Sample records for alternating current voltammetry

  1. Trace-metal determination by second-harmonic alternating-current anodic stripping voltammetry.

    PubMed

    Locatelli, C; Fagioli, F; Bighi, C; Garai, T

    1986-03-01

    Second-harmonic alternating-current voltammetry can be used for the sequential determination of two electroactive species having very similar half-wave potentials (deltaE(1 2 ) < 50 mV). Since the concentrations of such metals in samples of special interest are often at trace levels, for their determination second-harmonic a.c. voltammetry (extremely selective but not sufficiently sensitive) can usefully be combined with the anodic stripping method, which has a very high analytical sensitivity. The determination of tin and lead as well as of indium and cadmium in 1M hydrochloric acid is described. The half-wave potentials are only 35 and 45 mV apart, respectively, for these systems. A three-electrode cell was used with a long-lasting sessile-drop mercury electrode as the working electrode, with a drop-time of 240-300 sec. The detection limit was found to be 10(-8)M for all four elements studied. The precision expressed as the relative standard deviation was 2-3% and the relative error was 1-2%. PMID:18964073

  2. Alternating current anodic stripping voltammetry in the study of cadmium complexation by a reference Suwannee river fulvic acid: a model case with strong electrode adsorption and weak binding

    Microsoft Academic Search

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

    2008-01-01

    The possibilities of anodic stripping voltammetry (ASV) using an alternating current (AC) scan in the stripping step have\\u000a been checked through the study of the complexation of cadmium by Suwannee river fulvic acid (SRFA), a reference fulvic acid\\u000a from the International Humic Substances Society. Because of the strong electrode adsorption of SRFA, AC mode appears to be\\u000a a good approach

  3. Catalytic reduction currents in the stripping voltammetry of solutions of the system copper(II)-ascorbic acid and their application in analytical chemistry

    Microsoft Academic Search

    P. M. Zaitsev; D. V. Krasnyi; K. V. Surmeleva

    2011-01-01

    It has been found that the analytical signal from copper(II), cadmium(II), and zinc(II) in alternating-current stripping voltammetry\\u000a in the presence of ascorbic acid (AA) increases only for copper(II) ions, which have significant oxidative potential. It is associated with the appearance of\\u000a a catalytic current of the reducer in stripping voltammetry, where the reducer is AA. A scheme has been proposed

  4. Superconducting alternating current cable

    Microsoft Academic Search

    Kafka

    1971-01-01

    A superconducting alternating current cable has a space for conducting a fluid of insulating helium and a carrier member for conducting a fluid of cooling helium. The carrier member maintains the insulating helium separate from the cooling helium, the insulating helium being kept at a pressure different from that of the cooling helium.

  5. Alternating to Direct: Rectifying Alternating Current

    NSDL National Science Digital Library

    The Materials Science and Technology Teacher's Workshop (MAST) provides this activity for classes learning about diodes and electrical currents. The laboratory illustrates how diodes can be used to rectify alternating current. It uses a galvanometer to determine the direction of current flow when an AC or DC current is applied to the circuit containing a diode in series with a resistor and a galvanometer.The lesson includes step by step directions for the experiment.The activity should require about 20-30 minutes of class time to complete. Discussion questions and teacher notes are included.

  6. Alternating Current Corrosion of Aluminum

    Microsoft Academic Search

    William French

    1973-01-01

    A comprehensive study of ac corrosion of aluminum alloys has led to a proposed mechanism of attack based on local pH changes. A critical alternating current density of 0.5 ma\\/in2 has been defined below which no corrosion occurs. At higher current densities the corrosion is time dependent. Engineering design data is presented.

  7. 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)

  8. Energy Storage: Current landscape for alternative energy

    E-print Network

    Energy Storage: Current landscape for alternative energy storage technologies and what the future may hold for multi-scale storage applications Presented by: Dave Lucero, Director Alternative Energy · Industry initiatives · Technology · Energy Storage Market · EaglePicher initiatives · Summary #12

  9. Fault current limiter and alternating current circuit breaker

    DOEpatents

    Boenig, Heinrich J. (Los Alamos, NM)

    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.

  10. 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.

  11. ALTERNATING CURRENT ELECTROCOAGULATION FOR SUPERFUND SITE REMEDIATION

    EPA Science Inventory

    The technical and economical feasibility of alternating current electrocoagulation (ACE) developed by Electro-Pure Systems, Inc., was evaluated for a 2-year period. CE is an electrochemical technology where highly-charged aluminum polyhydroxide species are introduced into aqueous...

  12. Ultrahigh frequency voltammetry: effect of electrode material and frequency of alternating potential modulation on mass transport at hot-disk microelectrodes.

    PubMed

    Baranski, Andrzej S; Boika, Aliaksei

    2012-02-01

    Ultrahigh frequency voltammetry involves low scan rate voltammetric measurements with microelectrodes polarized by high-frequency large-amplitude alternating potential. The method provides a simple means for studying electrothermal and dielectrophoretic effects, which are important in micro and nanofluidic systems. The method also allows for indirect measurements of electrode impedance at gigahertz frequencies. This increases the upper frequency limit in impedance measurements about 1000 times. In this work we demonstrated, for the first time, that the effect of dielectric relaxation of water can be observed in a simple voltammetric experiment. The paper focuses on the description of electrothermal convection at ac heated disk microelectrodes as a function of frequency and provides a comparison of numerical simulations with experimental results. PMID:22243033

  13. Alternating Current Circuit Jee-Hwan Ryu

    E-print Network

    Ryu, Jee-Hwan

    Korea University of Technology and Education Example ( ) ( ) ( ) ( ) I I dttIdtti T i wtIti T rms 707 of Technology and Education EFS161 Korea University of Technology and Education (Direct Current) #12;Korea University of Technology and Education (Alternating Current) Korea University of Technology

  14. Detection and assessment of alternating current corrosion

    Microsoft Academic Search

    A. Pourbaix; P. Carpentiers; R. Gregoor

    2000-01-01

    A measuring system to determine the rue peak potential, without ohmic drop error, is described. There is no alternating current (AC)-induced corrosion when the true max. peak potential is below the potential for cathodic protection (CP). Methods are studied to determine the importance of AC corrosion when the potential is higher than the critical potential for CP during a part

  15. 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.

  16. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, Duncan W. (Los Alamos, NM); McAtee, James L. (Los Alamos, NM)

    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.

  17. Detection and assessment of alternating current corrosion

    SciTech Connect

    Pourbaix, A.; Carpentiers, P.; Gregoor, R.

    2000-03-01

    A measuring system to determine the rue peak potential, without ohmic drop error, is described. There is no alternating current (AC)-induced corrosion when the true max. peak potential is below the potential for cathodic protection (CP). Methods are studied to determine the importance of AC corrosion when the potential is higher than the critical potential for CP during a part of the AC period.

  18. A Nafion-coated bismuth film electrode for the determination of heavy metals in vegetable using differential pulse anodic stripping voltammetry: An alternative to mercury-based electrodes.

    PubMed

    Xu, He; Zeng, Liping; Huang, Dekun; Xian, Yuezhong; Jin, Litong

    2008-08-15

    Mercury electrodes have been traditionally employed for achieving high reproducibility and sensitivity of the stripping technique. However, new alternative electrode materials are highly desired because of the toxicity of mercury. Bismuth is an electrode material characterized by its low toxicity and its ability to form alloys with some metals such as cadmium, lead and zinc, allowing their preconcentration at the electrode surface. In this work, we reported the simultaneous determination of Pb(II), Cd(II) and Zn(II) at the low ?g/l concentration levels by differential pulse anodic stripping voltammetry (DPASV) on a Nafion-coated bismuth film electrode (NCBFE) plated in situ, and investigated the application of NCBFE to heavy metals analysis in vegetable samples. The analytical performance of NCBFE was evaluated for simultaneous determination of Pb(II), Cd(II) and Zn(II) in non-deaerated solution, with the limits of determination of 0.30?g/l for Zn, 0.17?g/l for Cd and Pb at a preconcentration time of 180s. High reproducibility for NCBFE was indicated from the relative standard deviations of 2.4% for Pb, 2.0% for Cd and 3.4% for Zn at the 15?g/l level (n=15). The NCBFE was successfully applied to determine Pb and Cd in vegetable samples, and the results were in agreement with those of graphite furnace atomic absorption spectrometry (GFAAS). PMID:26049998

  19. 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…

  20. Stability of alternating current gliding arcs

    NASA Astrophysics Data System (ADS)

    Kusano, Yukihiro; Salewski, Mirko; Leipold, Frank; Zhu, Jiajian; Ehn, Andreas; Li, Zhongshan; Aldén, Marcus

    2014-10-01

    A gliding arc is a quenched plasma that can be operated as a non-thermal plasma at atmospheric pressure and that is thus suitable for large-scale plasma surface treatment. For its practical industrial use the discharge should be extended stably in ambient air. A simple analytical calculation based on Ohm's law indicates that the critical length of alternating current (AC) gliding arc discharge columns can be larger than that of a corresponding direct current (DC) gliding arc. This finding is supported by previously published images of AC and DC gliding arcs. Furthermore, the analysis shows that the critical length can be increased by increasing the AC frequency, decreasing the serial resistance and lowering the gas flow rate. The predicted dependence of gas flow rate on the arc length is experimentally demonstrated. The gap width is varied to study an optimal electrode design, since the extended non-equilibrium discharge can be extinguished due to the ignition of an arc discharge at the closest electrode gap. It is experimentally found that as the gap is wider, the discharge column tends to be longer.

  1. 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…

  2. Method of measuring direct and alternating currents with galvanic decoupling

    SciTech Connect

    Provotorov, I.V.; Simakov, S.R.; Che En Un

    1995-09-01

    A method is described for measuring direct and alternating microcurrents with galvanic decoupling. The method is based on the dependence of the current drawn by an operational amplifier circuit on the current measured. The measuring circuit is galvanically decoupled by a transformer which also supplies the power for the electronics. The error of measurement is less than 0.4% for direct current and 0.8% for alternating currents in the frequency band 20 Hz to 10 kHz.

  3. Alternating current neutral potentials on underground gas piping systems

    Microsoft Academic Search

    Lathrop

    1978-01-01

    Consumers Power Co. presents field-test and laboratory results to characterize alternating currents encountered on underground gas-piping systems. The currents measured are those deemed sufficient to cause arcing or shocks. Alternating currents occur in proximity to low-voltage electrical distribution systems, seemingly as the result of load differences among the conductors. Experiments prove that underground gas piping usually carries a majority or

  4. 27. LEUPOLD AND STEVENS MIDGET CURRENT METER (WITH ALTERNATE IMPELLER) ...

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

    27. LEUPOLD AND STEVENS MIDGET CURRENT METER (WITH ALTERNATE IMPELLER) AND FOLDING SCALE (MEASURED IN INCHES). - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  5. A Nafion-coated bismuth film electrode for the determination of heavy metals in vegetable using differential pulse anodic stripping voltammetry: An alternative to mercury-based electrodes

    Microsoft Academic Search

    He Xu; Liping Zeng; Dekun Huang; Yuezhong Xian; Litong Jin

    2008-01-01

    Mercury electrodes have been traditionally employed for achieving high reproducibility and sensitivity of the stripping technique. However, new alternative electrode materials are highly desired because of the toxicity of mercury. Bismuth is an electrode material characterized by its low toxicity and its ability to form alloys with some metals such as cadmium, lead and zinc, allowing their preconcentration at the

  6. Synthesis of Pt nanoparticles on electrochemically reduced graphene oxide by potentiostatic and alternate current methods

    SciTech Connect

    Molina, J.; Fernández, J.; Río, A.I. del; Bonastre, J.; Cases, F., E-mail: fjcases@txp.upv.es

    2014-03-01

    Reduced graphene oxide (RGO) has been synthesized on Pt wires by means of a potentiodynamic method between + 0.6 V and ? 1.4 V for 20 scans. Cyclic voltammetry characterization of the coatings showed the typical capacitative behavior of graphene. Pt nanoparticles were synthesized on Pt–RGO electrodes by means of potentiostatic methods and a comparison between different synthesis potentials (? 0.16, 0, + 0.2 and + 0.4 V) for the same synthesis charge (mC·cm{sup ?2}) was established. The electrodes obtained were characterized in 0.5 M H{sub 2}SO{sub 4} solution to observe the characteristic oxidation and reduction processes of the Pt surface. A 0.5 M H{sub 2}SO{sub 4}/0.5 M CH{sub 3}OH solution was used to measure the catalytic properties of the deposits against methanol oxidation. The most appropriate potential to perform the synthesis was 0 V followed by ? 0.16 V and + 0.2 V. The morphology of the coatings varied depending on the potential applied as observed by scanning electron microscopy. Alternate current methods were also used to synthesize Pt nanoparticles and compare the results with the traditional potentiostatic method. Different frequencies were used: 0.1, 1, 10, 100, 1000 and 10 000 Hz. Alternate current synthesis is more efficient than traditional potentiostatic methods, obtaining more electroactive coatings with less effective synthesis time. - Highlights: • Reduced graphene oxide has been obtained by electrochemical reduction on Pt wires. • Pt nanoparticles have been obtained potentiostatically at different potentials. • Pt nanoparticles have been obtained by ac methods with different frequencies. • ac synthesis is a better synthesis method than potentiostatic synthesis.

  7. Nonlinear response of superconductors to alternating fields and currents

    SciTech Connect

    McDonald, J.

    1997-10-08

    This report discusses the following topics on superconductivity: nonlinearities in hard superconductors such as surface impedance of a type II superconductimg half space and harmonic generation and intermodulation due to alternating transport currents; and nonlinearities in superconducting weak links such as harmonic generation by a long Josephson Junction in a superconducting slab.

  8. Adjunctive and alternative approaches to current reperfusion therapy

    PubMed Central

    Barreto, Andrew D.; Alexandrov, Andrei V.

    2012-01-01

    Background and Purpose Current ischemic stroke reperfusion therapy consists of intravenous (IV) thrombolysis given in eligible patients after review of a non-contrast CT scan and a time-based window of opportunity. Rapid clot lysis has a strong association with clinical improvement, but remains incomplete in many patients. This review appraises novel adjunctive or alternative approaches to current reperfusion strategies being tested in all trial phases. Summary of Review Alternative approaches to current reperfusion therapy can be separated into four main categories: 1) combinatory approaches with other drugs or devices; 2) novel systemic thrombolytic agents; 3) endovascular medical or mechanical reperfusion treatments and 4) non-invasive or minimally-invasive methods to augment cerebral blood flow and alleviate intracranial blood flow steal. Conclusions Reperfusion treatments must be provided as fast as possible in patients most likely to benefit. Patients who fail to rapidly reperfuse may benefit from other strategies that maintain collateral flow or protect tissue at risk. PMID:22223237

  9. Electrical Characteristics of an Alternating Current Plasma Igniter in Airflow

    NASA Astrophysics Data System (ADS)

    Zhao, Bingbing; He, Liming; Du, Hongliang; Zhang, Hualei

    2014-04-01

    The electrical characteristics of an alternating current (AC) plasma igniter were investigated for a working gas of air at atmospheric pressure. The discharge voltage and current were measured in air in both breakdown and stable combustion processes, respectively, and the current-zero phenomena, voltage-current (V-I) characteristics were studied for different working gas flow rates. The results indicated that the working gas between anode and cathode could be ionized to generate gas discharge when the voltage reached 8 kV, and the maximum current was 33.36 A. When the current came to zero, current-zero phenomena appeared with duration of 2 ?s. At the current-zero moment, dynamic resistance between electrodes became extremely high, and the maximum value could reach 445 k?, which was the main factor to restrain the current. With increasing working gas flow rates, the gradient of V-I characteristic curves was increased, as was the dynamic resistance. At a constant driven power, the discharge voltage increased.

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

    SciTech Connect

    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 to 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.

  11. A Treatise on the Theory of Alternating Currents

    NASA Astrophysics Data System (ADS)

    Russell, Alexander

    2014-05-01

    1. Introduction. Electrostatics. Magnetism. Electrodynamics; 2. Alternating current in an inductive circuit. Self inductance formulae. Rectangle concentric main. Cylindrical wires; 3. The inductance of circular and helical currents. Rayleigh's formula. Maximum inductance. Mutual inductance of coaxial coils. Lorenz's formula. Mathematical tables; 4. Effective values. Choking coil and condenser currents. Effects of wave shape. Resonance; 5. Electrostatic capacity. Maxwell's equations. Capacity formulae for parallel cylinders. The capacities of three core cables in terms of Maxwell's coefficients; 6. Capacity formulae for cables. The capacity coefficients of overhead wires; 7. High frequency currents. Complete solution for a concentric main. Parallel conductors. Mathematical tables; 8. Problems in connection with spherical electrodes. The capacity coefficients. The attractions and repulsion. The maximum value of the electric stress; 9. Current oscillations. Inductively coupled electric circuits. Forced oscillations; 10. The theory of the power factor. Phase difference; 11. The method of the complex variable. Graphical solution; 12. Vectors in space. Failure of graphical methods; 13. The measurement of power. Watt-hour meters; 14. The air core transformer. Circle diagrams; 15. The theory of three phase currents. Power measurement; 16. The theory of two phase currents. Power measurement; 17. The conversion of polyphase systems. Phase indicators; 18. Rotating magnetic fields. Guiding magnetic fields; 19. The magnetic field bound single and polyphase cables. Losses in single, two and three phase cables. Dielectric losses; 20. Eddy current losses. Metal plates. Metal cylinders; 21. The method of duality. Reciprocal theorems; Index; Symbols; Index.

  12. Experimental Study on Current Decay Characteristics of Persistent Current HTS Magnet by Alternating Magnetic Field

    NASA Astrophysics Data System (ADS)

    Park, Young Gun; Lee, Chang Young; Hwang, Young Jin; Lee, Woo Seung; Lee, Jiho; Jo, Hyun Chul; Chung, Yoon Do; Ko, Tae Kuk

    This paper deals with a current decay characteristics of a high temperature superconducting (HTS) magnet operated in persistent current mode (PCM). In superconducting synchronous machine applications such as linear synchronous motor (LSM), the superconducting coil is designed to operate in the PCM to obtain steady magnetic field with DC transport current. This superconducting magnet operates on a direct current, but it can be exposed to alternating magnetic field due to the armature winding. When the magnet is subjected to an external time-varying magnetic field, it is possible to result in a decay of the current in PCM system due to AC loss. In this research, a PCM system with armature coil which generates time-varying magnetic field was fabricated to verify current decay characteristics by external alternating magnetic field. The current decay rate was measured by using a hall sensor as functions of amplitude and frequency of armature coil.

  13. Some effects of alternating current on pipeline operation

    Microsoft Academic Search

    Hamlin

    1980-01-01

    Consumers Power Co. coupled field-test data with results of an IIT Research Institute study on powerline-pipeline interaction to characterize a pipeline's reaction to alternating current. An analysis of impedance relationships revealed that values of a-c pipe resistance for wall thicknesses over 0.188 in. (48 mm) vary in direct proportion to the pipe diameter. The corrosion engineer can measure the a-c

  14. A Simple Alternating Current Magnetometer of the Automatic Balancing Type

    Microsoft Academic Search

    Naoshi Ikeda; Kay Kohn

    1990-01-01

    An improvement of a Hartshorn type alternating current magnetometer is reported. The use of a dual channel oscillator, a two-phase lock-in amplifier and a personal computer enabled us to obtain a simple feedback system for automatic balancing of the bridge. The resolution of this system is about 3× 10-7 emu of magnetic moment or higher at the field of 0.8

  15. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Alternating-current ship's service switchboards. 111.30-25...111.30-25 Alternating-current ship's service switchboards. (a) Except...this section, each alternating-current ship's service switchboard must have...

  16. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Alternating-current ship's service switchboards. 111.30-25...111.30-25 Alternating-current ship's service switchboards. (a) Except...this section, each alternating-current ship's service switchboard must have...

  17. Flexible and transparent SWCNT electrodes for alternating current electroluminescence devices.

    PubMed

    Schrage, Christian; Kaskel, Stefan

    2009-08-01

    The application of transparent single-walled carbon nanotube (SWCNT) electrodes in rigid and flexible alternating current electroluminescence (ACEL) devices is demonstrated. SWCNT thin-film electrodes (50-160 nm) were made using a spray-coating process suitable for adjusting the transparency and sheet resistance. The dispersing procedure was optimized by comparing the transparency to sheet resistance ratio (T/R) of the electrodes. The emission intensity was as high as that for indium-tin oxide (ITO)-based ACEL devices with transparencies comparable to those of ITO-coated polymer slides. PMID:20355777

  18. Alternating current flow in internally flawed conductors: A tomographic analysis

    NASA Astrophysics Data System (ADS)

    Saguy, H.; Rittel, D.

    2006-08-01

    The alternating current potential drop technique is a nondestructive testing method that is mostly applied to estimate the depth of surface breaking flaws (e.g., cracks) in metallic conductors. When the flaw is hidden (internal or bottom cracks), other techniques (e.g., radiographic) must be used, which may only provide limited information on the location and dimensions of the hidden flaw. This work presents a detailed numerical analysis of ac flow in internally flawed conductors. The results can be used to reveal and estimate the dimensions and location of hidden flaws.

  19. 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…

  20. The development of monolithic alternating current light-emitting diode

    NASA Astrophysics Data System (ADS)

    Yeh, Wen-Yung; Yen, Hsi-Hsuan; Chan, Yi-Jen

    2011-02-01

    The monolithic alternating current light emitting diode (ACLED) has been revealed for several years and was regarded as a potential device for solid state lighting. In this study, we will discuss the characteristics, development status, future challenges, and ITRI's development strategy about ACLED, especially focusing on the development progress of the monolithic GaN-based Schottky barrier diodes integrated ACLED (SBD-ACLED). The SBD-ACLED design can not only improve the chip area utilization ratio but also provide much higher reverse breakdown voltage by integrating four SBDs with the micro-LEDs array in a single chip, which was regarded as a good on-chip ACLED design. According to the experimental results, higher chip efficiency can be reached through SBD-ACLED design since the chip area utilization ratio was increased. Since the principle and the operation condition of ACLED is quite different from those of the typical DCLED, critical issues for ACLED like the current droops, the flicker phenomenon, the safety regulations, the measurement standards and the power fluctuation have been studied for getting a practical and reliable ACLED design. Besides, the "AC LED application and research alliance" (AARA) lead by ITRI in Taiwan for the commercialization works of ACLED has also been introduced.

  1. Stripping Voltammetry of Pb and Cu using a Microcantilever Electrode

    SciTech Connect

    Bange, Adam [ORNL; Brown, Gilbert M [ORNL; Senesac, Larry R [ORNL; Thundat, Thomas George [ORNL

    2009-01-01

    Microfabricated silicon microcantilevers coated with gold on one side have been used as working electrode in a three-electrode electrochemical arrangement. In addition to electrochemical current, cantilever bending has been used as a signal for monitoring electrode reactions on the cantilever surface. The microcantilever bending was measured by an optical beam deflection method as the surface potential was scanned and electrochemical reactions occurred on the surface. The microcantilever bending due to differential surface stress was used to sense Pb and Cu using cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV).

  2. Stripping voltammetry of Pb and Cu using a microcantilever electrode

    NASA Astrophysics Data System (ADS)

    Bange, A. F.; Brown, G. M.; Senesac, L. R.; Thundat, T.

    2009-11-01

    Microfabricated silicon microcantilevers coated with gold on one side have been used as working electrode in a three-electrode electrochemical arrangement. In addition to electrochemical current, cantilever bending has been used as a signal for monitoring electrode reactions on the cantilever surface. The microcantilever bending was measured by an optical beam deflection method as the surface potential was scanned and electrochemical reactions occurred on the surface. The microcantilever bending due to differential surface stress was used to sense Pb and Cu using cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV).

  3. Influence of alternating, direct and superimposed alternating and direct current on the corrosion of mild steel in marine environments

    Microsoft Academic Search

    Srinivasan Muralidharan; Dae-Kyeong Kim; Tae-Hyun Ha; Jeong-Hyo Bae; Yoon-Cheol Ha; Hyun-Goo Lee; J. D. Scantlebury

    2007-01-01

    The corrosion of mild steel in marine environments was studied with respect to induced alternating current (AC), direct current (DC) and the superimposed AC+DC sources. Corrosion rate determination at the different applied AC, DC and AC+DC current densities was carried out by conventional weight loss method for the exposure period of 24 h. The quantitative estimation of leaching of iron

  4. Square wave voltammetry at the dropping mercury electrode: Theory

    USGS Publications Warehouse

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

    1977-01-01

    The theoretical aspects of square wave voltammetry at the dropping mercury electrode are presented. The technique involves scanning the entire potential range of interest on a single drop of a DME. Asymmetries in the waveform as well as variations in current measurement parameters are discussed. Indications are that previous uses of the waveform may not have utilized all its capabilities.

  5. Hardware model of a shipboard zonal electrical distribution system (ZEDS) : alternating current/direct current (AC/DC)

    E-print Network

    Tidd, Chad N. (Chad Norman)

    2010-01-01

    A hardware model of a shipboard electrical distribution system based on aspects of the DDG 51 Flight IIA, Arleigh Burke class, 60Hz Alternating Current (AC) and the future direct current (DC), zonal electrical distribution ...

  6. Investigation of properties of human epidermal membrane under constant conductance alternating current iontophoresis

    Microsoft Academic Search

    Honggang Zhu; Kendall D Peck; David J Miller; Mark R Liddell; Guang Yan; William I Higuchi; S. Kevin Li

    2003-01-01

    Previous studies in our laboratory have shown that enhanced, constant permeant fluxes across human skin can be achieved by applying an alternating current (AC) to maintain skin electrical conductance at a constant level. Relative to conventional direct current (DC) iontophoresis, for which current is maintained at a constant level, this newly developed constant conductance alternating current (CCAC) method achieves constant

  7. 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…

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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 have 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 one to two 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 that improvements in spectral quality may benefit certain compounds or classes of compounds, on an individual basis.

  9. Alternating current sensor with second-harmonic detection.

    PubMed

    Ferrari, J A; Perciante, C D; Dubra, A; Arnaud, A; Frins, E M

    2000-09-01

    We describe a novel optical sensor based on the Faraday effect for measuring ac. The sensing element is a piece of material of high Verdet constant placed between polarizers. When the angle between the polarizers differs by 45 degrees, a signal of twice the frequency of the ac is generated--in addition to the usual signal with the same frequency as the current. The quotient of these two signals allows a normalized output to be obtained that is proportional to the amplitude of the current. Experimental results demonstrating the practicality of the procedure are presented. PMID:18350054

  10. Hysterectomy—Current Methods and Alternatives for Benign Indications

    PubMed Central

    Papadopoulos, Michail S.; Tolikas, Athanasios C.; Miliaras, Dimosthenis E.

    2010-01-01

    Hysterectomy is the commonest gynecologic operation performed not only for malignant disease but also for many benign conditions such as fibroids, endometrial hyperplasia, adenomyosis, uterine prolapse, dysfunctional uterine bleeding, and cervical intraepithelial neoplasia. There are many approaches to hysterectomy for benign disease: abdominal hysterectomy, vaginal hysterectomy, laparoscopic assisted vaginal hysterectomy (LAVH) where a vaginal hysterectomy is assisted by laparoscopic procedures that do not include uterine artery ligation, total laparoscopic hysterectomy (TLH) where the laparoscopic procedures include uterine artery ligation, and subtotal laparoscopic hysterectomy (STLH) where there is no vaginal component and the uterine body is removed using a morcelator. In the last decades, many new techniques, alternative to hysterectomy with conservation of the uterus have been developed. They use modern technologies and their results are promising and in many cases comparable with hysterectomy. This paper is a review of all the existing hysterectomy techniques and the alternative methods for benign indications. PMID:20798870

  11. Current complementary and alternative therapies for multiple sclerosis

    Microsoft Academic Search

    Allen C. Bowling; Thomas M. Stewart

    2003-01-01

    Opinion statement  The use of complementary and alternative medicine (CAM) appears to be high in the general population and in patients with\\u000a multiple sclerosis (MS). There are no diets or dietary supplements that are definitely effective in altering the disease course\\u000a in MS. However, diets and dietary supplements that increase the intake of polyunsaturated fatty acids may produce mildly beneficial\\u000a effects.

  12. Investigation of the dissolution process of platinized titanium electrodes during electrolysis with alternating current

    Microsoft Academic Search

    E. K. Spasskaya; V. R. Kalinachenko; S. D. Khodkevich; I. V. Modestova; V. I. Tkachenko; L. M. Yalomenko

    1986-01-01

    The existence of a relative relationship between radiometrically determined corrosion rate of platinized electrodes was indicated during normal electrolysis with direct current and their polarization with alternating current in carbonate solutions. It is proposed to use the selected conditions of electrolysis with alternating current for comparative evaluation of corrosion resistance of the platinum coatings of various thicknesses and quantity. The

  13. Josephson effects in an alternating current biased transition edge sensor

    NASA Astrophysics Data System (ADS)

    Gottardi, L.; Kozorezov, A.; Akamatsu, H.; van der Kuur, J.; Bruijn, M. P.; den Hartog, R. H.; Hijmering, R.; Khosropanah, P.; Lambert, C.; van der Linden, A. J.; Ridder, M. L.; Suzuki, T.; Gao, J. R.

    2014-10-01

    We report the experimental evidence of the ac Josephson effect in a transition edge sensor (TES) operating in a frequency domain multiplexer and biased by ac voltage at MHz frequencies. The effect is observed by measuring the non-linear impedance of the sensor. The TES is treated as a weakly linked superconducting system and within the resistively shunted junction model framework. We provide a full theoretical explanation of the results by finding the analytic solution of the non-inertial Langevian equation of the system and calculating the non-linear response of the detector to a large ac bias current in the presence of noise.

  14. 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

    ...portable or mobile three-phase alternating current equipment; circuit breakers. 77...Low- and Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage...portable or mobile three-phase alternating current equipment; circuit breakers....

  15. 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

    ...circuits serving three-phase alternating current equipment; circuit breakers. 75...Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage...circuits serving three-phase alternating current equipment; circuit breakers....

  16. 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

    ...portable or mobile three-phase alternating current equipment; circuit breakers. 77...Low- and Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage...portable or mobile three-phase alternating current equipment; circuit breakers....

  17. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...circuits serving three-phase alternating current equipment; circuit breakers. 75...Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage...circuits serving three-phase alternating current equipment; circuit breakers....

  18. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...portable or mobile three-phase alternating current equipment; circuit breakers. 77...Low- and Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage...portable or mobile three-phase alternating current equipment; circuit breakers....

  19. 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

    ...circuits serving three-phase alternating current equipment; circuit breakers. 75...Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage...circuits serving three-phase alternating current equipment; circuit breakers....

  20. Modeling the Effects of Ion Association on Alternating Current Impedance of Solid Polymer Electrolytes

    E-print Network

    Modeling the Effects of Ion Association on Alternating Current Impedance of Solid Polymer model describing the transport of ions and associated ion pairs in solid polymer electrolytes subjected to small amplitude alternating current ac excitation. The model treats ion association as a reversible

  1. An alternative low-cost current-sensing scheme for high-current power electronics circuits

    Microsoft Academic Search

    Arthur Radun

    1995-01-01

    A lightweight and low-cost current sensor for application in high-current, high-frequency inverters and power converters is described. The current sensor consists of three elements. The first is a Rogowski coil, also known as a Maxwell Worm, which is a nonmagnetic toroid wound like an inductor. The output voltage at the open terminals of this winding is proportional to the time

  2. Alternating spin-polarized current induces parametric resonance in spin valves

    NASA Astrophysics Data System (ADS)

    Clerc, Marcel G.; Coulibaly, Saliya; Laroze, David; León, Alejandro O.; Núñez, Álvaro S.

    2015-06-01

    Ferromagnetic systems under the influence of spin-polarized currents exhibit rich spatiotemporal dynamics at nanoscales. We study spin-transfer nano-oscillators driven by the combination of alternating and direct spin-polarized electric currents. We show here that the alternating current induces parametric instabilities on spin valves, that is, the magnetization responses at half the forcing frequency. A spatial self-organization emerges as a result of the oscillatory current, which includes dissipative solitons and Faraday-type waves. The parametric regime is described analytically by means of the Landau-Lifshitz-Gilbert-Slonczewski equation, in good agreement with micromagnetic simulations including the full dipolar field.

  3. Improvement of photo-current density by alternative deposition method for organic photovoltaic cell

    Microsoft Academic Search

    T. Taima; Y. Shibata; J. Sakai; T. Miyadeara; T. Yamanari; Y. Yoshida

    2010-01-01

    Recently, power conversion efficiency of organic photovoltaic cell (OPV) has been upgraded due to high photo current density. An aggregation of organic molecules causes a reduction of photovoltaic performance owning to decline in film uniformity of organic layer. Here, we investigate the effect of alternative deposition method on controlling the aggregation and crystallization of organic layers. Advantage of the alternative

  4. Effect of Induced Alternating Current Voltage on Cathodically Protected Pipelines Paralleling Electric Power Transmission Lines

    Microsoft Academic Search

    F. Kajiyama; Y. Nakamura

    1999-01-01

    A field study was conducted to evaluate the effect of induced alternating current (AC) voltage on a cathodically protected pipeline paralleling an electric power transmission line. The study used the instant-off method, with steel probes simulating coating defects. Data regarding probe potentials and currents were compared with the proposed tentative criterion for cathodic protection (CP). Positive proof of the adequacy

  5. Current State of Research of Alternate Fuel Sources for Passenger Vehicles

    NASA Astrophysics Data System (ADS)

    Massey, Lee

    2008-03-01

    The purpose of this project is to report on the current state of research in the field of alternate fuel sources for passenger vehicles. Because the number of alternate fuel options is very large, this study focuses on selected bio-fuels and briefly describes a couple of the most popular non-bio and non-renewable alternatives. The fuel and energy sources studied are compared using well-to-wheel and well-to-tank net energy balances. Data also includes relative production capabilities by volume in terms of current fossil fuels. Qualitative data includes production methods and transportability.

  6. Direct-current-like Phase Space Manipulation Using Chirped Alternating Current Fields

    SciTech Connect

    P.F. Schmit and N.J. Fisch

    2010-02-01

    Waves in plasmas can accelerate particles that are resonant with the wave. A dc electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. Whereas wave-particle acceleration mechanisms have been widely discussed in the literature, this work discusses the direct analogy between wave acceleration and dc field acceleration in a particular parameter regime explored in previous works. Apart from the academic interest of this correspondence, there may be practical advantages in using waves to mimic dc electric fields, for example, in driving plasma current with high efficiency.

  7. Effects of alternating bias current on the low-frequency noise in dc SQUIDs

    SciTech Connect

    Kuriki, S.; Matsuda, M.; Matachi, A.

    1988-07-01

    We have analyzed the characteristics of flux modulated voltages of a dc SQUID for both positive and negative bias currents. It is shown that the change in the modulated voltage caused by fluctuations of the junction critical currents is eliminated after subtraction between the modulated voltages for the two biased currents. In the flux feedback mode using an alternating bias current, a large reduction of 1/f noise is observed for dc SQUIDs made of NbN junctions with amorphous Si tunnel barriers.

  8. Voltammetry based on fractional diffusion.

    PubMed

    Mirceski, Valentin; Tomovski, Zivorad

    2009-03-01

    A cyclic voltammetric experiment governed by anomalous diffusion of an electroactive species is theoretically analyzed by means of fractional calculus. The diffusion mass transfer under semi-infinite conditions at a planar electrode is ascribed by a Fick's second law-like differential equation in which the time derivative of the concentration function is of a fractional order alpha, ranging from 0 to 1. Rigorous solutions relating the concentrations of electroactive species with the electric current are derived by means of the Wright function for the case of a simple reversible electrode reaction of two chemically stable redox-active species having identical diffusion coefficients. A general mathematical solution for a voltammetric experiment, relating the surface concentrations with the current and electrode potential, is presented in the form of an integral equation. On the basis of the latter solution, the cyclic voltammetric experiment is simulated under variety of conditions, in order to inspect the influence of the fractional parameter alpha and to reveal its physical significance. Aiming to explain peculiar features of cyclic voltammograms, concentration profiles of electroactive species, together with the Cottrell-like equation, are analyzed for various alpha values. It has been established that the shape of a cyclic voltammogram depends strongly on alpha, varying from a steady-state sigmoid shape when alpha --> 0 to a conventional peak-like shape for alpha --> 1. Whereas the midpeak potential is independent of alpha, the peak currents are proportional to upsilon(alpha/2), where upsilon is the sweep rate. PMID:19243202

  9. 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 ? g/sq · cm compared to 744.81 ± 125.41 ? 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 ? 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. PMID:24959580

  10. Bridging thin and thick skin solutions for alternating currents in cracked conductors

    NASA Astrophysics Data System (ADS)

    Saguy, H.; Rittel, D.

    2005-08-01

    The alternating current potential drop (ACPD) technique is used to monitor surface cracks in electrical conductors. At high frequencies, the current flows in a superficial skin layer. Two distinct solutions are currently available for the thin and thick skin cases. However, there is no general solution that bridges these two modes in a seamless fashion. A numerical model is used to analyze the ACPD of a surface crack with uniform depth. A general solution is given that bridges the thin and thick skin solutions, which closely matches the numerical results, irrespective of the skin thickness.

  11. Micropumping of biofluids by alternating current electrothermal effects Meng Lian, and Kai Yang

    E-print Network

    Wu, Jayne

    Micropumping of biofluids by alternating current electrothermal effects Jie Wu,a Meng Lian, and Kai, effective micropumping and mixing still remain a challenge. Due to high surface/volume ratio at microscale fluids. Here we report a type of micropumps by ac electrothermal ACET effect. Pumping was demonstrated

  12. Study on optical efficiency of alternating-current thin-film electroluminescent devices

    Microsoft Academic Search

    Y. Yonghong; Zhang Jiayu; Gu Peifu; Tang jinfa

    1998-01-01

    An expression of the optical efficiency for alternating current thin film electroluminescent (ACTFEL) devices is given by a model of an optical microscopic cavity, and the optimization of the structure of the ACTFEL device is discussed. The model is reasonable since the radiation patterns developed by it coincide with the experimental results. The model indicates that in the ACTFEL device,

  13. Experimental Demonstration of the Equivalence of a Mechanically Oscillated Electrostatic Charge to an Alternating Current

    Microsoft Academic Search

    Richard C. Tolman; Daniel B. McRae

    1929-01-01

    Method of testing equivalence of a mechanically osciallted charge to an alternating current.-The apparatus consisted of a cylinder approximately 4 inches in diameter by 9 inches long, constructed of insulating material, but coated on the out-side with a thin sheet of copper foil which could be charged to potentials which varied from 1400 to 2600 volts. The cylinder was arranged

  14. Alternating Current Driven Electroluminescence from ZnSe/ZnS:Mn/

    E-print Network

    Alternating Current Driven Electroluminescence from ZnSe/ZnS:Mn/ ZnS Nanocrystals Vanessa Wood. Synthesis for stable ZnSe/ZnS:Mn/ZnS nanocrystals that exhibit a quantum yield of 65 ( 5% is outlined-TFEL devices consist of a phosphor layer, such as manganese-doped zinc sulfide (ZnS:Mn), vertically sandwiched

  15. 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…

  16. Determining pulsed alternator thyristor converter firing angles to produce a desired launcher current

    Microsoft Academic Search

    John A. Mallick; Mark Crawford

    2004-01-01

    Proposed electromagnetic launch systems using pulsed alternators usually employ a phase-angle-controlled thyristor converter to supply DC to the railgun launcher. By carefully choosing the firing angles of the individual thyristors, the system designers can control shape of the current pulse delivered to the launcher, thereby controlling projectile acceleration and magnetic energy recovery from the launcher after muzzle exit. This paper

  17. Determining pulsed alternator thyristor converter firing angles to produce a desired launcher current

    Microsoft Academic Search

    J. A. Mallick; M. Crawford

    2005-01-01

    Proposed electromagnetic launch systems using pulsed alternators usually employ a phase-angle-controlled thyristor converter to supply dc to the railgun launcher. By carefully choosing the firing angles of the individual thyristors, the system designers can control shape of the current pulse delivered to the launcher, thereby controlling projectile acceleration and magnetic energy recovery from the launcher after muzzle exit. This paper

  18. A simulation model for predicting the performance of a solar photovoltaic system with alternating current loads

    Microsoft Academic Search

    Y. Sukamongkol; S. Chungpaibulpatana; W. Ongsakul

    2002-01-01

    This paper describes the development of a simulation model for predicting the performance of a solar photovoltaic (PV) system under specified load requirements and prevailing meteorological conditions at the site location. This study is aimed at situations where the loads are provided by alternating current (AC) electrical devices. The model consists of several submodels for each of the main components

  19. Evaluation of Corrosive Degradation in Coated Steel Using Alternating Current Impedance Spectroscopy

    Microsoft Academic Search

    D. F. Wei; D. A. Jones; I. F. Chatterjee

    1995-01-01

    Alternating current (AC) impedance spectroscopy was applied to measure the degradation of steel coatings previously exposed to corrosive solutions such as tap water and 3% sodium chloride (NaCl). The method used was simple and quick and did not utilize electrochemical (potentiostatic) control. Previously immersed specimens of three types of coated steel were sandwiched between metallic foil electrodes and connected to

  20. Chemical synthesis of FePt nanoparticles with high alternate current magnetic susceptibility for biomedical applications

    Microsoft Academic Search

    Yoshitaka Kitamoto; Jing-Sha He

    2009-01-01

    The present paper describes ordered alloy FePt nanoparticles with high magnetic susceptibility to alternate current (ac) fields at around room temperature for biomedical applications such as magnetic sensing devices for diagnostics and magnetic hyperthermia for cancer therapy. Since ac magnetic susceptibility takes the maximum value at a temperature near the blocking temperature of magnetic nanoparticles, the blocking temperature of the

  1. Fabrication of nanoelectrodes based on controlled placement of carbon nanotubes using alternating-current electric field

    E-print Network

    Chen, Zhi

    . However, Chen et al.15 only obtained dense carbon nano- tubes aligned across two electrodes. In order modifying multiwalled nano- tubes MWNTs was demonstrated by using current-induced breakdown to eliminateFabrication of nanoelectrodes based on controlled placement of carbon nanotubes using alternating

  2. 9/18/09 2:43 PM'Big Wave' Theory Offers Alternative to Dark Energy // Current Page 1 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy.htm

    E-print Network

    Temple, Blake

    9/18/09 2:43 PM'Big Wave' Theory Offers Alternative to Dark Energy // Current Page 1 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy.htm login | register |home tv shows schedule to Dark Energy // Current Page 2 of 11http://current.com/items/90718274_big-wave-theory-offers-alternative-to-dark-energy

  3. Assessment of flow and cure monitoring using direct current and alternating current sensing in vacuum-assisted resin transfer molding

    NASA Astrophysics Data System (ADS)

    Vaidya, Uday K.; Jadhav, Nitesh C.; Hosur, Mahesh V.; Gillespie, John W., Jr.; Fink, Bruce K.

    2000-12-01

    Vacuum-assisted resin transfer molding (VARTM) is an emerging manufacturing technique that holds promise as an affordable alternative to traditional autoclave molding and automated fiber placement for producing large-scale structural parts. In VARTM, the fibrous preform is laid on a single-sided tool, which is then bagged along with the infusion and vacuum lines. The resin is then infused through the preform, which causes simultaneous wetting in its in-plane and transverse directions. An effective sensing technique is essential so that comprehensive information pertaining to the wetting of the preform, arrival of resin at various locations, cure gradients associated with thickness and presence of dry spots may be monitored. In the current work, direct current (dc) and alternating current sensing/monitoring techniques were adopted for developing a systematic understanding of the resin position and cure on plain weave S2-glass preforms with Dow Derakane vinyl ester VE 411-350, Shell EPON RSL 2704/2705 and Si-AN epoxy as the matrix systems. A SMARTweave dc sensing system was utilized to conduct parametric studies: (a) to compare the flow and cure of resin through the stitched and non-stitched preforms; (b) to investigate the influence of sensor positioning, i.e. top, middle and bottom layers; and (c) to investigate the influence of positioning of the process accessories, i.e. resin infusion point and vacuum point on the composite panel. The SMARTweave system was found to be sensitive to all the parametric variations introduced in the study. Furthermore, the results obtained from the SMARTweave system were compared to the cure monitoring studies conducted by using embedded interdigitated (IDEX) dielectric sensors. The results indicate that SMARTweave sensing was a viable alternative to obtaining resin position and cure, and was more superior in terms of obtaining global information, in contrast to the localized dielectric sensing approach.

  4. 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.

  5. 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

  6. Alternatives for blocking direct current in AC system neutrals at the Radisson/LG2 complex

    SciTech Connect

    Eitzmann, M.A.; Walling, R.A.; Sublich, M.; Kah, A. (GE Industrial and Power Systems, Power Systems Engineering Dept., Schenectady, NY (US)); Huynh, H.; Granger, M.; Dutil, A. (Hydro-Quebec, Montreal, Quebec (CA))

    1992-07-01

    Severe offset saturation results from the passage of direct current through power transformers. Such direct current can arise from geomagnetic disturbances, or resistive coupling of the substation ground to HVDC earth electrodes. This paper documents the development of alternative approaches for the design and application of blocking devices placed between transformer neutrals and the substation ground. System constraints on the impedance and overvoltage limitation of the neutral blocking device (NBD) are covered. Three alternative NBD schemes are developed and optimized. System performance of the NBD is discussed, as are the practical implementation considerations for this unconventional equipment application. Although the paper focuses on the NBD requirements of Hydro-Quebec's Radisson/LG2 complex, the fundamental information is applicable to any situation where dc must be clocked from a power transformer neutral in a system designed for effectively-grounded operation.

  7. 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.

  8. Alternating current and infrared produce an onset-free reversible nerve block

    PubMed Central

    Lothet, Emilie H.; Kilgore, Kevin L.; Bhadra, Niloy; Bhadra, Narendra; Vrabec, Tina; Wang, Yves T.; Jansen, E. Duco; Jenkins, Michael W.; Chiel, Hillel J.

    2014-01-01

    Abstract. Nerve block can eliminate spasms and chronic pain. Kilohertz frequency alternating current (KHFAC) produces a safe and reversible nerve block. However, KHFAC-induced nerve block is associated with an undesirable onset response. Optical inhibition using infrared (IR) laser light can produce nerve block without an onset response, but heats nerves. Combining KHFAC with IR inhibition [alternating current and infrared (ACIR)] produces a rapidly reversible nerve block without an onset response. ACIR can be used to rapidly and reversibly provide onset-free nerve block in the unmyelinated nerves of the marine mollusk Aplysia californica and may have significant advantages over either modality alone. ACIR may be of great clinical utility in the future.

  9. Effect of calcium, temperature, and polarizing currents upon alternating current excitation of space-clamped squid axons.

    PubMed

    Guttman, R; Hachmeister, L

    1971-09-01

    Alternating current threshold excitation of space-clamped squid giant axons was measured as a function of frequency, external calcium concentration, temperature (from 10 degrees to 35 degrees C), and hyper- and depolarizing steps. In normal axons there is usually an optimum frequency at about 120 Hz, at which the threshold is a minimum. The threshold rises at both lower and higher frequencies to give a resonance curve. Low calcium causes an increase in optimum frequency, a decrease in current threshold, and an increase in sharpness of tuning in both real axons and axons computed according to the Hodgkin-Huxley formulation; high calcium causes opposite effects. An increase in temperature causes an increase of optimum frequency, an increase in sharpness of tuning, and an increase in threshold current in both real and computed axons. The Q(10) for the effect of temperature upon optimum frequency is 1.8 in real and computed axons at moderate temperatures. Hyperpolarization causes (a) a decrease in optimum frequency, (b) a decrease in sharpness of tuning, and (c) an increase in threshold. Depolarization causes opposite effects. PMID:5095681

  10. Frequency dependence of the cardiac threshold to alternating current between 10 Hz and 160 Hz

    Microsoft Academic Search

    R. A. Malkin; A. de Jongh Curry

    2003-01-01

    It is still unclear what fundamental criteria influence the ability of alternating current (AC) to induce ventricular fibrillation\\u000a (VF) in vivo. As the VF threshold has a bowl-shaped relationship with frequency (showing a minimum threshold at some frequency),\\u000a similar to the nervous system, one proposed model has assumed that the mechanisms underlying AC stimulation of nerves are\\u000a at work for

  11. 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.

  12. Axial-time distribution of the basic parameters of an alternating-current arc plasma

    Microsoft Academic Search

    A. N. Kapitonov; M. A. Alekseev

    1976-01-01

    The conditions of atomic excitation i~ an alternating current arc have certain features connected with the periodic burning of the arc and the change in polarity of the electrodes. A series of papers [1-8] has been devoted to studying these features, part of these [1-41 is connected with investigations of a plasma arc between metal electrodes; the other part [6-8

  13. Alternating Current (AC) Iontophoretic Transport across Human Epidermal Membrane: Effects of AC Frequency and Amplitude

    Microsoft Academic Search

    Guang Yan; Qingfang Xu; Yuri G. Anissimov; Jinsong Hao; William I. Higuchi; S. Kevin Li

    2008-01-01

    Purpose  As a continuing effort to understand the mechanisms of alternating current (AC) transdermal iontophoresis and the iontophoretic\\u000a transport pathways in the stratum corneum (SC), the objectives of the present study were to determine the interplay of AC\\u000a frequency, AC voltage, and iontophoretic transport of ionic and neutral permeants across human epidermal membrane (HEM) and\\u000a use AC as a means to

  14. The Influence of Frequency of Alternating or Infrequently Reversed Current on Electrolytic Corrosion

    Microsoft Academic Search

    Burton McCollum; G. H. Ahlborn

    1916-01-01

    This paper describes experimental work done to determine the co-efficient of corrosion of iron and lead in soil with varying frequencies of alternating or reversed current with 60 cycles per second as the highest frequency and a two-week period as lowest?? some d-c. tests being made as a check on the methods. The results show (1), that a decrease of

  15. 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.

  16. Determination of Cadmium and Zinc in Water and Alloys by Adsorption Stripping Voltammetry

    Microsoft Academic Search

    Ali A. Ensafi; A. Benvidi; T. Khayamian

    2005-01-01

    A selective and sensitive method to determine of cadmium and zinc in water and alloy samples is proposed by adsorption stripping differential pulse cathodic voltammetry. The complexes of cadmium and zinc ions with xylenol orange (XO) are analyzed based on the adsorption collection onto a hanging mercury drop electrode (HMDE). The variation of peak currents with pH, XO concentration, potential

  17. 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. PMID:22504892

  18. Atmospheric pressure chemical ionization of explosives using alternating current corona discharge ion source.

    PubMed

    Usmanov, Dilshadbek Tursunbaevich; Chen, Lee Chuin; Yu, Zhan; Yamabe, Shinichi; Sakaki, Shigeyoshi; Hiraoka, Kenzo

    2015-04-01

    Ensuring public safety and security in today's mobile society requires robust detection technologies that are field-deployable and offer ever-improving sensitivity and specificity. Atmospheric pressure ionization is well suited to field-based sampling but pumping requirements to offset high gas loads can restrict an instrument's deployability and detection sensitivity. In the Special Feature, Usmanov and co-workers describe improved detection for nitrogen-containing explosive compounds using Atmospheric Pressure Chemical Ionization with an alternating current corona discharge source. An electromolded capillary yields a more stable ac corona allowing it to be positioned within 1mm from the inlet for detection limits in the tens of pg. PMID:26149117

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

    SciTech Connect

    Amutha Rani, D. [Department of Civil and Environmental Engineering, Imperial College, London SW7 2AZ (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom); Boccaccini, A.R. [Department of Materials, Imperial College, London SW7 2AZ (United Kingdom); Deegan, D. [Tetronics Ltd., South Marston Business Park, Swindon, Wiltshire SN3 4DE (United Kingdom); Cheeseman, C.R. [Department of Civil and Environmental Engineering, Imperial College, London SW7 2AZ (United Kingdom)], E-mail: c.cheeseman@imperial.ac.uk

    2008-11-15

    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.

  20. Effects of alternating and direct current in electrocoagulation process on the removal of cadmium from water.

    PubMed

    Vasudevan, Subramanyan; Lakshmi, Jothinathan; Sozhan, Ganapathy

    2011-08-15

    In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of cadmium from water using aluminum alloy as anode and cathode. The results showed that the removal efficiency of 97.5 and 96.2% with the energy consumption of 0.454 and 1.002 kWh kl(-1) was achieved at a current density of 0.2A/dm(2) and pH of 7.0 using aluminum alloy as electrodes using AC and DC, respectively. For both AC and DC, the adsorption of cadmium was preferably fitting Langmuir adsorption isotherm, the adsorption process follows second order kinetics and the temperature studies showed that adsorption was exothermic and spontaneous in nature. PMID:21612863

  1. 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. PMID:25616528

  2. Current Perspectives on the Use of Alternative Species in Human Health and Ecological Hazard Assessments

    PubMed Central

    Ankley, Gerald T.; Crofton, Kevin M.; Garcia-Reyero, Natàlia; LaLone, Carlie A.; Johnson, Mark S.; Tietge, Joseph E.; Villeneuve, Daniel L.

    2013-01-01

    Background: Traditional animal toxicity tests can be time and resource intensive, thereby limiting the number of chemicals that can be comprehensively tested for potential hazards to humans and/or to the environment. Objective: We compared several types of data to demonstrate how alternative models can be used to inform both human and ecological risk assessment. Methods: We reviewed and compared data derived from high throughput in vitro assays to fish reproductive tests for seven chemicals. We investigated whether human-focused assays can be predictive of chemical hazards in the environment. We examined how conserved pathways enable the use of nonmammalian models, such as fathead minnow, zebrafish, and Xenopus laevis, to understand modes of action and to screen for chemical risks to humans. Results: We examined how dose-dependent responses of zebrafish embryos exposed to flusilazole can be extrapolated, using pathway point of departure data and reverse toxicokinetics, to obtain human oral dose hazard values that are similar to published mammalian chronic toxicity values for the chemical. We also examined how development/safety data for human health can be used to help assess potential risks of pharmaceuticals to nontarget species in the environment. Discussion: Using several examples, we demonstrate that pathway-based analysis of chemical effects provides new opportunities to use alternative models (nonmammalian species, in vitro tests) to support decision making while reducing animal use and associated costs. Conclusions: These analyses and examples demonstrate how alternative models can be used to reduce cost and animal use while being protective of both human and ecological health. Citation: Perkins EJ, Ankley GT, Crofton KM, Garcia-Reyero N, LaLone CA, Johnson MS, Tietge JE, Villeneuve DL. 2013. Current perspectives on the use of alternative species in human health and ecological hazard assessments. Environ Health Perspect 121:1002–1010;?http://dx.doi.org/10.1289/ehp.1306638 PMID:23771518

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

    PubMed Central

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

    2015-01-01

    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/cm2 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. PMID:26084051

  4. Alternating Current Dielectrophoresis Optimization of Pt-Decorated Graphene Oxide Nanostructures for Proficient Hydrogen Gas Sensor.

    PubMed

    Wang, Jianwei; Rathi, Servin; Singh, Budhi; Lee, Inyeal; Joh, Han-Ik; Kim, Gil-Ho

    2015-07-01

    Alternating current dielectrophoresis (DEP) is an excellent technique to assemble nanoscale materials. For efficient DEP, the optimization of the key parameters like peak-to-peak voltage, applied frequency, and processing time is required for good device. In this work, we have assembled graphene oxide (GO) nanostructures mixed with platinum (Pt) nanoparticles between the micro gap electrodes for a proficient hydrogen gas sensors. The Pt-decorated GO nanostructures were well located between a pair of prepatterned Ti/Au electrodes by controlling the DEP technique with the optimized parameters and subsequently thermally reduced before sensing. The device fabricated using the DEP technique with the optimized parameters showed relatively high sensitivity (?10%) to 200 ppm hydrogen gas at room temperature. The results indicates that the device could be used in several industry applications, such as gas storage and leak detection. PMID:26042360

  5. Microalgae harvesting and cell disruption: a preliminary evaluation of the technology electroflotation by alternating current.

    PubMed

    de Carvalho Neto, Riamburgo Gomes; do Nascimento, José Gilmar da Silva; Costa, Mayara Carantino; Lopes, Alexandre Colzi; Abdala Neto, Eliezer Fares; Filho, César Rossas Mota; Dos Santos, André Bezerra

    2014-01-01

    Some species of microalgae have high productivity and lipid content, which makes them good candidates for biodiesel production. Biomass separation and cell disruption are important steps in biodiesel production from microalgae. In this work, we explored the fundamentals of electroflotation by alternating current (EFAC) with non-consumable electrodes to simultaneously harvest microalgae and disrupt cells from mixed microalgae obtained from waste stabilization ponds. The harvesting efficiency was evaluated using chlorophyll-a and turbidity, which reached removals of 99% and 95%, respectively, during a batch time of 140 min. Cell disruption was evaluated using lipid extraction, and the best results were achieved with a batch time of 140 min, which resulted in a 14% yield. Therefore, EFAC was shown to be an attractive potential technology for simultaneous microalgal harvesting and cell disruption. PMID:25051479

  6. 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

    2015-01-01

    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. PMID:26084051

  7. Alternating current cloud point extraction on a microchip: the effect of electrode geometry.

    PubMed

    Sasaki, Naoki; Maekawa, Chisaki; Sato, Kae

    2015-02-01

    We report on the effect of electrode geometry on alternating current cloud point extraction (ACPE). ACPE is a technique utilized to extract membrane-associated biomolecules in an electrode-integrated microfluidic channel. In this study, we investigated the effect of gap size (4?22 ?m) between microband electrodes on ACPE. A decrease in gap size resulted in efficient and rapid concentration of fluorescent-labeled phospholipids, a model of membrane-associated biomolecules. We also investigated the effect of applied voltage amplitude on ACPE using devices with decreased electrode gap size. When the gap was small, ACPE was achieved with low applied voltages. ACPE of membrane proteins extracted from HeLa cells was also studied to demonstrate the applicability of the ACPE to real samples. The results provide a guideline to improve the performance of ACPE and facilitate application of the ACPE technique as part of an overall analytical process. PMID:25224325

  8. The effects of alternating electric fields in glioblastoma: current evidence on therapeutic mechanisms and clinical outcomes.

    PubMed

    Rehman, Azeem A; Elmore, Kevin B; Mattei, Tobias A

    2015-03-01

    Glioblastoma is both the most common and most lethal primary CNS malignancy in adults, accounting for 45.6% of all malignant CNS tumors, with a 5-year survival rate of only 5.0%, despite the utilization of multimodal therapy including resection, chemotherapy, and radiation. Currently available treatment options for glioblastoma often remain limited, offering brief periods of improved survival, but with substantial side effects. As such, improvements in current treatment strategies or, more likely, the implementation of novel strategies altogether are warranted. In this topic review, the authors provide a comprehensive review on the potential of alternating electric fields (AEFs) in the treatment of glioblastoma. Alternating electric fields-also known as tumor-treating fields (TTFs)-represent an entirely original therapeutic modality with preliminary studies suggesting comparable, and at times improved, efficacy to standard chemotherapeutic agents in the treatment of recurrent glioblastoma. A recent multicenter, Phase III, randomized clinical trial comparing NovoTTF-100A monotherapy to physician's best choice chemotherapy in patients with recurrent glioblastoma revealed that AEFs have similar efficacy to standard chemotherapeutic agents with a more favorable side-effects profile and improved quality of life. In particular, AEFs were shown to have limited systemic adverse effects, with the most common side effect being contact dermatitis on the scalp at the sites of transducer placement. This study prompted FDA approval of the NovoTTF-100A system in April 2011 as a standalone therapy for treatment of recurrent glioblastoma refractory to surgical and radiation treatment. In addition to discussing the available clinical evidence regarding the utilization of AEFs in glioblastoma, this article provides essential information regarding the supposed therapeutic mechanism as well as modes of potential tumor resistance to such novel therapy, delineating future perspectives regarding basic science research on the issue. PMID:25727223

  9. Adsorptive stripping voltammetry of antibiotics rifamycin SV and rifampicin at renewable pencil electrodes.

    PubMed

    Kawde, Abdel-Nasser; Temerk, Yassein; Farhan, Nasser

    2014-01-01

    Adsorptive stripping voltammetry of antibiotics of rifamycin SV (RSV) and rifampicin (RIF) was investigated by cyclic voltammetry and differential pulse voltammetry using a renewable pencil graphite electrode (PGE). The nature of the oxidation process of RSV and RIF taking place at the PGE was characterized. The results show that the determination of highly sensitive oxidation peak current is the basis of a simple, accurate and rapid method for quantification of RSV and RIF in bulk forms, pharmaceutical formulations and biological fluids by differential pulse adsorptive stripping voltammetry (DPASV). Factors influencing the trace measurement of RSV and RIF at PGE are assessed. The limits of detection for the determination of RSV and RIF in bulk forms are 6.0 × 10(-8) mol/L and 1.3 × 10(-8) mol/L, respectively. Moreover, the proposed procedure was successfully applied to assay both RSV and RIF in pharmaceutical formulations and in biological fluids. The capability of the proposed procedure for simultaneous assay of antibiotics RSV-isoniazid and RIF-isoniazid was achieved. The statistical analysis and calibration curve data for trace determination of RSV and RIF are reported. PMID:25125124

  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 electrophoretic deposition (EPD) of TiO2 nanoparticles in aqueous suspensions.

    PubMed

    Chávez-Valdez, A; Herrmann, M; Boccaccini, A R

    2012-06-01

    TiO(2)-nanostructured coatings from aqueous suspensions have been successfully prepared by the application of alternating current (AC) instead of direct current (DC) during electrophoretic deposition (EPD). No organic additives in suspension were required for successful EPD. The quality of the AC-EPD TiO(2) coatings in terms of homogeneity and extent of microcracking, upon drying, observed by SEM, was superior to that of DC-EPD coatings made from the same type of suspensions. The main difference between AC- and DC-EPD was the suppression of bubble formation. The absence of water electrolysis at the electrodes can be explained by the particular distribution of the electric field during AC mode, which prevents the nucleation of bubbles. The preparation of TiO(2) coatings from aqueous suspension and without the aid of organic stabilizers opens the possibility for co-deposition of sensitive materials such as biomolecules and even cells for biomedical applications, given the high biocompatibility of TiO(2). The deposition of TiO(2) coatings from aqueous suspensions is also attractive from environmental and economical points of view. PMID:22429587

  12. Effects of high-frequency alternating current on axonal conduction through the vagus nerve

    NASA Astrophysics Data System (ADS)

    Waataja, Jonathan J.; Tweden, Katherine S.; Honda, Christopher N.

    2011-10-01

    High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both A? and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The A? waves were more sensitive than C waves to HFAC blockade, but they required more time to recover.

  13. Alternating current electrical stimulation enhanced chemotherapy: a novel strategy to bypass multidrug resistance in tumor cells

    PubMed Central

    Janigro, Damir; Perju, Catalin; Fazio, Vincent; Hallene, Kerri; Dini, Gabriele; Agarwal, Mukesh K; Cucullo, Luca

    2006-01-01

    Background Tumor burden can be pharmacologically controlled by inhibiting cell division and by direct, specific toxicity to the cancerous tissue. Unfortunately, tumors often develop intrinsic pharmacoresistance mediated by specialized drug extrusion mechanisms such as P-glycoprotein. As a consequence, malignant cells may become insensitive to various anti-cancer drugs. Recent studies have shown that low intensity very low frequency electrical stimulation by alternating current (AC) reduces the proliferation of different tumor cell lines by a mechanism affecting potassium channels while at intermediate frequencies interfere with cytoskeletal mechanisms of cell division. The aim of the present study is to test the hypothesis that permeability of several MDR1 over-expressing tumor cell lines to the chemotherapic agent doxorubicin is enhanced by low frequency, low intensity AC stimulation. Methods We grew human and rodent cells (C6, HT-1080, H-1299, SKOV-3 and PC-3) which over-expressed MDR1 in 24-well Petri dishes equipped with an array of stainless steel electrodes connected to a computer via a programmable I/O board. We used a dedicated program to generate and monitor the electrical stimulation protocol. Parallel cultures were exposed for 3 hours to increasing concentrations (1, 2, 4, and 8 ?M) of doxorubicin following stimulation to 50 Hz AC (7.5 ?A) or MDR1 inhibitor XR9576. Cell viability was assessed by determination of adenylate kinase (AK) release. The relationship between MDR1 expression and the intracellular accumulation of doxorubicin as well as the cellular distribution of MDR1 was investigated by computerized image analysis immunohistochemistry and Western blot techniques. Results By the use of a variety of tumor cell lines, we show that low frequency, low intensity AC stimulation enhances chemotherapeutic efficacy. This effect was due to an altered expression of intrinsic cellular drug resistance mechanisms. Immunohistochemical, Western blot and fluorescence analysis revealed that AC not only decreases MDR1 expression but also changes its cellular distribution from the plasma membrane to the cytosol. These effects synergistically contributed to the loss of drug extrusion ability and increased chemo-sensitivity. Conclusion In the present study, we demonstrate that low frequency, low intensity alternating current electrical stimulation drastically enhances chemotherapeutic efficacy in MDR1 drug resistant malignant tumors. This effect is due to an altered expression of intrinsic cellular drug resistance mechanisms. Our data strongly support a potential clinical application of electrical stimulation to enhance the efficacy of currently available chemotherapeutic protocols. PMID:16545134

  14. Functional MRI of galvanic vestibular stimulation with alternating currents at different frequencies.

    PubMed

    Stephan, Thomas; Deutschländer, Angela; Nolte, Annina; Schneider, Erich; Wiesmann, Martin; Brandt, Thomas; Dieterich, Marianne

    2005-07-01

    Functional MRI was performed in 28 healthy volunteers to study the effects of galvanic vestibular stimulation with alternating currents (AC-GVS) of different frequencies on brain activation patterns. The aims of this study were (1) to identify specific areas within the vestibular cortical network that are involved in the processing of frequency-specific aspects by correlation analyses, (2) to determine the optimal frequency for stimulation of the vestibular system with respect to perception, and (3) to analyze whether different frequencies of AC-GVS are mediated in different cortical areas or different sites within the vestibular cortex. AC-GVS was performed using sinusoidal stimulation currents with an amplitude of +/-2.5 mA, and frequencies of 0.1 Hz, 0.3 Hz, 0.8 Hz, 1.0 Hz, 2.0 Hz, and 5.0 Hz were applied. Regardless of the applied stimulation frequency, AC-GVS elicited activations within a network of multisensory areas similar to those described in earlier studies using direct currents. No mapping of different stimulation frequencies to different cortical locations was observed. Additional activations of somatosensory cortex areas were observed during stimulation with 5 Hz only. The strongest vestibular sensations were reported during stimulation with 1 Hz and 2 Hz. Correlation analyses between blood oxygenation level dependent (BOLD) signal changes and stimulation frequency revealed a positive dependency in areas of the supramarginal gyrus, posterolateral thalamus, cerebellar vermis, posterior insula, and in the hippocampal region/uncus. These regions represent areas involved in the processing of vestibular information for head and body orientation in space. PMID:15955481

  15. Measuring bioavailable copper using anodic stripping voltammetry

    SciTech Connect

    Deaver, E.; Rodgers, J.H. Jr. [Univ. of Mississippi, University, MS (United States). Dept. of Biology

    1996-11-01

    Since speciation can affect bioavailability and toxicity of copper in aquatic systems, accurate predictions of effects of bioavailable forms require detection and/or measurement of these forms. To develop an approach for measurement of bioavailable copper, a copper sulfate solution was used in 10-d aqueous and sediment toxicity tests with Hyalella azteca Saussure. These tests encompassed ranges of pH, alkalinity, hardness, and conductivity. Changes in copper speciation were measured using atomic absorption spectroscopy (AA) for dissolved copper and differential pulse anodic stripping voltammetry (DPASV) for labile copper, and concentrations were evaluated relative to amphipod survival. Ten-day LC50s based on AA-measured aqueous copper concentrations ranged from 42 to 142 {micro}g Cu/L, and LC50s based on DPASV-measured copper concentrations ranged from 17.4 to 24.8 {micro}g Cu/L. In 10-d tests using copper-amended sediments with diverse characteristics and AA-measured copper concentrations spanning an order of magnitude, total copper concentrations were not predictive of sediment toxicity, but H. azteca survival was explained by DPASV measurements that varied by {le}4%. In order to make defensible estimates of the potential risk of metals in sediments or water, it is essential to identify the fraction of total metal that is bioavailable. In these experiments, DPASV was useful for measuring bioavailable copper in aqueous and sediment tests with H. azteca.

  16. Alternative solutions to the current situation of oocyte donation in Singapore.

    PubMed

    Heng, Boon Chin

    2006-03-01

    The rising incidence of age-related female infertility in Singapore, coupled with the prohibition on commercialized oocyte donation and egg sharing, has resulted in a severe shortage of donor oocytes. Infertile women are routinely encouraged by fertility doctors here to seek their close relatives and friends as prospective oocyte donors, which does not alleviate the shortage. A number of alternative solutions are discussed. The use of substantial financial remuneration to encourage oocyte donation is rejected as being legally, ethically and morally incompatible with present day Singaporean society. Egg sharing in return for subsidized fertility may have a strong case for ethical justification, but implementation would need amendment of the current legislation in Singapore. Cross- and mirror-exchange oocyte donations face less of a legal challenge in Singapore and also have a strong case for ethical justification. However, special consideration must be given to the unique socio-cultural values of Singaporean society, i.e. traditional Chinese culture. Finally, if no changes are made to restrictive regulations governing oocyte donation in Singapore, and shortage of donor oocytes still persists, then reproductive tourism abroad may be the solution for some patients; referrals by local fertility doctors are unlikely to be allowed in Singapore. PMID:16569312

  17. A simple separation method with a microfluidic channel based on alternating current potential modulation.

    PubMed

    Noh, Hui-Bog; Chandra, Pranjal; Kim, You-Jeong; Shim, Yoon-Bo

    2012-11-20

    A simple separation and detection system based on an electrochemical potential modulated microchannel (EPMM) device was developed for the first time. The application of alternating current (AC) potential to the microfluidic separation channel walls, which were composed of screen printed carbon electrodes, resulted in the oscillation and fluctuation of analytes and in the formation of a perfect flat flow front. These events resulted in an increase in the effective concentration and in the fine separation of samples. The performance of the EPMM device was examined through the analysis of endocrine disruptors (EDs) and heavy metal ions (HMIs) as model compounds. The analytical parameters that affected the separation and detection of EDs and HMIs were studied in terms of AC amplitude, AC frequency, flow rate, buffer concentration, pH, detection potential, and temperature. The separation efficiency was evaluated through measurements of the theoretical plate number (N), the retention time, and the half-peak width. Linear calibration plots for the detection of EDs and HMIs were obtained between 0.15 and 250.0 nM (detection limit 86.4 ± 2.9 pM) and between 0.01 and 10.0 nM (detection limit 9.5 ± 0.3 pM), respectively. The new device was successfully demonstrated with authentic and real samples. PMID:23075295

  18. Demagnetization treatment of remanent composite microspheres studied by alternating current susceptibility measurements.

    PubMed

    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

  19. Manipulating single annealed polyelectrolyte under alternating current electric fields: Collapse versus accumulation.

    PubMed

    Wang, Shengqin; Zhu, Yingxi

    2012-06-01

    Effective manipulation and understanding of the structural and dynamic behaviors of a single polyelectrolyte (PE) under alternating current (AC) electric fields are of great scientific and technological importance because of its intimate relevance to emerging bionanotechnology. In this work, we employ fluorescence correlation spectroscopy (FCS) to study the conformational and AC-electrokinetic behaviors of a model annealed PE, poly(2-vinyl pyridine) (P2VP) under both spatially uniform and non-uniform AC fields at a single molecule level. Under spatially uniform AC-fields, we observe a gradual and continuous coil-to-globule conformational transition (CGT) of single P2VP at varied AC-frequency when a critical AC-field strength is exceeded, in contrast to the pH-induced abrupt CGT in the absence of AC-fields. On the contrary, under spatially non-uniform AC-fields, we observe field-driven net flow and accumulation of P2VP near high AC-field regions due to combined AC electro-osmosis and dielectrophoresis but surprisingly no conformational change. Thus, distinct AC-electric polarization effect on single annealed PE subject to AC-field homogeneity is suggested. PMID:22655024

  20. Manipulating single annealed polyelectrolyte under alternating current electric fields: Collapse versus accumulation

    PubMed Central

    Wang, Shengqin; Zhu, Yingxi

    2012-01-01

    Effective manipulation and understanding of the structural and dynamic behaviors of a single polyelectrolyte (PE) under alternating current (AC) electric fields are of great scientific and technological importance because of its intimate relevance to emerging bionanotechnology. In this work, we employ fluorescence correlation spectroscopy (FCS) to study the conformational and AC-electrokinetic behaviors of a model annealed PE, poly(2-vinyl pyridine) (P2VP) under both spatially uniform and non-uniform AC fields at a single molecule level. Under spatially uniform AC-fields, we observe a gradual and continuous coil-to-globule conformational transition (CGT) of single P2VP at varied AC-frequency when a critical AC-field strength is exceeded, in contrast to the pH-induced abrupt CGT in the absence of AC-fields. On the contrary, under spatially non-uniform AC-fields, we observe field-driven net flow and accumulation of P2VP near high AC-field regions due to combined AC electro-osmosis and dielectrophoresis but surprisingly no conformational change. Thus, distinct AC-electric polarization effect on single annealed PE subject to AC-field homogeneity is suggested. PMID:22655024

  1. Spatially variant red blood cell crenation in alternating current non-uniform fieldsa

    PubMed Central

    An, Ran; Wipf, David O.; Minerick, Adrienne R.

    2014-01-01

    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??m 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. PMID:24753734

  2. Alternating current potential drop for measuring the case depth of hardened steel

    NASA Astrophysics Data System (ADS)

    Quddes, Mohammad R.; Ji, Yuan; Bowler, John R.

    2015-03-01

    Multi-frequency alternate current potential drop measurements have been made to estimate the case depth of case hardened steels using four point probes. The probes have four parallel sprung loaded pins in a line with a 1.5 mm separation between the contact points. A printed circuit board has been used to ensure the electrical connections to the pins are close to the surface of the material. This has the effect of reducing the mutual induction between driver and pick-up pins. The case depth is estimated from measurements at frequencies typically from 10 Hz to 10 kHz. The real part of the voltage phasor representing the AC potential drop is used to evaluate the case depth. The imaginary part includes the contribution due to mutual induction. To estimate the case depth of the hardened samples, the measured potential drop has been fitted to theoretical predictions. The substrate material properties of the hardened samples are extracted from multi-frequency potential drop measurements on non-harden samples. The estimated case hardened depths, deduced from potential drop measurements, are similar to those found from destructive measurements.

  3. 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. PMID:26149109

  4. Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.

    PubMed

    Keithley, Richard B; Takmakov, Pavel; Bucher, Elizabeth S; Belle, Anna M; Owesson-White, Catarina A; Park, Jinwoo; Wightman, R Mark

    2011-05-01

    Fast-scan cyclic voltammetry (FSCV) with carbon-fiber microelectrodes has been successfully used to detect catecholamine release in vivo. Generally, waveforms with anodic voltage limits of 1.0 or 1.3 V (vs Ag/AgCl) are used for detection. The 1.0 V excursion provides good temporal resolution but suffers from a lack of sensitivity. The 1.3 V excursion increases sensitivity but also increases response time, which can blur the detection of neurochemical events. Here, the scan rate was increased to improve the sensitivity of the 1.0 V excursion while maintaining the rapid temporal response. However, increasing scan rate increases both the desired faradaic current response and the already large charging current associated with the voltage sweep. Analog background subtraction was used to prevent the analog-to-digital converter from saturating from the high currents generated with increasing scan rate by neutralizing some of the charging current. In vitro results with the 1.0 V waveform showed approximately a 4-fold increase in signal-to-noise ratio with maintenance of the desired faster response time by increasing scan rate up to 2400 V/s. In vivo, stable stimulated release was detected with an approximate 4-fold increase in peak current. The scan rate of the 1.3 V waveform was also increased, but the signal was unstable with time in vitro and in vivo. Adapting the 1.3 V triangular wave into a sawhorse design prevented signal decay and increased the faradaic response. The use of the 1.3 V sawhorse waveform decreased the detection limit of dopamine with FSCV to 0.96 ± 0.08 nM in vitro and showed improved performance in vivo without affecting the neuronal environment. Electron microscopy showed dopamine sensitivity is in a quasi-steady state with carbon-fiber microelectrodes scanned to potentials above 1.0 V. PMID:21473572

  5. Stoichiometry and Formation Constant Determination by Linear Sweep Voltammetry.

    ERIC Educational Resources Information Center

    Schultz, Franklin A.

    1979-01-01

    In this paper an experiment is described in which the equilibrium constants necessary for determining the composition and distribution of lead (II)-oxalate species may be measured by linear sweep voltammetry. (Author/BB)

  6. Orchestrating neuronal networks: sustained after-effects of transcranial alternating current stimulation depend upon brain states

    PubMed Central

    Neuling, Toralf; Rach, Stefan; Herrmann, Christoph S.

    2013-01-01

    The interest in transcranial alternating current stimulation (tACS) has significantly increased in the past decade. It has potential to modulate brain oscillations in a frequency specific manner, offering the possibility to demonstrate a causal nature of oscillation behavior relationships. TACS is a strong candidate as a tool for clinical applications, however, to fulfill this potential, certain parameters have yet to be evaluated. First, little is known about long-lasting after-effects of tACS with respect to the modulations of rhythmic brain activity. Second, the power of endogenous brain oscillations might play a crucial role in the efficacy of tACS. We hypothesize that the after-effects of tACS depend on the endogenous power of oscillations. To this end, we modulated the power of endogenous occipital alpha oscillations via tACS. In two experiments, participants either had their eyes open or closed to keep endogenous alpha power either low or high while they were stimulated for 20 min with their individual alpha frequency (IAF) and simultaneously performing a vigilance task. After-effects on IAF power were evaluated over a course of 30 min with a pre stimulation period serving as baseline. After-effects were strongly dependent on IAF power. Enhanced IAF power was observed for at least 30 min after tACS under conditions of low endogenous IAF power, whereas, IAF power could not be further enhanced by tACS under conditions of high IAF power. The current study demonstrates, for the first time, a long lasting effect after tACS on endogenous EEG power in the range of the stimulation frequency. Additionally, we present conclusive evidence that the power of the endogenous oscillations has a critical impact on tACS efficacy. Long lasting after-effects foster the role of tACS as a tool for non-invasive brain stimulation and demonstrate the potential for therapeutic application to reestablish the balance of altered brain oscillations. PMID:23641206

  7. Monitoring the Escape of DNA from a Nanopore Using an Alternating Current Signal

    PubMed Central

    Lathrop, Daniel K.; Ervin, Eric N.; Barrall, Geoffrey A.; Keehan, Michael G.; Kawano, Ryuji; Krupka, Michael A.; White, Henry S.; Hibbs, Andrew H.

    2010-01-01

    We present the use of an alternating current (AC) signal as a means to monitor the conductance of an ?-hemolysin (?HL) pore as a DNA hairpin with a polydeoxyadenosine tail is driven into and released from the pore. Specifically, a 12 base pair DNA hairpin attached to a 50-nucleotide poly-A tail (HP-A50) is threaded into an ?HL channel using a DC driving voltage. Once the HP-A50 molecule is trapped within the ?HL channel, the DC driving voltage is turned off and the conductance of the channel is monitored using an AC voltage. The escape time, defined as the time it takes the HP-A50 molecule to transport out of the ?HL channel, is then measured. This escape time has been monitored as a function of AC amplitude (20 to 250 mVac), AC frequency (60–200 kHz), DC drive voltage (0 to 100 mVdc), and temperature (?10 to 20 °C), in order to determine their effect on the predominantly diffusive motion of the DNA through the nanopore. The applied AC voltage used to monitor the conductance of the nanopore has been found to play a significant role in the DNA/nanopore interaction. The experimental results are described by a one-dimensional asymmetric periodic potential model that includes the influence of the AC voltage. An activation enthalpy barrier of 1.74 × 10?19 J and a periodic potential asymmetry parameter of 0.575 are obtained for the diffusion at zero electrical bias of a single nucleotide through ?HL. PMID:20099878

  8. Disposable copper-based electrochemical sensor for anodic stripping voltammetry.

    PubMed

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

    2014-05-20

    In this work, we report the first copper-based point-of-care sensor for electrochemical measurements demonstrated by zinc determination in blood serum. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Electrochemistry offers a simple approach to metal detection on the microscale, but traditional carbon, gold (Au), or platinum (Pt) electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor features a new low-cost electrode material, copper, which offers simple fabrication and compatibility with microfabrication and PCB processing, while maintaining competitive performance in electrochemical detection. Anodic stripping voltammetry of zinc using our new copper-based sensors exhibited a 140 nM (9.0 ppb) limit of detection (calculated) and sensitivity greater than 1 ?A/?M in the acetate buffer. The sensor was also able to determine zinc in a bovine serum extract, and the results were verified with independent sensor measurements. These results demonstrate the advantageous qualities of this lab-on-a-chip electrochemical sensor for clinical applications, which include a small sample volume (?L scale), reduced cost, short response time, and high accuracy at low concentrations of analyte. PMID:24773513

  9. Simultaneous Determination of Urinary Cadmium, Cobalt, Lead, and Nickel Concentrations in Steel Production Workers by Differential Pulse Stripping Voltammetry

    Microsoft Academic Search

    Ching-Jyi Horng; Ping-Hua Horng; John W. Hsu; Jin-Lian Tsai

    2003-01-01

    Screening for metals in urine is important because toxic levels of these elements are linked to disease. In the current study, the authors used differential pulse stripping voltammetry on a hanging mercury drop electrode for the simultaneous determination of cadmium, cobalt, lead, and nickel in the urine of 63 production and 63 quality control workers in a steel production plant,

  10. Investigation of resonant ac-dc (alternating current-direct current) magnetic field effects. Final report, May 1986-July 1989

    SciTech Connect

    Durney, C.H.; Janata, J.; Rappaport, C.; Kaminski, M.; Bruckner-Lea, C.

    1989-07-10

    Recently reported observations by others indicate that a combination of a weak dc magnetic field and extra-low-frequency ac magnetic fields can produce resonant effects in biological systems. Our studies of resonant magnetic field effects consist of three parts: (1) calculations aimed at identifying the basic mechanism underlying the resonance, (2) measurements of the effects of combined dc and ac magnetic fields on the dc current through plain (containing no channels) planar phospholipid membranes, and (3) measurements of the effects of combined dc and ac magnetic fields on the binding of metallochromic dyes and calmodulin to calcium. The calculations have provided insight and a physical mechanism that explains both frequency and amplitude windows in an elementary model consisting of one charged particle in a viscous medium. The combined dc-ac magnetic fields did affect the dc current through planar phospholipid membranes, but not in every membrane, and not consistently at the same values of magnetic field strength and frequency. No effect of the magnetic fields were seen on the binding of metallochromic dyes and calmodulin to calcium. None of our measurements showed any resonant response like the cyclotron like resonance reported in the literature in diatoms and lymphocytes. Keywords: Magnetic fields; Phospholipid membranes; Calcium bindings; Cyclotron resonance. Reprints. (JHD)

  11. Alternating and Direct Current Electrochemical Studies of a Wool Wax-Based Corrosion Preventive Coating on Aluminum Alloy 2024

    Microsoft Academic Search

    P.-C. Su; O. F. Devereux

    1998-01-01

    The corrosion behavior of Al 2024-T3 treated with a wool wax (lanolin)-based corrosion preventive coating in aqueous 0.5 M sodium chloride was studied using electrochemical impedance spectroscopy (EIS) and direct current electrode polarization. DC measurements were modeled by three reactions: oxidation of aluminum, reduction of oxygen, and reduction of hydrogen. Alternating current behavior of untreated specimens was modeled using the

  12. Electrochemical studies on the alternating current corrosion of mild steel under cathodic protection condition in marine environments

    Microsoft Academic Search

    Dae-Kyeong Kim; Srinivasan Muralidharan; Tae-Hyun Ha; Jeong-Hyo Bae; Yoon-Cheol Ha; Hyun-Goo Lee; J. D. Scantlebury

    2006-01-01

    Alternating current (AC) corrosion of mild steel in marine environments under cathodic protection (CP) condition was studied. Electrochemical studies at the two protection potentials namely ?780 and ?1100mV versus SCE were examined by different techniques. DC polarization study was carried out for mild steel in natural seawater and 18.5g\\/L NaCl solution to evolve corrosion current density. The corrosion rate determination,

  13. Corrosion by alternating current: a study of the anodic polarization of mild steel in NaâSOâ solution

    Microsoft Academic Search

    D. T. Chin; T. W. Fu

    1979-01-01

    A study has been made of the anodic polarization of mild steel in NaâSOâ solutions (pH 3-9) in the presence of a sinusoidal electric current. The measurement was carried out over a range of alternating current (ac) densities from 0 to 200 mA\\/cm² and ac frequencies from 20 to 6000 Hz. It was found that the corrosion potential of mild

  14. Utilizing lateral current spreading in multijunction solar cells: An alternative approach to detecting mechanical defects

    Microsoft Academic Search

    C. G. Zimmermann

    2006-01-01

    Lateral current transport in forward biased triple junction solar cells is analyzed. A model based on distributed sheet resistances in combination with ideal p-n junctions is developed. Experimentally, the spatial distribution of the electroluminescence radiation is recorded and used as a tool to deduce the current densities in the individual junctions. In a specific test case, a cell which contains

  15. Thermoelectric instability induced by single pulses and alternating currents in second-generation superconducting tapes

    Microsoft Academic Search

    P. N. Degtyarenko; I. N. Dul’kin; L. M. Fisher; A. V. Kalinov; I. F. Voloshin; V. A. Yampol’skii

    2011-01-01

    We have studied current flow instabilities in a second-generation superconducting tapes and the transition of the tapes into the resistive state. Contrary to the usual quasisteady instability regimes, here we consider the adiabatic case in which the sample is heated rapidly. Two kinds of measurements of the current-voltage characteristics (CVC) have been made, specifically, with excitation of the tape by

  16. Effects of alternating and direct current in electrocoagulation process on the removal of cadmium from water

    Microsoft Academic Search

    Subramanyan Vasudevan; Jothinathan Lakshmi; Ganapathy Sozhan

    2011-01-01

    In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by

  17. Utilizing lateral current spreading in multijunction solar cells: An alternative approach to detecting mechanical defects

    NASA Astrophysics Data System (ADS)

    Zimmermann, C. G.

    2006-07-01

    Lateral current transport in forward biased triple junction solar cells is analyzed. A model based on distributed sheet resistances in combination with ideal p-n junctions is developed. Experimentally, the spatial distribution of the electroluminescence radiation is recorded and used as a tool to deduce the current densities in the individual junctions. In a specific test case, a cell which contains both area with and without externally injected current, the current spreading across the boundary between the two cell areas is reproduced accurately. Subsequently the impact of a mechanical defect on the current distributions in the individual junctions is addressed through this model. It is demonstrated that the carrier recombination at the surface of the crack acts as a current sink with a long range impact on the current densities. In addition a characteristic splitting of the current densities in top cell and middle cell is observed which implies that mechanical defects can be easily identified in a cell by their electroluminescence signature. The dependence of this phenomenon on the semiconductor properties in the basic cell structure is identified.

  18. Alternating current thin-film electroluminescence of GaN:Er J. Heikenfeld and A. J. Steckla)

    E-print Network

    Steckl, Andrew J.

    Alternating current thin-film electroluminescence of GaN:Er J. Heikenfeld and A. J. Steckla; accepted for publication 7 October 2000 Thin-film electroluminescence has been obtained from GaN:Er deposited directly on amorphous dielectric layers. Electroluminescent device ELD structures consisting

  19. Study of Corrosion of Super Martensitic Stainless Steel Under Alternating Current in Artificial Seawater with Electrochemical Impedance Spectroscopy

    Microsoft Academic Search

    T. Reyes; S. Bhola; D. L. Olson; B. Mishra

    2011-01-01

    The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as

  20. Frequency spectrum of alternating current magnetic susceptibility: A new rock magnetic property

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2011-12-01

    Low-field alternating current magnetic susceptibility (MS) is among the most commonly used magnetic property, from fundamental rock magnetism to various applied fields such as environmental magnetism studies. The prevalence of MS is mainly due to the rapid and simple measurements by means of commercially available devices. Frequency dependent susceptibility, a magnetic parameter defined as the change in MS per decade frequency, has also been frequently used in environmental magnetism. However, the performance of conventional instruments has put some constraint when characterizing SP-SD particle ensemble in terms of grain size distribution. The limitation is due to the specific operating frequencies, generally with one fixed frequency in hundreds of Hz associated with one or two more frequency steps in the range of kHz at the highest. This study proposes a new MS-derived magnetic property, or Frequency Spectrum of MS (FSM), which consists of MS values measured at multiple frequencies ranging in three orders of magnitudes from hundreds of Hz to hundreds of kHz. The FSM analyses were made for selected volcanic rocks and sediments, each characterized by the inclusion of SP, SD, MD particles, or their mixtures. The studied samples include andesite (Sakurajima, Japan), basalt (Kilauea), granite (Minnesota), and less and paleosol (Luochuan, China). Most remarkable is the FSM from the andesite samples showing a susceptibility increase, as much as 5%, observed over a specific frequency interval between 16 kHz and 128 kHz. This anomalous increase is superimposed on a linear decay of MS over the entire frequency range, which obviously shows a broad distribution of SP particle ensemble. In contrast, the FSM of granite shows no frequency dependence, while the basalt and paleosol exhibit the patterns indicating the presence of SP grains with broad volume distributions. The characteristic FSM pattern from the andesite suggests a new rock magnetic phenomena, which is most likely a magnetic resonance of domain wall oscillations of specific-size MD grains occurring as phenocrysts. Considering the specific frequency range, the hypothetical resonance appears to be relevant to some magnetoelastic phenomenon, where magnetic energy could be dissipated through a long-range, magnetostructural coupling, probably magnetostriction. Another observational fact that the thermally demagnetized andesite samples of them show less noticeable FSM anomaly supports this hypothesis, because thermal annealing generally lowers the internal stress that eventually could lead to the reduction of resistance in a forced oscillation system. Measurements of both in-phase and out-of-phase components of MS at low temperatures were made by means of combined frequency and temperature scans with MPMS. The results show that the out-of-phase component is maximized at a certain frequency over one temperature scan and the frequency at each maximum increases with increasing temperature. Those results at low temperatures also suggest the above hypothesis. Analyses of FSM in terms of grain size, domain state and grain size distribution will serve as a new rock magnetic method to be useful in not only fundamental rock magnetism but also their applications in environmental studies.

  1. 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. PMID:25476591

  2. Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps

    SciTech Connect

    Sasada, Ichiro, E-mail: sasada@ence.kyushu-u.ac.jp [Applied Science for Electronics and Materials, Kyushu University, Kasuga (Japan)

    2014-05-07

    A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

  3. Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps

    NASA Astrophysics Data System (ADS)

    Sasada, Ichiro

    2014-05-01

    A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

  4. Future Carbon Regulations and Current Investments in Alternative Coal-Fired Power Plant Designs

    E-print Network

    Sekar, Ram C.

    This paper assesses the role of uncertainty over future U.S. carbon regulations in shaping the current choice of which type of power plant to build. The pulverized coal technology (PC) still offer the lowest cost power— ...

  5. Shapiro steps in Josephson junctions with alternating critical current density M. Moshe and R. G. Mints*

    E-print Network

    Mints, Roman G.

    in the voltage-current curves of the asymmetric grain boundaries in yttrium barium copper oxide thin films-integer Shapiro steps has been reported recently for asymmetric grain bound- aries in yttrium barium copper oxide

  6. Alternating Current Electrospraying Siddharth Maheshwari, Nishant Chetwani, and Hsueh-Chia Chang*

    E-print Network

    Chang, Hsueh-Chia

    the dispersion and delivery of nanomaterials. All these applications have employed dc (direct current electrospraying from dc behavior and highlight its key features. We begin by providing a brief overview of dc

  7. Grid-connected inverters for alternative energy sources with a combined voltage and current control strategy

    Microsoft Academic Search

    D. Menniti; C. Picardi; A. Pinnarelli; D. Sgro

    2007-01-01

    Renewable energy sources are considered as important generation alternatives in electric power systems due to their no exhausted nature and benign environmental effects. In order to utilize the infrastructure of the actual distribution network, grid-connected inverters are needed. In this paper a new control strategy for a pulse width modulation (PWM) three-phase voltage source inverter (VSI) connected to the grid

  8. 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…

  9. EVALUATION OF CURRENTLY AVAILABLE ALTERNATIVES TO METHYL BROMIDE FOR ORNAMENTAL CROP PRODUCTION IN FLORIDA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies were designed to test the efficacy of the chemical alternatives, Midas™ (iodomethane:chloropicrin (pic) 50:50 [MI 50:50] and 98:2 [MI 98:2], Arysta LifeScience Corp., Cary, NC) and dimethyl disulfide:pic (Paladin™ 79:21 [DMDS], United Phosphorous, Inc., King of Prussia, PA) compared with met...

  10. 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.

  11. Field-angle dependence of alternating current loss in multifilamentary high-Tc superconducting tapes

    NASA Astrophysics Data System (ADS)

    Oomen, M. P.; Rieger, J.; Leghissa, M.; ten Kate, H. H. J.

    1997-06-01

    The energy loss in multifilamentary superconducting tapes has been measured for various orientations of the external ac magnetic field. When the ac loss in parallel and perpendicular fields is known, the loss at intermediate field angles can be predicted over a wide range of field amplitudes. The prediction is based upon the following assumptions: For low-field amplitudes, the current patterns that would be induced in the tape by the parallel and perpendicular field components can be summed. For high-field amplitudes, the tape only carries the current pattern induced by the perpendicular field component. These assumptions are supported by theory.

  12. High frequency alternating current power supply for automobile auxiliary electrical systems

    Microsoft Academic Search

    C. Antaloae; J. Marco; N. D. Vaughan

    2010-01-01

    This paper presents an HFAC power source concept for vehicle auxiliary electrical systems. The proposed power supply is based on a resonant DC to HFAC inverter, which constructs the output sinusoidal voltage and current. Mathematical modelling is employed to design the control strategy and Matlab Simulink is used to model and simulate the circuit operation under various load conditions. Simulation

  13. Variable Uses of Alternative Conceptions: A Case Study in Current Electricity.

    ERIC Educational Resources Information Center

    Heller, Patricia; Finley, Fred

    In order to investigate the nature of students' prior knowledge of current electricity and how they applied their knowledge to different problems, 5 middle school science teachers and 11 elementary school teachers were given a written test that required them to: (1) predict what happens to the brightness of a bulb if a change is made to the…

  14. 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.

  15. Frequency of current utilisation of complementary and alternative medicine by patients with multiple sclerosis

    Microsoft Academic Search

    Annett Apel; Brigitte Greim; Nicolaus König; Uwe K. Zettl

    2006-01-01

    Objective  The purpose of the study was to examine the frequency and characteristics of complementary and alternative medicine (CAM)\\u000a use among patients with multiple sclerosis (MS).\\u000a \\u000a \\u000a \\u000a Method  In order to collect sociodemographic and disease related variables as well as aspects of CAM utilisation 254 MS patients were\\u000a examined with an interview. The investigation was completed by data of the neurological examination.\\u000a \\u000a \\u000a \\u000a Results  At the

  16. A circuit for the power supply of laser-pumping lamps by current pulses of alternating direction

    Microsoft Academic Search

    V. V. Valiavko; B. V. Krylov; A. A. Mozgo

    1980-01-01

    A symmetrical power supply circuit for laser-pumping lamps is described. The circuit provides for the automatic alternation of the direction of discharge-current pulses, which makes it possible to eliminate temperature gradients and thermal stresses associated with conventional lamps. Pump energy is regulated by the extraction of excess energy into an auxiliary storage unit (i.e., an induction coil). The operation of

  17. Precursor sites for localised corrosion on lacquered tinplates visualised by means of alternating current scanning electrochemical microscopy

    Microsoft Academic Search

    Bernardo Ballesteros Katemann; Carlota González Inchauspe; Pablo A Castro; Albert Schulte; Ernesto J Calvo; Wolfgang Schuhmann

    2003-01-01

    In solutions of low conductivity and at high frequencies the impedance of a SECM tip-auxiliary electrode cell is dominated by the solution resistance between the tip and counter electrode. Alternating current scanning electrochemical microscopy (AC-SECM) utilises the effect of an increasing (decreasing) solution resistance as the SECM tip approaches an insulator (conductor) for mapping domains of different conductivity\\/electrochemical activity on

  18. Alternating current anodizing of titanium in halogen acids combined with Anodic Spark Deposition: Morphological and structural variations

    Microsoft Academic Search

    Maria Vittoria Diamanti; Marco Ormellese; MariaPia Pedeferri

    2010-01-01

    The identification of anodic processes able to generate high surface area TiO2 layers is a key requirement, whenever applications focused on its photoactivity or the integration between titanium implants and human body are considered. To achieve this goal, this research proposes an innovative two-step anodizing procedure. The first step consists of supplying alternating current to titanium in halogen acid electrolyte

  19. Effects of alternating current on corrosion of a coated pipeline steel in a chloride-containing carbonate\\/bicarbonate solution

    Microsoft Academic Search

    A. Q. Fu; Y. F. Cheng

    2010-01-01

    In this work, the alternating current (AC)-induced corrosion of a coated pipeline steel was studied in a chloride-containing, concentrated carbonate\\/bicarbonate solution, which simulated the trapped high pH electrolyte under coating, by potentiodynamic polarization measurements, immersion tests and surface characterization technique. It was found that an application of AC resulted in a negative shift of corrosion potential of the steel, caused

  20. Nonaqueous Inhibition of Iron-Boron-Silicon Amorphous Electrodes in Hydrochloric Acid: An Alternating Current Impedance Study

    Microsoft Academic Search

    K. Habib; A. Abdullah

    1994-01-01

    Iron-boron-silicon (Fe-B-Si) amorphous electrodes were studied using electrochemical impedance spectroscopy (EIS) to determine the alternating current (AC) impedance and the capacitance of four Fe-B-Si alloys in various acid solutions. The AC impedance and the capacitance of Fe-B-Si, Fe-B-Si with carbon (C), Fe-B-Si with cobalt (Co), and Fe-B-Si with chromium (Cr) were obtained in 25%, 50%, 75%, and 100% hydrochloric acid

  1. Potential attenuation and anode current output determination alternatives for marine pipelines and risers

    SciTech Connect

    Pierson, P.; Hartt, W.H.; Bethune, K.P.

    1999-07-01

    Potential attenuation along a pipeline that is catholically polarized by multiple, equally spaced anodes is evaluated using three approaches boundary element modeling, a newly developed attenuation equation, and the classical equation of Uhlig, where the first two consider the net resistance to be comprised of electrolyte (anode), coating, and metallic path components, whereas the last approach neglects electrolyte resistance. It is demonstrated that results from the BEM analysis correspond to a first principles based projection of resistance change along a pipeline; and so results obtained by this method (BEM) are judged to be the most accurate of the three. Distinctions between the BEM and the newly developed attenuation equation, which is also first principles based, are discussed in terms of assumptions that are made in arriving at a closed form solution to the latter. The Uhlig equation is judged to be the least accurate of the three and to be non-conservative. While the closed form solution for the newly developed equation projects a potential attenuation that is non-conservative, the corresponding anode current output is conservative. Based upon this, a protocol for design of galvanic cathodic protection systems upon marine pipelines is proposed.

  2. Wavefront velocity oscillations of carbon-nanotube-guided thermopower waves: nanoscale alternating current sources.

    PubMed

    Abrahamson, Joel T; Choi, Wonjoon; Schonenbach, Nicole S; Park, Jungsik; Han, Jae-Hee; Walsh, Michael P; Kalantar-Zadeh, Kourosh; Strano, Michael S

    2011-01-25

    The nonlinear coupling between exothermic chemical reactions and a nanowire or nanotube with large axial heat conduction results in a self-propagating thermal wave guided along the nanoconduit. The resulting reaction wave induces a concomitant thermopower wave of high power density (>7 kW/kg), resulting in an electrical current along the same direction. We develop the theory of such waves and analyze them experimentally, showing that for certain values of the chemical reaction kinetics and thermal parameters, oscillating wavefront velocities are possible. We demonstrate such oscillations experimentally using a cyclotrimethylene-trinitramine/multiwalled carbon nanotube system, which produces frequencies in the range of 400 to 5000 Hz. The propagation velocity oscillations and the frequency dispersion are well-described by Fourier's law with an Arrhenius source term accounting for reaction and a linear heat exchange with the nanotube scaffold. The frequencies are in agreement with oscillations in the voltage generated by the reaction. These thermopower oscillations may enable new types of nanoscale power and signal processing sources. PMID:21182252

  3. A Current Update on the Rule of Alternative and Complementary Medicine in the Treatment of Liver Diseases

    PubMed Central

    Guan, Yong-Song; He, Qing

    2013-01-01

    There is a vast body of knowledge which is ever-increasing about the treatment of liver disease with alternative and complementary medicine for which hundreds of thousands of literatures have been documented. Liver disease is a general term. This term covers all the potential problems that cause the liver to fail to perform its specified operations. Liver disease has a variety of presentations and causes a great public health problem worldwide which threatens the wellness of billions of people. Incidences of many types of liver disease are currently rising. Although there is still a debate about the entity of alternative and complementary medicine, it is now widely used and it is improving. And it covers the shortages and compensates for the weaknesses of conventional methods in the treatment of liver diseases. Alternative and complementary medicine for liver diseases provides benefits by regulating immunity, controlling disease progression, improving quality of life, and prolonging survival. This paper reviews the increasing interest and growing research into alternative and complementary medicine for liver diseases, with a look at the rough classification, principle of management, evidence-based applications, and issues for prescription and perspectives. PMID:24109491

  4. Electrical detection of direct and alternating spin current injected from a ferromagnetic insulator into a ferromagnetic metal

    NASA Astrophysics Data System (ADS)

    Hyde, P.; Bai, Lihui; Kumar, D. M. J.; Southern, B. W.; Hu, C.-M.; Huang, S. Y.; Miao, B. F.; Chien, C. L.

    2014-05-01

    We report dual spin pumping in magnetic bilayers made of a ferromagnetic insulator yttrium iron garnet (YIG) and a ferromagnetic metal permalloy (Py). At the YIG ferromagnetic resonance (FMR), we detect a charge voltage in Py caused by YIG spin pumping. At the Py FMR, we measure the charge voltage generated by Py spin rectification. A striking simultaneous enhancement of both voltages is found at the equal resonance condition of both FMRs, which we attribute to dynamic coupling of the dual spin pumping. Our results demonstrate that Py enables electrical detection of both dc and ac spin currents in the spin pumping from YIG, which reveals an alternative path for developing insulator spintronics.

  5. Influence of wall-charge accumulation on the gas dielectric barrier discharge in alternating current plasma display panel

    SciTech Connect

    Guo Bingang; Wei Wei; Shinoda, Tsutae; Liu Chunliang [Advanced Display Research Center, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba Meguro-Ku, Tokyo 153-8505 (Japan); Key Laboratory for Physical Electronics and Devices of the Ministry of Education of China, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049 (China)

    2007-03-05

    Influences of wall-charge accumulation on gas dielectric barrier discharge (DBD) breakdown threshold and sustaining voltage margin of alternating current plasma display panel (AC-PDP) were investigated. It is observed that wall-charge accumulation results in a remarkable increase of gas DBD breakdown threshold during sustaining discharge period. Sustaining voltage margin is reduced by the threshold increase. A larger margin can be obtained when the threshold is decreased by removing unfavorable influence of wall-charge accumulation. Compared with normal margin, improved margin has a larger value and a faster linear increase with increasing wall-charge voltage. That indicates a way to improve AC-PDP performances remarkably.

  6. Study of Corrosion of Super Martensitic Stainless Steel Under Alternating Current in Artificial Seawater with Electrochemical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Reyes, T.; Bhola, S.; Olson, D. L.; Mishra, B.

    2011-06-01

    The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as well as to characterize pitting. When EIS is applied at the open circuit potential, the technique is nondestructive and predicts the corrosion behavior of the electrode. It can also be used at cathodic potentials while still being nondestructive, providing information about the electrode reaction kinetics, diffusion and electrical double layer.

  7. Study of corrosion of super martensitic stainless steel under alternating current in artificial seawater with electrochemical impedance spectroscopy

    SciTech Connect

    Reyes, T.; Bhola, S.; Olson, D. L.; Mishra, B. [Colorado School of Mines, Golden CO 80401 (United States)

    2011-06-23

    The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as well as to characterize pitting. When EIS is applied at the open circuit potential, the technique is nondestructive and predicts the corrosion behavior of the electrode. It can also be used at cathodic potentials while still being nondestructive, providing information about the electrode reaction kinetics, diffusion and electrical double layer.

  8. Analysis of operations and cyber security policies for a system of cooperating Flexible Alternating Current Transmission System (FACTS) devices.

    SciTech Connect

    Phillips, Laurence R.; Tejani, Bankim; Margulies, Jonathan; Hills, Jason L.; Richardson, Bryan T.; Baca, Micheal J.; Weiland, Laura

    2005-12-01

    Flexible Alternating Current Transmission Systems (FACTS) devices are installed on electric power transmission lines to stabilize and regulate power flow. Power lines protected by FACTS devices can increase power flow and better respond to contingencies. The University of Missouri Rolla (UMR) is currently working on a multi-year project to examine the potential use of multiple FACTS devices distributed over a large power system region in a cooperative arrangement in which the FACTS devices work together to optimize and stabilize the regional power system. The report describes operational and security challenges that need to be addressed to employ FACTS devices in this way and recommends references, processes, technologies, and policies to address these challenges.

  9. Substituted catechols as complexing agents for the determination of bismuth, lead, copper and cadmium by adsorptive stripping voltammetry

    Microsoft Academic Search

    Janice Limson; Tebello Nyokong

    1997-01-01

    Copper, cadmium, lead and bismuth (> 5 ?g ml?1) are determined by adsorptive cathodic stripping voltammetry (AdCSV) on a mercury film glassy carbon electrode, using catechol, 4-methylcatechol, 4-t-butylcatechol and resorcinol as complexing ligands. Complexes of lead, copper and bismuth with resorcinol showed the largest increase in current with increase in metal concentration, whereas complexes of these metals with 4-t-butylcatechol showed

  10. Diffusional surface voltammetry as a probe of adsorption energetics.

    PubMed

    Calvente, Juan José; Molero, Miguel; Andreu, Rafael; López-Pérez, Germán; Luque, Antonio M

    2012-01-17

    Direct determination of the adsorption free energy for extremely low surface coverages (Henry limit) requires the use of a technique that must be highly sensitive to both the amount and the energetics of adsorbed molecules. Herein, we demonstrate that diffusional surface voltammetry (DSV), which embodies film and stripping voltammetries as two limiting cases, can be used to achieve this goal for electroactive adsorbates. To this end, a general analytical expression for the surface voltammetric peak potential of DSV is derived, which covers the full range of scan rates, bulk concentrations, and adsorptivity of the freely diffusing form of the redox couple, so that the surface redox conversion can be either equilibrated with or transport-isolated from the solution bulk. Strategies to get a quantitative insight into the energetics of electrosorption are outlined, and diagnostic criteria for their application are developed. In particular, it is demonstrated that DSV can be used in its stripping mode to determine group contributions to the adsorption free energy, avoiding possible interferences from intermolecular interactions or formation of oligomeric species. Application of this protocol to the reductive desorption of distinct homologous series of alkylthiolates adsorbed at mercury electrodes has allowed us to determine the contributions of the CH(n) groups (n = 0-3) to the free energy of adsorption of these molecules. These estimates are shown to correlate linearly with the corresponding group contributions to the octanol-water partition coefficient, revealing that adsorption of individual hydrocarbon groups at the mercury/solution interface scales with their hydrophobicity. Overall, the present work enlarges the capability of surface voltammetry to probe adsorption energetics down to the micromolar level, and it represents a first step toward the development of a unified treatment of stripping and film voltammetries. PMID:22128825

  11. Data Smoothing in Stripping Voltammetry by Simplex Function Fitting

    Microsoft Academic Search

    A. Economou; P. R. Fielden; A. J. Packham

    1997-01-01

    Stripping voltammetry (SV), in common with all trace voltammetric analytical techniques, suffers from poor signal-to-noise (S\\/N) ratios due to external interference pick up and inherent generation of noise in the electrochemical system. In addition to other methods developed to smooth noisy data (such as time and frequency domain filtering), optimisation methods can also be used to reject the noise present

  12. ANALYSIS OF SELENIUM SPECIES USING CATHODIC STRIPPING VOLTAMMETRY

    Microsoft Academic Search

    RUGAYAH MOHAMED; LEONG WEI LEE

    2007-01-01

    Differential pulse cathodic stripping voltammetry of an inorganic selenium (selenite, Se(IV)) and organic selenium (dimethyl diselenide, DMDSe) was investigated using hanging mercury drop electrode (HMDE). The reduction peaks of selenite and dimethyl diselenide were obtained at -472 mV and -304 mV vs Ag\\/AgCl electrode respectively in acidic media. Various voltammetric parameters such as supporting electrolyte, accumulation potential and accumulation time

  13. Determination of cadmium by differential pulse adsorptive stripping voltammetry

    Microsoft Academic Search

    Pompilia Suciu; Marisol Vega; Liviu Roman

    2000-01-01

    A study of the adsorptive stripping voltammetry of cadmium on a mercury drop electrode is reported in which 2-mercapto-5-phenil-ammino-1,3,4-thiadiazole (MPATD), synthesized at home has been used as a chelating agent. The most suitable operating conditions and parameters such as buffer, pH, deposition potential, deposition time, ligand concentration, scan rate and others were selected and the determination of cadmium from aqueous

  14. Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

    NASA Astrophysics Data System (ADS)

    Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G.; Bruno, Emanuela; Marino, Lucia; Scaramuzza, Nicola

    2014-02-01

    Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.

  15. Calorimetric AC loss measurement of MgB2 superconducting tape in an alternating transport current and direct magnetic field

    NASA Astrophysics Data System (ADS)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2012-11-01

    Applications of MgB2 superconductors in electrical engineering have been widely reported, and various studies have been made to define their alternating current (AC) losses. However, studies on the transport losses with an applied transverse DC magnetic field have not been conducted, even though this is one of the favored conditions in applications of practical MgB2 tapes. Methods and techniques used to characterize and measure these losses have so far been grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

  16. Effect of alternating current on corrosion of Zn-22Al alloy and galvanized steel wires in synthetic sea water

    SciTech Connect

    Grovas, T.J.; Perez, T.; Genesca, J. [Univ. Nacional Autonoma de Mexico, Mexico City (Mexico)

    1996-10-01

    Submarine AC cables generally, have a metallic armor, constituted by one or two layers of wires or strips wound with long lay on the outside of the cable. The armor is required in order to sustain part of the mechanical stresses during the laying and recovery of the cable, since the conductor alone as a rule is not sufficient for this purpose. The armor also plays an important role in the conduction of the return current. Moreover, due to the large distance between the cables in usual submarine laying practice, the return current can be very large, approaching the central conductor current value, The armor as a rule is not insulated but is in electric contact with the sea along all the cable length. This is not due to electric reasons, since the e.m.f. between armor and sea is negligible, but to practical ones. In fact it is quite difficult to assure a complete protection along all the armor length, without impairing it during the laying operations, and a single break in the insulation, would be a very strong corrosion point. The contact between the metal which constitutes the armor, galvanized steel in the case of Mexico, and the sea, in presence also of AC electric fields, requires a thorough study, of the corrosion problems which might arise. Such a study is given in this communication. It includes an experimental investigation on the behavior of Zn-22 Al and galvanized steel wires in sea water under AC. In particular, it is demonstrated that Zn-22 Al has an optimum corrosion rate of 15.86 mm/year versus 29.98 mm/year for Galvanized steel at a fixed alternating current density. A mechanism is proposed to explain this behavior, mainly, based in the presence of Al as alloy, element in Zn-22 Al and the formation of a film, Al{sub 2}O{sub 3}{center_dot}xH{sub 2}O.

  17. Individually addressable multi-chamber electroporation platform with dielectrophoresis and alternating-current-electro-osmosis assisted cell positioning.

    PubMed

    Park, Sinwook; Bassat, Dana Ben; Yossifon, Gilad

    2014-03-01

    A multi-functional microfluidic platform was fabricated to demonstrate the feasibility of on-chip electroporation integrated with dielectrophoresis (DEP) and alternating-current-electro-osmosis (ACEO) assisted cell/particle manipulation. A spatial gradient of electroporation parameters was generated within a microchamber array and validated using normal human dermal fibroblast (NHDF) cells and red fluorescent protein-expressing human umbilical vein endothelial cells (RFP-HUVECs) with various fluorescent indicators. The edge of the bottom electrode, coinciding with the microchamber entrance, may act as an on-demand gate, functioning under either positive or negative DEP. In addition, at sufficiently low activation frequencies, ACEO vortices can complement the DEP to contribute to a rapid trapping/alignment of particles. As such, results clearly indicate that the microfluidic platform has the potential to achieve high-throughput screening for electroporation with spatial control and uniformity, assisted by DEP and ACEO manipulation/trapping of particles/cells into individual microchambers. PMID:24803966

  18. The history and current status of fallopian tube pressures - developing alternate methods for confirmation of tubal occlusion.

    PubMed

    Patil, Eva; Thurmond, Amy

    2015-08-01

    Permanent contraception with hysteroscopic tubal ligation is an increasingly popular choice for women around the world. However, inconveniences associated with the required confirmation test for tubal occlusion can be prohibitive. As new methods of permanent contraception are being investigated, ways of making all aspects of the procedure more accessible and comfortable for women should be considered. Means of examining tubal patency in the infertility population, such as tubal perfusion pressures measured at the time of hysterosalpingogram (HSG), provide inspiration for alternative methods of tubal occlusion confirmation after contraception. Evaluation of intrauterine pressures measured by a manometer attached to an intrauterine balloon catheter could serve as a preliminary tool for verification of tubal occlusion; higher pressures would indicate tubal occlusion and lower pressures would indicate the need for confirmatory HSG. The development and validation of this technique is ongoing and could reduce overall costs and patient burdens associated with the current tubal occlusion confirmation procedure. PMID:25592081

  19. Inducing self-rotation of cells with natural and artificial melanin in a linearly polarized alternating current electric field

    PubMed Central

    Ouyang, Mengxing; Ki Cheung, Wing; Liang, Wenfeng; Mai, John D.; Keung Liu, Wing; Jung Li, Wen

    2013-01-01

    The phenomenon of self-rotation observed in naturally and artificially pigmented cells under an applied linearly polarized alternating current (non-rotating) electrical field has been investigated. The repeatable and controllable rotation speeds of the cells were quantified and their dependence on dielectrophoretic parameters such as frequency, voltage, and waveform was studied. Moreover, the rotation behavior of the pigmented cells with different melanin content was compared to quantify the correlation between self-rotation and the presence of melanin. Most importantly, macrophages, which did not originally rotate in the applied non-rotating electric field, began to exhibit self-rotation that was very similar to that of the pigmented cells, after ingesting foreign particles (e.g., synthetic melanin or latex beads). We envision the discovery presented in this paper will enable the development of a rapid, non-intrusive, and automated process to obtain the electrical conductivities and permittivities of cellular membrane and cytoplasm in the near future. PMID:24404075

  20. Individually addressable multi-chamber electroporation platform with dielectrophoresis and alternating-current-electro-osmosis assisted cell positioning

    PubMed Central

    Park, Sinwook; Bassat, Dana Ben; Yossifon, Gilad

    2014-01-01

    A multi-functional microfluidic platform was fabricated to demonstrate the feasibility of on-chip electroporation integrated with dielectrophoresis (DEP) and alternating-current-electro-osmosis (ACEO) assisted cell/particle manipulation. A spatial gradient of electroporation parameters was generated within a microchamber array and validated using normal human dermal fibroblast (NHDF) cells and red fluorescent protein-expressing human umbilical vein endothelial cells (RFP-HUVECs) with various fluorescent indicators. The edge of the bottom electrode, coinciding with the microchamber entrance, may act as an on-demand gate, functioning under either positive or negative DEP. In addition, at sufficiently low activation frequencies, ACEO vortices can complement the DEP to contribute to a rapid trapping/alignment of particles. As such, results clearly indicate that the microfluidic platform has the potential to achieve high-throughput screening for electroporation with spatial control and uniformity, assisted by DEP and ACEO manipulation/trapping of particles/cells into individual microchambers. PMID:24803966

  1. Frequency-dependent alternating-current scanning electrochemical microscopy (4D AC-SECM) for local visualisation of corrosion sites.

    PubMed

    Eckhard, Kathrin; Erichsen, Thomas; Stratmann, Martin; Schuhmann, Wolfgang

    2008-01-01

    For a better understanding of the initiation of localised corrosion, there is a need for analytical tools that are capable of imaging corrosion pits and precursor sites with high spatial resolution and sensitivity. The lateral electrochemical contrast in alternating-current scanning electrochemical microscopy (AC-SECM) has been found to be highly dependent on the frequency of the applied alternating voltage. In order to be able to obtain data with optimum contrast and high resolution, the AC frequency is swept in a full spectrum at each point in space instead of performing spatially resolved measurements at one fixed perturbation frequency. In doing so, four-dimensional data sets are acquired (4D AC-SECM). Here, we describe the instrument set-up and modus operandi, along with the first results from the imaging of corroding surfaces. Corrosion precursor sites and local defects in protective organic coatings, as well as an actively corroding pit on 304 stainless steel, have been successfully visualised. Since the lateral electrochemical contrast in these images varies with the perturbation frequency, the proposed approach constitutes an indispensable tool for obtaining optimum electrochemical contrast. PMID:18351698

  2. Alternating and direct current electrochemical studies of a wool wax-based corrosion preventive coating on aluminum alloy 2024

    SciTech Connect

    Su, P.C.; Devereux, O.F. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Metallurgy and Materials Engineering

    1998-06-01

    The corrosion behavior of Al 2024-T3 treated with a wool wax (lanolin)-based corrosion preventive coating in aqueous 0.5 M sodium chloride was studied using electrochemical impedance spectroscopy (EIS) and direct current electrode polarization. DC measurements were modeled by three reactions: oxidation of aluminum, reduction of oxygen, and reduction of hydrogen. Alternating current behavior of untreated specimens was modeled using the Randles circuit, and that of inhibited specimens was modeled using parallel resistance-capacitance circuits representing the coating and the charge-transfer process. AC and DC estimates of the polarization resistance of coated specimens were 50 M{Omega}-cm{sup 2} and 32 M{Omega}-cm{sup 2}, respectively. AC and DC values for bare control specimens were of the order of 3 k{Omega}-cm{sup 2} and 15 k{Omega}-cm{sup 2}, respectively. The wool wax coating was found to be a very effective corrosion preventative for this alloy in the aqueous saline environment whether applied to freshly prepared surfaces or to corroded specimens removed from simulated service.

  3. Extremely bright full color alternating current electroluminescence of solution-blended fluorescent polymers with self-assembled block copolymer micelles.

    PubMed

    Cho, Sung Hwan; Jo, Seong Soon; Hwang, Ihn; Sung, Jinwoo; Seo, Jungmok; Jung, Seok-Heon; Bae, Insung; Choi, Jae Ryung; Cho, Himchan; Lee, Taeyoon; Lee, Jin Kyun; Lee, Tae-Woo; Park, Cheolmin

    2013-12-23

    Electroluminescent (EL) devices operating at alternating current (AC) electricity have been of great interest due to not only their unique light emitting mechanism of carrier generation and recombination but also their great potential for applications in displays, sensors, and lighting. Despite great success of AC-EL devices, most device properties are far from real implementation. In particular, the current state-of-the art brightness of the solution-processed AC-EL devices is a few hundred candela per square meter (cd m(-2)) and most of the works have been devoted to red and white emission. In this manuscript, we report extremely bright full color polymer AC-EL devices with brightness of approximately 2300, 6000, and 5000 cd m(-2) for blue (B), green (G), and red (R) emission, respectively. The high brightness of blue emission was attributed to individually networked multiwalled carbon nanotubes (MWNTs) for the facile carrier injection as well as self-assembled block copolymer micelles for suppression of interchain nonradiative energy quenching. In addition, effective FRET from a solution-blended thin film of B-G and B-G-R fluorescent polymers led to very bright green and red EL under AC voltage, respectively. The solution-processed AC-EL device also worked properly with vacuum-free Ag paste on a mechanically flexible polymer substrate. Finally, we successfully demonstrated the long-term operation reliability of our AC-EL device for over 15 h. PMID:24279731

  4. Voltammetry of chromium(VI) at the liquid|liquid interface

    Microsoft Academic Search

    Aoife M. O’Mahony; Micheál D. Scanlon; Alfonso Berduque; Valerio Beni; Damien W. M. Arrigan; Enrico Faggi; Andrea Bencini

    2005-01-01

    The voltammetry of hexavalent chromium (ammonium dichromate) at the interface between two immiscible electrolyte solutions is reported. Detection of Cr(VI) by ion transfer voltammetry is possible by use of an organic phase ionophore, which facilitates the transfer of Cr(VI) from the aqueous into the organic phase. The ionophore was the penta protonated form of polyamine macrocycle 2,5,8,11,14-pentaaza[15]-16,29-phenanthrolinophane (NeoTT). Cyclic voltammetry

  5. Monitoring of freshness of milk by an electronic tongue on the basis of voltammetry

    NASA Astrophysics Data System (ADS)

    Winquist, F.; Krantz-Rülcker, C.; Wide, P.; Lundström, I.

    1998-12-01

    We describe an electronic tongue which consists of a reference electrode, an auxiliary electrode and five wires of different metals (gold, iridium, palladium, platinum and rhodium) as working electrodes. The measurement principle is based on pulsed voltammetry, in which successive voltage pulses of gradually changing amplitudes are applied to the working electrodes connected in a standard three-electrode configuration. The five working electrodes were successively connected and corresponding current-response transients are recorded. The electronic tongue was used to follow the deterioration of the quality of milk due to microbial growth when milk is stored at room temperature. The data obtained were treated with principal component analysis and the deterioration process could clearly be followed in the diagrams. To make models for predictions, projections to latent structure and artificial neural networks were used. When they had been trained, both models could satisfactorily predict the course of bacterial growth in the milk samples.

  6. Current Efforts to Develop Alternate "TB 700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.; Butcher, A. Garn

    2002-04-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (less than or = 304.8-millimeter (less than or = 12-inch)) diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  7. Current Efforts to Develop Alternate "TB700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.

    2001-09-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (equal to or greater than) 304.8-millimeter (equal to or greater than 12-inch diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  8. Current Efforts to Develop Alternate "TB 700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.

    1998-01-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (greater than or equal 304.8-millimeter (greater than or equal l2-inch)) diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  9. Alternating Current Electric Fields of Varying Frequencies: Effects on Proliferation and Differentiation of Porcine Neural Progenitor Cells

    PubMed Central

    Lim, Ji-Hey; McCullen, Seth D.; Piedrahita, Jorge A.

    2013-01-01

    Abstract Application of sinusoidal electric fields (EFs) has been observed to affect cellular processes, including alignment, proliferation, and differentiation. In the present study, we applied low-frequency alternating current (AC) EFs to porcine neural progenitor cells (pNPCs) and investigated the effects on cell patterning, proliferation, and differentiation. pNPCs were grown directly on interdigitated electrodes (IDEs) localizing the EFs to a region accessible visually for fluorescence-based assays. Cultures of pNPCs were exposed to EFs (1 V/cm) of 1?Hz, 10?Hz, and 50?Hz for 3, 7, and 14 days and compared to control cultures. Immunocytochemistry was performed to evaluate the expression of neural markers. pNPCs grew uniformly with no evidence of alignment to the EFs and no change in cell numbers when compared with controls. Nestin expression was shown in all groups at 3 and 7 days, but not at 14 days. NG2 expression was low in all groups. Co-expression of glial fibrillary acidic protein (GFAP) and TUJ1 was significantly higher in the cultures exposed to 10- and 50-Hz EFs than the controls. In summary, sinusoidal AC EFs via IDEs did not alter the alignment and proliferation of pNPCs, but higher frequency stimulation appeared to delay differentiation into mature astrocytes. PMID:23961767

  10. Alternating current field measurement (ACFM): A new technique for the NDT of process plant and piping components

    SciTech Connect

    Raine, G.A. [Technical Software Consultants Limited, Wolverton Mill (United Kingdom); Monahan, C.C. [Memorial Univ., St. John`s, Newfoundland (Canada). Faculty of Engineering and Applied Science

    1996-12-31

    This paper describes a new electromagnetic-based NDT technology that is suitable for inspecting process plant and pipework fabricated from some of the more advanced materials, in addition to the traditional carbon steels. The name given to this new NDT technique is Alternating Current Field Measurement, or ACFM. ACFM is an extremely versatile NDT tool with a wide range of practical applications. A major advantage of ACFM over conventional NDT systems is that no calibration is required; crack detection and sizing is based on a theoretical interpretation of the measured signals. The technique is non-contacting and can be used on a wide range of electrically conductive materials (e.g., carbon steel, stainless steel, duplex steel, monel, inconel, aluminum, nickel, titanium, carbon reinforced plastics) without the need for extensive surface cleaning or removal of protective coatings. The flaws may be surface, sub-surface or remote face, depending on the material, and the probes can be designed to suppress signals from features that are not cracks (e.g., corrosion, undercuts, heat-affected zones, etc.), thus overcoming many of the problems associated with other electromagnetic systems and minimizing the probability of spurious indications.

  11. Evaluation of calcium alginate gel as electrode material for alternating current iontophoresis of lidocaine using excised rat skin.

    PubMed

    Ebisawa, Tomoko; Nakajima, Atsushi; Haida, Haruka; Wakita, Ryo; Ando, Shizuka; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Tanaka, Junzo; Fukayama, Haruhisa

    2014-01-01

    Iontophoresis (IOP) is a noninvasive method of delivering medication transcutaneously through the skin. The electrodes used in this method should tightly fit to rough and irregular surfaces and be biologically safe, easy to handle and prepare, and cost-effective. To satisfy these requirements, calcium alginate gel can be a candidate electrode for IOP. Using calcium alginate gel electrodes, we examined whether lidocaine can be effectively transported across an excised rat skin by squarewave alternating current (AC) application. A squarewave AC with either a 70 % or 80 % duty cycle was continuously applied to 0.5 % calcium alginate gel electrodes containing 10 % lidocaine at 10 V and 1 kHz for 60 min. Lidocaine concentration was measured using a spectrophotometer and the temperature of the gel was determined. The lidocaine concentrations for AC-IOP at the 70 % and 80 % duty cycles were significantly higher than that without AC-IOP. Furthermore, the group with the 80 % duty cycle showed higher lidocaine concentrations than the group with the 70 % duty cycle. The temperatures of all the groups were lower than 28 °C throughout the procedure. In conclusion, the calcium alginate gel can be used as a possible matrix for IOP electrodes. PMID:25952356

  12. Pore formation in lipid bilayer membranes made of phosphatidylinositol and oxidized cholesterol followed by means of alternating current.

    PubMed Central

    Gallucci, E; Micelli, S; Monticelli, G

    1996-01-01

    The kinetics of porin incorporation into black lipid membranes (BLM) made of phosphatidylinositol (PI) or oxidized cholesterol (Ox Ch) were studied by means of alternating current; the set-up was able to acquire resistance and capacitance simultaneously by means of a mixed double-frequency approach at 1 Hz and 1 KHz, respectively. Conductance was dependent on the interaction between protein-forming pores and lipids. For PI membranes below a porin concentration of 12.54 ng/ml, there was no membrane conductivity, whereas at 200 ng/ml a steady-state value was reached. Different behavior was displayed by Ox Ch membranes, in which a concentration of 12.54 ng/ml was sufficient to reach a steady state. The incorporation kinetics when porin was added after membrane formation were sigmoidal. When porin was present in the medium before membrane formation, the kinetics were sigmoidal for PI membranes but became exponential for Ox Ch membranes. Furthermore, for BLM made of PI, the conductance-versus-porin concentration relationship is sigmoidal, with a Hill coefficient of 5.6 +/- 0.07, which is functional evidence corroborating the six-channel repeating units seen previously. For BLM made of Ox Ch, this relationship followed a binding isotherm curve with a Hill coefficient of 0.934 +/- 0.129. PMID:8842220

  13. In situ measurement of alternating current magnetic susceptibility of Pd-hydrogen system for determination of hydrogen concentration in bulk.

    PubMed

    Akamaru, Satoshi; Hara, Masanori; Matsuyama, Masao

    2012-07-01

    An alternating current magnetic susceptometer for use as a hydrogen gauge for hydrogen-storage materials was designed and developed. The experimental system can simultaneously measure the hydrogen equilibrium pressure and the magnetic susceptibility of metal hydrides. The background voltage of the susceptometer was stabilized for a long period of time, without any adjustments, by attaching an efficient compensation circuit. The performance of the susceptometer at a static hydrogen concentration was demonstrated by measuring the magnetic susceptibility of a Pd-hydrogen system under equilibrium conditions. The in situ measurement of the magnetic susceptibility of Pd during hydrogen absorption was carried out using the susceptometer. Since the in situ magnetic susceptibility obtained at a lower initial hydrogen pressure agreed with the magnetic susceptibility measured at a static hydrogen concentration, the susceptometer could be used to determine the hydrogen concentration in Pd in situ. At a higher initial hydrogen pressure, enhancement of the magnetic susceptibility was observed at the beginning of hydrogen absorption because the magnetic moments induced by the large temporary strain generated in the Pd affected the magnetic susceptibility. PMID:22852719

  14. Heating ability of La-Sr-Mn-Cu perovskite spheres under an alternating current magnetic field for magnetic hyperthermia mediators

    NASA Astrophysics Data System (ADS)

    Horiki, Mayumi; Nakagawa, Takashi; Seino, Satoshi; Yamamoto, Takao A.

    2013-03-01

    La0.666Sr0.373Mn0.943Cu0.018O3 spheres (average diameter: 2.4 mm) were used as magnetic hyperthermia mediators. They were prepared by the polymerized complex method and alginate gelation. A starch paste containing nine such spheres (0.1034 g) was maintained at a constant temperature when it was exposed to an alternating current magnetic field (frequency: 1 MHz; magnetic field strength: 20-55 Oe-rms). After exposure to a magnetic field with a field strength of 55 Oe-rms for 60 min, a temperature of T60=73.5 °C was obtained. T60 for field strengths of 40 and 55 Oe-rms differed by only 2.6 °C. La0.666Sr0.373Mn0.943Cu0.018O3 spheres satisfy the following important requirements for heating mediators: their amount can be controlled in tumors, their temperature can be controlled without monitoring, and their heating ability is independent of the field strength and direction. Thus, La0.666Sr0.373Mn0.943Cu0.018O3 spheres are promising heating mediators for inducing magnetic hyperthermia.

  15. Experimental setup for calorimetric alternating current loss measurements on high-temperature superconductor tapes in applied longitudinal magnetic fields carrying transport currents at variable temperatures

    Microsoft Academic Search

    Torbjörn Wass; Sven Hörnfeldt

    2004-01-01

    In most power devices, the conductor is carrying an ac transport current while it is exposed to an ac magnetic field transverse to the current path. In certain applications, such as multilayer power cables or the control winding in a controllable reactor, the conductors are exposed to a magnetic field component parallel with the current path that is longitudinal to

  16. Multielement determination in biological materials by differential pulse voltammetry

    SciTech Connect

    Adeloju, S.B.; Bond, A.M.; Briggs, M.H.

    1985-06-01

    A simple and reliable multielement approach for the determination of up to eight elements in a single biological sample digest at major, minor, trace, and/or ultratrace levels has been developed. The method employs a wide range of voltammetric techniques such as polarography, cathodic stripping, anodic stripping, and adsorption voltammetry in their differential pulse mode together with some chemical manipulations for sequential simultaneous determination of selenium, cadmium, lead, copper, zinc, nickel, and cobalt in the same solution. Arsenic can also be determined under favorable conditions. The determination of the eight elements in the digested samples takes about 3 h or approximately 25 min for each element per sample. The precision and accuracy, as demonstrated by the use of standard reference materials, are excellent. 14 references, 4 figures, 2 tables.

  17. Electrochemical characterization of bronze historical objects using voltammetry of microparticles

    NASA Astrophysics Data System (ADS)

    Elia, Alice; Dowsett, Mark; Adriaens, Annemie

    2015-02-01

    This work presents the application of voltammetry of microparticles (VMP) to the characterization of metallic artefacts. The paper illustrates the principle of the technique and the methods for the identification of metals and copper minerals. VMP can be considered a non-invasive technique as it requires a minimum amount of material for performing the analyses. To emphasize the efficacy of this technique regarding characterization of cultural heritage materials, two bronze artefacts of different historical periods were investigated. By using a paraffin-impregnated graphite electrode, the composition of the alloy and the copper minerals present in their patinas were analysed and identified. The results obtained from the electrochemical characterization were confirmed by complementary analysis carried out with X-ray fluorescence and X-ray diffraction.

  18. 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. PMID:25996561

  19. Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (?-tACS) Reflects Plastic Changes Rather Than Entrainment

    PubMed Central

    Vossen, Alexandra; Gross, Joachim; Thut, Gregor

    2015-01-01

    Background Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (?) frequency (8–12 Hz) enhances electroencephalographic (EEG) ?-oscillation long after tACS-offset. Two mechanisms have been suggested to underlie these changes in oscillatory EEG activity: tACS-induced entrainment of brain oscillations and/or tACS-induced changes in oscillatory circuits by spike-timing dependent plasticity. Objective We tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment “echoes.” To this end, we used a novel, intermittent tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and endogenous ?-frequency. Methods 12 healthy participants were stimulated at around individual ?-frequency for 11–15 min in four sessions using intermittent tACS or sham. Successive tACS events were either phase-continuous or phase-discontinuous, and either 3 or 8 s long. EEG ?-phase and power changes were compared after and between episodes of ?-tACS across conditions and against sham. Results ?-aftereffects were successfully replicated after intermittent stimulation using 8-s but not 3-s trains. These aftereffects did not reveal any of the characteristics of entrainment echoes in that they were independent of tACS phase-continuity and showed neither prolonged phase alignment nor frequency synchronization to the exact stimulation frequency. Conclusion Our results indicate that plasticity mechanisms are sufficient to explain ?-aftereffects in response to ?-tACS, and inform models of tACS-induced plasticity in oscillatory circuits. Modifying brain oscillations with tACS holds promise for clinical applications in disorders involving abnormal neural synchrony. PMID:25648377

  20. Cross-hemispheric Alternating Current Stimulation During a Nap Disrupts Slow Wave Activity and Associated Memory Consolidation

    PubMed Central

    Garside, Peter; Arizpe, Joseph; Lau, Chi-Ieong; Goh, Crystal; Walsh, Vincent

    2015-01-01

    Background Slow Wave Activity (SWA), the low frequency (<4 Hz) oscillations that characterize Slow Wave Sleep (SWS) are thought to relate causally to declarative memory consolidation during nocturnal sleep. Evidence is conflicting relating SWA to memory consolidation during nap however. Objective/hypothesis We applied transcranial alternating current stimulation (tACS) – which, with a cross-hemispheric electrode montage (F3 and F4 – International 10:20 EEG system), is able to disrupt brain oscillations–to determine if disruption of low frequency oscillation generation during afternoon nap is causally related to disruption in declarative memory consolidation. Methods Eight human subjects each participated in stimulation and sham nap sessions. A verbal paired associate learning (PAL) task measured memory changes. During each nap period, five 5-min stimulation (0.75 Hz cross-hemispheric frontal tACS) or sham intervals were applied with 1-min post-stimulation intervals (PSI's). Spectral EEG power for Slow (0.7–0.8 Hz), Delta (1.0–4.0 Hz), Theta (4.0–8.0 Hz), Alpha (8.0–12.0 Hz), and Spindle-range (12.0–14.0) frequencies was analyzed during the 1-min preceding the onset of stimulation and the 1-min PSI's. Results As hypothesized, power reduction due to stimulation positively correlated with reduction in word-pair recall post-nap specifically for Slow (P < 0.0022) and Delta (P < 0.037) frequency bands. Conclusions These results provide preliminary evidence suggesting a causal and specific role of SWA in declarative memory consolidation during nap. PMID:25697588

  1. Complementary and Alternative Medicine: Comparison of Current Knowledge, Attitudes and Interest among German Medical Students and Doctors

    PubMed Central

    Münstedt, Karsten; Harren, Hildegard; von Georgi, Richard; Hackethal, Andreas

    2011-01-01

    Although it has been agreed that complementary and alternative medicine (CAM) should be included in the German medical curriculum, there is no consensus on which methods and how it should be taught. This study aimed to assess needs for CAM education by evaluating current knowledge, attitudes and interests of medical students, general physicians and gynecologists. Two instruments based on established and validated questionnaires were developed. One was given to seventh semester medical students and the other to office-based doctors. Data were analyzed by bivariate correlation and cross-tabulation. Altogether 550 questionnaires were distributed—280 to doctors and 270 to medical students. Completed questionnaires were returned by 80.4% of students and 78.2% of doctors. Although 73.8% (160/219) of doctors and 40% (87/217) of students had already informed themselves about CAM, neither group felt that they knew much about CAM. Doctors believed that CAM was most useful in general medicine, supportive oncology, pediatrics, dermatology and gynecology, while students believed that dermatology, general medicine, psychiatry and rheumatology offered opportunities; both recommended that CAM should be taught in these areas. Both groups believed that CAM should be included in medical education; however, they believed that CAM needed more investigation and should be taught “critically". German doctors and students would like to be better informed about CAM. An approach which teaches fundamental competences to students, chooses specific content based on evidence, demographics and medical conditions and provides students with the skills they need for future learning should be adopted. PMID:19098296

  2. Increase in short-term memory capacity induced by down-regulating individual theta frequency via transcranial alternating current stimulation

    PubMed Central

    Vosskuhl, Johannes; Huster, René J.; Herrmann, Christoph S.

    2015-01-01

    Working memory (WM) and short-term memory (STM) supposedly rely on the phase-amplitude coupling (PAC) of neural oscillations in the theta and gamma frequency ranges. The ratio between the individually dominant gamma and theta frequencies is believed to determine an individual’s memory capacity. The aim of this study was to establish a causal relationship between the gamma/theta ratio and WM/STM capacity by means of transcranial alternating current stimulation (tACS). To achieve this, tACS was delivered at a frequency below the individual theta frequency. Thereby the individual ratio of gamma to theta frequencies was changed, resulting in an increase of STM capacity. Healthy human participants (N = 33) were allocated to two groups, one receiving verum tACS, the other underwent a sham control protocol. The electroencephalogram (EEG) was measured before stimulation and analyzed with regard to the properties of PAC between theta and gamma frequencies to determine individual stimulation frequencies. After stimulation, EEG was recorded again in order to find after-effects of tACS in the oscillatory features of the EEG. Measures of STM and WM were obtained before, during and after stimulation. Frequency spectra and behavioral data were compared between groups and different measurement phases. The tACS- but not the sham stimulated group showed an increase in STM capacity during stimulation. WM was not affected in either groups. An increase in task-related theta amplitude after stimulation was observed only for the tACS group. These augmented theta amplitudes indicated that the manipulation of individual theta frequencies was successful and caused the increase in STM capacity. PMID:26005411

  3. Electrochemical sensor with substitutional stripping voltammetry for highly sensitive endotoxin assay.

    PubMed

    Takano, Shinichiro; Inoue, Kumi Y; Takahashi, Satoko; Ino, Kosuke; Shiku, Hitoshi; Matsue, Tomokazu

    2014-10-01

    We have developed a novel method for detection of endotoxin with extra-high sensitivity by using substitutional stripping voltammetry (SSV). In this method, a p-aminophenol (pAP) conjugated peptide (Boc-Leu-Gly-Arg-pAP; LGR-pAP) was used as a substrate for a protease, which is activated at the last step of the endotoxin-induced Limulus amebocyte lysate (LAL) cascade reaction. Extra-highly sensitive detection of pAP liberated by the endotoxin-induced LAL reaction was successfully realized with SSV, based on the accumulation of an amperometric signal owing to exchange of the oxidation current of pAP generated at an electrode in a reaction cell with silver deposition on another electrode in a deposition cell. This reaction is driven by the difference in the redox potential between pAP/quinoneimine and silver/silver ion. The amount of the deposited silver is quantified by anodic stripping voltammetry (ASV). This SSV-based endotoxin assay was performed with a chip device comprising two cells, each of which was connected via a liquid junction made of Vycor® glass. The reaction cell and the deposition cell contained a standard endotoxin sample with LAL regents containing LGR-pAP and AgNO3 solution, respectively. After the cells were electrically connected for 60 min, ASV was conducted in the deposition cell to quantify the total electrical charge derived by the oxidation of free pAP in the reaction cell. The ASV signal increased with the increase of the endotoxin concentration in the sample solution in the range of 0.5-1000 EU L(-1). PMID:25096015

  4. Determination of poly(vinyl alcohol) by adsorptive stripping voltammetry based on its copper(II) complex

    Microsoft Academic Search

    Ming Song; Hui-Min Ma; Yue-Xian Huang; Shu-Chuan Liang

    1997-01-01

    Adsorptive stripping voltammetry with a hanging mercury-drop electrode based on the adsorptive enhancement of Cu(II)-poly (vinyl alcohol) (PVA) has been developed for PVA determination. In a 0.1 mol l?1 sodium carbonate buffer solution of pH 11.0 containing l0 ?mol l?1 Cu(II), the adsorptive peak of Cu(II)-PVA has a potential of -0.125V (vs. Ag\\/AgCl). The increase in peak current is proportional

  5. Investigation of parameters of the three phase high-voltage alternating current plasma generator with power up to 100 kW working on steam

    NASA Astrophysics Data System (ADS)

    Rutberg, Ph G.; Lukyanov, S. A.; Kiselev, A. A.; Kuschev, S. A.; Nakonechny, Gh V.; Nikonov, A. V.; Popov, S. D.; Serba, E. O.; Spodobin, V. A.; Surov, A. V.

    2011-01-01

    The paper presents the results of experimental investigation of parameters of the three-phase high voltage alternating current plasma generator with power up to 100 kW operating on steam with gas protection of the electrodes. Researches were carried out over a range of arc current from 25 to 50 A and range of steam consumption of 3-5 g/s. Current-voltage and volt consumable characteristics, operation oscillograms and dependence of power versus the flow rate of steam and protective gas are presented.

  6. Transient eddy current distribution in the shield of the passively compensated, compensated pulsed alternator: iron-core machines

    Microsoft Academic Search

    S. B. Pratap

    1990-01-01

    A model describing the transient eddy current distribution in the shield of a passively compensated compulsator is derived. An analytical solution of the two-dimensional convective diffusion equation is obtained. In obtaining the solution, a response to a step excitation is solved. This is convolved with specific time functions corresponding to the nature of the excitation current. The responses to step

  7. Imaging localised corrosion of NiTi shape memory alloys by means of alternating current scanning electrochemical microscopy (AC-SECM)

    Microsoft Academic Search

    A. Schulte; S. Belger; M. Etienne; W. Schuhmann

    2004-01-01

    This communication aims at the investigation of NiTi shape memory alloys (nitinol) with respect to visualisation of localised corrosion phenomena. Alternating current scanning electrochemical microscopy (AC-SECM) has been used as an approach to detect inhomogeneities in the passive oxide layer of nitinol with high spatial resolution. The appearance of microscopic corroding spots on the surface can be imaged due to

  8. 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

    2015-01-01

    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

  9. 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.

  10. 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

  11. Manganese Detection with a Metal Catalyst Free Carbon Nanotube Electrode: Anodic versus Cathodic Stripping Voltammetry

    PubMed Central

    Yue, Wei; Bange, Adam; Riehl, Bill L.; Riehl, Bonnie D.; Johnson, Jay M.; Papautsky, Ian; Heineman, William R.

    2013-01-01

    Anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120 nM and 93 nM were achieved for ASV and CSV, respectively, with a deposition time of 60 s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements. PMID:24235806

  12. Manganese Detection with a Metal Catalyst Free Carbon Nanotube Electrode: Anodic versus Cathodic Stripping Voltammetry.

    PubMed

    Yue, Wei; Bange, Adam; Riehl, Bill L; Riehl, Bonnie D; Johnson, Jay M; Papautsky, Ian; Heineman, William R

    2012-10-01

    Anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120 nM and 93 nM were achieved for ASV and CSV, respectively, with a deposition time of 60 s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements. PMID:24235806

  13. An approximate model for three-dimensional alternating current potential drop analyses using a commercial finite element code

    E-print Network

    Nagy, Peter B.

    depth of penetration d, also referred to as skin depth, can be estimated by the well-known formula d ¼ 1 25 October 2009 Keywords: Potential drop Modelling Finite element method a b s t r a c t Alternating or permeability [6,7]. Measurements are commonly done with a four-point probe which uses one pair of electrodes

  14. Iron organic speciation determination in rainwater using cathodic stripping voltammetry.

    PubMed

    Cheize, Marie; Sarthou, Géraldine; Croot, Peter L; Bucciarelli, Eva; Baudoux, Anne-Claire; Baker, Alex R

    2012-07-29

    A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17±0.05 nM (n=14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10-70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52-6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of ?'(Fe(3+)(NN)(3)) increased linearly with increasing pH according to log ?'(Fe(3+)(NN)(3)) (salinity=2.9, T=20 °C). The validation of the method was carried out using desferrioxamine mesylate B (DFOB) as a natural model ligand for Fe. Adequate detection windows were defined to detect this class of ligands in rainwater with 40 ?M of NN from pH 5.52 to 6.20. The concentration of Fe-complexing natural ligands was determined for the first time in three unfiltered and one filtered rainwater samples. Organic Fe-complexing ligand concentrations varied from 104.2±4.1 nM equivalent of Fe(III) to 336.2±19.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe(3+), varied from 21.1±0.2 to 22.8±0.3. This method will provide important data for improving our understanding of the role of wet deposition in the biogeochemical cycling of iron. PMID:22769004

  15. Alternating-current measurement and noninvasive data ring utilizing the Faraday effect in a closed-loop fiber magnetometer.

    PubMed

    Berwick, M; Jones, J D; Jackson, D A

    1987-04-01

    A novel fiber-optic polarimetric configuration for a magnetometer utilizing the Faraday effect is described. The system is operated in a closed-loop mode using magneto-optic feedback through a simple current-driven solenoid to maintain the azimuth of the optical output from the polarimeter constant. In this mode of operation scale-factor errors due to changes in the Verdet constant of the fiber are effectively eliminated. The minimum detectable current was less than 1 mA, with linear operation up to several amperes. A multiplexed system was also demonstrated, with potential application as a multiaccess noninvasive data ring. PMID:19738869

  16. Studies on substituted phenols by differential pulse cathodic stripping voltammetry: 1. Pentachlorophenol

    Microsoft Academic Search

    Rozali bin Othman; John O. Hill; Robert J. Magee

    1986-01-01

    A study of chlorophenols using differential pulse cathodic stripping voltammetry (dpcsv) is reported. Of the wide range of chlorophenols investigated, only pentachlorophenol and 2,3,4,6-tetrachlorophenol yield stripping peaks.

  17. A study of certain trace metals in sea water using anodic stripping voltammetry

    E-print Network

    Fitzgerald, William Francis, 1926-

    1970-01-01

    Anodic stripping voltammetry utilizing a thin film mercury composite graphite electrode has been evaluated and applied for the direct analysis of the metals, Zn,J Cu, Pb, and Cd in sea water. The electrode was observed to ...

  18. A Study of Second-Year Engineering Students' Alternative Conceptions about Electric Potential, Current Intensity and Ohm's Law

    ERIC Educational Resources Information Center

    Periago, M. Cristina; Bohigas, Xavier

    2005-01-01

    The aim of this research was to evaluate and analyse second-year industrial engineering and chemical engineering students prior knowledge of conceptual aspects of "circuit theory". Specifically, we focused on the basic concepts of electric potential and current intensity and on the fundamental relationship between them as expressed by Ohm's law.…

  19. Metal Ion Uptake and Voltammetry on a Dithiocarbamate Containing Polymer Modified Electrode

    Microsoft Academic Search

    M. D. Imisides; D. M. T. ORiordan; G. G. Wallace

    1988-01-01

    There is a need to expand the range of working electrodes which can be us in analytical voltammetry.In this work, the synthesis of a thio containing (poly) N-Ethyl Tyramine electrode is described. Cyclic voltammetry, SEM and EPMA were used to characterise the modified electrode.The ability of this electrode to uptake copper, nickel, mercury or cobalt ions from solution was investigated.

  20. ON-State Reliability of Solid-Electrolyte Switch under Pulsed Alternating Current Stress for Programmable Logic Device

    Microsoft Academic Search

    Naoki Banno; Toshitsugu Sakamoto; Munehiro Tada; Makoto Miyamura; Koichiro Okamoto; Hiromitsu Hada; Masakazu Aono

    2011-01-01

    In this paper, we describes the ON-state reliability of a nonvolatile solid-electrolyte switch for a programmable logic device (PLD). The ON-state requirement for this application is different from that of a Cu via or an interconnect, since the pulsed-AC current is applied to the switch when the voltage changes in the interconnect. We experimentally demonstrate a recovering phenomenon in the

  1. The influence of insulator properties on the electro-optical performance of flexible ZnS:ErF 3 alternating current thin film electroluminescent devices

    Microsoft Academic Search

    Nigel Shepherd; David C. Morton; Eric W. Forsythe; Dave Chiu

    2006-01-01

    We have developed flexible ZnS:ErF3 alternating current thin film electroluminescent devices on molybdenum foils, and quantified the effect of insulator properties for the case of alumina (Al2O3) and barium tantalate (BaTa2O6) on the device electrical characteristics, and infrared emission. The inverted, full-stack structures could be flexed in tension and compression without mechanical failure or deterioration of optical output, and flex

  2. Can an AC (alternating current) electrical system replace the present DC system in the automobile? An investigative feasibility study. II. Comparison and tradeoffs

    Microsoft Academic Search

    M. Abul Masrur; Daryl S. Sitar; V. A. Sankaran

    1998-01-01

    For Part I see ibid., vol.47, no.3, p.1072-80 (1998). In Part I of this paper, the possibility of using an AC (alternating current) electrical system instead of the present DC system in the automobile was discussed. The various possible architectures were described in Part I. Part II continues with the issues of various tradeoffs related to cost, size, and overall

  3. Spatiotemporal Behavior of Excited Xenon-Atom Density in Accordance With Xenon Mole Fraction to Neon in Alternating-Current Plasma Display Panels by Laser-Absorption Spectroscopy

    Microsoft Academic Search

    Phil Yong Oh; Jung Hyun Kim; Youngjune Hong; Seok Ho Cho; Guangsup Cho; Eun Ha Choi

    2008-01-01

    In this paper, spatiotemporal behavior of the excited Xe-atom density of metastable state was investigated by laser-absorption spectroscopy in alternating-current plasma display panel in accordance with the Xe mole fraction to Ne, which can be connected to the relative luminous efficiency over all spaces in a discharge cell. The various test panels with Xe mole fractions of 4%, 7%, 10%,

  4. Excited xenon density and ion-induced secondary electron emission coefficient for vacuum ultraviolet luminous efficiency in alternating current plasma display panel

    Microsoft Academic Search

    Eun Ha Choi; Philyong Oh; Byoung Hee Hong; Yun Ki Kim; Byoung Joo Park; Jaewon Cho; Yoonho Seo; Guangsup Cho

    2008-01-01

    It is shown for Xe content ratio of 10% that the excited xenon atom density for the 1s5 metastable state is 3.0×1012 cm?3 with a gap distance of 50 ?m under a fixed gas pressure of 5.3×104 Pa in alternating current plasma display panels. It is observed that the VUV emission of 173 nm continues after its peak and lasts much longer than 147 nm

  5. Determination of buprenorphine by differential pulse voltammetry on carbon paste electrode using SDS as an enhancement factor.

    PubMed

    Behpour, Mohsen; Valipour, Akram; Keshavarz, Mahin

    2014-09-01

    In the present study, a facile electrochemical approach is proposed for the determination of buprenorphine (BPR) in the presence of sodium dodecyl sulfate (SDS). SDS was applied for amplification of oxidation signal. Carbon paste electrode (CPE) used as working electrode and cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were carried out in phosphate buffer solution (pH3.0). Under optimal experimental conditions, the oxidation current increased with the addition of BPR in the sample and two dynamic ranges obtained from 4.00 nM to 0.126 ?M and from 0.126 to 0.317 ?M by DPV and exhibited a low detection limit (LOD) of 1.33 nM (S/N=3). This offered method has been used for the determination of BPR in the real samples and has validated with the recovery test for BPR spiked urine samples. The result demonstrated that this method is a simple, sensitive, rapid, low-cost, and stable method for BPR detection. PMID:25063147

  6. Determination of water in room temperature ionic liquids by cathodic stripping voltammetry at a gold electrode.

    PubMed

    Zhao, Chuan; Bond, Alan M; Lu, Xunyu

    2012-03-20

    An electrochemical method based on cathodic stripping voltammetry at a gold electrode has been developed for the determination of water in ionic liquids. The technique has been applied to two aprotic ionic liquids, (1-butyl-3-ethylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate), and two protic ionic liquids, (bis(2-hydroxyethyl)ammonium acetate and triethylammonium acetate). When water is present in an ionic liquid, electrooxidation of a gold electrode forms gold oxides. Thus, application of an anodic potential scan or holding the potential of the electrode at a very positive value leads to accumulation of an oxide film. On applying a cathodic potential scan, a sensitive stripping peak is produced as a result of the reduction of gold oxide back to gold. The magnitude of the peak current generated from the stripping process is a function of the water concentration in an ionic liquid. The method requires no addition of reagents and can be used for the sensitive and in situ determination of water present in small volumes of ionic liquids. Importantly, the method allows the determination of water in the carboxylic acid-based ionic liquids, such as acetate-based protic ionic liquids, where the widely used Karl Fischer titration method suffering from an esterification side reaction which generates water as a side product. PMID:22372467

  7. 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

    2015-05-01

    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-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. PMID:25785694

  8. High-resolution hepatitis C virus subtyping using NS5B deep sequencing and phylogeny, an alternative to current methods.

    PubMed

    Quer, Josep; Gregori, Josep; Rodríguez-Frias, Francisco; Buti, Maria; Madejon, Antonio; Perez-del-Pulgar, Sofia; Garcia-Cehic, Damir; Casillas, Rosario; Blasi, Maria; Homs, Maria; Tabernero, David; Alvarez-Tejado, Miguel; Muñoz, Jose Manuel; Cubero, Maria; Caballero, Andrea; del Campo, Jose Antonio; Domingo, Esteban; Belmonte, Irene; Nieto, Leonardo; Lens, Sabela; Muñoz-de-Rueda, Paloma; Sanz-Cameno, Paloma; Sauleda, Silvia; Bes, Marta; Gomez, Jordi; Briones, Carlos; Perales, Celia; Sheldon, Julie; Castells, Lluis; Viladomiu, Lluis; Salmeron, Javier; Ruiz-Extremera, Angela; Quiles-Pérez, Rosa; Moreno-Otero, Ricardo; López-Rodríguez, Rosario; Allende, Helena; Romero-Gómez, Manuel; Guardia, Jaume; Esteban, Rafael; Garcia-Samaniego, Javier; Forns, Xavier; Esteban, Juan Ignacio

    2015-01-01

    Hepatitis C virus (HCV) is classified into seven major genotypes and 67 subtypes. Recent studies have shown that in HCV genotype 1-infected patients, response rates to regimens containing direct-acting antivirals (DAAs) are subtype dependent. Currently available genotyping methods have limited subtyping accuracy. We have evaluated the performance of a deep-sequencing-based HCV subtyping assay, developed for the 454/GS-Junior platform, in comparison with those of two commercial assays (Versant HCV genotype 2.0 and Abbott Real-time HCV Genotype II) and using direct NS5B sequencing as a gold standard (direct sequencing), in 114 clinical specimens previously tested by first-generation hybridization assay (82 genotype 1 and 32 with uninterpretable results). Phylogenetic analysis of deep-sequencing reads matched subtype 1 calling by population Sanger sequencing (69% 1b, 31% 1a) in 81 specimens and identified a mixed-subtype infection (1b/3a/1a) in one sample. Similarly, among the 32 previously indeterminate specimens, identical genotype and subtype results were obtained by direct and deep sequencing in all but four samples with dual infection. In contrast, both Versant HCV Genotype 2.0 and Abbott Real-time HCV Genotype II failed subtype 1 calling in 13 (16%) samples each and were unable to identify the HCV genotype and/or subtype in more than half of the non-genotype 1 samples. We concluded that deep sequencing is more efficient for HCV subtyping than currently available methods and allows qualitative identification of mixed infections and may be more helpful with respect to informing treatment strategies with new DAA-containing regimens across all HCV subtypes. PMID:25378574

  9. The use of cyclic voltammetry for wine analysis: determination of polyphenols and free sulfur dioxide.

    PubMed

    Makhotkina, Olga; Kilmartin, Paul A

    2010-06-01

    The use of cyclic voltammetry to characterize wines and wine polyphenols in a pH 3.3 model wine solution has been extended to take into account the effects of sulfur dioxide and polyphenol adsorption processes. A good correlation was obtained between a cyclic voltammetric measure, based upon the response produced before and after acetaldehyde additions, and the concentration of free sulfur dioxide in eight white wines (r(2)=0.974). By the addition of acetaldehyde to the white wines, an important new step in the methodology, the area under the anodic scan in the potential range from -100 to 1200 mV (Ag/AgCl) closely matched the spectroscopic measure of total polyphenols (absorbance at 280 nm) for the white wines, when both were measured in terms of caffeic acid equivalents (r(2)=0.949). The anodic peak area accounted for about 70% of the 280 nm total phenols measure, in catechin equivalents, for the red wines, and a good linear correlation was also obtained (r(2)=0.942). The level of catechol and galloyl-containing polyphenols in the wines was calculated by measuring the size of the first anodic peak at around 450 mV after treatment of the wines with acetaldehyde; the peak current correlated well with the total caffeic acid derivatives in the white wines determined by HPLC (r(2)=0.982). The concentration of flavonols was estimated by selective adsorption of these compounds onto the carbon electrode and determining the anodic peak current at 1120 mV, with good correlations obtained when compared to total flavonols as measured by HPLC (r(2)=0.984 for the red wines, and r(2)=0.987 for the white wines). PMID:20493292

  10. Alternating-current white aC:H thin-film light-emitting diodes with composition-graded carrier injection layers

    Microsoft Academic Search

    Shih-Yung Lo; Tzu-Kang Wang; Rong-Hwei Yeh; Jyh-Wong Hong

    2008-01-01

    The optoelectronic characteristics of hydrogenated intrinsic amorphous carbon (i-a-C:H) alternating-current white thin-film light-emitting diodes (ACW-TFLEDs) with composition-graded (CG) hydrogenated intrinsic amorphous silicon carbide (i-a-SiC:H, CG C) layers had been obviously improved with additionally incorporated CG hydrogenated intrinsic amorphous silicon germanium (i-a-SiGe:H, CG Ge) carrier injection layers. For an ACW-TFLED with CG Ge carrier injection layers, the electroluminescence (EL) threshold voltage

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

    NASA Astrophysics Data System (ADS)

    Wen, Rui-Tao; Granqvist, Claes G.; Niklasson, Gunnar A.

    2014-10-01

    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+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 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 104 cycles when the applied voltage was limited to 4.1 V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a "smart window" for energy-efficient buildings.

  12. Alloy corrosion studied by a combination of stripping voltammetry and the rotating ring-disk electrode. Lead-cadmium alloy

    SciTech Connect

    Zhdanov, V.V.; Filanovskii, B.K.

    1984-08-01

    The authors have used the rotating ring-disk electrode (RRDE) in combination with stripping voltammetry (SVA) at solid electrodes in order to determine partial dissolution rates of alloy components in the vicinity of the steady potential and also under cathodic and anodic polarization. The method of SVA is used in the analytical determination of trace amounts of heavy metals dissolved in electrolytes. The method was used to investigate the electrolytic dissolution of lead-cadmium alloy in the vicinity of the steady potential and under cathodic polarization. Results obtained when studying the corrosion behavior of the lead-cadmium alloy are given. The results indicate that selective cadmium dissolution occurs initially, but then this is replaced by uniform alloy dissolution. The data shows that the partial currents of alloy component dissolution can be determined by a combination of SVA and RRDE.

  13. 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

  14. Model predictions of copper speciation in coastal water compared to measurements by analytical voltammetry.

    PubMed

    Ndungu, Kuria

    2012-07-17

    Trace metal toxicity to aquatic biota is highly dependent on the meta?s chemical speciation. Accordingly, metal speciation is being incorporated in to water quality criteria and toxicity regulations using the Biotic Ligand Model (BLM) but there are currently no BLM for biota in marine and estuarine waters. In this study, I compare copper speciation measurements in a typical coastal water made using Competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) to model calculations using Visual MINTEQ. Both Visual MINTEQ and BLM use similar programs to model copper interactions with dissolved organic matter-DOM (i.e., the Stockholm Humic Model and WHAM-Windermere Humic Aqueous Model, respectively). The total dissolved (<0.4 ?m filter) copper concentration, [CuT] in the study sites ranged from <10 nM close to the open Baltic Sea to ca. 50 nM in the vicinity of a marina in the Stockholm Archipelago. The corresponding free copper concentration [Cu2+], measured by CLE-ACSV ranged from 10–13.2 M to 10–12.0 M for the reference and marina sites, respectively, whereas the corresponding [Cu2+] modeled calculations ranged from 10–12.5 M to 10–11.6 M. The low copper to DOM ratios (similar to 0.0004 mg Cu per mg DOC) in these coastal waters ensured that ambient dissolved copper was overwhelmingly chelated to strong Cu–binding ligands (12 < log KCuL1,Cu2+Cond >14). The modeled [Cu2+] could be fitted to the experimental values better after the conditional stability constant for copper binding to fulvic acid (FA) complexes in DOM in the SHM was adjusted to account for higher concentration of strong Cu-binding sites in FA. PMID:22724636

  15. Current Efforts to Develop Alternate

    Microsoft Academic Search

    Daniel F. Schwartz; Robert R. Bennett; Kenneth J. Graham; Thomas L. Boggs; Alice I. Atwood

    1998-01-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB

  16. Current Efforts to Develop Alternate

    Microsoft Academic Search

    Daniel F. Schwartz; Robert R. Bennett; Kenneth J. Graham; Thomas L. Boggs; Alice I. Atwood

    2001-01-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB

  17. Current Efforts to Develop Alternate

    Microsoft Academic Search

    Daniel F. Schwartz; Robert R. Bennett; Kenneth J. Graham; Thomas L. Boggs; Alice I. Atwood; A. Garn Butcher

    2002-01-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2)

  18. Start-up phase of the high pressure mercury lamp fed by an alternating current. Application to the study of a dynamic regime for lighting micro-network

    SciTech Connect

    Stambouli, M.; Charrada, K.; Zissis, G.

    1997-12-31

    The lamps electrical characteristics evolution during their warm-up phases generates variable harmonic currents circulation. These harmonic currents induce, in some cases, constraints that cause ominous effects on the supply network (regime of the neutral, unnecessary losses in ballasts and the transformer of feeding, etc.). To understand and analyze the electrical phenomenon evolution in a lighting network, it is desirable to simulate the lamps-circuit system. It has been shown that the behavior description of the discharge, in the course of the transitory phase, can be obtained by assimilating this phase to three phases successive describe by appropriate models (Phase A corresponding to a non LTE regime, Phase B corresponding to an intermediate regime, Phase C corresponding to a regime close to LTE). From the point of view of the network behavior description, these three phases do not present the same importance. It will be shown, in this work, that the phase C accounts for the essential electrical phenomenon linked to lamps. While during phases A and B the behavior of the system differs few that the one observed when lamps are in short circuit. So, here the authors have studied the interaction lamp-circuit supplied by alternating current with a variable pressure LTE model that describes the most important phase of the dynamic regime. This phase covers the most interesting electrical phenomenon (variation of the arc voltage of 40 to 150V).

  19. Simultaneous determination of Pt and Rh by catalytic adsorptive stripping voltammetry, using hexamethylene tetramine (HMTA) as complexing agent.

    PubMed

    Dalvi, Aditi A; Satpati, A K; Palrecha, M M

    2008-06-15

    Characteristics of the adsorption/electro-reduction of Pt/Rh hexamethylene tetramine (HMTA) complex on static mercury drop electrode surface were studied. Cyclic voltammetry was carried out to get the insight about the mechanistic behaviour of the catalytic current obtained in the voltammetric scan of Pt/Rh HMTA complex in acidic solution. Adsorptive stripping voltammetry using HMTA as the complexing agent was found to be highly sensitive method for the determination of Pt/Rh. Voltammetric measurements were carried out using hanging mercury drop electrode (HMDE) as the working electrode, a glassy carbon rod as the counter and an Ag/AgCl/KCl(saturated) as the reference electrode. Various electrochemical parameters like deposition potential, deposition time, concentration of the ligand, supporting electrolyte etc. were optimized. The detection limit of Pt and Rh was found to be 4.38 pM L(-1) and 2.80 pM L(-1), respectively for the deposition time of 30 s. Simultaneous determination of Pt(II) and Rh(III) in water samples was possible. The method was found to be free from the commonly occurring interfering ions such as Cu(II), Cd(II), Zn(II), Pb(II), Cr(III), Cr(VI), Fe(III), Fe(II), Ni(II) and Co(II). Spike recovery tests for both Pt and Rh in tap water and sea water samples were also carried out. The method has been verified by analyzing certified reference material (WMG-1). PMID:18585228

  20. Simultaneous determination of ultra trace amounts of lead and cadmium in food samples by adsorptive stripping voltammetry

    Microsoft Academic Search

    Shahryar Abbasi; Kobra Khodarahmiyan; Freshteh Abbasi

    2011-01-01

    A selective and sensitive method for simultaneous determination of lead and cadmium by adsorptive differential pulse cathodic stripping voltammetry is presented. The method is based on adsorptive accumulation of the complexes of Pb (II) and Cd (II) ions with 2-mercaptobenzothiazole onto hanging mercury drop electrode (HMDE), followed by the reduction of the adsorbed species by differential pulse cathodic stripping voltammetry.

  1. Differential pulse anodic stripping voltammetry of barium and lead in gunshot residues

    Microsoft Academic Search

    Curt A. Woolever; Howard D. Dewald

    2001-01-01

    Differential pulse anodic stripping voltammetry (DPASV) has been applied for characterization and quantitative detection of barium and lead from gunshot residues (GSR). Previous electrochemical techniques have detected antimony and lead from GSR, however barium has never been detected. This technique allows for simultaneous detection of Ba and Pb that is simple, fast, and nondestructive.

  2. 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…

  3. Phase-inversion cellulose acetate membranes for suppression of protein interferences in anodic stripping voltammetry

    Microsoft Academic Search

    Boy Hoyer; Nina Jensen

    1995-01-01

    The phase-inversion (PI) method was used to cast permselective cellulose acetate membranes on glassy carbon electrodes with the aim of suppressing protein interferences in anodic stripping voltammetry (ASV). By using cadmium and lead as test analytes and differential pulse ASV as detection method, it was found that the modification of the electrode greatly reduces the interference from albumin. Cellulose acetate

  4. Anodic stripping voltammetry of lead and cadmium using a mercury film electrode and thiocyanate

    Microsoft Academic Search

    Eric Fischer; Constant M. G van den Berg

    1999-01-01

    It is well known that lead and cadmium can be determined with good sensitivity using anodic stripping voltammetry (ASV) and a mercury film electrode. However, the mercury film formation is poorly reproducible and cannot fully be removed electrochemically. We have evaluated procedures to improve the reproducibility and sensitivity of the ASV method and found that in the presence of thiocyanate

  5. An inexpensive and renewable pencil electrode for use in field-based stripping voltammetry

    Microsoft Academic Search

    Alan M. Bond; Peter J. Mahon; Jörg Schiewe; Victoria Vicente-Beckett

    1997-01-01

    Renewable graphite pencil writing devices have been available for many years. In this work it is shown that those writing tools are readily adapted to produce a “low tech”, renewable and minimal cost electrode which, when employed for anodic stripping voltammetry under mercury plated thin-film conditions, performs equally well as commercially available “high tech” carbon electrodes. In the absence of

  6. DETERMINATION OF ZINC, CADMIUM, LEAD, AND COPPER IN WATER BY ANODIC STRIPPING VOLTAMMETRY

    EPA Science Inventory

    The Tennessee Valley Authority developed a method of differential pulse anodic stripping voltammetry for determining total concentrations of cadmium and lead in water samples from ash ponds at steam-electric generating plants. After digestion of the sample and addition of reagent...

  7. 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…

  8. Measuring mercury ion concentration with a carbon nano tube paste electrode using the cyclic voltammetry method

    Microsoft Academic Search

    Suw Young LY; Sung Kuk Kim; Tae Hyun Kim; Young Sam Jung; Sang Min Lee

    2005-01-01

    A simply prepared carbon nano tube paste electrode (CNTPE) was utilized for monitoring mercury ion concentration using the cyclic voltammetry (CV) method and the square wave anodic stripping voltammetric (SWASV) method. The CNTPE was compared with various conventional electrodes. The CNTPE method was applied to determine the concentration of trace levels of Hg(II) in several water samples, which yielded a

  9. Determination of selected drugs in human urine by differential pulse voltammetry technique

    Microsoft Academic Search

    Irena Baranowska; Piotr Markowski; Anna Gerle; Jacek Baranowski

    2008-01-01

    A new, simple and selective differential pulse voltammetry (DPV) method for the simultaneous determination of selected drugs in model solutions and spiked human urine samples with prior extraction was developed and validated. The objects of analysis were paracetamol, furosemide, dipyrone, cefazolin and dexamethasone belonging to four different therapeutic groups (antibiotics, analgesic, demulcent and diuretic). Analytical methods for the preparation of

  10. Square-wave voltammetry assays for glycoproteins on nanoporous gold.

    PubMed

    Pandey, Binod; Bhattarai, Jay K; Pornsuriyasak, Papapida; Fujikawa, Kohki; Catania, Rosa; Demchenko, Alexei V; Stine, Keith J

    2014-03-15

    Electrochemical enzyme-linked lectinsorbent assays (ELLA) were developed using nanoporous gold (NPG) as a solid support for protein immobilization and as an electrode for the electrochemical determination of the product of the reaction between alkaline phosphatase (ALP) and p-aminophenyl phosphate (p-APP), which is p-aminophenol (p-AP). Glycoproteins or concanavalin A (Con A) and ALP conjugates were covalently immobilized onto lipoic acid self-assembled monolayers on NPG. The binding of Con A - ALP (or soybean agglutinin - ALP) conjugate to glycoproteins covalently immobilized on NPG and subsequent incubation with p-APP substrate was found to result in square-wave voltammograms whose peak difference current varied with the identity of the glycoprotein. NPG presenting covalently bound glycoproteins was used as the basis for a competitive electrochemical assay for glycoproteins in solution (transferrin and IgG). A kinetic ELLA based on steric hindrance of the enzyme-substrate reaction and hence reduced enzymatic reaction rate after glycoprotein binding is demonstrated using immobilized Con A-ALP conjugates. Using the immobilized Con A-ALP conjugate, the binding affinity of immunoglobulin G (IgG) was found to be 105 nM, and that for transferrin was found to be 650 nM. Minimal interference was observed in the presence of 5 mg mL(-1) BSA as a model serum protein in both the kinetic and competitive ELLA. Inhibition studies were performed with methyl D-mannoside for the binding of TSF and IgG to Con A-ALP; IC50 values were found to be 90 ?M and 286 ?M, respectively. Surface coverages of proteins were estimated using solution depletion and the BCA protein concentration assay. PMID:24611035

  11. Square-wave voltammetry assays for glycoproteins on nanoporous gold

    PubMed Central

    Pandey, Binod; Bhattarai, Jay K.; Pornsuriyasak, Papapida; Fujikawa, Kohki; Catania, Rosa; Demchenko, Alexei V.; Stine, Keith J.

    2014-01-01

    Electrochemical enzyme-linked lectinsorbent assays (ELLA) were developed using nanoporous gold (NPG) as a solid support for protein immobilization and as an electrode for the electrochemical determination of the product of the reaction between alkaline phosphatase (ALP) and p-aminophenyl phosphate (p-APP), which is p-aminophenol (p-AP). Glycoproteins or concanavalin A (Con A) and ALP conjugates were covalently immobilized onto lipoic acid self-assembled monolayers on NPG. The binding of Con A – ALP (or soybean agglutinin – ALP) conjugate to glycoproteins covalently immobilized on NPG and subsequent incubation with p-APP substrate was found to result in square-wave voltammograms whose peak difference current varied with the identity of the glycoprotein. NPG presenting covalently bound glycoproteins was used as the basis for a competitive electrochemical assay for glycoproteins in solution (transferrin and IgG). A kinetic ELLA based on steric hindrance of the enzyme-substrate reaction and hence reduced enzymatic reaction rate after glycoprotein binding is demonstrated using immobilized Con A–ALP conjugates. Using the immobilized Con A-ALP conjugate, the binding affinity of immunoglobulin G (IgG) was found to be 105 nM, and that for transferrin was found to be 650 nM. Minimal interference was observed in the presence of 5 mg mL?1 BSA as a model serum protein in both the kinetic and competitive ELLA. Inhibition studies were performed with methyl D-mannoside for the binding of TSF and IgG to Con A-ALP; IC50 values were found to be 90 ?M and 286 ?M, respectively. Surface coverages of proteins were estimated using solution depletion and the BCA protein concentration assay. PMID:24611035

  12. Detection and classification of gaseous sulfur compounds by solid electrolyte cyclic voltammetry of cermet sensor array.

    PubMed

    Kramer, Kirsten E; Rose-Pehrsson, Susan L; Hammond, Mark H; Tillett, Duane; Streckert, Holger H

    2007-02-12

    Electrochemical sensors composed of a ceramic-metallic (cermet) solid electrolyte are used for the detection of gaseous sulfur compounds SO(2), H(2)S, and CS(2) in a study involving 11 toxic industrial chemical (TIC) compounds. The study examines a sensor array containing four cermet sensors varying in electrode-electrolyte composition, designed to offer selectivity for multiple compounds. The sensors are driven by cyclic voltammetry to produce a current-voltage profile for each analyte. Raw voltammograms are processed by background subtraction of clean air, and the four sensor signals are concatenated to form one vector of points. The high-resolution signal is compressed by wavelet transformation and a probabilistic neural network is used for classification. In this study, training data from one sensor array was used to formulate models which were validated with data from a second sensor array. Of the 11 gases studied, 3 that contained sulfur produced the strongest responses and were successfully analyzed when the remaining compounds were treated as interferents. Analytes were measured from 10 to 200% of their threshold-limited value (TLV) according to the 8-h time weighted average (TWA) exposure limits defined by the National Institute of Occupational Safety and Health (NIOSH). True positive classification rates of 93.3, 96.7, and 76.7% for SO(2), H(2)S, and CS(2), respectively, were achieved for prediction of one sensor unit when a second sensor was used for modeling. True positive rates of 83.3, 90.0, and 90.0% for SO(2), H(2)S, and CS(2), respectively, were achieved for the second sensor unit when the first sensor unit was used for modeling. Most of the misclassifications were for low concentration levels (such 10-25% TLV) in which case the compound was classified as clean air. Between the two sensors, the false positive rates were 2.2% or lower for the three sulfur compounds, 0.9% or lower for the interferents (eight remaining analytes), and 5.8% or lower for clean air. The cermet sensor arrays used in this analysis are rugged, low cost, reusable, and show promise for multiple compound detection at parts-per-million (ppm) levels. PMID:17386588

  13. Use of a modified, high-sensitivity, anodic stripping voltammetry method for determination of zinc speciation in the North Atlantic Ocean.

    PubMed

    Jakuba, Rachel Wisniewski; Moffett, James W; Saito, Mak A

    2008-05-01

    Zinc speciation is considered to be an important determinant of the biological availability of zinc. Yet in oceanic surface waters, characterization of zinc speciation is difficult due to the low concentrations of this essential micronutrient. In this study, an anodic stripping voltammetry method previously developed for the total determination of cadmium and lead was successfully adapted to the measurement of zinc speciation. The method differs from previous zinc speciation anodic stripping voltammetry methods in that a fresh mercury film is plated with each sample aliquot. The fresh film anodic stripping voltammetry method was compared to competitive ligand exchange cathodic stripping voltammetry in a profile from the North Atlantic Ocean. Results using the fresh film anodic stripping voltammetry method were similar to those determined using the cathodic stripping voltammetry method, though ligand concentrations determined by fresh film anodic stripping voltammetry were generally slightly higher than those determined by cathodic stripping voltammetry. There did not seem to be a systematic difference between methods for the estimates of conditional stability constants. The ligand concentration in the North Atlantic profile ranged from 0.9 to 1.5 nmol L(-1) as determined by fresh film anodic stripping voltammetry and 0.6 to 1.3 nmol L(-1) as determined by cathodic stripping voltammetry. The conditional stability constants determined by fresh film anodic stripping voltammetry were 10(9.8)-10(10.5) and by cathodic stripping voltammetry were 10(9.8)-10(11.3). PMID:18420044

  14. Electrochemistry in Media of Exceptionally Low Polarity: Voltammetry with a Fluorous Solvent

    PubMed Central

    Olson, Eric J.; Boswell, Paul G.; Givot, Bradley L.; Yao, Letitia J.; Bühlmann, Philippe

    2009-01-01

    This work demonstrates the first cyclic voltammetry in a perfluorocarbon solvent without use of a cosolvent. The novel electrolyte tetrabutylammonium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate (NBu4BArF104; 80 mM) allows for voltammetry of ferrocene in perfluoro(methylcyclohexane) by lowering the specific resistance to ?268 k cm at 20.8 °C. Despite significant solution resistance, the resulting voltammograms can be fitted quantitatively without difficulty. The thus determined standard electron transfer rate constant, k°, for the oxidation of ferrocene in perfluoro(methylcyclohexane) is somewhat smaller than for many solvents commonly used in electrochemistry, but can be explained readily as the result of the viscosity and size of the solvent using Marcus theory. Dielectric dispersion spectroscopy verifies that addition of NBu4BArF104 does not significantly raise the overall polarity of the solution over that of neat perfluoro(methylcyclohexane). PMID:20212920

  15. Anodic stripping voltammetry of silver nanoparticles: aggregation leads to incomplete stripping.

    PubMed

    Cloake, Samantha J; Toh, Her Shuang; Lee, Patricia T; Salter, Chris; Johnston, Colin; Compton, Richard G

    2015-02-01

    The influence of nanoparticle aggregation on anodic stripping voltammetry is reported. Dopamine-capped silver nanoparticles were chosen as a model system, and melamine was used to induce aggregation in the nanoparticles. Through the anodic stripping of the silver nanoparticles that were aggregated to different extents, it was found that the peak area of the oxidative signal corresponding to the stripping of silver to silver(I) ions decreases with increasing aggregation. Aggregation causes incomplete stripping of the silver nanoparticles. Two possible mechanisms of 'partial oxidation' and 'inactivation' of the nanoparticles are proposed to account for this finding. Aggregation effects must be considered when anodic stripping voltammetry is used for nanoparticle detection and quantification. Hence, drop casting, which is known to lead to aggregation, is not encouraged for preparing electrodes for analytical purposes. PMID:25861566

  16. Time-dependent phase lag of biofunctionalized magnetic nanoparticles conjugated with biotargets studied with alternating current magnetic susceptometor for liquid phase immunoassays

    NASA Astrophysics Data System (ADS)

    Liao, S. H.; Yang, H. C.; Horng, H. E.; Chieh, J. J.; Chen, K. L.; Chen, H. H.; Chen, J. Y.; Liu, C. I.; Liu, C. W.; Wang, L. M.

    2013-12-01

    In this work, the time-dependent phase lag ? of biofunctionalized magnetic nanoparticles (BMNs) conjugated with biotargets is studied with a home-made alternating current (ac) susceptometor for liquid phase immunoassays. The sensing unit of the ac susceptometor composed of excitation, pick-up, and compensation coils are balanced to 0.03 ppm. The BMNs are anti-goat C-reactive protein coated onto dextran-coated magnetic nanoparticles composed of Fe3O4, labeled as Fe3O4-antiCRP. The bio-targets are human CRP. As the human CRP is conjugated with reagents Fe3O4-antiCRP, the magnetic clusters of Fe3O4-antiCRP-CRP are formulated. Due to the clustering effect, the Brownian relaxation of BMNs will be depressed, which in turn enhances the effective relaxation time. By monitoring the dynamic phase lag, we demonstrate a sensitive platform of assaying human CRP. The detection platform is robust, easy to use and can be applied for assaying a wide variety of biotargets including viruses, proteins, tumor markers, chemicals, etc.

  17. A network thermodynamic two-port element to represent the coupled flow of salt and current. Improved alternative for the equivalent circuit.

    PubMed Central

    Mikulecky, D C

    1979-01-01

    A two-port for coupled salt and current flow is created by using the network thermodynamic approach in the same manner as that for coupled solute and volume flow (Mikulecky et al., 1977b; Mikulecky, 1977). This electrochemical two-port has distinct advantages over the equivalent circuit representation and overcomes difficulties pointed out by Finkelstein and Mauro (1963). The electrochemical two-port is used to produce a schematic diagram of the coupled flows through a tissue. The network is superimposable on the tissue morphology and preserves the physical qualities of the flows and forces in each part of an organized structure (e.g., an epithelium). The topological properties are manipulated independently from the constitutive (flow-force) relations. The constitutive relations are chosen from a number of alternatives depending on the detail and rigor desired. With the topology and constitutive parameters specified, the steady-state behavior is simulated with a network simulation program. By using capacitance to represent the filling and depletion of compartments, as well as the traditional electrical capacitances, time-dependent behavior is also simulated. Nonlinear effects arising from the integration of equations describing local behavior (e.g., the Nernst-Planck equations) are dealt with explicitly. The network thermodynamic approach provides a simple, straightforward method for representing a system diagrammatically and then simulating the system's behavior from the diagram with a minimum of mathematical manipulation. PMID:262391

  18. Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2ZnCl4

    NASA Astrophysics Data System (ADS)

    Ben Bechir, M.; Karoui, K.; Tabellout, M.; Guidara, K.; Ben Rhaiem, A.

    2014-04-01

    [N(CH3)3H]2ZnCl4 has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH3)3H]2ZnCl4 hybrid compound is crystallized at room temperature (T ? 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T1 = 255 K, T2 = 282 K, T3 = 302 K, T4 = 320 K, and T5 = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10-1-107 Hz frequency range and 233-363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH3)3H]2ZnCl4 is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

  19. Differential pulse anodic stripping voltammetry of lead and antimony in gunshot residues

    Microsoft Academic Search

    Curt A Woolever; Dustin E Starkey; Howard D Dewald

    1999-01-01

    Differential pulse anodic stripping voltammetry (DPASV) using a glassy carbon\\/mercury film electrode (GC\\/MFE) has been applied for characterization and quantitative detection of gunshot residues (GSR). This technique allows for simultaneous detection of Pb and Sb from GSR hand swabs that is simple, fast, and non-destructive. The use of a KNO3\\/hydrazine sulfate matrix, instead of HCl, reduces possible interferences and allows

  20. DIFFERENTIAL PULSE ADSORPTIVE STRIPPING VOLTAMMETRY DETERMINATION OF EPINEPHRINE WITH ?-MERCAPTOETHANOL SELF-ASSEMBLED MONOLAYERS MODIFIED ELECTRODE

    Microsoft Academic Search

    Xiu-Hua Zhang; Sheng-Fu Wang

    2002-01-01

    ?-Mercaptoethanol self-assembled monolayer modified electrode (ME\\/Au SAMs) has been fabricated on bare gold. ATR-FTIR was used for the characterization and surface structure of the films. The films, as mediator, accelerated the electron transfer and showed an excellent electrocatalytic activity for the oxidation of the EP. The electrochemical behavior of epinephrine at ME\\/Au SAMs has been studied by cyclic voltammetry. The

  1. Cyclic voltammetry of metallic acetylacetonate salts in quaternary ammonium and phosphonium based deep eutectic solvents

    Microsoft Academic Search

    M. H. Chakrabarti; N. P. Brandon; F. S. Mjalli; L. Bahadori; I. M. Al Nashef; M. A. Hashim; M. A. Hussain; C. T. J. Low; V. Yufit

    2013-01-01

    Seven commercially sourced acetylacetonate salts were investigated in deep eutectic solvents (DESs that were prepared from ethylene glycol and trifluoroacetamide hydrogen bond donors) by cyclic voltammetry, to identify electrolytes suitable for future applications in electrochemical energy storage devices. Although the solubilities are low and on the order of 0.02 mol·L-1 for the most soluble salts, some were found to display

  2. 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.

  3. Determination of Caffeine Using a Simple Graphite Pencil Electrode with Square-Wave Anodic Stripping Voltammetry

    Microsoft Academic Search

    Suw Young Ly; Young Sam Jung; Myung Hoon Kim; In kwon Han; Woon Won Jung; Hyun Sook Kim

    2004-01-01

    A simple commercial graphite pencil electrode (GPE) was utilized for monitoring caffeine using the square-wave anodic stripping voltammetry (SWASV) method. This method was applied to determine the caffeine levels in several tea samples, which yielded a relative error of 1% in the concentrations. Caffeine was deposited at 0.0?V (vs. Ag\\/AgCl), then reduced at +1.40?V to strip it on the GPE.

  4. Nafion-coated mercury thin film electrodes for batch-injection analysis with anodic stripping voltammetry

    Microsoft Academic Search

    Christopher M. A. Brett; Ana Maria Oliveira Brett; Frank-Michael Matysik; Silke Matysik; Sunita Kumbhat

    1996-01-01

    Batch-injection analysis exhibits the advantages of rapid and simple electroanalysis of microlitre samples. Nafion-coated mercury thin film electrodes have been evaluated for use in batch-injection analysis with anodic stripping voltammetry (BIA-ASV). The advantages of Nafion-coated electrodes in reducing electrode contamination by components of complex matrices are combined with the analysis of small microlitre sample volumes. The measurement of traces of

  5. Simultaneous determination of copper, lead and cadmium by cathodic adsorptive stripping voltammetry using artificial neural network

    Microsoft Academic Search

    Ali A. Ensafi; T. Khayamian; A. Benvidi; E. Mirmomtaz

    2006-01-01

    In this work, simultaneous determination of two groups of elements consisting of Pb(II)–Cd(II) and Cu(II)–Pb(II)–Cd(II) using adsorptive cathodic stripping voltammetry are described. The method is based on accumulation of these metal ions on mercury electrode using xylenol orange as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. The

  6. Determination of azinphos-methyl and parathion-methyl in honey by stripping voltammetry

    Microsoft Academic Search

    Constantinos G. Tsiafoulis; Christos G. Nanos

    2010-01-01

    An electrochemical method for the determination of azinphos-methyl and parathion-methyl in honey is presented. The determination is established by adsorptive stripping differential pulse voltammetry at hanging mercury working electrode.In contrast to the chromatographic methods for the determination of pesticide residues, the sample preparation of the proposed method is minimal; analytes were extracted from honey samples with a mixture of (acetone):(Britton–Robinson

  7. Multicomponent Determination of Organophosphorus Pesticides in Grain Samples by Linear Sweep Stripping Voltammetry and Multivariate Calibration

    Microsoft Academic Search

    Ping Qiu; Yongnian Ni; Serge Kokot

    2006-01-01

    Organophosphorus pesticides, such as parathion methyl (PTM), fenitrothion (FT), parathion (PT), and isocarbophos (ICP), have sensitive but overlapped voltammetric peaks with peak potentials ?309, ?364, ?317, and ?480 mV, respectively, in Britton?Robinson buffer of pH 4.8 by application of linear sweep stripping voltammetry (LSSV). In this work, two multivariate calibration methods, partial least squares (both PLS?1 and PLS?2), and principal component

  8. Determination of Chlorfenvinphos in Soils by Microwave?Assisted Extraction and Stripping Voltammetry with an Ultramicroelectrode

    Microsoft Academic Search

    Simone Morais; Oriza Tavares; Paula Paíga

    2007-01-01

    A methodology for the determination of the pesticide chlorfenvinphos by microwave?assisted solvent extraction and square?wave cathodic stripping voltammetry at a mercury film ultramicroelectrode in soil samples is proposed. Optimization of microwave solvent extraction performed with two soils, selected for having significantly different properties, indicated that the optimum solvent for extracting chlorfenvinphos is hexane?acetone (1?1, v\\/v). The voltammetric procedure is based

  9. Electrochemical study of taxol (paclitaxel) by cathodic stripping voltammetry: determination in human urine

    Microsoft Academic Search

    T. Molina Holgado; M. C. Quintana; J. M. Pinilla

    2003-01-01

    An analytical method for the determination of taxol (paclitaxel) via cathodic stripping square wave voltammetry has been developed. The method allows to achieve a detection limit of 5.2 ngml?1 and a determination limit of 11.0 ngml?1 working with a mercury drop electrode in 0.05 M boric acid\\/borate buffer pH 9.0, previously accumulated at ?0.1 V (v.s. Ag\\/AgCl\\/KCl 3 M) for

  10. Direct voltammetry and electrochemical catalysis with horseradish peroxidase in polyacrylamide hydrogel films.

    PubMed

    Huang, Rong; Hu, Naifei

    2003-05-01

    This paper reports the direct voltammetry of horseradish peroxidase (HRP) incorporated in amphiphilic polyacrylamide (PAM) films modified on pyrolytic graphite (PG) electrodes. Cyclic voltammetry of HRP-PAM films showed a pair of well-defined, nearly reversible peaks at approximately -0.33 V vs. SCE in pH 7.0 buffers, characteristic of HRP heme Fe(III)/Fe(II) redox couple. The PAM films in solution contained large amounts of water and formed a hydrogel, and provided a favorable microenvironment for HRP and facilitated its direct electron transfer with underlying PG electrodes. The apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E*') were estimated by fitting the data of square wave voltammetry (SWV) with the non-linear regression analysis. UV-vis absorption spectra demonstrated that HRP in PAM films retained its secondary structure similar to its native state. The embedded HRP in PAM films showed the electrocatalytic activity to various substrates such as nitrite, oxygen and hydrogen peroxide. The possible mechanism of catalytic reaction of H(2)O(2) with HRP-PAM films was proposed. PMID:12834838

  11. Staining of wool using the reaction products of ABTS oxidation by laccase: synergetic effects of ultrasound and cyclic voltammetry.

    PubMed

    Munteanu, Florentina-Daniela; Basto, Carlos; Gübitz, Georg M; Cavaco-Paulo, Artur

    2007-03-01

    The effects of ultrasound on 2,2'-Azinobis(3-ethylbenzothiazoline-6-sulfonate) enzymatic oxidation by laccase (Trametes villosa) has been studied by means of cyclic voltammetry. The reaction was allowed to proceed in the presence of a piece of wool and the coloration depth of the wool fabric was measured by means of K/S. It was observed that cyclic voltammetry is influenced the dyeing process and higher K/S values were obtained when the cyclic voltammetry was combined with the ultrasonic irradiation. Moreover, the K/S value is the sum of the values obtained when the wool staining is done in just the presence of cyclic voltammetry or in just the presence of ultrasound. The results obtained on the indigo carmine decolourization gives information on the importance of controlling the amount of ABTS(+) formed during the ultrasonication process. PMID:16979370

  12. Direct determination of brucine by square wave voltammetry on 4-amino-2-mercaptopyrimidine self-assembled monolayer gold electrode

    Microsoft Academic Search

    Xiu-Hua Zhang; Sheng-Fu Wang; Ni-Juan Sun

    2004-01-01

    4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs\\/Au) was prepared on a gold electrode. The AMP SAMs\\/Au was characterized by using attenuated total reflection-fourier transform infrared (ATR-FTIR) and A.C. Impedance. The electrochemical behavior of brucine on AMP SAMs\\/Au was studied by cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWASV). The modified electrode showed an excellent electrocatalytic activity for the redox of

  13. Identification of inorganic pigments from paintings and polychromed sculptures immobilized into polymer film electrodes by stripping differential pulse voltammetry

    Microsoft Academic Search

    A Doménech-Carbó; M. T Doménech-Carbó; M Moya-Moreno; J. V Gimeno-Adelantado; F Bosch-Reig

    2000-01-01

    Inorganic pigments in paintings and polychromed sculptures are studied by cyclic voltammetry and differential pulse stripping voltammetry using micro-sample coatings in Paraloid B72-film modified electrodes. Characteristic cathodic and anodic differential pulse profiles were obtained in the +0.4 to ?1.0V vs. SCE potential range for different cadmium, copper, lead, mercury and zinc pigments used in traditional colour palettes. Under optimized conditions,

  14. Visualization of local electrochemical activity and local nickel ion release on laser-welded NiTi/steel joints using combined alternating current mode and stripping mode SECM.

    PubMed

    Ruhlig, D; Gugel, H; Schulte, A; Theisen, W; Schuhmann, W

    2008-12-01

    Smoothly polished cross-sections of laser-fabricated welds between NiTi shape memory alloy and stainless steel (SS) microwires of approximately the same diameter and, for comparison, between identical stainless steel or NiTi wires have been subjected to local chemical activity and nickel release measurements using scanning electrochemical microscopy (SECM). In the alternating current mode (AC-SECM), the measurements detected clear differences in the local interfacial chemical activity of the passivated weld and the base metals only for the heterogeneous joints of the type NiTi-SS. In this case the local electrochemical acvtivity was lower above the weld material. Subjecting cross-sections of NiTi-SS to stripping mode SECM (SM-SECM), higher Ni(2+) concentrations were measured above the regions of the parental NiTi wire, which correlates well with the results from AC-SECM imaging which showed this region as being less passivated. An energy-dispersive elemental analysis of the specimen in a scanning electron microscope revealed the coexistence of Ti and Cr in the weld mass. Possibly, a joint action of these two metals in terms of protective oxide formation is better for passivation of the weld region than the individual action of one or the other element for passivating the original wires. Better passivation of course led to decreased electrochemical activity of the weld surface. Apparently, AC- and SM-mode SECM imaging were sufficiently sensitive to detect and visualize the impact of the changed surface passivation upon laser welding. PMID:19082072

  15. Magnetostrictive Alternator

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger; Bruder, Geoffrey

    2013-01-01

    This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

  16. Redox magnetohydrodynamic enhancement of stripping voltammetry: toward portable analysis using disposable electrodes, permanent magnets, and small volumes.

    PubMed

    Weston, Melissa C; Anderson, Emily C; Arumugam, Prabhu U; Narasimhan, Padhmodhbhava Yoga; Fritsch, Ingrid

    2006-12-01

    The use of redox magnetohydrodynamics (MHD) to enhance the anodic stripping voltammetry (ASV) response of heavy metals has been investigated, with respect to achieving portability: disposable electrodes consisting of screen-printed carbon (SPC) on a low temperature co-fired ceramic (LTCC) substrate, small volumes, and permanent magnets. The analytes tested (Cd(2+), Cu(2+), and Pb(2+)) were codeposited on SPC with Hg(2+) to form a Hg thin film electrode. High concentrations of Fe(3+) were used to produce a high cathodic current which generates a significant Lorentz force in the presence of a magnetic field. This Lorentz force induces solution convection during the deposition step, enhancing the mass transport of analytes to the electrode and increasing their preconcentrated quantity in the mercury thin film. Therefore, larger ASV peaks and improved sensitivities are obtained, compared to analyses performed without a magnet. The effects on ASV signal of varying Hg(2+) concentration (0.10 and 1.0 mM), deposition time (10-600 s), and electrode surface roughness were investigated. In addition, analyses were performed using a real lake water matrix. By using the disposable LTCC-SPC working electrodes in small volumes (150 microL) and with small permanent magnets (0.78 T), peak areas were increased by 75% when compared to the signal obtained in the absence of a magnetic field. A limit of detection of 25 nM for Cd(2+) was observed with only a 1 min preconcentration time. PMID:17124540

  17. Enhanced electroreduction of oxygen and stripping voltammetry on PdPt nanoparticles

    NASA Astrophysics Data System (ADS)

    Loganathan, Moorthi; Kakade, Bhalchandra; Swami, Anita; Tamaki, Takanori; Yamaguchi, Takeo

    2015-06-01

    Enhanced oxygen reduction reaction (ORR) on PdPt nanopartiles has been demonstrated after their synthesis using a simple co-precipitation method in presence of reducing agent like N-methylpyrrolidone. Enhancement in the ORR activity of PdPt over commercial Pt catalyst has been discussed based on formation of extent of deleterious oxygenated species on catalytic active sites and the same has been studied quantitatively using stripping voltammetry. An improved specific activity (Is) of 500 µA/cm2.Pt for PdPt has been observed versus 200 µA/cm2.Pt for Pt catalyst at 0.9 V.

  18. Comparison of the brain penetration injury associated with microdialysis and voltammetry

    PubMed Central

    Jaquins-Gerstl, Andrea; Michael, Adrian C.

    2009-01-01

    Emerging evidence suggests that differences between microdialysis- and voltammetry-based estimates of extracellular dopamine in the brain might originate in the different penetration injury associated with each technique. To address this issue in a direct fashion, microdialysis probes and voltammetric microelectrodes were implanted in the rat striatum for 1, 4, or 24 hrs. Tissues were perfused with a suspension of fluorescently labeled nanobeads to assess blood vessels near the implant. Tissue sections (30 ?m) were labeled with antibodies for PECAM, an endothelial cell marker, or GFAP, a glial marker. In non-implanted control tissue, blood vessels were reliably double-labeled with nanobeads and antiPECAM. Tissue near microdialysis probe tracks exhibited ischemia in the form of PECAM immunoreactive blood vessels devoid of nanobeads. Ischemia was most apparent after the 4-hr implants. Probe tracks were surrounded by endothelial cell debris, which appeared as a diffuse halo of PECAM immunoreactivity. The halo intensity decreased with implant duration, indicative of an active wound-healing process. Consistent with this, after 24-hr implants, the probe tracks were surrounded by hyperplasic and hypertrophic glia and glial processes were extending towards, and engulfing, the track. Carbon fiber microelectrodes produced a diffuse disruption of nanobead labeling but no focal disruption of blood vessels, no PECAM immunoreactive halo, and no glial activation. These findings illuminate the differences between the extent and nature of the penetration injuries associated with microdialysis and voltammetry. PMID:19559724

  19. Zinc Detection in Serum by Anodic Stripping Voltammetry on Microfabricated Bismuth Electrodes

    PubMed Central

    Jothimuthu, Preetha; Wilson, Robert A.; Herren, Josi; Pei, Xing; Kang, Wenjing; Daniels, Rodney; Wong, Hector; Beyette, Fred; Heineman, William R.; Papautsky, Ian

    2013-01-01

    Zinc (Zn) homeostasis is required for a functional immune system. Critically ill patients often exhibit decreased Zn serum concentrations and could potentially benefit from Zn supplementation as a therapeutic strategy. However, the conventional approaches to monitoring Zn are time consuming and costly. This work reports on detection of Zn by anodic stripping voltammetry (ASV) on bismuth electrodes in a microfabricated electrochemical cell. The working potential window of the electrodeposited bismuth film electrode was investigated by cyclic voltammetry, while square wave ASV was used for measuring Zn in acetate buffer and blood serum. Conditions critical to sensing, such as preconcentration potential, preconcentration time, and buffer pH, were optimized for Zn detection. The sensor was successfully calibrated with pH 6 acetate buffer in the physiologically-relevant range of 5 ?M to 50?M Zn and exhibited well-defined and highly repeatable peaks. The sensor was used to demonstrate measurement of Zn in blood serum digested in HCl. The results of this work show that Zn detection in serum is possible with smaller sample volumes (?L vs. ?L) and faster turnaround time (hours vs. days) as compared with the conventional spectroscopic methods. PMID:24235807

  20. 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. PMID:24054650

  1. Determination of chromium in estuarine waters by catalytic cathodic stripping voltammetry using a vibrating silver amalgam microwire electrode.

    PubMed

    Espada-Bellido, Estrella; Bi, Zhaoshun; van den Berg, Constant M G

    2013-02-15

    Chromium (Cr(VI)) in water can be determined by adsorptive catalytic cathodic stripping voltammetry in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate on the hanging mercury drop electrode (HMDE). Predominately Cr(VI) is detected and the water is UV-digested to convert all Cr to Cr(VI) prior to analysis. We develop here an alternative to the HMDE by using a silver amalgam electrode based on a vibrating microwire. The microwire electrodes were 12.5 ?m in diameter and electrochemically coated with mercury, and were stable for a week. Conditions were re-optimised, and we used a DTPA concentration of 5mM, 30 mM acetate pH buffer (pH 5.5 in seawater and pH 5.8 in pure water), and 1.5M nitrate solution. The microwire was reactivated prior to each scan by applying a negative potential (-3V) for 2s which removed all deposited Cr. The detection limit for chromium in pH buffer was found to be 0.2 nM Cr(VI) and in seawater 0.3 nM Cr(VI) at a deposition time of 30s. The response increased linearly with the concentration of Cr(VI) up to 60 nM Cr(VI) in seawater. The limit of detection is less good than using the HMDE, but the linear range is good and the microwire electrode could form the basis of apparatus for flow-analysis. The method was successfully tested on water samples from the estuary of the river Mersey (Liverpool Bay) giving chromium concentrations between 1.48 nM and 2.29 nM. PMID:23598021

  2. Perspectives on the Current State of Alternate Assessments based on Modified Academic Achievement Standards: Commentary on Peabody Journal of Education Special Issue

    Microsoft Academic Search

    Susan Weigert

    2009-01-01

    In this commentary on the Peabody Journal of Education special edition, the author addresses implications of the contributing articles to three central domains of interest to states engaged in or considering the development of an alternate assessment on modified academic achievement standards: (a) identifying an eligible student population, (b) ensuring eligible students are provided access to appropriate instruction, and (c)

  3. Direct in situ measurement of dissolved zinc in the presence of zinc oxide nanoparticles using anodic stripping voltammetry.

    PubMed

    Jiang, Chuanjia; Hsu-Kim, Heileen

    2014-11-01

    The wide use of metal-based nanomaterials such as zinc oxide (ZnO) nanoparticles (NPs) has generated concerns regarding their environmental and health risks. For ZnO NPs, their toxicity in aquatic systems often depends on the release of dissolved zinc species, and the rate of dissolution is influenced by water chemistry, including the presence of zinc-chelating ligands. A challenge, however, remains in quantifying the dissolution of ZnO NPs, particularly for time scales that are short enough to determine rates. This paper reports the application of anodic stripping voltammetry (ASV) with a hanging mercury drop electrode to directly measure the concentration of dissolved zinc in ZnO NP suspensions, without separation of the ZnO NPs from the aqueous phase. The effects of the deposition time and the electrochemical potential scan rate on the ASV measurement were consistent with expectations for dissolved phase measurements. The dissolved zinc concentration measured by ASV ([Zn]ASV) was compared with that measured by inductively coupled plasma mass spectrometry (ICP-MS) after ultracentrifugation ([Zn]ICP-MS), for four types of ZnO NPs with different coatings and primary particle diameters. For small ZnO NPs (4-5 nm), [Zn]ASV was 20% higher than [Zn]ICP-MS, suggesting that these small NPs contributed to the voltammetric measurement. For larger ZnO NPs (approximately 20 nm), [Zn]ASV was (79 ± 19)% of [Zn]ICP-MS, despite the high concentrations of ZnO NPs in suspension. Using ASV, the dissolution of ZnO NPs was studied, with or without Suwannee River Fulvic Acid (SRFA). Although SRFA diminished the ASV stripping current, dissolution of 20 nm ZnO NPs was significantly promoted at high fulvic acid to ZnO NP ratios. The ASV method described in this paper provides a useful tool for studying the dissolution kinetics of ZnO NPs in complex environmental matrices. PMID:25220562

  4. Comparison of differential pulse and alternating current polarography in the soft-modelling study of the complexation of Cd(II) by the fragment Cys-Gly and by the phytochelatin (?-Glu-Cys) 2 Gly

    Microsoft Academic Search

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

    2008-01-01

    A comparison of a differential pulse polarographic with a phase sensitive alternating current polarographic study of the Cd-Cys-Gly\\u000a and Cd-PC2 systems [PC2 being a phytochelatin of general structure (?-Glu-Cys)\\u000a n\\u000a -Gly, with n?=?2] has been performed. The chemometric multivariate curve resolution method with alternating least squares was applied\\u000a in the experimental data analysis. The results obtained by both polarographic techniques

  5. Three-dimensional voltammetry: a chemometrical analysis of electrochemical data for determination of dopamine in the presence of unexpected interference by a biosensor based on gold nanoparticles.

    PubMed

    Khoobi, Asma; Ghoreishi, Sayed Mehdi; Behpour, Mohsen; Masoum, Saeed

    2014-09-16

    Multivariate curve resolution by alternating least-squares (MCR-ALS) was used for voltammetric determination of dopamine (DA) in the presence of epinephrine (EP) at a gold nanoparticles chemically modified carbon paste electrode (AuNPs/CPE). Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques were applied for characterization of the nanostructure modified electrode. Central composite rotatable design (CCRD) was employed to generate an experimental program to offer data to model the effects of different parameters on voltammetric responses. Response surface methodology (RSM) was applied to show the individual and interactive effects of chemical and instrumental variables at five levels, combined according to CCRD. For determination of DA in the presence of unexpected interference, three-way data were achieved from various pulse heights in differential pulse voltammetry (DPV) technique. This type of data construction, analyzed by MCR-ALS, makes it possible to exploit the so-called "second-order advantage". The second-order advantage provided unbiased results even in the presence of electroactive interferences with highly overlapped peaks. Also, an algorithm was applied to correct the detected potential shift in the voltammetric data. The voltammograms of the samples were then deposited in an augmented data matrix (column-wise) and subsequently analyzed by MCR-ALS. The effect of rotational ambiguity associated with a particular MCR-ALS solution under a set of constraints was also studied. The proposed method could be applied for the determination of DA and EP in the presence of each other in a wide concentration range of 0.1-205.0 ?M, and the detection limit of DA has been found to be 35.5 nM. Finally, the technique has been used for the reliable analysis of DA in real samples. PMID:25191974

  6. 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. PMID:25476311

  7. 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. PMID:24262520

  8. Dendrimer modified graphite sensors for detection of anticancer drug Daunorubicin by voltammetry and electrochemical impedance spectroscopy.

    PubMed

    Erdem, Arzum; Karadeniz, Hakan; Caliskan, Ayfer

    2011-03-01

    The development of amino-terminated G4 PAMAM dendrimer (PDR) modified disposable electrodes were developed as the first time in our study by using the dendrimer modified disposable graphite (PDR-PGE) and multiwalled carbon nanotube based screen-printed graphite (PDR-MWCNT-SPE) electrodes. Firstly, the microscopic characterization of bare PGEs and PDR modified PGEs was performed. These sensors were then applied for electrochemical monitoring of an anticancer drug, Daunorubicin (DNR). The enhanced oxidation signal of DNR was measured at +0.50 V by using differential pulse voltammetry (DPV) in combination with the PDR-PGEs. The detection limit, estimated from S/N = 3, corresponds accordingly to 317 nM and 128 nM for DNR respectively at the PGE and PDR-PGE. The voltammetric results were consistent with electrochemical impedance spectroscopy (EIS) that was used to characterize the successful modification of PDR onto the surface of PGE and MWCNT-SPE. PMID:21203608

  9. Signal stability of Nafion-coated thin mercury film electrodes for stripping voltammetry.

    PubMed

    Hoyer, B; Jensen, N

    1994-03-01

    The signal stability of the Nafion-coated thin mercury film electrode (NCTMFE) was studied by using cadmium and lead as test analytes and differential pulse anodic stripping voltammetry as detection method. In particular, the effect of the casting solvent and the curing procedure employed in the preparation of the polymer film was examined. Best results were obtained with N,N-dimethylacetamide as casting solvent and a two-step curing procedure in which the polymer was evaporated to dryness at 55 degrees and cured at 105 degrees with a hot-air gun. Mercury plating was performed ex situ. An NCTMFE prepared in this manner has a better signal stability than ex situ-plated as well as in situ-plated conventional mercury film electrodes. PMID:18965949

  10. 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 ?g/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.

  11. Determination of Lamotrigine in Pharmaceutical Preparations by Adsorptive Stripping Voltammetry Using Screen Printed Electrodes

    PubMed Central

    Domínguez-Renedo, Olga; Calvo, M. Encarnación Burgoa; Arcos-Martínez, M. Julia

    2008-01-01

    This paper describes a procedure that has been optimized for the determination of lamotrigine by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using carbon screen-printed electrodes (CSPE) and mercury coated carbon screen-printed electrodes. Selection of the experimental parameters was made using experimental design methodology. The detection limit found was 5.0 × 10-6 M and 2.0 × 10-6 M for the non modified and Hg modified CSPE, respectively. In terms of reproducibility, the precision of the above mentioned methods was calculated in %RSD values at 9.83% for CSPE and 2.73% for Hg-CSPE. The Hg-coated CSPEs developed in this work were successfully applied in the determination of lamotrigine in pharmaceutical preparations.

  12. Identification and on-line monitoring of reduced sulphur species (RSS) by voltammetry in oxic waters.

    PubMed

    Superville, Pierre-Jean; Pižeta, Ivanka; Omanovi?, 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. PMID:23708537

  13. 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 ?A 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

  14. The influence of electrostimulation with the use of direct and alternating current on the corrosion of Cr-Ni-Mo steel implants.

    PubMed

    Szewczenko, J; Marciniak, J

    2000-09-30

    This paper presents results of researches of influence of different methods of electrostimulation of a bone union on the corrosion of implants made of AISI 316 L steel with the passive and passive-carbon layer deposited on their surface. The electrostimulation was carrying out for 28 days in Tyrode's physiological solution of temperature 36,6 +/- 10C. The pH was varying in the 7,6 - 8,6. A direct, pulsating and sinusoidal current was used for the electrostimulation. Mass decrements and corrosion damages of implants were estimated for individual methods of electrostimulation. Furthermore the paper presents results of infiltration of corrosion products. The corrosion products come into being as the result of stimulation of union bone with the use direct current and invasive methods. A ratio of the corrosion product infiltration was estimated with use of X-ray microanalysis. PMID:18034143

  15. Spatiotemporal behavior of the excited Xe atom density in the 1s5 metastable state according to the hoof?type electrode structure in an alternating?current plasma display panel

    Microsoft Academic Search

    Yong Hee Kim; Young June Hong; Joon Ho Choi; Byeong Seong Cho; Han Sub Uhm; Eun Ha Choi

    2010-01-01

    To improve the luminescence characteristics of high?efficiency alternating?current plasma display panels (AC?PDPs), we developed a new hoof?type electrode structure, and we studied the spatiotemporal behavior of the density of the excited Xenon atom in the 1s5 metastable state via laser absorption spectroscopy. Using this structure, the maximum density of the excited Xenon atom per cell was improved by 2.4 times

  16. Developing Random Network Theory for Carbon Nanotube Modified Electrode Voltammetry: Introduction and Application to Estimating the Potential Drop between

    E-print Network

    Craven, David A.

    using electrodes modified with multiwalled-CNT (MWCNT) films produced by the casting method, so applications.10,11 Common methods of immobilizing the CNTs on an electrode surface include: (i) mechanicalDeveloping Random Network Theory for Carbon Nanotube Modified Electrode Voltammetry: Introduction

  17. Studies of structural disorder of self-assembled thiol monolayers on gold by cyclic voltammetry and ac impedance

    Microsoft Academic Search

    Peng Diao; Dianlu Jiang; Xiaoli Cui; Dengping Gu; Ruting Tong; Bing Zhong

    1999-01-01

    Self-assembly of octadecyl mercaptan on gold has been investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV experiments show that well-assembled thiol monolayers on gold are essentially free of pinhole defects. Support for the existence of ‘collapsed’ sites in thiol monolayers is obtained by comparing the apparent electron transfer rate constant, which is obtained from CV experiments at

  18. Simultaneous determination of copper, lead, cadmium and zinc using differential pulse anodic stripping voltammetry in a flow system

    Microsoft Academic Search

    J. F. van Staden; M. C. Matoetoe

    2000-01-01

    The use of differential pulse anodic stripping voltammetry (DPASV) in a flow system for the simultaneous determination of Cu, Cd, Fe, Pb and Zn was evaluated for applicability with a glassy carbon electrode. Simultaneous quantitative analysis for these elements is possible at low concentrations of Fe when using pyrophosphate as a supporting electrolyte (pH 4.0). An application of the proposed

  19. Simultaneous assessment of zinc, cadmium, lead and copper in poultry feeds by differential pulse anodic stripping voltammetry

    Microsoft Academic Search

    S. A. Mahesar; S. T. H. Sherazi; Abdul Niaz; M. I. Bhanger; Siraj uddin; Abdul Rauf

    2010-01-01

    In the present work four metals (Zn, Cd, Pb and Cu) were determined simultaneously in 28 commercial broiler poultry feeds by differential pulse anodic stripping voltammetry (DPASV) using hanging mercury drop electrode (HMDE). The digestion of poultry feeds was carried out with concentrated nitric acid and hydrogen peroxide (2:1) with the help of microwave heating. Acetate buffer of pH 5

  20. Alloy corrosion studied by a combination of stripping voltammetry and the rotating ring-disk electrode. Lead-cadmium alloy

    Microsoft Academic Search

    V. V. Zhdanov; B. K. Filanovskii

    1984-01-01

    The authors have used the rotating ring-disk electrode (RRDE) in combination with stripping voltammetry (SVA) at solid electrodes in order to determine partial dissolution rates of alloy components in the vicinity of the steady potential and also under cathodic and anodic polarization. The method of SVA is used in the analytical determination of trace amounts of heavy metals dissolved in

  1. Differential pulse anodic stripping voltammetry of cadmium(II) with a rotating membrane-covered mercury film electrode

    Microsoft Academic Search

    Edward E. Stewart; Ronald B. Smart

    1984-01-01

    A rotating membrane-covered mercury film electrode (MCMFE) was constructed by placing a dialysis membrane over a glassy carbon rotating disk electrode and plating a thin mercury film onto the electrode surface through the membrane. Differential pulse anodic stripping voltammetry of cadmium was used to evaluate the effects of pH, rotation rate, deposition time, and concentration on the MCMFE. The response

  2. Femtomolar detection of a cancer biomarker protein in serum with ultralow background current by anodic stripping voltammetry.

    PubMed

    Shiddiky, Muhammad J A; Kithva, Prakash H; Rauf, Sakandar; Trau, Matt

    2012-05-22

    An electrochemical immunosensor for the detection of a cancer biomarker protein in serum at femtomolar concentrations with ultralow background response has been developed, which consists of (i) a hydrophilic polyacrylic acid brush-modified indium tin oxide substrate as an antifouling substrate and (ii) a graphene-quantum dots-antibody 'bionanoconjugate' as a signal amplification label in voltammetric detection of targets in a glassy carbon electrode. PMID:22618633

  3. Calculation of synchronous reactances of small permanent-magnet alternating-current motors: Comparison of analytical approach and finite element method with measurements

    SciTech Connect

    Gieras, J.F.; Wing, M. [Univ. of Cape Town, Rondebosch (South Africa). Dept. of Electrical Engineering] [Univ. of Cape Town, Rondebosch (South Africa). Dept. of Electrical Engineering; Santini, E. [Univ. of Rome (Italy). Dept. of Electrical Engineering] [Univ. of Rome (Italy). Dept. of Electrical Engineering

    1998-09-01

    The synchronous reactances of permanent magnet (PM) motors have been determined using: (1) analytical method, i.e., form factors of the stator field (armature reaction factors), (2) finite element method (FEM), and (3) experimental tests on a special machine set. The analytical method is widely used in calculations of synchronous reactances of salient pole synchronous machines with electromagnetic excitation. Rotors of PM synchronous machines have more complicated structures, hence it is more difficult to predict accurately the magnetic field distribution in their airgaps in order to find the form factors of the stator field. Numerical methods of field analysis can easily solve this problem. The FEM can predict both the synchronous and mutual (armature reaction) reactances in the d and q axes. The leakage reactance can then be evaluated as a difference between synchronous and mutual reactances. As an example, a small, three-phase, four-pole motor with SmCo surface mounted PM`s (three parallel magnets per pole), and mild-steel pole shoes has been investigated. Such a complicated rotor structure has been intentionally designed in order to be able to compare the advantages and disadvantages of the analytical method and the FEM. In the FEM, the reactances have been calculated using both the flux linkage and current/energy perturbation method. Synchronous reactances as functions of the stator current and load angle obtained analytically from the FEM modeling and from measurements have been compared.

  4. A review of the development and use of video image analysis (VIA) for beef carcass evaluation as an alternative to the current EUROP system and other subjective systems.

    PubMed

    Craigie, C R; Navajas, E A; Purchas, R W; Maltin, C A; Bünger, L; Hoskin, S O; Ross, D W; Morris, S T; Roehe, R

    2012-12-01

    The current EUROP beef carcass classification scheme is still largely dependent on visually assessed fatness and conformation and its purpose is to provide a common basis for the description of carcasses for use in trade, price reporting and intervention. The meat industry, however, aims for accurately predicted saleable meat yield (SMY%) to which the EUROP carcass classification shows highly variable correlations due in part to the variable distribution of fat throughout the carcass as affected by breed, sex, diet, and the level of fat trimming. Video image analysis (VIA) technology is capable of improving the precision and accuracy of SMY% prediction even for specific carcass joints and simultaneously mimics the visual assessment to comply with EU regulations on carcass classification. This review summarises the development and use of VIA for evaluation of beef carcasses and discusses the advantages and shortfalls of the technology and its application. PMID:22726699

  5. Alternative Medicine

    MedlinePLUS

    Alternative Medicine en Español email Send this article to a friend by filling out the fields below: Your name: ... Send Thanks for emailing that article! Tweet Alternative medicine may be defined as non-standard, unconventional treatments ...

  6. Use of LC-MS-MS as an alternative to currently available immunoassay methods to quantitate corticosterone in egg yolk and albumen.

    PubMed

    De Baere, Siegrid; Rosendahl Larsen, Tom; Devreese, Mathias; De Backer, Patrick; De Neve, Liesbeth; Fairhurst, Graham; Lens, Luc; Croubels, Siska

    2015-06-01

    Corticosterone (CORT) is the dominant plasma glucocorticoid in birds. There has been increasing interest in the function of CORT in avian egg yolk and in the potential to use CORT concentrations in eggs to quantify stress and to assess the effect of maternal stress on offspring. The concentration of CORT in egg yolk is most frequently assessed using enzyme or radioimmunoassays, alone or in combination with high-performance liquid chromatography. However, the quantification of CORT is frequently hampered by the presence of high concentrations of other steroid hormones which cross-react with the CORT antibody. As an alternative, we developed a sensitive and specific LC-MS-MS method. The sample-preparation procedure consisted of a protein-lipid precipitation step, followed by defatting and clean-up using a C18 SPE column. Chromatography was performed on an Acquity C18 BEH column (50 mm?×?2.1 mm i.d., dp: 1.7 ?m, run-time: 6 min), using 0.1 % formic acid in both water (A) and acetonitrile (B) as mobile phases. The MS-MS instrument was operated in the positive-electrospray-ionization mode. The method was validated in-house according to European Guidelines (linearity, accuracy and precision, limits of quantification and detection, specificity, stability) and the results fell within the accepted ranges. The method was successfully used for the analysis of CORT in yolk and albumen of eggs collected from eight breeding lesser black-backed gulls at a Flemish coastal colony. CORT concentrations were in the range 42.4-166.3 pg g(-1) in albumen and?

  7. Effects of skin blood flow and temperature on skin--electrode impedance and offset potential: measurements at low alternating current density.

    PubMed

    Smith, D C

    1992-01-01

    Skin--electrode impedance was determined at 100 Hz and 1 kHz between two disposable electrodes, 5 cm apart, at current densities < 65 microA.cm-2. Measurements were made on the volar skin of the forearm during cooling on cardiopulmonary bypass, and on the dorsum of the foot in the absence of skin blood flow during aortic aneurysm repair. Both the resistive and reactive components of the skin-electrode impedence showed an inverse linear relationship to temperature between 26 and 36 degrees C. The magnitude of the impedance change was different for each patient studied; resistance changes ranged from 0.03 to 23.2 k omega. Degrees C-1 at 100 Hz and from 0.03 to 2.7 k omega. Degrees C-1 at 1 kHz, while reactance changes ranged from 0.4 to 2.1 k omega. Degrees C-1 at 100 Hz and from 0.04 to 0.18 k omega. Degrees C-1 at 1 kHz. Changes in skin-electrode impedance were not due to changes in skin blood flow. There was no consistent change in offset potential with temperature. Although the skin-electrode impedance increases as temperature falls, it is concluded that temperature effects at the skin-electrode interface are not responsible for the observed failure of evoked electromyography during clinical monitoring of neuromuscular function. PMID:1404312

  8. 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 contaminations of wine. PMID:24209365

  9. Alternative Security Metrics

    Microsoft Academic Search

    Jennifer L. Bayuk

    2011-01-01

    Today's security metrics support management practices rather than measure system capability to withstand attacks. This eliminates consideration of security features that are not currently used to manage systems as the basis for security metrics. Rather than judge security metrics by a utility standard with respect to current security management practices, they should instead be appreciated for proposing alternatives ways to

  10. Probing electric fields inside microfluidic channels during electroosmotic flow with fast-scan cyclic voltammetry.

    PubMed

    Forry, Samuel P; Murray, Jacqueline R; Heien, Michael L A V; Locascio, Laurie E; Wightman, R Mark

    2004-09-01

    Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used in microfluidic channels. This method offers the advantage that it can resolve electroactive species not separated in the channel. In addition, this method provides a route to investigate the distribution of applied electrophoretic fields in microfluidic channels. To probe this, microelectrodes were inserted at various distances into channels and cyclic voltammograms recorded at 300 V/s were repeated at 0.1-s intervals. The use of a battery-powered laptop computer and potentiostat provided galvanic isolation between the applied electrophoretic field and the electrochemical measurements. In the absence of an external field, the peak potential for oxidation of the test solute, Ru(bpy)3(2+), was virtually unaltered by insertion of the microelectrode tip into the channel. When an electrophoretic field was applied, the peak potential for Ru(bpy)3(2+) oxidation shifted to more positive potentials in a manner that was directly proportional to the field in the channel. The shifts in peak potential observed with FSCV enabled direct compensation of the applied electrochemical potential. This approach was used to explore the electrophoretic field at the channel terminus. It was found to persist for more than 50 microm from the channel terminus. In addition, the degree of analyte dispersion was found to depend critically on the electrode position outside the channel. PMID:15373427

  11. Speciation study of aluminium in beverages by Competitive Ligand Exchange-Adsorptive Stripping Voltammetry.

    PubMed

    Magnier, A; Fekete, V; Van Loco, J; Bolle, F; Elskens, M

    2014-05-01

    Competitive Ligand Exchange-Adsorptive Stripping Voltammetry (CLE-AdSV) was used for determining the speciation of aluminium in commonly consumed beverages (water, tea, infusion, coffee, orange juice, tomato juice, beer and red wine). Aluminium determination involves the adsorption of Al-complexes with the ligand cupferron onto a hanging mercury drop electrode. All samples were studied at pH 6.5 with an accumulation step at -0.60 V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3 M reference electrode) during 60 s, and a final cupferron concentration of 4 × 10(-4)M. These conditions were used to establish (i) the concentration of electro-labile aluminium, (ii) the range of ligand concentrations and (iii) the conditional stability constants of beverage samples using titration procedures. The results based on Ruzic plots were compared to computer simulation with Visual MINTEQ. This comparison suggests that labile monomeric Al-forms and soluble organic complexes of low molecular weight can be quantified by the CLE-AdSV procedure. Overall the relative uncertainties on the determination of the electro-active Al fraction and the complexing parameters, i.e., concentration and conditional stability constant of natural ligands in the samples, are less than 15%. Thanks to these results, information on Al bioavailability in beverages was collected and discussed. This study also illustrates the value of computer simulations when complex, time-consuming voltammetric techniques are applied. PMID:24720958

  12. Determination of copper speciation in highway stormwater runoff using competitive ligand exchange - Adsorptive cathodic stripping voltammetry.

    PubMed

    Nason, Jeffrey A; Sprick, Matthew S; Bloomquist, Don J

    2012-11-01

    Low concentrations of dissolved copper have been shown to adversely affect the olfactory system of salmonid species, impairing their ability to avoid predators and likely increasing mortality. These studies have resulted in increased regulatory scrutiny of stormwater discharges to surface waters inhabited by threatened and endangered salmonid species. Because it is primarily the free ionic (Cu(2+)) and weakly complexed forms of copper that are bioavailable, it is critical to understand the speciation of copper in stormwater. This paper reports on the characterization of copper binding ligands and copper speciation in composite samples of highway stormwater runoff collected at four sites in Oregon, USA using competitive ligand exchange - adsorptive cathodic stripping voltammetry (CLE-ACSV). Although the concentration and strength of copper binding ligands in stormwater varied considerable between sites and storms, the vast majority (>99.9%) of the total dissolved copper in composite samples was complexed by organic ligands in stormwater. Although total dissolved copper concentrations range from 2 to 20 ?g/L, the analytically determined free ionic copper concentrations did not exceed 10(-10) M (6.3 ng/L) in any of the fully characterized samples, suggesting that much of the copper in highway stormwater is not bioavailable. Analytically determined free ionic copper concentrations were compared with those predicted by a readily available chemical equilibrium models and found to be in reasonable agreement. PMID:22921394

  13. Fast-Scan Cyclic Voltammetry Analysis of Dynamic Serotonin Reponses to Acute Escitalopram

    PubMed Central

    2013-01-01

    The treatment of depression with selective serotonin reuptake inhibitors, SSRIs, is important to study on a neurochemical level because of the therapeutic variability experienced by many depressed patients. We employed the rapid temporal capabilities of fast scan cyclic voltammetry at carbon fiber microelectrodes to study the effects of a popular SSRI, escitalopram (ESCIT), marketed as Lexapro, on serotonin in mice. We report novel, dynamic serotonin behavior after acute ESCIT doses, characterized by a rapid increase in stimulated serotonin release and a gradual rise in serotonin clearance over 120 min. Dynamic changes after acute SSRI doses may be clinically relevant to the pathology of increased depression or suicidality after onset of antidepressant treatment. Due to the short-term variability of serotonin responses after acute ESCIT, we outline difficulties in creating dose response curves and we suggest effective means to visualize dynamic serotonin changes after SSRIs. Correlating chemical serotonin patterns to clinical findings will allow a finer understanding of SSRI mechanisms, ultimately providing a platform for reducing therapeutic variability. PMID:23597074

  14. Ultrasensitive and selective measurements of tin by adsorptive stripping voltammetry of the tin-tropolone complex.

    PubMed

    Wang, J; Zadeii, J

    1987-11-01

    Trace levels of tin can be determined by voltammetry after controlled adsorptive preconcentration of the tin-tropolone complex on a hanging mercury drop electrode. The resulting adsorptive stripping procedure offers better sensitivity and selectivity than conventional stripping methods for tin. Optimal conditions include 4 x 10(-6)M tropolone in a stirred acetate buffer (pH 4.0), a preconcentration potential of -0.40 V, and differential-pulse stripping. For an 8-min preconcentration period, the detection limit is 2.3 x 10(-10)M (28 ng/l.). Linear calibration plots of i(p)vs. C are obtained at low concentrations, with linear plots of 1/i(p)vs. 1/C at high concentrations. The relative standard deviation (at the 6-mug/1. level) is 2.6%. The response is not affected by the presence of lead, cadmium, indium and thallium, which commonly interfere severely in analogous anodic stripping measurements. Results are reported for river and orange-juice samples. PMID:18964431

  15. Nafion-coated mercury thin film electrodes for batch-injection analysis with anodic stripping voltammetry.

    PubMed

    Brett, C M; Maria Oliveira Brett, A; Matysik, F M; Matysik, S; Kumbhat, S

    1996-11-01

    Batch-injection analysis exhibits the advantages of rapid and simple electroanalysis of microlitre samples. Nafion-coated mercury thin film electrodes have been evaluated for use in batch-injection analysis with anodic stripping voltammetry (BIA-ASV). The advantages of Nafion-coated electrodes in reducing electrode contamination by components of complex matrices are combined with the analysis of small microlitre sample volumes. The measurement of traces of lead and cadmium is used to illustrate the approach. An optimised procedure for formation of Nafion-coated mercury thin film electrodes is evolved. The relative sensitivity for BIA-ASV at electrodes with and without Nafion coatings is 0.9 and 0.8 for cadmium and lead respectively; detection limits are 2 x 10(-9) M and 4 x 10(-9) M. Studies were done concerning the influence of surfactants and their effect was found to be much less with the Nafion film coating. Applications to real environmental samples are demonstrated. PMID:18966693

  16. Cathodic stripping voltammetry of nickel: sonoelectrochemical exploitation of the Ni(III)/Ni(II) couple.

    PubMed

    Davis, James; Vaughan, D Huw; Stirling, David; Nei, Lembit; Compton, Richard G

    2002-07-19

    The exploitation of the Ni(III)/Ni(II) transition as a means of quantifying the concentration of nickel within industrial samples was assessed. The methodology relies upon the reagentless electrodeposition of Ni onto a glassy carbon electrode and the subsequent oxidative conversion of the metallic layer to Ni(III). The analytical signal is derived from a cathodic stripping protocol in which the reduction of the Ni(III) layer to Ni(II) is monitored through the use of square wave voltammetry. The procedure was refined through the introduction of an ultrasonic source which served to both enhance the deposition of nickel and to remove the nickel hydroxide layer that results from the measurement process. A well-defined stripping peak was observed at +0.7 V (vs. Agmid R:AgCl) with the response found to be linear over the range 50 nM to 1 muM (based on a 30 s deposition time). Other metal ions such as Cu(II), Mn(II), Cr(III), Pb(II), Cd(II), Zn(II), Fe(III) and Co(II) did not interfere with the response when present in hundred fold excess. The viability of the technique was evaluated through the determination of nickel within a commercial copper nickel alloy and validated through an independent comparison with a standard ICP-AES protocol. PMID:18968710

  17. Miniaturization in voltammetry: ultratrace element analysis and speciation with twenty-fold sample size reduction.

    PubMed

    Monticelli, D; Laglera, L M; Caprara, S

    2014-10-01

    Voltammetric techniques have emerged as powerful methods for the determination and speciation of trace and ultratrace elements without any preconcentration in several research fields. Nevertheless, large sample volumes are typically required (10 mL), which strongly limits their application and/or the precision of the results. In this work, we report a 20-fold reduction in sample size for trace and ultratrace elemental determination and speciation by conventional voltammetric instrumentation, introducing the lowest amount of sample (0.5 mL) in which ultratrace detection has been performed up to now. This goal was achieved by a careful design of a new sample holder. Reliable, validated results were obtained for the determination of trace/ultratrace elements in rainwater (Cd, Co, Cu, Ni, Pb) and seawater (Cu). Moreover, copper speciation in seawater samples was consistently determined by competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV). The proposed apparatus showed several advantages: (1) 20-fold reduction in sample volume (the sample size is lowered from 120 to 6 mL for the CLE-CSV procedure); (2) decrease in analysis time due to the reduction in purging time up to 2.5 fold; (3) 20-fold drop in reagent consumption. Moreover, the analytical performances were not affected: similar detection capabilities, precision and accuracy were obtained. Application to sample of limited availability (e.g. porewaters, snow, rainwater, open ocean water, biological samples) and to the description of high resolution temporal trends may be easily foreseen. PMID:25059160

  18. Detecting Naturally-Produced Sulfide Nanoparticles by Adsorptive, Cathodic Stripping Voltammetry.

    NASA Astrophysics Data System (ADS)

    Helz, G. R.; Krznaric, D.; Bura-Nakic, E.; Ciglenecki, I.

    2007-12-01

    Growing evidence implies that metal sulfide nanoparticles of natural origin exist in some aquatic environments. These nanoparticles could play important roles as mediators of trace metal nutrition and toxicity. Thermodynamics suggests that in sulfidic environments (total transition metaltotal sulfide) the most insoluble metal sulfide (usually Hg or Cu) will form the predominant sulfide nanoparticle. New experimental methods for detecting and distinguishing between such nanoparticles are needed. We report that mercury electrodes effectively preconcentrate a number of different metal sulfide nanoparticles, enabling their detection by adsorptive cathodic stripping voltammetry. Voltammetrically, nanoparticulate analytes differ fundamentally from dissolved analytes; e.g. analyte accumulation is very sensitive to electrolyte composition and concentration in accord with the Schulze-Hardy Rule. EDTA or acid treatment of samples is useful for distinguishing highly insoluble nanoparticles (HgS, CuS) from FeS. Nanoparticulate sulfur potentially interferes. Supersaturated solutions can generate artifactual analyte on Hg electrode surfaces. Despite such potential pitfalls, progress is encouraging. Preliminary, qualitative results from natural waters will be reported.

  19. Evaluation of PEMFC System Contaminants on the Performance of Pt Catalyst via Cyclic Voltammetry: Preprint

    SciTech Connect

    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. Therefore 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.

  20. The effect of external magnetic field on the remagnetization process in FeCuNbSiB/Al/FeCuNbSiB films induced by an alternating current

    NASA Astrophysics Data System (ADS)

    Buznikov, N. A.; Antonov, A. S.; D'yachkov, A. L.; Rakhmanov, A. A.

    2004-02-01

    The alternating current induced remagnetization process in FeCuNbSiB/Al/FeCuNbSiB films is studied. The frequency spectra of the voltage arising in the pick-up coil wound around the sample are measured as a function of an external dc magnetic field. It is shown that the frequency spectra differ substantially for the transverse and longitudinal external magnetic field directions. For the transverse field, several harmonics have high amplitudes, whereas for the longitudinal field, even harmonics dominate in the frequency spectrum. A high field sensitivity of the voltage response is demonstrated. The experimental results are interpreted within the framework of a simple rotational model.

  1. 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.

  2. 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.

  3. Alternative fuels

    SciTech Connect

    Not Available

    1991-07-01

    This paper presents the preliminary results of a review, of the experiences of Brazil, Canada, and New Zealand, which have implemented programs to encourage the use of alternative motor fuels. It will also discuss the results of a separate completed review of the Department of Energy's (DOE) progress in implementing the Alternative Motor Fuels Act of 1988. The act calls for, among other things, the federal government to use alternative-fueled vehicles in its fleet. The Persian Gulf War, environmental concerns, and the administration's National Energy Strategy have greatly heightened interest in the use of alternative fuels in this country.

  4. Refreshable mercury film silver based electrode for determination of chromium(VI) using catalytic adsorptive stripping voltammetry

    Microsoft Academic Search

    Bogus?aw Ba?

    2006-01-01

    The refreshable mercury film silver based electrode Hg(Ag)FE applied for determination of Cr(VI) traces using catalytic adsorptive striping voltammetry (CAdSV) will be presented. The film electrode is characterized by its very good surface reproducibility (not less than 2%) and long-term stability (1500–2000 measurement cycles). The mechanical refreshing of mercury film is realized in the specially constructed device, in a time

  5. Development of a portable electroanalytical system for the stripping voltammetry of metals: Determination of copper in acetic acid soil extracts

    Microsoft Academic Search

    Valerio Beni; Vladimir I. Ogurtsov; Nikolai V. Bakunin; Damien W. M. Arrigan; Martin Hill

    2005-01-01

    The development, characterisation and evaluation of a prototype portable electrochemical trace metal analyser are presented. The instrument is a battery-powered microcontroller-based potentiostat, which implements anodic stripping voltammetry (ASV) at suitable sensor electrodes. It is capable of operating away from the laboratory, in the absence of an external power source and is usable by low-skilled personnel. The distinguishing feature of the

  6. Square?Wave Voltammetry Determination of Aspartame in Dietary Products Using a Boron?Doped Diamond Electrode

    Microsoft Academic Search

    Roberta Antigo Medeiros; Adriana Evaristo de Carvalho

    2007-01-01

    The use of square?wave voltammetry in conjunction with a cathodically pretreated boron?doped diamond electrode for the analytical determination of aspartame in dietary products is described. In this determination, the samples were analyzed without previous treatment in a 0.5 mol l H2SO4 solution. A single oxidation peak at a potential of 1.6 V vs. Ag\\/AgCl (3.0 mol l KCl) with the characteristics of an irreversible reaction

  7. Determination of Lead and Cadmium by Stripping Voltammetry After Separation from Humic Acid by Thin-Layer Chromatography

    Microsoft Academic Search

    Steven C. Petrovic; Howard D. Dewald

    1998-01-01

    Interferences resulting from the presence of humic acid (HA) and other surface-active substances in a sample matrix decrease the reliability of Pb and Cd determinations obtained by square-wave anodic stripping voltammetry (SWASV). The implementation of thin-layer chromatography (TLC) prior to SWASV minimizes the effect of these interferents by physically separating Pb and Cd from the sample matrix prior to analysis.

  8. Electrochemical identification of anthraquinone-based dyes in solid microsamples by square wave voltammetry using graphite\\/polyester composite electrodes

    Microsoft Academic Search

    A. Doménech-Carbó; M. T. Doménech-Carbó; M. C. Saurí-Peris; J. V. Gimeno-Adelantado; F. Bosch-Reig

    2003-01-01

    An electrochemical method for identifying anthraquinone-type dyes in microsamples from works of art, based in the voltammetry of microparticles approach, is reported. Upon attachment onto graphite\\/polyester composite electrodes, natural pigments aloe, henna, cochineal red, madder lake, kermes, shellac, and alizarin and purpurin taken as reference materials can be identified from their square wave voltammetric profiles in MeCN (0.10 mol Lу

  9. Lowering of the firing voltage and reducing of the discharge delay time in alternating current plasma display panels by a discontinuous spin-coated LaB6 film on the MgO protective layer

    NASA Astrophysics Data System (ADS)

    Deng, Jiang; Zeng, Baoqing; Wang, Xiaoju; Lin, Zulun; Qi, Kangcheng; Cao, Guichuan

    2014-03-01

    A spin coated LaB6 discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB6 powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB6/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB6. Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.

  10. Lowering of the firing voltage and reducing of the discharge delay time in alternating current plasma display panels by a discontinuous spin-coated LaB{sub 6} film on the MgO protective layer

    SciTech Connect

    Deng, Jiang, E-mail: dj78291@163.com [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China)] [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zeng, Baoqing [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China) [School of Physical Electronic, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China); Zhongshan Institute, University of Electronic Science and Technology of China, 528402 zhongshan (China); Wang, Xiaoju; Lin, Zulun; Qi, Kangcheng; Cao, Guichuan [School of Opto-electronic Information, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China)] [School of Opto-electronic Information, University of Electronic Science and Technology of China, No.4, Section 2, Jianshe North Road, 610054 Chengdu (China)

    2014-03-15

    A spin coated LaB{sub 6} discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB{sub 6} powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB{sub 6}/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB{sub 6.} Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.

  11. Alternative fuels

    Microsoft Academic Search

    Rezendes

    1991-01-01

    This paper reports that in reviewing programs in Brazil, Canada, and New Zealand to encourage the use of alternative fuels, GAO found that each country was able, to some extent, to get motorists to use alternative fuels, although not without problems and setbacks. GAO also found remarkable consistency in the experiences and lessons reported. GAO testified that the experiences of

  12. 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.

  13. Voltammetry of 6,6'-dithiodinicotinic acid on a self-assembled phospholipid monolayer prive

    NASA Astrophysics Data System (ADS)

    Herrero, R.; Vilariño, T.; Barriada, J. L.; Sastre de Vicente, M. E.; López-Fonseca, J. M.; Moncelli, M. R.

    1999-04-01

    This paper reports a voltammetric study of 6,6'-dithiodinicotinic acid (CPDS) across a biomimetic membrane system consisting of a monolayer of dioleoylphosphatidylcholine, deposited on mercury. Because of the low solubility of this compound and its potential decomposition in alkaline media, estimation of pK values for the carboxyl and amino groups of the pyridine ring of the CPDS entailed using the Hammett equation. UV spectra seem to confirm the presence of the dianionic form of CPDS above pH=3-4. Differential capacity and cyclic voltammetry measurements were made in order to characterize the voltammetric behavior directly on mercury and through a monolayer of dioleoylphosphatidylcholine. Estimation of the CPDS hydrophobicity degree from the partition coefficient in octanol/ water suggests no penetration of the dianion into the monolayer and supports the fact that the named dianion undergoes protonation at the phospholipid/solution interface to give a neutral specie which penetration into the phospholipid region, favored by its higher hydrophobicity, is followed by electrochemical reduction at the mercury surface. Nous avons étudié par voltampérométrie le comportement de l'acide 6,6'-dithiodinicotinique (CPDS) sur l'électrode de mercure couverte par une monocouche de dioleoyl-phosphatidylcholine. La caractérisation électrochimique a été effectuée par des mesures de la capacité différentielle et par voltamétrie cyclique au dessus d'un pH 3-4. Le spectre UV paraît confirmer la présence de la forme dianionique du CPDS. Cependant les données expérimentales associées à une estimation de l'hydrophobicité de la forme dianionique suggèrent que seule la forme neutre du CPDS peut être réduite sur la surface de l'électrode.

  14. Determination of monomethylcadmium in the environment by differential pulse anodic stripping voltammetry.

    PubMed

    Pongratz, R; Heumann, K G

    1996-04-01

    A differential pulse anodic stripping voltammetric (DPASV) method was used to differentiate between the cadmium species Cd(2+) and MeCd(+) (Me = methyl) in aquatic systems. These two species show peaks in the DPASV voltammogram which differ by 112 mV. In model experiments, it was demonstrated that monomethylcadmium is not stable at pH 2, but under higher pH conditions, normally found in fresh and ocean water samples, the identity of MeCd(+) was verified by different investigations, including cyclic voltammetry, selective extraction of a complex of diethyldithiocarbamate with MeCd(+) into n-hexane, and photochemical dissociation of MeCd(+) by UV irradiation. It was also shown that humic acids do not influence the voltammetric determination of monomethylcadmium. For the first time, it was possible to analyze MeCd(+) in environmental samples. During different expeditions with the German research vessel Polarstern, monomethylcadmium could be determined above the detection limit of 470 pg L(-1) in nearly all surface water samples of the South Atlantic with spot concentrations of up to about 700 pg L(-1), whereas in the North Atlantic only 15-30% of the total samples showed MeCd(+) concentrations above this limit. The existence of MeCd(+) in the remote area of the South Atlantic, as well as positive correlations with the local bioactivity in the ocean, indicates biomethylation as the most probable formation process for this methylated cadmium species. This assumption is supported by the simultaneous occurrence of other methylated heavy metal compounds, such as Me(3)Pb(+). Up to 48% of the total cadmium was found to be monomethylcadmium in some Arctic meltwater ponds. PMID:21619159

  15. Nonlinear alternating-current tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Kochanski, Greg P.

    1989-05-01

    A new method of scanning tunneling microscopy is proposed that should allow atomic resolution imaging on insulators. A nonlinear ac technique is used that is shown to allow stable control of a microscope tip above insulating surfaces where dc tunneling is not possible, including aluminum oxide and liquid-crystal layers. Images of copper oxide and WSe2 have been obtained using this technique. Nanometer features have been observed.

  16. Cyclic Voltammetry Studies of Octadecanethiol Self-Assembled Monolayers in Different Concentrations of Fe(CN)6 \\/ Fe(CN)6

    Microsoft Academic Search

    X. L. Cui; D. L. Jiang; P. Diao; J. X. Li; R. T. Tong; X. K. Wang

    1999-01-01

    Octadecanethiol self-assembled monolayers derivatized gold electrode in different concentrations of Fe(CN)6 was studied by cyclic voltammetry. The cyclic voltammetric responses display a series of inverse sigmoidal curves for the SAMs in the solution of various concentration of Fe(CN)6 . A new concept of apparent effective thickness of self-assembled monolayers is established on the base of the measurements of cyclic voltammetry.

  17. Alternative Schools.

    ERIC Educational Resources Information Center

    Pritchett, Stanley; Kimsey, Steve

    2002-01-01

    Describes the design of the DeKalb Alternative School in Atlanta, Georgia, located in a renovated shopping center. Purchasing commercial land and renovating the existing building saved the school system time and money. (EV)

  18. Development of the Wireless Instantaneous Neurotransmitter Concentration System for intraoperative neurochemical monitoring using fast-scan cyclic voltammetry

    PubMed Central

    Bledsoe, Jonathan M.; Kimble, Christopher J.; Covey, Daniel P.; Blaha, Charles D.; Agnesi, Filippo; Mohseni, Pedram; Whitlock, Sidney; Johnson, David M.; Horne, April; Bennet, Kevin E.; Lee, Kendall H.; Garris, Paul A.

    2009-01-01

    Object Emerging evidence supports the hypothesis that modulation of specific central neuronal systems contributes to the clinical efficacy of deep brain stimulation (DBS) and motor cortex stimulation (MCS). Real-time monitoring of the neurochemical output of targeted regions may therefore advance functional neurosurgery by, among other goals, providing a strategy for investigation of mechanisms, identification of new candidate neurotransmitters, and chemically guided placement of the stimulating electrode. The authors report the development of a device called the Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for intraoperative neurochemical monitoring during functional neurosurgery. This device supports fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) for real-time, spatially and chemically resolved neurotransmitter measurements in the brain. Methods The FSCV study consisted of a triangle wave scanned between ?0.4 and 1 V at a rate of 300 V/second and applied at 10 Hz. All voltages were compared with an Ag/AgCl reference electrode. The CFM was constructed by aspirating a single carbon fiber (r = 2.5 ?m) into a glass capillary and pulling the capillary to a microscopic tip by using a pipette puller. The exposed carbon fiber (that is, the sensing region) extended beyond the glass insulation by ~ 100 ?m. The neurotransmitter dopamine was selected as the analyte for most trials. Proof-of-principle tests included in vitro flow injection and noise analysis, and in vivo measurements in urethane-anesthetized rats by monitoring dopamine release in the striatum following high-frequency electrical stimulation of the medial forebrain bundle. Direct comparisons were made to a conventional hardwired system. Results The WINCS, designed in compliance with FDA-recognized consensus standards for medical electrical device safety, consisted of 4 modules: 1) front-end analog circuit for FSCV (that is, current-to-voltage transducer); 2) Bluetooth transceiver; 3) microprocessor; and 4) direct-current battery. A Windows-XP laptop computer running custom software and equipped with a Universal Serial Bus–connected Bluetooth transceiver served as the base station. Computer software directed wireless data acquisition at 100 kilosamples/second and remote control of FSCV operation and adjustable waveform parameters. The WINCS provided reliable, high-fidelity measurements of dopamine and other neurochemicals such as serotonin, norepinephrine, and ascorbic acid by using FSCV at CFM and by flow injection analysis. In rats, the WINCS detected subsecond striatal dopamine release at the implanted sensor during high-frequency stimulation of ascending dopaminergic fibers. Overall, in vitro and in vivo testing demonstrated comparable signals to a conventional hardwired electrochemical system for FSCV. Importantly, the WINCS reduced susceptibility to electromagnetic noise typically found in an operating room setting. Conclusions Taken together, these results demonstrate that the WINCS is well suited for intraoperative neurochemical monitoring. It is anticipated that neurotransmitter measurements at an implanted chemical sensor will prove useful for advancing functional neurosurgery. PMID:19425890

  19. Alternating and direct current field effects on the structure-property relationships in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-x%BaTiO{sub 3} textured ceramics

    SciTech Connect

    Ge, Wenwei; Li, Jiefang; Viehland, D. [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, Deepam; Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-06-03

    The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]{sub PC} textured Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T{sub d} in poled samples resulted from a tetragonal {yields} pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T{sub d}: ac drive decreased the T{sub d}, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature.

  20. Comparative energies of alternative fuels

    Microsoft Academic Search

    E. M. Goodger

    1978-01-01

    In order to provide additional design data on candidate alternative fuels, a broad comparison is made of the net calorific values of a wide variety of gaseous, liquid and solid fuels, including a number of alternatives of current interest, against a background of conventional fuels, some of which may have alternative applications. In general, higher gravimetric calorific values are shown

  1. Alternating Hemiplegia

    MedlinePLUS

    ... and balance and gait problems continue. Over time, walking unassisted becomes difficult or impossible. What research is being done? The NINDS supports research on paralytic disorders such as alternating hemiplegia, with the goals of learning more about these disorders and finding ways to ...

  2. Axion alternatives

    E-print Network

    I. Antoniadis; A. Boyarsky; Oleg Ruchayskiy

    2006-06-29

    If recent results of the PVLAS collaboration proved to be correct, some alternative to the traditional axion models are needed. We present one of the simplest possible modifications of axion paradigm, which explains the results of PVLAS experiment, while avoiding all the astrophysical and cosmological restrictions. We also mention other possible models that possess similar effects.

  3. Conditions and chemometrics for the determination of heavy metals in natural and waste waters by stripping voltammetry with UV irradiation

    SciTech Connect

    Volkova, V.N.; Zakharova, E.A.; Khustenko, L.A.

    1987-07-20

    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.

  4. Resolution of quaternary mixtures of cadaverine, histamine, putrescine and tyramine by the square wave voltammetry and partial least squares method.

    PubMed

    Henao-Escobar, W; Domínguez-Renedo, O; Alonso-Lomillo, M A; Arcos-Martínez, M J

    2015-10-01

    This work presents the simultaneous determination of cadaverine, histamine, putrescine and tyramine by square wave voltammetry using a boron-doped diamond electrode. A multivariate calibration method based on partial least square regressions has allowed the resolution of the very high overlapped voltammetric signals obtained for the analyzed biogenic amines. Prediction errors lower than 9% have been obtained when concentration of quaternary mixtures were calculated. The developed procedure has been applied in the analysis of ham samples, which results are in good agreement with those obtained using the standard HPLC method. PMID:26078134

  5. Investigation of an alternating current plasma as an element selective atomic emission detector for high-resolution capillary gas chromatography and as a source for atomic absorption and atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Ombaba, Jackson M.

    This thesis deals with the construction and evaluation of an alternating current plasma (ACP) as an element-selective detector for high resolution capillary gas chromatography (GC) and as an excitation source for atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES). The plasma, constrained in a quartz discharge tube at atmospheric pressure, is generated between two copper electrodes and utilizes helium as the plasma supporting gas. The alternating current plasma power source consists of a step-up transformer with a secondary output voltage of 14,000 V at a current of 23 mA. The device exhibits a stable signal because the plasma is self-seeding and reignites itself every half cycle. A tesla coil is not required to commence generation of the plasma if the ac voltage applied is greater than the breakdown voltage of the plasma-supporting gas. The chromatographic applications studied included the following: (1) the separation and selective detection of the organotin species, tributyltin chloride (TBT) and tetrabutyltin (TEBT), in environmental matrices including mussels (Mvutilus edullus) and sediment from Boston Harbor, industrial waste water and industrial sludge, and (2) the detection of methylcyclopentadienyl manganesetricarbonyl (MMT) and similar compounds used as gasoline additives. An ultrasonic nebulizer (common room humidifier) was utilized as a sample introduction device for aqueous solutions when the ACP was employed as an atomization source for atomic absorption spectrometry and as an excitation source for atomic emission spectrometry. Plasma diagnostic parameters studied include spatial electron number density across the discharge tube, electronic, excitation and ionization temperatures. Interference studies both in absorption and emission modes were also considered. Figures of merits of selected elements both in absorption and emission modes are reported. The evaluation of a computer-aided optimization program, Drylab GC, using spearmint oil and Environmental Protection Agency (EPA) standard mixture as probes is also discussed. The program supplied by LC Resources (Lafayette, CA) is used for separation optimization and prediction of gas chromatographic parameters. Column dead-time and average plate number were used as input data in conjunction with the retention times and peak areas of solutes at two different temperature programming rates. Once input data are entered into an IBM or IBM compatible personal computer, the program produces a 'relative resolution map' (RRM) which guides the analyst in selecting the most favorable temperature programming rate for the separation.

  6. Alternative energy technologies

    Microsoft Academic Search

    M. S. Dresselhaus; I. L. Thomas

    2001-01-01

    Fossil fuels currently supply most of the world's energy needs, and however unacceptable their long-term consequences, the supplies are likely to remain adequate for the next few generations. Scientists and policy makers must make use of this period of grace to assess alternative sources of energy and determine what is scientifically possible, environmentally acceptable and technologically promising.

  7. One Institution: Six Alternatives.

    ERIC Educational Resources Information Center

    Adkins, Winthrop R.; And Others

    1971-01-01

    This expanded issue of the Research Review examines six alternatives to current patterns in the community college. In the first article, the authors offer guidelines for formulating institution-building capabilities, developing curricula, and designing a Personal Development program according to a Life Skills Education model. The second paper…

  8. 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…

  9. 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 ?g 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. PMID:25059140

  10. 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 ?M and 2–100 ?M for NFX and CFX, respectively. The lowest detectable levels were estimated to be 0.3±0.1 ?M (n=7) for NFX and 1.6±0.1 ?M (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

  11. Simultaneous determination of ultra trace amounts of lead and cadmium in food samples by adsorptive stripping voltammetry.

    PubMed

    Abbasi, Shahryar; Khodarahmiyan, Kobra; Abbasi, Freshteh

    2011-09-01

    A selective and sensitive method for simultaneous determination of lead and cadmium by adsorptive differential pulse cathodic stripping voltammetry is presented. The method is based on adsorptive accumulation of the complexes of Pb (II) and Cd (II) ions with 2-mercaptobenzothiazole onto hanging mercury drop electrode (HMDE), followed by the reduction of the adsorbed species by differential pulse cathodic stripping voltammetry. Optimal conditions were obtained at pH 8.0, 2-mercaptobenzothiazole concentration of 1.0×10(-4)M, the accumulation potential of -0.4V (vs. Ag/AgCl), the accumulation time of 160s, and the scan rate of 100mV/s. Under optimised conditions, linear calibration curves were established for the concentration of Pb (II) and Cd (II) in the range of 0.5-70 and 0.2-30ng/ml, respectively, with detection limit of 0.017ng/ml for Pb (II) and 0.01ng/ml for Cd (II). The procedure was successfully applied to the simultaneous determination of both ions in food samples (rice, soya and sugar). PMID:25214357

  12. Stripping voltammetry study of ultra-trace toxic metal ions on highly selectively adsorptive porous magnesium oxide nanoflowers.

    PubMed

    Wei, Yan; Yang, Ran; Yu, Xin-Yao; Wang, Lun; Liu, Jin-Huai; Huang, Xing-Jiu

    2012-05-01

    We have demonstrated highly selective and sensitive detection of Pb(II) and Cd(II) using a highly selective adsorptive porous magnesium oxide (MgO) nanoflowers. The MgO nanoflower-modified glassy carbon electrode was electrochemically characterized using cyclic voltammetry; and the anodic stripping voltammetric performance of bound Pb(II) and Cd(II) was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The MgO nanoflower-modified electrode exhibited excellent sensing performance toward Pb(II) and Cd(II) that was never observed previously at bismuth (Bi)-based electrodes. Simultaneous additions of Pb(II) and Cd(II) were investigated in the linear range from 3.3 to 22 nM for Pb(II) and 40 to 140 nM for Cd(II), and detection limits of 2.1 pM and 81 pM were obtained, respectively. Some foreign ions, such as Cu(II), Zn(II) and Cr(III) do not interfere with the detection of Pb(II) and Cd(II). To the best of our knowledge, this is the first example of a highly adsorptive metal oxide with hierarchical micro/nanostructure that allows the detection of both Pb(II) and Cd(II) ions. PMID:22421740

  13. Is microwave digestion using TFM vessels a suitable preparation method for Pt determination in biological samples by adsorptive cathodic stripping voltammetry?

    PubMed

    Haus, Nadine; Eybe, Tanja; Zimmermann, Sonja; Sures, Bernd

    2009-03-01

    The occurrence of Pt in environmental matrices is increasing since the introduction of automobile catalytic converters. Given that Pt is bioavailable and causes biological effects in plants and animals, respective biomonitoring programs are in high demand. But the analytical methods for conducting such programs have not yet been sufficiently established. Therefore, a study was carried out to develop a microwave digestion of biological samples, which allows a rapid determination of Pt by adsorptive cathodic stripping voltammetry. A high pressure microwave system was used and the digestion was performed in HNO(3) and HCl. After digestion the HNO(3) was evaporated with a microwave assisted vacuum concentration set. The study resulted in a procedural detection limit of 37.5 ng L(-1) and a relative standard deviation of 18%. A recovery study resulted in a Pt loss below 5%. The microwave assisted evaporation of HNO(3) performed satisfactorily and up to 500 mL of the sample solution could be used for the voltammetric measurements without any effect on the peak heights. A direct comparison of Pt concentrations conducted after microwave digestion and digestion by high pressure ashing showed similar values. However, these promising results were not persistent throughout the repeated analysis using the same Teflon vessels. The vessels did not endure the harsh conditions and due to aging processes the Pt loss consistently increased until Pt determination in environmental relevant concentrations became impossible. Quartz vessels could not be employed as an alternative to the Teflon vessels, due to a lack of compatibility with the vacuum concentration system. Consequently, the results of this paper show that there is a need for further development of more resistant Teflon materials. PMID:19200478

  14. Enhancing selectivity in stripping voltammetry by different adsorption behaviors: the use of nanostructured Mg-Al-layered double hydroxides to detect Cd(II).

    PubMed

    Xu, Ren-Xia; Yu, Xin-Yao; Gao, Chao; Liu, Jin-Huai; Compton, Richard G; Huang, Xing-Jiu

    2013-03-21

    We report the use of nanostructured layered double hydroxides (LDHs) for the highly selective and sensitive detection of Cd(2+) using anodic stripping voltammetry (ASV). In particular, the modification of a glassy carbon electrode promotes the sensitivity and selectivity towards Cd(2+) in the presence of Pb(2+), Hg(2+), Cu(2+) and Zn(2+). The electrochemical characterization and anodic stripping voltammetric performance of Cd(2+) were evaluated using cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV) analysis. Operational parameters, including supporting electrolytes, pH value, deposition potential and deposition time were optimized. In addition, the selectivity, interference and stability were also investigated under the optimized conditions. The results showed that the fabricated electrode possessed good selectivity, stability and reproducibility. The proposed electrochemical sensing strategy is thus expected to open new opportunities to broaden the use of ASV in analysis for detecting heavy metal ions in the environment. PMID:23370265

  15. Alternative drugs of abuse.

    PubMed

    Sutter, M E; Chenoweth, J; Albertson, T E

    2014-02-01

    The incidence of drug abuse with alternative agents is increasing. The term "alternative drugs of abuse" is a catch-all term for abused chemicals that do not fit into one of the classic categories of drugs of abuse. The most common age group abusing these agents range from 17 to 25 years old and are often associated with group settings. Due to their diverse pharmacological nature, legislative efforts to classify these chemicals as a schedule I drug have lagged behind the development of new alternative agents. The potential reason for abuse of these agents is their hallucinogenic, dissociative, stimulant, anti-muscarinic, or sedative properties. Some of these drugs are easily obtainable such as Datura stramonium (Jimson Weed) or Lophophora williamsii (Peyote) because they are natural plants indigenous to certain regions. The diverse pharmacology and clinical effects of these agents are so broad that they do not produce a universal constellation of signs and symptoms. Detailed physical exams are essential for identifying clues leading one to suspect an alternative drug of abuse. Testing for the presence of these agents is often limited, and even when available, the results do not return in a timely fashion. Intoxications from these agents pose unique challenges for health care providers. Physician knowledge of the physiological effects of these alternative agents and the local patterns of drug of abuse are important for the accurate diagnosis and optimal care of poisoned patients. This review summarizes the current knowledge of alternative drugs of abuse and highlights their clinical presentations. PMID:23636733

  16. Development of a sequential injection-square wave voltammetry method for determination of paraquat in water samples employing the hanging mercury drop electrode.

    PubMed

    dos Santos, Luciana B O; Infante, Carlos M C; Masini, Jorge C

    2010-03-01

    This work describes the development and optimization of a sequential injection method to automate the determination of paraquat by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h(-1). Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of 25 mV, a potential step of 2 mV, and a flow rate of 100?µL s(-1). For a concentration range between 0.010 and 0.25 mg L(-1), the current (i(p), µA) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration (mg L(-1)): i(p) = (-20.5?±?0.3)C (paraquat) - (0.02?±?0.03). The limits of detection and quantification were 2.0 and 7.0?µg L(-1), respectively. The accuracy of the method was evaluated by recovery studies using spiked water samples that were also analyzed by molecular absorption spectrophotometry after reduction of paraquat with sodium dithionite in an alkaline medium. No evidence of statistically significant differences between the two methods was observed at the 95% confidence level. PMID:20084371

  17. Lab-on-a-Chip Sensor with Evaporated Bismuth Film Electrode for Anodic Stripping Voltammetry of Zinc.

    PubMed

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

    2013-12-01

    In this work, we report on the development of a lab-on-a-chip electrochemical sensor that uses an evaporated bismuth electrode to detect zinc using square wave anodic stripping voltammetry. The microscale electrochemical cell consists of a bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor demonstrated linear response in 0.1 M acetate buffer at pH 6 with zinc concentrations ranging from 1 ?M to 30 ?M and a calculated detection limit of 60 nM. The sensor was also able to successfully detect zinc in a bovine serum extract and the results were verified with independent AAS measurements. These results demonstrate the advantageous qualities of this lab-on-a-chip electrochemical sensor for clinical applications, which include a small sample volume (?L scale), reduced cost, short response time and high accuracy at low concentrations of analyte. PMID:24436575

  18. Controlling the diffusion profile of electroactive species for selective anodic stripping voltammetry of cadmium at boron-doped diamond electrodes.

    PubMed

    Sugitani, Ai; Watanabe, Takeshi; Ivandini, Tribidasari A; Iguchi, Tatsuo; Einaga, Yasuaki

    2013-01-01

    Selective anodic stripping voltammetry of trace metal ions in a mixture solution with another interfering metal was developed based on Fick's law concerning the diffusion profile of interfering metals at the electrode surface after electrolysis treatment. A boron-doped diamond film was used as the sensing electrode, while a perforated carbon sheet was used for the interference-depleting electrode. The influence of the electrode distance and the time of electrolysis on the formation of the diffusion profile was studied. As a working model, the detection of cadmium with copper interference was investigated. The advantage of the method in comparison to general electrolysis was also discussed. The method offers a new perspective for improving the selective detection of metal ions by analyzing the diffusion profiles of the interfering species at the surface of electrodes. PMID:23147907

  19. Differential pulse voltammetry detection of dopamine and ascorbic acid by permselective silica mesochannels vertically attached to the electrode surface.

    PubMed

    Li, Wanzhen; Ding, Longhua; Wang, Qiaohong; Su, Bin

    2014-08-21

    A thin film consisting of highly ordered and vertically oriented silica mesochannels (SMCs) was prepared on the indium tin oxide (ITO) coated glass electrode surface by chronopotentiometry. The mesochannel has a uniform pore size of 2-3 nm in diameter and a positively charged surface due to grafted ammonium groups. The electrostatic and steric effects resulted from control of the surface charge and the ionic buffer concentration make the SMCs permselective, favoring the mass transport of oppositely charged species and repelling that of similarly charged ones. By using differential pulse voltammetry (DPV), the SMCs with this charge selectivity can be employed for permselective detection of ascorbic acid (AA) and dopamine (DA) that are oppositely charged compounds. The obtained linear detection range was 49-2651 ?M for AA and 20-226 ?M for DA, respectively. AA and DA in real samples were also determined by the SMC film modified electrode. PMID:24949496

  20. Real-time processing of fast-scan cyclic voltammetry (FSCV) data using a field-programmable gate array (FPGA).

    PubMed

    Bozorgzadeh, Bardia; Covey, Daniel P; Heidenreich, Byron A; Garris, Paul A; Mohseni, Pedram

    2014-01-01

    This paper reports the hardware implementation of a digital signal processing (DSP) unit for real-time processing of data obtained by fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM), an electrochemical transduction technique for high-resolution monitoring of brain neurochemistry. Implemented on a field-programmable gate array (FPGA), the DSP unit comprises a decimation filter and an embedded processor to process the oversampled FSCV data and obtain in real time a temporal profile of concentration variation along with a chemical signature to identify the target neurotransmitter. Interfaced with an integrated, FSCV-sensing front-end, the DSP unit can successfully process FSCV data obtained by bolus injection of dopamine in a flow cell as well as electrically evoked, transient dopamine release in the dorsal striatum of an anesthetized rat. PMID:25570384

  1. Compensated pulsed alternator

    SciTech Connect

    Weldon, William F. (Austin, TX); Driga, Mircea D. (Austin, TX); Woodson, Herbert H. (Austin, TX)

    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.

  2. Application of multivariate curve resolution alternating least squares method for determination of caffeic acid in the presence of catechin interference.

    PubMed

    Meshki, Marzieh; Behpour, Mohsen; Masoum, Saeed

    2015-03-15

    In the current article, preparation and application of a graphene oxide nanosheets-based sensor for electrochemical determination of caffeic acid (CA) in the presence of catechin is described. This measurement was performed using the differential pulse voltammetry (DPV) technique and chemometric methods such as multivariate curve resolution-alternating least squares (MCR-ALS). The modified sensor was characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet-visible, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Operating conditions and influencing variables (involving several chemical and instrumental variables) were optimized with central composite rotatable design and response surface methodology. The second-order electrochemical data were generated by changing the pulse height in DPV, and after potential shift correction MCR-ALS was applied. Under the optimized conditions, the dynamic range for CA was from 0.5 to 100.0 ?M and the detection limit was found to be 1.1×10(-9) M. The results revealed that the modified electrode shows an improvement in anodic oxidation activity of CA due to a marked enhancement in the current response compared with the bare carbon paste electrode. The modified electrode demonstrated good sensitivity, selectivity, and stability. The proposed method was successfully applied in determination of caffeic acid in the presence of unexpected electroactive interferences with a very high degree of overlapping such as catechin in real samples. PMID:25432066

  3. A new green phosphor of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} for alternating current driven light-emitting diodes

    SciTech Connect

    Chen, Lei, E-mail: chichengfeiyang@yahoo.com.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China) [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Semiconductor and Optoelectronic Technology Engineering Research Center of Anhui Province, Wuhu 241000 (China); Zhang, Yao; Liu, Fayong; Luo, Anqi; Chen, Zhixin; Jiang, Yang [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)] [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Chen, Shifu, E-mail: chshifu@chnu.edu.cn [Department of Chemistry, Huaibei Normal University, Huaibei 235000 (China)] [Department of Chemistry, Huaibei Normal University, Huaibei 235000 (China); Liu, Ru-Shi, E-mail: rsliu@ntu.edu.tw [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China)] [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ? This work focuses on exploring new phosphors of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} for AC LEDs. ? The work provides a new route to synthesize the pure phase of SrAl{sub 2}O{sub 4}. ? The formation of the impurity phase of Sr{sub 4}Al{sub 14}O{sub 25} was suppressed by using Ce{sup 3+}. ? Charger defects were compensated by using Li{sup +}. ? The luminescence intensity was enhanced significantly by co-doping Ce{sup 3+} and Li{sup +}. -- Abstract: New phosphors are desired to overcoming the flickering luminescence of alternating current light-emitting diodes (AC-LEDs) by compensating dark duration with appropriately persistent luminescence. Here, the phosphor of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} was developed for this application. The phosphor was synthesized with solid-state reaction method by using H{sub 3}BO{sub 3} as flux. The XRD patterns show that the impurity phase of Sr{sub 4}Al{sub 14}O{sub 25} which always formed together with SrAl{sub 2}O{sub 4} during reaction was suppressed by using Ce. The charger defects caused by the non-equivalent substitution of Sr{sup 2+} with Ce{sup 3+} were compensated with Li{sup +}. Thus, the luminescence intensity of SrAl{sub 2}O{sub 4}:Eu{sup 2+} was enhanced significantly by co-doping Ce{sup 3+} and Li{sup +}. The fluorescence lifetime of the phosphor is about 36.5 ms. The energy dispersive spectra (EDS) assisted with scanning electron microscope (SEM) pictures reveal that Ce ions mainly distribute along grain boundary.

  4. Alternative Farm Bills: Impacts on Minnesota Farms

    Microsoft Academic Search

    Kent D. Olson; Matthew R. DalSanto

    2007-01-01

    With the current federal farm bill set to expire at the end of September this year, many proposals have been made to redesign the next bill. The objectives of this study are to compare the current policy with major proposed alternatives and estimate the potential payments of farmers under each of the alternatives. The alternative policies are compared in two

  5. Adsorption of pyrantel pamoate on mercury from aqueous solutions: studies by stripping voltammetry.

    PubMed

    Gupta, Vinod K; Jain, Rajeev; Jadon, N; Radhapyari, K

    2010-10-01

    Adsorption and electrochemical reduction of pyrantel pamoate are studied in Britton Robinson buffer medium at hanging mercury drop electrode (HMDE) by Adsorptive Stripping Voltammetric technique. The peak current shows a linear dependence with the drug concentration over the range 250 ng mL(-1) to 64 microg mL(-1). Applicability to assay the drug in urine samples is illustrated in the concentration range 5-20 microg mL(-1). PMID:20643413

  6. An optimized digestion method coupled to electrochemical sensor for the determination of Cd, Cu, Pb and Hg in fish by square wave anodic stripping voltammetry

    Microsoft Academic Search

    V. Meucci; S. Laschi; M. Minunni; C. Pretti; L. Intorre; G. Soldani; M. Mascini

    2009-01-01

    An optimized digestion method coupled to electrochemical detection to monitor lead, copper, cadmium and mercury in fish tissues was developed. Square wave anodic stripping voltammetry (SWASV) coupled to disposable screen-printed electrodes (SPEs) was employed as fast and sensitive electroanalytical method for heavy metals detection. Different approaches in digestion protocols were assessed. The study was focused on Atlantic hake fillets because

  7. IMPLEMENTATION OF A DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY (DPASV) AT A HANGING MERCURY DROP ELECTRODE (HMDE) PROCEDURE FOR THE ANALYSIS OF AIRBORNE HEAVY METALS

    Microsoft Academic Search

    M. H. Barceló-Quintal; J. A. Manzanilla-Cano; E. O. Reyes-Salas; J. Flores-Rodríguez

    2001-01-01

    A procedure to determine cadmium, lead, zinc and copper in urban aerosol samples was developed. Differential-pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode (HMDE) was used as the analytical method, and accuracy of the procedure was checked using certified standard solutions. Metal concentrations were calculated from the corresponding regression line using the standard addition method; limits of

  8. In-situ electrochemical measurements of total concentration and speciation of heavy metals in acid mine drainage (AMD): assessment of the use of anodic stripping voltammetry

    Microsoft Academic Search

    Hun-Bok Jung; Seong-Taek Yun; Soon-Oh Kim; Myung Chae Jung; Chil-Sup So; Yong-Kwon Koh

    2006-01-01

    We assessed the use of anodic stripping voltammetry (ASV) for in-situ determinations of both total concentration and speciation of dissolved heavy metals (Cd, Cu, Pb and Zn) in acid mine drainage (AMD). In the Kwangyang Au–Ag mine area of South Korea, different sites with varying water chemistry within an AMD were studied with a field portable anodic stripping voltammeter. Anodic

  9. Determination of cadmium with a sequential injection lab-on-valve by anodic stripping voltammetry using a nafion coated bismuth film electrode

    Microsoft Academic Search

    Yang Wang; Zaiqing Liu; Guojun Yao; Peihua Zhu; Xiaoya Hu; Qin Xu; Chun Yang

    2010-01-01

    This work exploited a sequential injection lab-on-valve (LOV) system for the determination of cadmium by anodic stripping voltammetry (ASV). A miniaturized electrochemical flow cell (EFC) was fabricated in LOV, in which a nafion coated bismuth film electrode was used as working electrode. The cadmium was electrodeposited on the electrode surface in bismuth solution, and measured with the subsequential stripping scan.

  10. L'electrode a Pate de Carbone Modifiee Son Utilisation en Voltammetrie par Redissolution Anodique a Impulsions Differentielles en Presence d'Un Film de Mercure

    Microsoft Academic Search

    J. M. Kauffmann; A. Laudet; G. J. Patriarche

    1982-01-01

    The various problems which are associated with the use of carbon paste electrode as thin mercury film electrode (TKFE) for anodic stripping voltammetry (ASV) can be overcame in a very easy and rapid way. The procedure consists to coat the carbon paste surface by spraying a graphite based conductive solution. For example, the dispersion of colloidal graphite in a mixture

  11. Use of a modified, high-sensitivity, anodic stripping voltammetry method for determination of zinc speciation in the North Atlantic Ocean

    Microsoft Academic Search

    Rachel Wisniewski Jakuba; James W. Moffett; Mak A. Saito

    2008-01-01

    Zinc speciation is considered to be an important determinant of the biological availability of zinc. Yet in oceanic surface waters, characterization of zinc speciation is difficult due to the low concentrations of this essential micronutrient. In this study, an anodic stripping voltammetry method previously developed for the total determination of cadmium and lead was successfully adapted to the measurement of

  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. PMID:24364929

  13. Recycling wood pulping chemicals by molten salt electrolysis: cyclic voltammetry of mixtures containing Na 2 CO 3 and Na 2 SO 4

    Microsoft Academic Search

    R. Wartena; J. Winnick; P. H. Pfromm

    2002-01-01

    We are investigating a novel electrochemical pathway for efficient recycling of inorganic chemicals from the kraft pulping process. To analyse this process, cyclic voltammetry was conducted on molten salts containing sodium carbonate, or sodium carbonate and sodium sulfate on gold and nickel\\/nickel oxide electrodes. Pure sodium carbonate at 860 °C was determined to exhibit oxidation to carbon dioxide and oxygen.

  14. Steady-State Voltammetry of a Microelectrode in a Closed Bipolar Cell

    PubMed Central

    Cox, Jonathan T.; Guerrette, Joshua P.; Zhang, Bo

    2012-01-01

    Here we report the theory and experimental study of the steady-state voltammetric behavior of a microelectrode used as a limiting pole in a closed bipolar electrochemical cell. We show that the steady-state voltammetric response of a microelectrode used in a closed bipolar cell can be quantitatively understood by considering the responses of both poles in their respective conventional two-electrode setups. In comparison to a conventional electrochemical cell the voltammetric response of the bipolar cell has a similar sigmoidal shape and limiting current, however, the response is often slower than that of the typical two-electrode setup. This leads to a broader voltammogram and a decreased wave slope which can be somewhat misleading and appear that the process being studied is irreversible when it instead can be a result of the coupling of two reversible processes. We show that a large limiting current on the excess pole would facilitate the observation of a faster voltammetric response and both redox concentration and electrode area of the excess pole affect the wave shape. Both factors should be maximized in electroanalytical experiments in order to obtain fast voltammetric responses on the main electrode of interest and to detect quick changes in analyte concentrations. PMID:22992030

  15. Electric Currents Electric Current

    E-print Network

    Yu, Jaehoon

    of charge per unit time: = . Unit of current: Ampere (A). The purpose of a battery is to produce, and fire. To prevent this we use circuit breaker or fuses. - Each wire has a limit up to which it can hold

  16. Determining trace concentrations of copper in water by cathodic film stripping voltammetry with adsorptive collection

    SciTech Connect

    van den Berg, C.M.G.

    1984-01-01

    Trace concentrations of copper (II) in natural water samples were determined by CSV of a film of copper-catechol complex ions adsorbed on a hanging mercury drop electrode (HMDE). Complexation with copper (II) is not selective for copper, but complexes with copper (II) are rather strong; additionally, the reduction potentials of various competing heavy metal ions such as lead (II) and cadmium (II) are well separated from that of copper (II). Addition of a large surplus of catechol (0.0001 to 0.001 M) further ensures that effectively 100% of all copper (II) ions is present in the catechol-complex ion form. After collection the current is measured for the reduction of copper (II) to copper (O) by CVS of the collected film using differential pulse modulation. The detection limit of the technique is below 10 to the minus 10th power M copper (II) for a collection time of 3 minutes, but the sensitivity can be further increased four-fold by collecting for 15 minutes. The sensitivity is reduced by high concentrations of competing trace metals and of surfactants. 10 references, 3 figures, 1 table.

  17. Wireless transmission of fast-scan cyclic voltammetry at a carbon-fiber microelectrode: proof of principle.

    PubMed

    Garris, Paul A; Ensman, Robert; Poehlman, John; Alexander, Andy; Langley, Paul E; Sandberg, Stefan G; Greco, Phillip G; Wightman, R Mark; Rebec, George V

    2004-12-30

    Fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) provides exquisite temporal and spatial resolution for monitoring brain chemistry. The utility of this approach has recently been demonstrated by measuring sub-second dopamine changes associated with behavior. However, one drawback is the cable link between animal and recording equipment that restricts behavior and precludes monitoring in complex environments. As a first step towards developing new instrumentation to overcome this technical limitation, the goal of the present study was to establish proof of principle for the wireless transmission of FSCV at a CFM. Proof of principle was evaluated in terms of measurement stability, fidelity, and susceptibility to ambient electrical noise. Bluetooth digital telemetry provided bi-directional communication between remote and home-base units and stable, high-fidelity data transfer comparable to conventional, wired systems when tested using a dummy cell (i.e., a resistor and capacitor in series simulating electrical properties of a CFM), and dopamine measurements with flow injection analysis and in the anesthetized rat with electrical stimulation. The wireless system was also less susceptible to interference from ambient electrical noise. Taken together, the present findings establish proof of principle for the wireless transmission of FSCV at a CFM. PMID:15589340

  18. Cadmium speciation assessed by voltammetry, ion exchange and geochemical calculation in soil solutions collected after soil rewetting.

    PubMed

    Cornu, J Y; Parat, C; Schneider, A; Authier, L; Dauthieu, M; Sappin-Didier, V; Denaix, L

    2009-07-01

    Analytical techniques and speciation models have been developed to characterize the speciation of Cd in soil solution. They provide an estimate of operationally defined species of Cd that need to be compared, especially for soil solutions highly concentrated in organic matter as are the solutions collected after soil rewetting. This work deals with the comparison between the speciation of Cd measured by anodic stripping voltammetry (ASV) and ion exchange and the speciation of Cd calculated using Visual MINTEQ. The aim of this study was to quantify and explain the differences in Cd speciation observed between the three approaches. Cd speciation was assessed in soil solutions collected 4, 8, 24, 48, 96 and 144h after the rewetting of an air-dried contaminated soil. To optimize the computed speciation of Cd, other physico-chemical parameters were followed (e.g. pH, ionic strength and the concentrations of major anions, major cations and dissolved organic carbon) and a brief characterisation of dissolved organic matter (DOM) was performed. The discrepancy between model predictions and analytical measurements highlighted the need for caution in the interpretation of geochemical speciated data for Cd. The major result of this study was that a characterization of DOM based on its specific UV-absorbance at 254 nm improved the accuracy of model predictions. Another finding is that labile Cd complexes, even organic, may have been included in the electrochemically labile fraction of Cd measured by ASV. PMID:19356783

  19. Photoinduced electron transfer occurs between 2-aminopurine and the DNA nucleic acid monophosphates: results from cyclic voltammetry and fluorescence quenching.

    PubMed

    Narayanan, Madhavan; Kodali, Goutham; Xing, Yangjun; Stanley, Robert J

    2010-08-19

    2-Aminopurine (2AP) is a fluorescent adenine analogue that is useful in part because its substantial fluorescence quantum yield is sensitive to base stacking with native bases in ss- and ds-DNA. However, the degree of quenching is sequence dependent and the mechanism of quenching is still a matter of some debate. Here we show that the most likely quenching mechanism in aqueous solution involves photoinduced electron transfer (PET), as revealed by cyclic voltammetry (CV) performed in aprotic organic solvents. These potentials were used with spectroscopic data to obtain excited-state reduction and oxidation potentials. Stern-Volmer (S-V) experiments using the native base monophosphate nucleotides (NMPs) rGMP, rAMP, rCMP, and dTMP were performed in aqueous solution to obtain quenching rate constants kq. The results suggest that 2AP* can act as either an electron donor or an electron acceptor depending on the particular NMP but that PET proceeds for all NMPs tested. PMID:20734496

  20. Disposable electrochemical flow cells for catalytic adsorptive stripping voltammetry (CAdSV) at a bismuth film electrode (BiFE)

    PubMed Central

    Gharib Naseri, Nahid; Economou, Anastasios; Goddard, Nicholas J.; Fielden, Peter R.

    2008-01-01

    Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required. PMID:18351328

  1. In vivo voltammetry monitoring of electrically evoked extracellular norepinephrine in subregions of the bed nucleus of the stria terminalis

    PubMed Central

    Herr, Natalie R.; Park, Jinwoo; McElligott, Zoé A.; Belle, Anna M.; Carelli, Regina M.

    2012-01-01

    Norepinephrine (NE) is an easily oxidized neurotransmitter that is found throughout the brain. Considerable evidence suggests that it plays an important role in neurocircuitry related to fear and anxiety responses. In certain subregions of the bed nucleus of the stria terminalis (BNST), NE is found in large amounts. In this work we probed differences in electrically evoked release of NE and its regulation by the norepinephrine transporter (NET) and the ?2-adrenergic autoreceptor (?2-AR) in two regions of the BNST of anesthetized rats. NE was monitored in the dorsomedial BNST (dmBNST) and ventral BNST (vBNST) by fast-scan cyclic voltammetry at carbon fiber microelectrodes. Pharmacological agents were introduced either by systemic application (intraperitoneal injection) or by local application (iontophoresis). The iontophoresis barrels were attached to a carbon fiber microelectrode to allow simultaneous detection of evoked NE release and quantitation of iontophoretic delivery. Desipramine (DMI), an inhibitor of NET, increased evoked release and slowed clearance of released NE in both regions independent of the mode of delivery. However, the effects of DMI were more robust in the vBNST than in the dmBNST. Similarly, the ?2-AR autoreceptor inhibitor idazoxan (IDA) enhanced NE release in both regions but to a greater extent in the vBNST by both modes of delivery. Since both local application by iontophoresis and systemic application of IDA had similar effects on NE release, our results indicate that terminal autoreceptors play a predominant role in the inhibition of subsequent release. PMID:22190618

  2. Characterization of graphite–polyurethane composite electrodes modified with organofunctionalized SBA15 nanostructured silica in the presence of heavy metal ions. Application to anodic stripping voltammetry

    Microsoft Academic Search

    Ivana Cesarino; Éder T. G. Cavalheiro; Christopher M. A. Brett

    2010-01-01

    A graphite–polyurethane composite electrode with Santa Barbara Amorphous 15, SBA-15, mesoporous silica organofunctionalized\\u000a with 2-benzothiazolethiol (BTSBA) as bulk modifier has been characterized electrochemically by voltammetry and electrochemical\\u000a impedance spectroscopy (EIS) in the presence of cadmium ions, as an example of a toxic trace heavy metal, as well as by solid-state\\u000a 13C-NMR and by scanning electron microscopy. EIS measurements performed on

  3. Complexation Study of Humic Acids Extracted from Forest and Sahara Soils with Zinc (II) and Cadmium (II) by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Conductimetric Methods

    Microsoft Academic Search

    Achour Terbouche; Safia Djebbar; Ouassini Benali-Baitich; Didier Hauchard

    2011-01-01

    The complexation of heavy metals, present in their dissolved state at relevant trace levels, with new humic acids (HAs) isolated\\u000a from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils has been studied by differential pulse anodic stripping voltammetry\\u000a (DPASV) at a hanging mercury drop electrode and conductimetry methods. After extraction and purification, humic acids were\\u000a characterized by elemental analyses, atomic

  4. A Comparison of Methods for Determining Lead Content in Drinking Water: A Portable Anodic Stripping Voltammetry Instrument Method versus the Standard EPA 239.2 Method

    Microsoft Academic Search

    Susanne M. Savely; Robert J. Emery; Thomas H. Connor

    2000-01-01

    Lead levels in drinking water were measured by the standard U.S. Environmental Protection Agency (EPA)-approved atomic absorption spectroscopy-graphite furnace Method 239.2 and compared with determinations made with a newly available portable anodic stripping voltammetry (PASV) instrument. A standard curve was prepared at 2, 5, 10, 15, 20, 25, and 30 µg\\/L of lead. PASV instrument readings were lower than standard

  5. Redox kinetic measurements of glutathione at the mercury electrode by means of square-wave voltammetry. The role of copper, cadmium and zinc ions

    Microsoft Academic Search

    Mitko Mladenov; Valentin Mir?eski; Icko Gjorgoski; Blagoja Jordanoski

    2004-01-01

    The electrode reaction of glutathione (GSH) at the hanging mercury drop electrode is studied by means of square-wave voltammetry (SWV). At potentials more positive than ?0.350 V (vs. Ag\\/AgCl (3 mol\\/l KCl)) the oxidation of the mercury electrode in the presence of GSH leads to creation of a sparingly soluble mercury–GSH complex that deposits onto the electrode surface. Under cathodic

  6. Determination of lead and cadmium in seawater by differential pulse anodic stripping voltammetry: fit-for-purpose partial validation and internal quality aspects

    Microsoft Academic Search

    K. Bisetty; N. J. Gumede; L. Escuder-Gilabert; S. Sagrado

    2008-01-01

    The main thrust of this work involves method validation, quality control and sample uncertainty estimations related to the\\u000a determination of cadmium and lead in marine water by anodic stripping voltammetry. We have followed a step-by-step protocol\\u000a to evaluate and harmonize the internal quality aspects of this method. Such protocol involves a statement of the method’s\\u000a scope (analytes, matrices, concentration level)

  7. Simultaneous determination of ultra-trace lead and cadmium at a hydroxyapatite-modified carbon ionic liquid electrode by square-wave stripping voltammetry

    Microsoft Academic Search

    Yonghong Li; Xiaoying Liu; Xiandong Zeng; Yong Liu; Xiaotao Liu; Wanzhi Wei; Shenglian Luo

    2009-01-01

    In this paper, a hydroxyapatite-modified carbon ionic liquid electrode (HAP-CILE) for the simultaneous determination of lead and cadmium was developed. The hydroxyapatite which combines with ionic liquid plays an important role in remarkable responses of metals. Trace analysis of the selected heavy metals was performed by square-wave anodic stripping voltammetry (SWASV). The oxidation of two metals yielded well-defined, separated square-wave

  8. A stannum\\/bismuth\\/poly(p-aminobenzene sulfonic acid) film electrode for measurement of Cd(II) using square wave anodic stripping voltammetry

    Microsoft Academic Search

    Chang Hong Xiong; Hong Qun Luo; Nian Bing Li

    2011-01-01

    In the present work, a new method for a trace analysis of metal cadmium ion has been developed on the stannum\\/bismuth\\/poly(p-aminobenzene sulfonic acid) film electrode in combination with square wave anodic stripping voltammetry. This new electrode was prepared by in situ depositing stannum, bismuth and target metal on the poly(p-aminobenzene sulfonic acid)(p-ABSA) coated glassy carbon electrode. Some key factors including

  9. Electrochemical Characterization of and Stripping Voltammetry at Screen Printed Electrodes Modified with Different Brands of Multiwall Carbon Nanotubes and Bismuth Films

    Microsoft Academic Search

    Adil Mandil; Rasa Pauliukaite; Aziz Amine; Christopher M. A. Brett

    2012-01-01

    A screen-printed electrode sensor has been fabricated by modifying the carbon ink surface with different brands of multiwall carbon nanotubes (MWCNTs) and bismuth film (BiF) for the determination of traces of lead, cadmium and zinc ions by square wave anodic stripping voltammetry. The MWCNTs, from three different sources, were functionalized and dispersed in Nafion (MWCNT-Nafion) solution and placed on screen

  10. Determination of mercury in hair by square-wave anodic stripping voltammetry at a rotating gold disk electrode after microwave digestion

    Microsoft Academic Search

    Gaston A. East; Epitácio P. Marinho

    2005-01-01

    A simple and reliable method for the determination of mercury in hair on a rotating gold disk electrode using subtractive\\u000a anodic stripping voltammetry without removal of oxygen is reported. Voltammetric and microwave parameters were optimized to\\u000a obtain the best analytical results. Parameters such as supporting electrolyte concentration, influence of chloride in the\\u000a Hg peak, deposition potential, scan rate, accumulation time,

  11. A study of the copper electrode behavior in borax buffer solutions containing chloride ions and benzotriazole-type inhibitors by voltammetry and the photocurrent response method

    Microsoft Academic Search

    Guo-Ding Zhou; Hua Shao; B. H. Loo

    1997-01-01

    The electrochemical behavior of the Cu electrode in borax buffer solutions containing chloride ions and benzotriazole (BTA)-type inhibitors was studied by voltammetry and the photocurrent response method. A p-type photoresponse was observed from the Cu electrode in the pure borax buffer solutions. However, an n-type photoresponse was observed in chloride-containing borax buffer solutions if the Cl? concentration exceeded 0.08%. The

  12. Determination of brilliant blue FCF in the presence and absence of erythrosine and quinoline yellow food colours by cathodic stripping voltammetry

    Microsoft Academic Search

    M. Florian; H. Yamanaka; P. A. Carneiro; M. Valnice Boldrin Zanoni

    2002-01-01

    A study of the voltammetric behaviour of the food colours brilliant blue FCF (C.I. 42090), erythrosine (C.I. 45430) and quinoline yellow (C.I. 47005) in the pH range 2–10 have been carried out by cathodic stripping voltammetry. At pH 4.5 (acetate buffer) with an accumulation potential of 0V and accumulation time of 30s, the voltammograms presented well-defined reduction peaks at potential

  13. The influence of edge-plane defects and oxygen-containing surface groups on the voltammetry of acid-treated, annealed and “super-annealed” multiwalled carbon nanotubes

    Microsoft Academic Search

    Andrew F. Holloway; Gregory G. Wildgoose; Richard G. Compton; Lidong Shao; Malcolm L. H. Green

    2008-01-01

    The role of edge-plane-like defects at the open ends of multiwalled carbon nanotubes (MWCNTs) and at hole defects in the tube\\u000a walls is explored using cyclic voltammetry with two charged redox probes, namely potassium ferrocyanide and hexaamineruthenium(III)\\u000a chloride in unbuffered aqueous solutions, and one neutral redox probe, norepinephrine, in pH 5.7 buffer. Further, the presence\\u000a of oxygen-containing functional groups (such

  14. Determination of the antioxidant Irganox 1076 by anodic voltammetry and flow injection with pulsed amperometric detection at a glassy carbon electrode

    Microsoft Academic Search

    M. L. Agüí; E. Calavia; P. Yáñez-Sedeño; J. M. Pingarrón

    1995-01-01

    An electroanalytical study of the Irganox 1076 oxidation process at a glassy carbon electrode in an aqueous 60% ethanolic medium using different voltammetric techniques has been carried out. The results obtained by differential pulse voltammetry allowed the development of a method for the determination of this antioxidant using a calibration graph in the 1.0 × 10?6?2.5 × 10?5moll?1 Irganox 1076

  15. HHydrogen could well be the ultimate fuel--a plentiful, clean-burning, planet-healthy alternative to oil. But first, numerous obstacles must be overcome. Heading the list of challenges is storage. Currently,

    E-print Network

    Yaghi, Omar M.

    on Fuel Cell Technology Abundantly available in nature, hydrogen gas when broken down produces only waterHHydrogen could well be the ultimate fuel--a plentiful, clean-burning, planet-healthy alternative." With the assistance of UM Tech Transfer, Yaghi and his research team have patented designs and production protocols

  16. Low-frequency alternative-current magnetic susceptibility, photoelectric properties, and adhesive properties of Ni80Fe20 (XÅ)/ZnO(500Å) and ZnO(500Å)/Ni80Fe20(YÅ) on glass substrate

    NASA Astrophysics Data System (ADS)

    Chen, Yuan-Tsung

    2015-08-01

    The following conditions are deposited: (a) glass/Ni80Fe20(XÅ)/ZnO(500Å) and (b) glass/ZnO(500Å)/Ni80Fe20(YÅ), where each of X and Y is 1000Å, 1500Å, 2000Å or 2500Å. The substrate temperature was maintained at room temperature (RT), and post-annealing was performed with heating at (TA) = 150 °C for 1 h or (TA) = 250 °C for 1 h. The sputtering sequence and the thickness of the NiFe film were varied to study the effects of these factors on the low-frequency alternative-current magnetic susceptibility (?ac), maximum ?ac with corresponding optimal resonance frequency (fres), transmission, electrical resistivity (?), and surface energy of the multilayered glass/Ni80Fe20(XÅ)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(YÅ). Experimental results demonstrate that ZnO(500Å)/Ni80Fe20(YÅ) is superior to Ni80Fe20/ZnO(500Å) because diffraction from the ZnO (0 0 2) crystals at the bottom of ZnO(500Å)/Ni80Fe20(YÅ) improves the magneto crystalline anisotropy of Ni80Fe20, improving its magnetic and photoelectrical properties. X-ray diffraction patterns (XRD) reveal that the ZnO (0 0 2), ZnO (2 2 0), and NiFe (1 1 1) peaks of ZnO(500Å)/Ni80Fe20(YÅ) are more intense than those of Ni80Fe20/ZnO(500Å) under three substrate conditions, indicating the ZnO (0 0 2) peak reflects magneto crystalline anisotropy in the crystalline NiFe layer of ZnO(500Å)/Ni80Fe20(YÅ), yielding the highest ?ac of approximately 3.16 with an fres of 250 Hz upon post-annealing TA = 250 °C for 1 h. The (1 1 1) diffracted intensity and grain size of the thicker and post-annealed Ni80Fe20 thin films exceeded those of the thinner and as-deposited Ni80Fe20 thin films. A spectral analyzer was used to measure transmittance through NiFe of various thicknesses. The transmittance declined slightly as the thickness and grain size increased, because increasing thickness reduced penetration. Post-annealing promoted grain growth, increased the average size of the grains and reduced transmittance. Both as-deposited glass/Ni80Fe20(XÅ)/ZnO(500Å) and as-deposited glass/ZnO(500Å)/Ni80Fe20(YÅ) had the highest penetration, when X, Y = 1000Å, and the highest transmittances of 87% and 93%, respectively. The highest transmittance of glass/ZnO(500Å)/Ni80Fe20(YÅ) exceeded that of glass/Ni80Fe20(XÅ)/ZnO(500Å) owing to ZnO (0 0 2) crystallization. Furthermore, ? decreased as the Ni80Fe20 thickness increased, because grain boundaries and the surface of thin films scattered the electrons, so thinner films had greater resistance. Electrical measurements revealed that the maximum resistivities of glass/Ni80Fe20(1000Å)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(1000Å) were 292 ?? cm and 288 ?? cm, and the resistivity declined as the thickness of the film increased. The surface energy of the as-deposited and thinner NiFe layers exceeded that of post-annealed and thicker NiFe layers, revealing that the adhesion of the as-deposited and thinner NiFe films was stronger than that of the post-annealed and thicker films, on account of the degrees of crystallinity. Glass/Ni80Fe20(1000Å)/ZnO(500Å) and glass/ZnO(500Å)/Ni80Fe20(1000Å) had the highest surface energies of 64 mJ/mm2 and 59 mJ/mm2; the surface energy worsened as the temperature increased, suggesting that the adhesion of the as-deposited and thinner NiFe films in glass/Ni80Fe20(XÅ)/ZnO(500Å) was stronger than in glass/ZnO(500Å)/Ni80Fe20(YÅ). The results indicate that the magnetic and photoelectric properties of glass/ZnO(500Å)/Ni80Fe20(YÅ) were better than those of glass/Ni80Fe20(XÅ)/ZnO(500Å) because the strong ZnO (0 0 2) crystallization in ZnO(500Å)/Ni80Fe20(YÅ) increased the magneto crystalline anisotropy NiFe (1 1 1) and importantly affected the magnetic and photoelectrical properties.

  17. Analysis of biogenic amines in a single Drosophila larva brain by capillary electrophoresis with fast-scan cyclic voltammetry detection

    PubMed Central

    Fang, Huaifang; Vickrey, Trisha L.; Venton, B. Jill

    2011-01-01

    Drosophila, the fruit fly, is a common model organism in biology, however quantifying neurotransmitters in Drosophila is challenging because of the small size of the central nervous system (CNS). Here, we develop neurotransmitter quantification by capillary electrophoresis with fast-scan cyclic voltammetry detection, which allows peak identification by both migration time and the cyclic voltammogram, in contrast to traditional amperometric detection which provides no chemical identification. Tissue content of biogenic amine neurotransmitters was determined in a single CNS dissected from a Drosophila larva. Low detection limits, 1 nM for dopamine and serotonin, 2.5 nM for tyramine, and 4 nM for octopamine, were achieved using field-amplified sample stacking by diluting the homogenized tissue with percholoric acid and acetonitrile. Two different strains of wild-type flies, Oregon R and Canton S, have similar dopamine and serotonin levels but different octopamine content. When flies are fed NSD-1015, which inhibits dopamine decarboxylase (Ddc) a synthesis enzyme in the dopamine and serotonin pathways, dopamine significantly decreases by 52%. A genetically altered driver line, Ddc-GAL4, had lower serotonin and dopamine content as did w118 flies. When the Ddc-GAL4 line was used to produce flies overexpressing the serotonin synthesis enzyme tryptophan hydroxylase (Ddc-GAL4;UAS-Trh), serotonin tissue content was greater than for Ddc-GAL4, but not significantly different than wild-type. These results show that CE-FSCV is useful for monitoring the impact of genetic and pharmacological manipulations on the content of multiple neurotransmitters in a CNS from a Drosophila larva. PMID:21322586

  18. Determination of para-arsanilic acid with improved diazotization reaction using differential pulse cathodic stripping voltammetry in aqueous system.

    PubMed

    Misni, Marpongahtun; Sathishkumar, Palanivel; Ahamad, Rahmalan; MohdYusoff, Abdull Rahim

    2015-09-01

    Para-arsanilic acid (p-ASA) has been widely used in the poultry industry to promote growth and prevent dysentery. It is excreted unchanged in the manure and released into non-target sites causing organoarsenic pollution risk to the environment and living system. Therefore, simple and effective analytical strategies are demanded for determining the samples that contain p-ASA. However, direct determination of both p-ASA and ortho-arsanilic acid (o-ASA) using differential pulse cathodic stripping voltammetry (DPCSV) gives the similar voltammograms that directly hamper the analysis used by the DPCSV technique. In this study, a method to determine and differentiate p-ASA from o-ASA via diazotization and coupling reaction of the amine groups followed by the direct DPCSV determination of diazo compounds is presented. The diazotization reaction carried out at pH 1.5 and 0?±?1°C for 10?min showed two reduction peaks in DPCSV at-70?mV and -440?mV vs. Ag/AgCl (KCl 3?M). However, when the diazotization reaction was performed at pH 12.5 and 0?±?1°C for 40?min, a coloured azo compound was produced and the DPCSV showed only one reduction peak that appeared at -600?mV vs. Ag/AgCl (3?M of KCl). The results of this study show that only p-ASA compound gave a reduction peak, whereas o-ASA compound did not give any peak. The detection limit of p-ASA was found to be 4?×?10(-8?)M. As a result, the proposed electro-analytical technique might be a good candidate to determine and differentiate the p-ASA present in the poultry and environmental samples. PMID:25749108

  19. Application of stripping voltammetry and microelectrodes in vitro biocompatibility and in vivo toxicity tests of AISI 316L corrosion products.

    PubMed

    Morais, S; Pereira, M C

    2000-04-01

    Adsorptive stripping voltammetric procedures, using mercury film microelectrodes, were optimised and applied to quantify total iron, chromium and nickel in samples of osteoblast-like cells culture medium and mice organs (liver, kidney and spleen) obtained from, respectively, in vitro and in vivo 316L stainless steel corrosion products biocompatibility and toxicity studies. The methods were based on the pre-concentration of the iron-catechol complex by adsorption at the potential of -1.80 V (vs. Ag/AgCl), of the chromium-diethylenetriaminepentaacetic acid complex at -1.00 V or -1.15 V (vs. Ag/AgCl) and of the nickel-dimethylglyoxime complex at -0.70 V (vs. Ag/AgCl). The detection limits achieved for each metal ion (i) in the culture medium were 1.93x10(-8) mol/L Fe, 2.80x10(-10) mol/L Cr and 7.70x10(-9) mol/L Ni for a collection time of 30 s, 40 s and 10 s, respectively, and (ii) in the mice organ solutions were 1.37x10(-8) mol/L Fe, 1.54x10(-8) mol/L Cr and 1.58x10(-9) mol/L Ni for an adsorption time of 25 s, 25 s and 15 s, respectively. The accuracy of the proposed procedures was verified by comparison of the results obtained by adsorptive stripping voltammetry with those attained by atomic absorption spectrometry for the same set of samples and good agreement was found. The in vitro study showed that stainless steel corrosion products affect the expression of the osteogenic phenotype. The in vivo mice model, used to investigate the systemic effects provoked by the corrosion products per se, indicated that Fe, Cr and Ni are partially accumulated in the organs studied and that Ni induced the more significant morphological alterations. PMID:10836534

  20. Compositional analysis of electrodeposited bismuth telluride thermoelectric thin films using combined electrochemical quartz crystal microgravimetry--stripping voltammetry.

    PubMed

    Ham, Sunyoung; Jeon, Soyeon; Lee, Ungki; Park, Minsoon; Paeng, Ki-Jung; Myung, Noseung; Rajeshwar, Krishnan

    2008-09-01

    Bismuth telluride (Bi 2Te 3 ) is a benchmark material for thermoelectric power generation and cooling applications. Electrodeposition is a versatile technique for preparing thin films of this material; however, it affords films of variable composition depending on the preparation history. A simple and rapid assay of electrodeposited films, therefore, has both fundamental and practical importance. In this study, a new protocol for the electroanalysis of Bi 2Te 3 thin films is presented by combining the two powerful and complementary techniques of electrochemical quartz crystal microgravimetry (EQCM) and stripping voltammetry. First, any free (and excess) tellurium in the electrodeposited film was reduced to soluble Te ( 2- ) species by scanning to negative potentials in a 0.1 M Na 2SO 4 electrolyte, and the accompanying frequency increase (mass loss) was used to determine the content of free tellurium. The film was again subjected to cathodic stripping in the same medium (to generate Bi (0) and soluble Te (2-) from the Bi 2 Te 3 film component of interest), and the EQCM frequency change was used to determine the content of chemically bound Te in the Bi 2Te 3 thin film and thereby the compound stoichiometry. Finally, the EQCM frequency change during Bi oxidation to Bi (3+) and the difference between total Bi and Bi in Bi 2Te 3 resulted in the assay of free (excess) Bi in the electrodeposited film. Problems associated with the chemical/electrochemical stability of the free Bi species were circumvented by a flow electroanalysis approach. Data are also presented on the sensitivity of electrodeposited Bi 2Te 3 film composition to the electrodeposition potential. This newly developed method can be used for the compositional analysis of other thermoelectric thin-film material candidates in general. PMID:18672891

  1. WINCS-BASED WIRELESS ELECTROCHEMICAL MONITORING OF SEROTONIN (5-HT) USING FAST-SCAN CYCLIC VOLTAMMETRY: PROOF OF PRINCIPLE

    PubMed Central

    Griessenauer, Christoph J.; Chang, Su-Youne; Tye, Susannah J.; Kimble, Christopher J.; Bennet, Kevin E.; Garris, Paul A.; Lee, Kendall H.

    2010-01-01

    Object We previously reported the development of a Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for measuring dopamine and suggested that this technology may be useful for evaluating deep brain stimulation (DBS)-related neuromodulatory effects on neurotransmitter systems. WINCS supports fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) for real-time, spatially resolved neurotransmitter measurements. The FSCV parameters used to establish WINCS dopamine measurements are not suitable for serotonin, a neurotransmitter implicated in depression, because they lead to CFM fouling and a loss of sensitivity. Here, we incorporate into WINCS a previously described N-shaped waveform applied at a high scan rate to establish wireless serotonin monitoring. Methods FSCV optimized for the detection of serotonin consisted of an N-shaped waveform scanned linearly from a resting potential of, in V, +0.2 to +1.0, then to ?0.1 and back to +0.2 at a rate of 1000 V/s. Proof of principle tests included flow injection analysis and electrically evoked serotonin release in the dorsal raphe nucleus of rat brain slices. Results Flow cell injection analysis demonstrated that the N waveform applied at a scan rate of 1000 V/s significantly reduced serotonin fouling of the CFM, relative to that observed with FSCV parameters for dopamine. In brain slices, WINCS reliably detected sub-second serotonin release in the dorsal raphe nucleus evoked by local high-frequency stimulation. Conclusion WINCS supported high-fidelity wireless serotonin monitoring by FSCV at a CFM. In the future such measurements of serotonin in large animal models and in humans may help to establish the mechanism of DBS for psychiatric disease. PMID:20415521

  2. Syllabus for Chem. 3700 Alternative Energy

    E-print Network

    Houston, Paul L.

    Syllabus for Chem. 3700 Alternative Energy Class Meetings: Tuesdays and Thursdays popular alternative energy sources which are currently being used or developed to help relieve with the most popular alternate energy options. Due to the interdisciplinary nature of the topic, the course

  3. The effect of acetate concentration, solution pH and conductivity on the anodic stripping voltammetry of lead and cadmium ions at in situ bismuth-plated carbon microelectrodes

    Microsoft Academic Search

    L. Baldrianova; P. Agrafiotou; I. Svancara; A. D. Jannakoudakis; S. Sotiropoulos

    2011-01-01

    The use of carbon microdisc electrode substrates allowed Pb(II) and Cd(II) anodic stripping voltammetry at in situ plated bismuth films to be studied in an extended acetate buffer\\/electrolyte concentration range that includes very low or zero acetate levels. The change of the Pb and Cd Square Wave Anodic Stripping Voltammetry (SWASV) peak height with acetate concentration, pH and conductivity has

  4. Biotherapeutics as alternatives to antibiotics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  5. 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…

  6. Alternative aircraft fuels

    NASA Technical Reports Server (NTRS)

    Longwell, J. P.; Grobman, J.

    1978-01-01

    In connection with the anticipated impossibility to provide on a long-term basis liquid fuels derived from petroleum, an investigation has been conducted with the objective to assess the suitability of jet fuels made from oil shale and coal and to develop a data base which will allow optimization of future fuel characteristics, taking energy efficiency of manufacture and the tradeoffs in aircraft and engine design into account. The properties of future aviation fuels are examined and proposed solutions to problems of alternative fuels are discussed. Attention is given to the refining of jet fuel to current specifications, the control of fuel thermal stability, and combustor technology for use of broad specification fuels. The first solution is to continue to develop the necessary technology at the refinery to produce specification jet fuels regardless of the crude source.

  7. 1-Butyl-3-methylimidazolium hexafluorophosphate ionic liquid as a new solvent for the determination of lead(II) and cadmium(II) by anodic stripping voltammetry after extraction of the iodide complexes.

    PubMed

    Kamio, Akihiro; Nagaosa, Yukio

    2008-10-01

    The use of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM x PF(6)) as a solvent for the anodic stripping analysis of Pb(II) and Cd(II) after extraction of the iodide complexes has been investigated. This method is based on the extraction of the metal iodide complexes into BMIM x PF(6), followed by differential-pulse anodic stripping voltammetry with an in-situ plated bismuth film electrode onto an edge-plane type of pyrolytic graphite substrate. When tetra-n-propylammonium iodide at a concentration of 0.20 mol L(-1) was used as an extractant and a supporting electrolyte, the reduced lead and cadmium produced well-defined anodic peaks at -414 and -736 mV vs. Ag/AgCl, respectively. The peak currents for Pb(II) and Cd(II) were directly proportional to the initial metal concentration in the ranges of 0.01-0.50 microg mL(-1) and 0.05-1.0 microg mL(-1) under the optimized conditions. A detection limit (S/N = 3) of 0.001 microg mL(-1) Pb(II) was obtained with a volume ratio (V(aq)/V(BMIM x PF(6))) of 2.0 at 300 s deposition time. The relative standard deviation was 3.2% on replicate runs (n = 10) for the determinations of 0.20 microg mL(-1) Pb(II). PMID:18845902

  8. Highly sensitive determination of mercury using copper enhancer by diamond electrode coupled with sequential injection-anodic stripping voltammetry.

    PubMed

    Chaiyo, Sudkate; Chailapakul, Orawon; Siangproh, Weena

    2014-12-10

    A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection-anodic stripping voltammetry (SI-ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5 M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at -1.0 V (vs. Ag/AgCl, 3 M KCl) for 150 s with a flow rate of 14 ?L s(-1). An anodic stripping voltammogram was recorded from -0.4 V to 0.25 V using a frequency of 60 Hz, an amplitude of 50 mV, and a step potential of 10 mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at -0.25 V and +0.05 V (vs. Ag/AgCl, 3 M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1-30.0 ng mL(-1) and 5.0-60.0 ng mL(-1)). The limit of detection (S/N=3) obtained from the experiment was found to be 0.04 ng mL(-1). The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20 ng mL(-1), respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg(II), according to the paired t-test at a 95% confidence level. PMID:25441879

  9. Characterisation of weak magnetic field effects in an aqueous glutamic acid solution by nonlinear dielectric spectroscopy and voltammetry.

    PubMed

    Pazur, Alexander

    2004-11-30

    BACKGROUND: Previous reports indicate altered metabolism and enzyme kinetics for various organisms, as well as changes of neuronal functions and behaviour of higher animals, when they were exposed to specific combinations of weak static and alternating low frequency electromagnetic fields. Field strengths and frequencies, as well as properties of involved ions were related by a linear equation, known as the formula of ion cyclotron resonance (ICR, abbreviation mentioned first by Liboff). Under certain conditions already a aqueous solution of the amino acid and neurotransmitter glutamate shows this effect. METHODS: An aqueous solution of glutamate was exposed to a combination of a static magnetic field of 40 muT and a sinusoidal electromagnetic magnetic field (EMF) with variable frequency (2-7 Hz) and an amplitude of 50 nT. The electric conductivity and dielectric properties of the solution were investigated by voltammetric techniques in combination with non linear dielectric spectroscopy (NLDS), which allow the examination of the dielectric properties of macromolecules and molecular aggregates in water. The experiments target to elucidate the biological relevance of the observed EMF effect on molecular level. RESULTS: An ion cyclotron resonance (ICR) effect of glutamate previously reported by the Fesenko laboratory 1998 could be confirmed. Frequency resolution of the sample currents was possible by NLDS techniques. The spectrum peaks when the conditions for ion cyclotron resonance (ICR) of glutamate are matched. Furthermore, the NLDS spectra are different under ICR- and non-ICR conditions: NLDS measurements with rising control voltages from 100-1100 mV show different courses of the intensities of the low order harmonics, which could possibly indicate "intensity windows". Furthermore, the observed magnetic field effects are pH dependent with a narrow optimum around pH 2.85. CONCLUSIONS: Data will be discussed in the context with recent published models for the interaction of weak EMF with biological matter including ICR. A medical and health relevant aspect of such sensitive effects might be given insofar, because electromagnetic conditions for it occur at many occasions in our electromagnetic all day environment, concerning ion involvement of different biochemical pathways. PMID:15571630

  10. Characterisation of weak magnetic field effects in an aqueous glutamic acid solution by nonlinear dielectric spectroscopy and voltammetry

    PubMed Central

    Pazur, Alexander

    2004-01-01

    Background Previous reports indicate altered metabolism and enzyme kinetics for various organisms, as well as changes of neuronal functions and behaviour of higher animals, when they were exposed to specific combinations of weak static and alternating low frequency electromagnetic fields. Field strengths and frequencies, as well as properties of involved ions were related by a linear equation, known as the formula of ion cyclotron resonance (ICR, abbreviation mentioned first by Liboff). Under certain conditions already a aqueous solution of the amino acid and neurotransmitter glutamate shows this effect. Methods An aqueous solution of glutamate was exposed to a combination of a static magnetic field of 40 ?T and a sinusoidal electromagnetic magnetic field (EMF) with variable frequency (2–7 Hz) and an amplitude of 50 nT. The electric conductivity and dielectric properties of the solution were investigated by voltammetric techniques in combination with non linear dielectric spectroscopy (NLDS), which allow the examination of the dielectric properties of macromolecules and molecular aggregates in water. The experiments target to elucidate the biological relevance of the observed EMF effect on molecular level. Results An ion cyclotron resonance (ICR) effect of glutamate previously reported by the Fesenko laboratory 1998 could be confirmed. Frequency resolution of the sample currents was possible by NLDS techniques. The spectrum peaks when the conditions for ion cyclotron resonance (ICR) of glutamate are matched. Furthermore, the NLDS spectra are different under ICR- and non-ICR conditions: NLDS measurements with rising control voltages from 100–1100 mV show different courses of the intensities of the low order harmonics, which could possibly indicate "intensity windows". Furthermore, the observed magnetic field effects are pH dependent with a narrow optimum around pH 2.85. Conclusions Data will be discussed in the context with recent published models for the interaction of weak EMF with biological matter including ICR. A medical and health relevant aspect of such sensitive effects might be given insofar, because electromagnetic conditions for it occur at many occasions in our electromagnetic all day environment, concerning ion involvement of different biochemical pathways. PMID:15571630

  11. 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

    2013-08-01

    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. PMID:23870406

  12. Alternate policies for alternate energy sources

    Microsoft Academic Search

    Hall

    1985-01-01

    Some ''alternates within alternates'' are studied and possible improvement of our energy policies are explored. The viability of a hydrogen fuel economy is reviewed. Methanol, ethanol or ammonia versus hydrogen is one area of interest. Others include liquid hydrogen versus jet fuels, the use of geothermal, solar, wind or water energy for production of hydrogen gas versus development of deep

  13. Alternative Fuels Research Laboratory

    NASA Technical Reports Server (NTRS)

    Surgenor, Angela D.; Klettlinger, Jennifer L.; Nakley, Leah M.; Yen, Chia H.

    2012-01-01

    NASA Glenn has invested over $1.5 million in engineering, and infrastructure upgrades to renovate an existing test facility at the NASA Glenn Research Center (GRC), which is now being used as an Alternative Fuels Laboratory. Facility systems have demonstrated reliability and consistency for continuous and safe operations in Fischer-Tropsch (F-T) synthesis and thermal stability testing. This effort is supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing project. The purpose of this test facility is to conduct bench scale F-T catalyst screening experiments. These experiments require the use of a synthesis gas feedstock, which will enable the investigation of F-T reaction kinetics, product yields and hydrocarbon distributions. Currently the facility has the capability of performing three simultaneous reactor screening tests, along with a fourth fixed-bed reactor for catalyst activation studies. Product gas composition and performance data can be continuously obtained with an automated gas sampling system, which directly connects the reactors to a micro-gas chromatograph (micro GC). Liquid and molten product samples are collected intermittently and are analyzed by injecting as a diluted sample into designated gas chromatograph units. The test facility also has the capability of performing thermal stability experiments of alternative aviation fuels with the use of a Hot Liquid Process Simulator (HLPS) (Ref. 1) in accordance to ASTM D 3241 "Thermal Oxidation Stability of Aviation Fuels" (JFTOT method) (Ref. 2). An Ellipsometer will be used to study fuel fouling thicknesses on heated tubes from the HLPS experiments. A detailed overview of the test facility systems and capabilities are described in this paper.

  14. Analysis of the alternating current conductivity and magnetic behaviors for the polycrystalline Y-type Ba0.5Sr1.5Co2(Fe1-xAlx)12O22 hexaferrites

    NASA Astrophysics Data System (ADS)

    Wu, M. X.; Zhong, W. J.; Gao, X. S.; Liu, L. J.; Liu, Z. W.

    2014-12-01

    Co2Y hexaferrites have attracted intensive interests due to its potential high temperature magnetoelectricity as the single phase multiferroics. Numerous efforts have been paid to enhance their magnetoelectric properties at high temperatures through increasing the magnetic transition temperature and decreasing the conductivity. In this work, we investigated the conductivity and magnetic properties of the polycrystalline Ba0.5Sr1.5Co2(Fe1-xAlx)12O22 (0 ? x ? 0.12) hexaferrites and found that Al-doping has important effects on both the conductivity and magnetic properties. The underlying physical mechanisms were also systematically analyzed. Most importantly, a very much enhanced resistivity (over 10 M? cm), and a high magnetic transition temperature (˜346 K) have been obtained at a doping amount of x = 0.04. These improvements are very promising for achieving significant magnetoelectric effect at room temperature. The current research can provide the basic understanding of the Y-type ferrites for future applications in magnetoelectric and other fields.

  15. State Energy Alternatives: Alternative Energy Resources by State

    DOE Data Explorer

    This U.S. map provides state by state information on incentives and laws related to alternative fuels and advanced vehicles. Discover what's available in each state for innovation grants, infrastructure grants, and production grants and who to contact. Find out how many alternative refueling stations are available in each state and where they are. Tennessee, for example, in 2009, has 114 alternative refueling stations: 36 biodiesel, 1 electrical, 29 ethanol, 4 natural gas, and 44 propane. There are also 5 Truck Stop Electrification (TSE) sites in Tennessee. Users can also find out from this map interface the contacts for Clean Cities in a state, information about renewable energy projects and activities in each state, fuel prices across a state, and biomass potential resources and current production in each state.

  16. Current Controlled Current Source (CCCS)

    NSDL National Science Digital Library

    Svoboda, James A.

    This interactive website from professor James A. Svoboda of Clarkson University describes current controlled current source (CCCS). The interactive applet depicts a circuit that contains a Current Controlled Current Source (CCCS). The gain of the CCCS can be changed using the scroll bar.

  17. Field Initiation Design Fundamentals for Pulsed Alternators

    Microsoft Academic Search

    Jon R. Kitzmiller; Mircea D. Driga

    2007-01-01

    Efficient high-performance pulsed alternator (PA) systems have low-impedance field windings that rely on very fast current rise times in order to maintain attractive system efficiencies. These systems rely on positive feedback self-excitation, or \\

  18. Improving Reproducibility of Lab-on-a-Chip Sensor with Bismuth Working Electrode for Determining Zn in Serum by Anodic Stripping Voltammetry.

    PubMed

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

    2014-02-01

    This work reports on the continuing development of a lab-on-a-chip electrochemical sensor for determination of zinc in blood serum using square wave anodic stripping voltammetry. The microscale sensor consists of a three electrode system, including an environmentally friendly bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor demonstrates a linear response in 0.1 M acetate buffer at pH 6 for zinc concentrations in the 1-30 ?M range. By optimizing bismuth film deposition and better control of the fabrication process, repeatability of the sensor was improved, reducing variability from 42% to <2%. Through optimization of electrolyte and stripping voltammetry parameters, limit of detection was greatly improved to 60 nM. The optimized sensor was also able to measure zinc in the extracted blood serum. Ultimately, with integrated sample preparation, the sensor will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for clinical applications. PMID:24729629

  19. Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step.

    PubMed

    Laffont, Laure; Hezard, Teddy; Gros, Pierre; Heimbürger, Lars-Eric; Sonke, Jeroen E; Behra, Philippe; Evrard, David

    2015-08-15

    Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs-GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs-GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10(-2)M range. Finally, the AuNPs-GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM). PMID:25966376

  20. Determination of Cu, Pb, Cd, and Zn in river sediment extracts by sequential injection anodic stripping voltammetry with thin mercury film electrode.

    PubMed

    da Silva, C L; Masini, J C

    2000-06-01

    Determination of Cu, Pb, Cd and Zn was performed in sediment extracts obtained according to the three steps sequential extraction procedure proposed by the European Community Standards, Measurements and Testing Program. The metal content was determined by anodic stripping voltammetry with a thin mercury film electrode controlled by a sequential injection (SIA) system. The proposed method improved the reproducibility of conventional anodic stripping voltammetry, as well as the sample throughput, allowing analysis of 30 to 45 samples per hour. The influence of flow rate and sample volume was studied to achieve an adequate sensitivity for the leachate studied. No interferences due to adsorption of organic matter, colloids, or complexes with slow rate of dissociation were observed. The intermetallic formation of Cu-Zn was avoided by forming the mercury film in presence of Ga(III) ions in the SIA system, resulting in low consumption of reagent in comparison to flow injection or continuous flow systems. Results were in good agreement with those obtained by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES). PMID:11227460

  1. Simultaneous determination of mycophenolate mofetil and its active metabolite, mycophenolic acid, by differential pulse voltammetry using multi-walled carbon nanotubes modified glassy carbon electrode.

    PubMed

    Madrakian, Tayyebeh; Soleimani, Mohammad; Afkhami, Abbas

    2014-09-01

    A highly sensitive electrochemical sensor for the simultaneous determination of mycophenolate mofetil (MPM) and mycophenolic acid (MPA) was fabricated by multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE). The electrochemical behavior of these two drugs was studied at the modified electrode using cyclic voltammetry and adsorptive differential pulse voltammetry. MPM and MPA were oxidized at the GCE during an irreversible process. DPV analysis showed two oxidation peaks at 0.87V and 1.1V vs. Ag/AgCl for MPM and an oxidation peak at 0.87V vs. Ag/AgCl for MPA in phosphate buffer solution of pH5.0. The MWCNTs/GCE displayed excellent electrochemical activities toward oxidation of MPM and MPA relative to the bare GCE. The experimental design algorithm was used for optimization of DPV parameters. The electrode represents linear responses in the range 5.0×10(-6) to 1.6×10(-4)molL(-1) and 2.5×10(-6)molL(-1) to 6.0×10(-5)molL(-1) for MPM and MPA, respectively. The detection limit was found to be 9.0×10(-7)molL(-1) and 4.0×10(-7)molL(-1) for MPM and MPA, respectively. The modified electrode showed a good sensitivity and stability. It was successfully applied to the simultaneous determination of MPM and MPA in plasma and urine samples. PMID:25063089

  2. Improving Reproducibility of Lab-on-a-Chip Sensor with Bismuth Working Electrode for Determining Zn in Serum by Anodic Stripping Voltammetry

    PubMed Central

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

    2014-01-01

    This work reports on the continuing development of a lab-on-a-chip electrochemical sensor for determination of zinc in blood serum using square wave anodic stripping voltammetry. The microscale sensor consists of a three electrode system, including an environmentally friendly bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor demonstrates a linear response in 0.1 M acetate buffer at pH 6 for zinc concentrations in the 1–30 ?M range. By optimizing bismuth film deposition and better control of the fabrication process, repeatability of the sensor was improved, reducing variability from 42% to <2%. Through optimization of electrolyte and stripping voltammetry parameters, limit of detection was greatly improved to 60 nM. The optimized sensor was also able to measure zinc in the extracted blood serum. Ultimately, with integrated sample preparation, the sensor will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for clinical applications. PMID:24729629

  3. Determination of Silver(I) by Differential Pulse Voltammetry Using a Glassy Carbon Electrode Modified with Synthesized N-(2-Aminoethyl)-4,4?-Bipyridine

    PubMed Central

    Radulescu, Maria-Cristina; Chira, Ana; Radulescu, Medeea; Bucur, Bogdan; Bucur, Madalina Petruta; Radu, Gabriel Lucian

    2010-01-01

    A new modified glassy carbon electrode (GCE) based on a synthesized N-(2-aminoethyl)-4,4?-bipyridine (ABP) was developed for the determination of Ag(I) by differential pulse voltammetry (DPV). ABP was covalently immobilized on GC electrodes surface using 4-nitrobenzendiazonium (4-NBD) and glutaraldehyde (GA). The Ag(I) ions were preconcentrated by chemical interaction with bipyridine under a negative potential (?0.6 V); then the reduced ions were oxidized by differential pulse voltammetry and a peak was observed at 0.34 V. The calibration curve was linear in the concentration range from 0.05 ?M to 1 ?M Ag(I) with a detection limit of 0.025 ?M and RSD = 3.6%, for 0.4 ?M Ag(I). The presence of several common ions in more than 125-fold excess had no effect on the determination of Ag(I). The developed sensor was applied to the determination of Ag(I) in water samples using a standard addition method. PMID:22163530

  4. A new quenching alternative

    SciTech Connect

    Brennan, R.J.; Faulkner, C.H. [Houghton International, Valley Forge, PA (United States)

    1996-12-31

    The quenching of ferrous alloys implies the controlled extraction of heat from a part at a rate sufficient to harden the part and still control the desired dimensional limitations. Quenchants in common use today are: molten metals, molten salts, petroleum oils, polymer solutions, water, and salt/water solutions. Each type of quenchant has its benefits and limitations. With current waste legislation and the trends toward environmentally friendlier industrial working fluids, many of these quenching products are coming under close scrutiny by the users and legislators. The most widely used quenchant is petroleum oil due to its favorable heat extraction characteristics. The dependence upon imports, price vulnerability, and contamination potential have caused suppliers and users to look into alternative products. Research into renewable resource, non-petroleum, vegetable oils has been going on globally for several years. The drawbacks encountered with many vegetable oils were widely known and only years of research enabled them to be overcome. The presently formulated product not only performs as well as petroleum oil but shows some characteristics better than those of the petroleum products, especially in the biodegradability and ecological aspects of the products. Stability and reproducible quenching properties have been proven with over two and one half years of field testing.

  5. FHA restructuring proposals: Alternatives and implications

    Microsoft Academic Search

    Kerry D. Vandell

    1995-01-01

    This article evaluates problems of the Federal Housing Administration (FHA) under its current structure, develops criteria for judging alternative structures, and suggests one alternative—an assigned risk pool—that encourages efficiency in the insurance function while still promoting low? and moderate?income housing. A historical introduction explains how the current institutional relationships came about and created FHA's problems.FHA's decline resulted from the mixing

  6. Density Currents

    NSDL National Science Digital Library

    David Kopaska-Merkel

    In this activity, students will make a turbidity current. They will discover how fluids of differing densities interact with one another, learn some ways the densities of fluids can be changed and observe how density currents transport and deposit tremendous amounts of sediment in lakes and in the ocean. Additional options allow students to create and observe different kinds of density currents.

  7. Centre for Alternative Technology

    NSDL National Science Digital Library

    CAT is an environmental nonprofit that promotes sustainable living. Its key areas of work are renewable energy, environmental building, energy efficiency, organic growing and alternative sewage systems. The group offers workshops on alternative energy, including wind, solar, and microhydroelectric.

  8. Differentiably simple alternative algebras

    Microsoft Academic Search

    A. A. Popov

    2010-01-01

    Differentiably simple alternative nonassociative algebras of characteristic p > 0 are described in terms of differentiably simple associative commutative algebras. Also we look at some properties of\\u000a differentiably simple alternative nonassociative algebras of characteristic 0.

  9. Center for Alternative Fuels

    NSDL National Science Digital Library

    The success of the HEV programs under this grant prompted Macomb to launch this resource, the Center for Alternative Fuels. The center holds forums in which academic and industry experts discuss the technical and societal impact of alternative fuels.

  10. Alternative medicine - pain relief

    MedlinePLUS

    Alternative medicine refers to treatments that are used instead of conventional (standard) ones. If you use an alternative ... considered complementary therapy. There are many forms of ... Acupuncture involves stimulating certain acupoints on the body ...

  11. Assessment "Honest Alternatives".

    ERIC Educational Resources Information Center

    Mandel, Susan Glazer

    1995-01-01

    Addresses the challenge of finding or creating alternatives to tests and traditional grading systems. Reflects on and describes the experience of creating an assessment tool and cautions against choosing alternatives that merely camouflage the grades. Encourages educators to find authentic alternatives to describe children's growth. (BAC)

  12. ALTERNATIVE DEER MANAGEMENT PLAN

    E-print Network

    Theimer, Tad

    ALTERNATIVE DEER MANAGEMENT PLAN FOR GAME MANAGEMENT UNITS 12A, 12B, 13A, 13B, 16A, 45A, 45B, 45C, and White-tailed Deer Units Arizona Game and Fish Department April 4, 2006 #12;Alternative Deer Management on subsequent Commission direction, and this document addresses alternative deer management in Units 12A, 12B

  13. IDCS NETWORK ALTERNATIVES ANALYSIS

    SciTech Connect

    R.T. Rosche

    1995-02-03

    The purpose of this design analysis is to determine the feasibility of network alternatives available to support the Exploratory Study Facilities (ESF) site characterization test data gathering activity as well as the facility control and monitoring systems. If it is found that more than one feasible alternative exists, a cost analysis will also be conducted to determine the least costly alternative.

  14. Chicano Alternative Education.

    ERIC Educational Resources Information Center

    Galicia, H. Homero; Almaguer, Clementina

    Alternative schooling is challenging some basic notions of curriculum, operation, and structure of traditional schools; it is not challenging the basic concept of schooling. Chicano alternative education, an elusive concept, lacks a precise definition. Chicano alternative schools reflect a vast diversity in structure, focus, and goals. The Chicano…

  15. Characterisation of weak magnetic field effects in an aqueous glutamic acid solution by nonlinear dielectric spectroscopy and voltammetry

    Microsoft Academic Search

    Alexander Pazur

    2004-01-01

    BACKGROUND: Previous reports indicate altered metabolism and enzyme kinetics for various organisms, as well as changes of neuronal functions and behaviour of higher animals, when they were exposed to specific combinations of weak static and alternating low frequency electromagnetic fields. Field strengths and frequencies, as well as properties of involved ions were related by a linear equation, known as the

  16. Alternative Fuels Data Center

    NSDL National Science Digital Library

    The National Renewable Energy Laboratory operates the Alternative Fuels Data Center, a Web site with vast amounts of information on alternative fuels and the vehicles that use them. A general table of fuel properties gives a quick comparison of gasoline to several alternatives, while sections devoted to eight different fuels go into much greater depth. There are several documents that examine new alternative fuel vehicles, including performance tests, fact sheets, statistics, and case studies. The site also has common questions and answers about converting a gasoline vehicle to one that uses alternative fuels.

  17. Depleted uranium management alternatives

    SciTech Connect

    Hertzler, T.J.; Nishimoto, D.D.

    1994-08-01

    This report evaluates two management alternatives for Department of Energy depleted uranium: continued storage as uranium hexafluoride, and conversion to uranium metal and fabrication to shielding for spent nuclear fuel containers. The results will be used to compare the costs with other alternatives, such as disposal. Cost estimates for the continued storage alternative are based on a life-cycle of 27 years through the year 2020. Cost estimates for the recycle alternative are based on existing conversion process costs and Capital costs for fabricating the containers. Additionally, the recycle alternative accounts for costs associated with intermediate product resale and secondary waste disposal for materials generated during the conversion process.

  18. Alternative Certification Isn't Alternative

    ERIC Educational Resources Information Center

    Walsh, Kate; Jacobs, Sandi

    2007-01-01

    While nearly all states now have something on their books labeled "alternate route to certification," these programs defy standard definition due to their enormous variability. States differ in the types of candidates allowed to apply (e.g., career changers or recent college graduates) and in the academic backgrounds these individuals must…

  19. Wind electric plant with improved alternator field excitation

    Microsoft Academic Search

    M. L. Jacobs; P. R. Jacobs

    1977-01-01

    In a wind electric plant of the type including a wind-driven propeller or the like and an alternating current alternator connected to be driven thereby to generate electrical energy for charging storage batteries or other desired use, electrical circuitry connected with the alternator and a storage battery is described which includes controls responsive to alternator speed and battery voltage to

  20. 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...

  1. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance studies of buckminsterfullerene (C{sub 60}) film electrodeposition and tetra-n-butylammonium electrodoping in acetonitrile

    SciTech Connect

    Wonyong Koh; Dubois, D.; Kutner, W.; Jones, M.T.; Kadish, K.M. [Univ. of Houston, TX (United States)

    1992-05-28

    A simple and efficient method is presented for preparation of insoluble thin films of C{sub 60} and the (TBA{sup +})(C{sub 60}{sup {minus}}) and (TBA{sup +}){sub 2}(C{sub 60}{sup 2{minus}}) salts where TBA{sup +} represents the tetra-n-butylammonium cation. The method consists of bulk electroreducing a fine suspension of solid C{sub 60} in acetonitrile solutions under a controlled potential which is sufficiently negative to generate the soluble C{sub 60}{sup 3{minus}} anion, followed by electrooxidative deposition of a neutral C{sub 60} film on the surface of a gold/quartz crystal working electrode. The properties of the electrodeposited films were examined by simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance experiments which enabled determination of the stoichiometry and mass of the film. 11 refs., 21 figs.

  2. Corrosion Cyclic Voltammetry of Two Types of Heat-Affected Zones (HAZs) of API-X100 Steel in Bicarbonate Solutions

    NASA Astrophysics Data System (ADS)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2014-12-01

    This paper examined the electrochemical corrosion behavior and corrosion products of two types of heat-affected HAZs made from API-X100 steel. Cyclic voltammetry, with different scan rates and potential ranges at 10 cycles, was applied to analyze the interdependent corrosion reactions of cathodic reduction, anodic dissolution, passivation, and transpassivation. The HAZ cooled at 60 K/s, from a peak temperature of 1470 K (1197 °C) that was held for 15 seconds, exhibited better passivation and lower cathodic activity than the HAZ cooled at 10 K/s. Increasing bicarbonate concentration, from 0.05 and 0.2 to 0.6 M, increases the anodic activity and cathodic reduction, but accordingly protects the active surfaces and enhances passivation.

  3. Stripping Voltammetry of Cu Overlayers Deposited on Self-Assembled Monolayers: Field Emission of Electrons through A Phenylene Ethynylene Oligomer

    E-print Network

    Myrick, Michael Lenn

    in macroscopic systems is either due to high densities of charge carriers, as in copper, or high charge carrier islands were oxidized via electron transport through the TTEB SAM. A barrier height of 1.17 eV to charge injection was calculated from the tunneling current and overpotential by a Fowler-Nordheim-type analysis

  4. Elemental composition of surface copper sulfide in alternating current electroluminophors

    SciTech Connect

    Kovalev, B.A.; Chapaikin, S.P.; Valyukhov, D.S.

    1986-09-01

    The authors studied the elemental composition of surface copper sulfide as a function of the copper concentration in luminophors, obtained the profiles of the distribution of the elements over the depth of the Cu /SUB 2-x/ S layer, and determined the thickness of this layer. The samples were studied by the x-ray method of photoelectronic spectroscopy (XPES). Layerwise analysis of the copper sulfide showed that the XPE spectra change. The composition of the copper sulfide depends on the copper content in the luminophor and on the distance from the surface layer.

  5. Ferrofluid clustering driven by dilution: An alternating current susceptibility investigation

    NASA Astrophysics Data System (ADS)

    Zhong, Jing; Liu, Wenzhong; Li, Yin; Wu, Mian; Morais, Paulo Cesar

    2012-03-01

    The influence of sample dilution upon cluster disruption/formation within a ferrofluid sample is investigated by monitoring the temperature dependence of the initial AC susceptibility. The effective magnetic response of the ferrofluid sample is described by a combination of Langevin's functions modulated by the relative content of monomers and clusters. Deviations from the linearity found in the inverse susceptibility versus temperature (?-1-T) data were successfully described via the disruption of clusters into monomers within the approach of a second order phase transition at the critical temperature T*. We found T* increasing monotonically from 386 K to 412 K as the stock ferrofluid sample is diluted up to a factor of 5. In the same dilution range, we found the normalized relative content of clusters increasing from about 38% up to 42%, whereas the average effective magnetic moment of the clusters increased by a factor of 1.7.

  6. Analysis of the alternating current properties of ionic conductors

    Microsoft Academic Search

    A. K. Jonscher

    1978-01-01

    A method of analysis of inclined semicircular complex impedance (Z) diagrams for ionic conductors has been developed on the basis of the concept of “non-Debye” behaviour of solid dielectrics. This approach replaces the rather arbitrary distribution of relaxation times by the physically much simpler concept of a frequency-independent ratio of energy lost per cycle to energy stored. This criterion of

  7. High-speed ground transportation: some current and future alternatives

    SciTech Connect

    Morita, T.

    1984-01-01

    High-speed ground transportation (HSGT), the value of time, and the social and technological considerations of inter-city transportation are discussed in this article. A particularly promising mode of high-speed ground transportation (MAGLEV) is discussed in some detail. An average speed for HSGT service, 400 kilometers per hour, seems to be attainable. In conclusion, the proposal for a hypersonic subway will be analyzed. 2 figures, 1 table.

  8. EMERGING TECHNOLOGY SUMMARY: ELECTRO-PURE ALTERNATING CURRENT ELECTROCOAGULATION

    EPA Science Inventory

    The Superfund Innovative Technology Evaluation (SITE) Program was authorized as part of the 1986 amendments to the Superfund legislation. It represents a joint effort between the U.S. Environmental Protection Agency?s (EPA) Office of Research and Development and Office of Solid W...

  9. Contactless measurement of alternating current conductance in quantum Hall structures

    SciTech Connect

    Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Ilyinskaya, N. D.; Usikova, A. A. [A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Galperin, Y. M. [Department of Physics, University of Oslo, P.O. Box 1048 Blindern, 0316 Oslo (Norway); A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Kummer, M.; Känel, H. von [Laboratorium für Festkörperphysik ETH Zürich, CH-8093 Zürich (Switzerland)

    2014-10-21

    We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods—acoustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

  10. The magnetic amplifier with alternating-current control 

    E-print Network

    Andrew, Edward Harris

    1954-01-01

    - _ 4 - _ I 1 rl+! 4 - \\ M ? J ___sL T\\T ____ S . ?en = i nRn + Ln? - + - / i ndt + > N ,? ? ; ( n ) n n 11 ndt Cn / n g ,j = 1 nJ Si S jdt and for all f > F , iidin M n u ,A . dir _ J- i t -L \\ TVT __0__*Le. = i .R . + Ln? =? + - i...,dt + > N ? ,? a ,(12) 1 1 1 xdt C-lF 1 g ,j = 1 s. SJdt * dik 1 R U 1A 1 di = ivRv + L, ? + ? l ivdt + > T WF-WU- m ? a ,(13 ) k k k kdt c / k ^ 1 1 kj s g jdt O dij. i R n u'.'a. di en = 1nRn + Ln ^ + b yWCdw + ? ( 14)n n n -^dt CMF ar j " = ^ l...

  11. Alternating current techniques for corrosion monitoring in water reactor systems

    Microsoft Academic Search

    H. S. Isaacs

    1977-01-01

    Corrosion in both nuclear and fossil fueled steam generators is generally a consequence of the presence of aggressive impurities introduced into the coolant system through condenser leakage. The impurities concentrate in regions of the steam generator protected from coolant flow, in crevices or under deposited corrosion products and adjacent to heat transfer surfaces. These three factors, the aggressive impurity, crevice

  12. Alternating current (AC) impedance testing of coated traycans

    NASA Astrophysics Data System (ADS)

    Lawson, Kurt; Beavers, John

    1993-01-01

    The overall objective of the program was to evaluate the relative resistance of several candidate coatings prior to retorting to a solution containing NaCl and citric acid (simulating saline, acidic food product) at ambient temperature. An additional objective of the program was to perform an initial assessment of the applicability of the AC impedance technique as a quality assurance technique for traycan coatings. The performance of the coatings was evaluated by means of an Electrochemical Impedance Spectroscopy (EIS) technique, also referred to as AC impedance. The EIS technique was found to be a sensitive technique for measuring coating degradation on the traycans. Of the coatings analyzed, the VMC coating, in general was found to be the best performer, followed closely by DMS and VMS. The control coating was found to be the poorest coating, of the coatings analyzed.

  13. Alternating current electrokinetic properties of gold-coated microspheres.

    PubMed

    García-Sánchez, Pablo; Ren, Yukun; Arcenegui, Juan J; Morgan, Hywel; Ramos, Antonio

    2012-10-01

    We present dielectrophoresis (DEP) and electrorotation (ROT) measurements of gold-coated polystyrene microspheres as a function of frequency and for several electrolyte conductivities. Particle rotation was counterfield with a maximum rotation rate observed at a single characteristic frequency. Negative DEP was observed for frequencies lower than this characteristic frequency and positive DEP for signal frequencies higher than this. These experimental observations are in agreement with predictions for the force and torque on the induced dipole of a perfectly polarizable metal sphere. We present a theoretical model for this case, and good agreement is found for both ROT and DEP measurements if we take into account the viscous friction for a spherical particle near a wall. From the characteristic frequency for rotation, we obtain the capacitance of the electrical double layer at the electrolyte-particle interface. Remarkably, no effect of induced charge electroosmosis around the particles can be inferred from DEP measurements. PMID:22931290

  14. High frequency alternating current chip nano calorimeter with laser heating

    SciTech Connect

    Shoifet, E.; Schick, C. [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany) [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany); Department “Life, Light and Matter”, Faculty of Interdisciplinary Research, University of Rostock, 18051 Rostock (Germany); Chua, Y. Z.; Huth, H. [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany)] [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany)

    2013-07-15

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3?-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (?1 ?m) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 ?m thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 ?m{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup ?3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  15. CURRENTLY AVAILABLE TECHNOLOGIES DEMONSTRATION FOR ALTERNATIVES TO RADIOLOGICAL SOURCES

    EPA Science Inventory

    EPA's Office of Radiation and Indoor Air awarded a contract to demonstrate that non-nuclear measurement using optical and magnetic technology can replace radioactive devices used to measure the thickness and density of various paper, film, and plastic sheets....

  16. The magnetic amplifier with alternating-current control

    E-print Network

    Andrew, Edward Harris

    1954-01-01

    I ) . (49) (48) - ^ a Xm2 - ^ b Xm2 * (50) (51) 52 Es = Rl^ b + Xb> + V^rnl + iTaXl + Jxixl " JIoxm2 + + J ? 2 ? (52) 0 ? (Ib - V R1 + - U - JI=Xml - J Ia*l - JIbXl - JI oXm2 + ^ a X2 + JIbX2 ? (53) ^s = ^a + *b : (54) and (55) I L...

  17. Current Cites

    NSDL National Science Digital Library

    With the ever-growing interest in information technology and digital initiatives and projects, the Current Cites website will be of great interest to persons working in these various fields. Edited by Roy Tennant (a librarian working at the California Digital Library in Oakland), Current Cites is a monthly publication that contains 10-15 annotated citations of the best literature currently available in the field of information technology. Of course, visitors to the site may elect to sign up to receive Current Cites every month, or they may peruse the contents of the publication back to its founding in August 1990. Equally helpful is the Bibliography On-Demand feature that allows users to construct their own bibliography culled from the Current Cites database of bibliographic citations. Additionally, the items that are freely available on the Internet are also retrieved and indexed so that users may perform an article search of the full-text of these various items.

  18. Piston engine configuration alternatives

    SciTech Connect

    Wyczalek, F.A.

    1989-01-01

    This paper provides a technological assessment of alternate engine component configuration and material alternatives. It includes a comparative analysis of key characteristics of Gasoline, Diesel and Gas Turbine engines built by Daihatsu, Honda, Isuzu, Mazda, Mitsubishi, Nissan, Suburu, Suzuki and Toyota. The piston engines range from two to ten cylinders with inline, vee and opposed configurations. Furthermore, additional special features and alternative choices include variable compression ratio, ceramic structural components, supercharger, turbocharger, twin turbocharger, supercharger-turbocharger combined and the regenerative gas turbine.

  19. Alternator insulation evaluation tests

    NASA Technical Reports Server (NTRS)

    Penn, W. B.; Schaefer, R. F.; Balke, R. L.

    1972-01-01

    Tests were conducted to predict the remaining electrical insulation life of a 60 KW homopolar inductor alternator following completion of NASA turbo-alternator endurance tests for SNAP-8 space electrical power systems application. The insulation quality was established for two alternators following completion of these tests. A step-temperature aging test procedure was developed for insulation life prediction and applied to one of the two alternators. Armature winding insulation life of over 80,000 hours for an average winding temperature of 248 degrees C was predicted using the developed procedure.

  20. Rapid determination of bisacodyl in flow injection system combination by a novel sensitive adsorptive square-wave voltammetry

    Microsoft Academic Search

    Parandis Daneshgar; Parviz Norouzi; Mohammad Reza Ganjali

    2009-01-01

    A continuous square-wave voltammetric study of bisacodyl at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorpted at ?300mV, giving rise to change in the current of well-defined oxidation peak of gold. Signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response

  1. Determination of trace amounts of copper(II) by adsorptive stripping voltammetry of its complex with pyrogallol red

    Microsoft Academic Search

    A Safavi; E Shams

    1999-01-01

    A sensitive and selective procedure is presented for the voltammetric determination of copper. The procedure involves an adsorptive accumulation of copper pyrogallol red on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at ?0.2V (vs. Ag\\/AgCl). The optimum conditions for the analysis of copper include pH (3.0–4.5), 20?M pyrogallol red and

  2. Alternative Work Programs

    ERIC Educational Resources Information Center

    Kuehn, Kerri L.

    2004-01-01

    Employers are feeling the strain of needing to offer alternative work arrangements to retain and recruit employees. Due to a change in demographics, dual-career couples and increased technology; people are demanding a transformation in the workplace environment. Two alternatives, which are being offered by employers, are flextime and…

  3. Alternatives as Education

    ERIC Educational Resources Information Center

    Bremer, John

    1973-01-01

    Focuses on the wider meaning of the growth of alternative schooling in our society. Suggests that the survival of society depends on the widespread existence of decisionmaking powers, that such power is learned by making decisions, and that alternatives are needed in order that decisions may be made. (Author/DN)

  4. Concepts in alternative medicine

    Microsoft Academic Search

    C. W. Aakster

    1986-01-01

    After discussing some important alternative approaches, different interpretations are presented of the concepts of health, disease, diagnosis, therapy and patient. These differences are elucidated in three main frames of medical thinking: the pharmaceutical, the integrational and the holistic model. Attention is given to the problem of scientific proof, especially in relation to the effectiveness of alternative therapies. In a concluding

  5. Alternative Fuel Vehicle Data

    EIA Publications

    2013-01-01

    Annual data released on the number of on-road alternative fuel vehicles and hybrid vehicles made available by both the original equipment manufacturers and aftermarket vehicle conversion facilities. Data on the use of alternative fueled vehicles and the amount of fuel they consume is also available.

  6. Alternative Automobile Engines

    ERIC Educational Resources Information Center

    Wilson, David Gordon

    1978-01-01

    Requirements for cleaner and more efficient engines have stimulated a search for alternatives to the conventional spark-ignition engine. So far, the defects of the alternative engines are clearer than the virtues. The following engines are compared: spark ignition, diesel, vapor-cycle, Stirling, and gas turbine. (Author/MA)

  7. Compensation in pulsed alternators

    Microsoft Academic Search

    S. B. Pratap; M. D. Driga

    1999-01-01

    This paper presents a generic discussion on compensation in pulsed alternators. It covers all aspects of compensation i.e., types of compensation, alternative methods for the physical realization of the various compensation schemes, the pros and cons of compensation or the rationale for compensation. The intent of this paper is to form a guiding reference on the issues of compensation in

  8. ALTERNATIVE DEER FENCES

    E-print Network

    ALTERNATIVE DEER FENCES IN CORE CAPERCAILLIE and BLACK GROUSE HABITATS AN INTERIM BEST GUIDANCE This advice note provides interim guidance on deer fencing in order to reduce mortality to capercaillie in core woodland grouse habitats. As an alternative strategy, various materials have been fixed onto deer

  9. ALTERNATIVES TO RESEARCH PAPERS

    E-print Network

    Alpay, S. Pamir

    , 2010 Creative alternatives to traditional research papers: Undergrads and Scholarly CommunicationALTERNATIVES TO RESEARCH PAPERS Compiled by Kathy Labadorf kathy.labadorf@uconn.edu December 30 The ability to write a finely crafted, well documented, and thought provoking research paper is a hallmark

  10. Rip Currents

    NSDL National Science Digital Library

    Earth Science Picture of the Day

    This Earth Science Photo of the Day shows how rip currents form along shorelines. The annotated photo describes how waves, sand bars, and gravity interact to form this dangerous feature. Clicking on the image affords a larger view.

  11. Optical currents

    NASA Astrophysics Data System (ADS)

    Berry, M. V.

    2009-09-01

    For scalar light, the current is the familiar expectation value of the intensity-weighted momentum operator. Current is distinct from the local wavevector (not weighted) that could be observed by means of quantum weak measurement. For vector light, the current (Poynting vector) contains an additional term corresponding to the photon spin, recently identified for paraxial light by Bekshaev and Soskin but valid generally after a modification to restore 'electric-magnetic democracy'; this term has physical consequences. A number of examples demonstrate that there is usually no connection between optical vortices and angular momentum, and between C singularities and angular momentum. The optical wave current is distinct from the rays of geometrical optics in all nontrivial cases.

  12. Alternative substrates to glass mirrors

    NASA Astrophysics Data System (ADS)

    Ruch, Eric

    1993-10-01

    Traditionally glass represents the common choice for mirror substrates and the current development of new techniques such as glass ceramics, lightweighted blanks or honeycomb structures even increase the fields of application of glass mirrors. However, the research on alternative substrates for mirrors covers a large variety of materials: metals, silicon, silicon carbide, metal matrix, etc... This presentation concentrates on the machining, polishing and testing of aluminum mirrors to demonstrate that the optical performance of these substrates can be compared to the more classical glass mirrors.

  13. Alternative fuel transit buses

    SciTech Connect

    Motta, R.; Norton, P.; Kelly, K. [and others

    1996-10-01

    The National Renewable Energy Laboratory (NREL) is a U.S. Department of Energy (DOE) national laboratory; this project was funded by DOE. One of NREL`s missions is to objectively evaluate the performance, emissions, and operating costs of alternative fuel vehicles so fleet managers can make informed decisions when purchasing them. Alternative fuels have made greater inroads into the transit bus market than into any other. Each year, the American Public Transit Association (APTA) surveys its members on their inventory and buying plans. The latest APTA data show that about 4% of the 50,000 transit buses in its survey run on an alternative fuel. Furthermore, 1 in 5 of the new transit buses that members have on order are alternative fuel buses. This program was designed to comprehensively and objectively evaluate the alternative fuels in use in the industry.

  14. A highly sensitive method for simultaneous determination of ultra trace levels of copper and cadmium in food and water samples with luminol as a chelating agent by adsorptive stripping voltammetry

    Microsoft Academic Search

    Shahryar Abbasi; Atousa Bahiraei; Freshteh Abbasai

    2011-01-01

    In the present study a selective method is presented for the simultaneous determination of copper and cadmium in food samples by adsorptive stripping voltammetry. In preliminary studies, it has been proven that the copper and cadmium react with 3-aminophthalhydrazide (luminol), giving rise to the formation of these complexes. These complexes have adsorptive characteristics on hanging mercury drop electrode (HMDE) and

  15. Alternate policies for alternate energy sources

    SciTech Connect

    Hall, F.F.

    1985-09-01

    Some ''alternates within alternates'' are studied and possible improvement of our energy policies are explored. The viability of a hydrogen fuel economy is reviewed. Methanol, ethanol or ammonia versus hydrogen is one area of interest. Others include liquid hydrogen versus jet fuels, the use of geothermal, solar, wind or water energy for production of hydrogen gas versus development of deep earth supplies of natural gas is another. Energy enhancement as opposed to energy conservation is investigated with regard to polar climate and what might be done to improve natural energy balances, particularly in the northern hemisphere. Pumping Arctic Ocean water out into the Pacific Ocean via the Bering Strait would be an energy debit as opposed to energy gains such as biomass conversion of future plant growth throughout the Siberian and Canadian tundra regions and presently very arid desert regions, improved access to northern region fuel, metal ore and mineral resources, year-round shipping and fishing fleet operations in the Arctic Ocean and development of the tremendous Greenland hydro-electric power potential.

  16. Alternatives and developing countries.

    PubMed

    Milstien, J B; Dellepiane, N

    1999-01-01

    Alternative tests have a role in vaccine testing, especially to confirm production consistency. Given the characteristics of these alternative tests and of the products for which they may be used, there are several factors which will influence their use. These include a good understanding of the test and the product to be tested, strong national regulatory infrastructure, a laboratory run in accordance with the principles of laboratory quality systems, and the ability to validate the alternative method. This means that national regulatory authorities will need strong expertise in epidemiology and quality assurance to complement laboratory experience. PMID:10566794

  17. Alternative and Complementary Therapies

    MedlinePLUS

    ... always designed to treat a particular illness: Some alternative therapies treat the whole person, not an illness. They might restore harmony, balance, or normal energy flow. Acupuncturists, for example, use the pulse to ...

  18. Marketing alternative fueled automobiles

    E-print Network

    Zheng, Alex (Yi Alexis)

    2011-01-01

    Marketing alternative fueled vehicles is a difficult challenge for automakers. The foundation of the market, the terms of competition, and the customer segments involved are still being defined. But automakers can draw ...

  19. Enhanced next generation alternator

    E-print Network

    Lorilla, Leandro M. (Leandro Manalac), 1977-

    2005-01-01

    The power requirements of automotive alternators are increasing significantly due to the introduction of new vehicle electrical loads. Moreover, the possible transition to a 42 V electrical system is introducing new concerns ...

  20. Alternative fuel information sources

    SciTech Connect

    Not Available

    1994-06-01

    This short document contains a list of more than 200 US sources of information (Name, address, phone number, and sometimes contact) related to the use of alternative fuels in automobiles and trucks. Electric-powered cars are also included.

  1. Alternative energy design toolkit

    E-print Network

    Sukkasi, Sittha

    2004-01-01

    This thesis concerns the concepts, structure, and applications of the Alternative Energy Design Toolkit. The toolkit is aimed to provide a widely accessible, easy to use, flexible, yet powerful modeling environment for ...

  2. Alternative disinfectant water treatments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alternative disinfestant water treatments are disinfestants not as commonly used by the horticultural industry. Chlorine products that produce hypochlorous acid are the main disinfestants used for treating irrigation water. Chlorine dioxide will be the primary disinfestant discussed as an alternativ...

  3. Alternatives to Nursing Homes

    MedlinePLUS

    ... this website may not be available. Alternatives to nursing homes Before you make any decisions about long ... live and what help you may need. A nursing home may not be your only choice. Discharge ...

  4. Alternative Energy Evaluation

    NSDL National Science Digital Library

    Scevola, Misty

    This document from Misty Scevola serves as an assessment of student knowledge of alternative energy technologies. This document would be useful for instructors looking to expand their students' knowledge of alternative energy and sustainability. The document is intended to be used twice: once before learning about the concepts outlined, and once after the class has been completed. This document may be downloaded in PDF file format.

  5. Complementary and Alternative Medicine

    Microsoft Academic Search

    Janice Post-White; Elena Ladas

    \\u000a Complementary and alternative medicine (CAM) encompasses practices and therapeutic modalities that fall outside of the mainstream\\u000a of conventional medicine. The National Center for Complementary and Alternative Medicine of the National Institutes of Health\\u000a (NCCAM, NIH)(2008) identifies four domains of CAM therapies, including mind–body, touch, energy, and biological therapies\\u000a (www.nccam.nih.gov). Children with cancer use therapies from all domains; most often used

  6. Alternative Fuels Infrastructure Development

    SciTech Connect

    Bloyd, Cary N.

    2010-06-30

    This summary reviews the status of alternate transportation fuels development and utilization in Thailand. An understanding of the issues and experiences associated with the introduction of alternative fuels in other countries can help the US in anticipation potential problems as it introduces new automotive fuels. Thailand is of particular interest since it introduced E20 to its commercial market in 2007 and the US is now considering introducing E20 into the US market.

  7. ALTERNATIVE FUELS AND CHEMICALS FROM SYNTHESIS GAS

    SciTech Connect

    Unknown

    1998-01-01

    The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE's LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

  8. Convection Current

    NSDL National Science Digital Library

    The Exploratorium

    2012-06-26

    In this activity, learners make their own heat waves in an aquarium. Warmer water rising through cooler water creates turbulence effects that bend light, allowing you to project swirling shadows onto a screen. Use this demonstration to show convection currents in water as well as light refraction in a simple, visually appealing way.

  9. Electric Current

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-13

    Explore how electric current works. Start at an atomic level and use interactive models to investigate how temperature can affect conductivity and resistivity in a substance by monitoring a virtual ammeter. Explore how factors such as resistivity and voltage affect the flow of electrons and learn about Ohm?s law. Students will be able to:

  10. Unusually stable and highly electrochemically reversible n-doping of regioregular alternate copolymer of dialkylthiophene and fluorenone

    Microsoft Academic Search

    M. D. Levi; R. Demadrille; E. Markevich; Y. Gofer; A. Pron; D. Aurbach

    2006-01-01

    We describe detailed studies on the electrochemical activity of thin films of a new conjugated copolymer, namely, poly[(2,7-fluoren-9-one)-alt-(5,5?-(3,3?-di-n-octyl-2,2?-bithiophene))] (abbreviated PFDOBT-HH (HH=head-to-head)), which has been synthesized electrochemically by a mild oxidation process at low current density. The dynamics of both p- and n-dopings of PFDOBT-HH in sulfolane\\/TEABF4 solution was fully characterized by a combination of cyclic voltammetry (CV) and electrochemical impedance

  11. Alternating-Gradient Photodetector For Far Infrared

    NASA Technical Reports Server (NTRS)

    Overhauser, Albert W.; Maserjian, Joseph

    1989-01-01

    Proposed detector of photons of wavelengths in range of 30 to 200 micrometer made of alternating layers of lightly and heavily negatively doped germanium. Formed in sequence by conventional chemical-vapor deposition. Alternating-gradient structure enhances collection of photogenerated charge carriers while suppressing dark current, thus achieving high detectivity. Alternating layers of n+ and n- germanium provides high detectivity in far-infrared spectral region. Also possible to make similar structures with positive doping and with other semiconductors as silicon or gallium arsenide to obtain various spectral response.

  12. Field Coil Insulation Testing for Pulse Power Alternators

    Microsoft Academic Search

    Clay S. Hearn; Jon J. Hahne; Steven M. Manifold; Scott P. Pish

    2007-01-01

    Current pulse power alternator designs operate at high speeds and high current densities. The field coil insulation systems for pulse power alternators must provide sufficient stand-off voltage while limiting the amount of thermal resistance for actively cooled designs, and also withstand the strain excursions experienced at full operating speed. Repetitive cycling of the strain excursion overtime may induce cracks in

  13. Corrosion of Iron Under Alternating Wet and Dry Conditions

    Microsoft Academic Search

    D. S. Dunn; G. A. Cragnolino; M. B. Bogart; C. S. Brossia

    2000-01-01

    In-situ alternating current (AC) and direct current (DC) electrochemical techniques were used to determine the corrosion rate and corrosion potential of high-purity iron under alternate wet and dry conditions. Comparisons between DC electrochemical measurements and weight loss were conducted to verify the validity of the corrosion rate measurements. Identification of the corrosion products was performed using Raman spectroscopy. Corrosion products

  14. Alternative energy technologies for the Caribbean islands

    SciTech Connect

    Pytlinski, J.T. (Univ. of Puerto Rico, San Juan (Puerto Rico))

    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 Caribbean 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.

  15. Induced Currents, Eddy Currents and

    E-print Network

    Tobar, Michael

    - is this useful? yes - e.g. hard-drive heads, metal detectors, electrical power generators, credit-card readers(E + v Ã? B) = 0 dE = vB dr = rB dr |E| = R 0 rB dr = 1 2 BR2 2 Faraday Disc Machine at ANU 2MA supply!! 3, alternators in cars etc etc Can it be fun - also YES! 4 #12;Driving too fast? - Arago's Disk 5 Can Crusher Can

  16. Current Awareness

    NSDL National Science Digital Library

    Compiled monthly by the Education Information Center of the North Carolina Department of Public Instruction in association with The Landmark Project, Current Awareness is a bibliographic database of the most recent literature on issues related to education and technology. Garnered from an extensive journal collection, the citations in the database are indexed into more than 200 topic areas. Educators may browse the database by topic or conduct keyword searches on topic or title. Queries yield brief citations in a tabular format.

  17. Eddy Currents

    NSDL National Science Digital Library

    The Exploratorium

    2011-12-05

    In this activity related to magnetism and electricity, learners discover that a magnet falls more slowly through a metallic tube than it does through a nonmetallic tube. Use this activity to illustrate how eddy currents in an electrical conductor create a magnetic field that exerts an opposing force on the falling magnet, which makes it fall at a slower rate. This activity guide also includes demonstration instructions involving two thick, flat pieces of aluminum to illustrate the same principle.

  18. Biodiesel: an alternative fuel.

    PubMed

    Manzanera, Maximino; Molina-Muñoz, Maria L; González-López, Jesús

    2008-01-01

    Biodiesel is an alternative energy source and could be a substitute for petroleum-based diesel fuel. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. Most of the sources, methods and apparatus to produce biodiesel are reviewed here. Some of the patents propose the use of oils and fats of animal or vegetal origin and other kind of sources. Many others focus on the methods for the production or oxidation stability of the biofuel in order to make its production economically competitive. Several apparatus comprising reactors and refineries are also presented. This review article summarizes recent and important patents relating to the production of biodiesel to make its production a viable alternative. PMID:19075850

  19. Current Mirrors Basic Current Mirror

    E-print Network

    Leach Jr.,W. Marshall

    , it follows that both must have the same currents. Thus, we can write the equation IREF = IO + 2IO Solution for IO yields IO = IREF 1 + 2/ Because the Early effect has been neglected in solving for IO, the output in the solution for IO, the output resistance is given by rout = r02 = VCB2 + VA IO For a more accurate analysis

  20. 3 CFR - Demonstration Grants for the Development, Implementation, and Evaluation of Alternatives to the...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...Evaluation of Alternatives to the Current Medical Liability System Presidential Documents...Evaluation of Alternatives to the Current Medical Liability System Memorandum for the Secretary...specialty and by State. The cost of insurance continues...