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1

Bismuth electrodes, an alternative in stripping voltammetry  

NASA Astrophysics Data System (ADS)

The heavy metals are known as highly toxic contaminants, the processes carried out in industry contribute that finally they remain dispersed in effluents and sewage, doing part of the food chain. The importance of controlling the levels of these heavy metals has become an international policy, so it has generated interest in developing new analytical methodologies for its determination [1, 2, 3, 4]. The stripping voltammetry has been considered as a family of electro-sensitive analytical techniques useful for the determination of trace levels of many metals in environmental, clinical and industrial samples [3, 4]. This work presents an overview of these bismuth-based electrodes which were introduced around 2000, which have interesting characteristics for detection of heavy metals and which represent an alternative to mercury electrodes.

Barón-Jaimez, J.; Joya, M. R.; Barba-Ortega, J.

2013-11-01

2

Current Alternative Engine Fuels  

Microsoft Academic Search

In this study, methyl and ethyl alcohols, hydrogen, biodiesel, boron, natural gas, liquefied petroleum gas, p-series, electricity, and solar fuels were concluded as alternative engine fuels. Alternative engine fuels are competitive fuels to petroleum. These fuels are important because they replace petroleum fuels. There are many benefits the environment, economy and consumers in using alternative fuels.

MUSTAFA BALAT

2005-01-01

3

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.

4

The Generation of Alternate Current  

NSDL National Science Digital Library

Created by Terry L.M. Bartelt of Wisconsin Online Resource Center is a learning object lesson of the generation of alternate current. This is a nice brief introduction for those interested in basic electronic theories.

Bartelt, Terry L. M.

5

Alternating Current Jee-Hwan Ryu  

E-print Network

and Education MEC240 Korea University of Technology and Education (Direct Current) #12;Korea University of Technology and Education (Alternating Current) Korea University of Technology and Education Why AC ? , , , #12;Korea University of Technology and Education

Ryu, Jee-Hwan

6

Alternating Current Circuit Jee-Hwan Ryu  

E-print Network

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 and Education Why AC ? , , , #12;Korea University of Technology and Education

Ryu, Jee-Hwan

7

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 Implantable Devices Aerospace Systems Satellites Aircraft Commercial Alternative Energy #12;4Copyright© 2010

8

Multivariate curve resolution-alternating least squares assisted by voltammetry for simultaneous determination of betaxolol and atenolol using carbon nanotube paste electrode.  

PubMed

In the present work differential pulse voltammetry coupled with multivariate curve resolution-alternating least squares (MCR-ALS) was applied for simultaneous determination of betaxolol (Bet) and atenolol (Ate) in 0.20 M Britton-Robinson (B-R) buffer solution at the surface of a multi-walled carbon nanotube modified carbon paste electrode (MWCNT/CPE). Characterization of the modified electrode was carried out by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A strategy based on experimental design was followed. Operating conditions were improved with central composite rotatable design (CCRD) and response surface methodology (RSM), involving several chemical and instrumental parameters. Then second order data were built from variable pulse heights of DPV and after correction in potential shift analyzed by MCR-ALS. Analytical parameters such as linearity, repeatability, and stability were also investigated and a detection limit (DL) of 0.19 and 0.29 ?M for Bet and Ate was achieved, respectively. The proposed method was successfully applied in simultaneous determining the two analytes in human plasma. PMID:23632433

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

2013-12-01

9

Fault current limiter and alternating current circuit breaker  

DOEpatents

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.

Boenig, Heinrich J. (Los Alamos, NM)

1998-01-01

10

Fault current limiter and alternating current circuit breaker  

DOEpatents

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.

Boenig, H.J.

1998-03-10

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

Josephson junctions with alternating critical current density  

SciTech Connect

The magnetic-field dependence of the critical current I{sub c}(H) is considered for a short Josephson junction with the critical current density j{sub c} alternating along the tunnel contact. Two model cases, periodic and randomly alternating j{sub c}, are treated in detail. Recent experimental data on I{sub c}(H) for grain-boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub x} are discussed. {copyright} {ital 1997} {ital The American Physical Society}

Mints, R.G. [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel)] [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Kogan, V.G. [Ames Laboratory and Physics Department, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Physics Department, Iowa State University, Ames, Iowa 50011 (United States)

1997-04-01

13

Solar cell system having alternating current output  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

14

Electrochemical Processes in an Alternating Current  

Microsoft Academic Search

The theory of electrochemical impedance is reviewed. Alternating current circuits equivalent to an electrochemical reaction proceeding via an adsorption state are examined for reversible and irreversible systems. The dynamic adsorption equation for a non-equilibrium electrode is discussed. The theoretical circuits are compared with experimental data for the iodine–iodide system. The bibliography includes 59 references.

Boris M Grafov; E A Ukshe

1975-01-01

15

Electrochemical Processes in an Alternating Current  

Microsoft Academic Search

The theory of electrochemical impedance is reviewed. Alternating current circuits equivalent to an electrochemical reaction proceeding via an adsorption state are examined for reversible and irreversible systems. The dynamic adsorption equation for a non-equilibrium electrode is discussed. The theoretical circuits are compared with experimental data for the iodine-iodide system. The bibliography includes 59 references.

Boris M. Grafov; E. A. Ukshe

1975-01-01

16

Alternating current long range alpha particle detector  

DOEpatents

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.

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

1993-02-16

17

Tiling by rectangles and alternating current  

E-print Network

This paper is on tilings of polygons by rectangles. A celebrated physical interpretation of such tilings due to R.L. Brooks, C.A.B. Smith, A.H. Stone and W.T. Tutte uses direct-current circuits. The new approach of the paper is an application of alternating-current circuits. The following results are obtained: - a necessary condition for a rectangle to be tilable by rectangles of given shapes; - a criterion for a rectangle to be tilable by rectangles similar to it but not all homothetic to it; - a criterion for a generic polygon to be tilable by squares. These results generalize the ones of C. Freiling, R. Kenyon, M. Laczkovich, D. Rinne and G. Szekeres.

M. Prasolov; M. Skopenkov

2010-02-06

18

Tiling by rectangles and alternating current  

E-print Network

This paper is on tilings of polygons by rectangles. A celebrated physical interpretation of such tilings due to R.L. Brooks, C.A.B. Smith, A.H. Stone and W.T. Tutte uses direct-current circuits. The new approach of the paper is an application of alternating-current circuits. The following results are obtained: - a necessary condition for a rectangle to be tilable by rectangles of given shapes; - a criterion for a rectangle to be tilable by rectangles similar to it but not all homothetic to it; - a criterion for a generic polygon to be tilable by squares. These results generalize the ones of C. Freiling, R. Kenyon, M. Laczkovich, D. Rinne and G. Szekeres.

Prasolov, M

2010-01-01

19

Affordable Cyclic Voltammetry  

ERIC Educational Resources Information Center

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…

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

2009-01-01

20

Stability of alternating current gliding arcs  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

21

Transcranial alternating current stimulation (tACS)  

PubMed Central

Transcranial alternating current stimulation (tACS) seems likely to open a new era of the field of noninvasive electrical stimulation of the human brain by directly interfering with cortical rhythms. It is expected to synchronize (by one single resonance frequency) or desynchronize (e.g., by the application of several frequencies) cortical oscillations. If applied long enough it may cause neuroplastic effects. In the theta range it may improve cognition when applied in phase. Alpha rhythms could improve motor performance, whereas beta intrusion may deteriorate them. TACS with both alpha and beta frequencies has a high likelihood to induce retinal phosphenes. Gamma intrusion can possibly interfere with attention. Stimulation in the “ripple” range induces intensity dependent inhibition or excitation in the motor cortex (M1) most likely by entrainment of neuronal networks, whereas stimulation in the low kHz range induces excitation by neuronal membrane interference. TACS in the 200 kHz range may have a potential in oncology. PMID:23825454

Antal, Andrea; Paulus, Walter

2013-01-01

22

Direct determination of uranium traces by adsorptive stripping voltammetry  

Microsoft Academic Search

Ultratrace concentrations of uranium(VI) have been determined using adsorptive stripping voltammetry of the uranium-chloranilic acid complex (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone). The detection limit was calculated to 24 ng\\/l. The most significant advantage of the method described is its ease of application to the analysis of natural water and drainage water from a uranium slag heap. Alternating current investigations have been carried out to

Sylvia Sander; Wolfram Wagner; Günter Henze

1995-01-01

23

Alternative pain medicine: Current modalities and principles  

Microsoft Academic Search

Conventional pain medicine does not solve all the problems of chronic pain patients. In this technological era, patients are\\u000a more demanding and in their frustration may seek alternative modalities for managing their chronic pain. Recent studies have\\u000a shown that this tendency may in fact expose patients not only to useless therapies but occasionally harmful ones. Many alternative\\u000a modalities have been

Winston C. V. Parris

1997-01-01

24

Alternating current electromagnetic servo induction meter  

NASA Technical Reports Server (NTRS)

Electromagnetic device accurately indicates the responses of various sensors in high performance flight research aircraft to conditions encountered in flight. The device responds to sensor inputs to move a slideable armature along an indicator scale by the force of currents induced in the armature winding.

Bogue, R. K.

1968-01-01

25

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

26

Method for sputtering with low frequency alternating current  

DOEpatents

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

Timberlake, J.R.

1996-04-30

27

Method for sputtering with low frequency alternating current  

DOEpatents

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

Timberlake, John R. (Allentown, NJ)

1996-01-01

28

Semiconductor alternating-current motor drives and energy conservation  

Microsoft Academic Search

Energy conservation by means of semiconductor alternating-current control of electric motor drives used in variable-rate industrial processes is presented and applications of the concept are discussed. The need for electrical energy conservation in the process industrial sector is pointed out for the case of drives used to operate industrial pumps, compressors, fans and blowers which typically involve ac electric motors

D. J. Bendaniel; E. E. David Jr.

1979-01-01

29

Pulse-loaded ferroelectric nanowire as an alternating current source.  

PubMed

The behavior of an uniaxially pulse-loaded ferroelectric nanowire is simulated using a Landau-Ginzburg type thermodynamic model. Our results show that under a load of suitable magnitude and frequency, an appropriately dimensioned ferroelectric nanowire can produce a sizable alternating current voltage, sufficient for applications as a nanopower source for energy harvesting, or as an effective nanomechanical sensor. PMID:18781805

Zheng, Yue; Woo, C H; Wang, B

2008-10-01

30

Nonlinear response of superconductors to alternating fields and currents  

SciTech Connect

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.

McDonald, J.

1997-10-08

31

Current reversal equilibrium configurations in the alternating-current operation of tokamaks  

SciTech Connect

The equilibrium configurations with central current density reversal and those with two oppositely flowing current components on the high-field side and low-field side have been numerically modeled by using the exact solution of the Grad-Shafranov-Helmholtz equation, with the parameters chosen according to the tokamak alternating-current operation experiments. The modeling results (the magnetic flux surface configurations, the current density profiles, the plasma pressure, and the loop voltage) agree well with the experimental observations.

Yu Jun; Wang Shaojie; Li Jiangang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China) and Department of Physics, Fudan University, Shanghai, 200433 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

2006-05-15

32

Describing current and potential markets for alternative-fuel vehicles  

SciTech Connect

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.

NONE

1996-03-26

33

Effect of Potentiated Solutions on Mercury(II) Signal in Inversion Voltammetry  

Microsoft Academic Search

We studied the effects of homeopathically potentiated substances in ultralow doses on physicochemical properties of solutions. Inverse voltammetric signals during Hg(II) oxidation-reduction in the presence of potentiated water, lithium chloride, and mercury nitrate were studied by alternating-current inversion voltammetry. Potentiated substances modified oxidation-reduction processes in the electrochemical system. Potentiated solutions of Hg(II) increased the effective concentration (activity) of mercury ions.

S. I. Petrov; O. I. Epstein

2003-01-01

34

A Treatise on the Theory of Alternating Currents  

NASA Astrophysics Data System (ADS)

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.

Russell, Alexander

2014-05-01

35

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

NASA Astrophysics Data System (ADS)

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.

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

36

Depolarization of a piezoelectric film under an alternating current field  

Microsoft Academic Search

In this article, we demonstrate that a sol-gel-derived niobium-doped lead zirconate titanate film can be depolarized by the application of alternating current (ac) fields of diminishing amplitude and we explain the phenomenon based on the concept of the Preisach model. The amplitude of the ac fields is decreased from 20 to 2 MV\\/m in ten steps. The observed piezoelectric coefficient

K. W. Kwok; M. K. Cheung; H. L. W. Chan; C. L. Choy

2007-01-01

37

Unfolding Collapsed Polyelectrolytes in Alternating-Current Electric Fields  

E-print Network

We investigate the unfolding of single polyelectrolyte (PE) chains collapsed by trivalent salt under the action of alternating-current (AC) electric fields through computer simulations and theoretical scaling. The results show that a collapsed chain can be unfolded by an AC field when the field strength exceeds the direct-current (DC) threshold and the frequency is below a critical value, corresponding to the inverse charge relaxation/dissociation time of condensed trivalent counterions at the interface of the collapsed electrolyte. This relaxation time is also shown to be identical to the DC chain fluctuation time, suggesting that the dissociation of condensed polyvalent counterion on the collapsed PE interface controls the polyelectrolyte dipole formation and unfolding dynamics under an AC electric field.

Pai-Yi Hsiao; Yu-Fu Wei; Hsueh-Chia Chang

2010-10-19

38

Use of cyclic current reversal polarization voltammetry for investigating the relationship between corrosion resistance and heat-treatment induced variations in microstructures of 400 C martensitic stainless steels  

NASA Technical Reports Server (NTRS)

Software for running a cyclic current reversal polarization voltammagram has been developed for use with a EG&G Princeton Applied Research Model 273 potentiostat/galvanostat system. The program, which controls the magnitude, direction and duration of an impressed galvanostatic current, will produce data in ASCII spreadsheets (Lotus, Quattro) for graphical representation of CCRPV voltammograms. The program was used to determine differences in corrosion resistance of 440 C martenstic stainless steel produced as a result of changes in microstructure effected by tempering. It was determined that tempering at all temperatures above 400 F resulted in increased polarizability of the material, with the increased likelihood that pitting would be initiated upon exposure to marine environments. These results will be used in development of remedial procedures for lowering the susceptibility of these alloys toward the stress corrosion cracking experienced in bearings used in high pressure oxygen turbopumps used in the main engines of space shuttle orbiters.

Ambrose, John R.

1992-01-01

39

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

ERIC Educational Resources Information 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…

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

40

Reversible Nerve Conduction Block Using Kilohertz Frequency Alternating Current  

PubMed Central

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

Kilgore, Kevin L.; Bhadra, Niloy

2013-01-01

41

Transcranial Alternating Current Stimulation Attenuates Visual Motion Adaptation  

PubMed Central

Transcranial alternating current stimulation (tACS) is used in clinical applications and basic neuroscience research. Although its behavioral effects are evident from prior reports, current understanding of the mechanisms that underlie these effects is limited. We used motion perception, a percept with relatively well known properties and underlying neural mechanisms to investigate tACS mechanisms. Healthy human volunteers showed a surprising improvement in motion sensitivity when visual stimuli were paired with 10 Hz tACS. In addition, tACS reduced the motion-after effect, and this reduction was correlated with the improvement in motion sensitivity. Electrical stimulation had no consistent effect when applied before presenting a visual stimulus or during recovery from motion adaptation. Together, these findings suggest that perceptual effects of tACS result from an attenuation of adaptation. Important consequences for the practical use of tACS follow from our work. First, because this mechanism interferes only with adaptation, this suggests that tACS can be targeted at subsets of neurons (by adapting them), even when the applied currents spread widely throughout the brain. Second, by interfering with adaptation, this mechanism provides a means by which electrical stimulation can generate behavioral effects that outlast the stimulation. PMID:24849365

Krekelberg, Bart

2014-01-01

42

The development of monolithic alternating current light-emitting diode  

NASA Astrophysics Data System (ADS)

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.

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

2011-02-01

43

Precision electronic speed controller for an alternating-current  

DOEpatents

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

Bolie, Victor W. (Albuquerque, NM)

1988-01-01

44

Square wave voltammetry at the dropping mercury electrode: Theory  

USGS Publications Warehouse

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.

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

1977-01-01

45

An Alternative Introduction to Maxwell's Displacement Current  

ERIC Educational Resources Information Center

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…

Reich, Gary

2013-01-01

46

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

47

Alternatives to animal testing: current status and future perspectives  

Microsoft Academic Search

On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international\\u000a symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was\\u000a meant to celebrate the 50th anniversary of the publication of the book “The Principles of Humane Experimental Technique” by\\u000a Russell

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

2011-01-01

48

Glowing Connection Experiments With Alternating Currents Below 1  

Microsoft Academic Search

It was experimentally shown that a glowing connection can develop in an electrical switch at a terminal connection comprised of a connector that utilizes a spring action against a conductor to provide electrical contact in household electrical appliances where vibration exists, and when the connection is loose. This can happen at a current flow such as 0.6 Arms at 120-V.

Joe Urbas

2010-01-01

49

Glowing Connection Experiments with Alternating Currents below 1 Arms  

Microsoft Academic Search

It was experimentally proven that a glowing connection can develop in an electrical switch at a terminal connection comprising of a connector that utilizes a spring action against a conductor to provide electrical contact in household electrical appliances where vibration exists. This can happen at a current flow such as 0.6 Arms at 120 V. Further, the glow can provide

Joe Urbas

2008-01-01

50

The Conductivity of Flames for Rapidly Alternating Currents  

Microsoft Academic Search

Conductivity of salted flames for high frequency currents.-Theory. Expressions are developed for the capacity and series resistance of a parallel plate condenser in a flame, which enable certain constants to be computed from the measurements of Bryan given in the preceding paper. Calculated density of positive ions increases from.03 e.s.u. in the unsalted flame to 1.5 e.s.u. for the flame

H. A. Wilson; A. B. Bryan

1924-01-01

51

Josephson effects in an alternating current biased transition edge sensor  

NASA Astrophysics Data System (ADS)

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.

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

52

Expectation of ozone generation in alternating current corona discharges  

NASA Astrophysics Data System (ADS)

An analytical study was made in this paper to calculate the ozone generation inside an ac corona discharge reactor. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature and stressed by an ac voltage. Concentration of the ozone generated inside the reactor was measured as a function of the ac corona current under different discharge conditions. An empirical equation was derived from the experimental results for calculating the ozone concentration generated inside the reactor. The results, that have been calculated by using the derived equation, have agreed with the experimental results over the whole range of the investigated parameters. Therefore, the derived equation represents a suitable criterion for expecting the ozone concentration that will generate by ac coronas in dry air fed coaxial wire-cylinder reactors under any discharge conditions in range of the investigated parameters.

Yehia, Ashraf; Mizuno, Akira

2012-03-01

53

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

Microsoft Academic Search

This study compared between alternating and pulsed current electrical muscle stimulation (EMS) for muscle oxygenation and\\u000a blood volume during isometric contractions. Nine healthy men (23–48 years) received alternating current EMS (2500 Hz) modulated\\u000a at 75 Hz on the knee extensors of one leg, and pulsed current EMS (75 Hz) for the other leg separated by 2 weeks in a randomised,\\u000a counter-balanced order. Pulse duration (400 ?s),

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

2011-01-01

54

Steady state oxygen reduction and cyclic voltammetry.  

PubMed

The catalytic activity of Pt and Pt3Ni for the oxygen reduction reaction is investigated by applying a Sabatier model based on density functional calculations. We investigate the role of adsorbed OH on the activity, by comparing cyclic voltammetry obtained from theory with previously published experimental results with and without molecular oxygen present. We find that the simple Sabatier model predicts both the potential dependence of the OH coverage and the measured current densities seen in experiments, and that it offers an understanding of the oxygen reduction reaction (ORR) at the atomic level. To investigate kinetic effects we develop a simple kinetic model for ORR. Whereas kinetic corrections only matter close to the volcano top, an interesting outcome of the kinetic model is a first order dependence on the oxygen pressure. Importantly, the conclusion obtained from the simple Sabatier model still persists: an intermediate binding of OH corresponds to the highest catalytic activity, i.e. Pt is limited by a too strong OH binding and Pt3Ni is limited by a too weak OH binding. PMID:19213325

Rossmeisl, Jan; Karlberg, Gustav S; Jaramillo, Thomas; Nørskov, Jens K

2008-01-01

55

Stable overload conditions of high-temperature superconductors at alternating current injection  

NASA Astrophysics Data System (ADS)

The stability of alternating current injected into a high-temperature superconductor or into a current-carrying element on its basis is studied under weak cooling. The stability conditions of the current varying with time by a sinusoidal law are studied versus its frequency. It is shown that before unstable states set in, the peak values of the electric field intensity, current, and temperature in the superconductor are higher than the values determining a thermal electrodynamic stability boundary of the current permanently flowing through the superconductor—the so-called thermal quench current. It is found that ultimate stable alternating currents cause high stable thermal losses in superconductors; these losses being not considered in the modern theory of losses. Such stable conditions can be referred to as overload conditions. Analysis shows that there are characteristic times determining the time intervals within which alternating current is stable under overload conditions. Main thermoelectrodynamic mechanisms behind the existence of these intervals are formulated. They explain why the superconductor stable overheating and induced electric field reach high values before the injected alternating current becomes unstable. The existence of overload conditions considerably extends the application area of high-temperature superconductors.

Romanovskii, V. R.

2015-01-01

56

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

ERIC Educational Resources Information Center

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

Yates, Steven Lowell

2009-01-01

57

Alternative conceptions and their orgins of science teachers about current electricity  

Microsoft Academic Search

Alternative conceptions are the ideas which children and adults use to explain various scientific concepts which do not match with the generally accepted scientific explanation of those concepts. The focus of this qualitative research study was to explore the alternative conceptions of science teachers and their origins about basic concepts of current electricity. The concepts were taken from the science

Yasmeen Bano

1998-01-01

58

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks  

DOEpatents

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

Beverly, Leon H. (Lockport, IL); Hance, Richard D. (Elburn, IL); Kristalinski, Alexandr L. (Naperville, IL); Visser, Age T. (Geneva, IL)

1996-01-01

59

Method and apparatus for reducing the harmonic currents in alternating-current distribution networks  

DOEpatents

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

1996-11-19

60

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

SciTech Connect

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.

P.F. Schmit and N.J. Fisch

2010-02-01

61

Solution voltammetry of 4 nm magnetite iron oxide nanoparticles.  

PubMed

The voltammetry of solution-dispersed magnetite iron oxide Fe3O4 nanoparticles is described. Their currents are controlled by nanoparticle transport rates, as shown with potential step chronoamperometry and rotated disk voltammetry. In pH 2 citrate buffer with added NaClO4 electrolyte, solution cyclic voltammetry of these nanoparticles (average diameter 4.4 ± 0.9 nm, each containing ca. 30 Fe sites) displays an electrochemically irreversible oxidation with E(PEAK) at ca. +0.52 V and an irreversible reduction with E(PEAK) at ca. +0.2 V vs Ag/AgCl reference electrode. These processes are presumed to correspond to the formal potentials for one-electron oxidation of Fe(II) and reduction of Fe(III) at their different sites in the magnetite nanoparticle structure. The heterogeneous electrode reaction rates of the nanoparticles are very slow, in the 10(-5) cm/s range. The nanoparticles are additionally characterized by a variety of tools, e.g., TEM, UV/vis, and XPS spectroscopies. PMID:25046101

Roberts, Joseph J P; Westgard, John A; Cooper, Laura M; Murray, Royce W

2014-07-30

62

Effect of an alternating current for crystallization of CaCO3 on a porous membrane.  

PubMed

Calcium carbonate formation on a porous membrane was accelerated by using an alternating current system. A hydrophilic-treated polytetrafluoroethylene (PTFE) porous membrane was utilized for the calcium carbonate formation. The PTFE membrane was interposed with two pairs of glass cells. Calcium chloride and sodium carbonate solutions were filled in each glass cell, and an alternating current of 10 Hz was applied for 30 min. The resulting membrane was characterized in terms of crystal morphology and polymorph using scanning electron microscopy and X-ray diffraction. The major component of the resulting calcium carbonate was spheroidal vaterite, along with rhombohedral calcite. The composition of polymorphs was slight different on the two sides of the membrane. In the absence of the alternating current, only calcite was formed on the membrane. It is considered that the alteration of calcium carbonate formation is regulated by supersaturation, including electric migration, diffusion and electrolysis, during application of the alternating current. The resulting supersaturation was different on the two sides of the membrane, and different quantities of the polymorphs were formed. Taking this result into account, the alternating current catalyzed the development of supersaturation around the membrane, enabling calcium carbonate crystal to be formed. PMID:19064338

Watanabe, Junji; Akashi, Mitsuru

2009-05-01

63

Limiting stable states of high-Tc superconductors in the alternating current modes  

NASA Astrophysics Data System (ADS)

The limiting current-carrying capacity of high- T c superconductor and superconducting tape has been studied in the alternating current states. The features that are responsible for their stable formation have been investigated under the conduction-cooled conditions when the operating peak values of the electric field and the current may essentially exceed the corresponding critical values of superconductor. Besides, it has been proved that these peak values are higher than the values of the electric field and the current, which lead to the thermal runaway phenomenon when the current instability onset occurs in the operating modes with direct current. As a result, the stable extremely high heat generation exists in these operating states, which can be called as overloaded states. The limiting stable peak values of charged currents and stability conditions have been determined taking into account the flux creep states of superconductors. The analysis performed has revealed that there exist characteristic times defining the corresponding time windows in the stable development of overloaded states of the alternating current. In order to explain their existence, the basic thermo-electrodynamics mechanisms have been formulated, which have allowed to explain the high stable values of the temperature and the induced electric field before the onset of alternating current instability. In general, it has been shown that the high- T c superconductors may stably operate in the overloaded alternating current states even under the not intensive cooling conditions at a very high level of heat generation, which is not considered in the existing theory of losses.

Romanovskii, Vladimir R.; Watanabe, Kazuo; Awaji, Satoshi

2014-08-01

64

A threshold analysis of cricket cercal interneurons by an alternating air-current stimulus  

Microsoft Academic Search

1.The wind-velocity threshold of cercal interneurons of the cricketGryllus bimaculatus D. was measured using a sinusoidally alternating aircurrent stimulus. Two stimulus parameters, peak velocity and alternating frequency of the air current, were separately controlled. The measurements of the minimum velocity evoking a response at a variety of frequencies gave a threshold curve. The stimulating apparatus was a wind tunnel which

Masamichi Kanou; Tateo Shimozawa

1984-01-01

65

Effectiveness of iontophoresis with alternating current (AC) in the treatment of patients with palmoplantar hyperhidrosis.  

PubMed

Conventionally, iontophoresis employing direct current (DC) has been used in the treatment of palmoplantar hyperhidrosis, but this is accompanied by side effects such as pain and burns. In the present study, a prototype apparatus using alternating current (AC) was constructed, and iontophoresis with AC was performed in palmoplantar hyperhidrosis patients to determine its effectiveness. The average amount of perspiration of the palmoplantar hyperhidrosis patients was significantly reduced after the third session when iontophoresis treatments were performed once per week. By the eighth treatment, perspiration was reduced to nearly the normal level, and there were no particular side-effects during the treatment period. This treatment therefore appears to be both safe and effective. The treatment effect tended to appear sooner when alternating current iontophoresis was combined with the administration of anticholinergic drugs than when alternating current iontophoresis was used alone. Alternating current iontophoresis is an effective treatment for palmoplantar hyperhidrosis. Guidelines for this treatment for patients with palmoplantar hyperhidrosis will need to be established in the future. PMID:12810991

Shimizu, Hirokazu; Tamada, Yasuhiko; Shimizu, Junko; Ohshima, Yuichiro; Matsumoto, Yoshinari; Sugenoya, Jun-ichi

2003-06-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

67

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

PubMed Central

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

Banga, Ajay K.

2014-01-01

68

Collective response to alternating current in the organic conductor ?-(bis(ethylenedithio)tetrathiafulvalene)2I3  

NASA Astrophysics Data System (ADS)

Interference phenomena between dc fields and ac currents are investigated in the two-dimensional charge-ordered organic conductor ?-(bis(ethylenedithio)tetrathiafulvalene)2I3. When alternating current is applied together with a dc electric field, steps analogous to Shapiro steps in the ac Josephson effect appear in the voltage-current characteristics at the internal frequency, where the step height follows the first-order Bessel function of the ac field. These results are discussed through an analogy with sliding charge-density waves.

Itose, Fumitake; Kawamoto, Tadashi; Mori, Takehiko

2013-06-01

69

Dehydration Efficiency of Water-in-Crude Oil Emulsions in Alternating Current Electrical Fields  

Microsoft Academic Search

The influence of several operational variables on the electrostatic separation of water-in-crude oil emulsions is investigated in a concentric cylinder rheometer equipped with an alternating current (AC) generator. Shear rate, temperature, emulsion water content, electric field strength, and application time are all found to play a role in the process. The droplet size distributions achieved across some of the experiments

Simone Less; Andreas Hannisdal; Johan Sjöblom

2010-01-01

70

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

ERIC Educational Resources Information Center

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…

Linney, Thomas J.

71

Dynamic fuzzy neural network based predictive control for alternating current excitation generators  

Microsoft Academic Search

Alternating current excitation generators (ACEG) can adjust the active power and inactive power flexibly and improve the stability of power system. The key to enhance the power system's stability is to choose appropriate ACEG's excitation control method. Conventional excitation controllers are unable to perform optimally over the full range of operation conditions and disturbances, due to the highly complex, nonlinear

Zhi-Fei Zhang; Xuan Wang

2010-01-01

72

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

PubMed Central

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

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

1982-01-01

73

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

Microsoft Academic Search

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

Y. Sukamongkol; S. Chungpaibulpatana; W. Ongsakul

2002-01-01

74

Evaluation of homogeneous electrocatalysts by cyclic voltammetry.  

PubMed

The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (?), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed. PMID:25247280

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

2014-10-01

75

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

ERIC Educational Resources Information Center

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

Pomeroy, R. S.; And Others

1989-01-01

76

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

DOEpatents

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

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

2012-06-05

77

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

PubMed Central

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

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

2014-01-01

78

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

NASA Technical Reports Server (NTRS)

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.

Mock, W C , Jr

1937-01-01

79

The solution of antenna array input impedances using an alternating current network calculator  

E-print Network

noticing how one source affected the other. With this knowledge and some experience 1n operating the calculators the sources may be set and the system balanced acourately. As the number of antennae in the array are increased the balancing process...THE SOLUT1ON OP ANTENNA ARRAY INPUT IMPFMNCES USING AN ALTERNATING CURRENT NETWORK CALCULATOR A Theeie Jack W. Pool Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial fulfillment of the requirements...

Pool, Jack William

1963-01-01

80

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

NASA Astrophysics Data System (ADS)

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

Hubbard, Allyn E.; Mountain, David C.

1983-11-01

81

Use of Biosensors as Alternatives to Current Regulatory Methods for Marine Biotoxins  

PubMed Central

Marine toxins are currently monitored by means of a bioassay that requires the use of many mice, which poses a technical and ethical problem in many countries. With the exception of domoic acid, there is a legal requirement for the presence of other toxins (yessotoxin, saxitoxin and analogs, okadaic acid and analogs, pectenotoxins and azaspiracids) in seafood to be controlled by bioassay, but other toxins, such as palytoxin, cyclic imines, ciguatera and tetrodotoxin are potentially present in European food and there are no legal requirements or technical approaches available to identify their presence. The need for alternative methods to the bioassay is clearly important, and biosensors have become in recent years a feasible alternative to animal sacrifice. This review will discuss the advantages and disadvantages of using biosensors as alternatives to animal assays for marine toxins, with particular focus on surface plasmon resonance (SPR) technology. PMID:22291571

Vilariño, Natalia; Fonfría, Eva S.; Louzao, M. Carmen; Botana, Luis M.

2009-01-01

82

Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

83

Arsenic speciation in natural waters by cathodic stripping voltammetry.  

PubMed

Contamination of groundwater with arsenic (As) is a major health risk through contamination of drinking and irrigation water supplies. In geochemically reducing conditions As is mostly present as As(III), its most toxic species. Various methods exist to determine As in water but these are not suitable for monitoring arsenic speciation at its original pH and without preparation. We present a method that uses cathodic stripping voltammetry (CSV) to determine reactive As(III) at a vibrating, gold, microwire electrode. The As(III) is detected after adsorptive deposition of As(OH)(3)(0), followed by a potential scan to measure the reduction current from As(III) to As(0). The method is suitable for waters of pH 7-12, has an analytical range of 1 nM to 100 microM As (0.07-7500 ppb) and a limit of detection of 0.5 nM with a 60 s deposition time. The As speciation protocol involves measuring reactive As(III) by CSV at the original pH and acidification to pH 1 to determine inorganic As(III)+As(V) by anodic stripping voltammetry (ASV) using the same electrode. Total dissolved As is determined by ASV after UV-digestion at pH 1. The method was successfully tested on various raw groundwater samples from boreholes in the UK and West Bengal. PMID:20152258

Gibbon-Walsh, Kristoff; Salaün, Pascal; van den Berg, Constant M G

2010-03-01

84

Iontophoresis with alternating current and direct current offset (AC/DC iontophoresis): a new approach for the treatment of hyperhidrosis.  

PubMed

Tap-water iontophoresis (TWI) using direct current (DC) is the most effective therapy in palmoplantar hyperhidrosis. Side-effects of this method are discomfort, with burning and tingling, and skin irritation, including erythema and vesicles. Incorrect use may induce iontophoretic burns at sites of minor skin injury. Elaborate safety measures are required to prevent electric shock. The aim of this study was to minimize side-effects and to increase technical and safety standards of TWI, without loss of efficacy. In a controlled blind study, treatment of palmar hyperhidrosis by alternating current (AC) or by AC with DC-offset (AC/DC) was compared with the conventional DC method. Palmar hyperhidrosis was completely controlled after an average of 11 treatments by either AC/DC iontophoresis or the conventional DC method. Virtually no effect was seen when AC without DC-offset was used for TWI. There were no signs of cutaneous irritation, or subjective sensations of discomfort when AC with or without DC-offset was employed. AC/DC iontophoresis should become the treatment of choice for palmoplantar hyperhidrosis. The mechanism of action is unknown. It is hypothesized that an interrupted stimulus-secretion-coupling leads to a functional disturbance of sweat secretion. PMID:7654577

Reinauer, S; Neusser, A; Schauf, G; Hölzle, E

1993-08-01

85

Determination of copper and arsenic in refined beet sugar by stripping voltammetry without sample pretreatment.  

PubMed

Copper and arsenic have been analysed in refined beet sugar at the microgram kg-1 level by anodic stripping voltammetry (copper) and cathodic stripping voltammetry (arsenic) in the differential-pulse mode (DPASV and DPCSV) at a hanging mercury drop electrode (HMDE). DPCSV measurements of arsenic are based on its accumulation onto the HMDE as an intermetallic Cu-As compound followed by the reduction of As0 to arsine in hydrochloric acid medium. Measurements were directly carried out on untreated sugar solutions. The performance of the procedures was compared with electrothermal atomic absorption spectrometry and stripping voltammetry applied to digested sugar samples, and showed in general better accuracy. The procedures were applied to the determination of these toxic elements in commercial beet sugar samples of concentrations below 50 micrograms kg-1 copper and 15 micrograms kg-1 arsenic were found, which are much lower that those allowed by the current regulations. PMID:9684407

Sancho, D; Vega, M; Debán, L; Pardo, R; González, G

1998-04-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

87

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

, Universe, Big Bang Theory, 2 more + add Anyother added this added August 18, 2009 51 views 1 responses9/18/09 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

Temple, Blake

88

Microwave-assisted domain-wall motion induced by alternating spin-polarized current  

NASA Astrophysics Data System (ADS)

We have studied the microwave-assisted domain-wall (DW) motion driven by the alternating spin-polarized current. It is found that the adiabatic spin-transfer torque alone can sustain a steady-state wall motion without Walker breakdown if a transverse microwave field is applied. The direction and velocity of the domain-wall motion can be effectively manipulated by tuning the phase difference between the ac and the microwave field. The wall motion is very sensitive to the microwave frequency and can be resonantly enhanced by exciting the DW thickness oscillation mode. The characteristics of this kind of DW motion are well accounted for by an analytical model.

Wang, Xi-guang; Guo, Guang-hua; Nie, Yao-zhuang; Wang, Dao-wei; Zeng, Zhong-ming; Li, Zhi-xiong; Tang, Wei

2014-04-01

89

Alternating current driven electroluminescence from ZnSe/ZnS:Mn/ZnS nanocrystals.  

PubMed

We present a novel technique for room temperature, solution-based fabrication of alternating current thin-film electroluminescent (AC-TFEL) devices using phosphor-doped nanocrystals. Synthesis for stable ZnSe/ZnS:Mn/ZnS nanocrystals that exhibit a quantum yield of 65 +/- 5% is outlined, and their electroluminescence is demonstrated in structures consisting of only wide band gap ceramic layers. Both the nanocrystal and the ceramic films have minimal absorption across the visible light spectrum, enabling us to demonstrate transparent AC-TFEL devices. PMID:19397294

Wood, Vanessa; Halpert, Jonathan E; Panzer, Matthew J; Bawendi, Moungi G; Bulovi?, Vladimir

2009-06-01

90

Stability of alternating current discharges between water drops on insulation surfaces  

NASA Astrophysics Data System (ADS)

Discharges between water drops are important in the ageing of hydrophobic outdoor insulators. They may also be important in the processes leading up to flashover of these insulators in high pollution conditions. This paper considers discharges between drops when a limited alternating current is available, as experienced by an ageing insulator in service. A phenomenon is identified in which the length of a discharge between two drops is reduced through a particular type of distortion of the drops. This is visually characterized as a liquid protrusion from each of a pair of water drops along the insulator surface. This process is distinct from vibration of the drops, general distortion of their shape and the very fast emission of jet streams seen in very high fields. The process depends upon the discharge current, the resistivity of the moisture and the hydrophobicity of the insulation surface.

Rowland, S. M.; Lin, F. C.

2006-07-01

91

Research on 0.1THz alternating current radiometric security inspection imaging for antiterrorism application  

NASA Astrophysics Data System (ADS)

For the purpose of security inspection, an alternating current (AC) radiometer is used in passive THz Wave (0.1THz) imaging for the first time in china. Giving a comparison of structure and spectrum characteristic between direct current (DC) radiometer and AC radiometer, we discussed the AC radiometer imaging mechanism and the noise image disposal method based on the medium filtering. Simulating the requirement of safety inspection in airports, ports etc, a 2-D imaging experiment of the person with canceled object has been did indoor, by THz Wave AC radiometer mechanical scanning. The results show that THz Wave AC radiometer possesses higher sensitivity and can be used to inspect the concealed metal objects hidden in the passenger body and their luggage.

Zhang, Guang-feng; Qin, Wen-jie; Lou, Guo-wei

2011-08-01

92

Transcranial alternating current stimulation affects motion adaptation in V1 and MT neurons in awake, behaving macaques  

E-print Network

Transcranial alternating current stimulation affects motion adaptation in V1 and MT neurons of transcranial alternating current stimulation (tACS) range from treating depression to augmenting human during which we presented a random dot stimulus moving in one of the eight directions. In the stimulation

Krekelberg, Bart

93

Solid state voltammetry of an anthraquinone molten salt  

SciTech Connect

The solid-state voltammetries of the two reduction steps of a novel redox polyether hybrid--an anthraquinone molten salt (triethyl(MePEG350)ammonium anthraquinone sulfonate, (Et{sub 3}NMePEG350{sup +})(AQSO{sub 3}{sup {minus}}))--and its disulfonated analogue, are reported. Multiple effects on charge transport rates are encountered. Currents for the first reduction wave are greater than 10-fold smaller. The relative charge transport rates of the two reductions are examined as a function of temperature and of incrementally replacing the AQSO{sub 3}{sup {minus}} anion in the melt with the electro-inactive BF{sub 4}{sup {minus}} anion. An analysis that includes ionic conductivity measurements shows that the apparent charge transport rate of the second anthraquinone reduction is attenuated primarily as a result of ionic migration of the products of comproportionation reactions occurring in the diffusion layer.

Williams, M.E.; Murray, R.W.

1999-11-18

94

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

PubMed Central

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

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

2013-01-01

95

Efficacy of lidocaine lontophoresis using either alternating or direct current in hairless rats.  

PubMed

The aim of this study was to determine transport of lidocaine ions through a hairless rat skin in vivo and to compare the efficacy of alternating current (AC) with that of direct current (DC) iontophoresis (IOP). We measured the concentration of lidocaine transported through a cellophane membrane or a hairless rat dorsal skin applying either AC-IOP or DC-IOP. The results revealed that lidocaine concentration increased in a time-dependent manner in vitro in both DC-IOP and AC-IOP. However, the in vivo study showed different tendencies in lidocaine concentration. In the DCIOP group, lidocaine concentration reached its maximum 20 min after current application and then decreased rapidly; the AC-IOP group showed an increase in lidocaine concentration in a time-dependent manner. There were no side effects such as electrical burns in the rats. In conclusion, AC can be applied for long periods and DC for short periods, or their application time can be appropriately scheduled. Our study also suggests the mechanism by which voltage waveforms affect the skin when applied by IOP. In the future, these findings will be a solid foundation for developing various kinds of medical equipment such as scheduled drug delivery system that can easily deliver various types of drug. PMID:24146168

Nakajima, Atsushi; Wakita, Ryo; Haida, Haruka; Fukayama, Haruhisa

2013-01-01

96

Gold nanoarray deposited using alternating current for emission rate-manipulating nanoantenna  

PubMed Central

We have proposed an easy and controllable method to prepare highly ordered Au nanoarray by pulse alternating current deposition in anodic aluminum oxide template. Using the ultraviolet–visible-near-infrared region spectrophotometer, finite difference time domain, and Green function method, we experimentally and theoretically investigated the surface plasmon resonance, electric field distribution, and local density of states enhancement of the uniform Au nanoarray system. The time-resolved photoluminescence spectra of quantum dots show that the emission rate increased from 0.0429 to 0.5 ns?1 (10.7 times larger) by the existence of the Au nanoarray. Our findings not only suggest a convenient method for ordered nanoarray growth but also prove the utilization of the Au nanoarray for light emission-manipulating antennas, which can help build various functional plasmonic nanodevices. PMID:23799880

2013-01-01

97

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

PubMed Central

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

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

2014-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

99

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

PubMed

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

Sasaki, Naoki; Maekawa, Chisaki; Sato, Kae

2015-02-01

100

Alternating current driven organic light emitting diodes using lithium fluoride insulating layers.  

PubMed

We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m(2) obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage. PMID:25523436

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

2014-01-01

101

Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation.  

PubMed

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

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

2015-02-01

102

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

PubMed

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

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

2015-03-01

103

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

PubMed

The 7th amendment to the EU Cosmetics Directive prohibits to put animal-tested cosmetics on the market in Europe after 2013. In that context, the European Commission invited stakeholder bodies (industry, non-governmental organisations, EU Member States, and the Commission's Scientific Committee on Consumer Safety) to identify scientific experts in five toxicological areas, i.e. toxicokinetics, repeated dose toxicity, carcinogenicity, skin sensitisation, and reproductive toxicity for which the Directive foresees that the 2013 deadline could be further extended in case alternative and validated methods would not be available in time. The selected experts were asked to analyse the status and prospects of alternative methods and to provide a scientifically sound estimate of the time necessary to achieve full replacement of animal testing. In summary, the experts confirmed that it will take at least another 7-9 years for the replacement of the current in vivo animal tests used for the safety assessment of cosmetic ingredients for skin sensitisation. However, the experts were also of the opinion that alternative methods may be able to give hazard information, i.e. to differentiate between sensitisers and non-sensitisers, ahead of 2017. This would, however, not provide the complete picture of what is a safe exposure because the relative potency of a sensitiser would not be known. For toxicokinetics, the timeframe was 5-7 years to develop the models still lacking to predict lung absorption and renal/biliary excretion, and even longer to integrate the methods to fully replace the animal toxicokinetic models. For the systemic toxicological endpoints of repeated dose toxicity, carcinogenicity and reproductive toxicity, the time horizon for full replacement could not be estimated. PMID:21533817

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

2011-05-01

104

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

105

Transcranial alternating current stimulation: a review of the underlying mechanisms and modulation of cognitive processes.  

PubMed

Brain oscillations of different frequencies have been associated with a variety of cognitive functions. Convincing evidence supporting those associations has been provided by studies using intracranial stimulation, pharmacological interventions and lesion studies. The emergence of novel non-invasive brain stimulation techniques like repetitive transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS) now allows to modulate brain oscillations directly. Particularly, tACS offers the unique opportunity to causally link brain oscillations of a specific frequency range to cognitive processes, because it uses sinusoidal currents that are bound to one frequency only. Using tACS allows to modulate brain oscillations and in turn to influence cognitive processes, thereby demonstrating the causal link between the two. Here, we review findings about the physiological mechanism of tACS and studies that have used tACS to modulate basic motor and sensory processes as well as higher cognitive processes like memory, ambiguous perception, and decision making. PMID:23785325

Herrmann, Christoph S; Rach, Stefan; Neuling, Toralf; Strüber, Daniel

2013-01-01

106

An Analysis of Alternatives to New York City's Current Marijuana Arrest and Detention Policy  

PubMed Central

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

Johnson, Bruce D.; Golub, Andrew; Dunlap, Eloise; Sifaneck, Stephen J.

2008-01-01

107

Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes  

NASA Astrophysics Data System (ADS)

Alternating current (AC) loss and current carrying capacity are two of the most crucial considerations in large-scale power applications of high temperature superconducting (HTS) conductors. AC losses result in an increased thermal load for cooling machines, and thus increased operating costs. Furthermore, AC losses can stimulate quenching phenomena or at least decrease the stability margin for superconducting devices. Thus, understanding AC losses is essential for the development of HTS AC applications. The main focus of this dissertation is to make reliable total AC loss measurements and interpret the experimental results in a theoretical framework. With a specially designed magnet, advanced total AC loss measurement system in liquid nitrogen (77 K) has been successfully built. Both calorimetric and electromagnetic methods were employed to confirm the validity of the measured results and to have a more thorough understanding of AC loss in HTS conductors. The measurement is capable of measuring total AC loss in HTS tapes over a wide range of frequency and amplitude of transport current and magnetic field. An accurate phase control technique allows measurement of total AC loss with any phase difference between the transport current and magnetic field by calorimetric method. In addition, a novel total AC loss measurement system with variable temperatures from 30 K to 100 K was successfully built and tested. Understanding the dependence of AC losses on temperature will enable optimization of the operating temperature and design of HTS devices. As a part of the dissertation, numerical calculations using Brandt's model were developed to study electrodynamics and total AC loss in HTS conductors. In the calculations, the superconducting electrical behavior is assumed to follow a power-law model. In general, the practical properties of conductors, including field-dependence of critical current density Jc, n-value and non-uniform distribution of Jc, can be accounted for in the numerical calculations. The numerical calculations are also capable of investigating eddy current loss in the stabilizer and ferromagnetic loss in the substrate of YBa2Cu3O 7-delta (YBCO) coated conductor. AC loss characteristics and electrodynamics in several (Bi,Pb)2 Sr2Ca2Cu3Ox (Bi-2223) and YBCO tapes were studied experimentally and numerically. It was found that AC loss behavior Ax in HTS tapes is strongly affected by the sample parameters such as cross-section, structure, dimensions, critical current distribution as well as by operation parameters including temperature, frequency, the phase difference between transport current and magnetic field, the orientation of magnetic field. The Ni-5%W substrate in YBCO conductors generates some ferromagnetic loss but this loss component is significantly reduced by a small parallel DC magnetic field. At a given AC magnetic field B0, there is a temperature Tmax at which the magnetization loss is maximum. The design of HTS devices needs to be optimized to avoid operating at that temperature. In general, the total AC loss in HTS tapes is still high for many power device applications, especially for those that present a rather high AC applied magnetic field. The development of low loss conductors is therefore crucial for HTS large-scale applications.

Nguyen, Doan Ngoc

108

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

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Low- and medium-voltage circuits serving three-phase...STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving...

2010-07-01

109

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

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Low- and medium-voltage circuits serving portable...OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving...

2010-07-01

110

Measuring bioavailable copper using anodic stripping voltammetry  

SciTech Connect

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.

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

1996-11-01

111

Activity-dependent alternative splicing increases persistent sodium current and promotes seizure  

PubMed Central

Activity of voltage-gated Na channels (Nav) is modified by alternative splicing. However, whether altered splicing of human Nav’s contributes to epilepsy remains to be conclusively shown. We show here that altered splicing of the Drosophila Nav (paralytic, DmNav) contributes to seizure-like behaviour in identified seizure-mutants. We focus attention on a pair of mutually-exclusive alternate exons (termed K and L), which form part of the voltage sensor (S4) in domain III of the expressed channel. The presence of exon L results in a large, non-inactivating, persistent INap. Many forms of human epilepsy are associated with an increase in this current. In wildtype (WT) Drosophila larvae ~70-80% of DmNav transcripts contain exon L, the remainder contain exon K. Splicing of DmNav to include exon L is increased to ~100% in both the slamdance and easily-shocked seizure-mutants. This change to splicing is prevented by reducing synaptic activity levels through exposure to the antiepileptic phenytoin or the inhibitory transmitter GABA. Conversely, enhancing synaptic activity in WT, by feeding of picrotoxin, is sufficient to increase INap and promote seizure through increased inclusion of exon L to 100%. We also show that the underlying activity-dependent mechanism requires the presence of Pasilla, an RNA-binding protein. Finally, we use computational modelling to show that increasing INap is sufficient to potentiate membrane excitability consistent with a seizure phenotype. Thus, increased synaptic excitation favors inclusion of exon L which, in turn, further increases neuronal excitability. Thus, at least in Drosophila, this self-reinforcing cycle may promote the incidence of seizure. PMID:22623672

Lin, Wei-Hsiang; Günay, Cengiz; Marley, Richard; Prinz, Astrid A.; Baines, Richard A.

2012-01-01

112

Alternating-current induced thermal fatigue of gold interconnects with nanometer-scale thickness and width  

NASA Astrophysics Data System (ADS)

With dramatic reduction in sizes of microelectronic devices, the characteristic width and thickness of interconnects in large-scale integrated circuits have reached nanometer scale. Thermal fatigue damage of so small interconnects has attracted more and more attentions. In this work, thermal fatigue of Au interconnects, 35 nm thick and 0.1-5 ?m wide, is investigated by applying various alternating current densities to generate cycling temperature and strain in them. A multi-probe measuring system is installed in a scanning electron microscope and a probe-type temperature sensor is for the first time introduced into the system for real-time measuring the temperatures on the pads of the tested interconnects. A one-dimensional heat conduction equation, which uses measured temperatures on the pads as boundary conditions and includes a term of heat dissipation through the interface between the interconnect and the oxidized silicon substrate, is proposed to calculate the time-resolved temperature distribution along the Au interconnects. The measured fatigue lifetimes are presented versus current density and thermal cyclic strain, and the results show that narrower Au lines are more reliable. The failure mechanism of those Au interconnects differs from what is observed in thick interconnects with relatively larger grain size. Topography change caused by localized plasticity on the less-constrained surfaces of the interconnects have not been observed. Instead, grain growing and reorienting due to local temperature varying appear, and grain boundary migration and mergence take place during high temperature fatigue in such thin and narrow interconnects. These results seem to reflect a strain-induced boundary migration mechanism, and the damage morphology also suggests that fatigue of the interconnects with decreased grain size and film thickness is controlled by diffusive mechanisms and interface properties rather than by dislocation glide. Open circuit eventually took place by melting at a region of severely damage cross-sectional area with the grain growing and reorienting.

Sun, Lijuan; Ling, Xue; Li, Xide

2011-10-01

113

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.  

PubMed

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (?APPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different ?APPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in ?APPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. PMID:22229729

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-01

114

Multiple dual mode counter-current chromatography with variable duration of alternating phase elution steps.  

PubMed

The multiple dual mode (MDM) counter-current chromatography separation processes consist of a succession of two isocratic counter-current steps and are characterized by the shuttle (forward and back) transport of the sample in chromatographic columns. In this paper, the improved MDM method based on variable duration of alternating phase elution steps has been developed and validated. The MDM separation processes with variable duration of phase elution steps are analyzed. Basing on the cell model, analytical solutions are developed for impulse and non-impulse sample loading at the beginning of the column. Using the analytical solutions, a calculation program is presented to facilitate the simulation of MDM with variable duration of phase elution steps, which can be used to select optimal process conditions for the separation of a given feed mixture. Two options of the MDM separation are analyzed: 1 - with one-step solute elution: the separation is conducted so, that the sample is transferred forward and back with upper and lower phases inside the column until the desired separation of the components is reached, and then each individual component elutes entirely within one step; 2 - with multi-step solute elution, when the fractions of individual components are collected in over several steps. It is demonstrated that proper selection of the duration of individual cycles (phase flow times) can greatly increase the separation efficiency of CCC columns. Experiments were carried out using model mixtures of compounds from the GUESSmix with solvent systems hexane/ethyl acetate/methanol/water. The experimental results are compared to the predictions of the theory. A good agreement between theory and experiment has been demonstrated. PMID:24819018

Kostanyan, Artak E; Erastov, Andrey A; Shishilov, Oleg N

2014-06-20

115

Alternating current electrophoretic deposition of antibacterial bioactive glass-chitosan composite coatings.  

PubMed

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

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

2014-01-01

116

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

PubMed Central

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

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

2014-01-01

117

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

PubMed Central

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

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

2014-01-01

118

Demagnetization Treatment of Remanent Composite Microspheres Studied by Alternating Current Susceptibility Measurements  

PubMed Central

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

van Berkum, Susanne; Erné, Ben H.

2013-01-01

119

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

PubMed

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

van Berkum, Susanne; Erné, Ben H

2013-01-01

120

The effects of theta transcranial alternating current stimulation (tACS) on fluid intelligence.  

PubMed

The objective of the study was to explore the influence of transcranial alternating current stimulation (tACS) on resting brain activity and on measures of fluid intelligence. Theta tACS was applied to the left parietal and left frontal brain areas of healthy participants after which resting electroencephalogram (EEG) data was recorded. Following sham/active stimulation, the participants solved two tests of fluid intelligence while their EEG was recorded. The results showed that active theta tACS affected spectral power in theta and alpha frequency bands. In addition, active theta tACS improved performance on tests of fluid intelligence. This influence was more pronounced in the group of participants that received stimulation to the left parietal area than in the group of participants that received stimulation to the left frontal area. Left parietal tACS increased performance on the difficult test items of both tests (RAPM and PF&C) whereas left frontal tACS increased performance only on the easy test items of one test (RAPM). The observed behavioral tACS influences were also accompanied by changes in neuroelectric activity. The behavioral and neuroelectric data tentatively support the P-FIT neurobiological model of intelligence. PMID:24998643

Pahor, Anja; Jaušovec, Norbert

2014-09-01

121

Alternating current cloud point extraction on a microchip: a comprehensive study.  

PubMed

We present a comprehensive study of alternating current cloud point extraction (ACPE) on a microchip. ACPE is an extraction technique for preconcentration of membrane-associated biomolecules. To characterize and optimize ACPE, we carried out ACPE experiments under various experimental conditions including amplitude and frequency of applied voltages, flow velocity, and concentration of surfactant, analyte, and salt. We found that ACPE has an amplitude threshold (15 V(p-p)), above which the extraction was more efficient. The dependence of the extraction on frequency (>5 MHz) was insignificant. Efficient extraction was achieved when the velocity of the test solution was 0.10?0.67 mm s?¹ and the concentration of surfactant was 0.10?1.0%. In contrast, the extraction was independent of the concentration of analytes (0.20?20 ?mol dm?³). The technique was applicable to solutions with a salt concentration of 0.050?0.15 mol dm?³ under temperature control of the devices. Solution temperature in ACPE was also studied. These results provide guidelines for use of the ACPE technique in microfluidic chemical and biochemical analyses. PMID:23027025

Sasaki, Naoki; Takemura, Azusa; Sato, Kae

2012-11-01

122

Application of broadband alternating current magnetic susceptibility to the characterization of magnetic nanoparticles in natural materials  

NASA Astrophysics Data System (ADS)

A new method is proposed for characterizing magnetic particles by measuring low-field alternating current magnetic susceptibility at a number of frequency steps spanning four orders of magnitude, from 125 Hz to 512 kHz. This method was tested using natural samples with various grain size distributions, including basalt (Kilauea, Hawaii), loess and paleosol (Luochuan, China), tuff (Yucca Mountain, Nevada), granite (Minnesota Valley, Minnesota), and andesite (Sakurajima, Japan). The resulting frequency spectrum of magnetic susceptibility (FSMS) of the basalt, loess/paleosol, and tuff decreases with increasing frequency, but at different rates of decrease. The FSMS of the basalt is characterized by a monotonic decrease with increasing frequency over the entire range. The FSMS of the loess/paleosol and the tuff decreases more markedly than that of the basalt, which agrees with previous results showing that superparamagnetic particles are dominant in such material. Quantitative estimates using FSMSs allow reconstruction of characteristic grain size distributions and clearly identify differences in the distribution of superparamagnetic particles. The multidomain granite sample has no distinct frequency dependence, which is probably due to the smooth displacement of domain walls in the presence of the external field. In contrast, the FSMSs of the andesite samples exhibit maxima over a limited frequency range, between 16 and 128 kHz. This behavior, together with low-temperature measurements, can be accounted for by magnetic resonance of domain walls in the multidomain phenocrysts.

Kodama, Kazuto

2013-01-01

123

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

PubMed

A light-emitting diode structure, consisting of a p-GaN layer, a CdZnO/ZnO quantum-well (QW) structure, a high-temperature-grown ZnO layer, and a GaZnO layer, is fabricated. Under forward bias, the device effectively emits green-yellow light, from the QW structure, at the rim of device mesa. Under reverse bias, electrons in the valence band of the p-GaN layer move into the conduction band of the GaZnO layer, through a QW-state-assisted tunneling process, to recombine with the injected holes in the GaZnO layer, for emitting yellow-red and shallow ultraviolet light over the entire mesa area. Also, carrier recombination in the p-GaN layer produces blue light. By properly designing the thickness of the high-temperature grown ZnO layer, the emission intensity under forward bias can be controlled such that, under alternating-current operation at 60 Hz, the spatial and spectral mixtures of the emitted lights of complementary colors, under forward and reverse biases, result in white light generation based on persistence of vision. PMID:25490471

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

2014-11-15

124

Alternating current conductivity and dielectric relaxation of PANI:PVDF composites  

NASA Astrophysics Data System (ADS)

In this work, PANI:PVDF composites films were prepared with different PANI contents (p = 1, 2, 3, 4 and 5%). The resulting films were dried at various temperatures such as 30, 90 and 120 °C. The alternating current mechanisms and dielectric relaxation and of PANI:PVDF films were studied using complex impedance spectroscopy over a wide range of temperature (303-453 K) and a frequency range (1 kHz to 1 MHz). We found that the ac conductivity in PANI:PVDF composite is governed by correlated barrier hopping (CBH) model. In dielectric loss modulus study, two relaxation processes were identified. The first peak was associated to Maxwell Wagner-Sillas (MWS) relaxation whereas the second one which obtained at higher frequency was attributed to the ?c relaxation. For PANI:PVDF film which dried at 30 °C, the MWS relaxation appears only at higher temperature. The temperature dependence of ?c relaxation was suitably fitted according to Vogel Flucher Temman model whereas MWS relaxation follows Arrhenius type behavior. The effect of drying temperature on microstructure and phase crystallization of PVDF in the composites was carried out using atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. These results were used to find a reasonable correlation between microstructure and electrical properties.

Saïdi, Sami; Mannaî, Aymen; Bouzitoun, Mouna; Belhadj Mohamed, Abdellatif

2014-04-01

125

Rapid immunohistochemistry based on alternating current electric field for intraoperative diagnosis of brain tumors.  

PubMed

Rapid immunohistochemistry (R-IHC) can contribute to the intraoperative diagnosis of central nervous system (CNS) tumors. We have recently developed a new IHC method based on an alternating current electric field to facilitate the antigen-antibody reaction. To ensure the requirement of R-IHC for intraoperative diagnosis, 183 cases of CNS tumors were reviewed regarding the accuracy rate of diagnosis without R-IHC. The diagnostic accuracy was 90.7 % (166/183 cases) [corrected] in which definitive diagnoses were not provided in 17 cases because of the failure of glioma grading and differential diagnosis of lymphoma and glioma. To establish the clinicopathological application, R-IHC for frozen specimens was compared with standard IHC for permanent specimens. 33 gliomas were analyzed, and the Ki-67/MIB-1 indices of frozen specimens by R-IHC were consistent with the grade and statistically correlated with those of permanent specimens. Thus, R-IHC provided supportive information to determine the grade of glioma. For discrimination between glioma and lymphoma, R-IHC was able to provide clear results of CD20 and Ki-67/MIB-1 in four frozen specimens of CNS lymphoma as well as standard IHC. We conclude that the R-IHC for frozen specimens can provide important information for intraoperative diagnosis of CNS tumors. PMID:24807101

Tanino, Mishie; Sasajima, Toshio; Nanjo, Hiroshi; Akesaka, Shiori; Kagaya, Masami; Kimura, Taichi; Ishida, Yusuke; Oda, Masaya; Takahashi, Masataka; Sugawara, Taku; Yoshioka, Toshiaki; Nishihara, Hiroshi; Akagami, Yoichi; Goto, Akiteru; Minamiya, Yoshihiro; Tanaka, Shinya

2015-01-01

126

Control of the dielectric microrods rotation in liquid by alternating current electric field  

NASA Astrophysics Data System (ADS)

Microfluidics is a promising system for the manipulation of micro-nano particles and fluids. In this platform, alternating current (AC) electric field is usual an effective tool for the general particles control. However, traditional work paid more attention on the regular spherical particles with no obvious distinction when rotating, resulting in imprecise rotation speed calculation. In essence, non-spherical especially biocompatible particles are not only important for biology application but also significant for obtaining accurate rotating results. Hence, in this paper, SU-8, one of the most biocompatible materials was selected as the manipulation object. AC electric field is employed to rotate SU-8 microrods, in order to obtain a controllable rotation angle for both the accurate experimental results and biosensor applications. Firstly, Clausius-Mossotti(CM) factors frequency spectra with different surface conductance and medium conductivities are presented, thereby the theoretical formula is carried out, including both the torque and rotation velocity expressions of SU-8 microrods. Moreover, simulations for the electric field distribution are developed, indicating the rotating direction. Secondly, the quadrupole electrodes are used to generate rotating electric field, and the electrorotation of SU-8 microrods in different medium is carried out, showing that the particles rotate in the opposite direction of the electric field, meanwhile, the peak frequency increases with the conductivity increases. Finally, the experimental results are discussed and compared with theoretical analysis, and the comparison result shows that they have a good agreement. This work proposes an effective and controllable method to rotate microrods, showing extend application potentials in microelectronics and biosensors.

Ren, Yukun; Li, Bin; Jiang, Hongyuan

2014-05-01

127

Evaluation of vascular wall elasticity of human digital arteries using alternating current-signal photoplethysmography  

PubMed Central

Purpose A simple method of estimating arterial elasticity in the human finger using a volume-oscillometric technique with photoplethysmography was principally studied under the various effects of age, sex, and cold-stress stimulation for testing the capability of using this technique in arterial elasticity analysis. Methods Amplitude variations in the alternating current signal of the photoplethysmograph during a continuous change in transmural pressure were analyzed to obtain the blood pressure and the transmural pressure–relative volume difference relationship of the arteries. We first tested the effect of the occluding cuff size on the arterial elasticity analysis in eight subjects (ages 20–45 years) to obtain a suitable cuff size, resulting in the selection of a middle cuff with a 22 mm diameter. Blood pressure and arterial elasticity were measured in six groups of subjects separated into three age-groups of women and men (ages 20–25, 32–45, and over 50 years) for testing the effect of age and sex. Twelve subjects (ages 20–25 years) also had their blood pressure and arterial elasticity measured in three conditions under the influence of the cold-stress stimulation. Results Age, sex, and cold-stress stimulation had an impact on mean blood pressure (P < 0.0005, 0.025), whereas pulse pressure and heart rate were statistically unchanged by those factors. Furthermore, an advanced age (over 50 years) was found to induce an increase in relative volume difference values (P < 0.025) and upward shifting of the transmural pressure–relative volume difference relationships, whereas sex, level of mean blood pressure, and cold-stress stimulation had no influence on these forms of the index. Conclusion This study showed the usefulness of the relative volume difference as being a mean blood pressure-independent indicator for changes in arterial elasticity. PMID:23766653

Uangpairoj, Pichitra; Shibata, Masahiro

2013-01-01

128

Stoichiometry and Formation Constant Determination by Linear Sweep Voltammetry.  

ERIC Educational Resources Information Center

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)

Schultz, Franklin A.

1979-01-01

129

Radiation from large space structures in low earth orbit with induced alternating currents  

Microsoft Academic Search

Large conducting space structures in low Earth orbit will have a nonnegligible motionally induced potential across their structures. The induced current flow through the body and the ionosphere causes the radiation of Alfvén and lower hybrid waves. This current flow is taken to be ac, and the radiated power is studied as a function of the ac frequency. The current

D. E. Hastings; A. Barnett; S. Olbert

1988-01-01

130

Disposable copper-based electrochemical sensor for anodic stripping voltammetry.  

PubMed

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

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

2014-05-20

131

Current Status of Conducting Alternative Testing to Mammalian Toxicity Studies in the Japan Pharmaceutical Manufacturers Association  

Microsoft Academic Search

To measure the use of alternatives to in vivo mammalian toxicity studies dur- ing drug research and development, the Japan Pharmaceutical Manufacturers Association (JPMA) distributed a questionnaire to its 99 member companies, of which 85 responded and 50 (59%) of them had some experiences in using alter- natives to in vivo mammalian toxicity studies. The results show alternative methods have

Toshiaki Matsuzawa; Akira Koda; Masaharu Hashimato; Toshiji Igarashi

1998-01-01

132

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

EPA Science Inventory

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

133

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

PubMed Central

Purpose As a continuing effort to understand the mechanisms of alternating current (AC) transdermal iontophoresis and the iontophoretic transport pathways in the stratum corneum (SC), the objectives of the present study were to determine the interplay of AC frequency, AC voltage, and iontophoretic transport of ionic and neutral permeants across human epidermal membrane (HEM) and use AC as a means to characterize the transport pathways. Materials and Methods Constant AC voltage iontophoresis experiments were conducted with HEM in 0.10 M tetraethyl ammonium pivalate (TEAP). AC frequencies ranging from 0.0001 to 25 Hz and AC applied voltages of 0.5 and 2.5 V were investigated. Tetraethyl ammonium (TEA) and arabinose (ARA) were the ionic and neutral model permeants, respectively. In data analysis, the logarithm of the permeability coefficients of HEM for the model permeants was plotted against the logarithm of the HEM electrical resistance for each AC condition. Results As expected, linear correlations between the logarithms of permeability coefficients and the logarithms of resistances of HEM were observed, and the permeability data were first normalized and then compared at the same HEM electrical resistance using these correlations. Transport enhancement of the ionic permeant was significantly larger than that of the neutral permeant during AC iontophoresis. The fluxes of the ionic permeant during AC iontophoresis of 2.5 V in the frequency range from 5 to 1,000 Hz were relatively constant and were approximately 4 times over those of passive transport. When the AC frequency decreased from 5 to 0.001 Hz at 2.5 V, flux enhancement increased to around 50 times over passive transport. Conclusion While the AC frequency for achieving the full effect of iontophoretic enhancement at low AC frequency was lower than anticipated, the frequency for approaching passive diffusion transport at high frequency was higher than expected from the HEM morphology. These observations are consistent with a transport model of multiple barriers in series and the previous hypothesis that the iontophoresis pathways across HEM under AC behave like a series of reservoirs interconnected by short pore pathways. PMID:17703345

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

2008-01-01

134

Alternating current impedance spectroscopic analysis of biofunctionalized vertically-aligned silica nanospring surface for biosensor applications  

NASA Astrophysics Data System (ADS)

In this dissertation, a process of vertically-aligned (silica) nanosprings (VANS) based biosensor development is presented. Alternating current (AC) impedance spectroscopy has been used to analyze sensor response as a function of saline phosphate (SP) buffer and biological solutions. The sensor is a parallel plate capacitor consisting of two glass substrates coated with indium tin oxide (ITO), where the VANS [or randomly-aligned nanosprings (RANS)] grown on one substrate serve as the dielectric spacer layer. The response of a VANS device as a function of ionic concentration in SP buffer was examined and an equivalent circuit model was developed. The results demonstrated that VANS sensors exhibited greater sensitivity to the changes in SP concentration relative to the ITO sensors, which serve as controls. The biofunctionalized VANS surface via physisorption and the cross-linker method demonstrates the repeatability, specificity, and selectivity of the binding. The physisorption of biotinylated immunoglobulin G (B-IgG) onto the VANS surface simplifies the whole sensing procedure for the detection of glucose oxidase, since the avidin-conjugated glucose oxidase (Av-GOx) can directly be immobilized on the B-IgG. The cross linker method involves the covalent attachment of antibodies onto the functionalized VANS surface via imine bond. The experiments revealed that the VANS sensor response is solely the result of the interaction of target molecule i.e. mouse IgG with the probe layer, i.e. goat antimouse IgG (GalphaM IgG). It was determined that VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls above 100 Hz, which indicates that the addition of biomolecules inhibits the diffusion of ions and changes the effective dielectric response of the VANS via biomolecular polarization. The study of ionic transport in nanosprings suggested that conductance follows a scaling law. It was demonstrated that a VANS-based device exhibits a greater magnitude of change relative to the RANS device below 10 kHz, which has equivalent property of the ITO controls. This dissertation demonstrates the potential for VANS as a novel nanomaterial platform for the development of highly sensitive, selective, low cost, and label free biosensors.

Timalsina, Yukta P.

135

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

PubMed

Black disease is an acute disease of sheep and cattle. The pathogen is the obligate anaerobe, Clostridium novyi. Due to difficulties of anaerobic culturing in the country or disaster sites, a simple, rapid, and sensitive method is required. In this study, an electrochemical method, the cyclic voltammetry method, basing on loop-mediated isothermal amplification (LAMP), electrochemical ion bonding (positive dye, methylene blue), was introduced. DNA extracted from C. novyi specimens was amplified through the LAMP reaction. Then the products combined were with methylene blue, which lead to a reduction in the oxidation peak current (ipA) and the reduction peak current (ipC) of the cyclic voltammetry. The changes of ipA/ipC were real-time measured by special designed electrode, so the DNA was quantitatively detected. The results displayed that this electrochemical detection of C. novyi could be completed in 1-2 h with the lowest bacterial concentration of 10(2) colony forming units/mL, and high accuracy (96.5%), sensitivity (96%), and specificity (97%) compared to polymerase chain reation. The cyclic voltammetry method was a simple and fast method, with high sensitivity and high specificity, and has great potential to be a usable molecular tool for fast diagnosis of Black disease. PMID:24446342

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

2014-01-01

136

High-frequency alternating-current inductive heating in a toroidal stellarator  

Microsoft Academic Search

Inductive heating of a stellarator plasma at frequencies higher than the inverse of the resistive diffusion time is studied experimentally. Two magnetic field configurations are investigated: a classical stellerator and a doublestar-a stellarator with two large magnetic islands. Profiles of plasma density, temperature, and induced toroidal current are measured, and it is found that in both configurations the induced current

D. Wróblewski; J. L. Shohet

1987-01-01

137

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

Microsoft Academic Search

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,

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

2003-01-01

138

Fast determination of salbutamol, abused by athletes for doping, in pharmaceuticals and human biological fluids by square wave voltammetry  

Microsoft Academic Search

The determination of salbutamol, used for doping, has been carried out at nano gold particles modified indium tin oxide (NGITO) electrode using Osteryoung square wave voltammetry. The NGITO electrode exhibited an effective catalytic response towards salbutamol oxidation as compared to bare ITO and bulk gold electrodes. The peak current was also found to be significantly increased. The determination was carried

Rajendra N. Goyal; Munetaka Oyama; Sudhanshu P. Singh

2007-01-01

139

Inactivation of Bacillus subtilis Spores in Orange Juice and the Quality Change by High Electric Field Alternating Current  

Microsoft Academic Search

Heat treatment is commonly used to inactivate micro-organisms in liquid foods in order to improve food safety and extend shelf life. However, using heat treatment to kill spores also thermally damages the food, which can adversely affect the flavor and lead to loss of nutrients. We have developed an apparatus to apply a high electric field alternating current (HEF-AC) that

Kunihiko UEMURA; Isao KOBAYASHI; Takashi INOUE

2010-01-01

140

Radiation from an alternating current high-pressure mercury discharge: A comparison between experiments and model calculations  

Microsoft Academic Search

An alternating current (ac) high-pressure mercury arc has been experimentally investigated, and the results have been compared with model calculations. In the model, only radial dependencies are considered, and a careful treatment of the radiation transport is included. The absolutely measured side-on radiance in the visible and near ultraviolet spectral range can now be quantitatively reproduced by this model starting

G. Hartel; H. Schöpp; H. Hess; L. Hitzschke

1999-01-01

141

A study of second-year engineering students' alternative conceptions about electric potential, current intensity and Ohm's law  

Microsoft Academic Search

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. In order to find out what the students' alternative conceptions

M. Cristina Periago; Xavier Bohigas

2005-01-01

142

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

E-print Network

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— ...

Sekar, Ram C.

143

The diagnostic classification of eating disorders: current situation, possible alternatives and future perspectives.  

PubMed

The current nosography of eating disorders (ED) has various limitations in terms of validity and accuracy. The changes adopted in the DSM-5 limit some of the current problems, such as excessive prevalence of ED not otherwise specified (EDNOS) and the lack of longitudinal stability, but are unlikely to adequately capture the clinical complexity of ED. Many authors suggest the need for a thorough review of the current nosography to support evidence-based classification. In this paper, we discuss the validity of the current diagnostic categories and their possible reorganization. Furthermore, we review the main empirical models of classification and the diagnostic approach from a personality perspective, with particular attention to research and to the prognostic and therapeutic implications. PMID:24104389

Dazzi, F; Di Leone, F G

2014-03-01

144

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

Microsoft Academic Search

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

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

2007-01-01

145

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...

146

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

PubMed

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

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

2014-12-16

147

Assessing the Liquidity of Firms: Robust Neural Network Regression as an Alternative to the Current Ratio  

NASA Astrophysics Data System (ADS)

Artificial neural networks have proven to be useful tools for solving financial analysis problems such as financial distress prediction and audit risk assessment. In this paper we focus on the performance of robust (least absolute deviation-based) neural networks on measuring liquidity of firms. The problem of learning the bivariate relationship between the components (namely, current liabilities and current assets) of the so-called current ratio is analyzed, and the predictive performance of several modelling paradigms (namely, linear and log-linear regressions, classical ratios and neural networks) is compared. An empirical analysis is conducted on a representative data base from the Spanish economy. Results indicate that classical ratio models are largely inadequate as a realistic description of the studied relationship, especially when used for predictive purposes. In a number of cases, especially when the analyzed firms are microenterprises, the linear specification is improved by considering the flexible non-linear structures provided by neural networks.

de Andrés, Javier; Landajo, Manuel; Lorca, Pedro; Labra, Jose; Ordóñez, Patricia

148

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

ERIC Educational Resources Information Center

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…

Heller, Patricia; Finley, Fred

149

Assessment of Alternative Student Aid Delivery Systems: Assessment of the Current Delivery System.  

ERIC Educational Resources Information Center

The effects of the current system for delivering federal financial assistance to students under the Pell Grant, Guaranteed Student Loan (GSL), and campus-based programs are analyzed. Information is included on the use of the assessment model, which combines program evaluation, systems research, and policy analysis methodologies. "Baseline"…

Advanced Technology, Inc., Reston, VA.

150

Formula Apportionment: Is it better than the current system and are there better alternatives?  

Microsoft Academic Search

This analysis of formula apportionment compared to the current system is based on the observation that income shifting has two sources, intangible income and debt. The analysis also recognizes that a major goal of the transfer pricing or income allocation system is to preserve the tax neutrality between arm’s length and related party transactions and between multinational and single jurisdiction

Rosanne Altshuler; Harry Grubert

2009-01-01

151

Square wave voltammetry at the dropping mercury electrode: Experimental  

USGS Publications Warehouse

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.

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

1977-01-01

152

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

Microsoft Academic Search

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

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

1980-01-01

153

Frequency-dependent, alternating current-driven, field-induced polymer electroluminescent devices with high power efficiency.  

PubMed

A significant enhancement in power efficiency for alternating current-driven field-induced polymer electroluminescent devices is demonstrated by employing a high-k ferroelectric polymer dielectric through impedance matching of the device with the driving source. A peak power efficiency of 34.1 lm W(-1) at a frequency of 65 kHz is achieved, which is 2 to 12 times higher than the previous highest reports. PMID:25219753

Chen, Yonghua; Xia, Yingdong; Smith, Gregory M; Carroll, David L

2014-12-23

154

Compact-Size and High-Conversion-Efficiency Regulator for Alternating-Current-Operated Light-Emitting Diodes  

Microsoft Academic Search

A compact-size and high-conversion-efficiency regu- lator used to stabilize the luminous flux of alternating-current- operated light-emitting diodes (ACOLEDs) is proposed. The presented regulator is composed of a full-bridge rectifier and a power switch to supply directly from ac power source for the ACOLEDs without any ac\\/dc converter. Commonly adopted pulsewidth modulation techniques are utilized to regulate the in- put power

Yao-Te Huang; Yie-Tone Chen; Yi-Hwa Liu; Horng-Ching Hsiao; Wen-Tian Tsai

2011-01-01

155

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

NASA Technical Reports Server (NTRS)

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

Weidner, John W.

1991-01-01

156

Low Frequency Sound for Effective Sensitivity Enhancement in Staircase Voltammetry  

Microsoft Academic Search

The success of improving the sensitivity in differential pulse anodic stripping voltammetry by exposure of low frequency sound has been reported in earlier papers.It has been found that audible sound in the low frequency range, of about 100 Hz or lower is very effective for this purpose, with an increase of the signal up to about 300%, without any significant

Ø. Mikkelsen; K. Schrøder

2000-01-01

157

Including Alternative Resources in State Renewable Portfolio Standards: Current Design and Implementation Experience  

SciTech Connect

Currently, 29 states, the District of Columbia, and Puerto Rico have instituted a renewable portfolio standard (RPS). An RPS sets a minimum threshold for how much renewable energy must be generated in a given year. Each state policy is unique, varying in percentage targets, timetables, and eligible resources. This paper examines state experience with implementing renewable portfolio standards that include energy efficiency, thermal resources, and non-renewable energy and explores compliance experience, costs, and how states evaluate, measure, and verify energy efficiency and convert thermal energy. It aims to gain insights from the experience of states for possible federal clean energy policy as well as to share experience and lessons for state RPS implementation.

Heeter, J.; Bird, L.

2012-11-01

158

Effect of dual gate control on the alternating current performance of graphene radio frequency device  

NASA Astrophysics Data System (ADS)

The excellent electrical properties of graphene, such as its high carrier mobility, gate tunability, and mechanical flexibility makes it a very promising material for radio frequency (RF) electronics. Here we study the impact of top and bottom gate control on the essential performance metrics of graphene RF transistors. We find that the maximum cut-off frequency improves as the bottom gate voltage is tuned towards the same polarity as the top gate bias voltage. These results can be explained by the bottom-gate tunable doping of the graphene underneath the metal contacts and in the under-lap region. These effects become more dramatic with device down-scaling. We also find that the minimum output conductance occurs, when the drain voltage roughly equals an effective gate voltage (Veff?VTG+VBG?CBG/CTG, where VTG and VBG are top and bottom gate voltage, CTG and CBG are the respective gate capacitance). The minimum output conductance is reduced as the bottom gate bias increases, due to the stronger control of the channel from the bottom gate, lessening the influence of the drain voltage on the drain current. As a result of these two influences, when the bottom gate voltage is tuned towards the same polarity as the top gate voltage, both the maximum oscillation frequency (fmax) and the intrinsic gain significantly improve. The intrinsic gain can increase as high as 3-4 times as the gain without the bottom gate bias. Tuning the bottom gate to enhance fmax and gain will be very important elements in the effort to enable graphene RF devices for practical use.

Zhu, Wenjuan; Low, Tony; Farmer, Damon B.; Jenkins, Keith; Ek, Bruce; Avouris, Phaedon

2013-07-01

159

Dynamic microparticle manipulation with an electroosmotic flow gradient in low-frequency alternating current dielectrophoresis.  

PubMed

In this study, the potential of low-frequency AC insulator-based DEP (iDEP) was explored for the separation of polystyrene microparticles and yeast cells. An EOF gradient was generated by employing an asymmetrical, 20 Hz AC electrical signal in an iDEP device consisting of a microchannel with diamond-shaped insulating posts. Two types of samples were analyzed, the first sample contained three types of polystyrene particles with different diameters (0.5, 1.0, and 2.0 ?m) and the second sample contained two types of polystyrene particles (1.0 and 2 ?m) and yeast cells (6.3 ?m). This particular scheme uses a tapered AC signal that allows for all particles to be trapped and concentrated at the insulating post array, as the signal becomes asymmetrical (more positive), particles are selectively released. The smallest particles in each sample were released first, since they require greater dielectrophoretic forces to remain trapped. The largest particles in each sample were released last, when the applied signal became cyclical. A dielectropherogram, which is analogous to a chromatogram, was obtained for each sample, demonstrating successful separation of the particles by showing "peaks" of the released particles. These separations were achieved at lower applied potentials than those reported in previous studies that used solely direct current electrical voltages. Additionally, mathematical modeling with COMSOL Multiphysics was carried out to estimate the magnitude of the dielectrophoretic and EOF forces acting on the particles considering the low-frequency, asymmetrical AC signal used in the experiments. The results demonstrated the potential of low-frequency AC-iDEP systems for handling and separating complex mixtures of microparticles and biological cells. PMID:24166858

Gencoglu, Aytug; Olney, David; LaLonde, Alexandra; Koppula, Karuna S; Lapizco-Encinas, Blanca H

2014-02-01

160

Internal heating of lithium-ion batteries using alternating current based on the heat generation model in frequency domain  

NASA Astrophysics Data System (ADS)

This study develops a method to internally preheat lithium-ion batteries at low temperatures with sinusoidal alternating current (AC). A heat generation rate model in frequency domain is developed based on the equivalent electrical circuit. Using this model as the source term, a lumped energy conservation model is adopted to predict the temperature rise. These models are validated against the experimental results of preheating an 18650 cell at different thermal insulation conditions. The effects of current amplitude and frequency on the heating rate are illustrated with a series of simulated contours of heating time. These contours indicate that the heating rate increases with higher amplitude, lower frequency and better thermal insulation. The cell subjected to an alternating current with an amplitude of 7 A (2.25 C) and a frequency of 1 Hz, under a calibrated heat transfer coefficient of 15.9 W m-2 K-1, can be heated from -20 °C to 5 °C within 15 min and the temperature distribution remains essentially uniform. No capacity loss is found after repeated AC preheating tests, indicating this method incurs little damage to the battery health. These models are computationally-efficient and can be used in real time to control the preheating devices in electric vehicles.

Zhang, Jianbo; Ge, Hao; Li, Zhe; Ding, Zhanming

2015-01-01

161

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

PubMed Central

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

Guan, Yong-Song; He, Qing

2013-01-01

162

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

PubMed

Anodic stripping voltammetry (ASV) of colloidal gold-nanoparticles (AuNPs) was investigated at boron-doped diamond (BDD) electrodes in 50 mM HClO4. A deposition time of 300 s at-0.2 V (vs. Ag/AgCl) was fixed as the condition for the ASV. The voltammograms showed oxidation peaks that could be attributed to the oxidation of gold. These oxidation peaks were then investigated for potential application in immunochromatographic strip tests for the selective and quantitative detection of melamine, in which AuNPs were used as the label for the antibody of melamine. Linear regression of the oxidation peak currents appeared in the concentration range from 0.05-0.6 ?g/mL melamine standard, with an estimated LOD of 0.069 ?g/mL and an average relative standard deviation of 8.0%. This indicated that the method could be considered as an alternative method for selective and quantitative immunochromatographic applications. The validity was examined by the measurements of melamine injected into milk samples, which showed good recovery percentages during the measurements. PMID:25618650

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

2015-03-01

163

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

E-print Network

Zinc Detection in Serum by Anodic Stripping Voltammetry on Microfabricated Bismuth Electrodes reports on detection of Zn by anodic stripping voltammetry (ASV) on bismuth electrodes in a microfabricated electrochemical cell. The work- ing potential window of the electrodeposited bismuth film

Papautsky, Ian

164

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

SciTech Connect

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.

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

2011-06-23

165

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

SciTech Connect

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.

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

2005-12-01

166

Thin-film voltammetry and its analytical applications: a review.  

PubMed

Electrochemical reactions at the interfaces of immiscible electrolyte solutions (ITIES) are of fundamental importance in the fields of chemical, biological and pharmaceutical sciences. Four-electrode cell setup, scanning electrochemical microscopy (SECM) and thin-film voltammetry are the three most frequently used methods for studying the electrochemical processes at these interfaces. The principle, experimental design, advantages and challenges of the three methods are described and compared. The thin-film voltammetry is highlighted for its simplicity in experimental operation and kinetic data analysis. Its versatile analytical applications are discussed in detail, including the study of redox properties of hydrophobic compounds, evaluation of interfacial electron transfer kinetics, synthesis of nanoparticles/nanostructures, and illustration of cross-membrane ion transport phenomena. PMID:25542084

Tian, Huihui; Li, Yunchao; Shao, Huibo; Yu, Hua-Zhong

2015-01-15

167

An alternative to current psychiatric classifications: a psychological landscape hypothesis based on an integrative, dynamical and multidimensional approach  

PubMed Central

Background Mental disorders as defined by current classifications are not fully supported by scientific evidence. It is unclear whether main disorders should be broken down into separate categories or disposed along a continuous spectrum. In the near future, new classes of mental disorders could be defined through associations of so-called abnormalities observed at the genetic, molecular and neuronal circuitry levels. Methods We propose an alternative hypothesis to these classifications based on an integrative, dynamical and multidimensional approach. Results We suggest that observed data collected in the general population can be used to build a psychological landscape. Innovative techniques issued from information processing and system dynamics can prove helpful in this task. Information preserving techniques can reduce the high dimensional data collected and provide an intrinsic map for psychological characteristics or behaviors. Dynamical patterns called attractors, which are linked to each other through continuous pathways, can be identified. Specific attractors can define mental disorders. Their causal structure can be investigated with causal networks. Conclusions Powerful and reliable tools are available so that an alternative to current psychiatric classifications can be built based on a genuine biopsychosocial model. The proposed model is ready to be tested on real data. PMID:25033795

2014-01-01

168

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

SciTech Connect

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.

Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria); Bruno, Emanuela [Dipartimento di Fisica, Università della Calabria, Via Pietro Bucci, Cubo 31C, 87036 Rende (CS) (Italy); Marino, Lucia, E-mail: lucia.marino@fis.unical.it [CNR-IPCF UoS di Cosenza, Licryl Laboratory, and Centro di Eccellenza CEMIF.CAL, Università della Calabria, 87036 Rende (CS) (Italy); Scaramuzza, Nicola [Dipartimento di Fisica, Università della Calabria, Via Pietro Bucci, Cubo 31C, 87036 Rende (CS) (Italy); CNR-IPCF UoS di Cosenza, Licryl Laboratory, and Centro di Eccellenza CEMIF.CAL, Università della Calabria, 87036 Rende (CS) (Italy)

2014-02-28

169

Concentric rings of polystyrene and titanium dioxide nanoparticles patterned by alternating current signal guided coffee ring effect  

NASA Astrophysics Data System (ADS)

The authors studied the surface deposition of nanoparticles by introducing an alternating current (AC) signal into the millimeter-sized nanoparticle droplet. For both polystyrene (PS) in deionized (DI) water and titanium dioxide (TiO2) in toluene, the nanoparticles self-assembled into regular concentric rings over a larger area on the substrate during the droplet drying process. The patterned area decreased, and the inter-ring spacing increased with higher AC frequencies for the TiO2/toluene system, while those for the PS/DI water system only changed slightly. The frequency dependent pattern formation was interpreted by the interaction between different factors such as capillary flow and the AC signal introduced dielectrophoresis force.

Mu, Jinhua; Lin, Peng; Xia, Qiangfei

2014-06-01

170

Elicitors as alternative strategy to pesticides in grapevine? Current knowledge on their mode of action from controlled conditions to vineyard.  

PubMed

Development and optimisation of alternative strategies to reduce the use of classic chemical inputs for protection against diseases in vineyard is becoming a necessity. Among these strategies, one of the most promising consists in the stimulation and/or potentiation of the grapevine defence responses by the means of elicitors. Elicitors are highly diverse molecules both in nature and origins. This review aims at providing an overview of the current knowledge on these molecules and will highlight their potential efficacy from the laboratory in controlled conditions to vineyards. Recent findings and concepts (especially on plant innate immunity) and the new terminology (microbe-associated molecular patterns, effectors, etc.) are also discussed in this context. Other objectives of this review are to highlight the difficulty of transferring elicitors use and results from the controlled conditions to the vineyard, to determine their practical and effective use in viticulture and to propose ideas for improving their efficacy in non-controlled conditions. PMID:23719689

Delaunois, Bertrand; Farace, Giovanni; Jeandet, Philippe; Clément, Christophe; Baillieul, Fabienne; Dorey, Stéphan; Cordelier, Sylvain

2014-04-01

171

A new laser direct etching method of indium tin oxide electrode for application to alternative current plasma display panel  

NASA Astrophysics Data System (ADS)

For cost effective fabrication and time of alternative current plasma display panels (AC PDPs), an indium tin oxide (ITO) layer was patterned directly with a Q-switched diode pumped Nd:YVO 4 laser ( ? = 1064 nm). As experimental results, 500 mm/s scan speed with 40 kHz repetition rate was suitable for the application to AC PDP ITO electrode. In comparison with the chemically wet-etched ITO patterns by photolithography method, laser-ablated ITO patterns showed the formation of shoulders at the edge of the ITO lines and a ripple-like structure of the etched bottom. By dipping the laser-ablated ITO films in the chemical etching solution for 30 s at 50 °C, the shoulders were effectively removed without affecting the discharging properties of AC PDP.

Li, Zhao Hui; Cho, Eou Sik; Kwon, Sang Jik

2009-09-01

172

Signature of cluster disruption within magnetic fluid samples: The key information provided by low frequency alternating current susceptibility measurements  

NASA Astrophysics Data System (ADS)

This paper is focused on the signature of thermal-assisted cluster disruption while analyzing the inverse alternating current (AC) susceptibility (1/?) versus temperature (T) curves recorded at lower AC frequencies (f), below 300 Hz. A commercial oil-based magnetic fluid (MF) sample was used in the experiments to investigate the critical temperature (T*) that characterizes the thermal disruption of aggregates suspended within the MF sample. T* was found to reduce as f increased within the frequency range of our investigation (63-263 Hz). Furthermore, T* was found to scale with the square of the applied AC frequency. Both theoretical and experimental evidences support that the excitation field frequency (f) dependence of the critical temperature (T*) is well described by T*(f)=T*(0)-Af/21+Bf2. The model is based on energy absorption of magnetic nanoparticles in an AC magnetic field.

Du, Zhongzhou; Liu, Wenzhong; Zhong, Jing; Zhou, Ming; Zhang, Pu; Cesar Morais, Paulo

2014-05-01

173

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

SciTech Connect

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.

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

1998-06-01

174

An alternative analysis of low- and high-altitude observations of ring current ions during a storm recovery phase  

NASA Technical Reports Server (NTRS)

Explorer 45 equatorial observations of ring current ions during a storm recovery phase have shown pitch angle distributions and decay rates inconsistent with proton charge exchange with neutral hydrogen. This inconsistency has led to the suggestion that recovery phase ring current ions at L less than or equal to 4 and energies not greater than 50 keV are dominated by He(+) rather than protons. The absence of He(+) on flux tubes from which H(+) and O(+) were precipitating in ion mass spectrometer measurements made during the same period by the low-altitude polar-orbiting satellite 1971-089A led Sharp et al. to suggest a source of H(+) and O(+) to L = 3 during this period. An alternative explanation, in which the magnetic field lines labeled L = 3 at the earth's surface near local midnight were mapped to about 3.7 earth radii in the equatorial plane during the storm recovery phase and during the period of enhanced activity, is proposed. If the proposed explanation is correct, the observations of Sharp et al. are not incompatible with the conclusion that the recovery phase ions at less than 50 keV were dominated by He(+) for L not greater than 3.7.

Lyons, L. R.

1977-01-01

175

Changes in Na+, K+ concentrations in perspiration and perspiration volume with alternating current iontophoresis in palmoplantar hyperhidrosis patients.  

PubMed

Various treatments are currently available for palmoplantar hyperhidrosis. We have treated palmoplantar hyperhidrosis patients effectively with the use of alternating current (AC) iontophoresis. However, much remains unknown about the physiological changes that occur with AC iontophoresis, and its mechanism of action. We measured the changes in Na(+), K(+) concentration in perspiration and perspiration volume with AC iontophoresis in palmoplantar hyperhidrosis patients. We found that hyperhidrosis patients have significantly higher perspiration volume and Na(+) concentration in perspiration than healthy controls. Looking at the temporal changes with AC iontophoresis, we found a significant decrease in perspiration volume and Na(+) concentration in perspiration after six iontophoresis treatments. This result is further evidence that Na(+) concentration in perspiration is closely involved with perspiration volume. However, looking at the changes in perspiration volume and Na(+) concentration in perspiration before and after a single AC iontophoresis treatment, we found that while perspiration volume did not decrease in hyperhidrosis patients after a single treatment, there was a significant decrease in Na(+) concentration. In healthy controls as well, Na(+) concentration in perspiration decreased significantly after a single treatment. These findings suggest that the effect of AC iontophoresis may be due to a complex mechanism involving changes in reabsorption of ductal Na(+). PMID:18677499

Ohshima, Yuichiro; Shimizu, Hirokazu; Yanagishita, Takeshi; Watanabe, Daisuke; Tamada, Yasuhiko; Sugenoya, Junichi; Tsuda, Takao; Matsumoto, Yoshinari

2008-11-01

176

Aneurysm Sac Pressure Measurement with Minimally Invasive Implantable Pressure Sensors: An Alternative to Current Surveillance Regimes after EVAR?  

SciTech Connect

Current protocols for surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms are mostly based on costly and time-consuming imaging procedures and aim to detect adverse events such as graft migration, endoleaks or aneurysm sac enlargement. These imaging procedures are either associated with radiation exposure to the patients or may be harmful to the patient due to the use of iodine- or gadolinium-containing contrast agents. Furthermore the advantages of EVAR in the short term might be negated by the necessity for endograft surveillance over years. Thus, alternative modalities for follow-up are being investigated. One of these technologies provides pressure information directly from the aneurysm sac. This noninvasive, telemetric pressure sensing was tested in vitro as well as in first clinical trials and was able to identify successful aneurysm exclusion after EVAR. The telemetric pressure sensors showed a promising efficacy and accuracy in detecting type I and type III endoleaks and will help to clarify the clinical relevance of type II endoleaks. This article provides an overview of the in vitro sensors investigated as well as the first clinical trials and the sensors' potential to change the current endograft surveillance regimes.

Springer, Fabian [Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Applied Medical Engineering (Germany)], E-mail: fabian.springer@med.uni-tuebingen.de; Guenther, Rolf W. [University Hospital RWTH Aachen University, Department of Diagnostic Radiology (Germany); Schmitz-Rode, Thomas [Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Applied Medical Engineering (Germany)

2008-05-15

177

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

PubMed

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

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

178

Cyclic voltammetry of aquocobalamin on clay-modified electrodes  

SciTech Connect

Halogenated synthetic compounds are widespread contaminants of the environment. Although corrinoids reductively dehalogenate synthetic contaminants in solution, the redox behavior of sorbed tetrapyrroles has received limited attention. Colloidal clay suspensions were prepared as Ca{sup 2+} forms of hectorite (SHCa-1), montmorillonite (SWy-1, Syn-1, and SAz-1), and vermiculite (VTx-1) and spin coated on platinum electrodes. Cyclic voltammetry was performed with the clay-modified electrodes immersed in buffered solutions containing 1.0 mM aquocobalamin. Aquocobalamin in the presence of vermiculite-coated electrodes displayed the same cathodic and anodic peak potentials as unmodified electrodes immersed in aquocobalamin solutions. All other clay-modified electrodes shifted cathodic peaks to more negative values, while anodic peak shifts varied with the clay. Hectorite caused the largest shift in formal redox potential as compared to aquocobalamin in solution. The redox behavior of aquocobalamin as modified by sorption to clay minerals potentially affects dehalogenation rates of synthetic organic compounds in the environment. Clays lowering the formal redox potential of the tetrapyrrole create a potentially more efficient catalyst for pollutant degradation. However, thermodynamic data as obtained using cyclic voltammetry cannot be used to make definitive predictions about the kinetics of contaminant dehalogenation. Reductive dehalogenation will be a function of altered electrochemical properties of the tetrapyrrole as well as rates of contaminant diffusion to the site of tetrapyrrole sorption.

Borek, V.; Morra, M.J. [Univ. of Idaho, Moscow, ID (United States). Soil Science Div.] [Univ. of Idaho, Moscow, ID (United States). Soil Science Div.

1998-07-15

179

Significant sensitivity improvement of alternating current driven-liquid discharge by using formic acid medium for optical determination of elements.  

PubMed

A method has been developed to improve the performance of alternating-current electrolyte atmospheric liquid discharge (ac-EALD) optical emission spectrometry for the determination of elements. Significant enhancement of emission intensity was achieved by adding organic substance into the nitric acid electrolyte solutions. Under the optimized conditions, 3% (v/v) formic acid in nitric acid (pH 1.0) produced 13 times enhancement for Ag and 7% (v/v) formic acid resulted in 17 times enhancement for Cd. The emission of Pb was even enhanced 78 times in the presence of 3% formic acid. In addition, the signal stability was also improved compared with that in the absence of organic substances. Repeatability was 0.8% for 0.1 mg L(-1) Ag, 0.7% for 0.2 mg L(-1) Cd and 2.6% for 1 mg L(-1) Pb standard solutions (n=5). The limits of detection of Ag, Cd and Pb were 1, 17 and 45 ?g L(-1), respectively. The accuracy of the method was demonstrated by determination of elements in simulated natural water samples (GBW(E)080402 and GBW(E)080399). PMID:23598107

Xiao, Qing; Zhu, Zhenli; Zheng, Hongtao; He, Haiyang; Huang, Chunying; Hu, Shenghong

2013-03-15

180

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

SciTech Connect

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.

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

181

Laser direct patterning of the T-shaped ITO electrode for high-efficiency alternative current plasma display panels  

NASA Astrophysics Data System (ADS)

The laser direct patterning technique is one of the new methods of direct etching process to replace the conventional photolithography. In this experiment, a Q-switched diode-pumped Nd:YVO 4 ( ? = 1064 nm) laser was used to produce the indium-tin oxide (ITO) patterns with a complex T-shaped structure on glass substrate. The results showed that the overlapping rate of laser beam had a major effect on the quality of the edge of the ITO electrode. When the overlapping rate was about 75%, it was possible to obtain optimum linearity in the edge of patterned ITO electrode. By using the optimum conditions of 75% overlapping rate, 500 mm/s scanning speed, and 40 kHz repetition rate, an alternative current plasma display panels (AC PDPs) with T-shaped ITO electrode was fabricated and characterized. The discharging results showed that the AC PDPs with the laser ablated T-shaped ITO electrode had a better discharging characteristics compared to the conventional sample with wet-etched stripe-type ITO electrode.

Li, Zhao-Hui; Cho, Eou Sik; Kwon, Sang Jik

2010-11-01

182

Hot-electron impact excitation of ZnS:Tb alternating-current thin-film electroluminescent devices  

NASA Astrophysics Data System (ADS)

A new method of performing hot-electron impact excitation experiments using alternating-current thin-film electroluminescent (ACTFEL) devices is reported. This method relies on the use of a field-control circuit to control the magnitude of the phosphor field and consists of plotting the intensity of a given electroluminescence transition, normalized by the amount of conduction charge which flows while the field-control circuit is asserted (the electroluminescence intensity of a given transition divided by the conduction charge is denoted the impact excitation quantum yield ?ie), as a function of the phosphor field Fp. ?ie vs Fp is measured for ZnS:Tb ACTFEL devices fabricated by atomic layer epitaxy (ALE) and by sputtering. ?ie exhibits a threshold at approximately 0.5 MV/cm and saturation at approximately 1.5 MV/cm. The magnitude of ?ie for the ALE ACTFEL device depends strongly on temperature; in contrast, ?ie for the sputtered ACTFEL device is virtually temperature independent.

Streicher, K.; Plant, T. K.; Wager, J. F.

1995-08-01

183

Electrochemical characterization of bronze historical objects using voltammetry of microparticles  

NASA Astrophysics Data System (ADS)

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.

Elia, Alice; Dowsett, Mark; Adriaens, Annemie

2015-02-01

184

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

PubMed

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

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

2014-10-01

185

386 Anal. Chem. 1987, 59,386-389 Square Wave Anodic Stripping Voltammetry at the Mercury  

E-print Network

386 Anal. Chem. 1987, 59,386-389 Square Wave Anodic Stripping Voltammetry at the Mercury Film treatment of square wave anodic stripping voltammetry at a mercury film electrode Is presented. Nu- merlcal) frequency ( f ) and amount of metal depostted In the mercury layer (9R) and glves a response 6 tlmes

Kounaves, Samuel P.

186

Assessment of Alternative Student and Delivery Systems: Assessment of the Current Delivery System. Supplement I to the Final Report.  

ERIC Educational Resources Information Center

The effects of the current student financial aid delivery system on five major participant groups are examined: federal government, states/guarantee agencies, postsecondary institutions, lenders and secondary markets, and applicants and families. Attention is directed to effects of the current system, including: administrative costs, fund…

Advanced Technology, Inc., Reston, VA.

187

Cyclic voltammetry and RBS study of paint components  

NASA Astrophysics Data System (ADS)

Heavy metals and metalloid ions are found in environmental matrices. The most toxic are lead, cadmium and mercury. These three heavy metals have no biological function and are toxic at all concentrations. Lead is one of the most insidious heavy metals and is introduced into the environment by many different means. It persists in both urban and rural settings, being found in paint chips, pottery, crystal and pharmaceutical and nutritional products. The analysis of heavy elements such as lead in soil is of particular importance [W.T. Sturges, R.M. Harrison, Sci. Total Environ. 44 (3) (1985) 225; M.L. Lepow, L. Bruckman, M. Gillette, S. Markowitz, R. Robino, J. Kapish, Environ. Res. 10 (3) (1975) 415; A.E. Daniels, J.R. Kominsky, P.J. Clark, J. Hazard. Mater. B 87 (2001) 117; G. Hutter, D. Moshman, J. Hazard. Mater. 40 (1995) 1]. In preparing the methods for lead detection in paint, we have used Rutherford backscattering spectrometry (RBS) in order to study the type and amount of heavy metal content in paint samples collected at various sites in the historic campus at A&M University (AAMU). We will show the results of our study with emphasis on comparison of what we learned about presence of lead in paints using our ion beam methods compared with the analysis of lead in paints using cyclic voltammetry.

Bowman, Lynn; Spencer, Dirk; Muntele, Claudiu; Muntele, Iulia; Ila, D.

2007-08-01

188

Fully printed flexible and disposable wireless cyclic voltammetry tag  

NASA Astrophysics Data System (ADS)

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.

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

189

Fully printed flexible and disposable wireless cyclic voltammetry tag  

PubMed Central

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

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

190

Fully printed flexible and disposable wireless cyclic voltammetry tag.  

PubMed

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

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

191

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

E-print Network

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

Nagy, Peter B.

192

A Regional Survey of Health Insurance Coverage for Complementary and Alternative Medicine: Current Status and Future Ramifications  

Microsoft Academic Search

Objective: The purpose of this survey is to evaluate the extent of health insurance coverage for complementary and alternative medicine (CAM) within one region in the United States, a study prompted by the increased utilization of CAM. Design: Prospective telephone interview of health insurance representatives. Location:A contiguous three-state area (New York, New Jersey, and Connecticut) in the North- east. Results:

Maria B. Cleary-Guida; Heather A. Okvat; Mehmet C. Oz; Windsor Ting

2001-01-01

193

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

PubMed Central

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

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

2013-01-01

194

Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative  

Microsoft Academic Search

The control of water pollution has become of increasing importance in recent years. The release of dyes into the environment constitutes only a small proportion of water pollution, but dyes are visible in small quantities due to their brilliance. Tightening government legislation is forcing textile industries to treat their waste effluent to an increasingly high standard. Currently, removal of dyes

Tim Robinson; Geoff McMullan; Roger Marchant; Poonam Nigam

2001-01-01

195

Analysis of the differential (alternating current) technique for measuring Young's modulus during ultra-low load indentation  

Microsoft Academic Search

of the indentor about its mean position x relative to the displacement gauge built into the tester. Knowledge of 6Po and 6xo and of the dynamic characteristics of the tester permits determination of the current value of the stiffness S of the contact between the indentor and the specimen, and from S it is possible to obtain a useful estimate

E. Söderlund; N. H. MacMillan

1991-01-01

196

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

ERIC Educational Resources Information Center

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.…

Periago, M. Cristina; Bohigas, Xavier

2005-01-01

197

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

E-print Network

of metal/dielectric/GaN:Er/ dielectric were fabricated on p -Si substrates. In contrast to previous GaN direct current dc operation of GaN:Er films grown on crys- talline Si and sapphire substrates. GaN-nitride'' ac­TFEL using Si3N4 or AlN dielectric layers, and the GaN phosphor . The electroluminescent devices

Steckl, Andrew J.

198

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

E-print Network

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 ...

Fitzgerald, William Francis, 1926-

1970-01-01

199

Influence of ZrO2 addition on the microstructure and discharge properties of Mg-Zr-O protective layers in alternating current plasma display panels  

Microsoft Academic Search

Mg-Zr-O protective layers for alternating current plasma display panels were deposited by e-beam evaporation. The effect of the ZrO2 addition on both the discharge properties [firing voltage Vf, minimum sustaining voltage Vs, and memory coefficient (MC)] and the microstructure of deposited Mg-Zr-O films were investigated. The results show that the film microstructure changes and the electron emission enhancement due to

Bingang Guo; Chunliang Liu; Zhongxiao Song; Liu Liu; Yufeng Fan; Xing Xia; Duowang Fan

2005-01-01

200

Determination of arsenic in polluted waters by differential pulse anodic-stripping voltammetry.  

PubMed

Experimental parameters affecting the analytical response of arsenic in differential pulse anodic-stripping voltammetry (DPASV) have been examined. DPASV offers higher sensitivity than linear-scan anodic-stripping voltammetry for similar analysis times. Both techniques have been applied to the NBS Standard Reference Water (SRM 1643) and some polluted water samples. The results on polluted waters compared favourably with those obtained by graphite-furnace atomic-absorption spectroscopy. PMID:18963176

Leung, P C; Subramanian, K S; Méranger, J C

1982-06-01

201

Nitrite detection in meat products samples by square-wave voltammetry at a new single walled carbon naonotubes - myoglobin modified electrode.  

PubMed

A new modified electrode was realized in a simple way, consisting by the immobilization of a myoglobin (My) - single walled carbon nanotubes (SWCNT) mixture on the surface of a graphite electrode with a Nafion film. The cyclic voltammetry investigations realized with the obtained electrode (G/My-SWCNT/Nafion) showed a voltammetric signal due to a one-step redox reaction of the surface-confined myoglobin, in a deaerated 0.1M phosphate buffer, pH 7. Also, the G/My-SWCNT/Nafion modified electrode demonstrated a great potential for the analytical determination of nitrite ions by square-wave voltammetry and an alternative for the already existing methods. The use of the sensor for the detection of nitrite ions in samples of meat products leads to comparable results with those obtained with the standard Griess spectrophotometric assay (ISO 2918/1975), proving the suitability of using immobilized myoglobin as electrocatalyst in the nitrite reduction process. PMID:25722172

Turdean, Graziella L; Szabo, Gabriella

2015-07-15

202

A study of the interaction tyrosine and DNA using voltammetry and spectroscopy methods.  

PubMed

The interaction of tyrosine (Tyr) with double stranded DNA was studied by cyclic voltammetry, fluorescence emission spectroscopy, and UV-vis spectroscopy. The presence of DNA on a single-walled carbon nanotubes (DNA/SWCNT/GCE) and multi-walled carbon nanotubes (DNA/MWCNT/GCE) modified glassy carbon electrode showed a decrease in the current and a positive shift in the Tyr oxidation peak, indicating the intercalative interaction. The transfer coefficient (?), heterogeneous rate constant (k(s)), and surface concentration (?) were calculated in the absence and presence of DNA. The corresponding binding constant of Tyr with DNA and Hill coefficient were obtained from cooperative Hill model. The UV spectroscopic data confirmed the interaction between Tyr and DNA is intercalative with the binding constant of 3.98×10(3) mol(-1) L. Furthermore, the mechanism of fluorescence quenching has been discussed and the binding constant and numbers of binding sites were obtained as 3.37×10(3) mol(-1) L and 2, respectively from the Stern-Volmer plot. PMID:24239711

Fotouhi, Lida; Tabatabaee, Raziyeh

2014-01-01

203

Apparatus for calorimetric measurements of losses in MgB2 superconductors exposed to alternating currents and external magnetic fields  

NASA Astrophysics Data System (ADS)

Inexpensive superconducting wires with low AC losses would open up for a large superconductor market in AC electrical power applications. One candidate for this market is the MgB2 conductor. In the development of an AC optimized superconductor, high-quality measurements of the AC losses under application-like conditions must be available. This article describes an apparatus built for this purpose. The measurement method is calorimetric. The temperature increase of the superconductor sample is measured and compared to the temperature increase due to a heater with known heat input. The system is designed for measurements of losses due to magnetic fields combined with transport currents. Results from tests verifying the capabilities of the system are given, as well as from initial AC loss measurements on a tape-shaped MgB2 superconductor.

Taxt, H.; Magnusson, N.; Runde, M.

2013-02-01

204

Evaluation of Current Pharmacological Treatment Options in the Management of Rett Syndrome: From the Present to Future Therapeutic Alternatives  

PubMed Central

Neurodevelopmental disorders are a large family of conditions of genetic or environmental origin that are characterized by deficiencies in cognitive and behavioral functions. The therapeutic management of individuals with these disorders is typically complex and is limited to the treatment of specific symptoms that characterize each disorder. The neurodevelopmental disorder Rett syndrome (RTT) is the leading cause of severe intellectual disability in females. Mutations in the gene encoding the transcriptional regulator methyl-CpG-binding protein 2 (MECP2), located on the X chromosome, have been confirmed in more than 95% of individuals meeting diagnostic criteria for classical RTT. RTT is characterized by an uneventful early infancy followed by stagnation and regression of growth, motor, language, and social skills later in development. This review will discuss the genetics, pathology, and symptoms that distinguish RTT from other neurodevelopmental disorders associated with intellectual disability. Because great progress has been made in the basic and clinical science of RTT, the goal of this review is to provide a thorough assessment of current pharmacotherapeutic options to treat the symptoms associated with this disorder. Furthermore, we will highlight recent discoveries made with novel pharmacological interventions in experimental preclinical phases, and which have reversed pathological phenotypes in mouse and cell culture models of RTT and may result in clinical trials. PMID:24050745

Chapleau, Christopher A.; Lane, Jane; Pozzo-Miller, Lucas; Percy, Alan K.

2012-01-01

205

Milk production, water consumption, and somatic cell count responses of cows subject to one to two volts of alternating current.  

PubMed

A dairy farm located in central New York was visited because of complaints of electrical shock in the farmhouse shower and the milk house sink. As much as 2 volts AC of potential difference was measured between the waterline and the cow platform (cow-contact voltage). Voltage was coming from the primary neutral wire. The farm's electrical service was modified so that the farmstead could be connected or disconnected from the primary neutral wire at 2-week intervals for 12 weeks. When connected to the primary neutral wire, voltage between waterline and floor ranged between 0 and 1.8 volts, producing estimated current flow through cows of 3.6 to 4.9 mA; when disconnected from primary neutral wire, voltage between waterline and floor was less than 0.1 volt. There was no difference in mean milk production, bulk tank milk somatic cell count, or water consumption among periods when cows were exposed or unexposed to voltage. Despite statistical nonsignificance, the values for somatic cell count were lower and water consumption was higher when cows were exposed to voltage than when they were not. PMID:1506248

Southwick, L H; Wilson, D J; Sears, P M

1992-08-01

206

Evaluation of current pharmacological treatment options in the management of Rett syndrome: from the present to future therapeutic alternatives.  

PubMed

Neurodevelopmental disorders are a large family of conditions of genetic or environmental origin that are characterized by deficiencies in cognitive and behavioral functions. The therapeutic management of individuals with these disorders is typically complex and is limited to the treatment of specific symptoms that characterize each disorder. The neurodevelopmental disorder Rett syndrome (RTT) is the leading cause of severe intellectual disability in females. Mutations in the gene encoding the transcriptional regulator methyl-CpG-binding protein 2 (MECP2), located on the X chromosome, have been confirmed in more than 95% of individuals meeting diagnostic criteria for classical RTT. RTT is characterized by an uneventful early infancy followed by stagnation and regression of growth, motor, language, and social skills later in development. This review will discuss the genetics, pathology, and symptoms that distinguish RTT from other neurodevelopmental disorders associated with intellectual disability. Because great progress has been made in the basic and clinical science of RTT, the goal of this review is to provide a thorough assessment of current pharmacotherapeutic options to treat the symptoms associated with this disorder. Furthermore, we will highlight recent discoveries made with novel pharmacological interventions in experimental preclinical phases, and which have reversed pathological phenotypes in mouse and cell culture models of RTT and may result in clinical trials. PMID:24050745

Chapleau, Christopher A; Lane, Jane; Pozzo-Miller, Lucas; Percy, Alan K

2013-11-01

207

Designing and Diagnosing Novel Electrode Materials for Na-ion Batteries: Potential Alternatives to Current Li-ion Batteries  

NASA Astrophysics Data System (ADS)

Owing to outstanding energy density, Li-ion batteries have dominated the portable electronic industry for the past 20 years and they are now moving forward powering electric vehicles. In light of concerns over limited lithium reserve and rising lithium costs in the future, Na-ion batteries have re-emerged as potential alternatives for large scale energy storage. On the other hand, though both sodium and lithium are alkali metals sharing many chemical similarities, research on Na-ion batteries is still facing many challenges due to the larger size and unique bonding characteristics of Na ions. In this thesis, a series of sodium transition metal oxides are investigated as cathode materials for Na-ion batteries. P2 - Na2/3[Ni1/3 Mn2/3]O2 is firstly studied with a combination of first principles calculation and experiment, and battery performance is improved by excluding the phase transformation region. Li substituted compound, P2-Na0.8[Li0.12Ni0.22Mn0.66]O 2, is then explored. Its crystal / electronic structure evolution upon cycling is tracked by combing in situ synchrotron X-ray diffraction, ex situ X-ray absorption spectroscopy and solid state NMR. It is revealed that the presence of Li-ions in the transition metal layer allows increased amount of Na-ions to maintain the P2 structure during cycling. The design principles for the P2 type Na cathodes are devised based on this in-depth understanding and an optimized composition is proposed. The idea of Li substitution is then transferred to O3 type cathode. The new material, O3 - Na0.78 Li0.18Ni0.25Mn0.583O2, shows discharge capacity of 240 mAh/g, which is the highest capacity and highest energy density so far among cathode materials in Na-ion batteries. With significant progress on cathode materials, a comprehensive understanding of Na2Ti3O7 as anode for Na-ion batteries is discussed. The electrochemical performance is enhanced, due to increased electronic conductivity and reduced SEI formation with carbon coating. Na full cell with high operating voltage is demonstrated by taking advantage of the ultra-low voltage of Na2Ti3O7 anode. The self-relaxation for fully intercalated phase, Na4Ti3O 7, is shown for the first time, which results from structural instability as suggested by first principles calculation. Ti4+ / Ti 3+ is the active redox couple upon cycling based on XANES characterization. These findings unravel the underlying relation between unique properties and battery performance of Na2Ti3O7 anode, which should ultimately shed light on possible strategies for future improvement.

Xu, Jing

208

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

PubMed

Fast-scan cyclic voltammetry (FSCV) is an electrochemical method that can assess real-time in vivo dopamine (DA) concentration changes to study the kinetics of DA neurotransmission. Electrical stimulation of dopaminergic (DAergic) pathways can elicit FSCV DA responses that largely reflect a balance of DA release and reuptake. Interpretation of these evoked DA responses requires a framework to discern the contribution of DA release and reuptake. The current, widely implemented interpretive framework for doing so is the Michaelis-Menten (M-M) model, which is grounded on two assumptions- (1) DA release rate is constant during stimulation, and (2) DA reuptake occurs through dopamine transporters (DAT) in a manner consistent with M-M enzyme kinetics. Though the M-M model can simulate evoked DA responses that rise convexly, response types that predominate in the ventral striatum, the M-M model cannot simulate dorsal striatal responses that rise concavely. Based on current neurotransmission principles and experimental FSCV data, we developed a novel, quantitative, neurobiological framework to interpret DA responses that assumes DA release decreases exponentially during stimulation and continues post-stimulation at a diminishing rate. Our model also incorporates dynamic M-M kinetics to describe DA reuptake as a process of decreasing reuptake efficiency. We demonstrate that this quantitative, neurobiological model is an extension of the traditional M-M model that can simulate heterogeneous regional DA responses following manipulation of stimulation duration, frequency, and DA pharmacology. The proposed model can advance our interpretive framework for future in vivo FSCV studies examining regional DA kinetics and their alteration by disease and DA pharmacology. PMID:25527399

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

2015-03-01

209

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

210

Adsorptive-catalytic stripping voltammetry for determination of ultratrace titanium.  

PubMed

An extremely sensitive stripping voltammetric procedure for determination of ultratrace titanium is reported. The method is based on the interfacial preconcentration of titanium-cupferron complex onto the hanging mercury drop electrode, followed by catalytic reduction of the adsorbed complex for the presence of cupferron. The peak currents are directly proportional to titanium in the ranges of 0.06-1.0 ng/ml and 1.0-30.0 ng/ml. Moreover, the character of stripping current has also been studied with various polarographic methods. Such coupling of catalytic and adsorptive collection processes holds great promise for the development of an ultrasensitive voltammetric procedure for other metals. PMID:18965961

Baoxian, Y; Shuxun, Y

1994-04-01

211

Electrochemical drilling using alternating current  

Microsoft Academic Search

The attraction of using a.c. compared with d.c. is the opportunity it offers to simply transform normal workshop power supply down to a sensible potential value for electrochemical machining without having to incorporate rectifying equipment. Its success will normally depend on the ability to find tool materials which are not affected by electrolytic action while at positive potential and on

C. F. Noble; S. J. Shine

1975-01-01

212

Reinterpretation of reduction potential measurements done by linear sweep voltammetry in silicate melts  

NASA Technical Reports Server (NTRS)

The equilibrium concentrations of Ni between silicate melt and Pt were determined experimentally as a function of oxygen fugacity. The results demonstrate that metallic species derived in linear sweep voltammetry experiments in silicate melts are diffusing into Pt electrodes and not into the melt, as was concluded by previoius studies. This requires reinterpretation of previous linear sweep voltammetry results and recalculation and correction of reported reduction potentials. This paper reports these corrected reduction potentials. Also reported are the activity coefficients for Ni in synthetic basalt and diopsidic melts and for Co in diopsidic melt.

Colson, R. O.; Haskin, L. A.; Keedy, C. R.

1991-01-01

213

Investigation of the reduction process of dopamine using paired pulse voltammetry  

PubMed Central

The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around ?0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scanrates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at ?0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to ?0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (?0.4V). These tests showed that relatively large amounts of DOQ are reduced to DA during the holding potential. The rate-limited reduction process was also confirmed with the increase of reduction in a lower pH environment. In addition to the mechanism of the reduction process of DA, we found that the differences between the responses of primary and secondary pulses in PPV were mainly dependent on the rate-limited reduction process during the holding potential. In conclusion, the reduction process may be one of the important factors to be considered in the kinetic analysis of DA and other electroactive species in brain tissue and in the design of new types of waveform in FSCV. PMID:24926227

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

2014-01-01

214

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

PubMed Central

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

Atila, Alptug; Yilmaz, Bilal

2015-01-01

215

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

ERIC Educational Resources Information Center

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…

Messersmith, Stephania J.

2014-01-01

216

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

ERIC Educational Resources Information Center

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…

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

2004-01-01

217

Polymyxin-Coated Au and Carbon Nanotube Electrodes for Stable [NiFe]-Hydrogenase Film Voltammetry  

E-print Network

Polymyxin-Coated Au and Carbon Nanotube Electrodes for Stable [NiFe]-Hydrogenase Film Voltammetry report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier-planegraphite(EPG)withthecycliccationic lipodecapeptide polymyxin7 (PM, Chart 1) has been particularly successful in obtaining an active enzyme coverage.2

Dekker, Cees

218

Square-wave voltammetry assays for glycoproteins on nanoporous gold.  

PubMed

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

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

2014-03-15

219

Square-wave voltammetry assays for glycoproteins on nanoporous gold  

PubMed Central

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

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

2014-01-01

220

Electrochemical Genotoxicity Assay Based on a SOS/umu Test Using Hydrodynamic Voltammetry in a Droplet  

PubMed Central

The SOS/umu genotoxicity assay evaluates the primary DNA damage caused by chemicals from the ?-galactosidase activity of S. typhimurium. One of the weaknesses of the common umu test system based on spectrophotometric detection is that it is unable to measure samples containing a high concentration of colored dissolved organic matters, sediment, and suspended solids. However, umu tests with electrochemical detection techniques prove to be a better strategy because it causes less interference, enables the analysis of turbid samples and allows detection even in small volumes without loss of sensitivity. Based on this understanding, we aim to develop a new umu test system with hydrodynamic chronoamperometry using a rotating disk electrode (RDE) in a microliter droplet. PAPG when used as a substrate is not electroactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current response of chronoamperometry resulting from the oxidation of PAP to PQI is directly proportional to the enzymatic activity of S. typhimurium. This was achieved by performing genotoxicity tests for 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide (AF-2) and 2-aminoanthracene (2-AA) as model genotoxic compounds. The results obtained in this study indicated that the signal detection in the genotoxicity assay based on hydrodynamic voltammetry was less influenced by the presence of colored components and sediment particles in the samples when compared to the usual colorimetric signal detection. The influence caused by the presence of humic acids (HAs) and artificial sediment on the genotoxic property of selected model compounds such as 4-nitroquinoline-N-oxide (4-NQO), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 1,8-dinitropyrene (1,8-DNP) and 1-nitropyrene (1-NP) were also investigated. The results showed that the genotoxicity of 1-NP and MX changed in the presence of 10 mg·L?1 HAs. The genotoxicity of tested chemicals with a high hydrophobicity such as 1,8-DNP and 1-NP were decreased substantially with the presence of 1 g·L?1 sediment. This was not observed in the case of genotoxins with a low log Kow value. PMID:23242275

Kuramitz, Hideki; Sazawa, Kazuto; Nanayama, Yasuaki; Hata, Noriko; Taguchi, Shigeru; Sugawara, Kazuharu; Fukushima, Masami

2012-01-01

221

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

PubMed Central

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

Mikulecky, D C

1979-01-01

222

Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}  

SciTech Connect

[N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ? 300?K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1}?=?255?K, T{sub 2}?=?282?K, T{sub 3}?=?302?K, T{sub 4}?=?320?K, and T{sub 5}?=?346?K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup ?1}-10{sup 7}?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(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} 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.

Ben Bechir, M., E-mail: mohamedbenbechir@hotmail.fr; Karoui, K.; Guidara, K.; Ben Rhaiem, A. [Laboratory of Condensed Matter, Faculty of Sciences, University of Sfax, BP1171, 3018 Sfax (Tunisia); Tabellout, M. [LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des Molécules et Matériaux du Mans (IMMM), Avenue Olivier Messiaen, F-72085, Le Mans Cedex 09 (France)

2014-04-21

223

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

NASA Astrophysics Data System (ADS)

[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.

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

2014-04-01

224

Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2CuCl4  

NASA Astrophysics Data System (ADS)

The [N(CH3)3H]2CuCl4 single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH3)3H]2CuCl4 crystallizes at room temperature in the monoclinic system with P21/C space group. Three phase transitions at T1 = 226 K, T2 = 264 K, and T3 = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10-1-107 Hz frequency range and 203-313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH3)3H]2CuCl4 compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

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

2014-05-01

225

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)

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.

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

226

Alternative solar indices  

NASA Astrophysics Data System (ADS)

Possible alternative Solar Indices which could either be a perturbation from the currently defined Solar Index or possible indices based on current technologies for other media markets are discussed. An overview is given of the current project, including the logic that was utilized in defining its current structure and then alternative indices and definitions are presented and finally, recommendations are made for adopting alternative indices.

Lantz, L. J.

1980-07-01

227

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

PubMed Central

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

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

2009-01-01

228

Sensitive electrochemical detection of arsenic (III) using gold nanoparticle modified carbon nanotubes via anodic stripping voltammetry.  

PubMed

Gold nanoparticles were deposited electrolessly on multiwalled carbon nanotubes (CNTs) via in situ reduction of HAuCl(4) by NaBH(4). The resulting gold covered nanotubes were immobilised onto the surface of a glassy carbon electrode via evaporation of a suspension in chloroform. Anodic stripping voltammetry was performed with the modified electrode in As(III) solutions. A limit of detection (LOD based on 3 sigma) of 0.1 microgL(-1) was obtained but more importantly a sensitivity of 1985 microA microM(-1) was obtained with square wave voltammetry (SWV) in an optimised system with a deposition time of 120s. These values, particularly the high sensitivity compare favourably with previously reported methods in the area of electrochemical arsenic detection. PMID:18558122

Xiao, Lei; Wildgoose, Gregory G; Compton, Richard G

2008-07-14

229

Anodic stripping voltammetry of arsenic(III) using gold nanoparticle-modified electrodes.  

PubMed

A novel method for the detection of arsenic(III) in 1 M HCl at a gold nanoparticle-modified glassy carbon electrode has been developed. The gold nanoparticles were electrodeposited onto the glassy carbon electrode via a potential step from +1.055 to -0.045 V vs SCE for 15 s from 0.5 M H2SO4 containing 0.1 mM HAuCl4. The resulting electrode surfaces were characterized with both AFM and cyclic voltammetry. Anodic stripping voltammetry of arsenic(III) on the modified electrode was performed. After optimization, a LOD of 0.0096 ppb was obtained with LSV. PMID:15456316

Dai, Xuan; Nekrassova, Olga; Hyde, Michael E; Compton, Richard G

2004-10-01

230

Anodic Stripping Voltammetry of Silver Nanoparticles: Aggregation Leads to Incomplete Stripping  

PubMed Central

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

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

2015-01-01

231

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

PubMed

During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry. PMID:24767077

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

2014-09-15

232

Determination of saponin in sugar juices from sugar refining processes by stripping voltammetry  

Microsoft Academic Search

Saponins were determined as oleanolic acid in refined sugar and sugar juices from beet sugar refining processes by differential?pulse cathodic stripping voltammetry (DPCSV) at the hanging mercury drop electrode (HMDE) after acidic hydrolysis of the saponin. Measurements were performed on diluted samples at the mg\\/1 level without further pretreatment. The optimised procedure allowed the determination of saponin at the mg\\/kg

Daniel Sancho; Rafael Pardo; Marisol Vega

2000-01-01

233

Protonation and inhibition of Nitrosomonas europaea cytochrome c peroxidase observed with protein film voltammetry  

Microsoft Academic Search

The impact of protonation and inhibitor binding of the diheme cytochrome c peroxidase (CCP) from Nitrosomonas europaea has been examined by the technique of catalytic protein film voltammetry (PFV). Previous efforts have shown that the low-potential heme active site (L) binds substrate and yields electrocatalysis at an pyrolytic graphite edge electrode, with properties evocative of a high-potential intermediate, with Em>540mV

Sean J. Elliott; Amy L. Bradley; David M. Arciero; Alan B. Hooper

2007-01-01

234

Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

235

Development and Characterization of Carbon-Fiber Microbiosensors for Fast-Scan Cyclic Voltammetry  

NASA Astrophysics Data System (ADS)

Electrochemistry has been shown to be a robust tool in neuroscience. The use of carbon-fiber microelectrodes coupled with background-subtracted fast-scan cyclic voltammetry (FSCV) offers high sensitivity, selectivity, as well as the spatial and temporal resolution necessary for monitoring rapid fluctuations of electroactive molecules in live brain tissue. Dopamine (DA) is a neurotransmitter playing a key role in the regulation of reward and motivated behavior. FSCV has been used to understand DA dynamics and how these underlie discrete aspects of brain function. The methodological aspects of real-time DA detection at carbon-fiber microelectrodes using FSCV in anesthetized and awake animals are presented. Furthermore, the combination of FSCV with other neuroanalytical techniques is also explained. The advantages of FSCV and carbon-fiber microelectrodes can be expanded to the detection of non-electroactive analytes. This broadens the scope of FSCV such that it can be used to investigate how changes in non-electroactive chemicals underlie disease, cognition, and behavior. Carbon-fiber microelectrodes can be modified with an enzyme to monitor non-electroactive molecules, generating an electroactive product (usually hydrogen peroxide, H2O2). The first voltammetric detection of H2O 2 at bare carbon-fiber microelectrodes using FSCV has recently been reported. Thus, an avenue exists to utilize FSCV at enzyme-modified microelectrodes to voltammetrically identify and quantify non-electroactive analytes in real-time. Such an approach will overcome many limitations associated with the traditional amperometric detection scheme, which lacks electrochemical selectivity. Electrodeposition of the biopolymer chitosan with glucose oxidase (GOx) at the carbon surface yields a stable, sensitive, and selective glucose microbiosensor that has been utilized to detect glucose fluctuations in vivo with unprecedented speed. This new method has revealed the first rapid glucose fluctuations in live brain tissue. It will allow countless investigations that require the real-time detection of glucose fluctuations, and will fulfill a critical need in neuroscience because it should be broadly applicable to H2O2-generating oxidase enzymes in general. Indeed, this technology has been adapted to the detection of choline fluctuations by encapsulation of choline oxidase (ChOx). Alternate methods of enzyme immobilization are also feasible. Enzymes can be entrapped in a matrix of electrospun nanofibers on the carbon electrode surface. Prototype devices using GOx immobilized within poly(vinyl alcohol) nanofibers are sensitive and respond rapidly (second timescale) to physiological glucose concentrations. This immobilization strategy offers an alternative way to make microbiosensors for FSCV measurements. Quality early science education is essential to develop an informed public that is interested in, and able to advance, an economy that is highly dependent on technology. An additional topic presented herein is the development of an outreach program to promote generalized interest in chemistry among public school educators. A chemistry workshop was developed and conducted for local public teachers. Participants learned how to use dynamic and low-cost activities and demonstrations to creatively introduce science concepts and generate interactive engagement in their classrooms. Expansions of these efforts will help to expand the mission of generating interest in the chemistry field with long-term benefits to the US economy. In summary, the work presented herein describes innovative technology that will allow for new and exciting studies on non-electroactive molecule dynamics in vivo. These fundamental studies will ultimately lead to broadly applicable technologies for rapid molecular monitoring of unprecedented quality. They will allow future studies to assess how fluctuations of electroactive and non-electroactive molecules are integrated into a more coherent picture of brain function (or dysfunction), providing new insights into the fundamental way in which infor

Lugo-Morales, Leyda Zoraida

236

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

PubMed

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

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

2007-03-01

237

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

PubMed Central

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

2013-01-01

238

Staining of wool using the reaction products of ABTS oxidation by Laccase: Synergetic effects of ultrasound and cyclic voltammetry  

Microsoft Academic Search

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

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

2007-01-01

239

Magnetostrictive Alternator  

NASA Technical Reports Server (NTRS)

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.

Dyson, Rodger; Bruder, Geoffrey

2013-01-01

240

Using of Rhizopus arrhizus as a sensor modifying component for determination of Pb(II) in aqueous media by voltammetry.  

PubMed

For the sensitive determination of Pb(II) from aqueous solutions, a new voltammetric biosensor based on carbon paste electrode modified with Rhizopus arrhizus was developed. The preconcentrated ions at open circuit were reduced by using differential pulse stripping voltammetry technique. The obtained current values were related to the concentration of Pb(II) in the solutions. The best results were achieved at pH 7 with 0.01 M Tris-HCl buffer solution applying a preconcentration time of 12 min. The linear range for the biosensor was found to be within 1.0 x 10(-7)-1.25 x 10(-5) M, with a detection limit of 0.5 x 10(-8) M. The selectivity of the microbial biosensor was explored by adding interfering heavy metals to accumulation medium one by one, and their matrix effects were also investigated in the model metal solutions. Energy dispersive X-ray spectra analysis were applied to show the specific effect of the fungal biomass on the Pb(II) determination. PMID:20576569

Yüce, Meral; Nazir, Hasan; Dönmez, Gönül

2010-10-01

241

Effect of ohmic, mass-transfer, and kinetic resistances on linear-sweep voltammetry in a cylindrical-pore electrode  

NASA Technical Reports Server (NTRS)

A means is presented to account for the effect of ohmic, mass-transfer, and kinetic resistances on linear-sweep voltammograms by modeling a pore in a porous matrix as a cylindrical-pore electrode, and solving the mass and charge conservation equations in the context of this geometry for the simply redox reaction O + ne(-) yield R where both O and R are soluble species. Both analytical and numerical techniques are used to solve the governing equations. The calculated peak currents and potentials are correlated by empirical formulas to the measurable parameters: sweep rate, concentration of the redox species, diffusion coefficient, conductivity of the electrolyte, and pore dimensions. Using the correlations, a methodology is established for determining if the redox reaction kinetics are irreversible or reversible (Nernstian). If the reaction is irreversible, it is shown how the standard rate constant and the transfer coefficient may be extracted from linear-sweep voltammetry data, or, if the reaction is reversible, how the number of electrons transferred may be deduced.

Weidner, John W.; Fedkiw, Peter S.

1991-01-01

242

Determination of EDTA species in water by square-wave voltammetry using a chitosan-coated glassy carbon electrode.  

PubMed

The electrochemical behavior of Fe(EDTA)(-/2-) on a chitosan-coated glassy carbon electrode (GCE) and the determining method of the EDTA species in water samples by square-wave voltammetry (SWV) have been investigated. Fe(EDTA)(-) can be adsorbed on the positively charged chitosan membrane assembled on a GCE and be reduced at a potential of -0.095V vs. Ag/AgCl. On the chitosan-coated GCE, the cathodic stripping peak current is proportional to the concentration of EDTA after the operating parameters of SWV were optimized. The measuring range of EDTA was from 2.0x10(-6) to 8.0x10(-5)mol/L with a correlation coefficient of r=0.998 and a detection limit of 2.0x10(-7)mol/L. The relative standard deviation was less than 6.4% (n=5) and the recovery was in the range of 98-105% for the determination of practical samples. The result was consistent with that from the HPLC method. PMID:12946910

Zhao, Changzhi; Pan, Yuzhen; Su, Yan; Zhang, Zhihui; Guo, Zhen; Sun, Licheng

2003-10-01

243

Electrochemical identification of corrosion products on historical and archaeological bronzes using the voltammetry of micro-particles attached to a carbon paste electrode.  

PubMed

An overview of the electrochemical method for the identification of microsampled corrosion products from historical and archaeological bronzes is reported. Two characteristic examples of long-term air and subterranean formed patinas and two artificial patinas formed on Cu-6%Sn bronze in sulphate and chloride solutions, were investigated in 0.1M HCl(aq) by means of the cyclic voltammetry of micro-particles attached to a carbon paste electrode. Patina constituent phases were identified by comparing the electrochemical parameters of the patina samples to those of reference compounds: CuO, Cu(2)O, SnO, SnO(2), CuCl, CuCl(2) x 2H(2)O and CuSO(4) x 5H(2)O. An identification scheme was suggested which may be applied to discern the various corrosion products of bronze based on electrochemical data (voltammetric peak potentials). The presence of two prevalent phases of sulphate and chloride patinas, CuSO(4) and CuCl, as well as the presence of Sn compounds was clearly indicated by the cyclic voltammetry of microparticles, in both, naturally and artificially formed samples. A comparison to the ATR-FTIR results revealed that the methods are complementary and that their simultaneous application could prove particularly valuable in drawing conclusions about the current shape and prospects of the conservation and restoration of bronze artefacts. PMID:20441970

Satovi?, D; Martinez, S; Bobrowski, A

2010-06-15

244

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

PubMed Central

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

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

2013-01-01

245

Cyclic voltammetry response of coprecipitated Ni(OH) 2 electrode in 5 M KOH solution  

NASA Astrophysics Data System (ADS)

A study of the cyclic voltammetry response of a coprecipitated nickel hydroxide electrode in 5 M KOH solution shows that cobalt, manganese and zinc are beneficial additives in practical nickel batteries because they can increase the overpotentials for oxygen evolution reaction at the nickel hydroxide electrodes and decrease redox peak potentials. By contrast, iron and lead are considered harmful to nickel batteries because they can decrease the overpotentials at the nickel hydroxide electrode. On the other hand, the addition of iron is beneficial to the water electrolysis process. Cobalt can act as antidote to iron and lead in batteries.

Ding Yunchang; Yuan Jiongliang; Chang Zhaorong

246

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

PubMed

Lysergic acid diethylamide (LSD) is hardly detectable and quantifiable in biological samples because of its low active dose. Although several analytical tests are available, routine analysis of this drug is rarely performed. In this article, we report a simple and accurate method for the determination of LSD, based on adsorptive stripping voltammetry in DMF/tetrabutylammonium perchlorate, with a linear range of 1-90 ng L(-1) for deposition times of 50s. LOD of 1.4 ng L(-1) and LOQ of 4.3 ng L(-1) were found. The method can be also applied to biological samples after a simple extraction with 1-chlorobutane. PMID:25159435

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

2014-12-01

247

SPR imaging combined with cyclic voltammetry for the detection of neural activity  

NASA Astrophysics Data System (ADS)

Surface plasmon resonance (SPR) detects changes in refractive index at a metal-dielectric interface. In this study, SPR imaging (SPRi) combined with cyclic voltammetry (CV) was applied to detect neural activity in isolated bullfrog sciatic nerves. The neural activities induced by chemical and electrical stimulation led to an SPR response, and the activities were recorded in real time. The activities of different parts of the sciatic nerve were recorded and compared. The results demonstrated that SPR imaging combined with CV is a powerful tool for the investigation of neural activity.

Li, Hui; Zhang, Lulu; Chen, Xing; Sun, Jianhai; Cui, Dafu

2014-03-01

248

Hydrodynamic voltammetry as a rapid and simple method for evaluating soil enzyme activities.  

PubMed

Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on spectroscopic detection is a complicated operation that requires the removal of soil particles. The purpose of this study was to develop a new soil enzyme assay based on hydrodynamic electrochemical detection using a rotating disk electrode in a microliter droplet. The activities of enzymes were determined by measuring the electrochemical oxidation of p-aminophenol (PAP), following the enzymatic conversion of substrate-conjugated PAP. The calibration curves of ?-galactosidase (?-gal), ?-glucosidase (?-glu) and acid phosphatase (AcP) showed good linear correlation after being spiked in soils using chronoamperometry. We also performed electrochemical detection using real soils. Hydrodynamic chronoamperometry can be used to assess the AcP in soils, with a detection time of only 90 s. Linear sweep voltammetry was used to measure the amount of PAP released from ?-gal and ?-glu by enzymatic reaction after 60 min. For the assessment of soil enzymes, the results of hydrodynamic voltammetry assay compared favorably to those using a standard assay procedure, but this new procedure is more user-friendly, rapid and simple. PMID:25746097

Sazawa, Kazuto; Kuramitz, Hideki

2015-01-01

249

Voltammetry and In Situ Scanning Tunneling Microscopy of Cytochrome c Nitrite Reductase on Au(111) Electrodes  

PubMed Central

Escherichia coli cytochrome c nitrite reductase (NrfA) catalyzes the six-electron reduction of nitrite to perform an important role in the biogeochemical cycling of nitrogen. Here we describe NrfA adsorption on single-crystal Au(111) electrodes as an electrocatalytically active film in which the enzyme undergoes direct electron exchange with the electrode. The adsorbed NrfA has been imaged to molecular resolution by in situ scanning tunneling microscopy (in situ STM) under full electrochemical potential control and under conditions where the enzyme is electrocatalytically active. Details of the density and orientational distribution of NrfA molecules are disclosed. The submonolayer coverage resolved by in situ STM is readily reconciled with the failure to detect nonturnover signals in cyclic voltammetry of the NrfA films. The molecular structures show a range of lateral dimensions. These are suggestive of a distribution of orientations that could account for the otherwise anomalously low turnover number calculated for the total population of adsorbed NrfA molecules when compared with that determined for solutions of NrfA. Thus, comparison of the voltammetric signals and in situ STM images offers a direct approach to correlate electrocatalytic and molecular properties of the protein layer, a long-standing issue in protein film voltammetry. PMID:16935959

Gwyer, James D.; Zhang, Jingdong; Butt, Julea N.; Ulstrup, Jens

2006-01-01

250

Beyond the hydrogen wave: new frontier in the detection of trace elements by stripping voltammetry.  

PubMed

Stripping voltammetry is limited in acidic conditions to relatively high deposition potentials because of the interfering effects of the hydrogen produced at the working electrode. We report here a simple procedure to perform reliable and sensitive trace metal analysis in such conditions. Measurements are made at a gold microwire electrode. After applying a simple electrochemical conditioning procedure, hydrogen does not block the electrode, allowing reproducible analysis and smooth stripping signals to be obtained. Advantages of working inside the hydrogen wave are exemplified through the detection of the often considered electroinactive antimony(V). Sb(V) is detected in relatively low acidic conditions (pH ? 1) using low deposition potentials (?-1.8 V). The detection limit is 5 pM (0.63 ppt), the lowest ever reported for an electroanalytical technique and one of the lowest analytical methods. The method is simple, robust, and free from the common arsenic interference due to selective electrochemical hydride generation of arsine over stibine during the deposition step. Analytical methods were optimized and tested on mineral, river, tap, and coastal seawater. Results favorably compare against Certified Reference Materials data (NASS-4 and SLRS-3) and ICPMS analysis. Deposition well below the hydrogen wave pushes the frontier of stripping voltammetry, and new analytical applications in this combined range of acidity and deposition potential are to be expected. PMID:21456613

Salaün, Pascal; Gibbon-Walsh, Kristoff; van den Berg, Constant M G

2011-05-15

251

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

PubMed

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

Keithley, Richard B; Wightman, R Mark

2011-06-01

252

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

PubMed

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

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

2013-10-15

253

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

PubMed

Water analysis is one of the greatest challenges in the field of environmental analysis. In particular, seawater analysis is often difficult because a large amount of NaCl may mask the determination of other ions, i.e., nutrients, halides, and carbonate species. We demonstrate here the use of thin-layer samples controlled by cyclic voltammetry to analyze water samples for chloride, bromide, and iodide. The fabrication of a microfluidic electrochemical cell based on a Ag/AgX wire (working electrode) inserted into a tubular Nafion membrane is described, which confines the sample solution layer to less than 15 ?m. By increasing the applied potential, halide ions present in the thin-layer sample (X(-)) are electrodeposited on the working electrode as AgX, while their respective counterions are transported across the perm-selective membrane to an outer solution. Thin-layer cyclic voltammetry allows us to obtain separated peaks in mixed samples of these three halides, finding a linear relationship between the halide concentration and the corresponding peak area from about 10(-5) to 0.1 M for bromide and iodide and from 10(-4) to 0.6 M for chloride. This technique was successfully applied for the halide analysis in tap, mineral, and river water as well as seawater. The proposed methodology is absolute and potentially calibration-free, as evidenced by an observed 2.5% RSD cell to cell reproducibility and independence from the operating temperature. PMID:25315854

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

2014-11-18

254

Influence of the nature of the pasting liquid on the accumulation of nitroanilines at carbon paste electrode during determination by absorptive stripping voltammetry.  

PubMed

ABSTRACT. The accumulation of ortho-, para-nitroanilines, 2,4-dimetyl-6-nitroaniline, and meta-nitrobenzoic acid at carbon paste electrode (CPE) has been studied. For the preparation of CPE different pasting liquids have been used: esters, aromatic hydrocarbons, saturated hydrocarbons, and polymethylsiloxane. Distribution ratios of o- and p-nitroanilines between the pasting liquid and water have been determined. Correlation between peak current constants and distribution ratios has been found. It has been demonstrated that during the determination of analyte on the CPE with aromatic hydrocarbons, the main influence on nitro-compound accumulation is executed by the extraction into the pasting liquids, and on the CPE with saturated hydrocarbons - by the process of depolarizer sorption onto the graphite. The selective determination of nitroanilines in the presence of hindering compounds with adsorptive stripping voltammetry has been carried out. PMID:12733036

Kuz'mina, N V; Kudasheva, F Kh; Maistrenko, V N; Sapel'nikova, S V

2003-04-01

255

Alternative security  

SciTech Connect

This book contains the following chapters: The Military and Alternative Security: New Missions for Stable Conventional Security; Technology and Alternative Security: A Cherished Myth Expires; Law and Alternative Security: Toward a Just World Peace; Politics and Alternative Security: Toward a More Democratic, Therefore More Peaceful, World; Economics and Alternative Security: Toward a Peacekeeping International Economy; Psychology and Alternative Security: Needs, Perceptions, and Misperceptions; Religion and Alternative Security: A Prophetic Vision; and Toward Post-Nuclear Global Security: An Overview.

Weston, B.H. (Iowa Univ., Iowa City, IA (United States))

1990-01-01

256

The influence of the capping agent on the oxidation of silver nanoparticles: nano-impacts versus stripping voltammetry.  

PubMed

The influence of capping agents on the oxidation of silver nanoparticles was studied by using the electrochemical techniques of anodic stripping voltammetry and anodic particle coulometry ("nano-impacts"). Five spherical silver nanoparticles each with a different capping agent (branched polyethylenimine (BPEI), citrate, lipoic acid, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP)) were used to perform comparative experiments. In all cases, regardless of the capping agent, complete oxidation of the single nanoparticles was seen in anodic particle coulometry. The successful quantitative detection of the silver nanoparticle size displays the potential application of anodic particle coulometry for nanoparticle characterisation. In contrast, for anodic stripping voltammetry using nanoparticles drop casting, it was observed that the capping agent has a very significant effect on the extent of silver oxidation. All five samples gave a low oxidative charge corresponding to partial oxidation. It is concluded that the use of anodic stripping voltammetry to quantify nanoparticles is unreliable, and this is attributed to nanoparticle aggregation. PMID:25581121

Toh, Her Shuang; Jurkschat, Kerstin; Compton, Richard G

2015-02-01

257

Multiple DNA binding modes of a metallointercalator revealed by DNA film voltammetry.  

PubMed

Binding and the redox reaction of the metallointercalator Ru(bpy)2(dppz)2+ (bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine) with DNA was investigated by DNA film voltammetry. Calf-thymus DNA (CT-DNA) was assembled on a tin-doped indium oxide electrode by layer-by-layer electrostatic adsorption. Voltammetry of Ru(bpy)2(dppz)2+ (Ru-dppz) bound to the DNA film was measured in a redox-free electrolyte and showed strong dependence on the concentration of the metallointercalator. At low Ru-dppz concentrations, a single oxidation peak was observed, the potential of which shifted from 1.25 to 1.1 V with increasing Ru-dppz concentration (peak 1). At high metal chelate concentrations, an additional oxidation peak emerged with a potential of 1.25 V which was unaffected by the Ru-dppz concentration (peak 2). Three experiments were performed to investigate the mechanism and structural basis of the multiple peaks. First, voltammetry of Os(bpy)2(dppz)2+ bound to the CT-DNA film displayed only one peak at its oxidation potential of about 0.75 V. Second, the concentration dependence of Ru-dppz bound to a poly-(AU) film (which does not contain any guanine bases) exhibited only one oxidation peak at about 1.22 V that was independent of the Ru-dppz concentration. Third, when the guanine concentration in a mixed film of CT-DNA and poly-(AU) was changed and the bound Ru-dppz was kept constant, a pre-peak emerged and shifted to 1.1 V with increasing guanines. Based on these results, the appearance of two peaks in the voltammetric measurements of CT-DNA was rationalized by invoking two different DNA binding modes for the Ru-dppz complex: intercalation and electrostatic association. Peak 2 arises from slow oxidation of guanines catalyzed by Ru-dppz electrostatically associated with the DNA film, since the addition of Mg2+ decreases the magnitude of peak 2. Peak 1 was not affected by Mg2+ ions, leading us to conclude that it is due to intercalated Ru-dppz. The intercalation positions the metal complex in close contact with the guanines inside DNA resulting in fast electrocatalytic reaction, giving rise to a catalytic pre-peak. PMID:17034245

Guo, Liang-Hong; Wei, Ming-Yuan; Chen, Hao

2006-10-19

258

Electrochemical characterization of gelatinized starch dispersions: Voltammetry and electrochemical impedance spectroscopy on platinum surface.  

PubMed

The electrochemical properties of gelatinized starch dispersions (GSD; 5% w/w) from different botanical sources were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests over a platinum surface. The phenomenological modelling of EIS data using equivalent circuits indicated that after gelatinization the electrical resistance was determined mainly by the resistance of insoluble material (i.e., ghosts). Sonication of the GSD disrupted the ghost microstructure, and produced an increase in electrical conductivity by reducing the resistance of the insoluble material. The CV data showed three oxidation peaks at potentials where glucose solutions displayed oxidation waves. It is postulated that hydrolysis at the bulk and electrocatalyzed oxidation on the Pt-surface are reactions involved in the starch transformation. Starches peak intensity increased with the amylose content, suggesting that the amylose-rich matrix played an important role in the charge transfer in the electrolytic system. PMID:25839788

Hernandez-Jaimes, C; Lobato-Calleros, C; Sosa, E; Bello-Pérez, L A; Vernon-Carter, E J; Alvarez-Ramirez, J

2015-06-25

259

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

PubMed

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

Erdem, Arzum; Karadeniz, Hakan; Caliskan, Ayfer

2011-03-01

260

Roughness of ZnS:Pr,Ce\\/Ta2O5 interface and its effects on electrical performance of alternating current thin-film electroluminescent devices  

Microsoft Academic Search

Roughness effects of neighboring dielectrics on electrical characteristics of thin-film electroluminescent devices were investigated in order to improve the understanding of physics for the devices. Atomic force microscopy analysis reveal that thicker bottom layer of Ta2O5 shows rougher surface resulting in the rougher surface of ZnS:Pr,Ce layer. It can be easily seen that the dc leakage current increases rapidly with

Yun-Hi Lee; Young-Sik Kim; Byeong-Kwon Ju; Myung-Hwan Oh

1999-01-01

261

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

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

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

2014-09-16

262

Diclofenac sodium topical solution with dimethyl sulfoxide, a viable alternative to oral nonsteroidal anti-inflammatories in osteoarthritis: review of current evidence  

PubMed Central

Topical nonsteroidal anti-inflammatory drugs (NSAIDs) may offer a safer alternative to their oral counterparts for the management of osteoarthritis. Diclofenac sodium topical solution with dimethyl sulfoxide (TDiclo) was evaluated in five randomized, controlled trials and is indicated for treatment of the signs and symptoms associated with osteoarthritis of the knee. Three studies showed that TDiclo is superior to placebo and vehicle control with respect to pain, physical function, and perception of osteoarthritis symptoms. Two studies showed that benefits are similar to those of oral diclofenac, with one study demonstrating statistical equivalence. The most common adverse event associated with TDiclo in these studies was dry skin. Incidences of gastrointestinal adverse events and abnormal levels of liver enzymes were lower with TDiclo compared with oral diclofenac in active-controlled studies. Based on these studies, TDiclo represents a practical, evidence-based option for the management of osteoarthritis of the knee. PMID:21811389

Fuller, Philip; Roth, Sanford

2011-01-01

263

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser.  

PubMed

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S?/? (F = 3) - 6P?/? (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S?/? (F = 4) - 6P?/? (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states. PMID:22453427

Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin

2012-03-26

264

Mapping Activity Variations for Ru2O3 in Lunar Volcanic Green Glass Analogs Using Differential Pulse Voltammetry  

NASA Technical Reports Server (NTRS)

Using differential pulse voltammetry, we are mapping variations in activities for NiO and Ru2O3 as a function of compositional variation for compositions centered around an Apollo 15 green glass analog. Additional information is contained in the original extended abstract.

Malum, K. M.; Colson, R. O.; Sawarynski, M.

2001-01-01

265

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

E-print Network

Lab-on-a-Chip Sensor with Evaporated Bismuth Film Electrode for Anodic Stripping Voltammetry of Zinc Wenjing Kang,a Xing Pei,a Wei Yue,b Adam Bange,c William R. Heineman,b Ian Papautsky*a a Bio 24, 2013 Abstract In this work, we report on the development of a lab-on-a-chip electrochemical

Papautsky, Ian

266

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

267

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

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

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

268

A medicare current beneficiary survey-based investigation of alternative primary care models in nursing homes: functional ability and health status outcomes.  

PubMed

This study assessed how the health status and functioning of Medicare beneficiaries residing in nursing homes varies systematically with nurse practitioners (NPs) and physician assistants (PAs) providing primary care services. A secondary analysis was conducted using data from the 2006, 2007, and 2008 Medicare Current Beneficiary Surveys. The study sample included 433 participant-year observations within one of three cohorts: (a) medical doctor (MD)-only, those who received primary care services exclusively from a physician; (b) MD-dominant, those who received some primary care services from an NP or PA, but those visits accounted for less than one half of total primary care visits; and (c) NP/PA-dominant, those who received more than one half of their primary care visits from an NP or PA. Participants in the MD-only cohort had significantly less orientation and independence in activities of daily living compared to participants in the NP/PA-dominant cohort. Other study variables did not vary significantly by practice model. Although the study provides some evidence that NP/PA involvement is associated with improved functioning, it is premature to draw strong inferences. [Res Gerontol Nurs. 2015; 8(2):85-93.]. PMID:25643375

Abdallah, Lisa M; Van Etten, Deborah; Lee, A James; Melillo, Karen Devereaux; Remington, Ruth; Gautam, Ramraj; Gore, Rebecca J

2015-01-01

269

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

PubMed

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

Smith, D C

1992-01-01

270

Cyclic voltammetry: a tool to quantify 2,4,6-trichloroanisole in aqueous samples from cork planks boiling industrial process.  

PubMed

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

Peres, António M; Freitas, Patrícia; Dias, Luís G; Sousa, Mara E B C; Castro, Luís M; Veloso, Ana C A

2013-12-15

271

Alternate drop pulse polarography  

USGS Publications Warehouse

The new technique of alternate drop pulse polarography is presented. An experimental evaluation of alternate drop pulse polarography shows complete compensation of the capacitative background due to drop expansion. The capillary response phenomenon was studied in the absence of faradaic reaction and the capillary response current was found to depend on the pulse width to the -0.72 power. Increased signal-to-noise ratios were obtained using alternate drop pulse polarography at shorter drop times.

Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

1976-01-01

272

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

SciTech Connect

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.

Wang, H.; Macomber, C.; Dinh, H. N.

2012-07-01

273

Inorganic arsenic speciation in water and seawater by anodic stripping voltammetry with a gold microelectrode.  

PubMed

The determination of arsenic in sea and freshwater by anodic stripping voltammetry (ASV) was revisited because of problems related to unstable peaks and inconveniently strong acidic conditions used by existing methods. Contrary to previous work it was found, that As(III) can be determined by ASV using a gold microwire electrode at any pH including the neutral pH typical for natural waters. As(V) on the other hand, requires acidification to pH 1, but this is still a much milder condition than used previously. This is the basis of a new method for the chemical speciation of arsenic in natural waters. The limits of detection are 0.2 nM As(III) at pH 8 and 0.3 nM combined arsenic (III+V) at pH 1 with a 30 s deposition time. These limits are lowered by extending the deposition time. The detection step at pH 8 was stripping chronopotentiometry (SC) as this was found to give a lower detection limit than ASV. Copper is co-determined simultaneously with arsenic. The method was applied successfully to the determination of arsenic as well as copper in samples from the Irish Sea, mineral water and tap water. PMID:17386680

Salaün, Pascal; Planer-Friedrich, Britta; van den Berg, Constant M G

2007-03-01

274

Analysis of total arsenic in urine and blood by high speed anodic stripping voltammetry.  

PubMed

A method for the measurement of parts per billion levels of total arsenic in urine and blood is described. Samples are wet ashed with a mixture of HNO3, HCIO4, and H2SO4 acids. Ashed materials are subjected to a reductillationTM procedure to reduce As (V) to As (III) and to separate arsenic from the sample matrix. Collected arsenic is then quantitated by anodic stripping voltammetry (ASV) at a gold film electrode. ASV analysis time is only 2 minutes. By simultaneous reductillation of 4 samples, ppb arsenic determinations can be accomplished at a rate of about 12 per hour. The method is as accurate, precise and reliable at the nanogram level as the more universally accepted colorimetric techniques are at the microgram and milligram levels. For replicate analysis of real samples, method precision ranged from +/- 1.4 ppb at the 5 ppb level to +/- 0.96 ppb at the 25 ppb level. Accuracy is estimated at +/- 6% over the range 5 to 500 ppb arsenic. PMID:685828

Davis, P H; Berlandi, F J; Dullude, G R; Griffin, R M; Matson, W R; Zink, E W

1978-06-01

275

Computer Simulations of Cyclic Voltammetry and phase ordering of Br on Ag(100)  

NASA Astrophysics Data System (ADS)

Extensive dynamic and equilibrium Monte Carlo simulations have been performed to study the response of a submonolayer of Br electrochemically deposited from aqueous solution onto a Ag(100) single-crystal surface (S.J. Mitchell, G. Brown, P.A. Rikvold, J. Electroanal. Chem. 493), 684 (2000); Surf. Sci. in press.. This system has a second-order phase transition in the two-dimensional Ising universality class, which separates a disordered low-coverage phase at low electrode potential from an ordered phase consisting of 1/2 monolayer of Br for higher potentials. The various features seen in simulations of cyclic voltammetry (in which the potential is swept across the phase transition in a saw-tooth fashion) are explained, including slowing-down at the phase transition, a broad shoulder caused by local fluctuations in the disordered phase, and the ordering/disordering asymmetry. The poster focuses on graphical presentations of our results. Additional information is available at www.csit.fsu.edu/ ~matsci. Supported by NSF Grant No. DMR-9981815, DOE through NERSC, and FSU through MARTECH and CSIT.

Mitchell, S. J.; Brown, G.; Rikvold, P. A.

2001-03-01

276

Rapid Detection of Endogenous Dopamine Changes in Drosophila melanogaster using Fast-Scan Cyclic Voltammetry  

PubMed Central

Drosophila melanogaster, the fruit fly, is a commonly used model organism because of its homology to mammals and facile genetic manipulations. However, the size of the nervous system is very small. We report a method to evoke and detect rapid changes in extracellular dopamine in a single nerve cord isolated from a Drosophila larva. Flies were genetically modified to express Channelrhodopsin-2, a blue-light activated cation channel, in only dopaminergic neurons. Extracellular dopamine changes were measured with fast-scan cyclic voltammetry at an implanted carbon-fiber microelectrode. Seven-second stimulations with blue light result in an average peak dopamine concentration of 810 ± 60 nM, similar to electrically-stimulated release in mammals. Stimulations repeated at 15-minute intervals are stable for 65 minutes, allowing pharmacological experiments in the same sample. Peak duration is extended after cocaine or nisoxetine, inhibitors of the dopamine transporter (DAT). Release was reduced upon exposure to reserpine, which inhibits vesicular packaging. Chronic administration of NSD-1015, a dopamine synthesis inhibitor, decreased dopamine release and inhibited pupation, showing a link between neurotransmission and physiology. This is the first method to measure endogenous dopamine in an intact larval Drosophila nervous system and will allow studies of genetic and pharmacological manipulations of dopamine release and uptake. PMID:19842636

Vickrey, Trisha L.; Condron, Barry; Venton, B. Jill

2010-01-01

277

Electrochemical Protease Biosensor Based on Enhanced AC Voltammetry Using Carbon Nanofiber Nanoelectrode Arrays  

PubMed Central

We report an electrochemical method for measuring the activity of proteases using nanoelectrode arrays (NEAs) fabricated with vertically aligned carbon nanofibers (VACNFs). The VACNFs of ~150 nm in diameter and 3 to 5 ?m in length were grown on conductive substrates and encapsulated in SiO2 matrix. After polishing and plasma etching, controlled VACNF tips are exposed to form an embedded VACNF NEA. Two types of tetrapeptides specific to cancer-mediated proteases legumain and cathepsin B are covalently attached to the exposed VACNF tip, with a ferrocene (Fc) moiety linked at the distal end. The redox signal of Fc can be measured with AC voltammetry (ACV) at ~1 kHz frequency on VACNF NEAs, showing distinct properties from macroscopic glassy carbon electrodes due to VACNF’s unique interior structure. The enhanced ACV properties enable the kinetic measurements of proteolytic cleavage of the surface-attached tetrapeptides by proteases, further validated with a fluorescence assay. The data can be analyzed with a heterogeneous Michaelis-Menten model, giving “specificity constant” kcat/Km as (4.3 ± 0.8) × 104 M?1s?1 for cathepsin B and (1.13 ± 0.38) × 104 M?1s?1 for legumain. This method could be developed as portable multiplex electronic techniques for rapid cancer diagnosis and treatment monitoring. PMID:23814632

Swisher, Luxi Z.; Syed, Lateef U.; Prior, Allan M.; Madiyar, Foram R.; Carlson, Kyle R.; Nguyen, Thu A.; Hua, Duy H.; Li, Jun

2013-01-01

278

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

PubMed

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

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

2014-05-01

279

Coulometric differential FFT admittance voltammetry determination of Amlodipine in pharmaceutical formulation by nano-composite electrode.  

PubMed

An electrochemical detection technique based on combination of was coulometric differential fast Fourier transformation admittance voltammetry (CDFFTAV) and nano-composite film modified glassy carbon electrode was successfully applied for sensitive determination of Amlodipine. The nano-composite film was made by a mixture of ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4), multiwall carbon nanotube and Au nanoparticles as electrochemical mediators. Studies reveal that the irreversible oxidation of Amlodipine was highly facile on the electrode surface. The electrochemical response was established on calculation of the charge under the admittance peak, which was obtained by discrete integration of the admittance response in a selected potential range, obtained in a flow injection analysis. Once established the best operative optimum conditions, the resulting nano-composite film electrode showed a catalytic effect on the oxidation of the analyte. The response is linear in the Amlodipine concentration range of 1.0 × 10(-9) to 2.0 × 10(-7)M with a detection limit of 1.25 × 10(-10)M. Moreover, the proposed technique exhibited high sensitivity, fast response time (less than 6s) and long-term stability and reproducibility around 96%, and it was successfully used to the determination of Amlodipine content in the pharmaceutical formulation. PMID:25281143

Norouzi, Parviz; Gupta, Vinod Kumar; Larijani, Bagher; Rasoolipour, Solmaz; Faridbod, Farnoush; Ganjali, Mohammad R

2015-01-01

280

The anodic stripping voltammetry of nanoparticles: electrochemical evidence for the surface agglomeration of silver nanoparticles.  

PubMed

Analytical expressions for the anodic stripping voltammetry of metallic nanoparticles from an electrode are provided. First, for reversible electron transfer, two limits are studied: that of diffusionally independent nanoparticles and the regime where the diffusion layers originating from each particle overlap strongly. Second, an analytical expression for the voltammetric response under conditions of irreversible electron transfer kinetics is also derived. These equations demonstrate how the peak potential for the stripping process is expected to occur at values negative of the formal potential for the redox process in which the surface immobilised nanoparticles are oxidised to the corresponding metal cation in the solution phase. This work is further developed by considering the surface energies of the nanoparticles and its effect on the formal potential for the oxidation. The change in the formal potential is modelled in accordance with the equations provided by Plieth [J. Phys. Chem., 1982, 86, 3166-3170]. The new analytical expressions are used to investigate the stripping of silver nanoparticles from a glassy carbon electrode. The relative invariance of the stripping peak potential at low surface coverages of silver is shown to be directly related to the surface agglomeration of the nanoparticles. PMID:23624744

Toh, Her Shuang; Batchelor-McAuley, Christopher; Tschulik, Kristina; Uhlemann, Margitta; Crossley, Alison; Compton, Richard G

2013-06-01

281

Alternatives for Jet Engine Control  

NASA Technical Reports Server (NTRS)

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.

Leake, R. J.; Sain, M. K.

1976-01-01

282

Comparison of Differential Pulse Voltammetry (DPV)—a new method of carbamazepine analysis—with Fluorescence Polarization Immunoassay (FPIA)  

Microsoft Academic Search

Carbamazepine is a widely used anti-epileptic drug with narrow therapeutic range. Many methods have been developed for monitoring\\u000a the serum drug level. Differential pulse voltammetry (DPV), an electrochemical method advantaged by simple, inexpensive, and relatively short analysis time, has recently been developed\\u000a for carbamazepine detection. We used a newly developed DPV method with glassy carbon as a working electrode to

H. Y. Wang; M. L. Pan; Y. L. Oliver Su; S. C. Tsai; C. H. Kao; S. S. Sun; W. Y. Lin

2011-01-01

283

Separation and direct detection of heavy lanthanides using new ion-exchange chromatography: fast Fourier transform continuous cyclic voltammetry system  

Microsoft Academic Search

In this study, possibilities of heavy lanthanides (Ho3+, Er3+, Tm3+, Yb3+, and Lu3+) separation on Nucleosil 100-5-SA, an ion-exchange column, was investigated. Separation of lanthanides was carried out using\\u000a an isocratic program of ?-hydroxyisobutyric acid (HIBA) eluent. Fast Fourier transform continuous cyclic voltammetry (FFT-CCV)\\u000a at a gold microelectrode was used as the detection method. Simplicity, high precision and accuracy, time

Mohammad Reza Pourjavid; Parviz Norouzi; Hamid Rashedi; Mohammad Reza Ganjali

2010-01-01

284

Die aufschlußfreie Bestimmung von Schwermetallen (Zn, Cd, Pb, Cu) in Getränken (Wein) durch inverse Voltammetrie in einer Durchflußzelle  

Microsoft Academic Search

Digestion-free determination of trace-metals (Zn, Cd, Pb, Cu) in beverages by inverse voltammetry in a flow-through cell equipped with a mercury film-electrode is described. Optimal enrichment potentials are obtained by inspection of the pseudopolarograms of the elements in the original diluted sample solution. After the deposition step in the untreated sample solution stripping is effected in a proper supporting electrolyte

Faramarz Wahdat; Rolf Neeb

1987-01-01

285

Determination of clindamycin in dosage forms and biological samples by adsorption stripping voltammetry with carbon paste electrode  

Microsoft Academic Search

The electrochemical behavior of antibiotic drugs, clindamycin hydrochloride (I) and its phosphate salt (II), on carbon paste electrode (CPE) is thoroughly investigated. Chemical and electrical parameters affecting the adsorption\\u000a stripping voltammetry (ASV) measurements are optimized. Two different modes of sweep, viz., differential pulse (DP) and square wave (SW), are compared over a potential range of +400 to +1100 mV in

I. H. I. Habib; M. S. Rizk; Th. R. El-Aryan

2011-01-01

286

Determination of fenitrothion in river water and commercial formulations by adsorptive stripping voltammetry with a carbon ceramic electrode.  

PubMed

A sol-gel carbon ceramic electrode (CCE) without any assigned electron transfer mediator or specific reagents was used for the determination of fenitrothion by square-wave adsorptive stripping voltammetry. Fenitrothion strongly adsorbs on a CCE surface, which enables the development of facile electrochemical quantitative methods. Operational parameters such as pH value, initial potential value, and pulse frequency were optimized, and the stripping voltammetric performance was studied by using square-wave voltammetry. Square-wave adsorptive stripping voltammetry was used to obtain calibration curves with 2 linear ranges, 0.005-0.1 and 0.1-50 microM; the lower linear range was used to calculate the detection limit, 0.0016 microM (5 min adsorption). The effect of interference species on the determination of fenitrothion was also studied. The inherent stability, high sensitivity, low detection limit, and low cost of analysis are the advantages of this sensor. The present method was successfully applied to the determination of fenitrothion in a commercial formulation and river water samples. Analysis of real water samples by using the sensor demonstrated the feasibility of applying the sensor to the on-site monitoring of organophosphate compounds. PMID:19485215

Majidi, Mir Reza; Asadpour-Zeynali, Karim; Nazarpur, Mohammad

2009-01-01

287

Aternating current photovoltaic building block  

DOEpatents

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.

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

2004-06-15

288

Alternative Assessment.  

ERIC Educational Resources Information Center

This special double issue focuses on the issue of alternative assessment and its place in educational reform. "Alternative Assessment: A National Perspective" (T. Stefonek) emphasizes that the fundamental purposes of new assessment methods are grounded in educational goals, meaningful outcomes, and curricular and instructional programs promoting…

Stefonek, Tom; And Others

1991-01-01

289

Current management of syncope: Treatment alternatives  

Microsoft Academic Search

Opinion statement  Syncope, defined as a transient loss of consciousness and postural tone with spontaneous recovery and no neurologic sequelae,\\u000a is among one of the most common causes of consultation with a physician. The diagnostic workup is complex but can be simplified\\u000a if focused on the underlying condition. Prognosis is highly dependent on the presence or absence of structural heart disease,

Carlos A. Morillo; Adrián Baranchuk

2004-01-01

290

Nonlinear alternating current conduction in polycrystalline manganites  

SciTech Connect

The real part of ac conductance ?(T, f) of yttrium-doped mixed-valent polycrystalline manganite systems La{sub 1?x?y}Y{sub y}Ca{sub x}MnO{sub 3} with x?=?0.33 and 0.05 and y?=?0.07 and iron doped LaMn{sub 1?x}Fe{sub x}O{sub 3} with x?=?0.15 is measured as a function of frequency f by varying zero-frequency Ohmic conductance ?{sub 0} by T. The former shows a metal-insulator transition, whereas the latter exhibits insulating character throughout the measured temperature range. At a fixed temperature T, ?(T, f) remains almost constant to the value ?{sub 0} up to a certain frequency, known as the onset frequency f{sub c} and increases from ?{sub 0} as frequency is increased from f{sub c}. Scaled appropriately, the data for ?(T, f) at different T fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductance. f{sub c} scales with ?{sub 0} as f{sub c}??{sub 0}{sup x{sub f}}, where x{sub f} is the nonlinearity exponent characterising the onset. With the help of data for ac conduction, it is shown that x{sub f} is very much phase sensitive and can be used to characterize the different phases in a manganite system originated due to change in temperature or disorder. Scaling theories and existing theoretical models are used to analyze the results of ac conduction and the nonlinearity exponent x{sub f}.

Ghosh, T. N. [Department of Electronics, Vidyasagar University, Midnapore, West Bengal 721 102 (India); Nandi, U. N., E-mail: unphys@scottishchurch.ac.in [Department of Physics, Scottish Church College, 1 and 3, Urquhart Square, Kolkata 700 006 (India); Jana, D. [Department of Physics, University of Calcutta, 92, A P C Road, Kolkata 700 009 (India); Dey, K.; Giri, S. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

2014-06-28

291

RENEWABLE ENERGY ALTERNATIVES: CURRENT STATUS AND CAPACITIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

A key to the United States’ economic growth is an ever-increasing demand for energy, which has traditionally been met primarily by combusting the hydrocarbons found in fossil fuels. As environmental concerns grow, renewable energy resources are gaining increasing attention. To aid both researchers...

292

Method development for the determination of arsenic by sequential injection/anodic stripping voltammetry using long-lasting gold-modified screen-printed carbon electrode.  

PubMed

An automated method has been developed for determining the concentration of inorganic arsenic. The technique uses sequential injection/anodic stripping voltammetry with a long-lasting gold-modified screen-printed carbon electrode. The long-lasting gold electrode was electrochemically deposited onto a screen-printed carbon electrode at a potential of -0.5 V vs. Ag/AgCl in a supporting electrolyte solution of 1M hydrochloric acid. Under optimal conditions and the applied potentials, the electrode demonstrated that it can be used for a long time without a renewal process. The linear range for the determination of arsenic(III) was 1-100 ?g L(-1), and the limit of detection (LOD) in standard solutions was as low as 0.03 ?g L(-1) for a deposition time of 120 s and sample volume of 1 mL. This method was used to determine the concentration of arsenic(III) in water samples with satisfactory results. The LOD in real samples was found to be 0.5 ?g L(-1). In addition, speciation between arsenic(III) and arsenic(V) has been achieved with the proposed method using deposition potentials of -0.5 V and -1.5 V for the determination of the arsenic(III) concentration and the total arsenic concentration, respectively; the results were acceptable. The proposed method is an automated system that offers a less expensive alternative for determining trace amounts of inorganic arsenic. PMID:24148510

Punrat, Eakkasit; Chuanuwatanakul, Suchada; Kaneta, Takashi; Motomizu, Shoji; Chailapakul, Orawon

2013-11-15

293

IL-4 type 1 receptor signaling up-regulates KCNN4 expression, and increases the KCa3.1 current and its contribution to migration of alternative-activated microglia  

PubMed Central

The Ca2+-activated K+ channel, KCa3.1 (KCNN4/IK1/SK4), contributes to “classical,” pro-inflammatory activation of microglia, and KCa3.1 blockers have improved the outcome in several rodent models of CNS damage. For instance, blocking KCa3.1 with TRAM-34 rescued retinal ganglion neurons after optic nerve damage in vivo and, reduced p38 MAP kinase activation, production of reactive oxygen and nitrogen species, and neurotoxicity by microglia in vitro. In pursuing the therapeutic potential of KCa3.1 blockers, it is crucial to assess KCa3.1 contributions to other microglial functions and activation states, especially the IL-4-induced “alternative” activation state that can counteract pro-inflammatory states. We recently found that IL-4 increases microglia migration – a crucial function in the healthy and damaged CNS – and that KCa3.1 contributes to P2Y2 receptor-stimulated migration. Here, we discovered that KCa3.1 is greatly increased in alternative-activated rat microglia and then contributes to an enhanced migratory capacity. IL-4 up-regulated KCNN4 mRNA (by 6 h) and greatly increased the KCa3.1 current by 1 day, and this required de novo protein synthesis. The increase in current was sustained for at least 6 days. IL-4 increased microglial migration and this was reversed by blocking KCa3.1 with TRAM-34. A panel of inhibitors of signal-transduction mediators was used to analyze contributions of IL-4-related signaling pathways. Induction of KCNN4 mRNA and KCa3.1 current was mediated specifically through IL-4 binding to the type I receptor and, surprisingly, it required JAK3, Ras/MEK/ERK signaling and the transcription factor, activator protein-1, rather than JAK2, STAT6, or phosphatidylinositol 3-kinase.The same receptor subtype and pathway were required for the enhanced KCa3.1-dependent migration. In providing the first direct signaling link between an IL-4 receptor, expression and roles of an ion channel, this study also highlights the potential importance of KCa3.1 in alternative-activated microglia. PMID:25071444

Ferreira, Roger; Lively, Starlee; Schlichter, Lyanne C.

2014-01-01

294

Alternative immunoassays  

SciTech Connect

This book contains 13 chapters. Some of the chapter titles are: Uses of immunoassay; Particle immunoassays; Immunoradiometric assays; Enzyme immunoassays; and Current concepts and future developments.

Collins, W.P.

1985-01-01

295

Alternative Assessment  

NSDL National Science Digital Library

As an alternative method of assessment, students create portfolios by submitting monthly entries that demonstrate and expand their understanding of science concepts. Teachers can also use the portfolios to assess the success of their teaching practices an

Penelope S. Valdez

2001-11-01

296

Alternative Schools.  

ERIC Educational Resources Information Center

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)

Pritchett, Stanley; Kimsey, Steve

2002-01-01

297

Alternative Medicine  

MedlinePLUS

... that some of these treatment alternatives have no proven clinical effect. Regular exercise and relaxation techniques can ... use homeopathic remedies and dismiss valid therapies, delaying proven treatment for serious conditions. Holistic Treatments Holistic medicine ...

298

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

PubMed Central

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

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

299

Electrochemical deposition and stripping of copper, nickel and copper nickel alloy thin films at a polycrystalline gold surface: a combined voltammetry-coulometry-electrochemical quartz crystal microgravimetry study  

Microsoft Academic Search

Cyclic voltammetry, anodic stripping voltammetry (ASV) and coulometry were used in conjunction with electrochemical quartz crystal microgravimetry (EQCM) and ex situ X-ray photoelectron spectroscopy (XPS) for a study of the electrodeposition and stripping of Cu, Ni and Cu?Ni alloy thin films at a polycrystalline Au surface. A deaerated Watts bath was employed for the electrodeposition of Ni and Cu?Ni thin

M. Zhou; N. Myung; X. Chen; K. Rajeshwar

1995-01-01

300

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

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.

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

301

Computational aided-molecular imprinted polymer design for solid phase extraction of metaproterenol from plasma and determination by voltammetry using modified carbon nanotube electrode.  

PubMed

A molecular imprinted polymer (MIP) was computationally designed and synthesized for the selective extraction of metaproterenol (MTP), from human plasma. In this regards semi empirical MP3 and mechanical quantum (DFT) calculations were used to find a suitable functional monomers. On the basis of computational and experimental results, acrylic acid (AA) and DMSO:MeOH (90:10 %V/V) were found to be the best choices of functional monomer and polymerization solvents, respectively. This polymer was then used as a selective sorbent to develop a molecularly imprinted solid-phase extraction (MISPE) procedure followed by differential pulse voltammetry by using modified carbon nanotube electrode. The analysis was performed in phosphate buffer, pH 7.0. Peak currents were measured at +0.67 V versus Ag/AgCl. The linear calibration range was 0.026-8.0 ?g mL(-1) with a limit of detection 0.01 ?g mL(-1). The relative standard deviation at 0.5 ?g mL(-1) was 4.76% (n=5). The mean recoveries of 5 ?g mL(-1) MTP from plasma was 92.2% (n=5). The data of MISPE-DPV were compared with the MISPE-HPLC-UV. Although, the MISPE-DPV was more sensitive but both techniques have similar accuracy and precision. PMID:25237337

Ahmadi, Farhad; Karamian, Ehsan

2014-01-01

302

Trace analysis of Ponceau 4R in soft drinks using differential pulse stripping voltammetry at SWCNTs composite electrodes based on PEDOT:PSS derivatives.  

PubMed

Ponceau 4R, an edible synthetic colorant used in drinks, syrups, and sweets, has been successfully detected using differential pulse voltammetry at a single-walled carbon nanotubes-modified composite electrode based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) and two derivatives thereof. The electrochemical parameters of three Ponceau 4R sensors, such as pH value, pre-concentration time, and scan rate, have been optimized, and their electrochemical performances have been compared. A poly(acrylate-modified 3,4-ethylenedioxythiophene-co-3,4-ethylenedioxythiophene):poly(styrene sulfonate)-single-walled carbon nanotubes-poly(vinyl alcohol)-modified electrode showed the best electrocatalytic activity, with the highest response current, lowest detection limit (1.8nm), widest linear range (0.0055-110.6?m), and best sensing stability. Additionally, the modified electrode has also been successfully employed for real sample analysis with soft drinks. Satisfactory results were obtained, demonstrating this to be an easy and effective approach for trace analysis of Ponceau 4R in food samples. PMID:25766817

Wang, Zifei; Zhang, Hui; Wang, Zhipeng; Zhang, Jie; Duan, Xuemin; Xu, Jingkun; Wen, Yangping

2015-08-01

303

Gold-deferrioxamine nanometric interface for selective recognition of Fe(III) using square wave voltammetry and electrochemical impedance spectroscopy methods.  

PubMed

Deferrioxamine, a bacterial hydroxamic siderophore having high binding affinity for Fe(III), is used in its immobilized form, as self-assembled monolayer on Au, for accumulation and recognition of Fe(III) from the solution phase. The accumulated Fe(III) is detected via both active mode based on faradaic reduction current of Fe(III), and inactive mode based on impedimetric effect of accumulated Fe(III) against redox reaction of a suitable probe. Appropriate electrochemical techniques, square wave voltammetry and electrochemical impedance spectroscopy, are used for the transduction of analytical signals obtained by this sensor. Then, the parameters influencing the sensor response are optimized. In the best conditions, a linear response, from 1.0×10(-10) to 1.0×10(-7)M Fe(III) in logarithmic scale with a detection limit of 2.0×10(-11)M, and mean relative standard deviation of 1.7% for n=4 is observed. The results show that the sensor can be used for determination of Fe(III) in the presence of various inorganic ions and biological species. Validity of the method and applicability of the sensor are successfully tested by determination of Fe(III) in various real samples including plant tissue (corn leaves), industrial alloy (Ferrotitanium), and pharmaceutical samples (Venofer(®) ampoule, Ironorm(®) capsule, and V.M. Protein(®) powder). PMID:22796024

Shervedani, Reza Karimi; Akrami, Zakyeh

2013-01-15

304

Computational Aided-Molecular Imprinted Polymer Design for Solid Phase Extraction of Metaproterenol from Plasma and Determination by Voltammetry Using Modified Carbon Nanotube Electrode  

PubMed Central

A molecular imprinted polymer (MIP) was computationally designed and synthesized for the selective extraction of metaproterenol (MTP), from human plasma. In this regards semi empirical MP3 and mechanical quantum (DFT) calculations were used to find a suitable functional monomers. On the basis of computational and experimental results, acrylic acid (AA) and DMSO:MeOH (90:10 %V/V) were found to be the best choices of functional monomer and polymerization solvents, respectively. This polymer was then used as a selective sorbent to develop a molecularly imprinted solid-phase extraction (MISPE) procedure followed by differential pulse voltammetry by using modified carbon nanotube electrode. The analysis was performed in phosphate buffer, pH 7.0. Peak currents were measured at +0.67 V versus Ag/AgCl. The linear calibration range was 0.026–8.0 ?g mL-1 with a limit of detection 0.01 ?g mL-1. The relative standard deviation at 0.5 ?g mL-1 was 4.76% (n=5). The mean recoveries of 5 ?g mL-1 MTP from plasma was 92.2% (n=5). The data of MISPE-DPV were compared with the MISPE-HPLC-UV. Although, the MISPE-DPV was more sensitive but both techniques have similar accuracy and precision. PMID:25237337

Ahmadi, Farhad; Karamian, Ehsan

2014-01-01

305

A new Methimazole sensor based on nanocomposite of CdS NPs-RGO/IL-carbon paste electrode using differential FFT continuous linear sweep voltammetry.  

PubMed

A Methimazole sensor was designed and constructed based on nanocomposite of carbon, ionic liquid, reduced graphene oxide (RGO) and CdS nanoparticles. The sensor signal was obtained by Differential FFT continuous linear sweep voltammetry (DFFTCLSV) technique. The potential waveform contains two sections, preconcentration potential and potential ramp. In this detection technique, after subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The combination of RGO and CdS nanoparticles can catalyze the electron transfer, which outcomes of the amplification of the sensor signal. The result showed that the sensor response was proportional to the concentrations of Methimazole in the range of 2.0 to 300 nM, with a detection limit of 5.5×10(-10) M. The sensor showed good reproducibility, long-term of usage stability and accuracy. The characterization of the sensor surface was studied by atomic force Microscopy and Electrochemical Impedance Spectroscopy. Moreover, the proposed sensor exhibited good accuracy, and R.S.D value of 2.82%, and the response time of less than 7 s. PMID:24913862

Norouzi, Parviz; Gupta, Vinod Kumar; Larijani, Bagher; Ganjali, Mohammad Reza; Faridbod, Farnoush

2014-09-01

306

Alternative Thinking.  

ERIC Educational Resources Information Center

Explains how advances in diesel and alternative fuels has caused schools to reconsider their use for their bus fleets. Reductions in air pollution emissions, cost-savings developments, and the economies experienced from less downtime and maintenance requirements are explored. (GR)

Herman, Dan

1999-01-01

307

Alternative Conceptualizations.  

ERIC Educational Resources Information Center

This theme issue of the serial "Educational Foundations" contains five articles devoted to the topic of "Alternative Conceptualizations" of the foundations of education. In "The Concept of Place in the New Sociology of Education," Paul Theobald examines the notion of place in educational theory and practice. Janice Jipson and Nicholas Paley, in…

Borman, Kathryn M., Ed.; O'Reilly, Patricia, Ed.

1992-01-01

308

The kinetics of neutral methyl viologen in acidic H 2O+DMF mixed solutions studied by cyclic voltammetry  

Microsoft Academic Search

The chemistry of the two-electron reduction product of viologen (1,1?-dialkyl-4,4?-bipyridinium, V2+) neutral species, is important in understanding the electrochemical behavior of viologens and their utilization. The kinetics for the reactions of neutral methyl viologen (V0) in the presence of H+ (from HCl), CH3COOH (pKa=4.75), ClCH2CH2COOH (pKa=4.00), HCOOH (pKa=3.75) in aqueous media was examined by cyclic voltammetry according to the EECi

Ji Yoen Kim; Chongmok Lee; Joon Woo Park

2001-01-01

309

Simultaneous determination of trace uranium(VI) and zinc(II) by adsorptive cathodic stripping voltammetry with aluminon ligand  

Microsoft Academic Search

Uranium(VI) complexed with aluminon (3-[bis(3-carboxy-4-hydroxy-phenyl)methylene]-6-oxo-1,4-cyclohexadiene-1-carboxylic acid triammonium salt) was determined by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode. Trace uranium(VI) and zinc(II) can be simultaneously determined in a single scan in the presence of aluminon and urea. Optimal conditions were found to be: accumulation time; 180–200 s, accumulation potential; 50 mV versus Ag\\/AgCl, scan rate; 40

Ki-Won Cha; Chan-Il Park; Sang-Hyun Park

2000-01-01

310

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

PubMed

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 L(-1) Bu(4)NPF(6)) and aqueous (0.25 mol L(-1) acetic acid+0.25 mol L(-1) sodium acetate) electrolytes. PMID:12733034

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

2003-04-01

311

Alternative energy technologies  

Microsoft Academic Search

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.

M. S. Dresselhaus; I. L. Thomas

2001-01-01

312

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

PubMed Central

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

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

2015-01-01

313

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

PubMed

The cyclic voltammetry at electrodes composed of multiple electroactive materials, where zones of one highly active material are distributed over a substrate of a second, less active material, is investigated by simulation. The two materials are assumed to differ in terms of their electrochemical rate constants towards any given redox couple. For a one-electron oxidation or reduction, the effect on voltammetry of the size and relative surface coverages of the zones as well as the rate constant of the slower zone are considered for systems where it is much slower than the rate constant of the faster zones. The occurrence of split peak cyclic voltammetry where two peaks are observed in the forward sweep, is studied in terms of the diffusional effects present in the system. A number of surface geometries are compared: specifically the more active zones are modelled as long, thin bands, as steps in the surface, as discs, and as rings (similar to a partially blocked electrode). Similar voltammetry for the band, step and ring models is seen but the disc geometry shows significant differences. Finally, the simulation technique is applied to the modelling of highly-ordered pyrolytic graphite (HOPG) surface and experimental conditions under which it may be possible to observe split peak voltammetry are predicted. PMID:22513756

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

2012-05-28

314

Alternative fuels  

NASA Technical Reports Server (NTRS)

Potential problems related to the use of alternative aviation turbine fuels are discussed and both ongoing and required research into these fuels is described. This discussion is limited to aviation turbine fuels composed of liquid hydrocarbons. The advantages and disadvantages of the various solutions to the problems are summarized. The first solution is to continue to develop the necessary technology at the refinery to produce specification jet fuels regardless of the crude source. The second solution is to minimize energy consumption at the refinery and keep fuel costs down by relaxing specifications.

Grobman, J. S.; Butze, H. F.; Friedman, R.; Antoine, A. C.; Reynolds, T. W.

1977-01-01

315

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

PubMed

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

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

2009-03-01

316

A Simple and Inexpensive Function Generator and a Four-Electrode Cell for Cyclic Voltammetry.  

ERIC Educational Resources Information Center

Describes construction and operation of an inexpensive signal generator and a four-electrode electrochemical cell for use in voltammetric experiments. Also describes construction and operation of a four-electrode electrochemical cell used to illustrate elimination (or minimization) of background currents due to electrochemical reactions by species…

Albahadily, F. N.; Mottola, Horacio A.

1986-01-01

317

Development of a method for total inorganic arsenic analysis using anodic stripping voltammetry and a Au-coated, diamond thin-film electrode.  

PubMed

We demonstrate that a Au-coated, boron-doped, diamond thin-film electrode provides a sensitive, reproducible, and stable response for total inorganic arsenic (As(III) and As(V)) using differential pulse anodic stripping voltammetry (DPASV). As is preconcentrated with Au on the diamond surface during the deposition step and detected oxidatively during the stripping step. Au deposition was uniform over the electrode surface with a nominal particle size of 23 +/- 5 nm and a particle density of 109 cm-2. The electrode and method were used to measure the As(III) concentration in standard and river water samples. The detection figures of merit were compared with those obtained using conventional Au-coated glassy carbon and Au foil electrodes. The method was also used to determine the As(V) concentration in standard solutions after first being chemically reduced to As(III) with Na2SO3, followed by the normal DPASV determination of As(III). Sharp and symmetric stripping peaks were generally observed for the Au-coated diamond electrode. LODs were 0.005 ppb (S/N = 3) for As(III) and 0.08 ppb (S/N = 3) for As(V) in standard solutions. An As(III) concentration of 0.6 ppb was found in local river water. The relative standard deviation of the As stripping peak current for river water was 1.5% for 10 consecutive measurements and was less than 9.1% over a 10-h period. Excellent electrode response stability was observed even in the presence of up to 5 ppm of added humic acid. In summary, the Au-coated diamond electrode exhibited better performance for total inorganic As analysis than did Au-coated glassy carbon or Au foil electrodes. Clearly, the substrate on which the Au is supported influences the detection figures of merit. PMID:17302386

Song, Yang; Swain, Greg M

2007-03-15

318

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode  

PubMed Central

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10?8 M. The linear range obtained was between 0.99 × 10?8 ? 8.26 × 10?8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples. PMID:22389596

Domínguez-Renedo, Olga; Gómez González, M. Jesús; Arcos-Martínez, M. Julia

2009-01-01

319

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

PubMed Central

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

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

2013-01-01

320

Novel application of square-wave adsorptive-stripping voltammetry for the determination of xanthohumol in spent hops.  

PubMed

This paper reports the development of a novel electrochemical assay for xanthohumol (XN) by square-wave adsorptive-stripping voltammetry (SWAdSV) with a hanging mercury drop electrode. The method showed good repeatability (CV < 2%) and linearity (between 10 and 250 ?g L(-1)), as well as suitable limits of detection (2.6 ?g L(-1)) and quantification (8.8 ?g L(-1)). The method was applied for the quantification of this compound in spent hops, and the results obtained were compared with the HPLC-UV method. XN contents determined by the SWAdSV method were 16 ± 1 and 100 ± 4 ?g L(-1) for aqueous and methanolic extracts, respectively. The developed new methodology considerably reduces the analysis time, approximately from 25 min (HPLC-UV method) to 7 min, enabling a high sample throughput. In addition, the detection and quantification limits were approximately 5-fold lower than those obtained with the chromatographic method. PMID:21671607

Moreira, Manuela M; Carvalho, Ana M; Valente, Ines M; Goncalves, Luis M; Rodrigues, Jose A; Barros, Aquiles A; Guido, Luis F

2011-07-27

321

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

PubMed

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

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

2014-01-01

322

SQUID magnetometry combined with in situ cyclic voltammetry: A case study of tunable magnetism of ?-Fe2O3 nanoparticles  

PubMed Central

SQUID magnetometry combined with in situ cyclic voltammetry by means of a three-electrode chemical cell opens up novel potentials for studying correlations between electrochemical processes and magnetic behaviour. The combination of these methods shows that the charge-induced variation of the magnetic moment of nanocrystalline maghemite (?-Fe2O3) of about 4% strongly depends on the voltage regime of charging. Upon positive charging, the charge-induced variation of the magnetic moment is suppressed due to adsorption layers. The pronounced charge-sensitivity of the magnetic moment in the regime of negative charging may either be associated with a redox reaction or with charge-induced variations of the magnetic anisotropy or magnetoelastic coupling. PMID:23471175

Topolovec, Stefan; Jerabek, Peter; Szabó, Dorothée Vinga; Krenn, Heinz; Würschum, Roland

2013-01-01

323

On the essential role of current density in electrocatalytic activity of the electrodeposited platinum for oxidation of ammonia  

NASA Astrophysics Data System (ADS)

Fabrication by electrolytic deposition of platinum (Pt) electrocatalyst provides a promising alternative for oxidation of ammonia. This work investigated the role of current density in the electrocatalytic activity of the prepared Pt electrocatalysts by cyclic voltammetry and surface characterization. The Pt loading amount is determined by inductively coupled plasma. Results demonstrated that, the electrodeposited Pt has a much higher electrocatalytic activity than the pure Pt electrode due to the high electroactive surface area of the Pt deposit. The electrocatalytic activity of the Pt catalyst is improved with the increase of the Pt loading. Moreover, the electrocatalytic activity of Pt increases with the depositing current density which results in an increasing Pt loading amount. The depositing current density also affects the surface morphology of the prepared Pt. The high depositing current density generates small Pt particles at a nanometer scale, or sheet-like dendritic structure. However, the low current density leads to large Pt particles at several hundreds of nanometer with a relatively smooth morphology. The Pt electrocatalyst with the former morphological feature exhibits a higher electrocatalytic activity than the later due to the higher electroactive surface area.

Zhong, C.; Hu, W. B.; Cheng, Y. F.

2011-10-01

324

Demon voltammetry and analysis software: Analysis of cocaine-induced alterations in dopamine signaling using multiple kinetic measures  

PubMed Central

The fast sampling rates of fast scan cyclic voltammetry make it a favorable method for measuring changes in brain monoamine release and uptake kinetics in slice, anesthetized, and freely moving preparations. The most common analysis technique for evaluating changes in dopamine signaling uses well-established Michaelis-Menten kinetic methods that can accurately model dopamine release and uptake parameters across multiple experimental conditions. Nevertheless, over the years, many researchers have turned to other measures to estimate changes in dopamine release and uptake, yet to our knowledge no systematic comparison amongst these measures has been conducted. To address this lack of uniformity in kinetic analyses, we have created the Demon Voltammetry and Analysis software suite, which is freely available to academic and non-profit institutions. Here we present an explanation of the Demon Acquisition and Analysis features, and demonstrate its utility for acquiring voltammetric data under in vitro, in vivo anesthetized, and freely moving conditions. Additionally, the software was used to compare the sensitivity of multiple kinetic measures of release and uptake to cocaine-induced changes in electrically evoked dopamine efflux in nucleus accumbens core slices. Specifically, we examined and compared tau, full width at half height, half-life, T20, T80, slope, peak height, calibrated peak dopamine concentration, and area under the curve to the well-characterized Michaelis-Menten parameters, dopamine per pulse, maximal uptake rate, and apparent affinity. Based on observed results we recommend tau for measuring dopamine uptake and calibrated peak dopamine concentration for measuring dopamine release. PMID:21392532

Yorgason, Jordan T.; España, Rodrigo A.; Jones, Sara R.

2011-01-01

325

Alternatives to Antimicrobials  

Microsoft Academic Search

The emergence of multidrug resistant pathogens has stimulated a need to find alternatives to antimicrobials. Currently, no\\u000a single treatment is available that can eliminate the need for antimicrobials; particularly for immunocompromised individuals.\\u000a Prudent use to protocols have been called for to decrease the consumption of antimicrobials. This includes the use to antimicrobials\\u000a for individuals clinically diagnosed with bacterial infections and

Toni L. Poole; Todd R. Callaway; David J. Nisbet

326

Compensated pulsed alternator  

DOEpatents

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.

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

1980-01-01

327

Determination of nitroaromatic and nitramine type energetic materials in synthetic and real mixtures by cyclic voltammetry.  

PubMed

Nitro-explosives contain reducible aromatic -NO2 groups or cyclic >N-NO2 bonds that may undergo reductive cleavage. This work reports the development of a cyclic voltammetric (CV) assay for nitro-aromatics (trinitrotoluene (TNT), dinitrotoluene (DNT)) and nitramines (1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) using a glassy carbon electrode. This determination was first used for these energetic materials by resolving current responses of reduction potentials primarily due to one constituent but partly contributed by other constituents. Calibration curves of current intensity versus concentration were linear in the range of 30-120 mg L(-1) for RDX with a limit of detection (LOD) of 10.2 mg L(-1), 40-120 mg L(-1) for HMX (LOD=11.7 mg L(-1)), 40-120 mg L(-1) for TNT (LOD=11.2 mg L(-1)), and 40-140 mg L(-1) for DNT (LOD=10.8 mg L(-1)). Results showed that the CV method could provide a sensitive approach for the simultaneous determination of RDX and TNT in synthetic and real mixtures. Deconvolution of current contributions of mixtures at peak potentials of constituents was performed by multiple linear regression. The proposed method was successfully applied to the analysis of military explosives comp A5 and octol, and method validation was performed both against HPLC on a comp B (TNT+RDX) sample and against GC-MS on real post-blast residual samples containing both explosives. PMID:24054661

Üzer, Ay?em; Sa?lam, Sener; Tekdemir, Yasemin; Ustamehmeto?lu, Belk?s; Sezer, Esma; Erça?, Erol; Apak, Re?at

2013-10-15

328

Augmented and alternative NLP techniques for augmentative and alternative communication  

Microsoft Academic Search

Current communication devices designed for non-speaking users are inadequate to support conversation because the speed with which a user can input information is typically very limited. We describe some practical work on word prediction, and discuss its limitations as a technique for speeding up free text entry. We then out- line an alternative approach, currently un- der development, which combines

Ann Copestake

1997-01-01

329

APPLICATION OF AVIDIN-BIOTIN TECHNOLOGY AND ADSORPTIVE TRANSFER STRIPPING SQUARE-WAVE VOLTAMMETRY FOR DETECTION OF DNA HYBRIDIZATION AND AVIDIN IN TRANSGENIC AVIDIN MAIZE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The proteins streptavidin and avidin were electrochemically detected in solution by adsorptive transfer stripping square wave voltammetry (AdTS SWV) at a carbon paste electrode (CPE). AdTS SWV was used to quantify biotinylated oligonucleotides, DNA hybridizations, and avidin in extracts of transgeni...

330

Sulfuric acid-methanol electrolytes as an alternative to sulfuric-hydrofluoric acid mixtures for electropolishing of niobium  

SciTech Connect

Attainment of the greatest possible interior surface smoothness is critical to meeting the performance demands placed upon niobium superconducting radiofrequency (SRF) accelerator cavities by next generation projects. Electropolishing with HF-H{sub 2}SO{sub 4} electrolytes yields cavities that meet SRF performance goals, but a less-hazardous, more environmentally-friendly process is desirable. Reported studies of EP on chemically-similar tantalum describe the use of sulfuric acid-methanol electrolytes as an HF-free alternative. Reported here are the results of experiments on niobium samples with this electrolyte. Voltammetry experiments indicate a current plateau whose voltage range expands with increasing acid concentration and decreasing temperature. Impedance spectroscopy indicates that a compact salt film is responsible for the current plateau. Equivalent findings in electropolishing chemically-similar tantalum with this electrolyte were interpreted due to as mass transfer limitation by diffusion of Ta ions away from the anode surface. We infer that a similar mechanism is at work here. Conditions were found that yield leveling and brightening comparable to that obtained with HF-H{sub 2}SO{sub 4} mixtures.

Zhao, Xin [JLAB; Corcoran, Sean G. [Virginia Tech; Kelley, Michael J. [W& amp; M, JLAB

2011-06-01

331

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

PubMed

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

Meshki, Marzieh; Behpour, Mohsen; Masoum, Saeed

2015-03-15

332

Total inorganic arsenic detection in real water samples using anodic stripping voltammetry and a gold-coated diamond thin-film electrode.  

PubMed

An accurate method for total inorganic arsenic determination in real water samples was developed using differential pulse anodic stripping voltammetry (DPASV) and a Au-coated boron-doped diamond thin-film electrode. Keys to the method are the use of a conducting diamond platform and solid phase extraction for sample preparation. In the method, the As(III) present in the sample is first detected by DPASV. The As(V) present is then reduced to As(III) by reaction with Na2SO3 and this is followed by a second detection of As(III) by DPASV. Interfering metal ions (e.g., Cu(II)) that cause decreased electrode response sensitivity for arsenic in real samples are removed by solid phase extraction as part of the sample preparation. For example, Cu(II) caused a 30% decrease in the As stripping peak current at a solution concentration ratio of 3:1 (Cu(II)/As(III)). This loss was mitigated by passage of the solution through a Chelex 100 cation exchange resin. After passage, only a 5% As stripping current response loss was seen. The effect of organic matter on the Au-coated diamond electrode response for As(III) was also evaluated. Humic acid at a 5 ppm concentration caused only a 9% decrease in the As stripping peak charge for Au-coated diamond. By comparison, a 50% response decrease was observed for Au foil. Clearly, the chemical properties of the diamond surface in the vicinity of the metal deposits inhibit molecular adsorption on at least some of the Au surface. The method provided reproducible and accurate results for total inorganic arsenic in two contaminated water samples provided by the U.S. Bureau of Reclamation. The total inorganic As concentration in the two samples, quantified by the standard addition method, was 23.2+/-2.9 ppb for UV plant influent water and 16.4+/-0.9 ppb for Well 119 water (n=4). These values differed from the specified concentrations by less than 4%. PMID:17531818

Song, Yang; Swain, Greg M

2007-06-12

333

Adsorptive stripping voltammetry of nickel with 1-nitroso-2-napthol using a bismuth film electrode.  

PubMed

A sensitive procedure is presented for the voltammetric determination of nickel. The procedure involves an adsorptive accumulation of nickel 1-nitroso-2-napthol (NN) complex on a bismuth film electrode prepared ex situ by electrodeposition. The most suitable operating conditions and parameters such as pH, ligand concentration (C(NN)), adsorptive potential (E(ads)), adsorptive time (t(ads)), scan rate and others were selected and the determination of nickel in aqueous solutions using the standard addition method was possible. The adsorbed Ni-NN complex gives a well defined cathodic stripping peak current at -0.70 V, which was used for the determination of nickel in the concentration range of 10.0-70.0 ?g L(-1) (pH 7.5; C(NN) 6.5 ?mol L(-1); E(ads) -0.30 V; t(ads) 60s) with a detection limit of 0.1 ?g L(-1). The relative standard deviation for a solution containing 10.0 ?g L(-1) of Ni(II) was 3.5% (n=4). The proposed method was validated determining Ni(II) in certified reference waste water (SPS-WW1) and Certified Reference Water for Trace Elements (TMDA 51.3) with satisfactory results. Then lake water samples were analyzed. PMID:21962648

Segura, Rodrigo; Pradena, Milenco; Pinto, Deny; Godoy, Fernando; Nagles, Edgar; Arancibia, Verónica

2011-10-15

334

Electric Currents Electric Current  

E-print Network

material. #12;Problem 1: A hair dryer draws 13.5 A when plugged into a 120V line. a) What is the resistance ? b) How much charge passes through it in 15 min. (Assume direct current ). Solution: a) Ohm's Law: V=IR

Yu, Jaehoon

335

Lab-on-a-chip sensor for detection of highly electronegative heavy metals by anodic stripping voltammetry.  

PubMed

This work describes development of a lab-on-a-chip sensor for electrochemical detection of highly electronegative heavy metals such as manganese and zinc by anodic stripping voltammetry. The sensor consists of a three-electrode system, with a bismuth working electrode, a Ag/AgCl reference electrode, and a Au auxiliary electrode. Hydrolysis at the auxiliary electrode is a critical challenge in such electrochemical sensors as its onset severely limits the ability to detect electronegative metals. The bismuth working electrode is used due to its comparable negative detection window and reduced toxicity with respect to a conventional mercury electrode. Through optimization of the sensor layout and the working electrode surface, effects of hydrolysis were substantially reduced and the potential window was extended to the -0.3 to -1.9 V range (vs. Ag/AgCl reference electrode), which is far more negative than what is possible with conventional Au, Pt, or carbon electrodes. The described lab-on-a-chip sensor for the first time permits reliable and sensitive detection of the highly electronegative manganese. The favorable performance of the bismuth electrode coupled with its environmentally-friendly nature make the described sensor attractive for applications where disposable chips are desirable. With further development and integrated sample preparation, the lab-on-a-chip may be converted into a point-of-care platform for monitoring heavy metals in blood (e.g., assessment of manganese exposure). PMID:21479538

Jothimuthu, Preetha; Wilson, Robert A; Herren, Josi; Haynes, Erin N; Heineman, William R; Papautsky, Ian

2011-08-01

336

Head-to-Head Comparisons of Carbon Fiber Microelectrode Coatings for Sensitive and Selective Neurotransmitter Detection by Voltammetry  

PubMed Central

Voltammetry is widely used to investigate neurotransmission and other biological processes but is limited by poor chemical selectivity and fouling of commonly used carbon fiber microelectrodes (CFMs). We performed direct comparisons of three key coating materials purported to impart selectivity and fouling resistance to electrodes: Nafion, base-hydrolyzed cellulose acetate (BCA), and fibronectin. We systematically evaluated the impact on a range of electrode parameters. Fouling due to exposure to brain tissue was investigated using an approach that minimizes the use of animals while enabling evaluation of statistically significant populations of electrodes. We find that BCA is relatively fouling resistant. Moreover, detection at BCA-coated CFMs can be tuned by altering hydrolysis times to minimize the impact on sensitivity losses while maintaining fouling resistance. Fibronectin coating is associated with moderate losses in sensitivity after coating and fouling. Nafion imparts increased sensitivity for dopamine and norepinephrine but not serotonin, as well as the anticipated selectivity for cationic neurotransmitters over anionic metabolites. However, while Nafion has been suggested to resist fouling, both dip-coating and electro-deposition of Nafion are associated with substantial fouling, similar to levels observed at bare electrodes after exposure to brain tissue. Direct comparisons of these coatings identified unique electroanalytical properties of each that can be used to guide selection tailored to the goals and environment of specific studies. PMID:21770471

Singh, Yogesh S.; Sawarynski, Lauren E.; Dabiri, Pasha D.; Choi, Wonwoo R.; Andrews, Anne M.

2011-01-01

337

Lab-on-a-chip sensor for detection of highly electronegative heavy metals by anodic stripping voltammetry  

PubMed Central

This work describes development of a lab-on-a-chip sensor for electrochemical detection of highly electro-negative heavy metals such as manganese and zinc by anodic stripping voltammetry. The sensor consists of a three-electrode system, with a bismuth working electrode, a Ag/AgCl reference electrode, and a Au auxiliary electrode. Hydrolysis at the auxiliary electrode is a critical challenge in such electrochemical sensors as its onset severely limits the ability to detect electronegative metals. The bismuth working electrode is used due to its comparable negative detection window and reduced toxicity with respect to a conventional mercury electrode. Through optimization of the sensor layout and the working electrode surface, effects of hydrolysis were substantially reduced and the potential window was extended to the ?0.3 to ?1.9 V range (vs. Ag/AgCl reference electrode), which is far more negative than what is possible with conventional Au, Pt, or carbon electrodes. The described lab-on-a-chip sensor for the first time permits reliable and sensitive detection of the highly electronegative manganese. The favorable performance of the bismuth electrode coupled with its environmentally-friendly nature make the described sensor attractive for applications where disposable chips are desirable. With further development and integrated sample preparation, the lab-on-a-chip may be converted into a point-of-care platform for monitoring heavy metals in blood (e.g., assessment of manganese exposure). PMID:21479538

Jothimuthu, Preetha; Wilson, Robert A.; Herren, Josi; Haynes, Erin N.; Heineman, William R.; Papautsky, Ian

2013-01-01

338

Electrochemically assisted fabrication of size-exclusion films of organically modified silica and application to the voltammetry of phospholipids  

PubMed Central

Modification of electrodes with nm-scale organically modified silica films with pores diameters controlled at 10- and 50-nm is described. An oxidation catalyst, mixed-valence ruthenium oxide with cyano crosslinks or gold nanoparticles protected by dirhodium-substituted phosophomolybdate (AuNP-Rh2PMo11), was immobilized in the pores. These systems comprise size-exclusion films at which the biological compounds, phosphatidylcholine and cardiolipin, were electrocatalytically oxidized without interference from surface-active concomitants such as bovine serum albumin. 10-nm pores were obtained by adding generation-4 poly(amidoamine) dendrimer, G4-PAMAM, to a (CH3)3SiOCH3 sol. 50-nm pores were obtained by modifying a glassy carbon electrode (GC) with a sub-monolayer film of aminopropyltriethoxylsilane, attaching 50-nm diameter poly(styrene sulfonate), PSS, spheres to the protonated amine, transferring this electrode to a (CH3)3SiOCH3 sol, and electrochemically generating hydronium at uncoated GC sites, which catalyzed ormosil growth around the PSS. Voltammetry of Fe(CN)63? and Ru(NH3)63+ demonstrated the absence of residual charge after removal of the templating agents. With the 50-nm system, the pore structure was sufficiently defined to use layer-by-layer electrostatic assembly of AuNP-Rh2PMo11 therein. Flow injection amperometry of phosphatidylcholine and cardiolipin demonstrated analytical utility of these electrodes. PMID:23935394

Mehdi, B. Layla; Rutkowska, Iwona A.; Kulesza, Pawel J.

2013-01-01

339

Determination of the Antiretroviral Drug Acyclovir in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode  

PubMed Central

This paper describes a stripping method for the determination of acyclovir at the submicromolar concentration level. This method is based on controlled adsorptive accumulation of acyclovir at thin-film mercury electrode, followed by a linear cyclic scan voltammetry measurement of the surface species. Optimal experimental conditions include a NaOH solution of 2.0 × 10?3 mol L?1 (supporting electrolyte), an accumulation potential of ?0.40 V, and a scan rate of 100 mV s?1. The response of acyclovir is linear over the concentration range 0.02 to 0.12 ppm. For an accumulation time of 4 minutes, the detection limit was found to be 0.42 ppb (1.0 × 10?9 mol L?1). More convenient methods to measure the acyclovir in presence of the didanosine, efavirenz, nevirapine, nelfinavir, lamivudine, and zidovudine were also investigated. The utility of this method is demonstrated by the presence of acyclovir together with Adenosine triphosphate (ATP) or DNA. PMID:23761958

Castro, Arnaldo Aguiar; Cordoves, Ana Isa Perez; Farias, Percio Augusto Mardini

2013-01-01

340

On-line preconcentration and determination of lead and cadmium by sequential injection/anodic stripping voltammetry.  

PubMed

The highly sensitive determination of lead (Pb(II)) and cadmium (Cd(II)) ions, with a limit of detection of 0.01?gL(-1) for Pb(II) and Cd(II), by on-line preconcentration and anodic stripping voltammetry (ASV) controlled by a sequential injection analysis (SIA) system is reported here. The SIA system consisted of a syringe pump, an 8-port selection valve and a 6-port switching valve and was incorporated with a bismuth coated screen-printed carbon nanotube electrode (Bi-SPCNTE). The preconcentration of metal ions was performed by solid phase extraction using an Analig TE-05 chelating resin mini-column on a switching valve. The metal ions collected were then eluted from the resin with 1M hydrochloric acid (HCl), deposited on the electrode surface at -1.3V vs. Ag/AgCl and then measured with ASV. The pH of the sample, eluent volume, flow rate, concentration of the bismuth plating solution and the square-wave voltammetric parameters were optimized. Under the optimum conditions, an enrichment factor of 11.9-fold and 6.6-fold for Pb(II) and Cd(II) ions, respectively, was attained. Detection of Pb(II) and Cd(II) had two different linear ranges (0.5-15?gL(-1) and 15-70?gL(-1)). PMID:22817931

Ninwong, Benjawan; Chuanuwatanakul, Suchada; Chailapakul, Orawon; Dungchai, Wijitar; Motomizu, Shoji

2012-07-15

341

Simultaneous recording of dorsal raphe unit activity and serotonin release in the striatum using voltammetry in awake, behaving cats.  

PubMed

Simultaneous recordings of unit activity in the dorsal raphe nucleus (RD) and serotonin (5HT) release in the striatum were made in the cat. Unit recordings were made using Formvar-coated 32 microns diameter nichrome wires. 5HT release was measured using linear sweep voltammetry with semi-differentiation using electrodes prepared from Teflon-coated 32-gauge stainless steel wire filled with carbon paste and Ag/AgCl electrodes and 27-gauge stainless steel needles as reference and auxiliary electrodes, respectively. The working electrodes were scanned at a rate of 10 mV/s over the range of -0.1 to +0.5 V every 5 minutes using a BAS CV37 voltammograph. During REM sleep RD unit activity was decreased 94% from quiet waking (QW) baseline, while the voltammetric response was decreased by only 57%. Chloral hydrate anesthesia decreased RD unit activity by 18% from QW while the voltammetric response was decreased by 39%. LSD decreased RD unit activity by 50% from QW, but the voltammetric response was decreased by 88%. P-chlorophenylalanine produced no significant change in RD unit activity but decreased the voltammetric response by 82%. These data suggest that RD unit activity and 5HT release often differed dramatically. PMID:2933569

Trulson, M E

1985-12-01

342

Determination of vanillin in commercial food product by adsorptive stripping voltammetry using a boron-doped diamond electrode.  

PubMed

A method for the determination of food additive vanillin was developed by adsorptive stripping voltammetry. Its determination was carried out at the anodically pre-treated boron-doped diamond electrode in aqueous solutions. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in phosphate buffer, pH 2.5 at +1.14 V (vs. Ag/AgCl) (a pre-concentration step being carried out at open-circuit condition for 60s). A linear calibration graph was obtained in the concentration range of 0.5-15.0 ?g mL(-1) (3.3×10(-6)-9.8×10(-5) mol L(-1)) with a detection limit of 0.024 ?g mL(-1) (1.6×10(-7) mol L(-1)). As an example, the practical applicability of the proposed method was tested for the determination of this flavouring agent in commercial pudding powder of Keshkule (Turkish milk pudding with almond flour). PMID:23870896

Yard?m, Yavuz; Gülcan, Mehmet; ?entürk, Zühre

2013-12-01

343

SnO? tube-in-tube nanostructures: Cu@C nanocable templated synthesis and their mutual interferences between heavy metal ions revealed by stripping voltammetry.  

PubMed

SnO2 tube-in-tube nanostructures are synthesized using Cu@C nanocables as effective sacrificial templates. It is revealed by stripping voltammetry that SnO2 tube-in-tube nanostructures show excellent performances in the determination of heavy metal ions, which might be related to the extraordinary adsorbing capacities of the hollow structure to metal ions, i.e., metal ions could diffuse into the interior of tubular structure. PMID:23364917

Chen, Xing; Liu, Zhong-Gang; Zhao, Zhi-Qiang; Liu, Jin-Huai; Huang, Xing-Jiu

2013-07-01

344

New approach to evaluating dissolved iodine speciation in natural waters using cathodic stripping voltammetry and a storage study for preserving iodine species  

Microsoft Academic Search

A simple and fast new method to measure dissolved total reducible iodine in natural waters using cathodic stripping voltammetry is presented here. Iodate is promptly reduced to iodide by ascorbic acid (0.5 mM) at pH ? 2.7, and total iodine is measured as iodide. This new method minimises possible interference and contamination from the relatively high concentration of added chemicals

M. Lucia A. M. Campos

1997-01-01

345

Total oxidant-scavenging capacities of plasma from glycogen storage disease type Ia patients as measured by cyclic voltammetry, FRAP and luminescence techniques  

Microsoft Academic Search

Summary  It has been suggested that the very low incidence of atherosclerosis in glycogen storage disease type Ia (GSD Ia) subjects\\u000a might be attributed to elevated levels of uric acid, one of the potent low-molecular-weight antioxidants found in plasma.\\u000a The present communication describes a use of two analytical methods—cyclic voltammetry and ferric reducing ability of plasma—and\\u000a also two chemiluminescence methods to

E. Koren; J. Lipkin; A. Klar; E. Hershkovitz; I. Ginsburg; R. Kohen

2009-01-01

346

Application of a Deconvolutive Procedure to Analyze Several Chlorophenol Species in Natural Waters by Square?Wave Voltammetry on the Boron?Doped Diamond Electrode  

Microsoft Academic Search

The anodic voltammetric behavior of 4?chlorophenol (4?CP) on a boron?doped diamond electrode (BDD) in aqueous solution was studied by square?wave voltammetry. After optimization of the experimental conditions, 4?CP was determined in a Britton?Robinson buffer solution with pH 6.0, prepared with pure water. Moreover, mixtures of some different chlorophenols were also investigated and an analytical method was developed for the simultaneous

Valber A. Pedrosa; Sergio A. S. Machado; Luis A. Avaca

2006-01-01

347

New chemical insights using weakly supported voltammetry: ion pairing in the EC2 reduction of 2,6-diphenylpyrylium in acetonitrile.  

PubMed

Pairing effect: Varying the concentration of support electrolyte in the electrochemical EC(2) reduction of 2,6-diphenylpyrylium reveals the presence of ion pairing between the electroactive species and BF(4)(-). Experiment and theory are shown to be in good agreement only if ion pairing is included in the simulations. This previously unanticipated effect is only observable if voltammetry is performed under conditions of weak support. PMID:22106031

Barnes, Edward O; Wang, Yijun; Belding, Stephen R; Compton, Richard G

2012-01-16

348

Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry  

PubMed Central

In donor–acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers—present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor–acceptor vintage—can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing ?-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two ?-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes—one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites—the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor–acceptor interactions brought about by both ?-electron-rich recognition sites being part of a macrocyclic polyether. PMID:22135467

Fahrenbach, Albert C.; Barnes, Jonathan C.; Li, Hao; Benítez, Diego; Basuray, Ashish N.; Fang, Lei; Sue, Chi-Hau; Barin, Gokhan; Dey, Sanjeev K.; Goddard, William A.; Stoddart, J. Fraser

2011-01-01

349

The Alternative Museum  

NSDL National Science Digital Library

Founded in 1975, the Alternative Museum existed in analog form for 25 years, occupying space in New York City, presenting four to six major exhibitions per year. While I was unable to find a definitive statement to this effect at the site, it appears that the Museum has decided to move all current exhibitions to the Web, to expand its reach to millions more art patrons while still remaining true to its original mission: "providing a professional showcase for artists." At the moment, there are five current exhibitions at the site, including Tools as Art: The Hechinger Collection, presenting 25 works that use tools as either subject matter, for example Bernice Abbot's photograph "Spinning Wrench," or as medium, for example, Mark Blumenstein's "Saw Bird." Other current exhibitions are Tourists on the Moon, by Yoshio Itagaki, a collection of photographs that resemble 19th-century, hand-colored tourist photographs, but that are given a 20th-century slant; I-Section: Do-It-Yourself Human Dissection, a Website by Friederike Paetzold; Between the Real and the Unreal, photographs by Simen Johan; and GenoChoice: Create Your Own Genetically Healthy Child Online! by Virgil Wong. Also available is an archive of selected past exhibitions and art depot, the online museum shop.

350

Community alternatives to psychotherapy  

Microsoft Academic Search

Increasingly, individuals are turning to and being confronted by alternatives to dynamically-oriented therapy. Among these alternative change systems are alternative therapies such as Alcoholics Anonymous, and alternatives to therapy, such as the spiritual approaches based on various meditations. There are important theoretical conflicts between dynamic therapy and these alternatives. However, combinations of dynamic therapy and these alternatives are being forged

Richard Katz; Edward Rolde

1981-01-01

351

Augmented and alternative NLP techniques for augmentative and alternative communication  

E-print Network

as a technique for speeding up free text entry. We then out­ line an alternative approach, currently un­ der was prompted by the needs of an individual who has lost the ability to speak due to amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). Such users would prefer to continue using their original language

Copestake, Ann

352

Syllabus for Chem. 3700 Alternative Energy  

E-print Network

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

Houston, Paul L.

353

Current sensor  

DOEpatents

A current sensor is described that uses a plurality of magnetic field sensors positioned around a current carrying conductor. The sensor can be hinged to allow clamping to a conductor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging.

Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

2007-01-16

354

Alternate assemblies of platinum nanoparticles and metalloporphyrins as tunable electrocatalysts for dioxygen reduction.  

PubMed

Through electrostatic layer-by-layer (LBL) assembly, negatively charged citrate-stabilized platinum nanoparticles (PtNPs) and positively charged [tetrakis(N-methylpyridyl)porphyrinato] cobalt were alternately deposited on a 4-aminobenzoic acid-modified glassy carbon electrode and also on indium tin oxide substrates, directly forming the three-dimensional nanostructured materials. Thus-prepared multilayer films were characterized by UV--visible spectroscopy, surface plasmon resonance (SPR) spectroscopy, atomic force microscopy (AFM), and cyclic voltammetry. Regular growth of the multilayer films is monitored by UV--visible spectroscopy and SPR spectroscopy. AFM provides the morphology of the multilayer films. The PtNPs containing multilayer films exhibit high electrocatalytic activity for the reduction of dioxygen with high stability. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry demonstrate that the PtNP-containing multilayer films can catalyze an almost four-electron reduction of O(2) to H(2)O in an air-saturated 0.5 M H(2)SO(4) solution. Furthermore, the electrocatalytic activity of the films could be further tailored by simply choosing different cycles in the LBL process or more specifically the amount of the assembly components in the films. The high electrocatalytic activity and good stability for dioxygen reduction make the PtNP-containing multilayer films potential candidates for the efficient cathode material in fuel cells. PMID:15620321

Huang, Minghua; Shao, Yong; Sun, Xuping; Chen, Hongjun; Liu, Baifeng; Dong, Shaojun

2005-01-01

355

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...

356

Alternative aircraft fuels  

NASA Technical Reports Server (NTRS)

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.

Longwell, J. P.; Grobman, J.

1978-01-01

357

Extraction of arsenic as the diethyl dithiophosphate complex with supercritical fluid and quantitation by cathodic stripping voltammetry.  

PubMed

The separation of arsenic based on in situ chelation with ammonium diethyl dithiophosphate (ADDTP) has been carried out using methanol-modified supercritical CO(2). Aliquots of extract were added to an electroanalytical cell and arsenic was determined by square wave cathodic stripping voltammetry (SWCSV) at a hanging mercury drop electrode (HMDE). Quantitative extractions of As(DDTP)(3) were achieved when the experiments were carried out at a pressure of 2500psi, a temperature of 90 degrees C, 2.0mL of methanol, 20.0min of static extraction and 5.0min of dynamic extraction in the presence of 18mg of ADDTP. Analysis of arsenic was made using 150mgL(-1) of Cu(II) in 1M HCl solution as supporting electrolyte in the presence of ADDTP as ligand. Preconcentration was carried out by deposition at a potential of -0.50V and the intermetallic compound Cu(x)As(y) was reduced at a potential of -0.77 to -0.82V, depending on ligand concentration. The results showed that the presence of ligand plays an important role, increasing the method's sensitivity and preventing the oxidation of As(III). The calibration graph of the As(DDTP)(3) solution was linear from 0.8 to 12.5mugL(-1) of arsenic (LOD 0.5mugL(-1), R=0.9992, t(acc)=60s). The method was validated using carrot pulp spiked with arsenic solution. This method was applied to the determination of arsenic in samples of carrots, beets and irrigation water. Arsenic in beets was: skin 4.10+/-0.18mgkg(-1); pulp 3.83+/-0.19mgkg(-1) and juice 0.71+/-0.09mgL(-1); arsenic in carrots was: skin 2.15+/-0.09mgkg(-1); pulp 0.59+/-0.11mgkg(-1) and juice 0.71+/-0.03mgL(-1). Arsenic in water were: Chiu-Chiu 0.08mgL(-1), Inacaliri 1.12mgL(-1), and Salado river 0.17+/-0.07mgL(-1). PMID:18970500

Arancibia, Verónica; López, Alex; Zúñiga, M Carolina; Segura, Rodrigo

2006-02-28

358

Highly sensitive determination of mercury using copper enhancer by diamond electrode coupled with sequential injection-anodic stripping voltammetry.  

PubMed

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

Chaiyo, Sudkate; Chailapakul, Orawon; Siangproh, Weena

2014-12-10

359

Peat as an energy alternative  

SciTech Connect

The importance of developing alternative energy sources to augment supplies of fossil fuels is growing all over the world. Coal, oil shale, tar sands, biomass, solar, geothermal, nuclear, and hydroelectric power have received considerable attention as alternative energy sources. One large energy resource, however, has received little attention until recently. That resource is peat. Although peat is used as an energy source in some countries such as Russia, Ireland, and Finland, it is virtually unexploited in many countries including the United States. This paper provides an understanding of peat: its varieties, abundance, and distribution; its value as an energy alternative; its current and future role as an energy alternative; and the environmental and socioeconomic impacts of large-scale peat utilization.

Punwani, D.V.

1980-07-01

360

Current Controlled Current Source (CCCS)  

NSDL National Science Digital Library

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.

Svoboda, James A.

361

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)

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.

Wu, M. X.; Zhong, W. J.; Gao, X. S.; Liu, L. J.; Liu, Z. W.

2014-12-01

362

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

ERIC Educational Resources Information Center

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

Verdini, Roxana A.; Lagier, Claudia M.

2004-01-01

363

Current responsive devices for synchronous generators  

DOEpatents

A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current.

Karlicek, Robert F. (Fullerton, CA)

1983-01-01

364

Current responsive devices for synchronous generators  

DOEpatents

A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current. 11 figs.

Karlicek, R.F.

1983-09-27

365

November 2008 Alternative Energy  

E-print Network

on conventional fossil fuels even further. Two questions then naturally arise: which alternative energyNovember 2008 Alternative Energy Technologies for BC R.L. Evans CleaN eNergy researCh CeNtre, UNiversity of british ColUmbia PaCifiC iNstitUte for Climate solUtioNs AlternAtive energy #12;Pacific

Pedersen, Tom

366

Alternative Fuels Research Laboratory  

NASA Technical Reports Server (NTRS)

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.

Surgenor, Angela D.; Klettlinger, Jennifer L.; Nakley, Leah M.; Yen, Chia H.

2012-01-01

367

Electroplated reticulated vitreous carbon current collectors for lead–acid batteries: opportunities and challenges  

Microsoft Academic Search

Reticulated, open-cell structures based on vitreous carbon substrates electroplated with a Pb–Sn (1wt.%) alloy were investigated as current collectors for lead–acid batteries. Scanning and backscattered electron microscopy, cyclic voltammetry, anodic polarization and flooded 2V single-cell battery testing was employed to characterize the performance of the proposed collectors. A battery equipped with pasted electroplated reticulated vitreous carbon (RVC) electrodes of 137cm2

Elod Gyenge; Joey Jung; Basanta Mahato

2003-01-01

368

Density Currents  

NSDL National Science Digital Library

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.

David Kopaska-Merkel

369

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.

370

Nov/15/2006 Power Alternatives for the OTG Power Alternatives for the  

E-print Network

by a renewable energy alternative. #12;Nov/15/2006 Photovoltaic Technology-PV · Based on photoelectric effect Alternatives for the OTG Photovoltaic Technology-PV · PV Cell, basic building block ­ Semiconductors ­ PN junction- photodiode ­ By photoelectric effect generates current #12;Nov/15/2006 Power Alternatives

Cruz-Pol, Sandra L.

371

Determination of As(III) by anodic stripping voltammetry using a lateral gold electrode: experimental conditions, electron transfer and monitoring of electrode surface.  

PubMed

The aim of this work is to evaluate the efficiency of the determination of As(III) by anodic stripping voltammetry (ASV) using a lateral gold electrode and to study the modifications of the electrode surface during use. Potential waveforms (differential pulse and square wave), potential scan parameters, deposition time, deposition potential and surface cleaning procedure were examined for they effect on arsenic peak intensity and shape. The best responses were obtained with differential pulse potential wave form and diluted 0.25 M HCl as supporting electrolyte. The repeatability, linearity, accuracy and detection limit of the procedure and the interferences of cations and anions in solution were evaluated. The applicability of the procedure for As(III) determination in drinking waters was tested. Cyclic voltammetry (CV) was used to study the electrochemical behaviour of As(III) and for the daily monitoring of electrode surface. Also scanning electron microscopy (SEM) analysis was used to control the electron surface. Finally we evaluated the possibility to apply the equations valid for flow systems also to a stirred system, in order to calculate the number of electrons transferred per molecule during the stripping step. PMID:21238732

Giacomino, Agnese; Abollino, Ornella; Lazzara, Marco; Malandrino, Mery; Mentasti, Edoardo

2011-02-15

372

Micropatterned ferrocenyl monolayers covalently bound to hydrogen-terminated silicon surfaces: effects of pattern size on the cyclic voltammetry and capacitance characteristics.  

PubMed

The effect of the size of patterns of micropatterned ferrocene (Fc)-functionalized, oxide-free n-type Si(111) surfaces was systematically investigated by electrochemical methods. Microcontact printing with amine-functionalized Fc derivatives was performed on a homogeneous acid fluoride-terminated alkenyl monolayer covalently bound to n-type H-terminated Si surfaces to give Fc patterns of different sizes (5 × 5, 10 × 10, and 20 × 20 ?m(2)), followed by backfilling with n-butylamine. These Fc-micropatterned surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The charge-transfer process between the Fc-micropatterned and underlying Si interface was subsequently studied by cyclic voltammetry and capacitance. By electrochemical studies, it is evident that the smallest electroactive ferrocenyl patterns (i.e., 5 × 5 ?m(2) squares) show ideal surface electrochemistry, which is characterized by narrow, perfectly symmetric, and intense cyclic voltammetry and capacitance peaks. In this respect, strategies are briefly discussed to further improve the development of photoswitchable charge storage microcells using the produced redox-active monolayers. PMID:24885588

Fabre, Bruno; Pujari, Sidharam P; Scheres, Luc; Zuilhof, Han

2014-06-24

373

Improving Reproducibility of Lab-on-a-Chip Sensor with Bismuth Working Electrode for Determining Zn in Serum by Anodic Stripping Voltammetry  

PubMed Central

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

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

2014-01-01

374

Characterization of carbon nanotubes decorated with NiFe2O4 magnetic nanoparticles as a novel electrochemical sensor: application for highly selective determination of sotalol using voltammetry.  

PubMed

A magnetic nano-composite of multiwall carbon nanotube, decorated with NiFe2O4 nanoparticles, was synthesized with citrate sol-gel method. The multiwall carbon nanotubes decorated with NiFe2O4 nanoparticles (NiFe2O4-MWCNTs) were characterized with different methods such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The new nano-composite acts as a suitable electrocatalyst for the oxidation of sotalol at a potential of 500 mV at the surface of the modified electrode. Linear sweep voltammetry exhibited two wide linear dynamic ranges of 0.5-1000 ?mol L(-1) sotalol with a detection limit of 0.09 ?mol L(-1). The modified electrode was used as a novel electrochemical sensor for the determination of sotalol in real samples such as pharmaceutical, patient and safe human urine. PMID:25428063

Ensafi, Ali A; Allafchian, Ali R; Rezaei, B; Mohammadzadeh, R

2013-01-01

375

Enzyme-Modified Carbon-Fiber Microelectrode for the Quantification of Dynamic Fluctuations of Non-Electroactive Analytes Using Fast-Scan Cyclic Voltammetry  

PubMed Central

Neurotransmission occurs on a millisecond timescale, but conventional methods for monitoring non-electroactive neurochemicals are limited by slow sampling rates. Despite a significant global market, a sensor capable of measuring the dynamics of rapidly fluctuating, non-electroactive molecules at a single recording site with high sensitivity, electrochemical selectivity, and a subsecond response time is still lacking. To address this need, we have enabled the real-time detection of dynamic glucose fluctuations in live brain tissue using background-subtracted, fast-scan cyclic voltammetry. The novel microbiosensor consists of a simple carbon fiber surface modified with an electrodeposited chitosan hydrogel encapsulating glucose oxidase. The selectivity afforded by voltammetry enables quantitative and qualitative measurements of enzymatically-generated H2O2 without the need for additional strategies to eliminate interferents. The microbiosensors possess a sensitivity and limit of detection for glucose of 19.4 ± 0.2 nA mM?1 and 13.9 ± 0.7 ?M, respectively. They are stable, even under deviations from physiological normoxic conditions, and show minimal interference from endogenous electroactive substances. Using this approach, we have quantitatively and selectively monitored pharmacologically, evoked glucose fluctuations with unprecedented chemical and spatial resolution. Furthermore, this novel biosensing strategy is widely applicable to the immobilization of any H2O2 producing enzyme, enabling rapid monitoring of many non-electroactive enzyme substrates. PMID:23919631

Lugo-Morales, Leyda Z.; Loziuk, Philip L.; Corder, Amanda K.; Toups, J. Vincent; Roberts, James G.; McCaffrey, Katherine A.; Sombers, Leslie A.

2013-01-01

376

Electrochemical study of the antiplatelet agent clopidogrel and its determination using differential pulse voltammetry in bulk form and pharmaceutical preparations with a glassy carbon electrode.  

PubMed

In the present study, the electroanalytical behaviour of clopidogrel (CLP) bisulfate, an antithrombotic drug, was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques using a glassy carbon electrode (GCE). The anodic oxidation of clopidogrel bisulfate was investigated with a GCE to determine the oxidation conditions. The voltammograms of solutions having various concentrations of clopidogrel were recorded in order to obtain the optimum oxidation conditions of this drug on a GCE. To determine the effects of the nature of the supporting electrolyte, pH and scan rate on the anodic oxidation reactions, the experiments were performed in 0.2 M sulphuric acid, and in Britton-Robinson (BR) (pH 2-5) and acetate (pH 3.5-5.63) buffers with a 10-400 mVs(-1) scan rate interval. The oxidation of clopidogrel bisulfate was found to be diffusion-controlled over a concentration range of 0.08 mM-1.0 mM in pH 3.7 acetate buffer by an optimized DPV technique. The voltammetric method developed was applied to the tablet form of pharmaceutical preparation of this compound and the accuracy, precision, selectivity, sensitivity, repeatibility within and between days and reproducibility of the proposed method was investigated statistically. The results were compared with the spectrophotometric and HPLC methods developed in our laboratory and found to be in good agreement. No interference was observed from common pharmaceutical adjuvants. PMID:20383936

Dermi?, S; Aydo?an, E

2010-03-01

377

An Approach to Examining Technical Alternatives  

E-print Network

­ Some Methods of Technology Selection · Cost-Benefit Analysis · The Role of Probability · Risk · Current Operational Effectiveness Analysis Cost Analysis Concept Development Specific Ship Impacts Signature Control, ship design, cost analysis, and operations research analysis to examine alternative approaches

378

Evaluation of alternative leachate liner materials  

E-print Network

The purpose of this study is to evaluate alternative landfill liner materials that could be utilized in conjunction with current liners in order to improve the liner's performance by preventing the release of hazardous chemicals into the subsurface...

Biles, Daniel Franklin

1994-01-01

379

Alternative Compression Garments  

NASA Technical Reports Server (NTRS)

Orthostatic intolerance after spaceflight is still an issue for astronauts as no in-flight countermeasure has been 100% effective. Future anti-gravity suits (AGS) may be similar to the Shuttle era inflatable AGS or may be a mechanical compression device like the Russian Kentavr. We have evaluated the above garments as well as elastic, gradient compression garments of varying magnitude and determined that breast-high elastic compression garments may be a suitable replacement to the current AGS. This new garment should be more comfortable than the AGS, easy to don and doff, and as effective a countermeasure to orthostatic intolerance. Furthermore, these new compression garments could be worn for several days after space flight as necessary if symptoms persisted. We conducted two studies to evaluate elastic, gradient compression garments. The purpose of these studies was to evaluate the comfort and efficacy of an alternative compression garment (ACG) immediately after actual space flight and 6 degree head-down tilt bed rest as a model of space flight, and to determine if they would impact recovery if worn for up to three days after bed rest.

Stenger, M. B.; Lee, S. M. C.; Ribeiro, L. C.; Brown, A. K.; Westby, C. M.; Platts, S. H.

2011-01-01

380

A new quenching alternative  

SciTech Connect

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.

Brennan, R.J.; Faulkner, C.H. [Houghton International, Valley Forge, PA (United States)

1996-12-31

381

A coulometric normalization procedure for comparing high surface area methanol anode catalysts by rotating disk electrode voltammetry  

Microsoft Academic Search

A new method that allows one to normalize the current observed at electrocatalytic rotating disk electrodes (RDEs), based on coulometric analysis of hydrogen desorption waves, is presented. Current-voltage curves for methanol oxidation, using various platinum alloy compositions and application methods, were analyzed by this method. Mass-normalized I-V curves showed considerable scatter among similar alloys (Pt, Pt-Ru, and Pt-Ru-Os) applied by

Renxuan Liu; K. Triantafillou; L. Liu; C. Pu; C. Smith; E. S. Smotkin

1997-01-01

382

Alternative and Integrative Medicine  

MedlinePLUS

... from, the development of conventional medicine. Examples include: Traditional Medicine: These alternative medicine systems often are the healthcare rituals practiced by a given culture (eg, Asian, Indian, African). Homeopathic Medicine: This alternative medicine system is ...

383

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.

384

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.

385

ALTERNATIVE SPRING BREAK!  

E-print Network

SIGN UP TODAY! ALTERNATIVE SPRING BREAK! The Community Service Center, Boston University's volunteer hub, just keeps growing. Lining Up toServe BOSTON UNIVERSITY Spring 2009 SIGN UP TODAY! ALTERNATIVE SPRING BREAK! #12;BUParentSpring2009 1 SIGN UP TODAY! ALTERNATIVE SPRING BREAK! Features 5 Online

Goldberg, Bennett

386

The Alternate Atomic Model  

Microsoft Academic Search

An alternate atomic model posits concentric electron and nucleon fields spinning together about an empty center. It is alternative to the generally accepted planetary system in which electron point particles orbit about a center clump of nucleon point particles. Introduced in 1992 as an alternative to the standard model of the nucleus it applies scientific space-time knowledge unknown when the

Evan Ragland

2008-01-01

387

APAP and Alternative Titration Methods.  

PubMed

PURPOSE OF REVIEW: Positive airway pressure therapy (PAP) is commonly prescribed treatment for obstructive sleep apnea (OSA). Traditionally, the determination of the optimal pressure for treatment of sleep-disordered breathing was made by manual titration of the device by a sleep technician in attendance during polysomnography. However, the advent of alternative methods for determination of optimal PAP - such as auto-titrating PAP (APAP) - has seen tremendous growth over the past decade. The purpose of this review is to improve our understanding of the currently available alternative methods for titration of PAP in patients with sleep-disordered breathing (SDB) with special emphasis on obstructive sleep apnea. RECENT FINDINGS: Recent prospective-randomized studies of alternative methods of titration suggest that pressure determinations made by such devices are comparable to traditional manual titrations made in the sleep laboratory. Obstacles to the adoption of such alternative modes of titration into day-to-day practice may be attributable to issues surrounding appropriate patient selection, differences between devices, re-imbursement policies of third party payors, consensus amongst sleep experts, and individual physicians' practice patterns and volumes. While newer generations and types of auto-titrating PAP devices are entering the sleep field constantly, providers' knowledge and time availability remain limiting factors. SUMMARY: There is tremendous growth in the technology and scientific evidence in support of alternative modes of PAP titration for sleep-disordered breathing, but barriers to implementation remain. PMID:20806054

Ahmed, Omer; Parthasarathy, Sairam

2010-09-01

388

Industry experience with alternative methods.  

PubMed

L'OREAL has been using alternative methods for almost 30 years and this has led to their current widespread in-house use for evaluation of local effects in safety and efficacy. Alternative methods are used daily to assess eye and skin tolerance, phototoxicity, photoprotection, skin sensitization, percutaneous absorption and skin and hair care. For eye irritation, many years of in-house studies have enabled us to develop and to select the most reliable tests. New in vitro methods have also been developed to help to understand the ocular irritation mechanisms which underlie the irritative properties of new chemicals. In the field of skin irritation, L'OREAL's work has focused mainly on the wide possibilities offered by reconstructed human skins to evaluate the skin tolerance of cosmetics. Today we have managed to introduce Langerhans cells in reconstructed epidermis to develop an alternative to skin sensitization. Besides these in-house investigations either in research or in evaluation, our laboratories have contributed actively to multicentric studies to help the prevalidation/validation process in various fields. The alternative approach is now totally integrated into the safety evaluation strategy, and this allowed L'OREAL to totally ban animal testing on cosmetic products several years ago. In vitro alternatives are very powerful tools: they allow the study of fine mechanisms and the use of human cells. This overall 'in vitro' approach is a scientific, ethical and industrial breakthrough. PMID:10022316

LeClaire, J; de Silva, O

1998-12-28

389

APAP and Alternative Titration Methods  

PubMed Central

Purpose of review Positive airway pressure therapy (PAP) is commonly prescribed treatment for obstructive sleep apnea (OSA). Traditionally, the determination of the optimal pressure for treatment of sleep-disordered breathing was made by manual titration of the device by a sleep technician in attendance during polysomnography. However, the advent of alternative methods for determination of optimal PAP – such as auto-titrating PAP (APAP) – has seen tremendous growth over the past decade. The purpose of this review is to improve our understanding of the currently available alternative methods for titration of PAP in patients with sleep-disordered breathing (SDB) with special emphasis on obstructive sleep apnea. Recent Findings Recent prospective-randomized studies of alternative methods of titration suggest that pressure determinations made by such devices are comparable to traditional manual titrations made in the sleep laboratory. Obstacles to the adoption of such alternative modes of titration into day-to-day practice may be attributable to issues surrounding appropriate patient selection, differences between devices, re-imbursement policies of third party payors, consensus amongst sleep experts, and individual physicians’ practice patterns and volumes. While newer generations and types of auto-titrating PAP devices are entering the sleep field constantly, providers’ knowledge and time availability remain limiting factors. Summary There is tremendous growth in the technology and scientific evidence in support of alternative modes of PAP titration for sleep-disordered breathing, but barriers to implementation remain. PMID:20806054

Ahmed, Omer; Parthasarathy, Sairam

2010-01-01

390

Electrochemical behavior of copper current collector in imidazolium-based ionic liquid electrolytes  

Microsoft Academic Search

The electrochemical behaviors of copper current collector in 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide\\u000a ionic liquid electrolytes were investigated and compared with that in ethylene carbonate\\/dimethyl carbonate solutions. Cyclic\\u000a voltammetry results showed that large oxidation–reduction current of the copper foil appeared in ethylene carbonate\\/dimethyl\\u000a carbonate solutions, while a much smaller current in the room temperature ionic liquid electrolytes decreased gradually, indicating\\u000a that the

Chengxin Peng; Li Yang; Shaohua Fang; Jixian Wang; Zhengxi Zhang; Kazuhiro Tachibana; Yong Yang; Shiyong Zhao

2010-01-01

391

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.

392

Depleted uranium management alternatives  

SciTech Connect

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.

Hertzler, T.J.; Nishimoto, D.D.

1994-08-01

393

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.

394

Alternative Certification Isn't Alternative  

ERIC Educational Resources Information Center

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…

Walsh, Kate; Jacobs, Sandi

2007-01-01

395

Normetex Pump Alternatives Study  

SciTech Connect

A mainstay pump for tritium systems, the Normetex scroll pump, is currently unavailable because the Normetex company went out of business. This pump was an all-metal scroll pump that served tritium processing facilities very well. Current tritium system operators are evaluating replacement pumps for the Normetex pump and for general used in tritium service. An all-metal equivalent alternative to the Normetex pump has not yet been identified. 1. The ideal replacement tritium pump would be hermetically sealed and contain no polymer components or oils. Polymers and oils degrade over time when they contact ionizing radiation. 2. Halogenated polymers (containing fluorine, chlorine, or both) and oils are commonly found in pumps. These materials have many properties that surpass those of hydrocarbon-based polymers and oils, including thermal stability (higher operating temperature) and better chemical resistance. Unfortunately, they are less resistant to degradation from ionizing radiation than hydrocarbon-based materials (in general). 3. Polymers and oils can form gaseous, condensable (HF, TF), liquid, and solid species when exposed to ionizing radiation. For example, halogenated polymers form HF and HCl, which are extremely corrosive upon reaction with water. If a pump containing polymers or oils must be used in a tritium system, the system must be designed to be able to process the unwanted by-products. Design features to mitigate degradation products include filters and chemical or physical traps (eg. cold traps, oil traps). 4. Polymer components can work in tritium systems, but must be replaced regularly. Polymer components performance should be monitored or be regularly tested, and regular replacement of components should be viewed as an expected normal event. A radioactive waste stream must be established to dispose of used polymer components and oil with an approved disposal plan developed based on the facility location and its regulators. Polymers have varying resistances to ionizing radiation - aromatic polymers such as polyimide Vespel (TM) and the elastomer EPDM (ethylene propylene diene monomer) have been found to be more resistant to degradation in tritium than other polymers. This report presents information to help select replacement pumps for Normetex pumps in tritium systems. Several pumps being considered as Normetex replacement pumps are discussed.

Clark, E.

2013-04-25

396

Alternating current OHMIC heating in a toroidal stellerator  

Microsoft Academic Search

High frequency inductive heating in a toroidal stellarator was studied. It is demonstrated that high frequency power can be efficiently coupled to the plasma by a mechanism which circumvents the limitations of the classical skin effect. This mechanism, is studied for two magnetic field configurations: a classical stellarator and a doublestar-- a stellarator with two large magnetic islands. The plasma

D. Wroblewski

1984-01-01

397

Application of alternating current impedance to fuel cell modeling  

SciTech Connect

AC impedance has provided a useful diagnostic tool in the Los Alamos polymer electrolyte fuel cell (PEFC) program. The author reviews the techniques he has used in ac impedance modeling. These techniques include equation implementation, model simplification and verification, least squares fitting, application of two-dimensional Laplace equation solvers handling complex interfacial boundary conditions, and interpretation of impedance features. The separate features of the complete electrode model are explained by analytic examples.

Springer, T.E.

1999-05-02

398

Alternating current electrokinetic properties of gold-coated microspheres.  

PubMed

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

García-Sánchez, Pablo; Ren, Yukun; Arcenegui, Juan J; Morgan, Hywel; Ramos, Antonio

2012-10-01

399

The Chernobyl NPP decommissioning: Current status and alternatives  

SciTech Connect

After the Chernobyl accident of April 26, 1986, many contradictory decisions were taken concerning the Chernobyl nuclear power plant (NPP) future. The principal source of contradictions was a deadline for a final shutdown of the Chernobyl NPP units. Alterations in a political and socioeconomic environment resulted in the latest decision of the Ukrainian Authorities about 2000 as a deadline for a beginning of the Chernobyl NPP decommissioning. The date seems a sound compromise among the parties concerned. However, in order to meet the data a lot of work should be done. First of all, a decommissioning strategy has to be established. The problem is complicated due to both site-specific aspects and an absence of proven solutions for the RBMK-type reactor decommissioning. In the paper the problem of decommissioning option selection is considered taking into account an influence of the following factors: relevant legislative and regulatory requirements; resources required to carry out decommissioning (man-power, equipment, technologies, waste management infrastructure, etc.); radiological and physical status of the plant, including structural integrity and predictable age and weather effects; impact of planned activities at the destroyed unit 4 and within the 30-km exclusion zone of the Chernobyl NPP; planed use of the site; socio-economic considerations.

Mikolaitchouk, H. [Atomaudit Ltd., Kiev (Ukraine); Steinberg, N. [Atomaudit Ltd., Kiev (Ukraine)

1996-08-01

400

Contactless measurement of alternating current conductance in quantum Hall structures  

SciTech Connect

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.

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

401

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...

402

The magnetic amplifier with alternating-current control  

E-print Network

-cored inductances used consisted of toroidal ferromagnetic cores, each wound with many windings, and by connecting windings in series or parallel a variety of turns ratios were made available. The toroids used are made of Deltamax iron, which is a trade name... for a 5Nl nickel, iron alloy made by The Allegheny Ludlum Steel Corporation. The core material is grain oriented by rolling, and the toroidal core is formed by winding a single continuous strip of the alloy into a coil. This construction permits...

Andrew, Edward Harris

1954-01-01

403

Elemental composition of surface copper sulfide in alternating current electroluminophors  

SciTech Connect

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.

Kovalev, B.A.; Chapaikin, S.P.; Valyukhov, D.S.

1986-09-01

404

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....

405

Alternating current response of carbon nanotubes with randomly distributed impurities  

NASA Astrophysics Data System (ADS)

The increasing need for nanodevices has necessitated a better understanding of the electronic transport behavior of nanomaterials. We therefore theoretically examine the AC transport properties of metallic carbon nanotubes with randomly distributed impurities. We find that the long-range impurity scattering increases the emittance, but does not affect the DC conductance. The estimated dwell time of electrons increases with the potential amplitudes. That is, multiple scattering by the impurities increases the kinetic inductance in proportion to the dwell time, which eventually increases the emittance. We believe that our findings can contribute significantly to nanodevice development.

Hirai, Daisuke; Yamamoto, Takahiro; Watanabe, Satoshi

2014-10-01

406

Current limiters  

SciTech Connect

The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

Loescher, D.H. [Sandia National Labs., Albuquerque, NM (United States). Systems Surety Assessment Dept.; Noren, K. [Univ. of Idaho, Moscow, ID (United States). Dept. of Electrical Engineering

1996-09-01

407

Spectroscopic properties and cyclic voltammetry on a series of meso-tetra( p-alkylamidophenyl)porphyrin liquid crystals and their Mn complexes  

NASA Astrophysics Data System (ADS)

A series of meso-tetra( p-alkylamidophenyl)porphyrin ligands and their manganese(III) complexes are reported in this paper. The mesomorphism was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) and the results show that only the porphyrin ligands with long side chains show liquid crystalline behavior, and they exhibit a high phase transition temperature and a broad mesophase temperature span. Furthermore, we investigated the properties of the compounds by means of UV-vis spectra, infrared spectra, Resonance Raman spectra, fluorescence spectra, thermal analysis and cyclic voltammetry. These studies indicate that the length of side chains has little effect on the properties of porphyrin compounds. According to thermal studies, the decomposition of porphyrin ligand and Mn complex is a continuous process.

Sun, Erjun; Shi, Yuhua; Zhang, Ping; Zhou, Mi; Zhang, Yihua; Tang, Xuexin; Shi, Tongshun

2008-10-01

408

Scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry study on the enhanced visible photocatalytic mechanism of carbon-TiO2 nanohybrids  

NASA Astrophysics Data System (ADS)

Carbon-TiO2 nanohybrids (CTs, 5-10 nm TiO2 nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO2 nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6 m2/g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K2Cr2O7) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.

Ming, Hai; Zhang, Hengchao; Ma, Zheng; Huang, Hui; Lian, Suoyuan; Wei, Ying; Liu, Yang; Kang, Zhenhui

2012-02-01

409

Corrosion Cyclic Voltammetry of Two Types of Heat-Affected Zones (HAZs) of API-X100 Steel in Bicarbonate Solutions  

NASA Astrophysics Data System (ADS)

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.

Eliyan, Faysal Fayez; Alfantazi, Akram

2014-12-01

410

Cyclic voltammetry at TCNQ and TTF-TCNQ modified platinum electrodes: A study of the glucose oxidase/glucose and galactose oxidase/galactose systems  

SciTech Connect

Recent work has shown that the synthetic metal TTF-TCNQ can be used as an electrode material for the oxidation of enzymes containing the prosthetic group flavin adenine dinucleotide (FAD). This direct electron transfer (direct in the sense that oxygen is not a mediator) between reduced enzyme and electrode, a process which does not occur to any measurable extent at a typical metal electrode, is not very well understood. In the present work, electron transfer between reduced glucose oxidase and TTF-TCNQ is investigated using cyclic voltammetry, and it is also shown that TCNQ itself can mediate this electron transfer between the enzyme and a platinum electrode. In addition to the glucose oxidase studies, cyclic voltammetric experiments have been performed on the galactose oxidase system, which contains a copper redox center rather than FAD. The results of these experiments demonstrate that the catalytic ability of TTF-TCNQ in enzyme-based electrochemical sensors is quite general. 15 refs., 4 figs.

Hale, P.D.; Skotheim, T.A.

1988-01-01

411

Determination of EDTA species in water by second-derivative square-wave voltammetry using a chitosan-coated glassy carbon electrode.  

PubMed

Based on the adsorption of Fe(EDTA)- on a chitosan-coated glassy carbon electrode, a second-derivative square-wave voltammetry for the determination of the EDTA species in water samples was investigated. The measuring range of EDTA was from 6.0 x 10(-7) to 5.0 x 10(-5) mol/L with a correlation coefficient of 0.998 and a detection limit of 2.8 x 10(-7) mol/L. The relative standard deviation was less than 6.2% (n = 5) and the recovery was in the range of 98-105% for the determination of practical samples. The result was consistent with that from the HPLC method. PMID:12725401

Zhao, Changzhi; Pan, Yuzhen; He, Chunxiang; Guo, Zhen; Sun, Licheng

2003-04-01

412

Induced Currents, Eddy Currents and  

E-print Network

= µ0(Ireal + 0 dE dt ) 12 #12;James Clerk Maxwell wait till Thursday for final installment 1865Lecture 11 Induced Currents, Eddy Currents and Maxwell's Equations 1 Faraday Disk Dynamo F = q · dl = µ0Ipenetrating { Maxwell'sEquations(Nearly) F = q(E + v × B)Lorentz Force Law: Gauss's Law Gauss

Tobar, Michael

413

Rip Currents  

NSDL National Science Digital Library

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.

Earth Science Picture of the Day

414

Current Rusume  

E-print Network

Fabrice Baudoin. EDUCATION ... I am currently working on a problem about stochastic analysis on Riemannian folia- tion. EXPERIENCE ... Tianjin Excellent level of Summer Social Practice Team Best Paper Award in summer social practice.

2015-02-09

415

Dark currents  

Microsoft Academic Search

Dark current stadies in the S-band structures and the DC electrodes have been primarily pointed at elucidating the causal relationships between the internally generated field emission currents and breakdown electric fields at high gradient. The experiment was focused to improve the material and fabrication method. An S-band nose cone shape TM010 single standing-wave cavity was successfully operates surface electrical gradient

H. Matsumoto

1996-01-01

416

Current Events  

NSDL National Science Digital Library

This lesson on the cause of currents and water circulation in the Arctic Ocean will require students to investigate the influence of salinity and temperature on the density of seawater to determine what factors drive water circulation in the Arctic Ocean. Students identify the primary driving forces for ocean currents and infer the type of water circulation to be expected in the Arctic Ocean, given information on temperature, salinity, and bathymetry.

417

Current Events  

NSDL National Science Digital Library

Learners model the ocean currents that carry hot water from the tropics to northern latitudes. By placing small containers of hot and cold water inside a larger container of cold water, learners can see convection currents in action. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Bug Blaster game after they've completed several activities.

American Association for the Advancement of Science

2009-01-01

418

On an Alternative Cosmology  

E-print Network

The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key words: standard cosmological model, alternative cosmology, barionic symmetry, typical universe, quasars, cosmic rays.

A. Vankov

1998-11-10

419

Annual Weeds, Alternative Crops for Alternative Fuel  

Technology Transfer Automated Retrieval System (TEKTRAN)

All cropland acreage in Alabama is infested with one or more species of annual weeds. Weeds are estimated to cost producers in the state approximately 8% of their potential yield, even with the current weed control technology available. Weed management continues to be the most expensive row crop pr...

420

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...

421

Alternator insulation evaluation tests  

NASA Technical Reports Server (NTRS)

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.

Penn, W. B.; Schaefer, R. F.; Balke, R. L.

1972-01-01

422

Individual and simultaneous determination of lead, cadmium, and zinc by anodic stripping voltammetry at a bismuth bulk electrode  

PubMed Central

A bismuth bulk electrode (BiBE) has been investigated as an alternative electrode for the anodic stripping voltammetric (ASV) analysis of Pb(II), Cd(II), and Zn(II). The BiBE, which is fabricated in house, shows results comparable to those of similar analyses at other Bi-based electrodes. Metal accumulation is achieved by holding the electrode potential at ?1.4 V (vs. Ag/AgCl) for 180 s followed by a square wave voltammetric stripping scan from ?1.4 to ?0.35 V. Calibration plots are obtained for all three metals, individually and simultaneously, in the 10–100 ?g L?1 range, with a detection limit of 105, 54, and 396 ng L?1 for Pb(II), Cd(II), Zn(II), respectively. A slight reduction in slope is observed for Cd(II) and Pb(II) when the three metals are calibrated simultaneously vs. individually. Comparing the sensitivities of the metals when calibrated individually vs in a mixture reveals that Zn(II) is not affected by stripping in a mixture. However, Pb(II) and Cd(II) have decreasing sensitivities in a mixture. The optimized method has been successfully used to test contaminated river water by standard addition. The results demonstrate the ability of the BiBE as an alternative electrode material in heavy metal analysis. PMID:20602953

Armstrong, Kristie C.; Tatum, Clarissa E.; Dansby-Sparks, Royce N.; Chambers, James Q.; Xue, Zi-Ling

2010-01-01

423

The Anderson Current Loop  

NASA Technical Reports Server (NTRS)

Four-wire-probe concept applied to electrical-resistance transducers. Anderson current loop is excitation-and-signal-conditioning circuit suitable for use with strain gauges, resistance thermometers, and other electrical-resistance transducers mounted in harsh environments. Used as alternative to Wheatstone bridge. Simplifies signal-conditioning problem, enabling precise measurement of small changes in resistance of transducer. Eliminates some uncertainties in Wheatstone-bridge resistance-change measurements in flight research. Current loop configuration makes effects of lead-wire and contact resistances insignificantly small. Also provides output voltage that varies linearly with change in gauge resistance, and does so at double sensitivity of Wheatstone bridge.

Anderson, Karl F.

1994-01-01

424

Industrial research on alternative fluorocarbons.  

PubMed

Fluorocarbons containing chlorine or bromine have been associated with stratospheric ozone depletion and the search for suitable alternatives is progressing at an accelerated pace. The Program for Alternative Fluorocarbon Toxicity Testing (PAFT), an international group representing most of the world's CFC producers, has been conducting comprehensive toxicological evaluations on several possible replacements for current fire-extinguishing agents--1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124), pentafluoroethane (HFC-125), and 1-fluoro-2,2,2-trifluoroethane (HFC-134a). Results from short-term experimental studies showing a low order of acute toxicity, as well as results from longer-term toxicity studies on these replacements, will be discussed. PMID:8516770

Trochimowicz, H J

1993-05-01

425

ALTERNATIVES TO RESEARCH PAPERS  

E-print Network

ALTERNATIVES TO RESEARCH PAPERS Compiled by Kathy Labadorf kathy.labadorf@uconn.edu December 30, 2010 Creative alternatives to traditional research papers: Undergrads and Scholarly Communication The ability to write a finely crafted, well documented, and thought provoking research paper is a hallmark

Alpay, S. Pamir

426

Developing Alternative Assessment Success.  

ERIC Educational Resources Information Center

Two case studies describe the development of alternative assessment within urban North Carolina elementary schools, examining each assessment development process, identifying commonalities and differences, and relating real-world endeavors to the change process. The studies argue for placing alternative assessment on the school reform agenda,…

Hudson, Martha B.; Penta, Mary Q.

1998-01-01

427

Teaching (With) Alternative Media  

Microsoft Academic Search

This essay examines a variety of approaches to teaching about and with alternative media across a media studies curriculum. I locate this discussion in the context of ongoing debates surrounding the theory and practice of critical media literacy (Kellner and Share, 2005; Lewis and Jhally, 1998). The essay proceeds with examples of teaching (with) alternative media in two courses: an

Kevin Howley

428

Alternative Retirement Plans.  

ERIC Educational Resources Information Center

Alternative college retirement programs and features of a desirable retirement program are discussed. The historical, social, and economic forces that prompt institutions to consider alternative programs are identified. The present position of college faculty in terms of retirement options is also addressed. Since its inception, the Teachers…

Hogan, John D.

1984-01-01

429

Alternative Fuel Vehicle Data  

EIA Publications

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.

2013-01-01

430

Alternative Work Programs  

ERIC Educational Resources Information Center

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…

Kuehn, Kerri L.

2004-01-01

431

Alternative Automobile Engines  

ERIC Educational Resources Information Center

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)

Wilson, David Gordon

1978-01-01

432

ALTERNATIVE DEER FENCES  

E-print Network

ALTERNATIVE DEER FENCES IN CORE CAPERCAILLIE and BLACK GROUSE HABITATS AN INTERIM BEST GUIDANCE, Surrey, GU10 4LH 2 RSPB Scotland, Dunedin House, 25 Ravelston Terrace, Edinburgh, EH4 3TP #12;2 Purpose in core woodland grouse habitats. As an alternative strategy, various materials have been fixed onto deer

433

Complex Alternative Splicing  

PubMed Central

Alternative splicing is a powerful means of controlling gene expression and increasing protein diversity. Most genes express a limited number of mRNA isoforms, but there are several examples of genes that use alternative splicing to generate hundreds, thousands, and even tens of thousands of isoforms. Collectively such genes are considered to undergo complex alternative splicing. The best example is the Drosophila Down syndrome cell adhesion molecule (Dscam) gene, which can generate 38,016 isoforms by the alternative splicing of 95 variable exons. In this review, we will describe several genes that use complex alternative splicing to generate large repertoires of mRNAs and what is known about the mechanisms by which they do so. PMID:18380340

Park, Jung Woo; Graveley, Brenton R.

2015-01-01

434

Alternative fuel transit buses  

SciTech Connect

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.

Motta, R.; Norton, P.; Kelly, K. [and others

1996-10-01

435

Alternate policies for alternate energy sources  

SciTech Connect

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.

Hall, F.F.

1985-09-01

436

Electric Current  

NSDL National Science Digital Library

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:

2012-07-19

437

Convection Current  

NSDL National Science Digital Library

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.

The Exploratorium

2012-06-26

438

Current Titles  

SciTech Connect

This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

Various

2006-06-01

439

Generalized theory of steady-state voltammetry without a supporting electrolyte. Effect of product and substrate diffusion coefficient diversity.  

PubMed

A generalized theory of the steady-state voltammetric response of a microelectrode in the absence of supporting electrolyte and for any values of diffusion coefficients of the substrate and the product of an electrode process is presented. The treatment applies to any reasonable combination of the charge numbers of the substrate, its counterion, and the product. A way to incorporate the activation polarization into the model is also demonstrated. It has been shown that the height, position, and shape of the migrational voltammogram are affected by the ratio of the product to substrate diffusivity (theta). In particular, for the electrode processes with sign retention, unequal diffusivities of electroactive species influence both characteristic points of the voltammogram (the limiting current and the half-wave potential). For charge neutralization processes (uncharged product), the changes in theta parameter are accompanied only by a shift in the half-wave potential. The most dramatic changes in the I-E relation can be observed for the charge reversal processes. In this case, a consecutive increase in theta results in the transition of the voltammogram shape from rapid exponential growth (theta < 1), through ramp shape (theta = 1), to common wave shape (theta > 1). On the basis of the expressions derived for the limiting current (exact and linearized), a possibility of the determination of the diffusion coefficient of the electrode reaction product is demonstrated. In addition, the ranges of theta where the assumption of equal diffusivities of the substrate and the product is obeyed within an insignificant error have been determined quantitatively. The theory has been experimentally verified using voltammetric oxidation of hexacyanoferrate(II). PMID:12349987

Hyk, Wojciech; Stojek, Zbigniew

2002-09-15

440

Towards the superconducting fault current limiter  

Microsoft Academic Search

The advent of low loss alternating current superconducting wires opens the way to a whole new current limiting technique: that of extremely fast transition from a superconducting state to a resistive state when the fault current exceeds the conductor's critical current. The 25 kV single phase prototype is constituted of a Nb Ti superconducting coil without iron core and very

V. D. Pham; Y. Laumond; T. Verhaege; A. Fenrier; M. Collet; M. Bekhaled

1991-01-01

441

Alternatives for the Future  

ERIC Educational Resources Information Center

Excerpts from a study conducted for the Rhode Island Special Commission to Study the Entire Field of Education outlining a criteria for public policy and suggesting alternatives regarding public support of nonpublic education. (LN)

Brickell, Henry M.

1970-01-01

442

Complementary and Alternative Medicine  

MedlinePLUS

Complementary and alternative medicine (CAM) is the term for medical products and practices that are not part of standard care. Standard care is ... such as nurses and physical therapists, practice. Complementary medicine is used together with standard medical care. An ...

443

Alternating projections on manifolds  

E-print Network

Jul 27, 2006 ... By contrast, for nonconvex sets, the projection mapping can no longer ..... consider two manifolds M and N in the space E, and study the alternating projection sequence ...... Journal of the Optical Society of America,. 19(7) ...

2006-07-27

444

Some Natural Pesticide Alternatives  

MedlinePLUS

... Pest Management web site. http://www.epa.gov/pesticides/factsheets/ipm.htm City of Tucson/ Pima County ... Grant Road Printed on recycled paper. SOME NATURAL PESTICIDE ALTERNATIVES For the safety of you, your family ...

445

Enhanced next generation alternator  

E-print Network

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 ...

Lorilla, Leandro M. (Leandro Manalac), 1977-

2005-01-01

446

Alternative energy design toolkit  

E-print Network

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 ...

Sukkasi, Sittha

2004-01-01

447

Seal design alternatives study  

SciTech Connect

This report presents the results from a study of various sealing alternatives for the WIPP sealing system. Overall, the sealing system has the purpose of reducing to the extent possible the potential for fluids (either gas or liquid) from entering or leaving the repository. The sealing system is divided into three subsystems: drift and panel seals within the repository horizon, shaft seals in each of the four shafts, and borehole seals. Alternatives to the baseline configuration for the WIPP seal system design included evaluating different geometries and schedules for seal component installations and the use of different materials for seal components. Order-of-magnitude costs for the various alternatives were prepared as part of the study. Firm recommendations are not presented, but the advantages and disadvantages of the alternatives are discussed. Technical information deficiencies are identified and studies are outlined which can provide required information.

Van Sambeek, L.L. [RE/SPEC Inc., Rapid City, SD (US); Luo, D.D.; Lin, M.S.; Ostrowski, W.; Oyenuga, D. [Parsons Brinckerhoff Quade & Douglas, Inc., San Francisco, CA (US)

1993-06-01

448

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 ...

449

Alternative Refractive Surgery Procedures  

MedlinePLUS

... of artificial lenses. Following are some of the alternative refractive surgery procedures to LASIK . Wavefront-Guided LASIK ... that releases controlled amounts of radio frequency (RF) energy, instead of a laser, to apply heat to ...

450

SOLVENT WASTE REDUCTION ALTERNATIVES  

EPA Science Inventory

This publication contains edited versions of presentations on this subject made at five Technology Transfer seminars in 1988. Chapters are included on land disposal regulations and requirements; waste solvent disposal alternatives from various industries such as process equipment...

451

Alternative therapies for headache  

Microsoft Academic Search

Opinion statement  Although alternative therapies are widely used for the treatment of headache disorders, physicians often know little about\\u000a the available options or about the risks and benefits of the treatments their patients may already be using. Alternative treatments\\u000a or complementary medicine can provide significant benefit for the headache sufferers, be neutral, distract the headache patient\\u000a from using more effective therapies,

William B. Young; Patricia Pozo-Rosich; Mary F. Paolone

2003-01-01

452

Alternative Energy Evaluation  

NSDL National Science Digital Library

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.

Scevola, Misty

453

Alternative Addition Strategies  

NSDL National Science Digital Library

This lesson explores recall of multiple alternative addition strategies of two-digit numbers. The lesson focus is to encourage students to use more than one strategy to solve addition problems. By reinforcing the multiple alternative addition strategies students will develop a strong understanding of addition structures and mechanics before moving on to three-digit addition. The lesson includes making an Addition Strategies Mini Booklet, which students can keep and use as a reference tool.

Judith Scapecchi

2012-07-31

454

Alternative Fuels Infrastructure Development  

SciTech Connect

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.

Bloyd, Cary N.

2010-06-30

455

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.

456

Eddy Currents  

NSDL National Science Digital Library

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.

The Exploratorium

2011-12-05

457

35 Alternative Transportation Fuels in California ALTERNATIVE TRANSPORTATION  

E-print Network

35 Alternative Transportation Fuels in California Chapter 4 ALTERNATIVE TRANSPORTATION FUELS IN CALIFORNIA INTRODUCTION The introduction of alternative fuels into California's transportation market has resources remains an appropriate objective. Developing and commercializing alternative fuels is one

458

Alternative fuels and chemicals from synthesis gas  

SciTech Connect

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.

Unknown

1998-08-01

459

ALTERNATIVE FUELS AND CHEMICALS FROM SYNTHESIS GAS  

SciTech Connect

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.

Unknown

1999-01-01

460

ALTERNATIVE FUELS AND CHEMICALS FROM SYNTHESIS GAS  

SciTech Connect

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.

Unknown

2000-10-01

461

Alternative Fuels and Chemicals From Synthesis Gas  

SciTech Connect

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.

none

1998-07-01

462

General theory for migrational voltammetry. Strong influence of diversity in redox species diffusivities on charge reversal electrode processes.  

PubMed

High sensitivity of the microelectrode response to the difference between the substrate and the product diffusion coefficients is predicted for the charge reversal processes. This effect is anticipated from the general theoretical model developed for the diffusional-migrational transport to microelectrodes. The model predicts the voltammetric wave heights for any type of electrode processes carried out in the presence of any number and concentration of nonelectroactive ions. It involves changes in diffusion coefficients of the redox species and assumes no homogeneous complications. Handy, analytical expressions for the limiting current and limiting potential can be derived for a system of a univalent product and univalent ions of supporting electrolyte. This case covers charge reversal processes of the following type: S(z) --> P(+/-) + ne (n + z = sgn(n), absolute value(n) > or = 2). It has been shown that under migrational conditions the change in the ratio of the product and the substrate diffusivities (D(P)/D(S)) by as little as 10% results in significant changes in the voltammetric wave height. For 2-e charge reversal processes, a 10% increase in D(P) versus D(S) leads to a drop in the voltammetric wave height of 18.3% compared to that calculated for equal diffusion coefficients. The reversed change, i.e., the 10% decrease of the D(P) value with respect to D(S), increases the voltammetric wave height by 30.5% compared to that obtained for equal diffusivities. The theoretical predictions were confronted with our recent experimental results obtained for the 2-e oxidation of sodium (6,8-diferrocenylmethylthio)octanoate, which process can be classified as the charge reversal reaction. The best fit was obtained for D(P)/D(S) equal to 0.71. PMID:16194116

Hyk, Wojciech; Stojek, Zbigniew

2005-10-01

463

Current titles  

SciTech Connect

This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Gretchen Hermes at (510) 486-5006 or address below for a User`s Guide. Copies of available papers can be ordered from: Theda Crawford National Center for Electron Microscopy, Lawrence Berkeley Laboratory, One Cyclotron Rd., MS72, Berkeley, California, USA 94720.

NONE

1995-07-01

464

Ocean Currents  

NSDL National Science Digital Library

A joint effort of NOAA Research and the College of Education at the University of South Alabama, this site seeks to provide middle school science students and teachers with research and investigation experiences using on-line resources. It contains activities pertaining to ocean currents (their properties and influence on weather and sea life). Students gather data from other websites, apply the data to answer a series of questions, and participate in related enrichment exercises. A downloadable teacher's guide, student guide, and all necessary activity sheets are included.

465

A Role for Adenosine A1 Receptors in GABA and NMDA-Receptor Mediated Modulation of Dopamine Release: Studies Using Fast Cyclic Voltammetry  

PubMed Central

In the striatum many neurotransmitters including GABA, glutamate, acetylcholine, dopamine, nitric oxide and adenosine interact to regulate synaptic transmission. Dopamine release in the striatum is regulated by a number of pre- and post-synaptic receptors including adenosine. We have recently shown using isolated rat striatal slices, and the technique of fast cyclic voltammetry, that adenosine A1 receptor-mediated inhibition of dopamine release is modulated by dopamine D1 receptors. In the present study we have investigated the influence of NMDA and GABA receptor activation on the modulation of electrically stimulated dopamine release by adenosine. Application of the adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA), concentration-dependently inhibited dopamine release to a maxiumum of 50%. Perfusion of the glutamate receptor agonist, NMDA, in low magnesium, caused a rapid and concentration-dependent inhibition of dopamine release. Prior perfusion with the adenosine A1 receptor antagonist, DPCPX, significantly reduced the effect of 5 ?M and 10 ?M NMDA on dopamine release. The GABAA receptor agonist, isoguvacine, had a significant concentration-dependent inhibitory effect on dopamine release which was reversed by prior application of the GABAA receptor antagonist, picrotoxin, but not DPCPX. Finally inhibition of dopamine release by CPA (1?M) was significantly enhanced by prior perfusion with picrotoxin. These data demonstrate an important role for GABA, NMDA and adenosine in the modulation of dopamine release.

O?Connor, John J.; O?Neill, Carmel

2008-01-01