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1

Fentanyl increases catecholamine oxidation current measured by in vivo voltammetry in the rat striatum  

Microsoft Academic Search

A proposed mechanism for fentanyl-induced muscular rigidity is the effect of opioids on dopaminergic transmission in the striatum.\\u000a The objective of this study was to observe the effect of fentanyl on the rat striatal catechol oxidation current (CA.OC) which\\u000a reflects extracellular DOPAC (3-4,dihydroxyphenylacetic acid) concentration (a major metabolite of dopamine), as measured\\u000a by in vivo voltammetry. Male Sprague-Dawley rats, anaesthetized

Brian Milne; Luc Quintin; Jean-François Pujol

1989-01-01

2

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

3

Alternating to Direct: Rectifying Alternating Current  

NSDL National Science Digital Library

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

2012-12-03

4

The Generation of Alternate Current  

NSDL National Science Digital Library

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

Bartelt, Terry L.

2010-09-24

5

Chemometrics assisted resolving of net faradaic current contribution from total current in potential step and staircase cyclic voltammetry.  

PubMed

Total current in the electroanalytical data is assumed to be consisting of three main constituents: faradaic current, step charging current and induced charging current. Both charging currents can cause an interfering effect on precise determination of faradaic currents, and hence insert direct effects on sensitivity and detection limit of the electroanalytical techniques. Despite the widespread techniques introduced until now, the extraction of the net faradaic current from total current still remains a challenge. In this work, by using multivariate curve resolution-alternating least square (MCR-ALS) as a powerful curve resolution-based chemometrics method, a straightforward method has been introduced for resolving faradaic current from the two types of charging currents (step charging current and induced charging current) in single potential step and staircase cyclic voltammetric methods. By simultaneous analyses of the current data matrices for different electrochemical systems, the three sources of current were successfully identified and their contributions in the total signal were easily calculated. Also, in this manner, the cell time constant can be obtained easily. Contrary to the previously reported methods, the present method does not need any pre-determined mathematical method; particularly there is no need to know the cell time constant. PMID:23427798

Safavi, Afsaneh; Hemmateenejad, Bahram; Honarasa, Fatemeh

2013-03-01

6

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...

7

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

8

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

9

Solar cell system having alternating current output  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

10

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

PubMed

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

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

2013-12-01

11

Nonlinear alternating current responses of electrorheological solids  

E-print Network

When a composite containing nonlinear dielectric particles suspended in a host medium is subjected to a sinusoidal alternating current (ac) electric field, the dielectric response of the composite will generally consist of ac fields at frequencies of higher-order harmonics. For an electrorheological (ER) solid under structure transformations due to external fields, we apply the Ewald-Kornfeld formulation to derive the local electric fields and induced dipole moments explicitly, and then we perform the perturbation expansion method to extract their fundamental and third-order harmonics analytically. It is shown that the degree of anisotropy of the ER solid can affect these harmonics significantly. Our results are well understood in the spectral representation theory. Thus, it seems possible to perform a real-time monitoring of the structure transformation by measuring the nonlinear ac responses of ER solids.

J. P. Huang

2004-12-11

12

Stability of alternating current gliding arcs  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

13

Transcranial alternating current stimulation (tACS)  

PubMed Central

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

Antal, Andrea; Paulus, Walter

2013-01-01

14

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

15

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

16

Pulse Voltammetry  

NASA Astrophysics Data System (ADS)

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

Stojek, Zbigniew

17

Application of cyclic voltammetry to investigate enhanced catalytic current generation by biofilm-modified anodes of Geobacter sulfurreducens strain  

E-print Network

on an anode surface and catalyze the generation of an electrical current by oxidizing acetate and utilizing rate-limiting steps in current generation. Strain KN400 generates approximately 2 to 8-fold greater transport of acetate, carbon dioxide and protons into and out of the biofilm, Step 2 is microbial turnover

Lovley, Derek

18

Alternating current-excited magnetoresistive sensor  

Microsoft Academic Search

Thin-film anisotropic magnetoresistors are superior to semiconductor magnetic field sensors. ac excitation of the sensor bridge reduced the noise level to 10 nT p-p. The offset reduction and sensor characteristic stabilization was achieved by periodical flipping by means of 100 mA\\/100 ?s current pulses into a 400 turns coil wound across the sensor perpendicular to the sensitive axis. The use

P. Ripka

1996-01-01

19

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

2013-10-01

20

Novel application of scanning tunneling microscopy — tip current voltammetry of n-GaAs and p-GaP in electrolyte solution  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy (STM) has been modified for use on semiconductors in an electrolyte solution providing a new technique, tip current voltammetry (TCV), for characterization of semiconductor/electrolyte interfaces. It provides information about chemical reactions on the surface, the interface energetics, and the current transport mechanisms. The TCV technique has been applied to the study of n-GaAs (with two different doping levels) and p-GaP in 2 mM NaOH. The tip current is measured, while scanning the potential on the semiconductor electrode versus a reference electrode, keeping the tip at constant potential versus the reference electrode. With the semiconductor potential in the accumulation region, tunneling is obtained in the normal way. When changing the potential into the depletion region, the distance between tip and electrode surface goes to zero, the instrument goes into "contact mode". In the depletion region the p-GaP and n-GaAs samples behaved differently. At the p-GaP sample the tip current drastically dropped at the flat-band potential, while at the n-GaAs sample the "tunneling mode" is maintained even at depletion, + 700 mV from the flat-band potential. At the very highly doped n-GaAs sample, a new tunneling mode is obtained again when the semiconductor potential reaches the inversion region. The tip current voltammograms are affected by surface reactions and by illumination. The transition potential between tunneling and contact modes is shifted negatively at an oxidized surface and returns to its original value if the electrode is held at negative potentials.

Carlsson, P.; Holmström, B.; Kita, H.; Uosaki, K.

1990-11-01

21

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

22

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

23

An Alternating Current Amplitude Sensor Utilizing Saturating Magnetic Cores  

Microsoft Academic Search

Toroidal magnetic cores are used for noncontacting alternating current-sensing in applications such as circuit breakers and ground fault interrupters. In such applications, it is often desirable to maximize the voltage induced in the sense coil on the core. In order to maximize this voltage with respect to the sensed current, core design parameters are developed for 60- and 400-Hz applications.

THEODORE BERNSTEIN

1970-01-01

24

Method for sputtering with low frequency alternating current  

DOEpatents

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

Timberlake, John R. (Allentown, NJ)

1996-01-01

25

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

26

Alternatives to the Current AASHTO Standard Bridge Sections  

Microsoft Academic Search

The main objective of this study was evaluate feasible alternatives to the current AASHTO bridge girders used in Indiana. This evaluation included precast pretensioned bridge girders for spans from 30 to 130 feet with girder spacing between 5 and 10 feet up to 12 feet for the longer spans. Other criteria included girder design concrete compressive strengths up to 7000

Joseffa Viktoria Meir; Michael Ramon Cicciarelli; J. A. Ramirez; Robert H. Lee

1995-01-01

27

Nonlinear response of superconductors to alternating fields and currents  

SciTech Connect

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

McDonald, J.

1997-10-08

28

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

29

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

30

Adjunctive and alternative approaches to current reperfusion therapy  

PubMed Central

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

Barreto, Andrew D.; Alexandrov, Andrei V.

2012-01-01

31

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

32

Electromagnetic stirring with alternating current during electroslag remelting  

Microsoft Academic Search

An alternating current (AC)-operated electromagnetic stirring (EMS) device, using line frequency, was designed and built to\\u000a operate on a laboratory electroslag remelting (ESR) furnace for 150-mm-diameter ingots. Laboratory-scale experiments were\\u000a conducted employing both 4340 alloy steel and INCONEL 718 alloy as electrode material. The initiation of stirring is accompanied\\u000a by a thin strip of segregated material and favors the formation

Alec Mitchell; Bernardo Hernandez-Morales

1990-01-01

33

A Treatise on the Theory of Alternating Currents  

NASA Astrophysics Data System (ADS)

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

Russell, Alexander

2014-05-01

34

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.

35

Nonlinear dynamics of carbon nanotubes under soft alternating current actuation  

NASA Astrophysics Data System (ADS)

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

Luo, Le

36

Cyclic voltammetry studies on pure lead  

Microsoft Academic Search

The behavior of pure lead in sulfuric acid was studied by cyclic voltammetry. The appearance of an anodic current peak on the cathodic portion of the sweep, previously attributed to a phase change in the lead dioxide film, is re-interpreted in the light of this work as being due to the oxidation of water by an intermediate lead III species.

J. G. Sunderland

1976-01-01

37

Entrainment of brain oscillations by transcranial alternating current stimulation.  

PubMed

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

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

2014-02-01

38

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

39

Pulse Voltammetry in Single Cells Using Platinum Microelectrodes.  

National Technical Information Service (NTIS)

Multiple pulse voltammetry at platinum microelectrodes is described for intracellular measurements. In this technique, a sequence of three potential pulses is used for each current point measured. This pulse sequence provides a fixed cathodic activation p...

T. K. Chen, Y. Y. Lau, D. K. Wong, A. G. Ewing

1991-01-01

40

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

41

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

42

Taxation of Fringe Benefits: Alternative Approaches to Current Problems.  

ERIC Educational Resources Information Center

The current IRS tax treatment of fringe benefits is seen as inadequate, and the judicial precept confusing, because groups of employee benefits are inappropriately excluded from taxation as perquisites. A tax equalization approach is proposed. Available from Suffolk University Law Review Office, 41 Temple St., Boston, MA 02114. (MSE)

Cohen, Anita E.

1979-01-01

43

Dielectrophoretic and electrothermal effects at alternating current heated disk microelectrodes.  

PubMed

When a disk microelectrode is polarized with an alternating potential of very high frequency (0.1-2 GHz) and a high amplitude (up to 2.8 V rms), the electrode is heated up, and at the same time, a very intense electric field is created around the electrode (>10(6) V/m for electrodes 1 microm in radius). This strong electric field gives rise to positive or negative dielectrophoretic effects. Positive dielectrophoretic effects can be used to assemble nanowires from nanoparticles at the electrode edge. On the other hand, a negative dielectrophoretic effect is probably responsible for "jet boiling" observed at overheated microelectrodes. In addition, a combination of a high temperature gradient and a high potential gradient generates an intense electrothermal flow of solution which very strongly enhances the mass transport and is responsible for intense convection in such systems. The electrothermal flow and dielectrophoretic forces can be generated directly on a microelectrode employed in electrochemical detection because the high frequency ac polarization of the electrode does not interfere with the acquisition of analytical signals. PMID:18771275

Boika, Aliaksei; Baranski, Andrzej S

2008-10-01

44

The magnetic amplifier with alternating-current control  

E-print Network

by including this additional factor. The circuit is shown in Figure 1. R^, C^, and L .^ are the external circuit elements in the kth mesh, and e^ is the external emf in the kth mesh, i^ is the current in the kth mesh, and 0^ is the resultant flux in the jth... necessary to consider the emfs which are applied in each of the n meshes. I f the emfs are nonperi? odic, but time varying, the equilibrium equations (17 through 22 are examples) can be solved graphically. Caution must be exercised however. As the emfs...

Andrew, Edward Harris

2013-10-04

45

Engineering aspects of the ISTTOK operation in a multicycle alternating flat-top plasma current regime  

Microsoft Academic Search

The main engineering aspects of the tokamak ISTTOK operation in a multicycle alternating flat-top plasma current regime are presented. AC discharges have been obtained feeding the ohmic and vertical magnetic field circuits with a specially designed alternating power supply, based on a single electrolytic capacitor bank and a fast insulated gate bipolar transistor (IGBT) H-bridge, feedback controlled by a discreet

H Fernandes; C. A. F Varandas; J. A. C Cabral; H Figueiredo; R Galvão

1998-01-01

46

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

ERIC Educational Resources Information Center

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

Yates, Steven Lowell

2009-01-01

47

Eddy Current Losses in the Rotor Teeth of Aerospace Homopolar Alternators  

Microsoft Academic Search

The eddy current losses in rotor tooth-heads of homopolar alternators are generally high and a limiting factor of design. A method is established to calculate eddy current losses in rotor designs with titanium wedges in the intertooth space. A computer program solves numerically the boundary value problem that yields the electric field intensity in the conducting materials. Inverter loads on

E. A. Erdelyi; R. F. Jackson; S. V. Ahamed; M. J. Shah

1965-01-01

48

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

Microsoft Academic Search

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

Masamichi Kanou; Tateo Shimozawa

1984-01-01

49

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

50

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

SciTech Connect

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

P.F. Schmit and N.J. Fisch

2010-02-01

51

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

52

Cyclic voltammetry of supported BLMs  

NASA Astrophysics Data System (ADS)

The transfer of an electron across a bilayer lipid membrane (BLM) is one of the BLMs most exciting processes. A number of well known electron mediators have been investigated using the method of cyclic voltammetry on a Teflon coated platinum wire, the tip of which has been modified by a self-assembled bilayer lipid membrane (s-BLM). The electrical capacitance of the s-BLM system was measured as a function of frequency. The results are discussed in terms of electron transfer and redox reactions.

Murgasova, Renata; Sabo, Jan; Ottova, Angelica L.; Tien, H. T.

1996-06-01

53

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

54

Engineering aspects of the ISTTOK operation in a multicycle alternating flat-top plasma current regime  

Microsoft Academic Search

The main engineering aspects concerning the operation of the tokamak ISTTOK in a multicycle alternating flat-top plasma current regime are presented. AC discharges have been obtained feeding the ohmic and vertical field circuits with a power supply based on two capacitor banks and a fast Insulated Gate Bipolar Transistor (IGBT) H-bridge, feedback controlled by a discrete power DAC implemented with

H. Fernandes; C. A. F. Varandas; J. A. C. Cabral; H. Figueiredo; R. Galvao; A. J. Batista

1997-01-01

55

Time averaged temperature distribution in a cylindrical resistor with alternating current  

Microsoft Academic Search

The non-uniform heat generation in a cylindrical resistor crossed by an alternating electric current is considered. The time averaged and dimensionless temperature distribution in the resistor is analytically evaluated. Two dimensionless functions are reported in tables which allow one to determine the time averaged temperature field for arbitrarily chosen values of the physical properties and of the radius of the

A. Barletta; E. Zanchini

1994-01-01

56

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

Microsoft Academic Search

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

Allyn E. Hubbard

1983-01-01

57

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

Microsoft Academic Search

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

John A. Mallick; Mark Crawford

2004-01-01

58

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

Microsoft Academic Search

Purpose – During the 1990s, the New York City Police Department (NYPD) instituted a policy of arresting and detaining people for minor offenses that occur in public as part of their quality-of-life (QOL) policing initiative. The purpose of this paper is to examine the pros and cons of the current policy and compare it with possible alternatives including: arrest and

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

2008-01-01

59

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.

60

VARIATION OF THE ELECTRIC RESISTANCE OF PLANT TISSUES FOR ALTERNATING CURRENTS OF DIFFERENT FREQUENCIES DURING DEATH  

Microsoft Academic Search

The study of the electric resistance of riving ceils, in relation to variation of frequency of alternating current, developed during the last 20 years by HtJber (1910), Gildemeister (1919), Phirippson (1920), Waterman (1922), Fricke (1923), McClendon (1924), Fricke and Morse (1925), Brinks (1928), and Remington (1929), has been used chiefly in determining physical characteristics of various tissues such as muscle,

BASILE J. LUYET

1932-01-01

61

12 In Vivo Voltammetry with Telemetry  

E-print Network

12 In Vivo Voltammetry with Telemetry Paul A. Garris, Phillip G. Greco, Stefan G. Sandberg, Greg ............................................................................................. 238 Principles of Telemetry ........................................................................................... 240 Digital Telemetry at 2.4 GHz

Casto, Joseph M.

62

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

NASA Astrophysics Data System (ADS)

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

Itose, Fumitake; Kawamoto, Tadashi; Mori, Takehiko

2013-06-01

63

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

Vilarino, Natalia; Fonfria, Eva S.; Louzao, M. Carmen; Botana, Luis M.

2009-01-01

64

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

NASA Technical Reports Server (NTRS)

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

Mock, W C , Jr

1937-01-01

65

Measurement of the refining degree of bamboo charcoal by an alternating current method  

Microsoft Academic Search

We investigated a method for measuring the refining degree of bamboo charcoal using an alternating current. The bamboo charcoal\\u000a was made under heating conditions of 400°–900°C (set temperature) and 0—3 h (holding time at each set temperature). The qualities\\u000a of the bamboo charcoal could not be estimated from the yield, and electric tests were required. The effect of the variation

Yoshitaka Kubojima; Youki Suzuki

2011-01-01

66

An Evaluation of Current and Alternative Systems for Quality Grading Carcasses of Mature Slaughter Cows  

Microsoft Academic Search

Strip loins from 354 female bovine carcasses, selected to represent 30 skeletal maturity (A, B, C, D, and E) × marbling score (SA\\/MA\\/AB, MD, MT, SM, SL, and TR\\/PD) subclasses, were used to evaluate current and alternative systems for classifying cow carcasses into expected-palatability groups. Strip loins were vacuum-packaged, stored for 14 d postmortem at 2°C, and frozen ( -27°C).

G. G. Hilton; J. D. Tatum; S. E. Williams; K. E. Belk; F. L. Williams; J. W. Wise; G. C. Smith

2010-01-01

67

Dielectrophoretic particle dynamics in alternating-current electro-osmotic micropumps  

NASA Astrophysics Data System (ADS)

This letter deals with the dynamics of dielectric microparticles in alternating-current electro-osmotic micropumps, which is based on the competitive interplay of inertial, dielectrophoretic, and viscous drag forces. The electric field and the electro-osmotic flow are modeled and computed by means of finite elements and particle trajectories are evaluated taking into account the forces above. Thereby, mean traveling height and velocity depend on driving voltage and frequency, which allows for an effective type of particle manipulation and separation. The obtained particle velocities show good agreement with measured velocities of hollow glass beads in a device realized in SU8/glass technology.

Weiss, Bernhard; Hilber, Wolfgang; Holly, Roman; Gittler, Philipp; Jakoby, Bernhard; Hingerl, Kurt

2008-05-01

68

The effect of alternating and biphasic currents on humans' wound healing: a literature review.  

PubMed

Although different types of currents, including bidirectional currents, have been used to promote healing, there is neither a summary about their effects nor consensus on best parameters to be used. The aim of this article is to provide an overview of current evidence on the effectiveness of bidirectional electrical stimulation on wound healing in accordance with the parameters used. Relevant articles were selected following a search of Medline, Cochrane, Embase, CINAHL, and PEDro for English, Spanish, Portuguese, Italian, or French articles published between 1980 and 2011. Ten trials and four case-series were found that deal with pressure ulcers, diabetic ulcers, venous ulcers, skin flaps, and amputation. Eight trials were of low-quality. Five of ten controlled trials found a statistically significant difference on wound healing, and another four trials found positive trends. Both of the two skin flap trials, one of two diabetic trials, and two of five pressure ulcer trials found a significant difference in bidirectional stimulated groups. Both TENS and NMES types of currents were used, but many parameters were not specified. In general, bidirectional currents appear to increase wound healing rates and reduce size of wounds, above all in skin flaps. However, there is a lack of well-designed studies on biphasic and alternating stimulation, and there is a need for improvement in description of parameters and in uniformity of nomenclature. PMID:23786603

Martínez-Rodríguez, Alicia; Bello, Olalla; Fraiz, Manuel; Martinez-Bustelo, Sandra

2013-09-01

69

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

SciTech Connect

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

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

2008-11-15

70

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

71

Gas microsensors using cyclic voltammetry with a cermet electrochemical cell.  

SciTech Connect

The sensing characteristics of a cermet electrochemical cell, expressed as NiO|Pt|solid electrolyte|Pt were investigated by applying cyclic voltammetry to the Pt electrodes and measuring changes in ionic current through the solid electrolyte. Features of the current-voltage response (voltammograms) appear to depend uniquely on the type of gas exposed to the cell surface and the solid electrolyte material used. The novel sensors can selectively detect O{sub 2}, CO{sub 2}, and a variety of hydrocarbons. Performance characteristics such as selectivity, sensitivity, speed of response, and temperature dependence were also reported.

Shoemaker, E. L.; Vogt, M. C.; Dudek, F. J.; Turner, T.; Energy Systems

1997-07-15

72

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

... 2014-07-01 false Low- and medium-voltage circuits serving portable...OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving...

2014-07-01

73

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

... 2014-07-01 false Low- and medium-voltage circuits serving three-phase...STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving...

2014-07-01

74

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

PubMed

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

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

2013-01-01

75

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

PubMed Central

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

2013-01-01

76

Standard practice for examination of welds using the alternating current field measurement technique  

E-print Network

1.1 This practice describes procedures to be followed during alternating current field measurement examination of welds for baseline and service-induced surface breaking discontinuities. 1.2 This practice is intended for use on welds in any metallic material. 1.3 This practice does not establish weld acceptance criteria. 1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. The values stated in each system might not be exact equivalents; therefore, each system shall be used independently of the other. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

American Society for Testing and Materials. Philadelphia

2007-01-01

77

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

78

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

79

Stripping voltammetry in environmental and food analysis.  

PubMed

The review covers over 230 papers published mostly in the last 5 years. The goal of the review is to attract the attention of researchers and users to stripping voltammetry in particular, its application in environmental monitoring and analysis of foodstuffs. The sensors employed are impregnated graphite, carbon paste, thick film carbon/graphite and thin film metallic electrodes modified in-situ or beforehand. Hanging mercury drop electrodes and mercury coated glassy carbon electrodes are also mentioned. Strip and long-lived sensors for portable instruments and flow through systems are discussed as devices for future development and application of stripping voltammetry. PMID:11227498

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

2000-10-01

80

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

PubMed Central

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; Struber, Daniel

2013-01-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

82

The Inequity in Illinois School Finance. An Analysis of: The Current Situation, the Historical Record, and Alternative Solutions. Second Edition.  

ERIC Educational Resources Information Center

This report provides an analysis of current inequities in school finance in Illinois, the historical roots of those inequities, and an analysis of alternative options for funding primary and secondary education. An introduction briefly describes the basis for the constitutional challenge to the current funding system. The next section describes…

Hess, G. Alfred, Jr.; And Others

83

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

PubMed Central

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

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

2012-01-01

84

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

85

The effect of 10 Hz transcranial alternating current stimulation (tACS) on corticomuscular coherence  

PubMed Central

Synchronous oscillatory activity at alpha (8–12 Hz), beta (13–30 Hz), and gamma (30–90 Hz) frequencies is assumed to play a key role for motor control. Corticomuscular coherence (CMC) represents an established measure of the pyramidal system's integrity. Transcranial alternating current stimulation (tACS) offers the possibility to modulate ongoing oscillatory activity. Behaviorally, 20 Hz tACS in healthy subjects has been shown to result in movement slowing. However, the neurophysiological changes underlying these effects are not entirely understood yet. The present study aimed at ascertaining the effects of tACS at 10 and 20 Hz in healthy subjects on CMC and local power of the primary sensorimotor cortex. Neuromagnetic activity was recorded during isometric contraction before and at two time points (2–10 min and 30–38 min) after tACS of the left primary motor cortex (M1), using a 306 channel whole head magnetoencephalography (MEG) system. Additionally, electromyography (EMG) of the right extensor digitorum communis (EDC) muscle was measured. TACS was applied at 10 and 20 Hz, respectively, for 10 min at 1 mA. Sham stimulation served as control condition. The data suggest that 10 Hz tACS significantly reduced low gamma band CMC during isometric contraction. This implies that tACS does not necessarily cause effects at stimulation frequency. Rather, the findings suggest cross-frequency interplay between alpha and low gamma band activity modulating functional interaction between motor cortex and muscle. PMID:24009573

Wach, Claudia; Krause, Vanessa; Moliadze, Vera; Paulus, Walter; Schnitzler, Alfons; Pollok, Bettina

2013-01-01

86

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

Microsoft Academic Search

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

Joan J. Mathews; Kathleen Zadak

1991-01-01

87

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 (Ecat), observed rate constant (kobs), 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

88

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...

89

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

PubMed Central

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

Uangpairoj, Pichitra; Shibata, Masahiro

2013-01-01

90

SAR216471, an alternative to the use of currently available P2Y?? receptor inhibitors?  

PubMed

P2Y12 antagonism is a key therapeutic strategy in the management and prevention of arterial thrombosis. The objective of this study was to characterize the pharmacodynamic (PD) and pharmacokinetic (PK) properties of SAR216471, a novel P2Y12 receptor antagonist. SAR216471 blocks the binding of 2MeSADP to P2Y12 receptors in vitro (IC50=17 nM). This inhibition was shown to be reversible. It potently antagonized ADP-induced platelet aggregation in human and rat platelet-rich plasma (IC50=108 and 62 nM, respectively). It also inhibited platelet aggregation when blood was exposed to collagen or thromboxane A2. Its high selectivity was demonstrated against a large panel of receptors, enzymes, and ion channels. Despite its moderate bioavailability in rats, oral administration of SAR216471 resulted in a fast, potent, and sustained inhibition of platelet aggregation where the extent and duration of platelet inhibition were directly proportional to its circulating plasma levels. Pre-clinical study of SAR216471 in a rat shunt thrombosis model demonstrated a dose-dependent antithrombotic activity after oral administration (ED50=6.7 mg/kg). By comparison, ED50 values for clopidogrel, prasugrel and ticagrelor were 6.3, 0.35 and 2.6 mg/kg, respectively. Finally, the anti-hemostatic effect of SAR216471 and its competitors was investigated in a rat tail bleeding model, revealing a favorable safety profile of SAR216471. Together, these findings have established a reliable antiplatelet profile of SAR216471, and support its potential use in clinical practice as an alternative to currently available P2Y12 receptor antagonists. PMID:25064036

Delesque-Touchard, N; Pflieger, A M; Bonnet-Lignon, S; Millet, L; Salel, V; Boldron, C; Lassalle, G; Herbert, J M; Savi, P; Bono, F

2014-09-01

91

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

PubMed Central

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

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

2013-01-01

92

The Effects of Current and Alternative Intra-District Allocation Procedures on Coverage of Disadvantaged Students. Working Paper.  

ERIC Educational Resources Information Center

The objectives of this paper were to examine the effects of current school and student selection procedures on the proportions of student groups that have access to and/or receive Elementary and Secondary Education Act Title I services and to explore the effects of actual and simulated alternative procedures on these proportions. Data from school…

Hennessy, Michael; And Others

93

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.

94

Plasma electrochemistry: voltammetry in a flame plasma electrolyte.  

PubMed

In this paper we present detailed dynamic electrochemical measurements in a flame plasma electrolyte in the presence of tungsten oxide salts. Defined reproducible redox processes are measured using conventional cyclic voltammetry in an operational potential window between 1 and -9 V. This wide potential window is possible due to the absence of solvent and its associated limits due to solvent electrolysis at high over potentials. The measurements were enabled through the development of a new reference electrode, composed of yttria stabilised zirconia (YSZ) which maintains a stable potential at 1100 K. In this paper we focus on developing a phenomenological understanding of electron transfer at the solid-gas interface, using cyclic voltammetry. The effect of working electrode surface area and material, as well as potential scan rate on the voltammetric redox features is presented. We discuss the physical origin of the observed Faradaic current peaks measured in a flame plasma electrolyte, and propose a simple model to describe the redox processes occurring. We conclude that redox processes at the solid-gas interface are actually similar to the analogous processes at the solid-liquid interface described by conventional electrochemical theory; the departures are mainly due to the mass transport processes that dominate in the gas phase. We associate migration effects with the total absence of any oxidation processes. PMID:23223382

Elahi, Atif; Caruana, Daren J

2013-01-28

95

The effect of the heliospheric current sheet on cosmic ray intensities at solar maximum - Two alternative hypotheses  

NASA Technical Reports Server (NTRS)

The capabilities of two alternative models for accounting for the reversal of the solar magnetic field polarity at the point of solar maximum and for the associated modulation of cosmic ray intensities at 1 AU are assessed. One model posits a continuous increase in the inclination of the heliospheric current sheet to a point of verticality at maximum, when it overturns and the reversal occurs. The alternative view is that the sun sheds the magnetic field of the previous cycle and generates a new field of opposite polarity. Some data do exist for a tilted current sheet which increases its tilt with proximity to the solar maximum. However, coronal data also support the presence of isolated regions of anomalous polarity which spread over the surface of the sun as maximum approaches, a condition commensurate with flux shedding. Both models predict heliospheric current sheet configurations which would produce some cosmic ray modulations observed over the course of the solar cycle.

Thomas, B. T.; Goldstein, B. E.; Smith, E. J.

1986-01-01

96

Determination of moxifloxacin in tablets and human urine by square-wave adsorptive voltammetry  

Microsoft Academic Search

This work presents an electroanalytical methodology developed for square-wave voltammetry based in the electrochemical reduction in hanging mercury drop electrode (HMDE), which is simple, fast, reliable and sensitive for determination of moxifloxacin (MOXI) in tablets and spiked urine human samples. The support electrolyte that provided a more defined and intense peak current for MOXI determination was the phosphate buffer 0.04

Magno Aparecido G. Trindade; Glaucia Maria da Silva; Valdir Souza Ferreira

2005-01-01

97

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

98

First-principles investigation of alternating current density distribution in molecular devices  

NASA Astrophysics Data System (ADS)

Using the nonequilibrium Green's function (NEGF) formalism, we derive the current density formula for ac quantum transport by including the self-consistent Coulomb interaction. It is well known that the Coulomb interaction is very important in determining ac current in nanostructures. As pointed out by Büttiker that the Coulomb interaction must be included to conserve the ac current. Theoretically, the displacement current can be accounted for by including a self-consistent Hartree term in the Hamiltonian as well as the exchange and correlation term while the ac current is calculated from particle current, i.e., <Î?(t)>=q where N?? is the number operator of the ? lead. For the ac current density, however, the Coulomb interaction contributes in two ways. As the case of ac current, the self-consistent Coulomb interaction has to be included in the conventional particle current density. In addition, we have to consider the displacement current density explicitly, which is proportional to the time derivative of displacement field. Once the ac current density is obtained, one can calculate the ac current by integrating it over a cross-section area along the transport direction. It is shown that ac current obtained from the total ac current density is conserved and equal to that calculated directly from the lead using NEGF theory. We have applied our formalism to calculate ac current density for nanodevices by combining the density functional theory (DFT) with NEGF theory. Specifically, we have calculated the ac current density to the first order of frequency in a molecular device Al-C4-Al from first principles. It is found that Al-C4-Al system exhibits inductive-like behavior under ac bias in the low-frequency limit. Furthermore, nonequilibrium charge distribution is obtained that enables us to study electrochemical capacitance of the molecular devices.

Zhang, Lei; Wang, Bin; Wang, Jian

2012-10-01

99

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

uploads viewer ads groups News Movies Music Green Tech Comedy google.com welcome to current.com Our alien, contribute your own videos, and pick the news that goes on TV. Related Groups News Max and Jason: Stil-wave-theory-offers-alternative-to-dark-energy.htm the journal. 1. 2. groups: News, Max and Jason: Still Up, Weird Science, Universe 3. tags: Science, Space

Temple, Blake

100

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

ERIC Educational Resources Information Center

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

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

2012-01-01

101

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

Microsoft Academic Search

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

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

1985-01-01

102

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.

103

Model-based characterization of homogeneous metal plates by four-point alternating current potential drop measurements  

Microsoft Academic Search

We determined the conductivity, relative permeability, and thickness of homogeneous metal plates from four-point measurements of alternating current potential drop (ACPD) over the frequency range 1 Hz to 10 kHz. We developed simple analytical expressions from which these parameters can be calculated. In the low-frequency regime, in which the measured voltage tends to a constant, real value, the relative permeability

Nicola Bowler; Yongqiang Huang

2005-01-01

104

Current status of reduced-intensity allogeneic stem cell transplantation using alternative donors  

Microsoft Academic Search

The optimal donor for a patient undergoing reduced-intensity stem cell transplantation remains a human leukocyte antigen (HLA)-matched relative. Alternative donors such as matched unrelated donors (MUDs), mismatched related donors (haploidentical), or unrelated umbilical cord blood (UCB) units have emerged as options as well. The most experience thus far has been with MUD donors, mostly attributed to the development of allele-specific

Y-B Chen; T R Spitzer

2008-01-01

105

Three-dimensional magneto-resistive random access memory devices based on resonant spin-polarized alternating currents  

NASA Astrophysics Data System (ADS)

Selective switching of a magneto-resistive random access memory (MRAM) multilayer stack is demonstrated using resonant spin-polarized alternating currents (AC) superimposed on spin-polarized direct currents. Finite element micromagnetic simulations show that the use of frequency triggered AC allows one to maximize the transferred spin transfer torque selectively in order to merely reverse the magnetization of a single storage layer in a stack. Using layers with different resonance frequencies, which are realized by altering the anisotropy constants, allows one to address them by tuning the AC frequency. A rapid increase of the storage density of MRAM devices is shown by using three-dimensional sandwich structures.

Vogler, Christoph; Bruckner, Florian; Fuger, Markus; Bergmair, Bernhard; Huber, Thomas; Fidler, Josef; Suess, Dieter

2011-06-01

106

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.

107

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

PubMed

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

Dazzi, F; Di Leone, F G

2014-03-01

108

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

PubMed Central

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

Guan, Yong-Song; He, Qing

2013-01-01

109

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

NASA Astrophysics Data System (ADS)

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

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

110

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.

111

A study of phase transition behaviors of chalcogenide layers using in situ alternative-current impedance spectroscopy  

NASA Astrophysics Data System (ADS)

Electrical properties of chalcogenide thin films, both pristine Ge2Sb2Te5 (GST) and cerium-doped GST, were investigated by in situ alternative-current (AC) impedance spectroscopy. With the aid of brick-layer model and nano-grain composite model, the roles of grain and grain-boundary on the phase transition of chalcogenides were distinguished and the dominance of grain boundary was observed. Tangent loss behaviors deduced by impedance analysis revealed alien-element doping alters the interfacial polarization and delays the phase-transition rate of GST. Analytical results also illustrated that the in situ AC impedance spectroscopy can be an alternative tool for characterizing the phase-change kinetics of chalcogenides thin films with nano-scale grain sizes.

Huang, Yin-Hsien; Huang, Yu-Jen; Hsieh, Tsung-Eong

2012-06-01

112

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

PubMed

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

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

2014-01-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

115

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

116

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

117

Small-diameter casing for standpipe monitoring wells: A comparison of current alternatives  

SciTech Connect

The standpipe monitoring well is the most common and accepted system for monitoring the chemical quality of ground water. The majority of these wells have a diameter of 2 inches or less. The lower cost of the small-diameter wells makes them the preferred choice. However, the technology available to properly develop, sample, and monitor such wells has evolved gradually over the last several years, and with its changes and improvements have been made in the design of the standpipe monitoring well. The variety of threaded couplings used to join sections of casing or screen are quite diverse, and current designs of the flush-threaded type are surprisingly incompatible. The designs differ in the types of threading and seals, the variety of materials, the actual pipe and coupling lengths, the pipe thickness (schedule), and pipe cleaning procedures. A national standard design is needed for flush-threaded casting used to construct monitoring wells.

Schalla, R.; Myers, D.A.

1987-01-01

118

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

119

Determination of free chlorine based on anodic voltammetry using platinum, gold, and glassy carbon electrodes  

Microsoft Academic Search

The oxidation of free chlorine on platinum, gold, and glassy carbon disk electrodes has been investigated by using anodic voltammetry to determine the free-chlorine concentration. The voltammetric curves exhibited well-defined anodic peaks. The influences of pH, free-chlorine concentration, and potential sweep rate on the electrode response were investigated. The results show that the measurement of the oxidation peak current can

Fumihiro Kodera; Minoru Umeda; Akifumi Yamada

2005-01-01

120

Cyclic voltammetry of pulsed laser deposited LiâMnâOâ thin films  

Microsoft Academic Search

Electrochemical properties of thin films of LiâMnâOâ spinel prepared by pulsed laser deposition were studied using constant current cycling and cyclic voltammetry. Films have been cycled more than 220 times with no significant capacity fading. The shape of the cyclic voltammogram is very sensitive to the composition and morphology of the film., The diffusion process for the LiâMnâOâ thin films

A. Rougier; K. A. Striebel; S. J. Wen; E. J. Cairns

1998-01-01

121

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 ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

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

2012-11-01

122

Stoichiometry and Formation Constant Determination by Linear Sweep Voltammetry.  

ERIC Educational Resources Information Center

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

Schultz, Franklin A.

1979-01-01

123

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

124

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

PubMed Central

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

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

2013-01-01

125

Synthesis and characterization of cadmium selenide nanostructures on porous aluminum oxide templates by high frequency alternating current electrolysis  

NASA Astrophysics Data System (ADS)

We have successfully deposited nanostructured cadmium selenide (CdSe) inside anodic aluminum oxide (AAO) templates from aqueous electrolyte containing cadmium sulfate, selenium oxide and mercuric chloride by using high frequency alternating current (19 V rms, 200 Hz). Addition of mercury ions aids in the deposition of CdSe inside anodic oxide pores. Scanning and transmission electron microscopy studies of the deposit etched in phosphoric acid showed the presence of end standing nanostrips. Energy dispersive X-ray analysis of the deposit confirmed the presence of cadmium and selenium in the deposit. X-ray diffraction (XRD) studies of the deposit showed small but broad diffraction peaks consistent with the presence of hexagonal CdSe. Optical studies revealed blue shift in band gap energy due to quantum confinement.

Sankar, P. Ram; Tiwari, Pragya; Kumar, Ravi; Ganguli, Tapas; Mukherjee, C.; Srivastava, A. K.; Oak, S. M.; Pathak, Rajesh K.

126

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 µg 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

127

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

PubMed

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

Pandey, Kavita; Yadav, Pankaj; Mukhopadhyay, Indrajit

2014-03-20

128

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

129

Disposable copper-based electrochemical sensor for anodic stripping voltammetry.  

PubMed

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

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

2014-05-20

130

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

PubMed

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

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

2014-01-01

131

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

SciTech Connect

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

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

2008-05-15

132

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

133

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

NASA Technical Reports Server (NTRS)

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

Lyons, L. R.

1977-01-01

134

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

Microsoft Academic Search

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

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

2003-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

1984-11-01

136

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

NASA Astrophysics Data System (ADS)

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

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

1998-01-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2001-09-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2002-04-01

139

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

PubMed Central

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

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

2013-01-01

140

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

ERIC Educational Resources Information Center

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

Forsyth Technical Inst., Winston-Salem, NC.

141

Alternative fuel buses currently in use in China: Life-cycle fossil energy use, GHG emissions and policy recommendations  

Microsoft Academic Search

The Chinese government has enacted policies to promote alternative vehicle fuels (AVFs) and alternative fuel vehicles (AFVs), including city bus fleets. The life cycle (LC), energy savings (ES) and GHG reduction (GR) profiles of AVFs\\/AFVs are critical to those policy decisions. The well-to-wheels module of the Tsinghua-CA3EM model is employed to investigate actual performance data. Compared with conventional buses, AFVs

Xunmin Ou; Xiliang Zhang; Shiyan Chang

2010-01-01

142

The effect of glassy carbon surface oxides in non-aqueous voltammetry: the case of quinones in acetonitrile.  

PubMed

Glassy carbon (GC) electrodes are well-known to contain oxygenated functional groups such as phenols, carbonyls, and carboxylic acids on their surface. The effects of these groups on voltammetry in aqueous solution are well-studied, but there has been little discussion of their possible effects in nonaqueous solution. In this study, we show that the acidic functional groups, particularly phenols, are likely causes of anomalous features often seen in the voltammetry of quinones in nonaqueous solution. These features, a too small second cyclic voltammetric wave and extra current between the two waves that sometimes appears to be a small, broad third voltammetric wave, have previously been attributed to different types of dimerization. In this work, concentration-dependent voltammetry in acetonitrile rules out dimerization with a series of alkyl-benzoquinones because the anomalous features get larger as the concentration decreases. At low concentrations, solution bimolecular reactions will be relatively less important than reactions with surface groups. Addition of substoichiometric amounts of naphthol at higher quinone concentrations produces almost identical behavior as seen at low quinone concentrations with no added naphthol. This implicates hydrogen bonding and proton transfer from the surface phenolic groups as the cause of the anomalous features in quinone voltammetry at GC electrodes. This conclusion is supported by the perturbation of surface oxide coverage on GC electrodes through different electrode pretreatments. PMID:25279716

Staley, Patrick A; Newell, Christina M; Pullman, David P; Smith, Diane K

2014-11-01

143

Alternative Splicing at C Terminus of CaV1.4 Calcium Channel Modulates Calcium-dependent Inactivation, Activation Potential, and Current Density  

PubMed Central

The CaV1.4 voltage-gated calcium channel is predominantly expressed in the retina, and mutations to this channel have been associated with human congenital stationary night blindness type-2. The L-type CaV1.4 channel displays distinct properties such as absence of calcium-dependent inactivation (CDI) and slow voltage-dependent inactivation (VDI) due to the presence of an autoinhibitory domain (inhibitor of CDI) in the distal C terminus. We hypothesized that native CaV1.4 is subjected to extensive alternative splicing, much like the other voltage-gated calcium channels, and employed the transcript scanning method to identify alternatively spliced exons within the CaV1.4 transcripts isolated from the human retina. In total, we identified 19 alternative splice variations, of which 16 variations have not been previously reported. Characterization of the C terminus alternatively spliced exons using whole-cell patch clamp electrophysiology revealed a splice variant that exhibits robust CDI. This splice variant arose from the splicing of a novel alternate exon (43*) that can be found in 13.6% of the full-length transcripts screened. Inclusion of exon 43* inserts a stop codon that truncates half the C terminus. The CaV1.4 43* channel exhibited robust CDI, a larger current density, a hyperpolarized shift in activation potential by ?10 mV, and a slower VDI. Through deletional experiments, we showed that the inhibitor of CDI was responsible for modulating channel activation and VDI, in addition to CDI. Calcium currents in the photoreceptors were observed to exhibit CDI and are more negatively activated as compared with currents elicited from heterologously expressed full-length CaV1.4. Naturally occurring alternative splice variants may in part contribute to the properties of the native CaV1.4 channels. PMID:22069316

Tan, Gregory Ming Yeong; Yu, Dejie; Wang, Juejin; Soong, Tuck Wah

2012-01-01

144

Weldability of thin sheet metals during small-scale resistance spot welding using an alternating-current power supply  

Microsoft Academic Search

The resistance weldability of 0.2-mm-thick sheet aluminum, brass, and copper in small-scale resistance spot welding (SSRSW)\\u000a was studied. The effects of electrode materials and process parameters on joint strength and nugget size were investigated.\\u000a The welding current ranges for SSRSW of the sheet metals were determined based on the minimum current that produced a required\\u000a nugget diameter and maximum currents

Y. Zhou; P. Gorman; W. Tan; K. J. Ely

2000-01-01

145

Alternating-current conductivity and dielectric properties of Ge25Sb15- xBixS60 bulk and thin-film glasses  

Microsoft Academic Search

The effect of the replacement of antimony atoms by bismuth atoms on the electrical properties of compounds of the melt-quenched and thermally evaporated Ge25Sb15-xBixS60 (x = 0, 5, 10 and 15) chalcogenide system are reported for the first time. The results for the alternating-current (ac) conductivity sigmaac and the dielectric constant ?1 of some bulk and thin-film samples of the

M. M. El-Samanoudy

2002-01-01

146

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

PubMed

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

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

2014-01-01

147

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

148

The Inequity in Illinois School Finance. An Analysis of the Current Situation, the Historical Record, and Alternative Solutions.  

ERIC Educational Resources Information Center

In November 1990, a group of 47 school districts filed suit against the state of Illinois, charging that inequity in school financing violates the right to equal protection under the state constitution. This report, prepared by a coalition of 17 Chicago-based nonprofit organizations, provides Illinois citizens with an analysis of current school…

Hess, G. Alfred, Jr.; And Others

149

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

150

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

2014-10-15

151

Quasi-Steady-State Voltammetry of Rapid Electron Transfer Reactions at the Macroscopic Substrate of the Scanning Electrochemical Microscope  

PubMed Central

We report on novel theory and experiment for scanning electrochemical microscopy (SECM) to enable quasi-steady-state voltammetry of rapid electron transfer (ET) reactions at macroscopic substrates. With this powerful approach, substrate potential is cycled widely across the formal potential of a redox couple while the reactant or product of a substrate reaction is amperometrically detected at the tip in the feedback or substrate generation/tip collection mode, respectively. The plot of tip current versus substrate potential features the retraceable sigmoidal shape of a quasi-steady-state voltammogram although a transient voltammogram is obtained at the macroscopic substrate. Finite element simulations reveal that a short tip–substrate distance and a reversible substrate reaction (except under the tip) are required for quasi-steady-state voltammetry. Advantageously, a pair of quasi-steady-state voltammograms is obtained by employing both operation modes to reliably determine all transport, thermodynamic, and kinetic parameters as confirmed experimentally for rapid ET reactions of ferrocenemethanol and 7,7,8,8-tetracyanoquinodimethane at a Pt substrate with ?0.5-?m-radius Pt tips positioned at 90 nm–1 ?m distances. Standard ET rate constants of ?7 cm/s were obtained for the latter mediator as the largest determined for a substrate reaction by SECM. The various potential applications of quasi-steady-state voltammetry are also proposed. PMID:21175129

Nioradze, Nikoloz; Kim, Jiyeon; Amemiya, Shigeru

2011-01-01

152

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

PubMed

Electrochemical detection is becoming increasingly important for the detection of biological species. Most current biological research with electrochemical detection is done with carbon fiber electrodes due to their many beneficial properties. The ability to build electrochemical sensor from noble metals instead of carbon fibers may be beneficial in developing inexpensive multiplexed electrochemical detection schemes. To advance understanding and to test the feasibility of using noble metal electrochemical sensors the detection of dopamine, a biologically important small molecule was studied here. Specifically, dopamine detection on gold microelectrodes was characterized and compared to P-55 carbon fiber microelectrodes of the same geometry, using background subtracted fast scan cyclic voltammetry. While not as sensitive to dopamine as carbon fibers, it was observed that gold microelectrodes have six times the saturation coverage per area and 40 times the linear working range. Selectivity to dopamine, in comparison to several other neurotransmitters and their derivatives, is also quantitatively described. PMID:19319208

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

2008-01-01

153

Electrochemical determination of cadmium(II) at platinum electrode modified with kaolin by square wave voltammetry.  

PubMed

In this work, determination of cadmium(II) using square wave voltammetry (SWV) was described. The method is based on accumulation of these metal ions on kaolin platinum electrode (K/Pt). The K/Pt performance was optimized with respect to the surface modification and operating conditions. The optimized conditions were obtained in pH of 5.0 and accumulation time of 25 min. Under the optimal conditions, the relationship between the peak current versus concentration was linear over the range of 9 x 10(-8) to 8.3 x 10(-6) mol L(-1). The detection limit (DL, 3sigma) was 5.4 x 10(-9) mol L(-1). The analytical methodology was successfully applied to monitor the Cd(II) content in natural water. Interferences were also evaluated. PMID:19560266

Mhammedi, M A El; Achak, M; Hbid, M; Bakasse, M; Hbid, T; Chtaini, A

2009-10-30

154

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

PubMed Central

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

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

2012-01-01

155

Fe 3+ --gluconate and Ca 2+ Fe 3+ --gluconate complexes as mediators for indirect cathodic reduction of vat dyes – Cyclic voltammetry and batch electrolysis experiments  

Microsoft Academic Search

The indirect cathodic reduction of dispersed vat dyes CI Vat Yellow 1 and CI Vat Blue 5 was investigated by cyclic voltammetry and with batch electrolysis experiments. 0.01molL-1 solutions of the complexes Fe3‰+--gluconate and Ca2‰+-Fe3‰+--gluconate were studied. The addition of dispersed dyestuff to the mediator solution lead to a catalytic current. While the cathodic peak currents of both complexes is

Thomas Bechtold; Aurora Turcanu

2004-01-01

156

Application of a magnetohydrodynamic generator-detector electrode to hydrodynamic voltammetry  

SciTech Connect

Utilizing a fluid motion induced by electromagnetic force, a new method of voltammetry under forced convection was developed. The electrolytic cell was composed of two pairs of electrodes, viz., generator and detector pairs embedded on the bottom and top innerwalls of a rectangular channel. An intermediate produced on the surface of one of the first generator pair of the electrodes was swept downstream by the induced liquid flow to the neighboring electrode of the second detector pair and measured as a current. Examination of the mechanism between the induced flow of the electrolyte solution and the diffusion process of the intermediate permitted deriving the several expressions of electrolytic current for each pair of the electrodes as functions of bulk concentration of reacting species and externally applied magnetic field. It was also predicted that the detecting current interacts with the generating current, which can be depicted in terms of the collection efficiency of the intermediate. Observed results in experiments were in good agreement with these predictions.

Aogaki, R.; Fueki, K.

1984-06-01

157

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

PubMed

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

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

2014-10-01

158

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

PubMed

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

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

2011-06-15

159

ELECTROCHEMICAL DEPOSITION INDUCED STRESS MEASUREMENTS ON A MICROCANTILEVER INVESTIGATED WITH CYCLIC VOLTAMMETRY  

Microsoft Academic Search

Electrochemical cyclic voltammetry for solution-based metallic deposit characterization is a standard method in solid- liquid interfacial surface science. We have carried out cyclic voltammetry on a microcantilever along with adsorption- induced cantilever deflection monitoring for investigating the surface stresses introduced by a deposited metal layer. Specifically, we have investigated the deposition of lead onto polycrystalline gold-coated microcantilevers. Confining the electrodeposition

P. I. Oden; T. Thundat; R. J. Warmack

1997-01-01

160

Elimination Voltammetry with Linear Scan as a New Detection Method for DNA Sensors  

PubMed Central

The paper describes successful coupling of adsorptive transfer stripping (AdTS) and elimination voltammetry with linear scan (EVLS) for the resolution of reduction signals of cytosine (C) and adenine (A) residues in hetero-oligodeoxynucleotides (ODNs). Short ODNs (9-mers and 20-mers) were adsorbed from a small volume on a hanging mercury drop electrode (HMDE). After washing of the ODN-modified electrode by water and its transferring to an electrochemical cell, voltammetric curves were measured. The AdTS EVLS was able to determine of C/A ratio of ODNs through the elimination function conserving the diffusion current component and eliminating kinetic and charging current components. This function, which provides the elimination signal in a peak-counterpeak form, increased the current sensitivity for A and C resolution, and for the recognition of bases sequences in ODN chains. Optimal conditions of elimination experiments such as pH, time of adsorption, and scan rate were found. The combination of EVLS with AdTS procedure can be considered as a new detection method in a DNA sensor.

Trnkova, Libuse; Jelen, Frantisek; Petrlova, Jitka; Adam, Vojtech; Potesil, David; Kizek, Rene

2005-01-01

161

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

Frohlich, Flavio

2014-01-01

162

Cyclic voltammetry and RBS study of paint components  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

163

Solid electrolyte gas sensors based on cyclic voltammetry with one active electrode  

NASA Astrophysics Data System (ADS)

Solid state gas sensors are cost effective, small, rugged and reliable. Typically electrochemical solid state sensors operate in either potentiometric or amperometric mode. However, a lack of selectivity is sometimes a shortcoming of such sensors. It seems that improvements of selectivity can be obtained in case of the electrocatalytic sensors, which operate in cyclic voltammetry mode. Their working principle is based on acquisition of an electric current, while voltage ramp is applied to the sensor. The current-voltage response depends in a unique way on the type and concentration of ambient gas. Most electrocatalytic sensors have symmetrical structure. They are in a form of pellets with two electrodes placed on their opposite sides. Electrochemical reactions occur simultaneously on both electrodes. In this paper results for sensors with only one active electrode exposed to ambient gas are presented. The other electrode was isolated from ambient gas with dielectric sealing. This sensor construction allows application of advanced measuring procedures, which permit sensor regeneration acceleration. Experiments were conducted on Nasicon sensors. Properties of two sensors, one with one active electrode and second with symmetrical structure, used for the detection of mixtures of NO2 and synthetic air are compared.

Jasinski, G.; Jasinski, P.

2011-10-01

164

Iron organic speciation determination in rainwater using cathodic stripping voltammetry.  

PubMed

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

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

2012-07-29

165

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

E-print Network

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

Fitzgerald, William Francis, 1926-

1970-01-01

166

AC impedance and cyclic voltammetry studies on PbS semiconducting film prepared by electrodeposition  

Microsoft Academic Search

Semiconducting lead sulfide film was deposited on Stainless Steel (SS) electrode by cyclic voltammetry (CV) at room temperature. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to investigate the electrochemical properties of PbS film in Na2SO4 solution. The voltammetric results showed that oxidative dissolution of PbS film occurred at about 0.21V vs. Ag\\/AgCl and total film detachment from the

A. Aghassi; M. Jafarian; I. Danaee; F. Gobal; M. G. Mahjani

2011-01-01

167

Direct voltammetry and electrocatalytic properties of catalase incorporated in polyacrylamide hydrogel films  

Microsoft Academic Search

The direct voltammetry and electrocatalytic properties of catalase (Cat) in polyacrylamide (PAM) hydrogel films cast on pyrolytic graphite (PG) electrodes were investigated. Cat-PAM film electrodes showed a pair of well-defined and nearly reversible cyclic voltammetry peaks for Cat Fe(III)\\/Fe(II) redox couples at approximately ?0.46 V vs. SCE in pH 7.0 buffers. The electron transfer between catalase and PG electrodes was

Haiyun Lu; Zhen Li; Naifei Hu

2003-01-01

168

Vehicle propulsion system by individual stepping motors from continuously-running engine-driven alternator and\\/or pulsating battery current  

Microsoft Academic Search

A description is given of an engine-driven-alternator individual-wheel-motorized electric propulsion system for a four-wheel motor vehicle provided with a steering mechanism, said system comprising an engine-driven two-phase alternator having a two-phase alternator output, a plurality of electric stepping motors adapted to be drivingly connected one of each vehicle wheel and having motor inputs, each stepping motor having a rotor and

Fengler

1980-01-01

169

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

PubMed

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

Behpour, Mohsen; Valipour, Akram; Keshavarz, Mahin

2014-09-01

170

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

171

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

172

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

173

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

174

HHydrogen could well be the ultimate fuel--a plentiful, clean-burning, planet-healthy alternative to oil. But first, numerous obstacles must be overcome. Heading the list of challenges is storage. Currently,  

E-print Network

on Fuel Cell Technology Abundantly available in nature, hydrogen gas when broken down produces only waterHHydrogen could well be the ultimate fuel--a plentiful, clean-burning, planet-healthy alternative. Currently, storing hydrogen in sufficient quantities for use in vehicles or electronic devices requires

Yaghi, Omar M.

175

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

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

2014-01-01

176

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

177

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

178

Adsorption of formaldehyde on Pt(111) and Pt(100) electrodes: cyclic voltammetry and scanning tunneling microscopy.  

PubMed

The adsorption of formaldehyde (HCHO) on Pt(111) and Pt(100) electrodes was examined by cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM) in 0.1 M HClO(4). The extent of HCHO adsorption at both Pt electrodes was evaluated by comparing the CVs, particularly for the hydrogen adsorption and desorption between 0.05 and 0.4 V, obtained in 0.1 M HClO(4) with and without HCHO. The adsorption of HCHO on these Pt electrodes was significant only when [HCHO] >/= 10 mM. Adsorbed organic intermediate species acted as poisons, blocking Pt surfaces and causing delays in the oxidation of HCHO. Compared to Pt(111), Pt(100) was more prone to poisoning, as indicated by a 200 mV positive shift of the onset of HCHO oxidation. However, Pt(100) exhibited an activity 3 times higher than that of Pt(111), as indicated by the difference in peak current density of HCHO oxidation. Molecular resolution STM revealed highly ordered structures of Pt(111)-( radical7 x radical7)R19.1 degrees and Pt(100)-( radical2 x radical2) in the potential region between 0.1 and 0.3 V. Voltammetric measurements further showed that the organic poisons produced by HCHO adsorption behaved differently from the intentionally dosed CO admolecules, which supports the assumption for the formation of HCO or COH adspecies, rather than CO, as the poison. On both Pt electrodes, HCHO oxidation commenced preferentially at step sites at the onset potential of this reaction, but it occurred uniformly at the peak potentials. PMID:15896037

Mai, Chen-Fu; Shue, Chia-Haw; Yang, Yaw-Chia; Ou Yang, Liang-Yueh; Yau, Shueh-Lin; Itaya, Kingo

2005-05-24

179

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

180

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

Microsoft Academic Search

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

Susan Weigert

2009-01-01

181

Dopamine measurement during prolonged deep brain stimulation: a proof-of-principle study of paired pulse voltammetry  

PubMed Central

Purpose Deep Brain Stimulation (DBS) has been effective in treating various neurological and psychiatric disorders; however, its underlying mechanism hasn’t been completely understood. Fast scan cyclic voltammetry (FSCV) is a valuable tool to elucidate underlying neurotransmitter mechanisms of DBS, due to its sub-second temporal resolution and direct identification of analytes. However, since DBS-like high frequency stimulation evokes neurotransmitter release as well as extracellular pH shift, it is hard to isolate the neurotransmitter signal from the complex environment. Here we demonstrate the efficacy of a modified FSCV technique, Paired Pulse Voltammetry (PPV), in detecting dopamine (DA) release in the caudate nucleus during long-term electrical stimulation of the medial forebrain bundle (MFB) in the rat. Methods Unlike traditional FSCV applying a single triangular waveform, PPV employs a binary waveform with a specific time gap (2.2 ms) in between the comprising pulses. DA measurement was performed with a carbon fiber microelectrode placed in the caudate nucleus and a twisted bipolar stimulating electrode in the MFB. PPV data was collected with the Wireless Instantaneous Neurochemical Concentration Sensing System (WINCS). Results Using PPV, the detection of DA was evident throughout the long-term stimulation (5 minutes); however, without PPV, in vivo environmental changes including pH shift eventually obscured the characteristic oxidation current of DA at 0.6V. Conclusions These results indicate that PPV can be a valuable tool to accurately determine DA dynamics in a complex in vivo environment during long-term electrical stimulation. PMID:24688801

Paek, Seungleal (Brian); Knight, Emily Jane; Chang, Su-Youne; Lujan, J. Luis; Jang, Dong Pyo; Bennet, Kevin E.; Lee, Kendall H.

2014-01-01

182

Cyclic Voltammetry Study of Ice Formation in the PEFC Catalyst Layer during Cold Start  

E-print Network

of Nafion 112 membrane does not change and no degradation in catalyst per- formance occurs for the dry MEACyclic Voltammetry Study of Ice Formation in the PEFC Catalyst Layer during Cold Start Shanhai Ge developed to investigate the effect of ice formation in the cathode catalyst layer CL on electrochemically

183

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...

184

Abrasive stripping voltammetry of silver and tin at boron-doped diamond electrodes  

Microsoft Academic Search

Abrasive stripping voltammetry, using chemical vapour deposition (CVD) diamond electrodes and reference substrates comprising silver and tin, has been investigated. The abrasion process produced metallic particulates on the electrode surface, and both the mechanical and electrical contact were sensitively dependent on the abrasive force used. Only a small fraction of the material transferred was removed during electrochemical stripping. The silver

Arnab Chatterjee; Richard Wiltshire; Katherine B. Holt; Richard G. Compton; John S. Foord; Frank Marken

2002-01-01

185

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

ERIC Educational Resources Information Center

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

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

2004-01-01

186

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

187

A DEMS and cyclic voltammetry study of NH 3 oxidation on platinized platinum  

Microsoft Academic Search

The oxidation of ammonia on platinized platinum has been studied with cyclic voltammetry and differential electrochemical mass spectrometry (DEMS). These techniques show the surface to be highly covered with adsorbates during the selective oxidation of ammonia to N2 at potentials where platinum is free of oxides. These adsorbates are inactive in the formation of N2 and consist of NHx, probably

J. F. E. Gootzen; A. H. Wonders; WHM Visscher; R. A. van Santen; J. A. R. van Veen

1998-01-01

188

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

Microsoft Academic Search

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

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

2005-01-01

189

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

190

Alternate drop pulse polarography  

USGS Publications Warehouse

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

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

1976-01-01

191

EXPLORING ALTERNATIVE ENERGY SOURCES  

NSDL National Science Digital Library

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

Lisa Prososki (;)

2007-09-25

192

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

NASA Astrophysics Data System (ADS)

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

Lugo-Morales, Leyda Zoraida

193

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

PubMed Central

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

Fuller, Philip; Roth, Sanford

2011-01-01

194

Abstract Freshwater environments are currently experiencing an alarming decline in biodiversity. As a result, scientists and managers must look for alternative man-  

E-print Network

Abstract Freshwater environments are currently experiencing an alarming decline in biodiversity these aquatic systems. One such option that has po- tential to protect freshwater environments from numerous threats is the use of freshwater protected areas (FPAs). FPAs are portions of the freshwater environment

Cooke, Steven J.

195

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

PubMed

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

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

2007-02-12

196

Highly sensitive and selective determination of pyrazinamide at poly-L-methionine/reduced graphene oxide modified electrode by differential pulse voltammetry in human blood plasma and urine samples.  

PubMed

In this current study we used electrochemically active film which contains poly-L-methionine (PMET) and electrochemically reduced graphene oxide (ERGO) on glassy carbon electrode (GCE) for pyrazinamide (PZM) detection. The electrocatalytic response of analyte at PMET/ERGO/GCE film was measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In addition, electrochemical impedance studies revealed that the smaller R(ct) value observed at PMET/ERGO film modified GCE which authenticates its good conductivity and faster electron transfer rate. The prepared PMET/ERGO/GCE film exhibits excellent DPV response towards PZM and the reduction peak current increased linearly with respect to PZM concentration in the linear range between 0.4 ?M to 1129 ?M with a sensitivity of 0.266 ?A ?M(-1) cm(-2). Real sample studies were carried out in human blood plasma and urine samples, which offered good recovery and revealed the promising practicality of the sensor for PZM detection. The proposed sensor displayed a good selectivity, repeatability, sensitivity with appreciable consistency and good reproducibility. In addition, the proposed electrochemical sensor showed good results towards the commercial pharmaceutical PZM samples. PMID:24461828

Cheemalapati, Srikanth; Devadas, Balamurugan; Chen, Shen-Ming

2014-03-15

197

Facilitated ion transfer of protonated primary organic amines studied by square wave voltammetry and chronoamperometry.  

PubMed

The transfer of the protonated forms of heptylamine, octylamine, decylamine, procaine and procainamide facilitated by dibenzo-18-crown-6 from water to a solvent polymeric membrane has been investigated by using cyclic square wave voltammetry. The experimental voltammograms obtained are in good agreement with theoretical predictions. The values of the standard ion transfer potential, complexation constant and diffusion coefficient in water have been obtained from these experiments, and have been used to draw some conclusions about the lipophilicity of these species and the relative stability of the organic ammonium complexes with dibenzo-18-crown-6. The results have been compared with those provided by linear sweep voltammetry. Calibration graphs were obtained with both techniques. An interesting chronoamperometric method for the determination of the diffusion coefficient of the target ion in the membrane has been developed and applied to all these protonated amines. PMID:24793848

Torralba, E; Ortuño, J A; Molina, A; Serna, C; Karimian, F

2014-05-15

198

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. Rodríguez Flores; M. J. Villaseñor Llerena

1997-01-01

199

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

Microsoft Academic Search

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

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

2007-01-01

200

Ligand-receptor contact interactions using supported bilayer lipid membranes: cyclic voltammetry studies with electron mediators  

NASA Astrophysics Data System (ADS)

Using the method of cyclic voltammetry a number of well known electron mediators have been investigated on a teflon coated platinum wire, the tip of which has been modified by a self-assembled bilayer lipid membrane (s-BLM). Electrical capacitance of the s-BLM system was measured as a function of the frequency. The findings of this work are discussed in terms of the electron transfer phenomena and the redox reactions.

Murgasova, Renata; Sabo, Jan; Ottova, Angelica L.; Tien, H. Ti

1995-05-01

201

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

Microsoft Academic Search

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

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

2004-01-01

202

Investigations on the use of anodic stripping voltammetry for the analyses of lead in saline environments  

Microsoft Academic Search

Research is reported directed to modification of the anodic stripping voltammetry (ASV) analytic method in order to acquire data for lead from ambient sea water conditions, and development of a chemical model which uses these data to identify inorganic lead species for saline environments. Laboratory and field samples were analyzed for lead partitioning in: (a) KCl electrolyte solutions; (b) I.A.P.S.O.

1978-01-01

203

Determination of bromadiolone in pheasants and foxes by differential pulse voltammetry  

Microsoft Academic Search

Bromadiolone, a commercially used anticoagulant rodenticide, was determined in tissues of various animals by differential pulse voltammetry with a carbon-paste electrode. Under the most suitable experimental conditions (step potential of 25?mV?s and 0.2?mol?L acetate buffer, pH 4.2), the limit of detection was 0.5?ng?mL. The electroanalytical method was consequently used to investigate the bromadiolone transport within the food chain. Pheasants were

Miroslava Beklova; Sona Krizkova; Veronika Supalkova; Radka Mikelova; Vojtech Adam; Jiri Pikula; Rene Kizek

2007-01-01

204

Voltammetry study of Cr(III)\\/Cr(II) system in aqueous methanesulfonate solutions  

Microsoft Academic Search

In this paper, some electrochemical and spectral parameters of Cr(III) methanesulfonate (MS) complexes were investigated. Trivalent chromium ions were stated to exist in methanesulfonate aqueous solutions both in a violet form and in a green one. The kinetic parameters of one-electron Cr(III) electroreduction in methanesulfonate electrolytes were determined by means of cyclic voltammetry on the lead, cadmium and tin electrodes.

V. S. Protsenko; A. A. Kityk; F. I. Danilov

2011-01-01

205

Alternative Remedies  

MedlinePLUS

... or remedies that are not part of the traditional medical treatment prescribed by their healthcare professional. Using this type of alternative therapy along with traditional treatments is called complementary medicine . Alternative remedies can ...

206

Photocatalytic degradation of flexible PVC\\/TiO 2 nanohybrid as an eco-friendly alternative to the current waste landfill and dioxin-emitting incineration of post-use PVC  

Microsoft Academic Search

Photo-degradable poly(vinyl chloride) (PVC)\\/titanium dioxide (TiO2) nanohybrid has been investigated to be utilized as an eco-friendly alternative strategy to the current waste landfill and toxic byproduct-emitting incineration of PVC wastes. Thus, the present study suggests a novel idea related to preparing the photocatalytically degradable nanohybrid through TiO2 nanoparticle-integrated hyperbranched poly(?-caprolactone) (HPCL–TiO2). The main aim of this study is to find

Sung Ho Kim; Seung-Yeop Kwak; Takenori Suzuki

2006-01-01

207

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

208

Development of adenosine sensor: effect of physiological buffers on activity and sensitivity in adenosine determinations by fast scan voltammetry.  

PubMed

A new fast scan voltammetry (FSV) method was tested in the determinations of adenosine in physiological buffers at pH 7.4. The buffers can be used in the determinations of adenosine in vivo and include 7 x 10(-2) M phosphate, Krebs-Henseleit (K-H) and Hanks' Balanced Salts (HBSS). A new method of fabrication of carbon fiber electrodes (CFEs) by polishing, followed by electrochemical pretreatment (ECP) was developed for the determination. After the ECP of CFE, CFE background current was stable in FSV determinations even though an increase in the background current was observed after the ECP in the buffers at pH 7.4. The sensitivity in FSV determinations of adenosine at the pretreated electrodes was tested in the physiological buffers at the potential scan rate of 500 V s(-1) at pH 7.4. Buffer composition and pH was the same during the ECP of CFE and in the FSV determinations. The sensitivity in the FSV determinations of adenosine at the new CFEs was high, compared to that previously reported at CFEs prepared by other methods, and showed a limited dependence on buffer composition. However, a small increase in buffer pH above 7.4 resulted in a decrease in sensitivity in the determinations of adenosine. The decrease in sensitivity was associated with an additional increase in CFE background current at pH > 7.4. At pH 7.4 best sensitivity and limit of detection was obtained in 7 x 10(-2) M phosphate buffer, where the background current was lowest. The sensitivity was half that in K-H and HBSS. Standard deviation of measurements was ca. 1%. The results demonstrate the feasibility of sensitive FSV determinations of adenosine in physiological buffers at pH 7.4 at CFEs. PMID:12964607

El-Nour, Kholoud Abou; Brajter-Toth, Anna

2003-08-01

209

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

Microsoft Academic Search

An in situ technique for layer-by-layer electrochemical analysis of solid surfaces using the voltammetry of microparticles is presented. The method is based on the determination of several shape-dependent parameters for voltammetric curves recorded at a graphite pencil working electrode in contact with the sample, all immersed into aqueous electrolytes. Repetitive square wave voltammetry and sequential application of constant potential reductive

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

2010-01-01

210

Direct voltammetry of catalase immobilized on silica sol–gel and cysteine modified gold electrode and its application  

Microsoft Academic Search

The direct voltammetry of catalase (CAT) immobilized in silica sol–gel film in the presence of cysteine on gold electrode was investigated. The CAT electrode showed a pair of well-defined and quasi-reversible cyclic voltammetry peaks. It can be used as an electrochemical biosensor for the determination of hydrogen peroxide. The calibration range of H2O2 was from 1 to 30?molL?1 and the

Junwei Di; Min Zhang; Kaian Yao; Shuping Bi

2006-01-01

211

Interactions of the baicalin and baicalein with bilayer lipid membranes investigated by cyclic voltammetry and UV-Vis spectroscopy.  

PubMed

The baicalin and baicalein are the major flavonoids found in Radix Scutellariae, an essential herb in traditional Chinese medicine for thousands of years. The interactions of the baicalin and baicalein with lipid bilayer membranes were studied using cyclic voltammetry and UV-Vis spectroscopy. The thickness d of supported bilayer lipid membranes was calculated as d=4.59(±0.36) nm using AC impedance spectroscopy. The baicalein interacted with egg PC bilayer membranes in a dose-dependent manner. The responses of K3Fe(CN)6 on lipid bilayer membrane modified Pt electrode linearly increased in a concentration range of baicalein from 6.25?M to 25?M with a detection limit of 0.1?M and current-concentration sensitivity of 0.11(±0.01) ?A/?M, and then reached a plateau from 25?M to 50?M. However the baicalin showed much weaker interactions with egg PC bilayer membranes. UV-Vis spectroscopy also confirmed that the baicalein could interact with egg PC membranes noticeably, but the interaction of baicalin with membranes was hard to be detected. The results provide useful information on understanding the mechanism of action of Radix Scutellariae in vivo. PMID:24239871

Zhang, Ying; Wang, Xuejing; Wang, Lei; Yu, Miao; Han, Xiaojun

2014-02-01

212

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  

SciTech Connect

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 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 (mytilus edullus) and sediment from Boston Harbor, industrial waste water and industrial sludge, and (2) the detection of methylcyclopentadienylmanganesetricarbonyl (MMT) and similar compounds used as gasoline additives. An ultrasonic nebulizer 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 considered. The evaluation of a computer-aided optimization program, Drylab GC, using spearmint oil and Environmental Protection Agency (EPA) standard mixture as probes is discussed. The program is used for separation optimization and prediction of gas chromatographic parameters. The program produces a relative resolution map (RRM) which guides the analyst in selecting the most favorable temperature programming rate for the separation.

Ombaba, J.M.

1992-01-01

213

Alternatives to blood transfusion.  

PubMed

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

Spahn, Donat R; Goodnough, Lawrence T

2013-05-25

214

Alternative automotive fuels  

SciTech Connect

A survey of the current state of the art throughout the world in the use of alternative fuels in automotive engines. The fuels discussed are propane, compressed natural gas, liquid natural gas, alcohols, and hydrogen. Knowles covers the equipment necessary to utilize the fuel, including bulk storage, transfer to vehicles, and vehicle fuel tanks. He also includes the vehicle hardware and engine modifications necessary to use the alternative fuels. Advantages, disadvantages, cost, safety precautions, and applicable regulations are also discussed.

Knowles, D.

1984-01-01

215

Application of a nanoporous gold electrode for the sensitive detection of copper via mercury-free anodic stripping voltammetry.  

PubMed

This paper describes how a new mercury-free alternative electrode material, nanoporous gold (NPG), was applied to improve the performance of detecting trace metals in stripping voltammetry. The NPG electrode was obtained by dealloying Zn from Au(x)Zn(1-x) in a 40-60 mol% zinc chloride-1-ethyl-3-methylimidazolium chloride (ZnCl(2)-EMIC) ionic liquid. To prevent electrode fouling from surfactant adsorption, the short carbon-chain organothiol (3-mercaptopropyl)sulfonate (MPS) was selected to modify the NPG electrode through the formation of a self-assembled monolayer (SAM). The MPS-modified NPG (MPS@NPG) electrode not only significantly enhanced the sensitivity in detecting Cu(2+) but also effectively prevented electrode surface fouling from surfactant adsorption. The electrode is easy to prepare and can be readily renewed after each stripping experiment. The dynamic range of calibration curve, y = 58.76x (in microA microM(-1)) + 3.90 (R(2) = 0.999), showed very linear behavior with slope of 58.76 microA microM(-1) (0.1-5 microg L(-1)). The detection limit is as low as 0.002 microg L(-1) (0.031 nM). Non-ionic, anionic, and cationic surfactants were found to have no effect on Cu(2+) detection when using the MPS@NPG electrode as a sensing probe. This method was applied to determining the Cu(2+) in a reference material and three real water samples. The results agreed satisfactorily with the certified values. PMID:19838420

Huang, Jing-Fang; Lin, Bo-Tsuen

2009-11-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

217

Screening of pharmacologic adulterant classes in herbal formulations using voltammetry of microparticles.  

PubMed

A solid state electrochemical method for screening different families of adulterant chemicals illegally added to commercial phytotherapuetic formulations is described. The proposed method, based on the voltammetry of microparticles approach, permits a fast and sensitive way to distinguish between anorexics (amfepramone, fenproporex, sibutramine), benzozodiazepinic anxiolytics (clonazepam, flurazepam, alprazolam, midazolam, medazepam, chlordiazepoxide, diazepam), antidepressants (bupropione, fluoxetine, sertraline, paroxetine), diuretics (hydrochlorothiazide, furosemide, chlortalidone, amiloride, spironolactone), and hypoglycemics (glimepiride, chlorpropamide, glibenclamide) based on characteristic voltammetric signals recorded on solid micro- or nanosamples attached to graphite electrodes immersed into aqueous electrolytes. PMID:23245251

Doménech-Carbó, Antonio; Martini, Mariele; de Carvalho, Leandro Machado; Viana, Carine; Doménech-Carbó, María Teresa; Silva, Miguel

2013-02-23

218

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

219

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

220

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

221

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

222

A Flexible Software Platform for Fast-Scan Cyclic Voltammetry Data Acquisition and Analysis  

PubMed Central

Over the last several decades, fast-scan cyclic voltammetry (FSCV) has proved to be a valuable analytical tool for the real-time measurement of neurotransmitter dynamics in vitro and in vivo. Indeed, FSCV has found application in a wide variety of disciplines including electrochemistry, neurobiology and behavioral psychology. The maturation of FSCV as an in vivo technique led users to pose increasingly complex questions that require a more sophisticated experimental design. To accommodate recent and future advances in FSCV application, our lab has developed High Definition Cyclic Voltammetry (HDCV). HDCV is an electrochemical software suite, and includes data acquisition and analysis programs. The data collection program delivers greater experimental flexibility and better user feedback through live displays. It supports experiments involving multiple electrodes with customized waveforms. It is compatible with TTL-based systems that are used for monitoring animal behavior and it enables simultaneous recording of electrochemical and electrophysiological data. HDCV analysis streamlines data processing with superior filtering options, seamlessly manages behavioral events, and integrates chemometric processing. Furthermore, analysis is capable of handling single files collected over extended periods of time, allowing the user to consider biological events on both sub-second and multi-minute time scales. Here we describe and demonstrate the utility of HDCV for in vivo experiments. PMID:24083898

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

2013-01-01

223

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

PubMed

Pulsed voltammetry has been used to detect and quantify glyphosate on buffered water in presence of ammonium nitrate and humic substances. Glyphosate is the most widely used herbicide active ingredient in the world. It is a non-selective broad spectrum herbicide but some of its health and environmental effects are still being discussed. Nowadays, glyphosate pollution in water is being monitored but quantification techniques are slow and expensive. Glyphosate wastes are often detected in countryside water bodies where organic substances and fertilizers (commonly based on ammonium nitrate) may also be present. Glyphosate also forms complexes with humic acids so these compounds have also been taken into consideration. The objective of this research is to study the interference of these common pollutants in glyphosate measurements by pulsed voltammetry. The statistical treatment of the voltammetric data obtained lets us discriminate glyphosate from the other studied compounds and a mathematical model has been built to quantify glyphosate concentrations in a buffer despite the presence of humic substances and ammonium nitrate. In this model, the coefficient of determination (R(2)) is 0.977 and the RMSEP value is 2.96 × 10(-5) so the model is considered statistically valid. PMID:24054650

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

2013-10-15

224

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

PubMed

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

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

2014-11-18

225

Energy Storage: Current landscape for alternative energy  

E-print Network

Reliable Power Innovative Power HQ in Joplin, Missouri 11 Plants Joplin, Missouri Seneca, Missouri Manganese Dioxide Lithium Carbon Monofluoride Lithium Thionyl Chloride Microcell Launchers: Silver Zinc Monofluoride Lithium Thionyl Chloride Aircraft: Lithium Ion Nickel Cadmium Primary Lithium Energetic

226

Alternative Schools.  

ERIC Educational Resources Information Center

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

Pritchett, Stanley; Kimsey, Steve

2002-01-01

227

Alternative Medicine  

MedlinePLUS

... be defined as non-standard, unconventional treatments for glaucoma. Use of alternative medicine continues to increase, although ... positive impact on your overall health and other glaucoma risk factors including high blood pressure. Always talk ...

228

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.

229

Alternative automotive fuels  

Microsoft Academic Search

A survey of the current state of the art throughout the world in the use of alternative fuels in automotive engines. The fuels discussed are propane, compressed natural gas, liquid natural gas, alcohols, and hydrogen. Knowles covers the equipment necessary to utilize the fuel, including bulk storage, transfer to vehicles, and vehicle fuel tanks. He also includes the vehicle hardware

Knowles

1984-01-01

230

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

231

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

2014-10-20

232

Steady-state macroscale voltammetry in a supercritical carbon dioxide medium.  

PubMed

The electrochemical oxidation and reduction of decamethylferrocene is demonstrated in supercritical carbon dioxide at a macro gold disc electrode at 100 bar and 313 K. Fast mass transport effects were exhibited and the corresponding steady-state voltammetry was observed at high scan rates. A highly lipophilic room temperature ionic liquid that readily dissolved in supercritical CO(2) with acetonitrile as a co-solvent was used as an electrolyte, allowing for a conducting supercritical single phase. Experimental observations along with simulation results confirmed the hypothesis that a thin layer of liquid-like phase of co-solvent is formed at the electrode surface and is restricted by a more supercritical phase of high natural convection and bulk concentration. PMID:23212608

Toghill, Kathryn E; Voyame, Patrick; Momotenko, Dmitry; Olaya, Astrid J; Girault, Hubert H

2013-01-21

233

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

234

Electrochemical behaviour of Venlafaxine and its determination in pharmaceutical products using square wave voltammetry.  

PubMed

An electrochemical method for the determination of Venlafaxine in pharmaceutical formulations recently available on the European market is described. The electrochemical oxidation of Venlafaxine was studied at a HMDE electrode over a wide pH range (1.9-10.0) of buffered aqueous solutions using different potential sweep techniques. The results obtained showed that the best definition of the analytical signals was found in boric acid/potassium tetrahydroxoborate buffer at pH 8.7 using anodic stripping square wave voltammetry. Recovery trials were performed to assess the accuracy of results and these were compared to those provided by a HPLC technique according to the method described in literature and to the features of the pharmaceutical formulations. A relative deviation of < 0.2% was obtained. With the developed methodology, the limit of detection was 0.124 mg/l. PMID:10371026

Lima, J L; Loo, D V; Delerue-Matos, C; da Silva, A S

1999-03-31

235

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, Jesús F; Rodríguez Mellado, Jose M

2014-01-22

236

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

PubMed

The process and the kinetics of the electrochemical oxidation of morin in an anhydrous electrolyte have been investigated using cyclic and differential pulse voltammetry. The oxidation mechanism proceeds in sequential steps related to the hydroxyl groups in the three aromatic rings. The oxidation of the 2',4'dihydroxy moiety at the B ring of morin occurs first, at very low positive potentials, and is a one-electron, one-proton irreversible reaction. The rate constant, electron transfer coefficient and diffusion coefficients involved in the electrochemical oxidation of morin were determined. The influence of the deprotonation of the ring B hydroxyl moiety is related to the electron/proton donating capacity of morin and to its radical scavenging antioxidant activity. PMID:24262520

Masek, Anna; Chrzescijanska, Ewa; Zaborski, Marian

2014-04-01

237

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...

238

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

239

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

PubMed

Chloroanisoles, namely 2,4,6-trichloroanisole, are pointed out as the primary responsible of the development of musty off-flavours in bottled wine, due to their migration from cork stoppers, which results in huge economical losses for wine industry. A prevention step is the detection of these compounds in cork planks before stoppers are produced. Mass spectrometry gas chromatography is the reference method used although it is far beyond economical possibilities of the majority of cork stoppers producers. In this work, a portable cyclic voltammetry approach was used to detect 2,4,6-trichloroanisole extracted from natural cork planks to the aqueous phase during the cork boiling industrial treatment process. Analyses were carried out under ambient conditions, in less than 15 min with a low use of solvent and without any sample pre-treatment. The proposed technique had detection (0.31±0.01 ng/L) and quantification (0.95±0.05 ng/L) limits lower than the human threshold detection level. For blank solutions, without 2,4,6-trichloroanisole addition, a concentration in the order of the quantification limit was estimated (1.0±0.2 ng/L), which confirms the satisfactory performance of the proposed methodology. For aqueous samples from the industrial cork planks boiling procedure, intra-day repeatabilities were lower than 3%, respectively. Also, 2,4,6-trichloroanisole contents in the aqueous samples determined by this novel approach were in good agreement with those obtained by GC-MS (correlation coefficient equal to 0.98), confirming the satisfactory accuracy of the proposed methodology. So, since this novel approach is a fast, low-cost, portable and user-friendly method, it can be an alternative and helpful tool for in-situ industrial applications, allowing accurate detection of releasable 2,4,6-trichloroanisole in an earlier phase of cork stoppers production, which may allow implementing more effective cork treatments to reduce or avoid future 2,4,6-trichloroanisole contaminations of wine. PMID:24209365

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

2013-12-15

240

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

241

Theoretical and experimental study of Differential Pulse Voltammetry at spherical electrodes: Measuring diffusion coefficients and formal potentials  

Microsoft Academic Search

Rigorous and approximate analytical expressions are deduced for Differential Pulse Voltammetry at spherical electrodes of any size, including microelectrodes, when the electrogenerated species is soluble in the electrolytic solution. From these, we examine the utility of DPV for the determination of diffusion coefficients and formal potentials, establishing the optimum conditions for this purpose. The experimental validation of the theoretical results

Ángela Molina; Eduardo Laborda; Emma I. Rogers; Francisco Martínez-Ortiz; Carmen Serna; Juan G. Limon-Petersen; Neil V. Rees; Richard G. Compton

2009-01-01

242

Molecularly-imprinted solid phase extraction of catechol from aqueous effluents for its selective determination by differential pulse voltammetry  

Microsoft Academic Search

A polymeric sorbent based on molecular imprinting technology has been synthesized and applied to selectively extract catechol from water samples with subsequent determination by differential pulse voltammetry (DPV). The non-covalent polymer was prepared by bulk polymerization using catechol and 4-vinylpyridine as template and monomer, respectively. The effect of the flow and chemical variables associated to the performance of the solid

César Ricardo Teixeira Tarley; Lauro Tatsuo Kubota

2005-01-01

243

Direct Determination of Zn Heavy Metal in Tap Water of Canakkale (TURKEY) by Anodic Stripping Voltammetry Technique  

Microsoft Academic Search

In this work, the direct determination of zinc heavy metal in the tap water was carried out by differential pulse anodic stripping voltammetry (DPASV) technique at the glassy carbon electrode (GCE). The zinc ions were deposited by reduction at -1.5 V on a bare glassy carbon surface. Then, the deposited metal was oxidized by scanning the potential of the electrode

Selehattin Yilmaz; Sultan Yagmur; Gulsen Saglikoglu; Murat Sadikoglu

2009-01-01

244

Evaluation of metal fractions in river sediments and waters: application of chelation chromatography-differential pulse anodic stripping voltammetry  

Microsoft Academic Search

The ability of chelation chromatography in combination with differential pulse anodic stripping voltammetry (DPASV) to provide a simple, fast and reliable way of dealing with interionic interferences, competitive complexations, re-adsorption of released metal ions and sorption of spiking metal ions by organic\\/inorganic materials in the complex matrixes of real natural samples has been critically examined. The technique is based on

S. Sundd; B. B. Prasad

1995-01-01

245

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

246

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

E-print Network

of Zinc Wenjing Kang,a Xing Pei,a Wei Yue,b Adam Bange,c William R. Heineman,b Ian Papautsky*a a Bio sensor that uses an evaporated bis- muth electrode to detect zinc using square wave anodic stripping voltammetry. The microscale electrochemical cell consists of a bismuth working electrode, an integrated silver/silver

Papautsky, Ian

247

Drug–GSH interaction on GSH–Au modified electrodes: A cyclic voltammetry and electrochemical impedance spectroscopy study  

Microsoft Academic Search

Gold electrode was functionalized with glutathione (GSH) by adsorption and analyzed by cyclic voltammetry and electrochemical impedance techniques. The structure and properties of the surface film are strongly dependent on the modification procedure, pH value and supporting electrolyte. The blocking properties and the electron transfer through the GSH film and the «ion gating» effect of Ca2+ ions was analyzed in

Alina Latus; Mirela Enache; Elena Volanschi

2011-01-01

248

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

249

Alternatives to Antimicrobials  

Microsoft Academic Search

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

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

250

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

SciTech Connect

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

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

2012-12-15

251

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

252

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

PubMed Central

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

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

2009-01-01

253

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.

254

Augmented and alternative NLP techniques for augmentative and alternative communication  

Microsoft Academic Search

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

Ann Copestake

1997-01-01

255

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

PubMed

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

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

2010-05-15

256

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

NASA Astrophysics Data System (ADS)

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

John, Richard; Lord, Daniel

1999-09-01

257

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

258

Affecting of aquatic vascular plant Lemna minor by cisplatin revealed by voltammetry.  

PubMed

Within the context of application of platinum derivates based effective cytostatics, we can suppose that these risk metals can get into aquatic ecosystems where they can show biologic availability for food chain. In the present work we report on investigation of affecting of duckweed (Lemna minor) by various doses of cisplatin (0, 5, 10, 20, 40, 80 and 160 microM) for 4 days. The toxic influence of cisplatin was evaluated on the basis of growth inhibition expressed as number of leaves, growth rate, and total amount of biomass. The result value of 96hEC50, calculated from growth inhibition with comparison of growth rates, was 6.93 microM. Moreover we aimed on determination of cisplatin content using differential pulse voltammetry. The highest content of cisplatin (320 ng g(-1) of fresh weight) was determined in plants treated by 80 microM at the second day of treatment. Plants protect themselves against heavy metals by means of synthesis of cysteine-rich peptides such as glutathione and phytochelatins. Thus thiol determination in the treated plants by means of Brdicka reaction followed. The marked increase in thiol concentration detected is associated with defence reaction of the plant against stress caused by cisplatin. PMID:18201947

Supalkova, Veronika; Beklova, Miroslava; Baloun, Jiri; Singer, Christoph; Sures, Bernd; Adam, Vojtech; Huska, Dalibor; Pikula, Jiri; Rauscherova, Libuse; Havel, Ladislav; Zehnalek, Josef; Kizek, Rene

2008-02-01

259

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

260

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

261

Rapid determination of adenosine deaminase kinetics using fast-scan cyclic voltammetry.  

PubMed

Adenosine deaminase is an enzyme involved in purine metabolism and its inhibitors are used as anticancer and antiviral drugs. In this study, we show that fast-scan cyclic voltammetry at carbon-fiber microelectrodes can be used to study the kinetics of adenosine deaminase by electrochemically monitoring decreases in adenosine concentration. Buffer and salt concentrations were shown to affect the enzyme kinetics and the inhibition by erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and deoxycoformycin (DCF). In a Tris buffer containing salts that mimic cerebrospinal fluid, EHNA and DCF showed non-competitive inhibition with a K(i) of 1.7 +/- 0.6 nM and 1.2 +/- 0.2 nM, respectively. However, removing the divalent cations from the Tris buffer caused the inhibition to be competitive and reduced the K(i) for DCF by two orders of magnitude. In phosphate-buffered saline, the K(i) was 1.0 +/- 0.2 nM for EHNA and 3.6 +/- 0.3 pM for DCF, similar to literature values. Adenosine deaminase was also competitively inhibited by AgNO(3), showing it is susceptible to silver toxicity. Caffeine was found to increase adenosine deaminase activity. This is a fast, easy method for screening drug effects on enzyme kinetics and could be applied to other enzymatic reactions where there is a significant difference in the electroactivity of the reactant and product. PMID:20577678

Xu, Yida; Venton, B Jill

2010-09-14

262

Methionine ligand lability of type I cytochromes c: detection of ligand loss using protein film voltammetry.  

PubMed

Protein film voltammetry (PFV) is used to interrogate the behavior of a variety of bacterial and mitochondrial His/Met-ligated cytochromes c. While analogous studies upon alkanethiol-modified gold electrodes reveal the anticipated Fe(II/III) couple only, PFV using pyrolytic graphite edge (PGE) electrodes demonstrates the presence of a lower-potential form of each of the cyts c studied, with a potential of approximately -100 mV (vs hydrogen). The generation of the novel, lower-potential state is shown to arise specifically from the interaction with the PGE electrode. Simultaneously, the typical Fe(II/III) couple can be observed. PFV of a series of wild-type cytochromes and mutants in the Met-donating loop show that the lower-potential state is highly similar between proteins from Pseudomonas aeruginosa (PA), Hydrogenobacter thermophilus (HT), and horse heart. The generation of the lower-potential form correlates inversely with the stability of the Met-Fe interaction for each of the cytochromes. Comparison with chemically unfolded cyts c indicates that the lower-potential forms detected here are unique, and this distinct state is ascribed to the loss of the Met ligand. Thus, PGE is demonstrated to be a non-innocent electrode surface in PFV studies of His/Met-ligated cytochromes c. PMID:18454519

Ye, Tao; Kaur, Ravinder; Senguen, F Timur; Michel, Lea V; Bren, Kara L; Elliott, Sean J

2008-05-28

263

Tunable linear current mirror  

Microsoft Academic Search

A new tunable linear current mirror topology using a BJT differential pair as a current divider is proposed which is to be an alternative to tunable devices used in analog electronics. The structure has the advantage of simplicity, wide tuning range of five decades and a linear operating region of two decades.

Umut Guvenc; Ali Zeki

2008-01-01

264

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

PubMed

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

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

2010-11-01

265

Determination of levofloxacin in human urine by adsorptive square-wave anodic stripping voltammetry on a glassy carbon electrode.  

PubMed

The adsorption behavior of levofloxacin on a glassy carbon electrode was explored by cyclic and square-wave voltammetry. The drug was accumulated on a glassy carbon electrode and a well-defined oxidation peak was obtained in acetate buffer pH 5.0. Using square-wave anodic stripping voltammetry and accumulation at +0.4 V versus Ag/AgCl (saturated KCl) for 300 s, linear calibration graph was obtained from 6.0x10(-9) to 5.0x10(-7) M levofloxacin. The detection limit was calculated to be 5.0x10(-9) M. The R.S.D. determined from ten determinations at the 1.0x10(-7) M level was 1.7%. The method was applied for the direct determination of levofloxacin in diluted urine samples. It was validated using high-performance liquid chromatography (HPLC) as a reference method. PMID:18968756

Radi, A; El-Sherif, Z

2002-08-23

266

Study of antioxidant properties of a water-soluble Vitamin E derivative—tocopherol monoglucoside (TMG) by differential pulse voltammetry  

Microsoft Academic Search

Study of antioxidant properties of tocopherol monoglucoside (TMG), a water-soluble Vitamin E derivative, by differential pulse voltammetry has been carried out in this work. The pH influence on the antioxidant properties of TMG has been also investigated. It was observed that the antioxidant activity of TMG is greater at 6.90

E. I. Korotkova; O. A. Avramchik; T. V. Kagiya; Y. A. Karbainov; N. V. Tcherdyntseva

2004-01-01

267

A study of pencil-lead bismuth-film electrodes for the determination of trace metals by anodic stripping voltammetry  

Microsoft Academic Search

This work reports the utility of inexpensive and disposable pencil-lead graphite as a substrate for bismuth-film electrodes (BFEs) for the simultaneous determination of Cd(II), Pb(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV). The BFE was generated in situ by depositing simultaneously the bismuth film and the metal cations by reduction at ?1.4V on the pencil graphite substrate. Then, the

D Demetriades; A Economou; A Voulgaropoulos

2004-01-01

268

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

PubMed

2-Heptyl-3-hydroxy-4-quinolone, known as the Pseudomonas Quinolone Signal, is a key regulator of bacterial cooperative behaviour known as quorum sensing. A simple electrochemical strategy was employed for its sensitive detection using a bare boron-doped diamond electrode by cyclic voltammetry and amperometry. PQS (and potentially other quinolones) was then detected in cultures of P. aeruginosa pqsL(-) mutant strains. PMID:21853180

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

2011-10-01

269

Novel immunoassay for carcinoembryonic antigen based on protein A-conjugated immunosensor chip by surface plasmon resonance and cyclic voltammetry  

Microsoft Academic Search

In this study, an immunosensor chip utilizing surface plasmon resonance (SPR) and cyclic voltammetry (CV) was fabricated for\\u000a detecting carcinoembryonic antigen (CEA). Specifically, we applied in parallel an SPR instrument and a CV device to monitor\\u000a the assembly of carcinoembryonic antibody (anti-CEA) on a protein A-conjugated surface and the subsequent ligand reaction.\\u000a The immunosensor chips were constructed by various concentrations

Dian-Ping Tang; Ruo Yuan; Ya-Qin Chai

2006-01-01

270

Influence of ionic size on the mechanism of electrochemical doping of polypyrrole films studied by cyclic voltammetry  

Microsoft Academic Search

Charging\\/discharging process of a polypyrrole film has been studied in contact with a large-size anion (tetraphenylborate) solution in acetonitrile with a comparison to that in perchlorate solutions. The overall redox activity in the former case is significantly reduced. Nevertheless, we have been able to give a clear cyclic-voltammetry characterization of the film at various bulk-electrolyte concentrations for different sweeping rates.

Mikhail D. Levi; Christian Lopez; Eric Vieil; Mikhail A. Vorotyntsev

1997-01-01

271

Differential Pulse Voltammetric Determination of L-Cysteine after Cyclic Voltammetry in Presence of Catechol with Glassy Carbon Electrode  

Microsoft Academic Search

An electrochemical method of determination of cysteine has been developed in the solution containing catechol as indicator. Nucleophilic addition of the thiol species to the electrogenerated o-quinone results in the formation of an o-quinone-cysteine adduct which easily accumulates at the surface of the electrode in the acidic solution. Therefore, the conduct of cyclic voltammetry leads to the amplification of the

Xinfei Liu; Hui Lv; Qiaohua Sun; Yan Zhong; Jian Zhao; Jiabao Fu; Mi Lin; Jianguo Wang

2012-01-01

272

Syllabus for Chem. 3700 Alternative Energy  

E-print Network

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

Houston, Paul L.

273

Ion-transfer voltammetry of perfluoroalkanesulfonates and perfluoroalkanecarboxylates: picomolar detection limit and high lipophilicity.  

PubMed

Here we report on ion-transfer voltammetry of perfluoroalkanesulfonates and perfluoroalkanecarboxylates at the interface between a plasticized polymer membrane and water to enable the ultrasensitive detection of these persistent environmental contaminants with adverse health effects. The ion-transfer cyclic voltammograms of the perfluoroalkyl oxoanions are obtained by using a ?1 ?m thick poly(vinyl chloride) membrane plasticized with 2-nitrophenyl octyl ether. The cyclic voltammograms are numerically analyzed to determine formal ion-transfer potentials as a measure of ion lipophilicity. The fragmental analysis of the formal potentials reveals that the 10(4) times higher lipophilicity of a perfluoroalkanesulfonate in comparison to the alkanesulfonate with the same chain length is due to the inductive effect of perfluorination on lowering the electron density of the adjacent sulfonate group, thereby weakening its hydration. The fragmental analysis also demonstrates that the lipophilicities of perfluoroalkyl and alkyl groups with the same length are nearly identical and vary with the length. Advantageously, the high lipophilicity of perfluorooctanesulfonate allows for its stripping voltammetric detection at 50 pM in the presence of 1 mM aqueous supporting electrolytes, a ?10(7) times higher concentration. Significantly, this detection limit for perfluorooctanesulfonate is unprecedentedly low for electrochemical sensors and is lower than its minimum reporting level in drinking water set by the U.S. Environmental Protection Agency. In comparison, the voltammetric detection of perfluoroalkanecarboxylates is compromised not only by the lower lipophilicity of the carboxylate group but also by its oxidative decarboxylation at the underlying poly(3-octylthiophene)-modified gold electrode during voltammetric ion-to-electron transduction. PMID:25313994

Garada, Mohammed B; Kabagambe, Benjamin; Kim, Yushin; Amemiya, Shigeru

2014-11-18

274

Multiple scan rate voltammetry for selective quantification of real-time enkephalin dynamics.  

PubMed

Methionine-enkephalin (M-ENK) and leucine-enkephalin (L-ENK) are small endogenous opioid peptides that have been implicated in a wide variety of complex physiological functions, including nociception, reward processing, and motivation. However, our understanding of the role that these molecules play in modulating specific brain circuits remains limited, largely due to challenges in determining where, when, and how specific neuropeptides are released in tissue. Background-subtracted fast-scan cyclic voltammetry coupled with carbon-fiber microelectrodes has proven to be sensitive and selective for detecting rapidly fluctuating neurochemicals in vivo; however, many challenges exist for applying this approach to the detection of neuropeptides. We have developed and characterized a novel voltammetric waveform for the selective quantification of small tyrosine-containing peptides, such as the ENKs, with rapid temporal (subsecond) and precise spatial (10s of micrometers) resolution. We have established that the main contributor to the electrochemical signal inherent to M-ENK is tyrosine and that conventional waveforms provide poor peak resolution and lead to fouling of the electrode surface. By employing two distinct scan rates in each anodic sweep of this analyte-specific waveform, we have selectively distinguished M-ENK from common endogenous interfering agents, such as ascorbic acid, pH shifts, and even L-ENK. Finally, we have used this approach to simultaneously quantify catecholamine and M-ENK fluctuations in live tissue. This work provides a foundation for real-time measurements of endogenous ENK fluctuations in biological locations, and the underlying concept of using multiple scan rates is adaptable to the voltammetric detection of other tyrosine-containing neuropeptides. PMID:24967837

Schmidt, Andreas C; Dunaway, Lars E; Roberts, James G; McCarty, Gregory S; Sombers, Leslie A

2014-08-01

275

Sawhorse waveform voltammetry for selective detection of adenosine, ATP, and hydrogen peroxide.  

PubMed

Fast-scan cyclic voltammetry (FSCV) is an electrochemistry technique which allows subsecond detection of neurotransmitters in vivo. Adenosine detection using FSCV has become increasingly popular but can be difficult because of interfering agents which oxidize at or near the same potential as adenosine. Triangle shaped waveforms are traditionally used for FSCV, but modified waveforms have been introduced to maximize analyte sensitivity and provide stability at high scan rates. Here, a modified sawhorse waveform was used to maximize the time for adenosine oxidation and to manipulate the shapes of cyclic voltammograms (CVs) of analytes which oxidize at the switching potential. The optimized waveform consists of scanning at 400 V/s from -0.4 to 1.35 V and holding briefly for 1.0 ms followed by a ramp back down to -0.4 V. This waveform allows the use of a lower switching potential for adenosine detection. Hydrogen peroxide and ATP also oxidize at the switching potential and can interfere with adenosine measurements in vivo; however, their CVs were altered with the sawhorse waveform and they could be distinguished from adenosine. Principal component analysis (PCA) was used to determine that the sawhorse waveform was better than the triangle waveform at discriminating between adenosine, hydrogen peroxide, and ATP. In slices, mechanically evoked adenosine was identified with PCA and changes in the ratio of ATP to adenosine were observed after manipulation of ATP metabolism by POM-1. The sawhorse waveform is useful for adenosine, hydrogen peroxide, and ATP discrimination and will facilitate more confident measurements of these analytes in vivo. PMID:25005825

Ross, Ashley E; Venton, B Jill

2014-08-01

276

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 étudié par voltampérométrie le comportement de l'acide 6,6'-dithiodinicotinique (CPDS) sur l'électrode de mercure couverte par une monocouche de dioleoyl-phosphatidylcholine. La caractérisation électrochimique a été effectuée par des mesures de la capacité différentielle et par voltamétrie cyclique au dessus d'un pH 3-4. Le spectre UV paraît confirmer la présence de la forme dianionique du CPDS. Cependant les données expérimentales associées à une estimation de l'hydrophobicité de la forme dianionique suggèrent que seule la forme neutre du CPDS peut être réduite sur la surface de l'électrode.

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

1999-04-01

277

Voltammetry of L-cysteine and 2-mercaptopyridine on a self-assembled phospholipid monolayer  

NASA Astrophysics Data System (ADS)

The redox behaviour of 2-mercaptopyridine and the aminoacid L-cysteine was studied through a self-assembled monolayer of dioleoylphosphatidylcholine adsorbed on mercury by using cyclic voltammetry. 2-Mercaptopyridine penetrates into monolayer in the zone of stability of the phospholipid layer and shows an quasi-reversible behaviour while reversibility is observed in the absence of a monolayer. This fact is reflected in the occurrence of voltammetric peaks in the above mentioned region of potentials. Conversely, cysteine was found not to penetrate in the lipid layer as long as the latter behaves like a half-membrane. Voltammetric signal of cysteine was only obtained when the potential was scanned to values positive to -0.2 V. Beyond this potential the cyclic voltammograms show a series of anodic peaks, due to a rearrangement of the lipid film and to the formation of Hg(RS)2, followed by three cathodic peaks when the scan is reversal. The behaviour of these peaks was analized. Le comportement voltampérometrique de la 2-mercaptopyridine et de l'aminoacid L-cysteine a eté etudié sur l'électrode de mercure couverte par une monocouche de dioleoylphosphatidylcholine. Pour la 2-mercaptopyridine on peut constater la pénétration de ce composé dans la zone de stabilité de la monocouche. La constante de vitesse a eté calculée seulement pour des basses concentrations. Lorsque la concentration augmente le comportement devient très compliqué. Par contre, pour la cysteine on observe seulement un signal de courant pour des potentiels superieurs à -0.2V oú la monocouche de phospholipide ne peut pas être considerée très stable. La differente structure chimique des deux substances permet de rendre compte du different comportement voltammetrique observé.

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

1999-09-01

278

Electric Currents Electric Current  

E-print Network

connection). - When a wire carries more that its safe, the circuit is called overloaded, which causes heating a constant potential difference, which can then make charges move. Current can flow in a circuit only if there is a continuous conducting path. We then have a complete or `closed' circuit. A circuit where there is a break

Yu, Jaehoon

279

Looking for an Alternative.  

ERIC Educational Resources Information Center

Argues that high school newspapers might do well to create stronger ties with alternative weeklies. Discusses issues of niche marketing, alternative content, and alternative presentation. Notes that high school papers could learn a lot from alternative newspapers. (SR)

Kennedy, Jack

1999-01-01

280

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

281

Adsorptive stripping voltammetry determination of methyldopa on the surface of a carboxylated multiwall carbon nanotubes modified glassy carbon electrode in biological and pharmaceutical samples.  

PubMed

In the present work, a simple carboxylated multiwall carbon nanotubes (CMWCNTs) modified glassy carbon electrode was developed for sensitive determination of methyldopa (MTD). The study of modified electrode and MTD electrochemical behavior at its surface was investigated employing SEM, adsorptive stripping voltammetry, electrochemical impedance spectroscopy and chronocoulometry. These studies show that the oxidation of MTD is facilitated at the surface of GCE which is casted with CMWCNTs and remarkably peak current enhanced comparing to the bare electrode due to its adsorption on the electrode surface. Also, because of the catalytic property of modified electrode onset potential decreased for oxidation of MTD. Under optimized conditions, the calibration curve was linear in two concentration ranges of 0.1-30 and 30.0-300.0 ?M with a detection limit of 0.08 ?M and relative standard deviation (R.S.D.%) lower than 3.0% (n=5). This modified electrode was used as a sensor for determination of MTD in pharmaceutical and human urine samples with satisfactory results. PMID:23665091

Rezaei, Behzad; Askarpour, Neda; Ensafi, Ali A

2013-09-01

282

Direct electrochemical determination of methyl jasmonate in wheat spikelet at a nano-montmorillonite film modified electrode by derivative square wave voltammetry.  

PubMed

The direct electrochemical determination of methyl jasmonate (MeJA) at a nano-montmorillonite modified glassy carbon electrode (nano-MMT/GCE) is reported. The modified electrode, prepared by a simple casting-drying method and characterized by scanning electron microscope (SEM) and electrochemical impedance spectra (EIS), was proved to process a uniform nanostructured surface with a large surface area and a fast electron transfer rate. This electrode exhibited a sensitive electrochemical response for the direct oxidation of MeJA in 0.1 mol L(-1) HClO4, which could be further improved by using a derivative square wave voltammetry technique. Thus, a simple and fast electrochemical method for the determination of MeJA is proposed. Under optimal working conditions, the oxidation current of MeJA linearly increased with its concentration in the range of 7.0 × 10(-7)-1.0 × 10(-3) mol L(-1) with a detection limit of 5.0 × 10(-7) mol L(-1). This method had been applied to the determination of MeJA content in wheat spikelet samples. PMID:23654231

Gan, Tian; Hu, Chengguo; Chen, Zilin; Hu, Shengshui

2010-08-25

283

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

284

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

PubMed Central

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

Ahmadi, Farhad; Karamian, Ehsan

2014-01-01

285

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...

286

For a complete list of current vacancies and information on the application process please refer to www.ucd.ie/vacancies or alternatively contact UCD HR on 01 716 4900.  

E-print Network

for all standards of players. The annual membership is 45. Our Club night is Thursday evenings and we check out our website: www.ucd.ie/stennis. You are welcome to drop down to the courts on club night://www.ucd.ie/sport/sportscamps alternatively you can ring us at 01 7162145/ 01 7162185. UCD STAFF AND POSTGRADUATE TENNIS CLUB MEMBERSHIP

287

Evaluation of the electrochemical stability of graphite foams as current collectors for lead acid batteries  

Microsoft Academic Search

Graphite foams with high electrical and thermal conductivities, good mechanical strength, and low mass have been synthesized and evaluated as possible current collector materials to replace lead alloys for the development of lightweight lead acid batteries. Cyclic voltammetry and galvanostatic charge–discharge tests were performed on these foams prior to and after graphitization to evaluate their electrochemical properties. In the voltage

Young-Il. Jang; Nancy J. Dudney; Terry N. Tiegs; James William Klett

2006-01-01

288

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

PubMed

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

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

2011-11-15

289

Theoretically optimized geometry based qualitative explanations for the 1H NMR and voltammetry behaviors of [Mg(OBTTAP)  

NASA Astrophysics Data System (ADS)

PM3 and DFT calculations have been used to obtain fully optimized geometries of [Mg(OBTTAP)] (where, OBTTAP = octakis(benzylthiotetraazaporphyrin)). Both methods gave Mg-TAP structural features that are in agreement with the crystallographic data on analogous methylthio compounds. The position of the -S-CH 2C 6H 5 vis-à-vis the M-TAP core in the PM3 optimized geometry was used to qualitatively explain 1H NMR signals and the electro-oxidation behavior of complex in cyclic voltammetry.

Kumar, Ajay; Thankachan, P. P.; Kumar, Rajeev; Prasad, Rajendra

2007-02-01

290

Peat as an energy alternative  

SciTech Connect

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

Punwani, D.V.

1980-07-01

291

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, André; Baldan, Mauricio R; Cristovan, Fernando H; Ferreira, Neidenei G

2014-10-01

292

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

293

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 °C in the presence of ambient oxygen and water. The half-lives of the ferrocenium, carboxylate ferrocenium, and decamethyl ferrocenium cations were found to be 1.27 × 10(3), 1.52 × 10(3), and ?11.0 × 10(3) s, respectively, in acetonitrile solvent having a 0.5 M tetrabutylammonium hexafluorophosphate electrolyte. These results are in agreement with the previous reports, i.e. the ferrocenium cation is unstable whereas the decamethyl ferrocenium cation has superior stability. The new methodology has been established by performing various experiments using different concentrations of ferrocene, variable scan rates in cyclic voltammetry, different time periods for amperometry, and in situ spectroelectrochemical experiments. PMID:25270846

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

2014-10-15

294

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.

295

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

296

Amperometric and fast scan-rate cyclic voltammetry detection at a microelectrode for gel permeation high-performance liquid chromatography of fullerenes  

SciTech Connect

Amperometry and fast scan-rate cyclic voltammetry (CV) at a 10-[mu]m-diameter platinum microelectrode were utilized for detection and in situ identification of fullerenes which were separated by gel permeation high-performance liquid chromatography. The microelectrode and inlet capillary nozzle were arranged perpendicularly. The limiting currents were virtually independent of the mobile phase flow rate in the range 0.1--2.0 mL min[sup [minus]1] for a distance between the microelectrode and inlet capillary nozzle [le] 0.10 mm. A toluene extract of the laser-vaporized soot containing low molecular mass fullerenes was resolved on two gel permeation columns which were connected in series. The mobile phase was dichloromethane/cyclohexane, 90/10 (v/v), 0.01 M tetra-n-butylammonium perchlorate. C[sub 60] and C[sub 70] were the major components of the extract and were present in a 3:1 mass ratio. Other higher fullerenes were also present in a 3:1 major concentration. The number and shapes of the peaks in chromatograms obtained with amperometric detection at [minus]1.3 V vs SCE were the same as those obtained with UV-visible spectroscopic detection at 366 nm, thus indicating that all of the detected compounds both absorb UV-visible light and are electrochemically active. Extracolumn peak broadenings due to detection and detectability (83.8 ng for C[sub 60]) were also the same in both detection techniques. In situ fast scan-rate voltammograms of C[sub 60] and C[sub 70] were obtained during elution, and the reversible E[sub 1/2] values of the third and fourth electroreductions could be used for their identification. 40 refs., 4 figs., 1 tab.

Soucaze-Guillous, B.; Kutner, W.; Kadish, K.M. (Univ. of Houston, TX (United States))

1993-03-15

297

Differential pulse voltammetry in the dorsal horn of the spinal cord of the anesthetized rat: are the voltammograms related to 5-HT and/or to 5-HIAA?  

PubMed

Treated carbon fiber microelectrodes were used with the differential pulse voltammetry method for in vitro and in vivo determination of indoleamines. Under these conditions a peak of oxidation current which is characteristic of 5-hydroxyindoles is recorded at 280-300 mV. Treated carbon fiber microelectrodes respond in vitro linearly over a large range of concentrations of 5-hydroxytryptamine (5-HT) and of 5-hydroxyindoleacetic acid (5-HIAA), but are 5-8 times more sensitive to 5-HT than to 5-HIAA. In vivo, the question remains as to the exact nature of the peak because the oxidation potentials of 5-HT and 5-HIAA are close together and cannot be monitored separately. Pharmacological investigations were hence carried out in order to characterize the electrochemical signal detected at 300 mV in the dorsal horn of the lumbar spinal cord of chloral hydrate-anesthetized rats. Using 250 micron long carbon fiber microelectrodes, the electrochemical signal stabilizes at 30-90 min and the peak remains constant for up to 210 min. Administration of the monoamine oxidase inhibitor (MAOI) clorgyline produced a progressive decrease of the signal which reached a decrease of 33% of control at 180 min after injection. At this time biochemical measures demonstrated a 117% increase in 5-HT and a 32% decrease in 5-HIAA in the dorsal half of the spinal cord. Reserpine provoked an increase of 20% in the electrochemical peak and the 5-HIAA outflow blocker probenecid gave rise to a sustained plateau of about 60% above control values.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6194856

Rivot, J P; Ory-Lavollee, L; Chiang, C Y

1983-09-26

298

Recommendations for Developing Alternative Test Methods for Developmental Neurotoxicity  

EPA Science Inventory

There is great interest in developing alternative methods for developmental neurotoxicity testing (DNT) that are cost-efficient, use fewer animals and are based on current scientific knowledge of the developing nervous system. Alternative methods will require demonstration of the...

299

46 CFR 183.130 - Alternative standards.  

Code of Federal Regulations, 2010 CFR

...with the requirements of this part in their entirety: (1) Section 183.420; and (2) The following American Boat and Yacht Council (ABYC) Projects where applicable: (i) E-8, “Alternating Current (AC) Electrical Systems on Boats;”...

2010-10-01

300

46 CFR 183.130 - Alternative standards.  

Code of Federal Regulations, 2013 CFR

...with the requirements of this part in their entirety: (1) Section 183.420; and (2) The following American Boat and Yacht Council (ABYC) Projects where applicable: (i) E-8, “Alternating Current (AC) Electrical Systems on Boats;”...

2013-10-01

301

46 CFR 183.130 - Alternative standards.  

Code of Federal Regulations, 2011 CFR

...with the requirements of this part in their entirety: (1) Section 183.420; and (2) The following American Boat and Yacht Council (ABYC) Projects where applicable: (i) E-8, “Alternating Current (AC) Electrical Systems on Boats;”...

2011-10-01

302

[Alternatives to lid reconstruction. Systematic presentation].  

PubMed

Eyelid reconstruction cannot be planned only by following current concepts. A systematic analysis of the defect considering the concentric zones, function, esthetics, and surgical trauma can help to select the appropriate technique among the possible alternatives. PMID:15014965

Pfeiffer, M J

2004-05-01

303

Evaluation of alternative leachate liner materials  

E-print Network

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

Biles, Daniel Franklin

2012-06-07

304

November 2008 Alternative Energy  

E-print Network

? In this paper we will discuss a range of alternative primary energy sources and alternative energy carriersNovember 2008 Alternative Energy Technologies for BC R.L. Evans CleaN eNergy researCh CeNtre, UNiversity of british ColUmbia PaCifiC iNstitUte for Climate solUtioNs AlternAtive energy #12;Pacific

Pedersen, Tom

305

Development of cyclic Voltammetry Assays and Instrumentaion for detection and Quantification of Analyte Concentration  

E-print Network

, but lower cost electronic lab-on- a-chip systems can be built using electrodes to measure the rate used this as the working electrode. We controlled the voltage and measured the current the voltage waveform, speed, and integration time. Further work will involve trying to replace the counter

Mountziaris, T. J.

306

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

307

Electrosynthesis of poly(para)phenylene in an ionic liquid: cyclic voltammetry and in situ STM/tunnelling spectroscopy studies.  

PubMed

The electropolymerization of benzene in the air and water-stable ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIm)FAP is investigated. The study comprises cyclic voltammetry, IR and in situ STM/tunnelling spectroscopy measurements. The IR results indicate that poly(para)phenylene is the end product of the electropolymerization of benzene in the employed ionic liquid. The resulting conjugation lengths of the product fall between 19 and 21. A polymer reference electrode is used successfully for the electrochemical polymerization of benzene. The first in situ STM results show that the electropolymerization of benzene in the ionic liquid can be probed on the nanoscale and the band gap of the prepared polymer can be determined. The electrodeposited polymer film obtained at a constant potential of 1.0 V vs PPP (polyparaphenylene) exhibits a band gap of 2.9+/-0.2 eV. PMID:18247438

Carstens, T; El Abedin, S Zein; Endres, F

2008-02-22

308

Preparation and electrochemical properties of pitch-based carbon foam as current collectors for lead acid batteries  

Microsoft Academic Search

Pitch-based carbon foam with large pore size in the cell walls was prepared and evaluated as possible current collectors of lead acid batteries. Cyclic voltammetry and galvanostatic charge–discharge experiments were performed on the material to evaluate its electrochemical properties. The carbon foam is electrochemically stable in the voltage range where the negative electrodes of lead acid batteries operate, while oxygen

Ya Chen; Bai-Zhen Chen; Xi-Chang Shi; Hui Xu; Wei Shang; Yan Yuan; Lu-Ping Xiao

2008-01-01

309

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

310

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

311

Industry experience with alternative methods.  

PubMed

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

LeClaire, J; de Silva, O

1998-12-28

312

Density Currents  

NSDL National Science Digital Library

In this activity, students will make a turbidity current. They will discover how fluids of differing densities interact with one another, learn some ways the densities of fluids can be changed and observe how density currents transport and deposit tremendous amounts of sediment in lakes and in the ocean. Additional options allow students to create and observe different kinds of density currents.

Kopaska-Merkel, David

313

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

Microsoft Academic Search

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

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

2006-01-01

314

Research diagnosis of current depressive disorder: A comparison of methods using current symptoms and lifetime history  

Microsoft Academic Search

Data from the WHO international study of Psychological Problems in General Health Care were used to compare two alternative algorithms for diagnosing current major depression using the Composite International Diagnostic Interview: the traditional method based on lifetime diagnosis and an alternative method based on number of current symptoms. Using DSM-IV criteria for current major depression, 6.2% of 5394 primary care

Gregory E. Simon; Wolfgang Maier; T. Bedirhan Ustun; Michael Linden; Patrice Boyer

1995-01-01

315

Alternative Fuels Research Laboratory  

NASA Technical Reports Server (NTRS)

NASA Glenn has invested over $1.5 million in engineering, and infrastructure upgrades to renovate an existing test facility at the NASA Glenn Research Center (GRC), which is now being used as an Alternative Fuels Laboratory. Facility systems have demonstrated reliability and consistency for continuous and safe operations in Fischer-Tropsch (F-T) synthesis and thermal stability testing. This effort is supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing project. The purpose of this test facility is to conduct bench scale F-T catalyst screening experiments. These experiments require the use of a synthesis gas feedstock, which will enable the investigation of F-T reaction kinetics, product yields and hydrocarbon distributions. Currently the facility has the capability of performing three simultaneous reactor screening tests, along with a fourth fixed-bed reactor for catalyst activation studies. Product gas composition and performance data can be continuously obtained with an automated gas sampling system, which directly connects the reactors to a micro-gas chromatograph (micro GC). Liquid and molten product samples are collected intermittently and are analyzed by injecting as a diluted sample into designated gas chromatograph units. The test facility also has the capability of performing thermal stability experiments of alternative aviation fuels with the use of a Hot Liquid Process Simulator (HLPS) (Ref. 1) in accordance to ASTM D 3241 "Thermal Oxidation Stability of Aviation Fuels" (JFTOT method) (Ref. 2). An Ellipsometer will be used to study fuel fouling thicknesses on heated tubes from the HLPS experiments. A detailed overview of the test facility systems and capabilities are described in this paper.

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

2012-01-01

316

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

317

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

318

Steady-state voltammetry of a microelectrode in a closed bipolar cell.  

PubMed

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

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

2012-10-16

319

Anodic stripping voltammetry of sulphide at a nickel film: towards the development of a reagentless sensor.  

PubMed

The determination of sulphide at an electrochemically generated nickel oxide layer at glassy carbon and screen-printed electrodes in acidic media has been examined and appraised. The NiO layer was found to produce a stripping-like signal to sulphide and gave a linear peak current response from 20 to 90 muM. The response was further enhanced by repetitive cycling allowing accumulation of nickel sulphide at the electrode surface such that lower micromolar levels of sulphide (i.e. 5 muM) can be determined. The response at the NiO layer to sulphide is shown to be reproducible over a period of 24 h, thereby offering the development of a disposable amperometric sensor for sulphide. PMID:18969180

Giovanelli, Debora; Lawrence, Nathan S; Wilkins, Shelley J; Jiang, Li; Jones, Timothy G J; Compton, Richard G

2003-10-17

320

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.

321

Depleted uranium management alternatives  

SciTech Connect

This report evaluates two management alternatives for Department of Energy depleted uranium: continued storage as uranium hexafluoride, and conversion to uranium metal and fabrication to shielding for spent nuclear fuel containers. The results will be used to compare the costs with other alternatives, such as disposal. Cost estimates for the continued storage alternative are based on a life-cycle of 27 years through the year 2020. Cost estimates for the recycle alternative are based on existing conversion process costs and Capital costs for fabricating the containers. Additionally, the recycle alternative accounts for costs associated with intermediate product resale and secondary waste disposal for materials generated during the conversion process.

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

1994-08-01

322

Simultaneous determination of copper, bismuth and lead by adsorptive stripping voltammetry in the presence of thymolphthalexone.  

PubMed

A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of copper, bismuth and lead is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of copper, lead and bismuth were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 4.0 microM, pH of 9.0, and accumulation potential at -800 mV vs. Ag/AgCl with an accumulation time of 80 s. The peak currents are proportional to the concentration of copper, bismuth and lead over the 0.4-300, 1-200 and 1-100 ng mL(-1) ranges with detection limits of 0.4, 0.8 and 0.7 ng mL(-1), respectively. The procedure was applied to the simultaneous determination of copper, bismuth and lead in the tap water and some synthetic samples with satisfactory results. PMID:16837745

Babaei, Ali; Shams, Esmaeil; Samadzadeh, Ali

2006-07-01

323

Current limiters  

SciTech Connect

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

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

1996-09-01

324

Low-level determination of silicon in steels by anodic stripping voltammetry on a hanging mercury drop electrode.  

PubMed

The sensitive differential pulse anodic stripping voltammetry (DPASV) proposed originally by Ishiyama et al. (2001) has been revised and improved to allow the accurate measurement of silicon on a hanging mercury drop electrode (HMDE) instead of a glassy carbon electrode. We assessed the rate of formation of the partially reduced ?-silicododecamolybdate and found that metallic mercury promotes the reaction in the presence of a large concentration of Fe(3+). The scope of the method has been broadened by carrying out the measurements in the presence of a constant amount of Fe(3+). The limit of detection (LOD) of the method described in the present paper is 100 ?g Sig(-1) of steel, with a relative precision ranging from 5% to 12%. It can be further enhanced to 700 ng Sig(-1) of steel provided the weight of the sample, the dilution factors, the duration of the electrolysis and the ballast of iron are adequately revised. The tolerance to several interfering species has been examined, especially regarding Al(3+), Cr(3+) and Cr VI species. The method was validated using four low-alloy ferritic steels certified by the National Institute of Standards and Technology (NIST). Its application to nickel base alloys as well as to less complicated matrixes is straightforward. It has also been successfully applied to the determination of free silicon into silicon carbide nano-powder. PMID:20875585

Rahier, A H; Lunardi, S; Nicolle, F; George, S M

2010-10-15

325

Comparative Behavior of Aromatic Disulfide and Diselenide Monolayers on Polycrystalline Gold Films Using Cyclic Voltammetry, STM, and Quartz Crystal Microbalance.  

PubMed

A comparative investigation of the self-assembled monolayers of diphenyl disulfide (DDS), diphenyl diselenide (DDSe), and naphthalene disulfide (NDS) on polycrystalline gold films using STM, QCM, and electrochemical techniques is presented. The geometric constraint imposed by the rigid naphthalene ring for NDS inhibits the cleavage of the S-S bond, thus adversely affecting the monolayer organization and stability relative to the monolayers formed with DDS and DDSe. A comparative analysis using techniques like cyclic voltammetry and quartz-crystal microbalance indicates that, for DDS, the facile cleavage of the S-S bond leads to strong binding of the adsorbate molecules at the preferred surface sites, resulting in a rather well-organized self-assembled structure. The STM pattern of NDS reveals a periodic domain (i.e., less than 10 nm in size) while no such small domains are seen in the case of DDS and DDSe due to the orientational flexibility of the rings. Copyright 2001 Academic Press. PMID:11161528

Aslam, Mohammed; Bandyopadhyay, Krisanu; Vijayamohanan, K.; Lakshminarayanan, V.

2001-02-15

326

Comparison of electrode materials for the detection of rapid hydrogen peroxide fluctuations using background-subtracted fast scan cyclic voltammetry.  

PubMed

Hydrogen peroxide (H(2)O(2)) is a critically important signaling molecule. Endogenous H(2)O(2) mediates diverse physiological processes both intra- and intercellularly; and enzymatically generated H(2)O(2) is a widely used reporter molecule at biosensors that rely on enzymes to detect non-electroactive species. However, the development and application of electroanalytical methods for the direct detection of this molecule has been challenging because the electron transfer kinetics for the irreversible oxidation of H(2)O(2) are slow. We comparatively characterize the electrochemical oxidation of H(2)O(2) on bare and Nafion(®)-coated platinum and carbon-fiber microdisc electrodes using fast-scan cyclic voltammetry (FSCV). Using a waveform ranging from +0.2 to +1.3 V at 400 V s(-1), the electrocatalytic properties of the platinum surface were not readily apparent, and the carbon-fiber microelectrode demonstrated greater sensitivity and selectivity toward H(2)O(2). Nafion(®)-coating further enhanced detection on carbon electrodes. These results confirm that platinum electrodes, with or without Nafion(®), will not work acceptably with this approach, and confirm the value of carbon-fiber microelectrodes relative to more traditionally used platinum electrodes in the direct detection of rapid H(2)O(2) fluctuations using FSCV. PMID:21727955

Roberts, James G; Hamilton, Keri L; Sombers, Leslie A

2011-09-01

327

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.

328

Disposable electrochemical flow cells for catalytic adsorptive stripping voltammetry (CAdSV) at a bismuth film electrode (BiFE)  

PubMed Central

Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required. PMID:18351328

Gharib Naseri, Nahid; Economou, Anastasios; Goddard, Nicholas J.; Fielden, Peter R.

2008-01-01

329

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

PubMed

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

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

2012-07-15

330

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

331

Head-to-head comparisons of carbon fiber microelectrode coatings for sensitive and selective neurotransmitter detection by voltammetry.  

PubMed

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. Although Nafion has been suggested to resist fouling, both dip-coating and electrodeposition 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

2011-09-01

332

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

333

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.

334

Alternation for sublogarithmic space-bounded alternating pushdown automata  

Microsoft Academic Search

This paper investigates infinite hierarchies on alternation-depth and alternation-size of alternating pushdown automata (apda's) with sublogarithmic space. We first show that there is an infinite hierarchy on alternation-depth for apda's with sublogarithmic space. We next investigate a relationship between alternation-depth and alternation-size, and show that for sublogarithmic space-bounded apda's, alternation-depth k is better than alternation-size k for each k?3. We

Jianliang Xu; Tsunehiro Yoshinaga; Katsushi Inoue; Yue Wang; Akira Ito

2001-01-01

335

On an Alternative Cosmology  

E-print Network

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

A. Vankov

1998-11-10

336

Current Events  

NSDL National Science Digital Library

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

337

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

338

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

339

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

340

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.

Peter J. Tijrn

2000-06-30

341

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

1999-04-01

342

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

343

Pitch-based carbon foam electrodeposited with lead as positive current collectors for lead acid batteries  

Microsoft Academic Search

Lead electrodeposited carbon foam (LCF), whose substrate was made from pitch by a template method, was investigated as possible\\u000a positive current collectors for lead acid batteries. Scanning electron microscopy, cyclic voltammetry, and galvanostatic charge–discharge\\u000a tests were employed to characterize the effect of the proposed collector on the structure and electrochemical properties of\\u000a the positive active material (PAM). The LCF with

Li-Wen Ma; Bai-Zhen Chen; Ya Chen; Yan Yuan

2009-01-01

344

Influence of lead dioxide electrodes morphology on kinetics and current efficiency of oxygen-ozone evolution reactions  

Microsoft Academic Search

Influence of electrode morphology on electrochemical properties of lead dioxide electrodes (?-PbO2) for oxygen-ozone evolution reactions in acid medium was investigated using scanning electronic microscopy (SEM), cyclic\\u000a voltammetry (CV), polarization curves (PC), and determination of the current efficiency (?). Experimental findings revealed that application of high electrodeposition current densities furnishes more rough ?-PbO2 films. Surface characteristics were verified by SEM

Élen C. G. Rufino; Mario H. P. Santana; Luiz A. De Faria; Leonardo M. Da Silva

2010-01-01

345

Effect of the supporting electrolytes on voltammetry at liquid\\/liquid microinterfaces between water and nitrobenzene, 1,2-dichloroethane or 1,6-dichlorohexane  

Microsoft Academic Search

The transfers of the ions of tetraalkylammonium picrates (-methyl, -ethyl, -propyl, -butyl), from water (W) to nitrobenzene (NB), 1,2-dichloroethane (DCE) or 1,6-dichlorohexane (DCH), have been studied by voltammetry at liquid\\/liquid microinterfaces. Electrochemistry is possible in the absence of supporting electrolytes in both phases, even in the less dissociating solvents, DCE and DCH, when the concentration of the picrate is lower

Mickaël Rimboud; Kevin Charreteur; Vladimir Sladkov; Catherine Elleouet; François Quentel; Maurice L’Her

2009-01-01

346

Interaction of triflupromazine with distearoylphosphatidylglycerol films studied by surface pressure isotherms and cyclic voltammetry at a 1,2-dichloroethane\\/water interface  

Microsoft Academic Search

The effect of triflupromazine (TFP) on molecular packing of distearoylphosphatidylglycerol (DSPG), adsorbed at the water\\/1,2-dichloroethane interface, was investigated using cyclic voltammetry (CV) and surface pressure–molecular area isotherm. TFP partition in the DSPG monolayer changes the structure of the film. The results indicate that a fluidizing effect, dependent on the time and the drug concentration, takes place leading to an increase

Mónica V. Colqui Quiroga; Lorena M. A. Monzón; Lidia M. Yudi

2010-01-01

347

Redox kinetic measurements of glutathione at the mercury electrode by means of square-wave voltammetry. The role of copper, cadmium and zinc ions  

Microsoft Academic Search

The electrode reaction of glutathione (GSH) at the hanging mercury drop electrode is studied by means of square-wave voltammetry (SWV). At potentials more positive than ?0.350 V (vs. Ag\\/AgCl (3 mol\\/l KCl)) the oxidation of the mercury electrode in the presence of GSH leads to creation of a sparingly soluble mercury–GSH complex that deposits onto the electrode surface. Under cathodic

Mitko Mladenov; Valentin Mir?eski; Icko Gjorgoski; Blagoja Jordanoski

2004-01-01

348

Simultaneous determination of phenol isomers in binary mixtures by differential pulse voltammetry using carbon fibre electrode and neural network with pruning as a multivariate calibration tool  

Microsoft Academic Search

Neural networks with pruning were applied to model overlapped peaks obtained in differential pulse voltammetry (DPV) with modified carbon fibre electrode with TiO2 of binary mixtures of catechol and hydroquinone. The best condition for electrochemical response was obtained with 0.05moll?1 Tris–HCl buffer at pH 6.0 and T-800 sized carbon fibre electrode. Initially the voltammograms were processed using Fourier transform filter

Rosangela M de Carvalho; Cesar Mello; Lauro T Kubota

2000-01-01

349

Strategy for copper speciation in white wine by differential pulse anodic stripping voltammetry, potentiometry with an ion-selective electrode and kinetic photometric determination  

Microsoft Academic Search

Differential pulse anodic stripping voltammetry (DPASV), potentiometry with a copper ion-selective electrode and a kinetic\\u000a photometric method were used to determine copper species in white wines. The kinetic method is based on the catalytic effect\\u000a of labile copper(II) species on the oxidation of 3-hydroxybenzaldehyde azine by potassium peroxidisulfate in an ammonical\\u000a medium at room temperature. The total copper concentrations were

Claudia Wiese; Georg Schwedt

1997-01-01

350

Electrochemical Determination of Phenothrin in Agricultural Formulations, Vegetables, and Storage Bags of Wheat and Rice by Differential Pulse Adsorptive Stripping Voltammetry (DP-AdSV)  

Microsoft Academic Search

An electroanalytical method has been developed for the determination of the pesticide phenothrin by differential pulse adsorptive\\u000a stripping voltammetry on a hanging mercury drop electrode in universal buffer as supporting electrolyte. The best adsorption\\u000a conditions were found to be pH 6.0, an accumulation potential of ?0.6 V, and an accumulation time of 75 s. Effects of stirring\\u000a rate, scan rate, pulse amplitude, and

T. Thriveni; J. Rajesh Kumar; Jin-Young Lee; N. Y. Sreedhar

2009-01-01

351

Water–Gas Shift Reaction Over Aluminum Promoted Cu\\/CeO 2 Nanocatalysts Characterized by XRD, BET, TPR and Cyclic Voltammetry (CV)  

Microsoft Academic Search

A series of aluminum promoted Cu\\/CeO2 nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect\\u000a to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H2-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content\\u000a at first,

Lei Li; Yingying Zhan; Qi Zheng; Yuanhui Zheng; Xingyi Lin; Dalin Li; Junjiang Zhu

2007-01-01

352

Transport across poly( o-aminophenol) modified electrodes in contact with media containing redox active couples. A study using rotating disc electrode voltammetry  

Microsoft Academic Search

The electrochemistry of poly(o-aminophenol) modified electrodes in the presence of different electroactive solutes (Fe(CN)64?\\/3?, hydroquinone\\/benzoquinone (HQ\\/Q), Sn2+) able to diffuse through the polymer film was studied by rotating disc electrode voltammetry. Experimental results relating to the diffusion of these electroactive species through the polymer were interpreted on the basis of the membrane–diffusion theory for the rotating disc electrode. The electron

A Bonfranceschi; A Pérez Córdoba; S Keunchkarian; S Zapata; R Tucceri

1999-01-01

353

Deposition of thin TiO 2 layers on platinum by means of cyclic voltammetry of selected complex Ti(IV) media leading to anatase  

Microsoft Academic Search

Thin layers of anatase TiO2, up to 1?m, were produced on the surface of a platinum electrode by means of cycling voltammetry from the aqueous solutions of the peroxo-oxalate complexes and the oxalate complexes of titanium(IV). Mechanisms of TiO2 electrodeposition as well as different electrochemical reactions causing pH changes at the electrode were studied. The electroreduction processes of hydrogen peroxide

Pawe? Marek Dziewo?ski; Maria Grzeszczuk

2009-01-01

354

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

Microsoft Academic Search

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

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

1977-01-01

355

Complexation Study of Humic Acids Extracted from Forest and Sahara Soils with Zinc (II) and Cadmium (II) by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Conductimetric Methods  

Microsoft Academic Search

The complexation of heavy metals, present in their dissolved state at relevant trace levels, with new humic acids (HAs) isolated\\u000a from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils has been studied by differential pulse anodic stripping voltammetry\\u000a (DPASV) at a hanging mercury drop electrode and conductimetry methods. After extraction and purification, humic acids were\\u000a characterized by elemental analyses, atomic

Achour Terbouche; Safia Djebbar; Ouassini Benali-Baitich; Didier Hauchard

2011-01-01

356

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

357

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

358

Alternative Schools, Mainstream Education  

ERIC Educational Resources Information Center

Alternative education has its own history. Having emerged in the sixties as a response to the social crisis, its goal was primarily to fight increasing bureaucracy and the depersonalization of public education by giving students more freedom and minimal adult supervision. In the eighties, the understanding of "alternative education" narrowed to…

McKee, Jan; Conner, Evguenia

2007-01-01

359

Alternative Schools. Research Brief  

ERIC Educational Resources Information Center

Estimates suggest that there are more than 20,000 alternative schools in operation in the United States. The number of alternative schools as well as the number of students educated in these schools has increased significantly over recent years. Oftentimes these schools serve students who are not successful in the traditional school setting, and…

Muir, Mike

2004-01-01

360

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

361

Electrical properties of blood and its constitutents: Alternating current spectroscopy  

Microsoft Academic Search

The electrical properties of blood and its constituents are reviewed over the frequency range from less than 100 Hz to nearly 100 GHz. The conductivity and dielectric constant display strongly dispersive behavior with three distinct relaxation regions. Mechanism responsible for this behavior are stated and possible applications indicated.

H. P. Schwan

1983-01-01

362

Nonlinear alternating current responses of dipolar fluids J. P. Huang  

E-print Network

only. The harmonics of the Fröhlich field can be affected by the field frequency, temperature], and combining it with microfluidic devices [10] to analyze cells, proteins, and bacteria noninvasively and without chemically modifying the system. The nonlinear dielectric effect in dipolar fluids is not a result

Huang, Ji-Ping

363

High-speed ground transportation: some current and future alternatives  

SciTech Connect

High-speed ground transportation (HSGT), the value of time, and the social and technological considerations of inter-city transportation are discussed in this article. A particularly promising mode of high-speed ground transportation (MAGLEV) is discussed in some detail. An average speed for HSGT service, 400 kilometers per hour, seems to be attainable. In conclusion, the proposal for a hypersonic subway will be analyzed. 2 figures, 1 table.

Morita, T.

1984-01-01

364

High frequency alternating current chip nano calorimeter with laser heating  

SciTech Connect

Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3?-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (?1 ?m) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 ?m thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 ?m{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup ?3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

Shoifet, E.; Schick, C. [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany) [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany); Department “Life, Light and Matter”, Faculty of Interdisciplinary Research, University of Rostock, 18051 Rostock (Germany); Chua, Y. Z.; Huth, H. [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany)] [Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock (Germany)

2013-07-15

365

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

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

2014-10-01

366

Inhalation studies in laboratory animals--current concepts and alternatives.  

PubMed

Highly standardized and controlled inhalation studies are required for hazard identification to make test results reproducible and comparable and to fulfill general regulatory requirements for the registration of new drugs, pesticides, or chemicals. Despite significant efforts, the results of inhalation studies have to be analyzed judiciously due to the great number of variables. These variables may be related to technical issues or to the specific features of the animal model. Although inhalation exposure of animals mimics human exposure best, ie, error-prone route-to-route extrapolations are not necessary, not all results obtained under such very rigorous test conditions may necessarily also occur under real-life exposure conditions. Attempts are often made to duplicate as closely as possible these real-life exposure conditions of humans in appropriate bioassays. However, this in turn might affect established baseline data, rendering the interpretation of new findings difficult. In addition, specific use patterns, eg, of inhalation pharmaceuticals or pesticide-containing consumer products, may impose test agent-specific constraints that challenge traditional approaches. Moreover, specific modes of action of the substance under investigation, the evaluation of specific endpoints, or the clarification of equivocal findings in common rodent species may require exposure paradigms or the use of animal species not commonly used in inhalation toxicology. However, particularly in inhalation toxicology, the choice of animal models for inhalation toxicity testing is usually based on guideline requirements and practical considerations, such as exposure technology, expediency, and previous experience rather than validity for use in human beings. Larger animal species, apart from the welfare aspects, may require larger inhalation chambers to accommodate the animals, but for technical reasons and the difficulty of generating homogeneous exposure atmospheres in such inhalation chambers, this may jeopardize the outcome of the study. Some of the many variables and possible artifacts likely to occur in animal inhalation studies are addressed in this paper. PMID:11026610

Pauluhn, J; Mohr, U

2000-01-01

367

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

368

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....

369

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

370

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

PubMed Central

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

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

2011-01-01

371

Andropause: Current concepts.  

PubMed

Andropause or late-onset hypogonadism is a common disorder which increases in prevalence with advancing age. Diagnosis of late-onset of hypogonadism is based on presence of symptoms suggestive of testosterone deficiency - prominent among them are sexual symptoms like loss of libido, morning penile erection and erectile dysfunction; and demonstration of low testosterone levels. Adequate therapeutic modalities are currently available, but disparate results of clinical trial suggest further evaluation of complex interaction between androgen deficiency and ageing. Before initiating therapy benefits and risk should be discussed with patients and in case of poor response, alternative cause should be investigated. PMID:24910824

Singh, Parminder

2013-12-01

372

Andropause: Current concepts  

PubMed Central

Andropause or late-onset hypogonadism is a common disorder which increases in prevalence with advancing age. Diagnosis of late-onset of hypogonadism is based on presence of symptoms suggestive of testosterone deficiency - prominent among them are sexual symptoms like loss of libido, morning penile erection and erectile dysfunction; and demonstration of low testosterone levels. Adequate therapeutic modalities are currently available, but disparate results of clinical trial suggest further evaluation of complex interaction between androgen deficiency and ageing. Before initiating therapy benefits and risk should be discussed with patients and in case of poor response, alternative cause should be investigated. PMID:24910824

Singh, Parminder

2013-01-01

373

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

374

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 (2–7 Hz) and an amplitude of 50 nT. The electric conductivity and dielectric properties of the solution were investigated by voltammetric techniques in combination with non linear dielectric spectroscopy (NLDS), which allow the examination of the dielectric properties of macromolecules and molecular aggregates in water. The experiments target to elucidate the biological relevance of the observed EMF effect on molecular level. Results An ion cyclotron resonance (ICR) effect of glutamate previously reported by the Fesenko laboratory 1998 could be confirmed. Frequency resolution of the sample currents was possible by NLDS techniques. The spectrum peaks when the conditions for ion cyclotron resonance (ICR) of glutamate are matched. Furthermore, the NLDS spectra are different under ICR- and non-ICR conditions: NLDS measurements with rising control voltages from 100–1100 mV show different courses of the intensities of the low order harmonics, which could possibly indicate "intensity windows". Furthermore, the observed magnetic field effects are pH dependent with a narrow optimum around pH 2.85. Conclusions Data will be discussed in the context with recent published models for the interaction of weak EMF with biological matter including ICR. A medical and health relevant aspect of such sensitive effects might be given insofar, because electromagnetic conditions for it occur at many occasions in our electromagnetic all day environment, concerning ion involvement of different biochemical pathways. PMID:15571630

Pazur, Alexander

2004-01-01

375

Convection Currents  

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.

2008-06-19

376

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

377

Some Natural Pesticide Alternatives  

MedlinePLUS

... Pest Management web site. http://www.epa.gov/pesticides/factsheets/ipm.htm City of Tucson/ Pima County ... Grant Road Printed on recycled paper. SOME NATURAL PESTICIDE ALTERNATIVES For the safety of you, your family ...

378

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

379

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

380

Enhanced next generation alternator  

E-print Network

The power requirements of automotive alternators are increasing significantly due to the introduction of new vehicle electrical loads. Moreover, the possible transition to a 42 V electrical system is introducing new concerns ...

Lorilla, Leandro M. (Leandro Manalac), 1977-

2005-01-01

381

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

382

Alternatives to Nursing Homes  

MedlinePLUS

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

383

Alternatives to Blood Transfusion  

MedlinePLUS

... Find Local ACS Find Support & Treatment » Treatments and Side Effects » Treatment Types » Blood Product Donation and Transfusion » Alternatives to ... Basics Cancer Prevention & Detection Signs & Symptoms of Cancer Treatments & Side Effects Cancer Facts & Statistics News About Cancer Expert Voices ...

384

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.

Scapecchi, Judith

2012-07-31

385

Funerals: Alternatives and Arrangements.  

E-print Network

the traditional funeral section. Memorial Service and Cremation Cremation followed by a memorial service is one of the least expensive alternatives. A con tainer made of cardboard or fiberboard may be used in place of a casket; however, a casket similar... the traditional funeral section. Memorial Service and Cremation Cremation followed by a memorial service is one of the least expensive alternatives. A con tainer made of cardboard or fiberboard may be used in place of a casket; however, a casket similar...

McCormick, Linda J.; Kerbel, Claudia M.

1981-01-01

386

1-Butyl-3-methylimidazolium hexafluorophosphate ionic liquid as a new solvent for the determination of lead(II) and cadmium(II) by anodic stripping voltammetry after extraction of the iodide complexes.  

PubMed

The use of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM x PF(6)) as a solvent for the anodic stripping analysis of Pb(II) and Cd(II) after extraction of the iodide complexes has been investigated. This method is based on the extraction of the metal iodide complexes into BMIM x PF(6), followed by differential-pulse anodic stripping voltammetry with an in-situ plated bismuth film electrode onto an edge-plane type of pyrolytic graphite substrate. When tetra-n-propylammonium iodide at a concentration of 0.20 mol L(-1) was used as an extractant and a supporting electrolyte, the reduced lead and cadmium produced well-defined anodic peaks at -414 and -736 mV vs. Ag/AgCl, respectively. The peak currents for Pb(II) and Cd(II) were directly proportional to the initial metal concentration in the ranges of 0.01-0.50 microg mL(-1) and 0.05-1.0 microg mL(-1) under the optimized conditions. A detection limit (S/N = 3) of 0.001 microg mL(-1) Pb(II) was obtained with a volume ratio (V(aq)/V(BMIM x PF(6))) of 2.0 at 300 s deposition time. The relative standard deviation was 3.2% on replicate runs (n = 10) for the determinations of 0.20 microg mL(-1) Pb(II). PMID:18845902

Kamio, Akihiro; Nagaosa, Yukio

2008-10-01

387

Current titles  

SciTech Connect

This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Gretchen Hermes at (510) 486-5006 or address below for a User`s Guide. Copies of available papers can be ordered from: Theda Crawford National Center for Electron Microscopy, Lawrence Berkeley Laboratory, One Cyclotron Rd., MS72, Berkeley, California, USA 94720.

NONE

1995-07-01

388

Alternate policies for alternate energy sources  

SciTech Connect

Some ''alternates within alternates'' are studied and possible improvement of our energy policies are explored. The viability of a hydrogen fuel economy is reviewed. Methanol, ethanol or ammonia versus hydrogen is one area of interest. Others include liquid hydrogen versus jet fuels, the use of geothermal, solar, wind or water energy for production of hydrogen gas versus development of deep earth supplies of natural gas is another. Energy enhancement as opposed to energy conservation is investigated with regard to polar climate and what might be done to improve natural energy balances, particularly in the northern hemisphere. Pumping Arctic Ocean water out into the Pacific Ocean via the Bering Strait would be an energy debit as opposed to energy gains such as biomass conversion of future plant growth throughout the Siberian and Canadian tundra regions and presently very arid desert regions, improved access to northern region fuel, metal ore and mineral resources, year-round shipping and fishing fleet operations in the Arctic Ocean and development of the tremendous Greenland hydro-electric power potential.

Hall, F.F.

1985-09-01

389

Functional Fast Scan Cyclic Voltammetry Assay to Characterize Dopamine D2 and D3 Autoreceptors in the Mouse Striatum  

PubMed Central

Dopamine D2 and D3 autoreceptors are located on presynaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate putamen and nucleus accumbens core and shell. The dopamine D2 agonists (?)-quinpirole hydrochloride and 5,6,7,8-tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate putamen and nucleus accumbens (core and shell) on the basis of their EC50 values and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (±)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in the caudate putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.1 ?M lowered the uptake rate in caudate putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the preagonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonists as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum. PMID:20567609

2010-01-01

390

Ionization tube simmer current circuit  

DOEpatents

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current. 6 figures.

Steinkraus, R.F. Jr.

1994-12-13

391

Ionization tube simmer current circuit  

DOEpatents

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Steinkraus, Jr., Robert F. (Livermore, CA)

1994-01-01

392

Load Analysis of Nonlinear Homopolar Inductor Alternators  

Microsoft Academic Search

For a more accurate load analysis of the Homopolar Inductor Alternator (HIA), a magnetic vector potential analysis must be used which considers the nonlinearities of the iron and the actual current density fields. A nonlinear quasi-Poissonian partial differential equation, subject to the appropriate boundary conditions, is defined to solve for the vector potential in the middle cross section of the

K. E. Schenk; E. F. Fuchs; F. C. Trutt

1973-01-01

393

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

PubMed

Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd(2+), Pb(2+), Cu(2+) and Hg(2+) was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186nM, 0.247nM, 0.169nM and 0.375nM for Cd(2+), Pb(2+), Cu(2+) and Hg(2+)) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb(2+) increased in the presence of certain concentrations of other metal ions, such as Cd(2+), Cu(2+) and Hg(2+) both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment. PMID:23870406

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

2013-08-01

394

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.

395

Simultaneous determination of trace aluminum (III), copper (II) and cadmium (II) in water samples by square-wave adsorptive cathodic stripping voltammetry in the presence of oxine  

Microsoft Academic Search

A validated adsorptive cathodic stripping voltammetry method is described for simultaneous determination of Al(III), Cu(II)\\u000a and Cd(II) in water samples. In acetate buffer (pH 5) containing 10 ?M oxine, these metal ions were determined as oxine complexes\\u000a following adsorptive accumulation onto the HMDE at ?0.05 V versus Ag\\/AgCl\\/KCls. The best signal to noise ratio was obtained using a square wave of scan increment

A. M. Beltagi; M. M. Ghoneim

2009-01-01

396

pH Dependent redox behaviour of Alizarin Red S (1,2-dihydroxy-9,10-anthraquinone-3-sulfonate) – Cyclic voltammetry in presence of dispersed vat dye  

Microsoft Academic Search

The redox chemistry of Alizarin Red S (1,2-dihydroxy-9,10-anthraquinone-3-sulfonate) was studied as function of pH by photometry, potentiometric titration and cyclic voltammetry. Dependent upon solution pH three species of the oxidised form of Alizarin Red S are present. Electrochemical reduction of the anthraquinone group leads to 1,2,9,10-tetrahydroxy-anthracene-3-sulfonate. The four phenolic hydroxyl groups dissociate with increasing pH value, above pH 12 a

Aurora Turcanu; Thomas Bechtold

2011-01-01

397

Alternative Energy Sources  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education program, this module introduces students to the most common alternative energy sources that they may encounter in electronic work including fuel cells, solar power, and ultracapacitors. The module includes course materials covering each of these alternative energy sources along with three "Knowledge Probes" which provide an opportunity for students to master the objectives of the module. By clicking on "Learning Resources" at the top of the page, users will also find supplemental learning activities and additional resources for practice and research. The module also includes a glossary of terms and a notebook function.

2008-09-09

398

Alternative Fuel Vehicles  

SciTech Connect

This Federal Technology Alert on alternative fuel vehicles (AFVs), prepared for the U.S. Department of Energy's Federal Energy Management Program (FEMP), is intended for fleet managers in government agencies and other government officials who need to use more alternative fuels and AFVs in their fleets of cars and trucks. This publication describes the government's plans and progress in meeting goals for the use of AFVs, which are stated in the Energy Policy Act and various Executive Orders. It describes the types of AFVs available, lists actual and potential federal uses, makes some general recommendations, and presents field experiences to date.

Not Available

2003-09-01

399

Anodic stripping of zinc deposits for aqueous batteries: effects of anions, additives, current densities, and plating modes  

Microsoft Academic Search

Effects of anions of Zn salts and additives in the plating baths, current densities and modes of electroplating on the anodic stripping behavior of Zn deposits were investigated for the possible application to Zn-based batteries. The anodic stripping behavior was examined using linear sweep voltammetry (LSV) in a 0.5M Na2SO4 solution containing 0.5M ethylene-diamine-tetraacetic acid (EDTA). Effects of the above

Chi-Chang Hu; Chia-Yuan Chang

2004-01-01

400

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

401

Alternative Fuels in Transportation  

Microsoft Academic Search

The realization of dwindling fossil fuel supplies and their adverse environmental impacts has accelerated research and development activities in the domain of renewable energy sources and technologies. Global energy demand is expected to rise during the next few decades, and the majority of today's energy is based on fossil fuels. Alternative energy sources and technologies can play a vital role

Denis Kouroussis; Shahram Karimi

2006-01-01

402

ALTERNATIVE SEWER STUDIES  

EPA Science Inventory

An evaluation of design and operational aspects for two popular alternative sewering techniques, i.e., pressure and small-diameter gravity sewers, was performed. The results provided insights useful to designers of these systems with regard to sulfide concentrations in these sewe...

403

Formative Evaluation Alternatives.  

ERIC Educational Resources Information Center

Discussion of formative evaluation highlights alternative formative evaluation methods and tools and explains their advantages, disadvantages, and applicable contexts. Methods described include two-on-one evaluation; think-aloud protocols; computer interviewing; self-evaluation; panel reviews; evaluation meetings; computer journals and networks;…

Tessmer, Martin

1994-01-01

404

Recent Problems Alternative Routes  

E-print Network

#12; History Recent Problems Alternative Routes #12; Built in 1936 Length: 8.4 miles Made up Completion date slotted for late 2013 #12; One mile stretch linking Interstate 80 to Bay Bridge Needed Span 1.2 miles Five Lanes, 10 foot shoulders to keep traffic moving #12; Will connect Interstate 80

Nagurney, Anna

405

Canadian alternative fuels activities  

Microsoft Academic Search

Canada, along with Italy and New Zealand, promotes domestic natural gas as a motor vehicle fuel. Government grants and gas utility loan programs encourage conversion of commercial vehicles to compressed natural gas (CNG) and the establishment of a network of public access refueling stations, where business is good. In addition to buses, alternative fuels activities include a 26-car ferry, locomotives,

McCoy

2009-01-01

406

ALTERNATIVE FUELS RESEARCH STRATEGY  

EPA Science Inventory

The purpose of this document was to lay a foundation for developing the scientific information needed to compare the benefits and risks of various motor vehicle fuels, especially alternative and reformulated fuels in relation to conventional gasoline and diesel fuels. Among the f...

407

Augmentative & Alternative Communication  

ERIC Educational Resources Information Center

There is no definitive recipe for augmentative and alternative communication (AAC) success, but its universal ingredients can be found at home. The main ones are: (1) Understanding that all children need to express themselves, however outgoing or shy they may be; (2) Willingness to embrace the technology that may help your child regardless of your…

Murphy, Patti

2007-01-01

408

The Alternate Atomic Model  

NASA Astrophysics Data System (ADS)

An alternate atomic model posits concentric electron and nucleon fields spinning together about an empty center. It is alternative to the generally accepted planetary system in which electron point particles orbit about a center clump of nucleon point particles. Introduced in 1992 as an alternative to the standard model of the nucleus it applies scientific space-time knowledge unknown when the standard model was conceived. Originally advanced in the spirit of alternative equivalence it evolved to model the entire atomic structure plus many features of space-time. Structural definitions assume space-time properties of: unidirectional expansion, special relativity, electrical field, magnetic field, spin field, gravity field, and space-time surface effect. Field effects are associated with Faraday lines of field force. Model properties feature symmetry and complementarily. Mass structures of the electron, proton,neutron, and protium atom plus the atomic and nuclear constituencies of all elements are developed. In addition the nuclear strong force is defined, the magnetic anomaly explained, etc. Model logic constructs the neutron as the complement of the hydrogen (protium) atom.

Ragland, Evan

2008-03-01

409

Alternative Work Schedules: Definitions  

ERIC Educational Resources Information Center

The term "alternative work schedules" encompasses any variation of the requirement that all permanent employees in an organization or one shift of employees adhere to the same five-day, seven-to-eight-hour schedule. This article defines staggered hours, flexible working hours (flexitour and gliding time), compressed work week, the task system, and…

Journal of the College and University Personnel Association, 1977

1977-01-01

410

Environment and Alternative Development.  

ERIC Educational Resources Information Center

Stressing the global dimension to the adversary relationship between economic development and environmental conservation, this monograph examines the philosophical, historical, cultural, and ethnic underpinnings of modern science and technology. In addition, the monograph spells out policy implications of an alternative concept of development and…

Kothari, Rajni

411

Expanding Alternative Delivery Systems.  

ERIC Educational Resources Information Center

Alternative educational delivery systems that might be useful to community colleges are considered. The following categories of delivery systems are covered: broadcast delivery systems; copy delivery systems, print delivery systems, computer delivery systems, telephone delivery systems, and satellites. Among the applications for broadcast…

Baltzer, Jan A.

412

Alternative Break Service Trips  

ERIC Educational Resources Information Center

Even as educators understand how their millennial students learn in such different ways than previous generations (watching how-to videos downloaded from YouTube or engaging in experiential learning adventures), colleges still rely heavily on in-the-classroom learning. The author can't offer an alternative to this classroom format, but she…

DuPre, Carrie

2010-01-01

413

The Conservation Alternative  

E-print Network

of this alternative going all the way back to before the oil embargo. Most vivid, perhaps, in our memories is an early major study of our national energy problem; the Ford Foundation's "A Time To Choose" and its controversial proposal of zero energy growth as a...

Allaire, W. F.

1979-01-01

414

Alternative energy sources III  

Microsoft Academic Search

This book is based upon the 3rd Clean Energy Research Institute International Conference on Alternative Energy Sources. It provides coverage on the latest advances and developments in the scientific and technical search for energy sources with reduced health and environmental hazards. Topics covered in this book include solar energy; ocean thermal energy; wind energy; geothermal power; hydropower; nuclear breeders and

Veziroglu

1983-01-01

415

Alternative energy sources VII  

Microsoft Academic Search

This book presents the papers given at a conference on the economic aspects of renewable energy sources. Topics considered at the conference included socio-economic factors affecting energy source development, an economic evaluation of solar thermal energy systems, energy planning and management, alternative energy in developing countries, energy conservation, environmental policy, and energy education.

Veziroglu

1985-01-01

416

Alternative Schools: New Findings.  

ERIC Educational Resources Information Center

Identifies elements of effective alternative high schools for New York City's truants, dropouts, and potential dropouts, including: (1) well-defined student populations; (2) strong academic leadership; (3) increased teacher participation in management; (4) academic innovation; (5) clear standards for conduct; and (6) small school size. Presents…

Foley, Eileen

1983-01-01

417

Alternative Fuels in Transportation  

ERIC Educational Resources Information Center

The realization of dwindling fossil fuel supplies and their adverse environmental impacts has accelerated research and development activities in the domain of renewable energy sources and technologies. Global energy demand is expected to rise during the next few decades, and the majority of today's energy is based on fossil fuels. Alternative

Kouroussis, Denis; Karimi, Shahram

2006-01-01

418

Alternative Energy Busing  

ERIC Educational Resources Information Center

In recent years, school districts have converted portions of their bus fleets to cleaner-burning, sometimes cheaper, alternative fossil fuels, such as compressed natural gas or propane. Others have adopted biodiesel, which combines regular diesel with fuel derived from organic sources, usually vegetable oils or animal fats. The number of biodiesel…

LaFee, Scott

2012-01-01

419

The SOLAR Alternative.  

ERIC Educational Resources Information Center

Only when the sun's energy can be captured at a comparable or lower opportunity cost than that of competing sources will solar energy systems become viable alternatives. Economic issues of solar energy are discussed. The legitimate role of government is also examined. (RM)

Warren, E. H., Jr.; Walton, A. L.

1984-01-01

420

Alternatives in solar energy  

NASA Technical Reports Server (NTRS)

Although solar energy has the potential of providing a significant source of clean and renewable energy for a variety of applications, it is expected to penetrate the nation's energy economy very slowly. The alternative solar energy technologies which employ direct collection and conversion of solar radiation as briefly described.

Schueler, D. G.

1978-01-01

421

Alternative non-CFC mobile air conditioning  

SciTech Connect

Concern about the destruction of the global environment by chlorofluorocarbon (CFC) fluids has become an impetus in the search for alternative, non-CFC refrigerants and cooling methods for mobile air conditioning (MAC). While some alternative refrigerants have been identified, they are not considered a lasting solution because of their high global warming potential, which could result in their eventual phaseout. In view of this dilemma, environmentally acceptable alternative cooling methods have become important. This report, therefore, is aimed mainly at the study of alternative automotive cooling methodologies, although it briefly discusses the current status of alternative refrigerants. The alternative MACs can be divided into work-actuated and heat-actuated systems. Work-actuated systems include conventional MAC, reversed Brayton air cycle, rotary vane compressor air cycle, Stirling cycle, thermoelectric (TE) cooling, etc. Heat-actuated MACs include metal hydride cooling, adsorption cooling, ejector cooling, absorption cycle, etc. While we are better experienced with some work-actuated cycle systems, heat-actuated cycle systems have a high potential for energy savings with possible waste heat applications. In this study, each altemative cooling method is discussed for its advantages and its limits.

Mei, V.C.; Chen, F.C.; Kyle, D.M.

1992-09-01

422

Surface Tension of Alternative Refrigerants  

NASA Astrophysics Data System (ADS)

In this paper, current researches for surface tension of alternative refrigerants are reviewed. The refrigerants of interests are seven HCFCs: namely R-123, R-123a, R-124, R -141b, R-142b, R-225ca and R-225cb, and six HFCs; namely R-23, R-32, R-125, R-134, R- 134a and R-152a. The available data and correlations of experimental surface tension for HCFCs and HFCs are summarized. Most of experimental data were obtained by using capillary rise method. With regard to R-123 and R-134a, new surface tension correlations have been developed and are accepted as the international standard. For other refrigerants, the author selected one correlation for each refrigerant as a recommended correlation. In addition, graphical estimation method of surface tension for binary mixture is introduced. In particular, more research is expected on the surface tension of mixture in the future.

Okada, Masaaki

423

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

424

Coupling efficiency in piezoelectric actuators with direct current and alternating current excitation  

NASA Astrophysics Data System (ADS)

This paper gives a theoretically rigorous description of energy coupling in piezoelectric actuators considering both DC and AC excitations. It is shown that these different excitations schemes give different actuator efficiencies, in general, but that DC and AC efficiencies converge at low frequencies given a suitable definition of efficiency in each case. This result is plausable but non-obvious: the DC and AC calculations are different since the former is transient and the latter based on a steady state excitation. In the low frequency analytical results presented here, the system efficiency can be expressed solely in terms of the piezoelectric's coupling factor and a factor which relates to the load the piezoelectric is attached to. However, we show that this simple formalism breaks down at high frequencies and then efficiency depends on all material and geometric properties separately. In that case, the calculated efficiency can differ significantly from what may be expected from a simpler DC analysis. At high frequencies, we therefore recommend the use of the high frequency efficiency formulas presented here. We also give a comparison between the theory and experimental results showing good agreement with no fitting parameters used. Hence, advice is given on how to optimise efficiency and absolute energy coupled. In this paper, we do not make the assumption that strain or electric field is spatially constant: piezoelectrics will, in fact, show both spatial and temporal variations of stress, strain, and electric fields—and these are accounted for correctly. In fact, an analytical calculation, in both the DC and AC regimes, can be made without making such assumptions. We show the reasons why this is the case.

Blackburn, J. F.; Cain, M. G.

2013-05-01

425

Note: Circuit design for direct current and alternating current electrochemical etching of scanning probe microscopy tips  

NASA Astrophysics Data System (ADS)

We present control circuits designed for electrochemically etching, reproducibly sharp STM probes. The design uses an Arduino UNO microcontroller to allow for both ac and dc operation, as well as a comparator driven shut-off that allows for etching to be stopped in 0.5-1 ?s. The Arduino allows the instrument to be customized to suit a wide variety of potential applications without significant changes to hardware. Data is presented for coarse chemical etching of 80:20 platinum-iridium, tungsten, and nickel tips.

Jobbins, Matthew M.; Raigoza, Annette F.; Kandel, S. Alex

2012-03-01

426

Note: Circuit design for direct current and alternating current electrochemical etching of scanning probe microscopy tips.  

PubMed

We present control circuits designed for electrochemically etching, reproducibly sharp STM probes. The design uses an Arduino UNO microcontroller to allow for both ac and dc operation, as well as a comparator driven shut-off that allows for etching to be stopped in 0.5-1 ?s. The Arduino allows the instrument to be customized to suit a wide variety of potential applications without significant changes to hardware. Data is presented for coarse chemical etching of 80:20 platinum-iridium, tungsten, and nickel tips. PMID:22462971

Jobbins, Matthew M; Raigoza, Annette F; Kandel, S Alex

2012-03-01

427

Virginia Power's alternative energy study  

Microsoft Academic Search

In June 1981, the management of Virginia Electric and Power Company (now Virginia Power, or the Power Company) appointed a committee to formulate a study of conventional and alternative energy sources to meet future growth in electric power demand in a least-cost manner. This Committee on Conventional and Alternative Energy Sources recommended several energy alternatives for evaluation. The alternatives for

1986-01-01

428

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

429

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

430

Supports and Enhancements Designed for Alternative School Programming  

ERIC Educational Resources Information Center

In this informational survey, the author briefly explores the needs of professional staff and administrators who serve students in alternative educational settings and special education and provides a listing of helpful Internet resources. Initially, the author provides general information concerning the current state of alternative education…

Menendez, Anthony L.

2007-01-01

431

Simultaneous determination of mycophenolate mofetil and its active metabolite, mycophenolic acid, by differential pulse voltammetry using multi-walled carbon nanotubes modified glassy carbon electrode.  

PubMed

A highly sensitive electrochemical sensor for the simultaneous determination of mycophenolate mofetil (MPM) and mycophenolic acid (MPA) was fabricated by multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE). The electrochemical behavior of these two drugs was studied at the modified electrode using cyclic voltammetry and adsorptive differential pulse voltammetry. MPM and MPA were oxidized at the GCE during an irreversible process. DPV analysis showed two oxidation peaks at 0.87V and 1.1V vs. Ag/AgCl for MPM and an oxidation peak at 0.87V vs. Ag/AgCl for MPA in phosphate buffer solution of pH5.0. The MWCNTs/GCE displayed excellent electrochemical activities toward oxidation of MPM and MPA relative to the bare GCE. The experimental design algorithm was used for optimization of DPV parameters. The electrode represents linear responses in the range 5.0×10(-6) to 1.6×10(-4)molL(-1) and 2.5×10(-6)molL(-1) to 6.0×10(-5)molL(-1) for MPM and MPA, respectively. The detection limit was found to be 9.0×10(-7)molL(-1) and 4.0×10(-7)molL(-1) for MPM and MPA, respectively. The modified electrode showed a good sensitivity and stability. It was successfully applied to the simultaneous determination of MPM and MPA in plasma and urine samples. PMID:25063089

Madrakian, Tayyebeh; Soleimani, Mohammad; Afkhami, Abbas

2014-09-01

432

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

PubMed Central

This work reports on the continuing development of a lab-on-a-chip electrochemical sensor for determination of zinc in blood serum using square wave anodic stripping voltammetry. The microscale sensor consists of a three electrode system, including an environmentally friendly bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor demonstrates a linear response in 0.1 M acetate buffer at pH 6 for zinc concentrations in the 1–30 ?M range. By optimizing bismuth film deposition and better control of the fabrication process, repeatability of the sensor was improved, reducing variability from 42% to <2%. Through optimization of electrolyte and stripping voltammetry parameters, limit of detection was greatly improved to 60 nM. The optimized sensor was also able to measure zinc in the extracted blood serum. Ultimately, with integrated sample preparation, the sensor will permit rapid (min) measurements of zinc from a sub-mL sample (a few drops of blood) for clinical applications. PMID:24729629

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

2014-01-01

433

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

434

Platinum and rhodium associated with the leaves of Nerium oleander L.; analytical method using voltammetry; assessment of air quality in the Palermo (Italy) area.  

PubMed

A rapid accumulation of the catalytic active noble metals in the environmental and biological matrices was observed and concern arose about potential environmental and health risks. The development of reliable analytic methods to measure very low Pt and Rh concentrations is required. The main purpose of this work was to develop a reliable method for the determination of Pt and Rh in environmental matrices because of inherent difficulties in using conventional techniques used, in particular, the ICP-OES technique. A direct determination of Pt using ICP-MS, for instance, is problematic, due to interfering signals. In this work, differential pulse voltammetry (DPV/a) and adsorptive stripping voltammetry (AdSV) were used for the determination of Pt and Rh in Nerium oleander leaves. Pt and Rh concentrations were found in the ranges 0.33-25 and 0.40-4.6 microg/kg d.w., respectively. We carried out linear regression analysis between total PAH concentrations in leaves of oleander and of Quercus ilex measured in previous researches and the data obtained in this work. The high correlation coefficients were obtained; which demonstrates that oleander leaves can be used to establish the presence and the distribution of pollutants in a chosen area. PMID:19846253

Orecchio, Santino; Amorello, Diana

2010-02-15

435

Alternatives to animal experimentation: The regulatory background  

SciTech Connect

The framework, in which alternatives to animal experiments can be developed, standardized, respectively formally validated, has to be seen in a global context. The ever increasing demand of testing for hazard and risk assessment in health and environment, exemplified by the EU REACH program, subsequently triggers laboratory animal testing. This holds especially true, if no valid alternative methods agreed to by the regulatory authorities and the scientific community are available. At least for regulatory toxicity testing, the global frame and network are given by institutions such as OECD, ICH, and alike. However, due to the necessity of global consent of states, organizations, and stakeholders, the time gap between availability of a novel alternative test method and its final acceptance by authorities and implementation thereafter is widening. The lack of new technologies or opportunities for alternative method application such as, for example, the broad use of transgenic animals for refinement of existing tests, adds to the problem. The bare existence of certain in vivo tests increases also the gap between public demands for testing versus availability of alternative tests. Industries operating on a worldwide basis support the alternative test development in their respective area of research and operational business. However, a more coordinating approach such as that of the ecopa-organization (European Consensus Platform on Alternatives) is needed to exploit the existing possibilities within the current regulatory framework. This will speed up the process of acceptance and challenge the political worldto feel responsible for the sequels of their demanding more testing, that is, by funding alternative method development in academia and industry.

Garthoff, Bernward [Bayer CropScience AG, Alfred-Nobel-Strasse 50, D 40789 Monheim (Germany)]. E-mail: bernward.garthoff@bayercropscience.com

2005-09-01

436

78 FR 68076 - Request for Information on Alternative Skin Sensitization Test Methods and Testing Strategies and...  

Federal Register 2010, 2011, 2012, 2013

...to replace the use of animals in skin sensitization testing for hazard and potency...Laboratory for Alternatives to Animal Testing (EURL ECVAM), and by...Alternative (non- animal) methods for cosmetics testing: current status and...

2013-11-13

437

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,

438

Finding alternatives to antibiotics.  

PubMed

The spread of antibiotic-resistant pathogens requires new treatments. As the rate of development of new antibiotics has severely declined, alternatives to antibiotics must be considered in both animal agriculture and human medicine. Products for disease prevention are different from those for disease treatment, and examples of both are discussed here. For example, modulating the gut microbial community, either through feed additives or fecal transplantation, could be a promising way to prevent certain diseases; for disease treatment, non-antibiotic approaches include phage therapy, phage lysins, bacteriocins, and predatory bacteria. Interestingly, several of these methods augment antibiotic efficacy by improving bacterial killing and decreasing antibiotic resistance selection. Because bacteria can ultimately evolve resistance to almost any therapeutic agent, it is important to continue to use both antibiotics and their alternatives judiciously. PMID:24953233

Allen, Heather K; Trachsel, Julian; Looft, Torey; Casey, Thomas A

2014-09-01

439

Alternative Work Arrangements  

Microsoft Academic Search

In recent years there has been increased employer use of alternative forms of employment contracts to supplement more traditional\\u000a employment arrangements. Using data from Swedish health-care workers (N=711; 86% women), this study compares full-time and\\u000a part-time permanent employees with contingent workers and sets out to answer the following questions: Do workers on non-traditional\\u000a work schedules experience more or less (1)

Magnus Sverke; Daniel G. Gallagher; Johnny Hellgren

440

Alternative Energy Lessons  

NSDL National Science Digital Library

This website has 23 lesson plans in alternative energy developed by the New York State Energy Research and Development Authority. The lesson plans include the following topics: the photoelectric effect, efficiency of energy conversion, the photoelectric effect in photocells, chemical consequences of burning fossil fuels, The Geology of Oil and Coal, environmental pollution, Where Do Plants Get Their Food?, considerations in heating a house, and many more valuable and useful classroom lessons.

2008-11-12

441

Biodiesel: Current Trends and Properties  

Microsoft Academic Search

Biodiesel, an alternative to petroleum-derived diesel fuel, is defined as the mono-alkyl esters of vegetable oils and animal\\u000a fats. Several current issues affecting biodiesel that are briefly discussed include the role of new feedstocks in meeting\\u000a increased demand for biodiesel and circumventing the food versus fuel issue, biodiesel production, as well as fuel properties\\u000a and their improvement.

Gerhard Knothe

2010-01-01

442

Noninvasive valve monitor using alternating electromagnetic field  

DOEpatents

One or more electrical coils are carefully located on the outside of a valve body. An alternating current passing through the coil(s) results in an alternating electromagnetic field being transmitted into the valve body and valve internals. The electromagnetic field varies in intensity and polarity in the valve. As the position of a valve internal part is changed, the electromagnetic field throughout the valve body and its internals is altered. A passive receiver coil carefully located on the outside of the valve body detects the intensity of the electromagnetic field at that location as an induced electrical voltage in the coil. With the change in position of the valve internal part, there is a corresponding change in the induced voltage as a result of the alteration in the alternating electromagnetic field at that location. Changes in the voltage provide an indication of the position and motion of valve internals.

Eissenberg, D.M.; Haynes, H.D.; Casada, D.A.

1993-03-16

443

Noninvasive valve monitor using alternating electromagnetic field  

DOEpatents

One or more electrical coils are carefully located on the outside of a valve body. An alternating current passing through the coil(s) results in an alternating electromagnetic field being transmitted into the valve body and valve internals. The electromagnetic field varies in intensity and polarity in the valve. As the position of a valve internal part is changed, the electromagnetic field throughout the valve body and its internals is altered. A passive receiver coil carefully located on the outside of the valve body detects the intensity of the electromagnetic field at that location as an induced electrical voltage in the coil. With the change in position of the valve internal part, there is a corresponding change in the induced voltage as a result of the alteration in the alternating electromagnetic field at that location. Changes in the voltage provide an indication of the position and motion of valve internals.

Eissenberg, David M. (Oak Ridge, TN); Haynes, Howard D. (Knoxville, TN); Casada, Donald A. (Knoxville, TN)

1993-01-01

444

Alternative futures lesson  

NSDL National Science Digital Library

Alternative futures studies are a valuable yet resource-intensive way in which environmental scientists try to conduct informed debates about policies for specific geographic regions. These studies require modeling what the future would look like if different stakeholder groups had their way. The modeling is carried out by applying historical trend data to future projections that are rooted in the preferences of the different groups. Alternative future studies can be controversial due to the limitations of modeling and to the extent to which the models represent fully the different possible scenarios. Yet, they can be especially valuable for decision making about which areas in the region would be most appropriate and most acceptable for the applications of different policies such as development and restoration. Through a series of hands-on classroom activities that are the culmination of a variety of field trips, case studies, and analyses of GIS data about river systems and river restoration options, the students build deep understanding about what alternative futures studies entail and what are the applications of such studies to specific rivers in the Puget Sound area.

Zalles, Dan

445

Alternative: Manage Drought  

Microsoft Academic Search

About 75 percent of the demand in the Jemez y Sangre region is currently met with surface water supplies, which are highly variable. When drought conditions occur, the available surface water is not sufficient to meet all of the current demands. As population and water use increase in the future, even greater discrepancies between supplies and demands are expected. Localities

Daniel B. Stephens

446

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

PubMed Central

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

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

2010-01-01

447

Branch-and-bound Formulations alternatives Sujet 4 : Formulations alternatives  

E-print Network

: Planification de production et gestion des op´erations Andrew J. Miller Derni`ere mise `a jour: November 14-and-bound Formulations alternatives Application Ajax #12;Branch-and-bound Formulations alternatives Autres applications

Miller, Andrew J.

448

Alternative Anode Reaction for Copper Electrowinning  

SciTech Connect

This report describes a project funded by the Department of Energy, with additional funding from Bechtel National, to develop a copper electrowinning process with lower costs and lower emissions than the current process. This new process also includes more energy efficient production by using catalytic-surfaced anodes and a different electrochemical couple in the electrolyte, providing an alternative oxidation reaction that requires up to 50% less energy than is currently required to electrowin the same quantity of copper. This alternative anode reaction, which oxidizes ferric ions to ferrous, with subsequent reduction back to ferric using sulfur dioxide, was demonstrated to be technically and operationally feasible. However, pure sulfur dioxide was determined to be prohibitively expensive and use of a sulfur burner, producing 12% SO{sub 2}, was deemed a viable alternative. This alternate, sulfur-burning process requires a sulfur burner, waste heat boiler, quench tower, and reaction towers. The electrolyte containing absorbed SO{sub 2} passes through activated carbon to regenerate the ferrous ion. Because this reaction produces sulfuric acid, excess acid removal by ion exchange is necessary and produces a low concentration acid suitable for leaching oxide copper minerals. If sulfide minerals are to be leached or the acid unneeded on site, hydrogen was demonstrated to be a potential reductant. Preliminary economics indicate that the process would only be viable if significant credits could be realized for electrical power produced by the sulfur burner and for acid if used for leaching of oxidized copper minerals on site.

Not Available

2005-07-01

449

A search for space energy alternatives  

NASA Technical Reports Server (NTRS)

This paper takes a look at a number of schemes for converting radiant energy in space to useful energy for man. These schemes are possible alternatives to the currently most studied solar power satellite concept. Possible primary collection and conversion devices discussed include the space particle flux devices, solar windmills, photovoltaic devices, photochemical cells, photoemissive converters, heat engines, dielectric energy conversion, electrostatic generators, plasma solar collectors, and thermionic schemes. Transmission devices reviewed include lasers and masers.

Gilbreath, W. P.; Billman, K. W.

1978-01-01

450

Alternate Rules of Association  

NASA Astrophysics Data System (ADS)

The Weyl correspondence rule (107) is not unique: there are a host of alternate equivalent association rules which specify corresponding representations. All these representations with equivalent formalisms are typified by characteristic quasi-distribution functions and ?-products, all systematically inter-convertible among themselves. They have been surveyed comparatively and organized in [Lee95, BJ84], on the basis of seminal classification work by Cohen [Coh66, Coh76]. Like different coordinate transformations, they may be favored by virtue of their different characteristic properties in varying applications...

Curtright, Thomas L.; Fairlie, David B.; Zachos, Cosmas K.

2014-11-01

451

Alternatives to Seesaw  

SciTech Connect

The seesaw mechanism is attractive not only because it"explains'' small neutrino mass, but also because of its packaging with the SUSY-GUT, leptogenesis, Dark Matter, and electroweak symmetry breaking. However, this package has the flavor, CP, and gravitino problems. I discuss two alternatives to the seesaw mechanism. In one of them, the anomaly-mediated supersymmetry breaking solves these problems, while predicts naturally light Dirac neutrinos. In the other, the light Majorana neutrinos arise from supersymmetry breaking with right-handed neutrinos below TeV, and the Dark Matter and collider phenomenology are significantly different.

Murayama, Hitoshi

2004-10-10

452

Potential alternate life biochemistries  

NASA Astrophysics Data System (ADS)

While life on Earth continues to be discovered in unlikely environments, the underlying biochemistry is all very similar, based on the element carbon, and requiring liquid water. We consider alternate biochemistries based on elements other than carbon, including other group IVA elements, such as silicon and germanium, and solvents other than water. Terminal electron acceptors other than oxygen are also discussed. A fundamental issue is raised related to the detection of, and even the definition of life, whether it is carbon or non-carbon based. An extreme example of this issue would be in consideration of speculative life based on electrically charged dusty plasmas, which may have no physical body.

Konesky, Gregory

2013-09-01

453

Thermal Modeling of Lundell Alternators  

E-print Network

Thermal analysis of Lundell alternators used in automobiles is presented. An analytical thermal model for Lundell alternators is proposed, and procedures for acquiring the model parameters are elucidated. Based on the ...

Tang, Sai Chun

454

Segmental alternations and metrical theory  

E-print Network

This dissertation focuses on phonological alternations that are influenced or constrained by word-internal prosody, i.e. prominence and foot structure, and what these alternations can tell us about metrical theory. Detailed ...

Vaysman, Olga

2009-01-01

455

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

NASA Astrophysics Data System (ADS)

This paper examined the electrochemical corrosion behavior and corrosion products of two types of heat-affected HAZs made from API-X100 steel. Cyclic voltammetry, with different scan rates and potential ranges at 10 cycles, was applied to analyze the interdependent corrosion reactions of cathodic reduction, anodic dissolution, passivation, and transpassivation. The HAZ cooled at 60 K/s, from a peak temperature of 1470 K (1197 °C) that was held for 15 seconds, exhibited better passivation and lower cathodic activity than the HAZ cooled at 10 K/s. Increasing bicarbonate concentration, from 0.05 and 0.2 to 0.6 M, increases the anodic activity and cathodic reduction, but accordingly protects the active surfaces and enhances passivation.

Eliyan, Faysal Fayez; Alfantazi, Akram

2014-08-01

456

Standard additions-dilution method for absolute quantification in voltammetry of microparticles. Application for determining psychoactive 1,4-benzodiazepine and antidepressants drugs as adulterants in phytotherapeutic formulations.  

PubMed

A standard additions-dilution solid-state electrochemical method for the determination of psychoactive 1,4-benzodiazepine and antidepressants drugs used as adulterants in commercial slimming herbal formulations is described and compared with conventional standard addition method. The proposed method, based on the voltammetry of microparticles approach, permits quantify, via standard additions methodology, 1,4-benzodiazepine and antidepressants drugs in phytotherapeutic formulations with no need of sample dissolution using dilution with a reference electroactive compound. The method was used to measure 1,4-benzobenzodiazepines (clonazepam, flurazepam, alprazolam, midazolam, bromazepam, chlordiazepoxide, lorazepam and diazepam) and antidepressants (bupropion, sertraline, paroxetine and fluoxetine) in slimming formulations that have been commercialized in Brazil. PMID:23571127

Doménech-Carbó, Antonio; Martini, Mariele; de Carvalho, Leandro Machado; Viana, Carine; Doménech-Carbó, María Teresa; Silva, Miguel

2013-06-01

457

Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance studies of buckminsterfullerene (C{sub 60}) film electrodeposition and tetra-n-butylammonium electrodoping in acetonitrile  

SciTech Connect

A simple and efficient method is presented for preparation of insoluble thin films of C{sub 60} and the (TBA{sup +})(C{sub 60}{sup {minus}}) and (TBA{sup +}){sub 2}(C{sub 60}{sup 2{minus}}) salts where TBA{sup +} represents the tetra-n-butylammonium cation. The method consists of bulk electroreducing a fine suspension of solid C{sub 60} in acetonitrile solutions under a controlled potential which is sufficiently negative to generate the soluble C{sub 60}{sup 3{minus}} anion, followed by electrooxidative deposition of a neutral C{sub 60} film on the surface of a gold/quartz crystal working electrode. The properties of the electrodeposited films were examined by simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance experiments which enabled determination of the stoichiometry and mass of the film. 11 refs., 21 figs.

Wonyong Koh; Dubois, D.; Kutner, W.; Jones, M.T.; Kadish, K.M. [Univ. of Houston, TX (United States)

1992-05-28

458

Determination of picomolar levels of platinum in estuarine waters: a comparison of cathodic stripping voltammetry and isotope dilution-inductively coupled plasma mass spectrometry.  

PubMed

A comparative study to determine picomolar concentrations of platinum in natural waters was performed using two different analytical techniques. Results obtained by cathodic stripping voltammetry (CSV) were compared with those obtained by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICPMS) combined with anion exchange resin column extraction method. Using successive UV irradiations with low-pressure mercury (L-Hg) lamp for 4h prior to CSV analysis, the results of both methods were comparable. Without adequate photolytic decomposition, the results obtained using CSV were generally lower than those obtained using ID-ICPMS in the estuarine waters around Tokyo Bay. This difference implies the presence of organically complexed Pt species in the estuarine waters. The Pt enrichment in the middle of the Tokyo Bay estuaries probably reflects the anthropogenic release of Pt from highly populated areas in Tokyo. PMID:17723753

Obata, Hajime; Yoshida, Tetsuaki; Ogawa, Hiroshi

2006-10-27

459

On-site fuel electroanalysis: determination of lead, copper and mercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes.  

PubMed

The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067 mol L(-1) HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2 ?g L(-1)) for a 240 s deposition time, linear range between 5 and 300 ?g L(-1), and adequate recovery values (96-104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification. PMID:25000856

Almeida, Eduardo S; Richter, Eduardo M; Munoz, Rodrigo A A

2014-07-21

460

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

PubMed

We assessed the use of anodic stripping voltammetry (ASV) for in-situ determinations of both total concentration and speciation of dissolved heavy metals (Cd, Cu, Pb and Zn) in acid mine drainage (AMD). In the Kwangyang Au-Ag mine area of South Korea, different sites with varying water chemistry within an AMD were studied with a field portable anodic stripping voltammeter. Anodic stripping voltammetry after wet oxidation (acidification) was very sensitive enough to determine total concentration of dissolved Cd because Cd was dominantly present as 'labile' species, whilst the technique was not so effective for determining total Cu especially in the downstream sites from the retention pond, due to its complexation with organic matter. For dissolved Pb, the concentrations determined by ASV after wet oxidation generally agreed with those by ICP-AES. In the downstream samples (pH>5), however, ASV data after wet oxidation were lower than ICP-AES data because a significant fraction of dissolved Pb was present in those samples as 'inert' species associated with colloidal iron oxide particles. The determination of total dissolved Zn by ASV after wet oxidation appeared to be unsatisfactory for the samples with high Cu content, possibly due to the interference by the formation of Zn-Cu intermetallic compounds on the mercury coated electrode. In AMD samples with high dissolved iron, use of ultraviolet irradiation was not effective for determining total concentrations because humate destruction by UV irradiation possibly resulted in the removal of a part of dissolved heavy metals from waters through the precipitation of iron hydroxides. PMID:16767566

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

2006-06-01

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