MΩ Resistor Research Articles

Low-Voltage Ultraviolet Detectors Using ZnO Thin-Film Transistor Isolated by B Ion Implantation

We report on the fabrication of a photo-detector and a photo-inverter adopting ZnO thin-film transistors (TFTs) that have been electrically isolated by implanting B ions onto peripheral ZnO area around active ZnO channel. Our isolated ZnO-TFT exhibited a fine mobility of 0.8 cm2/(V·s) and on/off current ratio of ∼104. Since the device also showed quite a high threshold voltage of 21 V, it was effective to be a photo-detector under a zero gate bias. When our photo-devices were composed of a ZnO-TFT and a 100 MΩ resistor, a minimum response time of ∼5 ms under 364 nm ultraviolet light was achieved, thereby dynamically showing photo-inverting and detecting behaviors.

EHD flow measured by 3D PIV in a narrow electrostatic precipitator with longitudinal-to-flow wire electrode and smooth or flocking grounded plane electrode

In this work, results of three-dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) flow velocity fields in a narrow electrostatic precipitator (ESP) with a longitudinal-to-flow placed wire electrode are presented. The ESP was a narrow transparent acrylic box (90 mm×30 mm×30 mm). The electrode set consisted of a single wire discharge electrode and two plane collecting electrodes. Either two smooth stainless-steel plates or two stainless-steel plane meshes with nylon flocks were used as the collecting electrodes. The 3D PIV measurements were carried out in two parallel planes, placed longitudinally to the flow duct. The positive DC voltage of up to 9.5 kV was applied to the wire electrode through a 10 MΩ resistor. The collecting electrodes were grounded. The measurements were carried out at a primary flow velocity of 0.5 m/s. Obtained results show that the flow patterns for the smooth-plate electrodes and for the flocking plane electrodes are similar in the bulk of the flow. However, the flow velocities near the flocking plane electrodes are much lower than those near the smooth-plate electrodes. This is a beneficial phenomenon, because the lower the flow near the collecting electrodes, the lower re-entrainment of the particles deposited on the collecting electrodes occurs.

Large Store-operated Calcium Selective Currents Due to Co-expression of Orai1 or Orai2 with the Intracellular Calcium Sensor, Stim1

The molecular nature of store-operated Ca(2+)-selective channels has remained an enigma, due largely to the continued inability to convincingly demonstrate Ca(2+)-selective store-operated currents resulting from exogenous expression of known genes. Recent findings have implicated two proteins, Stim1 and Orai1, as having essential roles in store-operated Ca(2+) entry across the plasma membrane. However, transient overexpression of these proteins on their own results in little or no increase in store-operated entry. Here we demonstrate dramatic synergism between these two mediators; co-transfection of HEK293 cells with Stim1 and Orai1 results in an approximate 20-fold increase in store-operated Ca(2+) entry and Ca(2+)-selective current. This demonstrates that these two proteins are limiting for both the signaling and permeation mechanisms for Ca(2+)-selective store-operated Ca(2+) entry. There are three mammalian homologs of Orai1, and in expression experiments they all produced or augmented store-operated Ca(2+) entry with efficacies in the order Orai1 > Orai2 > Orai3. Stim1 apparently initiates the signaling process by acting as a Ca(2+) sensor in the endoplasmic reticulum. This results in rearrangement of Stim1 within the cell and migration toward the plasma membrane to regulate in some manner Orai1 located in the plasma membrane. However, we demonstrate that Stim1 does not incorporate in the surface membrane, and thus likely regulates or interacts with Orai1 at sites of close apposition between the plasma membrane and an intracellular Stim1-containing organelle.

Decreased Subunit Stability as a Novel Mechanism for Potassium Current Impairment by a KCNQ2 C Terminus Mutation Causing Benign Familial Neonatal Convulsions

KCNQ2 and KCNQ3 K+ channel subunits underlie the muscarinic-regulated K+ current (I(KM)), a widespread regulator of neuronal excitability. Mutations in KCNQ2- or KCNQ3-encoding genes cause benign familiar neonatal convulsions (BFNCs), a rare autosomal-dominant idiopathic epilepsy of the newborn. In the present study, we have investigated, by means of electrophysiological, biochemical, and immunocytochemical techniques in transiently transfected cells, the consequences prompted by a BFNC-causing 1-bp deletion (2043deltaT) in the KCNQ2 gene; this frameshift mutation caused the substitution of the last 163 amino acids of the KCNQ2 C terminus and the extension of the subunit by additional 56 residues. The 2043deltaT mutation abolished voltage-gated K+ currents produced upon homomeric expression of KCNQ2 subunits, dramatically reduced the steady-state cellular levels of KCNQ2 subunits, and prevented their delivery to the plasma membrane. Metabolic labeling experiments revealed that mutant KCNQ2 subunits underwent faster degradation; 10-h treatment with the proteasomal inhibitor MG132 (20 microm) at least partially reversed such enhanced degradation. Co-expression with KCNQ3 subunits reduced the degradation rate of mutant KCNQ2 subunits and led to their expression on the plasma membrane. Finally, co-expression of KCNQ2 2043deltaT together with KCNQ3 subunits generated functional voltage-gated K+ currents having pharmacological and biophysical properties of heteromeric channels. Collectively, the present results suggest that mutation-induced reduced stability of KCNQ2 subunits may cause epilepsy in neonates.

Improvement of Corona Charging System for High Speed Electrophotography

For the purpose of improving the speed of the charging process of electrophotography, a new electrode system was investigated. The system consists of a blade electrode and a metal drum coated with a polymer film. The sharp edge of the blade electrode was retained perpendicularly for the drum surface by opening 2 to 6 mm gap. In order to prevent spark discharge, an 8 MΩ resistor was inserted between the blade and a dc high voltage source, and a glow-like discharge was observed in the space between the blade edge and the surface of the polymer film. As the discharge current obtained by the present electrode system was much higher than that obtained by a single wire corona charger, the charging speed attained by the present system was 7.2 times as fast as the case of the corona charging system.

APMP.EM-S6: Bilateral supplementary comparison of resistance

A bilateral supplementary comparison of resistance, APMP.EM-S6, was conducted between the National Institute of Metrology Thailand (NIMT) and the CSIRO National Measurement Laboratory of Australia (NML). The comparison covered seven values of resistance, 0.1 Ω, 1 Ω, 100 Ω, 10 kΩ, 100 kΩ, 1 MΩ and 100 MΩ. The 0.1 Ω resistor was a YEW type 2792, the 100 MΩ resistor was an IET type SRC and the other five resistors were Fluke type 742A.The resistors were supplied by NIMT, and NML was the pilot laboratory for the comparison. The measurements for the comparison were made between December 2003 and April 2004.The resistors were measured on three separate occasions by NIMT and between each of these occasions the resistors were sent to NML for measurement. The resistors of nominal values 0.1 Ω, 1 Ω, 100 Ω and 10 kΩ were measured as four-terminal resistors while the 100 kΩ, 1 MΩ and 100 MΩ resistors were measured as two-terminal resistors.The quantity En (the absolute value of the difference between the values obtained at the two laboratories divided by the root sum square of the expanded uncertainties of the two values) was calculated for each resistance value used in the comparison. In all cases En was less than 0.5.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the Mutual Recognition Arrangement (MRA).

Current-sensing noise thermometry from [formula omitted] to below [formula omitted] using a DC SQUID preamplifier

We are using a low- T c DC SQUID to perform current-sensing noise thermometry, by measuring the thermal noise currents in a copper resistor. The temperature is obtained from the Nyquist formula. This is a practical thermometer for use from 4.2 K to below 1 mK , with a percentage precision independent of temperature. Using a 0.34 mΩ resistor, the thermometer had an amplifier noise temperature T N of 8 μK . A precision of 1.5% was obtained in 200 s . The thermometer was in good agreement with the PLTS-2000 3 He melting curve scale down to 4.5 mK . We have cooled the thermometer successfully below 1 mK , achieving a minimum electron temperature of 300 μK .

Overexpression of SERCA2a accelerates repolarisation in rabbit ventricular myocytes

Overexpression of the sarcoplasmic reticulum Ca ATPase (SERCA2a) produces positive inotropism and it has been proposed as a promising strategy to counteract defective excitation–contraction coupling in the failing heart. However, the effects of overexpressing SERCA2a on action potential duration (APD), which can affect diastolic parameters in the heart, is unknown. We, therefore, investigated the relationship between SERCA2a overexpression and APD in adult rabbit ventricular myocytes which were cultured for 48 h. Overexpression of SERCA2a was achieved by infection with an adenovirus carrying both SERCA2a and GFP independently driven by CMV promoters, Ad.SERCA2a. Myocytes infected with Ad.GFP only and/or non-infected myocytes were used as controls. Electrophysiological measurements were taken using switch clamping with 15–25 MΩ resistance microelectrodes. In Ad.SERCA2a infected myocytes, APD was significantly reduced compared with both groups of control cells at 0.5 Hz (APD50 (ms) non-infected: 481±98, n=12; Ad.GFP: 464±85, n=11; Ad.SERCA2a: 285±69, n=13 (mean±S.E.M.) and at 1 Hz (APD50 (ms) non-infected: 375±64, n=22; Ad.GFP: 363±47, n=18; Ad.SERCA2a: 231±54, n=24). Using AP voltage-clamping, we recorded a 0.2 mM Cd-sensitive current which can be ascribed to Ca current flowing during the AP. The integral of this current was reduced in Ad.SERCA2a myocytes compared with control (non-infected charge (pC): 27.5±4.2, n=8; Ad.SERCA2a: 15.5±4.1, n=11; P<0.01). Using AP clamping during the loading protocol, to take into account changes in APD, SR Ca content (assessed by integrating a 20 mM caffeine-induced inward current) was significantly larger in Ad.SERCA2a compared with both controls (SR Ca content (μM/l non-mitochondrial volume): non-infected: 25.5±7, n=8; Ad.GFP: 25.7±11, n=6; Ad.SERCA2a: 80.5±19, n=8). In conclusion, this study shows that SR Ca content is increased despite decreased Ca entry after overexpression of SERCA2a, and this can lead to positive inotropism. This effect coupled with shorter APD may be a useful therapeutic modality in heart failure.

Synergistic effect of pulsed corona discharges and ozonation on decolourization of methylene blue in water

The effect of O2 and O3 bubbling on decolourization of methylene blue by pulsed corona discharges in water was studied. The pulsed corona discharges were produced by charging an 80 pF capacitor with a 40 kV DC source, through a 100 MΩ resistor, and discharging it into a needle-plate type reactor at 60 Hz through a rotating spark gap switch. A 20 ml sample of 13.25 mg l-1 methylene blue in distilled water was decolourized in 120 min. Bubbling O2 at 10 ml min-1 through the discharge region reduced the decolourization time to 25 min. Bubbling O2 containing 1500 µmol O3 l-1 at 10 ml min-1 reduced the decolourization time to 8 min. The O3 was produced by fractionating input energy between a water treatment reactor and a O3 generator, i.e. no additional energy was consumed for O3 production. Under the same experimental conditions methylene blue solution in tap water was decolourized in >210 min by corona discharge in solution, in 30 min by corona discharge with O2 bubbling, and in 11 min by corona discharge with bubbling of O2 containing 1500 µmol O3 l-1.

Bilateral comparison of 1 Ω, 10 kΩ and 100 MΩ resistance standards between the PTB and the UME

In order to evaluate the agreement between the Physikalisch-Technische Bundesanstalt (PTB, Germany) and the Ulusal Metroloji Enstitüsü (TÜBTAK-UME, Turkey) and to establish a firm basis for traceability, a bilateral comparison has been carried out using 1 Ω, 10 kΩ and 100 MΩ resistors. Measurements obtained by the PTB, based on their quantum Hall resistance standard (QHRS), differ from the UME results by 46 nΩ/Ω (standard uncertainty u = 0.19 µΩ/Ω) at the 1 Ω level, and by 3.0 nΩ/Ω (u = 0.25 µΩ/Ω) at the 10 kΩ level. The 100 MΩ resistors were compared using both a UME-constructed Wheatstone bridge and a commercial bridge. Measurement results obtained with the Wheatstone bridge show better agreement with those of the PTB, within 0.34 µΩ/Ω (u = 8.7 µΩ/Ω), than the results obtained with the commercial bridge, within 3.6 µΩ/Ω (u = 5.1 µΩ/Ω).

Construction and Analytical Applications of a Si-Gold Strip Enzyme Electrode Using Constant - Current Potentiometry

The development and the evaluation of a new Si-gold strip enzyme electrode (SGSEE) with immobilized glucose oxidase (GO) is described. The construction comprised the immobilization of GO in the presence of glutaraldehyde, on a home-made Si-gold strip electrode (SGSE) modified with a self-assembled monolayer (SAM) of 2-aminoethanethiol. A constant-current potentiometric technique was applied for the SGSEE evaluation and the analytical determination of glucose. A constant current of 0.2 μA at 35 V DC was produced across a 270 KΩ resistor and a 184 MΩ resistor, from a simple home-designed electronic circuit. The current was applied between the SGSEE working as cathode and a Pt-anode, in the presence of a SCE. A standard concentration of diphenylamine sulfonic acid (DPASA) in the measured samples was used as potential poiser. The decrease of the Pt-anode potential vs. SCE, due to H2O2 formation, is monitored by a Corning pH/mV meter and displayed on a PC-monitor via a Data Acquisition Card. The slope of the initial part of the analytical signal (E, mV vs. time, sec) is related to the glucose concentration. Different factors concerning the response of the electrochemical system, such as current, reaction volume and DPASA concentration were studied. The effect of pH, temperature, storage time, etc. on the behaviour of the SGSEE was also examined. The designed SGSEE showed good characteristics in a working range of 5.0x10−4 M to 5.00x103 M glucose concentration and usefulness for over one month. The technique was applied successfully for the glucose estimation in samples of serum, foodstuffs and drugs.

Design of a parallel-plate energy spread analyzer

A 45° parallel-plate energy spread analyzer has been designed and built for the ISAC project at TRIUMF. It features an energy resolution of ⩽0.04% and a spectrometer constant of k=1.29. Nineteen 0.1 mm by 10 mm metal guard frames with 1 MΩ resistors are used to equalize the electric field in the analyzer to an order of ⩽0.5%. Electric field simulation is done by a code POISSON. This article describes the design of the analyzer. Preliminary experimental results are also presented.

Gp60 activation mediates albumin transcytosis in endothelial cells by tyrosine kinase-dependent pathway.

We investigated the function of gp60, an endothelial cell membrane 60-kDa albumin-binding protein localized in caveolae, and the mechanism of its activation in regulating endothelial permeability of albumin. Gp60 organization on the bovine pulmonary microvessel endothelial cell (BPMVEC) surface was punctate as shown by immunofluorescence using an anti-gp60 antibody (Ab) conjugated with bisfunctional, N-hydroxysuccinimidyl fluorophore (Cy3). Addition of a secondary Ab to anti-gp60 Ab-treated BPMVEC induced cross-linking of gp60 as evident by increased size of fluorescent particles and cell surface gp60 clustering. Gp60 cross-linking also produced 2-3-fold increases in the endothelial cell uptake and the luminal to abluminal permeability of 125I-albumin as well as the fluid-phase tracer, horseradish peroxidase. The increased transendothelial permeability of macromolecules was the result of transcytosis as it was not associated with an increase in the paracellular pathway. Incubation of anti-gp60 Ab with BPMVEC at 37 degrees C caused internalization of gp60, and thereby reduced the uptake of the macromolecules. Activation of gp60 by either albumin (the gp60 ligand) or gp60 cross-linking induced the phosphorylation of both gp60 and caveolin-1 (the major structural caveolar protein) on tyrosine residues. Gp60 activation also phosphorylated the Src family tyrosine kinases pp60(c-Src) and Fyn. The activated pp60(c-Src) and Fyn co-immunoprecipitated with caveolin-1 in BPMVEC membrane. Protein tyrosine kinase (PTK) inhibitors, herbimycin A and genistein, prevented gp60-activated macromolecule uptake and transcytosis in a concentration-dependent manner, indicating the functional significance of the PTK pathway in activating albumin transcytosis. These findings indicate that activation of gp60 stimulates the Src PTK signaling pathway, and thus regulates the transcytosis of albumin across the endothelial cell monolayer.

Vacuum breakdown mechanisms, and X-ray pulses in accelerators

During the conditioning of evacuated accelerator tubes, groups of discrete X-ray signals with apparent energies of greater than 300 keV are observed. A mechanism to explain the X-ray emission is proposed in terms of a series of transient vacuum arc discharges. A review is given of vacuum breakdown mechanisms, and of the most likely processes occurring in accelerator tubes during the conditioning process. In the case of the vacuum accelerator tube, there is initially no gaseous medium, but the applied voltage of 30 kV between the tube electrodes is sufficient to lead to the formation of a vacuum arc if there are fine whiskers, impurities, or accelerated dust particles present. Such a vacuum discharge will have a very short life (∼1 μs), as the current of the arc will cause the collapse of the electrode voltage which is maintained by a small current through 600 MΩ resistors. During the discharge, electrons will escape into the accelerator tube, and fall through several sections to be finally arrested, producing the discrete X-ray signals. The vacuum arc will release charged molten droplets of anode material into the high-field region; after some delay, these droplets will trigger further arcs in different sections of the tube. The triggered arcs will be at the inner edges of the electrode where the droplets hit the electrode, and where electrons are most readily released into the accelerator tube. Thus a whole series of high energy X-ray signals are observed.

Calibration of DC Voltage Dividers up to 100 kV

A system for calibrating dc voltage dividers up to 100 kV with an uncertainty (1α) of the order of 5 X 10-6 is described. The main component is a 200 MΩ guarded resistive device rated for the maximum voltage, forced-air cooled, and made up of 100 individually screened 2 MΩ resistors connected in series. An arrangement for series-to-parallel connection of the 100 resistors is provided in order to evaluate the total series resistance and the self-heating effect at full current and low voltage.

Diisopropylfluorophosphate and tetanic stimulation fail to reverse mecamylamine antagonism of Renshaw cells

Mecamylamine-induced antagonism of Renshaw cells was studied in the spinal cord of DIAL anesthetized adult male or spayed female mongrel cats. Renshaw cell unit responses to 1- or 2-Hz supramaximal antidromic stimulation of lumbar segment 7 ventral root were recorded by conventional means from glass micropipettes (2.7 m NaCl, tip diameter 1.0 to 1.6 μm, 2.0 to 4.0 MΩ resistance). Data were analyzed by computer. Mecamylamine (1.0 mg/kg iv) antagonizes the response to 1- or 2-Hz stimulation. The onset occurs within 60 sec, only the first one or two spikes remain after 2 min, and this antagonism is observed 30 min after injection. Persistence of action of acetylcholine (ACh) induced by diisopropylfluorophosphate (DFP 2.0 to 2.5 mg/kg iv) increases the spike frequency of the Renshaw cell burst and reduces the variability in the number of spikes per discharge in response to 1- or 2-Hz antidromic stimulation. Excess ACh generated by 2 min of 20-Hz antidromic stimulation fails to reverse the mecamylamine-induced antagonism to 1- or 2-Hz antidromic stimulation. Also, DFP-induced persistence of action of ACh or 20-Hz (2 min) antidromic stimulation to induce excess ACh in the presence of DFP, fails to reverse the mecamylamine-induced antagonism of response to 1- or 2-Hz antidromic stimulation. It is concluded that the data agree with a mechanism of action of mecamylamine as a noncompetitive open channel blocker of the nicotinic receptor ion-channel complex which renders it nonresponsive to the agonist ACh and to the open channel blocker, DFP.

Diisopropylfluorophosphate and Tetanic Stimulation Fail to Reverse Mecamylamine Antagonism of Renshaw Cells

Diisopropylfluorophosphate and Tetanic Stimulation Fail to Reverse Mecamylamine Antagonism of Renshaw Cells. VANMETER, W. G. (1984). Fundam. Appl. Toxicol. 4, S150–S155. Mecamylamine-induced antagonism of Renshaw cells was studied in the spinal cord of DIAL anesthetized adult male or spayed female mongrel cats. Renshaw cell unit responses to 1- or 2-Hz supramaximal antidromic stimulation of lumbar segment 7 ventral root were recorded by conventional means from glass micropipettes (2.7 M NaCl, tip diameter 1.0 to 1.6 μm, 2.0 to 4.0 MΩ resistance). Data were analyzed by computer. Mecamylamine (1.0 mg/kg iv) antagonizes the response to 1- or 2-Hz stimulation. The onset occurs within 60 sec, only the first one or two spikes remain after 2 min, and this antagonism is observed 30 min after injection. Persistence of action of acetylcholine (ACh) induced by diisopropylfluorophosphate (DFP 2.0 to 2.5 mg/kg iv) increases the spike frequency of the Renshaw cell burnt and reduces the variability in the number of spikes per discharge in response to 1- or 2-Hz antidromic stimulation. Excess ACh generated by 2 min of 20-Hz antidromic stimulation fails to reverse the mecamylamine-induced antagonism to 1- or 2-Hz antidromic stimulation. Also, DFP-induced persistence of action of ACh or 20-Hz (2 min) antidromic stimulation to induce excess ACh in the presence of DFP, fails to reverse the mecamylamine-induced antagonism of response to 1- or 2-Hz antidromic stimulation. It is concluded that the data agree with a mechanism of action of mecamylamine as a noncompetitive open channel blocker of the nicotinic receptor ion-channel complex which renders it nonresponsive to the agonist ACh and to the open channel blocker, DFP.

High voltage stability of steel electrodes in an ultra-high vacuum at extremely small electrode separations

The voltage stability of highly polished spherical electrodes degassed at 300°C was studied at voltages between 10 and 20 kV and electrode separations between 50 and 100 μm in an ultra-high vacuum of 10 −8 Pa. Up to field strengths of 1.4 × 10 8 V cm −1 no surface damage affecting the voltage stability occurred at currents below 10 −11 A. Current-voltage characteristics measured at higher field strengths were in agreement with the Fowler-Nordheim equation. They were measured at field strengths up to 3 × 10 6 V cm −1 and currents between 10 −11 and 10 −7 A, above which a weakly glowing arc discharge occurred, which had to be limited by a 150 MΩ resistor.

Intra-cellular potential of rabbit corneal endothelial cells

A stable potential difference across corneal endothelial cell membranes (−45±2 mV, 301 impalements) was measured by minimizing mechanical disturbances and penetrating the cells with microelectrodes of 50–150 MΩ resistance. A microelectrode tip could be kept in a cell for as long as 40 min. The highest stable potential difference obtained was −75 mV. In addition, the input resistance of the cells was 29 MΩ in the average (20 impalements; range 3·5 to 93 MΩ). Treatment with 10 −4 m ouabain and high [K +] in the external medium decreased the intra-cellular potential difference.

ハルセル試験における電位および電流分布の測定

A new type of Hull cell, which can minimize the temperature rise in high current electrolysis, has been constructed and compared with two kinds of Hull cells commonly used at present. A printed circuit board divided into twenty portions was employed as the Hull cell panel to measure the potential and current distributions on the cathode. It was found that, by using this cell, the temperature variations in the cell were able to be controlled within a small range, and yet the current distribution was not disturbed even in the baths which require high current such as for chromium plating. The current distribution was measured easily, with a high input impedance electrometer, by dividing the panel accurately into twenty portions and connecting each portion with a very small (1.2mΩ) resistance. The current density distributions measured for copper sulfate bath and Watt's bath were similar to those as calculated from Nagasaka's formula.