WorldWideScience

Sample records for nonlinear rectifying synaptic

  1. Feedback loop compensates for rectifier nonlinearity

    Science.gov (United States)

    1966-01-01

    Signal processing circuit with two negative feedback loops rectifies two sinusoidal signals which are 180 degrees out of phase and produces a single full-wave rectified output signal. Each feedback loop incorporates a feedback rectifier to compensate for the nonlinearity of the circuit.

  2. Rectifiers

    CERN Document Server

    Visintini, R

    2006-01-01

    In particle accelerators, rectifiers are used to convert the AC voltage into DC or low-frequency AC to supply loads like magnets or klystrons. Some loads require high currents, others high voltages, and others both high current and high voltage. This presentation deals with the particular class of line commutated rectifiers (the switching techniques are treated elsewhere). The basic principles of rectification are presented. The effects of real world parameters are then taken into consideration. Some aspects related to the filtering of the harmonics both on the DC side and on the AC side are presented. Some protection issues associated with the use of thyristors and diodes are also treated. An example of power converter design, referring to a currently operating magnet power supply, is included. An extended bibliography (including some internet links) ends this presentation.

  3. Estimation of Synaptic Conductances in Presence of Nonlinear Effects Caused by Subthreshold Ionic Currents

    Directory of Open Access Journals (Sweden)

    Catalina Vich

    2017-07-01

    Full Text Available Subthreshold fluctuations in neuronal membrane potential traces contain nonlinear components, and employing nonlinear models might improve the statistical inference. We propose a new strategy to estimate synaptic conductances, which has been tested using in silico data and applied to in vivo recordings. The model is constructed to capture the nonlinearities caused by subthreshold activated currents, and the estimation procedure can discern between excitatory and inhibitory conductances using only one membrane potential trace. More precisely, we perform second order approximations of biophysical models to capture the subthreshold nonlinearities, resulting in quadratic integrate-and-fire models, and apply approximate maximum likelihood estimation where we only suppose that conductances are stationary in a 50–100 ms time window. The results show an improvement compared to existent procedures for the models tested here.

  4. Estimation of Synaptic Conductances in Presence of Nonlinear Effects Caused by Subthreshold Ionic Currents

    DEFF Research Database (Denmark)

    Vich, Catalina; Berg, Rune W.; Guillamon, Antoni

    2017-01-01

    Subthreshold fluctuations in neuronal membrane potential traces contain nonlinear components, and employing nonlinear models might improve the statistical inference. We propose a new strategy to estimate synaptic conductances, which has been tested using in silico data and applied to in vivo...... recordings. The model is constructed to capture the nonlinearities caused by subthreshold activated currents, and the estimation procedure can discern between excitatory and inhibitory conductances using only one membrane potential trace. More precisely, we perform second order approximations of biophysical...... models to capture the subthreshold nonlinearities, resulting in quadratic integrate-and-fire models, and apply approximate maximum likelihood estimation where we only suppose that conductances are stationary in a 50–100 ms time window. The results show an improvement compared to existent procedures...

  5. Volterra representation enables modeling of complex synaptic nonlinear dynamics in large-scale simulations.

    Science.gov (United States)

    Hu, Eric Y; Bouteiller, Jean-Marie C; Song, Dong; Baudry, Michel; Berger, Theodore W

    2015-01-01

    Chemical synapses are comprised of a wide collection of intricate signaling pathways involving complex dynamics. These mechanisms are often reduced to simple spikes or exponential representations in order to enable computer simulations at higher spatial levels of complexity. However, these representations cannot capture important nonlinear dynamics found in synaptic transmission. Here, we propose an input-output (IO) synapse model capable of generating complex nonlinear dynamics while maintaining low computational complexity. This IO synapse model is an extension of a detailed mechanistic glutamatergic synapse model capable of capturing the input-output relationships of the mechanistic model using the Volterra functional power series. We demonstrate that the IO synapse model is able to successfully track the nonlinear dynamics of the synapse up to the third order with high accuracy. We also evaluate the accuracy of the IO synapse model at different input frequencies and compared its performance with that of kinetic models in compartmental neuron models. Our results demonstrate that the IO synapse model is capable of efficiently replicating complex nonlinear dynamics that were represented in the original mechanistic model and provide a method to replicate complex and diverse synaptic transmission within neuron network simulations.

  6. Phase controlled rectifier study

    International Nuclear Information System (INIS)

    Bronner, G.; Murray, J.G.

    1976-03-01

    This report introduces the results of an engineering study incorporating a computer program to determine the transient and steady-state voltage and current wave shapes for a 12-pulse rectifier system. Generally, rectifier engineering studies are completed by making simplified assumptions and neglecting many circuit parameters. The studies incorporate the 3-phase AC parameters including nonlinear source or generator, 3-winding transformer impedances, and shunt and series capacitors. It includes firing angle control, and DC filter circuits with inductive loads

  7. Field-effect transistors as electrically controllable nonlinear rectifiers for the characterization of terahertz pulses

    Science.gov (United States)

    Lisauskas, Alvydas; Ikamas, Kestutis; Massabeau, Sylvain; Bauer, Maris; ČibiraitÄ--, DovilÄ--; Matukas, Jonas; Mangeney, Juliette; Mittendorff, Martin; Winnerl, Stephan; Krozer, Viktor; Roskos, Hartmut G.

    2018-05-01

    We propose to exploit rectification in field-effect transistors as an electrically controllable higher-order nonlinear phenomenon for the convenient monitoring of the temporal characteristics of THz pulses, for example, by autocorrelation measurements. This option arises because of the existence of a gate-bias-controlled super-linear response at sub-threshold operation conditions when the devices are subjected to THz radiation. We present measurements for different antenna-coupled transistor-based THz detectors (TeraFETs) employing (i) AlGaN/GaN high-electron-mobility and (ii) silicon CMOS field-effect transistors and show that the super-linear behavior in the sub-threshold bias regime is a universal phenomenon to be expected if the amplitude of the high-frequency voltage oscillations exceeds the thermal voltage. The effect is also employed as a tool for the direct determination of the speed of the intrinsic TeraFET response which allows us to avoid limitations set by the read-out circuitry. In particular, we show that the build-up time of the intrinsic rectification signal of a patch-antenna-coupled CMOS detector changes from 20 ps in the deep sub-threshold voltage regime to below 12 ps in the vicinity of the threshold voltage.

  8. Nonlinear control techniques of a controllable rectifier/inverter-motor drive system with a small dc-link capacitor

    International Nuclear Information System (INIS)

    Liutanakul, Pisit; Pierfederici, Serge; Meibody-Tabar, Farid

    2008-01-01

    The necessity of the converters compactness in many applications imposes the reduction of their different components size when it is possible. In this paper, a control method allowing the use of a small size dc-link capacitor for the cascade of voltage controlled-rectifier/inverter-motor drive system is proposed. This is achieved by adding the power balance equation in the system's model and the application of an exact input/output feedback linearization technique in a way that the rectifier controller compensates any sudden change in the inverter load, which is here an induction motor. Since the exact input/output feedback linearization technique is sensitive to the uncertainties over system parameters, a robust control strategy based on sliding mode controller is proposed. By this approach, the dc-link voltage becomes almost insensitive to the load variations. As a result, the level of the dc-link voltage could be stabilized with a small size dc-link capacitor. Without any considerations of the RMS current stress on this dc-link capacitor, a calculation method of a minimum value of this capacitor based on its storage energy is proposed. All the investigations are shown by computer simulations and the performance of controlled system is verified by experimentation results

  9. Rectifier Filters

    Directory of Open Access Journals (Sweden)

    Y. A. Bladyko

    2010-01-01

    Full Text Available The paper contains definition of a smoothing factor which is suitable for any rectifier filter. The formulae of complex smoothing factors have been developed for simple and complex passive filters. The paper shows conditions for application of calculation formulae and filters. 

  10. Semi-conductor rectifiers

    International Nuclear Information System (INIS)

    1981-01-01

    A method is described for treating a semiconductor rectifier, comprising: heating the rectifier to a temperature in the range of 100 0 C to 500 0 C, irradiating the rectifier while maintaining its temperature within the said range, and then annealing the rectifier at a temperature of between 280 0 C and 350 0 C for between two and ten hours. (author)

  11. On the sample complexity of learning for networks of spiking neurons with nonlinear synaptic interactions.

    Science.gov (United States)

    Schmitt, Michael

    2004-09-01

    We study networks of spiking neurons that use the timing of pulses to encode information. Nonlinear interactions model the spatial groupings of synapses on the neural dendrites and describe the computations performed at local branches. Within a theoretical framework of learning we analyze the question of how many training examples these networks must receive to be able to generalize well. Bounds for this sample complexity of learning can be obtained in terms of a combinatorial parameter known as the pseudodimension. This dimension characterizes the computational richness of a neural network and is given in terms of the number of network parameters. Two types of feedforward architectures are considered: constant-depth networks and networks of unconstrained depth. We derive asymptotically tight bounds for each of these network types. Constant depth networks are shown to have an almost linear pseudodimension, whereas the pseudodimension of general networks is quadratic. Networks of spiking neurons that use temporal coding are becoming increasingly more important in practical tasks such as computer vision, speech recognition, and motor control. The question of how well these networks generalize from a given set of training examples is a central issue for their successful application as adaptive systems. The results show that, although coding and computation in these networks is quite different and in many cases more powerful, their generalization capabilities are at least as good as those of traditional neural network models.

  12. Structural Optimization of Non-Newtonian Rectifiers

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Okkels, Fridolin

    When the size of fluidic devices is scaled down, inertial effects start to vanish such that the governing equation becomes linear. Some microfluidic devices rely on the non-linear term related to the inertia of the fluid, and one example is fluid rectifiers (diodes) e.g. related to some micropumps....... These rectifiers rely on the device geometry for their working mechanism, but on further downscaling the inertial effect vanishes and the governing equation starts to show symmetry properties. These symmetry properties reduce the geometry influence to the point where fluid rectifiers cease to function....... In this context it is natural to look for other sources of non-linearity and one possibility is to introduce a non-Newtonian working fluid. Non-Newtonian properties are due to stretching of large particles/molecules in the fluid and this is commonly seen for biological samples in “lab-on-a-chip” systems...

  13. SPS rectifier stations

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    The first of the twelves SPS rectifier stations for the bending magnets arrived at CERN at the end of the year. The photograph shows a station with the rectifiers on the left and in the other three cubicles the chokes, capacitors and resistor of the passive filter.

  14. Rectifier cabinet static breaker

    International Nuclear Information System (INIS)

    Costantino, R.A. Jr; Gliebe, R.J.

    1992-01-01

    A rectifier cabinet static breaker replaces a blocking diode pair with an SCR and the installation of a power transistor in parallel with the latch contactor to commutate the SCR to the off state. The SCR serves as a static breaker with fast turnoff capability providing an alternative way of achieving reactor scram in addition to performing the function of the replaced blocking diodes. The control circuitry for the rectifier cabinet static breaker includes on-line test capability and an LED indicator light to denote successful test completion. Current limit circuitry provides high-speed protection in the event of overload. 7 figs

  15. Rectifier cabinet static breaker

    Science.gov (United States)

    Costantino, Jr, Roger A.; Gliebe, Ronald J.

    1992-09-01

    A rectifier cabinet static breaker replaces a blocking diode pair with an SCR and the installation of a power transistor in parallel with the latch contactor to commutate the SCR to the off state. The SCR serves as a static breaker with fast turnoff capability providing an alternative way of achieving reactor scram in addition to performing the function of the replaced blocking diodes. The control circuitry for the rectifier cabinet static breaker includes on-line test capability and an LED indicator light to denote successful test completion. Current limit circuitry provides high-speed protection in the event of overload.

  16. Topology optimization of viscoelastic rectifiers

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Szabo, Peter; Okkels, Fridolin

    2012-01-01

    An approach for the design of microfluidic viscoelastic rectifiers is presented based on a combination of a viscoelastic model and the method of topology optimization. This presumption free approach yields a material layout topologically different from experimentally realized rectifiers...

  17. EMC Increasing of PWM Rectifier in Comparison with Classical Rectifier

    Directory of Open Access Journals (Sweden)

    R. Dolecek

    2008-12-01

    Full Text Available Pulse width modulated rectifier is a very popular topic nowadays. The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage is its capability of energy recuperation. The PWM rectifier can assert itself for its good behavior in many applications, for example as an input rectifier in indirect frequency converter, or in traction. Traction vehicles equipped with PWM rectifier do not consume reactive power, do not load the supply network with higher harmonics, and the recuperation is possible. The paper deals with the PWM rectifier functional model realization and examination. Electromagnetic compatibility of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

  18. Solid state thermal rectifier

    Science.gov (United States)

    None

    2016-07-05

    Thermal rectifiers using linear nanostructures as core thermal conductors have been fabricated. A high mass density material is added preferentially to one end of the nanostructures to produce an axially non-uniform mass distribution. The resulting nanoscale system conducts heat asymmetrically with greatest heat flow in the direction of decreasing mass density. Thermal rectification has been demonstrated for linear nanostructures that are electrical insulators, such as boron nitride nanotubes, and for nanostructures that are conductive, such as carbon nanotubes.

  19. A perturbation-based model for rectifier circuits

    Directory of Open Access Journals (Sweden)

    Vipin B. Vats

    2006-01-01

    Full Text Available A perturbation-theoretic analysis of rectifier circuits is presented. The governing differential equation of the half-wave rectifier with capacitor filter is analyzed by expanding the output voltage as a Taylor series with respect to an artificially introduced parameter in the nonlinearity of the diode characteristic as is done in quantum theory. The perturbation parameter introduced in the analysis is independent of the circuit components as compared to the method presented by multiple scales. The various terms appearing in the perturbation series are then modeled in the form of an equivalent circuit. This model is subsequently used in the analysis of full-wave rectifier. Matlab simulation results are included which confirm the validity of the theoretical formulations. Perturbation analysis acts a helpful tool in analyzing time-varying systems and chaotic systems.

  20. Synchronous Half-Wave Rectifier

    Science.gov (United States)

    Rippel, Wally E.

    1989-01-01

    Synchronous rectifying circuit behaves like diode having unusually low voltage drop during forward-voltage half cycles. Circuit particularly useful in power supplies with potentials of 5 Vdc or less, where normal forward-voltage drops in ordinary diodes unacceptably large. Fabricated as monolithic assembly or as hybrid. Synchronous half-wave rectifier includes active circuits to attain low forward voltage drop and high rectification efficiency.

  1. Synaptic Cell Adhesion

    OpenAIRE

    Missler, Markus; Südhof, Thomas C.; Biederer, Thomas

    2012-01-01

    Chemical synapses are asymmetric intercellular junctions that mediate synaptic transmission. Synaptic junctions are organized by trans-synaptic cell adhesion molecules bridging the synaptic cleft. Synaptic cell adhesion molecules not only connect pre- and postsynaptic compartments, but also mediate trans-synaptic recognition and signaling processes that are essential for the establishment, specification, and plasticity of synapses. A growing number of synaptic cell adhesion molecules that inc...

  2. EDITORIAL: Synaptic electronics Synaptic electronics

    Science.gov (United States)

    Demming, Anna; Gimzewski, James K.; Vuillaume, Dominique

    2013-09-01

    Conventional computers excel in logic and accurate scientific calculations but make hard work of open ended problems that human brains handle easily. Even von Neumann—the mathematician and polymath who first developed the programming architecture that forms the basis of today's computers—was already looking to the brain for future developments before his death in 1957 [1]. Neuromorphic computing uses approaches that better mimic the working of the human brain. Recent developments in nanotechnology are now providing structures with very accommodating properties for neuromorphic approaches. This special issue, with guest editors James K Gimzewski and Dominique Vuillaume, is devoted to research at the serendipitous interface between the two disciplines. 'Synaptic electronics', looks at artificial devices with connections that demonstrate behaviour similar to synapses in the nervous system allowing a new and more powerful approach to computing. Synapses and connecting neurons respond differently to incident signals depending on the history of signals previously experienced, ultimately leading to short term and long term memory behaviour. The basic characteristics of a synapse can be replicated with around ten simple transistors. However with the human brain having around 1011 neurons and 1015 synapses, artificial neurons and synapses from basic transistors are unlikely to accommodate the scalability required. The discovery of nanoscale elements that function as 'memristors' has provided a key tool for the implementation of synaptic connections [2]. Leon Chua first developed the concept of the 'The memristor—the missing circuit element' in 1971 [3]. In this special issue he presents a tutorial describing how memristor research has fed into our understanding of synaptic behaviour and how they can be applied in information processing [4]. He also describes, 'The new principle of local activity, which uncovers a minuscule life-enabling "Goldilocks zone", dubbed the

  3. Tunable all-optical plasmonic rectifier in nanoscale metal-insulator-metal waveguides.

    Science.gov (United States)

    Xu, Yi; Wang, Xiaomeng; Deng, Haidong; Guo, Kangxian

    2014-10-15

    We propose a tunable all-optical plasmonic rectifier based on the nonlinear Fano resonance in a metal-insulator-metal plasmonic waveguide and cavities coupling system. We develop a theoretical model based on the temporal coupled-mode theory to study the device physics of the nanoscale rectifier. We further demonstrate via the finite difference time domain numerical experiment that our idea can be realized in a plasmonic system with an ultracompact size of ~120×800  nm². The tunable plasmonic rectifier could facilitate the all-optical signal processing in nanoscale.

  4. Fully superconducting rectifiers and fluxpumps

    International Nuclear Information System (INIS)

    Klundert, L.J.M. van de; Kate, H.H.J. ten

    1981-01-01

    Reviewing the basic principles of operation of fluxpumps, mechanical devices such as flux compressors and dynamos are discussed and electrically driven rectifier fluxpumps, with which current levels of over 10 KA can be obtained with high performance, are considered. 132 references. (U.K.)

  5. RTD application in low power UHF rectifiers

    International Nuclear Information System (INIS)

    Sinyakin, V Yu; Makeev, M O; Meshkov, S A

    2016-01-01

    In the current work, the problem of UHF RFID passive tag sensitivity increase is considered. Tag sensitivity depends on HF signal rectifier efficiency and antenna-rectifier impedance matching. Possibility of RFID passive tag sensitivity increase up to 10 times by means of RTD use in HF signal rectifier in comparison with tags based on Schottky barrier diode is shown. (paper)

  6. Analysis and control of high power synchronous rectifier

    Energy Technology Data Exchange (ETDEWEB)

    Singh Tejinder.

    1993-01-01

    The description, steady state/dynamic analysis and control design of a high power synchronous rectifier is presented. The proposed rectifier system exploits selective harmonic elimination modulation techniques to minimize filtering requirements, and overcomes the dc voltage limitations of prior art equipment. A detailed derivation of the optimum pulse width modulation switching patterns, in the low frequency range for high power applications is presented. A general mathematical model of the rectifier is established which is non-linear and time-invariant. The transformation of reference frame and small signal linearization techniques are used to obtain closed form solutions from the mathematical model. The modelling procedure is verified by computer simulation. The closed loop design of the synchronous rectifier based on a phase and amplitude control strategy is investigated. The transfer functions derived from this analysis are used for the design of the regulators. The steady-state and dynamic results predicted by computer simulation are verified by PECAN. A systematic design procedure is developed and a detailed design example of a 1 MV-amp rectifer system is presented. 23 refs., 33 figs.

  7. An overview of self-switching diode rectifiers using green materials

    Science.gov (United States)

    Kasjoo, Shahrir Rizal; Zailan, Zarimawaty; Zakaria, Nor Farhani; Isa, Muammar Mohamad; Arshad, Mohd Khairuddin Md; Taking, Sanna

    2017-09-01

    A unipolar two-terminal nanodevice, known as the self-switching diode (SSD), has recently been demonstrated as a room-temperature rectifier at microwave and terahertz frequencies due to its nonlinear current-voltage characteristic. The planar architecture of SSD not only makes the fabrication process of the device faster, simpler and at a lower cost when compared with other rectifying diodes, but also allows the use of various materials to realize and fabricate SSDs. This includes the utilization of `green' materials such as organic and graphene thin films for environmental sustainability. This paper reviews the properties of current `green' SSD rectifiers with respect to their operating frequencies and rectifying performances, including responsivity and noise-equivalent power of the devices, along with the applications.

  8. Thermally and magnetically controlled superconducting rectifiers

    International Nuclear Information System (INIS)

    Mulder, G.B.J.; TenKate, H.H.J.; Krooshoop, H.J.G.; Van de Klundert, L.J.M.

    1989-01-01

    The switches of a superconducting rectifier can be controlled either magnetically or thermally. The main purpose of this paper is to point out the differences between both methods of switching and discuss the consequences for the operation of the rectifier. The discussion is illustrated by the experimental results of a rectifier which was tested with magnetically as well as thermally controlled switches. It has an input current of 30 A, an output current of more than 1 kA and an operating frequency of a few Hertz. A superconducting magnet connected to this rectifier can be energized at a rate exceeding 1 MJ/hour and an efficiency of about 97%

  9. G-protein-coupled inward rectifier potassium channels involved in corticostriatal presynaptic modulation.

    Science.gov (United States)

    Meneses, David; Mateos, Verónica; Islas, Gustavo; Barral, Jaime

    2015-09-01

    Presynaptic modulation has been associated mainly with calcium channels but recent data suggests that inward rectifier potassium channels (K(IR)) also play a role. In this work we set to characterize the role of presynaptic K(IR) channels in corticostriatal synaptic transmission. We elicited synaptic potentials in striatum by stimulating cortical areas and then determined the synaptic responses of corticostriatal synapsis by using paired pulse ratio (PPR) in the presence and absence of several potassium channel blockers. Unspecific potassium channels blockers Ba(2+) and Cs(+) reduced the PPR, suggesting that these channels are presynaptically located. Further pharmacological characterization showed that application of tertiapin-Q, a specific K(IR)3 channel family blocker, also induced a reduction of PPR, suggesting that K(IR)3 channels are present at corticostriatal terminals. In contrast, exposure to Lq2, a specific K(IR)1.1 inward rectifier potassium channel, did not induce any change in PPR suggesting the absence of these channels in the presynaptic corticostriatal terminals. Our results indicate that K(IR)3 channels are functionally expressed at the corticostriatal synapses, since blockage of these channels result in PPR decrease. Our results also help to explain how synaptic activity may become sensitive to extracellular signals mediated by G-protein coupled receptors. A vast repertoire of receptors may influence neurotransmitter release in an indirect manner through regulation of K(IR)3 channels. © 2015 Wiley Periodicals, Inc.

  10. Laserlike Vibrational Instability in Rectifying Molecular Conductors

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Hedegård, Per; Brandbyge, Mads

    2011-01-01

    We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor (D-A) type molecular rectifiers. At finite voltage additional nonequilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission....... We investigate the effect in realistic molecular rectifier structures using first-principles calculations....

  11. High current and high power superconducting rectifiers

    International Nuclear Information System (INIS)

    Kate, H.H.J. ten; Bunk, P.B.; Klundert, L.J.M. van de; Britton, R.B.

    1981-01-01

    Results on three experimental superconducting rectifiers are reported. Two of them are 1 kA low frequency flux pumps, one thermally and magnetically switched. The third is a low-current high-frequency magnetically switched rectifier which can use the mains directly. (author)

  12. Extremal vectors and rectifiability | Enflo | Quaestiones Mathematicae

    African Journals Online (AJOL)

    Extremal vectors and rectifiability. ... The concept of extremal vectors of a linear operator with a dense range but not onto on a Hilbert space was introduced by P. Enflo in 1996 as a new approach to study invariant subspaces ... We show that in general curves that map numbers to backward minimal vectors are not rectifiable.

  13. Chapter 13 - Active Rectifiers and Their Control

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Abdelhakim, Ahmed

    2018-01-01

    This chapter investigates the control design of active rectifiers and their applications in power electronics-based power system. The harmonic emission and measures are firstly addressed as a basis of evaluating the active rectifier's effectiveness. Furthermore, the importance of new coming...... standards is highlighted. Application-oriented design of active rectifiers as a main reason behind evolvement of different topologies is discussed. Then, the main principle in designing different control schemes in single-phase and three-phase rectifiers is investigated, analyzed, and experimentally...... verified. The influence of nonideal operating conditions with possible solutions is addressed. Finally, future prospective of active rectifiers as a one of the key enabler of carbon-free power system is summarized....

  14. Rectifier transformer saturation on commutation failure

    International Nuclear Information System (INIS)

    Lu, E.; Bronner, G.

    1989-01-01

    The rectifier transformer's service differs from the power transformer's service because of the rectifier load. Under certain fault conditions, such as a commutation failure, d.c. magnetization may be introduced into the rectifier transformer cores, resulting in possible saturation of the magnetic circuit, thus in degradation of the performance of the transformer. It is the purpose of this paper to present an approach for evaluating the electromagnetic transient process under such a fault condition. The studies were made on the operating 1000MVA converter system at the Princeton Plasma Physics Laboratory

  15. A boron nitride nanotube peapod thermal rectifier

    International Nuclear Information System (INIS)

    Loh, G. C.; Baillargeat, D.

    2014-01-01

    The precise guidance of heat from one specific location to another is paramount in many industrial and commercial applications, including thermal management and thermoelectric generation. One of the cardinal requirements is a preferential conduction of thermal energy, also known as thermal rectification, in the materials. This study introduces a novel nanomaterial for rectifying heat—the boron nitride nanotube peapod thermal rectifier. Classical non-equilibrium molecular dynamics simulations are performed on this nanomaterial, and interestingly, the strength of the rectification phenomenon is dissimilar at different operating temperatures. This is due to the contingence of the thermal flux on the conductance at the localized region around the scatterer, which varies with temperature. The rectification performance of the peapod rectifier is inherently dependent on its asymmetry. Last but not least, the favourable rectifying direction in the nanomaterial is established.

  16. A boron nitride nanotube peapod thermal rectifier

    Energy Technology Data Exchange (ETDEWEB)

    Loh, G. C., E-mail: jgloh@mtu.edu [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 (Singapore); Baillargeat, D. [CNRS-International-NTU-Thales Research Alliance (CINTRA), 50 Nanyang Drive, Singapore 637553 (Singapore)

    2014-06-28

    The precise guidance of heat from one specific location to another is paramount in many industrial and commercial applications, including thermal management and thermoelectric generation. One of the cardinal requirements is a preferential conduction of thermal energy, also known as thermal rectification, in the materials. This study introduces a novel nanomaterial for rectifying heat—the boron nitride nanotube peapod thermal rectifier. Classical non-equilibrium molecular dynamics simulations are performed on this nanomaterial, and interestingly, the strength of the rectification phenomenon is dissimilar at different operating temperatures. This is due to the contingence of the thermal flux on the conductance at the localized region around the scatterer, which varies with temperature. The rectification performance of the peapod rectifier is inherently dependent on its asymmetry. Last but not least, the favourable rectifying direction in the nanomaterial is established.

  17. A 62GHz inductor-peaked rectifier with 7% efficiency

    NARCIS (Netherlands)

    Gao, H.; Matters - Kammerer, M.; Milosevic, D.; Roermund, van A.H.M.; Baltus, P.G.M.

    2013-01-01

    This paper presents the first 62 GHz fully onchip RF-DC rectifier in 65nm CMOS technology. The rectifier is the bottleneck in realizing on-chip wireless power receivers. In this paper, efficiency problems of the mm-wave rectifier are discussed and the inductor-peaked rectifier structure is proposed

  18. Electron transport in InAs/AlGaSb ballistic rectifiers

    International Nuclear Information System (INIS)

    Maemoto, Toshihiko; Koyama, Masatoshi; Furukawa, Masashi; Takahashi, Hiroshi; Sasa, Shigehiko; Inoue, Masataka

    2006-01-01

    Nonlinear transport properties of a ballistic rectifier fabricated from InAs/AlGaSb heterostructures are reported. The operation of the ballistic rectifier is based on the guidance of carriers by a square anti-dot structure. The structure was defined by electron beam lithography and wet chemical etching. The DC characteristics and magneto-transport properties of the ballistic rectifier have been measured at 77 K and 4.2 K. Rectification effects relying on the ballistic transport were observed. From the four-terminal resistance measured at low magnetic fields, we also observed magneto-resistance fluctuations corresponding to the electron trajectories and symmetry-breaking electron scattering, which are influenced by the magnetic field strength

  19. Synaptic Plasticity and Nociception

    Institute of Scientific and Technical Information of China (English)

    ChenJianguo

    2004-01-01

    Synaptic plasticity is one of the fields that progresses rapidly and has a lot of success in neuroscience. The two major types of synaptie plasticity: long-term potentiation ( LTP and long-term depression (LTD are thought to be the cellular mochanisms of learning and memory. Recently, accumulating evidence suggests that, besides serving as a cellular model for learning and memory, the synaptic plasticity involves in other physiological or pathophysiological processes, such as the perception of pain and the regulation of cardiovascular system. This minireview will focus on the relationship between synaptic plasticity and nociception.

  20. Banach Synaptic Algebras

    Science.gov (United States)

    Foulis, David J.; Pulmannov, Sylvia

    2018-04-01

    Using a representation theorem of Erik Alfsen, Frederic Schultz, and Erling Størmer for special JB-algebras, we prove that a synaptic algebra is norm complete (i.e., Banach) if and only if it is isomorphic to the self-adjoint part of a Rickart C∗-algebra. Also, we give conditions on a Banach synaptic algebra that are equivalent to the condition that it is isomorphic to the self-adjoint part of an AW∗-algebra. Moreover, we study some relationships between synaptic algebras and so-called generalized Hermitian algebras.

  1. Full-wave current conveyor precision rectifier

    Directory of Open Access Journals (Sweden)

    Đukić Slobodan R.

    2008-01-01

    Full Text Available A circuit that provides precision rectification of small signal with low temperature sensitivity for frequencies up to 100 kHz without waveform distortion is presented. It utilizes an improved second type current conveyor based on current-steering output stage and biased silicon diodes. The use of a DC current source to bias the rectifying diodes provides higher temperature stability and lower DC offset level at the output. Proposed design of the precision rectifier ensures good current transfer linearity in the range that satisfy class A of the amplifier and good voltage transfer characteristic for low level signals. Distortion during the zero crossing of the input signal is practically eliminated. Design of the proposed rectifier is realized with standard components.

  2. Pharmacological Conversion of a Cardiac Inward Rectifier into an Outward Rectifier Potassium Channel.

    Science.gov (United States)

    Moreno-Galindo, Eloy G; Sanchez-Chapula, Jose A; Tristani-Firouzi, Martin; Navarro-Polanco, Ricardo A

    2016-09-01

    Potassium (K(+)) channels are crucial for determining the shape, duration, and frequency of action-potential firing in excitable cells. Broadly speaking, K(+) channels can be classified based on whether their macroscopic current outwardly or inwardly rectifies, whereby rectification refers to a change in conductance with voltage. Outwardly rectifying K(+) channels conduct greater current at depolarized membrane potentials, whereas inward rectifier channels conduct greater current at hyperpolarized membrane potentials. Under most circumstances, outward currents through inwardly rectifying K(+) channels are reduced at more depolarized potentials. However, the acetylcholine-gated K(+) channel (KACh) conducts current that inwardly rectifies when activated by some ligands (such as acetylcholine), and yet conducts current that outwardly rectifies when activated by other ligands (for example, pilocarpine and choline). The perplexing and paradoxical behavior of KACh channels is due to the intrinsic voltage sensitivity of the receptor that activates KACh channels, the M2 muscarinic receptor (M2R). Emerging evidence reveals that the affinity of M2R for distinct ligands varies in a voltage-dependent and ligand-specific manner. These intrinsic receptor properties determine whether current conducted by KACh channels inwardly or outwardly rectifies. This review summarizes the most recent concepts regarding the intrinsic voltage sensitivity of muscarinic receptors and the consequences of this intriguing behavior on cardiac physiology and pharmacology of KACh channels. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

  3. DC Motor Drive with PFC Rectifier

    Directory of Open Access Journals (Sweden)

    Lascu Mihaela

    2008-05-01

    Full Text Available The goal of this work is to study theperformances of a hybrid controller used to controlDC Motor drive with a single-phase power factorcorrection rectifier. This study is made usingcomputer simulation (Simulink. The first part isdevoted to the control system of the DC Motors. Inthe second part, the design of the hybrid controllerwill be presented. The third part is the design ofthe fast response single-phase boost power factorcorrection rectifier. The last parts are devoted tosimulation and experimental results.

  4. Mitigating impact of thermal and rectified radio-frequency sheath potentials on edge localized modes

    Energy Technology Data Exchange (ETDEWEB)

    Gui, B. [Institute of Plasma Physics Chinese Academy of Sciences, Hefei (China); Lawerence Livermore National Lab, Livermore, California 94550 (United States); Xu, X. Q. [Lawerence Livermore National Lab, Livermore, California 94550 (United States); Myra, J. R.; D' Ippolito, D. A. [Lodestar Research Corporation, Boulder, Colorado 80301 (United States)

    2014-11-15

    The mitigating impact of thermal and rectified radio frequency (RF) sheath potentials on the peeling-ballooning modes is studied non-linearly by employing a two-fluid three-field simulation model based on the BOUT++ framework. Additional shear flow and the Kelvin-Helmholtz effect due to the thermal and rectified RF sheath potential are induced. It is found that the shear flow increases the growth rate while the K-H effect decreases the growth rate slightly when there is a density gradient, but the energy loss of these cases is suppressed in the nonlinear phase. The stronger external electrostatic field due to the sheaths has a more significant effect on the energy loss suppression. From this study, it is found the growth rate in the linear phase mainly determines the onset of edge-localized modes, while the mode spectrum width in the nonlinear phase has an important impact on the turbulent transport. The wider mode spectrum leads to weaker turbulent transport and results in a smaller energy loss. Due to the thermal sheath and rectified RF sheath potential in the scrape-off-layer, the modified shear flow tears apart the peeling-ballooning filament and makes the mode spectrum wider, resulting in less energy loss. The perturbed electric potential and the parallel current near the sheath region is also suppressed locally due to the sheath boundary condition.

  5. Harmonic Distortion of Rectifier Topologies for Adjustable Speed Drives

    DEFF Research Database (Denmark)

    Hansen, Steffan

    This thesis deals with the harmonic distortion of the diode rectifier and a number of alternative rectifier topologies for adjustable speed drives. The main intention of this thesis is to provide models and tools that allow easy prediction of the harmonic distortion of ASD’s in a given system...... rectifier are presented. The first level is an ideal model where the diode rectifier basically is treated as an independent (harmonic) current source. The second level is an empirical model, where simulated (or measured) values of the harmonic currents of the diode rectifier for different parameters......-angle of the individual harmonic currents of different diode rectifier types is analyzed. Four selected rectifier topologies with a high input power factor are presented. It is shown that using ac- or dc-coils is a very simple and efficient method to reduce the harmonic currents compared to the basic diode rectifier...

  6. Stochastic lattice model of synaptic membrane protein domains.

    Science.gov (United States)

    Li, Yiwei; Kahraman, Osman; Haselwandter, Christoph A

    2017-05-01

    Neurotransmitter receptor molecules, concentrated in synaptic membrane domains along with scaffolds and other kinds of proteins, are crucial for signal transmission across chemical synapses. In common with other membrane protein domains, synaptic domains are characterized by low protein copy numbers and protein crowding, with rapid stochastic turnover of individual molecules. We study here in detail a stochastic lattice model of the receptor-scaffold reaction-diffusion dynamics at synaptic domains that was found previously to capture, at the mean-field level, the self-assembly, stability, and characteristic size of synaptic domains observed in experiments. We show that our stochastic lattice model yields quantitative agreement with mean-field models of nonlinear diffusion in crowded membranes. Through a combination of analytic and numerical solutions of the master equation governing the reaction dynamics at synaptic domains, together with kinetic Monte Carlo simulations, we find substantial discrepancies between mean-field and stochastic models for the reaction dynamics at synaptic domains. Based on the reaction and diffusion properties of synaptic receptors and scaffolds suggested by previous experiments and mean-field calculations, we show that the stochastic reaction-diffusion dynamics of synaptic receptors and scaffolds provide a simple physical mechanism for collective fluctuations in synaptic domains, the molecular turnover observed at synaptic domains, key features of the observed single-molecule trajectories, and spatial heterogeneity in the effective rates at which receptors and scaffolds are recycled at the cell membrane. Our work sheds light on the physical mechanisms and principles linking the collective properties of membrane protein domains to the stochastic dynamics that rule their molecular components.

  7. Minimum component high frequency current mode rectifier | Sampe ...

    African Journals Online (AJOL)

    In this paper a current mode full wave rectifier circuit is proposed. The current mode rectifier circuit is implemented utilizing a floating current source (FCS) as an active element. The minimum component full wave rectifier utilizes only a single floating current source, two diodes and two grounded resistors. The extremely ...

  8. 46 CFR 183.360 - Semiconductor rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor rectifier systems. (a) Each semiconductor rectifier system must have an adequate heat removal system that prevents...

  9. 46 CFR 129.360 - Semiconductor-rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor-rectifier systems. 129.360 Section 129.360... INSTALLATIONS Power Sources and Distribution Systems § 129.360 Semiconductor-rectifier systems. (a) Each semiconductor-rectifier system must have an adequate heat-removal system to prevent overheating. (b) If a...

  10. 46 CFR 120.360 - Semiconductor rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 120.360 Section 120.360... INSTALLATION Power Sources and Distribution Systems § 120.360 Semiconductor rectifier systems. (a) Each semiconductor rectifier system must have an adequate heat removal system that prevents overheating. (b) Where a...

  11. High Power Factor Hybrid Rectifier | Odeh | Nigerian Journal of ...

    African Journals Online (AJOL)

    This paper presents the analysis of a new single-phase hybrid rectifier with high power factor (PF) and low harmonic distortion current. The proposed rectifier structure is composed of an ordinary single-phase diode rectifier with parallel connection of a switched converter. It is outlined that the switched converter is capable of ...

  12. Single-Phase Full-Wave Rectifier as an Effective Example to Teach Normalization, Conduction Modes, and Circuit Analysis Methods

    Directory of Open Access Journals (Sweden)

    Predrag Pejovic

    2013-12-01

    Full Text Available Application of a single phase rectifier as an example in teaching circuit modeling, normalization, operating modes of nonlinear circuits, and circuit analysis methods is proposed.The rectifier supplied from a voltage source by an inductive impedance is analyzed in the discontinuous as well as in the continuous conduction mode. Completely analytical solution for the continuous conduction mode is derived. Appropriate numerical methods are proposed to obtain the circuit waveforms in both of the operating modes, and to compute the performance parameters. Source code of the program that performs such computation is provided.

  13. Reduction of Harmonics by 18-Pulse Rectifier

    Directory of Open Access Journals (Sweden)

    Stanislav Kocman

    2008-01-01

    Full Text Available Operation of such electrical devices as data processing and electronics devices, adjustable speed drives or uninterruptible power supply can cause problems by generating harmonic currents into the network, from which they are supplied. Effects of these harmonic currents are various, they can get worse the quality of supply voltage in the network or to have negative influences on devices connected to this network. There are various technical solutions for reduction of harmonics. One of them is using of multi-pulse rectifiers, whereas the 18-pulse rectifier in the structure of adjustable speed drive is briefly presented in this paper including some results of its behaviour. The examined experimental measurements confirmed its very good efficiency in the harmonic mitigation.

  14. Engineered Asymmetric Composite Membranes with Rectifying Properties.

    Science.gov (United States)

    Wen, Liping; Xiao, Kai; Sainath, Annadanam V Sesha; Komura, Motonori; Kong, Xiang-Yu; Xie, Ganhua; Zhang, Zhen; Tian, Ye; Iyoda, Tomokazu; Jiang, Lei

    2016-01-27

    Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Time-division-multiplex control scheme for voltage multiplier rectifiers

    Directory of Open Access Journals (Sweden)

    Bin-Han Liu

    2017-03-01

    Full Text Available A voltage multiplier rectifier with a novel time-division-multiplexing (TDM control scheme for high step-up converters is proposed in this study. In the proposed TDM control scheme, two full-wave voltage doubler rectifiers can be combined to realise a voltage quadrupler rectifier. The proposed voltage quadrupler rectifier can reduce transformer turn ratio and transformer size for high step-up converters and also reduce voltage stress for the output capacitors and rectifier diodes. An N-times voltage rectifier can be straightforwardly produced by extending the concepts from the proposed TDM control scheme. A phase-shift full-bridge (PSFB converter is adopted in the primary side of the proposed voltage quadrupler rectifier to construct a PSFB quadrupler converter. Experimental results for the PSFB quadrupler converter demonstrate the performance of the proposed TDM control scheme for voltage quadrupler rectifiers. An 8-times voltage rectifier is simulated to determine the validity of extending the proposed TDM control scheme to realise an N-times voltage rectifier. Experimental and simulation results show that the proposed TDM control scheme has great potential to be used in high step-up converters.

  16. Manufacture of the rectifier of the HT-7U PFPS

    International Nuclear Information System (INIS)

    Gao Ge; Fu Peng; Tang Lunjun; Wang Linsen

    2005-01-01

    The rectifiers of the HT-7U poloidal field power supply (PFPS) are introduced. A new control method, four quadrants converter, is brought forward, which overcomes the short-coming of both the circulating current mode and the non-circulating current mode. This control mode also resolves the problem of DC circulating current in the identical phase anti-parallel connection rectifiers when these rectifiers run in the circulating current mode. (authors)

  17. MAGUKs: multifaceted synaptic organizers.

    Science.gov (United States)

    Won, Sehoon; Levy, Jon M; Nicoll, Roger A; Roche, Katherine W

    2017-04-01

    The PSD-95 family of proteins, known as MAGUKs, have long been recognized to be central building blocks of the PSD. They are categorized as scaffolding proteins, which link surface-expressed receptors to the intracellular signaling molecules. Although the four members of the PSD-95 family (PSD-95, PSD-93, SAP102, and SAP97) have many shared roles in regulating synaptic function, recent studies have begun to delineate specific binding partners and roles in plasticity. In the current review, we will highlight the conserved and unique roles of these proteins. Published by Elsevier Ltd.

  18. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting.

    Science.gov (United States)

    Lu, Shaohua; Boussaid, Farid

    2015-11-19

    This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD) capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier.

  19. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting

    Directory of Open Access Journals (Sweden)

    Shaohua Lu

    2015-11-01

    Full Text Available This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier.

  20. High Voltage GaN Schottky Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  1. UV/ozone assisted local graphene (p)/ZnO(n) heterojunctions as a nanodiode rectifier

    Science.gov (United States)

    Sahatiya, Parikshit; Badhulika, Sushmee

    2016-07-01

    Here we report the fabrication of a novel graphene/ZnO nanodiode by UV/ozone assisted oxidation of graphene and demonstrate its application as a half-wave rectifier to generate DC voltage. The method involves the use of electrospinning for one-step in situ synthesis and alignment of single Gr/ZnO nanocomposite across metal electrodes. On subsequent UV illumination, graphene oxidizes, which induces p type doping and ZnO being an n type semiconductor, thus resulting in the formation of a nanodiode. The as-fabricated device shows strong non-linear current-voltage characteristic similar to that of conventional semiconductor p-n junction diodes. Excellent rectifying behavior with a rectification ratio of ~103 was observed and the nanodiodes were found to exhibit long-term repeatability in their performance. Ideality factor and barrier height, as calculated by the thermionic emission model, were found to be 1.6 and 0.504 eV respectively. Due to the fact that diodes are the basic building blocks in the electronics and semiconductor industry, the successful fabrication of these nanodiodes based on UV assisted p type doping of graphene indicates that this approach can be used for developing highly scalable and efficient components for nanoelectronics, such as rectifiers and logic gates that find applications in numerous fields.

  2. Universal Voltage Conveyor and Current Conveyor in Fast Full-Wave Rectifier

    Directory of Open Access Journals (Sweden)

    Josef Burian

    2012-12-01

    Full Text Available This paper deals about the design of a fast voltage-mode full-wave rectifier, where universal voltage conveyor and second-generation current conveyor are used as active elements. Thanks to the active elements, the input and output impedance of the non-linear circuit is infinitely high respectively zero in theory. For the rectification only two diodes and three resistors are required as passive elements. The performance of the circuit is shown on experimental measurement results showing the dynamic range, time response, frequency dependent DC transient value and RMS error for different values of input voltage amplitudes.

  3. Synaptic electronics: materials, devices and applications.

    Science.gov (United States)

    Kuzum, Duygu; Yu, Shimeng; Wong, H-S Philip

    2013-09-27

    In this paper, the recent progress of synaptic electronics is reviewed. The basics of biological synaptic plasticity and learning are described. The material properties and electrical switching characteristics of a variety of synaptic devices are discussed, with a focus on the use of synaptic devices for neuromorphic or brain-inspired computing. Performance metrics desirable for large-scale implementations of synaptic devices are illustrated. A review of recent work on targeted computing applications with synaptic devices is presented.

  4. Synaptic electronics: materials, devices and applications

    International Nuclear Information System (INIS)

    Kuzum, Duygu; Yu, Shimeng; Philip Wong, H-S

    2013-01-01

    In this paper, the recent progress of synaptic electronics is reviewed. The basics of biological synaptic plasticity and learning are described. The material properties and electrical switching characteristics of a variety of synaptic devices are discussed, with a focus on the use of synaptic devices for neuromorphic or brain-inspired computing. Performance metrics desirable for large-scale implementations of synaptic devices are illustrated. A review of recent work on targeted computing applications with synaptic devices is presented. (topical review)

  5. Application data for the PLT stabilizing field rectifier

    International Nuclear Information System (INIS)

    Bronner, G.; Murray, J.G.; Oliaro, G.E.

    1975-11-01

    This paper describes the 12-pulse stabilizing field rectifier used for vertical field production in the Princeton Large Torus (PLT). It is essential that the rectifier be reliable, and protect itself from all faults including induced transient overvoltage produced by switching and plasma instabilities. To this end, computer simulations were run to insure protection under various fault conditions

  6. Nanofibrous p-n Junction and Its Rectifying Characteristics

    Directory of Open Access Journals (Sweden)

    Jian Fang

    2013-01-01

    Full Text Available Randomly oriented tin oxide (SnO2 nanofibers and poly(3,4-ethylenedioxythiophene-poly(styrenesulfonate/polyvinylpyrrolidone (PEDOT:PSS/PVP nanofibers were prepared by a two-step electrospinning technique to form a layered fibrous mat. The current-voltage measurement revealed that the fibrous mat had an obvious diode-rectifying characteristic. The thickness of the nanofiber layers was found to have a considerable influence on the device resistance and rectifying performance. Such an interesting rectifying property was attributed to the formation of a p-n junction between the fibrous SnO2 and PEDOT:PSS/PVP layers. This is the first report that a rectifying junction can be formed between two layers of electrospun nanofiber mats, and the resulting nanofibrous diode rectifier may find applications in sensors, energy harvest, and electronic textiles.

  7. Irregular persistent activity induced by synaptic excitatory feedback

    Directory of Open Access Journals (Sweden)

    Francesca Barbieri

    2007-11-01

    Full Text Available Neurophysiological experiments on monkeys have reported highly irregular persistent activity during the performance of an oculomotor delayed-response task. These experiments show that during the delay period the coefficient of variation (CV of interspike intervals (ISI of prefrontal neurons is above 1, on average, and larger than during the fixation period. In the present paper, we show that this feature can be reproduced in a network in which persistent activity is induced by excitatory feedback, provided that (i the post-spike reset is close enough to threshold , (ii synaptic efficacies are a non-linear function of the pre-synaptic firing rate. Non-linearity between presynaptic rate and effective synaptic strength is implemented by a standard short-term depression mechanism (STD. First, we consider the simplest possible network with excitatory feedback: a fully connected homogeneous network of excitatory leaky integrate-and-fire neurons, using both numerical simulations and analytical techniques. The results are then confirmed in a network with selective excitatory neurons and inhibition. In both the cases there is a large range of values of the synaptic efficacies for which the statistics of firing of single cells is similar to experimental data.

  8. Superconducting transformers, rectifiers, and switches. (Review paper)

    International Nuclear Information System (INIS)

    Ignatov, V.E.; Koval'kov, G.A.; Moskvitin, A.I.

    Cryogenic rectifiers using power cryotrons have been fabricated by many foreign firms since 1960. Present-day flux pumps require a low voltage power supply (several tens of millivolts) and a high current (kiloamperes). Increasing the power supply voltage will quadratically increase the flux pump losses and, given the limitations of existing materials, are not economically profitable. Present-day, cryotron-type flux pumps can best be used in power systems as a power supply for superconducting magnets, solenoids, storage devices, and superconducting exciting coils for turbogenerators. To increase the voltage of the next generation of transformers for superconducting dc power transmission, a research program must be set up to improve the cryotrons and to develop systems based on a different principle of operation, for example, semiconductor devices based on the principle of the volume effect in the intermediate environment

  9. Isolation of Synaptosomes, Synaptic Plasma Membranes, and Synaptic Junctional Complexes.

    Science.gov (United States)

    Michaelis, Mary L; Jiang, Lei; Michaelis, Elias K

    2017-01-01

    Isolation of synaptic nerve terminals or synaptosomes provides an opportunity to study the process of neurotransmission at many levels and with a variety of approaches. For example, structural features of the synaptic terminals and the organelles within them, such as synaptic vesicles and mitochondria, have been elucidated with electron microscopy. The postsynaptic membranes are joined to the presynaptic "active zone" of transmitter release through cell adhesion molecules and remain attached throughout the isolation of synaptosomes. These "post synaptic densities" or "PSDs" contain the receptors for the transmitters released from the nerve terminals and can easily be seen with electron microscopy. Biochemical and cell biological studies with synaptosomes have revealed which proteins and lipids are most actively involved in synaptic release of neurotransmitters. The functional properties of the nerve terminals, such as responses to depolarization and the uptake or release of signaling molecules, have also been characterized through the use of fluorescent dyes, tagged transmitters, and transporter substrates. In addition, isolated synaptosomes can serve as the starting material for the isolation of relatively pure synaptic plasma membranes (SPMs) that are devoid of organelles from the internal environment of the nerve terminal, such as mitochondria and synaptic vesicles. The isolated SPMs can reseal and form vesicular structures in which transport of ions such as sodium and calcium, as well as solutes such as neurotransmitters can be studied. The PSDs also remain associated with the presynaptic membranes during isolation of SPM fractions, making it possible to isolate the synaptic junctional complexes (SJCs) devoid of the rest of the plasma membranes of the nerve terminals and postsynaptic membrane components. Isolated SJCs can be used to identify the proteins that constitute this highly specialized region of neurons. In this chapter, we describe the steps involved

  10. Inhibition of cardiac inward rectifier currents by cationic amphiphilic drugs.

    Science.gov (United States)

    van der Heyden, M A G; Stary-Weinzinger, A; Sanchez-Chapula, J A

    2013-09-01

    Cardiac inward rectifier channels belong to three different classes of the KIR channel protein family. The KIR2.x proteins generate the classical inward rectifier current, IK1, while KIR3 and KIR6 members are responsible for the acetylcholine responsive and ATP sensitive inward rectifier currents IKAch and IKATP, respectively. Aberrant function of these channels has been correlated with severe cardiac arrhythmias, indicating their significant contribution to normal cardiac electrophysiology. A common feature of inward rectifier channels is their dependence on the lipid phosphatidyl-4,5-bisphospate (PIP2) interaction for functional activity. Cationic amphiphilic drugs (CADs) are one of the largest classes of pharmaceutical compounds. Several widely used CADs have been associated with inward rectifier current disturbances, and recent evidence points to interference of the channel-PIP2 interaction as the underlying mechanism of action. Here, we will review how six of these well known drugs, used for treatment in various different conditions, interfere in cardiac inward rectifier functioning. In contrast, KIR channel inhibition by the anionic anesthetic thiopental is achieved by a different mechanism of channel-PIP2 interference. We will discuss the latest basic science insights of functional inward rectifier current characteristics, recently derived KIR channel structures and specific PIP2-receptor interactions at the molecular level and provide insight in how these drugs interfere in the structure-function relationships.

  11. Secreted factors as synaptic organizers.

    Science.gov (United States)

    Johnson-Venkatesh, Erin M; Umemori, Hisashi

    2010-07-01

    A critical step in synaptic development is the differentiation of presynaptic and postsynaptic compartments. This complex process is regulated by a variety of secreted factors that serve as synaptic organizers. Specifically, fibroblast growth factors, Wnts, neurotrophic factors and various other intercellular signaling molecules are proposed to regulate presynaptic and/or postsynaptic differentiation. Many of these factors appear to function at both the neuromuscular junction and in the central nervous system, although the specific function of the molecules differs between the two. Here we review secreted molecules that organize the synaptic compartments and discuss how these molecules shape synaptic development, focusing on mammalian in vivo systems. Their critical role in shaping a functional neural circuit is underscored by their possible link to a wide range of neurological and psychiatric disorders both in animal models and by mutations identified in human patients. © The Authors (2010). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

  12. InGaAs-based planar barrier diode as microwave rectifier

    Science.gov (United States)

    Farhani Zakaria, Nor; Rizal Kasjoo, Shahrir; Zailan, Zarimawaty; Mohamad Isa, Muammar; Arshad, Mohd Khairuddin Md; Taking, Sanna

    2018-06-01

    In this report, we proposed and simulated a new planar nonlinear rectifying device fabricated using InGaAs substrate and referred to as a planar barrier diode (PBD). Using an asymmetrical inverse-arrowhead-shaped structure between the electrodes, a nonuniform depletion region is developed, which creates a triangular energy barrier in the conducting channel. This barrier is voltage dependent and can be controlled by the applied voltage across the PBD, thus resulting in nonlinear diode-like current–voltage characteristics; thus it can be used as a rectifying device. The PBD’s working principle is explained using thermionic emission theory. Furthermore, by varying the PBD’s geometric design, the asymmetry of the current–voltage characteristics can be optimized to realize superior rectification performance. By employing the optimized structural parameters, the obtained cut-off frequency of the device was approximately 270 GHz with a curvature coefficient peak of 14 V‑1 at a low DC bias voltage of 50 mV.

  13. Cardiac Delayed Rectifier Potassium Channels in Health and Disease

    Science.gov (United States)

    Chen, Lei; Sampson, Kevin J.; Kass, Robert S.

    2016-01-01

    Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this chapter, we will review the molecular identities and biophysical properties of these channels. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the possibility and prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia. PMID:27261823

  14. Cardiac Delayed Rectifier Potassium Channels in Health and Disease.

    Science.gov (United States)

    Chen, Lei; Sampson, Kevin J; Kass, Robert S

    2016-06-01

    Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Rectified factor networks for biclustering of omics data.

    Science.gov (United States)

    Clevert, Djork-Arné; Unterthiner, Thomas; Povysil, Gundula; Hochreiter, Sepp

    2017-07-15

    Biclustering has become a major tool for analyzing large datasets given as matrix of samples times features and has been successfully applied in life sciences and e-commerce for drug design and recommender systems, respectively. actor nalysis for cluster cquisition (FABIA), one of the most successful biclustering methods, is a generative model that represents each bicluster by two sparse membership vectors: one for the samples and one for the features. However, FABIA is restricted to about 20 code units because of the high computational complexity of computing the posterior. Furthermore, code units are sometimes insufficiently decorrelated and sample membership is difficult to determine. We propose to use the recently introduced unsupervised Deep Learning approach Rectified Factor Networks (RFNs) to overcome the drawbacks of existing biclustering methods. RFNs efficiently construct very sparse, non-linear, high-dimensional representations of the input via their posterior means. RFN learning is a generalized alternating minimization algorithm based on the posterior regularization method which enforces non-negative and normalized posterior means. Each code unit represents a bicluster, where samples for which the code unit is active belong to the bicluster and features that have activating weights to the code unit belong to the bicluster. On 400 benchmark datasets and on three gene expression datasets with known clusters, RFN outperformed 13 other biclustering methods including FABIA. On data of the 1000 Genomes Project, RFN could identify DNA segments which indicate, that interbreeding with other hominins starting already before ancestors of modern humans left Africa. https://github.com/bioinf-jku/librfn. djork-arne.clevert@bayer.com or hochreit@bioinf.jku.at. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

  16. Synaptic consolidation across multiple timescales

    Directory of Open Access Journals (Sweden)

    Lorric Ziegler

    2014-03-01

    Full Text Available The brain is bombarded with a continuous stream of sensory events, but retains only a small subset in memory. The selectivity of memory formation prevents our memory from being overloaded with irrelevant items that would rapidly bring the brain to its storage limit; moreover, selectivity also prevents overwriting previously formed memories with new ones. Memory formation in the hippocampus, as well as in other brain regions, is thought to be linked to changes in the synaptic connections between neurons. In this view, sensory events imprint traces at the level of synapses that reflect potential memory items. The question of memory selectivity can therefore be reformulated as follows: what are the reasons and conditions that some synaptic traces fade away whereas others are consolidated and persist? Experimentally, changes in synaptic strength induced by 'Hebbian' protocols fade away over a few hours (early long-term potentiation or e-LTP, unless these changes are consolidated. The experiments and conceptual theory of synaptic tagging and capture (STC provide a mechanistic explanation for the processes involved in consolidation. This theory suggests that the initial trace of synaptic plasticity sets a tag at the synapse, which then serves as a marker for potential consolidation of the changes in synaptic efficacy. The actual consolidation processes, transforming e-LTP into late LTP (l-LTP, require the capture of plasticity-related proteins (PRP. We translate the above conceptual model into a compact computational model that accounts for a wealth of in vitro data including experiments on cross-tagging, tag-resetting and depotentiation. A central ingredient is that synaptic traces are described with several variables that evolve on different time scales. Consolidation requires the transmission of information from a 'fast' synaptic trace to a 'slow' one through a 'write' process, including the formation of tags and the production of PRP for the

  17. Towards Rectifying Performance at the Molecular Scale.

    Science.gov (United States)

    Zhang, Guang-Ping; Xie, Zhen; Song, Yang; Hu, Gui-Chao; Wang, Chuan-Kui

    2017-10-24

    Molecular diode, proposed by Mark Ratner and Arieh Aviram in 1974, is the first single-molecule device investigated in molecular electronics. As a fundamental device in an electric circuit, molecular diode has attracted an enduring and extensive focus during the past decades. In this review, the theoretical and experimental progresses of both charge-based and spin-based molecular diodes are summarized. For the charge-based molecular diodes, the rectifying properties originated from asymmetric molecules including D-σ-A, D-π-A, D-A, and σ-π type compounds, asymmetric electrodes, asymmetric nanoribbons, and their combination are analyzed. Correspondingly, the rectification mechanisms are discussed in detail. Furthermore, a series of strategies for modulating rectification performance is figured out. Discussion on concept of molecular spin diode is also involved based on a magnetic co-oligomer. At the same time, the intrinsic mechanism as well as the modulation of the spin-current rectification performance is introduced. Finally, several crucial issues that need to be addressed in the future are given.

  18. 2010 NOAA Ortho-rectified Mosaic of Lake Champlain, Vermont

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2012 NOAA Ortho-rectified Color Mosaic of Astoria, Oregon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2011 NOAA Ortho-rectified Mosaic of Intracoastal Waterway, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2011 NOAA Ortho-rectified Mosaic of Galveston, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. Comparison of thyristor rectifier characteristics with different gate control systems

    International Nuclear Information System (INIS)

    Gula, V.; Cherepakhin, A.A.

    1982-01-01

    Some thyristor gate control systems both synchronous and nonsynchronous ones are described. The experimental results of supply voltage asymmetry influence on spectral contents of rectified. output voltage are quoted. Dynamic and frequency responses of these systems are investigated too. Results of comparison of the spectral content of 100 Hz subharmonic of rectified voltage on loading current showed the advantage of the systems with feedback [ru

  3. 19 rectifiers to supply the coils of the TCV tokamak

    International Nuclear Information System (INIS)

    Fasel, D.; Perez, A.; Depreville, G.; Puchar, F.; Pahud, J.D.

    1990-01-01

    This paper describes the electrical network designed to supply the 19 coils of the TCV (Tokamak a Configuration Variable) tokamak. After a brief description of the main purpose of TCV, the general characteristics of the TCV network are given. Then the technical choices made for the rectifier power stage are detailed. There follows a description of the rectifier digital control electronics. Comments on simulations carried out and the actual status conclude the paper. (author) 3 refs., 5 figs., 2 tabs

  4. Noise rectifier based on the two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Cheremisin, M. V., E-mail: tcher_max@yahoo.com [Ioffe Physical-Technical Institute (Russian Federation)

    2012-09-15

    The dc voltage observed at low temperatures in a 2D electron sample in the absence of noticeable external excitations [1] is accounted by the Schottky contact rectification of the noise generated in the measuring circuit. The rectified voltage is shown to depend on the asymmetry of the contact pair. The dependence of the rectified voltage on the noise amplitude first follows the trivial quadratic law, then exhibits a nearly linear behavior, and finally, levels off.

  5. Wireless power transmission for biomedical implants: The role of near-zero threshold CMOS rectifiers.

    Science.gov (United States)

    Mohammadi, Ali; Redoute, Jean-Michel; Yuce, Mehmet R

    2015-01-01

    Biomedical implants require an electronic power conditioning circuitry to provide a stable electrical power supply. The efficiency of wireless power transmission is strongly dependent on the power conditioning circuitry specifically the rectifier. A cross-connected CMOS bridge rectifier is implemented to demonstrate the impact of thresholds of rectifiers on wireless power transfer. The performance of the proposed rectifier is experimentally compared with a conventional Schottky diode full wave rectifier over 9 cm distance of air and tissue medium between the transmitter and receiver. The output voltage generated by the CMOS rectifier across a 1 KΩ resistive load is around twice as much as the Schottky rectifier.

  6. Synaptic Effects of Electric Fields

    Science.gov (United States)

    Rahman, Asif

    Learning and sensory processing in the brain relies on the effective transmission of information across synapses. The strength and efficacy of synaptic transmission is modifiable through training and can be modulated with noninvasive electrical brain stimulation. Transcranial electrical stimulation (TES), specifically, induces weak intensity and spatially diffuse electric fields in the brain. Despite being weak, electric fields modulate spiking probability and the efficacy of synaptic transmission. These effects critically depend on the direction of the electric field relative to the orientation of the neuron and on the level of endogenous synaptic activity. TES has been used to modulate a wide range of neuropsychiatric indications, for various rehabilitation applications, and cognitive performance in diverse tasks. How can a weak and diffuse electric field, which simultaneously polarizes neurons across the brain, have precise changes in brain function? Designing therapies to maximize desired outcomes and minimize undesired effects presents a challenging problem. A series of experiments and computational models are used to define the anatomical and functional factors leading to specificity of TES. Anatomical specificity derives from guiding current to targeted brain structures and taking advantage of the direction-sensitivity of neurons with respect to the electric field. Functional specificity originates from preferential modulation of neuronal networks that are already active. Diffuse electric fields may recruit connected brain networks involved in a training task and promote plasticity along active synaptic pathways. In vitro, electric fields boost endogenous synaptic plasticity and raise the ceiling for synaptic learning with repeated stimulation sessions. Synapses undergoing strong plasticity are preferentially modulated over weak synapses. Therefore, active circuits that are involved in a task could be more susceptible to stimulation than inactive circuits

  7. Electrophysical properties, synaptic transmission and neuromodulation in serotonergic caudal raphe neurons.

    Science.gov (United States)

    Li, Y W; Bayliss, D A

    1998-06-01

    1. We studied electrophysiological properties, synaptic transmission and modulation by 5-hydroxytryptamine (5-HT) of caudal raphe neurons using whole-cell recording in a neonatal rat brain slice preparation; recorded neurons were identified as serotonergic by post-hoc immunohistochemical detection of tryptophan hydroxylase, the 5-HT-synthesizing enzyme. 2. Serotonergic neurons fired spontaneously (approximately 1 Hz), with maximal steady state firing rates of < 4 Hz. 5-Hydroxytryptamine caused hyperpolarization and cessation of spike activity in these neurons by activating inwardly rectifying K+ conductance via somatodendritic 5-HT1A receptors. 3. Unitary glutamatergic excitatory post-synaptic potentials (EPSP) and currents (EPSC) were evoked in serotonergic neurons by local electrical stimulation. Evoked EPSC were potently inhibited by 5-HT, an effect mediated by presynaptic 5-HT1B receptors. 4. In conclusion, serotonergic caudal raphe neurons are spontaneously active in vitro; they receive prominent glutamatergic synaptic inputs. 5-Hydroxytryptamine regulates serotonergic neuronal activity of the caudal raphe by decreasing spontaneous activity via somatodendritic 5-HT1A receptors and by inhibiting excitatory synaptic transmission onto these neurons via presynaptic 5-HT1B receptors. These local modulatory mechanisms provide multiple levels of feedback autoregulation of serotonergic raphe neurons by 5-HT.

  8. Effects of active conductance distribution over dendrites on the synaptic integration in an identified nonspiking interneuron.

    Directory of Open Access Journals (Sweden)

    Akira Takashima

    Full Text Available The synaptic integration in individual central neuron is critically affected by how active conductances are distributed over dendrites. It has been well known that the dendrites of central neurons are richly endowed with voltage- and ligand-regulated ion conductances. Nonspiking interneurons (NSIs, almost exclusively characteristic to arthropod central nervous systems, do not generate action potentials and hence lack voltage-regulated sodium channels, yet having a variety of voltage-regulated potassium conductances on their dendritic membrane including the one similar to the delayed-rectifier type potassium conductance. It remains unknown, however, how the active conductances are distributed over dendrites and how the synaptic integration is affected by those conductances in NSIs and other invertebrate neurons where the cell body is not included in the signal pathway from input synapses to output sites. In the present study, we quantitatively investigated the functional significance of active conductance distribution pattern in the spatio-temporal spread of synaptic potentials over dendrites of an identified NSI in the crayfish central nervous system by computer simulation. We systematically changed the distribution pattern of active conductances in the neuron's multicompartment model and examined how the synaptic potential waveform was affected by each distribution pattern. It was revealed that specific patterns of nonuniform distribution of potassium conductances were consistent, while other patterns were not, with the waveform of compound synaptic potentials recorded physiologically in the major input-output pathway of the cell, suggesting that the possibility of nonuniform distribution of potassium conductances over the dendrite cannot be excluded as well as the possibility of uniform distribution. Local synaptic circuits involving input and output synapses on the same branch or on the same side were found to be potentially affected under

  9. Negative differential resistance and rectifying performance induced by doped graphene nanoribbons p–n device

    International Nuclear Information System (INIS)

    Zhou, Yuhong; Qiu, Nianxiang; Li, Runwei; Guo, Zhansheng; Zhang, Jian; Fang, Junfeng; Huang, Aisheng; He, Jian; Zha, Xianhu; Luo, Kan; Yin, Jingshuo; Li, Qiuwu; Bai, Xiaojing; Huang, Qing; Du, Shiyu

    2016-01-01

    Employing nonequilibrium Green's Functions in combination with density functional theory, the electronic transport properties of armchair graphene nanoribbon (GNR) devices with various widths are investigated in this work. In the adopted model, two semi-infinite graphene electrodes are periodically doped with boron or nitrogen atoms. Our calculations reveal that these devices have a striking nonlinear feature and show notable negative differential resistance (NDR). The results also indicate the diode-like properties are reserved and the rectification ratios are high. It is found the electronic transport properties are strongly dependent on the width of doped nanoribbons and the positions of dopants and three distinct families are elucidated for the current armchair GNR devices. The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage. These findings suggest that the doped armchair GNR is a promising candidate for the next generation nanoscale device. - Highlights: • The negative differential resistance (NDR) and rectification phenomena have been observed for the B- and N-doping armchair graphene nanoribbon (GNR) devices. • The electronic transport properties are strongly dependent on the width of doped nanoribbons and exhibit three distinct families. • The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage.

  10. Negative differential resistance and rectifying performance induced by doped graphene nanoribbons p–n device

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yuhong; Qiu, Nianxiang; Li, Runwei [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); Guo, Zhansheng [Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072 (China); Zhang, Jian; Fang, Junfeng; Huang, Aisheng [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); He, Jian [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Zha, Xianhu; Luo, Kan; Yin, Jingshuo; Li, Qiuwu; Bai, Xiaojing; Huang, Qing [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); Du, Shiyu, E-mail: dushiyu@nimte.ac.cn [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China)

    2016-03-06

    Employing nonequilibrium Green's Functions in combination with density functional theory, the electronic transport properties of armchair graphene nanoribbon (GNR) devices with various widths are investigated in this work. In the adopted model, two semi-infinite graphene electrodes are periodically doped with boron or nitrogen atoms. Our calculations reveal that these devices have a striking nonlinear feature and show notable negative differential resistance (NDR). The results also indicate the diode-like properties are reserved and the rectification ratios are high. It is found the electronic transport properties are strongly dependent on the width of doped nanoribbons and the positions of dopants and three distinct families are elucidated for the current armchair GNR devices. The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage. These findings suggest that the doped armchair GNR is a promising candidate for the next generation nanoscale device. - Highlights: • The negative differential resistance (NDR) and rectification phenomena have been observed for the B- and N-doping armchair graphene nanoribbon (GNR) devices. • The electronic transport properties are strongly dependent on the width of doped nanoribbons and exhibit three distinct families. • The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage.

  11. A metamaterial electromagnetic energy rectifying surface with high harvesting efficiency

    Directory of Open Access Journals (Sweden)

    Xin Duan

    2016-12-01

    Full Text Available A novel metamaterial rectifying surface (MRS for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a harvesting efficiency up to 66.9% under an incident power density of 5 mW/cm2, compared with a simulated efficiency of 72.9%. This high harvesting efficiency makes the proposed MRS an effective receiving device in practical microwave power transmission applications.

  12. A two-phase full-wave superconducting rectifier

    International Nuclear Information System (INIS)

    Ariga, T.; Ishiyama, A.

    1989-01-01

    A two-phase full-wave superconducting rectifier has been developed as a small cryogenic power supply of superconducting magnets for magnetically levitation trains. Those magnets are operated in the persistent current mode. However, small ohmic loss caused at resistive joints and ac loss induced by the vibration of the train cannot be avoided. Therefore, the low-power cryogenic power supply is required to compensate for the reduction in magnet current. The presented superconducting rectifier consists of two identical full-wave rectifiers connected in series. Main components of each rectifier are a troidal shape superconducting set-up transformer and two thermally controlled switches. The test results using a 47.5 mH load magnet at 0.2 Hz and 0.5 Hz operations are described. To estimate the characteristics of the superconducting rectifier, the authors have developed a simulation code. From the experiments and the simulations, the transfer efficiency is examined. Furthermore, the optimal design of thermally controlled switches based on the finite element analysis is also discussed

  13. A metamaterial electromagnetic energy rectifying surface with high harvesting efficiency

    Science.gov (United States)

    Duan, Xin; Chen, Xing; Zhou, Lin

    2016-12-01

    A novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a harvesting efficiency up to 66.9% under an incident power density of 5 mW/cm2, compared with a simulated efficiency of 72.9%. This high harvesting efficiency makes the proposed MRS an effective receiving device in practical microwave power transmission applications.

  14. Temperature-gated thermal rectifier for active heat flow control.

    Science.gov (United States)

    Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

    2014-08-13

    Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

  15. Control system for a superconducting rectifier using a microcomputer

    International Nuclear Information System (INIS)

    ten Kate, H.H.J.; Kamphuis, D.A.; Caspari, M.; van de Klundert, L.J.M.; Houkes, Z.

    1981-01-01

    Within the scope of a research program of superconducting rectifiers software is being developed to take care of the control of such systems. The hardware architecture which interferes with the in and output signals is based on a LSI-11/2 microprocessor with sufficient mass storage for data logging, console and printer. The flexibility inherent to this hardware configuration is desired for optimization of the rectifier concerning maximum current, power, efficiency and quench stability. The paper describes the structure of the program and the interaction between both computer hardware and software and the superconducting rectifier. However, because the reliability of computer systems is unsatisfactory, an additional hardware protection system still handles the most important alarms. 2 refs

  16. Rectified motion in an asymmetrically structured channel due to induced-charge electrokinetic and thermo-kinetic phenomena

    International Nuclear Information System (INIS)

    Sugioka, Hideyuki

    2016-01-01

    It would be advantageous to move fluid by the gradient of random thermal noises that are omnipresent in the natural world. To achieve this motion, we propose a rectifier that uses a thermal noise along with induced-charge electroosmosis and electrophoresis (ICEO and ICEP) around a metal post cylinder in an asymmetrically structured channel and numerically examine its rectification performance. By the boundary element method combined with the thin double layer approximation, we find that rectified motion occurs in the asymmetrically structured channel due to ICEO and ICEP. Further, by thermodynamical and equivalent circuit methods, we discuss a thermal voltage that drives a rectifier consisting of a fluidic channel of an electrolyte and an impedance as a noise source. Our calculations show that fluid can be moved in the asymmetrically structured channel by the fluctuation of electric fields due to a thermal noise only when there is a temperature difference. In addition, our simple noise argument provides a different perspective for the thermo-kinetic phenomena (around a metal post) which was predicted based on the electrolyte Seebeck effect in our previous paper [H. Sugioka, “Nonlinear thermokinetic phenomena due to the Seebeck effect,” Langmuir 30, 8621 (2014)

  17. Rectified motion in an asymmetrically structured channel due to induced-charge electrokinetic and thermo-kinetic phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Sugioka, Hideyuki, E-mail: hsugioka@shinshu-u.ac.jp [Frontier Research Center, Canon Inc. 30-2, Shimomaruko 3-chome, Ohta-ku, Tokyo 146-8501, Japan and Department of Mechanical Systems Engineering, Shinshu University 4-17-1 Wakasato, Nagano 380-8553 (Japan)

    2016-02-15

    It would be advantageous to move fluid by the gradient of random thermal noises that are omnipresent in the natural world. To achieve this motion, we propose a rectifier that uses a thermal noise along with induced-charge electroosmosis and electrophoresis (ICEO and ICEP) around a metal post cylinder in an asymmetrically structured channel and numerically examine its rectification performance. By the boundary element method combined with the thin double layer approximation, we find that rectified motion occurs in the asymmetrically structured channel due to ICEO and ICEP. Further, by thermodynamical and equivalent circuit methods, we discuss a thermal voltage that drives a rectifier consisting of a fluidic channel of an electrolyte and an impedance as a noise source. Our calculations show that fluid can be moved in the asymmetrically structured channel by the fluctuation of electric fields due to a thermal noise only when there is a temperature difference. In addition, our simple noise argument provides a different perspective for the thermo-kinetic phenomena (around a metal post) which was predicted based on the electrolyte Seebeck effect in our previous paper [H. Sugioka, “Nonlinear thermokinetic phenomena due to the Seebeck effect,” Langmuir 30, 8621 (2014)].

  18. Synaptic control of motoneuronal excitability

    DEFF Research Database (Denmark)

    Rekling, J C; Funk, G D; Bayliss, D A

    2000-01-01

    important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization......, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions...... and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K(+) current, cationic inward...

  19. An experimental study on the effects of rectifiers on fluid flow

    International Nuclear Information System (INIS)

    Kawashima, G.

    1985-01-01

    This paper reports studies of various combinations of rectifiers and rectifying nets to measure fluid flow and in particular, the measurement of the flow through an orifice or nozzle, since they help to shorten the inlet length

  20. Synaptic and functional linkages between spinal premotor interneurons and hand-muscle activity during precision grip

    Directory of Open Access Journals (Sweden)

    Tomohiko eTakei

    2013-04-01

    Full Text Available Grasping is a highly complex movement that requires the coordination of a number of hand joints and muscles. Previous studies showed that spinal premotor interneurons (PreM-INs in the primate cervical spinal cord have divergent synaptic effects on hand motoneurons and that they might contribute to hand-muscle synergies. However, the extent to which these PreM-IN synaptic connections functionally contribute to modulating hand-muscle activity is not clear. In this paper, we explored the contribution of spinal PreM-INs to hand-muscle activation by quantifying the synaptic linkage (SL and functional linkage (FL of the PreM-INs with hand-muscle activities. The activity of 23 PreM-INs was recorded from the cervical spinal cord (C6–T1, with EMG signals measured simultaneously from hand and arm muscles in two macaque monkeys performing a precision grip task. Spike-triggered averages (STAs of rectified EMGs were compiled for 456 neuron–muscle pairs; 63 pairs showed significant post-spike effects (i.e., SL. Conversely, 231 of 456 pairs showed significant cross-correlations between the IN firing rate and rectified EMG (i.e., FL. Importantly, a greater proportion of the neuron–muscle pairs with SL showed FL (43/63 pairs, 68% compared with the pairs without SL (203/393, 52%, and the presence of SL was significantly associated with that of FL. However, a significant number of pairs had SL without FL (SL∩!FL, n = 20 or FL without SL (!SL∩FL, n = 203, and the proportions of these incongruities exceeded the number expected by chance. These results suggested that spinal PreM-INs function to significantly modulate hand-muscle activity during precision grip, but the contribution of other neural structures is also needed to recruit an adequate combination of hand-muscle motoneurons.

  1. Fully controlled 5-phase, 10-pulse, line commutated rectifier

    Directory of Open Access Journals (Sweden)

    Mahmoud I. Masoud

    2015-12-01

    Full Text Available The development and production of multiphase machines either generators or motors, specially five-phase, offers improved performance compared to three-phase counterpart. Five phase generators could generate power in applications such as, but not limited to, wind power generation, electric vehicles, aerospace, and oil and gas. The five-phase generator output requires converter system such as ac–dc converters. In this paper, a fully controlled 10-pulse line commutated rectifier, suitable to be engaged with wind energy applications, fed from five-phase source is introduced. A shunt active power filter (APF is used to improve power factor and supply current total harmonic distortion (THD. Compared to three-phase converters, 6-pulse or 12-pulse rectifiers, the 10-pulse rectifier engaged with 5-phase source alleviate their drawbacks such as high dc ripples and no need for electric gear or phase shifting transformer. MATLAB/SIMULINK platform is used as a simulation tool to investigate the performance of the proposed rectifier.

  2. Rectifier analysis for radio frequency energy harvesting and power transport

    NARCIS (Netherlands)

    Keyrouz, S.; Visser, H.J.; Tijhuis, A.G.

    2012-01-01

    Wireless Power Transmission (WPT) is an attractive powering method for wireless sensor nodes, battery-less sensors, and Radio-Frequency Identification (RFID) tags. The key element on the receiving side of a WPT system is the rectifying antenna (rectenna) which captures the electromagnetic power and

  3. Control Strategy of PWM Rectifiers Connected to Unbalanced Grids

    Czech Academy of Sciences Publication Activity Database

    Bejvl, Martin; Švec, J.; Tlustý, J.; Valouch, V.

    -, č. 11 (2013) ISSN 2172-038X. [International Conference on Renewable Energies and Power Quality (ICREPQ´13). Bilbao, 20.03.2013-22.03.2013] Institutional support: RVO:61388998 Keywords : electric power system * PWM rectifier * dc voltage ripple Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  4. Measurement of Phase Dependent Impedance for 3-phase Diode Rectifier

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2016-01-01

    This paper presents a new method to measure the phase dependent impedance from an experimental set up. Though most of power electronics based system is gradually migrating to IGBT based voltage source converter due to their controllability, the rectifier composed of diode or thyristor components...

  5. A thermally switched 9 kA superconducting rectifier fluxpump

    NARCIS (Netherlands)

    ten Kate, Herman H.J.; Bunk, Paul B.; Steffens, Harry A.; van de Klundert, Louis J.M.

    1981-01-01

    The feasibility of superconducting rectifier-fluxpumps has to be demonstrated at current levels of 10 - 100 kA, where is asked for in the superconducting devices now being planned. An intensive program has been started at the low temperature division of the University of Twente to construct such

  6. Frequency Support from OWPPs connected to HVDC via Diode Rectifiers

    DEFF Research Database (Denmark)

    Saborío-Romano, Oscar; Bidadfar, Ali; Göksu, Ömer

    This paper presents a study assessing the actual capability of an offshore wind power plant (offshore WPP, OWPP) to provide frequency support (FS) to an onshore network, when connected through a high-voltage direct-current (HVDC) link having a diode rectifier (DR) offshore terminal and a voltage...

  7. Stability analysis of direct current control in current source rectifier

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...

  8. Rectified heat transfer into translating and pulsating vapor bubbles

    NARCIS (Netherlands)

    Hao, Y.; Prosperetti, Andrea

    2002-01-01

    It is well known that, when a stationary vapor bubble is subject to a sufficiently intense acoustic field, it will grow by rectified heat transfer even in a subcooled liquid. The object of this paper is to study how translation, and the ensuing convective effects, influence this process. It is shown

  9. Rectifier Current Control for an LLC Resonant Converter Based on a Simplified Linearized Model

    OpenAIRE

    Zhijian Fang; Junhua Wang; Shanxu Duan; Liangle Xiao; Guozheng Hu; Qisheng Liu

    2018-01-01

    In this paper, a rectifier current control for an LLC resonant converter is proposed, based on a simplified, two-order, linearized model that adds a rectifier current feedback inner loop to improve dynamic performance. Compared to the traditional large-signal model with seven resonant states, this paper utilizes a rectifier current state to represent the characteristics of the resonant states, simplifying the LLC resonant model from seven orders to two orders. Then, the rectifier current feed...

  10. Location-dependent excitatory synaptic interactions in pyramidal neuron dendrites.

    Directory of Open Access Journals (Sweden)

    Bardia F Behabadi

    Full Text Available Neocortical pyramidal neurons (PNs receive thousands of excitatory synaptic contacts on their basal dendrites. Some act as classical driver inputs while others are thought to modulate PN responses based on sensory or behavioral context, but the biophysical mechanisms that mediate classical-contextual interactions in these dendrites remain poorly understood. We hypothesized that if two excitatory pathways bias their synaptic projections towards proximal vs. distal ends of the basal branches, the very different local spike thresholds and attenuation factors for inputs near and far from the soma might provide the basis for a classical-contextual functional asymmetry. Supporting this possibility, we found both in compartmental models and electrophysiological recordings in brain slices that the responses of basal dendrites to spatially separated inputs are indeed strongly asymmetric. Distal excitation lowers the local spike threshold for more proximal inputs, while having little effect on peak responses at the soma. In contrast, proximal excitation lowers the threshold, but also substantially increases the gain of distally-driven responses. Our findings support the view that PN basal dendrites possess significant analog computing capabilities, and suggest that the diverse forms of nonlinear response modulation seen in the neocortex, including uni-modal, cross-modal, and attentional effects, could depend in part on pathway-specific biases in the spatial distribution of excitatory synaptic contacts onto PN basal dendritic arbors.

  11. Reversed synaptic effects of hypocretin and NPY mediated by excitatory GABA-dependent synaptic activity in developing MCH neurons.

    Science.gov (United States)

    Li, Ying; Xu, Youfen; van den Pol, Anthony N

    2013-03-01

    In mature neurons, GABA is the primary inhibitory neurotransmitter. In contrast, in developing neurons, GABA exerts excitatory actions, and in some neurons GABA-mediated excitatory synaptic activity is more prevalent than glutamate-mediated excitation. Hypothalamic neuropeptides that modulate cognitive arousal and energy homeostasis, hypocretin/orexin and neuropeptide Y (NPY), evoked reversed effects on synaptic actions that were dependent on presynaptic GABA release onto melanin-concentrating hormone (MCH) neurons. MCH neurons were identified by selective green fluorescent protein (GFP) expression in transgenic mice. In adults, hypocretin increased GABA release leading to reduced excitation. In contrast, in the developing brain as studied here with analysis of miniature excitatory postsynaptic currents, paired-pulse ratios, and evoked potentials, hypocretin acted presynaptically to enhance the excitatory actions of GABA. The ability of hypocretin to enhance GABA release increases inhibition in adult neurons but paradoxically enhances excitation in developing MCH neurons. In contrast, NPY attenuation of GABA release reduced inhibition in mature neurons but enhanced inhibition during development by attenuating GABA excitation. Both hypocretin and NPY also evoked direct actions on developing MCH neurons. Hypocretin excited MCH cells by activating a sodium-calcium exchanger and by reducing potassium currents; NPY reduced activity by increasing an inwardly rectifying potassium current. These data for the first time show that both hypocretin and NPY receptors are functional presynaptically during early postnatal hypothalamic development and that both neuropeptides modulate GABA actions during development with a valence of enhanced excitation or inhibition opposite to that of the adult state, potentially allowing neuropeptide modulation of use-dependent synapse stabilization.

  12. Junction barrier Schottky rectifier with an improved P-well region

    International Nuclear Information System (INIS)

    Wang Ying; Li Ting; Cao Fei; Shao Lei; Chen Yu-Xian

    2012-01-01

    A junction barrier Schottky (JBS) rectifier with an improved P-well on 4H—SiC is proposed to improve the V F —I R trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3×10 −8 times that of the common JBS rectifier at no expense of the forward voltage drop. This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P + grid, resulting in a lower spreading current and tunneling current. As a result, the breakdown voltage of the proposed JBS rectifier is over 1.6 kV, that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field. Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier, the figure of merit (FOM) of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier. Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge (ESD) in the human body model (HBM) circuits, the failure energy of the proposed JBS rectifier increases 17% compared with that of the common JBS rectifier. (interdisciplinary physics and related areas of science and technology)

  13. Controllable SET process in O-Ti-Sb-Te based phase change memory for synaptic application

    Science.gov (United States)

    Ren, Kun; Li, Ruiheng; Chen, Xin; Wang, Yong; Shen, Jiabin; Xia, Mengjiao; Lv, Shilong; Ji, Zhenguo; Song, Zhitang

    2018-02-01

    The nonlinear resistance change and small bit resolution of phase change memory (PCM) under identical operation pulses will limit its performance as a synaptic device. The octahedral Ti-Te units in Ti-Sb-Te, regarded as nucleation seeds, are degenerated when Ti is bonded with O, causing a slower crystallization and a controllable SET process in PCM cells. A linear resistance change under identical pulses, a resolution of ˜8 bits, and an ON/OFF ratio of ˜102 has been achieved in O-Ti-Sb-Te based PCM, showing its potential application as a synaptic device to improve recognition performance of the neural network.

  14. MPC-SVM method for Vienna rectifier with PMSG used in Wind Turbine Systems

    DEFF Research Database (Denmark)

    Lee, June-Seok; Bak, Yeongsu; Lee, Kyo-Beum

    2016-01-01

    Using a Vienna rectifier as the machine-side rectifier of back-to-back converter is advantageous in terms of size and cost compared to three-level topologies and for this reason, the Vienna rectifier has been used in Wind Turbine Systems (WTS). This paper proposes a Model Predictive Control (MPC......) method for the Vienna rectifier used in WTS with a Permanent Magnet Synchronous Generator (PMSG). The proposed MPC method considers the feasible eight-voltage vectors of the Vienna rectifier. In addition, the voltage vectors, which are the center voltage vectors of two feasible adjacent voltage vectors...

  15. Development of Op-Amp Based Piezoelectric Rectifier for Low Power Energy Harvesting Applications

    Directory of Open Access Journals (Sweden)

    Syazmie Bin Sepeeh Muhamad

    2018-01-01

    Full Text Available In this study, the development of operational amplifier (op-amp based rectifier for piezoelectric energy harvesting applications was studied. The two stage op-amp full wave rectifier was used to convert the AC signal to DC signal voltage received by piezoelectric devices. The inverted half wave rectifier integrated with full wave rectifier were designed and simulated using MultiSIM software. The circuit was then fabricated onto a printed circuit board (PCB, using standard fabrication process. The achievement of this rectifier was able to boost up the maximum voltage of 5 V for input voltage of 800 mV. The output of the rectifier was in DC signal after the rectification by the op-amp. In term of power, the power dissipation was reduced consequently the waste power decreases. Future work includes optimization of the rectifying circuit to operate more efficiently can be made to increase the efficiency of the devices.

  16. Experimental investigation of radiative thermal rectifier using vanadium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Kota, E-mail: kotaito@mosk.tytlabs.co.jp [Toyota Central Research and Development Labs, Nagakute, Aichi 480-1192 (Japan); Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Nishikawa, Kazutaka; Iizuka, Hideo [Toyota Central Research and Development Labs, Nagakute, Aichi 480-1192 (Japan); Toshiyoshi, Hiroshi [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

    2014-12-22

    Vanadium dioxide (VO{sub 2}) exhibits a phase-change behavior from the insulating state to the metallic state around 340 K. By using this effect, we experimentally demonstrate a radiative thermal rectifier in the far-field regime with a thin film VO{sub 2} deposited on the silicon wafer. A rectification contrast ratio as large as two is accurately obtained by utilizing a one-dimensional steady-state heat flux measurement system. We develop a theoretical model of the thermal rectifier with optical responses of the materials retrieved from the measured mid-infrared reflection spectra, which is cross-checked with experimentally measured heat flux. Furthermore, we tune the operating temperatures by doping the VO{sub 2} film with tungsten (W). These results open up prospects in the fields of thermal management and thermal information processing.

  17. Common rectifier diodes in temperature measurement applications below 50 K

    International Nuclear Information System (INIS)

    Jaervelae, J; Stenvall, A; Mikkonen, R

    2010-01-01

    In this paper we studied the use of common electronic semiconductor diodes in temperature measurements at cryogenic atmosphere. The motivation for this is the high price of calibrated cryogenic temperature sensors since there are some applications, like quench detection, in which a cheaper and a less accurate sensor would suffice. We measured the forward voltage as a function of temperature, V f (T), of several silicon rectifier diodes to determine the accuracy and interchangeability of the diodes. The experimental results confirmed that V f (T) of common rectifier diodes are similar to cryogenic sensor diodes, but the variability between two samples is much larger. The interchangeability of the diodes proved to be poor if absolute temperatures are to be measured. However for sensing changes in temperature they proved to be adequate and thus can be used to measure e.g. quench propagation or sense quench ignition at multiple locations with cheap price.

  18. Performance evaluation of a rectifier column using gamma column scanning

    Directory of Open Access Journals (Sweden)

    Aquino Denis D.

    2017-12-01

    Full Text Available Rectifier columns are considered to be a critical component in petroleum refineries and petrochemical processing installations as they are able to affect the overall performance of these facilities. It is deemed necessary to monitor the operational conditions of such vessels to optimize processes and prevent anomalies which could pose undesired consequences on product quality that might lead to huge financial losses. A rectifier column was subjected to gamma scanning using a 10-mCi Co-60 source and a 2-inch-long detector in tandem. Several scans were performed to gather information on the operating conditions of the column under different sets of operating parameters. The scan profiles revealed unexpected decreases in the radiation intensity at vapour levels between trays 2 and 3, and between trays 4 and 5. Flooding also occurred during several scans which could be attributed to parametric settings.

  19. Wind Solar Hybrid System Rectifier Stage Topology Simulation

    OpenAIRE

    Anup M. Gakare; Subhash Kamdi

    2014-01-01

    This paper presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer. The hybrid system allows maximum utilization of freely available renewable sources like wind and photovoltaic energies. This paper presents a new system configuration of the multi input rectifier stage for a hybrid wind and photovoltaic energy system. This configuration allows the two sources to supply the load simultaneously depending on the availability of...

  20. Delayed Maturation of Fast-Spiking Interneurons Is Rectified by Activation of the TrkB Receptor in the Mouse Model of Fragile X Syndrome.

    Science.gov (United States)

    Nomura, Toshihiro; Musial, Timothy F; Marshall, John J; Zhu, Yiwen; Remmers, Christine L; Xu, Jian; Nicholson, Daniel A; Contractor, Anis

    2017-11-22

    Fragile X syndrome (FXS) is a neurodevelopmental disorder that is a leading cause of inherited intellectual disability, and the most common known cause of autism spectrum disorder. FXS is broadly characterized by sensory hypersensitivity and several developmental alterations in synaptic and circuit function have been uncovered in the sensory cortex of the mouse model of FXS ( Fmr1 KO). GABA-mediated neurotransmission and fast-spiking (FS) GABAergic interneurons are central to cortical circuit development in the neonate. Here we demonstrate that there is a delay in the maturation of the intrinsic properties of FS interneurons in the sensory cortex, and a deficit in the formation of excitatory synaptic inputs on to these neurons in neonatal Fmr1 KO mice. Both these delays in neuronal and synaptic maturation were rectified by chronic administration of a TrkB receptor agonist. These results demonstrate that the maturation of the GABAergic circuit in the sensory cortex is altered during a critical developmental period due in part to a perturbation in BDNF-TrkB signaling, and could contribute to the alterations in cortical development underlying the sensory pathophysiology of FXS. SIGNIFICANCE STATEMENT Fragile X (FXS) individuals have a range of sensory related phenotypes, and there is growing evidence of alterations in neuronal circuits in the sensory cortex of the mouse model of FXS ( Fmr1 KO). GABAergic interneurons are central to the correct formation of circuits during cortical critical periods. Here we demonstrate a delay in the maturation of the properties and synaptic connectivity of interneurons in Fmr1 KO mice during a critical period of cortical development. The delays both in cellular and synaptic maturation were rectified by administration of a TrkB receptor agonist, suggesting reduced BDNF-TrkB signaling as a contributing factor. These results provide evidence that the function of fast-spiking interneurons is disrupted due to a deficiency in neurotrophin

  1. Fast switching wideband rectifying circuit for future RF energy harvesting

    Science.gov (United States)

    Asmeida, Akrem; Mustam, Saizalmursidi Md; Abidin, Z. Z.; Ashyap, A. Y. I.

    2017-09-01

    This paper presents the design and simulation of fast switching microwave rectifying circuit for ultra wideband patch antenna over a dual-frequency band (1.8 GHz for GSM and 2.4 GHz for ISM band). This band was chosen due to its high signal availability in the surrounding environment. New rectifying circuit topology with pair-matching trunks is designed using Advanced Design System (ADS) software. These trunks are interfaced with power divider to achieve good bandwidth, fast switching and high efficiency. The power divider acts as a good isolator between the trunks and its straightforward design structure makes it a good choice for a single feed UWB antenna. The simulated results demonstrate that the maximum output voltage is 2.13 V with an input power of -5 dBm. Moreover, the rectifier offers maximum efficiency of 86% for the input power of -5 dBm at given band, which could easily power up wireless sensor networks (WSN) and other small devices sufficiently.

  2. Modelling a single phase voltage controlled rectifier using Laplace transforms

    Science.gov (United States)

    Kraft, L. Alan; Kankam, M. David

    1992-01-01

    The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

  3. Nonlinear behavior of three-terminal graphene junctions at room temperature

    International Nuclear Information System (INIS)

    Kim, Wonjae; Riikonen, Juha; Lipsanen, Harri; Pasanen, Pirjo

    2012-01-01

    We demonstrate nonlinear behavior in three-terminal T-branch graphene devices at room temperature. A rectified nonlinear output at the center branch is observed when the device is biased by a push–pull configuration. Nonlinearity is assumed to arise from a difference in charge transfer through the metal–graphene contact barrier between two contacts. The sign of the rectification can be altered by changing the carrier type using the back-gate voltage. (paper)

  4. Synaptic vesicle distribution by conveyor belt.

    Science.gov (United States)

    Moughamian, Armen J; Holzbaur, Erika L F

    2012-03-02

    The equal distribution of synaptic vesicles among synapses along the axon is critical for robust neurotransmission. Wong et al. show that the continuous circulation of synaptic vesicles throughout the axon driven by molecular motors ultimately yields this even distribution. Copyright © 2012 Elsevier Inc. All rights reserved.

  5. Spontaneous Vesicle Recycling in the Synaptic Bouton

    Directory of Open Access Journals (Sweden)

    Sven eTruckenbrodt

    2014-12-01

    Full Text Available The trigger for synaptic vesicle exocytosis is Ca2+, which enters the synaptic bouton following action potential stimulation. However, spontaneous release of neurotransmitter also occurs in the absence of stimulation in virtually all synaptic boutons. It has long been thought that this represents exocytosis driven by fluctuations in local Ca2+ levels. The vesicles responding to these fluctuations are thought to be the same ones that release upon stimulation, albeit potentially triggered by different Ca2+ sensors. This view has been challenged by several recent works, which have suggested that spontaneous release is driven by a separate pool of synaptic vesicles. Numerous articles appeared during the last few years in support of each of these hypotheses, and it has been challenging to bring them into accord. We speculate here on the origins of this controversy, and propose a solution that is related to developmental effects. Constitutive membrane traffic, needed for the biogenesis of vesicles and synapses, is responsible for high levels of spontaneous membrane fusion in young neurons, probably independent of Ca2+. The vesicles releasing spontaneously in such neurons are not related to other synaptic vesicle pools and may represent constitutively releasing vesicles (CRVs rather than bona fide synaptic vesicles. In mature neurons, constitutive traffic is much dampened, and the few remaining spontaneous release events probably represent bona fide spontaneously releasing synaptic vesicles (SRSVs responding to Ca2+ fluctuations, along with a handful of CRVs that participate in synaptic vesicle turnover.

  6. Active hippocampal networks undergo spontaneous synaptic modification.

    Directory of Open Access Journals (Sweden)

    Masako Tsukamoto-Yasui

    Full Text Available The brain is self-writable; as the brain voluntarily adapts itself to a changing environment, the neural circuitry rearranges its functional connectivity by referring to its own activity. How the internal activity modifies synaptic weights is largely unknown, however. Here we report that spontaneous activity causes complex reorganization of synaptic connectivity without any external (or artificial stimuli. Under physiologically relevant ionic conditions, CA3 pyramidal cells in hippocampal slices displayed spontaneous spikes with bistable slow oscillations of membrane potential, alternating between the so-called UP and DOWN states. The generation of slow oscillations did not require fast synaptic transmission, but their patterns were coordinated by local circuit activity. In the course of generating spontaneous activity, individual neurons acquired bidirectional long-lasting synaptic modification. The spontaneous synaptic plasticity depended on a rise in intracellular calcium concentrations of postsynaptic cells, but not on NMDA receptor activity. The direction and amount of the plasticity varied depending on slow oscillation patterns and synapse locations, and thus, they were diverse in a network. Once this global synaptic refinement occurred, the same neurons now displayed different patterns of spontaneous activity, which in turn exhibited different levels of synaptic plasticity. Thus, active networks continuously update their internal states through ongoing synaptic plasticity. With computational simulations, we suggest that with this slow oscillation-induced plasticity, a recurrent network converges on a more specific state, compared to that with spike timing-dependent plasticity alone.

  7. Synaptic plasticity in drug reward circuitry.

    Science.gov (United States)

    Winder, Danny G; Egli, Regula E; Schramm, Nicole L; Matthews, Robert T

    2002-11-01

    Drug addiction is a major public health issue worldwide. The persistence of drug craving coupled with the known recruitment of learning and memory centers in the brain has led investigators to hypothesize that the alterations in glutamatergic synaptic efficacy brought on by synaptic plasticity may play key roles in the addiction process. Here we review the present literature, examining the properties of synaptic plasticity within drug reward circuitry, and the effects that drugs of abuse have on these forms of plasticity. Interestingly, multiple forms of synaptic plasticity can be induced at glutamatergic synapses within the dorsal striatum, its ventral extension the nucleus accumbens, and the ventral tegmental area, and at least some of these forms of plasticity are regulated by behaviorally meaningful administration of cocaine and/or amphetamine. Thus, the present data suggest that regulation of synaptic plasticity in reward circuits is a tractable candidate mechanism underlying aspects of addiction.

  8. Synaptic Correlates of Low-Level Perception in V1.

    Science.gov (United States)

    Gerard-Mercier, Florian; Carelli, Pedro V; Pananceau, Marc; Troncoso, Xoana G; Frégnac, Yves

    2016-04-06

    The computational role of primary visual cortex (V1) in low-level perception remains largely debated. A dominant view assumes the prevalence of higher cortical areas and top-down processes in binding information across the visual field. Here, we investigated the role of long-distance intracortical connections in form and motion processing by measuring, with intracellular recordings, their synaptic impact on neurons in area 17 (V1) of the anesthetized cat. By systematically mapping synaptic responses to stimuli presented in the nonspiking surround of V1 receptive fields, we provide the first quantitative characterization of the lateral functional connectivity kernel of V1 neurons. Our results revealed at the population level two structural-functional biases in the synaptic integration and dynamic association properties of V1 neurons. First, subthreshold responses to oriented stimuli flashed in isolation in the nonspiking surround exhibited a geometric organization around the preferred orientation axis mirroring the psychophysical "association field" for collinear contour perception. Second, apparent motion stimuli, for which horizontal and feedforward synaptic inputs summed in-phase, evoked dominantly facilitatory nonlinear interactions, specifically during centripetal collinear activation along the preferred orientation axis, at saccadic-like speeds. This spatiotemporal integration property, which could constitute the neural correlate of a human perceptual bias in speed detection, suggests that local (orientation) and global (motion) information is already linked within V1. We propose the existence of a "dynamic association field" in V1 neurons, whose spatial extent and anisotropy are transiently updated and reshaped as a function of changes in the retinal flow statistics imposed during natural oculomotor exploration. The computational role of primary visual cortex in low-level perception remains debated. The expression of this "pop-out" perception is often assumed

  9. Neuromodulation, development and synaptic plasticity.

    Science.gov (United States)

    Foehring, R C; Lorenzon, N M

    1999-03-01

    We discuss parallels in the mechanisms underlying use-dependent synaptic plasticity during development and long-term potentiation (LTP) and long-term depression (LTD) in neocortical synapses. Neuromodulators, such as norepinephrine, serotonin, and acetylcholine have also been implicated in regulating both developmental plasticity and LTP/LTD. There are many potential levels of interaction between neuromodulators and plasticity. Ion channels are substrates for modulation in many cell types. We discuss examples of modulation of voltage-gated Ca2+ channels and Ca(2+)-dependent K+ channels and the consequences for neocortical pyramidal cell firing behaviour. At the time when developmental plasticity is most evident in rat cortex, the substrate for modulation is changing as the densities and relative proportions of various ion channels types are altered during ontogeny. We discuss examples of changes in K+ and Ca2+ channels and the consequence for modulation of neuronal activity.

  10. RF rectifiers for EM power harvesting in a Deep Brain Stimulating device.

    Science.gov (United States)

    Hosain, Md Kamal; Kouzani, Abbas Z; Tye, Susannah; Kaynak, Akif; Berk, Michael

    2015-03-01

    A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectifier, to harvest energy from electromagnetic fields for its operation. This paper presents optimization of radio frequency rectifier circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efficiency, and high output voltage rectifier. Four different rectifiers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadrupler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simulation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectifiers. The performance of the fabricated rectifiers is evaluated using a 915 MHz radio frequency (RF) energy source. The maximum measured conversion efficiency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectifiers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5-15 kΩ. The conversion efficiency of the rectifiers decreases significantly with the increase in the input power level. The Delon doubler rectifier provides the highest efficiency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectifier gives the lowest efficiency for the same inputs. By considering both efficiency and DC output voltage, the charge pump rectifier outperforms the other three rectifiers. Accordingly, the optimised 2-stage charge pumped rectifier is used together with an antenna to harvest energy in our DBS device.

  11. Synaptic transmission modulates while non-synaptic processes govern the transition from pre-ictal to seizure activity in vitro

    OpenAIRE

    Jefferys, John; Fox, John; Jiruska, Premysl; Kronberg, Greg; Miranda, Dolores; Ruiz-Nuño, Ana; Bikson, Marom

    2018-01-01

    It is well established that non-synaptic mechanisms can generate electrographic seizures after blockade of synaptic function. We investigated the interaction of intact synaptic activity with non-synaptic mechanisms in the isolated CA1 region of rat hippocampal slices using the 'elevated-K+' model of epilepsy. Elevated K+ ictal bursts share waveform features with other models of electrographic seizures, including non-synaptic models where chemical synaptic transmission is suppressed, such as t...

  12. Zero sequence blocking transformers for multi-pulse rectifier in aerospace applications

    DEFF Research Database (Denmark)

    Yao, Wenli; Blaabjerg, Frede; Zhang, Xiaobin

    2014-01-01

    The power electronics technology plays an even more important role in the aerospace applications of More Electric Aircrafts (MEA). AutoTransformer Rectifier Units (ATRU) have been widely adopted in aircrafts due to its simplicity and reliability. In this paper, Zero Sequence Blocking Transformers...... (ZSBT) are employed in the DC link to realize parallel rectifier bridges for ATRU, being the proposed 24-pulse rectifier. A star-connected autotransformer is used in this topology to divide the primary side voltage into four three-phase voltage groups, among which there is a phase shift of 15......°. The autotransformer then feeds the load through rectifier bridges, which are in parallel with ZSBTs. Compared to the traditional method that is using six interphase transformers to parallel the rectifier bridges; the proposed 24-pulse rectifier only requires four ZSBTs. This will contribute to a reduction of weight...

  13. Rectifying calibration error of Goldmann applanation tonometer is easy!

    Directory of Open Access Journals (Sweden)

    Nikhil S Choudhari

    2014-01-01

    Full Text Available Purpose: Goldmann applanation tonometer (GAT is the current Gold standard tonometer. However, its calibration error is common and can go unnoticed in clinics. Its company repair has limitations. The purpose of this report is to describe a self-taught technique of rectifying calibration error of GAT. Materials and Methods: Twenty-nine slit-lamp-mounted Haag-Streit Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Switzerland were included in this cross-sectional interventional pilot study. The technique of rectification of calibration error of the tonometer involved cleaning and lubrication of the instrument followed by alignment of weights when lubrication alone didn′t suffice. We followed the South East Asia Glaucoma Interest Group′s definition of calibration error tolerance (acceptable GAT calibration error within ±2, ±3 and ±4 mm Hg at the 0, 20 and 60-mm Hg testing levels, respectively. Results: Twelve out of 29 (41.3% GATs were out of calibration. The range of positive and negative calibration error at the clinically most important 20-mm Hg testing level was 0.5 to 20 mm Hg and -0.5 to -18 mm Hg, respectively. Cleaning and lubrication alone sufficed to rectify calibration error of 11 (91.6% faulty instruments. Only one (8.3% faulty GAT required alignment of the counter-weight. Conclusions: Rectification of calibration error of GAT is possible in-house. Cleaning and lubrication of GAT can be carried out even by eye care professionals and may suffice to rectify calibration error in the majority of faulty instruments. Such an exercise may drastically reduce the downtime of the Gold standard tonometer.

  14. Optical force rectifiers based on PT-symmetric metasurfaces

    Science.gov (United States)

    Alaee, Rasoul; Gurlek, Burak; Christensen, Johan; Kadic, Muamer

    2018-05-01

    We introduce here the concept of optical force rectifier based on parity-time symmetric metasurfaces. Directly linked to the properties of non-Hermitian systems engineered by balanced loss and gain constituents, we show that light can exert asymmetric pulling or pushing forces on metasurfaces depending on the direction of the impinging light. This generates a complete force rectification in the vicinity of the exceptional point. Our findings have the potential to spark the design of applications in optical manipulation where the forces, strictly speaking, act unidirectionally.

  15. Resonant Rectifier ICs for Piezoelectric Energy Harvesting Using Low-Voltage Drop Diode Equivalents.

    Science.gov (United States)

    Din, Amad Ud; Chandrathna, Seneke Chamith; Lee, Jong-Wook

    2017-04-19

    Herein, we present the design technique of a resonant rectifier for piezoelectric (PE) energy harvesting. We propose two diode equivalents to reduce the voltage drop in the rectifier operation, a minuscule-drop-diode equivalent (MDDE) and a low-drop-diode equivalent (LDDE). The diode equivalents are embedded in resonant rectifier integrated circuits (ICs), which use symmetric bias-flip to reduce the power used for charging and discharging the internal capacitance of a PE transducer. The self-startup function is supported by synchronously generating control pulses for the bias-flip from the PE transducer. Two resonant rectifier ICs, using both MDDE and LDDE, are fabricated in a 0.18 μm CMOS process and their performances are characterized under external and self-power conditions. Under the external-power condition, the rectifier using LDDE delivers an output power P OUT of 564 μW and a rectifier output voltage V RECT of 3.36 V with a power transfer efficiency of 68.1%. Under self-power conditions, the rectifier using MDDE delivers a P OUT of 288 μW and a V RECT of 2.4 V with a corresponding efficiency of 78.4%. Using the proposed bias-flip technique, the power extraction capability of the proposed rectifier is 5.9 and 3.0 times higher than that of a conventional full-bridge rectifier.

  16. Torsion angle dependence of the rectifying performance in molecular device with asymmetrical anchoring groups

    International Nuclear Information System (INIS)

    Wang, L.H.; Guo, Y.; Tian, C.F.; Song, X.P.; Ding, B.J.

    2010-01-01

    Using first-principles density functional theory and nonequilibrium Green's function formalism, we investigate the effect of torsion angle on the rectifying characteristics of 4'-thiolate-biphenyl-4-dithiocarboxylate sandwiched between two Au(111) electrodes. The results show that the torsion angle has an evident influence on rectifying performance of such devices. By increasing the dihedral angle between two phenyl rings, namely changing the magnitude of the intermolecular coupling effect, a different rectifying behavior can be observed in these systems. Our findings highlight that the rectifying characteristics are intimately related to dihedral angles and can provide fundamental guidelines for the design of functional molecular devices.

  17. Study of 18-Pulse Rectifier Utilizing Hexagon Connected 3-Phase to 9-Phase Transformer

    Directory of Open Access Journals (Sweden)

    Ahmad Saudi Samosir

    2008-04-01

    Full Text Available The 18-pulse converter, using Y or -connected differential autotransformer, is very interesting since it allows natural high power factor correction. The lowest input current harmonic components are the 17th and 19th. The Transformer is designed to feed three six-pulse bridge rectifiers displaced in phase by 200. This paper present a high power factor three-phase rectifier bases on 3-phase to 9-phase transformer and 18-pulse rectifier. The 9-phase polygon-connected transformer followed by 18-pulse diode rectifiers ensures the fundamental concept of natural power factor correction. Simulation results to verify the proposed concept are shown in this paper.

  18. Realistic-contact-induced enhancement of rectifying in carbon-nanotube/graphene-nanoribbon junctions

    International Nuclear Information System (INIS)

    Zhang, Xiang-Hua; Li, Xiao-Fei; Wang, Ling-Ling; Xu, Liang; Luo, Kai-Wu

    2014-01-01

    Carbon-nanotube/graphene-nanoribbon junctions were recently fabricated by the controllable etching of single-walled carbon-nanotubes [Wei et al., Nat. Commun. 4, 1374 (2013)] and their electronic transport properties were studied here. First principles results reveal that the transmission function of the junctions show a heavy dependence on the shape of contacts, but rectifying is an inherent property which is insensitive to the details of contacts. Interestingly, the rectifying ratio is largely enhanced in the junction with a realistic contact and the enhancement is insensitive to the details of contact structures. The stability of rectifying suggests a significant feasibility to manufacture realistic all-carbon rectifiers in nanoelectronics

  19. Resonant Rectifier ICs for Piezoelectric Energy Harvesting Using Low-Voltage Drop Diode Equivalents

    Science.gov (United States)

    Din, Amad Ud; Chandrathna, Seneke Chamith; Lee, Jong-Wook

    2017-01-01

    Herein, we present the design technique of a resonant rectifier for piezoelectric (PE) energy harvesting. We propose two diode equivalents to reduce the voltage drop in the rectifier operation, a minuscule-drop-diode equivalent (MDDE) and a low-drop-diode equivalent (LDDE). The diode equivalents are embedded in resonant rectifier integrated circuits (ICs), which use symmetric bias-flip to reduce the power used for charging and discharging the internal capacitance of a PE transducer. The self-startup function is supported by synchronously generating control pulses for the bias-flip from the PE transducer. Two resonant rectifier ICs, using both MDDE and LDDE, are fabricated in a 0.18 μm CMOS process and their performances are characterized under external and self-power conditions. Under the external-power condition, the rectifier using LDDE delivers an output power POUT of 564 μW and a rectifier output voltage VRECT of 3.36 V with a power transfer efficiency of 68.1%. Under self-power conditions, the rectifier using MDDE delivers a POUT of 288 μW and a VRECT of 2.4 V with a corresponding efficiency of 78.4%. Using the proposed bias-flip technique, the power extraction capability of the proposed rectifier is 5.9 and 3.0 times higher than that of a conventional full-bridge rectifier. PMID:28422085

  20. Analysis of an inverter-supplied multi-winding transformer with a full-wave rectifier at the output

    International Nuclear Information System (INIS)

    Klopcic, Beno; Dolinar, Drago; Stumberger, Gorazd

    2008-01-01

    This paper deals with the magnetic analysis of an inverter-supplied multi-winding transformer frequently used in resistance spot welding applications. The basic structure of the analyzed system consists of an inverter, a single-phase transformer with two secondary windings and a full-wave rectifier mounted at the output of the transformer, which assure a very short rise time of the welding current. The disturbing current spikes often appear in the transformer's primary in the steady-state operation, which can activate the over-current protection switch-off of the system. The results of numerical analysis performed on the nonlinear model of the discussed system have shown that very strong magnetic saturation of the transformer's iron core, caused by the interaction among the different ohmic resistances of secondary windings and different characteristics of the output rectifier diodes, provokes unwanted current spikes. Magnetic saturation could be efficiently eliminated using very simple passive method proposed in this paper. All findings are confirmed by systematic analysis numerically and experimentally

  1. Finite post synaptic potentials cause a fast neuronal response

    Directory of Open Access Journals (Sweden)

    Moritz eHelias

    2011-02-01

    Full Text Available A generic property of the communication between neurons is the exchange of pulsesat discrete time points, the action potentials. However, the prevalenttheory of spiking neuronal networks of integrate-and-fire model neuronsrelies on two assumptions: the superposition of many afferent synapticimpulses is approximated by Gaussian white noise, equivalent to avanishing magnitude of the synaptic impulses, and the transfer oftime varying signals by neurons is assessable by linearization. Goingbeyond both approximations, we find that in the presence of synapticimpulses the response to transient inputs differs qualitatively fromprevious predictions. It is instantaneous rather than exhibiting low-passcharacteristics, depends non-linearly on the amplitude of the impulse,is asymmetric for excitation and inhibition and is promoted by a characteristiclevel of synaptic background noise. These findings resolve contradictionsbetween the earlier theory and experimental observations. Here wereview the recent theoretical progress that enabled these insights.We explain why the membrane potential near threshold is sensitiveto properties of the afferent noise and show how this shapes the neuralresponse. A further extension of the theory to time evolution in discretesteps quantifies simulation artifacts and yields improved methodsto cross check results.

  2. Absence of synaptic regulation by phosducin in retinal slices.

    Directory of Open Access Journals (Sweden)

    James H Long

    Full Text Available Phosducin is an abundant photoreceptor protein that binds G-protein βγ subunits and plays a role in modulating synaptic transmission at photoreceptor synapses under both dark-adapted and light-adapted conditions in vivo. To examine the role of phosducin at the rod-to-rod bipolar cell (RBC synapse, we used whole-cell voltage clamp recordings to measure the light-evoked currents from both wild-type (WT and phosducin knockout (Pd(-/- RBCs, in dark- and light-adapted retinal slices. Pd(-/- RBCs showed smaller dim flash responses and steeper intensity-response relationships than WT RBCs, consistent with the smaller rod responses being selectively filtered out by the non-linear threshold at the rod-to-rod bipolar synapse. In addition, Pd(-/- RBCs showed a marked delay in the onset of the light-evoked currents, similar to that of a WT response to an effectively dimmer flash. Comparison of the changes in flash sensitivity in the presence of steady adapting light revealed that Pd(-/- RBCs desensitized less than WT RBCs to the same intensity. These results are quantitatively consistent with the smaller single photon responses of Pd(-/- rods, owing to the known reduction in rod G-protein expression levels in this line. The absence of an additional synaptic phenotype in these experiments suggests that the function of phosducin at the photoreceptor synapse is abolished by the conditions of retinal slice recordings.

  3. Molecular mechanisms of synaptic remodeling in alcoholism.

    Science.gov (United States)

    Kyzar, Evan J; Pandey, Subhash C

    2015-08-05

    Alcohol use and alcohol addiction represent dysfunctional brain circuits resulting from neuroadaptive changes during protracted alcohol exposure and its withdrawal. Alcohol exerts a potent effect on synaptic plasticity and dendritic spine formation in specific brain regions, providing a neuroanatomical substrate for the pathophysiology of alcoholism. Epigenetics has recently emerged as a critical regulator of gene expression and synaptic plasticity-related events in the brain. Alcohol exposure and withdrawal induce changes in crucial epigenetic processes in the emotional brain circuitry (amygdala) that may be relevant to the negative affective state defined as the "dark side" of addiction. Here, we review the literature concerning synaptic plasticity and epigenetics, with a particular focus on molecular events related to dendritic remodeling during alcohol abuse and alcoholism. Targeting epigenetic processes that modulate synaptic plasticity may yield novel treatments for alcoholism. Published by Elsevier Ireland Ltd.

  4. Nonlinear optics

    International Nuclear Information System (INIS)

    Boyd, R.W.

    1992-01-01

    Nonlinear optics is the study of the interaction of intense laser light with matter. This book is a textbook on nonlinear optics at the level of a beginning graduate student. The intent of the book is to provide an introduction to the field of nonlinear optics that stresses fundamental concepts and that enables the student to go on to perform independent research in this field. This book covers the areas of nonlinear optics, quantum optics, quantum electronics, laser physics, electrooptics, and modern optics

  5. Lateral regulation of synaptic transmission by astrocytes.

    Science.gov (United States)

    Covelo, A; Araque, A

    2016-05-26

    Fifteen years ago the concept of the "tripartite synapse" was proposed to conceptualize the functional view that astrocytes are integral elements of synapses. The signaling exchange between astrocytes and neurons within the tripartite synapse results in the synaptic regulation of synaptic transmission and plasticity through an autocrine form of communication. However, recent evidence indicates that the astrocyte synaptic regulation is not restricted to the active tripartite synapse but can be manifested through astrocyte signaling at synapses relatively distant from active synapses, a process termed lateral astrocyte synaptic regulation. This phenomenon resembles the classical heterosynaptic modulation but is mechanistically different because it involves astrocytes and its properties critically depend on the morphological and functional features of astrocytes. Therefore, the functional concept of the tripartite synapse as a fundamental unit must be expanded to include the interaction between tripartite synapses. Through lateral synaptic regulation, astrocytes serve as an active processing bridge for synaptic interaction and crosstalk between synapses with no direct neuronal connectivity, supporting the idea that neural network function results from the coordinated activity of astrocytes and neurons. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarty, Soubhik; Wasey, A. H. M. Abdul; Das, G. P., E-mail: msgpd@iacs.res.in, E-mail: ranjit.t@res.srmuniv.ac.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032 (India); Thapa, Ranjit, E-mail: msgpd@iacs.res.in, E-mail: ranjit.t@res.srmuniv.ac.in [SRM Research Institute, SRM University, Kattankulathur - 603203, Tamil Nadu (India)

    2015-08-15

    We have studied using density functional theory and non-equilibrium Green’s function based approach, the electronic structures of 555-777 divacancy (DV) defected armchair edged graphene nanoribbons (AGNR) as well as the transport properties of AGNR based two-terminal devices constructed with one defected electrode and one N doped electrode. Introduction of 555-777 DV defect into AGNR results in shifting of the π and π∗ bands towards the higher energy value indicating a downward shift of the Fermi level. Formation of a potential barrier, analogous to that of conventional p-n junction, has been observed across the junction of defected and N-doped AGNR. The two terminal devices show diode like property with high rectifying efficiency for a wide range of bias voltages. The devices also show robust negative differential resistance with very high peak-to-valley ratio. Shift of the electrode energy states and modification of the transmission function with applied bias have been analyzed, in order to gain an insight into the nonlinear and asymmetric behavior of the current-voltage characteristics. Variation of the transport properties on the width of the ribbons has also been discussed.

  7. First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device

    Directory of Open Access Journals (Sweden)

    Soubhik Chakrabarty

    2015-08-01

    Full Text Available We have studied using density functional theory and non-equilibrium Green’s function based approach, the electronic structures of 555-777 divacancy (DV defected armchair edged graphene nanoribbons (AGNR as well as the transport properties of AGNR based two-terminal devices constructed with one defected electrode and one N doped electrode. Introduction of 555-777 DV defect into AGNR results in shifting of the π and π∗ bands towards the higher energy value indicating a downward shift of the Fermi level. Formation of a potential barrier, analogous to that of conventional p-n junction, has been observed across the junction of defected and N-doped AGNR. The two terminal devices show diode like property with high rectifying efficiency for a wide range of bias voltages. The devices also show robust negative differential resistance with very high peak-to-valley ratio. Shift of the electrode energy states and modification of the transmission function with applied bias have been analyzed, in order to gain an insight into the nonlinear and asymmetric behavior of the current-voltage characteristics. Variation of the transport properties on the width of the ribbons has also been discussed.

  8. Energy-harvesting shock absorber with a mechanical motion rectifier

    Science.gov (United States)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-02-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges.

  9. Energy-harvesting shock absorber with a mechanical motion rectifier

    International Nuclear Information System (INIS)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-01-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges. (paper)

  10. Boosting the signal: Endothelial inward rectifier K+ channels.

    Science.gov (United States)

    Jackson, William F

    2017-04-01

    Endothelial cells express a diverse array of ion channels including members of the strong inward rectifier family composed of K IR 2 subunits. These two-membrane spanning domain channels are modulated by their lipid environment, and exist in macromolecular signaling complexes with receptors, protein kinases and other ion channels. Inward rectifier K + channel (K IR ) currents display a region of negative slope conductance at membrane potentials positive to the K + equilibrium potential that allows outward current through the channels to be activated by membrane hyperpolarization, permitting K IR to amplify hyperpolarization induced by other K + channels and ion transporters. Increases in extracellular K + concentration activate K IR allowing them to sense extracellular K + concentration and transduce this change into membrane hyperpolarization. These properties position K IR to participate in the mechanism of action of hyperpolarizing vasodilators and contribute to cell-cell conduction of hyperpolarization along the wall of microvessels. The expression of K IR in capillaries in electrically active tissues may allow K IR to sense extracellular K + , contributing to functional hyperemia. Understanding the regulation of expression and function of microvascular endothelial K IR will improve our understanding of the control of blood flow in the microcirculation in health and disease and may provide new targets for the development of therapeutics in the future. © 2016 John Wiley & Sons Ltd.

  11. Inward rectifier potassium currents in mammalian skeletal muscle fibres

    Science.gov (United States)

    DiFranco, Marino; Yu, Carl; Quiñonez, Marbella; Vergara, Julio L

    2015-01-01

    Inward rectifying potassium (Kir) channels play a central role in maintaining the resting membrane potential of skeletal muscle fibres. Nevertheless their role has been poorly studied in mammalian muscles. Immunohistochemical and transgenic expression were used to assess the molecular identity and subcellular localization of Kir channel isoforms. We found that Kir2.1 and Kir2.2 channels were targeted to both the surface andthe transverse tubular system membrane (TTS) compartments and that both isoforms can be overexpressed up to 3-fold 2 weeks after transfection. Inward rectifying currents (IKir) had the canonical features of quasi-instantaneous activation, strong inward rectification, depended on the external [K+], and could be blocked by Ba2+ or Rb+. In addition, IKir records show notable decays during large 100 ms hyperpolarizing pulses. Most of these properties were recapitulated by model simulations of the electrical properties of the muscle fibre as long as Kir channels were assumed to be present in the TTS. The model also simultaneously predicted the characteristics of membrane potential changes of the TTS, as reported optically by a fluorescent potentiometric dye. The activation of IKir by large hyperpolarizations resulted in significant attenuation of the optical signals with respect to the expectation for equal magnitude depolarizations; blocking IKir with Ba2+ (or Rb+) eliminated this attenuation. The experimental data, including the kinetic properties of IKir and TTS voltage records, and the voltage dependence of peak IKir, while measured at widely dissimilar bulk [K+] (96 and 24 mm), were closely predicted by assuming Kir permeability (PKir) values of ∼5.5 × 10−6 cm s−1 and equal distribution of Kir channels at the surface and TTS membranes. The decay of IKir records and the simultaneous increase in TTS voltage changes were mostly explained by K+ depletion from the TTS lumen. Most importantly, aside from allowing an accurate estimation of

  12. Nonlinear optics

    CERN Document Server

    Bloembergen, Nicolaas

    1996-01-01

    Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe

  13. Mechanism underlying selective regulation of G protein-gated inwardly rectifying potassium channels by the psychostimulant-sensitive sorting nexin 27

    Science.gov (United States)

    Balana, Bartosz; Maslennikov, Innokentiy; Kwiatkowski, Witek; Stern, Kalyn M.; Bahima, Laia; Choe, Senyon; Slesinger, Paul A.

    2011-01-01

    G protein-gated inwardly rectifying potassium (GIRK) channels are important gatekeepers of neuronal excitability. The surface expression of neuronal GIRK channels is regulated by the psychostimulant-sensitive sorting nexin 27 (SNX27) protein through a class I (-X-Ser/Thr-X-Φ, where X is any residue and Φ is a hydrophobic amino acid) PDZ-binding interaction. The G protein-insensitive inward rectifier channel (IRK1) contains the same class I PDZ-binding motif but associates with a different synaptic PDZ protein, postsynaptic density protein 95 (PSD95). The mechanism by which SNX27 and PSD95 discriminate these channels was previously unclear. Using high-resolution structures coupled with biochemical and functional analyses, we identified key amino acids upstream of the channel's canonical PDZ-binding motif that associate electrostatically with a unique structural pocket in the SNX27-PDZ domain. Changing specific charged residues in the channel's carboxyl terminus or in the PDZ domain converts the selective association and functional regulation by SNX27. Elucidation of this unique interaction site between ion channels and PDZ-containing proteins could provide a therapeutic target for treating brain diseases. PMID:21422294

  14. A nonlinear model for AC induced corrosion

    Directory of Open Access Journals (Sweden)

    N. Ida

    2012-09-01

    Full Text Available The modeling of corrosion poses particular difficulties. The understanding of corrosion as an electrochemical process has led to simple capacitive-resistive models that take into account the resistance of the electrolytic cell and the capacitive effect of the surface potential at the interface between conductors and the electrolyte. In some models nonlinear conduction effects have been added to account for more complex observed behavior. While these models are sufficient to describe the behavior in systems with cathodic protection, the behavior in the presence of induced AC currents from power lines and from RF sources cannot be accounted for and are insufficient to describe the effects observed in the field. Field observations have shown that a rectifying effect exists that affects the cathodic protection potential and this effect is responsible for corrosion in the presence of AC currents. The rectifying effects of the metal-corrosion interface are totally missing from current models. This work proposes a nonlinear model based on finite element analysis that takes into account the nonlinear behavior of the metal-oxide interface and promises to improve modeling by including the rectification effects at the interface.

  15. A Voltage Modulated DPC Approach for Three-Phase PWM Rectifier

    DEFF Research Database (Denmark)

    Gui, Yonghao; Li, Mingshen; Lu, Jinghang

    2018-01-01

    In this paper, a voltage modulated direct power control for three-phase pulse-width modulated rectifier is proposed. With the suggested method, the differential equations describing the rectifier dynamics are changing from a linear time-varying system into a linear time-invariant one. In this way...

  16. Three Phase Six-Switch PWM Buck Rectifier with Power Factor Improvement

    DEFF Research Database (Denmark)

    Zafar Ullah Khan, M; Mohsin Naveed, M.; Hussain, Dil Muhammad Akbar

    2013-01-01

    Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, Three Phase Six-Switch PWM Buck Rectifier[1] is presented which operates at nearly unity power factor and provides...

  17. A low cost rapid prototype platform for a three phase PFC rectifier application

    DEFF Research Database (Denmark)

    Haase, Frerk; Kouchaki, Alireza; Nymand, Morten

    2015-01-01

    In this paper the design and development of a low cost rapid prototype platform for a Three Phase PFC rectifier application is presented. The active rectifier consists of a SiC-MOSFET based PWM converter and a low cost rapid prototype platform for simulating and implementing the digital control...

  18. A high-power magnetically switched superconducting rectifier operating at 5 Hz

    NARCIS (Netherlands)

    Mulder, G.B.J.; Krooshoop, Hendrikus J.G.; Nijhuis, Arend; ten Kate, Herman H.J.; van de Klundert, L.J.M.

    1987-01-01

    Above a certain current level, the use of a superconducting rectifier as a cryogenic current source offers advantages compared to the use of a power supply at room temperature which requires large current feed-throughs into the cryostat. In some cases, the power of such a rectifier is immaterial,

  19. G-protein-coupled inward rectifier potassium current contributes to ventricular repolarization

    DEFF Research Database (Denmark)

    Liang, Bo; Nissen, Jakob D; Laursen, Morten

    2014-01-01

    The purpose of this study was to investigate the functional role of G-protein-coupled inward rectifier potassium (GIRK) channels in the cardiac ventricle.......The purpose of this study was to investigate the functional role of G-protein-coupled inward rectifier potassium (GIRK) channels in the cardiac ventricle....

  20. A Novel Current-Mode Full-Wave Rectifier Based on One CDTA and Two Diodes

    Directory of Open Access Journals (Sweden)

    F. Khateb

    2010-09-01

    Full Text Available Precision rectifiers are important building blocks for analog signal processing. The traditional approach based on diodes and operational amplifiers (OpAmps exhibits undesirable effects caused by limited OpAmp slew rate and diode commutations. In the paper, a full-wave rectifier based on one CDTA and two Schottky diodes is presented. The PSpice simulation results are included.

  1. Self-Biased Differential Rectifier with Enhanced Dynamic Range for Wireless Powering

    KAUST Repository

    Ouda, Mahmoud H.

    2016-08-29

    A self-biased, cross-coupled, differential rectifier is proposed with enhanced power-conversion efficiency over an extended range of input power. A prototype is designed for UHF 433MHz RF power-harvesting applications and is implemented using 0.18μm CMOS technology. The proposed rectifier architecture is compared to the conventional cross-coupled rectifier. It demonstrates an improvement of more than 40% in the rectifier power conversion efficiency (PCE) and an input power range extension of more than 50% relative to the conventional crosscoupled rectifier. A sensitivity of -15.2dBm (30μW) input power for 1V output voltage and a peak power-conversion efficiency of 65% are achieved for a 50kω load. © 2004-2012 IEEE.

  2. A passive UHF RFID tag with a dynamic-Vth-cancellation rectifier

    International Nuclear Information System (INIS)

    Shen Jinpeng; Wang Bo; Liu Shan; Wang Xin'an; Ruan Zhengkun; Li Shoucheng

    2013-01-01

    This paper presents a passive UHF RFID tag with a dynamic-V th -cancellation (DVC) rectifier. In the rectifier, the threshold voltages of MOSFETs are cancelled by applying gate bias voltages, which are dynamically changed according to the states of the MOSFETs. The DVC rectifier enables both low ON-resistance and small reverse leakage of the MOSFETs, resulting in high power conversion efficiency (PCE). An area-efficient demodulator with a novel average detector is also designed, which takes advantage of the rectifier's first stage as the envelope detector. The whole tag chip is implemented in a 0.18 μm CMOS process with a die size of 880 × 950 μm 2 . Measurement results show that the rectifier achieves a maximum PCE of 53.7% with 80 kΩ resistor load. (semiconductor integrated circuits)

  3. Diacylglycerol kinases in the coordination of synaptic plasticity

    Directory of Open Access Journals (Sweden)

    Dongwon Lee

    2016-08-01

    Full Text Available Synaptic plasticity is activity-dependent modification of the efficacy of synaptic transmission. Although detailed mechanisms underlying synaptic plasticity are diverse and vary at different types of synapses, diacylglycerol (DAG-associated signaling has been considered as an important regulator of many forms of synaptic plasticity, including long-term potentiation (LTP and long-term depression (LTD. Recent evidence indicate that DAG kinases (DGKs, which phosphorylate DAG to phosphatidic acid to terminate DAG signaling, are important regulators of LTP and LTD, as supported by the results from mice lacking specific DGK isoforms. This review will summarize these studies and discuss how specific DGK isoforms distinctly regulate different forms of synaptic plasticity at pre- and postsynaptic sites. In addition, we propose a general role of DGKs as coordinators of synaptic plasticity that make local synaptic environments more permissive for synaptic plasticity by regulating DAG concentration and interacting with other synaptic proteins.

  4. Metabolic Turnover of Synaptic Proteins: Kinetics, Interdependencies and Implications for Synaptic Maintenance

    Science.gov (United States)

    Cohen, Laurie D.; Zuchman, Rina; Sorokina, Oksana; Müller, Anke; Dieterich, Daniela C.; Armstrong, J. Douglas; Ziv, Tamar; Ziv, Noam E.

    2013-01-01

    Chemical synapses contain multitudes of proteins, which in common with all proteins, have finite lifetimes and therefore need to be continuously replaced. Given the huge numbers of synaptic connections typical neurons form, the demand to maintain the protein contents of these connections might be expected to place considerable metabolic demands on each neuron. Moreover, synaptic proteostasis might differ according to distance from global protein synthesis sites, the availability of distributed protein synthesis facilities, trafficking rates and synaptic protein dynamics. To date, the turnover kinetics of synaptic proteins have not been studied or analyzed systematically, and thus metabolic demands or the aforementioned relationships remain largely unknown. In the current study we used dynamic Stable Isotope Labeling with Amino acids in Cell culture (SILAC), mass spectrometry (MS), Fluorescent Non–Canonical Amino acid Tagging (FUNCAT), quantitative immunohistochemistry and bioinformatics to systematically measure the metabolic half-lives of hundreds of synaptic proteins, examine how these depend on their pre/postsynaptic affiliation or their association with particular molecular complexes, and assess the metabolic load of synaptic proteostasis. We found that nearly all synaptic proteins identified here exhibited half-lifetimes in the range of 2–5 days. Unexpectedly, metabolic turnover rates were not significantly different for presynaptic and postsynaptic proteins, or for proteins for which mRNAs are consistently found in dendrites. Some functionally or structurally related proteins exhibited very similar turnover rates, indicating that their biogenesis and degradation might be coupled, a possibility further supported by bioinformatics-based analyses. The relatively low turnover rates measured here (∼0.7% of synaptic protein content per hour) are in good agreement with imaging-based studies of synaptic protein trafficking, yet indicate that the metabolic load

  5. Slope stability of rectify coal waste embankments on mining areas

    International Nuclear Information System (INIS)

    Klossek, C.

    1999-01-01

    The paper is of a theoretical and experimental character, focusing on the results of field tests on the load-bearing capacity and stability of high (> 20m.) transportation embankments rectified with coal waste. The embankments are located in industrial areas subjected to the intense impact of underground mining. Such phenomena are also accompanied by essential changes in the water conditions of the subsoil. The results of model tests by SIR geo-radar used to non-damaging estimation of the suffusion occurring in the embankment constructed on non-waste materials are discussed. The numerical assessment of the filtration process has been based on the MFE and MBE programs, which are extended calculation procedures enabling the overall estimation of the redistribution of all the stress-strain components in the structure, in consideration of any hypothesis of the boundary state

  6. The harmonic composition of the output voltage of a rectifier unit with a PWM voltage booster converter.

    OpenAIRE

    ПАНЧЕНКО, В В

    2015-01-01

    The author investigates a rectifier unit constructed on the basis of cascade connection of the main non-controlled m-pulse rectifier and PWM voltage booster converter. The research presents the analysis of the harmonic composition of the output voltage of a rectifier unit with a PWM voltage booster converter on completely controlled keys. The dependence of the relative harmonic amplitude on the commutation corner is defined. The estimation of a rectifier unit electromagnetic compatibility wit...

  7. Creation of anticorrosion coatings for contact devices of rectifying columns

    Directory of Open Access Journals (Sweden)

    KATAMANOV Vladimir Leonidovich

    2018-02-01

    Full Text Available Today the main corrosion protection methods applied in contact devices of rectifying oil processing equipment, in particular, in mesh nozzles made of stainless steel, under relatively high temperatures (150–250оC and in the presence of aggressive components in oil raw materials (hydrogen sulfide, sulfides, mercaptans, other sulphurous compounds, chloride ions, organochlorine connections, water are to use special alloys as protecting covers as well as corrosion inhibitors that reduce corrosion action of hostile environment. At the same time, the disadvantages of the majority of these methods concern high operational costs, insufficient efficiency or protection ability designed only for a certain factor, but not for combination of them. In this regard corrosion resistance of mesh contact devices made of stainless steel (brand SUS 321 has been studied on three types of samples: alloy wire, welded grid, thin leaf. Titanium nitride (TiN and metallic coatings from nickel (Ni, titanium (Ti and chrome (Cr were used as anticorrosion coatings for the mentioned samples. These coverings were applied on samples in two ways: by means of electrolytic method and vacuum ion-plasma dusting. It was determined that optimal coating thickness is 10–15 microns as it is the thickness at which the produced films possess sufficient plasticity and do not exfoliate from the surface of the corresponding corrosion-proof alloy. The research of corrosion of samples of stainless steel SUS 321 with applied coverings and without them was performed by immersing the samples into compositions that contain oil as well as into the modeling hostile oil-containing environment. As a result of the conducted researches it was determined that the protecting covers of chrome and titanium nitride applied with vacuum ion-plasma dusting method are the most effective coatings from the point of view of anticorrosive protection for mesh contact devices of stainless steel used in rectifying

  8. Nonlinear Science

    CERN Document Server

    Yoshida, Zensho

    2010-01-01

    This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl

  9. Nonlinear oscillations

    CERN Document Server

    Nayfeh, Ali Hasan

    1995-01-01

    Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

  10. Predicting seizure by modeling synaptic plasticity based on EEG signals - a case study of inherited epilepsy

    Science.gov (United States)

    Zhang, Honghui; Su, Jianzhong; Wang, Qingyun; Liu, Yueming; Good, Levi; Pascual, Juan M.

    2018-03-01

    This paper explores the internal dynamical mechanisms of epileptic seizures through quantitative modeling based on full brain electroencephalogram (EEG) signals. Our goal is to provide seizure prediction and facilitate treatment for epileptic patients. Motivated by an earlier mathematical model with incorporated synaptic plasticity, we studied the nonlinear dynamics of inherited seizures through a differential equation model. First, driven by a set of clinical inherited electroencephalogram data recorded from a patient with diagnosed Glucose Transporter Deficiency, we developed a dynamic seizure model on a system of ordinary differential equations. The model was reduced in complexity after considering and removing redundancy of each EEG channel. Then we verified that the proposed model produces qualitatively relevant behavior which matches the basic experimental observations of inherited seizure, including synchronization index and frequency. Meanwhile, the rationality of the connectivity structure hypothesis in the modeling process was verified. Further, through varying the threshold condition and excitation strength of synaptic plasticity, we elucidated the effect of synaptic plasticity to our seizure model. Results suggest that synaptic plasticity has great effect on the duration of seizure activities, which support the plausibility of therapeutic interventions for seizure control.

  11. A 50–60 GHz mm-wave rectifier with bulk voltage bias in 65-nm CMOS

    NARCIS (Netherlands)

    Gao, H.; Matters-Kammerer, M.; Harpe, P.; Baltus, P.

    2016-01-01

    This letter presents a 50∼60 GHz fully integrated 3-stage rectifier with bulk voltage bias for threshold voltage modulation in a 65-nm CMOS technology, which can be integrated in a mm-wave hybrid rectifier structure as the main rectifier. In this letter, the new technique of bulk voltage bias is

  12. 75 FR 24747 - SCI, LLC/Zener-Rectifier Operations Division A Wholly Owned Subsidiary of SCI, LLC/ON...

    Science.gov (United States)

    2010-05-05

    ... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-70,235] SCI, LLC/Zener-Rectifier... Adjustment Assistance on October 19, 2009, applicable to workers of SCI LLC/Zener-Rectifier, Operations... Technical Resources were employed on-site at the Phoenix Arizona location of SCI LLC/Zener-Rectifier...

  13. Synaptic Correlates of Working Memory Capacity.

    Science.gov (United States)

    Mi, Yuanyuan; Katkov, Mikhail; Tsodyks, Misha

    2017-01-18

    Psychological studies indicate that human ability to keep information in readily accessible working memory is limited to four items for most people. This extremely low capacity severely limits execution of many cognitive tasks, but its neuronal underpinnings remain unclear. Here we show that in the framework of synaptic theory of working memory, capacity can be analytically estimated to scale with characteristic time of short-term synaptic depression relative to synaptic current time constant. The number of items in working memory can be regulated by external excitation, enabling the system to be tuned to the desired load and to clear the working memory of currently held items to make room for new ones. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. The Corticohippocampal Circuit, Synaptic Plasticity, and Memory

    Science.gov (United States)

    Basu, Jayeeta; Siegelbaum, Steven A.

    2015-01-01

    Synaptic plasticity serves as a cellular substrate for information storage in the central nervous system. The entorhinal cortex (EC) and hippocampus are interconnected brain areas supporting basic cognitive functions important for the formation and retrieval of declarative memories. Here, we discuss how information flow in the EC–hippocampal loop is organized through circuit design. We highlight recently identified corticohippocampal and intrahippocampal connections and how these long-range and local microcircuits contribute to learning. This review also describes various forms of activity-dependent mechanisms that change the strength of corticohippocampal synaptic transmission. A key point to emerge from these studies is that patterned activity and interaction of coincident inputs gives rise to associational plasticity and long-term regulation of information flow. Finally, we offer insights about how learning-related synaptic plasticity within the corticohippocampal circuit during sensory experiences may enable adaptive behaviors for encoding spatial, episodic, social, and contextual memories. PMID:26525152

  15. Electric Dipole Theory of Chemical Synaptic Transmission

    Science.gov (United States)

    Wei, Ling Y.

    1968-01-01

    In this paper we propose that chemicals such as acetylcholine are electric dipoles which when oriented and arranged in a large array could produce an electric field strong enough to drive positive ions over the junction barrier of the post-synaptic membrane and thus initiate excitation or produce depolarization. This theory is able to explain a great number of facts such as cleft size, synaptic delay, nonregeneration, subthreshold integration, facilitation with repetition, and the calcium and magnesium effects. It also shows why and how acetylcholine could act as excitatory or inhibitory transmitters under different circumstances. Our conclusion is that the nature of synaptic transmission is essentially electrical, be it mediated by electrical or chemical transmitters. PMID:4296121

  16. Astroglial Metabolic Networks Sustain Hippocampal Synaptic Transmission

    Science.gov (United States)

    Rouach, Nathalie; Koulakoff, Annette; Abudara, Veronica; Willecke, Klaus; Giaume, Christian

    2008-12-01

    Astrocytes provide metabolic substrates to neurons in an activity-dependent manner. However, the molecular mechanisms involved in this function, as well as its role in synaptic transmission, remain unclear. Here, we show that the gap-junction subunit proteins connexin 43 and 30 allow intercellular trafficking of glucose and its metabolites through astroglial networks. This trafficking is regulated by glutamatergic synaptic activity mediated by AMPA receptors. In the absence of extracellular glucose, the delivery of glucose or lactate to astrocytes sustains glutamatergic synaptic transmission and epileptiform activity only when they are connected by gap junctions. These results indicate that astroglial gap junctions provide an activity-dependent intercellular pathway for the delivery of energetic metabolites from blood vessels to distal neurons.

  17. Astroglial metabolic networks sustain hippocampal synaptic transmission.

    Science.gov (United States)

    Rouach, Nathalie; Koulakoff, Annette; Abudara, Veronica; Willecke, Klaus; Giaume, Christian

    2008-12-05

    Astrocytes provide metabolic substrates to neurons in an activity-dependent manner. However, the molecular mechanisms involved in this function, as well as its role in synaptic transmission, remain unclear. Here, we show that the gap-junction subunit proteins connexin 43 and 30 allow intercellular trafficking of glucose and its metabolites through astroglial networks. This trafficking is regulated by glutamatergic synaptic activity mediated by AMPA receptors. In the absence of extracellular glucose, the delivery of glucose or lactate to astrocytes sustains glutamatergic synaptic transmission and epileptiform activity only when they are connected by gap junctions. These results indicate that astroglial gap junctions provide an activity-dependent intercellular pathway for the delivery of energetic metabolites from blood vessels to distal neurons.

  18. Synaptic Vesicle Endocytosis in Different Model Systems

    Directory of Open Access Journals (Sweden)

    Quan Gan

    2018-06-01

    Full Text Available Neurotransmission in complex animals depends on a choir of functionally distinct synapses releasing neurotransmitters in a highly coordinated manner. During synaptic signaling, vesicles fuse with the plasma membrane to release their contents. The rate of vesicle fusion is high and can exceed the rate at which synaptic vesicles can be re-supplied by distant sources. Thus, local compensatory endocytosis is needed to replenish the synaptic vesicle pools. Over the last four decades, various experimental methods and model systems have been used to study the cellular and molecular mechanisms underlying synaptic vesicle cycle. Clathrin-mediated endocytosis is thought to be the predominant mechanism for synaptic vesicle recycling. However, recent studies suggest significant contribution from other modes of endocytosis, including fast compensatory endocytosis, activity-dependent bulk endocytosis, ultrafast endocytosis, as well as kiss-and-run. Currently, it is not clear whether a universal model of vesicle recycling exist for all types of synapses. It is possible that each synapse type employs a particular mode of endocytosis. Alternatively, multiple modes of endocytosis operate at the same synapse, and the synapse toggles between different modes depending on its activity level. Here we compile review and research articles based on well-characterized model systems: frog neuromuscular junctions, C. elegans neuromuscular junctions, Drosophila neuromuscular junctions, lamprey reticulospinal giant axons, goldfish retinal ribbon synapses, the calyx of Held, and rodent hippocampal synapses. We will compare these systems in terms of their known modes and kinetics of synaptic vesicle endocytosis, as well as the underlying molecular machineries. We will also provide the future development of this field.

  19. Nonlinear systems

    CERN Document Server

    Palmero, Faustino; Lemos, M; Sánchez-Rey, Bernardo; Casado-Pascual, Jesús

    2018-01-01

    This book presents an overview of the most recent advances in nonlinear science. It provides a unified view of nonlinear properties in many different systems and highlights many  new developments. While volume 1 concentrates on mathematical theory and computational techniques and challenges, which are essential for the study of nonlinear science, this second volume deals with nonlinear excitations in several fields. These excitations can be localized and transport energy and matter in the form of breathers, solitons, kinks or quodons with very different characteristics, which are discussed in the book. They can also transport electric charge, in which case they are known as polarobreathers or solectrons. Nonlinear excitations can influence function and structure in biology, as for example, protein folding. In crystals and other condensed matter, they can modify transport properties, reaction kinetics and interact with defects. There are also engineering applications in electric lattices, Josephson junction a...

  20. Dendritic nonlinearities are tuned for efficient spike-based computations in cortical circuits.

    Science.gov (United States)

    Ujfalussy, Balázs B; Makara, Judit K; Branco, Tiago; Lengyel, Máté

    2015-12-24

    Cortical neurons integrate thousands of synaptic inputs in their dendrites in highly nonlinear ways. It is unknown how these dendritic nonlinearities in individual cells contribute to computations at the level of neural circuits. Here, we show that dendritic nonlinearities are critical for the efficient integration of synaptic inputs in circuits performing analog computations with spiking neurons. We developed a theory that formalizes how a neuron's dendritic nonlinearity that is optimal for integrating synaptic inputs depends on the statistics of its presynaptic activity patterns. Based on their in vivo preynaptic population statistics (firing rates, membrane potential fluctuations, and correlations due to ensemble dynamics), our theory accurately predicted the responses of two different types of cortical pyramidal cells to patterned stimulation by two-photon glutamate uncaging. These results reveal a new computational principle underlying dendritic integration in cortical neurons by suggesting a functional link between cellular and systems--level properties of cortical circuits.

  1. 3-D printed 2.4 GHz rectifying antenna for wireless power transfer applications

    Science.gov (United States)

    Skinner, Matthew

    In this work, a 3D printed rectifying antenna that operates at the 2.4GHz WiFi band was designed and manufactured. The printed material did not have the same properties of bulk material, so the printed materials needed to be characterized. The antenna and rectifying circuit was printed out of Acrylonitrile Butadiene Styrene (ABS) filament and a conductive silver paste, with electrical components integrated into the circuit. Before printing the full rectifying antenna, each component was printed and evaluated. The printed antenna operated at the desired frequency with a return loss of -16 dBm with a bandwidth of 70MHz. The radiation pattern was measured in an anechoic chamber with good matching to the model. The rectifying circuit was designed in Ansys Circuit Simulation using Schottky diodes to enable the circuit to operate at lower input power levels. Two rectifying circuits were manufactured, one by printing the conductive traces with silver ink, and one with traces made from copper. The printed silver ink is less conductive than the bulk copper and therefore the output voltage of the printed rectifier was lower than the copper circuit. The copper circuit had an efficiency of 60% at 0dBm and the printed silver circuit had an efficiency of 28.6% at 0dBm. The antenna and rectifying circuits were then connected to each other and the performance was compared to a fully printed integrated rectifying antenna. The rectifying antennas were placed in front of a horn antenna while changing the power levels at the antenna. The efficiency of the whole system was lower than the individual components but an efficiency of 11% at 10dBm was measured.

  2. Flexible Proton-Gated Oxide Synaptic Transistors on Si Membrane.

    Science.gov (United States)

    Zhu, Li Qiang; Wan, Chang Jin; Gao, Ping Qi; Liu, Yang Hui; Xiao, Hui; Ye, Ji Chun; Wan, Qing

    2016-08-24

    Ion-conducting materials have received considerable attention for their applications in fuel cells, electrochemical devices, and sensors. Here, flexible indium zinc oxide (InZnO) synaptic transistors with multiple presynaptic inputs gated by proton-conducting phosphorosilicate glass-based electrolyte films are fabricated on ultrathin Si membranes. Transient characteristics of the proton gated InZnO synaptic transistors are investigated, indicating stable proton-gating behaviors. Short-term synaptic plasticities are mimicked on the proposed proton-gated synaptic transistors. Furthermore, synaptic integration regulations are mimicked on the proposed synaptic transistor networks. Spiking logic modulations are realized based on the transition between superlinear and sublinear synaptic integration. The multigates coupled flexible proton-gated oxide synaptic transistors may be interesting for neuroinspired platforms with sophisticated spatiotemporal information processing.

  3. Detection of vortex-core dynamics using current-induced self-bistable rectifying effect

    International Nuclear Information System (INIS)

    Goto, M; Hata, H; Yamaguchi, A; Miyajima, H; Nozaki, Y; Nakatani, Y; Yamaoka, T

    2011-01-01

    A magnetic vortex core confined in a micron-scale magnetic disk is resonantly excited by spin-polarized radio-frequency (rf) current and rf field. We show that rectifying voltage spectra caused by the vortex core resonance is dependent on the core polarity. Rectifying voltage spectra are given by the superposition of the polarity-dependent term and the polarity-independent term. The sign of the polarity-dependent rectifying voltage reverses when the sign of polarity P or external field H is reversed. This experimental result can be explained by the anisotropic magnetoresistance effect caused by the vortex core motion.

  4. A Theoretical Investigation on Rectifying Performance of a Single Motor Molecular Device

    International Nuclear Information System (INIS)

    Lei Hui; Tan Xun-Qiong

    2015-01-01

    We report ab initio calculations of the transport behavior of a phenyl substituted molecular motor. The calculated results show that the transport behavior of the device is sensitive to the rotation degree of the rotor part. When the rotor part is parallel with the stator part, a better rectifying performance can be found in the current-voltage curve. However, when the rotor part revolves to vertical with the stator part, the currents in the positive bias region decrease slightly. More importantly, the rectifying performance disappears. Thus this offers us a new method to modulate the rectifying behavior in molecular devices. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

    International Nuclear Information System (INIS)

    Zhao Peng; Zhang Ying; Wang Pei-Ji; Zhang Zhong; Liu De-Sheng

    2011-01-01

    Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C 60 nanotube caps. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  6. Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers

    Directory of Open Access Journals (Sweden)

    J. Koton

    2011-04-01

    Full Text Available In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.

  7. Synaptic ribbon. Conveyor belt or safety belt?

    Science.gov (United States)

    Parsons, T D; Sterling, P

    2003-02-06

    The synaptic ribbon in neurons that release transmitter via graded potentials has been considered as a conveyor belt that actively moves vesicles toward their release sites. But evidence has accumulated to the contrary, and it now seems plausible that the ribbon serves instead as a safety belt to tether vesicles stably in mutual contact and thus facilitate multivesicular release by compound exocytosis.

  8. P2X Receptors and Synaptic Plasticity

    Czech Academy of Sciences Publication Activity Database

    Pankratov, Y.; Lalo, U.; Krishtal, A.; Verkhratsky, Alexei

    2009-01-01

    Roč. 158, č. 1 (2009), s. 137-148 ISSN 0306-4522 Institutional research plan: CEZ:AV0Z50390512 Keywords : ATP * P2X receptors * synaptic plasticity Subject RIV: FH - Neurology Impact factor: 3.292, year: 2009

  9. Synaptic plasticity and the warburg effect

    KAUST Repository

    Magistretti, Pierre J.

    2014-01-01

    Functional brain imaging studies show that in certain brain regions glucose utilization exceeds oxygen consumption, indicating the predominance of aerobic glycolysis. In this issue, Goyal et al. (2014) report that this metabolic profile is associated with an enrichment in the expression of genes involved in synaptic plasticity and remodeling processes. © 2014 Elsevier Inc.

  10. Neuronal cytoskeleton in synaptic plasticity and regeneration.

    Science.gov (United States)

    Gordon-Weeks, Phillip R; Fournier, Alyson E

    2014-04-01

    During development, dynamic changes in the axonal growth cone and dendrite are necessary for exploratory movements underlying initial axo-dendritic contact and ultimately the formation of a functional synapse. In the adult central nervous system, an impressive degree of plasticity is retained through morphological and molecular rearrangements in the pre- and post-synaptic compartments that underlie the strengthening or weakening of synaptic pathways. Plasticity is regulated by the interplay of permissive and inhibitory extracellular cues, which signal through receptors at the synapse to regulate the closure of critical periods of developmental plasticity as well as by acute changes in plasticity in response to experience and activity in the adult. The molecular underpinnings of synaptic plasticity are actively studied and it is clear that the cytoskeleton is a key substrate for many cues that affect plasticity. Many of the cues that restrict synaptic plasticity exhibit residual activity in the injured adult CNS and restrict regenerative growth by targeting the cytoskeleton. Here, we review some of the latest insights into how cytoskeletal remodeling affects neuronal plasticity and discuss how the cytoskeleton is being targeted in an effort to promote plasticity and repair following traumatic injury in the central nervous system. © 2013 International Society for Neurochemistry.

  11. Realization of synaptic learning and memory functions in Y2O3 based memristive device fabricated by dual ion beam sputtering

    Science.gov (United States)

    Das, Mangal; Kumar, Amitesh; Singh, Rohit; Than Htay, Myo; Mukherjee, Shaibal

    2018-02-01

    Single synaptic device with inherent learning and memory functions is demonstrated based on a forming-free amorphous Y2O3 (yttria) memristor fabricated by dual ion beam sputtering system. Synaptic functions such as nonlinear transmission characteristics, long-term plasticity, short-term plasticity and ‘learning behavior (LB)’ are achieved using a single synaptic device based on cost-effective metal-insulator-semiconductor (MIS) structure. An ‘LB’ function is demonstrated, for the first time in the literature, for a yttria based memristor, which bears a resemblance to certain memory functions of biological systems. The realization of key synaptic functions in a cost-effective MIS structure would promote much cheaper synapse for artificial neural network.

  12. Synaptic remodeling, synaptic growth and the storage of long-term memory in Aplysia.

    Science.gov (United States)

    Bailey, Craig H; Kandel, Eric R

    2008-01-01

    Synaptic remodeling and synaptic growth accompany various forms of long-term memory. Storage of the long-term memory for sensitization of the gill-withdrawal reflex in Aplysia has been extensively studied in this respect and is associated with the growth of new synapses by the sensory neurons onto their postsynaptic target neurons. Recent time-lapse imaging studies of living sensory-to-motor neuron synapses in culture have monitored both functional and structural changes simultaneously so as to follow remodeling and growth at the same specific synaptic connections continuously over time and to examine the functional contribution of these learning-related structural changes to the different time-dependent phases of memory storage. Insights provided by these studies suggest the synaptic differentiation and growth induced by learning in the mature nervous system are highly dynamic and often rapid processes that can recruit both molecules and mechanisms used for de novo synapse formation during development.

  13. Synaptic Plasticity, Dementia and Alzheimer Disease.

    Science.gov (United States)

    Skaper, Stephen D; Facci, Laura; Zusso, Morena; Giusti, Pietro

    2017-01-01

    Neuroplasticity is not only shaped by learning and memory but is also a mediator of responses to neuron attrition and injury (compensatory plasticity). As an ongoing process it reacts to neuronal cell activity and injury, death, and genesis, which encompasses the modulation of structural and functional processes of axons, dendrites, and synapses. The range of structural elements that comprise plasticity includes long-term potentiation (a cellular correlate of learning and memory), synaptic efficacy and remodelling, synaptogenesis, axonal sprouting and dendritic remodelling, and neurogenesis and recruitment. Degenerative diseases of the human brain continue to pose one of biomedicine's most intractable problems. Research on human neurodegeneration is now moving from descriptive to mechanistic analyses. At the same time, it is increasing apparently that morphological lesions traditionally used by neuropathologists to confirm post-mortem clinical diagnosis might furnish us with an experimentally tractable handle to understand causative pathways. Consider the aging-dependent neurodegenerative disorder Alzheimer's disease (AD) which is characterised at the neuropathological level by deposits of insoluble amyloid β-peptide (Aβ) in extracellular plaques and aggregated tau protein, which is found largely in the intracellular neurofibrillary tangles. We now appreciate that mild cognitive impairment in early AD may be due to synaptic dysfunction caused by accumulation of non-fibrillar, oligomeric Aβ, occurring well in advance of evident widespread synaptic loss and neurodegeneration. Soluble Aβ oligomers can adversely affect synaptic structure and plasticity at extremely low concentrations, although the molecular substrates by which synaptic memory mechanisms are disrupted remain to be fully elucidated. The dendritic spine constitutes a primary locus of excitatory synaptic transmission in the mammalian central nervous system. These structures protruding from dendritic

  14. ANALISA SISTEM KENDALI PUTARAN MOTOR DC MENGGUNAKAN SILICON CONTROLLED RECTIFIERS

    Directory of Open Access Journals (Sweden)

    M. Khairudin, Efendi, N Purwantiningsih,

    2016-01-01

    Full Text Available ABSTRAK Paper ini bertujuan untuk menganalisa rangkaian sistem kendali putaran motor menggunakan Silicon Controlled Rectifier (SCR atau Thyristor. Eksperimen sistem kendali putaran motor ini menggunakan dua rangkaian yang berbeda. Rangkaian pertama menggunakan dua sumber, yaitu sumber tegangan DC 12 v terhubung dengan motor universal secara seri dengan resistor dan SCR, sedangkan sumber tegangan DC variabel 0 sampai 1.5 v dihubung paralel dengan kapasitor dan resistor. Rangkaian kedua menggunakan satu sumber tegangan AC 5 v yang dihubungkan dengan saklar dan motor. Pada rangkaian kedua ini motor dihubungkan dengan potensio, SCR, dioda serta kapasitor yang dipasang paralel dengan sumber tegangan AC. Hasil eksperimen menunjukkan dalam rangkaian menggunakan sumber tegangan DC, motor DC akan berputar saat saklar S1 tertutup. Kondisi motor akan berputar lebih cepat ketika sumber tegangan variabel diatur lebih besar dari 0 v sehingga arus gate Ig lebih bear dari 400 mA. Adapun Eksperimen dengan sumber tegangan AC, motor akan berputar dengan menambahkan dioda D3 dan pengaturan kecepatan melalui potensio meter Rv sampai posisi maksimum. Kata kunci: analisa, motor DC, SCR, sistem kendali ABSTRACT The objective of this study is to analyse the circuit of DC motor control system using Silicon Controlled Rectifier (SCR or Thyristor. In this experiment the circuit of control system for the motor using two different circuits. The first circuit using two sources, the 12 v DC voltage is connected to universal motor and series with a resistor and SCR, while the DC variable voltage source of 0 to 1.5 v connected in parallel to the capacitor and resistor. The second circuit uses a single source of 5 V AC voltage connected to the switch and the motor. In the second circuit, the motor is connected to the potentio meter, SCR, diode and capacitor in parallel with the AC voltage source. The experimental results showed the circuit using a DC voltage source impacted the

  15. An RF energy harvester system using UHF micropower CMOS rectifier based on a diode connected CMOS transistor.

    Science.gov (United States)

    Shokrani, Mohammad Reza; Khoddam, Mojtaba; Hamidon, Mohd Nizar B; Kamsani, Noor Ain; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18  μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology.

  16. Nonlinear optics

    CERN Document Server

    Boyd, Robert W

    2013-01-01

    Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q

  17. Nonlinear systems

    National Research Council Canada - National Science Library

    Drazin, P. G

    1992-01-01

    This book is an introduction to the theories of bifurcation and chaos. It treats the solution of nonlinear equations, especially difference and ordinary differential equations, as a parameter varies...

  18. Nonlinear analysis

    CERN Document Server

    Gasinski, Leszek

    2005-01-01

    Hausdorff Measures and Capacity. Lebesgue-Bochner and Sobolev Spaces. Nonlinear Operators and Young Measures. Smooth and Nonsmooth Analysis and Variational Principles. Critical Point Theory. Eigenvalue Problems and Maximum Principles. Fixed Point Theory.

  19. Terahertz Detection and Imaging Using Graphene Ballistic Rectifiers.

    Science.gov (United States)

    Auton, Gregory; But, Dmytro B; Zhang, Jiawei; Hill, Ernie; Coquillat, Dominique; Consejo, Christophe; Nouvel, Philippe; Knap, Wojciech; Varani, Luca; Teppe, Frederic; Torres, Jeremie; Song, Aimin

    2017-11-08

    A graphene ballistic rectifier is used in conjunction with an antenna to demonstrate a rectenna as a terahertz (THz) detector. A small-area (<1 μm 2 ) local gate is used to adjust the Fermi level in the device to optimize the output while minimizing the impact on the cutoff frequency. The device operates in both n- and p-type transport regimes and shows a peak extrinsic responsivity of 764 V/W and a corresponding noise equivalent power of 34 pW Hz -1/2 at room temperature with no indications of a cutoff frequency up to 0.45 THz. The device also demonstrates a linear response for more than 3 orders of magnitude of input power due to its zero threshold voltage, quadratic current-voltage characteristics and high saturation current. Finally, the device is used to take an image of an optically opaque object at 0.685 THz, demonstrating potential in both medical and security imaging applications.

  20. Graphene ballistic nano-rectifier with very high responsivity

    Science.gov (United States)

    Auton, Gregory; Zhang, Jiawei; Kumar, Roshan Krishna; Wang, Hanbin; Zhang, Xijian; Wang, Qingpu; Hill, Ernie; Song, Aimin

    2016-01-01

    Although graphene has the longest mean free path of carriers of any known electronic material, very few novel devices have been reported to harness this extraordinary property. Here we demonstrate a ballistic nano-rectifier fabricated by creating an asymmetric cross-junction in single-layer graphene sandwiched between boron nitride flakes. A mobility ∼200,000 cm2 V−1 s−1 is achieved at room temperature, well beyond that required for ballistic transport. This enables a voltage responsivity as high as 23,000 mV mW−1 with a low-frequency input signal. Taking advantage of the output channels being orthogonal to the input terminals, the noise is found to be not strongly influenced by the input. Hence, the corresponding noise-equivalent power is as low as 0.64 pW Hz−1/2. Such performance is even comparable to superconducting bolometers, which however need to operate at cryogenic temperatures. Furthermore, output oscillations are observed at low temperatures, the period of which agrees with the lateral size quantization. PMID:27241162

  1. Finite element modeling of electrically rectified piezoelectric energy harvesters

    International Nuclear Information System (INIS)

    Wu, P H; Shu, Y C

    2015-01-01

    Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique. (paper)

  2. Finite element modeling of electrically rectified piezoelectric energy harvesters

    Science.gov (United States)

    Wu, P. H.; Shu, Y. C.

    2015-09-01

    Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique.

  3. Generalized space vector control for current source inverters and rectifiers

    Directory of Open Access Journals (Sweden)

    Roseline J. Anitha

    2016-06-01

    Full Text Available Current source inverters (CSI is one of the widely used converter topology in medium voltage drive applications due to its simplicity, motor friendly waveforms and reliable short circuit protection. The current source inverters are usually fed by controlled current source rectifiers (CSR with a large inductor to provide a constant supply current. A generalized control applicable for both CSI and CSR and their extension namely current source multilevel inverters (CSMLI are dealt in this paper. As space vector pulse width modulation (SVPWM features the advantages of flexible control, faster dynamic response, better DC utilization and easy digital implementation it is considered for this work. This paper generalizes SVPWM that could be applied for CSI, CSR and CSMLI. The intense computation involved in framing a generalized space vector control are discussed in detail. The algorithm includes determination of band, region, subregions and vectors. The algorithm is validated by simulation using MATLAB /SIMULINK for CSR 5, 7, 13 level CSMLI and for CSR fed CSI.

  4. 2012 NOAA Color Ortho-rectified Mosaic of Corpus Christi to Saint Charles Bay, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of LAKE CHARLES

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of LAKE CHARLES. The...

  6. 2016 NOAA NGS Ortho-rectified Color Mosaic of Anchorage, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2010 NOAA Ortho-rectified Near-infrared Mosaic of Port Arthur - Beaumont, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of BEAUMONT, ORANGE, PORT AUTHUR

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of BEAUMONT, ORANGE,...

  9. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Cleveland, Ohio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of CHOCTAWHATCHEE BAY

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of CHOCTAWHATCHEE BAY....

  11. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of LAKE CHARLES (NODC Accession 0075827)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of LAKE CHARLES. The...

  12. 2014 NOAA Ortho-rectified Mosaic of Delaware Coastline: Hurricane Sandy Impact Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles at 0.10m GSD. This data set was created for NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative in the...

  13. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of MISSISSIPPI RIVER - LAPLACE TO VENICE

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of MISSISSIPPI RIVER -...

  14. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Alabama: Eastern Mississippi Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2015 NOAA Ortho-rectified Near-Infrared Mosaic of the port of Silver Bay, Minnesota

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2015 NOAA Ortho-rectified Color Mosaic of the port of Silver Bay, Minnesota

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Pescadero Point to Bodega Bay, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2012 NOAA Ortho-rectified Near-Infrared Mosaic of Oregon: Lake Umatilla to Clarkson

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2011 NOAA Ortho-rectified Mosaic of Intracoastal City, Louisiana (NODC Accession 0075831)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2010 NOAA Ortho-rectified Mosaic of Savannah River, Georgia (NODC Accession 0092435)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2011 NOAA Ortho-rectified Mosaic of Tallaboa, Puerto Rico (NODC Accession 0074381)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. Positive Temperature Coefficient of Breakdown Voltage in 4H-SiC PN Junction Rectifiers

    National Research Council Canada - National Science Library

    Neudeck, Philip

    1998-01-01

    ...-suited SiC polytype for power device implementation. This paper reports the first experimental measurements of stable positive temperature coefficient behavior observed in 4H-SiC pn junction rectifiers...

  3. Influence of load type on power factor and harmonic composition of three-phase rectifier current

    Science.gov (United States)

    Nikolayzin, N. V.; Vstavskaya, E. V.; Konstantinov, V. I.; Konstantinova, O. V.

    2018-05-01

    This article is devoted to research of the harmonic composition of the three-phase rectifier current consumed when it operates with different types of load. The results are compared with Standard requirements.

  4. Design and control of an LCL-filter-based three-phase active rectifier

    DEFF Research Database (Denmark)

    Liserre, Marco; Blaabjerg, Frede; Hansen, Steffan

    2005-01-01

    This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized...... by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier...... a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes....

  5. 2016 NOAA NGS Ortho-rectified Color Mosaic of Whittier, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Alabama: Eastern Mississippi Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. A novel approach to determine the interphase transformer inductance of 18 pulse rectifiers

    International Nuclear Information System (INIS)

    Sefa, Ibrahim; Altin, Necmi

    2009-01-01

    The interphase transformer inductance seriously affects the performance of 18 pulse rectifiers. Low inductance values cause non-characteristic harmonics whereas high inductance values increase the rectifier cost and size. Hence, determination of the interphase transformer inductance value is an important problem in the design of 18 pulse rectifiers. In this paper, an approach to determine the optimum inductance value of an interphase transformer is proposed and a practical formula is introduced. The proposed approach has been validated with simulation and experimental studies carried out with designed capacitive loaded autotransformer based 18 pulse rectifier for different IPT inductance values at different load levels. Experimental and simulation results show that cost effective interphase transformer inductance value can be determined with the proposed approach and this value reduces the line current harmonics and improves power factor drastically.

  8. The energizing of a NMR superconducting coil by a superconducting rectifier

    International Nuclear Information System (INIS)

    Sikkenga, J.; ten Kate, H.H.J.; van der Klundert, L.J.M.; Knoben, J.; Kraaij, G.J.; Spuorenberg, C.J.G.

    1985-01-01

    NMR magnets require a good homogeneity within a certain volume and an excellent field stability. The homogeneity can be met using a superconducting shim coil system. The field stability requires a constant current, although in many cases the current decay time constant is too low, due to imperfections in the superconducting wire and joints. This can be overcome using a rectifier. The rectifier can also be used to load the coil. The combination and interaction of the superconducting NMR coil (2.0 Tesla and 0.35 m cold bore) and the rectifier (20 W / 1 kA) is tested. The safety of the system is discussed. The shim coil system can compensate the strayfield of the rectifier. The field decay compensation will be discussed

  9. 2013 NOAA Ortho-rectified Color Mosaic of California: Port of San Diego

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2013 NOAA Ortho-rectified Color Mosaic of Intercoastal Waterway - Calcasieu Lake to Vermillion Bay, Louisiana

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Bodega Bay to Shelter Cove, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2017 NOAA NGS Ortho-rectified Color Mosaic of Houston Ship Channel, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2016 NOAA NGS Ortho-rectified Mean High Water Color Mosaic of Venice Inlet ICW, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Seal Rock to Lopez Rock, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2011 NOAA Ortho-rectified Mosaic of Intracoastal Waterway, Texas (NODC Accession 0105604)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2012 NOAA Ortho-rectified Color Mosaic of Sacramento Deep Water Ship Channel, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2009 NOAA Near-Infrared Ortho-rectified Mosaic of Brunswick, Georgia (NODC Accession 0092435)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2012 NOAA Ortho-rectified Color MHW Mosaic of Washington: Seattle and Lake Washington Ship Canal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Lopez Rock to Pescadero Point, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2012 NOAA Ortho-rectified Color Mosaic of Del Mar Boat Basin and Oceanside Harbor, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2013 NOAA Ortho-rectified Near-Infrared Mosaic of the Port of Panama City, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2016 NOAA NGS Ortho-rectified Color Mosaic of Baton Rouge, Louisiana

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2009 NOAA Ortho-rectified RGB Mosaic of Savannah, Georgia (NODC Accession 0092435)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2011 NOAA Ortho-rectified Mosaic of Texas: Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2012 NOAA Color MLLW Ortho-rectified Mosaic of Amelia Island and Nassau River, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2011 NOAA Color MHW Ortho-rectified Mosaic of Amelia Island and Nassau River, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2011 NOAA Ortho-rectified Near-Infrared Mosaic of Isle of Shoals, New Hampshire (MHW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2016 NOAA NGS Ortho-rectified Color Mosaic of Kenai and Nikiski, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2014 NOAA Ortho-rectified Mosaic of Hurricane Sandy Coastal Impact Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles at 0.35m GSD created for NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative in Hurricane Sandy coastal...

  10. 2010 NOAA Ortho-rectified Mosaic of Louisiana: Mississippi River - Baton Rouge to Southwest Pass

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2013 NOAA Ortho-rectified Color Mosaic of California: Port of Los Angeles and Long Beach

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2016 NOAA NGS Ortho-rectified Color Mosaic of Cleveland, Ohio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2015 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Port Canaveral, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2010 NOAA Ortho-rectified Mosaic of Lake Michigan - West Coast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of PORT OF GEORGETOWN - CSCAP

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of PORT OF GEORGETOWN...

  16. 2012 NOAA Ortho-rectified Color Mosaic of Bremerton and Manchester, Washington

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. Performance improvement of three phase rectifier by employing electronic smoothing inductor

    DEFF Research Database (Denmark)

    Singh, Yash Veer; Rasmussen, Peter Omand; Andersen, Torben O.

    2014-01-01

    density of the rectifier. In case of an inverter connected to the output of the rectifier, peak to peak voltage ripples to the front end of the inverter reduces significantly by the ESI, and it increases lifetime of the capacitor connected to the dc link and reduces the voltage stress of the active power...... semiconductors of the inverter. In this paper, an average model of the ESI and its control schemes are presented....

  18. Dynamic and Control Analysis of Modular Multi-Parallel Rectifiers (MMR)

    DEFF Research Database (Denmark)

    Zare, Firuz; Ghosh, Arindam; Davari, Pooya

    2017-01-01

    This paper presents dynamic analysis of a Modular Multi-Parallel Rectifier (MMR) based on state-space modelling and analysis. The proposed topology is suitable for high power application which can reduce line current harmonics emissions significantly. However, a proper controller is required...... to share and control current through each rectifier. Mathematical analysis and preliminary simulations have been carried out to verify the proposed controller under different operating conditions....

  19. Design and test of a 2.25-MW transformer rectifier assembly

    Science.gov (United States)

    Cormier, R.; Daeges, J.

    1989-01-01

    A new 2.25-MW transformer rectifier assembly was fabricated for DSS-13 at Goldstone, California. The transformer rectifier will provide constant output power of 2.25 MW at any voltage from 31 kV to 125 kV. This will give a new capability of 1 MW of RF power at X-band, provided appropriate microwave tubes are in the power amplifier. A description of the design and test results is presented.

  20. Wideband Small-Signal Input dq Admittance Modeling of Six-Pulse Diode Rectifiers

    DEFF Research Database (Denmark)

    Yue, Xiaolong; Wang, Xiongfei; Blaabjerg, Frede

    2018-01-01

    This paper studies the wideband small-signal input dq admittance of six-pulse diode rectifiers. Considering the frequency coupling introduced by ripple frequency harmonics of d-and q-channel switching function, the proposed model successfully predicts the small-signal input dq admittance of six......-pulse diode rectifiers in high frequency regions that existing models fail to explain. Simulation and experimental results verify the accuracy of the proposed model....

  1. Superhigh-frequency circuit for the EPR spectrometer with rectifier screening

    International Nuclear Information System (INIS)

    Zhizhchenko, G.A.; Tsvirko, L.V.

    1983-01-01

    The hamodyne SHF circuit of a 3-cm EPR spectrometer with a reflecting resonator is described. The optimum operating mode of SHF-rectifier at a constant phase difference is automatically assured in the circuit. The circuit employs a reflecting p-i-n- attenuator and a SHF-rectifier sereen which simplify the spectrometer tuming. The circuit is used in a miniature EPR radiospectrometer Minsk EPR-6-type

  2. Changes in Inward Rectifier K+ Channels in Hepatic Stellate Cells During Primary Culture

    Science.gov (United States)

    Lee, Dong Hyeon; Kong, In Deok; Lee, Joong-Woo

    2008-01-01

    Purpose This study examined the expression and function of inward rectifier K+ channels in cultured rat hepatic stellate cells (HSC). Materials and Methods The expression of inward rectifier K+ channels was measured using real-time RT-PCR, and electrophysiological properties were determined using the gramicidin-perforated patch-clamp technique. Results The dominant inward rectifier K+ channel subtypes were Kir2.1 and Kir6.1. These dominant K+ channel subtypes decreased significantly during the primary culture throughout activation process. HSC can be classified into two subgroups: one with an inward-rectifying K+ current (type 1) and the other without (type 2). The inward current was blocked by Ba2+ (100 µM) and enhanced by high K+ (140 mM), more prominently in type 1 HSC. There was a correlation between the amplitude of the Ba2+-sensitive current and the membrane potential. In addition, Ba2+ (300 µM) depolarized the membrane potential. After the culture period, the amplitude of the inward current decreased and the membrane potential became depolarized. Conclusion HSC express inward rectifier K+ channels, which physiologically regulate membrane potential and decrease during the activation process. These results will potentially help determine properties of the inward rectifier K+ channels in HSC as well as their roles in the activation process. PMID:18581597

  3. DEVELOPMENT OF CONTROLLED RECTIFIERS BASED ON THE BIPOLAR WITH STATIC INDUCTION TRANSISTORS (BSIT

    Directory of Open Access Journals (Sweden)

    F. I. Bukashev

    2016-01-01

    Full Text Available Aim. The aim of this study is to develop one of the most perspective semiconductor device suitable for creation and improvement of controlled rectifiers, bipolar static induction transistor.Methods. Considered are the structural and schematic circuit controlled rectifier based on bipolar static induction transistor (BSIT, and the criterion of effectiveness controlled rectifiers - equivalent to the voltage drop.Results. Presented are the study results of controlled rectifier layout on BSIT KT698I. It sets the layout operation at an input voltage of 2.0 V at a frequency up to 750 kHz. The efficiency of the studied layouts at moderate current densities as high as 90 % .Offered is optimization of technological route microelectronic controlled rectifier manufacturing including BSIT and integrated bipolar elements of the scheme management.Conclusion. It is proved that the most efficient use of the bipolar static induction transistor occurs at the low voltage controlled rectifiers 350-400 kHz, at frequencies in conjunction with a low-voltage control circuit.It is proved that the increase of the functional characteristics of the converters is connected to the expansion of the input voltage and output current ranges

  4. New analysis and design of a RF rectifier for RFID and implantable devices.

    Science.gov (United States)

    Liu, Dong-Sheng; Li, Feng-Bo; Zou, Xue-Cheng; Liu, Yao; Hui, Xue-Mei; Tao, Xiong-Fei

    2011-01-01

    New design and optimization of charge pump rectifiers using diode-connected MOS transistors is presented in this paper. An analysis of the output voltage and Power Conversion Efficiency (PCE) is given to guide and evaluate the new design. A novel diode-connected MOS transistor for UHF rectifiers is presented and optimized, and a high efficiency N-stage charge pump rectifier based on this new diode-connected MOS transistor is designed and fabricated in a SMIC 0.18-μm 2P3M CMOS embedded EEPROM process. The new diode achieves 315 mV turn-on voltage and 415 nA reverse saturation leakage current. Compared with the traditional rectifier, the one based on the proposed diode-connected MOS has higher PCE, higher output voltage and smaller ripple coefficient. When the RF input is a 900-MHz sinusoid signal with the power ranging from -15 dBm to -4 dBm, PCEs of the charge pump rectifier with only 3-stage are more than 30%, and the maximum output voltage is 5.5 V, and its ripple coefficients are less than 1%. Therefore, the rectifier is especially suitable to passive UHF RFID tag IC and implantable devices.

  5. Influence of Synaptic Depression on Memory Storage Capacity

    Science.gov (United States)

    Otsubo, Yosuke; Nagata, Kenji; Oizumi, Masafumi; Okada, Masato

    2011-08-01

    Synaptic efficacy between neurons is known to change within a short time scale dynamically. Neurophysiological experiments show that high-frequency presynaptic inputs decrease synaptic efficacy between neurons. This phenomenon is called synaptic depression, a short term synaptic plasticity. Many researchers have investigated how the synaptic depression affects the memory storage capacity. However, the noise has not been taken into consideration in their analysis. By introducing ``temperature'', which controls the level of the noise, into an update rule of neurons, we investigate the effects of synaptic depression on the memory storage capacity in the presence of the noise. We analytically compute the storage capacity by using a statistical mechanics technique called Self Consistent Signal to Noise Analysis (SCSNA). We find that the synaptic depression decreases the storage capacity in the case of finite temperature in contrast to the case of the low temperature limit, where the storage capacity does not change.

  6. Ultrafast Synaptic Events in a Chalcogenide Memristor

    Science.gov (United States)

    Li, Yi; Zhong, Yingpeng; Xu, Lei; Zhang, Jinjian; Xu, Xiaohua; Sun, Huajun; Miao, Xiangshui

    2013-04-01

    Compact and power-efficient plastic electronic synapses are of fundamental importance to overcoming the bottlenecks of developing a neuromorphic chip. Memristor is a strong contender among the various electronic synapses in existence today. However, the speeds of synaptic events are relatively slow in most attempts at emulating synapses due to the material-related mechanism. Here we revealed the intrinsic memristance of stoichiometric crystalline Ge2Sb2Te5 that originates from the charge trapping and releasing by the defects. The device resistance states, representing synaptic weights, were precisely modulated by 30 ns potentiating/depressing electrical pulses. We demonstrated four spike-timing-dependent plasticity (STDP) forms by applying programmed pre- and postsynaptic spiking pulse pairs in different time windows ranging from 50 ms down to 500 ns, the latter of which is 105 times faster than the speed of STDP in human brain. This study provides new opportunities for building ultrafast neuromorphic computing systems and surpassing Von Neumann architecture.

  7. Long-pore Electrostatics in Inward-rectifier Potassium Channels

    Science.gov (United States)

    Robertson, Janice L.; Palmer, Lawrence G.; Roux, Benoît

    2008-01-01

    Inward-rectifier potassium (Kir) channels differ from the canonical K+ channel structure in that they possess a long extended pore (∼85 Å) for ion conduction that reaches deeply into the cytoplasm. This unique structural feature is presumably involved in regulating functional properties specific to Kir channels, such as conductance, rectification block, and ligand-dependent gating. To elucidate the underpinnings of these functional roles, we examine the electrostatics of an ion along this extended pore. Homology models are constructed based on the open-state model of KirBac1.1 for four mammalian Kir channels: Kir1.1/ROMK, Kir2.1/IRK, Kir3.1/GIRK, and Kir6.2/KATP. By solving the Poisson-Boltzmann equation, the electrostatic free energy of a K+ ion is determined along each pore, revealing that mammalian Kir channels provide a favorable environment for cations and suggesting the existence of high-density regions in the cytoplasmic domain and cavity. The contribution from the reaction field (the self-energy arising from the dielectric polarization induced by the ion's charge in the complex geometry of the pore) is unfavorable inside the long pore. However, this is well compensated by the electrostatic interaction with the static field arising from the protein charges and shielded by the dielectric surrounding. Decomposition of the static field provides a list of residues that display remarkable correspondence with existing mutagenesis data identifying amino acids that affect conduction and rectification. Many of these residues demonstrate interactions with the ion over long distances, up to 40 Å, suggesting that mutations potentially affect ion or blocker energetics over the entire pore. These results provide a foundation for understanding ion interactions in Kir channels and extend to the study of ion permeation, block, and gating in long, cation-specific pores. PMID:19001143

  8. Synaptic theory of Replicator-like melioration

    Directory of Open Access Journals (Sweden)

    Yonatan Loewenstein

    2010-06-01

    Full Text Available According to the theory of Melioration, organisms in repeated choice settings shift their choice preference in favor of the alternative that provides the highest return. The goal of this paper is to explain how this learning behavior can emerge from microscopic changes in the efficacies of synapses, in the context of two-alternative repeated-choice experiment. I consider a large family of synaptic plasticity rules in which changes in synaptic efficacies are driven by the covariance between reward and neural activity. I construct a general framework that predicts the learning dynamics of any decision-making neural network that implements this synaptic plasticity rule and show that melioration naturally emerges in such networks. Moreover, the resultant learning dynamics follows the Replicator equation which is commonly used to phenomenologically describe changes in behavior in operant conditioning experiments. Several examples demonstrate how the learning rate of the network is affected by its properties and by the specifics of the plasticity rule. These results help bridge the gap between cellular physiology and learning behavior.

  9. Dynamic Control of Synaptic Adhesion and Organizing Molecules in Synaptic Plasticity

    Energy Technology Data Exchange (ETDEWEB)

    Rudenko, Gabby (Texas-MED)

    2017-01-01

    Synapses play a critical role in establishing and maintaining neural circuits, permitting targeted information transfer throughout the brain. A large portfolio of synaptic adhesion/organizing molecules (SAMs) exists in the mammalian brain involved in synapse development and maintenance. SAMs bind protein partners, formingtrans-complexes spanning the synaptic cleft orcis-complexes attached to the same synaptic membrane. SAMs play key roles in cell adhesion and in organizing protein interaction networks; they can also provide mechanisms of recognition, generate scaffolds onto which partners can dock, and likely take part in signaling processes as well. SAMs are regulated through a portfolio of different mechanisms that affect their protein levels, precise localization, stability, and the availability of their partners at synapses. Interaction of SAMs with their partners can further be strengthened or weakened through alternative splicing, competing protein partners, ectodomain shedding, or astrocytically secreted factors. Given that numerous SAMs appear altered by synaptic activity, in vivo, these molecules may be used to dynamically scale up or scale down synaptic communication. Many SAMs, including neurexins, neuroligins, cadherins, and contactins, are now implicated in neuropsychiatric and neurodevelopmental diseases, such as autism spectrum disorder, schizophrenia, and bipolar disorder and studying their molecular mechanisms holds promise for developing novel therapeutics.

  10. Characterization and extraction of the synaptic apposition surface for synaptic geometry analysis

    Science.gov (United States)

    Morales, Juan; Rodríguez, Angel; Rodríguez, José-Rodrigo; DeFelipe, Javier; Merchán-Pérez, Angel

    2013-01-01

    Geometrical features of chemical synapses are relevant to their function. Two critical components of the synaptic junction are the active zone (AZ) and the postsynaptic density (PSD), as they are related to the probability of synaptic release and the number of postsynaptic receptors, respectively. Morphological studies of these structures are greatly facilitated by the use of recent electron microscopy techniques, such as combined focused ion beam milling and scanning electron microscopy (FIB/SEM), and software tools that permit reconstruction of large numbers of synapses in three dimensions. Since the AZ and the PSD are in close apposition and have a similar surface area, they can be represented by a single surface—the synaptic apposition surface (SAS). We have developed an efficient computational technique to automatically extract this surface from synaptic junctions that have previously been three-dimensionally reconstructed from actual tissue samples imaged by automated FIB/SEM. Given its relationship with the release probability and the number of postsynaptic receptors, the surface area of the SAS is a functionally relevant measure of the size of a synapse that can complement other geometrical features like the volume of the reconstructed synaptic junction, the equivalent ellipsoid size and the Feret's diameter. PMID:23847474

  11. Nonlinear optimization

    CERN Document Server

    Ruszczynski, Andrzej

    2011-01-01

    Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates the theory and the methods of nonlinear optimization in a unified, clear, and mathematically rigorous fashion, with detailed and easy-to-follow proofs illustrated by numerous examples and figures. The book covers convex analysis, the theory of optimality conditions, duality theory, and numerical methods for solving unconstrained and constrained optimization problems. It addresses not only classical material but also modern top...

  12. Mechanisms of glycine release, which build up synaptic and extrasynaptic glycine levels: the role of synaptic and non-synaptic glycine transporters.

    Science.gov (United States)

    Harsing, Laszlo G; Matyus, Peter

    2013-04-01

    Glycine is an amino acid neurotransmitter that is involved in both inhibitory and excitatory neurochemical transmission in the central nervous system. The role of glycine in excitatory neurotransmission is related to its coagonist action at glutamatergic N-methyl-D-aspartate receptors. The glycine levels in the synaptic cleft rise many times higher during synaptic activation assuring that glycine spills over into the extrasynaptic space. Another possible origin of extrasynaptic glycine is the efflux of glycine occurring from astrocytes associated with glutamatergic synapses. The release of glycine from neuronal or glial origins exhibits several differences compared to that of biogenic amines or other amino acid neurotransmitters. These differences appear in an external Ca(2+)- and temperature-dependent manner, conferring unique characteristics on glycine as a neurotransmitter. Glycine transporter type-1 at synapses may exhibit neural and glial forms and plays a role in controlling synaptic glycine levels and the spill over rate of glycine from the synaptic cleft into the extrasynaptic biophase. Non-synaptic glycine transporter type-1 regulates extrasynaptic glycine concentrations, either increasing or decreasing them depending on the reverse or normal mode operation of the carrier molecule. While we can, at best, only estimate synaptic glycine levels at rest and during synaptic activation, glycine concentrations are readily measurable via brain microdialysis technique applied in the extrasynaptic space. The non-synaptic N-methyl-D-aspartate receptor may obtain glycine for activation following its spill over from highly active synapses or from its release mediated by the reverse operation of non-synaptic glycine transporter-1. The sensitivity of non-synaptic N-methyl-D-aspartate receptors to glutamate and glycine is many times higher than that of synaptic N-methyl-D-aspartate receptors making the former type of receptor the primary target for drug action. Synaptic

  13. Economic modelling of energy services: Rectifying misspecified energy demand functions

    International Nuclear Information System (INIS)

    Hunt, Lester C.; Ryan, David L.

    2015-01-01

    Although it is well known that energy demand is derived, since energy is required not for its own sake but for the energy services it produces – such as heating, lighting, and motive power – energy demand models, both theoretical and empirical, often fail to take account of this feature. In this paper, we highlight the misspecification that results from ignoring this aspect, and its empirical implications – biased estimates of price elasticities and other measures – and provide a relatively simple and empirically practicable way to rectify it, which has a strong theoretical grounding. To do so, we develop an explicit model of consumer behaviour in which utility derives from consumption of energy services rather than from the energy sources that are used to produce them. As we discuss, this approach opens up the possibility of examining many aspects of energy demand in a theoretically sound way that have not previously been considered on a widespread basis, although some existing empirical work could be interpreted as being consistent with this type of specification. While this formulation yields demand equations for energy services rather than for energy or particular energy sources, these are shown to be readily converted, without added complexity, into the standard type of energy demand equation(s) that is (are) typically estimated. The additional terms that the resulting energy demand equations include, compared to those that are typically estimated, highlight the misspecification that is implicit when typical energy demand equations are estimated. A simple solution for dealing with an apparent drawback of this formulation for empirical purposes, namely that information is required on typically unobserved energy efficiency, indicates how energy efficiency can be captured in the model, such as by including exogenous trends and/or including its possible dependence on past energy prices. The approach is illustrated using an empirical example that involves

  14. Synaptic Contacts Enhance Cell-to-Cell Tau Pathology Propagation

    Directory of Open Access Journals (Sweden)

    Sara Calafate

    2015-05-01

    Full Text Available Accumulation of insoluble Tau protein aggregates and stereotypical propagation of Tau pathology through the brain are common hallmarks of tauopathies, including Alzheimer’s disease (AD. Propagation of Tau pathology appears to occur along connected neurons, but whether synaptic contacts between neurons are facilitating propagation has not been demonstrated. Using quantitative in vitro models, we demonstrate that, in parallel to non-synaptic mechanisms, synapses, but not merely the close distance between the cells, enhance the propagation of Tau pathology between acceptor hippocampal neurons and Tau donor cells. Similarly, in an artificial neuronal network using microfluidic devices, synapses and synaptic activity are promoting neuronal Tau pathology propagation in parallel to the non-synaptic mechanisms. Our work indicates that the physical presence of synaptic contacts between neurons facilitate Tau pathology propagation. These findings can have implications for synaptic repair therapies, which may turn out to have adverse effects by promoting propagation of Tau pathology.

  15. Attractor neural networks with resource-efficient synaptic connectivity

    Science.gov (United States)

    Pehlevan, Cengiz; Sengupta, Anirvan

    Memories are thought to be stored in the attractor states of recurrent neural networks. Here we explore how resource constraints interplay with memory storage function to shape synaptic connectivity of attractor networks. We propose that given a set of memories, in the form of population activity patterns, the neural circuit choses a synaptic connectivity configuration that minimizes a resource usage cost. We argue that the total synaptic weight (l1-norm) in the network measures the resource cost because synaptic weight is correlated with synaptic volume, which is a limited resource, and is proportional to neurotransmitter release and post-synaptic current, both of which cost energy. Using numerical simulations and replica theory, we characterize optimal connectivity profiles in resource-efficient attractor networks. Our theory explains several experimental observations on cortical connectivity profiles, 1) connectivity is sparse, because synapses are costly, 2) bidirectional connections are overrepresented and 3) are stronger, because attractor states need strong recurrence.

  16. Defective Glycinergic Synaptic Transmission in Zebrafish Motility Mutants

    OpenAIRE

    Hirata, Hiromi; Carta, Eloisa; Yamanaka, Iori; Harvey, Robert J.; Kuwada, John Y.

    2010-01-01

    Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Recently, in vivo analysis of glycinergic synaptic transmission has been pursued in zebrafish using molecular genetics. An ENU mutagenesis screen identified two behavioral mutants that are defective in glycinergic synaptic transmission. Zebrafish bandoneon (beo) mutants have a defect in glrbb, one of the duplicated glycine receptor (GlyR) β subunit genes. These mutants exhibit a loss of glycinergic synaptic ...

  17. Statistical mechanics of attractor neural network models with synaptic depression

    International Nuclear Information System (INIS)

    Igarashi, Yasuhiko; Oizumi, Masafumi; Otsubo, Yosuke; Nagata, Kenji; Okada, Masato

    2009-01-01

    Synaptic depression is known to control gain for presynaptic inputs. Since cortical neurons receive thousands of presynaptic inputs, and their outputs are fed into thousands of other neurons, the synaptic depression should influence macroscopic properties of neural networks. We employ simple neural network models to explore the macroscopic effects of synaptic depression. Systems with the synaptic depression cannot be analyzed due to asymmetry of connections with the conventional equilibrium statistical-mechanical approach. Thus, we first propose a microscopic dynamical mean field theory. Next, we derive macroscopic steady state equations and discuss the stabilities of steady states for various types of neural network models.

  18. Experimental Implementation of a Biometric Laser Synaptic Sensor

    Directory of Open Access Journals (Sweden)

    Alexander N. Pisarchik

    2013-12-01

    Full Text Available We fabricate a biometric laser fiber synaptic sensor to transmit information from one neuron cell to the other by an optical way. The optical synapse is constructed on the base of an erbium-doped fiber laser, whose pumped diode current is driven by a pre-synaptic FitzHugh–Nagumo electronic neuron, and the laser output controls a post-synaptic FitzHugh–Nagumo electronic neuron. The implemented laser synapse displays very rich dynamics, including fixed points, periodic orbits with different frequency-locking ratios and chaos. These regimes can be beneficial for efficient biorobotics, where behavioral flexibility subserved by synaptic connectivity is a challenge.

  19. A pivotal role of GSK-3 in synaptic plasticity

    Directory of Open Access Journals (Sweden)

    Clarrisa A Bradley

    2012-02-01

    Full Text Available Glycogen synthase kinase-3 (GSK-3 has many cellular functions. Recent evidence suggests that it plays a key role in certain types of synaptic plasticity, in particular a form of long-term depression (LTD that is induced by the synaptic activation of N-methyl-D-aspartate (NMDA receptors. In the present article we summarise what is currently known concerning the roles of GSK-3 in synaptic plasticity at both glutamatergic and GABAergic synapses. We summarise its role in cognition and speculate on how alterations in the synaptic functioning of GSK-3 may be a major factor in certain neurodegenerative disorders.

  20. proBDNF Negatively Regulates Neuronal Remodeling, Synaptic Transmission, and Synaptic Plasticity in Hippocampus

    Directory of Open Access Journals (Sweden)

    Jianmin Yang

    2014-05-01

    Full Text Available Experience-dependent plasticity shapes postnatal development of neural circuits, but the mechanisms that refine dendritic arbors, remodel spines, and impair synaptic activity are poorly understood. Mature brain-derived neurotrophic factor (BDNF modulates neuronal morphology and synaptic plasticity, including long-term potentiation (LTP via TrkB activation. BDNF is initially translated as proBDNF, which binds p75NTR. In vitro, recombinant proBDNF modulates neuronal structure and alters hippocampal long-term plasticity, but the actions of endogenously expressed proBDNF are unclear. Therefore, we generated a cleavage-resistant probdnf knockin mouse. Our results demonstrate that proBDNF negatively regulates hippocampal dendritic complexity and spine density through p75NTR. Hippocampal slices from probdnf mice exhibit depressed synaptic transmission, impaired LTP, and enhanced long-term depression (LTD in area CA1. These results suggest that proBDNF acts in vivo as a biologically active factor that regulates hippocampal structure, synaptic transmission, and plasticity, effects that are distinct from those of mature BDNF.

  1. Evaluation of the Acceleration and Deceleration Phase-Rectified Slope to Detect and Improve IUGR Clinical Management

    Directory of Open Access Journals (Sweden)

    Salvatore Tagliaferri

    2015-01-01

    Full Text Available Objective. This study used a new method called Acceleration (or Deceleration Phase-Rectified Slope, APRS (or DPRS to analyze computerized Cardiotocographic (cCTG traces in intrauterine growth restriction (IUGR, in order to calculate acceleration- and deceleration-related fluctuations of the fetal heart rate, and to enhance the prediction of neonatal outcome. Method. Cardiotocograms from a population of 59 healthy and 61 IUGR fetuses from the 30th gestation week matched for gestational age were included. APRS and DPRS analysis was compared to the standard linear and nonlinear cCTG parameters. Statistical analysis was performed through the t-test, ANOVA test, Pearson correlation test and receiver operator characteristic (ROC curves (p<0,05. Results. APRS and DPRS showed high performance to discriminate between Healthy and IUGR fetuses, according to gestational week. A linear correlation with the fetal pH at birth was found in IUGR. The area under the ROC curve was 0.865 for APRS and 0.900 for DPRS before the 34th gestation week. Conclusions. APRS and DPRS could be useful in the identification and management of IUGR fetuses and in the prediction of the neonatal outcome, especially before the 34th week of gestation.

  2. Theoretical study on the rectifying performance of organoimido derivatives of hexamolybdates.

    Science.gov (United States)

    Wen, Shizheng; Yang, Guochun; Yan, Likai; Li, Haibin; Su, Zhongmin

    2013-02-25

    We design a new type of molecular diode, based on the organoimido derivatives of hexamolybdates, by exploring the rectifying performances using density functional theory combined with the non-equilibrium Green's function. Asymmetric current-voltage characteristics were obtained for the models with an unexpected large rectification ratio. The rectifying behavior can be understood by the asymmetrical shift of the transmission peak observed under different polarities. It is interesting to find that the preferred electron-transport direction in our studied system is different from that of the organic D-bridge-A system. The results show that the studied organic-inorganic hybrid systems have an intrinsically robust rectifying ratio, which should be taken into consideration in the design of the molecular diodes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Thirty-six pulse rectifier scheme based on zigzag auto-connected transformer

    Directory of Open Access Journals (Sweden)

    Xiao-Qiang Chen

    2016-03-01

    Full Text Available In this paper, a low kilo-volt-ampere rating zigzag connected autotransformer based 36-pulse rectifier system supplying vector controlled induction motor drives (VCIMD is designed, modeled and simulated. Detailed design procedure and magnetic rating calculation of the proposed autotransformer and interphase reactor is studied. Moreover, the design process of the autotransformer is modified to make it suitable for retrofit applications. Simulation results confirm that the proposed 36-pulse rectifier system is able to suppress less than 35th harmonics in the utility line current. The influence of load variation and load character is also studied to demonstrate the performance and effectiveness of the proposed 36-pulse rectifiers. A set of power quality indices at AC mains and DC link are presented to compare the performance of 6-, 24- and 36-pulse AC-DC converters.

  4. Possibility designing half-wave and full-wave molecular rectifiers by using single benzene molecule

    Science.gov (United States)

    Abbas, Mohammed A.; Hanoon, Falah H.; Al-Badry, Lafy F.

    2018-02-01

    This work focused on possibility designing half-wave and full-wave molecular rectifiers by using single and two benzene rings, respectively. The benzene rings were threaded by a magnetic flux that changes over time. The quantum interference effect was considered as the basic idea in the rectification action, the para and meta configurations were investigated. All the calculations are performed by using steady-state theoretical model, which is based on the time-dependent Hamiltonian model. The electrical conductance and the electric current are considered as DC output signals of half-wave and full-wave molecular rectifiers. The finding in this work opens up the exciting potential to use these molecular rectifiers in molecular electronics.

  5. Competitive inhibition can linearize dose-response and generate a linear rectifier.

    Science.gov (United States)

    Savir, Yonatan; Tu, Benjamin P; Springer, Michael

    2015-09-23

    Many biological responses require a dynamic range that is larger than standard bi-molecular interactions allow, yet the also ability to remain off at low input. Here we mathematically show that an enzyme reaction system involving a combination of competitive inhibition, conservation of the total level of substrate and inhibitor, and positive feedback can behave like a linear rectifier-that is, a network motif with an input-output relationship that is linearly sensitive to substrate above a threshold but unresponsive below the threshold. We propose that the evolutionarily conserved yeast SAGA histone acetylation complex may possess the proper physiological response characteristics and molecular interactions needed to perform as a linear rectifier, and we suggest potential experiments to test this hypothesis. One implication of this work is that linear responses and linear rectifiers might be easier to evolve or synthetically construct than is currently appreciated.

  6. Analysis of Three-Phase Rectifier Systems with Controlled DC-Link Current Under Unbalanced Grids

    DEFF Research Database (Denmark)

    Kumar, Dinesh; Davari, Pooya; Zare, Firuz

    2017-01-01

    Voltage unbalance is the most common disturbance in distribution networks, which give undesirable effects on many grid connected power electronics systems including Adjustable Speed Drive (ASD). Severe voltage unbalance can force three-phase rectifiers into almost single-phase operation, which...... degrades the grid power quality and also imposes a significant negative impact on the ASD system. This major power quality issue affecting the conventional rectifiers can be attenuated by controlling the DC-link current based on an Electronic Inductor (EI) technique. The purpose of this digest...... is to analyze and compare the performance of an EI with a conventional three-phase rectifier under unbalanced grid conditions. Experimental and simulation results validate the proposed mathematical modelling. Further analysis and benchmarking will be provided in the final paper....

  7. Countermeasures for electrolytic corrosion - Part II: Implementation of a rapid potential-controlled rectifier

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae-Hyun; Kim, Dae-Kyeong; Lee, Hyun-Goo; Ha, Yoon-Cheol; Bae, Jeong-Hyo [Underground Systems Group, Korea Electrotechnology Research Institute, 28-1 Sungju-dong, Changwon, 641-120 (Korea)

    2004-07-01

    In electrolytic interference circumstances such as underground pipelines in the vicinity of DC electrified railroads, drainage method or impressed current cathodic protection method has been widely used as a countermeasure for the electrolytic corrosion. In the former method, forced or polarized drainage is commonly adopted and in the latter, the phase-controlled rectifier with thyristor is in common use. Both methods, however, does not show as the optimal measure for the integrity of the pipeline, since the pipe-to-soil potential fluctuates highly positive to the cathodic protection criterion. In particular, as the potential of the pipeline near the railroad varies rapidly, a new rapidly responding countermeasure is necessary. In this paper, we introduce a new rapid potential controlled rectifier and report the result in field tests. Comparison with the existing forced drainage method is also made. The pipe-to-soil potential data show the effectiveness of the rapid potential-controlled rectifier. (authors)

  8. Timed Synaptic Inhibition Shapes NMDA Spikes, Influencing Local Dendritic Processing and Global I/O Properties of Cortical Neurons

    Directory of Open Access Journals (Sweden)

    Michael Doron

    2017-11-01

    Full Text Available The NMDA spike is a long-lasting nonlinear phenomenon initiated locally in the dendritic branches of a variety of cortical neurons. It plays a key role in synaptic plasticity and in single-neuron computations. Combining dynamic system theory and computational approaches, we now explore how the timing of synaptic inhibition affects the NMDA spike and its associated membrane current. When impinging on its early phase, individual inhibitory synapses strongly, but transiently, dampen the NMDA spike; later inhibition prematurely terminates it. A single inhibitory synapse reduces the NMDA-mediated Ca2+ current, a key player in plasticity, by up to 45%. NMDA spikes in distal dendritic branches/spines are longer-lasting and more resilient to inhibition, enhancing synaptic plasticity at these branches. We conclude that NMDA spikes are highly sensitive to dendritic inhibition; sparse weak inhibition can finely tune synaptic plasticity both locally at the dendritic branch level and globally at the level of the neuron’s output.

  9. Microrectenna: A Terahertz Antenna and Rectifier on a Chip

    Science.gov (United States)

    Siegel, Peter

    2007-01-01

    A microrectenna that would operate at a frequency of 2.5 THz has been designed and partially fabricated. The circuit is intended to be a prototype of an extremely compact device that could be used to convert radio-beamed power to DC to drive microdevices (see Figure 1). The microrectenna (see Figure 2) circuit consists of an antenna, a diode rectifier and a DC output port. The antenna consists of a twin slot array in a conducting ground plane (denoted the antenna ground plane) over an enclosed quarter-wavelength-thick resonant cavity (denoted the reflecting ground plane). The circuit also contains a planar high-frequency low-parasitic Schottky-barrier diode, a low-impedance microstrip transmission line, capacitors, and contact beam leads. The entire 3-D circuit is fabricated monolithically from a single GaAs wafer. The resonant cavity renders the slot radiation pattern unidirectional with a half-power beam width of about 65. A unique metal mesh on the rear of the wafer forms the backplate for the cavity but allows the GaAs to be wet etched from the rear surface of the twin slot antennas and ground plane. The beam leads protrude past the edge of the chip and are used both to mount the microrectenna and to make the DC electrical connection with external circuitry. The antenna ground plane and the components on top of it are formed on a 2- m thick GaAs membrane that is grown in the initial wafer MBE (molecular beam epitaxy) process. The side walls of the antenna cavity are not metal coated and, hence, would cause some loss of power; however, the relatively high permittivity (epsilon=13) of the GaAs keeps the cavity modes well confined, without the usual surface-wave losses associated with thick dielectric substrates. The Schottky-barrier diode has the usual submicron dimensions associated with THz operation and is formed in a mesa process above the antenna ground plane. The diode is connected at the midpoint of a microstrip transmission line, which is formed on 1- m

  10. Robust and reliable rectifier based on electronic inductor with improved performance

    DEFF Research Database (Denmark)

    Singh, Yash Veer; Rasmussen, Peter Omand; Andersen, Torben Ole

    2014-01-01

    of the rectifier, peak to peak voltage ripples to the front end of the inverter reduces significantly by the ESI, and it increases lifetime of the capacitor connected at the output and also reduces the voltage stress of the active power semiconductors of the inverter if any connected to the output. In this paper...... harmonic distortions (THDs) of the ac mains current in a three phase diode bridge rectifier. The ESI reduces the low frequency ripples and controls the intermediate dc-link voltage to a dc value and peak value of the mains current also reduces. In case of an inverter connected to the output...

  11. Rectifier Design Challenges for RF Wireless Power Transfer and Energy Harvesting Systems

    Directory of Open Access Journals (Sweden)

    A. Collado

    2017-06-01

    Full Text Available The design of wireless power transfer (WPT and energy harvesting (EH solutions poses different challenges towards achieving maximum RF-DC conversion efficiency in these systems. This paper covers several selected challenges when developing WPT and electromagnetic EH solutions, such as the design of multiband and broadband rectifiers, the minimization of the effect that load and input power variations may have on the system performance and finally the most optimum power combining mechanisms that can be used when dealing with multi-element rectifiers.

  12. High Efficiency Three-phase Power Factor Correction Rectifier using Wide Band-Gap Devices

    DEFF Research Database (Denmark)

    Kouchaki, Alireza

    Improving the conversion efficiency of power factor correction (PFC) rectifiers has become compelling due to their wide applications such as adjustable speed drives, uninterruptible power supplies (UPS), and battery chargers for electric vehicles (EVs). The attention to PFCs has increased even more....... Therefore, current controllers are also important to be investigated in this project. In this PhD research work, a comprehensive design of a two-level three-phase PFC rectifier using silicon-carbide (SiC) switches to achieve high efficiency is presented. The work is divided into two main parts: 1) Optimum...

  13. Modeling and control of three phase rectifier with electronic smoothing inductor

    DEFF Research Database (Denmark)

    Singh, Yash Veer; Rasmussen, Peter Omand; Andersen, Torben Ole

    2011-01-01

    This paper presents a simple, direct method for deriving the approximate, small-signal, average model and control strategy for three-phase diode bridge rectifier operating with electronic smoothing technique. Electronic smoothing inductor (ESI) performs the function of an inductor that has...... controlled variable impedance. This increases power factor (PF) and reduces total harmonic distortions (THDs) in mains current. The ESI based rectifier enables compact and cost effective design of three phase electric drive as size of passive components is reduced significantly. In order to carry out...

  14. Synaptic Democracy and Vesicular Transport in Axons

    Science.gov (United States)

    Bressloff, Paul C.; Levien, Ethan

    2015-04-01

    Synaptic democracy concerns the general problem of how regions of an axon or dendrite far from the cell body (soma) of a neuron can play an effective role in neuronal function. For example, stimulated synapses far from the soma are unlikely to influence the firing of a neuron unless some sort of active dendritic processing occurs. Analogously, the motor-driven transport of newly synthesized proteins from the soma to presynaptic targets along the axon tends to favor the delivery of resources to proximal synapses. Both of these phenomena reflect fundamental limitations of transport processes based on a localized source. In this Letter, we show that a more democratic distribution of proteins along an axon can be achieved by making the transport process less efficient. This involves two components: bidirectional or "stop-and-go" motor transport (which can be modeled in terms of advection-diffusion), and reversible interactions between motor-cargo complexes and synaptic targets. Both of these features have recently been observed experimentally. Our model suggests that, just as in human societies, there needs to be a balance between "efficiency" and "equality".

  15. Nonlinear Elliptic Differential Equations with Multivalued Nonlinearities

    Indian Academy of Sciences (India)

    In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is defined on all R R . Assuming the existence of an upper and of a lower ...

  16. Subcellular localization of the delayed rectifier K(+) channels KCNQ1 and ERG1 in the rat heart

    DEFF Research Database (Denmark)

    Rasmussen, Hanne Borger; Møller, Morten; Knaus, Hans-Günther

    2003-01-01

    In the heart, several K(+) channels are responsible for the repolarization of the cardiac action potential, including transient outward and delayed rectifier K(+) currents. In the present study, the cellular and subcellular localization of the two delayed rectifier K(+) channels, KCNQ1 and ether...

  17. Inward rectifier K+ channel and T-type Ca2+ channel contribute to enhancement of GABAergic transmission induced by β1-adrenoceptor in the prefrontal cortex.

    Science.gov (United States)

    Luo, Fei; Zheng, Jian; Sun, Xuan; Tang, Hua

    2017-02-01

    The functions of prefrontal cortex (PFC) are sensitive to norepinephrine (NE). Endogenously released NE influences synaptic transmission through activation of different subtypes of adrenergic receptors in PFC including α 1 , α 2 , β 1 or β 2 -adrenoceptor. Our recent study has revealed that β 1 -adrenoceptor (β 1 -AR) activation modulates glutamatergic transmission in the PFC, whereas the roles of β 1 -AR in GABAergic transmission are elusive. In the current study, we probed the effects of the β 1 -AR agonist dobutamine (Dobu) on GABAergic transmission onto pyramidal neurons in the PFC of juvenile rats. Dobu increased both the frequency and amplitude of miniature IPSCs (mIPSCs). Ca 2+ influx through T-type voltage-gated Ca 2+ channel was required for Dobu-enhanced mIPSC frequency. We also found that Dobu facilitated GABA release probability and the number of releasable vesicles through regulating T-type Ca 2+ channel. Dobu depolarized GABAergic fast-spiking (FS) interneurons with no effects on the firing rate of action potentials (APs) of interneurons. Dobu-induced depolarization of FS interneurons required inward rectifier K + channel (Kir). Our results suggest that Dobu increase GABA release via inhibition of Kir, which further depolarizes FS interneurons resulting in Ca 2+ influx via T-type Ca 2+ channel. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. A presynaptic role for PKA in synaptic tagging and memory.

    Science.gov (United States)

    Park, Alan Jung; Havekes, Robbert; Choi, Jennifer Hk; Luczak, Vince; Nie, Ting; Huang, Ted; Abel, Ted

    2014-10-01

    Protein kinase A (PKA) and other signaling molecules are spatially restricted within neurons by A-kinase anchoring proteins (AKAPs). Although studies on compartmentalized PKA signaling have focused on postsynaptic mechanisms, presynaptically anchored PKA may contribute to synaptic plasticity and memory because PKA also regulates presynaptic transmitter release. Here, we examine this issue using genetic and pharmacological application of Ht31, a PKA anchoring disrupting peptide. At the hippocampal Schaffer collateral CA3-CA1 synapse, Ht31 treatment elicits a rapid decay of synaptic responses to repetitive stimuli, indicating a fast depletion of the readily releasable pool of synaptic vesicles. The interaction between PKA and proteins involved in producing this pool of synaptic vesicles is supported by biochemical assays showing that synaptic vesicle protein 2 (SV2), Rim1, and SNAP25 are components of a complex that interacts with cAMP. Moreover, acute treatment with Ht31 reduces the levels of SV2. Finally, experiments with transgenic mouse lines, which express Ht31 in excitatory neurons at the Schaffer collateral CA3-CA1 synapse, highlight a requirement for presynaptically anchored PKA in pathway-specific synaptic tagging and long-term contextual fear memory. These results suggest that a presynaptically compartmentalized PKA is critical for synaptic plasticity and memory by regulating the readily releasable pool of synaptic vesicles. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Glutamatergic synaptic plasticity in the mesocorticolimbic system in addiction

    Directory of Open Access Journals (Sweden)

    Aile evan Huijstee

    2015-01-01

    Full Text Available Addictive drugs remodel the brain’s reward circuitry, the mesocorticolimbic dopamine system, by inducing widespread adaptations of glutamatergic synapses. This drug-induced synaptic plasticity is thought to contribute to both the development and the persistence of addiction. This review highlights the synaptic modifications that are induced by in vivo exposure to addictive drugs and describes how these drug-induced synaptic changes may contribute to the different components of addictive behaviour, such as compulsive drug use despite negative consequences and relapse. Initially, exposure to an addictive drug induces synaptic changes in the ventral tegmental area (VTA. This drug-induced synaptic potentiation in the VTA subsequently triggers synaptic changes in downstream areas of the mesocorticolimbic system, such as the nucleus accumbens (NAc and the prefrontal cortex (PFC, with further drug exposure. These glutamatergic synaptic alterations are then thought to mediate many of the behavioural symptoms that characterize addiction. The later stages of glutamatergic synaptic plasticity in the NAc and in particular in the PFC play a role in maintaining addiction and drive relapse to drug-taking induced by drug-associated cues. Remodelling of PFC glutamatergic circuits can persist into adulthood, causing a lasting vulnerability to relapse. We will discuss how these neurobiological changes produced by drugs of abuse may provide novel targets for potential treatment strategies for addiction.

  20. Phosphodiesterase Inhibition to Target the Synaptic Dysfunction in Alzheimer's Disease

    Science.gov (United States)

    Bales, Kelly R.; Plath, Niels; Svenstrup, Niels; Menniti, Frank S.

    Alzheimer's Disease (AD) is a disease of synaptic dysfunction that ultimately proceeds to neuronal death. There is a wealth of evidence that indicates the final common mediator of this neurotoxic process is the formation and actions on synaptotoxic b-amyloid (Aβ). The premise in this review is that synaptic dysfunction may also be an initiating factor in for AD and promote synaptotoxic Aβ formation. This latter hypothesis is consistent with the fact that the most common risk factors for AD, apolipoprotein E (ApoE) allele status, age, education, and fitness, encompass suboptimal synaptic function. Thus, the synaptic dysfunction in AD may be both cause and effect, and remediating synaptic dysfunction in AD may have acute effects on the symptoms present at the initiation of therapy and also slow disease progression. The cyclic nucleotide (cAMP and cGMP) signaling systems are intimately involved in the regulation of synaptic homeostasis. The phosphodiesterases (PDEs) are a superfamily of enzymes that critically regulate spatial and temporal aspects of cyclic nucleotide signaling through metabolic inactivation of cAMP and cGMP. Thus, targeting the PDEs to promote improved synaptic function, or 'synaptic resilience', may be an effective and facile approach to new symptomatic and disease modifying therapies for AD. There continues to be a significant drug discovery effort aimed at discovering PDE inhibitors to treat a variety of neuropsychiatric disorders. Here we review the current status of those efforts as they relate to potential new therapies for AD.

  1. Synaptogenic proteins and synaptic organizers: "many hands make light work".

    Science.gov (United States)

    Brose, Nils

    2009-03-12

    Synaptogenesis is thought to be mediated by cell adhesion proteins, which induce the initial contact between an axon and its target cell and subsequently recruit and organize the presynaptic and postsynaptic protein machinery required for synaptic transmission. A new study by Linhoff and colleagues in this issue of Neuron identifies adhesion proteins of the LRRTM family as novel synaptic organizers.

  2. Synaptic Tagging, Evaluation of Memories, and the Distal Reward Problem

    Science.gov (United States)

    Papper, Marc; Kempter, Richard; Leibold, Christian

    2011-01-01

    Long-term synaptic plasticity exhibits distinct phases. The synaptic tagging hypothesis suggests an early phase in which synapses are prepared, or "tagged," for protein capture, and a late phase in which those proteins are integrated into the synapses to achieve memory consolidation. The synapse specificity of the tags is consistent with…

  3. Glutamatergic synaptic plasticity in the mesocorticolimbic system in addiction

    Science.gov (United States)

    van Huijstee, Aile N.; Mansvelder, Huibert D.

    2015-01-01

    Addictive drugs remodel the brain’s reward circuitry, the mesocorticolimbic dopamine (DA) system, by inducing widespread adaptations of glutamatergic synapses. This drug-induced synaptic plasticity is thought to contribute to both the development and the persistence of addiction. This review highlights the synaptic modifications that are induced by in vivo exposure to addictive drugs and describes how these drug-induced synaptic changes may contribute to the different components of addictive behavior, such as compulsive drug use despite negative consequences and relapse. Initially, exposure to an addictive drug induces synaptic changes in the ventral tegmental area (VTA). This drug-induced synaptic potentiation in the VTA subsequently triggers synaptic changes in downstream areas of the mesocorticolimbic system, such as the nucleus accumbens (NAc) and the prefrontal cortex (PFC), with further drug exposure. These glutamatergic synaptic alterations are then thought to mediate many of the behavioral symptoms that characterize addiction. The later stages of glutamatergic synaptic plasticity in the NAc and in particular in the PFC play a role in maintaining addiction and drive relapse to drug-taking induced by drug-associated cues. Remodeling of PFC glutamatergic circuits can persist into adulthood, causing a lasting vulnerability to relapse. We will discuss how these neurobiological changes produced by drugs of abuse may provide novel targets for potential treatment strategies for addiction. PMID:25653591

  4. Modulation of synaptic plasticity by stress hormone associates with plastic alteration of synaptic NMDA receptor in the adult hippocampus.

    Directory of Open Access Journals (Sweden)

    Yiu Chung Tse

    Full Text Available Stress exerts a profound impact on learning and memory, in part, through the actions of adrenal corticosterone (CORT on synaptic plasticity, a cellular model of learning and memory. Increasing findings suggest that CORT exerts its impact on synaptic plasticity by altering the functional properties of glutamate receptors, which include changes in the motility and function of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid subtype of glutamate receptor (AMPAR that are responsible for the expression of synaptic plasticity. Here we provide evidence that CORT could also regulate synaptic plasticity by modulating the function of synaptic N-methyl-D-aspartate receptors (NMDARs, which mediate the induction of synaptic plasticity. We found that stress level CORT applied to adult rat hippocampal slices potentiated evoked NMDAR-mediated synaptic responses within 30 min. Surprisingly, following this fast-onset change, we observed a slow-onset (>1 hour after termination of CORT exposure increase in synaptic expression of GluN2A-containing NMDARs. To investigate the consequences of the distinct fast- and slow-onset modulation of NMDARs for synaptic plasticity, we examined the formation of long-term potentiation (LTP and long-term depression (LTD within relevant time windows. Paralleling the increased NMDAR function, both LTP and LTD were facilitated during CORT treatment. However, 1-2 hours after CORT treatment when synaptic expression of GluN2A-containing NMDARs is increased, bidirectional plasticity was no longer facilitated. Our findings reveal the remarkable plasticity of NMDARs in the adult hippocampus in response to CORT. CORT-mediated slow-onset increase in GluN2A in hippocampal synapses could be a homeostatic mechanism to normalize synaptic plasticity following fast-onset stress-induced facilitation.

  5. MPTP-meditated hippocampal dopamine deprivation modulates synaptic transmission and activity-dependent synaptic plasticity

    International Nuclear Information System (INIS)

    Zhu Guoqi; Chen Ying; Huang Yuying; Li Qinglin; Behnisch, Thomas

    2011-01-01

    Parkinson's disease (PD)-like symptoms including learning deficits are inducible by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Therefore, it is possible that MPTP may disturb hippocampal memory processing by modulation of dopamine (DA)- and activity-dependent synaptic plasticity. We demonstrate here that intraperitoneal (i.p.) MPTP injection reduces the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) within 7 days. Subsequently, the TH expression level in SN and hippocampus and the amount of DA and its metabolite DOPAC in striatum and hippocampus decrease. DA depletion does not alter basal synaptic transmission and changes pair-pulse facilitation (PPF) of field excitatory postsynaptic potentials (fEPSPs) only at the 30 ms inter-pulse interval. In addition, the induction of long-term potentiation (LTP) is impaired whereas the duration of long-term depression (LTD) becomes prolonged. Since both LTP and LTD depend critically on activation of NMDA and DA receptors, we also tested the effect of DA depletion on NMDA receptor-mediated synaptic transmission. Seven days after MPTP injection, the NMDA receptor-mediated fEPSPs are decreased by about 23%. Blocking the NMDA receptor-mediated fEPSP does not mimic the MPTP-LTP. Only co-application of D1/D5 and NMDA receptor antagonists during tetanization resembled the time course of fEPSP potentiation as observed 7 days after i.p. MPTP injection. Together, our data demonstrate that MPTP-induced degeneration of DA neurons and the subsequent hippocampal DA depletion alter NMDA receptor-mediated synaptic transmission and activity-dependent synaptic plasticity. - Highlights: → I.p. MPTP-injection mediates death of dopaminergic neurons. → I.p. MPTP-injection depletes DA and DOPAC in striatum and hippocampus. → I.p. MPTP-injection does not alter basal synaptic transmission. → Reduction of LTP and enhancement of LTD after i.p. MPTP-injection. → Attenuation of NMDA-receptors mediated

  6. Comparative Evaluation of Three-Phase Isolated Matrix-Type PFC Rectifier Concepts for High Efficiency 380VDC Supplies of Future Telco and Data Centers

    DEFF Research Database (Denmark)

    Cortes, Patricio; Bortis, Dominik; Pittini, Riccardo

    2014-01-01

    rectifier and in many cases a mains transformer is used to provide galvanic isolation. In order to achieve a high efficiency in the DC voltage generation and to implement the required isolation, a single-stage concept, such as a matrix-type rectifier that enables PFC functionality and galvanic isolation...... in a single conversion, can be beneficial. In addition, due to the fact that with the matrix-type rectifier the galvanic isolation is performed with a high-frequency transformer, this results in a more compact rectifier system compared to conventional systems where the mains-frequency isolation transformer...... is located at the input of the PFC rectifier. In this paper, an overview of isolated matrix-type PFC rectifier topologies is given and a new converter circuit is proposed, analyzed and comparatively evaluated against another promising PFC rectifier concept, the phase-modular IMY-rectifier....

  7. Nicotinic mechanisms influencing synaptic plasticity in the hippocampus

    Institute of Scientific and Technical Information of China (English)

    Andon Nicholas PLACZEK; Tao A ZHANG; John Anthony DANI

    2009-01-01

    Nicotinic acetylcholine receptors (nAChRs) are expressed throughout the hippocampus, and nicotinic signaling plays an important role in neuronal function. In the context of learning and memory related behaviors associated with hippocampal function, a potentially significant feature of nAChR activity is the impact it has on synaptic plasticity. Synaptic plasticity in hippocampal neurons has long been considered a contributing cellular mechanism of learning and memory. These same kinds of cellular mechanisms are a factor in the development of nicotine addiction. Nicotinic signaling has been demonstrated by in vitro studies to affect synaptic plasticity in hippocampal neurons via multiple steps, and the signaling has also been shown to evoke synaptic plasticity in vivo. This review focuses on the nAChRs subtypes that contribute to hippocampal synaptic plasticity at the cellular and circuit level. It also considers nicotinic influences over long-term changes in the hippocampus that may contribute to addiction.

  8. Synaptic transmission block by presynaptic injection of oligomeric amyloid beta

    Science.gov (United States)

    Moreno, Herman; Yu, Eunah; Pigino, Gustavo; Hernandez, Alejandro I.; Kim, Natalia; Moreira, Jorge E.; Sugimori, Mutsuyuki; Llinás, Rodolfo R.

    2009-01-01

    Early Alzheimer's disease (AD) pathophysiology is characterized by synaptic changes induced by degradation products of amyloid precursor protein (APP). The exact mechanisms of such modulation are unknown. Here, we report that nanomolar concentrations of intraaxonal oligomeric (o)Aβ42, but not oAβ40 or extracellular oAβ42, acutely inhibited synaptic transmission at the squid giant synapse. Further characterization of this phenotype demonstrated that presynaptic calcium currents were unaffected. However, electron microscopy experiments revealed diminished docked synaptic vesicles in oAβ42-microinjected terminals, without affecting clathrin-coated vesicles. The molecular events of this modulation involved casein kinase 2 and the synaptic vesicle rapid endocytosis pathway. These findings open the possibility of a new therapeutic target aimed at ameliorating synaptic dysfunction in AD. PMID:19304802

  9. [Involvement of aquaporin-4 in synaptic plasticity, learning and memory].

    Science.gov (United States)

    Wu, Xin; Gao, Jian-Feng

    2017-06-25

    Aquaporin-4 (AQP-4) is the predominant water channel in the central nervous system (CNS) and primarily expressed in astrocytes. Astrocytes have been generally believed to play important roles in regulating synaptic plasticity and information processing. However, the role of AQP-4 in regulating synaptic plasticity, learning and memory, cognitive function is only beginning to be investigated. It is well known that synaptic plasticity is the prime candidate for mediating of learning and memory. Long term potentiation (LTP) and long term depression (LTD) are two forms of synaptic plasticity, and they share some but not all the properties and mechanisms. Hippocampus is a part of limbic system that is particularly important in regulation of learning and memory. This article is to review some research progresses of the function of AQP-4 in synaptic plasticity, learning and memory, and propose the possible role of AQP-4 as a new target in the treatment of cognitive dysfunction.

  10. Alteration of synaptic connectivity of oligodendrocyte precursor cells following demyelination

    Science.gov (United States)

    Sahel, Aurélia; Ortiz, Fernando C.; Kerninon, Christophe; Maldonado, Paloma P.; Angulo, María Cecilia; Nait-Oumesmar, Brahim

    2015-01-01

    Oligodendrocyte precursor cells (OPCs) are a major source of remyelinating oligodendrocytes in demyelinating diseases such as Multiple Sclerosis (MS). While OPCs are innervated by unmyelinated axons in the normal brain, the fate of such synaptic contacts after demyelination is still unclear. By combining electrophysiology and immunostainings in different transgenic mice expressing fluorescent reporters, we studied the synaptic innervation of OPCs in the model of lysolecithin (LPC)-induced demyelination of corpus callosum. Synaptic innervation of reactivated OPCs in the lesion was revealed by the presence of AMPA receptor-mediated synaptic currents, VGluT1+ axon-OPC contacts in 3D confocal reconstructions and synaptic junctions observed by electron microscopy. Moreover, 3D confocal reconstructions of VGluT1 and NG2 immunolabeling showed the existence of glutamatergic axon-OPC contacts in post-mortem MS lesions. Interestingly, patch-clamp recordings in LPC-induced lesions demonstrated a drastic decrease in spontaneous synaptic activity of OPCs early after demyelination that was not caused by an impaired conduction of compound action potentials. A reduction in synaptic connectivity was confirmed by the lack of VGluT1+ axon-OPC contacts in virtually all rapidly proliferating OPCs stained with EdU (50-ethynyl-20-deoxyuridine). At the end of the massive proliferation phase in lesions, the proportion of innervated OPCs rapidly recovers, although the frequency of spontaneous synaptic currents did not reach control levels. In conclusion, our results demonstrate that newly-generated OPCs do not receive synaptic inputs during their active proliferation after demyelination, but gain synapses during the remyelination process. Hence, glutamatergic synaptic inputs may contribute to inhibit OPC proliferation and might have a physiopathological relevance in demyelinating disorders. PMID:25852473

  11. Power converter for raindrop energy harvesting application: Half-wave rectifier

    Science.gov (United States)

    Izrin, Izhab Muhammad; Dahari, Zuraini

    2017-10-01

    Harvesting raindrop energy by capturing vibration from impact of raindrop have been explored extensively. Basically, raindrop energy is generated by converting the kinetic energy of raindrop into electrical energy by using polyvinylidene fluoride (PVDF) piezoelectric. In this paper, a power converter using half-wave rectifier for raindrop harvesting energy application is designed and proposed to convert damping alternating current (AC) generated by PVDF into direct current (DC). This research presents parameter analysis of raindrop simulation used in the experiment and resistive load effect on half-wave rectifier converter. The experiment is conducted by using artificial raindrop from the height of 1.3 m to simulate the effect of different resistive load on the output of half-wave rectifier converter. The results of the 0.68 MΩ resistive load showed the best performance of the half-wave rectifier converter used in raindrop harvesting energy system, which generated 3.18 Vaverage. The peak instantaneous output generated from this experiment is 15.36 µW.

  12. Rectifying effect of heterojunctions between metals and doped conducting polymer nanostructure pellets

    International Nuclear Information System (INIS)

    Long Yunze; Yin Zhihua; Hui Wen; Chen Zhaojia; Wan Meixiang

    2008-01-01

    This paper reports that the Schottky junctions between low work function metals (e.g. Al and In) and doped semiconducting polymer pellets (e.g. polyaniline (PANI) microsphere pellet and polypyrrole (PPy) nanotube pellet) have been prepared and studied. Since Ag is a high work function metal which can make an ohmic contact with polymer, silver paste was used to fabricate the electrodes. The Al/PANI/Ag heterojunction shows an obvious rectifying effect as shown in I – V characteristic curves (rectifying ratio γ = 5 at ±6 V bias at room temperature). As compared to the Al/PANI/Ag, the heterojunction between In and PANI (In/PANI/Ag) exhibits a lower rectifying ratio γ = 1.6 at ±2 V bias at room temperature. In addition, rectifying effect was also observed in the heterojunctions Al/PPy/Ag (γ = 3.2 at ±1.6 V bias) and In/PPy/Ag (γ = 1.2 at ±3.0 V bias). The results were discussed in terms of thermoionic emission theory. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  13. Connection of OWPPs to HVDC networks using VSCs and Diode Rectifiers: an Overview

    DEFF Research Database (Denmark)

    Saborío-Romano, Oscar; Bidadfar, Ali; Göksu, Ömer

    This paper provides an overview of two technologies for connecting offshore wind power plants (offshore WPPs, OWPPs) to high-voltage direct current (HVDC) networks: voltage source converters (VSCs) and diode rectifiers (DRs). Current grid code requirements for the connection of such power plants...

  14. Active and reactive power control of a current-source PWM-rectifier using space vectors

    Energy Technology Data Exchange (ETDEWEB)

    Salo, M.; Tuusa, H. [Tampere University of Technology (Finland). Department of Electrical Engineering, Power Electronics

    1997-12-31

    In this paper the current-source PWM-rectifier with active and reactive power control is presented. The control system is realized using space vector methods. Also, compensation of the reactive power drawn by the line filter is discussed. Some simulation results are shown. (orig.) 8 refs.

  15. Self-Biased Differential Rectifier with Enhanced Dynamic Range for Wireless Powering

    KAUST Repository

    Ouda, Mahmoud H.; Khalil, Waleed; Salama, Khaled N.

    2016-01-01

    A self-biased, cross-coupled, differential rectifier is proposed with enhanced power-conversion efficiency over an extended range of input power. A prototype is designed for UHF 433MHz RF power-harvesting applications and is implemented using 0.18μm

  16. Electric vehicle battery charging algorithm using PMSM windings and an inverter as an active rectifier

    DEFF Research Database (Denmark)

    Zaja, Mario; Oprea, Matei-lon; Suárez, Carlos Gómez

    2014-01-01

    for battery charging. Alternatively, charging could be done using the motor windings as grid side inductors and controlling the inverter to operate as an active boost rectifier. The challenge in this approach is the unequal phase inductances which depend on the rotor position. Another problem appears when...... an integrated charger control algorithm to charge the battery through a permanent magnet synchronous machine (PMSM) windings....

  17. 28.3THz bowtie antenna integrated rectifier for infrared energy harvesting

    KAUST Repository

    Gadalla, Mena N.; Shamim, Atif

    2014-01-01

    The design, fabrication and characterization of an asymmetric 28.3 THz antenna integrated rectifier (rectenna) using Au/Al2O3/Pt is presented. The rectenna design comprises a sharp tip bowtie antenna and a tunneling Metal-insulator-Metal (MIM) diode

  18. Effect of ethanol at clinically relevant concentrations on atrial inward rectifier potassium current sensitive to acetylcholine

    Czech Academy of Sciences Publication Activity Database

    Bébarová, M.; Matejovič, P.; Pásek, Michal; Hořáková, Z.; Hošek, J.; Šimurdová, M.; Šimurda, J.

    2016-01-01

    Roč. 389, č. 10 (2016), s. 1049-1058 ISSN 0028-1298 Institutional support: RVO:61388998 Keywords : arrhythmias * atrial cardiomyocyte * inward rectifier potasssium current * ethanol * rat atrial cell model Subject RIV: BO - Biophysics Impact factor: 2.558, year: 2016

  19. Current Mode Full-Wave Rectifier Based on a Single MZC-CDTA

    Directory of Open Access Journals (Sweden)

    Neeta Pandey

    2013-01-01

    Full Text Available This paper presents a current mode full-wave rectifier based on single modified Z copy current difference transconductance amplifier (MZC-CDTA and two switches. The circuit is simple and is suitable for IC implementation. The functionality of the circuit is verified with SPICE simulation using 0.35 μm TSMC CMOS technology parameters.

  20. US Mains Stacked Very High Frequency Self-oscillating Resonant Power Converter with Unified Rectifier

    DEFF Research Database (Denmark)

    Pedersen, Jeppe Arnsdorf; Madsen, Mickey Pierre; Mønster, Jakob Døllner

    2016-01-01

    This paper describes a Very High Frequency (VHF) converter made with three Class-E inverters and a single ClassDE rectifier. The converter is designed for the US mains (120 V, 60 Hz) and can deliver 9 W to a 60 V LED. The converter has a switching frequency of 37 MHz and achieves an efficiency...

  1. Modeling removal of accumulated potassium from T-tubules by inward rectifier potassium channels

    NARCIS (Netherlands)

    Wallinga, W.; Vliek, M.; Wienk, E.D.; Alberink, M.J.; Ypey, D.L.; Ypey, D.L.

    1996-01-01

    The membrane models of Cannon et al. (1993) and Alberink et al. (1995) for mammalian skeletal muscle fibers are based upon Hodgkin-Huxley descriptions of sodium, potassium delayed rectifier and leak conductances and the capacitive current taking into account fast inactivation of sodium channels. Now

  2. Predictive Duty Cycle Control of Three-Phase Active-Front-End Rectifiers

    DEFF Research Database (Denmark)

    Song, Zhanfeng; Tian, Yanjun; Chen, Wei

    2016-01-01

    This paper proposed an on-line optimizing duty cycle control approach for three-phase active-front-end rectifiers, aiming to obtain the optimal control actions under different operating conditions. Similar to finite control set model predictive control strategy, a cost function previously...

  3. Design of the LC+trap filter for a current source rectifier

    DEFF Research Database (Denmark)

    Min, Huang; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    This paper investigates an LC + trap filter for current source converters to improve the switching harmonic attenuation. The resonant frequency characteristics of the filter of current source rectifier are analyzed. A filter design procedure is proposed based on the input power factor, filter...

  4. Ac loss measurements on a superconducting transformer for a 25 kA superconducting rectifier

    NARCIS (Netherlands)

    ten Kate, Herman H.J.; Mulders, J.M.; de Reuver, J.L.; van de Klundert, L.J.M.

    1984-01-01

    Ac loss measurements have been performed on a superconducting transformer. The transformer is a part of a 25 kA thermally switched superconducting rectifier operating at a frequency of 0.1 Hz. The loss measurements have been automatized by means of a microcomputer sampling four relevant signals and

  5. Development of a thermally switched superconducting rectifier for 100 kA

    NARCIS (Netherlands)

    Mulder, G.B.J.; Mulder, G.B.J.; ten Kate, Herman H.J.; Krooshoop, Hendrikus J.G.; van de Klundert, L.J.M.; van de Klundert, L.J.M.

    1991-01-01

    A full-wave superconducting rectifier for 100 kA has been developed. Typical design values of this device are: a secondary current of 100 kA, a primary amplitude of 20 A, an operating frequency of 0.5 Hz, and an average power on the order of 100 W. The rectification is achieved by means of thermally

  6. Development of a 50-60 Hz thermally switched superconducting rectifier

    NARCIS (Netherlands)

    Chevtchenko, O.A.; ten Kate, Herman H.J.; Krooshoop, Hendrikus J.G.; Markovsky, N.V.; Mulder, G.B.J.; Mulder, G.B.J.

    1993-01-01

    A full-wave thermally switched superconducting rectifier, able to operate directly from the mains at the 50-60-Hz frequency, has been developed. Typical design output values of this device are a current of 300 A, a voltage of up to 1 V, an average power of up to 100 VA, and an efficiency better than

  7. A high-efficiency low-voltage CMOS rectifier for harvesting energy in implantable devices.

    Science.gov (United States)

    Hashemi, S Saeid; Sawan, Mohamad; Savaria, Yvon

    2012-08-01

    We present, in this paper, a new full-wave CMOS rectifier dedicated for wirelessly-powered low-voltage biomedical implants. It uses bootstrapped capacitors to reduce the effective threshold voltage of selected MOS switches. It achieves a significant increase in its overall power efficiency and low voltage-drop. Therefore, the rectifier is good for applications with low-voltage power supplies and large load current. The rectifier topology does not require complex circuit design. The highest voltages available in the circuit are used to drive the gates of selected transistors in order to reduce leakage current and to lower their channel on-resistance, while having high transconductance. The proposed rectifier was fabricated using the standard TSMC 0.18 μm CMOS process. When connected to a sinusoidal source of 3.3 V peak amplitude, it allows improving the overall power efficiency by 11% compared to the best recently published results given by a gate cross-coupled-based structure.

  8. Self-Oscillating Resonant Gate Drive for Resonant Inverters and Rectifiers Composed Solely of Passive Components

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Pedersen, Jeppe Arnsdorf; Knott, Arnold

    2014-01-01

    to improve the performance of the gate drive and how the gate drive can be implemented in a class E inverter, a class DE inverter and in class E inverter with a synchronous class E rectifier. The paper shows practical implementations of all the proposed inverters and converters operating in the Very High...

  9. Impedance-based Analysis of DC Link Control in Voltage Source Rectifiers

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2018-01-01

    This paper analyzes the dynamics influences of the outer dc link control in the voltage source rectifiers based on the impedance model. The ac-dc interactions are firstly presented by means of full order small signal model in dq frame, which shows the input voltage and load condition are the two...

  10. Accumulation of slowly activating delayed rectifier potassium current (IKs) in canine ventricular myocytes

    DEFF Research Database (Denmark)

    Stengl, Milan; Volders, Paul G A; Thomsen, Morten Bækgaard

    2003-01-01

    In guinea-pig ventricular myocytes, in which the deactivation of slowly activating delayed rectifier potassium current (IKs) is slow, IKs can be increased by rapid pacing as a result of incomplete deactivation and subsequent current accumulation. Whether accumulation of IKs occurs in dogs, in which...

  11. Diode rectifier bridge-based structure for DFIG-based wind turbine

    DEFF Research Database (Denmark)

    Zhu, Rongwu; Chen, Zhe; Wu, Xiaojie

    2015-01-01

    This paper proposes a new structure for the doubly-fed induction generator (DFIG)-based wind turbine. The proposed structure consists of a DFIG controlled by a partial rated power converter in the rotor side, a three-phase diode rectifier bridge (DRB) connected to the stator, and a DC/AC full rated...

  12. Delayed rectifier potassium channels are involved in SO2 derivative-induced hippocampal neuronal injury.

    Science.gov (United States)

    Li, Guangke; Sang, Nan

    2009-01-01

    Recent studies implicate the possible neurotoxicity of SO(2), however, its mechanisms remain unclear. In the present study, we investigated SO(2) derivative-induced effect on delayed rectifier potassium channels (I(K)) and cellular death/apoptosis in primary cultured hippocampal neurons. The results demonstrate that SO(2) derivatives (NaHSO(3) and Na(2)SO(3), 3:1M/M) effectively augmented I(K) and promoted the activation of delayed rectifier potassium channels. Also, SO(2) derivatives increased neuronal death percentage and contributed to the formation of DNA ladder in concentration-dependent manners. Interestingly, the neuronal death and DNA ladder formation, caused by SO(2) derivatives, could be attenuated by the delayed rectifier potassium channel blocker (tetraethylammonium, TEA), but not by the transient outward potassium channel blocker (4-aminopyridine, 4-AP). It implies that stimulating delayed rectifier potassium channels were involved in SO(2) derivative-caused hippocampal neuronal insults, and blocking these channels might be one of the possibly clinical treatment for SO(2)-caused neuronal dysfunction.

  13. Stability Improvements of an LCL-filter based Three-phase Active Rectifier

    DEFF Research Database (Denmark)

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

    2002-01-01

    Three-phase active rectifiers guarantee sinusoidal input currents and controllable dc voltage at the price of a high switching frequency ripple that can disturb and reduce efficiency of other EMI sensitive equipment connected to the grid. This problem could be solved choosing a high value...

  14. Energy Saving in Three-Phase Diode Rectifiers Using EI Technique with Adjustable Switching Frequency Scheme

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Yang, Yongheng

    2016-01-01

    A front-end rectifier can significantly impact a power electronics system performance and efficiency for applications such as motor drive where the system commonly operates under partial loading conditions. This paper proposes an adjustable switching frequency scheme using an electronic inductor...

  15. Designing single phase Current-Programmed-Controlled rectifiers by harmonic currents

    DEFF Research Database (Denmark)

    Andersen, Gert Karmisholt; Blaabjerg, Frede

    2002-01-01

    The grid current harmonics of a Current-Programmed-Controlled (CPC) pfc rectifier strongly depends on the choice of switching frequency and switching inductance. This paper describes a new simple and vert fast method to calculate the grid current of a CPC controlled pfc converter. The method...

  16. Crossbar memory array of organic bistable rectifying diodes for nonvolatile data storage

    NARCIS (Netherlands)

    Asadi, Kamal; Li, Mengyuan; Stingelin, Natalie; Blom, Paul W. M.; de Leeuw, Dago M.

    2010-01-01

    Cross-talk in memories using resistive switches in a cross-bar geometry can be prevented by integration of a rectifying diode. We present a functional cross bar memory array using a phase separated blend of a ferroelectric and a semiconducting polymer as storage medium. Each intersection acts

  17. Rectifier Current Control for an LLC Resonant Converter Based on a Simplified Linearized Model

    Directory of Open Access Journals (Sweden)

    Zhijian Fang

    2018-03-01

    Full Text Available In this paper, a rectifier current control for an LLC resonant converter is proposed, based on a simplified, two-order, linearized model that adds a rectifier current feedback inner loop to improve dynamic performance. Compared to the traditional large-signal model with seven resonant states, this paper utilizes a rectifier current state to represent the characteristics of the resonant states, simplifying the LLC resonant model from seven orders to two orders. Then, the rectifier current feedback inner loop is proposed to increase the control system damping, improving dynamic performance. The modeling and design methodology for the LLC resonant converter are also presented in this paper. A frequency analysis is conducted to verify the accuracy of the simplified model. Finally, a 200 W LLC resonant converter prototype is built to verify the effectiveness of the proposed control strategy. Compared to a traditional single-loop controller, the settling time and voltage droop were reduced from 10.8 ms to 8.6 ms and from 6.8 V to 4.8 V, respectively, using the proposed control strategy.

  18. Leucine-rich repeat-containing synaptic adhesion molecules as organizers of synaptic specificity and diversity.

    Science.gov (United States)

    Schroeder, Anna; de Wit, Joris

    2018-04-09

    The brain harbors billions of neurons that form distinct neural circuits with exquisite specificity. Specific patterns of connectivity between distinct neuronal cell types permit the transfer and computation of information. The molecular correlates that give rise to synaptic specificity are incompletely understood. Recent studies indicate that cell-surface molecules are important determinants of cell type identity and suggest that these are essential players in the specification of synaptic connectivity. Leucine-rich repeat (LRR)-containing adhesion molecules in particular have emerged as key organizers of excitatory and inhibitory synapses. Here, we discuss emerging evidence that LRR proteins regulate the assembly of specific connectivity patterns across neural circuits, and contribute to the diverse structural and functional properties of synapses, two key features that are critical for the proper formation and function of neural circuits.

  19. Ankyrins: Roles in synaptic biology and pathology.

    Science.gov (United States)

    Smith, Katharine R; Penzes, Peter

    2018-05-03

    Ankyrins are broadly expressed adaptors that organize diverse membrane proteins into specialized domains and link them to the sub-membranous cytoskeleton. In neurons, ankyrins are known to have essential roles in organizing the axon initial segment and nodes of Ranvier. However, recent studies have revealed novel functions for ankyrins at synapses, where they organize and stabilize neurotransmitter receptors, modulate dendritic spine morphology and control adhesion to the presynaptic site. Ankyrin genes have also been highly associated with a range of neurodevelopmental and psychiatric diseases, including bipolar disorder, schizophrenia and autism, which all demonstrate overlap in their genetics, mechanisms and phenotypes. This review discusses the novel synaptic functions of ankyrin proteins in neurons, and places these exciting findings in the context of ANK genes as key neuropsychiatric disorder risk-factors. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Alzheimer's disease: synaptic dysfunction and Abeta

    LENUS (Irish Health Repository)

    Shankar, Ganesh M

    2009-11-23

    Abstract Synapse loss is an early and invariant feature of Alzheimer\\'s disease (AD) and there is a strong correlation between the extent of synapse loss and the severity of dementia. Accordingly, it has been proposed that synapse loss underlies the memory impairment evident in the early phase of AD and that since plasticity is important for neuronal viability, persistent disruption of plasticity may account for the frank cell loss typical of later phases of the disease. Extensive multi-disciplinary research has implicated the amyloid β-protein (Aβ) in the aetiology of AD and here we review the evidence that non-fibrillar soluble forms of Aβ are mediators of synaptic compromise. We also discuss the possible mechanisms of Aβ synaptotoxicity and potential targets for therapeutic intervention.

  1. Optogenetic acidification of synaptic vesicles and lysosomes.

    Science.gov (United States)

    Rost, Benjamin R; Schneider, Franziska; Grauel, M Katharina; Wozny, Christian; Bentz, Claudia; Blessing, Anja; Rosenmund, Tanja; Jentsch, Thomas J; Schmitz, Dietmar; Hegemann, Peter; Rosenmund, Christian

    2015-12-01

    Acidification is required for the function of many intracellular organelles, but methods to acutely manipulate their intraluminal pH have not been available. Here we present a targeting strategy to selectively express the light-driven proton pump Arch3 on synaptic vesicles. Our new tool, pHoenix, can functionally replace endogenous proton pumps, enabling optogenetic control of vesicular acidification and neurotransmitter accumulation. Under physiological conditions, glutamatergic vesicles are nearly full, as additional vesicle acidification with pHoenix only slightly increased the quantal size. By contrast, we found that incompletely filled vesicles exhibited a lower release probability than full vesicles, suggesting preferential exocytosis of vesicles with high transmitter content. Our subcellular targeting approach can be transferred to other organelles, as demonstrated for a pHoenix variant that allows light-activated acidification of lysosomes.

  2. Shank synaptic scaffold proteins: keys to understanding the pathogenesis of autism and other synaptic disorders.

    Science.gov (United States)

    Sala, Carlo; Vicidomini, Cinzia; Bigi, Ilaria; Mossa, Adele; Verpelli, Chiara

    2015-12-01

    Shank/ProSAP proteins are essential to synaptic formation, development, and function. Mutations in the family of SHANK genes are strongly associated with autism spectrum disorders (ASD) and other neurodevelopmental and neuropsychiatric disorders, such as intellectual disability (ID), and schizophrenia. Thus, the term 'Shankopathies' identifies a number of neuronal diseases caused by alteration of Shank protein expression leading to abnormal synaptic development. With this review we want to summarize the major genetic, molecular, behavior and electrophysiological studies that provide new clues into the function of Shanks and pave the way for the discovery of new therapeutic drugs targeted to treat patients with SHANK mutations and also patients affected by other neurodevelopmental and neuropsychiatric disorders. Shank/ProSAP proteins are essential to synaptic formation, development, and function. Mutations in the family of SHANK genes are strongly associated with autism spectrum disorders (ASD) and other neurodevelopmental and neuropsychiatric disorders, such as intellectual disability (ID), and schizophrenia (SCZ). With this review we want to summarize the major genetic, molecular, behavior and electrophysiological studies that provide new clues into the function of Shanks and pave the way for the discovery of new therapeutic drugs targeted to treat patients with SHANK mutations. © 2015 International Society for Neurochemistry.

  3. Fixture and method for rectifying damaged guide thimble insert sleeves in a reconstitutable fuel assembly

    International Nuclear Information System (INIS)

    Shallenberger, J.M.; Ferlan, S.J.

    1987-01-01

    A guide thimble damage-rectifying method is described for use on a reconstitutable fuel assembly being held in a work station with its top nozzle removed to expose a plurality of guide thimbles having one of several different types of damage. The method consists of: (a) providing a base having a plurality of tool positioning openings defined therein in a pattern matched with that of the guide thimbles of the fuel assembly; (b) mounting the base on the work station with its tool positioning openings in alignment with the guide thimbles of the fuel assembly and such that the base is movable toward the guide thimbles; (c) providing a plurality of different tools each operable to rectify one of the different types of guide thimble damage; (d) mounting selected ones of the different tools in respective ones of the openings of the base in alignment with ones of the thimbles having the respective types of guide thimble damage capable of being rectified by the selected tools such that upon movement of the base toward the guide thimbles the respective types of guide thimble damage will be rectified by the selected tools; (e) providing a group of positioning elements; (f) mounting the positioning elements in selected ones of the base openings corresponding to undamaged ones of the guide thimbles such that upon movement of the base toward the guide thimbles the positioning elements become mounted on upper end portions of the corresponding undamaged ones of the guide thimbles for precisely locating the fixture relative to the guide thimble upper end portions for accurate performance of the repairable damage rectifying operation by the tools as the base is moved toward the guide thimbles; and (g) moving the base toward the guide thimbles so as to mount the positioning elements on the corresponding ones of the undamaged guide thimbles and effect rectification of the damaged guide thimbles by the selected tools

  4. Specific residues of the cytoplasmic domains of cardiac inward rectifier potassium channels are effective antifibrillatory targets

    Science.gov (United States)

    Noujaim, Sami F.; Stuckey, Jeanne A.; Ponce-Balbuena, Daniela; Ferrer-Villada, Tania; López-Izquierdo, Angelica; Pandit, Sandeep; Calvo, Conrado J.; Grzeda, Krzysztof R.; Berenfeld, Omer; Sánchez Chapula, José A.; Jalife, José

    2010-01-01

    Atrial and ventricular tachyarrhythmias can be perpetuated by up-regulation of inward rectifier potassium channels. Thus, it may be beneficial to block inward rectifier channels under conditions in which their function becomes arrhythmogenic (e.g., inherited gain-of-function mutation channelopathies, ischemia, and chronic and vagally mediated atrial fibrillation). We hypothesize that the antimalarial quinoline chloroquine exerts potent antiarrhythmic effects by interacting with the cytoplasmic domains of Kir2.1 (IK1), Kir3.1 (IKACh), or Kir6.2 (IKATP) and reducing inward rectifier potassium currents. In isolated hearts of three different mammalian species, intracoronary chloroquine perfusion reduced fibrillatory frequency (atrial or ventricular), and effectively terminated the arrhythmia with resumption of sinus rhythm. In patch-clamp experiments chloroquine blocked IK1, IKACh, and IKATP. Comparative molecular modeling and ligand docking of chloroquine in the intracellular domains of Kir2.1, Kir3.1, and Kir6.2 suggested that chloroquine blocks or reduces potassium flow by interacting with negatively charged amino acids facing the ion permeation vestibule of the channel in question. These results open a novel path toward discovering antiarrhythmic pharmacophores that target specific residues of the cytoplasmic domain of inward rectifier potassium channels.—Noujaim, S. F., Stuckey, J. A., Ponce-Balbuena, D., Ferrer-Villada, T., López-Izquierdo, A., Pandit, S., Calvo, C. J., Grzeda, K. R., Berenfeld, O., Sánchez Chapula, J. A., Jalife, J. Specific residues of the cytoplasmic domains of cardiac inward rectifier potassium channels are effective antifibrillatory targets. PMID:20585026

  5. Effect of rotor rectifier on motor performance in slip recovery drives

    Energy Technology Data Exchange (ETDEWEB)

    Al Zahawi, B.A.T.; Jones, B.L.; Drury, W.

    1987-01-01

    The static Kramer system, comprising a slip-ring induction motor and a slip energy recovery circuit, is one of the simplest and most efficient forms of ac variable-speed drive. It is sometimes used to upgrade drives which had originally been designed for fixed speed operation, often with substantial energy savings. In such cases, it is important to know how the inclusion of a rectifier in the slip energy recovery circuit affects motor performance. A satisfactory model for the motor-rectifier combination is also needed to provide a sound basis for assessing alternative forms of recovery systems which aim to overcome the principal shortcomings of the drive, namely the magnitude and variability of its reactive power. Despite its simplicity, the Kramer drive presents a formidable analytical challenge. Rigorous analysis is particularly difficult and there is a need for a simpler form of analysis when calculating ratings and steady-state performance. The approach taken in this paper uses a transformer-type model for the motor, and largely analytical expressions for predicting torque, stator power, stator reactive power and rectifier output voltage. Motor resistances, diode characteristics, and the several possible rectifier overlap modes are included. It is shown that the rectifier has an adverse effect on stator reactive power, power factor, and peak torque, particularly at speeds well below synchronous, requiring some derating of motors designed for resistance control and also requiring additional power factor correction. While the analysis does not cater to variations caused by harmonics at some speeds, it does provide a quick, accurate method of predicting performance over most sections of the operating range. 12 refs., 11 figs.

  6. Spine Calcium Transients Induced by Synaptically-Evoked Action Potentials Can Predict Synapse Location and Establish Synaptic Democracy

    Science.gov (United States)

    Meredith, Rhiannon M.; van Ooyen, Arjen

    2012-01-01

    CA1 pyramidal neurons receive hundreds of synaptic inputs at different distances from the soma. Distance-dependent synaptic scaling enables distal and proximal synapses to influence the somatic membrane equally, a phenomenon called “synaptic democracy”. How this is established is unclear. The backpropagating action potential (BAP) is hypothesised to provide distance-dependent information to synapses, allowing synaptic strengths to scale accordingly. Experimental measurements show that a BAP evoked by current injection at the soma causes calcium currents in the apical shaft whose amplitudes decay with distance from the soma. However, in vivo action potentials are not induced by somatic current injection but by synaptic inputs along the dendrites, which creates a different excitable state of the dendrites. Due to technical limitations, it is not possible to study experimentally whether distance information can also be provided by synaptically-evoked BAPs. Therefore we adapted a realistic morphological and electrophysiological model to measure BAP-induced voltage and calcium signals in spines after Schaffer collateral synapse stimulation. We show that peak calcium concentration is highly correlated with soma-synapse distance under a number of physiologically-realistic suprathreshold stimulation regimes and for a range of dendritic morphologies. Peak calcium levels also predicted the attenuation of the EPSP across the dendritic tree. Furthermore, we show that peak calcium can be used to set up a synaptic democracy in a homeostatic manner, whereby synapses regulate their synaptic strength on the basis of the difference between peak calcium and a uniform target value. We conclude that information derived from synaptically-generated BAPs can indicate synapse location and can subsequently be utilised to implement a synaptic democracy. PMID:22719238

  7. Nonlinear Elasticity

    Science.gov (United States)

    Fu, Y. B.; Ogden, R. W.

    2001-05-01

    This collection of papers by leading researchers in the field of finite, nonlinear elasticity concerns itself with the behavior of objects that deform when external forces or temperature gradients are applied. This process is extremely important in many industrial settings, such as aerospace and rubber industries. This book covers the various aspects of the subject comprehensively with careful explanations of the basic theories and individual chapters each covering a different research direction. The authors discuss the use of symbolic manipulation software as well as computer algorithm issues. The emphasis is placed firmly on covering modern, recent developments, rather than the very theoretical approach often found. The book will be an excellent reference for both beginners and specialists in engineering, applied mathematics and physics.

  8. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  9. Synapse geometry and receptor dynamics modulate synaptic strength.

    Directory of Open Access Journals (Sweden)

    Dominik Freche

    Full Text Available Synaptic transmission relies on several processes, such as the location of a released vesicle, the number and type of receptors, trafficking between the postsynaptic density (PSD and extrasynaptic compartment, as well as the synapse organization. To study the impact of these parameters on excitatory synaptic transmission, we present a computational model for the fast AMPA-receptor mediated synaptic current. We show that in addition to the vesicular release probability, due to variations in their release locations and the AMPAR distribution, the postsynaptic current amplitude has a large variance, making a synapse an intrinsic unreliable device. We use our model to examine our experimental data recorded from CA1 mice hippocampal slices to study the differences between mEPSC and evoked EPSC variance. The synaptic current but not the coefficient of variation is maximal when the active zone where vesicles are released is apposed to the PSD. Moreover, we find that for certain type of synapses, receptor trafficking can affect the magnitude of synaptic depression. Finally, we demonstrate that perisynaptic microdomains located outside the PSD impacts synaptic transmission by regulating the number of desensitized receptors and their trafficking to the PSD. We conclude that geometrical modifications, reorganization of the PSD or perisynaptic microdomains modulate synaptic strength, as the mechanisms underlying long-term plasticity.

  10. A Voltage Mode Memristor Bridge Synaptic Circuit with Memristor Emulators

    Directory of Open Access Journals (Sweden)

    Leon Chua

    2012-03-01

    Full Text Available A memristor bridge neural circuit which is able to perform signed synaptic weighting was proposed in our previous study, where the synaptic operation was verified via software simulation of the mathematical model of the HP memristor. This study is an extension of the previous work advancing toward the circuit implementation where the architecture of the memristor bridge synapse is built with memristor emulator circuits. In addition, a simple neural network which performs both synaptic weighting and summation is built by combining memristor emulators-based synapses and differential amplifier circuits. The feasibility of the memristor bridge neural circuit is verified via SPICE simulations.

  11. Genetic Algorithm-Based Design of the Active Damping for an LCL-Filter Three-Phase Active Rectifier

    DEFF Research Database (Denmark)

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

    2004-01-01

    Active rectifiers/inverters are becoming used more and more often in regenerative systems and distributed power systems. Typically, the interface between the grid and rectifier is either an inductor or an LCL-filter. The use of an LCL-filter mitigates the switching ripple injected in the grid...... by a three-phase active rectifier. However, stability problems can arise in the current control loop. In order to overcome them, a damping resistor can be inserted, at the price of a reduction of efficiency. The use of active damping by means of control may seem attractive, but it is often limited by the use...

  12. Sensitivity analysis of an LCL-filter-based three-phase active rectifier via a virtual circuit approach

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Chiarantoni, Ernesto; Aquila, Antonio Dell’

    2004-01-01

    Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue......, to the grid side stiffness and to the parameters of the controller has never been detailed considered. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analysed with the circuit theory approach. A ?virtual circuit? is synthesized in role of the digital controller...

  13. Characterizing synaptic protein development in human visual cortex enables alignment of synaptic age with rat visual cortex

    Directory of Open Access Journals (Sweden)

    Joshua G.A Pinto

    2015-02-01

    Full Text Available Although many potential neuroplasticity based therapies have been developed in the lab, few have translated into established clinical treatments for human neurologic or neuropsychiatric diseases. Animal models, especially of the visual system, have shaped our understanding of neuroplasticity by characterizing the mechanisms that promote neural changes and defining timing of the sensitive period. The lack of knowledge about development of synaptic plasticity mechanisms in human cortex, and about alignment of synaptic age between animals and humans, has limited translation of neuroplasticity therapies. In this study, we quantified expression of a set of highly conserved pre- and post-synaptic proteins (Synapsin, Synaptophysin, PSD-95, Gephyrin and found that synaptic development in human primary visual cortex continues into late childhood. Indeed, this is many years longer than suggested by neuroanatomical studies and points to a prolonged sensitive period for plasticity in human sensory cortex. In addition, during childhood we found waves of inter-individual variability that are different for the 4 proteins and include a stage during early development (<1 year when only Gephyrin has high inter-individual variability. We also found that pre- and post-synaptic protein balances develop quickly, suggesting that maturation of certain synaptic functions happens within the first year or two of life. A multidimensional analysis (principle component analysis showed that most of the variance was captured by the sum of the 4 synaptic proteins. We used that sum to compare development of human and rat visual cortex and identified a simple linear equation that provides robust alignment of synaptic age between humans and rats. Alignment of synaptic ages is important for age-appropriate targeting and effective translation of neuroplasticity therapies from the lab to the clinic.

  14. [Nonlinear magnetohydrodynamics

    International Nuclear Information System (INIS)

    1994-01-01

    Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday's law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm's law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile

  15. A presynaptic role for PKA in synaptic tagging and memory

    NARCIS (Netherlands)

    Park, Alan Jung; Havekes, Robbert; Choi, Jennifer H K; Luczak, Vincent; Nie, Ting; Huang, Ted; Abel, Ted

    2014-01-01

    Protein kinase A (PKA) and other signaling molecules are spatially restricted within neurons by A-kinase anchoring proteins (AKAPs). Although studies on compartmentalized PKA signaling have focused on postsynaptic mechanisms, presynaptically anchored PKA may contribute to synaptic plasticity and

  16. Memristor-based neural networks: Synaptic versus neuronal stochasticity

    KAUST Repository

    Naous, Rawan; Alshedivat, Maruan; Neftci, Emre; Cauwenberghs, Gert; Salama, Khaled N.

    2016-01-01

    In neuromorphic circuits, stochasticity in the cortex can be mapped into the synaptic or neuronal components. The hardware emulation of these stochastic neural networks are currently being extensively studied using resistive memories or memristors

  17. Neuro-inspired computing using resistive synaptic devices

    CERN Document Server

    2017-01-01

    This book summarizes the recent breakthroughs in hardware implementation of neuro-inspired computing using resistive synaptic devices. The authors describe how two-terminal solid-state resistive memories can emulate synaptic weights in a neural network. Readers will benefit from state-of-the-art summaries of resistive synaptic devices, from the individual cell characteristics to the large-scale array integration. This book also discusses peripheral neuron circuits design challenges and design strategies. Finally, the authors describe the impact of device non-ideal properties (e.g. noise, variation, yield) and their impact on the learning performance at the system-level, using a device-algorithm co-design methodology. • Provides single-source reference to recent breakthroughs in resistive synaptic devices, not only at individual cell-level, but also at integrated array-level; • Includes detailed discussion of the peripheral circuits and array architecture design of the neuro-crossbar system; • Focuses on...

  18. Learning and Memory, Part II: Molecular Mechanisms of Synaptic Plasticity

    Science.gov (United States)

    Lombroso, Paul; Ogren, Marilee

    2009-01-01

    The molecular events that are responsible for strengthening synaptic connections and how these are linked to memory and learning are discussed. The laboratory preparations that allow the investigation of these events are also described.

  19. Multistate Resistive Switching Memory for Synaptic Memory Applications

    KAUST Repository

    Hota, Mrinal Kanti; Hedhili, Mohamed N.; Wehbe, Nimer; McLachlan, Martyn A.; Alshareef, Husam N.

    2016-01-01

    memory performance is observed. Conventional synaptic operation in terms of potentiation, depression plasticity, and Ebbinghaus forgetting process are also studied. The memory mechanism is shown to originate from the migration of the oxygen vacancies

  20. Binocular Rivalry in a Competitive Neural Network with Synaptic Depression

    KAUST Repository

    Kilpatrick, Zachary P.; Bressloff, Paul C.

    2010-01-01

    We study binocular rivalry in a competitive neural network with synaptic depression. In particular, we consider two coupled hypercolums within primary visual cortex (V1), representing orientation selective cells responding to either left or right

  1. Synaptic Control of Secretory Trafficking in Dendrites

    Directory of Open Access Journals (Sweden)

    Cyril Hanus

    2014-06-01

    Full Text Available Localized signaling in neuronal dendrites requires tight spatial control of membrane composition. Upon initial synthesis, nascent secretory cargo in dendrites exits the endoplasmic reticulum (ER from local zones of ER complexity that are spatially coupled to post-ER compartments. Although newly synthesized membrane proteins can be processed locally, the mechanisms that control the spatial range of secretory cargo transport in dendritic segments are unknown. Here, we monitored the dynamics of nascent membrane proteins in dendritic post-ER compartments under regimes of low or increased neuronal activity. In response to activity blockade, post-ER carriers are highly mobile and are transported over long distances. Conversely, increasing synaptic activity dramatically restricts the spatial scale of post-ER trafficking along dendrites. This activity-induced confinement of secretory cargo requires site-specific phosphorylation of the kinesin motor KIF17 by Ca2+/calmodulin-dependent protein kinases (CaMK. Thus, the length scales of early secretory trafficking in dendrites are tuned by activity-dependent regulation of microtubule-dependent transport.

  2. Design principles of electrical synaptic plasticity.

    Science.gov (United States)

    O'Brien, John

    2017-09-08

    Essentially all animals with nervous systems utilize electrical synapses as a core element of communication. Electrical synapses, formed by gap junctions between neurons, provide rapid, bidirectional communication that accomplishes tasks distinct from and complementary to chemical synapses. These include coordination of neuron activity, suppression of voltage noise, establishment of electrical pathways that define circuits, and modulation of high order network behavior. In keeping with the omnipresent demand to alter neural network function in order to respond to environmental cues and perform tasks, electrical synapses exhibit extensive plasticity. In some networks, this plasticity can have dramatic effects that completely remodel circuits or remove the influence of certain cell types from networks. Electrical synaptic plasticity occurs on three distinct time scales, ranging from milliseconds to days, with different mechanisms accounting for each. This essay highlights principles that dictate the properties of electrical coupling within networks and the plasticity of the electrical synapses, drawing examples extensively from retinal networks. Copyright © 2017 The Author. Published by Elsevier B.V. All rights reserved.

  3. Epigenetic Basis of Neuronal and Synaptic Plasticity.

    Science.gov (United States)

    Karpova, Nina N; Sales, Amanda J; Joca, Samia R

    2017-01-01

    Neuronal network and plasticity change as a function of experience. Altered neural connectivity leads to distinct transcriptional programs of neuronal plasticity-related genes. The environmental challenges throughout life may promote long-lasting reprogramming of gene expression and the development of brain disorders. The modifications in neuronal epigenome mediate gene-environmental interactions and are required for activity-dependent regulation of neuronal differentiation, maturation and plasticity. Here, we highlight the latest advances in understanding the role of the main players of epigenetic machinery (DNA methylation and demethylation, histone modifications, chromatin-remodeling enzymes, transposons, and non-coding RNAs) in activity-dependent and long- term neural and synaptic plasticity. The review focuses on both the transcriptional and post-transcriptional regulation of gene expression levels, including the processes of promoter activation, alternative splicing, regulation of stability of gene transcripts by natural antisense RNAs, and alternative polyadenylation. Further, we discuss the epigenetic aspects of impaired neuronal plasticity and the pathogenesis of neurodevelopmental (Rett syndrome, Fragile X Syndrome, genomic imprinting disorders, schizophrenia, and others), stressrelated (mood disorders) and neurodegenerative Alzheimer's, Parkinson's and Huntington's disorders. The review also highlights the pharmacological compounds that modulate epigenetic programming of gene expression, the potential treatment strategies of discussed brain disorders, and the questions that should be addressed during the development of effective and safe approaches for the treatment of brain disorders.

  4. Cholesterol asymmetry in synaptic plasma membranes.

    Science.gov (United States)

    Wood, W Gibson; Igbavboa, Urule; Müller, Walter E; Eckert, Gunter P

    2011-03-01

    Lipids are essential for the structural and functional integrity of membranes. Membrane lipids are not randomly distributed but are localized in different domains. A common characteristic of these membrane domains is their association with cholesterol. Lipid rafts and caveolae are examples of cholesterol enriched domains, which have attracted keen interest. However, two other important cholesterol domains are the exofacial and cytofacial leaflets of the plasma membrane. The two leaflets that make up the bilayer differ in their fluidity, electrical charge, lipid distribution, and active sites of certain proteins. The synaptic plasma membrane (SPM) cytofacial leaflet contains over 85% of the total SPM cholesterol as compared with the exofacial leaflet. This asymmetric distribution of cholesterol is not fixed or immobile but can be modified by different conditions in vivo: (i) chronic ethanol consumption; (ii) statins; (iii) aging; and (iv) apoE isoform. Several potential candidates have been proposed as mechanisms involved in regulation of SPM cholesterol asymmetry: apoE, low-density lipoprotein receptor, sterol carrier protein-2, fatty acid binding proteins, polyunsaturated fatty acids, P-glycoprotein and caveolin-1. This review examines cholesterol asymmetry in SPM, potential mechanisms of regulation and impact on membrane structure and function. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

  5. Reduced Synaptic Vesicle Recycling during Hypoxia in Cultured Cortical Neurons

    OpenAIRE

    Fedorovich, Sergei; Hofmeijer, Jeannette; van Putten, Michel Johannes Antonius Maria; le Feber, Jakob

    2017-01-01

    Improvement of neuronal recovery in the ischemic penumbra, an area around the core of a brain infarct with some remaining perfusion, has a large potential for the development of therapy against acute ischemic stroke. However, mechanisms that lead to either recovery or secondary damage in the penumbra largely remain unclear. Recent studies in cultured networks of cortical neurons showed that failure of synaptic transmission (referred to as synaptic failure) is a critical factor in the penumbra...

  6. Common mechanisms of synaptic plasticity in vertebrates and invertebrates

    Science.gov (United States)

    Glanzman, David L.

    2016-01-01

    Until recently, the literature on learning-related synaptic plasticity in invertebrates has been dominated by models assuming plasticity is mediated by presynaptic changes, whereas the vertebrate literature has been dominated by models assuming it is mediated by postsynaptic changes. Here I will argue that this situation does not reflect a biological reality and that, in fact, invertebrate and vertebrate nervous systems share a common set of mechanisms of synaptic plasticity. PMID:20152143

  7. Aviram–Ratner rectifying mechanism for DNA base-pair sequencing through graphene nanogaps

    International Nuclear Information System (INIS)

    Agapito, Luis A; Gayles, Jacob; Wolowiec, Christian; Kioussis, Nicholas

    2012-01-01

    We demonstrate that biological molecules such as Watson–Crick DNA base pairs can behave as biological Aviram–Ratner electrical rectifiers because of the spatial separation and weak hydrogen bonding between the nucleobases. We have performed a parallel computational implementation of the ab initio non-equilibrium Green’s function (NEGF) theory to determine the electrical response of graphene—base-pair—graphene junctions. The results show an asymmetric (rectifying) current–voltage response for the cytosine–guanine base pair adsorbed on a graphene nanogap. In sharp contrast we find a symmetric response for the thymine–adenine case. We propose applying the asymmetry of the current–voltage response as a sensing criterion to the technological challenge of rapid DNA sequencing via graphene nanogaps. (paper)

  8. Atomic Scale Modulation of Self-Rectifying Resistive Switching by Interfacial Defects

    KAUST Repository

    Wu, Xing; Yu, Kaihao; Cha, Dong Kyu; Bosman, Michel; Raghavan, Nagarajan; Zhang, Xixiang; Li, Kun; Liu, Qi; Sun, Litao; Pey, Kinleong

    2018-01-01

    Higher memory density and faster computational performance of resistive switching cells require reliable array‐accessible architecture. However, selecting a designated cell within a crossbar array without interference from sneak path currents through neighboring cells is a general problem. Here, a highly doped n++ Si as the bottom electrode with Ni‐electrode/HfOx/SiO2 asymmetric self‐rectifying resistive switching device is fabricated. The interfacial defects in the HfOx/SiO2 junction and n++ Si substrate result in the reproducible rectifying behavior. In situ transmission electron microscopy is used to quantitatively study the properties of the morphology, chemistry, and dynamic nucleation–dissolution evolution of the chains of defects at the atomic scale. The spatial and temporal correlation between the concentration of oxygen vacancies and Ni‐rich conductive filament modifies the resistive switching effect. This study has important implications at the array‐level performance of high density resistive switching memories.

  9. Atomic Scale Modulation of Self-Rectifying Resistive Switching by Interfacial Defects

    KAUST Repository

    Wu, Xing

    2018-04-14

    Higher memory density and faster computational performance of resistive switching cells require reliable array‐accessible architecture. However, selecting a designated cell within a crossbar array without interference from sneak path currents through neighboring cells is a general problem. Here, a highly doped n++ Si as the bottom electrode with Ni‐electrode/HfOx/SiO2 asymmetric self‐rectifying resistive switching device is fabricated. The interfacial defects in the HfOx/SiO2 junction and n++ Si substrate result in the reproducible rectifying behavior. In situ transmission electron microscopy is used to quantitatively study the properties of the morphology, chemistry, and dynamic nucleation–dissolution evolution of the chains of defects at the atomic scale. The spatial and temporal correlation between the concentration of oxygen vacancies and Ni‐rich conductive filament modifies the resistive switching effect. This study has important implications at the array‐level performance of high density resistive switching memories.

  10. CMOS single-stage input-powered bridge rectifier with boost switch and duty cycle control

    Science.gov (United States)

    Radzuan, Roskhatijah; Mohd Salleh, Mohd Khairul; Hamzah, Mustafar Kamal; Ab Wahab, Norfishah

    2017-06-01

    This paper presents a single-stage input-powered bridge rectifier with boost switch for wireless-powered devices such as biomedical implants and wireless sensor nodes. Realised using CMOS process technology, it employs a duty cycle switch control to achieve high output voltage using boost technique, leading to a high output power conversion. It has only six external connections with the boost inductance. The input frequency of the bridge rectifier is set at 50 Hz, while the switching frequency is 100 kHz. The proposed circuit is fabricated on a single 0.18-micron CMOS die with a space area of 0.024 mm2. The simulated and measured results show good agreement.

  11. Development of 24GHz Rectenna for Receiving and Rectifying Modulated Waves

    International Nuclear Information System (INIS)

    Shinohara, Naoki; Hatano, Ken

    2014-01-01

    In this paper, we show experimental results of RF-DC conversion with modulated 24GHz waves. We have already developed class-F MMIC rectenna with resonators for higher harmonics at no modulated 24GHz microwave for RF energy transfer. Dimensions of the MMIC rectifying circuit is 1 mm × 3 mm on GaAs. Maximum RF-DC conversion efficiency is measured 47.9% for a 210 mW microwave input of 24 GHz with a 120 Ω load. The class-F rectenna is based on a single shunt full-wave rectifier. For future application of a simultaneous energy and information transfer system or an energy harvesting from broadcasting waves, input microwave will be modulated. In this paper, we show an experimental result of RF-DC conversion of the class-F rectenna with 24GHz waves modulated by 16QAM as 1st modulation and OFDM as 2nd modulation

  12. Development of 24GHz Rectenna for Receiving and Rectifying Modulated Waves

    Science.gov (United States)

    Shinohara, Naoki; Hatano, Ken

    2014-11-01

    In this paper, we show experimental results of RF-DC conversion with modulated 24GHz waves. We have already developed class-F MMIC rectenna with resonators for higher harmonics at no modulated 24GHz microwave for RF energy transfer. Dimensions of the MMIC rectifying circuit is 1 mm × 3 mm on GaAs. Maximum RF-DC conversion efficiency is measured 47.9% for a 210 mW microwave input of 24 GHz with a 120 Ω load. The class-F rectenna is based on a single shunt full-wave rectifier. For future application of a simultaneous energy and information transfer system or an energy harvesting from broadcasting waves, input microwave will be modulated. In this paper, we show an experimental result of RF-DC conversion of the class-F rectenna with 24GHz waves modulated by 16QAM as 1st modulation and OFDM as 2nd modulation.

  13. A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ruxi [Virginia Polytechnic Institute and State University (Virginia Tech); Wang, Fei [ORNL; Boroyevich, Dushan [Virginia Polytechnic Institute and State University (Virginia Tech); Burgos, Rolando [ABB; Lai, Rixin [General Electric; Ning, Puqi [ORNL; Rajashekara, Kaushik [Rolls Royce

    2011-01-01

    It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

  14. Rectifiability of Line Defects in Liquid Crystals with Variable Degree of Orientation

    Science.gov (United States)

    Alper, Onur

    2018-04-01

    In [2], H ardt, L in and the author proved that the defect set of minimizers of the modified Ericksen energy for nematic liquid crystals consists locally of a finite union of isolated points and Hölder continuous curves with finitely many crossings. In this article, we show that each Hölder continuous curve in the defect set is of finite length. Hence, locally, the defect set is rectifiable. For the most part, the proof closely follows the work of D e L ellis et al. (Rectifiability and upper minkowski bounds for singularities of harmonic q-valued maps, arXiv:1612.01813, 2016) on harmonic Q-valued maps. The blow-up analysis in A lper et al. (Calc Var Partial Differ Equ 56(5):128, 2017) allows us to simplify the covering arguments in [11] and locally estimate the length of line defects in a geometric fashion.

  15. Molecular Basis of Cardiac Delayed Rectifier Potassium Channel Function and Pharmacology.

    Science.gov (United States)

    Wu, Wei; Sanguinetti, Michael C

    2016-06-01

    Human cardiomyocytes express 3 distinct types of delayed rectifier potassium channels. Human ether-a-go-go-related gene (hERG) channels conduct the rapidly activating current IKr; KCNQ1/KCNE1 channels conduct the slowly activating current IKs; and Kv1.5 channels conduct an ultrarapid activating current IKur. Here the authors provide a general overview of the mechanistic and structural basis of ion selectivity, gating, and pharmacology of the 3 types of cardiac delayed rectifier potassium ion channels. Most blockers bind to S6 residues that line the central cavity of the channel, whereas activators interact with the channel at 4 symmetric binding sites outside the cavity. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. A gate enhanced power U-shaped MOSFET integrated with a Schottky rectifier

    International Nuclear Information System (INIS)

    Wang Ying; Jiao Wen-Li; Hu Hai-Fan; Liu Yun-Tao; Cao Fei

    2012-01-01

    An accumulation gate enhanced power U-shaped metal-oxide-semiconductor field-effect-transistor (UMOSFET) integrated with a Schottky rectifier is proposed. In this device, a Schottky rectifier is integrated into each cell of the accumulation gate enhanced power UMOSFET. Specific on-resistances of 7.7 mΩ·mm 2 and 6.5 mΩ·mm 2 for the gate bias voltages of 5 V and 10 V are achieved, respectively, and the breakdown voltage is 61 V. The numerical simulation shows a 25% reduction in the reverse recovery time and about three orders of magnitude reduction in the leakage current as compared with the accumulation gate enhanced power UMOSFET. (condensed matter: structural, mechanical, and thermal properties)

  17. $L^{p}$-square function estimates on spaces of homogeneous type and on uniformly rectifiable sets

    CERN Document Server

    Hofmann, Steve; Mitrea, Marius; Morris, Andrew J

    2017-01-01

    The authors establish square function estimates for integral operators on uniformly rectifiable sets by proving a local T(b) theorem and applying it to show that such estimates are stable under the so-called big pieces functor. More generally, they consider integral operators associated with Ahlfors-David regular sets of arbitrary codimension in ambient quasi-metric spaces. The local T(b) theorem is then used to establish an inductive scheme in which square function estimates on so-called big pieces of an Ahlfors-David regular set are proved to be sufficient for square function estimates to hold on the entire set. Extrapolation results for L^p and Hardy space versions of these estimates are also established. Moreover, the authors prove square function estimates for integral operators associated with variable coefficient kernels, including the Schwartz kernels of pseudodifferential operators acting between vector bundles on subdomains with uniformly rectifiable boundaries on manifolds.

  18. Synaptic Contacts Enhance Cell-to-Cell Tau Pathology Propagation.

    Science.gov (United States)

    Calafate, Sara; Buist, Arjan; Miskiewicz, Katarzyna; Vijayan, Vinoy; Daneels, Guy; de Strooper, Bart; de Wit, Joris; Verstreken, Patrik; Moechars, Diederik

    2015-05-26

    Accumulation of insoluble Tau protein aggregates and stereotypical propagation of Tau pathology through the brain are common hallmarks of tauopathies, including Alzheimer's disease (AD). Propagation of Tau pathology appears to occur along connected neurons, but whether synaptic contacts between neurons are facilitating propagation has not been demonstrated. Using quantitative in vitro models, we demonstrate that, in parallel to non-synaptic mechanisms, synapses, but not merely the close distance between the cells, enhance the propagation of Tau pathology between acceptor hippocampal neurons and Tau donor cells. Similarly, in an artificial neuronal network using microfluidic devices, synapses and synaptic activity are promoting neuronal Tau pathology propagation in parallel to the non-synaptic mechanisms. Our work indicates that the physical presence of synaptic contacts between neurons facilitate Tau pathology propagation. These findings can have implications for synaptic repair therapies, which may turn out to have adverse effects by promoting propagation of Tau pathology. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  19. BDNF-induced local protein synthesis and synaptic plasticity.

    Science.gov (United States)

    Leal, Graciano; Comprido, Diogo; Duarte, Carlos B

    2014-01-01

    Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptic transmission and long-term potentiation (LTP) in the hippocampus and in other brain regions, playing a role in the formation of certain forms of memory. The effects of BDNF in LTP are mediated by TrkB (tropomyosin-related kinase B) receptors, which are known to be coupled to the activation of the Ras/ERK, phosphatidylinositol 3-kinase/Akt and phospholipase C-γ (PLC-γ) pathways. The role of BDNF in LTP is best studied in the hippocampus, where the neurotrophin acts at pre- and post-synaptic levels. Recent studies have shown that BDNF regulates the transport of mRNAs along dendrites and their translation at the synapse, by modulating the initiation and elongation phases of protein synthesis, and by acting on specific miRNAs. Furthermore, the effect of BDNF on transcription regulation may further contribute to long-term changes in the synaptic proteome. In this review we discuss the recent progress in understanding the mechanisms contributing to the short- and long-term regulation of the synaptic proteome by BDNF, and the role in synaptic plasticity, which is likely to influence learning and memory formation. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Self-organised criticality via retro-synaptic signals

    Science.gov (United States)

    Hernandez-Urbina, Victor; Herrmann, J. Michael

    2016-12-01

    The brain is a complex system par excellence. In the last decade the observation of neuronal avalanches in neocortical circuits suggested the presence of self-organised criticality in brain networks. The occurrence of this type of dynamics implies several benefits to neural computation. However, the mechanisms that give rise to critical behaviour in these systems, and how they interact with other neuronal processes such as synaptic plasticity are not fully understood. In this paper, we present a long-term plasticity rule based on retro-synaptic signals that allows the system to reach a critical state in which clusters of activity are distributed as a power-law, among other observables. Our synaptic plasticity rule coexists with other synaptic mechanisms such as spike-timing-dependent plasticity, which implies that the resulting synaptic modulation captures not only the temporal correlations between spiking times of pre- and post-synaptic units, which has been suggested as requirement for learning and memory in neural systems, but also drives the system to a state of optimal neural information processing.

  1. SYNAPTIC DEPRESSION IN DEEP NEURAL NETWORKS FOR SPEECH PROCESSING.

    Science.gov (United States)

    Zhang, Wenhao; Li, Hanyu; Yang, Minda; Mesgarani, Nima

    2016-03-01

    A characteristic property of biological neurons is their ability to dynamically change the synaptic efficacy in response to variable input conditions. This mechanism, known as synaptic depression, significantly contributes to the formation of normalized representation of speech features. Synaptic depression also contributes to the robust performance of biological systems. In this paper, we describe how synaptic depression can be modeled and incorporated into deep neural network architectures to improve their generalization ability. We observed that when synaptic depression is added to the hidden layers of a neural network, it reduces the effect of changing background activity in the node activations. In addition, we show that when synaptic depression is included in a deep neural network trained for phoneme classification, the performance of the network improves under noisy conditions not included in the training phase. Our results suggest that more complete neuron models may further reduce the gap between the biological performance and artificial computing, resulting in networks that better generalize to novel signal conditions.

  2. Novel composite resonance DC-DC converter with voltage doubler rectifier

    OpenAIRE

    Kato, Hisatsugu; Matsuo, Hirohumi; Eguchi, Masaki; Sakamoto, Yukitaka; Nakaishi, Masaki

    2009-01-01

    This paper deals with a novel composite resonance DC-DC converter with the voltage doubler rectifier, which is developed to be applied to the power conditioner of the photovoltaic generation system. The proposed DC-DC converter has the current and voltage resonance functions. Therefore, the output voltage regulation can be achieved for the large variations of the input voltage and load. Also, this converter has the high power efficiency. The maximum power efficiency 96.1% can be realized.

  3. Direct Driven Permanent Magnet Synchronous Generators with Diode Rectifiers for Use in Offshore Wind Turbines

    OpenAIRE

    Reigstad, Tor Inge

    2007-01-01

    This work is focused on direct-driven permanent magnets synchronous generators (PMSG) with diode rectifiers for use in offshore wind turbines. Reactive compensation of the generator, power losses and control of the generator are studied. Configurations for power transmission to onshore point of common connection are also considered. Costs, power losses, reliability and interface with the PMSG are discussed. The purpose of the laboratory tests and simulations are to learn how a PMSG with dio...

  4. Thirty-six pulse rectifier scheme based on zigzag auto-connected transformer

    OpenAIRE

    Xiao-Qiang Chen; Chun-Ling Hao; Hao Qiu; Min Li

    2016-01-01

    In this paper, a low kilo-volt-ampere rating zigzag connected autotransformer based 36-pulse rectifier system supplying vector controlled induction motor drives (VCIMD) is designed, modeled and simulated. Detailed design procedure and magnetic rating calculation of the proposed autotransformer and interphase reactor is studied. Moreover, the design process of the autotransformer is modified to make it suitable for retrofit applications. Simulation results confirm that the proposed 36-pulse re...

  5. Acoustic pressure amplitude thresholds for rectified diffusion in gaseous microbubbles in biological tissue

    DEFF Research Database (Denmark)

    Lewin, Peter A.; Jensen, Leif Bjørnø

    1981-01-01

    One of the mechanisms often suggested for the biological action of ultrasonic beams irradiating human tissues is concerned with the presence in the tissues of minute gaseous bubbles which may, under the influence of the ultrasonic field be stimulated to grow to a size at which resonance or collap...... of calculations for typical (transient) exposure conditions from pulse-echo equipment are presented, indicating that rectified diffusion and stable cavitation are improbable phenomena in these circumstances....

  6. Contribution of delayed rectifier potassium currents to the electrical activity of murine colonic smooth muscle

    Science.gov (United States)

    Koh, S D; Ward, S M; Dick, G M; Epperson, A; Bonner, H P; Sanders, K M; Horowitz, B; Kenyon, J L

    1999-01-01

    We used intracellular microelectrodes to record the membrane potential (Vm) of intact murine colonic smooth muscle. Electrical activity consisted of spike complexes separated by quiescent periods (Vm≈−60 mV). The spike complexes consisted of about a dozen action potentials of approximately 30 mV amplitude. Tetraethylammonium (TEA, 1–10 mM) had little effect on the quiescent periods but increased the amplitude of the action potential spikes. 4-Aminopyridine (4-AP, ⋧ 5 mM) caused continuous spiking.Voltage clamp of isolated myocytes identified delayed rectifier K+ currents that activated rapidly (time to half-maximum current, 11.5 ms at 0 mV) and inactivated in two phases (τf = 96 ms, τs = 1.5 s at 0 mV). The half-activation voltage of the permeability was −27 mV, with significant activation at −50 mV.TEA (10 mM) reduced the outward current at potentials positive to 0 mV. 4-AP (5 mM) reduced the early current but increased outward current at later times (100–500 ms) consistent with block of resting channels relieved by depolarization. 4-AP inhibited outward current at potentials negative to −20 mV, potentials where TEA had no effect.Qualitative PCR amplification of mRNA identified transcripts encoding delayed rectifier K+ channel subunits Kv1.6, Kv4.1, Kv4.2, Kv4.3 and the Kvβ1.1 subunit in murine colon myocytes. mRNA encoding Kv 1.4 was not detected.We find that TEA-sensitive delayed rectifier currents are important determinants of action potential amplitude but not rhythmicity. Delayed rectifier currents sensitive to 4-AP are important determinants of rhythmicity but not action potential amplitude. PMID:10050014

  7. Inhibition of the cardiac inward rectifier potassium currents by KB-R7943.

    Science.gov (United States)

    Abramochkin, Denis V; Alekseeva, Eugenia I; Vornanen, Matti

    2013-09-01

    KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea) was developed as a specific inhibitor of the sarcolemmal sodium-calcium exchanger (NCX) with potential experimental and therapeutic use. However, KB-R7943 is shown to be a potent blocker of several ion currents including inward and delayed rectifier K(+) currents of cardiomyocytes. To further characterize KB-R7943 as a blocker of the cardiac inward rectifiers we compared KB-R7943 sensitivity of the background inward rectifier (IK1) and the carbacholine-induced inward rectifier (IKACh) currents in mammalian (Rattus norvegicus; rat) and fish (Carassius carassius; crucian carp) cardiac myocytes. The basal IK1 of ventricular myocytes was blocked with apparent IC50-values of 4.6×10(-6) M and 3.5×10(-6) M for rat and fish, respectively. IKACh was almost an order of magnitude more sensitive to KB-R7943 than IK1 with IC50-values of 6.2×10(-7) M for rat and 2.5×10(-7) M for fish. The fish cardiac NCX current was half-maximally blocked at the concentration of 1.9-3×10(-6) M in both forward and reversed mode of operation. Thus, the sensitivity of three cardiac currents to KB-R7943 block increases in the order IK1~INCXrectifier potassium currents, in particular IKACh, should be taken into account when interpreting the data with this inhibitor from in vivo and in vitro experiments in both mammalian and fish models. © 2013.

  8. Electrical and Optical Properties of Rectifying ZnO Homojunctions Fabricated by Wet Chemistry Methods

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Tiagulkyi, Stanislav; Grym, Jan; Černohorský, Ondřej

    2018-01-01

    Roč. 215, č. 2 (2018), č. článku 1700592. ISSN 1862-6300 R&D Projects: GA ČR(CZ) GA17-00546S; GA ČR(CZ) GA15-17044S Institutional support: RVO:67985882 Keywords : Rectifying ZnO homojunctions * Photoluminescence * N-type nanorods Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electronic engineering Impact factor: 1.775, year: 2016

  9. Dynamics of the inward rectifier K+ current during the action potential of guinea pig ventricular myocytes

    OpenAIRE

    Ibarra, J.; Morley, G.E.; Delmar, M.

    1991-01-01

    The potassium selective, inward rectifier current (IK1) is known to be responsible for maintaining the resting membrane potential of quiescent ventricular myocytes. However, the contribution of this current to the different phases of the cardiac action potential has not been adequately established. In the present study, we have used the action potential clamp (APC) technique to characterize the dynamic changes of a cesium-sensitive (i.e., Ik1) current which occur during the action potential. ...

  10. 2011 NOAA Ortho-rectified Mosaic of Hampton Harbor to Frost Point, New Hampshire (Mean High Water)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2011 NOAA Ortho-rectified Near Infrared Mosaic of Hampton Harbor to Frost Point, New Hampshire (Mean Lower Low Water)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Lopez Rock to Pescadero Point, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2013 NOAA Ortho-rectified Near-Infrared Mosaic of Virginia: Norfolk, Hampton Roads,and Newport News

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. Design Criteria for DC Link Filters in a Synchronous Generator-Phase Controlled Rectifier-Filter-Load System

    National Research Council Canada - National Science Library

    Greseth, Gregory

    1999-01-01

    .... The proposed Navy DC Zonal Electrical Distribution System (DC ZEDS) being designed for the new DD-21 utilizes a rectified ac generator output which is filtered and stepped to usable voltages by local dc-dc converters...

  15. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of BEAUMONT, ORANGE, PORT AUTHUR (NODC Accession 0074380)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of BEAUMONT, ORANGE,...

  16. NOAA Ortho-rectified Mosaic from Color Aerial Imagery of CHOCTAWHATCHEE BAY, FL, 2009 - 2010 (NODC Accession 0086137)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of CHOCTAWHATCHEE BAY....

  17. 2014 NOAA Ortho-rectified Mean High Water Near- Infrared Mosaic of Cedar Key to Tarpon Springs, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2011 NOAA Ortho-rectified Mosaic of Hampton Harbor to Frost Point, New Hampshire (Mean Lower Low Water)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2010 NOAA Ortho-rectified Near-Infrared MHW Mosaic of South Carolina: Hilton Head to St. Helena Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2010 NOAA Ortho-rectified Color MHW Mosaic of South Carolina: Hilton Head to St. Helena Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Alabama: Bon Secour Bay and Weeks Bay NERR

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Alabama: Bon Secour Bay and Weeks Bay NERR

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Pescadero Point to Bodega Bay, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2015 NOAA Ortho-rectified Color Mosaic of San Diego, California: Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2010 NOAA Near Infrared Ortho-rectified Mosaic of Louisiana: Mississippi River - Baton Rouge to Southwest Pass (NODC Accession 0104414)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2011 NOAA Ortho-rectified Mosaic of Merrimack River and Plum Island Sound, Massachusetts (Mean High Water)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2012 NOAA Ortho-rectified Near-Infrared Mosaic of Oregon: Columbia River - Bonneville Dam to Lake Umatilla

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2016 NOAA NGS Ortho-rectified Mean High Water Near-Infrared Mosaic of Venice Inlet ICW, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2016 NOAA NGS Ortho-rectified Mean High Water Color Mosaic of South Venice to Marco Island, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2014 NOAA NGS Ortho-rectified Mean Low Low Water Color Mosaic of Venice Inlet ICW, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2014 NOAA NGS Ortho-rectified Mean Low Low Water Near-Infrared Mosaic of Venice Inlet ICW, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Seal Rock to Lopez Rock, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2011 NOAA Ortho-rectified Mosaic of Maine: Reversing Falls at Whiting Bay, Mean Lower Low Water

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2015 NOAA Ortho-rectified Color Mosaic of Los Angeles and Long Beach, California: Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2016 NOAA NGS Ortho-rectified Mean High Water Color Mosaic of St. Johns River at Mile Point Turn, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2016 NOAA NGS Ortho-rectified Mean Low Low Water Color Mosaic of St Johns River, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2012 NOAA Near Infrared MLLW Ortho-rectified Mosaic of Northeast Point to Murphy Island, South Carolina

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of MISSISSIPPI RIVER - BATON ROUGE TO LAPLACE (NODC Accession 0074374)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of MISSISSIPPI RIVER -...

  19. Low cost, p-ZnO/n-Si, rectifying, nano heterojunction diode: Fabrication and electrical characterization

    Directory of Open Access Journals (Sweden)

    Vinay Kabra

    2014-11-01

    Full Text Available A low cost, highly rectifying, nano heterojunction (p-ZnO/n-Si diode was fabricated using solution-processed, p-type, ZnO nanoparticles and an n-type Si substrate. p-type ZnO nanoparticles were synthesized using a chemical synthesis route and characterized by XRD and a Hall effect measurement system. The device was fabricated by forming thin film of synthesized p-ZnO nanoparticles on an n-Si substrate using a dip coating technique. The device was then characterized by current–voltage (I–V and capacitance–voltage (C–V measurements. The effect of UV illumination on the I–V characteristics was also explored and indicated the formation of a highly rectifying, nano heterojunction with a rectification ratio of 101 at 3 V, which increased nearly 2.5 times (232 at 3 V under UV illumination. However, the cut-in voltage decreases from 1.5 V to 0.9 V under UV illumination. The fabricated device could be used in switches, rectifiers, clipper and clamper circuits, BJTs, MOSFETs and other electronic circuitry.

  20. Multi-service highly sensitive rectifier for enhanced RF energy scavenging.

    Science.gov (United States)

    Shariati, Negin; Rowe, Wayne S T; Scott, James R; Ghorbani, Kamran

    2015-05-07

    Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478-496 and 852-869 MHz) and exhibits favorable impedance matching over a broad input power range (-40 to -10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of -10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments.

  1. Pharmacological modulations of cardiac ultra-rapid and slowly activating delayed rectifier currents: potential antiarrhythmic approaches.

    Science.gov (United States)

    Islam, Mohammed A

    2010-01-01

    Despite the emerging new insights into our understandings of the cellular mechanisms underlying cardiac arrhythmia, medical therapy for this disease remains unsatisfactory. Atrial fibrillation (AF), the most prevalent arrhythmia, is responsible for significant morbidity and mortality. On the other hand, ventricular fibrillation results in sudden cardiac deaths in many instances. Prolongation of cardiac action potential (AP) is a proven principle of antiarrhythmic therapy. Class III antiarrhythmic agents prolong AP and QT interval by blocking rapidly activating delayed rectifier current (I(Kr)). However, I(Kr) blocking drugs carry the risk of life-threatening proarrhythmia. Recently, modulation of atrial-selective ultra-rapid delayed rectifier current (I(Kur)), has emerged as a novel therapeutic approach to treat AF. A number of I(Kur) blockers are being evaluated for the treatment of AF. The inhibition of slowly activating delayed rectifier current (I(Ks)) has also been proposed as an effective and safer antiarrhythmic approach because of its distinguishing characteristics that differ in remarkable ways from other selective class III agents. Selective I(Ks) block may prolong AP duration (APD) at rapid rates without leading to proarrhythmia. This article reviews the pathophysiological roles of I(Kur) and I(Ks) in cardiac repolarization and the implications of newly developed I(Kur) and I(Ks) blocking agents as promising antiarrhythmic approaches. Several recent patents pertinent to antiarrhythmic drug development have been discussed. Further research will be required to evaluate the efficacy and safety of these agents in the clinical setting.

  2. Biradical and triradical organic magnetic molecules as spin filters and rectifiers

    International Nuclear Information System (INIS)

    Zhu, L.; Yao, K.L.; Liu, Z.L.

    2012-01-01

    Graphical abstract: (a) Negative differential resistance (NDR) characteristic and antiparallel spin-current (ASC) rectification; (b) spin-current (SC) rectification and charge-current (CC) rectification properties Display Omitted Highlights: ► Organic magnetic molecules at gold electrodes as spin/charge rectifier. ► Spin diode/rectification stems from length and asymmetry of molecular framework. ► Negative differential resistance, spin-filtering and switching evidenced. - Abstract: We have theoretically investigated the spin-polarized transport properties of molecular junctions consisting of biradical and triradical organic magnetic molecules sandwiched between two symmetric gold electrodes, respectively. It shows that these junctions function as a spin rectifier or a combination of spin and charge rectifiers with high spin rectification ratios exceeding 100, wherein the spin diode/rectification effect stems from the conjugated length and asymmetry of the molecular framework, which is the pre-requisite for electronic asymmetry of the adsorbed species. The negative differential resistance, spin-filtering and switching properties are also unveiled. In particular, it is revealed that the strong couplings between the electrodes and molecules are responsible for the negative differential resistance.

  3. Biradical and triradical organic magnetic molecules as spin filters and rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, L. [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, K.L., E-mail: klyao@hust.edu.cn [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Science, Shengyang 110015 (China); Liu, Z.L. [School of Physics, School of Optoelectronics Science and Engineering, Wuhan Pulsed Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-03-13

    Graphical abstract: (a) Negative differential resistance (NDR) characteristic and antiparallel spin-current (ASC) rectification; (b) spin-current (SC) rectification and charge-current (CC) rectification properties Display Omitted Highlights: Black-Right-Pointing-Pointer Organic magnetic molecules at gold electrodes as spin/charge rectifier. Black-Right-Pointing-Pointer Spin diode/rectification stems from length and asymmetry of molecular framework. Black-Right-Pointing-Pointer Negative differential resistance, spin-filtering and switching evidenced. - Abstract: We have theoretically investigated the spin-polarized transport properties of molecular junctions consisting of biradical and triradical organic magnetic molecules sandwiched between two symmetric gold electrodes, respectively. It shows that these junctions function as a spin rectifier or a combination of spin and charge rectifiers with high spin rectification ratios exceeding 100, wherein the spin diode/rectification effect stems from the conjugated length and asymmetry of the molecular framework, which is the pre-requisite for electronic asymmetry of the adsorbed species. The negative differential resistance, spin-filtering and switching properties are also unveiled. In particular, it is revealed that the strong couplings between the electrodes and molecules are responsible for the negative differential resistance.

  4. Multi-Service Highly Sensitive Rectifier for Enhanced RF Energy Scavenging

    Science.gov (United States)

    Shariati, Negin; Rowe, Wayne S. T.; Scott, James R.; Ghorbani, Kamran

    2015-01-01

    Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478–496 and 852–869 MHz) and exhibits favorable impedance matching over a broad input power range (−40 to −10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of −10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments. PMID:25951137

  5. Microfluidic rectifier based on poly(dimethylsiloxane) membrane and its application to a micropump.

    Science.gov (United States)

    Wang, Yao-Nan; Tsai, Chien-Hsiung; Fu, Lung-Ming; Lin Liou, Lung-Kai

    2013-01-01

    A microfluidic rectifier incorporating an obstructed microchannel and a PDMS membrane is proposed. During forward flow, the membrane deflects in the upward direction; thereby allowing the fluid to pass over the obstacle. Conversely, during reverse flow, the membrane seals against the obstacle, thereby closing the channel and preventing flow. It is shown that the proposed device can operate over a wide pressure range by increasing or decreasing the membrane thickness as required. A microfluidic pump is realized by integrating the rectifier with a simple stepper motor mechanism. The experimental results show that the pump can achieve a vertical left height of more than 2 m. Moreover, it is shown that a maximum flow rate of 6.3 ml/min can be obtained given a membrane thickness of 200 μm and a motor velocity of 80 rpm. In other words, the proposed microfluidic rectifier not only provides an effective means of preventing reverse flow but also permits the realization of a highly efficient microfluidic pump.

  6. Adding rectifying/stripping section type heat integration to a pressure-swing distillation (PSD) process

    International Nuclear Information System (INIS)

    Huang Kejin; Shan Lan; Zhu Qunxiong; Qian Jixin

    2008-01-01

    This paper studies the economical effect of considering rectifying/stripping section type heat integration in a pressure-swing distillation (PSD) process separating a binary homogeneous pressure-sensitive azeotrope. The schemes for arranging heat integration between the rectifying section and the stripping section of the high- and low-pressure distillation columns, respectively, are derived and an effective procedure is devised for the conceptual process design of the heat-integrated PSD processes. In terms of the separation of a binary azeotropic mixture of acetonitrile and water, intensive comparisons are made between the conventional and heat-integrated PSD processes. It is demonstrated that breaking a pressure-sensitive azeotropic mixture can be made more economical than the current practice with the conventional PSD process. For boosting further the thermodynamic efficiency of a PSD process, it is strongly suggested to consider simultaneously the condenser/reboiler type heat integration with the rectifying/stripping section type heat integration in process synthesis and design

  7. Adding rectifying/stripping section type heat integration to a pressure-swing distillation (PSD) process

    Energy Technology Data Exchange (ETDEWEB)

    Huang Kejin [School of Information Science and Technology, Beijing University of Chemical Technology, Chaoyang-qu, Beijing-shi, Beijing 100029 (China)], E-mail: huangkj@mail.buct.edu.cn; Shan Lan; Zhu Qunxiong [School of Information Science and Technology, Beijing University of Chemical Technology, Chaoyang-qu, Beijing-shi, Beijing 100029 (China); Qian Jixin [School of Information Science and Technology, Zhejiang University, Xihu-qu, Hangzhou-shi, Zhejiang 300027 (China)

    2008-06-15

    This paper studies the economical effect of considering rectifying/stripping section type heat integration in a pressure-swing distillation (PSD) process separating a binary homogeneous pressure-sensitive azeotrope. The schemes for arranging heat integration between the rectifying section and the stripping section of the high- and low-pressure distillation columns, respectively, are derived and an effective procedure is devised for the conceptual process design of the heat-integrated PSD processes. In terms of the separation of a binary azeotropic mixture of acetonitrile and water, intensive comparisons are made between the conventional and heat-integrated PSD processes. It is demonstrated that breaking a pressure-sensitive azeotropic mixture can be made more economical than the current practice with the conventional PSD process. For boosting further the thermodynamic efficiency of a PSD process, it is strongly suggested to consider simultaneously the condenser/reboiler type heat integration with the rectifying/stripping section type heat integration in process synthesis and design.

  8. Influence of cavitation bubble growth by rectified diffusion on cavitation-enhanced HIFU

    Science.gov (United States)

    Okita, Kohei; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro

    2017-11-01

    Cavitation is becoming increasingly important in therapeutic ultrasound applications such as diagnostic, tumor ablation and lithotripsy. Mass transfer through gas-liquid interface due to rectified diffusion is important role in an initial stage of cavitation bubble growth. In the present study, influences of the rectified diffusion on cavitation-enhanced high-intensity focused ultrasound (HIFU) was investigated numerically. Firstly, the mass transfer rate of gas from the surrounding medium to the bubble was examined as function of the initial bubble radius and the driving pressure amplitude. As the result, the pressure required to bubble growth was decreases with increasing the initial bubble radius. Next, the cavitation-enhanced HIFU, which generates cavitation bubbles by high-intensity burst and induces the localized heating owing to cavitation bubble oscillation by low-intensity continuous waves, was reproduced by the present simulation. The heating region obtained by the simulation is agree to the treatment region of an in vitro experiment. Additionally, the simulation result shows that the localized heating is enhanced by the increase of the equilibrium bubble size due to the rectified diffusion. This work was supported by JSPS KAKENHI Grant Numbers JP26420125,JP17K06170.

  9. Nonlinear beam mechanics

    NARCIS (Netherlands)

    Westra, H.J.R.

    2012-01-01

    In this Thesis, nonlinear dynamics and nonlinear interactions are studied from a micromechanical point of view. Single and doubly clamped beams are used as model systems where nonlinearity plays an important role. The nonlinearity also gives rise to rich dynamic behavior with phenomena like

  10. Synaptic dimorphism in Onychophoran cephalic ganglia

    Directory of Open Access Journals (Sweden)

    Z Peña-Contreras

    2007-03-01

    Full Text Available The taxonomic location of the Onychophora has been controversial because of their phenotypic and genotypic characteristics, related to both annelids and arthropods. We analyzed the ultrastructure of the neurons and their synapses in the cephalic ganglion of a poorly known invertebrate, the velvet worm Peripatus sedgwicki, from the mountainous region of El Valle, Mérida, Venezuela. Cephalic ganglia were dissected, fixed and processed for transmission electron microscopy. The animal has a high degree of neurobiological development, as evidenced by the presence of asymmetric (excitatory and symmetric (inhibitory synapses, as well as the existence of glial cell processes in a wide neuropile zone. The postsynaptic terminals were seen to contain subsynaptic cisterns formed by membranes of smooth endoplasmic reticulum beneath the postsynaptic density, whereas the presynaptic terminal showed numerous electron transparent synaptic vesicles. From the neurophylogenetic perspectives, the ultrastructural characteristics of the central nervous tissue of the Onychophora show important evolutionary acquirements, such as the presence of both excitatory and inhibitory synapses, indicating functional synaptic transmission, and the appearance of mature glial cells. Rev. Biol . Trop. 55 (1: 261-267. Epub 2007 March. 31.Estudiamos la ultraestructura de las neuronas y sus sinapsis del ganglio cefálico de un invertebrado poco conocido del phylum Onychophora: Peripatus sedgwicki de los Andes Venezolanos, utilizando para ello la microscopía electrónica de transmisión. La localización taxonómica de los onicóforos ha sido controversial debido a sus características fenotípicas y genotípicas que los relacionan tanto con los anélidos como con los artrópodos. Para este trabajo se estudió el ganglio cefálico de P. sedgwicki de la zona montañosa de El Valle, Mérida, Venezuela. El ganglio cefálico se localiza en la región anterior del animal y fue diseccionado

  11. Characterizing synaptic protein development in human visual cortex enables alignment of synaptic age with rat visual cortex

    Science.gov (United States)

    Pinto, Joshua G. A.; Jones, David G.; Williams, C. Kate; Murphy, Kathryn M.

    2015-01-01

    Although many potential neuroplasticity based therapies have been developed in the lab, few have translated into established clinical treatments for human neurologic or neuropsychiatric diseases. Animal models, especially of the visual system, have shaped our understanding of neuroplasticity by characterizing the mechanisms that promote neural changes and defining timing of the sensitive period. The lack of knowledge about development of synaptic plasticity mechanisms in human cortex, and about alignment of synaptic age between animals and humans, has limited translation of neuroplasticity therapies. In this study, we quantified expression of a set of highly conserved pre- and post-synaptic proteins (Synapsin, Synaptophysin, PSD-95, Gephyrin) and found that synaptic development in human primary visual cortex (V1) continues into late childhood. Indeed, this is many years longer than suggested by neuroanatomical studies and points to a prolonged sensitive period for plasticity in human sensory cortex. In addition, during childhood we found waves of inter-individual variability that are different for the four proteins and include a stage during early development (visual cortex and identified a simple linear equation that provides robust alignment of synaptic age between humans and rats. Alignment of synaptic ages is important for age-appropriate targeting and effective translation of neuroplasticity therapies from the lab to the clinic. PMID:25729353

  12. An RF Energy Harvester System Using UHF Micropower CMOS Rectifier Based on a Diode Connected CMOS Transistor

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Shokrani

    2014-01-01

    Full Text Available This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18 μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier’s output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology.

  13. An Integrated Power-Efficient Active Rectifier With Offset-Controlled High Speed Comparators for Inductively Powered Applications

    Science.gov (United States)

    Lee, Hyung-Min; Ghovanloo, Maysam

    2011-01-01

    We present an active full-wave rectifier with offset-controlled high speed comparators in standard CMOS that provides high power conversion efficiency (PCE) in high frequency (HF) range for inductively powered devices. This rectifier provides much lower dropout voltage and far better PCE compared to the passive on-chip or off-chip rectifiers. The built-in offset-control functions in the comparators compensate for both turn-on and turn-off delays in the main rectifying switches, thus maximizing the forward current delivered to the load and minimizing the back current to improve the PCE. We have fabricated this active rectifier in a 0.5-μm 3M2P standard CMOS process, occupying 0.18 mm2 of chip area. With 3.8 V peak ac input at 13.56 MHz, the rectifier provides 3.12 V dc output to a 500 Ω load, resulting in the PCE of 80.2%, which is the highest measured at this frequency. In addition, overvoltage protection (OVP) as safety measure and built-in back telemetry capabilities have been incorporated in our design using detuning and load shift keying (LSK) techniques, respectively, and tested. PMID:22174666

  14. Identification of synaptic targets of Drosophila pumilio.

    Directory of Open Access Journals (Sweden)

    Gengxin Chen

    2008-02-01

    Full Text Available Drosophila Pumilio (Pum protein is a translational regulator involved in embryonic patterning and germline development. Recent findings demonstrate that Pum also plays an important role in the nervous system, both at the neuromuscular junction (NMJ and in long-term memory formation. In neurons, Pum appears to play a role in homeostatic control of excitability via down regulation of para, a voltage gated sodium channel, and may more generally modulate local protein synthesis in neurons via translational repression of eIF-4E. Aside from these, the biologically relevant targets of Pum in the nervous system remain largely unknown. We hypothesized that Pum might play a role in regulating the local translation underlying synapse-specific modifications during memory formation. To identify relevant translational targets, we used an informatics approach to predict Pum targets among mRNAs whose products have synaptic localization. We then used both in vitro binding and two in vivo assays to functionally confirm the fidelity of this informatics screening method. We find that Pum strongly and specifically binds to RNA sequences in the 3'UTR of four of the predicted target genes, demonstrating the validity of our method. We then demonstrate that one of these predicted target sequences, in the 3'UTR of discs large (dlg1, the Drosophila PSD95 ortholog, can functionally substitute for a canonical NRE (Nanos response element in vivo in a heterologous functional assay. Finally, we show that the endogenous dlg1 mRNA can be regulated by Pumilio in a neuronal context, the adult mushroom bodies (MB, which is an anatomical site of memory storage.

  15. Inward rectifier potassium channels in the HL-1 cardiomyocyte-derived cell line.

    Science.gov (United States)

    Goldoni, Dana; Zhao, YouYou; Green, Brian D; McDermott, Barbara J; Collins, Anthony

    2010-11-01

    HL-1 is a line of immortalized cells of cardiomyocyte origin that are a useful complement to native cardiomyocytes in studies of cardiac gene regulation. Several types of ion channel have been identified in these cells, but not the physiologically important inward rectifier K(+) channels. Our aim was to identify and characterize inward rectifier K(+) channels in HL-1 cells. External Ba(2+) (100 µM) inhibited 44 ± 0.05% (mean ± s.e.m., n = 11) of inward current in whole-cell patch-clamp recordings. The reversal potential of the Ba(2+)-sensitive current shifted with external [K(+)] as expected for K(+)-selective channels. The slope conductance of the inward Ba(2+)-sensitive current increased with external [K(+)]. The apparent Kd for Ba(2+) was voltage dependent, ranging from 15 µM at -150  mV to 148 µM at -75  mV in 120  mM external K(+). This current was insensitive to 10 µM glybenclamide. A component of whole-cell current was sensitive to 150 µM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), although it did not correspond to the Ba(2+)-sensitive component. The effect of external 1 mM Cs(+) was similar to that of Ba(2+). Polymerase chain reaction using HL-1 cDNA as template and primers specific for the cardiac inward rectifier K(ir)2.1 produced a fragment of the expected size that was confirmed to be K(ir)2.1 by DNA sequencing. In conclusion, HL-1 cells express a current that is characteristic of cardiac inward rectifier K(+) channels, and express K(ir)2.1 mRNA. This cell line may have use as a system for studying inward rectifier gene regulation in a cardiomyocyte phenotype. © 2010 Wiley-Liss, Inc.

  16. Synaptic vesicle dynamic changes in a model of fragile X.

    Science.gov (United States)

    Broek, Jantine A C; Lin, Zhanmin; de Gruiter, H Martijn; van 't Spijker, Heleen; Haasdijk, Elize D; Cox, David; Ozcan, Sureyya; van Cappellen, Gert W A; Houtsmuller, Adriaan B; Willemsen, Rob; de Zeeuw, Chris I; Bahn, Sabine

    2016-01-01

    Fragile X syndrome (FXS) is a single-gene disorder that is the most common heritable cause of intellectual disability and the most frequent monogenic cause of autism spectrum disorders (ASD). FXS is caused by an expansion of trinucleotide repeats in the promoter region of the fragile X mental retardation gene (Fmr1). This leads to a lack of fragile X mental retardation protein (FMRP), which regulates translation of a wide range of messenger RNAs (mRNAs). The extent of expression level alterations of synaptic proteins affected by FMRP loss and their consequences on synaptic dynamics in FXS has not been fully investigated. Here, we used an Fmr1 knockout (KO) mouse model to investigate the molecular mechanisms underlying FXS by monitoring protein expression changes using shotgun label-free liquid-chromatography mass spectrometry (LC-MS(E)) in brain tissue and synaptosome fractions. FXS-associated candidate proteins were validated using selected reaction monitoring (SRM) in synaptosome fractions for targeted protein quantification. Furthermore, functional alterations in synaptic release and dynamics were evaluated using live-cell imaging, and interpretation of synaptic dynamics differences was investigated using electron microscopy. Key findings relate to altered levels of proteins involved in GABA-signalling, especially in the cerebellum. Further exploration using microscopy studies found reduced synaptic vesicle unloading of hippocampal neurons and increased vesicle unloading in cerebellar neurons, which suggests a general decrease of synaptic transmission. Our findings suggest that FMRP is a regulator of synaptic vesicle dynamics, which supports the role of FMRP in presynaptic functions. Taken together, these studies provide novel insights into the molecular changes associated with FXS.

  17. Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc.

    Science.gov (United States)

    Anderson, Charles T; Radford, Robert J; Zastrow, Melissa L; Zhang, Daniel Y; Apfel, Ulf-Peter; Lippard, Stephen J; Tzounopoulos, Thanos

    2015-05-19

    Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling.

  18. Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc

    Science.gov (United States)

    Anderson, Charles T.; Radford, Robert J.; Zastrow, Melissa L.; Zhang, Daniel Y.; Apfel, Ulf-Peter; Lippard, Stephen J.; Tzounopoulos, Thanos

    2015-01-01

    Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling. PMID:25947151

  19. Novel low harmonics 3-phase rectifiers for efficient motor systems; Novel low harmonics 3-phase rectifiers for efficient motor systems. Konzeptstudie - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Pietkiewicz, A.; Melly, S.; Tucker, A.; Haeberle, N. [Schaffner EMV AG, Luterbach (Switzerland); Biner, H.-P. [Haute Ecole Specialisee de Suisse occidentale, HES-SO Valais, Sion (Switzerland)

    2010-07-15

    This final report for the Swiss Federal Office of Energy (SFOE) presents the results of a concept study made concerning novel low harmonics 3-phase rectifiers for efficient motor systems. The harmonic distortions which are produced by these systems are discussed and ways of minimising them are examined. The authors discuss novel, passive, multi-pulse current splitters that are considered to be cost efficient, compact and highly-reliable harmonics mitigation concepts for three-phase loads. According to the authors, functional prototypes for a nominal load of 4 kW proved, in laboratory tests, the outstanding properties of multi-pulse current splitters with respect to harmonics cancellation and robustness against voltage asymmetry. The design process, prototype construction and application tests are discussed, as are energy-saving potentials and marketing aspects.

  20. Synaptic membrane rafts: traffic lights for local neurotrophin signaling?

    Science.gov (United States)

    Zonta, Barbara; Minichiello, Liliana

    2013-10-18

    Lipid rafts, cholesterol and lipid rich microdomains, are believed to play important roles as platforms for the partitioning of transmembrane and synaptic proteins involved in synaptic signaling, plasticity, and maintenance. There is increasing evidence of a physical interaction between post-synaptic densities and post-synaptic lipid rafts. Localization of proteins within lipid rafts is highly regulated, and therefore lipid rafts may function as traffic lights modulating and fine-tuning neuronal signaling. The tyrosine kinase neurotrophin receptors (Trk) and the low-affinity p75 neurotrophin receptor (p75(NTR)) are enriched in neuronal lipid rafts together with the intermediates of downstream signaling pathways, suggesting a possible role of rafts in neurotrophin signaling. Moreover, neurotrophins and their receptors are involved in the regulation of cholesterol metabolism. Cholesterol is an important component of lipid rafts and its depletion leads to gradual loss of synapses, underscoring the importance of lipid rafts for proper neuronal function. Here, we review and discuss the idea that translocation of neurotrophin receptors in synaptic rafts may account for the selectivity of their transduced signals.

  1. Synaptic membrane rafts: traffic lights for local neurotrophin signalling?

    Directory of Open Access Journals (Sweden)

    Barbara eZonta

    2013-10-01

    Full Text Available Lipid rafts, cholesterol and lipid rich microdomains, are believed to play important roles as platforms for the partitioning of transmembrane and synaptic proteins involved in synaptic signalling, plasticity and maintenance. There is increasing evidence of a physical interaction between post-synaptic densities and post-synaptic lipid rafts. Localization of proteins within lipid rafts is highly regulated, and therefore lipid rafts may function as traffic lights modulating and fine-tuning neuronal signalling. The tyrosine kinase neurotrophin receptors (Trk and the low-affinity p75 neurotrophin receptor (p75NTR are enriched in neuronal lipid rafts together with the intermediates of downstream signalling pathways, suggesting a possible role of rafts in neurotrophin signalling. Moreover, neurotrophins and their receptors are involved in the regulation of cholesterol metabolism. Cholesterol is an important component of lipid rafts and its depletion leads to gradual loss of synapses, underscoring the importance of lipid rafts for proper neuronal function. Here, we review and discuss the idea that translocation of neurotrophin receptors in synaptic rafts may account for the selectivity of their transduced signals.

  2. Limited distal organelles and synaptic function in extensive monoaminergic innervation.

    Science.gov (United States)

    Tao, Juan; Bulgari, Dinara; Deitcher, David L; Levitan, Edwin S

    2017-08-01

    Organelles such as neuropeptide-containing dense-core vesicles (DCVs) and mitochondria travel down axons to supply synaptic boutons. DCV distribution among en passant boutons in small axonal arbors is mediated by circulation with bidirectional capture. However, it is not known how organelles are distributed in extensive arbors associated with mammalian dopamine neuron vulnerability, and with volume transmission and neuromodulation by monoamines and neuropeptides. Therefore, we studied presynaptic organelle distribution in Drosophila octopamine neurons that innervate ∼20 muscles with ∼1500 boutons. Unlike in smaller arbors, distal boutons in these arbors contain fewer DCVs and mitochondria, although active zones are present. Absence of vesicle circulation is evident by proximal nascent DCV delivery, limited impact of retrograde transport and older distal DCVs. Traffic studies show that DCV axonal transport and synaptic capture are not scaled for extensive innervation, thus limiting distal delivery. Activity-induced synaptic endocytosis and synaptic neuropeptide release are also reduced distally. We propose that limits in organelle transport and synaptic capture compromise distal synapse maintenance and function in extensive axonal arbors, thereby affecting development, plasticity and vulnerability to neurodegenerative disease. © 2017. Published by The Company of Biologists Ltd.

  3. Synaptic contacts impaired by styrene-7,8-oxide toxicity

    International Nuclear Information System (INIS)

    Corsi, P.; D'Aprile, A.; Nico, B.; Costa, G.L.; Assennato, G.

    2007-01-01

    Styrene-7,8-oxide (SO), a chemical compound widely used in industrial applications, is a potential hazard for humans, particularly in occupational settings. Neurobehavioral changes are consistently observed in occupationally exposed individuals and alterations of neurotransmitters associated with neuronal loss have been reported in animal models. Although the toxic effects of styrene have been extensively documented, the molecular mechanisms responsible for SO-induced neurotoxicity are still unclear. A possible dopamine-mediated effect of styrene neurotoxicity has been previously demonstrated, since styrene oxide alters dopamine neurotransmission in the brain. Thus, the present study hypothesizes that styrene neurotoxicity may involve synaptic contacts. Primary striatal neurons were exposed to styrene oxide at different concentrations (0.1-1 mM) for different time periods (8, 16, and 24 h) to evaluate the dose able to induce synaptic impairments. The expression of proteins crucial for synaptic transmission such as Synapsin, Synaptophysin, and RAC-1 were considered. The levels of Synaptophysin and RAC-1 decreased in a dose-dependent manner. Accordingly, morphological alterations, observed at the ultrastructural level, primarily involved the pre-synaptic compartment. In SO-exposed cultures, the biochemical cascade of caspases was activated affecting the cytoskeleton components as their target. Thus the impairments in synaptic contacts observed in SO-exposed cultures might reflect a primarily morphological alteration of neuronal cytoskeleton. In addition, our data support the hypothesis developed by previous authors of reactive oxygen species (ROS) initiating events of SO cytotoxicity

  4. Readily releasable pool of synaptic vesicles measured at single synaptic contacts.

    Science.gov (United States)

    Trigo, Federico F; Sakaba, Takeshi; Ogden, David; Marty, Alain

    2012-10-30

    To distinguish between different models of vesicular release in brain synapses, it is necessary to know the number of vesicles of transmitter that can be released immediately at individual synapses by a high-calcium stimulus, the readily releasable pool (RRP). We used direct stimulation by calcium uncaging at identified, single-site inhibitory synapses to investigate the statistics of vesicular release and the size of the RRP. Vesicular release, detected as quantal responses in the postsynaptic neuron, showed an unexpected stochastic variation in the number of quanta from stimulus to stimulus at high intracellular calcium, with a mean of 1.9 per stimulus and a maximum of three or four. The results provide direct measurement of the RRP at single synaptic sites. They are consistent with models in which release proceeds from a small number of vesicle docking sites with an average occupancy around 0.7.

  5. Synaptic proteins and receptors defects in autism spectrum disorders

    Directory of Open Access Journals (Sweden)

    Jianling eChen

    2014-09-01

    Full Text Available Recent studies have found that hundreds of genetic variants, including common and rare variants, rare and de novo mutations, and common polymorphisms have contributed to the occurrence of autism spectrum disorders (ASDs. The mutations in a number of genes such as neurexin, neuroligin, postsynaptic density protein 95 (PSD-95, SH3 and multiple ankyrin repeat domains 3 (SHANK3, synapsin, gephyrin, cadherin (CDH and protocadherin (PCDH, thousand-and-one-amino acid 2 kinase (TAOK2, and contactin (CNTN, have been shown to play important roles in the development and function of synapses. In addition, synaptic receptors, such as gamma-aminobutyric acid (GABA receptors and glutamate receptors, have also been associated with ASDs. This review will primarily focus on the defects of synaptic proteins and receptors associated with ASDs and their roles in the pathogenesis of ASDs via synaptic pathways.

  6. Interregional synaptic maps among engram cells underlie memory formation.

    Science.gov (United States)

    Choi, Jun-Hyeok; Sim, Su-Eon; Kim, Ji-Il; Choi, Dong Il; Oh, Jihae; Ye, Sanghyun; Lee, Jaehyun; Kim, TaeHyun; Ko, Hyoung-Gon; Lim, Chae-Seok; Kaang, Bong-Kiun

    2018-04-27

    Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  7. Integrated neuron circuit for implementing neuromorphic system with synaptic device

    Science.gov (United States)

    Lee, Jeong-Jun; Park, Jungjin; Kwon, Min-Woo; Hwang, Sungmin; Kim, Hyungjin; Park, Byung-Gook

    2018-02-01

    In this paper, we propose and fabricate Integrate & Fire neuron circuit for implementing neuromorphic system. Overall operation of the circuit is verified by measuring discrete devices and the output characteristics of the circuit. Since the neuron circuit shows asymmetric output characteristic that can drive synaptic device with Spike-Timing-Dependent-Plasticity (STDP) characteristic, the autonomous weight update process is also verified by connecting the synaptic device and the neuron circuit. The timing difference of the pre-neuron and the post-neuron induce autonomous weight change of the synaptic device. Unlike 2-terminal devices, which is frequently used to implement neuromorphic system, proposed scheme of the system enables autonomous weight update and simple configuration by using 4-terminal synapse device and appropriate neuron circuit. Weight update process in the multi-layer neuron-synapse connection ensures implementation of the hardware-based artificial intelligence, based on Spiking-Neural- Network (SNN).

  8. PRRT2: from Paroxysmal Disorders to Regulation of Synaptic Function.

    Science.gov (United States)

    Valtorta, Flavia; Benfenati, Fabio; Zara, Federico; Meldolesi, Jacopo

    2016-10-01

    In the past few years, proline-rich transmembrane protein (PRRT)2 has been identified as the causative gene for several paroxysmal neurological disorders. Recently, an important role of PRRT2 in synapse development and function has emerged. Knock down of the protein strongly impairs the formation of synaptic contacts and neurotransmitter release. At the nerve terminal, PRRT2 endows synaptic vesicle exocytosis with Ca 2+ sensitivity by interacting with proteins of the fusion complex and with the Ca 2+ sensors synaptotagmins (Syts). In the postsynaptic compartment, PRRT2 interacts with glutamate receptors. The study of PRRT2 and of its mutations may help in refining our knowledge of the process of synaptic transmission and elucidating the pathogenetic mechanisms leading to derangement of network function in paroxysmal disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Synaptic clustering within dendrites: an emerging theory of memory formation

    Science.gov (United States)

    Kastellakis, George; Cai, Denise J.; Mednick, Sara C.; Silva, Alcino J.; Poirazi, Panayiota

    2015-01-01

    It is generally accepted that complex memories are stored in distributed representations throughout the brain, however the mechanisms underlying these representations are not understood. Here, we review recent findings regarding the subcellular mechanisms implicated in memory formation, which provide evidence for a dendrite-centered theory of memory. Plasticity-related phenomena which affect synaptic properties, such as synaptic tagging and capture, synaptic clustering, branch strength potentiation and spinogenesis provide the foundation for a model of memory storage that relies heavily on processes operating at the dendrite level. The emerging picture suggests that clusters of functionally related synapses may serve as key computational and memory storage units in the brain. We discuss both experimental evidence and theoretical models that support this hypothesis and explore its advantages for neuronal function. PMID:25576663

  10. Defective glycinergic synaptic transmission in zebrafish motility mutants

    Directory of Open Access Journals (Sweden)

    Hiromi Hirata

    2010-01-01

    Full Text Available Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Recently, in vivo analysis of glycinergic synaptic transmission has been pursued in zebrafish using molecular genetics. An ENU mutagenesis screen identified two behavioral mutants that are defective in glycinergic synaptic transmission. Zebrafish bandoneon (beo mutants have a defect in glrbb, one of the duplicated glycine receptor (GlyR β subunit genes. These mutants exhibit a loss of glycinergic synaptic transmission due to a lack of synaptic aggregation of GlyRs. Due to the consequent loss of reciprocal inhibition of motor circuits between the two sides of the spinal cord, motor neurons activate simultaneously on both sides resulting in bilateral contraction of axial muscles of beo mutants, eliciting the so-called ‘accordion’ phenotype. Similar defects in GlyR subunit genes have been observed in several mammals and are the basis for human hyperekplexia/startle disease. By contrast, zebrafish shocked (sho mutants have a defect in slc6a9, encoding GlyT1, a glycine transporter that is expressed by astroglial cells surrounding the glycinergic synapse in the hindbrain and spinal cord. GlyT1 mediates rapid uptake of glycine from the synaptic cleft, terminating synaptic transmission. In zebrafish sho mutants, there appears to be elevated extracellular glycine resulting in persistent inhibition of postsynaptic neurons and subsequent reduced motility, causing the ‘twitch once’ phenotype. We review current knowledge regarding zebrafish ‘accordion’ and ‘twitch once’ mutants, including beo and sho, and report the identification of a new α2 subunit that revises the phylogeny of zebrafish GlyRs.

  11. Precise synaptic efficacy alignment suggests potentiation dominated learning

    Directory of Open Access Journals (Sweden)

    Christoph eHartmann

    2016-01-01

    Full Text Available Recent evidence suggests that parallel synapses from the same axonal branch onto the same dendritic branch have almost identical strength. It has been proposed that this alignment is only possible through learning rules that integrate activity over long time spans. However, learning mechanisms such as spike-timing-dependent plasticity (STDP are commonly assumed to be temporally local. Here, we propose that the combination of temporally local STDP and a multiplicative synaptic normalization mechanism is sufficient to explain the alignment of parallel synapses.To address this issue, we introduce three increasingly complex models: First, we model the idealized interaction of STDP and synaptic normalization in a single neuron as a simple stochastic process and derive analytically that the alignment effect can be described by a so-called Kesten process. From this we can derive that synaptic efficacy alignment requires potentiation-dominated learning regimes. We verify these conditions in a single-neuron model with independent spiking activities but more realistic synapses. As expected, we only observe synaptic efficacy alignment for long-term potentiation-biased STDP. Finally, we explore how well the findings transfer to recurrent neural networks where the learning mechanisms interact with the correlated activity of the network. We find that due to the self-reinforcing correlations in recurrent circuits under STDP, alignment occurs for both long-term potentiation- and depression-biased STDP, because the learning will be potentiation dominated in both cases due to the potentiating events induced by correlated activity. This is in line with recent results demonstrating a dominance of potentiation over depression during waking and normalization during sleep. This leads us to predict that individual spine pairs will be more similar in the morning than they are after sleep depriviation.In conclusion, we show that synaptic normalization in conjunction with

  12. Emergence of Functional Specificity in Balanced Networks with Synaptic Plasticity.

    Directory of Open Access Journals (Sweden)

    Sadra Sadeh

    2015-06-01

    Full Text Available In rodent visual cortex, synaptic connections between orientation-selective neurons are unspecific at the time of eye opening, and become to some degree functionally specific only later during development. An explanation for this two-stage process was proposed in terms of Hebbian plasticity based on visual experience that would eventually enhance connections between neurons with similar response features. For this to work, however, two conditions must be satisfied: First, orientation selective neuronal responses must exist before specific recurrent synaptic connections can be established. Second, Hebbian learning must be compatible with the recurrent network dynamics contributing to orientation selectivity, and the resulting specific connectivity must remain stable for unspecific background activity. Previous studies have mainly focused on very simple models, where the receptive fields of neurons were essentially determined by feedforward mechanisms, and where the recurrent network was small, lacking the complex recurrent dynamics of large-scale networks of excitatory and inhibitory neurons. Here we studied the emergence of functionally specific connectivity in large-scale recurrent networks with synaptic plasticity. Our results show that balanced random networks, which already exhibit highly selective responses at eye opening, can develop feature-specific connectivity if appropriate rules of synaptic plasticity are invoked within and between excitatory and inhibitory populations. If these conditions are met, the initial orientation selectivity guides the process of Hebbian learning and, as a result, functionally specific and a surplus of bidirectional connections emerge. Our results thus demonstrate the cooperation of synaptic plasticity and recurrent dynamics in large-scale functional networks with realistic receptive fields, highlight the role of inhibition as a critical element in this process, and paves the road for further computational

  13. Depression as a Glial-Based Synaptic Dysfunction

    Directory of Open Access Journals (Sweden)

    Daniel eRial

    2016-01-01

    Full Text Available Recent studies combining pharmacological, behavioral, electrophysiological and molecular approaches indicate that depression results from maladaptive neuroplastic processing occurring in defined frontolimbic circuits responsible for emotional processing such as the prefrontal cortex, hippocampus, amygdala and ventral striatum. However, the exact mechanisms controlling synaptic plasticity that are disrupted to trigger depressive conditions have not been elucidated. Since glial cells (astrocytes and microglia tightly and dynamically interact with synapses, engaging a bi-directional communication critical for the processing of synaptic information, we now revisit the role of glial cells in the etiology of depression focusing on a dysfunction of the ‘quad-partite’ synapse. This interest is supported by the observations that depressive-like conditions are associated with a decreased density and hypofunction of astrocytes and with an increase microglia ‘activation’ in frontolimbic regions, which is expected to contribute for the synaptic dysfunction present in depression. Furthermore, the traditional culprits of depression (glucocorticoids, biogenic amines, BDNF affect glia functioning, whereas antidepressant treatments (SSRIs, electroshock, deep brain stimulation recover glia functioning. In this context of a quad-partite synapse, systems modulating glia-synapse bidirectional communication - such as the purinergic neuromodulation system operated by ATP and adenosine - emerge as promising candidates to re-normalize synaptic function by combining direct synaptic effects with an ability to also control astrocyte and microglia function. This proposed triple action of purines to control aberrant synaptic function illustrates the rationale to consider the interference with glia dysfunction as a mechanism of action driving the design of future pharmacological tools to manage depression.

  14. Defective Glycinergic Synaptic Transmission in Zebrafish Motility Mutants

    Science.gov (United States)

    Hirata, Hiromi; Carta, Eloisa; Yamanaka, Iori; Harvey, Robert J.; Kuwada, John Y.

    2009-01-01

    Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Recently, in vivo analysis of glycinergic synaptic transmission has been pursued in zebrafish using molecular genetics. An ENU mutagenesis screen identified two behavioral mutants that are defective in glycinergic synaptic transmission. Zebrafish bandoneon (beo) mutants have a defect in glrbb, one of the duplicated glycine receptor (GlyR) β subunit genes. These mutants exhibit a loss of glycinergic synaptic transmission due to a lack of synaptic aggregation of GlyRs. Due to the consequent loss of reciprocal inhibition of motor circuits between the two sides of the spinal cord, motor neurons activate simultaneously on both sides resulting in bilateral contraction of axial muscles of beo mutants, eliciting the so-called ‘accordion’ phenotype. Similar defects in GlyR subunit genes have been observed in several mammals and are the basis for human hyperekplexia/startle disease. By contrast, zebrafish shocked (sho) mutants have a defect in slc6a9, encoding GlyT1, a glycine transporter that is expressed by astroglial cells surrounding the glycinergic synapse in the hindbrain and spinal cord. GlyT1 mediates rapid uptake of glycine from the synaptic cleft, terminating synaptic transmission. In zebrafish sho mutants, there appears to be elevated extracellular glycine resulting in persistent inhibition of postsynaptic neurons and subsequent reduced motility, causing the ‘twitch-once’ phenotype. We review current knowledge regarding zebrafish ‘accordion’ and ‘twitch-once’ mutants, including beo and sho, and report the identification of a new α2 subunit that revises the phylogeny of zebrafish GlyRs. PMID:20161699

  15. Hardwiring of fine synaptic layers in the zebrafish visual pathway

    Directory of Open Access Journals (Sweden)

    Taylor Michael R

    2008-12-01

    Full Text Available Abstract Background Neuronal connections are often arranged in layers, which are divided into sublaminae harboring synapses with similar response properties. It is still debated how fine-grained synaptic layering is established during development. Here we investigated two stratified areas of the zebrafish visual pathway, the inner plexiform layer (IPL of the retina and the neuropil of the optic tectum, and determined if activity is required for their organization. Results The IPL of 5-day-old zebrafish larvae is composed of at least nine sublaminae, comprising the connections between different types of amacrine, bipolar, and ganglion cells (ACs, BCs, GCs. These sublaminae were distinguished by their expression of cell type-specific transgenic fluorescent reporters and immunohistochemical markers, including protein kinase Cβ (PKC, parvalbumin (Parv, zrf3, and choline acetyltransferase (ChAT. In the tectum, four retinal input layers abut a laminated array of neurites of tectal cells, which differentially express PKC and Parv. We investigated whether these patterns were affected by experimental disruptions of retinal activity in developing fish. Neither elimination of light inputs by dark rearing, nor a D, L-amino-phosphono-butyrate-induced reduction in the retinal response to light onset (but not offset altered IPL or tectal lamination. Moreover, thorough elimination of chemical synaptic transmission with Botulinum toxin B left laminar synaptic arrays intact. Conclusion Our results call into question a role for activity-dependent mechanisms – instructive light signals, balanced on and off BC activity, Hebbian plasticity, or a permissive role for synaptic transmission – in the synaptic stratification we examined. We propose that genetically encoded cues are sufficient to target groups of neurites to synaptic layers in this vertebrate visual system.

  16. β1-Adrenoceptor autoantibodies affect action potential duration and delayed rectifier potassium currents in guinea pigs.

    Science.gov (United States)

    Zhao, Yuhui; Huang, Haixia; Du, Yunhui; Li, Xiao; Lv, Tingting; Zhang, Suli; Wei, Hua; Shang, Jianyu; Liu, Ping; Liu, Huirong

    2015-01-01

    β1-Adrenoceptor autoantibodies (β1-AAs) affect the action potential duration (APD) in cardiomyocytes and are related to ventricular arrhythmias. The delayed rectifier potassium current (I K) plays a crucial role in APD, but the effects of β1-AAs on I K have not been completely illuminated. This work aimed to observe the effects of β1-AAs on I K and APD and further explore the mechanisms of β1-AA-mediated ventricular arrhythmias. β1-AAs were obtained from sera of patients with coronary heart disease (CHD) and nonsustained ventricular tachycardia. With whole-cell patch clamp technique, action potentials and I K were recorded. The results illustrated 0.1 μmol/L β1-AAs shortened APD at 50 % (APD50) and 90 % (APD90) of the repolarization. However, at 0.01 μmol/L, β1-AAs had no effects on either APD90 or APD50 (P > 0.05). At 0.001 μmol/L, β1-AAs significantly prolonged APD90 and APD50. Moreover, β1-AAs (0.001, 0.01, 0.1 μmol/L) dose-dependently increased the rapidly activating delayed rectifier potassium current (I Kr), but similarly decreased the slowly activating delayed rectifier potassium current (I Ks) and increased L-type calcium currents at the different concentrations. Taken together, the IKr increase induced by high β1-AA concentrations is responsible for a significant APD reduction which would contribute to repolarization changes and trigger the malignant ventricular arrhythmias in CHD patients.

  17. Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock.

    Science.gov (United States)

    Farajnia, Sahar; Meijer, Johanna H; Michel, Stephan

    2016-10-01

    One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN), is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light-dark 16:8) and short-day (light-dark 8:16) photoperiods and membrane properties as well as K + currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K + current, that is, the circadian modulation of this ion channel's activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K + currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment. © The Author(s) 2016.

  18. Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock

    Directory of Open Access Journals (Sweden)

    Sahar Farajnia

    2016-09-01

    Full Text Available One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN, is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light–dark 16:8 and short-day (light–dark 8:16 photoperiods and membrane properties as well as K+ currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K+ current, that is, the circadian modulation of this ion channel’s activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K+ currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment.

  19. On Poisson Nonlinear Transformations

    Directory of Open Access Journals (Sweden)

    Nasir Ganikhodjaev

    2014-01-01

    Full Text Available We construct the family of Poisson nonlinear transformations defined on the countable sample space of nonnegative integers and investigate their trajectory behavior. We have proved that these nonlinear transformations are regular.

  20. Synaptic model for spontaneous activity in developing networks

    DEFF Research Database (Denmark)

    Lerchner, Alexander; Rinzel, J.

    2005-01-01

    Spontaneous rhythmic activity occurs in many developing neural networks. The activity in these hyperexcitable networks is comprised of recurring "episodes" consisting of "cycles" of high activity that alternate with "silent phases" with little or no activity. We introduce a new model of synaptic...... dynamics that takes into account that only a fraction of the vesicles stored in a synaptic terminal is readily available for release. We show that our model can reproduce spontaneous rhythmic activity with the same general features as observed in experiments, including a positive correlation between...

  1. Molecular motors that digest their track to rectify Brownian motion: processive movement of exonuclease enzymes.

    Science.gov (United States)

    Xie, Ping

    2009-09-16

    A general model is presented for the processive movement of molecular motors such as λ-exonuclease, RecJ and exonuclease I that use digestion of a DNA track to rectify Brownian motion along this track. Using this model, the translocation dynamics of these molecular motors is studied. The sequence-dependent pausing of λ-exonuclease, which results from a site-specific high affinity DNA interaction, is also studied. The theoretical results are consistent with available experimental data. Moreover, the model is used to predict the lifetime distribution and force dependence of these paused states.

  2. Molecular motors that digest their track to rectify Brownian motion: processive movement of exonuclease enzymes

    International Nuclear Information System (INIS)

    Xie Ping

    2009-01-01

    A general model is presented for the processive movement of molecular motors such as λ-exonuclease, RecJ and exonuclease I that use digestion of a DNA track to rectify Brownian motion along this track. Using this model, the translocation dynamics of these molecular motors is studied. The sequence-dependent pausing of λ-exonuclease, which results from a site-specific high affinity DNA interaction, is also studied. The theoretical results are consistent with available experimental data. Moreover, the model is used to predict the lifetime distribution and force dependence of these paused states.

  3. Rectifying the Optical-Field-Induced Current in Dielectrics: Petahertz Diode.

    Science.gov (United States)

    Lee, J D; Yun, Won Seok; Park, Noejung

    2016-02-05

    Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (m_{h}^{*}≪m_{e}^{*}) and low electron mass (m_{e}^{*}≪m_{h}^{*}), respectively. This proposition introduces the novel concept of a petahertz (10^{15}  Hz) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction.

  4. Power supply and stabilization of the supply system on board using decentralized voltage rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Grueb, W; Wegerer, K

    1987-04-01

    The functionally redundant power supply system of the Transrapid 06 II maglev train is described; it comprises four independent, battery-buffered networks and 30 linear generators per train section. Voltage rectifiers adapt the velocity- and load-dependent linear generator voltage to the 440 V d.c. networks and assure dynamic stabilisation as well as buffer battery loading. The result is a high-reliability power supply system on board with optimum utilisation of the power supplied by the linear generators while the train is running.

  5. High-performance digital triggering system for phase-controlled rectifiers

    International Nuclear Information System (INIS)

    Olsen, R.E.

    1983-01-01

    The larger power supplies used to power accelerator magnets are most commonly polyphase rectifiers using phase control. While this method is capable of handling impressive amounts of power, it suffers from one serious disadvantage, namely that of subharmonic ripple. Since the stability of the stored beam depends to a considerable extent on the regulation of the current in the bending magnets, subharmonic ripple, especially that of low frequency, can have a detrimental effect. At the NSLS, we have constructed a 12-pulse, phase control system using digital signal processing techniques that essentially eliminates subharmonic ripple

  6. Single Phase Current-Source Active Rectifier for Traction: Control System Design and Practical Problems

    Directory of Open Access Journals (Sweden)

    Jan Michalik

    2006-01-01

    Full Text Available This research has been motivated by industrial demand for single phase current-source active rectifier dedicated for reconstruction of older types of dc machine locomotives. This paper presents converters control structure design and simulations. The proposed converter control is based on the mathematical model and due to possible interaction with railway signaling and required low switching frequency employs synchronous PWM. The simulation results are verified by experimental tests performed on designed laboratory prototype of power of 7kVA

  7. Control of SiC Based Front-End Rectifier under Unbalanced Supply Voltage

    DEFF Research Database (Denmark)

    Maheshwari, Ramkrishan; Trintis, Ionut; Gohil, Ghanshyamsinh Vijaysinh

    2015-01-01

    A voltage source converter is used as a front end converter typically. In this paper, a converter which is realized using SiC MOSFET is considered. Due to SiC MOSFET, a switching frequency more than 50 kHz can be achieved. This can help increasing the current control loop bandwidth, which is not ...... together with a positive-sequence current controller for the front-end rectifier. A gain in the feedforward term can be changed to control the negative-sequence current. Simulation results are presented to verify the theory....

  8. Design Research on Three-Phase PWM Rectifier Based on Double Closed Loop Control Technology

    Directory of Open Access Journals (Sweden)

    Guang Ya LIU

    2014-02-01

    Full Text Available Based on the high frequency of three-phase voltage source PWM rectifier, this paper established a mathematical model of three phase current inner ring and outer ring voltage, and put forward the setting method of three phase double closed loop control. Finally, it was verified through simulation. The experimental results show that Three-phase output of DC voltage is stable with the operation of regulating systems, the current flowing into the grid tends to be sinusoidal and power factor is close to 1, which greatly reduce the interference of harmonics on the grid, thus improve grid operation.

  9. Comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier.

    Science.gov (United States)

    Tsai, Cheng-Tao; Su, Jye-Chau; Tseng, Sheng-Yu

    2013-01-01

    This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications.

  10. Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

    Directory of Open Access Journals (Sweden)

    Cheng-Tao Tsai

    2013-01-01

    Full Text Available This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR or a coupled current-doubler rectifier (CCDR is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications.

  11. Enhancement of delayed-rectifier potassium conductance by low concentrations of local anaesthetics in spinal sensory neurones

    Science.gov (United States)

    Olschewski, Andrea; Wolff, Matthias; Bräu, Michael E; Hempelmann, Gunter; Vogel, Werner; Safronov, Boris V

    2002-01-01

    Combining the patch-clamp recordings in slice preparation with the ‘entire soma isolation' method we studied action of several local anaesthetics on delayed-rectifier K+ currents in spinal dorsal horn neurones.Bupivacaine, lidocaine and mepivacaine at low concentrations (1–100 μM) enhanced delayed-rectifier K+ current in intact neurones within the spinal cord slice, while exhibiting a partial blocking effect at higher concentrations (>100 μM). In isolated somata 0.1–10 μM bupivacaine enhanced delayed-rectifier K+ current by shifting its steady-state activation characteristic and the voltage-dependence of the activation time constant to more negative potentials by 10–20 mV.Detailed analysis has revealed that bupivacaine also increased the maximum delayed-rectifier K+ conductance by changing the open probability, rather than the unitary conductance, of the channel.It is concluded that local anaesthetics show a dual effect on delayed-rectifier K+ currents by potentiating them at low concentrations and partially suppressing at high concentrations. The phenomenon observed demonstrated the complex action of local anaesthetics during spinal and epidural anaesthesia, which is not restricted to a suppression of Na+ conductance only. PMID:12055132

  12. Synaptic excitation in spinal motoneurons alternates with synaptic inhibition and is balanced by outward rectification during rhythmic motor network activity

    DEFF Research Database (Denmark)

    Guzulaitis, Robertas; Hounsgaard, Jorn

    2017-01-01

    channels. Intrinsic outward rectification facilitates spiking by focusing synaptic depolarization near threshold for action potentials. By direct recording of synaptic currents, we also show that motoneurons are activated by out-of-phase peaks in excitation and inhibition during network activity, whereas......Regular firing in spinal motoneurons of red-eared turtles (Trachemys scripta elegans, either sex) evoked by steady depolarization at rest is replaced by irregular firing during functional network activity. The transition caused by increased input conductance and synaptic fluctuations in membrane...... potential was suggested to originate from intense concurrent inhibition and excitation. We show that the conductance increase in motoneurons during functional network activity is mainly caused by intrinsic outward rectification near threshold for action potentials by activation of voltage and Ca2+ gated K...

  13. Advances in nonlinear optics

    CERN Document Server

    Chen, Xianfeng; Zeng, Heping; Guo, Qi; She, Weilong

    2015-01-01

    This book presents an overview of the state of the art of nonlinear optics from weak light nonlinear optics, ultrafast nonlinear optics to electro-optical theory and applications. Topics range from the fundamental studies of the interaction between matter and radiation to the development of devices, components, and systems of tremendous commercial interest for widespread applications in optical telecommunications, medicine, and biotechnology.

  14. Spike Pattern Structure Influences Synaptic Efficacy Variability Under STDP and Synaptic Homeostasis. I: Spike Generating Models on Converging Motifs

    Directory of Open Access Journals (Sweden)

    Zedong eBi

    2016-02-01

    Full Text Available In neural systems, synaptic plasticity is usually driven by spike trains. Due to the inherent noises of neurons and synapses as well as the randomness of connection details, spike trains typically exhibit variability such as spatial randomness and temporal stochasticity, resulting in variability of synaptic changes under plasticity, which we call efficacy variability. How the variability of spike trains influences the efficacy variability of synapses remains unclear. In this paper, we try to understand this influence under pair-wise additive spike-timing dependent plasticity (STDP when the mean strength of plastic synapses into a neuron is bounded (synaptic homeostasis. Specifically, we systematically study, analytically and numerically, how four aspects of statistical features, i.e. synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations, as well as their interactions influence the efficacy variability in converging motifs (simple networks in which one neuron receives from many other neurons. Neurons (including the post-synaptic neuron in a converging motif generate spikes according to statistical models with tunable parameters. In this way, we can explicitly control the statistics of the spike patterns, and investigate their influence onto the efficacy variability, without worrying about the feedback from synaptic changes onto the dynamics of the post-synaptic neuron. We separate efficacy variability into two parts: the drift part (DriftV induced by the heterogeneity of change rates of different synapses, and the diffusion part (DiffV induced by weight diffusion caused by stochasticity of spike trains. Our main findings are: (1 synchronous firing and burstiness tend to increase DiffV, (2 heterogeneity of rates induces DriftV when potentiation and depression in STDP are not balanced, and (3 heterogeneity of cross-correlations induces DriftV together with heterogeneity of rates. We anticipate our

  15. Cell-specific gain modulation by synaptically released zinc in cortical circuits of audition.

    Science.gov (United States)

    Anderson, Charles T; Kumar, Manoj; Xiong, Shanshan; Tzounopoulos, Thanos

    2017-09-09

    In many excitatory synapses, mobile zinc is found within glutamatergic vesicles and is coreleased with glutamate. Ex vivo studies established that synaptically released (synaptic) zinc inhibits excitatory neurotransmission at lower frequencies of synaptic activity but enhances steady state synaptic responses during higher frequencies of activity. However, it remains unknown how synaptic zinc affects neuronal processing in vivo. Here, we imaged the sound-evoked neuronal activity of the primary auditory cortex in awake mice. We discovered that synaptic zinc enhanced the gain of sound-evoked responses in CaMKII-expressing principal neurons, but it reduced the gain of parvalbumin- and somatostatin-expressing interneurons. This modulation was sound intensity-dependent and, in part, NMDA receptor-independent. By establishing a previously unknown link between synaptic zinc and gain control of auditory cortical processing, our findings advance understanding about cortical synaptic mechanisms and create a new framework for approaching and interpreting the role of the auditory cortex in sound processing.

  16. A Ca2+-based computational model for NDMA receptor-dependent synaptic plasticity at individual post-synaptic spines in the hippocampus

    Directory of Open Access Journals (Sweden)

    Owen Rackham

    2010-07-01

    Full Text Available Associative synaptic plasticity is synapse specific and requires coincident activity in presynaptic and postsynaptic neurons to activate NMDA receptors (NMDARs. The resultant Ca2+ influx is the critical trigger for the induction of synaptic plasticity. Given its centrality for the induction of synaptic plasticity, a model for NMDAR activation incorporating the timing of presynaptic glutamate release and postsynaptic depolarization by back-propagating action potentials could potentially predict the pre- and post-synaptic spike patterns required to induce synaptic plasticity. We have developed such a model by incorporating currently available data on the timecourse and amplitude of the postsynaptic membrane potential within individual spines. We couple this with data on the kinetics of synaptic NMDARs and then use the model to predict the continuous spine [Ca2+] in response to regular or irregular pre- and post-synaptic spike patterns. We then incorporate experimental data from synaptic plasticity induction protocols by regular activity patterns to couple the predicted local peak [Ca2+] to changes in synaptic strength. We find that our model accurately describes [Ca2+] in dendritic spines resulting from NMDAR activation during presynaptic and postsynaptic activity when compared to previous experimental observations. The model also replicates the experimentally determined plasticity outcome of regular and irregular spike patterns when applied to a single synapse. This model could therefore be used to predict the induction of synaptic plasticity under a variety of experimental conditions and spike patterns.

  17. Quantum Nonlinear Optics

    CERN Document Server

    Hanamura, Eiichi; Yamanaka, Akio

    2007-01-01

    This graduate-level textbook gives an introductory overview of the fundamentals of quantum nonlinear optics. Based on the quantum theory of radiation, Quantum Nonlinear Optics incorporates the exciting developments in novel nonlinear responses of materials (plus laser oscillation and superradiance) developed over the past decade. It deals with the organization of radiation field, interaction between electronic system and radiation field, statistics of light, mutual manipulation of light and matter, laser oscillation, dynamics of light, nonlinear optical response, and nonlinear spectroscopy, as well as ultrashort and ultrastrong laser pulse. Also considered are Q-switching, mode locking and pulse compression. Experimental and theoretical aspects are intertwined throughout.

  18. Nonlinear dynamics and complexity

    CERN Document Server

    Luo, Albert; Fu, Xilin

    2014-01-01

    This important collection presents recent advances in nonlinear dynamics including analytical solutions, chaos in Hamiltonian systems, time-delay, uncertainty, and bio-network dynamics. Nonlinear Dynamics and Complexity equips readers to appreciate this increasingly main-stream approach to understanding complex phenomena in nonlinear systems as they are examined in a broad array of disciplines. The book facilitates a better understanding of the mechanisms and phenomena in nonlinear dynamics and develops the corresponding mathematical theory to apply nonlinear design to practical engineering.

  19. COST-BENEFIT ANALYSIS OF BIOCONVERSION NEUFCHATEL WHEY INTO RECTIFIED ETHANOL AND ORGANIC LIQUID FERTILIZER IN SEMI PILOT SCALE

    Directory of Open Access Journals (Sweden)

    Gemilang Lara UTAMA

    2015-10-01

    Full Text Available Aims of the study was to determine the cost-benefit analysis in neufchatel whey bioconversion into rectified ethanol and organic liquid fertilizer. Bioconversion whey into rectified ethanol and organic liquid fertilizer has shown great potential as a way to reduce the pollution resulting from cheese-making process. Semi pilot scale experiment was done to ferment 5 L neufchatel whey using 5% K. lactis at 33°C for 24 h in semi anaerobic plastic container without agitation and then distilled into 96.2% purity. Data collected and analyzed descriptively related to benefit cost ratio/BCR, net present value/NPV and internal rate returns/IRR. The result showed that semi pilot scale bioconversion of neufchatel whey resulting in 106.42 ml rectified ethanol and 4404.22 ml distillery residue. Economic benefit could achieved by the support of distillery residue sales as organic liquid fertilizer.

  20. Plasmas in saline solutions sustained using rectified ac voltages: polarity and frequency effects on the discharge behaviour

    International Nuclear Information System (INIS)

    Chang Hungwen; Hsu Chengche

    2012-01-01

    In this work, three major problems, namely severe electrode damage, poor plasma stability and excess power consumption, arising in ac-driven plasmas in saline solutions are solved using a rectified power source. Diagnostic studies on the effects of power source polarity and frequency on the plasma behaviour are performed. Examination of I-V characteristics and temporally resolved light emission shows that the polarity significantly influences the current amplitude when the plasma exists, while the frequency alters the bubble dynamics, which in turn affects the plasma ignition voltage. When the plasma is driven by a rectified ac power source, the electrode erosion is reduced substantially. With a low frequency, moderate applied voltage and positively rectified ac power source (e.g. 100 Hz and 350 V), a stable plasma is ignited in nearly every power cycle. (paper)

  1. A new pH-sensitive rectifying potassium channel in mitochondria from the embryonic rat hippocampus.

    Science.gov (United States)

    Kajma, Anna; Szewczyk, Adam

    2012-10-01

    Patch-clamp single-channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of two different potassium ion channels: a large-conductance (288±4pS) calcium-activated potassium channel and second potassium channel with outwardly rectifying activity under symmetric conditions (150/150mM KCl). At positive voltages, this channel displayed a conductance of 67.84pS and a strong voltage dependence at holding potentials from -80mV to +80mV. The open probability was higher at positive than at negative voltages. Patch-clamp studies at the mitoplast-attached mode showed that the channel was not sensitive to activators and inhibitors of mitochondrial potassium channels but was regulated by pH. Moreover, we demonstrated that the channel activity was not affected by the application of lidocaine, an inhibitor of two-pore domain potassium channels, or by tertiapin, an inhibitor of inwardly rectifying potassium channels. In summary, based on the single-channel recordings, we characterised for the first time mitochondrial pH-sensitive ion channel that is selective for cations, permeable to potassium ions, displays voltage sensitivity and does not correspond to any previously described potassium ion channels in the inner mitochondrial membrane. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Simulation study of a rectifying bipolar ion channel: Detailed model versus reduced model

    Directory of Open Access Journals (Sweden)

    Z. Ható

    2016-02-01

    Full Text Available We study a rectifying mutant of the OmpF porin ion channel using both all-atom and reduced models. The mutant was created by Miedema et al. [Nano Lett., 2007, 7, 2886] on the basis of the NP semiconductor diode, in which an NP junction is formed. The mutant contains a pore region with positive amino acids on the left-hand side and negative amino acids on the right-hand side. Experiments show that this mutant rectifies. Although we do not know the structure of this mutant, we can build an all-atom model for it on the basis of the structure of the wild type channel. Interestingly, molecular dynamics simulations for this all-atom model do not produce rectification. A reduced model that contains only the important degrees of freedom (the positive and negative amino acids and free ions in an implicit solvent, on the other hand, exhibits rectification. Our calculations for the reduced model (using the Nernst-Planck equation coupled to Local Equilibrium Monte Carlo simulations reveal a rectification mechanism that is different from that seen for semiconductor diodes. The basic reason is that the ions are different in nature from electrons and holes (they do not recombine. We provide explanations for the failure of the all-atom model including the effect of all the other atoms in the system as a noise that inhibits the response of ions (that would be necessary for rectification to the polarizing external field.

  3. Rectifier Fault Diagnosis and Fault Tolerance of a Doubly Fed Brushless Starter Generator

    Directory of Open Access Journals (Sweden)

    Liwei Shi

    2015-01-01

    Full Text Available This paper presents a rectifier fault diagnosis method with wavelet packet analysis to improve the fault tolerant four-phase doubly fed brushless starter generator (DFBLSG system reliability. The system components and fault tolerant principle of the high reliable DFBLSG are given. And the common fault of the rectifier is analyzed. The process of wavelet packet transforms fault detection/identification algorithm is introduced in detail. The fault tolerant performance and output voltage experiments were done to gather the energy characteristics with a voltage sensor. The signal is analyzed with 5-layer wavelet packets, and the energy eigenvalue of each frequency band is obtained. Meanwhile, the energy-eigenvalue tolerance was introduced to improve the diagnostic accuracy. With the wavelet packet fault diagnosis, the fault tolerant four-phase DFBLSG can detect the usual open-circuit fault and operate in the fault tolerant mode if there is a fault. The results indicate that the fault analysis techniques in this paper are accurate and effective.

  4. RF Rectification on LAPD and NSTX: the relationship between rectified currents and potentials

    Science.gov (United States)

    Perkins, R. J.; Carter, T.; Caughman, J. B.; van Compernolle, B.; Gekelman, W.; Hosea, J. C.; Jaworski, M. A.; Kramer, G. J.; Lau, C.; Martin, E. H.; Pribyl, P.; Tripathi, S. K. P.; Vincena, S.

    2017-10-01

    RF rectification is a sheath phenomenon important in the fusion community for impurity injection, hot spot formation on plasma-facing components, modifications of the scrape-off layer, and as a far-field sink of wave power. The latter is of particular concern for the National Spherical Torus eXperiment (NSTX), where a substantial fraction of the fast-wave power is lost to the divertor along scrape-off layer field lines. To assess the relationship between rectified currents and rectified voltages, detailed experiments have been performed on the Large Plasma Device (LAPD). An electron current is measured flowing out of the antenna and into the limiters, consistent with RF rectification with a higher RF potential at the antenna. The scaling of this current with RF power will be presented. The limiters are also floated to inhibit this DC current; the impact of this change on plasma-potential and wave-field measurements will be shown. Comparison to data from divertor probes in NSTX will be made. These experiments on a flexible mid-sized experiment will provide insight and guidance into the effects of ICRF on the edge plasma in larger fusion experiments. Funded by the DOE OFES (DE-FC02-07ER54918 and DE-AC02-09CH11466), NSF (NSF- PHY 1036140), and the Univ. of California (12-LR- 237124).

  5. Optimal Design of a Resonance-Based Voltage Boosting Rectifier for Wireless Power Transmission.

    Science.gov (United States)

    Lim, Jaemyung; Lee, Byunghun; Ghovanloo, Maysam

    2018-02-01

    This paper presents the design procedure for a new multi-cycle resonance-based voltage boosting rectifier (MCRR) capable of delivering a desired amount of power to the load (PDL) at a designated high voltage (HV) through a loosely-coupled inductive link. This is achieved by shorting the receiver (Rx) LC-tank for several cycles to harvest and accumulate the wireless energy in the RX inductor before boosting the voltage by breaking the loop and transferring the energy to the load in a quarter cycle. By optimizing the geometries of the transmitter (Tx) and Rx coils and the number of cycles, N , for energy harvesting, through an iterative design procedure, the MCRR can achieve the highest PDL under a given set of design constraints. Governing equations in the MCRR operation are derived to identify key specifications and the design guidelines. Using an exemplary set of specs, the optimized MCRR was able to generate 20.9 V DC across a 100 kΩ load from a 1.8 V p , 6.78 MHz sinusoid input in the ISM-band at a Tx/Rx coil separation of 1.3 cm, power transfer efficiency (PTE) of 2.2%, and N = 9 cycles. At the same coil distance and loading, coils optimized for a conventional half-wave rectifier (CHWR) were able to reach only 13.6 V DC from the same source.

  6. Highly efficient integrated rectifier and voltage boosting circuits for energy harvesting applications

    Directory of Open Access Journals (Sweden)

    D. Maurath

    2008-05-01

    Full Text Available This paper presents novel circuit concepts for integrated rectifiers and voltage converting interfaces for energy harvesting micro-generators. In the context of energy harvesting, usually only small voltages are supplied by vibration-driven generators. Therefore, rectification with minimum voltage losses and low reverse currents is an important issue. This is realized by novel integrated rectifiers which were fabricated and are presented in this article. Additionally, there is a crucial need for dynamic load adaptation as well as voltage up-conversion. A circuit concept is presented, which is able to obtain both requirements. This generator interface adapts its input impedance for an optimal energy transfer efficiency. Furthermore, this generator interface provides implicit voltage up-conversion, whereas the generator output energy is stored on a buffer, which is connected to the output of the voltage converting interface. As simulations express, this fully integrated converter is able to boost ac-voltages greater than |0.35 V| to an output dc-voltage of 2.0 V–2.5 V. Thereby, high harvesting efficiencies above 80% are possible within the entire operational range.

  7. Au/n-ZnO rectifying contact fabricated with hydrogen peroxide pretreatment

    Science.gov (United States)

    Gu, Q. L.; Cheung, C. K.; Ling, C. C.; Ng, A. M. C.; Djurišić, A. B.; Lu, L. W.; Chen, X. D.; Fung, S.; Beling, C. D.; Ong, H. C.

    2008-05-01

    Au contacts were deposited on n-type ZnO single crystals with and without hydrogen peroxide pretreatment for the ZnO substrate. The Au/ZnO contacts fabricated on substrates without H2O2 pretreatment were Ohmic and those with H2O2 pretreatment were rectifying. With an aim of fabricating a good quality Schottky contact, the rectifying property of the Au/ZnO contact was systemically investigated by varying the treatment temperature and duration. The best performing Schottky contact was found to have an ideality factor of 1.15 and a leakage current of ˜10-7 A cm-2. A multispectroscopic study, including scanning electron microscopy, positron annihilation spectroscopy, deep level transient spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence, showed that the H2O2 treatment removed the OH impurity and created Zn-vacancy related defects hence decreasing the conductivity of the ZnO surface layer, a condition favorable for forming good Schottky contact. However, the H2O2 treatment also resulted in a deterioration of the surface morphology, leading to an increase in the Schottky contact ideality factor and leakage current in the case of nonoptimal treatment time and temperature.

  8. OSR1 regulates a subset of inward rectifier potassium channels via a binding motif variant.

    Science.gov (United States)

    Taylor, Clinton A; An, Sung-Wan; Kankanamalage, Sachith Gallolu; Stippec, Steve; Earnest, Svetlana; Trivedi, Ashesh T; Yang, Jonathan Zijiang; Mirzaei, Hamid; Huang, Chou-Long; Cobb, Melanie H

    2018-04-10

    The with-no-lysine (K) (WNK) signaling pathway to STE20/SPS1-related proline- and alanine-rich kinase (SPAK) and oxidative stress-responsive 1 (OSR1) kinase is an important mediator of cell volume and ion transport. SPAK and OSR1 associate with upstream kinases WNK 1-4, substrates, and other proteins through their C-terminal domains which interact with linear R-F-x-V/I sequence motifs. In this study we find that SPAK and OSR1 also interact with similar affinity with a motif variant, R-x-F-x-V/I. Eight of 16 human inward rectifier K + channels have an R-x-F-x-V motif. We demonstrate that two of these channels, Kir2.1 and Kir2.3, are activated by OSR1, while Kir4.1, which does not contain the motif, is not sensitive to changes in OSR1 or WNK activity. Mutation of the motif prevents activation of Kir2.3 by OSR1. Both siRNA knockdown of OSR1 and chemical inhibition of WNK activity disrupt NaCl-induced plasma membrane localization of Kir2.3. Our results suggest a mechanism by which WNK-OSR1 enhance Kir2.1 and Kir2.3 channel activity by increasing their plasma membrane localization. Regulation of members of the inward rectifier K + channel family adds functional and mechanistic insight into the physiological impact of the WNK pathway.

  9. Role of an inward rectifier K+ current and of hyperpolarization in human myoblast fusion

    Science.gov (United States)

    Liu, J-H; Bijlenga, P; Fischer-Lougheed, J; Occhiodoro, T; Kaelin, A; Bader, C R; Bernheim, L

    1998-01-01

    The role of K+ channels and membrane potential in myoblast fusion was evaluated by examining resting membrane potential and timing of expression of K+ currents at three stages of differentiation of human myogenic cells: undifferentiated myoblasts, fusion-competent myoblasts (FCMBs), and freshly formed myotubes. Two K+ currents contribute to a hyperpolarization of myoblasts prior to fusion: IK(NI), a non-inactivating delayed rectifier, and IK(IR), an inward rectifier. IK(NI) density is low in undifferentiated myoblasts, increases in FCMBs and declines in myotubes. On the other hand, IK(IR) is expressed in 28 % of the FCMBs and in all myotubes. IK(IR) is reversibly blocked by Ba2+ or Cs+. Cells expressing IK(IR) have resting membrane potentials of −65 mV. A block by Ba2+ or Cs+ induces a depolarization to a voltage determined by IK(NI) (−32 mV). Cs+ and Ba2+ ions reduce myoblast fusion. It is hypothesized that the IK(IR)-mediated hyperpolarization allows FCMBs to recruit Na+, K+ and T-type Ca2+ channels which are present in these cells and would otherwise be inactivated. FCMBs, rendered thereby capable of firing action potentials, could amplify depolarizing signals and may accelerate fusion. PMID:9705997

  10. Update on the slow delayed rectifier potassium current (I(Ks)): role in modulating cardiac function.

    Science.gov (United States)

    Liu, Zhenzhen; Du, Lupei; Li, Minyong

    2012-01-01

    The slow delayed rectifier current (I(Ks)) is the slow component of cardiac delayed rectifier current and is critical for the late phase repolarization of cardiac action potential. This current is also an important target for Sympathetic Nervous System (SNS) to regulate the cardiac electivity to accommodate to heart rate alterations in response to exercise or emotional stress and can be up-regulated by β- adrenergic or other signal molecules. I(Ks) channel is originated by the co-assembly of pore-forming KCNQ1 α-subunit and accessory KCNE1 β-subunit. Mutations in any subunit can bring about severe long QT syndrome (LQT-1, LQT-5) as characterized by deliquium, seizures and sudden death. This review summarizes the normal physiological functions and molecular basis of I(Ks) channels, as well as illustrates up-to-date development on its blockers and activators. Therefore, the current extensive survey should generate fundamental understanding of the role of I(Ks) channel in modulating cardiac function and donate some instructions to the progression of I(Ks) blockers and activators as potential antiarrhythmic agents or pharmacological tools to determine the physiological and pathological function of I(Ks).

  11. Structural basis of control of inward rectifier Kir2 channel gating by bulk anionic phospholipids.

    Science.gov (United States)

    Lee, Sun-Joo; Ren, Feifei; Zangerl-Plessl, Eva-Maria; Heyman, Sarah; Stary-Weinzinger, Anna; Yuan, Peng; Nichols, Colin G

    2016-09-01

    Inward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP2) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(-)) with a distinct second site is required for high PIP2 sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP2 sensitivity, even in the absence of PL(-) Furthermore, high-resolution x-ray crystal structures of Kir2.2[K62W], with or without added PIP2 (2.8- and 2.0-Å resolution, respectively), reveal tight tethering of the C-terminal domain (CTD) to the transmembrane domain (TMD) in each condition. Our results suggest a refined model for phospholipid gating in which PL(-) binding at the second site pulls the CTD toward the membrane, inducing the formation of the high-affinity primary PIP2 site and explaining the positive allostery between PL(-) binding and PIP2 sensitivity. © 2016 Lee et al.

  12. Agonist of inward rectifier K+ channels enhances the protection of ischemic postconditioning in isolated rat hearts.

    Science.gov (United States)

    Liao, Z; Feng, Z; Long, C

    2014-07-01

    Selective inhibition of inward rectifier K + channels could abolish the protection mediated by ischemic preconditioning, but the roles of these channels in ischemic postconditioning have not been well characterized. Our study aims to evaluate the effect of inward rectifier K + channels on the protection induced by ischemic postconditioning. Langendorff-perfused rat hearts (n=8 per group) were split into four groups: postconditioning hearts (IPO group); ischemic postconditioning with BaCl 2 hearts (PB group); ischemic postconditioning with zacopride hearts (PZ group); and without ischemic postconditioning (CON group). After suffering 30 minutes of global ischemia, groups IPO, PB and PZ went through 10 seconds of ischemic postconditioning with three different perfusates: respectively, Krebs-Henseleit buffer (IPO group); 20 μmol/L BaCl 2 (antagonist of the channel, PB group); 1 μmol/L zacopride (agonist of the channel, PZ group). At the end of reperfusion, the myocardial performance was better preserved in the PZ group than the other three groups. The PB group showed no significant differences from the CON group. Our study has shown that the I K1 channel agonist zacopride is associated with the enhancement of ischemic postconditioning. © The Author(s) 2014.

  13. Chemical profile of sugarcane spirits produced by double distillation methodologies in rectifying still

    Directory of Open Access Journals (Sweden)

    André Ricardo Alcarde

    2011-06-01

    Full Text Available The objective of this study was to determine the chemical profile of sugarcane spirits produced by different double distillation methodologies in rectifying still. Fermented sugarcane juice was distilled in rectifying still according to three double distillation methodologies: the methodology used for cognac production; the methodology used for whisky production; and the 10-80-10 percentage composition methodology, referring to the volumes of head, heart and tail of the distillate fractions from the second distillation. For comparison purposes, a simple distilled spirit was also produced. The distillates were analyzed for concentrations of ethanol, copper, volatile acidity, furfural and hydroxymethylfurfural, aldehydes, esters, methanol and higher alcohols. The spirits were also evaluated on the sensory attributes of aroma, taste and preference. Compared to simple distillation, double distillation improved the chemical quality of the spirits, since it has reduced the concentrations of acids, aldehydes, esters, methanol, higher alcohols and, consequently, their coefficient of congeners. Regardless of the methodology employed, the double distillation improved the sensory quality of the spirits since they obtained higher sensory acceptance in relation to spirits produced by simple distillation. Among double distilled spirits, the one produced according to whisky methodology obtained the best scores from appraisers on the aroma and flavor parameters and it was also the most preferred.

  14. Structural determinants of PIP(2) regulation of inward rectifier K(ATP) channels.

    Science.gov (United States)

    Shyng, S L; Cukras, C A; Harwood, J; Nichols, C G

    2000-11-01

    Phosphatidylinositol 4,5-bisphosphate (PIP(2)) activates K(ATP) and other inward rectifier (Kir) channels. To determine residues important for PIP(2) regulation, we have systematically mutated each positive charge in the COOH terminus of Kir6.2 to alanine. The effects of these mutations on channel function were examined using (86)Rb efflux assays on intact cells and inside-out patch-clamp methods. Both methods identify essentially the same basic residues in two narrow regions (176-222 and 301-314) in the COOH terminus that are important for the maintenance of channel function and interaction with PIP(2). Only one residue (R201A) simultaneously affected ATP and PIP(2) sensitivity, which is consistent with the notion that these ligands, while functionally competitive, are unlikely to bind to identical sites. Strikingly, none of 13 basic residues in the terminal portion (residues 315-390) of the COOH terminus affected channel function when neutralized. The data help to define the structural requirements for PIP(2) sensitivity of K(ATP) channels. Moreover, the regions and residues defined in this study parallel those uncovered in recent studies of PIP(2) sensitivity in other inward rectifier channels, indicating a common structural basis for PIP(2) regulation.

  15. An isolated bridgeless AC-DC PFC converter using a LC resonant voltage doubler rectifier

    Science.gov (United States)

    Lee, Sin-woo; Do, Hyun-Lark

    2016-12-01

    This paper proposed an isolated bridgeless AC-DC power factor correction (PFC) converter using a LC resonant voltage doubler rectifier. The proposed converter is based on isolated conventional single-ended primary inductance converter (SEPIC) PFC converter. The conduction loss of rectification is reduced than a conventional one because the proposed converter is designed to eliminate a full-bridge rectifier at an input stage. Moreover, for zero-current switching (ZCS) operation and low voltage stresses of output diodes, the secondary of the proposed converter is designed as voltage doubler with a LC resonant tank. Additionally, an input-output electrical isolation is provided for safety standard. In conclusion, high power factor is achieved and efficiency is improved. The operational principles, steady-state analysis and design equations of the proposed converter are described in detail. Experimental results from a 60 W prototype at a constant switching frequency 100 kHz are presented to verify the performance of the proposed converter.

  16. Sleep and protein synthesis-dependent synaptic plasticity: impacts of sleep loss and stress

    Science.gov (United States)

    Grønli, Janne; Soulé, Jonathan; Bramham, Clive R.

    2014-01-01

    Sleep has been ascribed a critical role in cognitive functioning. Several lines of evidence implicate sleep in the consolidation of synaptic plasticity and long-term memory. Stress disrupts sleep while impairing synaptic plasticity and cognitive performance. Here, we discuss evidence linking sleep to mechanisms of protein synthesis-dependent synaptic plasticity and synaptic scaling. We then consider how disruption of sleep by acute and chronic stress may impair these mechanisms and degrade sleep function. PMID:24478645

  17. Polymer-electrolyte-gated nanowire synaptic transistors for neuromorphic applications

    Science.gov (United States)

    Zou, Can; Sun, Jia; Gou, Guangyang; Kong, Ling-An; Qian, Chuan; Dai, Guozhang; Yang, Junliang; Guo, Guang-hua

    2017-09-01

    Polymer-electrolytes are formed by dissolving a salt in polymer instead of water, the conducting mechanism involves the segmental motion-assisted diffusion of ion in the polymer matrix. Here, we report on the fabrication of tin oxide (SnO2) nanowire synaptic transistors using polymer-electrolyte gating. A thin layer of poly(ethylene oxide) and lithium perchlorate (PEO/LiClO4) was deposited on top of the devices, which was used to boost device performances. A voltage spike applied on the in-plane gate attracts ions toward the polymer-electrolyte/SnO2 nanowire interface and the ions are gradually returned after the pulse is removed, which can induce a dynamic excitatory postsynaptic current in the nanowire channel. The SnO2 synaptic transistors exhibit the behavior of short-term plasticity like the paired-pulse facilitation and self-adaptation, which is related to the electric double-effect regulation. In addition, the synaptic logic functions and the logical function transformation are also discussed. Such single SnO2 nanowire-based synaptic transistors are of great importance for future neuromorphic devices.

  18. The Predominance of Electric Transport in Synaptic Transmission

    OpenAIRE

    Hamid Reza Noori

    2008-01-01

    The quantitative description of the motion of neurotransmitters in the synaptic cleft appears to be one of the most difficult problems in the modeling of synapses. Here we show in contradiction to the common view, that this process is merely governed by electric transport than diffusion forces.

  19. Synaptically evoked glutamate transporter currents in Spinal Dorsal Horn Astrocytes

    Directory of Open Access Journals (Sweden)

    Dougherty Patrick M

    2009-07-01

    Full Text Available Abstract Background Removing and sequestering synaptically released glutamate from the extracellular space is carried out by specific plasma membrane transporters that are primarily located in astrocytes. Glial glutamate transporter function can be monitored by recording the currents that are produced by co-transportation of Na+ ions with the uptake of glutamate. The goal of this study was to characterize glutamate transporter function in astrocytes of the spinal cord dorsal horn in real time by recording synaptically evoked glutamate transporter currents. Results Whole-cell patch clamp recordings were obtained from astrocytes in the spinal substantia gelatinosa (SG area in spinal slices of young adult rats. Glutamate transporter currents were evoked in these cells by electrical stimulation at the spinal dorsal root entry zone in the presence of bicuculline, strychnine, DNQX and D-AP5. Transporter currents were abolished when synaptic transmission was blocked by TTX or Cd2+. Pharmacological studies identified two subtypes of glutamate transporters in spinal astrocytes, GLAST and GLT-1. Glutamate transporter currents were graded with stimulus intensity, reaching peak responses at 4 to 5 times activation threshold, but were reduced following low-frequency (0.1 – 1 Hz repetitive stimulation. Conclusion These results suggest that glutamate transporters of spinal astrocytes could be activated by synaptic activation, and recording glutamate transporter currents may provide a means of examining the real time physiological responses of glial cells in spinal sensory processing, sensitization, hyperalgesia and chronic pain.

  20. Inflammation subverts hippocampal synaptic plasticity in experimental multiple sclerosis.

    Directory of Open Access Journals (Sweden)

    Robert Nisticò

    Full Text Available Abnormal use-dependent synaptic plasticity is universally accepted as the main physiological correlate of memory deficits in neurodegenerative disorders. It is unclear whether synaptic plasticity deficits take place during neuroinflammatory diseases, such as multiple sclerosis (MS and its mouse model, experimental autoimmune encephalomyelitis (EAE. In EAE mice, we found significant alterations of synaptic plasticity rules in the hippocampus. When compared to control mice, in fact, hippocampal long-term potentiation (LTP induction was favored over long-term depression (LTD in EAE, as shown by a significant rightward shift in the frequency-synaptic response function. Notably, LTP induction was also enhanced in hippocampal slices from control mice following interleukin-1β (IL-1β perfusion, and both EAE and IL-1β inhibited GABAergic spontaneous inhibitory postsynaptic currents (sIPSC without affecting glutamatergic transmission and AMPA/NMDA ratio. EAE was also associated with selective loss of GABAergic interneurons and with reduced gamma-frequency oscillations in the CA1 region of the hippocampus. Finally, we provided evidence that microglial activation in the EAE hippocampus was associated with IL-1β expression, and hippocampal slices from control mice incubated with activated microglia displayed alterations of GABAergic transmission similar to those seen in EAE brains, through a mechanism dependent on enhanced IL-1β signaling. These data may yield novel insights into the basis of cognitive deficits in EAE and possibly of MS.