Sample records for alternating current voltammetry

  1. Alternating current scanning electrochemical microscopy with simultaneous fast-scan cyclic voltammetry.

    PubMed

    Koch, Jason A; Baur, Melinda B; Woodall, Erica L; Baur, John E

    2012-11-06

    Fast-scan cyclic voltammetry (FSCV) is combined with alternating current scanning electrochemical microscopy (AC-SECM) for simultaneous measurements of impedance and faradaic current. Scan rates of 10-1000 V s(-1) were used for voltammetry, while a high-frequency (100 kHz), low-amplitude (10 mV rms) sine wave was added to the voltammetric waveform for the ac measurement. Both a lock-in amplifier and an analog circuit were used to measure the amplitude of the resultant ac signal. The effect of the added sine wave on the voltammetry at a carbon fiber electrode was investigated and found to have negligible effect. The combined FSCV and ac measurements were used to provide simultaneous chemical and topographical information about a substrate using a single carbon fiber probe. The technique is demonstrated in living cell culture, where cellular respiration and topography were simultaneously imaged without the addition of a redox mediator. This approach promises to be useful for the topographical and multidimensional chemical imaging of substrates.

  2. Characterization of an electrochemical mercury sensor using alternating current, cyclic, square wave and differential pulse voltammetry.

    PubMed

    Guerreiro, Gabriela V; Zaitouna, Anita J; Lai, Rebecca Y

    2014-01-31

    Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Probing Electrode Heterogeneity Using Fourier-Transformed Alternating Current Voltammetry: Application to a Dual-Electrode Configuration.

    PubMed

    Tan, Sze-Yin; Unwin, Patrick R; Macpherson, Julie V; Zhang, Jie; Bond, Alan M

    2017-03-07

    Quantitative studies of electron transfer processes at electrode/electrolyte interfaces, originally developed for homogeneous liquid mercury or metallic electrodes, are difficult to adapt to the spatially heterogeneous nanostructured electrode materials that are now commonly used in modern electrochemistry. In this study, the impact of surface heterogeneity on Fourier-transformed alternating current voltammetry (FTACV) has been investigated theoretically under the simplest possible conditions where no overlap of diffusion layers occurs and where numerical simulations based on a 1D diffusion model are sufficient to describe the mass transport problem. Experimental data that meet these requirements can be obtained with the aqueous [Ru(NH 3 ) 6 ] 3+/2+ redox process at a dual-electrode system comprised of electrically coupled but well-separated glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Simulated and experimental FTACV data obtained with this electrode configuration, and where distinctly different heterogeneous charge transfer rate constants (k 0 values) apply at the individual GC and BDD electrode surfaces, are in excellent agreement. Principally, because of the far greater dependence of the AC current magnitude on k 0 , it is straightforward with the FTACV method to resolve electrochemical heterogeneities that are ∼1-2 orders of magnitude apart, as applies in the [Ru(NH 3 ) 6 ] 3+/2+ dual-electrode configuration experiments, without prior knowledge of the individual kinetic parameters (k 0 1 and k 0 2 ) or the electrode size ratio (θ 1 :θ 2 ). In direct current voltammetry, a difference in k 0 of >3 orders of magnitude is required to make this distinction.

  4. Effect of Alternating Current on the Cathodic Protection and Interface Structure of X80 Steel.

    PubMed

    Wang, Huiru; Du, Cuiwei; Liu, Zhiyong; Wang, Luntao; Ding, De

    2017-07-25

    This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at an AC current density of 100 A/m². In an alkaline solution at pH 9.6, more serious AC corrosion occurs at more negative cathodic protection (CP) potential, whereas without CP the steel suffers negligible corrosion. In addition, the interface capacitance increases with AC amplitude. Based on these results, the AC corrosion mechanisms that function under various conditions are analyzed and described.

  5. Effect of Alternating Current on the Cathodic Protection and Interface Structure of X80 Steel

    PubMed Central

    Wang, Huiru; Du, Cuiwei; Liu, Zhiyong; Wang, Luntao; Ding, De

    2017-01-01

    This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at an AC current density of 100 A/m2. In an alkaline solution at pH 9.6, more serious AC corrosion occurs at more negative cathodic protection (CP) potential, whereas without CP the steel suffers negligible corrosion. In addition, the interface capacitance increases with AC amplitude. Based on these results, the AC corrosion mechanisms that function under various conditions are analyzed and described. PMID:28773211

  6. Detailed electrochemical studies of the tetraruthenium polyoxometalate water oxidation catalyst in acidic media: identification of an extended oxidation series using Fourier transformed alternating current voltammetry.

    PubMed

    Lee, Chong-Yong; Guo, Si-Xuan; Murphy, Aidan F; McCormac, Timothy; Zhang, Jie; Bond, Alan M; Zhu, Guibo; Hill, Craig L; Geletii, Yurii V

    2012-11-05

    The electrochemistry of the water oxidation catalyst, Rb(8)K(2)[{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(γ-SiW(10)O(36))(2)] (Rb(8)K(2)-1(0)) has been studied in the presence and absence of potassium cations in both hydrochloric and sulfuric acid solutions by transient direct current (dc) cyclic voltammetry, a steady state dc method in the rotating disk configuration and the kinetically sensitive technique of Fourier transformed large-amplitude alternating current (ac) voltammetry. In acidic media, the presence of potassium ions affects the kinetics (apparent rate of electron transfer) and thermodynamics (reversible potentials) of the eight processes (A'/A to H/H') that are readily detected under dc voltammetric conditions. The six most positive processes (A'/A to F/F'), each involve a one electron ruthenium based charge transfer step (A'/A, B'/B are Ru(IV/V) oxidation and C/C' to F/F' are Ru(IV/III) reduction). The apparent rate of electron transfer of the ruthenium centers in sulfuric acid is higher than in hydrochloric acid. The addition of potassium cations increases the apparent rates and gives rise to a small shift of reversible potential. Simulations of the Fourier transformed ac voltammetry method show that the B'/B, E/E', and F/F' processes are quasi-reversible, while the others are close to reversible. A third Ru(IV/V) oxidation process is observed just prior to the positive potential limit via dc methods. Importantly, the ability of the higher harmonic components of the ac method to discriminate against the irreversible background solvent process allows this (process I) as well as an additional fourth reversible ruthenium based process (J) to be readily identified. The steady-state rotating disk electrode (RDE) method confirmed that all four Ru-centers in Rb(8)K(2)-1(0) are in oxidation state IV. The dc and ac data indicate that reversible potentials of the four ruthenium centers are evenly spaced, which may be relevant to understanding of the water oxidation

  7. Channel microband electrode arrays for mechanistic electrochemistry. Two-dimensional voltammetry:  transport-limited currents.

    PubMed

    Alden, J A; Feldman, M A; Hill, E; Prieto, F; Oyama, M; Coles, B A; Compton, R G; Dobson, P J; Leigh, P A

    1998-05-01

    A channel electrode array, with electrodes ranging in size from the millimeter to the submicrometer scale, is used for the amperometric interrogation of mechanistically complex electrode processes. In this way, the transport-limited current, measured as a function of both electrode size and electrolyte flow rate (convection), is shown to provide a highly sensitive probe of mechanism and kinetics. The application of "two-dimensional voltammetry" to diverse electrode processes, including E, ECE, ECEE, EC', and DISP2 reactions, is reported.

  8. Fault current limiter and alternating current circuit breaker

    DOEpatents

    Boenig, Heinrich J.

    1998-01-01

    A solid-state circuit breaker and current limiter for a load served by an alternating current source having a source impedance, the solid-state circuit breaker and current limiter comprising a thyristor bridge interposed between the alternating current source and the load, the thyristor bridge having four thyristor legs and four nodes, with a first node connected to the alternating current source, and a second node connected to the load. A coil is connected from a third node to a fourth node, the coil having an impedance of a value calculated to limit the current flowing therethrough to a predetermined value. Control means are connected to the thyristor legs for limiting the alternating current flow to the load under fault conditions to a predetermined level, and for gating the thyristor bridge under fault conditions to quickly reduce alternating current flowing therethrough to zero and thereafter to maintain the thyristor bridge in an electrically open condition preventing the alternating current from flowing therethrough for a predetermined period of time.

  9. Fault current limiter and alternating current circuit breaker

    DOEpatents

    Boenig, H.J.

    1998-03-10

    A solid-state circuit breaker and current limiter are disclosed for a load served by an alternating current source having a source impedance, the solid-state circuit breaker and current limiter comprising a thyristor bridge interposed between the alternating current source and the load, the thyristor bridge having four thyristor legs and four nodes, with a first node connected to the alternating current source, and a second node connected to the load. A coil is connected from a third node to a fourth node, the coil having an impedance of a value calculated to limit the current flowing therethrough to a predetermined value. Control means are connected to the thyristor legs for limiting the alternating current flow to the load under fault conditions to a predetermined level, and for gating the thyristor bridge under fault conditions to quickly reduce alternating current flowing therethrough to zero and thereafter to maintain the thyristor bridge in an electrically open condition preventing the alternating current from flowing therethrough for a predetermined period of time. 9 figs.

  10. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  11. Voltammetry Method Evaluation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hoyt, N.; Pereira, C.; Willit, J.

    2016-07-29

    The purpose of the ANL MPACT Voltammetry project is to evaluate the suitability of previously developed cyclic voltammetry techniques to provide electroanalytical measurements of actinide concentrations in realistic used fuel processing scenarios. The molten salts in these scenarios are very challenging as they include high concentrations of multiple electrochemically active species, thereby creating a variety of complications. Some of the problems that arise therein include issues related to uncompensated resistance, cylindrical diffusion, and alloying of the electrodeposited metals. Improvements to the existing voltammetry technique to account for these issues have been implemented, resulting in good measurements of actinide concentrations acrossmore » a wide range of adverse conditions.« less

  12. Thermoelectric converters for alternating current standards

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Taschuk, D. D.

    2012-06-01

    Thermoelectric converters of alternating current remain priority instruments when creating standard equipment. This work presents the results of design and manufacture of alternating current converter for a military standard of alternating current in Ukraine. Results of simulation of temperature distribution in converter elements, ways of optimization to improve the accuracy of alternating current signal reproduction are presented. Results of metrological trials are given. The quality of thermoelectric material specially created for alternating current metrology is verified. The converter was used in alternating current standard for the frequency range from 10 Hz to 30 MHz. The efficiency of using thermoelectric signal converters in measuring instruments is confirmed.

  13. Recent Advances in Voltammetry

    PubMed Central

    Batchelor-McAuley, Christopher; Kätelhön, Enno; Barnes, Edward O; Compton, Richard G; Laborda, Eduardo; Molina, Angela

    2015-01-01

    Recent progress in the theory and practice of voltammetry is surveyed and evaluated. The transformation over the last decade of the level of modelling and simulation of experiments has realised major advances such that electrochemical techniques can be fully developed and applied to real chemical problems of distinct complexity. This review focuses on the topic areas of: multistep electrochemical processes, voltammetry in ionic liquids, the development and interpretation of theories of electron transfer (Butler–Volmer and Marcus–Hush), advances in voltammetric pulse techniques, stochastic random walk models of diffusion, the influence of migration under conditions of low support, voltammetry at rough and porous electrodes, and nanoparticle electrochemistry. The review of the latter field encompasses both the study of nanoparticle-modified electrodes, including stripping voltammetry and the new technique of ‘nano-impacts’. PMID:26246984

  14. Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes.

    PubMed

    Walsh, Darren A; Lovelock, Kevin R J; Licence, Peter

    2010-11-01

    The high viscosity and unusual properties of room temperature ionic liquids (RTILs) present a number of challenges when performing steady-state voltammetry and scanning electrochemical microscopy in RTILs. These include difficulties in recording steady-state currents at ultramicroelectrode surfaces due to low diffusion coefficients of redox species and problems associated with unequal diffusion coefficients of oxidised and reduced species in RTILs. In this tutorial review, we highlight the recent progress in the use of RTILs as electrolytes for ultramicroelectrode voltammetry and SECM. We describe the basic principles of ultramicroelectrode voltammetry and SECM and, using examples from the recent literature, we discuss the conditions that must be met to perform steady-state voltammetry and SECM measurements in RTILs. Finally, we briefly discuss the electrochemical insights that can be obtained from such measurements.

  15. Differential thermal voltammetry for tracking of degradation in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wu, Billy; Yufit, Vladimir; Merla, Yu; Martinez-Botas, Ricardo F.; Brandon, Nigel P.; Offer, Gregory J.

    2015-01-01

    Monitoring of lithium-ion batteries is of critical importance in electric vehicle applications in order to manage the operational condition of the cells. Measurements on a vehicle often involve current, voltage and temperature which enable in-situ diagnostic techniques. This paper presents a novel diagnostic technique, termed differential thermal voltammetry, which is capable of monitoring the state of the battery using voltage and temperature measurements in galvanostatic operating modes. This tracks battery degradation through phase transitions, and the resulting entropic heat, occurring in the electrodes. Experiments to monitor battery degradation using the new technique are compared with a pseudo-2D cell model. Results show that the differential thermal voltammetry technique provides information comparable to that of slow rate cyclic voltammetry at shorter timescale and with load conditions easier to replicate in a vehicle.

  16. Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

    PubMed Central

    Allagui, Anis; Freeborn, Todd J.; Elwakil, Ahmed S.; Maundy, Brent J.

    2016-01-01

    The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal SsC behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance Rs in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (Rs, Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical RsC model. We validate our formulae with the experimental measurements of different EDLCs. PMID:27934904

  17. Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

    NASA Astrophysics Data System (ADS)

    Allagui, Anis; Freeborn, Todd J.; Elwakil, Ahmed S.; Maundy, Brent J.

    2016-12-01

    The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal SsC behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance Rs in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (Rs, Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical RsC model. We validate our formulae with the experimental measurements of different EDLCs.

  18. Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry.

    PubMed

    Allagui, Anis; Freeborn, Todd J; Elwakil, Ahmed S; Maundy, Brent J

    2016-12-09

    The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal R s C behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics [corrected]. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance R s in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (R s , Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical R s C model. We validate our formulae with the experimental measurements of different EDLCs.

  19. Cyclic Voltammetry.

    ERIC Educational Resources Information Center

    Evans, Dennis H.; And Others

    1983-01-01

    Cyclic voltammetry is a simple experiment that has become popular in chemical research because it can provide useful information about redox reactions in a form which is easily obtained and interpreted. Discusses principles of the method and illustrates its use in the study of four electrode reactions. (Author/JN)

  20. Voltammetry at the Thin-Film Mercury Electrode (TFME).

    ERIC Educational Resources Information Center

    Pomeroy, R. S.; And Others

    1989-01-01

    Reviewed is the use of the Thin-Film Mercury Electrode for anodic stripping voltammetry, simple voltammetry of solution cations and cathodic stripping voltammetry for the determination of an environmentally important molecule, thiourea. The construction of a simple potentiostat and applications for student laboratory courses are included. (CW)

  1. Pulse Voltammetry in Single Cells Using Platinum Microelectrodes

    DTIC Science & Technology

    1991-11-22

    E. and the range for Ed in multiple pulse voltammetry can be chosen from examination of voltammograms obtained by cyclic voltammetry or lin-ir sweep ... voltametry [3,13]. As pointed out by Sinru et al. [14) the potential and time of each pulse has a direct effect on the nature of the voltammetry

  2. Cyclic Voltammetry Experiment.

    ERIC Educational Resources Information Center

    Van Benschoten, James J.; And Others

    1983-01-01

    Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

  3. The Rise of Voltammetry: From Polarography to the Scanning Electrochemical Microscope

    ERIC Educational Resources Information Center

    Bard, Allen J.

    2007-01-01

    The drooping mercury electrode (DME) was previously used to carry out electrochemical experiments but invention of polarography technique changed this. Voltammetry with DME was given the term polarography and are used in measurement of current as a function of potential at small electrodes.

  4. Diagnostic criteria for the characterization of quasireversible electron transfer reactions by cyclic square wave voltammetry.

    PubMed

    Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A

    2014-08-19

    Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

  5. Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry.

    PubMed

    Ammar, Hafedh Belhadj; Brahim, Mabrouk Ben; Abdelhédi, Ridha; Samet, Youssef

    2016-02-01

    The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2μmolL(-1), with a detection limit of 0.065μmolL(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Stripping Voltammetry

    NASA Astrophysics Data System (ADS)

    Lovrić, Milivoj

    Electrochemical stripping means the oxidative or reductive removal of atoms, ions, or compounds from an electrode surface (or from the electrode body, as in the case of liquid mercury electrodes with dissolved metals) [1-5]. In general, these atoms, ions, or compounds have been preliminarily immobilized on the surface of an inert electrode (or within it) as the result of a preconcentration step, while the products of the electrochemical stripping will dissolve in the electrolytic solution. Often the product of the electrochemical stripping is identical to the analyte before the preconcentration. However, there are exemptions to these rules. Electroanalytical stripping methods comprise two steps: first, the accumulation of a dissolved analyte onto, or in, the working electrode, and, second, the subsequent stripping of the accumulated substance by a voltammetric [3, 5], potentiometric [6, 7], or coulometric [8] technique. In stripping voltammetry, the condition is that there are two independent linear relationships: the first one between the activity of accumulated substance and the concentration of analyte in the sample, and the second between the maximum stripping current and the accumulated substance activity. Hence, a cumulative linear relationship between the maximum response and the analyte concentration exists. However, the electrode capacity for the analyte accumulation is limited and the condition of linearity is satisfied only well below the electrode saturation. For this reason, stripping voltammetry is used mainly in trace analysis. The limit of detection depends on the factor of proportionality between the activity of the accumulated substance and the bulk concentration of the analyte. This factor is a constant in the case of a chemical accumulation, but for electrochemical accumulation it depends on the electrode potential. The factor of proportionality between the maximum stripping current and the analyte concentration is rarely known exactly. In fact

  7. Linear-sweep voltammetry of a soluble redox couple in a cylindrical electrode

    NASA Technical Reports Server (NTRS)

    Weidner, John W.

    1991-01-01

    An approach is described for using the linear sweep voltammetry (LSV) technique to study the kinetics of flooded porous electrodes by assuming a porous electrode as a collection of identical noninterconnected cylindrical pores that are filled with electrolyte. This assumption makes possible to study the behavior of this ideal electrode as that of a single pore. Alternatively, for an electrode of a given pore-size distribution, it is possible to predict the performance of different pore sizes and then combine the performance values.

  8. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, Duncan W.; McAtee, James L.

    1993-01-01

    An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  9. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, D.W.; McAtee, J.L.

    1993-02-16

    An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  10. A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents--Proof-of-principle application in microfluidic separations and voltammetry.

    PubMed

    Koutilellis, G D; Economou, A; Efstathiou, C E

    2016-03-01

    This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

  11. Transcranial Alternating Current Stimulation Attenuates Neuronal Adaptation.

    PubMed

    Kar, Kohitij; Duijnhouwer, Jacob; Krekelberg, Bart

    2017-03-01

    We previously showed that brief application of 2 mA (peak-to-peak) transcranial currents alternating at 10 Hz significantly reduces motion adaptation in humans. This is but one of many behavioral studies showing that weak currents applied to the scalp modulate neural processing. Transcranial stimulation has been shown to improve perception, learning, and a range of clinical symptoms. Few studies, however, have measured the neural consequences of transcranial current stimulation. We capitalized on the strong link between motion perception and neural activity in the middle temporal (MT) area of the macaque monkey to study the neural mechanisms that underlie the behavioral consequences of transcranial alternating current stimulation. First, we observed that 2 mA currents generated substantial intracranial fields, which were much stronger in the stimulated hemisphere (0.12 V/m) than on the opposite side of the brain (0.03 V/m). Second, we found that brief application of transcranial alternating current stimulation at 10 Hz reduced spike-frequency adaptation of MT neurons and led to a broadband increase in the power spectrum of local field potentials. Together, these findings provide a direct demonstration that weak electric fields applied to the scalp significantly affect neural processing in the primate brain and that this includes a hitherto unknown mechanism that attenuates sensory adaptation. SIGNIFICANCE STATEMENT Transcranial stimulation has been claimed to improve perception, learning, and a range of clinical symptoms. Little is known, however, how transcranial current stimulation generates such effects, and the search for better stimulation protocols proceeds largely by trial and error. We investigated, for the first time, the neural consequences of stimulation in the monkey brain. We found that even brief application of alternating current stimulation reduced the effects of adaptation on single-neuron firing rates and local field potentials; this mechanistic

  12. Method for sputtering with low frequency alternating current

    DOEpatents

    Timberlake, John R.

    1996-01-01

    Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking.

  13. Method for sputtering with low frequency alternating current

    DOEpatents

    Timberlake, J.R.

    1996-04-30

    Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking. 6 figs.

  14. Development of a cyclic voltammetry method for the detection of Clostridium novyi in black disease.

    PubMed

    Liu, L L; Jiang, D N; Xiang, G M; Liu, C; Yu, J C; Pu, X Y

    2014-03-17

    Black disease is an acute disease of sheep and cattle. The pathogen is the obligate anaerobe, Clostridium novyi. Due to difficulties of anaerobic culturing in the country or disaster sites, a simple, rapid, and sensitive method is required. In this study, an electrochemical method, the cyclic voltammetry method, basing on loop-mediated isothermal amplification (LAMP), electrochemical ion bonding (positive dye, methylene blue), was introduced. DNA extracted from C. novyi specimens was amplified through the LAMP reaction. Then the products combined were with methylene blue, which lead to a reduction in the oxidation peak current (ipA) and the reduction peak current (ipC) of the cyclic voltammetry. The changes of ipA/ipC were real-time measured by special designed electrode, so the DNA was quantitatively detected. The results displayed that this electrochemical detection of C. novyi could be completed in 1-2 h with the lowest bacterial concentration of 10(2) colony forming units/mL, and high accuracy (96.5%), sensitivity (96%), and specificity (97%) compared to polymerase chain reation. The cyclic voltammetry method was a simple and fast method, with high sensitivity and high specificity, and has great potential to be a usable molecular tool for fast diagnosis of Black disease.

  15. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... the ground connection, is able to withstand the maximum available fault current without damage, and... 46 Shipping 4 2011-10-01 2011-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral...

  16. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the ground connection, is able to withstand the maximum available fault current without damage, and... 46 Shipping 4 2010-10-01 2010-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral...

  17. A Practical Beginner's Guide to Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Elgrishi, Noémie; Rountree, Kelley J.; McCarthy, Brian D.; Rountree, Eric S.; Eisenhart, Thomas T.; Dempsey, Jillian L.

    2018-01-01

    Despite the growing popularity of cyclic voltammetry, many students do not receive formalized training in this technique as part of their coursework. Confronted with self-instruction, students can be left wondering where to start. Here, a short introduction to cyclic voltammetry is provided to help the reader with data acquisition and…

  18. Copper-Based Electrochemical Sensor with Palladium Electrode for Cathodic Stripping Voltammetry of Manganese

    PubMed Central

    2015-01-01

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River. PMID:25476591

  19. Copper-based electrochemical sensor with palladium electrode for cathodic stripping voltammetry of manganese.

    PubMed

    Kang, Wenjing; Pei, Xing; Bange, Adam; Haynes, Erin N; Heineman, William R; Papautsky, Ian

    2014-12-16

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River.

  20. Microelectrode voltammetry of multi-electron transfers complicated by coupled chemical equilibria: a general theory for the extended square scheme.

    PubMed

    Laborda, Eduardo; Gómez-Gil, José María; Molina, Angela

    2017-06-28

    A very general and simple theoretical solution is presented for the current-potential-time response of reversible multi-electron transfer processes complicated by homogeneous chemical equilibria (the so-called extended square scheme). The expressions presented here are applicable regardless of the number of electrons transferred and coupled chemical processes, and they are particularized for a wide variety of microelectrode geometries. The voltammetric response of very different systems presenting multi-electron transfers is considered for the most widely-used techniques (namely, cyclic voltammetry, square wave voltammetry, differential pulse voltammetry and steady state voltammetry), studying the influence of the microelectrode geometry and the number and thermodynamics of the (electro)chemical steps. Most appropriate techniques and procedures for the determination of the 'interaction' between successive transfers are discussed. Special attention is paid to those situations where homogeneous chemical processes, such as protonation, complexation or ion association, affect the electrochemical behaviour of the system by different stabilization of the oxidation states.

  1. Dynamics of laser-guided alternating current high voltage discharges

    NASA Astrophysics Data System (ADS)

    Daigle, J.-F.; Théberge, F.; Lassonde, P.; Kieffer, J.-C.; Fujii, T.; Fortin, J.; Châteauneuf, M.; Dubois, J.

    2013-10-01

    The dynamics of laser-guided alternating current high voltage discharges are characterized using a streak camera. Laser filaments were used to trigger and guide the discharges produced by a commercial Tesla coil. The streaking images revealed that the dynamics of the guided alternating current high voltage corona are different from that of a direct current source. The measured effective corona velocity and the absence of leader streamers confirmed that it evolves in a pure leader regime.

  2. Stripping voltammetry in environmental and food analysis.

    PubMed

    Brainina, K Z; Malakhova, N A; Stojko, N Y

    2000-10-01

    The review covers over 230 papers published mostly in the last 5 years. The goal of the review is to attract the attention of researchers and users to stripping voltammetry in particular, its application in environmental monitoring and analysis of foodstuffs. The sensors employed are impregnated graphite, carbon paste, thick film carbon/graphite and thin film metallic electrodes modified in-situ or beforehand. Hanging mercury drop electrodes and mercury coated glassy carbon electrodes are also mentioned. Strip and long-lived sensors for portable instruments and flow through systems are discussed as devices for future development and application of stripping voltammetry.

  3. Catalytic mechanism in cyclic voltammetry at disc electrodes: an analytical solution.

    PubMed

    Molina, Angela; González, Joaquín; Laborda, Eduardo; Wang, Yijun; Compton, Richard G

    2011-08-28

    The theory of cyclic voltammetry at disc electrodes and microelectrodes is developed for a system where the electroactive reactant is regenerated in solution using a catalyst. This catalytic process is of wide importance, not least in chemical sensing, and it can be characterized by the resulting peak current which is always larger than that of a simple electrochemical reaction; in contrast the reverse peak is always relatively diminished in size. From the theoretical point of view, the problem involves a complex physical situation with two-dimensional mass transport and non-uniform surface gradients. Because of this complexity, hitherto the treatment of this problem has been tackled mainly by means of numerical methods and so no analytical expression was available for the transient response of the catalytic mechanism in cyclic voltammetry when disc electrodes, the most popular practical geometry, are used. In this work, this gap is filled by presenting an analytical solution for the application of any sequence of potential pulses and, in particular, for cyclic voltammetry. The induction principle is applied to demonstrate mathematically that the superposition principle applies whatever the geometry of the electrode, which enabled us to obtain an analytical equation valid whatever the electrode size and the kinetics of the catalytic reaction. The theoretical results obtained are applied to the experimental study of the electrocatalytic Fenton reaction, determining the rate constant of the reduction of hydrogen peroxide by iron(II).

  4. Theory of linear sweep voltammetry with diffuse charge: Unsupported electrolytes, thin films, and leaky membranes

    NASA Astrophysics Data System (ADS)

    Yan, David; Bazant, Martin Z.; Biesheuvel, P. M.; Pugh, Mary C.; Dawson, Francis P.

    2017-03-01

    Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. In this paper, we provide a comprehensive mathematical theory of voltammetry in electrochemical cells with unsupported electrolytes and for other situations where diffuse charge effects play a role, and present analytical and simulated solutions of the time-dependent Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions for a 1:1 electrolyte and a simple reaction. Using these solutions, we construct theoretical and simulated current-voltage curves for liquid and solid thin films, membranes with fixed background charge, and cells with blocking electrodes. The full range of dimensionless parameters is considered, including the dimensionless Debye screening length (scaled to the electrode separation), Damkohler number (ratio of characteristic diffusion and reaction times), and dimensionless sweep rate (scaled to the thermal voltage per diffusion time). The analysis focuses on the coupling of Faradaic reactions and diffuse charge dynamics, although capacitive charging of the electrical double layers is also studied, for early time transients at reactive electrodes and for nonreactive blocking electrodes. Our work highlights cases where diffuse charge effects are important in the context of voltammetry, and illustrates which regimes can be approximated using simple analytical expressions and which require more careful consideration.

  5. Training Course for Power Operating Personnel. Lesson No. 6: Alternating-Current Generator Excitation.

    ERIC Educational Resources Information Center

    Department of the Interior, Denver, CO. Engineering and Research Center.

    Subjects covered in this text are controlling the hydroelectric generator, generator excitation, basic principles of direct current generation, direction of current flow, basic alternating current generator, alternating and direct current voltage outputs, converting alternating current to direct current, review of the basic generator and…

  6. Combined characterization of bovine polyhemoglobin microcapsules by UV-Vis absorption spectroscopy and cyclic voltammetry.

    PubMed

    Knirsch, Marcos Camargo; Dell'Anno, Filippo; Salerno, Marco; Larosa, Claudio; Polakiewicz, Bronislaw; Eggenhöffner, Roberto; Converti, Attilio

    2017-03-01

    Polyhemoglobin produced from pure bovine hemoglobin by reaction with PEG bis(N-succynimidil succinate) as a cross-linking agent was encapsulated in gelatin and dehydrated by freeze-drying. Free carboxyhemoglobin and polyhemoglobin microcapsules were characterized by UV-Vis spectroscopy in the absorption range 450-650 nm and cyclic voltammetry in the voltage range from -0.8 to 0.6 mV to evaluate the ability to break the bond with carbon monoxide and to study the carrier's affinity for oxygen, respectively. SEM used to observe the shape of cross-linked gelatin-polyhemoglobin microparticles showed a regular distribution of globular shapes, with mean size of ~750 nm, which was ascribed to gelatin. Atomic absorption spectroscopy was also performed to detect iron presence in microparticles. Cyclic voltammetry using an Ag-AgCl electrode highlighted characteristic peaks at around -0.6 mV that were attributed to reversible oxygen bonding with iron in oxy-polyhemoglobin structure. These results suggest this technique as a powerful, direct and alternative method to evaluate the extent of hemoglobin oxygenation.

  7. Asymmetric Marcus-Hush theory for voltammetry.

    PubMed

    Laborda, Eduardo; Henstridge, Martin C; Batchelor-McAuley, Christopher; Compton, Richard G

    2013-06-21

    The current state-of-the-art in modeling the rate of electron transfer between an electroactive species and an electrode is reviewed. Experimental studies show that neither the ubiquitous Butler-Volmer model nor the more modern symmetric Marcus-Hush model are able to satisfactorily reproduce the experimental voltammetry for both solution-phase and surface-bound redox couples. These experimental deviations indicate the need for revision of the simplifying approximations used in the above models. Within this context, models encompassing asymmetry are considered which include different vibrational and solvation force constants for the electroactive species. The assumption of non-adiabatic electron transfer is also examined. These refinements have provided more satisfactory models of the electron transfer process and they enable us to gain more information about the microscopic characteristics of the system by means of simple electrochemical measurements.

  8. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's service...

  9. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's service...

  10. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's service...

  11. Electrochemical characterisation and anodic stripping voltammetry at mesoporous platinum rotating disc electrodes.

    PubMed

    Lozano-Sanchez, Pablo; Elliott, Joanne M

    2008-02-01

    Using the technique of liquid crystal templating a rotating disc electrode (RDE) was modified with a high surface area mesoporous platinum film. The surface area of the electrode was characterised by acid voltammetry, and found to be very high (ca. 86 cm(2)). Acid characterisation of the electrode produced distorted voltammograms was interpreted as being due to the extremely large surface area which produced a combination of effects such as localised pH change within the pore environment and also ohmic drop effects. Acid voltammetry in the presence of two different types of surfactant, namely Tween 20 and Triton X-100, suggested antifouling properties associated with the mesoporous deposit. Further analysis of the modified electrode using a redox couple in solution showed typical RDE behaviour although extra capacitive currents were observed due to the large surface area of the electrode. The phenomenon of underpotential deposition was exploited for the purpose of anodic stripping voltammetry and results were compared with data collected for microelectrodes. Underpotential deposition of metal ions at the mesoporous RDE was found to be similar to that at conventional platinum electrodes and mesoporous microelectrodes although the rate of surface coverage was found to be slower at a mesoporous RDE. It was found that a mesoporous RDE forms a suitable system for quantification of silver ions in solution.

  12. Transcranial alternating current stimulation modulates auditory temporal resolution in elderly people.

    PubMed

    Baltus, Alina; Vosskuhl, Johannes; Boetzel, Cindy; Herrmann, Christoph Siegfried

    2018-05-13

    Recent research provides evidence for a functional role of brain oscillations for perception. For example, auditory temporal resolution seems to be linked to individual gamma frequency of auditory cortex. Individual gamma frequency not only correlates with performance in between-channel gap detection tasks but can be modulated via auditory transcranial alternating current stimulation. Modulation of individual gamma frequency is accompanied by an improvement in gap detection performance. Aging changes electrophysiological frequency components and sensory processing mechanisms. Therefore, we conducted a study to investigate the link between individual gamma frequency and gap detection performance in elderly people using auditory transcranial alternating current stimulation. In a within-subject design, twelve participants were electrically stimulated with two individualized transcranial alternating current stimulation frequencies: 3 Hz above their individual gamma frequency (experimental condition) and 4 Hz below their individual gamma frequency (control condition) while they were performing a between-channel gap detection task. As expected, individual gamma frequencies correlated significantly with gap detection performance at baseline and in the experimental condition, transcranial alternating current stimulation modulated gap detection performance. In the control condition, stimulation did not modulate gap detection performance. In addition, in elderly, the effect of transcranial alternating current stimulation on auditory temporal resolution seems to be dependent on endogenous frequencies in auditory cortex: elderlies with slower individual gamma frequencies and lower auditory temporal resolution profit from auditory transcranial alternating current stimulation and show increased gap detection performance during stimulation. Our results strongly suggest individualized transcranial alternating current stimulation protocols for successful modulation of performance

  13. Synthesis of Benzofuran-2-One Derivatives and Evaluation of Their Antioxidant Capacity by Comparing DPPH Assay and Cyclic Voltammetry.

    PubMed

    Miceli, Martina; Roma, Elia; Rosa, Paolo; Feroci, Marta; Loreto, M Antonietta; Tofani, Daniela; Gasperi, Tecla

    2018-03-21

    The present work aimed to synthesise promising antioxidant compounds as a valuable alternative to the currently expensive and easily degradable molecules that are employed as stabilizers in industrial preparation. Taking into account our experience concerning domino Friedel-Crafts/lactonization reactions, we successfully improved and extended the previously reported methodology toward the synthesis of 3,3-disubstituted-3 H -benzofuran-2-one derivatives 9 - 20 starting from polyphenols 1 - 6 as substrates and either diethylketomalonate ( 7 ) or 3,3,3-trifluoromethyl pyruvate ( 8 ) as electrophilic counterpart. The antioxidant capacity of the most stable compounds ( 9 - 11 and 15 - 20 ) was evaluated by both DPPH assay and Cyclic Voltammetry analyses performed in alcoholic media (methanol) as well as in aprotic solvent (acetonitrile). By comparing the recorded experimental data, a remarkable activity can be attributed to few of the tested lactones.

  14. Alternating currents and shear waves in viscous electronics

    NASA Astrophysics Data System (ADS)

    Semenyakin, M.; Falkovich, G.

    2018-02-01

    Strong interaction among charge carriers can make them move like viscous fluid. Here we explore alternating current (ac) effects in viscous electronics. In the Ohmic case, incompressible current distribution in a sample adjusts fast to a time-dependent voltage on the electrodes, while in the viscous case, momentum diffusion makes for retardation and for the possibility of propagating slow shear waves. We focus on specific geometries that showcase interesting aspects of such waves: current parallel to a one-dimensional defect and current applied across a long strip. We find that the phase velocity of the wave propagating along the strip respectively increases/decreases with the frequency for no-slip/no-stress boundary conditions. This is so because when the frequency or strip width goes to zero (alternatively, viscosity go to infinity), the wavelength of the current pattern tends to infinity in the no-stress case and to a finite value in a general case. We also show that for dc current across a strip with a no-stress boundary, there are only one pair of vortices, while there is an infinite vortex chain for all other types of boundary conditions.

  15. Development and Use of a Cyclic Voltammetry Simulator to Introduce Undergraduate Students to Electrochemical Simulations

    ERIC Educational Resources Information Center

    Brown, Jay H.

    2015-01-01

    Cyclic voltammetry (CV) is a popular technique for the study of electrochemical mechanisms because the method can provide useful information on the redox couple. The technique involves the application of a potential ramp on an unstirred solution while the current is monitored, and then the ramp is reversed for a return sweep. CV is sometimes…

  16. Transient analysis for alternating over-current characteristics of HTSC power transmission cable

    NASA Astrophysics Data System (ADS)

    Lim, S. H.; Hwang, S. D.

    2006-10-01

    In this paper, the transient analysis for the alternating over-current distribution in case that the over-current was applied for a high-TC superconducting (HTSC) power transmission cable was performed. The transient analysis for the alternating over-current characteristics of HTSC power transmission cable with multi-layer is required to estimate the redistribution of the over-current between its conducting layers and to protect the cable system from the over-current in case that the quench in one or two layers of the HTSC power cable happens. For its transient analysis, the resistance generation of the conducting layers for the alternating over-current was reflected on its equivalent circuit, based on the resistance equation obtained by applying discrete Fourier transform (DFT) for the voltage and the current waveforms of the HTSC tape, which comprises each layer of the HTSC power transmission cable. It was confirmed through the numerical analysis on its equivalent circuit that after the current redistribution from the outermost layer into the inner layers first happened, the fast current redistribution between the inner layers developed as the amplitude of the alternating over-current increased.

  17. Solar cell system having alternating current output

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr. (Inventor)

    1980-01-01

    A monolithic multijunction solar cell was modified by fabricating an integrated circuit inverter on the back of the cell to produce a device capable of generating an alternating current output. In another embodiment, integrated curcuit power conditioning electronics was incorporated in a module containing a solar cell power supply.

  18. Anodic stripping voltammetry enhancement by redox magnetohydrodynamics.

    PubMed

    Clark, Emily A; Fritsch, Ingrid

    2004-04-15

    The effect of an external magnetic field on linear scan anodic stripping voltammetry (ASV) in solutions of 10(-6)-10(-7) M concentrations of lead, cadmium, and copper at mercury films on glassy carbon electrodes has been investigated. A high concentration of Hg(2+) was added to the analyte solution to induce a large cathodic current during the deposition step. Therefore, a large Lorentz force from the net flux of charge through the magnetic field resulted in convection due to magnetohydrodynamics. The faster delivery of analytes to the mercury film electrode during deposition caused an increase in the anodic stripping peaks. The effect of varying Hg(2+) concentrations (0-60 mM) and magnetic field strengths (0-1.77 T) on the enhancement of the stripping peaks was investigated. Enhancements as large as 129% for peak currents and 167% for peak areas were observed. An enhancement of approximately 100% was observed when 60 mM Fe(3+) replaced high concentrations of Hg(2+). This method of convection exhibits promise for small-volume ASV analysis with possible improved limits of detection and decreased preconcentration times.

  19. Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor.

    PubMed

    Heydari, Hamid; Gholivand, Mohammad B; Abdolmaleki, Abbas

    2016-09-01

    In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. Copyright © 2016. Published by Elsevier B.V.

  20. Square wave voltammetry at the dropping mercury electrode: Experimental

    USGS Publications Warehouse

    Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.

    1977-01-01

    Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.

  1. Direct current contamination of kilohertz frequency alternating current waveforms.

    PubMed

    Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

    2014-07-30

    Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. Published by Elsevier B.V.

  2. Direct Current Contamination of Kilohertz Frequency Alternating Current Waveforms

    PubMed Central

    Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

    2014-01-01

    Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. PMID:24820914

  3. Evaluation of homogeneous electrocatalysts by cyclic voltammetry.

    PubMed

    Rountree, Eric S; McCarthy, Brian D; Eisenhart, Thomas T; Dempsey, Jillian L

    2014-10-06

    The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (η), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed.

  4. Describing current and potential markets for alternative-fuel vehicles

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1996-03-26

    Motor vehicles are a major source of greenhouse gases, and the rising numbers of motor vehicles and miles driven could lead to more harmful emissions that may ultimately affect the world`s climate. One approach to curtailing such emissions is to use, instead of gasoline, alternative fuels: LPG, compressed natural gas, or alcohol fuels. In addition to the greenhouse gases, pollutants can be harmful to human health: ozone, CO. The Clean Air Act Amendments of 1990 authorized EPA to set National Ambient Air Quality Standards to control this. The Energy Policy Act of 1992 (EPACT) was the first new law tomore » emphasize strengthened energy security and decreased reliance on foreign oil since the oil shortages of the 1970`s. EPACT emphasized increasing the number of alternative-fuel vehicles (AFV`s) by mandating their incremental increase of use by Federal, state, and alternative fuel provider fleets over the new few years. Its goals are far from being met; alternative fuels` share remains trivial, about 0.3%, despite gains. This report describes current and potential markets for AFV`s; it begins by assessing the total vehicle stock, and then it focuses on current use of AFV`s in alternative fuel provider fleets and the potential for use of AFV`s in US households.« less

  5. A pipette-based calibration system for fast-scan cyclic voltammetry with fast response times.

    PubMed

    Ramsson, Eric S

    2016-01-01

    Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique that utilizes the oxidation and/or reduction of an analyte of interest to infer rapid changes in concentrations. In order to calibrate the resulting oxidative or reductive current, known concentrations of an analyte must be introduced under controlled settings. Here, I describe a simple and cost-effective method, using a Petri dish and pipettes, for the calibration of carbon fiber microelectrodes (CFMs) using FSCV.

  6. Cyclic voltammetry of fast conducting electrocatalytic films.

    PubMed

    Costentin, Cyrille; Savéant, Jean-Michel

    2015-07-15

    In the framework of contemporary energy challenges, cyclic voltammetry is a particularly useful tool for deciphering the kinetics of catalytic films. The case of fast conducting films is analyzed, whether conduction is of the ohmic type or proceeds through rapid electron hopping. The rate-limiting factors are then the diffusion of the substrate in solution and through the film as well as the catalytic reaction itself. The dimensionless combination of the characteristics of these factors allows reducing the number of actual parameters to a maximum of two. The kinetics of the system may then be fully analyzed with the help of a kinetic zone diagram. Observing the variations of the current-potential responses with operational parameters such as film thickness, the potential scan rate and substrate concentration allows a precise assessment of the interplay between these factors and of the values of the rate controlling factors. A series of thought experiments is described in order to render the kinetic analysis more palpable.

  7. Study of Copper and Purine-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry

    PubMed Central

    Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek

    2008-01-01

    Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes. PMID:27879715

  8. On the behavior of reduced graphene oxide based electrodes coated with dispersed platinum by alternate current methods in the electrochemical degradation of reactive dyes.

    PubMed

    Del Río, A I; García, C; Molina, J; Fernández, J; Bonastre, J; Cases, F

    2017-09-01

    The electrochemical behavior of different carbon-based electrodes with and without nanoparticles of platinum electrochemically dispersed on their surface has been studied. Among others, reduced graphene oxide based electrodes was used to determine the best conditions for the decolorization/degradation of the reactive dye C.I. Reactive Orange 4 in sulfuric medium. Firstly, the electrochemical behavior was evaluated by cyclic voltammetry. Secondly, different electrolyses were performed using two cell configurations: cell with anodic and cathodic compartments separated (divided configuration) and without any separation (undivided configuration). The best results were obtained when reduced graphene oxide based anodes were used. The degree of decolorization was monitored by spectroscopic methods and high performance liquid chromatography. It was found that all of them followed pseudo-first order kinetics. When reduced graphene oxide-based electrodes coated with dispersed platinum by alternate current methods electrodes were used, the lowest energy consumption and the higher decolorization kinetics rate were obtained. Scanning Electronic Microscopy was used to observe the morphological surface differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Cyclic Square Wave Voltammetry of Surface-Confined Quasireversible Electron Transfer Reactions.

    PubMed

    Mann, Megan A; Bottomley, Lawrence A

    2015-09-01

    The theory for cyclic square wave voltammetry of surface-confined quasireversible electrode reactions is presented and experimentally verified. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. These criteria were experimentally confirmed using two well-established surface-confined analytes. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

  10. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-phase alternating current equipment; circuit breakers. 75.900 Section 75.900 Mineral Resources MINE... Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit breakers. [Statutory Provisions] Low- and medium-voltage power circuits serving three-phase alternating current...

  11. Voltammetry as a Tool for Characterization of CdTe Quantum Dots

    PubMed Central

    Sobrova, Pavlina; Ryvolova, Marketa; Hubalek, Jaromir; Adam, Vojtech; Kizek, Rene

    2013-01-01

    Electrochemical detection of quantum dots (QDs) has already been used in numerous applications. However, QDs have not been well characterized using voltammetry, with respect to their characterization and quantification. Therefore, the main aim was to characterize CdTe QDs using cyclic and differential pulse voltammetry. The obtained peaks were identified and the detection limit (3 S/N) was estimated down to 100 fg/mL. Based on the convincing results, a new method for how to study stability and quantify the dots was suggested. Thus, the approach was further utilized for the testing of QDs stability. PMID:23807507

  12. A Cyclic Voltammetry Experiment for the Instrumental Analysis Laboratory.

    ERIC Educational Resources Information Center

    Baldwin, Richard P.; And Others

    1984-01-01

    Background information and procedures are provided for experiments that illustrate the nature of cyclic voltammetry and its application in the characterization of organic electrode processes. The experiments also demonstrate the concepts of electrochemical reversibility and diffusion-controlled mass transfer. (JN)

  13. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral...-1 Approved methods of grounding of equipment receiving power from ungrounded alternating current... receiving power from ungrounded alternating current power systems, the following methods of grounding will...

  14. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral... receiving power from ungrounded alternating current power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current power...

  15. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral... receiving power from ungrounded alternating current power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current power...

  16. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral...-1 Approved methods of grounding of equipment receiving power from ungrounded alternating current... receiving power from ungrounded alternating current power systems, the following methods of grounding will...

  17. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... portable or mobile three-phase alternating current equipment; circuit breakers. 77.900 Section 77.900... mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits supplying power to portable or mobile three-phase alternating current equipment shall be protected by...

  18. Anodic stripping voltammetry of gold nanoparticles at boron-doped diamond electrodes and its application in immunochromatographic strip tests.

    PubMed

    Ivandini, Tribidasari A; Wicaksono, Wiyogo P; Saepudin, Endang; Rismetov, Bakhadir; Einaga, Yasuaki

    2015-03-01

    Anodic stripping voltammetry (ASV) of colloidal gold-nanoparticles (AuNPs) was investigated at boron-doped diamond (BDD) electrodes in 50 mM HClO4. A deposition time of 300 s at-0.2 V (vs. Ag/AgCl) was fixed as the condition for the ASV. The voltammograms showed oxidation peaks that could be attributed to the oxidation of gold. These oxidation peaks were then investigated for potential application in immunochromatographic strip tests for the selective and quantitative detection of melamine, in which AuNPs were used as the label for the antibody of melamine. Linear regression of the oxidation peak currents appeared in the concentration range from 0.05-0.6 μg/mL melamine standard, with an estimated LOD of 0.069 μg/mL and an average relative standard deviation of 8.0%. This indicated that the method could be considered as an alternative method for selective and quantitative immunochromatographic applications. The validity was examined by the measurements of melamine injected into milk samples, which showed good recovery percentages during the measurements. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Muscle oxygenation of vastus lateralis and medialis muscles during alternating and pulsed current electrical stimulation.

    PubMed

    Aldayel, Abdulaziz; Muthalib, Makii; Jubeau, Marc; McGuigan, Michael; Nosaka, Kazunori

    2011-05-01

    This study compared between alternating and pulsed current electrical muscle stimulation (EMS) for muscle oxygenation and blood volume during isometric contractions. Nine healthy men (23-48 years) received alternating current EMS (2500 Hz) modulated at 75 Hz on the knee extensors of one leg, and pulsed current EMS (75 Hz) for the other leg separated by 2 weeks in a randomised, counter-balanced order. Pulse duration (400 μs), on-off ratio (5-15 s) and other stimulation parameters were matched between conditions and 30 isometric contractions were induced at the knee joint angle of 100° (0° full extension). Changes in tissue oxygenation index (∆TOI) and total hemoglobin volume (∆tHb) of vastus lateralis and medialis muscles over 30 contractions were assessed by a near-infrared spectroscopy, and were compared between conditions by a two-way repeated measures ANOVA. Peak torque produced during EMS increased over 30 contractions in response to the increase in the stimulation intensity for pulsed current, but not for the alternating current EMS. The torque during each isometric contraction was less stable in alternating than pulsed current EMS. The changes in ∆TOI amplitude during relaxation phases and ∆tHb amplitude were not significantly different between conditions. However, the decreases in ∆TOI amplitude during contraction phases from baseline were significantly (P < 0.05) greater for the pulsed current than alternating current from the 18th contraction (-15.6 ± 2.3 vs. -8.9 ± 1.8%) to 30th contraction (-10.7 ± 1.8 vs. -4.8 ± 1.5%). These results suggest that the muscles were less activated in the alternating current EMS when compared with the pulsed current EMS.

  20. Quasi-steady-state voltammetry of rapid electron transfer reactions at the macroscopic substrate of the scanning electrochemical microscope.

    PubMed

    Nioradze, Nikoloz; Kim, Jiyeon; Amemiya, Shigeru

    2011-02-01

    We report on a novel theory and experiment for scanning electrochemical microscopy (SECM) to enable quasi-steady-state voltammetry of rapid electron transfer (ET) reactions at macroscopic substrates. With this powerful approach, the substrate potential is cycled widely across the formal potential of a redox couple while the reactant or product of a substrate reaction is amperometrically detected at the tip in the feedback or substrate generation/tip collection mode, respectively. The plot of tip current versus substrate potential features the retraceable sigmoidal shape of a quasi-steady-state voltammogram although a transient voltammogram is obtained at the macroscopic substrate. Finite element simulations reveal that a short tip-substrate distance and a reversible substrate reaction (except under the tip) are required for quasi-steady-state voltammetry. Advantageously, a pair of quasi-steady-state voltammograms is obtained by employing both operation modes to reliably determine all transport, thermodynamic, and kinetic parameters as confirmed experimentally for rapid ET reactions of ferrocenemethanol and 7,7,8,8-tetracyanoquinodimethane at a Pt substrate with ∼0.5 μm-radius Pt tips positioned at 90 nm-1 μm distances. Standard ET rate constants of ∼7 cm/s were obtained for the latter mediator as the largest determined for a substrate reaction by SECM. Various potential applications of quasi-steady-state voltammetry are also proposed.

  1. Lead-Testing Service to Elementary and Secondary Schools Using Anodic Stripping Voltammetry

    NASA Astrophysics Data System (ADS)

    Goebel, Amanda; Vos, Tracy; Louwagie, Anne; Lundbohm, Laura; Brown, Jay H.

    2004-02-01

    This article outlines a successful community service project that involved members of our undergraduate chemistry club and area elementary schools. Elementary school students from various science classes throughout the region collected drinking water samples and mailed them to the university for analysis. Chemistry club members analyzed the water samples for possible lead contamination using anodic stripping voltammetry. The results and experimental data were returned to the science teachers for use in a variety of class projects. Chemistry club members presented their work during our annual Environmental Chemistry Conference. All participating science classes were invited to the conference. Over the years, participation in this project has steadily increased to its current enrollment of 28 science classes throughout the region.

  2. Ferrocene-Boronic Acid-Fructose Binding Based on Dual-Plate Generator-Collector Voltammetry and Square-Wave Voltammetry.

    PubMed

    Li, Meng; Xu, Su-Ying; Gross, Andrew J; Hammond, Jules L; Estrela, Pedro; Weber, James; Lacina, Karel; James, Tony D; Marken, Frank

    2015-06-10

    The interaction of ferrocene-boronic acid with fructose is investigated in aqueous 0.1 m phosphate buffer at pH 7, 8 and 9. Two voltammetric methods, based on 1) a dual-plate generator-collector micro-trench electrode (steady state) and 2) a square-wave voltammetry (transient) method, are applied and compared in terms of mechanistic resolution. A combination of experimental data is employed to obtain new insights into the binding rates and the cumulative binding constants for both the reduced ferrocene-boronic acid (pH dependent and weakly binding) and for the oxidised ferrocene-boronic acid (pH independent and strongly binding).

  3. The redox status of experimental hemorrhagic shock as measured by cyclic voltammetry.

    PubMed

    Mittal, Anubhav; Göke, Friederike; Flint, Richard; Loveday, Benjamin P T; Thompson, Nichola; Delahunt, Brett; Kilmartin, Paul A; Cooper, Garth J S; MacDonald, Julia; Hickey, Anthony; Windsor, John A; Phillips, Anthony R J

    2010-05-01

    Hemorrhagic shock (HS) leads to reactive oxygen species production. However, clinicians do not have access to bedside measurements of the redox status during HS. Cyclic voltammetry (CyV) is a simple electrochemical method of measuring redox status. The aims of this study were to 1) report the first application of cyclic voltammetry to measure the acute changes in serum redox status after HS, 2) to contrast it with another severe systemic disease with a different redox pathology (acute pancreatitis [AP]), and 3) to describe the response of CyV over time in a resolving model of AP. In the acute study, 24 male Wistar rats were randomized into three groups: groups 1 (control), 2 (AP), and 3 (HS). In the time-course study, 28 rats were randomized to a sham-control as well as 6 and 24 h post-AP cohorts, respectively.Cyclic voltammetry was performed using a three-electrode system. In the acute study, the first and second voltammetric peaks increased significantly in HS. In contrast, within the AP group, only the first voltammetric peak showed a significant increase. The first voltammetric peak correlated with plasma protein carbonyls (PCs) and with thiobarbituric acid-reactive substances, whereas the second voltammetric peak correlated positively with plasma protein carbonyls. In the second study, the first voltammetric peak correlated with physiological improvements. Here, we showed that serum CyV could respond to the serum redox change in HS and AP. Cyclic voltammetry warrants evaluation as a potential real-time beside measure of a patient's redox status during shock.

  4. Alternating current circuit theory and pulsed NMR (Nuclear Magnetic Resonance)

    NASA Astrophysics Data System (ADS)

    Gerstein, B. C.

    1987-06-01

    Pulsed NMR, by definition, deals with time varying excitations. These excitations, supplied by resonant circuits which provide a pulse of radiofrequency (frequencies in the megahertz region) power to a resonant circuit containing, among other things, a coil of wire, or inductor, in which a sample under investigation is placed for purposes of the nuclear magnetic resonance experiment. There are therefore two features of the pulse NMR experiment. First is the fact that we have available a source of continuous wave (CW) alternating current at some angular frequency, omega, measured in radians per second. This source is generally supplied by an ultrastable device called a frequency synthesizer. The second feature of the pulsed NMR experiment is that the sample is not continuously irradiated, but a pulse of radiofrequency oscillation is applied to the sample. This report discusses alternating current theory, resonant circuits and the equipment used in this experiment.

  5. Removal of Differential Capacitive Interferences in Fast-Scan Cyclic Voltammetry.

    PubMed

    Johnson, Justin A; Hobbs, Caddy N; Wightman, R Mark

    2017-06-06

    Due to its high spatiotemporal resolution, fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes enables the localized in vivo monitoring of subsecond fluctuations in electroactive neurotransmitter concentrations. In practice, resolution of the analytical signal relies on digital background subtraction for removal of the large current due to charging of the electrical double layer as well as surface faradaic reactions. However, fluctuations in this background current often occur with changes in the electrode state or ionic environment, leading to nonspecific contributions to the FSCV data that confound data analysis. Here, we both explore the origin of such shifts seen with local changes in cations and develop a model to account for their shape. Further, we describe a convolution-based method for removal of the differential capacitive contributions to the FSCV current. The method relies on the use of a small-amplitude pulse made prior to the FSCV sweep that probes the impedance of the system. To predict the nonfaradaic current response to the voltammetric sweep, the step current response is differentiated to provide an estimate of the system's impulse response function and is used to convolute the applied waveform. The generated prediction is then subtracted from the observed current to the voltammetric sweep, removing artifacts associated with electrode impedance changes. The technique is demonstrated to remove select contributions from capacitive characteristics changes of the electrode both in vitro (i.e., in flow-injection analysis) and in vivo (i.e., during a spreading depression event in an anesthetized rat).

  6. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's service... regulator unit acting on the exciter field, each switchboard must have: (1) A generator field rheostat; (2...

  7. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's service... regulator unit acting on the exciter field, each switchboard must have: (1) A generator field rheostat; (2...

  8. Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms▿ †

    PubMed Central

    Marsili, Enrico; Rollefson, Janet B.; Baron, Daniel B.; Hozalski, Raymond M.; Bond, Daniel R.

    2008-01-01

    While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 μm) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes. At low scan rates, cyclic voltammetry revealed catalytic electron transfer between cells and the electrode, similar to what has been observed for pure enzymes attached to electrodes under continuous turnover conditions. Differential pulse voltammetry and electrochemical impedance spectroscopy also revealed features that were consistent with electron transfer being mediated by an adsorbed catalyst. Multiple redox-active species were detected, revealing complexity at the outer surfaces of this bacterium. These techniques provide the basis for cataloging quantifiable, defined electron transfer phenotypes as a function of potential, electrode material, growth phase, and culture conditions and provide a framework for comparisons with other species or communities. PMID:18849456

  9. Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

    NASA Astrophysics Data System (ADS)

    Luo, X. M.; Zhang, B.; Zhang, G. P.

    2014-09-01

    Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

  10. Examining the Complex Regulation and Drug-Induced Plasticity of Dopamine Release and Uptake Using Voltammetry in Brain Slices

    PubMed Central

    2013-01-01

    Fast scan cyclic voltammetry in brain slices (slice voltammetry) has been used over the last several decades to increase substantially our understanding of the complex local regulation of dopamine release and uptake in the striatum. This technique is routinely used for the study of changes that occur in the dopamine system associated with various disease states and pharmacological treatments, and to study mechanisms of local circuitry regulation of dopamine terminal function. In the context of this Review, we compare the relative advantages of voltammetry using striatal slice preparations versus in vivo preparations, and highlight recent advances in our understanding of dopamine release and uptake in the striatum specifically from studies that use slice voltammetry in drug-naïve animals and animals with a history of psychostimulant self-administration. PMID:23581570

  11. Determination of Bosentan in Pharmaceutical Preparations by Linear Sweep, Square Wave and Differential Pulse Voltammetry Methods

    PubMed Central

    Atila, Alptug; Yilmaz, Bilal

    2015-01-01

    In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation. PMID:25901151

  12. Determination of bosentan in pharmaceutical preparations by linear sweep, square wave and differential pulse voltammetry methods.

    PubMed

    Atila, Alptug; Yilmaz, Bilal

    2015-01-01

    In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation.

  13. Evaluation of constant current alternating current iontophoresis for transdermal drug delivery.

    PubMed

    Yan, Guang; Li, S Kevin; Higuchi, William I

    2005-12-10

    Previous studies in our laboratory have demonstrated that alternating current (AC) iontophoresis can significantly decrease skin electric resistance and enhance the transport of charged permeants across skin. Flux variability of neutral permeants during AC iontophoresis was also found to be less than that of conventional direct current (DC) iontophoresis. The objectives of the present study were to evaluate flux enhancement of constant current AC transdermal iontophoresis and compare the AC flux with that of constant current DC iontophoresis. Iontophoresis studies of AC amplitude of 1, 2, and 5 mA were conducted in side-by-side diffusion cells with donor solution of 0.015, 0.15, and 1.0 M tetraethylammonium (TEA) chloride and receiver solution of phosphate buffered saline (PBS) using human epidermal membrane (HEM). Conventional constant current DC iontophoresis of 0.2 mA was also performed under similar conditions. TEA and mannitol were the model permeants. The following are the major findings in the present study. The flux of TEA increased proportionally with the AC current for all three TEA chloride concentrations and at the AC frequency used in the present study. When the permeant and its counter ion were the only ionic species in the donor chamber, the fluxes during DC iontophoresis were weakly dependent of its donor concentration. The fluxes of TEA during constant current AC iontophoresis were moderately related to the donor concentration with the highest TEA flux observed under the 1.0 M TEA chloride condition although the relationship between flux and donor concentration was not linear. A trend of decreasing electroosmotic transport with increasing donor TEA chloride concentration was observed with significant sample-to-sample variability during DC iontophoresis. Mannitol permeability was also observed to decrease with increasing TEA chloride concentration in the donor under the AC conditions, but data variability under AC was significantly smaller than that

  14. Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

    PubMed Central

    2016-01-01

    17α-Ethinyl estradiol (EE2), which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs) in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV) with a hanging mercury drop electrode (HMDE) in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at −1.16 ± 0.02 V versus Ag/AgCl. The experimental parameters were as follows: −0.7 V accumulation potential, 150 s accumulation time, and 60 mV s−1 scan rate. The limit of detection was 0.49 μg L−1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%. PMID:27738548

  15. In vivo voltammetry: from wire to wireless measurements.

    PubMed

    Crespi, Francesco; Dalessandro, Davide; Annovazzi-Lodi, Valerio; Heidbreder, Christian; Norgia, Michele

    2004-12-30

    A novel telemetric system based on either differential pulse voltammetry (DPV) or direct current amperometry (DCA) by using a diffused infrared transmission channel is presented. Unlike similar pre-existing instruments based on infrared transmission, the present system works on a single-way communication, thus avoiding problems related to cross-talking between two-way channels. The infrared channel is also immune from electromagnetic interferences from the surrounding environment. Further advancement is the development of an original miniaturised system (dimension 1cm x 1.2 cm x 0.5 cm) with reduced weight (5-6 g), suitable for affixing to the rat head and allowing real time telemetric monitoring using DCA sampling of neurotransmitters such as dopamine or serotonin every 100 ms. The set-up is based on a transmitter (TX) circuit mounted on the animal's head and connected to the electrodes inserted into its brain. The TX circuit generates the proper electrical signals for DPV or DCA, collects the electrical response of the brain and transmits it, via an infrared channel, to a receiving station (RX) interfaced with a personal computer. The PC performs the sampling and elaboration of polarographic traces in a flexible and programmable way.

  16. C-FSCV: Compressive Fast-Scan Cyclic Voltammetry for Brain Dopamine Recording.

    PubMed

    Zamani, Hossein; Bahrami, Hamid Reza; Chalwadi, Preeti; Garris, Paul A; Mohseni, Pedram

    2018-01-01

    This paper presents a novel compressive sensing framework for recording brain dopamine levels with fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode. Termed compressive FSCV (C-FSCV), this approach compressively samples the measured total current in each FSCV scan and performs basic FSCV processing steps, e.g., background current averaging and subtraction, directly with compressed measurements. The resulting background-subtracted faradaic currents, which are shown to have a block-sparse representation in the discrete cosine transform domain, are next reconstructed from their compressively sampled counterparts with the block sparse Bayesian learning algorithm. Using a previously recorded dopamine dataset, consisting of electrically evoked signals recorded in the dorsal striatum of an anesthetized rat, the C-FSCV framework is shown to be efficacious in compressing and reconstructing brain dopamine dynamics and associated voltammograms with high fidelity (correlation coefficient, ), while achieving compression ratio, CR, values as high as ~ 5. Moreover, using another set of dopamine data recorded 5 minutes after administration of amphetamine (AMPH) to an ambulatory rat, C-FSCV once again compresses (CR = 5) and reconstructs the temporal pattern of dopamine release with high fidelity ( ), leading to a true-positive rate of 96.4% in detecting AMPH-induced dopamine transients.

  17. 10 CFR 50.63 - Loss of all alternating current power.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., Limitations, and Conditions of Licenses and Construction Permits § 50.63 Loss of all alternating current power... manufacturing license under part 52 of this chapter must be able to withstand for a specified duration and recover from a station blackout as defined in § 50.2. The specified station blackout duration shall be...

  18. Study of quinones reactions with wine nucleophiles by cyclic voltammetry.

    PubMed

    Oliveira, Carla M; Barros, António S; Ferreira, António C S; Silva, Artur M S

    2016-11-15

    Quinones are electrophilic species which can react with various nucleophiles, like wine antioxidants, such as sulfur dioxide or ascorbic acid, thiols, amino acids, and numerous polyphenols. These reactions are very important in wine aging because they mediate oxygen reactions during both production and bottle aging phases. In this work, the major challenge was to determine the interaction between ortho-quinones and wine nucleophiles (amino acids, thiols, and the antioxidants SO2 and ascorbic acid), by cyclic voltammetry. Wine-model solutions with gallic acid, caffeic acid, or (+)-catechin and nucleophilic compounds were used. To understand the effect of nucleophilic addition in wine, a white wine with the same added nucleophiles was also analysed. Cyclic voltammograms were taken with glassy carbon electrode or screen-printed carbon electrodes, respectively, for wine-model and white wines solutions, in the absence and in the presence of nucleophiles. A nucleophilic order profile related to the cathodic current intensity decrease was observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. 59. View of high voltage (4160 volts alternating current) electric ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    59. View of high voltage (4160 volts alternating current) electric load center and motor control center at mezzanine level in transmitter building no. 102. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  20. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit breakers...

  1. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit breakers...

  2. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit breakers...

  3. Recent Advances in Alternating Current-Driven Organic Light-Emitting Devices.

    PubMed

    Pan, Yufeng; Xia, Yingdong; Zhang, Haijuan; Qiu, Jian; Zheng, Yiting; Chen, Yonghua; Huang, Wei

    2017-11-01

    Organic light-emitting devices (OLEDs), typically operated with constant-voltage or direct-current (DC) power sources, are candidates for next-generation solid-state lighting and displays, as they are light, thin, inexpensive, and flexible. However, researchers have focused mainly on the device itself (e.g., development of novel materials, design of the device structure, and optical outcoupling engineering), and little attention has been paid to the driving mode. Recently, an alternative concept to DC-driven OLEDs by directly driving devices using time-dependent voltages or alternating current (AC) has been explored. Here, the effects of different device structures of AC-driven OLEDs, for example, double-insulation, single-insulation, double-injection, and tandem structure, on the device performance are systematically investigated. The formation of excitons and the dielectric layer, which are important to achieve high-performance AC-driven OLEDs, are carefully considered. The importance of gaining further understanding of the fundamental properties of AC-driven OLEDs is then discussed, especially as they relate to device physics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Cortical inhibition and excitation by bilateral transcranial alternating current stimulation.

    PubMed

    Cancelli, Andrea; Cottone, Carlo; Zito, Giancarlo; Di Giorgio, Marina; Pasqualetti, Patrizio; Tecchio, Franca

    2015-01-01

    Transcranial electric stimulations (tES) with amplitude-modulated currents are promising tools to enhance neuromodulation effects. It is essential to select the correct cortical targets and inhibitory/excitatory protocols to reverse changes in specific networks. We aimed at assessing the dependence of cortical excitability changes on the current amplitude of 20 Hz transcranial alternating current stimulation (tACS) over the bilateral primary motor cortex. We chose two amplitude ranges of the stimulations, around 25 μA/cm2 and 63 μA/cm2 from peak to peak, with three values (at steps of about 2.5%) around each, to generate, respectively, inhibitory and excitatory effects of the primary motor cortex. We checked such changes online through transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). Cortical excitability changes depended upon current density (p = 0.001). Low current densities decreased MEP amplitudes (inhibition) while high current densities increased them (excitation). tACS targeting bilateral homologous cortical areas can induce online inhibition or excitation as a function of the current density.

  5. Effect of modulated alternating and direct current iontophoresis on transdermal delivery of lidocaine hydrochloride.

    PubMed

    Bhatia, Gaurav; Banga, Ajay K

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μ g/sq · cm compared to 744.81 ± 125.41 μ g/sq · cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μ g/sq · cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  6. Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.

    PubMed

    Barus, C; Romanytsia, I; Striebig, N; Garçon, V

    2016-11-01

    A Square Wave Voltammetry electrochemical method is proposed to measure phosphate in seawater as pulse techniques offer a higher sensitivity as compared to classical cyclic voltammetry. Chronoamperometry cannot be either adapted for an in situ sensor since this method requires to have controlled convection which will be impossible in a miniaturised sensor. Tests and validation of Square Wave Voltammetry parameters have been performed using an open cell and for the first time with a small volume (<400µL) laboratory prototypes. Two designs of prototypes have been compared. Using high frequency (f=250Hz) allows to obtain a linear behaviour between 0.1 and 1µmolL(-1) with a very low limit of detection of 0.05 µmolL(-1) after 60min of complexation waiting time. In order to obtain a linear regression for a larger concentration range i.e. 0.25-4µmolL(-1), a lower frequency of 2.5Hz is needed. A limit of detection of 0.1µmolL(-1) is obtained in this case after 30min of complexation waiting time for the peak measured at E=0.12V. Changing the position of the molybdenum electrode for the complexation step and moving the detection into another electrochemical cell allow to decrease the reaction time down to 5min. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Alternatives to Tenure. AAHE-ERIC/Higher Education Research Currents. March 1979.

    ERIC Educational Resources Information Center

    Linney, Thomas J.

    An overview of current literature about alternatives and variations to existing concepts of tenure of faculty is presented. Tenure continues the appointment of faculty until retirement unless there is dismissal for adequate cause or unavoidable termination because of financial exigency or change of institutional program. Academic freedom is…

  8. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral... power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current power systems, the following methods of grounding will...

  9. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral... power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current power systems, the following methods of grounding will...

  10. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral... power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current power systems, the following methods of grounding will...

  11. Cyclic voltammetry of apple fruits: Memristors in vivo.

    PubMed

    Volkov, Alexander G; Nyasani, Eunice K; Tuckett, Clayton; Blockmon, Avery L; Reedus, Jada; Volkova, Maya I

    2016-12-01

    A memristor is a resistor with memory that exhibits a pinched hysteretic relationship in cyclic voltammetry. Recently, we have found memristors in the electrical circuitry of plants and seeds. There are no publications in literature about the possible existence of memristors and electrical differentiators in fruits. Here we found that the electrostimulation of Golden Delicious or Arkansas Black apple fruits by bipolar periodic waves induces hysteresis loops with pinched points in cyclic voltammograms at low frequencies between 0.1MHz and 1MHz. At high frequencies of 1kHz, the pinched hysteresis loop transforms to a non-pinched hysteresis loop instead of a single line I=V/R for ideal memristors because the amplitude of electrical current depends on capacitance of a fruit's tissue and electrodes, frequency and direction of scanning. Electrostimulation of electrical circuits in apple fruits by periodic voltage waves also induces electrotonic potential propagation due to cell-to-cell electrical coupling with electrical differentiators. A differentiator is an electrical circuit in which the output of the circuit is approximately directly proportional to the rate of change of the input. The information gained from electrostimulation can be used to elucidate and to observe electrochemical and electrophysiological properties of electrical circuits in fruits. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride

    PubMed Central

    Banga, Ajay K.

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μg/sq·cm compared to 744.81 ± 125.41 μg/sq·cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μg/sq·cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h. PMID:24959580

  13. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits...

  14. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits...

  15. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits...

  16. Adsorptive Stripping Voltammetry of Environmental Indicators: Determination of Zinc in Algae

    ERIC Educational Resources Information Center

    Collado-Sanchez, C.; Hernandez-Brito, J. J.; Perez-Pena, J.; Torres-Padron, M. E.; Gelado-Caballero, M. D.

    2005-01-01

    A method for sample preparation and for the determination of average zinc content in algae using adsorptive stripping voltammetry are described. The students gain important didactic advantages through metal determination in environmental matrices, which include carrying out clean protocols for sampling and handling, and digesting samples using…

  17. Preparation of scanning tunneling microscopy tips using pulsed alternating current etching

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Valencia, Victor A.; Thaker, Avesh A.; Derouin, Jonathan

    An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. An Arduino Uno microcontroller was used to control the number and duration of the alternating current (AC) pulses, allowing for ready optimization of the procedures for both Pt:Ir and W tips using a single apparatus. W tips prepared using constant and pulsed AC power were compared. Tips fashioned using PACE were sharper than those etched with continuous AC power alone. Pt:Ir tips were prepared with an initial coarse etching stage using continuous AC power followed by fine etching using PACE.more » The number and potential of the finishing AC pulses was varied and scanning electron microscope imaging was used to compare the results. Finally, tip quality using the optimized procedures was verified by UHV-STM imaging. With PACE, at least 70% of the W tips and 80% of the Pt:Ir tips were of sufficiently high quality to obtain atomically resolved images of HOPG or Ni(111)« less

  18. Alternatives to animal testing: current status and future perspectives.

    PubMed

    Liebsch, Manfred; Grune, Barbara; Seiler, Andrea; Butzke, Daniel; Oelgeschläger, Michael; Pirow, Ralph; Adler, Sarah; Riebeling, Christian; Luch, Andreas

    2011-08-01

    On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book "The Principles of Humane Experimental Technique" by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on "Toxicology in the twenty-first Century", as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper.

  19. Training Effects of Alternated and Pulsed Currents on the Quadriceps Muscles of Athletes.

    PubMed

    Oliveira, Pedro; Modesto, Karenina Arrais Guida; Bottaro, Martim; Babault, Nicolas; Durigan, João Luiz Quagliotti

    2018-05-22

    The aim of the study was to evaluate the effects of 6 weeks training with different neuromuscular electrical stimulation (NMES) currents (medium alternated and low-frequency pulsed current) on muscle architecture and neuromuscular performance of competitive athletes. A double-blind controlled and randomized experimental study was carried out with 33 athletes (22.2±2.6 yrs, 74.7±9.8 kg, 176.8±6.0 cm), divided into 3 groups: mid-frequency current (MF, n=12), pulsed current (PC, n=11) and the control group (CG, n=10). Quadriceps maximal voluntary peak torque (PT) and corresponding vastus lateralis electromyographic activity, evoked torque (PT-NMES), vastus lateralis muscle thickness, fascicle length, pennation angle, and level of discomfort were assessed before and after the interventions. NMES training was performed 3 times per week and consisted of 18 sessions, 15 min/session, 6 s duration in each contraction interspersed with 18 s rest. After the training period, muscle thickness increased in the MF and PC groups (p<0.05). PT-NMES increased only in the PC group (p<0.05). All currents produced similar levels of discomfort (p>0.05). Quadriceps NMES training applied through alternated or pulsed currents produced similar effects in architecture and neuromuscular performance in competitive athletes. © Georg Thieme Verlag KG Stuttgart · New York.

  20. Simultaneous voltammetry detection of dopamine and uric acid in human serum and urine with a poly(procaterol hydrochloride) modified glassy carbon electrode.

    PubMed

    Kong, Dexian; Zhuang, Qizhao; Han, Yejian; Xu, Lanping; Wang, Zeming; Jiang, Lili; Su, Jinwei; Lu, Chun-Hua; Chi, Yuwu

    2018-08-01

    In the present study, procaterol hydrochloride (ProH) was successfully electropolymerized onto a glass carbon electrode (GCE) with simply cyclic voltammetry scans to construct a poly(procaterol hydrochloride) (p-ProH) membrane modified electrode. Compared with the bare GCE, much higher oxidation peak current responses and better peak potentials separation could be obtained for the simultaneous oxidation of dopamine (DA) and uric acid (UA), owning to the excellent electrocatalytic ability of the p-ProH membrane. And it's based on that a square wave voltammetry (SWV) method was developed to selective and simultaneous measurement of DA and UA. Under the optimum conditions, the linear dependence of oxidation peak current on analyte concentrations were found to be 1.0-100 μmol/L and 2-100 μmol/L, giving detection limits of 0.3 μmol/L and 0.5 μmol/L for DA and UA, separately. The as prepared modified electrode shows simplicity in construction with the merits of good reproducibility, high stability, passable selectivity and nice sensitivity. Finally, the proposed p-ProH membrane modified electrode was successfully devoted to the detection of DA and UA in biological fluids such as human serum and urine with acceptable results. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Evaluating the Passivation of Corrosion of API-X100 Steel with Cyclic Voltammetry

    NASA Astrophysics Data System (ADS)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2017-10-01

    In this research, cyclic voltammetry, in oxygen-free low bicarbonate-carbonate solutions, was used to study the corrosion reactions of a high-strength steel, API-X100. With cycles of different scan ranges, the effects of cycling, transpassivation, and cathodic reduction on the electrochemistry of the passive films were analyzed. It was found that carbonate in higher concentrations reduces the anodic activity and the cathodic reactions of the surface. Bicarbonate in small concentrations in solutions that contained low carbonate concentrations catalyzed dissolution and disrupted the formation of the passive films, in reference to the measured anodic currents. From the experiments, there was electrochemical evidence that with more cycles, the passive films were growing thicker, the transpassivation deteriorated the passive films, and during the cathodic reduction, the dissolution was occurring at lower potentials to facilitate later the passivation at higher potentials.

  2. Transcranial Alternating Current Stimulation (tACS) Mechanisms and Protocols

    PubMed Central

    Tavakoli, Amir V.; Yun, Kyongsik

    2017-01-01

    Perception, cognition and consciousness can be modulated as a function of oscillating neural activity, while ongoing neuronal dynamics are influenced by synaptic activity and membrane potential. Consequently, transcranial alternating current stimulation (tACS) may be used for neurological intervention. The advantageous features of tACS include the biphasic and sinusoidal tACS currents, the ability to entrain large neuronal populations, and subtle control over somatic effects. Through neuromodulation of phasic, neural activity, tACS is a powerful tool to investigate the neural correlates of cognition. The rapid development in this area requires clarity about best practices. Here we briefly introduce tACS and review the most compelling findings in the literature to provide a starting point for using tACS. We suggest that tACS protocols be based on functional brain mechanisms and appropriate control experiments, including active sham and condition blinding. PMID:28928634

  3. Alternating steady state free precession for estimation of current-induced magnetic flux density: A feasibility study.

    PubMed

    Lee, Hyunyeol; Jeong, Woo Chul; Kim, Hyung Joong; Woo, Eung Je; Park, Jaeseok

    2016-05-01

    To develop a novel, current-controlled alternating steady-state free precession (SSFP)-based conductivity imaging method and corresponding MR signal models to estimate current-induced magnetic flux density (Bz ) and conductivity distribution. In the proposed method, an SSFP pulse sequence, which is in sync with alternating current pulses, produces dual oscillating steady states while yielding nonlinear relation between signal phase and Bz . A ratiometric signal model between the states was analytically derived using the Bloch equation, wherein Bz was estimated by solving a nonlinear inverse problem for conductivity estimation. A theoretical analysis on the signal-to-noise ratio of Bz was given. Numerical and experimental studies were performed using SSFP-FID and SSFP-ECHO with current pulses positioned either before or after signal encoding to investigate the feasibility of the proposed method in conductivity estimation. Given all SSFP variants herein, SSFP-FID with alternating current pulses applied before signal encoding exhibits the highest Bz signal-to-noise ratio and conductivity contrast. Additionally, compared with conventional conductivity imaging, the proposed method benefits from rapid SSFP acquisition without apparent loss of conductivity contrast. We successfully demonstrated the feasibility of the proposed method in estimating current-induced Bz and conductivity distribution. It can be a promising, rapid imaging strategy for quantitative conductivity imaging. © 2015 Wiley Periodicals, Inc.

  4. Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

    PubMed

    Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

    2017-05-09

    The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

  5. Cyclic Voltammetry Simulations with DigiSim Software: An Upper-Level Undergraduate Experiment

    ERIC Educational Resources Information Center

    Messersmith, Stephania J.

    2014-01-01

    An upper-division undergraduate chemistry experiment is described which utilizes DigiSim software to simulate cyclic voltammetry (CV). Four mechanisms were studied: a reversible electron transfer with no subsequent or proceeding chemical reactions, a reversible electron transfer followed by a reversible chemical reaction, a reversible chemical…

  6. Detection of gamma-irradiation effect on DNA and protein using magnetic sensor and cyclic voltammetry.

    PubMed

    Park, Duck-Gun; Song, Hoon; Kishore, M B; Vértesy, G; Lee, Duk-Hyun

    2013-11-01

    In this study, a magnetic sensor utilizing Planar Hall Resistance (PHR) and cyclic Voltammetry (CV) for detecting the radiation effect was fabricated. Specifically, we applied in parallel a PHR sensor and CV device to monitor the irradiation effect on DNA and protein respectively. Through parallel measurements, we demonstrated that the PHR sensor and CV are sensitive enough to measure irradiation effect. The PHR voltage decreased by magnetic nanobead labeled DNA was slightly recovered after gamma ray irradiation. The behavior of cdk inhibitor protein p21 having a sandwich structure of Au/protein G/Ab/Ag/Ab was checked by monitoring the cyclic Voltammetry signal in analyzing the gamma ray irradiation effect.

  7. Lead-Testing Service to Elementary and Secondary Schools Using Anodic Stripping Voltammetry

    ERIC Educational Resources Information Center

    Goebel, Amanda; Vos, Tracy; Louwagie, Anne; Lundbohm, Laura; Brown, Jay H.

    2004-01-01

    The undergraduate chemistry club of the Southwest Minnesota State University offers assistance in lead-testing through the anodic stripping voltammetry (ASV) technique to elementary and secondary schools. Emphasis is given to this community service activity, which has increased club membership, and promoted discussion of water quality problems in…

  8. Oxidation management of white wines using cyclic voltammetry and multivariate process monitoring.

    PubMed

    Martins, Rui C; Oliveira, Raquel; Bento, Fatima; Geraldo, Dulce; Lopes, Vitor V; Guedes de Pinho, Paula; Oliveira, Carla M; Silva Ferreira, Antonio C

    2008-12-24

    The development of a fingerprinting strategy capable to evaluate the "oxidation status" of white wines based on cyclic voltammetry is proposed here. It is known that the levels of specific antioxidants and redox mechanisms may be evaluated by cyclic voltammetry. This electrochemical technique was applied on two sets of samples. One group was composed of normal aged white wines and a second group obtained from a white wine forced aging protocol with different oxygen, SO(2), pH, and temperature regimens. A study of antioxidant additions, namely ascorbic acid, was also made in order to establish a statistical link between voltammogram fingerprints and chemical antioxidant substances. It was observed that the oxidation curve presented typical features, which enables sample discrimination according to age, oxygen consumption, and antioxidant additions. In fact, it was possible to place the results into four significant orthogonal directions, compressing 99.8% of nonrandom features. Attempts were made to make voltammogram fingerprinting a tool for monitoring oxidation management. For this purpose, a supervised multivariate control chart was developed using a control sample as reference. When white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity. Finally, quantification of substances implicated in the oxidation process as reagents (antioxidants) and products (off-flavors) was tried using a supervised algorithmic the partial least square regression analysis. Good correlations (r > 0.93) were observed for ascorbic acid, Folin-Ciocalteu index, total SO(2), methional, and phenylacetaldehyde. These results show that cyclic voltammetry fingerprinting can be used to monitor and diagnose the effects of wine oxidation.

  9. Effect of polyvinylpyrrolidone content on alternating current conductivity of polyaniline

    NASA Astrophysics Data System (ADS)

    Megha, R.; Kumar, T. G. Naveen; Ravikiran, Y. T.; Prakash, H. G. Raj; Revanasiddappa, M.; Kumari, S. C. Vijaya

    2018-05-01

    In the present work, Polyaniline (PANI) and Polyaniline-polyvinylpyrrolidone (PANI-PVP) composites of two different weight percentages of PVP were synthesized separately by simple chemical polymerization method. The interaction between PANI and PVP in each of the composite was confirmed by Attenuated total reflection infrared spectroscopic (AT-IR) technique. The alternate current (AC) response characteristics at room temperature of PANI and the composites in the frequency range 50 Hz-1 MHz were comparatively studied. Both the composites have shown decreased conductivity as compared to that of PANI.

  10. Current Faculty Development Practices for Alternative Delivery Systems in Christian Higher Education Institutions: A Qualitative Study

    ERIC Educational Resources Information Center

    Yates, Steven Lowell

    2009-01-01

    This research study was an investigation of current faculty development practices for alternative delivery systems. Attention was given to faculty development in general as well as specific facets of faculty development for alternative delivery systems. Future or intended faculty development practices were pursued, along with factors that…

  11. Dimensionless factors for an alternating-current non-thermal arc plasma

    NASA Astrophysics Data System (ADS)

    Zhang, Si-Yuan; Li, Xiao-Song; Liu, Jin-Bao; Liu, Jing-Lin; Li, He-Ping; Zhu, Ai-Min

    2016-12-01

    A gliding arc discharge, as a source of warm plasma combining advantages of both thermal and cold plasmas, would have promising application prospects in the fields of fuel conversion, combustion enhancement, material synthesis, surface modifications, pollution control, etc. In order to gain insight into the features of an alternating-current gliding arc discharge plasma, three dimensionless factors, i.e., the extinction span (ψ), current lag (δ), and heating lag (χ) factors are proposed in this letter based on the measured waveforms of the discharge voltage and current in an AC gliding arc discharge plasma. The influences of the driving frequency of the power supply (f) on these three dimensionless parameters are investigated experimentally with the explanations on the physical meanings of these factors. The experimental results show that a higher value of f would lead to the lower values of ψ and δ, as well as a higher value of χ. These experimental phenomena indicate a lower threshold ignition voltage of the discharges, a lower current-growth inertia of the gliding arcs and a larger relative thermal inertia of the plasmas with increase the driving frequency of the power supply in the operating parameter range studied in this letter.

  12. Hitchhiker's Guide to Voltammetry: Acute and Chronic Electrodes for in Vivo Fast-Scan Cyclic Voltammetry.

    PubMed

    Rodeberg, Nathan T; Sandberg, Stefan G; Johnson, Justin A; Phillips, Paul E M; Wightman, R Mark

    2017-02-15

    Fast-scan cyclic voltammetry (FSCV) has been used for over 20 years to study rapid neurotransmission in awake and behaving animals. These experiments were first carried out with carbon-fiber microelectrodes (CFMs) encased in borosilicate glass, which can be inserted into the brain through micromanipulators and guide cannulas. More recently, chronically implantable CFMs constructed with small diameter fused-silica have been introduced. These electrodes can be affixed in the brain with minimal tissue response, which permits longitudinal measurements of neurotransmission in single recording locations during behavior. Both electrode designs have been used to make novel discoveries in the fields of neurobiology, behavioral neuroscience, and psychopharmacology. The purpose of this Review is to address important considerations for the use of FSCV to study neurotransmitters in awake and behaving animals, with a focus on measurements of striatal dopamine. Common issues concerning experimental design, data collection, and calibration are addressed. When necessary, differences between the two methodologies (acute vs chronic recordings) are discussed. The topics raised in this Review are particularly important as the field moves beyond dopamine toward new neurochemicals and brain regions.

  13. Method and apparatus for detecting cyber attacks on an alternating current power grid

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McEachern, Alexander; Hofmann, Ronald

    A method and apparatus for detecting cyber attacks on remotely-operable elements of an alternating current distribution grid. Two state estimates of the distribution grid are prepared, one of which uses micro-synchrophasors. A difference between the two state estimates indicates a possible cyber attack.

  14. Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

    DOEpatents

    Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

    2012-06-05

    A system is provided for controlling two alternating current (AC) machines via a five-phase PWM inverter module. The system comprises a first control loop, a second control loop, and a current command adjustment module. The current command adjustment module operates in conjunction with the first control loop and the second control loop to continuously adjust current command signals that control the first AC machine and the second AC machine such that they share the input voltage available to them without compromising the target mechanical output power of either machine. This way, even when the phase voltage available to either one of the machines decreases, that machine outputs its target mechanical output power.

  15. Alternating current breakdown voltage of ice electret

    NASA Astrophysics Data System (ADS)

    Oshika, Y.; Tsuchiya, Y.; Okumura, T.; Muramoto, Y.

    2017-09-01

    Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

  16. Effect of an alternating current electric field on Co(OH)2 periodic precipitation

    NASA Astrophysics Data System (ADS)

    Karam, Tony; Sultan, Rabih

    2013-02-01

    The present paper studies the effect of an alternating current (AC) electric field on Co(OH)2 Liesegang patterns. In the presence of an AC electric field, the band spacing increases with spacing number, but reaches a plateau at large spacing (or band) numbers. The band spacing increases with applied AC voltage, but to a much lesser extent than the effect of a DC electric field under the same applied voltage [see R. Sultan, R. Halabieh, Chem. Phys. Lett. 332 (2000) 331][1]. At low enough applied voltage, the band spacing increases with frequency. At higher voltages, the band spacing becomes independent of the field frequency. The effect of concentration of the inner electrolyte (Co2+), exactly opposes that observed under DC electric field; i.e., the band spacing decreases with increasing concentration. The dynamics were shown to be governed by a competitive scenario between the diffusion gradient and the alternating current electric field factor.

  17. Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro

    2014-12-01

    Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating current (AC) power source. The plasma column extended beyond the water-cooled stainless steel electrodes and was stabilized by matching the flow speed of the turbulent air jet with the rated output power. Comprehensive investigations were performed using high-speed movies measured over the plasma column, synchronized with simultaneously recorded current and voltage waveforms. Dynamic details of the novel non-equilibrium discharge are revealed, which is characterized by a sinusoidal current waveform with amplitude stabilized at around 200 mA intermediate between thermal arc and glow discharge, shedding light to the governing mechanism of the sustained spark-suppressed AC gliding arc discharge.

  18. Microbial biosensor for detection of methyl parathion using screen printed carbon electrode and cyclic voltammetry.

    PubMed

    Kumar, Jitendra; D'Souza, S F

    2011-07-15

    Whole cells of recombinant Escherichia coli were immobilized on the screen printed carbon electrode (SPCE) using glutaraldehyde. Recombinant E. coli was having high periplasmic expression of organophosphorus hydrolase enzyme, which hydrolyzes the methyl parathion into two products, p-nitrophenol and dimethyl thiophosphoric acid. Cells immobilized SPCE was studied under SEM. Cells immobilized SPCE was associated with cyclic voltammetry and cyclic voltammograms were recorded before and after hydrolysis of methyl parathion. Detection was calibrated based on the relationship between the changes in the current observed at +0.1 V potential, because of redox behavior of the hydrolyzed product p-nitrophenol. As concentration of methyl parathion was increased the oxidation current also increased. Only 20 μl volume of the sample was required for analysis. Detection range of biosensor was calibrated between 2 and 80 μM of methyl parathion from the linear range of calibration plot. A single immobilized SPCE was reused for 32 reactions with retention of 80% of its initial enzyme activity. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Voltammetry of naltrexone in commercial formulation and human body fluids: Quantification and pharmacokinetic studies.

    PubMed

    Ghoneim, Mohamed M; El-Desoky, Hanaa S; Abdel-Galeil, Mohamed M

    2011-06-01

    Naltrexone HCl (NAL.HCl) has been reduced at the mercury electrode in Britton-Robinson universal buffer of pH values 2-11 with a mechanism involving the quasi-reversible uptake of the first transferring electron followed by a rate-determining protonation step of its C=O double bond at position C-6. Simple, sensitive, selective and reliable linear-sweep and square-wave adsorptive cathodic stripping voltammetry methods have been described for trace quantitation of NAL.HCl in bulk form, commercial formulation and human body fluids without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis. Limits of quantitation of 6.0×10(-9)M and 8.0×10(-10)M NAL.HCl in bulk form or commercial formulation and of 9.0×10(-9) and 1.0×10(-9)M NAL.HCl in spiked human serum samples were achieved by the described linear and square-wave stripping voltammetry methods, respectively. Furthermore, pharmacokinetic parameters of the drug in human plasma samples of healthy volunteers following the administration of an oral single dose of 50mg NAL.HCl (one Revia(®) tablet) were estimated by means of the described square-wave stripping voltammetry method without interferences from the drug's metabolites and/or endogenous human plasma constituents. The estimated pharmacokinetic parameters were favorably compared with those reported in literature. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Thin-layer voltammetry of soluble species on screen-printed electrodes: proof of concept.

    PubMed

    Botasini, S; Martí, A C; Méndez, E

    2016-10-17

    Thin-layer diffusion conditions were accomplished on screen-printed electrodes by placing a controlled-weight onto the cast solution and allowing for its natural spreading. The restricted diffusive conditions were assessed by cyclic voltammetry at low voltage scan rates and electrochemical impedance spectroscopy. The relationship between the weight exerted over the drop and the thin-layer thickness achieved was determined, in such a way that the simple experimental set-up designed for this work could be developed into a commercial device with variable control of the thin-layer conditions. The experimental results obtained resemble those reported for the voltammetric features of electroactive soluble species employing electrodes modified with carbon nanotubes or graphene layers, suggesting that the attainment of the benefits reported for these nanomaterials could be done simply by forcing the solution to spread over the screen-printed electrodic system to form a thin layer solution. The advantages of thin-layer voltammetry in the kinetic characterization of quasi-reversible and irreversible processes are highlighted.

  1. An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes.

    PubMed

    Wu, Xiaojian; Ramiah Rajasekaran, Pradeep; Martin, Charles R

    2016-04-26

    Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an electrokinetic phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.

  2. Large amplitude Fourier transformed ac voltammetry at a rotating disc electrode: a versatile technique for covering Levich and flow rate insensitive regimes in a single experiment.

    PubMed

    Bano, Kiran; Kennedy, Gareth F; Zhang, Jie; Bond, Alan M

    2012-04-14

    The theory for large amplitude Fourier transformed ac voltammetry at a rotating disc electrode is described. Resolution of time domain data into dc and ac harmonic components reveals that the mass transport for the dc component is controlled by convective-diffusion, while the background free higher order harmonic components are flow rate insensitive and mainly governed by linear diffusion. Thus, remarkable versatility is available; Levich behaviour of the dc component limiting current provides diffusion coefficient values and access to higher harmonics allows fast electrode kinetics to be probed. Two series of experiments (dc and ac voltammetry) have been required to extract these parameters; here large amplitude ac voltammetry with RDE methodology is used to demonstrate that kinetics and diffusion coefficient information can be extracted from a single experiment. To demonstrate the power of this approach, theoretical and experimental comparisons of data obtained for the reversible [Ru(NH(3))(6)](3+/2+) and quasi-reversible [Fe(CN)(6)](3-/4-) electron transfer processes are presented over a wide range of electrode rotation rates and with different concentrations and electrode materials. Excellent agreement of experimental and simulated data is achieved, which allows parameters such as electron transfer rate, diffusion coefficient, uncompensated resistance and others to be determined using a strategically applied approach that takes into account the different levels of sensitivity of each parameter to the dc or the ac harmonic.

  3. Inhibition of motor cortex excitability with 15Hz transcranial alternating current stimulation (tACS).

    PubMed

    Zaghi, Soroush; de Freitas Rezende, Larissa; de Oliveira, Laís Machado; El-Nazer, Rasheda; Menning, Sanne; Tadini, Laura; Fregni, Felipe

    2010-08-02

    There remains a lack of solid evidence showing whether transcranial stimulation with weak alternating current (transcranial alternating current stimulation, tACS) can in fact induce significant neurophysiological effects. Previously, a study in which tACS was applied for 2 and 5min with current density=0.16-0.25A/m(2) was unable to show robust effects on cortical excitability. Here we applied tACS at a significantly higher current density (0.80A/m(2)) for a considerably longer duration (20min) and were indeed able to demonstrate measurable changes to cortical excitability. Our results show that active 15Hz tACS of the motor cortex (electrodes placed at C3 and C4) significantly diminished the amplitude of motor evoked potentials and decreased intracortical facilitation (ICF) as compared to baseline and sham stimulation. In addition, we show that our method of sham tACS is a reliable control condition. These results support the notion that AC stimulation with weak currents can induce significant changes in brain excitability; in this case, 15Hz tACS led to a pattern of inhibition of cortical excitability. We propose that tACS may have a dampening effect on cortical networks and perhaps interfere with the temporal and spatial summation of weak subthreshold electric potentials. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

  4. Alternating current corona discharge/atmospheric pressure chemical ionization for mass spectrometry.

    PubMed

    Habib, Ahsan; Usmanov, Dilshadbek; Ninomiya, Satoshi; Chen, Lee Chuin; Hiraoka, Kenzo

    2013-12-30

    Although alternating current (ac) corona discharge has been widely used in the fields of material science and technology, no reports have been published on its application to an atmospheric pressure chemical ionization (APCI) ion source. In this work, ac corona discharge for an APCI ion source has been examined for the first time. The ambient atmospheric pressure ac corona discharge (15 kHz, 2.6 kVptp ) was generated by using a stainless steel acupuncture needle. The generated ions were measured using an ion trap mass spectrometer. A comparative study on ac and direct current (dc) corona APCI ion sources was carried out using triacetone triperoxide and trinitrotoluene as test samples. The ac corona discharge gave ion signals as strong as dc corona discharge for both positive and negative ion modes. In addition, softer ionization was obtained with ac corona discharge than with dc corona discharge. The erosion of the needle tip induced by ac corona was less than that obtained with positive mode dc corona. A good 'yardstick' for assessing ac corona is that it can be used for both positive and negative ion modes without changing the polarity of the high-voltage power supply. Thus, ac corona can be an alternative to conventional dc corona for APCI ion sources. Copyright © 2013 John Wiley & Sons, Ltd.

  5. Tracking degradation in lithium iron phosphate batteries using differential thermal voltammetry

    NASA Astrophysics Data System (ADS)

    Shibagaki, Toshio; Merla, Yu; Offer, Gregory J.

    2018-01-01

    Diagnosing the state-of-health of lithium ion batteries in-operando is becoming increasingly important for multiple applications. We report the application of differential thermal voltammetry (DTV) to lithium iron phosphate (LFP) cells for the first time, and demonstrate that the technique is capable of diagnosing degradation in a similar way to incremental capacity analysis (ICA). DTV has the advantage of not requiring current and works for multiple cells in parallel, and is less sensitive to temperature introducing errors. Cells were aged by holding at 100% SOC or cycling at 1C charge, 6D discharge, both at an elevated temperature of 45 °C under forced air convection. Cells were periodically characterised, measuring capacity fade, resistance increase (power fade), and DTV fingerprints. The DTV results for both cells correlated well with both capacity and power, suggesting they could be used to diagnose SOH in-operando for both charge and discharge. The DTV peak-to-peak capacity correlated well with total capacity fade for the cycled cell, suggesting that it should be possible to estimate SOC and SOH from DTV for incomplete cycles within the voltage hysteresis region of an LFP cell.

  6. Real-time monitoring of electrically evoked catecholamine signals in the songbird striatum using in vivo fast-scan cyclic voltammetry

    PubMed Central

    Smith, Amanda R.; Garris, Paul A.; Casto, Joseph M.

    2015-01-01

    Fast-scan cyclic voltammetry is a powerful technique for monitoring rapid changes in extracellular neurotransmitter levels in the brain. In vivo fast-scan cyclic voltammetry has been used extensively in mammalian models to characterize dopamine signals in both anesthetized and awake preparations, but has yet to be applied to a non-mammalian vertebrate. The goal of this study was to establish in vivo fast-scan cyclic voltammetry in a songbird, the European starling, to facilitate real-time measurements of extracellular catecholamine levels in the avian striatum. In urethane-anesthetized starlings, changes in catecholamine levels were evoked by electrical stimulation of the ventral tegmental area and measured at carbon-fiber microelectrodes positioned in the medial and lateral striata. Catecholamines were elicited by different stimulations, including trains related to phasic dopamine signaling in the rat, and were analyzed to quantify presynaptic mechanisms governing exocytotic release and neuronal uptake. Evoked extracellular catecholamine dynamics, maximal amplitude of the evoked catecholamine signal, and parameters for catecholamine release and uptake did not differ between striatal regions and were similar to those determined for dopamine in the rat dorsomedial striatum under similar conditions. Chemical identification of measured catecholamine by its voltammogram was consistent with the presence of both dopamine and norepinephrine in striatal tissue content. However, the high ratio of dopamine to norepinephrine in tissue content and the greater sensitivity of the carbon-fiber microelectrode to dopamine compared to norepinephrine favored the measurement of dopamine. Thus, converging evidence suggests that dopamine was the predominate analyte of the electrically evoked catecholamine signal measured in the striatum by fast-scan cyclic voltammetry. Overall, comparisons between the characteristics of these evoked signals suggested a similar presynaptic regulation of

  7. Determination of diclofenac using electromembrane extraction coupled with stripping FFT continuous cyclic voltammetry.

    PubMed

    Mofidi, Zahra; Norouzi, Parviz; Seidi, Shahram; Ganjali, Mohammad Reza

    2017-06-15

    For the first time, on-line and ultra-sensitive determination of trace amount of diclofenac in whole blood sample was performed by coupling of electromembrane extraction (EME) and stripping fast Fourier transform continuous cyclic voltammetry (SFFTCCV). In SFFTCCV, the potential waveform was continuously applied on a carbon paste electrode and the electrode response was obtained by subtracting the background current and integrating the current in potential range of the analyte oxidation. A central composite design was used for the optimization of the parameters influencing the extraction efficiency. By applying a DC potential of 20 V during 28 min of extraction, diclofenac was migrated from the sample solution (pH 5), into a thin layer of 1-octanol immobilized in the pores of a porous flat sheet membrane and then into the acceptor solution (pH 7). The method presented a good linearity within the range of 5-1000 ng mL -1 with a determination coefficient of 0.993 in whole blood samples. Limits of detection (LOD) and quantification (LOQ) were found to be 1.0 ng mL -1 and 5.0 ng mL -1 respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

    NASA Astrophysics Data System (ADS)

    Takmakov, Pavel; McKinney, Collin J.; Carelli, Regina M.; Wightman, R. Mark

    2011-07-01

    Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals.

  9. Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

    PubMed Central

    Takmakov, Pavel; McKinney, Collin J.; Carelli, Regina M.; Wightman, R. Mark

    2011-01-01

    Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals. PMID:21806203

  10. The theory of cyclic voltammetry of electrochemically heterogeneous surfaces: comparison of different models for surface geometry and applications to highly ordered pyrolytic graphite.

    PubMed

    Ward, Kristopher R; Lawrence, Nathan S; Hartshorne, R Seth; Compton, Richard G

    2012-05-28

    The cyclic voltammetry at electrodes composed of multiple electroactive materials, where zones of one highly active material are distributed over a substrate of a second, less active material, is investigated by simulation. The two materials are assumed to differ in terms of their electrochemical rate constants towards any given redox couple. For a one-electron oxidation or reduction, the effect on voltammetry of the size and relative surface coverages of the zones as well as the rate constant of the slower zone are considered for systems where it is much slower than the rate constant of the faster zones. The occurrence of split peak cyclic voltammetry where two peaks are observed in the forward sweep, is studied in terms of the diffusional effects present in the system. A number of surface geometries are compared: specifically the more active zones are modelled as long, thin bands, as steps in the surface, as discs, and as rings (similar to a partially blocked electrode). Similar voltammetry for the band, step and ring models is seen but the disc geometry shows significant differences. Finally, the simulation technique is applied to the modelling of highly-ordered pyrolytic graphite (HOPG) surface and experimental conditions under which it may be possible to observe split peak voltammetry are predicted.

  11. Electrochemical investigation of [Co4(μ3-O)4(μ-OAc)4(py)4] and peroxides by cyclic voltammetry.

    PubMed

    Clatworthy, Edwin B; Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

    2016-12-13

    Two oxidative redox processes of the neutral cobalt(iii) cubane, [Co 4 (μ 3 -O) 4 (μ-OAc) 4 (py) 4 ], were investigated by cyclic voltammetry at a glassy carbon electrode in acetonitrile. In addition to the first quasi-reversible one-electron oxidation at E 1/2 = 0.283 V vs. Fc 0/+ , a second quasi-reversible one-electron oxidation was observed at E 1/2 = 1.44 V vs. Fc 0/+ . Oxidation at this potential does not facilitate water oxidation. In the presence of tert-butylhydroperoxide the peak current of this second oxidation increases, suggesting oxidation of the peroxide by the doubly oxidised cubane.

  12. Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing

    NASA Technical Reports Server (NTRS)

    Chung, Deborah D. L.; Shui, Xiaoping; Frysz, Christine A.

    1993-01-01

    Hairy carbon is a new material developed by growing submicron carbon filaments on conventional carbon substrates. Typical substrate materials include carbon black, graphite powder, carbon fibers, and glassy carbon. A catalyst is used to initiate hair growth with carbonaceous gases serving as the carbon source. To study the electrochemical behavior of hairy carbons, cyclic voltammetry (CV) and discharge testing were conducted. In both cases, hairy carbon results surpassed those of the substrate material alone.

  13. Current Pharmaceutical Treatments and Alternative Therapies of Parkinson's Disease

    PubMed Central

    Dong, Jie; Cui, Yanhua; Li, Song; Le, Weidong

    2016-01-01

    Over the decades, pharmaceutical treatments, particularly dopaminergic (DAergic) drugs have been considered as the main therapy against motor symptoms of Parkinson's disease (PD). It is proposed that DAergic drugs in combination with other medications, such as monoamine oxidase type B inhibitors, catechol-O-methyl transferase inhibitors, anticholinergics and other newly developed non-DAergic drugs can make a better control of motor symptoms or alleviate levodopa-induced motor complications. Moreover, non-motor symptoms of PD, such as cognitive, neuropsychiatric, sleep, autonomic and sensory disturbances caused by intrinsic PD pathology or drug-induced side effects, are gaining increasing attention and urgently need to be taken care of due to their impact on quality of life. Currently, neuroprotective therapies have been investigated extensively in pre-clinical studies, and some of them have been subjected to clinical trials. Furthermore, non-pharmaceutical treatments, including deep brain stimulation (DBS), gene therapy, cell replacement therapy and some complementary managements, such as Tai chi, Yoga, traditional herbs and molecular targeted therapies have also been considered as effective alternative therapies to classical pharmaceutics. This review will provide us updated information regarding the current drugs and non-drugs therapies for PD. PMID:26585523

  14. Experimental Analysis of Critical Current and Alternating Current Losses of High-Temperature Superconductor Tape with Resin and Gallium-Indium-Tin

    PubMed Central

    Sun, Yajie; Zhang, Huiming; Meng, Yuanzhu

    2018-01-01

    This paper experimentally analyzes the critical current degradation and AC (alternating current) losses of second-generation (2G) high-temperature superconductor (HTS) tape during the impregnation process. Two impregnation materials were utilized: Gallium-Indium-Tin (GaInSn), and an epoxy resin, Araldite. The critical current of the impregnation materials was measured after different thermal cycles and compared with the tape with no impregnation process. The experimental results show that the critical current of Yttrium Barium Copper Oxide (YBCO) short samples varies between differently impregnated materials. The resin, Araldite, degraded the critical current; however, the GaInSn showed no degradation. Two degradation patterns with Araldite were identified due to the impregnation process, and the corresponding causes were analyzed. We further measured the AC losses of tapes impregnated with liquid metal at different frequencies, up to 600 Hz. Based on the experimental results, GaInSn liquid metal should be the most suitable impregnation material in terms of critical current degradation. PMID:29642490

  15. Experimental Analysis of Critical Current and Alternating Current Losses of High-Temperature Superconductor Tape with Resin and Gallium-Indium-Tin.

    PubMed

    Yu, Dongmin; Sun, Yajie; Zhang, Huiming; Meng, Yuanzhu; Liu, Huanan

    2018-04-08

    This paper experimentally analyzes the critical current degradation and AC (alternating current) losses of second-generation (2G) high-temperature superconductor (HTS) tape during the impregnation process. Two impregnation materials were utilized: Gallium-Indium-Tin (GaInSn), and an epoxy resin, Araldite. The critical current of the impregnation materials was measured after different thermal cycles and compared with the tape with no impregnation process. The experimental results show that the critical current of Yttrium Barium Copper Oxide (YBCO) short samples varies between differently impregnated materials. The resin, Araldite, degraded the critical current; however, the GaInSn showed no degradation. Two degradation patterns with Araldite were identified due to the impregnation process, and the corresponding causes were analyzed. We further measured the AC losses of tapes impregnated with liquid metal at different frequencies, up to 600 Hz. Based on the experimental results, GaInSn liquid metal should be the most suitable impregnation material in terms of critical current degradation.

  16. Exhaustive thin-layer cyclic voltammetry for absolute multianalyte halide detection.

    PubMed

    Cuartero, Maria; Crespo, Gastón A; Ghahraman Afshar, Majid; Bakker, Eric

    2014-11-18

    Water analysis is one of the greatest challenges in the field of environmental analysis. In particular, seawater analysis is often difficult because a large amount of NaCl may mask the determination of other ions, i.e., nutrients, halides, and carbonate species. We demonstrate here the use of thin-layer samples controlled by cyclic voltammetry to analyze water samples for chloride, bromide, and iodide. The fabrication of a microfluidic electrochemical cell based on a Ag/AgX wire (working electrode) inserted into a tubular Nafion membrane is described, which confines the sample solution layer to less than 15 μm. By increasing the applied potential, halide ions present in the thin-layer sample (X(-)) are electrodeposited on the working electrode as AgX, while their respective counterions are transported across the perm-selective membrane to an outer solution. Thin-layer cyclic voltammetry allows us to obtain separated peaks in mixed samples of these three halides, finding a linear relationship between the halide concentration and the corresponding peak area from about 10(-5) to 0.1 M for bromide and iodide and from 10(-4) to 0.6 M for chloride. This technique was successfully applied for the halide analysis in tap, mineral, and river water as well as seawater. The proposed methodology is absolute and potentially calibration-free, as evidenced by an observed 2.5% RSD cell to cell reproducibility and independence from the operating temperature.

  17. Development and Use of an Open-Source, User-Friendly Package to Simulate Voltammetry Experiments

    ERIC Educational Resources Information Center

    Wang, Shuo; Wang, Jing; Gao, Yanjing

    2017-01-01

    An open-source electrochemistry simulation package has been developed that simulates the electrode processes of four reaction mechanisms and two typical electroanalysis techniques: cyclic voltammetry and chronoamperometry. Unlike other open-source simulation software, this package balances the features with ease of learning and implementation and…

  18. Enhancement of multitasking performance and neural oscillations by transcranial alternating current stimulation

    PubMed Central

    Zanto, Theodore P.; van Schouwenburg, Martine R.; Gazzaley, Adam

    2017-01-01

    Multitasking is associated with the generation of stimulus-locked theta (4–7 Hz) oscillations arising from prefrontal cortex (PFC). Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that influences endogenous brain oscillations. Here, we investigate whether applying alternating current stimulation within the theta frequency band would affect multitasking performance, and explore tACS effects on neurophysiological measures. Brief runs of bilateral PFC theta-tACS were applied while participants were engaged in a multitasking paradigm accompanied by electroencephalography (EEG) data collection. Unlike an active control group, a tACS stimulation group showed enhancement of multitasking performance after a 90-minute session (F1,35 = 6.63, p = 0.01, ηp2 = 0.16; effect size = 0.96), coupled with significant modulation of posterior beta (13–30 Hz) activities (F1,32 = 7.66, p = 0.009, ηp2 = 0.19; effect size = 0.96). Across participant regression analyses indicated that those participants with greater increases in frontal theta, alpha and beta oscillations exhibited greater multitasking performance improvements. These results indicate frontal theta-tACS generates benefits on multitasking performance accompanied by widespread neuronal oscillatory changes, and suggests that future tACS studies with extended treatments are worth exploring as promising tools for cognitive enhancement. PMID:28562642

  19. Enhancement of multitasking performance and neural oscillations by transcranial alternating current stimulation.

    PubMed

    Hsu, Wan-Yu; Zanto, Theodore P; van Schouwenburg, Martine R; Gazzaley, Adam

    2017-01-01

    Multitasking is associated with the generation of stimulus-locked theta (4-7 Hz) oscillations arising from prefrontal cortex (PFC). Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that influences endogenous brain oscillations. Here, we investigate whether applying alternating current stimulation within the theta frequency band would affect multitasking performance, and explore tACS effects on neurophysiological measures. Brief runs of bilateral PFC theta-tACS were applied while participants were engaged in a multitasking paradigm accompanied by electroencephalography (EEG) data collection. Unlike an active control group, a tACS stimulation group showed enhancement of multitasking performance after a 90-minute session (F1,35 = 6.63, p = 0.01, ηp2 = 0.16; effect size = 0.96), coupled with significant modulation of posterior beta (13-30 Hz) activities (F1,32 = 7.66, p = 0.009, ηp2 = 0.19; effect size = 0.96). Across participant regression analyses indicated that those participants with greater increases in frontal theta, alpha and beta oscillations exhibited greater multitasking performance improvements. These results indicate frontal theta-tACS generates benefits on multitasking performance accompanied by widespread neuronal oscillatory changes, and suggests that future tACS studies with extended treatments are worth exploring as promising tools for cognitive enhancement.

  20. Direct-current arc and alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials

    USGS Publications Warehouse

    Grimes, D.J.; Marranzino, A.P.

    1968-01-01

    Two spectrographic methods are used in mobile field laboratories of the U. S. Geological Survey. In the direct-current arc method, the ground sample is mixed with graphite powder, packed into an electrode crater, and burned to completion. Thirty elements are determined. In the spark method, the sample, ground to pass a 150-mesh screen, is digested in hydrofluoric acid followed by evaporation to dryness and dissolution in aqua regia. The solution is fed into the spark gap by means of a rotating-disk electrode arrangement and is excited with an alternating-current spark discharge. Fourteen elements are determined. In both techniques, light is recorded on Spectrum Analysis No. 1, 35-millimeter film, and the spectra are compared visually with those of standard films.

  1. Nitrate removal from pharmaceutical wastewater using microbial electrochemical system supplied through low frequency-low voltage alternating electric current.

    PubMed

    Hoseinzadeh, Edris; Rezaee, Abbas; Farzadkia, Mahdi

    2018-04-01

    In this study, a microbial electrochemical system (MES) was designed to evaluate the effects of a low frequency-low voltage alternating electrical current on denitrification efficacy in the presence of ibuprofen as a low biodegradable organic carbon source. Cylindrical carbon cloth and stainless steel mesh electrodes containing a consortium of heterotrophic and autotrophic bacteria were mounted in the wall of the designed laboratory-scale bioreactor. The effects of inlet nitrate concentration (50-800mgL -1 ), retention time (2.5-24h), waveform magnitude (0.1-9.6V p-p ), adjustable direct current voltage added to offset voltage (0.1-4.9V), alternating current frequency (10-60Hz), and waveforms (sinusoidal, square, and ramp) were studied in this work. The results showed that the proposed system removes 800mgL -1 nitrate up to 95% during 6.5h. Optimum conditions were obtained in the 8V p-p using a frequency of 10Hz of a sinusoidal waveform. The morphology studies confirmed bacterial morphology change when applying the alternating current. Dehydrogenase activity of biofilms formed on surface of stainless steel electrodes increased to 15.24μgTFmg biomass cm -2 d. The maximum bacterial activity was obtained at a voltage of 8V p-p . The experimental results revealed that the MES using a low frequency-low voltage alternating electrical current is a promising technique for nitrate removal from pharmaceutical wastewaters in the presence of low biodegradability of carbon sources such as ibuprofen. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Anodic stripping voltammetry with gold electrodes as an alternative method for the routine determination of mercury in fish. Comparison with spectroscopic approaches.

    PubMed

    Giacomino, Agnese; Ruo Redda, Andrea; Squadrone, Stefania; Rizzi, Marco; Abete, Maria Cesarina; La Gioia, Carmela; Toniolo, Rosanna; Abollino, Ornella; Malandrino, Mery

    2017-04-15

    The applicability to the determination of mercury in tuna of square wave anodic stripping voltammetry (SW-ASV) conducted at both solid gold electrode (SGE) and a gold nanoparticle-modified glassy carbon electrode (AuNPs-GCE) was demonstrated. Mercury content in two certified materials and in ten samples of canned tuna was measured. The performances of the electrodes were compared with one another as well as with two spectroscopic techniques, namely cold vapour atomic absorption spectroscopy (CV-AAS) and a direct mercury analyser (DMA). The results found pointed out that both SW-ASV approaches were suitable and easy-to-use method to monitor mercury concentration in tunas, since they allowed accurate quantification at concentration values lower than the maximum admissible level in this matrix ([Hg]=1mg/kg wet weight,ww ). In particular, mercury detection at the AuNPs-GCE showed a LOQ in fish-matrix of 0.1μg/l, corresponding to 0.06mg/kg ww , with performance comparable to that of DMA. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Determination of the wine preservative sulphur dioxide with cyclic voltammetry using inkjet printed electrodes.

    PubMed

    Schneider, Marion; Türke, Alexander; Fischer, Wolf-Joachim; Kilmartin, Paul A

    2014-09-15

    During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Current-induced alternating reversed dual-echo-steady-state for joint estimation of tissue relaxation and electrical properties.

    PubMed

    Lee, Hyunyeol; Sohn, Chul-Ho; Park, Jaeseok

    2017-07-01

    To develop a current-induced, alternating reversed dual-echo-steady-state-based magnetic resonance electrical impedance tomography for joint estimation of tissue relaxation and electrical properties. The proposed method reverses the readout gradient configuration of conventional, in which steady-state-free-precession (SSFP)-ECHO is produced earlier than SSFP-free-induction-decay (FID) while alternating current pulses are applied in between the two SSFPs to secure high sensitivity of SSFP-FID to injection current. Additionally, alternating reversed dual-echo-steady-state signals are modulated by employing variable flip angles over two orthogonal injections of current pulses. Ratiometric signal models are analytically constructed, from which T 1 , T 2 , and current-induced B z are jointly estimated by solving a nonlinear inverse problem for conductivity reconstruction. Numerical simulations and experimental studies are performed to investigate the feasibility of the proposed method in estimating relaxation parameters and conductivity. The proposed method, if compared with conventional magnetic resonance electrical impedance tomography, enables rapid data acquisition and simultaneous estimation of T 1 , T 2 , and current-induced B z , yielding a comparable level of signal-to-noise ratio in the parameter estimates while retaining a relative conductivity contrast. We successfully demonstrated the feasibility of the proposed method in jointly estimating tissue relaxation parameters as well as conductivity distributions. It can be a promising, rapid imaging strategy for quantitative conductivity estimation. Magn Reson Med 78:107-120, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  5. Development of Alternating Current Potential Drop (ACPD) Procedures for Crack Detection in Aluminum Aircraft Panels.

    DOT National Transportation Integrated Search

    1993-12-01

    The Alternating Current Potential Drop (ACPD) method is investigated as a means of making measurements in laboratory experiments on the initiation and growth of multiple site damage (MSD) cracks in a common aluminum alloy used for aircraft constructi...

  6. A Comparison of Alternating Current and Direct Current Electrospray Ionization for Mass Spectrometry

    PubMed Central

    Sarver, Scott A.; Gartner, Carlos A.; Chetwani, Nishant; Go, David B.; Dovichi, Norman J.

    2014-01-01

    A series of studies comparing the performance of alternating current electrospray ionization (AC ESI) mass spectrometry (MS) and direct current electrospray ionization (DC ESI) MS has been conducted, exploring the absolute signal intensity and signal-to-background ratios produced by both methods using caffeine and a model peptide as targets. Because the high-voltage AC signal was more susceptible to generating gas discharges, the operating voltage range of AC ESI was significantly smaller than that for DC ESI, such that the absolute signal intensities produced by DC ESI at peak voltages were 1 - 2 orders of magnitude greater than those for AC ESI. Using an electronegative nebulizing gas, sulfur hexafluoride (SF6), instead of nitrogen (N2) increased the operating range of AC ESI by ~50%, but did not appreciably improve signal intensities. While DC ESI generated far greater signal intensities, both ionization methods produced comparable signal-to-background noise, with AC ESI spectra appearing qualitatively cleaner. A quantitative calibration analysis was performed for two analytes, caffeine and the peptide MRFA. AC ESI utilizing SF6 outperforms all other techniques for the detection of MRFA, producing chromatographic limits of detection nearly one order of magnitude lower than that of DC ESI utilizing N2, and one half that of DC ESI utilizing SF6. However, DC ESI outperforms AC ESI for the analysis of caffeine, indicating improvements in spectral quality may benefit certain compounds, or classes of compounds, on an individual basis. PMID:24464359

  7. LabVIEW-based sequential-injection analysis system for the determination of trace metals by square-wave anodic and adsorptive stripping voltammetry on mercury-film electrodes.

    PubMed

    Economou, Anastasios; Voulgaropoulos, Anastasios

    2003-01-01

    The development of a dedicated automated sequential-injection analysis apparatus for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) is reported. The instrument comprised a peristaltic pump, a multiposition selector valve and a home-made potentiostat and used a mercury-film electrode as the working electrodes in a thin-layer electrochemical detector. Programming of the experimental sequence was performed in LabVIEW 5.1. The sequence of operations included formation of the mercury film, electrolytic or adsorptive accumulation of the analyte on the electrode surface, recording of the voltammetric current-potential response, and cleaning of the electrode. The stripping step was carried out by applying a square-wave (SW) potential-time excitation signal to the working electrode. The instrument allowed unattended operation since multiple-step sequences could be readily implemented through the purpose-built software. The utility of the analyser was tested for the determination of copper(II), cadmium(II), lead(II) and zinc(II) by SWASV and of nickel(II), cobalt(II) and uranium(VI) by SWAdSV.

  8. LabVIEW-based sequential-injection analysis system for the determination of trace metals by square-wave anodic and adsorptive stripping voltammetry on mercury-film electrodes

    PubMed Central

    Economou, Anastasios; Voulgaropoulos, Anastasios

    2003-01-01

    The development of a dedicated automated sequential-injection analysis apparatus for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) is reported. The instrument comprised a peristaltic pump, a multiposition selector valve and a home-made potentiostat and used a mercury-film electrode as the working electrodes in a thin-layer electrochemical detector. Programming of the experimental sequence was performed in LabVIEW 5.1. The sequence of operations included formation of the mercury film, electrolytic or adsorptive accumulation of the analyte on the electrode surface, recording of the voltammetric current-potential response, and cleaning of the electrode. The stripping step was carried out by applying a square-wave (SW) potential-time excitation signal to the working electrode. The instrument allowed unattended operation since multiple-step sequences could be readily implemented through the purpose-built software. The utility of the analyser was tested for the determination of copper(II), cadmium(II), lead(II) and zinc(II) by SWASV and of nickel(II), cobalt(II) and uranium(VI) by SWAdSV. PMID:18924623

  9. Real-time monitoring of electrically evoked catecholamine signals in the songbird striatum using in vivo fast-scan cyclic voltammetry.

    PubMed

    Smith, Amanda R; Garris, Paul A; Casto, Joseph M

    2015-01-01

    Fast-scan cyclic voltammetry is a powerful technique for monitoring rapid changes in extracellular neurotransmitter levels in the brain. In vivo fast-scan cyclic voltammetry has been used extensively in mammalian models to characterize dopamine signals in both anesthetized and awake preparations, but has yet to be applied to a non-mammalian vertebrate. The goal of this study was to establish in vivo fast-scan cyclic voltammetry in a songbird, the European starling, to facilitate real-time measurements of extracellular catecholamine levels in the avian striatum. In urethane-anesthetized starlings, changes in catecholamine levels were evoked by electrical stimulation of the ventral tegmental area and measured at carbon-fiber microelectrodes positioned in the medial and lateral striata. Catecholamines were elicited by different stimulations, including trains related to phasic dopamine signaling in the rat, and were analyzed to quantify presynaptic mechanisms governing exocytotic release and neuronal uptake. Evoked extracellular catecholamine dynamics, maximal amplitude of the evoked catecholamine signal, and parameters for catecholamine release and uptake did not differ between striatal regions and were similar to those determined for dopamine in the rat dorsomedial striatum under similar conditions. Chemical identification of measured catecholamine by its voltammogram was consistent with the presence of both dopamine and norepinephrine in striatal tissue content. However, the high ratio of dopamine to norepinephrine in tissue content and the greater sensitivity of the carbon-fiber microelectrode to dopamine compared to norepinephrine favored the measurement of dopamine. Thus, converging evidence suggests that dopamine was the predominate analyte of the electrically evoked catecholamine signal measured in the striatum by fast-scan cyclic voltammetry. Overall, comparisons between the characteristics of these evoked signals suggested a similar presynaptic regulation of

  10. A Brief Review of the Current Status of Alternatives of Chlorine Disinfection of Water

    PubMed Central

    Anderson, A. C.; Reimers, R. S.; DeKernion, P.

    1982-01-01

    This paper briefly outlines some of the alternative disinfectants being considered in lieu of chlorination. Methods currently in use as well as those in the research stage are included. Each method is assessed with respect to disinfection efficiency and environmental impact. (Am J Public Health 1982; 72:1290-1293.) PMID:7125035

  11. Failure of Standard Training Sets in the Analysis of Fast-Scan Cyclic Voltammetry Data.

    PubMed

    Johnson, Justin A; Rodeberg, Nathan T; Wightman, R Mark

    2016-03-16

    The use of principal component regression, a multivariate calibration method, in the analysis of in vivo fast-scan cyclic voltammetry data allows for separation of overlapping signal contributions, permitting evaluation of the temporal dynamics of multiple neurotransmitters simultaneously. To accomplish this, the technique relies on information about current-concentration relationships across the scan-potential window gained from analysis of training sets. The ability of the constructed models to resolve analytes depends critically on the quality of these data. Recently, the use of standard training sets obtained under conditions other than those of the experimental data collection (e.g., with different electrodes, animals, or equipment) has been reported. This study evaluates the analyte resolution capabilities of models constructed using this approach from both a theoretical and experimental viewpoint. A detailed discussion of the theory of principal component regression is provided to inform this discussion. The findings demonstrate that the use of standard training sets leads to misassignment of the current-concentration relationships across the scan-potential window. This directly results in poor analyte resolution and, consequently, inaccurate quantitation, which may lead to erroneous conclusions being drawn from experimental data. Thus, it is strongly advocated that training sets be obtained under the experimental conditions to allow for accurate data analysis.

  12. Probing biological redox chemistry with large amplitude Fourier transformed ac voltammetry

    PubMed Central

    Adamson, Hope

    2017-01-01

    Biological electron-exchange reactions are fundamental to life on earth. Redox reactions underpin respiration, photosynthesis, molecular biosynthesis, cell signalling and protein folding. Chemical, biomedical and future energy technology developments are also inspired by these natural electron transfer processes. Further developments in techniques and data analysis are required to gain a deeper understanding of the redox biochemistry processes that power Nature. This review outlines the new insights gained from developing Fourier transformed ac voltammetry as a tool for protein film electrochemistry. PMID:28804798

  13. Reversible Nerve Conduction Block Using Kilohertz Frequency Alternating Current

    PubMed Central

    Kilgore, Kevin L.; Bhadra, Niloy

    2013-01-01

    Objectives The features and clinical applications of balanced-charge kilohertz frequency alternating currents (KHFAC) are reviewed. Preclinical studies of KHFAC block have demonstrated that it can produce an extremely rapid and reversible block of nerve conduction. Recent systematic analysis and experimentation utilizing KHFAC block has resulted in a significant increase in interest in KHFAC block, both scientifically and clinically. Materials and Methods We review the history and characteristics of KHFAC block, the methods used to investigate this type of block, the experimental evaluation of block, and the electrical parameters and electrode designs needed to achieve successful block. We then analyze the existing clinical applications of high frequency currents, comparing the early results with the known features of KHFAC block. Results Although many features of KHFAC block have been characterized, there is still much that is unknown regarding the response of neural structures to rapidly fluctuating electrical fields. The clinical reports to date do not provide sufficient information to properly evaluate the mechanisms that result in successful or unsuccessful treatment. Conclusions KHFAC nerve block has significant potential as a means of controlling nerve activity for the purpose of treating disease. However, early clinical studies in the use of high frequency currents for the treatment of pain have not been designed to elucidate mechanisms or allow direct comparisons to preclinical data. We strongly encourage the careful reporting of the parameters utilized in these clinical studies, as well as the development of outcome measures that could illuminate the mechanisms of this modality. PMID:23924075

  14. Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

    NASA Technical Reports Server (NTRS)

    Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

    2017-01-01

    The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

  15. A pre-heating method based on sinusoidal alternating current for lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Fan, Wentao; Sun, Fengchun; Guo, Shanshan

    2018-04-01

    In this paper, a method of low temperature pre-heating of sinusoidal alternating current (SAC) is proposed. Generally, the lower the frequency of the AC current, the higher the heat generation rate. Yet at low frequency, there is a risk of lithium-ion deposition during the half cycle of charging. This study develops a temperature-adaptive, deposition-free AC pre-heating method. a equivalent electric circuit(EEC) model is established to predict the heat generation rate and temperature status, whose parameters are calibrated from the EIS impedance measurements. The effects of current frequency and amplitude on the heating effect are investigated respectively. A multistep temperature-adaptive amplitude strategy is proposed and the cell can be heated from -20°C to 5°C within 509s at 100Hz frequency with this method.

  16. Flexible software platform for fast-scan cyclic voltammetry data acquisition and analysis.

    PubMed

    Bucher, Elizabeth S; Brooks, Kenneth; Verber, Matthew D; Keithley, Richard B; Owesson-White, Catarina; Carroll, Susan; Takmakov, Pavel; McKinney, Collin J; Wightman, R Mark

    2013-11-05

    Over the last several decades, fast-scan cyclic voltammetry (FSCV) has proved to be a valuable analytical tool for the real-time measurement of neurotransmitter dynamics in vitro and in vivo. Indeed, FSCV has found application in a wide variety of disciplines including electrochemistry, neurobiology, and behavioral psychology. The maturation of FSCV as an in vivo technique led users to pose increasingly complex questions that require a more sophisticated experimental design. To accommodate recent and future advances in FSCV application, our lab has developed High Definition Cyclic Voltammetry (HDCV). HDCV is an electrochemical software suite that includes data acquisition and analysis programs. The data collection program delivers greater experimental flexibility and better user feedback through live displays. It supports experiments involving multiple electrodes with customized waveforms. It is compatible with transistor-transistor logic-based systems that are used for monitoring animal behavior, and it enables simultaneous recording of electrochemical and electrophysiological data. HDCV analysis streamlines data processing with superior filtering options, seamlessly manages behavioral events, and integrates chemometric processing. Furthermore, analysis is capable of handling single files collected over extended periods of time, allowing the user to consider biological events on both subsecond and multiminute time scales. Here we describe and demonstrate the utility of HDCV for in vivo experiments.

  17. Remediation in Practicing Physicians: Current and Alternative Conceptualizations.

    PubMed

    Bourgeois-Law, Gisèle; Teunissen, Pim W; Regehr, Glenn

    2018-04-24

    Suboptimal performance in practicing physicians is a decades-old problem. The lack of a universally accepted definition of remediation, the paucity of research on best remediation practices, and the ongoing controversy regarding the institutional responsibility for enacting and overseeing this activity suggests that the remediation of physicians is not merely a difficult problem to solve, but a problem that the community does not grapple with meaningfully. Undoubtedly, logistical and political considerations contribute to this state of affairs; however, other underlying conceptual issues may also play a role in the medical profession's difficulties in engaging with the challenges around remediation.Through a review of the medical education and other literatures, the authors examined current conceptualizations of both remediation itself and the individual being remediated, as well as how the culture of medicine influences these conceptions. The authors explored how conceptualizations of remediation and the surrounding culture might affect not only the medical community's ability to support, but also its willingness to engage with physicians in need of remediation.Viewing remediation as a means of supporting practice change-rather than as a means of redressing gaps in knowledge and skill-might be a useful alternative conceptualization, providing a good place to start exploring new avenues of research. However, moving forward will require more than simply a reconceptualizion of remediation; it will also necessitate a change in how the community views its struggling members and a change in the medical culture that currently positions professional autonomy as the foundational premise for individual practice improvement.

  18. Assessing Principal Component Regression Prediction of Neurochemicals Detected with Fast-Scan Cyclic Voltammetry

    PubMed Central

    2011-01-01

    Principal component regression is a multivariate data analysis approach routinely used to predict neurochemical concentrations from in vivo fast-scan cyclic voltammetry measurements. This mathematical procedure can rapidly be employed with present day computer programming languages. Here, we evaluate several methods that can be used to evaluate and improve multivariate concentration determination. The cyclic voltammetric representation of the calculated regression vector is shown to be a valuable tool in determining whether the calculated multivariate model is chemically appropriate. The use of Cook’s distance successfully identified outliers contained within in vivo fast-scan cyclic voltammetry training sets. This work also presents the first direct interpretation of a residual color plot and demonstrated the effect of peak shifts on predicted dopamine concentrations. Finally, separate analyses of smaller increments of a single continuous measurement could not be concatenated without substantial error in the predicted neurochemical concentrations due to electrode drift. Taken together, these tools allow for the construction of more robust multivariate calibration models and provide the first approach to assess the predictive ability of a procedure that is inherently impossible to validate because of the lack of in vivo standards. PMID:21966586

  19. Assessing principal component regression prediction of neurochemicals detected with fast-scan cyclic voltammetry.

    PubMed

    Keithley, Richard B; Wightman, R Mark

    2011-06-07

    Principal component regression is a multivariate data analysis approach routinely used to predict neurochemical concentrations from in vivo fast-scan cyclic voltammetry measurements. This mathematical procedure can rapidly be employed with present day computer programming languages. Here, we evaluate several methods that can be used to evaluate and improve multivariate concentration determination. The cyclic voltammetric representation of the calculated regression vector is shown to be a valuable tool in determining whether the calculated multivariate model is chemically appropriate. The use of Cook's distance successfully identified outliers contained within in vivo fast-scan cyclic voltammetry training sets. This work also presents the first direct interpretation of a residual color plot and demonstrated the effect of peak shifts on predicted dopamine concentrations. Finally, separate analyses of smaller increments of a single continuous measurement could not be concatenated without substantial error in the predicted neurochemical concentrations due to electrode drift. Taken together, these tools allow for the construction of more robust multivariate calibration models and provide the first approach to assess the predictive ability of a procedure that is inherently impossible to validate because of the lack of in vivo standards.

  20. Alternating Current Delivered into the Scala Media Alters Sound Pressure at the Eardrum

    NASA Astrophysics Data System (ADS)

    Hubbard, Allyn E.; Mountain, David C.

    1983-11-01

    Alternating current delivered into the scala media of the gerbil cochlea modulates the amplitude of a test tone measured near the eardrum. Variations in the electromechanical effect with acoustic stimulus parameters and observed physiological vulnerability suggest that cochlear hair cells are the biophysical origin of the process. Cochlear hair cells have traditionally been thought of as passive receptor cells, but they may play an active role in cochlear micromechanics.

  1. Diagnostic Criteria for the Characterization of Electrode Reactions with Chemically Coupled Reactions Preceding the Electron Transfer by Cyclic Square Wave Voltammetry.

    PubMed

    Helfrick, John C; Mann, Megan A; Bottomley, Lawrence A

    2016-08-18

    Theory for cyclic square wave voltammetry of electrode reactions with chemical reactions preceding the electron transfer is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Current progress on truffle submerged fermentation: a promising alternative to its fruiting bodies.

    PubMed

    Tang, Ya-Jie; Liu, Rui-Sang; Li, Hong-Mei

    2015-03-01

    Truffle (Tuber spp.), also known as "underground gold," is popular in various cuisines because of its unique and characteristic aroma. Currently, truffle fruiting bodies are mostly obtained from nature and semi-artificial cultivation. However, the former source is scarce, and the latter is time-consuming, usually taking 4 to 12 years before harvest of the fruiting body. The truffle submerged fermentation process was first developed in Tang's lab as an alternative to its fruiting bodies. To the best of our knowledge, most reports of truffle submerged fermentation come from Tang's group. This review examines the current state of the truffle submerged fermentation process. First, the strategy to optimize the truffle submerged fermentation process is summarized; the final conditions yielded not only the highest reported truffle biomass but also the highest production of extracellular and intracellular polysaccharides. Second, the comparison of metabolites produced by truffle fermentation and fruiting bodies is presented, and the former were superior to the latter. Third, metabolites (i.e., volatile organic compounds, equivalent umami concentration, and sterol) derived from truffle fermentation could be regulated by fermentation process optimization. These findings indicated that submerged fermentation of truffles can be used for commercial production of biomass and metabolites as a promising alternative to generating its fruiting bodies in bioreactor.

  3. A potentiostat featuring an integrator transimpedance amplifier for the measurement of very low currents—Proof-of-principle application in microfluidic separations and voltammetry

    NASA Astrophysics Data System (ADS)

    Koutilellis, G. D.; Economou, A.; Efstathiou, C. E.

    2016-03-01

    This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 μA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

  4. Printing of highly conductive solution by alternating current electrohydrodynamic direct-write

    NASA Astrophysics Data System (ADS)

    Jiang, Jiaxin; Zheng, Gaofeng; Wang, Xiang; Zheng, Jianyi; Liu, Juan; Liu, Yifang; Li, Wenwang; Guo, Shumin

    2018-03-01

    Electrohydrodynamic Direct-Write (EDW) is a novel technology for the printing of micro/nano structures. In this paper, Alternating Current (AC) electrical field was introduced to improve the ejection stability of jet with highly conductive solution. By alternating the electrical field, the polarity of free charges on the surface of jet was changed and the average density of charge, as well as the repulsive force, was reduced to stabilize the jet. When the frequency of AC electrical field increased, the EDW process became more stable and the shape of deposited droplets became more regular. The diameter of printed droplets decreased and the deposition frequency increased with the increase of voltage frequency. The phenomenon of corona discharge was overcome effectively as well. To further evaluate the performance of AC EDW for highly conductive solution, more NaCl was added to the solution and the conductivity was increased to 2810μs/cm. With such high conductivity, the problem of serious corona discharge could still be prevented by AC EDW, and the diameter of printed droplets decreased significantly. This work provides an effective way to accelerate industrial applications of EDW.

  5. Alternating current conduction studies on polypyrrole-iron nanocomposite at room temperature

    NASA Astrophysics Data System (ADS)

    Kumar, T. G. Naveen; Megha, R.; Revanasiddappa, M.; Ravikiran, Y. T.; Kumari, S. C. Vijaya

    2018-05-01

    In the present work, Polypyrrole (PPy) and Polypyrrole-Iron (PPy-Fe) nanocomposite were synthesized separately by chemical polymerisation method and then they were structurally characterised by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM) techniques. The alternate current (AC) response characteristics at room temperature of PPy and the composite were comparatively studied in the frequency range 100Hz-1MHz. The real part of conductivities of both PPy and the composite were interpreted as power law of frequency and the frequency exponent s was found to lie in the range 0< s<1 in both the cases. The nanocomposite has shown significant improvement in conductivity as compared to PPy.

  6. Cloud Point Extraction for Electroanalysis: Anodic Stripping Voltammetry of Cadmium.

    PubMed

    Rusinek, Cory A; Bange, Adam; Papautsky, Ian; Heineman, William R

    2015-06-16

    Cloud point extraction (CPE) is a well-established technique for the preconcentration of hydrophobic species from water without the use of organic solvents. Subsequent analysis is then typically performed via atomic absorption spectroscopy (AAS), UV-vis spectroscopy, or high performance liquid chromatography (HPLC). However, the suitability of CPE for electroanalytical methods such as stripping voltammetry has not been reported. We demonstrate the use of CPE for electroanalysis using the determination of cadmium (Cd(2+)) by anodic stripping voltammetry (ASV). Rather than using the chelating agents which are commonly used in CPE to form a hydrophobic, extractable metal complex, we used iodide and sulfuric acid to neutralize the charge on Cd(2+) to form an extractable ion pair. This offers good selectivity for Cd(2+) as no interferences were observed from other heavy metal ions. Triton X-114 was chosen as the surfactant for the extraction because its cloud point temperature is near room temperature (22-25 °C). Bare glassy carbon (GC), bismuth-coated glassy carbon (Bi-GC), and mercury-coated glassy carbon (Hg-GC) electrodes were compared for the CPE-ASV. A detection limit for Cd(2+) of 1.7 nM (0.2 ppb) was obtained with the Hg-GC electrode. ASV with CPE gave a 20x decrease (4.0 ppb) in the detection limit compared to ASV without CPE. The suitability of this procedure for the analysis of tap and river water samples was demonstrated. This simple, versatile, environmentally friendly, and cost-effective extraction method is potentially applicable to a wide variety of transition metals and organic compounds that are amenable to detection by electroanalytical methods.

  7. Cloud Point Extraction for Electroanalysis: Anodic Stripping Voltammetry of Cadmium

    PubMed Central

    Rusinek, Cory A.; Bange, Adam; Papautsky, Ian; Heineman, William R.

    2016-01-01

    Cloud point extraction (CPE) is a well-established technique for the pre-concentration of hydrophobic species from water without the use of organic solvents. Subsequent analysis is then typically performed via atomic absorption spectroscopy (AAS), UV-Vis spectroscopy, or high performance liquid chromatography (HPLC). However, the suitability of CPE for electroanalytical methods such as stripping voltammetry has not been reported. We demonstrate the use of CPE for electroanalysis using the determination of cadmium (Cd2+) by anodic stripping voltammetry (ASV) as a representative example. Rather than using the chelating agents which are commonly used in CPE to form a hydrophobic, extractable metal complex, we used iodide and sulfuric acid to neutralize the charge on Cd2+ to form an extractable ion pair. Triton X-114 was chosen as the surfactant for the extraction because its cloud point temperature is near room temperature (22–25° C). Bare glassy carbon (GC), bismuth-coated glassy carbon (Bi-GC), and mercury-coated glassy carbon (Hg-GC) electrodes were compared for the CPE-ASV. A detection limit for Cd2+ of 1.7 nM (0.2 ppb) was obtained with the Hg-GC electrode. Comparison of ASV analysis without CPE was also investigated and a 20x decrease (4.0 ppb) in the detection limit was observed. The suitability of this procedure for the analysis of tap and river water samples was also demonstrated. This simple, versatile, environmentally friendly and cost-effective extraction method is potentially applicable to a wide variety of transition metals and organic compounds that are amenable to detection by electroanalytical methods. PMID:25996561

  8. Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wen, Rui-Tao, E-mail: Ruitao.Wen@angstrom.uu.se; Granqvist, Claes G.; Niklasson, Gunnar A.

    2014-10-20

    Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li{sup +} ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO{sub 4} in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 10{sup 4} cycles when the applied voltage was limited to 4.1 V vs Li/Li{sup +}. Our results allow lifetime assessments for one of themore » essential components in an electrochromic device such as a “smart window” for energy-efficient buildings.« less

  9. Analytical solutions of the planar cyclic voltammetry process for two soluble species with equal diffusivities and fast electron transfer using the method of eigenfunction expansions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Samin, Adib; Lahti, Erik; Zhang, Jinsuo, E-mail: zhang.3558@osu.edu

    Cyclic voltammetry is a powerful tool that is used for characterizing electrochemical processes. Models of cyclic voltammetry take into account the mass transport of species and the kinetics at the electrode surface. Analytical solutions of these models are not well-known due to the complexity of the boundary conditions. In this study we present closed form analytical solutions of the planar voltammetry model for two soluble species with fast electron transfer and equal diffusivities using the eigenfunction expansion method. Our solution methodology does not incorporate Laplace transforms and yields good agreement with the numerical solution. This solution method can be extendedmore » to cases that are more general and may be useful for benchmarking purposes.« less

  10. Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, Bing-Ang; Li, Bin; Lin, Jie

    This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

  11. Multidimensional Cyclic Voltammetry Simulations of Pseudocapacitive Electrodes with a Conducting Nanorod Scaffold

    DOE PAGES

    Mei, Bing-Ang; Li, Bin; Lin, Jie; ...

    2017-10-27

    This paper aims to understand the effect of nanoarchitecture on the performance of pseudocapacitive electrodes consisting of conducting scaffold coated with pseudocapacitive material. To do so, two-dimensional numerical simulations of ordered conducting nanorods coated with a thin film of pseudocapacitive material were performed. The simulations reproduced three-electrode cyclic voltammetry measurements based on a continuum model derived from first principles. Two empirical approaches commonly used experimentally to characterize the contributions of surface-controlled and diffusion-controlled charge storage mechanisms to the total current density with respect to scan rate were theoretically validated for the first time. Moreover, the areal capacitive capacitance, attributed tomore » EDL formation, remained constant and independent of electrode dimensions, at low scan rates. However, at high scan rates, it decreased with decreasing conducting nanorod radius and increasing pseudocapacitive layer thickness due to resistive losses. By contrast, the gravimetric faradaic capacitance, due to reversible faradaic reactions, decreased continuously with increasing scan rate and pseudocapacitive layer thickness but was independent of conducting nanorod radius. Note that the total gravimetric capacitance predicted numerically featured values comparable to experimental measurements. Finally, an optimum pseudocapacitive layer thickness that maximizes total areal capacitance was identified as a function of scan rate and confirmed by scaling analysis.« less

  12. Determination of complex formation constants by phase sensitive alternating current polarography: Cadmium-polymethacrylic acid and cadmium-polygalacturonic acid.

    PubMed

    Garrigosa, Anna Maria; Gusmão, Rui; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

    2007-10-15

    The use of phase sensitive alternating current polarography (ACP) for the evaluation of complex formation constants of systems where electrodic adsorption is present has been proposed. The applicability of the technique implies the previous selection of the phase angle where contribution of capacitive current is minimized. This is made using Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) in the analysis of ACP measurements at different phase angles. The method is checked by the study of the complexation of Cd by polymethacrylic (PMA) and polygalacturonic (PGA) acids, and the optimal phase angles have been ca. -10 degrees for Cd-PMA and ca. -15 degrees for Cd-PGA systems. The goodness of phase sensitive ACP has been demonstrated comparing the determined complex formation constants with those obtained by reverse pulse polarography, a technique that minimizes the electrode adsorption effects on the measured currents.

  13. Cyclic voltammetry using silver as cathode material: a simple method for determining electro and chemical features and solubility values of CO2 in ionic liquids.

    PubMed

    Reche, Irene; Gallardo, Iluminada; Guirado, Gonzalo

    2015-01-28

    A report is presented on the use of cyclic voltammetry using silver as a working electrode. The combined electrocatalytic properties of silver and ionic liquids allow cyclic voltammetry to be turned into an ideal tool for the rapid and accurate access to diffusion coefficient values and solubility values of carbon dioxide in ionic liquids under standard conditions.

  14. Alternating-Current Equipment for the Measurement of Fluctuations of Air Speed in Turbulent Flow

    NASA Technical Reports Server (NTRS)

    Mock, W C , Jr

    1937-01-01

    Recent electrical and mechanical improvements have been made in the equipment developed at the National Bureau of Standards for measurement of fluctuations of air speed in turbulent flow. Data useful in the design of similar equipment are presented. The design of rectified alternating-current power supplies for such apparatus is treated briefly, and the effect of the power supplies on the performance of the equipment is discussed.

  15. Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry

    PubMed Central

    Pisoschi, Aurelia Magdalena; Danet, Andrei Florin; Kalinowski, Slawomir

    2008-01-01

    A method was developed for assessing ascorbic acid concentration in commercial fruit juice by cyclic voltammetry. The anodic oxidation peak for ascorbic acid occurs at about 490 mV on a Pt disc working electrode (versus SCE). The influence of the potential sweep speed on the peak height was studied. The obtained calibration graph shows a linear dependence between peak height and ascorbic acid concentration in the domain (0.1–10 mmol·L−1). The equation of the calibration graph was y = 6.391x + 0.1903 (where y represents the value of intensity measured for the anodic peak height, expressed as μA and x the analyte concentration, as mmol·L−1, r2 = 0.9995, r.s.d. = 1.14%, n = 10, Cascorbic acid = 2 mmol·L−1). The developed method was applied to ascorbic acid assessment in fruit juice. The ascorbic acid content determined ranged from 0.83 to 1.67 mmol·L−1 for orange juice, from 0.58 to 1.93 mmol·L−1 for lemon juice, and from 0.46 to 1.84 mmol·L−1 for grapefruit juice. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.35% and 104%. Ascorbic acid determination results obtained by cyclic voltammetry were compared with those obtained by the volumetric method with dichlorophenol indophenol. The results obtained by the two methods were in good agreement. PMID:19343183

  16. From Inflammation to Current and Alternative Therapies Involved in Wound Healing

    PubMed Central

    Serra, Mariana Barreto; da Silva, Neemias Neves; Abreu, Iracelle Carvalho

    2017-01-01

    Wound healing is a complex event that develops in three overlapping phases: inflammatory, proliferative, and remodeling. These phases are distinct in function and histological characteristics. However, they depend on the interaction of cytokines, growth factors, chemokines, and chemical mediators from cells to perform regulatory events. In this article, we will review the pathway in the skin healing cascade, relating the major chemical inflammatory mediators, cellular and molecular, as well as demonstrating the local and systemic factors that interfere in healing and disorders associated with tissue repair deficiency. Finally, we will discuss the current therapeutic interventions in the wounds treatment, and the alternative therapies used as promising results in the development of new products with healing potential. PMID:28811953

  17. Inappropriate Implantable Cardioverter-Defibrillator Shocks Attributed to Alternating-Current Leak in a Swimming Pool

    PubMed Central

    Makaryus, John N.; Angert-Gilman, Julia; Yacoub, Mena; Patel, Apoor

    2014-01-01

    Implantable cardioverter-defibrillators (ICDs) are the standard of care for preventing sudden cardiac death in patients who are predisposed to malignant ventricular arrhythmias. Causes of inappropriate ICD shock include equipment malfunction, improper arrhythmia evaluation, misinterpretation of myopotentials, and electromagnetic interference. As the number of implanted ICDs has increased, other contributors to inappropriate therapy have become known, such as minimal electrical current leaks that mimic ventricular fibrillation. We present the case of a 63-year-old man with a biventricular ICD who received 2 inappropriate shocks, probably attributable to alternating-current leaks in a swimming pool. In addition, we discuss ICD sensitivity and offer recommendations to avoid similar occurrences. PMID:24512403

  18. Alternating current cranial electrotherapy stimulation (CES) for depression.

    PubMed

    Kavirajan, Harish C; Lueck, Kristin; Chuang, Kenneth

    2014-07-08

    Depression is a mood disorder with a prevalence of approximately 1% to 3% worldwide, representing the fourth leading cause of disease burden globally. The current standard treatments of psychological therapy and antidepressant medications are not effective for everyone, and psychotropic drugs may be associated with significant adverse effects. Cranial electrical stimulation (CES) treatment, in which a low intensity electrical current is administered through the use of a small, portable electrical device, has been reported to have efficacy in the treatment of depression with minimal adverse effects. This systematic review investigated the scientific evidence regarding the efficacy and safety of CES in treatment of acute depression compared to sham, or simulated, CES treatment. To assess the effectiveness and safety of alternating current cranial electrotherapy stimulation (CES) compared with sham CES for acute depression. We searched The Cochrane Collaboration Depression, Anxiety and Neurosis review group's specialized register (CCDANCTR-Studies and CCDANCTR-References) to February 24, 2014 This register contains relevant randomized controlled trials from: The Cochrane Library (all years), MEDLINE (1950 to date), EMBASE (1974 to date), and PsycINFO (1967 to date). We examined reference lists of review papers and books on CES. We contacted authors, other experts in the field and CES manufacturing companies for knowledge of suitable published or unpublished trials. Randomized controlled trials of CES versus sham CES for the acute treatment of depressive disorder in adults aged 18 to 75 years. We planned to extract data from the original reports of included studies independently by two authors. The main outcomes to be assessed were:(1) the efficacy of CES in reducing symptoms of depression as reflected in change scores on standardized depression rating scales.(2) the tolerability of CES treatment to participants, as reflected in rates of discontinuation due to adverse

  19. Optimizing the Temporal Resolution of Fast-Scan Cyclic Voltammetry

    PubMed Central

    2012-01-01

    Electrochemical detection with carbon-fiber microelectrodes has become an established method to monitor directly the release of dopamine from neurons and its uptake by the dopamine transporter. With constant potential amperometry (CPA), the measured current provides a real time view of the rapid concentration changes, but the method lacks chemical identification of the monitored species and markedly increases the difficulty of signal calibration. Monitoring with fast-scan cyclic voltammetry (FSCV) allows species identification and concentration measurements but often exhibits a delayed response time due to the time-dependent adsorption/desorption of electroactive species at the electrode. We sought to improve the temporal resolution of FSCV to make it more comparable to CPA by increasing the waveform repetition rate from 10 to 60 Hz with uncoated carbon-fiber electrodes. The faster acquisition led to diminished time delays of the recordings that tracked more closely with CPA measurements. The measurements reveal that FSCV at 10 Hz underestimates the normal rate of dopamine uptake by about 18%. However, FSCV collection at 10 and 60 Hz provide identical results when a dopamine transporter (DAT) blocker such as cocaine is bath applied. To verify further the utility of this method, we used transgenic mice that overexpress DAT. After accounting for the slight adsorption delay time, FSCV at 60 Hz adequately monitored the increased uptake rate that arose from overexpression of DAT and, again, was similar to CPA results. Furthermore, the utility of collecting data at 60 Hz was verified in an anesthetized rat by using a higher scan rate (2400 V/s) to increase sensitivity and the overall signal. PMID:22708011

  20. Alternating current electroosmotic flow in polyelectrolyte-grafted nanochannel.

    PubMed

    Li, Fengqin; Jian, Yongjun; Chang, Long; Zhao, Guangpu; Yang, Liangui

    2016-11-01

    In this work, we investigate the time periodic electroosmotic flow (EOF) of an electrolyte solution through a slit polyelectrolyte-grafted (PE-grafted) nanochannel under applied alternating current (AC) electrical field. The PE-grafted nanochannel is represented by a rigid surface covered by a polyelectrolyte layer (PEL) in a brush-like configuration. Under Debye-Hückel approximation, we obtain analytical solutions of electrical potential in decoupled regime of PE-grafted nanochannel, where the thickness of PEL is independent of the electrostatic effects triggered by polyelectrolyte charges. Based upon the electrical potential obtained above, we calculate EOF velocities with uniform and non-uniform drag coefficients for PE-grafted nanochannel and compare their results. The effects of pertinent dimensionless parameters on EOF velocity amplitude are discussed in detail. Moreover, the amplitude of EOF velocity in a PE-grafted nanochannel is compared with that in a rigid one. It is shown that larger EOF velocity and volume flow rate are found for a PE-grafted nanochannel. In addition, AC EOF velocity is further investigated. The oscillation of velocity reduces and is restricted within the region near the PEL-electrolyte interface for higher oscillating Reynolds number Re. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Precision electronic speed controller for an alternating-current

    DOEpatents

    Bolie, Victor W.

    1988-01-01

    A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for and is particularly suitable for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. In the preferred embodiment, the motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of readonly memories, and a pair of digital-to-analog converters.

  2. Temporal differentiation of pH-dependent capacitive current from dopamine.

    PubMed

    Yoshimi, Kenji; Weitemier, Adam

    2014-09-02

    Voltammetric recording of dopamine (DA) with fast-scan cyclic voltammetry (FSCV) on carbon fiber microelectrodes have been widely used, because of its high sensitivity to dopamine. However, since an electric double layer on a carbon fiber surface in a physiological ionic solution behaves as a capacitor, fast voltage manipulation in FSCV induces large capacitive current. The faradic current from oxidation/reduction of target chemicals must be extracted from this large background current. It is known that ionic shifts, including H(+), influence this capacitance, and pH shift can cause confounding influences on the FSCV recordings within a wide range of voltage. Besides FSCV with a triangular waveform, we have been using rectangular pulse voltammetry (RPV) for dopamine detection in the brain. In this method, the onset of a single pulse causes a large capacitive current, but unlike FSCV, the capacitive current is restricted to a narrow temporal window of just after pulse onset (<5 ms). In contrast, the peak of faradic current from dopamine oxidation occurs after a delay of more than a few milliseconds. Taking advantage of the temporal difference, we show that RPV could distinguish dopamine from pH shifts clearly and easily. In addition, the early onset current was useful to evaluate pH shifts. The narrow voltage window of our RPV pulse allowed a clear differentiation of dopamine and serotonin (5-HT), as we have shown previously. Additional recording with RPV, alongside FSCV, would improve identification of chemicals such as dopamine, pH, and 5-HT.

  3. Determination of band structure parameters and the quasi-particle gap of CdSe quantum dots by cyclic voltammetry.

    PubMed

    Inamdar, Shaukatali N; Ingole, Pravin P; Haram, Santosh K

    2008-12-01

    Band structure parameters such as the conduction band edge, the valence band edge and the quasi-particle gap of diffusing CdSe quantum dots (Q-dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q-dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi-empirical pseudopotential method (SEPM)-especially in the strong size-confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q-dots, the difference between the quasi-particle gap and the optical band gap gives the electron-hole Coulombic interaction energy (J(e1,h1)). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.

  4. Application field and ways to control alternating-current plasma torch with rail electrodes

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. E.; Safronov, A. A.; Vasilieva, O. B.; Shiryaev, V. N.; Dudnik, Yu D.; Pavlov, A. V.; Kuchina, Yu A.

    2018-01-01

    The paper deals with the investigation of parameters of the high voltage alternating-current plasma torch with rail electrodes. Usage of the injector and its variation allows controlling of operation of the ac plasma torch with rail electrodes. Also the possibility to protect the electric arc chamber without protective gas has been studied. It was found that increasing in the injector power causes the repeated breakdown at lower voltage and hence the arc dimensions decreases. The results of experiments are presented in the paper.

  5. A baseline drift detrending technique for fast scan cyclic voltammetry.

    PubMed

    DeWaele, Mark; Oh, Yoonbae; Park, Cheonho; Kang, Yu Min; Shin, Hojin; Blaha, Charles D; Bennet, Kevin E; Kim, In Young; Lee, Kendall H; Jang, Dong Pyo

    2017-11-06

    Fast scan cyclic voltammetry (FSCV) has been commonly used to measure extracellular neurotransmitter concentrations in the brain. Due to the unstable nature of the background currents inherent in FSCV measurements, analysis of FSCV data is limited to very short amounts of time using traditional background subtraction. In this paper, we propose the use of a zero-phase high pass filter (HPF) as the means to remove the background drift. Instead of the traditional method of low pass filtering across voltammograms to increase the signal to noise ratio, a HPF with a low cutoff frequency was applied to the temporal dataset at each voltage point to remove the background drift. As a result, the HPF utilizing cutoff frequencies between 0.001 Hz and 0.01 Hz could be effectively used to a set of FSCV data for removing the drifting patterns while preserving the temporal kinetics of the phasic dopamine response recorded in vivo. In addition, compared to a drift removal method using principal component analysis, this was found to be significantly more effective in reducing the drift (unpaired t-test p < 0.0001, t = 10.88) when applied to data collected from Tris buffer over 24 hours although a drift removal method using principal component analysis also showed the effective background drift reduction. The HPF was also applied to 5 hours of FSCV in vivo data. Electrically evoked dopamine peaks, observed in the nucleus accumbens, were clearly visible even without background subtraction. This technique provides a new, simple, and yet robust, approach to analyse FSCV data with an unstable background.

  6. Laboratory animal science in China: current status and potential for adoption of Three R alternatives.

    PubMed

    Kong, Qi; Qin, Chuan

    2010-03-01

    R alternatives, and animal welfare, and shows that there is currently great potential for the adoption of alternatives. The information will help scientists and organisations around the world to gain better insight into the current state of laboratory animal science in China, and hopefully, will enable them to give advice on how we can improve the adoption of Three R alternatives in our country. 2010 FRAME.

  7. Use of alternating and pulsed direct current electrified fields for zebra mussel control

    USGS Publications Warehouse

    Luoma, James A.; Dean, Jan C.; Severson, Todd J.; Wise, Jeremy K.; Barbour, Matthew

    2017-01-01

    Alternatives to chemicals for controlling dreissenid mussels are desirable for environmental compatibility, but few alternatives exist. Previous studies have evaluated the use of electrified fields for stunning and/or killing planktonic life stages of dreissenid mussels, however, the available literature on the use of electrified fields to control adult dreissenid mussels is limited. We evaluated the effects of sinusoidal alternating current (AC) and 20% duty cycle square-wave pulsed direct current (PDC) exposure on the survival of adult zebra mussels at water temperatures of 10, 15, and 22 °C. Peak voltage gradients of ~ 17 and 30 Vp/cm in the AC and PDC exposures, respectively, were continuously applied for 24, 48, or 72 h. Peak power densities ranged from 77,999 to 107,199 µW/cm3 in the AC exposures and 245,320 to 313,945 µW/cm3 in the PDC exposures. The peak dose ranged from 6,739 to 27,298 Joules/cm3 and 21,306 to 80,941 Joules/cm3 in the AC and PDC exposures, respectively. The applied power ranged from 16.6 to 68.9 kWh in the AC exposures and from 22.2 to 86.4 kWh in the PDC exposures. Mortality ranged from 2.7 to 92.7% in the AC exposed groups and from 24.0 to 98.7% in PDC exposed groups. Mortality increased with corresponding increases in water temperature and exposure duration, and we observed more zebra mussel mortality in the PDC exposures. Exposures conducted with AC required less of a peak dose (Joules/cm3) but more applied power (kWh) to achieve the same level of adult zebra mussel mortality as corresponding PDC exposures. The results demonstrate that 20% duty cycle square-wave PDC requires less energy than sinusoidal AC to inducing the same level of adult zebra mussel mortality.

  8. Electrochemical and spectroscopic study on the interaction between isoprenaline and DNA using multivariate curve resolution-alternating least squares.

    PubMed

    Ni, Yongnian; Wei, Min; Kokot, Serge

    2011-11-01

    Interaction of isoprenaline (ISO) with calf-thymus DNA was studied by spectroscopic and electrochemical methods. The behavior of ISO was investigated at a glassy carbon electrode (GCE) by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV); ISO was oxidized and an irreversible oxidation peak was observed. The binding constant K and the stoichiometric coefficient m of ISO with DNA were evaluated. Also, with the addition of DNA, hyperchromicity of the UV-vis absorption spectra of ISO was noted, while the fluorescence intensity decreased significantly. Multivariate curve resolution-alternating least squares (MCR-ALS) chemometrics method was applied to resolve the combined spectroscopic data matrix, which was obtained by the UV-vis and fluorescence methods. Pure spectra of ISO, DNA and ISO-DNA complex, and their concentration profiles were then successfully obtained. The results indicated that the ISO molecule intercalated into the base-pairs of DNA, and the complex of ISO-DNA was formed. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Investigation of antioxidant capacity of the extracts of bilberry (VACCINUM MYRTILLIS L.) by voltammetry

    NASA Astrophysics Data System (ADS)

    Vtorushina, A. N.; Nikonova, E. D.

    2016-02-01

    This paper deals with the urgent issue of the search of new drugs based on plant raw materials that have an influence on various stages of oxidation processes occurring in the human body. The aim of this paper is to determine the antioxidant activity of the bilberry extracts that are used in the medicine practice by a cathodic voltammetry method. We consider the influence of water and alcohol bilberry extracts on the process of oxygen electroreduction. From these extracts the most activity relation to the process of cathodic oxygen reduction showed alcohol (40%) bilberry extract. It was also stated that the alcohol extract of bilberry has a greater antioxidant activity than other known antioxidants such as ascorbic acid, glucose, dihydroquercetin. Thus, after consideration of a number of plant objects, we showed the possibility of applying the method of cathodic voltammetry for the determination of total antioxidant activity of plant material and identifying and highlighting the most perspective sources of biologically active substances (BAS), as well as the ability of identifying extractants that fully extract BAS from plant raw materials. The activity data of extracts of plant raw materials gives an opportunity of establishing an effective yield phytopreparation based on bilberry that has an antioxidant effect.

  10. Aternating current photovoltaic building block

    DOEpatents

    Bower, Ward Issac; Thomas, Michael G.; Ruby, Douglas S.

    2004-06-15

    A modular apparatus for and method of alternating current photovoltaic power generation comprising via a photovoltaic module, generating power in the form of direct current; and converting direct current to alternating current and exporting power via one or more power conversion and transfer units attached to the module, each unit comprising a unitary housing extending a length or width of the module, which housing comprises: contact means for receiving direct current from the module; one or more direct current-to-alternating current inverters; an alternating current bus; and contact means for receiving alternating current from the one or more inverters.

  11. Investigation of the reduction process of dopamine using paired pulse voltammetry

    PubMed Central

    Kim, Do Hyoung; Oh, Yoonbae; Shin, Hojin; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.; Kim, In Young; Jang, Dong Pyo

    2014-01-01

    The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around −0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scanrates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at −0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to −0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (−0.4V). These tests showed that

  12. Variation sweep rate cyclic voltammetry on the capacitance electrode activated carbon/PVDF with polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Rohmawati, L.; Setyarsih, W.; Nurjannah, T.

    2018-03-01

    Sweep rate of the process voltammetry cyclic characterization is very influential towards the electrode capacitance value, especially on activated carbon electrodes/PVDF. A simple method of this research by use a mixing for electrode activated carbon/10 wt. % PVDF and the separator is made of a polymer electrolyte (PVA/H3PO4) by a sol gel method. The prototype supercapacitor is made in the form of a sandwich with a separator placed between two electrodes. Electrodes and separators are arranged in layers at a pressure of 1500 psi, then heated at 50°C for 10 minutes. Next done cyclic voltammetry in a potential range of -1 V to 1 V with a sweep rate of 5 mV/s, 10 mV/s, 20 mV/s, 25 mV/s and 50 mV/s. This results of curves voltammogram is reversible, the most wide curve on the sweep rate of 5 mV/s and most narrow curve on a sweep rate of 50 mV/s. Supercapacitor capacitance values obtained by 86 F/g, 43 F/g, 21 F/g, 16 F/g, and 8 F/g.

  13. Phosphor-free, white-light LED under alternating-current operation.

    PubMed

    Yao, Yu-Feng; Chen, Hao-Tsung; Su, Chia-Ying; Hsieh, Chieh; Lin, Chun-Han; Kiang, Yean-Woei; Yang, C C

    2014-11-15

    A light-emitting diode structure, consisting of a p-GaN layer, a CdZnO/ZnO quantum-well (QW) structure, a high-temperature-grown ZnO layer, and a GaZnO layer, is fabricated. Under forward bias, the device effectively emits green-yellow light, from the QW structure, at the rim of device mesa. Under reverse bias, electrons in the valence band of the p-GaN layer move into the conduction band of the GaZnO layer, through a QW-state-assisted tunneling process, to recombine with the injected holes in the GaZnO layer, for emitting yellow-red and shallow ultraviolet light over the entire mesa area. Also, carrier recombination in the p-GaN layer produces blue light. By properly designing the thickness of the high-temperature grown ZnO layer, the emission intensity under forward bias can be controlled such that, under alternating-current operation at 60 Hz, the spatial and spectral mixtures of the emitted lights of complementary colors, under forward and reverse biases, result in white light generation based on persistence of vision.

  14. Copper Sensing in Alkaline Electrolyte Using Anodic Stripping Voltammetry by Means of a Lead Mediator

    DOE PAGES

    Duay, Jonathon; Ortiz-Santiago, Joed E.; Lambert, Timothy N.

    2017-10-05

    Anodic stripping voltammetry (ASV) is an analysis technique that permits the selective and quantitative analysis of metal ion species in solution. It is most commonly applied in neutral to acidic electrolyte largely due to inherent metal ion solubility. Bismuth (Bi) is a common film used for ASV due to its good sensitivity, overall stability and insensitivity to O2. ASV, utilizing a Bi film, along with cadmium (Cd) and lead (Pb) as the plating mediators, has recently been adapted to determine zinc (Zn) concentrations in highly alkaline environments (30 % NaOH or 35 % M KOH). Successful analysis of Zn inmore » alkaline relies on the ability of the hydroxide to form soluble metal anion species, such as Bi(OH) 4 – and Zn(OH) 4 2–. Here, we look to extend this technique to detect and quantify copper (Cu) ions in these highly basic electrolytes. However, in general, the use of ASV to detect and quantify Cu ion concentrations is notoriously difficult as the Cu stripping peak potential overlays with that of Bi from the common Bi film electrode. Here, an ASV method for determining Cu concentration in alkaline solutions is developed utilizing Pb as a deposition mediator. As such, it was found that when analyzing Cu solutions in the presence of Pb, the stripping voltammetry curves present separate and defined Cu stripping peaks. Different analyzes were made to find the best stripping voltammetry performance conditions. As such, an accumulation time of 5 minutes, an accumulation potential of ≤–1.45 V vs. Hg/HgO, and a concentration of 35 wt% KOH were determined to be the conditions that presented the best ASV results. Utilizing these conditions, calibration curves in the presence of 5.0 ppm Pb showed the best linear stripping signal correlation with an r-squared value of 0.991 and a limit of detection (LOD) of 0.67 ppm. Lastly, these results give way to evaluating Cu concentrations using ASV in aqueous alkaline solutions.« less

  15. Copper Sensing in Alkaline Electrolyte Using Anodic Stripping Voltammetry by Means of a Lead Mediator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Duay, Jonathon; Ortiz-Santiago, Joed E.; Lambert, Timothy N.

    Anodic stripping voltammetry (ASV) is an analysis technique that permits the selective and quantitative analysis of metal ion species in solution. It is most commonly applied in neutral to acidic electrolyte largely due to inherent metal ion solubility. Bismuth (Bi) is a common film used for ASV due to its good sensitivity, overall stability and insensitivity to O2. ASV, utilizing a Bi film, along with cadmium (Cd) and lead (Pb) as the plating mediators, has recently been adapted to determine zinc (Zn) concentrations in highly alkaline environments (30 % NaOH or 35 % M KOH). Successful analysis of Zn inmore » alkaline relies on the ability of the hydroxide to form soluble metal anion species, such as Bi(OH) 4 – and Zn(OH) 4 2–. Here, we look to extend this technique to detect and quantify copper (Cu) ions in these highly basic electrolytes. However, in general, the use of ASV to detect and quantify Cu ion concentrations is notoriously difficult as the Cu stripping peak potential overlays with that of Bi from the common Bi film electrode. Here, an ASV method for determining Cu concentration in alkaline solutions is developed utilizing Pb as a deposition mediator. As such, it was found that when analyzing Cu solutions in the presence of Pb, the stripping voltammetry curves present separate and defined Cu stripping peaks. Different analyzes were made to find the best stripping voltammetry performance conditions. As such, an accumulation time of 5 minutes, an accumulation potential of ≤–1.45 V vs. Hg/HgO, and a concentration of 35 wt% KOH were determined to be the conditions that presented the best ASV results. Utilizing these conditions, calibration curves in the presence of 5.0 ppm Pb showed the best linear stripping signal correlation with an r-squared value of 0.991 and a limit of detection (LOD) of 0.67 ppm. Lastly, these results give way to evaluating Cu concentrations using ASV in aqueous alkaline solutions.« less

  16. Simultaneous determination of hydroquinone, catechol and resorcinol by voltammetry using graphene screen-printed electrodes and partial least squares calibration.

    PubMed

    Aragó, Miriam; Ariño, Cristina; Dago, Àngela; Díaz-Cruz, José Manuel; Esteban, Miquel

    2016-11-01

    Catechol (CC), resorcinol (RC) and hydroquinone (HQ) are dihydroxybenzene isomers that usually coexist in different samples and can be determined using voltammetric techniques taking profit of their fast response, high sensitivity and selectivity, cheap instrumentation, simple and timesaving operation modes. However, a strong overlapping of CC and HQ signals is observed hindering their accurate analysis. In the present work, the combination of differential pulse voltammetry with graphene screen-printed electrodes (allowing detection limits of 2.7, 1.7 and 2.4µmolL(-1) for HQ, CC and RC respectively) and the data analysis by partial least squares calibration (giving root mean square errors of prediction, RMSEP values, of 2.6, 4.1 and 2.3 for HQ, CC and RC respectively) has been proposed as a powerful tool for the quantification of mixtures of these dihydroxybenzene isomers. The commercial availability of the screen-printed devices and the low cost and simplicity of the analysis suggest that the proposed method can be a valuable alternative to chromatographic and electrophoretic methods for the considered species. The method has been applied to the analysis of these isomers in spiked tap water. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Neurobiological model of stimulated dopamine neurotransmission to interpret fast-scan cyclic voltammetry data.

    PubMed

    Harun, Rashed; Grassi, Christine M; Munoz, Miranda J; Torres, Gonzalo E; Wagner, Amy K

    2015-03-02

    Fast-scan cyclic voltammetry (FSCV) is an electrochemical method that can assess real-time in vivo dopamine (DA) concentration changes to study the kinetics of DA neurotransmission. Electrical stimulation of dopaminergic (DAergic) pathways can elicit FSCV DA responses that largely reflect a balance of DA release and reuptake. Interpretation of these evoked DA responses requires a framework to discern the contribution of DA release and reuptake. The current, widely implemented interpretive framework for doing so is the Michaelis-Menten (M-M) model, which is grounded on two assumptions- (1) DA release rate is constant during stimulation, and (2) DA reuptake occurs through dopamine transporters (DAT) in a manner consistent with M-M enzyme kinetics. Though the M-M model can simulate evoked DA responses that rise convexly, response types that predominate in the ventral striatum, the M-M model cannot simulate dorsal striatal responses that rise concavely. Based on current neurotransmission principles and experimental FSCV data, we developed a novel, quantitative, neurobiological framework to interpret DA responses that assumes DA release decreases exponentially during stimulation and continues post-stimulation at a diminishing rate. Our model also incorporates dynamic M-M kinetics to describe DA reuptake as a process of decreasing reuptake efficiency. We demonstrate that this quantitative, neurobiological model is an extension of the traditional M-M model that can simulate heterogeneous regional DA responses following manipulation of stimulation duration, frequency, and DA pharmacology. The proposed model can advance our interpretive framework for future in vivo FSCV studies examining regional DA kinetics and their alteration by disease and DA pharmacology. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. A Cuprous Oxide Thin Film Non-Enzymatic Glucose Sensor Using Differential Pulse Voltammetry and Other Voltammetry Methods and a Comparison to Different Thin Film Electrodes on the Detection of Glucose in an Alkaline Solution

    PubMed Central

    Molazemhosseini, Alireza; Liu, Chung Chiun

    2018-01-01

    A cuprous oxide (Cu2O) thin layer served as the base for a non-enzymatic glucose sensor in an alkaline medium, 0.1 NaOH solution, with a linear range of 50–200 mg/dL using differential pulse voltammetry (DPV) measurement. An X-ray photoelectron spectroscopy (XPS) study confirmed the formation of the cuprous oxide layer on the thin gold film sensor prototype. Quantitative detection of glucose in both phosphate-buffered saline (PBS) and undiluted human serum was carried out. Neither ascorbic acid nor uric acid, even at a relatively high concentration level (100 mg/dL in serum), interfered with the glucose detection, demonstrating the excellent selectivity of this non-enzymatic cuprous oxide thin layer-based glucose sensor. Chronoamperometry and single potential amperometric voltammetry were used to verify the measurements obtained by DPV, and the positive results validated that the detection of glucose in a 0.1 M NaOH alkaline medium by DPV measurement was effective. Nickel, platinum, and copper are commonly used metals for non-enzymatic glucose detection. The performance of these metal-based sensors for glucose detection using DPV were also evaluated. The cuprous oxide (Cu2O) thin layer-based sensor showed the best sensitivity for glucose detection among the sensors evaluated. PMID:29316652

  19. The use of cyclic voltammetry to study the oxidation of l-5-methyltetrahydrofolate and its preservation by ascorbic acid.

    PubMed

    Rozoy, Elodie; Simard, Stephan; Liu, Yazheng; Kitts, David; Lessard, Jean; Bazinet, Laurent

    2012-06-01

    A cyclic voltammetry study of 1mM l-5-methyltetrahydrofolate (l-5-MTHF) was performed in pH 5.5 Britton-Robinson buffer at room temperature to study the stability of l-5-MTHF alone and in combination with ascorbic acid (AA). The degradation of l-5-MTHF and AA over a period of 12h both followed first order reaction kinetics. Using this technique, oxidation peaks of l-5-MTHF were identified at +0.17 and +1.18V, and another oxidation peak appeared after 4h under air at +0.89V. Cyclic voltammetry and HPLC quantification enable us to confirm that l-5-MTHF can be highly preserved by the addition of an equimolar concentration of AA. This treatment was equivalent to a purge of nitrogen used to remove oxygen and thus minimise oxidation of l-5-MTHF when present in aqueous solutions. HPLC confirmed the fact that a full regeneration of oxidised l-5-MTHF occurred with the addition of sodium ascorbate, thus denoting that the redox character of l-5-MTHF can be controlled by the presence of reducing agents. Cyclic voltammetry proved to be a sensitive and accurate method for characterising l-5-MTHF oxidation and potential preservation with ascorbic acid. To our knowledge, this is the first study that has demonstrated the number of oxidation sites on l-5-MTHF. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Practical aspects of the use of three-phase alternating current electric machines in electricity storage system

    NASA Astrophysics Data System (ADS)

    Ciucur, Violeta

    2015-02-01

    Of three-phase alternating current electric machines, it brings into question which of them is more advantageous to be used in electrical energy storage system by pumping water. The two major categories among which are given dispute are synchronous and the asynchronous machine. To consider the synchronous machine with permanent magnet configuration because it brings advantages compared with conventional synchronous machine, first by removing the necessary additional excitation winding. From the point of view of loss of the two types of machines, the optimal adjustment of the magnetic flux density is obtained to minimize the copper loss by hysteresis and eddy currents.

  1. Determination of genotoxic effects of methidathion alkaline hydrolysis in human lymphocytes using the micronucleus assay and square-wave voltammetry.

    PubMed

    Stivaktakis, Polychronis D; Giannakopoulos, Evangelos; Vlastos, Dimitris; Matthopoulos, Demetrios P

    2017-02-01

    The interaction of pesticides with environmental factors, such as pH, may result in alterations of their physicochemical properties and should be taken into consideration in regard to their classification. This study investigates the genotoxicity of methidathion and its alkaline hydrolysis by-products in cultured human lymphocytes, using the square-wave voltammetry (square wave-adsorptive cathodic stripping voltammetry (SW-AdCSV) technique) and the cytokinesis block micronucleus assay (CBMN assay). According to the SW-AdCSV data the alkaline hydrolysis of methidathion results in two new molecules, one non-electro-active and a second electro-active which is more genotoxic than methidathion itself in cultured human lymphocytes, inducing higher micronuclei frequencies. The present study confirms the SW-AdCSV technique as a voltammetric method which can successfully simulates the electrodynamics of the cellular membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Pseudo-stir bar hollow fiber solid/liquid phase microextraction combined with anodic stripping voltammetry for determination of lead and cadmium in water samples

    PubMed Central

    Es’haghi, Zarrin; Hoseini, Hasan Ali; Mohammadi-Nokhandani, Saeed; Ebrahimi, Javad

    2013-01-01

    A new procedure is presented for the determination of low concentrations of lead and cadmium in water samples. Ligand assisted pseudo-stir bar hollow fiber solid/liquid phase microextraction using sol–gel sorbent reinforced with carbon nanotubes was combined with differential pulse anodic stripping voltammetry for simultaneous determination of cadmium and lead in tap water, and Darongar river water samples. In the present work, differential pulse anodic stripping voltammetry (DPASV) using a hanging mercury drop electrode (HMDE) was used in order to determine the ultra trace level of lead and cadmium ions in real samples. This method is based on accumulation of lead and cadmium ions on the electrode using different ligands; Quinolin-8-ol, 5,7-diiodo quinoline-8-ol, 4,5-diphenyl-1H-imidazole-2(3H)-one and 2-{[2-(2-Hydroxy-ethylamino)-ethylamino]-methyl}-phenol as the complexing agent. The optimized conditions were obtained. The relationship between the peak current versus concentration was linear over the range of 0.05–500 ng mL−1 for Cd (II) and Pb (II). The limits of detection for lead and cadmium were 0.015 ng mL−1 and 0.012 ng mL−1, respectively. Under the optimized conditions, the pre-concentration factors are 2440 and 3710 for Cd (II) and Pb (II) in 5 mL of water sample, respectively. PMID:25685537

  3. Integrated wireless fast-scan cyclic voltammetry recording and electrical stimulation for reward-predictive learning in awake, freely moving rats

    NASA Astrophysics Data System (ADS)

    Li, Yu-Ting; Wickens, Jeffery R.; Huang, Yi-Ling; Pan, Wynn H. T.; Chen, Fu-Yu Beverly; Chen, Jia-Jin Jason

    2013-08-01

    Objective. Fast-scan cyclic voltammetry (FSCV) is commonly used to monitor phasic dopamine release, which is usually performed using tethered recording and for limited types of animal behavior. It is necessary to design a wireless dopamine sensing system for animal behavior experiments. Approach. This study integrates a wireless FSCV system for monitoring the dopamine signal in the ventral striatum with an electrical stimulator that induces biphasic current to excite dopaminergic neurons in awake freely moving rats. The measured dopamine signals are unidirectionally transmitted from the wireless FSCV module to the host unit. To reduce electrical artifacts, an optocoupler and a separate power are applied to isolate the FSCV system and electrical stimulator, which can be activated by an infrared controller. Main results. In the validation test, the wireless backpack system has similar performance in comparison with a conventional wired system and it does not significantly affect the locomotor activity of the rat. In the cocaine administration test, the maximum electrically elicited dopamine signals increased to around 230% of the initial value 20 min after the injection of 10 mg kg-1 cocaine. In a classical conditioning test, the dopamine signal in response to a cue increased to around 60 nM over 50 successive trials while the electrically evoked dopamine concentration decreased from about 90 to 50 nM in the maintenance phase. In contrast, the cue-evoked dopamine concentration progressively decreased and the electrically evoked dopamine was eliminated during the extinction phase. In the histological evaluation, there was little damage to brain tissue after five months chronic implantation of the stimulating electrode. Significance. We have developed an integrated wireless voltammetry system for measuring dopamine concentration and providing electrical stimulation. The developed wireless FSCV system is proven to be a useful experimental tool for the continuous

  4. Integrated wireless fast-scan cyclic voltammetry recording and electrical stimulation for reward-predictive learning in awake, freely moving rats.

    PubMed

    Li, Yu-Ting; Wickens, Jeffery R; Huang, Yi-Ling; Pan, Wynn H T; Chen, Fu-Yu Beverly; Chen, Jia-Jin Jason

    2013-08-01

    Fast-scan cyclic voltammetry (FSCV) is commonly used to monitor phasic dopamine release, which is usually performed using tethered recording and for limited types of animal behavior. It is necessary to design a wireless dopamine sensing system for animal behavior experiments. This study integrates a wireless FSCV system for monitoring the dopamine signal in the ventral striatum with an electrical stimulator that induces biphasic current to excite dopaminergic neurons in awake freely moving rats. The measured dopamine signals are unidirectionally transmitted from the wireless FSCV module to the host unit. To reduce electrical artifacts, an optocoupler and a separate power are applied to isolate the FSCV system and electrical stimulator, which can be activated by an infrared controller. In the validation test, the wireless backpack system has similar performance in comparison with a conventional wired system and it does not significantly affect the locomotor activity of the rat. In the cocaine administration test, the maximum electrically elicited dopamine signals increased to around 230% of the initial value 20 min after the injection of 10 mg kg(-1) cocaine. In a classical conditioning test, the dopamine signal in response to a cue increased to around 60 nM over 50 successive trials while the electrically evoked dopamine concentration decreased from about 90 to 50 nM in the maintenance phase. In contrast, the cue-evoked dopamine concentration progressively decreased and the electrically evoked dopamine was eliminated during the extinction phase. In the histological evaluation, there was little damage to brain tissue after five months chronic implantation of the stimulating electrode. We have developed an integrated wireless voltammetry system for measuring dopamine concentration and providing electrical stimulation. The developed wireless FSCV system is proven to be a useful experimental tool for the continuous monitoring of dopamine levels during animal learning

  5. Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

    PubMed Central

    Liu, Shang-Yi; Chang, Jung-Hung; -Wen Wu, I.; Wu, Chih-I

    2014-01-01

    We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m2 obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage. PMID:25523436

  6. Alternating current transport and dielectric relaxation of nanocrystalline graphene oxide

    NASA Astrophysics Data System (ADS)

    Zedan, I. T.; El-Menyawy, E. M.

    2018-07-01

    Graphene oxide (GO) has been synthesized from natural graphite using modified Hummer's method and is subjected to sonication for 1 h. X-ray diffraction (XRD) showed that the prepared GO has nanocrystalline structure with particle size of about 5 nm and high-resolution transmission electron microscope showed that it had a layered structure. The nanocrystalline GO powder was pressed as a disk and the alternating current (AC) electrical conductivity, σAC, and dielectric properties have been investigated in the frequency range 50Hz-5 MHz and temperature range 298-523K using parallel plate spectroscopic technique. Analysis of σ AC as a function of frequency shows that the relation follows Jonscher's universal law with frequency exponent decreases with increasing temperature in which the correlated barrier hopping model is applicable to describe the behavior. The dielectric constant and dielectric loss are studied as functions of frequency and temperature. The dielectric modulus formalism is used for describing the relaxation process in which the relaxation time and its activation energy were evaluated.

  7. Determination of carmine food dye (E120) in foodstuffs by stripping voltammetry.

    PubMed

    Alghamdi, Ahmad H; Alshammery, Hamed M; Abdalla, Mohamed A; Alghamdi, Ali F

    2009-01-01

    The behavior of the food colorant agent carmine (E120) was studied by square-wave adsorptive stripping voltammetry (SW-AdSV) at the hanging mercury drop electrode. It was observed that carmine gave a sensitive stripping voltammetric peak at -350 mV in pH 3 acetate buffer. The cyclic voltammetric technique was also used to characterize the electrochemical reduction process of carmine. The adsorptive voltammetric signal was evaluated with respect to various experimental conditions, and the optimized values were supporting electrolyte, acetate buffer; buffer acidity, pH 3; dye concentration, 3 x 10(-7) M; accumulation time, 150 s; accumulation potential, -0.2 V; scan rate, 300 mV/s; pulse amplitude, 185 mV; SW frequency, 20 Hz; working electrode area, 0.6 mm2; and convection rate, 2600 rpm. The SW-AdSV peak currents depended linearly on the concentration of carmine from 5 x 10(-8) to 1.25 x 10(-7) mol/L (r = 0.99). A detection limit of 1.43 x 10(-9) mol/L with an RSD of 2.2% and a mean recovery of 97.9% were obtained. Possible interferences by several substances usually present in food products such as food additive dyes (E102, E100, E123, E127, and E129), artificial sweeteners, preservatives, and antioxidants were also evaluated. The proposed electrochemical procedure was successfully applied to the determination of carmine food dye in spiked commercially available ice cream and soft drinks.

  8. Regional economic impacts of current and proposed management alternatives for Don Edwards National Wildlife Refuge

    USGS Publications Warehouse

    Richardson, Leslie; Huber, Chris; Koontz, Lynne

    2012-01-01

    The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan. The Comprehensive Conservation Plan must describe the desired future conditions of a Refuge and provide long-range guidance and management direction to achieve refuge purposes. The Don Edwards San Francisco Bay National Wildlife Refuge, located at the south end of California's San Francisco Bay and one of seven refuges in the San Francisco Bay National Wildlife Refuge Complex, is in the process of developing a range of management goals, objectives, and strategies for the Comprehensive Conservation Plan. The Comprehensive Conservation Plan must contain an analysis of expected effects associated with current and proposed Refuge management strategies. For Refuge Comprehensive Conservation Plan planning, a regional economic analysis provides a means of estimating how current management (No Action Alternative) and proposed management activities (alternatives) affect the local economy. This type of analysis provides two critical pieces of information: (1) it illustrates the Don Edwards San Francisco Bay National Wildlife Refuge's contribution to the local community, and (2) it can help in determining whether economic effects are or are not a real concern in choosing among management alternatives. This report first presents a description of the local community and economy near the Don Edwards San Francisco Bay National Wildlife Refuge. Next, the methods used to conduct a regional economic impact analysis are described. An analysis of the final Comprehensive Conservation Plan management strategies that could affect stakeholders, residents, and the local economy is then presented. The management activities of economic concern in this analysis are: * Spending in the local community by Refuge visitors; * Refuge personnel salary spending; and * Refuge purchases of goods and services within the local

  9. Nanoalloy electrocatalysis: simulating cyclic voltammetry from configurational thermodynamics with adsorbates.

    PubMed

    Wang, Lin-Lin; Tan, Teck L; Johnson, Duane D

    2015-11-14

    We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd-Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites that is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. The method provides a more complete means to design nanoalloys for electrocatalysis.

  10. Determination of trace mercury in water based on N-octylpyridinium ionic liquids preconcentration and stripping voltammetry.

    PubMed

    Li, Zhenhan; Xia, Shanhong; Wang, Jinfen; Bian, Chao; Tong, Jianhua

    2016-01-15

    A novel method for determination of trace mercury in water is developed. The method is performed by extracting mercury firstly with ionic liquids (ILs) and then detecting the concentration of mercury in organic media with anodic stripping voltammetry. Liquid-liquid extraction of mercury(II) ions by four ionic liquids with N-octylpyridinium cations ([OPy](+)) was studied. N-octylpyridinium tetrafluoroborate and N-octylpyridinium trifluoromethylsulfonate were found to be efficient and selective extractant for mercury. Temperature controlled dispersive liquid phase microextraction (TC-DLPME) technique was utilized to improve the performance of preconcentration. After extraction, precipitated IL was diluted by acetonitrile buffer and mercury was detected by differential pulse stripping voltammetry (DPSV) with gold disc electrode. Mercury was enriched by 17 times while interfering ions were reduced by two orders of magnitude in the organic media under optimum condition. Sensitivity and selectivity for electrochemical determination of mercury were improved by using the proposed method. Tap, pond and waste water samples were analyzed with recoveries ranging from 81% to 107% and detection limit of 0.05 μg/L. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Alternating-Current InGaN/GaN Tunnel Junction Nanowire White-Light Emitting Diodes.

    PubMed

    Sadaf, S M; Ra, Y-H; Nguyen, H P T; Djavid, M; Mi, Z

    2015-10-14

    The current LED lighting technology relies on the use of a driver to convert alternating current (AC) to low-voltage direct current (DC) power, a resistive p-GaN contact layer to inject positive charge carriers (holes) for blue light emission, and rare-earth doped phosphors to down-convert blue photons into green/red light, which have been identified as some of the major factors limiting the device efficiency, light quality, and cost. Here, we show that multiple-active region phosphor-free InGaN nanowire white LEDs connected through a polarization engineered tunnel junction can fundamentally address the afore-described challenges. Such a p-GaN contact-free LED offers the benefit of carrier regeneration, leading to enhanced light intensity and reduced efficiency droop. Moreover, through the monolithic integration of p-GaN up and p-GaN down nanowire LED structures on the same substrate, we have demonstrated, for the first time, AC operated LEDs on a Si platform, which can operate efficiently in both polarities (positive and negative) of applied voltage.

  12. An alternative explanation for the occurrence of short circuit current increases in the small intestine following challenge by bacterial enterotoxins.

    PubMed

    Lucas, M L

    2013-10-01

    Secretory diarrhoeal disease due to enterotoxins is thought to arise from the enhancement to pathologically high rates of normally occurring chloride ion and therefore fluid secretion from enterocytes. In support of this concept, many enterotoxins increase intestinal short-circuit current, regarded now as faithfully reflecting the increased chloride ion secretion. Contradicting this assumption, STa reduces absorption but does not cause secretion in vivo although short-circuit current is increased in vitro. There is therefore a mismatch between an assumed enterocyte mediated secretory event that should but does not cause net fluid secretion and an undoubtedly increased short-circuit current. It is proposed here that short-circuit current increases are not themselves secretory events but result from interrupted fluid absorption. A noteworthy feature of compounds that inhibit the increase in short-circuit current is that the majority are vasoactive, neuroactive or both. In general, vasodilator substances increase current. An alternative hypothesis for the origin of short-circuit current increases is that these result from reflex induction of electrogenic fluid absorption. This reflex enhances a compensatory response that is also present at a cellular level. An intestinal reflex is therefore proposed by which decreases in interstitial and intravascular volume or pressure within the intestine initiate an electrogenic fluid absorption mechanism that compensates for the loss of electrically neutral fluid absorption. This hypothesis would explain the apparently complex pharmacology of short-circuit current increases since many depressor substances have receptors in common with enterocytes and enteric nerves. The proposed alternative view of the origin of short-circuit current increases assumes that these do not represent chloride secretion from the enterocytes. This view may therefore aid the successful development of anti-diarrhoeal drugs to overcome a major cause of

  13. Limiting diffusion current at rotating disk electrode with dense particle layer.

    PubMed

    Weroński, P; Nosek, M; Batys, P

    2013-09-28

    Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

  14. Evaluation of Delamination of X80 Pipeline Steel Coating Under Alternating Stray Current Via Scanning Electrochemical Microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Xinhua; Liu, Qiang; Chun, Yingchun; Li, Yingchao; Wang, Zuquan

    2018-04-01

    The delamination of epoxy coating on X80 pipeline steel was evaluated under various stray alternating current (AC) interferences (0-300 A/m2). Qualitative and quantitative analyses were carried out using scanning electrochemical microscopy (SECM), electrochemical impedance spectroscopy (EIS), and three-dimensional digital microscopy. The results show that the SECM current is directly proportional to the soaking time and applied current density. The variation in SECM current curve shape indicates the delamination distance of epoxy coatings at the defect area. The depths of corrosion pits at 50, 100, and 300 A/m2 stray currents were 140, 160, and 240 μm, respectively. The corrosion pits also became wider with increasing current densities. With increasing stray AC densities, both the coating delamination and pit depth became more severe at the same soaking time. The EIS results show that the change in impedance was not significant without stray current, whereas the impedance first decreased and then increased when stray current was applied. These results are consistent with the SECM measurements.

  15. Cyclic voltammetry modeling of proton transport effects on redox charge storage in conductive materials: application to a TiO2 mesoporous film.

    PubMed

    Kim, Y S; Balland, V; Limoges, B; Costentin, C

    2017-07-21

    Cyclic voltammetry is a particularly useful tool for characterizing charge accumulation in conductive materials. A simple model is presented to evaluate proton transport effects on charge storage in conductive materials associated with a redox process coupled with proton insertion in the bulk material from an aqueous buffered solution, a situation frequently encountered in metal oxide materials. The interplay between proton transport inside and outside the materials is described using a formulation of the problem through introduction of dimensionless variables that allows defining the minimum number of parameters governing the cyclic voltammetry response with consideration of a simple description of the system geometry. This approach is illustrated by analysis of proton insertion in a mesoporous TiO 2 film.

  16. Fabrication strategies, sensing modes and analytical applications of ratiometric electrochemical biosensors.

    PubMed

    Jin, Hui; Gui, Rijun; Yu, Jianbo; Lv, Wei; Wang, Zonghua

    2017-05-15

    Previously developed electrochemical biosensors with single-electric signal output are probably affected by intrinsic and extrinsic factors. In contrast, the ratiometric electrochemical biosensors (RECBSs) with dual-electric signal outputs have an intrinsic built-in correction to the effects from system or background electric signals, and therefore exhibit a significant potential to improve the accuracy and sensitivity in electrochemical sensing applications. In this review, we systematically summarize the fabrication strategies, sensing modes and analytical applications of RECBSs. First, the different fabrication strategies of RECBSs were introduced, referring to the analytes-induced single- and dual-dependent electrochemical signal strategies for RECBSs. Second, the different sensing modes of RECBSs were illustrated, such as differential pulse voltammetry, square wave voltammetry, cyclic voltammetry, alternating current voltammetry, electrochemiluminescence, and so forth. Third, the analytical applications of RECBSs were discussed based on the types of target analytes. Finally, the forthcoming development and future prospects in the research field of RECBSs were also highlighted. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Sampling phasic dopamine signaling with fast-scan cyclic voltammetry in awake behaving rats

    PubMed Central

    Fortin, SM; Cone, JJ; Ng-Evans, S; McCutcheon, JE; Roitman, MF

    2015-01-01

    Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique which permits the in vivo measurement of extracellular fluctuations in multiple chemical species. The technique is frequently utilized to sample sub-second (phasic) concentration changes of the neurotransmitter dopamine in awake and behaving rats. Phasic dopamine signaling is implicated in reinforcement, goal-directed behavior, and locomotion and FSCV has been used to investigate how rapid changes in striatal dopamine concentration contribute to these and other behaviors. This unit describes the instrumentation and construction, implantation, and use of necessary components required to sample and analyze dopamine concentration changes in awake rats with FSCV. PMID:25559005

  18. Alternative (non-animal) methods for cosmetics testing: current status and future prospects-2010.

    PubMed

    Adler, Sarah; Basketter, David; Creton, Stuart; Pelkonen, Olavi; van Benthem, Jan; Zuang, Valérie; Andersen, Klaus Ejner; Angers-Loustau, Alexandre; Aptula, Aynur; Bal-Price, Anna; Benfenati, Emilio; Bernauer, Ulrike; Bessems, Jos; Bois, Frederic Y; Boobis, Alan; Brandon, Esther; Bremer, Susanne; Broschard, Thomas; Casati, Silvia; Coecke, Sandra; Corvi, Raffaella; Cronin, Mark; Daston, George; Dekant, Wolfgang; Felter, Susan; Grignard, Elise; Gundert-Remy, Ursula; Heinonen, Tuula; Kimber, Ian; Kleinjans, Jos; Komulainen, Hannu; Kreiling, Reinhard; Kreysa, Joachim; Leite, Sofia Batista; Loizou, George; Maxwell, Gavin; Mazzatorta, Paolo; Munn, Sharon; Pfuhler, Stefan; Phrakonkham, Pascal; Piersma, Aldert; Poth, Albrecht; Prieto, Pilar; Repetto, Guillermo; Rogiers, Vera; Schoeters, Greet; Schwarz, Michael; Serafimova, Rositsa; Tähti, Hanna; Testai, Emanuela; van Delft, Joost; van Loveren, Henk; Vinken, Mathieu; Worth, Andrew; Zaldivar, José-Manuel

    2011-05-01

    The 7th amendment to the EU Cosmetics Directive prohibits to put animal-tested cosmetics on the market in Europe after 2013. In that context, the European Commission invited stakeholder bodies (industry, non-governmental organisations, EU Member States, and the Commission's Scientific Committee on Consumer Safety) to identify scientific experts in five toxicological areas, i.e. toxicokinetics, repeated dose toxicity, carcinogenicity, skin sensitisation, and reproductive toxicity for which the Directive foresees that the 2013 deadline could be further extended in case alternative and validated methods would not be available in time. The selected experts were asked to analyse the status and prospects of alternative methods and to provide a scientifically sound estimate of the time necessary to achieve full replacement of animal testing. In summary, the experts confirmed that it will take at least another 7-9 years for the replacement of the current in vivo animal tests used for the safety assessment of cosmetic ingredients for skin sensitisation. However, the experts were also of the opinion that alternative methods may be able to give hazard information, i.e. to differentiate between sensitisers and non-sensitisers, ahead of 2017. This would, however, not provide the complete picture of what is a safe exposure because the relative potency of a sensitiser would not be known. For toxicokinetics, the timeframe was 5-7 years to develop the models still lacking to predict lung absorption and renal/biliary excretion, and even longer to integrate the methods to fully replace the animal toxicokinetic models. For the systemic toxicological endpoints of repeated dose toxicity, carcinogenicity and reproductive toxicity, the time horizon for full replacement could not be estimated.

  19. Lead detection using micro/nanocrystalline boron-doped diamond by square-wave anodic stripping voltammetry.

    PubMed

    Arantes, Tatiane M; Sardinha, André; Baldan, Mauricio R; Cristovan, Fernando H; Ferreira, Neidenei G

    2014-10-01

    Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 μg L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Application of catalytic adsorptive stripping voltammetry of the cobalt-alpha-benzil dioxime complex to analysis of cobalt traces in metallic zinc.

    PubMed

    Bobrowski, A

    1994-05-01

    The catalytic adsorptive stripping voltammetric method with alpha-benzil dioxime and nitrite affords numerous advantages in cobalt determination. The detailed conditions of the determination of the cobalt traces in metallic zinc by catalytic adsorptive stripping voltammetry have been investigated. Both the linear sweep and the differential pulse stripping modes can be used with similar sensitivity. Possible interferences by Mn, Pb, Cu, Ni and Fe are evaluated. In the presence of 5 x 10(5) fold excess of Zn the linear dependence of the cobalt CASV peak current on concentration ranged from 0.05 mug/l to 3 mug/l. Optimal conditions include the accumulation potential of -0.65 V and the accumulation time of 10 sec. The results of the determination of 10(-5)% level of Co in the metallic zinc showed good reproducibility (relative standard deviation, RSD = 0.07) and reliability.

  1. Nanoalloy electrocatalysis: Simulating cyclic voltammetry from configurational thermodynamics with adsorbates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Lin -Lin; Tan, Teck L.; Johnson, Duane D.

    2015-02-27

    We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd–Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites thatmore » is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. As a result, the method provides a more complete means to design nanoalloys for electrocatalysis.« less

  2. Determination of cadmium in sewage sludge by differential pulse anodic stripping voltammetry.

    PubMed

    Pacer, R A; Scott Ellis, C K; Peng, R

    1999-07-12

    A procedure was developed for the determination of cadmium in sewage sludge by differential pulse anodic stripping voltammetry. A sodium peroxide fusion carried out in zirconium crucibles was found to give satisfactory results, based on analysis of standard reference materials. Samples collected from the municipal sludge lagoon in Fort Wayne, Indiana were found to have cadmium abundances ranging from 120 to 250 ppm, with most samples falling in the 120 to 170 ppm range. Interference from zinc is easily eliminated by carrying out the deposition step at -0.95 V vs. Ag/AgCl. Lead-to-cadmium ratios as high as 50:1 (ppm basis) have no effect on the height of the cadmium peak.

  3. Characterization of Local pH Changes in Brain Using Fast-Scan Cyclic Voltammetry with Carbon Microelectrodes

    PubMed Central

    Takmakov, Pavel; Zachek, Matthew K.; Keithley, Richard B.; Bucher, Elizabeth; McCarty, Gregory S.; Wightman, R. Mark

    2010-01-01

    Transient local pH changes in the brain are important markers of neural activity that can be used to follow metabolic processes that underlie the biological basis of behavior, learning and memory. There are few methods that can measure pH fluctuations with sufficient time resolution in freely moving animals. Previously, fast-scan cyclic voltammetry at carbon-fiber microelectrodes was used for the measurement of such pH transients. However, the origin of the potential dependent current in the cyclic voltammograms for pH changes recorded in vivo was unclear. The current work explored the nature of these peaks and established the origin for some of them. A peak relating to the capacitive nature of the pH CV was identified. Adsorption of electrochemically inert species, such as aromatic amines and calcium could suppress this peak, and is the origin for inconsistencies regarding in vivo and in vitro data. Also, we identified an extra peak in the in vivo pH CV relating to the presence of 3,4-dihydroxyacetic acid (DOPAC) in the brain extracellular fluid. To evaluate the in vivo performance of the carbon-fiber sensor, carbon dioxide inhalation by an anesthetized rat was used to induce brain acidosis induced by hypercapnia. Hypercapnia is demonstrated to be a useful tool to induce robust in vivo pH changes, allowing confirmation of the pH signal observed with FSCV. PMID:21047096

  4. Cyclic Voltammetry Probe Approach Curves with Alkali Amalgams at Mercury Sphere-Cap Scanning Electrochemical Microscopy Probes.

    PubMed

    Barton, Zachary J; Rodríguez-López, Joaquín

    2017-03-07

    We report a method of precisely positioning a Hg-based ultramicroelectrode (UME) for scanning electrochemical microscopy (SECM) investigations of any substrate. Hg-based probes are capable of performing amalgamation reactions with metal cations, which avoid unwanted side reactions and positive feedback mechanisms that can prove problematic for traditional probe positioning methods. However, prolonged collection of ions eventually leads to saturation of the amalgam accompanied by irreversible loss of Hg. In order to obtain negative feedback positioning control without risking damage to the SECM probe, we implement cyclic voltammetry probe approach surfaces (CV-PASs), consisting of CVs performed between incremental motor movements. The amalgamation current, peak stripping current, and integrated stripping charge extracted from a shared CV-PAS give three distinct probe approach curves (CV-PACs), which can be used to determine the tip-substrate gap to within 1% of the probe radius. Using finite element simulations, we establish a new protocol for fitting any CV-PAC and demonstrate its validity with experimental results for sodium and potassium ions in propylene carbonate by obtaining over 3 orders of magnitude greater accuracy and more than 20-fold greater precision than existing methods. Considering the timescales of diffusion and amalgam saturation, we also present limiting conditions for obtaining and fitting CV-PAC data. The ion-specific signals isolated in CV-PACs allow precise and accurate positioning of Hg-based SECM probes over any sample and enable the deployment of CV-PAS SECM as an analytical tool for traditionally challenging conditions.

  5. Alternating-current conductivity and dielectric relaxation of bulk iodoargentate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Duan, Hai-Bao, E-mail: duanhaibao4660@163.com; Yu, Shan-Shan; Zhou, Hong

    Graphical abstract: The electric modulus shows single dielectric relaxation process in the measured frequency range. - Highlights: • The conduction mechanism is described by quantum mechanical tunneling model. • The applications of dielectric modulus give a simple method for evaluating the activation energy of the dielectric relaxation. • The [Ag{sub 2}I{sub 4}]{sup 2−}1-D chain and [Cu(en){sub 2}]{sup 2+} cation column form the layered stacks by hydrogen bond interactions. - Abstract: An inorganic-organic hybrid compound Cu(en){sub 2}Ag{sub 2}I{sub 4} (en = ethylenediamine) (1) was synthesized and single crystal structurally characterized. Along the [001] direction, the inorganic parts form an infinite 1-Dmore » chain and [Cu(en){sub 2}]{sup 2+} cations are separated by inorganic chain. The electrical conductivity and dielectric properties of 1 have been investigated over wide ranges of frequency. The alternating-current conductivities have been fitted to the Almond–West type power law expression with use of a single value of S. It is found that S values for 1 are nearly temperature-independent, which indicates that the conduction mechanism could be quantum mechanical tunneling (QMT) model. The dielectric loss and electric modulus show single dielectric relaxation process. The activation energy obtained from temperature-dependent electric modulus compare with the calculated from the dc conductivity plots.« less

  6. Characterizing AISI 1045 steel surface duplex-treated by alternating current field enhanced pack aluminizing and nitriding

    NASA Astrophysics Data System (ADS)

    Xie, Fei; Zhang, Ge; Pan, Jianwei

    2018-02-01

    Thin cases and long treating time are shortcomings of conventional duplex treatment of aluminizing followed by nitriding (DTAN). Alternating current field (ACF) enhanced DTAN was carried out on AISI 1045 steel by applying an ACF to treated samples and treating agents with a pair of electrodes for overcoming those shortcomings. By investigating cases' structures, phases, composition and hardness distributions of differently treated samples, preliminary studies were made on characterizations of the ACF enhanced duplex treatment to AISI 1045 steel. The results show that, with the help of the ACF, the surface Al-rich phase Al5Fe2 formed in conventional pack aluminizing can be easily avoided and the aluminizing process is dramatically promoted. The aluminizing case can be nitrided either with conventional pack nitriding or ACF enhanced pack nitriding. By applying ACF to pack nitriding, the diffusion of nitrogen into the aluminizing case is promoted. AlN, Fe2∼3N and solid solution of N in iron are efficiently formed as a result of reactions of N with the aluminizing case. A duplex treated case with an effective thickness of more than 170 μm can be obtained by the alternating current field enhanced 4 h pack aluminizing plus 4 h pack nitriding.

  7. A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Samin, Adib J.

    In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level and may be useful for analyzing qualitative features observed in experimentally recorded signals.

  8. A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects

    NASA Astrophysics Data System (ADS)

    Samin, Adib J.

    2016-05-01

    In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level and may be useful for analyzing qualitative features observed in experimentally recorded signals.

  9. Estimation of the composition of intermetallic compounds in LiCl-KCl molten salt by cyclic voltammetry.

    PubMed

    Liu, Ya L; Liu, Kui; Yuan, Li Y; Chai, Zhi F; Shi, Wei Q

    2016-08-15

    In this work, the compositions of Ce-Al, Er-Al and La-Bi intermetallic compounds were estimated by the cyclic voltammetry (CV) technique. At first, CV measurements were carried out at different reverse potentials to study the co-reduction processes of Ce-Al, Er-Al and La-Bi systems. The CV curves obtained were then re-plotted with the current as a function of time, and the coulomb number of each peak was calculated. By comparing the coulomb number of the related peaks, the compositions of the Ce-Al, Er-Al and La-Bi intermetallic compounds formed in the co-reduction process could be estimated. The results showed that Al11Ce3, Al3Ce, Al2Ce and AlCe could be formed by the co-reduction of Ce(iii) and Al(iii). For the co-reduction of Er(iii) and Al(iii), Al3Er2, Al2Er and AlEr were formed. In a La(iii) and Bi(iii) co-existing system in LiCl-KCl melts, LaBi2, LaBi and Li3Bi were the major products as a result of co-reduction.

  10. Influence of direct and alternating current electric fields on efficiency promotion and leaching risk alleviation of chelator assisted phytoremediation.

    PubMed

    Luo, Jie; Cai, Limei; Qi, Shihua; Wu, Jian; Sophie Gu, Xiaowen

    2018-03-01

    Direct and alternating current electric fields with various voltages were used to improve the decontamination efficiency of chelator assisted phytoremediation for multi-metal polluted soil. The alleviation effect of electric field on leaching risk caused by chelator application during phytoremediation process was also evaluated. Biomass yield, pollutant uptake and metal leaching retardation under alternating current (AC) and direct current (DC) electric fields were compared. The biomass yield of Eucalyptus globulus under AC fields with various voltages (2, 4 and 10 V) were 3.91, 4.16 and 3.67kg, respectively, significantly higher than the chelator treatment without electric field (2.71kg). Besides growth stimulation, AC fields increased the metal concentrations of plant tissues especially in aerial parts manifested by the raised translocation factor of different metals. Direct current electric fields with low and moderate voltages increased the biomass production of the species to 3.45 and 3.12kg, respectively, while high voltage on the contrary suppressed the growth of the plants (2.66kg). Under DC fields, metal concentrations elevated obviously with increasing voltages and the metal translocation factors were similar under all voltages. Metal extraction per plant achieved the maximum value under moderate voltage due to the greatest biomass production. DC field with high voltage (10V) decreased the volume of leachate from the chelator treatment without electric field from 1224 to 56mL, while the leachate gathered from AC field treatments raised from 512 to 670mL. DC field can retard the downward movement of metals caused by chelator application more effectively relative to AC field due to the constant water flow and electroosmosis direction. Alternating current field had more promotive effect on chelator assisted phytoremediation efficiency than DC field illustrated by more metal accumulation in the species. However, with the consideration of leaching risk, DC

  11. Glyphosate detection with ammonium nitrate and humic acids as potential interfering substances by pulsed voltammetry technique.

    PubMed

    Martínez Gil, Pablo; Laguarda-Miro, Nicolas; Camino, Juan Soto; Peris, Rafael Masot

    2013-10-15

    Pulsed voltammetry has been used to detect and quantify glyphosate on buffered water in presence of ammonium nitrate and humic substances. Glyphosate is the most widely used herbicide active ingredient in the world. It is a non-selective broad spectrum herbicide but some of its health and environmental effects are still being discussed. Nowadays, glyphosate pollution in water is being monitored but quantification techniques are slow and expensive. Glyphosate wastes are often detected in countryside water bodies where organic substances and fertilizers (commonly based on ammonium nitrate) may also be present. Glyphosate also forms complexes with humic acids so these compounds have also been taken into consideration. The objective of this research is to study the interference of these common pollutants in glyphosate measurements by pulsed voltammetry. The statistical treatment of the voltammetric data obtained lets us discriminate glyphosate from the other studied compounds and a mathematical model has been built to quantify glyphosate concentrations in a buffer despite the presence of humic substances and ammonium nitrate. In this model, the coefficient of determination (R(2)) is 0.977 and the RMSEP value is 2.96 × 10(-5) so the model is considered statistically valid. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid.

    PubMed

    Yang, Guangming; Li, Ling; Jiang, Jinhe; Yang, Yunhui

    2012-08-01

    Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3 min and 2 min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02×10(-7)-5.23×10(-4) mol L(-1) and 1.43×10(-7)-4.64×10(-4) mol L(-1), the detection limits were 1.12×10(-8) mol L(-1) and 2.24×10(-8) mol L(-1), respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Alternating current line-filter based on electrochemical capacitor utilizing template-patterned graphene.

    PubMed

    Wu, Zhenkun; Li, Liyi; Lin, Ziyin; Song, Bo; Li, Zhuo; Moon, Kyoung-Sik; Wong, Ching-Ping; Bai, Shu-Lin

    2015-06-17

    Aluminum electrolytic capacitors (AECs) are widely used for alternating current (ac) line-filtering. However, their bulky size is becoming more and more incompatible with the rapid development of portable electronics. Here we report a scalable process to fabricate miniaturized graphene-based ac line-filters on flexible substrates at room temperature. In this work, graphene oxide (GO) is reduced by patterned metal interdigits at room temperature and used directly as the electrode material. The as-fabricated device shows a phase angle of -75.4° at 120 Hz with a specific capacitance of 316 µF/cm(2) and a RC time constant of 0.35 ms. In addition, it retains 97.2% of the initial capacitance after 10000 charge/discharge cycles. These outstanding performance characteristics of our device demonstrate its promising to replace the conventional AECs for ac line filtering.

  14. Transcranial Alternating Current Stimulation: A Potential Risk for Genetic Generalized Epilepsy Patients (Study Case)

    PubMed Central

    San-Juan, Daniel; Sarmiento, Carlos Ignacio; Hernandez-Ruiz, Axel; Elizondo-Zepeda, Ernesto; Santos-Vázquez, Gabriel; Reyes-Acevedo, Gerardo; Zúñiga-Gazcón, Héctor; Zamora-Jarquín, Carol Marina

    2016-01-01

    Transcranial alternating current stimulation (tACS) is a re-emergent neuromodulation technique that consists in the external application of oscillating electrical currents that induces changes in cortical excitability. We present the case of a 16-year-old female with pharmaco-resistant juvenile myoclonic epilepsy to 3 antiepileptic’s drugs characterized by 4 myoclonic and 20 absence seizures monthly. She received tACS at 1 mA at 3 Hz pulse train during 60 min over Fp1–Fp2 (10–20 EEG international system position) during 4 consecutive days using an Endeavor™ IOM Systems device® (Natus Medical Incorporated, Middleton, WI, USA). At the 1-month follow-up, she reported a 75% increase in seizures frequency (only myoclonic and tonic–clonic events) and developed a 24-h myoclonic status epilepticus that resolved with oral clonazepam and intravenous valproate. At the 2-month follow-up, the patient reported a 15-day seizure-free period. PMID:27965623

  15. Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications.

    PubMed

    Bertoluzzi, Luca; Badia-Bou, Laura; Fabregat-Santiago, Francisco; Gimenez, Sixto; Bisquert, Juan

    2013-04-18

    A simple model is proposed that allows interpretation of the cyclic voltammetry diagrams obtained experimentally for photoactive semiconductors with surface states or catalysts used for fuel production from sunlight. When the system is limited by charge transfer from the traps/catalyst layer and by detrapping, it is shown that only one capacitive peak is observable and is not recoverable in the return voltage scan. If the system is limited only by charge transfer and not by detrapping, two symmetric capacitive peaks can be observed in the cathodic and anodic directions. The model appears as a useful tool for the swift analysis of the electronic processes that limit fuel production.

  16. Sampling phasic dopamine signaling with fast-scan cyclic voltammetry in awake, behaving rats.

    PubMed

    Fortin, S M; Cone, J J; Ng-Evans, S; McCutcheon, J E; Roitman, M F

    2015-01-05

    Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique that permits the in vivo measurement of extracellular fluctuations in multiple chemical species. The technique is frequently utilized to sample sub-second (phasic) concentration changes of the neurotransmitter dopamine in awake and behaving rats. Phasic dopamine signaling is implicated in reinforcement, goal-directed behavior, and locomotion, and FSCV has been used to investigate how rapid changes in striatal dopamine concentration contribute to these and other behaviors. This unit describes the instrumentation and construction, implantation, and use of components required to sample and analyze dopamine concentration changes in awake rats with FSCV. Copyright © 2015 John Wiley & Sons, Inc.

  17. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry

    PubMed Central

    Alatraktchi, Fatima AlZahra’a; Breum Andersen, Sandra; Krogh Johansen, Helle; Molin, Søren; Svendsen, Winnie E.

    2016-01-01

    Pyocyanin is a virulence factor uniquely produced by the pathogen Pseudomonas aeruginosa. The fast and selective detection of pyocyanin in clinical samples can reveal important information about the presence of this microorganism in patients. Electrochemical sensing of the redox-active pyocyanin is a route to directly quantify pyocyanin in real time and in situ in hospitals and clinics. The selective quantification of pyocyanin is, however, limited by other redox-active compounds existing in human fluids and by other metabolites produced by pathogenic bacteria. Here we present a direct selective method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between −1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58–0.82 V that is unaffected by other redox-active interferents. The linear quantification of pyocyanin has an R2 value of 0.991 across the clinically relevant concentration range of 2–100 µM. The proposed method was tested on human saliva showing a standard deviation of 2.5% ± 1% (n = 5) from the known added pyocyanin concentration to the samples. This inexpensive procedure is suggested for clinical use in monitoring the presence and state of P. aeruginosa infection in patients. PMID:27007376

  18. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry.

    PubMed

    Alatraktchi, Fatima AlZahra'a; Andersen, Sandra Breum; Johansen, Helle Krogh; Molin, Søren; Svendsen, Winnie E

    2016-03-19

    Pyocyanin is a virulence factor uniquely produced by the pathogen Pseudomonas aeruginosa. The fast and selective detection of pyocyanin in clinical samples can reveal important information about the presence of this microorganism in patients. Electrochemical sensing of the redox-active pyocyanin is a route to directly quantify pyocyanin in real time and in situ in hospitals and clinics. The selective quantification of pyocyanin is, however, limited by other redox-active compounds existing in human fluids and by other metabolites produced by pathogenic bacteria. Here we present a direct selective method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between -1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58-0.82 V that is unaffected by other redox-active interferents. The linear quantification of pyocyanin has an R² value of 0.991 across the clinically relevant concentration range of 2-100 µM. The proposed method was tested on human saliva showing a standard deviation of 2.5% ± 1% (n = 5) from the known added pyocyanin concentration to the samples. This inexpensive procedure is suggested for clinical use in monitoring the presence and state of P. aeruginosa infection in patients.

  19. Fish Alternatives in Environmental Risk Assessment: Overview of the Current Landscape

    EPA Science Inventory

    The need for alternative testing strategies has recently expanded into the realm of environmental risk assessment leading to the development of new alternatives to standard aquatic vertebrate testing such as the OECD 203 acute fish toxicity test. The fish embryo test (FET) is one...

  20. Electrooxidation of morin hydrate at a Pt electrode studied by cyclic voltammetry.

    PubMed

    Masek, Anna; Chrzescijanska, Ewa; Zaborski, Marian

    2014-04-01

    The process and the kinetics of the electrochemical oxidation of morin in an anhydrous electrolyte have been investigated using cyclic and differential pulse voltammetry. The oxidation mechanism proceeds in sequential steps related to the hydroxyl groups in the three aromatic rings. The oxidation of the 2',4'dihydroxy moiety at the B ring of morin occurs first, at very low positive potentials, and is a one-electron, one-proton irreversible reaction. The rate constant, electron transfer coefficient and diffusion coefficients involved in the electrochemical oxidation of morin were determined. The influence of the deprotonation of the ring B hydroxyl moiety is related to the electron/proton donating capacity of morin and to its radical scavenging antioxidant activity. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Chemometric study of Maya Blue from the voltammetry of microparticles approach.

    PubMed

    Doménech, Antonio; Doménech-Carbó, María Teresa; de Agredos Pascual, María Luisa Vazquez

    2007-04-01

    The use of the voltammetry of microparticles at paraffin-impregnated graphite electrodes allows for the characterization of different types of Maya Blue (MB) used in wall paintings from different archaeological sites of Campeche and YucatAn (Mexico). Using voltammetric signals for electron-transfer processes involving palygorskite-associated indigo and quinone functionalities generated by scratching the graphite surface, voltammograms provide information on the composition and texture of MB samples. Application of hierarchical cluster analysis and other chemometric methods allows us to characterize samples from different archaeological sites and to distinguish between samples proceeding from different chronological periods. Comparison between microscopic, spectroscopic, and electrochemical examination of genuine MB samples and synthetic specimens indicated that the preparation procedure of the pigment evolved in time via successive steps anticipating modern synthetic procedures, namely, hybrid organic-inorganic synthesis, temperature control of chemical reactivity, and template-like synthesis.

  2. The outcomes of complementary and alternative medicine use among pregnant and birthing women: current trends and future directions.

    PubMed

    Steel, Amie; Adams, Jon; Sibbritt, David; Broom, Alex

    2015-06-01

    Complementary and alternative medicine is used by a substantial number of pregnant women and maternity care providers are often faced with the task of ensuring women are using safe and effective treatments while respecting a woman's right to autonomous decision-making. In the era of evidence-based medicine maternity health professionals are expected to draw upon the best available evidence when making clinical decisions and providing health advice. This review will outline the current trends in research evidence associated with the outcomes of complementary and alternative medicine use amongst pregnant and birthing women as well as highlight some potential directions for future development in this important yet largely unknown topic in contemporary maternity care.

  3. Alternating Current Electrophoretic Deposition of Antibacterial Bioactive Glass-Chitosan Composite Coatings

    PubMed Central

    Seuss, Sigrid; Lehmann, Maja; Boccaccini, Aldo R.

    2014-01-01

    Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings. PMID:25007822

  4. Quantitative study of electrophoretic and electroosmotic enhancement during alternating current iontophoresis across synthetic membranes.

    PubMed

    Yan, Guang; Li, S Kevin; Peck, Kendall D; Zhu, Honggang; Higuchi, William I

    2004-12-01

    One of the primary safety and tolerability limitations of direct current iontophoresis is the potential for electrochemical burns associated with the necessary current densities and/or application times required for effective treatment. Alternating current (AC) transdermal iontophoresis has the potential to eliminate electrochemical burns that are frequently observed during direct current transdermal iontophoresis. Although it has been demonstrated that the intrinsic permeability of skin can be increased by applying low-to-moderate AC voltages, transdermal transport phenomena and enhancement under AC conditions have not been systematically studied and are not well understood. The aim of the present work was to study the fundamental transport mechanisms of square-wave AC iontophoresis using a synthetic membrane system. The model synthetic membrane used was a composite Nuclepore membrane. AC frequencies ranging from 20 to 1000 Hz and AC fields ranging from 0.25 to 0.5 V/membrane were investigated. A charged permeant, tetraethyl ammonium, and a neutral permeant, arabinose, were used. The transport studies showed that flux was enhanced by increasing the AC voltage and decreasing AC frequency. Two theoretical transport models were developed: one is a homogeneous membrane model; the other is a heterogeneous membrane model. Experimental transport data were compared with computer simulations based on these models. Excellent agreement between model predictions and experimental data was observed when the data were compared with the simulations from the heterogeneous membrane model. (c) 2004 Wiley-Liss, Inc. and the American Pharmacists Association

  5. Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study.

    PubMed

    Sarkar, Tanmay; Kumar, Parveen; Bharadwaj, Mridula Dixit; Waghmare, Umesh

    2016-04-14

    A double layer δ-NH4V4O10, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids. While it possesses better stability, and higher ionic and electronic conductivity than the most widely explored V2O5, the mechanisms of its cyclability are yet to be understood. Here, we present a theoretical cyclic voltammetry as a tool based on first-principles calculations, and uncover structural transformations that occur during Li(+)/Na(+) insertion (x) into (Lix/Nax)NH4V4O10. Structural distortions associated with single-phase and multi-phase structural changes during the insertion of Li(+)/Na(+), identified through the analysis of voltage profile and theoretical cyclic voltammetry are in agreement with the reported experimental electrochemical measurements on δ-NH4V4O10. We obtain an insight into its electronic structure with a lower band gap that is responsible for the high rate capability of (Lix/Nax) δ-NH4V4O10. The scheme of theoretical cyclic voltammetry presented here will be useful for addressing issues of cyclability and energy rate in other electrode materials.

  6. A novel automated alternating current biosusceptometry method to characterization of controlled-release magnetic floating tablets of metronidazole.

    PubMed

    Ferrari, Priscileila Colerato; dos Santos Grossklauss, Dany Bruno Borella; Alvarez, Matheus; Paixão, Fabiano Carlos; Andreis, Uilian; Crispim, Alexandre Giordano; de Castro, Ana Dóris; Evangelista, Raul Cesar; de Arruda Miranda, José Ricardo

    2014-08-01

    Alternating Current Biosusceptometry is a magnetically method used to characterize drug delivery systems. This work presents a system composed by an automated ACB sensor to acquire magnetic images of floating tablets. The purpose of this study was to use an automated Alternating Current Biosusceptometry (ACB) to characterize magnetic floating tablets for controlled drug delivery. Floating tablets were prepared with hydroxypropyl methylcellulose (HPMC) as hydrophilic gel material, sodium bicarbonate as gas-generating agent and ferrite as magnetic marker. ACB was used to characterize the floating lag time and the tablet hydration rate, by quantification of the magnetic images to magnetic area. Besides the buoyancy, the floating tablets were evaluated for weight uniformity, hardness, swelling and in vitro drug release. The optimized tablets were prepared with equal amounts of HPMC and ferrite, and began to float within 4 min, maintaining the flotation during more than 24 h. The data of all physical parameters lied within the pharmacopeial limits. Drug release at 24 h was about 40%. The ACB results showed that this study provided a new approach for in vitro investigation of controlled-release dosage forms. Moreover, using automated ACB will also be possible to test these parameters in humans allowing to establish an in vitro.in vivo correlation (IVIVC).

  7. Electrochemistry and analytical determination of lysergic acid diethylamide (LSD) via adsorptive stripping voltammetry.

    PubMed

    Merli, Daniele; Zamboni, Daniele; Protti, Stefano; Pesavento, Maria; Profumo, Antonella

    2014-12-01

    Lysergic acid diethylamide (LSD) is hardly detectable and quantifiable in biological samples because of its low active dose. Although several analytical tests are available, routine analysis of this drug is rarely performed. In this article, we report a simple and accurate method for the determination of LSD, based on adsorptive stripping voltammetry in DMF/tetrabutylammonium perchlorate, with a linear range of 1-90 ng L(-1) for deposition times of 50s. LOD of 1.4 ng L(-1) and LOQ of 4.3 ng L(-1) were found. The method can be also applied to biological samples after a simple extraction with 1-chlorobutane. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Characterization of inclusion complexes of organic ions with hydrophilic hosts by ion transfer voltammetry with solvent polymeric membranes.

    PubMed

    Olmos, José Manuel; Laborda, Eduardo; Ortuño, Joaquín Ángel; Molina, Ángela

    2017-03-01

    The quantitative characterization of inclusion complexes formed in aqueous phase between organic ions and hydrophilic hosts by ion-transfer voltammetry with solvent polymeric membrane ion sensors is studied, both in a theoretical and experimental way. Simple analytical solutions are presented for the determination of the binding constant of the complex from the variation with the host concentration of the electrochemical signal. These solutions are valid for any voltammetric technique and for solvent polymeric membrane ion sensors comprising one polarisable interface (1PI) and also, for the first time, two polarisable interfaces (2PIs). Suitable experimental conditions and data analysis procedures are discussed and applied to the study of the interactions of a common ionic liquid cation (1-octyl-3-metyl-imidazolium) and an ionisable drug (clomipramine) with two hydrophilic cyclodextrins: α-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. The experimental study is performed via square wave voltammetry with 2PIs and 1PI solvent polymeric membranes and in both cases the electrochemical experiments enable the detection of inclusion complexes and the determination of the corresponding binding constant. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Quantitative Determining of Ultra-Trace Aluminum Ion in Environmental Samples by Liquid Phase Microextraction Assisted Anodic Stripping Voltammetry.

    PubMed

    Zhang, Liuyang; Luo, Jinju; Shen, Xinyu; Li, Chunya; Wang, Xian; Nie, Bei; Fang, Huaifang

    2018-05-10

    Direct detecting of trace amount Al(III) in aqueous solution by stripping voltammetry is often frustrated by its irreversible reduction, resided at −1.75 V (vs. Ag/AgCl reference), which is in a proximal potential of proton reduction. Here, we described an electroanalytical approach, combined with liquid phase microextraction (LPME) using ionic liquid (IL), to quantitatively assess trace amount aluminum in environmental samples. The Al(III) was caged by 8-hydroxyquinoline, forming a superb hydrophobic metal⁻chelate, which sequentially transfers and concentrates in the bottom layer of IL-phase during LPME. The preconcentrated Al(III) was further analyzed by a square-wave anodic stripping voltammetry (SW-ASV). The resulting Al-deposited electrodes were characterized by scanning electron microscopy and powder X-ray diffraction, showing the intriguing amorphous nanostructures. The method developed provides a linear calibration ranging from 0.1 to 1.2 ng L −1 with a correlation coefficient of 0.9978. The LOD attains as low as 1 pmol L −1 , which reaches the lowest report for Al(III) detection using electroanalytical techniques. The applicable methodology was implemented for monitoring Al(III) in commercial distilled water.

  10. A kinetic study of ferrocenium cation decomposition utilizing an integrated electrochemical methodology composed of cyclic voltammetry and amperometry.

    PubMed

    Singh, Archana; Chowdhury, Debarati Roy; Paul, Amit

    2014-11-21

    A novel, easy, quick, and inexpensive integrated electrochemical methodology composed of cyclic voltammetry and amperometry has been developed for the determination of the kinetic stability of higher oxidation states for inorganic complexes. In this study, ferrocene and its derivatives have been used as model systems and the corresponding ferrocenium cations were generated in situ during the electrochemical experiments to determine their kinetic stabilities. The study found that the ferrocenium cations decompose following the first-order kinetics at 27 ± 3 °C in the presence of ambient oxygen and water. The half-lives of the ferrocenium, carboxylate ferrocenium, and decamethyl ferrocenium cations were found to be 1.27 × 10(3), 1.52 × 10(3), and ≫11.0 × 10(3) s, respectively, in acetonitrile solvent having a 0.5 M tetrabutylammonium hexafluorophosphate electrolyte. These results are in agreement with the previous reports, i.e. the ferrocenium cation is unstable whereas the decamethyl ferrocenium cation has superior stability. The new methodology has been established by performing various experiments using different concentrations of ferrocene, variable scan rates in cyclic voltammetry, different time periods for amperometry, and in situ spectroelectrochemical experiments.

  11. Robotic voltammetry with carbon nanotube-based sensors: a superb blend for convenient high-quality antimicrobial trace analysis.

    PubMed

    Theanponkrang, Somjai; Suginta, Wipa; Weingart, Helge; Winterhalter, Mathias; Schulte, Albert

    2015-01-01

    A new automated pharmacoanalytical technique for convenient quantification of redox-active antibiotics has been established by combining the benefits of a carbon nanotube (CNT) sensor modification with electrocatalytic activity for analyte detection with the merits of a robotic electrochemical device that is capable of sequential nonmanual sample measurements in 24-well microtiter plates. Norfloxacin (NFX) and ciprofloxacin (CFX), two standard fluoroquinolone antibiotics, were used in automated calibration measurements by differential pulse voltammetry (DPV) and accomplished were linear ranges of 1-10 μM and 2-100 μM for NFX and CFX, respectively. The lowest detectable levels were estimated to be 0.3±0.1 μM (n=7) for NFX and 1.6±0.1 μM (n=7) for CFX. In standard solutions or tablet samples of known content, both analytes could be quantified with the robotic DPV microtiter plate assay, with recoveries within ±4% of 100%. And recoveries were as good when NFX was evaluated in human serum samples with added NFX. The use of simple instrumentation, convenience in execution, and high effectiveness in analyte quantitation suggest the merger between automated microtiter plate voltammetry and CNT-supported electrochemical drug detection as a novel methodology for antibiotic testing in pharmaceutical and clinical research and quality control laboratories.

  12. Alternative medicine in the workplace.

    PubMed

    Lippin, R A

    1996-01-01

    Workplace settings are ripe for the application of alternative medical interventions for a variety of reasons. Included among them are a shared interest in prevention by both the occupational and alternative medicine communities, economic incentives by corporations as major purchasers of healthcare to reduce healthcare costs and improve employee productivity, and the willingness of corporations to be differentially creative in their approach to delivering and purchasing healthcare. This paper describes the US workforce in transition, provides an overview of occupational medicine including current programs and emerging issues, describes the current applications of alternative medicine interventions in the workplace, and argues for future expanded application of alternative medicine in workplace settings.

  13. Detection and evaluation of weld defects in stainless steel using alternating current field measurement

    NASA Astrophysics Data System (ADS)

    Wei-Li, Ma, Weiping; Pan-Qi, Wen-jiao, Dou; Yuan, Xin'an; Yin, Xiaokang

    2018-04-01

    Stainless steel is widely used in nuclear power plants, such as various high-radioactive pool, tools storage and fuel transportation channel, and serves as an important barrier to stop the leakage of high-radioactive material. NonDestructive Evaluation (NDE) methods, eddy current testing (ET), ultrasonic examination (UT), penetration testing (PT) and hybrid detection method, etc., have been introduced into the inspection of a nuclear plant. In this paper, the Alternating Current Field Measurement (ACFM) was fully applied to detect and evaluate the defects in the welds of the stainless steel. Simulations were carried out on different defect types, crack lengths, and orientation to reveal the relationship between the signals and dimensions to determine whether methods could be validated by the experiment. A 3-axis ACFM probe was developed and three plates including 16 defects, which served in nuclear plant before, were examined by automatic detection equipment. The result shows that the minimum detectable crack length on the surface is 2mm and ACFM shows excellent inspection results for a weld in stainless steel and gives an encouraging prospect of broader application.

  14. Alternating current response studies on nickel ferrite-niobium composite at room temperature

    NASA Astrophysics Data System (ADS)

    Reddy, L. P. Babu; Rajprakash, H. G.; Chethan, B.; Vijayakumari, S. C.; Ravikiran, Y. T.

    2018-05-01

    In the present research NDNF -Niobium Pentaxide doped Nickel Ferrite [NiFe2O4-Nb2O5-50%] composite was prepared by Mechano-Chemical mixing of NiFe2O4 [NF] with Nb2O5. NF and the NDNF were structurally characterized by four transform infrared spectroscopy [FTIR] and X-ray diffraction [XRD] techniques. The presence of characteristic absorption bands of NF and Nb2O5 in the FTIR spectrum of NDNF with small shift confirmed interfacial interaction of NF with Nb2O5. XRD studies also confirm interfacial interaction between NF and Nb2O5 in the composite and crystalline nature with an average crystallite size of 30nm. The Alternating Current (AC) response parameters of NF and the NDNF were comparatively studied in the frequency range 100Hz-1MHz at room temperature. Increase in AC conductivity of the NDNF has compared to NF was observed and discussed based on the electron hole exchange mechanism.

  15. Lab-on-a-chip sensor for measuring Zn by stripping voltammetry

    NASA Astrophysics Data System (ADS)

    Pei, Xing; Kang, Wenjing; Yue, Wei; Bange, Adam; Wong, Hector R.; Heineman, William R.; Papautsky, Ian

    2012-03-01

    This work reports on continuing development of a lab-on-a-chip sensor for electrochemical detection of heavy metal zinc in blood serum. The sensor consists of a three electrode system, including an environmentally-friendly bismuth working electrode, a Ag/AgCl reference electrode, and a gold auxiliary electrode. By optimizing the electrodeposition of bismuth film, better control of fabrication steps and improving interface between the sensor and potentiostat, repeatability and sensitivity of the lab-on-a-chip sensor has been improved. Through optimization of electrolyte and stripping voltammetry parameters, limits of detection were greatly improved. The optimized sensor was able to measure zinc in in the physiological range of 65-95 μg/dL. Ultimately, with further development and integrated sample preparation sensor system will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for bedside monitoring.

  16. Simultaneous determination of three herbicides by differential pulse voltammetry and chemometrics.

    PubMed

    Ni, Yongnian; Wang, Lin; Kokot, Serge

    2011-01-01

    A novel differential pulse voltammetry method (DPV) was researched and developed for the simultaneous determination of Pendimethalin, Dinoseb and sodium 5-nitroguaiacolate (5NG) with the aid of chemometrics. The voltammograms of these three compounds overlapped significantly, and to facilitate the simultaneous determination of the three analytes, chemometrics methods were applied. These included classical least squares (CLS), principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural networks (RBF-ANN). A separately prepared verification data set was used to confirm the calibrations, which were built from the original and first derivative data matrices of the voltammograms. On the basis relative prediction errors and recoveries of the analytes, the RBF-ANN and the DPLS (D - first derivative spectra) models performed best and are particularly recommended for application. The DPLS calibration model was applied satisfactorily for the prediction of the three analytes from market vegetables and lake water samples.

  17. Determination of cobalt in vegetable animal foodstuffs by differential pulse adsorptive voltammetry using alpha-benzil dioxime.

    PubMed

    Giroussi, S; Voulgaropoulos, A; Ayiannidis, A K; Golimowski, J; Janicki, M

    1995-12-22

    A selective and sensitive voltammetric method for the determination of cobalt in vegetable animal foodstuffs is developed. The method is based on the use of alpha-benzil dioxime (alpha-BD) as a chelating agent for differential pulse adsorptive stripping voltammetry (DPASV) and is free from zinc interferences. The influence of pH, time and alpha-BD concentration on the peak resolution and height are discussed. The method was successfully applied in some typical vegetable animal foodstuffs with R.S.D. < 6%.

  18. Bus Propulsion Alternatives Overview

    DOT National Transportation Integrated Search

    1982-04-01

    The Urban Mass Transportation Administration (UMTA) is currently investigating propulsion alternatives which would conserve petroleum-based fuels and would be practical for use by U.S. transit operators. A discussion of these alternatives (electric p...

  19. Determination of allura red in some food samples by adsorptive stripping voltammetry.

    PubMed

    Alghamdi, Ahmad H

    2005-01-01

    Square wave (SW) voltammetry was used to explore the adsorption properties of the food additive dye Allura Red on a hanging mercury drop electrode (HMDE). By using the adsorptive stripping voltammetric approach, we developed a sensitive electroanalytical method for the determination of this azo dye. A well-developed voltammetric peak probably related to the cathodic reduction of the azo moiety was obtained in pH 9 Britton-Robinson (B-R) buffer at 613 mV. Cyclic voltammetric studies indicated that the reduction process was irreversible and primarily controlled by adsorption. The adsorptive voltammetric signal was evaluated with respect to various experimental conditions; the optimized values were supporting electrolyte, B-R buffer; pH 11; accumulation time, 180 s; accumulation potential, 0.0 V; scan rate, 900 mV/s; pulse amplitude, 75 mV; and SW frequency, 90 Hz. Adsorptive voltammetric peak current showed a linear response for Allura Red in the concentration range of 2.5 x 10(-8) to 2.0 x 10(-7) mol/L (r = 0.998). The limit of detection was 8.5 x 10(-9) mol/L (4.2 ng/mL), the precision in terms of relative standard deviation was 1.3%, and the mean recovery was 102%. Possible interferences by several substances usually present in food products such as food additive azo dyes (E110, E102), gelatin, natural and artificial sweeteners, preservatives, and antioxidants were also evaluated. The proposed electrochemical procedure was successfully applied to the determination of this food dye in commercially available candy and a soft drink. The results were compared by statistical evaluation with those obtained by a reference spectrophotometric method.

  20. Trace vanadium analysis by catalytic adsorptive stripping voltammetry using mercury-coated micro-wire and polystyrene-coated bismuth film electrodes

    PubMed Central

    Dansby-Sparks, Royce; Chambers, James Q.; Xue, Zi-Ling

    2009-01-01

    An electrochemical technique has been developed for ultra trace (ngL−1) vanadium (V) measurement. Catalytic adsorptive stripping voltammetry for V analysis was developed at mercury-coated gold micro-wire (MWE, 100 μm) electrodes in the presence of gallic acid (GA) and bromate ion. A potential of −0.275 V (vs Ag/AgCl) was used to accumulate the complex in acetate buffer (pH 5.0) at the electrode surface followed by a differential pulse voltammetric scan. Parameters affecting the electrochemical response, including pH, concentration of GA and bromate, deposition potential and time have been optimized. Linear response was obtained in the 0–1000 ngL−1 range (2 min deposition), with a detection limit of 0.88 ngL−1. The method was validated by comparison of results for an unknown solution of V by atomic absorption measurement. The protocol was evaluated in a real sample by measuring the amount of V in river water samples. Thick bismuth film electrodes with protective polystyrene films have also been made and evaluated as a mercury free alternative. However, ngL−1 level detection was only attainable with extended (10 min) deposition times. The proposed use of MWEs for the detection of V is sensitive enough for future use to test V concentration in biological fluids treated by the advanced oxidation process (AOP). PMID:19446059

  1. Studying Current-Potential Curves Using a Bipotentiometric Lodometric Back-Titration for the Determination of Ascorbic Acid in Fruits and Vegetables

    ERIC Educational Resources Information Center

    Verdini, Roxana A.; Lagier, Claudia M.

    2004-01-01

    Voltammetry principles are introduced to students by means of a bipotentiometric method to determine vitamin C in fruits and vegetables. The aim is to draw attention to voltammetric methods, particular to the study of current-potential curves, stressing the potential applicability in areas of food quality control.

  2. Numerical simulations of electric potential field for alternating current potential drop associated with surface cracks in low-alloy steel nuclear material

    NASA Astrophysics Data System (ADS)

    Yeh, Chun-Ping; Huang, Jiunn-Yuan

    2018-04-01

    Low-alloy steels used as structural materials in nuclear power plants are subjected to cyclic stresses during power plant operations. As a result, cracks may develop and propagate through the material. The alternating current potential drop technique is used to measure the lengths of cracks in metallic components. The depth of the penetration of the alternating current is assumed to be small compared to the crack length. This assumption allows the adoption of the unfolding technique to simplify the problem to a surface Laplacian field. The numerical modelling of the electric potential and current density distribution prediction model for a compact tension specimen and the unfolded crack model are presented in this paper. The goal of this work is to conduct numerical simulations to reduce deviations occurring in the crack length measurements. Numerical simulations were conducted on AISI 4340 low-alloy steel with different crack lengths to evaluate the electric potential distribution. From the simulated results, an optimised position for voltage measurements in the crack region was proposed.

  3. Alternatives to current fumigation practices in western states raspberry

    USDA-ARS?s Scientific Manuscript database

    Red raspberry production systems in the western United States are heavily reliant on preplant soil fumigation to ensure the successful establishment and productivity of a planting. However, due to issues related to the regulation, availability, and economics of soil fumigation alternatives are need ...

  4. Simultaneous measurement and quantitation of 4-hydroxyphenylacetic acid and dopamine with fast-scan cyclic voltammetry.

    PubMed

    Shin, Mimi; Kaplan, Sam V; Raider, Kayla D; Johnson, Michael A

    2015-05-07

    Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of -0.4 V to +1.3 V to -0.4 V at 600 V s(-1), repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores.

  5. Simultaneous Measurement and Quantitation of 4-Hydroxyphenylacetic acid and Dopamine with Fast-Scan Cyclic Voltammetry

    PubMed Central

    Shin, Mimi; Kaplan, Sam V.; Raider, Kayla D.; Johnson, Michael A.

    2015-01-01

    Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenylacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of −0.4 V to +1.3 V to −0.4 V at 600 V/s, repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores. PMID:25785694

  6. Air pollution control residues from waste incineration: current UK situation and assessment of alternative technologies.

    PubMed

    Rani, D Amutha; Boccaccini, A R; Deegan, D; Cheeseman, C R

    2008-11-01

    Current disposal options for APC residues in the UK and alternative treatment technologies developed world-wide have been reviewed. APC residues are currently landfilled in the UK where they undergo in situ solidification, although the future acceptability of this option is uncertain because the EU waste acceptance criteria (WAC) introduce strict limits on leaching that are difficult to achieve. Other APC residue treatment processes have been developed which are reported to reduce leaching to below relevant regulatory limits. The Ferrox process, the VKI process, the WES-PHix process, stabilisation/solidification using cementitious binders and a range of thermal treatment processes are reviewed. Thermal treatment technologies convert APC residues combined with other wastes into inert glass or glass-ceramics that encapsulate heavy metals. The waste management industry will inevitably use the cheapest available option for treating APC residues and strict interpretation and enforcement of waste legislation is required if new, potentially more sustainable technologies are to become commercially viable.

  7. Neuronal responses to an asymmetrical alternating current field can mimic those produced by an imposed direct current field in vitro.

    PubMed

    Pan, Linjie; Cirillo, John; Borgens, Richard Ben

    2012-08-01

    The remarkable polarity-dependent growth and anatomical organization of neurons in vitro produced by imposed direct current (DC) voltage gradients (electrical fields; Ef) can be mimicked by another type of electrical cue. This is a properly structured asymmetrical alternating current (AC) electrical field (A-ACEf). Here we provide details on the construction of an AC signal generator in which all components of an AC waveform can be individually controlled. We show that 1) conventional symmetrical AC voltage gradients will not induce growth, guidance, or architectural changes in sympathetic neurons. We also provide the first qualitative and quantitative data showing that an asymmetric AC application can indeed mimic the DC response in chick sympathetic neurons and their growing neurites. This shift in orientation and neuronal anatomy requires dieback of some neurites and the extension of others to produce a preferred orientation perpendicular to the gradient of voltage. Our new results may lead to a noninvasive means to modify nerve growth and organization by magnetic inductive coupling at distance. These data also indicate the possibility of a means to mimic DC-dependent release of drugs or other biologically active molecules from electrically sensitive that can be loaded with these chemical cargos. Copyright © 2012 Wiley Periodicals, Inc.

  8. Potential Alternatives Report for Validation of Alternative Low-Emission Surface PreparationlDepainting Technologies for Structural Steel

    NASA Technical Reports Server (NTRS)

    Lewis, Pattie

    2006-01-01

    For this project, particulates and solvents used during the depainting process of steel structures were the identified hazardous material (HazMat) targeted for elimination or reduction. This Potential Alternatives Report (PAR) provides technical analyses of identified alternatives to the current coating removal processes, criteria used to select alternatives for further analysis, and a list of those alternatives recommended for testing. The initial coating removal alternatives list was compiled using literature searches and center participant recommendations. The involved project participants initially considered fifteen (15) alternatives. In late 2004, stakeholders down-selected the list and identified specific processes as potential alternatives to the current depainting methods. The selected alternatives were: 1. Plastic Blast Media 2. Hard Abrasive Media 3. Sponge Blast Media 4. Mechanical Removal with Vacuum Attachment 5. Liquid Nitrogen 6. Laser Coating Removal Available information about these processes was used to analyze the technical merits and the potential environmental, safety, and occupational health (ESOH) impacts of these methods. A preliminary cost benefit analysis will be performed to determine if implementation of alternative technologies is economically justified. NASA AP2

  9. Compensated pulsed alternator

    DOEpatents

    Weldon, William F.; Driga, Mircea D.; Woodson, Herbert H.

    1980-01-01

    This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

  10. DoD use of Domestically-Produced Alternative Fuels and Alternative Fuel Vehicles

    DTIC Science & Technology

    2014-04-10

    based fuels and biodiesel , in DoD vehicles; (2) current and projected actions by the DoD to increase the use of alternative fuels in vehicles; (3) a...fuels and vehicles. 15. SUBJECT TERMS alternative fuel infrastructure, electric vehicles, biofuels, ethanol, biodiesel , drop-in, synthetic fuel...of: (1) use and potential use of domestically-produced alternative fuels including but not limited to, natural gas based fuels and biodiesel , in DoD

  11. Monitoring In Vivo Changes in Tonic Extracellular Dopamine Level by Charge-Balancing Multiple Waveform Fast-Scan Cyclic Voltammetry.

    PubMed

    Oh, Yoonbae; Park, Cheonho; Kim, Do Hyoung; Shin, Hojin; Kang, Yu Min; DeWaele, Mark; Lee, Jeyeon; Min, Hoon-Ki; Blaha, Charles D; Bennet, Kevin E; Kim, In Young; Lee, Kendall H; Jang, Dong Pyo

    2016-11-15

    Dopamine (DA) modulates central neuronal activity through both phasic (second to second) and tonic (minutes to hours) terminal release. Conventional fast-scan cyclic voltammetry (FSCV), in combination with carbon fiber microelectrodes, has been used to measure phasic DA release in vivo by adopting a background subtraction procedure to remove background capacitive currents. However, measuring tonic changes in DA concentrations using conventional FSCV has been difficult because background capacitive currents are inherently unstable over long recording periods. To measure tonic changes in DA concentrations over several hours, we applied a novel charge-balancing multiple waveform FSCV (CBM-FSCV), combined with a dual background subtraction technique, to minimize temporal variations in background capacitive currents. Using this method, in vitro, charge variations from a reference time point were nearly zero for 48 h, whereas with conventional background subtraction, charge variations progressively increased. CBM-FSCV also demonstrated a high selectivity against 3,4-dihydroxyphenylacetic acid and ascorbic acid, two major chemical interferents in the brain, yielding a sensitivity of 85.40 ± 14.30 nA/μM and limit of detection of 5.8 ± 0.9 nM for DA while maintaining selectivity. Recorded in vivo by CBM-FSCV, pharmacological inhibition of DA reuptake (nomifensine) resulted in a 235 ± 60 nM increase in tonic extracellular DA concentrations, while inhibition of DA synthesis (α-methyl-dl-tyrosine) resulted in a 72.5 ± 4.8 nM decrease in DA concentrations over a 2 h period. This study showed that CBM-FSCV may serve as a unique voltammetric technique to monitor relatively slow changes in tonic extracellular DA concentrations in vivo over a prolonged time period.

  12. Anodic stripping voltammetry of nickel ions and nickel hydroxide nanoparticles at boron-doped diamond electrodes

    NASA Astrophysics Data System (ADS)

    Musyarofah, N. R. R.; Gunlazuardi, J.; Einaga, Y.; Ivandini, T. A.

    2017-04-01

    Anodic stripping voltammetry (ASV) of nickel ions in phosphate buffer solution (PBS) have been investigated at boron-doped diamond (BDD) electrodes. The deposition potential at 0.1 V (vs. Ag/AgCl) for 300 s in 0.1 M PBS pH 3 was found as the optimum condition. The condition was applied for the determination of nickel contained in nickel hydroxide nanoparticles. A linear calibration curve can be achieved of Ni(OH)2-NPs in the concentration range of x to x mM with an estimated limit of detection (LOD) of 5.73 × 10-6 mol/L.

  13. Non-conductive nanomaterial enhanced electrochemical response in stripping voltammetry: The use of nanostructured magnesium silicate hollow spheres for heavy metal ions detection.

    PubMed

    Xu, Ren-Xia; Yu, Xin-Yao; Gao, Chao; Jiang, Yu-Jing; Han, Dong-Dong; Liu, Jin-Huai; Huang, Xing-Jiu

    2013-08-06

    Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd(2+), Pb(2+), Cu(2+) and Hg(2+) was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186nM, 0.247nM, 0.169nM and 0.375nM for Cd(2+), Pb(2+), Cu(2+) and Hg(2+)) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb(2+) increased in the presence of certain concentrations of other metal ions, such as Cd(2+), Cu(2+) and Hg(2+) both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Expanding neurochemical investigations with multi-modal recording: simultaneous fast-scan cyclic voltammetry, iontophoresis, and patch clamp measurements.

    PubMed

    Kirkpatrick, D C; McKinney, C J; Manis, P B; Wightman, R M

    2016-08-02

    Multi-modal recording describes the simultaneous collection of information across distinct domains. Compared to isolated measurements, such studies can more easily determine relationships between varieties of phenomena. This is useful for neurochemical investigations which examine cellular activity in response to changes in the local chemical environment. In this study, we demonstrate a method to perform simultaneous patch clamp measurements with fast-scan cyclic voltammetry (FSCV) using optically isolated instrumentation. A model circuit simulating concurrent measurements was used to predict the electrical interference between instruments. No significant impact was anticipated between methods, and predictions were largely confirmed experimentally. One exception was due to capacitive coupling of the FSCV potential waveform into the patch clamp amplifier. However, capacitive transients measured in whole-cell current clamp recordings were well below the level of biological signals, which allowed the activity of cells to be easily determined. Next, the activity of medium spiny neurons (MSNs) was examined in the presence of an FSCV electrode to determine how the exogenous potential impacted nearby cells. The activities of both resting and active MSNs were unaffected by the FSCV waveform. Additionally, application of an iontophoretic current, used to locally deliver drugs and other neurochemicals, did not affect neighboring cells. Finally, MSN activity was monitored during iontophoretic delivery of glutamate, an excitatory neurotransmitter. Membrane depolarization and cell firing were observed concurrently with chemical changes around the cell resulting from delivery. In all, we show how combined electrophysiological and electrochemical measurements can relate information between domains and increase the power of neurochemical investigations.

  15. Polytetrafluorethylene film-based liquid-three phase micro extraction coupled with differential pulse voltammetry for the determination of atorvastatin calcium.

    PubMed

    Ensafi, Ali A; Khoddami, Elaheh; Rezaei, Behzad

    2013-01-01

    In this paper, we describe a new combination method based on polytetrafluorethylene (PTFE) film-based liquid three-phase micro extraction coupled with differential pulse voltammetry (DPV) for the micro extraction and quantification of atorvastatin calcium (ATC) at the ultra-trace level. Different factors affecting the liquid-three phases micro extraction of atorvastatin calcium, including organic solvent, pH of the donor and acceptor phases, concentration of salt, extraction time, stirring rate and electrochemical factors, were investigated, and the optimal extraction conditions were established. The final stable signal was achieved after a 50 min extraction time, which was used for analytical applications. An enrichment factor of 21 was achieved, and the relative standard deviation (RSD) of the method was 4.5% (n = 4). Differential pulse voltammetry exhibited two wide linear dynamic ranges of 20.0-1000.0 pmol L(-1) and 0.001-11.0 µmol L(-1) of ATC. The detection limit was found to be 8.1 pmol L(-1) ATC. Finally, the proposed method was used as a new combination method for the determination of atorvastatin calcium in real samples, such as human urine and plasma.

  16. Robotic voltammetry with carbon nanotube-based sensors: a superb blend for convenient high-quality antimicrobial trace analysis

    PubMed Central

    Theanponkrang, Somjai; Suginta, Wipa; Weingart, Helge; Winterhalter, Mathias; Schulte, Albert

    2015-01-01

    A new automated pharmacoanalytical technique for convenient quantification of redox-active antibiotics has been established by combining the benefits of a carbon nanotube (CNT) sensor modification with electrocatalytic activity for analyte detection with the merits of a robotic electrochemical device that is capable of sequential nonmanual sample measurements in 24-well microtiter plates. Norfloxacin (NFX) and ciprofloxacin (CFX), two standard fluoroquinolone antibiotics, were used in automated calibration measurements by differential pulse voltammetry (DPV) and accomplished were linear ranges of 1–10 μM and 2–100 μM for NFX and CFX, respectively. The lowest detectable levels were estimated to be 0.3±0.1 μM (n=7) for NFX and 1.6±0.1 μM (n=7) for CFX. In standard solutions or tablet samples of known content, both analytes could be quantified with the robotic DPV microtiter plate assay, with recoveries within ±4% of 100%. And recoveries were as good when NFX was evaluated in human serum samples with added NFX. The use of simple instrumentation, convenience in execution, and high effectiveness in analyte quantitation suggest the merger between automated microtiter plate voltammetry and CNT-supported electrochemical drug detection as a novel methodology for antibiotic testing in pharmaceutical and clinical research and quality control laboratories. PMID:25670899

  17. Guanine oxidation signal enhancement in DNA via a polyacrylonitrile nanofiber-coated and cyclic voltammetry-treated pencil graphite electrode

    NASA Astrophysics Data System (ADS)

    Aladag Tanik, Nilay; Demirkan, Elif; Aykut, Yakup

    2018-07-01

    This study investigated the electrochemical detection of specific nucleic acid hybridization sequences using a nanofiber-coated pencil graphite biosensor. The biosensor was developed to detect Val66Met single point mutations in the brain-derived neurotrophic factor gene, which is frequently observed in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and bipolar disorder. The oxidation signal of the most electroactive and stable DNA base, i.e., guanine, was used at approximately +1.0 V. Pencil graphite electrode (PGE) surfaces were coated with polyacrylonitrile nanofibers by electrospinning. Cyclic voltammetry was applied to the nanofiber-coated PGE to pretreat its surfaces. The application of cyclic voltammetry to the nanofiber-coated PGE surfaces before attaching the probe yielded a four fold increase in the oxidation signal for guanine compared with that using the untreated and uncoated PGE surface. The signal reductions were 70% for hybridization, 10% for non-complementary binding, and 14% for a single mismatch compared with the probe. The differences in full match, non-complementary, and mismatch binding indicated that the biosensor selectively detected the target, and that it was possible to determine hybridization in about 65 min. The detection limit was 0.19 μg/ml at a target concentration of 10 ppm.

  18. Fully printed flexible and disposable wireless cyclic voltammetry tag.

    PubMed

    Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

    2015-01-29

    A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to -500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health.

  19. Fully printed flexible and disposable wireless cyclic voltammetry tag

    NASA Astrophysics Data System (ADS)

    Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

    2015-01-01

    A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to -500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health.

  20. Pulse Voltammetry

    NASA Astrophysics Data System (ADS)

    Stojek, Zbigniew

    The idea of imposing potential pulses and measuring the currents at the end of each pulse was proposed by Barker in a little-known journal as early as in 1958 [1]. However, the first reliable trouble-free and affordable polarographs offering voltammetric pulse techniques appeared on the market only in the 1970s. This delay was due to some limitations on the electronic side. In the 1990s, again substantial progress in electrochemical pulse instrumentation took place. This was related to the introduction of microprocessors, computers, and advanced software.

  1. Detection of the Pseudomonas Quinolone Signal (PQS) by cyclic voltammetry and amperometry using a boron doped diamond electrode.

    PubMed

    Zhou, Lin; Glennon, Jeremy D; Luong, John H T; Reen, F Jerry; O'Gara, Fergal; McSweeney, Christina; McGlacken, Gerard P

    2011-10-07

    2-Heptyl-3-hydroxy-4-quinolone, known as the Pseudomonas Quinolone Signal, is a key regulator of bacterial cooperative behaviour known as quorum sensing. A simple electrochemical strategy was employed for its sensitive detection using a bare boron-doped diamond electrode by cyclic voltammetry and amperometry. PQS (and potentially other quinolones) was then detected in cultures of P. aeruginosa pqsL(-) mutant strains. This journal is © The Royal Society of Chemistry 2011

  2. Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koizumi, H.; Uda, S.; Fujiwara, K.

    X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

  3. Determination of glucose in human urine by cyclic voltammetry method using gold electrode

    NASA Astrophysics Data System (ADS)

    Riyanto; Supwatul Hakim, Muh.

    2018-01-01

    This study has been the determination of glucose in human urine by cyclic voltammetry method using gold electrode. The gold electrode was prepared using gold wire with purity 99.99%, size 1.0 mm by length and wide respectively, connected with silver wire using silver conductive paint. The effect of electrolyte, pH and glucose concentration has been determined to produce the optimum method. The research showed the KNO3 is a good electrolyte for determination of glucose in human urine using gold electrode. The effect of glucose concentration have the coefficient correlation is R2 = 0.994. The results of the recovery using addition method showed at range95-105%. As a conclusion isa gold electrode is a good electrode for electrochemical sensors to the determination of glucose in human urine.

  4. Microfluidic platform for neurotransmitter sensing based on cyclic voltammetry and dielectrophoresis for in vitro experiments.

    PubMed

    Mathault, Jessy; Zamprogno, Pauline; Greener, Jesse; Miled, Amine

    2015-08-01

    This paper presents a new microfluidic platform that can simultaneously measure and locally modulate neurotransmitter concentration in a neuron network. This work focuses on the development of a first prototype including a potentiostat and electrode functionalization to detect several neurotransmitter's simultaneously. We tested dopamine as proof of concept to validate functionality. The system is based on 320 bidirectional electrode array for dielectrophoretic manipulation and cyclic voltammetry. Each electrode is connected to a mechanical multiplexer in order to reduce noise interference and fully isolate the electrode. The multiplexing rate is 476 kHz and each electrode can drive a signal with an amplitude of 60 V pp for dielectrophoretic manipulation.

  5. Bead-on-string structure printed by electrohydrodynamic jet under alternating current electric field

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Lin, Yihuang; Jiang, Jiaxin; Liu, Haiyan; Zhao, Yang; Zheng, Gaofeng

    2016-09-01

    Electrohydrodynamic printing (EHDP) under alternating current (AC) electric field provides a novel way for the precise micro-/nano-droplet printing. The AC electric field induces the free charge to reciprocate along the EHDP jet and changes the electric field force on the jet periodically. The stability of jet can be enhanced by increasing the voltage frequency, and the regular bead-on-string structure is direct-written along the trajectory of collector. The deposition frequency of bead structure increases with the increasing of voltage frequency, due to the short period of AC electric field. As the voltage frequency is increased from 10 to 60 Hz, the diameter of bead structure decreases from 200 to 110 µm. As the duty ration increased from 10 to 60 %, the diameter of bead structure increased from 100 to 140 µm. This work would accelerate the development and the application of micro-/nano-printing technology in the fields of flexible electronic and micro-/nano-system.

  6. Transcranial Alternating Current Stimulation Modulates Risky Decision Making in a Frequency-Controlled Experiment

    PubMed Central

    Awasthi, Bhuvanesh

    2017-01-01

    Abstract In this study, we investigated the effect of transcranial alternating current stimulation (tACS) on voluntary risky decision making and executive control in humans. Stimulation was delivered online at 5 Hz (θ), 10 Hz (α), 20 Hz (β), and 40 Hz (γ) on the left and right frontal area while participants performed a modified risky decision-making task. This task allowed participants to voluntarily select between risky and certain decisions associated with potential gains or losses, while simultaneously measuring the cognitive control component (voluntary switching) of decision making. The purpose of this experimental design was to test whether voluntary risky decision making and executive control can be modulated with tACS in a frequency-specific manner. Our results revealed a robust effect of a 20-Hz stimulation over the left prefrontal area that significantly increased voluntary risky decision making, which may suggest a possible link between risky decision making and reward processing, underlined by β-oscillatory activity. PMID:29379865

  7. Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation (tACS)

    PubMed Central

    Fröhlich, Flavio; Sellers, Kristin K.; Cordle, Asa L.

    2015-01-01

    Cognitive impairment represents one of the most debilitating and most difficult symptom to treat of many psychiatric illnesses. Human neurophysiology studies have suggested specific pathologies of cortical network activity correlate with cognitive impairment. However, we lack (1) demonstration of causal relationships between specific network activity patterns and cognitive capabilities and (2) treatment modalities that directly target impaired network dynamics of cognition. Transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation approach, may provide a crucial tool to tackle these challenges. We here propose that tACS can be used to elucidate the causal role of cortical synchronization in cognition and, eventually, to enhance pathologically weakened synchrony that may underlie cognitive deficits. To accelerate such development of tACS as a treatment for cognitive deficits, we discuss studies on tACS and cognition (all performed in healthy participants) according to the Research Domain Criteria (RDoC) of the National Institute of Mental Health. PMID:25547149

  8. Transcranial Alternating Current Stimulation Modulates Risky Decision Making in a Frequency-Controlled Experiment.

    PubMed

    Yaple, Zachary; Martinez-Saito, Mario; Feurra, Matteo; Shestakova, Anna; Klucharev, Vasily

    2017-01-01

    In this study, we investigated the effect of transcranial alternating current stimulation (tACS) on voluntary risky decision making and executive control in humans. Stimulation was delivered online at 5 Hz (θ), 10 Hz (α), 20 Hz (β), and 40 Hz (γ) on the left and right frontal area while participants performed a modified risky decision-making task. This task allowed participants to voluntarily select between risky and certain decisions associated with potential gains or losses, while simultaneously measuring the cognitive control component (voluntary switching) of decision making. The purpose of this experimental design was to test whether voluntary risky decision making and executive control can be modulated with tACS in a frequency-specific manner. Our results revealed a robust effect of a 20-Hz stimulation over the left prefrontal area that significantly increased voluntary risky decision making, which may suggest a possible link between risky decision making and reward processing, underlined by β-oscillatory activity.

  9. Bi-frontal transcranial alternating current stimulation in the ripple range reduced overnight forgetting.

    PubMed

    Ambrus, Géza Gergely; Pisoni, Alberto; Primaßin, Annika; Turi, Zsolt; Paulus, Walter; Antal, Andrea

    2015-01-01

    High frequency oscillations in the hippocampal structures recorded during sleep have been proved to be essential for long-term episodic memory consolidation in both animals and in humans. The aim of this study was to test if transcranial Alternating Current Stimulation (tACS) of the dorsolateral prefrontal cortex (DLPFC) in the hippocampal ripple range, applied bi-frontally during encoding, could modulate declarative memory performance, measured immediately after encoding, and after a night's sleep. An associative word-pair learning test was used. During an evening encoding phase, participants received 1 mA 140 Hz tACS or sham stimulation over both DLPFCs for 10 min while being presented twice with a list of word-pairs. Cued recall performance was investigated 10 min after training and the morning following the training session. Forgetting from evening to morning was observed in the sham condition, but not in the 140 Hz stimulation condition. 140 Hz tACS during encoding may have an effect on the consolidation of declarative material.

  10. Hydrogen-bonding effect on spin-center transfer of tetrathiafulvalene-linked 6-oxophenalenoxyl evaluated using temperature-dependent cyclic voltammetry and theoretical calculations.

    PubMed

    Nishida, Shinsuke; Fukui, Kozo; Morita, Yasushi

    2014-02-01

    The stable tetrathiafulvalene (TTF)-linked 6-oxophenalenoxyl neutral radical exhibits a spin-center transfer with a continuous color change in solution caused by an intramolecular electron transfer, which is dependent on solvent and temperature. Cyclic voltammetry measurements showed that addition of 2,2,2-trifluoroethanol (TFE) to a benzonitrile solution of the neutral radical induces a redox potential shift that is favorable for the spin-center transfer. Temperature-dependent cyclic voltammetry of the neutral radical using a novel low-temperature electrochemical cell demonstrated that the redox potentials change with decreasing temperature in a 199:1 CH2Cl2/TFE mixed solvent. Furthermore, theoretical calculation revealed that the energy levels of the frontier molecular orbitals involved in the spin-center transfer are lowered by the hydrogen-bonding interaction of TFE with the neutral radical. These results indicate that the hydrogen-bonding effect is a key factor for the occurrence of the spin-center transfer of TTF-linked 6-oxophenalenoxyl. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Potential Alternatives Report for Validation of Alternatives to Aliphatic Isocyanate Polyurethanes

    NASA Technical Reports Server (NTRS)

    Lewis, pattie

    2011-01-01

    Identifying and selecting alternative materials and technologies that have the potential to reduce the identified HazMats and hazardous air pollutants (HAPs), while incorporating sound corrosion prevention and control technologies, is a complicated task due to the fast pace at which new technologies emerge and rules change. The alternatives are identified through literature searches, electronic database and Internet searches, surveys, and/or personal and professional contacts. Available test data was then compiled on the proposed alternatives to determine if the materials meet the test objectives or if further)laboratory or field-testing will be required. After reviewing technical information documented in the PAR, government representatives, technical representatives from the affected facilities, and other stakeholders involved in the process will select the list of viable alternative coatings for consideration and testing under the project's Joint Test Protocol entitled Joint Test Protocol for Validation of Alternatives to Aliphatic Isocyanate Polyurethanes and Field Test Plan entitled Field Evaluations Test Plan for Validation of Alternatives to Aliphatic Isocyanate Polyurethanes, both prepared by ITB. Test results will be reported in a Joint Test Report upon completion oftesting. The selection rationale and conclusions are documented in this PAR. A cost benefit analysis will be prepared to quantify the estimated capital and process costs of coating alternatives and cost savings relative to the current coating processes, however, some initial cost data has been included in this PAR. For this coatings project, isocyanates, as found in aliphatic isocyanate polyurethanes, were identified as the target HazMat to be eliminated. Table 1-1 lists the target HazMats, the related process and application, current specifications, and affected programs.

  12. Alternatives for Jet Engine Control

    NASA Technical Reports Server (NTRS)

    Leake, R. J.; Sain, M. K.

    1976-01-01

    Approaches are developed as alternatives to current design methods which rely heavily on linear quadratic and Riccati equation methods. The main alternatives are discussed in two broad categories, local multivariable frequency domain methods and global nonlinear optimal methods.

  13. Enhanced dopamine release by dopamine transport inhibitors described by a restricted diffusion model and fast scan cyclic voltammetry

    PubMed Central

    Hoffman, Alexander F.; Spivak, Charles E.; Lupica, Carl R.

    2016-01-01

    Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple, 5 parameter, two compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using non-linear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altered Ca2+/Mg2+ ratio or tetrodotoxin (TTX), reduced the release parameter with no effect on the uptake parameter. The DAT inhibitors methylenedioxypyrovalerone (MDPV), cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa-opioid receptor (KOR) agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data. PMID:27018734

  14. Enhanced Dopamine Release by Dopamine Transport Inhibitors Described by a Restricted Diffusion Model and Fast-Scan Cyclic Voltammetry.

    PubMed

    Hoffman, Alexander F; Spivak, Charles E; Lupica, Carl R

    2016-06-15

    Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple five-parameter, two-compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using nonlinear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altering the Ca(2+)/Mg(2+) ratio or adding tetrodotoxin reduced the release parameter with no effect on the uptake parameter. DAT inhibitors methylenedioxypyrovalerone, cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa opioid receptor agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data.

  15. Cyclic voltammetry to evaluate the antioxidant potential in winemaking by-products.

    PubMed

    José Jara-Palacios, M; Luisa Escudero-Gilete, M; Miguel Hernández-Hierro, J; Heredia, Francisco J; Hernanz, Dolores

    2017-04-01

    Grape pomace is composed of seeds, skins and stems that are an important source of phenolic substances, which have antioxidant properties and potential benefits to human health. Cyclic voltammetry (CV) has been used to measure the total antioxidant potential of different winemaking by-products. The electrochemical behavior of pomace, seeds, skins and stems was measured by CV and lipid peroxidation inhibition by thiobarbituric acid reactive substances (TBARS) method. Differences for the electrochemical parameter were found between the by-products, pomace and seeds, which presented the greatest voltammetric peak area. Furthermore, the by-products induced inhibition of lipid peroxidation in rat liver homogenates. Pomace and seeds showed higher capacity to inhibit lipid peroxidation than stems and skins, which could be because these by-products are richer in flavanols. Simple regression analyses showed that voltammetric parameters are highly correlated to the values obtained for lipid peroxidation inhibition. CV is a promising technique to estimate the total antioxidant potential of phenolic extract from winemaking by-products. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Fully printed flexible and disposable wireless cyclic voltammetry tag

    PubMed Central

    Jung, Younsu; Park, Hyejin; Park, Jin-Ah; Noh, Jinsoo; Choi, Yunchang; Jung, Minhoon; Jung, Kyunghwan; Pyo, Myungho; Chen, Kevin; Javey, Ali; Cho, Gyoujin

    2015-01-01

    A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56 MHz RF reader, the printed CV tag generates 320 mHz of triangular sweep wave from +500 mV to −500 mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10 mM of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56 MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health. PMID:25630250

  17. Optimization and performance comparison for galloping-based piezoelectric energy harvesters with alternating-current and direct-current interface circuits

    NASA Astrophysics Data System (ADS)

    Tan, Ting; Yan, Zhimiao; Lei, Hong

    2017-07-01

    Galloping-based piezoelectric energy harvesters scavenge small-scale wind energy and convert it into electrical energy. For piezoelectric energy harvesting with the same vibrational source (galloping) but different (alternating-current (AC) and direct-current (DC)) interfaces, general analytical solutions of the electromechanical coupled distributed parameter model are proposed. Galloping is theoretically proven to appear when the linear aerodynamic negative damping overcomes the electrical damping and mechanical damping. The harvested power is demonstrated as being done by the electrical damping force. Via tuning the load resistance to its optimal value for optimal or maximal electrical damping, the harvested power of the given structure with the AC/DC interface is maximized. The optimal load resistances and the corresponding performances of such two systems are compared. The optimal electrical damping are the same but with different optimal load resistances for the systems with the AC and DC interfaces. At small wind speeds where the optimal electrical damping can be realized by only tuning the load resistance, the performances of such two energy harvesting systems, including the minimal onset speeds to galloping, maximal harvested powers and corresponding tip displacements are almost the same. Smaller maximal electrical damping with larger optimal load resistance is found for the harvester with the DC interface when compared to those for the harvester with the AC interface. At large wind speeds when the maximal electrical damping rather than the optimal electrical damping can be reached by tuning the load resistance alone, the harvester with the AC interface circuit is recommended for a higher maximal harvested power with a smaller tip displacement. This study provides a method using the general electrical damping to connect and compare the performances of piezoelectric energy harvesters with same excitation source but different interfaces.

  18. Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry.

    PubMed

    Battistel, Dario; Baldi, Franco; Gallo, Michele; Faleri, Claudia; Daniele, Salvatore

    2015-01-01

    Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Interactions of the baicalin and baicalein with bilayer lipid membranes investigated by cyclic voltammetry and UV-Vis spectroscopy.

    PubMed

    Zhang, Ying; Wang, Xuejing; Wang, Lei; Yu, Miao; Han, Xiaojun

    2014-02-01

    The baicalin and baicalein are the major flavonoids found in Radix Scutellariae, an essential herb in traditional Chinese medicine for thousands of years. The interactions of the baicalin and baicalein with lipid bilayer membranes were studied using cyclic voltammetry and UV-Vis spectroscopy. The thickness d of supported bilayer lipid membranes was calculated as d=4.59(±0.36) nm using AC impedance spectroscopy. The baicalein interacted with egg PC bilayer membranes in a dose-dependent manner. The responses of K3Fe(CN)6 on lipid bilayer membrane modified Pt electrode linearly increased in a concentration range of baicalein from 6.25μM to 25μM with a detection limit of 0.1μM and current-concentration sensitivity of 0.11(±0.01) μA/μM, and then reached a plateau from 25μM to 50μM. However the baicalin showed much weaker interactions with egg PC bilayer membranes. UV-Vis spectroscopy also confirmed that the baicalein could interact with egg PC membranes noticeably, but the interaction of baicalin with membranes was hard to be detected. The results provide useful information on understanding the mechanism of action of Radix Scutellariae in vivo. © 2013.

  20. Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

    NASA Technical Reports Server (NTRS)

    Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

    2016-01-01

    The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid-electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid-electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of AC and DC for power transmission. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power generation, transmission, and distribution systems, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of dual-fed induction machines, which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the project along with the system architecture, development status and preliminary results.

  1. Determination of Cd2+ and Pb2+ Based on Mesoporous Carbon Nitride/Self-Doped Polyaniline Nanofibers and Square Wave Anodic Stripping Voltammetry

    PubMed Central

    Zhang, Chang; Zhou, Yaoyu; Tang, Lin; Zeng, Guangming; Zhang, Jiachao; Peng, Bo; Xie, Xia; Lai, Cui; Long, Beiqing; Zhu, Jingjing

    2016-01-01

    The fabrication and evaluation of a glassy carbon electrode (GCE) modified with self-doped polyaniline nanofibers (SPAN)/mesoporous carbon nitride (MCN) and bismuth for simultaneous determination of trace Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV) are presented here. The morphology properties of SPAN and MCN were characterized by transmission electron microscopy (TEM), and the electrochemical properties of the fabricated electrode were characterized by cyclic voltammetry (CV). Experimental parameters, such as deposition time, pulse potential, step potential, bismuth concentration and NaCl concentration, were optimized. Under the optimum conditions, the fabricated electrode exhibited linear calibration curves ranging from 5 to 80 nM for Cd2+ and Pb2+. The limits of detection (LOD) were 0.7 nM for Cd2+ and 0.2 nM for Pb2+ (S/N = 3). Additionally, the repeatability, reproducibility, anti-interference ability and application were also investigated, and the proposed electrode exhibited excellent performance. The proposed method could be extended for other heavy metal determination. PMID:28344264

  2. Microbial fuel cells as an alternative energy source: current status.

    PubMed

    Javed, Muhammad Mohsin; Nisar, Muhammad Azhar; Ahmad, Muhammad Usman; Yasmeen, Nighat; Zahoor, Sana

    2018-06-22

    Microbial fuel cell (MFC) technology is an emerging area for alternative renewable energy generation and it offers additional opportunities for environmental bioremediation. Recent scientific studies have focused on MFC reactor design as well as reactor operations to increase energy output. The advancement in alternative MFC models and their performance in recent years reflect the interests of scientific community to exploit this technology for wider practical applications and environmental benefit. This is reflected in the diversity of the substrates available for use in MFCs at an economically viable level. This review provides an overview of the commonly used MFC designs and materials along with the basic operating parameters that have been developed in recent years. Still, many limitations and challenges exist for MFC development that needs to be further addressed to make them economically feasible for general use. These include continued improvements in fuel cell design and efficiency as well scale-up with economically practical applications tailored to local needs.

  3. Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

    2013-01-01

    In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

  4. A uniform laminar air plasma plume with large volume excited by an alternating current voltage

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

    2015-12-01

    Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

  5. The current status of animal use and alternatives in Korean veterinary medical schools.

    PubMed

    Lee, Gwi Hyang; Choe, Byung In; Kim, Jin Suk; Hart, Lynette A; Han, Jin Soo

    2010-06-01

    Two new Korean laws regulating animal welfare and the humane use of animals in science came into effect in 2008 and 2009. Both these laws impose ethical committee review prior to the performance of animal experiments in research, testing and education. This study briefly summarises the new Korean laws, and investigates the current status regarding the numbers of animals used, the alternatives to animals which are used, the curricula relating to the humane use of animals, and ethical review practices in Korean veterinary education. Approximately 4,845 animals, representing 20 different species, were used in veterinary medical education in Korea in 2007. Korea has begun to introduce formal courses on animal welfare for the humane treatment of animals used in experiments, and an ethical protocol review system prior to animal use in education. Korea is moving toward better animal welfare, by incorporating practices consistent with international standards. The information presented represents the first such data gathered in Korea, which should prove useful for monitoring the implementation of replacement, reduction, and refinement measures in animal use for education purposes.

  6. Electrochemical Determination of Chlorpyrifos on a Nano-TiO₂Cellulose Acetate Composite Modified Glassy Carbon Electrode.

    PubMed

    Kumaravel, Ammasai; Chandrasekaran, Maruthai

    2015-07-15

    A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature.

  7. Regional economic analysis of current and proposed management alternatives for Rappahannock River Valley National Wildlife Refuge

    USGS Publications Warehouse

    Koontz, Lynne; Sexton, Natalie; Donovan, Ryan

    2009-01-01

    The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan. The Comprehensive Conservation Plan must describe the desired future conditions of a refuge and provide long-range guidance and management direction to achieve refuge purposes. The Rappahannock River Valley National Wildlife Refuge (refuge) is in the process of developing a range of management goals, objectives, and strategies for the Comprehensive Conservation Plan. The Comprehensive Conservation Plan for the refuge must contain an analysis of expected effects associated with current and proposed refuge management strategies. The purpose of this study was to assess the regional economic implications associated with draft Comprehensive Conservation Plan management strategies. Special interest groups and local residents often criticize a change in refuge management, especially if there is a perceived negative impact to the local economy. Having objective data on economic impacts may show that these fears are overstated. Quite often, the extent of economic benefits a refuge provides to a local community is not fully recognized, yet at the same time the effects of negative changes is overstated. Spending associated with refuge recreational activities, such as wildlife viewing and hunting, can generate considerable tourist activity for surrounding communities. Additionally, refuge personnel typically spend considerable amounts of money purchasing supplies in local stores, repairing equipment and purchasing fuel at the local service stations, and reside and spend their salaries in the local community. For refuge Comprehensive Conservation Plan planning, a regional economic assessment provides a means of estimating how current management (no action alternative) and proposed management activities (alternatives) could affect the local economy. This type of analysis provides two critical pieces of

  8. Transcranial Alternating Current Stimulation (tACS) Enhances Mental Rotation Performance during and after Stimulation

    PubMed Central

    Kasten, Florian H.; Herrmann, Christoph S.

    2017-01-01

    Transcranial alternating current stimulation (tACS) has been repeatedly demonstrated to modulate endogenous brain oscillations in a frequency specific manner. Thus, it is a promising tool to uncover causal relationships between brain oscillations and behavior or perception. While tACS has been shown to elicit a physiological aftereffect for up to 70 min, it remains unclear whether the effect can still be elicited if subjects perform a complex task interacting with the stimulated frequency band. In addition, it has not yet been investigated whether the aftereffect is behaviorally relevant. In the current experiment, participants performed a Shepard-like mental rotation task for 80 min. After 10 min of baseline measurement, participants received either 20 min of tACS at their individual alpha frequency (IAF) or sham stimulation (30 s tACS in the beginning of the stimulation period). Afterwards another 50 min of post-stimulation EEG were recorded. Task performance and EEG were acquired during the whole experiment. While there were no effects of tACS on reaction times or event-related-potentials (ERPs), results revealed an increase in mental rotation performance in the stimulation group as compared to sham both during and after stimulation. This was accompanied by increased ongoing alpha power and coherence as well as event-related-desynchronization (ERD) in the alpha band in the stimulation group. The current study demonstrates a behavioral and physiological aftereffect of tACS in parallel. This indicates that it is possible to elicit aftereffects of tACS during tasks interacting with the alpha band. Therefore, the tACS aftereffect is suitable to achieve an experimental manipulation. PMID:28197084

  9. Micropatterned ferrocenyl monolayers covalently bound to hydrogen-terminated silicon surfaces: effects of pattern size on the cyclic voltammetry and capacitance characteristics.

    PubMed

    Fabre, Bruno; Pujari, Sidharam P; Scheres, Luc; Zuilhof, Han

    2014-06-24

    The effect of the size of patterns of micropatterned ferrocene (Fc)-functionalized, oxide-free n-type Si(111) surfaces was systematically investigated by electrochemical methods. Microcontact printing with amine-functionalized Fc derivatives was performed on a homogeneous acid fluoride-terminated alkenyl monolayer covalently bound to n-type H-terminated Si surfaces to give Fc patterns of different sizes (5 × 5, 10 × 10, and 20 × 20 μm(2)), followed by backfilling with n-butylamine. These Fc-micropatterned surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The charge-transfer process between the Fc-micropatterned and underlying Si interface was subsequently studied by cyclic voltammetry and capacitance. By electrochemical studies, it is evident that the smallest electroactive ferrocenyl patterns (i.e., 5 × 5 μm(2) squares) show ideal surface electrochemistry, which is characterized by narrow, perfectly symmetric, and intense cyclic voltammetry and capacitance peaks. In this respect, strategies are briefly discussed to further improve the development of photoswitchable charge storage microcells using the produced redox-active monolayers.

  10. Electrochemical Deposition of Si-Ca/P on Nanotube Formed Beta Ti Alloy by Cyclic Voltammetry Method.

    PubMed

    Jeong, Yong-Hoon; Choe, Han-Cheol

    2015-08-01

    The purpose of this study was to investigate electrochemical deposition of Si-Ca/P on nanotube formed Ti-35Nb-10Zr alloy by cyclic voltammetry method. Electrochemical deposition of Si substituted Ca/P was performed by pulsing the applied potential on nanotube formed surface. The surface characteristics were observed by field-emission scanning electron microscopy, X-ray diffractometer, and potentiodynamic polarization test. The phase structure and surface morphologies of Si-Ca/P deposition were affected by deposition cycles. From the anodic polarization test, nanotube formed surface at 20 V showed the high corrosion resistance with lower value of Icorr, I300, and Ipass.

  11. Precision electronic speed controller for an alternating-current motor

    DOEpatents

    Bolie, V.W.

    A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. The motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The speed error signal is generated by a novel vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error is also computed by digital logic, with adjustable sensitivity around a 0 mid-scale value. The drift error signal, generated by long-term counting of the phase error, is used to compensate for any slow changes in the average friction drag on the motor. An auxillary drift-byte status sensor prevents any disruptive overflow or underflow of the drift-error counter. An adjustable clocked-delay unit is inserted between the controller and the source of the reference pulse train to permit phase alignment of the rotor to any desired offset angle. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of read-only memories, and a pair of digital-to-analog converters.

  12. Alternative RNA splicing and cancer

    PubMed Central

    Liu, Sali; Cheng, Chonghui

    2015-01-01

    Alternative splicing of pre-messenger RNA (mRNA) is a fundamental mechanism by which a gene can give rise to multiple distinct mRNA transcripts, yielding protein isoforms with different, even opposing, functions. With the recognition that alternative splicing occurs in nearly all human genes, its relationship with cancer-associated pathways has emerged as a rapidly growing field. In this review, we summarize recent findings that have implicated the critical role of alternative splicing in cancer and discuss current understandings of the mechanisms underlying dysregulated alternative splicing in cancer cells. PMID:23765697

  13. Demon voltammetry and analysis software: Analysis of cocaine-induced alterations in dopamine signaling using multiple kinetic measures

    PubMed Central

    Yorgason, Jordan T.; España, Rodrigo A.; Jones, Sara R.

    2011-01-01

    The fast sampling rates of fast scan cyclic voltammetry make it a favorable method for measuring changes in brain monoamine release and uptake kinetics in slice, anesthetized, and freely moving preparations. The most common analysis technique for evaluating changes in dopamine signaling uses well-established Michaelis-Menten kinetic methods that can accurately model dopamine release and uptake parameters across multiple experimental conditions. Nevertheless, over the years, many researchers have turned to other measures to estimate changes in dopamine release and uptake, yet to our knowledge no systematic comparison amongst these measures has been conducted. To address this lack of uniformity in kinetic analyses, we have created the Demon Voltammetry and Analysis software suite, which is freely available to academic and non-profit institutions. Here we present an explanation of the Demon Acquisition and Analysis features, and demonstrate its utility for acquiring voltammetric data under in vitro, in vivo anesthetized, and freely moving conditions. Additionally, the software was used to compare the sensitivity of multiple kinetic measures of release and uptake to cocaine-induced changes in electrically evoked dopamine efflux in nucleus accumbens core slices. Specifically, we examined and compared tau, full width at half height, half-life, T20, T80, slope, peak height, calibrated peak dopamine concentration, and area under the curve to the well-characterized Michaelis-Menten parameters, dopamine per pulse, maximal uptake rate, and apparent affinity. Based on observed results we recommend tau for measuring dopamine uptake and calibrated peak dopamine concentration for measuring dopamine release. PMID:21392532

  14. [Current view and critic of alternatives to transurethral surgery of prostatic benign prostate].

    PubMed

    Rodríguez, José Vicente

    2003-11-01

    Critical update of transurethral surgery options based on the last decade most relevant bibliography. Comparative study between Incision/TUR of the prostate and alternative techniques, accordingly to data from 30 randomized studies and 28 clinical studies. We evaluate efficiency, retreatment index, morbidity, post operative number of days with catheter, anesthetic requirements, and cost. Data are expressed as percentages resulting from a differential formula in randomized studies and simple percentages or numeric expression for relevant clinical data. Efficiency: all alternative treatments show a symptomatic improvement (> 50%) similar to that achieved by transurethral surgery; post treatment flowmetry percentage increase is inferior in all alternatives except vaporization, holmium laser and prosthesis. Re-Treatment requirements: they were higher in all alternatives except the ablative ones (vaporization and holmium laser). Morbidity: all of them had an operative estimated blood loss inferior to TUR and similar to prostatic incision; contact laser and vaporization had more irritative symptoms than incision, and VLAP and TUMT more than TUR; TUMT and interstitial laser have a higher rate of post operative infection; all alternatives except the ablative ones had lower percentages of urethral stenosis and retrograde ejaculation. Number of days of catheter post operative: it was comparatively longer after vaporization and very long after VLAP, interstitial laser and TUMT. All treatments except TUNA and TUMT require the same anesthesia than transurethral surgery. The cost/benefit has not been sufficiently evaluated, but it is superior with holmium laser, contact laser and vaporization than with transurethral surgery. Based on study data we can accept holmium laser as a real alternative, TUMT in cases when surgery is questioned and intraprostatic prosthesis when it is not possible.

  15. Lead migration from toys by anodic stripping voltammetry using a bismuth film electrode.

    PubMed

    Leal, M Fernanda C; Catarino, Rita I L; Pimenta, Adriana M; Souto, M Renata S; Afonso, Christelle S; Fernandes, Ana F Q

    2016-09-02

    Metals may be released from toys via saliva during mouthing, via sweat during dermal contact, or via gastric and intestinal fluids after partial or whole ingestion. In this study, we determined the lead migration from toys bought on the Portuguese market for children below 3 years of age. The lead migration was performed according to the European Committee for Standardization EN 71-3, which proposes a 2-hour migration test that simulates human gastric conditions. The voltammetric determination of migrated lead was performed by anodic stripping voltammetry (ASV) at a bismuth film electrode (BiFE). For all the analyzed toys, the values of migrated lead did not exceed the limits imposed by the European Committee for Standardization EN 71-3 (90 mg kg -1 ) and by the EU Directive 2009/48/EC (13.5 mg kg -1 ) on the safety of toys.

  16. Examination of Rapid Dopamine Dynamics with Fast Scan Cyclic Voltammetry During Intra-oral Tastant Administration in Awake Rats.

    PubMed

    Wickham, Robert J; Park, Jinwoo; Nunes, Eric J; Addy, Nii A

    2015-08-12

    Rapid, phasic dopamine (DA) release in the mammalian brain plays a critical role in reward processing, reinforcement learning, and motivational control. Fast scan cyclic voltammetry (FSCV) is an electrochemical technique with high spatial and temporal (sub-second) resolution that has been utilized to examine phasic DA release in several types of preparations. In vitro experiments in single-cells and brain slices and in vivo experiments in anesthetized rodents have been used to identify mechanisms that mediate dopamine release and uptake under normal conditions and in disease models. Over the last 20 years, in vivo FSCV experiments in awake, freely moving rodents have also provided insight of dopaminergic mechanisms in reward processing and reward learning. One major advantage of the awake, freely moving preparation is the ability to examine rapid DA fluctuations that are time-locked to specific behavioral events or to reward or cue presentation. However, one limitation of combined behavior and voltammetry experiments is the difficulty of dissociating DA effects that are specific to primary rewarding or aversive stimuli from co-occurring DA fluctuations that mediate reward-directed or other motor behaviors. Here, we describe a combined method using in vivo FSCV and intra-oral infusion in an awake rat to directly investigate DA responses to oral tastants. In these experiments, oral tastants are infused directly to the palate of the rat--bypassing reward-directed behavior and voluntary drinking behavior--allowing for direct examination of DA responses to tastant stimuli.

  17. Voltammetry of ion transfer across a polarized room-temperature ionic liquid membrane facilitated by valinomycin: theoretical aspects and application.

    PubMed

    Langmaier, Jan; Samec, Zdenek

    2009-08-01

    Cyclic voltammetry is used to investigate the transfer of alkali-metal cations, protons, and ammonium ions facilitated by the complex formation with valinomycin at the interface between an aqueous electrolyte solution and a room-temperature ionic liquid (RTIL) membrane. The membrane is made of a thin (approximately 112 microm) microporous filter impregnated with an RTIL that is composed of tridodecylmethylammonium cations and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anions. An extension of the existing theory of voltammetry of ion transfer across polarized liquid membranes makes it possible to evaluate the standard ion-transfer potentials for the hydrophilic cations studied, as well as the stability constants (K(i)) of their 1:1 complexes with valinomycin, as log K(i) = 9.0 (H(+)), 11.1 (Li(+)), 12.8 (Na(+)), 17.2 (K(+)), 15.7 (Rb(+)), 15.1 (Cs(+)), and 14.7 (NH(4)(+)). These data point to the remarkably enhanced stability of the valinomycin complexes within RTIL, and to the enhanced selectivity of valinomycin for K(+) over all other univalent ions studied, compared to the conventional K(+) ion-selective liquid-membrane electrodes. Selective complex formation allows one to resolve voltammetric responses of K(+) and Na(+) in the presence of an excess of Mg(2+) or Ca(2+), which is demonstrated by determination of K(+) and Na(+) in the table and tap water samples.

  18. Enzyme-modified carbon-fiber microelectrode for the quantification of dynamic fluctuations of nonelectroactive analytes using fast-scan cyclic voltammetry.

    PubMed

    Lugo-Morales, Leyda Z; Loziuk, Philip L; Corder, Amanda K; Toups, J Vincent; Roberts, James G; McCaffrey, Katherine A; Sombers, Leslie A

    2013-09-17

    Neurotransmission occurs on a millisecond time scale, but conventional methods for monitoring nonelectroactive neurochemicals are limited by slow sampling rates. Despite a significant global market, a sensor capable of measuring the dynamics of rapidly fluctuating, nonelectroactive molecules at a single recording site with high sensitivity, electrochemical selectivity, and a subsecond response time is still lacking. To address this need, we have enabled the real-time detection of dynamic glucose fluctuations in live brain tissue using background-subtracted, fast-scan cyclic voltammetry. The novel microbiosensor consists of a simple carbon fiber surface modified with an electrodeposited chitosan hydrogel encapsulating glucose oxidase. The selectivity afforded by voltammetry enables quantitative and qualitative measurements of enzymatically generated H2O2 without the need for additional strategies to eliminate interfering agents. The microbiosensors possess a sensitivity and limit of detection for glucose of 19.4 ± 0.2 nA mM(-1) and 13.1 ± 0.7 μM, respectively. They are stable, even under deviations from physiological normoxic conditions, and show minimal interference from endogenous electroactive substances. Using this approach, we have quantitatively and selectively monitored pharmacologically evoked glucose fluctuations with unprecedented chemical and spatial resolution. Furthermore, this novel biosensing strategy is widely applicable to the immobilization of any H2O2 producing enzyme, enabling rapid monitoring of many nonelectroactive enzyme substrates.

  19. Demagnetization Treatment of Remanent Composite Microspheres Studied by Alternating Current Susceptibility Measurements

    PubMed Central

    van Berkum, Susanne; Erné, Ben H.

    2013-01-01

    The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample. PMID:24009021

  20. Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release

    PubMed Central

    Nguyen, Michael D.; Venton, B. Jill

    2014-01-01

    Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future. PMID:26900429

  1. Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release.

    PubMed

    Nguyen, Michael D; Venton, B Jill

    2015-01-01

    Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future.

  2. RF generator interlock by plasma grid bias current - An alternate to Hα interlock

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, M.; Gahlaut, A.; Yadav, R. K.; Pandya, K.; Tyagi, H.; Vupugalla, M.; Bhuyan, M.; Bhagora, J.; Chakraborty, A.

    2017-08-01

    ROBIN is inductively coupled plasma (ICP) based negative hydrogen ion source, operated with a 100kW, 1MHz Tetrode based RF generator (RFG). Inductive plasma ignition by the RFG in ROBIN is associated with electron seeding by a hot filament and a gas puff. RFG is triggered by the control system to deliver power just at the peak pressure of the gas puff. Once plasma is ignited due to proper impedance matching, a bright light, dominated by Hα (˜656nm wavelength) radiation is available inside RF driver which is used as a feedback signal to the RFG to continue its operation. If impedance matching is not correct, plasma is not produced due to lack of power coupling and bright light is not available. During such condition, reflected RF power may damage the RFG. Therefore, to protect the RFG, it needs to be switched off automatically within 200ms by the control system in such cases. This plasma light based RFG interlock is adopted from BATMAN ion source. However, in case of vacuum immersed RF ion source in reactor grade NBI system, such plasma light based interlock may not be feasible due to lack of adequate optical fiber interfaces. In reactor grade NBI system, neutron and gamma radiations have impact on materials which may lead to frequent maintenance and machine down time. The present demonstration of RFG interlock by Bias Current (BC) in ROBIN testbed gives an alternate option in this regard. In ROBIN, a bias plate (BP) is placed in the plasma chamber near the plasma grid (PG). BP is electrically connected to the plasma chamber wall of the ion source and PG is isolated from the wall. A high current ˜85 A direct current (DC) power supply of voltage in the range of 0 - 33V is connected between the PG and the BP in such a way that PG can be biased positively with respect to the BP or plasma chamber. This arrangement is actually made to absorb electrons and correspondingly reduce co-extracted electron current during beam extraction. However, in case of normal plasma

  3. Testing Alternative Definitions of Chronic Homelessness.

    PubMed

    Byrne, Thomas; Culhane, Dennis P

    2015-09-01

    This study examined the potential impact of a proposed change to the official federal definition of chronic homelessness. Using administrative data from the emergency shelters in a large U.S. city, this study estimated the number of persons identified as chronically homeless under the current definition of chronic homelessness, a proposed new federal definition, and two alternative definitions and examined shelter utilization for each group. Fewer than half as many people were considered chronically homeless under the proposed new federal definition compared with the current definition. Persons considered chronically homeless by the proposed new definition and, to a lesser extent, by the two alternative definitions, made heavier use of shelter compared with persons who met the current definition. A proposed new and two alternative definitions of chronic homelessness are better suited than the existing federal definition for identifying persons with the most protracted experiences of homelessness.

  4. Anodic Stripping Voltammetry with Pencil Graphite Electrode for Determination of Chromium (III)

    NASA Astrophysics Data System (ADS)

    Wyantuti, S.; Hafidza, R. A.; Ishmayana, S.; Hartati, Y. W.

    2017-02-01

    Chromium is required as micronutrient that has roles in insulin metabolism and blood glucose level regulation. Chromium (III) deficiency can cause hyperglycemia and glycosuria. However, a high amount of chromium in body can cause allergic reaction, organ damage, and even death because of its toxicity. Chromium is commonly used in steel industries. Simultaneously with the development of industry, the waste disposal that can endanger environment also increased. Therefore, a sensitive and specific analysis method for chromium detection is required. Stripping voltammetry is one of the voltammetric methods that is commonly used for heavy metal analysis due to the very low limit of detection (sub ppb). The present study was conducted to develop an analysis method for chromium (III) determination using pencil graphite electrode. Quantitative determination was performed for chromium (III) which measured at -0.8 to +1.0 V with deposition time for 60 s and 50 mV/s scan rate. Stripping voltammetric analysis of chromium (III) using pencil graphite electrode gave linear range at 12.5 to 75 ppm with limit of detection of 0.31 ppm.

  5. Free piston variable-stroke linear-alternator generator

    DOEpatents

    Haaland, Carsten M.

    1998-01-01

    A free-piston variable stroke linear-alternator AC power generator for a combustion engine. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod.

  6. Nanostructured biosensors built by layer-by-layer electrostatic assembly of enzyme-coated single-walled carbon nanotubes and redox polymers.

    PubMed

    Wang, Youdan; Joshi, Pratixa P; Hobbs, Kevin L; Johnson, Matthew B; Schmidtke, David W

    2006-11-07

    In this study, we describe the construction of glucose biosensors based on an electrostatic layer-by-layer (LBL) technique. Gold electrodes were initially functionalized with negatively charged 11-mercaptoundecanoic acid followed by alternate immersion in solutions of a positively charged redox polymer, poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)], and a negatively charged enzyme, glucose oxidase (GOX), or a GOX solution containing single-walled carbon nanotubes (SWNTs). The LBL assembly of the multilayer films were characterized by UV-vis spectroscopy, ellipsometry, and cyclic voltammetry, while characterization of the single-walled nanotubes was performed with transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. When the GOX solution contained single-walled carbon nanotubes (GOX-SWNTs), the oxidation peak currents during cyclic voltammetry increased 1.4-4.0 times, as compared to films without SWNTs. Similarly the glucose electro-oxidation current also increased (6-17 times) when SWNTs were present. By varying the number of multilayers, the sensitivity of the sensors could be controlled.

  7. Embedded 32-bit Differential Pulse Voltammetry (DPV) Technique for 3-electrode Cell Sensing

    NASA Astrophysics Data System (ADS)

    N, Aqmar N. Z.; Abdullah, W. F. H.; Zain, Z. M.; Rani, S.

    2018-03-01

    This paper addresses the development of differential pulse voltammetry (DPV) embedded algorithm using an ARM cortex processor with new developed potentiostat circuit design for in-situ 3-electrode cell sensing. This project is mainly to design a low cost potentiostat for the researchers in laboratories. It is required to develop an embedded algorithm for analytical technique to be used with the designed potentiostat. DPV is one of the most familiar pulse technique method used with 3-electrode cell sensing in chemical studies. Experiment was conducted on 10mM solution of Ferricyanide using the designed potentiostat and the developed DPV algorithm. As a result, the device can generate an excitation signal of DPV from 0.4V to 1.2V and produced a peaked voltammogram with relatively small error compared to the commercial potentiostat; which is only 6.25% difference in peak potential reading. The design of potentiostat device and its DPV algorithm is verified.

  8. UCB current detector experiment on Swedish auroral payloads. [ionospheric current and plasma flow measurements

    NASA Technical Reports Server (NTRS)

    Mozer, F.

    1974-01-01

    A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

  9. DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

    NASA Astrophysics Data System (ADS)

    Nikam, Pravin N.; Deshpande, Vineeta D.

    2016-05-01

    Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al2O3) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σAC) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher's universal power law of solids. It revealed that σAC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σDC), critical frequency (ωc), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σDC) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

  10. An Analysis of Alternatives to New York City's Current Marijuana Arrest and Detention Policy

    PubMed Central

    Johnson, Bruce D.; Golub, Andrew; Dunlap, Eloise; Sifaneck, Stephen J.

    2008-01-01

    During the 1990s, the New York Police Department (NYPD) instituted a policy of arresting and detaining people for minor offenses that occur in public as part of their quality-of-life (hereafter QOL) policing initiative. The number of NYPD arrests for smoking marijuana in public view (MPV) increased from 3,000 in 1994 to over 50,000 in 2000, and have been about 30,000 in the mid 2000s. Most of these arrestees (84%) have been minority; blacks have been 2.7 more likely and Hispanics 1.8 times more likely to be detained than whites for an MPV arrest. Minorities have been most likely to receive more severe dispositions, even controlling for demographics and prior arrest histories. This paper examines the pros and cons of the current policy; this is compared with possible alternatives including the following: arrest and issue a desk appearance ticket (DAT); issue a non-criminal citation (violation); street warnings; and tolerate public marijuana smoking. The authors recommend that the NYPD change to issuing DATs on a routine basis. Drug policy reformers might wish to further pursue changing statutes regarding smoking marijuana in public view into a violation (noncriminal) or encourage the wider use of street warnings. Any of these policy changes would help reduce the disproportionate burden on minorities associated with the current arrest and detention policy. These policies could help maintain civic norms against smoking marijuana in public. PMID:18726007

  11. Alternating-Current Motor Drive for Electric Vehicles

    NASA Technical Reports Server (NTRS)

    Krauthamer, S.; Rippel, W. E.

    1982-01-01

    New electric drive controls speed of a polyphase as motor by varying frequency of inverter output. Closed-loop current-sensing circuit automatically adjusts frequency of voltage-controlled oscillator that controls inverter frequency, to limit starting and accelerating surges. Efficient inverter and ac motor would give electric vehicles extra miles per battery charge.

  12. Mixing enhancement by biologically inspired convection in a micro-chamber using alternating current galvanotactic control of the Tetrahymena pyriformis

    NASA Astrophysics Data System (ADS)

    Kim, Jihoon; Jang, Yonghee; Byun, Doyoung; Hyung Kim, Dal; Jun Kim, Min

    2013-09-01

    Recently, there has been increasing interest in the swimming behavior of microorganisms and biologically inspired micro-robots. In this study, we investigated biologically induced convection flow with living microorganism using galvanotaxis. We fabricated and evaluated our micro-mixer with motile cells. For the cell based active micro-mixers, two miscible fluids were used to measure the mixing index. Under alternating current (AC) electric fields with varying frequency, a group of motile Tetrahymena pyriformis cells generated reciprocal motion with circulating flows around their pathline, enhancing the mixing ratio.

  13. The opinion of Turkish cardiologists on current malpractice system and an alternative patient compensation system proposal: PCS study group.

    PubMed

    Olcay, Ayhan; Emren, Sadık Volkan; Babür Güler, Gamze; Güler, Ekrem; Ertunç, Vedat; Berilgen, Rida; Aslan, Abdullah; Şimşek, Ersin Çağrı; Gölcük, Şükriye Ebru; Yalın, Kıvanç

    2017-10-01

    Cardiologists participate in the diagnosis and interventional treatment of numerous high-risk patients. The goal of this study was to investigate how the current malpractice system in Turkey influences cardiologists' diagnostic and interventional behavior and to obtain their opinions about an alternative patient compensation system. The present cross-sectional study assessed the practice of defensive medicine among cardiologists who are actively working in various types of workplace within the Turkish healthcare system. A 24-item questionnaire was distributed to cardiology residents, specialists, and academics in Turkey in print format, by electronic mail, or via cell phone message. A total of 253 cardiologists responded to the survey. Among them, 29 (11.6%) had been sued for malpractice claims in the past. Of the cardiologists who had been sued, 2 (6.9%) had been ordered to pay financial compensation, and 1 (3.4%) was given a sentence of imprisonment due to negligence. In all, 132 (52.8%) of the surveyed cardiologists reported that they had changed their practices due to fear of litigation, and 232 (92.8%) reported that they would prefer the new proposed patient compensation system to the current malpractice system. Among the cardiologists surveyed, 78.8% indicated that malpractice fear had affected their decision-making with regard to requesting computed tomography angiography or thallium scintigraphy, 71.6% for coronary angiography, 20% for stent implantation, and 83.2% for avoiding treating high-risk patients. The results of this survey demonstrated that cardiologists may request unnecessary tests and perform unneeded interventions due to the fear of malpractice litigation fear. Many also avoid high-risk patients and interventions. The majority indicated that they would prefer the proposed alternative patient compensation system to the current malpractice system.

  14. Use of fast-scan cyclic voltammetry to assess phasic dopamine release in rat models of early postpartum maternal behavior and neglect.

    PubMed

    Shnitko, Tatiana A; Mace, Kyla D; Sullivan, Kaitlin M; Martin, W Kyle; Andersen, Elizabeth H; Williams Avram, Sarah K; Johns, Josephine M; Robinson, Donita L

    2017-12-01

    Maternal behavior (MB) is a complex response to infant cues, orchestrated by postpartum neurophysiology. Although mesolimbic dopamine contributes toward MB, little is known about real-time dopamine fluctuations during the postpartum period. Thus, we used fast-scan cyclic voltammetry to measure individual dopamine transients in the nucleus accumbens of early postpartum rats and compared them with dopamine transients in virgins and in postpartum females exposed to cocaine during pregnancy, which is known to disrupt MB. We hypothesized that dopamine transients are normally enhanced postpartum and support MB. In anesthetized rats, electrically evoked dopamine release was larger and clearance was faster in postpartum females than in virgins and gestational cocaine exposure blocked the change in clearance. In awake rats, control mothers showed more dopamine transients than cocaine-exposed mothers during MB. Salient pup-produced stimuli may contribute toward differences in maternal phasic dopamine by evoking dopamine transients; supporting the feasibility of this hypothesis, urine composition (glucose, ketones, and leukocytes) differed between unexposed and cocaine-exposed infants. These data, resulting from the novel application of fast-scan cyclic voltammetry to models of MB, support the hypothesis that phasic dopamine signaling is enhanced postpartum. Future studies with additional controls can delineate which aspects of gestational cocaine reduce dopamine clearance and transient frequency.

  15. Apparatus and method for critical current measurements

    DOEpatents

    Martin, Joe A.; Dye, Robert C.

    1992-01-01

    An apparatus for the measurement of the critical current of a superconductive sample, e.g., a clad superconductive sample, the apparatus including a conductive coil, a means for maintaining the coil in proximity to a superconductive sample, an electrical connection means for passing a low amplitude alternating current through the coil, a cooling means for maintaining the superconductive sample at a preselected temperature, a means for passing a current through the superconductive sample, and, a means for monitoring reactance of the coil, is disclosed, together with a process of measuring the critical current of a superconductive material, e.g., a clad superconductive material, by placing a superconductive material into the vicinity of the conductive coil of such an apparatus, cooling the superconductive material to a preselected temperature, passing a low amplitude alternating current through the coil, the alternating current capable of generating a magnetic field sufficient to penetrate, e.g., any cladding, and to induce eddy currents in the superconductive material, passing a steadily increasing current through the superconductive material, the current characterized as having a different frequency than the alternating current, and, monitoring the reactance of the coil with a phase sensitive detector as the current passed through the superconductive material is steadily increased whereby critical current of the superconductive material can be observed as the point whereat a component of impedance deviates.

  16. Free piston variable-stroke linear-alternator generator

    DOEpatents

    Haaland, C.M.

    1998-12-15

    A free-piston variable stroke linear-alternator AC power generator for a combustion engine is described. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod. 8 figs.

  17. The dynamics of charge transfer with and without a barrier: A very simplified model of cyclic voltammetry.

    PubMed

    Ouyang, Wenjun; Subotnik, Joseph E

    2017-05-07

    Using the Anderson-Holstein model, we investigate charge transfer dynamics between a molecule and a metal surface for two extreme cases. (i) With a large barrier, we show that the dynamics follow a single exponential decay as expected; (ii) without any barrier, we show that the dynamics are more complicated. On the one hand, if the metal-molecule coupling is small, single exponential dynamics persist. On the other hand, when the coupling between the metal and the molecule is large, the dynamics follow a biexponential decay. We analyze the dynamics using the Smoluchowski equation, develop a simple model, and explore the consequences of biexponential dynamics for a hypothetical cyclic voltammetry experiment.

  18. Improvement of immunoassay detection system by using alternating current magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Kawabata, R.; Mizoguchi, T.; Kandori, A.

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  19. Hyper-Transcranial Alternating Current Stimulation: Experimental Manipulation of Inter-Brain Synchrony

    PubMed Central

    Szymanski, Caroline; Müller, Viktor; Brick, Timothy R.; von Oertzen, Timo; Lindenberger, Ulman

    2017-01-01

    We walk together, we watch together, we win together: Interpersonally coordinated actions are omnipresent in everyday life, yet the associated neural mechanisms are not well understood. Available evidence suggests that the synchronization of oscillatory activity across brains may provide a mechanism for the temporal alignment of actions between two or more individuals. In an attempt to provide a direct test of this hypothesis, we applied transcranial alternating current stimulation simultaneously to two individuals (hyper-tACS) who were asked to drum in synchrony at a set pace. Thirty-eight female-female dyads performed the dyadic drumming in the course of 3 weeks under three different hyper-tACS stimulation conditions: same-phase-same-frequency; different-phase-different-frequency; sham. Based on available evidence and theoretical considerations, stimulation was applied over right frontal and parietal sites in the theta frequency range. We predicted that same-phase-same-frequency stimulation would improve interpersonal action coordination, expressed as the degree of synchrony in dyadic drumming, relative to the other two conditions. Contrary to expectations, both the same-phase-same-frequency and the different-phase-different-frequency conditions were associated with greater dyadic drumming asynchrony relative to the sham condition. No influence of hyper-tACS on behavioral performance was seen when participants were asked to drum separately in synchrony to a metronome. Individual and dyad preferred drumming tempo was also unaffected by hyper-tACS. We discuss limitations of the present version of the hyper-tACS paradigm, and suggest avenues for future research. PMID:29167638

  20. Improvement of immunoassay detection system by using alternating current magnetic susceptibility.

    PubMed

    Kawabata, R; Mizoguchi, T; Kandori, A

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  1. Local Network-Level Integration Mediates Effects of Transcranial Alternating Current Stimulation.

    PubMed

    Fuscà, Marco; Ruhnau, Philipp; Neuling, Toralf; Weisz, Nathan

    2018-05-01

    Transcranial alternating current stimulation (tACS) has been proposed as a tool to draw causal inferences on the role of oscillatory activity in cognitive functioning and has the potential to induce long-term changes in cerebral networks. However, effectiveness of tACS underlies high variability and dependencies, which, as previous modeling works have suggested, may be mediated by local and network-level brain states. We used magnetoencephalography to record brain activity from 17 healthy participants at rest as they kept their eyes open (EO) or eyes closed (EC) while being stimulated with sham, weak, or strong alpha-tACS using a montage commonly assumed to target occipital areas. We reconstructed the activity of sources in all stimulation conditions by means of beamforming. The analysis of resting-state brain activity revealed an interaction of the external stimulation with the endogenous alpha power increase from EO to EC. This interaction was localized to the posterior cingulate, a region remote from occipital cortex. This suggests state-dependent (EO vs. EC) long-range effects of tACS. In a follow-up analysis of this online-tACS effect, we find evidence that this state-dependency effect is mediated by functional network changes: connection strength from the precuneus was significantly correlated with the state-dependency effect in the posterior cingulate during tACS. No analogous correlation could be found for alpha power modulations in occipital cortex. Altogether, this is the first strong evidence to illustrate how functional network architectures can shape tACS effects.

  2. Alternate-Fueled Combustion-Sector Emissions

    NASA Technical Reports Server (NTRS)

    Saxena, Nikita T.; Thomas, Anna E.; Shouse, Dale T.; Neuroth, Craig; Hendricks, Robert C.; Lynch, Amy; Frayne, Charles W.; Stutrud, Jeffrey S.; Corporan, Edwin; Hankins, Terry

    2012-01-01

    In order to meet rapidly growing demand for fuel, as well as address environmental concerns, the aviation industry has been testing alternate fuels for performance and technical usability in commercial and military aircraft. Currently, alternate aviation fuels must satisfy MIL-DTL- 83133F(2008) (military) or ASTM D 7566- Annex(2011) (commercial) standards and are termed drop-in fuel replacements. Fuel blends of up to 50% alternative fuel blended with petroleum (JP-8), which have become a practical alternative, are individually certified on the market. In order to make alternate fuels (and blends) a viable option for aviation, the fuel must be able to perform at a similar or higher level than traditional petroleum fuel. They also attempt to curb harmful emissions, and therefore a truly effective alternate fuel would emit at or under the level of currently used fuel. This paper analyzes data from gaseous and particulate emissions of an aircraft combustor sector. The data were evaluated at various inlet conditions, including variation in pressure and temperature, fuel-to-air ratios, and percent composition of alternate fuel. Traditional JP-8+100 data were taken as a baseline, and blends of JP- 8+100 with synthetic-paraffinic-kerosene (SPK) fuel (Fischer-Tropsch (FT)) were used for comparison. Gaseous and particulate emissions, as well as flame luminosity, were assessed for differences between FT composition of 0%, 50%, and 100%. The data showed that SPK fuel (a FT-derived fuel) had slightly lower harmful gaseous emissions, and smoke number information corroborated the hypothesis that SPK-FT fuels are cleaner burning fuels.

  3. Development of square wave voltammetry method for the assessment of organophosphorus compound impact on the cholinesterase of Pheretima with 2,6-dichloroindophenol as a redox indicator.

    PubMed

    Qiu, Jingxia; Chen, Jin; Ma, Qianqian; Miao, Yuqing

    2009-09-01

    A square wave voltammetry method was developed for the assessment of organophosphorus (OPs) compound impact on the cholinesterase of Pheretima with 2,6-dichloroindophenol (2,6-DCIP) as a redox indicator. The substrate of acetylthiocholine is hydrolysed by the cholinesterase (ChE) from soil animal pheretima, and the produced thiocholine reacts with the 2,6-DCIP to give obvious shift of electrochemical signal. The inhibition of ChE was assessed by measuring the enzyme activity before and after incubating with parathion-methyl. The reduction peak current of 2,6-DCIP decreases with the time of enzymatical reaction. The ChE loses almost 32.74% activity after 10 min incubation with 1ng mL(-1) paraoxon and 54.62% with 10 microg mL(-1) paraoxon, while the activity that corresponds to 100 microg mL(-1) paraoxon was nearly completely inhibited. This method can be employed to assess the inhibition of ChE and investigate OPs impact on environmental animals.

  4. Determination of antioxidant activity of spices and their active principles by differential pulse voltammetry.

    PubMed

    Palma, Alberto; Ruiz Montoya, Mercedes; Arteaga, Jesús F; Rodríguez Mellado, Jose M

    2014-01-22

    The anodic oxidation of mercury in the presence of hydrogen peroxide in differential pulse voltammetry (DPV) was used to determine the antioxidant (AO) character of radical scavengers. Hydroperoxide radical is formed at the potentials of the oxidation peak on mercury electrodes, such radical reacting with the antioxidants in different extension. The parameter C10 (antioxidant concentration at which the peak area decreases by 10%) is used to measure the scavenging activity of the individual antioxidants. To establish the scavenging activity of antioxidant mixtures as a whole, the parameter, μ10 as the reverse of V10, V10 being the volume necessary to decrease the peak area in DPV by 10%, was selected. Higher μ10 values correspond to higher scavenging activity. The studies have been extended to aqueous extracts of some species. The results may be useful in explaining the effect of spices in vitro and in vivo studies.

  5. Extreme Basicity of Biguanide Drugs in Aqueous Solutions: Ion Transfer Voltammetry and DFT Calculations.

    PubMed

    Langmaier, Jan; Pižl, Martin; Samec, Zdeněk; Záliš, Stanislav

    2016-09-22

    Ion transfer voltammetry is used to estimate the acid dissociation constants Ka1 and Ka2 of the mono- and diprotonated forms of the biguanide drugs metformin (MF), phenformin (PF), and 1-phenylbiguanide (PB) in an aqueous solution. Measurements gave the pKa1 values for MFH(+), PFH(+), and PBH(+) characterizing the basicity of MF, PF, and PB, which are significantly higher than those reported in the literature. As a result, the monoprotonated forms of these biguanides should prevail in a considerably broader range of pH 1-15 (MFH(+), PFH(+)) and 2-13 (PBH(+)). DFT calculations with solvent correction were performed for possible tautomeric forms of neutral, monoprotonated, and diprotonated species. Extreme basicity of all drugs is confirmed by DFT calculations of pKa1 for the most stable tautomers of the neutral and protonated forms with explicit water molecules in the first solvation sphere included.

  6. Mechanism-Based Condition Screening for Sustainable Catalysis in Single-Electron Steps by Cyclic Voltammetry.

    PubMed

    Liedtke, Theresa; Spannring, Peter; Riccardi, Ludovico; Gansäuer, Andreas

    2018-04-23

    A cyclic-voltammetry-based screening method for Cp 2 TiX-catalyzed reactions is introduced. Our mechanism-based approach enables the study of the influence of various additives on the electrochemically generated active catalyst Cp 2 TiX, which is in equilibrium with catalytically inactive [Cp 2 TiX 2 ] - . Thioureas and ureas are most efficient in the generation of Cp 2 TiX in THF. Knowing the precise position of the equilibrium between Cp 2 TiX and [Cp 2 TiX 2 ] - allowed us to identify reaction conditions for the bulk electrolysis of Cp 2 TiX 2 complexes and for Cp 2 TiX-catayzed radical arylations without having to carry out the reactions. Our time- and resource-efficient approach is of general interest for the design of catalytic reactions that proceed in single-electron steps. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Flicker-Driven Responses in Visual Cortex Change during Matched-Frequency Transcranial Alternating Current Stimulation

    PubMed Central

    Ruhnau, Philipp; Keitel, Christian; Lithari, Chrysa; Weisz, Nathan; Neuling, Toralf

    2016-01-01

    We tested a novel combination of two neuro-stimulation techniques, transcranial alternating current stimulation (tACS) and frequency tagging, that promises powerful paradigms to study the causal role of rhythmic brain activity in perception and cognition. Participants viewed a stimulus flickering at 7 or 11 Hz that elicited periodic brain activity, termed steady-state responses (SSRs), at the same temporal frequency and its higher order harmonics. Further, they received simultaneous tACS at 7 or 11 Hz that either matched or differed from the flicker frequency. Sham tACS served as a control condition. Recent advances in reconstructing cortical sources of oscillatory activity allowed us to measure SSRs during concurrent tACS, which is known to impose strong artifacts in magnetoencephalographic (MEG) recordings. For the first time, we were thus able to demonstrate immediate effects of tACS on SSR-indexed early visual processing. Our data suggest that tACS effects are largely frequency-specific and reveal a characteristic pattern of differential influences on the harmonic constituents of SSRs. PMID:27199707

  8. Method development for the determination of arsenic by sequential injection/anodic stripping voltammetry using long-lasting gold-modified screen-printed carbon electrode.

    PubMed

    Punrat, Eakkasit; Chuanuwatanakul, Suchada; Kaneta, Takashi; Motomizu, Shoji; Chailapakul, Orawon

    2013-11-15

    An automated method has been developed for determining the concentration of inorganic arsenic. The technique uses sequential injection/anodic stripping voltammetry with a long-lasting gold-modified screen-printed carbon electrode. The long-lasting gold electrode was electrochemically deposited onto a screen-printed carbon electrode at a potential of -0.5 V vs. Ag/AgCl in a supporting electrolyte solution of 1M hydrochloric acid. Under optimal conditions and the applied potentials, the electrode demonstrated that it can be used for a long time without a renewal process. The linear range for the determination of arsenic(III) was 1-100 μg L(-1), and the limit of detection (LOD) in standard solutions was as low as 0.03 μg L(-1) for a deposition time of 120 s and sample volume of 1 mL. This method was used to determine the concentration of arsenic(III) in water samples with satisfactory results. The LOD in real samples was found to be 0.5 μg L(-1). In addition, speciation between arsenic(III) and arsenic(V) has been achieved with the proposed method using deposition potentials of -0.5 V and -1.5 V for the determination of the arsenic(III) concentration and the total arsenic concentration, respectively; the results were acceptable. The proposed method is an automated system that offers a less expensive alternative for determining trace amounts of inorganic arsenic. © 2013 Elsevier B.V. All rights reserved.

  9. Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

    PubMed

    Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

    2012-02-07

    A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

  10. DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nikam, Pravin N., E-mail: pravinya26@gmail.com; Deshpande, Vineeta D., E-mail: drdeshpandevd@gmail.com

    Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al{sub 2}O{sub 3}) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observedmore » at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σ{sub AC}) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher’s universal power law of solids. It revealed that σ{sub AC} of PET/alumina nanocomposites can be well characterized by the DC conductivity (σ{sub DC}), critical frequency (ω{sub c}), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σ{sub DC}) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.« less

  11. Validation of alternative methods for toxicity testing.

    PubMed Central

    Bruner, L H; Carr, G J; Curren, R D; Chamberlain, M

    1998-01-01

    Before nonanimal toxicity tests may be officially accepted by regulatory agencies, it is generally agreed that the validity of the new methods must be demonstrated in an independent, scientifically sound validation program. Validation has been defined as the demonstration of the reliability and relevance of a test method for a particular purpose. This paper provides a brief review of the development of the theoretical aspects of the validation process and updates current thinking about objectively testing the performance of an alternative method in a validation study. Validation of alternative methods for eye irritation testing is a specific example illustrating important concepts. Although discussion focuses on the validation of alternative methods intended to replace current in vivo toxicity tests, the procedures can be used to assess the performance of alternative methods intended for other uses. Images Figure 1 PMID:9599695

  12. A Manpower Comparison of Three U.S. Navies: The Current Fleet, a Projected 313 Ship Fleet, and a More Distributed Bimodal Alternative

    DTIC Science & Technology

    2009-09-01

    Large, Medium-speed, Roll-on/Roll-off Ships T- AKR ,” 2009) The ships can support humanitarian missions as well. LMSRs normally have a crew size of 26...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited A MANPOWER...COMPARISON OF THREE U. S. NAVIES: THE CURRENT FLEET, A PROJECTED 313 SHIP FLEET, AND A MORE DISTRIBUTED BIMODAL ALTERNATIVE by Juan L. Carrasco

  13. Conditions and chemometrics for the determination of heavy metals in natural and waste waters by stripping voltammetry with UV irradiation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Volkova, V.N.; Zakharova, E.A.; Khustenko, L.A.

    The number of supporting electrolytes for stripping voltammetry with photochemical oxygen deactivation was broadened. The following agents are recommended: formic, lactic, tartaric, citric, and malonic acids at pH 2-4; salts of lactic, tartaric, and citric acids at pH 6-7; and salts of lactic, tartaric, citric, and glutaric acids at pH 12-14. A rapid method was developed for simultaneously determining Zn, Cd, Pb, and Cu in a 0.5 M formic acid supporting electrolyte. The method is chemometrically sound and cost-effective.

  14. Cyclic voltammetry study of PEO processing of porous Ti and resulting coatings

    NASA Astrophysics Data System (ADS)

    Shbeh, Mohammed; Yerokhin, Aleksey; Goodall, Russell

    2018-05-01

    Ti is one of the most commonly used materials for biomedical applications. However, there are two issues associated with the use of it, namely its bio-inertness and high elastic modulus compared to the elastic modulus of the natural bone. Both of these hurdles could potentially be overcome by introducing a number of pores in the structure of the Ti implant to match the properties of the bone as well as improve the mechanical integration between the bone and implant, and subsequently coating it with a biologically active ceramic coating to promote chemical integration. Hence, in this study we investigated the usage of cyclic voltammetry in PEO treatment of porous Ti parts with different amount of porosity produced by both Metal Injection Moulding (MIM) and MIM in combination with a space holder. It was found that porous samples with higher porosity and open pores develop much thicker surface layers that penetrate through the inner structure of the samples forming a network of surface and subsurface coatings. The results are of potential benefit in producing surface engineered porous samples for biomedical applications which do not only address the stress shielding problem, but also improve the chemical integration.

  15. Advancing practice relating to SEA alternatives

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    González, Ainhoa, E-mail: agonzal@tcd.ie; Thérivel, Riki, E-mail: levett-therivel@phonecoop.coop; Fry, John, E-mail: john.fry@ucd.ie

    Developing and assessing alternatives is a key and central stage to Strategic Environmental Assessment (SEA). However, research has repeatedly reported this stage as one of the most poorly undertaken aspects of the SEA process. Current practice limitations include belated consideration of reasonable alternatives, narrow scope of alternatives that often include unrealistic or retrofitted options, limited stakeholder and public involvement in their identification, assessment and selection, lack of systematic approaches to their assessment and comparison, and inadequate reporting of the ‘storyline’ on how they were identified, what the potential impacts are and why the preferred alternative was selected. These issues havemore » resulted in objections and judicial reviews. On the positive side, a number of good practice case studies enable extraction of key lessons and formulation of a set of general recommendations to advance practice in SEA alternatives. In this paper, practical guidance on the identification and development of alternatives, their assessment and comparison, selection of the preferred option, and documentation of the process and the reasons for selection is provided and discussed to frame good practice approaches. - Highlights: • Alternatives are one of the most poorly completed aspects of Strategic Environmental Assessment. • Current practice limitations need to be addressed to enhance SEA effectiveness. • A set of recommendations are extracted from good practice case studies. • These recommendations can be applied across jurisdictions and sectors and tailored as necessary.« less

  16. Identification and on-line monitoring of reduced sulphur species (RSS) by voltammetry in oxic waters.

    PubMed

    Superville, Pierre-Jean; Pižeta, Ivanka; Omanović, Dario; Billon, Gabriel

    2013-08-15

    Based on automatic on-line measurements on the Deûle River that showed daily variation of a peak around -0.56V (vs Ag|AgCl 3M), identification of Reduced Sulphur Species (RSS) in oxic waters was performed applying cathodic stripping voltammetry (CSV) with the hanging mercury drop electrode (HMDE). Pseudopolarographic studies accompanied with increasing concentrations of copper revealed the presence of elemental sulphur S(0), thioacetamide (TA) and reduced glutathione (GSH) as the main sulphur compounds in the Deûle River. In order to resolve these three species, a simple procedure was developed and integrated in an automatic on-line monitoring system. During one week monitoring with hourly measurements, GSH and S(0) exhibited daily cycles whereas no consequential pattern was observed for TA. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Determination of Benzyl-hexadecyldimethylammonium 1,4-Bis(2-ethylhexyl)sulfosuccinate Vesicle Permeability by Using Square Wave Voltammetry and an Enzymatic Reaction.

    PubMed

    Cobo Solis, Airam K; Correa, N Mariano; Molina, Patricia G

    2017-10-31

    This report describes the studies performed to determine the permeability coefficient value (P) of 1-naphthyl phosphate (1-NP) through the benzyl-hexadecyldimethylammonium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT-BHD) vesicle bilayer. 1-NP was added in the external phase and must cross the bilayer of the vesicle to react with the encapsulated enzyme (alkaline phosphatase) to yield 1-naphtholate (NPh - ), the product of the enzymatic hydrolysis. This product is electrochemically detected, at basic pH value, by a square wave voltammetry technique, which can be a good alternative over the spectroscopic one, to measure the vesicle solutions because scattering (due to its turbidity) does not make any influence in the electrochemical signal. The experimental data allow us to propose a mathematical model, and a value of P = (1.00 ± 0.15) × 10 -9 cm s -1 was obtained. Also, a value of P = (2.0 ± 0.5) × 10 -9 cm s -1 was found by using an independent technique, ultraviolet-visible spectroscopy, for comparison. It is evident that the P values obtained from both the techniques are comparable (within the experimental error of both techniques) under the same experimental conditions. This study constitutes the first report of the 1-NP permeability determination in this new vesicle. We want to highlight the importance of the introduction of a new method and the electrochemical response of the product generated through an enzymatic reaction that occurs in the inner aqueous phase of the vesicle, where the enzyme is placed.

  18. Spatially variant red blood cell crenation in alternating current non-uniform fields.

    PubMed

    An, Ran; Wipf, David O; Minerick, Adrienne R

    2014-03-01

    Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments. Human red blood cells (RBCs) are observed to crenate, or shrink due to changing osmotic pressure, over 10 min experiments in non-uniform AC electric fields. Cell crenation magnitude is examined as functions of frequency from 250 kHz to 1 MHz and potential from 10 Vpp to 17.5 Vpp over a 100 μm perpendicular electrode gap. Experimental results show higher peak to peak potential and lower frequency lead to greater cell volume crenation up to a maximum volume loss of 20%. A series of experiments are conducted to elucidate the physical mechanisms behind the red blood cell crenation. Non-uniform and uniform electrode systems as well as high and low ion concentration experiments are compared and illustrate that AC electroporation, system temperature, rapid temperature changes, medium pH, electrode reactions, and convection do not account for the crenation behaviors observed. AC electroosmotic was found to be negligible at these conditions and AC electrothermal fluid flows were found to reduce RBC crenation behaviors. These cell deformations were attributed to medium hypertonicity induced by ion concentration gradients in the spatially nonuniform AC electric fields.

  19. An Alternative Introduction to Maxwell's Displacement Current

    ERIC Educational Resources Information Center

    Reich, Gary

    2013-01-01

    In introductory texts Ampere's law is generally introduced in the steady-current form ?B · dl = µ[subscript 0]I, and it is later extended to a more general form involving the so-called displacement current I[subscript d], ?B · dl = µ[subscript 0](I + I[subscript d]) · (1). Here the line integral is to be taken along a closed…

  20. Electrochemical characterization of gelatinized starch dispersions: voltammetry and electrochemical impedance spectroscopy on platinum surface.

    PubMed

    Hernandez-Jaimes, C; Lobato-Calleros, C; Sosa, E; Bello-Pérez, L A; Vernon-Carter, E J; Alvarez-Ramirez, J

    2015-06-25

    The electrochemical properties of gelatinized starch dispersions (GSD; 5% w/w) from different botanical sources were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests over a platinum surface. The phenomenological modelling of EIS data using equivalent circuits indicated that after gelatinization the electrical resistance was determined mainly by the resistance of insoluble material (i.e., ghosts). Sonication of the GSD disrupted the ghost microstructure, and produced an increase in electrical conductivity by reducing the resistance of the insoluble material. The CV data showed three oxidation peaks at potentials where glucose solutions displayed oxidation waves. It is postulated that hydrolysis at the bulk and electrocatalyzed oxidation on the Pt-surface are reactions involved in the starch transformation. Starches peak intensity increased with the amylose content, suggesting that the amylose-rich matrix played an important role in the charge transfer in the electrolytic system. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Kinetics and Antioxidant Capacity of Proanthocyanidins Encapsulated in Zein Electrospun Fibers by Cyclic Voltammetry.

    PubMed

    Wang, Hualin; Hao, Lilan; Niu, Baicheng; Jiang, Suwei; Cheng, Junfeng; Jiang, Shaotong

    2016-04-20

    The proanthocyanidins encapsulated in zein (zein-PA) fibers was via electrospinning technique. The kinetics and antioxidant capacity of PA from zein fibers was investigated by cyclic voltammetry. Circular dichroism was used to investigate the secondary structure change of zein and its influence on the shape of fibers. The addition of PA caused a significant increase in viscosity and made fibers wider. These hydrogen bonds between zein and PA molecules would favor the α-helix change and decrease the β-folds of zein in electrospinning solutions, leading to a round-shaped tendency of fibers and enhancing the thermal properties slightly. Zein-PA fibers showed high encapsulation efficiency close to 100%, and the encapsulated PA retained its antioxidant capacity in fibers. Zein-PA fibers showed a good controlled release toward PA, and the predominant release of PA from fibers was Fickian diffusion, which could be well described by first-order model and Hixson-Crowell model.

  2. Direct mapping of local redox current density on a monolith electrode by laser scanning.

    PubMed

    Lee, Seung-Woo; Lopez, Jeffrey; Saraf, Ravi F

    2013-09-15

    An optical method of mapping local redox reaction over a monolith electrode using simple laser scanning is described. As the optical signal is linearly proportional to the maximum redox current that is measured concomitantly by voltammetry, the optical signal quantitatively maps the local redox current density distribution. The method is demonstrated on two types of reactions: (1) a reversible reaction where the redox moieties are ionic, and (2) an irreversible reaction on two different types of enzymes immobilized on the electrode where the reaction moieties are nonionic. To demonstrate the scanning capability, the local redox behavior on a "V-shaped" electrode is studied where the local length scale and, hence, the local current density, is nonuniform. The ability to measure the current density distribution by this method will pave the way for multianalyte analysis on a monolith electrode using a standard three-electrode configuration. The method is called Scanning Electrometer for Electrical Double-layer (SEED). Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Ratiometric biosensor array for multiplexed detection of microRNAs based on electrochemiluminescence coupled with cyclic voltammetry.

    PubMed

    Feng, Xiaobin; Gan, Ning; Zhang, Huairong; Li, Tianhua; Cao, Yuting; Hu, Futao; Jiang, Qianli

    2016-01-15

    A novel multiplexed ratiometric biosensor array was fabricated on a homemade screen-printed carbon electrode (SPCE) for near-simultaneous detection of microRNA (miRNA)-21 and miRNA-141 based on electrochemiluminescence (ECL) coupled with cyclic voltammetry (CV) method. In the detection system, the ECL signal tags (Ru-SiO2@PLL-Au) were fabricated using poly-l-lysine (PLL) as bridging agent and co-reactant to connect Ru-SiO2 (Ru(bpy)3(2+)-doped silica) and gold nanoparticles (Au NPs), which were respectively modified on two spatial resolved working electrodes (WE1 and WE2) of SPCE. Then the ferrocene (Fc)-labeled hairpin DNA (Fc-HDNA1 and Fc-HDNA2) as CV signal tags and ECL quenching material were immobilized on Ru-SiO2@PLL-Au. Upon miRNA-21 and miRNA-141 adding, the target miRNAs could hybridize with corresponding Fc-HDNA, which could lead to Fc away from Ru-SiO2@PLL-Au. Such conformational changes could recover the ECL of Ru-SiO2@PLL-Au and decreased the CV current of Fc, respectively. This "signal-on" of ECL and "signal-off" of CV were employed for dual-signal ratiometric readout. With the help of a multiplexed switch, two dual-signals from WE1 and WE2 were used for multiplexed detection of miRNA-21 and miRNA-141 down to 6.3 and 8.6fM, respectively. This approach was used in real sample analysis and has significant potential for miRNA biomarkers detection in a clinical laboratory setting. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Alternative Splicing as a Target for Cancer Treatment.

    PubMed

    Martinez-Montiel, Nancy; Rosas-Murrieta, Nora Hilda; Anaya Ruiz, Maricruz; Monjaraz-Guzman, Eduardo; Martinez-Contreras, Rebeca

    2018-02-11

    Alternative splicing is a key mechanism determinant for gene expression in metazoan. During alternative splicing, non-coding sequences are removed to generate different mature messenger RNAs due to a combination of sequence elements and cellular factors that contribute to splicing regulation. A different combination of splicing sites, exonic or intronic sequences, mutually exclusive exons or retained introns could be selected during alternative splicing to generate different mature mRNAs that could in turn produce distinct protein products. Alternative splicing is the main source of protein diversity responsible for 90% of human gene expression, and it has recently become a hallmark for cancer with a full potential as a prognostic and therapeutic tool. Currently, more than 15,000 alternative splicing events have been associated to different aspects of cancer biology, including cell proliferation and invasion, apoptosis resistance and susceptibility to different chemotherapeutic drugs. Here, we present well established and newly discovered splicing events that occur in different cancer-related genes, their modification by several approaches and the current status of key tools developed to target alternative splicing with diagnostic and therapeutic purposes.

  5. Multiple dual mode counter-current chromatography with variable duration of alternating phase elution steps.

    PubMed

    Kostanyan, Artak E; Erastov, Andrey A; Shishilov, Oleg N

    2014-06-20

    The multiple dual mode (MDM) counter-current chromatography separation processes consist of a succession of two isocratic counter-current steps and are characterized by the shuttle (forward and back) transport of the sample in chromatographic columns. In this paper, the improved MDM method based on variable duration of alternating phase elution steps has been developed and validated. The MDM separation processes with variable duration of phase elution steps are analyzed. Basing on the cell model, analytical solutions are developed for impulse and non-impulse sample loading at the beginning of the column. Using the analytical solutions, a calculation program is presented to facilitate the simulation of MDM with variable duration of phase elution steps, which can be used to select optimal process conditions for the separation of a given feed mixture. Two options of the MDM separation are analyzed: 1 - with one-step solute elution: the separation is conducted so, that the sample is transferred forward and back with upper and lower phases inside the column until the desired separation of the components is reached, and then each individual component elutes entirely within one step; 2 - with multi-step solute elution, when the fractions of individual components are collected in over several steps. It is demonstrated that proper selection of the duration of individual cycles (phase flow times) can greatly increase the separation efficiency of CCC columns. Experiments were carried out using model mixtures of compounds from the GUESSmix with solvent systems hexane/ethyl acetate/methanol/water. The experimental results are compared to the predictions of the theory. A good agreement between theory and experiment has been demonstrated. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Effects of 10 Hz and 20 Hz Transcranial Alternating Current Stimulation on Automatic Motor Control.

    PubMed

    Cappon, Davide; D'Ostilio, Kevin; Garraux, Gaëtan; Rothwell, John; Bisiacchi, Patrizia

    2016-01-01

    In a masked prime choice reaction task, presentation of a compatible prime increases the reaction time to the following imperative stimulus if the interval between mask and prime is around 80-250 ms. This is thought to be due to automatic suppression of the motor plan evoked by the prime, which delays reaction to the imperative stimulus. Oscillatory activity in motor networks around the beta frequency range of 20 Hz is important in suppression of movement. Transcranial alternating current at 20 Hz may be able to drive oscillations in the beta range. To investigate whether transcranial alternating current stimulation (tACS) at 20 Hz would increase automatic inhibition in a masked prime task. As a control we used 10 Hz tACS. Stimulation was delivered at alpha (10 Hz) and beta (20 Hz) frequency over the supplementary motor area and the primary motor cortex (simultaneous tACS of SMA-M1), which are part of the BG-cortical motor loop, during the execution of the subliminal masked prime left/right choice reaction task. We measured the effects on reaction times. Corticospinal excitability was assessed by measuring the amplitude of motor evoked potentials (MEPs) evoked in the first dorsal interosseous muscle by transcranial magnetic stimulation (TMS) over M1. The 10 and 20-Hz tACS over SMA-M1 had different effects on automatic inhibition. The 20 Hz tACS increased the duration of automatic inhibition whereas it was decreased by 10 Hz tACS. Neurophysiologically, 20 Hz tACS reduced the amplitude of MEPs evoked from M1, whereas there was no change after 10 Hz tACS. Automatic mechanisms of motor inhibition can be modulated by tACS over motor areas of cortex. tACS may be a useful additional tool to investigate the causal links between endogenous brain oscillations and specific cognitive processes. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. New alternate bearing surfaces in total hip arthroplasty: A review of the current literature.

    PubMed

    Grieco, Preston W; Pascal, Scott; Newman, Jared M; Shah, Neil V; Stroud, Sarah G; Sheth, Neil P; Maheshwari, Aditya V

    2018-01-01

    As indications for total hip arthroplasty (THA) have expanded, the incidence of THA has increased among younger patients, who live longer and tend to place more strain on implants via higher activity levels. This demographical shift accentuates the importance of advancing innovation to ensure implant longevity for younger and more active patients. Future innovation, as it pertains to THA components, is likely to focus on modifying implant designs and tribology in conjunction with identification and application of newer biomaterials. By reviewing the literature for development status of various materials and novel design advancements in THA component outside of the standard highly cross-linked polyethylene, this investigation provided an update on the current and future status of design initiatives as they pertain to THA. Though the highlighted alternative bearing surfaces have shown promising in vitro and limited, yet encouraging clinical data, they lack larger and longer-term clinical trial results. Further research and innovation is warranted to identify the optimal bearing surface to most effectively accommodate for the trend of younger and more active patients undergoing THA. Implant longevity is crucial if the clinical success of THA is to be maintained.

  8. Evaluation of alternative snowplowable markers and snowplowing procedures.

    DOT National Transportation Integrated Search

    2013-06-01

    The objectives of this study were to investigate viable alternatives to the currently approved snowplowable raised pavement marker and alternative methods and equipment used to snowplow roadways. The study included evaluating any potential durable an...

  9. A paper-based analytical device for the determination of hydrogen sulfide in fuel oils based on headspace liquid-phase microextraction and cyclic voltammetry.

    PubMed

    Nechaeva, Daria; Shishov, Andrey; Ermakov, Sergey; Bulatov, Andrey

    2018-06-01

    An easily performed miniaturized, cheap, selective and sensitive procedure for the determination of H 2 S in fuel oil samples based on a headspace liquid-phase microextraction followed by a cyclic voltammetry detection using a paper-based analytical device (PAD) was developed. A modified wax dipping method was applied to fabricate the PAD. The PAD included hydrophobic zones of sample and supporting electrolyte connecting by hydrophilic channel. The zones of sample and supporting electrolyte were connected with nickel working, platinum auxiliary and Ag/AgCl reference electrodes. The analytical procedure included separation of H 2 S from fuel oil sample based on the headspace liquid-phase microextraction in alkaline solution. Then, sulfide ions solution obtained and supporting electrolyte were dropped on the zones followed by analyte detection at + 0.45 V. Under the optimized conditions, H 2 S concentration in the range from 2 to 20 mg kg -1 had a good linear relation with the peak current. The limit of detection (3σ) was 0.6 mg kg -1 . The procedure was successfully applied to the analysis of fuel oil samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Enhanced labeling of microalgae cellular lipids by application of an electric field generated by alternating current.

    PubMed

    Su, Li-Chien; Hsu, Yi-Hsiang; Wang, Hsiang-Yu

    2012-05-01

    An alternating current was used to generate an electric field to enhance the fluorescent labeling of microalgae cellular lipids with Nile red and LipidTOX. The decay of the fluorescence intensity of Chlorella vulgaris cells in 0 V/cm was more than 50% after 10 min, and the intensity variation was as high as 7% in 20s. At 2000 V/cm, the decay rate decreased to 1.22% per minute and the intensity fluctuation was less than 1% for LipidTOX-labeled cells. For Spirulina sp. cells at 0 V/cm, the fluorescence intensity increased by 10% after 10 min, whereas at 2000 V/cm, labeling was more rapid and fluorescence intensity doubled. These results show that applying an electric field can improve the quality of fluorescence detection by alleviating decay and fluctuation or by enhancing signal intensity. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. An experimental comparison of the Marcus-Hush and Butler-Volmer descriptions of electrode kinetics applied to cyclic voltammetry. The one electron reductions of europium (III) and 2-methyl-2-nitropropane studied at a mercury microhemisphere electrode

    NASA Astrophysics Data System (ADS)

    Henstridge, Martin C.; Wang, Yijun; Limon-Petersen, Juan G.; Laborda, Eduardo; Compton, Richard G.

    2011-11-01

    We present a comparative experimental evaluation of the Butler-Volmer and Marcus-Hush models using cyclic voltammetry at a microelectrode. Numerical simulations are used to fit experimental voltammetry of the one electron reductions of europium (III) and 2-methyl-2-nitropropane, in water and acetonitrile, respectively, at a mercury microhemisphere electrode. For Eu (III) very accurate fits to experiment were obtained over a wide range of scan rates using Butler-Volmer kinetics, whereas the Marcus-Hush model was less accurate. The reduction of 2-methyl-2-nitropropane was well simulated by both models, however Marcus-Hush required a reorganisation energy lower than expected.

  12. Atmospheric pressure chemical ionization of explosives using alternating current corona discharge ion source.

    PubMed

    Usmanov, D T; Chen, L C; Yu, Z; Yamabe, S; Sakaki, S; Hiraoka, K

    2015-04-01

    The high-sensitive detection of explosives is of great importance for social security and safety. In this work, the ion source for atmospheric pressure chemical ionization/mass spectrometry using alternating current corona discharge was newly designed for the analysis of explosives. An electromolded fine capillary with 115 µm inner diameter and 12 mm long was used for the inlet of the mass spectrometer. The flow rate of air through this capillary was 41 ml/min. Stable corona discharge could be maintained with the position of the discharge needle tip as close as 1 mm to the inlet capillary without causing the arc discharge. Explosives dissolved in 0.5 µl methanol were injected to the ion source. The limits of detection for five explosives with 50 pg or lower were achieved. In the ion/molecule reactions of trinitrotoluene (TNT), the discharge products of NOx (-) (x = 2,3), O3 and HNO3 originating from plasma-excited air were suggested to contribute to the formation of [TNT - H](-) (m/z 226), [TNT - NO](-) (m/z 197) and [TNT - NO + HNO3 ](-) (m/z 260), respectively. Formation processes of these ions were traced by density functional theory calculations. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Archive Storage Media Alternatives.

    ERIC Educational Resources Information Center

    Ranade, Sanjay

    1990-01-01

    Reviews requirements for a data archive system and describes storage media alternatives that are currently available. Topics discussed include data storage; data distribution; hierarchical storage architecture, including inline storage, online storage, nearline storage, and offline storage; magnetic disks; optical disks; conventional magnetic…

  14. Gas-solid carbonation as a current alternative origin for carbonates in Martian regolith

    NASA Astrophysics Data System (ADS)

    Garenne, A.; Montes-Hernandez, G.; Beck, P.; Schmitt, B.; Brissaud, O.

    2011-12-01

    Carbonates are abundant sedimentary minerals at the surface and sub-surface of Earth and they have been proposed as tracers of liquid water in extraterrestrial environments (e.g. at Mars surface). Its formation mechanism is since generally associated with aqueous alteration processes. Recently, carbonates minerals have been discovered on Mars surface by different orbital or rovers missions. In particular, the phoenix mission has measured from 1 to 5% of calcium carbonate (calcite type). These occurrences have been reported in area were the relative humidity is significantly high (Boynton et al., 2009). The small concentration of carbonates suggests an alternative process than carbonation in aqueous conditions. Such an observation might rather point toward a possible formation mechanism by dust-gas reaction under current Martian conditions. For this reason, in the present study, we designed an experimental setup consisting of an infrared microscope coupled to a cryogenic reaction cell (IR-CryoCell setup) in order to investigate the gas-solid carbonation of three different mineral precursors for carbonates (Ca and Mg hydroxides, and a hydrated Ca silicate formed from Ca2SiO4) at low temperature (from -10 to 25°C) and at reduced CO2 pressure (from 100 to 1000 mbar). These mineral materials are crucial precursors to form respective Ca and Mg carbonates in humid environments (0 < relative humidity < 100%) at dust-CO2 or dust-water ice-CO2 interfaces. The results have revealed a significant and fast carbonation process for Ca hydroxide and hydrated Ca silicate. Conversely, slight carbonation process was observed for Mg hydroxide. These results suggest that gas-solid carbonation process or carbonate formation at the dust-water ice-CO2 interfaces could be a currently active Mars surface process. We note that the carbonation process at low temperature (<0°C) described in the present study could also have important implications on the dust-water ice-CO2 interactions in

  15. Affecting of aquatic vascular plant Lemna minor by cisplatin revealed by voltammetry.

    PubMed

    Supalkova, Veronika; Beklova, Miroslava; Baloun, Jiri; Singer, Christoph; Sures, Bernd; Adam, Vojtech; Huska, Dalibor; Pikula, Jiri; Rauscherova, Libuse; Havel, Ladislav; Zehnalek, Josef; Kizek, Rene

    2008-02-01

    Within the context of application of platinum derivates based effective cytostatics, we can suppose that these risk metals can get into aquatic ecosystems where they can show biologic availability for food chain. In the present work we report on investigation of affecting of duckweed (Lemna minor) by various doses of cisplatin (0, 5, 10, 20, 40, 80 and 160 microM) for 4 days. The toxic influence of cisplatin was evaluated on the basis of growth inhibition expressed as number of leaves, growth rate, and total amount of biomass. The result value of 96hEC50, calculated from growth inhibition with comparison of growth rates, was 6.93 microM. Moreover we aimed on determination of cisplatin content using differential pulse voltammetry. The highest content of cisplatin (320 ng g(-1) of fresh weight) was determined in plants treated by 80 microM at the second day of treatment. Plants protect themselves against heavy metals by means of synthesis of cysteine-rich peptides such as glutathione and phytochelatins. Thus thiol determination in the treated plants by means of Brdicka reaction followed. The marked increase in thiol concentration detected is associated with defence reaction of the plant against stress caused by cisplatin.

  16. A "signal on" protection-displacement-hybridization-based electrochemical hepatitis B virus gene sequence sensor with high sensitivity and peculiar adjustable specificity.

    PubMed

    Li, Fengqin; Xu, Yanmei; Yu, Xiang; Yu, Zhigang; He, Xunjun; Ji, Hongrui; Dong, Jinghao; Song, Yongbin; Yan, Hong; Zhang, Guiling

    2016-08-15

    One "signal on" electrochemical sensing strategy was constructed for the detection of a specific hepatitis B virus (HBV) gene sequence based on the protection-displacement-hybridization-based (PDHB) signaling mechanism. This sensing system is composed of three probes, one capturing probe (CP) and one assistant probe (AP) which are co-immobilized on the Au electrode surface, and one 3-methylene blue (MB) modified signaling probe (SP) free in the detection solution. One duplex are formed between AP and SP with the target, a specific HBV gene sequence, hybridizing with CP. This structure can drive the MB labels close to the electrode surface, thereby producing a large detection current. Two electrochemical testing techniques, alternating current voltammetry (ACV) and cyclic voltammetry (CV), were used for characterizing the sensor. Under the optimized conditions, the proposed sensor exhibits a high sensitivity with the detection limit of ∼5fM for the target. When used for the discrimination of point mutation, the sensor also features an outstanding ability and its peculiar high adjustability. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Ionic current rectification in organic solutions with quartz nanopipettes.

    PubMed

    Yin, Xiaohong; Zhang, Shudong; Dong, Yitong; Liu, Shujuan; Gu, Jing; Chen, Ye; Zhang, Xin; Zhang, Xianhao; Shao, Yuanhua

    2015-09-01

    The study of behaviors of ionic current rectification (ICR) in organic solutions with quartz nanopipettes is reported. ICR can be observed even in organic solutions using quartz pipettes with diameters varied from several to dozens of nanometers, and the direction of ICR is quite different from the ICR observed in aqueous phase. The influences of pore size, electrolyte concentration, and surface charge on the ICR have been investigated carefully. Water in organic solutions affects the direction and extent of ICR significantly. Mechanisms about the formation of an electrical double layer (EDL) on silica in organic solutions with different amount of water have been proposed. An improved method, which can be employed to detect trace water in organic solutions, has been implemented based on Au ultramicroelectrodes with cathodic differential pulse stripping voltammetry.

  18. Alternatives to Methyl Bromide (1993)

    EPA Pesticide Factsheets

    The report examines the alternatives that have been discussed as substitutes for current methyl bromide uses if methyl bromide should no longer be available and discusses the economic implications of such a phaseout.

  19. Background Signal as an in Situ Predictor of Dopamine Oxidation Potential: Improving Interpretation of Fast-Scan Cyclic Voltammetry Data.

    PubMed

    Meunier, Carl J; Roberts, James G; McCarty, Gregory S; Sombers, Leslie A

    2017-02-15

    Background-subtracted fast-scan cyclic voltammetry (FSCV) has emerged as a powerful analytical technique for monitoring subsecond molecular fluctuations in live brain tissue. Despite increasing utilization of FSCV, efforts to improve the accuracy of quantification have been limited due to the complexity of the technique and the dynamic recording environment. It is clear that variable electrode performance renders calibration necessary for accurate quantification; however, the nature of in vivo measurements can make conventional postcalibration difficult, or even impossible. Analyte-specific voltammograms and scaling factors that are critical for quantification can shift or fluctuate in vivo. This is largely due to impedance changes, and the effects of impedance on these measurements have not been characterized. We have previously reported that the background current can be used to predict electrode-specific scaling factors in situ. In this work, we employ model circuits to investigate the impact of impedance on FSCV measurements. Additionally, we take another step toward in situ electrode calibration by using the oxidation potential of quinones on the electrode surface to accurately predict the oxidation potential for dopamine at any point in an electrochemical experiment, as both are dependent on impedance. The model, validated both in adrenal slice and live brain tissue, enables information encoded in the shape of the background voltammogram to determine electrochemical parameters that are critical for accurate quantification. This improves data interpretation and provides a significant next step toward more automated methods for in vivo data analysis.

  20. Corrosion Behavior of X80 Steel with Coupled Coating Defects under Alternating Current Interference in Alkaline Environment

    PubMed Central

    Li, Zhong; Li, Caiyu; Qian, Hongchang; Li, Jun; Huang, Liang; Du, Cuiwei

    2017-01-01

    The corrosion behavior of X80 steel in the presence of coupled coating defects was simulated and studied under the interference of alternating current (AC) in an alkaline environment. The results from electrochemical measurements showed that the electrode potential of the coating defect with the smaller exposed area was lower than that with the larger area, which indicated that the steel with the smaller coating defect was more prone to corrosion. The result of weight loss tests also showed that the smaller coating defect had induced a higher corrosion rate. However, the corrosion rate of X80 steel at the larger coating defect decreased gradually with the increase of the larger defect area at a constant smaller defect area. The corrosion morphology images showed that the coating defects with smaller areas suffered from more severe pitting corrosion. PMID:28773078

  1. Regioselective electrochemical reduction of 2,4-dichlorobiphenyl - Distinct standard reduction potentials for carbon-chlorine bonds using convolution potential sweep voltammetry

    NASA Astrophysics Data System (ADS)

    Muthukrishnan, A.; Sangaranarayanan, M. V.; Boyarskiy, V. P.; Boyarskaya, I. A.

    2010-04-01

    The reductive cleavage of carbon-chlorine bonds in 2,4-dichlorobiphenyl (PCB-7) is investigated using the convolution potential sweep voltammetry and quantum chemical calculations. The potential dependence of the logarithmic rate constant is non-linear which indicates the validity of Marcus-Hush theory of quadratic activation-driving force relationship. The ortho-chlorine of the 2,4-dichlorobiphenyl gets reduced first as inferred from the quantum chemical calculations and bulk electrolysis. The standard reduction potentials pertaining to the ortho-chlorine of 2,4-dichlorobiphenyl and that corresponding to para chlorine of the 4-chlorobiphenyl have been estimated.

  2. Alternative Tobacco Product Use and Smoking Cessation: A National Study

    PubMed Central

    Popova, Lucy

    2013-01-01

    Objectives. We investigated the frequency of alternative tobacco product use (loose leaf, moist snuff, snus, dissolvables, electronic cigarettes [e-cigarettes]) among smokers and the association with quit attempts and intentions. Methods. A nationally representative probability-based cross-sectional survey of 1836 current or recently former adult smokers was completed in November 2011. Multivariate logistic regressions evaluated associations between alternative tobacco product use and smoking cessation behaviors. Results. Of the smokers, 38% had tried an alternative tobacco product, most frequently e-cigarettes. Alternative tobacco product use was associated with having made a quit attempt, and those intending to quit were significantly more likely to have tried and to currently use the products than were smokers with no intentions to quit. Use was not associated with successful quit attempts. Interest in future use of alternative tobacco products was low, except for e-cigarettes. Conclusions. Alternative tobacco products are attractive to smokers who want to quit smoking, but these data did not indicate that alternative tobacco products promote cessation. Unsubstantiated overt and implied claims that alternative tobacco products aid smoking cessation should be prohibited. PMID:23488521

  3. Dynamic Charge Storage in Ionic Liquids-Filled Nanopores: Insight from a Computational Cyclic Voltammetry Study.

    PubMed

    He, Yadong; Huang, Jingsong; Sumpter, Bobby G; Kornyshev, Alexei A; Qiao, Rui

    2015-01-02

    Understanding the dynamic charge storage in nanoporous electrodes with room-temperature ionic liquid electrolytes is essential for optimizing them to achieve supercapacitors with high energy and power densities. Herein, we report coarse-grained molecular dynamics simulations of the cyclic voltammetry of supercapacitors featuring subnanometer pores and model ionic liquids. We show that the cyclic charging and discharging of nanopores are governed by the interplay between the external field-driven ion transport and the sloshing dynamics of ions inside of the pore. The ion occupancy along the pore length depends strongly on the scan rate and varies cyclically during charging/discharging. Unlike that at equilibrium conditions or low scan rates, charge storage at high scan rates is dominated by counterions while the contribution by co-ions is marginal or negative. These observations help explain the perm-selective charge storage observed experimentally. We clarify the mechanisms underlying these dynamic phenomena and quantify their effects on the efficiency of the dynamic charge storage in nanopores.

  4. Evaluation of PEMFC System Contaminants on the Performance of Pt Catalyst via Cyclic Voltammetry: Preprint

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, H.; Macomber, C.; Dinh, H. N.

    2012-07-01

    Using electrochemical cyclic voltammetry as a quick ex-situ screening tool, the impact of the extracted solution and the individual leachable constituents from prospective BOP component materials on the performance and recoverability of the platinum catalyst were evaluated. Taking an extract from Zytel{trademark} HTN51G35HSLR (PPA) as an example, the major leachable organic components are caprolactam and 1,6 hexanediol. While these organic compounds by themselves do poison the Pt catalyst to some extent, such influence is mostly recoverable by means of potential holding and potential cycling. The extracted solution, however, shows a more drastic poisoning effect and it was not recoverable. Thereforemore » the non-recoverable poisoning effect observed for the extracted solution is not from the two organic species studied. This demonstrates the complexity of such a contaminant study. Inorganic compounds that are known poisons like sulfur even in very low concentrations, may have a more dominant effect on the Pt catalyst and the recoverability.« less

  5. Alternatives to Traditional Notation.

    ERIC Educational Resources Information Center

    Gaare, Mark

    1997-01-01

    Provides a introduction and overview to alternative music notation systems. Describes guitar tablature, accordion tablature, klavarskribo (a keyboard notational system developed by Cornelius Pot, a Dutch engineer), and the digital piano roll. Briefly discusses the history of notation reform and current efforts. Includes examples from scores. (MJP)

  6. Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes

    NASA Astrophysics Data System (ADS)

    Nguyen, Doan Ngoc

    Alternating current (AC) loss and current carrying capacity are two of the most crucial considerations in large-scale power applications of high temperature superconducting (HTS) conductors. AC losses result in an increased thermal load for cooling machines, and thus increased operating costs. Furthermore, AC losses can stimulate quenching phenomena or at least decrease the stability margin for superconducting devices. Thus, understanding AC losses is essential for the development of HTS AC applications. The main focus of this dissertation is to make reliable total AC loss measurements and interpret the experimental results in a theoretical framework. With a specially designed magnet, advanced total AC loss measurement system in liquid nitrogen (77 K) has been successfully built. Both calorimetric and electromagnetic methods were employed to confirm the validity of the measured results and to have a more thorough understanding of AC loss in HTS conductors. The measurement is capable of measuring total AC loss in HTS tapes over a wide range of frequency and amplitude of transport current and magnetic field. An accurate phase control technique allows measurement of total AC loss with any phase difference between the transport current and magnetic field by calorimetric method. In addition, a novel total AC loss measurement system with variable temperatures from 30 K to 100 K was successfully built and tested. Understanding the dependence of AC losses on temperature will enable optimization of the operating temperature and design of HTS devices. As a part of the dissertation, numerical calculations using Brandt's model were developed to study electrodynamics and total AC loss in HTS conductors. In the calculations, the superconducting electrical behavior is assumed to follow a power-law model. In general, the practical properties of conductors, including field-dependence of critical current density Jc, n-value and non-uniform distribution of Jc, can be accounted for in

  7. Alteration of Membrane Permeability of Bacteria and Yeast by High Frequency Alternating Current (HFAC)

    PubMed Central

    Cassanelli, C; Marchese, A; Cagnacci, S; Debbia, E.A

    2008-01-01

    Aims: Endox® Endodontic System (Endox) is used for endodontic treatment by a high frequency alternating current (HFAC). This device damaged the envelopes of spores and vegetative organisms. If the integrity of the envelope is compromised, the transit of compounds in the two directions is possible. This latter aspect was investigated here. Methods: The instrument delivered a 60ms pulse at a frequency 300 kHz, and power 800 KV/m. DNA transfer was verified using Escherichia coli K-12 strain carrying a non conjugative plasmid pBP517 (gyrA+) as donor and a rifampicin and nalidixic acid resistant recipient. 0.2 ml of mixture of donor and recipient strains in saline was exposed to HFAC and plated on selective media. Uptake of antimicrobials and a delay in re-growth was assessed exposing the strains to HFAC. Results: Plasmid transfer was detected under different experimental conditions. From 9 to 27 recombinants were found. Representative recombinants cured from plasmid showed the original phenotype. HFAC promoted the uptake of ineffective antibiotics, and induces a 1 h of delay in re-growth on the strains. Conclusions: Endox exhibited an effect on microrganisms which is reminiscent with that occuring in electroporation, but with a mode of action that saved materials and time. PMID:19088909

  8. Rapid immunohistochemistry based on alternating current electric field for intraoperative diagnosis of brain tumors.

    PubMed

    Tanino, Mishie; Sasajima, Toshio; Nanjo, Hiroshi; Akesaka, Shiori; Kagaya, Masami; Kimura, Taichi; Ishida, Yusuke; Oda, Masaya; Takahashi, Masataka; Sugawara, Taku; Yoshioka, Toshiaki; Nishihara, Hiroshi; Akagami, Yoichi; Goto, Akiteru; Minamiya, Yoshihiro; Tanaka, Shinya

    2015-01-01

    Rapid immunohistochemistry (R-IHC) can contribute to the intraoperative diagnosis of central nervous system (CNS) tumors. We have recently developed a new IHC method based on an alternating current electric field to facilitate the antigen-antibody reaction. To ensure the requirement of R-IHC for intraoperative diagnosis, 183 cases of CNS tumors were reviewed regarding the accuracy rate of diagnosis without R-IHC. The diagnostic accuracy was 90.7 % (166/183 cases) [corrected] in which definitive diagnoses were not provided in 17 cases because of the failure of glioma grading and differential diagnosis of lymphoma and glioma. To establish the clinicopathological application, R-IHC for frozen specimens was compared with standard IHC for permanent specimens. 33 gliomas were analyzed, and the Ki-67/MIB-1 indices of frozen specimens by R-IHC were consistent with the grade and statistically correlated with those of permanent specimens. Thus, R-IHC provided supportive information to determine the grade of glioma. For discrimination between glioma and lymphoma, R-IHC was able to provide clear results of CD20 and Ki-67/MIB-1 in four frozen specimens of CNS lymphoma as well as standard IHC. We conclude that the R-IHC for frozen specimens can provide important information for intraoperative diagnosis of CNS tumors.

  9. Aneurysm Sac Pressure Measurement with Minimally Invasive Implantable Pressure Sensors: An Alternative to Current Surveillance Regimes after EVAR?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Springer, Fabian; Guenther, Rolf W.; Schmitz-Rode, Thomas

    Current protocols for surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms are mostly based on costly and time-consuming imaging procedures and aim to detect adverse events such as graft migration, endoleaks or aneurysm sac enlargement. These imaging procedures are either associated with radiation exposure to the patients or may be harmful to the patient due to the use of iodine- or gadolinium-containing contrast agents. Furthermore the advantages of EVAR in the short term might be negated by the necessity for endograft surveillance over years. Thus, alternative modalities for follow-up are being investigated. One of these technologies provides pressure informationmore » directly from the aneurysm sac. This noninvasive, telemetric pressure sensing was tested in vitro as well as in first clinical trials and was able to identify successful aneurysm exclusion after EVAR. The telemetric pressure sensors showed a promising efficacy and accuracy in detecting type I and type III endoleaks and will help to clarify the clinical relevance of type II endoleaks. This article provides an overview of the in vitro sensors investigated as well as the first clinical trials and the sensors' potential to change the current endograft surveillance regimes.« less

  10. Alternative Work Schedules: The State of the Art.

    ERIC Educational Resources Information Center

    Newstrom, John W.; Pierce, Jon L.

    1979-01-01

    Presents a typology of modifications to the standard work week, reviews the current state of research-based knowledge regarding the effectiveness of each major type of alternative, and presents implementation suggestions for personnel interested in adopting one or more of the alternative forms. (Author/IRT)

  11. Current responsive devices for synchronous generators

    DOEpatents

    Karlicek, R.F.

    1983-09-27

    A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current. 11 figs.

  12. Current responsive devices for synchronous generators

    DOEpatents

    Karlicek, Robert F.

    1983-01-01

    A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current.

  13. Direct quantification of test bacteria in synthetic water-polluted samples by square wave voltammetry and chemometric methods.

    PubMed

    Carpani, Irene; Conti, Paolo; Lanteri, Silvia; Legnani, Pier Paolo; Leoni, Erica; Tonelli, Domenica

    2008-02-28

    A home-made microelectrode array, based on reticulated vitreous carbon, was used as working electrode in square wave voltammetry experiments to quantify the bacterial load of Escherichia coli ATCC 13706 and Pseudomonas aeruginosa ATCC 27853, chosen as test microorganisms, in synthetic samples similar to drinking water (phosphate buffer). Raw electrochemical signals were analysed with partial least squares regression coupled to variable selection in order to correlate these values with the bacterial load estimated by aerobic plate counting. The results demonstrated the ability of the method to detect even low loads of microorganisms in synthetic water samples. In particular, the model detects the bacterial load in the range 3-2,020 CFU ml(-1) for E. coli and in the range 76-155,556 CFU ml(-1) for P. aeruginosa.

  14. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean's critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  15. Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin

    NASA Astrophysics Data System (ADS)

    Dhifaoui, Selma; Mchiri, Chadlia; Quatremare, Pierre; Marvaud, Valérie; Bujacz, Anna; Nasri, Habib

    2018-02-01

    In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV-visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C-H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.

  16. Development and Characterization of Carbon-Fiber Microbiosensors for Fast-Scan Cyclic Voltammetry

    NASA Astrophysics Data System (ADS)

    Lugo-Morales, Leyda Zoraida

    Electrochemistry has been shown to be a robust tool in neuroscience. The use of carbon-fiber microelectrodes coupled with background-subtracted fast-scan cyclic voltammetry (FSCV) offers high sensitivity, selectivity, as well as the spatial and temporal resolution necessary for monitoring rapid fluctuations of electroactive molecules in live brain tissue. Dopamine (DA) is a neurotransmitter playing a key role in the regulation of reward and motivated behavior. FSCV has been used to understand DA dynamics and how these underlie discrete aspects of brain function. The methodological aspects of real-time DA detection at carbon-fiber microelectrodes using FSCV in anesthetized and awake animals are presented. Furthermore, the combination of FSCV with other neuroanalytical techniques is also explained. The advantages of FSCV and carbon-fiber microelectrodes can be expanded to the detection of non-electroactive analytes. This broadens the scope of FSCV such that it can be used to investigate how changes in non-electroactive chemicals underlie disease, cognition, and behavior. Carbon-fiber microelectrodes can be modified with an enzyme to monitor non-electroactive molecules, generating an electroactive product (usually hydrogen peroxide, H2O2). The first voltammetric detection of H2O 2 at bare carbon-fiber microelectrodes using FSCV has recently been reported. Thus, an avenue exists to utilize FSCV at enzyme-modified microelectrodes to voltammetrically identify and quantify non-electroactive analytes in real-time. Such an approach will overcome many limitations associated with the traditional amperometric detection scheme, which lacks electrochemical selectivity. Electrodeposition of the biopolymer chitosan with glucose oxidase (GOx) at the carbon surface yields a stable, sensitive, and selective glucose microbiosensor that has been utilized to detect glucose fluctuations in vivo with unprecedented speed. This new method has revealed the first rapid glucose fluctuations in

  17. Alternative Fueling Station Locator - Android

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    The Alternative Fueling Station Locator app helps users locate fueling stations that offer electricity, natural gas, biodiesel, E85, propane, or hydrogen. The users' current location or a custom location can be used to find the 20 closest stations within a 30-mile radius. View the stations on a map or see a list of stations ordered by distance from your location. Select your alternative fuel of choice and adjust the custom filters to fit your needs. Select a station from the map or list to view contact info and other details: address, phone number, and hours of operation; payment types accepted;more » public or private access; special services; compression (natural gas); vehicle size access (natural gas); number and types of chargers (electric); blends available (biodiesel); and blender pumps (ethanol) The app draws information from the U.S. Department of Energy's Alternative Fuels Data Center, which houses the most comprehensive, up-to-date database of alternative fueling stations in the United States. The database contains location information for more than 20,000 alternative fueling stations throughout the country.« less

  18. Complementary and Alternative Medicine in Rural Communities: Current Research and Future Directions

    ERIC Educational Resources Information Center

    Wardle, Jon; Lui, Chi-Wai; Adams, Jon

    2012-01-01

    Contexts: The consumption of complementary and alternative medicine (CAM) in rural areas is a significant contemporary health care issue. An understanding of CAM use in rural health can provide a new perspective on health beliefs and practice as well as on some of the core service delivery issues facing rural health care generally. Purpose: This…

  19. Carbon paste electrode modified molecularly imprinted polymer as a sensor for creatinine analysis by stripping voltammetry

    NASA Astrophysics Data System (ADS)

    Khasanah, M.; Darmokoesoemo, H.; Rizki, D. A.

    2017-09-01

    Modification of carbon paste electrode with molecularly imprinted polymer (CP-MIP) as a voltammetric sensor for creatinine has been developed. MIP was synthesized by reacting melamine, chloranil and creatinine with a mole ratio of 1:1:0.1. Creatinine was extracted from polymer chain by using hot water to form a specific imprinted for creatinine molecule. Carbon paste-MIP electrode was prepared by mixing activated carbon, solid paraffin, and MIP in a 45:40:15(w/w %) ratio. The optimum conditions of creatinine analysis by differential pulse stripping voltammetry (DPSV) using the developed electrode were the accumulation potential -1000 mV during 90 s at pH 5. The precision of the method for 0.1-0.5 μlg/L creatinine was 88.7-96.3%, while the detection limit of this method was 0.0315 μlg/L. The accuracy compared by spectrophotometric method was 95.3-103.6%

  20. Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots.

    PubMed

    Osipovich, Nikolai P; Poznyak, Sergei K; Lesnyak, Vladimir; Gaponik, Nikolai

    2016-04-21

    The application of electrochemical methods for the characterization of colloidal quantum dots (QDs) attracts considerable attention as these methods may allow for monitoring of some crucial parameters, such as energetic levels of conduction and valence bands as well as surface traps and ligands under real conditions of colloidal solution. In the present work we extend the applications of cyclic voltammetry (CV) to in situ monitoring of degradation processes of water-soluble CdTe QDs. This degradation occurs under lowering of pH to the values around 5, i.e. under conditions relevant to bioimaging applications of these QDs, and is accompanied by pronounced changes of their photoluminescence. Observed correlations between characteristic features of CV diagrams and the fluorescence spectra allowed us to propose mechanisms responsible for evolution of the photoluminescence properties as well as degradation pathway of CdTe QDs at low pH.

  1. Commercial Training Issues: Heavy Duty Alternative Fuel Vehicles.

    ERIC Educational Resources Information Center

    Eckert, Douglas

    The needs and opportunities in the heavy-duty alternative fuel vehicle training arena were examined in an informal ethnographic study of the appropriateness and effectiveness of the instructional materials currently being used in such training. Interviews were conducted with eight instructors from the National Alternative Fuels Training Program…

  2. Recommendations for Developing Alternative Test Methods for Developmental Neurotoxicity

    EPA Science Inventory

    There is great interest in developing alternative methods for developmental neurotoxicity testing (DNT) that are cost-efficient, use fewer animals and are based on current scientific knowledge of the developing nervous system. Alternative methods will require demonstration of the...

  3. Combined micro-droplet and thin-film-assisted pre-concentration of lead traces for on-line monitoring using anodic stripping voltammetry.

    PubMed

    Belostotsky, Inessa; Gridin, Vladimir V; Schechter, Israel; Yarnitzky, Chaim N

    2003-02-01

    An improved analytical method for airborne lead traces is reported. It is based on using a Venturi scrubber sampling device for simultaneous thin-film stripping and droplet entrapment of aerosol influxes. At least threefold enhancement of the lead-trace pre-concentration is achieved. The sampled traces are analyzed by square-wave anodic stripping voltammetry. The method was tested by a series of pilot experiments. These were performed using contaminant-controlled air intakes. Reproducible calibration plots were obtained. The data were validated by traditional analysis using filter sampling. LODs are comparable with the conventional techniques. The method was successfully applied to on-line and in situ environmental monitoring of lead.

  4. Alternatives in Teacher Education.

    ERIC Educational Resources Information Center

    Clements, Millard

    This paper on alternatives in teacher education begins by analyzing the current emphasis on the scientific approach in education. The author finds the promise of the scientific approach to be illusory. He defines it as education that promotes behavior change in some desirable direction. However, this definition, which the author finds equally…

  5. [Alternative approaches in thyroid surgery].

    PubMed

    Maurer, E; Wächter, S; Bartsch, D K

    2017-08-01

    In thyroid surgery multiple different cervical minimally invasive (partly endoscopically assisted) and extracervical endoscopic (partly robot-assisted) approaches have been developed in the last 20 years. The aim of all these alternative approaches to the thyroid gland is optimization of the cosmetic result. The indications for the use of alternative and conventional approaches are principally the same. Important requirements for the use of alternative methods are nevertheless a broad experience in conventional thyroid operations of the thyroid and adequate patient selection under consideration of the size of the thyroid and the underlying pathology. Contraindications for the use of alternative approaches are a large size of the thyroid gland including local symptoms, advanced carcinomas, reoperations and previous radiations of the anterior neck. The current article gives an overview of the clinically implemented alternative approaches for thyroid surgery. Of those the majority must still be considered as experimental. The alternative approaches to the thyroid gland can be divided in cervical minimally invasive, extracervical endosopic (robot-assisted) and transoral operations (natural orifice transluminal endoscopic surgery, NOTES). Since conventional thyroid operations are standardized procedures with low complication rates, alternative approaches to the thyroid gland are considered critically in Germany. The request for a perfect cosmetic result should not overweigh patients' safety. Only a few alternative approaches (e. g. MIVAT, RAT) can yet be considered as a safe addition in experienced hands in highly selected patients.

  6. Alternative, complementary and traditional medicine in Malaysia.

    PubMed

    Talib, N

    2006-09-01

    This paper sets out the practice of traditional, alternative and/or complementary medicine in Malaysia. It gives an overview of the types of alternative medicine available, and the legal regulation, or lack of it within the current setting. The relevant policies and governmental action in this area are highlighted. Relevant case law decisions in this area are also included. The practice of spiritual healing as one form of traditional medicine, and its role within the spectrum of alternative medicine is dealt with briefly. The significant question of integration of alternative medicine within the existing allopathic system is addressed. The paper concludes that as interest in, and usage of alternative medicine is not likely to decrease, certain measures must be taken by the relevant authorities to ensure among others, the safety and efficacy of these medicines.

  7. Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng

    2016-06-15

    The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under amore » higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.« less

  8. Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

    NASA Astrophysics Data System (ADS)

    Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng; Mu, Hai-Bao; Zhang, Guan-Jun; Li, Feng; Wang, Meng

    2016-06-01

    The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under a higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.

  9. Evolution and Biological Roles of Alternative 3'UTRs.

    PubMed

    Mayr, Christine

    2016-03-01

    More than half of human genes use alternative cleavage and polyadenylation to generate alternative 3' untranslated region (3'UTR) isoforms. Most efforts have focused on transcriptome-wide mapping of alternative 3'UTRs and on the question of how 3'UTR isoform ratios may be regulated. However, it remains less clear why alternative 3'UTRs have evolved and what biological roles they play. This review summarizes our current knowledge of the functional roles of alternative 3'UTRs, including mRNA localization, mRNA stability, and translational efficiency. Recent work suggests that alternative 3'UTRs may also enable the formation of protein-protein interactions to regulate protein localization or to diversify protein functions. These recent findings open an exciting research direction for the investigation of new biological roles of alternative 3'UTRs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Alternating current characterization of nano-Pt(II) octaethylporphyrin (PtOEP) thin film as a new organic semiconductor

    NASA Astrophysics Data System (ADS)

    M, Dongol; M, M. El-Nahass; A, El-Denglawey; A, A. Abuelwafa; T, Soga

    2016-06-01

    Alternating current (AC) conductivity and dielectric properties of thermally evaporated Au/PtOEP/Au thin films are investigated each as a function of temperature (303 K-473 K) and frequency (50 Hz-5 MHz). The frequency dependence of AC conductivity follows the Jonscher universal dynamic law. The AC-activation energies are determined at different frequencies. It is found that the correlated barrier hopping (CBH) model is the dominant conduction mechanism. The variation of the frequency exponent s with temperature is analyzed in terms of the CBH model. Coulombic barrier height W m , hopping distance R ω , and the density of localized states N(E F) are valued at different frequencies. Dielectric constant ɛ 1(ω,T) and dielectric loss ɛ 2(ω,T) are discussed in terms of the dielectric polarization process. The dielectric modulus shows the non-Debye relaxation in the material. The extracted relaxation time by using the imaginary part of modulus (M″) is found to follow the Arrhenius law.

  11. Determination of tryptamine in foods using square wave adsorptive stripping voltammetry.

    PubMed

    Costa, Daniel J E; Martínez, Ana M; Ribeiro, Williame F; Bichinho, Kátia M; Di Nezio, María Susana; Pistonesi, Marcelo F; Araujo, Mario C U

    2016-07-01

    Tryptamine, a biogenic amine, is an indole derivative with an electrophilic substituent at the C3 position of the pyrrole ring of the indole moiety. The electrochemical oxidation of tryptamine was investigated using glassy carbon electrode (GCE), and focusing on trace level determination in food products by square wave adsorptive stripping voltammetry (SWAdSV). The electrochemical responses of tryptamine were evaluated using differing voltammetric techniques over a wide pH range, a quasi-reversible electron-transfer to redox system represented by coupled peaks P1-P3, and an irreversible reaction for peak P2 were demonstrated. The proton and electron counts associated with the oxidation reactions were estimated. The nature of the mass transfer process was predominantly diffusion-limited for the oxidation process of P1, the most selective and sensitive analytical response (acetate buffer solution pH 5.3), being used for the development of SWAdSV method, under optimum conditions. The excellent response allowed the development of an electroanalytical method with a linear response range of from 4.7-54.5)×10(-)(8)molL(-1), low detection limit (0.8×10(-)(9)molL(-)(1)), and quantification limit (2.7×10(-9)molL(-1)), and acceptable levels of repeatability (3.6%), and reproducibility (3.8%). Tryptamine content was determined in bananas, tomatoes, cheese (mozzarella and gorgonzola), and cold meats (chicken sausage and pepperoni sausage), yielding recoveries above 90%, with excellent analytical performance using simple and low cost instrumentation. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Detection of Norepinephrine in Whole Blood via Fast Scan Cyclic Voltammetry.

    PubMed

    Nicolai, Evan N; Trevathan, James K; Ross, Erika K; Lujan, J Luis; Blaha, Charles D; Bennet, Kevin E; Lee, Kendall H; Ludwig, Kip A

    2017-05-01

    Bioelectronic Medicines is an emerging field that capitalizes on minimally-invasive technology to stimulate the autonomic nervous system in order to evoke therapeutic biomolecular changes at the end-organ. The goal of Bioelectronic Medicines is to realize both 'precision and personalized' medicine. 'Precise' stimulation of neural circuitry creates biomolecular changes targeted exactly where needed to maximize therapeutic effects while minimizing off-target changes associated with side-effects. The therapy is then 'personalized' by utilizing implanted sensors to measure the biomolecular concentrations at, or near, the end-organ of interest and continually adjusting therapy to account for patient-specific biological changes throughout the day. To realize the promise of Bioelectronic Medicines, there is a need for minimally invasive, real-time measurement of biomarkers associated with the effects of autonomic nerve stimulation to be used for continuous titration of therapy. In this study we examine the feasibility of using fast scan cyclic voltammetry (FSCV) to measure norepinephrine levels, a neurochemical relevant to end-organ function, directly from blood. FSCV is a well-understood method for measuring electroactive neurochemicals in the central nervous system with high temporal and high spatial resolution that has yet to be adapted to the study of the autonomic nervous system. The results demonstrate that while detecting the electroactive neurochemical norepinephrine in blood is more challenging than obtaining the same FSCV measurements in a buffer solution due to biofouling of the electrode, it is feasible to utilize a minimally invasive FSCV electrode to obtain neurochemical measurements in blood.

  13. Detection of Norepinephrine in Whole Blood via Fast Scan Cyclic Voltammetry

    PubMed Central

    Nicolai, Evan N.; Trevathan, James K.; Ross, Erika K.; Lujan, J. Luis; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.; Ludwig, Kip A.

    2017-01-01

    Bioelectronic Medicines is an emerging field that capitalizes on minimally-invasive technology to stimulate the autonomic nervous system in order to evoke therapeutic biomolecular changes at the end-organ. The goal of Bioelectronic Medicines is to realize both ‘precision and personalized’ medicine. ‘Precise’ stimulation of neural circuitry creates biomolecular changes targeted exactly where needed to maximize therapeutic effects while minimizing off-target changes associated with side-effects. The therapy is then ‘personalized’ by utilizing implanted sensors to measure the biomolecular concentrations at, or near, the end-organ of interest and continually adjusting therapy to account for patient-specific biological changes throughout the day. To realize the promise of Bioelectronic Medicines, there is a need for minimally invasive, real-time measurement of biomarkers associated with the effects of autonomic nerve stimulation to be used for continuous titration of therapy. In this study we examine the feasibility of using fast scan cyclic voltammetry (FSCV) to measure norepinephrine levels, a neurochemical relevant to end-organ function, directly from blood. FSCV is a well-understood method for measuring electroactive neurochemicals in the central nervous system with high temporal and high spatial resolution that has yet to be adapted to the study of the autonomic nervous system. The results demonstrate that while detecting the electroactive neurochemical norepinephrine in blood is more challenging than obtaining the same FSCV measurements in a buffer solution due to biofouling of the electrode, it is feasible to utilize a minimally invasive FSCV electrode to obtain neurochemical measurements in blood. PMID:29177248

  14. Steady-state voltammetry of hydroxide ion oxidation in aqueous solutions containing ammonia.

    PubMed

    Daniele, Salvatore; Baldo, M Antonietta; Bragato, Carlo; Abdelsalam, Mamdouh Elsayed; Denuault, Guy

    2002-07-15

    An oxidation process observed in dilute aqueous solutions of ammonia was investigated under steady-state conditions with gold microelectrodes with radii in the range 2.5-30 microm. Over the ammonia concentration range 0.1-10 mM, a well-defined voltammetric wave was observed at approximately 1.4 V versus Ag/AgCl. It was attributed to the oxidation of hydroxide ions that arise from the dissociation of the weak base. The steady-state limiting current was found to depend on the concentration of supporting electrolyte, and in solution with low electrolyte, it was enhanced by migration contribution, as expected for a negatively charged species that oxidizes on a positively charged electrode. In addition, the steady-state limiting current was proportional to both the ammonia concentration and the electrode radius. The overall electrode process was analyzed in terms of a CE mechanism (homogeneous chemical reaction preceding the heterogeneous electron transfer) with a fast chemical reaction when measurements were carried out in solutions containing NH3 at < or = 5 mM and with electrodes having a radius of > or = 5 microm. This was ascertained by comparing experimental and theoretical data obtained by simulation. The formation of the soluble complex species Au(NH3)2+ was also considered as a possible alternative to explain the presence of the oxidation wave. This process however was ruled out, as the experimental data did not fit theoretical predictions in any of the conditions employed in the investigation. Instead, the direct oxidation of NH3, probably to N2O, was invoked to explain the anomalous currents found when the CE process was strongly kinetically hindered. Throughout this study, a parallel was made between the CE mechanism investigated here and that known to occur during the hydrogen evolution reaction from weak acids.

  15. Mono-Mercury Doping of Au25 and the HOMO/LUMO Energies Evaluation Employing Differential Pulse Voltammetry.

    PubMed

    Liao, Lingwen; Zhou, Shiming; Dai, Yafei; Liu, Liren; Yao, Chuanhao; Fu, Cenfeng; Yang, Jinlong; Wu, Zhikun

    2015-08-05

    Controlling the bimetal nanoparticle with atomic monodispersity is still challenging. Herein, a monodisperse bimetal nanoparticle is synthesized in 25% yield (on gold atom basis) by an unusual replacement method. The formula of the nanoparticle is determined to be Au24Hg1(PET)18 (PET: phenylethanethiolate) by high-resolution ESI-MS spectrometry in conjunction with multiple analyses including X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). X-ray single-crystal diffraction reveals that the structure of Au24Hg1(PET)18 remains the structural framework of Au25(PET)18 with one of the outer-shell gold atoms replaced by one Hg atom, which is further supported by theoretical calculations and experimental results as well. Importantly, differential pulse voltammetry (DPV) is first employed to estimate the highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) energies of Au24Hg1(PET)18 based on previous calculations.

  16. The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry.

    PubMed

    Wang, Xinghao; Liu, Jiaoqin; Qu, Ruijuan; Wang, Zunyao; Huang, Qingguo

    2017-08-10

    Nanostructured manganese oxides, e.g. MnO 2 , have shown laccase-like catalytic activities, and are thus promising for pollutant oxidation in wastewater treatment. We have systematically compared the laccase-like reactivity of manganese oxide nanomaterials of different crystallinity, including α-, β-, γ-, δ-, and ɛ-MnO 2 , and Mn 3 O 4 , with 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 17β-estradiol (E2) as the probing substrates. The reaction rate behaviors were examined with regard to substrate oxidation and oxygen reduction to evaluate the laccase-like catalysis of the materials, among which γ-MnO 2 exhibits the best performance. Cyclic voltammetry (CV) was employed to assess the six MnO x nanomaterials, and the results correlate well with their laccase-like catalytic activities. The findings help understand the mechanisms of and the factors controlling the laccase-like reactivity of different manganese oxides nanomaterials, and provide a basis for future design and application of MnO x -based catalysts.

  17. Featuring of transient tunneling current by voltage pulse and application to an electrochemical biosensor

    NASA Astrophysics Data System (ADS)

    Yun, Jun Yeon; Lee, Won Cheol; Choi, Seong Wook; Park, Young June

    2018-03-01

    We suggest a voltage pulse method for detecting the transient tunneling current component (faradaic current component) in a metal/redox-active monolayer/electrolyte system. After applying the pulse to the metal electrode, the capacitive current prevails; therefore, it is difficult to extract the tunneling current, which carries information on the biochemical reactions occurring between the biomarkers in the electrolyte and the self-assembled monolayer (SAM) as the probe peptide system. Instead of waiting until the capacitive current diminishes, and thereby, the tunneling current also decreases, we try to extract the tunneling current in an early stage of the pulse. The method is based on the observation that the capacitive current becomes symmetrized in the positive and negative pulses after introducing the SAM on the metal electrode. When the energy level of the redox molecule is higher than the Fermi level of the metal under zero-bias condition, the tunneling current in the negative pulse can be extracted by subtracting the capacitive current obtained from the positive pulse, where the tunneling current is neglected. The experiment conducted for detecting trypsin as a biomarker shows that the method enhances the sensitivity and the specific-to-nonspecific ratio of the sensor device in the case of the nonspecific protein-abundant electrolyte solution, as evinced by cyclic voltammetry measurements in comparison.

  18. Study of antioxidant properties of a water-soluble Vitamin E derivative-tocopherol monoglucoside (TMG) by differential pulse voltammetry.

    PubMed

    Korotkova, E I; Avramchik, O A; Kagiya, T V; Karbainov, Y A; Tcherdyntseva, N V

    2004-06-17

    Study of antioxidant properties of tocopherol monoglucoside (TMG), a water-soluble Vitamin E derivative, by differential pulse voltammetry has been carried out in this work. The pH influence on the antioxidant properties of TMG has been also investigated. It was observed that the antioxidant activity of TMG is greater at 6.90

  19. Alternative Certification for Science Teachers: Policy and Context

    ERIC Educational Resources Information Center

    Zhao, Yijie

    2005-01-01

    The purpose of this paper is to review literature on the alternative certification policy so as to identify key features and issues as the basis for suggesting a more systematic approach to the study of the policy efforts. Alternative teacher certification has become a proliferating phenomenon in the United States in response to current and…

  20. Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

    DOEpatents

    Beverly, Leon H.; Hance, Richard D.; Kristalinski, Alexandr L.; Visser, Age T.

    1996-01-01

    An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

  1. Biotherapeutics as alternatives to antibiotics

    USDA-ARS?s Scientific Manuscript database

    Increasing pressure to limit antibiotic use in agriculture is heightening the need for alternative methods to reduce the adverse effects of clinical and subclinical disease on livestock performance that are currently managed by in-feed antibiotic usage. Immunomodulators have long been sought as such...

  2. Anodic stripping voltammetry with carbon paste electrodes for rapid Ag(I) and Cu(II) determinations.

    PubMed

    Labar, C; Lamberts, L

    1997-05-01

    The simultaneous determination of silver(I) and copper(II) is realized for the routine analysis of trace levels of these elements by anodic stripping voltammetry (ASV) at the carbon paste electrode (CPE). The electrochemical response is studied in 14 different supporting electrolytes, ranging from acidic solutions (pH 0.1) to neutral and basic (pH 9.7) media, and the parameters governing electrodeposition and stripping steps are characterized for each medium by the use of pseudo-voltammograms. Comparison between different modes of matter transport mechanisms is also given. The dynamic range of the method is 0.05 to 150 mug 1(-1) Ag(I) in the majority of the media studied and can be extended to 400 mug l(-1) in selected media, with a general reproducibility in the +/- 2% range for five replicate measurements. The total analysis time lies between approximately 30 s and 10 min. Activation of the CPE surface has been studied, but this pretreatment is demonstrated to be unfavourable and is replaced by a simpler unique 'cleaning' procedure of dipping the CPE in diluted nitric acid.

  3. Alternative Aviation Fuels: Overview of Challenges, Opportunities, and Next Steps

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None, None

    The Alternative Aviation Fuels: Overview of Challenges, Opportunities, and Next Steps report, published by the U.S. Department of Energy’s Bioenergy Technologies Office (BETO) provides an overview of the current state of alternative aviation fuels, based upon findings from recent peer-reviewed studies, scientific working groups, and BETO stakeholder input provided during the Alternative Aviation Fuel Workshop.

  4. Resurgence with and without an alternative response.

    PubMed

    Kimball, Ryan T; Kelley, Michael E; Podlesnik, Christopher A; Forton, Alex; Hinkle, Brandy

    2018-05-10

    Resurgence is the reemergence of a previously reinforced response that occurs after the elimination or reduction of reinforcement for an alternative response. Resurgence is problematic in the context of treatment because the reemergence of a previously reinforced destructive response could be detrimental to treatment gains. In the current translational study, we examined a modified resurgence procedure in which the alternative response was either present or absent during extinction. Four participants were exposed to three phases that consisted of (1) reinforcement of a target response, (2) extinction of the target response and differential reinforcement of an alternative response, and (3) extinction of both responses. Results for four out of five assessments showed greater resurgence when the alternative response was absent during Phase 3. Results suggest that more robust resurgence might occur if the alternative response is not available as opposed to the alternative response contacting extinction. © 2018 Society for the Experimental Analysis of Behavior.

  5. Forbidden fruit: inattention to attractive alternatives provokes implicit relationship reactance.

    PubMed

    DeWall, C Nathan; Maner, Jon K; Deckman, Timothy; Rouby, D Aaron

    2011-04-01

    Being inattentive to attractive relationship alternatives can enhance relationship well-being. The current investigation, however, demonstrates that implicitly preventing people from attending to desirable relationship alternatives may undermine, rather than bolster, the strength of that person's romantic relationship. Consistent with the notion of "forbidden fruit," we found that subtly limiting people's attention to attractive alternatives reduced relationship satisfaction and commitment and increased positive attitudes toward infidelity (Experiment 1), increased memory for attractive relationship alternatives (Experiment 2), and increased attention to attractive alternatives (Experiment 3). Findings suggest that although attention to attractive alternatives can harm one's relationship, situations that implicitly limit one's attention to alternatives can, rather ironically, increase the temptation of alternatives and undermine relationship well-being.

  6. Alternative right ventricular pacing sites.

    PubMed

    Łuciuk, Dariusz; Łuciuk, Marek; Gajek, Jacek

    2015-01-01

    The main adverse effect of chronic stimulation is stimulation-induced heart failure in case of ventricular contraction dyssynchrony. Because of this fact, new techniques of stimulation should be considered to optimize electrotherapy. One of these methods is pacing from alternative right ventricular sites. The purpose of this article is to review currently accumulated data about alternative sites of cardiac pacing. Medline and PubMed bases were used to search English and Polish reports published recently. Recent studies report a deleterious effect of long term apical pacing. It is suggested that permanent apical stimulation, by omitting physiological conduction pattern with His-Purkinie network, may lead to electrical and mechanical dyssynchrony of heart muscle contraction. In the long term this pathological situation can lead to severe heart failure and death. Because of this, scientists began to search for some alternative sites of cardiac pacing to reduce the deleterious effect of stimulation. Based on current accumulated data, it is suggested that the right ventricular outflow tract, right ventricular septum, direct His-bundle or biventricular pacing are better alternatives due to more physiological electrical impulse propagation within the heart and the reduction of the dyssynchrony effect. These methods should preserve a better left ventricular function and prevent the development of heart failure in permanent paced patients. As there is still not enough, long-term, randomized, prospective, cross-over and multicenter studies, further research is required to validate the benefits of using this kind of therapy. The article should pay attention to new sites of cardiac stimulation as a better and safer method of treatment.

  7. Alternative models in developmental toxicology.

    PubMed

    Lee, Hyung-yul; Inselman, Amy L; Kanungo, Jyotshnabala; Hansen, Deborah K

    2012-02-01

    In light of various pressures, toxicologists have been searching for alternative methods for safety testing of chemicals. According to a recent policy in the European Union (Regulation, Evaluation Authorisation and Restriction of Chemicals, REACH), it has been estimated that over the next twelve to fifteen years, approximately 30,000 chemicals may need to be tested for safety, and under current guidelines such testing would require the use of approximately 7.2 million laboratory animals [ Hofer et al. 2004 ]. It has also been estimated that over 80% of all animals used for safety testing under REACH legislation would be used for examining reproductive and developmental toxicity [Hofer et al., 2004]. In addition to REACH initiatives, it has been estimated that out of 5,000 to 10,000 new drug entities that a pharmaceutical company may start with, only one is finally approved by the Food and Drug Administration at a cost of over one billion dollars [ Garg et al. 2011 ]. A large portion of this cost is due to animal testing. Therefore, both the pharmaceutical and chemical industries are interested in using alternative models and in vitro tests for safety testing. This review will examine the current state of three alternative models - whole embryo culture (WEC), the mouse embryonic stem cell test (mEST), and zebrafish. Each of these alternatives will be reviewed, and advantages and disadvantages of each model will be discussed. These models were chosen because they are the models most commonly used and would appear to have the greatest potential for future applications in developmental toxicity screening and testing.

  8. Adolescent cigarette smokers' and non-cigarette smokers' use of alternative tobacco products.

    PubMed

    Saunders, Charles; Geletko, Karen

    2012-08-01

    This study uses the most recent data from the nationally representative National Youth Tobacco Survey (NYTS) to examine the use of alternative tobacco products among U.S. cigarette smokers and non-cigarette smokers aged 14-17. Alternative tobacco product use is defined as use of one or more of the following products: smokeless tobacco, cigars, pipes, bidis, or kreteks. Using the results from the 2004, 2006, and 2009 NYTS, multivariate logistic regressions were used to investigate separately the extent of alternative tobacco product use in current cigarette smokers and in those who reported not smoking cigarettes controlling for demographic and other independent influences. The results indicate that for adolescent smokers and nonsmokers, the use of one type of alternative tobacco product made it much more likely the individual would use one or more of the other alternative tobacco products. Non-cigarette smokers using these tobacco products appeared to exhibit symptoms of nicotine dependence comparable to those of cigarette smokers. More information on adolescent use of alternative tobacco products is needed. Current cigarette use declined 3.4% annually over 2004-2009 for the NYTS 14- to 17-year-old population, but this cohort's use of alternative tobacco products was unchanged. The number of adolescents aged 14-17 who did not smoke cigarettes but used alternative tobacco products increased 5.9% per year over the same period. Current surveillance measures need to be expanded in order to gain a more comprehensive understanding of adolescent alternative tobacco use.

  9. Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

    DOEpatents

    Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

    1996-11-19

    An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

  10. Bulawayo water supplies: Sustainable alternatives for the next decade

    NASA Astrophysics Data System (ADS)

    Mkandla, Noel; Van der Zaag, Pieter; Sibanda, Peter

    Bulawayo is the second largest city in Zimbabwe with a population of nearly one million people. It is located on the watershed of Umzingwane and Gwayi catchments. The former is part of the Limpopo basin, while the latter drains into the Zambezi basin. Bulawayo has a good potential of economic development but has been stymied by lack of sufficient water. The city currently relies on five surface sources in the Umzingwane catchment where it has to compete with evaporation. The well field from the Nyamandlovu aquifer in the Gwayi catchment, which was constructed as an emergency measure during the 1992 drought, is currently not operational. Alternative water supply sources are far and expensive. A multilinear regression model was developed to analyse and quantify the factors affecting water consumption. It was found that per capita water consumption is very low, indicating suppressed demand. Water rationing, tariffs, rainfall, population growth and gross domestic product are the main factors influencing water consumption in Bulawayo. Assuming that these factors will continue to be influential, future water consumption was projected for intensive, regular and slack water demand management. Future water consumption was then compared with the current water supply capacity in order to determine the date by which the next water supply source is required. With slack demand management, the Nyamandlovu well field should have been operational by 2003, while by the year 2007 an additional source of water is required. With intensive demand management and assuming low population growth, current capacities may suffice to satisfy the suppressed demand until the year 2015, by which time Nyamandlovu wells should be operational again. The additional water supply sources that are currently being considered for Bulawayo (namely the Zambezi water pipeline; Gwayi Shangani dam; Mtshabezi dam; Lower Tuli dam; and Glass block dam) were then compared with an alternative water source not yet

  11. Study of temperature, air dew point temperature and reactant flow effects on proton exchange membrane fuel cell performances using electrochemical spectroscopy and voltammetry techniques

    NASA Astrophysics Data System (ADS)

    Wasterlain, S.; Candusso, D.; Hissel, D.; Harel, F.; Bergman, P.; Menard, P.; Anwar, M.

    A single PEMFC has been operated by varying the assembly temperature, the air dew point temperature and the anode/cathode stoichiometry rates with the aim to identify the parameters and combinations of factors affecting the cell performance. Some of the experiments were conducted with low humidified reactants (relative humidity of 12%). The FC characterizations tests have been conducted using in situ electrochemical methods based on load current and cell voltage signal analysis, namely: polarization curves, EIS measurements, cyclic and linear sweep voltammetries (CV and LSV). The impacts of the parameters on the global FC performances were observed using the polarization curves whereas EIS, CV and LSV test results were used to discriminate the different voltage loss sources. The test results suggest that some parameter sets allow maximal output voltages but can also induce material degradation. For instance, higher FC temperature and air flow values can induce significant electrical efficiency benefits, notably by increasing the reversible potential and the reaction kinetics. However, raising the cell temperature can also gradually dry the FC and increase the risk of membrane failure. LSV has also shown that elevated FC temperature and relative humidity can also accelerate the electrolyte degradation (i.e. slightly higher fuel crossover rate) and reduce the lifetime consequently.

  12. From amusic to musical?--Improving pitch memory in congenital amusia with transcranial alternating current stimulation.

    PubMed

    Schaal, Nora K; Pfeifer, Jasmin; Krause, Vanessa; Pollok, Bettina

    2015-11-01

    Brain imaging studies highlighted structural differences in congenital amusia, a life-long perceptual disorder that is associated with pitch perception and pitch memory deficits. A functional anomaly characterized by decreased low gamma oscillations (30-40 Hz range) in the right dorsolateral prefrontal cortex (DLPFC) during pitch memory has been revealed recently. Thus, the present study investigates whether applying transcranial alternating current stimulation (tACS) at 35 Hz to the right DLPFC would improve pitch memory. Nine amusics took part in two tACS sessions (either 35 Hz or 90 Hz) and completed a pitch and visual memory task before and during stimulation. 35 Hz stimulation facilitated pitch memory significantly. No modulation effects were found with 90 Hz stimulation or on the visual task. While amusics showed a selective impairment of pitch memory before stimulation, the performance during 35 Hz stimulation was not significantly different to healthy controls anymore. Taken together, the study shows that modulating the right DLPFC with 35 Hz tACS in congenital amusia selectively improves pitch memory performance supporting the hypothesis that decreased gamma oscillations within the DLPFC are causally involved in disturbed pitch memory and highlight the potential use of tACS to interact with cognitive processes. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Cyclic voltammetry: a tool to quantify 2,4,6-trichloroanisole in aqueous samples from cork planks boiling industrial process.

    PubMed

    Peres, António M; Freitas, Patrícia; Dias, Luís G; Sousa, Mara E B C; Castro, Luís M; Veloso, Ana C A

    2013-12-15

    Chloroanisoles, namely 2,4,6-trichloroanisole, are pointed out as the primary responsible of the development of musty off-flavours in bottled wine, due to their migration from cork stoppers, which results in huge economical losses for wine industry. A prevention step is the detection of these compounds in cork planks before stoppers are produced. Mass spectrometry gas chromatography is the reference method used although it is far beyond economical possibilities of the majority of cork stoppers producers. In this work, a portable cyclic voltammetry approach was used to detect 2,4,6-trichloroanisole extracted from natural cork planks to the aqueous phase during the cork boiling industrial treatment process. Analyses were carried out under ambient conditions, in less than 15 min with a low use of solvent and without any sample pre-treatment. The proposed technique had detection (0.31±0.01 ng/L) and quantification (0.95±0.05 ng/L) limits lower than the human threshold detection level. For blank solutions, without 2,4,6-trichloroanisole addition, a concentration in the order of the quantification limit was estimated (1.0±0.2 ng/L), which confirms the satisfactory performance of the proposed methodology. For aqueous samples from the industrial cork planks boiling procedure, intra-day repeatabilities were lower than 3%, respectively. Also, 2,4,6-trichloroanisole contents in the aqueous samples determined by this novel approach were in good agreement with those obtained by GC-MS (correlation coefficient equal to 0.98), confirming the satisfactory accuracy of the proposed methodology. So, since this novel approach is a fast, low-cost, portable and user-friendly method, it can be an alternative and helpful tool for in-situ industrial applications, allowing accurate detection of releasable 2,4,6-trichloroanisole in an earlier phase of cork stoppers production, which may allow implementing more effective cork treatments to reduce or avoid future 2,4,6-trichloroanisole

  14. Boosting the LTP-like plasticity effect of intermittent theta-burst stimulation using gamma transcranial alternating current stimulation.

    PubMed

    Guerra, Andrea; Suppa, Antonio; Bologna, Matteo; D'Onofrio, Valentina; Bianchini, Edoardo; Brown, Peter; Di Lazzaro, Vincenzo; Berardelli, Alfredo

    2018-03-24

    Transcranial Alternating Current Stimulation (tACS) consists in delivering electric current to the brain using an oscillatory pattern that may entrain the rhythmic activity of cortical neurons. When delivered at gamma frequency, tACS modulates motor performance and GABA-A-ergic interneuron activity. Since interneuronal discharges play a crucial role in brain plasticity phenomena, here we co-stimulated the primary motor cortex (M1) in healthy subjects by means of tACS during intermittent theta-burst stimulation (iTBS), a transcranial magnetic stimulation paradigm known to induce long-term potentiation (LTP)-like plasticity. We measured and compared motor evoked potentials before and after gamma, beta and sham tACS-iTBS. While we delivered gamma-tACS, we also measured short-interval intracortical inhibition (SICI) to detect any changes in GABA-A-ergic neurotransmission. Gamma, but not beta and sham tACS, significantly boosted and prolonged the iTBS-induced after-effects. Interestingly, the extent of the gamma tACS-iTBS after-effects correlated directly with SICI changes. Overall, our findings point to a link between gamma oscillations, interneuronal GABA-A-ergic activity and LTP-like plasticity in the human M1. Gamma tACS-iTBS co-stimulation might represent a new strategy to enhance and prolong responses to plasticity-inducing protocols, thereby lending itself to future applications in the neurorehabilitation setting. Copyright © 2018 Elsevier Inc. All rights reserved.

  15. SF6-alternative gases for application in gas-insulated switchgear

    NASA Astrophysics Data System (ADS)

    Li, Xingwen; Zhao, Hu; Murphy, Anthony B.

    2018-04-01

    The environmental problems caused by greenhouse gases have received unprecedented attention. Sulfur hexafluoride (SF6), which is the preferred gas for use in gas-insulated switchgear (circuit breakers, disconnect switches, etc. for high-voltage electrical circuits), has a very high global warming potential, and there is a large international effort to find alternative gases. Recently, this effort has made important progress, with promising alternative gases being identified and tested. An overview, in particular the current state of the art, of the study of SF6-alternative gases is presented in the paper. The review focuses on the application of the SF6-alternative gases in gas-insulated switchgear, with detailed analysis of calculations and measurements of their basic physical properties, dielectric strengths, and arc-quenching capabilities. Finally, a discussion of and perspectives on current research and future research directions are presented.

  16. Alternative tobacco use among college students: who is at highest risk?

    PubMed

    Enofe, Nosayaba; Berg, Carla J; Nehl, Eric J

    2014-03-01

    To examines smoking status, substance use, sociodemographics, and psychosocial characteristics in relation to alternative tobacco use among college students. Current tobacco use (cigarettes, cigar-like products, hookah, chew, snus) and correlates (sociodemographics, sensation-seeking, attitudes toward tobacco and smokers, social factors) were assessed among students aged 18-25 at 6 Southeastern US colleges using an online survey. Those who were younger, male, black, cigarette and marijuana users, and demonstrating at-risk psychosocial factors were at increased risk of alternative tobacco product use (p < .001). Among current smokers, never daily nondaily smokers were 3 times as likely as former daily non-daily smokers and daily smokers to use alternative tobacco products (p < .001). Important risk factors for alternative tobacco use included important sociodemographic and psychosocial characteristics.

  17. Reductive electrografting of benzene (p-bisdiazonium hexafluorophosphate): a simple and effective protocol for creating diazonium-functionalized thin films.

    PubMed

    Marshall, Nicholas; Locklin, Jason

    2011-11-01

    In this Article, we describe a protocol for surface functionalization of benzenediazonium hexafluorophosphate monolayers by in situ electrochemical reduction of bis(benzenediazonium) hexafluorophosphate. Due to the considerable difference in potential between the first and second reduction of this species, it is possible to form a high density of surface-bound diazonium groups by use of a mild potential which selectively reduces only one diazonium group per ring. The resulting diazonium-containing monolayer reacts readily with solutions of electron-rich aromatic compounds. The reaction with ferrocene produces a dense (2.7 × 10(-10) mol/cm(2)) ferrocene-containing monolayer through a Gomberg-Bachmann type arylation. The resulting ferrocene group exhibits relatively rapid electron transfer to the electrode due to the conjugated linker layer as measured by alternating current voltammetry (ACV) and cyclic voltammetry. Aromatic systems with π-donor substitutents (N,N-dimethylaniline, N,N,N',N'-tetramethyldiaminobenzophenone, and hydroquinone) react through an azo-coupling to form monolayers linked to the surface through an azobenzene moiety. The redox properties of these electron-rich species tethered to the surface were observed and quantified using cyclic voltammetry. This simple and versatile functionalization procedure has a wide variety of potential applications in surface science and materials research.

  18. Brain extracellular glucose assessed by voltammetry throughout the rat sleep-wake cycle.

    PubMed

    Netchiporouk, L; Shram, N; Salvert, D; Cespuglio, R

    2001-04-01

    In the present study, cortical extracellular levels of glucose were monitored for the first time throughout the sleep-wake states of the freely moving rat. For this purpose, polygraphic recordings (electroencephalogram of the fronto-occipital cortices and electromyogram of the neck muscles) were achieved in combination with differential normal pulse voltammetry (DNPV) using a specific glucose sensor. Data obtained reveal that the basal extracellular glucose concentration in the conscious rat is 0.59 +/- 0.3 m M while under chloral hydrate anaesthesia (0.4 g/kg, i.p.) it increases up to 180% of its basal concentration. Regarding the sleep-wake cycle, the existence of spontaneous significant variations in the mean glucose level during slow-wave sleep (SWS = +13%) and paradoxical sleep (PS = -11%) compared with the waking state (100%) is also reported. It is to be noticed that during long periods of active waking, glucose level tends towards a decrease that becomes significant after 15 min (active waking = -32%). On the contrary, during long episodes of slow-wave sleep, it tends towards an increase which becomes significant after 12 min (SWS = +28%). It is suggested that voltammetric techniques using enzymatic biosensors are useful tools allowing direct glucose measurements in the freely moving animal. On the whole, paradoxical sleep is pointed out as a state highly dependent on the availability of energy and slow-wave sleep as a period of energy saving.

  19. An Amperometric Immunosensor Based on Multi-Walled Carbon Nanotubes-Thionine-Chitosan Nanocomposite Film for Chlorpyrifos Detection

    PubMed Central

    Sun, Xia; Cao, Yaoyao; Gong, Zhili; Wang, Xiangyou; Zhang, Yan; Gao, Jinmei

    2012-01-01

    In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 105 ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits. PMID:23443396

  20. Allele-Specific Alternative mRNA processing (ASARP) | Informatics Technology for Cancer Research (ITCR)

    Cancer.gov

    A software pipeline for prediction of allele-specific alternative RNA processing events using single RNA-seq data. The current version focuses on prediction of alternative splicing and alternative polyadenylation modulated by genetic variants.

  1. Teaching Electrical Energy, Voltage and Current: An Alternative Approach.

    ERIC Educational Resources Information Center

    Licht, Pieter

    1991-01-01

    A program for teaching the concepts of electric energy, voltage, and current is proposed. The ideas and concepts are introduced in a sequence that places more emphasis on some aspects that are normally treated very briefly. A phenomenological orientation, qualitative and quantitative micro- and macroscopic treatments, and the inclusion of the…

  2. Emerging trends in alternative aviation fuels

    NASA Astrophysics Data System (ADS)

    Corbett, Cody

    The days of petroleum-based aviation fuels are numbered. New regulations to be set in place in the coming years will force current fuels to be phased out in favor of cleaner fuels with less toxic emissions. The alternative fuel industry has already taken its foothold in other modes of transportation, and aviation will soon follow suit. Many companies have cropped up over the last decade, and a few have been around longer, that work hard to develop the alternative aviation fuels of the future. It is important, however, for the aviation community to know what to expect and when to expect it concerning alternative fuels. This study investigates where various companies in the alternative aviation fuel industry currently stand in their development and production processes, and how their products will affect aircraft owners and operators. By interviewing representatives from these companies and analyzing their responses to identify trends, an educated prediction can be made about where the industry is headed and when the aviation community can expect these fuel to be available. The findings of this study indicate that many companies are still in their developmental stages, with a few notable outliers, and that most of these companies expect to see production of their product by 2017. Also, the fuel manufacturers are dealing with all the legal hurdles regarding alternative fuels, so little to no effort will be required on the part of the consumer. These findings, along with their analysis, will enable the aviation community to make educated decisions concerning fuel and their aircraft, as well and do their part to help these beneficial fuels get to market.

  3. Alternative strategies: a better alternative.

    PubMed

    Doody, Dennis

    2010-05-01

    Alternatives can be defined as being any financial asset other than traditional stocks and bonds. They include marketable alternatives, private capital, and equity real estate. There are two primary reasons for investing in alternatives: the potential for greater return and the opportunity to diversify a portfolio. Although alternatives were challenged in the highly volatile environment that existed in 2008 and early 2009, they generally lived up to expectations.

  4. Petersburg National Battlefield : alternative transportation feasibility study

    DOT National Transportation Integrated Search

    2012-11-13

    This report studies the feasibility of alternative solutions to several transportation problems affecting Petersburg National Battlefield in Petersburg, Virginia. Current transportation problems include site-specific access issues, wayfinding and nav...

  5. Why Current Statistics of Complementary Alternative Medicine Clinical Trials is Invalid.

    PubMed

    Pandolfi, Maurizio; Carreras, Giulia

    2018-06-07

    It is not sufficiently known that frequentist statistics cannot provide direct information on the probability that the research hypothesis tested is correct. The error resulting from this misunderstanding is compounded when the hypotheses under scrutiny have precarious scientific bases, which, generally, those of complementary alternative medicine (CAM) are. In such cases, it is mandatory to use inferential statistics, considering the prior probability that the hypothesis tested is true, such as the Bayesian statistics. The authors show that, under such circumstances, no real statistical significance can be achieved in CAM clinical trials. In this respect, CAM trials involving human material are also hardly defensible from an ethical viewpoint.

  6. Total inorganic arsenic detection in real water samples using anodic stripping voltammetry and a gold-coated diamond thin-film electrode.

    PubMed

    Song, Yang; Swain, Greg M

    2007-06-12

    An accurate method for total inorganic arsenic determination in real water samples was developed using differential pulse anodic stripping voltammetry (DPASV) and a Au-coated boron-doped diamond thin-film electrode. Keys to the method are the use of a conducting diamond platform and solid phase extraction for sample preparation. In the method, the As(III) present in the sample is first detected by DPASV. The As(V) present is then reduced to As(III) by reaction with Na2SO3 and this is followed by a second detection of As(III) by DPASV. Interfering metal ions (e.g., Cu(II)) that cause decreased electrode response sensitivity for arsenic in real samples are removed by solid phase extraction as part of the sample preparation. For example, Cu(II) caused a 30% decrease in the As stripping peak current at a solution concentration ratio of 3:1 (Cu(II)/As(III)). This loss was mitigated by passage of the solution through a Chelex 100 cation exchange resin. After passage, only a 5% As stripping current response loss was seen. The effect of organic matter on the Au-coated diamond electrode response for As(III) was also evaluated. Humic acid at a 5 ppm concentration caused only a 9% decrease in the As stripping peak charge for Au-coated diamond. By comparison, a 50% response decrease was observed for Au foil. Clearly, the chemical properties of the diamond surface in the vicinity of the metal deposits inhibit molecular adsorption on at least some of the Au surface. The method provided reproducible and accurate results for total inorganic arsenic in two contaminated water samples provided by the U.S. Bureau of Reclamation. The total inorganic As concentration in the two samples, quantified by the standard addition method, was 23.2+/-2.9 ppb for UV plant influent water and 16.4+/-0.9 ppb for Well 119 water (n=4). These values differed from the specified concentrations by less than 4%.

  7. Alternative Splicing Control of Abiotic Stress Responses.

    PubMed

    Laloum, Tom; Martín, Guiomar; Duque, Paula

    2018-02-01

    Alternative splicing, which generates multiple transcripts from the same gene, is an important modulator of gene expression that can increase proteome diversity and regulate mRNA levels. In plants, this post-transcriptional mechanism is markedly induced in response to environmental stress, and recent studies have identified alternative splicing events that allow rapid adjustment of the abundance and function of key stress-response components. In agreement, plant mutants defective in splicing factors are severely impaired in their response to abiotic stress. Notably, mounting evidence indicates that alternative splicing regulates stress responses largely by targeting the abscisic acid (ABA) pathway. We review here current understanding of post-transcriptional control of plant stress tolerance via alternative splicing and discuss research challenges for the near future. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Alternatives to Afrocentrism. Second Edition.

    ERIC Educational Resources Information Center

    Miller, John J., Ed.

    The essays in this collection place the current Afrocentric movement in its historical context and offer alternative suggestions about how to teach African American students about their history. The first section deals with the roots of Afrocentrism, analyzes the content of Afrocentric books and curricula, and discusses the impact of Afrocentrism…

  9. Cyclic-Voltammetry-Based Solid-State Gas Sensor for Methane and Other VOC Detection.

    PubMed

    Gross, Pierre-Alexandre; Jaramillo, Thomas; Pruitt, Beth

    2018-05-15

    We present the fabrication, characterization, and testing of an electrochemical volatile organic compound (VOC) sensor operating in gaseous conditions at room temperature. It is designed to be microfabricated and to prove the sensing principle based on cyclic voltammetry (CV). It is composed of a working electrode (WE), a counter electrode (CE), a reference electrode (RE), and a Nafion solid-state electrolyte. Nafion is a polymer that conducts protons (H + ) generated from redox reactions from the WE to the CE. The sensor needs to be activated prior to exposure to gases, which consists of hydrating the Nafion layer to enable its ion conduction properties. During testing, we have shown that our sensor is not only capable of detecting methane, but it can also quantify its concentration in the gas flow as well as differentiate its signal from carbon monoxide (CO). These results have been confirmed by exposing the sensor to two different concentrations of methane (50% and 10% of methane diluted in N 2 ), as well as pure CO. Although the signal is positioned in the H ads region of Pt, because of thermodynamic reasons it cannot be directly attributed to methane oxidation into CO 2 . However, its consistency suggests the presence of a methane-related oxidation process that can be used for detection, identification, and quantification purposes.

  10. Computational Aided-Molecular Imprinted Polymer Design for Solid Phase Extraction of Metaproterenol from Plasma and Determination by Voltammetry Using Modified Carbon Nanotube Electrode

    PubMed Central

    Ahmadi, Farhad; Karamian, Ehsan

    2014-01-01

    A molecular imprinted polymer (MIP) was computationally designed and synthesized for the selective extraction of metaproterenol (MTP), from human plasma. In this regards semi empirical MP3 and mechanical quantum (DFT) calculations were used to find a suitable functional monomers. On the basis of computational and experimental results, acrylic acid (AA) and DMSO:MeOH (90:10 %V/V) were found to be the best choices of functional monomer and polymerization solvents, respectively. This polymer was then used as a selective sorbent to develop a molecularly imprinted solid-phase extraction (MISPE) procedure followed by differential pulse voltammetry by using modified carbon nanotube electrode. The analysis was performed in phosphate buffer, pH 7.0. Peak currents were measured at +0.67 V versus Ag/AgCl. The linear calibration range was 0.026–8.0 μg mL-1 with a limit of detection 0.01 μg mL-1. The relative standard deviation at 0.5 μg mL-1 was 4.76% (n=5). The mean recoveries of 5 μg mL-1 MTP from plasma was 92.2% (n=5). The data of MISPE-DPV were compared with the MISPE-HPLC-UV. Although, the MISPE-DPV was more sensitive but both techniques have similar accuracy and precision. PMID:25237337

  11. Development of a Low Inductance Linear Alternator for Stirling Power Convertors

    NASA Technical Reports Server (NTRS)

    Geng, Steven M.; Schifer, Nicholas A.

    2017-01-01

    The free-piston Stirling power convertor is a promising technology for high efficiency heat-to-electricity power conversion in space. Stirling power convertors typically utilize linear alternators for converting mechanical motion into electricity. The linear alternator is one of the heaviest components of modern Stirling power convertors. In addition, state-of-art Stirling linear alternators usually require the use of tuning capacitors or active power factor correction controllers to maximize convertor output power. The linear alternator to be discussed in this paper, eliminates the need for tuning capacitors and delivers electrical power output in which current is inherently in phase with voltage. No power factor correction is needed. In addition, the linear alternator concept requires very little iron, so core loss has been virtually eliminated. This concept is a unique moving coil design where the magnetic flux path is defined by the magnets themselves. This paper presents computational predictions for two different low inductance alternator configurations, and compares the predictions with experimental data for one of the configurations that has been built and is currently being tested.

  12. 3 CFR - Demonstration Grants for the Development, Implementation, and Evaluation of Alternatives to the...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., Implementation, and Evaluation of Alternatives to the Current Medical Liability System Presidential Documents..., Implementation, and Evaluation of Alternatives to the Current Medical Liability System Memorandum for the... report that fear of lawsuits leads them to practice defensive medicine, which may contribute to higher...

  13. Thermal modulation voltammetry with laser heating at an aqueous|nitrobenzene solution microinterface: determination of the standard entropy changes of transfer for tetraalkylammonium ions.

    PubMed

    Hinoue, Teruo; Ikeda, Eiji; Watariguchi, Shigeru; Kibune, Yasuyuki

    2007-01-01

    Thermal modulation voltammetry (TMV) with laser heating was successfully performed at an aqueous|nitrobenzene (NB) solution microinterface, by taking advantage of the fact that laser light with a wavelength of 325.0 nm is optically transparent to the aqueous solution but opaque to the NB solution. When the laser beam impinges upon the interface from the aqueous solution side, a temperature is raised around the interface through the thermal diffusion subsequent to the light-to-heat conversion following the optical absorption by the NB solution near the interface. Based on such a principle, we achieved a fluctuating temperature perturbation around the interface for TMV by periodically irradiating the interface with the laser beam. On the other hand, the fluctuating temperature perturbation has influence on currents for transfer of an ion across the interface to produce fluctuating currents synchronized with the perturbation through temperature coefficients of several variables concerning the transfer, such as the standard transfer potential and the diffusion coefficient of the ion. Consequently, TMV has the possibility of providing information about the standard entropy change of transfer corresponding to a temperature coefficient of the standard transfer potential and a temperature coefficient of the diffusion coefficient. In this work, the aqueous|NB solution interface of 30 microm in diameter was irradiated with the laser beam at 10 Hz, and the currents synchronized with the periodical irradiation were recorded as a function of the potential difference across the interface in order to construct a TM voltammogram. TM voltammograms were measured for transfer of tetramethylammonium, tetraethylammonium, tetrapropylammonium, and tetra-n-butylammonium ions from the aqueous solution to the NB solution, and the standard entropy change of transfer was determined for each ion, according to an analytical procedure based on a mathematical expression of the TM voltammogram

  14. [Alternative treatments in irritable bowel syndrome].

    PubMed

    Hagège, H

    2009-02-01

    Managing irritable bowel syndrome (IBS) is difficult and often a source of dissatisfaction for the patient, explaining the increasingly frequent recourse to alternative treatments. These highly varied treatments are often associated. They can be classed into four categories: reflexology methods, interventions on the psyche, biological therapies, and treatments using certain forms of energy. Although some studies show interesting results, currently there are not sufficient scientific arguments to recommend one or another of these alternative treatments. Multicenter controlled studies are needed to better evaluate the strategies that appear to be cost-effective.

  15. Method for measuring the alternating current half-wave voltage of a Mach-Zehnder modulator based on opto-electronic oscillation.

    PubMed

    Hong, Jun; Chen, Dongchu; Peng, Zhiqiang; Li, Zulin; Liu, Haibo; Guo, Jian

    2018-05-01

    A new method for measuring the alternating current (AC) half-wave voltage of a Mach-Zehnder modulator is proposed and verified by experiment in this paper. Based on the opto-electronic self-oscillation technology, the physical relationship between the saturation output power of the oscillating signal and the AC half-wave voltage is revealed, and the value of the AC half-wave voltage is solved by measuring the saturation output power of the oscillating signal. The experimental results show that the measured data of this new method involved are in agreement with a traditional method, and not only an external microwave signal source but also the calibration for different frequency measurements is not needed in our new method. The measuring process is simplified with this new method on the premise of ensuring the accuracy of measurement, and it owns good practical value.

  16. Probing phase- and frequency-dependent characteristics of cortical interneurons using combined transcranial alternating current stimulation and transcranial magnetic stimulation.

    PubMed

    Hussain, Sara J; Thirugnanasambandam, Nivethida

    2017-06-01

    Paired-pulse transcranial magnetic stimulation (TMS) and peripheral stimulation combined with TMS can be used to study cortical interneuronal circuitry. By combining these procedures with concurrent transcranial alternating current stimulation (tACS), Guerra and colleagues recently showed that different cortical interneuronal populations are differentially modulated by the phase and frequency of tACS-imposed oscillations (Guerra A, Pogosyan A, Nowak M, Tan H, Ferreri F, Di Lazzaro V, Brown P. Cerebral Cortex 26: 3977-2990, 2016). This work suggests that different cortical interneuronal populations can be characterized by their phase and frequency dependency. Here we discuss how combining TMS and tACS can reveal the frequency at which cortical interneuronal populations oscillate, the neuronal origins of behaviorally relevant cortical oscillations, and how entraining cortical oscillations could potentially treat brain disorders. Copyright © 2017 the American Physiological Society.

  17. High Frequency Alternator, Power Frequency Conversion (HFA-PFC) Technology for Lightweight Tactical Power Generation

    DTIC Science & Technology

    1995-09-22

    Modules 345-800 Amperes/400-3000 Votts - Current and Thermal Ratings of Module * Circuit Currents Element Data Model* Current Thermal Units...IGBTs modules (Powerex) 56 Main components for rectifiers, Diode Bridge modules (Powerex) 65 Heat Sinks (Aavid Engineering) 85 Westinghouse...exciter circuit , are not reliable enough for military applications, and they were replaced by brushless alternators. The brushless AC alternator

  18. Alternative energy technologies for the Caribbean islands

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pytlinski, J.T.

    1992-01-01

    All islands in the Caribbean except Puerto Rico can be classified as developing islands. Of these islands, all except Trinidad and Tobago are oil importers. Uncertainties concerning uninterrupted oil supply and increasing oil prices causes economic, social and political instability and jeopardizes further development of these islands. The paper discusses the energy situation of the Caribbean islands and presents alternative energy options. Several alternative energy projects financed by local, federal and international organizations are presented. Present and future uses of alternative energy technologies are described in different islands. Barrier which handicap developing and implementing alternative energy sources in the Caribbeanmore » are discussed. The potential and possible applications of alternative energy technologies such as: solar-thermal energy, photovoltaics, wind energy, ocean thermal energy conversion (OTEC), ocean currents and tides energy, biomass, peat energy, municipal solid wastes, bioconversion, hydropower, geothermal energy, nuclear energy and energy conservation are discussed in detail as means to alleviate the energy situation in the Caribbean islands.« less

  19. EJSCREEN Version 1, EJ Index Alternatives

    EPA Pesticide Factsheets

    This map service displays alternative environmental justice (EJ) indexes used in EJSCREEN. The alternative EJ indexes combine each of the 12 environmental indicators and one of two demographic indexes using different methods than the Primary EJ Index. EJ Index Alternative 1 is a combination of a blockgroup environmental factor, the populaiton of the blockgroup, and the demographic index. This EJ Index measures how much a particular place contributes to the total burden faced by subpopulations highlighted by the demographic index. EJ Index Alternative 2 is a combination of a blockgroup environmental factor and the demographic index. Two options are presented for both EJ Index Alternative 1 and Alternative 2-- they are combined with the primary demographic index and alternative demographic index. EJSCREEN is an environmental justice screening tool that provides EPA with a nationally consistent approach to screening for potential areas of EJ concern that may warrant further investigation. The EJ indexes are block group level results that combine multiple demographic factors with a single environmental variable (such as proximity to traffic) that can be used to help identify communities living with the greatest potential for negative environmental and health effects. The EJSCREEN tool is currently for internal EPA use only. It is anticipated that as users become accustomed to this new tool, individual programs within the Agency will develop program use guidelines a

  20. Synthetic tactile perception induced by transcranial alternating-current stimulation can substitute for natural sensory stimulus in behaving rabbits.

    PubMed

    Márquez-Ruiz, Javier; Ammann, Claudia; Leal-Campanario, Rocío; Ruffini, Giulio; Gruart, Agnès; Delgado-García, José M

    2016-01-21

    The use of brain-derived signals for controlling external devices has long attracted the attention from neuroscientists and engineers during last decades. Although much effort has been dedicated to establishing effective brain-to-computer communication, computer-to-brain communication feedback for "closing the loop" is now becoming a major research theme. While intracortical microstimulation of the sensory cortex has already been successfully used for this purpose, its future application in humans partly relies on the use of non-invasive brain stimulation technologies. In the present study, we explore the potential use of transcranial alternating-current stimulation (tACS) for synthetic tactile perception in alert behaving animals. More specifically, we determined the effects of tACS on sensory local field potentials (LFPs) and motor output and tested its capability for inducing tactile perception using classical eyeblink conditioning in the behaving animal. We demonstrated that tACS of the primary somatosensory cortex vibrissa area could indeed substitute natural stimuli during training in the associative learning paradigm.

  1. A validation study of an alternate state science assessment: Alignment of the Pennsylvania Alternate System of Assessment (PASA) science assessment

    NASA Astrophysics Data System (ADS)

    Heh, Peter

    The current study examined the validation and alignment of the PASA-Science by determining whether the alternate science assessment anchors linked to the regular education science anchors; whether the PASA-Science assessment items are science; whether the PASA-Science assessment items linked to the alternate science eligible content, and what PASA-Science assessment content was considered important by parents and teachers. Special education and science education university faculty determined all but one alternate science assessment anchor linked to the regular science assessment anchors. Special education and science education teachers determined that the PASA-Science assessment items are indeed science and linked to the alternate science eligible content. Finally, parents and teachers indicated the most important science content assessed in the PASA-Science involved safety and independence.

  2. Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified Poisson-Nernst-Planck Model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Hainan; Thiele, Alexander; Pilon, Laurent

    2013-11-15

    This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |z i| of either ion species. By contrast, the ionmore » diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τ CV and the “RC time scale” τ RC corresponding to the characteristic time of ions’ electrodiffusion. For τ RC ← τ CV, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τ RC → τ CV, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.« less

  3. Determination of mercury in ambient water samples by anodic stripping voltammetry on screen-printed gold electrodes.

    PubMed

    Bernalte, E; Marín Sánchez, C; Pinilla Gil, E

    2011-03-09

    The applicability of commercial screen-printed gold electrodes (SPGEs) for the determination of Hg(II) in ambient water samples by square wave anodic stripping voltammetry has been demonstrated. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved mercury in the low ng mL(-1) range (detection limit 1.1 ng mL(-1)), useful for pollution monitoring or screening purposes. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material (recoveries 90.0-110%) and the NCS ZC 76303 Mercury in Water Certified Reference Material (recoveries 82.5-90.6%). Waste water samples from industrial origin and fortified rain water samples were assayed for mercury by the proposed method and by a reference ICP-MS method, with good agreement. Screen printing technology thus opens a useful way for the construction of reliable electrochemical sensors for decentralized or even field Hg(II) testing. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Quantitative weaknesses of the Marcus-Hush theory of electrode kinetics revealed by Reverse Scan Square Wave Voltammetry: The reduction of 2-methyl-2-nitropropane at mercury microelectrodes

    NASA Astrophysics Data System (ADS)

    Laborda, Eduardo; Wang, Yijun; Henstridge, Martin C.; Martínez-Ortiz, Francisco; Molina, Angela; Compton, Richard G.

    2011-08-01

    The Marcus-Hush and Butler-Volmer kinetic electrode models are compared experimentally by studying the reduction of 2-methyl-2-nitropropane in acetonitrile at mercury microelectrodes using Reverse Scan Square Wave Voltammetry. This technique is found to be very sensitive to the electrode kinetics and to permit critical comparison of the two models. The Butler-Volmer model satisfactorily fits the experimental data whereas Marcus-Hush does not quantitatively describe this redox system.

  5. Simulation of fault performance of a diesel engine driven brushless alternator through PSPICE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Narayanan, S.S.Y.; Ananthakrishnan, P.; Hangari, V.U.

    1995-12-31

    Analysis of the fault performance of a brushless alternator with damper windings in the main alternator has been handled ab initio as a total modeling and simulation problem through proper application of Park`s equivalent circuit approach individually to the main exciter alternator units of the brushless alternator and the same has been implemented through PSPICE. The accuracy of the parameters used in the modeling and results obtained through PSPICE implementation are then evaluated for a specific 125 kVA brushless alternator in two stages as followed: first, by comparison of the predicted fault performance obtained from simulation of the 125 kVAmore » main alternator alone treated as a conventional alternator with the results obtained through the use of closed form analytical expressions available in the literature for fault currents and torques in such conventional alternators. Secondly, by comparison of some of the simulation results with those obtained experimentally on the brushless alternator itself. To enable proper calculation of derating factors to be used in the design of such brushless alternators, simulation results then include harmonic analysis of the steady state fault currents and torques. Throughout these studies, the brushless alternator is treated to be on no load at the instant of occurrence of fault.« less

  6. Electrochemical Genotoxicity Assay Based on a SOS/umu Test Using Hydrodynamic Voltammetry in a Droplet

    PubMed Central

    Kuramitz, Hideki; Sazawa, Kazuto; Nanayama, Yasuaki; Hata, Noriko; Taguchi, Shigeru; Sugawara, Kazuharu; Fukushima, Masami

    2012-01-01

    The SOS/umu genotoxicity assay evaluates the primary DNA damage caused by chemicals from the β-galactosidase activity of S. typhimurium. One of the weaknesses of the common umu test system based on spectrophotometric detection is that it is unable to measure samples containing a high concentration of colored dissolved organic matters, sediment, and suspended solids. However, umu tests with electrochemical detection techniques prove to be a better strategy because it causes less interference, enables the analysis of turbid samples and allows detection even in small volumes without loss of sensitivity. Based on this understanding, we aim to develop a new umu test system with hydrodynamic chronoamperometry using a rotating disk electrode (RDE) in a microliter droplet. PAPG when used as a substrate is not electroactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current response of chronoamperometry resulting from the oxidation of PAP to PQI is directly proportional to the enzymatic activity of S. typhimurium. This was achieved by performing genotoxicity tests for 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide (AF-2) and 2-aminoanthracene (2-AA) as model genotoxic compounds. The results obtained in this study indicated that the signal detection in the genotoxicity assay based on hydrodynamic voltammetry was less influenced by the presence of colored components and sediment particles in the samples when compared to the usual colorimetric signal detection. The influence caused by the presence of humic acids (HAs) and artificial sediment on the genotoxic property of selected model compounds such as 4-nitroquinoline-N-oxide (4-NQO), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 1,8-dinitropyrene (1,8-DNP) and 1-nitropyrene (1-NP) were also investigated. The results showed that the genotoxicity of 1-NP and MX changed in the presence of 10 mg·L−1 HAs. The genotoxicity of tested chemicals with a high hydrophobicity such as 1,8-DNP

  7. Guide to alternative fuel vehicle incentives and laws: September 1998

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Riley, C.; O'Connor, K.

    1998-12-22

    This guide provides information in support of the National Clean Cities Program, which will assist one in becoming better informed about the choices and options surrounding the use of alternative fuels and the purchase of alternative fuel vehicles. The information printed in this guide is current as of September 15, 1998. For recent additions or more up-to-date information, check the Alternative Fuels Data Center Web site at http://www.afdc.doe.gov

  8. Alternation blindness in the representation of binary sequences.

    PubMed

    Yu, Ru Qi; Osherson, Daniel; Zhao, Jiaying

    2018-03-01

    Binary information is prevalent in the environment and contains 2 distinct outcomes. Binary sequences consist of a mixture of alternation and repetition. Understanding how people perceive such sequences would contribute to a general theory of information processing. In this study, we examined how people process alternation and repetition in binary sequences. Across 4 paradigms involving estimation, working memory, change detection, and visual search, we found that the number of alternations is underestimated compared with repetitions (Experiment 1). Moreover, recall for binary sequences deteriorates as the sequence alternates more (Experiment 2). Changes in bits are also harder to detect as the sequence alternates more (Experiment 3). Finally, visual targets superimposed on bits of a binary sequence take longer to process as alternation increases (Experiment 4). Overall, our results indicate that compared with repetition, alternation in a binary sequence is less salient in the sense of requiring more attention for successful encoding. The current study thus reveals the cognitive constraints in the representation of alternation and provides a new explanation for the overalternation bias in randomness perception. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  9. AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XVII, LEARNING ABOUT AC GENERATOR (ALTERNATOR) PRINCIPLES (PART II).

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES AND THE SERVICING AND TESTING PROCEDURES FOR ALTERNATING CURRENT (AC) GENERATORS AND REGULATORS USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE REVIEW OF ALTERNATOR PRINCIPLES, ALTERNATOR SERVICING AND TESTING, ALTERNATOR REGULATOR OPERATING…

  10. Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation.

    PubMed

    Neuling, Toralf; Ruhnau, Philipp; Fuscà, Marco; Demarchi, Gianpaolo; Herrmann, Christoph S; Weisz, Nathan

    2015-09-01

    Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior. Copyright © 2015. Published by Elsevier Inc.

  11. Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation

    PubMed Central

    Neuling, Toralf; Ruhnau, Philipp; Fuscà, Marco; Demarchi, Gianpaolo; Herrmann, Christoph S.; Weisz, Nathan

    2015-01-01

    Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior. PMID:26080310

  12. Mobilization and Defense Management Technical Reports Series. Alternative Service for Conscientious Objectors.

    DTIC Science & Technology

    1983-03-01

    THIS STUDY EXAMINES THE DIFFERENCE BETWEEN THE SELECTIVE SERVICE SYSTEM’S (SSS) CONCEPT OF ALTERNATIVE SERVICE AND THOSE ESPOUSED BY THE MENNONITE CHURCH...System’s (SSS) concept of Alternative Service and those espoused by the Mnnonite Church, the most articulate opponent of current administration planning...adminisrat-ion of an alternative service program. on January 22, the SSS puiblished its proposed concept for alternative service in the Federal Register and

  13. ASSESSING ALTERNATIVE FUTURES FOR AGRICULTURE IN IOWA, U.S.A.

    EPA Science Inventory

    The contributions of current industrial agricultural practices to environmental degradation and the social problems facing agricultural regions are well known. However, landscape-scale alternatives to current conditions have not been fully explored nor their potential impacts qua...

  14. Electrochemical behavior of phytochelatins and related peptides at the hanging mercury drop electrode in the presence of cobalt(II) ions.

    PubMed

    Dorcák, Vlastimil; Sestáková, Ivana

    2006-01-01

    Direct current voltammetry and differential pulse voltammetry have been used to investigate the electrochemical behaviour of two phytochelatins: heptapeptide (gamma-Glu-Cys)3-Gly and pentapeptide (gamma-Glu-Cys)2-Gly, tripeptide glutathione gamma-Glu-Cys-Gly and its fragments: dipeptides Cys-Gly and gamma-Glu-Cys at the hanging mercury drop electrode in the presence of cobalt(II) ions. Most interesting results were obtained with direct current voltammetry in the potential region of -0.80 V up to -1.80 V. Differential pulse voltammetry of the same solutions of Co(II) with peptides gives more complicated voltammograms with overlapping peaks, probably in connection with the influence of adsorption at slow scan rates necessarily used in this method. However, in using Brdicka catalytic currents for analytical purposes, differential pulse voltammograms seem to be more helpful. Presented investigations have shown that particularly the prewave of cobalt(II) allows distinguishing among phytochelatins, glutathione, and its fragments.

  15. Assessing performance of alternative pavement marking materials.

    DOT National Transportation Integrated Search

    2010-01-01

    Pavement markings need to be restriped from time to time to maintain retroreflectivity. : Knowing which material provides the most economically efficient solution is important. : Currently, no agreed upon method by which to evaluate the use of altern...

  16. Combined Effect of Alternating Current Interference and Cathodic Protection on Pitting Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in Near-Neutral pH Environment.

    PubMed

    Wang, Liwei; Cheng, Lianjun; Li, Junru; Zhu, Zhifu; Bai, Shuowei; Cui, Zhongyu

    2018-03-22

    Influence of alternating current (AC) on pitting corrosion and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the near-neutral pH environment under cathodic protection (CP) was investigated. Both corrosion and SCC are inhibited by -0.775 V SCE CP without AC interference. With the superimposition of AC current (1-10 mA/cm²), the direct current (DC) potential shifts negatively under the CP of -0.775 V SCE and the cathodic DC current decreases and shifts to the anodic direction. Under the CP potential of -0.95 V SCE and -1.2 V SCE , the applied AC current promotes the cathodic reaction and leads to the positive shift of DC potential and increase of cathodic current. Local anodic dissolution occurs attributing to the generated anodic current transients in the positive half-cycle of the AC current, resulting in the initiation of corrosion pits (0.6-2 μm in diameter). AC enhances the SCC susceptibility of X70 steel under -0.775 V SCE CP, attributing to the promotion of anodic dissolution and hydrogen evolution. Even an AC current as low as 1 mA/cm² can enhance the SCC susceptibility.

  17. Eddy Currents: Levitation, Metal Detectors, and Induction Heating

    ERIC Educational Resources Information Center

    Wouch, G.; Lord, A. E., Jr.

    1978-01-01

    A simple and accessible calculation is given of the effects of eddy currents for a sphere in the field of a single circular loop of alternating current. These calculations should help toward the inclusion of eddy current effects in upper undergraduate physics courses. (BB)

  18. Alternative Fuels Data Center: Alternative Fueling Station Locator

    Science.gov Websites

    Locate Stations Printable Version Share this resource Send a link to Alternative Fuels Data Center : Alternative Fueling Station Locator to someone by E-mail Share Alternative Fuels Data Center: Alternative Fuels Data Center: Alternative Fueling Station Locator on Digg Find More places to share Alternative

  19. ENVIRONMENTAL LIFE CYCLE ASSESSMENT OF GASOLINE ALTERNATIVES: MTBE AND ETHANOL ADDITIVES

    EPA Science Inventory

    Currently, the U.S. is considering options for additives to reformulated gasoline. To inform this debate the U.S. EPA's Office of Research and Development is conducting a screening life cycle assessment (LCA) of three gasoline alternatives. These alternatives include gasoline w...

  20. Alternatives to animal testing: information resources via the Internet and World Wide Web.

    PubMed

    Hakkinen, P J Bert; Green, Dianne K

    2002-04-25

    Many countries, including the United States, Canada, European Union member states, and others, require that a comprehensive search for possible alternatives be completed before beginning some or all research involving animals. Completing comprehensive alternatives searches and keeping current with information associated with alternatives to animal testing is a challenge that will be made easier as people throughout the world gain access to the Internet and World Wide Web. Numerous Internet and World Wide Web resources are available to provide guidance and other information on in vitro and other alternatives to animal testing. A comprehensive Web site is Alternatives to Animal Testing on the Web (Altweb), which serves as an online clearinghouse for resources, information, and news about alternatives to animal testing. Examples of other important Web sites include the joint one for the (US) Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and the National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) and the Norwegian Reference Centre for Laboratory Animal Science and Alternatives (The NORINA database). Internet mailing lists and online access to bulletin boards, discussion areas, newsletters, and journals are other ways to access and share information to stay current with alternatives to animal testing.