CONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2007
M. Kr.
Abstract This article reports about the ion sheath thickness variation occurring in front of a negatively biased plate immersed in the target plasma region of a double plasma device. The target plasma is produced due to the local ionization of neutral gas by the high energetic electrons coming from the source region (main discharge region). It is observed that for an increase in cathode voltage (filament bias voltage) in the source region, the ion flux into the plate increases. As a result, the sheath at the plate contracts. Again, for an increase in source anode voltage (magnetic cage bias), the ion flux to the plate decreases. As a result, the sheath expands at the plate. The ion sheath formed at the separation grid of the device is found to expand for an increase in cathode voltage and it contracts for an increase in the anode voltage of the main discharge region. One important observation is that the applied anode bias can control the Bohm speed of the ions towards the separation grid. Furthermore, it is observed that the ion current collected by the separation grid is independent of changes in plasma density in the diffusion region but is highly dependent on the source plasma parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Voltage- and Ca2+ -activated potassium channels in Ca2+ store control Ca2+ release

FEBS JOURNAL, Issue 15 2006
Masayuki Yamashita
Ca2+ release from Ca2+ stores is a ,quantal' process; it terminates after a rapid release of stored Ca2+. To explain the quantal nature, it has been supposed that a decrease in luminal Ca2+ acts as a ,brake' on store release. However, the mechanism for the attenuation of Ca2+ efflux remains unknown. We show that Ca2+ release is controlled by voltage- and Ca2+ -activated potassium channels in the Ca2+ store. The potassium channel was identified as the big or maxi-K (BK)-type, and was activated by positive shifts in luminal potential and luminal Ca2+ increases, as revealed by patch-clamp recordings from an exposed nuclear envelope. The blockage or closure of the store BK channel due to Ca2+ efflux developed lumen-negative potentials, as revealed with an organelle-specific voltage-sensitive dye [DiOC5(3); 3,3'-dipentyloxacarbocyanine iodide], and suppressed Ca2+ release. The store BK channels are reactivated by Ca2+ uptake by Ca2+ pumps regeneratively with K+ entry to allow repetitive Ca2+ release. Indeed, the luminal potential oscillated bistably by ,45 mV in amplitude. Our study suggests that Ca2+ efflux-induced store BK channel closures attenuate Ca2+ release with decreases in counter-influx of K+. [source]

The Origin of the High Voltage in DPM12/P3HT Organic Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Antonio Sánchez-Díaz
Abstract Organic solar cells made using a blend of DPM12 and P3HT are studied. The results show that higher Voc can be obtained when using DPM12 in comparison to the usual mono-substituted PCBM electron acceptor. Moreover, better device performances are also registered when the cells are irradiated with sun-simulated light of 10,50 mW cm,2 intensity. Electrochemical and time-resolved spectroscopic measurements are compared for both devices and a 100-mV shift in the density of states (DOS) is observed for DPM12/P3HT devices with respect to PCBM/P3HT solar cells and slow polaron-recombination dynamics are found for the DPM12/P3HT devices. These observations can be directly correlated with the observed increase in Voc, which is in contrast with previous results that correlated the higher Voc with different ideality factors obtained using dark-diode measurements. The origin for the shift in the DOS can be correlated to the crystallinity of the blend that is influenced by the properties of the included fullerene. [source]

Controllable Shifts in Threshold Voltage of Top-Gate Polymer Field-Effect Transistors for Applications in Organic Nano Floating Gate Memory

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2010
Kang-Jun Baeg
Abstract Organic field-effect transistor (FET) memory is an emerging technology with the potential to realize light-weight, low-cost, flexible charge storage media. Here, solution-processed poly[9,9-dioctylfluorenyl-2,7-diyl]-co-(bithiophene)] (F8T2) nano floating gate memory (NFGM) with a top-gate/bottom-contact device configuration is reported. A reversible shift in the threshold voltage (VTh) and reliable memory characteristics was achieved by the incorporation of thin Au nanoparticles (NPs) as charge storage sites for negative charges (electrons) at the interface between polystyrene and cross-linked poly(4-vinylphenol). The F8T2 NFGM showed relatively high field-effect mobility (µFET) (0.02,cm2 V,1 s,1) for an amorphous semiconducting polymer with a large memory window (ca. 30,V), a high on/off ratio (more than 104) during writing and erasing with an operation voltage of 80,V of gate bias in a relatively short timescale (less than 1,s), and a retention time of a few hours. This top-gated polymer NFGM could be used as an organic transistor memory element for organic flash memory. [source]

Intermediate Temperature Anode-Supported Fuel Cell Based on BaCe0.9Y0.1O3 Electrolyte with Novel Pr2NiO4 Cathode

FUEL CELLS, Issue 1 2010
G. Taillades
Abstract A proton conducting ceramic fuel cell (PCFC) operating at intermediate temperature has been developed that incorporates electrolyte and electrode materials prepared by flash combustion (yttrium-doped barium cerate) and auto-ignition (praseodymium nickelate) methods. The fuel cell components were assembled using an anode-support approach, with the anode and proton ceramic layers prepared by co-pressing and co-firing, and subsequent deposition of the cathode by screen-printing onto the proton ceramic surface. When the fuel cell was fed with moist hydrogen and air, a high Open Circuit Voltage (OCV,>,1.1,V) was observed at T,>,550,°C, which was stable for 300,h (end of test), indicating excellent gas-tightness of the proton ceramic layer. The power density of the fuel cell increased with temperature of operation, providing more than 130,mW,cm,2 at 650,°C. Symmetric cells incorporating Ni-BCY10 cermet and BCY10 electrolyte on the one hand, and Pr2NiO4,+,, and BCY10 electrolyte on the other hand, were also characterised and area specific resistances of 0.06,,,cm2 for the anode material and 1,2,,,cm2 for the cathode material were obtained at 600,°C. [source]

Single-InN-Nanowire Nanogenerator with Upto 1 V Output Voltage

ADVANCED MATERIALS, Issue 36 2010
Chi-Te Huang
Piezoelectric potential of a InN nanowire (NW) growing along [0110] can be positive, negative, and zero depending on the direction of the applied transverse force. By measuring the output voltage of a InN-NW-based nanogenerator, about 40% to 55% of output voltages are within the range of -1 and -20 mV, and 25% to 30% of output voltages would exceed -100 mV. Some output voltages could reach the magnitude of -1000 mV, showing its great potential for fabricating high-output nanogenerators. [source]

Space Charge Measurement in MgO/LDPE Nanocomposite up to Breakdown under DC Ramp Voltage

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2010
Yoshinobu Murakami Member
Abstract To understand the basic electric properties of nanosized magnesium oxide (MgO)/low-density polyethylene (LDPE) nanocomposites under an applied DC voltage, the DC breakdown strength and space charge up to the breakdown under a DC ramp voltage were investigated. Compared to that of the LDPE sample, the sample containing a MgO nanofiller (hereafter, called a nanocomposite) had a higher DC breakdown strength. In the case of the LDPE sample, the homo charges, which contained a large negative charge and a small positive charge, were only observed near the electrodes just prior to breakdown. However, in the case of the nanocomposite sample, the positive charge increased as the average field increased until the average field reached a certain value. After that, the positive charge decreased as the average field increased until breakdown occurred. The field enhancement rate (=maximum field/average field) of the nanocomposite sample increased with the average field, until it became saturated. After peaking, the field enhancement rate of the nanocomposite sample decreased as the average field increased. These observations suggest that, instead of the MgO nanofiller suppressing the electronic avalanche, it suppresses the conduction current, which was determined by the space charge, leading to the higher DC breakdown strength. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Influence of a Measuring System to a Transient Voltage on a Vertical Conductor

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010
Peerawut Yutthagowith Student Member
Abstract This paper studies the effect of a horizontal reference voltage wire, a current lead wire, and the impedance of a voltage probe when measuring a transient voltage on a vertical conductor. A hybrid frequency-time domain (HFTD) method and a finite-different time domain (FDTD) method with the help of VSTL are applied to investigate the effect of the horizontal reference voltage wire, the current lead wire, and the impedance of the voltage probe on measurement at the top of the vertical conductor. The obtained results show that the horizontal reference voltage wire perpendicular to the vertical conductor causes a minor effect, but the input capacitance of the voltage probe affects significantly the voltage measurement. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Optimal Control of Voltage in Distribution Systems by Voltage Reference Management

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2009
Tomonobu Senjyu Student member
Abstract Recently, renewable energy technologies such as wind turbine generators and photovoltaic (PV) systems have been introduced as distributed generations (DGs). Connections of a large amount of distributed generations may cause voltage deviation beyond the statutory range in distribution systems. A reactive power control of DGs can be a solution of this problem, and it also has a possibility to reduce distribution loss. In this paper, we propose a control methodology of voltage profile in a distribution system using reactive power control of inverters interfaced with DGs and tap changing transformers. In the proposed method, a one-day schedule of voltage references for the control devices are determined by an optimization technique based on predicted values of load demand and PV power generation. Reactive power control of interfaced inverters is implemented within the inverter capacity without reducing active power output. The proposed method accomplishes voltage regulation within the acceptable range and reduction of distribution loss. The effectiveness of the proposed method is confirmed by simulations. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Evaluation of Humidity Correction Factor of Disruptive Discharge Voltage of Standard Sphere Air Gaps

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2008
Osamu Fujii Member
Abstract The humidity correction method prescribed in the existing IEC standard is based on experimental data obtained under absolute humidity between 5 and 12 g/m3. A discussion on the humidity correction method is needed for higher absolute humidity regions, which is experienced during summer in Japan, and also throughout the year in tropical countries. The effect of absolute humidity on disruptive discharge voltages of standard sphere air gaps has been studied experimentally for several years under conditions of natural humidity, between 2 and 22 g/m3. In the cases of a.c. and lightning impulse voltage application, it was found that the existing IEC humidity correction method seems to be proper for most of the gap spacings studied under absolute humidity up to 22 g/m3. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Nanoscale Logic Circuits: Hybrid Complementary Logic Circuits of One-Dimensional Nanomaterials with Adjustment of Operation Voltage (Adv. Mater.

ADVANCED MATERIALS, Issue 21 2009
21/2009)
A new layout of complementary logic circuits based on p-channel carbon nanotube and n-channel zinc oxide nanowire transistors is presented by Takhee Lee and co-workers on p. 2156. The processing is a hybrid approach, combining advantageous characteristic functions for the modulation of the current and operating voltage in transistors through proton radiation-generated charges, allowing a simple method of designing favorable logic circuits. [source]

Hybrid Complementary Logic Circuits of One-Dimensional Nanomaterials with Adjustment of Operation Voltage

ADVANCED MATERIALS, Issue 21 2009
Gunho Jo
A new layout of complementary logic circuits based on p-channel carbon nanotube and n-channel zinc oxide nanowire transistors is presented, providing a hybrid approach to combine advantageous characteristic functions for the modulation of the current and operating voltage in transistors through proton radiation-generated charges, which allow a simple way to design favorable logic circuits. [source]

Hexyl-Derivatized Poly(3,4-ethylenedioxyselenophene): Novel Highly Stable Organic Electrochromic Material with High Contrast Ratio, High Coloration Efficiency, and Low-Switching Voltage

ADVANCED MATERIALS, Issue 17 2009
Mao Li
A novel family of electrochromic materials has been discovered. The electropolymerized poly(hexyl-3,4-ethylenedioxyselenophene) film switches color between a highly absorbing pure blue and a nearly colorless bleached state, achieves both a high contrast ratio of 88,89% and a high CE of up to 773,cm2 C,1 while showing a fast switching time and remarkable stability with the contrast ratio remaining 48% after 10000 cycles. [source]

Stability of poly(3,4-ethylene dioxythiophene) materials intended for implants,

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010
Elin M. Thaning
Abstract This study presents experiments designed to study the stability of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions using phosphate-buffered saline (PBS) and hydrogen peroxide (H2O2) (0.01M) at 37°C over a 5- to 6-week period. Voltage pulsing in PBS was used as an additional test environment. The influence of switching the counter ion used in electropolymerization from polystyrene sulphonate (PSS) to heparin was investigated. Absorbance spectroscopy and cyclic voltammetry were used to evaluate the material properties. Most of the samples in H2O2 lost both electroactivity and optical absorbance within the study period, but PEDOT:PSS was found slightly more stable than PEDOT:heparin. Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after 5 weeks, disregarding delamination, which was a significant problem especially for polymer on indium tin oxide substrates. Voltage pulsing in PBS did not increase degradation. The counter ion influenced the time course of degradation in oxidizing agents. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2010 [source]

Flavin-based Blue-light Photosensors: A Photobiophysics Update

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2007
Aba Losi
This review deals with the biophysical aspects of flavin-based photosensors, comprising cryptochromes, LOV (Light, Oxygen and Voltage) and BLUF (Blue Light sensing Using FAD) proteins. Special emphasis is given to structural issues, photocycle quantum yields and energetics, mechanism of the light-triggered reactions, early stages in signal transduction and oligomeric states of the light sensing protein modules. For BLUF and LOV domains important parallels are emerging, despite their different ,/, fold arrangement, whereas there is increasing evidence for a mechanicistic and functional splitting of the cryptochrome family. [source]

Three Putative Photosensory Light, Oxygen or Voltage (LOV) Domains with Distinct Biochemical Properties from the Filamentous Cyanobacterium Anabaena sp.

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2006
PCC 7120
Light, oxygen or voltage (LOV) domains function as blue-light sensors in the phototropin family of photoreceptors found in plants, algae and bacteria. We detected putative LOV domains (Alr3170-LOV, A112875-LOV and A1r1229-LOV) in the genome of a filamentous cyanobacterium, Anabaena sp. PCC 7120. These cyanobacterial LOV domains are closely clustered with the known LOV domains. Alr3170-LOV and A112875-LOV carry the conserved cysteine residue unique to the photoactive LOV, whereas A1r1229-LOV does not. We expressed these three LOV domains in Escherichia coli and purified them. In fact, Alr3170-LOV and A112875-LOV that are conserved in Nostoc punctiforme, a related species, bound flavin mononuclcotide and showed spectral changes unique to known LOV domains on illumination with blue light. A1r3170-LOV was completely photoreduced and dark reversion was slow, whereas A112875-LOV was slowly photoreduced and dark reversion was rapid. For comparison, AvA112875-LOV in a closely related A. variabilis was also studied as a homolog of A112875-LOV. Finally, we observed that A1r1229-LOV that is not conserved in N. punctiforme showed no flavin binding. [source]

A review of charge transport and recombination in polymer/fullerene organic solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2007
A. Pivrikas
Abstract The charge carrier transport and recombination in two types of thermally treated bulk-heterojunction solar cells is reviewed: in regioregular poly(3-hexylthiophene) (RRP3HT) mixed with 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) and in the blend of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) mixed with PCBM. The charge carrier mobility and bimolecular recombination coefficient have been comparatively studied by using various techniques including Time-of-Flight (ToF), Charge Extraction by Linearly Increasing Voltage (CELIV), Double Injection (DI) transients, Current,Voltage (I,V) technique. It was found that the carrier mobility is at least an order of magnitude higher in RRP3HT/PCBM blends compared to MDMO-PPV/PCBM. Moreover, all used techniques demonstrate a heavily reduced charge carrier recombination in RRP3HT/PCBM films compared to Langevin-type carrier bimolecular recombination in MDMO-PPV/PCBM blends. As a result of long carrier lifetimes the formation of high carrier concentration plasma in RRP3HT/PCBM blends is demonstrated and plasma extraction methods were used to directly estimate the charge carrier mobility and bimolecular recombination coefficients simultaneously. A weak dependence of bimolecular recombination coefficient on the applied electric field and temperature demonstrates that carrier recombination is not dominated by charge carrier mobility (Langevin-type recombination) in RRP3HT/PCBM blends. Furthermore, we found from CELIV techniques that electron mobility in RRP3HT/PCBM blends is independent on relaxation time in the experimental time window (approx. hundreds of microseconds to tens of milliseconds). This reduced carrier bimolecular recombination in RRP3HT/PCBM blends implies that the much longer carrier lifetimes can be reached at the same concentrations which finally results in higher photocurrent and larger power conversion efficiency of RRP3HT/PCBM solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Electromechanical reshaping of septal cartilage,,

THE LARYNGOSCOPE, Issue 11 2003
Ki-Hong Kevin Ho BS
Abstract Objectives: This study describes the process of tissue electroforming and how shape changes in cartilage can be produced by the application of direct current (DC). The dependence of shape change on voltage and application time is explored. Study Design: Basic investigation using ex vivo porcine septal cartilage grafts and electromechanical cartilage deformation focused on development of a new surgical technique. Methods: Uniform flat porcine nasal septal cartilage specimens were mechanically deformed between two semicircular aluminum electrodes. DC current was applied to establish charge separation and electrical streaming potential. Voltage (0,3.5 V) and application time (0,5 minutes) were varied. Shape change was measured, and shape retention was calculated using analytic representation. The effect of the direction of applied current on shape change was evaluated by switching the polarities of electrodes and using parameters of 0 to 5.5 V and 5 minutes. Temperature during reshaping was monitored with a thermocouple, and surface features were evaluated using light microscopy. Results: Reshaped specimen demonstrated mechanical stability similar to native cartilage tissue. Shape retention strongly correlated with increasing voltage and application time. Only a small current (<0.1 A) through the tissue was measured. Temperature change was less than 2°C during electroforming, suggesting that electroforming likely results from some nonthermal mechanisms. Surface features indicated that electrodeposition may occur depending on electrode material and magnitude of the applied voltage. Conclusions: These findings demonstrate that cartilage can be reshaped through the process we have described as "electroforming" by generating intrinsic differences in charge separation with negligible heat production. [source]

Tantalum-Doped Titanium Dioxide Nanowire Arrays for Dye-Sensitized Solar Cells with High Open-Circuit Voltage,

ANGEWANDTE CHEMIE, Issue 43 2009
Xinjian Feng Dr.
Nanodrähte in der Sonne: Durch Hydrothermalsynthese wurden homogen tantaldotierte Titanoxid-Nanodrahtanordnungen auf transparenten leitfähigen Oxidsubstraten hergestellt. Mit dieser Methode sollten Titanoxid-Nanodrähte mit unterschiedlichen Übergangsmetallen dotiert werden können. So hergestellte Funktionseinheiten sind leistungsstärker, wie farbstoffsensibilisierte Solarzellen mit sehr hoher Photo-Ruhespannung belegen (siehe Bild). [source]

Electrical and Structural Remodeling in Left Ventricular Hypertrophy,A Substrate for a Decrease in QRS Voltage?

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2007
Ljuba Bacharova M.D., M.B.A., Ph.D.
Electrical remodeling in advanced stages of cardiovascular diseases creates a substrate for triggering and maintenance of arrhythmias. The electrical remodeling is a continuous process initiated already in the early stages of cardiological pathology. The aim of this opinion article was to discuss the changes in electrical properties of myocardium in left ventricular hypertrophy (LVH), with special focus on its early stage, as well as their possible reflection in the QRS amplitude of the electrocardiogram. It critically appraises the classical hypothesis related to the QRS voltage changes in LVH. The hypothesis of the relative voltage deficit is discussed in the context of supporting evidence from clinical studies, animal experiments, and simulation studies. The underlying determinants of electrical impulse propagation which may explain discrepancies between "normal" ECG findings and increased left ventricular size/mass in LVH are reviewed. [source]

Variation of Cell Voltage with Reaction Time in Electrochemical Synthesis Process of Sodium Dichromate

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2006
C. W. Li
Abstract To address the problems existing in the traditional production technique of sodium dichromate, a new green technology of producing sodium dichromate with an electrochemical synthesis method was studied. Using a self-made electrosynthesis reactor of pure titanium and stainless steel, with a multiple-unit metal oxides combination anode, a cathode of stainless steel, and a reinforcing combination cation exchange membrane with perfluorosulfonic and perfluorocarboxylic polymers, experiments were carried out on the direct electrochemical synthesis of sodium dichromate from sodium chromate. From the experimental results and electrochemical reaction principles, it was shown that the electrochemical synthesis reaction process of sodium dichromate may be quantitatively determined from the variation of the cell voltage measured macroscopically with reaction time. Cell voltages were experimentally measured at different initial sodium chromate concentrations in the anolyte, and the dependence of the cell voltage on reaction time was discussed. The mathematical model of the variation of cell voltage with reaction time and the change rate equation of cell voltage were established, and satisfactorily formulated the change law of cell voltage in the electrochemical synthesis process of sodium dichromate. [source]

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005
V. Lj.
Abstract Statistically based measurements of breakdown voltages Ub and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages Ub for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s,1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients , , , and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y0 (, ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas-phase model. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

New Host Containing Bipolar Carrier Transport Moiety for High-Efficiency Electrophosphorescence at Low Voltages

ADVANCED MATERIALS, Issue 6 2009
Zhi Qiang Gao
A new host material for use in phosphorescent OLEDs with desirable electronic properties has been synthesized. The material exhibits superior carrier-transport properties, a narrow optical band gap, relatively high triplet energy, and high thermal stability. It is synthesized by integrating hole-transporting carbazole groups into an electron-transporting phenanthroline core (see figure), and is demonstrated to be an excellent host for phosphorescent dopant emitters. [source]

Extracellular cAMP inhibits P2X3 receptors in rat sensory neurones through G protein-mediated mechanism

ACTA PHYSIOLOGICA, Issue 2 2010
M. V. Mamenko
Abstract Aim:, To identify the mechanisms of P2X3 receptor inhibition by extracellular cyclic adenosine monophosphate (cAMP) in rat dorsal root ganglion (DRG) neurones. Methods:, Whole-cell currents were measured in cultured DRG neurones using the combination of voltage and concentration clamp. Results:, We have found that extracellular cAMP inhibits P2X3 -mediated currents in a concentration- and use-dependent manner. The P2X3 currents, activated by ATP applied every 4 min, were inhibited by 55% in the presence of 10 ,m cAMP and by 81% in the presence of 30 ,m cAMP. At 8 min interval between ATP applications the same concentration of cAMP did not alter the currents. Addition of 0.5 mm of guanosine 5,- O -(2-thiodiphosphate) to intracellular solution blocked the inhibitory action of cAMP. The inhibitory effects of cAMP were not mimicked by extracellular application of 30 ,m adenosine. Conclusions:, In this paper, we demonstrate, for the first time, that extracellular application of cAMP to rat sensory neurones inhibits P2X3 receptors via a G protein-coupled mechanism in a use-dependent manner, thus indicating the neuronal expression of specific plasmalemmal cAMP receptor. [source]

Indirect evidence for increased mechanosensitivity of jejunal secretomotor neurones in patients with idiopathic bile acid malabsorption

ACTA PHYSIOLOGICA, Issue 2 2009
A. Bajor
Abstract Aim:, The interdigestive motor rhythm, the migrating motor complex (MMC), is accompanied by active secretion of chloride during periods of distally propagating maximal motor activity (MMC phase III). We studied the behaviour of this system in bile acid malabsorption (BAM), a relative common cause of chronic diarrhoea. We measured motor activity and transmucosal potential difference (PD, reflecting active chloride secretion), in the proximal jejunum in healthy controls (n = 18) and in a group of patients with BAM (n = 11). The phase III-generated voltage was related to the degree of BAM quantified by the 75SeHCAT test. Methods:, We used a multi-channel intestinal infusion system to simultaneously measure jejunal pressure and PD. Saline passing calomel half-cells was infused into the jejunum and subcutaneously. Pressure and PD were recorded in the fasting state and after a test meal. Results:, In the absence of motor activity, jejunal PD was not significantly different from zero in either group. During MMC phase III, PD reached significantly higher mean and peak levels in BAM patients. The product of MMC phase III length multiplied by voltage, over 3 h, was also significantly higher in BAM patients (controls: median 307 mV × cm, range 70,398; BAM: median 511, range 274,2271, P < 0.01). This value was also significantly correlated with the degree of BAM as reflected by the 75SeHCAT test (P < 0.05). Conclusion:, Phase III induced jejunal secretion may be upregulated in BAM patients, resulting in overload of colonic reabsorption capacity. [source]

Characterization of a 2.8 kJ Small Plasma Focus Using a Five Phase Radiative Model

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2009
Sh. Al-Hawat
Abstract A radiative five-phase plasma focus model (axial phase, inward radial phase, reflected shock phase, radiative phase and expanded phase) was applied to a 2.8 kJ plasma focus device to find the structure of the plasma focus formation and to calculate the plasma parameters and emitted radiation from the plasma pinch. To verify the model, the radiation probability of such device in neon plasma has been studied; a linear approximation method was applied by a FORTRAN program which has been written for this purpose. The theoretical and experimental results of the temporal development of current and voltage at 0.9 mbar of neon and spike voltages at different filling gas pressures were obtained and compared. In addition to that our plasma focus (PF) device was compared with different PF devices in relation to the plasma energy density and the drive parameter (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Simultaneous Measurements of Ion Temperature by Segmented Tunnel and Katsumata Probe

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-7 2008
J. Adámek
Abstract Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe in the CASTOR tokamak are reported. The segmented tunnel probe measures two ion saturation currents Iseg 1, Iseg 2 towards two segments of the tunnel. The axis of the tunnel is aligned with the total magnetic field. The value of the ratio of these two currents combined with the results of the PIC modeling provides the ion temperature. Design and experimental arrangement of the Katsumata probe enable us to measure the pure ion current by sweeping the applied voltage. The ion temperature is then estimated from the exponential part of the measured I , V characteristic. Simultaneous measurements of the ion temperature by the segmented tunnel and Katsumata probe agree within a few eV. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Effect of Cathode and Anode Voltage on an Ion Sheath Thickness in a Magnetically Confined Diffusion Plasma

Comparison of Langmuir Probe and Laser Thomson Scattering Methods in the Electron Temperature Measurement in Divertor Simulator MAP-II

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2006
A. Okamoto
Abstract In order to investigate details of anomaly in the Langmuir probe current (I)-voltage (V) characteristics, electron temperatures and densities are measured by both Langmuir probe and laser Thomson scattering methods. The electron densities measured with both methods show good agreement in hydrogen-molecular assisted recombination (H2 -MAR) plasmas. On the other hand, the electron temperatures measured with Langmuir probe are overestimated compared with that obtained from the Thomson scattering spectrum in the H2 -MAR plasmas. Histogram of electron current deviated from its average shows that fluctuation appeared in the electron current becomes large and the histogram distorted in temperature-overestimated condition, especially when the probe voltage is negatively biased. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]