WorldWideScience

Sample records for two-electrode voltage-clamp method

  1. Characterization of heterologously expressed transporter genes by patch- and voltage-clamp methods: Application to cyclic nucleotide-dependent responses

    KAUST Repository

    Lemtiri-Chlieh, Fouad

    2013-09-03

    The application of patch- and voltage-clamp methods to study ion transport can be limited by many hurdles: the size of the cells to be patched and/or stabbed, the subcellular localization of the molecule of interest, and its density of expression that could be too low even in their own native environment. Functional expression of genes using recombinant DNA technology not only overcomes those hurdles but also affords additional and elegant investigations such as single-point mutation studies and subunit associations/regulations. In this chapter, we give a step-by-step description of two electrophysiological methods, patch clamp and two-electrode voltage clamp (TEVC), that are routinely used in combination with heterologous gene expression to assist researchers interested in the identification and characterization of ion transporters. We describe how to (1) obtain and maintain the cells suitable for the use with each of the above-mentioned methods (i.e., HEK-293 cells and yeast spheroplasts to use with the patch-clamp methodology and Xenopus laevis oocytes with TEVC), (2) transfect/inject them with the gene of interest, and (3) record ion transport activities. © Springer Science+Business Media New York 2013.

  2. Suppression of Spiral Waves by Voltage Clamp Techniques in a Conductance-Based Cardiac Tissue Model

    Institute of Scientific and Technical Information of China (English)

    YU Lian-Chun; MA Jun; ZHANG Guo-Yong; CHEN Yong

    2008-01-01

    A new control method is proposed to control the spatio-temporal dynamics in excitable media, which is described by the Morris-Lecar cells model. It is confirmed that successful suppression of spiral waves can be obtained by spatially clamping the membrane voltage of the excitable cells. The low voltage clamping induces breakup of spiral waves and the fragments are soon absorbed by low voltage obstacles, whereas the high voltage clamping generates travel waves that annihilate spiral waves through collision with them. However, each method has its shortcomings. Furthermore, a two-step method that combines both low and high voltage clamp techniques is then presented as a possible way of out this predicament.

  3. Novel Low Loss Active Voltage Clamp Circuit for Series Connection of RCGCT thyristors

    Science.gov (United States)

    Ito, Hiroshi; Suzuki, Akihiro; Iwata, Akihiko

    This paper describes novel low loss active voltage clamp circuits for the series connection of RCGCT thyristors. For high voltage converters the series connection of power semiconductor devices is an essential technique for direct switching of high voltages. Several protection circuits have been applied to the series connection of RCGCT thyristors such as CRD snubber circuits which suppress over-voltages across RCGCT thyristors, and voltage balancing resistors to equalize voltage sharing in steady states. However, significant losses in these protection circuits lower the converter’s efficiency. We propose novel low-loss protection circuits, which have active voltage clamp snubber circuits and static voltage balancing circuits. The clamp capacitor voltage of the active voltage clamp snubber circuits are designed to be higher than the equally divided DC-Link voltage. This method can reduce the loss of the clamp circuit to no more than 1/10 of that of the conventional CRD snubber. Also the static voltage balancing circuits compensate for the voltage imbalance generated by the difference in the leakage current between the series connection RCGCT thyristors.

  4. Modeling CICR in rat ventricular myocytes: voltage clamp studies

    Directory of Open Access Journals (Sweden)

    Palade Philip T

    2010-11-01

    Full Text Available Abstract Background The past thirty-five years have seen an intense search for the molecular mechanisms underlying calcium-induced calcium-release (CICR in cardiac myocytes, with voltage clamp (VC studies being the leading tool employed. Several VC protocols including lowering of extracellular calcium to affect Ca2+ loading of the sarcoplasmic reticulum (SR, and administration of blockers caffeine and thapsigargin have been utilized to probe the phenomena surrounding SR Ca2+ release. Here, we develop a deterministic mathematical model of a rat ventricular myocyte under VC conditions, to better understand mechanisms underlying the response of an isolated cell to calcium perturbation. Motivation for the study was to pinpoint key control variables influencing CICR and examine the role of CICR in the context of a physiological control system regulating cytosolic Ca2+ concentration ([Ca2+]myo. Methods The cell model consists of an electrical-equivalent model for the cell membrane and a fluid-compartment model describing the flux of ionic species between the extracellular and several intracellular compartments (cell cytosol, SR and the dyadic coupling unit (DCU, in which resides the mechanistic basis of CICR. The DCU is described as a controller-actuator mechanism, internally stabilized by negative feedback control of the unit's two diametrically-opposed Ca2+ channels (trigger-channel and release-channel. It releases Ca2+ flux into the cyto-plasm and is in turn enclosed within a negative feedback loop involving the SERCA pump, regulating[Ca2+]myo. Results Our model reproduces measured VC data published by several laboratories, and generates graded Ca2+ release at high Ca2+ gain in a homeostatically-controlled environment where [Ca2+]myo is precisely regulated. We elucidate the importance of the DCU elements in this process, particularly the role of the ryanodine receptor in controlling SR Ca2+ release, its activation by trigger Ca2+, and its

  5. Potassium Chloride Versus Voltage Clamp Contractures in Ventricular Muscle

    Science.gov (United States)

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

    1981-01-01

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

  6. Simulation of 2D Brain's Potential Distribution Based on Two Electrodes ECVT Using Finite Element Method

    Science.gov (United States)

    Sirait, S. H.; Edison, R. E.; Baidillah, M. R.; Taruno, W. P.; Haryanto, F.

    2016-08-01

    The aim of this study is to simulate the potential distribution of 2D brain geometry based on two electrodes ECVT. ECVT (electrical capacitance tomography) is a tomography modality which produces dielectric distribution image of a subject from several capacitance electrodes measurements. This study begins by producing the geometry of 2D brain based on MRI image and then setting the boundary conditions on the boundaries of the geometry. The values of boundary conditions follow the potential values used in two electrodes brain ECVT, and for this reason the first boundary is set to 20 volt and 2.5 MHz signal and another boundary is set to ground. Poisson equation is implemented as the governing equation in the 2D brain geometry and finite element method is used to solve the equation. Simulated Hodgkin-Huxley action potential is applied as disturbance potential in the geometry. We divide this study into two which comprises simulation without disturbance potential and simulation with disturbance potential. From this study, each of time dependent potential distributions from non-disturbance and disturbance potential of the 2D brain geometry has been generated.

  7. Standard test method for measurement of soil resistivity using the two-electrode soil box method

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers the equipment and a procedure for the measurement of soil resistivity, for samples removed from the ground, for use in the control of corrosion of buried structures. 1.2 Procedures allow for this test method to be used n the field or in the laboratory. 1.3 The test method procedures are for the resistivity measurement of soil samples in the saturated condition and in the as-received condition. 1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. Soil resistivity values are reported in ohm-centimeter. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

  8. Imperfect space clamp permits electrotonic interactions between inhibitory and excitatory synaptic conductances, distorting voltage clamp recordings.

    Directory of Open Access Journals (Sweden)

    Alon Poleg-Polsky

    Full Text Available The voltage clamp technique is frequently used to examine the strength and composition of synaptic input to neurons. Even accounting for imperfect voltage control of the entire cell membrane ("space clamp", it is often assumed that currents measured at the soma are a proportional indicator of the postsynaptic conductance. Here, using NEURON simulation software to model somatic recordings from morphologically realistic neurons, we show that excitatory conductances recorded in voltage clamp mode are distorted significantly by neighboring inhibitory conductances, even when the postsynaptic membrane potential starts at the reversal potential of the inhibitory conductance. Analogous effects are observed when inhibitory postsynaptic currents are recorded at the reversal potential of the excitatory conductance. Escape potentials in poorly clamped dendrites reduce the amplitude of excitatory or inhibitory postsynaptic currents recorded at the reversal potential of the other conductance. In addition, unclamped postsynaptic inhibitory conductances linearize the recorded current-voltage relationship of excitatory inputs comprising AMPAR and NMDAR-mediated components, leading to significant underestimation of the relative contribution by NMDARs, which are particularly sensitive to small perturbations in membrane potential. Voltage clamp accuracy varies substantially between neurons and dendritic arbors of different morphology; as expected, more reliable recordings are obtained from dendrites near the soma, but up to 80% of the synaptic signal on thin, distant dendrites may be lost when postsynaptic interactions are present. These limitations of the voltage clamp technique may explain how postsynaptic effects on synaptic transmission could, in some cases, be attributed incorrectly to presynaptic mechanisms.

  9. Calcium Release in Frog Cut Twitch Fibers Exposed to Different Ionic Environments under Voltage Clamp

    National Research Council Canada - National Science Library

    Hui, Chiu Shuen

    1999-01-01

    Calcium release was measured in highly stretched frog cut twitch fibers mounted in a double Vaseline-gap voltage clamp chamber, with the internal solution containing 20 mM EGTA plus 0.4 or 1.8 mM added calcium...

  10. Direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify the design, increase...... efficiency, reduce the product volume and lower its cost. As an example, the principle of operation and the measurements made on a direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp are presented....

  11. FPGA in-the-loop simulations of cardiac excitation model under voltage clamp conditions

    Science.gov (United States)

    Othman, Norliza; Adon, Nur Atiqah; Mahmud, Farhanahani

    2017-01-01

    Voltage clamp technique allows the detection of single channel currents in biological membranes in identifying variety of electrophysiological problems in the cellular level. In this paper, a simulation study of the voltage clamp technique has been presented to analyse current-voltage (I-V) characteristics of ion currents based on Luo-Rudy Phase-I (LR-I) cardiac model by using a Field Programmable Gate Array (FPGA). Nowadays, cardiac models are becoming increasingly complex which can cause a vast amount of time to run the simulation. Thus, a real-time hardware implementation using FPGA could be one of the best solutions for high-performance real-time systems as it provides high configurability and performance, and able to executes in parallel mode operation. For shorter time development while retaining high confidence results, FPGA-based rapid prototyping through HDL Coder from MATLAB software has been used to construct the algorithm for the simulation system. Basically, the HDL Coder is capable to convert the designed MATLAB Simulink blocks into hardware description language (HDL) for the FPGA implementation. As a result, the voltage-clamp fixed-point design of LR-I model has been successfully conducted in MATLAB Simulink and the simulation of the I-V characteristics of the ionic currents has been verified on Xilinx FPGA Virtex-6 XC6VLX240T development board through an FPGA-in-the-loop (FIL) simulation.

  12. Direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.; Andersen, Michael A.E.

    2005-07-01

    This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify design, increase efficiency and integration level, reduce product volume and lower its cost. As an example, the principle of operation and the measurements made on a direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp are presented. (au)

  13. How the early voltage clamp studies of José del Castillo inform "modern" neuroscience.

    Science.gov (United States)

    Zottoli, Steven J

    2012-10-01

    The description of ionic currents that flow across the membrane of the squid giant axon during an action potential sparked an interest in determining whether there were similar currents in vertebrates. The preparation of choice was the node of Ranvier in single myelinated fibers in frog. José del Castillo spent 3 years on the United States mainland from 1956 to 1959. During that time, he collaborated with Jerome Y. Lettvin and John W. Moore. I discuss how these individuals met one another and some of their scientific discoveries using the voltage clamp to study squid giant axons and frog nodes. Much of this work was conducted at the Marine Biological Laboratory in Woods Hole, MA, and I attempt to convey a sense of the unique scientific "melting pot" that existed at the Marine Biological Laboratory and the broader effect that del Castillo had on "modern" neuroscience.

  14. A numerical approach to ion channel modelling using whole-cell voltage-clamp recordings and a genetic algorithm.

    Directory of Open Access Journals (Sweden)

    Meron Gurkiewicz

    2007-08-01

    Full Text Available The activity of trans-membrane proteins such as ion channels is the essence of neuronal transmission. The currently most accurate method for determining ion channel kinetic mechanisms is single-channel recording and analysis. Yet, the limitations and complexities in interpreting single-channel recordings discourage many physiologists from using them. Here we show that a genetic search algorithm in combination with a gradient descent algorithm can be used to fit whole-cell voltage-clamp data to kinetic models with a high degree of accuracy. Previously, ion channel stimulation traces were analyzed one at a time, the results of these analyses being combined to produce a picture of channel kinetics. Here the entire set of traces from all stimulation protocols are analysed simultaneously. The algorithm was initially tested on simulated current traces produced by several Hodgkin-Huxley-like and Markov chain models of voltage-gated potassium and sodium channels. Currents were also produced by simulating levels of noise expected from actual patch recordings. Finally, the algorithm was used for finding the kinetic parameters of several voltage-gated sodium and potassium channels models by matching its results to data recorded from layer 5 pyramidal neurons of the rat cortex in the nucleated outside-out patch configuration. The minimization scheme gives electrophysiologists a tool for reproducing and simulating voltage-gated ion channel kinetics at the cellular level.

  15. Substance P-mediated membrane currents in voltage-clamped guinea pig inferior mesenteric ganglion cells.

    Science.gov (United States)

    Griffith, W H; Hills, J M; Brown, D A

    1988-01-01

    Responses to substance P (SP) and to hypogastric nerve stimulation were recorded from voltage-clamped guinea pig inferior mesenteric ganglion (IMG) neurons, and compared with those to muscarine. Muscarine produced a voltage-dependent inward current accompanied by a reduced input conductance and inhibition of IM a time- and voltage-dependent K+-current (Brown and Adams: Nature 283:673-676, 1980). SP also produced an inward current, accompanied by a fall in input conductance (20 out of 31 cells) or a rise in input conductance (7 out of 31 cells). The fall in input conductance was not accompanied by an inhibition of M-current (unlike frog ganglia: Adams et al.: British Journal of Pharmacology 79:330-333, 1983) or an inhibition of the inward rectifier current (unlike globus pallidus neurons: Stanfield et al.: Nature 315:498-501, 1985). Repetitive hypogastric nerve stimulation (10-20 Hz, 2-10 s) produced a slow inward postsynaptic current lasting 1-3 min, with decreases or increases of input conductance matching those produced by SP. The postsynaptic current did not show a consistent or reproducible change in amplitude on varying the holding potential between -90 and -25 mV. It is concluded that SP and hypogastric stimulation produce complex and variable changes in ionic conductance in IMG neurons.

  16. Voltage-clamp predictions by gompertz kinetics model relating squid-axon Na+-gating and ionic currents.

    Science.gov (United States)

    Easton, Dexter M

    2005-10-01

    Gompertz kinetics is a simple, realistic, accurate, and computationally parsimonious alternative for prediction of macroscopic changes in Na+ conductance during voltage clamp. Conductance delay and time course depend on initial amplitudes and decay rates of surrogates for the macroscopic gating currents. The model is tested by the fit to published data of other authors. The proposed physical basis for the model is that membrane potential perturbation triggers motion of charged "gating" components of the axon membrane at rapid (activating) and at slow (inactivating) rates. The resulting distortion increases and more slowly diminishes the probability that conduction channels will be open.

  17. Isolated PWM DC-AC SICAM with an active capacitive voltage clamp[Pulse Density Modulated; Pulse Width Modulation

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.

    2004-03-15

    In this report an isolated PWM DC-AC SICAM with an active capacitive voltage clamp is presented. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitors and possibly with an EMC filter on the mains entrance. Isolation from the AC mains is achieved using a high frequency (HF) transformer, whose voltages are not audio-modulated. The latter simplifies the design and is expected to have many advantages over the approach where the transformer voltages are modulated in regards to the audio signal reference. Input stage is built as a DC-AC inverter (push-pull, half-bridge or a full-bridge) and operated with 50% duty cycle, with all the challenges to avoid transformer saturation and obtain symmetrical operation. On the secondary side the output section is implemented as rectifier+inverter AC-AC stage, i.e. a true bidirectional bridge, which operation is aimed towards amplification of the audio signal. In order to solve the problem with the commutation of the load current, a dead time between the incoming and outgoing bidirectional switch is implemented, while a capacitive voltage clamp is used to keep the induced overvoltage to reasonable levels. The energy stored in the clamping capacitor is not wasted as in the dissipative clamps, but is rather transferred back to the primary side for further processing using an auxiliary isolated single-switch converter, i.e. an active clamping technique is used. (au)

  18. Voltage-clamp studies of transient inward current and mechanical oscillations induced by ouabain in ferret papillary muscle.

    Science.gov (United States)

    Karagueuzian, H S; Katzung, B G

    1982-06-01

    1. We studied the effects of a toxic concentration of ouabain on transmembrane electrical activity and on mechanical behaviour of right ventricular papillary muscles from ferrets in a single sucrose-gap using current clamp and voltage clamp.2. Ouabain (1.4-1.8 muM) induced oscillatory after-potentials and after-concentrations in current-clamp experiments. Voltage clamp showed that the oscillatory after-potential was caused by a transient inward current, similar to that in Purkinje fibres.3. The transient current had a sigmoidal dependence on the preceding (activating) voltage step V1, with a treshold around -13 mV and a plateau between +10 and 20 mV. There was a decline in current amplitude for more positive clamps. When activated by a fixed V1 voltage step, and measured at different repolarization levels V2, the transient current manifested an inverse dependence on V2 between -50 and -10 mV. No outward transient current could be detected. Total replacement of Na in the bathing medium by Tris or by sucrose abolished the transient current.4. Ouabain caused an increase of phasic (twitch) tension responses to voltage steps at all potentials without shifting the curve relating these variables on the voltage axis. The drug evoked an even greater increase in the tonic tension responses.5. After prolonged exposure, oscillatory mechanical responses were frequently recorded during positive voltage steps. Unlike the after-contraction, these mechanical fluctuations were not consistently damped and were not accompanied by detectable synchronous current fluctuations. Catecholamines and dibutyryl cyclic AMP markedly reduced the amplitude of the tonic contraction and the mechanical oscillations but increased their frequency. Caffeine had no effect on the tonic contraction amplitude but abolished the fluctuations.6. These results support the proposal that Ca is transiently released from the overloaded sarcoplasmic reticulum in ouabain-intoxicated muscle and may evoke oscillatory

  19. How cesium dialysis affects the passive properties of pyramidal neurons: implications for voltage clamp studies of persistent sodium current

    Energy Technology Data Exchange (ETDEWEB)

    Fleidervish, Ilya A; Libman, Lior [Koret School of Veterinary Medicine, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100 (Israel)], E-mail: fleider@agri.huji.ac.il

    2008-03-15

    In order to accurately understand and model neuronal integration in the brain, we must know the biophysical properties of channels that are located far from the soma, in the axonal and dendritic membranes of central nerve cells. Reliable electrophysiological measurements in these regions are difficult to obtain, because the processes are too tiny to directly study with an electrode. One common strategy is to record with a somatic electrode that contains Cs{sup +}, to dialyze the intracellular space with this K{sup +} channel blocker, and thereby to render the neuron electrotonically compact. Does this work? Here, we combine the experimental and modeling techniques to determine the extent to which a whole-cell voltage clamp, established with a Cs{sup +}-containing pipette in the soma of a cortical pyramidal cell, attains adequate voltage control of distal neuronal processes. We focus on the low-voltage-activated, slowly inactivating 'persistent' Na{sup +} current (I{sub NaP}), that plays a crucial role in determining neuronal excitability and synaptic integration.

  20. How cesium dialysis affects the passive properties of pyramidal neurons: implications for voltage clamp studies of persistent sodium current

    Science.gov (United States)

    Fleidervish, Ilya A.; Libman, Lior

    2008-03-01

    In order to accurately understand and model neuronal integration in the brain, we must know the biophysical properties of channels that are located far from the soma, in the axonal and dendritic membranes of central nerve cells. Reliable electrophysiological measurements in these regions are difficult to obtain, because the processes are too tiny to directly study with an electrode. One common strategy is to record with a somatic electrode that contains Cs+, to dialyze the intracellular space with this K+ channel blocker, and thereby to render the neuron electrotonically compact. Does this work? Here, we combine the experimental and modeling techniques to determine the extent to which a whole-cell voltage clamp, established with a Cs+-containing pipette in the soma of a cortical pyramidal cell, attains adequate voltage control of distal neuronal processes. We focus on the low-voltage-activated, slowly inactivating 'persistent' Na+ current (INaP), that plays a crucial role in determining neuronal excitability and synaptic integration.

  1. Analysis of the effects of calcium or magnesium on voltage-clamp currents in perfused squid axons bathed in solutions of high potassium.

    Science.gov (United States)

    Rojas, E; Taylor, R E; Atwater, I; Bezanilla, F

    1969-10-01

    Isolated axons from the squid, Dosidicus gigas, were internally perfused with potassium fluoride solutions. Membrane currents were measured following step changes of membrane potential in a voltage-clamp arrangement with external isosmotic solution changes in the order: potassium-free artificial seawater; potassium chloride; potassium chloride containing 10, 25, 40 or 50, mM calcium or magnesium; and potassium-free artificial seawater. The following results suggest that the currents measured under voltage clamp with potassium outside and inside can be separated into two components and that one of them, the predominant one, is carried through the potassium system. (a) Outward currents in isosmotic potassium were strongly and reversibly reduced by tetraethylammonium chloride. (b) Without calcium or magnesium a progressive increase in the nontime-dependent component of the currents (leakage) occurred. (c) The restoration of calcium or magnesium within 15-30 min decreases this leakage. (d) With 50 mM divalent ions the steady-state current-voltage curve was nonlinear with negative resistance as observed in intact axons in isosmotic potassium. (e) The time-dependent components of the membrane currents were not clearly affected by calcium or magnesium. These results show a strong dependence of the leakage currents on external calcium or magnesium concentration but provide no support for the involvement of calcium or magnesium in the kinetics of the potassium system.

  2. Effect of terfenadine and pentamidine on the HERG channel and its intracellular trafficking: combined analysis with automated voltage clamp and confocal microscopy.

    Science.gov (United States)

    Tanaka, Hikaru; Takahashi, Yukiko; Hamaguchi, Shogo; Iida-Tanaka, Naoko; Oka, Takayuki; Nishio, Masato; Ohtsuki, Atsushi; Namekata, Iyuki

    2014-01-01

    The effects of terfenadine and pentamidine on the human ether-a-go-go related gene (hERG) channel current and its intracellular trafficking were evaluated. Green fluorescent protein (GFP)-linked hERG channels were expressed in HEK293 cells, and the membrane current was measured by an automated whole cell voltage clamp system. To evaluate drug effects on channel trafficking to the cell membrane, the fraction of channel present on the cell membrane was quantified by current measurement after drug washout and confocal microscopy. Terfenadine directly blocked the hERG channel current but had no effect on trafficking of hERG channels to the cell membrane after application in culture medium for 2 d. In contrast, pentamidine had no direct effect on the hERG channel current but reduced trafficking of hERG channels. The two drugs inhibited hERG channel function through different mechanisms: terfenadine through direct channel blockade and pentamidine through inhibition of channel trafficking to the cell membrane. Combined use of automated voltage clamp and confocal microscopic analyses would provide insights into the mechanisms of drug-induced QT-prolongation and arrhythmogenesis.

  3. Unloaded speed of shortening in voltage-clamped intact skeletal muscle fibers from wt, mdx, and transgenic minidystrophin mice using a novel high-speed acquisition system.

    Science.gov (United States)

    Friedrich, O; Weber, C; von Wegner, F; Chamberlain, J S; Fink, R H A

    2008-06-01

    Skeletal muscle unloaded shortening has been indirectly determined in the past. Here, we present a novel high-speed optical tracking technique that allows recording of unloaded shortening in single intact, voltage-clamped mammalian skeletal muscle fibers with 2-ms time resolution. L-type Ca(2+) currents were simultaneously recorded. The time course of shortening was biexponential: a fast initial phase, tau(1), and a slower successive phase, tau(2,) with activation energies of 59 kJ/mol and 47 kJ/mol. Maximum unloaded shortening speed, v(u,max), was faster than that derived using other techniques, e.g., approximately 14.0 L(0) s(-1) at 30 degrees C. Our technique also allowed direct determination of shortening acceleration. We applied our technique to single fibers from C57 wild-type, dystrophic mdx, and minidystrophin-expressing mice to test whether unloaded shortening was affected in the pathophysiological mechanism of Duchenne muscular dystrophy. v(u,max) and a(u,max) values were not significantly different in the three strains, whereas tau(1) and tau(2) were increased in mdx fibers. The results were complemented by myosin heavy and light chain (MLC) determinations that showed the same myosin heavy chain IIA profiles in the interossei muscles from the different strains. In mdx muscle, MLC-1f was significantly increased and MLC-2f and MLC-3f somewhat reduced. Fast initial active shortening seems almost unaffected in mdx muscle.

  4. Sites and mechanisms of antibiotic-induced neuromuscular block: a pharmacological analysis using quantal content, voltage clamped end-plate currents and single channel analysis.

    Science.gov (United States)

    Fiekers, J F

    1999-01-01

    Since the original observation of Vital Brazil and Corrado (1957) concerning the antibiotic induced neuromuscular block produced by streptomycin, there has been considerable interest in the mechanisms responsible for not only neuromuscular block but also the effects of antibiotics on different systems. We used the voltage clamped end-plate of transacted skeletal muscle to examine the concentration-dependent actions of several groups of antibiotics. The aminoglycoside antibiotics, neomycin and streptomycin, were both more effective at reducing quantal release of acetylcholine (ACh) than interacting with the postjunctional ACh receptor-channel complex. Neomycin was approximately 10 X more potent prejunctionally than streptomycin and the prejunctional effects of each antibiotic were reversed competitively by raising extracellular calcium. Both neomycin and streptomycin also had postjunctional actions at higher concentrations. Neomycin interacted with the open state of the ACh receptor ion channel complex while streptomycin blocks the ACh receptor. The lincosamide antibiotics, lincomycin and clindamycin produced their neuromuscular block postjunctionally by interacting with the open state of the ACh-receptor channel complex. Clindamycin is approximately 20 X more effective at blocking the open channel than was lincomycin. Using cell attached patch clamp recordings in cultured rat myotubes, we demonstrated a lincosamide-induced block of open ion channels with clindamycin having a much slower unblocking rate than lincomycin. Using epimers of the lincosamides, we demonstrated that lipophilicity of the molecule, rather than stereochemical considerations, is important for open channel blockade affecting primarily the "off" rate of channel blocking. This mechanism appears important for not only the lincosamide antibiotics but also for the postjunctional actions of the aminoglycoside antibiotics, particularly neomycin.

  5. Control of gastric H,K-ATPase activity by cations, voltage and intracellular pH analyzed by voltage clamp fluorometry in Xenopus oocytes.

    Directory of Open Access Journals (Sweden)

    Katharina L Dürr

    Full Text Available Whereas electrogenic partial reactions of the Na,K-ATPase have been studied in depth, much less is known about the influence of the membrane potential on the electroneutrally operating gastric H,K-ATPase. In this work, we investigated site-specifically fluorescence-labeled H,K-ATPase expressed in Xenopus oocytes by voltage clamp fluorometry to monitor the voltage-dependent distribution between E(1P and E(2P states and measured Rb(+ uptake under various ionic and pH conditions. The steady-state E(1P/E(2P distribution, as indicated by the voltage-dependent fluorescence amplitudes and the Rb(+ uptake activity were highly sensitive to small changes in intracellular pH, whereas even large extracellular pH changes affected neither the E(1P/E(2P distribution nor transport activity. Notably, intracellular acidification by approximately 0.5 pH units shifted V(0.5, the voltage, at which the E(1P/E(2P ratio is 50∶50, by -100 mV. This was paralleled by an approximately two-fold acceleration of the forward rate constant of the E(1P→E(2P transition and a similar increase in the rate of steady-state cation transport. The temperature dependence of Rb(+ uptake yielded an activation energy of ∼90 kJ/mol, suggesting that ion transport is rate-limited by a major conformational transition. The pronounced sensitivity towards intracellular pH suggests that proton uptake from the cytoplasmic side controls the level of phosphoenzyme entering the E(1P→E(2P conformational transition, thus limiting ion transport of the gastric H,K-ATPase. These findings highlight the significance of cellular mechanisms contributing to increased proton availability in the cytoplasm of gastric parietal cells. Furthermore, we show that extracellular Na(+ profoundly alters the voltage-dependent E(1P/E(2P distribution indicating that Na(+ ions can act as surrogates for protons regarding the E(2P→E(1P transition. The complexity of the intra- and extracellular cation effects can be

  6. Advantage of four-electrode over two-electrode defibrillators

    Science.gov (United States)

    Bragard, J.; Šimić, A.; Laroze, D.; Elorza, J.

    2015-12-01

    Defibrillation is the standard clinical treatment used to stop ventricular fibrillation. An electrical device delivers a controlled amount of electrical energy via a pair of electrodes in order to reestablish a normal heart rate. We propose a technique that is a combination of biphasic shocks applied with a four-electrode system rather than the standard two-electrode system. We use a numerical model of a one-dimensional ring of cardiac tissue in order to test and evaluate the benefit of this technique. We compare three different shock protocols, namely a monophasic and two types of biphasic shocks. The results obtained by using a four-electrode system are compared quantitatively with those obtained with the standard two-electrode system. We find that a huge reduction in defibrillation threshold is achieved with the four-electrode system. For the most efficient protocol (asymmetric biphasic), we obtain a reduction in excess of 80% in the energy required for a defibrillation success rate of 90%. The mechanisms of successful defibrillation are also analyzed. This reveals that the advantage of asymmetric biphasic shocks with four electrodes lies in the duration of the cathodal and anodal phase of the shock.

  7. Electrochemical quartz crystal microbalance study on the two-electrode-system cyclic voltammetric behavior of Prussian blue films

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A two-channel electrochemical quartz crystal microbalance (EQCM) was used to investigate the cyclic voltammetric behavior of two Prussian blue (PB) film-modified Au electrodes in a two-electrode con-figuration in aqueous solution. The redox peaks observed in the two-electrode cyclic voltammogram (CV) are assigned to the intrinsic redox transitions among the Everitt’s salt, PB, and Prussian yellow for the film itself, the redox process of the Au substrate and the redox process of small-quantity ferri-/ferrocyanide impurities entrapped in the PB film, as also supported by ultraviolet-visible (UV-Vis) spectroelectrochemical data. The profile of the two-electrode solid-state CV for the PB powder sand-wiched between two gold-coated indium-tin oxide (ITO) electrodes is similar to that for two PB-modified Au electrodes in aqueous solution, implying similar origins for the corresponding redox peaks. The two-channel EQCM method is expected to become a highly effective technique for the studies of the two-electrode electrochemical behaviors of many other species/materials.

  8. Amplified spontaneous emission spectrum and gain characteristic of a two-electrode semiconductor optical amplifier*

    Institute of Scientific and Technical Information of China (English)

    Wang Hanchao; Huang Lirong; Shi Zhongwei

    2011-01-01

    A two-electrode multi-quantum-well semiconductor optical amplifier is designed and fabricated. The amplified spontaneous emission (ASE) spectrum and gain were measured and analyzed. It is shown that the ASE spectrum and gain characteristic are greatly influenced by the distribution of the injection current density. By changing the injection current density of two electrodes, the full width at half maximum, peak wavelength, peak power of the ASE spectrum and the gain characteristic can be easily controlled.

  9. EEG-Based Person Authentication Using a Fuzzy Entropy-Related Approach with Two Electrodes

    Directory of Open Access Journals (Sweden)

    Zhendong Mu

    2016-12-01

    Full Text Available Person authentication, based on electroencephalography (EEG signals, is one of the directions possible in the study of EEG signals. In this paper, a method for the selection of EEG electrodes and features in a discriminative manner is proposed. Given that EEG signals are unstable and non-linear, a non-linear analysis method, i.e., fuzzy entropy, is more appropriate. In this paper, unlike other methods using different signal sources and patterns, such as rest state and motor imagery, a novel paradigm using the stimuli of self-photos and non-self-photos is introduced. Ten subjects are selected to take part in this experiment, and fuzzy entropy is used as a feature to select the minimum number of electrodes that identifies individuals. The experimental results show that the proposed method can make use of two electrodes (FP1 and FP2 in the frontal area, while the classification accuracy is greater than 87.3%. The proposed biometric system, based on EEG signals, can provide each subject with a unique key and is capable of human recognition.

  10. Electrochemical surface plasmon resonance sensor based on two-electrode configuration

    Science.gov (United States)

    Zhang, Bing; Li, Yazhuo; Dong, Wei; Wen, Yizhang; Pang, Kai; Zhan, Shuyue; Wang, Xiaoping

    2016-10-01

    To obtain detailed information about electrochemistry reactions, a two-electrode electrochemical surface plasmon resonance (EC-SPR) sensor has been proposed. We describe the theory of potential modulation for this novel sensor and determine the factors that can change the SPR resonance angle. The reference electrode in three-electrode configuration was eliminated, and comparing with several other electrode materials, activated carbon (AC) is employed as the suitable counter electrode for its potential stability. Just like three-electrode configuration, the simpler AC two-electrode system can also obtain detailed information about the electrochemical reactions.

  11. New active load voltage clamp for HF-link converters

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.; Andersen, M.A.E.

    2005-07-01

    This paper proposes a new active clamp for HF-link converters, which features very high efficiency by returning the clamped energy back to the primary side through a small auxiliary converter. It also increases the reliability of HF-link converters by providing an alternative load current path during malfunctions of the secondary bidirectional bridge. The feasibility of the approach is shown on audio power amplifier prototype. New integrated magnetics design is presented that incorporates both the main power and auxiliary transformer on the same magnetic core. (au)

  12. New active load voltage clamp for HF-link converters

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper proposes a new active clamp for HF-link converters, which features very high efficiency by returning the clamped energy back to the primary side through a small auxiliary converter. It also increases the reliability of HF-link converters by providing an alternative load current path du...... during malfunctions of the secondary bidirectional bridge. The feasibility of the approach is shown on audio power amplifier prototype. New integrated magnetics design is presented that incorporates both the main power and auxiliary transformer on the same magnetic core....

  13. Electrical impedance tomography in 3D using two electrode planes: characterization and evaluation.

    Science.gov (United States)

    Wagenaar, Justin; Adler, Andy

    2016-06-01

    Electrical impedance tomography (EIT) uses body surface electrical stimulation and measurements to create conductivity images; it shows promise as a non-invasive technology to monitor the distribution of lung ventilation. Most applications of EIT have placed electrodes in a 2D ring around the thorax, and thus produced 2D cross-sectional images. These images are unable to distinguish out-of-plane contributions, or to image volumetric effects. Volumetric EIT can be calculated using multiple electrode planes and a 3D reconstruction algorithm. However, while 3D reconstruction algorithms are available, little has been done to understand the performance of 3D EIT in terms of the measurement configurations available. The goal of this paper is to characterize the phantom and in vivo performance of 3D EIT with two electrode planes. First, phantom measurements are used to measure the reconstruction characteristics of seven stimulation and measurement configurations. Measurements were then performed on eight healthy volunteers as a function of body posture, postures, and with various electrode configurations. Phantom results indicate that 3D EIT using two rings of electrodes provides reasonable resolution in the electrode plane but low vertical resolution. For volunteers, functional EIT images are created from inhalation curve features to analyze the effect of posture (standing, sitting, supine and decline) on regional lung behaviour. An ability to detect vertical changes in lung volume distribution was shown for two electrode configurations. Based on tank and volunteer results, we recommend the use of the 'square' stimulation and measurement pattern for two electrode plane EIT.

  14. Long QT 1 mutation KCNQ1A344V increases local anesthetic sensitivity of the slowly activating delayed rectifier potassium current

    DEFF Research Database (Denmark)

    Siebrands, Cornelia C; Binder, Stephan; Eckhoff, Ulrike

    2006-01-01

    a nonspecific but also a specific pharmacogenetic risk factor for anesthesia. METHODS: The authors examined electrophysiologic and pharmacologic properties of wild-type and mutant KCNQ1 channels. The effects of bupivacaine, ropivacaine, and mepivacaine were investigated using two-electrode voltage clamp...

  15. Electro-chemical deposition of zinc oxide nanostructures by using two electrodes

    Directory of Open Access Journals (Sweden)

    B. A. Taleatu

    2011-09-01

    Full Text Available One of the most viable ways to grow nanostructures is electro deposition. However, most electrodeposited samples are obtained by three-electrode electrochemical cell. We successfully use a much simpler two-electrode cell to grow different ZnO nanostructures from common chemical reagents. Concentration, pH of the electrolytes and growth parameters like potentials at the electrodes, are tailored to allow fast growth without complexity. Morphology and surface roughness are investigated by Scanning Electron and Air Force Microscopy (SEM and AFM respectively, crystal structure by X-Ray Diffraction measurements (XRD and ZnO stoichiometry by core level photoemission spectroscopy (XPS.

  16. Electrochemical synthesis and characterization of stable colloidal suspension of graphene using two-electrode cell system

    Energy Technology Data Exchange (ETDEWEB)

    Danial, Wan Hazman, E-mail: hazmandanial@gmail.com; Majid, Zaiton Abdul, E-mail: zaiton@kimia.fs.utm.my; Aziz, Madzlan [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor (Malaysia); Chutia, Arunabhiram [Institute of Fluid Sciences, Tohoku University, Sendai 980-8577 (Japan); Sahnoun, Riadh [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor (Malaysia)

    2015-07-22

    The present work reports the synthesis and characterization of graphene via electrochemical exfoliation of graphite rod using two-electrode system assisted by Sodium Dodecyl Sulphate (SDS) as a surfactant. The electrochemical process was carried out with sequence of intercalation of SDS onto the graphite anode followed by exfoliation of the SDS-intercalated graphite electrode when the anode was treated as cathode. The effect of intercalation potential from 5 V to 9 V and concentration of the SDS surfactant of 0.1 M and 0.01 M were investigated. UV-vis Spectroscopic analysis indicated an increase in the graphene production with higher intercalation potential. Transmission Electron Microscopy (TEM) analysis showed a well-ordered hexagonal lattice of graphene image and indicated an angle of 60° between two zigzag directions within the honeycomb crystal lattice. Raman spectroscopy analysis shows the graphitic information effects after the exfoliation process.

  17. Supercapacitive properties of symmetry and the asymmetry two electrode coin type supercapacitor cells made from MWCNTS/nickel oxide nanocomposite

    CSIR Research Space (South Africa)

    Adekunle, AS

    2011-10-01

    Full Text Available Supercapacitive properties of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in a two-electrode coin cell type supercapacitor were investigated. Successful formation of the MWCNT-NiO nanocomposite...

  18. Design of two electrode system for detection of antioxidant capacity with photoelectrochemical platform.

    Science.gov (United States)

    Han, Dongxue; Ma, Weiguang; Wang, Lingnan; Ni, Shuang; Zhang, Nan; Wang, Wei; Dong, Xiandui; Niu, Li

    2016-01-15

    Recently, a flow photoelectrochemical cell has been first developed and applied to assay global antioxidant capacity in our group. Yet, shortcomings of liquid reference electrode such as sample contaminations from the leaking of the reference solution, mechanically fragile, temperature and light sensitivity, etc. are significant restrictions for integration and miniaturization of photoelectrochemical sensing instruments, which have greatly limited their practical applications. Bearing these problems, in this work a novel two electrode flow photoelectron-chemical system (two-EPCS) has been developed for detection of antioxidant capacity. It is noteworthy that the electrochemical modulation-free mode (detection at the potential of 0.0V) is performed, which has greatly simplified the analysis process and will result in significant simplifications of the instrument integrations. During the sample analysis, both standard antioxidants and commercial beverages were detected. Results evaluated from the two-EPCS are well agreed with those of the traditional three-EPCS at low potentials. By unloading of the reference electrode, it is of great convenience to design a novel photoelectrochemical microfluidic chip based on the two-EPCS, which has also been successfully applied for antioxidant capacity assay. It is satisfactory that comparable detection concentration range and sensitivity were accomplished by applying the microfluidic chip technique. Moreover, the two-EPCS is verified to be a universal platform which does not depend on selected optoelectronic materials but pervasive for general photocatalysts. Such a two-EPCS should be considered as a feasible alternative to the three-EPCS, which will become a promising candidate for industrial and commercial photoelectrochemical sensing instrument integrations in the future.

  19. Evaluation of in-channel amperometric detection using a dual-channel microchip electrophoresis device and a two-electrode potentiostat for reverse polarity separations.

    Science.gov (United States)

    Meneses, Diogenes; Gunasekara, Dulan B; Pichetsurnthorn, Pann; da Silva, José A F; de Abreu, Fabiane C; Lunte, Susan M

    2015-02-01

    In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration.

  20. Electrochemical Deposition of CdTe Semiconductor Thin Films for Solar Cell Application Using Two-Electrode and Three-Electrode Configurations: A Comparative Study

    Directory of Open Access Journals (Sweden)

    O. K. Echendu

    2016-01-01

    Full Text Available Thin films of CdTe semiconductor were electrochemically deposited using two-electrode and three-electrode configurations in potentiostatic mode for comparison. Cadmium sulphate and tellurium dioxide were used as cadmium and tellurium sources, respectively. The layers obtained using both configurations exhibit similar structural, optical, and electrical properties with no specific dependence on any particular electrode configuration used. These results indicate that electrochemical deposition (electrodeposition of CdTe and semiconductors in general can equally be carried out using two-electrode system as well as the conventional three-electrode system without compromising the essential qualities of the materials produced. The results also highlight the advantages of the two-electrode configuration in process simplification, cost reduction, and removal of a possible impurity source in the growth system, especially as the reference electrode ages.

  1. Comparative supercapacitive properties of asymmetry two electrode coin type supercapacitor cells made from MWCNTs/cobalt oxide and MWCNTs/iron oxide nanocomposite

    CSIR Research Space (South Africa)

    Adekunle, AS

    2015-04-01

    Full Text Available Supercapacitive properties of synthesized metal oxide nanoparticles (MO) vis a vis iron oxides (Fe(sub2)O(sub3)) and cobalt oxide (Co(sub3)O(sub4)) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in a two-electrode coin cell type...

  2. Evaluation of Metals (Al, Fe, Zn) in Alternative Fuels by Electrochemical Impedance Spectroscopy in Two Electrode Cell

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yon Kyun [POSCO Technical Research Laboratories, Gwnagyang (Korea, Republic of); Lim, Geun Woong; Kim, Hee San [Hongik University, Chochiwon (Korea, Republic of)

    2010-04-15

    Many kinds of alternative fuels such as biodiesel, ethanol, methanol, and natural gas have been developed in order to overcome the limited deposits in fossil fuels. In some cases, the alternative fuels have been reported to cause degrade materials. The corrosion rates of metals were measured by immersion test, a kind of time consuming test because low conductivity of these fuels was not allowed to employ electrochemical tests. With twin two-electrode cell newly designed for the study, however, electrochemical impedance spectroscopy (EIS) test was successfully applied to evaluation of the corrosion resistance (R{sub p}) of zinc, iron, aluminum, and its alloys in an oxidized biodiesel and gasoline/ethanol solutions and the corrosion resistance from EIS was compared with the corrosion rate from immersion test. In biodiesel, R{sub p} increased in the order of zinc, iron, and aluminum, which agreed with the corrosion resistance measured from immersion test. In addition, on aluminum showing the best corrosion resistance (R{sub p}), the effect of magnesium as an alloying element was evaluated in gasoline/ethanol solutions as well as the oxidized biodiesel. R{sub p} increased with addition of magnesium in gasoline/ethanol solutions containing chloride and the oxidized biodiesel. In the mean while, in gasoline/ethanol solutions containing formic acid, Al-Mg alloy added 1% magnesium had the highest R{sub p} and the further addition of magnesium decreased R{sub p}. It can be explained with the fact that the addition of more than 1% magnesium increases the passive current density of Al-Mg alloys.

  3. Test of blockers of AQP1 water permeability by a high-resolution method: no effects of tetraethylammonium ions or acetazolamide

    DEFF Research Database (Denmark)

    Søgaard, Rikke; Zeuthen, Thomas

    2007-01-01

    The effects of putative water channel blockers were tested on AQP1-expressing Xenopus laevis oocytes by a fast optical method with a time resolution of 1 s and a volume resolution of 20 pl. The oocytes were exposed to external hyposmolarity and the osmotic water permeability (Lp) derived from...... will be underestimated. (b) Hyposmotic gradients implemented by dilution with water will entail changes in the ionic strength as well; this may enhance loss of salt from the oocyte. (c) By voltage clamping the AQP1-expressing oocytes during hyposmotic challenges, we found that TEA+-treated oocytes were more electrically...

  4. Measurement and analysis of postsynaptic potentials using a novel voltage-deconvolution method.

    Science.gov (United States)

    Richardson, Magnus J E; Silberberg, Gilad

    2008-02-01

    Accurate measurement of postsynaptic potential amplitudes is a central requirement for the quantification of synaptic strength, dynamics of short-term and long-term plasticity, and vesicle-release statistics. However, the intracellular voltage is a filtered version of the underlying synaptic signal and so a method of accounting for the distortion caused by overlapping postsynaptic potentials must be used. Here a voltage-deconvolution technique is demonstrated that defilters the entire voltage trace to reveal an underlying signal of well-separated synaptic events. These isolated events can be cropped out and reconvolved to yield a set of isolated postsynaptic potentials from which voltage amplitudes may be measured directly-greatly simplifying this common task. The method also has the significant advantage of providing a higher temporal resolution of the dynamics of the underlying synaptic signal. The versatility of the method is demonstrated by a variety of experimental examples, including excitatory and inhibitory connections to neurons with passive membranes and those with activated voltage-gated currents. The deconvolved current-clamp voltage has many features in common with voltage-clamp current measurements. These similarities are analyzed using cable theory and a multicompartment cell reconstruction, as well as direct comparison to voltage-clamp experiments.

  5. Pulse and Trapezoidal Voltage Clamp Applied To Jurkat Cells: A T- Lymphocyte Cell Line

    Science.gov (United States)

    1993-04-01

    clamp. (Upward deflection represents depolarization). Low frequency oscillations are clearly visible. Such oscillations have been described by Maltsev ...1952. (8) Maltsev , V. A. Oscillating and triggering properties of T cell membrane potential. Imun. Lett. 26:277-282, 1990. 13 (9) Gallin, E. K

  6. Active gate driver for dv/dt control and active voltage clamping in an IGBT stack

    DEFF Research Database (Denmark)

    Rasmussen, Tonny Wederberg

    2005-01-01

    For high voltages converters stacks of IGBTs can be used if the static and dynamic voltage sharing among the IGBTs can be applied. dVCE/dt should also be controlled in order not to damage insulation material. This paper describes theory and measurements of an active gate driver for stacking IGBTs...

  7. Brain-computer interface combining eye saccade two-electrode EEG signals and voice cues to improve the maneuverability of wheelchair.

    Science.gov (United States)

    Wang, Ker-Jiun; Zhang, Lan; Luan, Bo; Tung, Hsiao-Wei; Liu, Quanfeng; Wei, Jiacheng; Sun, Mingui; Mao, Zhi-Hong

    2017-07-01

    Brain-computer interfaces (BCIs) largely augment human capabilities by translating brain wave signals into feasible commands to operate external devices. However, many issues face the development of BCIs such as the low classification accuracy of brain signals and the tedious human-learning procedures. To solve these problems, we propose to use signals associated with eye saccades and blinks to control a BCI interface. By extracting existing physiological eye signals, the user does not need to adapt his/her brain waves to the device. Furthermore, using saccade signals to control an external device frees the limbs to perform other tasks. In this research, we use two electrodes placed on top of the left and right ears of thirteen participants. Then we use Independent Component Analysis (ICA) to extract meaningful EEG signals associated with eye movements. A sliding-window technique was implemented to collect relevant features. Finally, we classified the features as horizontal or blink eye movements using KNN and SVM. We were able to achieve a mean classification accuracy of about 97%. The two electrodes were then integrated with off-the-shelf earbuds to control a wheelchair. The earbuds can generate voice cues to indicate when to rotate the eyeballs to certain locations (i.e., left or right) or blink, so that the user can select directional commands to drive the wheelchair. In addition, through properly designing the contents of voice menus, we can generate as many commands as possible, even though we only have limited numbers of states of the identified eye saccade movements.

  8. Actions of Tefluthrin on Rat Nav1.7 Voltage-Gated Sodium Channels Expressed in Xenopus Oocytes

    OpenAIRE

    Tan, Jianguo; Soderlund, David M.

    2011-01-01

    In rats expression of the Nav1.7 voltage-gated sodium channel isoform is restricted to the peripheral nervous system and is abundant in the sensory neurons of the dorsal root ganglion. We expressed the rat Nav1.7 sodium channel α subunit together with the rat auxiliary β1 and β2 subunits in Xenopus laevis oocytes and assessed the effects of the pyrethroid insecticide tefluthrin on the expressed currents using the two-electrode voltage clamp method. Tefluthrin at 100 µM modified of Nav1.7 chan...

  9. Substrate and Inhibitor-Specific Conformational Changes in the Human Serotonin Transporter Revealed by Voltage-Clamp Fluorometry

    DEFF Research Database (Denmark)

    Söderhielm, Pella C; Andersen, Jacob; Munro, Lachlan

    2015-01-01

    of TM6, Ala419 in the interface between TM8 and extracellular loop (EL) 4, and Leu481 in EL5. The reporter positions were used for time-resolved measurement of conformational changes during 5-HT transport and binding of cocaine and the selective serotonin reuptake inhibitors fluoxetine and escitalopram....... At all reporter positions, fluorescence changes observed upon substrate application were distinctly different from those observed upon inhibitor application, with respect to relative amplitude or direction. Furthermore, escitalopram, fluoxetine, and cocaine induced a very similar pattern of fluorescent...

  10. 基于两电极体系的水质检测分析平台设计%The Design of a Inspection and Analysis Platform of Aqueous Solution Based on Two-Electrode System

    Institute of Scientific and Technical Information of China (English)

    魏佳莉; 章颖强; 李雅卓; 王晓萍

    2012-01-01

    A new inspection and analysis platform based on two-electrode system was constructed. The two-electrode system based on minimizing polarizing current theory was realized by maximizing the ratio of the area of working electrode and auxiliary electrode, and hardware & software were designed. Therefore the reference electrode can be abandoned, which overcomes the shortcomings of traditional three-electrode system while reproducing the function of electrochemical workstation. Research on Electric Conductivity( EC) ,pH and the concentrations of heavy metal ions of water had been carried out on this platform, and effective results had received which demonstrated the ability of multiple water quality parameters inspection. This platform can be used on solution properties analysis in laboratory or industry locale.%为实现对水质的多参数检测,设计了一个基于两电极体系的水质检测分析平台.该检测平台通过最小化极化电流的思想,采用辅助电极面积远大于工作电极的电极参数,设计了基于两电极体系的集成电极和软硬件系统,摈弃了传统三电极体系的参比电极,同时克服了传统三电极体系容易污染样品的缺点,能实现电化学工作站的诸多功能.本研究在该检测平台上开展了水样的电导率(EC)、pH和重金属浓度的检测研究,获得了较好的结果,可用于实验室及工业现场的水质监测.

  11. Tetrazolyl isoxazole amino acids as ionotropic glutamate receptor antagonists: synthesis, modelling and molecular pharmacology

    DEFF Research Database (Denmark)

    Frølund, Bente; Greenwood, Jeremy R; Holm, Mai Marie

    2005-01-01

    and 1b were pharmacologically characterized in receptor binding assays, and electrophysiologically on homomeric AMPA receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) kainic acid receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these receptors...

  12. A study on twin-tungsten TIG welding method

    Institute of Scientific and Technical Information of China (English)

    Leng Xuesong; Zhang Guangjun; Gao Hongming; Wu Lin

    2006-01-01

    A new twin-tungsten TIG (T-TIG) welding method was studied. This method differs from the conventional TIG method, it places two electrodes insulated from each other in the same welding torch, and a coupling arc is generated from the two electrodes. The coupling arc pressure was measured and preliminary welding experiment was made. The results show that the coupling arc can keep arc pressure at a low level compared with conventional TIG arc, and welding can be achieved under higher current and high travel speed with sound appearance of weld. Therefore, this new method can applied widely in high efficiency welding.

  13. Purinergic signalling - a possible mechanism for KCNQ1 channel response to cell volume challenges

    DEFF Research Database (Denmark)

    Bomholtz, Sofia Hammami; Willumsen, Niels J.; Meinild, A.-K.

    2013-01-01

    to ion channel stimulation and cell volume back-regulation. Our aim was to investigate whether volume sensitivity of the voltage-gated K(+) channel, KCNQ1, is dependent on ATP release and regulation by purinergic signalling. METHODS: We used Xenopus oocytes heterologously expressing human KCNQ1, KCNE1......, water channels (AQP1) and P2Y2 receptors. ATP release was monitored by a luciferin-luciferase assay and ion channel conductance was recorded by two-electrode voltage clamp. RESULTS: The luminescence assay showed that oocytes released ATP in response to mechanical, hypoosmotic stimuli and hyperosmotic...... to mechanical stimuli and cell volume changes. Purinergic P2 and P1 receptors confer some of the KCNQ1 channel volume sensitivity, although endogenous adenosine receptors and expressed P2Y2 receptors do so in the negative direction....

  14. Intestinal drug transport via the proton-coupled amino acid transporter PAT1 (SLC36A1) is inhibited by Gly-X(aa) dipeptides

    DEFF Research Database (Denmark)

    Frølund, Sidsel; Langthaler, Louise; Kall, Morten A

    2012-01-01

    The oral absorption of some drug substances is mediated by nutrient transporters. As a consequence, nutrients and drugs may compete for available transporters, and interactions at the level of intestinal absorption are possible. Recently, we have identified δ-aminolevulinic acid, Gly-Gly, and Gly......-Sar as substrates of the amino acid transporter PAT1. The aim of the present study is to investigate if other Gly-containing dipeptides interact with PAT1, and whether they can inhibit PAT1 mediated drug absorption, in vitro and in vivo. The in vitro methods included two-electrode voltage clamp measurements on h......PAT1 expressing Xenopus laevis oocytes, which were used to investigate the PAT1-mediated transport of 17 different Gly-containing dipeptides (Gly-X(aa) or X(aa)-Gly). Also, the transepithelial transport of the PAT1 substrate gaboxadol was investigated across Caco-2 cell monolayers in the presence...

  15. Voltage balancing of series' connected IGBTs using voltage clamping control%采用电压箝位控制实现串联IGBT的动态均压

    Institute of Scientific and Technical Information of China (English)

    张春朋; 姜齐荣; 刘博超

    2009-01-01

    研究了电压箝位控制方法,它将lGBT的集-射电压变化快速反馈至门极,改变门极驱动电压的大小,从而将集一射电压实时箝位于控制阈值之内,实现串联IGBT的动态均压.通过2个和8个IGBT串联的实验,验证了该方法的有效性.

  16. Centruroides toxin, a selective blocker of surface Na+ channels in skeletal muscle: voltage-clamp analysis and biochemical characterization of the receptor.

    OpenAIRE

    Jaimovich, E.; Ildefonse, M; Barhanin, J; Rougier, O; Lazdunski, M

    1982-01-01

    This paper describes the effects of a toxin from the scorpion Centruroides suffusus suffusus on frog skeletal muscle. The main findings are the following, (i) Centruroides toxin (CssII) blocks the early phase of the inward sodium current in the muscle that arises from influx via Na+ channels in the surface membrane, but it does not affect the late phase of the inward current that represents flux through Na+ channels in the T-tubule membranes, (ii) CssII, in marked contrast to tetrodotoxin, do...

  17. Centruroides toxin, a selective blocker of surface Na+ channels in skeletal muscle: voltage-clamp analysis and biochemical characterization of the receptor.

    Science.gov (United States)

    Jaimovich, E; Ildefonse, M; Barhanin, J; Rougier, O; Lazdunski, M

    1982-06-01

    This paper describes the effects of a toxin from the scorpion Centruroides suffusus suffusus on frog skeletal muscle. The main findings are the following, (i) Centruroides toxin (CssII) blocks the early phase of the inward sodium current in the muscle that arises from influx via Na+ channels in the surface membrane, but it does not affect the late phase of the inward current that represents flux through Na+ channels in the T-tubule membranes, (ii) CssII, in marked contrast to tetrodotoxin, does not affect contraction of the muscle, (iii) Measurements of the binding of 125I-labeled CssII to a partially purified membrane preparation from the muscle indicate that the Kd of the CssII--receptor complex is approximately 0.4 nM. The half-life for the dissociation of this complex is 3 min at 22 degrees C and 16 min at 2 degrees C. Binding of the radiolabeled toxin varies markedly with pH and becomes insignificant at pH greater than 8.5. Proteolytic digestion of the membrane preparation decreases its ability to bind CssII, suggesting that the receptor is a protein. (iv) The number of binding sites for a radiolabeled derivative of tetrodotoxin on the membrane preparation was similar to that for CssII. However, neither tetrodotoxin nor any of seven other neurotoxins and some local anesthetics that alter the functioning of the Na+ channel have any effect on the binding of CssII to the muscle membrane. These results therefore indicate that CssII belongs to a different class of neurotoxins that has a different receptor on the Na+ channel.

  18. ZP123 increases gap junctional conductance and prevents reentrant ventricular tachycardia during myocardial ischemia in open chest dogs

    DEFF Research Database (Denmark)

    Xing, Dezhi; Kjølbye, Anne Louise; Nielsen, Morten S

    2003-01-01

    INTRODUCTION: The aim of this study was to determine if the stable antiarrhythmic peptide (AAP) analogue ZP123 increases gap junctional intercellular conductance and prevents reentrant ventricular tachycardia (VT) during coronary artery occlusion. METHODS AND RESULTS: Voltage clamp experiments...

  19. Substrate specificity and functional characterisation of the H+/amino acid transporter rat PAT2 (Slc36a2)

    OpenAIRE

    Kennedy, David J.; Gatfield, Kelly M.; Winpenny, John P; Ganapathy, Vadivel; Thwaites, David T.

    2004-01-01

    Functional characteristics and substrate specificity of the rat proton-coupled amino acid transporter 2 (rat PAT2 (rPAT2)) were determined following expression in Xenopus laevis oocytes using radiolabelled uptake measurements, competition experiments and measurements of substrate-evoked current using the two-electrode voltage-clamp technique. The aim of the investigation was to determine the structural requirements and structural limitations of potential substrates for rPAT2.Amino (and imino)...

  20. Conformational basis for the Li(+)-induced leak current in the rat gamma-aminobutyric acid (GABA) transporter-1

    DEFF Research Database (Denmark)

    MacAulay, Nanna; Zeuthen, Thomas; Gether, Ulrik

    2002-01-01

    The rat gamma-aminobutyric acid transporter-1 (GAT-1) was expressed in Xenopus laevis oocytes and the substrate-independent Li(+)-induced leak current was examined using two-electrode voltage clamp. The leak current was not affected by the addition of GABA and was not due to H(+) permeation. The ...... of Na(+) restrains the transporter from moving into a leak conductance mode as well as allowing maintenance of GABA-elicited transport-associated current....

  1. A de novo loss-of-function GRIN2A mutation associated with childhood focal epilepsy and acquired epileptic aphasia

    Science.gov (United States)

    Zhang, Yujia; Kusumoto, Hirofumi; Zhang, Jin; Chen, Wenjuan; XiangWei, Wenshu; Shaulsky, Gil H.; Hu, Chun; Traynelis, Stephen F.; Yuan, Hongjie; Jiang, Yuwu

    2017-01-01

    Objective N-methyl-D-aspartate receptors (NMDAR) subunit GRIN2A/GluN2A mutations have been identified in patients with various neurological diseases, such as epilepsy and intellectual disability / developmental delay (ID/DD). In this study, we investigated the phenotype and underlying molecular mechanism of a GRIN2A missense mutation identified by next generation sequencing on idiopathic focal epilepsy using in vitro electrophysiology. Methods Genomic DNA of patients with epilepsy and ID/DD were sequenced by targeted next-generation sequencing within 300 genes related to epilepsy and ID/DD. The effects of one missense GRIN2A mutation on NMDAR function were evaluated by two-electrode voltage clamp current recordings and whole cell voltage clamp current recordings. Results We identified one de novo missense GRIN2A mutation (Asp731Asn, GluN2A(D731N)) in a child with unexplained epilepsy and DD. The D731N mutation is located in a portion of the agonist-binding domain (ABD) in the GluN2A subunit, which is the binding pocket for agonist glutamate. This residue in the ABD is conserved among vertebrate species and all other NMDAR subunits, suggesting an important role in receptor function. The proband shows developmental delay as well as EEG-confirmed seizure activity. Functional analyses reveal that the GluN2A(D731N) mutation decreases glutamate potency by over 3,000-fold, reduces amplitude of current response, shortens synaptic-like response time course, and decreases channel open probability, while enhancing sensitivity to negative allosteric modulators, including extracellular proton and zinc inhibition. The combined effects reduce NMDAR function. Significance We identified a de novo missense mutation in the GRIN2A gene in a patient with childhood focal epilepsy and acquired epileptic aphasia. The mutant decreases NMDAR activation suggesting NMDAR hypofunction may contribute to the epilepsy pathogenesis. PMID:28182669

  2. method

    Directory of Open Access Journals (Sweden)

    L. M. Kimball

    2002-01-01

    Full Text Available This paper presents an interior point algorithm to solve the multiperiod hydrothermal economic dispatch (HTED. The multiperiod HTED is a large scale nonlinear programming problem. Various optimization methods have been applied to the multiperiod HTED, but most neglect important network characteristics or require decomposition into thermal and hydro subproblems. The algorithm described here exploits the special bordered block diagonal structure and sparsity of the Newton system for the first order necessary conditions to result in a fast efficient algorithm that can account for all network aspects. Applying this new algorithm challenges a conventional method for the use of available hydro resources known as the peak shaving heuristic.

  3. Structure of gold monoatomic wires connected to two electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Zoubkoff, Remi [Centre de Recherche en Matiere Condensee et Nanosciences, CNRS, Campus de Luminy, Case 913, 13288 Marseille Cedex 9 (France)]. E-mail: zoubkoff@crmcn.univ-mrs.fr; Vega, L. de la [Departamento de Fisica de la Materia Condensada C-V, Facultad de Ciencias, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Martin-Rodero, A. [Departamento de Fisica de la Materia Condensada C-V, Facultad de Ciencias, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Levy Yeyati, A. [Departamento de Fisica de la Materia Condensada C-V, Facultad de Ciencias, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Saul, Andres [Centre de Recherche en Matiere Condensee et Nanosciences, CNRS, Campus de Luminy, Case 913, 13288 Marseille Cedex 9 (France)

    2007-09-01

    In this work, we present calculations concerning the stability of infinite monoatomic Au wires and finite Au wires between electrodes. For the systems with the electrodes, that we represent by FCC slabs with (0 0 1) surfaces, the total energy calculations have been performed with a spd non-orthogonal tight-binding Hamiltonian. For the infinite wires, the calculations were also compared to semi-empirical and first principle ones. For the infinite wires and small enough inter-atomic distances, we find that a zig-zag structure is most stable than the linear one, in agreement with previous calculations. For the system between electrodes, one gets an almost concave or a symmetric broken edges structure depending on the inter-atomic distance.

  4. Methods of rock burst prediction

    Energy Technology Data Exchange (ETDEWEB)

    Genkin, V.A.; Minin, Yu.Ya.; Morozov, G.D.; Proskuryakov, V.M.; Cmirnov, V.A.

    1979-07-01

    Some methods of predicting rock bursts in underground coal and iron ore mines are evaluated: using BP-18 indenters and the MGD indenter with automatic recording; seismic method consisting in measuring the speed of shock waves travelling through various layers (apparatus SB-20 is designed for use in coal mines); electrometric method (measuring resistance between two electrodes when electric currents flow through coal and rocks). The design of the AEhSSh-1 measuring instrument, used in the electrometric method in coal mines is also described. Each of the methods is described and mathematical fomulae used as their theoretical basis are presented. The calculating process is explained and brief information on the design and use of the measuring instrument is given. The methods are evaluated from the viewpoint of precision. (In Russian)

  5. Method

    Directory of Open Access Journals (Sweden)

    Xixin Wang

    2012-01-01

    Full Text Available ZrO2 nanotube arrays were prepared by anodization method in aqueous electrolyte containing (NH42SO4 and NH4F. The morphology and structure of nanotube arrays were characterized through scanning electron microscope, X-ray diffraction, and infrared spectra analysis. The zirconia nanotube arrays were used as catalyst in esterification reaction. The effects of calcination temperature and electrolyte concentration on catalytic esterification activity have been investigated in detail. Experiments indicate that nanotube arrays have highest catalytic activity when the concentration of (NH42SO4 is 1 mol/L, the concentration of NH4F is 1 wt%, and the calcination temperature is 400°C. Esterification reaction yield of as much as 97% could be obtained under optimal conditions.

  6. A quantitative method to assess extrasynaptic NMDA receptor function in the protective effect of synaptic activity against neurotoxicity

    Directory of Open Access Journals (Sweden)

    Bading Hilmar

    2008-01-01

    Full Text Available Abstract Background Extrasynaptic NMDA receptors couple to a CREB shut-off pathway and cause cell death, whereas synaptic NMDA receptors and nuclear calcium signaling promote CREB-mediated transcription and neuronal survival. The distribution of NMDA receptors (synaptic versus extrasynaptic may be an important parameter that determines the susceptibility of neurons to toxic insults. Changes in receptor surface expression towards more extrasynaptic NMDA receptors may lead to neurodegeneration, whereas a reduction of extrasynaptic NMDA receptors may render neurons more resistant to death. A quantitative assessment of extrasynaptic NMDA receptors in individual neurons is needed in order to investigate the role of NMDA receptor distribution in neuronal survival and death. Results Here we refined and verified a protocol previously used to isolate the effects of extrasynaptic NMDA receptors using the NMDA receptor open channel blocker, MK-801. Using this method we investigated the possibility that the known neuroprotective shield built up in hippocampal neurons after a period of action potential bursting and stimulation of synaptic NMDA receptors is due to signal-induced trafficking of extrasynaptic NMDA receptors or a reduction in extrasynaptic NMDA receptor function. We found that extrasynaptic NMDA receptor-mediated calcium responses and whole cell currents recorded under voltage clamp were surprisingly invariable and did not change even after prolonged (16 to 24 hours periods of bursting and synaptic NMDA receptor activation. Averaging a large number of calcium imaging traces yielded a small (6% reduction of extrasynaptic NMDA receptor-mediated responses in hippocampal neurons that were pretreated with prolonged bursting. Conclusion The slight reduction in extrasynaptic NMDA receptor function following action potential bursting and synaptic NMDA receptor stimulation could contribute to but is unlikely to fully account for activity

  7. Method

    Directory of Open Access Journals (Sweden)

    Andrey Gnatov

    2015-01-01

    Full Text Available Recently repair and recovery vehicle body operations become more and more popular. A special place here is taken by equipment that provides performance of given repair operations. The most interesting things are methods for recovery of car body panels that allow the straightening without disassembling of car body panels and damaging of existing protective coating. Now, there are several technologies for repair and recovery of car body panels without their disassembly and dismantling. The most perspective is magnetic-pulse technology of external noncontact straightening. Basics of magnetic-pulse attraction, both ferromagnetic and nonferromagnetic thin-walled sheet metal, are explored. Inductor system calculation models of magnetic-pulse straightening tools are presented. Final analytical expressions for excited efforts calculation in the tools under consideration are introduced. According to the obtained analytical expressions, numerical evaluations of excited forces were executed. The volumetric epures of the attractive force radial distributions for different types of inductors were built. The practical testing of magnetic-pulse straightening with research tools is given. Using the results of the calculations we can create effective tools for an external magnetic-pulse straightening of car body panels.

  8. Modulating effect of ginseng saponins on heterologously expressed HERG currents in Xenopus oocytes

    Institute of Scientific and Technical Information of China (English)

    Cuk-seong KIM; Sook-jin SON; Hyo-shin KIM; Yong-duk KIM; Kyu-seung LEE; Byeong-hwa JEON; Kwang-jin KIM; Jin-kyu PARK; Jin-bong PARK

    2005-01-01

    Aim: To examine the effects of ginseng saponins on the heterologously expressed human ether-a-go-go related gene (HERG) that encodes the rapid component of the delayed rectifier K+ channel. Methods: A two-electrode voltage clamp tech nique was used. HERG currents were recorded in Xenopus oocytes injected with HERG cRNA. Results: Crude saponins of Korean red ginseng (GS) induced a minimal increase of the maximal HERG conductance without changes in the voltage-dependent HERG current activation and inactivation curves. GS, however,decelerated HERG current deactivation in a concentration-dependent manner,which was more noticeable with panaxitriol (PT) than panaxidiol (PD). Consistently,ginseng saponins increased the HERG deactivation time constants with the order of potency of Rg1 (a major component of PT)>Rf 1>Rb1 (a major component of PD).Re had little effect on HERG deactivation. During a cardiac action Potential, GS increased the outward HERG current. Conclusion: Ginseng saponins enhance HERG currents, which could be in part a possible mechanism of the shortening cardiac action potential of ginseng saponins.

  9. Food-aversive classical conditioning increases a persistent sodium current in molluscan withdrawal interneurons in a transcription dependent manner.

    Science.gov (United States)

    Kiss, Tibor; Pirger, Zsolt; Kemenes, György

    2009-07-01

    In this study we examined changes in a persistent sodium current (I(NaP)) after behavioral aversive classical conditioning in the snail Helix pomatia. We trained animals by pairing food with a mild electric shock that triggered the whole-body withdrawal reflex. This aversive training resulted in transcription dependent long-term associative memory. Isolated central nervous system preparations were set up from trained, random control and naive animals and using two-electrode voltage clamp methods, I(NaP) was activated and measured in identified body withdrawal interneurons RPa3 and LPa3. We show here that in preparations from conditioned animals I(NaP) is increased, suggesting that modifications in intrinsic cellular properties contribute to the formation of the memory trace. Blocking RNA synthesis by systemic injection of actinomycin D (0.12microM) suppressed both memory consolidation in intact animals and the learning-induced increase of I(NaP) in withdrawal interneurons, suggesting that aversive classical conditioning affects sodium channel expression at the transcriptional level.

  10. Effects of Glutamic Acid on C-type Inactivation of Kvl.4△N Channel

    Institute of Scientific and Technical Information of China (English)

    Cheng Ye; Xiaoyan Li; Zhouwu Shu; Xuejun Jiang

    2008-01-01

    Objectives Acidosis has an inhibitory effect on the inactivation of Kvl.4 AN channel through the position H508.So in order to show the effects of glutamic acid on the mutant Kv 1.4 channel that lacks N-type inactivation(Kvl.4A2-146),we studied in the expression system of the Xenopus oocytes.Methods The two-electrode voltage-clamp technique(TEV)was used to record the currents.Results Acidosis increased fKvl.4 △2-146 C-type inactivation.After application of glutamic acid(1 mmol/L) to Kvl.4 △2-146 increased C-type inactivation further,changed inactivation time constants from (2.02±0.39s)to(1.71±0.23 s)(P<0.05)at +50my,and shifted the steadystate inactivation curves of Kvl.4 △N to positive potential,which was from(-44.30±0.59 mV) to(-39.88±0.29 mV)(P<0.05 ).and slowed the rate of recovery from inactivation,which was from(1.64±0.19s) to (1.91±0.23 s)(P<0.05).Conclusions Together,these results suggest that 1 mmol/L glutamic acid accelerates the Ctype inactivation of Kvl.4 AN in pH 6.8.

  11. Examining the conformational dynamics of membrane proteins in situ with site-directed fluorescence labeling.

    Science.gov (United States)

    Richards, Ryan; Dempski, Robert E

    2011-05-29

    Two electrode voltage clamp electrophysiology (TEVC) is a powerful tool to investigate the mechanism of ion transport1 for a wide variety of membrane proteins including ion channels, ion pumps, and transporters. Recent developments have combined site-specific fluorophore labeling alongside TEVC to concurrently examine the conformational dynamics at specific residues and function of these proteins on the surface of single cells. We will describe a method to study the conformational dynamics of membrane proteins by simultaneously monitoring fluorescence and current changes using voltage-clamp fluorometry. This approach can be used to examine the molecular motion of membrane proteins site-specifically following cysteine replacement and site-directed fluorophore labeling. Furthermore, this method provides an approach to determine distance constraints between specific residues. This is achieved by selectively attaching donor and acceptor fluorophores to two mutated cysteine residues of interest. In brief, these experiments are performed following functional expression of the desired protein on the surface of Xenopus leavis oocytes. The large surface area of these oocytes enables facile functional measurements and a robust fluorescence signal. It is also possible to readily change the extracellular conditions such as pH, ligand or cations/anions, which can provide further information on the mechanism of membrane proteins. Finally, recent developments have also enabled the manipulation of select internal ions following co-expression with a second protein. Our protocol is described in multiple parts. First, cysteine scanning mutagenesis proceeded by fluorophore labeling is completed at residues located at the interface of the transmembrane and extracellular domains. Subsequent experiments are designed to identify residues which demonstrate large changes in fluorescence intensity (<5%) upon a conformational change of the protein. Second, these changes in fluorescence

  12. Method for producing edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure

    Science.gov (United States)

    Hunt, Brian D. (Inventor); Leduc, Henry G. (Inventor)

    1992-01-01

    A method for fabricating an edge geometry superconducting tunnel junction device is discussed. The device is comprised of two niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier sandwiched between the two electrodes. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 C to 500 C for improved quality of the electrode.

  13. A Core Facility for the Study of Neurotoxins of Biological Origin

    Science.gov (United States)

    1992-02-15

    Kvl, and the dendrotoxin-sensitive K channel, Kv3 . N-terminal sequences of the cloned K channels were collected between a Sfi I restriction site located...34delayed- rectifier-type" channels, Kvl, Kv2, Kv3 , and the "A-type" channel, mShal, have been expressed in Xenopus oocytes and K channel currents...measured by two electrode voltage- clamp. These currents are shown in figure 2. Figure 3 shows that Kv2 and Kv3 K channels are sensitive to block by DaTX

  14. Structural Basis for Ether-a-go-go-Related Gene K+ Channel Subtype-Dependent Activation by Niflumic Acid[S

    OpenAIRE

    Fernandez, David; Sargent, John; Frank B Sachse; Sanguinetti, Michael C.

    2008-01-01

    Niflumic acid [2-((3-(trifluoromethyl)phenyl)amino)-3-pyridin-ecarboxylic acid, NFA] is a nonsteroidal anti-inflammatory drug that also blocks or modulates the gating of a wide spectrum of ion channels. Here we investigated the mechanism of channel activation by NFA on ether-a-go-go-related gene (ERG) K+ channel subtypes expressed in Xenopus laevis oocytes using two-electrode voltage-clamp techniques. NFA acted from the extracellular side of the membrane to differentially enhance ERG channel ...

  15. Curare Alkaloids: Constituents of a Matis Dart Poison.

    Science.gov (United States)

    Malca Garcia, Gonzalo R; Hennig, Lothar; Shelukhina, Irina V; Kudryavtsev, Denis S; Bussmann, Rainer W; Tsetlin, Victor I; Giannis, Athanassios

    2015-11-25

    A phytochemical study of dart and arrow poison from the Matis tribe led to the identification of D-(-)-quinic acid, L-malic acid, ethyldimethylamine, magnoflorine, and five new bisbenzyltetrahydroisoquinoline alkaloids (BBIQAs), 1-5. D-Tubocurarine could not be identified among these products. BBIQA (3) contains a unique linkage at C-8 and C-11'. All structures were characterized by a combination of NMR and HRESIMS data. The effects of Matis poison and individual BBIQAs (1-3) on rat muscle nAChR expressed in Xenopus oocytes have been investigated using the two-electrode voltage clamp technique.

  16. Mifepristone modulates serotonin transporter function

    Institute of Scientific and Technical Information of China (English)

    Chaokun Li; Linlin Shan; Xinjuan Li; Linyu Wei; Dongliang Li

    2014-01-01

    Regulating serotonin expression can be used to treat psychotic depression. Mifepristone, a glu-cocorticoid receptor antagonist, is an effective candidate for psychotic depression treatment. However, the underlying mechanism related to serotonin transporter expression is poorly un-derstood. In this study, we cloned the human brain serotonin transporter into Xenopus oocytes, to establish an in vitro expression system. Two-electrode voltage clamp recordings were used to detect serotonin transporter activity. Our results show that mifepristone attenuates serotonin transporter activity by directly inhibiting the serotonin transporter, and suggests that the se-rotonin transporter is a pharmacological target of mifepristone for the treatment of psychotic depression.

  17. Consequences and mechanisms of spike broadening of R20 cells in Aplysia californica.

    Science.gov (United States)

    Ma, M; Koester, J

    1995-10-01

    We studied frequency-dependent spike broadening in the two electrically coupled R20 neurons in the abdominal ganglion of Aplysia. The peptidergic R20 cells excite the R25/L25 interneurons (which trigger respiratory pumping) and inhibit the RB cells. When fired at 1-10 Hz, the duration of the falling phase of the action potential in R20 neurons increases 2-10 fold during a spike train. Spike broadening recorded from the somata of the R20 cells affected synaptic transmission to nearby follower cells. Chemically mediated synaptic output was reduced by approximately 50% when recorded trains of nonbroadened action potentials were used as command signals for a voltage-clamped R20 cell. Electrotonic EPSPs between the R20 cells, which normally facilitated by two- to fourfold during a high frequency spike train, showed no facilitation when spike broadening was prevented under voltage-clamp control. To examine the mechanism of frequency-dependent spike broadening, we applied two-electrode voltage-clamp and pharmacological techniques to the somata of R20 cells. Several voltage-gated ionic currents were isolated, including INa, a multicomponent ICa, and three K+ currents--a high threshold, fast transient A-type K+ current (IAdepol), a delayed rectifier K+ current (IK-V), and a Ca(2+)-sensitive K+ current (IK-Ca), made up of two components. The influences of different currents on spike broadening were determined by using the recorded train of gradually broadening action potentials as the command for the voltage clamp. We found the following. (1) IAdepol is the major outward current that contributes to repolarization of nonbroadened spikes. It undergoes pronounced cumulative inactivation that is a critical determinant of spike broadening. (2) Activity-dependent changes in IK-V, IK-Ca, and ICa have complex effects on the kinetics and extent of broadening. (3) The time integral of ICa during individual action potentials increases approximately threefold during spike broadening.

  18. Chloride channels in toad skin

    DEFF Research Database (Denmark)

    Larsen, Erik Hviid; Rasmussen, B E

    1982-01-01

    A study of the voltage and time dependence of a transepithelial Cl- current in toad skin (Bufo bufo) by the voltage-clamp method leads to the conclusion that potential has a dual role for Cl- transport. One is to control the permeability of an apical membrane Cl-pathway, the other is to drive Cl...

  19. Pulsatile Drug Delivery System Based on Electrohydrodynamic Method

    CERN Document Server

    Zheng, Yi; Hu, Junqiang; Gao, Wenle

    2012-01-01

    Electrohydrodynamic (EHD) generation, a commonly used method in BioMEMS, plays a significant role in the pulsatile drug delivery system for a decade. In this paper, an EHD based drug delivery system is well designed, which can be used to generate a single drug droplet as small as 2.83 nL in 8.5 ms with a total device of 2\\times2\\times3 mm^3, and an external supplied voltage of 1500 V. Theoretically, we derive the expressions for the size and the formation time of a droplet generated by EHD method, while taking into account the drug supply rate, properties of liquid, gap between two electrodes, nozzle size, and charged droplet neutralization. This work proves a repeatable, stable and controllable droplet generation and delivery system based on EHD method experimentally as well as theoretically.

  20. A new method of measuring the spatial distribution of depletion fraction of silane plasma by mass spectrometer

    Institute of Scientific and Technical Information of China (English)

    Wang Zhao-Kui; Lin Kui-Xun; Lin Xuan-Ying; Qiu Gui-Ming; Zhu Zu-Song

    2005-01-01

    A newly established movable sampling apparatus of mass spectrometer is used to measure the spatial distribution of depletion fraction of silane plasma. A straight-line fit method of deducing the depletion fraction of silane is proposed.Theoretical analysis and test results demonstrate that the proposed new method is universal and more accurate than the existing one. There exist a largest peak near the middle of two electrodes and two peaks near the electrodes in the spatial distribution of silane depletion fraction, which are related to the distribution of electric field and the silane plasma sheaths.

  1. Effects of Propafenone, Amiodarone and Dilthiazem on the potassium channel of c-Type Kv1.4△N%普罗帕酮、胺碘酮、地尔硫卓对Kv1.4△N钾通道的作用

    Institute of Scientific and Technical Information of China (English)

    王智泉; 蒋学俊; 王世敏; 徐林; 王能; 张冬

    2011-01-01

    目的 探讨不同类别抗心律失常药物普罗帕酮、胺碘酮和地尔硫卓对去N端Kv1.4通道(Kv1.4△N)的作用方式,以及这些作用的差异性.方法 将Kv1.4△N的mRNA注射入非洲爪蟾卵母细胞并使用双电极钳制法(two electrodes voltage clamp,TEV),运用Clampfit 9.0软件分别观察三种药物对KV1..4△N电生理特性的影响.结果 三种药物对ELvl.4△N通道的作用都具有浓度、频率和电压依赖性.在亲和力方面,propafenone的IC50最小,dilthiazem次之,amiodarone的IC50最大(P=0.031);在频率抑制性方面,propafenone组达到稳态时为对照组的41%,amiodarone为32%左右,dilthiazem为21%左右(P=0.045);在电压抑制性方面,100μMpropafenone,500μM amiodarone、350μM dilthjazem在+50 mV电压下分别能使fKv1.4△N通道电流抑制到对照组的(54.6±1.9)%,(46.3±3.5)%和(52.8±2.8)%(P=0.046).结论 三者都是fKv1.4△N通道的开放通道阻滞剂,对fKv1.4△N通道的作用和机制既有相同之处,又有不同特点,这可能是三者抗心律失常的机制之一.%Objective To study the effects of the antiarrhythmic drugs of propafenone, amiodarone and dilthiazem on c-type Kv1. 4 channels in Xenopus laevis oocytes with two-electrode voltage-clamp technique. Methods Defolliculated oocytes ( stage Ⅴ - Ⅵ) had transcribed cRNAs of ferret Kv1. 4△N channels injected. The oocytes were continuously perfused with control solution or propafenone, amiodarone and dilthiazem under monitoring of software of Clampfit v 9. 0. Results All of the three drugs blocked ferret Kv1. 4△N channel in voltage-, frequency- and concentration-dependent manners. The values of IC50 (50%inhibiting concentration ) of propafenone, amiodarone and dilthiazem were ( 103.4± 2. 2 ) μ mol/L,(501.22 +5.9) μmol/L and (353.62 +9.9) μmol/L, respectively. The currents under the actions of propafenone , amiodarone and dilthiazem were decreased to 41%, 32% and 21% of control group, respectively. Propafenone

  2. The selective activation of the glutamate receptor GluR5 by ATPA is controlled by serine 741.

    Science.gov (United States)

    Nielsen, Mai Marie; Liljefors, Tommy; Krogsgaard-Larsen, Povl; Egebjerg, Jan

    2003-01-01

    Only a few agonists exhibit selectivity between the AMPA and the kainate subtypes of the glutamate receptor. The most commonly used kainate receptor preferring agonist, (S)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid [(S)-ATPA], is an (R,S)-2-amino-3-(5-methyl-3-hydroxy-4-isoxazolyl)propionic acid (AMPA) derivative in which the methyl group at the 5-position of the isoxazole ring has been replaced by a tert-butyl group. When characterized by the two-electrode voltage clamp method in Xenopus laevis oocytes, ATPA exhibits at least 50-fold higher potency on the kainate receptor subtype, GluR5, compared with the AMPA receptors. Through mutagenesis studies of GluR5 and the AMPA receptor subtype, GluR1, we demonstrate that this pronounced selectivity for ATPA can be ascribed to Ser741 in GluR5 and Met722 in GluR1. Examination of other aliphatic substitutions at the 5-position of the isoxazole ring revealed that (R,S)-2-amino-3-(5-isopropyl-3-hydroxy-4-isoxazolyl)propionic acid (isopropyl-AMPA) displayed a 6-fold higher potency for GluR5 than for GluR1, whereas the analogs, propyl-AMPA and isobutyl-AMPA, did not exhibit significantly different potencies. Our study suggests that the GluR5 selectivity was a result not only of steric interference between the bulky tert-butyl group in ATPA and the methionine (Met722) in GluR1 but also a serine-dependent stabilization of the active conformation of GluR5 induced by ATPA. The stabilization was agonist-dependent and observed only for ATPA and isopropyl-AMPA, not for other AMPA analogs with bulky substitutions at the 5-position of the isoxazole ring.

  3. Upregulation of the Creatine Transporter Slc6A8 by Klotho

    Directory of Open Access Journals (Sweden)

    Ahmad Almilaji

    2014-11-01

    Full Text Available Background/Aims: The transmembrane Klotho protein contributes to inhibition of 1,25(OH2D3 formation. The extracellular domain of Klotho protein could function as an enzyme with e.g. β-glucuronidase activity, be cleaved off and be released into blood and cerebrospinal fluid. Klotho regulates several cellular transporters. Klotho protein deficiency accelerates the appearance of age related disorders including neurodegeneration and muscle wasting and eventually leads to premature death. The main site of Klotho protein expression is the kidney. Klotho protein is also appreciably expressed in other tissues including chorioid plexus. The present study explored the effect of Klotho protein on the creatine transporter CreaT (Slc6A8, which participates in the maintenance of neuronal function and survival. Methods: To this end cRNA encoding Slc6A8 was injected into Xenopus oocytes with and without additional injection of cRNA encoding Klotho protein. Creatine transporter CreaT (Slc6A8 activity was estimated from creatine induced current determined by two-electrode voltage-clamp. Results: Coexpression of Klotho protein significantly increased creatine-induced current in Slc6A8 expressing Xenopus oocytes. Coexpression of Klotho protein delayed the decline of creatine induced current following inhibition of carrier insertion into the cell membrane by brefeldin A (5 µM. The increase of creatine induced current by coexpression of Klotho protein in Slc6A8 expressing Xenopus oocytes was reversed by β-glucuronidase inhibitor (DSAL. Similarly, treatment of Slc6A8 expressing Xenopus oocytes with recombinant human alpha Klotho protein significantly increased creatine induced current. Conclusion: Klotho protein up-regulates the activity of creatine transporter CreaT (Slc6A8 by stabilizing the carrier protein in the cell membrane, an effect requiring β-glucuronidase activity of Klotho protein.

  4. Effects of α-Asarone on the Neuronal Glutamate Transporter EAAC1

    Institute of Scientific and Technical Information of China (English)

    顾全保; 杜慧明; Heike FOTIS; 马春辉; 黄成钢; Wolfgang SCHWARZ

    2008-01-01

    Objective: α-asarone is a major effective component that can be isolated from Acorus tatarinowii Schott,a Chinese herbal medicine. Clinical investigations have shown that α-asarone has strong sedative and anti-convulsive action in the central nervous system. In recent years, several medicines containing a-asarone were applied in treatment of asthma, bronchitis, expectorant, or epilepsy. However, the underlying cellular mechanism of ct-asarone is still unknown. Here the authors considered EAAC1, the transporter for the excitatory glutamate, as a possible target. Methods: Supercritical CO2 fluid extraction and silica gel column chromatography were used to obtain ct-asarone from the rhizomes of Acorus tatarinowii Schott. Xenopus oocytes with heterologously expressed EAAC 1 were used as a model system. Rate of glutamate uptake was measured by means of isotopic tracer technique. Glutamate-induced current was recorded under two-electrode voltage clamp. 40μg/mL of ct-asarone was used for testing its effect on EAAC1 activity. Results: ct-asarone induced a slight, but still significant stimulation of rate of glutamate uptake by 15%. In contrast, EAACl-mediated current became reduced (by 30% at -100 mV). Since EAAC 1 can operate in transport and also in an ion-channel mode, the result indicates strong inhibition of the channel mode. This inhibition is voltage-dependent becoming larger at more negative potentials. Conclusion: The stimulation of glutamate uptake reduces glutamate concentration in the synaptic cleft and, hence, reduces excitatory synaptic activity. The inhibition on the ion-channel mode stabilizes the membrane potential, and therefore, also contributes to reduced excitatory activity.

  5. K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

    Science.gov (United States)

    2010-01-01

    Background Lung epithelial Na+ channels (ENaC) are regulated by cell Ca2+ signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K+ channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K+ channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC) by up-regulating both apical and basolateral ion transport. Methods Verapamil-induced depression of heterologously expressed human αβγ ENaC in Xenopus oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441), and in vivo alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca2+ signal in H441 cells was analyzed using Fluo 4AM. Results The rate of in vivo AFC was reduced significantly (40.6 ± 6.3% of control, P minoxidil) channel openers significantly recovered AFC. In addition to short-circuit current (Isc) in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca2+ signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca2+ in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, KV (pyrithione-Na), K Ca3.1 (1-EBIO), and KATP (minoxidil) channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na+ and K+ transport pathways. Conclusions Our observations demonstrate that K+ channel openers are capable of rescuing reduced vectorial Na+ transport across lung epithelial cells with impaired Ca2+ signal. PMID:20507598

  6. Effects of diltiazem and propafenone on the inactivation and recovery kinetics of fKvl.4 channel currents expressed in Xenopus oocytes

    Institute of Scientific and Technical Information of China (English)

    Dong ZHANG; Shi-min WANG; Hui CHEN; Xue-jun JIANG; Sheng-ping CHAO

    2011-01-01

    Alm: TO investigate the effects of diltiazem. an L-type calcium channel blocker, and propafenone, a sodium channel blocker,on the inactivation and recovery kinetics of fKvl.4.a potassium channel that generates the cardiac transient outward potassium current.Methods:The cRNA for fKv1.4△N.an N-rerminal deleted mutant of the flerret Kvl.4 potassium channel.was injected into Xenopusoocytes to express the fKv1.4△N channel in these cells. Currents were recorded using a two electrode voltage clamp technique. Results: Diltiazem(10 to 1000 μmol/L)inhibited the fKv1.4△N channel in a frequency-dependent,voltage-dependent,and concerttration-dependent manneh Suggesting an open channel block.The ICso was 241.04±23.06 μmol/L for the fKvl.4&N channel(at+50mY).and propafenone(10 to 500 μmol/L)showed a similar effect(IC50=103.68±10.13 μmol/L).After application of diltiazem and propafenone, fKv1.4AN inactivation was bi-exponential.with a faster drug-induced inactivation and a slower C-type inactivation.Diltiazem increased the C-type inactivation rate and slowed recovery in fKv1.4△N channels.Howeve, propafenone had no effect on either the slow inactivation time constant or the recovery.Conclusion:Diltiazem and propafenone accelerate the inactivation of the Kvl.4AN channeI by binding to the open state of the channel.Unlike propafenone, diltiazem slows the recovery of the Kv1.4AN channel.

  7. Differential zinc permeation and blockade of L-type Ca2+ channel isoforms Cav1.2 and Cav1.3.

    Science.gov (United States)

    Park, So-Jung; Min, Se-Hong; Kang, Ho-Won; Lee, Jung-Ha

    2015-10-01

    Certain voltage-activated Ca2+ channels have been reported to act as potential zinc entry routes. However, it remains to be determined whether zinc can permeate individual Ca2+ channel isoforms. We expressed recombinant Ca2+ channel isoforms in Xenopus oocytes and attempted to record zinc currents from them using a two-electrode voltage clamp method. We found that, in an extracellular zinc solution, inward currents arising from zinc permeation could be recorded from Xenopus oocytes expressing L-type Cav1.2 or Cav1.3 isoforms, but not from oocytes expressing Cav2.2, Cav2.3, Cav3.1, or Cav3.2. Zinc currents through Cav1.2 and Cav1.3 were blocked by nimodipine, but enhanced by (±)Bay K8644, supporting the finding that zinc can permeate both L-type Cav1.2 and Cav1.3 channel isoforms. We also examined the blocking effects of low concentrations of zinc on Ca2+ currents through the L-type channel isoforms. Low micro-molar zinc potently blocked Ca2+ currents through Cav1.2 and Cav1.3 with different sensitivities (IC50 for Cav1.2 and Cav1.3=18.4 and 34.1 μM) and de-accelerated the activation and inactivation kinetics in a concentration-dependent manner. Notably, mild acidifications of the external zinc solution increased zinc currents through Cav1.2 and Cav1.3, with the increment level for Cav1.3 being greater than that for Cav1.2. In overall, we provide evidence that Cav1.2 and Cav1.3 isoforms are capable of potentially functioning as zinc permeation routes, through which zinc entry can be differentially augmented by mild acidifications.

  8. K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

    Directory of Open Access Journals (Sweden)

    Su Xue-Feng

    2010-05-01

    Full Text Available Abstract Background Lung epithelial Na+ channels (ENaC are regulated by cell Ca2+ signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K+ channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K+ channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC by up-regulating both apical and basolateral ion transport. Methods Verapamil-induced depression of heterologously expressed human αβγ ENaC in Xenopus oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441, and in vivo alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca2+ signal in H441 cells was analyzed using Fluo 4AM. Results The rate of in vivo AFC was reduced significantly (40.6 ± 6.3% of control, P Ca3.1 (1-EBIO and KATP (minoxidil channel openers significantly recovered AFC. In addition to short-circuit current (Isc in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca2+ signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca2+ in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, KV (pyrithione-Na, K Ca3.1 (1-EBIO, and KATP (minoxidil channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na+ and K+ transport pathways. Conclusions Our observations demonstrate that K+ channel openers are capable of rescuing reduced vectorial Na+ transport across lung epithelial cells with impaired Ca2+ signal.

  9. Bistable organic materials in optoelectrical switches: Two-electrode devices vs. organic field effect transistors

    CERN Document Server

    Sworakowski, Juliusz

    2011-01-01

    The paper presents a short overview of research into properties of organic materials and structures that could be used in optoelectrical switches, i.e., switches in which changes in electrical properties are triggered by light of appropriate wavelengths. In particular, described are the structures acting by virtue of reversible photochemical reactions occurring in photochromic molecular materials.

  10. Application of geophysical methods to investigation of old castle, especially of the moat; Joshi no chosa ni okeru butsuri tansa no tekiyo (horiato no tansa)

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, A.; Karube, F.; Kobayashi, M.; Toge, M. [OYO Corp., Tokyo (Japan)

    1996-05-01

    An explanation is made about the application of geophysical methods to the investigation of the ruins of old castles especially of their moats. Techniques currently in use for exploration of the ruins of castles are mainly underground radar exploration and electric exploration. The underground radar method sends electromagnetic waves through the ground and receives the reflection for a high-precision exploration of the layers shallow in the ground. Therefore, this method is suitable for probing the ruins of castles relatively shallow in the flat land, hills, and mountains. The electric method (resistivity image method) do the probing by use of the two-electrode arrangement, performs inverse analysis on the basis of the obtained data for the determination of the underground resistivity distribution, and displays the distribution in an image easy to read. This method, when there is a great separation between the two electrodes, explores relatively deep into the ground. Thanks to this feature, this method is effective in probing relatively wide and deep ruins of moats, that is, the ruins of moats of castles built in later years, especially of those then filled with water. 2 refs., 5 figs.

  11. The Response Clamp: Functional characterization of neural systems using closed-loop control

    Directory of Open Access Journals (Sweden)

    Avner eWallach

    2013-01-01

    Full Text Available The voltage clamp method, pioneered by Hodgkin, Huxley and Katz, laid the foundations to neurophysiological research. Its core rationale is the use of closed-loop control as a tool for system characterization. A recently introduced method, the response clamp, extends the voltage clamp rationale to the functional, phenomenological level. The method consists of on-line estimation of a response variable of interest (e.g. the probability of response or its latency and a simple feedback control mechanism designed to tightly converge this variable towards a desired trajectory. In the present contribution I offer a perspective on this novel method and its applications in the broader context of system identification and characterization. First, I demonstrate how internal state variables are exposed using the method, and how the use of several controllers may allow for a detailed, multi-variable characterization of the system. Second, I discuss three different categories of applications of the method: (i exploration of intrinsically generated dynamics, (ii exploration of extrinsically generated dynamics and (iii generation of input-output trajectories. The relation of these categories to similar uses in the voltage clamp and other techniques is also discussed. Finally, I discuss the method’s limitations, as well as its possible synthesis with existing complementary approaches.

  12. Archaeological prospecting using electrical resistivity method. Case history of Kaibukiyama ancient tomb; Denki tansaho ni yoru iseki tansa. Kaibukiyama kofun no chosarei

    Energy Technology Data Exchange (ETDEWEB)

    Mizunaga, H.; Ushijima, K.; Kishikawa, H. [Kyushu University, Fukuoka (Japan). Faculty of Engineering

    1997-05-27

    To grasp the three-dimensional structure of ancient tomb during the archaeological prospecting of Kaibukiyama ancient tomb, various electrical resistivity methods were tried. For the survey, firstly, in order to clarify the electrical resistivity structure of rear circular part of ancient tomb, roughly, mapping was conducted by means of two-electrode method using a multi-channel measuring system. Then, the vertical prospecting was conducted densely with a mesh form having VES intervals of 2 m as a detailed survey by means of Schlumberger method. For the three-dimensional inverse analysis of apparent electrical resistivity data by the two-electrode method, a program with high calculation speed was developed by using algorithm where Jacobian with a homogeneous model is adopted for the Jacobian calculation. As a result of the analysis, an outline of underground 3-D resistivity structure was determined. The resistivity anomaly with high values obtained from the results of 2-D inverse analysis of VES curve by means of Schlumberger method agreed well with the central part of the ancient tomb, which was confirmed during the archaeological survey. 4 refs., 8 figs.

  13. A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials

    DEFF Research Database (Denmark)

    Calloe, Kirstine; Di Diego, José M; Hansen, Rie Schultz

    2016-01-01

    in cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration. METHODS AND RESULTS: Ventricular myocytes were isolated and cultured for up to 48h. Current and voltage clamp recordings were made using patch...... of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure....

  14. Methods of electrophoretic deposition for functionally graded porous nanostructures and systems thereof

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Joe H; Olson, Tammy Y; Kuntz, Joshua D; Rose, Klint A

    2015-03-03

    In one embodiment, an aerogel includes a layer of shaped particles having a particle packing density gradient in a thickness direction of the layer, wherein the shaped particles are characterized by being formed in an electrophoretic deposition (EPD) process using an impurity. In another embodiment, a method for forming a functionally graded porous nanostructure includes adding particles of an impurity and a solution to an EPD chamber, applying a voltage difference across the two electrodes of the EPD chamber to create an electric field in the EPD chamber, and depositing the material onto surfaces of the particles of the impurity to form shaped particles of the material. Other functionally graded materials and methods are described according to more embodiments.

  15. Imaging fast calcium currents beyond the limitations of electrode techniques.

    Science.gov (United States)

    Jaafari, Nadia; De Waard, Michel; Canepari, Marco

    2014-09-16

    The current understanding of Ca(2+) channel function is derived from the use of the patch-clamp technique. In particular, the measurement of fast cellular Ca(2+) currents is routinely achieved using whole-cell voltage-clamp recordings. However, this experimental approach is not applicable to the study of local native Ca(2+) channels during physiological changes of membrane potential in complex cells, since the voltage-clamp configuration constrains the membrane potential to a given value. Here, we report for the first time to our knowledge that Ca(2+) currents from individual cells can be quantitatively measured beyond the limitations of the voltage-clamp approach using fast Ca(2+) imaging with low-affinity indicators. The optical measurement of the Ca(2+) current was correlated with the membrane potential, simultaneously measured with a voltage-sensitive dye to investigate the activation of Ca(2+) channels along the apical dendrite of the CA1 hippocampal pyramidal neuron during the back-propagation of an action potential. To validate the method, we analyzed the voltage dependence of high- and low-voltage-gated Ca(2+) channels. In particular, we measured the Ca(2+) current component mediated by T-type channels, and we investigated the mechanisms of recovery from inactivation of these channels. This method is expected to become a reference approach to investigate Ca(2+) channels in their native physiological environment.

  16. Functionality and stability data of detergent purified nAChR from Torpedo using lipidic matrixes and macroscopic electrophysiology

    Directory of Open Access Journals (Sweden)

    Luis F. Padilla-Morales

    2016-03-01

    Full Text Available The presented data provides additional information about the assessment of affinity purified nicotinic acetylcholine receptor (nAChR rich membrane solubilized with long chain (16 saturated carbons lysophospholipid with glycerol headgroup (LFG-16. The assessment of stability and functionality of solubilized membrane protein is a critical step prior to further crystallization trails. One of the key factors for this task is the appropriate choice of a detergent that can support nAChR activity and stability comparable to the crude membranes. The stability of the nAChR-LFG-16 complex incorporated into lipid cubic phase (LCP was monitored for a period of 30 days by means of fluorescence recovery after photobleaching (FRAP and the functionality was evaluated after its incorporation into Xenopus oocyte by means of the two electrode voltage clamp technique.

  17. Hypoosmotic cell swelling as a novel mechanism for modulation of cloned HCN2 channels

    DEFF Research Database (Denmark)

    Calloe, Kirstine; Elmedyb, Pernille; Olesen, Søren-Peter

    2005-01-01

    This work demonstrates cell swelling as a new regulatory mechanism for the cloned hyperpolarization-activated, cyclic nucleotide-gated channel 2 (HCN2). HCN2 channels were coexpressed with aquaporin1 in Xenopus laevis oocytes and currents were monitored using a two-electrode voltage-clamp. HCN2...... channels were activated by hyperpolarization to -100 mV and the currents were measured before and during hypoosmotic cell swelling. Cell swelling increased HCN2 currents by 30% without changing the kinetics of the currents. Injection of 50 nl intracellular solution resulted in a current increase of 20......%, indicating that an increase in cell volume also under isoosmotic conditions may lead to activation of HCN2. In the absence of aquaporin1 only negligible changes in oocyte cell volume occur during exposure to hypoosmotic media and no significant change in HCN2 channel activity was observed during perfusion...

  18. The acrylamide (S)-1 differentially affects Kv7 (KCNQ) potassium channels

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Schmitt, Nicole; Calloe, Kirstine;

    2006-01-01

    .g., retigabine) for treatment of epilepsy and neuropathic pain. We investigated the effect of a Bristol-Myers Squibb compound (S)-N-[1-(3-morpholin-4-yl-phenyl)-ethyl]-3-phenyl-acrylamide [(S)-1] on cloned human Kv7.1-5 potassium channels expressed in Xenopus laevis oocytes. Using two-electrode voltage......-clamp recordings we found that (S)-1 blocks Kv7.1 and Kv7.1/KCNE1 currents. In contrast, (S)-1 produced a hyperpolarizing shift of the activation curve for Kv7.2, Kv7.2/Kv7.3, Kv7.4 and Kv7.5. Further, the compound enhanced the maximal current amplitude at all potentials for Kv7.4 and Kv7.5 whereas the combined...

  19. The corticosteroid hormone induced factor: a new modulator of KCNQ1 channels?

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Grunnet, Morten; Rasmussen, Hanne B

    2006-01-01

    laevis oocytes, but recently CHIF has attracted attention as a modulatory subunit of the Na,K-pump. In renal and intestinal epithelia, the expression of CHIF is dramatically up-regulated in response to aldosterone stimulation, and regulation of epithelial ion channels by CHIF is an attractive hypothesis....... To study a potential regulatory effect of the CHIF subunit on KCNQ1 channels, co-expression experiments were performed in Xenopus laevis oocytes and mammalian CHO-K1 cells. Electrophysiological characterization was obtained by two-electrode voltage-clamp and patch-clamp, respectively. In both expression...... systems, we find that CHIF drastically modulates the KCNQ1 current; in the presence of CHIF, the KCNQ1 channels open at all membrane potentials. Thereby, CHIF is the first accessory subunit shown to be capable of modulating both the Na,K-pump and an ion channel. To find a possible physiological function...

  20. A functional EXXEK motif is essential for proton coupling and active glucosinolate transport by NPF2.11

    DEFF Research Database (Denmark)

    Jørgensen, Morten Egevang; Olsen, Carl Erik; Geiger, Dietmar

    2015-01-01

    The proton-dependent oligopeptide transporter (POT/PTR) family shares a highly conserved E1X1X2E2RFXYY (E1X1X2E2R) motif across all kingdoms of life. This motif is suggested to have a role in proton coupling and active transport in bacterial homologs. For the plant POT/PTR family, also known......K motif variant in a plant NPF transporter. Using liquid chromatography-mass spectrometry (LC-MS)-based uptake assays and two-electrode voltage clamp (TEVC) electrophysiology, we demonstrate an essential role for the E1X1X2E2K motif for accumulation of substrate by NPF2.11. Our data suggest...

  1. Cells exposed to a huntingtin fragment containing an expanded polyglutamine tract show no sign of ion channel formation: results arguing against the ion channel hypothesis

    DEFF Research Database (Denmark)

    Nørremølle, Anne; Grunnet, Morten; Hasholt, Lis

    2003-01-01

    tract to form ion channels in two cell types. Whole cell current from Xenopus oocytes was recorded using two-electrode voltage-clamp technique, and whole cell current from CHO-K1 cells was recorded by patch-clamp technique. The fragment with an expanded polyglutamine sequence induced no change......Ion channels formed by expanded polyglutamine tracts have been proposed to play an important role in the pathological processes leading to neurodegeneration in Huntington's disease and other CAG repeat diseases. We tested the capacity of a huntingtin fragment containing an expanded polyglutamine...... in the currents recorded in any of the two expression systems, indicating no changes in ion channel activity. The results therefore argue against the proposed hypothesis of expanded polyglutamines forming ion channels....

  2. Electrochemical Li-storage Properties of Nanosized FeSb2 Prepared by Solvothermal Method

    Institute of Scientific and Technical Information of China (English)

    Jian XIE; Xinbing ZHAO; Gaoshao CAO; Mingjian ZHAO

    2006-01-01

    Li-storage intermetallic compound FeSb2 was prepared by solvothermal method and was studied as a promising anode material for secondary lithium-ion batteries. The as-prepared powder was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The electrochemical Li-storage performances of this intermetallic anode were evaluated in a two-electrode cell Li/LiPF6 (EC+-DMC)/FeSb2.It was found that the particle size of FeSb2 powder is in nanoscale and this intermetallic anode exhibited enhanced cycling behavior comparing to its microscaled counterpart prepared by levitation-melting/ball-milling route.

  3. Experimental Evaluation of the Applicability of Capacitive and Optical Measurement Methods for the Determination of Liquid Hydrogen Volume Flow

    Directory of Open Access Journals (Sweden)

    Gert HOLLER

    2009-08-01

    Full Text Available This paper presents a capacitive and a vision-based method for measuring the velocity of cryogenic hydrogen flows. The capacitive sensing principle exploits the spatial frequency signature of perturbations moving through a multi-electrode structure. This setup increases the sensitivity to dielectric permittivity variations compared to a simple two-electrode structure while preserving the ability to detect small perturbations. The vision-based method relies on a high-speed camera system that monitors the liquid hydrogen flow through an optical window yielding the flow velocity by cross-correlating subsequent images of the flow. Although a comprehensive analysis of the obtainable measurement uncertainty was not performed yet, current measurement results show the applicability of both principles for the non-invasive measurement of the volume flow of cryogenic fuels inside conveyor pipes.

  4. Functional study of the effect of phosphatase inhibitors on KCNQ4 channels expressed in Xenopus oocytes

    Institute of Scientific and Technical Information of China (English)

    Tzu-rong SU; Cay-huyen CHEN; Shih-jen HUANG; Chun-yi LEE; Mao-chang SU; Gwan-hong CHEN; Shuan-yow LI; Jiann-jou YANG; Min-jon LIN

    2009-01-01

    Aim: KCNQ4 channels play an important part in adjusting the function of cochlear outer hair cells. The aim of this study was to investigate the effects of ser/thr phosphatase inhibitors on human KCNQ4 channels expressed in Xenopus laevis oocytes. Methods: Synthetic cRNA encoding human KCNQ4 channels was injected into Xenopus oocytes. We used a two-electrode voltage clamp to measure the ion currents in the oocytes. Results: Wild-type KCNQ4 expressed in Xenopus oocytes showed the typical properties of slow activation kinetics and low threshold activation. The outward K~+ current was almost completely blocked by a KCNQ4 blocker, linopirdine (0.25 mmol/L). BIMI (a PKC inhibitor) prevented the effects of PMA (a PKC activator) on the KCNQ4 current, indicating that PKC may be involved in the regulation of KCNQ4 expressed in the Xenopus oocyte system. Treatment with the ser/thr phosphatase inhibitors, cyclosporine (2 μmoVL), calyculin A (2 μmol/L) or okadaic acid (1 μmol/L), caused a significant positive shift in V_(1/2) and a decrease in the conductance of KCNQ4 chan-nels. The V_(1/2) was shifted from-14.6±0.5 to-6.4±0.4 mV by cyclosporine, -18.8±0.5 to-9.2±0.4 mV by calyculin A, and-14.1±0.5 to -0.7±0.6 mV by okadaic acid. Moreover, the effects of these phosphatase inhibitors (okadaic acid or calyculin A) on the induction of a positive shift of V_(1/2) were augmented by further addition of PMA. Conclusion: These results indicate that ser/thr phosphatase inhibitors can induce a shift to more positive potentials of the activation curve of the KCNQ4 current. It is highly likely that the phosphatase functions to balance the phosphorylated state of substrate protein and thus has an important role in the regulation of human KCNQ4 channels expressed in Xenopus oocytes.

  5. Inhibition of the Na/bicarbonate cotransporter NBCe1-A by diBAC oxonol dyes relative to niflumic acid and a stilbene.

    Science.gov (United States)

    Liu, Xiaofen; Williams, Jennifer B; Sumpter, Brandon R; Bevensee, Mark O

    2007-02-01

    Na/HCO(3) cotransporters (NBCs) are important regulators of intracellular pH (pH(i) in a variety of organ systems where acid-base status is critical for tissue function. To characterize the pharmacology of NBCs in more detail, we used the two-electrode voltage-clamp technique to examine the effect of previously identified inhibitors of anion exchanger 1 (AE1) on the activity of rat NBCe1-A expressed in Xenopus laevis oocytes. NBC-expressing oocytes voltage-clamped at -60 mV and exposed to a 5% CO(2)/33 mM HCO(3)(-) solution displayed NBC-mediated outward currents that were inhibited by either niflumic acid or one of the two bis-oxonol dyes diBA(3)C4 and diBA(5)C4. NBCe1-A was less sensitive to niflumic acid (apparent K(i) of 100 microM) than 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, apparent K(i) of 36 microM) but more sensitive to the diBAC dyes (apparent K(i) of approximately 10 microM). Based on current-voltage relationships, the diBAC dyes inhibited HCO(3)(-) -induced NBCe1-mediated inward currents more so than outward currents. NBCe1 sensitivity to the dyes was (1) lower in the presence of 40 microM DIDS, (2) unaffected by changes in external HCO(3)(-) concentration and (3) only modestly higher at an external Na(+) concentration of 5, but not 15 or 33, mM. Therefore, the diBAC dyes compete with DIDS but not appreciably with Na(+) or HCO(3)(-) for binding. The mechanism of diBAC inhibition of NBCe1 appears similar to that previously reported for AE1.

  6. Perturbation methods

    CERN Document Server

    Nayfeh, Ali H

    2008-01-01

    1. Introduction 1 2. Straightforward Expansions and Sources of Nonuniformity 23 3. The Method of Strained Coordinates 56 4. The Methods of Matched and Composite Asymptotic Expansions 110 5. Variation of Parameters and Methods of Averaging 159 6. The Method of Multiple Scales 228 7. Asymptotic Solutions of Linear Equations 308 References and Author Index 387 Subject Index 417

  7. A library of analog operators based on the hodgkin-huxley formalism for the design of tunable, real-time, silicon neurons.

    Science.gov (United States)

    Saïghi, S; Bornat, Y; Tomas, J; Le Masson, G; Renaud, S

    2011-02-01

    In this paper, we present a library of analog operators used for the analog real-time computation of the Hodgkin-Huxley formalism. These operators make it possible to design a silicon (Si) neuron that is dynamically tunable, and that reproduces different kinds of neurons. We used an original method in neuromorphic engineering to characterize this Si neuron. In electrophysiology, this method is well known as the "voltage-clamp" technique. We also compare the features of an application-specific integrated circuit built with this library with results obtained from software simulations. We then present the complex behavior of neural membrane voltages and the potential applications of this Si neuron.

  8. Photoelectric recording of mechanical responses of cardiac myocytes.

    Science.gov (United States)

    Meyer, R; Wiemer, J; Dembski, J; Haas, H G

    1987-04-01

    A method to monitor contraction of isolated myocytes by transmicroscopic photometry is illustrated. Two photodiodes are mounted inside an inverse microscope used for visual control of a cell. Illumination of one diode varies in proportion to changes in cell length. The contraction signal is amplified in a comparator circuit. Spatial resolution of the device is in the order of 1 micron which corresponds to about 5% of cell shortening in the fully activated state of contraction. The method was tested on isolated myocytes from guinea-pig ventricle. Optical records of contraction in response to action potentials or during voltage clamp compare well with the contractile behavior of multicellular preparations.

  9. Basic methods for monitoring intracellular Ca2+ in cardiac myocytes using Fluo-3.

    Science.gov (United States)

    Bito, Virginie; Sipido, Karin R; Macquaide, Niall

    2015-04-01

    In cardiac myocytes, the physiological increase of intracellular calcium, the [Ca(2+)]i transient, elicited during excitation-contraction coupling typically reaches a peak amplitude of up to 1 µm, from a resting value of ∼100 nm, within 50-100 msec, depending on the species. Various conditions will affect the amplitude and rise time of the [Ca(2+)]i transient and, depending on the nature of the Ca(2+) signals under study, a variety of different probes are available for monitoring changes in intracellular Ca(2+). In this protocol, we focus on Fluo-3, which exists in the cytosol in its salt form K5Fluo-3. This form is practically nonfluorescent in the absence of Ca(2+), but the fluorescence increases dramatically on Ca(2+) binding. Although Fluo-3 is a single excitation-emission dye, it has a number of advantages for investigators, including an ideal dissociation constant (Kd) value and high quantum yield, meaning that it can be used at low concentrations that introduce minimal buffering. Here, we describe the basic setup and methodology for recording the global cytosolic [Ca(2+)]i transient with this probe during simultaneous patch-clamp and whole-cell recording of membrane voltage or of ionic currents under voltage clamp. © 2015 Cold Spring Harbor Laboratory Press.

  10. Effect of Canagliflozin on Renal Threshold for Glucose, Glycemia, and Body Weight in Normal and Diabetic Animal Models

    OpenAIRE

    Yin Liang; Kenji Arakawa; Kiichiro Ueta; Yasuaki Matsushita; Chiaki Kuriyama; Tonya Martin; Fuyong Du; Yi Liu; June Xu; Bruce Conway; Jamie Conway; David Polidori; Kirk Ways; Keith Demarest

    2012-01-01

    BACKGROUND: Canagliflozin is a sodium glucose co-transporter (SGLT) 2 inhibitor in clinical development for the treatment of type 2 diabetes mellitus (T2DM). METHODS: (14)C-alpha-methylglucoside uptake in Chinese hamster ovary-K cells expressing human, rat, or mouse SGLT2 or SGLT1; (3)H-2-deoxy-d-glucose uptake in L6 myoblasts; and 2-electrode voltage clamp recording of oocytes expressing human SGLT3 were analyzed. Graded glucose infusions were performed to determine rate of urinary glucose e...

  11. Water transport by the Na+/glucose cotransporter under isotonic conditions

    DEFF Research Database (Denmark)

    Zeuthen, T; Meinild, A K; Klaerke, D A

    1997-01-01

    in Xenopus oocytes. We present a method which allows short-term exposures to sugar under voltage clamp conditions. We demonstrate that water is cotransported with the solutes despite no osmotic differences between the external and intracellular solutions. There is a fixed ratio of 195:1 between the number...... of water molecules and the number of Na+ ions transported, equivalent to 390 water molecules per glucose molecule. Unstirred layer effects are ruled out on the basis of experiments on native oocytes incubated with the ionophores gramicidin D or nystatin....

  12. Vortex methods

    Energy Technology Data Exchange (ETDEWEB)

    Chorin, A.J. [California Univ., Berkeley, CA (United States). Dept. of Mathematics]|[Lawrence Berkeley Lab., CA (United States)

    1993-06-01

    Vortex methods originated from the observation that in incompressible inviscid flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus, if the vorticity is known at time t=0, one can find the flow at a later time by simply following the vorticity. In this narrow context, a vortex method is a numerical method that follows vorticity. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (blobs) and those whose analysis contributes to the understanding of blob methods. Blob methods started in the 1930`s.

  13. Mining Method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Shik; Lee, Kyung Woon; Kim, Oak Hwan; Kim, Dae Kyung [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    The reducing coal market has been enforcing the coal industry to make exceptional rationalization and restructuring efforts since the end of the eighties. To the competition from crude oil and natural gas has been added the growing pressure from rising wages and rising production cost as the workings get deeper. To improve the competitive position of the coal mines against oil and gas through cost reduction, studies to improve mining system have been carried out. To find fields requiring improvements most, the technologies using in Tae Bak Colliery which was selected one of long running mines were investigated and analyzed. The mining method appeared the field needing improvements most to reduce the production cost. The present method, so-called inseam roadway caving method presently is using to extract the steep and thick seam. However, this method has several drawbacks. To solve the problems, two mining methods are suggested for a long term and short term method respectively. Inseam roadway caving method with long-hole blasting method is a variety of the present inseam roadway caving method modified by replacing timber sets with steel arch sets and the shovel loaders with chain conveyors. And long hole blasting is introduced to promote caving. And pillar caving method with chock supports method uses chock supports setting in the cross-cut from the hanging wall to the footwall. Two single chain conveyors are needed. One is installed in front of chock supports to clear coal from the cutting face. The other is installed behind the supports to transport caved coal from behind. This method is superior to the previous one in terms of safety from water-inrushes, production rate and productivity. The only drawback is that it needs more investment. (author). 14 tabs., 34 figs.

  14. Projection Methods

    DEFF Research Database (Denmark)

    Wagner, Falko Jens; Poulsen, Mikael Zebbelin

    1999-01-01

    When trying to solve a DAE problem of high index with more traditional methods, it often causes instability in some of the variables, and finally leads to breakdown of convergence and integration of the solution. This is nicely shown in [ESF98, p. 152 ff.].This chapter will introduce projection...... methods as a way of handling these special problems. It is assumed that we have methods for solving normal ODE systems and index-1 systems....

  15. Computing methods

    CERN Document Server

    Berezin, I S

    1965-01-01

    Computing Methods, Volume 2 is a five-chapter text that presents the numerical methods of solving sets of several mathematical equations. This volume includes computation sets of linear algebraic equations, high degree equations and transcendental equations, numerical methods of finding eigenvalues, and approximate methods of solving ordinary differential equations, partial differential equations and integral equations.The book is intended as a text-book for students in mechanical mathematical and physics-mathematical faculties specializing in computer mathematics and persons interested in the

  16. Effect of electrode fabrication methods on the electrode performance for ethanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Yuan-Hang; Li, Hui-Cheng; Yang, Hou-Hua; Zhang, Xin-Sheng; Zhou, Xing-Gui; Yuan, Wei-Kang [State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237 (China); Niu, Li [State Key Laboratory of Electroanalytical Chemistry, Chang Chun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2011-01-01

    Two palladium/carbon nanofibers modified glassy carbon electrodes, Pd/CNFs/GC-C and Pd/CNFs/GC-E, are fabricated by the conventional powder type method and by the electrophoretic deposition in conjunction with pulse electrodeposition method, respectively. Field emission scanning electron microscopy and high resolution transmission electron microscopy reveal that Pd particles are uniformly dispersed on the two electrodes and X-ray diffraction shows the average Pd particle size of the Pd/CNFs/GC-E electrode is slightly larger than that of the Pd/CNFs/GC-C electrode. Cyclic voltammetric analysis shows that the electrocatalytic activity of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode for ethanol oxidation in alkaline media, although the latter has higher Pd loading than the former. This is believed to be due to the higher utilization of Pd catalyst on Pd/CNFs/GC-E electrode than on Pd/CNFs/GC-C electrode, which is confirmed by the electrochemically active surface area measurements. In addition, chronopotentiometric analysis shows the long-term operation stability of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode. (author)

  17. Morphology and Structure of ZnO Nanoparticles Produced by Electrochemical Method

    Directory of Open Access Journals (Sweden)

    Barbara STYPUŁA

    2014-04-01

    Full Text Available This article presents studies of the morphology and structure of ZnO nanoparticles synthesized by the electrochemical method. Colloidal solutions of the nanoparticles are obtained by an anodic dissolution of metallic zinc in alcohol solutions of lithium chloride containing a small amount of water (5 % vol.. The parameters chosen for the synthesis are based on Zn polarization curves(obtained using the the potentiokinetic (Linear Sweep Voltammetry – LSV and the chronoamperometric method. The synthesis of zinc oxide nanoparticles is carried out in 0.05m LiCl + 5 % H2O alcohol (methanol or propanol solutions during galvanostatic polarization of Zn at 3 mA/cm2 current density. The process is performed in a two-electrode system, where both electrodes (the working anode and cathode are made of zinc. Optical properties, morphology and structure of the colloidal solutions and powders (obtained after evaporating the solvent were studied using the following spectroscopic and microscopic techniques: UltraViolet and Visible Spectroscopy (UV-VIS, Fourier Transform Infrared Spectroscopy (FTIR, Scanning Electron Microscopy (SEM and Transmission Electron Microscopy (TEM.DOI: http://dx.doi.org/10.5755/j01.ms.20.1.4417

  18. Method 59

    DEFF Research Database (Denmark)

    Kjellsson, G.

    1994-01-01

    OCDE/GD(94)41. Er supplerende rapport til rapport: The OECD Workshop on Methods for Monitoring Organisms in the Environment, Ottawa 14-17 September 1992. Environment Monograph 90.......OCDE/GD(94)41. Er supplerende rapport til rapport: The OECD Workshop on Methods for Monitoring Organisms in the Environment, Ottawa 14-17 September 1992. Environment Monograph 90....

  19. A New Method for Water Desalination Using Microbial Desalination Cells

    KAUST Repository

    Cao, Xiaoxin

    2009-09-15

    Current water desalination techniques are energy intensive and some use membranes operated at high pressures. It is shownhere that water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water. A microbial fuel cell was modified by placing two membranes between the anode and cathode, creating a middle chamber for water desalination between the membranes. An anion exchange membrane was placed adjacent to the anode, and a cation exchange membrane was positioned next to the cathode. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber. Proof-of-concept experiments for this approach, using what we call a microbial desalination cell (MDC), was demonstrated using water at different initial salt concentrations (5, 20, and 35 g/L) with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m2 (31 W/m3) while at the same time removing about 90% of the salt in a single desalination cycle. As the salt was removed from the middle chamber the ohmic resistance of the MDC (measured using electrochemical impedance spectroscopy) increased from 25 Ω to 970 Ω at the end of the cycle. This increased resistance was reflected by a continuous decrease in the voltage produced over the cycle. These results demonstrate for the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria. © 2009 American Chemical Society.

  20. A new method for water desalination using microbial desalination cells.

    Science.gov (United States)

    Cao, Xiaoxin; Huang, Xia; Liang, Peng; Xiao, Kang; Zhou, Yingjun; Zhang, Xiaoyuan; Logan, Bruce E

    2009-09-15

    Current water desalination techniques are energy intensive and some use membranes operated at high pressures. It is shown here that water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water. A microbial fuel cell was modified by placing two membranes between the anode and cathode, creating a middle chamber for water desalination between the membranes. An anion exchange membrane was placed adjacent to the anode, and a cation exchange membrane was positioned next to the cathode. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber. Proof-of-concept experiments for this approach, using what we call a microbial desalination cell (MDC), was demonstrated using water at different initial salt concentrations (5, 20, and 35 g/L) with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m2 (31 W/m3) while at the same time removing about 90% of the salt in a single desalination cycle. As the salt was removed from the middle chamber the ohmic resistance of the MDC (measured using electrochemical impedance spectroscopy) increased from 25 Omega to 970 Omega at the end of the cycle. This increased resistance was reflected by a continuous decrease in the voltage produced over the cycle. These results demonstrate for the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria.

  1. Method Mixins

    DEFF Research Database (Denmark)

    Ernst, Erik

    2005-01-01

    , where traditional invocation is optimized for as-is reuse of existing behavior. Tight coupling reduces flexibility, and traditional invocation tightly couples transfer of information and transfer of control. Method mixins decouple these two kinds of transfer, thereby opening the doors for new kinds......The world of programming has been conquered by the procedure call mechanism, including object-oriented method invocation which is a procedure call in context of an object. This paper presents an alternative, method mixin invocations, that is optimized for flexible creation of composite behavior...

  2. Method Mixins

    DEFF Research Database (Denmark)

    Ernst, Erik

    2002-01-01

    invocation is optimized for as-is reuse of existing behavior. Tight coupling reduces flexibility, and traditional invocation tightly couples transfer of information and transfer of control. Method mixins decouple these two kinds of transfer, thereby opening the doors for new kinds of abstraction and reuse......The procedure call mechanism has conquered the world of programming, with object-oriented method invocation being a procedure call in context of an object. This paper presents an alternative, method mixin invocations, that is optimized for flexible creation of composite behavior, where traditional...

  3. Dosimetry methods

    DEFF Research Database (Denmark)

    McLaughlin, W.L.; Miller, A.; Kovacs, A.;

    2003-01-01

    Chemical and physical radiation dosimetry methods, used for the measurement of absorbed dose mainly during the practical use of ionizing radiation, are discussed with respect to their characteristics and fields of application.......Chemical and physical radiation dosimetry methods, used for the measurement of absorbed dose mainly during the practical use of ionizing radiation, are discussed with respect to their characteristics and fields of application....

  4. Ensemble Methods

    Science.gov (United States)

    Re, Matteo; Valentini, Giorgio

    2012-03-01

    Ensemble methods are statistical and computational learning procedures reminiscent of the human social learning behavior of seeking several opinions before making any crucial decision. The idea of combining the opinions of different "experts" to obtain an overall “ensemble” decision is rooted in our culture at least from the classical age of ancient Greece, and it has been formalized during the Enlightenment with the Condorcet Jury Theorem[45]), which proved that the judgment of a committee is superior to those of individuals, provided the individuals have reasonable competence. Ensembles are sets of learning machines that combine in some way their decisions, or their learning algorithms, or different views of data, or other specific characteristics to obtain more reliable and more accurate predictions in supervised and unsupervised learning problems [48,116]. A simple example is represented by the majority vote ensemble, by which the decisions of different learning machines are combined, and the class that receives the majority of “votes” (i.e., the class predicted by the majority of the learning machines) is the class predicted by the overall ensemble [158]. In the literature, a plethora of terms other than ensembles has been used, such as fusion, combination, aggregation, and committee, to indicate sets of learning machines that work together to solve a machine learning problem [19,40,56,66,99,108,123], but in this chapter we maintain the term ensemble in its widest meaning, in order to include the whole range of combination methods. Nowadays, ensemble methods represent one of the main current research lines in machine learning [48,116], and the interest of the research community on ensemble methods is witnessed by conferences and workshops specifically devoted to ensembles, first of all the multiple classifier systems (MCS) conference organized by Roli, Kittler, Windeatt, and other researchers of this area [14,62,85,149,173]. Several theories have been

  5. Simulation method for cardiac stroke volume estimation by intracardiac electrical impedance measurement.

    Science.gov (United States)

    Barak, C; Leviatan, Y; Inbar, G F; Hoekstein, K N

    1992-09-01

    Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model. The behaviour of the estimation is examined with respect to the electrode configuration on the catheter and to catheter location with respect to the ventricle walls. Cardiac stroke volume estimation was found to be robust to catheter location generating a 10 per cent error for an offset of 40 per cent of the catheter from the chamber axis and rotation of 20 degrees with respect to the axis. The electrode configuration has a dominant effect on the sensitivity and accuracy of the estimation. Certain configurations gave high accuracy, whereas in others high sensitivity was found with lower accuracy. This led to the conclusion that the electrode configuration should be carefully chosen according to the desired criteria.

  6. Statistical methods

    CERN Document Server

    Szulc, Stefan

    1965-01-01

    Statistical Methods provides a discussion of the principles of the organization and technique of research, with emphasis on its application to the problems in social statistics. This book discusses branch statistics, which aims to develop practical ways of collecting and processing numerical data and to adapt general statistical methods to the objectives in a given field.Organized into five parts encompassing 22 chapters, this book begins with an overview of how to organize the collection of such information on individual units, primarily as accomplished by government agencies. This text then

  7. Sieve methods

    CERN Document Server

    Halberstam, Heine

    2011-01-01

    Derived from the techniques of analytic number theory, sieve theory employs methods from mathematical analysis to solve number-theoretical problems. This text by a noted pair of experts is regarded as the definitive work on the subject. It formulates the general sieve problem, explores the theoretical background, and illustrates significant applications.""For years to come, Sieve Methods will be vital to those seeking to work in the subject, and also to those seeking to make applications,"" noted prominent mathematician Hugh Montgomery in his review of this volume for the Bulletin of the Ameri

  8. Spectral Methods

    CERN Document Server

    Shen, Jie; Wang, Li-Lian

    2011-01-01

    Along with finite differences and finite elements, spectral methods are one of the three main methodologies for solving partial differential equations on computers. This book provides a detailed presentation of basic spectral algorithms, as well as a systematical presentation of basic convergence theory and error analysis for spectral methods. Readers of this book will be exposed to a unified framework for designing and analyzing spectral algorithms for a variety of problems, including in particular high-order differential equations and problems in unbounded domains. The book contains a large

  9. Statistical methods

    CERN Document Server

    Freund, Rudolf J; Wilson, William J

    2010-01-01

    Statistical Methods, 3e provides students with a working introduction to statistical methods offering a wide range of applications that emphasize the quantitative skills useful across many academic disciplines. This text takes a classic approach emphasizing concepts and techniques for working out problems and intepreting results. The book includes research projects, real-world case studies, numerous examples and data exercises organized by level of difficulty. This text requires that a student be familiar with algebra. New to this edition: NEW expansion of exercises a

  10. Evaluation of alpha7 nicotinic acetylcholine receptor agonists and positive allosteric modulators using the parallel oocyte electrophysiology test station.

    Science.gov (United States)

    Malysz, John; Grønlien, Jens H; Timmermann, Daniel B; Håkerud, Monika; Thorin-Hagene, Kirsten; Ween, Hilde; Trumbull, Jonathan D; Xiong, Yongli; Briggs, Clark A; Ahring, Philip K; Dyhring, Tino; Gopalakrishnan, Murali

    2009-08-01

    Neuronal acetylcholine receptors (nAChRs) of the alpha7 subtype are ligand-gated ion channels that are widely distributed throughout the central nervous system and considered as attractive targets for the treatment of various neuropsychiatric and neurodegenerative diseases. Both agonists and positive allosteric modulators (PAMs) are being developed as means to enhance the function of alpha7 nAChRs. The in vitro characterization of alpha7 ligands, including agonists and PAMs, relies on multiple technologies, but only electrophysiological measurements assess the channel activity directly. Traditional electrophysiological approaches utilizing two-electrode voltage clamp or patch clamp in isolated cells have very low throughput to significantly impact drug discovery. Abbott (Abbott Park, IL) has developed a two-electrode voltage clamp-based system, the Parallel Oocyte Electrophysiology Test Station (POETs()), that allows for the investigation of ligand-gated ion channels such as alpha7 nAChRs in a higher-throughput manner. We describe the utility of this technology in the discovery of selective alpha7 agonists and PAMs. With alpha7 agonists, POETs experiments involved both single- and multiple-point concentration-response testing revealing diverse activation profiles (zero efficacy desensitizing, partial, and full agonists). In the characterization of alpha7 PAMs, POETs testing has served as a reliable primary or secondary screen identifying compounds that fall into distinct functional types depending on the manner in which current potentiation occurred. Type I PAMs (eg, genistein, NS1738, and 5-hydroxyindole) increase predominantly the peak amplitude response, type II PAMs affect the peak current and current decay (eg, PNU-120,596 and 4-(naphthalen-1-yl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide), and anothertype slowing the current decay kinetics in the absence of increases in the peak current. In summary, POETs technology allows for significant

  11. Digital Methods

    NARCIS (Netherlands)

    Rogers, R.

    2013-01-01

    In Digital Methods, Richard Rogers proposes a methodological outlook for social and cultural scholarly research on the Web that seeks to move Internet research beyond the study of online culture. It is not a toolkit for Internet research, or operating instructions for a software package; it deals wi

  12. Characterization methods

    Energy Technology Data Exchange (ETDEWEB)

    Glass, J.T. [North Carolina State Univ., Raleigh (United States)

    1993-01-01

    Methods discussed in this compilation of notes and diagrams are Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and other surface analysis techniques (auger electron spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, and scanning tunnelling microscopy). A comparative evaluation of different techniques is performed. In-vacuo and in-situ analyses are described.

  13. Radiofluorination method

    DEFF Research Database (Denmark)

    2014-01-01

    A method of conducting radiofluorination of a substrate, comprising the steps of: (a) contacting an aqueous solution of [18F] fluoride with a polymer supported phosphazene base for sufficient time for trapping of [18F] fluoride on the polymer supported phosphazene base; and (b) contacting...

  14. Contraceptive Methods.

    Science.gov (United States)

    Colquitt, Charlie W; Martin, Tonya S

    2017-02-01

    The prevention of pregnancy remains an important part of the practice of medicine. Contraception can occur at a number of points in the basic reproductive biological process and through a number of contraceptive product options. Pharmacists are health care providers appropriately positioned to assist patients in suitable contraceptive product selection based on their personal situations and lifestyles. This article provides an overview of available products for prevention of pregnancy and associated risks and benefits. Contraceptive products are categorized by their hormonal content and method of action. Hormonal options include oral contraceptive pills, contraceptive patch, implants, injection, intravaginal, and intrauterine devices. Barrier products prevent pregnancy by creating a physical obstacle to the successful fertilization of an egg by sperm. All products and methods are associated with benefits and potential complications that must be considered as patients, and health care providers select the most satisfactory option.

  15. Numerical methods

    CERN Document Server

    Dahlquist, Germund

    2003-01-01

    ""Substantial, detailed and rigorous . . . readers for whom the book is intended are admirably served."" - MathSciNet (Mathematical Reviews on the Web), American Mathematical Society.Practical text strikes fine balance between students' requirements for theoretical treatment and needs of practitioners, with best methods for large- and small-scale computing. Prerequisites are minimal (calculus, linear algebra, and preferably some acquaintance with computer programming). Text includes many worked examples, problems, and an extensive bibliography.

  16. Hodgkin-Huxley revisited: reparametrization and identifiability analysis of the classic action potential model with approximate Bayesian methods.

    Science.gov (United States)

    Daly, Aidan C; Gavaghan, David J; Holmes, Chris; Cooper, Jonathan

    2015-12-01

    As cardiac cell models become increasingly complex, a correspondingly complex 'genealogy' of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models.

  17. Analysis and fabrication of micro scale self-terminated electrochemical growth by a pressure-driven method

    Science.gov (United States)

    Soltani, Fatemeh; Wlasenko, Alex; Steeves, Geoff

    2010-03-01

    A self-terminated electrochemical method was used to fabricate microscopic-scale contacts between two Au electrodes in a microfluidic channel. The conductance of contacts varies in a stepwise fashion with a tendency to quantize near the integer multiples of the conductance quantum (G0). The mechanism works by a pressure-driven flow parallel with a pair of Au electrodes with a gap in order of micron in an electrolyte of HCl. When applying a bias voltage between electrodes, metal atoms are etched off the anode and deposited onto the cathode. Consequently, the gap decreases to the atomic scale and then completely closed as the two electrodes form a contact. The electrochemical fabrication approach introduces large variance in the formation and location of individual junctions. Controlling this process will enable the precise positioning of reproducible geometries into nano-electronic devices. To investigate the high speed behavior of a QPC, it can be integrated with a transmission line structure patterned on a photoconductive GaAs substrate. The nonlinear conductance of the QPC (due to the finite density of states of the conductors) can be examined and compared with recent theoretical studies. Samples are fabricated in situ using an electrochemical procedure to produce QPCs along the transmission line structure. This method may provide insight into Terahertz Optoelectronic devices and ultrafast communication systems.

  18. Methods for specific electrode resistance measurement during transcranial direct current stimulation.

    Science.gov (United States)

    Khadka, Niranjan; Rahman, Asif; Sarantos, Chris; Truong, Dennis Q; Bikson, Marom

    2015-01-01

    Monitoring of electrode resistance during tDCS is considered important for tolerability and safety. Conventional resistance measurement methods do not isolate individual electrode resistance and for HD-tDCS devices, cross talk across electrodes makes concurrent resistance monitoring unreliable. We propose a novel method to monitor individual electrode resistance during tDCS, using a super-position of direct current with a test-signal (low intensity and low frequency sinusoids with electrode-specific frequencies) and a sentinel electrode (not used for DC). We developed and solved lumped-parameter models of tDCS electrodes with or without a sentinel electrode to validate this methodology. Assumptions were tested and parameterized in participants using forearm stimulation combining tDCS (2 mA) and test-signals (38 and 76 μA pk-pk at 1 Hz, 10 Hz, & 100 Hz) and an in vitro test (creating electrode failure modes). DC and AC component voltages across the electrodes were compared and participants were asked to rate subjective pain. A sentinel electrode is required to isolate electrode resistance in a two-electrode tDCS system. Cross talk aggravated with electrode proximity and resistance mismatch in multi-electrode resistance tracking could be corrected using proposed approaches. Average voltage and pain scores were not significantly different across test current intensities and frequencies. Using our developed method, a test signal can predict DC electrode resistance. Since unique test frequencies can be used at each tDCS electrode, specific electrode resistance can be resolved for any number of stimulating channels - a process made still more robust by the use of a sentinel electrode. Published by Elsevier Inc.

  19. Physiological concentrations of zinc reduce taurine-activated GlyR responses to drugs of abuse

    Science.gov (United States)

    Kirson, Dean; Cornelison, Garrett L.; Philpo, Ashley E.; Todorovic, Jelena; Mihic, S. John

    2013-01-01

    Taurine is an endogenous ligand acting on glycine receptors in many brain regions, including the hippocampus, prefrontal cortex, and nucleus accumbens (nAcc). These areas also contain low concentrations of zinc, which is known to potentiate glycine receptor responses. Despite an increasing awareness of the role of the glycine receptor in the rewarding properties of drugs of abuse, the possible interactions of these compounds with zinc has not been thoroughly addressed. Two-electrode voltage-clamp electrophysiological experiments were performed on α1, α2 α1β and a2β glycine receptors expressed in Xenopus laevis oocytes. The effects of zinc alone, and zinc in combination with other positive modulators on the glycine receptor, were investigated when activated by the full agonist glycine versus the partial agonist taurine. Low concentrations of zinc enhanced responses of maximally-effective concentrations of taurine but not glycine. Likewise, chelation of zinc from buffers decreased responses of taurine- but not glycine-mediated currents. Potentiating concentrations of zinc decreased ethanol, isoflurane, and toluene enhancement of maximal taurine currents with no effects on maximal glycine currents. Our findings suggest that the concurrence of high concentrations of taurine and low concentrations of zinc attenuate the effects of additional modulators on the glycine receptor, and that these conditions are more representative of in vivo functioning than effects seen when these modulators are applied in isolation. PMID:23973295

  20. Physiological concentrations of zinc reduce taurine-activated GlyR responses to drugs of abuse.

    Science.gov (United States)

    Kirson, Dean; Cornelison, Garrett L; Philpo, Ashley E; Todorovic, Jelena; Mihic, S John

    2013-12-01

    Taurine is an endogenous ligand acting on glycine receptors in many brain regions, including the hippocampus, prefrontal cortex, and nucleus accumbens (nAcc). These areas also contain low concentrations of zinc, which is known to potentiate glycine receptor responses. Despite an increasing awareness of the role of the glycine receptor in the rewarding properties of drugs of abuse, the possible interactions of these compounds with zinc has not been thoroughly addressed. Two-electrode voltage-clamp electrophysiological experiments were performed on α1, α2 α1β and α2β glycine receptors expressed in Xenopus laevis oocytes. The effects of zinc alone, and zinc in combination with other positive modulators on the glycine receptor, were investigated when activated by the full agonist glycine versus the partial agonist taurine. Low concentrations of zinc enhanced responses of maximally-effective concentrations of taurine but not glycine. Likewise, chelation of zinc from buffers decreased responses of taurine- but not glycine-mediated currents. Potentiating concentrations of zinc decreased ethanol, isoflurane, and toluene enhancement of maximal taurine currents with no effects on maximal glycine currents. Our findings suggest that the concurrence of high concentrations of taurine and low concentrations of zinc attenuate the effects of additional modulators on the glycine receptor, and that these conditions are more representative of in vivo functioning than effects seen when these modulators are applied in isolation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Inhibition of human Kv3.1 current expressed in Xenopus oocytes by the toxic venom fraction of Androctonus australis hector.

    Science.gov (United States)

    Cheikh, Amani; Benkhalifa, Rym; Landoulsi, Zied; Chatti, Imen; Ayeb, Mohamed El

    2014-11-01

    AahG50, the toxic fraction of Androctonus australis hector venom, was studied on human Kv3.1 channels activation, stably expressed in Xenopus oocytes using the two-electrode voltage clamp technique. AahG50 reduced Kv3.1 currents in a reversible concentration-dependent manner, with an IC50 value and a Hill coefficient of 40.4 ± 0.2 μg/ml and 1.3 ± 0.05, respectively. AahG50 inhibited IKv3.1 without modifying the current activation kinetics. The AahG50-induced inhibition of Kv3.1 channels was voltage-dependent, with a gradual increase at lower concentrations and over the voltage range of channels opening. However, at higher concentrations, the inhibition exhibited voltage dependence only in the first range of channels opening from -20 to +10 mV, but demonstrates a low degree of voltage-dependence when channels are fully activated. In the literature, toxins have previously been isolated from AahG50, KAaH1 and KAaH2 and were reported not to have any effect on IKv3.1. The present article's findings suggest that AahG50 may contain a peptidic component active on Kv3.1 channels, which inhibits IKv3.1 in a selective manner.

  2. Serrumab: a novel human single chain-fragment antibody with multiple scorpion toxin-neutralizing capacities.

    Science.gov (United States)

    Pucca, Manuela Berto; Cerni, Felipe Augusto; Peigneur, Steve; Arantes, Eliane Candiani; Tytgat, Jan; Barbosa, José Elpidio

    2014-01-01

    In Brazil, scorpion envenomation is an important public health problem. The yellow scorpion, Tityus serrulatus (Ts), is considered the most dangerous species in the country, being responsible for the most severe clinical cases of envenomation. Currently, the administration of serum produced in horses is recognized and used as a treatment for accidents with scorpions. However, horse herds' maintenance is costly and the antibodies are heterologous, which can cause anaphylaxis and Serum Sickness. In the present work, a human monoclonal fragment antibody, Serrumab, has been analysed. Toxin neutralizing effects of Serrumab were evaluated using a two-electrode voltage-clamp technique. The results show that Serrumab presented a high neutralizing effect against Ts β-toxins (Ts1, 43.2% and Ts2, 68.8%) and none or low neutralizing effect against α-toxins (Ts3, 0% and Ts5, 10%). Additional experiments demonstrated that Serrumab was also able to neutralize the action of toxins from other scorpion genus (Css II, 45.96% and Lqh III, 100%/β- and α-toxins, respectively). This work indicated that Serrumab is able to neutralize many toxins in Ts venom, and could being considered as a neutralizing antibody for formulating a human anti-scorpion serum in Brazil. Additionally, this work demonstrated that Serrumab could neutralize different toxins from distinct scorpion genus. All these results reinforce the idea that Serrumab is a scFv antibody with multiple neutralizing capacities and a promising candidate for inclusion in scorpion anti-venoms against different genera.

  3. The pharmacology of spontaneously open alpha 1 beta 3 epsilon GABA A receptor-ionophores.

    Science.gov (United States)

    Maksay, Gábor; Thompson, Sally A; Wafford, Keith A

    2003-06-01

    Human alpha(1)beta(3) epsilon GABA(A) receptors were expressed in Xenopus oocytes and examined using the conventional two-electrode voltage-clamp technique and compared to alpha(1)beta(3)gamma(2) receptors. The effects of several GABA(A) agonists were studied, and the allosteric modulation of the channel by a number of GABAergic modulators investigated. The presence of the epsilon subunit increased the potency and efficacy of direct activation by partial GABA(A) agonists (piperidine-4-sulphonic acid and thio-4-PIOL), pentobarbital and neuro-steroids. Direct activation by 3-hydroxylated neurosteroids was restricted to 3alpha epimers, while chirality at C5 was indifferent. The 3beta-sulfate esters of pregnenolone and dehydroepiandrosterone inhibited the spontaneous currents with efficacies higher, while bicuculline methiodide and SR 95531 did so lower than picrotoxin and TBPS. Furosemide, fipronil, triphenylcyanoborate and Zn(2+) blocked the spontaneous currents of alpha(1)beta(3) epsilon receptors with different efficacies. Flunitrazepam and 4'-chlorodiazepam inhibited the spontaneous currents with micromolar potencies. In conclusion, spontaneously active alpha(1)beta(3) epsilon GABA(A) receptors can be potentiated and blocked by GABAergic agents within a broad range of efficacy.

  4. Menthol binding and inhibition of α7-nicotinic acetylcholine receptors.

    Science.gov (United States)

    Ashoor, Abrar; Nordman, Jacob C; Veltri, Daniel; Yang, Keun-Hang Susan; Al Kury, Lina; Shuba, Yaroslav; Mahgoub, Mohamed; Howarth, Frank C; Sadek, Bassem; Shehu, Amarda; Kabbani, Nadine; Oz, Murat

    2013-01-01

    Menthol is a common compound in pharmaceutical and commercial products and a popular additive to cigarettes. The molecular targets of menthol remain poorly defined. In this study we show an effect of menthol on the α7 subunit of the nicotinic acetylcholine (nACh) receptor function. Using a two-electrode voltage-clamp technique, menthol was found to reversibly inhibit α7-nACh receptors heterologously expressed in Xenopus oocytes. Inhibition by menthol was not dependent on the membrane potential and did not involve endogenous Ca(2+)-dependent Cl(-) channels, since menthol inhibition remained unchanged by intracellular injection of the Ca(2+) chelator BAPTA and perfusion with Ca(2+)-free bathing solution containing Ba(2+). Furthermore, increasing ACh concentrations did not reverse menthol inhibition and the specific binding of [(125)I] α-bungarotoxin was not attenuated by menthol. Studies of α7- nACh receptors endogenously expressed in neural cells demonstrate that menthol attenuates α7 mediated Ca(2+) transients in the cell body and neurite. In conclusion, our results suggest that menthol inhibits α7-nACh receptors in a noncompetitive manner.

  5. The effects of S4 segments on the voltage-dependence of inactivation for Cav3.1 calcium channels

    Institute of Scientific and Technical Information of China (English)

    LI JunYing

    2007-01-01

    T-type calcium channels exhibit fast voltage-dependent inactivation,for which the underlying structure-function relationship still remains unclear.To investigate the roles of S4 segments in voltage-dependent inactivation of T-type calcium channels,we created S4 replacement chimeras between Cav3.1 calcium channels(fast voltage-dependent inactivation)and Cav1.2 calcium channels(little oltage-dependent inactivation)by replacing S4s in Cav3.1 with the corresponding regions in Cav1.2.Wild type and chimeric channels were expressed in Xenopus oocytes and channel currents were recorded with two-electrode voltage-clamp.We showed that replacing S4 region in domain I shifted voltage-dependence for inactivation of Cav3.1 to the left,and the V0.5 inact and kinact value were significantly changed.However replacing S4s in domains Ⅱ-Ⅳ had no effects on the voltage-dependent inactivation properties.These results suggest that the roles of S4 segments in domains Ⅰ-Ⅳ are different,and S4 in domain I is likely to be involved in voltage-dependent Inactivation process.Its movement during membrane depolarization may trigger a conformational change in the inactivation gate.

  6. Menthol binding and inhibition of α7-nicotinic acetylcholine receptors.

    Directory of Open Access Journals (Sweden)

    Abrar Ashoor

    Full Text Available Menthol is a common compound in pharmaceutical and commercial products and a popular additive to cigarettes. The molecular targets of menthol remain poorly defined. In this study we show an effect of menthol on the α7 subunit of the nicotinic acetylcholine (nACh receptor function. Using a two-electrode voltage-clamp technique, menthol was found to reversibly inhibit α7-nACh receptors heterologously expressed in Xenopus oocytes. Inhibition by menthol was not dependent on the membrane potential and did not involve endogenous Ca(2+-dependent Cl(- channels, since menthol inhibition remained unchanged by intracellular injection of the Ca(2+ chelator BAPTA and perfusion with Ca(2+-free bathing solution containing Ba(2+. Furthermore, increasing ACh concentrations did not reverse menthol inhibition and the specific binding of [(125I] α-bungarotoxin was not attenuated by menthol. Studies of α7- nACh receptors endogenously expressed in neural cells demonstrate that menthol attenuates α7 mediated Ca(2+ transients in the cell body and neurite. In conclusion, our results suggest that menthol inhibits α7-nACh receptors in a noncompetitive manner.

  7. Pressure-selective modulation of NMDA receptor subtypes may reflect 3D structural differences

    Directory of Open Access Journals (Sweden)

    Amir eMor

    2012-09-01

    Full Text Available Professional deep-water divers exposed to high pressure (HP above 1.1 MPa suffer from High Pressure Neurological Syndrome (HPNS, which is associated with CNS hyperexcitability. We have previously reported that HP augments N-methyl-D-aspartate receptor (NMDAR synaptic responses, increases neuronal excitability, and potentially causes irreversible neuronal damage. We now report that HP (10.1 MPa differentially affects eight specific NMDAR subtypes. GluN1(1a or 1b was co-expressed with one of the four GluN2(A-D subunits in Xenopus laevis oocytes. HP increased ionic currents (measured by two electrode voltage clamps of one subtype, reduced the current in four others, and did not affect the current in the remaining three. 3D theoretical modeling was aimed at revealing specific receptor domains involved with HP selectivity. In light of the information on the CNS spatial distribution of the different NMDAR subtypes, we conclude that the NMDAR’s diverse responses to HP may lead to selective HP effects on different brain regions. These discoveries call for further and more specific investigation of deleterious HP effects and suggest the need for a re-evaluation of deep-diving safety guidelines.

  8. Oxaliplatin neurotoxicity – no general ion channel surface-charge effect

    Directory of Open Access Journals (Sweden)

    Ehrsson Hans

    2009-01-01

    Full Text Available Abstract Background Oxaliplatin is a platinum-based chemotherapeutic drug. Neurotoxicity is the dose-limiting side effect. Previous investigations have reported that acute neurotoxicity could be mediated via voltage-gated ion channels. A possible mechanism for some of the effects is a modification of surface charges around the ion channel, either because of chelation of extracellular Ca2+, or because of binding of a charged biotransformation product of oxaliplatin to the channel. To elucidate the molecular mechanism, we investigated the effects of oxaliplatin and its chloride complex [Pt(dachoxCl]- on the voltage-gated Shaker K channel expressed in Xenopus oocytes. The recordings were made with the two-electrode and the cut-open oocyte voltage clamp techniques. Conclusion To our surprise, we did not see any effects on the current amplitudes, on the current time courses, or on the voltage dependence of the Shaker wild-type channel. Oxaliplatin is expected to bind to cysteines. Therefore, we explored if there could be a specific effect on single (E418C and double-cysteine (R362C/F416C mutated Shaker channels previously shown to be sensitive to cysteine-specific reagents. Neither of these channels were affected by oxaliplatin. The clear lack of effect on the Shaker K channel suggests that oxaliplatin or its monochloro complex has no general surface-charge effect on the channels, as has been suggested before, but rather a specific effect to the channels previously shown to be affected.

  9. Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH

    DEFF Research Database (Denmark)

    Søgaard, Rikke; Alsterfjord, Magnus; Macaulay, Nanna

    2009-01-01

    It is unclear how ammonia is transported by proteins from the Amt/Mep/Rh superfamily. We investigated this for the ammonium transporter TaAMT1;1 from wheat expressed in Xenopus oocytes by two-electrode voltage clamp and radio-labeled uptakes. Inward currents were activated by NH (4......) (+) or methylammonium ions (MeA(+)). Importantly, currents increased fivefold when the external pH was decreased from 7.4 to 5.5; this type of pH dependence is unique and is a strong indication of NH (4) (+) or MeA(+) transport. This was confirmed by the close correlation between the uptake of radio-labeled Me......A(+) and MeA(+)-induced currents. Homology models of members of the Amt/Mep/Rh superfamily exhibited major divergences in their cytoplasmic regions. A point mutation in this region of TaAMT1;1 abolished the pH sensitivity and decreased the apparent affinities for NH (4) (+) and MeA(+). We suggest a model...

  10. Hyperkalemic periodic paralysis M1592V mutation modifies activation in human skeletal muscle Na+ channel.

    Science.gov (United States)

    Rojas, C V; Neely, A; Velasco-Loyden, G; Palma, V; Kukuljan, M

    1999-01-01

    Mutations in the human skeletal muscle Na+ channel underlie the autosomal dominant disease hyperkalemic periodic paralysis (HPP). Muscle fibers from affected individuals exhibit sustained Na+ currents thought to depolarize the sarcolemma and thus inactivate normal Na+ channels. We expressed human wild-type or M1592V mutant alpha-subunits with the beta1-subunit in Xenopus laevis oocytes and recorded Na+ currents using two-electrode and cut-open oocyte voltage-clamp techniques. The most prominent functional difference between M1592V mutant and wild-type channels is a 5- to 10-mV shift in the hyperpolarized direction of the steady-state activation curve. The shift in the activation curve for the mutant results in a larger overlap with the inactivation curve than that observed for wild-type channels. Accordingly, the current through M1592V channels displays a larger noninactivating component than does that through wild-type channels at membrane potentials near -40 mV. The functional properties of the M1592V mutant resemble those of the previously characterized HPP T704M mutant. Both clinically similar phenotypes arise from mutations located at a distance from the putative voltage sensor of the channel.

  11. Structural Basis for Ether-a-go-go-Related Gene K+ Channel Subtype-Dependent Activation by Niflumic Acid[S

    Science.gov (United States)

    Fernandez, David; Sargent, John; Sachse, Frank B.; Sanguinetti, Michael C.

    2008-01-01

    Niflumic acid [2-((3-(trifluoromethyl)phenyl)amino)-3-pyridin-ecarboxylic acid, NFA] is a nonsteroidal anti-inflammatory drug that also blocks or modulates the gating of a wide spectrum of ion channels. Here we investigated the mechanism of channel activation by NFA on ether-a-go-go-related gene (ERG) K+ channel subtypes expressed in Xenopus laevis oocytes using two-electrode voltage-clamp techniques. NFA acted from the extracellular side of the membrane to differentially enhance ERG channel currents independent of channel state. At 1 mM, NFA shifted the half-point for activation by −6, −18, and −11 mV for ERG1, ERG2, and ERG3 channels, respectively. The half-point for channel inactivation was shifted by +5 to +9 mV by NFA. The structural basis for the ERG subtype-specific response to NFA was explored with chimeric channels and site-directed mutagenesis. The molecular determinants of enhanced sensitivity of ERG2 channels to NFA were isolated to an Arg and a Thr triplet in the extracellular S3-S4 linker. PMID:18218980

  12. Niflumic acid activates additional currents of the human glial L-glutamate transporter EAAT1 in a substrate-dependent manner.

    Science.gov (United States)

    Takahashi, Kanako; Ishii-Nozawa, Reiko; Takeuchi, Koichi; Nakazawa, Ken; Sekino, Yuko; Sato, Kaoru

    2013-01-01

    The astrocytic L-glutamate (L-Glu) transporter EAAT1 participates in the removal of L-Glu from the synaptic cleft and maintenance of non-toxic concentrations in the extracellular fluid. We have shown that niflumic acid (NFA), a non-steroidal anti-inflammatory drug (NSAIDs), alters L-Glu-induced EAAT1 currents in a voltage-dependent manner using the two-electrode voltage clamp technique in Xenopus oocytes expressing EAAT1. In this study, we characterised the effects of NFA on each type of ion-flux through EAAT1. NFA modulated currents induced by both L-Glu and L-aspartate (L-Asp) in a voltage-dependent manner. Ion-substitution experiments revealed that the activation of additional H(+) conductance was involved in the modulation of currents induced by L-Asp and L-Glu, but Cl(-) was involved only with the L-Asp currents. NFA activated additional currents of EAAT1 in a substrate-dependent manner.

  13. Structural basis for ether-a-go-go-related gene K+ channel subtype-dependent activation by niflumic acid.

    Science.gov (United States)

    Fernandez, David; Sargent, John; Sachse, Frank B; Sanguinetti, Michael C

    2008-04-01

    Niflumic acid [2-((3-(trifluoromethyl)phenyl)amino)-3-pyridinecarboxylic acid, NFA] is a nonsteroidal anti-inflammatory drug that also blocks or modulates the gating of a wide spectrum of ion channels. Here we investigated the mechanism of channel activation by NFA on ether-a-go-go-related gene (ERG) K(+) channel subtypes expressed in Xenopus laevis oocytes using two-electrode voltage-clamp techniques. NFA acted from the extracellular side of the membrane to differentially enhance ERG channel currents independent of channel state. At 1 mM, NFA shifted the half-point for activation by -6, -18, and -11 mV for ERG1, ERG2, and ERG3 channels, respectively. The half-point for channel inactivation was shifted by +5 to +9 mV by NFA. The structural basis for the ERG subtype-specific response to NFA was explored with chimeric channels and site-directed mutagenesis. The molecular determinants of enhanced sensitivity of ERG2 channels to NFA were isolated to an Arg and a Thr triplet in the extracellular S3-S4 linker.

  14. The pungent substances piperine, capsaicin, 6-gingerol and polygodial inhibit the human two-pore domain potassium channels TASK-1, TASK-3 and TRESK.

    Science.gov (United States)

    Beltrán, Leopoldo R; Dawid, Corinna; Beltrán, Madeline; Gisselmann, Guenter; Degenhardt, Katharina; Mathie, Klaus; Hofmann, Thomas; Hatt, Hanns

    2013-01-01

    For a long time, the focus of trigeminal chemoperception has rested almost exclusively on TRP channels. However, two-pore domain (K2P) potassium channels have recently been identified as targets for substances associated with typical trigeminal sensations, such as numbing and tingling. In addition, they have been shown to be modulated by several TRP agonists. We investigated whether the pungent substances piperine, capsaicin, 6-gingerol and polygodial have an effect on human K2P channels. For this purpose, we evaluated the effects of these pungent substances on both wild-type and mutant K2P channels by means of two-electrode voltage-clamp experiments using Xenopus laevis oocytes. All four pungent substances were found to inhibit the basal activity of TASK-1 (K2P 3.1), TASK-3 (K2P 9.1), and TRESK (K2P 18.1) channels. This inhibitory effect was dose-dependent and, with the exception of polygodial on TASK-1, fully reversible. However, only piperine exhibited an IC50 similar to its reported EC50 on TRP channels. Finally, we observed for TASK-3 that mutating H98 to E markedly decreased the inhibition induced by piperine, capsaicin, and 6-gingerol, but not by polygodial. Our data contribute to the relatively sparse knowledge concerning the pharmacology of K2P channels and also raise the question of whether K2P channels could be involved in the pungency perception of piperine.

  15. The pungent substances piperine, capsaicin, 6-gingerol and polygodial inhibit the human two-pore domain potassium channels TASK-1, TASK-3 and TRESK

    Directory of Open Access Journals (Sweden)

    Leopoldo Raul Beltran

    2013-11-01

    Full Text Available For a long time, the focus of trigeminal chemoperception has rested almost exclusively on TRP channels. However, two-pore domain (K2P potassium channels have recently been identified as targets for substances associated with typical trigeminal sensations, such as numbing and tingling. In addition, they have been shown to be modulated by several TRP agonists. We investigated whether the pungent substances piperine, capsaicin, 6-gingerol and polygodial have an effect on human K2P channels. For this purpose, we evaluated the effects of these pungent substances on both wild-type and mutant K2P channels by means of two-electrode voltage-clamp experiments using Xenopus laevis oocytes. All four pungent substances were found to inhibit the basal activity of TASK-1 (K2P 3.1, TASK-3 (K2P 9.1, and TRESK (K2P 18.1 channels. This inhibitory effect was dose-dependent and, with the exception of polygodial on TASK-1, fully reversible. However, only piperine exhibited an IC50 similar to its reported EC50 on TRP channels. Finally, we observed for TASK-3 that mutating H98 to E markedly decreases the inhibition induced by piperine, capsaicin, and 6-gingerol, but not by polygodial. Our data contribute to the relatively sparse knowledge concerning the pharmacology of K2P channels and also raise the question of whether K2P channels could be involved in the pungency perception of piperine.

  16. Chinese-scorpion (Buthus martensi Karsch) toxin BmK alphaIV, a novel modulator of sodium channels: from genomic organization to functional analysis.

    Science.gov (United States)

    Chai, Zhi-Fang; Zhu, Mang-Mang; Bai, Zhan-Tao; Liu, Tong; Tan, Miao; Pang, Xue-Yan; Ji, Yong-Hua

    2006-11-01

    In the present study, BmK alphaIV, a novel modulator of sodium channels, was cloned from venomous glands of the Chinese scorpion (Buthus martensi Karsch) and expressed successfully in Escherichia coli. The BmK alphaIV gene is composed of two exons separated by a 503 bp intron. The mature polypeptide contains 66 amino acids. BmK alphaIV has potent toxicity in mice and cockroaches. Surface-plasmon-resonance analysis found that BmK alphaIV could bind to both rat cerebrocortical synaptosomes and cockroach neuronal membranes, and shared similar binding sites on sodium channels with classical AaH II (alpha-mammal neurotoxin from the scorpion Androctonus australis Hector), BmK AS (beta-like neurotoxin), BmK IT2 (the depressant insect-selective neurotoxin) and BmK abT (transitional neurotoxin), but not with BmK I (alpha-like neurotoxin). Two-electrode voltage clamp recordings on rNav1.2 channels expressed in Xenopus laevis oocytes revealed that BmK alphaIV increased the peak amplitude and prolonged the inactivation phase of Na+ currents. The structural and pharmacological properties compared with those of other scorpion alpha-toxins suggests that BmK alphaIV represents a novel subgroup or functional hybrid of alpha-toxins and might be an evolutionary intermediate neurotoxin for alpha-toxins.

  17. Functional characterization of a transition metal ion transporter, OsZIP6 from rice (Oryza sativa L.).

    Science.gov (United States)

    P G, Kavitha; Kuruvilla, Sam; Mathew, M K

    2015-12-01

    Micronutrients are important for the growth and development of plants, which deploy families of transporters for their uptake and distribution. We have functionally characterized a novel transition metal ion transporter from rice, OsZIP6 (Oryza sativa zinc regulated transporter, iron regulated transporter-like protein 6). The transporter was found to be transcriptionally activated in shoot and root tissues in response to deficiency in Fe(2+), Zn(2+) and Mn(2+). OsZIP6 was expressed in Xenopus laevis oocytes, where currents were observed on addition of Co(2+), Fe(2+) and Cd(2+) but not Zn(2+), Mn(2+) and Ni(2+). This substrate range for OsZIP6, identified using two-electrode voltage clamp electrophysiology was confirmed by atomic absorption spectroscopy. Ion transport by OsZIP6 was found to be pH dependent and enhanced transport was observed at acidic pH. Radioisotope uptake suggested that Co(2+) competitively inhibits Fe(2+) uptake by OsZIP6. Identification and characterization of ZIP family members from crop plants will contribute to an understanding of nutrient mineral homeostasis in these plants.

  18. Covalent Trapping of Methyllycaconitine at the α4-α4 Interface of the α4β2 Nicotinic Acetylcholine Receptor

    DEFF Research Database (Denmark)

    Absalom, Nathan L; Quek, Gracia; Lewis, Trevor M

    2013-01-01

    ), but their pharmacological profiles are not fully understood. Methyllycaconitine (MLA) is known to be an antagonist of nAChRs. Using the two-electrode voltage clamp technique and α4β2 nAChRs in the Xenopus oocyte expression system, we demonstrate that inhibition by MLA occurs via two different mechanisms; that is, a direct...... competitive antagonism and an apparently insurmountable mechanism that only occurs after preincubation with MLA. We hypothesized an additional MLA binding site in the α4-α4 interface that is unique to this stoichiometry. To prove this, we covalently trapped a cysteine-reactive MLA analog at an α4β2 receptor...... containing an α4(D204C) mutation predicted by homology modeling to be within reach of the reactive probe. We demonstrate that covalent trapping results in irreversible reduction of ACh-elicited currents in the (α4)3(β2)2 stoichiometry, indicating that MLA binds to the α4-α4 interface of the (α4)3(β2...

  19. Two spatially and temporally distinct Ca(2+) signals convey Arabidopsis thaliana responses to K(+) deficiency.

    Science.gov (United States)

    Behera, Smrutisanjita; Long, Yu; Schmitz-Thom, Ina; Wang, Xue-Ping; Zhang, Chunxia; Li, Hong; Steinhorst, Leonie; Manishankar, Prabha; Ren, Xiao-Ling; Offenborn, Jan Niklas; Wu, Wei-Hua; Kudla, Jörg; Wang, Yi

    2017-01-01

    In plants, potassium (K(+) ) homeostasis is tightly regulated and established against a concentration gradient to the environment. Despite the identification of Ca(2+) -regulated kinases as modulators of K(+) channels, the immediate signaling and adaptation mechanisms of plants to low-K(+) conditions are only partially understood. To assess the occurrence and role of Ca(2+) signals in Arabidopsis thaliana roots, we employed ratiometric analyses of Ca(2+) dynamics in plants expressing the Ca(2+) reporter YC3.6 in combination with patch-clamp analyses of root cells and two-electrode voltage clamp (TEVC) analyses in Xenopus laevis oocytes. K(+) deficiency triggers two successive and distinct Ca(2+) signals in roots exhibiting spatial and temporal specificity. A transient primary Ca(2+) signature arose within 1 min in the postmeristematic stelar tissue of the elongation zone, while a secondary Ca(2+) response occurred after several hours as sustained Ca(2+) elevation in defined tissues of the elongation and root hair differentiation zones. Patch-clamp and TEVC analyses revealed Ca(2+) dependence of the activation of the K(+) channel AKT1 by the CBL1-CIPK23 Ca(2+) sensor-kinase complex. Together, these findings identify a critical role of cell group-specific Ca(2+) signaling in low K(+) responses and indicate an essential and direct role of Ca(2+) signals for AKT1 K(+) channel activation in roots. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  20. Differential effects of five ‘classical’ scorpion β-toxins on rNav1.2a and DmNav1 provide clues on species-selectivity

    Science.gov (United States)

    Bosmans, Frank; Martin-Eauclaire, Marie-France; Tytgat, Jan

    2007-01-01

    In general, scorpion β-toxins have been well examined. However, few in-depth studies have been devoted to species selectivity and affinity comparisons on the different voltage-activated Na+ channels since they have become available as cloned channels that can be studied in heterologous expression systems. As a result, their classification is largely historical and dates from early in vivo experiments on mice and cockroach and fly larvae. In this study, we aimed to provide an updated overview of selectivity and affinity of scorpion β-toxins towards voltage-activated Na+ channels of vertebrates or invertebrates. As pharmacological tools, we used the classic β-toxins AaHIT, Css II, Css IV, Css VI and Ts VII and tested them on the neuronal vertebrate voltage-activated Na+ channel, rNav1.2a. For comparison, its invertebrate counterpart, DmNav1, was also tested. Both these channels were expressed in Xenopus laevis oocytes and the currents measured with the two-electrode voltage-clamp technique. We supplemented this data with several binding displacement studies on rat brain synaptosomes. The results lead us to propose a general classification and a novel nomenclature of scorpion β-toxins based on pharmacological activity. PMID:17118417

  1. Effects of penicillin on procaine-elicited bursts of potential in central neuron of snail, Achatina fulica.

    Science.gov (United States)

    Chen, Yi-Hung; Lu, Kuan-Ling; Hsiao, Ru-Wan; Lee, Ya-Ling; Tsai, Hong-Chieh; Lin, Chia Hsien; Tsai, Ming-Cheng

    2008-08-01

    Effects of penicillin on changes in procaine-elicited bursts of potential (BoP) were studied in a central neuron (RP4) of snail, Achatina fulica Ferussac. Procaine elicited BoP in the RP4 neuron while penicillin elicited depolarization of the neuron. Penicillin decreased the BoP elicited by procaine in a concentration-dependent manner. The effect of penicillin on the procaine-elicited BoP was not altered in the preparations treated with ascorbate or L-NAME (N-nitro-L-arginine methyl ester). However, the inhibitory effect of penicillin on the procaine-elicited BoP was enhanced with a decrease in extracellular sodium ion. Sodium ion was one of the important ions contributing to the action potential of the neuron. Two-electrode voltage-clamp studies revealed that penicillin decreased the fast sodium inward current of the neuron. It is concluded that penicillin inhibited the BoP elicited by procaine and sodium ion altered the effect of penicillin on procaine-elicited BoP.

  2. Synthesis and pharmacology of glutamate receptor ligands: new isothiazole analogues of ibotenic acid.

    Science.gov (United States)

    Jørgensen, Charlotte G; Clausen, Rasmus P; Hansen, Kasper B; Bräuner-Osborne, Hans; Nielsen, Birgitte; Metzler, Bjørn; Metzler, Birgitte Bjørn; Kehler, Jan; Krogsgaard-Larsen, Povl; Madsen, Ulf

    2007-02-07

    The naturally occurring heterocyclic amino acid ibotenic acid (Ibo) and the synthetic analogue thioibotenic acid (Thio-Ibo) possess interesting but dissimilar pharmacological activity at ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs). Therefore, a series of Thio-Ibo analogues was synthesized. The synthesis included introduction of substituents by Suzuki and Grignard reactions on 4-halogenated 3-benzyloxyisothiazolols, reduction of the obtained alcohols, followed by introduction of the amino acid moiety by use of 2-(N-tert-butoxycarbonylimino)malonic acid diethyl ester. The obtained Thio-Ibo analogues (1, 2a-g) were characterized in functional assays on recombinant mGluRs and in receptor binding assays on native iGluRs. At mGluRs, the activity at Group II was retained for compounds with small substituents (2a-2d), whereas the Group I and Group III receptor activities for all new compounds were lost. Detection of NMDA receptor affinity prompted further characterization, and two-electrode voltage-clamp recordings at recombinant NMDA receptor subtypes NR1/NR2A-D expressed in Xenopus oocytes were carried out for compounds with small substituents (chloro, bromo, methyl or ethyl, compounds 2a-d). This series of Thio-Ibo analogues defines a structural threshold for NMDA receptor activation and reveals that the individual subtypes have different steric requirements for receptor activation. The compounds 2a and 2c are the first examples of agonists discriminating individual NMDA subtypes.

  3. Extracts from plants used in Mexican traditional medicine activate Ca(2+)-dependent chloride channels in Xenopus laevis oocytes.

    Science.gov (United States)

    Rojas, A; Mendoza, S; Moreno, J; Arellano, R O

    2003-01-01

    The two-electrode voltage-clamp technique was employed to investigate the effects of chloroform-methanol (1:1) extracts derived from five medicinal plants on Xenopus laevis oocytes. When evaluated at concentrations of 1 to 500 microg/ml, the extracts prepared from the aerial parts of Baccharis heterophylla H.B.K (Asteraceae), Chenopodium murale L. (Chenopodiaceae), Desmodium grahami Gray (Leguminosae) and Solanum rostratum Dun (Solanaceae) produced concentration-dependent oscillatory inward currents in the oocytes, while the extract of Gentiana spathacea did not induce any response. The reversal potential of the currents elicited by the active extracts was -17 +/- 2 mV and was similar to the chloride equilibrium potential in oocytes. These ionic responses were independent of extracellular calcium. However, they were eliminated by overnight incubation with BAPTA-AM (10 microM), suggesting that the currents were dependent on intracellular Ca2+ increase. Thus the plant extracts activate the typical oscillatory Ca(2+)-dependent Cl- currents generated in the Xenopus oocyte membrane more probably via a mechanism that involves release of Ca2+ from intracellular reservoirs. These observations suggest that Xenopus oocyte electrophysiological recording constitutes a suitable assay for the study of the mechanisms of action of herbal medicines.

  4. Deltamethrin Inhibits the Human T-type Voltage-Sensitive Calcium Channel (Cav3.2

    Directory of Open Access Journals (Sweden)

    Steven B. Symington

    2009-01-01

    Full Text Available The goal of this study was to determine the effect of deltamethrin, a pyrethroid insecticide, on CaV3.2, a human T-type voltage-sensitive calcium channel expressed in Xenopus laevis (X.laevis oocytes. Cav3.2 cDNA was transcribed into cRNA; the cRNA was then injected into X.laevis oocytes and electrophysiologically characterized using the two-electrode voltage clamp technique with Ba2+ as a charge carrier. Deltamethrin (10-7 M reduced peak current in a nonreversible manner compared to the untreated control, but had no effect on the voltagedependent activation and inactivation kinetics. These findings confirm that human CaV3.2 is a target for deltamethrin and quite possibly other pyrethroid insecticides. These studies provide insight into the molecular mechanisms of the effect that pyrethroids have on voltage-sensitive calcium channels in general. This information will allow a more complete understanding of the molecular and cellular nature of pyrethroid-induced toxicity and expand our knowledge of the structure-activity relationships of pyrethroids with regard to their action on voltage-sensitive calcium channels.

  5. Tweaking subtype-selectivity and agonist efficacy at (S)-2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptors in a small series of BnTetAMPA analogues

    DEFF Research Database (Denmark)

    Wang, Shuang-Yan; Larsen, Younes; Navarrete, Cristina V.

    2016-01-01

    A series of analogues of the (S)-2-Amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptor agonist BnTetAMPA (5b) were synthesized and characterized pharmacologically in radioligand binding assays at native and cloned AMPA receptors and functionally by two-electrode voltage clamp...... electrophysiology at the four homomeric AMPA receptors expressed in Xenopus laevis oocytes. The analogues 6 and 7 exhibit very different pharmacological profiles with binding affinity preference for the subtypes GluA1 and GluA3, respectively. X-ray crystal structures of three ligands (6, 7, and 8) in complex...... with the agonist binding domain (ABD) of GluA2 show that they induce full domain closure despite their low agonist efficacies. Trp767 in GluA2 ABD could be an important determinant for partial agonism of this compound series at AMPA receptors, since agonist efficacy also correlated with the location of the Trp767...

  6. A repulsion mechanism explains magnesium permeation and selectivity in CorA.

    Science.gov (United States)

    Dalmas, Olivier; Sandtner, Walter; Medovoy, David; Frezza, Ludivine; Bezanilla, Francisco; Perozo, Eduardo

    2014-02-25

    Magnesium (Mg(2+)) plays a central role in biology, regulating the activity of many enzymes and stabilizing the structure of key macromolecules. In bacteria, CorA is the primary source of Mg(2+) uptake and is self-regulated by intracellular Mg(2+). Using a gating mutant at the divalent ion binding site, we were able to characterize CorA selectivity and permeation properties to both monovalent and divalent cations under perfused two-electrode voltage clamp. The present data demonstrate that under physiological conditions, CorA is a multioccupancy Mg(2+)-selective channel, fully excluding monovalent cations, and Ca(2+), whereas in absence of Mg(2+), CorA is essentially nonselective, displaying only mild preference against other divalents (Ca(2+) > Mn(2+) > Co(2+) > Mg(2+) > Ni(2)(+)). Selectivity against monovalent cations takes place via Mg(2+) binding at a high-affinity site, formed by the Gly-Met-Asn signature sequence (Gly312 and Asn314) at the extracellular side of the pore. This mechanism is reminiscent of repulsion models proposed for Ca(2+) channel selectivity despite differences in sequence and overall structure.

  7. Allosteric modulation of alpha4beta2 nicotinic acetylcholine receptors by HEPES.

    Science.gov (United States)

    Weltzin, Maegan M; Huang, Yanzhou; Schulte, Marvin K

    2014-06-05

    A number of new positive allosteric modulators (PAMs) have been reported that enhance responses of neuronal alpha7 and alpha4beta2 nicotinic acetylcholine receptor subtypes to orthosteric ligands. PAMs represent promising new leads for the development of therapeutic agents for disorders involving alterations in nicotinic neurotransmission including Autism, Alzheimer's and Parkinson's disease. During our recent studies of alpha4beta2 PAMs, we identified a novel effect of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). The effects of HEPES were evaluated in a phosphate buffered recording solution using two-electrode voltage clamp techniques and alpha4beta2 and alpha7 nicotinic acetylcholine receptor subtypes expressed in Xenopus laevis oocytes. Acetylcholine induced responses of high-sensitivity alpha4beta2 receptors were potentiated 190% by co-exposure to HEPES. Responses were inhibited at higher concentrations (bell-shaped concentration/response curve). Coincidentally, at concentrations of HEPES typically used in oocyte recording (5-10mM), the potentiating effects of HEPES are matched by its inhibitory effects, thus producing no net effect. Mutagenesis results suggest HEPES potentiates the high-sensitivity stoichiometry of the alpha4beta2 receptors through action at the beta2+/beta2- interface and is dependent on residue beta2D218. HEPES did not potentiate low-sensitivity alpha4beta2 receptors and did not produce any observable effect on acetylcholine induced responses on alpha7 nicotinic acetylcholine receptors.

  8. TcPho91 is a contractile vacuole phosphate sodium symporter that regulates phosphate and polyphosphate metabolism in Trypanosoma cruzi.

    Science.gov (United States)

    Jimenez, Veronica; Docampo, Roberto

    2015-09-01

    We have identified a phosphate transporter (TcPho91) localized to the bladder of the contractile vacuole complex (CVC) of Trypanosoma cruzi, the etiologic agent of Chagas disease. TcPho91 has 12 transmembrane domains, an N-terminal regulatory SPX (named after SYG1, Pho81 and XPR1) domain and an anion permease domain. Functional expression in Xenopus laevis oocytes followed by two-electrode voltage clamp showed that TcPho91 is a low-affinity transporter with a Km for Pi in the millimolar range, and sodium-dependency. Epimastigotes overexpressing TcPho91-green fluorescent protein have significantly higher levels of pyrophosphate (PPi ) and short-chain polyphosphate (polyP), suggesting accumulation of Pi in these cells. Moreover, when overexpressing parasites were maintained in a medium with low Pi , they grew at higher rates than control parasites. Only one allele of TcPho91 in the CL strain encodes for the complete open reading frame, while the other one is truncated encoding for only the N-terminal domain. Taking advantage of this characteristic, knockdown experiments were performed resulting in cells with reduced growth rate as well as a reduction in PPi and short-chain polyP levels. Our results indicate that TcPho91 is a phosphate sodium symporter involved in Pi homeostasis in T. cruzi.

  9. A G326E substitution in the glutamate-gated chloride channel 3 (GluCl3) of the two-spotted spider mite Tetranychus urticae abolishes the agonistic activity of macrocyclic lactones.

    Science.gov (United States)

    Mermans, Catherine; Dermauw, Wannes; Geibel, Sven; Van Leeuwen, Thomas

    2017-07-24

    The macrocyclic lactones abamectin and milbemectin are frequently used to control phytophagous mites such as Tetranychus urticae. Consequently, resistance has developed and was genetically linked with substitutions in the glutamate-gated chloride channel (GluCl) subunits TuGluCl1 and TuGluCl3. Here, we functionally validated a G326E substitution in TuGluCl3 by functional expression in Xenopus laevis oocytes followed by two-electrode voltage-clamp electrophysiology. Homomeric wild-type and mutated GluCl3 were successfully expressed. l-glutamic-acid-induced currents exhibited a rapid onset equal in both channels and EC50 for l-glutamic-acid was in the micromolar range (384.2 μm and 292.7 μm, respectively). Abamectin and milbemycin A4 elicited sustained currents in wild-type GluCl3, but the G326E substitution completely abolished the agonistic activity of macrocyclic lactones. A target-site mutation in Tu GluCl3 contributes to avermectin resistance in T. urticae. However, given the multitude of channel genes and the potential additive or synergistic effects of mutations, to what extent mutations determine the often extremely strong resistance phenotype in the field deserves further study. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  10. Studies of the effect of ionomycin on the KCNQ4 channel expressed in Xenopus oocytes.

    Science.gov (United States)

    Su, Ching-Chyuan; Li, Shuan-Yow; Yang, Jiann-Jou; Su, Mao-Chang; Lin, Min-Jon

    2006-09-15

    The effect of ionomycin on the human KCNQ4 channels expressed in Xenopus leavis oocytes was investigated. KCNQ4 channels expressed in Xenopus oocytes were measured using two-electrode voltage clamp. The activation of KCNQ4 current had slow activation kinetics and low threshold (approximately -50 mV). The expressed current of KCNQ4 showed the half-maximal activation (V(1/2)) was -17.8 mV and blocked almost completely by KCNQ4 channel blockers, linopirdine (300 microM) or bepridil (200 microM). The significant increase of KCNQ4 outward current induced by ionomycin (calcium salt) is about 1.7-fold of control current amplitude at +60 mV and shifted V(1/2) by approximately -8 mV (from -17.8 to -26.0 mV). This effect of ionomycin could be reversed by the further addition of BAPTA-AM (0.3 mM), a membrane-permeable calcium chelator. Furthermore, the increased effect of ionomycin on KCNQ4 current is abolished by pretreatment of linopirdine or bepridil. In contrast, direct cytoplasmic injection of calcium medium (up to 1 mM calcium, 50 nl) did not mimic the effect of ionomycin. In conclusion, the effect of ionomycin on enhancement of KCNQ4 current is independent of intracellular calcium mobilization and possibly acts on intramembrane hydrophobic site of KCNQ4 protein expressed in Xenopus oocytes.

  11. Discovery of novel ligands for mouse olfactory receptor MOR42-3 using an in silico screening approach and in vitro validation.

    Directory of Open Access Journals (Sweden)

    Selvan Bavan

    Full Text Available The ligands for many olfactory receptors remain largely unknown despite successful heterologous expression of these receptors. Understanding the molecular receptive range of olfactory receptors and deciphering the olfactory recognition code are hampered by the huge number of odorants and large number of olfactory receptors, as well as the complexity of their combinatorial coding. Here, we present an in silico screening approach to find additional ligands for a mouse olfactory receptor that allows improved definition of its molecular receptive range. A virtual library of 574 odorants was screened against a mouse olfactory receptor MOR42-3. We selected the top 20 candidate ligands using two different scoring functions. These 40 odorant candidate ligands were then tested in vitro using the Xenopus oocyte heterologous expression system and two-electrode voltage clamp electrophysiology. We experimentally confirmed 22 of these ligands. The candidate ligands were screened for both agonist and antagonist activity. In summary, we validated 19 agonists and 3 antagonists. Two of the newly identified antagonists were of low potency. Several previously known ligands (mono- and dicarboxylic acids are also confirmed in this study. However, some of the newly identified ligands were structurally dissimilar compounds with various functional groups belonging to aldehydes, phenyls, alkenes, esters and ethers. The high positive predictive value of our in silico approach is promising. We believe that this approach can be used for initial deorphanization of olfactory receptors as well as for future comprehensive studies of molecular receptive range of olfactory receptors.

  12. Modulation by Divalent Cations of GABAρ1 Receptor From Human Retina Expressed in Xenopus Oocytes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective To investigate functional homooligomeric GABAρ1 receptors expressed in Xenopus oocytes and the modulation of divalent cations. Methods GABAρ1 cDNA from human retina was transcribed in vitro to obtain sense ρ1 mRNA, which was microinjected into Xenopus oocytes. Two-electrodes voltage clamp technique was performed to record GABA-induced currents. Results  Expressed receptors were found to have similar properties to GABAC receptors characterized in the retina. Cl-currents induced by GABA were blocked by picrotoxin instead of bicuculline. GABA-induced currents reversed at -19±2.5 mV, and EC50 was 3.3 μmol/L. Zn+ + modulated GABA-induced currents with an IC50=9.6 μ mol/L. Ni+ +, Cu+ + and Cd+ + inhibited GABA ρ1 obviously, too. Their rank order of potency was Zn+ +>Ni+ +>Cu+ +>Cd+ +. Conclusion Zinc(10 μmol/L) inhibited GABA-induced currents in a competitive manner, and its action was sensitive to extracellular pH. Site-directed mutagenesis revealed that substitution of a single histidine residue (H44 and H48) failed to affect zinc sensitivity.

  13. Pressure-selective modulation of NMDA receptor subtypes may reflect 3D structural differences.

    Science.gov (United States)

    Mor, Amir; Kuttner, Yosef Y; Levy, Shiri; Mor, Merav; Hollmann, Michael; Grossman, Yoram

    2012-01-01

    Professional deep-water divers exposed to high pressure (HP) above 1.1 MPa suffer from High Pressure Neurological Syndrome (HPNS), which is associated with CNS hyperexcitability. We have previously reported that HP augments N-methyl-D-aspartate receptor (NMDAR) synaptic responses, increases neuronal excitability, and potentially causes irreversible neuronal damage. We now report that HP (10.1 MPa) differentially affects eight specific NMDAR subtypes. GluN1(1a or 1b) was co-expressed with one of the four GluN2(A-D) subunits in Xenopus laevis oocytes. HP increased ionic currents (measured by two electrode voltage clamps) of one subtype, reduced the current in four others, and did not affect the current in the remaining three. 3D theoretical modeling was aimed at revealing specific receptor domains involved with HP selectivity. In light of the information on the CNS spatial distribution of the different NMDAR subtypes, we conclude that the NMDAR's diverse responses to HP may lead to selective HP effects on different brain regions. These discoveries call for further and more specific investigation of deleterious HP effects and suggest the need for a re-evaluation of deep-diving safety guidelines.

  14. Functional characterization of the 1,5-benzodiazepine clobazam and its major active metabolite N-desmethylclobazam at human GABAA receptors expressed in Xenopus laevis oocytes

    DEFF Research Database (Denmark)

    Hammer, Harriet; Ebert, Bjarke; Jensen, Henrik S.

    2015-01-01

    The 1,5-benzodiazepine clobazam is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older in the United States, and for treatment of anxiety and various forms of epilepsy elsewhere. Clobazam has been reported to exhibit...... different in vivo adverse effects and addiction liability profile than the classic 1,4-benzodiazepines. In this study, it was investigated whether the in vitro pharmacological properties of clobazam and its major active metabolite N-desmethylclobazam could explain some of these clinical differences....... The functional properties of the two 1,5-benzodiazepines were characterized at the human γ-aminobutyric acid type A receptor (GABAAR) subtypes α1β2γ2S, α2β2γ2S, α3β2γ2S, α5β2γ2S and α6β2δ expressed in Xenopus laevis oocytes by use of two-electrode voltage-clamp electrophysiology and compared to those exhibited...

  15. Poling of VDF/TrFe copolymers using a step-wise method

    NARCIS (Netherlands)

    Setiadi, D.; Binnie, T.D.; Regtien, P.P.L.; Wubbenhorst, M.

    1996-01-01

    A new poling technique is presented, in which a series of five consecutive pulses of electric field, and with successively increasing strength is applied between the two electrodes of 65/35 VDF/TrFE copolymer based sensor. Between each pulse, the applied electric field is reduced to zero (short circ

  16. Influence of two-electrode montages on the level-specific (LS) CE-Chirp auditory brainstem response (ABR) at multiple intensity levels.

    Science.gov (United States)

    Dzulkarnain, Ahmad Aidil Arafat; Noor Ibrahim, Siti Hajra Mu'minah; Anuar, Nur Farah Aida; Abdullah, Siti Aisyah; Tengku Zam Zam, Tengku Zulaila Hasma; Rahmat, Sarah; Mohd Ruzai, Muhammad Amar

    2017-10-01

    To investigate the influence of two different electrode montages (ipsilateral: reference to mastoid and vertical: reference to nape of neck) to the ABR results recorded using a level-specific (LS)-CE-Chirp® in normally hearing subjects at multiple intensities levels. Quasi-experimental and repeated measure study designs were applied in this study. Two different stopping criteria were used, (1) a fixed-signal averaging 4000 sweeps and, (2) a minimum quality indicator of Fmp = 3.1 with a minimum of 800 sweeps. Twenty-nine normally hearing adults (18 females, 11 male) participated. Wave V amplitudes were significantly larger in the LS CE-Chirp® recorded from the vertical montage than the ipsilateral montage. Waves I and III amplitudes were significantly larger from the ipsilateral LS CE-Chirp® than from the other montages and stimulus combinations. The differences in the quality of the ABR recording between the vertical and ipsilateral montages were marginal. Overall, the result suggested that the vertical LS CE-Chirp® ABR had a high potential for a threshold-seeking application, because it produced a higher wave V amplitude. The Ipsilateral LS CE-Chirp® ABR, on the other hand, might also have a high potential for the site of lesion application, because it produced larger waves I and III amplitudes.

  17. 石墨型高能两电极气体开关%High power graphite two-electrode spark gap switch

    Institute of Scientific and Technical Information of China (English)

    郭良福; 李黎; 赖贵友; 林福昌; 陈德怀; 力一峥; 李冬梅; 栾永平

    2010-01-01

    为大型激光装置能源模块研制了一种采用石墨电极的两电极气体开关,阐述了石墨应用于高能两电极气体开关的技术关键,对气体开关中气体间隙的最优结构进行了电场强度分析.参考美国国家点火装置(NIF)能源模块中ST-300气体开关的已知参数,对研制成功的石墨型两电极开关进行了电气特性试验,证明了石墨型气体开关能够实现峰值电流达300 kA以上,单次转移电荷量100 C以上,寿命超过1 000次,满足1.2 MJ大型激光装置能源模块的工程技术要求.

  18. A facile method to prepare a high performance solid-state flexible paper-based supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Shieh, Jen-Yu; Zhang, Sheng-Hui; Wu, Cheng-Hung [Institute of Electro-Optical and Materials Science, National Formosa University, 64 Wenhua Road, Huwei, Yunlin 63208, Taiwan (China); Yu, Hsin Her, E-mail: hhyu@nfu.edu.tw [Department of Biotechnology, National Formosa University, 64 Wenhua Road, Huwei, Yunlin 63208, Taiwan (China)

    2014-09-15

    Graphical abstract: A flexible paper-based supercapacitor was assembled into a sandwich structure, which exhibits well-retained triangular-shaped curves. The cycle life stability of this device still retains about 96% of the initial capacitance after 2000 cycles at a scan rate of 400 mV/s. An as-fabricated paper-based supercapacitor could light a red LED well after charging at constant potential of 3 V. - Highlights: • A facile approach is proposed to fabricate paper-based supercapacitors. • Apple pectin is an excellent dispersant for MWCNTs. • Paper provides a strong binding and flexible characteristic for electrode. • A paper-based supercapacitor could light a red LED after charging. • This device shows excellent electrochemical performance and cycling stability. - Abstract: We propose a low cost and simple method to prepare a paper-based supercapacitor in this study. Multi-walled carbon nanotubes (MWCNTs) were dispersed with a pectin solution under an ultrasonic homogenizer. Carbon nanotube suspension was prepared using a centrifuge to eliminate impurities. The dispersed MWCNTs suspension was dropped and dried onto the shallow surface of commercial copy paper. A paper-based conductive paper was formed as the electrodes. The electrical conductivity and dispersed morphology of the paper-based conductive paper were examined by four probes, atomic force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The solid-state electrolyte was prepared by casting a solution of phosphoric acid and polyvinyl alcohol onto a glass plate. The paper-based supercapacitor was constructed with one solid-state electrolyte inserted between two electrodes, which were assembled into a sandwich structure by hot press. The specific capacitance and cycle-life stability of the paper-based supercapacitor was investigated by cyclic voltammetry analysis.

  19. Birth Control Methods

    Science.gov (United States)

    ... Home A-Z Health Topics Birth control methods Birth control methods > A-Z Health Topics Birth control methods ... To receive Publications email updates Enter email Submit Birth control methods Birth control (contraception) is any method, medicine, ...

  20. The clinical method and the scientific method

    Directory of Open Access Journals (Sweden)

    José Arteaga Herrera

    2010-12-01

    Full Text Available This paper is the chapter dedicated to the scientific method and the clinical method in the authors’ Handbook “Teaching of Clinics”. Philosophycal principles of the scientific method and its stages are presented as well as the clinical method as a scientific one and its stages. A relationship between the clinical method and the medical record is established, the role of technology in the clinical method is stated and the most frequent mistakes when applying it in clinical practice are provided. Finally, the teaching of the clinical method and the appropriate settings to do it are discussed.

  1. The effects and interaction of ketamine and magnesium on NMDA receptors expressed in xenopus oocytes%镁和氯胺酮对表达于Xenopus卵细胞的N-甲基-D-天冬氨酸受体的影响及其相互作用

    Institute of Scientific and Technical Information of China (English)

    刘洪涛; 刘伟华; 王俊科

    2001-01-01

    目的观测单独或联合应用氯胺酮和镁在重组NMDA受体中的作用及相互影响.方法应用电压钳测试和记录受体的反应电流,所测试的受体为表达于蛙卵细胞上的NR1/NR2A和NR1/NR2B受体.支持电压为-70mV,以谷氨酸和甘氨酸作为受体激动剂,分别测试单独和联合应用s(+)-氯胺酮和镁时反应电流的情况.结果单独应用镁和氯胺酮均对NMDA受体产生非竞争性抑制作用.镁在NR1/NR2A和NR1/NR2B中的IC50分别为(4.2±1.2)×10-4mol和(6.3±2.4)×10-4mol/L,两组无差别;s(+)-氯胺酮在NRl/NR2A和NR1/NR2B中的IC50分别为(4.1±2.5)×10-6mol/L和(3.0±0.3)×10-6mol/L,两组亦无差别.当联合应用镁和氯胺酮时二者的IC50在NR1/NR2A和NR1/NR2B中均减少了90%以上,显示二者有显著的协同作用.结论镁和氯胺酮均对NMDA受体产生非竞争性抑制作用,当二者联合应用时具有协同作用.%Objective It has been shown that ketamine and magnesium used in combination provide more effective analgesia than either drug alone. The purpose of this study was to investigate the effects and interaction of the two drugs on recombinantly expressed NMDA receptors. Methods Xenopus oocytes expressing NR1/NR2A or NR1/NR2B glutamate receptors were stimulated with glutamate/glycine and studied at a holding potential of -70mV using two electrode voltage clamp. The effects of magnesium and s ( + )-ketamine alone or in combination on NMDA signaling were determined. Results Magnesium and s( + )-ketamine alone inhibited NMDA receptors non-competitively. IC50s of magnesium were (4.2 ± 1.2)×10-4mol/L and (6.3 ± 2.4) × 10-4 mol/L on NR1/NR2A and NR1/NR2B, while IC50s of s( + )-ketamine on NR1/NR2A and NR1/NR2B were (4.1 ± 2.5) × 10-6 mol/L and (3.0 ± 0.3 ) × 10-6 mol/Lrespectively. Magnesium and s( + )-ketamine used in combination decreased IC50s more than 90% at both receptors. Isobolographic analysis demonstrated superadditive interactions. Conclusions s

  2. A facile method for high yield synthesis of carbon nano onions for designing binder-free flexible supercapacitor

    Science.gov (United States)

    Mohapatra, Debananda; Badrayyana, Subramanya; Parida, Smrutiranjan

    2017-05-01

    Carbon nano onion (CNO) is a promising material for diverse application areas such as energy devices, catalysis, lubrication, biology and gas storage, etc. However, its implementation is fraught with the production of high-quality powders in bulk quantity. Herein, we report a facile scalable and one-step "wick-and-oil" flame synthesis of pure and water dispersible CNO nanopowder. Other forms of carbon did not contaminate the as-prepared CNO; hence, a post processing purification procedure was not necessary. Brunauer Emmett Teller (BET) specific surface area of as-prepared CNO was 218 m2/g, which is higher as compared to other reported flame synthesis methods. Locally available daily used cotton wipe has been used for fabrication of such an ideal electrode by "dipping and drying" process providing outstanding strechability and mechanical flexibility with strong adhesion between CNOs and porous wipe. The specific capacitance 102.16 F/g, energy density 14.18 Wh/kg and power density 2448 W/kg at 20 mV/s scan rate are the highest values that ever recorded and reported so far in symmetrical two electrode cell configuration with 1M Na2SO4 electrolyte; indicating a very good synthesis conditions employed with optimum pore size in agreement with electrolyte ion size. This free standing CNOs electrode also showed an excellent cyclic performance and stability retaining 95% original capacity after 5000 charge -discharge cycles. Simple preparation of high-purity CNOs and excellent electrochemical behavior of functionalized CNOs make them a promising electrode material for supercapacitor applications. Furthermore, this unique method not only affords binder free - freestanding electrode, but also provide a general way of fabricating such multifunctional promising CNOs based nanocomposites for their potential device applications in flexible solar cells and lithium ion batteries.

  3. An Inexact Halley's Method

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    An inexact Halley's method-Halley-PCG(preconditioned conjugate gradient) method is proposed for solving the systems of linear equations for improved Halley method either by Cholesky factorization exactly or by preconditioned conjugate gradient method approximately. The convergence result is given and the efficiency of the method compared to the improved Halley's method is shown.

  4. Meshless Methods Coupled with Other Numerical Methods

    Institute of Scientific and Technical Information of China (English)

    Y.T.GU; G.R.LIU

    2005-01-01

    Meshless or mesh-free (or shorten as MFree) methods have been proposed and achieved remarkable progress over the past few years. The idea of combining MFree methods with other existing numerical techniques such as the finite element method (FEM) and the boundary element method (BEM), is naturally of great interest in many practical applications. However, the shape functions used in some MFree methods do not have the Kronecker delta function property. In order to satisfy the combined conditions of displacement compatibility, two numerical techniques, using the hybrid displacement shape function and the modified variational form, are developed and discussed in this paper. In the first technique, the original MFree shape functions are modified to the hybrid forms that possess the Kronecker delta function property. In the second technique, the displacement compatibility is satisfied via a modified variational form based on the Lagrange multiplier method. Formulations of several coupled methods are presented. Numerical examples are presented to demonstrate the effectiveness of the present coupling methods.

  5. From Method to Post Method: A Panacea!

    Science.gov (United States)

    Masouleh, Nima Shakouri

    2012-01-01

    The foundation of language teaching has undergone many changes. The rise and fall of language teaching methods depends upon a variety of factors extrinsic to a method itself and often reflects the influence of profit-seekers and promoters, as well as the forces of the intellectual marketplace. There was always a source of contention among people…

  6. The Multidimensional WKB Method.

    Science.gov (United States)

    Knudson, Stephen K.; Noid, D. W.

    1989-01-01

    Discusses a new method for determining the eigenvalues of the Schroedinger equation when the potential energy function does not have a simple form. Describes the mathematical methods and provides an application. Lists limitations to the method. (MVL)

  7. ANALYSIS OF MULTISCALE METHODS

    Institute of Scientific and Technical Information of China (English)

    Wei-nan E; Ping-bing Ming

    2004-01-01

    The heterogeneous multiscale method gives a general framework for the analysis of multiscale methods. In this paper, we demonstrate this by applying this framework to two canonical problems: The elliptic problem with multiscale coefficients and the quasicontinuum method.

  8. Ensemble Data Mining Methods

    Data.gov (United States)

    National Aeronautics and Space Administration — Ensemble Data Mining Methods, also known as Committee Methods or Model Combiners, are machine learning methods that leverage the power of multiple models to achieve...

  9. Simplifications of CQC method and CCQC method

    Institute of Scientific and Technical Information of China (English)

    Yu Ruifang; Zhou Xiyuan

    2007-01-01

    The response-spectrum mode superposition method is widely used for seismic response analyses of linear systems. In using this method, the complete quadratic combination (CQC) is adopted for classically damped linear systems and the complex complete quadratic combination (CCQC) formula is adopted for non-classically damped linear systems.However, in both cases, the calculation of seismic response analyses is very time consuming. In this paper, the variation of the modal correlation coefficients of displacement, velocity and displacement-velocity with frequency and damping ratios of two modes of interest are studied, Moreover, the calculation errors generated by using CQC and square-root-of-the-sum-of-the-squares (SRSS) methods (or CCQC and CSRSS methods) for different damping combinations are compared. In these analyses,some boundary lines for classically and non-classically damped systems are plotted to distinguish the allowed minimum frequency ratio at given geometric mean of the damping ratios of both modes if their relativity is neglected. Furthermore,the simplified method, which is a special mode quadratic combination method considering only relativity of adjacent modes in CQC method and named simplified CQC or partial quadratic combination (PQC) method for classically damped linear system, is proposed to improve computational efficiency, and the criterion for determination of how many correlated modes should be adopted is proposed. Similarly, the simplified CCQC or complex partial quadratic combination (CPQC) method for the non-classically damped linear system and the corresponding criterion are also deduced. Finally, a numerical example is given to illustrate the applicability, computational accuracy and efficiency of the PQC and CPQC methods.

  10. Simulations using meshfree methods

    CERN Document Server

    P, Kirana Kumara

    2015-01-01

    In this paper, attempt is made to solve a few problems using the Polynomial Point Collocation Method (PPCM), the Radial Point Collocation Method (RPCM), Smoothed Particle Hydrodynamics (SPH), and the Finite Point Method (FPM). A few observations on the accuracy of these methods are recorded. All the simulations in this paper are three dimensional linear elastostatic simulations, without accounting for body forces.

  11. Numerical Methods for Multilattices

    CERN Document Server

    Abdulle, Assyr; Shapeev, Alexander V

    2011-01-01

    Among the efficient numerical methods based on atomistic models, the quasicontinuum (QC) method has attracted growing interest in recent years. The QC method was first developed for crystalline materials with Bravais lattice and was later extended to multilattices (Tadmor et al, 1999). Another existing numerical approach to modeling multilattices is homogenization. In the present paper we review the existing numerical methods for multilattices and propose another concurrent macro-to-micro method in the homogenization framework. We give a unified mathematical formulation of the new and the existing methods and show their equivalence. We then consider extensions of the proposed method to time-dependent problems and to random materials.

  12. Constituents of the roots of Boerhaavia diffusa L. III. Identification of Ca2+ channel antagonistic compound from the methanol extract.

    Science.gov (United States)

    Lami, N; Kadota, S; Kikuchi, T; Momose, Y

    1991-06-01

    Two known lignans, liriodendrin and syringaresinol mono-beta-D-glucoside, have been isolated from the methanol extract of the roots of Boerhaavia diffusa L. (Nyctaginaceae), and the former compound was found to exhibit a significant calcium (Ca2+) channel antagonistic effect in frog heart single cells using the whole-cell voltage clamp method. Reexamination of the carbon-13 nuclear magnetic resonance (13C-NMR) spectra of these compounds was also carried out by the use of two-dimensional NMR techniques including a 1H-detected heteronuclear multiple bond connectivity (HMBC) experiment, and it was found that the previous signal assignments for C-1' and C-4' have to be revised.

  13. New diterpenoid alkaloids from Aconitum coreanum and their anti-arrhythmic effects on cardiac sodium current.

    Science.gov (United States)

    Xing, Bei-Ni; Jin, Si-Si; Wang, Hao; Tang, Qing-Fa; Liu, Jing-Han; Li, Rui-Yang; Liang, Jing-Yu; Tang, Yi-Qun; Yang, Chun-Hua

    2014-04-01

    Two new diterpenoid alkaloids, Guan-Fu base J (GFJ, 1) and Guan-Fu base N (GFN, 2) along with nineteen known alkaloids (3-21) were isolated from the roots of Aconitum coreanum (Lèvl.) Rapaics, which is the raw material of a new approval anti-arrhythmia drug "Acehytisine Hydrochloride". The structures of isolated compounds were established by means of 1D, 2D NMR spectroscopic and chemical methods. All isolates obtained in the present study were evaluated for their inhibitory effects on blocking the ventricular specific sodium current using a whole-cell patch voltage-clamp technique. Among these 21 compounds, Guan-Fu base S (GFS, 3) showed the strongest inhibitory effect with an IC50 value of 3.48 μM, and only hetisine-type C20 diterpenoid alkaloids showed promising IC50 values for further development.

  14. Inflammation unmasks gabapentin's effect on Aδ-fiber evoked excitatory postsynaptic currents in substantia gelatinosa neurons of rat spinal cord

    Institute of Scientific and Technical Information of China (English)

    刘智良; 徐如祥; 杨鲲

    2003-01-01

    ObjectiveTo study the analgesic mechanism of gabapentin, an anticonvulsant, during antinociceptive clinical treatment. MethodsWhole-cell voltage-clamp recordings were taken from adult rat spinal cord slices to investigate the effect of gabapentin on primary afferent Aδ-fiber evokedexcitatory postsynaptic currents (EPSCs) to substantia gelatinosa (SG) neurons in normal and inflamed (established by plantar injection of carrageenan) rats. Results Gabapentin (5-20 μmol/L for 5 min) depressed dorsal root Aδ fiber evoked polysynaptic, but not monosynaptic EPSCs to SG experiencing inflammation by about 25ptic or monosynaptic EPSCs in normal rats. Gabapentin failed to block a glutamate receptor subtype, N-methyl-D-aspartate (NMDA), -induced slow excitatory currents on SG neurons.ConclusionsInflammation, at least in part, unmasks the gabapentin depression on nociception transmission in the dorsal horn, and this depression is not due to the blockade of postsynaptic NMDA receptor.

  15. Water transport by the Na+/glucose cotransporter under isotonic conditions

    DEFF Research Database (Denmark)

    Zeuthen, T; Meinild, A K; Klaerke, D A;

    1997-01-01

    Solute cotransport in the Na+/glucose cotransporter is directly coupled to significant water fluxes. The water fluxes are energized by the downhill fluxes of the other substrates by a mechanism within the protein itself. In the present paper we investigate the Na+/glucose cotransporter expressed...... in Xenopus oocytes. We present a method which allows short-term exposures to sugar under voltage clamp conditions. We demonstrate that water is cotransported with the solutes despite no osmotic differences between the external and intracellular solutions. There is a fixed ratio of 195:1 between the number...... of water molecules and the number of Na+ ions transported, equivalent to 390 water molecules per glucose molecule. Unstirred layer effects are ruled out on the basis of experiments on native oocytes incubated with the ionophores gramicidin D or nystatin....

  16. Inhibitory effect of morphine on excitatory synaptic transmission via presynaptic mechanism in rat SON neurons in brain slices

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-bin; HU San-jue; JU Gong

    2001-01-01

    To observe the effects of morphine on the excitatory postsynaptic currents (EPSCs) and miniature EPSCs (mEPSCs) in rat supraoptic nucleus (SON) neurons and to explore its synaptic mechanism. Methods: Using whole-cell voltage-clamp recording technique in the brain slices, the EPSCS and mEPSCs of rat SON neurons were recorded, respectively. Results: Morphine (20 μmol/L) decreased the frequency of EPSCs and mEPSCs (by 65% for EPSCS and by 45% for mEPSCs), and reduced the amplitude of EPSCs by 44% in all SON neurons, but the amplitude distribution ofmEPSCs was not affected. Conclusion: Morphine inhibits the excitatory transmissions via presynaptic mechanisms in SON neurons from rat brain slices.

  17. Real time measures of prestin charge and fluorescence during plasma membrane trafficking reveal sub-tetrameric activity.

    Directory of Open Access Journals (Sweden)

    Shumin Bian

    Full Text Available Prestin (SLC26a5 is the outer hair cell integral membrane motor protein that drives cochlear amplification, and has been described as an obligate tetramer. We studied in real time the delivery of YFP-prestin to the plasma membrane of cells from a tetracycline-inducible cell line. Following the release of temperature block to reinstate trans Golgi network delivery of the integral membrane protein, we measured nonlinear capacitance (NLC and membrane fluorescence during voltage clamp. Prestin was delivered exponentially to the plasma membrane with a time constant of less than 10 minutes, with both electrical and fluorescence methods showing high temporal correlation. However, based on disparity between estimates of prestin density derived from either fluorescence or NLC, we conclude that sub-tetrameric forms of prestin contribute to our electrical and fluorescence measures. Thus, in agreement with previous observations we find that functional prestin is not an obligate tetramer.

  18. Inflow Turbulence Generation Methods

    Science.gov (United States)

    Wu, Xiaohua

    2017-01-01

    Research activities on inflow turbulence generation methods have been vigorous over the past quarter century, accompanying advances in eddy-resolving computations of spatially developing turbulent flows with direct numerical simulation, large-eddy simulation (LES), and hybrid Reynolds-averaged Navier-Stokes–LES. The weak recycling method, rooted in scaling arguments on the canonical incompressible boundary layer, has been applied to supersonic boundary layer, rough surface boundary layer, and microscale urban canopy LES coupled with mesoscale numerical weather forecasting. Synthetic methods, originating from analytical approximation to homogeneous isotropic turbulence, have branched out into several robust methods, including the synthetic random Fourier method, synthetic digital filtering method, synthetic coherent eddy method, and synthetic volume forcing method. This article reviews major progress in inflow turbulence generation methods with an emphasis on fundamental ideas, key milestones, representative applications, and critical issues. Directions for future research in the field are also highlighted.

  19. Advanced differential quadrature methods

    CERN Document Server

    Zong, Zhi

    2009-01-01

    Modern Tools to Perform Numerical DifferentiationThe original direct differential quadrature (DQ) method has been known to fail for problems with strong nonlinearity and material discontinuity as well as for problems involving singularity, irregularity, and multiple scales. But now researchers in applied mathematics, computational mechanics, and engineering have developed a range of innovative DQ-based methods to overcome these shortcomings. Advanced Differential Quadrature Methods explores new DQ methods and uses these methods to solve problems beyond the capabilities of the direct DQ method.After a basic introduction to the direct DQ method, the book presents a number of DQ methods, including complex DQ, triangular DQ, multi-scale DQ, variable order DQ, multi-domain DQ, and localized DQ. It also provides a mathematical compendium that summarizes Gauss elimination, the Runge-Kutta method, complex analysis, and more. The final chapter contains three codes written in the FORTRAN language, enabling readers to q...

  20. Consumer Behavior Research Methods

    DEFF Research Database (Denmark)

    Chrysochou, Polymeros

    2017-01-01

    emphasizes the discussion of primary research methods. Based on the nature of the data primary research methods are further distinguished into qualitative and quantitative. The chapter describes the most important and popular qualitative and quantitative methods. It concludes with an overall evaluation......This chapter starts by distinguishing consumer behavior research methods based on the type of data used, being either secondary or primary. Most consumer behavior research studies phenomena that require researchers to enter the field and collect data on their own, and therefore the chapter...... of the methods and how to improve quality in consumer behavior research methods....

  1. Quality Control Analytical Methods: Method Validation.

    Science.gov (United States)

    Klang, Mark G; Williams, LaVonn A

    2016-01-01

    To properly determine the accuracy of a pharmaceutical product or compounded preparation, tests must be designed specifically for that evaluation. The procedures selected must be verified through a process referred to as method validation, an integral part of any good analytical practice. The results from a method validation procedure can be used to judge the quality, reliability, and consistency of analytical results. The purpose of this article is to deliver the message of the importance of validation of a pharmaceutical product or compounded preparation and to briefly discuss the results of a lack of such validation. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

  2. Applied Bayesian Hierarchical Methods

    CERN Document Server

    Congdon, Peter D

    2010-01-01

    Bayesian methods facilitate the analysis of complex models and data structures. Emphasizing data applications, alternative modeling specifications, and computer implementation, this book provides a practical overview of methods for Bayesian analysis of hierarchical models.

  3. Dissolution Methods Database

    Data.gov (United States)

    U.S. Department of Health & Human Services — For a drug product that does not have a dissolution test method in the United States Pharmacopeia (USP), the FDA Dissolution Methods Database provides information on...

  4. Dissolution Methods Database

    Data.gov (United States)

    U.S. Department of Health & Human Services — For a drug product that does not have a dissolution test method in the United States Pharmacopeia (USP), the FDA Dissolution Methods Database provides information on...

  5. Simulated floating zone method

    OpenAIRE

    Ozawa, Ryo; Kato, Yasuyuki; Motome, Yukitoshi

    2016-01-01

    This paper provides the simulated floating zone (SFZ) method that is an efficient simulation technique to obtain thermal equilibrium states, especially useful when domain formation prevents the system from reaching a spatially-uniform stable state. In the SFZ method, the system is heated up locally, and the heated region is steadily shifted, similar to the floating zone method for growing a single crystal with less lattice defect and impurity in experiments. We demonstrate that the SFZ method...

  6. Mixed methods research.

    Science.gov (United States)

    Halcomb, Elizabeth; Hickman, Louise

    2015-04-08

    Mixed methods research involves the use of qualitative and quantitative data in a single research project. It represents an alternative methodological approach, combining qualitative and quantitative research approaches, which enables nurse researchers to explore complex phenomena in detail. This article provides a practical overview of mixed methods research and its application in nursing, to guide the novice researcher considering a mixed methods research project.

  7. Geobacteraceae strains and methods

    Science.gov (United States)

    Lovley, Derek R.; Nevin, Kelly P.; Yi, Hana

    2015-07-07

    Embodiments of the present invention provide a method of producing genetically modified strains of electricigenic microbes that are specifically adapted for the production of electrical current in microbial fuel cells, as well as strains produced by such methods and fuel cells using such strains. In preferred embodiments, the present invention provides genetically modified strains of Geobacter sulfurreducens and methods of using such strains.

  8. Numerical methods using Matlab

    CERN Document Server

    Gupta, Abhishek

    2015-01-01

    Numerical Methods with MATLAB provides a highly-practical reference work to assist anyone working with numerical methods. A wide range of techniques are introduced, their merits discussed and fully working MATLAB code samples supplied to demonstrate how they can be coded and applied. Numerical methods have wide applicability across many scientific, mathematical, and engineering disciplines and are most often employed in situations where working out an exact answer to the problem by another method is impractical. Numerical Methods with MATLAB presents each topic in a concise and readable

  9. The Generalized Sturmian Method

    DEFF Research Database (Denmark)

    Avery, James Emil

    2011-01-01

    generations of researchers were left to work out how to achieve this ambitious goal for molecular systems of ever-increasing size. This book focuses on non-mainstream methods to solve the molecular electronic Schrödinger equation. Each method is based on a set of core ideas and this volume aims to explain...... these ideas clearly so that they become more accessible. By bringing together these non-standard methods, the book intends to inspire graduate students, postdoctoral researchers and academics to think of novel approaches. Is there a method out there that we have not thought of yet? Can we design a new method...

  10. Mimetic discretization methods

    CERN Document Server

    Castillo, Jose E

    2013-01-01

    To help solve physical and engineering problems, mimetic or compatible algebraic discretization methods employ discrete constructs to mimic the continuous identities and theorems found in vector calculus. Mimetic Discretization Methods focuses on the recent mimetic discretization method co-developed by the first author. Based on the Castillo-Grone operators, this simple mimetic discretization method is invariably valid for spatial dimensions no greater than three. The book also presents a numerical method for obtaining corresponding discrete operators that mimic the continuum differential and

  11. Methods for assessing geodiversity

    Science.gov (United States)

    Zwoliński, Zbigniew; Najwer, Alicja; Giardino, Marco

    2017-04-01

    The accepted systematics of geodiversity assessment methods will be presented in three categories: qualitative, quantitative and qualitative-quantitative. Qualitative methods are usually descriptive methods that are suited to nominal and ordinal data. Quantitative methods use a different set of parameters and indicators to determine the characteristics of geodiversity in the area being researched. Qualitative-quantitative methods are a good combination of the collection of quantitative data (i.e. digital) and cause-effect data (i.e. relational and explanatory). It seems that at the current stage of the development of geodiversity research methods, qualitative-quantitative methods are the most advanced and best assess the geodiversity of the study area. Their particular advantage is the integration of data from different sources and with different substantive content. Among the distinguishing features of the quantitative and qualitative-quantitative methods for assessing geodiversity are their wide use within geographic information systems, both at the stage of data collection and data integration, as well as numerical processing and their presentation. The unresolved problem for these methods, however, is the possibility of their validation. It seems that currently the best method of validation is direct filed confrontation. Looking to the next few years, the development of qualitative-quantitative methods connected with cognitive issues should be expected, oriented towards ontology and the Semantic Web.

  12. Design Methods in Practice

    DEFF Research Database (Denmark)

    Jensen, Torben Elgaard; Andreasen, Mogens Myrup

    2010-01-01

    The paper challenges the dominant and widespread view that a good design method will guarantee a systematic approach as well as certain results. First, it explores the substantial differences between on the one hand the conception of methods implied in Pahl & Beitz’s widely recognized text book...... subject to change; The goals of methods are less stable than assumed. The paper finally suggests that ethnomethodology and similar approaches direct our attention to the fact that method use is always a situated and socially interactive affair. It is crucial to attend to these dimensions of method use...... on engineering design, and on the other hand the understanding of method use, which has emerged from micro-sociological studies of practice (ethnomethodology). Second, it reviews a number of case studies conducted by engineering students, who were instructed to investigate the actual use of design methods...

  13. Consensus theoretic classification methods

    Science.gov (United States)

    Benediktsson, Jon A.; Swain, Philip H.

    1992-01-01

    Consensus theory is adopted as a means of classifying geographic data from multiple sources. The foundations and usefulness of different consensus theoretic methods are discussed in conjunction with pattern recognition. Weight selections for different data sources are considered and modeling of non-Gaussian data is investigated. The application of consensus theory in pattern recognition is tested on two data sets: 1) multisource remote sensing and geographic data and 2) very-high-dimensional remote sensing data. The results obtained using consensus theoretic methods are found to compare favorably with those obtained using well-known pattern recognition methods. The consensus theoretic methods can be applied in cases where the Gaussian maximum likelihood method cannot. Also, the consensus theoretic methods are computationally less demanding than the Gaussian maximum likelihood method and provide a means for weighting data sources differently.

  14. Methods of Software Verification

    Directory of Open Access Journals (Sweden)

    R. E. Gurin

    2015-01-01

    Full Text Available This article is devoted to the problem of software verification (SW. Methods of software verification designed to check the software for compliance with the stated requirements such as correctness, system security and system adaptability to small changes in the environment, portability and compatibility, etc. These are various methods both by the operation process and by the way of achieving result. The article describes the static and dynamic methods of software verification and paid attention to the method of symbolic execution. In its review of static analysis are discussed and described the deductive method, and methods for testing the model. A relevant issue of the pros and cons of a particular method is emphasized. The article considers classification of test techniques for each method. In this paper we present and analyze the characteristics and mechanisms of the static analysis of dependencies, as well as their views, which can reduce the number of false positives in situations where the current state of the program combines two or more states obtained both in different paths of execution and in working with multiple object values. Dependences connect various types of software objects: single variables, the elements of composite variables (structure fields, array elements, the size of the heap areas, the length of lines, the number of initialized array elements in the verification code using static methods. The article pays attention to the identification of dependencies within the framework of the abstract interpretation, as well as gives an overview and analysis of the inference tools.Methods of dynamic analysis such as testing, monitoring and profiling are presented and analyzed. Also some kinds of tools are considered which can be applied to the software when using the methods of dynamic analysis. Based on the work a conclusion is drawn, which describes the most relevant problems of analysis techniques, methods of their solutions and

  15. Effects of diltiazem on transmembrane potential and current of right ventricular papillary muscle of ferrets.

    Science.gov (United States)

    Kanaya, S; Katzung, B G

    1984-01-01

    We studied the effects of diltiazem on electrical properties of isolated ferret right ventricular papillary muscles. By using standard microelectrode recording techniques and current clamp and voltage clamp protocols (single sucrose gap method), we measured action potential variables, depolarization-induced automaticity, slow (or second) inward current (Isi) and time-dependent and isochronal (1 sec) outward current. Resting potential was unaffected at all concentrations studied (from 2 nM-11 microM). At concentrations below 2 microM and at slow rates of stimulation (0.5 Hz), a small reduction of overshoot and prolongation of the action potential duration at 80% of full repolarization were observed. At concentrations of 2.2 microM or greater, marked use-dependent reductions of overshoot and plateau duration were observed that reversed with rest. Depolarization-induced automaticity was selectively suppressed at less negative diastolic potentials. In voltage clamp studies, peak Isi was markedly diminished over the concentration range studied (50% inhibitory concentration, 0.5 microM), but the current-voltage relation for Isi was not shifted on the voltage axis. The diminution in Isi was strongly use-dependent and voltage-dependent. Diltiazem (1.1 microM) had small effects on outward currents. Steady-state (isochronal) outward current and the time-dependent outward current were both reduced by 10 to 20% over the entire voltage range. Diltiazem is a potent inhibitor of the slow inward current in ventricular muscle. Its interaction with slow channel receptors appears to be strongly modulated by the state of the channels.

  16. The effects of cell phone electromagnetic fields on the behavior of single OmpF nanochannel forming protein: a practical approach

    Directory of Open Access Journals (Sweden)

    Mohammadzadeh M

    2013-05-01

    Full Text Available Background: Widespread of telecommunication systems in recent years, have raised the concerns on the possible danger of cell phone radiations on human body. Thus, the study of the electromagnetic fields on proteins, particularly the membrane nano channel forming proteins is of great importance. These proteins are responsible for keeping certain physic-chemical condition within cells and managing cell communication. Here, the effects of cell phones radiation on the activity of a single nanopore ion channel forming protein, OmpF, have been studied biophysically.Methods: Planar lipid bilayers were made based on Montal and Muller technique, and the activity of single OmpF channel reconstituted by electrical shock was recorded and analyzed by means of voltage-clamp technique at 20 ˚C. The planar lipid bilayers were formed from the monolayers made on a 60 μm diameter aperture in the 20 μm thick Teflon film that separated two (cis and trans compartments of the glass chamber. In this practical approach we were able to analyze characteristics of an individual channel at different chemical and physical experimental conditions. The voltage clamp was used to measure the channel’s conductance, voltage sensitivity, gating patterns in time scales as low as microseconds in real time.  Results: Our results showed that exposure of single voltage dependent channel, OmpF, to EMF of cell phone at high-frequency has a significant influence on the voltage sensitivity, gating properties and substate numbers of the single channel but has no effect on single-channel conductance. Regarding to the relaxation time, the channel also recovers in the millisecond time range when the field is removed. Conclusion: We observed an increase in the voltage sensitivity of the OmpF single channel while it had no effect on the single-channel conductance, which is remained to be further elucidated.

  17. Performative Schizoid Method

    DEFF Research Database (Denmark)

    Svabo, Connie

    2016-01-01

    A performative schizoid method is developed as a method contribution to performance as research. The method is inspired by contemporary research in the human and social sciences urging experimentation and researcher engagement with creative and artistic practice. In the article, the method...... is presented and an example is provided of a first exploratory engagement with it. The method is used in a specific project Becoming Iris, making inquiry into arts-based knowledge creation during a three month visiting scholarship at a small, independent visual art academy. Using the performative schizoid...... method in Becoming Iris results in four audio-visual and performance-based productions, centered on an emergent theme of the scholartist as a bird in borrowed feathers. Interestingly, the moral lesson of the fable about the vain jackdaw, who dresses in borrowed peacock feathers and becomes a castout...

  18. Exoplanet Detection Methods

    CERN Document Server

    Wright, Jason T

    2012-01-01

    This chapter reviews various methods of detecting planetary companions to stars from an observational perspective, focusing on radial velocities, astrometry, direct imaging, transits, and gravitational microlensing. For each method, this chapter first derives or summarizes the basic observable phenomena that are used to infer the ex- istence of planetary companions, as well as the physical properties of the planets and host stars that can be derived from the measurement of these signals. This chapter then outlines the general experimental requirements to robustly detect the signals us- ing each method, by comparing their magnitude to the typical sources of measurement uncertainty. This chapter goes on to compare the various methods to each other by outlining the regions of planet and host star parameter space where each method is most sensitive, stressing the complementarity of the ensemble of the methods at our disposal. Finally, there is a brief review of the history of the young exoplanet field, from the f...

  19. Phenomenographic Research Method

    Directory of Open Access Journals (Sweden)

    Erdem ÇEKMEZ

    2012-12-01

    Full Text Available Phenomenography, an approach to educational research, emerged from the studies carried out by Ference Marton and his colleagues at the University of Göteborg, Sweden, in the early 1970s. Phenomenography is the empirical study of the different ways in which people experience, perceive, apprehend, understand, conceptualize various phenomena in the world around them. Not only this method has been used much in educational researches in Turkey, but also the books about research methods do not provide detailed information about this method in details. This study explains the aim, characteristics, historical background and how to ensure the generalization, validity and reliability of phenomenographic research outcomes, besides mentions to the studies in which phenomenographic research method was used. In addition, the differences and similarities between this method and methods similar to phenomenology are explained.

  20. The Schwinger Variational Method

    Science.gov (United States)

    Huo, Winifred M.

    1995-01-01

    Variational methods have proven invaluable in theoretical physics and chemistry, both for bound state problems and for the study of collision phenomena. For collisional problems they can be grouped into two types: those based on the Schroedinger equation and those based on the Lippmann-Schwinger equation. The application of the Schwinger variational (SV) method to e-molecule collisions and photoionization has been reviewed previously. The present chapter discusses the implementation of the SV method as applied to e-molecule collisions.

  1. Applied iterative methods

    CERN Document Server

    Hageman, Louis A

    2004-01-01

    This graduate-level text examines the practical use of iterative methods in solving large, sparse systems of linear algebraic equations and in resolving multidimensional boundary-value problems. Assuming minimal mathematical background, it profiles the relative merits of several general iterative procedures. Topics include polynomial acceleration of basic iterative methods, Chebyshev and conjugate gradient acceleration procedures applicable to partitioning the linear system into a "red/black" block form, adaptive computational algorithms for the successive overrelaxation (SOR) method, and comp

  2. Well testing: interpretation methods

    Energy Technology Data Exchange (ETDEWEB)

    Bourdarot, G. [Elf Aquitaine, 92 - Courbevoie (France)

    1998-12-31

    This book presents the different methods to use for interpreting well tests: conventional methods, type curves, derivative, according to the type of reservoir limits (faults, channels, secant faults, constant pressure limits, closed reservoir) and the well configuration (partial penetration, inclined, fractured, horizontal or injection well). It indicates the method to be used in the case of more complex reservoirs (fissured reservoirs, two-layered reservoirs), interference tests or pulse tests and when fluid produced is gas or polyphasic. (authors) 60 refs.

  3. Well testing: interpretation methods

    Energy Technology Data Exchange (ETDEWEB)

    Bourdarot, G. (Elf Aquitaine, 92 - Courbevoie (France))

    1998-01-01

    This book presents the different methods to use for interpreting well tests: conventional methods, type curves, derivative, according to the type of reservoir limits (faults, channels, secant faults, constant pressure limits, closed reservoir) and the well configuration (partial penetration, inclined, fractured, horizontal or injection well). It indicates the method to be used in the case of more complex reservoirs (fissured reservoirs, two-layered reservoirs), interference tests or pulse tests and when fluid produced is gas or polyphasic. (authors) 60 refs.

  4. The Box Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactor...... description of this momentum flow. The Box Method is a practical method for the description of an Air Terminal Device which will save grid points and ensure the right level of the momentum flow....

  5. Methods of inventory control.

    Science.gov (United States)

    Lindley, C; Mackowiak, J

    1985-01-01

    Various methods for controlling inventory are described, and the advantages and disadvantages of each are discussed. The open-to-buy (OTB) budget method limits purchases to a specific amount of funds available for purchasing pharmaceuticals during a specified period. The emphasis of the OTB method is financial control of the pharmacy inventory. Although it is useful in monitoring and adjusting the dollar value of the inventory, it should be combined with other methods for a total inventory control system. The primary emphasis of the short-list method is to provide accurate and timely inventory information to the person responsible for order placement. The short list identifies the items that are in short supply. It is the most common feedback and control mechanism in use, but it is best suited for settings where duplicate or reserve stock is maintained and monitored by more rigorous methods. The main objective of the minimum and maximum method is to determine when and how much to order of each item. It also provides limited dollar control. The major disadvantage of this method is the time it requires to establish the minimum and maximum levels and to update them regularly to reflect changes in demand. The stock record card method is used to record information on the movement of goods in and out of the storage area. Stock cards can also be used to monitor inventory levels and facilitate order initiation. It is probably the optimum method to be used alone. The most effective system of inventory control is one employing a combination of these methods tailored to meet the institution's needs and available resources.

  6. Methods for data classification

    Science.gov (United States)

    Garrity, George; Lilburn, Timothy G.

    2011-10-11

    The present invention provides methods for classifying data and uncovering and correcting annotation errors. In particular, the present invention provides a self-organizing, self-correcting algorithm for use in classifying data. Additionally, the present invention provides a method for classifying biological taxa.

  7. DISCOURSE ON METHODS.

    Science.gov (United States)

    BOUCHER, JOHN G.

    THE AUTHOR STATES THAT BEFORE PRESENT FOREIGN LANGUAGE TEACHING METHODS CAN BE DISCUSSED INTELLIGENTLY, THE RESEARCH IN PSYCHOLOGY AND LINGUISTICS WHICH HAS INFLUENCED THE DEVELOPMENT OF THESE METHODS MUST BE CONSIDERED. MANY FOREIGN LANGUAGE TEACHERS WERE BEGINNING TO FEEL COMFORTABLE WITH THE AUDIOLINGUAL APPROACH WHEN NOAM CHOMSKY, IN HIS 1966…

  8. Noise-Measuring Method

    DEFF Research Database (Denmark)

    Diamond, J. M.

    1965-01-01

    A noise-measuring method based on the use of a calibrated noise generator and an output meter with a special scale is described. The method eliminates the effect of noise contributions occurring in the circuits following the device under test....

  9. Method of forming nanodielectrics

    Science.gov (United States)

    Tuncer, Enis [Knoxville, TN; Polyzos, Georgios [Oak Ridge, TN

    2014-01-07

    A method of making a nanoparticle filled dielectric material. The method includes mixing nanoparticle precursors with a polymer material and reacting the nanoparticle mixed with the polymer material to form nanoparticles dispersed within the polymer material to form a dielectric composite.

  10. Soybean allergen detection methods

    DEFF Research Database (Denmark)

    Pedersen, Mona H; Holzhauser, Thomas; Bisson, Caroline

    2008-01-01

    Soybean containing products are widely consumed, thus reliable methods for detection of soy in foods are needed in order to make appropriate risk assessment studies to adequately protect soy allergic patients. Six methods were compared using eight food products with a declared content of soy...

  11. The Method of Archimedes.

    Science.gov (United States)

    Del Grande, John

    1993-01-01

    Describes the method that Archimedes utilized to calculate the volumes of spheres and other solids. The method found the volume of a sphere by comparing the mass of parallel slices of a sphere and a cone with that of a cylinder of known mass. (MDH)

  12. Research Methods in Education

    Science.gov (United States)

    Check, Joseph; Schutt, Russell K.

    2011-01-01

    "Research Methods in Education" introduces research methods as an integrated set of techniques for investigating questions about the educational world. This lively, innovative text helps students connect technique and substance, appreciate the value of both qualitative and quantitative methodologies, and make ethical research decisions.…

  13. METHOD FOR MAKING CHEESE

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention relates to a method for making Cheddar type and Continental type cheese with an adjunct culture comprising a Lactobacillus helveticus strain.......The present invention relates to a method for making Cheddar type and Continental type cheese with an adjunct culture comprising a Lactobacillus helveticus strain....

  14. Improved nonlinear prediction method

    Science.gov (United States)

    Adenan, Nur Hamiza; Md Noorani, Mohd Salmi

    2014-06-01

    The analysis and prediction of time series data have been addressed by researchers. Many techniques have been developed to be applied in various areas, such as weather forecasting, financial markets and hydrological phenomena involving data that are contaminated by noise. Therefore, various techniques to improve the method have been introduced to analyze and predict time series data. In respect of the importance of analysis and the accuracy of the prediction result, a study was undertaken to test the effectiveness of the improved nonlinear prediction method for data that contain noise. The improved nonlinear prediction method involves the formation of composite serial data based on the successive differences of the time series. Then, the phase space reconstruction was performed on the composite data (one-dimensional) to reconstruct a number of space dimensions. Finally the local linear approximation method was employed to make a prediction based on the phase space. This improved method was tested with data series Logistics that contain 0%, 5%, 10%, 20% and 30% of noise. The results show that by using the improved method, the predictions were found to be in close agreement with the observed ones. The correlation coefficient was close to one when the improved method was applied on data with up to 10% noise. Thus, an improvement to analyze data with noise without involving any noise reduction method was introduced to predict the time series data.

  15. Data center cooling method

    Energy Technology Data Exchange (ETDEWEB)

    Chainer, Timothy J.; Dang, Hien P.; Parida, Pritish R.; Schultz, Mark D.; Sharma, Arun

    2015-08-11

    A method aspect for removing heat from a data center may use liquid coolant cooled without vapor compression refrigeration on a liquid cooled information technology equipment rack. The method may also include regulating liquid coolant flow to the data center through a range of liquid coolant flow values with a controller-apparatus based upon information technology equipment temperature threshold of the data center.

  16. Studying Aid: Some Methods

    NARCIS (Netherlands)

    D.R. Gasper (Des)

    2003-01-01

    textabstractINVESTIGATING IDEAS, IDEOLOGIES AND PRACTICES This paper presents some methods for trying to make sense of international aid and of its study.1 Some of the methods may be deemed ethnographic; the others are important partners to them, but rather different. In the course of discussing q

  17. Research Methods in Education

    Science.gov (United States)

    Check, Joseph; Schutt, Russell K.

    2011-01-01

    "Research Methods in Education" introduces research methods as an integrated set of techniques for investigating questions about the educational world. This lively, innovative text helps students connect technique and substance, appreciate the value of both qualitative and quantitative methodologies, and make ethical research decisions.…

  18. METHODS OF MAGNETOTELLURIC ANALYSIS

    Science.gov (United States)

    Magnetotelluric prospecting is a method of geophysical exploration that makes use of the fluctuations in the natural electric and magnetic fields...function of the conductivity structure of the earth’s substrata. This report describes some new methods for analyzing and interpreting magnetotelluric

  19. Methods in Modern Biophysics

    CERN Document Server

    Nölting, Bengt

    2006-01-01

    Incorporating recent dramatic advances, this textbook presents a fresh and timely introduction to modern biophysical methods. An array of new, faster and higher-power biophysical methods now enables scientists to examine the mysteries of life at a molecular level. This innovative text surveys and explains the ten key biophysical methods, including those related to biophysical nanotechnology, scanning probe microscopy, X-ray crystallography, ion mobility spectrometry, mass spectrometry, proteomics, and protein folding and structure. Incorporating much information previously unavailable in tutorial form, Nölting employs worked examples and 267 illustrations to fully detail the techniques and their underlying mechanisms. Methods in Modern Biophysics is written for advanced undergraduate and graduate students, postdocs, researchers, lecturers and professors in biophysics, biochemistry and related fields. Special features in the 2nd edition: • Illustrates the high-resolution methods for ultrashort-living protei...

  20. Adaptive method of lines

    CERN Document Server

    Saucez, Ph

    2001-01-01

    The general Method of Lines (MOL) procedure provides a flexible format for the solution of all the major classes of partial differential equations (PDEs) and is particularly well suited to evolutionary, nonlinear wave PDEs. Despite its utility, however, there are relatively few texts that explore it at a more advanced level and reflect the method''s current state of development.Written by distinguished researchers in the field, Adaptive Method of Lines reflects the diversity of techniques and applications related to the MOL. Most of its chapters focus on a particular application but also provide a discussion of underlying philosophy and technique. Particular attention is paid to the concept of both temporal and spatial adaptivity in solving time-dependent PDEs. Many important ideas and methods are introduced, including moving grids and grid refinement, static and dynamic gridding, the equidistribution principle and the concept of a monitor function, the minimization of a functional, and the moving finite elem...

  1. Fast Distributed Gradient Methods

    CERN Document Server

    Jakovetic, Dusan; Moura, Jose M F

    2011-01-01

    The paper proposes new fast distributed optimization gradient methods and proves convergence to the exact solution at rate O(\\log k/k), much faster than existing distributed optimization (sub)gradient methods with convergence O(1/\\sqrt{k}), while incurring practically no additional communication nor computation cost overhead per iteration. We achieve this for convex (with at least one strongly convex,) coercive, three times differentiable and with Lipschitz continuous first derivative (private) cost functions. Our work recovers for distributed optimization similar convergence rate gains obtained by centralized Nesterov gradient and fast iterative shrinkage-thresholding algorithm (FISTA) methods over ordinary centralized gradient methods. We also present a constant step size distributed fast gradient algorithm for composite non-differentiable costs. A simulation illustrates the effectiveness of our distributed methods.

  2. Cooperative method development

    DEFF Research Database (Denmark)

    Dittrich, Yvonne; Rönkkö, Kari; Eriksson, Jeanette;

    2008-01-01

    research is not easily combined with the improvement orientation of an engineering discipline. During the last 6 years, we have applied an approach we call `cooperative method development', which combines qualitative social science fieldwork, with problem-oriented method, technique and process improvement....... The action research based approach focusing on shop floor software development practices allows an understanding of how contextual contingencies influence the deployment and applicability of methods, processes and techniques. This article summarizes the experiences and discusses the further development......The development of methods tools and process improvements is best to be based on the understanding of the development practice to be supported. Qualitative research has been proposed as a method for understanding the social and cooperative aspects of software development. However, qualitative...

  3. Engaging with mobile methods

    DEFF Research Database (Denmark)

    Jensen, Martin Trandberg

    2014-01-01

    This chapter showcases how mobile methods are more than calibrated techniques awaiting application by tourism researchers, but productive in the enactment of the mobile (Law and Urry, 2004). Drawing upon recent findings deriving from a PhD course on mobility and mobile methods it reveals...... the conceptual ambiguousness of the term ‘mobile methods’. In order to explore this ambiguousness the chapter provides a number of examples deriving from tourism research, to explore how mobile methods are always entangled in ideologies, predispositions, conventions and practice-realities. Accordingly......, the engagements with methods are acknowledged to be always political and contextual, reminding us to avoid essentialist discussions regarding research methods. Finally, the chapter draws on recent fieldwork to extend developments in mobilities-oriented tourism research, by employing auto-ethnography to call...

  4. Dipolar cortico-muscular electrical stimulation: a novel method that enhances motor function in both - normal and spinal cord injured mice

    Directory of Open Access Journals (Sweden)

    Ahmed Zaghloul

    2010-09-01

    Full Text Available Abstract Background Electrical stimulation of the central and peripheral nervous systems is a common tool that is used to improve functional recovery after neuronal injury. Methods Here we described a new configuration of electrical stimulation as it was tested in anesthetized control and spinal cord injury (SCI mice. Constant voltage output was delivered through two electrodes. While the negative voltage output (ranging from -1.8 to -2.6 V was delivered to the muscle via transverse wire electrodes (diameter, 500 μm located at opposite ends of the muscle, the positive output (ranging from + 2.4 to +3.2 V was delivered to the primary motor cortex (M1 (electrode tip, 100 μm. The configuration was named dipolar cortico-muscular stimulation (dCMS and consisted of 100 pulses (1 ms pulse duration, 1 Hz frequency. Results In SCI animals, after dCMS, cortically-elicited muscle contraction improved markedly at the contralateral (456% and ipsilateral (457% gastrocnemius muscles. The improvement persisted for the duration of the experiment (60 min. The enhancement of cortically-elicited muscle contraction was accompanied by the reduction of M1 maximal threshold and the potentiation of spinal motoneuronal evoked responses at the contralateral (313% and ipsilateral (292% sides of the spinal cord. Moreover, spontaneous activity recorded from single spinal motoneurons was substantially increased contralaterally (121% and ipsilaterally (54%. Interestingly, spinal motoneuronal responses and muscle twitches evoked by the test stimulation of non-treated M1 (received no dCMS were significantly enhanced as well. Similar results obtained from normal animals albeit the changes were relatively smaller. Conclusion These findings demonstrated that dCMS could improve functionality of corticomotoneuronal pathway and thus it may have therapeutic potential.

  5. Methods for age estimation

    Directory of Open Access Journals (Sweden)

    D. Sümeyra Demirkıran

    2014-03-01

    Full Text Available Concept of age estimation plays an important role on both civil law and regulation of criminal behaviors. In forensic medicine, age estimation is practiced for individual requests as well for request of the court. In this study it is aimed to compile the methods of age estimation and to make recommendations for the solution of the problems encountered. In radiological method the epiphyseal lines of the bones and views of the teeth are used. In order to estimate the age by comparing bone radiographs; Greulich-Pyle Atlas (GPA, Tanner-Whitehouse Atlas (TWA and “Adli Tıpta Yaş Tayini (ATYT” books are used. Bone age is found to be 2 years older averagely than chronologic age, especially in puberty, according to the forensic age estimations described in the ATYT book. For the age estimation with teeth, Demirjian method is used. In time different methods are developed by modifying Demirjian method. However no accurate method was found. Histopathological studies are done on bone marrow cellularity and dermis cells. No correlation was found between histopathoogical findings and choronologic age. Important ethical and legal issues are brought with current age estimation methods especially in teenage period. Therefore it is required to prepare atlases of bone age compatible with our society by collecting the findings of the studies in Turkey. Another recommendation could be to pay attention to the courts of age raising trials of teenage women and give special emphasis on birth and population records

  6. STATISTICAL METHODS IN HISTORY

    Directory of Open Access Journals (Sweden)

    Orlov A. I.

    2016-01-01

    Full Text Available We have given a critical analysis of statistical models and methods for processing text information in historical records to establish the times when there were certain events, ie, to build science-based chronology. There are three main kinds of sources of knowledge of ancient history: ancient texts, the remains of material culture and traditions. The specific date of the extracted by archaeologists objects in most cases can not be found. The group of Academician A.T. Fomenko has developed and applied new statistical methods for analysis of historical texts (Chronicle, based on the intensive use of computer technology. Two major scientific results were: the majority of historical records that we know now, are duplicated (in particular, chronicles, describing the so-called "Ancient Rome" and "Middle Ages", talking about the same events; the known historical chronicles tell us about real events, separated from the present time for not more than 1000 years. It was found that chronicles describing the history of "ancient times" and "Middle Ages" and the chronicle of Chinese history and the history of various European countries do not talk about different, but about the same events. We have the attempt of a new dating of historical events and restoring the true history of human society based on new data. From the standpoint of statistical methods of historical records and images of their fragments – they are special cases of non-numeric objects of nature. Therefore, developed by the group of A.T. Fomenko computer-statistical methods are the part of non-numerical statistics. We have considered some methods of statistical analysis of chronicles applied by the group of A.T. Fomenko: correlation method of maximums; dynasties method; the method of attenuation frequency; questionnaire method codes. New chronology allows us to understand much of the battle of ideas in modern science and mass consciousness. It becomes clear the root cause of cautious

  7. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...... description of this momentum flow. The Prescribed Velocity Method is a practical method for the description of an Air Terminal Device which will save grid points close to the opening and ensure the right level of the momentum flow....

  8. Methods in mummy research

    DEFF Research Database (Denmark)

    Lynnerup, Niels

    2009-01-01

    Mummies are human remains with preservation of non-bony tissue. Many mummy studies focus on the development and application of non-destructive methods for examining mummies, including radiography, CT-scanning with advanced 3-dimensional visualisations, and endoscopic techniques, as well as minima......Mummies are human remains with preservation of non-bony tissue. Many mummy studies focus on the development and application of non-destructive methods for examining mummies, including radiography, CT-scanning with advanced 3-dimensional visualisations, and endoscopic techniques, as well...... as minimally-destructive chemical, physical and biological methods for, e.g., stable isotopes, trace metals and DNA....

  9. Modern diffraction methods

    CERN Document Server

    Mittemeijer, E J

    2013-01-01

    The role of diffraction methods for the solid-state sciences has been pivotal to determining the (micro)structure of a material. Particularly, the expanding activities in materials science have led to the development of new methods for analysis by diffraction. This book offers an authoritative overview of the new developments in the field of analysis of matter by (in particular X-ray, electron and neutron) diffraction. It is composed of chapters written by leading experts on 'modern diffraction methods'. The focus in the various chapters of this book is on the current forefront of research on

  10. Methods in Bioengineering

    CERN Document Server

    Jayaraman, Arul

    2009-01-01

    This volume provides a detailed look at the two main aspects of systems biology: the design of sophisticated experimental methods and the development of complex models to analyze the data. Focusing on methods that are being used to solve current problems in biomedical science and engineering, this comprehensive, richly illustrated resource shows you how to design of state-of-the art methods for analyzing biological systems, implement experimental approaches for investigating cellular behavior in health and disease, use algorithms and modeling techniques for quantitatively describing biomedical

  11. Montessori Method and ICTs

    Directory of Open Access Journals (Sweden)

    Athanasios Drigas

    2016-03-01

    Full Text Available This article bridges the gap between the Montessori Method and Information and Communication Technologies (ICTs in contemporary education. It reviews recent research works which recall the Montessori philosophy, principles and didactical tools applying to today’s computers and supporting technologies in children’s learning process. This article reviews how important the stimulation of human senses in the learning process is, as well as the development of Montessori materials using the body and the hand in particular, all according to the Montessori Method along with recent researches over ICTs. Montessori Method within information society age acquires new perspectives, new functionality and new efficacy.

  12. Numerical methods using Matlab

    CERN Document Server

    Lindfield, George

    2012-01-01

    Numerical Methods using MATLAB, 3e, is an extensive reference offering hundreds of useful and important numerical algorithms that can be implemented into MATLAB for a graphical interpretation to help researchers analyze a particular outcome. Many worked examples are given together with exercises and solutions to illustrate how numerical methods can be used to study problems that have applications in the biosciences, chaos, optimization, engineering and science across the board. Numerical Methods using MATLAB, 3e, is an extensive reference offering hundreds of use

  13. Methods of flash sintering

    Energy Technology Data Exchange (ETDEWEB)

    Raj, Rishi; Cologna, Marco; Francis, John S.

    2016-05-10

    This disclosure provides methods of flash sintering and compositions created by these methods. Methods for sintering multilayered bodies are provided in which a sintered body is produced in less than one minute. In one aspect, each layer is of a different composition, and may be constituted wholly from a ceramic or from a combination of ceramic and metallic particles. When the body includes a layer of an anode composition, a layer of an electrolyte composition and a layer of a cathode composition, the sintered body can be used to produce a solid oxide fuel cell.

  14. Structural Reliability Methods

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager; Madsen, H. O.

    of structural reliability, including the theoretical basis for these methods. Partial safety factor codes under current practice are briefly introduced and discussed. A probabilistic code format for obtaining a formal reliability evaluation system that catches the most essential features of the nature......The structural reliability methods quantitatively treat the uncertainty of predicting the behaviour and properties of a structure given the uncertain properties of its geometry, materials, and the actions it is supposed to withstand. This book addresses the probabilistic methods for evaluation...

  15. Generalized subspace correction methods

    Energy Technology Data Exchange (ETDEWEB)

    Kolm, P. [Royal Institute of Technology, Stockholm (Sweden); Arbenz, P.; Gander, W. [Eidgenoessiche Technische Hochschule, Zuerich (Switzerland)

    1996-12-31

    A fundamental problem in scientific computing is the solution of large sparse systems of linear equations. Often these systems arise from the discretization of differential equations by finite difference, finite volume or finite element methods. Iterative methods exploiting these sparse structures have proven to be very effective on conventional computers for a wide area of applications. Due to the rapid development and increasing demand for the large computing powers of parallel computers, it has become important to design iterative methods specialized for these new architectures.

  16. Kv1.5 blockers preferentially inhibit TASK-1 channels: TASK-1 as a target against atrial fibrillation and obstructive sleep apnea?

    Science.gov (United States)

    Kiper, Aytug K; Rinné, Susanne; Rolfes, Caroline; Ramírez, David; Seebohm, Guiscard; Netter, Michael F; González, Wendy; Decher, Niels

    2015-05-01

    Atrial fibrillation and obstructive sleep apnea are responsible for significant morbidity and mortality in the industrialized world. There is a high medical need for novel drugs against both diseases, and here, Kv1.5 channels have emerged as promising drug targets. In humans, TASK-1 has an atrium-specific expression and TASK-1 is also abundantly expressed in the hypoglossal motor nucleus. We asked whether known Kv1.5 channel blockers, effective against atrial fibrillation and/or obstructive sleep apnea, modulate TASK-1 channels. Therefore, we tested Kv1.5 blockers with different chemical structures for their TASK-1 affinity, utilizing two-electrode voltage clamp (TEVC) recordings in Xenopus oocytes. Despite the low structural conservation of Kv1.5 and TASK-1 channels, we found all Kv1.5 blockers analyzed to be even more effective on TASK-1 than on Kv1.5. For instance, the half-maximal inhibitory concentration (IC50) values of AVE0118 and AVE1231 (A293) were 10- and 43-fold lower on TASK-1. Also for MSD-D, ICAGEN-4, S20951 (A1899), and S9947, the IC50 values were 1.4- to 70-fold lower than for Kv1.5. To describe this phenomenon on a molecular level, we used in silico models and identified unexpected structural similarities between the two drug binding sites. Kv1.5 blockers, like AVE0118 and AVE1231, which are promising drugs against atrial fibrillation or obstructive sleep apnea, are in fact potent TASK-1 blockers. Accordingly, block of TASK-1 channels by these compounds might contribute to the clinical effectiveness of these drugs. The higher affinity of these blockers for TASK-1 channels suggests that TASK-1 might be an unrecognized molecular target of Kv1.5 blockers effective in atrial fibrillation or obstructive sleep apnea.

  17. ROMK1 channel activity is regulated by monoubiquitination.

    Science.gov (United States)

    Lin, Dao-Hong; Sterling, Hyacinth; Wang, Zhijian; Babilonia, Elisa; Yang, Baofeng; Dong, Ke; Hebert, Steven C; Giebisch, Gerhard; Wang, Wen-Hui

    2005-03-22

    The ubiquitination of proteins can signal their degradation, modify their activity or target them to specific membranes or cellular organelles. Here, we show that monoubiquitination regulates the plasma membrane abundance and function of the potassium channel, ROMK. Immunoprecipitation of proteins obtained from renal cortex and outer medulla with ROMK antibody revealed that this channel was monoubiquitinated. To determine the ubiquitin binding site on ROMK1, all intracellular lysine (Lys) residues of ROMK1 were individually mutated to arginine (Arg), and a two-electrode voltage clamp was used to measure the ROMK1 channel activity in Xenopus oocytes. ROMK1 channel activity increased from 8.1 to 27.2 microA only when Lys-22 was mutated to Arg. Furthermore, Western blotting failed to detect the ubiquitinated ROMK1 in oocytes injected with R1K22R. Patch-clamp experiments showed that biophysical properties of R1K22R were identical to those of wild-type ROMK1. Although total protein expression levels of GFP-ROMK1 and GFP-R1K22R in oocytes were similar, confocal microscopy showed that the surface fluorescence intensity in oocytes injected with GFP-R1K22R was higher than that of GFP-ROMK1. In addition, biotin labeling of ROMK1 and R1K22R proteins expressed in HEK293 cells showed increased surface expression of the Lys-22 mutant channel. Finally, expression of R1K22R in COS7 cells significantly stimulated the surface expression of ROMK1. We conclude that ROMK1 can be monoubiquitinated and that Lys-22 is an ubiquitin-binding site. Thus, monoubiquitination of ROMK1 regulates channel activity by reducing the surface expression of channel protein. This finding implicates the linking of a single ubiquitin molecule to channels as an important posttranslational regulatory signal.

  18. Lubiprostone activates CFTR, but not ClC-2, via the prostaglandin receptor (EP(4)).

    Science.gov (United States)

    Norimatsu, Yohei; Moran, Aurelia R; MacDonald, Kelvin D

    2012-09-28

    The goal of this study was to determine the mechanism of lubiprostone activation of epithelial chloride transport. Lubiprostone is a bicyclic fatty acid approved for the treatment of constipation [1]. There is uncertainty, however, as to how lubiprostone increases epithelial chloride transport. Direct stimulation of ClC-2 and CFTR chloride channels as well as stimulation of these channels via the EP(4) receptor has been described [2-5]. To better define this mechanism, two-electrode voltage clamp was used to assay Xenopus oocytes expressing ClC-2, with or without co-expression of the EP(4) receptor or β adrenergic receptor (βAR), for changes in conductance elicited by lubiprostone. Oocytes co-expressing CFTR and either βAR or the EP(4) receptor were also studied. In oocytes co-expressing ClC-2 and βAR conductance was stimulated by hyperpolarization and acidic pH (pH = 6), but there was no response to the β adrenergic agonist, isoproterenol. Oocytes expressing ClC-2 only or co-expressing ClC-2 and EP(4) did not respond to the presence of 0.1, 1, or 10 μM lubiprostone in the superperfusate. Oocytes co-expressing CFTR and βAR did not respond to hyperpolarization, acidic pH, or 1 μM lubiprostone. However, conductance was elevated by isoproterenol and inhibited by CFTR(inh)172. Co-expression of CFTR and EP(4) resulted in lubiprostone-stimulated conductance, which was also sensitive to CFTR(inh)172. The EC(50) for lubiprostone mediated CFTR activation was ~10 nM. These results demonstrate no direct action of lubiprostone on either ClC-2 or CFTR channels expressed in oocytes. However, the results confirm that CFTR can be activated by lubiprostone via the EP(4) receptor in oocytes.

  19. Mercury and zinc differentially inhibit shark and human CFTR orthologues: involvement of shark cysteine 102.

    Science.gov (United States)

    Weber, Gerhard J; Mehr, Ali Poyan; Sirota, Jeffrey C; Aller, Stephen G; Decker, Sarah E; Dawson, David C; Forrest, John N

    2006-03-01

    The apical membrane is an important site of mercury toxicity in shark rectal gland tubular cells. We compared the effects of mercury and other thiol-reacting agents on shark CFTR (sCFTR) and human CFTR (hCFTR) chloride channels using two-electrode voltage clamping of cRNA microinjected Xenopus laevis oocytes. Chloride conductance was stimulated by perfusing with 10 microM forskolin (FOR) and 1 mM IBMX, and then thio-reactive species were added. In oocytes expressing sCFTR, FOR + IBMX mean stimulated Cl(-) conductance was inhibited 69% by 1 microM mercuric chloride and 78% by 5 microM mercuric chloride (IC(50) of 0.8 microM). Despite comparable stimulation of conductance, hCFTR was insensitive to 1 microM HgCl(2) and maximum inhibition was 15% at the highest concentration used (5 microM). Subsequent exposure to glutathione (GSH) did not reverse the inhibition of sCFTR by mercury, but dithiothreitol (DTT) completely reversed this inhibition. Zinc (50-200 microM) also reversibly inhibited sCFTR (40-75%) but did not significantly inhibit hCFTR. Similar inhibition of sCFTR but not hCFTR was observed with an organic mercurial, p-chloromercuriphenylsulfonic acid (pCMBS). The first membrane spanning domain (MSD1) of sCFTR contains two unique cysteines, C102 and C303. A chimeric construct replacing MSD1 of hCFTR with the corresponding sequence of sCFTR was highly sensitive to mercury. Site-specific mutations introducing the first but not the second shark unique cysteine in hCFTR MSD1 resulted in full sensitivity to mercury. These experiments demonstrate a profound difference in the sensitivity of shark vs. human CFTR to inhibition by three thiol-reactive substances, an effect that involves C102 in the shark orthologue.

  20. Mercury toxicity in the shark (Squalus acanthias) rectal gland: apical CFTR chloride channels are inhibited by mercuric chloride.

    Science.gov (United States)

    Ratner, Martha A; Decker, Sarah E; Aller, Stephen G; Weber, Gerhard; Forrest, John N

    2006-03-01

    In the shark rectal gland, basolateral membrane proteins have been suggested as targets for mercury. To examine the membrane polarity of mercury toxicity, we performed experiments in three preparations: isolated perfused rectal glands, primary monolayer cultures of rectal gland epithelial cells, and Xenopus oocytes expressing the shark cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. In perfused rectal glands we observed: (1) a dose-dependent inhibition by mercury of forskolin/3-isobutyl-1-methylxanthine (IBMX)-stimulated chloride secretion; (2) inhibition was maximal when mercury was added before stimulation with forskolin/IBMX; (3) dithiothrietol (DTT) and glutathione (GSH) completely prevented inhibition of chloride secretion. Short-circuit current (Isc) measurements in monolayers of rectal gland epithelial cells were performed to examine the membrane polarity of this effect. Mercuric chloride inhibited Isc more potently when applied to the solution bathing the apical vs. the basolateral membrane (23 +/- 5% and 68 +/- 5% inhibition at 1 and 10 microM HgCl2 in the apical solution vs. 2 +/- 0.9% and 14 +/- 5% in the basolateral solution). This inhibition was prevented by pre-treatment with apical DTT or GSH; however, only the permeant reducing agent DTT reversed mercury inhibition when added after exposure. When the shark rectal gland CFTR channel was expressed in Xenopus oocytes and chloride conductance was measured by two-electrode voltage clamping, we found that 1 microM HgCl2 inhibited forskolin/IBMX conductance by 69.2 +/- 2.0%. We conclude that in the shark rectal gland, mercury inhibits chloride secretion by interacting with the apical membrane and that CFTR is the likely site of this action.

  1. Compound-Specific Effects of Mutations at Val787 in DII-S6 of Nav1.4 Sodium Channels on the Action of Sodium Channel Inhibitor Insecticides

    Science.gov (United States)

    von Stein, Richard T.; Soderlund, David M.

    2012-01-01

    Sodium channel inhibitor (SCI) insecticides are hypothesized to inhibit voltage-gated sodium channels by binding selectively to the slow-inactivated state. Replacement of valine at position 787 in the S6 segment of homology domain II of the rat Nav1.4 sodium channel by lysine (V787K) enchances slow inactivation of this channel whereas replacement by alanine or cysteine (V787A, V787C) inhibits slow inactivation. To test the hypothesis that SCI insecticides bind selectively to the slow-inactivated state, we constructed mutated Nav1.4/V787A, Nav1.4/V787C, and Nav1.4/V787K cDNAs, expressed wildtype and mutated channels with the auxiliary β1 subunit in Xenopus oocytes, and used the two-electrode voltage clamp technique to examine the effects of these mutations on channel inhibition by four SCI insecticides (indoxacarb, its bioactivated metabolite DCJW, metaflumizone, and RH3421). Mutations at Val787 affected SCI insecticide sensitivity in a manner that was independent of mutation-induced changes in slow inactivation gating. Sensitivity to inhibition by 10 μM indoxacarb was significantly increased in all three mutated channels, whereas sensitivity to inhibition by 10 μM metaflumizone was significantly reduced in Nav1.4/V787A channels and completely abolished in Nav1.4/V787K channels. The effects of Val787 mutations on metaflumizone were correlated with the hydrophobicity of the substituted amino acid rather than the extent of slow inactivation. None of the mutations at Val787 significantly affected the sensitivity to inhibition by DCJW or RH3421. These results demonstrate that the impact of mutations at Val787 on sodium channel inhibition by SCI insecticides depends on the specific insecticide examined and is independent of mutation-induced changes in slow inactivation gating. We propose that Val787 may be a unique determinant of metaflumizone binding. PMID:22983119

  2. A potent potassium channel blocker from Mesobuthus eupeus scorpion venom.

    Science.gov (United States)

    Gao, Bin; Peigneur, Steve; Tytgat, Jan; Zhu, Shunyi

    2010-12-01

    Scorpion venom-derived peptidyl toxins are valuable pharmacological tools for investigating the structure-function relationship of ion channels. Here, we report the purification, sequencing and functional characterization of a new K(+) channel blocker (MeuKTX) from the venom of the scorpion Mesobuthus eupeus. Effects of MeuKTX on ten cloned potassium channels in Xenopus oocytes were evaluated using two-electrode voltage-clamp recordings. MeuKTX is the orthologue of BmKTX (α-KTx3.6), a known Kv1.3 blocker from the scorpion Mesobuthus martensii, and classified as α-KTx3.13. MeuKTX potently blocks rKv1.1, rKv1.2 and hKv1.3 channels with 50% inhibitory concentration (IC(50)) of 203.15 ± 4.06 pM, 8.92 ± 2.3 nM and 171 ± 8.56 pM, respectively, but does not affect rKv1.4, rKv1.5, hKv3.1, rKv4.3, and hERG channels even at 2 μM concentration. At this high concentration, MeuKTX is also active on rKv1.6 and Shaker IR. Our results also demonstrate that MeuKTX and BmKTX have the same channel spectrum and similar pharmacological potency. Analysis of the structure-function relationships of α-KTx3 subfamily toxins allows us to recognize several key sites which may be useful for designing toxins with improved activity on hKv1.3, an attractive target for T-cell mediated autoimmune diseases.

  3. Carbon Monoxide (CO) Is a Novel Inhibitor of Connexin Hemichannels*

    Science.gov (United States)

    León-Paravic, Carmen G.; Figueroa, Vania A.; Guzmán, Diego J.; Valderrama, Carlos F.; Vallejos, Antonio A.; Fiori, Mariana C.; Altenberg, Guillermo A.; Reuss, Luis; Retamal, Mauricio A.

    2014-01-01

    Hemichannels (HCs) are hexamers of connexins that can form gap-junction channels at points of cell contacts or “free HCs” at non-contacting regions. HCs are involved in paracrine and autocrine cell signaling, and under pathological conditions may induce and/or accelerate cell death. Therefore, studies of HC regulation are of great significance. Nitric oxide affects the activity of Cx43 and Cx46 HCs, whereas carbon monoxide (CO), another gaseous transmitter, modulates the activity of several ion channels, but its effect on HCs has not been explored. We studied the effect of CO donors (CORMs) on Cx46 HCs expressed in Xenopus laevis oocytes using two-electrode voltage clamp and on Cx43 and Cx46 expressed in HeLa cells using a dye-uptake technique. CORM-2 inhibited Cx46 HC currents in a concentration-dependent manner. The C-terminal domain and intracellular Cys were not necessary for the inhibition. The effect of CORM-2 was not prevented by guanylyl-cyclase, protein kinase G, or thioredoxin inhibitors, and was not due to endocytosis of HCs. However, the effect of CORM-2 was reversed by reducing agents that act extracellularly. Additionally, CO inhibited dye uptake of HeLa cells expressing Cx43 or Cx46, and MCF-7 cells, which endogenously express Cx43 and Cx46. Because CORM-2 carbonylates Cx46 in vitro and induces conformational changes, a direct effect of that CO on Cx46 is possible. The inhibition of HCs could help to understand some of the biological actions of CO in physiological and pathological conditions. PMID:25384983

  4. Meroterpenoid Chrodrimanins Are Selective and Potent Blockers of Insect GABA-Gated Chloride Channels.

    Science.gov (United States)

    Xu, Yan; Furutani, Shogo; Ihara, Makoto; Ling, Yun; Yang, Xinling; Kai, Kenji; Hayashi, Hideo; Matsuda, Kazuhiko

    2015-01-01

    Meroterpenoid chrodrimanins, produced from Talaromyces sp. YO-2, are known to paralyze silkworm (Bombyx mori) larvae, but their target is unknown. We have investigated the actions of chrodrimanin B on ligand-gated ion channels of silkworm larval neurons using patch-clamp electrophysiology. Chrodrimanin B had no effect on membrane currents when tested alone at 1 μM. However, it completely blocked the γ-aminobutyric acid (GABA)-induced current and showed less pronounced actions on acetylcholine- and L-glutamate-induced currents, when delivered at 1 μM for 1 min prior to co-application with transmitter GABA. Thus, chrodrimanins were also tested on a wild-type isoform of the B. mori GABA receptor (GABAR) RDL using two-electrode voltage-clamp electrophysiology. Chrodrimanin B attenuated the peak current amplitude of the GABA response of RDL with an IC50 of 1.66 nM. The order of the GABAR-blocking potency of chrodrimanins B > D > A was in accordance with their reported insecticidal potency. Chrodrimanin B had no open channel blocking action when tested at 3 nM on the GABA response of RDL. Co-application with 3 nM chrodrimanin B shifted the GABA concentration response curve to a higher concentration and further increase of chrodrimanin B concentration to 10 nM; it reduced maximum current amplitude of the GABA response, pointing to a high-affinity competitive action and a lower affinity non-competitive action. The A282S;T286V double mutation of RDL, which impairs the actions of fipronil, hardly affected the blocking action of chrodrimanin B, indicating a binding site of chrodrimanin B distinct from that of fipronil. Chrodrimanin B showed approximately 1,000-fold lower blocking action on human α1β2γ2 GABAR compared to RDL and thus is a selective blocker of insect GABARs.

  5. Variability of Potassium Channel Blockers in Mesobuthus eupeus Scorpion Venom with Focus on Kv1.1

    Science.gov (United States)

    Kuzmenkov, Alexey I.; Vassilevski, Alexander A.; Kudryashova, Kseniya S.; Nekrasova, Oksana V.; Peigneur, Steve; Tytgat, Jan; Feofanov, Alexey V.; Kirpichnikov, Mikhail P.; Grishin, Eugene V.

    2015-01-01

    The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus, and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here, we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands, and we compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis, we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β and inhibitor cystine knot types of fold. M. eupeus venom was then separated to individual components by multistage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore binding activity during venom separation. As a result, eight high affinity Kv1.1 channel blockers were identified, including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1–780 nm) by the two-electrode voltage clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs. PMID:25792741

  6. Variability of Potassium Channel Blockers in Mesobuthus eupeus Scorpion Venom with Focus on Kv1.1: AN INTEGRATED TRANSCRIPTOMIC AND PROTEOMIC STUDY.

    Science.gov (United States)

    Kuzmenkov, Alexey I; Vassilevski, Alexander A; Kudryashova, Kseniya S; Nekrasova, Oksana V; Peigneur, Steve; Tytgat, Jan; Feofanov, Alexey V; Kirpichnikov, Mikhail P; Grishin, Eugene V

    2015-05-08

    The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus, and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here, we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands, and we compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis, we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β and inhibitor cystine knot types of fold. M. eupeus venom was then separated to individual components by multistage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore binding activity during venom separation. As a result, eight high affinity Kv1.1 channel blockers were identified, including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1-780 nm) by the two-electrode voltage clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs.

  7. Altered GABAA Receptor Subunit Expression and Pharmacology in Human Angelman Syndrome Cortex

    Science.gov (United States)

    Roden, William H.; Peugh, Lindsey D.; Jansen, Laura A.

    2011-01-01

    The neurodevelopmental disorder Angelman syndrome is most frequently caused by deletion of the maternally-derived chromosome 15q11-q13 region, which includes not only the causative UBE3A gene, but also the β3-α5-γ3 GABAA receptor subunit gene cluster. GABAergic dysfunction has been hypothesized to contribute to the occurrence of epilepsy and cognitive and behavioral impairments in this condition. In the present study, analysis of GABAA receptor subunit expression and pharmacology was performed in cerebral cortex from four subjects with Angelman syndrome and compared to that from control tissue. The membrane fraction of frozen postmortem neocortical tissue was isolated and subjected to quantitative Western blot analysis. The ratios of β3/β2 and α5/α1 subunit protein expression in Angelman syndrome cortex were significantly decreased when compared with controls. An additional membrane fraction was injected into Xenopus oocytes, resulting in incorporation of the brain membrane vesicles with their associated receptors into the oocyte cellular membrane. Two-electrode voltage clamp analysis of GABAA receptor currents was then performed. Studies of GABAA receptor pharmacology in Angelman syndrome cortex revealed increased current enhancement by the α1-selective benzodiazepine site agonist zolpidem and by the barbiturate phenobarbital, while sensitivity to current inhibition by zinc was decreased. GABAA receptor affinity and modulation by neurosteroids were unchanged. This shift in GABAA receptor subunit expression and pharmacology in Angelman syndrome is consistent with impaired extrasynaptic but intact to augmented synaptic cortical GABAergic inhibition, which could contribute to the epileptic, behavioral, and cognitive phenotypes of the disorder. PMID:20692323

  8. Inhibitors of the influenza A virus M2 proton channel discovered using a high-throughput yeast growth restoration assay.

    Directory of Open Access Journals (Sweden)

    Aruna D Balgi

    Full Text Available The M2 proton channel of the influenza A virus is the target of the anti-influenza drugs amantadine and rimantadine. The effectiveness of these drugs has been dramatically limited by the rapid spread of drug resistant mutations, mainly at sites S31N, V27A and L26F in the pore of the channel. Despite progress in designing inhibitors of V27A and L26F M2, there are currently no drugs targeting these mutated channels in clinical trials. Progress in developing new drugs has been hampered by the lack of a robust assay with sufficient throughput for discovery of new active chemotypes among chemical libraries and sufficient sensitivity to provide the SAR data essential for their improvement and development as drugs. In this study we adapted a yeast growth restoration assay, in which expression of the M2 channel inhibits yeast growth and exposure to an M2 channel inhibitor restores growth, into a robust and sensitive high-throughput screen for M2 channel inhibitors. A screen of over 250,000 pure chemicals and semi-purified fractions from natural extracts identified 21 active compounds comprising amantadine, rimantadine, 13 related adamantanes and 6 non-adamantanes. Of the non-adamantanes, hexamethylene amiloride and a triazine derivative represented new M2 inhibitory chemotypes that also showed antiviral activity in a plaque reduction assay. Of particular interest is the fact that the triazine derivative was not sufficiently potent for detection as an inhibitor in the traditional two electrode voltage clamp assay for M2 channel activity, but its discovery in the yeast assay led to testing of analogues of which one was as potent as amantadine.

  9. Action of the pyrethroid insecticide cypermethrin on rat brain IIa sodium channels expressed in xenopus oocytes.

    Science.gov (United States)

    Smith, T J; Soderlund, D M

    1998-12-01

    Pyrethroid insecticides bind to a unique site on voltage-dependent sodium channels and prolong sodium currents, leading to repetitive bursts of action potentials or use-dependent nerve block. To further characterize the site and mode of action of pyrethroids on sodium channels, we injected synthetic mRNA encoding the rat brain IIa sodium channel alpha subunit, either alone or in combination with synthetic mRNA encoding the rat sodium channel beta1 subunit, into oocytes of the frog Xenopus laevis and assessed the actions of the pyrethroid insecticide [1R,cis,alphaS]-cypermethrin on expressed sodium currents by two-electrode voltage clamp. In oocytes expressing only the rat brain IIa alpha subunit, cypermethrin produced a slowly-decaying sodium tail current following a depolarizing pulse. In parallel experiments using oocytes expressing the rat brain IIa alpha subunit in combination with the rat beta1 subunit, cypermethrin produced qualitatively similar tail currents following a depolarizing pulse and also induced a sustained component of the sodium current measured during a step depolarization of the oocyte membrane. The voltage dependence of activation and steady-state inactivation of the cypermethrin-dependent sustained current were identical to those of the peak transient sodium current measured in the absence of cypermethrin. Concentration-response curves obtained using normalized tail current amplitude as an index of the extent of sodium channel modification by cypermethrin revealed that coexpression of the rat brain IIa alpha subunit with the rat beta1 subunit increased the apparent affinity of the sodium channel binding site for cypermethrin by more than 20-fold. These results confirm that the pyrethroid binding site is intrinsic to the sodium channel alpha subunit and demonstrate that coexpression of the rat brain IIa alpha subunit with the rat beta1 subunit alters the apparent affinity of this site for pyrethroids.

  10. Menthol inhibits 5-HT3 receptor-mediated currents.

    Science.gov (United States)

    Ashoor, Abrar; Nordman, Jacob C; Veltri, Daniel; Yang, Keun-Hang Susan; Shuba, Yaroslav; Al Kury, Lina; Sadek, Bassem; Howarth, Frank C; Shehu, Amarda; Kabbani, Nadine; Oz, Murat

    2013-11-01

    The effects of alcohol monoterpene menthol, a major active ingredient of the peppermint plant, were tested on the function of human 5-hydroxytryptamine type 3 (5-HT3) receptors expressed in Xenopus laevis oocytes. 5-HT (1 μM)-evoked currents recorded by two-electrode voltage-clamp technique were reversibly inhibited by menthol in a concentration-dependent (IC50 = 163 μM) manner. The effects of menthol developed gradually, reaching a steady-state level within 10-15 minutes and did not involve G-proteins, since GTPγS activity remained unaltered and the effect of menthol was not sensitive to pertussis toxin pretreatment. The actions of menthol were not stereoselective as (-), (+), and racemic menthol inhibited 5-HT3 receptor-mediated currents to the same extent. Menthol inhibition was not altered by intracellular 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid injections and transmembrane potential changes. The maximum inhibition observed for menthol was not reversed by increasing concentrations of 5-HT. Furthermore, specific binding of the 5-HT3 antagonist [(3)H]GR65630 was not altered in the presence of menthol (up to 1 mM), indicating that menthol acts as a noncompetitive antagonist of the 5-HT3 receptor. Finally, 5-HT3 receptor-mediated currents in acutely dissociated nodose ganglion neurons were also inhibited by menthol (100 μM). These data demonstrate that menthol, at pharmacologically relevant concentrations, is an allosteric inhibitor of 5-HT3 receptors.

  11. Four and a half LIM protein 1C (FHL1C: a binding partner for voltage-gated potassium channel K(v1.5.

    Directory of Open Access Journals (Sweden)

    Ivana Poparic

    Full Text Available Four-and-a-half LIM domain protein 1 isoform A (FHL1A is predominantly expressed in skeletal and cardiac muscle. Mutations in the FHL1 gene are causative for several types of hereditary myopathies including X-linked myopathy with postural muscle atrophy (XMPMA. We here studied myoblasts from XMPMA patients. We found that functional FHL1A protein is completely absent in patient myoblasts. In parallel, expression of FHL1C is either unaffected or increased. Furthermore, a decreased proliferation rate of XMPMA myoblasts compared to controls was observed but an increased number of XMPMA myoblasts was found in the G(0/G(1 phase. Furthermore, low expression of K(v1.5, a voltage-gated potassium channel known to alter myoblast proliferation during the G(1 phase and to control repolarization of action potential, was detected. In order to substantiate a possible relation between K(v1.5 and FHL1C, a pull-down assay was performed. A physical and direct interaction of both proteins was observed in vitro. In addition, confocal microscopy revealed substantial colocalization of FHL1C and K(v1.5 within atrial cells, supporting a possible interaction between both proteins in vivo. Two-electrode voltage clamp experiments demonstrated that coexpression of K(v1.5 with FHL1C in Xenopus laevis oocytes markedly reduced K(+ currents when compared to oocytes expressing K(v1.5 only. We here present the first evidence on a biological relevance of FHL1C.

  12. Role of hydrophobic and ionic forces in the movement of S4 of the Shaker potassium channel.

    Science.gov (United States)

    Elliott, David J S; Neale, Edward J; Munsey, Tim S; Bannister, John P; Sivaprasadarao, Asipu

    2012-12-01

    Voltage-gated ion (K(+), Na(+), Ca(2+)) channels contain a pore domain (PD) surrounded by four voltage sensing domains (VSD). Each VSD is made up of four transmembrane helices, S1-S4. S4 contains 6-7 positively charged residues (arginine/lysine) separated two hydrophobic residues, whereas S1-S3 contribute to two negatively charged clusters. These structures are conserved among all members of the voltage-gated ion channel family and play essential roles in voltage gating. The role of S4 charged residues in voltage gating is well established: During depolarization, they move out of the membrane electric field, exerting a mechanical force on channel gates, causing them to open. However, the role of the intervening hydrophobic residues in voltage sensing is unclear. Here we studied the role of these residues in the prototypical Shaker potassium channel. We have altered the physicochemical properties of both charged and hydrophobic positions of S4 and examined the effect of these modifications on the gating properties of the channel. For this, we have introduced cysteines at each of these positions, expressed the mutants in Xenopus oocytes, and examined the effect of in situ addition of charge, via Cd(2+), on channel gating by two-electrode voltage clamp. Our results reveal a face of the S4 helix (comprising residues L358, L361, R365 and R368) where introduction of charge at hydrophobic positions destabilises the closed state and removal of charges from charged positions has an opposite effect. We propose that hydrophobic residues play a crucial role in limiting gating to a physiological voltage range.

  13. Meroterpenoid Chrodrimanins Are Selective and Potent Blockers of Insect GABA-Gated Chloride Channels.

    Directory of Open Access Journals (Sweden)

    Yan Xu

    Full Text Available Meroterpenoid chrodrimanins, produced from Talaromyces sp. YO-2, are known to paralyze silkworm (Bombyx mori larvae, but their target is unknown. We have investigated the actions of chrodrimanin B on ligand-gated ion channels of silkworm larval neurons using patch-clamp electrophysiology. Chrodrimanin B had no effect on membrane currents when tested alone at 1 μM. However, it completely blocked the γ-aminobutyric acid (GABA-induced current and showed less pronounced actions on acetylcholine- and L-glutamate-induced currents, when delivered at 1 μM for 1 min prior to co-application with transmitter GABA. Thus, chrodrimanins were also tested on a wild-type isoform of the B. mori GABA receptor (GABAR RDL using two-electrode voltage-clamp electrophysiology. Chrodrimanin B attenuated the peak current amplitude of the GABA response of RDL with an IC50 of 1.66 nM. The order of the GABAR-blocking potency of chrodrimanins B > D > A was in accordance with their reported insecticidal potency. Chrodrimanin B had no open channel blocking action when tested at 3 nM on the GABA response of RDL. Co-application with 3 nM chrodrimanin B shifted the GABA concentration response curve to a higher concentration and further increase of chrodrimanin B concentration to 10 nM; it reduced maximum current amplitude of the GABA response, pointing to a high-affinity competitive action and a lower affinity non-competitive action. The A282S;T286V double mutation of RDL, which impairs the actions of fipronil, hardly affected the blocking action of chrodrimanin B, indicating a binding site of chrodrimanin B distinct from that of fipronil. Chrodrimanin B showed approximately 1,000-fold lower blocking action on human α1β2γ2 GABAR compared to RDL and thus is a selective blocker of insect GABARs.

  14. Modulation of voltage-gated Na+ and K+ channels by pumiliotoxin 251D: a "joint venture" alkaloid from arthropods and amphibians.

    Science.gov (United States)

    Vandendriessche, Thomas; Abdel-Mottaleb, Yousra; Maertens, Chantal; Cuypers, Eva; Sudau, Alexander; Nubbemeyer, Udo; Mebs, Dietrich; Tytgat, Jan

    2008-03-01

    Certain amphibians provide themselves with a chemical defense by accumulating lipophilic alkaloids into skin glands from dietary arthropods. Examples of such alkaloids are pumiliotoxins (PTXs). In general, PTXs are known as positive modulators of voltage-gated sodium channels (VGSCs). Unlike other PTXs, PTX 251D does not share this characteristic. However, mice and insect studies showed that PTX 251D is highly toxic and to date the basis of its toxicity remains unknown. In this work, we searched for the possible target of PTX 251D. The toxin was therefore made synthetically and tested on four VGSCs (mammalian rNa(v)1.2/beta(1), rNa(v)1.4/beta(1), hNa(v)1.5/beta(1) and insect Para/tipE) and five voltage-gated potassium channels (VGPCs) (mammalian rK(v)1.1-1.2, hK(v)1.3, hK(v)11.1 (hERG) and insect Shaker IR) expressed heterologously in Xenopus laevis oocytes, using the two-electrode voltage clamp technique. PTX 251D not only inhibited the Na(+) influx through the mammalian VGSCs but also affected the steady-state activation and inactivation. Interestingly, in the insect ortholog, the inactivation process was dramatically affected. Additionally, PTX 251D inhibited the K(+) efflux through all five tested VGPCs and slowed down the deactivation kinetics of the mammalian VGPCs. hK(v)1.3 was the most sensitive channel, with an IC(50) value 10.8+/-0.5 microM. To the best of our knowledge this is the first report of a PTX affecting VGPCs.

  15. Signal transduction pathways in the pentameric ligand-gated ion channels.

    Directory of Open Access Journals (Sweden)

    David Mowrey

    Full Text Available The mechanisms of allosteric action within pentameric ligand-gated ion channels (pLGICs remain to be determined. Using crystallography, site-directed mutagenesis, and two-electrode voltage clamp measurements, we identified two functionally relevant sites in the extracellular (EC domain of the bacterial pLGIC from Gloeobacter violaceus (GLIC. One site is at the C-loop region, where the NQN mutation (D91N, E177Q, and D178N eliminated inter-subunit salt bridges in the open-channel GLIC structure and thereby shifted the channel activation to a higher agonist concentration. The other site is below the C-loop, where binding of the anesthetic ketamine inhibited GLIC currents in a concentration dependent manner. To understand how a perturbation signal in the EC domain, either resulting from the NQN mutation or ketamine binding, is transduced to the channel gate, we have used the Perturbation-based Markovian Transmission (PMT model to determine dynamic responses of the GLIC channel and signaling pathways upon initial perturbations in the EC domain of GLIC. Despite the existence of many possible routes for the initial perturbation signal to reach the channel gate, the PMT model in combination with Yen's algorithm revealed that perturbation signals with the highest probability flow travel either via the β1-β2 loop or through pre-TM1. The β1-β2 loop occurs in either intra- or inter-subunit pathways, while pre-TM1 occurs exclusively in inter-subunit pathways. Residues involved in both types of pathways are well supported by previous experimental data on nAChR. The direct coupling between pre-TM1 and TM2 of the adjacent subunit adds new insight into the allosteric signaling mechanism in pLGICs.

  16. Identification of amino acids involved in histamine potentiation of GABA(A receptors

    Directory of Open Access Journals (Sweden)

    Ulrike eThiel

    2015-05-01

    Full Text Available Histamine is a neurotransmitter involved in a number of physiological and neuronal functions. In mammals, such as humans and rodents, the histaminergic neurons found in the tuberomamillary nucleus (TMN project widely throughout the central nervous system (CNS. Histamine acts as positive modulator of GABA(A receptors (GABA(ARs and, in high concentrations (10 mM, as negative modulator of the strychnine-sensitive glycine receptor. However, the exact molecular mechanisms by which histamine acts on GABA(ARs are unknown. In our study, we aimed to identify amino acids potentially involved in the modulatory effect of histamine on GABA(ARs. We expressed GABA(ARs with 12 different point mutations in Xenopus laevis oocytes and characterized the effect of histamine on GABA-induced currents using the two-electrode voltage clamp technique. Our data demonstrate that the amino acid residues ß2(N265 and ß2(M286, which are important for modulation by propofol, are not involved in the action of histamine. However, we found that histamine modulation is dependent on the amino acid residues alpha1(R120, ß2(Y157, ß3(D163, ß3(V175 and ß3(Q185. We showed that the amino acid residues ß2(Y157 and ß3(Q185 mediate the positive modulatory effect of histamine on GABA-induced currents, whereas alpha1(R120 and ß2(D163 form a potential histamine interaction site in GABA(ARs.

  17. Niflumic acid modulates uncoupled substrate-gated conductances in the human glutamate transporter EAAT4.

    Science.gov (United States)

    Poulsen, M V; Vandenberg, R J

    2001-07-01

    1. The effects of niflumic acid on the substrate-gated currents mediated by the glutamate transporter EAAT4 expressed in Xenopus laevis oocytes were examined using radiolabelled substrate flux measurements and two-electrode voltage clamp techniques. 2. Niflumic acid significantly enhanced the substrate-gated currents in EAAT4, without affecting the affinity of the substrates towards EAAT4. At a concentration of 300 microM, niflumic acid caused a 19 +/- 5 % reduction in L-[(3)H]glutamate uptake and no significant effect on the uptake of DL-[(3)H]aspartate. Thus, enhancement of the substrate-gated currents in EAAT4 does not correlate with the rate of substrate transport and suggests that the niflumic acid-induced currents are not thermodynamically coupled to the transport of substrate. 3. Niflumic acid and arachidonic acid co-applied with substrate to EAAT4-expressing oocytes had similar functional consequences. However, niflumic acid still enhanced the L-glutamate-gated current to the same extent in the presence and absence of a saturating dose of arachidonic acid, which suggests that the sites of action of the two compounds are distinct. 4. The EAAT4-mediated currents for the two substrates, L-glutamate and L-aspartate, were not enhanced equally by addition of the same dose of niflumic acid and the ionic composition of the niflumic acid-induced currents was not the same for the two substrates. Protons carry the L-glutamate-gated niflumic acid-induced current and both protons and chloride ions carry the L-aspartate-gated niflumic acid-induced current. 5. These results show that niflumic acid can be used to probe the functional aspects of EAAT4 and that niflumic acid and other non-steroid anti-inflammatory drugs could be used as the basis for the development of novel modulators of glutamate transporters.

  18. Niflumic acid alters gating of HCN2 pacemaker channels by interaction with the outer region of S4 voltage sensing domains.

    Science.gov (United States)

    Cheng, Lan; Sanguinetti, Michael C

    2009-05-01

    Niflumic acid, 2-[[3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid (NFA), is a nonsteroidal anti-inflammatory drug that also blocks or modifies the gating of many ion channels. Here, we investigated the effects of NFA on hyperpolarization-activated cyclic nucleotide-gated cation (HCN) pacemaker channels expressed in X. laevis oocytes using site-directed mutagenesis and the two-electrode voltage-clamp technique. Extracellular NFA acted rapidly and caused a slowing of activation and deactivation and a hyperpolarizing shift in the voltage dependence of HCN2 channel activation (-24.5 +/- 1.2 mV at 1 mM). Slowed channel gating and reduction of current magnitude was marked in oocytes treated with NFA, while clamped at 0 mV but minimal in oocytes clamped at -100 mV, indicating the drug preferentially interacts with channels in the closed state. NFA at 0.1 to 3 mM shifted the half-point for channel activation in a concentration-dependent manner, with an EC(50) of 0.54 +/- 0.068 mM and a predicted maximum shift of -38 mV. NFA at 1 mM also reduced maximum HCN2 conductance by approximately 20%, presumably by direct block of the pore. The rapid onset and state-dependence of NFA-induced changes in channel gating suggests an interaction with the extracellular region of the S4 transmembrane helix, the primary voltage-sensing domain of HCN2. Neutralization (by mutation to Gln) of any three of the outer four basic charged residues in S4, but not single mutations, abrogated the NFA-induced shift in channel activation. We conclude that NFA alters HCN2 gating by interacting with the extracellular end of the S4 voltage sensor domains.

  19. Golgi-specific DHHC Zinc Finger Protein GODZ Mediates Membrane Ca2+ Transport*

    Science.gov (United States)

    Hines, Rochelle M.; Kang, Rujun; Goytain, Angela; Quamme, Gary A.

    2010-01-01

    The Golgi-specific zinc finger protein GODZ (palmitoyl acyltransferase/DHHC-3) mediates the palmitoylation and post-translational modification of many protein substrates that regulate membrane-protein interactions. Here, we show that GODZ also mediates Ca2+ transport in expressing Xenopus laevis oocytes. Two-electrode voltage-clamp, fluorescence, and 45Ca2+ isotopic uptake determinations demonstrated voltage- and concentration-dependent, saturable, and substrate-inhibitable Ca2+ transport in oocytes expressing GODZ cRNA but not in oocytes injected with water alone. Moreover, we show that GODZ-mediated Ca2+ transport is regulated by palmitoylation, as the palmitoyl acyltransferase inhibitor 2-bromopalmitate or alteration of the acyltransferase DHHC motif (GODZ-DHHS) diminished GODZ-mediated Ca2+ transport by ∼80%. The GODZ mutation V61R abolished Ca2+ transport but did not affect palmitoyl acyltransferase activity. Coexpression of GODZ-V61R with GODZ-DHHS restored GODZ-DHHS-mediated Ca2+ uptake to values observed with wild-type GODZ, excluding an endogenous effect of palmitoylation. Coexpression of an independent palmitoyl acyltransferase (HIP14) with the GODZ-DHHS mutant also rescued Ca2+ transport. HIP14 did not mediate Ca2+ transport when expressed alone. Immunocytochemistry studies showed that GODZ and HIP14 co-localized to the Golgi and the same post-Golgi vesicles, suggesting that heteropalmitoylation might play a physiological role in addition to a biochemical function. We conclude that GODZ encodes a Ca2+ transport protein in addition to its ability to palmitoylate protein substrates. PMID:19955568

  20. Role of N-glycosylation in renal betaine transport.

    Science.gov (United States)

    Schweikhard, Eva S; Burckhardt, Birgitta C; Joos, Friedericke; Fenollar-Ferrer, Cristina; Forrest, Lucy R; Kempson, Stephen A; Ziegler, Christine

    2015-09-01

    The osmolyte and folding chaperone betaine is transported by the renal Na(+)-coupled GABA (γ-aminobutyric acid) symporter BGT-1 (betaine/GABA transporter 1), a member of the SLC6 (solute carrier 6) family. Under hypertonic conditions, the transcription, translation and plasma membrane (PM) insertion of BGT-1 in kidney cells are significantly increased, resulting in elevated betaine and GABA transport. Re-establishing isotonicity involves PM depletion of BGT-1. The molecular mechanism of the regulated PM insertion of BGT-1 during changes in osmotic stress is unknown. In the present study, we reveal a link between regulated PM insertion and N-glycosylation. Based on homology modelling, we identified two sites (Asn(171) and Asn(183)) in the extracellular loop 2 (EL2) of BGT-1, which were investigated with respect to trafficking, insertion and transport by immunogold-labelling, electron microscopy (EM), mutagenesis and two-electrode voltage clamp measurements in Xenopus laevis oocytes and uptake of radiolabelled substrate into MDCK (Madin-Darby canine kidney) and HEK293 (human embryonic kidney) cells. Trafficking and PM insertion of BGT-1 was clearly promoted by N-glycosylation in both oocytes and MDCK cells. Moreover, association with N-glycans at Asn(171) and Asn(183) contributed equally to protein activity and substrate affinity. Substitution of Asn(171) and Asn(183) by aspartate individually caused no loss of BGT-1 activity, whereas the double mutant was inactive, suggesting that N-glycosylation of at least one of the sites is required for function. Substitution by alanine or valine at either site caused a dramatic loss in transport activity. Furthermore, in MDCK cells PM insertion of N183D was no longer regulated by osmotic stress, highlighting the impact of N-glycosylation in regulation of this SLC6 transporter.

  1. Functional and molecular identification of a TASK-1 potassium channel regulating chloride secretion through CFTR channels in the shark rectal gland: implications for cystic fibrosis.

    Science.gov (United States)

    Telles, Connor J; Decker, Sarah E; Motley, William W; Peters, Alexander W; Mehr, Ali Poyan; Frizzell, Raymond A; Forrest, John N

    2016-12-01

    In the shark rectal gland (SRG), apical chloride secretion through CFTR channels is electrically coupled to a basolateral K(+) conductance whose type and molecular identity are unknown. We performed studies in the perfused SRG with 17 K(+) channel inhibitors to begin this search. Maximal chloride secretion was markedly inhibited by low-perfusate pH, bupivicaine, anandamide, zinc, quinidine, and quinine, consistent with the properties of an acid-sensitive, four-transmembrane, two-pore-domain K(+) channel (4TM-K2P). Using PCR with degenerate primers to this family, we identified a TASK-1 fragment in shark rectal gland, brain, gill, and kidney. Using 5' and 3' rapid amplification of cDNA ends PCR and genomic walking, we cloned the full-length shark gene (1,282 bp), whose open reading frame encodes a protein of 375 amino acids that was 80% identical to the human TASK-1 protein. We expressed shark and human TASK-1 cRNA in Xenopus oocytes and characterized these channels using two-electrode voltage clamping. Both channels had identical current-voltage relationships (outward rectifying) and a reversal potential of -90 mV. Both were inhibited by quinine, bupivicaine, and acidic pH. The pKa for current inhibition was 7.75 for shark TASK-1 vs. 7.37 for human TASK-1, values similar to the arterial pH for each species. We identified this protein in SRG by Western blot and confocal immunofluorescent microscopy and detected the protein in SRG and human airway cells. Shark TASK-1 is the major K(+) channel coupled to chloride secretion in the SRG, is the oldest 4TM 2P family member identified, and is the first TASK-1 channel identified to play a role in setting the driving force for chloride secretion in epithelia. The detection of this potassium channel in mammalian lung tissue has implications for human biology and disease.

  2. Tetrazolyl isoxazole amino acids as ionotropic glutamate receptor antagonists: synthesis, modelling and molecular pharmacology.

    Science.gov (United States)

    Frølund, Bente; Greenwood, Jeremy R; Holm, Mai M; Egebjerg, Jan; Madsen, Ulf; Nielsen, Birgitte; Bräuner-Osborne, Hans; Stensbøl, Tine B; Krogsgaard-Larsen, Povl

    2005-09-15

    Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b, of (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), a selective AMPA receptor agonist, and (RS)-2-amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in receptor binding assays, and electrophysiologically on homomeric AMPA receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) kainic acid receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these receptors. Both analogues proved to be antagonists at all AMPA receptor subtypes, showing potencies (Kb=38-161 microM) similar to that of the AMPA receptor antagonist (RS)-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic acid (AMOA) (Kb=43-76 microM). Furthermore, the AMOA analogue, 1a, blocked two kainic acid receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 (Kb=19 microM). Unlike the iGluR antagonist (S)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid [(S)-ATPO], the corresponding tetrazolyl analogue, 1b, lacks kainic acid receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA receptor subunit GluR2 and a homology model of the kainic acid receptor subunit GluR5, we were able to rationalize the observed structure-activity relationships.

  3. Site-directed mutation of arginine 282 to glutamate uncouples the movement of peptides and protons by the rabbit proton-peptide cotransporter PepT1.

    Science.gov (United States)

    Meredith, David

    2004-04-16

    A conserved positive residue in the seventh transmembrane domain of the mammalian proton-coupled di- and tripeptide transporter PepT1 has been shown by site-directed mutagenesis to be a key residue for protein function. Substitution of arginine 282 with a glutamate residue (R282E-PepT1) gave a protein at the plasma membrane of Xenopus laevis oocytes that was able to transport the non-hydrolyzable dipeptide [3H]d-Phe-l-Gln, although unlike the wild type, the rate of transport by R282E-PepT1 was independent of the extracellular pH level, and the substrate could not be accumulated above equilibrium. The binding affinity of the mutant transport protein was unchanged from the wild type. Thus, R282E-Pept1 appears to have been changed from a proton-driven to a facilitated transporter for peptides. In addition, peptide transport by R282E-PepT1 still induced depolarization as measured by microelectrode recordings of membrane potential. A more detailed study by two-electrode voltage clamping revealed that R282E-PepT1 behaved as a peptide-gated non-selective cation channel with the ion selectivity series lithium > sodium > N-methyl-d-glucamine at pH 7.4. There was also a proton conductance (comparing pH 7.4 and 8.4), and at pH 5.5 the predominant conductance was for potassium ions. Therefore, it can be concluded that changing arginine 282 to a glutamate not only uncouples the cotransport of protons and peptides of the wild-type PepT1 but also creates a peptide-gated cation channel in the protein.

  4. Implementation of a fluorescence-based screening assay identifies histamine H3 receptor antagonists clobenpropit and iodophenpropit as subunit-selective N-methyl-D-aspartate receptor antagonists.

    Science.gov (United States)

    Hansen, Kasper B; Mullasseril, Praseeda; Dawit, Sara; Kurtkaya, Natalie L; Yuan, Hongjie; Vance, Katie M; Orr, Anna G; Kvist, Trine; Ogden, Kevin K; Le, Phuong; Vellano, Kimberly M; Lewis, Iestyn; Kurtkaya, Serdar; Du, Yuhong; Qui, Min; Murphy, T J; Snyder, James P; Bräuner-Osborne, Hans; Traynelis, Stephen F

    2010-06-01

    N-Methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels that mediate a slow, Ca(2+)-permeable component of excitatory synaptic transmission in the central nervous system and play a pivotal role in synaptic plasticity, neuronal development, and several neurological diseases. We describe a fluorescence-based assay that measures NMDA receptor-mediated changes in intracellular calcium in a BHK-21 cell line stably expressing NMDA receptor NR2D with NR1 under the control of a tetracycline-inducible promoter (Tet-On). The assay selectively identifies allosteric modulators by using supramaximal concentrations of glutamate and glycine to minimize detection of competitive antagonists. The assay is validated by successfully identifying known noncompetitive, but not competitive NMDA receptor antagonists among 1800 screened compounds from two small focused libraries, including the commercially available library of pharmacologically active compounds. Hits from the primary screen are validated through a secondary screen that used two-electrode voltage-clamp recordings on recombinant NMDA receptors expressed in Xenopus laevis oocytes. This strategy identified several novel modulators of NMDA receptor function, including the histamine H3 receptor antagonists clobenpropit and iodophenpropit, as well as the vanilloid receptor transient receptor potential cation channel, subfamily V, member 1 (TRPV1) antagonist capsazepine. These compounds are noncompetitive antagonists and the histamine H3 receptor ligand showed submicromolar potency at NR1/NR2B NMDA receptors, which raises the possibility that compounds can be developed that act with high potency on both glutamate and histamine receptor systems simultaneously. Furthermore, it is possible that some actions attributed to histamine H3 receptor inhibition in vivo may also involve NMDA receptor antagonism.

  5. Modulation of human GABAA receptor function: a novel mode of action of drugs of abuse.

    Science.gov (United States)

    Hondebrink, L; Meulenbelt, J; van Kleef, R G D M; van den Berg, M; Westerink, R H S

    2011-12-01

    Drugs of abuse are known to mainly affect the dopaminergic and serotonergic system, although behavioral studies indicated that the GABA-ergic system also plays a role. We therefore investigated the acute effects of several commonly used drugs of abuse (methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and meta-chlorophenylpiperazine (mCPP)) on the function of the human α(1)β(2)γ(2) GABA(A) receptor (hGABA(A)-R), expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. Although none of the tested drugs acted as full agonist on the hGABA(A)-R, some drugs induced differential modulation of hGABA(A)-R function, depending on the degree of receptor occupancy. Methamphetamine did not affect the GABA-evoked current at high receptor occupancy, but induced a minor inhibition at low receptor occupancy. Its metabolite amphetamine slightly potentiated the GABA-evoked current. MDMA and its metabolite MDA both inhibited the current at low receptor occupancy. However, MDMA did not affect the current at high occupancy, whereas MDA induced a potentiation. mCPP induced a strong inhibition (max. ∼ 80%) at low receptor occupancy, but ∼ 25% potentiation at high receptor occupancy. Competitive binding to one of the GABA-binding sites could explain the drug-induced inhibitions observed at low receptor occupancy, whereas an additional interaction with a positive allosteric binding site may play a role in the observed potentiations at high receptor occupancy. This is the first study to identify direct modulation of hGABA(A)-Rs as a novel mode of action for several drugs of abuse. Consequently, hGABA(A)-Rs should be considered as target for psychiatric pharmaceuticals and in developing treatment for drug intoxications.

  6. Additive inhibition of human α1β2γ2 GABAA receptors by mixtures of commonly used drugs of abuse.

    Science.gov (United States)

    Hondebrink, Laura; Tan, Sijie; Hermans, Elise; van Kleef, Regina G D M; Meulenbelt, Jan; Westerink, Remco H S

    2013-03-01

    Yearly, exposure to drugs of abuse results in ∼1 million emergency department visits in the US. In ∼50% of the visits, stimulant drugs like cocaine and amphetamine-like substances (e.g. 3,4-methylenedioxymethamphetamine (MDMA, the main active ingredient of ecstasy)) are involved, whereas in ∼60% multiple drugs are involved. These drugs induce higher dopamine and serotonin levels resulting in drug-induced toxicity. Since GABA receptors (GABA-R) provide the main inhibitory input on dopaminergic and serotonergic neurons, drug-induced inhibition of GABA-R could contribute to higher neurotransmitter levels and thus toxicity. We therefore investigated the effects of combinations of commonly abused stimulant drugs (cocaine, MDMA, 3,4-methylenedioxyamphetamine (MDA) and meta-chlorophenylpiperazine (mCPP)) on the function of the human α1β2γ2 GABAA receptor (hGABAA-R), expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. These drugs concentration-dependently inhibited the GABA-evoked current (mCPP>cocaine>MDMA>MDA). Most drug combinations decreased the GABA-evoked current stronger than the single drug. Additivity was observed during combined exposure to low concentrations of cocaine and mCPP as well as during combined exposure to MDA with cocaine or mCPP. However, combinations containing MDMA mainly resulted in sub-additivity or no additivity. At drug concentrations relevant for clinical toxicology, co-exposure to ≥2 drugs can decrease the GABA-evoked current in an additive manner. Thus, in patients exposed to multiple drugs, inhibitory GABA-ergic input is reduced more prominently, likely resulting in higher brain dopamine levels. As this will increase the risk for drug-induced toxicity, treatment of drug-intoxicated patients with drugs that enhance GABA-ergic input should be further optimized.

  7. α4βδ GABA(A) receptors are high-affinity targets for γ-hydroxybutyric acid (GHB).

    Science.gov (United States)

    Absalom, Nathan; Eghorn, Laura F; Villumsen, Inge S; Karim, Nasiara; Bay, Tina; Olsen, Jesper V; Knudsen, Gitte M; Bräuner-Osborne, Hans; Frølund, Bente; Clausen, Rasmus P; Chebib, Mary; Wellendorph, Petrine

    2012-08-14

    γ-Hydroxybutyric acid (GHB) binding to brain-specific high-affinity sites is well-established and proposed to explain both physiological and pharmacological actions. However, the mechanistic links between these lines of data are unknown. To identify molecular targets for specific GHB high-affinity binding, we undertook photolinking studies combined with proteomic analyses and identified several GABA(A) receptor subunits as possible candidates. A subsequent functional screening of various recombinant GABA(A) receptors in Xenopus laevis oocytes using the two-electrode voltage clamp technique showed GHB to be a partial agonist at αβδ- but not αβγ-receptors, proving that the δ-subunit is essential for potency and efficacy. GHB showed preference for α4 over α(1,2,6)-subunits and preferably activated α4β1δ (EC(50) = 140 nM) over α4β(2/3)δ (EC(50) = 8.41/1.03 mM). Introduction of a mutation, α4F71L, in α4β1(δ)-receptors completely abolished GHB but not GABA function, indicating nonidentical binding sites. Radioligand binding studies using the specific GHB radioligand [(3)H](E,RS)-(6,7,8,9-tetrahydro-5-hydroxy-5H-benzocyclohept-6-ylidene)acetic acid showed a 39% reduction (P = 0.0056) in the number of binding sites in α4 KO brain tissue compared with WT controls, corroborating the direct involvement of the α4-subunit in high-affinity GHB binding. Our data link specific GHB forebrain binding sites with α4-containing GABA(A) receptors and postulate a role for extrasynaptic α4δ-containing GABA(A) receptors in GHB pharmacology and physiology. This finding will aid in elucidating the molecular mechanisms behind the proposed function of GHB as a neurotransmitter and its unique therapeutic effects in narcolepsy and alcoholism.

  8. The transport mechanism of the human sodium/myo-inositol transporter 2 (SMIT2/SGLT6), a member of the LeuT structural family.

    Science.gov (United States)

    Sasseville, Louis J; Longpré, Jean-Philippe; Wallendorff, Bernadette; Lapointe, Jean-Yves

    2014-09-01

    The sodium/myo-inositol transporter 2 (SMIT2) is a member of the SLC5A gene family, which is believed to share the five-transmembrane segment inverted repeat of the LeuT structural family. The two-electrode voltage-clamp (TEVC) technique was used to measure the steady-state and the pre-steady-state currents mediated by human SMIT2 after expression in Xenopus laevis oocytes. Phlorizin is first shown to be a poor inhibitor of pre-steady-state currents for depolarizing voltage pulse. From an up to threefold difference between the apparent ON and OFF transferred charges during a voltage pulse, we also show that a fraction of the transient current recorded for very negative potentials is not a true pre-steady-state current coming from the cotransporter conformational changes. We suggest that this transient current comes from a time-dependent leak current that can reach large amplitudes when external Na(+) concentration is reduced. A kinetic model was generated through a simulated annealing algorithm. This algorithm was used to identify the optimal connectivity among 19 different kinetic models and obtain the numerical values of the associated parameters. The proposed 5-state model includes cooperative binding of Na(+) ions, strong apparent asymmetry of the energy barriers, a rate-limiting step that is likely associated with the translocation of the empty transporter, and a turnover rate of 21 s(-1). The proposed model is a proof of concept for a novel approach to kinetic modeling of electrogenic transporters and allows insight into the transport mechanism of members of the LeuT structural family at the millisecond timescale.

  9. Selective inhibition of human heteromeric alpha9alpha10 nicotinic acetylcholine receptors at a low agonist concentration by low concentrations of ototoxic organic solvents.

    Science.gov (United States)

    van Kleef, Regina G D M; Vijverberg, Henk P M; Westerink, Remco H S

    2008-09-01

    Ethylbenzene and para-xylene (p-xylene), but not the chemically closely related organic solvents ortho-xylene (o-xylene) and meta-xylene (m-xylene), are known to cause ototoxicity and irreversible hearing loss, though the underlying mechanisms are still unknown. In this study, effects of ethylbenzene and of p-, o-, and m-xylene on human heteromeric alpha9alpha10 nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes were investigated using the two-electrode voltage clamp technique. ACh dose-dependently evoked an alpha9alpha10 nAChR-mediated ion current with an EC(50) of 137 microM. When ACh is applied at a low concentration (10 microM), the nAChR-mediated ion current is inhibited by a low concentration (10 microM) of ethylbenzene and p-xylene, but not by the same concentration of the non-ototoxic solvents. At a high solvent concentration (300 microM), all solvents cause inhibition of the ion currents evoked by 10 microM ACh. Ion currents evoked by a near maximum-effective concentration ACh (1mM) are inhibited by the selected organic solvents only at 300 microM. These results demonstrate that low concentrations of the known ototoxic solvents ethylbenzene and p-xylene inhibit alpha9alpha10 nAChR-mediated ion currents, whereas the structurally related, non-ototoxic solvents m-xylene and o-xylene do not, indicating that the alpha9alpha10 nAChR is a potential target for solvent-induced ototoxicity.

  10. GABA(A) receptor subtype-selectivity of novel bicuculline derivatives.

    Science.gov (United States)

    Ramerstorfer, Joachim; Foppa, Verena; Thiery, Hanna; Hermange, Philippe; Janody, Simon; Berger, Michael L; Dodd, Robert H; Sieghart, Werner

    2015-01-01

    GABA(A) receptors are the major inhibitory neurotransmitter receptors in the central nervous system and are targets of clinically important drugs modulating GABA induced ion flux by interacting with distinct allosteric binding sites. ROD 185 is a previously investigated structural analogue of the GABA site antagonist bicuculline, and a positive allosteric modulator acting via the benzodiazepine binding site. Here, we investigated 13 newly synthesized structural analogues of ROD 185 for their interaction with rat GABA(A) receptors. Using [(3)H]flunitrazepam binding assays, we identified four compounds exhibiting a higher affinity for the benzodiazepine binding site than ROD 185. Two electrode voltage clamp electrophysiology at recombinant GABA(A) receptors indicated that most of these compounds positively modulated GABA-induced currents at these receptors. Additionally, these experiments revealed that this compound class not only interacts with the benzodiazepine binding site at αβγ receptors but also with a novel, so far unidentified binding site present in αβ receptors. Compounds with a high affinity for the benzodiazepine binding site stimulated GABA-induced currents stronger at αβγ than at αβ receptors and preferred α3β3γ2 receptors. Compounds showing equal or smaller effects at αβγ compared to αβ receptors differentially interacted with various αβ or αβγ receptor subtypes. Surprisingly, five of these compounds interacting with αβ receptors showed a strong stimulation at α6β3γ2 receptors. The absence of any direct effects at GABA(A) receptors, as well as their potential selectivity for receptor subtypes not being addressed by benzodiazepines, make this compound class to a starting point for the development of drugs with a possible clinical importance.

  11. Effects of the abused solvent toluene on recombinant N-methyl-D-aspartate and non-N-methyl-D-aspartate receptors expressed in Xenopus oocytes.

    Science.gov (United States)

    Cruz, S L; Mirshahi, T; Thomas, B; Balster, R L; Woodward, J J

    1998-07-01

    Previous studies have shown that toluene, which is commonly abused, depresses neuronal activity and causes behavioral effects in both animals and man similar to those observed for ethanol. In this study, the oocyte expression system was used to test the hypothesis that toluene, like ethanol, inhibits the function of ionotropic glutamate receptors. Oocytes were injected with mRNA for specific N-methyl-D-aspartate (NMDA) or non-NMDA subunits and currents were recorded using conventional two-electrode voltage clamp. To enhance the low water solubility of toluene, drug solutions were prepared by mixing toluene with alkamuls (ethoxylated castor oil) at a 1:1 ratio (v:v) and diluting this mixture to the appropriate concentration with barium-containing normal frog Ringer solution. Alkamuls, up to 0.1%, had no significant effects on membrane leak currents or on NMDA-induced currents. Toluene, up to approximately 9 mM, had only minor effects on membrane leak currents but dose-dependently inhibited NMDA-mediated currents in oocytes. The inhibition of NMDA receptor currents by toluene was rapid, reversible and the potency for toluene's effects was subunit dependent. The NR1/2B subunit combination was the most sensitive with an IC50 value for toluene-induced inhibition of 0.17 mM. The NR1/2A and NR1/2C receptors were 6- and 12-fold less sensitive with IC50 values of 1.4 and 2.1 mM, respectively. In contrast, toluene up to approximately 9 mM did not inhibit kainate-induced currents in oocytes expressing GluR1, GluR1(+)R2 or GluR6 subunits. These results suggest that some of the effects of toluene on neuronal activity and behavior may be mediated by inhibition of NMDA receptors.

  12. Identification of an Inhibitory Alcohol Binding Site in GABAA ρ1 Receptors.

    Science.gov (United States)

    Borghese, Cecilia M; Ruiz, Carlos I; Lee, Ui S; Cullins, Madeline A; Bertaccini, Edward J; Trudell, James R; Harris, R Adron

    2016-01-20

    Alcohols inhibit γ-aminobutyric acid type A ρ1 receptor function. After introducing mutations in several positions of the second transmembrane helix in ρ1, we studied the effects of ethanol and hexanol on GABA responses using two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. The 6' mutations produced the following effects on ethanol and hexanol responses: small increase or no change (T6'M), increased inhibition (T6'V), and small potentiation (T6'Y and T6'F). The 5' mutations produced mainly increases in hexanol inhibition. Other mutations produced small (3' and 9') or no changes (2' and L277 in the first transmembrane domain) in alcohol effects. These results suggest an inhibitory alcohol binding site near the 6' position. Homology models of ρ1 receptors based on the X-ray structure of GluCl showed that the 2', 5', 6', and 9' residues were easily accessible from the ion pore, with 5' and 6' residues from neighboring subunits facing each other; L3' and L277 also faced the neighboring subunit. We tested ethanol through octanol on single and double mutated ρ1 receptors [ρ1(I15'S), ρ1(T6'Y), and ρ1(T6'Y,I15'S)] to further characterize the inhibitory alcohol pocket in the wild-type ρ1 receptor. The pocket can only bind relatively short-chain alcohols and is eliminated by introducing Y in the 6' position. Replacing the bulky 15' residue with a smaller side chain introduced a potentiating binding site, more sensitive to long-chain than to short-chain alcohols. In conclusion, the net alcohol effect on the ρ1 receptor is determined by the sum of its actions on inhibitory and potentiating sites.

  13. State-dependent block of rat Nav1.4 sodium channels expressed in xenopus oocytes by pyrazoline-type insecticides.

    Science.gov (United States)

    Silver, Kristopher; Soderlund, David M

    2005-06-01

    Insecticidal pyrazolines inhibit voltage-sensitive sodium channels of both insect and mammalian neurons in a voltage-dependent manner. Studies on the effects of pyrazoline insecticides on mammalian sodium channels have been limited to experimentation on the tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium channel populations of rat dorsal root ganglion (DRG) neurons. In this study, we examined the effects of the insecticidal pyrazolines indoxacarb, the N-decarbomethoxyllated metabolite of indoxacarb (DCJW), and RH 3421 on rat Na(v)1.4 sodium channels expressed in Xenopus laevis oocytes using the two-electrode voltage clamp technique. Both DCJW and RH 3421 were ineffective inhibitors of rat Na(v)1.4 sodium channels at a membrane potential of -120 mV, but depolarization to -60 mV or -30 mV during insecticide exposure resulted in substantial block. Inhibition by pyrazoline insecticides was nearly irreversible with washout, but repolarization of the membrane relieved block. DCJW and RH 3421 also caused hyperpolarizing shifts in the voltage dependence of slow inactivation without affecting the voltage dependence of activation or fast inactivation. These results suggest that DCJW and RH 3421 interact specifically with the slow inactivated state of the sodium channel. Indoxacarb did not cause block at any potential, yet it interfered with the ability of DCJW, but not RH 3421, to inhibit sodium current. Phenytoin, an anticonvulsant, reduced the efficacy of both DCJW and RH 3421. These data imply that the binding site for pyrazoline insecticides overlaps with that for therapeutic sodium channel blockers.

  14. Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na(v)1.6 sodium channels.

    Science.gov (United States)

    Tan, Jianguo; Soderlund, David M

    2010-09-15

    We expressed rat Na(v)1.6 sodium channels in combination with the rat beta(1) and beta(2) auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 microM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ~9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 microM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 microM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin approximately 15-fold and that tefluthrin was approximately 10-fold more potent than deltamethrin as a use-dependent modifier of Na(v)1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Na(v)1.2 sodium channel coexpressed with the rat beta(1) and beta(2) subunits in oocytes showed that the Na(v)1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na(v)1.2 isoform. These results implicate sodium channels containing the Na(v)1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.

  15. Point mutations at the local anesthetic receptor site modulate the state-dependent block of rat Na v1.4 sodium channels by pyrazoline-type insecticides.

    Science.gov (United States)

    Silver, Kristopher S; Soderlund, David M

    2007-05-01

    Pyrazoline-type insecticides (PTIs) selectively block sodium channels at membrane potentials that promote slow sodium channel inactivation and are proposed to interact with a site that overlaps the local anesthetic (LA) receptor site. Mutagenesis studies identified two amino acid residues in the S6 segment of homology domain IV (Phe-1579 and Tyr-1586 in the rat Na(v)1.4 sodium channel) as principal elements of the LA receptor. To test the hypothesis that PTIs bind to the LA receptor, we constructed mutated Na(v)1.4/F1579A and Na(v)1.4/Y1586A cDNAs, expressed native and mutated channels in Xenopus oocytes, and examined the effects of these mutations on channel block by three PTIs (indoxacarb, its bioactivation product DCJW, and RH3421) by two-electrode voltage clamp. DCJW and RH3421 had no effect on Na(v)1.4 channels held at -120mV but caused a slowly developing block upon depolarization to -30mV. Estimated IC(50) values following 15min of exposure were 1 and 4muM for DCJW and RH3421, respectively. Indoxacarb failed to block Na(v)1.4 channels under all experimental conditions. Sensitivity to block by DCJW and RH3421 at -30mV was significantly reduced in Na(v)1.4/F1579A channels, a finding that is consistent with the impact of this mutation on drug binding. In contrast to its effect on drug binding, the Y1586A mutation increased the sensitivity of Na(v)1.4 channels held at -30mV to all three compounds, conferring modest sensitivity to indoxacarb and increasing sensitivity to DCJW and RH3421 by 58- and 16-fold, respectively. These results provide direct evidence for the action of PTIs at the LA receptor.

  16. Comparison of cellular effects of starch-coated SPIONs and poly(lactic-co-glycolic acid) matrix nanoparticles on human monocytes

    Science.gov (United States)

    Gonnissen, Dominik; Qu, Ying; Langer, Klaus; Öztürk, Cengiz; Zhao, Yuliang; Chen, Chunying; Seebohm, Guiscard; Düfer, Martina; Fuchs, Harald; Galla, Hans-Joachim; Riehemann, Kristina

    2016-01-01

    Within the last years, progress has been made in the knowledge of the properties of medically used nanoparticles and their toxic effects, but still, little is known about their influence on cellular processes of immune cells. The aim of our comparative study was to present the influence of two different nanoparticle types on subcellular processes of primary monocytes and the leukemic monocyte cell line MM6. We used core-shell starch-coated superparamagnetic iron oxide nanoparticles (SPIONs) and matrix poly(lactic-co-glycolic acid) (PLGA) nanoparticles for our experiments. In addition to typical biocompatibility testing like the detection of necrosis or secretion of interleukins (ILs), we investigated the impact of these nanoparticles on the actin cytoskeleton and the two voltage-gated potassium channels Kv1.3 and Kv7.1. Induction of necrosis was not seen for PLGA nanoparticles and SPIONs in primary monocytes and MM6 cells. Likewise, no alteration in secretion of IL-1β and IL-10 was detected under the same experimental conditions. In contrast, IL-6 secretion was exclusively downregulated in primary monocytes after contact with both nanoparticles. Two-electrode voltage clamp experiments revealed that both nanoparticles reduce currents of the aforementioned potassium channels. The two nanoparticles differed significantly in their impact on the actin cytoskeleton, demonstrated via atomic force microscopy elasticity measurement and phalloidin staining. While SPIONs led to the disruption of the respective cytoskeleton, PLGA did not show any influence in both experimental setups. The difference in the effects on ion channels and the actin cytoskeleton suggests that nanoparticles affect these subcellular components via different pathways. Our data indicate that the alteration of the cytoskeleton and the effect on ion channels are new parameters that describe the influence of nanoparticles on cells. The results are highly relevant for medical application and further

  17. Apparent receptor-mediated activation of Ca2+-dependent conductive Cl- transport by shark-derived polyaminosterols.

    Science.gov (United States)

    Chernova, Marina N; Vandorpe, David H; Clark, Jeffrey S; Williams, Jon I; Zasloff, Michael A; Jiang, Lianwei; Alper, Seth L

    2005-12-01

    The shark liver antimicrobial polyaminosterol squalamine is an angiogenesis inhibitor under clinical investigation as an anti-cancer agent and as a treatment for the choroidal neovascularization associated with macular degeneration of the retina. The related polyaminosterol MSI-1436 is an appetite suppressant that decreases systemic insulin resistance. However, the mechanisms of action of these polyaminosterols are unknown. We report effects of MSI-1436 on Xenopus oocytes consistent with the existence of a receptor for polyaminosterols. MSI-1436 activates bidirectional, trans-chloride-independent Cl- flux in Xenopus oocytes. At least part of this DIDS-sensitive Cl- flux is conductive, as measured using two-electrode voltage-clamp and on-cell patch-clamp techniques. MSI-1436 also elevates cytosolic Ca2+ concentration ([Ca2+]) and increases bidirectional 45Ca2+ flux. Activation of Cl- flux and elevation of cytosolic [Ca2+] by MSI-1436 both are accelerated by lowering bath Ca2+ and are not acutely inhibited by extracellular EGTA. Elevation of cytosolic [Ca2+] by MSI-1436 requires heparin-sensitive intracellular Ca2+ stores. Although injected EGTA abolishes the increased conductive Cl- flux, that Cl- flux is not dependent on heparin-sensitive stores. In low-bath Ca2+ conditions, several structurally related polyaminosterols act as strong agonists or weak agonists of conductive Cl- flux in oocytes. Weak agonist polyaminosterols antagonize the strong agonist, MSI-1436, but upon addition of the conductive Cl- transport inhibitor DIDS, they are converted into strong agonists. Together, these properties operationally define a polyaminosterol receptor at or near the surface of the Xenopus oocyte, provide an initial description of receptor signaling, and suggest routes toward further understanding of a novel class of appetite suppressants and angiogenesis inhibitors.

  18. Expression and function of a CP339,818-sensitive K⁺ current in a subpopulation of putative nociceptive neurons from adult mouse trigeminal ganglia.

    Science.gov (United States)

    Sforna, Luigi; D'Adamo, Maria Cristina; Servettini, Ilenio; Guglielmi, Luca; Pessia, Mauro; Franciolini, Fabio; Catacuzzeno, Luigi

    2015-04-01

    Trigeminal ganglion (TG) neurons are functionally and morphologically heterogeneous, and the molecular basis of this heterogeneity is still not fully understood. Here we describe experiments showing that a subpopulation of neurons expresses a delayed-rectifying K(+) current (IDRK) with a characteristically high (nanomolar) sensitivity to the dihydroquinoline CP339,818 (CP). Although submicromolar CP has previously been shown to selectively block Kv1.3 and Kv1.4 channels, the CP-sensitive IDRK found in TG neurons could not be associated with either of these two K(+) channels. It could neither be associated with Kv2.1 channels homomeric or heteromerically associated with the Kv9.2, Kv9.3, or Kv6.4 subunits, whose block by CP, tested using two-electrode voltage-clamp recordings from Xenopus oocytes, resulted in the low micromolar range, nor to the Kv7 subfamily, given the lack of blocking efficacy of 3 μM XE991. Within the group of multiple-firing neurons considered in this study, the CP-sensitive IDRK was preferentially expressed in a subpopulation showing several nociceptive markers, such as small membrane capacitance, sensitivity to capsaicin, and slow afterhyperpolarization (AHP); in these neurons the CP-sensitive IDRK controls the membrane resting potential, the firing frequency, and the AHP duration. A biophysical study of the CP-sensitive IDRK indicated the presence of two kinetically distinct components: a fast deactivating component having a relatively depolarized steady-state inactivation (IDRKf) and a slow deactivating component with a more hyperpolarized V1/2 for steady-state inactivation (IDRKs). Copyright © 2015 the American Physiological Society.

  19. Ability of sat-1 to transport sulfate, bicarbonate, or oxalate under physiological conditions.

    Science.gov (United States)

    Krick, Wolfgang; Schnedler, Nina; Burckhardt, Gerhard; Burckhardt, Birgitta C

    2009-07-01

    Tubular reabsorption of sulfate is achieved by the sodium-dependent sulfate transporter, NaSi-1, located at the apical membrane, and the sulfate-anion exchanger, sat-1, located at the basolateral membrane. To delineate the physiological role of rat sat-1, [(35)S]sulfate and [(14)C]oxalate uptake into sat-1-expressing oocytes was determined under various experimental conditions. Influx of [(35)S]sulfate was inhibited by bicarbonate, thiosulfate, sulfite, and oxalate, but not by sulfamate and sulfide, in a competitive manner with K(i) values of 2.7 +/- 1.3 mM, 101.7 +/- 9.7 microM, 53.8 +/- 10.9 microM, and 63.5 +/- 38.7 microM, respectively. Vice versa, [(14)C]oxalate uptake was inhibited by sulfate with a K(i) of 85.9 +/- 9.5 microM. The competitive type of inhibition indicates that these compounds are most likely substrates of sat-1. Physiological plasma bicarbonate concentrations (25 mM) reduced sulfate and oxalate uptake by more than 75%. Simultaneous application of sulfate, bicarbonate, and oxalate abolished sulfate as well as oxalate uptake. These data and electrophysiological studies using a two-electrode voltage-clamp device provide evidence that sat-1 preferentially works as an electroneutral sulfate-bicarbonate or oxalate-bicarbonate exchanger. In kidney proximal tubule cells, sat-1 likely completes sulfate reabsorption from the ultrafiltrate across the basolateral membrane in exchange for bicarbonate. In hepatocytes, oxalate extrusion is most probably mediated either by an exchange for sulfate or bicarbonate.

  20. A single-point mutation enhances dual functionality of a scorpion toxin.

    Science.gov (United States)

    Wang, Xueli; Gao, Bin; Zhu, Shunyi

    2016-01-01

    Scorpion venom represents a tremendous, hitherto partially explored peptide library that has been proven to be useful not only for understanding ion channels but also for drug design. MeuTXKα3 is a functionally unknown scorpion toxin-like peptide. Here we describe new transcripts of this gene arising from alternative polyadenylation and its biological function as well as a mutant with a single-point substitution at site 30. Native-like MeuTXKα3 and its mutant were produced in Escherichia coli and their toxic function against Drosophila Shaker K(+) channel and its mammalian counterparts (rKv1.1-rKv1.3) were assayed by two-electrode voltage clamp technique. The results show that MeuTXKα3 is a weak toxin with a wide-spectrum of activity on both Drosophila and mammalian K(+) channels. The substitution of a proline at site 30 by an asparagine, an evolutionarily conserved functional residue in the scorpion α-KTx family, led to an increased activity on rKv1.2 and rKv1.3 but a decreased activity on the Shaker channel without changing the potency on rKv1.1, suggesting a key role of this site in species selectivity of scorpion toxins. MeuTXKα3 was also active on a variety of bacteria with lethal concentrations ranging from 4.66 to 52.01μM and the mutant even had stronger activity on some of these bacterial species. To the best of our knowledge, this is the first report on a bi-functional short-chain peptide in the lesser Asian scorpion venom. Further extensive mutations of MeuTXKα3 at site 30 could help improve its K(+) channel-blocking and antibacterial functions.

  1. The two Na+ sites in the human serotonin transporter play distinct roles in the ion coupling and electrogenicity of transport.

    Science.gov (United States)

    Felts, Bruce; Pramod, Akula Bala; Sandtner, Walter; Burbach, Nathan; Bulling, Simon; Sitte, Harald H; Henry, L Keith

    2014-01-17

    Neurotransmitter transporters of the SLC6 family of proteins, including the human serotonin transporter (hSERT), utilize Na(+), Cl(-), and K(+) gradients to induce conformational changes necessary for substrate translocation. Dysregulation of ion movement through monoamine transporters has been shown to impact neuronal firing potentials and could play a role in pathophysiologies, such as depression and anxiety. Despite multiple crystal structures of prokaryotic and eukaryotic SLC transporters indicating the location of both (or one) conserved Na(+)-binding sites (termed Na1 and Na2), much remains uncertain in regard to the movements and contributions of these cation-binding sites in the transport process. In this study, we utilize the unique properties of a mutation of hSERT at a single, highly conserved asparagine on TM1 (Asn-101) to provide several lines of evidence demonstrating mechanistically distinct roles for Na1 and Na2. Mutations at Asn-101 alter the cation dependence of the transporter, allowing Ca(2+) (but not other cations) to functionally replace Na(+) for driving transport and promoting 5-hydroxytryptamine (5-HT)-dependent conformational changes. Furthermore, in two-electrode voltage clamp studies in Xenopus oocytes, both Ca(2+) and Na(+) illicit 5-HT-induced currents in the Asn-101 mutants and reveal that, although Ca(2+) promotes substrate-induced current, it does not appear to be the charge carrier during 5-HT transport. These findings, in addition to functional evaluation of Na1 and Na2 site mutants, reveal separate roles for Na1 and Na2 and provide insight into initiation of the translocation process as well as a mechanism whereby the reported SERT stoichiometry can be obtained despite the presence of two putative Na(+)-binding sites.

  2. The Two Na+ Sites in the Human Serotonin Transporter Play Distinct Roles in the Ion Coupling and Electrogenicity of Transport*

    Science.gov (United States)

    Felts, Bruce; Pramod, Akula Bala; Sandtner, Walter; Burbach, Nathan; Bulling, Simon; Sitte, Harald H.; Henry, L. Keith

    2014-01-01

    Neurotransmitter transporters of the SLC6 family of proteins, including the human serotonin transporter (hSERT), utilize Na+, Cl−, and K+ gradients to induce conformational changes necessary for substrate translocation. Dysregulation of ion movement through monoamine transporters has been shown to impact neuronal firing potentials and could play a role in pathophysiologies, such as depression and anxiety. Despite multiple crystal structures of prokaryotic and eukaryotic SLC transporters indicating the location of both (or one) conserved Na+-binding sites (termed Na1 and Na2), much remains uncertain in regard to the movements and contributions of these cation-binding sites in the transport process. In this study, we utilize the unique properties of a mutation of hSERT at a single, highly conserved asparagine on TM1 (Asn-101) to provide several lines of evidence demonstrating mechanistically distinct roles for Na1 and Na2. Mutations at Asn-101 alter the cation dependence of the transporter, allowing Ca2+ (but not other cations) to functionally replace Na+ for driving transport and promoting 5-hydroxytryptamine (5-HT)-dependent conformational changes. Furthermore, in two-electrode voltage clamp studies in Xenopus oocytes, both Ca2+ and Na+ illicit 5-HT-induced currents in the Asn-101 mutants and reveal that, although Ca2+ promotes substrate-induced current, it does not appear to be the charge carrier during 5-HT transport. These findings, in addition to functional evaluation of Na1 and Na2 site mutants, reveal separate roles for Na1 and Na2 and provide insight into initiation of the translocation process as well as a mechanism whereby the reported SERT stoichiometry can be obtained despite the presence of two putative Na+-binding sites. PMID:24293367

  3. 6-Bromohypaphorine from Marine Nudibranch Mollusk Hermissenda crassicornis is an Agonist of Human α7 Nicotinic Acetylcholine Receptor

    Directory of Open Access Journals (Sweden)

    Igor E. Kasheverov

    2015-03-01

    Full Text Available 6-Bromohypaphorine (6-BHP has been isolated from the marine sponges Pachymatisma johnstoni, Aplysina sp., and the tunicate Aplidium conicum, but data on its biological activity were not available. For the nudibranch mollusk Hermissenda crassicornis no endogenous compounds were known, and here we describe the isolation of 6-BHP from this mollusk and its effects on different nicotinic acetylcholine receptors (nAChR. Two-electrode voltage-clamp experiments on the chimeric α7 nAChR (built of chicken α7 ligand-binding and glycine receptor transmembrane domains or on rat α4β2 nAChR expressed in Xenopus oocytes revealed no action of 6-BHP. However, in radioligand analysis, 6-BHP competed with radioiodinated α-bungarotoxin for binding to human α7 nAChR expressed in GH4C1 cells (IC50 23 ± 1 μM, but showed no competition on muscle-type nAChR from Torpedo californica. In Ca2+-imaging experiments on the human α7 nAChR expressed in the Neuro2a cells, 6-BHP in the presence of PNU120596 behaved as an agonist (EC50 ~80 μM. To the best of our knowledge, 6-BHP is the first low-molecular weight compound from marine source which is an agonist of the nAChR subtype. This may have physiological importance because H. crassicornis, with its simple and tractable nervous system, is a convenient model system for studying the learning and memory processes.

  4. A comparative study of the action of tolperisone on seven different voltage dependent sodium channel isoforms.

    Science.gov (United States)

    Hofer, Doris; Lohberger, Birgit; Steinecker, Bibiane; Schmidt, Kurt; Quasthoff, Stefan; Schreibmayer, Wolfgang

    2006-05-24

    The specific, acute interaction of tolperisone, an agent used as a muscle relaxant and for the treatment of chronic pain conditions, with the Na(v1.2), Na(v1.3), Na(v1.4), Na(v1.5), Na(v1.6), Na(v1.7), and Na(v1.8) isoforms of voltage dependent sodium channels was investigated and compared to that of lidocaine. Voltage dependent sodium channels were expressed in the Xenopus laevis oocyte expression system and sodium currents were recorded with the two electrode voltage clamp technique. Cumulative dose response relations revealed marked differences in IC(50) values between the two drugs on identical isoforms, as well as between isoforms. A detailed kinetic analysis uncovered that tolperisone as well as lidocaine exhibited their blocking action not only via state dependent association/dissociation with voltage dependent sodium channels, but a considerable fraction of inhibition is tonic, i.e. permanent and basic in nature. Voltage dependent activation was affected to a minor extent only. A shift in steady-state inactivation to more negative potentials could be observed for most drug/isoform combinations. The contribution of this shift to overall block was, however, small at drug concentrations resulting in considerable overall block. Recovery from inactivation was affected notably by both drugs. Lidocaine application led to a pronounced prolongation of the time constant of the fast recovery process for the Na(v1.3), Na(v1.5), and Na(v1.7) isoforms, indicating common structural properties in the local anesthetic receptor site of these three proteins. Interestingly, this characteristic drug action was not observed for tolperisone.

  5. The direct actions of cannabidiol and 2-arachidonoyl glycerol at GABAA receptors.

    Science.gov (United States)

    Bakas, T; van Nieuwenhuijzen, P S; Devenish, S O; McGregor, I S; Arnold, J C; Chebib, M

    2017-02-27

    Cannabidiol (CBD) is a major non-intoxicating component of cannabis and possesses anti-epileptic, anxiolytic and anti-hyperalgesic properties. The mechanism of action of CBD in producing such effects remains unclear. Despite evidence that some endogenous and synthetic cannabinoids interact with GABAA receptors, no-one has yet investigated the effects of CBD. Here we used two-electrode voltage clamp electrophysiology to compare the actions of CBD with those of the major central endocannabinoid, 2-arachidonoyl glycerol (2-AG) on human recombinant GABAA receptors (synaptic α1-6βγ2 and extrasynaptic α4β2δ) expressed on Xenopus oocytes. CBD and 2-AG were positive allosteric modulators at α1-6βγ2 receptors, with low micromolar potencies. The maximal level of enhancement seen with either CBD or 2-AG were on α2-containing GABAA receptor subtypes, with approximately a 4-fold enhancement of the GABA EC5 evoked current, more than twice the potentiation seen with other α-subunit receptor combinations. Further we observed β-subunit selectivity, whereby modulatory activity was higher at β2/β3 over β1 subunits. The β1-subunit homologous mutant β2(V436T) substantially diminished the efficacy of both drugs to a third of that obtained with wild-type β2 subunit combinations, but without changing potency. The potency of CBD increased and efficacy preserved in binary α1/α2β2 receptors indicating that their effects do not involve the classic benzodiazepine site. Exploration of extrasynaptic α4β2δ receptors revealed that both compounds enhanced GABA EC5 evoked currents at concentrations ranging from 0.01-1μM. Taken together these results reveal a mode of action of CBD on specifically configured GABAA receptors that may be relevant to the anticonvulsant and anxiolytic effects of the compound.

  6. Two P2X1 receptor transcripts able to form functional channels are present in most human monocytes.

    Science.gov (United States)

    López-López, Cintya; Jaramillo-Polanco, Josue; Portales-Pérez, Diana P; Gómez-Coronado, Karen S; Rodríguez-Meléndez, Jessica G; Cortés-García, Juan D; Espinosa-Luna, Rosa; Montaño, Luis M; Barajas-López, Carlos

    2016-12-15

    To characterize the presence and general properties of P2X1 receptors in single human monocytes we used RT-PCR, flow cytometry, and the patch-clamp and the two-electrode voltage-clamp techniques. Most human monocytes expressed the canonical P2X1 (90%) and its splicing variant P2X1del (88%) mRNAs. P2X1 receptor immunoreactivity was also observed in 70% of these cells. Currents mediated by P2X1 (EC50=1.9±0.8µm) and P2X1del (EC50 >1000µm) channels, expressed in Xenopus leavis oocytes, have different ATP sensitivity and kinetics. Both currents mediated by P2X1 and P2X1del channels kept increasing during the continuous presence of high ATP concentrations. Currents mediated by the native P2X1 receptors in human monocytes showed an EC50=6.3±0.2µm. Currents have kinetics that resemble those observed for P2X1 and P2X1del receptors in oocytes. Our study is the first to demonstrate the expression of P2X1 transcript and its splicing variant P2X1del in most human monocytes. We also, for the first time, described functional homomeric P2X1del channels and demonstrated that currents mediated by P2X1 or P2X1del receptors, during heterologous expression, increased in amplitude when activated with high ATP concentrations in a similar fashion to those channels that increase their conductance under similar conditions, such as P2X7, P2X2, and P2X4 channels.

  7. Functional contribution of alpha3L8' to the neuronal nicotinic alpha3 receptor.

    Science.gov (United States)

    Nieves-Cintrón, Madeline; Caballero-Rivera, Daniel; Silva, Walter I; Navedo, Manuel F; Lasalde-Dominicci, José A

    2008-10-01

    The role of position L8', located in transmembrane domain 1 of the neuronal nicotinic alpha3 subunit, was characterized by using two-electrode voltage clamp in Xenopus oocytes. Four amino acids (Ala, Ser, Phe, and Tyr) were inserted at this conserved position, and the mutant subunit was coexpressed with either wild-type beta2 or beta4 subunits. These substitutions led to significant alterations in the pharmacodynamic parameters of cholinergic agents, resulting in loss of function. Ala and Ser substitutions resulted in losses in agonist (ACh, nicotine, and DMPP) potency and intrinsic activity at both alpha3beta2 and alpha3beta4 receptors. Similarly, significant changes in antagonist potency were produced by the Ala and Ser substitutions. Phe and Tyr mutations did not alter the receptor's EC(50) for ACh or nicotine but reduced the EC(50) for DMPP at both receptors. The Phe mutation also reduced the intrinsic activity of all agonists tested at both receptors. The Tyr mutation, though, led to a decrease in intrinsic activity for all agonists at the alpha3beta2 receptor, yet resulted in no changes for DMPP, a decrease for nicotine, and an increase for ACh at the alpha3beta4 receptor. The most dramatic changes in the receptor's functional properties were produced by substitutions that introduced the largest changes in amino acid volume. Additional replacements (Gly, Thr, and Val) suggested an inverse correlation between amino acid volume at position alpha3L8' and EC(50) for alpha3beta4 nAChRs; however, alpha3beta2 nAChRs displayed a nonlinear correlation. These data demonstrate that structural alterations at position alpha3L8' could propagate to the agonist-binding site.

  8. Activation and modulation of recombinantly expressed serotonin receptor type 3A by terpenes and pungent substances.

    Science.gov (United States)

    Ziemba, Paul M; Schreiner, Benjamin S P; Flegel, Caroline; Herbrechter, Robin; Stark, Timo D; Hofmann, Thomas; Hatt, Hanns; Werner, Markus; Gisselmann, Günter

    2015-11-27

    Serotonin receptor type 3 (5-HT3 receptor) is a ligand-gated ion channel that is expressed in the central nervous system (CNS) as well as in the peripheral nervous system (PNS). The receptor plays an important role in regulating peristalsis of the gastrointestinal tract and in functions such as emesis, cognition and anxiety. Therefore, a variety of pharmacologically active substances target the 5-HT3 receptor to treat chemotherapy-induced nausea and vomiting. The 5-HT3 receptors are activated, antagonized, or modulated by a wide range of chemically different substances, such as 2-methyl-serotonin, phenylbiguanide, setrones, or cannabinoids. Whereas the action of all of these substances is well described, less is known about the effect of terpenoids or fragrances on 5-HT3A receptors. In this study, we screened a large number of natural odorous and pungent substances for their pharmacological action on recombinantly expressed human 5-HT3A receptors. The receptors were functionally expressed in Xenopus oocytes and characterized by electrophysiological recordings using the two-electrode voltage-clamp technique. A screening of two odorous mixes containing a total of 200 substances revealed that the monoterpenes, thymol and carvacrol, act as both weak partial agonists and positive modulators on the 5-HT3A receptor. In contrast, the most effective blockers were the terpenes, citronellol and geraniol, as well as the pungent substances gingerol, capsaicin and polygodial. In our study, we identified new modulators of 5-HT3A receptors out of the classes of monoterpenes and vanilloid substances that frequently occur in various plants.

  9. A molecular characterization of the agonist binding site of a nematode cys-loop GABA receptor

    Science.gov (United States)

    Kaji, Mark D; Kwaka, Ariel; Callanan, Micah K; Nusrat, Humza; Desaulniers, Jean-Paul; Forrester, Sean G

    2015-01-01

    Background and Purpose Cys-loop GABA receptors represent important targets for human chemotherapeutics and insecticides and are potential targets for novel anthelmintics (nematicides). However, compared with insect and mammalian receptors, little is known regarding the pharmacological characteristics of nematode Cys-loop GABA receptors. Here we have investigated the agonist binding site of the Cys-loop GABA receptor UNC-49 (Hco-UNC-49) from the parasitic nematode Haemonchus contortus. Experimental Approach We used two-electrode voltage-clamp electrophysiology to measure channel activation by classical GABA receptor agonists on Hco-UNC-49 expressed in Xenopus laevis oocytes, along with site-directed mutagenesis and in silico homology modelling. Key Results The sulphonated molecules P4S and taurine had no effect on Hco-UNC-49. Other classical Cys-loop GABAA receptor agonists tested on the Hco-UNC-49B/C heteromeric channel had a rank order efficacy of GABA > trans-4-aminocrotonic acid > isoguvacine > imidazole-4-acetic acid (IMA) > (R)-(−)-4-amino-3-hydroxybutyric acid [R(−)-GABOB] > (S)-(+)-4-amino-3-hydroxybutyric acid [S(+)-GABOB] > guanidinoacetic acid > isonipecotic acid > 5-aminovaleric acid (DAVA) (partial agonist) > β-alanine (partial agonist). In silico ligand docking revealed some variation in binding between agonists. Mutagenesis of a key serine residue in binding loop C to threonine had minimal effects on GABA and IMA but significantly increased the maximal response to DAVA and decreased twofold the EC50 for R(−)- and S(+)-GABOB. Conclusions and Implications The pharmacological profile of Hco-UNC-49 differed from that of vertebrate Cys-loop GABA receptors and insect resistance to dieldrin receptors, suggesting differences in the agonist binding pocket. These findings could be exploited to develop new drugs that specifically target GABA receptors of parasitic nematodes. PMID:25850584

  10. Control of Secretion by Encodes of Action Potentials in Neuronal Cells

    Institute of Scientific and Technical Information of China (English)

    Kailai Duan; Zhuan Zhou

    2003-01-01

    @@ Action potentials (APs) are principle physiological stimuli of neurotransmitter secretion or synaptic transmis sion. Most studies on stimulus-secretion-coupling have been performed under voltage clamp using artificial electric stimulations.

  11. Ensemble Data Mining Methods

    Science.gov (United States)

    Oza, Nikunj C.

    2004-01-01

    Ensemble Data Mining Methods, also known as Committee Methods or Model Combiners, are machine learning methods that leverage the power of multiple models to achieve better prediction accuracy than any of the individual models could on their own. The basic goal when designing an ensemble is the same as when establishing a committee of people: each member of the committee should be as competent as possible, but the members should be complementary to one another. If the members are not complementary, Le., if they always agree, then the committee is unnecessary---any one member is sufficient. If the members are complementary, then when one or a few members make an error, the probability is high that the remaining members can correct this error. Research in ensemble methods has largely revolved around designing ensembles consisting of competent yet complementary models.

  12. Adaptive Algebraic Multigrid Methods

    Energy Technology Data Exchange (ETDEWEB)

    Brezina, M; Falgout, R; MacLachlan, S; Manteuffel, T; McCormick, S; Ruge, J

    2004-04-09

    Our ability to simulate physical processes numerically is constrained by our ability to solve the resulting linear systems, prompting substantial research into the development of multiscale iterative methods capable of solving these linear systems with an optimal amount of effort. Overcoming the limitations of geometric multigrid methods to simple geometries and differential equations, algebraic multigrid methods construct the multigrid hierarchy based only on the given matrix. While this allows for efficient black-box solution of the linear systems associated with discretizations of many elliptic differential equations, it also results in a lack of robustness due to assumptions made on the near-null spaces of these matrices. This paper introduces an extension to algebraic multigrid methods that removes the need to make such assumptions by utilizing an adaptive process. The principles which guide the adaptivity are highlighted, as well as their application to algebraic multigrid solution of certain symmetric positive-definite linear systems.

  13. Methods for cellobiosan utilization

    Energy Technology Data Exchange (ETDEWEB)

    Linger, Jeffrey; Beckham, Gregg T.

    2017-07-11

    Disclosed herein are enzymes useful for the degradation of cellobiosan in materials such a pyrolysis oils. Methods of degrading cellobiosan using enzymes or organisms expressing the same are also disclosed.

  14. Compressive Spectral Renormalization Method

    CERN Document Server

    Bayindir, Cihan

    2016-01-01

    In this paper a novel numerical scheme for finding the sparse self-localized states of a nonlinear system of equations with missing spectral data is introduced. As in the Petviashivili's and the spectral renormalization method, the governing equation is transformed into Fourier domain, but the iterations are performed for far fewer number of spectral components (M) than classical versions of the these methods with higher number of spectral components (N). After the converge criteria is achieved for M components, N component signal is reconstructed from M components by using the l1 minimization technique of the compressive sampling. This method can be named as compressive spectral renormalization (CSRM) method. The main advantage of the CSRM is that, it is capable of finding the sparse self-localized states of the evolution equation(s) with many spectral data missing.

  15. Iii. Sleep assessment methods.

    Science.gov (United States)

    Sadeh, Avi

    2015-03-01

    Sleep is a complex phenomenon that could be understood and assessed at many levels. Sleep could be described at the behavioral level (relative lack of movements and awareness and responsiveness) and at the brain level (based on EEG activity). Sleep could be characterized by its duration, by its distribution during the 24-hr day period, and by its quality (e.g., consolidated versus fragmented). Different methods have been developed to assess various aspects of sleep. This chapter covers the most established and common methods used to assess sleep in infants and children. These methods include polysomnography, videosomnography, actigraphy, direct observations, sleep diaries, and questionnaires. The advantages and disadvantages of each method are highlighted.

  16. Stochastic optimization methods

    CERN Document Server

    Marti, Kurt

    2005-01-01

    Optimization problems arising in practice involve random parameters. For the computation of robust optimal solutions, i.e., optimal solutions being insensitive with respect to random parameter variations, deterministic substitute problems are needed. Based on the distribution of the random data, and using decision theoretical concepts, optimization problems under stochastic uncertainty are converted into deterministic substitute problems. Due to the occurring probabilities and expectations, approximative solution techniques must be applied. Deterministic and stochastic approximation methods and their analytical properties are provided: Taylor expansion, regression and response surface methods, probability inequalities, First Order Reliability Methods, convex approximation/deterministic descent directions/efficient points, stochastic approximation methods, differentiation of probability and mean value functions. Convergence results of the resulting iterative solution procedures are given.

  17. Methods for euclidean geometry

    CERN Document Server

    Byer, Owen; Smeltzer, Deirdre L

    2010-01-01

    Euclidean plane geometry is one of the oldest and most beautiful topics in mathematics. Instead of carefully building geometries from axiom sets, this book uses a wealth of methods to solve problems in Euclidean geometry. Many of these methods arose where existing techniques proved inadequate. In several cases, the new ideas used in solving specific problems later developed into independent areas of mathematics. This book is primarily a geometry textbook, but studying geometry in this way will also develop students' appreciation of the subject and of mathematics as a whole. For instance, despite the fact that the analytic method has been part of mathematics for four centuries, it is rarely a tool a student considers using when faced with a geometry problem. Methods for Euclidean Geometry explores the application of a broad range of mathematical topics to the solution of Euclidean problems.

  18. Methods in Modern Biophysics

    CERN Document Server

    Nölting, Bengt

    2010-01-01

    Incorporating recent dramatic advances, this textbook presents a fresh and timely introduction to modern biophysical methods. An array of new, faster and higher-power biophysical methods now enables scientists to examine the mysteries of life at a molecular level. This innovative text surveys and explains the ten key biophysical methods, including those related to biophysical nanotechnology, scanning probe microscopy, X-ray crystallography, ion mobility spectrometry, mass spectrometry, proteomics, and protein folding and structure. Incorporating much information previously unavailable in tutorial form, Nölting employs worked examples and about 270 illustrations to fully detail the techniques and their underlying mechanisms. Methods in Modern Biophysics is written for advanced undergraduate and graduate students, postdocs, researchers, lecturers, and professors in biophysics, biochemistry and related fields. Special features in the 3rd edition: Introduces rapid partial protein ladder sequencing - an important...

  19. Concrete compositions and methods

    Science.gov (United States)

    Chen, Irvin; Lee, Patricia Tung; Patterson, Joshua

    2015-06-23

    Provided herein are compositions, methods, and systems for cementitious compositions containing calcium carbonate compositions and aggregate. The compositions find use in a variety of applications, including use in a variety of building materials and building applications.

  20. Monte Carlo methods

    OpenAIRE

    Bardenet, R.

    2012-01-01

    ISBN:978-2-7598-1032-1; International audience; Bayesian inference often requires integrating some function with respect to a posterior distribution. Monte Carlo methods are sampling algorithms that allow to compute these integrals numerically when they are not analytically tractable. We review here the basic principles and the most common Monte Carlo algorithms, among which rejection sampling, importance sampling and Monte Carlo Markov chain (MCMC) methods. We give intuition on the theoretic...

  1. Business forecasting methods

    OpenAIRE

    Skribans, V.

    2002-01-01

    The paper comprises three parts: description of the forecasting conception, classification of forecasting methods, and the general forecasting model. The first part deals with the definition of business forecasting, the second classifies and deals in more detail with the most frequently practiced forecasting methods and comes up with recommendations how to apply them in specific situations. The third part present the analysis of newly established forecasting model.

  2. Bidirectional beam propagation method

    Science.gov (United States)

    Kaczmarski, P.; Lagasse, P. E.

    1988-05-01

    A bidirectional extension of the beam propagation method (BPM) to optical waveguides with a longitudinal discontinuity is presented. The algorithm is verified by computing a reflection of the TE(0) mode from a semiconductor laser facet. The bidirectional BPM is applicable to other configurations such as totally reflecting waveguide mirrors, an abruption transition in a waveguide, or a waveguide with many discontinuities generating multiple reflections. The method can also be adapted to TM polarization.

  3. Method of treating depression

    Energy Technology Data Exchange (ETDEWEB)

    Henn, Fritz

    2013-04-09

    Methods for treatment of depression-related mood disorders in mammals, particularly humans are disclosed. The methods of the invention include administration of compounds capable of enhancing glutamate transporter activity in the brain of mammals suffering from depression. ATP-sensitive K.sup.+ channel openers and .beta.-lactam antibiotics are used to enhance glutamate transport and to treat depression-related mood disorders and depressive symptoms.

  4. Method of treating depression

    Science.gov (United States)

    Henn, Fritz [East Patchogue, NY

    2012-01-24

    Methods for treatment of depression-related mood disorders in mammals, particularly humans are disclosed. The methods of the invention include administration of compounds capable of enhancing glutamate transporter activity in the brain of mammals suffering from depression. ATP-sensitive K.sup.+ channel openers and .beta.-lactam antibiotics are used to enhance glutamate transport and to treat depression-related mood disorders and depressive symptoms.

  5. On Danish Legal Method

    DEFF Research Database (Denmark)

    Schaumburg-Müller, Sten

    2014-01-01

    On the basis on 1) the Danish legal writer A.S.Ørsted (1778-1860) and 2) an enquete among present day Danish legal scholars, the contribution deals with special traits in Danish legal method......On the basis on 1) the Danish legal writer A.S.Ørsted (1778-1860) and 2) an enquete among present day Danish legal scholars, the contribution deals with special traits in Danish legal method...

  6. Methods for polymer synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Scott D.; Simoneau, Christopher A.; Keefe, William D.; Conuel, Jeff R.

    2016-12-06

    The present invention provides methods for reducing induction periods in epoxide-CO.sub.2 copolymerizations. In certain embodiments, the methods include the step of contacting an epoxide with CO.sub.2 in the presence of two catalysts: an epoxide hydrolysis catalyst and an epoxide CO.sub.2 copolymerization catalyst. In another aspect, the invention provides catalyst compositions comprising a mixture of an epoxide hydrolysis catalyst and an epoxide CO.sub.2 copolymerization catalyst.

  7. Modern Methods in Marketing

    OpenAIRE

    Jandová, Pavlína

    2007-01-01

    Traditional marketing methods are losing their effectiveness and credibility. It has been worse and worse to communicate with customers, and marketers are therefore looking for new techniques and way how to appeal buyers. They turn to the use of modern marketing methods, which typical features are possibility of accurate targeting and low costs, and, also, the fact that they are still not considered being a classic promotion. In the theoretical part of the diploma thesis the alternative marke...

  8. Painful Bile Extraction Methods

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    It was only in the past 20 years that countries in Asia began to search for an alternative to protect moon bears from being killed for their bile and other body parts. In the early 1980s, a new method of extracting bile from living bears was developed in North Korea. In 1983, Chinese scientists imported this technique from North Korea. According to the Animals Asia Foundation, the most original method of bile extraction is to embed a latex catheter, a narrow rubber

  9. [Unproven methods in oncology].

    Science.gov (United States)

    Jallut, O; Guex, P; Barrelet, L

    1984-09-08

    As in some other chronic diseases (rheumatism, multiple sclerosis, etc.), unproven methods of diagnosis and treatment have long been current in cancer. Since 1960 the American Cancer Society has published an abundant literature on these "unproven methods", which serves as a basis for a historical review: some substances (Krebiozen, Laetrile) have enjoyed tremendous if shortlived success. The present trend is back to nature and "mild medicine". The proponents of this so-called natural medicine are often disciples of a pseudoscientific religion using irrational arguments. Direct attacks on these erroneous theories and their public refutation fail to convince the adepts, who trust in these methods and are not amenable to a scientific approach. Study of their psychological motivations reveals that in fact they seek something more reassuring than plain medical explanation which is aware of its limits. They feel reassured by theories which often bear some resemblance to the old popular medicine. To protect patients against these dangerous methods and all the disillusionment they entail, the Swiss Society of Oncology and the Swiss Cancer League have decided to gather information and draw up a descriptive list of the commonest unproven methods in Switzerland (our File No. 2, "Total anti-cancer cure", is given as an example). The files are published in French, German and English and are available to physicians, nursing teams, and also patients who wish to have more objective information on these methods.

  10. Multicriteria identification sets method

    Science.gov (United States)

    Kamenev, G. K.

    2016-11-01

    A multicriteria identification and prediction method for mathematical models of simulation type in the case of several identification criteria (error functions) is proposed. The necessity of the multicriteria formulation arises, for example, when one needs to take into account errors of completely different origins (not reducible to a single characteristic) or when there is no information on the class of noise in the data to be analyzed. An identification sets method is described based on the approximation and visualization of the multidimensional graph of the identification error function and sets of suboptimal parameters. This method allows for additional advantages of the multicriteria approach, namely, the construction and visual analysis of the frontier and the effective identification set (frontier and the Pareto set for identification criteria), various representations of the sets of Pareto effective and subeffective parameter combinations, and the corresponding predictive trajectory tubes. The approximation is based on the deep holes method, which yields metric ɛ-coverings with nearly optimal properties, and on multiphase approximation methods for the Edgeworth-Pareto hull. The visualization relies on the approach of interactive decision maps. With the use of the multicriteria method, multiple-choice solutions of identification and prediction problems can be produced and justified by analyzing the stability of the optimal solution not only with respect to the parameters (robustness with respect to data) but also with respect to the chosen set of identification criteria (robustness with respect to the given collection of functionals).

  11. [Barrier methods of contraception].

    Science.gov (United States)

    Goldsmith, A; Edelman, D A

    1982-01-01

    Vaginal methods of contraception were the earliest types used and some references to them date back to antiquity. Most of the vaginal contraceptive agents identified by the ancient Greeks, Indians, Japanese, and Chinese have been found in modern laboratory tests to have spermicidal properties, but it is doubtful that the methods were fully reliable or were used by many people. During the 19th century the condom, vaginal spermicides, and diaphragm became available. The development of nonoxynol-9 and other nonirritating but effective spermicidal agents improved vaginal contraceptives greatly by the 1950s, but starting in the 1960s newer methods began to replace the vaginal methods. Interest in barrier methods has been reawakened somewhat by concern about the health effects of hormonal methods. At present all barrier methods leave something to be desired. Failure rates of 3-30% for barrier methods in general have been estimated, but the higher rates are believed due to incorrect or inconsistent use. Theoretical failure rates of condoms and diaphragms have been estimated at 3/100 women-years, but in actual use failure rates may reach 15 for condoms and 13 for diaphragms used with spermicides. Use-effectiveness rates are greatly influenced by motivation. For a variety of reasons, the acceptability of barrier methods is low, especially in developing countries. New developments in spermicidal agents include sperm inhibitors, which impede the fertilizing capacity of sperm rather than attempting a spermicidal effect; a number of such agents have been studied and have proven more effective in animal tests than conventional spermicides. Neosampoon, a new spermicidal foam, has attracted an increasing number of users, especially in developing countries. A new condom, made of thin polymers and containing a standard dose of nonoxynol-9, has been designed to dissolve in the vaginal fluid. Further studies are needed of its acceptability, efficacy, and side effects before it becomes

  12. The ICARE Method

    Science.gov (United States)

    Henke, Luke

    2010-01-01

    The ICARE method is a flexible, widely applicable method for systems engineers to solve problems and resolve issues in a complete and comprehensive manner. The method can be tailored by diverse users for direct application to their function (e.g. system integrators, design engineers, technical discipline leads, analysts, etc.). The clever acronym, ICARE, instills the attitude of accountability, safety, technical rigor and engagement in the problem resolution: Identify, Communicate, Assess, Report, Execute (ICARE). This method was developed through observation of Space Shuttle Propulsion Systems Engineering and Integration (PSE&I) office personnel approach in an attempt to succinctly describe the actions of an effective systems engineer. Additionally it evolved from an effort to make a broadly-defined checklist for a PSE&I worker to perform their responsibilities in an iterative and recursive manner. The National Aeronautics and Space Administration (NASA) Systems Engineering Handbook states, engineering of NASA systems requires a systematic and disciplined set of processes that are applied recursively and iteratively for the design, development, operation, maintenance, and closeout of systems throughout the life cycle of the programs and projects. ICARE is a method that can be applied within the boundaries and requirements of NASA s systems engineering set of processes to provide an elevated sense of duty and responsibility to crew and vehicle safety. The importance of a disciplined set of processes and a safety-conscious mindset increases with the complexity of the system. Moreover, the larger the system and the larger the workforce, the more important it is to encourage the usage of the ICARE method as widely as possible. According to the NASA Systems Engineering Handbook, elements of a system can include people, hardware, software, facilities, policies and documents; all things required to produce system-level results, qualities, properties, characteristics

  13. VALUATION METHODS- LITERATURE REVIEW

    Directory of Open Access Journals (Sweden)

    Dorisz Talas

    2015-07-01

    Full Text Available This paper is a theoretical overview of the often used valuation methods with the help of which the value of a firm or its equity is calculated. Many experts (including Aswath Damodaran, Guochang Zhang and CA Hozefa Natalwala classify the methods. The basic models are based on discounted cash flows. The main method uses the free cash flow for valuation, but there are some newer methods that reveal and correct the weaknesses of the traditional models. The valuation of flexibility of management can be conducted mainly with real options. This paper briefly describes the essence of the Dividend Discount Model, the Free Cash Flow Model, the benefit from using real options and the Residual Income Model. There are a few words about the Adjusted Present Value approach as well. Different models uses different premises, and an overall truth is that if the required premises are real and correct, the value will be appropriately accurate. Another important condition is that experts, analysts should choose between the models on the basis of the purpose of valuation. Thus there are no good or bad methods, only methods that fit different goals and aims. The main task is to define exactly the purpose, then to find the most appropriate valuation technique. All the methods originates from the premise that the value of an asset is the present value of its future cash flows. According to the different points of view of different techniques the resulted values can be also differed from each other. Valuation models and techniques should be adapted to the rapidly changing world, but the basic statements remain the same. On the other hand there is a need for more accurate models in order to help investors get as many information as they could. Today information is one of the most important resources and financial models should keep up with this trend.

  14. Molecular methods for biofilms

    KAUST Repository

    Ferrera, Isabel

    2014-08-30

    This chapter deals with both classical and modern molecular methods that can be useful for the identification of microorganisms, elucidation and comparison of microbial communities, and investigation of their diversity and functions. The most important and critical steps necessary for all molecular methods is DNA isolation from microbial communities and environmental samples; these are discussed in the first part. The second part provides an overview over DNA polymerase chain reaction (PCR) amplification and DNA sequencing methods. Protocols and analysis software as well as potential pitfalls associated with application of these methods are discussed. Community fingerprinting analyses that can be used to compare multiple microbial communities are discussed in the third part. This part focuses on Denaturing Gradient Gel Electrophoresis (DGGE), Terminal Restriction Fragment Length Polymorphism (T-RFLP) and Automated rRNA Intergenic Spacer Analysis (ARISA) methods. In addition, classical and next-generation metagenomics methods are presented. These are limited to bacterial artificial chromosome and Fosmid libraries and Sanger and next-generation 454 sequencing, as these methods are currently the most frequently used in research. Isolation of nucleic acids: This chapter discusses, the most important and critical steps necessary for all molecular methods is DNA isolation from microbial communities and environmental samples. Nucleic acid isolation methods generally include three steps: cell lysis, removal of unwanted substances, and a final step of DNA purification and recovery. The first critical step is the cell lysis, which can be achieved by enzymatic or mechanical procedures. Removal of proteins, polysaccharides and other unwanted substances is likewise important to avoid their interference in subsequent analyses. Phenol-chloroform-isoamyl alcohol is commonly used to recover DNA, since it separates nucleic acids into an aqueous phase and precipitates proteins and

  15. New oligosaccharyltransferase assay method.

    Science.gov (United States)

    Kohda, Daisuke; Yamada, Masaki; Igura, Mayumi; Kamishikiryo, Jun; Maenaka, Katsumi

    2007-11-01

    We developed a new in vitro assay for oligosaccharyltransferase (OST), which catalyzes the transfer of preassembled oligosaccharides on lipid carriers onto asparagine residues in polypeptide chains. The asparagine residues reside in the sequon, Asn-X-Thr/Ser, where X can be any amino acid residue except Pro. We demonstrate the potency of our assay using the OST from yeast. In our method, polyacrylamide gel electrophoresis is used to separate the glycopeptide products from the peptide substrates. The substrate peptide is fluorescently labeled and the formation of glycopeptides is analyzed by fluorescence gel imaging. Two in vitro OST assay methods are now widely used, but both the methods depend on previous knowledge of the oligosaccharide moiety: One method uses lectin binding as the separation mechanism and the other method uses biosynthetically or chemoenzymatically synthesized lipid-linked oligosaccharides as donors. N-linked protein glycosylation is found in all three domains of life, but little is known about the N-glycosylation in Archaea. Thus, our new assay, which does not require a priori knowledge of the oligosaccharides, will be useful in such cases. Indeed, we have detected the OST activity in the membrane fraction from a hyperthermophilic archaeon, Pyrococcus furiosus.

  16. Methods for Neutron Spectrometry

    Science.gov (United States)

    Brockhouse, Bertram N.

    1961-01-09

    The appropriate theories and the general philosophy of methods of measurement and treatment of data neutron spectrometry are discussed. Methods of analysis of results for liquids using the Van Hove formulation, and for crystals using the Born-von Karman theory, are reviewed. The most useful of the available methods of measurement are considered to be the crystal spectrometer methods and the pulsed monoenergetic beam/time-of-flight method. Pulsed-beam spectrometers have the advantage of higher counting rates than crystal spectrometers, especially in view of the fact that simultaneous measurements in several counters at different angles of scattering are possible in pulsed-beam spectrometers. The crystal spectrometer permits several valuable new types of specialized experiments to be performed, especially energy distribution measurements at constant momentum transfer. The Chalk River triple-axis crystal-spectrometer is discussed, with reference to its use in making the specialized experiments. The Chalk River rotating crystal (pulsed-beam) spectrometer is described, and a comparison of this type instrument with other pulsed-beam spectrometers is made. A partial outline of the theory of operation of rotating-crystal spectrometers is presented. The use of quartz-crystal filters for fast neutron elimination and for order elimination is discussed. (auth)

  17. The lod score method.

    Science.gov (United States)

    Rice, J P; Saccone, N L; Corbett, J

    2001-01-01

    The lod score method originated in a seminal article by Newton Morton in 1955. The method is broadly concerned with issues of power and the posterior probability of linkage, ensuring that a reported linkage has a high probability of being a true linkage. In addition, the method is sequential, so that pedigrees or lod curves may be combined from published reports to pool data for analysis. This approach has been remarkably successful for 50 years in identifying disease genes for Mendelian disorders. After discussing these issues, we consider the situation for complex disorders, where the maximum lod score (MLS) statistic shares some of the advantages of the traditional lod score approach but is limited by unknown power and the lack of sharing of the primary data needed to optimally combine analytic results. We may still learn from the lod score method as we explore new methods in molecular biology and genetic analysis to utilize the complete human DNA sequence and the cataloging of all human genes.

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

    OpenAIRE

    1990-01-01

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

  19. Fashion, Mediations & Method Assemblages

    DEFF Research Database (Denmark)

    Sommerlund, Julie; Jespersen, Astrid Pernille

    , respectively. The paper thus takes on aesthetics and the social in a manner closely related to a core argument of STS - namely that the scientific fact, and the social processes of constructing, distributing, and using that fact, are co-constructed (Callon, 1986; Latour, 1993). The paper thus contributes......, it is an important ambition of this paper to go into a methodological discussion of how "that which effectively happens" can be approached. To this end, the paper will combine Hennion's term of the "mediator" with John Laws methodological term of "method assemblages". Method assemblages is a suggested as a way...... of handling multiple, fluid realities with multiple, fluid methods. Empirically, the paper works with mediation in fashion - that is efforts the active shaping of relations between producer and consumer through communication, marketing and PR. Fashion mediation is by no means simple, but organise complex...

  20. Cytoskeleton - Methods and Protocols

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-03-01

    Full Text Available Cytoskeleton - Methods and ProtocolsSecond edition, 2010; Ray H. Gavin (Ed; Springer Protocols methods in molecular biology, vol. 586 Humana press, Totowa, New Jersey (USA; Pages: 390; €95.44; ISBN: 978-1-60761-375-6Ray H. Gavin, from the Brooklyn College of The City University of New York, Brooklyn, NY, USA, wrote a few line as preface of this book. This is quite understandable: there is not a great need of words when there are facts that sustain and favour the dissemination of a cultural product. This is the case of the second edition of Cytoskeleton - Methods and Protocols, which appears just ten years after the first edition...

  1. Geostatistical Methods in R

    Directory of Open Access Journals (Sweden)

    Adéla Volfová

    2012-10-01

    Full Text Available Geostatistics is a scientific field which provides methods for processing spatial data.  In our project, geostatistics is used as a tool for describing spatial continuity and making predictions of some natural phenomena. An open source statistical project called R is used for all calculations. Listeners will be provided with a brief introduction to R and its geostatistical packages and basic principles of kriging and cokriging methods. Heavy mathematical background is omitted due to its complexity. In the second part of the presentation, several examples are shown of how to make a prediction in the whole area of interest where observations were made in just a few points. Results of these methods are compared.

  2. Robust iterative methods

    Energy Technology Data Exchange (ETDEWEB)

    Saadd, Y.

    1994-12-31

    In spite of the tremendous progress achieved in recent years in the general area of iterative solution techniques, there are still a few obstacles to the acceptance of iterative methods in a number of applications. These applications give rise to very indefinite or highly ill-conditioned non Hermitian matrices. Trying to solve these systems with the simple-minded standard preconditioned Krylov subspace methods can be a frustrating experience. With the mathematical and physical models becoming more sophisticated, the typical linear systems which we encounter today are far more difficult to solve than those of just a few years ago. This trend is likely to accentuate. This workshop will discuss (1) these applications and the types of problems that they give rise to; and (2) recent progress in solving these problems with iterative methods. The workshop will end with a hopefully stimulating panel discussion with the speakers.

  3. Energy methods in dynamics

    CERN Document Server

    Le, Khanh Chau

    2012-01-01

    The above examples should make clear the necessity of understanding the mechanism of vibrations and waves in order to control them in an optimal way. However vibrations and waves are governed by differential equations which require, as a rule, rather complicated mathematical methods for their analysis. The aim of this textbook is to help students acquire both a good grasp of the first principles from which the governing equations can be derived, and the adequate mathematical methods for their solving. Its distinctive features, as seen from the title, lie in the systematic and intensive use of Hamilton's variational principle and its generalizations for deriving the governing equations of conservative and dissipative mechanical systems, and also in providing the direct variational-asymptotic analysis, whenever available, of the energy and dissipation for the solution of these equations. It will be demonstrated that many well-known methods in dynamics like those of Lindstedt-Poincare, Bogoliubov-Mitropolsky, Ko...

  4. Energy methods in dynamics

    CERN Document Server

    Le, Khanh Chau

    2014-01-01

    Energy Methods in Dynamics is a textbook based on the lectures given by the first author at Ruhr University Bochum, Germany. Its aim is to help students acquire both a good grasp of the first principles from which the governing equations can be derived, and the adequate mathematical methods for their solving. Its distinctive features, as seen from the title, lie in the systematic and intensive use of Hamilton's variational principle and its generalizations for deriving the governing equations of conservative and dissipative mechanical systems, and also in providing the direct variational-asymptotic analysis, whenever available, of the energy and dissipation for the solution of these equations. It demonstrates that many well-known methods in dynamics like those of Lindstedt-Poincare, Bogoliubov-Mitropolsky, Kolmogorov-Arnold-Moser (KAM), Wentzel–Kramers–Brillouin (WKB),  and Whitham are derivable from this variational-asymptotic analysis.   This second edition includes the solutions to all exercises as w...

  5. Sampling system and method

    Energy Technology Data Exchange (ETDEWEB)

    Decker, David L.; Lyles, Brad F.; Purcell, Richard G.; Hershey, Ronald Lee

    2017-03-07

    In one embodiment, the present disclosure provides an apparatus and method for supporting a tubing bundle during installation or removal. The apparatus includes a clamp for securing the tubing bundle to an external wireline. In various examples, the clamp is external to the tubing bundle or integral with the tubing bundle. According to one method, a tubing bundle and wireline are deployed together and the tubing bundle periodically secured to the wireline using a clamp. In another embodiment, the present disclosure provides an apparatus and method for coupling conduit segments together. A first pump obtains a sample and transmits it through a first conduit to a reservoir accessible by a second pump. The second pump further conducts the sample from the reservoir through a second conduit. In a specific example, one or more clamps are used to connect the first and/or second conduits to an external wireline.

  6. Grid generation methods

    CERN Document Server

    Liseikin, Vladimir D

    2017-01-01

    This new edition provides a description of current developments relating to grid methods, grid codes, and their applications to actual problems. Grid generation methods are indispensable for the numerical solution of differential equations. Adaptive grid-mapping techniques, in particular, are the main focus and represent a promising tool to deal with systems with singularities. This 3rd edition includes three new chapters on numerical implementations (10), control of grid properties (11), and applications to mechanical, fluid, and plasma related problems (13). Also the other chapters have been updated including new topics, such as curvatures of discrete surfaces (3). Concise descriptions of hybrid mesh generation, drag and sweeping methods, parallel algorithms for mesh generation have been included too. This new edition addresses a broad range of readers: students, researchers, and practitioners in applied mathematics, mechanics, engineering, physics and other areas of applications.

  7. Method of treating wells

    Energy Technology Data Exchange (ETDEWEB)

    Knox, J.A.; Lasater, R.M.

    1966-11-22

    Chemical compositions and methods are provided for treating underground formations to render their surfaces water-repellent or preferentially oil-wettable. Previous methods have provided only temporary water-repellency because they do not actually act chemically with the reservoir rock. This improvement is obtained by using a treating agent which does not form a precipitate upon hydrolysis with water, such as a liquid organo-halogen- silane or its ester. A water-soluble anhydrous solvent which is nonreactive with the silane is used as a carrier. This method may be used for treating non-oil-bearing aquifers for increasing the flow rate of water, such as in water supply wells, or in water input rate, such as in water disposal wells. (10 claims)

  8. Methods for RNA Analysis

    DEFF Research Database (Denmark)

    Olivarius, Signe

    of the transcriptome, 5’ end capture of RNA is combined with next-generation sequencing for high-throughput quantitative assessment of transcription start sites by two different methods. The methods presented here allow for functional investigation of coding as well as noncoding RNA and contribute to future......While increasing evidence appoints diverse types of RNA as key players in the regulatory networks underlying cellular differentiation and metabolism, the potential functions of thousands of conserved RNA structures encoded in mammalian genomes remain to be determined. Since the functions of most...... RNAs rely on interactions with proteins, the establishment of protein-binding profiles is essential for the characterization of RNAs. Aiming to facilitate RNA analysis, this thesis introduces proteomics- as well as transcriptomics-based methods for the functional characterization of RNA. First, RNA...

  9. Model Correction Factor Method

    DEFF Research Database (Denmark)

    Christensen, Claus; Randrup-Thomsen, Søren; Morsing Johannesen, Johannes

    1997-01-01

    The model correction factor method is proposed as an alternative to traditional polynomial based response surface techniques in structural reliability considering a computationally time consuming limit state procedure as a 'black box'. The class of polynomial functions is replaced by a limit...... statebased on an idealized mechanical model to be adapted to the original limit state by the model correction factor. Reliable approximations are obtained by iterative use of gradient information on the original limit state function analogously to previous response surface approaches. However, the strength...... of the model correction factor method, is that in simpler form not using gradient information on the original limit state function or only using this information once, a drastic reduction of the number of limit state evaluation is obtained together with good approximations on the reliability. Methods...

  10. Splines and variational methods

    CERN Document Server

    Prenter, P M

    2008-01-01

    One of the clearest available introductions to variational methods, this text requires only a minimal background in calculus and linear algebra. Its self-contained treatment explains the application of theoretic notions to the kinds of physical problems that engineers regularly encounter. The text's first half concerns approximation theoretic notions, exploring the theory and computation of one- and two-dimensional polynomial and other spline functions. Later chapters examine variational methods in the solution of operator equations, focusing on boundary value problems in one and two dimension

  11. Nonparametric statistical methods

    CERN Document Server

    Hollander, Myles; Chicken, Eric

    2013-01-01

    Praise for the Second Edition"This book should be an essential part of the personal library of every practicing statistician."-Technometrics  Thoroughly revised and updated, the new edition of Nonparametric Statistical Methods includes additional modern topics and procedures, more practical data sets, and new problems from real-life situations. The book continues to emphasize the importance of nonparametric methods as a significant branch of modern statistics and equips readers with the conceptual and technical skills necessary to select and apply the appropriate procedures for any given sit

  12. METHOD OF ROLLING URANIUM

    Science.gov (United States)

    Smith, C.S.

    1959-08-01

    A method is described for rolling uranium metal at relatively low temperatures and under non-oxidizing conditions. The method involves the steps of heating the uranium to 200 deg C in an oil bath, withdrawing the uranium and permitting the oil to drain so that only a thin protective coating remains and rolling the oil coated uranium at a temperature of 200 deg C to give about a 15% reduction in thickness at each pass. The operation may be repeated to accomplish about a 90% reduction without edge cracking, checking or any appreciable increase in brittleness.

  13. Electrorheological fluids and methods

    Energy Technology Data Exchange (ETDEWEB)

    Green, Peter F.; McIntyre, Ernest C.

    2015-06-02

    Electrorheological fluids and methods include changes in liquid-like materials that can flow like milk and subsequently form solid-like structures under applied electric fields; e.g., about 1 kV/mm. Such fluids can be used in various ways as smart suspensions, including uses in automotive, defense, and civil engineering applications. Electrorheological fluids and methods include one or more polar molecule substituted polyhedral silsesquioxanes (e.g., sulfonated polyhedral silsesquioxanes) and one or more oils (e.g., silicone oil), where the fluid can be subjected to an electric field.

  14. Tautomerism methods and theories

    CERN Document Server

    Antonov, Liudmil

    2013-01-01

    Covering the gap between basic textbooks and over-specialized scientific publications, this is the first reference available to describe this interdisciplinary topic for PhD students and scientists starting in the field. The result is an introductory description providing suitable practical examples of the basic methods used to study tautomeric processes, as well as the theories describing the tautomerism and proton transfer phenomena. It also includes different spectroscopic methods for examining tautomerism, such as UV-VIs, time-resolved fluorescence spectroscopy, and NMR spectrosc

  15. Unorthodox theoretical methods

    Energy Technology Data Exchange (ETDEWEB)

    Nedd, Sean [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    The use of the ReaxFF force field to correlate with NMR mobilities of amine catalytic substituents on a mesoporous silica nanosphere surface is considered. The interfacing of the ReaxFF force field within the Surface Integrated Molecular Orbital/Molecular Mechanics (SIMOMM) method, in order to replicate earlier SIMOMM published data and to compare with the ReaxFF data, is discussed. The development of a new correlation consistent Composite Approach (ccCA) is presented, which incorporates the completely renormalized coupled cluster method with singles, doubles and non-iterative triples corrections towards the determination of heats of formations and reaction pathways which contain biradical species.

  16. Exploring Monte Carlo methods

    CERN Document Server

    Dunn, William L

    2012-01-01

    Exploring Monte Carlo Methods is a basic text that describes the numerical methods that have come to be known as "Monte Carlo." The book treats the subject generically through the first eight chapters and, thus, should be of use to anyone who wants to learn to use Monte Carlo. The next two chapters focus on applications in nuclear engineering, which are illustrative of uses in other fields. Five appendices are included, which provide useful information on probability distributions, general-purpose Monte Carlo codes for radiation transport, and other matters. The famous "Buffon's needle proble

  17. Method through motion

    DEFF Research Database (Denmark)

    Steijn, Arthur

    2016-01-01

    Contemporary scenography often consists of video-projected motion graphics. The field is lacking in academic methods and rigour: descriptions and models relevant for the creation as well as in the analysis of existing works. In order to understand the phenomenon of motion graphics in a scenographic...... construction as a support to working systematically practice-led research project. The design model is being developed through design laboratories and workshops with students and professionals who provide feedback that lead to incremental improvements. Working with this model construction-as-method reveals...

  18. Methods of visualizing graphs

    Science.gov (United States)

    Wong, Pak C.; Mackey, Patrick S.; Perrine, Kenneth A.; Foote, Harlan P.; Thomas, James J.

    2008-12-23

    Methods for visualizing a graph by automatically drawing elements of the graph as labels are disclosed. In one embodiment, the method comprises receiving node information and edge information from an input device and/or communication interface, constructing a graph layout based at least in part on that information, wherein the edges are automatically drawn as labels, and displaying the graph on a display device according to the graph layout. In some embodiments, the nodes are automatically drawn as labels instead of, or in addition to, the label-edges.

  19. Methods of Multivariate Analysis

    CERN Document Server

    Rencher, Alvin C

    2012-01-01

    Praise for the Second Edition "This book is a systematic, well-written, well-organized text on multivariate analysis packed with intuition and insight . . . There is much practical wisdom in this book that is hard to find elsewhere."-IIE Transactions Filled with new and timely content, Methods of Multivariate Analysis, Third Edition provides examples and exercises based on more than sixty real data sets from a wide variety of scientific fields. It takes a "methods" approach to the subject, placing an emphasis on how students and practitioners can employ multivariate analysis in real-life sit

  20. Methods for pretreating biomass

    Science.gov (United States)

    Balan, Venkatesh; Dale, Bruce E; Chundawat, Shishir; Sousa, Leonardo

    2017-05-09

    A method for pretreating biomass is provided, which includes, in a reactor, allowing gaseous ammonia to condense on the biomass and react with water present in the biomass to produce pretreated biomass, wherein reactivity of polysaccharides in the biomass is increased during subsequent biological conversion as compared to the reactivity of polysaccharides in biomass which has not been pretreated. A method for pretreating biomass with a liquid ammonia and recovering the liquid ammonia is also provided. Related systems which include a biochemical or biofuel production facility are also disclosed.

  1. Apoptosis - Methods and Protocols

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-03-01

    Full Text Available Apoptosis - Methods and ProtocolsSecond edition, 2009; Peter Erhardt and Ambrus Toth (Eds; Springer Protocols - Methods in molecular biology, vol. 559; Humana press, Totowa, New Jersey (USA; Pages: 400; €88.35; ISBN: 978-1-60327-016-8The editors rightly begin the preface telling us that: “The ability to detect and quantify apoptosis, to understand its biochemistry and to identify its regulatory genes and proteins is crucial to biomedical research”. Nowadays this is a grounding concept of biology and medicine. What is particularly remarkable...

  2. Practical methods of optimization

    CERN Document Server

    Fletcher, R

    2013-01-01

    Fully describes optimization methods that are currently most valuable in solving real-life problems. Since optimization has applications in almost every branch of science and technology, the text emphasizes their practical aspects in conjunction with the heuristics useful in making them perform more reliably and efficiently. To this end, it presents comparative numerical studies to give readers a feel for possibile applications and to illustrate the problems in assessing evidence. Also provides theoretical background which provides insights into how methods are derived. This edition offers rev

  3. Essential numerical computer methods

    CERN Document Server

    Johnson, Michael L

    2010-01-01

    The use of computers and computational methods has become ubiquitous in biological and biomedical research. During the last 2 decades most basic algorithms have not changed, but what has is the huge increase in computer speed and ease of use, along with the corresponding orders of magnitude decrease in cost. A general perception exists that the only applications of computers and computer methods in biological and biomedical research are either basic statistical analysis or the searching of DNA sequence data bases. While these are important applications they only scratch the surface

  4. Analogue computing methods

    CERN Document Server

    Welbourne, D

    1965-01-01

    Analogue Computing Methods presents the field of analogue computation and simulation in a compact and convenient form, providing an outline of models and analogues that have been produced to solve physical problems for the engineer and how to use and program the electronic analogue computer. This book consists of six chapters. The first chapter provides an introduction to analogue computation and discusses certain mathematical techniques. The electronic equipment of an analogue computer is covered in Chapter 2, while its use to solve simple problems, including the method of scaling is elaborat

  5. Making Methods Choices.

    Science.gov (United States)

    Patton, Michael Quinn

    1980-01-01

    Methodological paradigms in evaluation research are discussed. This article is a response to the attacks on paradigmatic perspectives made by Reichardt and Cook in the opening chapter of their edited book, "Qualitative and Quantitative Methods in Evaluation Research." (Author/GK)

  6. communication method and apparatus

    DEFF Research Database (Denmark)

    2005-01-01

    The present invention relates to a non-lingual communication method and apparatus, wherein a physical or physiological signal consciously created by a first subject (1) is detected and converted into a transmitted output signal presented to a second subject (7) in order to communicate information...

  7. METHOD OF CENTRIFUGE OPERATION

    Science.gov (United States)

    Cohen, K.

    1960-05-10

    A method of isotope separation is described in which two streams are flowed axially of, and countercurrently through, a cylindrical centrifuge bowl. Under the influence of a centrifugal field, the light fraction is concentrated in a stream flowing through the central portion of the bowl, whereas the heavy fraction is concentrated in a stream at the periphery thereof.

  8. Ferrari's Method and Technology

    Science.gov (United States)

    Althoen, Steve

    2005-01-01

    Some tips that combine knowledge of mathematics history and technology for adapting Ferrar's method to factor quintics with a TI-83 graphing calculator are presented. A demonstration on the use of the root finder and regression capabilities of the graphing calculator are presented, so that the tips can be easily adapted for any graphing calculator…

  9. The Mnemonic Keyword Method.

    Science.gov (United States)

    Pressley, Michael; And Others

    1982-01-01

    Available experimental evidence is reviewed concerning the keyword method, a two-stage procedure for remembering materials having an associative component. The review examines subjects' memory for definitions, given vocabulary words; subjects' learning of other aspects of vocabulary, given definitions; group-administered keyword studies; and…

  10. Modern Reduction Methods

    CERN Document Server

    Andersson, Pher G

    2008-01-01

    With its comprehensive overview of modern reduction methods, this book features high quality contributions allowing readers to find reliable solutions quickly and easily. The monograph treats the reduction of carbonyles, alkenes, imines and alkynes, as well as reductive aminations and cross and heck couplings, before finishing off with sections on kinetic resolutions and hydrogenolysis. An indispensable lab companion for every chemist.

  11. Analysis of numerical methods

    CERN Document Server

    Isaacson, Eugene

    1994-01-01

    This excellent text for advanced undergraduates and graduate students covers norms, numerical solution of linear systems and matrix factoring, iterative solutions of nonlinear equations, eigenvalues and eigenvectors, polynomial approximation, and other topics. It offers a careful analysis and stresses techniques for developing new methods, plus many examples and problems. 1966 edition.

  12. The Method of "Currere."

    Science.gov (United States)

    Pinar, William Frederick

    In this presentation the author paints a conceptual portrait of his evolving relationships to his formal studies and thereby describes a method by which educators can reconceptualize the meaning of curriculum. By taking oneself and one's existential experience as a data source and using the psychoanalytical technique of free association, one can…

  13. Universal Image Steganalytic Method

    Directory of Open Access Journals (Sweden)

    V. Banoci

    2014-12-01

    Full Text Available In the paper we introduce a new universal steganalytic method in JPEG file format that is detecting well-known and also newly developed steganographic methods. The steganalytic model is trained by MHF-DZ steganographic algorithm previously designed by the same authors. The calibration technique with the Feature Based Steganalysis (FBS was employed in order to identify statistical changes caused by embedding a secret data into original image. The steganalyzer concept utilizes Support Vector Machine (SVM classification for training a model that is later used by the same steganalyzer in order to identify between a clean (cover and steganographic image. The aim of the paper was to analyze the variety in accuracy of detection results (ACR while detecting testing steganographic algorithms as F5, Outguess, Model Based Steganography without deblocking, JP Hide and Seek which represent the generally used steganographic tools. The comparison of four feature vectors with different lengths FBS (22, FBS (66 FBS(274 and FBS(285 shows promising results of proposed universal steganalytic method comparing to binary methods.

  14. Methods Evolved by Observation

    Science.gov (United States)

    Montessori, Maria

    2016-01-01

    Montessori's idea of the child's nature and the teacher's perceptiveness begins with amazing simplicity, and when she speaks of "methods evolved," she is unveiling a methodological system for observation. She begins with the early childhood explosion into writing, which is a familiar child phenomenon that Montessori has written about…

  15. Method card design dimensions

    DEFF Research Database (Denmark)

    Wölfel, Christiane; Merritt, T.

    2013-01-01

    . The card-based tools are explained in terms of five design dimensions including the intended purpose and scope of use, duration of use, methodology, customization, and formal/material qualities. Our analysis suggests three design patterns or archetypes for existing card-based design method tools...

  16. Statistical methods in astronomy

    OpenAIRE

    Long, James P.; de Souza, Rafael S.

    2017-01-01

    We present a review of data types and statistical methods often encountered in astronomy. The aim is to provide an introduction to statistical applications in astronomy for statisticians and computer scientists. We highlight the complex, often hierarchical, nature of many astronomy inference problems and advocate for cross-disciplinary collaborations to address these challenges.

  17. Methods of materiality

    DEFF Research Database (Denmark)

    Aagaard, Jesper; Matthiesen, Noomi

    2016-01-01

    , and the method of participant observation is suggested as a viable approach to achieve this end. An empirical example of how authority is produced in a parent-teacher conference, not only through language but also through material objects and embodied being, is then presented. The article concludes by suggesting...

  18. Research Methods in Sociolinguistics

    Science.gov (United States)

    Hernández-Campoy, Juan Manuel

    2014-01-01

    The development of Sociolinguistics has been qualitatively and quantitatively outstanding within Linguistic Science since its beginning in the 1950s, with a steady growth in both theoretical and methodological developments as well as in its interdisciplinary directions within the spectrum of language and society. Field methods in sociolinguistic…

  19. Ergonomics research methods

    Science.gov (United States)

    Uspenskiy, S. I.; Yermakova, S. V.; Chaynova, L. D.; Mitkin, A. A.; Gushcheva, T. M.; Strelkov, Y. K.; Tsvetkova, N. F.

    1973-01-01

    Various factors used in ergonomic research are given. They are: (1) anthrometric measurement, (2) polyeffector method of assessing the functional state of man, (3) galvanic skin reaction, (4) pneumography, (5) electromyography, (6) electrooculography, and (7) tachestoscopy. A brief summary is given of each factor and includes instrumentation and results.

  20. A method for sintering

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides a method for sintering, comprising in the following order the steps of: providing a body in the green state or in the pre-sintered state on a support; providing a load on at least one spacer on the support such that the load is located above said body in the green...

  1. Biomass treatment method

    Science.gov (United States)

    Friend, Julie; Elander, Richard T.; Tucker, III; Melvin P.; Lyons, Robert C.

    2010-10-26

    A method for treating biomass was developed that uses an apparatus which moves a biomass and dilute aqueous ammonia mixture through reaction chambers without compaction. The apparatus moves the biomass using a non-compressing piston. The resulting treated biomass is saccharified to produce fermentable sugars.

  2. Truth and Methods.

    Science.gov (United States)

    Dasenbrock, Reed Way

    1995-01-01

    Examines literary theory's displacing of "method" in the New Historicist criticism. Argues that Stephen Greenblatt and Lee Paterson imply that no objective historical truth is possible and as a result do not give methodology its due weight in their criticism. Questions the theory of "truth" advanced in this vein of literary…

  3. Software specification methods

    CERN Document Server

    Habrias, Henri

    2010-01-01

    This title provides a clear overview of the main methods, and has a practical focus that allows the reader to apply their knowledge to real-life situations. The following are just some of the techniques covered: UML, Z, TLA+, SAZ, B, OMT, VHDL, Estelle, SDL and LOTOS.

  4. Progress in variational methods

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ The International Conference on Variational Methods (ICVAM) was held from May 20th to 26th in 2007 at the Chern Institute of Mathematics, Nankai University, Tianjin, China. Twenty eight invited speakers from ten countries and areas worldwide gave their lectures at the conference.

  5. Heart imaging method

    Science.gov (United States)

    Collins, H. Dale; Gribble, R. Parks; Busse, Lawrence J.

    1991-01-01

    A method for providing an image of the human heart's electrical system derives time-of-flight data from an array of EKG electrodes and this data is transformed into phase information. The phase information, treated as a hologram, is reconstructed to provide an image in one or two dimensions of the electrical system of the functioning heart.

  6. Quality of regularization methods

    NARCIS (Netherlands)

    Bouwman, J.

    1998-01-01

    The solution of ill-posed problems is non-trivial in the sense that frequently applied methods like least-squares fail. The ill-posedness of the problem is refiected by very small changes in the input data which may result in very large changes in the output data. Hence, some sort of stabilization

  7. Methods of materiality

    DEFF Research Database (Denmark)

    Aagaard, Jesper; Matthiesen, Noomi

    2016-01-01

    , and the method of participant observation is suggested as a viable approach to achieve this end. An empirical example of how authority is produced in a parent-teacher conference, not only through language but also through material objects and embodied being, is then presented. The article concludes by suggesting...

  8. Proven Weight Loss Methods

    Science.gov (United States)

    Fact Sheet Proven Weight Loss Methods What can weight loss do for you? Losing weight can improve your health in a number of ways. ... limiting calories) usually isn’t enough to cause weight loss. But exercise plays an important part in helping ...

  9. Research Methods in Sociolinguistics

    Science.gov (United States)

    Hernández-Campoy, Juan Manuel

    2014-01-01

    The development of Sociolinguistics has been qualitatively and quantitatively outstanding within Linguistic Science since its beginning in the 1950s, with a steady growth in both theoretical and methodological developments as well as in its interdisciplinary directions within the spectrum of language and society. Field methods in sociolinguistic…

  10. Sampling system and method

    Science.gov (United States)

    Decker, David L.; Lyles, Brad F.; Purcell, Richard G.; Hershey, Ronald Lee

    2013-04-16

    The present disclosure provides an apparatus and method for coupling conduit segments together. A first pump obtains a sample and transmits it through a first conduit to a reservoir accessible by a second pump. The second pump further conducts the sample from the reservoir through a second conduit.

  11. Photothermal methods in medicine

    Science.gov (United States)

    Murphy, John C.

    2000-10-01

    Photothermal imaging and spectroscopy are being applied to a variety of medical problems for diagnosis and therapy. This paper reviews some aspects of this field including the opportunities presented by non-optical sources and by use of detection methods targeted to the application.

  12. Quality of regularization methods

    NARCIS (Netherlands)

    Bouwman, J.

    1998-01-01

    The solution of ill-posed problems is non-trivial in the sense that frequently applied methods like least-squares fail. The ill-posedness of the problem is refiected by very small changes in the input data which may result in very large changes in the output data. Hence, some sort of stabilization o

  13. Project execution methods

    National Research Council Canada - National Science Library

    John C Pfeiffer

    2004-01-01

      In the design/build (D/B) method of implementing plant construction projects, the owner contracts with the engineer/contractor or contractor/engineer company or team-depending upon who takes the lead in the project to develop...

  14. The Effective Equation Method

    Science.gov (United States)

    Kuksin, Sergei; Maiocchi, Alberto

    In this chapter we present a general method of constructing the effective equation which describes the behavior of small-amplitude solutions for a nonlinear PDE in finite volume, provided that the linear part of the equation is a hamiltonian system with a pure imaginary discrete spectrum. The effective equation is obtained by retaining only the resonant terms of the nonlinearity (which may be hamiltonian, or may be not); the assertion that it describes the limiting behavior of small-amplitude solutions is a rigorous mathematical theorem. In particular, the method applies to the three- and four-wave systems. We demonstrate that different possible types of energy transport are covered by this method, depending on whether the set of resonances splits into finite clusters (this happens, e.g. in case of the Charney-Hasegawa-Mima equation), or is connected (this happens, e.g. in the case of the NLS equation if the space-dimension is at least two). For equations of the first type the energy transition to high frequencies does not hold, while for equations of the second type it may take place. Our method applies to various weakly nonlinear wave systems, appearing in plasma, meteorology and oceanography.

  15. Teaching Materials and Methods.

    Science.gov (United States)

    Physiologist, 1987

    1987-01-01

    Contains abstracts of presented papers which deal with teaching materials and methods in physiology. Includes papers on preconceptual notions in physiology, somatosensory activity recorded in the dorsal root ganglion of the bull frog, and the use of the Apple Macintosh microcomputer in teaching human anatomy and physiology. (TW)

  16. Convergence of Arnoldi method

    Energy Technology Data Exchange (ETDEWEB)

    Nevanlinna, O. [Helsinki Univ. of Technology, Espoo (Finland)

    1994-12-31

    This note summarizes some results on (a monitored version of) the Arnoldi method in Hilbert spaces. The interest in working in infinite dimensional spaces comes partly from the fact that only then can one have meaningful asymptotical statements (which hopefully give some light to the convergence of Arnoldi in large dimensional problems with iteration indices far less than the dimension).

  17. Photovoltaic device and method

    Science.gov (United States)

    Cleereman, Robert; Lesniak, Michael J.; Keenihan, James R.; Langmaid, Joe A.; Gaston, Ryan; Eurich, Gerald K.; Boven, Michelle L.

    2015-11-24

    The present invention is premised upon an improved photovoltaic device ("PVD") and method of use, more particularly to an improved photovoltaic device with an integral locator and electrical terminal mechanism for transferring current to or from the improved photovoltaic device and the use as a system.

  18. Water-budget methods

    Science.gov (United States)

    Healy, Richard W.; Scanlon, Bridget R.

    2010-01-01

    A water budget is an accounting of water movement into and out of, and storage change within, some control volume. Universal and adaptable are adjectives that reflect key features of water-budget methods for estimating recharge. The universal concept of mass conservation of water implies that water-budget methods are applicable over any space and time scales (Healy et al., 2007). The water budget of a soil column in a laboratory can be studied at scales of millimeters and seconds. A water-budget equation is also an integral component of atmospheric general circulation models used to predict global climates over periods of decades or more. Water-budget equations can be easily customized by adding or removing terms to accurately portray the peculiarities of any hydrologic system. The equations are generally not bound by assumptions on mechanisms by which water moves into, through, and out of the control volume of interest. So water-budget methods can be used to estimate both diffuse and focused recharge, and recharge estimates are unaffected by phenomena such as preferential flow paths within the unsaturated zone. Water-budget methods represent the largest class of techniques for estimating recharge. Most hydrologic models are derived from a water-budget equation and can therefore be classified as water-budget models. It is not feasible to address all water-budget methods in a single chapter. This chapter is limited to discussion of the “residual” water-budget approach, whereby all variables in a water-budget equation, except for recharge, are independently measured or estimated and recharge is set equal to the residual. This chapter is closely linked with Chapter 3, on modeling methods, because the equations presented here form the basis of many models and because models are often used to estimate individual components in water-budget studies. Water budgets for streams and other surface-water bodies are addressed in Chapter 4. The use of soil-water budgets and

  19. Nonhazardous Urine Pretreatment Method

    Science.gov (United States)

    Akse, James R.; Holtsnider, John T.

    2012-01-01

    A method combines solid phase acidification with two non-toxic biocides to prevent ammonia volatilization and microbial proliferation. The safe, non-oxidizing biocide combination consists of a quaternary amine and a food preservative. This combination has exhibited excellent stabilization of both acidified and unacidified urine. During pretreatment tests, composite urine collected from donors was challenged with a microorganism known to proliferate in urine, and then was processed using the nonhazardous urine pre-treatment method. The challenge microorganisms included Escherichia coli, a common gram-negative bacteria; Enterococcus faecalis, a ureolytic gram-positive bacteria; Candida albicans, a yeast commonly found in urine; and Aspergillus niger, a problematic mold that resists urine pre-treatment. Urine processed in this manner remained microbially stable for over 57 days. Such effective urine stabilization was achieved using non-toxic, non-oxidizing biocides at higher pH (3.6 to 5.8) than previous methods in use or projected for use aboard the International Space Station (ISS). ISS urine pretreatment methods employ strong oxidants including ozone and hexavalent chromium (Cr(VI)), a carcinogenic material, under very acidic conditions (pH = 1.8 to 2.4). The method described here offers a much more benign chemical environment than previous pretreatment methods, and will lower equivalent system mass (ESM) by reducing containment volume and mass, system complexity, and crew time needed to handle pre-treatment chemicals. The biocides, being non-oxidizing, minimize the potential for chemical reactions with urine constituents to produce volatile, airborne contaminants such as cyanogen chloride. Additionally, the biocides are active under significantly less acidic conditions than those used in the current system, thereby reducing the degree of required acidification. A simple flow-through solid phase acidification (SPA) bed is employed to overcome the natural buffering

  20. Developments in Surrogating Methods

    Directory of Open Access Journals (Sweden)

    Hans van Dormolen

    2005-11-01

    Full Text Available In this paper, I would like to talk about the developments in surrogating methods for preservation. My main focus will be on the technical aspects of preservation surrogates. This means that I will tell you something about my job as Quality Manager Microfilming for the Netherlands’ national preservation program, Metamorfoze, which is coordinated by the National Library. I am responsible for the quality of the preservation microfilms, which are produced for Metamorfoze. Firstly, I will elaborate on developments in preservation methods in relation to the following subjects: · Preservation microfilms · Scanning of preservation microfilms · Preservation scanning · Computer Output Microfilm. In the closing paragraphs of this paper, I would like to tell you something about the methylene blue test. This is an important test for long-term storage of preservation microfilms. Also, I will give you a brief report on the Cellulose Acetate Microfilm Conference that was held in the British Library in London, May 2005.

  1. Motor degradation prediction methods

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, J.R.; Kelly, J.F.; Delzingaro, M.J.

    1996-12-01

    Motor Operated Valve (MOV) squirrel cage AC motor rotors are susceptible to degradation under certain conditions. Premature failure can result due to high humidity/temperature environments, high running load conditions, extended periods at locked rotor conditions (i.e. > 15 seconds) or exceeding the motor`s duty cycle by frequent starts or multiple valve stroking. Exposure to high heat and moisture due to packing leaks, pressure seal ring leakage or other causes can significantly accelerate the degradation. ComEd and Liberty Technologies have worked together to provide and validate a non-intrusive method using motor power diagnostics to evaluate MOV rotor condition and predict failure. These techniques have provided a quick, low radiation dose method to evaluate inaccessible motors, identify degradation and allow scheduled replacement of motors prior to catastrophic failures.

  2. Mitosis Methods & Protocols

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-06-01

    Full Text Available Mitosis Methods & Protocols Andrew D. McAinsh (Edt Humana press, Totowa, New Jersey (USA Series: Springer Protocols Methods in Molecular Biology, Volume 545, 2009 ISBN: 978-1-60327-992-5   It is quite clear from the contents of this book that the remarkably fascinating phenomenon of mitosis (that captured, and still is capturing, the attention of entire generations of scientists is still open to research. This is mainly due to our lack of knowledge of so many multifaced events of this extraordinarly complex process. The reader giving a glace through the Contents and Contributors sections is speechless: All of the first-class models (i.e., budding yeast, Caenorabditis, Drosophila, Xenopus and Human are presented..... 

  3. Method card design dimensions

    DEFF Research Database (Denmark)

    Wölfel, Christiane; Merritt, T.

    2013-01-01

    . The card-based tools are explained in terms of five design dimensions including the intended purpose and scope of use, duration of use, methodology, customization, and formal/material qualities. Our analysis suggests three design patterns or archetypes for existing card-based design method tools...... and highlights unexplored areas in the design space. The paper concludes with recommendations for the future development of card-based methods for the field of interaction design.......There are many examples of cards used to assist or provide structure to the design process, yet there has not been a thorough articulation of the strengths and weaknesses of the various examples. We review eighteen card-based design tools in order to understand how they might benefit designers...

  4. Jet vortex methods

    CERN Document Server

    Holm, Darryl D

    2015-01-01

    Vortex blob methods are typically characterized by a regularization length scale, below which the the dynamics are trivial for isolated blobs. In this article we will find that the dynamics need not be trivial if one is willing to consider distributional derivatives of Dirac delta functionals as valid vorticity distributions. More specifically, a new singular vortex theory is presented for regularised Euler fluid equations of ideal incompressible flow in the plane. We determine the conditions under which such regularised Euler fluid equations may admit vorticity singularities which are stronger than delta functions, e.g., derivatives of delta functions. We also characterise the Hamiltonian dynamics of the higher-order singular vortices. Applications to the design of numerical meth- ods similar to vortex blob methods are also discussed. Such findings shed light onto the rich dynamics which occur below the regularization length scale and enlighten our perspective on the multiscale aspects of regularized fluid m...

  5. The Montessori Method

    Directory of Open Access Journals (Sweden)

    Cathleen Haskins

    2010-06-01

    Full Text Available Dr. Maria Montessori provided the world with a powerful philosophy and practice for the advancement of humanity: change how we educate children and we change the world. She understood two things very clearly: One, that we can build a better world, a more just and peaceful place, when we educate for the realization of the individual and collective human potential; and two, that the only way to create an educational system that will that will serve this end is to scrap the current system entirely and replace it with a completely new system. She gave us a system through which to accomplish that goal: The Montessori Method. The following is a personal and professional account of the Montessori Method of educating children.

  6. in the DSMC Method

    Directory of Open Access Journals (Sweden)

    Fong-Zhi Chen

    2001-01-01

    Full Text Available In this study, the Plücker coordinates representation is used to formulate the ruled surface and the molecular path for pumping speed performance evaluation of a molecular vacuum pump. The ruled surface represented by the Pliicker coordinates is used to develop a criterion for when gas molecules hit the pump surface wall. The criterion is applied to analyze the flow rate of a new developed vacuum pump in transition regimes by using the DSMC (Direct Simulation Monte Carlo method. When a molecule flies in a neutral electrical field its path is a straight line. If the molecular path and the generators of a ruled surface are both represented by the Pliicker coordinates, the position of the molecular hit on the wall can be verified by the reciprocal condition of the lines. The Plücker coordinates representation is quite convenient in the DSMC method for this three-dimensional molecular flow simulation.

  7. Anthropological methods in ethnopharmacology.

    Science.gov (United States)

    Etkin, N L

    1993-03-01

    This paper reviews anthropological methods in ethnopharmacology to advance a critical and biobehavioral perspective for the construction of primary data in the light of indigenous paradigms of health and therapeutics. The unique contributions of anthropology are the conceptual and practical tools that allow one to develop the ethnography of plant use in sufficient depth to correlate with laboratory and clinical investigations of plant constituents and activities. This serves an ethnopharmacology that links bioscientific research to traditional empirical knowledge. Specific methods discussed include: key respondents, participant observation, focus groups, structured and unstructured interviews, survey instruments and questionnaires, lexical and semantic studies, and discourse and content analysis. The accommodation of rapid ethnographic techniques for ethnopharmacologic research is described, and several problem orientations based on assessments of efficacy are offered.

  8. INNOVATIVE SALES METHODS

    Directory of Open Access Journals (Sweden)

    Roxana L. IONESCU

    2014-06-01

    Full Text Available Companies operating in a global economy that is constantly changing and developming, especially during the financial crisis and political instability. It is necessary to adapt and develop sales methods in such environment. For large companies who base their activity on sales it has become a necessity to learn different types of sales approaches because their knowledge enables them to grow the number of customers and therefore the sales and the turnover. This paper aims to exame the most effective sales methods used on the highly sensitive economic and social environment – the insurance market. In the field of insurances, the sales process is even more important because sellers need to sell an intangible product that may materialize in the future, but there is no certainty.

  9. Dynamic encryption method

    DEFF Research Database (Denmark)

    2013-01-01

    Disclosed is a method of transmitting a data set using encryption, wherein the method comprises the steps of: selecting a first encryption technique, wherein said first encryption technique comprises a first encryption algorithm for encrypting plain data into cipher data, and a first decryption...... algorithm for on provision of a specific key, decrypting cipher data and reproduce plain data; encrypting the first data package comprising plain data, using a first encryption program implementing the first encryption algorithm of said first encryption technique, creating a first encrypted data package...... comprising cipher data; obtaining a first decryption program; and transmitting said first decryption program and said first encrypted data package to a receiver, wherein the first decryption, upon provision of the specific key and the first encrypted data package, will decrypt the cipher data in the first...

  10. by Lifting Line Method

    Directory of Open Access Journals (Sweden)

    Horia Dumitrescu

    1998-01-01

    Full Text Available The vortex model of propellers is modified and applied to the high-speed horizontal axis turbines. The turbine blades are replaced by lifting lines and trailing vortices which shed along the blade span. The model is not a free wake model, but it is still a nonlinear one which should be solved iteratively. In addition to the regular case where the trailing vortices are constrained to distribute along a helical surface, another version, where each trailing vortex sheding from the blade grows as a free helical vortex line, is also included. Performance parameters are calculated by application of the Biot-Savart law along with the Kutta-Joukowski theorem. Predictions are, shown to compare favorably with existing numerical data from more involved free wake methods, but require less computational effort. Thereby, the present method may be a very useful tool for calculating the aerodynamic loads on horizontal-axis wind turbine blades.

  11. THE ACTION RESEARCH METHOD

    Directory of Open Access Journals (Sweden)

    Petre GEORGIEVSKI

    1999-05-01

    Full Text Available The effort in this work to elaborate an action research method as a central research problem considering the recent contemporary sociological and educa­tional literature. The author begins with the statement that the method is a complex notion, composed of three main components: approach to the research problem, data gathering procedures and data analysis procedures. This point of view is further applied and elaborated in the author's text, emphasizing the action research characteristics: interruption with the positive tradition in social research and the divided of the objective and subjective, application of the qualitative data. The sub­stantial difference between the action research in regard with the other kinds of research, is not only in getting to new knowledge's, but also in problem solving or a change in the situation in a concrete social context.

  12. Nanoscale waveguiding methods.

    Science.gov (United States)

    Wang, Chia-Jean; Lin, Lih Y

    2007-05-01

    While 32 nm lithography technology is on the horizon for integrated circuit (IC) fabrication, matching the pace for miniaturization with optics has been hampered by the diffraction limit. However, development of nanoscale components and guiding methods is burgeoning through advances in fabrication techniques and materials processing. As waveguiding presents the fundamental issue and cornerstone for ultra-high density photonic ICs, we examine the current state of methods in the field. Namely, plasmonic, metal slot and negative dielectric based waveguides as well as a few sub-micrometer techniques such as nanoribbons, high-index contrast and photonic crystals waveguides are investigated in terms of construction, transmission, and limitations. Furthermore, we discuss in detail quantum dot (QD) arrays as a gain-enabled and flexible means to transmit energy through straight paths and sharp bends. Modeling, fabrication and test results are provided and show that the QD waveguide may be effective as an alternate means to transfer light on sub-diffraction dimensions.

  13. Methods for forming particles

    Energy Technology Data Exchange (ETDEWEB)

    Fox, Robert V.; Zhang, Fengyan; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin

    2016-06-21

    Single source precursors or pre-copolymers of single source precursors are subjected to microwave radiation to form particles of a I-III-VI.sub.2 material. Such particles may be formed in a wurtzite phase and may be converted to a chalcopyrite phase by, for example, exposure to heat. The particles in the wurtzite phase may have a substantially hexagonal shape that enables stacking into ordered layers. The particles in the wurtzite phase may be mixed with particles in the chalcopyrite phase (i.e., chalcopyrite nanoparticles) that may fill voids within the ordered layers of the particles in the wurtzite phase thus produce films with good coverage. In some embodiments, the methods are used to form layers of semiconductor materials comprising a I-III-VI.sub.2 material. Devices such as, for example, thin-film solar cells may be fabricated using such methods.

  14. Methods for forming particles

    Science.gov (United States)

    Fox, Robert V.; Zhang, Fengyan; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin

    2016-06-21

    Single source precursors or pre-copolymers of single source precursors are subjected to microwave radiation to form particles of a I-III-VI.sub.2 material. Such particles may be formed in a wurtzite phase and may be converted to a chalcopyrite phase by, for example, exposure to heat. The particles in the wurtzite phase may have a substantially hexagonal shape that enables stacking into ordered layers. The particles in the wurtzite phase may be mixed with particles in the chalcopyrite phase (i.e., chalcopyrite nanoparticles) that may fill voids within the ordered layers of the particles in the wurtzite phase thus produce films with good coverage. In some embodiments, the methods are used to form layers of semiconductor materials comprising a I-III-VI.sub.2 material. Devices such as, for example, thin-film solar cells may be fabricated using such methods.

  15. The random projection method

    CERN Document Server

    Vempala, Santosh S

    2005-01-01

    Random projection is a simple geometric technique for reducing the dimensionality of a set of points in Euclidean space while preserving pairwise distances approximately. The technique plays a key role in several breakthrough developments in the field of algorithms. In other cases, it provides elegant alternative proofs. The book begins with an elementary description of the technique and its basic properties. Then it develops the method in the context of applications, which are divided into three groups. The first group consists of combinatorial optimization problems such as maxcut, graph coloring, minimum multicut, graph bandwidth and VLSI layout. Presented in this context is the theory of Euclidean embeddings of graphs. The next group is machine learning problems, specifically, learning intersections of halfspaces and learning large margin hypotheses. The projection method is further refined for the latter application. The last set consists of problems inspired by information retrieval, namely, nearest neig...

  16. Glycoconjugates and methods

    Energy Technology Data Exchange (ETDEWEB)

    Bertozzi, Carolyn C. (Albany, CA); Yarema, Kevin J. (Albany, CA); Mahal; Lara K. (Berkeley, CA)

    2008-04-01

    Methods for making the functionalized glycoconjugates include (a) contacting a cell with a first monosaccharide, and (b) incubating the cell under conditions whereby the cell (i) internalizes the first monosaccharide, (ii) biochemically processes the first monosaccharide into a second saccharide, (iii) conjugates the saccharide to a carrier to form a glycoconjugate, and (iv) extracellularly expresses the glycoconjugate to form an extracellular glycoconjugate comprising a selectively reactive functional group. Methods for forming products at a cell further comprise contacting the functional group of the extracellularly expressed glycoconjugate with an agent which selectively reacts with the functional group to form a product. Subject compositions include cyto-compatible monosaccharides comprising a nitrogen or ether linked functional group selectively reactive at a cell surface and compositions and cells comprising such saccharides.

  17. Statistical Methods for Astronomy

    CERN Document Server

    Feigelson, Eric D

    2012-01-01

    This review outlines concepts of mathematical statistics, elements of probability theory, hypothesis tests and point estimation for use in the analysis of modern astronomical data. Least squares, maximum likelihood, and Bayesian approaches to statistical inference are treated. Resampling methods, particularly the bootstrap, provide valuable procedures when distributions functions of statistics are not known. Several approaches to model selection and good- ness of fit are considered. Applied statistics relevant to astronomical research are briefly discussed: nonparametric methods for use when little is known about the behavior of the astronomical populations or processes; data smoothing with kernel density estimation and nonparametric regression; unsupervised clustering and supervised classification procedures for multivariate problems; survival analysis for astronomical datasets with nondetections; time- and frequency-domain times series analysis for light curves; and spatial statistics to interpret the spati...

  18. MIXED METHOD RESEARCH

    Directory of Open Access Journals (Sweden)

    Masrizal Masrizal

    2012-03-01

    Full Text Available Mixed Method Research adalah metode penelitian yang diaplikasikan bila peneliti memiliki pertanyaan yang perlu diuji dari segi outcomes dan prosesnya, serta menyangkut kombinasi antara metode kuantitatif dan kualitatif dalam satu penelitian. Karena berfokus pada outcomes dan proses, maka desain MMR biasa digunakan dalam penelitian evaluasi program. Namun sekarang, MMR sudah sering digunakan untuk ilmu-ilmu sosial, seperti: konseling, psikologi social manajemen, dan pengorganisasian perilaku.

  19. MIXED METHOD RESEARCH

    OpenAIRE

    Masrizal Masrizal

    2012-01-01

    Mixed Method Research adalah metode penelitian yang diaplikasikan bila peneliti memiliki pertanyaan yang perlu diuji dari segi outcomes dan prosesnya, serta menyangkut kombinasi antara metode kuantitatif dan kualitatif dalam satu penelitian. Karena berfokus pada outcomes dan proses, maka desain MMR biasa digunakan dalam penelitian evaluasi program. Namun sekarang, MMR sudah sering digunakan untuk ilmu-ilmu sosial, seperti: konseling, psikologi social manajemen, dan pengorganisasian perilaku.

  20. Method for scavenging mercury

    Science.gov (United States)

    Chang, Shih-ger; Liu, Shou-heng; Liu, Zhao-rong; Yan, Naiqiang

    2009-01-20

    Disclosed herein is a method for removing mercury from a gas stream comprising contacting the gas stream with a getter composition comprising bromine, bromochloride, sulphur bromide, sulphur dichloride or sulphur monochloride and mixtures thereof. In one preferred embodiment the getter composition is adsorbed onto a sorbent. The sorbent may be selected from the group consisting of flyash, limestone, lime, calcium sulphate, calcium sulfite, activated carbon, charcoal, silicate, alumina and mixtures thereof. Preferred is flyash, activated carbon and silica.

  1. Statokinesigram normalization method.

    Science.gov (United States)

    de Oliveira, José Magalhães

    2017-02-01

    Stabilometry is a technique that aims to study the body sway of human subjects, employing a force platform. The signal obtained from this technique refers to the position of the foot base ground-reaction vector, known as the center of pressure (CoP). The parameters calculated from the signal are used to quantify the displacement of the CoP over time; there is a large variability, both between and within subjects, which prevents the definition of normative values. The intersubject variability is related to differences between subjects in terms of their anthropometry, in conjunction with their muscle activation patterns (biomechanics); and the intrasubject variability can be caused by a learning effect or fatigue. Age and foot placement on the platform are also known to influence variability. Normalization is the main method used to decrease this variability and to bring distributions of adjusted values into alignment. In 1996, O'Malley proposed three normalization techniques to eliminate the effect of age and anthropometric factors from temporal-distance parameters of gait. These techniques were adopted to normalize the stabilometric signal by some authors. This paper proposes a new method of normalization of stabilometric signals to be applied in balance studies. The method was applied to a data set collected in a previous study, and the results of normalized and nonnormalized signals were compared. The results showed that the new method, if used in a well-designed experiment, can eliminate undesirable correlations between the analyzed parameters and the subjects' characteristics and show only the experimental conditions' effects.

  2. Comments on PDF methods

    Science.gov (United States)

    Chen, J.-Y.

    1992-01-01

    Viewgraphs are presented on the following topics: the grand challenge of combustion engineering; research of probability density function (PDF) methods at Sandia; experiments of turbulent jet flames (Masri and Dibble, 1988); departures from chemical equilibrium; modeling turbulent reacting flows; superequilibrium OH radical; pdf modeling of turbulent jet flames; scatter plot for CH4 (methane) and O2 (oxygen); methanol turbulent jet flames; comparisons between predictions and experimental data; and turbulent C2H4 jet flames.

  3. Situational method engineering

    CERN Document Server

    Henderson-Sellers, Brian; Ågerfalk, Pär J; Rossi, Matti

    2014-01-01

    While previously available methodologies for software ? like those published in the early days of object technology ? claimed to be appropriate for every conceivable project, situational method engineering (SME) acknowledges that most projects typically have individual characteristics and situations. Thus, finding the most effective methodology for a particular project needs specific tailoring to that situation. Such a tailored software development methodology needs to take into account all the bits and pieces needed for an organization to develop software, including the software process, the

  4. Polymer compositions and methods

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Scott D.; Willkomm, Wayne R.

    2016-09-27

    The present invention encompasses polyurethane compositions comprising aliphatic polycarbonate chains. In one aspect, the present invention encompasses polyurethane foams, thermoplastics and elastomers derived from aliphatic polycarbonate polyols and polyisocyanates wherein the polyol chains contain a primary repeating unit having a structure: ##STR00001## In another aspect, the invention provides articles comprising the inventive foam and elastomer compositions as well as methods of making such compositions.

  5. Nearshore Pipeline Installation Methods.

    Science.gov (United States)

    1981-08-01

    179. 5. Aldridge, R. G., and Bomba , J. G., "Deep Water Pipelines - Interdependence of Design and Construction", ASCE Paper. 6. American Society Civil...October 13, 1967. 24. Bomba , J. G. and Seeds, K. J., "Pipelining in 600 feet of water .... A Case Study of Washington Natural Gas Company’s Puget Sound...Crossing", Offshore Technology Conference, paper OTC 1188, 1970. 25. Bomba , J., "Submarine Pipe Construction Methods", Petroleum Engineer, Vol. 32

  6. Methods in Bioengineering

    CERN Document Server

    Rege, Kaushal

    2009-01-01

    Filling a critical gap in the current literature, this new resource presents practical, step-by-step methods to help you synthesize, characterize, biofunctionalize and apply the nanomaterial that is most suitable for handling a given nanoscale bioengineering problem. Written and presented by leading scientists and engineers in their respective fields, the authors offer a clear and detailed understanding of how to carry out nanoparticle functionalization with biomolecules (including enzymes), nanoparticle analysis and characterization, in vitro evaluation of nanoparticles using different cell l

  7. Method of infusion extraction

    Science.gov (United States)

    Chang-Diaz, Franklin R. (Inventor)

    1989-01-01

    Apparatus and method of removing desirable constituents from an infusible material by infusion extraction, where a piston operating in a first chamber draws a solvent into the first chamber where it may be heated, and then moves the heated solvent into a second chamber containing the infusible material, and where infusion extraction takes place. The piston then moves the solvent containing the extract through a filter into the first chamber, leaving the extraction residue in the second chamber.

  8. Method for detecting biomolecules

    Science.gov (United States)

    Huo, Qisheng; Liu, Jun

    2008-08-12

    A method for detecting and measuring the concentration of biomolecules in solution, utilizing a conducting electrode in contact with a solution containing target biomolecules, with a film with controllable pore size distribution characteristics applied to at least one surface of the conducting electrode. The film is functionalized with probe molecules that chemically interact with the target biomolecules at the film surface, blocking indicator molecules present in solution from diffusing from the solution to the electrode, thereby changing the electrochemical response of the electrode

  9. Method for scavenging mercury

    Science.gov (United States)

    Chang, Shih-ger; Liu, Shou-heng; Liu, Zhao-rong; Yan, Naiqiang

    2010-07-13

    Disclosed herein is a method for removing mercury from a gas stream comprising contacting the gas stream with a getter composition comprising bromine, bromochloride, sulphur bromide, sulphur dichloride or sulphur monochloride and mixtures thereof. In one preferred embodiment the getter composition is adsorbed onto a sorbent. The sorbent may be selected from the group consisting flyash, limestone, lime, calcium sulphate, calcium sulfite, activated carbon, charcoal, silicate, alumina and mixtures thereof. Preferred is flyash, activated carbon and silica.

  10. Method of producing imines

    Science.gov (United States)

    Sithambaram, Shanthakumar; Son, Young-Chan; Suib, Steven L.

    2008-04-08

    A method for forming an imine comprises reacting a first reactant comprising a hydroxyl functionality, a carbonyl functionality, or both a hydroxyl functionality and a carbonyl functionality with a second reactant having an amine functionality in the presence of ordered porous manganese-based octahedral molecular sieves and an oxygen containing gas at a temperature and for a time sufficient for the imine to be produced.

  11. Methods in Bioengineering

    CERN Document Server

    Zahn, Jeffrey D

    2009-01-01

    This unique volume presents leading-edge microfluidics methods used to handle, manipulate, and analyze cells, particles, and biological components (e.g., proteins and DNA) for microdiagnostics. The authors offer clear and detailed guidance on microfabrication techniques utilized to create microfluidic devices and on-chip flow control and mixing Microsystems, protein and DNA handling devices for electrophoretic and isoelectric separations in microchromatography columns, microfluidic manipulations of droplets via electrowetting and particles via dielectrophoresis for separations and chemical rea

  12. Chromosome doubling method

    Science.gov (United States)

    Kato, Akio

    2006-11-14

    The invention provides methods for chromosome doubling in plants. The technique overcomes the low yields of doubled progeny associated with the use of prior techniques for doubling chromosomes in plants such as grasses. The technique can be used in large scale applications and has been demonstrated to be highly effective in maize. Following treatment in accordance with the invention, plants remain amenable to self fertilization, thereby allowing the efficient isolation of doubled progeny plants.

  13. Montessori Method and ICTs

    OpenAIRE

    Athanasios Drigas; Eugenia Gkeka

    2016-01-01

    This article bridges the gap between the Montessori Method and Information and Communication Technologies (ICTs) in contemporary education. It reviews recent research works which recall the Montessori philosophy, principles and didactical tools applying to today’s computers and supporting technologies in children’s learning process. This article reviews how important the stimulation of human senses in the learning process is, as well as the development of Montessori materials using the body a...

  14. Geometrical method of decoupling

    Science.gov (United States)

    Baumgarten, C.

    2012-12-01

    The computation of tunes and matched beam distributions are essential steps in the analysis of circular accelerators. If certain symmetries—like midplane symmetry—are present, then it is possible to treat the betatron motion in the horizontal, the vertical plane, and (under certain circumstances) the longitudinal motion separately using the well-known Courant-Snyder theory, or to apply transformations that have been described previously as, for instance, the method of Teng and Edwards. In a preceding paper, it has been shown that this method requires a modification for the treatment of isochronous cyclotrons with non-negligible space charge forces. Unfortunately, the modification was numerically not as stable as desired and it was still unclear, if the extension would work for all conceivable cases. Hence, a systematic derivation of a more general treatment seemed advisable. In a second paper, the author suggested the use of real Dirac matrices as basic tools for coupled linear optics and gave a straightforward recipe to decouple positive definite Hamiltonians with imaginary eigenvalues. In this article this method is generalized and simplified in order to formulate a straightforward method to decouple Hamiltonian matrices with eigenvalues on the real and the imaginary axis. The decoupling of symplectic matrices which are exponentials of such Hamiltonian matrices can be deduced from this in a few steps. It is shown that this algebraic decoupling is closely related to a geometric “decoupling” by the orthogonalization of the vectors E→, B→, and P→, which were introduced with the so-called “electromechanical equivalence.” A mathematical analysis of the problem can be traced down to the task of finding a structure-preserving block diagonalization of symplectic or Hamiltonian matrices. Structure preservation means in this context that the (sequence of) transformations must be symplectic and hence canonical. When used iteratively, the decoupling

  15. Electron cryomicroscopy methods.

    Science.gov (United States)

    Unger, V M

    2001-10-01

    Electron cryomicroscopy methods comprise a rapidly expanding field providing insights into the structure and function of biological macromolecules and their supramolecular assemblies. The 3.8 A resolution structure of the membrane protein aquaporin, a view of the herpesvirus capsid at 8.5 A and the 10 A resolution structure of the spliceosomal U1 small nuclear ribonucleoprotein complex are three outstanding examples emphasizing the versatility of this technique.

  16. Method for making nanomaterials

    Science.gov (United States)

    Fan, Hongyou; Wu, Huimeng

    2013-06-04

    A method of making a nanostructure by preparing a face centered cubic-ordered metal nanoparticle film from metal nanoparticles, such as gold and silver nanoparticles, exerting a hydrostatic pressure upon the film at pressures of several gigapascals, followed by applying a non-hydrostatic stress perpendicularly at a pressure greater than approximately 10 GPA to form an array of nanowires with individual nanowires having a relatively uniform length, average diameter and density.

  17. Bering Mission Navigation Method

    OpenAIRE

    2003-01-01

    "Bering", after the name of the famous Danish explorer, is a near Earth object (NEO) and main belt asteroids mapping mission envisaged by a consortium of Danish universities and research institutes. To achieve the ambitious goals set forth by this mission, while containing the costs and risks, "Bering" sports several new technological enhancements and advanced instruments under development at the Technical University of Denmark (DTU). The autonomous on-board orbit determination method is part...

  18. Methods of celestial mechanics

    CERN Document Server

    Brouwer, Dirk

    2013-01-01

    Methods of Celestial Mechanics provides a comprehensive background of celestial mechanics for practical applications. Celestial mechanics is the branch of astronomy that is devoted to the motions of celestial bodies. This book is composed of 17 chapters, and begins with the concept of elliptic motion and its expansion. The subsequent chapters are devoted to other aspects of celestial mechanics, including gravity, numerical integration of orbit, stellar aberration, lunar theory, and celestial coordinates. Considerable chapters explore the principles and application of various mathematical metho

  19. ARK methods: some recent developments

    Science.gov (United States)

    Moir, Nicolette

    2005-03-01

    Almost Runge-Kutta methods are a sub-class of the family of methods known as general linear methods, used for solving ordinary differential equations. They combine many of the favourable properties of traditional Runge-Kutta methods with some additional advantages. We will introduce these methods, concentrating on methods of order four, and present some recent results.

  20. Multigrid methods III

    CERN Document Server

    Trottenberg, U; Third European Conference on Multigrid Methods

    1991-01-01

    These proceedings contain a selection of papers presented at the Third European Conference on Multigrid Methods which was held in Bonn on October 1-4, 1990. Following conferences in 1981 and 1985, a platform for the presentation of new Multigrid results was provided for a third time. Multigrid methods no longer have problems being accepted by numerical analysts and users of numerical methods; on the contrary, they have been further developed in such a successful way that they have penetrated a variety of new fields of application. The high number of 154 participants from 18 countries and 76 presented papers show the need to continue the series of the European Multigrid Conferences. The papers of this volume give a survey on the current Multigrid situation; in particular, they correspond to those fields where new developments can be observed. For example, se­ veral papers study the appropriate treatment of time dependent problems. Improvements can also be noticed in the Multigrid approach for semiconductor eq...

  1. Stochastic Methods in Biology

    CERN Document Server

    Kallianpur, Gopinath; Hida, Takeyuki

    1987-01-01

    The use of probabilistic methods in the biological sciences has been so well established by now that mathematical biology is regarded by many as a distinct dis­ cipline with its own repertoire of techniques. The purpose of the Workshop on sto­ chastic methods in biology held at Nagoya University during the week of July 8-12, 1985, was to enable biologists and probabilists from Japan and the U. S. to discuss the latest developments in their respective fields and to exchange ideas on the ap­ plicability of the more recent developments in stochastic process theory to problems in biology. Eighteen papers were presented at the Workshop and have been grouped under the following headings: I. Population genetics (five papers) II. Measure valued diffusion processes related to population genetics (three papers) III. Neurophysiology (two papers) IV. Fluctuation in living cells (two papers) V. Mathematical methods related to other problems in biology, epidemiology, population dynamics, etc. (six papers) An important f...

  2. Validation of analytical methods

    Directory of Open Access Journals (Sweden)

    Xavier Rius, F.

    2002-03-01

    Full Text Available In this paper we shall discuss the concept of method validation, describe the various elements and explain its close relationship with fitness for purpose. Method validation is based on the assumption that a series of requirements are fulfilled and we shall explain how these requirements are selected, the way in which evidence is supplied and what work has to be carried out in the laboratory. The basic principles of method validation and the different ways to validate a methodology, by inter-laboratory comparison or performing an in-house validation, are also described.En este artículo se discute el concepto de validación del método, se describen los elementos que la componen y se explica la fuerte relación entre la validación y las características de ajuste. El método de validación se basa en el cumplimiento de una serie de requerimientos, se explica como seleccionar esos requerimientos, la forma en que se suministran evidencias, y que trabajo se debe llevar a cabo en el laboratorio. También se describen, los principios básicos del método de validación y los diferentes caminos para validar una metodología, tanto en la comparación entre laboratorios o como cuando se lleva a cabo una validación dentro del laboratorio.

  3. Generalized Agile Estimation Method

    Directory of Open Access Journals (Sweden)

    Shilpa Bahlerao

    2011-01-01

    Full Text Available Agile cost estimation process always possesses research prospects due to lack of algorithmic approaches for estimating cost, size and duration. Existing algorithmic approach i.e. Constructive Agile Estimation Algorithm (CAEA is an iterative estimation method that incorporates various vital factors affecting the estimates of the project. This method has lots of advantages but at the same time has some limitations also. These limitations may due to some factors such as number of vital factors and uncertainty involved in agile projects etc. However, a generalized agile estimation may generate realistic estimates and eliminates the need of experts. In this paper, we have proposed iterative Generalized Estimation Method (GEM and presented algorithm based on it for agile with case studies. GEM  based algorithm various project domain classes and vital factors with prioritization level. Further, it incorporates uncertainty factor to quantify the risk of project for estimating cost, size and duration. It also provides flexibility to project managers for deciding on number of vital factors, uncertainty level and project domains thereby maintaining the agility.

  4. Method Engineering: Engineering of Information Systems Development Methods and Tools

    NARCIS (Netherlands)

    Brinkkemper, J.N.; Brinkkemper, Sjaak

    1996-01-01

    This paper proposes the term method engineering for the research field of the construction of information systems development methods and tools. Some research issues in method engineering are identified. One major research topic in method engineering is discussed in depth: situational methods, i.e.

  5. The data embedding method

    Energy Technology Data Exchange (ETDEWEB)

    Sandford, M.T. II; Bradley, J.N.; Handel, T.G.

    1996-06-01

    Data embedding is a new steganographic method for combining digital information sets. This paper describes the data embedding method and gives examples of its application using software written in the C-programming language. Sandford and Handel produced a computer program (BMPEMBED, Ver. 1.51 written for IBM PC/AT or compatible, MS/DOS Ver. 3.3 or later) that implements data embedding in an application for digital imagery. Information is embedded into, and extracted from, Truecolor or color-pallet images in Microsoft{reg_sign} bitmap (.BMP) format. Hiding data in the noise component of a host, by means of an algorithm that modifies or replaces the noise bits, is termed {open_quote}steganography.{close_quote} Data embedding differs markedly from conventional steganography, because it uses the noise component of the host to insert information with few or no modifications to the host data values or their statistical properties. Consequently, the entropy of the host data is affected little by using data embedding to add information. The data embedding method applies to host data compressed with transform, or {open_quote}lossy{close_quote} compression algorithms, as for example ones based on discrete cosine transform and wavelet functions. Analysis of the host noise generates a key required for embedding and extracting the auxiliary data from the combined data. The key is stored easily in the combined data. Images without the key cannot be processed to extract the embedded information. To provide security for the embedded data, one can remove the key from the combined data and manage it separately. The image key can be encrypted and stored in the combined data or transmitted separately as a ciphertext much smaller in size than the embedded data. The key size is typically ten to one-hundred bytes, and it is in data an analysis algorithm.

  6. Data embedding method

    Science.gov (United States)

    Sandford, Maxwell T., II; Bradley, Jonathan N.; Handel, Theodore G.

    1996-01-01

    Data embedding is a new steganographic method for combining digital information sets. This paper describes the data embedding method and gives examples of its application using software written in the C-programming language. Sandford and Handel produced a computer program (BMPEMBED, Ver. 1.51 written for IBM PC/AT or compatible, MS/DOS Ver. 3.3 or later) that implements data embedding in an application for digital imagery. Information is embedded into, and extracted from, Truecolor or color-pallet images in MicrosoftTM bitmap (BMP) format. Hiding data in the noise component of a host, by means of an algorithm that modifies or replaces the noise bits, is termed `steganography.' Data embedding differs markedly from conventional steganography, because it uses the noise component of the host to insert information with few or no modifications to the host data values or their statistical properties. Consequently, the entropy of the host data is affected little by using data embedding to add information. The data embedding method applies to host data compressed with transform, or `lossy' compression algorithms, as for example ones based on discrete cosine transform and wavelet functions. Analysis of the host noise generates a key required for embedding and extracting the auxiliary data from the combined data. The key is stored easily in the combined data. Images without the key cannot be processed to extract the embedded information. To provide security for the embedded data, one can remove the key from the combined data and manage it separately. The image key can be encrypted and stored in the combined data or transmitted separately as a ciphertext much smaller in size than the embedded data. The key size is typically ten to one-hundred bytes, and it is derived from the original host data by an analysis algorithm.

  7. ZIRCONIUM PHOSPHATE ADSORPTION METHOD

    Science.gov (United States)

    Russell, E.R.; Adamson, A.S.; Schubert, J.; Boyd, G.E.

    1958-11-01

    A method is presented for separating plutonium values from fission product values in aqueous acidic solution. This is accomplished by flowing the solutlon containing such values through a bed of zirconium orthophosphate. Any fission products adsorbed can subsequently be eluted by washing the column with a solution of 2N HNO/sub 3/ and O.lN H/sub 3/PO/sub 4/. Plutonium values may subsequently be desorbed by contacting the column with a solution of 7N HNO/sub 3/ .

  8. Methods of graded rings

    CERN Document Server

    Nastasescu, Constantin

    2004-01-01

    The topic of this book, graded algebra, has developed in the past decade to a vast subject with new applications in noncommutative geometry and physics. Classical aspects relating to group actions and gradings have been complemented by new insights stemming from Hopf algebra theory. Old and new methods are presented in full detail and in a self-contained way. Graduate students as well as researchers in algebra, geometry, will find in this book a useful toolbox. Exercises, with hints for solution, provide a direct link to recent research publications. The book is suitable for courses on Master level or textbook for seminars.

  9. Control system design method

    Science.gov (United States)

    Wilson, David G [Tijeras, NM; Robinett, III, Rush D.

    2012-02-21

    A control system design method and concomitant control system comprising representing a physical apparatus to be controlled as a Hamiltonian system, determining elements of the Hamiltonian system representation which are power generators, power dissipators, and power storage devices, analyzing stability and performance of the Hamiltonian system based on the results of the determining step and determining necessary and sufficient conditions for stability of the Hamiltonian system, creating a stable control system based on the results of the analyzing step, and employing the resulting control system to control the physical apparatus.

  10. Calcium measurement methods

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-09-01

    Full Text Available Rightly stressed by prof. Wolfgang Walz in the Preface to the series Neuromethods series, the “careful application of methods is probably the most important step in the process of scientific inquiry”. Thus, I strongly suggest to all those interested in calcium signaling and especially to the new-comers in the hot topic of neuroscience (which has so much space even in science-society debate for its implications in legal issues and in the judge-decision process to take profit from this so well edited book. I am saying this since prof. Verkhratsky and prof. Petersen......

  11. Methods of thermodynamics

    CERN Document Server

    Reiss, Howard

    1997-01-01

    Since there is no shortage of excellent general books on elementary thermodynamics, this book takes a different approach, focusing attention on the problem areas of understanding of concept and especially on the overwhelming but usually hidden role of ""constraints"" in thermodynamics, as well as on the lucid exposition of the significance, construction, and use (in the case of arbitrary systems) of the thermodynamic potential. It will be especially useful as an auxiliary text to be used along with any standard treatment.Unlike some texts, Methods of Thermodynamics does not use statistical m

  12. Geometrical method of decoupling

    Directory of Open Access Journals (Sweden)

    C. Baumgarten

    2012-12-01

    Full Text Available The computation of tunes and matched beam distributions are essential steps in the analysis of circular accelerators. If certain symmetries—like midplane symmetry—are present, then it is possible to treat the betatron motion in the horizontal, the vertical plane, and (under certain circumstances the longitudinal motion separately using the well-known Courant-Snyder theory, or to apply transformations that have been described previously as, for instance, the method of Teng and Edwards. In a preceding paper, it has been shown that this method requires a modification for the treatment of isochronous cyclotrons with non-negligible space charge forces. Unfortunately, the modification was numerically not as stable as desired and it was still unclear, if the extension would work for all conceivable cases. Hence, a systematic derivation of a more general treatment seemed advisable. In a second paper, the author suggested the use of real Dirac matrices as basic tools for coupled linear optics and gave a straightforward recipe to decouple positive definite Hamiltonians with imaginary eigenvalues. In this article this method is generalized and simplified in order to formulate a straightforward method to decouple Hamiltonian matrices with eigenvalues on the real and the imaginary axis. The decoupling of symplectic matrices which are exponentials of such Hamiltonian matrices can be deduced from this in a few steps. It is shown that this algebraic decoupling is closely related to a geometric “decoupling” by the orthogonalization of the vectors E[over →], B[over →], and P[over →], which were introduced with the so-called “electromechanical equivalence.” A mathematical analysis of the problem can be traced down to the task of finding a structure-preserving block diagonalization of symplectic or Hamiltonian matrices. Structure preservation means in this context that the (sequence of transformations must be symplectic and hence canonical. When

  13. Method of joining ceramics

    Science.gov (United States)

    Henager, Jr., Charles H.; Brimhall, John L.

    2000-01-01

    According to the method of the present invention, joining a first bi-element carbide to a second bi-element carbide, has the steps of: (a) forming a bond agent containing a metal carbide and silicon; (b) placing the bond agent between the first and second bi-element carbides to form a pre-assembly; and (c) pressing and heating the pre-assembly in a non-oxidizing atmosphere to a temperature effective to induce a displacement reaction creating a metal silicon phase bonding the first and second bi-element carbides.

  14. Object oriented methods

    CERN Document Server

    Graham, Ian

    1994-01-01

    This book is a revision of Ian Graham's successful survey of the whole area of object technology. It covers object- oriented programming, object-oriented design, object- oriented analysis, object-oriented databases and treats several related technologies. New to this edition are more applications of object-oriented methods and more coverage of object-oriented database products available. Graham has also doubled the design and analysis material that examines over 60 different approaches - making this the most comprehensive book on the market. Also new is the foreword by Grady Booch.

  15. Electrical estimating methods

    CERN Document Server

    Del Pico, Wayne J

    2014-01-01

    Simplify the estimating process with the latest data, materials, and practices Electrical Estimating Methods, Fourth Edition is a comprehensive guide to estimating electrical costs, with data provided by leading construction database RS Means. The book covers the materials and processes encountered by the modern contractor, and provides all the information professionals need to make the most precise estimate. The fourth edition has been updated to reflect the changing materials, techniques, and practices in the field, and provides the most recent Means cost data available. The complexity of el

  16. Introduction to Numerical Methods

    Energy Technology Data Exchange (ETDEWEB)

    Schoonover, Joseph A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-14

    These are slides for a lecture for the Parallel Computing Summer Research Internship at the National Security Education Center. This gives an introduction to numerical methods. Repetitive algorithms are used to obtain approximate solutions to mathematical problems, using sorting, searching, root finding, optimization, interpolation, extrapolation, least squares regresion, Eigenvalue problems, ordinary differential equations, and partial differential equations. Many equations are shown. Discretizations allow us to approximate solutions to mathematical models of physical systems using a repetitive algorithm and introduce errors that can lead to numerical instabilities if we are not careful.

  17. Epitope prediction methods

    DEFF Research Database (Denmark)

    Karosiene, Edita

    on machine learning techniques. Several MHC class I binding prediction algorithms have been developed and due to their high accuracy they are used by many immunologists to facilitate the conventional experimental process of epitope discovery. However, the accuracy of these methods depends on data defining...... the NetMHCIIpan-3.0 predictor based on artificial neural networks, which is capable of giving binding affinities to any human MHC class II molecule. Chapter 4 of this thesis gives an overview of bioinformatics tools developed by the Immunological Bioinformatics group at Center for Biological Sequence...

  18. Formal Methods in Industry

    Directory of Open Access Journals (Sweden)

    Alexei Serna A.

    2012-12-01

    Full Text Available The application of formal methods in industry has progressed extensively over the past decade and the results are promising. But despite these achievements and it have been documented in numerous studies, it is still very common the skepticism about its usefulness and applicability. The goal of this paper is to show that its evolution over the past decade exceeds all previous processes and each time they do a better job to satisfy industrial needs. This is achieved by the description of some experiments and the result of various applications in industry and through an analyzing of the needs of companies that must be satisfy the research community in this field.

  19. Interval methods: An introduction

    DEFF Research Database (Denmark)

    Achenie, L.E.K.; Kreinovich, V.; Madsen, Kaj

    2006-01-01

    This chapter contains selected papers presented at the Minisymposium on Interval Methods of the PARA'04 Workshop '' State-of-the-Art in Scientific Computing ''. The emphasis of the workshop was on high-performance computing (HPC). The ongoing development of ever more advanced computers provides....... An important characteristic of the computer performance in scientific computing is the accuracy of the Computation results. Often, we can estimate this accuracy by using traditional statistical techniques. However, in many practical situations, we do not know the probability distributions of different...... '' techniques, and the applications of these techniques to various problems of scientific computing....

  20. Hydraulic mining method

    Science.gov (United States)

    Huffman, Lester H.; Knoke, Gerald S.

    1985-08-20

    A method of hydraulically mining an underground pitched mineral vein comprising drilling a vertical borehole through the earth's lithosphere into the vein and drilling a slant borehole along the footwall of the vein to intersect the vertical borehole. Material is removed from the mineral vein by directing a high pressure water jet thereagainst. The resulting slurry of mineral fragments and water flows along the slant borehole into the lower end of the vertical borehole from where it is pumped upwardly through the vertical borehole to the surface.

  1. QUATERNIONIC JACOBI METHOD APPLICATIONS

    OpenAIRE

    SANCREY RODRIGUES ALVES

    2008-01-01

    O método tipo-Jacobi quaterniônico foi proposto em 1993. Vários estudos provaram sua convergência e melhoram a teoria proposta desde então. O presente trabalho realiza uma síntese do método tipo- Jacobi quaterniônico, apresentando aplicações do mesmo a diferentes tipos de matrizes. The quaternionic Jacobi method was proposed on 1993. Lots of studies has proved his convergence and also has improved the theory proposed. This document makes a survey of this me...

  2. Methods in Bioengineering

    CERN Document Server

    Nahmias, Yaakov

    2009-01-01

    Offering a practical look into the field, this volume presents the science behind microscale device design and the engineering of its fabrication. Supported with dozens of full-color illustrations, this book offers you clear, step-by-step methods for the cell capture from whole blood, high-throughput study of transcriptional dynamics in living cells, temporal control of cell-cell interaction, nanoscale measurements of cellular forces, immobilizing living c. elegans, optical and electrical on-chip cell sorting and human-on-chip modeling of drug metabolism.

  3. Interior-point methods

    Science.gov (United States)

    Potra, Florian A.; Wright, Stephen J.

    2000-12-01

    The modern era of interior-point methods dates to 1984, when Karmarkar proposed his algorithm for linear programming. In the years since then, algorithms and software for linear programming have become quite sophisticated, while extensions to more general classes of problems, such as convex quadratic programming, semi-definite programming, and nonconvex and nonlinear problems, have reached varying levels of maturity. We review some of the key developments in the area, including comments on both the complexity theory and practical algorithms for linear programming, semi-definite programming, monotone linear complementarity, and convex programming over sets that can be characterized by self-concordant barrier functions.

  4. Mathematical methods for physicists

    CERN Document Server

    Arfken, George B

    1985-01-01

    Mathematical Methods for Physicists, Third Edition provides an advanced undergraduate and beginning graduate study in physical science, focusing on the mathematics of theoretical physics. This edition includes sections on the non-Cartesian tensors, dispersion theory, first-order differential equations, numerical application of Chebyshev polynomials, the fast Fourier transform, and transfer functions. Many of the physical examples provided in this book, which are used to illustrate the applications of mathematics, are taken from the fields of electromagnetic theory and quantum mechanics. The He

  5. Crystallographic Lattice Boltzmann Method

    Science.gov (United States)

    Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh

    2016-01-01

    Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows. PMID:27251098

  6. Research methods in information

    CERN Document Server

    Pickard, Alison Jane

    2013-01-01

    The long-awaited 2nd edition of this best-selling research methods handbook is fully updated and includes brand new coverage of online research methods and techniques, mixed methodology and qualitative analysis. There is an entire chapter contributed by Professor Julie McLeod, Sue Childs and Elizabeth Lomas focusing on research data management, applying evidence from the recent JISC funded 'DATUM' project. The first to focus entirely on the needs of the information and communications community, it guides the would-be researcher through the variety of possibilities open to them under the heading "research" and provides students with the confidence to embark on their dissertations. The focus here is on the 'doing' and although the philosophy and theory of research is explored to provide context, this is essentially a practical exploration of the whole research process with each chapter fully supported by examples and exercises tried and tested over a whole teaching career. The book will take readers through eac...

  7. Nanoscale waveguiding methods

    Directory of Open Access Journals (Sweden)

    Wang Chia-Jean

    2007-01-01

    Full Text Available AbstractWhile 32 nm lithography technology is on the horizon for integrated circuit (IC fabrication, matching the pace for miniaturization with optics has been hampered by the diffraction limit. However, development of nanoscale components and guiding methods is burgeoning through advances in fabrication techniques and materials processing. As waveguiding presents the fundamental issue and cornerstone for ultra-high density photonic ICs, we examine the current state of methods in the field. Namely, plasmonic, metal slot and negative dielectric based waveguides as well as a few sub-micrometer techniques such as nanoribbons, high-index contrast and photonic crystals waveguides are investigated in terms of construction, transmission, and limitations. Furthermore, we discuss in detail quantum dot (QD arrays as a gain-enabled and flexible means to transmit energy through straight paths and sharp bends. Modeling, fabrication and test results are provided and show that the QD waveguide may be effective as an alternate means to transfer light on sub-diffraction dimensions.

  8. Recombinant methods and materials

    Energy Technology Data Exchange (ETDEWEB)

    Roizman, B.; Post, L.E.

    1988-09-06

    This patent describes a method for stably effecting the insertion or deletion of a selected DNA sequence at a specific site in a viral genome. The method consists of: (1) isolating from the genome a linear DNA fragment comprising both (a) the specific site determined for insertion or deletion of selected DNA sequence and (b) flanking DNA sequences normally preceding and following the site; (2) preparing first and second altered genome fragments from the fragment isolated in step (1). (a) the first altered fragment comprising the fragment comprising a thymidine kinase gene in a position intermediate the ends of the fragment, and (b) the second altered fragment comprising the fragment having the selected DNA sequence inserted therein or deleted therefrom; (3) contacting the genome with the first altered fragment under conditions permitting recombination at sites of DNA sequence homology, selecting for a recombinant genome comprising the thymidine kinase gene, and isolating the recombinant genome; and (4) contacting the recombinant genome isolated in step (3) with the second altered fragment under conditions permitting recombination at sites of DNA sequence homology, selecting for a recombinant genome lacking the thymidine kinase gene, and isolating the recombinant genome product.

  9. Methods of Endotoxin Detection.

    Science.gov (United States)

    Su, Wenqiong; Ding, Xianting

    2015-08-01

    Endotoxin, present in the outer membrane of all gram-negative bacteria, can pose serious risks to human health, from irreversible shock to death. Therefore, it is essential to develop sensitive, accurate, and rapid methods for its detection. The rabbit pyrogen test is the first standard technique for endotoxin detection and, nowadays, has been replaced by the Limulus Amoebocyte Lysate test, which is the most popular detection technique for endotoxin. With in-depth understanding of endotoxin, biosensors based on endotoxin-sensing components are promising alternatives to pursue in developing low-cost, easy-operation, and fast-response endotoxin detection techniques. This article summarizes the recent advances of endotoxin detection methods with a particular emphasis on optical and electrochemical biosensors based on various sensing elements ranging from nature biomolecules to artificial materials. As the research and technological revolution continues, the highly integrated and miniaturized commercial devices for sensitively and reliably detecting endotoxin will provide a wide range of applications in people's daily life.

  10. Conjugated polymer nanoparticles, methods of using, and methods of making

    KAUST Repository

    Habuchi, Satoshi

    2017-03-16

    Embodiments of the present disclosure provide for conjugated polymer nanoparticle, method of making conjugated polymer nanoparticles, method of using conjugated polymer nanoparticle, polymers, and the like.

  11. Microencapsulation system and method

    Science.gov (United States)

    Morrison, Dennis R. (Inventor)

    2009-01-01

    A microencapsulation apparatus is provided which is configured to form co-axial multi-lamellar microcapsules from materials discharged from first and second microsphere dispensers of the apparatus. A method of fabricating and processing microcapsules is also provided which includes forming distinct droplets comprising one or more materials and introducing the droplets directly into a solution bath to form a membrane around the droplets such that a plurality of microcapsules are formed. A microencapsulation system is provided which includes a microcapsule production unit, a fluidized passage for washing and harvesting microcapsules dispensed from the microcapsule production unit and a flow sensor for sizing and counting the microcapsules. In some embodiments, the microencapsulation system may further include a controller configured to simultaneously operate the microcapsule production unit, fluidized passage and flow sensor to process the microcapsules in a continuous manner.

  12. Introduction to perturbation methods

    CERN Document Server

    Holmes, M

    1995-01-01

    This book is an introductory graduate text dealing with many of the perturbation methods currently used by applied mathematicians, scientists, and engineers. The author has based his book on a graduate course he has taught several times over the last ten years to students in applied mathematics, engineering sciences, and physics. The only prerequisite for the course is a background in differential equations. Each chapter begins with an introductory development involving ordinary differential equations. The book covers traditional topics, such as boundary layers and multiple scales. However, it also contains material arising from current research interest. This includes homogenization, slender body theory, symbolic computing, and discrete equations. One of the more important features of this book is contained in the exercises. Many are derived from problems of up- to-date research and are from a wide range of application areas.

  13. Extending the MINLO method

    CERN Document Server

    Frederix, Rikkert

    2015-01-01

    We consider improving POWHEG+MINLO simulations, so as to also render them NLO accurate in the description of observables receiving contributions from events with lower parton multiplicity than present in their underlying NLO calculation. On a conceptual level we follow the strategy of the so-called MINLO' programs. Whereas the existing MINLO' framework requires explicit analytic input from higher order resummation, here we derive an effective numerical approximation to these ingredients, by imposing unitarity. This offers a way of extending the MINLO' method to more complex processes, complementary to the known route which uses explicit computations of high-accuracy resummation inputs. Specifically, we have focused on Higgs-plus-two-jet production (HJJ) and related processes. We also consider how one can cover three units of multiplicity at NLO accuracy, i.e. we consider how the HJJ-MINLO simulation may yield NLO accuracy for inclusive H, HJ, and HJJ quantities. We perform a feasibility study assessing the po...

  14. Data mining methods

    CERN Document Server

    Chattamvelli, Rajan

    2015-01-01

    DATA MINING METHODS, Second Edition discusses both theoretical foundation and practical applications of datamining in a web field including banking, e-commerce, medicine, engineering and management. This book starts byintroducing data and information, basic data type, data category and applications of data mining. The second chapterbriefly reviews data visualization technology and importance in data mining. Fundamentals of probability and statisticsare discussed in chapter 3, and novel algorithm for sample covariants are derived. The next two chapters give an indepthand useful discussion of data warehousing and OLAP. Decision trees are clearly explained and a new tabularmethod for decision tree building is discussed. The chapter on association rules discusses popular algorithms andcompares various algorithms in summary table form. An interesting application of genetic algorithm is introduced inthe next chapter. Foundations of neural networks are built from scratch and the back propagation algorithm is derived...

  15. New methods in cytogenetics.

    Science.gov (United States)

    Buckle, V J; Kearney, L

    1994-06-01

    Developments in the technique of fluorescence in situ hybridization (FISH) now permit hybridization of sequences ranging from 1 kb to whole genomes. The technique can be used in applications from coarse mapping of whole chromosomes to high-resolution analysis of extended strands of DNA. The complexity, and hence the coverage, of 'paints' prepared by amplification is being improved to the extent that such methods are used in cloning strategies for the generation of region-specific probes. Interphase analysis and comparative genomic hybridization are becoming important tools in cancer cytogenetics, and the potential for routine analysis of fetal cells obtained from maternal blood may provide a fresh approach to prenatal cytogenetic screening. Functional studies of gene activity and nuclear organization are now also possible.

  16. Electrochemical catalyst recovery method

    Science.gov (United States)

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  17. Floating Silicon Method

    Energy Technology Data Exchange (ETDEWEB)

    Kellerman, Peter

    2013-12-21

    The Floating Silicon Method (FSM) project at Applied Materials (formerly Varian Semiconductor Equipment Associates), has been funded, in part, by the DOE under a “Photovoltaic Supply Chain and Cross Cutting Technologies” grant (number DE-EE0000595) for the past four years. The original intent of the project was to develop the FSM process from concept to a commercially viable tool. This new manufacturing equipment would support the photovoltaic industry in following ways: eliminate kerf losses and the consumable costs associated with wafer sawing, allow optimal photovoltaic efficiency by producing high-quality silicon sheets, reduce the cost of assembling photovoltaic modules by creating large-area silicon cells which are free of micro-cracks, and would be a drop-in replacement in existing high efficiency cell production process thereby allowing rapid fan-out into the industry.

  18. Cyclostationarity theory and methods

    CERN Document Server

    Leśkow, Jacek; Napolitano, Antonio; Sanchez-Ramirez, Andrea

    2014-01-01

    In the last decade the research in signal analysis was dominated by models that encompass nonstationarity as an important feature. This book presents the results of a workshop held in Grodek—Poland in February 2013 which was dedicated to the investigation of cyclostationary signals. Its main objective is to highlight the strong interactions between theory and applications of cyclostationary signals with the use of modern statistical tools. An important application of cyclostationary signals is the analysis of mechanical signals generated by a vibrating mechanism. Cyclostationary models are very important to perform basic operations on signals in both time and frequency domains. One of the fundamental problems in diagnosis of rotating machine is the identification of significant modulating frequencies that contribute to the cyclostationary nature of the signals. The book shows that there are modern tools available for analyzing cyclostationary signals without the assumption of gaussianity. Those methods are...

  19. METHOD OF RECOVERING THORIUM

    Science.gov (United States)

    Fisher, R.W.

    1957-12-10

    A method is described for recovering thorium from impurities found in a slag containing thorium and said impurities, comprising leaching a composition containing thorium with water, removing the water solution, treating the residue with hydrochloric acid, separating the solution from the insoluble residue, adjusting its acidity to 1 to 3 normal, adding oxalic acid, and thereafter separating the precipitated thorium oxalate digesting the residue from the hydrochloric acid treatment with a strong solution of sodium hydroxide at an elevated temperature, removing said solution and treating the insoluble residue with hydrochloric acid, separating the solution from the insoluble residue, adjusting the acidity of this solution to 1 to 3 normal, adding nitric acid to oxidize the iron present, adding oxalic acid and thereafter separating the thorium oxalate thus precipitated.

  20. Ticks and control methods.

    Science.gov (United States)

    Jongejan, F; Uilenberg, G

    1994-12-01

    Ticks are the most important ectoparasites of livestock in tropical and sub-tropical areas, and are responsible for severe economic losses both through the direct effects of blood sucking and indirectly as vectors of pathogens and toxins. Feeding by large numbers of ticks causes reduction in live weight gain and anaemia among domestic animals, while tick bites also reduce the quality of hides. However, the major losses caused by ticks are due to the ability to transmit protozoan, rickettsial and viral diseases of livestock, which are of great economic importance world-wide. The authors review general aspects of tick biology, the taxonomy, pathogenic effects and vector role of these species, and methods for the control of ticks. The distribution of ticks is continuously changing, as illustrated by the spread of the African tick Amblyomma variegatum in the Caribbean, where a large-scale eradication campaign is now under way.

  1. Radioactive air sampling methods

    CERN Document Server

    Maiello, Mark L

    2010-01-01

    Although the field of radioactive air sampling has matured and evolved over decades, it has lacked a single resource that assimilates technical and background information on its many facets. Edited by experts and with contributions from top practitioners and researchers, Radioactive Air Sampling Methods provides authoritative guidance on measuring airborne radioactivity from industrial, research, and nuclear power operations, as well as naturally occuring radioactivity in the environment. Designed for industrial hygienists, air quality experts, and heath physicists, the book delves into the applied research advancing and transforming practice with improvements to measurement equipment, human dose modeling of inhaled radioactivity, and radiation safety regulations. To present a wide picture of the field, it covers the international and national standards that guide the quality of air sampling measurements and equipment. It discusses emergency response issues, including radioactive fallout and the assets used ...

  2. Parametric lattice Boltzmann method

    Science.gov (United States)

    Shim, Jae Wan

    2017-06-01

    The discretized equilibrium distributions of the lattice Boltzmann method are presented by using the coefficients of the Lagrange interpolating polynomials that pass through the points related to discrete velocities and using moments of the Maxwell-Boltzmann distribution. The ranges of flow velocity and temperature providing positive valued distributions vary with regulating discrete velocities as parameters. New isothermal and thermal compressible models are proposed for flows of the level of the isothermal and thermal compressible Navier-Stokes equations. Thermal compressible shock tube flows are simulated by only five on-lattice discrete velocities. Two-dimensional isothermal and thermal vortices provoked by the Kelvin-Helmholtz instability are simulated by the parametric models.

  3. Method for radioactivity monitoring

    Science.gov (United States)

    Umbarger, C. John; Cowder, Leo R.

    1976-10-26

    The disclosure relates to a method for analyzing uranium and/or thorium contents of liquid effluents preferably utilizing a sample containing counting chamber. Basically, 185.7-keV gamma rays following .sup.235 U alpha decay to .sup.231 Th which indicate .sup.235 U content and a 63-keV gamma ray doublet found in the nucleus of .sup.234 Pa, a granddaughter of .sup.238 U, are monitored and the ratio thereof taken to derive uranium content and isotopic enrichment .sup.235 U/.sup.235 U + .sup.238 U) in the liquid effluent. Thorium content is determined by monitoring the intensity of 238-keV gamma rays from the nucleus of .sup.212 Bi in the decay chain of .sup.232 Th.

  4. Method for synthesizing HMX

    Science.gov (United States)

    McGuire, Raymond R.; Coon, Clifford L.; Harrar, Jackson E.; Pearson, Richard K.

    1984-01-01

    A method and apparatus for electrochemically synthesizing N.sub.2 O.sub.5 cludes oxidizing a solution of N.sub.2 O.sub.4 /HNO.sub.3 at an anode, while maintaining a controlled potential between the N.sub.2 O.sub.4 /HNO.sub.3 solution and the anode. A potential of about 1.35 to 2.0 V vs. SCE is preferred, while a potential of about 1.80 V vs. SCE is most preferred. Thereafter, the N.sub.2 O.sub.5 is reacted with either 1.5-diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooctane (DADN) or 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) to form cyclotetramethylenetetraamine (HMX).

  5. The Algebraic Method

    CERN Document Server

    Grassi, P A; Steinhauser, M

    2001-01-01

    Combining the effect of an intermediate renormalization prescription (zero momentum subtraction) and the background field method (BFM), we show that the algebraic renormalization procedure needed for the computation of radiative corrections within non-invariant regularization schemes is drastically simplified. The present technique is suitable for gauge models and, here, is applied to the Standard Model. The use of the BFM allows a powerful organization of the counterterms and avoids complicated Slavnov-Taylor identities. Furthermore, the Becchi-Rouet-Stora-Tyutin (BRST) variation of background fields plays a special role in disentangling Ward-Takahashi identities (WTI) and Slavnov-Taylor identities (STI). Finally, the strategy to be applied to physical processes is exemplified for the process $b\\to s\\gamma$.

  6. Unconventional methods for clustering

    Science.gov (United States)

    Kotyrba, Martin

    2016-06-01

    Cluster analysis or clustering is a task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). It is the main task of exploratory data mining and a common technique for statistical data analysis used in many fields, including machine learning, pattern recognition, image analysis, information retrieval, and bioinformatics. The topic of this paper is one of the modern methods of clustering namely SOM (Self Organising Map). The paper describes the theory needed to understand the principle of clustering and descriptions of algorithm used with clustering in our experiments.

  7. Dominant modal decomposition method

    Science.gov (United States)

    Dombovari, Zoltan

    2017-03-01

    The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.

  8. Method for maskless lithography

    Science.gov (United States)

    Sweatt, William C.; Stulen, Richard H.

    2000-01-01

    The present invention provides a method for maskless lithography. A plurality of individually addressable and rotatable micromirrors together comprise a two-dimensional array of micromirrors. Each micromirror in the two-dimensional array can be envisioned as an individually addressable element in the picture that comprises the circuit pattern desired. As each micromirror is addressed it rotates so as to reflect light from a light source onto a portion of the photoresist coated wafer thereby forming a pixel within the circuit pattern. By electronically addressing a two-dimensional array of these micromirrors in the proper sequence a circuit pattern that is comprised of these individual pixels can be constructed on a microchip. The reflecting surface of the micromirror is configured in such a way as to overcome coherence and diffraction effects in order to produce circuit elements having straight sides.

  9. Geophysical Methods: an Overview

    Science.gov (United States)

    Becker, A.; Goldstein, N. E.; Lee, K. H.; Majer, E. L.; Morrison, H. F.; Myer, L.

    1992-01-01

    Geophysics is expected to have a major role in lunar resource assessment when manned systems return to the Moon. Geophysical measurements made from a lunar rover will contribute to a number of key studies: estimating regolith thickness, detection of possible large-diameter lava tubes within maria basalts, detection of possible subsurface ice in polar regions, detection of conductive minerals that formed directly from a melt (orthomagmatic sulfides of Cu, Ni, Co), and mapping lunar geology beneath the regolith. The techniques that can be used are dictated both by objectives and by our abilities to adapt current technology to lunar conditions. Instrument size, weight, power requirements, and freedom from orientation errors are factors we have considered. Among the geophysical methods we believe to be appropriate for a lunar resource assessment are magnetics, including gradiometry, time-domain magnetic induction, ground-penetrating radar, seismic reflection, and gravimetry.

  10. Mathematical methods in engineering

    CERN Document Server

    Machado, José

    2014-01-01

    This book presents a careful selection of the contributions presented at the Mathematical Methods in Engineering (MME10) International Symposium, held at the Polytechnic Institute of Coimbra- Engineering Institute of Coimbra (IPC/ISEC), Portugal, October 21-24, 2010. The volume discusses recent developments about theoretical and applied mathematics toward the solution of engineering problems, thus covering a wide range of topics, such as:  Automatic Control, Autonomous Systems, Computer Science, Dynamical Systems and Control,  Electronics, Finance and Economics, Fluid Mechanics and Heat Transfer, Fractional Mathematics, Fractional Transforms and Their Applications,  Fuzzy Sets and Systems, Image and Signal Analysis, Image Processing, Mechanics, Mechatronics, Motor Control and Human Movement Analysis, Nonlinear Dynamics, Partial Differential Equations, Robotics, Acoustics, Vibration and Control, and Wavelets.

  11. Remanufacturability and Assessment Method

    Institute of Scientific and Technical Information of China (English)

    ZHU Sheng; CUI Pei-zhi; YAO Ju-kun

    2004-01-01

    Remanufacturing represents the combination of "three Rs" (reduce, reuse, recycle) into a single activity, which restores a wide variety of worn-out, discarded durable products to like-new condition, prolonging theit useful life,protecting the environment. The application of surface engineering has promoted the development of remanufacturing.Remanufacturing is an environmentally and economically sound way to achieve many of the goals of sustainable development. Through developing study of product design for remanufacturing, it can promote the surface technologies application in the remanufacturing, and markedly enhance the efficiency of remanufacturing. This paper gives some relative concepts about product design for remanufacturing, such as remanufacturability, and brings forward the remanufacturability research contents and assessment method of used product.

  12. Acoustophoresis separation method

    Science.gov (United States)

    Heyman, Joseph S. (Inventor)

    1993-01-01

    A method and apparatus are provided for acoustophoresis, i.e., the separation of species via acoustic waves. An ultrasonic transducer applies an acoustic wave to one end of a sample container containing at least two species having different acoustic absorptions. The wave has a frequency tuned to or harmonized with the point of resonance of the species to be separated. This wave causes the species to be driven to an opposite end of the sample container for removal. A second ultrasonic transducer may be provided to apply a second, oppositely directed acoustic wave to prevent undesired streaming. In addition, a radio frequency tuned to the mechanical resonance and coupled with a magnetic field can serve to identify a species in a medium comprising species with similar absorption coefficients, whereby an acoustic wave having a frequency corresponding to this gyrational rate can then be applied to sweep the identified species to one end of the container for removal.

  13. Remanufacturability and Assessment Method

    Institute of Scientific and Technical Information of China (English)

    ZHUSheng; CUIPei-zhi; YAOJu-kun

    2004-01-01

    Remanufacturing represents the combination of "three Rs" (reduce, reuse, recycle) into a single activity, which restores a wide variety of worn-out, discarded durable products to like-new condition, prolonging their useful life, protecting the environment. The application of surface engineering has promoted the development of remanufacturing. Remanufacturing is an environmentally and economically sound way to achieve many of the goals of sustainable development. Through developing study of product design for remanufacturing, it can promote the surface technologies application in the remanufacturing, and markedly enhance the efficiency of remanufacturing. This paper gives some relative concepts about product design for remanufacturing, such as remanufacturability, and brings forward the remanufacturability research contents and assessment method of used product.

  14. Gas centrifuge purge method

    Science.gov (United States)

    Theurich, Gordon R.

    1976-01-01

    1. In a method of separating isotopes in a high speed gas centrifuge wherein a vertically oriented cylindrical rotor bowl is adapted to rotate about its axis within an evacuated chamber, and wherein an annular molecular pump having an intake end and a discharge end encircles the uppermost portion of said rotor bowl, said molecular pump being attached along its periphery in a leak-tight manner to said evacuated chamber, and wherein end cap closure means are affixed to the upper end of said rotor bowl, and a process gas withdrawal and insertion system enters said bowl through said end cap closure means, said evacuated chamber, molecular pump and end cap defining an upper zone at the discharge end of said molecular pump, said evacuated chamber, molecular pump and rotor bowl defining a lower annular zone at the intake end of said molecular pump, a method for removing gases from said upper and lower zones during centrifuge operation with a minimum loss of process gas from said rotor bowl, comprising, in combination: continuously measuring the pressure in said upper zone, pumping gas from said lower zone from the time the pressure in said upper zone equals a first preselected value until the pressure in said upper zone is equal to a second preselected value, said first preselected value being greater than said second preselected value, and continuously pumping gas from said upper zone from the time the pressure in said upper zone equals a third preselected value until the pressure in said upper zone is equal to a fourth preselected value, said third preselected value being greater than said first, second and fourth preselected values.

  15. Characterization Methods of Encapsulates

    Science.gov (United States)

    Zhang, Zhibing; Law, Daniel; Lian, Guoping

    , reliable methods which can be used to characterize these properties of encapsulates are vital. In this chapter, the state-of-art of these methods, their principles and applications, and release mechanisms are described as follows.

  16. Location predicting methods for UAVs

    Science.gov (United States)

    Peng, Xiaodong; Zhang, Yu

    2017-08-01

    Location prediction of unmanned aerial vehicle (UAV) is important for fighting with its enemy and ensuring its normal operation. This paper presents the motion model of UAVs and reduces the state space into 7 dimensions. The Bayesian Network, Markov Chain, Curve Fitting and Neural Network are introduced for designing predicting methods. Then Curve Fitting Predicting method, Markov Chain Predicting method, Bayesian Network Predicting method and Neural Network Predicting method are designed for UAVs. The simulation result shows that 1) Neural Network Predicting method has highest predicting accuracy; 2) Markov Chain Predicting method and Bayesian Network Predicting method methods have similar performance and both are better than Bayesian Network Predicting method methods; 3) Neural Network Predicting method is the first choice when predicting the locations of UAVs.

  17. Section for qualitative methods (Letter)

    OpenAIRE

    Todd, Z.; Madill, A.

    2004-01-01

    Qualitative research methods are increasingly used in all areas of psychology. We have proposed a new Section – the Qualitative Methods in Psychology Section – for anyone with an interest in using these research methods.

  18. Methods and Technologies Branch (MTB)

    Science.gov (United States)

    The Methods and Technologies Branch focuses on methods to address epidemiologic data collection, study design and analysis, and to modify technological approaches to better understand cancer susceptibility.

  19. 40 years of formal methods

    DEFF Research Database (Denmark)

    Bjørner, Dines; Havelund, Klaus

    2014-01-01

    In this "40 years of formal methods" essay we shall first delineate, Sect. 1, what we mean by method, formal method, computer science, computing science, software engineering, and model-oriented and algebraic methods. Based on this, we shall characterize a spectrum from specification-oriented met......In this "40 years of formal methods" essay we shall first delineate, Sect. 1, what we mean by method, formal method, computer science, computing science, software engineering, and model-oriented and algebraic methods. Based on this, we shall characterize a spectrum from specification...

  20. Comparative law as method and the method of comparative law

    NARCIS (Netherlands)

    Hage, J.C.; Adams, M.; Heirbaut, D.

    2014-01-01

    This article addresses both the justificatory role of comparative law within legal research (comparative law as method) and the method of comparative law itself. In this connection two questions will be answered: 1. Is comparative law a method, or a set of methods, for legal research? 2. Does compar