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1

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

PubMed

Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. PMID:24439508

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

2014-01-31

2

Comparison of the stem-loop and linear probe-based electrochemical DNA sensors by alternating current voltammetry and cyclic voltammetry.  

PubMed

Here we systematically characterized the sensor performance of the stem-loop probe (SLP) and linear probe (LP) electrochemical DNA sensors using alternating current voltammetry (ACV) and cyclic voltammetry (CV), with the goal of generating the set of operational criteria that best suits each sensor architecture, in addition to elucidating the signaling mechanism behind these sensors. Although the LP sensor shows slightly better % signal suppression (SS) upon hybridization with the perfect match target at 10 Hz, our frequency-dependent study suggests that it shows optimal % SS only in a very limited AC frequency range. Similar results are observed in CV studies in which the LP sensor, when compared to the SLP sensor, displays a narrower range of voltammetric scan rates where the optimal % SS can be achieved. More importantly, the difference between the two sensors' performance is particularly pronounced if the change in integrated charge (Q) upon target hybridization, rather than the peak current (I), is measured in CV. The temperature-dependent study further highlights the differences between the two sensors, where the LP sensor, owing to the flexible linear probe architecture, is more readily perturbed by temperature changes. Both SLP and LP sensors, however, show a loss of % SS when operated at elevated temperatures, despite the significant improvement in the hybridization kinetics. In conjunction with the ACV, CV, and temperature-dependent studies, the electron-transfer kinetics study provides further evidence in support of the proposed signaling mechanism of these two sensors, in which the SLP sensor's signaling efficiency and sensor performance is directly linked to the hybridization-induced conformational change in the redox-labeled probe, whereas the performance of the LP sensor relies on the hybridization-induced change in probe dynamics. PMID:21981414

Yang, Weiwei; Lai, Rebecca Y

2011-12-01

3

Bismuth electrodes, an alternative in stripping voltammetry  

NASA Astrophysics Data System (ADS)

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

Bar髇-Jaimez, J.; Joya, M. R.; Barba-Ortega, J.

2013-11-01

4

Direct separation of faradaic and double layer charging current in potential step voltammetry.  

PubMed

Double layer charging current in electrochemical systems has been a challenging problem in the last several decades because it causes interference to the accurate measurement of faradaic current. A method for extracting faradaic current and double layer charging current directly from the measured total current in potential step voltammetry is developed by using iterative target transformation factor analysis (ITTFA). The method constructs initial target vectors based on the theoretical formulae of faradaic and charging current, and then calculates the weights of faradaic and charging current in the measured signal via the iterative transformation of the initial vectors. Therefore, the two currents in one experiment can be obtained simultaneously without any assumption. The potential step voltammetric signals of potassium ferricyanide, copper sulfate and paracetamol were analyzed with the proposed method. The results show that the shape of the obtained voltammogram is an ideal sigmoid curve with horizontal straight baseline and plateaus, and the intensity of the signal is greatly enhanced. Therefore, the method provides a new way to measure the pure faradic current in the potential step voltammetric experiment, and may provide an alternative for improving the sensitivity of quantitative analysis. PMID:24148448

Tu, Jiarun; Cai, Wensheng; Shao, Xueguang

2013-11-15

5

Sampled-current voltammetry at microdisk electrodes: kinetic information from pseudo steady state voltammograms.  

PubMed

In sampled-current voltammetry (SCV), current transients acquired after stepping the potential along the redox wave of interest are sampled at a fixed time to produce a sigmoidal current-potential curve akin to a pseudo steady state voltammogram. Repeating the sampling for different times yields a family of sampled-current voltammograms, one for each time scale. The concept has been used to describe the current-time-potential relationship at planar electrodes but rarely employed as an electroanalytical method except in normal pulse voltammetry where the chronoamperograms are sampled once to produce a single voltammogram. Here we combine the unique properties of microdisk electrodes with SCV and report a simple protocol to analyze and compare the microdisk sampled-current voltammograms irrespective of sampling time. This is particularly useful for microelectrodes where cyclic voltammograms change shape as the mass transport regime evolves from planar diffusion at short times to hemispherical diffusion at long times. We also combine microdisk sampled-current voltammetry (MSCV) with a conditioning waveform to produce voltammograms where each data point is recorded with the same electrode history and demonstrate that the waveform is crucial to obtaining reliable sampled-current voltammograms below 100 ms. To facilitate qualitative analysis of the voltammograms, we convert the current-potential data recorded at different time scales into a unique sigmoidal curve, which clearly highlights kinetic complications. To quantitatively model the MSCVs, we derive an analytical expression which accounts for the diffusion regime and kinetic parameters. The procedure is validated with the reduction of Ru(NH3)6(3+), a model one electron outer sphere process, and applied to the derivation of the kinetic parameters for the reduction of Fe(3+) on Pt microdisks. The methodology reported here is easily implemented on computer controlled electrochemical workstations as a new electroanalytical method to exploit the unique properties of microelectrodes, in particular at short times. PMID:25178385

Perry, Samuel C; Al Shandoudi, Laila M; Denuault, Guy

2014-10-01

6

Current Alternative Engine Fuels  

Microsoft Academic Search

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

MUSTAFA BALAT

2005-01-01

7

Cyclic Voltammetry.  

ERIC Educational Resources Information Center

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

Evans, Dennis H.; And Others

1983-01-01

8

Alternating Current Jee-Hwan Ryu  

E-print Network

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

Ryu, Jee-Hwan

9

Alternating Current Circuit Jee-Hwan Ryu  

E-print Network

of Technology and Education EFS161 Korea University of Technology and Education (Direct Current) #12;Korea University of Technology and Education (Alternating Current) Korea University of Technology and Education Why AC ? , , , #12;Korea University of Technology and Education

Ryu, Jee-Hwan

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

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

12

Energy Storage: Current landscape for alternative energy  

E-print Network

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

13

ALTERNATING CURRENT ELECTROCOAGULATION FOR SUPERFUND SITE REMEDIATION  

EPA Science Inventory

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

14

An Alternative to Maxwell's Displacement Current  

E-print Network

Though sufficient for local conservation of charge, we show that Maxwells displacement current is not necessary. An alternative to the Ampere Maxwell equation is exhibited and the alternative s electric and magnetic fields and scalar and vector potentials are expressed in terms of the charge and current densities. The alternative describes a theory in which action is instantaneous and so may provide a good approximation to Maxwells equations where and when the finite speed of light can be neglected. The result is reminiscent of the Darwin approximation which arose from the study classical charged point particles to order (v/c)2 in the Lagrangian. Unlike Darwin, this approach does not depend on the constitution of the electric current. Instead, this approach grows from a straightforward revision of the Ampere Equation which revision enforces the local conservation of charge.

Wolsky, Alan M

2014-01-01

15

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

16

Alternating current long range alpha particle detector  

DOEpatents

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

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

1993-02-16

17

Alternating current long range alpha particle detector  

DOEpatents

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

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

1993-01-01

18

Alternating-current thin-film electroluminescence  

NASA Astrophysics Data System (ADS)

Alternating-current thin-film electroluminescent (ACTFEL) phosphors have been studied and improved with respect to brightness, color and efficiency. It is shown that ex- situ co-doping of the sputter deposited ZnS:Mn active layer with K and Cl results in 53% improvement in brightness, 62% improvement in efficiency, and better 100-hour accelerated aging stability. This improvement was demonstrated to result from a 75% increase in excitation efficiency for conduction electrons, combined with a small decrease in both light outcoupling and non- radiative recombination. By studying the electrical behavior of the co-doped devices as compared to the undoped devices, it was determined that there is a reduced amount of static space charge in the films, resulting in a larger average field, increased excitation efficiency, and increased charge multiplication. The reduced space charge is attributed to the addition of charge compensating zinc vacancy-chlorine complexes and isolated chlorine point defects, which are acceptor and donor defects, respectively, and the reduction of zinc vacancy deep hole traps. It is postulated that there is sufficient electron multiplication or donor ionization to create a situation in which the current limit is set by the phosphor resistance rather than a capacitance or density of states. Thin film Zn2GeO4:Mn phosphor layers were evaluated as green-emitting ACTFEL devices. Devices with Zn2GeO 4:Mn magnetron sputter deposited films exhibited brightness and efficiency values of 74 cd/m2 and 0.19 lm/W, respectively at 40 V above threshold and 60 Hz. Poor outcoupling efficiency suggests an internal efficiency that is much higher. Optical spectroscopy reveals efficient charge transfer from the lattice and a 615 meV sub-band gap defect state to the Mn 2+ ion. Unique transient optical and electrical behavior under EL excitation is observed. A phenomenological model is presented to explain the behavior. The unique aspects of the model include a resistance-capacitance limit on charge injection, efficient charge injection for only one polarity, abnormally large space charge density for one polarity that allows efficient electron-hole pair recombination in low electric field regions, and near-resonant energy transfer to and from the Mn2+ excited state.

Lewis, John South, III

19

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

20

Alternative pain medicine: Current modalities and principles  

Microsoft Academic Search

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

Winston C. V. Parris

1997-01-01

21

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

22

Electrochemical conversion using alternating current and semiconductor electrodes  

SciTech Connect

A method is described for electrochemical conversion of chemical reactants to chemical products. The method comprising passing a source of alternating electrical current external to at least one electrode containing a non-degenerate semiconductor in an electrochemical cell. The electrode rectifies the alternating electrical current to generate direct electrical current. The direct electrical current provides energy to convert at least one chemical reactant contained in the electrochemical cell to at least one chemical product.

Switzer, J.A.

1987-05-05

23

Dynamics of laser-guided alternating current high voltage discharges  

NASA Astrophysics Data System (ADS)

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

Daigle, J.-F.; Th閎erge, F.; Lassonde, P.; Kieffer, J.-C.; Fujii, T.; Fortin, J.; Ch鈚eauneuf, M.; Dubois, J.

2013-10-01

24

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

25

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

26

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

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

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

27

Cyclic Voltammetry Experiment.  

ERIC Educational Resources Information Center

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

Van Benschoten, James J.; And Others

1983-01-01

28

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

29

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

30

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

Code of Federal Regulations, 2014 CFR

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

2014-10-01

31

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

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

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

32

Describing current and potential markets for alternative-fuel vehicles  

SciTech Connect

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

NONE

1996-03-26

33

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

NASA Astrophysics Data System (ADS)

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

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

34

Lidocaine transport through living rat skin using alternating current  

Microsoft Academic Search

The purpose of the study was to determine whether lidocaine could be transported through living rat skin using alternating\\u000a current and to determine whether lidocaine transport depends on voltage. The drug delivery cell was originally constructed\\u000a for the application of an electric field. Hairless rats were anaesthetised using sevoflurane, and a tracheotomy was performed.\\u000a The drug delivery cell, with lidocaine

H. Haga; T. Shibaji; M. Umino

2005-01-01

35

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

ERIC Educational Resources Information Center

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

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

36

Unfolding Collapsed Polyelectrolytes in Alternating-Current Electric Fields  

E-print Network

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

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

2010-10-19

37

Transcranial Alternating Current Stimulation Attenuates Visual Motion Adaptation  

PubMed Central

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

Krekelberg, Bart

2014-01-01

38

Comparison of current reversal chronopotentiometry (CRC) and small amplitude cyclic voltammetry (SACV) method to determine the long-term corrosion tendency of copper-nickel alloys in polluted and unpolluted seawater under jet-impingement conditions  

SciTech Connect

The cyclic current reversal chronopotentiometry (CRC) technique is utilized to determine the long-term corrosion tendency of UNS C70600 and UNS C71500 copper-nickel alloys in sulfide polluted and unpolluted seawater. The CRC results were compared with the corrosion tendency obtained by the modified linear polarization method small amplitude cyclic voltammetry (SACV) over a long exposure time and the results are in agreement for both C70600 and C71500 alloys. This contradicts the conclusions on the effects of sulfide on copper-nickel alloys by many previous investigators who misinterpreted the sharp active shift in potential as an indication of increase in corrosion rate. For an active/passive alloy such as C71500 a higher amplitude current per cycle is required (e.g., 100 {micro}A/20 seconds) in the CRC method and under jet-impingement conditions, while a lower amplitude current per cycle (e.g., 1{micro}A/20 seconds) is required for an alloy that does not exhibit active/passive behavior. The CRC technique was found to be unsuccessful in screening out the long-term corrosion tendency of copper alloys in polluted and unpolluted sea water and under stagnant or stirred conditions (i.e., non-jet-impingement conditions).

Reda, M.R. [Reda (Mahmoud R.), Burlington, Ontario (Canada); Alhajji, J.N. [Kuwait Univ., Safat (Kuwait)

1997-12-31

39

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

NASA Technical Reports Server (NTRS)

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

Ambrose, John R.

1992-01-01

40

Alternating current electrokinetics enhanced in situ capacitive immunoassay.  

PubMed

A rapid in situ capacitive immunoassay is presented herein. Conventional immunoassay typically relies on diffusion for transport of analytes in many cases causing long detection time and lack of sensitivity. By integrating alternating current electrokinetics (ACEK) and impedance sensing, this work provides a rapid in situ capacitive affinity biosensing. ACEK induces both fluid flow and particle motion, conveying target molecules toward electrodes immobilized with probes, resulting in rapid enrichment of target molecules and a capacitance change at the ''electrode-fluid'' interface. The benefit of ACEK enhanced immunoassay was demonstrated using the antigen and antibody from Johne's disease (JD) as an example. To clarify the importance of DEP and ACET effects for binding reaction, two different electrode pattern designs for capacitive immunoassay are studied. The asymmetric array and symmetric electrodes exhibit very similar response at lower electric field due to DEP effects, while asymmetric array has remarkable higher response at high-electric field because the convection becomes more important at high field. The disease positive and negative serum samples are distinguished in few minutes. PMID:25258204

Li, Shanshan; Ren, Yukun; Cui, Haochen; Yuan, Quan; Wu, Jie; Eda, Shigetoshi; Jiang, Hongyuan

2014-09-26

41

Alternating current impedance spectroscopy measurement under high pressure  

NASA Astrophysics Data System (ADS)

A microcircuit was designed and fabricated on a diamond anvil cell for alternating current impedance spectroscopy measurement under high pressure. Sputtered molybdenum film on a diamond anvil was used as an electrode, maintained the contact between the sample and the electrode stable, and reduced the electrode effect on the impedance measurement. By the empty cell and short circuit tests, the parasitic capacitive impedance from the sample chamber wall was observed to be larger than 105 ? at a frequency lower than 1.0 MHz and could be ignored for samples with higher conductivity. The wire inductance was only 1.0 ?H and just appeared at frequency higher than 20 kHz, which could be subtracted from measured impedance for the samples with higher impedance than several hundred ohms. Using this apparatus, the impedances of the II-VI group cadmium sulfide were measured. The pressure dependence of the grain interior conductance of CdS crystal was obtained, which reflected that the phase transitions of CdS under high pressure are the same as the single crystal measurement results.

He, Chunyuan; Liu, Bingguo; Li, Ming; Gao, Chunxiao

2011-01-01

42

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

43

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

E-print Network

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 ...

Tidd, Chad N. (Chad Norman)

2010-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

45

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

46

Current complementary and alternative therapies for multiple sclerosis  

Microsoft Academic Search

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

Allen C. Bowling; Thomas M. Stewart

2003-01-01

47

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 = 礫subscript 0]I, and it is later extended to a more general form involving the so-called displacement current I[subscript d], ?B dl = 礫subscript 0](I + I[subscript d]) (1). Here the line integral is to be taken along a closed

Reich, Gary

2013-01-01

48

Teaching Electrical Energy, Voltage and Current: An Alternative Approach.  

ERIC Educational Resources Information Center

A program for teaching the concepts of electric energy, voltage, and current is proposed. The ideas and concepts are introduced in a sequence that places more emphasis on some aspects that are normally treated very briefly. A phenomenological orientation, qualitative and quantitative micro- and macroscopic treatments, and the inclusion of the

Licht, Pieter

1991-01-01

49

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

50

Josephson effects in an alternating current biased transition edge sensor  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

51

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

52

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

Code of Federal Regulations, 2012 CFR

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

2012-07-01

53

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

Code of Federal Regulations, 2011 CFR

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

2011-07-01

54

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

55

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

Code of Federal Regulations, 2014 CFR

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

2014-07-01

56

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

57

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

Code of Federal Regulations, 2012 CFR

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

2012-07-01

58

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

59

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

Code of Federal Regulations, 2014 CFR

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

2014-07-01

60

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

Code of Federal Regulations, 2011 CFR

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

2011-07-01

61

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

62

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

E-print Network

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

Temple, Blake

63

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

64

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

65

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

66

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

67

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

PubMed Central

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

Banga, Ajay K.

2014-01-01

68

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

ERIC Educational Resources Information Center

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

Linney, Thomas J.

69

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

70

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

PubMed Central

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

Vilari駉, Natalia; Fonfr韆, Eva S.; Louzao, M. Carmen; Botana, Luis M.

2009-01-01

71

Comparison between alternating and pulsed current electrical muscle stimulation for muscle and systemic acute responses.  

PubMed

This study compared alternating current and pulsed current electrical muscle stimulation (EMS) for torque output, skin temperature (Tsk), blood lactate and hormonal responses, and skeletal muscle damage markers. Twelve healthy men (23-48 yr) received alternating current EMS (2.5 kHz delivered at 75 Hz, 400 micros) for the knee extensors of one leg and pulsed current (75 Hz, 400 micros) for the other leg to induce 40 isometric contractions (on-off ratio 5-15 s) at the knee joint angle of 100 degrees (0 degrees: full extension). The use of the legs for each condition was counterbalanced among subjects, and the two EMS bouts were separated by 2 wk. The current amplitude was consistently increased to maximally tolerable level, and the torque and perceived intensity were recorded over 40 isometric contractions. Tsk of the stimulated and contralateral knee extensors were measured before, during, and for 30 min after EMS. Blood lactate, growth hormone, testosterone, insulin-like growth factor 1, testosterone, and cortisol were measured before, during, and for 45 min following EMS. Muscle damage markers included maximal voluntary isometric contraction torque, muscle soreness with a 100-mm visual analog scale, and plasma creatine kinase (CK) activity, which were measured before and 1, 24, 48, 72, and 96 h after EMS. No significant differences in the torque induced during stimulation (approximately 30% maximal voluntary isometric contraction) and perceived intensity were found, and changes in Tsk, blood lactate, and hormones were not significantly different between conditions. However, all of the measures showed significant (P<0.05) changes from baseline values. Skeletal muscle damage was evidenced by prolonged strength loss, development of muscle soreness, and increases in plasma CK activity; however, the changes in the variables were not significantly different between conditions. It is concluded that acute effects of alternating and pulsed current EMS on the stimulated muscles are similar. PMID:20595542

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

2010-09-01

72

Alternating current potential-drop measurement of the depth of case hardening in steel rods  

Microsoft Academic Search

The case depth of induction-hardened steel rods has been determined using multi-frequency alternating current potential-drop measurements. Experimental results are analyzed using a model which approximates the variation in the material properties of a hardened rod by assuming that a homogeneous core is surrounded by a homogeneous case-hardened layer of uniform thickness. Experimental measurements on an untreated rod are used to

John R. Bowler; Yongqiang Huang; Haiyan Sun; Jonathan Brown; Nicola Bowler

2008-01-01

73

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

PubMed Central

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

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

2014-01-01

74

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

75

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

DOEpatents

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

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

2012-06-05

76

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

PubMed

The high viscosity and unusual properties of room temperature ionic liquids (RTILs) present a number of challenges when performing steady-state voltammetry and scanning electrochemical microscopy in RTILs. These include difficulties in recording steady-state currents at ultramicroelectrode surfaces due to low diffusion coefficients of redox species and problems associated with unequal diffusion coefficients of oxidised and reduced species in RTILs. In this tutorial review, we highlight the recent progress in the use of RTILs as electrolytes for ultramicroelectrode voltammetry and SECM. We describe the basic principles of ultramicroelectrode voltammetry and SECM and, using examples from the recent literature, we discuss the conditions that must be met to perform steady-state voltammetry and SECM measurements in RTILs. Finally, we briefly discuss the electrochemical insights that can be obtained from such measurements. PMID:20835469

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

2010-11-01

77

Ionic currents in the human serotonin transporter reveal inconsistencies in the alternating access hypothesis.  

PubMed

We have investigated the conduction states of human serotonin transporter (hSERT) using the voltage clamp, cut-open frog oocyte method under different internal and external ionic conditions. Our data indicate discrepancies in the alternating access model of cotransport, which cannot consistently explain substrate transport and electrophysiological data. We are able simultaneously to isolate distinct external and internal binding sites for substrate, which exert different effects upon currents conducted by hSERT, in contradiction to the alternating access model. External binding sites of coupled Na ions are likewise simultaneously accessible from the internal and external face. Although Na and Cl are putatively cotransported, they have opposite effects on the internal face of the transporter. Finally, the internal K ion does not compete with internal 5-hydroxytryptamine for empty transporters. These data can be explained more readily in the language of ion channels, rather than carrier models distinguished by alternating access mechanisms: in a channel model of coupled transport, the currents represent different states of the same permeation path through hSERT and coupling occurs in a common pore. PMID:12944272

Adams, Scott V; DeFelice, Louis J

2003-09-01

78

Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

79

Anodic Stripping Voltammetry: An Instrumental Analysis Experiment.  

ERIC Educational Resources Information Center

Describes an experiment designed to acquaint students with the theory and applications of anodic stripping voltammetry (ASV) as well as such ASV problems as contamination associated with trace analysis. The experimental procedure, instrumentation, and materials discussed are designed to minimize cost and keep procedures as simple as possible. (JM)

Wang, Joseph

1983-01-01

80

Plasmonic-based Imaging of Local Square Wave Voltammetry  

PubMed Central

Square wave voltammetry (SWV) is widely used in electrochemical analysis and sensors because of its high sensitivity and efficient rejection of background current, but SWV by conventional electrochemical detection method does not provide spatial resolution. We report here a plasmonic method to image local SWV, which opens the door for analyzing heterogeneous electrochemical reactions and for high throughput detections of microarrays. We describe the basic principle, validate the principle by comparing the plasmonic-based SWV with those obtained with the conventional method, and demonstrate imaging capability for local electrochemical analysis. PMID:21793508

Shan, Xiaonan; Wang, Shaopeng; Wang, Wei; Tao, Nongjian

2012-01-01

81

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

NASA Astrophysics Data System (ADS)

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

Koizumi, H.; Uda, S.; Fujiwara, K.; Tachibana, M.; Kojima, K.; Nozawa, J.

2014-10-01

82

Regional Economic Effects of Current and Proposed Management Alternatives for Arrowwood National Wildlife Refuge  

USGS Publications Warehouse

Introduction 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 (CCP). The CCP must describe the desired future conditions of a Refuge and provide long range guidance and management direction to achieve Refuge purposes. Arrowwood National Wildlife Refuge (NWR), located along the James River in east central North Dakota, is in the process of developing a range of management goals, objectives, and strategies for the CCP. The CCP for Arrowwood NWR must contain an analysis of expected effects associated with current and proposed Refuge 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 income and employment impacts may show that these economic fears are overstated. Quite often, residents do not realize the extent of economic benefits a Refuge provides to a local community, yet at the same time overestimate the impact of negative changes. Spending associated with Refuge recreational activities such as wildlife viewing and hunting can generate considerable tourism activity for the regional economy. Additionally, Refuge personnel typically spend considerable amounts of money purchasing supplies in the local lumber and hardware stores, repairing equipment and purchasing fuel at the local service stations, as well as reside and spend their salaries in the local community. The purpose of this study was to provide the economic analysis needed for the Arrowwood NWR CCP by evaluating the regional economic impacts associated with the Arrowwood NWR Draft CCP management strategies. For Refuge CCP planning, an economic impact analysis describes how current (No Action Alternative) and proposed management activities (alternatives) affect the local economy. This type of analysis provides two critical pieces of information: 1) it illustrates 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. Refuge personnel provided the information needed to analyze the economic impacts of the three alternatives evaluated in the draft CCP. This report first provides a description of the local community and economy near the Refuge. An analysis of current and proposed management strategies that could affect the local economy is then presented. The Refuge management activities of economic concern in this analysis are Refuge personnel staffing and Refuge spending within the local community, and spending in the local community by Refuge visitors.

Koontz, Lynne; Lambert, Heather

2005-01-01

83

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

Richardson, Leslie; Huber, Chris; Koontz, Lynne

2012-01-01

84

Analysis for discharge-radiation dynamics in alternating current plasma display panels  

SciTech Connect

An analytical method to study the discharge-radiation dynamics (DRD) in alternating current plasma display panels was developed. The input parameters for this DRD analysis were experimentally determined panel voltage and current wave forms. Discharge voltage, current, and power wave forms in the discharge volume of a cell were first obtained from the measured panel voltage and current wave forms using known geometrical configurations and electric circuit calculations. Intrinsic discharge parameters, such as electron temperature and density, were then determined to satisfy these discharge wave forms under the assumption of a hydrodynamic approach. A one-dimensional discharge structure with two regions (cathode fall and positive column) and several other assumptions which are plausible from the discharge physics point of view were also adopted. These assumptions took account of known cross sections and energies of electron-impact excitation and ionization of discharge gas atoms, and a secondary electron emission coefficient of the dielectric surface at the cathode side induced by ion bombardment. Radiation intensities from the discharge were calculated using the determined intrinsic discharge parameters, and the results were compared with those measured for the respective panel conditions used in the calculations, yielding a fair agreement. The luminous efficiency, defined as the radiation intensity divided by the discharge power, was also determined using the intrinsic discharge parameters. Discussion on the luminous efficiency change for different panel operating conditions revealed that the efficiency improvement at a lower voltage was attributable to a lower electron temperature for this condition.

Suzuki, Keizo; Yamamoto, Kenichi; Kajiyama, Hiroshi; Ho, Shirun; Uemura, Norihiro; Muraoka, Katsunori [Hitachi Research Laboratory, c/o Central Research Laboratory, Hitachi Ltd., 1-280, Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601 (Japan); Advanced Research Laboratory, c/o Central Research Laboratory, Hitachi Ltd., 1-280, Higashi-koigakubo, Kokubunji-shi, Tokyo 185-8601 (Japan); Fujitsu Hitachi Plasma Display Ltd., 1815 Tajiri, Kunitomi-cho, Higashimorokata-gun, Miyazaki-ken 880-1194 (Japan); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

2004-12-01

85

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

86

Evaluation of homogeneous electrocatalysts by cyclic voltammetry.  

PubMed

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

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

2014-10-01

87

Instrument design for pulse voltammetry with microvoltammetric electrodes  

NASA Astrophysics Data System (ADS)

The current measured during the back step of a double potential step chronoamperometry experiment at microvoltammetric electrodes is primarily nonfaradaic and can be used for residual current correction. An instrument has been designed which provides direct readout of the corrected current. This instrument also provides differential output and adjustable delay and step times which can be important for the unusual conditions of in vivo voltammetric experiments. All of these features are tailor made for use with microvoltammetric electrodes and are unavailable in commercial instrumentation. Experimental results indicate that potential step times as short as 100 ms can be used with back step correction with a faradaic accuracy of better than 5%. Pulse scans are compared to conventional cyclic voltammetry in the reduction of 510-5 M potassium ferricyanide.

Ewing, Andrew G.; Withnell, Ronald; Wightman, R. Mark

1981-03-01

88

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

89

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

PubMed

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

de Carvalho Neto, Riamburgo Gomes; do Nascimento, Jos Gilmar da Silva; Costa, Mayara Carantino; Lopes, Alexandre Colzi; Abdala Neto, Eliezer Fares; Filho, C閟ar Rossas Mota; Dos Santos, Andr Bezerra

2014-01-01

90

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

PubMed Central

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

2013-01-01

91

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

PubMed Central

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

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

2014-01-01

92

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

PubMed

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

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

2014-01-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

94

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

PubMed

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

Fr鰄lich, Flavio; Sellers, Kristin K; Cordle, Asa L

2015-02-01

95

Regional economic effects of current and proposed management alternatives for Sand Lake 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 (CCP). The CCP must describe the desired future conditions of a Refuge and provide long range guidance and management direction to achieve Refuge purposes. Sand Lake National Wildlife Refuge (NWR), located 27 miles northeast of Aberdeen, South Dakota, is in the process of developing a range of management goals, objectives, and strategies for the CCP. The CCP for Sand Lake NWR must contain an analysis of expected effects associated with current and proposed Refuge 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 income and employment impacts may show that these economic fears are drastically overstated. Quite often, residents do not realize the extent of economic benefits a Refuge provides to a local community; yet at the same time overestimate the impact of negative changes. Spending associated with Refuge recreational activities such as wildlife viewing and hunting can generate considerable tourism activity for the regional economy. Refuge personnel typically spend considerable amounts of money purchasing supplies in the local lumber and hardware stores, repairing equipment and purchasing fuel at the local service stations, as well as reside and spend their salaries in the community. The purpose of this study was to provide the economic analysis needed for the Sand Lake NWR CCP by evaluating the regional economic impacts associated with the Sank Lake NWR Draft CCP management strategies. For Refuge CCP planning, an economic impact analysis described how current (No Action Alternative) and proposed management activities (alternatives) affect the local economy. This type of analysis provided two critical pieces of information: (1) it illustrates a refugea??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 alternativesa?|

Koontz, Lynne; Lambert, Heather

2005-01-01

96

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

97

Thin film voltammetry of metabolic enzymes in rat liver microsomes  

PubMed Central

We report herein thin film voltammetry and kinetics of electron transfer for redox proteins in rat liver microsomes for the first time. Films were made layer-by-layer from liver microsomes and polycations on pyrolytic graphite electrodes. Cyclic voltammograms were chemically reversible with a midpoint potential of ?0.48 V vs SCE at 0.1 V s?1 in pH 7.0 phosphate buffer. Reduction peak potentials shifted negative at higher scan rates, and oxidation-reduction peak current ratios were ?1 consistent with non-ideal quasireversible thin film voltammetry. Analysis of oxidation-reduction peak separations gave an average apparent surface electron transfer rate constant of 30 s?1. Absence of significant electrocatalytic reduction of O2 or H2O2 and lack of shift in midpoint potential when CO is added that indicates lack of an iron heme cofactor suggest that peaks can be attributed to oxidoreductases present in the microsomes rather than cytochrome P450 enzymes. PMID:18037986

Krishnan, Sadagopan; Rusling, James F.

2007-01-01

98

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

PubMed

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

Herrmann, Christoph S; Rach, Stefan; Neuling, Toralf; Str黚er, Daniel

2013-01-01

99

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

PubMed Central

During the 1990s, the New York Police Department (NYPD) instituted a policy of arresting and detaining people for minor offenses that occur in public as part of their quality-of-life (hereafter QOL) policing initiative. The number of NYPD arrests for smoking marijuana in public view (MPV) increased from 3,000 in 1994 to over 50,000 in 2000, and have been about 30,000 in the mid 2000s. Most of these arrestees (84%) have been minority; blacks have been 2.7 more likely and Hispanics 1.8 times more likely to be detained than whites for an MPV arrest. Minorities have been most likely to receive more severe dispositions, even controlling for demographics and prior arrest histories. This paper examines the pros and cons of the current policy; this is compared with possible alternatives including the following: arrest and issue a desk appearance ticket (DAT); issue a non-criminal citation (violation); street warnings; and tolerate public marijuana smoking. The authors recommend that the NYPD change to issuing DATs on a routine basis. Drug policy reformers might wish to further pursue changing statutes regarding smoking marijuana in public view into a violation (noncriminal) or encourage the wider use of street warnings. Any of these policy changes would help reduce the disproportionate burden on minorities associated with the current arrest and detention policy. These policies could help maintain civic norms against smoking marijuana in public. PMID:18726007

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

2008-01-01

100

Electroencephalograms and physical reflexes of broilers after electrical waterbath stunning using an alternating current.  

PubMed

Stunning efficiency of broilers after electrical waterbath stunning with an alternating current was assessed using electroencephalograms (EEG) and physical reflexes. Four hundred eighty-nine broilers (246 males and 243 females) were stunned in an electrical waterbath with a rectangular alternating stunning current of 60, 80, 100, 120, and 150 mA and frequencies of 70, 100, 200, 400, 800, and 1,500 Hz. Stunning time was 10 s. The EEG was recorded for 120 s poststun. Occurrence of spontaneous breathing, eye blinking, and wing flapping and the corneal reflex were recorded. The EEG was analyzed regarding the occurrence of a profound suppression to less than 10% of the prestun level in the 2 to 30-Hz band and 13 to 30-Hz band. The occurrence of epileptiform patterns was assessed and the occurrence of clonic-tonic convulsions was recorded. Statistical analysis showed a highly significant effect of stunning frequency and stunning current for all groups in the EEG analysis. Stunning frequencies above 400 Hz or below 100 mA did not result in profound suppression of brain power to less than 10% of the prestun level in more than 90% of the broilers and can therefore not be recommended. More than 80% of the birds stunned with 70 or 100 Hz at 100 mA or 70, 100, and 200 Hz with 120 and 150 mA did not recover from stunning. The occurrence of epileptiform activity could only be observed in a few birds. It is assumed that this is due to the long stunning time of 10 s and epileptiform activity could have occurred just before EEG recording started. A maximum of 30% of birds with corneal reflexes and spontaneous eye blinking should not be exceeded, whereas at 15 s poststun, not more than 15% of birds should show spontaneous eye blinking. Wing flapping occurred in at least 50% of birds with adequate stunning results. This seems to be related to convulsions and could cause meat quality defects. PMID:20460673

Prinz, S; Van Oijen, G; Ehinger, F; Coenen, A; Bessei, W

2010-06-01

101

Transcranial Alternating Current Stimulation Enhances Individual Alpha Activity in Human EEG  

PubMed Central

Non-invasive electrical stimulation of the human cortex by means of transcranial direct current stimulation (tDCS) has been instrumental in a number of important discoveries in the field of human cortical function and has become a well-established method for evaluating brain function in healthy human participants. Recently, transcranial alternating current stimulation (tACS) has been introduced to directly modulate the ongoing rhythmic brain activity by the application of oscillatory currents on the human scalp. Until now the efficiency of tACS in modulating rhythmic brain activity has been indicated only by inference from perceptual and behavioural consequences of electrical stimulation. No direct electrophysiological evidence of tACS has been reported. We delivered tACS over the occipital cortex of 10 healthy participants to entrain the neuronal oscillatory activity in their individual alpha frequency range and compared results with those from a separate group of participants receiving sham stimulation. The tACS but not the sham stimulation elevated the endogenous alpha power in parieto-central electrodes of the electroencephalogram. Additionally, in a network of spiking neurons, we simulated how tACS can be affected even after the end of stimulation. The results show that spike-timing-dependent plasticity (STDP) selectively modulates synapses depending on the resonance frequencies of the neural circuits that they belong to. Thus, tACS influences STDP which in turn results in aftereffects upon neural activity. The present findings are the first direct electrophysiological evidence of an interaction of tACS and ongoing oscillatory activity in the human cortex. The data demonstrate the ability of tACS to specifically modulate oscillatory brain activity and show its potential both at fostering knowledge on the functional significance of brain oscillations and for therapeutic application. PMID:21072168

Zaehle, Tino; Rach, Stefan; Herrmann, Christoph S.

2010-01-01

102

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

103

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

104

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

105

Ability of Electric Field Strength, Frequency, and Current Duration to Stun Farmed Atlantic Salmon and Pollock and Relations to Observed Injuries Using Sinusoidal and Square Wave Alternating Current  

Microsoft Academic Search

The effects of electricity as a stunning method in the slaughtering process of Atlantic salmon Salmo salar and pollock Pollachius virens were studied. About 330 slaughter-sized Atlantic salmon were exposed to sinusoidal alternating current (AC) in seawater. Electrical field strength ranged from 25 to 100 V\\/m and current duration from 1 to 10 s at frequencies between 30 and 2,000

Bjorn Roth; Dag Moeller; Erik Slinde

2004-01-01

106

Space charge generation in ZnS:Mn alternating-current thin-film electroluminescent devices  

NASA Astrophysics Data System (ADS)

The electrical characteristics of ZnS:Mn alternating-current thin-film electroluminescent (ACTFEL) devices grown by atomic layer epitaxy are assessed as a function of the thickness of the phosphor layer using capacitance-voltage (C-V) and internal charge-phosphor field (Q-Fp) analysis. Deviations from the ideal in the measured C-V and Q-Fp characteristics are ascribed to the generation of space charge in the phosphor layer during ACTFEL device operation. C-V overshoot deviations are correlated to space charge generation via a simulation employing a single sheet of charge model which assumes that the centroid of the generated space charge is located at a discrete sheet within the phosphor. Space charge generation in these atomic layer epitaxy (ALE) ZnS:Mn ACTFEL devices is ascribed to impact ionization of the zinc vacancy portion of chlorine-zinc vacancy self-activated defect complexes. A thermodynamic argument is provided which suggests that zinc vacancies are created via self-compensation of ZnS when the ZnS is unintentionally doped with chlorine. It is contended that space charge generation could even be desirable in ALE ZnS:Mn ACTFEL devices because it leads to better aging stability and improved performance.

Shih, S.; Keir, P. D.; Wager, J. F.; Viljanen, J.

1995-11-01

107

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

PubMed Central

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 ?m and 2080 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

108

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

PubMed Central

The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample. PMID:24009021

van Berkum, Susanne; Ern, Ben H.

2013-01-01

109

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

Jau歰vec, Norbert; Jau歰vec, Ksenija

2014-02-01

110

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 癈. 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 癈, 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.

Sa飀i, Sami; Manna, Aymen; Bouzitoun, Mouna; Belhadj Mohamed, Abdellatif

2014-04-01

111

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; Ern, Ben H

2013-01-01

112

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? 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?). The technique was applicable to solutions with a salt concentration of 0.050?0.15 mol dm? 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

113

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 搉anoshearing 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杝ensor 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, Elo飐e; Shiddiky, Muhammad J A; Trau, Matt

2014-03-24

114

Cryogenically stabilized superconductor in cable form for large currents and alternating field stresses  

SciTech Connect

A cryogenically stabilized superconductor in cable form comprises several superconducting elements which contain twisted conductor filaments of superconductive material which are embedded in a matrix material of predetermined electric conductivity and which are twisted with several stabilizing elements of thermally and electrically highly conductive material which is electrically normal conducting at the operating temperature of the superconductor and the electric conductivity of which at the operating temperature is substantially higher than that of the matrix material of the superconducting elements disposed parallel thereto. So this superconductor will be capable of carrying large currents, will have high cryogenic stability and at the same time have only small alternating field losses, pairs of stabilizing elements and superconducting elements form respective stabilized subconductors, the stabilizing elements of which are connected in an electrically conducting manner only at individual points disposed one behind the other in the lengthwise direction of the conductor to the respective superconducting elements; and the subconductors are twisted together and are electrically insulated from each other in such a manner that an electrically highly conducting cross connection of all subconductors is provided only after one or more respective twisting lay lengths.

Ries, G.

1983-10-11

115

Molecular stretching of long DNA in agarose gel using alternating current electric fields.  

PubMed

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; 165.6 kb) 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 AC field when a frequency of approximately 10 Hz was used. The maximal length of the stretched DNA had the longest value when a field strength of 200 to 400 V/cm was used. Stretching was not sensitive to a range of agarose gel concentrations from 0.5 to 3%. Together, these experiments indicate that the optimal conditions for stretching long DNA in an AC electric field are a frequency of 10 Hz with a field strength of 200 V/cm and a gel concentration of 1% agarose. Using these conditions, we were able to successfully stretch Saccharomyces cerevisiae chromosomal DNA molecules (225-2,200 kb). These results may aid in the development of a novel method to stretch much longer DNA, such as human chromosomal DNA, and may contribute to the analysis of a single chromosomal DNA from a single cell. PMID:11751320

Kaji, Noritada; Ueda, Masanori; Baba, Yoshinobu

2002-01-01

116

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. PMID:22655024

Wang, Shengqin; Zhu, Yingxi

2012-01-01

117

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

118

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. PMID:22163578

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

2010-01-01

119

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杛elative 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 2045 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 2025, 3245, and over 50 years) for testing the effect of age and sex. Twelve subjects (ages 2025 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杛elative volume difference relationships, whereas sex, level of mean blood pressure, and cold-stress stimulation had no influence on these forms of the index. Conclusion This study showed the usefulness of the relative volume difference as being a mean blood pressure-independent indicator for changes in arterial elasticity. PMID:23766653

Uangpairoj, Pichitra; Shibata, Masahiro

2013-01-01

120

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

EPA Science Inventory

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

121

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.

122

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

Gonz醠ez, M Jes鷖 G髆ez; Renedo, Olga Dom? Nguez; Lomillo, M Asunci髇 Alonso; Mart? Nez, M Julia Arcos

2004-02-27

123

Collaborative Practices Related to Augmentative and Alternative Communication: Current Personnel Preparation Programs.  

ERIC Educational Resources Information Center

Data from a pilot survey of the preservice professional training experiences in the area of collaboration for speech-language pathologists (n=7) and special (n=4) and general (1) educators who teach students who use augmentative and alternative communication (AAC) are presented, as is information from 10 faculty who teach AAC courses. (Contains

DePaepe, Paris A.; Wood, Lisa A.

2001-01-01

124

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

125

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

E-print Network

structure which uses 300 nm of radio frequency sputtered Al2O3 dielectric layers. The GaN:Er phosphor dielectric/200 nm metal indium tin oxide ITO . The di- electrics (Al2O3, AlN, Si3N4, and SiON evaluatedAlternating current thin-film electroluminescence of GaN:Er J. Heikenfeld and A. J. Steckla

Steckl, Andrew J.

126

How a charge conserving alternative to Maxwells displacement current entails a Darwin like approximation to the solutions of Maxwells equations  

E-print Network

Though sufficient for local conservation of charge, Maxwells displacement current is not necessary. An alternative to the Ampere-Maxwell equation is exhibited and the alternatives electric and magnetic fields and scalar and vector potentials are expressed in terms of the charge and current densities. The magnetic field is shown to satisfy the Biot_Savart Law. The electric field is shown to be the sum of the gradient of a scalar potential and the time derivative of a vector potential which is different from but just as tractable as the simplest vector potential that yields the Biot_Savart Law The alternative describes a theory in which action is instantaneous and so may provide a good approximation to Maxwells equations where and when the finite speed of light can be neglected. The result recalls the Darwin approximation which arose from the study classical charged point particles to order (v/c)2 in the Lagrangian. Unlike Darwin, this approach does not depend on the constitution of the electric current. Instea...

Wolsky, Alan M

2014-01-01

127

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

128

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

129

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

Code of Federal Regulations, 2011 CFR

...connection, is able to withstand the maximum available fault current without damage, and provides continuous...provision must be included to compare indications under fault conditions with those under normal conditions. [CGD 94-108, 62 FR...

2011-10-01

130

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

Code of Federal Regulations, 2012 CFR

...connection, is able to withstand the maximum available fault current without damage, and provides continuous...provision must be included to compare indications under fault conditions with those under normal conditions. [CGD 94-108, 62 FR...

2012-10-01

131

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

Code of Federal Regulations, 2014 CFR

...connection, is able to withstand the maximum available fault current without damage, and provides continuous...provision must be included to compare indications under fault conditions with those under normal conditions. [CGD 94-108, 62 FR...

2014-10-01

132

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

Code of Federal Regulations, 2010 CFR

...connection, is able to withstand the maximum available fault current without damage, and provides continuous...provision must be included to compare indications under fault conditions with those under normal conditions. [CGD 94-108, 62 FR...

2010-10-01

133

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

Code of Federal Regulations, 2013 CFR

...connection, is able to withstand the maximum available fault current without damage, and provides continuous...provision must be included to compare indications under fault conditions with those under normal conditions. [CGD 94-108, 62 FR...

2013-10-01

134

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

E-print Network

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

Sekar, Ram C.

135

Quantitative electrochemical detection of cathepsin B activity in complex tissue lysates using enhanced AC voltammetry at carbon nanofiber nanoelectrode arrays.  

PubMed

The proteolytic activity of a cancer-related enzyme cathepsin B is measured with alternating current voltammetry (ACV) using ferrocene (Fc) labeled tetrapeptides attached to nanoelectrode arrays (NEAs) fabricated with vertically aligned carbon nanofibers (VACNFs). This combination enables the use of high AC frequencies (~1kHz) with enhanced electrochemical signals. The specific proteolysis of the Fc-peptide by cathepsin B produces decay in the ACV peak current versus the reaction time. The exponential component of the raw data can be extracted and defined as the "extracted proteolytic signal" which allows consistent quantitative analyses using a heterogeneous Michaelis-Menten model. A "specificity constant" kcat/KM = (3.68 0.50) 10(4)M(-1)s(-1) for purified cathepsin B was obtained. The detections of cathepsin B activity in different concentrations of whole lysate of human breast tissue, tissue lysate spiked with varied concentrations of cathepsin B, and the tissue lysate after immunoprecipitation showed that there is ~13.4 nM higher cathepsin B concentration in 29.1 礸 mL(-1) of whole tissue lysate than the immunoprecipitated sample. The well-defined regular VACNF NEAs by e-beam lithography show a much faster kinetics for cathepsin B proteolysis with kcat/KM = 9.2 10(4)M(-1)s(-1). These results illustrate the potential of this technique as a portable multiplex electronic system for cancer diagnosis by rapid protease profiling of serum or blood samples. PMID:24480132

Swisher, Luxi Z; Prior, Allan M; Shishido, Stephanie; Nguyen, Thu A; Hua, Duy H; Li, Jun

2014-06-15

136

Direct determination of uranium in water by cathodic stripping voltammetry  

SciTech Connect

Uranium was determined in fresh water and seawater by using 8-hydroxyquinoline(oxine) as the chelating agent in cathodic stripping voltammetry procedure. The peak height-uranium concentration relationship was linear up to about 30 nM U (at a peak current of 80 nA) when the scans were preceded by 1 min of stirred adsorption. The linear range is extended to higher uranium levels by reducing the sensitivity by adsorbing less complex ions on the electrode, i.e., by using a shorter adsorption time, or by adsorbing without stirring. The sensitivity for uranium in a synthetic electrolyte solution was about 10% greater than in seawater, presumably due to the absence of carbonate ions which compete with the oxine for uranyl ions and the major cations which partially saturate oxine in seawater. This similar sensitivity in fresh and seawater is in contrast to the poor sensitivity that was obtained by SCS when using catechol as the chelating compound in fresh water conditions, as its sensitivity was 10-20% of that in seawater.

van den Berg, C.M.G.; Nimmo, M.

1987-03-15

137

Current and future alternatives to warfarin for the prevention of stroke in atrial fibrillation.  

PubMed

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice and is associated with a nearly 5-fold increase in the risk of stroke. Warfarin has been the cornerstone of treatment to reduce stroke risk in AF patients for decades. Although effective in preventing thrombosis, warfarin is difficult to manage and is associated with a 1% to 7% yearly risk of major hemorrhage. Until recently, there were no effective oral alternatives to warfarin. Dabigatran etexilate, a direct thrombin inhibitor, was approved in 2010 for the reduction of stroke and systemic embolism in patients with nonvalvular AF, and the factor Xa inhibitor rivaroxaban was approved for a similar indication in 2011. Other late-stage orally administered agents that may be approved for this indication include apixaban and edoxaban; others at earlier stages of development will be discussed in this review as well. Nonpharmacological approaches to stroke prevention include left atrial appendage removal, ligation, or occlusion. This review examines advances in the management of stroke risk in AF patients, focusing on recently marketed and late-stage modalities. The advent of alternatives to warfarin for reducing stroke risk in AF patients may improve physicians' ability to offer safe and effective stroke prevention in all AF patients. PMID:22595814

Bommer, William J

2012-06-01

138

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

139

Ferrite plating of Fe3O4 films using alternate electric current  

Microsoft Academic Search

Magnetite (Fe3O4) films were synthesized at 95癈 on Au and stainless steel substrate from an aqueous solution (pH=~6.8) of FeSO4 by conducting ac current (Vp-p=1~40 V, f=10 Hz~100 kHz) between the substrate and a Pt electrode. The deposition rate increased from ~8 nm\\/min to ~18 nm\\/min as the frequency of the current increased from 10 Hz to 100 kHz. The

Q. Zhang; T. Itoh; M. Abe

1994-01-01

140

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

141

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

142

A survey of current worldwide research on the thermophysical properties of alternative refrigerants  

NASA Astrophysics Data System (ADS)

The survey represents an exhaustive compilation of the research activities throughout the world concerned with either measurements or correlations of the thermophysical properties of alternative refrigerants. The properties covered include thermodynamic, transport, phase equilibria, and other properties such as dielectric constant and refractive index. The survey included a wide range of fluids (including R23, R32, R125, R143a, R22, R134a, R152a, R134, R124, R142b, R123, R123a, R141b) along with mixtures containing at least one of these fluids. Summary information is presented in tabular form about each research activity; the survey does not present raw data or correlating equations.

McLinden, M. O.; Haynes, W. M.; Watson, J. T. R.; Watanabe, K.

1991-06-01

143

Hemispheric differences in word?meaning processing: Alternative interpretations of current evidence  

Microsoft Academic Search

Background: Drawing heavily on results from studies with divided visual field (dvf) presentation, current models of hemispheric differences in word semantic processing converge on a proposal (henceforth, 搕he standard model) that is increasingly being applied in studies of individuals with brain damage. According to this model, left hemisphere processes focus word meanings to their core, whereas right hemisphere processes keep

Wiltrud Fassbinder; Connie A. Tompkins

2006-01-01

144

Assessment of Alternative Student Aid Delivery Systems: Preliminary Specification of the Current System with Program Antecedents.  

ERIC Educational Resources Information Center

Specifications of the current delivery systems of the Pell Grant program, the Guaranteed Student Loan (GSL) program, and campus-based aid programs are provided. The relationship between features of the programs and delivery systems is also examined. The campus-based programs include the Supplemental Educational Opportunity Grant (SEOG) Program,

Advanced Technology, Inc., Reston, VA.

145

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

ERIC Educational Resources Information Center

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

Advanced Technology, Inc., Reston, VA.

146

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

147

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

148

A review of current methods for assessing hemostasis in vivo and introduction to a potential alternative approach  

PubMed Central

A validated method for assessing hemostasis in vivo is critical for testing the hemostatic efficacy of therapeutic agents in preclinical animal models and in patients with inherited bleeding disorders, such as von Willebrand disease (VWD) and hemophilia A, or with acquired bleeding disorders such as those resulting from medications or disease processes. In this review, we discuss current methods for assessing hemostasis in vivo and the associated challenges. We also present ARFI-Monitored Hemostatic Challenge; a new, potentially alternate method for in vivo hemostasis monitoring that is in development by our group. PMID:22405050

Scola, Mallory R.; Baggesen, Leslie M.; Nichols, Tim C.; Key, Nigel S.; Gallippi, Caterina M.

2014-01-01

149

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

SciTech Connect

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

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

2005-12-01

150

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

PubMed

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

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

2014-12-16

151

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

SciTech Connect

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

Heeter, J.; Bird, L.

2012-11-01

152

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

153

Reduction of alternating current loss in a high- TC superconducting transmission cable by means of helical pitch adjustment  

NASA Astrophysics Data System (ADS)

We have reported that the alternating current (ac) losses in a 66 kV rms 3-core high- TC superconducting (HTS) transmission cable fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries Ltd. are calculated correctly by using an electric-circuit model. According to the calculated results, the circumferential field losses are dominant in the total ac losses in compared with the self-field losses and the axial-field losses. The helical pitches of each layer in the HTS cable are designed to obtain almost same layer currents, which gives the minimum self-field losses. We think that the optimum helical pitches giving the minimum total losses are different from the helical pitches designed by the companies and calculate the optimum values in the condition of the same helical direction of each layer in the cable. As a result, for example, it is found that the ac loss of 2.1 W m -1 cc -1 at transporting 1 kA rms can be reduced to 1.8 W m -1 cc -1 (about 14% reductions) after redesigning the cable with the optimum helical pitches. The optimum helical pitches are obtained for each given transport current. After redesigning, the distribution of layer currents is not uniform and the circumferential fields are reduced.

Noji, H.; Ooyama, S.; Nakajima, K.

2004-03-01

154

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

PubMed

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

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

2015-03-01

155

Alternating current admittance of DNTT-based metal-insulator-semiconductor capacitors  

NASA Astrophysics Data System (ADS)

Frequency-dependent carrier dynamics in dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT)-based organic field-effect transistors and metal-insulator-semiconductor capacitors were studied by using admittance measurements. Both the real (conductance) and imaginary (capacitance) components of admittance, which have a mutually complementary relationship, were analyzed in the same way. On the basis of an experimental study of devices with different contact geometries, peaks observed in the conductance spectra corresponding to slopes in the capacitance spectra were classified into two groups. The high-frequency peak was attributed to the carrier injection from the top contact to the DNTT/insulator interface just underneath the contact while the low-frequency peaks were attributed to the drift current spreading all over the interface. The model calculation of carrier diffusion reproduces the low-frequency peaks very well. It is shown that the field-effect mobility from the accumulation region to the subthreshold region can be estimated by the fitting.

Hayashi, T.; Take, N.; Tamura, H.; Sekitani, T.; Someya, T.

2014-03-01

156

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

SciTech Connect

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

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

1999-07-01

157

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. PMID:22708011

2012-01-01

158

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

SciTech Connect

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

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

2014-02-28

159

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

160

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

PubMed

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

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

2014-02-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

162

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

NASA Astrophysics Data System (ADS)

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

Mu, Jinhua; Lin, Peng; Xia, Qiangfei

2014-06-01

163

Alternating current-driven non-thermal arc plasma torch working with air medium at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This work is devoted to the investigation of the discharge characteristics of high-frequency alternating current (ac) plasma torch working with air medium using electrical and spectroscopic techniques. A simple structure and compact ac plasma torch associated with a resonance power supply allows the generation of low power discharges (lower than 1 kW) with high voltage and low current. The discharge shows a negative resistance characteristic, and its curve shifts up with gas flow increased. The effects of power on the emission intensity of NO (A 2?+ ? X 2?), OH (A 2? ? X 2?, 0-0), N2(C 3?u ? B 3?g), H? and O (3p^{5}P \\to 3S^{5}S_{2}^{0}) and their spatial distributions in plasma jet axial direction were investigated. It has been found that the emission intensities of NO, OH, N2, H? and O rise with an increase in power dissipation. With increasing axial distances of plasma jet from nozzle exit, the emission intensity of OH increases and then decreases, while the emission intensities of other species decrease sharply. The vibrational temperature is much higher than the gas temperature, which demonstrates the ac-driven arc discharge deviation from thermal equilibrium plasma.

Ni, Guohua; Lin, Qifu; Li, Lei; Cheng, Cheng; Chen, Longwei; Shen, Jie; Lan, Yan; Meng, Yuedong

2013-11-01

164

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

SciTech Connect

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

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

1998-06-01

165

Alternating current loss calculation in a high-TC superconducting transmission cable considering the magnetic field distribution  

NASA Astrophysics Data System (ADS)

We have calculated the alternating current (ac) losses of a 114 MVA high-TC superconducting (HTS) transmission cable using an electric-circuit (EC) model. The HTS cable is fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd. The EC model is comprised of a resistive part and an inductive part. The resistive part is obtained by the approximated Norris equation for a HTS tape. The Norris equation indicates hysteresis losses due to self-fields. The inductive part has two components, i.e. inductances related to axial fields and those related to circumferential fields. The layer currents and applied fields of each layer were calculated by the EC model. By using both values, the ac losses of the one-phase HTS cable were obtained by calculation considering the self-field, the axial field and the circumferential field of the HTS tape. The measured ac loss transporting 1 kArms is 0.7 W m-1 ph-1, which is equal to the calculation. The distribution of each layer loss resembles in shape the distribution of the circumferential field in each layer, which indicates that the circumferential fields strongly influence the ac losses of the HTS cable.

Noji, H.; Haji, K.; Hamada, T.

2003-01-01

166

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

E-print Network

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

Papautsky, Ian

167

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

168

Comparison of atmospheric air plasmas excited by high-voltage nanosecond pulsed discharge and sinusoidal alternating current discharge  

NASA Astrophysics Data System (ADS)

In this paper, atmospheric pressure air discharge plasma in quartz tube is excited by 15 ns high-voltage nanosecond pulsed discharge (HVNPD) and sinusoidal alternating current discharge (SACD), respectively, and a comparison study of these two kinds of discharges is made through visual imaging, electrical characterization, optical detection of active species, and plasma gas temperature. The peak voltage of the power supplies is kept at 16 kV while the pulse repetition rate of nanosecond pulse power supply is 100 Hz, and the frequency of sinusoidal power supply is 10 kHz. Results show that the HVNPD is uniform while the SACD presents filamentary mode. For exciting the same cycles of discharge, the average energy consumption in HVNPD is about 1/13 of the SACD. However, the chemical active species generated by the HVNPD is about 2-9 times than that excited by the SACD. Meanwhile, the rotational and vibrational temperatures have been obtained via fitting the simulated spectrum of N2 (C3?u ? B3?g, 0-2) with the measured one, and the results show that the plasma gas temperature in the HVNPD remains close to room temperature whereas the plasma gas temperature in the SACD is about 200 K higher than that in HVNPD in the initial phase and continually increases as discharge exposure time goes on.

Zhang, Shuai; Wang, Wen-chun; Jiang, Peng-chao; Yang, De-zheng; Jia, Li; Wang, Sen

2013-10-01

169

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

170

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

SciTech Connect

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

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

1996-12-31

171

Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage  

NASA Astrophysics Data System (ADS)

The influence of the thickness of the insulating layer and the intrinsic organic layer on the driving voltage of p-i-n based alternating current driven organic light-emitting devices (AC-OLEDs) is investigated. A three-capacitor model is employed to predict the basic behavior of the devices, and good agreement with the experimental values is found. The proposed charge regeneration mechanism based on Zener tunneling is studied in terms of field strength across the intrinsic organic layers. A remarkable consistency between the measured field strength at the onset point of light emission (3-3.1 MV/cm) and the theoretically predicted breakdown field strength of around 3 MV/cm is obtained. The latter value represents the field required for Zener tunneling in wide band gap organic materials according to Fowler-Nordheim theory. AC-OLEDs with optimized thickness of the insulating and intrinsic layers show a reduction in the driving voltage required to reach a luminance of 1000 cd/m2 of up to 23% (8.9 V) and a corresponding 20% increase in luminous efficacy.

Fr鯾el, Markus; Hofmann, Simone; Leo, Karl; Gather, Malte C.

2014-02-01

172

Microcell for anodic stripping voltammetry of trace metals.  

PubMed

A microcell for batch injection stripping voltammetry of trace metals with the use of a rotating disk working electrode has been developed and tested for samples of 0.2-0.3 mL. The detection limits for Pb(2+), Cd(2+) and Zn(2+) are 0.03 ppb and 0.3 for a deposition time of 5.0 and 0.5 min, respectively. PMID:15048423

Tur'yan, Y I; Strochkova, E M; Kuselman, I; Shenhar, A

1996-02-01

173

Diffusion-controlled multisweep cyclic voltammetry. I. Reversible deposition on a rotating disk electrode  

SciTech Connect

A model is proposed for the behavior of a diffusion-controlled reversible deposition reaction occurring on a rotating disk electrode at unit activity of deposit under conditions of multisweep cyclic voltammetry. Results are presented for dimensionless concentration, current density, and charge density functions, obtained by the application of the Nernst-Siver approximation for transient convective diffusion. The existence of a periodic state is demonstrated for cycle times of the order of the characteristic time for the rotating disk. Diagnostic criteria of potential electroanalytical use associated with the periodic state are developed in terms of dimensionless sweep rate, reversal time, and cathodic reversal overpotential. Significant differences exist in the current and concentration functions as determined during the first and second, also periodic, cathodic sweeps. The potentiodynamic determination of diffusion-limiting current densities, as well as the applicability of a triangular periodic potential waveform, in plating are also briefly discussed. 13 references, 7 figures.

Andricacos, P.C.; Ross, P.N. Jr.

1983-06-01

174

Broadband alternating current magnetic susceptibility: Method and application to the characterization of magnetic particles in igneous rocks  

NASA Astrophysics Data System (ADS)

Low-field alternating current magnetic susceptibility (MS) is among the most commonly used magnetic property, not only in rock and mineral magnetism but also in environmental magnetism studies. This study proposes a new rock magnetic method, Frequency Spectrum of MS (FSM), based on the measurement of the real component of MS over a wide range of frequency (100 Hz to 500 kHz) and the measurement of the imaginary component at high frequencies in the order of 10-102 kHz. This study presents the FSM results at room and low temperatures obtained from a variety of igneous rocks with SP to SD grain sizes, including acidic to basic volcanic rocks in Japan and a basalt in Hawaii. The FSMs from the andesite samples at room temperature unexceptionally show small but anomalous increase, as much as 5%, over a specific frequency interval between 10 kHz and 120 kHz. In contrast, FSMs of basalts from Oshima and Hawaii show no such peak, a typical pattern indicating the presence of SP grain ensembles. The anomalous FSM from the andesites suggests a new rock and mineral magnetic behavior indicating either magnetic resonance or magnetic relaxation. Considering the anomalous FSM patterns and their variations at low temperatures, it is suggested that the hypothetical resonance could be relevant to some magnetoelastic phenomenon, in which magnetic energy could be dissipated through a long-range, magnetostructural coupling, most likely, magnetostriction. The fact that the annealed andesite samples showed less developed FSM anomaly strongly supports this hypothesis, because annealing generally lowers the internal stress leading to the reduction of resistance in a forced oscillation system. Analyses of the low temperature results confirm magnetic relaxation phenomena taking place at low temperatures, and consequently support the above interpretation.

Kodama, K.

2012-12-01

175

A novel electrochemical chiral sensor for 3,4-dihydroxyphenylalanine based on the combination of single-walled carbon nanotubes, sulfuric acid and square wave voltammetry.  

PubMed

We demonstrate, for the first time, an electrochemical sensor that provides antipodal signals upon application of square wave voltammetry (SWV), for enantioselective recognition of 3,4-dihydroxyphenylalanine based on chiral single-walled carbon nanotubes (SWCNTs) in the presence of sulphuric acid. Interestingly, the enantioselectivity was not observed using the common method of cyclic voltammetry (CV) but the SWV peak currents of enantiomers were found to be quite different and hence the enantiomers could be successfully recognized. Moreover, the antipodal signals provided by two SWV scan modes offer the possibility for results to be confirmed mutually, showing a great practical value and analytical application prospects. PMID:24652224

Chen, Lisha; Chang, Fengxia; Meng, Lingchen; Li, Meixian; Zhu, Zhiwei

2014-05-01

176

Introducing absorptive stripping voltammetry: wide concentration range voltammetric phenol detection.  

PubMed

Carbon paste electrodes are developed for the detection of phenols via a procedure in which the phenols are allowed to accumulate in the paste via transfer from an aqueous solution prior to electro-oxidation. Importantly, the use of such paste electrodes is shown to substantially overcome the "self-passivating" behaviour of the phenol oxidation which usually constrains the electrode process to low concentrations and single-shot experiments. In this paper, 4-phenoxyphenol could be detected in the range from 2.5 to 40 ?M, phenol from 2.5 ?M to 60 mM and 4-methoxyphenol from 5.0 to 40 ?M. The electrodes were re-usable without surface renewal for concentrations up to 1.0 mM. The use of a bulk phenol solution for pre-concentration via absorptive uptake into a bulk phase followed by electrochemical quantification represents a new form of electroanalysis, namely "absorptive stripping voltammetry" complementary to "adsorptive stripping voltammetry" where accumulation occurs via adsorption on an electrode surface. PMID:25244304

Nissim, Rita; Compton, Richard G

2014-11-21

177

Voltage biasing, cyclic voltammetry, & electrical impedance spectroscopy for neural interfaces.  

PubMed

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays. PMID:22395095

Wilks, Seth J; Richner, Tom J; Brodnick, Sarah K; Kipke, Daryl R; Williams, Justin C; Otto, Kevin J

2012-01-01

178

FEM-based determination of optimum current distribution in transcranial magnetic stimulation as an alternative to electroconvulsive therapy  

Microsoft Academic Search

In this study, we investigated dependences of the current distribution in transcranial magnetic stimulation (TMS) on coil current intensity, coil diameter, and coil position, and compared the current distribution with that of electroconvulsive therapy (ECT). The head model consisted of 4-mm finite elements. In the ECT model, a voltage of 100 V was applied between a pair of electrodes place

Masaki Sekino; Shoogo Ueno

2004-01-01

179

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

180

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

NASA Astrophysics Data System (ADS)

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

Winquist, F.; Krantz-R黮cker, C.; Wide, P.; Lundstr鰉, I.

1998-12-01

181

Use of Alternative Funding by Rural Schools for Supplemental Programs Which Address Current Social Issues and Special Education Needs.  

ERIC Educational Resources Information Center

Gadsden Independent School District (GISD) in rural New Mexico sought alternative funding sources to meet student needs in the areas of early childhood education, special education, at-risk programs, and partnership programs with communities and local colleges. Although this school district has been granted funds for many of its projects,

Brown, Darlene N.; Schenck, Rosalie A.

182

Detection of effect of chemotherapeutic agents to cancer cells on gold nanoflower patterned substrate using surface-enhanced Raman scattering and cyclic voltammetry.  

PubMed

In vitro assays have generally been carried out for cytological diagnosis and for evaluation of the cytotoxic effect of chemotherapeutic agents as an alternative to animal experiments. In this study, a method for fabrication and application of a gold nanoflower array on an ITO substrate for evaluation of the effect of chemotherapeutic agents on cancer cell behavior by the surface-enhanced Raman scattering (SERS) analysis, as well as the electrochemical detection was described. Due to the increased sensitivity provided by gold nanoflower substrates, the effect of chemotherapeutic agents at low concentration level was successfully detected based on SERS technique. This substrate was found to give enhanced Raman spectra with high surface plasmon field in the near infrared (NIR) spectral range, which minimize fluorescence interference and photo-toxicity. Cyclic voltammetry (CV) was further performed for confirmation of results obtained by SERS assay and showed increased intensity of current peaks for various concentrations at low levels. The developed Au nanoflowers modified ITO substrates developed in this study could be used as a simultaneous SERS and CV substrate to determine the effects of chemotherapeutic agents on cancer cells. PMID:20728335

El-Said, Waleed Ahmed; Kim, Tae-Hyung; Kim, Hyuncheol; Choi, Jeong-Woo

2010-12-15

183

Preparation and coercivity and saturation magnetization dependence of inductive heating property of Fe 3O 4 nanoparticles in an alternating current magnetic field for localized hyperthermia  

Microsoft Academic Search

The magnetite (Fe3O4) nanoparticles with different magnetic properties were prepared by coprecipitation of Fe3+ and Fe2+ with an aqueous NaOH solution. The inductive heating property of Fe3O4 nanoparticles in an alternating current (ac) magnetic field was investigated. The potential of Fe3O4 nanoparticles was evaluated for localized hyperthermia treatment of cancers. The maximum saturation magnetization Ms of Fe3O4 nanoparticles was 65.53emug?1,

Dong-Lin Zhao; Xian-Wei Zeng; Qi-Sheng Xia; Jin-Tian Tang

2009-01-01

184

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

Microsoft Academic Search

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

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

1998-01-01

185

Integrated Square Wave Voltammetry Redox Sensor System for Electrochemical Analysis  

NASA Astrophysics Data System (ADS)

An integrated square wave voltammetry (SWV) redox sensor has been developed on the basis of a standard complementary metal-oxide-semiconductor (CMOS) process technology. The sensor consists of a square wave (SW) pulse generator, a voltage controller, and two electrodes for electrochemical analysis. Our proposed sensor is the first integrated sensor system of a SW pulse generator. Potassium ferricyanide solution was measured to obtain the characteristics of the proposed sensor. We confirmed that the dynamic ranges of potassium ferricyanide concentration and SW frequency were obtained from 0.6 to 6 mM and from 20 to 500 Hz, respectively. To verify the accuracy of the proposed sensor system, we performed a comparison between the fabricated sensor and an electrochemical analyzer.

Lim, Byounghyun; Futagawa, Masato; Takahashi, Sou; Dasai, Fumihiro; Ishida, Makoto; Sawada, Kazuaki

2013-11-01

186

Electrochemical characterization of bronze historical objects using voltammetry of microparticles  

NASA Astrophysics Data System (ADS)

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

Elia, Alice; Dowsett, Mark; Adriaens, Annemie

2015-02-01

187

Current levels and composition profiles of PBDEs and alternative flame retardants in surface sediments from the Pearl River Delta, southern China: comparison with historical data.  

PubMed

Polybrominated diphenyl ethers (PBDEs) and alternative flame retardants were measured in surface sediments collected during 2009-2010 from the Pearl River Delta, southern China (a large manufacturing base for electronics/electrical products), to evaluate the influence of China's RoHS directive (adopted in 2006) on their environmental occurrence. The concentrations in sediments from different water systems ranged from 3.67 to 2,520 ng/g (average of 17.1-588 ng/g) for PBDEs and from 0.22 to 5,270 ng/g (average of 11.3-454 ng/g) for the alternative retardants. Although the PBDE levels have decreased significantly compared with those in sediments collected in 2002 in this region, the levels of alternative decabromodiphenyl ethane (DBDPE) have exceeded those of BDE209 (two predominant halogenated flame retardants (HFRs) in China) in the majority of sediments. This finding suggests a different contaminant pattern of HFRs in current sediments due to the replacement of the deca-BDE mixture with DBDPE in this region. In addition, sediment concentrations of discontinued PBDEs in the rural area are clearly elevated due to e-waste dismantling. The congener profiles of PBDEs in the current sediments (with more abundant lower-brominated congeners) differed substantially from those in 2002 and from the technical products, suggesting that biological or photolytic debromination of PBDEs may have occurred in the environment. PMID:23277320

Chen, She-Jun; Feng, An-Hong; He, Ming-Jing; Chen, Man-Ying; Luo, Xiao-Jun; Mai, Bi-Xian

2013-02-01

188

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

E-print Network

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

Kounaves, Samuel P.

189

Assessment of Alternative Student Aid Delivery Systems: Specification of the Current System. Supplement II to the Final Report.  

ERIC Educational Resources Information Center

Specifications of the current student financial aid system, with attention to the Pell Grant, Guaranteed Student Loan (GSL), and campus-based programs, are provided. The methodology used to develop the specifications is also described. The campus-based programs include the Supplemental Educational Opportunity Grant Program, the College Work Study

Advanced Technology, Inc., Reston, VA.

190

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

191

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

192

Direct current voltage sweep and alternating current impedance analysis of SrZrO3 memory device in ON and OFF states  

NASA Astrophysics Data System (ADS)

The resistive switching (RS) effect of sputtered SrZrO3 memory cell is investigated by current-voltage (I-V) and impedance spectroscopy (IS) measurements for ON and OFF states. While the ON-state conduction in I-V exhibits ohmic relation of slightly temperature dependence, the OFF-state transport follows Frenkel-Poole mechanism and Arrhenius plot detects a single trap at 0.37 eV. An equivalent circuit model derived from the combined impedance-modulus spectra is proposed to characterize the real IS response. The extracted film capacitance and contact resistance keep constant at 25-100 癈 and, by contrast, the film resistance reveals activation energy of 0.08 eV. Both I-V and IS analyses indicate the domination of the OFF-state film conduction on the observed RS behavior and thermal effect. For doped perovskites, the OFF-state electrical property is associated with the presence of film-interior oxygen vacancies.

Lai, Chun-Hung; Liu, Chih-Yi

2013-12-01

193

Fully printed flexible and disposable wireless cyclic voltammetry tag.  

PubMed

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56?MHz RF reader, the printed CV tag generates 320?mHz of triangular sweep wave from +500?mV to -500?mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10?mM of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56?MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health. PMID:25630250

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

2015-01-01

194

Fully printed flexible and disposable wireless cyclic voltammetry tag  

PubMed Central

A disposable cyclic voltammetry (CV) tag is printed on a plastic film by integrating wireless power transmitter, polarized triangle wave generator, electrochemical cell and signage through a scalable gravure printing method. By proximity of 13.56?MHz RF reader, the printed CV tag generates 320?mHz of triangular sweep wave from +500?mV to ?500?mV which enable to scan a printed electrochemical cell in the CV tag. By simply dropping any specimen solution on the electrochemical cell in the CV tag, the presence of solutes in the solution can be detected and shown on the signage of the CV tag in five sec. 10?mM of N,N,N?,N?-tetramethyl-p-phenylenediamine (TMPD) was used as a standard solute to prove the working concept of fully printed disposable wireless CV tag. Within five seconds, we can wirelessly diagnose the presence of TMPD in the solution using the CV tag in the proximity of the 13.56?MHz RF reader. This fully printed and wirelessly operated flexible CV tag is the first of its kind and marks the path for the utilization of inexpensive and disposable wireless electrochemical sensor systems for initial diagnose hazardous chemicals and biological molecules to improve public hygiene and health. PMID:25630250

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

2015-01-01

195

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.; S鴕ensen, Mads P.

2013-11-01

196

ALTERNATING CURRENT LOSSES IN AG-SHEATHED BSCCO (2212 AND 2223) TAPES AND WIRES AND YBCO (123) COATED CONDUCTORS  

SciTech Connect

In this study, we focus on the examination of ac losses in conductors utilizing Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O [BSCCO (2223)] high TC superconductors (HTS). In addition, we seek to assist other facilities such as the University of Wisconsin-Madison Applied Superconductivity Center (UW-ASC), Brookhaven National Laboratory, and other DoE facilities investigating the use of HTS in electric power applications (e.g., generators, motors, and transformers). To accomplish this we will develop an ac losses capability at Clark Atlanta University to complement the established ac losses efforts at Brookhaven National Laboratory (BSCCO) on BSCCO/Ag and various material characterization efforts taking place at the UW-ASC. Our goal is through this effort to gain a greater understanding of the effects on ac losses due to parameters such as ac/dc current, J{sub c}, tape geometry, voltage tap placement, field orientation, material anisotropy, surface irregularities, percolations and filament coupling effects. As a result, we expect to better understand how to minimize ac losses in applications requiring real or practical conductors. HTS conductors based on BSCCO-2223 are now being routinely produced in industrial lengths of high quality. Vendors such as Southwire and ASC are producing multi-filamentary tapes in lengths of 6 km or more carrying critical current densities of up to 3 kA/cm**2 at 77 K. While this is approaching the level of performance where some large-scale applications are considered to be economically viable, a number of problems remain to be solved. The remaining issues include: rapid reduction in JC in magnetic fields; and power dissipation due to varying magnetic fields or currents (ac losses).

Dr. John S. Hurley

2000-01-01

197

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

PubMed

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

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

2015-01-01

198

The voltammetry杙hotocurrent response study of passivation of carbon steel in slightly alkaline solutions containing the corrosion inhibitor phosphor-polymaleic acid朲nSO 4  

Microsoft Academic Search

The electro-oxidation\\/electro-reduction processes on the surface of a carbon steel electrode were studied in borate buffer solutions (pH=8.4) in the presence and absence of the corrosion inhibitor phosphor-polymaleic acid (PPMA)朲nSO4 at room temperature by using the voltammetry杙hotocurrent response method. For the carbon steel electrode in solutions containing the corrosion inhibitor, its voltammograms displayed a smaller oxidation peak current and a

Yi-Jiu Li; Bin Wu; Xin-Ping Zeng; Ya-Fei Liu; Ya-Ming Ni; Guo-Ding Zhou; Hong-Hua Ge

2002-01-01

199

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 0.170.05 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 癈). 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 104.24.1 nM equivalent of Fe(III) to 336.219.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe(3+), varied from 21.10.2 to 22.80.3. 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, G閞aldine; Croot, Peter L; Bucciarelli, Eva; Baudoux, Anne-Claire; Baker, Alex R

2012-07-29

200

Analysis of Dopamine Using Rotating Disk Voltammetry Andrew L. Robison, Veronica Chiu, and James O. Schenk  

E-print Network

Analysis of Dopamine Using Rotating Disk Voltammetry Andrew L. Robison, Veronica Chiu, and James O Electrodes Dopamine Uptake in Rat Brains Levich Equation: 路Dr. James O. Schenk 路Veronica Chiu 路Dr. James A

Collins, Gary S.

201

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. PMID:10653813

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

2000-01-01

202

On the relation of the strength-frequency curve in excitation by alternating current to the strength-duration and latent addition curves of the nerve fiber.  

PubMed

1. Determinations were done of the strength-duration, the strength-frequency, and the latent addition curves with single fiber preparations. 2. Calculation of the strength-duration and strength-frequency curves from the latent addition data by the Blair-Monnier-Hill-Rashevsky theory yielded results which showed a considerable divergence from the actual data. Calculation by the method of integrating the whole latent addition curve yielded satisfactory results. 3. The effects of electrotonus and the inactive tissues around the nerve fiber upon the strength-frequency relation were investigated. 4. It was suggested that, for alternating current stimuli and two-way condenser discharge stimuli of very high frequencies, threshold was lowered by the rectifying action of the plasma membrane. PMID:14824505

TASAKI, I; SATO, M

1951-01-01

203

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

PubMed Central

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

Fr鰄lich, Flavio

2014-01-01

204

Simultaneous, selective detection of catecholaminergic and indolaminergic signals using cyclic voltammetry with treated micro-sensor.  

PubMed

Selective and simultaneous voltammetric analysis of catechols and indoles in vivo and in vitro has until now been feasible only by means of 'slow' scanning methods (scan speed in tens of seconds) such as differential pulse (DPV) and differential normal pulse voltammetry in conjunction with electrically and/or chemically treated carbon-fiber micro-electrodes (mCFE). Faster electrochemical techniques, such as chronoamperometry and cyclic voltammetry (CV), allow more rapid (seconds or fractions of a second) and frequent measurements of these chemicals. However, these methods show poor sensitivity and selectivity in the presence of different electroactive compounds with similar oxidation potentials. In order to analyze whether the lack of sensitivity and selectivity of the fast voltammetric methods results from the rapidity of the measurement or from the use of untreated sensors, the methods of CV (scan speed: 1000 mV/s) and DPV (scan speed: 10 mV/s) have been applied with either untreated or electrically treated mCFE to analyze the in vitro oxidation potential and current values of DA and 5-HT. When associated with untreated mCFE, neither method was able to separate and selectively detect the two compounds dissolved together in an inert vehicle; the voltammogram recorded resulted in a single broad oxidation signal. In contrast, when these techniques were performed with electrically treated mCFE, oxidation signals for DA (peak A) and 5-HT (peak B) were monitored simultaneously at approximately + 65 mV and + 240 mV, with DPV respectively, and at + 120 mV and + 300 mV with CV, respectively. Additionally, CV with treated mCFE on anesthetized rats, simultaneously monitored two striatal signals at approximately + 100 mV and + 300 mV. The oxidation values (Em) and current levels (nA) of these peaks remained stable during control recordings. The current levels were selectively increased by peripheral injection of fluphenazine (DA antagonist) or of 5-hydroxytryptophan (precursor of serotonin). The chemical nature of these two peaks may therefore be considered catecholaminergic and indolaminergic, respectively. Hence, this report provides the first evidence for the feasibility of concomitant in vitro analysis of DA and 5-HT using a rapid scanning method such as CV. In addition, the values of current level (nA) obtained with CV-mCFE for DA and 5-HT are comparable to those monitored with DPV-mCFE, supporting the view that treatment of the sensor is a key point for increasing the selectivity and the sensitivity of these voltammetric techniques. The feasibility of using CV with electrically treated mCFE for fast in vivo analysis of catechol and indole activities is also demonstrated. PMID:8618420

Crespi, F; England, T G; Trist, D G

1995-01-01

205

Electro-oxidation and determination of benomyl by square-wave adsorptive stripping voltammetry.  

PubMed

The electro-oxidation of the benomyl fungicide was studied by square-wave adsorptive stripping voltammetry. The voltammetric current at a glassy carbon electrode was acquired within the pH range 1.0-10.0. The quantitation was performed using the peak generated at +1144 mV by scanning the potential from +0.00 to +1600 mV (versus an Ag/AgCI reference electrode, 3 M NaCl). Accumulation potential = 0.0 mV, accumulation time=45 s, frequency=75 Hz, pulse amplitude=-60 mV, and staircase step potential = 7 mV were used as square-wave parameters. The peak current versus concentrations plot were rectilinear over the range from 0.081 to 1.496 microg/mL with an LOD of 0.024 microg/mL. Mean recovery was 99.0% (0.198 +/- 0.011 microg/mL), which was very close to the benomyl content spiked into river water (0.20 microg/mL). The method was efficiently applied for benomyl determination in the pesticide formulation Minelate 50WG, and the average determined content of 49.8 +/- 0.16 (n = 5) was consistent with the 50% benomyl (w/w) quoted by the manufacturer. The benomyl voltammograms recorded between days exhibited a negligible degradation into carbendazim metabolite, and therefore all results were given as the total benomyl concentration. The high recoveries and low RSD gave evidence of good accuracy and precision. PMID:25145128

Sarig黮, Tuba; Inam, Recai; Demir, Ersin; Aboul-Enein, Hassan Y

2014-01-01

206

Hydrodynamics studies of cyclic voltammetry for electrochemical micro biosensors  

NASA Astrophysics Data System (ADS)

We investigate the effect of flow rate on the electrical current response to the applied voltage in a micro electrochemical system. To accomplish this, we considered an ion-transport model that is governed by the Nernst-Planck equation coupled to the Navier-Stokes equations for hydrodynamics. The Butler-Volmer relation provides the boundary conditions, which represent reaction kinetics at the electrode-electrolyte interface. The result shows that convection drastically affects the rate of surface kinetics. At a physically sufficient high flow rates and lower scan rates, the current response is limited by the convection due to fresh ions being brought to the electrode surface and immediately taken away before any surface reaction. However, at high flow and scan rates, the Faradaic current overrides current due to convection. The model also allows predicting the effect of varying electrolyte concentration and scan rates respectively.

Adesokan, B. J.; Quan, X.; Evgrafov, A.; S鴕ensen, M. P.; Heiskanen, A.; Boisen, A.

2015-01-01

207

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

NASA Astrophysics Data System (ADS)

Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 104 cycles when the applied voltage was limited to 4.1 V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a "smart window" for energy-efficient buildings.

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

2014-10-01

208

Effects of Sc- and Zr-doped MgO layers on electron emission and discharge characteristics of alternating-current plasma display panels  

NASA Astrophysics Data System (ADS)

To improve the material properties of a protective layer for alternating-current plasma display panels, a small amount of Sc or Zr was added to a conventional MgO protective layer. The electrical properties and surface characteristics of the Sc and Zr doped MgO protective layers deposited by an ion plating method were investigated. Experimental results show that the secondary electron emission coefficients of the Sc and Zr MgO protective layers are higher than those of conventional MgO protective layers, resulting in the reductions in firing voltage and address discharge delay time. To elucidate the reason for the increase in secondary electron emission, the changes in work function and energy band structure were investigated by cathodoluminescence (CL) measurement and ultraviolet photoelectron spectroscopy (UPS). The measurements show that the work functions of the Sc and Zr MgO protective layers markedly decreased in comparison with that of the conventional MgO protective layer. Experimental results reveal that the secondary electron emission has a strong correlation with the change in work function or energy band structure that is related to the defect level produced by doping, thereby resulting in changes in electrical discharge voltage and delay time.

Jung, Eun Young; Park, Choon-Sang; Hong, Tae Eun; Sohn, Sang Ho

2014-03-01

209

Enhancing the versatility of alternate current biosusceptometry (ACB) through the synthesis of a dextrose-modified tracer and a magnetic muco-adhesive cellulose gel.  

PubMed

Alternate Current Biosusceptometry (ACB) is a promising bio-magnetic method, radiation free and easily performed used for gastric emptying exams. Due to development on its sensitivity level, interesting nature, noninvasiveness and low cost it has attracted a lot of attention. In this work, magnetic nanoparticles of Mn-Zn ferrite as well as dextrose-modified nanoparticles were synthesized to be used as possible tracers in ACB gastric emptying exams. In addition, a magnetic muco-adhesive gel was obtained by modifying the ferrite nanoparticles with cellulose. Based on in-vivo tests in rats, we show that the pure ferrite nanoparticles, whose isoelectric point was found to be at pH=3.2, present a great sensitivity to pH variations along the gastrointestinal tract, while the reduction of the isoelectric point by the dextrose modification leads to suitable nanoparticles for rapid gastric emptying examinations. On the other hand, the in-vivo tests show that the muco-adhesive cellulose gel presents substantial stomach adhesion and is a potential drug delivery system easily traceable by the ACB system. PMID:25579899

Martins, Murillo L; Calabresi, Marcos F; Quini, Caio; Matos, Juliana F; Miranda, Jos R A; Saeki, Margarida J; Bordallo, Heloisa N

2015-03-01

210

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

211

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

SciTech Connect

The [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} crystallizes at room temperature in the monoclinic system with P2{sub 1}/{sub C} space group. Three phase transitions at T{sub 1}?=?226?K, T{sub 2}?=?264?K, and T{sub 3}?=?297?K have been evidenced by DSC measurements. The electrical technique was measured in the 10{sup ?1}10{sup 7}?Hz frequency range and 203313?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(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} 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., E-mail: mohamedbenbechir@hotmail.fr; Karoui, K.; Guidara, K.; Ben Rhaiem, A. [Laboratory of Condensed Matter, Faculty of Sciences, University of Sfax, BP1171, 3018 Sfax (Tunisia); Tabellout, M. [LUNAM Universit, Universit du Maine, CNRS UMR 6283, Institut des Mol閏ules et Mat閞iaux du Mans (IMMM), Avenue Olivier Messiaen, F-72085 Le Mans Cedex 09 (France)

2014-05-28

212

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

SciTech Connect

[N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ? 300?K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1}?=?255?K, T{sub 2}?=?282?K, T{sub 3}?=?302?K, T{sub 4}?=?320?K, and T{sub 5}?=?346?K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup ?1}-10{sup 7}?Hz frequency range and 233363?K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

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

2014-04-21

213

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 1013.2 M to 1012.0 M for the reference and marina sites, respectively, whereas the corresponding [Cu2+] modeled calculations ranged from 1012.5 M to 1011.6 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朾inding 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

214

Evaluation of plasma low molecular weight antioxidant capacity by cyclic voltammetry.  

PubMed

The low molecular weight antioxidants (LMWA) of biological samples include many compounds and contribute to the total antioxidant capacity of the system. They act as direct chemical scavengers neutralizing, reactive oxygen-derived species (ROS), and contribute to the ability of the sample to cope with oxidative stress. We propose cyclic voltammetry (CV) as a new method for evaluating the antioxidant capacity of plasma-LMWA and the severity of oxidative stress exerted on the plasma. It is based on the reducing properties of these molecules. CV has been proven to be a simple, sensitive and reliable method. Its tracing does not change during storage of frozen plasma for up to six months. We analyzed the CV tracings by the oxidation potential E1/2, and the current heights Ia of its anodic wave(s). E1/2 indicates the specific component of the LMWA and its ability to donate electron(s); Ia indicates the concentration of this component. Two anodic waves have been identified in human plasma, at E1/2 = 420 +/- 25 and 920 +/- 25 mV. Ascorbate (AA) and urate (UA) were identified as major LMWA components of the first anodic wave, and were confirmed by HPLC-electrochemical detection. Ia was shown to depend linearly on the concentration of either of these LMWA, both in buffer and in plasma. Oxidative stress exerted by exposure to peroxyl radicals, copper ions and ionizing irradiation caused marked changes in the CV tracing. These changes represent corresponding alterations particularly in la, rather than in E1/2. The Ia and E1/2 values reflect the antioxidant capacity of the plasma, while the change of Ia value represents the severity of the oxidative stress induced. PMID:8981032

Chevion, S; Berry, E M; Kitrossky, N; Kohen, R

1997-01-01

215

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

PubMed

Square wave (SW) voltammetry was used to explore the adsorption properties of the food additive dye Allura Red on a hanging mercury drop electrode (HMDE). By using the adsorptive stripping voltammetric approach, we developed a sensitive electroanalytical method for the determination of this azo dye. A well-developed voltammetric peak probably related to the cathodic reduction of the azo moiety was obtained in pH 9 Britton-Robinson (B-R) buffer at 613 mV. Cyclic voltammetric studies indicated that the reduction process was irreversible and primarily controlled by adsorption. The adsorptive voltammetric signal was evaluated with respect to various experimental conditions; the optimized values were supporting electrolyte, B-R buffer; pH 11; accumulation time, 180 s; accumulation potential, 0.0 V; scan rate, 900 mV/s; pulse amplitude, 75 mV; and SW frequency, 90 Hz. Adsorptive voltammetric peak current showed a linear response for Allura Red in the concentration range of 2.5 x 10(-8) to 2.0 x 10(-7) mol/L (r = 0.998). The limit of detection was 8.5 x 10(-9) mol/L (4.2 ng/mL), the precision in terms of relative standard deviation was 1.3%, and the mean recovery was 102%. Possible interferences by several substances usually present in food products such as food additive azo dyes (E110, E102), gelatin, natural and artificial sweeteners, preservatives, and antioxidants were also evaluated. The proposed electrochemical procedure was successfully applied to the determination of this food dye in commercially available candy and a soft drink. The results were compared by statistical evaluation with those obtained by a reference spectrophotometric method. PMID:16385987

Alghamdi, Ahmad H

2005-01-01

216

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

PubMed

The behavior of the food colorant agent carmine (E120) was studied by square-wave adsorptive stripping voltammetry (SW-AdSV) at the hanging mercury drop electrode. It was observed that carmine gave a sensitive stripping voltammetric peak at -350 mV in pH 3 acetate buffer. The cyclic voltammetric technique was also used to characterize the electrochemical reduction process of carmine. The adsorptive voltammetric signal was evaluated with respect to various experimental conditions, and the optimized values were supporting electrolyte, acetate buffer; buffer acidity, pH 3; dye concentration, 3 x 10(-7) M; accumulation time, 150 s; accumulation potential, -0.2 V; scan rate, 300 mV/s; pulse amplitude, 185 mV; SW frequency, 20 Hz; working electrode area, 0.6 mm2; and convection rate, 2600 rpm. The SW-AdSV peak currents depended linearly on the concentration of carmine from 5 x 10(-8) to 1.25 x 10(-7) mol/L (r = 0.99). A detection limit of 1.43 x 10(-9) mol/L with an RSD of 2.2% and a mean recovery of 97.9% were obtained. Possible interferences by several substances usually present in food products such as food additive dyes (E102, E100, E123, E127, and E129), artificial sweeteners, preservatives, and antioxidants were also evaluated. The proposed electrochemical procedure was successfully applied to the determination of carmine food dye in spiked commercially available ice cream and soft drinks. PMID:19916383

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

2009-01-01

217

Voltammetry as a Tool for Characterization of CdTe Quantum Dots  

PubMed Central

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

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

2013-01-01

218

Determination of ascorbic acid content of some fruit juices and wine by voltammetry performed at pt and carbon paste electrodes.  

PubMed

A method was developed for assessing ascorbic acid concentration in fruit juices and wine by differential pulse voltammetry. The oxidation peak for ascorbic acid occurs at about 530 mV (versus SCE) on a Pt strip working electrode and at about 470 mV on a carbon paste working electrode. The influence of the operational parameters like the pulse amplitude and the pulse period on the analytical signal was investigated. The obtained calibration graph shows a linear dependence between the peak height and ascorbic acid concentration within the range 0.31-20 mM with a Pt working electrode, and within the range 0.07-20 mM with a carbon paste working electrode. The equation of the calibration graph was y = 21.839x + 35.726, r = 0.9940, when a Pt strip electrode was used (where y represents the value of the current intensity measured for the peak height, expressed as 礎 and x the analyte concentration, as mM). R.S.D. = 2.09%, n = 10, C(ascorbic acid) = 2.5 mM. The equation of the calibration graph was y = 3.4429x + 5.7334, r = 0.9971, when a carbon paste electrode was used (where y represents the value of intensity measured for the peak height, expressed as 礎 and x the analyte concentration, as mM). R.S.D. = 2.35%, n = 10, C(ascorbic acid) = 2.5 mM. The developed method was applied to ascorbic acid assessment in fruit juices and wine. The ascorbic acid content determined ranged between 6.83 mg/100 mL juice for soft drinks (Fanta Madness) and 54.74 mg/100 mL for citrus (lemon) juices obtained by squeezing fruit. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.74 and 104.97%. The results of ascorbic acid assessment by differential pulse voltammetry were compared with those obtained by cyclic voltammetry. The results obtained by the two methods were in good agreement. PMID:21285920

Pisoschi, Aurelia Magdalena; Pop, Aneta; Negulescu, Gheorghe Petre; Pisoschi, Aurel

2011-01-01

219

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

220

The Green Phosphor SrAl2O4:Eu2+, R3+ (R=Y, Dy) and its Application in Alternating Current Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

The aim of the present investigation was to develop a phosphor to solve the flickering luminescence of alternating current (AC) light-emitting diodes (LED) by compensating the dark duration with appropriately persistent luminescence. The phosphor SrAl2O4:Eu2+ co-doped with Y3+ or Dy3+ was synthesized via solid-state reaction with H3BO3 as flux. The crystal structure and morphology were characterized by using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM), respectively. The photoluminescence spectra were collected with a fluorescence spectrometer. The results demonstrated that appropriate amount of Y3+ or DY3+ doped was beneficial to suppress the by-product of Sr4Al14O25 which easily co-existed with the SrAl2O4 phase brought by the flux of H3BO3. However, too much Y3+ or DY3+ doped resulted in the formation of another impurity phase, i.e., the yttrium aluminum garnet of Y3Al5O12 and Dy3Al5O12. Comparatively, the doped DY3+ was more helpful in prolonging the persistent luminescence, while Y3+ was more efficient in enhancing luminescence intensity. To demonstrate the feasibility of the phosphor applied in AC LEDs, a nearly white AC LED was fabricated by coating the phosphor on a blue AC LED chip. The persistent luminescence was radiated from the AC LED device after turning power off. Moreover, the effect of the phosphor on compensating the AC LED dark duration through persistent luminescence was revealed by using the Keyence VW-9000 High-speed Microscope for the first time.

Chen, Lei; Zhang, Yao; Xue, Shaochan; Deng, Xiaorong; Anqi; Luo; Liu, Fayong; Jiang, Yang; Chen, Shifu; Bahader, Ali

2013-08-01

221

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

222

Integrated VLSI Potentiostat For Cyclic Voltammetry In Electrolytic Reactions Harpreet S. Narula and John G. Harris  

E-print Network

Integrated VLSI Potentiostat For Cyclic Voltammetry In Electrolytic Reactions Harpreet S. Narula and John G. Harris Computational Neuro-Engineering Lab University of Florida, Gainesville, FL, USA harpreet. The design maintains a constant bias po- tential between the reference and working electrodes

Harris, John G.

223

Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified  

E-print Network

Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two

Pilon, Laurent

224

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

225

Application of Square Wave Voltammetry for Electrochemical Detection in Gradient Elution HPLC  

Microsoft Academic Search

The utility of square-wave voltammetry with a conventionally sized indicator electrode for use in the detection of gradient elution HPLC applications is demonstrated. A redesigned electrochemical detector cell, based upon a type of wall-jet design, provides more efficient potential control and allows the voltammetric detection. The minimum detectable quantity and linear dynamic range for the new detector design were found

John A. Roush; Mark R. Anderson

1993-01-01

226

Direct determination of molybdenum in seawater by adsorption cathodic stripping square-wave voltammetry  

Microsoft Academic Search

A reliable and very sensitive procedure for the determination of trace levels of molybdenum in seawater is proposed. The complex of molybdenum with 8-hydroxyquinoline (Oxine) is analyzed by cathodic stripping square-wave voltammetry based on the adsorption collection onto a hanging mercury drop electrode (HMDE). This procedure of molybdenum determination was found to be more favorable than differential pulse cathodic stripping

Yuh-Chang Sun; Jerzy Mierzwa; Chi-Ren Lan

2000-01-01

227

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

ERIC Educational Resources Information Center

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

Messersmith, Stephania J.

2014-01-01

228

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...

229

Detection of low concentrations of ne-grained iron oxides by voltammetry of microparticles  

E-print Network

Detection of low concentrations of 垄ne-grained iron oxides by voltammetry of microparticles I of the samples; concentrations of (anti)ferromagnetic iron(oxy)(hydr)oxides down to V0.1 wt% could be detected. ? Abstract Mineralogical discrimination of iron oxides in soils and sediments is not a trivial task, mainly

Utrecht, Universiteit

230

Journal of Electroanalytical Chemistry 466 (1999) 129143 Voltammetry in solutions of low ionic strength. Electrochemical and  

E-print Network

Journal of Electroanalytical Chemistry 466 (1999) 129颅143 Review Voltammetry in solutions of low / Journal of Electroanalytical Chemistry 466 (1999) 129颅143130 Measurements without supporting electrolyte a Department of Chemistry, Brooklyn College, The City Uni6ersity of New York, 2900 Bedford A6e., Brooklyn, NY

Ciszkowska, Malgorzata "Maggie"

231

The cyclic and linear sweep voltammetry of regular and random arrays of microdisc electrodes: Theory  

Microsoft Academic Search

Microdisc electrode arrays are popular tools in electroanalytical chemistry. In linear sweep and cyclic voltammetry experiments, for optimum performance the individual discs in the array must have a centre-to-centre separation large enough to avoid diffusion zone overlap (which is also known as 搒hielding), but not too large as to result in a waste of surface area. Using a 2-dimensional simulation

Trevor J. Davies; Richard G. Compton

2005-01-01

232

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稬?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稬?1 sediment. This was not observed in the case of genotoxins with a low log Kow value. PMID:23242275

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

2012-01-01

233

Cyclic voltammetry study of (5-ethoxycarbonylmethylidene-4-oxothiazolidin-2-ylidene)-N-phenylethanamide  

NASA Astrophysics Data System (ADS)

As a continuation of our ongoing project on electrochemical properties of push-pull 5-substituted 2-alkylidene-4-oxothiazolidines ( 1a) differing in substituent R at C5-position and electron withdrawing group (EWG), we nave investigated the electrochemical behaviour of (5-etoxycarbonylmethylidene-4-oxothiazolidin-2-ylidene)-N-phenylethanamide 1a (R: =CHCO2Et; EWG: CONHPh), consisting as a (2 E,5 Z)/(2 Z,5 Z) mixture, by cyclic voltammetry in polar as well as non-polar solvent (0.1 M TBAHFP in DMSO and CHCl3, respectively). Cyclic voltammetry at stationary electrode was employed to characterize the electron transfer steps. Based on electrochemical criteria and correlation with the DigiSim simulations, an ECE mechanism, involving two electrochemical steps and one isomerisation step, was suggested.

Ceki?-Laskovi?, I.; Mini?, D. M.; Baranac-Stojanovi?, M.; Markovi?, R.; Volanschi, E.

2009-09-01

234

Acidithiobacillus ferrooxidans fixation on mercuric surfaces and its application in stripping voltammetry.  

PubMed

The adsorption (fixation) of bacteria Acidithiobacillus ferrooxidans on Hg and Cu metallic surfaces was qualitatively studied owing to two independent methods: frequency measurement using a quartz crystal microbalance and light absorption measuring at the Hg/bacterial culture interface. A method using a dropping mercury electrode (DME) allowed quantifying this bacterial fixation. Determining the superficial tension at Hg/bacterial culture interface led to determine bacteria adsorption on Hg through the Gibbs isotherm. A modified stripping voltammetry was proposed taking benefit of both bacterial adsorption on Hg surface and metal fixation capacity on biomass. Metal preconcentration on the biologically modified Hg electrode appeared to improve the measurement sensitivity of differential pulse anodic stripping voltammetry (DPASV). The height of the detected peaks was thus increased of 17.6% for copper, 48.4% for lead, and 132% for cadmium determinations compared to those obtained with an unmodified mercury electrode. Such augmentation depended on bulk bacteria concentration and bacteria preconcentration. PMID:16223579

Zlatev, Roumen; Magnin, Jean-Pierre; Ozil, Patrick; Stoytcheva, Margarita

2006-03-15

235

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; T黵ke, Alexander; Fischer, Wolf-Joachim; Kilmartin, Paul A

2014-09-15

236

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

PubMed

In this study, a magnetic sensor utilizing Planar Hall Resistance (PHR) and cyclic Voltammetry (CV) for detecting the radiation effect was fabricated. Specifically, we applied in parallel a PHR sensor and CV device to monitor the irradiation effect on DNA and protein respectively. Through parallel measurements, we demonstrated that the PHR sensor and CV are sensitive enough to measure irradiation effect. The PHR voltage decreased by magnetic nanobead labeled DNA was slightly recovered after gamma ray irradiation. The behavior of cdk inhibitor protein p21 having a sandwich structure of Au/protein G/Ab/Ag/Ab was checked by monitoring the cyclic Voltammetry signal in analyzing the gamma ray irradiation effect. PMID:24245238

Park, Duck-Gun; Song, Hoon; Kishore, M B; V閞tesy, G; Lee, Duk-Hyun

2013-11-01

237

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

Microsoft Academic Search

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

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

2013-01-01

238

Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

239

Voltammetry with a Fluoride-Selective Electrode with SolidPhase Reference System  

Microsoft Academic Search

Experimental results obtained in a study of the voltammetric response of an all-solid fluoride-selective electrode based on LaF3 (Eu2+ 0.8 mol %), LaF3 (Sr2+ 5 mol %) and CeF3 (Sr2+ 5 mol %) single crystals brought in contact with Ag, Bi, and Sn metal samples are presented. The method of cathodic inversion voltammetry was applied to study the reduction of

M. S. Turaeva; S. A. Kot; O. V. Glumov; I. V. Murin

2001-01-01

240

Adsorptive stripping voltammetry of Tartrazine at the hanging mercury drop electrode in soft drinks  

Microsoft Academic Search

Adsorptive stripping voltammetry was used for the determination of trace amounts of the dye Tartrazine (E-102) by square-wave\\u000a (SWS) and differential pulse techniques (DPS). Its adsorptive voltammetric behaviour was investigated at different pH media.\\u000a NH4Cl\\/NH3 buffer solution was chosen as the most suitable, taking into account the sensitivity and definition of the reduction peaks\\u000a obtained. The effects of the experimental

J. J. Berzas Nevado; J. Rodr韌uez Flores; M. J. Villase駉r Llerena

1997-01-01

241

Prenatal Diagnosis of Fetal Complete Atrioventricular Block with QT Prolongation and Alternating Ventricular Pacemakers Using MultiChannel Magnetocardiography and Current-Arrow Maps  

Microsoft Academic Search

We report a case of fetal complete atrioventricular block (CAVB) with QT prolongation and alternating ventricular pacemakers diagnosed by magentocardiography (MCG). Fetal bradyarrhythmia of around 60 bpm was detected at 30 weeks of gestation. Ultrasonography revealed fetal CAVB without structural cardiac anomalies. MCG was recorded at 30 weeks of gestation using a 64-channel superconducting quantum interference device (MC-6400, Hitachi, Japan).

Takayoshi Hosono; Mika Shinto; Yoshihide Chiba; Akihiko Kandori; Keiji Tsukada

2002-01-01

242

Determination of Nifuroxazide by Flow Injection Linear Adsorptive Stripping Voltammetry on a Screen-Printed Carbon Nanofiber Modified Electrode .  

E-print Network

??A new, sensitive, reproducible and easy-to-use flow-injection method for determining nifuroxazide based on adsorptive stripping linear sweep voltammetry over screen-printed carbon electrodes is presented. The (more)

Mozo, J. D.

2012-01-01

243

High specific surface area, reticulated current collectors for lead朼cid batteries  

Microsoft Academic Search

The use of high specific surface area (>10 cm2 cm-3) reticulated current collectors in lead朼cid batteries was studied by cyclic voltammetry, 2 V battery testing and scanning electron microscopy (SEM). Comparative cyclic voltammetry experiments revealed differences in the electrochemical behaviour of reticulated and book-mould current collector designs, with regard to both PbSO4 and PbO2 film formation. Battery testing showed that

E. Gyenge; J. Jung; S. Splinter; A. Snaper

2002-01-01

244

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

PubMed Central

A new procedure is presented for the determination of low concentrations of lead and cadmium in water samples. Ligand assisted pseudo-stir bar hollow fiber solid/liquid phase microextraction using sol杇el sorbent reinforced with carbon nanotubes was combined with differential pulse anodic stripping voltammetry for simultaneous determination of cadmium and lead in tap water, and Darongar river water samples. In the present work, differential pulse anodic stripping voltammetry (DPASV) using a hanging mercury drop electrode (HMDE) was used in order to determine the ultra trace level of lead and cadmium ions in real samples. This method is based on accumulation of lead and cadmium ions on the electrode using different ligands; Quinolin-8-ol, 5,7-diiodo quinoline-8-ol, 4,5-diphenyl-1H-imidazole-2(3H)-one and 2-{[2-(2-Hydroxy-ethylamino)-ethylamino]-methyl}-phenol as the complexing agent. The optimized conditions were obtained. The relationship between the peak current versus concentration was linear over the range of 0.05500爊g爉L?1 for Cd (II) and Pb (II). The limits of detection for lead and cadmium were 0.015爊g爉L?1 and 0.012爊g爉L?1, respectively. Under the optimized conditions, the pre-concentration factors are 2440 and 3710 for Cd (II) and Pb (II) in 5爉L of water sample, respectively.

Es抙aghi, Zarrin; Hoseini, Hasan Ali; Mohammadi-Nokhandani, Saeed; Ebrahimi, Javad

2013-01-01

245

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

PubMed

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

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

2014-11-01

246

Glassy carbon electrodes modified with multiwalled carbon nanotubes for the determination of ascorbic acid by square-wave voltammetry  

PubMed Central

Summary Multiwalled carbon nanotubes were used to modify the surface of a glassy carbon electrode to enhance its electroactivity. Nafion served to immobilise the carbon nanotubes on the electrode surface. The modified electrode was used to develop an analytical method for the analysis of ascorbic acid (AA) by square-wave voltammetry (SWV). The oxidation of ascorbic acid at the modified glassy carbon electrode showed a peak potential at 315 mV, about 80 mV lower than that observed at the bare (unmodified) electrode. The peak current was about threefold higher than the response at the bare electrode. Replicate measurements of peak currents showed good precision (3% rsd). Peak currents increased with increasing ascorbic acid concentration (dynamic range = 0.00475.0 mmol/L) and displayed good linearity (R 2 = 0.994). The limit of detection was 1.4 ?mol/L AA, while the limit of quantitation was 4.7 ?mol/L AA. The modified electrode was applied to the determination of the amount of ascorbic acid in four brands of commercial orange-juice products. The measured content agreed well (96104%) with the product label claim for all brands tested. Recovery tests on spiked samples of orange juice showed good recovery (99104%). The reliability of the SWV method was validated by conducting parallel experiments based on high-performance liquid chromatography (HPLC) with absorbance detection. The observed mean AA contents of the commercial orange juice samples obtained by the two methods were compared statistically and were found to have no significant difference (P = 0.05). PMID:23016143

Kumar, Sushil

2012-01-01

247

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

248

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

PubMed

Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique that permits the in vivo measurement of extracellular fluctuations in multiple chemical species. The technique is frequently utilized to sample sub-second (phasic) concentration changes of the neurotransmitter dopamine in awake and behaving rats. Phasic dopamine signaling is implicated in reinforcement, goal-directed behavior, and locomotion, and FSCV has been used to investigate how rapid changes in striatal dopamine concentration contribute to these and other behaviors. This unit describes the instrumentation and construction, implantation, and use of components required to sample and analyze dopamine concentration changes in awake rats with FSCV. 2015 by John Wiley & Sons, Inc. PMID:25559005

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

2015-01-01

249

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

PubMed

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

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

2014-12-01

250

Augmented and alternative NLP techniques for augmentative and alternative communication  

E-print Network

Augmented and alternative NLP techniques for augmentative and alternative communication Ann. Techniques which have been used in augmentative and alternative communication (AAC) often involve the use 94305, USA aac@csli.stanford.edu Abstract Current communication devices designed for non颅speaking users

Copestake, Ann

251

Factors Affecting the Shape of Current-Potential Curves.  

ERIC Educational Resources Information Center

Voltammetry, the fundamental electrochemical experiment, is the measurement of the current which flows at an electrode as a function of the potential applied to the electrode. Such an experiment is discussed, focusing on factors which influence the shape of the current potential curve. (JN)

Maloy, J. T.

1983-01-01

252

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

PubMed Central

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

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

2013-01-01

253

Voltammetry of basal plane platinum electrodes in acetonitrile electrolytes: effect of the presence of water.  

PubMed

The first part of this report studies the electrochemical properties of single-crystal platinum electrodes in acetonitrile electrolytes by means of cyclic voltammetry. Potential difference infrared spectroscopy in conjunction with linear voltammetry was used to obtain a molecular-level picture of this interface. The second part of this report studies the hydrogen evolution and the hydrogen oxidation reactions on the three low-index faces of Pt electrodes in acetonitrile electrolytes. The data (CVs and IR spectra) strongly suggest that acetonitrile and CN(-) molecules are adsorbed on single-crystal platinum electrodes in the range of -1.5 to 0.3 V versus Ag/AgCl. Those species block part of the adsorption sites for hydrogen adatoms, and they decompose on the surface in the presence of water. The nature of the cation and the presence of water strongly affect the onset of acetonitrile electrolysis and the kinetics and stability of the adsorbed species on the electrode. Finally, the hydrogen evolution and the hydrogen oxidation reactions on platinum single-crystal surfaces in acetonitrile electrolytes are strongly affected by the surface-energy state of Pt electrodes. PMID:22369635

Su醨ez-Herrera, Marco F; Costa-Figueiredo, Marta; Feliu, Juan M

2012-03-20

254

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

PubMed

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

Cuartero, Maria; Crespo, Gast髇 A; Ghahraman Afshar, Majid; Bakker, Eric

2014-11-18

255

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

PubMed

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

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

2014-09-16

256

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. PMID:19096710

Shi, Changyan; Xie, Shaoai; Jia, Jinping

2008-01-01

257

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

PubMed

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

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

2003-04-01

258

On-line coupling of sequential injection lab-on-valve to differential pulse anodic stripping voltammetry for determination of Pb in water samples.  

PubMed

Sequential injection lab-on-valve (LOV) was first proposed for analyzing ultra-trace amounts of Pb using differential pulse anodic stripping voltammetry (DPASV) with a miniaturized electrochemical flow cell fabricated in the LOV unit. Deposition and stripping processes took place between the renewable mercury film carbon paste electrode and sample solution, the peak current was employed as the basis of quantification. The mercury film displayed a long-term stability and reproducibility for at least 50 cycles before next renewal, the properties of integrated miniature LOV unit not only enhanced the automation of the analysis procedure but also declined sample/reagent consumption. Potential factors that affect the present procedure were investigated in detail, i.e., deposition potential, deposition time, electrode renewable procedure and the volume of sample solution. The practical applicability of the present procedure was demonstrated by determination of Pb in environmental water samples. PMID:19064113

Wang, Yang; Liu, Zaiqing; Hu, Xiaoya; Cao, Jinglian; Wang, Fei; Xu, Qin; Yang, Chun

2009-01-15

259

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

PubMed

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

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

2014-11-19

260

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

261

The Influence of the Capping Agent on the Oxidation of Silver Nanoparticles: Nano-impacts versus Stripping Voltammetry.  

PubMed

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

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

2015-02-01

262

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

SciTech Connect

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

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

2014-03-15

263

Anodic Voltammetry of Thioacetamide and its Amperometric Determination in Aqueous Media  

PubMed Central

TAA is a harmful, presumptive pollutant in tap waters and waste waters. Several alternatives have been tested as new possibilities for the anodic determination of TAA in aqueous solutions, simulated waste waters and tap water. The electrochemical behaviour of thioacetamide (TAA) was investigated at a boron-doped diamond (BDD) electrode both in unbuffered 0.1 M Na2SO4 and buffered solutions as supporting electrolytes. The anodic oxidation of TAA showed well-defined limiting currents or current peaks and a good linearity of the amperometric signal vs. concentration plots. The analytical parameters of sensitivity, RSD and LOD, obtained under various experimental conditions, suggest the suitability of the BDD electrode for electroanalytical purposes. Low fouling effects, good reproducibility and stability, as well as the sharpness of the amperometric signals in both unbuffered/ buffered acidic or neutral media, highly superior to those obtained using a glassy carbon (GC) electrode, recommend the unmodified BDD electrode as a promising potential amperometric sensor for environmental applications, regarding the direct anodic determination of TAA in aqueous media.

Cinghi??, Dan; Radovan, Ciprian; Dasc?lu, Daniela

2008-01-01

264

Protein film voltammetry and co-factor electron transfer dynamics in spinach photosystem II core complex.  

PubMed

Direct protein film voltammetry (PFV) was used to investigate the redox properties of the photosystem II (PSII) core complex from spinach. The complex was isolated using an improved protocol not used previously for PFV. The PSII core complex had high oxygen-evolving capacity and was incorporated into thin lipid and polyion films. Three well-defined reversible pairs of reduction and oxidation voltammetry peaks were observed at 4 癈 in the dark. Results were similar in both types of films, indicating that the environment of the PSII-bound cofactors was not influenced by film type. Based on comparison with various control samples including Mn-depleted PSII, peaks were assigned to chlorophyll a (Chl a) (Em = -0.47 V, all vs. NHE, at pH 6), quinones (-0.12 V), and the manganese (Mn) cluster (Em = 0.18 V). PFV of purified iron heme protein cytochrome b-559 (Cyt b-559), a component of PSII, gave a partly reversible peak pair at 0.004 V that did not have a potential similar to any peaks observed from the intact PSII core complex. The closest peak in PSII to 0.004 V is the 0.18 V peak that was found to be associated with a two-electron process, and thus is inconsistent with iron heme protein voltammetry. The -0.47 V peak had a peak potential and peak potential-pH dependence similar to that found for purified Chl a incorporated into DMPC films. The midpoint potentials reported here may differ to various extents from previously reported redox titration data due to the influence of electrode double-layer effects. Heterogeneous electron transfer (hET) rate constants were estimated by theoretical fitting and digital simulations for the -0.47 and 0.18 V peaks. Data for the Chl a peaks were best fit to a one-electron model, while the peak assigned to the Mn cluster was best fit by a two-electron/one-proton model. PMID:23625504

Zhang, Yun; Magdaong, Nikki; Frank, Harry A; Rusling, James F

2014-05-01

265

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

PubMed

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

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

2012-12-01

266

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

PubMed

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

Jiang, Chuanjia; Hsu-Kim, Heileen

2014-11-01

267

Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry.  

PubMed

Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface. PMID:25476311

Battistel, Dario; Baldi, Franco; Gallo, Michele; Faleri, Claudia; Daniele, Salvatore

2015-01-15

268

Simultaneous determination of cadmium and lead in medicinal plants by anodic stripping voltammetry.  

PubMed

A simple method for the simultaneous determination of Cd and Pb in medicinal plants by differential pulse anodic stripping voltammetry, using a hanging mercury drop electrode, was developed. The pre-concentration of the metals was performed in 0.8 mol L(-1) HCl at -0.73V for 180s. The sample preparation was carried out by dry-ashing 1.0g of finely pulverized plant samples for 2.5h at 500 degrees C. The determination limit of the method was 0.12 and 0.010 mg kg(-1) for Pb and Cd, respectively. The method was applied to the quantification of cadmium and lead in samples of Hypericum perforatum, Mikania guaco, Mikania glomerata and Peamus boldus. The voltammetric method was shown to be useful for the control of contaminants in medicinal plants. PMID:15797792

Mamani, M髇ica Cecilia Vargas; Aleixo, Luiz Manoel; de Abreu, M鬾ica Ferreira; Rath, Susanne

2005-04-01

269

Determination of antioxidant activity of spices and their active principles by differential pulse voltammetry.  

PubMed

The anodic oxidation of mercury in the presence of hydrogen peroxide in differential pulse voltammetry (DPV) was used to determine the antioxidant (AO) character of radical scavengers. Hydroperoxide radical is formed at the potentials of the oxidation peak on mercury electrodes, such radical reacting with the antioxidants in different extension. The parameter C10 (antioxidant concentration at which the peak area decreases by 10%) is used to measure the scavenging activity of the individual antioxidants. To establish the scavenging activity of antioxidant mixtures as a whole, the parameter, ?10 as the reverse of V10, V10 being the volume necessary to decrease the peak area in DPV by 10%, was selected. Higher ?10 values correspond to higher scavenging activity. The studies have been extended to aqueous extracts of some species. The results may be useful in explaining the effect of spices in vitro and in vivo studies. PMID:25264569

Palma, Alberto; Ruiz Montoya, Mercedes; Arteaga, Jes鷖 F; Rodr韌uez Mellado, Jose M

2014-01-22

270

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

PubMed

A novel differential pulse voltammetry method (DPV) was researched and developed for the simultaneous determination of Pendimethalin, Dinoseb and sodium 5-nitroguaiacolate (5NG) with the aid of chemometrics. The voltammograms of these three compounds overlapped significantly, and to facilitate the simultaneous determination of the three analytes, chemometrics methods were applied. These included classical least squares (CLS), principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural networks (RBF-ANN). A separately prepared verification data set was used to confirm the calibrations, which were built from the original and first derivative data matrices of the voltammograms. On the basis relative prediction errors and recoveries of the analytes, the RBF-ANN and the DPLS (D - first derivative spectra) models performed best and are particularly recommended for application. The DPLS calibration model was applied satisfactorily for the prediction of the three analytes from market vegetables and lake water samples. PMID:21512931

Ni, Yongnian; Wang, Lin; Kokot, Serge

2011-01-01

271

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 (0.110 mmol稬?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稬?1, r2 = 0.9995, r.s.d. = 1.14%, n = 10, Cascorbic acid = 2 mmol稬?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稬?1 for orange juice, from 0.58 to 1.93 mmol稬?1 for lemon juice, and from 0.46 to 1.84 mmol稬?1 for grapefruit juice. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.35% and 104%. Ascorbic acid determination results obtained by cyclic voltammetry were compared with those obtained by the volumetric method with dichlorophenol indophenol. The results obtained by the two methods were in good agreement. PMID:19343183

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

2008-01-01

272

An expert consortium review of the EC-commissioned report "alternative (Non-Animal) methods for cosmetics testing: current status and future prospects - 2010".  

PubMed

The European cosmetics legislation foresees a review in 2011 and possible postponement of the 2013 marketing ban to enforce the testing ban for systemic and repeated-dose animal tests. For this purpose, a 119-page report commissioned by the European Commission was published recently. Here, a group of 17 independent experts from the US, Europe, and Japan was brought together to evaluate the report. The expert panel strongly endorsed the report and its conclusions. A number of important options not considered were identified; these do not, however, affect the overall conclusions regarding the current lack of availability of a full replacement, especially for the areas of repeated dose toxicity, carcinogenicity testing, and reproductive toxicity, though a roadmap for change is emerging. However, some of these options may provide adequate data for replacement of some animal studies in the near future pending validation. Various recommendations expand the original report. The reviewers agree with the report that there is greater promise in the short term for the areas of sensitization and toxicokinetics. Additional opportunities lie in more global collaborations and the inclusion of other industry sectors. PMID:21993956

Hartung, Thomas; Blaauboer, Bas J; Bosgra, Sieto; Carney, Edward; Coenen, Joachim; Conolly, Rory B; Corsini, Emanuela; Green, Sidney; Faustman, Elaine M; Gaspari, Anthony; Hayashi, Makoto; Wallace Hayes, A; Hengstler, Jan G; Knudsen, Lisbeth E; Knudsen, Thomas B; McKim, James M; Pfaller, Walter; Roggen, Erwin L

2011-01-01

273

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

PubMed

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

Smith, D C

1992-01-01

274

Alternative Assessment.  

ERIC Educational Resources Information Center

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

Stefonek, Tom; And Others

1991-01-01

275

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 (0.310.01 ng/L) and quantification (0.950.05 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 (1.00.2 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, Ant髇io M; Freitas, Patr韈ia; Dias, Lu韘 G; Sousa, Mara E B C; Castro, Lu韘 M; Veloso, Ana C A

2013-12-15

276

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

277

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

278

Journal of Electroanalytical Chemistry 458 (1998) 161173 Linear sweep voltammetry in flooded porous electrodes at low sweep  

E-print Network

Journal of Electroanalytical Chemistry 458 (1998) 161颅173 Linear sweep voltammetry in flooded. Srikumar et al. / Journal of Electroanalytical Chemistry 458 (1998) 161颅173162 vantage of their methodology for the design and optimization of porous electrodes. Unfortunately, electroanalytical techniques that work

Weidner, John W.

279

A study of the determination of the hypertensive drug captopril by square wave cathodic adsorptive stripping voltammetry  

Microsoft Academic Search

In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction

X Ioannides; A Economou; A Voulgaropoulos

2003-01-01

280

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

PubMed

A report is presented on the use of cyclic voltammetry using silver as a working electrode. The combined electrocatalytic properties of silver and ionic liquids allow cyclic voltammetry to be turned into an ideal tool for the rapid and accurate access to diffusion coefficient values and solubility values of carbon dioxide in ionic liquids under standard conditions. PMID:25503097

Reche, Irene; Gallardo, Iluminada; Guirado, Gonzalo

2015-01-28

281

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

282

Alternating Hemiplegia  

MedlinePLUS

... have a poor prognosis because intellectual and mental capacities do not respond to drug therapy, and balance ... Alternating Hemiplegia of Childhood Foundation (AHCF) 31250 Plymouth Road Livonia, MI 48150 sharon@ahckids.org http://www. ...

283

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

284

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

285

Alternatives to Traditional Notation.  

ERIC Educational Resources Information Center

Provides a introduction and overview to alternative music notation systems. Describes guitar tablature, accordion tablature, klavarskribo (a keyboard notational system developed by Cornelius Pot, a Dutch engineer), and the digital piano roll. Briefly discusses the history of notation reform and current efforts. Includes examples from scores. (MJP)

Gaare, Mark

1997-01-01

286

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

287

Alternative Education Options.  

ERIC Educational Resources Information Center

This guide deals with various areas of alternative education programs, including current practices and different options available to school and community personnel. Steps are outlined to assess present educational settings, design new programs, select the participants, and implement and evaluate the new program. The first appendix contains

Little (Arthur D.), Inc., Washington, DC.

288

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

289

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

290

Alternating copolymers of oligoarylenes and naphthalene bisimides as low band gap semiconductors: Synthesis, electrochemical and spectroelectrochemical behavior  

Microsoft Academic Search

Three novel electroactive copolymers, consisting of alternating naphthalene bisimide and oligoarylene segments have been synthesized and studied by cyclic voltammetry and UV杤is-NIR spectroelectrochemistry. These studies show that the conjugation between both copolymer segments is very weak and the reduction of the bisimide part is essentially uninfluenced by the oligoarylene segment. The oxidation of the oligoarylene segment strongly depends on its

Pawel Gawrys; Anna Zoltowska; Malgorzata Zagorska; Adam Pron

291

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

NASA Astrophysics Data System (ADS)

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

Ombaba, Jackson M.

292

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

293

Nonlinear alternating current conduction in polycrystalline manganites  

SciTech Connect

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

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

2014-06-28

294

Nonlinear alternating current conduction in polycrystalline manganites  

NASA Astrophysics Data System (ADS)

The real part of ac conductance ?(T, f) of yttrium-doped mixed-valent polycrystalline manganite systems La1-x -yYyCaxMnO3 with x = 0.33 and 0.05 and y = 0.07 and iron doped LaMn1-xFexO3 with x = 0.15 is measured as a function of frequency f by varying zero-frequency Ohmic conductance ?0 by T. The former shows a metal-insulator transition, whereas the latter exhibits insulating character throughout the measured temperature range. At a fixed temperature T, ?(T, f) remains almost constant to the value ?0 up to a certain frequency, known as the onset frequency fc and increases from ?0 as frequency is increased from fc. Scaled appropriately, the data for ?(T, f) at different T fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductance. fc scales with ?0 as fc?0xf, where xf is the nonlinearity exponent characterising the onset. With the help of data for ac conduction, it is shown that xf is very much phase sensitive and can be used to characterize the different phases in a manganite system originated due to change in temperature or disorder. Scaling theories and existing theoretical models are used to analyze the results of ac conduction and the nonlinearity exponent xf.

Ghosh, T. N.; Nandi, U. N.; Jana, D.; Dey, K.; Giri, S.

2014-06-01

295

RENEWABLE ENERGY ALTERNATIVES: CURRENT STATUS AND CAPACITIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

296

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 01000 ngL?1 range (2 min deposition), with a detection limit of 0.88 ngL?1. The method was validated by comparison of results for an unknown solution of V by atomic absorption measurement. The protocol was evaluated in a real sample by measuring the amount of V in river water samples. Thick bismuth film electrodes with protective polystyrene films have also been made and evaluated as a mercury free alternative. However, ngL?1 level detection was only attainable with extended (10 min) deposition times. The proposed use of MWEs for the detection of V is sensitive enough for future use to test V concentration in biological fluids treated by the advanced oxidation process (AOP). PMID:19446059

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

2009-01-01

297

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

PubMed

A new, simple and selective differential pulse voltammetry (DPV) method for the simultaneous determination of selected drugs in model solutions and spiked human urine samples with prior extraction was developed and validated. The objects of analysis were paracetamol, furosemide, dipyrone, cefazolin and dexamethasone belonging to four different therapeutic groups (antibiotics, analgesic, demulcent and diuretic). Analytical methods for the preparation of urine samples for voltammetric analysis (liquid-liquid extraction--LLE and solid-phase extraction--SPE) were worked out and optimized. Hanging mercury drop electrode (HMDE) and graphite electrode were used as working electrodes. Reference electrode was Ag|AgCl|KCl((sat.)), whereas auxiliary electrode--platinum electrode. The optimal conditions for quantitative determination were obtained in a Britton-Robinson (BR) buffer at pH 2.4. Quantification was performed by means of calibration curve and standard addition methods. The calibration curves of analysed drugs are linear within the range of concentration: 6.61-66.10, 6.05-54.42, 6.00-65.00, 4.20-33.58 and 0.51-3.06 microM for paracetamol, furosemide, dipyrone, cefazolin and dexamethasone, respectively. The levels of analysed compounds in human urine can be successfully determined using this developed method with no matrix effect. PMID:18515190

Baranowska, Irena; Markowski, Piotr; Gerle, Anna; Baranowski, Jacek

2008-06-01

298

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

PubMed Central

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

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

2013-01-01

299

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

SciTech Connect

Using electrochemical cyclic voltammetry as a quick ex-situ screening tool, the impact of the extracted solution and the individual leachable constituents from prospective BOP component materials on the performance and recoverability of the platinum catalyst were evaluated. Taking an extract from Zytel{trademark} HTN51G35HSLR (PPA) as an example, the major leachable organic components are caprolactam and 1,6 hexanediol. While these organic compounds by themselves do poison the Pt catalyst to some extent, such influence is mostly recoverable by means of potential holding and potential cycling. The extracted solution, however, shows a more drastic poisoning effect and it was not recoverable. Therefore the non-recoverable poisoning effect observed for the extracted solution is not from the two organic species studied. This demonstrates the complexity of such a contaminant study. Inorganic compounds that are known poisons like sulfur even in very low concentrations, may have a more dominant effect on the Pt catalyst and the recoverability.

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

2012-07-01

300

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

PubMed

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

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

2015-01-01

301

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

PubMed

We report an electrochemical method for measuring the activity of proteases using nanoelectrode arrays (NEAs) fabricated with vertically aligned carbon nanofibers (VACNFs). The VACNFs of ~150 nm in diameter and 3 to 5 ?m in length were grown on conductive substrates and encapsulated in SiO2 matrix. After polishing and plasma etching, controlled VACNF tips are exposed to form an embedded VACNF NEA. Two types of tetrapeptides specific to cancer-mediated proteases legumain and cathepsin B are covalently attached to the exposed VACNF tip, with a ferrocene (Fc) moiety linked at the distal end. The redox signal of Fc can be measured with AC voltammetry (ACV) at ~1 kHz frequency on VACNF NEAs, showing distinct properties from macroscopic glassy carbon electrodes due to VACNF's unique interior structure. The enhanced ACV properties enable the kinetic measurements of proteolytic cleavage of the surface-attached tetrapeptides by proteases, further validated with a fluorescence assay. The data can be analyzed with a heterogeneous Michaelis-Menten model, giving "specificity constant" kcat /Km as (4.3 0.8) 10(4) M(-1)s(-1) for cathepsin B and (1.13 0.38) 10(4) M(-1)s(-1) for legumain. This method could be developed as portable multiplex electronic techniques for rapid cancer diagnosis and treatment monitoring. PMID:23814632

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

2013-02-28

302

Gold nanoelectrode arrays and their evaluation by impedance spectroscopy and cyclic voltammetry.  

PubMed

A sol-gel strategy is developed to fabricate highly regular Au nanoelectrode arrays (NEAs) consisting of a nanoperforated ultrathin membrane of ZrO(2), which exhibits a well-ordered array of pores (65+/-5) nm in diameter with a mean center-to-center distance of (110+/-10) nm, on a polycrystalline gold surface. The structural properties are investigated by field-emission scanning electron microscopy (FE-SEM), while grazing incidence small-angle X-ray scattering (GISAXS) is used to assess the thickness homogeneity and the period of the array of electrodes. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out to describe quantitatively the accessibility, electrochemical behavior, and diffusion processes of the gold NEA. A model applying parameters obtained from FE-SEM, CV, and EIS analyses is proposed to simulate the experimental results. A fairly good agreement between the experimental and the simulated data is obtained, thus allowing the deconvolution of the different diffusion regimes at the NEA. PMID:20512837

Lantiat, David; Vivier, Vincent; Laberty-Robert, Christel; Grosso, David; Sanchez, Cl閙ent

2010-06-21

303

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. PMID:23597074

2013-01-01

304

Application of Carbon Nanotubes as Working Electrodes for Cyclic Voltammetry & Impedance Spectroscopy  

NASA Astrophysics Data System (ADS)

Research conducted focuses on applications of Multi Walled Carbon Nanotubes (MWCNTs) serving as working electrodes for cyclic voltammetry (CV) and impedance spectroscopy. Expectations of increased electrochemical properties of the working electrodes were confirmed and the analysis of CNTs electrical properties was obtained. Conditions for the MWCNTs are as follows: after acidic functionalization, MWCNTs bonded with N-hydroxysuccinimide, and MWCNTs bonded with the AChE protein. Iron cyanide was chosen as the optimal analyte solution. Concentration of MWCNTs on the working electrode was also investigated. With CV an increase in capacitance, sensitivity, and sensibility was noticed. When compared to the unmodified graphite carbon electrode the modified electrode yielded lower resistivity, and higher capacitance. When compared to NHS and the AChE protein, the functionalized CNTs yielded a higher capacitance, increased sensitivity and sensibility with decrease in surface roughness. Through FTIR analysis the presence of increased carboxyl groups, enzymes, and N-hydroxysuccinimide on the walls of the MWCNTs was confirmed. In conclusion the addition of MWCNTs improved the electrodes sensitivity and sensibility for CV.

Barrios, Joseph; Cabral, Murilo; Carrilho, Emanuel; Garcia, Carlos; Ayon, Arturo

2010-10-01

305

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

306

ALTERNATIVE OXIDANTS  

EPA Science Inventory

This chapter reports on the efforts of the USEPA to study chloramines, chlorine dioxide and ozone as alternative oxidants/disinfectants to chlorine for the control of disinfection by-rpdocuts (DBPs) in drinking water. It examines the control of DBPs like trihalomethanes and haloa...

307

Cogeneration alternative  

Microsoft Academic Search

Cogeneration is one alternative energy source with a long history of useful application and a potential for contributing up to 10% of US electricity. The high efficiency provided by the four basic cogeneration cycles, with steam- and combustion-turbine topping cycles dominating, has environmental as well as economic benefits for users. Two case studies demonstrate the advantages of cogeneration to utilities.

Schnorr

1983-01-01

308

Functional meaning of tryptophan-induced increase of 5-HT metabolism as clarified by in vivo voltammetry.  

PubMed

Differential pulse voltammetry with carbon fiber electrodes was used to study serotonin (5-HT) metabolism in freely moving rats. The electrodes implanted in the striatum recorded the extracellular 5-hydroxyindoleacetic acid (5-HIAA) oxidation peak after oral tryptophan (150 mg/kg). This 5-HT precursor did not modify the 5-HIAA peak in any rat tested, but it raised 5-HIAA levels determined in total tissue by a classical biochemical method (HPLC). The administration of 5-hydroxytryptophan (5-HTP) (25 mg/kg i.p.) induced an increase of 5-HIAA detectable both in the extracellular medium by voltammetry and in tissue samples. As previously shown, dorsal raphe electrical stimulation raises extracellular 5-HIAA in the striatum and this effect is enhanced by pretreatment with tryptophan. The results suggest that tryptophan in 'normal' conditions enhances 5-HT metabolism without affecting 5-HT release unless such release is stimulated. 5-HTP increases 5-HT metabolism and release. PMID:2440515

De Simoni, M G; Sokola, A; Fodritto, F; Dal Toso, G; Algeri, S

1987-05-12

309

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

PubMed Central

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

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

2011-01-01

310

Simultaneous Voltammetry Determination of Dihydroxybenzene Isomers by Poly-bromophenol Blue\\/Carbon Nanotubes Composite Modified Electrode  

Microsoft Academic Search

A novel modified electrode was constructed by electropolymerization of bromophenol blue at a multi-walled carbon nanotubes\\u000a modified glassy carbon electrode. The electrode developed was used for the simultaneous determination of the isomers of dihydroxybenzene\\u000a in environmental samples using a voltammetry method. There was a linear relationship over the range 10?610?4 mol L?1 of hydroquinone, catechol and resorcinol; the detection limits

Pinghua Yang; Wanzhi Wei; Chunyuan Tao; Jinxiang Zeng

2007-01-01

311

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

NASA Astrophysics Data System (ADS)

This paper reports a voltammetric study of 6,6'-dithiodinicotinic acid (CPDS) across a biomimetic membrane system consisting of a monolayer of dioleoylphosphatidylcholine, deposited on mercury. Because of the low solubility of this compound and its potential decomposition in alkaline media, estimation of pK values for the carboxyl and amino groups of the pyridine ring of the CPDS entailed using the Hammett equation. UV spectra seem to confirm the presence of the dianionic form of CPDS above pH=3-4. Differential capacity and cyclic voltammetry measurements were made in order to characterize the voltammetric behavior directly on mercury and through a monolayer of dioleoylphosphatidylcholine. Estimation of the CPDS hydrophobicity degree from the partition coefficient in octanol/ water suggests no penetration of the dianion into the monolayer and supports the fact that the named dianion undergoes protonation at the phospholipid/solution interface to give a neutral specie which penetration into the phospholipid region, favored by its higher hydrophobicity, is followed by electrochemical reduction at the mercury surface. Nous avons 閠udi par voltamp閞om閠rie le comportement de l'acide 6,6'-dithiodinicotinique (CPDS) sur l'閘ectrode de mercure couverte par une monocouche de dioleoyl-phosphatidylcholine. La caract閞isation 閘ectrochimique a 閠 effectu閑 par des mesures de la capacit diff閞entielle et par voltam閠rie cyclique au dessus d'un pH 3-4. Le spectre UV para顃 confirmer la pr閟ence de la forme dianionique du CPDS. Cependant les donn閑s exp閞imentales associ閑s une estimation de l'hydrophobicit de la forme dianionique sugg鑢ent que seule la forme neutre du CPDS peut 阾re r閐uite sur la surface de l'閘ectrode.

Herrero, R.; Vilari駉, T.; Barriada, J. L.; Sastre de Vicente, M. E.; L髉ez-Fonseca, J. M.; Moncelli, M. R.

1999-04-01

312

Alternate Work Location Policy, Page 1 (revised 5/09) Alternate Work Location Agreement  

E-print Network

the employee's current position description and classification. Working at an approved alternate location, and the University of Florida has the right to refuse to assign an alternate location to any employee and by the Alternate Work Location Policy. Conversely, employees have the right to refuse to work at an alternate

Wu, Dapeng Oliver

313

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

314

An atmospheric alternative  

NASA Astrophysics Data System (ADS)

A common goal of world governments is to reduce the anthropogenic effect on the global atmosphere within the next 100 to 200 years. But there may be more than one path to that goal, according to three scientists who offered an alternative to the current timetable recommendations of the Intergovernmental Panel on Climate Change and other United Nations panels.Current proposals from the IPCC recommend immediate and sizable reductions in carbon-dioxide emissions and a relatively rapid transition away from fossil fuels in order to gradually stabilize atmospheric CO2 concentrations by 2150.

315

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朿onnected Bluetooth transceiver served as the base station. Computer software directed wireless data acquisition at 100 kilosamples/second and remote control of FSCV operation and adjustable waveform parameters. The WINCS provided reliable, high-fidelity measurements of dopamine and other neurochemicals such as serotonin, norepinephrine, and ascorbic acid by using FSCV at CFM and by flow injection analysis. In rats, the WINCS detected subsecond striatal dopamine release at the implanted sensor during high-frequency stimulation of ascending dopaminergic fibers. Overall, in vitro and in vivo testing demonstrated comparable signals to a conventional hardwired electrochemical system for FSCV. Importantly, the WINCS reduced susceptibility to electromagnetic noise typically found in an operating room setting. Conclusions Taken together, these results demonstrate that the WINCS is well suited for intraoperative neurochemical monitoring. It is anticipated that neurotransmitter measurements at an implanted chemical sensor will prove useful for advancing functional neurosurgery. PMID:19425890

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

2009-01-01

316

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

317

Alternative fuels  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

318

Functioning of antimony film electrode in acid media under cyclic and anodic stripping voltammetry conditions.  

PubMed

New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of in situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. Five different carbon- and metal-based substrate transducer electrodes revealed a clear advantage of the former ones while the concentration of the precursor Sb(III) ion exhibited a distinct influence on the ASV functioning of the SbFE. Among six acids examined as potential supporting electrolytes the HNO3 was demonstrated to yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO3 is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. By carrying out a systematic CV and ASV investigation using a medium exchange protocol, we confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Finally, the practical analytical application of the proposed ASV method was successfully tested and evaluated by measuring the three metal analytes in ground (tap) and surface (river) water samples acidified with HNO3. Our results approved the appropriateness of the SbFE and the proposed method for measuring low ?g L(-1) levels of some toxic metals, particularly taking into account the possibility of on-field testing and the use of low cost instrumentation. PMID:23764442

Sebez, Bine; Ogorevc, Bozidar; Hocevar, Samo B; Veber, Marjan

2013-06-27

319

Electrochemical behaviors of native and thermally denatured fish DNA in the presence of cytosine derivatives and porphyrin by cyclic voltammetry using boron-doped diamond electrode.  

PubMed

The electrochemical behaviors of native and thermally denatured fish DNA was investigated using boron-doped diamond (BDD) film electrode by cyclic voltammetry. The BDD electrode afforded us to measure weak current less than muA for the DNA solution in 100 microl. The mixture of acetic acid and sodium acetate solution (0.2 M) was used as a supporting electrolyte. Two oxidation peaks were observed at about +1.1 V and +1.3 V at pH 4.6 for thermally denatured fish DNA. This is due to the oxidation of guanine and adenine in the denatured fish DNA, respectively. In contrast, the native fish DNA showed ill-defined peaks at +1.1 V. Furthermore, the electrochemical behaviors of thermally denatured fish DNA were studied in the presence of cytosine, cytidine, cytidine-5-monophosphate, tetrakis(1-methypyridinium-4-yl)porphyrin (H(2)(TMPyP)(4+)) and Ru(II)(TMPyP)(4+). The oxidation peak intensity at +1.1 V gradually decreased with the increase of the concentrations of the above compounds. Based on the above studies, electrochemical behaviors of the thermally denatured fish DNA at BDD electrode is discussed. PMID:16950664

Apilux, Amara; Tabata, Masaaki; Chailapakul, Orawon

2007-05-01

320

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

PubMed

A Methimazole sensor was designed and constructed based on nanocomposite of carbon, ionic liquid, reduced graphene oxide (RGO) and CdS nanoparticles. The sensor signal was obtained by Differential FFT continuous linear sweep voltammetry (DFFTCLSV) technique. The potential waveform contains two sections, preconcentration potential and potential ramp. In this detection technique, after subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The combination of RGO and CdS nanoparticles can catalyze the electron transfer, which outcomes of the amplification of the sensor signal. The result showed that the sensor response was proportional to the concentrations of Methimazole in the range of 2.0 to 300 nM, with a detection limit of 5.510(-10) M. The sensor showed good reproducibility, long-term of usage stability and accuracy. The characterization of the sensor surface was studied by atomic force Microscopy and Electrochemical Impedance Spectroscopy. Moreover, the proposed sensor exhibited good accuracy, and R.S.D value of 2.82%, and the response time of less than 7 s. PMID:24913862

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

2014-09-01

321

Anodic stripping voltammetry for detection of DNA hybridization with porous pseudo-carbon paste electrode by gold nanoparticle-catalyzed silver enhancement.  

PubMed

A novel and sensitive electrochemical DNA biosensor based on porous pseudo-carbon paste electrode (PPCPE) for DNA immobilization and enhanced hybridization detection is described. PPCPE was fabricated by mixing polymethyl methacrylate (PMMA) microspheres as the template, graphite powders as the filler, pyrrole as the precursor of polymer which actually acted as the paste. After the polymerization of pyrrole catalyzed by Fe3+, the template PMMA microspheres were removed to form PPCPE. The pore size were determined by SEM observations, their diameters were in the range from 2 to 5 microm, and the specific surface area of PPCPE was 42.76 m2/g by N2 adsorption at 77 K using the Brunauer Emmet Teller (BET) method. The hybridization reaction on the electrode was monitored by anodic stripping voltammetry (ASV) analysis using the method of gold nanoparticle-catalyzed silver enhancement. Compared with previous DNA sensors the attached DNA and complementary DNA detection sensitivity were dramatically increased. The experiments of ASV showed that the peak current of Ag at PPCPE were linear with the amount of complementary oligonucleotide ranging from 1 to 80 nM and 0.08 to 1 nM, the detection limit was as low as 0.05 nM. PMID:19438023

Xu, Lijian; Du, Jingjing; He, Nongyue; Deng, Yan; Li, Song; Wang, Ting

2009-04-01

322

Electrochemical behaviour of sertraline hydrochloride at a glassy carbon electrode and its determination in pharmaceutical products using osteryoung square wave voltammetry.  

PubMed

In this study the electrooxidation of sertraline (STR) hydrochloride in pH 8 Britton-Robinson buffer (BRb) -methanol (MeOH) (1:1,v/v) supporting electrolyte was investigated using Osteryoung Square Wave Voltammetry (OSWV) with the glassy carbon electrode. OSWV is a rapid and sensitive electro-analytical technique for sertraline determination. This study indicated that sertraline was susceptible to oxidation. The effects of the supporting electrolyte, pH and scan rate on the anodic reactions performed in BRb and a scan rate interval 5 - 1000 mVs(-1) were investigated. Sertraline hydrochloride was oxidized irreversibly and diffusion controlled. OSWV was selected for the quantitative determination. Using optimized OSWV technique, the current was linear within a concentration range of 0.04-0.8 mM in pH 8 BRb which at the equivalent volume with MeOH. The applicability of the proposed method was shown by the successful analysis of sertraline in tablet dosage forms. Accuracy, precision, selectivity, sensitivity, within day and between days reproducibility of the method were investigated statistically. Application of the suggested method to pharmaceutical formulation is presented and compared with the UV spectrophotometric and HPLC methods. The results were found to be in a good agreement. No interference was observed from common pharmaceutical adjuvants. PMID:20383937

Dermi?, S; Cay, H Y

2010-03-01

323

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

PubMed

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

Ahmadi, Farhad; Karamian, Ehsan

2014-01-01

324

Syllabus for Chem. 3700 Alternative Energy  

E-print Network

Syllabus for Chem. 3700 Alternative Energy Class Meetings: Tuesdays and Thursdays popular alternative energy sources which are currently being used or developed to help relieve with the most popular alternate energy options. Due to the interdisciplinary nature of the topic, the course

Houston, Paul L.

325

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

PubMed

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

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

2009-03-01

326

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

SciTech Connect

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

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

2011-06-01

327

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

PubMed

An electrochemical method for identifying anthraquinone-type dyes in microsamples from works of art, based in the voltammetry of microparticles approach, is reported. Upon attachment onto graphite/polyester composite electrodes, natural pigments aloe, henna, cochineal red, madder lake, kermes, shellac, and alizarin and purpurin taken as reference materials can be identified from their square wave voltammetric profiles in MeCN (0.10 mol L(-1) Bu(4)NPF(6)) and aqueous (0.25 mol L(-1) acetic acid+0.25 mol L(-1) sodium acetate) electrolytes. PMID:12733034

Dom閚ech-Carb, A; Dom閚ech-Carb, M T; Saur-Peris, M C; Gimeno-Adelantado, J V; Bosch-Reig, F

2003-04-01

328

Determination of Se(IV), Cd(II) and Pb(II) ions in homeopathic drugs by inversion voltammetry method.  

PubMed

The conditions for identification and quantification of Se(IV), Cd(II) and Pb(II) ions in homeopathic drugs by inversion voltammetry method with the use of EAGRAPH software were established. The studies proved that the method was of high sensitivity in established conditions. The detection limits were 0.66 microg/mL, 0.08 microg/mL and 0.12 microg/mL for Se(IV), Pb(II) and Cd(II) ions, respectively. This method was characterized by repeatability of measurements, a wide range of linearity and satisfactory percent recovery. PMID:22876602

Kierszniewska, Anna; Krzek, Jan

2012-01-01

329

Alternative Fuel Implementation Toolkit  

E-print Network

......................................................................................................................................................3 Considering Alternative Transportation Fuels who already know which fuels are the best fit for them. Considering Alternative Transportation Fuels? Alternative Fuels, the Smart Choice: Alternative fuels 颅 biodiesel, electricity, ethanol (E85), natural gas

330

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

PubMed

A novel, easy, quick, and inexpensive integrated electrochemical methodology composed of cyclic voltammetry and amperometry has been developed for the determination of the kinetic stability of higher oxidation states for inorganic complexes. In this study, ferrocene and its derivatives have been used as model systems and the corresponding ferrocenium cations were generated in situ during the electrochemical experiments to determine their kinetic stabilities. The study found that the ferrocenium cations decompose following the first-order kinetics at 27 3 癈 in the presence of ambient oxygen and water. The half-lives of the ferrocenium, carboxylate ferrocenium, and decamethyl ferrocenium cations were found to be 1.27 10(3), 1.52 10(3), and ?11.0 10(3) s, respectively, in acetonitrile solvent having a 0.5 M tetrabutylammonium hexafluorophosphate electrolyte. These results are in agreement with the previous reports, i.e. the ferrocenium cation is unstable whereas the decamethyl ferrocenium cation has superior stability. The new methodology has been established by performing various experiments using different concentrations of ferrocene, variable scan rates in cyclic voltammetry, different time periods for amperometry, and in situ spectroelectrochemical experiments. PMID:25270846

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

2014-11-21

331

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

PubMed

Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10 ?g L(-1). The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000 mg L(-1) in B/C ratio. PMID:25059140

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

2014-10-01

332

Fast voltammetry of metals at carbon-fiber microelectrodes: copper adsorption onto activated carbon aids rapid electrochemical analysis.  

PubMed

Rapid, in situ trace metal analysis is essential for understanding many biological and environmental processes. For example, trace metals are thought to act as chemical messengers in the brain. In the environment, some of the most damaging pollution occurs when metals are rapidly mobilized and transported during hydrologic events (storms). Electrochemistry is attractive for in situ analysis, primarily because electrodes are compact, cheap and portable. Electrochemical techniques, however, do not traditionally report trace metals in real-time. In this work, we investigated the fundamental mechanisms of a novel method, based on fast-scan cyclic voltammetry (FSCV), that reports trace metals with sub-second temporal resolution at carbon-fiber microelectrodes (CFMs). Electrochemical methods and geochemical models were employed to find that activated CFMs rapidly adsorb copper, a phenomenon that greatly advances the temporal capabilities of electrochemistry. We established the thermodynamics of surface copper adsorption and the electrochemical nature of copper deposition onto CFMs and hence identified a unique adsorption-controlled electrochemical mechanism for ultra-fast trace metal analysis. This knowledge can be exploited in the future to increase the sensitivity and selectivity of CFMs for fast voltammetry of trace metals in a variety of biological and environmental models. PMID:25051455

Pathirathna, Pavithra; Samaranayake, Srimal; Atcherley, Christopher W; Parent, Kate L; Heien, Michael L; McElmurry, Shawn P; Hashemi, Parastoo

2014-09-21

333

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

PubMed Central

A new automated pharmacoanalytical technique for convenient quantification of redox-active antibiotics has been established by combining the benefits of a carbon nanotube (CNT) sensor modification with electrocatalytic activity for analyte detection with the merits of a robotic electrochemical device that is capable of sequential nonmanual sample measurements in 24-well microtiter plates. Norfloxacin (NFX) and ciprofloxacin (CFX), two standard fluoroquinolone antibiotics, were used in automated calibration measurements by differential pulse voltammetry (DPV) and accomplished were linear ranges of 110 ?M and 2100 ?M for NFX and CFX, respectively. The lowest detectable levels were estimated to be 0.30.1 ?M (n=7) for NFX and 1.60.1 ?M (n=7) for CFX. In standard solutions or tablet samples of known content, both analytes could be quantified with the robotic DPV microtiter plate assay, with recoveries within 4% of 100%. And recoveries were as good when NFX was evaluated in human serum samples with added NFX. The use of simple instrumentation, convenience in execution, and high effectiveness in analyte quantitation suggest the merger between automated microtiter plate voltammetry and CNT-supported electrochemical drug detection as a novel methodology for antibiotic testing in pharmaceutical and clinical research and quality control laboratories.

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

2015-01-01

334

Is garlic alternative medicine?  

PubMed

Garlic has been used medicinally since antiquity. In virtually every early civilization known, such as ancient India, Egypt, Rome, China, and Japan, garlic was part of the therapeutic regimen for a variety of maladies. Therefore, the ancient medicinal tradition of garlic use would qualify it as a folk medicine or as an alternative or complementary medicine. But is garlic an alternative to established methods of disease prevention or treatment? Scientists from around the world have identified a number of bioactive substances in garlic that are water soluble (e.g., S-allyl methylcysteine), and fat soluble (e.g., diallyldisulfide). Mechanisms of action are being elucidated by modern technology. The validity of ancient medicine is now being evaluated critically in cell-free systems, animal models, and human populations. Preventive and therapeutic trials of garlic are still in early stages. There are many promising lines of research suggesting the potential effects of garlic. The current state of knowledge does not recognize garlic as a true alternative, but it will likely find a place for garlic as a complement to established methods of disease prevention and treatment. Our goal should be to examine garlic together with other agents to evaluate its possible efficacy and toxicity under conditions of actual use in humans. PMID:16484549

Rivlin, Richard S

2006-03-01

335

UPDATE/ADDITIONS TO CURRENT OUST PUBLICATION: "HOW TO EVALUATE ALTERNATIVE CLEANUP TECHNOLOGIES FOR UNDERGROUND STORAGE TANK SITES: A GUIDE FOR CORRECTIVE ACTION PLAN REVIEWERS"  

EPA Science Inventory

This guidance manual is comprised of several chapters, each of which describes in detail alternative cleanup technologies for underground storage tank sites. Each chapter provides diagrams and tables to aide in determining whether a particular technology may be applicable for cl...

336

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

PubMed

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

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

2014-08-01

337

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

PubMed Central

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.2710?8 M. The linear range obtained was between 0.99 10?8 ? 8.26 10?8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples. PMID:22389596

Dom韓guez-Renedo, Olga; G髆ez Gonz醠ez, M. Jes鷖; Arcos-Mart韓ez, M. Julia

2009-01-01

338

Potential application of voltammetry of microparticles for dating porcine blood-based binding media used in Taiwanese architectural polychromies.  

PubMed

A method for dating Hemoglobine-containing archaeological samples using the voltammetry of microparticles is described. This is based on the record of the voltammetric response of such materials attached to paraffin-impregnated graphite electrodes in contact with aqueous acetate buffer. Signals attributable to the Fe(III)/Fe(II) iron couple and their catalytic enhancement in the presence of H(2)O(2) can be correlated, via first-order reaction kinetics, with the time of aging of the samples. The method has been applied to the study and dating of the polychromed architectural decoration of different parts of the architectural complex of the Longshan Temple in Lukang (18(th) ?century, Taiwan). PMID:22786819

Dom閚ech, Antonio; Dom閚ech-Carb, Mar韆 Teresa; Lee, Yu; Osete-Cortina, Laura

2012-10-01

339

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

PubMed Central

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

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

2013-01-01

340

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

PubMed Central

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

Topolovec, Stefan; Jerabek, Peter; Szab, Doroth閑 Vinga; Krenn, Heinz; W黵schum, Roland

2013-01-01

341

Current Divider  

NSDL National Science Digital Library

This current divider produces an output current, Io, that is proportional to the input current, Is. The output current is measured using a ammeter. The input current is the current of the current source. The constant of proportionality is called the gain of the current divider. The value of the gain of the current divider is determined by the resistances, R1 and R2, of the two resistors that comprise the current divider. This is an interactive lab.

Svoboda, James A.

342

Current responsive devices for synchronous generators  

DOEpatents

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

Karlicek, R.F.

1983-09-27

343

CHEMOMETRIC DETERMINATION OF RABEPRAZOLE SODIUM IN PRESENCE OF ITS ACID INDUCED DEGRADATION PRODUCTS USING SPECTROPHOTOMETRY, POLAROGRAPHY AND ANODIC VOLTAMMETRY AT A GLASSY CARBON ELECTRODE  

Microsoft Academic Search

Chemometric stability indicating methods are presented for the determination of rabeprazole sodium in presence of its acid induced degradation products using spectrophotometry, differential pulse polarography and differential pulse anodic voltammetry at a glassy carbon electrode. The applied chemometric techniques are multivariate ones including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). A difference spectrophotometric (?A)

MARWA S. MONEEB

344

The Alternative Museum  

NSDL National Science Digital Library

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

345

Electrochemical behaviour of iron in a third-generation ionic liquid: cyclic voltammetry and micromachining investigations.  

PubMed

The electrochemical behaviour of Fe in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim](+)Ntf2(-)) and mixtures with Cl(-) is studied with the aim of investigating the applicability of ionic liquids (IL) for the electrochemical machining of iron. Whereas in pure IL iron could not be significantly dissolved, the addition of Cl(-) enables the active dissolution with anodic current densities up to several mA cm(-2). Although several anodic peaks appear in the cyclic voltammograms (CV), the distinct assignment of those electrochemical processes remain difficult. In particular no proof for the formation of FeCl(x) (2-x) complexes during Fe dissolution are deduced from the CV, although such complexes are shown to be stable in the employed electrolyte. In addition, we present electrochemical drilling experiments with short potential pulses, which demonstrate that electrochemical machining of Fe is, in principle, possible in IL based electrolytes, even though hampered by slow machining speed. PMID:19760696

Moustafa, Essam M; Mann, Olivier; F黵beth, Wolfram; Schuster, Rolf

2009-12-01

346

Alternative aircraft fuels  

NASA Technical Reports Server (NTRS)

In connection with the anticipated impossibility to provide on a long-term basis liquid fuels derived from petroleum, an investigation has been conducted with the objective to assess the suitability of jet fuels made from oil shale and coal and to develop a data base which will allow optimization of future fuel characteristics, taking energy efficiency of manufacture and the tradeoffs in aircraft and engine design into account. The properties of future aviation fuels are examined and proposed solutions to problems of alternative fuels are discussed. Attention is given to the refining of jet fuel to current specifications, the control of fuel thermal stability, and combustor technology for use of broad specification fuels. The first solution is to continue to develop the necessary technology at the refinery to produce specification jet fuels regardless of the crude source.

Longwell, J. P.; Grobman, J.

1978-01-01

347

State Energy Alternatives: Alternative Energy Resources by State  

DOE Data Explorer

This U.S. map provides state by state information on incentives and laws related to alternative fuels and advanced vehicles. Discover what's available in each state for innovation grants, infrastructure grants, and production grants and who to contact. Find out how many alternative refueling stations are available in each state and where they are. Tennessee, for example, in 2009, has 114 alternative refueling stations: 36 biodiesel, 1 electrical, 29 ethanol, 4 natural gas, and 44 propane. There are also 5 Truck Stop Electrification (TSE) sites in Tennessee. Users can also find out from this map interface the contacts for Clean Cities in a state, information about renewable energy projects and activities in each state, fuel prices across a state, and biomass potential resources and current production in each state.

348

Electrochemical characterization of various metal foils as a current collector of positive electrode for rechargeable lithium batteries  

Microsoft Academic Search

Electrochemical characterization of various metal foils as a current collector of the positive electrode for rechargeable lithium batteries was carried out by cyclic voltammetry, potentiostatic electrolysis and a.c. impedance measurement. Products of the potentiostatic electrolysis were determined by atomic absorption spectroscopy and gas chromatography\\/mass spectrometry. As a result, it was found that an aluminum foil seems to be the most

Chiaki Iwakura; Yuko Fukumoto; Hiroshi Inoue; Syunpei Ohashi; Satoshi Kobayashi; Hiroshi Tada; Masaaki Abe

1997-01-01

349

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

PubMed Central

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

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

2013-01-01

350

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

PubMed Central

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

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

2011-01-01

351

Molecularly imprinted polymer grafted graphene for simultaneous electrochemical sensing of 4, 4-methylene diphenylamine and aniline by differential pulse voltammetry.  

PubMed

A sensitive and selective electrochemical sensor based on molecular imprinting polymers grafted graphene (MIPs-G) was developed for simultaneous measurement of 4, 4-methylene diphenylamine (MDA) and aniline by differential pulse voltammetry (DPV). MIPs-G was synthesized via free radical polymerization reaction using MDA and 4-vinyl pyridine as template molecule and functional monomer respectively. The obtained nanocomposites were characterized by transmission electron microscope, scanning electron microscope, Fourier transform infrared spectrometry, Raman spectroscopy and thermal gravimetric analysis. After removal template molecules, MIPs-G was used as electrode material for aromatic amines measurements. Due to the high binding affinity towards MDA and the ?-? interaction with aniline, the MIPs-G based electrochemical sensor can be used for simultaneous detection of MDA and aniline by DPV. Under the optimized condition, the oxidation potentials for MDA and aniline were observed at 0.62 and 0.72V, respectively. Moreover, MIPs-G modified glassy carbon electrode shows linear response towards MDA and aniline simultaneously over the range of 1.0 to 15?M. The MIPs-G based electrochemical sensor has been applied for simultaneous measurement of MDA and aniline in plastic tableware. PMID:25476293

Chen, Ningning; Chen, Li; Cheng, Yuxiao; Zhao, Kai; Wu, Xiaohong; Xian, Yuezhong

2015-01-15

352

Square Wave Voltammetry of TNT at Gold Electrodes Modified with Self-Assembled Monolayers Containing Aromatic Structures  

PubMed Central

Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (礎/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen. PMID:25549081

Trammell, Scott A.; Zabetakis, Dan; Moore, Martin; Verbarg, Jasenka; Stenger, David A.

2014-01-01

353

Wireless transmission of fast-scan cyclic voltammetry at a carbon-fiber microelectrode: proof of principle.  

PubMed

Fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) provides exquisite temporal and spatial resolution for monitoring brain chemistry. The utility of this approach has recently been demonstrated by measuring sub-second dopamine changes associated with behavior. However, one drawback is the cable link between animal and recording equipment that restricts behavior and precludes monitoring in complex environments. As a first step towards developing new instrumentation to overcome this technical limitation, the goal of the present study was to establish proof of principle for the wireless transmission of FSCV at a CFM. Proof of principle was evaluated in terms of measurement stability, fidelity, and susceptibility to ambient electrical noise. Bluetooth digital telemetry provided bi-directional communication between remote and home-base units and stable, high-fidelity data transfer comparable to conventional, wired systems when tested using a dummy cell (i.e., a resistor and capacitor in series simulating electrical properties of a CFM), and dopamine measurements with flow injection analysis and in the anesthetized rat with electrical stimulation. The wireless system was also less susceptible to interference from ambient electrical noise. Taken together, the present findings establish proof of principle for the wireless transmission of FSCV at a CFM. PMID:15589340

Garris, Paul A; Ensman, Robert; Poehlman, John; Alexander, Andy; Langley, Paul E; Sandberg, Stefan G; Greco, Phillip G; Wightman, R Mark; Rebec, George V

2004-12-30

354

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

PubMed Central

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

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

2013-01-01

355

Redox properties of catechins and enriched green tea extracts effectively preserve L-5-methyltetrahydrofolate: assessment using cyclic voltammetry analysis.  

PubMed

A cyclic voltammetry (CV) study was performed in pH 5.5 Britton-Robinson buffer at room temperature to study the stability of 1mM l-5-methyltetrahydrofolate (l-5-MTHF) in combination with epigallocatechin-gallate-enriched extract (EGCGe) and epigallocatechin-enriched extract (EGCe). The combination of l-5-MTHF with enriched catechin extracts provided enhanced stability of l-5-MTHF over a period of 12h under ambient air conditions at pH 5.5. CV experiments showed that increasing the concentrations of EGCGe or EGCe extracts from 80 to 400mg/L produced a decrease in the second oxidation peak of l-5-MTHF. Thus, we calculated that l-5-MTHF remained at nearly 90% when in the presence of enriched tea extracts, compared to 74% without the tea antioxidants. The catechins responsible for this preservation were EGCG and C, confirmed by LC-MS. Compared to covalent link only low interaction (hydrogen bonds) between the different catechins present in the tea extract would stabilise l-5-MTHF. Rather, it was hypothesised that EGCGe and EGCe were effective agents to preserve l-5-MTHF, through a mechanism that also involved the redox potential of catechins to maintain l-5-MTHF in its reduced form. PMID:23411334

Rozoy, Elodie; Araya-Farias, Monica; Simard, St閜han; Kitts, David; Lessard, Jean; Bazinet, Laurent

2013-06-01

356

Investigation of reactant transport within a polymer electrolyte fuel cell using localised CO stripping voltammetry and adsorption transients  

NASA Astrophysics Data System (ADS)

The distribution of carbon monoxide (CO) within a simple one dimensional polymer electrolyte fuel cell (PEFC) is studied experimentally using localised stripping voltammetry and adsorption transients. The effect of varying the carrier gas flow rate and CO dosage is investigated. It is found that residence time within the fuel cell is the key factor in determining the extent of poisoning or CO adsorption. Low flow rates are seen to result in a more anisotropic distribution of CO with greater amounts found away from the channel. High flow rates lead to a much more uniform profile. Diffusion of reactant into the gas distribution layer (GDL) and adsorption onto the catalyst retards the flow of reactant down the channel which broadens the peak width of the bulk adsorption transient. With knowledge of the catalyst roughness factor, pseudo 2-D reactant distribution profiles can be derived. These diagrams provide the equivalent of 'snap-shots' of the flow of reactants through the simple one dimensional fuel cell. This technique has applications in optimising the lateral distribution of catalyst and MEA properties such as GDL porosity.

Brett, D. J. L.; Atkins, S.; Brandon, N. P.; Vesovic, V.; Vasileiadis, N.; Kucernak, A. R.

357

Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry  

PubMed Central

Electrical stimulation is an indispensible tool in studying electrically excitable tissues in neurobiology and neuroendocrinology. In this work, the consequences of high-intensity electrical stimulation on the release of catecholamines from adrenal gland slices were examined with fast-scan cyclic voltammetry at carbon fiber microelectrodes. A biphasic signal, consisting of a fast and slow phase, was observed when electrical stimulations typically used in tissue slices (10 Hz, 350 ?A biphasic, 2.0 ms/phase pulse width) were applied to bipolar tungsten-stimulating electrodes. This signal was found to be stimulation dependent, and the slow phase of the signal was abolished when smaller (?250 ?A) and shorter (1 ms/phase) stimulations were used. The slow phase of the biphasic signal was found to be tetrodotoxin and hexamethonium independent, while the fast phase was greatly reduced using these pharmacological agents. Two different types of calcium responses were observed, where the fast phase was abolished by perfusion with a low-calcium buffer while both the fast and slow phases could be modulated when Ca2+ was completely excluded from the solution using EGTA. Perfusion with nifedipine resulted in the reduction of the slow catecholamine release to 29% of the original signal, while the fast phase was only decreased to 74% of predrug values. From these results, it was determined that high-intensity stimulations of the adrenal medulla result in depolarizing not only the splanchnic nerves, but also the chromaffin cells themselves resulting in a biphasic catecholamine release. PMID:21048165

Walsh, Paul L.; Petrovic, Jelena

2011-01-01

358

Approach for discrimination and quantification of electroactive species: kinetics difference revealed by higher harmonics of fourier transformed sinusoidal voltammetry.  

PubMed

Discrimination and quantification of electroactive species are traditionally realized by a potential difference which is mainly determined by thermodynamics. However, the resolution of this approach is limited to tens of millivolts. In this paper, we described an application of Fourier transformed sinusoidal voltammetry (FT-SV) that provides a new approach for discrimination and quantitative evaluation of electroactive species, especially thermodynamic similar ones. Numerical simulation indicates that electron transfer kinetics difference between electroactive species can be revealed by the phase angle of higher order harmonics of FT-SV, and the difference can be amplified order by order. Thus, even a very subtle kinetics difference can be amplified to be distinguishable at a certain order of harmonics. This method was verified with structurally similar ferrocene derivatives which were chosen as the model systems. Although these molecules have very close redox potential (<10 mV), discrimination and selective detection were achieved by as high as the thirteenth harmonics. The results demonstrated the feasibility and reliability of the method. It was also implied that the combination of the traditional thermodynamic method and this kinetics method can form a two-dimension resolved detection method, and it has the potential to extend the resolution of voltammetric techniques to a new level. PMID:25437710

Fang, Yishan; Huang, Xinjian; Wang, Lishi

2015-01-01

359

Diesel Engine Alternatives  

SciTech Connect

There are basically three different modes of combustion possible for use in reciprocating engines. These include, diffusion burning, as occurs in current diesel engines, flame propagation combustion such as used in conventional SI engines, and homogeneous combustion such as is used in the SwRI HCCI engine. Diesel engines currently offer significant fuel consumption benefits relative to other powerplants for on and off road applications; however, costs and efficiency may become problems as the emissions standards become even more stringent. This presentation presents a discussion of the potentials of HCCI and flame propagation engines as alternatives to the diesel engines. It is suggested that as the emissions standards become more and more stringent, the advantages of the diesel may disappear. The potential for HCCI is limited by the availability of the appropriate fuel. The potential of flame propagation engines is limited by several factors including knock, EGR tolerance, high BMEP operation, and throttling. These limitations are discussed in the context of potential for improvement of the efficiency of the flame propagation engine.

Ryan, T

2003-08-24

360

ALFRED (Al) E. EBRON, JR. Executive Director, National Alternative Fuels Training Consortium  

E-print Network

ALFRED (Al) E. EBRON, JR. Executive Director, National Alternative Fuels Training Consortium) ______________________________________________________________________________________ HIGHLIGHTS OF QUALIFICATIONS * Current Executive Director, National Alternative Fuels Training Consortium). * Alternative Fuels Program Manager for Division of Air Quality, NC DENR. * AFV Fleet Manager for NC Division

Mohaghegh, Shahab

361

Regulated functional alternative splicing in Drosophila  

PubMed Central

Alternative splicing expands the coding capacity of metazoan genes, and it was largely genetic studies in the fruit-fly Drosophila melanogaster that established the principle that regulated alternative splicing results in tissue- and stage-specific protein isoforms with different functions in development. Alternative splicing is particularly prominent in germ cells, muscle and the central nervous system where it modulates the expression of various proteins including cell-surface molecules and transcription factors. Studies in flies have given us numerous insights into alternative splicing in terms of upstream regulation, the exquisite diversity of their forms and the key differential cellular functions of alternatively spliced gene products. The current inundation of transcriptome sequencing data from Drosophila provides an unprecedented opportunity to gain a comprehensive view of alternative splicing. PMID:21908400

Venables, Julian P.; Tazi, Jamal; Juge, Fran鏾is

2012-01-01

362

Center for Alternative Fuels  

NSDL National Science Digital Library

The success of the HEV programs under this grant prompted Macomb to launch this resource, the Center for Alternative Fuels. The center holds forums in which academic and industry experts discuss the technical and societal impact of alternative fuels.

2009-12-21

363

Centre for Alternative Technology  

NSDL National Science Digital Library

CAT is an environmental nonprofit that promotes sustainable living. Its key areas of work are renewable energy, environmental building, energy efficiency, organic growing and alternative sewage systems. The group offers workshops on alternative energy, including wind, solar, and microhydroelectric.

2007-06-28

364

November 2008 Alternative Energy  

E-print Network

November 2008 Alternative Energy Technologies for BC R.L. Evans CleaN eNergy researCh CeNtre, UNiversity of british ColUmbia PaCifiC iNstitUte for Climate solUtioNs AlternAtive energy #12;Pacific Ministry of the Environment. #12;3alternative energy ExECuTIvE SummAry British Columbia is well

Pedersen, Tom

365

Analysis of C朏 bond cleavages in methylfluorobenzoates桭ragmentation and dimerization of anion radicals using convolution potential sweep voltammetry  

Microsoft Academic Search

The electrochemical reduction of methylfluorobenzoates at glassy carbon electrodes is analyzed using the convolution potential sweep voltammetry (CPSV). The stabilization of the radical anion due to the electron-withdrawing group is shown to lead to intra-molecular stepwise dissociative electron transfer. While methyl 2-fluorobenzoate (ortho isomer) follows EC mechanism, the methyl 4-fluorobenzoate (para-isomer) undergoes electro-dimerization prior to C朏 bond cleavage. The first

A. Muthukrishnan; M. V. Sangaranarayanan

2010-01-01

366

Assessment "Honest Alternatives".  

ERIC Educational Resources Information Center

Addresses the challenge of finding or creating alternatives to tests and traditional grading systems. Reflects on and describes the experience of creating an assessment tool and cautions against choosing alternatives that merely camouflage the grades. Encourages educators to find authentic alternatives to describe children's growth. (BAC)

Mandel, Susan Glazer

1995-01-01

367

WINCS-BASED WIRELESS ELECTROCHEMICAL MONITORING OF SEROTONIN (5-HT) USING FAST-SCAN CYCLIC VOLTAMMETRY: PROOF OF PRINCIPLE  

PubMed Central

Object We previously reported the development of a Wireless Instantaneous Neurotransmitter Concentration System (WINCS) for measuring dopamine and suggested that this technology may be useful for evaluating deep brain stimulation (DBS)-related neuromodulatory effects on neurotransmitter systems. WINCS supports fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) for real-time, spatially resolved neurotransmitter measurements. The FSCV parameters used to establish WINCS dopamine measurements are not suitable for serotonin, a neurotransmitter implicated in depression, because they lead to CFM fouling and a loss of sensitivity. Here, we incorporate into WINCS a previously described N-shaped waveform applied at a high scan rate to establish wireless serotonin monitoring. Methods FSCV optimized for the detection of serotonin consisted of an N-shaped waveform scanned linearly from a resting potential of, in V, +0.2 to +1.0, then to ?0.1 and back to +0.2 at a rate of 1000 V/s. Proof of principle tests included flow injection analysis and electrically evoked serotonin release in the dorsal raphe nucleus of rat brain slices. Results Flow cell injection analysis demonstrated that the N waveform applied at a scan rate of 1000 V/s significantly reduced serotonin fouling of the CFM, relative to that observed with FSCV parameters for dopamine. In brain slices, WINCS reliably detected sub-second serotonin release in the dorsal raphe nucleus evoked by local high-frequency stimulation. Conclusion WINCS supported high-fidelity wireless serotonin monitoring by FSCV at a CFM. In the future such measurements of serotonin in large animal models and in humans may help to establish the mechanism of DBS for psychiatric disease. PMID:20415521

Griessenauer, Christoph J.; Chang, Su-Youne; Tye, Susannah J.; Kimble, Christopher J.; Bennet, Kevin E.; Garris, Paul A.; Lee, Kendall H.

2010-01-01

368

Redox intermediates of flavonoids and caffeic acid esters from propolis: an EPR spectroscopy and cyclic voltammetry study.  

PubMed

The redox properties of flavonoids: chrysin (1), tectochrysin (2), galangin (3), isalpinin (4), pinostrobin (5), pinobanksin (6), pinobanksin-3-acetate (7), and of caffeic acid ester (8) and diacetylcaffeic acid ester (9), all isolated from propolis, were investigated by cyclic voltammetry in acetonitrile. The choice of aprotic solvent lowered the reactivity of the radical intermediates and made possible to identify redox steps and intermediates not detected so far. The oxidation potentials (vs. saturated calomel electrode) of the investigated compounds were in the region of 1.5 V for 3 and 4; 1.9 V for 1, 2, and 5; 2.0 V for 6 and 7; 1.29 V for 8; and 2.3 V for 9. These oxidation potentials were mainly influenced by the presence of a double bond in 2,3-position and substituent R1 in position 3. Comparison with our earlier data revealed that flavonoids, 1-4, and caffeic acid ester 8 with lower oxidation potentials showed the maximal lipid antioxidant activity, whereas those with higher potentials (5, 6, 7, and 9) are less active. On reduction of 1-9 several one-electron-steps were typically observed in the potential regions: -1.5 V, -1.8 V, and -2 V. where in simultaneous EPR experiments anion radicals of 1 and 3 were observed with the center of unpaired spin density on ring A. Upon oxidation of flavonoids 1-4 carbonyl carbon-centered radicals, .C(O)R, were identified as consecutive products using the EPR spin trapping technique. PMID:7797098

Rapta, P; Mis韐, V; Stasko, A; Vr醔el, I

1995-05-01

369

Analysis of biogenic amines in a single Drosophila larva brain by capillary electrophoresis with fast-scan cyclic voltammetry detection  

PubMed Central

Drosophila, the fruit fly, is a common model organism in biology, however quantifying neurotransmitters in Drosophila is challenging because of the small size of the central nervous system (CNS). Here, we develop neurotransmitter quantification by capillary electrophoresis with fast-scan cyclic voltammetry detection, which allows peak identification by both migration time and the cyclic voltammogram, in contrast to traditional amperometric detection which provides no chemical identification. Tissue content of biogenic amine neurotransmitters was determined in a single CNS dissected from a Drosophila larva. Low detection limits, 1 nM for dopamine and serotonin, 2.5 nM for tyramine, and 4 nM for octopamine, were achieved using field-amplified sample stacking by diluting the homogenized tissue with percholoric acid and acetonitrile. Two different strains of wild-type flies, Oregon R and Canton S, have similar dopamine and serotonin levels but different octopamine content. When flies are fed NSD-1015, which inhibits dopamine decarboxylase (Ddc) a synthesis enzyme in the dopamine and serotonin pathways, dopamine significantly decreases by 52%. A genetically altered driver line, Ddc-GAL4, had lower serotonin and dopamine content as did w118 flies. When the Ddc-GAL4 line was used to produce flies overexpressing the serotonin synthesis enzyme tryptophan hydroxylase (Ddc-GAL4;UAS-Trh), serotonin tissue content was greater than for Ddc-GAL4, but not significantly different than wild-type. These results show that CE-FSCV is useful for monitoring the impact of genetic and pharmacological manipulations on the content of multiple neurotransmitters in a CNS from a Drosophila larva. PMID:21322586

Fang, Huaifang; Vickrey, Trisha L.; Venton, B. Jill

2011-01-01

370

Alternative Fuels Data Center  

NSDL National Science Digital Library

The National Renewable Energy Laboratory operates the Alternative Fuels Data Center, a Web site with vast amounts of information on alternative fuels and the vehicles that use them. A general table of fuel properties gives a quick comparison of gasoline to several alternatives, while sections devoted to eight different fuels go into much greater depth. There are several documents that examine new alternative fuel vehicles, including performance tests, fact sheets, statistics, and case studies. The site also has common questions and answers about converting a gasoline vehicle to one that uses alternative fuels.

371

Connections between Alternative Transcription and Alternative Splicing in Mammals  

E-print Network

The majority of mammalian genes produce multiple transcripts resulting from alternative splicing (AS) and/or alternative transcription initiation (ATI) and alternative transcription termination (ATT). Comparative analysis ...

Spiridonov, Alexey Nikolaevich

372

Current Controlled Current Source (CCCS)  

NSDL National Science Digital Library

This interactive website from professor James A. Svoboda of Clarkson University describes current controlled current source (CCCS). The interactive applet depicts a circuit that contains a Current Controlled Current Source (CCCS). The gain of the CCCS can be changed using the scroll bar.

Svoboda, James A.

2011-08-29

373

Characterisation of weak magnetic field effects in an aqueous glutamic acid solution by nonlinear dielectric spectroscopy and voltammetry  

PubMed Central

Background Previous reports indicate altered metabolism and enzyme kinetics for various organisms, as well as changes of neuronal functions and behaviour of higher animals, when they were exposed to specific combinations of weak static and alternating low frequency electromagnetic fields. Field strengths and frequencies, as well as properties of involved ions were related by a linear equation, known as the formula of ion cyclotron resonance (ICR, abbreviation mentioned first by Liboff). Under certain conditions already a aqueous solution of the amino acid and neurotransmitter glutamate shows this effect. Methods An aqueous solution of glutamate was exposed to a combination of a static magnetic field of 40 ?T and a sinusoidal electromagnetic magnetic field (EMF) with variable frequency (27 Hz) and an amplitude of 50 nT. The electric conductivity and dielectric properties of the solution were investigated by voltammetric techniques in combination with non linear dielectric spectroscopy (NLDS), which allow the examination of the dielectric properties of macromolecules and molecular aggregates in water. The experiments target to elucidate the biological relevance of the observed EMF effect on molecular level. Results An ion cyclotron resonance (ICR) effect of glutamate previously reported by the Fesenko laboratory 1998 could be confirmed. Frequency resolution of the sample currents was possible by NLDS techniques. The spectrum peaks when the conditions for ion cyclotron resonance (ICR) of glutamate are matched. Furthermore, the NLDS spectra are different under ICR- and non-ICR conditions: NLDS measurements with rising control voltages from 1001100 mV show different courses of the intensities of the low order harmonics, which could possibly indicate "intensity windows". Furthermore, the observed magnetic field effects are pH dependent with a narrow optimum around pH 2.85. Conclusions Data will be discussed in the context with recent published models for the interaction of weak EMF with biological matter including ICR. A medical and health relevant aspect of such sensitive effects might be given insofar, because electromagnetic conditions for it occur at many occasions in our electromagnetic all day environment, concerning ion involvement of different biochemical pathways. PMID:15571630

Pazur, Alexander

2004-01-01

374

A new quenching alternative  

SciTech Connect

The quenching of ferrous alloys implies the controlled extraction of heat from a part at a rate sufficient to harden the part and still control the desired dimensional limitations. Quenchants in common use today are: molten metals, molten salts, petroleum oils, polymer solutions, water, and salt/water solutions. Each type of quenchant has its benefits and limitations. With current waste legislation and the trends toward environmentally friendlier industrial working fluids, many of these quenching products are coming under close scrutiny by the users and legislators. The most widely used quenchant is petroleum oil due to its favorable heat extraction characteristics. The dependence upon imports, price vulnerability, and contamination potential have caused suppliers and users to look into alternative products. Research into renewable resource, non-petroleum, vegetable oils has been going on globally for several years. The drawbacks encountered with many vegetable oils were widely known and only years of research enabled them to be overcome. The presently formulated product not only performs as well as petroleum oil but shows some characteristics better than those of the petroleum products, especially in the biodegradability and ecological aspects of the products. Stability and reproducible quenching properties have been proven with over two and one half years of field testing.

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

1996-12-31

375

Alternative HTS coated conductors  

NASA Astrophysics Data System (ADS)

The availability of Bi-2223 high-temperature-superconductor (HTS) powder-in-tube (PIT) tape, with acceptable performance for long lengths, has provided the ability to construct a wide range of HTS electric power components. As a result, there are major worldwide projects in developing HTS electric power components for demonstration in a utility environment. Utility acceptance for superconducting power equipment will depend on several key factors: improved system performance, lower life-cycle costs, higher efficiency versus conventional technology, reliability and maintenance comparable to conventional power equipment, and a competitive installed cost. The latter is impacted by the current high cost of HTS conductors, which must be lowered to costs comparable to conventional Nb-Ti wire, i.e., $2-5/kAm. The present performance and cost of state-of-the-art Bi-2223 HTS tape, although acceptable for prototype construction, is viewed as a major deterrent that may compromise eventual commercialization for most of these electric power devices. The so-called second-generation coated conductor development, with emphasis on conductors employing HTS YBCO films, is viewed as the solution to this performance and cost issue. The potential for the Tl, Hg, and Bi-oxide superconductors for producing an HTS tape as alternatives to Bi-2223 PIT (and YBCO) will be discussed with some recent results on Bi-2212 揷oated conductor development.

Blaugher, R. D.; Bhattacharya, R. N.; Chen, J.; Padmanabhan, R.

2002-10-01

376

Alternative Compression Garments  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

377

Free piston variable-stroke linear-alternator generator  

DOEpatents

A free-piston variable stroke linear-alternator AC power generator for a combustion engine is described. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod. 8 figs.

Haaland, C.M.

1998-12-15

378

Free piston variable-stroke linear-alternator generator  

DOEpatents

A free-piston variable stroke linear-alternator AC power generator for a combustion engine. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod.

Haaland, Carsten M. (Dadeville, AL)

1998-01-01

379

Towards the superconducting fault current limiter  

Microsoft Academic Search

The advent of low loss alternating current superconducting wires opens the way to a whole new current limiting technique: that of extremely fast transition from a superconducting state to a resistive state when the fault current exceeds the conductor's critical current. The 25 kV single phase prototype is constituted of a Nb Ti superconducting coil without iron core and very

V. D. Pham; Y. Laumond; T. Verhaege; A. Fenrier; M. Collet; M. Bekhaled

1991-01-01

380

Corrosion of Iron Under Alternating Wet and Dry Conditions  

Microsoft Academic Search

In-situ alternating current (AC) and direct current (DC) electrochemical techniques were used to determine the corrosion rate and corrosion potential of high-purity iron under alternate wet and dry conditions. Comparisons between DC electrochemical measurements and weight loss were conducted to verify the validity of the corrosion rate measurements. Identification of the corrosion products was performed using Raman spectroscopy. Corrosion products

D. S. Dunn; G. A. Cragnolino; M. B. Bogart; C. S. Brossia

2000-01-01

381

Alternative energy technologies for the Caribbean islands  

SciTech Connect

All islands in the Caribbean except Puerto Rico can be classified as developing islands. Of these islands, all except Trinidad and Tobago are oil importers. Uncertainties concerning uninterrupted oil supply and increasing oil prices causes economic, social and political instability and jeopardizes further development of these islands. The paper discusses the energy situation of the Caribbean islands and presents alternative energy options. Several alternative energy projects financed by local, federal and international organizations are presented. Present and future uses of alternative energy technologies are described in different islands. Barrier which handicap developing and implementing alternative energy sources in the Caribbean are discussed. The potential and possible applications of alternative energy technologies such as: solar-thermal energy, photovoltaics, wind energy, ocean thermal energy conversion (OTEC), ocean currents and tides energy, biomass, peat energy, municipal solid wastes, bioconversion, hydropower, geothermal energy, nuclear energy and energy conservation are discussed in detail as means to alleviate the energy situation in the Caribbean islands.

Pytlinski, J.T. (Univ. of Puerto Rico, San Juan (Puerto Rico))

1992-01-01

382

Alternative fuels and chemicals from synthesis gas  

SciTech Connect

The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE's LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

Unknown

1998-08-01

383

ALTERNATIVE FUELS AND CHEMICALS FROM SYNTHESIS GAS  

SciTech Connect

The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE's LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

Unknown

1999-01-01

384

Alternative Fuels and Chemicals From Synthesis Gas  

SciTech Connect

The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE's LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

none

1998-07-01

385

ALTERNATIVE FUELS AND CHEMICALS FROM SYNTHESIS GAS  

SciTech Connect

The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE's LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

Unknown

1998-01-01

386

Cooperativity of copper and molybdenum centers in polyoxometalate-based electrocatalysts: cyclic voltammetry, EQCM, and AFM characterization.  

PubMed

Electrochemical behaviors of selected Dawson-type polytungstates including 2-K10[P2W15Mo2O61box] where the symbol [box] designates a vacant site, alpha2-K7[Fe(OH2)P2W15Mo2O61], alpha2-K8[Cu(OH2)P2W15Mo2O61], alpha1- and alpha2-K8[Cu(OH2)P2W17O61], alpha2-K8[Cu(OH2)P2W13Mo4O61], and alpha2-K8[Cu(OH2)P2W12Mo5O61] were investigated by cyclic voltammetry (CV) coupled with the electrochemical quartz microbalance (EQCM), and the results were completed by atomic force microscopy (AFM) observations of the electrodeposited films. The electrocatalytic abilities of these polyoxometalates (POMs) in the reduction of dioxygen, hydrogen peroxide, and NOx were also assessed by CV and EQCM. It turns out that the remarkable electrocatalysis obtained at the reduction potential of Mo centers within alpha2-K8[Cu(OH2)P2W15Mo2O61], but in a domain where Cu2+ is not deposited, benefits from the assistance of the copper center because such catalysis could not be observed in the absence of Cu2+. EQCM confirms that no copper deposition occurs under the experimental conditions used. Analogous behaviors are encountered in the electrocatalytic reduction of nitrite where assistance by the presence of the Cu2+ center induced the observation of catalysis at the potential location of Mo centers. Finally, the reduction of nitrate is triggered by electrodeposited copper but was remarkably favored by the presence of molybdenum atoms within these polyoxometalates (POMs). All of the results converge to indicate a cooperative effect between the Mo and Cu centers within these POMs. The various results suggest that copper deposition from these POMs should give morphologically different surfaces. AFM studies confirm this expectation, and the observed morphologies and sizes of particles were rationalized by taking into account the role of the POM skeleton and its atomic composition in the electrodeposition process. PMID:17129010

Keita, Bineta; Abdeljalil, Essadik; Nadjo, Louis; Contant, Roland; Belghiche, Robila

2006-12-01

387

Effect of viscosity on steady-state voltammetry and scanning electrochemical microscopy in room temperature ionic liquids.  

PubMed

The electrochemical properties of a series of room temperature ionic liquids (RTILs) were studied using voltammetric methods and scanning electrochemical microscopy (SECM). The RTILs consisted of 1-alkyl-3-methylimidazolium cations, [C(n)C(1)Im](+), and either bis[(trifluoromethyl)sulfonyl]imide anions, [Tf(2)N](-), or hexafluorophosphate anions, [PF(6)](-). The effect of RTIL viscosity on mass transfer dynamics within each RTIL was studied electrochemically using ferrocene as a redox probe. In the case of the [C(n)C(1)Im][Tf(2)N] RTILs, the viscosity was altered by changing the alkyl chain length. [C(4)C(1)Im][PF(6)] was used for comparison as its viscosity is significantly higher than that of the [C(n)C(1)Im][Tf(2)N] RTILs. The RTIL viscosity affected the ability to record steady-state voltammograms at ultramicroelectrodes (UMEs). For example, it was possible to record steady-state voltammograms at scan rates up to 10 mV s(-1) in [C(2)C(1)Im][Tf(2)N] using 1.5 mum radius disk UMEs, but non-steady-state behavior was observed at 50 mV s(-1). However, at 12.5 microm radius UMEs, steady-state voltammetry was only observed at 1 mV s(-1) in [C(2)C(1)Im][Tf(2)N]. The RTIL viscosity also affected the ability to record SECM feedback approach curves that agreed with conventional SECM theory. In the most viscous [C(n)C(1)Im][Tf(2)N] RTILs, feedback approach curves agreed with conventional theory only when very slow tip approach speeds were used (0.1 microm s(-1)). These observations were interpreted using the Peclet number, which describes the relative contributions of convective and diffusive mass transfer to the tip surface. By recording feedback approach curves in each RTIL at a range of tip approach speeds, we describe the experimental conditions that must be met to perform SECM in imidazolium-based RTILs. The rate of heterogeneous electron transfer across the RTIL/electrode interface was also studied using SECM and the standard heterogeneous electron transfer rate constant, k(0), for ferrocene oxidation recorded in each RTIL was higher than that determined previously using voltammetric methods. PMID:20225849

Lovelock, Kevin R J; Cowling, Frances N; Taylor, Alasdair W; Licence, Peter; Walsh, Darren A

2010-04-01

388

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

ERIC Educational Resources Information Center

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

Verdini, Roxana A.; Lagier, Claudia M.

2004-01-01

389

Alternator insulation evaluation tests  

NASA Technical Reports Server (NTRS)

Tests were conducted to predict the remaining electrical insulation life of a 60 KW homopolar inductor alternator following completion of NASA turbo-alternator endurance tests for SNAP-8 space electrical power systems application. The insulation quality was established for two alternators following completion of these tests. A step-temperature aging test procedure was developed for insulation life prediction and applied to one of the two alternators. Armature winding insulation life of over 80,000 hours for an average winding temperature of 248 degrees C was predicted using the developed procedure.

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

1972-01-01

390

ALTERNATIVE DEER MANAGEMENT PLAN  

E-print Network

, and White-tailed Deer Units Arizona Game and Fish Department April 4, 2006 #12;Alternative Deer Management, 13A, 13B, 16A, 45A, 45B, 45C, and white-tailed deer units. This operational plan describes how-only muzzleloader and late white-tailed deer hunts are included since they come under the direction of alternative

Theimer, Tad

391

Alternatives to Cosmological Inflation  

E-print Network

The inflationary paradigm, although very successful phenomenologically, suffers from several conceptual problems which motivate the search for alternative scenarios of early universe cosmology. Here, two possible alternatives will be reviewed. - "string gas cosmology" and the "matter bounce". Their successes and problems will be pointed out.

Brandenberger, Robert H

2009-01-01

392

Heterosexual alternatives to marriage  

Microsoft Academic Search

The purpose of this study is to test perceptions regarding the sexuality of older persons and the appropriateness of alternatives to marriage for intimacy. Using data gathered from a random sample of 211 adult residents of a Southern city, we find that older persons are judged to be sexual beings and that some support exists for alternative outlets for sexual

David L. Klemmack; Lucinda Lee Roff

1980-01-01

393

Alternative Fuel Vehicle Data  

EIA Publications

Annual data released on the number of on-road alternative fuel vehicles and hybrid vehicles made available by both the original equipment manufacturers and aftermarket vehicle conversion facilities. Data on the use of alternative fueled vehicles and the amount of fuel they consume is also available.

2013-01-01

394

Alternative Work Programs  

ERIC Educational Resources Information Center

Employers are feeling the strain of needing to offer alternative work arrangements to retain and recruit employees. Due to a change in demographics, dual-career couples and increased technology; people are demanding a transformation in the workplace environment. Two alternatives, which are being offered by employers, are flextime and

Kuehn, Kerri L.

2004-01-01

395

ALTERNATIVE DEER FENCES  

E-print Network

ALTERNATIVE DEER FENCES IN CORE CAPERCAILLIE and BLACK GROUSE HABITATS AN INTERIM BEST GUIDANCE and black grouse in the short term, whilst research seeks alternative solutions. Summary Research has highlighted fence collisions as a major source of mortality to black grouse and capercaillie but particularly

396

Alternating pushdown automata  

Microsoft Academic Search

1.1 Summary or Results Alternating Turing machines were introduced by Chandra and Stockmeyer [2] and by Kozen [12] as an interesting generali zation of nondeterministic Turing machines. In this paper we investigate the effect of adding alternation to the power of auxilia ry pushdown automata, first investigated by Cook [3], and to auxiliary stack automata, first investigated by Ibarra [9].

Richard E. Ladner; Richard J. Lipton; Larry J. Stockmeyer

1978-01-01

397

Alternative Automobile Engines  

ERIC Educational Resources Information Center

Requirements for cleaner and more efficient engines have stimulated a search for alternatives to the conventional spark-ignition engine. So far, the defects of the alternative engines are clearer than the virtues. The following engines are compared: spark ignition, diesel, vapor-cycle, Stirling, and gas turbine. (Author/MA)

Wilson, David Gordon

1978-01-01

398

Normetex Pump Alternatives Study  

SciTech Connect

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

Clark, E.

2013-04-25

399

Propulsion alternatives for suburban rail corridors. Final report  

SciTech Connect

This study examined 5 propulsion alternatives to extending existing capital-intensive electrification and using additional electric multiple-unit (MU) cars. The objectives of this study were: (1) to identify alternatives to existing electric MU cars and diesel locomotive hauled trains used for commuter rail service in the New York-New Jersey-Connecticut region, (2) to evaluate each alternative in terms of performance capability, reliability, and other technical factors or constraints, (3) to develop capital and operating cost data for each alternative and type of electrification, and (4) to compare each baseline electrification system with feasible propulsion alternatives. The following propulsion alternatives were compared: dual-powered locomotive, alternating current locomotive, direct current locomotive, and dual-powered MU car.

Ablamsky, R.A.; King, C.M.

1981-09-01

400

Alternative Press Center  

NSDL National Science Digital Library

The Alternative Press Center (APC), a non-profit collective, is devoted to "providing access to and increasing public awareness of the alternative press." The APC publishes the Alternative Press Index (API), a comprehensive quarterly subject index to more than 260 alternative periodicals in the social sciences and the humanities. The APC Website provides organizational information as well as information about the content and function of the API. The site also includes an online directory of periodicals in the API, listing subscription information, email addresses, and URLs. In addition, the APC compiles annotated links in a section entitled Alternative Viewpoints on the Internet. The compilation, comprised of over 330 sites, may be browsed by name or subject.

401

Alternative fuel transit buses  

SciTech Connect

The National Renewable Energy Laboratory (NREL) is a U.S. Department of Energy (DOE) national laboratory; this project was funded by DOE. One of NREL`s missions is to objectively evaluate the performance, emissions, and operating costs of alternative fuel vehicles so fleet managers can make informed decisions when purchasing them. Alternative fuels have made greater inroads into the transit bus market than into any other. Each year, the American Public Transit Association (APTA) surveys its members on their inventory and buying plans. The latest APTA data show that about 4% of the 50,000 transit buses in its survey run on an alternative fuel. Furthermore, 1 in 5 of the new transit buses that members have on order are alternative fuel buses. This program was designed to comprehensively and objectively evaluate the alternative fuels in use in the industry.

Motta, R.; Norton, P.; Kelly, K. [and others

1996-10-01

402

The cyclic voltammetry of lead and lead-antimony battery grid alloy in aqueous sulphuric acid at 25 to -40 deg C  

NASA Astrophysics Data System (ADS)

The cyclic voltammetry of lead and antimonial lead has been studied in 1.25 S.G. H2SO4, at 25 C to -40 C, at sweep rates of 0.42 to 42 mV/S, between hydrogen and oxygen evolution and over narrower regions of potential. The latter, coupled with systematic variation of the positive or negative reversal potential, has revealed peak shifting and hysteresis effects which give further insight into the nature of the reactions of the lead-acid battery. The significance of the results to the improvement of charge acceptance at low temperatures is discussed.

Chang, T. G.; Wright, M. M.; Valeriote, E. M. L.

1977-02-01

403

Quinone-annulated N-heterocyclic carbene-transition-metal complexes: observation of pi-backbonding using FT-IR spectroscopy and cyclic voltammetry.  

PubMed

A new N-heterocyclic carbene architecture comprising a 1,4-naphthoquinone annulated to 1,3-dimesitylimidazolylidene (NpQ-NHC) was synthesized in two high yielding steps from commercially available starting materials. The free NpQ-NHC was characterized (solution and solid-state) and was used to synthesize various Rh and Ag complexes that ranged in pi-electron density. Enabled by the quinone moiety, the pi-systems of these complexes were analyzed using infrared spectroscopy and cyclic voltammetry. In contrast to previous reports, pi-backbonding was found to be non-negligible and was directly influenced by the metal's electronic character. PMID:17177396

Sanderson, Matthew D; Kamplain, Justin W; Bielawski, Christopher W

2006-12-27

404

Induced Currents, Eddy Currents and  

E-print Network

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

Tobar, Michael

405

Rip Currents  

NSDL National Science Digital Library

This Earth Science Photo of the Day shows how rip currents form along shorelines. The annotated photo describes how waves, sand bars, and gravity interact to form this dangerous feature. Clicking on the image affords a larger view.

Day, Earth S.

406

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

PubMed

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

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

2014-06-24

407

Determination of Silver(I) by Differential Pulse Voltammetry Using a Glassy Carbon Electrode Modified with Synthesized N-(2-Aminoethyl)-4,4?-Bipyridine  

PubMed Central

A new modified glassy carbon electrode (GCE) based on a synthesized N-(2-aminoethyl)-4,4?-bipyridine (ABP) was developed for the determination of Ag(I) by differential pulse voltammetry (DPV). ABP was covalently immobilized on GC electrodes surface using 4-nitrobenzendiazonium (4-NBD) and glutaraldehyde (GA). The Ag(I) ions were preconcentrated by chemical interaction with bipyridine under a negative potential (?0.6 V); then the reduced ions were oxidized by differential pulse voltammetry and a peak was observed at 0.34 V. The calibration curve was linear in the concentration range from 0.05 ?M to 1 ?M Ag(I) with a detection limit of 0.025 ?M and RSD = 3.6%, for 0.4 ?M Ag(I). The presence of several common ions in more than 125-fold excess had no effect on the determination of Ag(I). The developed sensor was applied to the determination of Ag(I) in water samples using a standard addition method. PMID:22163530

Radulescu, Maria-Cristina; Chira, Ana; Radulescu, Medeea; Bucur, Bogdan; Bucur, Madalina Petruta; Radu, Gabriel Lucian

2010-01-01

408

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

PubMed

In this paper, we describe a new combination method based on polytetrafluorethylene (PTFE) film-based liquid three-phase micro extraction coupled with differential pulse voltammetry (DPV) for the micro extraction and quantification of atorvastatin calcium (ATC) at the ultra-trace level. Different factors affecting the liquid-three phases micro extraction of atorvastatin calcium, including organic solvent, pH of the donor and acceptor phases, concentration of salt, extraction time, stirring rate and electrochemical factors, were investigated, and the optimal extraction conditions were established. The final stable signal was achieved after a 50 min extraction time, which was used for analytical applications. An enrichment factor of 21 was achieved, and the relative standard deviation (RSD) of the method was 4.5% (n = 4). Differential pulse voltammetry exhibited two wide linear dynamic ranges of 20.0-1000.0 pmol L(-1) and 0.001-11.0 祄ol L(-1) of ATC. The detection limit was found to be 8.1 pmol L(-1) ATC. Finally, the proposed method was used as a new combination method for the determination of atorvastatin calcium in real samples, such as human urine and plasma. PMID:23474719

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

2013-01-01

409

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

PubMed Central

This work reports on the continuing development of a lab-on-a-chip electrochemical sensor for determination of zinc in blood serum using square wave anodic stripping voltammetry. The microscale sensor consists of a three electrode system, including an environmentally friendly bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor demonstrates a linear response in 0.1 M acetate buffer at pH 6 for zinc concentrations in the 130 ?M range. By optimizing bismuth film deposition and better control of the fabrication process, repeatability of the sensor was improved, reducing variability from 42% to <2%. Through optimization of electrolyte and stripping voltammetry parameters, limit of detection was greatly improved to 60 nM. The optimized sensor was also able to measure zinc in the extracted blood serum. Ultimately, with integrated sample preparation, the sensor will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for clinical applications. PMID:24729629

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

2014-01-01

410

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

PubMed Central

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

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

2013-01-01

411

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

PubMed

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

Dermi?, S; Aydo?an, E

2010-03-01

412

Contactless measurement of alternating current conductance in quantum Hall structures  

NASA Astrophysics Data System (ADS)

We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods梐coustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Galperin, Y. M.; Ilyinskaya, N. D.; Usikova, A. A.; Kummer, M.; von K鋘el, H.

2014-10-01

413

Application of alternating current impedance to fuel cell modeling  

SciTech Connect

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

Springer, T.E.

1999-05-02

414

The Chernobyl NPP decommissioning: Current status and alternatives  

SciTech Connect

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

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

1996-08-01

415

Adaptive Control of Velocity Profile of an Alternating Current Motor  

E-print Network

/velocity control in different electro mechanic configurations are servo and step motors. Tachogenerators three periods 颅 acceleration period, slewing at a desired target velocity for some time and deceleration smooth acceleration and deceleration curves with continuous and constrained derivative. For creation

Borissova, Daniela

416

Alternating Versus Direct Current for Aircraft-Radio Power Supply  

Microsoft Academic Search

Recent designs of aircraft-radio equipment have provided for operation from existing aircraft electric systems, and little attention has been given to providing the electric system that is best suited for radio equipment use. This has been a natural and proper approach, because of the relatively small load requirements of aircraft radio. Accordingly, comparatively little attention has been given to the

D. E. Fritz; C. K. Hooper

1944-01-01

417

CURRENTLY AVAILABLE TECHNOLOGIES DEMONSTRATION FOR ALTERNATIVES TO RADIOLOGICAL SOURCES  

EPA Science Inventory

EPA's Office of Radiation and Indoor Air awarded a contract to demonstrate that non-nuclear measurement using optical and magnetic technology can replace radioactive devices used to measure the thickness and density of various paper, film, and plastic sheets....

418

Contactless measurement of alternating current conductance in quantum Hall structures  

SciTech Connect

We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods梐coustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Ilyinskaya, N. D.; Usikova, A. A. [A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Galperin, Y. M. [Department of Physics, University of Oslo, P.O. Box 1048 Blindern, 0316 Oslo (Norway); A. F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Kummer, M.; K鋘el, H. von [Laboratorium f黵 Festk鰎perphysik ETH Z黵ich, CH-8093 Z黵ich (Switzerland)

2014-10-21

419

The magnetic amplifier with alternating-current control  

E-print Network

,dt + > N ? ,? a ,(12) 1 1 1 xdt C-lF 1 g ,j = 1 s. SJdt * dik 1 R U 1A 1 di = ivRv + L, ? + ? l ivdt + > T WF-WU- m ? a ,(13 ) k k k kdt c / k ^ 1 1 kj s g jdt O dij. i R n u'.'a. di en = 1nRn + Ln ^ + b yWCdw + ? ( 14)n n n -^dt CMF ar j " = ^ l... ? + 2 lI tal + n I tc l} and ml . U[_2X- E. 2nX j a i l ' Tcos b + 2 I tbl - n I tcl (136) Condition 2 Os OpC + n R? _ sin b + ^ 2I t a 2 + nI t c 2 ^e - ?.(? - ?2)x + 4 D weC: and (137) 'm2...

Andrew, Edward Harris

2013-10-04

420

Alternative energy design toolkit  

E-print Network

This thesis concerns the concepts, structure, and applications of the Alternative Energy Design Toolkit. The toolkit is aimed to provide a widely accessible, easy to use, flexible, yet powerful modeling environment for ...

Sukkasi, Sittha

2004-01-01

421

From Bidirectionality to Alternation  

Microsoft Academic Search

We describe an explicit simulation of 2-way nondeterministic automata by 1-way alternating automata with quadratic blow-up. We first describe the con- struction for automata on finite words, and extend it to automata on infinite words.

Nir Piterman; Moshe Y. Vardi

2001-01-01

422

Alternative and Integrative Medicine  

MedlinePLUS

... by a given culture (eg, Asian, Indian, African). Homeopathic Medicine: This alternative medicine system is based on ... organization does he/she represent? (A business? A college or university? A nonprofit organization?) What is his/ ...

423

Alternatives to Nursing Homes  

MedlinePLUS

... this website may not be available. Alternatives to nursing homes Before you make any decisions about long ... live and what help you may need. A nursing home may not be your only choice. Discharge ...

424

Alternative Cancer Cures: \\  

Microsoft Academic Search

Oncology has always coexisted with therapies offered outside of conventional cancer treatment centers and based on theories not found in biomedicine. These alternative cancer cures have often been described as \\

Andrew Vickers

425

Alternative fuel information sources  

SciTech Connect

This short document contains a list of more than 200 US sources of information (Name, address, phone number, and sometimes contact) related to the use of alternative fuels in automobiles and trucks. Electric-powered cars are also included.

Not Available

1994-06-01

426

Alternative and Complementary Therapies  

MedlinePLUS

... practices such as ayurveda (Fact Sheet 702) , Chinese acupuncture (Fact Sheet 703) , and Native American healing (Fact ... plans pay for therapies such as chiropractic or acupuncture. ARE THEY SAFE? Alternative therapies can have dangerous ...

427

Marketing alternative fueled automobiles  

E-print Network

Marketing alternative fueled vehicles is a difficult challenge for automakers. The foundation of the market, the terms of competition, and the customer segments involved are still being defined. But automakers can draw ...

Zheng, Alex (Yi Alexis)

2011-01-01

428

Seal design alternatives study  

SciTech Connect

This report presents the results from a study of various sealing alternatives for the WIPP sealing system. Overall, the sealing system has the purpose of reducing to the extent possible the potential for fluids (either gas or liquid) from entering or leaving the repository. The sealing system is divided into three subsystems: drift and panel seals within the repository horizon, shaft seals in each of the four shafts, and borehole seals. Alternatives to the baseline configuration for the WIPP seal system design included evaluating different geometries and schedules for seal component installations and the use of different materials for seal components. Order-of-magnitude costs for the various alternatives were prepared as part of the study. Firm recommendations are not presented, but the advantages and disadvantages of the alternatives are discussed. Technical information deficiencies are identified and studies are outlined which can provide required information.

Van Sambeek, L.L. [RE/SPEC Inc., Rapid City, SD (US); Luo, D.D.; Lin, M.S.; Ostrowski, W.; Oyenuga, D. [Parsons Brinckerhoff Quade & Douglas, Inc., San Francisco, CA (US)

1993-06-01

429

Alternative Refractive Surgery Procedures  

MedlinePLUS

... of artificial lenses. Following are some of the alternative refractive surgery procedures to LASIK . Wavefront-Guided LASIK ... that releases controlled amounts of radio frequency (RF) energy, instead of a laser, to apply heat to ...

430

Apparatus and method for critical current measurements  

DOEpatents

An apparatus for the measurement of the critical current of a superconductive sample, e.g., a clad superconductive sample, the apparatus including a conductive coil, a means for maintaining the coil in proximity to a superconductive sample, an electrical connection means for passing a low amplitude alternating current through the coil, a cooling means for maintaining the superconductive sample at a preselected temperature, a means for passing a current through the superconductive sample, and, a means for monitoring reactance of the coil, is disclosed, together with a process of measuring the critical current of a superconductive material, e.g., a clad superconductive material, by placing a superconductive material into the vicinity of the conductive coil of such an apparatus, cooling the superconductive material to a preselected temperature, passing a low amplitude alternating current through the coil, the alternating current capable of generating a magnetic field sufficient to penetrate, e.g., any cladding, and to induce eddy currents in the superconductive material, passing a steadily increasing current through the superconductive material, the current characterized as having a different frequency than the alternating current, and, monitoring the reactance of the coil with a phase sensitive detector as the current passed through the superconductive material is steadily increased whereby critical current of the superconductive material can be observed as the point whereat a component of impedance deviates.

Martin, Joe A. (Espanola, NM); Dye, Robert C. (Los Alamos, NM)

1992-01-01

431

Alternative Fuels Infrastructure Development  

SciTech Connect

This summary reviews the status of alternate transportation fuels development and utilization in Thailand. An understanding of the issues and experiences associated with the introduction of alternative fuels in other countries can help the US in anticipation potential problems as it introduces new automotive fuels. Thailand is of particular interest since it introduced E20 to its commercial market in 2007 and the US is now considering introducing E20 into the US market.

Bloyd, Cary N.

2010-06-30

432

Alternative pathway evaluation.  

PubMed

The alternative pathway of complement shares its terminal components (C3 and C5 through 9) with the classical pathway, but has several unique components, including factors D, B, and P (properdin). This unit presents methods for assaying total alternative pathway activity and the activity of factors B and D. Radial immunodiffusion (RID) can also be used to measure factor D, B, and P concentrations. PMID:18432715

Giclas, P C

2001-05-01

433

Alternative Addition Strategies  

NSDL National Science Digital Library

This lesson explores recall of multiple alternative addition strategies of two-digit numbers. The lesson focus is to encourage students to use more than one strategy to solve addition problems. By reinforcing the multiple alternative addition strategies students will develop a strong understanding of addition structures and mechanics before moving on to three-digit addition. The lesson includes making an Addition Strategies Mini Booklet, which students can keep and use as a reference tool.

Judith Scapecchi

2012-07-31

434

Alternative Energy Evaluation  

NSDL National Science Digital Library

This document from Misty Scevola serves as an assessment of student knowledge of alternative energy technologies. This document would be useful for instructors looking to expand their students' knowledge of alternative energy and sustainability. The document is intended to be used twice: once before learning about the concepts outlined, and once after the class has been completed. This document may be downloaded in PDF file format.

Scevola, Misty

2012-04-18

435

On-Site Sewage Treatment Alternatives  

E-print Network

-site Wastewater Treatment and Disposal Options, VCE publication 448-403, and Individual Homeowner & SmallOn-Site Sewage Treatment Alternatives C. Zipper,Extension specialist and associate professor, especially where current waste- water treatment is inadequate. This work is intended to provide information

Liskiewicz, Maciej

436

Alternative Linear Chiral Models for Nuclear Matter  

E-print Network

The equation of state of a family of alternative linear chiral models in the mean field approximation is discussed. We investigate the analogy between some of these models with current models in the literature, and we show that it is possible to reproduce very well the saturation properties of nuclear matter.

A. Delfino; F. S. Navarra; M. Nielsen; R. B. Prandini; M. Chiapparini

1998-06-05

437

Energy Implications of Alternative Water Futures  

E-print Network

Energy Implications of Alternative Water Futures First Western Forum on Energy & Water water, energy, and GHG emissions. Water-related energy use is expected to rise. Conservation canWaterUse(MAF) Historical Use More Resource Intensive Less Resource Intensive Current Trends #12;Water and Energy Link

Keller, Arturo A.

438

AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XVII, LEARNING ABOUT AC GENERATOR (ALTERNATOR) PRINCIPLES (PART II).  

ERIC Educational Resources Information Center

THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES AND THE SERVICING AND TESTING PROCEDURES FOR ALTERNATING CURRENT (AC) GENERATORS AND REGULATORS USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE REVIEW OF ALTERNATOR PRINCIPLES, ALTERNATOR SERVICING AND TESTING, ALTERNATOR REGULATOR OPERATING

Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

439

Biodiesel: Current Trends and Properties  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biodiesel, an alternative to petroleum-derived diesel fuel, is defined as the mono-alkyl esters of vegetable oils and animal fats. Several current issues affecting biodiesel that are briefly discussed include the role of new feedstocks in meeting increased demand for biodiesel and circumventing the...

440

REGULATION SCOPING Alternative and Renewable  

E-print Network

REGULATION SCOPING PAPER Alternative and Renewable Fuel and Vehicle Technology Program, Statutes of 2007) created the Alternative and Renewable Fuel and Vehicle Technology Program (Program California's fuel and vehicle types. The Program will help meet the state's alternative fuel use

441

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

PubMed Central

A bismuth bulk electrode (BiBE) has been investigated as an alternative electrode for the anodic stripping voltammetric (ASV) analysis of Pb(II), Cd(II), and Zn(II). The BiBE, which is fabricated in house, shows results comparable to those of similar analyses at other Bi-based electrodes. Metal accumulation is achieved by holding the electrode potential at ?1.4 V (vs. Ag/AgCl) for 180 s followed by a square wave voltammetric stripping scan from ?1.4 to ?0.35 V. Calibration plots are obtained for all three metals, individually and simultaneously, in the 10100 ?g L?1 range, with a detection limit of 105, 54, and 396 ng L?1 for Pb(II), Cd(II), Zn(II), respectively. A slight reduction in slope is observed for Cd(II) and Pb(II) when the three metals are calibrated simultaneously vs. individually. Comparing the sensitivities of the metals when calibrated individually vs in a mixture reveals that Zn(II) is not affected by stripping in a mixture. However, Pb(II) and Cd(II) have decreasing sensitivities in a mixture. The optimized method has been successfully used to test contaminated river water by standard addition. The results demonstrate the ability of the BiBE as an alternative electrode material in heavy metal analysis. PMID:20602953

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

2010-01-01

442

Lightweight, High-Current Welding Gun  

NASA Technical Reports Server (NTRS)

Lighweight resistance-welding, hand-held gun supplies alternating or direct current over range of 600 to 4,000 A and applies forces from 40 to 60 lb during welding. Used to weld metal sheets in multilayered stacks.

Starck, Thomas F.; Brennan, Andrew D.

1989-01-01

443

Current Titles  

SciTech Connect

This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

Various

2006-06-01

444

Convection Current  

NSDL National Science Digital Library

In this activity, learners make their own heat waves in an aquarium. Warmer water rising through cooler water creates turbulence effects that bend light, allowing you to project swirling shadows onto a screen. Use this demonstration to show convection currents in water as well as light refraction in a simple, visually appealing way.

Exploratorium, The

2012-06-26

445

Eddy Currents  

NSDL National Science Digital Library

This site from the Exploratorium provides a simple demonstration of the interaction between a moving magnet and its induced electromagnetic field. As the magnet is dropped down a metallic tube, it induces eddy currents that oppose its fall. The site contains a materials list, basic procedures for the activity, and an explanation of what happens in terms of the electric and magnetic fields produced.

2006-12-03

446

Alternative Green Solvents Project  

NASA Technical Reports Server (NTRS)

Necessary for safe and proper functioning of equipment. Mainly halogenated solvents. Tetrachloride, Trichloroethylene (TCE), CFC-113. No longer used due to regulatory/safety concerns. Precision Cleaning at KSC: Small % of total parts. Used for liquid oxygen (LOX) systems. Dual solvent process. Vertrel MCA (decafluoropentane (DFP) and trons-dichloroethylene) HFE-7100. DFP has long term environmental concerns. Project Goals: a) Identify potential replacements. b) 22 wet chemical processes. c) 3 alternative processes. d) Develop test procedures. e) Contamination and cleaning. f) Analysis. g) Use results to recommend alternative processes. Conclusions: a) No alternative matched Vertrel in this study. b) No clear second place solvent. c) Hydrocarbons- easy; Fluorinated greases- difficult. d) Fluorinated component may be needed in replacement solvent. e) Process may need to make up for shortcoming of the solvent. f) Plasma and SCC02 warrant further testing.

Maloney, Phillip R.

2012-01-01

447

EVALUATING THE IMPACT OF POLICY OPTIONS ON AGRICULTURAL LANDSCAPES: AN ALTERNATIVE-FUTURES APPROACH  

EPA Science Inventory

Alternative-futures analysis was used to analyze different scenarios of future growth patterns and attendant resource allocations on the agricultural system of Oregon's Willamette River Basin. A stakeholder group formulated three policy alternatives: a continuation of current tr...

448

Alternate-Fueled Combustion-Sector Emissions  

NASA Technical Reports Server (NTRS)

In order to meet rapidly growing demand for fuel, as well as address environmental concerns, the aviation industry has been testing alternate fuels for performance and technical usability in commercial and military aircraft. Currently, alternate aviation fuels must satisfy MIL-DTL- 83133F(2008) (military) or ASTM D 7566- Annex(2011) (commercial) standards and are termed drop-in fuel replacements. Fuel blends of up to 50% alternative fuel blended with petroleum (JP-8), which have become a practical alternative, are individually certified on the market. In order to make alternate fuels (and blends) a viable option for aviation, the fuel must be able to perform at a similar or higher level than traditional petroleum fuel. They also attempt to curb harmful emissions, and therefore a truly effective alternate fuel would emit at or under the level of currently used fuel. This paper analyzes data from gaseous and particulate emissions of an aircraft combustor sector. The data were evaluated at various inlet conditions, including variation in pressure and temperature, fuel-to-air ratios, and percent composition of alternate fuel. Traditional JP-8+100 data were taken as a baseline, and blends of JP- 8+100 with synthetic-paraffinic-kerosene (SPK) fuel (Fischer-Tropsch (FT)) were used for comparison. Gaseous and particulate emissions, as well as flame luminosity, were assessed for differences between FT composition of 0%, 50%, and 100%. The data showed that SPK fuel (a FT-derived fuel) had slightly lower harmful gaseous emissions, and smoke number information corroborated the hypothesis that SPK-FT fuels are cleaner burning fuels.

Saxena, Nikita T.; Thomas, Anna E.; Shouse, Dale T.; Neuroth, Craig; Hendricks, Robert C.; Lynch, Amy; Frayne, Charles W.; Stutrud, Jeffrey S.; Corporan, Edwin; Hankins, Terry

2012-01-01

449

35 Alternative Transportation Fuels in California ALTERNATIVE TRANSPORTATION  

E-print Network

35 Alternative Transportation Fuels in California Chapter 4 ALTERNATIVE TRANSPORTATION FUELS IN CALIFORNIA INTRODUCTION The introduction of alternative fuels into California's transportation market has supply at low prices. But, with an uncertain long-term future for oil supplies and prices, alternative

450

Alternative adaptations, speciation, and phylogeny (A Review)  

PubMed Central

Alternative adaptations梔ifferent adaptive phenotypes maintained in the same life stage and the same population but not necessarily simultaneously expressed in the same individual梤epresent contrasting character sets produced by the same genome, in effect allowing a single species to occupy more than one sympatric niche. Such alternatives are particularly likely to give rise to novel adaptations because of selection for extreme dissimilarity between them and because established traits buffer populations against extinction while independently expressed alternatives evolve in new directions. Particular alternatives can be suddenly fixed in populations with little or no genetic change, leading to a period of rapid evolution (especially, of morphology) exaggerating the characteristics of the newly fixed form. This burst of change would facilitate rapid speciation and could produce 損unctuated patterns of evolution. Evidence from a wide variety of organisms shows that alternative phenotypes are exceedingly common in nature and that they are probably important in speciation and macroevolution. Although many of these ideas and observations have been noted piecemeal by previous authors, bringing them together demonstrates the probable importance of alternative adaptations in the origin of major evolutionary novelties and calls for a revision of current and traditional ideas about the role of behavior and ontogeny in the genesis of organic diversity. PMID:16578790

West-Eberhard, Mary Jane

1986-01-01

451

Current balancing for battery strings  

DOEpatents

A battery plant is described which features magnetic circuit means for balancing the electrical current flow through a pluraliircuitbattery strings which are connected electrically in parallel. The magnetic circuit means is associated with the battery strings such that the conductors carrying the electrical current flow through each of the battery strings pass through the magnetic circuit means in directions which cause the electromagnetic fields of at least one predetermined pair of the conductors to oppose each other. In an alternative embodiment, a low voltage converter is associated with each of the battery strings for balancing the electrical current flow through the battery strings.

Galloway, James H. (New Baltimore, MI)

1985-01-01

452

Alternative Assessment: A Family and Consumer Sciences Teacher's Tool Kit.  

ERIC Educational Resources Information Center

This manual, which is designed for home economics teachers who are interested in using alternative forms of student assessment, shares current thinking, research, and practices regarding the use of alternative forms of assessment in family and consumer sciences occupational programs. The manual is divided into three parts. Part 1, which is devoted

Allenspach, Dee; And Others

453

Alternative financing methods for the strategic petroleum reserve  

Microsoft Academic Search

This paper discusses the authors' analysis of alternative, nontraditional methods of financing the Strategic Petroleum Reserve (SPR). While most of the alternative financing proposals the authors examined have some advantages, all of them also have economic costs or other disadvantages which do not allow us to recommend one as superior to the current method of financing the SPR. For example,

Fultz

1989-01-01

454

Interaction between Alternating Magnetic Fields and a Relativistic Collisionless Shock  

Microsoft Academic Search

We investigate the interaction between alternating magnetic fields with cold current sheets and a relativistic collisionless shock wave. Many kinds of high-energy astrophysical objects may involve such alternating magnetic fields and a relativistic shock. They can be potent sources for the generation of high-energy particles. We found that a precursor wave, propagating upstream from the shock front, accelerates a dense

K. Nagata; M. Hoshino; C. H. Jaroschek; H. Takabe

2008-01-01

455

Commercial Training Issues: Heavy Duty Alternative Fuel Vehicles.  

ERIC Educational Resources Information Center

The needs and opportunities in the heavy-duty alternative fuel vehicle training arena were examined in an informal ethnographic study of the appropriateness and effectiveness of the instructional materials currently being used in such training. Interviews were conducted with eight instructors from the National Alternative Fuels Training Program

Eckert, Douglas

456

Alternative Fuels Infrastructure Development  

SciTech Connect

This summary reviews the status of alternate transportation fuels development and utilization in Thailand. Thailand has continued to work to promote increased consumption of gasohol especially for highethanol content fuels like E85. The government has confirmed its effort to draw up incentives for auto makers to invest in manufacturing E85-compatible vehicles in the country. An understanding of the issues and experiences associated with the introduction of alternative fuels in other countries can help the US in anticipation potential problems as it introduces new automotive fuels.

Bloyd, Cary N.; Stork, Kevin

2011-02-01

457

Convection Current  

NSDL National Science Digital Library

This demonstration provides an aesthetic way to view convection currents in fluids. Water warmed by an electric circuit mixes with the surrounding cooler water creating turbulence effects that bend light; the resulting swirling shadows can be projected onto a screen. The site provides an explanation of what happens and a simpler method to demonstrate the same effect. Materials needed and assembly instructions are also given. This activity is part of Exploratorium's Science Snacks series.

2006-07-22

458

Eddy Currents  

NSDL National Science Digital Library

In this activity related to magnetism and electricity, learners discover that a magnet falls more slowly through a metallic tube than it does through a nonmetallic tube. Use this activity to illustrate how eddy currents in an electrical conductor create a magnetic field that exerts an opposing force on the falling magnet, which makes it fall at a slower rate. This activity guide also includes demonstration instructions involving two thick, flat pieces of aluminum to illustrate the same principle.

The Exploratorium

2011-12-05

459

Alternative Fuels and Chemicals from Synthesis Gas  

SciTech Connect

The overall objectives of this program are to investigate potential technologies for the conversion of synthesis gas to oxygenated and hydrocarbon fuels and industrial chemicals, and to demonstrate the most promising technologies at DOE?s LaPorte, Texas, Slurry Phase Alternative Fuels Development Unit (AFDU). The program will involve a continuation of the work performed under the Alternative Fuels from Coal-Derived Synthesis Gas Program and will draw upon information and technologies generated in parallel current and future DOE-funded contracts.

None

1998-12-02

460

DCTD Office of Cancer Complementary and Alternative Medicine (OCCAM)  

Cancer.gov

Skip to Content Click here to view the Site Map Home | Sitemap | Contact DCTD Search this site Office of Cancer Complementary and Alternative Medicine (OCCAM) Introduction Selected Funded Projects Current Funding Opportunities Partnerships and Collaborations Tools,

461

Alternative Treatment Technologies ? Working With the Pathogen Equivalency Committee  

EPA Science Inventory

Under current Federal regulations (40 CFR 503), municipal sludge must be treated prior to land application. The regulations identify two classes of treatment with respect to pathogen reduction: Class B (three alternatives) which provides a minimum acceptable level of treatment;...

462

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

NASA Astrophysics Data System (ADS)

This paper examined the electrochemical corrosion behavior and corrosion products of two types of heat-affected HAZs made from API-X100 steel. Cyclic voltammetry, with different scan rates and potential ranges at 10 cycles, was applied to analyze the interdependent corrosion reactions of cathodic reduction, anodic dissolution, passivation, and transpassivation. The HAZ cooled at 60 K/s, from a peak temperature of 1470 K (1197 癈) that was held for 15 seconds, exhibited better passivation and lower cathodic activity than the HAZ cooled at 10 K/s. Increasing bicarbonate concentration, from 0.05 and 0.2 to 0.6 M, increases the anodic activity and cathodic reduction, but accordingly protects the active surfaces and enhances passivation.

Eliyan, Faysal Fayez; Alfantazi, Akram

2014-12-01