained a rotational diffusion coefficient of the 70S ribosome isolated from Escherichia-coli (MRE-600), from the depolarized light scattering spectrum measured by photon correlation spectroscopy. The intensity correlation function of depolarized scattered light contains contributions due

  14. A rotational diffusion coefficient of the 70s ribosome determined by depolarized laser light scattering

    NARCIS (Netherlands)

    Bruining, J.; Fijnaut, H.M.

    1975-01-01

    We have obtained a rotational diffusion coefficient of the 70S ribosome isolated from Escherichia-coli (MRE-600), from the depolarized light scattering spectrum measured by photon correlation spectroscopy. The intensity correlation function of depolarized scattered light contains contributions due t

  15. Modulation of electromagnetic fields by a depolarizer of random polarizer array

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Wang, Wei

    2016-01-01

    The statistical properties of the electric fields with random changes of the polarization state in space generated by a depolarizer are investigated on the basis of the coherence matrix. The depolarizer is a polarizer array composed of a multitude of contiguous square cells of polarizers with ran...

  16. On Depolarization Lidar-Based Method for The Determination of Liquid-Cloud Microphysical Properties

    Directory of Open Access Journals (Sweden)

    Roy Gilles

    2016-01-01

    Full Text Available Under single scattering conditions, water droplets clouds do not depolarize the backscattered light. However, backscattered light from multiple scattering will be depolarized. The level of depolarization is a function of the droplets size, the cloud extinction coefficient value and profile; it has also an important dependency on the lidar field-of-view (FOV. The use of depolarization information to retrieve cloud microphysical properties, using Multiple-FOV has been the object of studies, [1], [2]. Recently the use of the depolarization, at a single FOV, has been studied for cloud with linear liquid water content profiles, [3], [4]. In this paper we present the mechanism leading to depolarization and identify the FOV values for which the information on particle size is high. Also Monte Carlo simulations for cloud with constant and ramp up profiles are presented. The degree of linear depolarization as a function of cloud penetration is significantly different for both cloud profiles. This suggests that the use of the degree of linear depolarization at a single FOV should be used with caution to determine clouds micro-physical parameters.

  17. Effects of extracellular calcium and sodium on depolarization-induced automaticity in guinea pig papillary muscle.

    Science.gov (United States)

    Katzung, B G

    1975-07-01

    Regenerative discharge of action potentials is induced in mammalian papillary muscles by passage of small depolarizing currents. In this paper, the effects of various extracellular calcium and sodium concentrations and of tetrodotoxin on this phenomenon were studied in guinea pig papillary muscles in a sucrose gap chamber. Phase 4 diastolic depolarization was found to be associated with an increase in membrane resistance. The slope of phase 4 depolarization was decreased by reductions in extracellular calcium or sodium concentration. The range of maximum diastolic potentials and the thresholds from which regenerative potentials arose were reduced, especially at the positive limit of potentials, by a reduction in either ion. It was concluded that both calcium and sodium influence diastolic depolarization and participate in the regenerative action potentials of depolarization-induced ventricular automaticity.

  18. Modulation of electromagnetic fields by a depolarizer of random polarizer array

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Wang, Wei

    2016-01-01

    The statistical properties of the electric fields with random changes of the polarization state in space generated by a depolarizer are investigated on the basis of the coherence matrix. The depolarizer is a polarizer array composed of a multitude of contiguous square cells of polarizers with ran......The statistical properties of the electric fields with random changes of the polarization state in space generated by a depolarizer are investigated on the basis of the coherence matrix. The depolarizer is a polarizer array composed of a multitude of contiguous square cells of polarizers...... with randomly distributed polarization angles, where the incident fields experience a random polarization modulation after passing through the depolarizer. The propagation of the modulated electric fields through any quadratic optical system is examined within the framework of the complex ABCD matrix to show...

  19. "Spreading Depolarization" bei Migräneaura und Schlaganfall im menschlichen Gehirn

    Directory of Open Access Journals (Sweden)

    Dreier JP

    2013-01-01

    Full Text Available Neuere Studien belegen eine hohe Frequenz von „Spreading Depolarizations“ bei Patienten mit aneurysmatischer Subarachnoidalblutung, verzögerter zerebraler Ischämie nach Subarachnoidalblutung, malignem ischämischem Schlaganfall, spontaner intrazerebraler Blutung und Schädel-Hirn-Trauma. „Spreading Depolarization“ führt in der grauen Substanz zum zytotoxischen Ödem. Langandauernde „Spreading Depolarizations“ leiten im Tierexperiment Kaskaden ein, die zum Zelltod führen. Therapien, die „Spreading Depolarization“ verkürzen oder die pathologische, inverse neurovaskuläre Kopplung an „Spreading Depolarization“ aufheben, könnten eine interessante Option in der Behandlung der oben genannten Erkrankungen darstellen.

  20. Spreading depolarizations have prolonged direct current shifts and are associated with poor outcome in brain trauma

    DEFF Research Database (Denmark)

    Hartings, Jed A; Watanabe, Tomas; Bullock, M Ross

    2011-01-01

    Cortical spreading depolarizations occur spontaneously after ischaemic, haemorrhagic and traumatic brain injury. Their effects vary spatially and temporally as graded phenomena, from infarction to complete recovery, and are reflected in the duration of depolarization measured by the negative direct...... current shift of electrocorticographic recordings. In the focal ischaemic penumbra, peri-infarct depolarizations have prolonged direct current shifts and cause progressive recruitment of the penumbra into the core infarct. In traumatic brain injury, the effects of spreading depolarizations are unknown......, although prolonged events have not been observed in animal models. To determine whether detrimental penumbral-type depolarizations occur in human brain trauma, we analysed electrocorticographic recordings obtained by subdural electrode-strip monitoring during intensive care. Of 53 patients studied, 10...

  1. Optogenetic Monitoring of Synaptic Activity with Genetically Encoded Voltage Indicators

    Science.gov (United States)

    Nakajima, Ryuichi; Jung, Arong; Yoon, Bong-June; Baker, Bradley J.

    2016-01-01

    The age of genetically encoded voltage indicators (GEVIs) has matured to the point that changes in membrane potential can now be observed optically in vivo. Improving the signal size and speed of these voltage sensors has been the primary driving forces during this maturation process. As a result, there is a wide range of probes using different voltage detecting mechanisms and fluorescent reporters. As the use of these probes transitions from optically reporting membrane potential in single, cultured cells to imaging populations of cells in slice and/or in vivo, a new challenge emerges—optically resolving the different types of neuronal activity. While improvements in speed and signal size are still needed, optimizing the voltage range and the subcellular expression (i.e., soma only) of the probe are becoming more important. In this review, we will examine the ability of recently developed probes to report synaptic activity in slice and in vivo. The voltage-sensing fluorescent protein (VSFP) family of voltage sensors, ArcLight, ASAP-1, and the rhodopsin family of probes are all good at reporting changes in membrane potential, but all have difficulty distinguishing subthreshold depolarizations from action potentials and detecting neuronal inhibition when imaging populations of cells. Finally, we will offer a few possible ways to improve the optical resolution of the various types of neuronal activities. PMID:27547183

  2. Depolarizing Effects of Daikenchuto on Interstitial Cells of Cajal from Mouse Small Intestine

    Science.gov (United States)

    Kim, Hyungwoo; Kim, Hyun Jung; Yang, Dongki; Jung, Myeong Ho; Kim, Byung Joo

    2017-01-01

    Background: Daikenchuto (DKT; TJ-100, TU-100), a traditional herbal medicineis used in modern medicine to treat gastrointestinal (GI) functional disorders. Interstitial cells of Cajal (ICCs) are the pacemaker cells of the GI tract and play important roles in the regulation of GI motility. Objective: The objective of this study was to investigate the effects of DKT on the pacemaker potentials (PPs) of cultured ICCs from murine small intestine. Materials and Methods: Enzymatic digestions were used to dissociate ICCs from mouse small intestine tissues. All experiments on ICCs were performed after 12 h of culture. The whole-cell patch-clamp configuration was used to record ICC PPs (current clamp mode). All experiments were performed at 30-32°C. Results: In current-clamp modeDKT depolarized and concentration-dependently decreased the amplitudes of PPs. Y25130 (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT4 receptor antagonist) did. Methoctramine (a muscarinic M2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-diphenylacetoxy-N-methylpiperidine methiodide (a muscarinic M3 receptor antagonist) facilitated blockade of DKT-induced PP depolarization. Pretreatment with an external Ca2+-free solution or thapsigargin abolished PPsand under these conditions, DKT did not induce PP depolarization. Furthermore Ginseng radix and Zingiberis rhizomes depolarized PPs, whereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Conclusion: These results suggest that DKT depolarizes ICC PPs in an internal or external Ca2+-dependent manner by stimulating 5-HT4 and M3 receptors. Furthermore, the authors suspect that the component in DKT largely responsible for depolarization is probably also a component of Ginseng radix and Zingiberis rhizomes. SUMMARY Daikenchuto (DKT) depolarized and concentration-dependently decreased the amplitudes of

  3. Voltage-gated sodium channels in taste bud cells

    Directory of Open Access Journals (Sweden)

    Williams Mark E

    2009-03-01

    Full Text Available Abstract Background Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. Results We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. Conclusion SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

  4. Thermally stimulated depolarization current studies of sulfonated polystyrene ionomers

    Science.gov (United States)

    Carvalho, Antonio José Felix; Viana, Vicente Galber Freitas; Faria, Roberto Mendonça

    2009-12-01

    A detailed study of thermally stimulated depolarization current (TSDC) was carried out to investigate dipolar relaxation and the charge storage phenomenon in films of sulfonated polystyrene (SPS) ionomers having lithium or potassium as counterions. Differential scanning calorimetry measurements were also applied as a complementary technique, mainly to follow the change of the glass transition temperature with the amount of sulfonated groups. It was observed that, since the glass transition does not change significantly with the amount of sulfonated groups, a cluster of multiplets is expected not to be formed in the range used in this work. TSDC of SPS samples polarized at temperatures higher than the glass transition temperature showed three peaks: one at lower temperature (peak β), an intermediate peak (peak α), and a third that appeared at a temperature coincident with the polarization temperature (peak ρ). Quantitative information about trapping-detrapping and dipolar relaxation and their corresponding activation energies was determined by fittings of the deconvoluted peaks with kinetic relaxation processes.

  5. Thermally stimulated depolarization current studies of sulfonated polystyrene ionomers

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Antonio Jose Felix [Universidade Federal de Sao Carlos, Laboratory of Polymers and Renewable Materials, Sorocaba, SP (Brazil); Viana, Vicente Galber Freitas [Universidade Federal do Piaui, Centro de Ciencias da Natureza, Teresina, PI (Brazil); Faria, Roberto Mendonca [USP, Instituto de Fisica de Sao Carlos, SP (Brazil)

    2009-12-15

    A detailed study of thermally stimulated depolarization current (TSDC) was carried out to investigate dipolar relaxation and the charge storage phenomenon in films of sulfonated polystyrene (SPS) ionomers having lithium or potassium as counterions. Differential scanning calorimetry measurements were also applied as a complementary technique, mainly to follow the change of the glass transition temperature with the amount of sulfonated groups. It was observed that, since the glass transition does not change significantly with the amount of sulfonated groups, a cluster of multiplets is expected not to be formed in the range used in this work. TSDC of SPS samples polarized at temperatures higher than the glass transition temperature showed three peaks: one at lower temperature (peak {beta}), an intermediate peak (peak {alpha}), and a third that appeared at a temperature coincident with the polarization temperature (peak {rho}). Quantitative information about trapping-detrapping and dipolar relaxation and their corresponding activation energies was determined by fittings of the deconvoluted peaks with kinetic relaxation processes. (orig.)

  6. Raised activity of L-type calcium channels renders neurons prone to form paroxysmal depolarization shifts.

    Science.gov (United States)

    Rubi, Lena; Schandl, Ulla; Lagler, Michael; Geier, Petra; Spies, Daniel; Gupta, Kuheli Das; Boehm, Stefan; Kubista, Helmut

    2013-09-01

    Neuronal L-type voltage-gated calcium channels (LTCCs) are involved in several physiological functions, but increased activity of LTCCs has been linked to pathology. Due to the coupling of LTCC-mediated Ca(2+) influx to Ca(2+)-dependent conductances, such as KCa or non-specific cation channels, LTCCs act as important regulators of neuronal excitability. Augmentation of after-hyperpolarizations may be one mechanism that shows how elevated LTCC activity can lead to neurological malfunctions. However, little is known about other impacts on electrical discharge activity. We used pharmacological up-regulation of LTCCs to address this issue on primary rat hippocampal neurons. Potentiation of LTCCs with Bay K8644 enhanced excitatory postsynaptic potentials to various degrees and eventually resulted in paroxysmal depolarization shifts (PDS). Under conditions of disturbed Ca(2+) homeostasis, PDS were evoked frequently upon LTCC potentiation. Exposing the neurons to oxidative stress using hydrogen peroxide also induced LTCC-dependent PDS. Hence, raising LTCC activity had unidirectional effects on brief electrical signals and increased the likeliness of epileptiform events. However, long-lasting seizure-like activity induced by various pharmacological means was affected by Bay K8644 in a bimodal manner, with increases in one group of neurons and decreases in another group. In each group, isradipine exerted the opposite effect. This suggests that therapeutic reduction in LTCC activity may have little beneficial or even adverse effects on long-lasting abnormal discharge activities. However, our data identify enhanced activity of LTCCs as one precipitating cause of PDS. Because evidence is continuously accumulating that PDS represent important elements in neuropathogenesis, LTCCs may provide valuable targets for neuroprophylactic therapy.

  7. EVALUATION OF PROTON-CONDUCTING MEMBRANES FOR USE IN A SULFUR-DIOXIDE DEPOLARIZED ELECTROLYZER

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, D.; Elvington, M.; Colon-Mercado, H.

    2009-11-11

    The chemical stability, sulfur dioxide transport, ionic conductivity, and electrolyzer performance have been measured for several commercially available and experimental proton exchange membranes (PEMs) for use in a sulfur dioxide depolarized electrolyzer (SDE). The SDE's function is to produce hydrogen by using the Hybrid Sulfur (HyS) Process, a sulfur based electrochemical/thermochemical hybrid cycle. Membrane stability was evaluated using a screening process where each candidate PEM was heated at 80 C in 60 wt. % H{sub 2}SO{sub 4} for 24 hours. Following acid exposure, chemical stability for each membrane was evaluated by FTIR using the ATR sampling technique. Membrane SO{sub 2} transport was evaluated using a two-chamber permeation cell. SO{sub 2} was introduced into one chamber whereupon SO{sub 2} transported across the membrane into the other chamber and oxidized to H{sub 2}SO{sub 4} at an anode positioned immediately adjacent to the membrane. The resulting current was used to determine the SO{sub 2} flux and SO{sub 2} transport. Additionally, membrane electrode assemblies (MEAs) were prepared from candidate membranes to evaluate ionic conductivity and selectivity (ionic conductivity vs. SO{sub 2} transport) which can serve as a tool for selecting membranes. MEAs were also performance tested in a HyS electrolyzer measuring current density versus a constant cell voltage (1V, 80 C in SO{sub 2} saturated 30 wt% H2SO{sub 4}). Finally, candidate membranes were evaluated considering all measured parameters including SO{sub 2} flux, SO{sub 2} transport, ionic conductivity, HyS electrolyzer performance, and membrane stability. Candidate membranes included both PFSA and non-PFSA polymers and polymer blends of which the non-PFSA polymers, BPVE-6F and PBI, showed the best selectivity.

  8. Recording, analysis, and interpretation of spreading depolarizations in neurointensive care : Review and recommendations of the COSBID research group

    NARCIS (Netherlands)

    Dreier, Jens P; Fabricius, Martin; Ayata, Cenk; Sakowitz, Oliver W; William Shuttleworth, C; Dohmen, Christian; Graf, Rudolf; Vajkoczy, Peter; Helbok, Raimund; Suzuki, Michiyasu; Schiefecker, Alois J; Major, Sebastian; Winkler, Maren Kl; Kang, Eun-Jeung; Milakara, Denny; Oliveira-Ferreira, Ana I; Reiffurth, Clemens; Revankar, Gajanan S; Sugimoto, Kazutaka; Dengler, Nora F; Hecht, Nils; Foreman, Brandon; Feyen, Bart; Kondziella, Daniel; Friberg, Christian K; Piilgaard, Henning; Rosenthal, Eric S; Westover, M Brandon; Maslarova, Anna; Santos, Edgar; Hertle, Daniel; Sánchez-Porras, Renán; Jewell, Sharon L; Balança, Baptiste; Platz, Johannes; Hinzman, Jason M; Lückl, Janos; Schoknecht, Karl; Schöll, Michael; Drenckhahn, Christoph; Feuerstein, Delphine; Eriksen, Nina; Horst, Viktor; Bretz, Julia S; Jahnke, Paul; Scheel, Michael; Bohner, Georg; Rostrup, Egill; Pakkenberg, Bente; Heinemann, Uwe; Claassen, Jan; Carlson, Andrew P; Kowoll, Christina M; Lublinsky, Svetlana; Chassidim, Yoash; Shelef, Ilan; Friedman, Alon; Brinker, Gerrit; Reiner, Michael; Kirov, Sergei A; Andrew, R David; Farkas, Eszter; Güresir, Erdem; Vatter, Hartmut; Chung, Lee S; Brennan, K C; Lieutaud, Thomas; Marinesco, Stephane; Maas, Andrew Ir; Sahuquillo, Juan; Dahlem, Markus A; Richter, Frank; Herreras, Oscar; Boutelle, Martyn G; Okonkwo, David O; Bullock, M Ross; Witte, Otto W; Martus, Peter; van den Maagdenberg, Arn Mjm; Ferrari, Michel D; Dijkhuizen, Rick M; Shutter, Lori A; Andaluz, Norberto; Schulte, André P; MacVicar, Brian; Watanabe, Tomas; Woitzik, Johannes; Lauritzen, Martin; Strong, Anthony J; Hartings, Jed A

    2017-01-01

    Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly

  9. Backscatter and depolarization measurements of aerosolized biological simulants using a chamber lidar system

    Science.gov (United States)

    Brown, David M.; Thrush, Evan P.; Thomas, Michael E.; Santarpia, Josh; Quizon, Jason; Carter, Christopher C.

    2010-04-01

    To ensure agent optical cross sections are well understood from the UV to the LWIR, volume integrated measurements of aerosolized agent material at a few key wavelengths is required to validate existing simulations. Ultimately these simulations will be used to assess the detection performance of various classes of lidar technology spanning the entire range of the optical spectrum. The present work demonstrates an optical measurement architecture based on lidar allowing the measurement of backscatter and depolarization ratio from biological aerosols released in a refereed, 1-m cubic chamber. During 2009, various upgrades have been made to the chamber LIDAR system, which operates at 1.064 μm with sub nanosecond pulses at a 120 Hz repetition rate. The first build of the system demonstrated a sensitivity of aerosolized Bacillus atrophaeus (BG) on the order of 5×105 ppl with 1 GHz InGaAs detectors. To increase the sensitivity and reduce noise, the InGaAs detectors were replaced with larger-area silicon avalanche photodiodes for the second build of the system. In addition, computer controlled step variable neutral density filters are now incorporated to facilitate calibrating the system for absolute back-scatter measurements. Calibrated hard target measurements will be combined with data from the ground truth instruments for cross-section determination of the material aerosolized in the chamber. Measured results are compared to theoretical simulations of cross-sections.

  10. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D C

    2013-01-01

    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  11. VSOP/Hv1 proton channels sustain calcium entry, neutrophil migration, and superoxide production by limiting cell depolarization and acidification.

    Science.gov (United States)

    El Chemaly, Antoun; Okochi, Yoshifumi; Sasaki, Mari; Arnaudeau, Serge; Okamura, Yasushi; Demaurex, Nicolas

    2010-01-18

    Neutrophils kill microbes with reactive oxygen species generated by the NADPH oxidase, an enzyme which moves electrons across membranes. Voltage-gated proton channels (voltage-sensing domain only protein [VSOP]/Hv1) are required for high-level superoxide production by phagocytes, but the mechanism of this effect is not established. We show that neutrophils from VSOP/Hv1-/- mice lack proton currents but have normal electron currents, indicating that these cells have a fully functional oxidase that cannot conduct protons. VSOP/Hv1-/- neutrophils had a more acidic cytosol, were more depolarized, and produced less superoxide and hydrogen peroxide than neutrophils from wild-type mice. Hydrogen peroxide production was rescued by providing an artificial conductance with gramicidin. Loss of VSOP/Hv1 also aborted calcium responses to chemoattractants, increased neutrophil spreading, and decreased neutrophil migration. The migration defect was restored by the addition of a calcium ionophore. Our findings indicate that proton channels extrude the acid and compensate the charge generated by the oxidase, thereby sustaining calcium entry signals that control the adhesion and motility of neutrophils. Loss of proton channels thus aborts superoxide production and causes a severe signaling defect in neutrophils.

  12. Modulation of voltage-gated sodium channels hyperpolarizes the voltage threshold for activation in spinal motoneurones.

    Science.gov (United States)

    Power, Kevin E; Carlin, Kevin P; Fedirchuk, Brent

    2012-03-01

    Previous work has shown that motoneurone excitability is enhanced by a hyperpolarization of the membrane potential at which an action potential is initiated (V(th)) at the onset, and throughout brainstem-evoked fictive locomotion in the adult decerebrate cat and neonatal rat. Modeling work has suggested the modulation of Na(+) conductance as a putative mechanism underlying this state-dependent change in excitability. This study sought to determine whether modulation of voltage-gated sodium channels could induce V(th) hyperpolarization. Whole-cell patch-clamp recordings were made from antidromically identified lumbar spinal motoneurones in an isolated neonatal rat spinal cord preparation. Recordings were made with and without the bath application of veratridine, a plant alkaloid neurotoxin that acts as a sodium channel modulator. As seen in HEK 293 cells expressing Nav1.2 channels, veratridine-modified channels demonstrated a hyperpolarizing shift in their voltage-dependence of activation and a slowing of inactivation that resulted in an enhanced inward current in response to voltage ramp stimulations. In the native rat motoneurones, veratridine-modified sodium channels induced a hyperpolarization of V(th) in all 29 neonatal rat motoneurones examined (mean hyperpolarization: -6.6 ± 4.3 mV). V(th) hyperpolarization was not due to the effects on Ca(2+) and/or K(+) channels as blockade of these currents did not alter V(th). Veratridine also significantly increased the amplitude of persistent inward currents (PICs; mean increase: 72.5 ± 98.5 pA) evoked in response to slow depolarizing current ramps. However, the enhancement of the PIC amplitude had a slower time course than the hyperpolarization of V(th), and the PIC onset voltage could be either depolarized or hyperpolarized, suggesting that PIC facilitation did not mediate the V(th) hyperpolarization. We therefore suggest that central neuronal circuitry in mammals could affect V(th) in a mechanism similar to that of

  13. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

    2008-04-09

    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  14. High voltage engineering

    CERN Document Server

    Rizk, Farouk AM

    2014-01-01

    Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

  15. High voltage test techniques

    CERN Document Server

    Kind, Dieter

    2001-01-01

    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  16. Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

    OpenAIRE

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar; Cecati, Carlo

    2013-01-01

    Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbala...

  17. The Control Unit of a Single Phase Voltage Regulator

    CERN Document Server

    Colak, Ilknur

    2010-01-01

    Supplying regulated voltage to critical loads is an important topic for several years. This paper presents a single-phase electronic voltage regulator based on high frequency switching of an isolated transformer where primary side voltage is controlled by two full-bridge converters sharing a common DC bus and operating at 50Hz and 20kHz switching frequencies. This allows 50Hz induced voltage on the primary side of the transformer, regulated by high frequency switching. Depending on the input voltage, voltage at the secondary side of the transformer add to (boost mode) or subtract (buck mode) from the supply voltage, therefore, maintaining a regulated voltage value across the load. The regulator is controlled by a digital controller allowing fast dynamic response. A 5kVA single-phase voltage regulator is realized to verify the operation of the proposed algorithm. The experimental results show that regulator maintains constant voltage across the load both in step-up (low supply voltage) and step-down (high supp...

  18. Characterization of homogenous depolarizing media based on Mueller matrix differential decomposition.

    Science.gov (United States)

    Arteaga, Oriol; Kahr, Bart

    2013-04-01

    In a depolarizing medium in which the optical properties are uniformly distributed, the logarithm of the Mueller matrix can be used to calculate the differential Mueller matrix. From the differential Mueller matrix, the 10 optical properties of a homogeneous depolarizing medium are recovered. A modified calculation is introduced for media showing small time-irreversal depolarization events. The benefits of this method are illustrated in the determination of circular dichroism and circular birefringence of a nickel sulfate hexahydrate crystal from spectroscopic Mueller matrix measurements.

  19. Statistical meaning of the differential Mueller matrix of depolarizing homogeneous media.

    Science.gov (United States)

    Ossikovski, Razvigor; Arteaga, Oriol

    2014-08-01

    By applying the statistical definition of a depolarizing Mueller matrix we formally derive and physically interpret the differential matrix of a depolarizing homogeneous medium. The depolarization phenomenon being a direct consequence of the fluctuations of the six elementary polarization properties of the medium, the differential matrix contains the mean values and the variances of the properties, thus fully describing those from a statistical viewpoint. Similarly, the reduced coherency matrix associated with the G-symmetric component of the differential matrix has an immediate physical interpretation as being the covariance matrix of the three basic groups of polarization properties. The formal developments are illustrated on experimental examples.

  20. Coherence and polarization speckle generated by a rough-surfaced retardation plate depolarizer

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Takeda, Mitsuo

    2015-01-01

    The coherence and polarization of polarization speckle, arising from a stochastic electromagnetic field with random change of polarization, modulated by a depolarizer are examined on the basis of the coherence matrix. The depolarizer is a rough-surfaced retardation plate with a random function...... of position introducing random phase differences between the two orthogonal components of the electric vector. Under the assumption of Gaussian statistics with zero mean, the surface model for the depolarizer of the rough-surfaced retardation plate is obtained. The propagation of the modulated fields through...

  1. Study of Depolarization Field Influence on Ferroelectric Films Within Transverse Ising Model

    Institute of Scientific and Technical Information of China (English)

    TAO Yong-Mei; SHI Qin-Fen; JIANG Qing

    2005-01-01

    An improved transverse Ising model is proposed by taking the depolarization field effect into account.Within the framework of mean-field theory we investigate the behavior of the ferroelectric thin film. Our results show that the influence of the depolarization field is to flatten the spontaneous polarization profile and make the films more homogeneous, which is consistent with Ginzburg-Landau theory. This fact shows that this model can be taken as an effective model to deal with the ferroelectric film and can be further extended to refer to quantum effect. The competition between quantum effect and depolarization field induces some interesting phenomena on ferroelectric thin films.

  2. Voltage verification unit

    Science.gov (United States)

    Martin, Edward J.

    2008-01-15

    A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

  3. Light depolarization induced by metallic tips in apertureless near-field optical microscopy and tip-enhanced Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gucciardi, P G [CNR-Istituto per i Processi Chimico-Fisici, sezione Messina, Salita Sperone, Contrada Papardo, I-98158 Faro Superiore, Messina (Italy); Lopes, M; Deturche, R; Julien, C; Barchiesi, D; Chapelle, M Lamy de la [Institut Charles Delaunay-CNRS FRE 2848, Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP2060, 10010 Troyes (France)

    2008-05-28

    We have investigated the depolarization effects of light scattered by sharp tips used for apertureless near-field optical microscopy. Dielectric and metal coated tips have been investigated and depolarization factors between 5 and 30% have been measured, changing as a function of the incident light polarization and of the tip shape. The experimental results are in good agreement with theoretical calculations performed by the finite element method, giving a near-field depolarization factor close to 10%. The effect of depolarization has been investigated in polarized tip-enhanced Raman spectroscopy (TERS) experiments; the depolarization gives rise to forbidden Raman modes in Si crystals.

  4. Aerosol Properties over Southeastern China from Multi-Wavelength Raman and Depolarization Lidar Measurements

    Directory of Open Access Journals (Sweden)

    Heese Birgit

    2016-01-01

    Full Text Available A dataset of particle optical properties of highly polluted urban aerosol over the Pearl River Delta, Guangzhou, China is presented. The data were derived from multi-wavelengths Raman and depolarization lidar PollyXT and AERONET sun photometer measurements. The measurement campaign was conducted from Nov 2011 to June 2012. High aerosol optical depth was observed in the polluted atmosphere over this megacity, with a mean value of 0.54 ± 0.33 and a peak value of even 1.9. For the particle characterization the lidar ratio and the linear particle depolarization ratio, both at 532 nm, were used. The mean values of these properties are 48.0 sr ± 10.7 sr for the lidar ratio and 4%+-4% for the particle depolarization ratio, which means most depolarization measurements stayed below 10%. So far, most of these results indicate urban pollution particles mixed with particles arisen from biomass and industrial burning.

  5. Aerosol Properties over Southeastern China from Multi-Wavelength Raman and Depolarization Lidar Measurements

    Science.gov (United States)

    Heese, Birgit; Althausen, Dietrich; Baars, Holger; Bohlmann, Stephanie; Deng, Ruru

    2016-06-01

    A dataset of particle optical properties of highly polluted urban aerosol over the Pearl River Delta, Guangzhou, China is presented. The data were derived from multi-wavelengths Raman and depolarization lidar PollyXT and AERONET sun photometer measurements. The measurement campaign was conducted from Nov 2011 to June 2012. High aerosol optical depth was observed in the polluted atmosphere over this megacity, with a mean value of 0.54 ± 0.33 and a peak value of even 1.9. For the particle characterization the lidar ratio and the linear particle depolarization ratio, both at 532 nm, were used. The mean values of these properties are 48.0 sr ± 10.7 sr for the lidar ratio and 4%+-4% for the particle depolarization ratio, which means most depolarization measurements stayed below 10%. So far, most of these results indicate urban pollution particles mixed with particles arisen from biomass and industrial burning.

  6. Depolarization properties of cirrus clouds from polarization lidar measurements over Hefei in spring

    Institute of Scientific and Technical Information of China (English)

    Zhenzhu Wang; Ruli Chi; Bo Liu; Jun Zhou

    2008-01-01

    @@ A new polarization lidar has been developed for detecting depolarization characteristics of aerosol and cirrus over Hefei (31.90°N, 117.16°E), China. The fundamental principle of polarization lidar is briefly introduced.

  7. Preliminary evidence that ketamine inhibits spreading depolarizations in acute human brain injury

    DEFF Research Database (Denmark)

    Sakowitz, Oliver W; Kiening, Karl L; Krajewski, Kara L

    2009-01-01

    by the noncompetitive N-methyl-d-aspartate receptor antagonist ketamine. This restored electrocorticographic activity. CONCLUSIONS: These anecdotal electrocorticographic findings suggest that ketamine has an inhibitory effect on spreading depolarizations in humans. This is of potential interest for future...

  8. Detection of spreading depolarization with intraparenchymal electrodes in the injured human brain

    DEFF Research Database (Denmark)

    Jeffcote, Toby; Hinzman, Jason M; Jewell, Sharon L

    2014-01-01

    BACKGROUND: Spreading depolarization events following ischemic and traumatic brain injury are associated with poor patient outcome. Currently, monitoring these events is limited to patients in whom subdural electrodes can be placed at open craniotomy. This study examined whether these events can ...... for craniotomy. The method provides a new investigative tool for the evaluation of the contribution of these events to secondary brain injury in human patients.......BACKGROUND: Spreading depolarization events following ischemic and traumatic brain injury are associated with poor patient outcome. Currently, monitoring these events is limited to patients in whom subdural electrodes can be placed at open craniotomy. This study examined whether these events can...... for traumatic brain injury or aneurysmal subarachnoid hemorrhage were monitored for depolarization events in an intensive care setting with concurrent strip (subdural) and depth (intra-parenchymal) electrode recordings. RESULTS: (1) Depolarization events can be reliably detected from intra-cortically placed...

  9. A unified numerical model of collisional depolarization and broadening rates due to hydrogen atom collisions

    CERN Document Server

    Derouich, M; Barklem, P S

    2015-01-01

    Interpretation of solar polarization spectra accounting for partial or complete frequency redistribution requires data on various collisional processes. Data for depolarization and polarization transfer are needed but often missing, while data for collisional broadening are usually more readily available. Recent work by Sahal-Br\\'echot and Bommier concluded that despite underlying similarities in the physics of collisional broadening and depolarization processes, relationships between them are not possible to derive purely analytically. We aim to derive accurate numerical relationships between the collisional broadening rates and the collisional depolarization and polarization transfer rates due to hydrogen atom collisions. Such relationships would enable accurate and efficient estimation of collisional data for solar applications. Using earlier results for broadening and depolarization processes based on general (i.e. not specific to a given atom), semi-classical calculations employing interaction potentials...

  10. Sensitivity of laser light depolarization analysis for detection of malaria in blood samples.

    Science.gov (United States)

    Padial, Manuel Martínez; Subirats, Mercedes; Puente, Sabino; Lago, Mar; Crespo, Santiago; Palacios, Gonzalo; Baquero, Margarita

    2005-05-01

    Automated light depolarization analysis could be a useful tool for diagnosing malarial infections. This work discusses the results of a diagnostic efficacy study on 411 samples from patients with suspected malaria infection performed with a Cell-Dyn 4000 analyser. Light dispersed at 90 degrees and depolarized can be used for identifying and counting eosinophils. However, other cell populations with depolarizing capacity occur in malarial samples; these result from leukocytes ingesting haemozoin that is derived from the degradation of the haem group of haemoglobin performed by the parasite. A sensitivity of 72 % and specificity of 98 % were recorded, with positive and negative predictive values of 78 % and 97 %, respectively. Although the sensitivity level of the automated light depolarization analysis is not adequate to replace the existing methods for the diagnosis of parasitic diseases, it could alert clinicians to unsuspected infections by parasites, particularly those from the genus Plasmodium.

  11. Efficient depolarization-loss-compensation of solid state lasers using only a Glan-Taylor polarizer

    Science.gov (United States)

    Mondal, S.; Singh, S. P.; Hussain, K.; Choubey, A.; Upadhyay, B. N.; Datta, P. K.

    2013-02-01

    A novel scheme for reducing the depolarization loss resulting from thermally induced stress birefringence of a free running flash-lamp pumped single Nd: YAG rod is reported here and measured under resonator configuration with the use of a Glan-Taylor polarizer only. The depolarization loss has been systematically investigated and compared with the quarter wave-plate scheme. The Glan-Taylor polarizer is given two rotations with respect to two perpendicular axes for obtaining Brewster's effect as well as phase retardation inside a stable resonator. This single optical element optimally reduces depolarization loss to ˜18% and performs better than quarter wave-plate in combination with a polarizer. Using Jones-vector formulation, we analyzed the effect of tilting of Glan-Taylor polarizer and accounted the measured data of depolarization loss.

  12. Isomerization and fluorescence depolarization of merocyanine 540 in polyacrylic acid. Effect of H

    Indian Academy of Sciences (India)

    Dipankar Sukul; Sobhan Sen; Partha Dutta; Kankan Bhattacharyya

    2002-10-01

    Dynamics of isomerization and fluorescence depolarization of merocyanine 540 (MC540) in an aqueous solution of polyacrylic acid (PAA) have been studied using picosecond time resolved fluorescence spectroscopy. It is observed that the dynamics of isomerization and depolarization are sensitive enough to monitor the uncoiling of PAA at high H (> 6). At low H (< 3), when the polymer remains in a hypercoiled form, polymer bound MC540 experiences very high microscopic friction and, hence, the isomerization and depolarization processes are very slow. At high H (> 6) a polyanion is formed and the polymer assumes an extended configuration due to electrostatic repulsion. At high H (> 6), the anionic probe MC540 is expelled from the polyanion to bulk water and the dynamics of isomerization and fluorescence depolarization become faster by 12 and 5 times respectively, compared to those at low H.

  13. Subharmonic Shapiro steps in high‐Tc Josephson junctions

    NARCIS (Netherlands)

    Terpstra, D.; IJsselsteijn, R.P.J.; Rogalla, H.

    1995-01-01

    We studied the response of high‐Tc biepitaxial grain boundaryjunctions to 100 GHz radiation in the presence of a magnetic field. Integer as well as subharmonic constant voltage steps are observed, even at one‐fifth of the voltage separation between integer (Shapiro) steps. Our results indicate that

  14. Neuronal trafficking of voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Jensen, Camilla S; Rasmussen, Hanne Borger; Misonou, Hiroaki

    2011-01-01

    The computational ability of CNS neurons depends critically on the specific localization of ion channels in the somatodendritic and axonal membranes. Neuronal dendrites receive synaptic inputs at numerous spines and integrate them in time and space. The integration of synaptic potentials....... The physiological significance of proper Kv channel localization is emphasized by the fact that defects in the trafficking of Kv channels are observed in several neurological disorders including epilepsy. In this review, we will summarize the current understanding of the mechanisms of Kv channel trafficking...... is regulated by voltage-gated potassium (Kv) channels, such as Kv4.2, which are specifically localized in the dendritic membrane. The synaptic potentials eventually depolarize the membrane of the axon initial segment, thereby activating voltage-gated sodium channels to generate action potentials. Specific Kv...

  15. Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

    Science.gov (United States)

    Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

    2017-03-01

    The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K(+) and Ca(2+) channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K(+) currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K(+) currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs(+) (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca(2+) channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

  16. Multi-objective optimization of distributed generation with voltage ...

    African Journals Online (AJOL)

    DR OKE

    1*Department of Electrical Engineering, Kamla Nehru Institute of Technology Sultanpurr, ... network. To keep the problem focused on study of impact of voltage step ..... Genetic programming—An approach to smart machine, J. Inst. Eng., Vol.

  17. Recurrent Spontaneous Spreading Depolarizations Facilitate Acute Dendritic Injury in the Ischemic Penumbra

    OpenAIRE

    Risher, W Christopher; Ard, Deborah; Yuan, Jianghe; Kirov, Sergei A.

    2010-01-01

    Spontaneous spreading depolarizations (SDs) occur in the penumbra surrounding ischemic core. These SDs, often referred to as peri-infarct depolarizations, cause vasoconstriction and recruitment of the penumbra into the ischemic core in the critical first hours after focal ischemic stroke; however, the real-time spatiotemporal dynamics of SD-induced injury to synaptic circuitry in the penumbra remain unknown. A modified cortical photothrombosis model was used to produce a square-shaped lesion ...

  18. Three-Signal Method for Accurate Measurements of Depolarization Ratio with Lidar

    Science.gov (United States)

    Reichardt, Jens; Baumgart, Rudolf; McGee, Thomsa J.

    2003-01-01

    A method is presented that permits the determination of atmospheric depolarization-ratio profiles from three elastic-backscatter lidar signals with different sensitivity to the state of polarization of the backscattered light. The three-signal method is insensitive to experimental errors and does not require calibration of the measurement, which could cause large systematic uncertainties of the results, as is the case in the lidar technique conventionally used for the observation of depolarization ratios.

  19. On the Use of Radar Depolarization Ratios for Estimating Shapes of Ice Hydrometeors in Winter Clouds.

    Science.gov (United States)

    Matrosov, Sergey Y.; Reinking, Roger F.; Kropfli, Robert A.; Martner, Brooks E.; Bartram, B. W.

    2001-03-01

    An approach is suggested to relate measurements of radar depolarization ratios and aspect ratios of predominant hydrometeors in nonprecipitating and weakly precipitating layers of winter clouds. The trends of elevation angle dependencies of depolarization ratios are first used to distinguish between columnar-type and plate-type particles. For the established particle type, values of depolarization ratios observed at certain elevation angles, for which the influence of particle orientation is minimal, are then used to estimate aspect ratios when information on particle effective bulk density is assumed or inferred from other measurements. The use of different polarizations, including circular, slant-45° linear, and two elliptical polarizations, is discussed. These two elliptical polarizations are quasi-circular and quasi-linear slant-45° linear, and both are currently achievable with the National Oceanic and Atmospheric Administration Environmental Technology Laboratory's Ka-band radar. In comparison with the true circular and slant-45° linear polarizations, the discussed elliptical polarizations provide a stronger signal in the `weak' radar receiver channel; however, it is at the expense of diminished dynamic range of depolarization ratio variations. For depolarization measurements at the radar elevation angles that do not show much sensitivity to particle orientations, the available quasi-circular polarization provides a better depolarization contrast between nonspherical and spherical particles than does the available quasi-linear slant-45°polarization. The use of the proposed approach is illustrated with the experimental data collected during a recent field experiment. It is shown that it allows successful differentiation among pristine planar crystals, rimed planar crystals, long columns, blocky columns, and graupel. When a reasonable assumption about particle bulk density is made, quantitative estimates of particle aspect ratios from radar depolarization

  20. Voltage-dependent gating of hERG potassium channels

    Directory of Open Access Journals (Sweden)

    Yen May eCheng

    2012-05-01

    Full Text Available The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4-S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-a-go-go related gene, hERG, which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure-function relationships underlying voltage-dependent gating in Shaker and hERG channels, with a focus on the roles of the voltage sensing domain and the S4-S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter charge interactions. More recent data suggest that key amino acid differences in the hERG voltage sensing unit and S4-S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor.

  1. Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

    Energy Technology Data Exchange (ETDEWEB)

    Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Clare, Jeffrey J. [Eaton Pharma Consulting, Eaton Socon, Cambridgeshire PE19 8EF (United Kingdom); Debanne, Dominique [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Alcaraz, Gisele, E-mail: gisele.alcaraz@univmed.fr [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France)

    2011-07-29

    Highlights: {yields} Both Ca{sup ++}-Calmodulin (CaM) and Ca{sup ++}-free CaM bind to the C-terminal region of Nav1.1. {yields} Ca{sup ++} and CaM have both opposite and convergent effects on I{sub Nav1.1}. {yields} Ca{sup ++}-CaM modulates I{sub Nav1.1} amplitude. {yields} CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. {yields} Ca{sup ++} alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca{sup ++} depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca{sup ++} could bind the Nav1.1 C-terminal region with micromolar affinity.

  2. Dibucaine mitigates spreading depolarization in human neocortical slices and prevents acute dendritic injury in the ischemic rodent neocortex.

    Directory of Open Access Journals (Sweden)

    W Christopher Risher

    Full Text Available Spreading depolarizations that occur in patients with malignant stroke, subarachnoid/intracranial hemorrhage, and traumatic brain injury are known to facilitate neuronal damage in metabolically compromised brain tissue. The dramatic failure of brain ion homeostasis caused by propagating spreading depolarizations results in neuronal and astroglial swelling. In essence, swelling is the initial response and a sign of the acute neuronal injury that follows if energy deprivation is maintained. Choosing spreading depolarizations as a target for therapeutic intervention, we have used human brain slices and in vivo real-time two-photon laser scanning microscopy in the mouse neocortex to study potentially useful therapeutics against spreading depolarization-induced injury.We have shown that anoxic or terminal depolarization, a spreading depolarization wave ignited in the ischemic core where neurons cannot repolarize, can be evoked in human slices from pediatric brains during simulated ischemia induced by oxygen/glucose deprivation or by exposure to ouabain. Changes in light transmittance (LT tracked terminal depolarization in time and space. Though spreading depolarizations are notoriously difficult to block, terminal depolarization onset was delayed by dibucaine, a local amide anesthetic and sodium channel blocker. Remarkably, the occurrence of ouabain-induced terminal depolarization was delayed at a concentration of 1 µM that preserves synaptic function. Moreover, in vivo two-photon imaging in the penumbra revealed that, though spreading depolarizations did still occur, spreading depolarization-induced dendritic injury was inhibited by dibucaine administered intravenously at 2.5 mg/kg in a mouse stroke model.Dibucaine mitigated the effects of spreading depolarization at a concentration that could be well-tolerated therapeutically. Hence, dibucaine is a promising candidate to protect the brain from ischemic injury with an approach that does not rely on

  3. Effect of spontaneous polarization change on current-voltage characteristics of thin ferroelectric films

    Science.gov (United States)

    Podgorny, Yu. V.; Lavrov, P. P.; Vorotilov, K. A.; Sigov, A. S.

    2015-03-01

    The role of a change in the spontaneous polarization charge in the formation of negative differential conductance regions of the current-voltage characteristics of thin ferroelectric films has been determined. It has been shown that the polarization recovery current, which appears due to partial depolarization of a preliminarily polarized film, prevails over the intrinsic leakage current of the ferroelectric film in the coercive field region and corresponds to the Weibull distribution. The influence of polarization recovery current decreases with decreasing voltage sweep rate.

  4. High Voltage Distribution

    Science.gov (United States)

    Norbeck, Edwin; Miller, Michael; Onel, Yasar

    2010-11-01

    For detector arrays that require 5 to 10 kV at a few microamps each for hundreds of detectors, using hundreds of HV power supplies is unreasonable. Bundles of hundreds of HV cables take up space that should be filled with detectors. A typical HV module can supply 1 ma, enough current for hundreds of detectors. It is better to use a single HV module and distribute the current as needed. We show a circuit that, for each detector, measures the current, cuts off the voltage if the current exceeds a set maximum, and allows the HV to be turned on or off from a control computer. The entire array requires a single HV cable and 2 or 3 control lines. This design provides the same voltage to all of the detectors, the voltage set by the single HV module. Some additional circuitry would allow a computer controlled voltage drop between the HV and each individual detector.

  5. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P

    1984-01-01

    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  6. Low-voltage gyrotrons

    Science.gov (United States)

    Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S.; Nusinovich, G. S.

    2013-03-01

    For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

  7. One-step electrolytic preparation of Si-Fe alloys as anodes for lithium ion batteries

    Science.gov (United States)

    Wang, Hailong; Sun, Diankun; Song, Qiqi; Xie, Wenqi; Jiang, Xu; Zhang, Bo

    2016-06-01

    One-step electrolytic formation of uniform crystalline Si-Fe alloy particles was successfully demonstrated in direct electro-reduction of solid mixed oxides of SiO2 and Fe2O3 in molten CaCl2 at 900∘C. Upon constant voltage electrolysis of solid mixed oxides at 2.8V between solid oxide cathode and graphite anode for 5h, electrolytic Si-Fe with the same Si/Fe stoichimetry of the precursory oxides was generated. The firstly generated Fe could function as depolarizers to enhance reduction rate of SiO2, resulting in the enhanced reduction kinetics to the electrolysis of individual SiO2. When evaluated as anode for lithium ion batteries, the prepared SiFe electrode showed a reversible lithium storage capacity as high as 470mAh g-1 after 100 cycles at 200mA g-1, promising application in high-performance lithium ion batteries.

  8. Device for monitoring cell voltage

    Science.gov (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

    2012-08-21

    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  9. Current-voltage characteristics and transition voltage spectroscopy of individual redox proteins.

    Science.gov (United States)

    Artés, Juan M; López-Martínez, Montserrat; Giraudet, Arnaud; Díez-Pérez, Ismael; Sanz, Fausto; Gorostiza, Pau

    2012-12-19

    Understanding how molecular conductance depends on voltage is essential for characterizing molecular electronics devices. We reproducibly measured current-voltage characteristics of individual redox-active proteins by scanning tunneling microscopy under potentiostatic control in both tunneling and wired configurations. From these results, transition voltage spectroscopy (TVS) data for individual redox molecules can be calculated and analyzed statistically, adding a new dimension to conductance measurements. The transition voltage (TV) is discussed in terms of the two-step electron transfer (ET) mechanism. Azurin displays the lowest TV measured to date (0.4 V), consistent with the previously reported distance decay factor. This low TV may be advantageous for fabricating and operating molecular electronic devices for different applications. Our measurements show that TVS is a helpful tool for single-molecule ET measurements and suggest a mechanism for gating of ET between partner redox proteins.

  10. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  11. 阶梯AlGaN外延新型Al0.25Ga0.75N/GaN HEMTs击穿特性分析%Breakdown voltage analysis for the new Al0.25 Ga0.75N/GaN HEMTs with the step AlGaN layers

    Institute of Scientific and Technical Information of China (English)

    段宝兴; 杨银堂

    2014-01-01

    In order to optimize the surface electric field of AlGaN/GaN high electron mobility transistors (HEMTs), a novel AlGaN/GaN HEMT has been grown with a step AlGaN layer, made for the first time as far as we know, to improve the breakdown voltage. The discipline of the 2DEG concentration varying with the thickness of the AlGaN epitaxy layer has been applied to the new AlGaN/GaN HEMTs with AlGaN/GaN heterostructure. By thinning the AlGaN layer near the gate edge, the 2DEG concentration in the channel is made to form the low concentration region near the gate edge. New electric field peak has appeared at the corner of the step AlGaN layer. The high electric field has been decreased effectively due to the emergence of new electric field peak; this optimizes the surface electric field of the new AlGaN/GaN HEMTs. Then the breakdown voltage is improved to 640 V in the new AlGaN/GaN HEMTs with the step AlGaN layer as compared with 446 V for the conventional structure. In order to let the breakdown curve consistent with the test results, a certain concentration of the acceptor-like traps is added to the GaN buffer to capture the leaking current coming from the source electrode. Simulation results verify the causes for doping acceptor type ions to the GaN buffer, given by foreign researchers. The breakdown curves have been obtained which are consistent with the test results in this paper.%为了优化AlGaN/GaN HEMTs器件表面电场,提高击穿电压,本文首次提出了一种新型阶梯Al-GaN/GaN HEMTs结构.新结构利用AlGaN/GaN异质结形成的2DEG浓度随外延AlGaN层厚度降低而减小的规律,通过减薄靠近栅边缘外延的AlGaN层,使沟道2DEG浓度分区,形成栅边缘低浓度2DEG区,低的2DEG使阶梯AlGaN交界出现新的电场峰,新电场峰的出现有效降低了栅边缘的高峰电场,优化了AlGaN/GaN HEMTs器件的表面电场分布,使器件击穿电压从传统结构的446 V,提高到新结构的640 V.为了获得与实际测试结

  12. CHARACTERIZING CALCIUM INFLUX VIA VOLTAGE- AND LIGAND-GATED CALCIUM CHANNELS IN EMBRYONIC ALLIGATOR NEURONS IN CULTURE

    Science.gov (United States)

    Ju, Weina; Wu, Jiang; Pritz, Michael B.; Khanna, Rajesh

    2013-01-01

    Vertebrate brains share many features in common. Early in development, both the hindbrain and diencephalon are built similarly. Only later in time do differences in morphology occur. Factors that could potentially influence such changes include certain physiological properties of neurons. As an initial step to investigate this problem, embryonic Alligator brain neurons were cultured and calcium responses were characterized. The present report is the first to document culture of Alligator brain neurons in artificial cerebrospinal fluid (ACSF) as well as in standard mammalian tissue culture medium supplemented with growth factors. Alligator brain neuron cultures were viable for at least 1 week with unipolar neurites emerging by 24 hours. Employing Fura-2 AM, robust depolarization-induced calcium influx, was observed in these neurons. Using selective blockers of the voltage-gated calcium channels, the contributions of N-, P/Q-, R-, T-, and L-type channels in these neurons were assessed and their presence documented. Lastly, Alligator brain neurons were challenged with an excitotoxic stimulus (glutamate + glycine) where delayed calcium deregulation could be prevented by a classical NMDA receptor antagonist. PMID:24260711

  13. A thermoelectric voltage effect in polyethylene oxide

    CERN Document Server

    Martin, B; Kliem, H

    2003-01-01

    The conductivity of polyethylene oxide (PEO) is described with a three-dimensional hopping model considering electrostatic interactions between the ions. Ions fluctuate over energy-barriers in a multi-well potential. To decide whether positive or negative charges are responsible for this conductivity, the thermoelectric voltage is measured. The samples are embedded between two aluminium-electrodes. The oxide on the interface between the electrodes and the PEO serves as a blocking layer. The temperature of each electrode is controlled by a Peltier element. A temperature step is applied to one electrode by changing the temperature of one of the Peltier elements. Due to this temperature gradient, the mobile charges fluctuate thermally activated from the warmer side to the colder side of the sample. The direction of the measured thermoelectric voltage indicates the type of mobile charges. It is found that positive charges are mobile. Further, it is shown that the absolute value of the thermoelectric voltage depen...

  14. Linear algebra step by step

    CERN Document Server

    Singh, Kuldeep

    2013-01-01

    Linear algebra is a fundamental area of mathematics, and is arguably the most powerful mathematical tool ever developed. It is a core topic of study within fields as diverse as: business, economics, engineering, physics, computer science, ecology, sociology, demography and genetics. For an example of linear algebra at work, one needs to look no further than the Google search engine, which relies upon linear algebra to rank the results of a search with respect to relevance. The strength of the text is in the large number of examples and the step-by-step explanation of each topic as it is introduced. It is compiled in a way that allows distance learning, with explicit solutions to set problems freely available online. The miscellaneous exercises at the end of each chapter comprise questions from past exam papers from various universities, helping to reinforce the reader's confidence. Also included, generally at the beginning of sections, are short historicalbiographies of the leading players in the field of lin...

  15. Energy transfer and depolarization in the photoluminescence of a plasmonic molecule.

    Science.gov (United States)

    Yin, Tingting; Jiang, Liyong; Dong, Zhaogang; Yang, Joel K W; Shen, Ze Xiang

    2017-02-02

    We report a comprehensive experimental study of the polarization dependence between excitation and photoluminescence (PL) emission from single dolmen-like metallic nanostructures that exhibit both Fano-like and Lorentz-like plasmon resonances. Though the PL spectra of this plasmonic "molecule" also exhibit the Fano and Lorentz signature, the emitted photons do not maintain the same polarization as the excitation. Surprisingly, the degree of depolarization correlates closely to the resonant excitation of the constituent atoms (single nanorod). More specifically, the excitation of a transverse plasmon mode results in a depolarized emission through the longitudinal plasmon modes of the constituent nanorods. In view of the recent evidence of on-resonant plasmon induced excitations in generating hot electrons, our results suggest that depolarized PL emissions could be enhanced through hot-electron decay. Both macroscopic and microscopic mechanisms are proposed to well-understand the excitation wavelength dependent depolarized photoluminescence behaviors in the plasmonic molecule. Our results lay a foundation for applying the depolarized photoluminescence of complex plasmonic nanostructures in polarization engineering.

  16. Block of inactivated sodium channels and of depolarization-induced automaticity in guinea pig papillary muscle by amiodarone.

    Science.gov (United States)

    Mason, J W; Hondeghem, L M; Katzung, B G

    1984-09-01

    The electrophysiological effects of amiodarone were studied in guinea pig papillary muscle by means of the single sucrose gap voltage clamp technique. The first time derivative of the upstroke of the action potential was measured as an indicator of the sodium current. The preparations were not voltage clamped during the action potential upstroke. Acute effects of amiodarone (4.4 X 10(-5) M and 8.8 X 10(-5) M; six experiments each) and effects of chronic administration at a single dose level (nine experimental vs. eight control animals) were studied. Results were qualitatively the same for all experimental conditions, and concentration dependent in the acute studies. Amiodarone caused marked use-dependent depression of the first time derivative of the upstroke of the action potential during stimulus trains. For example, at normal resting potential, chronic amiodarone treatment reduced the first time derivative of the upstroke of the action potential of the 16th beat of trains of cycle length 300 msec to 70 +/- 15% (mean +/- SD) of the initial value. This blocking effect was accentuated at more depolarized holding potentials and reduced at hyperpolarized holding potentials. Reduction of the first time derivative of the upstroke of the action potential was found to depend upon sodium channel inactivation. For all experiments, the mean normalized first time derivative of the upstroke of the action potential following a 1-second clamp in the -20 to +20 mV range was 0.92 +/- 0.08 in the control condition and 0.66 +/- 0.20 in the presence of amiodarone (less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Characteristics of the inward-rectifying potassium current in mouse ventricular myocytes and its relation to early after-depolarization

    Institute of Scientific and Technical Information of China (English)

    周盈颖; 郝雪梅; 范劲松; 刘泰(木逢)

    1996-01-01

    The properties of the inward-rectifying potassium current (IK1) were studied in the single myocytes isolated from adult mouse ventricles by the whole-cell patch-damp technique for the first time. Most of the properties of IK1 including channel conductances, activation, inactivation, rectification and external K+ sensitivity in mouse ventricular myocyte were similar to those in other species, but the current-voltage (1-V) curve of mouse ventricular myocyte showed no negative slope, i.e the slope in the range of membrane potential 50 mV positive to the reversal potential (VRev) was virtually flat and remained at a low current level ((59±39) pA). Under the superfusion of Tyrode’s solution with 3mmol/L K+ and 3mmol/L Cs+, IK1 in the above region nearly decreased to zero, and then the early after-depolarization (EAD) occurred. The results suggest that this distinctive characteristic of IK1 in mouse ventricular myocyte may relate to the high susceptibility to EA0 in mouse myocardium. The inhibition of IK1 se

  18. Dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl.

    Science.gov (United States)

    Sabin, Keith; Santos-Ferreira, Tiago; Essig, Jaclyn; Rudasill, Sarah; Echeverri, Karen

    2015-12-01

    Salamanders, such as the Mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. Unlike mammals they are able to regenerate a fully functional spinal cord after injury. However, the molecular circuitry required to initiate a pro-regenerative response after spinal cord injury is not well understood. To address this question we developed a spinal cord injury model in axolotls and used in vivo imaging of labeled ependymoglial cells to characterize the response of these cells to injury. Using in vivo imaging of ion sensitive dyes we identified that spinal cord injury induces a rapid and dynamic change in the resting membrane potential of ependymoglial cells. Prolonged depolarization of ependymoglial cells after injury inhibits ependymoglial cell proliferation and subsequent axon regeneration. Using transcriptional profiling we identified c-Fos as a key voltage sensitive early response gene that is expressed specifically in the ependymoglial cells after injury. This data establishes that dynamic changes in the membrane potential after injury are essential for regulating the specific spatiotemporal expression of c-Fos that is critical for promoting faithful spinal cord regeneration in axolotl.

  19. Voltage Regulators for Photovoltaic Systems

    Science.gov (United States)

    Delombard, R.

    1986-01-01

    Two simple circuits developed to provide voltage regulation for highvoltage (i.e., is greater than 75 volts) and low-voltage (i.e., is less than 36 volts) photovoltaic/battery power systems. Use of these circuits results in voltage regulator small, low-cost, and reliable, with very low power dissipation. Simple oscillator circuit controls photovoltaic-array current to regulate system voltage and control battery charging. Circuit senses battery (and system) voltage and adjusts array current to keep battery voltage from exceeding maximum voltage.

  20. Studying Voltage Transformer Ferroresonance

    Directory of Open Access Journals (Sweden)

    Hamid Radmanesh

    2012-09-01

    Full Text Available This study studies the effect of Circuit Breaker Shunt Resistance (CBSR, Metal Oxide Vaistor (MOV and Neutral earth Resistance (NR on the control of ferroresonance in the voltage transformer. It is expected that NR can controlled ferroresonance better than MOV and CBSR. Study has been done on a one phase voltage transformer rated 100 VA, 275 kV. The simulation results reveal that considering the CBSR and MOV exhibits a great mitigating effect on ferroresonance overvoltages, but these resistances cannot control these phenomena for all range of parameters. By applying NR to the system structure, ferroresonance has been controlled and its amplitude has been damped for all parameters values.

  1. A high voltage programmable ramp generator

    Science.gov (United States)

    Upadhyay, J.; Joshi, M. J.; Deshpande, P. P.; Sharma, M. L.; Navathe, C. P.

    2008-05-01

    In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1ns and provides continuous speed variation from 6to30ns for a ramp of 500V. This is being developed as a part of automated streak camera for deflection of electron beam.

  2. Assessment of lidar depolarization uncertainty by means of a polarimetric lidar simulator

    Science.gov (United States)

    Bravo-Aranda, Juan Antonio; Belegante, Livio; Freudenthaler, Volker; Alados-Arboledas, Lucas; Nicolae, Doina; José Granados-Muñoz, María; Guerrero-Rascado, Juan Luis; Amodeo, Aldo; D'Amico, Giusseppe; Engelmann, Ronny; Pappalardo, Gelsomina; Kokkalis, Panos; Mamouri, Rodanthy; Papayannis, Alex; Navas-Guzmán, Francisco; José Olmo, Francisco; Wandinger, Ulla; Amato, Francesco; Haeffelin, Martial

    2016-10-01

    Lidar depolarization measurements distinguish between spherical and non-spherical aerosol particles based on the change of the polarization state between the emitted and received signal. The particle shape information in combination with other aerosol optical properties allows the characterization of different aerosol types and the retrieval of aerosol particle microphysical properties. Regarding the microphysical inversions, the lidar depolarization technique is becoming a key method since particle shape information can be used by algorithms based on spheres and spheroids, optimizing the retrieval procedure. Thus, the identification of the depolarization error sources and the quantification of their effects are crucial. This work presents a new tool to assess the systematic error of the volume linear depolarization ratio (δ), combining the Stokes-Müller formalism and the complete sampling of the error space using the lidar model presented in Freudenthaler (2016a). This tool is applied to a synthetic lidar system and to several EARLINET lidars with depolarization capabilities at 355 or 532 nm. The lidar systems show relative errors of δ larger than 100 % for δ values around molecular linear depolarization ratios (˜ 0.004 and up to ˜ 10 % for δ = 0.45). However, one system shows only relative errors of 25 and 0.22 % for δ = 0.004 and δ = 0.45, respectively, and gives an example of how a proper identification and reduction of the main error sources can drastically reduce the systematic errors of δ. In this regard, we provide some indications of how to reduce the systematic errors.

  3. Number of independent parameters in the Mueller matrix representation of homogeneous depolarizing media.

    Science.gov (United States)

    Arteaga, Oriol

    2013-04-01

    In general the transmission of polarized light through a homogeneous depolarizing sample has motion-reversal symmetry because the response remains the same for light traveling in the opposite direction. As a consequence, the optical properties of a sample, characterized by the differential Mueller matrix, must be invariant upon motion reversal. This Letter shows that the 16 parameters of the differential Mueller matrix must therefore obey six conditions to satisfy this symmetry. This limits the number of independent parameters to 10. The 10 elementary optical properties of a depolarizing homogeneous medium are defined and discussed.

  4. Coupled mode theory approach to depolarization associated with propagation in turbulent media

    Science.gov (United States)

    Crosignani, B.; di Porto, P.; Clifford, Steven F.

    1988-06-01

    Marcuse's (1974) coupled-mode theory is invoked in the present consideration of the problem of light depolarization in a turbulent atmosphere, in order to allow the evaluation of the depolarization ratio for a plane wave and comparison of its expression with that obtained in the frame of two distinct approaches predicting different behaviors. It is found that both approaches yield the same result when calculated to the same order in both of the relevant smallness parameters, thereby resolving a long-standing controversy.

  5. Coherence and Polarization of Polarization Speckle Generated by Depolarizers and Their Changes through Complex ABCD Matrix

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Lee, Tim K.;

    2015-01-01

    of special depolarizer: the random roughness birefringent screen (RRBS) is introduced to meet this requirement. The statistical properties of the field generated by the depolarizer is investigated and illustrated in terms of the 2x2 beam coherence and polarization matrix (BCPM) with the corresponding degree...... of coherence (DoC). and degree of polarization (DoP) P. The changes of the coherence and polarization when the speckle field propagates through any optical system are analysed within the framework of the complex ABCD-matrix theory....

  6. To a Method of Polarization-Depolarization Currents for Diagnosis of Dielectric Isolation

    Science.gov (United States)

    Ambrozevich, S. A.; Sibatov, R. T.; Uchaikin, D. V.; Morozova, E. V.

    2016-01-01

    Fractional derivative formalism is proposed as the mathematical foundation of the polarization-depolarization current method for the diagnosis of dielectric isolation. Physical basis of the new approach is the observed deviation of the long-term relaxation from the Debye exponential law. We found that this behavior is consistent with the solution of the fractional differential equation: exponential behavior turns into the power dependence in the long-time asymptotics, and this part of the relaxation curve is more sensitive to the material state. The results of calculations for the polarization-depolarization currents in an oil-paper capacitor are in agreement with the specially performed experiments.

  7. VOLTAGE REGULATORS ASYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available A promising is currently the use of asynchronous generators with capacitive excitation as a source of electricity in stand-alone power systems. Drive asynchronous generators may exercise as a thermal engine and wind wheel wind power plant or turbines of small hydropower plants. The article discusses the structural and schematics of voltage stabilizers and frequency of asynchronous generators with improved operational and technical specifications. Technical novelty of design solutions of the magnetic system and stabilizers asynchronous generator of electricity parameters confirmed by the patents for the invention of the Russian Federation. The proposed technical solution voltage stabilizer asynchronous generators, can reduce the weight of the block capacitors excitation and reactive power compensation, as well as to simplify the control system power circuit which has less power electronic devices. For wind power plants it is an important issue not only to stabilize the voltage of the generator, but also the frequency of the current. Recommend functionality stabilizer schemes parameters of electric power made for direct frequency converters with artificial and natural switching power electronic devices. It is also proposed as part of stabilization systems use single-phase voltage, three-phase transformers with rotating magnetic field, reduce the level of electromagnetic interference generated by power electronic devices for switching, enhance the efficiency and reliability of the stabilizer.

  8. Geomagnetism and Induced Voltage

    Science.gov (United States)

    Abdul-Razzaq, W.; Biller, R. D.

    2010-01-01

    Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it…

  9. High-voltage picoamperemeter

    Energy Technology Data Exchange (ETDEWEB)

    Bugl, Andrea; Ball, Markus; Boehmer, Michael; Doerheim, Sverre; Hoenle, Andreas; Konorov, Igor [Technische Universitaet Muenchen, Garching (Germany); Ketzer, Bernhard [Technische Universitaet Muenchen, Garching (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2014-07-01

    Current measurements in the nano- and picoampere region on high voltage are an important tool to understand charge transfer processes in micropattern gas detectors like the Gas Electron Multiplier (GEM). They are currently used to e.g. optimize the field configuration in a multi-GEM stack to be used in the ALICE TPC after the upgrade of the experiment during the 2nd long shutdown of the LHC. Devices which allow measurements down to 1pA at high voltage up to 6 kV have been developed at TU Muenchen. They are based on analog current measurements via the voltage drop over a switchable shunt. A microcontroller collects 128 digital ADC values and calculates their mean and standard deviation. This information is sent with a wireless transmitting unit to a computer and stored in a root file. A nearly unlimited number of devices can be operated simultaneously and read out by a single receiver. The results can also be displayed on a LCD directly at the device. Battery operation and the wireless readout are important to protect the user from any contact to high voltage. The principle of the device is explained, and systematic studies of their properties are shown.

  10. The “Funny” Current (If Inhibition by Ivabradine at Membrane Potentials Encompassing Spontaneous Depolarization in Pacemaker Cells

    Directory of Open Access Journals (Sweden)

    Yael Yaniv

    2012-07-01

    Full Text Available Recent clinical trials have shown that ivabradine (IVA, a drug that inhibits the funny current (If in isolated sinoatrial nodal cells (SANC, decreases heart rate and reduces morbidity and mortality in patients with cardiovascular diseases. While IVA inhibits If, this effect has been reported at essentially unphysiological voltages, i.e., those more negative than the spontaneous diastolic depolarization (DD between action potentials (APs. We tested the relative potency of IVA to block If over a wide range of membrane potentials, including those that encompass DD governing to the SANC spontaneous firing rate. A clinically relevant IVA concentration of 3 μM to single, isolated rabbit SANC slowed the spontaneous AP firing rate by 15%. During voltage clamp the maximal If was 18 ± 3 pA/pF (at −120 mV and the maximal If reduction by IVA was 60 ± 8% observed at −92 ± 4 mV. At the maximal diastolic depolarization (~−60 mV If amplitude was only −2.9 ± 0.4 pA/pF, and was reduced by only 41 ± 6% by IVA. Thus, If amplitude and its inhibition by IVA at physiologically relevant membrane potentials are substantially less than that at unphysiological (hyperpolarized membrane potentials. This novel finding more accurately describes how IVA affects SANC function and is of direct relevance to numerical modeling of SANC automaticity.

  11. A biophysical model examining the role of low-voltage-activated potassium currents in shaping the responses of vestibular ganglion neurons.

    Science.gov (United States)

    Hight, Ariel E; Kalluri, Radha

    2016-08-01

    The vestibular nerve is characterized by two broad groups of neurons that differ in the timing of their interspike intervals; some fire at highly regular intervals, whereas others fire at highly irregular intervals. Heterogeneity in ion channel properties has been proposed as shaping these firing patterns (Highstein SM, Politoff AL. Brain Res 150: 182-187, 1978; Smith CE, Goldberg JM. Biol Cybern 54: 41-51, 1986). Kalluri et al. (J Neurophysiol 104: 2034-2051, 2010) proposed that regularity is controlled by the density of low-voltage-activated potassium currents (IKL). To examine the impact of IKL on spike timing regularity, we implemented a single-compartment model with three conductances known to be present in the vestibular ganglion: transient sodium (gNa), low-voltage-activated potassium (gKL), and high-voltage-activated potassium (gKH). Consistent with in vitro observations, removing gKL depolarized resting potential, increased input resistance and membrane time constant, and converted current step-evoked firing patterns from transient (1 spike at current onset) to sustained (many spikes). Modeled neurons were driven with a time-varying synaptic conductance that captured the random arrival times and amplitudes of glutamate-driven synaptic events. In the presence of gKL, spiking occurred only in response to large events with fast onsets. Models without gKL exhibited greater integration by responding to the superposition of rapidly arriving events. Three synaptic conductance were modeled, each with different kinetics to represent a variety of different synaptic processes. In response to all three types of synaptic conductance, models containing gKL produced spike trains with irregular interspike intervals. Only models lacking gKL when driven by rapidly arriving small excitatory postsynaptic currents were capable of generating regular spiking.

  12. Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle.

    Science.gov (United States)

    Hristov, Kiril L; Smith, Amy C; Parajuli, Shankar P; Malysz, John; Petkov, Georgi V

    2014-03-01

    Large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca(2+) imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca(2+) sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca(2+) levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca(2+)-dependent mechanism, thus increasing DSM contractility.

  13. Phosphoinositide 5- and 3-phosphatase activities of a voltage-sensing phosphatase in living cells show identical voltage dependence.

    Science.gov (United States)

    Keum, Dongil; Kruse, Martin; Kim, Dong-Il; Hille, Bertil; Suh, Byung-Chang

    2016-06-28

    Voltage-sensing phosphatases (VSPs) are homologs of phosphatase and tensin homolog (PTEN), a phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] 3-phosphatase. However, VSPs have a wider range of substrates, cleaving 3-phosphate from PI(3,4)P2 and probably PI(3,4,5)P3 as well as 5-phosphate from phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and PI(3,4,5)P3 in response to membrane depolarization. Recent proposals say these reactions have differing voltage dependence. Using Förster resonance energy transfer probes specific for different PIs in living cells with zebrafish VSP, we quantitate both voltage-dependent 5- and 3-phosphatase subreactions against endogenous substrates. These activities become apparent with different voltage thresholds, voltage sensitivities, and catalytic rates. As an analytical tool, we refine a kinetic model that includes the endogenous pools of phosphoinositides, endogenous phosphatase and kinase reactions connecting them, and four exogenous voltage-dependent 5- and 3-phosphatase subreactions of VSP. We show that apparent voltage threshold differences for seeing effects of the 5- and 3-phosphatase activities in cells are not due to different intrinsic voltage dependence of these reactions. Rather, the reactions have a common voltage dependence, and apparent differences arise only because each VSP subreaction has a different absolute catalytic rate that begins to surpass the respective endogenous enzyme activities at different voltages. For zebrafish VSP, our modeling revealed that 3-phosphatase activity against PI(3,4,5)P3 is 55-fold slower than 5-phosphatase activity against PI(4,5)P2; thus, PI(4,5)P2 generated more slowly from dephosphorylating PI(3,4,5)P3 might never accumulate. When 5-phosphatase activity was counteracted by coexpression of a phosphatidylinositol 4-phosphate 5-kinase, there was accumulation of PI(4,5)P2 in parallel to PI(3,4,5)P3 dephosphorylation

  14. Inactivation properties of sodium channel Nav1.8 maintain action potential amplitude in small DRG neurons in the context of depolarization

    Directory of Open Access Journals (Sweden)

    Waxman Stephen G

    2007-05-01

    Full Text Available Abstract Background Small neurons of the dorsal root ganglion (DRG express five of the nine known voltage-gated sodium channels. Each channel has unique biophysical characteristics which determine how it contributes to the generation of action potentials (AP. To better understand how AP amplitude is maintained in nociceptive DRG neurons and their centrally projecting axons, which are subjected to depolarization within the dorsal horn, we investigated the dependence of AP amplitude on membrane potential, and how that dependence is altered by the presence or absence of sodium channel Nav1.8. Results In small neurons cultured from wild type (WT adult mouse DRG, AP amplitude decreases as the membrane potential is depolarized from -90 mV to -30 mV. The decrease in amplitude is best fit by two Boltzmann equations, having V1/2 values of -73 and -37 mV. These values are similar to the V1/2 values for steady-state fast inactivation of tetrodotoxin-sensitive (TTX-s sodium channels, and the tetrodotoxin-resistant (TTX-r Nav1.8 sodium channel, respectively. Addition of TTX eliminates the more hyperpolarized V1/2 component and leads to increasing AP amplitude for holding potentials of -90 to -60 mV. This increase is substantially reduced by the addition of potassium channel blockers. In neurons from Nav1.8(-/- mice, the voltage-dependent decrease in AP amplitude is characterized by a single Boltzmann equation with a V1/2 value of -55 mV, suggesting a shift in the steady-state fast inactivation properties of TTX-s sodium channels. Transfection of Nav1.8(-/- DRG neurons with DNA encoding Nav1.8 results in a membrane potential-dependent decrease in AP amplitude that recapitulates WT properties. Conclusion We conclude that the presence of Nav1.8 allows AP amplitude to be maintained in DRG neurons and their centrally projecting axons even when depolarized within the dorsal horn.

  15. Kv1.1 channelopathy abolishes presynaptic spike width modulation by subthreshold somatic depolarization.

    Science.gov (United States)

    Vivekananda, Umesh; Novak, Pavel; Bello, Oscar D; Korchev, Yuri E; Krishnakumar, Shyam S; Volynski, Kirill E; Kullmann, Dimitri M

    2017-02-28

    Although action potentials propagate along axons in an all-or-none manner, subthreshold membrane potential fluctuations at the soma affect neurotransmitter release from synaptic boutons. An important mechanism underlying analog-digital modulation is depolarization-mediated inactivation of presynaptic Kv1-family potassium channels, leading to action potential broadening and increased calcium influx. Previous studies have relied heavily on recordings from blebs formed after axon transection, which may exaggerate the passive propagation of somatic depolarization. We recorded instead from small boutons supplied by intact axons identified with scanning ion conductance microscopy in primary hippocampal cultures and asked how distinct potassium channels interact in determining the basal spike width and its modulation by subthreshold somatic depolarization. Pharmacological or genetic deletion of Kv1.1 broadened presynaptic spikes without preventing further prolongation by brief depolarizing somatic prepulses. A heterozygous mouse model of episodic ataxia type 1 harboring a dominant Kv1.1 mutation had a similar broadening effect on basal spike shape as deletion of Kv1.1; however, spike modulation by somatic prepulses was abolished. These results argue that the Kv1.1 subunit is not necessary for subthreshold modulation of spike width. However, a disease-associated mutant subunit prevents the interplay of analog and digital transmission, possibly by disrupting the normal stoichiometry of presynaptic potassium channels.

  16. Electroanatomic Correlates of Depolarization Abnormalities in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

    NARCIS (Netherlands)

    Tanawuttiwat, Tanyanan; Te Riele, Anneline S J M; Philips, Binu; James, Cynthia A; Murray, Brittney; Tichnell, Crystal; Sawant, Abhishek C; Calkins, Hugh; Tandri, Harikrishna

    2016-01-01

    BACKGROUND: Epsilon waves and other depolarization abnormalities in the right precordial leads are thought to represent delayed activation of the right ventricular outflow tract in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). However, no study has directly correlated cardiac e

  17. Membrane depolarization and carbamoylcholine stimulate phosphatidylinositol turnover in intact nerve terminals

    Energy Technology Data Exchange (ETDEWEB)

    Audigier, S.M.P.; Wang, J.K.T.; Greengard, P.

    1988-04-01

    Synaptosomes, purified from rat cerebral cortex, were prelabeled with (/sup 3/H)inositol to study phosphatidylinositol turnover in nerve terminals. Labeled synaptosomes were either depolarized with 40 mM K/sup +/ or exposed to carbamoylcholine (carbachol). K/sup +/ depolarization increased the level of inositol phosphates in a time-dependent manner. The inositol bisphosphate level also increased rapidly, but its elevated level was sustained during continued depolarization. The elevated level of inositol bisphosphate was reversed upon repolarization of the synaptosomes. The level of inositol monophosphate increased slowly to 120-130% of control. These effects of K/sup +/ depolarization depended on the presence of Ca/sup 2 +/ in the incubation medium. Carbachol stimulated the turnover of phosphatidylinositol in a dose- and time-dependent manner. The level of inositol bisphosphate increased to 210% of control, and this maximal response was seen from 15 to 60 min. Accumulation of inositol monophosphate was larger than that of inositol bisphosphate, but its time course was slower. Atropine and pirenzepine inhibited the carbachol effect with high affinities. These data show that both Ca/sup 2 +/ influx and M/sub 1/ muscarinic receptor activation stimulate phospholipase C activity in synaptosomes, suggesting that phosphatidylinositol turnover may be involved in regulating neurotransmitter release from nerve terminals.

  18. Normal chemotaxis in Dictyostelium discoideum cells with a depolarized plasma membrane potential

    NARCIS (Netherlands)

    Duijn, Bert van; Vogelzang, Sake A.; Ypey, Dirk L.; Molen, Loek G. van der; Haastert, Peter J.M. van

    1990-01-01

    We examined a possible role for the plasma membrane potential in signal transduction during cyclic AMP-induced chemotaxis in the cellular slime mold Dictyostelium discoideum. Chemotaxis, cyclic GMP and cyclic AMP responses in cells with a depolarized membrane potential were measured. Cells can be

  19. Weaver mutant mouse cerebellar granule cells respond normally to chronic depolarization

    DEFF Research Database (Denmark)

    Bjerregaard, Annette; Mogensen, Helle Smidt; Hack, N;

    1997-01-01

    We studied the effects of chronic K(+)-induced membrane depolarization and treatment with N-methyl-D-aspartate (NMDA) on cerebellar granule cells (CGCs) from weaver mutant mice and non-weaver litter-mates. The weaver mutation is a Gly-to-Ser substitution in a conserved region of the Girk2 G prote...

  20. Two-body depolarized cils spectra of krypton and xenon at 295 K

    Science.gov (United States)

    Zoppi, M.; Moraldi, M.; Barocchi, F.; Magli, R.; Bafile, U.

    1981-10-01

    We have experimentally determined the two-body depolarized CILS spectra of krypton and xenon at room temperature between 2 and 120 cm-1. Comparison of the first three even experimental moments of the spectra with theoretical calculations shows, as in argon, the necessity of introducing a short-range negative contribution to the induced pair polarizability.

  1. Measurement of distinctive features of cortical spreading depolarizations with different MRI contrasts

    NARCIS (Netherlands)

    Umesh Rudrapatna, S.; Hamming, Arend M.; Wermer, Marieke J H; van der Toorn, A; Dijkhuizen, Rick M.

    2015-01-01

    Growing clinical evidence suggests critical involvement of spreading depolarizations (SDs) in the pathophysiology of neurological disorders such as migraine and stroke. MRI provides powerful tools to detect and assess co-occurring cerebral hemodynamic and cellular changes during SDs. This study

  2. Role of astrocytes in depolarization-coupled release of glutamate in cerebellar cultures

    DEFF Research Database (Denmark)

    Bak, Lasse K; Waagepetersen, Helle S; Schousboe, Arne

    2004-01-01

    Release of preloaded D-[3H]aspartate in response to depolarization induced by high potassium, N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) or the endogenous agonist glutamate was studied using cultured glutamatergic cerebellar granule neurons, cerebell...

  3. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  4. Measurement of distinctive features of cortical spreading depolarizations with different MRI contrasts

    NARCIS (Netherlands)

    Umesh Rudrapatna, S.; Hamming, Arend M.; Wermer, Marieke J H; van der Toorn, A; Dijkhuizen, Rick M.

    2015-01-01

    Growing clinical evidence suggests critical involvement of spreading depolarizations (SDs) in the pathophysiology of neurological disorders such as migraine and stroke. MRI provides powerful tools to detect and assess co-occurring cerebral hemodynamic and cellular changes during SDs. This study repo

  5. Molecular anisotropy effects in carbon K-edge scattering: Depolarized diffuse scattering and optical anisotropy

    Science.gov (United States)

    Stone, Kevin H.; Kortright, Jeffrey B.

    2014-09-01

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylenelike backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  6. Weaver mutant mouse cerebellar granule cells respond normally to chronic depolarization

    DEFF Research Database (Denmark)

    Bjerregaard, Annette; Mogensen, Helle Smidt; Hack, N

    1997-01-01

    We studied the effects of chronic K(+)-induced membrane depolarization and treatment with N-methyl-D-aspartate (NMDA) on cerebellar granule cells (CGCs) from weaver mutant mice and non-weaver litter-mates. The weaver mutation is a Gly-to-Ser substitution in a conserved region of the Girk2 G prote...

  7. Deployment of low-voltage regulator considering existing voltage control in medium-voltage distribution systems

    Directory of Open Access Journals (Sweden)

    Hiroshi Kikusato

    2016-01-01

    Full Text Available Many photovoltaic (PV systems have been installed in distribution systems. This installation complicates the maintenance of all voltages within the appropriate range in all low-voltage distribution systems (LVDSs because the trends in voltage fluctuation differ in each LVDS. The installation of a low-voltage regulator (LVR that can accordingly control the voltage in each LVDS has been studied as a solution to this problem. Voltage control in a medium-voltage distribution system must be considered to study the deployment of LVRs. In this study, we installed LVRs in the LVDSs in which the existing voltage-control scheme cannot prevent voltage deviation and performed a numerical simulation by using a distribution system model with PV to evaluate the deployment of the LVRs.

  8. Component-Minimized Buck-Boost Voltage Source Inverters

    DEFF Research Database (Denmark)

    Gao, F.; Loh, P.C.; Blaabjerg, Frede;

    2007-01-01

    the additional voltage relationship between dc input and ac output which is beyond the expectation when continuous inductor current is assumed. These theoretical findings, together with the inverter practicality, have been confirmed in Matlab/PLECS simulations and  experimentally using laboratory implemented......This paper presents the design of buck-boost B4 inverters that can be derived from either Ćuk- or SEPIC-derived buck-boost B6 inverters. Unlike traditional inverters, the integration of front-end voltage boost circuitry and inverter circuitry allows it to perform buck-boost voltage inversion....... In order to form a distinct neutral potential in the corresponding voltage boost circuitry for correct B4 inverter operation, necessary modifications are derived step by step. The resulted dc networks with symmetrical placement of passive components allow complete charging and equal energy distribution...

  9. Analyzing of Dynamic Voltage Restorer in Series Compensation Voltage

    Directory of Open Access Journals (Sweden)

    Naser Parhizgar

    2012-02-01

    Full Text Available The Dynamic Voltage Restorer (DVR is a series-connected compensator to generate a controllable voltage to against the short-term voltage disturbances. The technique of DVR is an effective and cost competitive approach to improve voltage quality at the load side. This study presents a single-phase and threephase DVR system with reduced switch-count topology to protect the sensitive load against abnormal voltage conditions. Most basic function, the DVR configuration consist of a two level Voltage Source Converter (VSC, a dc energy storage device, a coupling transformer Connected in shunt with the ac system This study presents the application of Dynamic Voltage Restorer (DVR on power distribution systems for mitigation of voltage sag at critical loads. DVR is one of the compensating types of custom power devices. The DVR, which is based on forced-commutated Voltage Source Converter (VSC has been proved suitable for the task of compensating voltage sags/swells. Simulation results are presented to illustrate and understand the performances of DVR in supporting load voltages under voltage sags/swells conditions.

  10. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  11. The retrieval of the Asian dust depolarization ratio in Korea with the correction of the polarization-dependent transmission

    Science.gov (United States)

    Shin, Sungkyun; Müller, Detlef; Kim, Y. J.; Tatarov, Boyan; Shin, Dongho; Seifert, Patric; Noh, Young Min

    2013-01-01

    The linear particle depolarization ratios were retrieved from the observation with a multiwavelength Raman lidar at the Gwangju Institute of Science and Technology (GIST), Korea (35.11°N, 126.54°E). The measurements were carried out in spring (March to May) 2011. The transmission ratio measurements were performed to solve problems of the depolarization-dependent transmission at a receiver of the lidar and applied to correct the retrieved depolarization ratio of Asian dust at first time in Korea. The analyzed data from the GIST multiwavelength Raman lidar were classified into three categories according to the linear particle depolarization ratios, which are pure Asian dust on 21 March, the intermediate case which means Asian dust mixed with urban pollution on 13 May, and haze case on 10 April. The measured transmission ratios were applied to these cases respectively. We found that the transmission ratio is needed to be used to retrieve the accurate depolarization ratio of Asian dust and also would be useful to distinguish the mixed dust particles between intermediate case and haze. The particle depolarization ratios of pure Asian dust were approximately 0.25 at 532 nm and 0.14 at 532 nm for the intermediate case. The linear particle depolarization ratios of pure Asian dust observed with the GIST multiwavelength Raman lidar were compared to the linear particle depolarization ratios of Saharan dust observed in Morocco and Asian dust observed both in Japan and China.

  12. Increased voltage photovoltaic cell

    Science.gov (United States)

    Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

    1985-01-01

    A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

  13. High Voltage Seismic Generator

    Science.gov (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  14. Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History.

    Science.gov (United States)

    Riedelsberger, Janin; Dreyer, Ingo; Gonzalez, Wendy

    2015-01-01

    Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories-hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.

  15. Temperature modulation of cerebral depolarization during focal cerebral ischemia in rats: correlation with ischemic injury.

    Science.gov (United States)

    Chen, Q; Chopp, M; Bodzin, G; Chen, H

    1993-05-01

    The role of cerebral depolarizations in focal cerebral ischemia is unknown. We therefore measured the direct current (DC) electrical activity in the cortex of Wistar rats subjected to transient occlusion of the middle cerebral artery (MCA). Focal ischemia was induced for 90 min by insertion of an intraluminal filament to occlude the MCA. To modulate cell damage, we subjected the rats to hypothermic (30 degrees C, n = 4), normothermic (37 degrees C, n = 4), and hyperthermic (40 degrees C, n = 6) ischemia. Controlled temperatures were also maintained during 1 h of reperfusion. Continuous cortical DC potential changes were measured using two active Ag-AgCl electrodes placed in the cortical lesion. Animals were killed 1 week after ischemia. The brains were sectioned and stained with hematoxylin and eosin, for evaluation of neuronal damage, and calculation of infarct volume. All animals exhibited an initial depolarization within 30 min of ischemia, followed by a single depolarization event in hypothermic animals, and multiple periodic depolarization events in both normothermic and hyperthermic animals. Hyperthermic animals exhibited significantly more (p < 0.05) DC potential deflections (n = 6.17 +/- 0.67) than normothermic animals (n = 2.75 +/- 0.96). The ischemic infarct volume (% of hemisphere) was significantly different for the various groups; hypothermic animals exhibited no measurable infarct volume, while the ischemic infarct volume was 10.2 +/- 12.3% in normothermic animals and 36.5 +/- 3.4% in hyperthermic animals (p < 0.05). A significant correlation was detected between the volume of infarct and number of depolarization events (r = 0.90, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Contractile responses to rat urotensin II in resting and depolarized basilar arteries.

    Science.gov (United States)

    Porras-González, Cristina; Ureña, Juan; Egea-Guerrero, Juan José; Gordillo-Escobar, Elena; Murillo-Cabezas, Francisco; González-Montelongo, María del Carmen; Muñoz-Sánchez, María Angeles

    2014-03-01

    The effects of human urotensin II (hUII) on the vascular tone of different animal species has been studied extensively. However, little has been reported on the vasoactive effects of rat urotensin (rUII) in murine models. The aim of the present study was to investigate the effects of rUII on vasoreactivity in rat basilar arteries. Basilar arteries from adult male Wistar rats (300-350 g) were isolated, cut in rings, and mounted on a small vessel myograph to measure isometric tension. rUII concentrations were studied in both resting and depolarized state. To remove endothelial nitric oxide effects from the rUII response, we treated selected arterial rings with Nω-nitro-L-arginine methyl ester (L-NAME). 10 μM rUII produced a potent vasoconstrictor response in rat basilar arteries with intact endothelium, while isometric forces remained unaffected in arterial rings treated with lower rUII concentrations. Although L-NAME did not have a significant effect on 10 μM rUII-evoked contraction, it slightly increased arterial ring contraction elicited by 1 μM rUII. In depolarized arteries, dose-dependent rUII increased depolarization-induced contractions. This effect was suppressed by L-NAME. Our results show that the rat basilar artery has a vasoconstrictor response to rUII. The most potent vasoconstrictor effect was produced by lower doses of rUII (0.1 and 1 μM) in depolarized arteries with intact endothelium. This effect could facilitate arterial vasospasm in vascular pathophysiological processes such as subarachnoid hemorrhage and hypertension, when sustained depolarization and L-type Ca(2+) channel activation are present.

  17. The voltage dependence of GABAA receptor gating depends on extracellular pH.

    Science.gov (United States)

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W

    2005-11-28

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the gamma-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid gamma-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating gamma-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH.

  18. The voltage dependence of GABAA receptor gating depends on extracellular pH

    Science.gov (United States)

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W.

    2007-01-01

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the γ-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid γ-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating γ-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH. PMID:16272885

  19. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform...... of the voltage-gated calcium channels (P/Q-type), is also expressed and contributes functionally to contraction of renal blood vessels in both mice and humans. Furthermore, preglomerular vascular SMCs and aortic SMCs coexpress L-, P-, and Q-type calcium channels within the same cell. Calcium channel blockers...... are widely used as pharmacological treatments. However, calcium channel antagonists vary in their selectivity for the various calcium channel subtypes, and the functional contribution from P/Q-type channels as compared with L-type should be considered. Confirming the presence of P/Q-type voltage...

  20. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar;

    2013-01-01

    problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0....

  1. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    . An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...

  2. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  3. Dual Regulation of Voltage-Sensitive Ion Channels by PIP(2).

    Science.gov (United States)

    Rodríguez-Menchaca, Aldo A; Adney, Scott K; Zhou, Lei; Logothetis, Diomedes E

    2012-01-01

    Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidylinositol 4,5-bisphosphate (PIP(2)). Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav) channels were shown to be regulated bidirectionally by PIP(2). On one hand, PIP(2) stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv) channels PIP(2) was first shown to prevent N-type inactivation regardless of whether the fast inactivation gate was part of the pore-forming α subunit or of an accessory β subunit. Careful examination of the effects of PIP(2) on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP(2) and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP(2) is the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel. PIP(2) has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP(2)-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP(2) dual effects on SpIH, with the proximal C-terminus implicated in the

  4. Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

    Directory of Open Access Journals (Sweden)

    Aldo A Rodríguez Menchaca

    2012-09-01

    Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

  5. High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

    Science.gov (United States)

    Shimer, Daniel W.; Lange, Arnold C.

    1995-01-01

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

  6. Transient voltage sharing in series-coupled high voltage switches

    Directory of Open Access Journals (Sweden)

    Editorial Office

    1992-07-01

    Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

  7. Mechanism of Modification, by Lidocaine, of Fast and Slow Recovery from Inactivation of Voltage-Gated Na⁺ Channels.

    Science.gov (United States)

    Gawali, Vaibhavkumar S; Lukacs, Peter; Cervenka, Rene; Koenig, Xaver; Rubi, Lena; Hilber, Karlheinz; Sandtner, Walter; Todt, Hannes

    2015-11-01

    The clinically important suppression of high-frequency discharges of excitable cells by local anesthetics (LA) is largely determined by drug-induced prolongation of the time course of repriming (recovery from inactivation) of voltage-gated Na(+) channels. This prolongation may result from periodic drug-binding to a high-affinity binding site during the action potentials and subsequent slow dissociation from the site between action potentials ("dissociation hypothesis"). For many drugs it has been suggested that the fast inactivated state represents the high-affinity binding state. Alternatively, LAs may bind with high affinity to a native slow-inactivated state, thereby accelerating the development of this state during action potentials ("stabilization hypothesis"). In this case, slow recovery between action potentials occurs from enhanced native slow inactivation. To test these two hypotheses we produced serial cysteine mutations of domain IV segment 6 in rNav1.4 that resulted in constructs with varying propensities to enter fast- and slow-inactivated states. We tested the effect of the LA lidocaine on the time course of recovery from short and long depolarizing prepulses, which, under drug-free conditions, recruited mainly fast- and slow-inactivated states, respectively. Among the tested constructs the mutation-induced changes in native slow recovery induced by long depolarizations were not correlated with the respective lidocaine-induced slow recovery after short depolarizations. On the other hand, for long depolarizations the mutation-induced alterations in native slow recovery were significantly correlated with the kinetics of lidocaine-induced slow recovery. These results favor the "dissociation hypothesis" for short depolarizations but the "stabilization hypothesis" for long depolarizations. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

  8. No-Voltage Meter

    Science.gov (United States)

    1976-02-01

    VW- IKft, 1/4 H4 -Wv- IK!1, I/4W INTERNAL VOLTAGE NOTE ALL TRANSISTORS ARE 2N43A OR EQUIVALENT GERMANIUM ALLOY PNP AA ALKALINE BATTERY...D-,, regardless of polarity. This signal is then full-wave rectified by the diode-connected Germanium transistor bridge, T,, T-,, T3, and T4... Transistor T5 acts as a second current limiter. Resistor R2 was selected to give 90 f# of full-scale meter deflection with an input signal of 115 volts

  9. The Mechanism of Voltage Dependent Gating of the NaChBac Prokaryotic Sodium Channel

    Science.gov (United States)

    Decaen, Paul G.

    Electrical signaling in cells depends on selective conductance of ions through membrane proteins called 'voltage gated ion channels'. These channels are characterized by their ability turn on and off the flow of ionic current by opening and closing their conductive pore in response to changes in membrane potential. The opening and closing of the pore is a mechanically linked to conformational movement of the positively charged fourth transmembrane segment (S4) in 'the voltage sensor' region. How the S4 moves in response to membrane potential is a controversial subject. In this thesis, we used the prokaryotic sodium channel NaChBac as our model sodium channel to study voltage dependent movement of the S4 in the voltage sensor. We use a disulfide-locking method where we introduced pairs of cysteines in the voltage sensor that crosslink and trap the S4 in its path after depolarization. We screened over one hundred mutations of the NaChBac channel in the whole cell patch clamp assay and demonstrated discrete and sequential voltage dependent ion pair interactions that occur in at least three states between the positively charged residues of the S4 segment and the acidic residues in the S1, S2 and S3 segments. In conjunction with structural modeling of the voltage sensor and our disulfide locking data, we propose that the S4 moves in and out of the plane of the membrane 8-13 A, forming distinct gating charge interactions with counter charges of the voltage sensor and adopts a 310 helix over a portion of its structure during activation. These findings are compatible with the sliding helix model and refine our understanding of the structural determinates of voltage sensor function in voltage gated ion channels.

  10. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...... to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution...

  11. Achievable peak electrode voltage reduction by neurostimulators using descending staircase currents to deliver charge.

    Science.gov (United States)

    Halpern, Mark

    2011-01-01

    This paper considers the achievable reduction in peak voltage across two driving terminals of an RC circuit when delivering charge using a stepped current waveform, comprising a chosen number of steps of equal duration, compared with using a constant current over the total duration. This work has application to the design of neurostimulators giving reduced peak electrode voltage when delivering a given electric charge over a given time duration. Exact solutions for the greatest possible peak voltage reduction using two and three steps are given. Furthermore, it is shown that the achievable peak voltage reduction, for any given number of steps is identical for simple series RC circuits and parallel RC circuits, for appropriate different values of RC. It is conjectured that the maximum peak voltage reduction cannot be improved using a more complicated RC circuit.

  12. Voltage dependence of rate functions for Na+ channel inactivation within a membrane

    CERN Document Server

    Vaccaro, Samuel R

    2015-01-01

    The inactivation of a Na+ channel occurs when the activation of the charged S4 segment of domain IV, with rate functions $\\alpha_{i}$ and $\\beta_{i}$, is followed by the binding of an intracellular hydrophobic motif which blocks conduction through the ion pore, with rate functions $\\gamma_{i}$ and $\\delta_{i}$. During a voltage clamp of the Na+ channel, the solution of the master equation for inactivation reduces to the relaxation of a rate equation when the binding of the inactivation motif is rate limiting ($\\alpha_{i} \\gg \\gamma_{i}$ and $\\beta_{i} \\gg \\delta_{i}$). The voltage dependence of the derived forward rate function for Na+ channel inactivation has an exponential dependence on the membrane potential for small depolarizations and approaches a constant value for larger depolarizations, whereas the voltage dependence of the backward rate function is exponential, and each rate has a similar form to the Hodgkin-Huxley empirical rate functions for Na+ channel inactivation in the squid axon.

  13. General model of depolarization and transfer of polarization of singly ionized atoms by collisions with hydrogen atoms

    Science.gov (United States)

    Derouich, M.

    2017-02-01

    Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the p-levels of ions for large number of values of the effective principal quantum number n* and the Unsöld energy Ep. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, n* and Ep are obtained, and are shown to reproduce the original data with accuracy clearly better than 10%. These relationships allow quick calculations of the depolarizing collisional rates of any simple ion which is very useful for the solar physics community. In addition, the depolarization rates associated to the complex ions and to the hyperfine levels can be easily derived from our results. In this work we have shown that by using powerful numerical approach and our collisional method, general model giving the depolarization of the ions can be obtained to be exploited for solar applications.

  14. High-frequency high-voltage high-power DC-to-DC converters

    Science.gov (United States)

    Wilson, T. G.; Owen, H. A.; Wilson, P. M.

    1982-01-01

    A simple analysis of the current and voltage waveshapes associated with the power transistor and the power diode in an example current-or-voltage step-up (buck-boost) converter is presented. The purpose of the analysis is to provide an overview of the problems and design trade-offs which must be addressed as high-power high-voltage converters are operated at switching frequencies in the range of 100 kHz and beyond. Although the analysis focuses on the current-or-voltage step-up converter as the vehicle for discussion, the basic principles presented are applicable to other converter topologies as well.

  15. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  16. Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

    Directory of Open Access Journals (Sweden)

    William J.B. Heffernan

    2014-12-01

    Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

  17. Depolarizing power and polarization entropy of light scattering media: experiment and theory

    CERN Document Server

    Puentes, G; Aiello, A; Woerdman, J P; Puentes, Graciana; Voigt, Dirk; Aiello, Andrea

    2004-01-01

    We experimentally investigate the depolarizing power and the polarization entropy of a broad class of scattering optical media. By means of polarization tomography, these quantities are derived from an effective Mueller matrix, which is introduced through a formal description of the multi-mode detection scheme we use, as recently proposed by Aiello and Woerdman (arXiv:quant-ph/0407234). This proposal emphasized an intriguing universality in the polarization aspects of classical as well as quantum light scattering; in this contribution we demonstrate experimentally that this universality is obeyed by a surprisingly wide class of depolarizing media. This, in turn, provides the experimentalist with a useful characterization of the polarization properties of any scattering media, as well as a universal criterion for the validity of the measured data.

  18. Generation of vector beams using a double-wedge depolarizer: Non-quantum entanglement

    Science.gov (United States)

    Samlan, C. T.; Viswanathan, Nirmal K.

    2016-07-01

    Propagation of horizontally polarized Gaussian beam through a double-wedge depolarizer generates vector beams with spatially varying state of polarization. Jones calculus is used to show that such beams are maximally nonseparable on the basis of even (Gaussian)-odd (Hermite-Gaussian) mode parity and horizontal-vertical polarization state. The maximum nonseparability in the two degrees of freedom of the vector beam at the double wedge depolarizer output is verified experimentally using a modified Sagnac interferometer and linear analyser projected interferograms to measure the concurrence 0.94±0.002 and violation of Clauser-Horne-Shimony-Holt form of Bell-like inequality 2.704±0.024. The investigation is carried out in the context of the use of vector beams for metrological applications.

  19. On the Sr I 4607 A Hanle depolarization signals in the quiet Sun

    CERN Document Server

    Almeida, J S

    2005-01-01

    The Hanle depolarization signals of Sr 4607 A have been used to estimate the unsigned magnetic flux and magnetic energy existing in the quiet Sun photosphere. However, the Sr 4607 A Hanle signals are not sensitive to the unsigned flux and energy. They only bear information on the fraction of photosphere occupied by magnetic field strengths smaller than the Hanle saturation, which do not contribute to the unsigned flux and energy. We deduce an approximate expression for the relationship between magnetic fill factor and Hanle signal. When applied to existing Hanle depolarization measurements, it indicates that only 40% of the quiet Sun is filled by magnetic fields with a strength smaller than 60 G. The remaining 60% of the surface has field strengths above this limit. Such constraint will be needed to determine the distribution of magnetic field strengths existing in the quiet Sun.

  20. Structure in the polarized Galactic synchrotron emission, in particular `depolarization canals'

    CERN Document Server

    Haverkorn, M; De Bruyn, A G

    2004-01-01

    The polarized component of the diffuse radio synchrotron emission of our Galaxy shows structure, which is apparently unrelated to the structure in total intensity, on many scales. The structure in the polarized emission can be due to several processes or mechanisms. Some of those are related to the observational setup, such as beam depolarization -- the vector combination and (partial) cancellation of polarization vectors within a synthesized beam --, or the insensitivity of a synthesis telescope to structure on large scales, also known as the 'missing short spacings problem'. Other causes for structure in the polarization maps are intrinsic to the radiative transfer of the emission in the warm ISM, which induces Faraday rotation and depolarization. We use data obtained with the Westerbork Synthesis Radio Telescope at 5 frequencies near 350 MHz to estimate the importance of the various mechanisms in producing structure in the linearly polarized emission. In the two regions studied here, which are both at posi...

  1. Diode-double-face-pumped Nd:YAG ceramic slab laser amplifier with low depolarization loss

    Science.gov (United States)

    Chen, Yanzhong; Fan, Zhongwei; Guo, Guangyan; Jia, Dan; He, Jianguo; Lang, Ye; Qiu, Jisi; Kang, Zhijun; Zhao, Tianzhuo; Lin, Weiran; Wang, Jiang; Xie, Tengfei; Li, Jiang; Kou, Huamin; Pan, Yubai

    2017-09-01

    A diode-double-face-pumped Nd:YAG ceramic slab laser amplifier with uniform gain distribution and low depolarization loss was presented. Energy storage of 2.6 J was achieved at 1064 nm with a repetition rate of 200 Hz and a pulse width of 200 us from a 140 mm × 40 mm × 7 mm ceramic slab at a total pump power of 1215 W, corresponding to an optical-to-optical efficiency of 42.8%. An average small signal gain of 5.45 was achieved with a standard deviation of only 0.09 in the cross section, which shown good concentration uniformity. An average depolarization loss of 2.6% at different positions of the slab was obtained due to small thermal gradient of the zigzag configuration.

  2. Resolving 4-D Nature of Magnetism with Depolarization and Faraday Tomography: Japanese SKA Cosmic Magnetism Science

    CERN Document Server

    Akahori, Takuya; Ichaki, Kiyotomo; Ideguchi, Shinsuke; Kudoh, Takahiro; Kudoh, Yuki; Machida, Mami; Nakanishi, Hiroyuki; Ohno, Hiroshi; Ozawa, Takeaki; Takahashi, Keitaro; Takizawa, Motokazu

    2016-01-01

    Magnetic fields play essential roles in various astronomical objects. Radio astronomy has revealed that magnetic fields are ubiquitous in our Universe. However, the real origin and evolution of magnetic fields is poorly proven. In order to advance our knowledge of cosmic magnetism in coming decades, the Square Kilometre Array (SKA) should have supreme sensitivity than ever before, which provides numerous observation points in the cosmic space. Furthermore, the SKA should be designed to facilitate wideband polarimetry so as to allow us to examine sightline structures of magnetic fields by means of depolarization and Faraday Tomography. The SKA will be able to drive cosmic magnetism of the interstellar medium, the Milky Way, galaxies, AGN, galaxy clusters, and potentially the cosmic web which may preserve information of the primeval Universe. The Japan SKA Consortium (SKA-JP) Magnetism Science Working Group (SWG) proposes the project "Resolving 4-D Nature of Magnetism with Depolarization and Faraday Tomography"...

  3. Depolarization of D-T plasmas by recycling in material walls

    Energy Technology Data Exchange (ETDEWEB)

    Greenside, H.S.; Budny, R.V.; Post, D.E.

    1984-02-01

    The feasibility of using polarized deuterium (D) and tritium (T) plasmas in fusion reactors may be seriously affected by recycling in material walls. Theoretical and experimental results are reviewed which show how the depolarization rates of absorbed D and T depend on first wall parameters such as the temperature, the bulk and surface diffusivities, the density of electronic states at the Fermi surface, the spectral density of microscopic fluctuating electric field gradients, and the concentration of paramagnetic impurities. Nuclear magnetic resonance (NMR) spectroscopy of hydrogenated and deuterated amorphous semiconductors suggests that low-Z nonmetallic materials may provide a satisfactory first wall or limiter coating under reactor conditions with characteristic depolarization times of several seconds. Experiments are proposed to test the consequences of our analysis.

  4. Neutron depolarization imaging of the hydrostatic pressure dependence of inhomogeneous ferromagnets

    Science.gov (United States)

    Schulz, M.; Neubauer, A.; Böni, P.; Pfleiderer, C.

    2016-05-01

    The investigation of fragile and potentially inhomogeneous forms of ferromagnetic order under extreme conditions, such as low temperatures and high pressures, is of central interest for areas such as geophysics, correlated electron systems, as well as the optimization of materials synthesis for applications where particular material properties are required. We report neutron depolarization imaging measurements on the weak ferromagnet Ni3Al under pressures up to 10 kbar using a Cu:Be clamp cell. Using a polychromatic neutron beam with wavelengths λ ≥ 4 Å in combination with 3He neutron spin filter cells as polarizer and analyzer, we were able to track differences of the pressure response in inhomogeneous samples by virtue of high resolution neutron depolarization imaging. This provides spatially resolved and non-destructive access to the pressure dependence of the magnetic properties of inhomogeneous ferromagnetic materials.

  5. Voltage Swells Improvement in Low Voltage Network Using Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    R. Omar

    2011-01-01

    Full Text Available Problem statement: Voltage disturbances are the most common power quality problem due to the increased use of a large numbers of sophisticated electronic equipment in industrial distribution system. The voltage disturbances such as voltage sags, swells, harmonics, unbalance and flickers. High quality in the power supply is needed, since failures due to such disturbances usually have a high impact on production cost. There are many different solutions to compensate voltage disturbances but the use of a DVR is considered to be the most cost effective method. The objective of this study is to propose a new topology of a DVR in order to mitigate voltage swells using a powerful power custom device namely the Dynamic Voltage Restorer (DVR. Approach: New configuration of a DVR with an improvement of a controller based on direct-quadrature-zero method has been introduced to compensate voltage swells in the network. Results: The effectiveness of the DVR with its controller were verify using Matlab/Simulinks SimPower Toolbox and then implemented using 5KVA DVR experimental setup. Simulations and experimental results demonstrate the effective dynamic performance of the proposed configuration. Conclusion: The implimentation of the proposed DVR validate the capabilities in mitigating of voltage swells effectiveness.During voltage swells, the DVR injects an appropriate voltage to maintain the load voltage at its nominal value.

  6. Activation of Ih and TTX-sensitive sodium current at subthreshold voltages during CA1 pyramidal neuron firing.

    Science.gov (United States)

    Yamada-Hanff, Jason; Bean, Bruce P

    2015-10-01

    We used dynamic clamp and action potential clamp techniques to explore how currents carried by tetrodotoxin-sensitive sodium channels and HCN channels (Ih) regulate the behavior of CA1 pyramidal neurons at resting and subthreshold voltages. Recording from rat CA1 pyramidal neurons in hippocampal slices, we found that the apparent input resistance and membrane time constant were strongly affected by both conductances, with Ih acting to decrease apparent input resistance and time constant and sodium current acting to increase both. We found that both Ih and sodium current were active during subthreshold summation of artificial excitatory postsynaptic potentials (EPSPs) generated by dynamic clamp, with Ih dominating at less depolarized voltages and sodium current at more depolarized voltages. Subthreshold sodium current-which amplifies EPSPs-was most effectively recruited by rapid voltage changes, while Ih-which blunts EPSPs-was maximal for slow voltage changes. The combined effect is to selectively amplify rapid EPSPs. We did similar experiments in mouse CA1 pyramidal neurons, doing voltage-clamp experiments using experimental records of action potential firing of CA1 neurons previously recorded in awake, behaving animals as command voltages to quantify flow of Ih and sodium current at subthreshold voltages. Subthreshold sodium current was larger and subthreshold Ih was smaller in mouse neurons than in rat neurons. Overall, the results show opposing effects of subthreshold sodium current and Ih in regulating subthreshold behavior of CA1 neurons, with subthreshold sodium current prominent in both rat and mouse CA1 pyramidal neurons and additional regulation by Ih in rat neurons.

  7. Isomerically Pure Tetramethylrhodamine Voltage Reporters.

    Science.gov (United States)

    Deal, Parker E; Kulkarni, Rishikesh U; Al-Abdullatif, Sarah H; Miller, Evan W

    2016-07-27

    We present the design, synthesis, and application of a new family of fluorescent voltage indicators based on isomerically pure tetramethylrhodamines. These new Rhodamine Voltage Reporters, or RhoVRs, use photoinduced electron transfer (PeT) as a trigger for voltage sensing, display excitation and emission profiles in the green to orange region of the visible spectrum, demonstrate high sensitivity to membrane potential changes (up to 47% ΔF/F per 100 mV), and employ a tertiary amide derived from sarcosine, which aids in membrane localization and simultaneously simplifies the synthetic route to the voltage sensors. The most sensitive of the RhoVR dyes, RhoVR 1, features a methoxy-substituted diethylaniline donor and phenylenevinylene molecular wire at the 5'-position of the rhodamine aryl ring, exhibits the highest voltage sensitivity to date for red-shifted PeT-based voltage sensors, and is compatible with simultaneous imaging alongside green fluorescent protein-based indicators. The discoveries that sarcosine-based tertiary amides in the context of molecular-wire voltage indicators prevent dye internalization and 5'-substituted voltage indicators exhibit improved voltage sensitivity should be broadly applicable to other types of PeT-based voltage-sensitive fluorophores.

  8. Presynaptic α2-GABAA Receptors in Primary Afferent Depolarization and Spinal Pain Control

    OpenAIRE

    2011-01-01

    Spinal dorsal horn GABAA receptors are found both postsynaptically on central neurons and presynaptically on axons and/or terminals of primary sensory neurons, where they mediate primary afferent depolarization (PAD) and presynaptic inhibition. Both phenomena have been studied extensively on a cellular level, but their role in sensory processing in vivo has remained elusive, due to inherent difficulties to selectively interfere with presynaptic receptors. Here, we address the contribution of ...

  9. Presynaptic {alpha}2-GABAA receptors in primary afferent depolarization and spinal pain control

    OpenAIRE

    2011-01-01

    Spinal dorsal horn GABA(A) receptors are found both postsynaptically on central neurons and presynaptically on axons and/or terminals of primary sensory neurons, where they mediate primary afferent depolarization (PAD) and presynaptic inhibition. Both phenomena have been studied extensively on a cellular level, but their role in sensory processing in vivo has remained elusive, due to inherent difficulties to selectively interfere with presynaptic receptors. Here, we address the contribution o...

  10. Seizures, refractory status epilepticus, and depolarization block as endogenous brain activities

    Science.gov (United States)

    El Houssaini, Kenza; Ivanov, Anton I.; Bernard, Christophe; Jirsa, Viktor K.

    2015-01-01

    Epilepsy, refractory status epilepticus, and depolarization block are pathological brain activities whose mechanisms are poorly understood. Using a generic mathematical model of seizure activity, we show that these activities coexist under certain conditions spanning the range of possible brain activities. We perform a detailed bifurcation analysis and predict strategies to escape from some of the pathological states. Experimental results using rodent data provide support of the model, highlighting the concept that these pathological activities belong to the endogenous repertoire of brain activities.

  11. In vivo cluster formation of nisin and lipid II is correlated with membrane depolarization.

    Science.gov (United States)

    Tol, Menno B; Morales Angeles, Danae; Scheffers, Dirk-Jan

    2015-01-01

    Nisin and related lantibiotics kill bacteria by pore formation or by sequestering lipid II. Some lantibiotics sequester lipid II into clusters, which were suggested to kill cells through delocalized peptidoglycan synthesis. Here, we show that cluster formation is always concomitant with (i) membrane pore formation and (ii) membrane depolarization. Nisin variants that cluster lipid II kill L-form bacteria with similar efficiency, suggesting that delocalization of peptidoglycan synthesis is not the primary killing mechanism of these lantibiotics.

  12. Structural relaxation mechanisms in liquid Eugenol. A depolarized light scattering study

    Science.gov (United States)

    Bezot, P.; Hesse-Bezot, C.; Roynard, D.; Jeanneaux, F.

    1988-07-01

    A depolarized light scattering study of liquid Eugenol, over a large temperature range including the supercooled region, is proposed. Comparisons with shear mechanical impedance measurements, obtained at lower frequencies, lead to more precise information on the viscoelastic parameters in the supercooled region. The structural relaxation process measurements by means of the photon correlation technique are compared to the dielectric and mechanical measurements. Molecular mechanisms are proposed.

  13. Modeling of thermally stimulated depolarization current (TSDC) using dipole–dipole interaction concept

    Indian Academy of Sciences (India)

    A E Kotp

    2011-04-01

    The study of thermally stimulated depolarization current (TSDC) using the dipole–dipole interaction model is described in this work. The dipole–dipole interactionmodel (DDIM) determines the TSDC peak successfully since it gives significant peak parameters (i.e. activation energy () and pre-exponential factor ($\\tau_{0}$)) in addition to the dipole–dipole interaction strength parameter ($d_{i}$). Application of this model to study the peak parameters of some polymeric systems is presented.

  14. Ultra-Step-Up DC-DC Converter with Integrated Autotransformer and Coupled Inductor

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Loh, Poh Chiang

    2016-01-01

    This paper introduces a new single-switch nonisolated dc-dc converter with very high voltage transfer ratio and reduced semiconductor voltage stress. The converter utilizes an integrated autotransformer and a coupled inductor on the same core to achieve a high step-up voltage gain without extreme...

  15. Computational simulation: astrocyte-induced depolarization of neighboring neurons mediates synchronous UP states in a neural network.

    Science.gov (United States)

    Kuriu, Takayuki; Kakimoto, Yuta; Araki, Osamu

    2015-09-01

    Although recent reports have suggested that synchronous neuronal UP states are mediated by astrocytic activity, the mechanism responsible for this remains unknown. Astrocytic glutamate release synchronously depolarizes adjacent neurons, while synaptic transmissions are blocked. The purpose of this study was to confirm that astrocytic depolarization, propagated through synaptic connections, can lead to synchronous neuronal UP states. We applied astrocytic currents to local neurons in a neural network consisting of model cortical neurons. Our results show that astrocytic depolarization may generate synchronous UP states for hundreds of milliseconds in neurons even if they do not directly receive glutamate release from the activated astrocyte.

  16. Uncoupling charge movement from channel opening in voltage-gated potassium channels by ruthenium complexes.

    Science.gov (United States)

    Jara-Oseguera, Andrés; Ishida, Itzel G; Rangel-Yescas, Gisela E; Espinosa-Jalapa, Noel; Pérez-Guzmán, José A; Elías-Viñas, David; Le Lagadec, Ronan; Rosenbaum, Tamara; Islas, León D

    2011-05-06

    The Kv2.1 channel generates a delayed-rectifier current in neurons and is responsible for modulation of neuronal spike frequency and membrane repolarization in pancreatic β-cells and cardiomyocytes. As with other tetrameric voltage-activated K(+)-channels, it has been proposed that each of the four Kv2.1 voltage-sensing domains activates independently upon depolarization, leading to a final concerted transition that causes channel opening. The mechanism by which voltage-sensor activation is coupled to the gating of the pore is still not understood. Here we show that the carbon-monoxide releasing molecule 2 (CORM-2) is an allosteric inhibitor of the Kv2.1 channel and that its inhibitory properties derive from the CORM-2 ability to largely reduce the voltage dependence of the opening transition, uncoupling voltage-sensor activation from the concerted opening transition. We additionally demonstrate that CORM-2 modulates Shaker K(+)-channels in a similar manner. Our data suggest that the mechanism of inhibition by CORM-2 may be common to voltage-activated channels and that this compound should be a useful tool for understanding the mechanisms of electromechanical coupling.

  17. Effects of Voltage-Gated K+ Channel on Cell Proliferation in Multiple Myeloma

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available Objective. To study the effects and underlying mechanisms of voltage-gated K+ channels on the proliferation of multiple myeloma cells. Methods. RPMI-8226 MM cell line was used for the experiments. Voltage-gated K+ currents and the resting potential were recorded by whole-cell patch-clamp technique. RT-PCR detected Kv channel mRNA expression. Cell viability was analyzed with MTT assay. Cell counting system was employed to monitor cell proliferation. DNA contents and cell volume were analyzed by flow cytometry. Results. Currents recorded in RPMI-8226 cells were confirmed to be voltage-gated K+ channels. A high level of Kv1.3 mRNA was detected but no Kv3.1 mRNA was detected in RPMI-8226 cells. Voltage-gated K+ channel blocker 4-aminopyridine (4-AP (2 mM depolarized the resting potential from −42 ± 1.7 mV to −31.8 ± 2.8 mV (P0.05. Conclusions. In RPMI-8226, voltage-gated K+ channels are involved in proliferation and cell cycle progression its influence on the resting potential and cell volume may be responsible for this process; the inhibitory effect of the voltage-gated K+ channel blocker on RPMI-8226 cell proliferation is a phase-specific event.

  18. Combating the Reliability Challenge of GPU Register File at Low Supply Voltage

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Jingweijia; Song, Shuaiwen; Yan, Kaige; Fu, Xin; Marquez, Andres; Kerbyson, Darren J.

    2016-09-11

    Supply voltage reduction is an effective approach to significantly reduce GPU energy consumption. As the largest on-chip storage structure, the GPU register file becomes the reliability hotspot that prevents further supply voltage reduction below the safe limit (Vmin) due to process variation effects. This work addresses the reliability challenge of the GPU register file at low supply voltages, which is an essential first step for aggressive supply voltage reduction of the entire GPU chip. We propose GR-Guard, an architectural solution that leverages long register dead time to enable reliable operations from unreliable register file at low voltages.

  19. Coordinated Voltage Control Scheme for SEIG-Based Wind Park Utilizing Substation STATCOM and ULTC Transformer

    DEFF Research Database (Denmark)

    S. El Moursi, Mohamed; Bak-Jensen, Birgitte; Abdel-Rahman, Mansour Hassan

    2011-01-01

    and optimal tracking secondary voltage control for wind parks based on self-excited induction generators which comprise STATCOM and under-load tap changer (ULTC) substation transformers. The voltage controllers for the STATCOM and ULTC transformer are coordinated and ensure the voltage support. In steady......-state operation, the voltage is controlled by only stepping the tap changer when the voltage is outside the deadband region of the ULTC to minimize the number of taps changes. Thus, the STATCOM will be unloaded and ready to react with higher reactive power margin during contingencies. In the paper, the effects...

  20. Ferroelectric behavior of a lead titanate nanosphere due to depolarization fields and mechanical stresses

    Energy Technology Data Exchange (ETDEWEB)

    Andrade Landeta, J.; Lascano, I.

    2017-07-01

    A theorical model has been developed based on the theory of Ginzburg-Landau-Devonshire to study and predict the effects the decreasing of size particle in a nanosphere of PbTiO3 subjected to the action of depolarization fields and mechanical stress. It was considered that the nanosphere is surrounded by a layer of space charges on its surface, and containing 180° domains generated by minimizing free energy of depolarization. Energy density of depolarization, wall domain and electro-elastic energy have been incorporated into the free energy of the theory Ginzburg-Landau-Devonshire. Free energy minimization was performed to determine the spontaneous polarization and transition temperature system. These results show that the transition temperature for nanosphere is substantially smaller than the corresponding bulk material. Also, it has been obtained that the stability of the ferroelectric phase of nanosphere is favored for configurations with a large number of 180° domains, with the decreasing of thickness space charge layer, and the application of tensile stress and decreases with compressive stress. (Author)

  1. Large plasma-membrane depolarization precedes rapid blue-light-induced growth inhibition in cucumber

    Science.gov (United States)

    Spalding, E. P.; Cosgrove, D. J.

    1989-01-01

    Blue-light (BL)-induced suppression of elongation of etiolated Cucumis sativus L. hypocotyls began after a 30-s lag time, which was halved by increasing the fluence rate from 10 to 100 micromoles m-2 s-1. Prior to the growth suppression, the plasma-membrane of the irradiated cells depolarized by as much as 100 mV, then returned within 2-3 min to near its initial value. The potential difference measured with surface electrodes changed with an identical time course but opposite polarity. The lag time for the change in surface potential showed an inverse dependence on fluence rate, similar to the lag for the growth inhibition. Green light and red light caused neither the electrical response nor the rapid inhibition of growth. The depolarization by BL did not propagate to nonirradiated regions and exhibited a refractory period of about 10 min following a BL pulse. Fluence-response relationships for the electrical and growth responses provide correlational evidence that the plasma-membrane depolarization reflects an event in the transduction chain of this light-growth response.

  2. Parkin Sensitizes toward Apoptosis Induced by Mitochondrial Depolarization through Promoting Degradation of Mcl-1

    Directory of Open Access Journals (Sweden)

    Richard G. Carroll

    2014-11-01

    Full Text Available Mitochondrial depolarization promotes Parkin- and PTEN-induced kinase 1 (PINK1-dependent polyubiquitination of multiple proteins on mitochondrial outer membranes, resulting in the removal of defective mitochondria via mitophagy. Because Parkin mutations occur in Parkinson’s disease, a condition associated with the death of dopaminergic neurons in the midbrain, wild-type Parkin is thought to promote neuronal survival. However, here we show that wild-type Parkin greatly sensitized toward apoptosis induced by mitochondrial depolarization but not by proapoptotic stimuli that failed to activate Parkin. Parkin-dependent apoptosis required PINK1 and was efficiently blocked by prosurvival members of the Bcl-2 family or knockdown of Bax and Bak. Upon mitochondrial depolarization, the Bcl-2 family member Mcl-1 underwent rapid Parkin- and PINK1-dependent polyubiquitination and degradation, which sensitized toward apoptosis via opening of the Bax/Bak channel. These data suggest that similar to other sensors of cell stress, such as p53, Parkin has cytoprotective (mitophagy or cytotoxic modes (apoptosis, depending on the degree of mitochondrial damage.

  3. Thermal Stress-Induced Depolarization Loss in Conventional and Panda-Shaped Photonic Crystal Fiber Lasers

    Science.gov (United States)

    Mousavi, Seyedeh Laleh; Sabaeian, Mohammad

    2016-10-01

    We report on the modeling of the depolarization loss in the conventional and panda-shaped photonic crystal fiber lasers (PCFLs) due to the self-heating of the fiber, which we call it thermal stress-induced depolarization loss (TSIDL). We first calculated the temperature distribution over the fiber cross sections and then calculated the thermal stresses/strains as a function of heat load per meter. Thermal stress-induced birefringence (TSIB), which is defined as | n x - n y |, in the core and cladding regions was calculated. Finally, TSIDL was calculated for the conventional and panda-shaped PCFLs as a function of fiber length and, respectively, saturated values of 22 and 25 % were obtained which were independent of heat load per meter. For panda-shaped PCFLs, prior to being saturated, an oscillating and damping behavior against the fiber length was seen where in some lengths reached 35 %. The results are close to an experimental value of 30 % reported for a pulsed PCFL (Limpert et al., Opt Express 12:1313-1319, 2004) where the authors reported a degree of polarization of 70 % (i.e., a depolarization of 30 %). The most important result of this work is a saturation behavior of TSIDL at long-enough lengths of the fiber laser which is independent of heat load per meter. To our knowledge, this the first report of TSIBL for PCFLs.

  4. Cortical hyperpolarization-activated depolarizing current takes part in the generation of focal paroxysmal activities

    Science.gov (United States)

    Timofeev, Igor; Bazhenov, Maxim; Sejnowski, Terrence; Steriade, Mircea

    2002-01-01

    During paroxysmal neocortical oscillations, sudden depolarization leading to the next cycle occurs when the majority of cortical neurons are hyperpolarized. Both the Ca2+-dependent K+ currents (IK(Ca)) and disfacilitation play critical roles in the generation of hyperpolarizing potentials. In vivo experiments and computational models are used here to investigate whether the hyperpolarization-activated depolarizing current (Ih) in cortical neurons also contributes to the generation of paroxysmal onsets. Hyperpolarizing current pulses revealed a depolarizing sag in ≈20% of cortical neurons. Intracellular recordings from glial cells indirectly indicated an increase in extracellular potassium concentration ([K+]o) during paroxysmal activities, leading to a positive shift in the reversal potential of K+-mediated currents, including Ih. In the paroxysmal neocortex, ≈20% of neurons show repolarizing potentials originating from hyperpolarizations associated with depth-electroencephalogram positive waves of spike-wave complexes. The onset of these repolarizing potentials corresponds to maximal [K+]o as estimated from dual simultaneous impalements from neurons and glial cells. Computational models showed how, after the increased [K+]o, the interplay between Ih, IK(Ca), and a persistent Na+ current, INa(P), could organize paroxysmal oscillations at a frequency of 2–3 Hz. PMID:12089324

  5. Single ice crystal measurements during nucleation experiments with the depolarization detector IODE

    Directory of Open Access Journals (Sweden)

    M. Nicolet

    2008-12-01

    Full Text Available In order to determine the efficiency of aerosol particles of several types to nucleate ice, an Ice Optical DEpolarization detector (IODE was developed to distinguish between water droplets and ice crystals in ice nucleation chambers. A laser beam polarized linearly (power: 50 mW, wavelength: 407 nm is directed through the chamber. The scattered light intensity from particles is measured at a scattering angle of Θ=175° in both polarization components (parallel and perpendicular. The ratio between the perpendicular intensity over the total one gives the depolarization ratio δ. Single particle detection is possible, using a peak detection algorithm. For high particle concentrations, a real-time signal averaging method can also be run simultaneously. The IODE detector was used in connection with the Zurich ice nucleation chamber during the ICIS 2007 workshop where ice nucleation experiments were performed with several aerosol types. In presence of ice crystals, peaks were detected in both channels, generating depolarization signals. Mean values of δ ranged from 0.24 to 0.37.

  6. Single ice crystal measurements during nucleation experiments with the depolarization detector IODE

    Directory of Open Access Journals (Sweden)

    M. Nicolet

    2010-01-01

    Full Text Available In order to determine the efficiency of different aerosol particles to nucleate ice, an Ice Optical DEpolarization detector (IODE was developed to distinguish between water droplets and ice crystals in ice nucleation chambers. A laser beam polarized linearly (power: 50 mW, wavelength: 407 nm is directed through the chamber. The scattered light intensity from particles is measured at a scattering angle of Θ=175° in both polarization components (parallel and perpendicular. The ratio between the perpendicular intensity over the total one yields the depolarization ratio δ. Single particle detection is possible, using a peak detection algorithm. For high particle concentrations, a real-time signal averaging method can also be run simultaneously.

    The IODE detector was used in connection with the Zurich ice nucleation chamber during the ICIS 2007 workshop where ice nucleation experiments were performed with several aerosol types. In presence of ice crystals, a depolarization ratio could be measured on a particle-by-particle basis. Mean values of δ ranged from 0.24 to 0.37 and agree well with theoretical calculations.

  7. Single ice crystal measurements during nucleation experiments with the depolarization detector IODE

    Science.gov (United States)

    Nicolet, M.; Stetzer, O.; Lüönd, F.; Möhler, O.; Lohmann, U.

    2010-01-01

    In order to determine the efficiency of different aerosol particles to nucleate ice, an Ice Optical DEpolarization detector (IODE) was developed to distinguish between water droplets and ice crystals in ice nucleation chambers. A laser beam polarized linearly (power: 50 mW, wavelength: 407 nm) is directed through the chamber. The scattered light intensity from particles is measured at a scattering angle of Θ=175° in both polarization components (parallel and perpendicular). The ratio between the perpendicular intensity over the total one yields the depolarization ratio δ. Single particle detection is possible, using a peak detection algorithm. For high particle concentrations, a real-time signal averaging method can also be run simultaneously. The IODE detector was used in connection with the Zurich ice nucleation chamber during the ICIS 2007 workshop where ice nucleation experiments were performed with several aerosol types. In presence of ice crystals, a depolarization ratio could be measured on a particle-by-particle basis. Mean values of δ ranged from 0.24 to 0.37 and agree well with theoretical calculations.

  8. Postsynaptic Depolarization Enhances GABA Drive to Dorsomedial Hypothalamic Neurons through Somatodendritic Cholecystokinin Release.

    Science.gov (United States)

    Crosby, Karen M; Baimoukhametova, Dinara V; Bains, Jaideep S; Pittman, Quentin J

    2015-09-23

    Somatodendritically released peptides alter synaptic function through a variety of mechanisms, including autocrine actions that liberate retrograde transmitters. Cholecystokinin (CCK) is a neuropeptide expressed in neurons in the dorsomedial hypothalamic nucleus (DMH), a region implicated in satiety and stress. There are clear demonstrations that exogenous CCK modulates food intake and neuropeptide expression in the DMH, but there is no information on how endogenous CCK alters synaptic properties. Here, we provide the first report of somatodendritic release of CCK in the brain in male Sprague Dawley rats. CCK is released from DMH neurons in response to repeated postsynaptic depolarizations, and acts in an autocrine fashion on CCK2 receptors to enhance postsynaptic NMDA receptor function and liberate the retrograde transmitter, nitric oxide (NO). NO subsequently acts presynaptically to enhance GABA release through a soluble guanylate cyclase-mediated pathway. These data provide the first demonstration of synaptic actions of somatodendritically released CCK in the hypothalamus and reveal a new form of retrograde plasticity, depolarization-induced potentiation of inhibition. Significance statement: Somatodendritic signaling using endocannabinoids or nitric oxide to alter the efficacy of afferent transmission is well established. Despite early convincing evidence for somatodendritic release of neurohypophysial peptides in the hypothalamus, there is only limited evidence for this mode of release for other peptides. Here, we provide the first evidence for somatodendritic release of the satiety peptide cholecystokinin (CCK) in the brain. We also reveal a new form of synaptic plasticity in which postsynaptic depolarization results in enhancement of inhibition through the somatodendritic release of CCK.

  9. Enhancement of light depolarization by random ensembles of titania-based low-dimensional nanoparticles

    Science.gov (United States)

    Zimnyakov, D. A.; Zdrajevsky, R. A.; Yuvchenko, S. A.; Ushakova, O. V.; Angelsky, O. V.; Yermolenko, S. B.

    2015-02-01

    Depolarization peculiarities of the light scattered by the random ensembles of titania-based low-dimensional nanoparticles are studied during the experiments with aqueous suspensions of potassium polytitanate nanoplatelets and nanoribbons. The obtained experimental results are compared with the theoretical data obtained for the random systems of oblate and prolate flattened ellipsoidal nanoparticles with various values of the shape factor and dielectric function corresponding the parent material (titanium dioxide). The possibility to recover the effective dielectric function from the depolarization ratio spectra using the ellipsoidal shape model is considered. Ellipsoidal approximation is appropriate for both the nanoplatelets and nanoribbons in the spectral region for which the real part of nanoparticles permittivity is sufficiently negative and the near-resonant excitation of longitudinal mode of charge oscillations in nanoparticles occurs. Also, ellipsoidal approximation is appropriate for nanoplatelets in the region of sufficiently po sitive real part of permittivity but gives remarkably underestimated values of the depolarization ratio for nanoribbons in the region. This is presumably caused by considerable difference in the light-induced charge distributions for nanoribbons and prolate flattened ellipsoidal nanoparticles with the decreasing efficiency in longitudinal mode excitation. The recovered values of nanoparticle permittivity exhibit the red shift with respect to the permittivity values of the parent material due to its modification in the course of nanoparticles synthesis.

  10. A voltage-dependent persistent sodium current in mammalian hippocampal neurons.

    Science.gov (United States)

    French, C R; Sah, P; Buckett, K J; Gage, P W

    1990-06-01

    Currents generated by depolarizing voltage pulses were recorded in neurons from the pyramidal cell layer of the CA1 region of rat or guinea pig hippocampus with single electrode voltage-clamp or tight-seal whole-cell voltage-clamp techniques. In neurons in situ in slices, and in dissociated neurons, subtraction of currents generated by identical depolarizing voltage pulses before and after exposure to tetrodotoxin revealed a small, persistent current after the transient current. These currents could also be recorded directly in dissociated neurons in which other ionic currents were effectively suppressed. It was concluded that the persistent current was carried by sodium ions because it was blocked by TTX, decreased in amplitude when extracellular sodium concentration was reduced, and was not blocked by cadmium. The amplitude of the persistent sodium current varied with clamp potential, being detectable at potentials as negative as -70 mV and reaching a maximum at approximately -40 mV. The maximum amplitude at -40 mV in 21 cells in slices was -0.34 +/- 0.05 nA (mean +/- 1 SEM) and -0.21 +/- 0.05 nA in 10 dissociated neurons. Persistent sodium conductance increased sigmoidally with a potential between -70 and -30 mV and could be fitted with the Boltzmann equation, g = gmax/(1 + exp[(V' - V)/k)]). The average gmax was 7.8 +/- 1.1 nS in the 21 neurons in slices and 4.4 +/- 1.6 nS in the 10 dissociated cells that had lost their processes indicating that the channels responsible are probably most densely aggregated on or close to the soma. The half-maximum conductance occurred close to -50 mV, both in neurons in slices and in dissociated neurons, and the slope factor (k) was 5-9 mV. The persistent sodium current was much more resistant to inactivation by depolarization than the transient current and could be recorded at greater than 50% of its normal amplitude when the transient current was completely inactivated. Because the persistent sodium current activates at

  11. Glucose stimulates neurotensin secretion from the rat small intestine by mechanisms involving SGLT1 and GLUT2, leading to cell depolarization and calcium influx.

    Science.gov (United States)

    Kuhre, Rune Ehrenreich; Bechmann, Louise Ellegaard; Wewer Albrechtsen, Nicolai Jacob; Hartmann, Bolette; Holst, Jens Juul

    2015-06-15

    Neurotensin (NT) is a neurohormone produced in the central nervous system and in the gut epithelium by the enteroendocrine N cell. NT may play a role in appetite regulation and may have potential in obesity treatment. Glucose ingestion stimulates NT secretion in healthy young humans, but the mechanisms involved are not well understood. Here, we show that rats express NT in the gut and that glucose gavage stimulates secretion similarly to oral glucose in humans. Therefore, we conducted experiments on isolated perfused rat small intestine with a view to characterize the cellular pathways of secretion. Luminal glucose (20% wt/vol) stimulated secretion but vascular glucose (5, 10, or 15 mmol/l) was without effect. The underlying mechanisms depend on membrane depolarization and calcium influx, since the voltage-gated calcium channel inhibitor nifedipine and the KATP channel opener diazoxide, which causes hyperpolarization, eliminated the response. Luminal inhibition of the sodium-glucose cotransporter 1 (SGLT1) (by phloridzin) eliminated glucose-stimulated release as well as secretion stimulated by luminal methyl-α-D-glucopyranoside (20% wt/vol), a metabolically inactive SGLT1 substrate, suggesting that glucose stimulates secretion by initial uptake by this transporter. However, secretion was also sensitive to GLUT2 inhibition (by phloretin) and blockage of oxidative phosphorylation (2-4-dinitrophenol). Direct KATP channel closure by sulfonylureas stimulated secretion. Therefore, glucose stimulates NT secretion by uptake through SGLT1 and GLUT2, both causing depolarization either as a consequence of sodium-coupled uptake (SGLT1) or by closure of KATP channels (GLUT2 and SGLT1) secondary to the ATP-generating metabolism of glucose.

  12. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  13. Depolarization thresholds for hippocampal damage, ischemic preconditioning, and changes in gene expression after global ischemia in the rat.

    Science.gov (United States)

    Halaby, Issam A; Takeda, Yoshimasa; Yufu, Katsumi; Nowak, Thaddeus S; Pulsinelli, William A

    2004-11-30

    Induced ischemic tolerance in rat hippocampus was investigated in a forebrain ischemia model of repeated 4-vessel occlusion (4-VO). Ischemic insult variability was reduced by the use of dc potential measurements to determine the duration of ischemic depolarization in hippocampus. The results demonstrate a depolarization threshold for ischemic injury to CA1 neurons of 4-6 min and a window for optimal preconditioning of 2.5-3.5 min. Levels of induced mRNAs encoding hsp72 and several immediate-early genes were also shown to vary with depolarization interval. Immediate-early genes were maximally induced after depolarization periods inducing optimal preconditioning, while hsp72 expression increased with insult severity over the range leading to neuron loss. These results are similar to those obtained in gerbil studies indicating that preconditioning does not require large increases in hsp72 expression, and demonstrate the fundamental comparability of rodent global ischemia models when monitored by this approach.

  14. General model of depolarization and transfer of polarization of singly ionized atoms by collisions with hydrogen atoms

    CERN Document Server

    Derouich, Moncef

    2016-01-01

    Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the $p$-levels of ions for large number of values of the effective principal quantum number $n^{*}$ and the Uns\\"old energy $E_p$. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, $n^{*}$ and $E_p$ are obtained, and are shown to reproduce the original data with accuracy clearly better than 10\\%. These relationships allow quick calculations of the ...

  15. High perfomance selectable value transportable high dc Voltage standard

    CERN Document Server

    Galliana, Flavio; Tet, Luca Roncaglione

    2016-01-01

    At National Institute of Metrological Research (INRIM), a selectable-value Transportable High dcVoltage Standard (THVS) operating in the range from 10 V to 100 V in steps of 10 V, was developed. This Standard was built to cover the lack of high level dc Voltage Standards at voltages higher than 10 V to employ as laboratory (local) or travelling Standards for Inter-Laboratory Comparisons (ILCs). A ground-mobile electronic technique was used to enhance the accuracy of the THVS at the higher values. The THVS shows better noise, better short-mid-term stability than top level dc Voltage and multifunction calibrators (MFCs) and better suitability and insensibility to be transported than these instruments. The project is extensible to 1000 V.

  16. Power conditioning for low-voltage piezoelectric stack energy harvesters

    Science.gov (United States)

    Skow, E.; Leadenham, S.; Cunefare, K. A.; Erturk, A.

    2016-04-01

    Low-power vibration and acoustic energy harvesting scenarios typically require a storage component to be charged to enable wireless sensor networks, which necessitates power conditioning of the AC output. Piezoelectric beam-type bending mode energy harvesters or other devices that operate using a piezoelectric element at resonance produce high voltage levels, for which AC-DC converters and step-down DC-DC converters have been previously investigated. However, for piezoelectric stack energy harvesters operating off-resonance and producing low voltage outputs, a step-up circuit is required for power conditioning, such as seen in electromagnetic vibration energy scavengers, RF communications, and MEMS harvesters. This paper theoretically and experimentally investigates power conditioning of a low-voltage piezoelectric stack energy harvester.

  17. Possible role of GABAergic depolarization in neocortical neurons in generating hyperexcitatory behaviors during emergence from sevoflurane anesthesia in the rat

    Directory of Open Access Journals (Sweden)

    Byung‑Gun Lim

    2014-04-01

    Full Text Available Hyperexcitatory behaviors occurring after sevoflurane anesthesia are of serious clinical concern, but the underlying mechanism is unknown. These behaviors may result from the potentiation by sevoflurane of GABAergic depolarization/excitation in neocortical neurons, cells implicated in the genesis of consciousness and arousal. The current study sought to provide evidence for this hypothesis with rats, the neocortical neurons of which are known to respond to GABA (γ-aminobutyric acid with depolarization/excitation at early stages of development (i.e., until the second postnatal week and with hyperpolarization/inhibition during adulthood. Employing behavioral tests and electrophysiological recordings in neocortical slice preparations, we found: (1 sevoflurane produced PAHBs (post-anesthetic hyperexcitatory behaviors in postnatal day (P1–15 rats, whereas it failed to elicit PAHBs in P16 or older rats; (2 GABAergic PSPs (postsynaptic potentials were depolarizing/excitatory in the neocortical neurons of P5 and P10 rats, whereas mostly hyperpolarizing/inhibitory in the cells of adult rats; (3 at P14–15, <50% of rats had PAHBs and, in general, the cells of the animals with PAHBs exhibited strongly depolarizing GABAergic PSPs, whereas those without PAHBs showed hyperpolarizing or weakly depolarizing GABAergic PSPs; (4 bumetanide [inhibitor of the Cl− importer NKCC (Na+–K+–2Cl− cotransporter] treatment at P5 suppressed PAHBs and depolarizing GABAergic responses; and (5 sevoflurane at 1% (i.e., concentration <1 minimum alveolar concentration potentiated depolarizing GABAergic PSPs in the neurons of P5 and P10 rats and of P14–15 animals with PAHBs, evoking action potentials in ≥50% of these cells. On the basis of these results, we conclude that sevoflurane may produce PAHBs by potentiating GABAergic depolarization/excitation in neocortical neurons.

  18. Faraday isolator based on a TSAG single crystal with compensation of thermally induced depolarization inside magnetic field

    Science.gov (United States)

    Snetkov, Ilya; Palashov, Oleg

    2015-04-01

    A Faraday isolator based on a terbium scandium aluminum garnet (TSAG) single crystal with compensation of thermally induced depolarization inside magnetic field was demonstrated. An isolation ratio of 32 dB at 350 W cw laser radiation power was achieved. Thermally induced depolarization and thermal lens were studied and compared with similar thermal effects arising in the widely used terbium gallium garnet crystal (TGG) for the first time.

  19. Observations of the spectral dependence of linear particle depolarization ratio of aerosols using NASA Langley airborne High Spectral Resolution Lidar

    Science.gov (United States)

    Burton, S. P.; Hair, J. W.; Kahnert, M.; Ferrare, R. A.; Hostetler, C. A.; Cook, A. L.; Harper, D. B.; Berkoff, T. A.; Seaman, S. T.; Collins, J. E.; Fenn, M. A.; Rogers, R. R.

    2015-12-01

    Linear particle depolarization ratio is presented for three case studies from the NASA Langley airborne High Spectral Resolution Lidar-2 HSRL-2). Particle depolarization ratio from lidar is an indicator of non-spherical particles and is sensitive to the fraction of non-spherical particles and their size. The HSRL-2 instrument measures depolarization at three wavelengths: 355, 532, and 1064 nm. The three measurement cases presented here include two cases of dust-dominated aerosol and one case of smoke aerosol. These cases have partial analogs in earlier HSRL-1 depolarization measurements at 532 and 1064 nm and in literature, but the availability of three wavelengths gives additional insight into different scenarios for non-spherical particles in the atmosphere. A case of transported Saharan dust has a spectral dependence with a peak of 0.30 at 532 nm with smaller particle depolarization ratios of 0.27 and 0.25 at 1064 and 355 nm, respectively. A case of aerosol containing locally generated wind-blown North American dust has a maximum of 0.38 at 1064 nm, decreasing to 0.37 and 0.24 at 532 and 355 nm, respectively. The cause of the maximum at 1064 nm is inferred to be very large particles that have not settled out of the dust layer. The smoke layer has the opposite spectral dependence, with the peak of 0.24 at 355 nm, decreasing to 0.09 and 0.02 at 532 and 1064 nm, respectively. The depolarization in the smoke case may be explained by the presence of coated soot aggregates. We note that in these specific case studies, the linear particle depolarization ratio for smoke and dust-dominated aerosol are more similar at 355 nm than at 532 nm, having possible implications for using the particle depolarization ratio at a single wavelength for aerosol typing.

  20. Possible Role of GABAergic Depolarization in Neocortical Neurons in Generating Hyperexcitatory Behaviors during Emergence from Sevoflurane Anesthesia in the Rat

    Directory of Open Access Journals (Sweden)

    Byung-Gun Lim

    2014-03-01

    Full Text Available Hyperexcitatory behaviors occurring after sevoflurane anesthesia are of serious clinical concern, but the underlying mechanism is unknown. These behaviors may result from the potentiation by sevoflurane of GABAergic depolarization/excitation in neocortical neurons, cells implicated in the genesis of consciousness and arousal. The current study sought to provide evidence for this hypothesis with rats, the neocortical neurons of which are known to respond to GABA (γ-aminobutyric acid with depolarization/excitation at early stages of development (i.e., until the second postnatal week and with hyperpolarization/inhibition during adulthood. Employing behavioral tests and electrophysiological recordings in neocortical slice preparations, we found: (1 sevoflurane produced PAHBs (post-anesthetic hyperexcitatory behaviors in postnatal day (P1–15 rats, whereas it failed to elicit PAHBs in P16 or older rats; (2 GABAergic PSPs (postsynaptic potentials were depolarizing/excitatory in the neocortical neurons of P5 and P10 rats, whereas mostly hyperpolarizing/inhibitory in the cells of adult rats; (3 at P14–15, <50 % of rats had PAHBs and, in general, the cells of the animals with PAHBs exhibited strongly depolarizing GABAergic PSPs, whereas those without PAHBs showed hyperpolarizing or weakly depolarizing GABAergic PSPs; (4 bumetanide [inhibitor of the Cl− importer NKCC (Na+ -K+−2Cl− cotransporter] treatment at P5 suppressed PAHBs and depolarizing GABAergic responses; and (5 sevoflurane at 1 % (i.e., concentration <1 minimum alveolar concentration potentiated depolarizing GABAergic PSPs in the neurons of P5 and P10 rats and of P14–15 animals with PAHBs, evoking action potentials in ≥50% of these cells. On the basis of these results, we conclude that sevoflurane may produce PAHBs by potentiating GABAergic depolarization/excitation in neocortical neurons.

  1. Voltage balancing strategies for serial connection of microbial fuel cells

    Science.gov (United States)

    Khaled, Firas; Ondel, Olivier; Allard, Bruno; Buret, François

    2015-07-01

    The microbial fuel cell (MFC) converts electrochemically organic matter into electricity by means of metabolisms of bacteria. The MFC power output is limited by low voltage and low current characteristics in the range of microwatts or milliwatts per litre. In order to produce a sufficient voltage level (>1.5 V) and sufficient power to supply real applications such as autonomous sensors, it is necessary to either scale-up one single unit or to connect multiple units together. Many topologies of connection are possible as the serial association to improve the output voltage, or the parallel connection to improve the output current or the series/parallel connection to step-up both voltage and current. The association of MFCs in series is a solution to increase the voltage to an acceptable value and to mutualize the unit's output power. The serial association of a large number of MFCs presents several issues. The first one is the hydraulic coupling among MFCs when they share the same substrate. The second one is the dispersion between generators that lead to a non-optimal stack efficiency because the maximum power point (MPP) operation of all MFCs is not permitted. Voltage balancing is a solution to compensate non-uniformities towards MPP. This paper presents solutions to improve the efficiency of a stack of serially connected MFCs through a voltage-balancing circuit. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014)", edited by Adel Razek

  2. A compact, all solid-state LC high voltage generator.

    Science.gov (United States)

    Fan, Xuliang; Liu, Jinliang

    2013-06-01

    LC generator is widely applied in the field of high voltage generation technology. A compact and all solid-state LC high voltage generator based on saturable pulse transformer is proposed in this paper. First, working principle of the generator is presented. Theoretical analysis and circuit simulation are used to verify the design of the generator. Experimental studies of the proposed LC generator with two-stage main energy storage capacitors are carried out. And the results show that the proposed LC generator operates as expected. When the isolation inductance is 27 μH, the output voltage is 1.9 times larger than the charging voltage on single capacitor. The multiplication of voltages is achieved. On the condition that the primary energy storage capacitor is charged to 857 V, the output voltage of the generator can reach to 59.5 kV. The step-up ratio is nearly 69. When self breakdown gas gap switch is used as main switch, the rise time of the voltage pulse on load resistor is 8.7 ns. It means that the series-wound inductance in the discharging circuit is very small in this system. This generator can be employed in two different applications.

  3. Voltage-gated sodium channels: mutations, channelopathies and targets.

    Science.gov (United States)

    Andavan, G S B; Lemmens-Gruber, R

    2011-01-01

    Voltage-gated sodium channels produce fast depolarization, which is responsible for the rising phase of the action potential in neurons, muscles and heart. These channels are very large membrane proteins and are encoded by ten genes in mammals. Sodium channels are a crucial component of excitable tissues; hence, they are a target for various neurotoxins that are produced by plants and animals for defence and protection, such as tetrodotoxin, scorpion toxins and batrachotoxin. Several mutations in various sodium channel subtypes cause multiple inherited diseases known as channelopathies. When these mutated sodium channel subtypes are expressed in various tissues, channelopathies in brain, skeletal muscle and cardiac muscle develop as well as neuropathic pain. In this review, we discuss aspects of voltage-gated sodium channel genes with an emphasis on cardiac muscle sodium channels. In addition, we report novel mutations that underlie a spectrum of diseases, such as Brugada, long QT syndrome and inherited conduction disorders. Furthermore, this review explains commonalities and differences among the channel subtypes, the channelopathies caused by the sodium channel gene mutation and the specificity of toxins and blockers of the channel subtypes.

  4. The voltage dependence of Ih in human myelinated axons

    Science.gov (United States)

    Howells, James; Trevillion, Louise; Bostock, Hugh; Burke, David

    2012-01-01

    HCN channels are responsible for Ih, a voltage-gated inwardly rectifying current activated by hyperpolarization. This current appears to be more active in human sensory axons than motor and may play a role in the determination of threshold. Differences in Ih are likely to be responsible for the high variability in accommodation to hyperpolarization seen in different subjects. The aim of this study was to characterise this current in human axons, both motor and sensory. Recordings of multiple axonal excitability properties were performed in 10 subjects, with a focus on the changes in threshold evoked by longer and stronger hyperpolarizing currents than normally studied. The findings confirm that accommodation to hyperpolarization is greater in sensory than motor axons in all subjects, but the variability between subjects was greater than the modality difference. An existing model of motor axons was modified to take into account the behaviour seen with longer and stronger hyperpolarization, and a mathematical model of human sensory axons was developed based on the data collected. The differences in behaviour of sensory and motor axons and the differences between different subjects are best explained by modulation of the voltage dependence, along with a modest increase of expression of the underlying conductance of Ih. Accommodation to hyperpolarization for the mean sensory data is fitted well with a value of −94.2 mV for the mid-point of activation (V0.5) of Ih as compared to −107.3 mV for the mean motor data. The variation in response to hyperpolarization between subjects is accounted for by varying this parameter for each modality (sensory: −89.2 to −104.2 mV; motor −87.3 to −127.3 mV). These voltage differences are within the range that has been described for physiological modulation of Ih function. The presence of slowly activated Ih isoforms on both motor and sensory axons was suggested by modelling a large internodal leak current and a masking of

  5. β-Adrenergic receptor agonist increases voltage-gated Na(+) currents in medial prefrontal cortex pyramidal neurons.

    Science.gov (United States)

    Szulczyk, Bartlomiej

    2015-05-19

    The prefrontal cortex does not function properly in neuropsychiatric diseases and during chronic stress. The aim of this study was to test the effects of isoproterenol, a β-adrenergic receptor agonist, on the voltage-dependent fast-inactivating Na(+) currents in medial prefrontal cortex (mPFC) pyramidal neurons obtained from young rats. The recordings were performed in the cell-attached configuration. Isoproterenol (2μM) did not change the peak Na(+) current amplitude but shifted the IV curve of the Na(+) currents toward hyperpolarization. Pretreatment of the cells with the β-adrenergic antagonists propranolol and metoprolol abolished the effect of isoproterenol on the Na(+) currents, suggesting the involvement of β1-adrenergic receptors. The effect of β-adrenergic receptor stimulation on the sodium currents was dependent on kinase A and kinase C; the effect was diminished in the presence of the kinase A antagonist H-89 and the kinase C antagonist chelerythrine and abolished when the antagonists were coapplied. Moreover, isoproterenol depolarized the membrane potential recorded using the perforated-patch method, and this depolarization was abolished by cesium ions. Thus, in mPFC pyramidal neurons, stimulation of β-adrenergic receptors up-regulates the fast-inactivating voltage-gated Na(+) currents evoked by suprathreshold depolarizations.

  6. Quantitative analysis of irreversibilities causes voltage drop in fuel cell (simulation and modeling)

    Energy Technology Data Exchange (ETDEWEB)

    Ghadamian, Hossein [Azad Univ., Dept. of Energy Engineering, Tehran (Iran); Saboohi, Yadolah [Sharif Energy Research Inst. (SERI), Tehran (Iran)

    2004-11-30

    Power level of a fuel cell depends on its operating condition, which is product of voltage and current-density the highest level of voltage is identified as reversible open circuit voltage (ROCV), which represents an ideal theoretical case [J. Larmin, A. Dicks, Fuel Cell System Explained, Wiley, 2000 (ISBN)]. Compared to that is ideal operating voltage which is usually characterized as open circuit voltage (OCV). An evaluation of deviation of operating voltage level from ideal operational case may provide information on the extent of improving efficiency and energy efficiency of a fuel cell. Therefore, quantification of operation deviation from OCV is the main point that is discussed in the present paper. The analysis procedure of voltage drop is based on step-by-step review of voltage drops over activation, internal currents (fuel-cross-over), Ohmic and mass-transport or concentration losses. Accumulated total voltage drops would be estimated as a sum of aforementioned losses. The accumulated voltage drops will then be reduced from OCV to obtain the operating voltage level. The above numerical analysis has been applied to identify the extents of voltage drop. The possible reducing variables in voltage drops reviewed and concluded that the activation loss has considerable impact on total voltage drops and it explains the most part of total losses. It is also found that the following correspondence parameters cause decrease in voltage drops: 1. Temperature increasing; 2. Pressure increasing; 3. Hydrogen or oxygen concentration increasing; 4. Electrode effective surface increasing; 5. Electrode and electrolyte, conductivity modification; 6. Electrolyte thickness reducing up to possible limitation; 7. Connection modification. (Author)

  7. Is Spreading Depolarization Characterized by an Abrupt, Massive Release of Gibbs Free Energy from the Human Brain Cortex?

    Science.gov (United States)

    Dreier, Jens P.; Isele, Thomas; Reiffurth, Clemens; Offenhauser, Nikolas; Kirov, Sergei A.; Dahlem, Markus A.; Herreras, Oscar

    2012-01-01

    In the evolution of the cerebral cortex, the sophisticated organization in a steady state far away from thermodynamic equilibrium has produced the side effect of two fundamental pathological network events: ictal epileptic activity and spreading depolarization. Ictal epileptic activity describes the partial disruption, and spreading depolarization describes the near-complete disruption of the physiological double Gibbs–Donnan steady state. The occurrence of ictal epileptic activity in patients has been known for decades. Recently, unequivocal electrophysiological evidence has been found in patients that spreading depolarizations occur abundantly in stroke and brain trauma. The authors propose that the ion changes can be taken to estimate relative changes in Gibbs free energy from state to state. The calculations suggest that in transitions from the physiological state to ictal epileptic activity to spreading depolarization to death, the cortex releases Gibbs free energy in a stepwise fashion. Spreading depolarization thus appears as a twilight state close to death. Consistently, electrocorticographic recordings in the core of focal ischemia or after cardiac arrest display a smooth transition from the initial spreading depolarization component to the later ultraslow negative potential, which is assumed to reflect processes in cellular death. PMID:22829393

  8. Voltage-Induced Ca²⁺ Release in Postganglionic Sympathetic Neurons in Adult Mice.

    Directory of Open Access Journals (Sweden)

    Hong-Li Sun

    Full Text Available Recent studies have provided evidence that depolarization in the absence of extracellular Ca2+ can trigger Ca2+ release from internal stores in a variety of neuron subtypes. Here we examine whether postganglionic sympathetic neurons are able to mobilize Ca2+ from intracellular stores in response to depolarization, independent of Ca2+ influx. We measured changes in cytosolic ΔF/F0 in individual fluo-4 -loaded sympathetic ganglion neurons in response to maintained K+ depolarization in the presence (2 mM and absence of extracellular Ca2+ ([Ca2+]e. Progressive elevations in extracellular [K+]e caused increasing membrane depolarizations that were of similar magnitude in 0 and 2 mM [Ca2+]e. Peak amplitude of ΔF/F0 transients in 2 mM [Ca2+]e increased in a linear fashion as the membrane become more depolarized. Peak elevations of ΔF/F0 in 0 mM [Ca2+]e were ~5-10% of those evoked at the same membrane potential in 2 mM [Ca2+]e and exhibited an inverse U-shaped dependence on voltage. Both the rise and decay of ΔF/F0 transients in 0 mM [Ca2+]e were slower than those of ΔF/F0 transients evoked in 2 mM [Ca2+]e. Rises in ΔF/F0 evoked by high [K+]e in the absence of extracellular Ca2+ were blocked by thapsigargin, an inhibitor of endoplasmic reticulum Ca2+ ATPase, or the inositol 1,4,5-triphosphate (IP3 receptor antagonists 2-aminoethoxydiphenyl borate and xestospongin C, but not by extracellular Cd2+, the dihydropyridine antagonist nifedipine, or by ryanodine at concentrations that caused depletion of ryanodine-sensitive Ca2+ stores. These results support the notion that postganglionic sympathetic neurons possess the ability to release Ca2+ from IP3-sensitive internal stores in response to membrane depolarization, independent of Ca2+ influx.

  9. Neutralization of Gating Charges in Domain II of the Sodium Channel α Subunit Enhances Voltage-Sensor Trapping by a β-Scorpion Toxin

    Science.gov (United States)

    Cestèle, Sandrine; Scheuer, Todd; Mantegazza, Massimo; Rochat, Hervé; Catterall, William A.

    2001-01-01

    β-Scorpion toxins shift the voltage dependence of activation of sodium channels to more negative membrane potentials, but only after a strong depolarizing prepulse to fully activate the channels. Their receptor site includes the S3–S4 loop at the extracellular end of the S4 voltage sensor in domain II of the α subunit. Here, we probe the role of gating charges in the IIS4 segment in β-scorpion toxin action by mutagenesis and functional analysis of the resulting mutant sodium channels. Neutralization of the positively charged amino acid residues in the IIS4 segment by mutation to glutamine shifts the voltage dependence of channel activation to more positive membrane potentials and reduces the steepness of voltage-dependent gating, which is consistent with the presumed role of these residues as gating charges. Surprisingly, neutralization of the gating charges at the outer end of the IIS4 segment by the mutations R850Q, R850C, R853Q, and R853C markedly enhances β-scorpion toxin action, whereas mutations R856Q, K859Q, and K862Q have no effect. In contrast to wild-type, the β-scorpion toxin Css IV causes a negative shift of the voltage dependence of activation of mutants R853Q and R853C without a depolarizing prepulse at holding potentials from −80 to −140 mV. Reaction of mutant R853C with 2-aminoethyl methanethiosulfonate causes a positive shift of the voltage dependence of activation and restores the requirement for a depolarizing prepulse for Css IV action. Enhancement of sodium channel activation by Css IV causes large tail currents upon repolarization, indicating slowed deactivation of the IIS4 voltage sensor by the bound toxin. Our results are consistent with a voltage-sensor–trapping model in which the β-scorpion toxin traps the IIS4 voltage sensor in its activated position as it moves outward in response to depolarization and holds it there, slowing its inward movement on deactivation and enhancing subsequent channel activation. Evidently

  10. Membrane voltage modulates the GABA(A) receptor gating in cultured rat hippocampal neurons.

    Science.gov (United States)

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W

    2006-02-01

    The kinetics of GABAergic currents in neurons is known to be modulated by the membrane voltage but the underlying mechanisms have not been fully explored. In particular, the impact of membrane potential on the GABA(A) receptor gating has not been elucidated. In the present study, the effect of membrane voltage on current responses elicited by ultrafast GABA applications was studied in cultured hippocampal neurons. The current to voltage relationship (I-V) for responses to saturating [GABA] (10 mM) showed an inward rectification (slope conductance at positive voltages was 0.62 +/- 0.05 of that at negative potentials). On the contrary, I-V for currents evoked by low [GABA] (1 microM) showed an outward rectification. The onset of currents elicited by saturating [GABA] was significantly accelerated at positive potentials. Analysis of currents evoked by prolonged applications of saturating [GABA] revealed that positive voltages significantly increased the rate and extent of desensitization. The onsets of current responses to non-saturating [GABA] were significantly accelerated at positive voltages indicating an enhancement of the binding rate. However, at low [GABA] at which the onset rate is expected to approach an asymptote set by opening/closing and unbinding rates, no significant modification of current onset by voltage was observed. Quantitative analysis based on model simulations indicated that the major effect of membrane depolarization was to increase the rates of binding, desensitization and of opening as well as to slightly reduce the rate of exit from desensitization. In conclusion, we provide evidence that membrane voltage affects the GABA(A) receptor microscopic gating.

  11. Kinetics properties of voltage induced colicin Ia channels into a lipid bilayer

    CERN Document Server

    Cassia-Moura, R

    1998-01-01

    The activation kinetics of the ion channels formed by colicin Ia incorporated into a planar bilayer lipid membrane (BLM) was investigated by the voltage clamp technique using different step voltage stimuli. The temporal behaviour of ion channels put in evidence a gain or a loss of memory, revealed by a specific sequence of electrical pulses used for stimulation.

  12. Development of voltage-dependent calcium, sodium, and potassium currents in Xenopus spinal neurons.

    Science.gov (United States)

    O'Dowd, D K; Ribera, A B; Spitzer, N C

    1988-03-01

    Action potentials of embryonic nerve and muscle cells often have a different ionic dependence and longer duration than those of mature cells. The action potential of spinal cord neurons from Xenopus laevis exhibits a prominent calcium component at early stages of development that diminishes with age as the impulse becomes principally sodium dependent. Whole-cell voltage-clamp analysis has been undertaken to characterize the changes in membrane currents during development of these neurons in culture. Four voltage-dependent currents of cells were identified and examined during the first day in vitro, when most of the change in the action potential occurs. There are no changes in the peak density of the calcium current (ICa), its voltage dependence, or time to half-maximal activation; a small increase in inactivation is apparent. The major change in sodium current (INa) is a 2-fold increase in its density. In addition, more subtle changes in the kinetics of the macroscopic sodium current were noted. The peak density of voltage-dependent potassium current (IKv) increases 3-fold, and this current becomes activated almost twice as fast. No changes were noted in the extent of its inactivation. The calcium-dependent potassium current (IKc) consists of an inactivating and a sustained component. The former increases 2-fold in peak current density, and the latter increases similarly at less depolarized voltages. The changes in these currents contribute to the decrease in duration and the change in ionic dependence of the impulse.

  13. Voltage-dependent currents in microvillar receptor cells of the frog vomeronasal organ.

    Science.gov (United States)

    Trotier, D; Døving, K B; Rosin, J F

    1993-08-01

    Vomeronasal receptor cells are differentiated bipolar neurons with a long dendrite bearing numerous microvilli. Isolated cells (with a mean dendritic length of 65 microns) and cells in mucosal slices were studied using whole-cell and Nystatin-perforated patch-clamp recordings. At rest, the membrane potential was -61 +/- 13 mV (mean +/- SD; n = 61). Sixty-four per cent of the cells had a resting potential in the range of -60 to -86 mV, with almost no spontaneous action potential. The input resistance was in the G omega range and overshooting repetitive action potentials were elicited by injecting depolarizing current pulses in the range of 2-10 pA. Voltage-dependent currents were characterized under voltage-clamp conditions. A transient fast inward current activating near -45 mV was blocked by tetrodotoxin. In isolated cells, it was half-deactivated at a membrane potential near -75 mV. An outward K+ current was blocked by internal Cs+ ions or by external tetraethylammonium or Ba2+ ions. A calcium-activated voltage-dependent potassium current was blocked by external Cd2+ ions. A voltage-dependent Ca2+ current was observed in an iso-osmotic BaCl2 solution. Finally, a hyperpolarization-activated inward current was recorded. Voltage-dependent currents in these microvillar olfactory receptor neurons appear qualitatively similar to those already described in ciliated olfactory receptor cells located in the principal olfactory epithelium.

  14. Ca2+ sparks evoked by depolarization of rat ventricular myocytes involve multiple release sites

    Institute of Scientific and Technical Information of China (English)

    ZANGWei-Jin; YUXiao-Jiang; ZANGYi-Min

    2003-01-01

    AIM:To investigate the fundamental nature of calcium release events (Ca2+‘sparks’) evoked in rat ventricular myocytes during excitation-contraction (E-C) coupling. METHODS: High-resolution line-scan confocal imaging with the fluorescent calcium indicator and patch-clamp techniques were used to study the spontaneous Ca2+ sparks and sparks evoked by depolarization. RESULTS: 1)Line scans oriented along the length of the cell showed that both spontaneous sparks and sparks evoked by depolarization to -35mV appeared to arise at single sites spacing about 1.80μm apart (ie, the sarcomere length), and measurements of their longitudinal spread (full-width at halfmaximal amplitude:FWHM) followed single Gaussian distributions with means of 2.6μm. 2)Different to this,transverse line scans often revealed spontaneous and evoked sparks that appeared to arise near-synchronously from paired sites. Measurements of transverse FWHM of both spontaneous and evoked sparks showed bimodal distributions, which were fit well by the sums of two Gaussian curves with means of 1.8 and 2.9μm for spontaneous sparks and ith means of 1.9 and 3.1 μm for evoked sparks. Relative areas under the two Gaussian curves were 1.73:1 and 1.85:1, respectively, for spontaneous and evoked sparks. CONCLUSIONS: Ca2+ sparks evoked by depolarization are not ′unitary′ events, but often involve multiple sites of origin along Z-lines, as previously shown for spontaneous sparks. Thus, Ca2+ released during sparks directly triggered by influx through L-type Ca2+ channels may, in turn, trigger neighboring sites. The restricted involvement of only a few transverse release sites preserves the essential feature of the ‘local control’ theory of E-C coupling.

  15. Depolarizing actions of GABA in immature neurons depend neither on ketone bodies nor on pyruvate.

    Science.gov (United States)

    Tyzio, Roman; Allene, Camille; Nardou, Romain; Picardo, Michel A; Yamamoto, Sumii; Sivakumaran, Sudhir; Caiati, Maddalena D; Rheims, Sylvain; Minlebaev, Marat; Milh, Mathieu; Ferré, Pascal; Khazipov, Rustem; Romette, Jean-Louis; Lorquin, Jean; Cossart, Rosa; Khalilov, Ilgam; Nehlig, Astrid; Cherubini, Enrico; Ben-Ari, Yehezkel

    2011-01-05

    GABA depolarizes immature neurons because of a high [Cl(-)](i) and orchestrates giant depolarizing potential (GDP) generation. Zilberter and coworkers (Rheims et al., 2009; Holmgren et al., 2010) showed recently that the ketone body metabolite DL-3-hydroxybutyrate (DL-BHB) (4 mM), lactate (4 mM), or pyruvate (5 mM) shifted GABA actions to hyperpolarizing, suggesting that the depolarizing effects of GABA are attributable to inadequate energy supply when glucose is the sole energy source. We now report that, in rat pups (postnatal days 4-7), plasma D-BHB, lactate, and pyruvate levels are 0.9, 1.5, and 0.12 mM, respectively. Then, we show that DL-BHB (4 mM) and pyruvate (200 μM) do not affect (i) the driving force for GABA(A) receptor-mediated currents (DF(GABA)) in cell-attached single-channel recordings, (2) the resting membrane potential and reversal potential of synaptic GABA(A) receptor-mediated responses in perforated patch recordings, (3) the action potentials triggered by focal GABA applications, or (4) the GDPs determined with electrophysiological recordings and dynamic two-photon calcium imaging. Only very high nonphysiological concentrations of pyruvate (5 mM) reduced DF(GABA) and blocked GDPs. Therefore, DL-BHB does not alter GABA signals even at the high concentrations used by Zilberter and colleagues, whereas pyruvate requires exceedingly high nonphysiological concentrations to exert an effect. There is no need to alter conventional glucose enriched artificial CSF to investigate GABA signals in the developing brain.

  16. Atropine-resistant depolarization in the guinea-pig small intestine.

    Science.gov (United States)

    Bywater, R A; Holman, M E; Taylor, G S

    1981-07-01

    1. Junction potentials were recorded from the circular muscle cells of the guinea-pig ileum following transmural stimulation in the presence of atropine at 30 degrees C.2. Single stimuli produced a transient hyperpolarization, the inhibitory junction potential (i.j.p.). At high stimulus strengths the i.j.p. was followed by a post-stimulus depolarization (PSD).3. During repetitive stimulation the magnitude of the hyperpolarization decreased; however, at the end of the stimulus period the PSD was enhanced and often reached threshold for the generation of action potentials. Thus, the size of the PSD was not directly related to the degree of the preceding hyperpolarization.4. Hyperpolarization of the circular muscle cells was produced by the application of anodal current using large external electrodes. Rapid cessation of the applied current produced a transient after-depolarization which was shorter in time course than the PSD following the i.j.p. If the applied anodal current was reduced slowly (at a rate which mimicked the decrease in the hyperpolarization during repetitive nerve stimulation) no after-depolarization was observed.5. Conditioning hyperpolarization of the circular muscle cells reduced the amplitude of the i.j.p. The i.j.p. was reversed at membrane potentials greater than approximately -90 mV.6. The PSD did not appear to be due to the extracellular accumulation of potassium ions following the i.j.p. since the PSD persisted even when the i.j.p. was reversed.7. The neurotoxin apamin reversibly abolished the i.j.p. and unmasked a transient excitatory junction potential (e.j.p.) with a variable latency (350-900 ms).

  17. Vanadate induces necrotic death in neonatal rat cardiomyocytes through mitochondrial membrane depolarization.

    Science.gov (United States)

    Soares, Sandra Sofia; Henao, Fernando; Aureliano, Manuel; Gutiérrez-Merino, Carlos

    2008-03-01

    Besides the well-known inotropic effects of vanadium in cardiac muscle, previous studies have shown that vanadate can stimulate cell growth or induce cell death. In this work, we studied the toxicity to neonatal rat ventricular myocytes (cardiomyocytes) of two vanadate solutions containing different oligovanadates distribution, decavanadate (containing decameric vanadate, V 10) and metavanadate (containing monomeric vanadate and also di-, tetra-, and pentavanadate). Incubation for 24 h with decavanadate or metavanadate induced necrotic cell death of cardiomyocytes, without significant caspase-3 activation. Only 10 microM total vanadium of either decavanadate (1 microM V 10) or metavanadate (10 microM total vanadium) was needed to produce 50% loss of cell viability after 24 h (assessed with MTT and propidium iodide assays). Atomic absorption spectroscopy showed that vanadium accumulation in cardiomyocytes after 24 h was the same when incubation was done with decavanadate or metavanadate. A decrease of 75% of the rate of mitochondrial superoxide anion generation, monitored with dihydroethidium, and a sustained rise of cytosolic calcium (monitored with Fura-2-loaded cardiomyocytes) was observed after 24 h of incubation of cardiomyocytes with decavanadate or metavanadate concentrations close to those inducing 50% loss of cell viability produced. In addition, mitochondrial membrane depolarization within cardiomyocytes, monitored with tetramethylrhodamine ethyl esther or with 3,3',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide, were observed after only 6 h of incubation with decavanadate or metavanadate. The concentration needed for 50% mitochondrial depolarization was 6.5 +/- 1 microM total vanadium for both decavanadate (0.65 microM V 10) and metavanadate. In conclusion, mitochondrial membrane depolarization was an early event in decavanadate- and monovanadate-induced necrotic cell death of cardiomyocytes.

  18. Deciphering voltage-gated Na(+) and Ca(2+) channels by studying prokaryotic ancestors.

    Science.gov (United States)

    Catterall, William A; Zheng, Ning

    2015-09-01

    Voltage-gated sodium channels (NaVs) and calcium channels (CaVs) are involved in electrical signaling, contraction, secretion, synaptic transmission, and other physiological processes activated in response to depolarization. Despite their physiological importance, the structures of these closely related proteins have remained elusive because of their size and complexity. Bacterial NaVs have structures analogous to a single domain of eukaryotic NaVs and CaVs and are their likely evolutionary ancestor. Here we review recent work that has led to new understanding of NaVs and CaVs through high-resolution structural studies of their prokaryotic ancestors. New insights into their voltage-dependent activation and inactivation, ion conductance, and ion selectivity provide realistic structural models for the function of these complex membrane proteins at the atomic level. Published by Elsevier Ltd.

  19. The way to collisions, step by step

    CERN Multimedia

    2009-01-01

    While the LHC sectors cool down and reach the cryogenic operating temperature, spirits are warming up as we all eagerly await the first collisions. No reason to hurry, though. Making particles collide involves the complex manoeuvring of thousands of delicate components. The experts will make it happen using a step-by-step approach.

  20. Internship guide : Work placements step by step

    NARCIS (Netherlands)

    Haag, Esther

    2013-01-01

    Internship Guide: Work Placements Step by Step has been written from the practical perspective of a placement coordinator. This book addresses the following questions : what problems do students encounter when they start thinking about the jobs their degree programme prepares them for? How do you

  1. Internship guide : Work placements step by step

    NARCIS (Netherlands)

    Haag, Esther

    2013-01-01

    Internship Guide: Work Placements Step by Step has been written from the practical perspective of a placement coordinator. This book addresses the following questions : what problems do students encounter when they start thinking about the jobs their degree programme prepares them for? How do you fi

  2. On Computational Small Steps and Big Steps

    DEFF Research Database (Denmark)

    Johannsen, Jacob

    rules in the small-step semantics cause the refocusing step of the syntactic correspondence to be inapplicable. Second, we propose two solutions to overcome this in-applicability: backtracking and rule generalization. Third, we show how these solutions affect the other transformations of the two...

  3. Depolarization corrections to the coercive field in thin-film ferroelectrics

    CERN Document Server

    Dawber, M; Littlewood, P B; Scott, J F

    2003-01-01

    Empirically, the coercive field needed to reverse the polarization in a ferroelectric increases with decreasing film thickness. For ferroelectric films of 100 mu m to 100 nm in thickness the coercive field has been successfully described by a semi-empirical scaling law. Accounting for depolarization corrections, we show that this scaling behaviour is consistent with field measurements of ultrathin ferroelectric capacitors down to one nanometre in film thickness. Our results also indicate that the minimum film thickness, determined by a polarization instability, can be tuned by the choice of electrodes, and recommendations for next-generation ferroelectric devices are discussed. (letter to the editor)

  4. Flux lattice behavior in high- T sub c materials studied by neutron depolarization

    Energy Technology Data Exchange (ETDEWEB)

    Crow, M.L.; Goyette, R.J.; Nunes, A.C.; Pickart, S.J. (University of Rhode Island, Kingston, Rhode Island 02881 (USA)); McGuire, T.R.; Shinde, S.; Shaw, T.M. (IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (USA))

    1990-05-01

    The depolarization of a neutron beam passing through a sample of the high-{ital T}{sub {ital c}} superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} has been measured as a function of temperature and applied field. The difference in behavior between field-cooled and zero-field-cooled states, the observation of hysteresis correlated with {ital H}{sub {ital c}1}, and the disappearance of the effect near 55 K (below {ital T}{sub {ital c}}) suggest an explanation in terms of vortex line lattice formation with possible connection to recently proposed flux line entanglement and melting.

  5. Numerical simulation study on spin resonant depolarization due to spin-orbit coupling

    Institute of Scientific and Technical Information of China (English)

    Lan Jie-Qin; Xu Hong-Liang

    2012-01-01

    The spin polarization phenomenon in lepton circular accelerators had been known for many years.It provides a new approach for physicists to study the spin feature of fundamental particles and the dynamics of spin-orbit coupling,such as spin resonances.We use numerical simulation to study the features of spin under the modulation of orbital motion in an electron storage ring.The various cases of depolarization due to spin-orbit coupling through an emitting photon and misalignment of magnets in the ring are discussed.

  6. Rotational relaxation of 70S ribosomes by a depolarization method using triplet probes.

    Science.gov (United States)

    Lavalette, D; Amand, B; Pochon, F

    1977-01-01

    Rotational relaxation on the microsecond time scale has been followed by a depolarization technique using the properties of the long-lived triplet state of covalently bound labels. Two triplet probes, which efficiently bind to ribosomal proteins, are described. The rotational correlation time of 70S ribosomes of Escherichia coli has been measured. The average hydrodynamic radius of the functionally active 70S particle in solution has been estimated to 147 A. A concentration dependence of the correlation time has been observed, which may result from an association of the 70S ribosomes to form 100S dimers. PMID:323851

  7. Local mobility of polymer chain grafted onto polyethylene monitored by fluorescence depolarization

    Science.gov (United States)

    Tsuneda, Satoshi; Endo, Toshihiro; Saito, Kyoichi; Sugita, Kazuyuki; Horie, Kazuyuki; Yamashita, Takashi; Sugo, Takanobu

    1997-08-01

    The fluorescence depolarization method was used for investigating the local mobility of polymer chains grafted onto a porous polyethylene membrane. The real value of the rotational diffusion coefficient of a dansyl probe attached to the grafted polymer chain was obtained by using a correction method which eliminated the effect of multiple scattering on fluorescence anisotropy. The rotational mobility of the dansyl probe attached to the grafted polymer chain was sensitive to both degree of grafting and solvent polarity, which indicated that the conformation of the grafted polymer chain and the pore size of the base membrane strongly governed the dynamic parameters of the grafted polymer chain.

  8. Depolarization Induced Suppression of Excitation and the Emergence of Ultraslow Rhythms in Neural Networks

    Science.gov (United States)

    Hlinka, J.; Coombes, S.

    2010-02-01

    Ultraslow fluctuations (0.01-0.1 Hz) are a feature of intrinsic brain activity of as yet unclear origin. We propose a candidate mechanism based on retrograde endocannabinoid signaling in a synaptically coupled network of excitatory neurons. This is known to cause depolarization-induced suppression of excitation (DISE), which we model phenomenologically. We construct emergent network oscillations in a globally coupled network and show that for strong synaptic coupling DISE can lead to a synchronized population burst at the frequencies of resting brain rhythms.

  9. Inhibitory nature of tiagabine-augmented GABAA receptor-mediated depolarizing responses in hippocampal pyramidal cells.

    Science.gov (United States)

    Jackson, M F; Esplin, B; Capek, R

    1999-03-01

    Tiagabine is a potent GABA uptake inhibitor with demonstrated anticonvulsant activity. GABA uptake inhibitors are believed to produce their anticonvulsant effects by prolonging the postsynaptic actions of GABA, released during episodes of neuronal hyperexcitability. However, tiagabine has recently been reported to facilitate the depolarizing actions of GABA in the CNS of adult rats following the stimulation of inhibitory pathways at a frequency (100 Hz) intended to mimic interneuronal activation during epileptiform activity. In the present study, we performed extracellular and whole cell recordings from CA1 pyramidal neurons in rat hippocampal slices to examine the functional consequences of tiagabine-augmented GABA-mediated depolarizing responses. Orthodromic population spikes (PSs), elicited from the stratum radiatum, were inhibited following the activation of recurrent inhibitory pathways by antidromic conditioning stimulation of the alveus, which consisted of either a single stimulus or a train of stimuli delivered at high-frequency (100 Hz, 200 ms). The inhibition of orthodromic PSs produced by high-frequency conditioning stimulation (HFS), which was always of much greater strength and duration than that produced by a single conditioning stimulus, was greatly enhanced following the bath application of tiagabine (2-100 microM). Thus, in the presence of tiagabine (20 microM), orthodromic PSs, evoked 200 and 800 ms following HFS, were inhibited to 7.8 +/- 2.6% (mean +/- SE) and 34.4 +/- 18.5% of their unconditioned amplitudes compared with only 35.4 +/- 12.7% and 98.8 +/- 12.4% in control. Whole cell recordings revealed that the bath application of tiagabine (20 microM) either caused the appearance or greatly enhanced the amplitude of GABA-mediated depolarizing responses (DR). Excitatory postsynaptic potentials (EPSPs) evoked from stratum radiatum at time points that coincided with the DR were inhibited to below the threshold for action-potential firing

  10. Accuracy of depolarization and delay spread predictions using advanced ray-based modeling in indoor scenarios

    Directory of Open Access Journals (Sweden)

    Mani Francesco

    2011-01-01

    Full Text Available Abstract This article investigates the prediction accuracy of an advanced deterministic propagation model in terms of channel depolarization and frequency selectivity for indoor wireless propagation. In addition to specular reflection and diffraction, the developed ray tracing tool considers penetration through dielectric blocks and/or diffuse scattering mechanisms. The sensitivity and prediction accuracy analysis is based on two measurement campaigns carried out in a warehouse and an office building. It is shown that the implementation of diffuse scattering into RT significantly increases the accuracy of the cross-polar discrimination prediction, whereas the delay-spread prediction is only marginally improved.

  11. Spatial evolution of depolarization in homogeneous turbid media within the differential Mueller matrix formalism.

    Science.gov (United States)

    Agarwal, Naman; Yoon, Jiho; Garcia-Caurel, Enric; Novikova, Tatiana; Vanel, Jean-Charles; Pierangelo, Angelo; Bykov, Alexander; Popov, Alexey; Meglinski, Igor; Ossikovski, Razvigor

    2015-12-01

    We show, through visible-range Mueller polarimetry, as well as numerical simulations, that the depolarization in a homogeneous turbid medium consisting of submicron spherical particles follows a parabolic law with the path-length traveled by light through the medium. This result is in full agreement with the phenomenological theory of the fluctuating medium within the framework of the differential Mueller matrix formalism. We further found that the standard deviations of the fluctuating elementary polarization properties of the medium depend linearly on the concentration of particles. These findings are believed to be useful for the phenomenological interpretation of polarimetric experiments, with special emphasis on biomedical applications.

  12. The S4-S5 linker couples voltage sensing and activation of pacemaker channels.

    Science.gov (United States)

    Chen, J; Mitcheson, J S; Tristani-Firouzi, M; Lin, M; Sanguinetti, M C

    2001-09-25

    Voltage-gated channels are normally opened by depolarization and closed by repolarization of the membrane. Despite sharing significant sequence homology with voltage-gated K(+) channels, the gating of hyperpolarization-activated, cyclic-nucleotide-gated (HCN) pacemaker channels has the opposite dependence on membrane potential: hyperpolarization opens, whereas depolarization closes, these channels. The mechanism and structural basis of the process that couples voltage sensor movement to HCN channel opening and closing is not understood. On the basis of our previous studies of a mutant HERG (human ether-a-go-go-related gene) channel, we hypothesized that the intracellular linker that connects the fourth and fifth transmembrane domains (S4-S5 linker) of HCN channels might be important for channel gating. Here, we used alanine-scanning mutagenesis of the HCN2 S4-S5 linker to identify three residues, E324, Y331, and R339, that when mutated disrupted normal channel closing. Mutation of a basic residue in the S4 domain (R318Q) prevented channel opening, presumably by disrupting S4 movement. However, channels with R318Q and Y331S mutations were constitutively open, suggesting that these channels can open without a functioning S4 domain. We conclude that the S4-S5 linker mediates coupling between voltage sensing and HCN channel activation. Our findings also suggest that opening of HCN and related channels corresponds to activation of a gate located near the inner pore, rather than recovery of channels from a C-type inactivated state.

  13. The effects of S4 segments on the voltage-dependence of inactivation for Cav3.1 calcium channels

    Institute of Scientific and Technical Information of China (English)

    LI JunYing

    2007-01-01

    T-type calcium channels exhibit fast voltage-dependent inactivation,for which the underlying structure-function relationship still remains unclear.To investigate the roles of S4 segments in voltage-dependent inactivation of T-type calcium channels,we created S4 replacement chimeras between Cav3.1 calcium channels(fast voltage-dependent inactivation)and Cav1.2 calcium channels(little oltage-dependent inactivation)by replacing S4s in Cav3.1 with the corresponding regions in Cav1.2.Wild type and chimeric channels were expressed in Xenopus oocytes and channel currents were recorded with two-electrode voltage-clamp.We showed that replacing S4 region in domain I shifted voltage-dependence for inactivation of Cav3.1 to the left,and the V0.5 inact and kinact value were significantly changed.However replacing S4s in domains Ⅱ-Ⅳ had no effects on the voltage-dependent inactivation properties.These results suggest that the roles of S4 segments in domains Ⅰ-Ⅳ are different,and S4 in domain I is likely to be involved in voltage-dependent Inactivation process.Its movement during membrane depolarization may trigger a conformational change in the inactivation gate.

  14. Aging-associated changes in motor axon voltage-gated Na(+) channel function in mice.

    Science.gov (United States)

    Moldovan, Mihai; Rosberg, Mette Romer; Alvarez, Susana; Klein, Dennis; Martini, Rudolf; Krarup, Christian

    2016-03-01

    Accumulating myelin abnormalities and conduction slowing occur in peripheral nerves during aging. In mice deficient of myelin protein P0, severe peripheral nervous system myelin damage is associated with ectopic expression of Nav1.8 voltage-gated Na(+) channels on motor axons aggravating the functional impairment. The aim of the present study was to investigate the effect of regular aging on motor axon function with particular emphasis on Nav1.8. We compared tibial nerve conduction and excitability measures by threshold tracking in 12 months (mature) and 20 months (aged) wild-type (WT) mice. With aging, deviations during threshold electrotonus were attenuated and the resting current-threshold slope and early refractoriness were increased. Modeling indicated that, in addition to changes in passive membrane properties, motor fibers in aged WT mice were depolarized. An increased Nav1.8 isoform expression was found by immunohistochemistry. The depolarizing excitability features were absent in Nav1.8 null mice, and they were counteracted in WT mice by a Nav1.8 blocker. Our data suggest that alteration in voltage-gated Na(+) channel isoform expression contributes to changes in motor axon function during aging.

  15. Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

    Science.gov (United States)

    Taft, William C.; Delorenzo, Robert J.

    1984-05-01

    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

  16. Voltage Sensors Monitor Harmful Static

    Science.gov (United States)

    2009-01-01

    A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

  17. Microsoft Office professional 2010 step by step

    CERN Document Server

    Cox, Joyce; Frye, Curtis

    2011-01-01

    Teach yourself exactly what you need to know about using Office Professional 2010-one step at a time! With STEP BY STEP, you build and practice new skills hands-on, at your own pace. Covering Microsoft Word, PowerPoint, Outlook, Excel, Access, Publisher, and OneNote, this book will help you learn the core features and capabilities needed to: Create attractive documents, publications, and spreadsheetsManage your e-mail, calendar, meetings, and communicationsPut your business data to workDevelop and deliver great presentationsOrganize your ideas and notes in one placeConnect, share, and accom

  18. Step-Up DC-DC Power Converter

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a step-up DC-DC power converter which comprises a primary side circuit and a secondary side circuit coupled through a galvanic isolation barrier. The primary side circuit comprises a positive and a negative input terminal for receipt of an input voltage and an input...... being charged from the input voltage and discharged to the output capacitor through the galvanic isolation barrier in accordance with a switch control signal to produce the converter output voltage. The step-up DC-DC power converter comprises an electrical short-circuit connection across the galvanic...... capacitor coupled between the positive and negative input terminals and the secondary side circuit comprises an output capacitor chargeable to a converter output voltage between a first positive electrode and a second negative electrode. A switched energy storage network is configured for alternatingly...

  19. Membrane depolarization induces calcium-dependent secretion of tissue plasminogen activator.

    Science.gov (United States)

    Gualandris, A; Jones, T E; Strickland, S; Tsirka, S E

    1996-04-01

    Tissue plasminogen activator (tPA), a serine protease that converts inactive plasminogen to active plasmin, is produced in the rat and mouse hippocampus and participates in neuronal plasticity. To help define the role of tPA in the nervous system, we have analyzed the regulation of its expression in the neuronal cell line PC12. In control cultures, tPA activity is exclusively cell-associated, and no activity is measurable in the culture medium. When the cells are treated with depolarizing agents, such as KCI, tPA activity becomes detectable in the medium. The increased secreted tPA activity is not accompanied by an increase in tPA mRNA levels, and it is not blocked by protein synthesis inhibitors. In contrast, tPA release is abolished by Ca2+ channel blockers, suggesting that chemically induced membrane depolarization stimulates the secretion of preformed enzyme. Moreover, KCI has a similar effect in vivo when administered to the murine brain via an osmotic pump: tPA activity increases along the CA2-CA3 regions and dentate gyrus of the hippocampal formation. These results demonstrate a neuronal activity-dependent secretory mechanism that can rapidly increase the amount of tPA in neuronal tissue.

  20. Low temperature thermal windowing (TW) thermally stimulated depolarization current (TSDC) setup

    Science.gov (United States)

    Jain, Deepti; Sharath Chandra, L. S.; Nath, R.; Ganesan, V.

    2012-02-01

    We report here the design and implementation of a precise and easy to operate thermally stimulated depolarization current (TSDC) measurement setup for temperature range 77-400 K. The sample loading is made simple by sandwiching the sample between two copper disk electrodes using a spring-shaft arrangement. The salient features of the setup are precise thermal windowing (TW) capability and linear heating rate over the entire temperature range. The resolution in the measurement of depolarization current is of the order of 7×10-14 A. This is achieved by means of good electrical insulation of the electrodes from the rest of the setup and utilization of low noise circuitry. Precision of the system is demonstrated by its capability to resolve constituent relaxations present in complex relaxation processes using the TW experiments. Study and detection of glass transition processes in polyethylene terephthalate, four relaxation processes in polymethyl methacrylate, glass and crystallization transitions along with the onset of ferroelectric Curie transitions in polyvinylidene fluoride and characterization of electret state in amino acids l-arginine, phenylalanine, tyrosine, tryptophan, glutamic acid, glutamine and methionine show the versatility of our setup.

  1. Depolarization of the tegument precedes morphological alterations in Echinococcus granulosus protoscoleces incubated with ivermectin.

    Science.gov (United States)

    Pérez-Serrano, J; Grosman, C; Urrea-París, M A; Denegri, G; Casado, N; Rodríguez-Caabeiro, F

    2001-10-01

    The nematocidal activity of ivermectin (IVM) largely arises from its activity as a potent agonist of muscular and neuronal glutamate-gated chloride channels. A cestocidal effect has also been suggested following in vitro treatments, but the molecular basis of this activity is not clear. We studied the effect of IVM on the metacestode stage of the tapeworm Echinococcus granulosus by assessing the viability, ultrastructure, and tegumental membrane potential as a function of drug concentration and incubation time. Concentrations of 0.1 and 1.0 microg/ml of IVM had no effect on any of these three parameters for up to 6 days of treatment. A concentration of 10 microg/ml, however, elicited a sequence of alterations that started with a approximately 20-mV depolarization of the tegumental membrane, and was followed by rostellar disorganization, rigid paralysis and, eventually, loss of viability. It is likely that the IVM-induced depolarization of the tegument acts as the signal that initiates the cascade of degenerative processes that leads to the parasite's death. This would place the tegument as the primary target of action of IVM on cestodes. As an appropriate chemotherapy for the hydatid disease is still lacking, the cestocidal effect of IVM reported here is worth considering.

  2. Constraining regular and turbulent magnetic field strengths in M51 via Faraday depolarization

    CERN Document Server

    Shneider, Carl; Fletcher, Andrew; Shukurov, Anvar

    2014-01-01

    We employ an analytical model that incorporates both wavelength-dependent and wavelength-independent depolarization to describe radio polarimetric observations of polarization at $\\lambda \\lambda \\lambda \\, 3.5, 6.2, 20.5$ cm in M51 (NGC 5194). The aim is to constrain both the regular and turbulent magnetic field strengths in the disk and halo, modeled as a two- or three-layer magneto-ionic medium, via differential Faraday rotation and internal Faraday dispersion, along with wavelength-independent depolarization arising from turbulent magnetic fields. A reduced chi-squared analysis is used for the statistical comparison of predicted to observed polarization maps to determine the best-fit magnetic field configuration at each of four radial rings spanning $2.4 - 7.2$ kpc in $1.2$ kpc increments. We find that a two-layer modeling approach provides a better fit to the observations than a three-layer model, where the near and far sides of the halo are taken to be identical, although the resulting best-fit magnetic...

  3. Depolarization Ratio of Clouds Measured by Multiple-Field of view Multiple Scattering Polarization Lidar

    Science.gov (United States)

    Okamoto, Hajime; Sato, Kaori; Makino, Toshiyuki; Nishizawa, Tomoaki; Sugimoto, Nobuo; Jin, Yoshitaka; Shimizu, Atsushi

    2016-06-01

    We have developed the Multiple Field of view Multiple Scattering Polarization Lidar (MFMSPL) system for the study of optically thick low-level clouds. It has 8 telescopes; 4 telescopes for parallel channels and another 4 for perpendicular channels. The MFMSPL is the first lidar system that can measure depolarization ratio for optically thick clouds where multiple scattering is dominant. Field of view of each channel was 10mrad and was mounted with different angles ranging from 0 mrad (vertical) to 30mrad. And footprint size from the total FOV was achieved to be close to that of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar at the altitude of 1km in order to reproduce similar degree of multiple scattering effects as observed from space. The MFMSPL has started observations since June 2014 and has been continuously operated at National Institute for Environmental Studies (NIES) in Tsukuba, Japan. Observations proved expected performance such that measured depolarization ratio was comparable to the one observed by CALIPSO lidar.

  4. What Is the Hidden Depolarization Mechanism in Low-luminosity AGNs?

    Science.gov (United States)

    Bower, Geoffrey C.; Dexter, Jason; Markoff, Sera; Rao, Ramprasad; Plambeck, R. L.

    2017-07-01

    Millimeter-wavelength polarimetry of accreting black hole systems can provide a tomographic probe of the accretion flow on a wide range of linear scales. We searched for linear polarization in two low-luminosity active galactic nuclei (LLAGNs), M81 and M84, using the Combined Array for Millimeter Astronomy and the Submillimeter Array. We find upper limits of ˜1%-2% averaging over the full bandwidth and with a rotation measure (RM) synthesis technique. These low polarization fractions, along with similarly low values for LLAGNs M87 and 3C 84, suggest that LLAGNs have qualitatively different polarization properties than radio-loud sources and Sgr A*. If the sources are intrinsically polarized and then depolarized by Faraday rotation, then we place lower limits on the RM of a few times {10}7 {rad} {{{m}}}-2 for the full bandwidth case and ˜ {10}9 {rad} {{{m}}}-2 for the RM synthesis analysis. These limits are inconsistent with or marginally consistent with expected accretion flow properties. Alternatively, the sources may be depolarized by cold electrons within a few Schwarzschild radii from the black hole, as suggested by numerical models.

  5. Anions Govern Cell Volume: A Case Study of Relative Astrocytic and Neuronal Swelling in Spreading Depolarization.

    Directory of Open Access Journals (Sweden)

    Niklas Hübel

    Full Text Available Cell volume changes are ubiquitous in normal and pathological activity of the brain. Nevertheless, we know little about the dynamics of cell and tissue swelling, and the differential changes in the volumes of neurons and glia during pathological states such as spreading depolarizations (SD under ischemic and non-ischemic conditions, and epileptic seizures. By combining the Hodgkin-Huxley type spiking dynamics, dynamic ion concentrations, and simultaneous neuronal and astroglial volume changes into a comprehensive model, we elucidate why glial cells swell more than neurons in SD and the special case of anoxic depolarization (AD, and explore the relative contributions of the two cell types to tissue swelling. Our results demonstrate that anion channels, particularly Cl-, are intrinsically connected to cell swelling and blocking these currents prevents changes in cell volume. The model is based on a simple and physiologically realistic description. We introduce model extensions that are either derived purely from first physical principles of electroneutrality, osmosis, and conservation of particles, or by a phenomenological combination of these principles and known physiological facts. This work provides insights into numerous studies related to neuronal and glial volume changes in SD that otherwise seem contradictory, and is broadly applicable to swelling in other cell types and conditions.

  6. Anoxic depolarization of hippocampal astrocytes: possible modulation by P2X7 receptors.

    Science.gov (United States)

    Leichsenring, Anna; Riedel, Thomas; Qin, Ying; Rubini, Patrizia; Illes, Peter

    2013-01-01

    Current responses from CA1 neurons and stratum oriens astrocytes were recorded from hippocampal brain slices by means of the whole-cell patch-clamp technique. Anoxic depolarization (AD) was induced by an oxygen/glucose-deprived (OGD) medium also containing sodium iodoacetate and antimycin, in order to block glycolysis and oxidative phosphorylation, respectively. Anoxic depolarization has been reported to be due to the sudden increase of the extracellular K(+) concentration and the accompanying explosive rise in glutamate concentration. We asked ourselves whether the release of ATP activating P2X7 receptors is also involved in the AD. Although, the AD was evoked in absolute synchrony in neurons and astrocytes, and the NMDA receptor antagonistic AP-5 depressed these responses, neither the non-selective P2 receptor antagonist PPADS, nor the highly selective P2X7 receptor antagonist A438079 interfered with the AD or its delay time in neurons/astrocytes after inducing chemical hypoxia. However, A438079, but not PPADS increased in astrocytes the slow inward current observed in a hypoxic medium. It is concluded that ATP co-released with glutamate by hypoxic stimulation has only a minor function in the present brain slice system.

  7. Understanding order in compositionally graded ferroelectrics: Flexoelectricity, gradient, and depolarization field effects

    Science.gov (United States)

    Zhang, J.; Xu, R.; Damodaran, A. R.; Chen, Z.-H.; Martin, L. W.

    2014-06-01

    A nonlinear thermodynamic formalism based on Ginzburg-Landau-Devonshire theory is developed to describe the total free energy density in (001)-oriented, compositionally graded, and monodomain ferroelectric films including the relative contributions and importance of flexoelectric, gradient, and depolarization energy terms. The effects of these energies on the evolution of the spontaneous polarization, dielectric permittivity, and the pyroelectric coefficient as a function of position throughout the film thickness, temperature, and epitaxial strain state are explored. In general, the presence of a compositional gradient and the three energy terms tend to stabilize a polar, ferroelectric state even in compositions that should be paraelectric in the bulk. Flexoelectric effects produce large built-in fields which diminish the temperature dependence of the polarization and susceptibilities. Gradient energy terms, here used to describe short-scale correlation between dipoles, have minimal impact on the polarization and susceptibilities. Finally, depolarization energy significantly impacts the temperature and strain dependence, as well as the magnitude, of the susceptibilities. This approach provides guidance on how to more accurately model compositionally graded films and presents experimental approaches that could enable differentiation and determination of the constitutive coefficients of interest.

  8. High-voltage pulsed generator for dynamic fragmentation of rocks.

    Science.gov (United States)

    Kovalchuk, B M; Kharlov, A V; Vizir, V A; Kumpyak, V V; Zorin, V B; Kiselev, V N

    2010-10-01

    A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300 μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ∼50 ns, current amplitude of ∼6 kA with the 40 Ω active load, and ∼20 kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.

  9. Low Voltage Power Supply Incorporating Ceramic Transformer

    CERN Document Server

    Imori, M

    2007-01-01

    A low voltage power supply provides the regulated output voltage of 1 V from the supply voltage around 48 V. The low voltage power supply incorporates a ceramic transformer which utilizes piezoelectric effect to convert voltage. The ceramic transformer isolates the secondary from the primary, thus providing the ground isolation between the supply and the output voltages. The ceramic transformer takes the place of the conventional magnetic transformer. The ceramic transformer is constructed from a ceramic bar and does not include any magnetic material. So the low voltage power supply can operate under a magnetic field. The output voltage is stabilized by feedback. A feedback loop consists of an error amplifier, a voltage controlled oscillator and a driver circuit. The amplitude ratio of the transformer has dependence on the frequency, which is utilized to stabilize the output voltage. The low voltage power supply is investigated on the analogy of the high voltage power supply similarly incorporating the cerami...

  10. Modular High Voltage Power Supply

    Energy Technology Data Exchange (ETDEWEB)

    Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-18

    The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

  11. Developing Instructional Videotapes Step by Step.

    Science.gov (United States)

    Sweet, Thomas E.

    1990-01-01

    Discusses the eight steps in developing an instructional videotape: planning, brainstorming content, sequencing the storyline, defining the treatment, developing the introduction and conclusion, scripting the video and audio, controlling the production, and specifying the postproduction. (DMM)

  12. Slew Rate and Step Response of the Noninverting Structure with an Operational Amplifier

    Directory of Open Access Journals (Sweden)

    Josef Puncochar

    2004-01-01

    Full Text Available When a large-step input voltage is applied to an operational amplifier (OP AMP input, the output waveform reises with a finite slope called the slex rate which is due to an amplifier input stage current limiting (Im and because of a compensating capacitor Ck. We will solve this step response for large-step input voltages which cannot be done by means of the linear analysis only.

  13. Reliability criteria for voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Carson W.; Silverstein, Brian L. [Bonneville Power Administration, Portland, OR (United States)

    1994-12-31

    In face of costs pressures, there is need to allocate scare resources more effectively in order to achieve voltage stability. This naturally leads to development of probabilistic criteria and notions of rick management. In this paper it is presented a discussion about criteria for long term voltage stability limited to the case in which the time frames are topically several minutes. (author) 14 refs., 1 fig.

  14. A Voltage Quality Detection Method

    DEFF Research Database (Denmark)

    Chen, Zhe; Wei, Mu

    2008-01-01

    This paper presents a voltage quality detection method based on a phase-locked loop (PLL) technique. The technique can detect the voltage magnitude and phase angle of each individual phase under both normal and fault power system conditions. The proposed method has the potential to evaluate vario...... power quality disturbances, such as interruptions, sags and imbalances. Simulation studies have been performed. The effectiveness of the proposed method has been demonstrated under the simulated typical power disturbances....

  15. Role of calcium stores and membrane voltage in the generation of slow wave action potentials in guinea-pig gastric pylorus.

    Science.gov (United States)

    van Helden, D F; Imtiaz, M S; Nurgaliyeva, K; von der Weid, P; Dosen, P J

    2000-04-01

    1. Intracellular recordings made in single bundle strips of a visceral smooth muscle revealed rhythmic spontaneous membrane depolarizations termed slow waves (SWs). These exhibited 'pacemaker' and 'regenerative' components composed of summations of more elementary events termed spontaneous transient depolarizations (STDs). 2. STDs and SWs persisted in the presence of tetrodotoxin, nifedipine and ryanodine, and upon brief exposure to Ca2+-free Cd2+-containing solutions; they were enhanced by ACh and blocked by BAPTA AM, cyclopiazonic acid and caffeine. 3. SWs were also inhibited in heparin-loaded strips. SWs were observed over a wide range of membrane potentials (e.g. -80 to -45 mV) with increased frequencies at more depolarized potentials. 4. Regular spontaneous SW activity in this preparation began after 1-3 h superfusion of the tissue with physiological saline following the dissection procedure. Membrane depolarization applied before the onset of this activity induced bursts of STD-like events (termed the 'initial' response) which, when larger than threshold levels initiated regenerative responses. The combined initial-regenerative waveform was termed the SW-like action potential. 5. Voltage-induced responses exhibited large variable latencies (typical range 0.3-4 s), refractory periods of approximately 11 s and a pharmacology that was indistinguishable from those of STDs and spontaneous SWs. 6. The data indicate that SWs arise through more elementary inositol 1,4,5-trisphosphate (IP3) receptor-induced Ca2+ release events which rhythmically synchronize to trigger regenerative Ca2+ release and induce inward current across the plasmalemma. The finding that action potentials, which were indistinguishable from SWs, could be evoked by depolarization suggests that membrane potential modulates IP3 production. Voltage feedback on intracellular IP3-sensitive Ca2+ release is likely to have a major influence on the generation and propagation of SWs.

  16. Step by step: Revisiting step tolling in the bottleneck model

    NARCIS (Netherlands)

    Lindsey, C.R.; Berg, van den V.A.C.; Verhoef, E.T.

    2010-01-01

    In most dynamic traffic congestion models, congestion tolls must vary continuously over time to achieve the full optimum. This is also the case in Vickrey's (1969) 'bottleneck model'. To date, the closest approximations of this ideal in practice have so-called 'step tolls', in which the toll takes o

  17. A matter of quantum voltages.

    Science.gov (United States)

    Sellner, Bernhard; Kathmann, Shawn M

    2014-11-14

    Voltages inside matter are relevant to crystallization, materials science, biology, catalysis, and aqueous chemistry. The variation of voltages in matter can be measured by experiment, however, modern supercomputers allow the calculation of accurate quantum voltages with spatial resolutions of bulk systems well beyond what can currently be measured provided a sufficient level of theory is employed. Of particular interest is the Mean Inner Potential (V(o))--the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate V(o) from quantum calculations. Voltages are very sensitive to the distribution of electrons and provide metrics to understand interactions in condensed phases. In the present study, we find excellent agreement with measurements of V(o) for vitrified water and salt crystals and demonstrate the impact of covalent and ionic bonding as well as intermolecular/atomic interactions. Certain aspects in this regard are highlighted making use of simple model systems/approximations. Furthermore, we predict V(o) as well as the fluctuations of these voltages in aqueous NaCl electrolytes and characterize the changes in their behavior as the resolution increases below the size of atoms.

  18. Ultra-low-voltage-trigger thyristor for on-chip ESD protection without extra process cost

    Science.gov (United States)

    Yi, Shan; Jun, He; Wenyi, Huang

    2009-07-01

    A new thyristor is proposed and realized in the foundry's 0.18-μm CMOS process for electrostatic discharge (ESD) protection. Without extra mask layers or process steps, the new ultra-low-voltage-trigger thyristor (ULVT thyristor) has a trigger voltage as low as 6.7 V and an ESD robustness exceeding 50 mA/μm, which enables effective ESD protection. Compared with the traditional medium-voltage-trigger thyristor (MVT thyristor), the new structure not only has a lower trigger voltage, but can also provide better ESD protection under both positive and negative ESD zapping conditions.

  19. Ultra-low-voltage-trigger thyristor for on-chip ESD protection without extra process cost

    Energy Technology Data Exchange (ETDEWEB)

    Shan Yi [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); He Jun; Huang Wenyi, E-mail: iamshanyi@163.co, E-mail: yi.shan@gracesemi.co [Grace Semiconductor Manufacturing Corporation, Shanghai 201203 (China)

    2009-07-15

    A new thyristor is proposed and realized in the foundry's 0.18-{mu}m CMOS process for electrostatic discharge (ESD) protection. Without extra mask layers or process steps, the new ultra-low-voltage-trigger thyristor (ULVT thyristor) has a trigger voltage as low as 6.7 V and an ESD robustness exceeding 50 mA/{mu}m, which enables effective ESD protection. Compared with the traditional medium-voltage-trigger thyristor (MVT thyristor), the new structure not only has a lower trigger voltage, but can also provide better ESD protection under both positive and negative ESD zapping conditions.

  20. Novel Interleaved Converter with Extra-High Voltage Gain to Process Low-Voltage Renewable-Energy Generation

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2016-10-01

    Full Text Available This paper presents a novel interleaved converter (NIC with extra-high voltage gain to process the power of low-voltage renewable-energy generators such as photovoltaic (PV panel, wind turbine, and fuel cells. The NIC can boost a low input voltage to a much higher voltage level to inject renewable energy to DC bus for grid applications. Since the NIC has two circuit branches in parallel at frond end to share input current, it is suitable for high power applications. In addition, the NIC is controlled in an interleaving pattern, which has the advantages that the NIC has lower input current ripple, and the frequency of the ripple is twice the switching frequency. Two coupled inductors and two switched capacitors are incorporated to achieve a much higher voltage gain than conventional high step-up converters. The proposed NIC has intrinsic features such as leakage energy totally recycling and low voltage stress on power semiconductor. Thorough theoretical analysis and key parameter design are presented in this paper. A prototype is built for practical measurements to validate the proposed NIC.

  1. Potential role of voltage-sensing phosphatases in regulation of cell structure through the production of PI(3,4)P2.

    Science.gov (United States)

    Yamaguchi, Shinji; Kurokawa, Tatsuki; Taira, Ikuko; Aoki, Naoya; Sakata, Souhei; Okamura, Yasushi; Homma, Koichi J

    2014-04-01

    Voltage-sensing phosphatase, VSP, consists of the transmembrane domain, operating as the voltage sensor, and the cytoplasmic domain with phosphoinositide-phosphatase activities. The voltage sensor tightly couples with the cytoplasmic phosphatase and membrane depolarization induces dephosphorylation of several species of phosphoinositides. VSP gene is conserved from urochordate to human. There are some diversities among VSP ortholog proteins; range of voltage of voltage sensor motions as well as substrate selectivity. In contrast with recent understandings of biophysical mechanisms of VSPs, little is known about its physiological roles. Here we report that chick ortholog of VSP (designated as Gg-VSP) induces morphological feature of cell process outgrowths with round cell body in DF-1 fibroblasts upon its forced expression. Expression of the voltage sensor mutant, Gg-VSPR153Q with shifted voltage dependence to a lower voltage led to more frequent changes of cell morphology than the wild-type protein. Coexpression of PTEN that dephosphorylates PI(3,4)P2 suppressed this effect by Gg-VSP, indicating that the increase of PI(3,4)P2 leads to changes of cell shape. In addition, visualization of PI(3,4)P2 with the fluorescent protein fused with the TAPP1-derived pleckstrin homology (PH) domain suggested that Gg-VSP influenced the distribution of PI(3,4)P2 . These findings raise a possibility that one of the VSP's functions could be to regulate cell morphology through voltage-sensitive tuning of phosphoinositide profile.

  2. Dynamical model of series-resonant converter with peak capacitor voltage predictor and switching frequency control

    Science.gov (United States)

    Pietkiewicz, A.; Tollik, D.; Klaassens, J. B.

    1989-08-01

    A simple small-signal low-frequency model of an idealized series resonant converter employing peak capacitor voltage prediction and switching frequency control is proposed. Two different versions of the model describe all possible conversion modes. It is found that step down modes offer better dynamic characteristics over most important network functions than do the step-up modes. The dynamical model of the series resonant converter with peak capacitor voltage prediction and switching frequency programming is much simpler than such popular control stategies as frequency VCO (voltage controlled oscillators) based control, or diode conduction angle control.

  3. VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK

    African Journals Online (AJOL)

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF RUMUOLA DISTRIBUTION NETWORK. ... The artificial neural networks controller engaged to controlling the dynamic voltage ... Article Metrics.

  4. A Pulsed Power Supply with Sag Compensation using Controlled Gradational Voltage

    Science.gov (United States)

    Suzuki, Akihiro; Yamada, Masaki; Tashiro, Shojirou; Iwata, Akihiko

    A pulsed power supply with sag compensation using controlled gradational voltage to increase the flatness of output waveforms has been developed.The sag compensation circuit consists of compensation units connected in series. Each compensation unit consists of capacitances, diodes, and semiconductor switches. The capacitances of each unit are charged with different voltages by 2n (V0, 2V0, 4V0, ···). The compensation voltages, which has 2n-1 steps, is generated by switching the semiconductor switches of each unit in a binary sequence. Using this method, compensation voltage waveforms up to 6.2kV with 31 steps can be obtained with 5 compensation units. The sag compensation circuit has been adapted to a direct switch type pulsed power supply, which generates 7kV pulsed voltage with a pulse width of 700μs, thus realizing sag compensation.

  5. Analysis of the depolarizing properties of normal and adenomatous polyps in colon mucosa for the early diagnosis of precancerous lesions

    Science.gov (United States)

    Ortega-Quijano, Noé; Fanjul-Vélez, Félix; de Cos-Pérez, Jesús; Arce-Diego, José Luis

    2011-09-01

    Optical characterization of biological tissues by means of polarimetric techniques is an area of growing interest. Polarized light can be used for malignant neoplasms detection. To our knowledge, few studies have so far focused on lesions that are prone to result in cancer. In this work we present a polarimetric study of depolarization in prepathological tissues. Specifically, we will focus on premalignant lesions in human colon due to their clinical relevance. Colonic adenoma, the potential precursor of malignant adenocarcinoma, provokes significant structural modifications in colon mucosa that affect light depolarization. The depolarizing properties of normal and adenomatous polyps mucosa are compared. The average linear degree of polarization is shown to present a strong dependence with the precancerous state of the colonic tissue. This method has the potential to enable an early diagnosis of colon cancer.

  6. Structure and function of the voltage sensor of sodium channels probed by a beta-scorpion toxin.

    Science.gov (United States)

    Cestèle, Sandrine; Yarov-Yarovoy, Vladimir; Qu, Yusheng; Sampieri, François; Scheuer, Todd; Catterall, William A

    2006-07-28

    Voltage sensing by voltage-gated sodium channels determines the electrical excitability of cells, but the molecular mechanism is unknown. beta-Scorpion toxins bind specifically to neurotoxin receptor site 4 and induce a negative shift in the voltage dependence of activation through a voltage sensor-trapping mechanism. Kinetic analysis showed that beta-scorpion toxin binds to the resting state, and subsequently the bound toxin traps the voltage sensor in the activated state in a voltage-dependent but concentration-independent manner. The rate of voltage sensor trapping can be fit by a two-step model, in which the first step is voltage-dependent and correlates with the outward gating movement of the IIS4 segment, whereas the second step is voltage-independent and results in shifted voltage dependence of activation of the channel. Mutations of Glu(779) in extracellular loop IIS1-S2 and both Glu(837) and Leu(840) in extracellular loop IIS3-S4 reduce the binding affinity of beta-scorpion toxin. Mutations of positively charged and hydrophobic amino acid residues in the IIS4 segment do not affect beta-scorpion toxin binding but alter voltage dependence of activation and enhance beta-scorpion toxin action. Structural modeling with the Rosetta algorithm yielded a three-dimensional model of the toxin-receptor complex with the IIS4 voltage sensor at the extracellular surface. Our results provide mechanistic and structural insight into the voltage sensor-trapping mode of scorpion toxin action, define the position of the voltage sensor in the resting state of the sodium channel, and favor voltage-sensing models in which the S4 segment spans the membrane in both resting and activated states.

  7. Structure and Function of the Voltage Sensor of Sodium Channels Probed by a β-Scorpion Toxin*S

    Science.gov (United States)

    Cestèle, Sandrine; Yarov-Yarovoy, Vladimir; Qu, Yusheng; Sampieri, François; Scheuer, Todd; Catterall, William A.

    2006-01-01

    Voltage sensing by voltage-gated sodium channels determines the electrical excitability of cells, but the molecular mechanism is unknown. β-Scorpion toxins bind specifically to neurotoxin receptor site 4 and induce a negative shift in the voltage dependence of activation through a voltage sensor-trapping mechanism. Kinetic analysis showed that β-scorpion toxin binds to the resting state, and subsequently the bound toxin traps the voltage sensor in the activated state in a voltage-dependent but concentration-independent manner. The rate of voltage sensor trapping can be fit by a two-step model, in which the first step is voltage-dependent and correlates with the outward gating movement of the IIS4 segment, whereas the second step is voltage-independent and results in shifted voltage dependence of activation of the channel. Mutations of Glu779 in extracellular loop IIS1–S2 and both Glu837 and Leu840 in extracellular loop IIS3–S4 reduce the binding affinity of β-scorpion toxin. Mutations of positively charged and hydrophobic amino acid residues in the IIS4 segment do not affect β-scorpion toxin binding but alter voltage dependence of activation and enhance β-scorpion toxin action. Structural modeling with the Rosetta algorithm yielded a three-dimensional model of the toxin-receptor complex with the IIS4 voltage sensor at the extracellular surface. Our results provide mechanistic and structural insight into the voltage sensor-trapping mode of scorpion toxin action, define the position of the voltage sensor in the resting state of the sodium channel, and favor voltage-sensing models in which the S4 segment spans the membrane in both resting and activated states. PMID:16679310

  8. Characteristics of Gintonin-Mediated Membrane Depolarization of Pacemaker Activity in Cultured Interstitial Cells of Cajal

    Directory of Open Access Journals (Sweden)

    Byung Joo Kim

    2014-08-01

    Full Text Available Background/Aims: Ginseng regulates gastrointestinal (GI motor activity but the underlying components and molecular mechanisms are unknown. We investigated the effect of gintonin, a novel ginseng-derived G protein-coupled lysophosphatidic acid (LPA receptor ligand, on the pacemaker activity of the interstitial cells of Cajal (ICC in murine small intestine and GI motility. Materials and Methods: Enzymatic digestion was used to dissociate ICC from mouse small intestines. The whole-cell patch-clamp configuration was used to record pacemaker potentials and currents from cultured ICC in the absence or presence of gintonin. In vivo effects of gintonin on gastrointestinal (GI motility were investigated by measuring the intestinal transit rate (ITR of Evans blue in normal and streptozotocin (STZ-induced diabetic mice. Results: We investigated the effects of gintonin on pacemaker potentials and currents in cultured ICC from mouse small intestine. Gintonin caused membrane depolarization in current clamp mode but this action was blocked by Ki16425, an LPA1/3 receptor antagonist, and by the addition of GDPβS, a GTP-binding protein inhibitor, into the ICC. To study the gintonin signaling pathway, we examined the effects of U-73122, an active PLC inhibitor, and chelerythrine and calphostin, which inhibit PKC. All inhibitors blocked gintonin actions on pacemaker potentials, but not completely. Gintonin-mediated depolarization was lower in Ca2+-free than in Ca2+-containing external solutions and was blocked by thapsigargin. We found that, in ICC, gintonin also activated Ca2+-activated Cl- channels (TMEM16A, ANO1, but not TRPM7 channels. In vivo, gintonin (10-100 mg/kg, p.o. not only significantly increased the ITR in normal mice but also ameliorated STZ-induced diabetic GI motility retardation in a dose-dependent manner. Conclusions: Gintonin-mediated membrane depolarization of pacemaker activity and ANO1 activation are coupled to the stimulation of GI

  9. Multiply scattered waves through a spatially random medium : entropy production and depolarization

    Science.gov (United States)

    Bicout, Dominique; Brosseau, Christian

    1992-11-01

    This paper deals with the depolarization and decoherence effects of an incident pure state of polarization and of arbitrary state of coherence by a linear scattering medium which changes randomly with position. Using symmetry arguments and a maximum entropy principle we deduce the general form of the Mueller matrix describing the scattering medium which is consistent with the explicit computation done in the context of the Bethe-Salpeter equation handled in the diffusion approximation. The main result expresses the output degree of polarization and degree of spatial coherence as a function of the number of scattering events. From these results, two main conclusions can be drawn. The first is that the entropy production per scattering due to the irreversible process of depolarization is an exponentially decreasing function of the number of scattering events. The second result obtained is that full depolarization of linearly polarized light by Rayleigh scatterers requires more scattering events (typically a factor-of-2) than are required for a circularly polarized lightwave. Dans cette étude, on considère les phénomènes de dépolarisation et de décohérence d'un faisceau d'ondes planes incident, d'état pur de polarisation et d'état arbitraire de cohérence, par intéraction avec un milieu diffusant désordonné. Par des arguments de symétrie et un principe d'entropie maximum, nous déduisons la forme de la matrice de Mueller caractérisant le milieu diffusant qui est en accord avec le calcul explicite basé sur l'équation de Bethe-Salpeter traitée dans l'approximation de la diffusion. Le résultat principal exprime les degrés de polarisation et de cohérence spatiale en fonction du nombre de diffusions. Deux faits saillants sont à noter. Le premier exprime la décroissance exponentielle de la production d'entropie due à l'irréversibilité du processus de dépolarisation, en fonction du nombre de diffusions. Le second indique que la dépolarisation compl

  10. Research progress in rebound depolarization of neurons%神经元去极化反跳现象的研究进展

    Institute of Scientific and Technical Information of China (English)

    李凌超; 朱梦叶; 张达颖; 柳涛

    2016-01-01

    [ ABSTRACT] Rebound depolarization is a special phenomenon of the neurons which generates action potential fol-lowed by a hyperpolarization stimulation.It can be recorded in many kinds of neurons and is the intrinsic membrane charac-teristic of them.Rebound depolarization plays an important role in regulating the firing pattern, rhythmic activity and sy-naptic plasticity of neurons.This review focuses on the basic characteristics, the function and mechanism of the rebound depolarization in physiological and pathological conditions, which provides reference for the clinical treatment of rebound depolarization-related diseases.

  11. Electrode voltage fall and total voltage of a transient arc

    Science.gov (United States)

    Valensi, F.; Ratovoson, L.; Razafinimanana, M.; Masquère, M.; Freton, P.; Gleizes, A.

    2016-06-01

    This paper deals with an experimental study of the components of a transient arc total voltage with duration of a few tens of ms and a current peak close to 1000 A. The cathode tip is made of graphite whereas the flat anode is made either of copper or of graphite; the electrodes gap is a few mm. The analysis of the electrical parameters is supported and validated by fast imaging and by two models: the first one is a 2D physical model of the arc allowing to calculate both the plasma temperature field and the arc voltage; the second model is able to estimate the transient heating of the graphite electrode. The main aim of the study was to detect the possible change of the cathode voltage fall (CVF) during the first instants of the arc. Indeed it is expected that during the first ms the graphite cathode is rather cool and the main mechanism of the electron emission should be the field effect emission, whereas after several tens of ms the cathode is strongly heated and thermionic emission should be predominant. We have observed some change in the apparent CVF but we have shown that this apparent change can be attributed to the variation of the solid cathode resistance. On the other hand, the possible change of CVF corresponding to the transition between a ‘cold’ and a ‘hot’ cathode should be weak and could not be characterized considering our measurement uncertainty of about 2 V. The arc column voltage (ACV) was estimated by subtracting the electrode voltage fall from the total arc voltage. The experimental transient evolution of the ACV is in very good agreement with the theoretical variation predicted by the model, showing the good ability of the model to study this kind of transient arc.

  12. Thyrotropin-releasing hormone (TRH) depolarizes a subset of inspiratory neurons in the newborn mouse brain stem in vitro

    DEFF Research Database (Denmark)

    Rekling, J C; Champagnat, J; Denavit-Saubié, M

    1996-01-01

    was accompanied by an increase in spontaneous excitatory synaptic activity that disappeared late during the TRH application. The duration of the inspiratory potentials was increased, indicating that the hypoglossal motoneurons received a longer duration synaptic input from the respiratory rhythm generator. 4...... markedly during TRH. Four cells showed a transient depolarization with an increase in input resistance during TRH with TTX present in the superfusing solution. Thus type-3 neurons are depolarized postsynaptically by TRH. 7. We conclude that TRH increases the frequency of the respiratory rhythm in newborn...

  13. Relationship between depolarization-induced force responses and Ca2+ content in skeletal muscle fibres of rat and toad.

    Science.gov (United States)

    Owen, V J; Lamb, G D; Stephenson, D G; Fryer, M W

    1997-02-01

    1. The relationship between the total Ca2+ content of a muscle fibre and the magnitude of the force response to depolarization was examined in mechanically skinned fibres from the iliofibularis muscle of the toad and the extensor digitorum longus muscle of the rat. The response to depolarization in each skinned fibre was assessed either at the endogenous level of Ca2+ content or after depleting the fibre of Ca2+ to some degree. Ca2+ content was determined by a fibre lysing technique. 2. In both muscle types, the total Ca2+ content could be reduced from the endogenous level of approximately 1.3 mmol l-1 (expressed relative to intact fibre volume) to approximately 0.25 mmol l-1 by either depolarization or caffeine application in the presence of Ca2+ chelators, showing that the great majority of the Ca2+ was stored in the sarcoplasmic reticulum (SR). Chelation of Ca2+ in the transverse tubular (T-) system, either by exposure of fibres to EGTA before skinning or by permeabilizing the T-system with saponin after skinning, reduced the lower limit of Ca2+ content to < or = 0.12 mmol l-1, indicating that 10-20% of the total fibre Ca2+ resided in the T-system. 3. In toad fibres, both the peak and the area (i.e. time integral) of the force response to depolarization were reduced by any reduction in SR Ca2+ content, with both decreasing to zero in an approximately linear manner as the SR Ca2+ content was reduced to < 15% of the endogenous level. In rat fibres, the peak size of the force response was less affected by small decreases in SR content, but both the peak and area of the response decreased to zero with greater depletion. In partially depleted toad fibres, inhibition of SR Ca2+ uptake potentiated the force response to depolarization almost 2-fold. 4. The results show that in this skinned fibre preparation: (a) T-system depolarization and caffeine application can each virtually fully deplete the SR of Ca2+, irrespective of any putative inhibitory effect of SR depletion

  14. Voltage-Gated Proton Channels: Molecular Biology, Physiology, and Pathophysiology of the HV Family

    Science.gov (United States)

    2013-01-01

    Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H+ concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current. The HV channel protein is strikingly similar to the voltage-sensing domain (VSD, the first four membrane-spanning segments) of voltage-gated K+ and Na+ channels. In higher species, HV channels exist as dimers in which each protomer has its own conduction pathway, yet gating is cooperative. HV channels are phylogenetically diverse, distributed from humans to unicellular marine life, and perhaps even plants. Correspondingly, HV functions vary widely as well, from promoting calcification in coccolithophores and triggering bioluminescent flashes in dinoflagellates to facilitating killing bacteria, airway pH regulation, basophil histamine release, sperm maturation, and B lymphocyte responses in humans. Recent evidence that hHV1 may exacerbate breast cancer metastasis and cerebral damage from ischemic stroke highlights the rapidly expanding recognition of the clinical importance of hHV1. PMID:23589829

  15. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    Science.gov (United States)

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  16. Molecular mechanism underlying β1 regulation in voltage- and calcium-activated potassium (BK) channels.

    Science.gov (United States)

    Castillo, Karen; Contreras, Gustavo F; Pupo, Amaury; Torres, Yolima P; Neely, Alan; González, Carlos; Latorre, Ramon

    2015-04-14

    Being activated by depolarizing voltages and increases in cytoplasmic Ca(2+), voltage- and calcium-activated potassium (BK) channels and their modulatory β-subunits are able to dampen or stop excitatory stimuli in a wide range of cellular types, including both neuronal and nonneuronal tissues. Minimal alterations in BK channel function may contribute to the pathophysiology of several diseases, including hypertension, asthma, cancer, epilepsy, and diabetes. Several gating processes, allosterically coupled to each other, control BK channel activity and are potential targets for regulation by auxiliary β-subunits that are expressed together with the α (BK)-subunit in almost every tissue type where they are found. By measuring gating currents in BK channels coexpressed with chimeras between β1 and β3 or β2 auxiliary subunits, we were able to identify that the cytoplasmic regions of β1 are responsible for the modulation of the voltage sensors. In addition, we narrowed down the structural determinants to the N terminus of β1, which contains two lysine residues (i.e., K3 and K4), which upon substitution virtually abolished the effects of β1 on charge movement. The mechanism by which K3 and K4 stabilize the voltage sensor is not electrostatic but specific, and the α (BK)-residues involved remain to be identified. This is the first report, to our knowledge, where the regulatory effects of the β1-subunit have been clearly assigned to a particular segment, with two pivotal amino acids being responsible for this modulation.

  17. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  18. Step by Step Microsoft Office Visio 2003

    CERN Document Server

    Lemke, Judy

    2004-01-01

    Experience learning made easy-and quickly teach yourself how to use Visio 2003, the Microsoft Office business and technical diagramming program. With STEP BY STEP, you can take just the lessons you need, or work from cover to cover. Either way, you drive the instruction-building and practicing the skills you need, just when you need them! Produce computer network diagrams, organization charts, floor plans, and moreUse templates to create new diagrams and drawings quicklyAdd text, color, and 1-D and 2-D shapesInsert graphics and pictures, such as company logosConnect shapes to create a basic f

  19. Updated equation to compute the soil voltage contour under fault condition

    Directory of Open Access Journals (Sweden)

    M. Nassereddine, J. Rizk, M. Nagrial, A. Hellany

    2015-01-01

    Full Text Available The neighboring rates between high voltage substation and residential buildings are amplified due to populations increase. Under fault or system malfunction, earth potential rise could reach an unsafe condition. This earth potential rise extends to the surrounding soil and known as the soil voltage. To guarantee safety acquiescence of the new system, earthing system design is required. Earthing system offers a safe working atmosphere for employees and people transitory by during a fault or malfunction of a power system. The soil voltage due to high voltage EPR plays important roles when it comes to step and touch voltage computation. In this paper, a new equation is studied to compute the soil voltage at distance x from the fault location. Numerous field tests is included to verify the proposed method.

  20. Membrane voltage differently affects mIPSCs and current responses recorded from somatic excised patches in rat hippocampal cultures.

    Science.gov (United States)

    Pytel, Maria; Mozrzymas, Jerzy W

    2006-01-30

    Recent analysis of current responses to exogenous GABA applications recorded from excised patches indicated that membrane voltage affected the GABAA receptor gating mainly by altering desensitization and binding [M. Pytel, K. Mercik, J.W. Mozrzymas, Membrane voltage modulates the GABAA receptor gating in cultured rat hippocampal neurons, Neuropharmacology, in press]. In order investigate the impact of such voltage effect on GABAA receptors in conditions of synaptic transmission, mIPSCs and current responses to rapid GABA applications were recorded from the same culture of rat hippocampal neurons. We found that I-V relationship for mIPSCs amplitudes showed a clear outward rectification while for current responses an inward rectification was seen, except for very low GABA concentrations. A clear shift in amplitude cumulative distributions indicated that outward rectification resulted from the voltage effect on the majority of mIPSCs. Moreover, the decaying phase of mIPSCs was clearly slowed down at positive voltages and this effect was represented by a shift in cumulative distributions of weighted decaying time constants. In contrast, deactivation of current responses was only slightly affected by membrane depolarization. These data indicate that the mechanisms whereby the membrane voltage modulates synaptic and extrasynaptic receptors are qualitatively different but the mechanism underlying this difference is not clear.

  1. Reversal of HCN channel voltage dependence via bridging of the S4-S5 linker and Post-S6.

    Science.gov (United States)

    Prole, David L; Yellen, Gary

    2006-09-01

    Voltage-gated ion channels possess charged domains that move in response to changes in transmembrane voltage. How this movement is transduced into gating of the channel pore is largely unknown. Here we show directly that two functionally important regions of the spHCN1 pacemaker channel, the S4-S5 linker and the C-linker, come into close proximity during gating. Cross-linking these regions with high-affinity metal bridges or disulfide bridges dramatically alters channel gating in the absence of cAMP; after modification the polarity of voltage dependence is reversed. Instead of being closed at positive voltage and activating with hyperpolarization, modified channels are closed at negative voltage and activate with depolarization. Mechanistically, this reversal of voltage dependence occurs as a result of selectively eliminating channel deactivation, while retaining an existing inactivation process. Bridging also alters channel activation by cAMP, showing that interaction of these two regions can also affect the efficacy of physiological ligands.

  2. Automated Voltage Control in LHCb

    CERN Document Server

    Granado Cardoso, L; Jacobsson, R

    2011-01-01

    LHCb is one of the 4 LHC experiments. In order to ensure the safety of the detector and to maximize efficiency, LHCb needs to coordinate its own operations, in particular the voltage configuration of the different subdetectors, according to the accelerator status. A control software has been developed for this purpose, based on the Finite State Machine toolkit and the SCADA system used for control throughout LHCb (and the other LHC experiments). This software permits to efficiently drive both the Low Voltage (LV) and High Voltage (HV) systems of the 10 different sub-detectors that constitute LHCb, setting each sub-system to the required voltage (easily configurable at run-time) based on the accelerator state. The control software is also responsible for monitoring the state of the Sub-detector voltages and adding it to the event data in the form of status-bits. Safe and yet flexible operation of the LHCb detector has been obtained and automatic actions, triggered by the state changes of the ...

  3. Decomposition of a depolarizing Mueller matrix into its nondepolarizing components by using symmetry conditions.

    Science.gov (United States)

    Kuntman, Ertan; Arteaga, Oriol

    2016-04-01

    A procedure for the parallel decomposition of a depolarizing Mueller matrix with an associated rank 2 covariance matrix into its two nondepolarizing components is presented. We show that, if one of the components agrees with certain symmetry conditions, the arbitrary decomposition becomes unique, and its calculation is straightforward. Solutions for six different symmetries, which are relevant for the physical interpretation of polarimetric measurements, are provided. With this procedure, a single polarimetric measurement is sufficient to fully disclose the complete polarimetric response of two different systems and evaluate their weights in the overall response. The decomposition method we propose is illustrated by obtaining the ellipsometric responses of a silicon wafer and a holographic grating from a single measurement in which the light spot illuminates sectors of both materials. In a second example, we use the decomposition to analyze an optical system in which a polarizing film is partially covered by another misaligned film.

  4. Structural relaxation and mode coupling in a non-glassforming liquid: depolarized light scattering in benzene

    Energy Technology Data Exchange (ETDEWEB)

    Wiebel, Sabine [Physik-Department E13, Technische Universitaet Muenchen, Garching (Germany); Wuttke, Joachim [Physik-Department E13, Technische Universitaet Muenchen, Garching (Germany) and Siemens AG, ICN ON RD AT 1, Munich (Germany)]. E-mail: jwuttke@ph.tum.de

    2002-07-01

    We have measured depolarized light scattering in liquid benzene over the whole accessible temperature range and over four decades in frequency. Between 40 and 180 GHz we find a susceptibility peak due to structural relaxation. This peak shows stretching and time-temperature scaling as known from alpha relaxation in glass-forming materials. A simple mode-coupling model provides consistent fits of the entire data set. These qualitative and quantitative results show that structural relaxation in ordinary liquids and alpha relaxation in glass-forming materials are one and the same physical process. Thus, a deeper understanding of equilibrium liquids is reached by applying concepts that were originally developed in the context of glass-transition research. (author)

  5. Depolarized SnO2-based gas anodes for electrowinning of silver in molten chlorides

    Directory of Open Access Journals (Sweden)

    Xiao S.

    2013-01-01

    Full Text Available SnO2-based porous anodes were prepared and the behavior of gas bubbles on the porous anodes with different original coarse grain size, immersed in ethanol to simulate molten chlorides, was primarily investigated. SnO2-based porous anodes were used as gas anodes for the electrowinning of silver in CaCl2-NaCl-CaO-AgCl melts at 680°C. Hydrogen was introduced to the anode/electrolyte interface through the gas anode. Carbon was used as the cathode. Obvious depolarization of the anode potential was observed after the introduction of hydrogen comparing with no reducing gas introduced, indicating the involvement of hydrogen in the anode reaction. Metallic silver was deposited on the cathode.

  6. Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum

    CERN Document Server

    Aurière, M; Ariste, López; Mathias, P; Lèbre, A; Josselin, E; Montargès, M; Petit, P; Chiavassa, A; Paletou, F; Fabas, N; Konstantinova-Antova, R; Donati, J -F; Grunhut, J H; Wade, G A; Herpin, F; Kervella, P; Perrin, G; Tessore, B

    2016-01-01

    Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. We have previously discovered linear polarization signatures associated with individual lines in the spectra of cool and evolved stars. Here, we investigate whether a similar linearly polarized spectrum exists for Betelgeuse. We used the spectropolarimeter Narval, combining multiple polarimetric sequences to obtain high signal-to-noise ratio spectra of individual lines, as well as the least-squares deconvolution (LSD) approach. We have discovered the existence of a linearly polarized spectrum for Betelgeuse, detecting a rather strong signal (at a few times 10$^{-4}$ of the continuum intensity level), both in individual lines and in the LSD profiles. Studying its properties and the signal observed for the resonant \\ion{Na}{i}\\,D lines, we conclude that we are mainly observing depolarization of the continuum by the absorption lines. The linear polarization of the Betelgeuse conti...

  7. Tensorial depolarization of alkali atoms by isotropic collisions with neutral hydrogen

    CERN Document Server

    Derouich, Moncef

    2012-01-01

    Results. We consider the problem of isotropic collisions between an alkali atom and neutral hydrogen. We calculate the collisional tensorial components of general p and s-states, characterized by their effective principal quantum number $n^{*}$. It is found that the behaviour of the tensorial components obey simple power laws allowing quick calculations of the depolarizing collisional rates. As application, our results should allow a rigorous treatment of the atomic polarization profiles of the D1 -D2 lines of alkali atoms. Conclusions. Close coupling treatments of atomic collisions are needed to decipher the information encoded in the polarized radiation from the Sun. Important problems remain unresolved like the role of collisions in the Paschen-Back conditions.

  8. Whole-exome sequencing and homozygosity analysis implicate depolarization-regulated neuronal genes in autism.

    Directory of Open Access Journals (Sweden)

    Maria H Chahrour

    Full Text Available Although autism has a clear genetic component, the high genetic heterogeneity of the disorder has been a challenge for the identification of causative genes. We used homozygosity analysis to identify probands from nonconsanguineous families that showed evidence of distant shared ancestry, suggesting potentially recessive mutations. Whole-exome sequencing of 16 probands revealed validated homozygous, potentially pathogenic recessive mutations that segregated perfectly with disease in 4/16 families. The candidate genes (UBE3B, CLTCL1, NCKAP5L, ZNF18 encode proteins involved in proteolysis, GTPase-mediated signaling, cytoskeletal organization, and other pathways. Furthermore, neuronal depolarization regulated the transcription of these genes, suggesting potential activity-dependent roles in neurons. We present a multidimensional strategy for filtering whole-exome sequence data to find candidate recessive mutations in autism, which may have broader applicability to other complex, heterogeneous disorders.

  9. Viscosity by Fluorescence Depolarization of Probe Molecules. A Physical Chemistry Laboratory Experiment.

    Energy Technology Data Exchange (ETDEWEB)

    Windisch, Charles F.; Exarhos, Gregory J.; Sharma, Shiv K.

    2005-06-01

    This two-session undergraduate laboratory experiment in physical chemistry involves the measurement of the viscosity of solutions using both a conventional method and a new method based on the fluorescence depolarization of a probe molecule. By comparing the results of the two approaches, students will come to a fundamental understanding of how a macroscopic property (viscosity) and molecular-level properties (molecular dynamics parameters) relate. They will also further their understandnig of the physical chemistry of fluorescence and learn how to perform spectroscopic measurements where polarization conditions are important. The experiment also has ramifications in the practical world, because the optical approach has shown promise as the basis for a sensor for in-situ viscostiy measurement.

  10. Free Modal Algebras Revisited: The Step-by-Step Method

    NARCIS (Netherlands)

    Bezhanishvili, N.; Ghilardi, Silvio; Jibladze, Mamuka

    2012-01-01

    We review the step-by-step method of constructing finitely generated free modal algebras. First we discuss the global step-by-step method, which works well for rank one modal logics. Next we refine the global step-by-step method to obtain the local step-by-step method, which is applicable beyond ran

  11. SYNTHESIS OF VOLTAGES OF UNIFORM PWM IN TIME REGULATION

    Directory of Open Access Journals (Sweden)

    A. G. Stryzhniou

    2014-01-01

    Full Text Available The article describes a process of synthesis and qualitative assessment of the harmonic composition of voltages of multiple and single PWM pulses in time regulation, being, along with amplitude, frequency and phase method, one of control methods of an asynchronous motor. The main point of time regulation is that a pause after any two single PWM pulses with different polarity or after any two groups of multiple PWM pulses with different polarity changes during a process of regulation. Feature of time regulation is that a motor has fast response in the range of small-signal of control and good linearity of speed-torque characteristics in the whole control range. Analytical expressions of parameters of PWM pulses ai and ti are obtained which allow to simplify considerably a process of formation and implementation of time regulation using tabular or indexed-tabular methods. These expressions allow not only to define voltage amplitude of  harmonic but also to perform qualitative assessment of harmonic composition of output voltages at time regulation. It is specified that harmonic frequencies wi = w0/q change in inverse proportion to magnitude of parameter q during a process of regulation and there is a replacement of a fundamental frequency by frequencies of higher harmonics.The offered approach allows to synthesize voltage of uniform single and multiple PWM pulses and to perform their comparative and qualitative analysis and the obtained expressions can be used at modeling of AC motor work. Voltage of multiple PWM pulses which is formed using stepped reference voltage with even quantity of steps in a half period and a pause on a zero level has the best parameters by criterion of a minimum of harmonic components and a maximum of a factor of anharmonicity Kнс at time regulation.

  12. Neuromagnetic field strength outside the human head due to impedance changes from neuronal depolarization.

    Science.gov (United States)

    Ahadzi, G M; Liston, A D; Bayford, R H; Holder, D S

    2004-02-01

    The holy grail of neuroimaging would be to have an imaging system, which could image neuronal electrical activity over milliseconds. One way to do this would be by imaging the impedance changes associated with ion channels opening in neuronal membranes in the brain during activity. In principle, we could measure this change by using electrical impedance tomography (EIT) but it is close to its threshold of detectability. With the inherent limitation in the use of electrodes, we propose a new scheme based on recording the magnetic field resulting from an injected current with superconducting quantum interference devices (SQUIDs), used in magnetoencephalography (MEG). We have performed a feasibility study using computer simulation. The head was modelled as concentric spheres to mimic the scalp, skull, cerebrospinal fluid and brain using the finite element method. The magnetic field 1 cm away from the scalp was estimated. An impedance change of 1% in a 2 cm radius volume in the brain was modelled as the region of depolarization. A constant current of 100 microA was injected into the head from diametrically opposite electrodes. The model predicts that the standing magnetic field is about 10 pT and changed by about 3 fT (0.03%) on depolarization. The spectral noise density in a typical MEG system in the frequency band 1-100 Hz is about 7 fT, so this places the change at the limit of detectability. This is similar to electrical recording, as in conventional EIT systems, but there may be advantages to MEG in that the magnetic field directly traverses the skull and instrumentation errors from the electrode-skin interface will be obviated.

  13. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect imm...... of THIP-treated cultures. This suggests that primarily low affinity GABAA-receptors are closely associated with Ca2+ channels and this may be important for the ability of these receptors to mediate an inhibitory action on transmitter release even under extreme depolarizing conditions....

  14. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    OpenAIRE

    Arash Toudeshki; Norman Mariun; Hashim Hizam; Noor Izzri Abdul Wahab

    2014-01-01

    For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  15. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  16. Simple buck/boost voltage regulator

    Science.gov (United States)

    Paulkovich, J.; Rodriguez, G. E.

    1980-01-01

    Circuit corrects low or high supply voltage, produces regulated output voltage. Circuit has fewer components because inductory/transformer combination and pulse-width modulator serve double duty. Regulator handles input voltage variation from as low as one half output voltage to as high as input transistor rating. Solar arrays, fuel cells, and thermionic generators might use this regulator.

  17. 30 CFR 18.47 - Voltage limitation.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Voltage limitation. 18.47 Section 18.47 Mineral... § 18.47 Voltage limitation. (a) A tool or switch held in the operator's hand or supported against his... particular voltage(s) are provided in the design and construction of the equipment, its wiring,...

  18. Diabetes PSA (:60) Step By Step

    Centers for Disease Control (CDC) Podcasts

    2009-10-24

    First steps to preventing diabetes. For Hispanic and Latino American audiences.  Created: 10/24/2009 by National Diabetes Education Program (NDEP), a joint program of the Centers for Disease Control and Prevention and the National Institutes of Health.   Date Released: 10/24/2009.

  19. Diabetes PSA (:30) Step By Step

    Centers for Disease Control (CDC) Podcasts

    2009-10-24

    First steps to preventing diabetes. For Hispanic and Latino American audiences.  Created: 10/24/2009 by National Diabetes Education Program (NDEP), a joint program of the Centers for Disease Control and Prevention and the National Institutes of Health.   Date Released: 10/24/2009.

  20. Cavity Voltage Phase Modulation MD

    CERN Document Server

    Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

  1. Portable High Voltage Impulse Generator

    Directory of Open Access Journals (Sweden)

    S. Gómez

    2011-07-01

    Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

  2. A low voltage CMOS low drop-out voltage regulator

    Science.gov (United States)

    Bakr, Salma Ali; Abbasi, Tanvir Ahmad; Abbasi, Mohammas Suhaib; Aldessouky, Mohamed Samir; Abbasi, Mohammad Usaid

    2009-05-01

    A low voltage implementation of a CMOS Low Drop-Out voltage regulator (LDO) is presented. The requirement of low voltage devices is crucial for portable devices that require extensive computations in a low power environment. The LDO is implemented in 90nm generic CMOS technology. It generates a fixed 0.8V from a 2.5V supply which on discharging goes to 1V. The buffer stage used is unity gain configured unbuffered OpAmp with rail-to-rail swing input stage. The simulation result shows that the implemented circuit provides load regulation of 0.004%/mA and line regulation of -11.09mV/V. The LDO provides full load transient response with a settling time of 5.2μs. Further, the dropout voltage is 200mV and the quiescent current through the pass transistor (Iload=0) is 20μA. The total power consumption of this LDO (excluding bandgap reference) is only 80μW.

  3. Implementation of Dynamic Voltage Restorer for Mitigation of Voltage Sag

    Directory of Open Access Journals (Sweden)

    K.Vinod Kumar

    2013-07-01

    Full Text Available Power quality is one of major concerns in the present. It has become important, especially with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. The dynamic voltage restorer (DVR is one of the modern devices used in distribution systems to improve the power quality. In this paper, emergency control in distribution systems is discussed by using the proposed multifunctional DVR control strategy.Also, themultiloop controller using the Posicast and P+Resonant controllers is proposed in order to improve the transient response and eliminate the steady state error in DVR response,respectively.The proposed process is applied to some riots in load voltage effected by induction motors starting, and a three-phase short circuit fault. The three-phase short circuits, and the large induction motors are suddenly started then voltage sags areoccurred.The innovation here is that by using the Multifunctional Dynamic Voltage Restorer, improve the power quality in distribution side. Simulation results show the capability of the DVR to control the emergency conditions of the distribution systems by using MATLAB/Simulink software.

  4. The high voltage homopolar generator

    Science.gov (United States)

    Price, J. H.; Gully, J. H.; Driga, M. D.

    1986-11-01

    System and component design features of proposed high voltage homopolar generator (HVHPG) are described. The system is to have an open circuit voltage of 500 V, a peak output current of 500 kA, 3.25 MJ of stored inertial energy and possess an average magnetic-flux density of 5 T. Stator assembly components are discussed, including the stator, mount structure, hydrostatic bearings, main and motoring brushgears and rotor. Planned operational procedures such as monitoring the rotor to full speed and operation with a superconducting field coil are delineated.

  5. High Voltage Operation of Helical Pulseline Structures for Ion Acceleration

    CERN Document Server

    Waldron, William; Reginato, Lou

    2005-01-01

    The basic concept for the acceleration of heavy ions using a helical pulseline requires the launching of a high voltage traveling wave with a waveform determined by the beam transport physics in order to maintain stability and acceleration.* This waveform is applied to the front of the helix, creating over the region of the ion bunch a constant axial acceleration electric field that travels down the line in synchronism with the ions. Several methods of driving the helix have been considered. Presently, the best method of generating the waveform and also maintaining the high voltage integrity appears to be a transformer primary loosely coupled to the front of the helix, generating the desired waveform and achieving a voltage step-up from primary to secondary (the helix). This can reduce the drive voltage that must be brought into the helix enclosure through the feedthroughs by factors of 5 or more. The accelerating gradient is limited by the voltage holding of the vacuum insulator, and the material and helix g...

  6. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa

    2013-01-01

    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  7. Comparative impact of voltage-gated calcium channels and NMDA receptors on mitochondria-mediated neuronal injury.

    Science.gov (United States)

    Stanika, Ruslan I; Villanueva, Idalis; Kazanina, Galina; Andrews, S Brian; Pivovarova, Natalia B

    2012-05-09

    Glutamate excitotoxicity, a major component of many neurodegenerative disorders, is characterized by excessive calcium influx selectively through NMDARs. However, there is a substantial uncertainty concerning why other known routes of significant calcium entry, in particular, VGCCs, are not similarly toxic. Here, we report that in the majority of neurons in rat hippocampal and cortical cultures, maximal L-type VGCC activation induces much lower calcium loading than toxic NMDAR activation. Consequently, few depolarization-activated neurons exhibit calcium deregulation and cell death. Activation of alternative routes of calcium entry induced neuronal death in proportion to the degree of calcium loading. In a small subset of neurons, depolarization evoked stronger calcium elevations, approaching those induced by toxic NMDA. These neurons were characterized by elevated expression of VGCCs and enhanced voltage-gated calcium currents, mitochondrial dysfunction and cell death. Preventing VGCC-dependent mitochondrial calcium loading resulted in stronger cytoplasmic calcium elevations, whereas inhibiting mitochondrial calcium clearance accelerated mitochondrial depolarization. Both observations further implicate mitochondrial dysfunction in VGCC-mediated cell death. Results indicate that neuronal vulnerability tracks the extent of calcium loading but does not appear to depend explicitly on the route of calcium entry.

  8. Membrane potential bistability in nonexcitable cells as described by inward and outward voltage-gated ion channels.

    Science.gov (United States)

    Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

    2014-10-30

    The membrane potential of nonexcitable cells, defined as the electrical potential difference between the cell cytoplasm and the extracellular environment when the current is zero, is controlled by the individual electrical conductance of different ion channels. In particular, inward- and outward-rectifying voltage-gated channels are crucial for cell hyperpolarization/depolarization processes, being amenable to direct physical study. High (in absolute value) negative membrane potentials are characteristic of terminally differentiated cells, while low membrane potentials are found in relatively depolarized, more plastic cells (e.g., stem, embryonic, and cancer cells). We study theoretically the hyperpolarized and depolarized values of the membrane potential, as well as the possibility to obtain a bistability behavior, using simplified models for the ion channels that regulate this potential. The bistability regions, which are defined in the multidimensional state space determining the cell state, can be relevant for the understanding of the different model cell states and the transitions between them, which are triggered by changes in the external environment.

  9. Implementation of depolarization due to beam-beam effects in the beam-beam interaction simulation tool GUINEA-PIG++

    Science.gov (United States)

    Rimbault, C.; Le Meur, G.; Blampuy, F.; Bambade, P.; Schulte, D.

    2009-12-01

    Depolarization is a new feature in the beam-beam simulation tool GUINEA-PIG++ (GP++). The results of this simulation are studied and compared with another beam-beam simulation tool, CAIN, considering different beam parameters for the International Linear Collider (ILC) with a centre-of-mass energy of 500 GeV.

  10. Hyposmotic membrane stretch potentiated muscarinic receptor agonist-induced depolarization of membrane potential in guinea-pig gastric myocytes

    Institute of Scientific and Technical Information of China (English)

    Lin Li; Nan-Ge Jin; Lin Piao; Ming-Yu Hong; Zheng-Yuan Jin; Ying Li; Wen-Xie Xu

    2002-01-01

    AIM: To investigate the relationship betweenhyposmotic membrane stretch and muscarinic receptoragonist-induced depolarization of membrane potentialin antral gastric circular myocytes of guinea-pig.METHODS: Using whole cell patch-clamp techniquerecorded membrane potential and current in singlegastric myocytes isolated by collagena se.RESULTS: Hyposmotic membrane stretch hyperpolarizedmembrane potential from -60.0mV±1.0mV to -67.9mV±1.0mV. TEA (10mmol/L), a nonselective potassiumchannel blocker significantly inhibited hyposmoticmembrane stretch-induced hyperpolarization. After KCIin the pipette and NaCI in the external solution werereplaced by CsCI to block the potassium current,hyposmotic membrane stretch depolarized the membranepotential from -60.0 mV±-1.0mV to -44.8 mV±2.3mV(P<0.05), and atropine (1 pmol/L) inhibited thedepolarization of the membrane potential. Muscarinicreceptor agonist Carbachol depolarized membranepotential from -60.0mV±1.0mV to -50.3 mV±0.3mV(P<0.05) and hyposmotic membrane stretchpotentiated the depolarization. Carbachol inducedmuscarinic current (Icch) was greatly increased byhyposmotic membrane stretch.CONCLUSION: Hyposmotic membrane stretchpotentiated muscarinic receptor agonist-induceddepolarization of membrane potential, which is relatedto hyposmotic membrane stretch-induced increase ofmuscarinic current.

  11. The collisional depolarization of OH(A (2)Σ(+)) and NO(A (2)Σ(+)) with Kr.

    Science.gov (United States)

    Chadwick, H; Brouard, M; Chang, Y-P; Eyles, C J; McCrudden, G; Perkins, T; Seamons, S A; Kłos, J; Alexander, M H; Dagdigian, P J; Herráez-Aguilar, D; Aoiz, F J

    2014-02-01

    Quantum beat spectroscopy has been used to measure rate coefficients at 300 K for collisional depolarization for NO(A (2)Σ(+)) and OH(A (2)Σ(+)) with krypton. Elastic depolarization rate coefficients have also been determined for OH(A) + Kr, and shown to make a much more significant contribution to the total depolarization rate than for NO(A) + Kr. While the experimental data for NO(A) + Kr are in excellent agreement with single surface quasiclassical trajectory (QCT) calculations carried out on the upper 2A(') potential energy surface, the equivalent QCT and quantum mechanical calculations cannot account for the experimental results for OH(A) + Kr collisions, particularly at low N. This disagreement is due to the presence of competing electronic quenching at low N, which requires a multi-surface, non-adiabatic treatment. Somewhat improved agreement with experiment is obtained by means of trajectory surface hopping calculations that include non-adiabatic coupling between the ground 1A(') and excited 2A(') states of OH(X/A) + Kr, although the theoretical depolarization cross sections still significantly overestimate those obtained experimentally.

  12. Microsoft Office Word 2007 step by step

    CERN Document Server

    Cox, Joyce

    2007-01-01

    Experience learning made easy-and quickly teach yourself how to create impressive documents with Word 2007. With Step By Step, you set the pace-building and practicing the skills you need, just when you need them!Apply styles and themes to your document for a polished lookAdd graphics and text effects-and see a live previewOrganize information with new SmartArt diagrams and chartsInsert references, footnotes, indexes, a table of contentsSend documents for review and manage revisionsTurn your ideas into blogs, Web pages, and moreYour all-in-one learning experience includes:Files for building sk

  13. Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

    Directory of Open Access Journals (Sweden)

    M. Haarig

    2017-09-01

    Full Text Available Triple-wavelength polarization lidar measurements in Saharan dust layers were performed at Barbados (13.1° N, 59.6° W, 5000–8000 km west of the Saharan dust sources, in the framework of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE-1, June–July 2013, SALTRACE-3, June–July 2014. Three case studies are discussed. High quality was achieved by comparing the dust linear depolarization ratio profiles measured at 355, 532, and 1064 nm with respective dual-wavelength (355, 532 nm depolarization ratio profiles measured with a reference lidar. A unique case of long-range transported dust over more than 12 000 km is presented. Saharan dust plumes crossing Barbados were measured with an airborne triple-wavelength polarization lidar over Missouri in the midwestern United States 7 days later. Similar dust optical properties and depolarization features were observed over both sites indicating almost unchanged dust properties within this 1 week of travel from the Caribbean to the United States. The main results of the triple-wavelength polarization lidar observations in the Caribbean in the summer seasons of 2013 and 2014 are summarized. On average, the particle linear depolarization ratios for aged Saharan dust were found to be 0.252 ± 0.030 at 355 nm, 0.280 ± 0.020 at 532 nm, and 0.225 ± 0.022 at 1064 nm after approximately 1 week of transport over the tropical Atlantic. Based on published simulation studies we present an attempt to explain the spectral features of the depolarization ratio of irregularly shaped mineral dust particles, and conclude that most of the irregularly shaped coarse-mode dust particles (particles with diameters > 1 µm have sizes around 1.5–2 µm. The SALTRACE results are also set into the context of the SAMUM-1 (Morocco, 2006 and SAMUM-2 (Cabo Verde, 2008 depolarization ratio studies. Again, only minor changes in the dust depolarization

  14. Orexins depolarize rostral ventrolateral medulla neurons and increase arterial pressure and heart rate in rats mainly via orexin 2 receptors.

    Science.gov (United States)

    Huang, Shang-Cheng; Dai, Yu-Wen E; Lee, Yen-Hsien; Chiou, Lih-Chu; Hwang, Ling-Ling

    2010-08-01

    An injection of orexin A or B into the cisterna magna or the rostral ventrolateral medulla (RVLM), where bulbospinal vasomotor neurons are located, elevated arterial pressure (AP) and heart rate (HR). We examined how orexins affected RVLM neurons to regulate cardiovascular functions by using in vitro recordings of neuronal activity of the RVLM and in vivo measurement of cardiovascular functions in rats. Orexin A and B concentration-dependently depolarized RVLM neurons. At 100 nM, both peptides excited 42% of RVLM neurons. Tetrodotoxin failed to block orexin-induced depolarization. In the presence of N-(2-methyl-6-benzoxazolyl)-N'-1, 5-naphthyridin-4-yl urea (SB-334867), an orexin 1 receptor (OX(1)R) antagonist, orexin A depolarized 42% of RVLM neurons with a smaller, but not significantly different, amplitude (4.9 +/- 0.8 versus 7.2 +/- 1.1 mV). In the presence of (2S)-1- (3,4-dihydro-6,7-dimethoxy-2(1H)-isoquinolinyl)-3,3-dimethyl-2-[(4-pyridinylmethyl)amino]-1-butanone hydrochloride (TCS OX2 29), an orexin 2 receptor (OX(2)R) antagonist, orexin A depolarized 25% of RVLM neurons with a significantly smaller amplitude (1.7 +/- 0.5 mV). Coapplication of both antagonists completely eliminated orexin A-induced depolarization. An OX(2)R agonist, [Ala(11),D-Leu(15)]-orexin B, concentration-dependently depolarized RVLM neurons. Regarding neuronal phenotypes, orexins depolarized 88% of adrenergic, 43% of nonadrenergic, and 36 to 41% of rhythmically firing RVLM neurons. Intracisternal TCS OX2 29 (3 and 10 nmol) suppressed intracisternal orexin A-induced increases of AP and HR, whereas intracisternal SB-334867 (3 and 10 nmol) had no effect on the orexin A-induced increase of HR but suppressed the orexin A-induced pressor response at 10 nmol. We concluded that orexins directly excite RVLM neurons, which include bulbospinal vasomotor neurons, and regulate cardiovascular function mainly via the OX(2)R, with a smaller contribution from the OX(1)R.

  15. VOLTAGE REGULATORS OF SYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available Synchronous generators are the primary source of electrical power autonomous electrosupply systems, including backup systems. They are also used in a structure of rotating electricity converters and are widely used in renewable energy as part of wind power plants of small, mini and micro hydroelectric plants. Increasing the speed and the accuracy of the system of the voltage regulation of synchronous generators is possible due to the development of combined systems containing more stabilizers. The article illustrates the functional schemes of circuit voltage stabilizers and frequency synchronous generators (with electromagnetic excitation and permanent magnet excitation and describes the features of their work, including two and three-aggregate rotating converters of electricity used in uninterruptible power supply systems. To improve the technical characteristics of the system of stabilization we have proposed functional solutions for stabilizers of synchronous generators made on the base of direct frequency converters and using a transformer with a rotating magnetic field. To improve the reliability of and to improve the operational characteristics of the autonomous independent sources of electricity we suggest creating the main functional blocks and the elements of the stabilization system in a modular way. The functional circuit solutions of voltage regulators of synchronous generators and the characteristics of their work considered in the article, are able to improve the efficiency of pre-design work in the development of new technical solutions for stabilizing the voltage and the frequency in synchronous generators of electrosupply autonomous systems

  16. Frequency-controlled voltage regulator

    Science.gov (United States)

    Mclyman, W. T.

    1980-01-01

    Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

  17. Recovery of slow potentials in AC-coupled electrocorticography: application to spreading depolarizations in rat and human cerebral cortex.

    Science.gov (United States)

    Hartings, Jed A; Watanabe, Tomas; Dreier, Jens P; Major, Sebastian; Vendelbo, Leif; Fabricius, Martin

    2009-10-01

    Cortical spreading depolarizations (spreading depressions and peri-infarct depolarizations) are a pathology intrinsic to acute brain injury, generating large negative extracellular slow potential changes (SPCs) that, lasting on the order of minutes, are studied with DC-coupled recordings in animals. The spreading SPCs of depolarization waves are observed in human cortex with AC-coupled electrocorticography (ECoG), although SPC morphology is distorted by the high-pass filter stage of the amplifiers. Here, we present a signal processing method to reverse these distortions and recover approximate full-band waveforms from AC-coupled recordings. We constructed digital filters that reproduced the phase and amplitude distortions introduced by specific AC-coupled amplifiers and, based on this characterization, derived digital inverse filters to remove these distortions from ECoG recordings. Performance of the inverse filter was validated by its ability to recover both simulated and real low-frequency input test signals. The inverse filter was then applied to AC-coupled ECoG recordings from five patients who underwent invasive monitoring after aneurysmal subarachnoid hemorrhage. For 117 SPCs, the inverse filter recovered full-band waveforms with morphologic characteristics typical of the negative DC shifts recorded in animals. Compared with those recorded in the rat cortex with the same analog and digital methods, the negative DC shifts of human depolarizations had significantly greater durations (1:47 vs. 0:45 min:sec) and peak-to-peak amplitudes (10.1 vs. 4.2 mV). The inverse filter thus permits the study of spreading depolarizations in humans, using the same assessment of full-band DC potentials as that in animals, and suggests a particular solution for recovery of biosignals recorded with frequency-limited amplifiers.

  18. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H+ for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens. PMID:23798303

  19. Computational Abstraction Steps

    DEFF Research Database (Denmark)

    Thomsen, Lone Leth; Thomsen, Bent; Nørmark, Kurt

    2010-01-01

    and class instantiations. Our teaching experience shows that many novice programmers find it difficult to write programs with abstractions that materialise to concrete objects later in the development process. The contribution of this paper is the idea of initiating a programming process by creating......In this paper we discuss computational abstraction steps as a way to create class abstractions from concrete objects, and from examples. Computational abstraction steps are regarded as symmetric counterparts to computational concretisation steps, which are well-known in terms of function calls...... or capturing concrete values, objects, or actions. As the next step, some of these are lifted to a higher level by computational means. In the object-oriented paradigm the target of such steps is classes. We hypothesise that the proposed approach primarily will be beneficial to novice programmers or during...

  20. Geometry and quadratic nonlinearity of charge transfer complexes in solution using depolarized hyper-Rayleigh scattering.

    Science.gov (United States)

    Pandey, Ravindra; Ghosh, Sampa; Mukhopadhyay, S; Ramasesha, S; Das, Puspendu K

    2011-01-28

    We report large quadratic nonlinearity in a series of 1:1 molecular complexes between methyl substituted benzene donors and quinone acceptors in solution. The first hyperpolarizability, β(HRS), which is very small for the individual components, becomes large by intermolecular charge transfer (CT) interaction between the donor and the acceptor in the complex. In addition, we have investigated the geometry of these CT complexes in solution using polarization resolved hyper-Rayleigh scattering (HRS). Using linearly (electric field vector along X direction) and circularly polarized incident light, respectively, we have measured two macroscopic depolarization ratios D=I(2ω,X,X)/I(2ω,Z,X) and D(')=I(2ω,X,C)/I(2ω,Z,C) in the laboratory fixed XYZ frame by detecting the second harmonic scattered light in a polarization resolved fashion. The experimentally obtained first hyperpolarizability, β(HRS), and the value of macroscopic depolarization ratios, D and D('), are then matched with the theoretically deduced values from single and double configuration interaction calculations performed using the Zerner's intermediate neglect of differential overlap self-consistent reaction field technique. In solution, since several geometries are possible, we have carried out calculations by rotating the acceptor moiety around three different axes keeping the donor molecule fixed at an optimized geometry. These rotations give us the theoretical β(HRS), D and D(') values as a function of the geometry of the complex. The calculated β(HRS), D, and D(') values that closely match with the experimental values, give the dominant equilibrium geometry in solution. All the CT complexes between methyl benzenes and chloranil or 1,2-dichloro-4,5-dicyano-p-benzoquinone investigated here are found to have a slipped parallel stacking of the donors and the acceptors. Furthermore, the geometries are staggered and in some pairs, a twist angle as high as 30° is observed. Thus, we have demonstrated in

  1. Electron transport in stepped Bi2Se3 thin films

    Science.gov (United States)

    Bauer, S.; Bobisch, C. A.

    2017-08-01

    We analyse the electron transport in a 16 quintuple layer thick stepped Bi2Se3 film grown on Si(1 1 1) by means of scanning tunnelling potentiometry (STP) and multi-point probe measurements. Scanning tunnelling microscopy images reveal that the local structure of the Bi2Se3 film is dominated by terrace steps and domain boundaries. From a microscopic study on the nm scale by STP, we find a mostly linear gradient of the voltage on the Bi2Se3 terraces which is interrupted by voltage drops at the position of the domain boundaries. The voltage drops indicate that the domain boundaries are scatterers for the electron transport. Macroscopic resistance measurements (2PP and in-line 4PP measurement) on the µm scale support the microscopic results. An additional rotational square 4PP measurement shows an electrical anisotropy of the sheet conductance parallel and perpendicular to the Bi2Se3 steps of about 10%. This is a result of the anisotropic step distribution at the stepped Bi2Se3 surface while domain boundaries are distributed isotropically. The determined value of the conductivity of the Bi2Se3 steps of about 1000 S cm-1 verifies the value of an earlier STP study.

  2. VSOP/Hv1 proton channels sustain calcium entry, neutrophil migration, and superoxide production by limiting cell depolarization and acidification

    National Research Council Canada - National Science Library

    El Chemaly, Antoun; Okochi, Yoshifumi; Sasaki, Mari; Arnaudeau, Serge; Okamura, Yasushi; Demaurex, Nicolas

    2010-01-01

    .... Voltage-gated proton channels (voltage-sensing domain only protein [VSOP]/Hv1) are required for high-level superoxide production by phagocytes, but the mechanism of this effect is not established...

  3. [An integral chip for the multiphase pulse-duration modulation used for voltage changer in biomedical microprocessor systems].

    Science.gov (United States)

    Balashov, A M; Selishchev, S V

    2004-01-01

    An integral chip (IC) was designed for controlling the step-down pulse voltage converter, which is based on the multiphase pulse-duration modulation, for use in biomedical microprocessor systems. The CMOS technology was an optimal basis for the IC designing. An additional feedback circuit diminishes the output voltage dispersion at dynamically changing loads.

  4. Direct evidence that scorpion α-toxins (site-3 modulate sodium channel inactivation by hindrance of voltage-sensor movements.

    Directory of Open Access Journals (Sweden)

    Zhongming Ma

    Full Text Available The position of the voltage-sensing transmembrane segment, S4, in voltage-gated ion channels as a function of voltage remains incompletely elucidated. Site-3 toxins bind primarily to the extracellular loops connecting transmembrane helical segments S1-S2 and S3-S4 in Domain 4 (D4 and S5-S6 in Domain 1 (D1 and slow fast-inactivation of voltage-gated sodium channels. As S4 of the human skeletal muscle voltage-gated sodium channel, hNav1.4, moves in response to depolarization from the resting to the inactivated state, two D4S4 reporters (R2C and R3C, Arg1451Cys and Arg1454Cys, respectively move from internal to external positions as deduced by reactivity to internally or externally applied sulfhydryl group reagents, methane thiosulfonates (MTS. The changes in reporter reactivity, when cycling rapidly between hyperpolarized and depolarized voltages, enabled determination of the positions of the D4 voltage-sensor and of its rate of movement. Scorpion α-toxin binding impedes D4S4 segment movement during inactivation since the modification rates of R3C in hNav1.4 with methanethiosulfonate (CH3SO2SCH2CH2R, where R = -N(CH33 (+ trimethylammonium, MTSET and benzophenone-4-carboxamidocysteine methanethiosulfonate (BPMTS were slowed ~10-fold in toxin-modified channels. Based upon the different size, hydrophobicity and charge of the two reagents it is unlikely that the change in reactivity is due to direct or indirect blockage of access of this site to reagent in the presence of toxin (Tx, but rather is the result of inability of this segment to move outward to the normal extent and at the normal rate in the toxin-modified channel. Measurements of availability of R3C to internally applied reagent show decreased access (slower rates of thiol reaction providing further evidence for encumbered D4S4 movement in the presence of toxins consistent with the assignment of at least part of the toxin binding site to the region of D4S4 region of the voltage

  5. Effect of temperature and loading on output voltage of lead zirconate titanate (PZT-5A) piezoelectric energy harvester

    Science.gov (United States)

    Butt, Z.; Pasha, R. A.

    2016-08-01

    Energy harvesting is the process of acquiring energy from the external sources and then further used to drive any system. Piezoelectric material was operated at various temperature but the characterization of the material mostly performed at room temperature. The depolarization in piezoelectric material occurs when the material is heated to its curie temperature and when mechanical stresses are high to disturb the properties of the material. The aim of this paper is to study the performance of lead zirconate titanate (PZT-5A) piezoelectric material under various temperatures and loading conditions. The output voltage of piezoelectric material decreases with increase of temperature. It was found that output voltage from the harvester increases when loading increases while its temperature decreases.

  6. Over-voltage protection system and method

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Song; Dong, Dong; Lai, Rixin

    2017-05-02

    An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device. A plurality of self-powered gate drive circuits are connected to the plurality of semiconductor devices, wherein the plurality of self-powered gate drive circuits receive over-voltage triggering pulses from the optocoupler during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit.

  7. Computational Abstraction Steps

    DEFF Research Database (Denmark)

    Thomsen, Lone Leth; Thomsen, Bent; Nørmark, Kurt

    2010-01-01

    and class instantiations. Our teaching experience shows that many novice programmers find it difficult to write programs with abstractions that materialise to concrete objects later in the development process. The contribution of this paper is the idea of initiating a programming process by creating......In this paper we discuss computational abstraction steps as a way to create class abstractions from concrete objects, and from examples. Computational abstraction steps are regarded as symmetric counterparts to computational concretisation steps, which are well-known in terms of function calls...

  8. Primary afferent depolarization and flexion reflexes produced by radiant heat stimulation of the skin.

    Science.gov (United States)

    Burke, R E; Rudomin, P; Vyklický, L; Zajac, F E

    1971-02-01

    1. The reflex effects of pulses of intense radiant heat applied to the skin of the central plantar pad have been studied in unanaesthetized (decerebrate) spinal cats.2. Pad heat pulses produced flexion of the ipsilateral hind limb and increased ipsilateral flexor monosynaptic reflexes, due to post-synaptic excitation of flexor alpha motoneurones. These effects were accompanied by reduction of extensor monosynaptic reflexes and post-synaptic inhibition of extensor motoneurones.3. Ipsilateral (and contralateral) pad heat pulses consistently evoked negative dorsal root potentials (DRPs) as well as increased excitability of both cutaneous and group Ib muscle afferent terminals. The excitability of group Ia afferents was sometimes also increased during pad heat pulses, but to a lesser extent.4. Pad heat pulses produced negative DRPs in preparations in which positive DRP components could be demonstrated following electrical stimulation of both skin and muscle nerves.5. The motor and primary afferent effects of heat pulses always accompanied one another, beginning after the pad surface temperature had reached rather high levels (usually 48-55 degrees C).6. Negative DRPs increased excitability of cutaneous and group Ib afferents, and motoneurone activation produced by pad heat pulses was essentially unmodified when conduction in large myelinated afferents from the central plantar pad was blocked by cooling the posterior tibial nerve trunk.7. It is concluded that adequate noxious activation of cutaneous afferents of small diameter produces primary afferent depolarization in a variety of large diameter afferent fibres, as well as post-synaptic effects in alpha motoneurones.

  9. The effect of depolarization fields on the electronic properties of two-dimensional materials

    Science.gov (United States)

    Shin, Young-Han; Kim, Hye Jung; Noor-A-Alam, Mohammad

    2015-03-01

    Graphene is a two-dimensional semimetal with a zero band gap. By weakening the sp2 covalent bonding of graphene with additional elements such as hydrogen or fluorine, however, it is possible to make it insulating. We can expect that the band gap converges to that of a three-dimensional analogue by repeating such two-dimensional layers along the normal to the layer. If we control the position of additional elements to make a dipole monolayer, the system will have an intrinsic internal field decreases as the number of layers increases. But, for two-dimensional bilayers, depolarization field is so strong that its electronic properties can be much different from its monolayer analogue. In this presentation, we show that the internal fields induced by dipole moments can change electronic properties of two-dimensional materials such as graphene-like structures and complex metal oxides. This work was supported by the National Research Foundation of Korea Grant by the Ministry of Education, Science, and Technology (2009-0093818, 2012-014007, 2014M3A7B4049367)

  10. Photo-elastic effect, thermal lensing and depolarization in a-cut tetragonal laser crystals

    Science.gov (United States)

    Yumashev, K. V.; Zakharova, A. N.; Loiko, P. A.

    2016-06-01

    We report on analytical description of thermal lensing effect in tetragonal crystals cut along the [1 0 0] crystallographic axis, for the two principal light polarizations, E ┴ c and E || c, under diode-pumping (plane stress approximation). Within this approach, we take into account anisotropy of elastic, photo-elastic, thermal and optical properties of the material. Expressions for the ‘generalized’ thermo-optic coefficient χ are presented. It is shown that astigmatism of thermal lens is determined both by the photo-elastic and end-bulging effects. The sign of the photo-elastic term χ″ can be either positive or negative affecting significantly the sign of the thermal lens. Depolarization loss in a-cut tetragonal crystals is few orders of magnitude lower than that in cubic crystals. Calculations are performed for a-cut tetragonal molybdates, Nd:CaMoO4, Nd:PbMoO4 and Nd:NaBi(MoO4)2.

  11. Redox-active nanoceria depolarize mitochondrial membrane of human colon cancer cells

    Science.gov (United States)

    Jana, Saikat Kumar; Banerjee, Priyanka; Das, Soumen; Seal, Sudipta; Chaudhury, Koel

    2014-06-01

    Nanotherapeutics is emerging as a promising option to the various limitations and side effects associated with conventional chemotherapy. The present study investigates the cytotoxic effect of redox-active cerium oxide nanoparticles (nanoceria) on human colorectal adenocarcinoma-derived cell line (HCT 15). Exposure of these cells to nanoceria for 24 h with concentration ranging between 10 and 100 μM resulted in a significant reduction of cell viability in a dose-dependent manner. Further, at a concentration of 10 µM, nanoceria exhibited time-dependent cytotoxic effect when exposed to the cells for 24, 48, and 72 h. Upon treatment of the cells with nanoceria, reactive oxygen species (ROS) and lipid peroxidation which are indicators of oxidative stress and cytotoxicity increased significantly, in a dose-dependent manner. Nanoceria was also found to depolarize the mitochondrial membrane, thereby collapsing the membrane potential and leading to initiation of apoptosis. Scanning electron microscopic study of nanoceria-treated HCT 15 cells showed morphological changes and loss of filopodia and lamellipodia, indicating arrest of metastatic spread. Summarizing, when cultured HCT 15 cells are exposed to nanoceria, a dose-dependent cytotoxic effect mediated by ROS generation is observed.

  12. Low temperature dielectric relaxation of poly (L-lactic acid) (PLLA) by Thermally Stimulated Depolarization Current

    Science.gov (United States)

    Mishra Patidar, Manju; Jain, Deepti; Nath, R.; Ganesan, V.

    2016-10-01

    Poly (L-lactic acid) (PLLA) is a biodegradable and biocompatible polyester that can be produced by renewable resources, like corn. Being non-toxic to human body, PLLA is used in biomedical applications, like surgical sutures, bone fixation devices, or controlled drug delivery. Besides its application studies, very few experiments have been done to study its dielectric relaxation in the low temperature region. Keeping this in mind we have performed a low temperature thermally stimulated depolarization current (TSDC) studies over the temperature range of 80K-400K to understand the relaxation phenomena of PLLA. We could observe a multi modal broad relaxation of small but significant intensity at low temperatures while a sharp and high intense peak around glass transition temperature, Tg∼ 333K, of PLLA has appeared. The fine structure of the low temperature TSDC peak may be attributed to the spherulites formation of crystallite regions inter twinned with the polymer as seen in AFM and appear to be produced due to an isothermal crystallization process. XRD analysis also confirms the semicrystalline nature of the PLLA film.

  13. Most robust and fragile two-qubit entangled states under depolarizing channels

    CERN Document Server

    Pang, Chao-Qian; Jiang, Yue; Liang, Mai-Lin

    2012-01-01

    In the two-qubit system under the local depolarizing channels, the most robust and the most fragile states for a given concurrence or negativity are derived. For the one-sided channel, with the aid of the evolution equation for entanglement given by Konrad \\emph{et al.} [Nat. Phys. 4, 99 (2008)], the pure states are proved to be the most robust. Based on a generalization of the evolution equation, we classify the ansatz states in our investigation by the amount of robustness, and consequently derive the most fragile states. For the two-sided channel, the pure states are proved to be the most robust for a fixed concurrence, but is the most fragile with a given negativity when the channel is uniform. Under the uniform channel, for a given negativity, the most robust states are the ones with the maximal concurrence, which are also the most fragile states when the concurrence is given in the region of [1/2,1]. When the entanglement approaches zero, the most fragile states for a given negativity become the pure st...

  14. Ketamine modulation of the haemodynamic response to spreading depolarization in the gyrencephalic swine brain.

    Science.gov (United States)

    Sánchez-Porras, Renán; Santos, Edgar; Schöll, Michael; Kunzmann, Kevin; Stock, Christian; Silos, Humberto; Unterberg, Andreas W; Sakowitz, Oliver W

    2017-05-01

    Spreading depolarization (SD) generates significant alterations in cerebral haemodynamics, which can have detrimental consequences on brain function and integrity. Ketamine has shown an important capacity to modulate SD; however, its impact on SD haemodynamic response is incompletely understood. We investigated the effect of two therapeutic ketamine dosages, a low-dose of 2 mg/kg/h and a high-dose of 4 mg/kg/h, on the haemodynamic response to SD in the gyrencephalic swine brain. Cerebral blood volume, pial arterial diameter and cerebral blood flow were assessed through intrinsic optical signal imaging and laser-Doppler flowmetry. Our findings indicate that frequent SDs caused a persistent increase in the baseline pial arterial diameter, which can lead to a diminished capacity to further dilate. Ketamine infused at a low-dose reduced the hyperemic/vasodilative response to SD; however, it did not alter the subsequent oligemic/vasoconstrictive response. This low-dose did not prevent the baseline diameter increase and the diminished dilative capacity. Only infusion of ketamine at a high-dose suppressed SD and the coupled haemodynamic response. Therefore, the haemodynamic response to SD can be modulated by continuous infusion of ketamine. However, its use in pathological models needs to be explored to corroborate its possible clinical benefit.

  15. Quantifying the polarization properties of non-depolarizing optical elements with virtual distorting elements.

    Science.gov (United States)

    Wang, Xiao; Yang, Feng; Yin, Jianhua

    2017-04-01

    It is well known that polarization can be potentially distorted by optical elements in optical paths, which intensively influences researches and techniques related to polarization analysis. For this, we proposed to exactly quantify the polarization properties of non-depolarizing optical elements with virtual distorting elements characterized by three parameters: orientation Θ, diattenuation Γ, and retardation Δ. Utilizing the least-squares fitting method, these three parameters can be determined by fitting the measured output polarization states from the optical element with the polarization responses of VDEs. The principle of this method is detailed, and a corresponding experimental setup is further presented. The feasibility of this method has been verified in reflective mirrors and a dichroic mirror. Based on the quantification results with our setup, we have successfully compensated the polarization distortion induced by a dichroic mirror. The precision of this method has been investigated in detail with Monte Carlo simulations. The investigation results show that this method has high precision at certain measurement conditions, and the precision can be further improved.

  16. Mechanisms of spreading depolarization in vertebrate and insect central nervous systems.

    Science.gov (United States)

    Spong, Kristin E; Andrew, R David; Robertson, R Meldrum

    2016-09-01

    Spreading depolarization (SD) is generated in the central nervous systems of both vertebrates and invertebrates. SD manifests as a propagating wave of electrical depression caused by a massive redistribution of ions. Mammalian SD underlies a continuum of human pathologies from migraine to stroke damage, whereas insect SD is associated with environmental stress-induced neural shutdown. The general cellular mechanisms underlying SD seem to be evolutionarily conserved throughout the animal kingdom. In particular, SD in the central nervous system of Locusta migratoria and Drosophila melanogaster has all the hallmarks of mammalian SD. Locust SD is easily induced and monitored within the metathoracic ganglion (MTG) and can be modulated both pharmacologically and by preconditioning treatments. The finding that the fly brain supports repetitive waves of SD is relatively recent but noteworthy, since it provides a genetically tractable model system. Due to the human suffering caused by SD manifestations, elucidating control mechanisms that could ultimately attenuate brain susceptibility is essential. Here we review mechanisms of SD focusing on the similarities between mammalian and insect systems. Additionally we discuss advantages of using invertebrate model systems and propose insect SD as a valuable model for providing new insights to mammalian SD.

  17. Depolarizing GABA/glycine synaptic events switch from excitation to inhibition during frequency increases

    Science.gov (United States)

    Branchereau, Pascal; Cattaert, Daniel; Delpy, Alain; Allain, Anne-Emilie; Martin, Elodie; Meyrand, Pierre

    2016-02-01

    By acting on their ionotropic chloride channel receptors, GABA and glycine represent the major inhibitory transmitters of the central nervous system. Nevertheless, in various brain structures, depolarizing GABAergic/glycinergic postsynaptic potentials (dGPSPs) lead to dual inhibitory (shunting) and excitatory components, the functional consequences of which remain poorly acknowledged. Indeed, the extent to which each component prevails during dGPSP is unclear. Understanding the mechanisms predicting the dGPSP outcome on neural network activity is therefore a major issue in neurobiology. By combining electrophysiological recordings of spinal embryonic mouse motoneurons and modelling study, we demonstrate that increasing the chloride conductance (gCl) favors inhibition either during a single dGPSP or during trains in which gCl summates. Finally, based on this summation mechanism, the excitatory effect of EPSPs is overcome by dGPSPs in a frequency-dependent manner. These results reveal an important mechanism by which dGPSPs protect against the overexcitation of neural excitatory circuits.

  18. Advances in high voltage engineering

    CERN Document Server

    Haddad, A

    2005-01-01

    This book addresses the very latest research and development issues in high voltage technology and is intended as a reference source for researchers and students in the field, specifically covering developments throughout the past decade. This unique blend of expert authors and comprehensive subject coverage means that this book is ideally suited as a reference source for engineers and academics in the field for years to come.

  19. High Voltage Pulse Testing Survey.

    Science.gov (United States)

    1985-10-01

    Cryogenic 23 E. Liquids 26 F. Solids 28 1. Polyethylene 28 2. Cross-Linked Polyethylene ( XLPE ) 29 3. Polyimide and Polyvenylchloride (PVC) 31 VI Benefits 35 A...Strength of XLPE Cables 29 vii * 4" I PROGRAM OBJECTIVES The Pulse Test Survey summarizes government, industry, and technical reports on high voltage pulse...system of silicone oil on a XLPE (cross-linked polyethylene) spacer tends to lower the impulse breakdown by approximately 10 percent. The negative impulse

  20. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    Science.gov (United States)

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  1. Low voltage electron beam accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Masafumi [Iwasaki Electric Co., Ltd., Tokyo (Japan)

    2003-02-01

    Widely used electron accelerators in industries are the electron beams with acceleration voltage at 300 kV or less. The typical examples are shown on manufactures in Japan, equipment configuration, operation, determination of process parameters, and basic maintenance requirement of the electron beam processors. New electron beam processors with acceleration voltage around 100 kV were introduced maintaining the relatively high dose speed capability of around 10,000 kGy x mpm at production by ESI (Energy Science Inc. USA, Iwasaki Electric Group). The application field like printing and coating for packaging requires treating thickness of 30 micron or less. It does not require high voltage over 110 kV. Also recently developed is a miniature bulb type electron beam tube with energy less than 60 kV. The new application area for this new electron beam tube is being searched. The drive force of this technology to spread in the industries would be further development of new application, process and market as well as the price reduction of the equipment, upon which further acknowledgement and acceptance of the technology to societies and industries would entirely depend. (Y. Tanaka)

  2. The position of the fast-inactivation gate during lidocaine block of voltage-gated Na+ channels.

    Science.gov (United States)

    Vedantham, V; Cannon, S C

    1999-01-01

    Lidocaine produces voltage- and use-dependent inhibition of voltage-gated Na+ channels through preferential binding to channel conformations that are normally populated at depolarized potentials and by slowing the rate of Na+ channel repriming after depolarizations. It has been proposed that the fast-inactivation mechanism plays a crucial role in these processes. However, the precise role of fast inactivation in lidocaine action has been difficult to probe because gating of drug-bound channels does not involve changes in ionic current. For that reason, we employed a conformational marker for the fast-inactivation gate, the reactivity of a cysteine substituted at phenylalanine 1304 in the rat adult skeletal muscle sodium channel alpha subunit (rSkM1) with [2-(trimethylammonium)ethyl]methanethiosulfonate (MTS-ET), to determine the position of the fast-inactivation gate during lidocaine block. We found that lidocaine does not compete with fast-inactivation. Rather, it favors closure of the fast-inactivation gate in a voltage-dependent manner, causing a hyperpolarizing shift in the voltage dependence of site 1304 accessibility that parallels a shift in the steady state availability curve measured for ionic currents. More significantly, we found that the lidocaine-induced slowing of sodium channel repriming does not result from a slowing of recovery of the fast-inactivation gate, and thus that use-dependent block does not involve an accumulation of fast-inactivated channels. Based on these data, we propose a model in which transitions along the activation pathway, rather than transitions to inactivated states, play a crucial role in the mechanism of lidocaine action.

  3. Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors

    Directory of Open Access Journals (Sweden)

    Salmela Iikka

    2012-08-01

    Full Text Available Abstract Background The importance of voltage-dependent conductances in sensory information processing is well-established in insect photoreceptors. Here we present the characterization of electrical properties in photoreceptors of the cockroach (Periplaneta americana, a nocturnal insect with a visual system adapted for dim light. Results Whole-cell patch-clamped photoreceptors had high capacitances and input resistances, indicating large photosensitive rhabdomeres suitable for efficient photon capture and amplification of small photocurrents at low light levels. Two voltage-dependent potassium conductances were found in the photoreceptors: a delayed rectifier type (KDR and a fast transient inactivating type (KA. Activation of KDR occurred during physiological voltage responses induced by light stimulation, whereas KA was nearly fully inactivated already at the dark resting potential. In addition, hyperpolarization of photoreceptors activated a small-amplitude inward-rectifying (IR current mediated at least partially by chloride. Computer simulations showed that KDR shapes light responses by opposing the light-induced depolarization and speeding up the membrane time constant, whereas KA and IR have a negligible role in the majority of cells. However, larger KA conductances were found in smaller and rapidly adapting photoreceptors, where KA could have a functional role. Conclusions The relative expression of KA and KDR in cockroach photoreceptors was opposite to the previously hypothesized framework for dark-active insects, necessitating further comparative work on the conductances. In general, the varying deployment of stereotypical K+ conductances in insect photoreceptors highlights their functional flexibility in neural coding.

  4. Voltage-dependent calcium channels from brain incorporated into planar lipid bilayers

    Science.gov (United States)

    Nelson, Mark T.; French, Robert J.; Krueger, Bruce K.

    1984-03-01

    Many important physiological processes, including neurotransmitter release and muscle contraction1-3, are regulated by the concentration of Ca2+ ions in the cell. Levels of cytoplasmic Ca2+ can be elevated by the entry of Ca2+ ions through voltage-dependent channels which are selective for Ca2+, Ba2+ and Sr2+ ions4-14. We have measured currents through single, voltage-dependent calcium channels from rat brain that have been incorporated into planar lipid bilayers. Channel gating was voltage-dependent: membrane depolarization increased the channel open times and decreased the closed times. The channels were selective for divalent cations over monovalent ions. The well-known calcium channel blockers, lanthanum and cadmium, produced a concentration-dependent reduction of the apparent single-channel conductance. Contrary to expectations14, the nature of the divalent cation carrying current through the channel affected not only the single-channel conductance, but also the channel open times, with mean open times being shortest for barium.

  5. High Efficiency Interleaved Active Clamped Dc-Dc Converter with Fuel Cell for High Voltage Applications

    Directory of Open Access Journals (Sweden)

    Sona P

    2014-02-01

    Full Text Available A high efficiency interleaved ZVS active clamped current fed dc-dc converter is proposed in this paper specially used for fuel cell applications. As the fuel cell output is very low we are in need of a step up dc-dc converter. Here a current fed dc-dc converter is used. Two current fed dc-dc converters are interleaved by connecting their inputs in parallel and outputs in series. With this proposed methodology input current ripples in the fuel cell stacks can be reduced and a regulated output voltage ripples can be obtained. The active clamping circuit used in this model absorbs the turn off voltage spikes hence low voltage devices with low on state resistance can be used.Voltage doubler circuits will give double the output voltage than normal with smaller transformer turns ratio and flexibility. The proposed method is simulated in MATLAB for verifying the accuracy of the proposed design.

  6. Suppression of Spiral Waves by Voltage Clamp Techniques in a Conductance-Based Cardiac Tissue Model

    Institute of Scientific and Technical Information of China (English)

    YU Lian-Chun; MA Jun; ZHANG Guo-Yong; CHEN Yong

    2008-01-01

    A new control method is proposed to control the spatio-temporal dynamics in excitable media, which is described by the Morris-Lecar cells model. It is confirmed that successful suppression of spiral waves can be obtained by spatially clamping the membrane voltage of the excitable cells. The low voltage clamping induces breakup of spiral waves and the fragments are soon absorbed by low voltage obstacles, whereas the high voltage clamping generates travel waves that annihilate spiral waves through collision with them. However, each method has its shortcomings. Furthermore, a two-step method that combines both low and high voltage clamp techniques is then presented as a possible way of out this predicament.

  7. Analysis of Antimicrobial-Triggered Membrane Depolarisation Using Voltage Sensitive Dyes

    Directory of Open Access Journals (Sweden)

    J. Derk te Winkel

    2016-04-01

    Full Text Available The bacterial cytoplasmic membrane is a major inhibitory target for antimicrobial compounds. Commonly, although not exclusively, these compounds unfold their antimicrobial activity by disrupting the essential barrier function of the cell membrane. As a consequence, membrane permeability assays are central for mode of action studies analysing membrane-targeting antimicrobial compounds. The most frequently used in vivo methods detect changes in membrane permeability by following internalization of normally membrane impermeable and relatively large fluorescent dyes. Unfortunately, these assays are not sensitive to changes in membrane ion permeability which are sufficient to inhibit and kill bacteria by membrane depolarization. In this manuscript, we provide experimental advice how membrane potential, and its changes triggered by membrane-targeting antimicrobials can be accurately assessed in vivo. Optimized protocols are provided for both qualitative and quantitative kinetic measurements of membrane potential. At last, single cell analyses using voltage-sensitive dyes in combination with fluorescence microscopy are introduced and discussed.

  8. Aging-associated changes in motor axon voltage-gated Na(+) channel function in mice

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Rosberg, Mette Romer; Alvarez, Susana

    2016-01-01

    Accumulating myelin abnormalities and conduction slowing occur in peripheral nerves during aging. In mice deficient of myelin protein P0, severe peripheral nervous system myelin damage is associated with ectopic expression of Nav1.8 voltage-gated Na(+) channels on motor axons aggravating...... the functional impairment. The aim of the present study was to investigate the effect of regular aging on motor axon function with particular emphasis on Nav1.8. We compared tibial nerve conduction and excitability measures by threshold tracking in 12 months (mature) and 20 months (aged) wild-type (WT) mice....... With aging, deviations during threshold electrotonus were attenuated and the resting current-threshold slope and early refractoriness were increased. Modeling indicated that, in addition to changes in passive membrane properties, motor fibers in aged WT mice were depolarized. An increased Nav1.8 isoform...

  9. Piezo Voltage Controlled Planar Hall Effect Devices

    OpenAIRE

    Bao Zhang; Kang-Kang Meng; Mei-Yin Yang; Edmonds, K. W.; Hao Zhang; Kai-Ming Cai; Yu Sheng; Nan Zhang; Yang Ji; Jian-Hua Zhao; Hou-Zhi Zheng; Kai-You Wang

    2015-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the pie...

  10. 49 CFR 234.221 - Lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lamp voltage. 234.221 Section 234.221 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION..., Inspection, and Testing Maintenance Standards § 234.221 Lamp voltage. The voltage at each lamp shall...

  11. Bootstrapped Low-Voltage Analog Switches

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1999-01-01

    Novel low-voltage constant-impedance analog switch circuits are proposed. The switch element is a single MOSFET, and constant-impedance operation is obtained using simple circuits to adjust the gate and bulk voltages relative to the switched signal. Low-voltage (1-volt) operation is made feasible...

  12. Modulation Voltage of High T c DC Superconducting Quantum Interference Device with Damping Resistance

    Science.gov (United States)

    Enpuku, Keiji; Doi, Hideki; Tokita, Go; Maruo, Taku

    1994-05-01

    The effect of damping resistance on the voltage versus flux (V -Φ) relation of the high T c dc superconducting quantum interference device (SQUID) is studied experimentally. Dc SQUID using YBaCuO step-edge junction and damping resistance in parallel with SQUID inductance is fabricated. Measured values of modulation voltage in the V -Φ relation are compared with those of the conventional SQUID without damping resistance. It is shown that modulation voltage is much improved by using damping resistance. The obtained experimental results agree reasonably with theoretical predictions reported previously.

  13. Measurement of the Linear Depolarization Ratio of Aged Dust at Three Wavelengths (355, 532 and 1064 nm Simultaneously over Barbados

    Directory of Open Access Journals (Sweden)

    Haarig Moritz

    2016-01-01

    Full Text Available A ground-based polarization Raman lidar is presented, that is able to measure the depolarization ratio at three wavelengths (355, 532 and 1064 nm simultaneously. This new feature is implemented for the first time in a Raman lidar. It provides a full dataset of 3 backscatter coefficients, two extinction coefficients and 3 depolarization ratios (3+2+3 lidar system. To ensure the data quality, it has been compared to the well characterized two-wavelength polarization lidar POLIS. Measurements of long-range transported dust have been performed in the framework of the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE in the Caribbean.

  14. Rf Depolarizing Resonances In The Presence Of A Full Siberian Snake And Full Snake Spin-flipping

    CERN Document Server

    Blinov, B B

    2000-01-01

    Frequent polarization reversals, or spin-flips, of a stored polarized beam in high energy scattering asymmetry experiments may greatly reduce systematic errors of spin asymmetry measurements. A spin-flipping technique is being developed by using rf magnets running at a frequency close to the spin precession frequency, thereby creating spin-depolarizing resonances; the spin can then be flipped by ramping the rf magnet's frequency through the resonance. We studied, at the Indiana University Cyclotron Facility Cooler Ring, properties of such rf depolarizing resonances in the presence of a nearly-full Siberian snake and their possible application for spin- flipping. By using an rf-solenoid magnet, we reached a 98.7 ± 1% efficiency of spin-flipping. However, an rf-dipole magnet is more practical at high energies; hence, studies of spin-flipping by an rf-dipole are underway at IUCF.

  15. High-Precision Calibration of Electron Beam Energy from the Hefei Light Source Using Spin Resonant Depolarization

    Science.gov (United States)

    Lan, Jie-Qin; Xu, Hong-Liang

    2014-12-01

    The electron beam energy at the Hefei Light Source (HLS) in the National Synchrotron Radiation Laboratory is highly precisely calibrated by using the method of spin resonant depolarization for the first time. The spin tune and the beam energy are determined by sweeping the frequency of a radial rf stripline oscillating magnetic field to artificially excite a spin resonance and depolarize the beam. The resonance signal is recognized by observing the sudden change of the Touschek loss counting rate of the beam. The possible systematic errors of the experiment are presented and the accuracy of the calibrated energy is shown to be about 10-4. A series of measurements show that the energy stability of the machine is of the order of 9 × 10-3.

  16. Intrinsic reduction the depolarization loss in electro-optical Q-switched laser using a rectangular KD*P crystal

    Science.gov (United States)

    Yin, Xingliang; Jiang, Menghua; Sun, Zhe; Hui, Yongling; Lei, Hong; Li, Qiang

    2017-09-01

    We presented the first demonstration of a new structure KD*P crystal as electro-optic switch, in which the thermal depolarization loss was intrinsically reduced. The thermally induced birefringence and depolarization of both cylindrical and rectangular crystalline structure were simulated. The higher pulse energy or average power output was achieved in the diode pumped E-O Q-switched laser using a rectangular KD*P crystal. At the repetition rate of 100 Hz, the maximum average output power was 27.2 W at 145 A pump current, corresponding to the pulse energy was 272 mJ with pulse width of 65 ns and the beam quality of M2=20.4. Comparing the highest average power or corresponding single pulse energy, the laser with the rectangular KD*P crystal was two times of the laser with the traditional cylindrical KD*P crystal.

  17. Regulated dc-to-dc converter for voltage step-up or step-down with input-output isolation

    Science.gov (United States)

    Feng, S. Y.; Wilson, T. G. (Inventor)

    1973-01-01

    A closed loop regulated dc-to-dc converter employing an unregulated two winding inductive energy storage converter is provided by using a magnetically coupled multivibrator acting as duty cycle generator to drive the converter. The multivibrator is comprised of two transistor switches and a saturable transformer. The output of the converter is compared with a reference in a comparator which transmits a binary zero until the output exceeds the reference. When the output exceeds the reference, the binary output of the comparator drives transistor switches to turn the multivibrator off. The multivibrator is unbalanced so that a predetermined transistor will always turn on first when the binary feedback signal becomes zero.

  18. Study Case of Air-Mass Modification over Poland and Romania Observed by the Means of Multiwavelength Raman Depolarization Lidars

    OpenAIRE

    Costa-Surós Montserrat; Janicka Lucja; Stachlewska Iwona S.; Nemuc Anca; Talianu Camelia; Heese Birgit; Engelmann Ronny

    2016-01-01

    An air-mass modification, on its way from Poland to Romania, observed between 19-21 July 2014 is discussed. The air-mass was investigated using data of two multi-wavelength lidars capable of performing regular elastic, depolarization and Raman measurements in Warsaw, Poland, and in Magurele, Romania. The analysis was focused on evaluating optical properties of aerosol in order to search for similarities and differences in the vertical profiles describing the atmospheric layers above the two s...

  19. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    DEFF Research Database (Denmark)

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis...

  20. Estimating Voltage Asymmetry Making by One Phase Micro-generator in Low Voltage Network

    Directory of Open Access Journals (Sweden)

    Marian Sobierajski

    2014-12-01

    Full Text Available Connection of one phase micro-generator to the low voltage network increases voltage asymmetry. The voltage asymmetry is defined as the quotient of negative and positive voltage components. The mathematical background of exact and rough computation of the asymmetry quotient is presented in the paper. Considerations are illustrated by simple examples.