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1

Purification of water by electrocoagulation with an alternating asymmetrical current for stripping voltammetry  

SciTech Connect

The influence of the flow velocity and the current density on the degree of purification of water by electrocoagulation with an alternating asymmetrical current has been studied. It has been demonstrated that under optimum conditions at pH/sub c/ 11.0-11.5 the residual metal content in the purified water drops to the level n x 10/sup -4/ g/ml; this allows its use in the practice of stripping voltammetry.

Gorodovykh, V.E.; Kaplin, A.A.; Svishchenko, N.M.; Obraztsov, S.V.

1987-11-20

2

Identification of current nature by elimination voltammetry with linear scan  

Microsoft Academic Search

This paper is devoted to the detailed description of mathematical procedures used in the elimination voltammetry with linear scan (EVLS), and their applications to the identification of current nature. It has been shown that the EVLS, based on an elimination function generated from total currents measured at different scan rates, is widely applicable in electrochemistry. The current nature can be

Libuše Trnková

2005-01-01

3

Alternating current electrode polarization  

Microsoft Academic Search

Summary This article summarizes principles of alternating current electrode polarization. The importance of alternating current electrode polarization in biological impedance studies is discussed. The following topics are treated in detail: Definition of Electrode Polarization Impedance; Linearity and Superpositioning Principle; Frequency Dependence of Electrode Impedance; Preparation of Electrodes (Optimal current density for platinum black application, Stability of electrode impedance, Cell design

H. P. Schwan

1966-01-01

4

Generation of Alternating Current  

NSDL National Science Digital Library

Based on work from the Wisconsin Online Resource Center, Teachers' Domain presents this interactive with reading material and animations to help students learn how a basic generator produces alternating current. The lesson includes graphics that show how the different components of a generator (slip rings, brushes, armature loop, and magnetic field) work together to produce single-phase and alternating current. On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

2010-10-05

5

Alternating to Direct: Rectifying Alternating Current  

NSDL National Science Digital Library

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

2012-12-03

6

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.

2010-09-24

7

Thermoelectric converters for alternating current standards  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

8

Coherent states of alternating current  

Microsoft Academic Search

We study counting statistics of electric current pumped by pulses of an\\u000aexternal field. The fluctuations depend on the pulse shape, and can be\\u000aminimized by choosing the pulse shape properly. For an optimal pulse shape, the\\u000afluctuations are reduced to the {\\\\it dc} level, i.e., they do not depend on the\\u000aduty cycle of the signal. We develop an

D. A. Ivanov; Hyunwoo Lee; L. S. Levitov

1997-01-01

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.  

National Technical Information Service (NTIS)

The technical and economical feasibility of alternating current electrocoagulation (ACE) was evaluated for a 2-year period. ACE is an electrochemical technology where highly-charged aluminum polyhydroxide species are introduced into aqueous media for the ...

N. P. Barkley C. W. Farrell T. W. Gardner-Clayson

1993-01-01

12

Alternating current driven instability in magnetic junctions.  

PubMed

An effect is considered of alternating (high-frequency) current on the spin-valve-type magnetic junction configuration. The stability with respect to small fluctuations is investigated in the macrospin approximation. When the current frequency is close to the eigenfrequency (precession frequency) of the free layer, parametric resonance occurs. Both collinear configurations, antiparallel and parallel, can become unstable under resonance conditions. The antiparallel configuration can also become unstable under non-resonant conditions. The threshold current density amplitude is of the order of the dc current density for switching of the magnetic junction. PMID:21825350

Epshtein, E M; Zilberman, P E

2009-04-01

13

Boston University Physics Applets: Alternating Current  

NSDL National Science Digital Library

This web page is an interactive physics simulation on alternating current. The user can see how the voltage and current are in phase for a resistor, and offset for capacitors and inductors. The page explains how to calculate root mean square (RMS) values, as well as finding the capacitive and inductive reactance. This item is part of a collection of similar simulation-based student activities.

Duffy, Andrew

2008-06-30

14

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

15

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

16

High frequency alternating current power distribution  

Microsoft Academic Search

The paper introduces high frequency alternating current (HFAC) power distribution as a new option in powering the equipment in telecommunications applications. A detailed comparison with powering schemes presently used in the telecommunication industry is part of the paper. The comparison is oriented towards the parameters of regulation, efficiency, input voltage range, output\\/input ripple, power density and EMI

J. Drobnik

1994-01-01

17

Scaling in nonstationary voltammetry representations.  

PubMed

Despite the widespread use of voltammetry for a range of chemical, biological, environmental, and industrial applications, there is still a lack of understanding regarding the functionality between the applied voltage and the resulting patterns in the current response. This is due to the highly nonlinear relation between the applied voltage and the nonstationary current response, which casts a direct association nonintuitive. In this Article, we focus on large-amplitude/high-frequency ac voltammetry, a technique that has shown to offer increased voltammetric detail compared to alternative methods, to study heterogeneous electrochemical reaction-diffusion cases using a nonstationary time-series analysis, the Hilbert transform, and symmetry considerations. We show that application of this signal processing technique minimizes the significant capacitance contribution associated with rapid voltammetric measurements. From a series of numerical simulations conducted for different voltage excitation parameters as well as kinetic, thermodynamic, and mass transport parameters, a number of scaling laws arise that are related to the underlying parameters/dynamics of the process. Under certain conditions, these observations allow the determination of all underlying parameters very rapidly, experiment duration typically

Anastassiou, Costas A; Parker, Kim H; O'Hare, Danny

2007-12-20

18

Direct current contamination of kilohertz frequency alternating current waveforms.  

PubMed

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

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

2014-07-30

19

Nonlinear alternating current responses of dipolar fluids  

NASA Astrophysics Data System (ADS)

The frequency-dependent nonlinear dielectric increment of dipolar fluids in nonpolar fluids is often measured by using a stationary relaxation method in which two electric fields are used: The static direct current (dc) field of high strength causing the dielectric nonlinearity, and the probing alternating current (ac) field of low strength and high frequency. When a nonlinear composite is subjected to a sinusoidal electric field, the electric response in the composite will, in general, consist of ac fields at frequencies of higher-order harmonics. Based on the Fröhlich model, we present a theory to investigate the nonlinear ac responses of dipolar fluids containing both polarizable monomers and dimers. In the case of monomers only, our theory reproduces the known results. We obtain the fundamental, second-, and third-order harmonics of the Fröhlich field by performing a perturbation expansion. The even-order harmonics are induced by the coupling between the ac and dc fields, although the system under consideration has a cubic nonlinearity only. The harmonics of the Fröhlich field can be affected by the field frequency, temperature, dispersion strength, and the characteristic frequency of the dipolar fluid, as well as the dielectric constant of the nonpolar fluid. The results are found to be in agreement with recent experimental observations.

Huang, J. P.; Yu, K. W.; Karttunen, Mikko

2004-07-01

20

Nonlinear alternating current responses of graded materials  

NASA Astrophysics Data System (ADS)

When a composite of nonlinear particles suspended in a host medium is subjected to a sinusoidal electric field, the electrical response in the composite will generally consist of alternating current (ac) fields at frequencies of higher-order harmonics. The situation becomes more interesting when the suspended particles are graded, with a spatial variation in the dielectric properties. The local electric field inside the graded particles can be calculated by the differential effective dipole approximation, which agrees very well with a first-principles approach. In this work, a nonlinear differential effective dipole approximation and a perturbation expansion method have been employed to investigate the effect of gradation on the nonlinear ac responses of these composites. The results showed that the fundamental and third-harmonic ac responses are sensitive to the dielectric-constant and/or nonlinear-susceptibility gradation profiles within the particles. Thus, by measuring the ac responses of the graded composites, it is possible to perform a real-time monitoring of the fabrication process of the gradation profiles within the graded particles.

Huang, J. P.; Gao, L.; Yu, K. W.; Gu, G. Q.

2004-03-01

21

Transcranial alternating current stimulation (tACS).  

PubMed

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

Alternating current electrocoagulation for superfund site remediation  

SciTech Connect

The technical and economical feasibility of alternating current electrocoagulation (ACE) was evaluated for a 2-year period. ACE is an electrochemical technology where highly-charged aluminum polyhydroxide species are introduced into aqueous media for the removal of suspended solids, oil droplets, and soluble ionic pollutants. ACE can break stable aqueous colloidal suspensions of up to 10% total solids and stable emulsions containing up to 5% oil. Major operating parameters have been defined for different classes of effluents based on experimental results using complex synthetic soil slurries and metals. Test results indicate that ACE produces aqueous and solid separations comparable to those produced by chemical flocculent additions, but with reduced filtration times and sludge volumes. The technology has application where removal of soluble and suspended pollutants from effluents is required, and in the recovery of fine-grained products from process streams. The technology however, has not yet been demonstrated at full-scale for Superfund site remediation. Summarized are the principal results of the SITE research program and results of ACE treatment on some different classes of industrial effluents, not part of the SITE Program.

Barkley, N.P.; Farrell, C.W.; Gardner-Clayson, T.W.

1993-01-01

23

Alternating current losses in superconductors of the second kind  

Microsoft Academic Search

The power (heating) losses occurring when an alternating current in a ; hard superconductor is used to produce a pulsed or alternating magnetic field are ; estimated. Heat losses for a solenoid are proportional to the conductor ; thickness, dictating the use of thin films for second-kind superconductors ; carrying alternating current. (D.C.W.);

1963-01-01

24

The Teaching of Three-Phase Alternating Current  

ERIC Educational Resources Information Center

Describes a series of experiments which use a modified automobile alternator as a portable source of three-phase alternating current. The low frequency capabilities of this source allow the phase relationships to be demonstrated using an ordinary galvanometer. (GS)

Bunker, C. A.

1976-01-01

25

Effects of alternating current iontophoresis on drug delivery  

Microsoft Academic Search

Objective: The duration of direct current (DC) iontophoresis is limited to 10- to 15-minute periods because of electrochemical burns from hydrogen and hydroxide ions generated by the DC current. A new iontophoretic device, the Lectro Patch, uses a low-frequency alternating current (AC). AC current is theorized to generate H+ ions during one phase and OH? when the current reverses polarity,

Juliet P. Howard; Thomas R. Drake; Dean L. Kellogg

1995-01-01

26

Calibrator for alternating voltage, current, and power  

Microsoft Academic Search

A computer-controlled calibrator capable of delivering ac sinusoidal and distorted waveform voltage, current, and power with an accuracy of several parts per million is described. The reference ac voltage is obtained using digital-to-analog conversion and the reference ac current by applying the reference voltage to a reference ac resistor. The phase relation is obtained digitally. A combination of feedback and

P. N. Miljanic

1989-01-01

27

Alternate considerations for current concepts in ITP.  

PubMed

Immune thrombocytopenia (ITP) is one of the most common forms of autoimmune disease affecting both adults and children. In recent years, there have been tremendous developments in the understanding of the pathogenesis and treatment of this condition. However, certain concepts related to ITP are worth consideration in view of alternative explanations and evidence available. These include (i) ITP is a disorder where thrombocytopenia is induced by autoantibodies against platelets or megakaryocytes, (ii) the mechanism of action of corticosteroids in ITP is through suppression of these autoantibodies, (iii) splenectomy is effective in ITP since spleen is the site of platelet destruction, and (iv) splenectomized ITP patients are at a major risk of infections. PMID:23683944

Thachil, Jecko

2014-04-01

28

An Alternating-Current Computing Station.  

National Technical Information Service (NTIS)

The a.c. analog computer described is a slightly modified version of a Soviet-made computer. It operates on 196 cycles with a reference voltage of 50, and a reference current of 0.1 amp. The computer consists of the following main components: (1) a signal...

1967-01-01

29

A conceptual alternative to current tendering practice  

Microsoft Academic Search

The research to date has borne a fundamental decision aid model to assist the construction owner in choosing a contractor. The model is currently being stabilized and validated. A comprehensive survey has been carried out to verify the variables and their weighting indices. Liaison with construction owners suggests that such a selection process developed into an expert system would be

Gary D. Holt; Paul O. Olomolaiye; Frank C. Harris

1993-01-01

30

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

31

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

32

Rapid determination of intraepithelial resistance barriers by alternating current spectroscopy  

Microsoft Academic Search

A method has been developed to determine rapidly and simultaneously the resistance of the tight junctions, the resistance of the lateral intercellular space, and the resistances and capacitances of the apical and basolateral cell membrane in leaky epithelia by alternating current spectroscopy. The present paper describes the experimental procedures. Multi-frequency sine-wave currents are simultaneously applied across the tissue and the

G. Kottra; E. Frömter

1984-01-01

33

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

34

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

35

Nonlinear Alternating Current Responses in Electrorheological Fluids:. Dynamic Effects  

NASA Astrophysics Data System (ADS)

By using a perturbation approach, we investigate dynamic effects on nonlinear alternating current (ac) responses in electrorheological (ER) fluids under an ac or a direct current electric field. We show that the dynamic effect due to a shear flow plays a significant role in the responses. Our results can be well interpreted in the dielectric dispersion spectral representation, and they offer a convenient method to determine the relaxation time and rotation velocity of ER particles by measuring the nonlinear ac responses.

Yu, K. W.; Tian, W. J.; Huang, J. P.

36

Hydrodynamic modulation voltammetry.  

PubMed

Highly efficient background-correction techniques applicable to voltammetric methods of trace analysis can be developed by modulating the convection rate of the solution at a solid electrode surface. The theoretical aspects, advantages, disadvantages, and analytical applications of the various batch and flow approaches to hydrodynamic modulation voltammetry are discussed, together with trends in future developments. PMID:18962941

Wang, J

1981-06-01

37

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

38

The Cross-Field Theory of Alternating-Current Machines  

Microsoft Academic Search

It is the purpose of this paper to show how analysis by the cross-field theory may be used to obtain accurate, purely numerical methods of calculating performance characteristics of alternating-current machines. Methods of calculation are derived and sample calculations are given for the single-phase induction motor and the repulsion motor.

H. R. West

1926-01-01

39

Alternating Currents: Integrating Study and Work in the Undergraduate Curriculum.  

ERIC Educational Resources Information Center

This article explores the meaning and importance of alternating currents of study and work in the Antioch College (Ohio) cooperative program from student and teacher perspectives. Examples are given of how students integrate their work and academic experiences and how teachers find their teaching is influenced by the school's cooperative program.…

Linn, Patricia L.; Jako, Katherine L.

1992-01-01

40

Precision Electronic Speed Controller for an Alternating-Current Motor.  

National Technical Information Service (NTIS)

A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-l...

V. W. Bolie

1984-01-01

41

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

42

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

Code of Federal Regulations, 2013 CFR

...Grounded neutral alternating current systems. 111.05-27...HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL...Grounded neutral alternating current systems. Grounded neutral...grounded neutral alternating current systems must have a...

2013-10-01

43

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

Code of Federal Regulations, 2010 CFR

... false Grounded neutral alternating current systems. 111.05-27...05-27 Grounded neutral alternating current systems. Grounded neutral...high-impedance grounded neutral alternating current systems must have a...

2010-10-01

44

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

Code of Federal Regulations, 2010 CFR

... false Grounded neutral alternating current systems. 111.05-27...05-27 Grounded neutral alternating current systems. Grounded neutral...high-impedance grounded neutral alternating current systems must have a...

2009-10-01

45

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

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Alternating-current ship's service switchboards...Switchboards § 111.30-25 Alternating-current ship's service switchboards...of this section, each alternating-current ship's service...

2009-10-01

46

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

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Alternating-current ship's service switchboards...Switchboards § 111.30-25 Alternating-current ship's service switchboards...of this section, each alternating-current ship's service...

2010-10-01

47

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Alternating-current ship's service switchboards. 111.30-25...111.30-25 Alternating-current ship's service switchboards. (a) Except...this section, each alternating-current ship's service switchboard must have...

2011-10-01

48

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

49

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Alternating-current ship's service switchboards. 111.30-25...111.30-25 Alternating-current ship's service switchboards. (a) Except...this section, each alternating-current ship's service switchboard must have...

2013-10-01

50

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

51

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

52

Square-Wave Voltammetry  

NASA Astrophysics Data System (ADS)

Square-wave voltammetry (SWV) is one of the four major voltammetric techniques provided by modern computer-controlled electroanalytical instruments, such as Autolab and ?Autolab (both EcoChemie, Utrecht), BAS 100 A (Bioanalytical Systems), and PAR Model 384 B (Princeton Applied Research) [1]. The other three important techniques are single scan and cyclic staircase, pulse, and differential pulse voltammetry (see Chap. II.2). All four are either directly applied or after a preconcentration to record the stripping process. The application of SWV boomed in the last decade, first because of the widespread use of the instruments mentioned above, second because of a well-developed theory, and finally, and most importantly, because of its high sensitivity to surface-confined electrode reactions. Adsorptive stripping SWV is the best electroanalytical method for the determination of electroactive organic molecules that are adsorbed on the electrode surface [2].

Lovri?, Milivoj

53

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

NASA Astrophysics Data System (ADS)

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

Gerstein, B. C.

1987-06-01

54

Electrical Characteristics of an Alternating Current Plasma Igniter in Airflow  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

55

Nerve conduction block utilising high-frequency alternating current  

Microsoft Academic Search

High-frequency alternating current (AC) waveforms have been shown to produce a quickly reversible nerve block in animal models,\\u000a but the parameters and mechanism of this block are not well understood. A frog sciatic nerve\\/gastrocnemius muscle preparation\\u000a was used to examine the parameters for nerve conduction block in vivo, and a computer simulation of the nerve membrane was\\u000a used to identify

K. L. Kilgore; N. Bhadra

2004-01-01

56

Dynamic effects on nonlinear alternating current responses in electrorheological fluids  

NASA Astrophysics Data System (ADS)

By using a perturbation approach, we investigate dynamic effects on nonlinear alternating current (ac) responses in electrorheological (ER) fluids under an ac or direct current electric field. We show that the dynamic effect due to a shear flow, which exerts a torque on ER particles and thus leads to the rotation of the particles about their centers, plays a significant role in the responses. Our results can be well interpreted in the dielectric dispersion spectral representation, and they offer a convenient method to determine the relaxation time and rotation velocity of ER particles by measuring the nonlinear ac responses.

Tian, W. J.; Huang, J. P.; Yu, K. W.

2006-03-01

57

Voltammetry of lithium polysulfides at metal electrodes  

SciTech Connect

The interaction of lithium polysulfides and metals which have shown promise for use a current collector/cell casing materials for lithium/sulfur cells is explored using cyclic voltammetry. The metals used were chromium and molybdenum, and data for 10-500 mV/s potential sweeps at 400/sup 0/C in Li/sub 2/S/sub 3.80/ are reported. The data were collected using an electrochemical cell designed specifically for this purpose. The results were analyzed using classical equations governing cyclic voltammetry, and a model was developed to describe specific melt-metal interactions.

Dobson, J.C.; McLarnon, F.R.; Cairns, E.J.

1986-08-01

58

Differential linear scan voltammetry: analytical performance in comparison with pulsed voltammetry techniques.  

PubMed

We report here on differential linear scan voltammetry, DLSV, that combines the working principles of linear scan voltammetry, LSV, and the numerous existing pulsed voltammetry techniques. DLSV preserves the information from continuous interrogation in voltage and high accuracy that LSV provides about electrochemical processes, and the much better sensitivity of differential pulsed techniques. DLSV also minimizes the background current compared to both LSV and pulsed voltammetry. An early version of DLSV, derivative stationary electrode polarography, DSEP, had been proposed in the 1960s but soon abandoned in favor of the emerging differential pulsed techniques. Relative to DSEP, DLSV takes advantage of the flexibility of discrete smoothing differentiation that was not available to early investigators. Also, DSEP had been explored in pure solutions and with reversible electrochemical reactions. DLSV is tested in this work in more challenging experimental contexts: the measurement of oxygen with a carbon fiber microelectrode in buffer, and with a gold microdisc electrode exposed to a live biological preparation. This work compares the analytical performance of DLSV and square wave voltammetry, the most popular pulsed voltammetry technique. PMID:23624955

Sheth, Disha B; Gratzl, Miklós

2013-06-01

59

Transcranial alternating current stimulation attenuates visual motion adaptation.  

PubMed

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

Kar, Kohitij; Krekelberg, Bart

2014-05-21

60

Alternatives to animal testing: current status and future perspectives.  

PubMed

On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book "The Principles of Humane Experimental Technique" by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on "Toxicology in the twenty-first Century", as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper. PMID:21607681

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

2011-08-01

61

Alternating current electrokinetic motion of colloidal particles on interdigitated microelectrodes.  

PubMed

Alternating current (ac) electrokinetic motion of colloidal particles suspended in an aqueous medium and subjected to a spatially nonuniform ac electric field are examined using a simple theoretical model that considers the relative magnitudes of dielectrophoresis, electrophoresis, ac-electroosmosis, and Brownian motion. Dominant electrokinetic forces are explained as a function of the electric field frequency, amplitude, and conductivity of the suspending medium for given material properties and geometry. Parametric experimental validations of the model are conducted utilizing interdigitated microelectrodes with polystyrene and gold particles and Clostridium sporogenes bacterial spores. The theoretical model provides quantitative descriptions of ac electrokinetic transport for the given target species in a wide spectrum of electric field amplitude and frequency and medium conductivity. The presented model can be used as an effective framework for design and optimization of ac electrokinetic devices. PMID:18318510

Park, Seungkyung; Beskok, Ali

2008-04-15

62

Addressing and sustaining in alternating current coplanar plasma display panels  

NASA Astrophysics Data System (ADS)

In a coplanar plasma display panel the discharges in each pixel are sustained between two parallel electrodes on the same substrate. A third electrode perpendicular to the sustaining electrodes and placed on a facing substrate is used to address the pixel. A self-consistent two-dimensional model of the microdischarge has been used to simulate and study the addressing and sustaining phases in an alternating current coplanar cell. The formation and decay of the transient plasma during the address and sustain discharge pulses are described. The time evolution of the charges on the dielectric surfaces above each electrode is also discussed and the model is used to derive the voltage margins of the address and sustain regimes.

Punset, C.; Cany, S.; Boeuf, J.-P.

1999-07-01

63

Nonlinear dynamics of carbon nanotubes under soft alternating current actuation  

NASA Astrophysics Data System (ADS)

This thesis work deals with electrostatically actuated Carbon nanotubes (CNTs) cantilevers. Four forces act on the CNTs cantilever, namely electrostatic, elastostatic, van der Waals and damping. The van der Waals force is significant for values of 50nm or lower of the gap between the CNTs and the ground substrate. As both forces electrostatic and van der Waals are nonlinear, and the CNTs electrostatic actuation is given by alternating current (AC) voltage, and CNTs undergoes nonlinear parametric dynamics. The method of multiple scales (MMS) and reduced order model (ROM) are used to investigate the system under soft excitation and weak nonlinearities. The frequency-amplitude and frequency-phase behavior are reported in the case of resonance due to AC near half natural frequency and AC near primary natural frequency.

Luo, Le

64

Nonlinear alternating current susceptibilities of rotating microparticles in electrorheological fluids  

NASA Astrophysics Data System (ADS)

A perturbation approach [1] has been employed to investigate the nonlinear alternating current (AC) responses of the rotating microparticles in electrorheological (ER) fluids under AC or direct current electric fields. The shear flow of ER fluids exerts a torque on the particles and leads to the rotational motion of the particles about their centers [2]. We show that the dynamic effects can play a significant role in the AC responses. Our results can be conveniently interpreted in the dielectric dispersion spectral representation [3], thus offering a convenient method to determine the relaxation time and the rotation velocity of the ER particles by measuring the nonlinear AC responses. [1] G. Q. Gu and K. W. Yu, Phys. Rev. B 46, 4502 (1992); K. W. Yu, P. M. Hui, and D. Stroud, Phys. Rev. B 47, 14150 (1993). [2] Jones T. K. Wan, K. W. Yu, and G. Q. Gu, Phys. Rev. E 62, 6846 (2000). [3] Jun Lei, Jones T. K. Wan, K. W. Yu, and Hong Sun, Phys. Rev. E 64, 012903 (2001).

Yu, Kin Wah; Huang, J. P.; Tian, W. J.

2006-03-01

65

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

66

Entrainment of brain oscillations by transcranial alternating current stimulation.  

PubMed

Novel methods for neuronal entrainment [1-4] provide the unique opportunity to modulate perceptually relevant brain oscillations [5, 6] in a frequency-specific manner and to study their functional impact on distinct cognitive functions. Recently, evidence has emerged that tACS (transcranial alternating current stimulation) can modulate cortical oscillations [7-9]. However, the study of electrophysiological effects has been hampered so far by the absence of concurrent electroencephalogram (EEG) recordings. Here, we applied 10 Hz tACS to the parieto-occipital cortex and utilized simultaneous EEG recordings to study neuronal entrainment during stimulation. We pioneer a novel approach for simultaneous tACS-EEG recordings and successfully separate stimulation artifacts from ongoing and event-related cortical activity. Our results reveal that 10 Hz tACS increases parieto-occipital alpha activity and synchronizes cortical oscillators with similar intrinsic frequencies to the entrainment frequency. Additionally, we demonstrate that tACS modulates target detection performance in a phase-dependent fashion highlighting the causal role of alpha oscillations for visual perception. PMID:24461998

Helfrich, Randolph F; Schneider, Till R; Rach, Stefan; Trautmann-Lengsfeld, Sina A; Engel, Andreas K; Herrmann, Christoph S

2014-02-01

67

Is transcranial alternating current stimulation effective in modulating brain oscillations?  

PubMed

Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations, as well as a possible therapeutic intervention. However, the lack of conclusive evidence on whether tACS is able to effectively affect cortical activity continues to limit its application. The present study aims to address this issue by exploiting the well-known inhibitory alpha rhythm in the posterior parietal cortex during visual perception and attention orientation. Four groups of healthy volunteers were tested with a Gabor patch detection and discrimination task. All participants were tested at the baseline and selective frequencies of tACS, including Sham, 6 Hz, 10 Hz, and 25 Hz. Stimulation at 6 Hz and 10 Hz over the occipito-parietal area impaired performance in the detection task compared to the baseline. The lack of a retinotopically organised effect and marginal frequency-specificity modulation in the detection task force us to be cautious about the effectiveness of tACS in modulating brain oscillations. Therefore, the present study does not provide significant evidence for tACS reliably inducing direct modulations of brain oscillations that can influence performance in a visual task. PMID:23457586

Brignani, Debora; Ruzzoli, Manuela; Mauri, Piercarlo; Miniussi, Carlo

2013-01-01

68

Hardware Model of a Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC).  

National Technical Information Service (NTIS)

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

C. N. Tidd

2010-01-01

69

Hardware Model Of A Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC).  

National Technical Information Service (NTIS)

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

C. N. Tidd

2010-01-01

70

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

Code of Federal Regulations, 2013 CFR

...from ungrounded alternating current power systems. 75.701-1...from ungrounded alternating current power systems. For purposes...from ungrounded alternating current power systems, the following...power conductor feeding the electrical equipment enclosed;...

2013-07-01

71

Applications of convolution voltammetry in electroanalytical chemistry.  

PubMed

The robustness of convolution voltammetry for determining accurate values of the diffusivity (D), bulk concentration (C(b)), and stoichiometric number of electrons (n) has been demonstrated by applying the technique to a series of electrode reactions in molecular solvents and room temperature ionic liquids (RTILs). In acetonitrile, the relatively minor contribution of nonfaradaic current facilitates analysis with macrodisk electrodes, thus moderate scan rates can be used without the need to perform background subtraction to quantify the diffusivity of iodide [D = 1.75 (±0.02) × 10(-5) cm(2) s(-1)] in this solvent. In the RTIL 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, background subtraction is necessary at a macrodisk electrode but can be avoided at a microdisk electrode, thereby simplifying the analytical procedure and allowing the diffusivity of iodide [D = 2.70 (±0.03) × 10(-7) cm(2) s(-1)] to be quantified. Use of a convolutive procedure which simultaneously allows D and nC(b) values to be determined is also demonstrated. Three conditions under which a technique of this kind may be applied are explored and are related to electroactive species which display slow dissolution kinetics, undergo a single multielectron transfer step, or contain multiple noninteracting redox centers using ferrocene in an RTIL, 1,4-dinitro-2,3,5,6-tetramethylbenzene, and an alkynylruthenium trimer, respectively, as examples. The results highlight the advantages of convolution voltammetry over steady-state techniques such as rotating disk electrode voltammetry and microdisk electrode voltammetry, as it is not restricted by the mode of diffusion (planar or radial), hence removing limitations on solvent viscosity, electrode geometry, and voltammetric scan rate. PMID:24444296

Bentley, Cameron L; Bond, Alan M; Hollenkamp, Anthony F; Mahon, Peter J; Zhang, Jie

2014-02-18

72

A comparison of alternating current and direct current electrospray ionization for mass spectrometry.  

PubMed

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. PMID:24464359

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

2014-04-01

73

Hysterectomy--Current Methods and Alternatives for Benign Indications  

PubMed Central

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

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

2010-01-01

74

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

75

Wireless Architectural Alternatives: Current Economic Valuations versus Broadband Options  

Microsoft Academic Search

Abstract There has been an assumption,that spectrum,can be divided into segments,and then auctioned,off. It has been assumed,that this is optimal in terms of its benefit to the public and that the FCC in so doing is optimizing the public good. There has been an alternative conjecture, termed the “Gilder” conjecture, that segmenting bandwidth,is not the best means,and that using all

Terrence P. Mcgarty; Muriel Medard

76

Rectification in mesoscopic alternating current-gated semiconductor devices  

NASA Astrophysics Data System (ADS)

We analyse the rectified dc currents resulting when a three-terminal semiconductor device with gate-dependent conductance is driven with an ac gate voltage. The rectified currents exhibit surprisingly complex behaviour as the dc source-drain bias voltage, the dc gate voltage, and the amplitude of the ac gate voltage are varied. We obtain good agreement between our data and a model based on simple assumptions about the stray impedances on the sample chip, over a wide frequency range. Secondly, we evaluate the small rectified currents flowing in tunable-barrier electron pumps operated in the pinched-off regime. These currents are at most 10-12 of the pumped current for a pump current of 100 pA. This result is encouraging for the development of tunable-barrier pumps as metrological current standards. Our method is applicable to many types of experiment which involve ac gating of a non-linear device, and where an undesirable rectified contribution to the measured signal is present.

Giblin, S. P.; Kataoka, M.; Fletcher, J. D.; See, P.; Janssen, T. J. B. M.; Griffiths, J. P.; Jones, G. A. C.; Farrer, I.; Ritchie, D. A.

2013-10-01

77

Determination of Cu in Tequila by Anodic Stripping Voltammetry  

Microsoft Academic Search

Concentrations of metals such as copper in alcoholic beverages must be strictly regulated due to negative effects ranging from beverage spoilage and hazing, to sensorial and health consequences. In this paper, a voltammetric alternative is presented for the analysis of copper in tequila, a Mexican spirituous alcoholic beverage. Anodic Stripping Voltammetry is applied and the standard addition method is used

Norberto Casillas; Jorge G. Ibanez; Fernando Hernandez; Sergio Go´mez-Salazar

2008-01-01

78

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

79

Alternating current losses of stabilized NbN.  

NASA Technical Reports Server (NTRS)

The ac losses of thin films of NbN have been measured on uncoated samples and samples coated with copper and aluminum. The reversibility of the superconducting to normal transition was studied under conditions of swept current at fixed field and swept field at fixed current. Results show that thin films of NbN can be stabilized by using normal metal overlays, and that ac losses in the stabilized material are substantially lower than those in the equivalent unstabilized material.

Deis, D. W.; Gavaler, J. R.; Jones, C. K.

1971-01-01

80

Voltammetry of sodium polysulfides at metal electrodes  

SciTech Connect

The interaction of sodium polysulfides and candidate metals for the current collector and cell casing in sodium/sulfur cells at 300/sup 0/ and 350/sup 0/C is explored using cyclic voltammetry. The metals investigated are chromium and molybdenum, and data for voltammetric sweeps at rates of 10-500 mV/s in Na/sub 2/S/sub 1/ are reported. The results are compared with those of previous experiments conducted at carbon and platinum electrodes, and mechanisms are proposed to explain the data in terms of specific melt-metal interactions. A model describing the observed cathodic sweep data is presented.

Dobson, J.C.; McLarnon, F.R.; Cairns, E.J.

1986-10-01

81

Alternating current OHMIC heating in a toroidal stellerator  

NASA Astrophysics Data System (ADS)

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 is produced by breaking down the hydrogen gas with the use of the same toroidal RF electric field which is employed for plasma heating. A simple model of the breakdown is proposed which allows to evaluate the particle confinement time of high-energy electron produced during the breakdown. The plasma response to the RF field is different in the two magnetic field configurations. In the stellarator, the plasma current exhibits a characteristic reversal with the current flowing in the direction of the RF coil current on the flow-field side of the torus and in the opposite direction on the high-field side of the torus. In the doublestar, the current is distributed more uniformly. The different response is attributed to the different geometry of the magnetic surfaces and to reconnection of the magnetic flux in the doublestar configuration.

Wroblewski, D.

82

Alternating-Current Motor Drive for Electric Vehicles  

NASA Technical Reports Server (NTRS)

New electric drive controls speed of a polyphase as motor by varying frequency of inverter output. Closed-loop current-sensing circuit automatically adjusts frequency of voltage-controlled oscillator that controls inverter frequency, to limit starting and accelerating surges. Efficient inverter and ac motor would give electric vehicles extra miles per battery charge.

Krauthamer, S.; Rippel, W. E.

1982-01-01

83

Noncancer Risk Assessment: A Probabilistic Alternative to Current Practice  

Microsoft Academic Search

Based on imperfect data and theory, agencies such as the United States Environmental Protection Agency (USEPA) currently derive “reference doses” (RfDs) to guide risk managers charged with ensuring that human exposures to chemicals are below population thresholds. The RfD for a chemical is typically reported as a single number, even though it is widely acknowledged that there are significant uncertainties

Sandra J. S. Baird; Joshua T. Cohen; John D. Graham; Alexander I. Shlyakhter; John S. Evans

1996-01-01

84

Integration and alternatives: Some current issues in psychoanalytic theory  

Microsoft Academic Search

The first great bridge between psychoanalysis and social work came with the concepts of ego psychology which provided a synthesis between the worlds of the social order and the psychological depths. Current psychoanalytic theorists now question whether any one psychological theory is sufficient to describe the complexity of human experience, and suggest that each theory has a piece of the

David G. Phillips

1993-01-01

85

Alternating current characterization of sputter deposited Ti oxide films  

NASA Astrophysics Data System (ADS)

Ti oxide films with varying stoichiometries and different crystal structures were prepared by reactive direct current magnetron sputtering in oxygen-depleted plasmas. The complex dielectric permittivity icons/Journals/Common/varepsilon" ALT="varepsilon" ALIGN="TOP"/> was determined in the 10-3 -107 Hz range from measurements using a capacitor configuration. The real and imaginary parts of icons/Journals/Common/varepsilon" ALT="varepsilon" ALIGN="TOP"/> displayed power-law dependences from ~10 Hz up to a value between 1 and 10 kHz. Our data could be rationalized in terms of a model for screened hopping of vacancy-induced charge carriers, but the details remain poorly understood.

Rodríguez, J.; Gómez, M.; Niklasson, G. A.; Granqvist, C. G.

2000-01-01

86

Alternative Schools Serving Students with and without Disabilities: What Are the Current Issues and Challenges?  

ERIC Educational Resources Information Center

Drawing from a current study, this article identifies critical issues and challenges for alternative educators and administrators. It contains a list of questions that can be used to identify and address key issues in alternative settings in order to promote successful school experiences for students with and without disabilities. (Contains…

Lehr, Camilla A.; Lange, Cheryl M.

2003-01-01

87

Chemical synthesis of polyaspartates: a biodegradable alternative to currently used polycar?ylate homo- and copolymers  

Microsoft Academic Search

In order to improve the environmental acceptability of water-soluble sequestrants and dispersants that can end up in the surface water, new alternatives to the currently used polycar?ylate homo- and copolymers are needed. One alternative might be polyaspartates, a group of acidic polyamides. These polymers, which are functional equivalents of existing products, are biodegradable. They can be used in many different

Michael Schwamborn

1998-01-01

88

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

89

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

90

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

National Technical Information Service (NTIS)

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

D. A. Jablonski

1993-01-01

91

Sensory, motor, and pain thresholds for stimulation with medium frequency alternating current  

Microsoft Academic Search

Objectives: To investigate the effect of frequency of alternating current on the sensory, motor, and pain thresholds in normal subjects, and to establish the optimal frequency for motor stimulation with minimal subject discomfort.Design: A repeated measures design using two groups of 11 subjects.Setting: A laboratory setting was used.Participants: Participants were volunteers who met the inclusion criteria.Interventions: Alternating current with 20

Alex R. Ward; Valma J. Robertson

1998-01-01

92

Current State of Research of Alternate Fuel Sources for Passenger Vehicles  

NASA Astrophysics Data System (ADS)

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

Massey, Lee

2008-03-01

93

Sea'S Examination of Windpower in 1952: Change of a Wind Power Mill from Direct Current to Alternating Current Production.  

National Technical Information Service (NTIS)

A wind power mill built in 1942 in Denmark is described. Various factors influencing the amount of electricity supplied by the mill are indicated. An experiment is described for changing the mill so that it could produce alternating current to be channele...

J. Juul

1974-01-01

94

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

Microsoft Academic Search

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

Arthur Radun; James Rulison

1990-01-01

95

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

Microsoft Academic Search

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

Arthur Radun

1995-01-01

96

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

Microsoft Academic Search

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

F. Kajiyama; Y. Nakamura

1999-01-01

97

Alternating current operation with multicycles in the CT6B tokamak  

Microsoft Academic Search

Stable and clean AC tokamak discharges with two, four and eight cycles of alternating plasma current have been achieved in the CT-6B tokamak. Although there are differences in the plasma-wall interactions in the two halves of each AC cycle, the purity of the plasma is not significantly affected. The finite electron densities during the current reversal phases of each cycle

Xuanzong Yang; Diming Jiang; Wenlai Li; Gonghe Han; Long Wang; Xiazhi Qi; Chunhua Feng; Zanliang Li; Zhaobai Zheng

1996-01-01

98

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

Microsoft Academic Search

Current disposal options for APC residues in the UK and alternative treatment technologies developed world-wide have been reviewed. APC residues are currently landfilled in the UK where they undergo in situ solidification, although the future acceptability of this option is uncertain because the EU waste acceptance criteria (WAC) introduce strict limits on leaching that are difficult to achieve. Other APC

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

2008-01-01

99

Square-wave voltammetry for ECE mechanisms  

SciTech Connect

The theory of square-wave voltammetry is extended to include the ECE mechanism in which an intermediate chemical step occurs between sequential electrode reactions. Exemplary calculations show how the thermodynamic and kinetic parameters of this mechanism affect the shapes of square-wave voltammograms. The theory is used with a nonlinear least-squares technique to obtain first-order rate constants for the chemical step of the reduction of p-nitrosophenol. This procedure discriminates against several experimental artifacts and does not require the usual separate determination of a normalization current. The rate constants obtained for the intermediate chemical step are 0.46 s{sup {minus}1} at 25{degree}C, 2.40 s{sup {minus}1} at 50{degree}C, and 17.3 s{sup {minus}1} at 80{degree}C (12% uncertainty at 95% confidence) in good agreement with previous studies.

O'Dea, J.J.; Wikiel, K.; Osteryoung, J. (State Univ. of New York, Buffalo (USA))

1990-05-03

100

Alternating current-assisted on-plate proteolysis for MALDI-TOF MS peptide mapping.  

PubMed

In this report, alternating current-assisted on-plate proteolysis has been developed for rapid peptide mapping. Protein solutions containing trypsin were allowed to digest directly on the spots of a stainless steel MALDI plate with the assistance of low-voltage alternating current electricity. Alternating current (AC) was allowed to pass through the protein solutions via the MALDI plate and a platinum disc electrode. The feasibility and performance of the novel proteolysis approach were investigated by the digestion of BSA and cytochrome c (Cyt-c). It was demonstrated that AC substantially enhanced the efficiency of proteolysis and the digestion time was significantly reduced to 5 min. The digests were identified by MALDI-TOF MS with sequence coverages of 42% (BSA) and 77% (Cyt-c) that were comparable to those obtained by using conventional in-solution tryptic digestion. The present proteolysis strategy is simple and efficient, offering great promise for MALDI-TOF MS peptide mapping. PMID:18924112

Wang, Sheng; Wei, Bangguo; Yang, Pengyuan; Chen, Gang

2008-11-01

101

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

102

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

103

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

104

Effect of induced alternating current voltage on cathodically protected pipelines paralleling electric power transmission lines  

SciTech Connect

A field study was conducted to evaluate the effect of induced alternating current (AC) voltage on a cathodically protected pipeline paralleling an electric power transmission line. The study used the instant-off method, with steel probes simulating coating defects. Data regarding probe potentials and currents were compared with the proposed tentative criterion for cathodic protection (CP). Positive proof of the adequacy of CP was obtained after field testing for 1 year, when probes were removed to ascertain corrosion rates.

Kajiyama, F.; Nakamura, Y. [Tokyo Gas Co., Ltd. (Japan). Fundamental Technology Research Lab.

1999-02-01

105

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.

Banga, Ajay K.

2014-01-01

106

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

Microsoft Academic Search

Functional MRI was performed in 28 healthy volunteers to study the effects of galvanic vestibular stimulation with alternating currents (AC-GVS) of different frequencies on brain activation patterns. The aims of this study were (1) to identify specific areas within the vestibular cortical network that are involved in the processing of frequency-specific aspects by correlation analyses, (2) to determine the optimal

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

2005-01-01

107

Disintegration of magnetic tablets in human stomach evaluated by alternate current Biosusceptometry  

Microsoft Academic Search

Oral administration is the most convenient route for drug therapy. The knowledge of the gastrointestinal transit and specific site for drug delivery is a prerequisite for development of dosage forms. The aim of this work was to demonstrate that is possible to monitor the disintegration process of film-coated magnetic tablets by multi-sensor alternate current Biosusceptometry (ACB) in vivo and in

Luciana A. Corá; Madileine F. Américo; Ricardo Brandt Oliveira; Oswaldo Baffa; Rogério Moraes; Fernando G. Romeiro; José Ricardo A. Miranda

2003-01-01

108

The addressing characteristics of an alternating current plasma display panel adopting a ramping reset pulse  

Microsoft Academic Search

The characteristics of the address discharge of an alternating current plasma display panel (ac PDP) adopting a ramping reset pulse were studied using two-dimensional (2-D) numerical simulation. We investigated the principal parameters of the reset pulse for a successful address discharge. In this paper, we suggest a new parameter, the terminal voltage of the ramping reset pulse, and its effects

Joong Kyun Kim; Jin Ho Yang; Woo Joon Chung; Ki Woong Whang

2001-01-01

109

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

110

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.)

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

1982-01-01

111

Molecular Stretching of Long DNA in Agarose Gel Using Alternating Current Electric Fields  

Microsoft Academic Search

We demonstrate a novel method for stretching a long DNA molecule in agarose gel with alternating current (AC) electric fields. The molecular motion of a long DNA (T4 DNA; 165.6kb) in agarose gel was studied using fluorescence microscopy. The effects of a wide range of field frequencies, field strengths, and gel concentrations were investigated. Stretching was only observed in the

Noritada Kaji; Masanori Ueda; Yoshinobu Baba

2002-01-01

112

An analysis of alternatives to New York City's current marijuana arrest and detention policy  

Microsoft Academic Search

Purpose – During the 1990s, the New York City 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 (QOL) policing initiative. The purpose of this paper is to examine the pros and cons of the current policy and compare it with possible alternatives including: arrest and

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

2008-01-01

113

PEAK RESOLUTION BY SEMIDERIVATIVE VOLTAMMETRY  

SciTech Connect

One of the limitations of dynamic electrochemistry, when used as a quantitative analytical technique, is the resolution of overlapping waves, Approaches used in the past have been either time intensive methods using many blanks, or have relied on many empirical peak parameters, Using an approach based on semidifferential voltammetry, two new techniques have been developed for rapid peak deconvolution. The first. NIFITl, is an iterative stripping routine, while the second, BIMFIT, is based on sequential simplex optimization. Both approaches were characterized by deconvolution of synthetic fused peak systems. subsequently, both WE!re applied to semidifferentited linear scan voltammograms of Cd{sup 2+} , Pb{sup 2+} and In{sup 3+} and to semidifferentiated linear scan anodic stripping voltammograms of Cd{sup 2+} , ln{sup 3+} and Tl{sup +}. Deconvolutions were directly characterized by peak height, peak potential and peak halfwidth, as well as by the total squared deviation of the fit peaks from the real fused peaks. Studies of individual peaks as well as of standard additions to fused peaks showed both methods worked well, with excellent deconvolution efficiencies. Synthetic data were totally deconvoluted with peak separation as small as 25 mv, while real systems were deconvoluted with separations below 40 mv. Peak parameters obtained from these deconvolutions allow observations of electrode processes, even in systems containing overlapping peaks.

Toman, J. J.; Brown, S. D.

1980-10-01

114

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

115

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

NASA Astrophysics Data System (ADS)

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

Karam, Tony; Sultan, Rabih

2013-02-01

116

SENSING DNA WITH ALTERNATING CURRENTS USING A NANOGAP SENSOR EMBEDDED IN A NANOCHANNEL DEVICE  

PubMed Central

We report an integrated nanochannel/nanoelectrode sensor for the detection of DNA using alternating currents. We find that DNA can be detected using platinum as the metal for the detecting electrodes, with a signal to noise ratio exceeding 10. We argue that the signal is at least in part electrochemical in nature, thus holds the promise to yield a sequence-dependent signal. However, we also find that for large voltages, DNA attaches irreversibly to the driving electrodes.

DAVIS, BRET H.; PAN, JUNHAN; TUNG, CHIH-KUAN; AUSTIN, ROBERT H.; RIEHN, ROBERT

2013-01-01

117

Ion Energy Distribution in Alternating-Current Plasma Display Panel Cell  

Microsoft Academic Search

In an alternating-current plasma display panel cell, elastic collisions between the neutral gas and ionskeep most ion energies much lower than the applied voltage.Two-dimensional kinetic simulation reveals that the majority (90%) of the plasma ions impinging on the dielectric layerhave energy at or below 10% of the applied voltage of 250 V calling forthe need for measurement of the secondary

Young Kyo Shin; Jae Koo Lee; Chae Hwa Shon; Woong Kim

1999-01-01

118

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

119

Power efficiency estimation of silicon nanocrystals based light emitting devices in alternating current regime  

NASA Astrophysics Data System (ADS)

The power efficiency of silicon nanocrystal light-emitting devices is studied in alternating current (ac) regime. An experimental method based on impedance spectroscopy is proposed. The power efficiency in ac regime is higher than the one measured in direct current before a threshold frequency and decreases significantly for higher frequencies. This decrease is attributed to an increase in electrical power injected at high frequencies and it is directly related to the disordered microscopic structure of the active material. The proposed method can be applied for any kind of device for which it is possible to measure the impedance characteristic.

Marconi, A.; Anopchenko, A.; Pucker, G.; Pavesi, L.

2011-05-01

120

Inappropriate implantable cardioverter-defibrillator shocks attributed to alternating-current leak in a swimming pool.  

PubMed

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; Goldner, Bruce

2014-02-01

121

Motions of quantized vortices attached to a boundary in alternating currents of superfluid {sup 4}He  

SciTech Connect

The motions of superfluid vortices attached to a boundary are investigated in alternating currents by using a vibrating wire. The attached vortices appear to form a layer on the wire and enhance the mass of the wire, even for low velocity currents. In turbulence, chaotic motions of vortices such as entanglement and reconnection reduce the thickness of the layer in spite of the fact that the vortices unstably expand. When turbulence subsides, the attached vortices appear to shrink, with the degree of shrinking influenced by thermal excitations in the superfluid.

Yano, H.; Hashimoto, N.; Handa, A.; Obara, K.; Ishikawa, O.; Hata, T. [Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Nakagawa, M. [Department of Physics, Hokkaido University of Education, Kushiro 085-8580 (Japan)

2007-01-01

122

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

SciTech Connect

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

123

A technique to form a porous silicon layer with no backside contact by alternating current electrochemical process  

NASA Astrophysics Data System (ADS)

We report here the formation of porous silicon under alternating current conditions. Instead of applying the usual direct current electrochemical process, an alternating current was applied with a given frequency and peak voltage. The porous silicon layer properties are equivalent to the properties that would be achieved by the standard direct current formation technique (i.e., same porosity level). The main advantages of this process are: (a) The alternating current formed porous silicon exhibits higher mechanical stability during the drying step than layers formed using the standard direct current technique. (b) The alternating current process can be performed without a deposited backside contact. These simplify the process and permit its integration with high temperature processing steps and clean furnaces of a modern very large sale-integrated technology.

El-Bahar, A.; Nemirovsky, Y.

2000-07-01

124

Ring currents that survive bond alternation in constrained 8? and 6? monocycles  

NASA Astrophysics Data System (ADS)

Current density maps are computed at the ipsocentric CTOCD-DZ/6-31G **//RHF/6-31G ** level for angle-constrained planar 1,3,5,7-cyclooctatetraenes (COT) and benzene. Constraint of ?(CCH) angles to 90° in D4 h COT ( 3b) leads to endo- 4 and exo- 4 valence isomers. The exo structure, with CH bonds perpendicular to long sides of the octagon, is lower in energy by 202 kJ/mol and has stronger bond alternation (? R 0.265 Å). However, endo- 4, exo- 4 and COT 3b at its best planar geometry all sustain intense paratropic ring currents, attributed to the rotational character of the HOMO-LUMO transition, and consistent, mutatis mutandis, with the diatropic current in D3 h benzene 5.

Havenith, Remco W. A.; Jenneskens, Leonardus W.; Fowler, Patrick W.

2003-01-01

125

Thermal analysis of high power LED packages under the alternating current operation  

NASA Astrophysics Data System (ADS)

In this paper we describe a novel thermal characterization method of GaN-based Light Emitting Diode (LED) package driven under the Alternating Current (AC) mode. The result was compared with the results from the thermal analysis for LED package operated under the Direct Current (DC) condition. Different from the DC condition, the junction temperature rise with the operation time of LED package was exhibited in a band formation. Finite Volume Method (FVM) was utilized to calculate the thermal performance of LED package under the AC condition using the input power extracted from the output current and voltage from the AC power supply. The experimental result was in a good agreement with the simulation data.

Shin, Moo Whan; Jang, Sun Ho

2012-02-01

126

Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films  

NASA Astrophysics Data System (ADS)

Alternating current (ac) and direct current (dc) conductivities have been measured in polymer-nanotube composite thin films. This was carried out for a range of concentrations of multiwall nanotubes in two polymer hosts, poly(m-phenylenevinylene-co-2,5-dioctyloxyp-phenylenevinylene) (PmPV) and polyvinylalcohol (PVA). In all cases the dc conductivity ?DC was ohmic in the voltage range studied. In general the ac conductivity displayed two distinct regions, a frequency independent region of magnitude ?0 at low frequency and a frequency dependent region at higher frequency. Both ?DC and ?0 followed a percolation scaling law of the form ?~(p-pc)t with pc=0.055% by mass and t=1.36. This extrapolates to a conductivity of 1×10-3 S/m for 100% nanotube content. Such a low value reflects the presence of a thick polymer coating, resulting in poor electrical connection between tubes. This leads to the suggestion that charge transport is controlled by fluctuation induced tunneling. In the high frequency regime the conductivity increases with frequency according to an approximate power law with exponent s~0.92, indicative of hopping transport. The onset of this frequency independent conductivity scales with mass fraction for the PmPV composite due to the variation of correlation length with nanotube content. This behavior is discussed in terms of a biased random walk in three dimensions. In addition ac universality is demonstrated by the construction of a mastercurve.

Kilbride, B. E.; Coleman, J. N.; Fraysse, J.; Fournet, P.; Cadek, M.; Drury, A.; Hutzler, S.; Roth, S.; Blau, W. J.

2002-10-01

127

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

PubMed

The remarkable polarity-dependent growth and anatomical organization of neurons in vitro produced by imposed direct current (DC) voltage gradients (electrical fields; Ef) can be mimicked by another type of electrical cue. This is a properly structured asymmetrical alternating current (AC) electrical field (A-ACEf). Here we provide details on the construction of an AC signal generator in which all components of an AC waveform can be individually controlled. We show that 1) conventional symmetrical AC voltage gradients will not induce growth, guidance, or architectural changes in sympathetic neurons. We also provide the first qualitative and quantitative data showing that an asymmetric AC application can indeed mimic the DC response in chick sympathetic neurons and their growing neurites. This shift in orientation and neuronal anatomy requires dieback of some neurites and the extension of others to produce a preferred orientation perpendicular to the gradient of voltage. Our new results may lead to a noninvasive means to modify nerve growth and organization by magnetic inductive coupling at distance. These data also indicate the possibility of a means to mimic DC-dependent release of drugs or other biologically active molecules from electrically sensitive that can be loaded with these chemical cargos. PMID:22504892

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

2012-08-01

128

Development of Alternating Current Potential Drop (ACPD) procedures for crack detection in aluminum aircraft panels  

NASA Astrophysics Data System (ADS)

The Alternating Current Potential Drop (ACPD) method is investigated as a means of making measurements in laboratory experiments on the initiation and growth of multiple site damage (MSD) cracks in a common aluminum alloy used for aircraft construction. Procedures for instrumenting MSD test specimens are recommended. The ACPD method is found to be capable of the following: (1) detecting crack initiation at a crack length of the order of 1 mm; (2) monitoring crack propagation at a resolution of the order of 5 micrometers; and (3) providing an indirect measurement of crack extension in R-curve type tests of fastener hole details.

Jablonski, D. A.

1993-12-01

129

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

130

Electrochemical oxidation of the carbide wastes of hard alloys using alternating current  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation of the carbide wastes of a W-Co alloy has been studied by gas, electron-probe microanalysis, and X-ray diffraction analyses. The experiments are carried out using halfwave sinusoidal alternating current. It is established that a CO2 + CO mixture forms under such conditions in a gaseous phase in volumetric ratio of 2: 1 and that a tungsten deposit forms in an anode sludge mainly in the form of hydrated tungsten oxide WO2(OH)2. Marketable products are obtained in the form of pure CO3O4 and WO3.

Bryukvin, V. A.; Palant, A. A.; Levchuk, O. M.; Tsybin, O. I.

2012-03-01

131

Thermomigration in flip-chip SnPb solder joints under alternating current stressing  

NASA Astrophysics Data System (ADS)

Thermomigration in flip-chip solder joints is investigated using alternating currents and infrared microscopy to decouple it from electromigration effect. It is found that the thermal gradient in solder bump can be as high as 2143 °C/cm when 9.2×104 A/cm2 was applied at 100 °C. Markers fabricated by focus ion beam are employed to measure the thermomigration rate. The thermomigration flux is measured to be 3.3×1013 at./cm2. With the known thermal gradient, the molar heat of 26.8 kJ/mole has been obtained for the transport of Pb.

Hsiao, Hsiang-Yao; Chen, Chih

2007-04-01

132

Lidocaine transport through a cellophane membrane by alternating current iontophoresis with a duty cycle.  

PubMed

The purpose of this study was to determine whether lidocaine can be efficiently transported across a cellophane membrane using a square-wave alternating current (AC) with an adjusted duty cycle. Three voltages at 1 kHz with 6 duty cycles were applied for 60 min to the diffusion cells on both sides of the cellophane membrane. The donor chamber was filled with 1% lidocaine hydrochloride solution. The transport of lidocaine was enhanced in a voltage-, and duty cycle-dependent manner. These findings indicate that voltage and the direct current (DC) component of the square-wave AC play important roles in generating the driving force necessary for lidocaine delivery. Additionally, the periodic polarity alteration could reduce the electrode polarization. The higher voltages and duty cycles induced a pH change. The practical electrical conditions which are preferable for clinical application were 10 V with a 70% duty cycle or 20 V with a 60% duty cycle. PMID:19110474

Hayashi, Shizuka; Ogami, Saori; Shibaji, Takao; Umino, Masahiro

2009-02-01

133

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

SciTech Connect

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

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

2008-11-15

134

Voltammetry based on fractional diffusion.  

PubMed

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

Mirceski, Valentin; Tomovski, Zivorad

2009-03-01

135

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

PubMed

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

Vasudevan, Subramanyan; Lakshmi, Jothinathan; Sozhan, Ganapathy

2011-08-15

136

Modelling cyclic voltammetry without digital simulation  

Microsoft Academic Search

A semi-analytical method of modelling cyclic voltammetry is described, derived, exemplified, verified, and advocated. A listing of the mechanistic schemes that can be addressed by the procedure includes E, EE, CE, EC and ECE, all with various degrees of reversibility. The approach has advantages and disadvantages when compared with digital simulation.

Keith B. Oldham; Jan C. Myland

137

Dental Amalgam in Voltammetry. Some Preliminary Results  

Microsoft Academic Search

Liquid mercury and liquid diluted mercury amalgams have been superior as electrode material for the use of voltammetry for analytical purposes. This is mainly due to the high overvoltage to hydrogen, which enables one to use a wide potential range for the measurements. Due to the toxicity of mercury and liquid diluted mercury compounds, the use of such compounds are

Ø. Mikkelsen

2000-01-01

138

Alternatives to the Current Use of Nitrite in Foods: Volume 2.  

National Technical Information Service (NTIS)

The status of research on proposed alternatives to the use of nitrite in cured meats was examined to determine if suitable alternatives are available. In addition, strategies for long-term research on alternatives to nitrite were developed. Several promis...

1982-01-01

139

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

140

Integration of electrodes in a suction cup-driven microchip for alternating current-accelerated proteolysis.  

PubMed

In this report, a pair of platinum wire electrodes was inserted in the main channel of a simple-cross PMMA microchip to perform on-chip alternating current-assisted proteolysis. Both terminals of the injection channel in the microchip were sharpened with a file to form sharp inlet tips to suck protein and trypsin solutions into the electrode-containing channel with the aid of a suction cup via the detection reservoir at the end of the chip. A solution containing BSA, cytochrome c, myoglobin, or hemoglobin was digested in the presence of alternating electric field after it was mixed with trypsin solution in the channel. The obtained digests were identified by MS with sequences that were comparable to those obtained by using conventional in-solution tryptic digestion while the digestion time was significantly reduced from 12 h to 4 min. The present proteolysis setup is simple and efficient and will find wide applications in high-throughput protein digestion. PMID:19705354

Liu, Ting; Bao, Huimin; Zhang, Luyan; Chen, Gang

2009-09-01

141

Water management in the Basin of Mexico: current state and alternative scenarios  

NASA Astrophysics Data System (ADS)

Water management policies in the Basin of Mexico, where Mexico City and its nearly 20 million inhabitants live, are analyzed. After a brief description of how water has been managed, possible water management plans that would change water management practices in the Basin are discussed and a call is made for a change in the defensive attitude towards water taken to date. As the aquifer’s replacement cost is considered to be the proxy for the implementation of water tariffs, this is determined, based on the cost of future water sources, and found to be 0.65-0.72 USD/m3. This is twice the amount currently charged in the Federal District (0.34 USD/m3), where 45% of the City's domestic water users are found. As another alternative, the development of an artificial recharge program is also analyzed and found to be a plausible way to increase water supply at a unitary cost of 0.605 USD/m3. Despite the presence of these alternatives, it is suggested that water management in the Basin needs to change from a water supply approach to a water demand approach.

Carrera-Hernández, Jaime J.; Gaskin, S. J.

2009-09-01

142

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

NASA Astrophysics Data System (ADS)

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.

Xue, Jiancai; Zhu, Qiangzhong; Liu, Jiaming; Li, Yinyin; Zhou, Zhang-Kai; Lin, Zhaoyong; Yan, Jiahao; Li, Juntao; Wang, Xue-Hua

2013-06-01

143

Effect of large-amplitude alternating current modulation on apparent reversibility of electrode processes.  

PubMed

We examined the effect of a large-amplitude high-frequency alternating potential modulation on direct currents associated with irreversible, quasi-reversible, and reversible electron-transfer processes occurring at microelectrodes under voltammetric conditions. All irreversible processes appear to be accelerated by the superimposed ac modulation, and under certain conditions this may even lead to an electrochemical etching of noble metal electrodes. In the case of electrode processes which are reversible on the time scale of a dc polarization, but quasi-reversible on the time scale of the ac modulation, the distortion of voltammograms caused by the ac modulation can provide useful information about the kinetics of fast electron-transfer processes. For completely reversible electrode processes the effect of the large-amplitude ac modulation is essentially trivial; the distortion of voltammetric curves causes broadening of analytical signals without providing any useful information. PMID:20825176

Baranski, Andrzej S; Boika, Aliaksei

2010-10-01

144

Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices  

NASA Astrophysics Data System (ADS)

In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

2013-01-01

145

Thermomigration in Pb-free SnAg solder joint under alternating current stressing  

NASA Astrophysics Data System (ADS)

Lead-free solders have been adopted by the microelectronics industry. However, their thermomigration behaviors are unclear. Thermomigration in eutectic SnAg3.5 solder joints was investigated using an alternating current (ac) of 0.57 A at 100 °C. The ac eliminates the electromigration effect and creates a thermal gradient of 2829 °C/cm, facilitating the study of thermomigration. Arrays of tiny markers fabricated by a focused ion beam are employed to measure the thermomigration rate. It is found that Sn atoms migrated toward the hot end. The thermomigration flux and molar heat of transport are measured to be 5.0×1012 atoms/cm2 and 1.36 kJ/mole, respectively.

Hsiao, Hsiang-Yao; Chen, Chih

2009-03-01

146

Alternating current plasma detector for selective mercury detection in gas chromatography  

SciTech Connect

Gas chromatograpy (GC) coupled with element-specific detectors has been employed in many applications to simplify the interpretation of complex chromatograms. Desirable characteristic of an element-specific detector are that it should be highly specific for a wide range of elements, sensitive for these elements over a wide linear range, simple to construct and maintain, and stable under many application conditions. This work describes the design, construction, and evaluation of a novel mercury-specific helium alternating current plasma detector (ACPD) for GC. The ACPD was designed to overcome some disadvantages suffered by other elements-selective detectors. The power source employed for the detector design includes a tee configuration discharge tube and a heated fused silica-coated megabore capillary tube as the effluent transfer tube which reduces band broadening and offers improved sensitivity. The ACPD is evaluated for sensitivity, selectivity, and linear dynamic range with methylmercury(II)chloride and ethylmercury(II) chloride.

Costanzo, R.B.; Barry, E.F.

1988-04-15

147

Optoelectronic Characteristics of Direct-Current and Alternating-Current White Thin-Film Light-Emitting Diodes Based on Hydrogenated Amorphous Silicon Nitride Film  

Microsoft Academic Search

Direct-current and alternating-current white thin- film light-emitting diodes (DCW and ACW TFLEDs) have been fabricated and demonstrated with the intrinsic hydrogenated amorphous silicon nitride (i-a-SiN:H) film as the luminescent layer. The achievable brightness of the representative DCW and ACW TFLEDs were 200 and 170 cd\\/m2 at an injection-current density of 600 and 100 mA\\/cm2, respectively. The electroluminescence (EL) threshold voltage

Rong-Hwei Yeh; Tai-Rong Yu; Te-Cheng Chung; Shih-Yung Lo; Jyh-Wong Hong

2008-01-01

148

Regional economic analysis of current and proposed management alternatives for Rappahannock River Valley National Wildlife Refuge  

USGS Publications Warehouse

The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan. The Comprehensive Conservation Plan must describe the desired future conditions of a refuge and provide long-range guidance and management direction to achieve refuge purposes. The Rappahannock River Valley National Wildlife Refuge (refuge) is in the process of developing a range of management goals, objectives, and strategies for the Comprehensive Conservation Plan. The Comprehensive Conservation Plan for the refuge must contain an analysis of expected effects associated with current and proposed refuge management strategies. The purpose of this study was to assess the regional economic implications associated with draft Comprehensive Conservation Plan management strategies. Special interest groups and local residents often criticize a change in refuge management, especially if there is a perceived negative impact to the local economy. Having objective data on economic impacts may show that these fears are overstated. Quite often, the extent of economic benefits a refuge provides to a local community is not fully recognized, yet at the same time the effects of negative changes is overstated. Spending associated with refuge recreational activities, such as wildlife viewing and hunting, can generate considerable tourist activity for surrounding communities. Additionally, refuge personnel typically spend considerable amounts of money purchasing supplies in local stores, repairing equipment and purchasing fuel at the local service stations, and reside and spend their salaries in the local community. For refuge Comprehensive Conservation Plan planning, a regional economic assessment provides a means of estimating how current management (no action alternative) and proposed management activities (alternatives) could affect the local economy. This type of analysis provides two critical pieces of information: (1) it illustrates a refuge's contribution to the local community; and (2) it can help in determining whether local economic effects are or are not a real concern in choosing among management alternatives. It is important to note that the economic value of a refuge encompasses more than just the impacts of the regional economy. Refuges also provide substantial nonmarket values (values for items not exchanged in established markets), such as maintaining endangered species, preserving wetlands, educating future generations, and adding stability to the ecosystem. However, quantifying these types of nonmarket values was beyond the scope of this study because of time and budget constraints.

Koontz, Lynne; Sexton, Natalie; Donovan, Ryan

2009-01-01

149

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

150

Experimental aspects of solid-state voltammetry  

SciTech Connect

This paper describes the properties of poly(ether) polymer electrolytes as solvent media for solid-state voltammetry. Experimental requirements for microelectrode voltammetry and results for the dependency of diffusive transport of electroactive solutes on polymer solvent molecular weight, structure, and temperature (and related phase state) are described for eight poly(ether)s: linear poly(ethylene oxides) MW = 400, 1000, 2000, and 600 000 (Me{sub 2}PEG-400, Me{sub 2}PEG-1000, Me{sub 2}PEG-2000, PEO-600 000), linear poly(propylene oxide) MW = 4000 (PPO-4000), the comb polymer poly(bis[(methoxyethoxy)ethoxy]phosphazine) (MEEP), the block copolymer poly(ether)-poly(urethane urea)(PEUU), and the cross-linked poly(ether) network PEO. 28 refs., 10 figs., 1 tab.

Wooster, T.T.; Longmire, M.L.; Zhang, H. [Univ. of North Carolina, Chapel Hill, NC (United States)] [and others

1992-05-15

151

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

152

Charge transfer kinetics from surface plasmon resonance voltammetry.  

PubMed

On the basis of a quantitative relationship between surface plasmon resonance signal and electrochemical current in the electrochemical surface plasmon resonance (EC-SPR), EC-SPR signal measures the semi-integral of faradaic current. We theoretically discussed the electrode potential and charge transfer kinetics to be determined from surface plasmon resonance voltammetry (or potential sweep EC-SPR) signals for the fully reversible, quasi-reversible, and irreversible redox reactions. The results indicated that the electroanalysis of EC-SPR signal is more straightforward than conventional electrochemical current. Then, we studied two model redox reactions of hexaammineruthenium chloride and 4-nitrotoluene, to obtain half wave potential of quasi-reversible redox reaction, transfer coefficient, and standard rate constant of irreversible redox reaction from EC-SPR signals. PMID:24654883

Lu, Jin; Li, Jinghong

2014-04-15

153

Current Status of Alternative Automotive Power Systems and Fuels. Volume I. Executive Summary.  

National Technical Information Service (NTIS)

A summary is given of technical information collected on: (1) alternatives to the conventional internal combustion engine for automobiles; and (2) nonpetroleum-based automotive fuels derived from domestic sources. Alternative heat engines considered were ...

D. E. Lapedes M. G. Hinton J. Meltzer T. Iura

1974-01-01

154

Depot Level Reparables: An Analysis of Current and Alternative Methods of Funding.  

National Technical Information Service (NTIS)

The objective of the study was to evaluate the efficacy of alternative Depot Level Reparable (DLR) funding mechanisms. An alternative investigation was the combining of the funding of both new procurement and repair of DLRs in one appropriation. A second ...

R. J. Moloney

1979-01-01

155

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.

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

2012-01-01

156

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

157

Ion-exchange voltammetry as a solid-phase microextraction analytical method:? factors influencing the mass transfer to perfluorosulfonated ionomer film-coated electrodes and some of their consequences on the current responses.  

PubMed

A simple theoretical model of mass transfer kinetics at an electrode coated with an ion-exchange film polymer is proposed. The model takes into account the analyte depletion in solution and gives the relationship between the ion-exchange voltammetric (IEV) peak current and the initial analyte concentration in the sample matrix. The verification of the model is investigated at disposable Nafion film-coated screen-printed electrodes, using the redox cationic (ferrocenylmethyl)trimethylammonium salt. It is shown that the theoretical model and the experimental data fit satisfactorily insofar as the variation of the extraction and apparent diffusion coefficients of the salt with the film thickness are taken into account. Indeed, the film thickness plays a crucial role for the optimization of the IEV sensitivity, because the physicochemical properties of the recast Nafion polymer are dependent on the amount per unit area of Nafion deposited on the electrode surface. PMID:21662910

Bagel, O; Degrand, C; Limoges, B

1999-08-01

158

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

PubMed Central

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

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

2013-01-01

159

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

160

Transcranial Alternating Current Stimulation Increases Risk-Taking Behavior in the Balloon Analog Risk Task  

PubMed Central

The process of evaluating risks and benefits involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). It has been proposed that in conflict and reward situations, theta-band (4–8?Hz) oscillatory activity in the frontal cortex may reflect an electrophysiological mechanism for coordinating neural networks monitoring behavior, as well as facilitating task-specific adaptive changes. The goal of the present study was to investigate the hypothesis that theta-band oscillatory balance between right and left frontal and prefrontal regions, with a predominance role to the right hemisphere (RH), is crucial for regulatory control during decision-making under risk. In order to explore this hypothesis, we used transcranial alternating current stimulation, a novel technique that provides the opportunity to explore the functional role of neuronal oscillatory activities and to establish a causal link between specific oscillations and functional lateralization in risky decision-making situations. For this aim, healthy participants were randomly allocated to one of three stimulation groups (LH stimulation/RH stimulation/Sham stimulation), with active AC stimulation delivered in a frequency-dependent manner (at 6.5?Hz; 1?mA peak-to-peak). During the AC stimulation, participants performed the Balloon Analog Risk Task. This experiment revealed that participants receiving LH stimulation displayed riskier decision-making style compared to sham and RH stimulation groups. However, there was no difference in decision-making behaviors between sham and RH stimulation groups. The current study extends the notion that DLPFC activity is critical for adaptive decision-making in the context of risk-taking and emphasis the role of theta-band oscillatory activity during risky decision-making situations.

Sela, Tal; Kilim, Adi; Lavidor, Michal

2011-01-01

161

Transcranial alternating current stimulation increases risk-taking behavior in the balloon analog risk task.  

PubMed

The process of evaluating risks and benefits involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). It has been proposed that in conflict and reward situations, theta-band (4-8?Hz) oscillatory activity in the frontal cortex may reflect an electrophysiological mechanism for coordinating neural networks monitoring behavior, as well as facilitating task-specific adaptive changes. The goal of the present study was to investigate the hypothesis that theta-band oscillatory balance between right and left frontal and prefrontal regions, with a predominance role to the right hemisphere (RH), is crucial for regulatory control during decision-making under risk. In order to explore this hypothesis, we used transcranial alternating current stimulation, a novel technique that provides the opportunity to explore the functional role of neuronal oscillatory activities and to establish a causal link between specific oscillations and functional lateralization in risky decision-making situations. For this aim, healthy participants were randomly allocated to one of three stimulation groups (LH stimulation/RH stimulation/Sham stimulation), with active AC stimulation delivered in a frequency-dependent manner (at 6.5?Hz; 1?mA peak-to-peak). During the AC stimulation, participants performed the Balloon Analog Risk Task. This experiment revealed that participants receiving LH stimulation displayed riskier decision-making style compared to sham and RH stimulation groups. However, there was no difference in decision-making behaviors between sham and RH stimulation groups. The current study extends the notion that DLPFC activity is critical for adaptive decision-making in the context of risk-taking and emphasis the role of theta-band oscillatory activity during risky decision-making situations. PMID:22347844

Sela, Tal; Kilim, Adi; Lavidor, Michal

2012-01-01

162

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

163

The current status of animal use and alternatives in Korean veterinary medical schools.  

PubMed

Two new Korean laws regulating animal welfare and the humane use of animals in science came into effect in 2008 and 2009. Both these laws impose ethical committee review prior to the performance of animal experiments in research, testing and education. This study briefly summarises the new Korean laws, and investigates the current status regarding the numbers of animals used, the alternatives to animals which are used, the curricula relating to the humane use of animals, and ethical review practices in Korean veterinary education. Approximately 4,845 animals, representing 20 different species, were used in veterinary medical education in Korea in 2007. Korea has begun to introduce formal courses on animal welfare for the humane treatment of animals used in experiments, and an ethical protocol review system prior to animal use in education. Korea is moving toward better animal welfare, by incorporating practices consistent with international standards. The information presented represents the first such data gathered in Korea, which should prove useful for monitoring the implementation of replacement, reduction, and refinement measures in animal use for education purposes. PMID:20602538

Lee, Gwi Hyang; Choe, Byung In; Kim, Jin Suk; Hart, Lynette A; Han, Jin Soo

2010-06-01

164

Alternating current surface photovoltage in thermally oxidized chromium-contaminated n-type silicon wafers  

NASA Astrophysics Data System (ADS)

We investigated a variation of frequency-dependent alternating current (AC) surface photovoltages (SPVs) in thermally oxidized, chromium-contaminated, n-type silicon (Si) wafers. As previously reported, immediately after rinsing in Cr-contaminated solution, a Cr(OH)3-Si contact causes a Schottky-barrier-type AC SPV on n-type Si. Upon oxidation at 373 K for 10 min, the Schottky barrier collapses and, with further oxidation, a metal-induced negative oxide charge, due to atomic bridging of (CrOSi)- and/or CrO2- networks, definitely grows over time in SiO2. For samples oxidized at temperatures between 823 and 1023 K for 30 min, the observed AC SPV gives evidence that the metal-induced negative oxide charge causes a strongly inverted state of the Si surface. At oxidation temperatures higher than 1023 K and /or for an oxidation time longer than 60 min, the level height of the AC SPV is reduced, implying that the strongly inverted state changes into a less depleted state, whilst, finally, the AC SPV disappears. In this case, the collapse of the (CrOSi)- and/or CrO2- networks is anticipated, with a possible change into Cr2O3. The existence of the (CrOSi)- and/or CrO2- networks has also been confirmed in p-type Si wafers.

Shimizu, Hirofumi; Nagase, Shintarou; Ikeda, Masanori

2011-09-01

165

Alternating current electrohydrodynamics induced nanoshearing and fluid micromixing for specific capture of cancer cells.  

PubMed

We report a new tuneable alternating current (ac) electrohydrodynamics (ac-EHD) force referred to as “nanoshearing” which involves fluid flow generated within a few nanometers of an electrode surface. This force can be externally tuned via manipulating the applied ac-EHD field strength. The ability to manipulate ac-EHD induced forces and concomitant fluid micromixing can enhance fluid transport within the capture domain of the channel (e.g., transport of analytes and hence increase target–sensor interactions). This also provides a new capability to preferentially select strongly bound analytes over nonspecifically bound cells and molecules. To demonstrate the utility and versatility of nanoshearing phenomenon to specifically capture cancer cells, we present proof-of-concept data in lysed blood using two microfluidic devices containing a long array of asymmetric planar electrode pairs. Under the optimal experimental conditions, we achieved high capture efficiency (e.g., approximately 90%; %RSD=2, n=3) with a 10-fold reduction in nonspecific adsorption of non-target cells for the detection of whole cells expressing Human Epidermal Growth Factor Receptor 2 (HER2). We believe that our ac-EHD devices and the use of tuneable nanoshearing phenomenon may find relevance in a wide variety of biological and medical applications. PMID:24677444

Vaidyanathan, Ramanathan; Rauf, Sakandar; Dray, Eloïse; Shiddiky, Muhammad J A; Trau, Matt

2014-03-24

166

Increasing working memory capacity with theta transcranial alternating current stimulation (tACS).  

PubMed

The study aimed to investigate the influence of transcranial alternating current stimulation (tACS) on working memory's (WM) storage capacity. Sham/verum tACS with individually determined theta frequency was applied to the left parietal (target electrode=P3) or frontal (target electrode=F3) brain areas (return electrode above the right eyebrow). After sham and verum stimulation, 24 respondents solved a task measuring the scope of attention while their electroencephalogram (EEG) was recorded. Verum tACS with the target electrode positioned over the left parietal brain area significantly increased WM storage capacity, as compared to sham tACS. No such influence was observed for tACS with the target electrode positioned over the left frontal area. Increased WM storage capacity was accompanied by event-related potential (ERP) P300 latency decrease in the left hemisphere. The obtained behavioral and neuroelectric data emphasize the causal relationship between WM storage capacity and theta frequency oscillations in the left parietal brain area. PMID:24291565

Jaušovec, Norbert; Jaušovec, Ksenija

2014-02-01

167

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

168

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

169

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.

van Berkum, Susanne; Erne, Ben H.

2013-01-01

170

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

171

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

PubMed

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

2014-03-01

172

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

PubMed Central

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

Wang, Shengqin; Zhu, Yingxi

2012-01-01

173

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

174

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

PubMed

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

Wang, Shengqin; Zhu, Yingxi

2012-06-01

175

Operational Requirements Document (ORD) for the Alternating Current/Direct Current (AC/DC) Clamp-on Ammeter, ME-563.  

National Technical Information Service (NTIS)

The ammeter shall operate in a frequency range of 45 Hertz (Hz) to 500 Hz with a resolution of no more than 100 mAMP on the low range scale and no more than 1 AMP on the high range scale. It will have a maximum AC current range to 300 AMP and a DC current...

1993-01-01

176

The Alternative Birth Movement in the United States: History and Current Status  

Microsoft Academic Search

The alternative birth movement is a consumer reaction to paternalistic and mechanistic medical obstetrical practices which developed in the United States early in this century. Alternative birth settings developed as single labor-delivery-recovery rooms in the hospital or as free-standing birth centers. Both alternatives offer family-centered, home-like, low technological maternity care. In order to overcome physician resistance to non-traditional maternity care,

Joan J. Mathews; Kathleen Zadak

1991-01-01

177

Alternating-current thin-film electroluminescent device fabrication and characterization  

NASA Astrophysics Data System (ADS)

The goals of this thesis are to provide an improved understanding of luminescent materials, and to exploit their properties to achieve bright, efficient, and manufacturable red, green, and blue (RGB) phosphors for use in full-color flat-panel displays. A high-luminance, high-efficiency, full-color alternating-current thin-film electroluminescent (ACTFEL) phosphor system, capable of being processed at temperatures below the glass substrate melting temperature, has been developed through the use of source layer diffusion doping (SLDD) of atomic layer epitaxy (ALE) deposited SrS thin-films. The development of ACTFEL phosphors has also been advanced through the exploration of alternate phosphor materials, such as SrxCa 1-xS:Eu,Cu and (Ba.Zn)S:Mn. This thesis offers new insight into the nature of ACTFEL device operation, especially SrS:Cu ACTFEL devices. A comparison of "EL" thermal quenching trends for evaporated ZnS:Mn, ALE ZnS:Mn, ALE SrS:Ce, sputtered SrS:Cu,Ag, and sputtered multi-layer SrS:Cu,Ag/SrS:Ce ACTFEL devices is presented. ZnS:Mn ACTFEL devices exhibit the least amount of EL thermal quenching, which is attributed to non-radiative recombination. SrS:Cu and SrS:Cu,Ag ACTFEL devices possess the greatest amount of thermal quenching, which is primarily EL thermal quenching. The extent of EL thermal quenching is significantly reduced in a multi-layer SrS:Cu,Ag/SrS:Ce ACTFEL device, compared to that of a single-layer SrS:Cu or SrS:Cu,Ag ACTFEL device. The operation of SrS:Cu is examined as a function of temperature; the space charge density is found to increase with temperature up to ˜250 K with an activation energy of 0.02 eV. The space charge density in SrS:Cu ACTFEL devices is estimated as ˜1.8 x 1016, which yields estimates of the cathode phosphor field and the interfacial trap depth of ˜1.3 MV/cm and ˜0.73 eV, respectively.

Baukol, Beau Alexander

178

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

179

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.

Uangpairoj, Pichitra; Shibata, Masahiro

2013-01-01

180

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

NASA Astrophysics Data System (ADS)

In this study, alternating current impedance spectroscopic analysis of the biofunctionalization process of a vertically-aligned (silica) nanosprings (VANS) surface is presented. The VANS surface is functionalized with a biotinylated immunoglobulin G (B-IgG) layer formed by physisorption of B-IgG from the solution phase. Bovine serum albumin passivation of the B-IgG layer reduces additional surface adsorption by blocking the potential sites of weak bond formation via electrostatic and hydrophobic interactions. As avidin acts as a receptor of biotinylated compounds, avidin conjugated glucose oxidase (Av-GOx) binds to the B-IgG layer via biotin. This avidin-biotin bond is a stable bond with high association affinity (Ka = 1015 M-1) that withstands wide variations in chemistry and pH. An IgG layer without biotin shows no binding to the Av-GOx, indicating that bonding is through the avidin-biotin interaction. Finally, fluoroscein iso-thiocyanate (FITC) labeled biotinylated bovine serum albumin (B-BSA) added to the Av-GOx surface is used to fluorescently label Av-GOx for fluorescent measurements that allow for the correlation of surface binding with impedance measurements. Modeling of impedance spectra measured after the addition of each biological solution indicates that the bimolecular layers behave as insulating layers. The impedance spectra for the VANS-based sensor are compared to simple parallel capacitor sensors, sans VANS, and serve as controls. VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls below 10 kHz. Changes in the magnitudes of the components of the VANS equivalent circuit indicate that the addition of biological layers changes the effective dielectric response of the VANS via the impediment of ionic motion and biomolecule polarization.

Timalsina, Yukta P.; Branen, Joshua; Aston, D. Eric; Noren, Kenneth; Corti, Giancarlo; Schumacher, Randi; McIlroy, David N.

2011-07-01

181

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

PubMed Central

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

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

2010-01-01

182

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

Microsoft Academic Search

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

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

2005-01-01

183

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

ERIC Educational Resources Information Center

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

Bard, Allen J.

2007-01-01

184

Eddy-current computation in the claws of a synchronous claw-pole alternator in generator mode  

Microsoft Academic Search

This paper deals with the three-dimensional finite-element (FE) calculation of eddy currents in the claws of a claw-pole alternator taking the rotational geometry movement into account. For this calculation a transient edge-based A&oarr;, A&oarr; - T&oarr; formulation is utilized. The generation of the FE model with a special focus on the discretization of eddy-current regions and air gap is presented.

Christian Kaehler; Gerhard Henneberger

2002-01-01

185

Transient 3-D FEM computation of eddy-current losses in the rotor of a claw-pole alternator  

Microsoft Academic Search

The three-dimensional finite-element method (FEM) allows for the calculation of eddy currents in the claws of synchronous claw-pole alternators taking the rotational geometry movement into account. A transient edge-based vector formulation is utilized to compute the induced eddy-current losses in the rotor caused by the stator slotting. The theory of this formulation is outlined and the FEM model of the

Christian Kaehler; Gerhard Henneberger

2004-01-01

186

Determination of electron mobility in a blue-emitting alternating block copolymer by space-charge-limited current measurements  

Microsoft Academic Search

In this communication we analyse current versus voltage data obtained using one carrier injection at metal\\/polymer\\/metal structures. The used polymer is a soluble blue-emitting alternating block copolymer. Our experimental results demonstrate that the electron current is limited by a large amount of traps with exponential energy distribution in the copolymer. The electron mobility of 5.1×10?10cm2\\/Vs is directly determined by space-charge-limited

D. Ma; I. A. Hümmelgen; B. Hu; F. E. Karasz; X. Jing; L. Wang; F. Wang

1999-01-01

187

The alternative birth movement in the United States: history and current status.  

PubMed

The alternative birth movement is a consumer reaction to paternalistic and mechanistic medical obstetrical practices which developed in the United States early in this century. Alternative birth settings developed as single labor-delivery-recovery rooms in the hospital or as free-standing birth centers. Both alternatives offer family-centered, home-like, low technological maternity care. In order to overcome physician resistance to non-traditional maternity care, alternative birth center policies eliminate all women who are expected to have a complicated pregnancy or delivery. Physician resistance to alternative birthing is publicly based on the issue of maternal and infant safety. Additional issues, however, are that physicians fear economic competition and resist loss of control over obstetric practice. This paper (1) traces the historical antecedents and social factors leading to the alternative birth movement, (2) describes the types of alternative birthing methods, and (3) describes ways in which the obstetrical community has maintained and rationalized dominance over the birthing process. PMID:2048321

Mathews, J J; Zadak, K

1991-01-01

188

Alternative Splicing in the Voltage-Gated Sodium Channel DmNav Regulates Activation, Inactivation, and Persistent Current  

PubMed Central

Diversity in neuronal signaling is a product not only of differential gene expression, but also of alternative splicing. However, although recognized, the precise contribution of alternative splicing in ion channel transcripts to channel kinetics remains poorly understood. Invertebrates, with their smaller genomes, offer attractive models to examine the contribution of splicing to neuronal function. In this study we report the sequencing and biophysical characterization of alternative splice variants of the sole voltage-gated Na+ gene (DmNav, paralytic), in late-stage embryos of Drosophila melanogaster. We identify 27 unique splice variants, based on the presence of 15 alternative exons. Heterologous expression, in Xenopus oocytes, shows that alternative exons j, e, and f primarily influence activation kinetics: when present, exon f confers a hyperpolarizing shift in half-activation voltage (V1/2), whereas j and e result in a depolarizing shift. The presence of exon h is sufficient to produce a depolarizing shift in the V1/2 of steady-state inactivation. The magnitude of the persistent Na+ current, but not the fast-inactivating current, in both oocytes and Drosophila motoneurons in vivo is directly influenced by the presence of either one of a pair of mutually exclusive, membrane-spanning exons, termed k and L. Transcripts containing k have significantly smaller persistent currents compared with those containing L. Finally, we show that transcripts lacking all cytoplasmic alternatively spliced exons still produce functional channels, indicating that splicing may influence channel kinetics not only through change to protein structure, but also by allowing differential modification (i.e., phosphorylation, binding of cofactors, etc.). Our results provide a functional basis for understanding how alternative splicing of a voltage-gated Na+ channel results in diversity in neuronal signaling.

Lin, Wei-Hsiang; Wright, Duncan E.; Muraro, Nara I.; Baines, Richard A.

2009-01-01

189

Two-dimensional modeling of a surface type alternating current plasma display panel cell: discharge dynamics and address voltage effects  

Microsoft Academic Search

To improve the luminance and efficiency of an alternating current plasma display panel, the direct measurement of infrared and vacuum ultra violet (VUV) imaging is performed to study discharge dynamics. Images show two emission regions. One is the cathode glow and the other is the anode glow. In the course of discharge cycle, the cathode glow propagates toward the outer

Jeong Hyun Seo; Woo Joon Chung; Cha Keun Yoon; Joong Kyun Kim; Ki-Woong Whang

2001-01-01

190

NDT of on and offshore oil and gas installations using the alternating current field measurement (ACFM) technique  

Microsoft Academic Search

Offshore inspection has been carried out in the UK waters for the last 25 years, but the techniques used have until recently remained stagnant. Innovative work carried out by University College London produced the mathematical modeling of the alternating current field measurement technique, which was then further developed and commercialized into a field usable technique. During detection and sizing trials,

G. A. Raine; N. Smith

1996-01-01

191

Modeling interfacial charge transport of quantum dots using cyclic voltammetry  

NASA Astrophysics Data System (ADS)

Quantum dot applications are numerous and range from photovoltaic devices and lasers, to bio labeling. Complexities in the electronic band structure of quantum dots create the necessity for analysis techniques that can accurately and reproducibly provide their absolute band energies. Cyclic voltammetry (CV) is a novel candidate for these studies and has the potential to become a useful tool in engineering new nanocrystal technology, by providing information necessary for predicting and modeling interfacial charge transfer to and from quantum dots. Advancing from previous reports of nanocrystal CV, a carbon paste electrode was utilized in an attempt to increase measured current by ensuring intimate contact between nanocrystals and the electrode. Our goal was to investigate band energies and model nanocrystal-molecule electron transfer systems.

Tobias, Andrew K.; Jones, Marcus

2011-09-01

192

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.

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

2008-01-01

193

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.

194

Voltammetry under a Controlled Temperature Gradient  

PubMed Central

Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nernst layer and enables more accurate control of the electrode response enhancement by a combination of diffusion and thermal diffusion. We have thus studied the effect of Soret phenomenon by cyclic voltammetry measurements in ferro/ferricyanide. The time dependence of sensor response disappears when applying the Soret phenomenon, and the complicated shape of the cyclic voltammogram is replaced by a simple exponential curve. We have derived the Cotrell-Soret equation describing the steady-state response with an applied temperature difference.

Krejci, Jan; Sajdlova, Zuzana; Krejci, Jan; Marvanek, Tomas

2010-01-01

195

Radiation from Large Space Structures in Low Earth Orbit with Induced Alternating Currents,  

National Technical Information Service (NTIS)

Large conducting space structures in low Earth orbit will have a nonnegligible induced potential across their structures. The induced current flow through the body and the ionosphere causes the radiation of Alfven and lower hybrid waves. This current flow...

D. E. Hastings A. Barnett S. Olbert

1988-01-01

196

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

197

Low-fidelity compensatory backup alternative DNA repair pathways may unify current carcinogenesis theories.  

PubMed

The somatic mutation carcinogenesis theory has dominated for decades. The alternative theory, tissue organization field theory, argues that the development of cancer is determined by the surrounding microenvironment. However, neither theory can explain all features of cancer. As cancers share the features of uncontrolled proliferation and genomic instability, they are likely to have the same pathogenesis. It has been found that various DNA repair pathways within a cell crosstalk with one another, forming a DNA repair network. When one DNA repair pathways is defective, the others may work as compensatory backups. The latter pathways are explored for synthetic lethal anticancer therapy. In this article, we extend the concept of compensatory alternative DNA repair to unify the theories. We propose that the microenvironmental stress can activate low-fidelity compensatory alternative DNA repair, causing mutations. If the mutation occurs to a DNA repair gene, this secondarily mutated gene can lead to even more mutated genes, including those related to other DNA repair pathways, eventually destabilizing the genome. Therefore, the low-fidelity compensatory alternative DNA repair may mediate microenvironment-dependent carcinogenesis. The proposal seems consistent with the view of evolution: the environmental stress causes mutations to adapt to the changing environment. PMID:24947263

Wu, Jiaxi; Starr, Shane

2014-05-01

198

Complementary and Alternative Medicine in Rural Communities: Current Research and Future Directions  

ERIC Educational Resources Information Center

Contexts: The consumption of complementary and alternative medicine (CAM) in rural areas is a significant contemporary health care issue. An understanding of CAM use in rural health can provide a new perspective on health beliefs and practice as well as on some of the core service delivery issues facing rural health care generally. Purpose: This…

Wardle, Jon; Lui, Chi-Wai; Adams, Jon

2012-01-01

199

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

200

Wireless Architectural Alternatives: Current Economic Valuations versus Broadband Options, The Gilder Conjectures1  

Microsoft Academic Search

There has been an assumption that spectrum can be divided into segments and then auctioned off. It has been assumed that this is optimal in terms of its benefit to the public and that the FCC in so doing is optimizing the public good. There has been an alternative conjecture, termed the \\

Terrence P. McGarty; Muriel Medard

201

FLAME-Foreign Language Alternative Mastery Example: Another Approach to FLES Models Currently in Use.  

ERIC Educational Resources Information Center

FLAME (Foreign Language Alternative Mastery Example) is a model for foreign language in the elementary school (FLES), conducted after school and focused on development of a broad vocabulary base, especially cognates and terms relevant to the student's everyday environment. In the program, FLES student teachers collaborate with a university-based…

Dulfano, Isabel

1997-01-01

202

Wickedness of land amenagement: a critique of current land-management techniques and an inquiry into alternative approaches  

SciTech Connect

Land should be considered a non-renewable resource acknowledging that interests in landed property need to adjust accordingly. Given that some problems are wicked (they don't have definitive solutions and can only be repeatedly resolved) current planning models and the present political-economic construct within which land is utilized are considered insufficient. The wickedness of land issues leads to the concept of land amenagement, proposed instead of planning. Combining planning-action-management-stewardship, a set of design variables is developed to describe alternative amenagement approaches. Using this model, first some traditional approaches to land management are outlined: The multi-use policy of National Forests, agribusiness and regulation are examined and their difficulties analysed. Issues are derived from this analysis; these are proposed as a checklist of concerns to address in land-amenagement alternatives. Then some current, more-innovative approaches to land amenagement, such as land trusts and conservancies, are examined to resolve these issues. Possible directions for implementing new programs proposed within these alternatives are also discussed. Finally some alternatives which are yet to be implemented are described and examined in view of the issue checklist.

Luckey, D.

1981-01-01

203

Digital Simulation of Anodic Stripping Voltammetry from Thin Film Electrodes.  

National Technical Information Service (NTIS)

The anodic stripping voltammetry (ASV) is routinely applied to control of Cu(II) in heavy water in the primary cooling loop of the Nuclear Power Reactor. The anodic stripping voltammetry (ASV) is a very well-known technique in electroanalytical chemistry....

J. F. Magallanes

1984-01-01

204

Induced Losses in Steel Plates in the Presence of an Alternating Current  

Microsoft Academic Search

The presence of current-carrying conductors near conducting surfaces induces eddy-current flow in the conducting surfaces and causes resistive and reactive losses to be reflected to the source of supply. In the heavy current field such losses appear in bus-bar installations, rotating equipment, transformers, and other electrical equipment. In large power transformers in which the low-voltage connections may carry 6,000 amperes

W. G. Deuring

1957-01-01

205

Eddy-current computation on a one pole-pitch model of a synchronous claw-pole alternator  

Microsoft Academic Search

This paper deals with 3D finite-element calculation of eddy currents in the claws of a claw-pole alternator taking the rotational geometry movement into account. Two transient edge-based vector formulations are utilised. The reduction of the model to only one pole pitch in combination with a special boundary pairing in the air gap for the applied lock-step method is presented. Calculations

Christian Kaehler; Gerhard Henneberger

2003-01-01

206

Bacteria capture, concentration and detection by alternating current dielectrophoresis and self-assembly of dispersed single-wall carbon nanotubes  

Microsoft Academic Search

The high polarizability and dielectrophoretic mobility of single-walled carbon nano- tubes (SWNT) are utilized to capture and detect low numbers of bacteria and sub- micron particles in milliliter-sized samples. Concentrated SWNT solutions are mixed with the sample and a high-frequency (.100 kHz) alternating current (AC) field is applied by a microelectrode array to enhance bulk absorption of the particles (bacteria

Ronghui Zhou; Ping Wang; Hsueh-Chia Chang

2006-01-01

207

Electrolytic decontamination of surface-contaminated metal by alternating electrolysis using square-wave current in a neutral salt electrolyte  

Microsoft Academic Search

Alternating square-wave current electrolysis using a Na2SO4 electrolyte was studied as a removal method for radioactive contaminated oxidation film on metal surfaces. After the oxidation film was selectively removed using the Na2SO4 electrolyte, base metal was removed. Based on a diffusion model in which the removal rate of the surface oxidation film depends on the diffusion rates of OS and

T. Izumida; K. Kato; F. Kawamura; H. Yusa

1985-01-01

208

Two-dimensional simulation of an alternating current matrix plasma display cell: Cross-talk and other geometric effects  

NASA Astrophysics Data System (ADS)

A two-dimensional, user-friendly model of the discharge occurring in a plasma display panel cell was developed. This model was used to study the transient discharges in an alternating current plasma display with a matrix electrode configuration. The space and time variations of the charge particle densities, excitation rates, electric potential, and surface charge densities are described. The model is also used to study the conditions of existence of electrical interaction between adjacent cells and the effects of electrode misalignment.

Punset, C.; Boeuf, J.-P.; Pitchford, L. C.

1998-02-01

209

FBG and Terfonel-D Based Alternating Current Sensor for Engineering Application  

Microsoft Academic Search

An FBG and GMM based optical fiber electrical current sensor for engineering application was developed. GMM exposure to AC current induced magnetic field to cause elongation of GMM and FBG and wavelength drifting of FBG. CWDM device was used for demodulation. Transfer function and frequency of the sensor were reported.

Zhao Hong; Xong Yanling; Zhang Jian; Lu Yuelan

2007-01-01

210

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

Microsoft Academic Search

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

C. G. Zimmermann

2006-01-01

211

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

Microsoft Academic Search

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

Subramanyan Vasudevan; Jothinathan Lakshmi; Ganapathy Sozhan

2011-01-01

212

Electrical induction of ventricular fibrillation in the human heart. A study of excitability levels with alternating current of different frequencies.  

PubMed

An experimental study was made on induction thresholds for ventricular fibrillation with alternating currents at frequencies ranging between 6 and 1 600 c/s. The tests were performed on experimental dogs and on patients in association with open-heart surgery. The most vulnerable range was found to be between 12 and 60 c/s. A close similarity was demonstrated between canine and human hearts. The induction of ventricular fibrillation during open-heart surgery is discussed. Ventricular fibrillation, caused by electricity, is either accidental or deliberately induced for medical purposes. The myocardial threshold of excitability towards alternating currents is dependent on two parameters, current and frequency. The vulnerability of the heart towards current has been thoroughly investigated by several authors (Walter, 1969; Dalziel & Lee, 1969; Nickel & Spang, 1965; Kugelberg, 1975). A frequency of 50-60 c/s was utilized in all these determinations, as this is the one of choice in networks for distribution of electric power all over the world. Thus, accidental ventricular fibrillation is most likely to occur with currents of this frequency, and inductions for medical purposes, i.e. during open-heart operations, are achieved in the easiest way with simple transformers delivering the same frequency. PMID:1006224

Kugelberg, J

1976-01-01

213

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

NASA Astrophysics Data System (ADS)

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

Sasada, Ichiro

2014-05-01

214

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

NASA Astrophysics Data System (ADS)

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 exhibits a substantial (~180°) phase shift within the plasma. The observed current profiles cannot be described by the classical (rigid-conductor) skin effect and are interpreted in terms of the plasma response to the externally driven modulation of the geometry of the magnetic surfaces.

Wróblewski, D.; Shohet, J. L.

1987-07-01

215

Determination of gallium by adsorptive stripping voltammetry.  

PubMed

A procedure for the determination of gallium by differential pulse adsorptive stripping voltammetry (DPADSV), using different complexing agents (ammonium pyrrolidine dithiocarbamate (APDC), pyrocatechol violet (PCV) and diethyldithiocarbamate (DDTC)), has been optimized. The selection of the experimental conditions was made using experimental design methodology. Under these conditions, the calibration was made and the detection limit was determined for each gallium-ligand complex. A robust regression method was applied which allowed the elimination of anomalous points. The detection limit, with alpha=beta=0.05, for gallium-APDC complex was 5.0x10(-8)moldm(-3), for gallium-PCV complex was 9.9x10(-9)moldm(-3), and the lowest detection limit (1.3x10(-9)moldm(-3)) was obtained with DDTC. For this reason, DDTC was selected for the determination of the gallium concentration in a certificate sample and in a spiked tap water sample. The linear dynamic range for gallium-APDC complex was from 5.0x10(-8) to 2.7x10(-7)moldm(-3), for gallium-PCV complex was from 5.0x10(-9) to 4.8x10(-7)moldm(-3), and for gallium-DDTC complex was from 1.0x10(-9) to 2.1x10(-7)moldm(-3). PMID:18969318

González, M Jesús Gómez; Renedo, Olga Dom? Nguez; Lomillo, M Asunción Alonso; Mart? Nez, M Julia Arcos

2004-02-27

216

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.

Guan, Yong-Song; He, Qing

2013-01-01

217

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

218

Electromagnetic form factors of the {lambda} and {sigma} baryons in an alternative baryonic current approach  

SciTech Connect

Light-cone sum rules are used to investigate the electromagnetic form factors of the {lambda} and {sigma} baryons by using the Ioffe-type interpolating currents. The sum rules are affected to some extent by the choice of the interpolating currents from a comparison. Numerical calculations show that the magnetic form factor can be well fitted by the dipole formula for {sigma} but not for {lambda}. The magnetic form factor of {lambda} approaches zero with the momentum transfer faster than the dipole formula estimation.

Liu Yonglu; Huang Mingqiu [Department of Physics, National University of Defense Technology, Hunan 410073 (China)

2009-06-01

219

A comparative study of alternating write-current-induced pole tip protrusion in perpendicular and longitudinal recording heads  

NASA Astrophysics Data System (ADS)

This paper presents a comparative study of alternating write-current-induced pole tip protrusions (WPTP) in perpendicular magnetic recording (PMR) and longitudinal magnetic recording (LMR) heads during writing operation. Both finite element modeling and experimental measurements were performed for this study. The results show that the writer resistance and inductance as well as the WPTP of PMR heads are all substantially lower than those of LMR heads within the write-current frequency range under consideration. It is found that the WPTP of a LMR head is mainly attributed to the eddy-current-induced Joule heating in yoke, whereas for a PMR head, the contribution to the WPTP from the Joule heating generated in write coils is comparable to that induced in yoke.

Song, Suping; Pan, Tao; Fang, Dori; Stoev, Kroum; Ho, Michael; Mao, Sining

2008-04-01

220

Multifilament, copper-stabilized superconductor tapes with low alternating current loss  

NASA Astrophysics Data System (ADS)

Multifilament fully stabilized second generation superconductor tapes have been fabricated with filaments widths as small as 180 ?m. Each superconducting filament is copper stabilized, with copper thickness up to 30 ?m, without compromising the beneficial effect of striations on magnetization AC losses. This has been accomplished by a combination of laser scribing (ablation), post-ablation oxidation, and subsequent selective electroplating of copper. Twelve millimeters wide superconductor tapes divided into 48 filaments with 10 ?m thick copper stabilizer is found to meet an AC loss target of 1 W/kA/m in applied alternating magnetic field of 0.075 T at 100 Hz. This technique has a potential to be transferred to a large scale manufacturing of stabilized, low loss multifilament coated conductors.

Kesgin, Ibrahim; Levin, George A.; Haugan, Timothy J.; Selvamanickam, Venkat

2013-12-01

221

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

222

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

NSDL National Science Digital Library

Fourteen elementary and middle school teachers from an inservice physics course were found to share a common core of strongly held propositions that formed a coherent, but incorrect and contradictory, model of the sequential flow of electrical current. Theoretical and practical implications of these teachers' beliefs with respect to both instructional techniques and curriculum design are discussed. (17 references)

Heller, Patricia; Finley, Fred

2006-06-22

223

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

ERIC Educational Resources Information Center

Fourteen elementary and middle school teachers from an inservice physics course were found to share a common core of strongly held propositions that formed a coherent, but incorrect and contradictory, model of the sequential flow of electrical current. Theoretical and practical implications of these teachers' beliefs with respect to both…

Heller, Patricia M.; Finley, Fred N.

1992-01-01

224

Decomposition of various materials used as electrodes in three-phase alternating current plasma generator  

Microsoft Academic Search

The behaviour of various materials has been investigated regarding the thermal decomposition of molybdenum disulphide in an argon or nitrogen three-phase plasma generator. Materials tested include molybdenum, copper, thoriated molybdenum and copper-tungsten. Results are presented in the form of erosion rates and voltage and current oscillograms.

C Bonet; M Foex; R Munz; W H Gauvin

1976-01-01

225

Advanced Medium-Range Air-to-Air Missile (AMRAAM): Current Plans and Alternatives.  

National Technical Information Service (NTIS)

Some 2,900 fighter aircraft in the inventories of the U.S. Air Force and Navy carry radar-guided missiles. These planes currently carry the Sparrow missile, which homes in on radar signals beamed out from the employing aircraft toward the target aircraft....

1986-01-01

226

Determination of 5-aminosalicylic acid in pharmaceutical formulation by differential pulse voltammetry.  

PubMed

The oxidative behaviour of 5-aminosalicylic acid (5-ASA) has been investigated by differential pulse voltammetry using a glassy carbon electrode in different buffer systems. Linear sweep voltammetry was used to study the influence of pH on the peak current and peak potential. The solution conditions and instrumental parameters were optimized to obtain a good sensitivity. The Britton-Robinson buffer of pH 1.81 was selected as a suitable analytical medium in which 5-ASA exhibited a sensitive diffusion controlled oxidative peak at 0.564 V (vs. Ag/AgCl). The peak current varied linearly with drug concentration in the range between 1 x 10(-4) and 2 x 10(-6) M. The proposed voltammetric method has been applied to the determination of the drug in commercial delayed-release tablet forms. A mean recovery of 101.23% with a relative standard deviation of 1.35% was obtained. PMID:12560061

Nigovi?, Biljana; Simuni?, Branimir

2003-02-01

227

Higher Sensitivity Dopamine Measurements with Faster-Scan Cyclic Voltammetry  

PubMed Central

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

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

2011-01-01

228

Reaction Mechanism and Improved Performance of Solution-Based Electrochemiluminescence Cell Driven by Alternating Current  

NASA Astrophysics Data System (ADS)

An AC-driven light-emitting cell based on the electrochemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)32+] was fabricated by simply placing the electrolyte solution between transparent electrodes, and this AC-driven ECL cell was demonstrated for comparison to a DC-ECL cell. The properties of the ECL cell were dramatically improved by using the AC method. The AC-ECL cell showed the luminance of 56.4 cd/m2, the current efficiency of 0.78 cd/A and the turn-on response time of ca. 15 ms under application of 4 V, 50 Hz AC. We also elucidated the detailed mechanisms of the AC-ECL reaction to monitor the faradaic current. These improved properties and the frequency dependence of the AC-ECL cell were discussed in the relation to the revealed mechanisms.

Nobeshima, Taiki; Nakamura, Kazuki; Kobayashi, Norihisa

2013-05-01

229

Effects of Surface and Plate-Gap Discharges on Panel-Aging Characteristics in Alternating-Current Plasma Display Panel  

NASA Astrophysics Data System (ADS)

In this study, we investigate the changes in surface morphology of the MgO layer on both the bus and indium tin oxide (ITO) electrodes in an alternating-current (AC) plasma display panel (PDP) under the surface and plate-gap discharges during the panel-aging process. It is found that the use of the surface discharge mixed with the plate-gap discharge during the panel-aging process contributes to obtaining uniform MgO surface morphologies for both bus and ITO electrodes within a fast panel-aging process time.

Park, Choon-Sang; Tae, Heung-Sik

2012-09-01

230

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

SciTech Connect

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

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

2007-03-05

231

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

232

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

233

Mixing enhancement by biologically inspired convection in a micro-chamber using alternating current galvanotactic control of the Tetrahymena pyriformis  

NASA Astrophysics Data System (ADS)

Recently, there has been increasing interest in the swimming behavior of microorganisms and biologically inspired micro-robots. In this study, we investigated biologically induced convection flow with living microorganism using galvanotaxis. We fabricated and evaluated our micro-mixer with motile cells. For the cell based active micro-mixers, two miscible fluids were used to measure the mixing index. Under alternating current (AC) electric fields with varying frequency, a group of motile Tetrahymena pyriformis cells generated reciprocal motion with circulating flows around their pathline, enhancing the mixing ratio.

Kim, Jihoon; Jang, Yonghee; Byun, Doyoung; Hyung Kim, Dal; Jun Kim, Min

2013-09-01

234

Determination of kinetic and thermodynamic parameters of surface confined species through ac voltammetry and a nonstationary signal processing technique: the Hilbert transform.  

PubMed

Data analysis of voltammetric responses has usually been done through application of the fast Fourier transform although it is widely accepted that electrochemical signals are intrinsically nonlinear and nonstationary. In this work, we present a time-series analysis based on the Hilbert transform (HT), a nonstationary signal processing technique, as an alternative tool that can overcome many of the difficulties associated with Fourier techniques. We use the HT to study the behavior of thin-film processes when the excitation perturbation is ac voltammetry. From the analysis of simulated data, we propose simple relations that enable species-specific kinetic and thermodynamic parameters to be estimated, without prior utilization of baseline subtraction even when double layer capacitance significantly influences the current response. We also propose a method to determine whether the characteristics of the applied voltage perturbation are adequate for the accurate estimation of these parameters. The methodology developed here will be applied to previously published experimental time series data (Guo, S. X.; Zhang, J.; Elton, D. M.; Bond, A. M. Anal. Chem. 2004, 76, 166-177.) obtained with ac voltammetry to show how a number of physical parameters can be directly extracted from the processed data. PMID:15889929

Anastassiou, Costas A; Parker, Kim H; O'Hare, Danny

2005-05-15

235

Cyclic Voltammetry of Polysulfide (Thiokol) Prepolymers and Related Compounds.  

National Technical Information Service (NTIS)

The cyclic voltammetry of polysulfide prepolymers and related monomeric sulfur compounds was examined at a gold wire electrode. Electrode processes were assigned to the polysulfide prepolymers on the basis of those occurring in the model compounds. It was...

W. Mazurek

1983-01-01

236

Design of air-gapped magnetic-core inductors for superimposed direct and alternating currents  

NASA Technical Reports Server (NTRS)

Using data on standard magnetic-material properties and standard core sizes for air-gap-type cores, an algorithm designed for a computer solution is developed which optimally determines the air-gap length and locates the quiescent point on the normal magnetization curve so as to yield an inductor design with the minimum number of turns for a given ac voltage and frequency and with a given dc bias current superimposed in the same winding. Magnetic-material data used in the design are the normal magnetization curve and a family of incremental permeability curves. A second procedure, which requires a simpler set of calculations, starts from an assigned quiescent point on the normal magnetization curve and first screens candidate core sizes for suitability, then determines the required turns and air-gap length.

Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

1976-01-01

237

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

238

Elucidating different mass flow direction induced polyaniline-ionic liquid interface properties: insight gained from DC voltammetry and impedance spectroscopy.  

PubMed

This work describes the use of direct current (DC) cyclic voltammetry (CV) and alternating current (AC) electrochemical impedance spectroscopy (EIS) as a means to monitor an electrochemical interface of different mass flow direction induced polyaniline (PANI) film in IL (BmimPF6). Observed by SEM, vertical mass flow (VMF) and horizontal mass flow (HMF) induce porous nanorod and compact granular morphology of PANI, respectively. The present work explores in detail analysis of double layer capacitance, polarization resistance, diffusion mechanism, as well as other electrochemical features associated with the PANI-IL interface. A comparatively higher value of capacitance obtained for VMF PANI film from CV measurement confirms the higher electroactivity at the VMF electrode than the HMF film. Impedance spectroscopy, using a small amplitude perturbation, confirms the CV result. Impedance measurement gives a value of capacitance larger than that from CV where the amplitude of the perturbation is much larger. The implications of these results for its potential application in energy storage devices are discussed. PMID:24564270

Pandey, Kavita; Yadav, Pankaj; Mukhopadhyay, Indrajit

2014-03-20

239

Effects of weak transcranial alternating current stimulation on brain activity--a review of known mechanisms from animal studies  

PubMed Central

Rhythmic neuronal activity is ubiquitous in the human brain. These rhythms originate from a variety of different network mechanisms, which give rise to a wide-ranging spectrum of oscillation frequencies. In the last few years an increasing number of clinical research studies have explored transcranial alternating current stimulation (tACS) with weak current as a tool for affecting brain function. The premise of these interventions is that tACS will interact with ongoing brain oscillations. However, the exact mechanisms by which weak currents could affect neuronal oscillations at different frequency bands are not well known and this, in turn, limits the rational optimization of human experiments. Here we review the available in vitro and in vivo animal studies that attempt to provide mechanistic explanations. The findings can be summarized into a few generic principles, such as periodic modulation of excitability, shifts in spike timing, modulation of firing rate, and shifts in the balance of excitation and inhibition. These effects result from weak but simultaneous polarization of a large number of neurons. Whether this can lead to an entrainment or a modulation of brain oscillations, or whether AC currents have no effect at all, depends entirely on the specific dynamic that gives rise to the different brain rhythms, as discussed here for slow wave oscillations (?1 Hz) and gamma oscillations (?30 Hz). We conclude with suggestions for further experiments to investigate the role of AC stimulation for other physiologically relevant brain rhythms.

Reato, Davide; Rahman, Asif; Bikson, Marom; Parra, Lucas C.

2013-01-01

240

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

241

An Assessment of Current Concepts for Hydrogeological Site Characterization, and Alternatives  

NASA Astrophysics Data System (ADS)

Characterization of the geological and hydrogeological conditions of contaminated sites is a critical element of risk management. Characterization includes data acquisition and interpretation that intends to provide the analytical tools needed for decision making related to transport of contaminants and for remediation. Despite many years of experience, site characterization is still not as well understood and regulated as it should be. The chasm between some of the newer concepts developed by researchers on the one hand, and the technology used in the field by service providers on the other, has never been wider than it is today. Consequently, questions that should be addressed using well-documented rational tools may continue to be addressed based on intuition and experience. Instead of coming up with defensible action plans and implementing them rapidly, such action plans are often a source of contention and end up in the courts. This paper evaluates concepts often used in the practice of hydrogeological site characterization, and tries to distinguish between myth and reality. It explores concepts such as: 1. Accurate descriptions of geological and hydrogeological conditions are attainable; 2. Sound planning and action plans in response to accidents require a large amount of data; 3. Investing in site characterization is a sound investment; 4. Experience gained in decontamination and decommissioning in the field is a sound basis for planning future efforts; 5. If you do not find the contaminants, they do not exist; 6. Numerical models for flow and transport processes in the subsurface are beneficial; 7. Current regulations in the area of hydrogeology are helpful. These concepts, while often invoked in applications, are often wrong and misleading or applied incorrectly, and reflect the many ambiguities prevailing in this area. This paper explores the issues raised above in detail. It also presents the elements of a consistent approach for site characterization, and demonstrates it through a case study that involves uncertainty in the hydrogeology as well as in human physiology.

Rubin, Y.; Barros, F.

2007-05-01

242

Determination of heavy metals by thin-layer chromatography-square-wave anodic stripping voltammetry  

SciTech Connect

A square-wave anodic stripping voltammetric method is described for low parts per million determination of heavy metals separated by thin-layer chromatography (TLC). Heavy metal samples are separated on carboxymethyl cellulose TLC plates and detected by anodic stripping voltammetry (ASV) using a cellulose dialysis membrane-covered mercury film electrode (CM-MFE) placed directly on the TLC plate surface in a thin film of supporting electrolyte solution. The fast scan rates possible in square-wave voltammetry during the stripping step eliminate the need to deoxygenate the sample. Results are presented for a mixture of Pb(II), Cd(II), Cu(II), and Zn(II). Calibration curves for Pb(II) were linear over the range 10-500 ng, with a relative standard deviation of the peak current over a set of eight separate 100-ng Pb(II) samples of 16%. 25 refs., 7 figs.

Aldstadt, J.H.; Dewald, H.D. (Ohio Univ., Athens (United States))

1992-12-15

243

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

244

Determination of lead in bonemeal by differential pulse anodic stripping voltammetry using a hydrochloric acid solubilization.  

PubMed

A safe, rapid method is described for the determination of lead in bonemeal. This method uses a hydrochloric acid solubilization performed under pressure followed by determination by differential pulse anodic stripping voltammetry. This provides an alternative to a nitric-perchloric acid wet ash. Data obtained using both methods are compared. The mean recovery of a standard Pb spike was 99.2 +/- 7%. The concentration of Pb in bonemeal ranged from 1.0 to 15.6 micrograms/g. PMID:6885703

Satzger, R D; Kuennen, R W; Fricke, F L

1983-07-01

245

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

NASA Astrophysics Data System (ADS)

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.; Bruno, Emanuela; Marino, Lucia; Scaramuzza, Nicola

2014-02-01

246

Voltammetry and coulometry with immersed thin layer electrodes. Part 1: Model for effects of solution resistivity in linear sweep voltammetry  

NASA Astrophysics Data System (ADS)

In non-aqueous solvent/electrolyte systems, solution resistivities as high as 3000 ohm-cm may be encountered. The resulting potential distribution problems are particularly severe, and it was suggested that implementation of thin layer methodology, even in solvents of relatively high dielectric constant, such as acetonitrile or dimethylformamide, would be difficult. It is in such poorly conducting media that the advantages of thin-layer methodology may often be most beneficial, however. In this paper the application of thin layer voltammetry in non-aqueous media is considered. The discussion is centered around immersed thin layer electrodes, i.e., those in which the edges of the thin layer cavity are immersed in bulk solution, since a greater cross sectional area is available for the flow of current, and the resulting potential distribution is therefore less severe. Such cell designs always suffer to some extent from diffusion of electroactive material from the bulk solution into the thin layer cavity, but it will be demonstrated experimentally that this does not seriously affect the usefulness of results.

Hinman, A. S.; Pons, S.; Cassidy, J.

1984-11-01

247

Alternating-current electroluminescence from an organic heterojunction sandwiched between two amorphous SiO2 layers  

NASA Astrophysics Data System (ADS)

We report alternating-current electroluminescence (ACEL) from an organic heterojunction sandwiched between two amorphous SiO2 (?-SiO2) layers, i.e., ITO\\?-SiO2\\poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV)\\Alq3\\?-SiO2\\Al. Besides the exciton radiation from Alq3 (peak at 520 nm) and MEH-PPV (peak at 587 nm), an additional broad blue emission around 410 nm is observed in its ACEL spectrum. By studying the ACEL and brightness wave form of the device, we found both hot-electron-impact excitation and injection carriers recombination are combined in its emission mechanism for this hybrid organic-inorganic structure, and the origin of the broad blue emission around 410 nm is discussed.

Yang, S. Y.; Qian, L.; Teng, F.; Xu, Z.; Xu, X. R.

2005-06-01

248

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

PubMed

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

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

2014-03-01

249

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

250

Nonaqueous inhibition of iron-boron-silicon amorphous electrodes in hydrochloric acid: An alternating current impedance study  

SciTech Connect

Iron-boron-silicon (Fe-B-Si) amorphous electrodes were studied using electrochemical impedance spectroscopy (EIS) to determine the alternating current (AC) impedance and the capacitance of four Fe-B-Si alloys in various acid solutions. The AC impedance and the capacitance of Fe-B-Si, Fe-B-Si with carbon (C), Fe-B-Si with cobalt (Co), and Fe-B-Si with chromium (Cr) were obtained in 25%, 50%, 75%, and 100% hydrochloric acid (HCl) at room temperature. The electrochemical parameters (i.e., impedance) varied depending on additions of C, Co, and Cr to the Fe-B-Si alloy; the acid concentration; and the nanoscopic surface roughness of the electrodes. Consequently, a correlation between the data obtained was established.

Habib, K.; Abdullah, A. (Kuwait Inst. for Scientific Research, Safat (Kuwait))

1994-07-01

251

Offering assisted peritoneal dialysis is a cost-effective alternative to the current care pathway in frail elderly Dutch patients  

PubMed Central

Background With the Dutch population aging, the number of individuals 75 years old or more needing dialysis is growing. This analysis assessed the cost-effectiveness of adding nurse-assisted peritoneal dialysis (aPD) to the usual care pathway in frail Dutch end-stage renal disease (ESRD) patients. Methods The current Dutch treatment pathway (conservative management, CM: 40% and PD in nursing home, nhPD: 60%) was compared in a decision-tree model with a new approach where the proportion of patients on dialysis would increase to 80% (i.e. CM: 20%; nhPD: 20%; and aPD: 60%). In-center hemodialysis was added in a secondary analysis. Inputs included survival (from literature), utility (from literature), and costs (2009 official tariffs). A healthcare payer's perspective was used with a 5-year horizon. Results The new approach was almost cost neutral in the primary analysis (despite more patients on dialysis) and dominant (more effective and less expensive) in the secondary analysis. The incremental cost-effectiveness ratio was only €52/QALY. In the sensitivity analyses (primary and secondary analyses), the new approach was either dominant or cost-effective in approximately 75% of the simulations. Conclusions Despite the investment required, offering aPD to frail elderly ESRD patients is a cost-effective alternative to the current pathway for Dutch healthcare payers.

Laplante, Suzanne; Krepel, Harmen; Simons, Bregje; Nijhoff, Aafke; van Liere, Rens; Simons, Michel

2013-01-01

252

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

253

Low-frequency alternative-current magnetic susceptibility of amorphous and nanocrystalline Co60Fe20B20 films  

NASA Astrophysics Data System (ADS)

This investigation experimentally studies the low-frequency alternating-current magnetic susceptibility (?ac) of amorphous and nanocrystalline CoFeB films by measuring the magnetic field established by passing currents of various frequencies through such films of various thicknesses (tf). A CoFeB film is sputtered onto a glass substrate with tf from 100 Å to 500 Å under the following conditions: (a) As-deposited films were maintained at room temperature (RT) and (b) films were post-annealed at TA=150 °C for 1 h. The samples thus obtained are analyzed in a magnetic field that was generated by an alternating current (AC) at various frequencies from 10 Hz to 25,000 Hz. The experimental results demonstrate that the ?ac declines as the thickness of the as-deposited sample and the post-annealed sample (TA=150 °C) increases because the lower coercivity (Hc) of thinner CoFeB films is similar to a soft magnetic characteristic and is associated with a higher ?ac value. The best ?ac value is obtained at a thickness of 100 Å under both conditions. The ?ac value of the post-annealed sample exceeds that of the RT sample at thicknesses from 100 Å to 500 Å because the magneto crystalline anisotropy of the post-annealed sample yields the highest ?ac value at the optimal resonance frequency (fres), at which the spin sensitivity is maximal. The X-ray diffraction patterns (XRD) of as-deposited CoFeB films reveal their amorphous structure. The XRD results for the post-annealed films include a main peak at 2?=44.7° from the body-centered cubic (BCC) nanocrystalline CoFe that indicated a (110) textured structure. Post-annealing treatment caused that the amorphous structure to become more crystalline by a thermally driven process, such that the ?ac value of the post-annealed sample exceeded that of the RT sample. This experimental result demonstrates that the ?ac value decreased as the thickness of the thin film increased. Finally, the CoFeB thin films had the best ?ac at low frequency (<50 Hz) following post-annealing treatment. The results obtained under the two conditions indicate that the maximum ?ac value and the optimal fres of a 100 Å-thick CoFeB thin film were 1.6 and 30 Hz, respectively, following post-annealing at TA=150 °C for 1 h, suggesting that a 100 Å-thick CoFeB thin film that has been post-annealed at TA=150 °C can be utilized as a gage sensor and in transformer applications at low frequencies.

Chen, Yuan-Tsung; Chang, Z. G.

2012-07-01

254

Optimizing the Temporal Resolution of Fast-Scan Cyclic Voltammetry  

PubMed Central

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

2012-01-01

255

An analysis and discussion of the voltage and current spectrum of claw-pole alternators for fault detection purposes  

Microsoft Academic Search

The 'claw-pole' type synchronous alternator is the heart of virtually all automotive Electric Power Generation and Storage (EPGS) system. Timely and accurate detection of alternator faults will not only decrease \\

Siwei Cheng; Thomas G. Habetler

2011-01-01

256

Surface-plasmon voltammetry using a gold grating  

NASA Astrophysics Data System (ADS)

Using a sensitive optical wavelength modulation technique the surface-plasmon excited on a gold grating surface immersed in sulfuric acid is studied at the same time as cyclic voltammetry is undertaken. Because of the optical sensitivity of the modulation technique significant optical effects are observed at potentials well below those at which any gross oxidation effects occur.

Jory, M. J.; Cann, P. S.; Sambles, J. R.

2010-09-01

257

NDT of on and offshore oil and gas installations using the alternating current field measurement (ACFM) technique  

SciTech Connect

Offshore inspection has been carried out in the UK waters for the last 25 years, but the techniques used have until recently remained stagnant. Innovative work carried out by University College London produced the mathematical modeling of the alternating current field measurement technique, which was then further developed and commercialized into a field usable technique. During detection and sizing trials, this technique proved to be better than even MPI for detection and as good as the existing sizing techniques. This was a major advance in NDT technology, a technique that could detect surface breaking defects through paint and other coatings of various thickness, then accurately size them in terms of length and depth. The technique was adopted for subsea inspection of welds and was then used for topside applications of numerous types. The adaptability of the technique to different materials and coatings has made it acceptable to not only the offshore industry, but it is now widely used in the petrochemical industry, the power generation industry, and in aerospace and outer space. A range of equipment and probes has allowed this new technology to be used where other techniques could not be applied.

Raine, G.A. [Technical Software Consultants Ltd., Milton Keynes (United Kingdom); Smith, N. [IESCO Inc., San Pedro, CA (United States)

1996-04-01

258

The influence of theta transcranial alternating current stimulation (tACS) on working memory storage and processing functions.  

PubMed

The study aimed to explore the role of the fronto-parietal brain network in working memory function--in temporary storage and manipulation of information. In a single blind sham controlled experiment 36 respondents solved different working memory tasks after theta transcranial alternating current stimulation (tACS) was applied to left frontal, left parietal and right parietal areas. Both verum tACS protocols stimulating parietal brain areas (target electrodes positioned at location P3, or P4) had a positive effect on WM storage capacity as compared with sham tACS, whereas no such influence was observed for the stimulation of the left frontal area (target electrode positioned at location F3). A second finding was that left parietal theta tACS had a more pronounced influence on backward recall than on forward recall, which was not related to task content (spatial or verbal). The influence of theta tACS on WM executive processes was most pronounced for right parietal stimulation. The results are discussed in the broad theoretical framework of the multicomponent model of working memory. PMID:24361739

Jaušovec, Norbert; Jaušovec, Ksenija; Pahor, Anja

2014-02-01

259

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

260

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

PubMed Central

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

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

2011-01-01

261

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

Code of Federal Regulations, 2010 CFR

...Approved methods of grounding of equipment...current power systems. 77.701-1...current power systems. For purposes of grounding metallic frames...current power systems, the following methods of grounding will be...

2010-07-01

262

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

Code of Federal Regulations, 2010 CFR

...Approved methods of grounding of equipment...current power systems. 77.701-1...current power systems. For purposes of grounding metallic frames...current power systems, the following methods of grounding will be...

2009-07-01

263

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

Code of Federal Regulations, 2010 CFR

...Approved methods of grounding of equipment...current power systems. 75.701-1...current power systems. For purposes of grounding metallic frames...current power systems, the following methods of grounding will be...

2010-07-01

264

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

Code of Federal Regulations, 2010 CFR

...Approved methods of grounding of equipment...current power systems. 75.701-1...current power systems. For purposes of grounding metallic frames...current power systems, the following methods of grounding will be...

2009-07-01

265

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

Code of Federal Regulations, 2013 CFR

...Approved methods of grounding of equipment...current power systems. 77.701-1...current power systems. For purposes of grounding metallic frames...current power systems, the following methods of grounding will be...

2013-07-01

266

Cyclic voltammetry of metal complexes of nitrones and nitroxides  

Microsoft Academic Search

Increasing interest in radicals bound to metals led to the present study of electron transfer to and from metal nitrone complexes and metal nitroxides. These are species involved in biological spin trapping and materials science applications, respectively. Cyclic voltammetry was used to study the redox behavior of complexes of the bidentate N-tert-butyl-?-(2-pyridyl)nitrone (2-PyBN) and the monodentate nitrone 2,5,5-trimethyl-1-pyrroline-N-oxide (M3PO) with

Frederick A. Villamena; Vaclav Horak; DeLanson R. Crist

2003-01-01

267

Vocational-Technical Physics Project. The Alternator: I. Current Electricity, II. Magnets from Electricity, III. Electricity from Magnets, IV. Energy Conversion. Field Test Edition.  

ERIC Educational Resources Information Center

This vocational physics individualized instructional student module on the alternator consists of the four units: Current electricity, magnets from electricity, electricity from magnets, and energy conversion. Designed with a laboratory orientation, the units present explanations of the concepts and experiments. Laboratory data sheets,…

Forsyth Technical Inst., Winston-Salem, NC.

268

Solid-state voltammetry in a three electrode electrochemical cell-on-a-chip with a microlithographically defined microelectrode  

SciTech Connect

Microlithographic procedures are employed to fabricate electrochemical microcells with three coplanar gold-film electrodes (working, auxiliary, and reference) resting on a silicon water. The working electrode can be a 11 /times/ 516 or 11 /times/ 256 ..mu..m microband or a 11 /times/ 11 ..mu..microsquare, and the cell solution of a film of an ionically conducting polymer such as lithium triflate dissolved in poly(ethylene oxide). The cyclic voltammetry and chronoamperometry of electroactive species dissolved in these cell media are reported, and the chronoamperometric data are compared to theoretical current-time curves calculated for band microelectrodes. Cyclic voltammetry in an aqueous droplet on the microsquare gives pseudo-steady-state-waves, the limiting currents of which quantitatively agree with those for microdisk electrodes of equivalent area. The microlithographically defined microcells can be produced in quantity and can be considered disposable electroanalytical devices, which can be advantageous for routine electroanalytical applications involving electrode-poisoning reaction systems.

Morita, M.; Longmire, M.L.; Murray, R.W.

1988-12-15

269

Electrochemical Fabrication of ZnO Nanowires in Anodized Aluminum Template Using Cyclic Voltammetry  

NASA Astrophysics Data System (ADS)

This thesis work studies in detail the fabrication ZnO in Anodic Aluminum Template using Cyclic Voltammetry which is one of the electrochemical deposition methods. In this current work the Aluminum is anodized in Oxalic and Sulphuric acids for different timings with constant current density of 10mA/cm 2. The hexagonal pores were observed after the anodization process. The pores are filled with Zinc using the Cyclic Voltammetry Method of Electrochemical deposition. The samples are then oxidized at 300°C to form the Zinc oxide nanowires. The presence of Zinc is tested using various techniques like Atomic Force Microscopy and Scanning Electron Microscopy which shows the presence of Zinc in the pores. To analytically prove the presence of Zinc Optical Spectroscopy is used. The absorption and reflection spectrums are studied to determine the presence of Zinc Oxide. The Zinc Oxide film was found to have strong absorbance at 0.50 at 340 nm. The thickness of the oxide layer is determined as 354.3 nm. The band gap of the Zinc oxide was found to be at 3.23eV.

Koney, Shalini Katyayani

270

Application of adsorptive stripping voltammetry to the speciation and determination of iron(III) and total iron in wines.  

PubMed

An analytical procedure for the determination of iron(III) and total iron in wines based on adsorptive stripping voltammetry is described. Iron(III) was determined by using Solochrome Violet Red as chelating agent while catechol was used for the determination of the total iron content. Each chelate was adsorbed on the hanging mercury electrode and the reduction current of the accumulated chelate was measured. The results obtained from the application of this procedure to wine samples are discussed. PMID:2757234

Wang, J; Mannino, S

1989-05-01

271

Effects of alternating and direct current, power frequency, temperature, and tension on the electrical parameters of ACSR conductors  

Microsoft Academic Search

Many high-voltage transmission lines are constructed with aluminum conductors, steel reinforced (ACSR). The stranded steel core supports much of the tension and the aluminum strands conduct most of the current. The current flowing in the strands spiraling around the core causes a longitudinal magnetic flux in the core, which increases its permeability and causes a redistribution of the currents in

Vincent T. Morgan

2003-01-01

272

Sensitive quantification of trace zinc in water samples by adsorptive stripping voltammetry.  

PubMed

A simple and sensitive adsorptive stripping voltammetry method was developed for determination of Zn using N-nitrozo-N-phenylhydroxylamine (cupferron) as a selective complexing agent. This complex absorbed on the hanging mercury drop electrode and created a sensitive peak current. The peak current and concentration of zinc accorded with a linear relationship in the range of 0.85-320 ng mL(-1). The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The relative standard deviation at a concentration level of 50 ng mL(-1) was 1.8%. The method was applied to the determination of zinc in city, river and mineral water samples, with satisfactory results. PMID:24473317

Abbasi, Shahryar; Farmany, Abbas; Roushani, Mahmoud; Mortazavi, Seyede Shima

2014-01-01

273

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

274

Thermal failure mechanism and voltammetry metrology for copper/barrier/low k integration  

NASA Astrophysics Data System (ADS)

The present study investigates the thermal stability of Cu/barrier/porous low kappa (PLK) integration first, and then a new characterization method based on voltammetry is developed to characterize quality of diffusion barrier and pore structure in low kappa materials and its thermal stability. The study of thermal stability reveals that Cu/barrier/PLK interconnect fails by Cu out-diffusion through the defects of diffusion barrier into the PLK structure, which is driven by oxidation and stress gradient within the interconnect structure. The failure appears to be triggered by defects in diffusion barrier, however, such defects are not effectively detected by TEM observation due to their small and localized nature. This motivates the development of a new method to characterize defects of diffusion barrier and pore structure of low kappa materials in as processed Cu/barrier/PLK interconnect. Firstly, a cyclic voltammetry-based method is developed to detect the quality of diffusion barrier by monitoring the current resulting from an applied voltage on the established cell. It utilizes a fact that electrolyte solution is able to infiltrate into the low k layer between two interconnects and creates a situation essentially the same as two-electrode electrolytic cell. When the barrier is intact (defectfree), the I-V shows simple hysteresis without the presence of current peaks. On the other hand, when the barrier is defective, Cu is exposed to electrolyte and current peak is present in the I-V curve due to Cu redox reactions. The application of the developed method on an extensive number of real interconnects provides sufficient evidence that the method is simple, fast, and accurate in detecting the defective barrier. Furthermore, it has a potential to quantify defect density based on the intensity of the current peak and the integration areas within the I-V curves. Secondly, a step voltammetry-based method is developed to characterize pore structure by measuring the effective ions diffusivity. The study produces the identical activation energy and diffusivity results for bulk solution which are in good agreement with references, and reveals that electrolyte ions migrate in dense low kappa (DLK) and PLK with different mechanism. The application of the method reveals that pores in low kappa materials are not thermally stable but can either collapse or coalesce depending on the stress conditions.

Meng, Dongmei

275

Current Status of Legislative Proposals on Greenhouse Gas Emissions and Alternative Energy in the U.S. Congress  

Microsoft Academic Search

The 110th Congress is now beginning to grapple with the issue of human-induced climate change and what, if anything, to do about it. A number of bills are currently being considered that would limit greenhouse gas emissions using various policy mechanisms and over various time frames. With a commitment by the current Congressional leadership to pass legislation addressing global warming,

L. J. Richardson

2007-01-01

276

Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field  

NASA Astrophysics Data System (ADS)

AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2010-11-01

277

Current Status of Legislative Proposals on Greenhouse Gas Emissions and Alternative Energy in the U.S. Congress  

NASA Astrophysics Data System (ADS)

The 110th Congress is now beginning to grapple with the issue of human-induced climate change and what, if anything, to do about it. A number of bills are currently being considered that would limit greenhouse gas emissions using various policy mechanisms and over various time frames. With a commitment by the current Congressional leadership to pass legislation addressing global warming, and significant hurdles remaining, it promises to be an eventful fall session. I will review the current status of these legislative proposals and their prospects of becoming law.

Richardson, L. J.

2007-12-01

278

Catalytic adsorptive stripping voltammetry determination of ultra trace amount of molybdenum using factorial design for optimization.  

PubMed

A highly sensitive procedure is presented for the determination of ultra-trace concentration of molybdenum by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the molybdenum (Mo)-pyrocatechol violet (PCV) complex on to a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. The influence of variables was completely studied by factorial design analysis. Optimum analytical conditions for the determination of molybdenum were established. Molybdenum can be determined in the range 1.0x10(-3)-100.0ngml(-1) with a limit of detection of 0.2pgml(-1). The influence of potential interfering ions on the determination of molybdenum was studied. The procedure was applied to the determination of molybdenum in mineral water and some analytical grade substances with satisfactory results. PMID:18970642

Zarei, K; Atabati, M; Ilkhani, H

2006-06-15

279

Electrochemical Dopamine Detection: Comparing Gold and Carbon Fiber Microelectrodes using Background Subtracted Fast Scan Cyclic Voltammetry  

PubMed Central

Electrochemical detection is becoming increasingly important for the detection of biological species. Most current biological research with electrochemical detection is done with carbon fiber electrodes due to their many beneficial properties. The ability to build electrochemical sensor from noble metals instead of carbon fibers may be beneficial in developing inexpensive multiplexed electrochemical detection schemes. To advance understanding and to test the feasibility of using noble metal electrochemical sensors the detection of dopamine, a biologically important small molecule was studied here. Specifically, dopamine detection on gold microelectrodes was characterized and compared to P-55 carbon fiber microelectrodes of the same geometry, using background subtracted fast scan cyclic voltammetry. While not as sensitive to dopamine as carbon fibers, it was observed that gold microelectrodes have six times the saturation coverage per area and 40 times the linear working range. Selectivity to dopamine, in comparison to several other neurotransmitters and their derivatives, is also quantitatively described.

Zachek, Matthew K.; Hermans, Andre; Wightman, R. Mark; McCarty, Gregory S.

2008-01-01

280

Influence of dislocation density on carrier injection in InGaN/GaN light-emitting diodes operated with alternating current  

NASA Astrophysics Data System (ADS)

The frequency dependence of current spreading and light output power (LOP) was investigated for InGaN/GaN light-emitting diodes (LEDs) grown on n-GaN templates with different threading dislocation densities (TDDs) that were operated using alternating-current (AC). By comparison with LEDs with low TDDs, the LEDs with high TDDs showed a strong frequency dependence for both current spreading and LOP during high-frequency AC operation. The results were attributed to a weak carrier injection into InGaN quantum wells (QWs) during high frequency AC operation, which resulted from the suppression of carrier transport induced by the carrier scattering around negatively charged dislocation cores.

Lee, Dong-Yul; Han, Sang-Heon; Ju Lee, Dong; Wook Lee, Jeong; Kim, Dong-Joon; Sun Kim, Young; Kim, Sung-Tae; Leem, Jae-Young

2013-01-01

281

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

282

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

283

Effects of alternating and direct current in electrocoagulation process on the removal of cadmium from water – A novel approach  

Microsoft Academic Search

The main objective of this study is to investigate the effects of AC and DC on the removal of cadmium from water using zinc as anode and as cathode. Various operating parameters on the removal efficiency of cadmium were investigated, such as initial cadmium ion concentration, initial pH, current density and temperature. The results showed that the removal efficiency of

Subramanyan Vasudevan; Jothinathan Lakshmi

2011-01-01

284

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

285

Computer-controlled instrumentation for fast voltammetry at ultramicroelectrodes  

NASA Astrophysics Data System (ADS)

In this article we describe an electrochemical experimental setup for cyclic voltammetry operating from low (1 V/s) to very high (200 kV/s) scan rates. The system is designed to achieve an acceptable cost and to be user friendly for nonexperts. The instrumentation is based on a commercial arbitrary wave form generator, a digital oscilloscope, a general purpose interface bus interface to a PC, and a laboratory-built potentiostat. There are no complicated manual operations, instead the software creates dialog with an operator to control commands for the instruments. Requirements for the wave form synthesis and the data acquisition are given. Various data-smoothing methods for treating 8-bit fast scan data are evaluated. The performance was tested on the oxidation of ferrocene in acetonitrile. The estimated value of the standard heterogeneous rate constant, k0=0.8+/-0.1 cm s-1, is in reasonable agreement with the most recent reports from other laboratories.

Pospíšil, L.; Fiedler, J.; Fanelli, N.

2000-04-01

286

Cyclic voltammetry and impedance studies of undoped diamond films  

NASA Astrophysics Data System (ADS)

The undoped, polycrystalline diamond films were deposited on tungsten wire substrates by hot filament chemical vapor deposition (HF CVD), using a precursor gas mixture of methanol with excess of hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy (SEM) and Raman spectroscopy. The surface morphology analyzed by SEM resembles a continuous and well faceted diamond film. Raman results showed essential differences in qualities of diamond films grown at different hydrocarbon concentrations. The electrochemical properties of diamond electrodes were examined with cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). The CV experiments revealed a large chemical window (>˜4.3 V) of undoped diamond. Analysis of the ferrocyanide-ferricyanide couple at a diamond electrode suggests some extent of electrochemical quasi-reversibility, but the rates of charge transfer across the diamond substrate interface vary with diamond quality.

Mosi?ska, L.; Kowalska, M.; Popielarski, P.; Fabisiak, K.; Paprocki, K.; Szybowicz, M.; Wrzyszczy?ski, A.; Zhusupkalieva, G. K.

2013-01-01

287

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

2014-03-01

288

Modelling of LHW-induced helical current filaments on EAST: study of an alternative method of applying RMPs  

NASA Astrophysics Data System (ADS)

The lower hybrid wave (LHW) heating experiments at the Experimental Advanced Superconducting Tokamak (EAST) show a wide range of similarities to effects known from applied resonant magnetic perturbations (RMPs) by in-vessel or external magnetic perturbation coils. These observations suggest a current flow understood to be along scrape-off layer (SOL) field lines; here called helical current filaments (HCFs). For a better understanding of the experimental observations, a model to incorporate the magnetic perturbation of HCFs in the magnetic topology has been developed. Modelled SOL field lines, starting in front of the LHW antenna, show agreement in position and pitch-angle with the experimentally observed radiation belts. The comparison of the pick-up coil signals and the modelled HCFs' perturbation allows for determination of the current strength depending on the filaments' distance from the plasma edge. Agreement of predicted footprint structures with experimentally observed heat load and particle flux profiles at different toroidal angles in the divertor region is found. Based on the modelling results, the idea of LHW-induced RMPs, originating from the experimental observations, is strongly supported.

Rack, M.; Zeng, L.; Denner, P.; Liang, Y.; Wingen, A.; Gan, K. F.; Wang, L.; Liu, F. K.; Shen, B.; Wan, B. N.; Li, J. G.; the EAST Team

2014-06-01

289

Supplemental examination of alternative materials in a model steam generator: Volume 2, Correlation of Model 10 defects with eddy-current indications: Final report  

SciTech Connect

The following report compares the nondestructive examination with the destructive metallographic examination of the tube bundle alternative materials, Model 10 steam generator. The model steam generator was fabricated using state-of-the-art tube processing (Alloys 600, 690 and 800) and corrosion resistant support alloys and designs. The model steam generator was operated for approximately one year with a secondary environment that was faulted with acidified simulated cooling tower water and sludge. The tube bundle was eddy current tested at the final inspection using multiple frequency differential and absolute mode probes and state-of-the-art eddy current equipment, including a computerized system for data analysis. Various frequency mixes were designed to suppress signals from deposits and to improve signal to noise ratios. Special tests were utilized to evaluate the Alloy 800 tubing. Eddy current data correlated favorably with results from the destructive examinations. Generally eddy current tests were most successful in detecting axial cracks, circumferential cracks, defects with depths greater than 10% throughwall and tube denting at trefoil supports. It was not possible to distinguish between cracks and deep wastage. Interpretation of the eddy current indications predicted corrosion damage deeper than that found metallographically for conservative depth estimates. Numerous false defect indications, with low signal to noise ratios, were produced by the presence of conductive deposits on the O.D. of the tubing. Absolute mode testing provided a reliable qualitative indication of tube corrosion despite the interference from the conductive deposits. 4 refs., 1 fig., 1 tab.

Marugg, K.E.; Edwards, L.J.; Krupowicz, J.J.

1989-01-01

290

Electrode calibration with a microfluidic flow cell for fast-scan cyclic voltammetry.  

PubMed

Fast-scan cyclic voltammetry (FSCV) is a common analytical electrochemistry tool used to measure chemical species. It has recently been adapted for measurement of neurotransmitters such as dopamine in awake and behaving animals (in vivo). Electrode calibration is an essential step in FSCV to relate observed current to concentration of a chemical species. However, existing methods require multiple components, which reduce the ease of calibrations. To this end, a microfluidic flow cell (?FC) was developed as a simple device to switch between buffer and buffer with a known concentration of the analyte of interest--in this case dopamine--in a microfluidic Y-channel. The ability to quickly switch solutions yielded electrode calibrations with faster rise times and that were more stable at peak current values. The ?FC reduced the number of external electrical components and produced linear calibrations over a range of concentrations. To demonstrate this, an electrode calibrated with the ?FC was used in FSCV recordings from a rat during the delivery of food reward--a stimulus that reliably evokes a brief increase in current due to the oxidation of dopamine. Using the linear calibration, dopamine concentrations were determined from the current responses evoked during the behavioral task. The ?FC is able to easily and quickly calibrate FSCV electrode responses to chemical species for both in vitro and in vivo experiments. PMID:22522908

Sinkala, Elly; McCutcheon, James E; Schuck, Matthew J; Schmidt, Eric; Roitman, Mitchell F; Eddington, David T

2012-07-01

291

Electrode Calibration with a Microfluidic Flow Cell for Fast-scan Cyclic Voltammetry  

PubMed Central

Fast-scan cyclic voltammetry (FSCV) is a common analytical electrochemistry tool used to measure chemical species. It has recently been adapted for measurement of neurotransmitters such as dopamine in awake and behaving animals (in vivo). Electrode calibration is an essential step in FSCV to relate observed current to concentration of a chemical species. However, existing methods require multiple components, which reduce the ease of calibrations. To this end, a microfluidic flow cell (µFC) was developed as a simple device to switch between buffer and buffer with a known concentration of the analyte of interest – in this case dopamine - in a microfluidic Y-channel. The ability to quickly switch solutions yielded electrode calibrations with faster rise times and that were more stable at peak current values. The µFC reduced the number of external electrical components and produced linear calibrations over a range of concentrations. To demonstrate this, an electrode calibrated with the µFC was used in FSCV recordings from a rat during the delivery of food reward – a stimulus that reliably evokes a brief increase in current due to the oxidation of dopamine. Using the linear calibration, dopamine concentrations were determined from the current responses evoked during the behavioral task. The µFC is able to easily and quickly calibrate FSCV electrode responses to chemical species for both in vitro and in vivo experiments.

Sinkala, Elly; McCutcheon, James E.; Schuck, Matt; Schmidt, Eric; Roitman, Mitchell F.; Eddington, David T.

2012-01-01

292

Calculation of alternating current losses in stacks and coils made of second generation high temperature superconducting tapes for large scale applications  

NASA Astrophysics Data System (ADS)

A homogenization method to model a stack of second generation High Temperature Superconducting tapes under AC applied transport current or magnetic field has been obtained. The idea is to find an anisotropic bulk equivalent for the stack such that the geometrical layout of the internal alternating structures of insulating, metallic, superconducting, and substrate layers is "washed" out while keeping the overall electromagnetic behavior of the original stack. We disregard assumptions upon the shape of the critical region and use a power law E-J relationship allowing for overcritical current densities to be considered. The method presented here allows for a computational speedup factor of up to 2 orders of magnitude when compared to full 2-D simulations taking into account the actual dimensions of the stacks without compromising accuracy.

Zermeno, Victor M. R.; Abrahamsen, Asger B.; Mijatovic, Nenad; Jensen, Bogi B.; Sørensen, Mads P.

2013-11-01

293

Dual mineralization of dicalcium phosphate and hydroxyapatite formation on both sides of porous membrane: Alternating current induces pH-modulated crystal deposition  

NASA Astrophysics Data System (ADS)

Dual mineralization on a porous membrane was carried out using an electrochemical approach. The porous membrane was interposed between a pair of glass cells, and calcium chloride (CaCl 2) and sodium hydrogenphosphate (Na 2HPO 4) solutions were separately injected into the cells. After inserting platinum electrodes into the cells, an alternating current with a sine waveform was applied for a given period of time. The resulting membrane was removed from the glass cells and rinsed with ultrapure water. The minerals formed on the membrane were analyzed by using spectroscopic methods such as scanning electron microscopy (SEM), infrared (IR) spectroscopy, and X-ray diffraction (XRD) and identified to be dicalcium phosphate and hydroxyapatite. It was noted that dicalcium phosphate formed on one side of the membrane, while hydroxyapatite was formed on the other side. Thus, dual mineralization could be successfully achieved on both sides of the porous membrane under an alternating current. This process of dual mineralization is very useful for the formation of versatile organic-inorganic hybrids and also for the regulation of the polymorphs on either side of a membrane.

Watanabe, Junji; Akashi, Mitsuru

2009-09-01

294

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.

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

2012-01-01

295

Current status of neonatal care and alternate strategies for reduction of neonatal mortality in the decade of nineties.  

PubMed

Improvement in neonatal care in India is needed in order to fulfill the National Health Policy to reduce infant and perinatal mortality and low birth weight babies. 50-60% of perinatal and infant mortality is due to neonatal mortality, specifically low birth weight. There have been no declines in any of the states even though there are literacy, fertility, poverty and health personnel differences between states. The health delivery system is described. Basic facilities are lacking in subcenters and primary health centers: weighing scales, blood pressure recorder, urine analysis, and blood transfusion capability; pregnancy registration is 40%. 40% of women believe that the female multipurpose worker (ANM) is a maternal and child health worker; Dais made postnatal visits to 25% of the women and infants, while physicians and ANM's visited 10%. The most frequent method of delivery is home delivery with a Dai or relative in attendance. Information on temperature control at birth, hand washing, feeding, and identification of high risk infants by health personnel is inadequate. There are no neonatal units in the entire country even though there are 8 million low birth weight babies/year and 1 million neonatal deaths/year. Neonatal causes are primarily birth injuries, aspiration syndrome, and neonatal infections (tetanus, pneumonia, and diarrhea). Studies have identified health service improvements to reduce neonatal mortality. In India, the priority should be to 1) establish delivery of neonatal and perinatal care at all 3 levels of care, 2) train and educate all health personnel in perinatal and neonatal care, and 3) improve community participation by involving the community in decision making on kind of care, perinatal care, and health education and by monitoring such services. Infant care must extend from prenatal through postnatal care, which is currently fragmented, through a 3-tiered system. 80-85% of all infants need care at Level I; 15-20% require Level II care; and 1-5% need Level III care. Health services and supplies may need to be provided at the village rather than the subcenter level and in postpartum services. Other possibilities are to include neonatal care within the Integrated Child Development Program or the Universal Immunization Program. Community leaders could monitor neonatal services. Regional institutes could provide training for all health personnel. PMID:1819563

Bhargava, S K; Ramji, S; Sachdev, H P

1991-12-01

296

Stripping voltammetry at micro-interface arrays: a review.  

PubMed

In this article, a comprehensive overview of the most recent developments in the field of stripping voltammetry at regular micro-interfaces (both solid-liquid and liquid-liquid interfaces) is presented. This review will report on the most conventional arrays of metallic micro-electrodes but also on the rapidly growing field of electrochemistry at arrays of micro-interfaces between two immiscible electrolyte solutions (?ITIES). The main fabrication methods, together with some design considerations and diffusion phenomena at such interfaces are discussed. Main applications of micro-interface arrays are presented including heavy metals detection at micro-electrode arrays and detection of organic molecules (amino acids, vitamins, peptides and drugs) at the ?ITIES. Stripping analysis at micro-interface arrays is suitable for the detection of analytes in several real media including water, soil extracts and biological fluids (blood and saliva) with high specificity, sensitivity (detection limits of nM, ppb level) and reliability. Stripping analysis at ?ITIES and micro-electrode arrays are two complementary approaches that have the advantages of being cost effective, simple to use and easily adaptable to field measurement. PMID:23498116

Herzog, Grégoire; Beni, Valerio

2013-03-26

297

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

298

An investigation on the new operational parameter effective in Cr(VI) removal efficiency: a study on electrocoagulation by alternating pulse current.  

PubMed

The performance of an electrocoagulation (EC) process with aluminum/iron electrodes for removal of chromium on laboratory scale was studied. The effect of operational parameters such as initial pH, current density (CD), reaction time, initial concentrations (50, 100, 500, 1000 mg/L), solution conductivity, electrical energy consumption (EEC) and type of circuit were studied in an attempt to reach higher Cr(VI) removal efficiency. Alternating pulse current (APC) was used to prevent the passivity or polarization of electrodes. Important operating parameters were optimized to access higher (99%) Cr(VI) removal efficiency as follows: EEC range: 4-58 kW h/m(3) wastewater, CD: 56-222 A/m(2), operating time: 20-110 min, pH 3-9 (pH(optimum) 5), voltage: 15-25 V. NaCl, KCl, PAC (poly aluminum chloride), NaNO(3) were used as supporting electrolytes. NaCl as well as KCl handled the EC with the best performance in every aspect; however, PAC and NaNO(3) did not have the same results (Applied conductivity is better than literature). The results of this work are comparable with those of recent studies. Equal removal efficiency was obtained in "direct current" (DC) and (APC); however, when "APC" was used, water recovery (0.92 m(3)/m(3) wastewater) was significant and the turbidity was 1 NTU. "APC" amazed our experimental team. PMID:21531074

Keshmirizadeh, Elham; Yousefi, Somayeh; Rofouei, Mohammad Kazem

2011-06-15

299

Voltammetry and coulometry with immersed thin layer electrodes. Part 2: Practical considerations and experimental results  

NASA Astrophysics Data System (ADS)

We have shown that geometrical considerations in the design of immersed thin layer electrochemical cells are important in the satisfactory performance of voltammetric experiments in solutions of high specific resistivity. In this paper, practical cell design and experimental results for a variety of systems are considered. In summary, we feel that reasonable care in the design of thin layer cells leads to the quantitative use of voltammetry and coulometry in systems with high specific resistivities. In the end, the effort is not much more than that required for conventional cyclic voltammetry, whereas the advantages of analysis using thin layer techniques are greater than those in conventional voltammetry.

Hinman, A. S.; Pons, S.; Cassidy, J.

1984-11-01

300

Iron organic speciation determination in rainwater using cathodic stripping voltammetry.  

PubMed

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

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

2012-07-29

301

Endogenous and exogenous electric fields as modifiers of brain activity: rational design of noninvasive brain stimulation with transcranial alternating current stimulation.  

PubMed

Synchronized neuronal activity in the cortex generates weak electric fields that are routinely measured in humans and animal models by electroencephalography and local field potential recordings. Traditionally, these endogenous electric fields have been considered to be an epiphenomenon of brain activity. Recent work has demonstrated that active cortical networks are surprisingly susceptible to weak perturbations of the membrane voltage of a large number of neurons by electric fields. Simultaneously, noninvasive brain stimulation with weak, exogenous electric fields (transcranial current stimulation, TCS) has undergone a renaissance due to the broad scope of its possible applications in modulating brain activity for cognitive enhancement and treatment of brain disorders. This review aims to interface the recent developments in the study of both endogenous and exogenous electric fields, with a particular focus on rhythmic stimulation for the modulation of cortical oscillations. The main goal is to provide a starting point for the use of rational design for the development of novel mechanism-based TCS therapeutics based on transcranial alternating current stimulation, for the treatment of psychiatric illnesses. PMID:24733974

Fröhlich, Flavio

2014-03-01

302

Cathodic Stripping Voltammetry of Thioamides on a Rotating Silver Disk Electrode.  

National Technical Information Service (NTIS)

Cathodic stripping voltammetry at a rotating silver disc electrode has been applied for the determination of five thioamides; thioacetamide (TAA), thiourea (TU), thionicotinamide (TNA), ethionamide (ETNA), and thiosemicarbazide (TSC). Well defined oxidati...

M. Iwamoto R. A. Osteryoung

1984-01-01

303

Development of a Low Cost Electrochemical CO Monitor Based on Stripping Voltammetry.  

National Technical Information Service (NTIS)

The quantitative measurement of atmospheric carbon monoxide was demonstrated using an electrochemical method based on stripping voltammetry. The method is based on the selective adsorption of carbon monoxide on the active surface of a platinum sensing ele...

M. W. Rupich G. L. Holleck H. F. Wise A. C. Makrides

1984-01-01

304

Determination of tryptophan and histidine by adsorptive cathodic stripping voltammetry using H-point standard addition method.  

PubMed

A sequential method is proposed for the determination of tryptophane and histidine by adsorptive cathodic stripping voltammetry using standard addition and H-point standard addition method (HPSAM). The complexes of copper(II) with the amino acids were accumulated onto the surface of a hanging mercury drop electrode for 60s. Then the preconcentrated complexes were reduced by square wave voltammetry and the peak currents were measured. The effect of various parameters such as pH, concentration of copper, accumulation potential, accumulation time and scan rate on the sensitivity were studied by one-at-a time and artificial neural network. Under the optimized conditions, the peak currents at about +0.05 to -0.30 V is proportional to the concentration of tryptophan and histidine over the concentration ranges of 5-220 and 100-1200 nM, respectively. Optimization of the parameters by one-at-a time showed that at accumulation potential of 0.10 V (versus Ag/AgCl reference electrode) the peak current is proportional only to the concentration of tryptophan and histidine does not have any contribution to the current. The optimization results by artificial neural network showed that at accumulation potential of -0.06 V (versus Ag/AgCl) the peak current is proportional to the both concentrations of tryptophan and histidine. Therefore, the method of H-point standard addition has been used for resolving overlap voltamograms for determination of histidine in the present of tryptophane. The method was successfully applied to the determination of tryptophan and histidine in synthetic and real samples. PMID:17723779

Ensafi, Ali A; Hajian, R

2006-11-24

305

Voltammetry of a flavocytochrome c(3): the lowest potential heme modulates fumarate reduction rates.  

PubMed Central

Iron-induced flavocytochrome c(3), Ifc(3), from Shewanella frigidimarina NCIMB400, derivatized with a 2-pyridyl disulfide label, self-assembles on gold electrodes as a functional array whose fumarate reductase activity as viewed by direct electrochemistry is indistinguishable from that of Ifc(3) adsorbed on gold or graphite electrodes. The enhanced stability of the labeled protein's array permits analysis at a rotating electrode and limiting catalytic currents fit well to a Michaelis-Menten description of enzyme kinetics with K(M) = 56 +/- 20 microM, pH 7.5, comparable to that obtained in solution assays. At fumarate concentrations above 145 microM cyclic voltammetry shows the catalytic response to contain two features. The position and width of the lower potential component centered on -290 mV and corresponding to a one-electron wave implicates the oxidation state of the lowest potential heme of Ifc(3) as a defining feature in the mechanism of fumarate reduction at high turnover rates. We propose the operation of dual pathways for electron transfer to the active site of Ifc(3) with the lowest potential heme acting as an electron relay on one of these pathways.

Butt, J N; Thornton, J; Richardson, D J; Dobbin, P S

2000-01-01

306

A new design of carbon fiber microelectrode for in vivo voltammetry using fused silica.  

PubMed

Voltammetric probes were constructed from stainless steel and fused silica tubing sheathing carbon fibers. Electrochemical tests were carried out to compare these electrodes with commercially available glass-sealed IVEC-5 electrodes. Electrodes of both types displayed a similar declining baseline and calculated coefficients of stabilization (tangent of baseline during a stable period). There were no significant differences in sensitivity between the two designs of electrodes to norepinephrine (NE) and dopamine (DA). All tested electrodes showed linear current responses to increasing concentrations of NE and DA. Fused silica (FS type) electrodes are suitable for electrochemical measurements (in vivo voltammetry) and display characteristics similar to those of commercially available IVEC-5 glass-sealed carbon fiber microelectrodes. Manufacture of FS type electrodes in a biochemical laboratory is easy and does not require any special equipment (such as a micropipette puller) or glass-handling skills. An additional fused silica tube can be glued to the electrode for microinjections. The electrodes are very robust, easy to handle and can be mounted on the arms of standard stereotaxic instruments. The electrodes can be made long enough to reach the deepest parts of brain of large animals. PMID:9130675

Swiergiel, A H; Palamarchouk, V S; Dunn, A J

1997-04-25

307

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

PubMed

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

Behpour, Mohsen; Valipour, Akram; Keshavarz, Mahin

2014-09-01

308

A FRAME response to the Draft Report on Alternative (Non-animal) Methods for Cosmetics Testing: Current Status and Future Prospects--2010.  

PubMed

This response on behalf of FRAME to the European Commission's consultation on the five chapters of the Draft Report on Alternative (Non-animal) Methods for Cosmetics Testing: Current Status and Future Prospects--2010, is via a Comment in ATLA, rather than via the template supplied by the Commission. This is principally so that a number of general points about cosmetic ingredient testing can be made. It is concluded that the five draft chapters do not provide a credible basis for the Commission's forthcoming report to the European Parliament and the European Council on the five cosmetic ingredient safety issues for which the 7th Amendment to the Cosmetic Directive's ban on animal testing was postponed until 2013. This is mainly because there is insufficient focus in the draft chapters on the specific nature of cosmetic ingredients, their uses, their local effects and metabolism at their sites of application, and, in particular, on whether their possible absorption into the body would be likely to lead to their accumulation in target sites at levels approaching Thresholds of Toxicological Concern. Meanwhile, there continues to be uncertainty about how the provisions of the Cosmetics Directive should be applied, given the requirements of the REACH system and directives concerned with the safety of other chemicals and products. PMID:21105753

Balls, Michael; Clothier, Richard

2010-10-01

309

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

310

Depressive symptoms and headaches in relation to proximity of residence to an alternating-current transmission line right-of-way.  

PubMed

Electric power transmission lines have become objects of public controversy. Hypotheses have linked neurobehavioral effects to the electric and magnetic fields that these lines produce. The authors conducted a telephone interview survey in November 1987 to assess the prevalence of depressive symptoms and headache in relation to proximity of residence to an alternating-current transmission line in the United States. Proximity to the line, defined as residing on a property abutting the right-of-way or being able to see the towers from one's house or yard, was positively associated with a measure of depressive symptoms. The association was not explained by demographic variables associated with depression or by attitudes about power lines or other environmental issues. The estimated prevalence odds ratio was 2.8 (95% confidence interval (CI) 1.6-5.1). The estimate did not change appreciably when the definitions of depressive symptoms or of proximity to the line were altered. Nonmigraine headaches had a weaker association with proximity to the line (odds ratio = 1.5, 95% CI 0.76-2.8), and self-reported migraine headaches exhibited no association (odds ratio = 0.99, 95% CI 0.29-3.4). Additional studies of psychological and behavioral measures should be conducted in relation to electric and magnetic fields, with a strong emphasis on improved exposure assessment. PMID:8452140

Poole, C; Kavet, R; Funch, D P; Donelan, K; Charry, J M; Dreyer, N A

1993-02-01

311

Application of Low-Frequency Alternating Current Electric Fields Via Interdigitated Electrodes: Effects on Cellular Viability, Cytoplasmic Calcium, and Osteogenic Differentiation of Human Adipose-Derived Stem Cells  

PubMed Central

Electric stimulation is known to initiate signaling pathways and provides a technique to enhance osteogenic differentiation of stem and/or progenitor cells. There are a variety of in vitro stimulation devices to apply electric fields to such cells. Herein, we describe and highlight the use of interdigitated electrodes to characterize signaling pathways and the effect of electric fields on the proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs). The advantage of the interdigitated electrode configuration is that cells can be easily imaged during short-term (acute) stimulation, and this identical configuration can be utilized for long-term (chronic) studies. Acute exposure of hASCs to alternating current (AC) sinusoidal electric fields of 1?Hz induced a dose-dependent increase in cytoplasmic calcium in response to electric field magnitude, as observed by fluorescence microscopy. hASCs that were chronically exposed to AC electric field treatment of 1?V/cm (4?h/day for 14 days, cultured in the osteogenic differentiation medium containing dexamethasone, ascorbic acid, and ?-glycerol phosphate) displayed a significant increase in mineral deposition relative to unstimulated controls. This is the first study to evaluate the effects of sinusoidal AC electric fields on hASCs and to demonstrate that acute and chronic electric field exposure can significantly increase intracellular calcium signaling and the deposition of accreted calcium under osteogenic stimulation, respectively.

McCullen, Seth D.; McQuilling, John P.; Grossfeld, Robert M.; Lubischer, Jane L.; Clarke, Laura I.

2010-01-01

312

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

313

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

314

A randomized, double-blind, sham-controlled study of static electric field therapy by high voltage alternating current for active rheumatoid arthritis.  

PubMed

Static electric field therapy by high voltage alternating current (EF-HVAC) is a traditional complementary Japanese medicine used for headache, shoulder stiffness, chronic constipation and insomnia. Open-label studies and clinical experience in Japan have suggested that this electric field therapy is safe and effective in treating chronic arthritis. We evaluated the efficacy of EF-HVAC therapy in a randomized, double-blinded, sham-controlled trial in patients with active rheumatoid arthritis (RA) in community-based general physician centers. Thirty patients fulfilling American College of Rheumatology (ACR) criteria for RA were treated with EF-HVAC therapy with the LEGACIS PLUS System (COCOROCA Corp., Tokyo, Japan) or sham therapy for 12 weeks and followed for 4 weeks without treatment. The disease activity score 28 (DAS28-CRP), visual analogue scale for pain (VAS), modified health assessment questionnaire (MHAQ), and inflammatory parameters were used as the outcome variable. Twenty four patients (n = 12 in each group) were analyzed by a per protocol analysis. Although a significant reduction in DAS28-CRP was observed in EF-HVAC group at 8 and 12 weeks compared to before treatment, there were no significant differences in DAS28-CRP scores during treatment between two groups. The scale of VAS was also significantly decreased by the treatment with EF-HVAC compared to before treatment, in addition, the scale of VAS in EF-HVAC group was significantly lower than sham group at 8 and 12 weeks. Changes in another parameters including MHAQ were not significant between before and after treatment, or by all comparative study between two groups. There were no adverse events related the treatment. In conclusion, the EF-HVAC therapy has a beneficial effect on the improvement to subjective pain of RA. PMID:23874073

Naito, Yuji; Yamaguchi, Shinnichi; Mori, Yasuhiro; Nakajima, Kouji; Hashimoto, Sanshiro; Tomaru, Masakazu; Satoh, Yoshihiko; Hitomi, Yuji; Karita, Masakazu; Hiwatashi, Tomoaki; Kawahito, Yutaka; Yoshikawa, Toshikazu

2013-07-01

315

An evaluation of antibacterial efficacy of 3% sodium hypochlorite, high-frequency alternating current and 2% chlorhexidine on Enterococcus faecalis: An in vitro study  

PubMed Central

Aim: The purpose of this study was to evaluate the antibacterial efficacy of 3% sodium hypochlorite (NaOCl), high-frequency alternating current (HFAC) (Endox Endodontic System), 2% chlorhexidine (CHX) in elimination of Enterococcus faecalis from experimentally infected root canals, in vitro. Materials and Methods: Eighty extracted, single rooted permanent upper anterior teeth were instrumented up to size 50, teeth were sterilized and inoculated with E. faecalis, subcultured in BHI broth which had its optical density adjusted to approximately 1.5?108 colony forming units (CFUs) ml-1 by comparing its turbidity to a McFarland 0.5 BaSO4 standard solution. After incubation for 24 h, the contaminated root canals were divided into four groups and subjected to action of NaOCl 3%, CHX 2%, and HFAC with physiological saline as a positive control. Sterile paper points were selected to take the sample of the bacteria and transferred to tubes containing 5ml of BHI broth and then incubated for 24 and 48 h, followed by agar plating of the resultant broth turbidity on Enterococcus confirmatory agar. Results: Data obtained were analyzed statistically for differences using chi-squared test, comparing different groups, with a significance level established at P<0.05 and 3% NaOCl showed no growth postoperatively, CHX and HFAC showed reduction of postoperative growth compared to physiological saline and, were statistically significant (P<0.05). Conclusion: In the present study, sodium hypochlorite, CHX, HFAC all were significantly effective in eliminating E. faecalis and sodium hypochlorite showed the maximum anti-bacterial activity against E. faecalis.

Karale, Rupali; Thakore, Ajay; Shetty, VK

2011-01-01

316

Alternative Instructional Grouping Practices.  

ERIC Educational Resources Information Center

Alternatives to the current system of graded classes and ability grouping are examined that would allow teachers to balance individual student needs with practical considerations in instructional delivery. In addition to reviewing the alternatives, the research that has examined these approaches is reviewed and synthesized. The three alternative

McGurk, Erin K.; Pimentle, Jodi A.

317

Determination of gaseous hydrogen sulfide by cathodic stripping voltammetry after preconcentration on a silver metalized porous membrane electrode  

SciTech Connect

Gaseous H/sub 2/S is accumulated on the surface of a porous silver membrane electrode at constant potential and directly determined by cathodic stripping voltammetry. The sensitivity of the method, expressed by the slope of the regression line for the dependence of the stipping peak current on the amount of H/sub 2/S in the gas sample, is 357 ..mu..g of H/sub 2/S/..mu..A. The reproducibility of the determination expressed in terms of the relative standard deviation is 3.2%. Phenomena observed during cathodic polarization of the silver porous membrane electrode, either clean or covered with deposited Ag/sub 2/S are briefly discussed and the resultant conditions for optimal analysis are given. 15 references, 4 figures.

Opekar, F.; Bruckenstein, S.

1984-01-01

318

LBM for cyclic voltammetry of electrochemically mediated enzyme reactions and Rayleigh-Bénard convection in electrochemical reactors  

NASA Astrophysics Data System (ADS)

A few of the applications of the Lattice Boltzmann Method have been used to model the complex bioelectrochemical phenomena presented here; cyclic voltammetry of electrically assisted enzyme reactions for one instance, and complex chemical reactions with simultaneous momentum, heat and mass transfer as another example. In the first case, we reproduce experimental data and predict new results (not feasible of being obtained by other numerical methods); the evolution of the diffusion boundary layer, which is important information from the numerical viewpoint to design reactors. As second, our model of non isothermal electrochemical enzyme reactor with a complex chemical-thermohydrodynamics involves an enzyme reaction taking place over two parallel rectangular enzyme immobilized electrodes, within a Rayleigh-Bénard convection system, a multifaceted subject not yet studied simultaneously. Realistic velocity, temperature, and concentration profiles as well as the corresponding Faradaic currents for different geometries and heating settings are provided, showing the goodness of our approach.

Amaya-Ventura, G. A.; Rodríguez-Romo, S.

2012-02-01

319

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

320

Microelectrode voltammetry and electron transport in an undiluted room temperature melt of an oligo(ethylene glycol)-tailed viologen  

SciTech Connect

This paper describes the synthesis, characterization, and voltammetry of a oligo(ethylene glycol) trimer derivative of 4,4`-bipyridine, [N,N`-(CH{sub 3}(OCH{sub 2}CH{sub 2}){sub 3}){sub 2}-4,4`-bipyridin e] [BF{sub 4}]{sub 2} [[E{sub 3}M]{sub 2}](BF{sub 4}){sub 2}. This `tailed` viologen is a room temperature molten salt. Its fast atom bombardment mass spectrum exhibits interesting aspects of cationation. Microelectrode voltammetry in the undiluted viologen melt shows the expected pair of reduction waves, but currents for the wave for the [[E{sub 3}M]{sub 2}]{sup 2+/1+} are smaller than those for the [[E{sub 3}M]{sub 2}]{sup 1+/0} couple. Analysis of the voltammetric behavior leads to the conclusion that the difference in currents arises from coupling of [[E{sub 3}M]{sub 2}]{sup 1+/0} homogeneous electron exchanges to the physical diffusion of viologen species in the mixed-valent diffusion layer at the electrode interface. The physical diffusivity of the [[E{sub 3}M]{sub 2}]{sup 2+} species, D{sub PHYS}, is much smaller than electron diffusivity through electron self-exchanges of the [[E{sub 3}M]{sub 2}]{sup 1+/0} couple. k{sub EX,1/0} is nearly 10{sup 6} M{sup -1} s{sup -1}, or at least 10-fold larger than K{sub EX,1/2}. 27 refs., 6 figs., 1 tab.

Hatazawa, Tsuyonobu; Terrill, R.H.; Murray, R.W. [Univ. of North Carolina, Chapel Hill, NC (United States)] [Univ. of North Carolina, Chapel Hill, NC (United States)

1996-02-15

321

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

322

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

323

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

PubMed

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

Ndungu, Kuria

2012-07-17

324

Diagnostics of CdTe Electrodeposition by Rest Potential Voltammetry  

Microsoft Academic Search

Due to the extreme sensitivity of the partial elemental currents (i.e., iCd, iTe) and, hence, stoichiometry to deposition voltage, temperature, mass transport, and ambient light intensity during electrodeposition of semiconductor films, it is important to implement in-situ methods for monitoring the stoichiometry and related semiconductor efficacy of the grow- ing film. We report investigation of open circuit rest potential (Eoc)

Brandon Kemp; Robert Engelken; Arif Raza; Arees Siddiqui; Omer Mustafa

325

Alternatives to current disease-modifying treatment in MS: what do we need and what can we expect in the future?  

PubMed

Disease-modifying treatments (DMTs) for multiple sclerosis (MS) are now widely available, and their beneficial effects on relapse rates, magnetic resonance imaging outcomes and, in some cases, relapse-related disability have been shown in numerous clinical studies. However, as these treatments are only partially effective in halting the MS disease process, the search for improved treatment regimens and novel therapies must continue. Strategies to improve our therapeutic armamentarium have to take into account the different phases or parts of the pathogenesis of the disease. Available treatments address systemic immune dysfunction, blood-brain barrier permeability and the inflammatory process in the central nervous system. Currently, patients who fail to respond adequately to first-line DMTs are often considered as candidates for intensive immunosuppression with cytostatic agents or even autologous stem cell transplantation. However, new approaches are being developed. Combination therapies offer an alternative approach that may have considerable potential to improve therapeutic yield and, although likely to present considerable challenges in terms of trial design, this certainly seems to be a logical step forward in view of the complex pathology of MS. Several new drugs are also being developed with the aim of providing more effective, convenient and/or specific modulation of the inflammatory component of the disease. These treatments include humanised monoclonal antibodies such as the anti-VLA-4 antibody natalizumab, inhibitors of intracellular activation, signalling pathways and T-cell proliferation, and oral immunomodulators such as sirolimus, teriflunomide or statins. There remains, however, an urgent need for treatments that protect against demyelination and axonal loss, or promote remyelination/regeneration. Due to the chronicity of MS, the therapeutic window for neuroprotective agents is wider than that following stroke or acute spinal cord injury, and may therefore allow the use of some drugs that have proven disappointing in other situations. Novel potential neuroprotective agents such as alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid antagonists and ion-channel blockers will be entering Phase II trials in MS in the near future, and it is hoped that these agents will mark the start of a new era for DMTs for MS. PMID:15549357

Kappos, Ludwig; Kuhle, Jens; Gass, Achim; Achtnichts, Lutz; Radue, Ernst-Wilhelm

2004-09-01

326

Quantitation of olanzapine in tablets by HPLC, CZE, derivative spectrometry and linear voltammetry  

Microsoft Academic Search

Four analytical methods have been developed for the quality control of pharmaceutical formulations containing the novel antipsychotic drug, olanzapine: high performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), derivative spectrometry and linear voltammetry. All methods require only a simple extraction procedure of olanzapine from the tablets before analysis. HPLC with ultraviolet detection at 260 nm is carried out with a

Maria Augusta Raggi; G Casamenti; R Mandrioli; G Izzo; E Kenndler

2000-01-01

327

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

EPA Science Inventory

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

328

Microbial Biofilm Voltammetry: Direct Electrochemical Characterization of Catalytic Electrode-Attached Biofilms  

Microsoft Academic Search

While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 m) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nonde- structive voltammetry techniques

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

2008-01-01

329

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

ERIC Educational Resources Information Center

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

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

2005-01-01

330

Voltammetry using a dental amalgam electrode for heavy metal monitoring of wines and spirits  

Microsoft Academic Search

We have introduced a non-toxic electrode material similar to dental amalgam for use in voltammetry. Its electrochemical properties are like a silver electrode. However, it possesses a higher overvoltage towards hydrogen than silver, and therefore enables detection of metals like zinc, nickel and cobalt. As such solid electrodes are found to give stable results over several weeks, without any maintenance,

Øyvind Mikkelsen; Knut H. Schrøder

2002-01-01

331

Quantitative Bestimmungen mittels cyclischer Voltammetrie an der Phasengrenze zweier mischbarer Elektrolytlösungen  

Microsoft Academic Search

Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate

J. Krause; F. Umland

1989-01-01

332

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

333

Supplemental examination of alternative materials in a model steam generator: Volume 2, Correlation of Model 10 defects with eddy-current indications: Final report  

Microsoft Academic Search

The following report compares the nondestructive examination with the destructive metallographic examination of the tube bundle alternative materials, Model 10 steam generator. The model steam generator was fabricated using state-of-the-art tube processing (Alloys 600, 690 and 800) and corrosion resistant support alloys and designs. The model steam generator was operated for approximately one year with a secondary environment that was

K. E. Marugg; L. J. Edwards; J. J. Krupowicz

1989-01-01

334

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

335

Electrochemical genotoxicity assay based on a SOS/umu test using hydrodynamic voltammetry in a droplet.  

PubMed

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 K(ow) value. PMID:23242275

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

2012-01-01

336

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.

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

2012-01-01

337

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

338

Anodic-stripping voltammetry of heavy metals in the presence of organic surfactants.  

PubMed

The efficacy of fumed silica for removal of sorption interferences by organic surfactants in the anodic-stripping voltammetry of heavy metals is demonstrated. Appropriate addition of silica to the sample solution rapidly "purifies" it from interfering surfactants during the nitrogen purge step. Up to at least 6 ppm of gelatin, Triton X-100, albumin or Liqui-Nox then does not affect the stripping response of cadmium, lead and zinc at the hanging mercury drop electrode. A relative standard deviation of 5.5% is obtained for 20 successive measurements of 1 x 10(-7)M lead in the presence of 2 ppm Triton X-100. Analogous improvements are observed at the mercury film electrode (in the presence of up to 60 ppm of these surfactants). The use of silica thus possesses the advantages of speed, efficiency, simplicity and low cost compared to other schemes for dealing with surfactant interferences in anodic-stripping voltammetry. PMID:18964813

Kubiak, W W; Wang, J

1989-08-01

339

New Cyclic Voltammetry Method for Examining Phase Transitions on Electrodes: Simulated Results  

NASA Astrophysics Data System (ADS)

We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The FORC diagram for a discontinuous phase transition is characterized by a negative (unstable) region separating two positive (stable) regions, while such a negative region does not exist for continuous phase transitions. Experimental data for Electrochemical FORC (EC-FORC) analysis could easily be obtained by simple reprogramming of a potentiostat designed for conventional cyclic-voltammetry experiments.I. Abou Hamad, D.T. Robb, P.A. Rikvold, J. Electroanal. Chem., in press.

Abou Hamad, Ibrahim; Robb, Daniel; Rikvold, Per Arne

2007-03-01

340

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

341

Growth behavior of poly( o-anisidine-co-o-toluidine) deposition by cyclic voltammetry  

Microsoft Academic Search

Electrochemical co-polymerization of o-anisidine (OA) with o-toluidine (OT) was carried out in 1 M H2SO4 by cyclic voltammetry. Polymeric films were deposited by employing different conditions such as cycle number and feed ration of co-monomers. Electrochemical homo-polymerization of OA with OT were also done. A growth equation for co-polymer deposition relating parameters of operation and charge associated for film deposition

D. D. Borole; U. R. Kapadi; P. P. Mahulikar; D. G. Hundiwale

2007-01-01

342

Growth Behavior of Poly(o-Anisidine-Co-Aniline) Deposition by Cyclic Voltammetry  

Microsoft Academic Search

Electrochemical copolymerization of o-anisidine (OA) with aniline (A) was carried out in 1 M H2SO4 by cyclic voltammetry. Polymeric films were deposited by employing different conditions such as cycle number and mole ratio of comonomers. Electrochemical homopolymerization of o-anisidine with aniline were also done. A growth equation for copolymer deposition relating parameters of operation and charge associated for film deposition was

D. D. Borole; U. R. Kapadi; P. P. Mahulikar; D. G. Hundiwale

2006-01-01

343

Cadmium detection via boron-doped diamond electrodes: surfactant inhibited stripping voltammetry  

Microsoft Academic Search

The deposition of cadmium on boron-doped diamond is investigated with square-wave anodic stripping voltammetry. The system was investigated in quiescent conditions, in the presence of an acoustic field and then in the presence of the neutral surfactant Triton® X-100. The effect of optimised insonation was to increase the sensitivity from 0.63 (under silent conditions) to 3.78?A?M?1 and to reduce the

Craig E. Banks; Michael E. Hyde; Peter Tom???k; Robert Jacobs; Richard G. Compton

2004-01-01

344

Square wave voltammetry on boron-doped diamond electrodes for analytical determinations  

Microsoft Academic Search

The use of square wave voltammetry in conjunction with a boron-doped diamond electrode for the analytical determination of pentachlorophenol is described. After optimization of the experimental conditions, that model molecule was analyzed in pure and natural waters using a Britton–Robinson buffer (pH=5.5) as the supporting electrolyte. Oxidation occurs at 0.80 V vs. Ag\\/AgCl in a two-electron process controlled by adsorption

L. Codognoto; S. A. S. Machado; L. A. Avaca

2002-01-01

345

Microdetermination of human serum albumin by differential pulse voltammetry at a l -cysteine modified silver electrode  

Microsoft Academic Search

A simple and highly sensitive electrochemical method for the determination of human serum albumin (HSA) using differential\\u000a pulse voltammetry (DPV), based on a silver electrode modified with a self-assembled monolayer of l-cysteine, was developed. l-cysteine can be modified onto a silver electrode by covalent bonding through the sulfur to give stable and long-lived chemical\\u000a electrodes. This electrode showed good sensitivity,

Liyuan Lu; Yanqin Zi; Hongling Wang

2008-01-01

346

Cathodic stripping voltammetry of cysteine using silver and copper solid amalgam electrodes  

Microsoft Academic Search

Silver and copper solid amalgam electrodes (modified with mercury meniscus and based on amalgamation of fine metallic powder) have been successfully tested for cathodic stripping voltammetry of cysteine. In the case of the silver solid amalgam electrode AgSAE the relative standard deviation (RSD) and the detection limit (3 SD) reached ±2.3% and 3×10?9 mol l?1 cysteine, respectively.

B. Yosypchuk; L. Novotný

2002-01-01

347

Aptamer biosensor for label-free square-wave voltammetry detection of angiogenin  

Microsoft Academic Search

Angiogenin (Ang), one of the most potent angiogenic factor, is related with the growth and metastasis of numerous tumors. This paper presents a very simple and label-free square-wave voltammetry (SWV) aptasensor to detect angiogenin, in which an anti-angiogenin-aptamer was used as a molecular recognition element, and the couple ferro\\/ferricyanide as a redox probe. At the bare gold electrode, the redox

Lidong Li; Hongtao Zhao; Zhengbo Chen; Xiaojiao Mu; Lin Guo

2011-01-01

348

Direct reversible voltammetry and electrocatalysis with surface-stabilised Fe 2O 3 redox states  

Microsoft Academic Search

Nanoparticle film voltammetry is employed to explore the presence and reactivity of surface-stabilised iron redox centers at the interface of immobilised Fe2O3 nanoparticles of ca. 4nm diameter and aqueous buffer media. Mesoporous films of Fe2O3 nanoparticles on tin-doped indium oxide (ITO) substrates are formed in a layer-by-layer deposition process from aqueous colloidal Fe2O3 and aqueous cyclohexyl-hexacarboxylate followed by thermal (500°C)

Charles Y. Cummings; Michael J. Bonné; Karen J. Edler; Matthew Helton; Anthony McKee; Frank Marken

2008-01-01

349

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

PubMed Central

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

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

2010-01-01

350

EXPLORING ALTERNATIVE ENERGY SOURCES  

NSDL National Science Digital Library

Students do research to determine the types of energy currently used in the U.S., study the economic effects of rising energy costs on average households, and come up with ideas for alternative energy sources.

Lisa Prososki (;)

2007-09-25

351

Investigation of the anodic behavior of Al current collector in room temperature ionic liquid electrolytes  

Microsoft Academic Search

We have investigated the anodic behaviors of aluminum as a cathodic current collector for lithium ion batteries in several kinds of room temperature ionic liquids (RTILs) and EC+DMC solutions containing LiN(CF3SO2)2 by cyclic voltammetry (CV), chronoamperometry (CA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry and chronoamperometry data showed that the current

Chengxin Peng; Li Yang; Zhengxi Zhang; Kazuhiro Tachibana; Yong Yang; Shiyong Zhao

2008-01-01

352

Nonlinear alternating current susceptibility studies of high-Tc rings: Influence of the structuring method and determination of the flux creep exponent  

NASA Astrophysics Data System (ADS)

We have studied the influence of the patterning procedure on the critical current density of high-Tc YBa2Cu3O7-? thin rings using the nonlinear ac susceptibility method. At no applied dc magnetic field have we found that laser ablation strongly degrades the critical current density whereas ion beam etching has only a weak influence on it. From the measurements at different frequencies and at dc magnetic fields we analyzed the influence of flux creep and obtained the field dependence of the flux creep exponent. Our data reconfirm the recently observed scaling relation for the nonlinear susceptibility response of type-II superconductors.

Streubel, S.; Mrowka, F.; Wurlitzer, M.; Esquinazi, P.; Zimmer, K.

2000-06-01

353

Comprehensive Study of Bisulfate Adsorption on Pt(111) by Radioactive Labeling and Voltammetry. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Adsorption of bisulfate anions on single crystal Pt(111) electrode, ordered and disordered and on polycrystalline platinum has been studied by the use of radioactive labeling method and cyclic voltammetry. The studies have revealed that the saturation sur...

A. Wieckowski P. Zelenay K. Varga

1991-01-01

354

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.

2013-01-01

355

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

PubMed

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

356

The role of the defect levels in MgO in the low firing voltage, wide driving voltage margin operation of an alternate current plasma display panel  

NASA Astrophysics Data System (ADS)

In order to study the relationship between the discharge characteristics of an ac plasma display panel and the surface conductivity of a MgO thin film, we measured the surface current across a ring-shaped MgO film temporally induced by exposure to monochromatic vacuum ultraviolet radiation from a synchrotron radiation source whose wavelength ranges from 60 to 240 nm (5.5-25 eV). The experimental results show that the surface current begins to increase rapidly at a photon energy of about 9 eV which might correspond to the valence band edge of MgO. The differences in the surface current level correlate well with the differences in the preparation method of the MgO films and their respective discharge characteristics, such as firing, minimum sustained voltages, address voltage margins, and address discharge delay times. Surface charge measurements using the linear electro-optic effect also show consistent correlations with the surface current measurement of each MgO sample.

Ha, Chang Hoon; Kim, Joong Kyun; Whang, Ki-Woong

2007-06-01

357

Alternatives to the Current Federal Role in Vocational Education: Inclusion of Vocational Education Programs in a Consolidated Educational Grants Program. Final Report.  

ERIC Educational Resources Information Center

A background and framework are established for use in assessing effects of possible proposals for consolidating the Vocational Education Act (VEA) with other federal programs assisting elementary and secondary education. The paper is organized into three sections. The first describes factors that have led to the current interest in consolidation…

Reisner, Elizabeth R.

358

Copper (II) complexation in northern California rice field waters: an investigation using differential pulse anodic and cathodic stripping voltammetry  

Microsoft Academic Search

Differential pulse anodic stripping voltammetry (DPASV) and competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV) demonstrated that?99% of the dissolved copper in five rice field waters, one river water and a catchment basin water collected at sites in northern California is complexed by natural organic matter. Concentrations of natural copper complexing ligands (CL) ranged from 81 to 426 nM determined by CLE-CSV

A. E Witter; S. A Mabury; A. D Jones

1998-01-01

359

Alternative Fuels.  

National Technical Information Service (NTIS)

Introduction: Transportation Market Evolution; Tactical Mobility Fuel. Single Fuel in the Battlefield: What is the Single Fuel. Certification/Qualification Pipeline; DARPA Alternative Jet Fuels Program. Coordinating the Overall Alternative Fuel Qualificat...

P. Muzzell

2009-01-01

360

Alternative Medicine  

MedlinePLUS

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

361

An investigation on the new operational parameter effective in Cr(VI) removal efficiency: A study on electrocoagulation by alternating pulse current  

Microsoft Academic Search

The performance of an electrocoagulation (EC) process with aluminum\\/iron electrodes for removal of chromium on laboratory scale was studied. The effect of operational parameters such as initial pH, current density (CD), reaction time, initial concentrations (50, 100, 500, 1000mg\\/L), solution conductivity, electrical energy consumption (EEC) and type of circuit were studied in an attempt to reach higher Cr(VI) removal efficiency.

Elham Keshmirizadeh; Somayeh Yousefi; Mohammad Kazem Rofouei

2011-01-01

362

Electrochemical stability of self-assembled monolayers of biphenyl based thiols studied by cyclic voltammetry and second harmonic generation  

NASA Astrophysics Data System (ADS)

The reductive desorption of self-assembled monolayers (SAMs) of ?-(4'-methyl-biphenyl-4-yl)-alkanethiols (CH 3-C 6H 4-C 6H 4-(CH 2) n-SH, BP n) on Au(1 1 1) on mica was studied in 0.5 M KOH solution as a function of the length of the aliphatic spacer chain ( n = 1-6 and 12) and for two different preparations temperatures (295 K and 343 K). Second harmonic generation (SHG) was applied in situ parallel to cyclic voltammetry (CV). Odd-even differences in the structure of the BP n monolayers are clearly reflected in the electrochemical stability, as well as by the charge and shape of the desorption peak. For n = 1-5 a single desorption peak is detected whereas multiple peaks occur for BP6 similar to hexadecane thiol which was also studied for comparison. An increased preparation temperature affects the shape and width of the desorption peak but not the position. BP1 exhibits a temperature dependence different from the other homologues. The relationship between coverage monitored by SHG and desorption charge determined from the CVs is found to be linear and surprisingly independent from the details of the SAMs. The combined SHG and CV experiments suggest that capacitive and faradaic current are always closely coupled even for BP6 and hexadecane thiol which exhibit multiple desorption peaks.

Thom, Ian; Buck, Manfred

2005-04-01

363

Complementary/Alternative therapies for the treatment of breast cancer. A systematic review of randomized clinical trials and a critique of current terminology.  

PubMed

The objectives of this study was to evaluate and critically analyze all randomized clinical trials (RCTs) of ''alternative cancer cures'' (ACCs) for breast cancer. The electronic databases Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Allied and Complementary Medicine, Scirus, BIOSIS, CancerLit and CINAHL and for ongoing trials the MetaRegister at http://www.controlled-trials.com/ and the National Research Register at http://www.update-software.com/national/ were searched from their inception. Bibliographies of located studies were scanned. Unpublished or ongoing trials were identified through correspondence with experts in the field. Our own files were hand searched for further RCTs. Review methods included a systematic review of RCTs involving breast cancer patients treated with ACCs, survival, parameters indicative of tumor burden, disease progression, cancer recurrence, and cancer cure. Results were tabulated and summarized. Thirteen RCTs met the inclusion criteria. In most cases their methodological quality is low, with only two RCTs scoring ''4'' and four RCTs scoring ''3'' out of 5 possible points for methodological quality. The treatments tested included various methods of psychosocial support such as group support therapy, cognitive behavioral therapy cognitive existential group therapy, a combination of muscle relaxation training and guided imagery, the Chinese herbal remedy Shi Quan Da Bu Tang, thymus extract, transfer factor, melatonin, and factor AF2. Encouraging but not fully convincing results emerged for melatonin. PMID:17238981

Ernst, Edzard; Schmidt, Katja; Baum, Michael

2006-01-01

364

The improvement of discharge characteristics and lifetime of alternate current plasma display panel by MgO deposition on the phosphor  

SciTech Connect

An alternate application of MgO film for the improvement of discharge characteristics and lifetime in an ac plasma display panel (PDP) is suggested. In the normal ramp reset, the accumulated wall charges on the phosphor surface just after the reset period are different as to their color (red, green, blue) of each phosphor, which reduces the common voltage margin of ac PDP. In general, MgO is used for the protective layer of dielectrics from ion sputtering and the improvement of secondary electron emission which affects the driving voltage in an ac PDP. In this research, we deposited MgO on the phosphor to get the same addressing characteristics irrespective to the color of each phosphor, high speed addressing, and prolonged lifetime of phosphor despite the vacuum ultraviolet irradiation and ion bombardment. An optimized MgO thickness was used to avoid the excessive luminance and luminous efficacy degradation by the MgO deposition on the phosphor. Results showed that PDP with MgO coated phosphor has more uniform formative delays in address discharges and improved degradation characteristics.

Ha, Chang Hoon; Kim, Jae Sung; Jeong, Dong Chul; Whang, Ki Woong [Plasma Laboratory, School of Electrical Engineering, Seoul National University, San 56-1, Shinlim-dong, Kwanak-gu, Seoul 151-742 (Korea, Republic of)

2004-11-01

365

Performance characteristics of a pilot sea-water activated battery with Pb/PbCl 2 cathodes, prepared by cyclic voltammetry  

NASA Astrophysics Data System (ADS)

Cyclic voltammetry was utilized in preparation of PbCl 2-active material on the surfaces of lead electrodes in 1.0 M HCl solutions. X-ray diffraction analysis proved that only PbCl 2 was formed and no other products could be detected. The morphology of the Pb/PbCl 2 surface layer, as revealed by scanning electron microscopy, showed a primitive dependence on the employed voltammetric conditions. The Pb/PbCl 2 electrodes prepared by cyclic voltammetry were employed as cathodes in a pilot sea-water activated cell using Mg-alloy anodes. The voltage-time and current-time discharge curves of the pilot cell were examined as a function of the Mg% in the anode material, magnitude of the load resistance and salinity of the electrolyte. The discharge characteristics of a pilot 5-cell battery were also tested. Under the optimum conditions, the voltage of a unit cell attained 1.2 V which agrees well with the voltage of the corresponding conventional cells. In addition to the easy method of preparation, the present cathodes are characterized by many advantages over those prepared by the traditional techniques.

Abd El-Halim, A. M.; Fawzy, M. H.; Saty, A.

366

CdTe nanocrystal-based electrochemical biosensor for the recognition of neutravidin by anodic stripping voltammetry at electrodeposited bismuth film.  

PubMed

CdTe quantum dots (QDs)-based electrochemical sensor for recognition of neutravidin, as a model protein, using anodic stripping voltammetry at electrodeposited bismuth film is presented. This biosensor involves the immobilization of the captured QDs conjugates which was dissolved with 1M HCl solution to release cadmium ions and metal components were quantified by anodic stripping voltammetry after a 3-min accumulation at -1.2V on bismuth-film electrode (BiFE) of the biotin, served as recognition element, onto the gold surface in connection with a cysteamine self-assembled monolayer. The modification procedure was characterized by electrochemical impedance spectroscopy and atomic force microscopy. We exploit QDs as labels for amplifying signal output and monitoring the extent of competition process between CdTe-labeled neutravidin and the target neutravidin for the limited binding sites on biotin. As expected for the competitive mechanism, the recognition event thus yields distinct cadmium stripping voltammetric current peak, whose response decreases upon increasing the level of target neutravidin concentrations. Under optimal conditions, the voltammetric response is highly linear over the range of 0.5-100 ngL(-1) neutravidin and the limit of detection is estimated to be 0.3 ngL(-1) (5 nM). Unlike earlier two-step sandwich bioassays, the present protocol relies on a one-step competitive assay, which is more accurate and sensitive, showing great promise for rapid, simple and cost-effective analysis of protein. PMID:18722762

Du, Dan; Ding, Jiawang; Tao, Yuan; Li, Haibing; Chen, Xi

2008-12-01

367

Fluid Modeling of a Nitrogen Atmospheric-Pressure Planar Dielectric Barrier Discharge Driven by a Realistic Distorted Sinusoidal Alternating Current Power Source  

NASA Astrophysics Data System (ADS)

One-dimensional self-consistent simulations of a parallel-plate atmospheric-pressure nitrogen dielectric barrier discharge (DBD) are presented. The DBD was driven by a realistic distorted-sinusoidal voltage power source with a frequency of 60 kHz. The simulated discharge currents are in quantitative agreement with experimental measurements. N4+ ions gain more of the input electric power than electrons, which is unlike most glow discharges. The densities of all charged and neutral species increase exponentially with increasing applied peak voltage in the range of 6.2--8.6 kV. The higher the permittivity of the dielectric material, the larger the discharge current and the longer the period of gas breakdown. In addition, the quantity of accumulated charges at each electrode increases with increasing permittivity of the dielectric material. Finally, the increase in dielectric thickness from 1.0 to 2.0 mm greatly reduces the densities of all species and also the plasma absorbed by the power.

Cheng, Kai-Wen; Hung, Chieh-Tsan; Lin, Kun-Mo; Chiu, Yuan-Ming; Wu, Jong-Shinn; Yu, Jen-Perng

2012-11-01

368

Alternative strategies: a better alternative.  

PubMed

Alternatives can be defined as being any financial asset other than traditional stocks and bonds. They include marketable alternatives, private capital, and equity real estate. There are two primary reasons for investing in alternatives: the potential for greater return and the opportunity to diversify a portfolio. Although alternatives were challenged in the highly volatile environment that existed in 2008 and early 2009, they generally lived up to expectations. PMID:20446422

Doody, Dennis

2010-05-01

369

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

PubMed

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

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

2013-02-15

370

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

371

Direct determination of iodide in sea water by cathodic stripping square wave voltammetry  

SciTech Connect

A procedure for the direct determination of iodide in sea water is described. By use of cathodic stripping square wave voltammetry, it is possible to determine low and subnanomolar levels of iodide in sea water, freshwater, and brackish water. Precision is typically +/-5% (1sigma). The minimum detection limit is 0.1-0.2 nM (12 parts per trillion) at a 180-s deposition time. Data obtained on Atlantic Ocean samples show similar trends to previously reported iodine speciation data. This method is more sensitive than previous methods by 1-2 orders of magnitude. Triton X-100 added to the sample enhances the mercury electrode's sensitivity to iodide.

Luther, G.W. III; Swartz, C.B.; Ullman, W.J.

1988-09-01

372

Demonstration of High Current Density YBCO Coated Conductors on RE2O3-Buffered Ni Substrates with Two New Alternative Architectures  

SciTech Connect

In continuation of our effort to develop single buffer layer architectures for YBCO (YBa2Cu3O7-g) coated tape conductors, we have studied RE2O3 (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE2O3 buffer layers were grown epitaxiahy on {100}<001> textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y2O3, Eu2O3, Gd2O3, and Yb2O3 were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High Jc YBCO films were grown on RE2O3-buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high Jc of 1.8 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb2O3 (sputtered)/Y2O3 (e-beam)/Ni. Also, a high Jc of over 1 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF2 process)/CeO2 (sputtered)YSZ sputtered)/RE2O3 (sol-gel or e-beam)Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.

Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Cui, X.; Feenstra, R.; Goyal, A.; Kroeger, D.M.; Lee, D.F.; Martin, P.M.; Mathis, J.E.; Morrell, J.S.; Norton, D.P.; Paranthaman, M.; Specht, E.D.; Verebelyi, D.T.

1999-07-12

373

Comparative energies of alternative fuels  

Microsoft Academic Search

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

E. M. Goodger

1978-01-01

374

Module Six: Alternate Energy Sources.  

National Technical Information Service (NTIS)

This module is designed to give the student an overview of current research and development in the following areas of alternate energy: solar, wind, oceanic, biomass conversion, geothermal, nuclear and others. A discussion of the current cost feasibility ...

1980-01-01

375

Measurement of nanomolar levels of psychoactive drugs in urine by adsorptive stripping voltammetry.  

PubMed

Adsorptive stripping voltammetry was used to determine nanomolar levels of the benzodiazepines pinazepam, camazepam, bromazepam and thienodiazepine (BrTDO) in urine. Measurements were made by differential pulse voltammetry at a hanging mercury drop electrode. The influences of various operational conditions on the stripping response were examined. The optimum accumulation potentials and accumulation times were -0.40 V and up to 60 sec for pinazepam, -0.60 V and up to 40 sec for camazepam, -0.40 V and up to 30 sec for bromazepam and -0.60 V and up to 60 sec for BrTDO, respectively. The effects of various urine components on the voltammetric response were also studied, and preliminary separation of the drugs was found necessary because of interference by creatinine and uric acid. The proposed method is appropriate for the determination of the four drugs in urine up to the 1000 ng/ml level with short accumulation periods (10-60 sec). The relative standard deviation for the 500 ng/ml level of the drugs in urine (30-sec accumulation) was less than 3%. PMID:18964514

Hernandez, L; Zapardiel, A; Perez Lopez, J A; Bermejo, E

1988-04-01

376

A contribution to the problem of increasing fhe sensitivity of anodic-stripping voltammetry.  

PubMed

A brief discussion of problems connected with increasing the sensitivity of anodic-stripping determinations is presented. A new microcell for anodic-stripping voltammetry in solution volumes down to about 0.01 ml was constructed. The effect of the solution volume, the mercury-drop electrode size, and of the pre-electrolysis time and potential on the sensitivity of determinations was studied and the reproducibility of results for determinations of lead in mineral acids is given. It was found that nanogram amounts of heavy metals can easily be determined in this way. In determination of 2 ng of Pb(2+) in 0.02 ml of solution the results were 2.00 +/- 0.13 ng (95% confidence limits), the mean relative deviation being 6.3%. For determination of copper in KNO(3), stripping microanalysis was compared with atomic-absorption spectrophotometry. Advantages and disadvantages of stripping voltammetry on the macro- and micro-scales are discussed. PMID:18961184

Huderová, L; Stulík, K

1972-11-01

377

Comparison of the brain penetration injury associated with microdialysis and voltammetry  

PubMed Central

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

Jaquins-Gerstl, Andrea; Michael, Adrian C.

2009-01-01

378

Alternative fuels  

SciTech Connect

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

Not Available

1991-07-01

379

Alternatives to blood transfusion.  

PubMed

The use of alternatives to allogeneic blood continues to rest on the principles that blood transfusions have inherent risks, associated costs, and affect the blood inventory available for health-care delivery. Increasing evidence exists of a fall in the use of blood because of associated costs and adverse outcomes, and suggests that the challenge for the use of alternatives to blood components will similarly be driven by costs and patient outcomes. Additionally, the risk-benefit profiles of alternatives to blood transfusion such as autologous blood procurement, erythropoiesis-stimulating agents, and haemostatic agents are under investigation. Nevertheless, the inherent risks of blood, along with the continued rise in blood costs are likely to favour the continued development and use of alternatives to blood transfusion. We summarise the current roles of alternatives to blood in the management of medical and surgical anaemias. PMID:23706802

Spahn, Donat R; Goodnough, Lawrence T

2013-05-25

380

The Study of a New Method to Determine Copper Ion by Square-Wave Voltammetry-Extraction Iodometry at the Liquid/Liquid Interfaces  

PubMed Central

A new method of indirect determination of Cu2+ was developed based on square-wave voltammetry by the oxidation of iodide in organic solvent at the liquid/liquid (L/L) interface. The limit of detection for the determination of Cu2+ in this method was found to be 5 × 10?4 mol/L, and the concentration ranged up to 1 × 10?2 mol/L gave a linear limiting current versus concentration response. For the same simulated wastewater, this method showed high accuracy compared with the result tested by sodium diethyldithiocarbamate extraction spectrophotometry. This approach could be applied to the indirect determination of the oxidative heavy metals in the industrial wastewater.

Shi, Changyan; Xie, Shaoai; Jia, Jinping

2008-01-01

381

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.

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

2014-01-01

382

Immobilization of hemoglobin on electrodeposited cobalt-oxide nanoparticles: direct voltammetry and electrocatalytic activity.  

PubMed

Cyclic voltammetry at potential range -1.1 to 0.5 V from aqueous buffer solution (pH 7) containing CoCl(2) produced a well defined cobalt oxide (CoOx) nanoparticles deposited on the surface of glassy carbon electrode. The morphology of the modified surface and cobalt oxide formation was examined with SEM and cyclic voltammetry techniques. Hemoglobin (Hb) was successfully immobilized in cobalt-oxide nanoparticles modified glassy carbon electrode. Immobilization of hemoglobin onto cobalt oxide nanoparticles have been investigated by cyclic voltammetry and UV-visible spectroscopy. The entrapped protein can take direct electron transfer in cobalt-oxide film. A pair of well defined, quasi-reversible cyclic voltammetric peaks at about -0.08 V vs. SCE (pH 7), characteristic of heme redox couple (Fe(III)/Fe(II)) of hemoglobin, and the response showed surface controlled electrode process. The dependence of formal potential (E(0')) on the solution pH (56 mV pH(-1)) indicated that the direct electron transfer reaction of hemoglobin was a one-electron transfer coupled with a one proton transfer reaction process. The average surface coverage of Hb immobilized on the cobalt oxide nanoparticles was about 5.2536x10(-11) mol cm(-2), indicating high loading ability of nanoparticles for hemoglobin entrapment. The heterogeneous electron transfer rate constant (k(s)) was 1.43 s(-1), indicating great of facilitation of the electron transfer between Hb and electrodeposited cobalt oxide nanoparticles. Modified electrode exhibits a remarkable electrocatalytic activity for the reduction of hydrogen peroxide and oxygen. The Michaels-Menten constant K(m) of 0.38 mM, indicating that the Hb immobilized onto cobalt oxide film retained its peroxidases activity. The biosensor exhibited a fast amperometric response <5 s, a linear response over a wide concentration range 5 microM to 700 microM and a low detection limit 0.5 microM. According to the direct electron transfer property and enhanced activity of Hb in cobalt oxide film, a third generation reagentless biosensor without using any electron transfer mediator or specific reagent can be constructed for determination of hydrogen peroxide in anaerobic solutions. PMID:17825977

Salimi, Abdollah; Hallaj, Rahman; Soltanian, Saied

2007-11-01

383

Current Drive  

SciTech Connect

Certain devices aimed at magnetic confinement of thermonuclear plasma rely on the steady flow of an electric current in the plasma. In view of the dominant place it occupies in both the world magnetic-confinement fusion effort and the author's own activity, the tokamak toroidal configuration is selected as prototype for discussing the question of how such a current can be maintained. Tokamaks require a stationary toroidal plasma current, this being traditionally provided by a pulsed magnetic induction which drives the plasma ring as the secondary of a transformer. Since this mechanism is essentially transient, and steady-state fusion reactor operation has manifold advantages, significant effort is now devoted to developing alternate steady-state means of generating toroidal current. These methods are classed under the global heading of 'noninductive current drive' or simply 'current drive', generally, though not exclusively, employing the injection of waves and/or toroidally directed particle beams. In what follows we highlight the physical mechanisms underlying surprisingly various approaches to driving current in a tokamak, downplaying a number of practical and technical issues. When a significant data base exists for a given method, its experimental current drive efficiency and future prospects are detailed.

Faulconer, D.W

2004-03-15

384

Alternating and direct current field effects on the structure-property relationships in Na0.5Bi0.5TiO3-x%BaTiO3 textured ceramics  

NASA Astrophysics Data System (ADS)

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]PC textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature Td in poled samples resulted from a tetragonal --> pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on Td: ac drive decreased the Td, 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; Maurya, Deepam; Li, Jiefang; Priya, Shashank; Viehland, D.

2013-06-01

385

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

386

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

387

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

PubMed

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

Hoyer, B; Jensen, N

1994-03-01

388

Cyclic voltammetry: A new strategy for the evaluation of oxidative damage to bovine insulin  

PubMed Central

Research on protein oxidative damage may give insight into the nature of protein functions and pathological conditions. In this work, the oxidative damage of bovine insulin on Au electrode was investigated by cyclic voltammetry (CV). The experimental results show that there are two anodic peaks for the oxidative damage of bovine insulin, which arise from the oxidation of the exposed disulfide bond S—SCYS7A,CYS7B, forming sulfenic acid RSOH (1.20 V, vs. SCE), sulfinic acid RSO2H and sulfonic acid RSO3H (1.35 V, vs. SCE). These in vitro findings not only demonstrate the applicability of CV in simulating/evaluating the oxidative damage of nonredox proteins but also find two promising candidates (two anodic peaks) for measuring insulin.

Zong, Wansong; Liu, Rutao; Sun, Feng; Wang, Meijie; Zhang, Pengjun; Liu, Yihong; Tian, Yanmin

2010-01-01

389

Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry  

PubMed Central

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

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

2008-01-01

390

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

Valdez, Penelope S.

2001-11-01

391

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

392

Alternating current losses in superconducting coils  

NASA Technical Reports Server (NTRS)

Report examines relationship between coil loss and frequency and heat loss in coil as a function of the magnetic field H. Information is of value to manufacturers of superconducting magnets, motors and generators.

Wipf, S. L.; Guderjahn, C. A.

1972-01-01

393

An alternative to current looping syntax  

Microsoft Academic Search

There has been a lot of discussion lately about the drawbacks of various language structures [2] and the lack of the same structures in older programming languages (Fortran) [1]. In this brief paper I propose a modest alteration to programming languages and present a simple pre-processor written in Fortran that implements the alteration.

David Taylor

1984-01-01

394

Alternating-Current Resistance of Rectangular Conductors  

Microsoft Academic Search

New experimental data are presented for conductors having ratios of width to thickness of 1 to 1 to 2400 to 1 for frequencies up to eight kilocycles. These data are co-ordinated with existing data furnishing an experimental proof of the \\

S. J. Haefner

1937-01-01

395

Alternating Current Spectroscopy of Biological Substances  

Microsoft Academic Search

The electrical properties of live matter are analyzed. The article first summarizes general principles which pertain to the frequency dependence of the electrical properties of any type of matter. It then states the particular mechanism which, at various parts of the total frequency spectrum, are predominantly responsible for observed data. They include time-dependent interface polarization, accumulation of charges due to

H. P. Schwan

1959-01-01

396

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

397

Alternatives in Teacher Education.  

ERIC Educational Resources Information Center

This paper on alternatives in teacher education begins by analyzing the current emphasis on the scientific approach in education. The author finds the promise of the scientific approach to be illusory. He defines it as education that promotes behavior change in some desirable direction. However, this definition, which the author finds equally…

Clements, Millard

398

Alternative energy technologies  

NASA Astrophysics Data System (ADS)

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.

Dresselhaus, M. S.; Thomas, I. L.

2001-11-01

399

Alternative energy technologies.  

PubMed

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. PMID:11713539

Dresselhaus, M S; Thomas, I L

2001-11-15

400

Alternatives to GPS  

Microsoft Academic Search

The U.S. Navy is currently pursuing several approaches to improving the reliability of precision navigation systems, including those that would still permit precision navigation in the event that the Global Positioning System (GPS) is denied or unavailable. This paper examines two alternatives to GPS: bathymetric and celestial navigation. Bathymetric navigation, a non-deniable source of position, determines a position by correlating

F. Pappalardi; S. J. Dunham; M. E. LeBlang; T. E. Jones; J. Bangert; G. Kaplan

2001-01-01

401

An Alternative to Failure.  

ERIC Educational Resources Information Center

Recommends six strategies to motivate underachieving students to perform better in reading and mathematics, including, for example, being honest with students about their current level of performance and expecting them to be responsible for their own progress. Discusses positive results of these strategies at Colorado's Finest Alternative High…

Tufly, Cher

2001-01-01

402

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

403

Archive Storage Media Alternatives.  

ERIC Educational Resources Information Center

Reviews requirements for a data archive system and describes storage media alternatives that are currently available. Topics discussed include data storage; data distribution; hierarchical storage architecture, including inline storage, online storage, nearline storage, and offline storage; magnetic disks; optical disks; conventional magnetic…

Ranade, Sanjay

1990-01-01

404

Note: High resolution alternating current/direct current Harman technique  

NASA Astrophysics Data System (ADS)

This note describes the construction and engineering of a high precision Harman set-up for metrology of the thermoelectric figure of merit (ZT) of modules and materials based on steady state AC and DC measurements. The Harman technique presented in this article has a resolution of milli-ZT and it does not employ lock-in amplifiers or AC bridges; rather, the technique is developed to avoid typical complications experienced in AC Harman systems. By one-time reference measurements the best operation point for the system is chosen, minimizing the effects of capacitive loads due to AC signals.

Chavez, R.; Becker, A.; Bartel, M.; Kessler, V.; Schierning, G.; Schmechel, R.

2013-10-01

405

Unprecedented stable aqueous semiquinone methide radical formation interferes with adsorptive cathodic stripping voltammetry of cobalt methyl thymol blue  

Microsoft Academic Search

A putatively highly sensitive and selective method for the determination of cobalt in aqueous samples by catalytic adsorptive cathodic stripping voltammetry using methyl thymol blue (MTB) as the ligand has been documented [A. Safavi, E. Shams, Talanta 51 (2000) 1117] and its underlying mechanism has been briefly explored [A. Safavi, E. Shams, Electroanalysis 14 (2002) 708]. In an attempt to

Alidin N. Niztayev; Wilfred R. Hagen

2005-01-01

406

Fast Fourier Transform Continuous Cyclic Voltammetry Development as a Highly Sensitive Detection System for Ultra Trace Monitoring of Thiamine  

Microsoft Academic Search

In this work, a highly sensitive method for the fast monitoring of thiamine hydrocholoride in flow?injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFCV) in flowing solution as a detection system was applied for the very fast monitoring of thiamine in its pharmaceutical formulations. This technique is very simple, precise, accurate, time?saving and economical, compared to

P. Norouzi; M. R. Ganjali; P. Daneshgar; A. Mohammadi

2007-01-01

407

An optimization procedure for determination of metallothionein by square wave cathodic stripping voltammetry: application to marine worms  

Microsoft Academic Search

Electrochemical determination of metallothionein (MT) is widely used for environmental studies. This article describes the development and optimization of the procedure for the quantification of metallothionein by square wave cathodic stripping voltammetry. The determination is based on the complexation of cisplatin and MT and the subsequent reduction of the complexes at the electrode. In order to achieve the highest possible

Arnaud Dudoit; Jean-Claude Amiard

2004-01-01

408

Flat-Band Potential of n-Type Semiconducting Molybdenum Disulfide by Cyclic Voltammetry of Two-Electron Reductants: Interface Energetics and the Sustained Photooxidation of Chloride.  

National Technical Information Service (NTIS)

Cyclic voltammetry has been used to locate the band edges of n-type MoS2 in CH3CN/ and EtOH/n-Bu4Nc104 solutions. The crucial experiments concern the study of the cyclic voltammetry of biferrocene (BF) and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) e...

L. F. Schneemeyer M. S. Wrighton

1979-01-01

409

Alternative treatment.  

PubMed

Alternatives to endometrial ablation include re-education of the 20% or more women complaining of menorrhagia whose blood loss is normal, less than 35 ml, and the use of an increasing variety of drugs to find an effective regime with minimal side effects. Endometrial resection is an effective treatment, particularly in the short term. Laparoscopic and vaginal hysterectomy have advantages over endometrial resection in the long term, avoiding failure and retreatment for menorrhagia. Hysteroscopic, laparoscopic and open myomectomy are more suitable in treating fibroids of significant size, although these techniques may be used with endometrial resection to avoid hysterectomy. Myoma reduction may become a less morbid alternative to myomectomy. PMID:7554619

Wood, C

1995-06-01

410

Imaging local electrochemical current via surface plasmon resonance.  

PubMed

We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals. PMID:20223983

Shan, Xiaonan; Patel, Urmez; Wang, Shaopeng; Iglesias, Rodrigo; Tao, Nongjian

2010-03-12

411

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

412

Alternative drugs of abuse.  

PubMed

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

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

2014-02-01

413

Complementary and Alternative Medicine for Multiple Sclerosis  

MedlinePLUS

... for PATIENTS and their FAMILIES COMPLEMENTARY AND ALTERNATIVE MEDICINE FOR MULTIPLE SCLEROSIS This fact sheet is provided ... understand the current evidence regarding complementary and alternative medicine (CAM) for treatment of multiple sclerosis (MS). The ...

414

Determination of lead and cadmium in titanium dioxide by differential pulse anodic stripping voltammetry.  

PubMed

A procedure for the simultaneous determination of lead and cadmium in TiO(2) by differential pulse anodic stripping voltammetry (ASV) has been developed. The key feature of the method is the use of triethanolamine (TEA) to remove titanium interference: TiO(2) undergoes acidic digestion with HF/H(2)SO(4) at atmospheric pressure, TEA is added to the HCl solution of the residue and the solution is analysed using a standard ASV instrumentation, equipped with a hanging mercury drop electrode. The calibration curves for both lead and cadmium are linear up to 50 mugl(-1) of solution, and the detection limits are 1 mugl(-1), corresponding to 1 mugg(-1) of TiO(2). Method reliability was tested by comparing the results with those given by electrothermal atomic absorption spectroscopy. The method has been successfully applied for determination of both contaminants in powdered titanium dioxide (raw materials) and in titanium dioxide-containing cosmetics (sunscreen products). PMID:18968775

Panigati, Monica; Piccone, Maria; D'Alfonso, Giuseppe; Orioli, Marica; Carini, Marina

2002-09-12

415

Rapid determination of picomolar titanium in seawater with catalytic cathodic stripping voltammetry.  

PubMed

Titanium (Ti) is present as a trace element in seawater at extremely low concentrations (5-350 pM, where 1 pM = 10(-12) mol L(-1)) throughout the water column. Presently, little is known about the marine biogeochemistry of Ti and there is a distinct lack of oceanic measurements of Ti , because of the combined difficulties of trace-metal clean sampling for an element at such low levels and the lack of a suitable shipboard method of analysis. Here, a new cathodic stripping voltammetry procedure is presented for the rapid determination of Ti at pM concentrations in seawater that is capable of being used directly at sea. This method utilizes the catalytic enhancement of the reduction of the complex formed between Cupferron (N-nitrosophenylhydroxylamine) and Ti(IV). While Cupferron itself acts as both a complexing agent and an oxidizing agent, it was found that the optimal sensitivity was with bromate as an auxiliary oxidant. An advantage of this method is that it is useable over the pH range of 5.5-8. Under the conditions employed in this work, detection limits ranged from 5 pM to 12 pM. This new catalytic method is significantly more sensitive than existing methods and has been extensively tested at sea in the Atlantic and Southern Oceans. PMID:21761912

Croot, Peter L

2011-08-15

416

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 -0.60V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3M reference electrode) during 60s, 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

417

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

418

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

PubMed

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

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

2014-10-01

419

Separation of organotin compounds by ion-exchange chromatography and their determination by inverse voltammetry.  

PubMed

An ion exchange procedure was developed for the enrichment, separation and quantification of butyltin and phenyltin species, which show very close half wave potentials by their voltammetric determination. As a case study the separation of dibutyltin (DBT) from triphenyltin (TPT) was investigated. Among different ion exchangers tested, the strong acid ion exchanger PUROLITE C100H, used for industrial purposes, was found to be the most suitable. By using a resin bed volume of 25 mL, a flow rate of the feed solution of 1 mL/min and 3 M HCl in methanol as eluent with a flow rate of 0.5 mL/min, a recovery rate of each species of about 80% could be achieved. The detection limit for the determination of DBT and TPT by anodic stripping voltammetry after their separation and enrichment by the above mentioned ion exchange procedure was found to be 0.4 ng/mL for DBT and 6 ng/mL for TPT in the feed solution, respectively. The applicability of the whole procedure was tested on a sediment candidate reference material of BCR (Bureau of Reference Community). PMID:11371062

Ochsenkühn, K M; Ochsenkühn-Petropoulou, M; Tsopelas, F; Mendrinos, L

2001-04-01

420

Square wave voltammetry in the determination of Ni2+ and Al3+ in biological sample.  

PubMed

In this contribution, the amounts of Ni (nickel) and Al (aluminum) in tilapias (Oreochromis niloticus) were determined using square wave voltammetry (SWV) with glassy carbon working microelectrode with a mercury thin film, platinum counter electrode, and Ag/AgCl reference electrode. Ni was studied through the formation of the dimethylglyoxime-Ni (Ni-DMG) complex, while Al was studied through the formation of the Alizarin R-Al complex. The detection limit found for Ni-DMG and Alizarin R-Al complexes were 1.70 x 10(-7) and 1.0 x 10(-8) mol L(-1), respectively. The voltammetric anodic curves for the Alizarin R-Al complex were recorded over the potential range from -0.8 to -0.05 V while the voltammetric cathodic curve for the Ni-DMG complex was recorded over the potential range from -0.7 to -1.2 V. These methods detected low concentrations of Ni and Al in biological samples efficiently. PMID:18997373

Paulino, Alexandre T; Vargas, Alexandro M M; Santos, Lídia B; Nozaki, Jorge; Muniz, Edvani C; Tambourgi, Elias B

2008-01-01

421

Determination of the leaching of polymeric ion-selective membrane components by stripping voltammetry.  

PubMed

This paper focuses on the quantitative determination of the loss of the components from plastic membranes of ion-selective electrodes (ISEs) during contact with aqueous bathing solutions. The leaching processes, which affect the ISE responses, are rarely characterized by independent methods. For this purpose, differential pulse cathodic stripping voltammetry (DP CSV) is used. This method, owing to its high sensitivity, acceptable recovery and accuracy, is a good tool to characterize the kinetics of leakage of the lipophilic salts. Sodium tetraphenylborate (NaTPB) leakage from the PVC-based sodium-selective membrane containing two different plasticizers, o-nitrophenyl octyl ether (o-NPOE) or di(2-ethylhexyl) sebacate (DOS) is presented. Correlation between the rate of leaching of the lipophilic salt and dielectric constants of the plasticizers is observed. The data obtained by DP CSV correlate well with potentiometric and electrochemical impedance responses. The observed outflow of TPB(-) is associated with decreasing potentiometric sensitivity to sodium and increasing bulk membrane resistance. PMID:20298885

Paczosa-Bator, Beata; Piech, Robert; Lewenstam, Andrzej

2010-05-15

422

Feedback Effects in Combined Fast-Scan Cyclic Voltammetry-Scanning Electrochemical Microscopy  

PubMed Central

Fast-scan cyclic voltammetry at scan rates between 5 and 1000 Vs?1 was performed at the tip of a scanning electrochemical microscope immersed in a solution of redox mediator. The effect of conducting and insulating substrates on the voltammetric signal was investigated as a function of scan rate and tip-substrate distance. It was found that diffusional interactions between the tip and the substrate are greatest at lower scan rates and on the reverse sweep of the voltammogram. At the fastest scan rates used, the tip could be brought to with 1 ?m of the substrate without appreciable perturbation of the voltammogram. By selecting scan rates and tip-substrate distances such that feedback effects were negligible, it was possible to image the diffusion layer of a 10 ?m Pt substrate electrode. With the tip placed 1 ?m above a biological cell, tip-substrate diffusional interactions were greatly diminished at a scan rate of 100 Vs?1, and absent at a scan rate of 1000 Vs?1. These results suggest conditions can be selected that allow chemical imaging of substrates without the feedback interactions typically encountered in scanning electrochemical microscopy.

Schrock, Daniel S.; Wipf, David O.; Baur, John E.

2008-01-01

423

Determination of Anionic Surfactants Using Atomic Absorption Spectrometry and Anodic Stripping Voltammetry  

NASA Astrophysics Data System (ADS)

An experiment has been developed for our undergraduate analytical chemistry course that demonstrates the indirect analysis of anionic surfactants by techniques normally associated with metal ion determination; that is, atomic absorption spectroscopy (AAS) and anodic stripping voltammetry (ASV). The method involves the formation of an extractable complex between the synthetic surfactant anion and the bis(ethylenediamine)diaqua copper(II) cation. This complex is extracted into chloroform and then back-extracted into dilute acid. The resulting Cu(II) ions are determined by AAS and ASV. Students are required to determine the concentration of a pre-prepared "unknown" anionic surfactant solution and to collect and analyze a real sample of their choice. After the two extraction processes, students typically obtain close to 100% analytical recovery. Correlation between student AAS and ASV results is very good, indicating that any errors that occur probably result from their technique (dilutions, extractions, preparation of standards, etc.) rather than from the end analyses. The experiment is a valuable demonstration of the following analytical principles: indirect analysis; compleximetric analysis; liquid-liquid (solvent) extraction; back-extraction (into dilute acid); analytical recovery; and metal ion analysis using flame-AAS and ASV.

John, Richard; Lord, Daniel

1999-09-01

424

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.

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

2010-01-01

425

Detection of endogenous dopamine changes in Drosophila melanogaster using fast-scan cyclic voltammetry.  

PubMed

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. Stimulations of 7 s 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 min intervals are stable for 65 min, 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

2009-11-15

426

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

PubMed Central

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

2013-01-01

427

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

PubMed Central

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

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

2009-01-01

428

Study of the Hg2+ binding with chelation therapy agents by differential pulse voltammetry on rotating Au-disk electrode and electrospray ionization mass-spectrometry.  

PubMed

A recently proposed electroanalytical method, using differential pulse voltammetry (DPV) on the rotating Au-disk electrode, and electrospray ionization mass-spectrometry (ESI-MS) has been applied to study the binding of the pharmaceutical chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropanesulfate (DMPS) and D-penicillamine (D-Pen) with Hg(2+). From the use of voltammetric titrations it was possible to obtain a detailed picture of the complexation processes at concentrations much lower than in previous studies. Predominant species were Hg(Pen)(2), Hg(2)(DMSA)(2) and Hg(DMPS)(2). For Pen, Hg(Pen) was also deduced from DPV data, while Hg(2)(Pen)(4) from ESI-MS. For DMSA and DMPS, Hg(2)L species were detected by DPV, and Hg(2)L(3), Hg(3)L(3) as well as Hg(2)(DMPS)(2) and Hg(DMSA)(2) by ESI-MS. When possible, DPV data were analyzed by multivariate curve resolution with alternating least squares (MCR-ALS). PMID:19800477

Chekmeneva, Elena; Díaz-Cruz, José Manuel; Ariño, Cristina; Esteban, Miquel

2009-10-19

429

Layer-by-layer identification of copper alteration products in metallic works of art using the voltammetry of microparticles.  

PubMed

An in situ technique for layer-by-layer electrochemical analysis of solid surfaces using the voltammetry of microparticles is presented. The method is based on the determination of several shape-dependent parameters for voltammetric curves recorded at a graphite pencil working electrode in contact with the sample, all immersed into aqueous electrolytes. Repetitive square wave voltammetry and sequential application of constant potential reductive steps and voltammetric scans yield discernible responses for the corrosion products distributed in stratified layers on metal-based surfaces. This methodology is applied to identify alteration products of copper and copper alloys distributed in different layers in copper coupons submitted to different corrosive treatments and a contemporary brass sculpture. PMID:20969984

Doménech, Antonio; Doménech-Carbó, María Teresa; Martínez-Lázaro, Isabel

2010-11-01

430

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

431

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

432

Use of Cyclic Voltammetry to Evaluate Sorption Properties of Cork Residues Towards Mn(II) in Waters  

Microsoft Academic Search

Cyclic voltammetry is proposed for evaluating the ability of cork wastes to remove Mn(II) ions by sorption from waters to\\u000a be used for public supply. As the first stage, the concentration of several naturally occurring cations (Ca2+, Mg2+, K+ and Na+) were analyzed in the acid washings that were performed to remove them from the cork. The obtained results were

Valeria M. Nurchi; Rosalba Pinna; Nuria Fiol; Isabel Villaescusa

2008-01-01

433

Direct determination of d-panthenol and salt of pantothenic acid in cosmetic and pharmaceutical preparations by differential pulse voltammetry  

Microsoft Academic Search

d-Panthenol (provitamin B5) and salt of pantothenic acid are used in many cosmetic and pharmaceutical preparations for their skin emollient, regenerating and hair conditioning properties. The cathodic reduction of d-panthenol and salt of pantothenic acid had been studied by differential pulse voltammetry (DPV) at carbon paste electrode (CPE) and metal oxides modified CPE in the presence of cationic surfactants (stearyltrimethylammonium

Lai-Hao Wang; Shih-Wen Tseng

2001-01-01

434

Temperature-programmed reduction and cyclic voltammetry of Pt\\/carbon-fibre paper catalysts for methanol electrooxidation  

Microsoft Academic Search

Temperature-programmed reduction (TPR) and cyclic voltammetry (CV) studies of platinum catalysts supported on pyrographite-coated carbon-fibre paper, and prepared by either ion exchange or impregnation, clearly demonstrate the nature of the interactions between the platinum species and the support. After drying the above catalysts at 120°C, the ion-exchanged preparation exhibits the stronger interaction with the carbon support, as might be expected

P. A. Attwood; B. D. McNicol; R. T. Short

1981-01-01

435

Determination of sub-nanomolar concentrations of lead in sea water by adsorptive stripping voltammetry with xylenol orange  

Microsoft Academic Search

Highly sensitive procedures are presented for the determination of sub-nanomolar concentrations of total dissolved lead and labile lead in sea water by adsorptive cathodic stripping voltammetry with ligand competition using xylenol orange (XO). Optimal analytical conditions were found to be an XO concentration of 1 × 10?5 M, a pH of 5, and an adsorption potential at ?1.2 V vs.

Qingguo Wu; Graeme E. Batley

1995-01-01

436

Gold Nanoparticle Determination by Inductively Coupled Plasma – Mass Spectrometry, Anodic Stripping Voltammetry, and Flame Atomic Absorption Spectrophotometry  

Microsoft Academic Search

Gold Nanoparticles (AuNP) were measured by Inductively Coupled Plasma–Mass Spectrometry (ICP-MS), Anodic Stripping Voltammetry (SV), and flame Atomic Absorption Spectrophotometry (AAS). Experiments investigated the relationships between counts per second (ICP-MS), absorbance (AAS), or ?A (SV) and Au concentrations in solutions bearing AuNP with sizes of 5, 15 and 50 nm. Similarly the impact of the solution matrix was assessed using deionized

Andrew Gillespie; Dave Jao; Angelo Andriola; Tyler Duda; Catherine F. Yang; Lei Yu

2012-01-01

437

Anodic stripping voltammetry of inorganic species of As 3+ and As 5+ at gold-modified boron doped diamond electrodes  

Microsoft Academic Search

Electrochemical detection of mixture solutions of As3+ and As5+ has been investigated by stripping voltammetry at gold-modified diamond electrodes. The method was performed based on stripping oxidation of As0 deposited at the electrode surface. Whereas As3+ can be deposited by simple electrochemical reduction of As3+ to As0 at ?0.4V (vs. Ag\\/AgCl), much higher potential is required to overcome the activation

Daisuke Yamada; Tribidasari A. Ivandini; Motoharu Komatsu; Akira Fujishima; Yasuaki Einaga

2008-01-01

438

Determination of trace impurities in high-purity reagents by mercury thin-film anodic-stripping voltammetry  

Microsoft Academic Search

Summary The use of an amalgamated silver-wire electrode, providing a relatively large rate of film area to volume of mercury, seems to present several advantages over the use of the hanging mercury drop electrode (HMDE) for the determination of trace impurities by anodic-stripping voltammetry (ASV). Peak resolution and sensitivity have both been improved by use of the mercury thin-film electrode

Y. Israel; T. Ofir; J. Rezek

1978-01-01

439

Cyclic voltammetry for the fabrication of high dense silver nanowire arrays with the assistance of AAO template  

Microsoft Academic Search

Highly ordered Ag nanowire arrays with high aspect ratio and highly dense self-supporting Ag nanowire patterns were successfully prepared using cyclic voltammetry with the assistance of anodic aluminum oxide (AAO) template from AgNO3 aqueous solution without any additives. The diameter of the Ag nanowire in the arrays is about 60nm and the length can be tuned from 30 to 1?m

Xiu-Yu Sun; Fa-Qiang Xu; Zong-Mu Li; Wen-Hua Zhang

2005-01-01

440

Cyclic voltammetry and viscosity measurements of aggregated assemblies of anionic surfactants with nonionic surfactants and triblock copolymers  

Microsoft Academic Search

Cyclic voltammetry (CV) and viscosity measurements have been employed to study the aggregation behavior of mixed micellar\\u000a systems of anionic surfactant (dioctyl sulfosuccinate sodium salt, AOT) with conventional nonionic surfactants such as Brij\\u000a 35\\/TritonX-100\\/Tween 20\\/Tween 80\\/Myrj 45 and two triblock copolymers (L64 and F68). Critical micelle concentration (cmc) values\\u000a have been determined for various micellar systems from CV measurements using

Rabia Sharma; Arifa Shaheen; Rakesh Kumar Mahajan

2011-01-01

441

Iron–cobalt and iron–cobalt–nickel nanowires deposited by means of cyclic voltammetry and pulse-reverse electroplating  

Microsoft Academic Search

Metal nanowires composed of Fe–Co and Fe–Co–Ni alloys were successfully prepared by means of cyclic voltammetry (CV) and pulse-reverse (PR) electroplating techniques from acidic metal chloride solutions. The anodic dissolution process in the CVs or in the reverse electroplating period was found to be the key factor influencing the formation of metal nanowires. The addition of nickel into the Fe–Co

Allen Bai; Chi-Chang Hu

2003-01-01

442

Detection of dopamine overflow and diffusion with voltammetry in slices of rat brain.  

PubMed

Voltammetric electrodes have been used to monitor extracellular dopamine in rat brain slices. The electrode tips are small enough to be immersed inside the slice. Specificity for dopamine is increased through the use of voltammetry and a cation exchange membrane at the electrode tip. Dopamine overflow is observed in the caudate nucleus following electrical stimulation (60 Hz, 1 s, 3 V) with an adjacent bipolar electrode. The amount of overflow observed is increased when the tissue is perfused with 10 microM cocaine or nomifensine, both recognized inhibitors of dopamine uptake. The ability of dopamine in the perfusion buffer to permeate the slice was monitored with two voltammetric electrodes, one in the cerebral cortex and the other in the caudate nucleus. At a high concentration (100 microM), dopamine rapidly appeared (2.7 +/- 0.4 min) in the interior of the cortex, but dopamine was not observed in the caudate until a significantly later time (8.9 +/- 1.0 min). To examine whether this difference is a reflection of the presence of different uptake systems in the two regions, pressure ejection was employed. In this experiment a double-barrelled pipette was used to eject dopamine or DOPAC at a fixed distance (approximately 70 micron) from the voltammetric electrode. Ejection of small amounts of both substances could be detected in the cortex. When the ejector-detector assembly was moved to the caudate, dopamine could only be observed following pressure ejection after perfusion of the slice with 10 microM nomifensine. Detection of DOPAC was unaffected. All of these experiments indicate that uptake systems in the caudate keep dopamine concentrations very low in the extracellular fluid of the slice. PMID:3676822

Kelly, R S; Wightman, R M

1987-10-13

443

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

SciTech Connect

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

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

2012-12-15

444

Investigation of mediated oxidation of ascorbic acid by ferrocenemethanol using large-amplitude Fourier transformed ac voltammetry under quasi-reversible electron-transfer conditions at an indium tin oxide electrode.  

PubMed

The ability of the technique of large-amplitude Fourier transformed (FT) ac voltammetry to facilitate the quantitative evaluation of electrode processes involving electron transfer and catalytically coupled chemical reactions has been evaluated. Predictions derived on the basis of detailed simulations imply that the rate of electron transfer is crucial, as confirmed by studies on the ferrocenemethanol (FcMeOH)-mediated electrocatalytic oxidation of ascorbic acid. Thus, at glassy carbon, gold, and boron-doped diamond electrodes, the introduction of the coupled electrocatalytic reaction, while producing significantly enhanced dc currents, does not affect the ac harmonics. This outcome is as expected if the FcMeOH (0/+) process remains fully reversible in the presence of ascorbic acid. In contrast, the ac harmonic components available from FT-ac voltammetry are predicted to be highly sensitive to the homogeneous kinetics when an electrocatalytic reaction is coupled to a quasi-reversible electron-transfer process. The required quasi-reversible scenario is available at an indium tin oxide electrode. Consequently, reversible potential, heterogeneous charge-transfer rate constant, and charge-transfer coefficient values of 0.19 V vs Ag/AgCl, 0.006 cm s (-1) and 0.55, respectively, along with a second-order homogeneous chemical rate constant of 2500 M (-1) s (-1) for the rate-determining step in the catalytic reaction were determined by comparison of simulated responses and experimental voltammograms derived from the dc and first to fourth ac harmonic components generated at an indium tin oxide electrode. The theoretical concepts derived for large-amplitude FT ac voltammetry are believed to be applicable to a wide range of important solution-based mediated electrocatalytic reactions. PMID:18666783

Lertanantawong, Benchaporn; O'Mullane, Anthony P; Zhang, Jie; Surareungchai, Werasak; Somasundrum, Mithran; Bond, Alan M

2008-09-01

445

Energy alternative  

SciTech Connect

A review of the world's peat resources and the technologies for peat harvesting, dewatering, and utilization demonstrates that depending on the location of the peat deposits, region of energy need, scale of operation, and cost of other energy sources, peat can be an economical energy alternative for either direct combustion or production of synthetic fuels. The ease with which peat can be harvested and its generally low sulfur and ash contents make it a good fuel for direct combustion, whereas its high hydrogen content gives it a high tendency to form hydrocarbon gases during thermal conversion. Hydrogasification tests with peat yielded 3 1/2 times the amount of hydrocarbon gases produced by the conversion of lignite and subbituminous coal under similar conditions.

Schora, F.C.; Punwani, D.V.

1980-01-01

446

Properties of an alternating copolymer and its applications in LEDs and photovoltaic cells  

Microsoft Academic Search

To obtain a dual-functional polymeric semiconductor for efficient red-light emission and high-performance photovoltaic cells, an alternating copolymer containing triphenylamine (TPA; as donors) and cyano-substituted phenylene (as acceptors), TPA-CNPPV, was synthesized by Wittig reaction. The polymer was characterized by FT-IR, 1H-NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Cyclic voltammetry (CV) measurements showed that the polymer presented reversible oxidation and

Hongmin Huang; Qingguo He; Hongzhen Lin; Fenglian Bai; Yong Cao

2005-01-01

447

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.

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

448

Constant Current Strain Gauge Bridge.  

National Technical Information Service (NTIS)

All the early electrical strain gauge bridge circuits employed constant voltage sources for bridge excitation. The techniques developed for the classical direct-current and alternating-current component-measuring bridges were transferred to the strain gau...

E. S. Moody

1984-01-01

449

Comparison of copper speciation in estuarine water measured using analytical voltammetry and supported liquid membrane techniques.  

PubMed

The supported liquid membrane (SLM) is a promising separation and preconcentration technique that is well-suited for trace metal speciation in natural waters. The technique is based on the selective complexation of metal ions by a hydrophobic ligand (carrier) dissolved in a water-immiscible organic solvent immobilized in a porous, inert membrane. This membrane separates two aqueous solutions: the test (or donor) solution and the strip (or acceptor) solution. The metal carrier complex is transported by diffusion across the membrane from the source to the strip solution where metal ions are back-extracted. The technique offers great potential to tune the selectivity by incorporating different complexing ligands in the membrane. A SLM was used to analyze the dissolved (<0.45 microm) copper speciation from two sites in the San Francisco Bay estuary; Dumbarton Bridge, [Cu]total approximately 27 nM, and San Bruno Shoals, [Cu]total approximately 23 nM. The sites were also characterized independently by differential pulse anodic stripping voltammetry (DPASV) using a Nafion-coated thin mercury film electrode (NCTMFE). The SLM employed 10 mM lasalocid, a naturally occurring carboxylic polyether ionophore, in nitrophenyl octyl ether (NPOE) asthe membrane complexing ligand, supported by a microporous, polypropylene, hydrophobic membrane. This is the first study where SLM technique has been compared with an independent speciation technique in marine waters. Results of copper speciation measurements from Dumbarton Bridge, a site in South San Francisco Bay where copper speciation has been well-characterized in previous studies using various voltammetric techniques, indicated that only about 3% (0.9 nM) of the total dissolved copper was SLM labile. The corresponding DPASV labile copper fraction was <0.4% (<0.1 nM) of total dissolved copper. The concentration of total copper binding ligands measured by the membrane technique was 471 nM as compared to 354 nM measured by DPASV, more than 1 order of magnitude higher than the total dissolved copper concentration. The SLM measurements were consistent with earlier copper speciation measurements that were made in South San Francisco Bay using other voltammetric stripping techniques. PMID:15926567

Ndungu, Kuria; Hurst, Matthew P; Bruland, Kenneth W

2005-05-01

450

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 300nM, 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 Spectrosc