scholarly journals Effect of Gaussian disorder on the voltage dependence of the current density in sandwich-type devices based on organic semiconductors

2008 ◽  
Vol 78 (8) ◽  
Author(s):  
S. L. M. van Mensfoort ◽  
R. Coehoorn
Keyword(s):  
Organic Semiconductors ◽  
Current Density ◽  
Voltage Dependence ◽  
Sandwich Type

scholarly journals Modeling and analysis of the three-dimensional current density in sandwich-type single-carrier devices of disordered organic semiconductors

2009 ◽  
Vol 79 (8) ◽  
Author(s):  
J. J. M. van der Holst ◽  
M. A. Uijttewaal ◽  
B. Ramachandhran ◽  
R. Coehoorn ◽  
P. A. Bobbert ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Current Density ◽  
Three Dimensional ◽  
Modeling And Analysis ◽  
Single Carrier ◽  
Sandwich Type

scholarly journals Calcium current modulation by the γ1 subunit depends on alternative splicing of CaV1.1

2021 ◽  
Author(s):  
Yousra El El Ghaleb ◽  
Nadine J. Ortner ◽  
Wilfried Posch ◽  
Monica L. Fernandez-Quintero ◽  
Wietske E. Tuinte ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Current Density ◽  
Voltage Dependence ◽  
Splice Variants ◽  
Calcium Currents ◽  
Developmentally Regulated ◽  
The Difference ◽  
Ion Conducting ◽  
And Shifts ◽  
Oppositely Charged

The skeletal muscle voltage-gated calcium channel (CaV1.1) primarily functions as voltage sensor for excitation-contraction coupling. Conversely, its ion-conducting function is modulated by multiple mechanisms within the pore-forming α1S subunit and the auxiliary α2δ-1 and γ1 subunits. Particularly, developmentally regulated alternative splicing of exon 29, which inserts 19 amino acids in the extracellular IVS3-S4 loop of CaV1.1a, greatly reduces the current density and shifts the voltage-dependence of activation to positive potentials outside the physiological range. We generated a new HEK293-cell line stably expressing α2δ-1, β3, and STAC3. When the adult (CaV1.1a) and the embryonic (CaV1.1e) splice variants were expressed in these cells, the difference in the voltage-dependence of activation observed in muscle cells was reproduced, but not the reduced current density of CaV1.1a. Only when we further co-expressed the γ1 subunit, the current density of CaV1.1a, but not of CaV1.1e, was reduced by >50 %. In addition, γ1 caused a shift of the voltage-dependence of inactivation to negative voltages in both variants. Thus, the current-reducing effect of γ1, but not its effect on inactivation, is specifically dependent on the inclusion of exon 29 in CaV1.1a. Molecular structure modeling revealed several direct ionic interactions between oppositely charged residues in the IVS3-S4 loop and the γ1 subunit. However, substitution of these residues by alanine, individually or in combination, did not abolish the γ1-dependent reduction of current density, suggesting that structural rearrangements of CaV1.1a induced by inclusion of exon 29 allosterically empower the γ1 subunit to exert its inhibitory action on CaV1.1 calcium currents.

Delayed rectifier K+ current of dog bronchial myocytes: effect of pollen sensitization and PKC activation

1998 ◽  
Vol 275 (2) ◽  
pp. L336-L347 ◽  
Author(s):  
Gareth J. Waldron ◽  
Stefan B. Sigurdsson ◽  
Ernesto A. Aiello ◽  
Andrew J. Halayko ◽  
Newman L. Stephens ◽  
...  
Keyword(s):  
Current Density ◽  
Voltage Dependence ◽  
Ragweed Pollen ◽  
Delayed Rectifier ◽  
Airway Smooth Muscle Cells ◽  
Average Current Density ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation ◽  
Pkc Activation ◽  
Hyperpolarizing Shift

The properties of delayed rectifier K+ current [ I K(dr)] of canine airway smooth muscle cells isolated from small bronchi and its modulation by protein kinase C (PKC) were studied by whole cell patch clamp. I K(dr) activated positive to −40 mV, with half-maximal activation at −16 ± 1.2 mV ( n = 15) and average current density of 31 ± 2.6 pA/pF ( n = 15) at +30 mV. The capacitive surface area, current density, and voltage dependence of activation of I K(dr) of myocytes of ragweed pollen-sensitized dogs were not different from age-matched control dogs. However, the sensitization reduced the availability of I K(dr) between −40 and −20 mV due to a hyperpolarizing shift in the voltage dependence of steady-state inactivation (−29.9 ± 1.2 in sensitized versus −26.0 ± 0.7 mV in control dogs, n = 9 and 11, respectively; P < 0.05). PKC activation with diacylglycerol analog or phorbol ester depressed I K(dr) amplitude, whereas an inactive diacylglycerol analog had no effect. The hyperpolarizing shift in voltage dependence of inactivation and/or modulation of I K(dr) by PKC may be two mechanisms that contribute to the enhanced reactivity of bronchial tissues from ragweed pollen-sensitized dogs.

Characteristics of L- and T-type Ca2+ currents in canine cardiac Purkinje cells

1989 ◽  
Vol 256 (5) ◽  
pp. H1478-H1492 ◽  
Author(s):  
Y. Hirano ◽  
H. A. Fozzard ◽  
C. T. January
Keyword(s):  
Kinetic Parameters ◽  
Voltage Clamp ◽  
Purkinje Cells ◽  
Current Density ◽  
Voltage Dependence ◽  
Cell Voltage ◽  
Voltage Clamp Technique ◽  
Recovery From Inactivation ◽  
Cardiac Purkinje Cells ◽  
Voltage Dependent

Two types of Ca2+ currents were recorded in single dialyzed canine cardiac Purkinje cells using a whole cell voltage clamp technique. T-type current was easily separated from L-type current, because its voltage dependence of inactivation and activation was more negative and it decayed rapidly. L-type current was available at more depolarized holding potentials, activated at more positive voltages, and decayed slowly. In 2 mM extracellular Ca2+ concentration [( Ca]o), the average peak T- and L-type current density was 1.70 and 2.87 pA/pF, respectively. T-type current was relatively insensitive to modification by Ca2+, nifedipine, Cd2+, BAY K 8644, or isoproterenol. T-type current was more sensitive to block by Ni2+ and amiloride. Replacement of Ca2+ by Ba2+ or Sr2+ did not increase T-type current. Changes in the Ca2+ or Ba2+ concentration caused parallel shifts in the voltage dependence of several kinetic parameters for L- and T-type current. In 2 mM [Ca]o, the V1/2 (Boltzmann fit) for inactivation of T-type current was -68 mV with a slope of 3.9, and for L-type current the V1/2 was -31 mV with a slope of 5.5. Recovery from inactivation of L- and T-type current was voltage dependent, and for similar conditions L-type current recovered from inactivation more rapidly than T-type current. These findings show that T- and L-type currents are large in cardiac Purkinje cells, and they can easily be separated by their voltage, kinetic, and pharmacological differences. Both may have important physiological roles.

Unraveling the temperature and voltage dependence of magnetic field effects in organic semiconductors

2013 ◽  
Vol 114 (17) ◽  
pp. 174909 ◽  
Author(s):  
Paul Janssen ◽  
Steinar H. W. Wouters ◽  
Matthijs Cox ◽  
Bert Koopmans
Keyword(s):  
Magnetic Field ◽  
Organic Semiconductors ◽  
Voltage Dependence ◽  
Magnetic Field Effects ◽  
Field Effects

Study on Photo-Catalytic Properties of Nano-TiO2/Anthraquinone in a Sandwich-Type Bipolar Membrane

2011 ◽  
Vol 694 ◽  
pp. 49-53
Author(s):  
Yu Xi Ren ◽  
Qiang Chen ◽  
Jin Huo Lin ◽  
Zhen Chen
Keyword(s):  
Current Density ◽  
Intermediate Layer ◽  
Potential Drop ◽  
Water Dissociation ◽  
Bipolar Membrane ◽  
Catalytic Center ◽  
Uv Illumination ◽  
Anionic Layer ◽  
Sandwich Type ◽  
Lower Impedance

A sandwich-type bipolar membrane (BPM) was prepared by a paste method, consisted of an anionic layer, a cationic layer and a catalytic intermediate layer. Carboxymethylcellulose (CMC) and chitosan (CS) were modified by Fe3+ and glutaraldehyde respectively to prepare the mCMC/mCS BPM. Semiconductor photocatalyst combined with photosensitizes was applied to improve the water dissociation at the intermediate layer of the bipolar membrane, using nanometer-sized titanium dioxide (TiO2) as a photocatalyst and anthraquinone (Anth) as a photosensitize. The impedance of bipolar membrane and the performance of hydrolysis influenced by the composite catalytic center were studied. The sandwich-type BPM exhibited several good properties, such as higher efficiency for the water splitting at the intermediate layer, protons and hydroxyl ions permeabilities, higher operational current density as well as lower impedance and potential drop. Under the UV illumination, the corresponding voltage reached as low as 5.0V when the operational current density was 125mA/cm2.

Human fetal central neurons in culture: voltage- and ligand-gated currents

1995 ◽  
Vol 74 (5) ◽  
pp. 1889-1899 ◽  
Author(s):  
D. W. Sah
Keyword(s):  
Current Density ◽  
Potassium Current ◽  
Time Course ◽  
Voltage Dependence ◽  
Sodium Current ◽  
Sodium Currents ◽  
Current Voltage ◽  
Channel Currents ◽  
Current Voltage Relationship ◽  
Voltage Relationship

1. The functional properties of sodium, potassium, calcium, N-methyl-D-aspartate (NMDA), kainate, and gamma-aminobutyric acid (GABA) currents were studied in dissociated monolayer cultures of fetal human brain neurons, using the whole cell patch-clamp technique. 2. Sodium currents were characterized with respect to the following properties: current density, voltage dependence of activation, voltage dependence of inactivation, and sensitivity to tetrodotoxin (TTX). All sodium currents exhibited voltage dependencies of activation and inactivation, and sensitivities to TTX that are characteristic of the neuronal form of the sodium current. 3. At least two types of potassium current were present, resembling the delayed rectifier and fast-inactivating potassium current. These two types of potassium current were distinguishable by their different kinetics, voltage dependencies of activation and inactivation, and sensitivities to 4-aminopyridine and tetraethylammonium. 4. High-voltage-activated calcium channel currents were present and were characterized with respect to current density, voltage dependencies of activation and inactivation, and sensitivity to cadmium. Low-voltage-activated calcium channel currents were also present. 5. NMDA- and kainate-gated currents were studied with respect to current density, time course, and current-voltage relationship. Kainate currents were also characterized with respect to inhibition by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In addition, NMDA and kainate responses were compared for cortical versus cerebellar neurons. NMDA responses, which are only found in neurons, were present, confirming the neuronal phenotype suggested by the presence of the neuronal form of the sodium current. Nondesensitizing kainate currents were also present, with a half-maximally effective concentration (EC50) of approximately 200 microM for kainate; CNQX inhibited the kainate current with a half-inactivating concentration of 0.55 microM. 6. GABA-gated currents were characterized with respect to current density, time course, receptor subtype, desensitization, dose response, current-voltage relationship, ionic selectivity, pharmacology, and potentiation by the neurosteroid 5 alpha-pregnan-3 alpha-ol-11,20-dione (alfaxalone). Desensitizing GABAA currents were selective for chloride, inhibited by bicuculline and tert-butyl-bicyclophosphorothionate, and potentiated by diazepam, pentobarbital sodium, and alfaxalone. The EC50 for GABA was 15 microM.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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