WorldWideScience

Sample records for voltammetry electronic resource

  1. A brief review: Ultrafast electron diffractive voltammetry: General formalism and applications

    CERN Document Server

    Chang, Kiseok; Tao, Zhensheng; Han, Tzong-Ru T; Ruan, Chong-Yu

    2013-01-01

    We present a general formalism of ultrafast diffractive voltammetry approach as a contact-free tool to investigate the ultrafast surface charge dynamics in nanostructured interfaces. As case studies, the photoinduced surface charging processes in oxidized silicon surface and the hot electron dynamics in nanoparticle-decorated interface are examined based on the diffractive voltammetry framework. We identify that the charge redistribution processes appear on the surface, sub-surface, and vacuum levels when driven by intense femtosecond laser pulses. To elucidate the voltammetry contribution from different sources, we perform controlled experiments using shadow imaging techniques and N-particle simulations to aid the investigation of the photovoltage dynamics in the presence of pho- toemission. We show that voltammetry contribution associated with photoemission has a long decay tail and plays a more visible role in the nanosecond timescale, whereas the ultrafast voltammetry are dominated by local charge transfe...

  2. Diagnostic criteria for the characterization of quasireversible electron transfer reactions by cyclic square wave voltammetry.

    Science.gov (United States)

    Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A

    2014-08-19

    Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

  3. Selection of Electronic Resources.

    Science.gov (United States)

    Weathers, Barbara

    1998-01-01

    Discusses the impact of electronic resources on collection development; selection of CD-ROMs, (platform, speed, video and sound, networking capability, installation and maintenance); selection of laser disks; and Internet evaluation (accuracy of content, authority, objectivity, currency, technical characteristics). Lists Web sites for evaluating…

  4. Theory of Square-Wave Voltammetry of Two-Electron Reduction with the Adsorption of Intermediate

    Directory of Open Access Journals (Sweden)

    Milivoj Lovric

    2012-01-01

    Full Text Available Thermodynamically unstable intermediate of fast and reversible two-electron electrode reaction can be stabilized by the adsorption to the electrode surface. In square-wave voltammetry of this reaction mechanism, the split response may appear if the electrode surface is not completely covered by the adsorbed intermediate. The dependence of the difference between the net peak potentials of the prepeak and postpeak on the square-wave frequency is analyzed theoretically. This relationship can be used for the estimation of adsorption constant.

  5. Electronic Resource Management Systems

    Directory of Open Access Journals (Sweden)

    Mark Ellingsen

    2004-10-01

    Full Text Available Computer applications which deal with electronic resource management (ERM are quite a recent development. They have grown out of the need to manage the burgeoning number of electronic resources particularly electronic journals. Typically, in the early years of e-journal acquisition, library staff provided an easy means of accessing these journals by providing an alphabetical list on a web page. Some went as far as categorising the e-journals by subject and then grouping the journals either on a single web page or by using multiple pages. It didn't take long before it was recognised that it would be more efficient to dynamically generate the pages from a database rather than to continually edit the pages manually. Of course, once the descriptive metadata for an electronic journal was held within a database the next logical step was to provide administrative forms whereby that metadata could be manipulated. This in turn led to demands for incorporating more information and more functionality into the developing application.

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

    Science.gov (United States)

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

    2014-05-01

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

  7. Electronic Resource Management and Design

    Science.gov (United States)

    Abrams, Kimberly R.

    2015-01-01

    We have now reached a tipping point at which electronic resources comprise more than half of academic library budgets. Because of the increasing work associated with the ever-increasing number of e-resources, there is a trend to distribute work throughout the library even in the presence of an electronic resources department. In 2013, the author…

  8. Electronic Resource Management and Design

    Science.gov (United States)

    Abrams, Kimberly R.

    2015-01-01

    We have now reached a tipping point at which electronic resources comprise more than half of academic library budgets. Because of the increasing work associated with the ever-increasing number of e-resources, there is a trend to distribute work throughout the library even in the presence of an electronic resources department. In 2013, the author…

  9. Cyclic Square Wave Voltammetry of Surface-Confined Quasireversible Electron Transfer Reactions.

    Science.gov (United States)

    Mann, Megan A; Bottomley, Lawrence A

    2015-09-01

    The theory for cyclic square wave voltammetry of surface-confined quasireversible electrode reactions is presented and experimentally verified. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. These criteria were experimentally confirmed using two well-established surface-confined analytes. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

  10. Pulse Voltammetry.

    Science.gov (United States)

    Osteryoung, Janet

    1983-01-01

    Discusses the nature of pulse voltammetry, indicating that its widespread use arises from good sensitivity and detection limits and from ease of application and low cost. Provides analytical and mechanistic applications of the procedure. (JN)

  11. Recent Advances in Voltammetry

    Science.gov (United States)

    Batchelor-McAuley, Christopher; Kätelhön, Enno; Barnes, Edward O; Compton, Richard G; Laborda, Eduardo; Molina, Angela

    2015-01-01

    Recent progress in the theory and practice of voltammetry is surveyed and evaluated. The transformation over the last decade of the level of modelling and simulation of experiments has realised major advances such that electrochemical techniques can be fully developed and applied to real chemical problems of distinct complexity. This review focuses on the topic areas of: multistep electrochemical processes, voltammetry in ionic liquids, the development and interpretation of theories of electron transfer (Butler–Volmer and Marcus–Hush), advances in voltammetric pulse techniques, stochastic random walk models of diffusion, the influence of migration under conditions of low support, voltammetry at rough and porous electrodes, and nanoparticle electrochemistry. The review of the latter field encompasses both the study of nanoparticle-modified electrodes, including stripping voltammetry and the new technique of ‘nano-impacts’. PMID:26246984

  12. Recent Advances in Voltammetry.

    Science.gov (United States)

    Batchelor-McAuley, Christopher; Kätelhön, Enno; Barnes, Edward O; Compton, Richard G; Laborda, Eduardo; Molina, Angela

    2015-06-01

    Recent progress in the theory and practice of voltammetry is surveyed and evaluated. The transformation over the last decade of the level of modelling and simulation of experiments has realised major advances such that electrochemical techniques can be fully developed and applied to real chemical problems of distinct complexity. This review focuses on the topic areas of: multistep electrochemical processes, voltammetry in ionic liquids, the development and interpretation of theories of electron transfer (Butler-Volmer and Marcus-Hush), advances in voltammetric pulse techniques, stochastic random walk models of diffusion, the influence of migration under conditions of low support, voltammetry at rough and porous electrodes, and nanoparticle electrochemistry. The review of the latter field encompasses both the study of nanoparticle-modified electrodes, including stripping voltammetry and the new technique of 'nano-impacts'.

  13. Electron reduction processes of nitrothiophenes. A systematic approach by DFT computations, cyclic voltammetry and E-ESR spectroscopy.

    Science.gov (United States)

    Boga, Carla; Calvaresi, Matteo; Franchi, Paola; Lucarini, Marco; Fazzini, Silvia; Spinelli, Domenico; Tonelli, Domenica

    2012-10-21

    In the framework of the interest in nitrothiophenes as drugs or hits with different pharmacological applications and considering that in several instances nitroreduction is an essential step for their biological activity, we have studied a complete series of mono-, di-, and tri-nitrothiophenes (1-6) and by comparison some mononitro benzo[b]thiophenes and benzo[b]furans (7-10). Their electroreduction behaviour has been investigated by different techniques: DFT calculations, cyclic voltammetry and electrochemical electron spin resonance spectroscopy. Although, the first reduction process for all of the compounds leads to the relevant radical anions, both the computational and experimental results indicate that there are significant differences in the fate of their corresponding forthcoming reductions, for example, formation of secondary radicals (open-shell electronic structures) or dianions. The effect of the relative positions of the nitro groups during the reduction has also been analysed and rationalised.

  14. Characterization and DNA binding studies of unexplored imidazolidines by electronic absorption spectroscopy and cyclic voltammetry.

    Science.gov (United States)

    Shah, Afzal; Nosheen, Erum; Munir, Shamsa; Badshah, Amin; Qureshi, Rumana; Rehman, Zia-Ur-; Muhammad, Niaz; Hussain, Hidayat

    2013-03-05

    UV-Vis spectroscopic behavior of four imidazolidine derivatives i.e., [5-benzylideneimidazolidine-2,4-dione (NBI), 5-(2-hydroxybenzylidene)imidazolidine-2,4-dione (HBI), 5-(4-methoxybenzylidene)imidazolidine-2,4-dione (MBI) and 5-(3,4-di-methoxybenzylidene)imidazolidine-2,4-dione (DBI)] was studied in a wide pH range. Spectroscopic response of the studied compounds was found sensitive to pH and the attached substituents. Incited by anti-tumor activity, structural miscellany and biological applications of imidazolidines, the DNA binding affinity of some novel derivatives of this class of compounds was examined by cyclic voltammetry (CV) and UV-Vis spectroscopy at pH values of blood (7.4) and lysosomes (4.5). The CV results showed the following order of binding strength: KNBI (6.40×10(6)M(-1))>KHBI (1.77×10(5)M(-1))>KMBI (2.06×10(4)M(-1))>KDBI (1.01×10(4)M(-1)) at pH 7.4. The same order was also obtained from UV-Vis spectroscopy. The greater affinity of NBI justified its preferred candidature as an effective anti-cancer drug. The DNA binding propensity of these compounds was found comparable or greater than most of the clinically used anticancer drugs. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Cyclic Voltammetry.

    Science.gov (United States)

    Evans, Dennis H.; And Others

    1983-01-01

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

  16. Cyclic Voltammetry.

    Science.gov (United States)

    Evans, Dennis H.; And Others

    1983-01-01

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

  17. Cyclic voltammetry and scanning electrochemical microscopy studies of the heterogeneous electron transfer reaction of some nitrosoaromatic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Bollo, S.; Finger, S.; Sturm, J.C.; Nunez-Vergara, L.J.; Squella, J.A. [Bioelectrochemistry Laboratory, Chemical and Pharmaceutical Sciences Faculty, University of Chile, P.O. Box 233, Santiago 1 (Chile)

    2007-04-20

    The heterogeneous electron transfer reaction for the reduction of some nitroso aromatic derivatives in aqueous-alcoholic medium was studied on both mercury and glassy carbon electrodes (GCE) by using cyclic voltammetry (CV) and scanning electrochemical microscopy techniques (SECM). The nitrosoaromatic derivatives followed a two-electron two-proton mechanism producing a quasi-reversible overall process. This strongly pH dependent mechanism varied from ECCE mechanism at pH < 8.5 to ECEC mechanism at pH > 8.5. The apparent heterogeneous rate constant for the reduction of the nitroso derivatives was calculated using CV or SECM. The rate constant for the electron transfer process depends on the nature of the electrode material. The heterogeneous rate constant on the GCE is almost two orders of magnitude smaller than that on mercury electrode i.e. (3.4 {+-} 0.3) x 10{sup -3} cm s{sup -1} on Hg and (7.0 {+-} 1.0) x 10{sup -5} cm s{sup -1} on GCE, for the same nitroso compound and pH. The heterogeneous rate constant values were checked by comparison between experimental and simulated cyclic voltammograms. (author)

  18. Cyclic Voltammetry Experiment.

    Science.gov (United States)

    Van Benschoten, James J.; And Others

    1983-01-01

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

  19. Cyclic Voltammetry Experiment.

    Science.gov (United States)

    Van Benschoten, James J.; And Others

    1983-01-01

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

  20. Diagnostic Criteria for the Characterization of Electrode Reactions with Chemically Coupled Reactions Preceding the Electron Transfer by Cyclic Square Wave Voltammetry.

    Science.gov (United States)

    Helfrick, John C; Mann, Megan A; Bottomley, Lawrence A

    2016-08-18

    Theory for cyclic square wave voltammetry of electrode reactions with chemical reactions preceding the electron transfer is presented. Theoretical voltammograms were calculated following systematic variation of empirical parameters to assess their impact on the shape of the voltammogram. From the trends obtained, diagnostic criteria for this mechanism were deduced. When properly applied, these criteria will enable non-experts in voltammetry to assign the electrode reaction mechanism and accurately measure reaction kinetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Separation of electron-transfer and coupled chemical reaction components of biocatalytic processes using Fourier transform ac voltammetry.

    Science.gov (United States)

    Fleming, Barry D; Zhang, Jie; Bond, Alan M; Bell, Stephen G; Wong, Luet-Lok

    2005-06-01

    The underlying electron-transfer and coupled chemical processes associated with biologically important catalytic reactions can be resolved using a combination of Fourier transform ac voltammetry with an analysis of the separated dc and ac components. This outcome can be achieved because the response associated with generation of the catalytic current is essentially confined to the steady-state dc component, whereas the electron-transfer step is dominant in the fundamental and higher harmonics. For the mediated oxidation of glucose with glucose oxidase, it was found that the underlying reversible redox chemistry of the mediator, ferrocenemonocarboxylic acid, as detected in the third and higher harmonics, was totally unaffected by introduction of the catalytic process. In contrast, for the catalytic reduction of molecular oxygen by cytochrome P450, slight changes in the P450 redox process were detected when the catalytic reaction was present. Simulations of a simple catalytic reaction scheme support the fidelity of this novel FT ac voltammetric approach for examining mechanistic nuances of catalytic forms of electrochemical reaction schemes.

  2. Method of evaluation of electron transfer kinetics of a surface-confined redox system by means of Fourier transformed square wave voltammetry.

    Science.gov (United States)

    Huang, Xinjian; Wang, Lishi; Liao, Shijun

    2008-07-15

    A new form of Fourier transformed square wave voltammetry (FT-SWV) is proposed to simplify and accelerate the electron transfer kinetics evaluation procedures for surface-confined redox systems. Even harmonic frequencies, which are derived from the nonlinear Faradaic response, will arise in the power spectrum after Fourier transformation of the current response of FT-SWV. The profile of the even harmonic power spectra is bell-shaped and shows a maximum at a certain frequency. The electrode kinetics-dependent maximum and the corresponding frequency are equivalent to the so-called "quasi-reversible maximum" and "critical frequency" (fmax) in traditional SWV, respectively. The critical frequency can be regarded as a frequency that is synchronized to the electron transfer rate constant (k(0)). As a result, it can serve as a probe of k(0) by means of a very simple equation, k(0) = kmax fmax. Compared with traditional cyclic voltammetry, square wave voltammetry, alternating current voltammetry, and several other voltammetric techniques, this method exhibits great advantages for its simplicity, rapidity, and sensitivity.

  3. Managing electronic resources a LITA guide

    CERN Document Server

    Weir, Ryan O

    2012-01-01

    Informative, useful, current, Managing Electronic Resources: A LITA Guide shows how to successfully manage time, resources, and relationships with vendors and staff to ensure personal, professional, and institutional success.

  4. Detailed analysis of the electron-transfer properties of azurin adsorbed on graphite electrodes using DC and large-amplitude Fourier transformed AC voltammetry.

    Science.gov (United States)

    Fleming, Barry D; Zhang, Jie; Elton, Darrell; Bond, Alan M

    2007-09-01

    The analysis of dc cyclic voltammograms of surface-confined metalloproteins is complicated by large background currents, significant ohmic iRu drop, and frequency dispersion related to protein and electrode surface inhomogeneity. The use of large-amplitude Fourier transform ac voltammetry for the quantification of the electron-transfer properties of a thin film of redox-active protein azurin adsorbed onto edge-plane, basal-plane, and highly oriented pyrolytic graphite electrode surfaces has been evaluated and compared to results obtained by dc cyclic voltammetry. In principle, it has been established that fourth and higher harmonic sine-wave data are ideally suited for analysis of electron-transfer processes as they are almost completely devoid of background capacitance current contributions. However, uncompensated resistance has a higher impact on these components, as is the case with fast scan rate dc techniques, so strategies to include this term in the simulations have been investigated. Application of recommended strategies for the evaluation of the electron-transfer properties of azurin adsorbed onto three forms of graphite, each having different background or uncompensated resistance values, is described and compared to results obtained by traditionally used forms of cyclic voltammetry. The electron-transfer rate constant, k0', of azurin at a highly oriented pyrolytic graphite electrode surface was approximately 250 s(-1), compared with > or =1000 s(-1) at edge-plane and basal-plane graphite electrodes. The significantly lower k0' value found at the highly oriented pyrolytic graphite electrode was related to the relatively low level of edge-plane defect sites present at the surface of this electrode. However, analysis of high ac harmonics suggests that frequency dispersion is substantial at all electrode surfaces. Such effects in these diffusionless situations are significantly enhanced relative to solution-phase voltammetry, where overlay of diffusion

  5. Electronic Resources Management Project Presentation 2012

    KAUST Repository

    Ramli, Rindra M.

    2012-11-05

    This presentation describes the electronic resources management project undertaken by the KAUST library. The objectives of this project is to migrate information from MS Sharepoint to Millennium ERM module. One of the advantages of this migration is to consolidate all electronic resources into a single and centralized location. This would allow for better information sharing among library staff.

  6. Implementing CORAL: An Electronic Resource Management System

    Science.gov (United States)

    Whitfield, Sharon

    2011-01-01

    A 2010 electronic resource management survey conducted by Maria Collins of North Carolina State University and Jill E. Grogg of University of Alabama Libraries found that the top six electronic resources management priorities included workflow management, communications management, license management, statistics management, administrative…

  7. Implementing CORAL: An Electronic Resource Management System

    Science.gov (United States)

    Whitfield, Sharon

    2011-01-01

    A 2010 electronic resource management survey conducted by Maria Collins of North Carolina State University and Jill E. Grogg of University of Alabama Libraries found that the top six electronic resources management priorities included workflow management, communications management, license management, statistics management, administrative…

  8. Resource Letter: TE-1: Teaching electronics

    Science.gov (United States)

    Henry, Dennis C.

    2002-01-01

    This Resource Letter examines the evolution, roles, and content of courses in electronics in the undergraduate physics curriculum, and provides a guide to resources for faculty teaching such courses. It concludes with a brief section addressing problems of electromagnetic interference in electronic systems, and provides an introduction to the literature and practice of electromagnetic compatibility. I have included textbooks, reference books, articles, collections of laboratory experiments and projects, sources of equipment and parts, software packages, videos, and websites.

  9. Electronic Resources Management System: Recommendation Report 2017

    KAUST Repository

    Ramli, Rindra M.

    2017-05-01

    This recommendation report provides an overview of the selection process for the new Electronic Resources Management System. The library has decided to move away from Innovative Interfaces Millennium ERM module. The library reviewed 3 system as potential replacements namely: Proquest 360 Resource Manager, Ex Libris Alma and Open Source CORAL ERMS. After comparing and trialling the systems, it was decided to go for Proquest 360 Resource Manager.

  10. Library Training to Promote Electronic Resource Usage

    DEFF Research Database (Denmark)

    Frandsen, Tove Faber; Tibyampansha, Dativa; Ibrahim, Glory

    2017-01-01

    Purpose: Increasing the usage of electronic resources is an issue of concern for many libraries all over the world. Several studies stress the importance of information literacy and instruction in order to increase the usage. Design/methodology/approach: The present article presents the results...

  11. Reviewing the Electronic Resources & Libraries Conference

    Science.gov (United States)

    Tijerina, Bonnie

    2008-01-01

    The third Electronic Resources & Libraries (ER&L) conference gathered at Georgia Institute of Technology's Global Learning and Conference Center in Atlanta, Georgia, March 18-21, 2008. Over 360 attendees, from six countries and from 80% of the United States, represented their libraries and organizations resulting in a diverse and…

  12. Making sense of the electronic resource marketplace: trends in health-related electronic resources.

    Science.gov (United States)

    Blansit, B D; Connor, E

    1999-07-01

    Changes in the practice of medicine and technological developments offer librarians unprecedented opportunities to select and organize electronic resources, use the Web to deliver content throughout the organization, and improve knowledge at the point of need. The confusing array of available products, access routes, and pricing plans makes it difficult to anticipate the needs of users, identify the top resources, budget effectively, make sound collection management decisions, and organize the resources effectively and seamlessly. The electronic resource marketplace requires much vigilance, considerable patience, and continuous evaluation. There are several strategies that librarians can employ to stay ahead of the electronic resource curve, including taking advantage of free trials from publishers; marketing free trials and involving users in evaluating new products; watching and testing products marketed to the clientele; agreeing to beta test new products and services; working with aggregators or republishers; joining vendor advisory boards; benchmarking institutional resources against five to eight competitors; and forming or joining a consortium for group negotiating and purchasing. This article provides a brief snapshot of leading biomedical resources; showcases several libraries that have excelled in identifying, acquiring, and organizing electronic resources; and discusses strategies and trends of potential interest to biomedical librarians, especially those working in hospital settings.

  13. Theoretical analysis of the two-electron transfer reaction and experimental studies with surface-confined cytochrome c peroxidase using large-amplitude Fourier transformed AC voltammetry.

    Science.gov (United States)

    Stevenson, Gareth P; Lee, Chong-Yong; Kennedy, Gareth F; Parkin, Alison; Baker, Ruth E; Gillow, Kathryn; Armstrong, Fraser A; Gavaghan, David J; Bond, Alan M

    2012-06-26

    A detailed analysis of the cooperative two-electron transfer of surface-confined cytochrome c peroxidase (CcP) in contact with pH 6.0 phosphate buffer solution has been undertaken. This investigation is prompted by the prospect of achieving a richer understanding of this biologically important system via the employment of kinetically sensitive, but background devoid, higher harmonic components available in the large-amplitude Fourier transform ac voltammetric method. Data obtained from the conventional dc cyclic voltammetric method are also provided for comparison. Theoretical considerations based on both ac and dc approaches are presented for cases where reversible or quasi-reversible cooperative two-electron transfer involves variation in the separation of their reversible potentials, including potential inversion (as described previously for solution phase studies), and reversibility of the electrode processes. Comparison is also made with respect to the case of a simultaneous two-electron transfer process that is unlikely to occur in the physiological situation. Theoretical analysis confirms that the ac higher harmonic components provide greater sensitivity to the various mechanistic nuances that can arise in two-electron surface-confined processes. Experimentally, the ac perturbation with amplitude and frequency of 200 mV and 3.88 Hz, respectively, was employed to detect the electron transfer when CcP is confined to the surface of a graphite electrode. Simulations based on cooperative two-electron transfer with the employment of reversible potentials of 0.745 ± 0.010 V, heterogeneous electron transfer rate constants of between 3 and 10 s(-1) and charge transfer coefficients of 0.5 for both processes fitted experimental data for the fifth to eighth ac harmonics. Imperfections in theory-experiment comparison are consistent with kinetic and thermodynamic dispersion and other nonidealities not included in the theory used to model the voltammetry of surface

  14. Affordable Cyclic Voltammetry

    Science.gov (United States)

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

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  15. Affordable Cyclic Voltammetry

    Science.gov (United States)

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

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  16. Electronic resource management systems a workflow approach

    CERN Document Server

    Anderson, Elsa K

    2014-01-01

    To get to the bottom of a successful approach to Electronic Resource Management (ERM), Anderson interviewed staff at 11 institutions about their ERM implementations. Among her conclusions, presented in this issue of Library Technology Reports, is that grasping the intricacies of your workflow-analyzing each step to reveal the gaps and problems-at the beginning is crucial to selecting and implementing an ERM. Whether the system will be used to fill a gap, aggregate critical data, or replace a tedious manual process, the best solution for your library depends on factors such as your current soft

  17. An experimental comparison of the Marcus-Hush and Butler-Volmer descriptions of electrode kinetics applied to cyclic voltammetry. The one electron reductions of europium (III) and 2-methyl-2-nitropropane studied at a mercury microhemisphere electrode

    Science.gov (United States)

    Henstridge, Martin C.; Wang, Yijun; Limon-Petersen, Juan G.; Laborda, Eduardo; Compton, Richard G.

    2011-11-01

    We present a comparative experimental evaluation of the Butler-Volmer and Marcus-Hush models using cyclic voltammetry at a microelectrode. Numerical simulations are used to fit experimental voltammetry of the one electron reductions of europium (III) and 2-methyl-2-nitropropane, in water and acetonitrile, respectively, at a mercury microhemisphere electrode. For Eu (III) very accurate fits to experiment were obtained over a wide range of scan rates using Butler-Volmer kinetics, whereas the Marcus-Hush model was less accurate. The reduction of 2-methyl-2-nitropropane was well simulated by both models, however Marcus-Hush required a reorganisation energy lower than expected.

  18. Cyclic voltammetry of supported BLMs

    Science.gov (United States)

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

    1996-06-01

    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.

  19. Voltammetry Method Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, N. [Argonne National Lab. (ANL), Argonne, IL (United States); Pereira, C. [Argonne National Lab. (ANL), Argonne, IL (United States); Willit, J. [Argonne National Lab. (ANL), Argonne, IL (United States); Williamson, M. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-07-29

    The purpose of the ANL MPACT Voltammetry project is to evaluate the suitability of previously developed cyclic voltammetry techniques to provide electroanalytical measurements of actinide concentrations in realistic used fuel processing scenarios. The molten salts in these scenarios are very challenging as they include high concentrations of multiple electrochemically active species, thereby creating a variety of complications. Some of the problems that arise therein include issues related to uncompensated resistance, cylindrical diffusion, and alloying of the electrodeposited metals. Improvements to the existing voltammetry technique to account for these issues have been implemented, resulting in good measurements of actinide concentrations across a wide range of adverse conditions.

  20. Electronic Resource Management System. Vernetzung von Lizenzinformationen

    Directory of Open Access Journals (Sweden)

    Michaela Selbach

    2014-12-01

    Full Text Available In den letzten zehn Jahren spielen elektronische Ressourcen im Bereich der Erwerbung eine zunehmend wichtige Rolle: Eindeutig lässt sich hier ein Wandel in den Bibliotheken (fort vom reinen Printbestand zu immer größeren E-Only-Beständen feststellen. Die stetig wachsende Menge an E-Ressourcen und deren Heterogenität stellt Bibliotheken vor die Herausforderung, die E-Ressourcen effizient zu verwalten. Nicht nur Bibliotheken, sondern auch verhandlungsführende Institutionen von Konsortial- und Allianzlizenzen benötigen ein geeignetes Instrument zur Verwaltung von Lizenzinformationen, welches den komplexen Anforderungen moderner E-Ressourcen gerecht wird. Die Deutsche Forschungsgemeinschaft (DFG unterstützt ein Projekt des Hochschulbibliothekszentrums des Landes Nordrhein-Westfalen (hbz, der Universitätsbibliothek Freiburg, der Verbundzentrale des Gemeinsamen Bibliotheksverbundes (GBV und der Universitätsbibliothek Frankfurt, in dem ein bundesweit verfügbares Electronic Ressource Managementsystem (ERMS aufgebaut werden soll. Ein solches ERMS soll auf Basis einer zentralen Knowledge Base eine einheitliche Nutzung von Daten zur Lizenzverwaltung elektronischer Ressourcen auf lokaler, regionaler und nationaler Ebene ermöglichen. Statistische Auswertungen, Rechteverwaltung für alle angeschlossenen Bibliotheken, kooperative Datenpflege sowie ein über standardisierte Schnittstellen geführter Datenaustausch stehen bei der Erarbeitung der Anforderungen ebenso im Fokus wie die Entwicklung eines Daten- und Funktionsmodells. In the last few years the importance of electronic resources in library acquisitions has increased significantly. There has been a shift from mere print holdings to both e- and print combinations and even e-only subscriptions. This shift poses a double challenge for libraries: On the one hand they have to provide their e-resource collections to library users in an appealing way, on the other hand they have to manage these

  1. Utilization of electronic information resources by academic staff at ...

    African Journals Online (AJOL)

    Utilization of electronic information resources by academic staff at Makerere University. ... AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search ... It examined the academic staff awareness of the resources available, the types ...

  2. Effectiveness Analysis of Electronic Resources at the Hacettepe University

    OpenAIRE

    2011-01-01

    It is important to collect and analyze the usage data of electronic databases and periodicals in order to make policies regarding the composition, improvement and more extensive utilization of electronic resources of libraries. The aim of this study is to investigate how efficiently the full text accessible electronic resources of Hacettepe University Libraries are used. For this purpose the usage data obtained from COUNTER Software regarding the electronic databases to which Hacettepe Univer...

  3. The Study of Analytical Model of Library Electronic Resources Usage-A Case of Medical Electronic Resources

    OpenAIRE

    Chung-Yen Yu; Jiann-Cherng Shieh

    2014-01-01

    With the advents of internet, the importance of electronic resources is growing. Due to the increasing expensiveness of electronic resources, university libraries normally received budgets from parent institutions annually. They necessarily applied effective and systematic methods for decision making in electronic resources purchase or re-subscription. However, there are some difficulties in practices: First of all, libraries are unable to receive user records; second, the COUNTER statistics ...

  4. The Role of the Acquisitions Librarian in Electronic Resources Management

    Science.gov (United States)

    Pomerantz, Sarah B.

    2010-01-01

    With the ongoing shift to electronic formats for library resources, acquisitions librarians, like the rest of the profession, must adapt to the rapidly changing landscape of electronic resources by keeping up with trends and mastering new skills related to digital publishing, technology, and licensing. The author sought to know what roles…

  5. Electronic resources preferred by pediatric hospitalists for clinical care.

    Science.gov (United States)

    Beck, Jimmy B; Tieder, Joel S

    2015-10-01

    There is little research on pediatric hospitalists' use of evidence-based resources. The aim of this study was to determine the electronic resources that pediatric hospitalists prefer. Using a web-based survey, the authors determined hospitalists' preferred electronic resources, as well as their attitudes toward lifelong learning, practice, and experience characteristics. One hundred sixteen hospitalists completed the survey. The most preferred resource for general information, patient handouts, and treatment was UpToDate. Online search engines were ranked second for general information and patient handouts. Pediatric hospitalists tend to utilize less rigorous electronic resources such as UpToDate and Google. These results can set a platform for discussing the quality of resources that pediatric hospitalists use.

  6. Voltammetry of Medical Biomaterials

    OpenAIRE

    Gulaboski, Rubin; Markovski, Velo

    2015-01-01

    The use of biomaterials in the medicine, dentistry and pharmacy represents probably a major breakthrough in tackling many diseases or disabilities in the last 50 years. We refer to varios techniques that are used for the characterization of the structure and the composition of the biomaterials. Voltammetry is an electrochemical technique that helps mainly in understanding the redox properties of various biomaterials containing some suitable redox centers in their structure. We give in this le...

  7. Ultrafast cyclic voltammetry with asymmetrical potential scan

    Institute of Scientific and Technical Information of China (English)

    Zhi Yong Guo; Xiang Qin Lin

    2008-01-01

    Based on the perfect ohmic drop compensation by online electronic positive feedback, ultrafast cyclic voltammetry withasymmetrical potential scan is achieved for the first time, with the reduction of anthracene acting as the test system. Compared withthe traditional cyclic voltammetry utilizing symmetrical triangular waveform as the excitation one, the new method allows a simplerapproach to mechanistic analysis of ultrafast chemical reactions coupled with a charge transfer. And perhaps more important, it alsoprovides a way to eliminate the interference of the adsorbed product in dynamic monitoring.

  8. Cataloging and Indexing of Electronic Information Resources

    Science.gov (United States)

    2003-04-01

    digital library, but it facilitates the exchange of these objects among digital libraries . METS provides an XML DTD that can point to metadata in other...International Federation of Library Associations and Institutions (IFLA). (2002). Digital Libraries : Metadata Resources. Retrieved May 3, 2002 from the

  9. Adoption and use of electronic information resources by medical ...

    African Journals Online (AJOL)

    ... were analysed with descriptive Statistics(Simple percentage and frequency count). ... for doing assignment, Google search, for personal development, and getting ... major problems encountered when using electronic Information Resources.

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

    Science.gov (United States)

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

    2008-09-01

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

  11. Euler European Libraries and Electronic Resources in Mathematical Sciences

    CERN Document Server

    The Euler Project. Karlsruhe

    The European Libraries and Electronic Resources (EULER) Project in Mathematical Sciences provides the EulerService site for searching out "mathematical resources such as books, pre-prints, web-pages, abstracts, proceedings, serials, technical reports preprints) and NetLab (for Internet resources), this outstanding engine is capable of simple, full, and refined searches. It also offers a browse option, which responds to entries in the author, keyword, and title fields. Further information about the Project is provided at the EULER homepage.

  12. Building an electronic resource collection a practical guide

    CERN Document Server

    Lee, Stuart D

    2004-01-01

    This practical book guides information professionals step-by-step through building and managing an electronic resource collection. It outlines the range of electronic products currently available in abstracting and indexing, bibliographic, and other services and then describes how to effectively select, evaluate and purchase them.

  13. Why and How to Measure the Use of Electronic Resources

    Directory of Open Access Journals (Sweden)

    Jean Bernon

    2008-11-01

    Full Text Available A complete overview of library activity implies a complete and reliable measurement of the use of both electronic resources and printed materials. This measurement is based on three sets of definitions: document types, use types and user types. There is a common model of definitions for printed materials, but a lot of questions and technical issues remain for electronic resources. In 2006 a French national working group studied these questions. It relied on the COUNTER standard, but found it insufficient and pointed out the need for local tools such as web markers and deep analysis of proxy logs. Within the French national consortium COUPERIN, a new working group is testing ERMS, SUSHI standards, Shibboleth authentication, along with COUNTER standards, to improve the counting of the electronic resources use. At this stage this counting is insufficient and its improvement will be a European challenge for the future.

  14. Access to electronic resources by visually impaired people

    Directory of Open Access Journals (Sweden)

    Jenny Craven

    2003-01-01

    Full Text Available Research into access to electronic resources by visually impaired people undertaken by the Centre for Research in Library and Information Management has not only explored the accessibility of websites and levels of awareness in providing websites that adhere to design for all principles, but has sought to enhance understanding of information seeking behaviour of blind and visually impaired people when using digital resources.

  15. The Study of Analytical Model of Library Electronic Resources Usage-A Case of Medical Electronic Resources

    Directory of Open Access Journals (Sweden)

    Chung-Yen Yu

    2014-10-01

    Full Text Available With the advents of internet, the importance of electronic resources is growing. Due to the increasing expensiveness of electronic resources, university libraries normally received budgets from parent institutions annually. They necessarily applied effective and systematic methods for decision making in electronic resources purchase or re-subscription. However, there are some difficulties in practices: First of all, libraries are unable to receive user records; second, the COUNTER statistics does not include details about users and their affiliation. As a result, one cannot conduct advanced user analysis based on the usage of users, institutions, and departments. To overcome the difficulties, this study presents a feasible model to analyze electronic resource usage effectively and flexibly. We set up a proxy server to collect actual usage raw data. By analyzing items in internet browsing records, associated with original library automatic system, this study aims at exploring how to use effective ways to analyze big data of website log data. We also propose the process of how original data to be transformed, cleared, integrated, and demonstrated. This study adopted a medical university library and its subscription of medical electronic resources as a case. Our data analysis includes (1 year of subscription,(2 title of journal, (3 affiliation, (4 subjects, and (5 specific journal requirements, etc. The findings of the study are contributed to obtain further understanding in policy making and user behavior analysis. The integrated data provides multiple applications in informatics research, information behavior, bibliomining, presenting diverse views and extended issues for further discussion.

  16. Practical guide to electronic resources in the humanities

    CERN Document Server

    Dubnjakovic, Ana

    2010-01-01

    From full-text article databases to digitized collections of primary source materials, newly emerging electronic resources have radically impacted how research in the humanities is conducted and discovered. This book, covering high-quality, up-to-date electronic resources for the humanities, is an easy-to-use annotated guide for the librarian, student, and scholar alike. It covers online databases, indexes, archives, and many other critical tools in key humanities disciplines including philosophy, religion, languages and literature, and performing and visual arts. Succinct overviews of key eme

  17. Discipline, availability of electronic resources and the use of Finnish National Electronic Library - FinELib

    Directory of Open Access Journals (Sweden)

    Sanna Torma

    2004-01-01

    Full Text Available This study elaborated relations between digital library use by university faculty, users' discipline and the availability of key resources in the Finnish National Electronic Library (FinELib, Finnish national digital library, by using nationwide representative survey data. The results show that the perceived availability of key electronic resources by researchers in FinELib was a stronger predictor of the frequency and purpose of use of its services than users' discipline. Regardless of discipline a good perceived provision of central resources led to a more frequent use of FinELib. The satisfaction with the services did not vary with the discipline, but with the perceived availability of resources.

  18. Providing Access to Electronic Information Resources in Further Education

    Science.gov (United States)

    Banwell, Linda; Ray, Kathryn; Coulson, Graham; Urquhart, Christine; Lonsdale, Ray; Armstrong, Chris; Thomas, Rhian; Spink, Sin; Yeoman, Alison; Fenton, Roger; Rowley, Jennifer

    2004-01-01

    This article aims to provide a baseline for future studies on the provision and support for the use of digital or electronic information services (EIS) in further education. The analysis presented is based on a multi-level model of access, which encompasses access to and availability of information and communication technology (ICT) resources,…

  19. ANALYTICAL REVIEW OF ELECTRONIC RESOURCES FOR THE STUDY OF LATIN

    Directory of Open Access Journals (Sweden)

    Olena Yu. Balalaieva

    2014-04-01

    Full Text Available The article investigates the current state of development of e-learning content in the Latin language. It is noted that the introduction of ICT in the educational space has expanded the possibility of studying Latin, opened access to digital libraries resources, made it possible to use scientific and educational potential and teaching Latin best practices of world's leading universities. A review of foreign and Ukrainian information resources and electronic editions for the study of Latin is given. Much attention was paid to the didactic potential of local and online multimedia courses of Latin, electronic textbooks, workbooks of interactive tests and exercises, various dictionaries and software translators, databases and digital libraries. Based on analysis of the world market of educational services and products the main trends in the development of information resources and electronic books are examined. It was found that multimedia courses with interactive exercises or workbooks with interactive tests, online dictionaries and translators are the most widely represented and demanded. The noticeable lagging of Ukrainian education and computer linguistics in quantitative and qualitative measures in this industry is established. The obvious drawback of existing Ukrainian resources and electronic editions for the study of Latin is their noninteractive nature. The prospects of e-learning content in Latin in Ukraine are outlined.

  20. Electronic Commerce Resource Centers. An Industry--University Partnership.

    Science.gov (United States)

    Gulledge, Thomas R.; Sommer, Rainer; Tarimcilar, M. Murat

    1999-01-01

    Electronic Commerce Resource Centers focus on transferring emerging technologies to small businesses through university/industry partnerships. Successful implementation hinges on a strategic operating plan, creation of measurable value for customers, investment in customer-targeted training, and measurement of performance outputs. (SK)

  1. Student Satisfaction with Electronic Library Resources at Wayne State University

    Science.gov (United States)

    Holley, Robert P.; Powell, Ronald R.

    2004-01-01

    This paper reports the results of a survey of student satisfaction with electronic library resources other than the online catalog at Wayne State University. Undertaken in Fall Term 2000 as a class project for a marketing course, a student team designed, administered, and analyzed a survey of a random sample of students. Almost 40% of the…

  2. Electronic Commerce Resource Centers. An Industry--University Partnership.

    Science.gov (United States)

    Gulledge, Thomas R.; Sommer, Rainer; Tarimcilar, M. Murat

    1999-01-01

    Electronic Commerce Resource Centers focus on transferring emerging technologies to small businesses through university/industry partnerships. Successful implementation hinges on a strategic operating plan, creation of measurable value for customers, investment in customer-targeted training, and measurement of performance outputs. (SK)

  3. Technical Communicator: A New Model for the Electronic Resources Librarian?

    Science.gov (United States)

    Hulseberg, Anna

    2016-01-01

    This article explores whether technical communicator is a useful model for electronic resources (ER) librarians. The fields of ER librarianship and technical communication (TC) originated and continue to develop in relation to evolving technologies. A review of the literature reveals four common themes for ER librarianship and TC. While the…

  4. Providing Access to Electronic Information Resources in Further Education

    Science.gov (United States)

    Banwell, Linda; Ray, Kathryn; Coulson, Graham; Urquhart, Christine; Lonsdale, Ray; Armstrong, Chris; Thomas, Rhian; Spink, Sin; Yeoman, Alison; Fenton, Roger; Rowley, Jennifer

    2004-01-01

    This article aims to provide a baseline for future studies on the provision and support for the use of digital or electronic information services (EIS) in further education. The analysis presented is based on a multi-level model of access, which encompasses access to and availability of information and communication technology (ICT) resources,…

  5. Evaluating the appropriateness of electronic information resources for learning.

    Science.gov (United States)

    Saparova, Dinara; Nolan, Nathanial S

    2016-01-01

    Current US medical students have begun to rely on electronic information repositories-such as UpToDate, AccessMedicine, and Wikipedia-for their pre-clerkship medical education. However, it is unclear whether these resources are appropriate for this level of learning due to factors involving information quality, level of evidence, and the requisite knowledgebase. This study evaluated appropriateness of electronic information resources from a novel perspective: amount of mental effort learners invest in interactions with these resources and effects of the experienced mental effort on learning. Eighteen first-year medical students read about three unstudied diseases in the above-mentioned resources (a total of fifty-four observations). Their eye movement characteristics (i.e., fixation duration, fixation count, visit duration, and task-evoked pupillary response) were recorded and used as psychophysiological indicators of the experienced mental effort. Post reading, students' learning was assessed with multiple-choice tests. Eye metrics and test results constituted quantitative data analyzed according to the repeated Latin square design. Students' perceptions of interacting with the information resources were also collected. Participants' feedback during semi-structured interviews constituted qualitative data and was reviewed, transcribed, and open coded for emergent themes. Compared to AccessMedicine and Wikipedia, UpToDate was associated with significantly higher values of eye metrics, suggesting learners experienced higher mental effort. No statistically significant difference between the amount of mental effort and learning outcomes was found. More so, descriptive statistical analysis of the knowledge test scores suggested similar levels of learning regardless of the information resource used. Judging by the learning outcomes, all three information resources were found appropriate for learning. UpToDate, however, when used alone, may be less appropriate for first

  6. Evaluation of homogeneous electrocatalysts by cyclic voltammetry.

    Science.gov (United States)

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

    2014-10-06

    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 (η), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed.

  7. DC and AC voltammetry of a free-base porphyrin adsorbed onto basal-plane graphite under acidic conditions: An example of a close to ideal reversible two-electron surface-confined redox process at sub-monolayer coverages

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Barry D. [School of Chemistry, Monash University, Wellington Rd, Clayton, Victoria 3800 (Australia)], E-mail: barry.fleming@sci.monash.edu.au; Bond, Alan M. [School of Chemistry, Monash University, Wellington Rd, Clayton, Victoria 3800 (Australia)], E-mail: alan.bond@sci.monash.edu.au

    2009-04-01

    The free-base porphyrin, 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine (H{sub 2}TMPyP), adsorbs onto a basal-plane graphite electrode. Under DC cyclic voltammetric conditions, the fully protonated dication, [H{sub 4}TMPyP(0)]{sup 2+}, undergoes an apparently close to ideal surface-confined two-electron reduction to the neutral [H{sub 4}TMPyP(-II)] species when the supporting electrolyte consists of aqueous 1 M HCl and 1 M NaCl and coverages are sub-monolayer. The reversible potential calculated from the average of the oxidation and reduction peak potentials is 0.138 {+-} 0.002 V (vs Ag/AgCl, 3 M NaCl) whilst their separation {delta}E{sub p}, approaches 0 mV at slow scan rates, as expected theoretically for an ideal surface-confined electron transfer process. Comparisons of simulated and experimental data imply that the increase in {delta}E{sub p} observed at scan rates above 10 V s{sup -1} is consistent with uncompensated Ohmic IR{sub u} drop effects, and not limitations imposed by electron transfer kinetics. Analysis of fundamental and higher harmonic components derived from large-amplitude sine-wave AC voltammetry is consistent with a very fast electron transfer rate constant, k{sup 0}, in excess of 10{sup 6} s{sup -1} for the overall two-electron process. However, careful comparison with AC theory highlights minor levels of non-ideality not attributable to purely capacitative background or uncompensated resistance effects. These are particularly evident when greater than monolayer surface coverages are employed. It is likely that subtle contributions from heterogeneity in the adsorbed layer and complexities in the reaction mechanism are present in this close to ideal surface-confined process, but they are more readily detected under conditions of large-amplitude Fourier transformed AC cyclic voltammetry than with the conventionally used DC cyclic format.

  8. MODEL OF AN ELECTRONIC EDUCATIONAL RESOURCE OF NEW GENERATION

    Directory of Open Access Journals (Sweden)

    Anatoliy V. Loban

    2016-01-01

    Full Text Available The mathematical structure of the modular architecture of an electronic educational resource (EER of new generation, which allows to decompose the process of studying the subjects of the course at a hierarchically ordered set of data (knowledge and procedures for manipulating them, to determine the roles of participants of process of training of and technology the development and use of EOR in the study procrate.

  9. Acid/base and hydrogen bonding effects on the proton-coupled electron transfer of quinones and hydroquinones in acetonitrile: Mechanistic investigation by voltammetry, {sup 1}H NMR and computation

    Energy Technology Data Exchange (ETDEWEB)

    Alligrant, Timothy M. [Department of Chemistry, Virginia Commonwealth University, 1001 West Main St., P.O. Box 842006, Richmond, VA 23284 (United States); Hackett, John C. [Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, P.O. Box 980133, Richmond, VA 23219 (United States); Alvarez, Julio C., E-mail: jcalvarez2@vcu.ed [Department of Chemistry, Virginia Commonwealth University, 1001 West Main St., P.O. Box 842006, Richmond, VA 23284 (United States)

    2010-09-01

    This report seeks to address the role of hydrogen bonding with Bronsted acids and bases in proton-coupled electron transfer (PCET) as it pertains to concerted or stepwise pathways of quinone (Q) and hydroquinone (QH{sub 2}) electrochemistry. This study was performed using a series of techniques that included cyclic voltammetry (CV), digital simulations, computational chemistry and {sup 1}H NMR. Hydrogen bonding was inferred by a decrease in diffusion coefficient (D) values measured using a pulsed gradient echo- (PGE-) {sup 1}H NMR technique. Changes of 40.8% and 37.9% in D values were only noted after the addition of two equivalents of acetate to 1,4-hydroquinone (1,4-QH{sub 2}) and catechol (1,2-QH{sub 2}), respectively. In contrast, the D values for the addition of selected amines (pyridine, N,N-diisopropylethylamine and triethylamine) changed only 3.2% on average. Quantum mechanical calculations were conducted to determine the pK{sub a} of all quinoid species to serve as a starting point for the determination of equilibrium constants in voltammetric simulations. Simulations indicate that 1,4-benzoquinone undergoes stepwise electron-proton transfer upon addition of acetic acid, N-ethyldiisopropylammonium perchlorate and pyridinium nitrate and were simulated without the presence of hydrogen bonds. The QH{sub 2} compounds show stepwise proton-electron transfers after addition of the both the conjugate amines and acetate.

  10. Evaluating increased resource use in fibromyalgia using electronic health records

    Directory of Open Access Journals (Sweden)

    Margolis JM

    2016-11-01

    Full Text Available Jay M Margolis,1 Elizabeth T Masters,2 Joseph C Cappelleri,3 David M Smith,1 Steven Faulkner4 1Truven Health Analytics, Life Sciences, Outcomes Research, Bethesda, MD, 2Pfizer Inc, Outcomes & Evidence, New York, NY, 3Pfizer Inc, Statistics, Groton, CT, 4Pfizer Inc, North American Medical Affairs, Medical Outcomes Specialists, St Louis, MO, USA Objective: The management of fibromyalgia (FM, a chronic musculoskeletal disease, remains challenging, and patients with FM are often characterized by high health care resource utilization. This study sought to explore potential drivers of all-cause health care resource utilization and other factors associated with high resource use, using a large electronic health records (EHR database to explore data from patients diagnosed with FM. Methods: This was a retrospective analysis of de-identified EHR data from the Humedica database. Adults (≥18 years with FM were identified based on ≥2 International Classification of Diseases, Ninth Revision codes for FM (729.1 ≥30 days apart between January 1, 2008 and December 31, 2012 and were required to have evidence of ≥12 months continuous care pre- and post-index; first FM diagnosis was the index event; 12-month pre- and post-index reporting periods. Multivariable analysis evaluated relationships between variables and resource utilization. Results: Patients were predominantly female (81.4%, Caucasian (87.7%, with a mean (standard deviation age of 54.4 (14.8 years. The highest health care resource utilization was observed for the categories of “medication orders” and “physician office visits,” with 12-month post-index means of 21.2 (21.5 drug orders/patient and 15.1 (18.1 office visits/patient; the latter accounted for 73.3% of all health care visits. Opioids were the most common prescription medication, 44.3% of all patients. The chance of high resource use was significantly increased (P<0.001 26% among African-Americans vs Caucasians and for patients

  11. Applications of convolution voltammetry in electroanalytical chemistry.

    Science.gov (United States)

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

    2014-02-18

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

  12. Online Electronic Resources and Slovenian Bibliography: a Case Study

    Directory of Open Access Journals (Sweden)

    Daniela Škerget

    2014-09-01

    Full Text Available AbstractConsidering the fact that the number of publications available online only is growing, the question whether to include online electronic resources into the Slovenian bibliography, and if so, in which way, and what are the requirements for the inclusion, is raised. To answer these questions, the research on the growth of the Slovenian online scientific production in comparison with production in printed form was conducted in the case of original scientific articles. Results showed a rapid growth of the number of original scientific articles available online only, which indicates the necessity to form a separate Slovenian bibliography of online resources. The selection criteria for the Slovenian bibliography of online resources are also presented. This kind of bibliography would, along with the informational value, add to the historical value of intellectual production in a given time frame, enriched with a link to the resource preserved in another location (archive, repository, in case of unavailability of the resource on its original location.

  13. Journals, Data and Abstracts Make an Integrated Electronic Resource

    Science.gov (United States)

    Boyce, P.

    1996-12-01

    Astronomy now has an integrated, Web-based information resource for research papers, data and bibliographic information. The major scholarly research journals, a comprehensive abstract service and the astronomical data centers are now linked together to provide an information resource which is not available to most other scientific disciplines. As of January, 1997, the Astrophysical Journal joins the ApJ Letters on the Web. Astronomy and Astrophysics Supplements now has a page image version. Elsevier's electronic journal New Astronomy has recently made its appearance. Over forty percent of the new peer-reviewed, astronomical literature is now available electronically. The main Astronomy and Astrophysics journal, the Astronomical Journal and others will be available by 1998, at which point ninety percent of the literature will be available electronically, a figure not approached by any other scientific discipline. With so many different sources, one of the challenges has been to integrate the on-line, peer-reviewed literature into a resource which serves the astronomical community in a unified and coherent manner. Following the lead of the AAS, the major publishers have chosen to rely upon the NASA-supported Astrophysics Data System (ADS) and the astronomical data centers to provide the means by which the various separate journals can interoperate. The data centers and the ADS have developed unique identification codes for journal articles. By adopting the existing standard "bibcodes" and integrating them into their WWW links, each of the major astronomical journals are able to link to the abstracts of most of the referenced articles. Since the ADS also serves as an on-line repository for page images of the past twenty years of the major astronomical journals, the full text of many of the referenced articles are available, too. The articles in the ADS have recently been linked through their references, both forward and backward in time. With the "bibcode" providing

  14. Analysis of Human Resources Management Strategy in China Electronic Commerce Enterprises

    Science.gov (United States)

    Shao, Fang

    The paper discussed electronic-commerce's influence on enterprise human resources management, proposed and proved the human resources management strategy which electronic commerce enterprise should adopt from recruitment strategy to training strategy, keeping talent strategy and other ways.

  15. Resources

    Science.gov (United States)

    ... resources Alzheimer's - resources Anorexia nervosa - resources Arthritis - resources Asthma and allergy - resources Autism - resources Blindness - resources BPH - resources Breastfeeding - resources Bulimia - resources Burns - resources Cancer - resources Cerebral ...

  16. Aptasensors Based on Stripping Voltammetry

    Directory of Open Access Journals (Sweden)

    Wenjing Qi

    2016-07-01

    Full Text Available Aptasensors based on stripping voltammetry exhibit several advantages, such as high sensitivity and multi-target detection from stripping voltammetric technology, and high selectivity from the specific binding of apamers with targets. This review comprehensively discusses the recent accomplishments in signal amplification strategies based on nanomaterials, such as metal nanoparticles, semiconductor nanoparticles, and nanocomposite materials, which are detected by stripping voltammetry after suitable dissolution. Focus will be put in discussing multiple amplification strategies that are widely applied in aptasensors for small biomolecules, proteins, disease markers, and cancer cells.

  17. Discipline, Availability of Electronic Resources and the Use of Finnish National Electronic Library-- FinELib

    Science.gov (United States)

    Törmä, Sanna; Vakkari, Pertti

    2004-01-01

    This study elaborated relations between digital library use by university faculty, users' discipline and the availability of key resources in the Finnish National Electronic Library (FinELib), Finnish national digital library, by using nationwide representative survey data. The results show that the perceived availability of key electronic…

  18. End-of-life resource recovery from emerging electronic products

    DEFF Research Database (Denmark)

    Parajuly, Keshav; Habib, Komal; Cimpan, Ciprian

    2016-01-01

    of emerging electronic product, in order to understand the recovery fate of different materials and its linkage to product design. Ten different brands of RVC were dismantled and their material composition and design profiles were studied. Another 125 RVCs (349 kg) were used for an experimental trial......Integrating product design with appropriate end-of-life (EoL) processing is widely recognized to have huge potentials in improving resource recovery from electronic products. In this study, we investigate both the product characteristics and EoL processing of robotic vacuum cleaner (RVC), as a case...... at a conventional ‘shred-and-separate’ type preprocessing plant in Denmark. A detailed material flow analysis was performed throughout the recycling chain. The results show a mismatch between product design and EoL processing, and the lack of practical implementation of ‘Design for EoL’ thinking. In the best...

  19. Electronic Resources and Mission Creep: Reorganizing the Library for the Twenty-First Century

    Science.gov (United States)

    Stachokas, George

    2009-01-01

    The position of electronic resources librarian was created to serve as a specialist in the negotiation of license agreements for electronic resources, but mission creep has added more functions to the routine work of electronic resources such as cataloging, gathering information for collection development, and technical support. As electronic…

  20. Effects of Electronic Information Resources Skills Training for Lecturers on Pedagogical Practices and Research Productivity

    Science.gov (United States)

    Bhukuvhani, Crispen; Chiparausha, Blessing; Zuvalinyenga, Dorcas

    2012-01-01

    Lecturers use various electronic resources at different frequencies. The university library's information literacy skills workshops and seminars are the main sources of knowledge of accessing electronic resources. The use of electronic resources can be said to have positively affected lecturers' pedagogical practices and their work in general. The…

  1. Asymmetric Marcus-Hush theory for voltammetry.

    Science.gov (United States)

    Laborda, Eduardo; Henstridge, Martin C; Batchelor-McAuley, Christopher; Compton, Richard G

    2013-06-21

    The current state-of-the-art in modeling the rate of electron transfer between an electroactive species and an electrode is reviewed. Experimental studies show that neither the ubiquitous Butler-Volmer model nor the more modern symmetric Marcus-Hush model are able to satisfactorily reproduce the experimental voltammetry for both solution-phase and surface-bound redox couples. These experimental deviations indicate the need for revision of the simplifying approximations used in the above models. Within this context, models encompassing asymmetry are considered which include different vibrational and solvation force constants for the electroactive species. The assumption of non-adiabatic electron transfer is also examined. These refinements have provided more satisfactory models of the electron transfer process and they enable us to gain more information about the microscopic characteristics of the system by means of simple electrochemical measurements.

  2. Electronic Document Management: A Human Resource Management Case Study

    Directory of Open Access Journals (Sweden)

    Thomas Groenewald

    2004-11-01

    Full Text Available This case study serve as exemplar regarding what can go wrong with the implementation of an electronic document management system. Knowledge agility and knowledge as capital, is outlined against the backdrop of the information society and knowledge economy. The importance of electronic document management and control is sketched thereafter. The literature review is concluded with the impact of human resource management on knowledge agility, which includes references to the learning organisation and complexity theory. The intervention methodology, comprising three phases, follows next. The results of the three phases are presented thereafter. Partial success has been achieved with improving the human efficacy of electronic document management, however the client opted to discontinue the system in use. Opsomming Die gevalle studie dien as voorbeeld van wat kan verkeerd loop met die implementering van ’n elektroniese dokumentbestuur sisteem. Teen die agtergrond van die inligtingsgemeenskap en kennishuishouding word kennissoepelheid en kennis as kapitaal bespreek. Die literatuurstudie word afgesluit met die inpak van menslikehulpbronbestuur op kennissoepelheid, wat ook die verwysings na die leerorganisasie en kompleksietydsteorie insluit. Die metodologie van die intervensie, wat uit drie fases bestaan, volg daarna. Die resultate van die drie fases word vervolgens aangebied. Slegs gedeelte welslae is behaal met die verbetering van die menslike doeltreffendheid ten opsigte van elektroniese dokumentbestuur. Die klient besluit egter om nie voort te gaan om die huidige sisteem te gebruik nie.

  3. Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

    Science.gov (United States)

    Tan, Yih Horng; Davis, Jason A.; Fujikawa, Kohki; Ganesh, N. Vijaya; Demchenko, Alexei V.

    2012-01-01

    Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N2 gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C18-SH (coverage of 2.94 × 1014 molecules cm−2 based from the decomposition of the C18-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the ‘C’ parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology. PMID:22822294

  4. Electronic Safety Resource Tools -- Supporting Hydrogen and Fuel Cell Commercialization

    Energy Technology Data Exchange (ETDEWEB)

    Barilo, Nick F.

    2014-09-29

    The Pacific Northwest National Laboratory (PNNL) Hydrogen Safety Program conducted a planning session in Los Angeles, CA on April 1, 2014 to consider what electronic safety tools would benefit the next phase of hydrogen and fuel cell commercialization. A diverse, 20-person team led by an experienced facilitator considered the question as it applied to the eight most relevant user groups. The results and subsequent evaluation activities revealed several possible resource tools that could greatly benefit users. The tool identified as having the greatest potential for impact is a hydrogen safety portal, which can be the central location for integrating and disseminating safety information (including most of the tools identified in this report). Such a tool can provide credible and reliable information from a trustworthy source. Other impactful tools identified include a codes and standards wizard to guide users through a series of questions relating to application and specific features of the requirements; a scenario-based virtual reality training for first responders; peer networking tools to bring users from focused groups together to discuss and collaborate on hydrogen safety issues; and a focused tool for training inspectors. Table ES.1 provides results of the planning session, including proposed new tools and changes to existing tools.

  5. Controlling user access to electronic resources without password

    Science.gov (United States)

    Smith, Fred Hewitt

    2015-06-16

    Described herein are devices and techniques for remotely controlling user access to a restricted computer resource. The process includes pre-determining an association of the restricted computer resource and computer-resource-proximal environmental information. Indicia of user-proximal environmental information are received from a user requesting access to the restricted computer resource. Received indicia of user-proximal environmental information are compared to associated computer-resource-proximal environmental information. User access to the restricted computer resource is selectively granted responsive to a favorable comparison in which the user-proximal environmental information is sufficiently similar to the computer-resource proximal environmental information. In at least some embodiments, the process further includes comparing user-supplied biometric measure and comparing it with a predetermined association of at least one biometric measure of an authorized user. Access to the restricted computer resource is granted in response to a favorable comparison.

  6. The Internet School of Medicine: use of electronic resources by medical trainees and the reliability of those resources.

    Science.gov (United States)

    Egle, Jonathan P; Smeenge, David M; Kassem, Kamal M; Mittal, Vijay K

    2015-01-01

    Electronic sources of medical information are plentiful, and numerous studies have demonstrated the use of the Internet by patients and the variable reliability of these sources. Studies have investigated neither the use of web-based resources by residents, nor the reliability of the information available on these websites. A web-based survey was distributed to surgical residents in Michigan and third- and fourth-year medical students at an American allopathic and osteopathic medical school and a Caribbean allopathic school regarding their preferred sources of medical information in various situations. A set of 254 queries simulating those faced by medical trainees on rounds, on a written examination, or during patient care was developed. The top 5 electronic resources cited by the trainees were evaluated for their ability to answer these questions accurately, using standard textbooks as the point of reference. The respondents reported a wide variety of overall preferred resources. Most of the 73 responding medical trainees favored textbooks or board review books for prolonged studying, but electronic resources are frequently used for quick studying, clinical decision-making questions, and medication queries. The most commonly used electronic resources were UpToDate, Google, Medscape, Wikipedia, and Epocrates. UpToDate and Epocrates had the highest percentage of correct answers (47%) and Wikipedia had the lowest (26%). Epocrates also had the highest percentage of wrong answers (30%), whereas Google had the lowest percentage (18%). All resources had a significant number of questions that they were unable to answer. Though hardcopy books have not been completely replaced by electronic resources, more than half of medical students and nearly half of residents prefer web-based sources of information. For quick questions and studying, both groups prefer Internet sources. However, the most commonly used electronic resources fail to answer clinical queries more than half

  7. Developing Humanities Collections in the Digital Age: Exploring Humanities Faculty Engagement with Electronic and Print Resources

    Science.gov (United States)

    Kachaluba, Sarah Buck; Brady, Jessica Evans; Critten, Jessica

    2014-01-01

    This article is based on quantitative and qualitative research examining humanities scholars' understandings of the advantages and disadvantages of print versus electronic information resources. It explores how humanities' faculty members at Florida State University (FSU) use print and electronic resources, as well as how they perceive these…

  8. Developing Humanities Collections in the Digital Age: Exploring Humanities Faculty Engagement with Electronic and Print Resources

    Science.gov (United States)

    Kachaluba, Sarah Buck; Brady, Jessica Evans; Critten, Jessica

    2014-01-01

    This article is based on quantitative and qualitative research examining humanities scholars' understandings of the advantages and disadvantages of print versus electronic information resources. It explores how humanities' faculty members at Florida State University (FSU) use print and electronic resources, as well as how they perceive these…

  9. Electronic resource management practical perspectives in a new technical services model

    CERN Document Server

    Elguindi, Anne

    2012-01-01

    A significant shift is taking place in libraries, with the purchase of e-resources accounting for the bulk of materials spending. Electronic Resource Management makes the case that technical services workflows need to make a corresponding shift toward e-centric models and highlights the increasing variety of e-formats that are forcing new developments in the field.Six chapters cover key topics, including: technical services models, both past and emerging; staffing and workflow in electronic resource management; implementation and transformation of electronic resource management systems; the ro

  10. Strategic Planning for Electronic Resources Management: A Case Study at Gustavus Adolphus College

    Science.gov (United States)

    Hulseberg, Anna; Monson, Sarah

    2009-01-01

    Electronic resources, the tools we use to manage them, and the needs and expectations of our users are constantly evolving; at the same time, the roles, responsibilities, and workflow of the library staff who manage e-resources are also in flux. Recognizing a need to be more intentional and proactive about how we manage e-resources, the…

  11. Strategic Planning for Electronic Resources Management: A Case Study at Gustavus Adolphus College

    Science.gov (United States)

    Hulseberg, Anna; Monson, Sarah

    2009-01-01

    Electronic resources, the tools we use to manage them, and the needs and expectations of our users are constantly evolving; at the same time, the roles, responsibilities, and workflow of the library staff who manage e-resources are also in flux. Recognizing a need to be more intentional and proactive about how we manage e-resources, the…

  12. The Relevancy of Graduate Curriculum to Human Resource Professionals' Electronic Communication.

    Science.gov (United States)

    Hoell, Robert C.; Henry, Gordon O.

    2003-01-01

    Electronic communications of human resource professionals and the content of 23 university human resource management courses were categorized using the Human Resource Certification Institute's body of knowledge. Differences between proportion of topics discussed and topics covered in curricula suggest some topics are over- or undertaught.…

  13. 2015 Utilization of Electronic Information Resources in Ramat ...

    African Journals Online (AJOL)

    intensely powerful and has permeated all segments and ... Web (WWW) and the internet to make information more accessible. On the other ... access points on the campus and computer literacy is till .... resources are often faster to consult than.

  14. Remote Electronic Resources and the OPAC: Illustrated by the Unisa Library Experience.

    Science.gov (United States)

    Van der Merwe, Ina; Van Eeden, Welna; Hartzer, Sandra

    This paper describes the Unisa (University of South Africa) Library's experience with cataloging remote electronic resources, including electronic journals, electronic text files, online databases, digital images, Unisa campus Web sites, and mailing list discussions. The first section discusses the decision to add bibliographic references for…

  15. In situ generation and detection of methyl radical by voltammetry

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In persulfate-acetate, dimethyl sulfoxide or tert-butyl alcohol systems, in situ generation and detection of methyl free radical are realized with voltammetry. It includes the following successive processes. The persulfate S2O82- is polarographically reduced via one-electron addition to sulfate radical SO4-., the SO4-. Initiates chain reaction with acetate, dimethyl sulfoxide, or tert-butyl alcohol on the electrode surface to produce a methyl radical, and one-electron reduction of the methyl radical yields its polarographic reduction wave. In comparison with the known techniques such as ultraviolet radiolysis coupling with electron spin resonance, etc., the proposed method is simple, sensitive and selective.

  16. Controlling user access to electronic resources without password

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Fred Hewitt

    2017-08-22

    Described herein are devices and techniques for remotely controlling user access to a restricted computer resource. The process includes obtaining an image from a communication device of a user. An individual and a landmark are identified within the image. Determinations are made that the individual is the user and that the landmark is a predetermined landmark. Access to a restricted computing resource is granted based on the determining that the individual is the user and that the landmark is the predetermined landmark. Other embodiments are disclosed.

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

    Science.gov (United States)

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

    2015-01-15

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

  18. Cyclic voltammetry of fast conducting electrocatalytic films.

    Science.gov (United States)

    Costentin, Cyrille; Savéant, Jean-Michel

    2015-07-15

    In the framework of contemporary energy challenges, cyclic voltammetry is a particularly useful tool for deciphering the kinetics of catalytic films. The case of fast conducting films is analyzed, whether conduction is of the ohmic type or proceeds through rapid electron hopping. The rate-limiting factors are then the diffusion of the substrate in solution and through the film as well as the catalytic reaction itself. The dimensionless combination of the characteristics of these factors allows reducing the number of actual parameters to a maximum of two. The kinetics of the system may then be fully analyzed with the help of a kinetic zone diagram. Observing the variations of the current-potential responses with operational parameters such as film thickness, the potential scan rate and substrate concentration allows a precise assessment of the interplay between these factors and of the values of the rate controlling factors. A series of thought experiments is described in order to render the kinetic analysis more palpable.

  19. Urban Mining and Electrochemistry: Cyclic  Voltammetry Study of Acidic Solutions from  Electronic Wastes (Printed Circuit Boards for  Recovery of Cu, Zn, and Ni

    Directory of Open Access Journals (Sweden)

    Ma. Isabel Reyes‐Valderrama

    2017-02-01

    Full Text Available We report potentiodynamic studies to characterize copper, nickel and zinc leaching solutions from electronic waste. The metals were leached using oxygen and sulfuric acid (pH = 1.5. As is known, reduction potentials are determined using thermodynamics laws, and metal recovery strategies from electronic waste are usually considered according these thermodynamic values. Pourbaix‐type diagrams are not appropriate to plan strategies in electrochemical processing. Therefore, knowledge of electrode potentials for the metal deposit/dissolution process is the basis for the selective recovery planning. For this reason, potentiodynamic studies, specifically cyclic voltammetry, are revealed as a good way to decide the best conditions for the process of electrochemical recovery of metals from electronic waste, which is also cost‐efficient and has no interference from strange ions, such as lead, in this case.

  20. An Evaluation of Electronic Product Design Education Using Hypermedia-Resourced Learning Environments

    Science.gov (United States)

    Page, Tom; Thorsteinsson, Gisli

    2006-01-01

    The work outlined here provides a comprehensive report and formative observations of the development and implementation of hypermedia resources for learning and teaching used in conjunction with a managed learning environment (MLE). These resources are used to enhance teaching and learning of an electronics module in product design at final year…

  1. A Study on Developing Evaluation Criteria for Electronic Resources in Evaluation Indicators of Libraries

    Science.gov (United States)

    Noh, Younghee

    2010-01-01

    This study aimed to improve the current state of electronic resource evaluation in libraries. While the use of Web DB, e-book, e-journal, and other e-resources such as CD-ROM, DVD, and micro materials is increasing in libraries, their use is not comprehensively factored into the general evaluation of libraries and may diminish the reliability of…

  2. Managing Selection for Electronic Resources: Kent State University Develops a New System to Automate Selection

    Science.gov (United States)

    Downey, Kay

    2012-01-01

    Kent State University has developed a centralized system that manages the communication and work related to the review and selection of commercially available electronic resources. It is an automated system that tracks the review process, provides selectors with price and trial information, and compiles reviewers' feedback about the resource. It…

  3. Where Do Electronic Books Fit in the College Research Arsenal of Resources?

    Science.gov (United States)

    Barbier, Patricia

    2007-01-01

    Student use of electronic books has become an accepted supplement to traditional resources. Student use and satisfaction was monitored through an online course discussion board. Increased use of electronic books indicate this service is an accepted supplement to the print book collection.

  4. Where Do Electronic Books Fit in the College Research Arsenal of Resources?

    Science.gov (United States)

    Barbier, Patricia

    2007-01-01

    Student use of electronic books has become an accepted supplement to traditional resources. Student use and satisfaction was monitored through an online course discussion board. Increased use of electronic books indicate this service is an accepted supplement to the print book collection.

  5. Solution voltammetry of 4 nm magnetite iron oxide nanoparticles.

    Science.gov (United States)

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

    2014-07-30

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

  6. MULER: Building an Electronic Resource Management (ERM Solution at York University

    Directory of Open Access Journals (Sweden)

    Aaron August Lupton

    2012-01-01

    Full Text Available Many university libraries now utilize an Electronic Resource Management (ERM system to assist with operations related to electronic resources. An ERM is a relational database containing information such as suppliers, costs, holdings, and renewal dates for electronic resources, both at the database and title levels. While commercial ERM products are widely available, some institutions are custom building their own ERM in- house. This article describes how York University in Toronto, Canada, did just that by building a system called Managing University Library Electronic Resources (MULER. The article details the background and history of how electronic resources were managed pre-MULER; why a new ERM was needed; the planning process; the current and innovative functions of MULER, including integration of MULER data into York University Libraries search and discovery layer, Vufind; subject tagging in MULER; new functions to be added; and lessons learned from the project. Positive and negative implications of choosing an in-house project over paying for a commercial product are also discussed.

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

    Science.gov (United States)

    Messersmith, Stephania J.

    2014-01-01

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

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

    Science.gov (United States)

    Messersmith, Stephania J.

    2014-01-01

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

  9. The National Site Licensing of Electronic Resources: An Institutional Perspective

    Directory of Open Access Journals (Sweden)

    Xiaohua Zhu

    2011-06-01

    Full Text Available While academic libraries in most countries are struggling to negotiate with publishers and vendors individually or collaboratively via consortia, a few countries have experimented with a different model, national site licensing (NSL. Because NSL often involves government and large-scale collaboration, it has the potential to solve many problems in the complex licensing world. However, not many nations have adopted it. This study uses historical research approach and the comparative case study research method to explore the seemingly low level of adoption. The cases include the Canadian National Site Licensing Project (CNSLP, the United Kingdom’s National Electronic Site Licensing Initiative (NESLI, and the United States, which has not adopted NSL. The theoretical framework guiding the research design and data collection is W. Richard Scott’s institutional theory, which utilizes three supporting pillars—regulative, normative, and cultural-cognitive—to analyze institutional processes. In this study, the regulative pillar and the normative pillar of NSL adoption— an institutional construction and change—are examined. Data were collected from monographs, research articles, government documents, and relevant websites. Based on the analysis of these cases, a preliminary model is proposed for the adoption of NSL. The factors that support a country’s adoption of NSL include the need for new institutions, a centralized educational policy-making system and funding system, supportive political trends, and the tradition of cooperation. The factors that may prevent a country from adopting NSL include decentralized educational policy and funding, diversity and the large number of institutions, the concern for the “Big Deal,” and the concern for monopoly.

  10. Analytical Study of Usage of Electronic Information Resources at Pharmacopoeial Libraries in India

    Directory of Open Access Journals (Sweden)

    Sunil Tyagi

    2014-02-01

    Full Text Available The objective of this study is to know the rate and purpose of the use of e-resource by the scientists at pharmacopoeial libraries in India. Among other things, this study examined the preferences of the scientists toward printed books and journals, electronic information resources, and pattern of using e-resources. Non-probability sampling specially accidental and purposive technique was applied in the collection of primary data through administration of user questionnaire. The sample respondents chosen for the study consists of principle scientific officer, senior scientific officer, scientific officer, and scientific assistant of different division of the laboratories, namely, research and development, pharmaceutical chemistry, pharmacovigilance, pharmacology, pharmacogonosy, and microbiology. The findings of the study reveal the personal experiences and perceptions they have had on practice and research activity using e-resource. The major findings indicate that of the total anticipated participants, 78% indicated that they perceived the ability to use computer for electronic information resources. The data analysis shows that all the scientists belonging to the pharmacopoeial libraries used electronic information resources to address issues relating to drug indexes and compendia, monographs, drugs obtained through online databases, e-journals, and the Internet sources—especially polices by regulatory agencies, contacts, drug promotional literature, and standards.

  11. Connecting knowledge resources to the veterinary electronic health record: opportunities for learning at point of care.

    Science.gov (United States)

    Alpi, Kristine M; Burnett, Heidi A; Bryant, Sheila J; Anderson, Katherine M

    2011-01-01

    Electronic health records (EHRs) provide clinical learning opportunities through quick and contextual linkage of patient signalment, symptom, and diagnosis data with knowledge resources covering tests, drugs, conditions, procedures, and client instructions. This paper introduces the EHR standards for linkage and the partners-practitioners, content publishers, and software developers-necessary to leverage this possibility in veterinary medicine. The efforts of the American Animal Hospital Association (AAHA) Electronic Health Records Task Force to partner with veterinary practice management systems to improve the use of controlled vocabulary is a first step in the development of standards for sharing knowledge at the point of care. The Veterinary Medical Libraries Section (VMLS) of the Medical Library Association's Task Force on Connecting the Veterinary Health Record to Information Resources compiled a list of resources of potential use at point of care. Resource details were drawn from product Web sites and organized by a metric used to evaluate medical point-of-care resources. Additional information was gathered from questions sent by e-mail and follow-up interviews with two practitioners, a hospital network, two software developers, and three publishers. Veterinarians with electronic records use a variety of information resources that are not linked to their software. Systems lack the infrastructure to use the Infobutton standard that has been gaining popularity in human EHRs. While some veterinary knowledge resources are digital, publisher sites and responses do not indicate a Web-based linkage of veterinary resources with EHRs. In order to facilitate lifelong learning and evidence-based practice, veterinarians and educators of future practitioners must demonstrate to veterinary practice software developers and publishers a clinically-based need to connect knowledge resources to veterinary EHRs.

  12. Improving access to information – defining core electronic resources for research and wellbeing

    Directory of Open Access Journals (Sweden)

    Kristiina Hormia-Poutanen

    2007-11-01

    Full Text Available Research and innovation are listed as the key success factors for the future development of Finnish prosperity and the Finnish economy. The Finnish libraries have developed a scenario to support this vision. University, polytechnic and research institute libraries as well as public libraries have defined the core electronic resources necessary to improve access to information in Finland. The primary aim of this work has been to provide information and justification for central funding for electronic resources to support the national goals. The secondary aim is to help with the reallocation of existing central funds to better support access to information.

  13. Elektronik Bilgi Kaynaklarının Seçimi / Selection of Electronic Information Resources

    Directory of Open Access Journals (Sweden)

    Pınar Al

    2003-04-01

    Full Text Available For many years, library users have used only from the printed media in order to get the information that they have needed. Today with the widespread use of the Web and the addition of electronic information resources to library collections, the use of information in the electronic environment as well as in printed media is started to be used. In time, such types of information resources as, electronic journals, electronic books, electronic encyclopedias, electronic dictionaries and electronic theses have been added to library collections. In this study, selection criteria that can be used for electronic information resources are discussed and suggestions are provided for libraries that try to select electronic information resources for their collections.

  14. Linear Sweep Voltammetry of Adsorbed Neutral Red.

    Science.gov (United States)

    1982-05-01

    E. Creager, G. T. Marks, D. A. Aikens and H. H. Richtol Prepared for Publication in Journal of Electroanalytical Chemistry Rensselaer Polytechnic... Electroanalytical Chemistry It. KEY WORDS (Continue oun reverse side It necessary mid Ideneliy by block ntaibor) Neutral Red, cyclic voltammetry, adsorbed dye 20

  15. Steady state oxygen reduction and cyclic voltammetry

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Karlberg, Gustav; Jaramillo, Thomas;

    2008-01-01

    The catalytic activity of Pt and Pt3Ni for the oxygen reduction reaction is investigated by applying a Sabatier model based on density functional calculations. We investigate the role of adsorbed OH on the activity, by comparing cyclic voltammetry obtained from theory with previously published...

  16. Voltammetry at porous electrodes: A theoretical study

    CERN Document Server

    Barnes, Edward O; Li, Peilin; Compton, Richard G

    2014-01-01

    Theory is presented to simulate both chronoamperometry and cyclic voltammetry at porous electrodes fabricated by means of electro-deposition around spherical templates. A theoretical method to extract heterogeneous rate constants for quasireversible and irreversible systems is proposed by the approximation of decoupling of the diffusion within the porous electrode and of bulk diffusion to the electrode surface.

  17. Anodic Stripping Voltammetry: An Instrumental Analysis Experiment.

    Science.gov (United States)

    Wang, Joseph

    1983-01-01

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

  18. Using Electronic Information Resources Centers by Faculty Members at University Education: Competencies, Needs and Challenges

    Science.gov (United States)

    Abouelenein, Yousri

    2017-01-01

    This study aimed at investigating the factual situation of electronic information resources centers to faculty members at university education. Competencies that faculty members should possess regarding this issue were determined. Also their needs for (scientific research skills and teaching) were assessed. In addition, problems that hinder their…

  19. Localising versus standardising electronic human resource management: complexities and tensions between HRM and IT departments

    NARCIS (Netherlands)

    Tate, Mary; Furtmueller, E.; Wilderom, C.P.M.

    2013-01-01

    In this paper, we provide an analysis of the complexities involved during global e-HRM (Electronic Human Resource Management) implementation. We present findings from a case study on the challenge of global integration versus local responsiveness of e-HRM systems. We take a local site lens, analysin

  20. Use of Electronic Information Resources among Research Scholars in the Islamia University of Bahawalpur, Pakistan

    Science.gov (United States)

    Amjad, Anam; Ahmed, Shamshad; Bin Naeem, Salman

    2013-01-01

    This study examined the use of electronic resources among academic scholars of The Islamia University of Bahawalpur (IUB), Punjab, Pakistan. A quantitative survey was found most convenient and useful for this study. The total population of the study was 169 research students in IUB. The response rate was 79% and 133 utilizable responses were coded…

  1. The Acquisition and Management of Electronic Resources: Can Use Justify Cost?

    Science.gov (United States)

    Koehn, Shona L.; Hawamdeh, Suliman

    2010-01-01

    As library collections increasingly become digital, libraries are faced with many challenges regarding the acquisition and management of electronic resources. Some of these challenges include copyright and fair use, the first-sale doctrine, licensing versus ownership, digital preservation, long-term archiving, and, most important, the issue of…

  2. Thin film voltammetry of metabolic enzymes in rat liver microsomes

    Science.gov (United States)

    Krishnan, Sadagopan; Rusling, James F.

    2007-01-01

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

  3. Differential pulse voltammetry and additive differential pulse voltammetry with solvent polymeric membrane ion sensors.

    Science.gov (United States)

    Ortuño, J A; Serna, C; Molina, A; Gil, A

    2006-12-01

    The ion transfer across the water-solvent polymeric membrane interface is investigated by using a new device based on a modification of a commercial ion-selective electrode body that permits the accommodation of a platinum counter electrode inside the inner filling solution compartment and, therefore, use of a four-electrode potentiostat with ohmic drop compensation. This device is used here to apply two different double potential pulse techniques--differential pulse voltammetry and additive differential pulse voltammetry--which are more advantageous than other voltammetric techniques, such as normal pulse voltammetry or cyclic voltammetry, for the determination of the characteristic electrochemical parameters of the system. This is due to the concurrence of two factors in these double potential pulse techniques, the peak-shaped response together with a considerable reduction of undesirable current contributions.

  4. 电子资源的编目策略%Cataloging Strategies of Electronic Resources

    Institute of Scientific and Technical Information of China (English)

    王亚林

    2012-01-01

    Compared with traditional paper resources, electronic resources have following characteristics which determine different cataloging strategies from paper resources. These characteristics are huge quantity, updating rapidly, coexistence of a variety of manifestations. The source data of electronic resources is usually provided by the database agent. The cataloging of electronic resources is based on the Chapter IX of Anglo-American Cataloging Rules, Library of Congress Rule Interpretations and rules of Cooperative Online Serials. There are two major cataloging methods for electronic resources abroad, they are single record approach and separate record approach. Peking University Library chooses the latter method and batches cataloging automatically using the source data.%电子资源吲传统纸质资源相比,具有数量大、更新快、多种载体表现并行等特点,且大部分出版机构能够提供数据源数据。这些特点决定了.电子资源应采取与纸质文献不同的编目策略。电子资源编日的主要依据是《英美编日条例》的第9章、美国《国会图书馆条例解释》及全美期刊合作编目计划的规定。对于电子资源的编目,国外有单一记录编目法和分散记录编目法。北京大学图书馆采用后者,同时利用数据源数据批舒自动编目。

  5. Cyclic Voltammetry And Linear Sweep Voltammetry Study Of Cyclic Tertiary Amines

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ping; TIAN JinPing; YIN YingWu

    2001-01-01

    @@ Cyclic six membered a-aminonitrile have proved to be very versatile synthetic intermediates and have been widely used in the construction of a large number of indole alkaloids. In order to obtain some information about the mechanisn of electrochemical synthesis of aaminonitrile. Electrochemistry behaviors that include cyclic voltammetry and linear sweep voltammetry of cyclic tertiary amines which including N-benzylpiperidine (NBP), 1-(l-Methoxycarbonyl ethyl) piperidine (MCEP), N-methylcarbonylppiperidine (NMCP), Nethylpiperidine(NEP) was studied.

  6. Cyclic Voltammetry And Linear Sweep Voltammetry Study Of Cyclic Tertiary Amines

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Ping

    2001-01-01

    Cyclic six membered a-aminonitrile have proved to be very versatile synthetic intermediates and have been widely used in the construction of a large number of indole alkaloids. In order to obtain some information about the mechanisn of electrochemical synthesis of aaminonitrile. Electrochemistry behaviors that include cyclic voltammetry and linear sweep voltammetry of cyclic tertiary amines which including N-benzylpiperidine (NBP), 1-(l-Methoxycarbonyl ethyl) piperidine (MCEP), N-methylcarbonylppiperidine (NMCP), Nethylpiperidine(NEP) was studied.……

  7. Power resource management and low-power remote wireless RF electronics

    Science.gov (United States)

    Jannson, Tomasz; Forrester, Thomas; Degrood, Kevin; Lee, Kang; Gans, Eric; Walter, Kevin

    2009-05-01

    Battery power resource management becomes a critical issue in the case of self-powered remote wireless RF electronics, where the basic parameter is time of system operation before battery recharging or battery replacement. In such cases, very often related to physical protection against antitampering (AT), proper theoretical modeling of a battery driven power supply in the context of a given digital electronic system is of utmost importance. Such modeling should include various types of batteries (primary and secondary), various self-discharge processes in different temperatures, and even energy harvesting, the latter to supply power for long-term content, low-power electronic subsystems. In this paper we analyze simple modeling of resource power management, including variations of all of these parameters and energy harvesting.

  8. Voltammetry as a Model for Teaching Chemical Instrumentation.

    Science.gov (United States)

    Gunasingham, H.; Ang, K. P.

    1985-01-01

    Voltammetry is used as a model for teaching chemical instrumentation to chemistry undergraduates at the National University of Singapore. Lists six criteria used to select a successful teaching model and shows how voltammetry satisfies each criterion. (JN)

  9. Electrochemical Studies of 1,4-Bis[2-(2-pyridyl)-vinyl] Benzene and 1,4-Bis[2-(4-pyridyl) vinyl] Benzene Laser Dyes via Cyclic Voltammetry, Convolutive Voltammetry and Digital Simulation Methods

    Institute of Scientific and Technical Information of China (English)

    EL-DALY, Samy A; EL-HALLAG,Ibrahirn S; EBEED, Ezeiny M; GHONEIM, Mohamed M

    2009-01-01

    Electrochemical properties of two diolefinic laser dyes namely 1,4-bis[2-(2-pyddyl)-vinyl] benzene (2PVB) and 1,4-bis[2-(4-pyridyl) vinyl] benzene (4PVB) have been investigated using cyclic voltammetry and convolutive voltammetry combined with digital simulation at a platinum electrode in 0.1 mol/L tetrabutyl ammonium perchlo-rate (TBAP) in the two different solvents acetonitrile (CH3CN) and dimethylformamide (DMF). The species were reduced via consumption of two sequential electrons to form radical anion and dianion. In switching the potential to positive direction, the two compounds were oxidized by loss of one electron, which was followed by a fast isomeri-sation process. The electrode reaction pathway and the electrochemical parameters of the investigated compounds were determined using cyclic voltammetry. The extracted electrochemical parameters were verified and confirmed via digital simulation and convolutive voltammetry methods.

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

    Science.gov (United States)

    Sheth, Disha B; Gratzl, Miklós

    2013-06-01

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

  11. Identifying and evaluating electronic learning resources for use in adult-gerontology nurse practitioner education.

    Science.gov (United States)

    Thompson, Hilaire J; Belza, Basia; Baker, Margaret; Christianson, Phyllis; Doorenbos, Ardith; Nguyen, Huong

    2014-01-01

    Enhancing existing curricula to meet newly published adult-gerontology advanced practice registered nurse (APRN) competencies in an efficient manner presents a challenge to nurse educators. Incorporating shared, published electronic learning resources (ELRs) in existing or new courses may be appropriate in order to assist students in achieving competencies. The purposes of this project were to (a) identify relevant available ELR for use in enhancing geriatric APRN education and (b) to evaluate the educational utility of identified ELRs based on established criteria. A multilevel search strategy was used. Two independent team members reviewed identified ELR against established criteria to ensure utility. Only resources meeting all criteria were retained. Resources were found for each of the competency areas and included formats such as podcasts, Web casts, case studies, and teaching videos. In many cases, resources were identified using supplemental strategies and not through traditional search or search of existing geriatric repositories. Resources identified have been useful to advanced practice educators in improving lecture and seminar content in a particular topic area and providing students and preceptors with additional self-learning resources. Addressing sustainability within geriatric APRN education is critical for sharing of best practices among educators and for sustainability of teaching and related resources. © 2014.

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

    Science.gov (United States)

    Pomeroy, R. S.; And Others

    1989-01-01

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

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

    Science.gov (United States)

    Pomeroy, R. S.; And Others

    1989-01-01

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

  14. Library Electronic Resource Sharing Among Liberal Arts Colleges: ACS Palladian Alliance Project

    Directory of Open Access Journals (Sweden)

    Wenxian Zhang

    1997-03-01

    Full Text Available 無Effective electronic resource sharing is critical to library information services of the 1990s. Explosion of data and increased cost of information force libraries to work together, and technological advancements present the library service profession a platform for resource sharing. The Palladian Alliance Project of the Associated Colleges of the South is designed to provides ACS member institutions an effective means to enhance information access for their faculty and students, and achieve significant cost containment in the years to come.

  15. Availability, Level of Use and Constraints to Use of Electronic Resources by Law Lecturers in Public Universities in Nigeria

    Science.gov (United States)

    Amusa, Oyintola Isiaka; Atinmo, Morayo

    2016-01-01

    (Purpose) This study surveyed the level of availability, use and constraints to use of electronic resources among law lecturers in Nigeria. (Methodology) Five hundred and fifty-two law lecturers were surveyed and four hundred and forty-two responded. (Results) Data analysis revealed that the level of availability of electronic resources for the…

  16. Voltammetry: mathematical modelling and Inverse Problem

    CERN Document Server

    Koshev, N A; Kuzina, V V

    2016-01-01

    We propose the fast semi-analytical method of modelling the polarization curves in the voltammetric experiment. The method is based on usage of the special func- tions and shows a big calculation speed and a high accuracy and stability. Low computational needs of the proposed algorithm allow us to state the set of Inverse Problems of voltammetry for the reconstruction of metal ions concentrations or the other parameters of the electrolyte under investigation.

  17. Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Ammar, Hafedh Belhadj, E-mail: hbelhadjammar@yahoo.fr; Brahim, Mabrouk Ben; Abdelhédi, Ridha; Samet, Youssef

    2016-02-01

    The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH 11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2–4.2 μmol L{sup −1}, with a detection limit of 0.065 μmol L{sup −1}. - Highlights: • SWV for the determination of MTZ • Boron-doped diamond as a new electrochemical sensor • Simple and rapid detection of MTZ • Efficiency of BDD for sensitive determination of MTZ.

  18. Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry.

    Science.gov (United States)

    Ammar, Hafedh Belhadj; Brahim, Mabrouk Ben; Abdelhédi, Ridha; Samet, Youssef

    2016-02-01

    The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2μmolL(-1), with a detection limit of 0.065μmolL(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Potential resource and toxicity impacts from metals in waste electronic devices.

    Science.gov (United States)

    Woo, Seung H; Lee, Dae Sung; Lim, Seong-Rin

    2016-04-01

    As a result of the continuous release of new electronic devices, existing electronic devices are quickly made obsolete and rapidly become electronic waste (e-waste). Because e-waste contains a variety of metals, information about those metals with the potential for substantial environmental impact should be provided to manufacturers, recyclers, and disposers to proactively reduce this impact. This study assesses the resource and toxicity (i.e., cancer, noncancer, and ecotoxicity) potentials of various heavy metals commonly found in e-waste from laptop computers, liquid-crystal display (LCD) monitors, LCD TVs, plasma TVs, color cathode ray tube (CRT) TVs, and cell phones and then evaluates such potentials using life cycle impact-based methods. Resource potentials derive primarily from Cu, Sb, Ag, and Pb. Toxicity potentials derive primarily from Pb, Ni, and Hg for cancer toxicity; from Pb, Hg, Zn, and As for noncancer toxicity; and from Cu, Pb, Hg, and Zn for ecotoxicity. Therefore, managing these heavy metals should be a high priority in the design, recycling, and disposal stages of electronic devices.

  20. Model of e-learning with electronic educational resources of new generation

    Directory of Open Access Journals (Sweden)

    A. V. Loban

    2017-01-01

    Full Text Available Purpose of the article: improving of scientific and methodical base of the theory of the е-learning of variability. Methods used: conceptual and logical modeling of the е-learning of variability process with electronic educational resource of new generation and system analysis of the interconnection of the studied subject area, methods, didactics approaches and information and communication technologies means. Results: the formalization complex model of the е-learning of variability with electronic educational resource of new generation is developed, conditionally decomposed into three basic components: the formalization model of the course in the form of the thesaurusclassifier (“Author of e-resource”, the model of learning as management (“Coordination. Consultation. Control”, the learning model with the thesaurus-classifier (“Student”. Model “Author of e-resource” allows the student to achieve completeness, high degree of didactic elaboration and structuring of the studied material in triples of variants: modules of education information, practical task and control tasks; the result of the student’s (author’s of e-resource activity is the thesaurus-classifier. Model of learning as management is based on the principle of personal orientation of learning in computer environment and determines the logic of interaction between the lecturer and the student when determining the triple of variants individually for each student; organization of a dialogue between the lecturer and the student for consulting purposes; personal control of the student’s success (report generation and iterative search for the concept of the class assignment in the thesaurus-classifier before acquiring the required level of training. Model “Student” makes it possible to concretize the learning tasks in relation to the personality of the student and to the training level achieved; the assumption of the lecturer about the level of training of a

  1. [Use of internet and electronic resources among Spanish intensivist physicians. First national survey].

    Science.gov (United States)

    Gómez-Tello, V; Latour-Pérez, J; Añón Elizalde, J M; Palencia-Herrejón, E; Díaz-Alersi, R; De Lucas-García, N

    2006-01-01

    Estimate knowledge and use habits of different electronic resources in a sample of Spanish intensivists: Internet, E-mail, distribution lists, and use of portable electronic devices. Self-applied questionnaire. A 50-question questionnaire was distributed among Spanish intensivists through the hospital marketing delegates of a pharmaceutical company and of electronic forums. A total of 682 questionnaires were analyzed (participation: 74%). Ninety six percent of those surveyed used Internet individually: 67% admitted training gap. Internet was the second source of clinical consultations most used (61%), slightly behind consultation to colleagues (65%). The pages consulted most were bibliographic databases (65%) and electronic professional journals (63%), with limited use of Evidence Based Medicine pages (19%). Ninety percent of those surveyed used e-mail regularly in the practice of their profession, although 25% admitted that were not aware of its possibilities. The use of E-mail decreased significantly with increase in age. A total of 62% of the intensivists used distribution lists. Of the rest, 42% were not aware of its existence and 32% admitted they had insufficient training to handle them. Twenty percent of those surveyed had portable electronic devices and 64% considered it useful, basically due to its rapid consultation at bedside. Female gender was a negative predictive factor of its use (OR 0.35; 95% CI 0.2-0.63; p=0.0002). A large majority of the Spanish intensivists use Internet and E-mail. E-mail lists and use of portable devices are still underused resources. There are important gaps in training and infrequent use of essential pages. There are specific groups that require directed educational policies.

  2. Review of material recovery from used electric and electronic equipment-alternative options for resource conservation.

    Science.gov (United States)

    Friege, Henning

    2012-09-01

    For waste from electric and electronic equipment, the WEEE Directive stipulates the separate collection of electric and electronic waste. As to new electric and electronic devices, the Restriction of Hazardous Substances (RoHS) Directive bans the use of certain chemicals dangerous for man and environment. From the implementation of the WEEE directive, many unsolved problems have been documented: poor collection success, emission of dangerous substances during collection and recycling, irretrievable loss of valuable metals among others. As to RoHS, data from the literature show a satisfying success. The problems identified in the process can be reduced to some basic dilemmas at the borders between waste management, product policy and chemical safety. The objectives of the WEEE Directive and the specific targets for use and recycling of appliances are not consistent. There is no focus on scarce resources. Extended producer responsibility is not sufficient to guarantee sustainable waste management. Waste management reaches its limits due to problems of implementation but also due to physical laws. A holistic approach is necessary looking at all branch points and sinks in the stream of used products and waste from electric and electronic equipment. This may be done with respect to the general rules for sustainable management of material streams covering the three dimensions of sustainable policy. The relationships between the players in the field of electric and electronic devices have to be taken into account. Most of the problems identified in the implementation process will not be solved by the current amendment of the WEEE Directive.

  3. Aufwand und Nutzen des Electronic Resource Management Systems RMS an der UB Kassel

    Directory of Open Access Journals (Sweden)

    Tobias Pohlmann

    2016-03-01

    The university library of Kassel therefore uses SemperTool’s web-based electronic resource management system RMS. This paper presents the functionality of this system and makes an estimate of the expenditure of work necessary to enter all relevant information about licensed databases, e-book and e-journal packages with the corresponding individual resources. It also describes existing and projected tools for analysis and evaluation, which are decisive for the usefulness of such a system, and concludes with the satisfaction reached at the university library of Kassel. These experiences may help other libraries to decide whether or not to introduce RMS or a comparable system.

  4. Mimicking protein-protein electron transfer: voltammetry of Pseudomonas aeruginosa azurin and the Thermus thermophilus Cu(A) domain at omega-derivatized self-assembled-monolayer gold electrodes.

    Science.gov (United States)

    Fujita, Kyoko; Nakamura, Nobufumi; Ohno, Hiroyuki; Leigh, Brian S; Niki, Katsumi; Gray, Harry B; Richards, John H

    2004-11-03

    Well-defined voltammetric responses of redox proteins with acidic-to-neutral pI values have been obtained on pure alkanethiol as well as on mixed self-assembled-monolayer (SAM) omega-derivatized alkanethiol/gold bead electrodes. Both azurin (P. aeruginosa) (pI = 5.6) and subunit II (Cu(A) domain) of ba(3)-type cytochrome c oxidase (T. thermophilus) (pI = 6.0) exhibit optimal voltammetric responses on 1:1 mixtures of [H(3)C(CH(2))(n)()SH + HO(CH(2))(n)()SH] SAMs. The electron transfer (ET) rate vs distance behavior of azurin and Cu(A) is independent of the omega-derivatized alkanethiol SAM headgroups. Strikingly, only wild-type azurin and mutants containing Trp48 give voltammetric responses: based on modeling, we suggest that electronic coupling with the SAM headgroup (H(3)C- and/or HO-) occurs at the Asn47 side chain carbonyl oxygen and that an Asn47-Cys112 hydrogen bond promotes intramolecular ET to the copper. Inspection of models also indicates that the Cu(A) domain of ba(3)-type cytochrome c oxidase is coupled to the SAM headgroup (H(3)C- and/or HO-) near the main chain carbonyl oxygen of Cys153 and that Phe88 (analogous to Trp143 in subunit II of cytochrome c oxidase from R. sphaeroides) is not involved in the dominant tunneling pathway. Our work suggests that hydrogen bonds from hydroxyl or other proton-donor groups to carbonyl oxygens potentially can facilitate intermolecular ET between physiological redox partners.

  5. ELECTRONIC EDUCATIONAL RESOURCES FOR ONLINE SUPPORT OF MODERN CHEMISTRY CLASSES IN SPECIALIZED SCHOOL

    Directory of Open Access Journals (Sweden)

    Maria D. Tukalo

    2013-09-01

    Full Text Available This article contains material of some modern electronic educational resources that can be used via the Internet to support the modern chemistry classes in specialized school. It was drawn attention to the educational chemical experiments as means of knowledge; simulated key motivational characteristics to enhance students interest for learning subjects, their cognitive and practical activity in the formation of self-reliance and self-creative; commented forecasts for creating of conditions to enhance the creative potential of students in a modern learning environment.

  6. Teachers' Link to Electronic Resources in the Library Media Center: A Local Study of Awareness, Knowledge, and Influence

    Science.gov (United States)

    Williams, Teresa D.; Grimble, Bonnie J.; Irwin, Marilyn

    2004-01-01

    High school students often use online databases and the Internet in the school library media center (SLMC) to complete teachers' assignments. This case study used a survey to assess teachers' awareness of electronic resources, and to determine whether their directions influence student use of these resources in the SLMC. Participants were teachers…

  7. Impact of Knowledge Resources Linked to an Electronic Health Record on Frequency of Unnecessary Tests and Treatments

    Science.gov (United States)

    Goodman, Kenneth; Grad, Roland; Pluye, Pierre; Nowacki, Amy; Hickner, John

    2012-01-01

    Introduction: Electronic knowledge resources have the potential to rapidly provide answers to clinicians' questions. We sought to determine clinicians' reasons for searching these resources, the rate of finding relevant information, and the perceived clinical impact of the information they retrieved. Methods: We asked general internists, family…

  8. Corrosive electrochemistry of jamesonite by cyclic voltammetry

    Institute of Scientific and Technical Information of China (English)

    余润兰; 胡岳华; 邱冠周; 覃文庆

    2004-01-01

    The corrosive electrochemistry of jamesonite was studied by cyclic voltammetry. Every peak in voltammograms was identified through thermodynamic calculation. The results show an irreversible electrode process by the strong adsorption of oxidation elemental sulfur on jamesonite. A deficient-metal and sulfur-rich compound is formed under the potential of 80 mV at pH 6.86. The passive action by elemental sulfur occurs from 80 to 470 mV and S2O23- , SO24- are produced at potential over 470 mV. The anodic peak producing SO24- is inhibited due to the deposition of PbSO4 at higher potential in Na2SO4 solution. The corrosive action of jamesonite becomes strong and the redox characterization similar to PbS, FeS and Sb2 S3 appears at pH 9.18.

  9. Determination of chitosan by cathodic stripping voltammetry.

    Science.gov (United States)

    Lu, Guanghan; Wang, Lirong; Wang, Ruixia; Zeng, Yan; Huang, Xi

    2006-04-01

    A sensitive method for the determination of chitosan (CTS) by cathodic stripping voltammetry is presented. The method exploits a pair of oxidation-reduction peaks of CTS at -0.62 V (vs. SCE) and -0.54 V (vs. SCE), and an enhancement of the peak current of CTS observed in a 0.05 mol l(-1) potassium hydrogenphthalate buffer solution (pH 2.5). The peak current is linear with the concentration of CTS from 5.0 x 10(-7) to 1.5 x 10(-5) g ml(-1), and the detection limit is 1.0 x 10(-7) g ml(-1). We studied the characteristics and the mechanism of the electrode reaction, which proved that this process was diffusion controlled. This method was applied to determine the content of CTS in real samples with satisfactory results.

  10. Reducing Clinical Trial Monitoring Resource Allocation and Costs Through Remote Access to Electronic Medical Records

    Science.gov (United States)

    Uren, Shannon C.; Kirkman, Mitchell B.; Dalton, Brad S.; Zalcberg, John R.

    2013-01-01

    Purpose: With electronic medical records (eMRs), the option now exists for clinical trial monitors to perform source data verification (SDV) remotely. We report on a feasibility study of remote access to eMRs for SDV and the potential advantages of such a process in terms of resource allocation and cost. Methods: The Clinical Trials Unit at the Peter MacCallum Cancer Centre, in collaboration with Novartis Pharmaceuticals Australia, conducted a 6-month feasibility study of remote SDV. A Novartis monitor was granted dedicated software and restricted remote access to the eMR portal of the cancer center, thereby providing an avenue through which perform SDV. Results: Six monitoring visits were conducted during the study period, four of which were performed remotely. The ability to conduct two thirds of the monitoring visits remotely in this complex phase III study resulted in an overall cost saving to Novartis. Similarly, remote monitoring eased the strain on internal resources, particularly monitoring space and hospital computer terminal access, at the cancer center. Conclusion: Remote access to patient eMRs for SDV is feasible and is potentially an avenue through which resources can be more efficiently used. Although this feasibility study involved limited numbers, there is no limit to scaling these processes to any number of patients enrolled onto large clinical trials. PMID:23633977

  11. Electronic theses and dissertations: a review of this valuable resource for nurse scholars worldwide.

    Science.gov (United States)

    Goodfellow, L M

    2009-06-01

    A worldwide repository of electronic theses and dissertations (ETDs) could provide worldwide access to the most up-to-date research generated by masters and doctoral students. Until that international repository is established, it is possible to access some of these valuable knowledge resources. ETDs provide a technologically advanced medium with endless multimedia capabilities that far exceed the print and bound copies of theses and dissertations housed traditionally in individual university libraries. CURRENT USE: A growing trend exists for universities worldwide to require graduate students to submit theses or dissertations as electronic documents. However, nurse scholars underutilize ETDs, as evidenced by perusing bibliographic citation lists in many of the research journals. ETDs can be searched for and retrieved through several digital resources such as the Networked Digital Library of Theses and Dissertations (http://www.ndltd.org), ProQuest Dissertations and Theses (http://www.umi.com), the Australasian Digital Theses Program (http://adt.caul.edu.au/) and through individual university web sites and online catalogues. An international repository of ETDs benefits the community of nurse scholars in many ways. The ability to access recent graduate students' research electronically from anywhere in the world is advantageous. For scholars residing in developing countries, access to these ETDs may prove to be even more valuable. In some cases, ETDs are not available for worldwide access and can only be accessed through the university library from which the student graduated. Public access to university library ETD collections is not always permitted. Nurse scholars from both developing and developed countries could benefit from ETDs.

  12. A preliminary categorization of end-of-life electrical and electronic equipment as secondary metal resources.

    Science.gov (United States)

    Oguchi, Masahiro; Murakami, Shinsuke; Sakanakura, Hirofumi; Kida, Akiko; Kameya, Takashi

    2011-01-01

    End-of-life electrical and electronic equipment (EEE) has recently received attention as a secondary source of metals. This study examined characteristics of end-of-life EEE as secondary metal resources to consider efficient collection and metal recovery systems according to the specific metals and types of EEE. We constructed an analogy between natural resource development and metal recovery from end-of-life EEE and found that metal content and total annual amount of metal contained in each type of end-of-life EEE should be considered in secondary resource development, as well as the collectability of the end-of-life products. We then categorized 21 EEE types into five groups and discussed their potential as secondary metal resources. Refrigerators, washing machines, air conditioners, and CRT TVs were evaluated as the most important sources of common metals, and personal computers, mobile phones, and video games were evaluated as the most important sources of precious metals. Several types of small digital equipment were also identified as important sources of precious metals; however, mid-size information and communication technology (ICT) equipment (e.g., printers and fax machines) and audio/video equipment were shown to be more important as a source of a variety of less common metals. The physical collectability of each type of EEE was roughly characterized by unit size and number of end-of-life products generated annually. Current collection systems in Japan were examined and potentially appropriate collection methods were suggested for equipment types that currently have no specific collection systems in Japan, particularly for video games, notebook computers, and mid-size ICT and audio/video equipment.

  13. From Millennium ERM to Proquest 360 Resource Manager: Implementing a new Electronic Resources Management System ERMS in an International Graduate Research University in Saudi Arabia

    KAUST Repository

    Ramli, Rindra M.

    2017-05-17

    An overview of the Recommendation Study and the subsequent Implementation of a new Electronic Resources Management system ERMS in an international graduate research university in the Kingdom of Saudi Arabia. It covers the timeline, deliverables and challenges as well as lessons learnt by the Project Team.

  14. Graphene electroanalysis: inhibitory effects in the stripping voltammetry of cadmium with surfactant free graphene.

    Science.gov (United States)

    Brownson, Dale A C; Lacombe, Alexandre C; Kampouris, Dimitrios K; Banks, Craig E

    2012-01-21

    We explore the use of surfactant free graphene towards the electroanalytical sensing of cadmium(II) ions via anodic stripping voltammetry. In line with literature methodologies, we modify an electrode substrate which exhibits relatively fast electron transfer with commercially available graphene which is free from surfactants. Surprisingly, we find that graphene reduces the analytical performance and hence inhibits the electrochemical detection of cadmium(II) ions, with calibration plots in model aqueous solutions revealing no advantages of employing graphene in this analytical context.

  15. Electronic tracking of human resource skills and knowledge, just in time training, manageable due diligence

    Energy Technology Data Exchange (ETDEWEB)

    Kolodziej, M.A. [Quick Test International Inc., (Canada). Canadian Technology Human Resource Board; Baker, O. [KeySpan Energy Canada, Calgary, AB (Canada)

    2001-06-01

    KeySpan Energy Canada is in the process of obtaining recognition of various occupational profiles including pipeline operators, inspectors, and field and plant operators from various certifying organizations. The process of allowing individuals to obtain certification is recognized by Canadian Technology Human Resources Board as a step towards national standards for technologists and technicians. Proven competency is a must for workers in todays oil industry in response to increasingly stringent government safety regulations, environmental concerns and high public scrutiny. Quick Test international Inc. has developed a management tool in collaboration with end users at KeySpan Energy Canada. It is an electronic, Internet based competency tool for tracking personal competencies and maintaining continued competency. Response to the tool has been favourable. 2 refs., 4 figs.

  16. [HYGIENIC REGULATION OF THE USE OF ELECTRONIC EDUCATIONAL RESOURCES IN THE MODERN SCHOOL].

    Science.gov (United States)

    Stepanova, M I; Aleksandrova, I E; Sazanyuk, Z I; Voronova, B Z; Lashneva, L P; Shumkova, T V; Berezina, N O

    2015-01-01

    We studied the effect of academic studies with the use a notebook computer and interactive whiteboard on the functional state of an organism of schoolchildren. Using a complex of hygienic and physiological methods of the study we established that regulation of the computer activity of students must take into account not only duration but its intensity either. Design features of a notebook computer were shown both to impede keeping the optimal working posture in primary school children and increase the risk offormation of disorders of vision and musculoskeletal system. There were established the activating influence of the interactive whiteboard on performance activities and favorable dynamics of indices of the functional state of the organism of students under keeping optimal density of the academic study and the duration of its use. There are determined safety regulations of the work of schoolchildren with electronic resources in the educational process.

  17. Medical Image Resource Center--making electronic teaching files from PACS.

    Science.gov (United States)

    Lim, C C Tchoyoson; Yang, Guo Liang; Nowinski, Wieslaw L; Hui, Francis

    2003-12-01

    A picture archive and communications system (PACS) is a rich source of images and data suitable for creating electronic teaching files (ETF). However, the potential for PACS to support nonclinical applications has not been fully realized: at present there is no mechanism for PACS to identify and store teaching files; neither is there a standardized method for sharing such teaching images. The Medical Image Resource Center (MIRC) is a new central image repository that defines standards for data exchange among different centers. We developed an ETF server that retrieves digital imaging and communication in medicine (DICOM) images from PACS, and enables users to create teaching files that conform to the new MIRC schema. We test-populated our ETF server with illustrative images from the clinical case load of the National Neuroscience Institute, Singapore. Together, PACS and MIRC have the potential to benefit radiology teaching and research.

  18. Electronic Human Resource Management (e-HRM of Hotel Business in Phuket

    Directory of Open Access Journals (Sweden)

    Kitimaporn Choochote

    2015-04-01

    Full Text Available This research aims to study the pattern of the electronic human resources management (e-HRM of the hotel business in Phuket. The study is conducted with the implementation of field data and in-depth interview of hotels’ HR managers. In consequence, the study reveals that the hotel business has applied the use of the e-HRM varying in job recruitment (15 percent, employee engagement (55 percent, organizational file structure (10 percent, idea and creativity exchanges (38 percent and assessment system (6 percent. However, considered as 100 percent, the hotel business has not prepared to apply the use of the e-HRM in salary system, learning and training program, welfare allocation and career development.

  19. Using mobile electronic devices to deliver educational resources in developing countries.

    Science.gov (United States)

    Mazal, Jonathan Robert; Ludwig, Rebecca

    2015-01-01

    Developing countries have far fewer trained radiography professionals than developed countries, which exacerbates the limited access to imaging services. The lack of trained radiographers reflects, in part, limited availability of radiographer-specific educational resources. Historically, organizations that provided such resources in the developing world faced challenges related to the limited stock of current materials as well as expenses associated with shipping and delivery. Four mobile electronic devices (MEDs) were loaded with educational content (e-books, PDFs, and digital applications) spanning major radiography topics. The MEDs were distributed to 4 imaging departments in Ghana, India, Nepal, and Nigeria based on evidence of need for radiography-specific resources, as revealed by survey responses. A cost comparison of postal delivery vs digital delivery of educational content was performed. The effectiveness of delivering additional content via Wi-Fi transmission also was evaluated. Feedback was solicited on users' experience with the MEDs as a delivery tool for educational content. An initial average per e-book expense of $30.05, which included the cost of the device, was calculated for the MED delivery method compared with $15.56 for postal delivery of printed materials. The cost of the MED delivery method was reduced to an average of $10.05 for subsequent e-book deliveries. Additional content was successfully delivered via Wi-Fi transmission to all recipients during the 3-month follow-up period. Overall user feedback on the experience was positive, and ideas for enhancing the MED-based method were identified. Using MEDs to deliver radiography-specific educational content appears to be more cost effective than postal delivery of printed materials on a long-term basis. MEDs are more efficient for providing updates to educational materials. Customization of content to department needs, and using projector devices could enhance the usefulness of MEDs for

  20. Anodic stripping voltammetry enhancement by redox magnetohydrodynamics.

    Science.gov (United States)

    Clark, Emily A; Fritsch, Ingrid

    2004-04-15

    The effect of an external magnetic field on linear scan anodic stripping voltammetry (ASV) in solutions of 10(-6)-10(-7) M concentrations of lead, cadmium, and copper at mercury films on glassy carbon electrodes has been investigated. A high concentration of Hg(2+) was added to the analyte solution to induce a large cathodic current during the deposition step. Therefore, a large Lorentz force from the net flux of charge through the magnetic field resulted in convection due to magnetohydrodynamics. The faster delivery of analytes to the mercury film electrode during deposition caused an increase in the anodic stripping peaks. The effect of varying Hg(2+) concentrations (0-60 mM) and magnetic field strengths (0-1.77 T) on the enhancement of the stripping peaks was investigated. Enhancements as large as 129% for peak currents and 167% for peak areas were observed. An enhancement of approximately 100% was observed when 60 mM Fe(3+) replaced high concentrations of Hg(2+). This method of convection exhibits promise for small-volume ASV analysis with possible improved limits of detection and decreased preconcentration times.

  1. Plastics disassembly versus bulk recycling: engineering design for end-of-life electronics resource recovery.

    Science.gov (United States)

    Rios, Pedro; Stuart, Julie Ann; Grant, Ed

    2003-12-01

    Annual plastic flows through the business and consumer electronics manufacturing supply chain include nearly 3 billion lb of high-value engineering plastics derived from petroleum. The recovery of resource value from this stream presents critical challenges in areas of materials identification and recycling process design that demand new green engineering technologies applied together with life cycle assessment and ecological supply chain analysis to create viable plastics-to-plastics supply cycles. The sustainable recovery of potentially high-value engineering plastics streams requires that recyclers either avoid mixing plastic parts or purify later by separating smaller plastic pieces created in volume reduction (shredding) steps. Identification and separation constitute significant barriers in the plastics-to-plastics recycling value proposition. In the present work, we develop a model that accepts randomly arriving electronic products to study scenarios by which a recycler might identify and separate high-value engineering plastics as well as metals. Using discrete eventsimulation,we compare current mixed plastics recovery with spectrochemical plastic resin identification and subsequent sorting. Our results show that limited disassembly with whole-part identification can produce substantial yields in separated streams of recovered engineering thermoplastics. We find that disassembly with identification does not constitute a bottleneck, but rather, with relatively few workers, can be configured to pull the process and thus decrease maximum staging space requirements.

  2. SAGES: a suite of freely-available software tools for electronic disease surveillance in resource-limited settings.

    Directory of Open Access Journals (Sweden)

    Sheri L Lewis

    Full Text Available Public health surveillance is undergoing a revolution driven by advances in the field of information technology. Many countries have experienced vast improvements in the collection, ingestion, analysis, visualization, and dissemination of public health data. Resource-limited countries have lagged behind due to challenges in information technology infrastructure, public health resources, and the costs of proprietary software. The Suite for Automated Global Electronic bioSurveillance (SAGES is a collection of modular, flexible, freely-available software tools for electronic disease surveillance in resource-limited settings. One or more SAGES tools may be used in concert with existing surveillance applications or the SAGES tools may be used en masse for an end-to-end biosurveillance capability. This flexibility allows for the development of an inexpensive, customized, and sustainable disease surveillance system. The ability to rapidly assess anomalous disease activity may lead to more efficient use of limited resources and better compliance with World Health Organization International Health Regulations.

  3. Pulse Voltammetry in Single Cells Using Platinum Microelectrodes

    Science.gov (United States)

    1991-11-22

    ring electrodes [18) in a solution of 1.OxlO’ M H2PtCl6 and 0.5 M H2SO4 and reducing platinum at 0.0 V vs SSCE for a desired deposition time. Cyclic ...E. and the range for Ed in multiple pulse voltammetry can be chosen from examination of voltammograms obtained by cyclic voltammetry or lin-ir sweep... voltametry [3,13]. As pointed out by Sinru et al. [14) the potential and time of each pulse has a direct effect on the nature of the voltammetry

  4. Electrochemical impedance spectroscopy and cyclic voltammetry studies of a proton exchange membrane fuel cell operated at low humidity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Malevich, D. [Fuel Cell Research Centre, Kingston, ON (Canada)

    2007-07-01

    This study investigated water balance issue in polymer electrolyte membrane fuel cells (PEMFCs) using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. Equivalent PEMFC circuits and microporous layers (MPL) were investigated. Bode and Nyquist plots were presented, and the effect of current density on EIS was explored. Membrane resistance, Warburg resistance, and electron transfer resistance was measured. The study also examined hydrogen underpotential deposition on platinum. Cyclic voltammetry was used to develop curves for electrochemically active surfaces and charge transfer resistance of the MPL. Polarization curves for the anode and cathode MPLs were presented along with impedance diagrams for the PEMFC operating at low humidity conditions. tabs., figs.

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

    Science.gov (United States)

    Schultz, Franklin A.

    1979-01-01

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

  6. Impact of Electronic Resources and Usage in Academic Libraries in Ghana: Evidence from Koforidua Polytechnic & All Nations University College, Ghana

    Science.gov (United States)

    Akussah, Maxwell; Asante, Edward; Adu-Sarkodee, Rosemary

    2015-01-01

    The study investigates the relationship between impact of electronic resources and its usage in academic libraries in Ghana: evidence from Koforidua Polytechnic & All Nations University College, Ghana. The study was a quantitative approach using questionnaire to gather data and information. A valid response rate of 58.5% was assumed. SPSS…

  7. Utilization of Electronic Information Resources by Undergraduate Students of University of Ibadan: A Case Study of Social Sciences and Education

    Science.gov (United States)

    Owolabi, Sola; Idowu, Oluwafemi A.; Okocha, Foluke; Ogundare, Atinuke Omotayo

    2016-01-01

    The study evaluated utilization of electronic information resources by undergraduates in the Faculties of Education and the Social Sciences in University of Ibadan. The study adopted a descriptive survey design with a study population of 1872 undergraduates in the Faculties of Education and the Social Sciences in University of Ibadan, from which a…

  8. Human resource requirements for quality-assured electronic data capture of the tuberculosis case register

    Directory of Open Access Journals (Sweden)

    Hoa Nguyen B

    2012-01-01

    Full Text Available Abstract Background The tuberculosis case register is the data source for the reports submitted by basic management units to the national tuberculosis program. Our objective was to measure the data entry time required to complete and double-enter one record, and to estimate the time for the correction of errors in the captured information from tuberculosis case registers in Cambodia and Viet Nam. This should assist in quantifying the additional requirements in human resources for national programs moving towards electronic recording and reporting. Methods Data from a representative sample of tuberculosis case registers from Cambodia and Viet Nam were double-entered and discordances resolved by rechecking the original case register. Computer-generated data entry time recorded the time elapsed between opening of a new record and saving it to disk. Results The dataset comprised 22,732 double-entered records of 11,366 patients (37.1% from Cambodia and 62.9% from Viet Nam. The mean data entry times per record were 97.5 (95% CI: 96.2-98.8 and 66.2 (95% CI: 59.5-73.0 seconds with medians of 90 and 31 s respectively in Cambodia and in Viet Nam. The percentage of records with an error was 6.0% and 39.0% respectively in Cambodia and Viet Nam. Data entry time was inversely associated with error frequency. We estimate that approximately 118-person-hours were required to produce 1,000 validated records. Conclusions This study quantifies differences between two countries for data entry time for the tuberculosis case register and frequencies of data entry errors and suggests that higher data entry speed is partially offset by requiring revisiting more records for corrections.

  9. Use and Cost of Electronic Resources in Central Library of Ferdowsi University Based on E-metrics

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Davarpanah

    2012-07-01

    Full Text Available The purpose of this study was to investigate the usage of electronic journals in Ferdowsi University, Iran based on e-metrics. The paper also aimed to emphasize the analysis of cost-benefit and the correlation between the journal impact factors and the usage data. In this study experiences of Ferdowsi University library on licensing and usage of electronic resources was evaluated by providing a cost-benefit analysis based on the cost and usage statistics of electronic resources. Vendor-provided data were also compared with local usage data. The usage data were collected by tracking web-based access locally, and by collecting vender-provided usage data. The data sources were one-year of vendor-supplied e-resource usage data such as Ebsco, Elsevier, Proquest, Emerald, Oxford and Springer and local usage data collected from the Ferdowsi university web server. The study found that actual usage values differ for vendor-provided data and local usage data. Elsevier has got the highest usage degree in searches, sessions and downloads. Statistics also showed that a small number of journals satisfy significant amount of use while the majority of journals were used less frequent and some were never used at all. The users preferred the PDF rather than HTML format. The data in subject profile suggested that the provided e-resources were best suited to certain subjects. There was no correlation between IF and electronic journal use. Monitoring the usage of e-resources gained increasing importance for acquisition policy and budget decisions. The article provided information about local metrics for the six surveyed vendors/publishers, e.g. usage trends, requests per package, cost per use as related to the scientific specialty of the university.

  10. Analytical possibilities of microelectrode use for stripping voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Matysik, F.M. (Leipzig Univ. (Germany). Dept. of Chemistry); Glaeser, P. (Leipzig Univ. (Germany). Dept. of Chemistry); Werner, G. (Leipzig Univ. (Germany). Dept. of Chemistry)

    1994-07-01

    The analytical utility of microelectrodes for stripping voltammetry is discussed from several points of view. The application of microelectrodes for microanalysis is demonstrated using a novel capillary flow injection system. Heavy metals at [mu]g l[sup -1] concentrations have been determined in [mu]l-samples. The influence of electrode size and convection during the deposition period of anodic stripping voltammetry on the reproducibility of trace metal determination was studied for various types of electrodes. In the case of mercury film microelectrodes, the precision can be improved if the accumulation of the analyte is performed under quiescent conditions. Practical examples of stripping voltammetry with microelectrodes such as copper determination in whisky and trace metal measurements in drinking water are given. (orig.)

  11. Manganese detection in marine sediments: anodic vs. cathodic stripping voltammetry.

    Science.gov (United States)

    Banks, Craig E; Kruusma, Jaanus; Moore, Ryan R; Tomcík, Peter; Peters, Judith; Davis, James; Komorsky-Lovrić, Sebojka; Compton, Richard G

    2005-01-30

    Three different electroanalytical techniques for the detection of manganese in marine sediments are evaluated. The anodic stripping voltammetry of manganese at an in situ bismuth-film-modified boron-doped diamond electrode and cathodic stripping voltammetry at a carbon paste electrode are shown to lack the required sensitivity and reproducibility whereas cathodic stripping voltammetry at a bare boron-doped diamond electrode is shown to be reliable and selective with a limit of detection, from applying a 60s accumulation period of 7.4 x 10(-7)M and a sensitivity of 0.24AM(-1). The method was used to evaluate the manganese content of marine sediments taken from Sibenik, Croatia.

  12. Pulse radiolysis and cyclic voltammetry studies of redox properties of phenothiazine radicals

    Energy Technology Data Exchange (ETDEWEB)

    Madej, Edyta [Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR (United Kingdom)]. E-mail: madej@gci.ac.uk; Wardman, Peter [Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR (United Kingdom)

    2006-09-15

    One-electron transfer equilibria between seven phenothiazines were characterized by pulse radiolysis, producing radical-cations via oxidation by Br{sub 2} {sup .-} or (SCN){sub 2} {sup .-} radicals. The reduction potentials of the phenothiazine radicals were determined by cyclic voltammetry. As an independent check, the redox equilibrium between one phenothiazine and the redox indicator ABTS was investigated. The data establish phenothiazines as useful indicators for radical redox properties. However, there are potential problems of aggregation, additional reactions with Br{sup -}/Br{sub 2} {sup .-} and reactivity of the radicals towards buffers or other nucleophiles.

  13. Electrodeposition of Iridium Oxide by Cyclic Voltammetry: Application of Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Kakooei Saeid

    2014-07-01

    Full Text Available The effects of scan rate, temperature, and number of cycles on the coating thickness of IrOX electrodeposited on a stainless steel substrate by cyclic voltammetry were investigated in a statistical system. The central composite design, combined with response surface methodology, was used to study condition of electrodeposition. All fabricated electrodes were characterized using electrochemical methods. Field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy were performed for IrOX film characterization. Results showed that scan rate significantly affects the thickness of the electrodeposited layer. Also, the number of cycles has a greater effect than temperature on the IrOX thickness.

  14. Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications.

    Science.gov (United States)

    Bertoluzzi, Luca; Badia-Bou, Laura; Fabregat-Santiago, Francisco; Gimenez, Sixto; Bisquert, Juan

    2013-04-18

    A simple model is proposed that allows interpretation of the cyclic voltammetry diagrams obtained experimentally for photoactive semiconductors with surface states or catalysts used for fuel production from sunlight. When the system is limited by charge transfer from the traps/catalyst layer and by detrapping, it is shown that only one capacitive peak is observable and is not recoverable in the return voltage scan. If the system is limited only by charge transfer and not by detrapping, two symmetric capacitive peaks can be observed in the cathodic and anodic directions. The model appears as a useful tool for the swift analysis of the electronic processes that limit fuel production.

  15. Use and User Perception of Electronic Information Resources: A Case Study of Siva Institute of Frontier Technology, India

    Directory of Open Access Journals (Sweden)

    Velmurugan Chandran

    2013-12-01

    Full Text Available The present study aims to explore the use and user perception of electronic resources in Siva Institute of Frontier Technology, India. A total number of 123 users were taken into account for the study through a questionnaire-based survey method. A well-structured questionnaire was designed and distributed to the selected 200 students and staff members. 123 copies of the questionnaires were returned dully filled in and the overall response rate was 61.50 percent. The questionnaire contained both open- and close-ended questions. The collected data were classified, analyzed, and tabulated by using simple statistical methods. This study covers the impact of electronic resources on students and faculty in their academic pursuit.

  16. How Human Resource Professionals Use Electronic Channels to Communicate CSR : A case study focused on Solvay's French industrial sites

    OpenAIRE

    Fournet, Clara; Pauly, Marissa

    2015-01-01

    Corporate Social Responsibility (CSR) has become a large concern for many companies with the rise of globalization. Oftentimes, companies are encouraged to communicate CSR externally, but not internally. This research focuses upon the internal communication of CSR, specifically how Human Resource (HR) professionals use electronic channels to communicate to employees. The scope of this research is focused solely upon HR professionals within Solvay’s French industrial sites, which produce chemi...

  17. Challenges in the implementation of an electronic surveillance system in a resource-limited setting: Alerta, in Peru

    Directory of Open Access Journals (Sweden)

    Soto Giselle

    2008-11-01

    Full Text Available Abstract Background Infectious disease surveillance is a primary public health function in resource-limited settings. In 2003, an electronic disease surveillance system (Alerta was established in the Peruvian Navy with support from the U.S. Naval Medical Research Center Detachment (NMRCD. Many challenges arose during the implementation process, and a variety of solutions were applied. The purpose of this paper is to identify and discuss these issues. Methods This is a retrospective description of the Alerta implementation. After a thoughtful evaluation according to the Centers for Disease Control and Prevention (CDC guidelines, the main challenges to implementation were identified and solutions were devised in the context of a resource-limited setting, Peru. Results After four years of operation, we have identified a number of challenges in implementing and operating this electronic disease surveillance system. These can be divided into the following categories: (1 issues with personnel and stakeholders; (2 issues with resources in a developing setting; (3 issues with processes involved in the collection of data and operation of the system; and (4 issues with organization at the central hub. Some of the challenges are unique to resource-limited settings, but many are applicable for any surveillance system. For each of these challenges, we developed feasible solutions that are discussed. Conclusion There are many challenges to overcome when implementing an electronic disease surveillance system, not only related to technology issues. A comprehensive approach is required for success, including: technical support, personnel management, effective training, and cultural sensitivity in order to assure the effective deployment of an electronic disease surveillance system.

  18. Tracking the Flow of Resources in Electronic Waste - The Case of End-of-Life Computer Hard Disk Drives.

    Science.gov (United States)

    Habib, Komal; Parajuly, Keshav; Wenzel, Henrik

    2015-10-20

    Recovery of resources, in particular, metals, from waste flows is widely seen as a prioritized option to reduce their potential supply constraints in the future. The current waste electrical and electronic equipment (WEEE) treatment system is more focused on bulk metals, where the recycling rate of specialty metals, such as rare earths, is negligible compared to their increasing use in modern products, such as electronics. This study investigates the challenges in recovering these resources in the existing WEEE treatment system. It is illustrated by following the material flows of resources in a conventional WEEE treatment plant in Denmark. Computer hard disk drives (HDDs) containing neodymium-iron-boron (NdFeB) magnets were selected as the case product for this experiment. The resulting output fractions were tracked until their final treatment in order to estimate the recovery potential of rare earth elements (REEs) and other resources contained in HDDs. The results further show that out of the 244 kg of HDDs treated, 212 kg comprising mainly of aluminum and steel can be finally recovered from the metallurgic process. The results further demonstrate the complete loss of REEs in the existing shredding-based WEEE treatment processes. Dismantling and separate processing of NdFeB magnets from their end-use products can be a more preferred option over shredding. However, it remains a technological and logistic challenge for the existing system.

  19. The impact of electronic healthcare associated infection surveillance software on infection prevention resources: A systematic review of the literature.

    Science.gov (United States)

    Russo, Philip L; Shaban, Ramon Z; MacBeth, Deborough; Carter, Abigail; Mitchell, Brett G

    2017-09-08

    Surveillance of healthcare-associated infections is fundamental for infection prevention. The methods and practices for surveillance have evolved as technology becomes more advanced. The availability of electronic surveillance software (ESS) has increased, and yet adoption of ESS is slow. It is argued that ESS deliver savings through automation, particularly in terms of human resourcing and infection prevention (IP) staff time. This paper describes the findings of a systematic review on the impact of ESS on IP resources. A systematic search was conducted of electronic databases Medline and the Cumulative Index to Nursing and Allied Health Literature published between 1st January 2006 and 31(st) December 2016 with analysis using Newcastle-Ottawa Scale. 2832 articles were reviewed of which 16 studies met the inclusion criteria. IP resources were identified as time undertaken on surveillance. A reduction in IP staff time to undertake surveillance was demonstrated in 13 studies. The reduction proportion ranged from 12.5% - 98.4% (mean 73.9%). The remaining three did not allow for any estimation of the effect in terms of IP staff time. None of the studies demonstrated an increase in IP staff time. The results of this review demonstrate that adopting ESS yield considerable dividends in IP staff time relating to data collection and case ascertainment whilst maintaining high levels of sensitivity and specificity. This has the potential to enable reinvestment into other components of IP to maximise efficient use of scare IP resources. Copyright © 2017. Published by Elsevier Ltd.

  20. HELP (INFORMATION ELECTRONIC RESOURCE "CHRONICLE OF ONU: DATES, FACTS, EVENTS": HISTORY OF UNIVERSITY IN INFORMATION SPACE

    Directory of Open Access Journals (Sweden)

    А. М. Гавриленко

    2016-03-01

    Object of research is the help information resource "The chronicle of the Odessa national university of I. I. Mechnikov: dates, facts, events". The main objective of our article – to state the main methodological bases of creation of information resource. One of advantages of information resource is possibility of continuous updating and replenishment by new information. Main objective of creation of this information resource is systematization of material on stories of the Odessa national university of I. I. Mechnikov from the date of his basis to the present, ensuring interactive access to information on the main dates, the most significant events in life of university. The base of research are sources on the history of university, chronology of historical development, formation of infrastructure, cadres and scientific researches. In information resource the main stages of development, functioning and transformation of the Odessa University are analyzed, information on its divisions is collected. For creation of this information resource in Scientific library the method of work was developed, the main selection criteria of data are allocated. This information resource have practical value for all who is interested in history of university, historians, scientists-researchers of history of science and the city of Odessa.

  1. Hitchhiker's Guide to Voltammetry: Acute and Chronic Electrodes for in Vivo Fast-Scan Cyclic Voltammetry.

    Science.gov (United States)

    Rodeberg, Nathan T; Sandberg, Stefan G; Johnson, Justin A; Phillips, Paul E M; Wightman, R Mark

    2017-02-15

    Fast-scan cyclic voltammetry (FSCV) has been used for over 20 years to study rapid neurotransmission in awake and behaving animals. These experiments were first carried out with carbon-fiber microelectrodes (CFMs) encased in borosilicate glass, which can be inserted into the brain through micromanipulators and guide cannulas. More recently, chronically implantable CFMs constructed with small diameter fused-silica have been introduced. These electrodes can be affixed in the brain with minimal tissue response, which permits longitudinal measurements of neurotransmission in single recording locations during behavior. Both electrode designs have been used to make novel discoveries in the fields of neurobiology, behavioral neuroscience, and psychopharmacology. The purpose of this Review is to address important considerations for the use of FSCV to study neurotransmitters in awake and behaving animals, with a focus on measurements of striatal dopamine. Common issues concerning experimental design, data collection, and calibration are addressed. When necessary, differences between the two methodologies (acute vs chronic recordings) are discussed. The topics raised in this Review are particularly important as the field moves beyond dopamine toward new neurochemicals and brain regions.

  2. Effect of Access to an Electronic Medical Resource on Performance Characteristics of a Certification Examination: A Randomized Controlled Trial.

    Science.gov (United States)

    Lipner, Rebecca S; Brossman, Bradley G; Samonte, Kelli M; Durning, Steven J

    2017-09-05

    Electronic resources are increasingly used in medical practice. Their use during high-stakes certification examinations has been advocated by many experts, but whether doing so would affect the capacity to differentiate between high and low abilities is unknown. To determine the effect of electronic resources on examination performance characteristics. Randomized controlled trial. Medical certification program. 825 physicians initially certified by the American Board of Internal Medicine (ABIM) who passed the Internal Medicine Certification examination or sat for the Internal Medicine Maintenance of Certification (IM-MOC) examination in 2012 to 2015. Participants were randomly assigned to 1 of 4 conditions: closed book using typical or additional time, or open book (that is, UpToDate [Wolters Kluwer]) using typical or additional time. All participants took the same modified version of the IM-MOC examination. Primary outcomes included item difficulty (how easy or difficult the question was), item discrimination (how well the question differentiated between high and low abilities), and average question response time. Secondary outcomes included examination dimensionality (that is, the number of factors measured) and test-taking strategy. Item response theory was used to calculate question characteristics. Analysis of variance compared differences among conditions. Closed-book conditions took significantly less time than open-book conditions (mean, 79.2 seconds [95% CI, 78.5 to 79.9 seconds] vs. 110.3 seconds [CI, 109.2 to 111.4 seconds] per question). Mean discrimination was statistically significantly higher for open-book conditions (0.34 [CI, 0.32 to 0.35] vs. 0.39 [CI, 0.37 to 0.41] per question). A strong single dimension showed that the examination measured the same factor with or without the resource. Only 1 electronic resource was evaluated. Inclusion of an electronic resource with time constraints did not adversely affect test performance and did not change

  3. Understanding intention to use electronic information resources: A theoretical extension of the technology acceptance model (TAM).

    Science.gov (United States)

    Tao, Donghua

    2008-11-06

    This study extended the Technology Acceptance Model (TAM) by examining the roles of two aspects of e-resource characteristics, namely, information quality and system quality, in predicting public health students' intention to use e-resources for completing research paper assignments. Both focus groups and a questionnaire were used to collect data. Descriptive analysis, data screening, and Structural Equation Modeling (SEM) techniques were used for data analysis. The study found that perceived usefulness played a major role in determining students' intention to use e-resources. Perceived usefulness and perceived ease of use fully mediated the impact that information quality and system quality had on behavior intention. The research model enriches the existing technology acceptance literature by extending TAM. Representing two aspects of e-resource characteristics provides greater explanatory information for diagnosing problems of system design, development, and implementation.

  4. Building and Managing Electronic Resources in Digital Era in India with Special Reference to IUCAA and NIV, Pune: A Comparative Case Study

    Science.gov (United States)

    Sahu, H. K.; Singh, S. N.

    2015-04-01

    This paper discusses and presents a comparative case study of two libraries in Pune, India, Inter-University Centre for Astronomy and Astrophysics and Information Centre and Library of National Institute of Virology (Indian Council of Medical Research). It compares how both libraries have managed their e-resource collections, including acquisitions, subscriptions, and consortia arrangements, while also developing a collection of their own resources, including pre-prints and publications, video lectures, and other materials in an institutional repository. This study illustrates how difficult it is to manage electronic resources in a developing country like India, even though electronic resources are used more than print resources. Electronic resource management can be daunting, but with a systematic approach, various problems can be solved, and use of the materials will be enhanced.

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

    Science.gov (United States)

    Masek, Anna; Chrzescijanska, Ewa; Zaborski, Marian

    2014-04-01

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

  6. Print and Electronic Resources: Usage Statistics at Guru Gobind Singh Indraprastha University Library

    Science.gov (United States)

    Kapoor, Kanta

    2010-01-01

    Purpose: The purpose of this paper is to quantify the use of electronic journals in comparison with the print collections in the Guru Gobind Singh Indraprastha University Library. Design/methodology/approach: A detailed analysis was made of the use of lending services, the Xerox facility and usage of electronic journals such as Science Direct,…

  7. Print and Electronic Resources: Usage Statistics at Guru Gobind Singh Indraprastha University Library

    Science.gov (United States)

    Kapoor, Kanta

    2010-01-01

    Purpose: The purpose of this paper is to quantify the use of electronic journals in comparison with the print collections in the Guru Gobind Singh Indraprastha University Library. Design/methodology/approach: A detailed analysis was made of the use of lending services, the Xerox facility and usage of electronic journals such as Science Direct,…

  8. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry

    DEFF Research Database (Denmark)

    Alatraktchi, Fatima AlZahra'a; Andersen, Sandra Breum; Johansen, Helle Krogh;

    2016-01-01

    method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between -1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58-0.82 V that is unaffected by other redox-active interferents...

  9. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry

    DEFF Research Database (Denmark)

    Al Atraktchi, Fatima Al-Zahraa; Breum Andersen, Sandra; Johansen, Helle Krogh;

    2016-01-01

    method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between –1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58–0.82 V that is unaffected by other redox-active interferents...

  10. Differential cyclic voltammetry for selective and amplified detection

    NARCIS (Netherlands)

    Megen, M.J.J; Odijk, M.; Wiedemair, J.; Olthuis, W.; Berg, van den A.

    2012-01-01

    We propose to combine two existing electrochemical techniques, cyclic voltammetry (CV) and redox cycling (RC), in order to obtain amplified and selective detection of redox active species. This combination is achieved by applying CV waveforms to two electrodes spaced 1.20 mu m apart, with one of the

  11. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry

    DEFF Research Database (Denmark)

    Alatraktchi, Fatima AlZahra'a; Andersen, Sandra Breum; Johansen, Helle Krogh

    2016-01-01

    method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between -1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58-0.82 V that is unaffected by other redox-active interferents...

  12. Differential cyclic voltammetry for selective and amplified detection

    NARCIS (Netherlands)

    van Megen, M.J.J.; Odijk, Mathieu; Wiedemair, Justyna; Olthuis, Wouter; van den Berg, Albert

    2012-01-01

    We propose to combine two existing electrochemical techniques, cyclic voltammetry (CV) and redox cycling (RC), in order to obtain amplified and selective detection of redox active species. This combination is achieved by applying CV waveforms to two electrodes spaced 1.20 mu m apart, with one of the

  13. A Cyclic Voltammetry Experiment for the Instrumental Analysis Laboratory.

    Science.gov (United States)

    Baldwin, Richard P.; And Others

    1984-01-01

    Background information and procedures are provided for experiments that illustrate the nature of cyclic voltammetry and its application in the characterization of organic electrode processes. The experiments also demonstrate the concepts of electrochemical reversibility and diffusion-controlled mass transfer. (JN)

  14. A Cyclic Voltammetry Experiment for the Instrumental Analysis Laboratory.

    Science.gov (United States)

    Baldwin, Richard P.; And Others

    1984-01-01

    Background information and procedures are provided for experiments that illustrate the nature of cyclic voltammetry and its application in the characterization of organic electrode processes. The experiments also demonstrate the concepts of electrochemical reversibility and diffusion-controlled mass transfer. (JN)

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

    Science.gov (United States)

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

    1977-01-01

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

  16. Intention to use and actual use of electronic information resources: further exploring Technology Acceptance Model (TAM).

    Science.gov (United States)

    Tao, Donghua

    2009-11-14

    Following up a previous study that examined public health students' intention to use e-resources for completing research paper assignments, the present study proposed two models to investigate whether or not public health students actually used the e-resources they intended to use and whether or not the determinants of intention to use predict actual use of e-resources. Focus groups and pre- and post-questionnaires were used to collect data. Descriptive analysis, data screening, and Structural Equation Modeling (SEM) techniques were used for data analysis. The study found that the determinants of intention-to-use significantly predict actual use behavior. Direct impact of perceived usefulness and indirect impact of perceived ease of use to both behavior intention and actual behavior indicated the importance of ease of use at the early stage of technology acceptance. Non-significant intention-behavior relationship prompted thoughts on the measurement of actual behavior and multidimensional characteristics of the intention construct.

  17. MendelWeb: An Electronic Science/Math/History Resource for the WWW.

    Science.gov (United States)

    Blumberg, Roger B.

    This paper describes a hypermedia resource, called MendelWeb that integrates elementary biology, discrete mathematics, and the history of science. MendelWeb is constructed from Gregor Menders 1865 paper, "Experiments in Plant Hybridization". An English translation of Mendel's paper, which is considered to mark the birth of classical and…

  18. QR Codes as Finding Aides: Linking Electronic and Print Library Resources

    Science.gov (United States)

    Kane, Danielle; Schneidewind, Jeff

    2011-01-01

    As part of a focused, methodical, and evaluative approach to emerging technologies, QR codes are one of many new technologies being used by the UC Irvine Libraries. QR codes provide simple connections between print and virtual resources. In summer 2010, a small task force began to investigate how QR codes could be used to provide information and…

  19. Electronic resources at the University of Sharjah medical library: an investigation of students' information-seeking behavior.

    Science.gov (United States)

    Boumarafi, Behdja

    2010-10-01

    Electronic information is becoming prevalent worldwide, and its use is growing exponentially as more and more users are recognizing the potential that it offers in terms of access and delivery. However, with the introduction of new tools for e-information searching and retrieval, users have to readjust their information-seeking behavior to cope with the corresponding changes. The University of Sharjah library is steadily increasing its investment in e-resources to offer ubiquitous access to the growing body of literature in areas that interest the community it serves. This study reports the findings of a survey conducted to investigate the information-seeking behavior of medical students at the medical library. Results showed evidence of use of e-resources, but they did not explicitly establish that some of the major problems mentioned by participants did hinder the information searches of the respondents. An extensive literature review sets the background for the study.

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

    Science.gov (United States)

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

    2014-10-07

    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

  1. 图书馆电子信息资源利用效果评价研究%Study on Utilization Effect Evaluation of Library Electronic Information Resources

    Institute of Scientific and Technical Information of China (English)

    晋晓强; 贺培风; 何忠印

    2012-01-01

    This paper discusses utilization effect of electronic information resources combining with the characteristics of electronic information resources, makes evaluation system of library electronic information resource utilization effect from three aspects : the library, the users and the data providers, hoping for providing valuable reference for the efficient use of library electronic resources.%本文结合电子信息资源的特性对电子信息资源的利用进行初步探讨,从图书馆、用户和数据服务商三个角度构建图书馆电子信息资源利用效果的评价体系,希望能为图书馆电子信息资源的高效利用提供参考。

  2. An Exploratory study on the use of LibAnswers to Resolve, Track and Monitor Electronic Resources Issues: The KAUST Library experience

    KAUST Repository

    Ramli, Rindra M.

    2017-05-03

    An Exploratory study on KAUST library use of LibAnswers in resolving electronic resources questions received in LibAnswers. It describes the findings of the questions received in LibAnswers. The author made suggestions based on the findings to improve the reference services in responding to e-resources questions.

  3. Eavesdropping on Electronic Guidebooks: Observing Learning Resources in Shared Listening Environments.

    Science.gov (United States)

    Woodruff, Allison; Aoki, Paul M.; Grinter, Rebecca E.; Hurst, Amy; Szymanski, Margaret H.; Thornton, James D.

    This paper describes an electronic guidebook, "Sotto Voce," that enables visitors to share audio information by eavesdropping on each others guidebook activity. The first section discusses the design and implementation of the guidebook device, key aspects of its user interface, the design goals for the audio environment, the eavesdropping…

  4. Electronic Resources in a Next-Generation Catalog: The Case of WorldCat Local

    Science.gov (United States)

    Shadle, Steve

    2009-01-01

    In April 2007, the University of Washington Libraries debuted WorldCat Local (WCL), a localized version of the WorldCat database that interoperates with a library's integrated library system and fulfillment services to provide a single-search interface for a library's physical and electronic content. This brief will describe how WCL incorporates a…

  5. Equalizing Access to Electronic Networked Resources: A Model for Rural Libraries in the United States.

    Science.gov (United States)

    Senkevitch, Judith J.; Wolfram, Dietmar

    1994-01-01

    Provides an overview of the current state of networking technology in rural libraries and describes a model for educating rural librarians in accessing electronic networks. Topics discussed include information needs in rural libraries; telecommunications technology access in rural areas; and examples of services to enhance information access.…

  6. Differential Pulse Anodic Stripping Voltammetry for Mercury Determination

    OpenAIRE

    2015-01-01

    In the present work voltammetric investigations have been performed on HgCl2 aqueous solutions prepared from a Cz 9024 reagent. Carbon paste electrode (CPE), eriochrome black T modified carbon paste electrode (MCPE/EBT) and KCl 1M as background electrolyte, were involved within the experimental procedures. Cyclic voltammetry (CV) has been performed in order to compare the behaviour of the two electrodes in both K3[Fe(CN)6] and mercury calibration aqueous solution. Differential pulse anodic st...

  7. New Cyclic Voltammetry Method for Examining Phase Transitions: Simulated Results

    OpenAIRE

    2006-01-01

    We propose a new experimental technique for cyclic voltammetry, based on the first-order reversal curve (FORC) method for analysis of systems undergoing hysteresis. The advantages of this electrochemical FORC (EC-FORC) technique are demonstrated by applying it to dynamical models of electrochemical adsorption. The method can not only differentiate between discontinuous and continuous phase transitions, but can also quite accurately recover equilibrium behavior from dynamic analysis of systems...

  8. Surface Catalytic Mechanism in Square-Wave Voltammetry

    OpenAIRE

    Mirceski, Valentin; Gulaboski, Rubin

    2001-01-01

    A pseudo-first-order catalytic mechanism in which both reactant and product of the redox reaction are strongly immobilized on the electrode surface is theoretically analyzed under conditions of square-wave voltammetry (SWV). A mathematical procedure is developed for diffusionless conditions. The relationships between the properties of the voltammetric response and both the kinetic parameters of the redox reaction and the parameters of the excitement signal are studied. The phenomenon...

  9. Determination of ziram in vegetable samples by square wave voltammetry

    Institute of Scientific and Technical Information of China (English)

    Ping Qiu; Yong Nian Ni

    2008-01-01

    The electrochemical behaviour and electrode reaction mechanism of ziram (zinc-dimethyl dithiocarbamate) on a hanging mercury drop electrode were investigated in Britton-Robinson (B-R) buffer by using cyclic and square wave voltammetry (SWV).Based on these studies a voltammetric method for determination of ziram was developed and applied to determine the ziram in synthetic and spiked vegetable samples,satisfactory results were obtained in both eases.

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

    Science.gov (United States)

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

    2011-07-01

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

  11. Quantification of the Vasoactive Agent Buflomedil HCl in Pharmaceutical Formulation and Human Serum by Stripping Voltammetry and Liquid Chromatography.

    Science.gov (United States)

    El-Desoky, Hanaa S; Ghoneim, Mohamed M; Abdel-Galeil, Mohamed M

    2010-06-01

    Buflomedil HCl, was reduced at the mercury electrode in buffered solutions of various pH values (2-11) via a single 2-electron irreversible step corresponding to reduction of its C=O double bond. Buflomedil HCl has interfacial adsorptive behavior onto the mercury electrode surface and a monolayer surface coverage of 2.37 × 10-10 mol cm-2 was estimated. Each adsorbed buflomedil HCl molecule was found to occupy an area of 0.69 nm2 onto the HMDE surface. Differential-pulse (DP), liner-sweep (LS) and square-wave (SW) adsorptive cathodic stripping voltammetry (AdCSV) methods were described for its determination in the bulk form. The sensitivity of the described electro-analytical methods increases in the direction: DP-AdCSV voltammetry method is much more sensitive than the described chromatographic one. However the described chromatographic method is substantially simpler, faster and more sensitive than the previously reported HPLC methods.

  12. Poly(glutamic acid) nanofibre modified glassy carbon electrode: Characterization by atomic force microscopy, voltammetry and electrochemical impedance

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daniela Pereira; Zanoni, Maria Valnice Boldrin; Bergamini, Marcio Fernando [Departamento de Quimica Analitica, Instituto de Quimica, Universidade Estadual Paulista, Caixa Postal 355, 14800-900 Araraquara, S.P. (Brazil); Chiorcea-Paquim, Ana-Maria; Diculescu, Victor Constantin [Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra (Portugal); Oliveira Brett, Ana-Maria [Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra (Portugal)], E-mail: brett@ci.uc.pt

    2008-04-20

    Glassy carbon electrodes (GCE) were modified with poly(glutamic acid) acid films prepared using three different procedures: glutamic acid monomer electropolymerization (MONO), evaporation of poly(glutamic acid) (PAG) and evaporation of a mixture of poly(glutamic acid)/glutaraldehyde (PAG/GLU). All three films showed good adherence to the electrode surface. The performance of the modified GCE was investigated by cyclic voltammetry and differential pulse voltammetry, and the films were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The three poly(glutamic acid) modified GCEs were tested using the electrochemical oxidation of ascorbic acid and a decrease of the overpotential and the improvement of the oxidation peak current was observed. The PAG modified electrode surfaces gave the best results. AFM morphological images showed a polymeric network film formed by well-defined nanofibres that may undergo extensive swelling in solution, allowing an easier electron transfer and higher oxidation peaks.

  13. Preference and Use of Electronic Information and Resources by Blind/Visually Impaired in NCR Libraries in India

    Directory of Open Access Journals (Sweden)

    Shailendra Kumar

    2013-06-01

    Full Text Available This paper aims to determine the preference and use of electronic information and resources by blind/visually impaired users in the leading National Capital Region (NCR libraries of India. Survey methodology has been used as the basic research tool for data collection with the help of questionnaires. The 125 in total users surveyed in all the five libraries were selected randomly on the basis of willingness of the users with experience of working in digital environments to participate in the survey. The survey results were tabulated and analyzed with descriptive statistics methods using Excel software and 'Stata version 11'. The findings reveal that ICT have a positive impact in the lives of people with disabilities as it helps them to work independently and increases the level of confidence among them. The Internet is the most preferred medium of access to information among the majority of blind/visually impaired users. The 'Complexity of content available on the net' is found as the major challenge faced during Internet use by blind users of NCR libraries. 'Audio books on CDs/DVDs and DAISY books' are the most preferred electronic resources among the majority of blind/visually impaired users. This study will help the library professionals and organizations/institutions serving people with disabilities to develop effective library services for blind/visually impaired users in the digital environment on the basis of findings on information usage behavior in the study.

  14. Electrochemical Studies of Betti Base and Its Copper(II Complex by Cyclic and Elimination Voltammetry

    Directory of Open Access Journals (Sweden)

    Shardul Bhatt

    2013-01-01

    Full Text Available The electrochemical behavior of Betti base 1-(α-amino benzyl-2-naphthol (BB and its copper(II complex by cyclic and elimination voltammetry (EVLS is reported in the present study. The cyclic voltammetric studies carried out at a glassy carbon working electrode, Ag/Ag+ reference electrode (0.01 M AgNO3 in acetonitrile in DCM at 100 mV/sec, 200 mV/sec, and 400 mV/sec scan rates indicated a preceding chemical oxidation of the adsorbed BB species to form an iminium ion followed by formation of a carbanion via two-step quasireversible reduction. The suggested reaction mechanism has been supported by the elimination voltammetry. The CV and EVLS studies revealed Cu(IIBB complex to undergo a chemical or a surface reaction before electron transfer from the electrode at −0.49 V to form Cu(IBB species. The oxidation of Cu(IBB species has been observed to be CV silent.

  15. Collaboration in electronic resource provision in university libraries: SHEDL, a Scottish case study

    OpenAIRE

    Kidd, T

    2009-01-01

    This case study examines the growth of collaboration among Scottish higher education institutions. Following a summary of the work of the Scottish Confederation of University and Research Libraries (SCURL), more detailed information is provided on collaboration in the fields of acquisition, licensing, selection, and purchasing. Some of the UK background is outlined, relating to NESLi2 in particular, in order to illuminate the options within Scotland. The origins of negotiations on electronic ...

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

    Science.gov (United States)

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

    2012-05-28

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

  17. Internet and electronic resources for inflammatory bowel disease: a primer for providers and patients.

    Science.gov (United States)

    Fortinsky, Kyle J; Fournier, Marc R; Benchimol, Eric I

    2012-06-01

    Patients with inflammatory bowel disease (IBD) are increasingly turning to the Internet to research their condition and engage in discourse on their experiences. This has resulted in new dynamics in the relationship between providers and their patients, with misinformation and advertising potentially presenting barriers to the cooperative patient-provider partnership. This article addresses important issues of online IBD-related health information and social media activity, such as quality, reliability, objectivity, and privacy. We reviewed the medical literature on the quality of online information provided to IBD patients, and summarized the most commonly accessed Websites related to IBD. We also assessed the activity on popular social media sites (such as Facebook, Twitter, and YouTube), and evaluated currently available applications for use by IBD patients and providers on mobile phones and tablets. Through our review of the literature and currently available resources, we developed a list of recommended online resources to strengthen patient participation in their care by providing reliable, comprehensive educational material.

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

    Science.gov (United States)

    Yang, Weiwei; Lai, Rebecca Y

    2011-12-06

    Here we systematically characterized the sensor performance of the stem-loop probe (SLP) and linear probe (LP) electrochemical DNA sensors using alternating current voltammetry (ACV) and cyclic voltammetry (CV), with the goal of generating the set of operational criteria that best suits each sensor architecture, in addition to elucidating the signaling mechanism behind these sensors. Although the LP sensor shows slightly better % signal suppression (SS) upon hybridization with the perfect match target at 10 Hz, our frequency-dependent study suggests that it shows optimal % SS only in a very limited AC frequency range. Similar results are observed in CV studies in which the LP sensor, when compared to the SLP sensor, displays a narrower range of voltammetric scan rates where the optimal % SS can be achieved. More importantly, the difference between the two sensors' performance is particularly pronounced if the change in integrated charge (Q) upon target hybridization, rather than the peak current (I), is measured in CV. The temperature-dependent study further highlights the differences between the two sensors, where the LP sensor, owing to the flexible linear probe architecture, is more readily perturbed by temperature changes. Both SLP and LP sensors, however, show a loss of % SS when operated at elevated temperatures, despite the significant improvement in the hybridization kinetics. In conjunction with the ACV, CV, and temperature-dependent studies, the electron-transfer kinetics study provides further evidence in support of the proposed signaling mechanism of these two sensors, in which the SLP sensor's signaling efficiency and sensor performance is directly linked to the hybridization-induced conformational change in the redox-labeled probe, whereas the performance of the LP sensor relies on the hybridization-induced change in probe dynamics. © 2011 American Chemical Society

  19. Granulometric composition study of mineral resources using opto-electronic devices and Elsieve software system

    Directory of Open Access Journals (Sweden)

    Kaminski Stanislaw

    2016-01-01

    Full Text Available The use of mechanical sieves has a great impact on measurement results because occurrence of anisometric particles causes undercounting the average size. Such errors can be avoided by using opto-electronic measuring devices that enable measurement of particles from 10 μm up to a few dozen millimetres in size. The results of measurement of each particle size fraction are summed up proportionally to its weight with the use of Elsieve software system and for every type of material particle-size distribution can be obtained. The software allows further statistical interpretation of the results. Beam of infrared radiation identifies size of particles and counts them precisely. Every particle is represented by an electronic impulse proportional to its size. Measurement of particles in aqueous suspension that replaces the hydrometer method can be carried out by using the IPS L analyser (range from 0.2 to 600 μm. The IPS UA analyser (range from 0.5 to 2000 μm is designed for measurement in the air. An ultrasonic adapter enables performing measurements of moist and aggregated particles from 0.5 to 1000 μm. The construction and software system allow to determine second dimension of the particle, its shape coefficient and specific surface area. The AWK 3D analyser (range from 0.2 to 31.5 mm is devoted to measurement of various powdery materials with subsequent determination of particle shape. The AWK B analyser (range from 1 to 130 mm measures materials of thick granulation and shape of the grains. The presented method of measurement repeatedly accelerates and facilitates study of granulometric composition.

  20. Application of power spectra patterns in Fourier transform square wave voltammetry to evaluate electrode kinetics of surface-confined proteins.

    Science.gov (United States)

    Fleming, Barry D; Barlow, Nicola L; Zhang, Jie; Bond, Alan M; Armstrong, Fraser A

    2006-05-01

    This paper describes an application of Fourier transform (FT) voltammetry that provides a quantitative evaluation of the electron-transfer kinetics of protein molecules attached to electrode surfaces. The potential waveform applied in these experiments consists of a large-amplitude square wave of frequency f superimposed onto the traditional triangular voltage used in dc cyclic voltammetry. The resultant current-time response, when Fourier transformed into the frequency domain, provides patterns of data at the even harmonic frequencies that arise from nonlinearity in the Faradaic response. These even harmonic contributions are ideally suited for kinetic evaluation of electron-transfer processes because they are highly selective to quasi-reversible behavior (insensitive to reversible or irreversible processes) and almost devoid of background charging current. Inverse FT methods can then be used to provide the wave shapes of the dc as well as the ac voltammetric components and other characteristics employed to detect the level of nonideality present relative to theoretical models based upon noninteracting surface-confined molecules. The new form of data evaluation has been applied to the electron-transfer properties of a typical biological electron carrier, the blue copper protein azurin, immobilized on polycrystalline gold electrodes modified with self-assembled monolayers of different length alkanethiols. Details of the electrode kinetics (rates of electron transfer, dispersion, and charge-transfer coefficients) as a function of alkanethiol, apparent surface coverage, and capacitance are all deduced from the square wave (FT-inverse FT) protocol, and the implications of these findings are considered.

  1. 试论图书馆电子资源与纸本资源的协调发展%The coordinated development of library electronic resources and paper resources

    Institute of Scientific and Technical Information of China (English)

    冯雷

    2012-01-01

      纸本资源和电子资源属于公共图书馆文献资源中两个非常重要的资源类型,纸本资源和电子资源的协调发展在图书馆的可持续发展过程中起着非常重要的作用。本文对如何实现图书馆电子资源和纸本资源之间的协调发展进行了探讨,希望能够为图书馆文献资源的管理提供一些参考。%  The paper and electronic resources are two very important types of literature resources of public libraries, the coordinated development of the paper and electronic resources play a very important role in the sustainable development process of the library. This article discusses how to realize the coordinated development of library electronic resources and paper resources, hope to provide some reference for library literature resource management.

  2. Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor.

    Science.gov (United States)

    Heydari, Hamid; Gholivand, Mohammad B; Abdolmaleki, Abbas

    2016-09-01

    In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. Copyright © 2016. Published by Elsevier B.V.

  3. Quantitative roughness characterization and 3D reconstruction of electrode surface using cyclic voltammetry and SEM image

    Energy Technology Data Exchange (ETDEWEB)

    Dhillon, Shweta; Kant, Rama, E-mail: rkant@chemistry.du.ac.in

    2013-10-01

    Area measurements from cyclic voltammetry (CV) and image from scanning electron microscopy (SEM) are used to characterize electrode statistical morphology, 3D surface reconstruction and its electroactivity. SEM images of single phased materials correspond to two-dimensional (2D) projections of 3D structures, leading to an incomplete characterization. Lack of third dimension information in SEM image is circumvented using equivalence between denoised SEM image and CV area measurements. This CV-SEM method can be used to estimate power spectral density (PSD), width, gradient, finite fractal nature of roughness and local morphology of the electrode. We show that the surface morphological statistical property like distribution function of gradient can be related to local electro-activity. Electrode surface gradient micrographs generated here can provide map of electro-activity sites. Finally, the densely and uniformly packed small gradient over the Pt-surface is the determining criterion for high intrinsic electrode activity.

  4. Electroanalytical Determination of Danofloxacin in Biological Samples Using Square Wave Voltammetry

    Directory of Open Access Journals (Sweden)

    Chirley Vanessa Boone

    2014-10-01

    Full Text Available The voltammetric behavior of danofloxacin (DFX has been studied, in aqueous solution, on a glassy carbon electrode using square wave voltammetry (SWV as electroanalytical technique. After optimization of the experimental conditions, DFX was analyzed in spiked biologic samples using a Britton-Robinson buffer with pH = 5.0 as the supporting electrolyte. Oxidation occurs at 0.98 V vs. Ag/AgCl in a two-electron process controlled by adsorption of the electrogenerated products on the electrode surface. A acceptable recovery was obtained for assay of spiked biologic samples, with value of 98.7% for the swine urine and 95.3 % for the bovine urine.

  5. On the Development of Electronic Resources and Paper Resources%关于电子资源与纸本资源协调发展的思考和建议

    Institute of Scientific and Technical Information of China (English)

    王军武

    2012-01-01

    In recent years, a large number of electronic resources was introduced to the libraries, which has become an im- portant component of library resource system. However, there are also a lot of hot debates about the following issues, such as how to build a traditional paper resources, how to deal with the relationship between paper resources and electronic resources, how to build a library resources development system, etc. These problems also confused many librarians who are building resources in the library. With the combination with the opinions from some experts, research scholars, the paper proposed some guiding principles to deal with the relationship between electronic resources and paper resources. Taking all the aspects into consideration, such as the concepts of the library, the funding of the resources, the policies and structure of the library, cooperative development, the paper also proposes some measures for the development of electronic resources and paper resources.%在复合图书馆环境下,如何协调发展电子资源与纸本资源是图书馆界专家、学者研究和探讨的热点问题,也是许多图书馆工作者在文献资源建设实践中十分困惑的问题。文章结合有关专家、学者的研究成果及图书馆的相关案例,概述了电子资源与纸本资源协调发展应遵循的指导性原则,并从馆藏理念、经费投入、馆藏政策、馆藏结构、合作发展、服务利用等几个方面提出了协调发展电子资源与纸本资源的若干举措。

  6. Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor

    Energy Technology Data Exchange (ETDEWEB)

    Heydari, Hamid [Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of); Gholivand, Mohammad B., E-mail: mbgholivand@razi.ac.ir [Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of); Abdolmaleki, Abbas [Department of Chemistry, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of)

    2016-09-01

    In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS–MWCNTs composite sensor (CuNS–MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800 μM with a low detection limit of 70 nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50–800 μM with the detection limit of 4.3 μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination. - Highlights: • The Copper nanostructures (CuNS) were prepared by cyclic voltammetry deposition. • The CuNS-MWCNT/PGE sensor shows high activity toward hydrazine (N{sub 2}H{sub 4}). • The proposed sensor exhibits a wide linear range (0.1 to 800 μM), low detection limit (70 nM), high sensitivity and stability for hydrazine.

  7. Green Supply Chain Collaboration for Fashionable Consumer Electronics Products under Third-Party Power Intervention—A Resource Dependence Perspective

    Directory of Open Access Journals (Sweden)

    Jiuh-Biing Sheu

    2014-05-01

    Full Text Available Under third-party power intervention (TPPI, which increases uncertainty in task environments, complex channel power interplays and restructuring are indispensable among green supply chain members as they move toward sustainable collaborative relationships for increased viability and competitive advantage. From the resource dependence perspective, this work presents a novel conceptual model to investigate the influence of political and social power on channel power restructuring and induced green supply chain collaboration in brander-retailer bidirectional green supply chains of fashionable consumer electronics products (FCEPs. An FCEP refers to the consumer electronics product (e.g., personal computers, mobile phones, computer notebooks, and game consoles with the features of a well-known brand associated, a short product lifecycle, timely and fashionable design fit for market trends, and quick responsiveness to the variations of market demands. The proposed model is tested empirically using questionnaire data obtained from retailers in the FCEP brander-retailer distribution channels. Analytical results reveal that as an extension of political and social power, TPPI positively affects the reciprocal interdependence of dyadic members and reduces power asymmetry, thereby enhancing the collaborative relationship of dyadic members and leading to improved green supply chain performance. Therein, reciprocal interdependence underlying collaborative relationship is the key to reducing the external environmental uncertainties in the TPPI context.

  8. Electronic medical record data to identify variables associated with a fibromyalgia diagnosis: importance of health care resource utilization

    Directory of Open Access Journals (Sweden)

    Masters ET

    2015-03-01

    Full Text Available Elizabeth T Masters,1 Jack Mardekian,1 Birol Emir,1 Andrew Clair,1 Max Kuhn,2 Stuart L Silverman,31Pfizer, Inc., New York, NY, 2Pfizer, Inc., Groton, CT, 3Cedars-Sinai Medical Center, Los Angeles, CA, USABackground: Diagnosis of fibromyalgia (FM is often challenging. Identifying factors associated with an FM diagnosis may guide health care providers in implementing appropriate diagnostic and management strategies.Methods: This retrospective study used the de-identified Humedica electronic medical record (EMR database to identify variables associated with an FM diagnosis. Cases (n=4,296 were subjects ≥18 years old with ≥2 International Classification of Diseases, Ninth Revision (ICD-9 codes for FM (729.1 ≥30 days apart during 2012, associated with an integrated delivery network, with ≥1 encounter with a health care provider in 2011 and 2012. Controls without FM (no-FM; n=583,665 did not have the ICD-9 codes for FM. Demographic, clinical, and health care resource utilization variables were extracted from structured EMR data. Univariate analysis identified variables showing significant differences between the cohorts based on odds ratios (ORs.Results: Consistent with FM epidemiology, FM subjects were predominantly female (78.7% vs 64.5%; P<0.0001 and slightly older (mean age 53.3 vs 52.7 years; P=0.0318. Relative to the no-FM cohort, the FM cohort was characterized by a higher prevalence of nearly all evaluated comorbidities; the ORs suggested a higher likelihood of an FM diagnosis (P<0.0001, especially for musculoskeletal and neuropathic pain conditions (OR 3.1 for each condition. Variables potentially associated with an FM diagnosis included higher levels of use of specific health care resources including emergency-room visits, outpatient visits, hospitalizations, and medications. Units used per subject for emergency-room visits, outpatient visits, hospitalizations, and medications were also significantly higher in the FM cohort (P<0

  9. Strategies for low detection limit measurements with cyclic voltammetry.

    Science.gov (United States)

    Wiedemann, D J; Kawagoe, K T; Kennedy, R T; Ciolkowski, E L; Wightman, R M

    1991-12-15

    Cyclic voltammetry of Nafion-coated, carbon-fiber electrodes is used to detect trace concentrations of dopamine, both in a flow injection apparatus and in the brain of an anaesthetized rat. To improve signal-to-noise ratios, the sources of noise during cyclic voltammetry have been determined and strategies have been developed to decrease the noise. With the potentiostat employed, the measured noise is comparable to that expected for Johnson noise from the feedback resistor of the current transducer. Additional noise arises from the waveform generator employed and, in some cases, line noise. Line noise is discriminated against by starting each cyclic voltammogram either in phase or 180 degrees out of phase with the line frequency. When used in vivo, additional noise also arises from the physiological activity of the animal. Detection limits are found to closely correspond to those predicted on the basis of simulation of the voltammetric shape and the measured noise. Detection limits are improved by the use of appropriate analog and digital filtering, ensemble averaging, and appropriate timing of repetitive cyclic voltammograms. The combined use of these techniques enables the in vivo detection of approximately 100 nM of dopamine with a signal-to-noise ratio of 25.

  10. Differential Pulse Anodic Stripping Voltammetry for Mercury Determination

    Directory of Open Access Journals (Sweden)

    Vereștiuc Paul C.

    2015-07-01

    Full Text Available In the present work voltammetric investigations have been performed on HgCl2 aqueous solutions prepared from a Cz 9024 reagent. Carbon paste electrode (CPE, eriochrome black T modified carbon paste electrode (MCPE/EBT and KCl 1M as background electrolyte, were involved within the experimental procedures. Cyclic voltammetry (CV has been performed in order to compare the behaviour of the two electrodes in both K3[Fe(CN6] and mercury calibration aqueous solution. Differential pulse anodic stripping voltammetry (DPASV was used to determine the most suitable parameters for mercury determination. All experiments were performed at 25 ± 1 ℃, using an electrochemical cell with three-electrodes connected to an Autolab PG STAT 302N (Metrohm-Autolab potentiostat that is equipped with Nova 1.11 software. The measured potential values were generated by using the silver chloride electrode (AgClE as reference and a platinum wire electrode as auxiliary. A series of time depending equations for the pre-concentration and concentration steps were established, with the observation that a higher sensitivity can be obtained while increasing the pre-concentration time. DPASV were drawn using the CPE in 11.16 % coriander, as mercury complex, the voltamograms signals indicating mercury oxidation, with signal intensity increasing in time.

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

    Science.gov (United States)

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

    2012-02-24

    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.

  12. Arsenic speciation in natural waters by cathodic stripping voltammetry.

    Science.gov (United States)

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

    2010-03-03

    Contamination of groundwater with arsenic (As) is a major health risk through contamination of drinking and irrigation water supplies. In geochemically reducing conditions As is mostly present as As(III), its most toxic species. Various methods exist to determine As in water but these are not suitable for monitoring arsenic speciation at its original pH and without preparation. We present a method that uses cathodic stripping voltammetry (CSV) to determine reactive As(III) at a vibrating, gold, microwire electrode. The As(III) is detected after adsorptive deposition of As(OH)(3)(0), followed by a potential scan to measure the reduction current from As(III) to As(0). The method is suitable for waters of pH 7-12, has an analytical range of 1 nM to 100 microM As (0.07-7500 ppb) and a limit of detection of 0.5 nM with a 60 s deposition time. The As speciation protocol involves measuring reactive As(III) by CSV at the original pH and acidification to pH 1 to determine inorganic As(III)+As(V) by anodic stripping voltammetry (ASV) using the same electrode. Total dissolved As is determined by ASV after UV-digestion at pH 1. The method was successfully tested on various raw groundwater samples from boreholes in the UK and West Bengal. Copyright 2010 Elsevier B.V. All rights reserved.

  13. Survey on User Satisfaction of Electronic Resources in University Libraries%高校图书馆电子资源用户满意度调查

    Institute of Scientific and Technical Information of China (English)

    陈姚竹; 马东

    2011-01-01

    通过分析影响用户对图书馆电子资源利用的因素,以美国顾客满意度指数模型为基础,提出关于各个因素的测量指标,对高校图书馆电子资源用户满意度进行测量。%Through analyzing the influencing factors on utilizing library electronic resources, based on the model of American customer satisfaction index, the paper puts forward corresponding measurement indexes, and then measures the user satisfaction on electronic resources of university library

  14. Determination of Platinum Metals in Carbonaceous Mineral Raw Materials by Stripping Voltammetry

    OpenAIRE

    Kolpakova, Nina Alexandrovna; Oskina, Yuliya Aleksandrovna; Dyachenko, Elena Nikolaevna; Pshenichkin, Anatoliy Yakovlevich

    2015-01-01

    The paper considers the possibility of determining platinum metals in mineral raw materials by stripping voltammetry on a graphite electrode modified by metals. Stripping voltammetry method is characterized by low determination limit, wide intervals of determined content and high sensitivity. As a result of the research the conditions for the determination of gold, platinum and palladium by stripping voltammetry have been selected. The comparison of the results of gold, palladium and platinum...

  15. Electrochemical Deposition of Si-Ca/P on Nanotube Formed Beta Ti Alloy by Cyclic Voltammetry Method.

    Science.gov (United States)

    Jeong, Yong-Hoon; Choe, Han-Cheol

    2015-08-01

    The purpose of this study was to investigate electrochemical deposition of Si-Ca/P on nanotube formed Ti-35Nb-10Zr alloy by cyclic voltammetry method. Electrochemical deposition of Si substituted Ca/P was performed by pulsing the applied potential on nanotube formed surface. The surface characteristics were observed by field-emission scanning electron microscopy, X-ray diffractometer, and potentiodynamic polarization test. The phase structure and surface morphologies of Si-Ca/P deposition were affected by deposition cycles. From the anodic polarization test, nanotube formed surface at 20 V showed the high corrosion resistance with lower value of Icorr, I300, and Ipass.

  16. Direct Electrochemical Evidence of the Dissociation and Adsorption Behavior of Acetonitrile at Gold Electrodes by Ultrafast Voltammetry

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Ultrafast cyclic voltammetry was used to study the redox behavior of a gold electrode in acetonitrile. The direct electrochemical evidence of the dissociation and adsorption behavior of acetonitrile at gold electrodes was found. It could be stated that two consecutive redox paths are involved, each with a special adsorption state acting as the reaction intermediate. The mean value,obtained of the electron-transfer rate constant of the second path, was 1.3 × 105 s-1 with a standard deviation of 0.24 × 105 s-1.

  17. Development of an electronic medical record based alert for risk of HIV treatment failure in a low-resource setting.

    Directory of Open Access Journals (Sweden)

    Nancy Puttkammer

    Full Text Available BACKGROUND: The adoption of electronic medical record systems in resource-limited settings can help clinicians monitor patients' adherence to HIV antiretroviral therapy (ART and identify patients at risk of future ART failure, allowing resources to be targeted to those most at risk. METHODS: Among adult patients enrolled on ART from 2005-2013 at two large, public-sector hospitals in Haiti, ART failure was assessed after 6-12 months on treatment, based on the World Health Organization's immunologic and clinical criteria. We identified models for predicting ART failure based on ART adherence measures and other patient characteristics. We assessed performance of candidate models using area under the receiver operating curve, and validated results using a randomly-split data sample. The selected prediction model was used to generate a risk score, and its ability to differentiate ART failure risk over a 42-month follow-up period was tested using stratified Kaplan Meier survival curves. RESULTS: Among 923 patients with CD4 results available during the period 6-12 months after ART initiation, 196 (21.2% met ART failure criteria. The pharmacy-based proportion of days covered (PDC measure performed best among five possible ART adherence measures at predicting ART failure. Average PDC during the first 6 months on ART was 79.0% among cases of ART failure and 88.6% among cases of non-failure (p<0.01. When additional information including sex, baseline CD4, and duration of enrollment in HIV care prior to ART initiation were added to PDC, the risk score differentiated between those who did and did not meet failure criteria over 42 months following ART initiation. CONCLUSIONS: Pharmacy data are most useful for new ART adherence alerts within iSanté. Such alerts offer potential to help clinicians identify patients at high risk of ART failure so that they can be targeted with adherence support interventions, before ART failure occurs.

  18. Characterization studies and cyclic voltammetry on nickel(II amino acid dithiocarbamates with triphenylphosphine in the coordination sphere

    Directory of Open Access Journals (Sweden)

    SUBBIAH THIRUMARAN

    2008-02-01

    Full Text Available Nickel(II amino acid dithiocarbamate complexes of the composition [Ni(AAdtc(PPh3(NCS], [Ni(AAdtc(PPh3(CN] and [Ni(AAdtc(PPh32]ClO4 [(AAdtc = dithiocarbamate derivatives of amino acids, i.e., glycine (glydtc, L-iso-leucine (i-leudtc and L-proline (prodtc] were synthesized. The compounds were characterized by IR and electronic spectroscopy, thermal analysis, cyclic voltammetry and conductivity measurements. In the case of the mixed ligand complexes, the thioureide n(C−N values were shifted to higher wave numbers compared to [Ni(AAdtc2]. This observation shows the increased strength of the thioureide bond due to the presence of the p-accepting phosphine. Electronic spectral studies suggest square planar geometry for the complexes. Thermal analyses of the complexes are in keeping with the proposed formulae. Almost all the complexes showed signs of decay above 170 °C. At around 390 °C, the final mass corresponded to NiS. Cyclic voltammetry showed a decrease of the electron density on the nickel in the mixed ligand complexes compared to [Ni(AAdtc2].

  19. Myoglobin immobilization on electrodeposited nanometer-scale nickel oxide particles and direct voltammetry.

    Science.gov (United States)

    Moghaddam, Abdolmajid Bayandori; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Ahadi, Sara; Saboury, Ali Akbar

    2008-04-01

    Prosperity of information on the reactions of redox-active sites in proteins can be attained by voltammetric studies in which the protein sample is located on a suitable surface. This work reports the presentation of myoglobin/nickel oxide nanoparticles/glassy carbon (Mb/NiO NPs/GC) electrode, ready by electrochemical deposition of the NiO NPs on glassy carbon electrode and myoglobin immobilization on their surfaces by the potential cycling method. Images of electrodeposited NiO NPs on the surface of glassy carbon electrode were obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A pair of well-defined redox peaks for Mb(Fe(III)-Fe(II)) was obtained at the prepared electrode by direct electron transfer between the protein and nanoparticles. Electrochemical parameters of immobilized myoglobin such as formal potential (E(0')), charge transfer coefficient (alpha) and apparent heterogeneous electron transfer rate constant (k(s)) were estimated by cyclic voltammetry and nonlinear regression analysis. Biocatalytic activity was exemplified at the prepared electrode for reduction of hydrogen peroxide.

  20. Computer-controlled instrumentation for fast voltammetry at ultramicroelectrodes

    Science.gov (United States)

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

    2000-04-01

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

  1. Study of quinones reactions with wine nucleophiles by cyclic voltammetry.

    Science.gov (United States)

    Oliveira, Carla M; Barros, António S; Ferreira, António C S; Silva, Artur M S

    2016-11-15

    Quinones are electrophilic species which can react with various nucleophiles, like wine antioxidants, such as sulfur dioxide or ascorbic acid, thiols, amino acids, and numerous polyphenols. These reactions are very important in wine aging because they mediate oxygen reactions during both production and bottle aging phases. In this work, the major challenge was to determine the interaction between ortho-quinones and wine nucleophiles (amino acids, thiols, and the antioxidants SO2 and ascorbic acid), by cyclic voltammetry. Wine-model solutions with gallic acid, caffeic acid, or (+)-catechin and nucleophilic compounds were used. To understand the effect of nucleophilic addition in wine, a white wine with the same added nucleophiles was also analysed. Cyclic voltammograms were taken with glassy carbon electrode or screen-printed carbon electrodes, respectively, for wine-model and white wines solutions, in the absence and in the presence of nucleophiles. A nucleophilic order profile related to the cathodic current intensity decrease was observed.

  2. Nanoalloy electrocatalysis: simulating cyclic voltammetry from configurational thermodynamics with adsorbates.

    Science.gov (United States)

    Wang, Lin-Lin; Tan, Teck L; Johnson, Duane D

    2015-11-14

    We simulate the adsorption isotherms for alloyed nanoparticles (nanoalloys) with adsorbates to determine cyclic voltammetry (CV) during electrocatalysis. The effect of alloying on nanoparticle adsorption isotherms is provided by a hybrid-ensemble Monte Carlo simulation that uses the cluster expansion method extended to non-exchangeable coupled lattices for nanoalloys with adsorbates. Exemplified here for the hydrogen evolution reaction, a 2-dimensional CV is mapped for Pd-Pt nanoalloys as a function of both electrochemical potential and the global Pt composition, and shows a highly non-linear alloying effect on CV. Detailed features in CV arise from the interplay among the H-adsorption in multiple sites that is closely correlated with alloy configurations, which are in turn affected by the H-coverage. The origins of specific features in CV curves are assigned. The method provides a more complete means to design nanoalloys for electrocatalysis.

  3. Underpotential deposition and anodic stripping voltammetry at mesoporous microelectrodes.

    Science.gov (United States)

    Sanchez, Pablo Lozano; Elliott, Joanne M

    2005-05-01

    Using the technique of liquid crystal templating a series of high surface area mesoporous platinum microelectrodes was fabricated. The underpotential deposition of metal ions at such electrodes was found to be similar to that at conventional platinum electrodes. The phenomena of underpotential deposition, in combination with the intrinsic properties of mesoporous microelectrodes (i.e. a high surface area and efficient mass transport) was exploited for the purpose of anodic stripping voltammetry. In particular the underpotential deposition of Ag(+), Pb(2+) and Cu(2+) ions was investigated and it was found that mesoporous microelectrodes were able to quantify the concentration of ions in solution down to the ppb range. The overall behaviour of the mesoporous electrodes was found to be superior to that of conventional microelectrodes and the effects of interference by surfactants were minimal.

  4. Square-wave adsorptive cathodic stripping voltammetry of pantoprazole.

    Science.gov (United States)

    Radi, A

    2003-11-24

    Adsorption and reduction of pantoprazole were investigated by cyclic and square-wave voltammetry on a hanging mercury drop electrode in Britton-Robinson buffers at pH 2.0-11.0. The reduction process gave rise to a single peak within the entire pH range. Study of the variation of the reduction signal with solution variables such as pH and concentration of pantoprazole and instrumental variables such as accumulation time and potential, frequency, pulse height and pulse amplitude, has resulted in optimization of the reduction signal for analytical purposes. The voltammetric procedure was applied successfully to give a rapid and precise assay of pantoprazole in a tablet dosage form.

  5. Determination of Pesticide Ethion by Linear Sweep Stripping Voltammetry

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The presence of the pesticide ethion was determined using an electroanalytical method, i. e. , linear sweep stripping voltammetry at a hanging mercury drop electrode in the Britton-Robbinson buffer with pH = 8. 36, based on its reduction peak observed at - 690 mV following its alkaline hydrolysis. The experimental parameters, namely, the preconcentration potential, the preconcentration time, and the scan rate were investigated and -300 mV (vs. Ag/AgCl), 270 s, and 100 mV/s were selected as the optimal values, respectively. The linear relationship between the peak current and the concentration was found to be in the range of 0. 02-0. 16 mg/L, with a detection limit of 0.0087 mg/L. The proposed method was applied to the determination of ethion in spiked vegetable and fruit samples via a preextraction with anhydrous ethanol.

  6. The BRIGHTEN Program: Implementation and Evaluation of a Program to Bridge Resources of an Interdisciplinary Geriatric Health Team via Electronic Networking

    Science.gov (United States)

    Emery, Erin E.; Lapidos, Stan; Eisenstein, Amy R.; Ivan, Iulia I.; Golden, Robyn L.

    2012-01-01

    Purpose: To demonstrate the feasibility of the BRIGHTEN Program (Bridging Resources of an Interdisciplinary Geriatric Health Team via Electronic Networking), an interdisciplinary team intervention for assessing and treating older adults for depression in outpatient primary and specialty medical clinics. The BRIGHTEN team collaborates "virtually"…

  7. The module of methodical support in system of electronic educational resources as the innovative element of the modern maintenance of formation

    Directory of Open Access Journals (Sweden)

    Ольга Николаевна Крылова

    2009-06-01

    Full Text Available The article introduces some results of research, which were devoted to evaluation of tearches' mobility to introduce innovations in the contents of education. The author considers innovative potential of modules of the methodical support for system of electronic educational resources.

  8. Charting a Course through CORAL: Texas A&M University Libraries' Experience Implementing an Open-Source Electronic Resources Management System

    Science.gov (United States)

    Hartnett, Eric; Beh, Eugenia; Resnick, Taryn; Ugaz, Ana; Tabacaru, Simona

    2013-01-01

    In 2010, after two previous unsuccessful attempts at electronic resources management system (ERMS) implementation, Texas A&M University (TAMU) Libraries set out once again to find an ERMS that would fit its needs. After surveying the field, TAMU Libraries selected the University of Notre Dame Hesburgh Libraries-developed, open-source ERMS,…

  9. The BRIGHTEN Program: Implementation and Evaluation of a Program to Bridge Resources of an Interdisciplinary Geriatric Health Team via Electronic Networking

    Science.gov (United States)

    Emery, Erin E.; Lapidos, Stan; Eisenstein, Amy R.; Ivan, Iulia I.; Golden, Robyn L.

    2012-01-01

    Purpose: To demonstrate the feasibility of the BRIGHTEN Program (Bridging Resources of an Interdisciplinary Geriatric Health Team via Electronic Networking), an interdisciplinary team intervention for assessing and treating older adults for depression in outpatient primary and specialty medical clinics. The BRIGHTEN team collaborates "virtually"…

  10. Electronic Information Resources (EIR Adoption in Private University Libraries: The Moderating Effect of Productivity and Relative Advantage on Perceived Usefulness

    Directory of Open Access Journals (Sweden)

    Izuagbe, Roland

    2016-03-01

    Full Text Available The study tested a hybrid model with constructs drawn from the Technology Acceptance Model (TAM and Diffusion of Innovation (DOI theory in order to examine the moderating effect of productivity and relative advantage (RA on perceived usefulness (PU vis-à-vis electronic information resources (EIR adoption in private university libraries in Ogun and Osun States of Nigeria. The descriptive research design was adopted in the study. The population consisted of 61 (55.0% librarians and 50 (45.0% library officers (totaling 116—100% in Babcock University, Bells University, Covenant University, Bowen University, Oduduwa University, and Redeemer's University. Purposive sampling procedure was adopted after which total enumeration was used since the total population is small. The questionnaire was used for data collection. Of the 116 copies of the questionnaire administered, 111 (95.7% were found usable. The instrument was structured based on a 4-point Likert agreement scale of Strongly Agree, Agree, Disagree, and Strongly Disagree. Data were analyzed using descriptive statistics like tables of frequency counts and percentage. The findings revealed that productivity and relative advantage are significant moderators of perceived usefulness of EIR adoption in private university libraries in Ogun and Osun States, Nigeria.

  11. Cloud Point Extraction for Electroanalysis: Anodic Stripping Voltammetry of Cadmium.

    Science.gov (United States)

    Rusinek, Cory A; Bange, Adam; Papautsky, Ian; Heineman, William R

    2015-06-16

    Cloud point extraction (CPE) is a well-established technique for the preconcentration of hydrophobic species from water without the use of organic solvents. Subsequent analysis is then typically performed via atomic absorption spectroscopy (AAS), UV-vis spectroscopy, or high performance liquid chromatography (HPLC). However, the suitability of CPE for electroanalytical methods such as stripping voltammetry has not been reported. We demonstrate the use of CPE for electroanalysis using the determination of cadmium (Cd(2+)) by anodic stripping voltammetry (ASV). Rather than using the chelating agents which are commonly used in CPE to form a hydrophobic, extractable metal complex, we used iodide and sulfuric acid to neutralize the charge on Cd(2+) to form an extractable ion pair. This offers good selectivity for Cd(2+) as no interferences were observed from other heavy metal ions. Triton X-114 was chosen as the surfactant for the extraction because its cloud point temperature is near room temperature (22-25 °C). Bare glassy carbon (GC), bismuth-coated glassy carbon (Bi-GC), and mercury-coated glassy carbon (Hg-GC) electrodes were compared for the CPE-ASV. A detection limit for Cd(2+) of 1.7 nM (0.2 ppb) was obtained with the Hg-GC electrode. ASV with CPE gave a 20x decrease (4.0 ppb) in the detection limit compared to ASV without CPE. The suitability of this procedure for the analysis of tap and river water samples was demonstrated. This simple, versatile, environmentally friendly, and cost-effective extraction method is potentially applicable to a wide variety of transition metals and organic compounds that are amenable to detection by electroanalytical methods.

  12. Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid.

    Science.gov (United States)

    Yang, Guangming; Li, Ling; Jiang, Jinhe; Yang, Yunhui

    2012-08-01

    Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3 min and 2 min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02×10(-7)-5.23×10(-4) mol L(-1) and 1.43×10(-7)-4.64×10(-4) mol L(-1), the detection limits were 1.12×10(-8) mol L(-1) and 2.24×10(-8) mol L(-1), respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Voltammetry and Electrocatalysis of Achrornobacter Xylosoxidans Copper Nitrite Reductase on Functionalized Au(111)-Electrode Surfaces

    DEFF Research Database (Denmark)

    Welinder, Anna C.; Zhang, Jingdong; Hansen, Allan G.;

    2007-01-01

    A long-standing issue in protein film voltammetry (PFV), particularly electrocatalytic voltammetry of redox enzyme monolayers, is the variability of protein adsorption modes, reflected in distributions of catalytic activity of the adsorbed protein/enzyme molecules. Use of well-defined, atomically...

  14. Electrochemical behavior of folic acid at calixarene based chemically modified electrodes and its determination by adsorptive stripping voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Vaze, Vishwanath D. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India); Srivastava, Ashwini K. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India)], E-mail: aksrivastava@chem.mu.ac.in

    2007-12-31

    Voltammetric behavior of folic acid at plain carbon paste electrode and electrode modified with calixarenes has been studied. Two peaks for irreversible oxidation were observed. Out of the three calixarenes chosen for modification of the electrodes, p-tert-butyl-calix[6]arene modified electrode (CME-6) was found to have better sensitivity for folic acid. Chronocoulometric and differential pulse voltammetric studies reveal that folic acid can assemble at CME-6 to form a monolayer whose electron transfer rate is 0.00273 s{sup -1} with 2-electron/2-proton transfer for the peak at +0.71 V against SCE. An adsorption equilibrium constant of 5 x 10{sup 3} l/mol for maximum surface coverage of 2.89 x 10{sup -10} mol/cm{sup 2} was obtained. The current is found to be rectilinear with concentration by differential pulse voltammetry. However, linearity in the lower range of concentration 8.79 x 10{sup -12} M to 1.93 x 10{sup -9} M with correlation coefficient of 0.9920 was achieved by adsorptive stripping voltammetry. The limit of detection obtained was found to be 1.24 x 10{sup -12} M. This method was used for the determination of folic acid in a variety of samples, viz. serum, asparagus, spinach, oranges and multivitamin preparations.

  15. Amperometric detection of gold by differential pulse voltammetry using a DNA biosensor

    Institute of Scientific and Technical Information of China (English)

    GAN Ning; WANG Zhiying; XU Weiming; PAN Jianguo

    2007-01-01

    A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru(Ⅲ)/Ru(Ⅱ) redox potential of-0.165 V versus Ag|AgCl in pH 7.4 0.1 mol· L-1 Tris-HCl. The electron transfer was expected across the double-strand DNA by an "electron tunneling" mechanism. When the DNA biosensor was immerged in gold (Ⅲ) buffer solution, the current peak signal (Ⅰ) of the RuL-DNA supramolecular depressed and △Ⅰ was linear in the concentration range of Au ion from 1 × 10-7 to 2 × 10-5 mol·L-1 with a regression coefficient of 0.9879. The detection limit was 5 × 10-8 mol·L-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.

  16. A Study on the Model for Resources Matching of Electronic Bartering%电子易货资源匹配模型研究

    Institute of Scientific and Technical Information of China (English)

    吴剑云; 张嵩

    2012-01-01

    By exchanging idle goods and services, electronic bartering can help enterprises solve dull sale problems, shortage of funds, overstocks and other problems without sufficient cash. Relying on the Internet and the e-commerce platform, electronic bartering removes the traditional bartering limitations, greatly expands the trading object and range, improves the transaction efficiency, and provides additional channels for economic development. How to promote more successful barters among multiple barterers? A key factor is the matching of barter resources. Focusing on the automatic matching of resources in the electronic barter, this paper proposes a network model to help maximize resources matching and provide recommendation information for barter participants, thereby raising the transaction rate and making the barter market prosperous.According to the type and quantity of barter resources, barter market can be divided into two types. In the first type, the supply and demand of the barter market is related to the same type of resources and each barterer owns only one type of resource. In the second type, the supply and demand of the barter market is linked to many types of resources and each barterer owns multiple resources to be exchanged. The first case has been resolved in the relevant document by using the graph theory to solve digraph circuits. This paper is interested in studying the second type of barter. Suppose the barter market has m barterers and n resources. Each barterer owns diverse types of barter resources, and is interested in other types of resources. The barterer a will provide other barterers his own resources only if he gets the resources he needs from the barterer b. Note that each of the bartered resource is regarded as having equal value to any other resources. The main objective is to maximize the number of resources that are bartered.Next, this paper proposes a math model of automatic resources matching by systematically analyzing resource

  17. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry

    Directory of Open Access Journals (Sweden)

    Fatima AlZahra’a Alatraktchi

    2016-03-01

    Full Text Available Pyocyanin is a virulence factor uniquely produced by the pathogen Pseudomonas aeruginosa. The fast and selective detection of pyocyanin in clinical samples can reveal important information about the presence of this microorganism in patients. Electrochemical sensing of the redox-active pyocyanin is a route to directly quantify pyocyanin in real time and in situ in hospitals and clinics. The selective quantification of pyocyanin is, however, limited by other redox-active compounds existing in human fluids and by other metabolites produced by pathogenic bacteria. Here we present a direct selective method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between −1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58–0.82 V that is unaffected by other redox-active interferents. The linear quantification of pyocyanin has an R2 value of 0.991 across the clinically relevant concentration range of 2–100 µM. The proposed method was tested on human saliva showing a standard deviation of 2.5% ± 1% (n = 5 from the known added pyocyanin concentration to the samples. This inexpensive procedure is suggested for clinical use in monitoring the presence and state of P. aeruginosa infection in patients.

  18. Cyclic voltammetry and RBS study of paint components

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, Lynn [Center for Irradiation of Materials, Alabama A and M University, 4900 Meridian Street, P.O. Box 1447, Normal, AL 35762 (United States); Spencer, Dirk [Plant and Soil Science Department, Alabama A and M University, Normal, AL 35762-1447 (United States); Muntele, Claudiu [Center for Irradiation of Materials, Alabama A and M University, 4900 Meridian Street, P.O. Box 1447, Normal, AL 35762 (United States)]. E-mail: claudiu@cim.aamu.edu; Muntele, Iulia [Center for Irradiation of Materials, Alabama A and M University, 4900 Meridian Street, P.O. Box 1447, Normal, AL 35762 (United States); Ila, D. [Center for Irradiation of Materials, Alabama A and M University, 4900 Meridian Street, P.O. Box 1447, Normal, AL 35762 (United States)

    2007-08-15

    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 and 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.

  19. In vivo histamine voltammetry in the mouse premammillary nucleus.

    Science.gov (United States)

    Samaranayake, Srimal; Abdalla, Aya; Robke, Rhiannon; Wood, Kevin M; Zeqja, Anisa; Hashemi, Parastoo

    2015-06-07

    Histamine plays a major role in the mediation of allergic reactions such as peripheral inflammation. This classical monoamine is also a neurotransmitter involved in the central nervous system but its role in this context is poorly understood. Studying histamine neurotransmission is important due to its implications in many neurological disorders. The sensitivity, selectivity and high temporal resolution of fast scan cyclic voltammetry (FSCV) offer many advantages for studying electroactive neurotransmitters. Histamine has previously been studied with FSCV; however, the lack of a robust Faradaic electrochemical signal makes it difficult to selectively identify histamine in complex media, as found in vivo. In this work, we optimize an electrochemical waveform that provides a stimulation-locked and unique electrochemical signal towards histamine. We describe in vitro waveform optimization and a novel in vivo physiological model for stimulating histamine release in the mouse premammillary nucleus via stimulation of the medial forebrain bundle. We demonstrate that a robust signal can be used to effectively identify histamine and characterize its in vivo kinetics.

  20. Cyclic voltammetry of apple fruits: Memristors in vivo.

    Science.gov (United States)

    Volkov, Alexander G; Nyasani, Eunice K; Tuckett, Clayton; Blockmon, Avery L; Reedus, Jada; Volkova, Maya I

    2016-12-01

    A memristor is a resistor with memory that exhibits a pinched hysteretic relationship in cyclic voltammetry. Recently, we have found memristors in the electrical circuitry of plants and seeds. There are no publications in literature about the possible existence of memristors and electrical differentiators in fruits. Here we found that the electrostimulation of Golden Delicious or Arkansas Black apple fruits by bipolar periodic waves induces hysteresis loops with pinched points in cyclic voltammograms at low frequencies between 0.1MHz and 1MHz. At high frequencies of 1kHz, the pinched hysteresis loop transforms to a non-pinched hysteresis loop instead of a single line I=V/R for ideal memristors because the amplitude of electrical current depends on capacitance of a fruit's tissue and electrodes, frequency and direction of scanning. Electrostimulation of electrical circuits in apple fruits by periodic voltage waves also induces electrotonic potential propagation due to cell-to-cell electrical coupling with electrical differentiators. A differentiator is an electrical circuit in which the output of the circuit is approximately directly proportional to the rate of change of the input. The information gained from electrostimulation can be used to elucidate and to observe electrochemical and electrophysiological properties of electrical circuits in fruits.

  1. Fully printed flexible and disposable wireless cyclic voltammetry tag.

    Science.gov (United States)

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

    2015-01-29

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

  2. Voltammetry of redox analytes at trace concentrations with nanoelectrode ensembles.

    Science.gov (United States)

    Moretto, Ligia Maria; Pepe, Niki; Ugo, Paolo

    2004-04-19

    Gold nanoelectrodes ensembles (NEEs) have been prepared by electroless plating of Au nanoelectrode elements within the pores of a microporous polycarbonate template membrane. Cyclic voltammograms recorded in (ferrocenylmethyl) trimethylammonium hexafluorophosphate (FA(+) PF(6)(-)) solutions showed that these NEEs operate in the "total-overlap" response regime, giving well resolved peak shaped voltammograms. Experimental results show that the faradaic/background currents ratios at the NEE are independent on the total geometric area of the ensemble, so that NEE can be enlarged or miniaturized at pleasure without influencing the very favorable signal/noise ratio. Differential pulse voltammetry (DPV) at the NEE is optimized for direct determinations at trace levels. DPV at NEE allowed the determination (with no preconcentration) of trace amounts of FA(+), with a detection limit of 0.02muM. The use of NEE and DPV in cytochrome c (cyt c) solutions showed the possibility to observe the direct electrochemistry of submicromolar concentration of the protein, even without the need of adding any promoter or mediator.

  3. Fast Selective Detection of Pyocyanin Using Cyclic Voltammetry.

    Science.gov (United States)

    Alatraktchi, Fatima AlZahra'a; Andersen, Sandra Breum; Johansen, Helle Krogh; Molin, Søren; Svendsen, Winnie E

    2016-03-19

    Pyocyanin is a virulence factor uniquely produced by the pathogen Pseudomonas aeruginosa. The fast and selective detection of pyocyanin in clinical samples can reveal important information about the presence of this microorganism in patients. Electrochemical sensing of the redox-active pyocyanin is a route to directly quantify pyocyanin in real time and in situ in hospitals and clinics. The selective quantification of pyocyanin is, however, limited by other redox-active compounds existing in human fluids and by other metabolites produced by pathogenic bacteria. Here we present a direct selective method to detect pyocyanin in a complex electroactive environment using commercially available electrodes. It is shown that cyclic voltammetry measurements between -1.0 V to 1.0 V reveal a potential detection window of pyocyanin of 0.58-0.82 V that is unaffected by other redox-active interferents. The linear quantification of pyocyanin has an R² value of 0.991 across the clinically relevant concentration range of 2-100 µM. The proposed method was tested on human saliva showing a standard deviation of 2.5% ± 1% (n = 5) from the known added pyocyanin concentration to the samples. This inexpensive procedure is suggested for clinical use in monitoring the presence and state of P. aeruginosa infection in patients.

  4. Electrochemical investigation of [Co4(μ3-O)4(μ-OAc)4(py)4] and peroxides by cyclic voltammetry.

    Science.gov (United States)

    Clatworthy, Edwin B; Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

    2016-12-13

    Two oxidative redox processes of the neutral cobalt(iii) cubane, [Co4(μ3-O)4(μ-OAc)4(py)4], were investigated by cyclic voltammetry at a glassy carbon electrode in acetonitrile. In addition to the first quasi-reversible one-electron oxidation at E1/2 = 0.283 V vs. Fc(0/+), a second quasi-reversible one-electron oxidation was observed at E1/2 = 1.44 V vs. Fc(0/+). Oxidation at this potential does not facilitate water oxidation. In the presence of tert-butylhydroperoxide the peak current of this second oxidation increases, suggesting oxidation of the peroxide by the doubly oxidised cubane.

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

    Science.gov (United States)

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

    2013-01-01

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

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

    Science.gov (United States)

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

    2012-10-01

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

  7. Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study.

    Science.gov (United States)

    Sarkar, Tanmay; Kumar, Parveen; Bharadwaj, Mridula Dixit; Waghmare, Umesh

    2016-04-14

    A double layer δ-NH4V4O10, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids. While it possesses better stability, and higher ionic and electronic conductivity than the most widely explored V2O5, the mechanisms of its cyclability are yet to be understood. Here, we present a theoretical cyclic voltammetry as a tool based on first-principles calculations, and uncover structural transformations that occur during Li(+)/Na(+) insertion (x) into (Lix/Nax)NH4V4O10. Structural distortions associated with single-phase and multi-phase structural changes during the insertion of Li(+)/Na(+), identified through the analysis of voltage profile and theoretical cyclic voltammetry are in agreement with the reported experimental electrochemical measurements on δ-NH4V4O10. We obtain an insight into its electronic structure with a lower band gap that is responsible for the high rate capability of (Lix/Nax) δ-NH4V4O10. The scheme of theoretical cyclic voltammetry presented here will be useful for addressing issues of cyclability and energy rate in other electrode materials.

  8. Large amplitude Fourier transformed ac voltammetry at a rotating disc electrode: a versatile technique for covering Levich and flow rate insensitive regimes in a single experiment.

    Science.gov (United States)

    Bano, Kiran; Kennedy, Gareth F; Zhang, Jie; Bond, Alan M

    2012-04-14

    The theory for large amplitude Fourier transformed ac voltammetry at a rotating disc electrode is described. Resolution of time domain data into dc and ac harmonic components reveals that the mass transport for the dc component is controlled by convective-diffusion, while the background free higher order harmonic components are flow rate insensitive and mainly governed by linear diffusion. Thus, remarkable versatility is available; Levich behaviour of the dc component limiting current provides diffusion coefficient values and access to higher harmonics allows fast electrode kinetics to be probed. Two series of experiments (dc and ac voltammetry) have been required to extract these parameters; here large amplitude ac voltammetry with RDE methodology is used to demonstrate that kinetics and diffusion coefficient information can be extracted from a single experiment. To demonstrate the power of this approach, theoretical and experimental comparisons of data obtained for the reversible [Ru(NH(3))(6)](3+/2+) and quasi-reversible [Fe(CN)(6)](3-/4-) electron transfer processes are presented over a wide range of electrode rotation rates and with different concentrations and electrode materials. Excellent agreement of experimental and simulated data is achieved, which allows parameters such as electron transfer rate, diffusion coefficient, uncompensated resistance and others to be determined using a strategically applied approach that takes into account the different levels of sensitivity of each parameter to the dc or the ac harmonic.

  9. The Use and Maintenance of University Library Electronic Resources%浅议大学图书馆电子资源的利用与维护

    Institute of Scientific and Technical Information of China (English)

    马鹏飞; 熊豫玲

    2011-01-01

    随着科学技术的飞速发展,高新信息技术的广泛应用,大学图书馆的工作内容和方法也面临新的挑战,为了使用户更好的利用大学图书馆的电子资源,提高电子资源利用率,实现大学图书馆数字化,本文主要从电子资源的利用和维护方面进行探讨。%With the rapid development of science and technology,the extensive application of high-tech information technology, University of content and methods of library work is also facing new challenges in order to make better use of university library users to electronic resources,improve the utilization of electronic resources to achieve the University Library digital,paper, from the use of electronic resources and maintenance were discussed.

  10. Study on surface acid-base property of carboxylic acid-terminated self-assembled monolayers by cyclic voltammetry and electro-chemical impedance spectroscopy

    Institute of Scientific and Technical Information of China (English)

    罗立强; 程志亮; 杨秀荣; 汪尔康

    2000-01-01

    Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the surface acid-base property of carboxylic acid-terminated self-assembled monolayers (SAMs). A carboxylic acid-terminated thiol, such as thioctic acid (1,2-dithiolane-3-pentanoic acid), was self-assembled on gold electrodes. Electron transfer between the bulk solution and the SAM modified electrode was studied at different pH using Fe(CN)63 as a probe. The surface pK. of thioctic acid was determined by cyclic voltammetry and electrochemical impedance spectroscopy to be 5.6±0.1 and 5.8±0.1, respectively. The method is compared with other methods of monolayer pK.measurement.

  11. A new approach for in situ cyclic voltammetry of a microbial fuel cell biofilm without using a potentiostat.

    Science.gov (United States)

    Cheng, Ka Yu; Cord-Ruwisch, Ralf; Ho, Goen

    2009-02-01

    Electrochemically active bacteria in a microbial fuel cell (MFC) usually exist as a biofilm attached to an electrode surface. Conventional cyclic voltammetry using potentiostat is considered as a powerful and reliable method to study electrochemical behavior of MFC biofilm. In this paper, we introduce a new approach to evaluate redox behavior of an electro-active MFC biofilm without using a potentiostat. Analogous to a conventional cyclic voltammetry study, we controlled the biofilm-electrode potential by computer-feedback controlling the external resistance of an operating MFC. In this way, the MFC can still operate as a "fuel cell" without being "interrupted" by an external device (i.e. potentiostat) that normally does not belong to the system. Relationship between current and biofilm-electrode potential was obtained and showed agreement with a potentiostat-controlled method under similar experimental conditions. The method could be added to our technical repertoire for analysis of bacterial mediator involved in the exocellular electron transfer of a MFC-biofilm, and it could potentially serve as a practical process monitoring method for MFC operation. The application of computer-control components should be further explored to facilitate control, diagnosis as well as optimization of MFC processes.

  12. Cyclic voltammetry investigation of diffusion of ferrocene within propylene carbonate organogel formed by gelator

    Energy Technology Data Exchange (ETDEWEB)

    Feng Guilong; Xiong Yun; Wang Hong [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074 (China); Yang Yajiang [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074 (China)], E-mail: yjyang@mail.hust.edu.cn

    2008-11-30

    Propylene carbonate organogel containing LiClO{sub 4} was formed in the presence of gelator bis-(4-stearoylaminophenyl) methane (BSAPM). The electrochemical behavior and diffusion of ferrocene (Fc) and ferricenium (Fc{sup +}) entrapped within the organogel was investigated by cyclic voltammetry. The Fc molecules still show redox activity within the organogels in comparison with corresponding solutions of propylene carbonate containing LiClO{sub 4}. The shape of the cyclic voltammograms of the Fc electrooxidation in organogel was similar to that in corresponding solutions. The results indicated that redox reactions of Fc/Fc{sup +} were a quasi-reversible process of diffusion-controlled single electron transfer in organogels. The diffusion coefficients of Fc and Fc{sup +} in organogels decreased with an increase of the concentration of gelator BSAPM, but increased with an increase of temperature. The temperature dependence of the diffusion coefficient in organogels followed classical Arrhenius equation. The activation energy in organogels was found of no difference from that in corresponding solutions.

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

    Science.gov (United States)

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

    2013-02-28

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

  14. Optimizing the Temporal Resolution of Fast-Scan Cyclic Voltammetry

    Science.gov (United States)

    2012-01-01

    Electrochemical detection with carbon-fiber microelectrodes has become an established method to monitor directly the release of dopamine from neurons and its uptake by the dopamine transporter. With constant potential amperometry (CPA), the measured current provides a real time view of the rapid concentration changes, but the method lacks chemical identification of the monitored species and markedly increases the difficulty of signal calibration. Monitoring with fast-scan cyclic voltammetry (FSCV) allows species identification and concentration measurements but often exhibits a delayed response time due to the time-dependent adsorption/desorption of electroactive species at the electrode. We sought to improve the temporal resolution of FSCV to make it more comparable to CPA by increasing the waveform repetition rate from 10 to 60 Hz with uncoated carbon-fiber electrodes. The faster acquisition led to diminished time delays of the recordings that tracked more closely with CPA measurements. The measurements reveal that FSCV at 10 Hz underestimates the normal rate of dopamine uptake by about 18%. However, FSCV collection at 10 and 60 Hz provide identical results when a dopamine transporter (DAT) blocker such as cocaine is bath applied. To verify further the utility of this method, we used transgenic mice that overexpress DAT. After accounting for the slight adsorption delay time, FSCV at 60 Hz adequately monitored the increased uptake rate that arose from overexpression of DAT and, again, was similar to CPA results. Furthermore, the utility of collecting data at 60 Hz was verified in an anesthetized rat by using a higher scan rate (2400 V/s) to increase sensitivity and the overall signal. PMID:22708011

  15. Barriers to electronic access and delivery of educational information in resource constrained public schools: a case of Greater Tubatse Municipality

    CSIR Research Space (South Africa)

    Pholotho, T

    2016-05-01

    Full Text Available Information and Communication Technologies (ICTs) are capable of expanding access to quality education, educational resources and provide teachers with new skills. Nevertheless, a majority of rural public schools have limited ICTs, mainly due...

  16. Electronic Grey Literature in Accelerator Science and Its Allied Subjects : Selected Web Resources for Scientists and Engineers

    CERN Document Server

    Rajendiran, P

    2006-01-01

    Grey literature Web resources in the field of accelerator science and its allied subjects are collected for the scientists and engineers of RRCAT (Raja Ramanna Centre for Advanced Technology). For definition purposes the different types of grey literature are described. The Web resources collected and compiled in this article (with an overview and link for each) specifically focus on technical reports, preprints or e-prints, which meet the main information needs of RRCAT users.

  17. Electrolyte Effects on the Cyclic Voltammetry of TCNQ (Tetracyanoquinodimethane) and TCNE (Tetracyanoethylene).

    Science.gov (United States)

    1986-07-30

    to form two radical anions. In this note we report a study by cyclic voltammetry of the reductions of TCNQ and TCNE to their radical anions and dianions at platinum and glassy carbon electrodes in acetonitrile.

  18. Theory of linear sweep voltammetry with diffuse charge: unsupported electrolytes, thin films, and leaky membranes

    CERN Document Server

    Yan, David; Pugh, Mary C; Dawson, Francis P

    2016-01-01

    Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. No general theory of linear-sweep voltammetry is available, however, for unsupported electrolytes and for other situations where diffuse charge effects play a role. In this paper, we provide a historical review of previous models and experiments and present a comprehensive mathematical theory of voltammetry in electrochemical cells with diffuse charge. We solve the time-dependent Poisson-Nernst-Planck (PNP) equations with generalized Frumkin-Butler-Volmer (FBV) boundary conditions, and show theoretical and simulated current-voltage curves for liquid and solid thin films, cells with blocking electrodes, and membranes with fixed background charge. The full range of dimensionless parameters is considered, including the dimensionless Debye screening ...

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

    DEFF Research Database (Denmark)

    Gwyer, James; Zhang, Jingdong; Butt, Julea

    2006-01-01

    of the density and orientational distribution of NrfA molecules are disclosed. The submonolayer coverage resolved by in situ STM is readily reconciled with the failure to detect nonturnover signals in cyclic voltammetry of the NrfA films. The molecular structures show a range of lateral dimensions...... a direct approach to correlate electrocatalytic and molecular properties of the protein layer, a long-standing issue in protein film voltammetry....

  20. 电子资源许可使用的发展与创新%The Development and Innovation of the Use of the Electronic Resource License

    Institute of Scientific and Technical Information of China (English)

    王军

    2012-01-01

      电子资源许可使用在我国发展时间较短,在其建立过程中还存在许可定价、购买模式、馆际互借以及电子资源的长期保存许可方式等难题。电子资源许可使用的发展与创新,需要根据用户需求制定发展战略,建立图书馆的读者监督管理制度和数字化资源服务制度,规范文献编目制度等,以提高电子信息资源与图书馆信息资源的使用效果和广泛的使用需求%  It's been a short time since the use of electronic resource licenses has developed in China; in addition, many problems ap-pear in the establishment process in terms of license pricing, purchase pattern, inter-library loan and long-term preservation ways of electronic resources. In order to develop and innovate the use of the license, libraries should develop strategies in accordance with the users' needs, establish a reader supervision system and a digital resource service system, and normalize the document cataloging sys-tem to enhance the utilization effect and meet the extensive demand for electronic and library information resources.

  1. Determination of tryptamine in foods using square wave adsorptive stripping voltammetry.

    Science.gov (United States)

    Costa, Daniel J E; Martínez, Ana M; Ribeiro, Williame F; Bichinho, Kátia M; Di Nezio, María Susana; Pistonesi, Marcelo F; Araujo, Mario C U

    2016-07-01

    Tryptamine, a biogenic amine, is an indole derivative with an electrophilic substituent at the C3 position of the pyrrole ring of the indole moiety. The electrochemical oxidation of tryptamine was investigated using glassy carbon electrode (GCE), and focusing on trace level determination in food products by square wave adsorptive stripping voltammetry (SWAdSV). The electrochemical responses of tryptamine were evaluated using differing voltammetric techniques over a wide pH range, a quasi-reversible electron-transfer to redox system represented by coupled peaks P1-P3, and an irreversible reaction for peak P2 were demonstrated. The proton and electron counts associated with the oxidation reactions were estimated. The nature of the mass transfer process was predominantly diffusion-limited for the oxidation process of P1, the most selective and sensitive analytical response (acetate buffer solution pH 5.3), being used for the development of SWAdSV method, under optimum conditions. The excellent response allowed the development of an electroanalytical method with a linear response range of from 4.7-54.5)×10(-)(8)molL(-1), low detection limit (0.8×10(-)(9)molL(-)(1)), and quantification limit (2.7×10(-9)molL(-1)), and acceptable levels of repeatability (3.6%), and reproducibility (3.8%). Tryptamine content was determined in bananas, tomatoes, cheese (mozzarella and gorgonzola), and cold meats (chicken sausage and pepperoni sausage), yielding recoveries above 90%, with excellent analytical performance using simple and low cost instrumentation.

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

    Science.gov (United States)

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

    2012-07-29

    A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17±0.05 nM (n=14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10-70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52-6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of β'(Fe(3+)(NN)(3)) increased linearly with increasing pH according to log β'(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 μM 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. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Controlled release of drugs from cellulose acetate matrices produced from sugarcane bagasse: monitoring by square-wave voltammetry.

    Science.gov (United States)

    Rodrigues Filho, Guimes; Almeida, Flávia; Ribeiro, Sabrina D; Tormin, Thiago F; Muñoz, Rodrigo A A; Assunção, Rosana M N; Barud, Hernane

    2016-01-01

    In this paper, cellulose triacetate (CTA) was produced from sugarcane bagasse and used as matrices for controlled release of paracetamol. Symmetric and asymmetric membranes were obtained by formulations of CTA/dichloromethane/drug and CTA/dichloromethane/water/drug, respectively, and they were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Different morphologies of membranes were observed by SEM, and the incorporation of paracetamol was confirmed by lowering of the glass transition temperature (Tg) in the DSC curves. This indicates the existence of interactions between the matrix and the drug. The evaluation of drug release was based on the electrochemical monitoring of paracetamol through its oxidation at a glassy carbon electrode surface using square-wave voltammetry (SWV), which provides fast, precise and accurate in situ measurements. The studies showed a content release of 27% and 45% by the symmetric and asymmetric membranes, respectively, during 8 h.

  4. Clinician‐selected Electronic Information Resources do not Guarantee Accuracy in Answering Primary Care Physicians’ Information Needs. A review of: McKibbon, K. Ann, and Douglas B. Fridsma. “Effectiveness of Clinician‐selected Electronic Information Resources for Answering Primary Care Physicians’ Information Needs.” Journal of the American Medical Informatics Association 13.6 (2006: 653‐9.

    Directory of Open Access Journals (Sweden)

    Martha Ingrid Preddie

    2008-03-01

    Full Text Available Objective – To determine if electronic information resources selected by primary care physicians improve their ability to answer simulated clinical questions.Design – An observational study utilizing hour‐long interviews and think‐aloud protocols.Setting – The offices and clinics of primary care physicians in Canada and the United States.Subjects – Twenty‐five primary care physicians of whom 4 were women, 17 were from Canada, 22 were family physicians,and 24 were board certified.Methods – Participants provided responses to 23 multiple‐choice questions. Each physician then chose two questions and looked for the answers utilizing information resources of their own choice. The search processes, chosen resources and search times were noted. These were analyzed along with data on the accuracy of the answers and certainties related to the answer to each clinical question prior to the search.Main results – Twenty‐three physicians sought answers to 46 simulated clinical questions. Utilizing only electronic information resources, physicians spent a mean of 13.0 (SD 5.5 minutes searching for answers to the questions, an average of 7.3(SD 4.0 minutes for the first question and 5.8 (SD 2.2 minutes to answer the second question. On average, 1.8 resources were utilized per question. Resources that summarized information, such as the Cochrane Database of Systematic Reviews, UpToDate and Clinical Evidence, were favored 39.2% of the time, MEDLINE (Ovid and PubMed 35.7%, and Internet resources including Google 22.6%. Almost 50% of the search and retrieval strategies were keyword‐based, while MeSH, subheadings and limiting were used less frequently. On average, before searching physicians answered 10 of 23 (43.5% questions accurately. For questions that were searched using clinician‐selected electronic resources, 18 (39.1% of the 46 answers were accurate before searching, while 19 (42.1% were accurate after searching. The difference of

  5. Flavins mediate extracellular electron transfer in Gram-positive Bacillus megaterium strain LLD-1

    DEFF Research Database (Denmark)

    Xiao, Yong; Liu, Lidan; You, Lexing;

    electrochemically active strain of Bacillus megatherium strain LLD-1, and its extracellular electron transfer mechanism was demonstrated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), HPLC, and chronoamperometric. The CV and DPV showed that a redox peaks ascribing to membrane proteins was found...

  6. Conceived on the City Electronic Waste Resource Mana oement Model%城市电子废弃物资源化管理模式构想

    Institute of Scientific and Technical Information of China (English)

    熊贵琍; 余涛

    2012-01-01

    Investigated e- waste collection system the investigation, the whereabouts and electronic waste disposal in Httizhou city, the paper analyzed the Huizhou city e- waste collection and disposal of a series of problems, combined with the actual, conceived urban electronic waste resources management mode.%通过对惠州市电子废弃物收集体系组成、去向以及电子废弃物处置方式的调查,分析惠州市电子废弃物收集和处置存在的一系列问题,结合实际提出了城市电子废弃物资源化管理模式的初步构想。

  7. Accessibility and Use of Web-Based Electronic Resources by Physicians in a Psychiatric Institution in Nigeria

    Science.gov (United States)

    Oduwole, Adebambo Adewale; Oyewumi, Olatundun

    2010-01-01

    Purpose: This study aims to examine the accessibility and use of web-based electronic databases on the Health InterNetwork Access to Research Initiative (HINARI) portal by physicians in the Neuropsychiatric Hospital, Aro--a psychiatry health institution in Nigeria. Design/methodology/approach: Collection of data was through the use of a three-part…

  8. Cyclic Voltammetry Measurement for Cu2O Based Homostructure Thin Film

    Science.gov (United States)

    Mohamad Arifin, Nurliyana Binti; Mohamad, Fariza Binti; Sikh Anuar, Nur Fathiah Binti; Ahmad, Nabihah Binti; Nor, Nik Hisyamudin Muhd; Izaki, Masanobu

    2017-08-01

    This experiment is about fabrication of homojunction Copper Oxide (Cu2O) thin film by using electrodeposition method. The p-n homojunction Cu2O was successfully prepared by consecutively depositing p-type Cu2O layer on n-type Cu2O layer by using copper acetate based solution through potentiostatic electrodeposition. At first, the n-type Cu2O was fabricated at pH 6.2 and 6.5 with fixed potential of -0.125V vs Ag/AgCl and time deposition at 30 minutes. Cyclic voltammetry (CV) measurement was carried out on this sample to determine the ideal potential range for fabrication of p-type Cu2O on n-type Cu2O/FTO substrate. From the result, deposition potential of -0.35V and -0.4V vs Ag/AgCl were appropriated for p-type Cu2O thin film fabrication. These potential values were variable with the selected pH values of 12.0 and 12.5 to fabricate the p-type Cu2O thin film. The other parameters such as deposition time fixed at 2 hours bath temperature was set up at 60°C. It was found that the optimum potential deposition was -0.4V vs Ag/AgCl and pH value appropriate for homostructure Cu2O thin film was pH 12.5. Morphological, structural, optical and conductivity characterization of p-n homojunction Cu2O thin film was characterized using Field Emission Scanning Electron Microscopy, X-Ray Diffractometer, Ultraviolet-Visible Spectroscopy and Photoelectrochemical (PEC) cells, respectively.

  9. Share and share alike: encouraging the reuse of academic resources through the Scottish electronic Staff Development Library

    Directory of Open Access Journals (Sweden)

    Lorna M. Campbell

    2001-12-01

    Full Text Available The Scottish electronic Staff Development Library (http://www.sesdl.scotcit.acuk is an ongoing collaborative project involving the Universities of Edinburgh, Paisley and Strathclyde which has been funded by SHEFC as part of their current ScotCIT Programme (http:llwww.scotcit.ac.uk. This project is being developed in response to the increasing demand for flexible, high-quality staff development materials.

  10. Adsorptive stripping voltammetry of trimethoprim: mechanistic studies and application to the fast determination in pharmaceutical suspensions.

    Science.gov (United States)

    Carapuça, Helena M; Cabral, David J; Rocha, Luciana S

    2005-06-15

    The adsorptive stripping voltammetric behaviour of trimethoprim (TMP) was studied at pH 3.8 and 7.0 by linear-sweep (LS) and cyclic voltammetry at the hanging mercury drop electrode. The charges and surface concentrations of the protonated TMP species were determined at both pH values. Taking advantage of the adsorption features of TMP fast voltammetric techniques (LS and square-wave (SW) voltammetry) were applied to the determination of TMP at the 10(-7)mol dm(-3) concentration level (pH 3.8). For these concentrations the relative standard deviations were cathodic stripping voltammetry originated a very fast and sensitive method for the direct analysis of TMP in pharmaceutical suspensions without any matrix effects or interference from sulfamethoxazole. No sample pre-treatments or solvent extraction procedures were needed. The quantitative results were in agreement with the data supplied by the manufacturer.

  11. Fast voltammetry of metals at carbon-fiber microelectrodes: towards an online speciation sensor.

    Science.gov (United States)

    Pathirathna, Pavithra; Siriwardhane, Thushani; McElmurry, Shawn P; Morgan, Stephen L; Hashemi, Parastoo

    2016-11-14

    Speciation controls the chemical behavior of trace metals. Thus, there is great demand for rapid speciation analysis in a variety of fields. In this study, we describe the application of fast scan cyclic voltammetry (FSCV) and fast scan adsorption controlled voltammetry (FSCAV) to trace metal speciation analysis. We show that Cu(2+) can be detected using FSCAV in different matrices. We find that matrices with different Cu(2+) binding ability do not affect the equilibrium of Cu(2+) adsorption onto CFMs, and thus are an excellent predictor for free Cu(2+) ([Cu(2+)]free) in solution. We modelled a correlation between the FSCV response, [Cu(2+)]free and log Kf for 15 different Cu(2+) complexes. Using our model, we rapidly predicted, and verified [Cu(2+)]free and Kf of a real groundwater sample spiked with Cu(2+). We thus highlight the potential of fast voltammetry as a rapid trace metal speciation sensor.

  12. Cyclic voltammetry and near edge X-ray absorption fine structure spectroscopy at the Ag L3-edge on electrochemical halogenation of Ag layers on Au(111)

    Science.gov (United States)

    Endo, Osamu; Nakamura, Masashi

    2011-05-01

    One to three layers of Ag grown on a Au(111) electrode were studied by cyclic voltammetry in chloride and bromide solutions and by ex-situ near-edge X-ray absorption fine structure spectroscopy at the Ag L3-edge (Ag L3-NEXAFS). The one and two layers obtained by underpotential deposition exhibited reduced intensity at the absorption edge in the Ag L3-NEXAFS spectra, which suggests the gain of d-electrons in these layers. The cyclic voltammograms and the Ag L3-NEXAFS spectra indicate that the second and third layers of Ag halogenated at positive potentials, whereas the first layer remained in metallic form.

  13. 重庆高校图书馆电子文献资源建设现状及对策%The Present Situation and Countermeasure of Electronic Literature Resources Construction about Chongqing University Library

    Institute of Scientific and Technical Information of China (English)

    刘子辉; 彭渝; 陈强; 吴晓英

    2014-01-01

    In the information society, Electronic document resources are very important for library development and the school's teaching and research. The university library should pay more at ention to the construction of electronic document resources. Through the survey of the electronic document resources in Chongqing, We have mastered the distribution of electronic document resources, analyzed the existing problems in resource construction, and proposed the related countermeasure. We hope to provide reference for the electronic document resources construction.%在信息社会,电子文献资源对高校图书馆建设、学校的教学与科研都起到非常重要的作用,各高校图书馆应该更加重视电子文献资源的建设。通过对重庆高校图书馆电子文献资源建设情况进行调查,掌握了本地区电子文献资源的分布情况,分析了资源建设中存在的问题,并提出了相关对策,希望为本地区高校图书馆电子文献资源建设提供参考。

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

    Science.gov (United States)

    Park, Duck-Gun; Song, Hoon; Kishore, M B; Vértesy, G; Lee, Duk-Hyun

    2013-11-01

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

  15. Cathodic adsorptive stripping square-wave voltammetry of the anti-inflammatory drug meloxicam.

    Science.gov (United States)

    Radi, A E; Ghoneim, M; Beltagi, A

    2001-10-01

    The adsorptive behavior of the anti-inflammatory drug meloxicam was studied by cyclic, differentia-pulse and square-wave voltammetry on a hanging mercury drop electrode (HMDE). The drug was accumulated at HMDE and a well-defined stripping peak current was obtained at -1.42 V vs. Ag/AgCl (saturated KCl) electrode in acetate buffer solution (pH 5.0). A voltammetric procedure was developed for the determination of meloxicam using square-wave cathodic adsorptive stripping voltammetry (SW-CASV). The optimum working conditions for the determination of the drug were established. The analysis of meloxicam in human plasma was carried out satisfactorily.

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

    Science.gov (United States)

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

    1991-01-01

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

  17. Supercapacitive evaluation of carbon black/exfoliated graphite/MnO{sub 2} ternary nanocomposite electrode by continuous cyclic voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Naderi, Hamid Reza, E-mail: hrnaderi@ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Norouzi, Parviz, E-mail: norouzi@khayam.ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Biosensor Research Center, Endocrinology & Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Ganjali, Mohammad Reza, E-mail: ganjali@khayam.ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Biosensor Research Center, Endocrinology & Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2015-08-01

    A new ternary nanocomposite was prepared by using MnO{sub 2}, carbon black (CB), and exfoliated graphite (EG) through a sonochemical method. In this process, the MnO{sub 2} nanoparticles was anchored on the mixture of CB and EG to maximize the specific capacitances of these materials. Structure and morphology of the CB/EG/MnO{sub 2} nanocomposites were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the CB/EG/MnO{sub 2} nanocomposites with different content of MnO{sub 2} were studied by cyclic voltammetry (CV), fast Fourier transformation continuous cyclic voltammetry (FFTCCV) technique, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). The best nanocomposite electrode displayed specific capacitance of 364 F g{sup −1} at the scan rate of 2 mV s{sup −1} in 0.5 M Na{sub 2}SO{sub 4} aqueous solution, which is higher than pure MnO{sub 2} (289 F g{sup −1}). The capacitance stability of the nanocomposite electrode was studied by FFTCCV at the scan rate of 500 mV s{sup −1}. The result shows that after recording 4000 CVs, the specific capacitance of the nanocomposite decline only 5%. Furthermore, the nanocomposite electrode showed higher energy density than MnO{sub 2} electrode. - Highlights: • MnO{sub 2}/exfoliated graphite/Carbon black nanocomposites were synthesized by ultrasonic vibration. • The best nanocomposite electrode exhibits specific capacitance of 364 F g{sup −1} in 2 mV s{sup −1}. • The stability of the nanocomposite electrode was study FFTCCV technique. • The capacitance decreases only 5.2% of initial capacitance after 4000 cycles.

  18. Probing Electrode Heterogeneity Using Fourier-Transformed Alternating Current Voltammetry: Application to a Dual-Electrode Configuration.

    Science.gov (United States)

    Tan, Sze-Yin; Unwin, Patrick R; Macpherson, Julie V; Zhang, Jie; Bond, Alan M

    2017-03-07

    Quantitative studies of electron transfer processes at electrode/electrolyte interfaces, originally developed for homogeneous liquid mercury or metallic electrodes, are difficult to adapt to the spatially heterogeneous nanostructured electrode materials that are now commonly used in modern electrochemistry. In this study, the impact of surface heterogeneity on Fourier-transformed alternating current voltammetry (FTACV) has been investigated theoretically under the simplest possible conditions where no overlap of diffusion layers occurs and where numerical simulations based on a 1D diffusion model are sufficient to describe the mass transport problem. Experimental data that meet these requirements can be obtained with the aqueous [Ru(NH3)6](3+/2+) redox process at a dual-electrode system comprised of electrically coupled but well-separated glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Simulated and experimental FTACV data obtained with this electrode configuration, and where distinctly different heterogeneous charge transfer rate constants (k(0) values) apply at the individual GC and BDD electrode surfaces, are in excellent agreement. Principally, because of the far greater dependence of the AC current magnitude on k(0), it is straightforward with the FTACV method to resolve electrochemical heterogeneities that are ∼1-2 orders of magnitude apart, as applies in the [Ru(NH3)6](3+/2+) dual-electrode configuration experiments, without prior knowledge of the individual kinetic parameters (k(0)1 and k(0)2) or the electrode size ratio (θ1:θ2). In direct current voltammetry, a difference in k(0) of >3 orders of magnitude is required to make this distinction.

  19. Exploring the Bioelectrochemical Characteristics of Activated Sludge Using Cyclic Voltammetry.

    Science.gov (United States)

    Khater, Dena Z; El-Khatib, K M; Hassan, Rabeay Y A

    2017-06-17

    Due to the potential interest, bioelectrochemical responses of activated sludge using the three-electrode system are tested. From the cyclic voltammograms, the oxidation current output is increasing due to incubation time increase, whereas 5, 25 and 39.33 μA are obtained after 3, 72 and 96 h, respectively. Changing the working electrode from glassy carbon to carbon paste led to the increase in the electrochemical signal from 0.3 to be 3.72 μA. On the other hand, the use of the lipophilic redox mediator (2,6-dichlorophenolindophenol (DCIP)) amplified the oxidation current to reach 19.9 μA instead of 2.1 μA. Based on these findings, the mixed microbial community of the activated sludge is exploited as a catalyst for the bio-oxidation of the degradable organic substrates, while DCIP is used as a mobile electron carrier from the intracellular matrix of the metabolically active cells to the carbon paste electrode which served as the final electron acceptor. Therefore, the extracellular electron transfer from the formed active biofilm at the electrode surface is assisted by the existence of DCIP.

  20. Direct electrodeposition of gold nanotube arrays of rough and porous wall by cyclic voltammetry and its applications of simultaneous determination of ascorbic acid and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Yang Guangming, E-mail: yangguangmingbs@126.com [Department of Resources and Environment, Baoshan University, Baoshan 678000 (China); Li Ling [Department of Resources and Environment, Baoshan University, Baoshan 678000 (China); Jiang Jinhe; Yang Yunhui [College of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming 650092 (China)

    2012-08-01

    Gold nanotube arrays of rough and porous wall has been synthesized by direct electrodeposition with cyclic voltammetry utilizing anodic aluminum oxide template (AAO) and polycarbonate membrane (PC) during short time (only 3 min and 2 min, respectively). The mechanism of the direct electrodeposition of gold nanotube arrays by cyclic voltammetry (CV) has been discussed. The morphological characterizations of the gold nanotube arrays have been investigated by scanning electron microscopy (SEM). A simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry (DPV) was constructed by attaching gold nanotube arrays (using AAO) onto the surface of a glassy carbon electrode (GCE). The electrochemical behavior of AA and UA at this modified electrode has been studied by CV and differential pulse voltammetry (DPV). The sensor offers an excellent response for AA and UA and the linear response range for AA and UA were 1.02 Multiplication-Sign 10{sup -7}-5.23 Multiplication-Sign 10{sup -4} mol L{sup -1} and 1.43 Multiplication-Sign 10{sup -7}-4.64 Multiplication-Sign 10{sup -4} mol L{sup -1}, the detection limits were 1.12 Multiplication-Sign 10{sup -8} mol L{sup -1} and 2.24 Multiplication-Sign 10{sup -8} mol L{sup -1}, respectively. This sensor shows good regeneration, stability and selectivity and has been used for the determination of AA and UA in real human urine and serum samples with satisfied results. - Graphical abstract: The schematic diagram of formation of Au nanotube arrays (a) and the stepwise procedure of the sensor (b). Highlights: Black-Right-Pointing-Pointer Gold nanotubes array has been synthesized by cyclic voltammetry. Black-Right-Pointing-Pointer The mechanism of deposition of gold nanotube has been discussed. Black-Right-Pointing-Pointer A determination of ascorbic acid and uric acid was constructed by gold array. Black-Right-Pointing-Pointer A satisfied determination of samples can be obtained by this sensor.

  1. Selection and Evaluation of Electronic Resources Elektronik Kaynakların Seçimi ve Değerlendirilmesi

    Directory of Open Access Journals (Sweden)

    Doğan Atılgan

    2009-12-01

    Full Text Available Publication boom and issues related to controlling and accession of printed sources have created some problems after World War II. Consequently, publishing industry has encountered the problem of finding possible solution for emerged situation. Industry of electronic publishing has started to improve with the rapid increase of the price of printed sources as well as the problem of publication boom. The first effects of electronic publishing were appeared on the academic and scholarly publications then electronic publishing became a crucial part of all types of publications. As a result of these developments, collection developments and service policies of information centers were also significantly changed. In this article, after a general introduction about selection and evaluation processes of electronic publications, the subscribed databases by a state and a privately owned university in Turkey and their usage were examined. İkinci dünya savaşından sonra görülen yayın patlaması, basılı kaynakların denetim ve erişiminde sorunlar yaşanmasına neden olmuştur. Bu da yayıncılık sektöründe yeni arayışlara yol açmıştır. 1980’li yıllardan sonra basılı yayın fiyatlarındaki hızlı artış da bu etmenlere eklenince elektronik yayıncılık sektörü gelişmeye başlamıştır. Öncelikle bilimsel ve akademik yayınlarla başlayan elektronik yayın günümüzde tüm yayın türlerini kapsamaktadır. Yayıncılıktaki bu gelişim bilgi merkezlerinin derme geliştirme ve hizmet politikalarını da önemli ölçüde değiştirmiştir. Bu çalışmada elektronik yayınların seçim, değerlendirme ve sağlama konularında genel bir girişten sonra bir devlet üniversitesinin bir de özel üniversitenin abone olduğu veritabanları ve bu veri tabanlarının kullanımının değerlendirilmesi yapılmaktadır.

  2. Theory of linear sweep voltammetry with diffuse charge: Unsupported electrolytes, thin films, and leaky membranes

    Science.gov (United States)

    Yan, David; Bazant, Martin Z.; Biesheuvel, P. M.; Pugh, Mary C.; Dawson, Francis P.

    2017-03-01

    Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. In this paper, we provide a comprehensive mathematical theory of voltammetry in electrochemical cells with unsupported electrolytes and for other situations where diffuse charge effects play a role, and present analytical and simulated solutions of the time-dependent Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions for a 1:1 electrolyte and a simple reaction. Using these solutions, we construct theoretical and simulated current-voltage curves for liquid and solid thin films, membranes with fixed background charge, and cells with blocking electrodes. The full range of dimensionless parameters is considered, including the dimensionless Debye screening length (scaled to the electrode separation), Damkohler number (ratio of characteristic diffusion and reaction times), and dimensionless sweep rate (scaled to the thermal voltage per diffusion time). The analysis focuses on the coupling of Faradaic reactions and diffuse charge dynamics, although capacitive charging of the electrical double layers is also studied, for early time transients at reactive electrodes and for nonreactive blocking electrodes. Our work highlights cases where diffuse charge effects are important in the context of voltammetry, and illustrates which regimes can be approximated using simple analytical expressions and which require more careful consideration.

  3. Differential Cyclic Voltammetry - a Novel Technique for Selective and Simultaneous Detection using Redox Cycling Based Sensors

    NARCIS (Netherlands)

    Odijk, M.; Wiedemair, J.; Megen, M.J.J; Olthuis, W.; Berg, van den A.

    2010-01-01

    Redox cycling (RC) is an effect that is used to amplify electrochemical signals. However, traditional techniques such as cyclic voltammetry (CV) do not provide clear insight for a mixture of multiple redox couples while RC is applied. Thus, we have developed a new measurement technique which deliver

  4. Characterization of Fe implanted yttria-stabilized zirconia by cyclic voltammetry

    NARCIS (Netherlands)

    Hassel, van B.A.; Burggraaf, A.J.

    1992-01-01

    The technique of cyclic voltammetry has been applied to study reduction and oxidation phenomena which are observed at low oxygen partial pressures during steady state current-overpotential measurements of the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface. The redox potential (EO) of th

  5. Differential Cyclic Voltammetry - a Novel Technique for Selective and Simultaneous Detection using Redox Cycling Based Sensors

    NARCIS (Netherlands)

    Odijk, Mathieu; Wiedemair, Justyna; van Megen, M.J.J.; Olthuis, Wouter; van den Berg, Albert

    2010-01-01

    Redox cycling (RC) is an effect that is used to amplify electrochemical signals. However, traditional techniques such as cyclic voltammetry (CV) do not provide clear insight for a mixture of multiple redox couples while RC is applied. Thus, we have developed a new measurement technique which

  6. Development and Use of a Cyclic Voltammetry Simulator to Introduce Undergraduate Students to Electrochemical Simulations

    Science.gov (United States)

    Brown, Jay H.

    2015-01-01

    Cyclic voltammetry (CV) is a popular technique for the study of electrochemical mechanisms because the method can provide useful information on the redox couple. The technique involves the application of a potential ramp on an unstirred solution while the current is monitored, and then the ramp is reversed for a return sweep. CV is sometimes…

  7. Characterization of Fe implanted yttria-stabilized zirconia by cyclic voltammetry

    NARCIS (Netherlands)

    van Hassel, B.A.; van Hassel, B.A.; Burggraaf, Anthonie; Burggraaf, A.J.

    1992-01-01

    The technique of cyclic voltammetry has been applied to study reduction and oxidation phenomena which are observed at low oxygen partial pressures during steady state current-overpotential measurements of the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface. The redox potential (EO) of

  8. Polymyxin-coated Au and carbon nanotube electrodes for stable [NiFe]-hydrogenase film voltammetry.

    NARCIS (Netherlands)

    Hoeben, F.J.M.; Heller, I.; Albracht, S.P.J.; Dekker, C.; Lemay, S.G.; Heering, H.A.

    2008-01-01

    We report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier for studying protein film voltammetry (PFV) on Au and single-walled carbon nanotube (SWNT) electrodes. Pretreating the electrodes with PM allows for the subsequent immobilization of an active

  9. Polymyxin-coated Au and carbon nanotube electrodes for stable [NiFe]-hydrogenase film voltammetry.

    NARCIS (Netherlands)

    Hoeben, F.J.M.; Heller, I.; Albracht, S.P.J.; Dekker, C.; Lemay, S.G.; Heering, H.A.

    2008-01-01

    We report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier for studying protein film voltammetry (PFV) on Au and single-walled carbon nanotube (SWNT) electrodes. Pretreating the electrodes with PM allows for the subsequent immobilization of an active submonol

  10. Development and Use of a Cyclic Voltammetry Simulator to Introduce Undergraduate Students to Electrochemical Simulations

    Science.gov (United States)

    Brown, Jay H.

    2015-01-01

    Cyclic voltammetry (CV) is a popular technique for the study of electrochemical mechanisms because the method can provide useful information on the redox couple. The technique involves the application of a potential ramp on an unstirred solution while the current is monitored, and then the ramp is reversed for a return sweep. CV is sometimes…

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

    Science.gov (United States)

    Bard, Allen J.

    2007-01-01

    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.

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

    Science.gov (United States)

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

    2004-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  14. Determination of bosentan in pharmaceutical preparations by linear sweep, square wave and differential pulse voltammetry methods.

    Science.gov (United States)

    Atila, Alptug; Yilmaz, Bilal

    2015-01-01

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

  15. Kinetic Diversity of Striatal Dopamine: Evidence from a Novel Protocol for Voltammetry.

    Science.gov (United States)

    Walters, Seth H; Robbins, Elaine M; Michael, Adrian C

    2016-05-18

    In vivo voltammetry reveals substantial diversity of dopamine kinetics in the rat striatum. To substantiate this kinetic diversity, we evaluate the temporal distortion of dopamine measurements arising from the diffusion-limited adsorption of dopamine to voltammetric microelectrodes. We validate two mathematical procedures for correcting adsorptive distortion, both of which substantiate that dopamine's apparent kinetic diversity is not an adsorption artifact.

  16. THE TRANSFER OF TMA+ ION AT THE WATERN NITROBENZENE INTERFACE USING SEMI-DIFFERENTIAL CYCLIC VOLTAMMETRY

    Institute of Scientific and Technical Information of China (English)

    范瑞溪; 王小平

    1990-01-01

    This paper describes the investigation of the electrochemical phenomena of TMA+ transfer at the w/nb interface using semi-differential cyclic voltammetry. The expressions for the peak potential, half-wave width and peak current are derived. All the experimental results are in good agreement with the theoretical ones.

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

    Science.gov (United States)

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

    2005-01-01

    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…

  18. Utility of the electronic information resource UpToDate for clinical decision-making at bedside rounds.

    Science.gov (United States)

    Phua, J; See, K C; Khalizah, H J; Low, S P; Lim, T K

    2012-02-01

    Clinical questions often arise at daily hospital bedside rounds. Yet, little information exists on how the search for answers may be facilitated. The aim of this prospective study was, therefore, to evaluate the overall utility, including the feasibility and usefulness of incorporating searches of UpToDate, a popular online information resource, into rounds. Doctors searched UpToDate for any unresolved clinical questions during rounds for patients in general medicine and respiratory wards, and in the medical intensive care unit of a tertiary teaching hospital. The nature of the questions and the results of the searches were recorded. Searches were deemed feasible if they were completed during the rounds and useful if they provided a satisfactory answer. A total of 157 UpToDate searches were performed during the study period. Questions were raised by all ranks of clinicians from junior doctors to consultants. The searches were feasible and performed immediately during rounds 44% of the time. Each search took a median of three minutes (first quartile: two minutes, third quartile: five minutes). UpToDate provided a useful and satisfactory answer 75% of the time, a partial answer 17% of the time and no answer 9% of the time. It led to a change in investigations, diagnosis or management 37% of the time, confirmed what was originally known or planned 38% of the time and had no effect 25% of the time. Incorporating UpToDate searches into daily bedside rounds was feasible and useful in clinical decision-making.

  19. Exploration of Electrochemical Intermediates of the Anticancer Drug Doxorubicin Hydrochloride Using Cyclic Voltammetry and Simulation Studies with an Evaluation for Its Interaction with DNA

    Directory of Open Access Journals (Sweden)

    Partha Sarathi Guin

    2014-01-01

    Full Text Available Electrochemical behavior of the anticancer drug doxorubicin hydrochloride was studied using cyclic voltammetry in aqueous medium using Hepes buffer (pH~7.4. At this pH, doxorubicin hydrochloride undergoes a reversible two-electron reduction with E1/2 value −665±5 mV (versus Ag/AgCl, saturated KCl. Depending on scan rates, processes were either quasireversible (at low scan rates or near perfect reversible (at high scan rates. This difference in behavior of doxorubicin hydrochloride with scan rate studied over the same potential range speaks of differences in electron transfer processes in doxorubicin hydrochloride. Attempt was made to identify and understand the species involved using simulation. The information obtained was used to study the interaction of doxorubicin hydrochloride with calf thymus DNA. Cathodic peak current gradually decreased as more calf thymus DNA was added. The decrease in cathodic peak current was used to estimate the interaction of the drug with calf thymus DNA. Nonlinear curve fit analysis was applied to evaluate the intrinsic binding constant and site size of interaction that was compared with previous results on doxorubicin hydrochloride-DNA interaction monitored by cyclic voltammetry or spectroscopic techniques.

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

    Science.gov (United States)

    Niztayev, Alidin N; Hagen, Wilfred R

    2005-09-15

    A putatively highly sensitive and selective method for the determination of cobalt in aqueous samples by catalytic adsorptive cathodic stripping voltammetry using methyl thymol blue (MTB) as the ligand has been documented [A. Safavi, E. Shams, Talanta 51 (2000) 1117] and its underlying mechanism has been briefly explored [A. Safavi, E. Shams, Electroanalysis 14 (2002) 708]. In an attempt to adapt the method for application in metalloprotein analysis we obtained erratic results, which were traced down to the redox non-innocence of the free ligand in the potential range prescribed for the metal analysis. On the hanging mercury drop electrode free methyl thymol blue is reversibly one-electron reduced to the semiquinone form with E(m,7.0)=-482mV versus NHE at 22 degrees C, and the radical is subsequently quasi-reversibly one-electron reduced to the quinol form with E(m,7) approximately -0.9V. This observation invalidates the use of MTB in electrochemical analysis of metal ions. This is also the first observation ever of a stable quinone methide radical in aqueous solution.

  1. 图书馆纸质资源与电子资源投入比例研究%The research of ratio between traditional and electronics resources in library

    Institute of Scientific and Technical Information of China (English)

    王以婧; 李明

    2012-01-01

    With the popularization of electronic product development,library is no longer the paper-based resources into a single information carrier the pattern,but has formed a paper resource and electronic resources coexist in the new situation.Because the library types of our country,the proportion of input between paper-based resources and other kinds of resources exist difference.This paper will discuss the relationship between the traditional and electronics resources,and also points out the existing problems and the countermeasures.%随着电子产品的普及发展,图书馆已不再以纸质资源为唯一的信息载体,而是形成了纸质资源和电子资源并存的新局面。由于国内图书馆类型的不同,纸质资源与电子资源的配比也会存在差异。通过讨论二者的关系,指出存在的问题及应对之策。

  2. Detailed electrochemical studies of the tetraruthenium polyoxometalate water oxidation catalyst in acidic media: identification of an extended oxidation series using Fourier transformed alternating current voltammetry.

    Science.gov (United States)

    Lee, Chong-Yong; Guo, Si-Xuan; Murphy, Aidan F; McCormac, Timothy; Zhang, Jie; Bond, Alan M; Zhu, Guibo; Hill, Craig L; Geletii, Yurii V

    2012-11-05

    The electrochemistry of the water oxidation catalyst, Rb(8)K(2)[{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(γ-SiW(10)O(36))(2)] (Rb(8)K(2)-1(0)) has been studied in the presence and absence of potassium cations in both hydrochloric and sulfuric acid solutions by transient direct current (dc) cyclic voltammetry, a steady state dc method in the rotating disk configuration and the kinetically sensitive technique of Fourier transformed large-amplitude alternating current (ac) voltammetry. In acidic media, the presence of potassium ions affects the kinetics (apparent rate of electron transfer) and thermodynamics (reversible potentials) of the eight processes (A'/A to H/H') that are readily detected under dc voltammetric conditions. The six most positive processes (A'/A to F/F'), each involve a one electron ruthenium based charge transfer step (A'/A, B'/B are Ru(IV/V) oxidation and C/C' to F/F' are Ru(IV/III) reduction). The apparent rate of electron transfer of the ruthenium centers in sulfuric acid is higher than in hydrochloric acid. The addition of potassium cations increases the apparent rates and gives rise to a small shift of reversible potential. Simulations of the Fourier transformed ac voltammetry method show that the B'/B, E/E', and F/F' processes are quasi-reversible, while the others are close to reversible. A third Ru(IV/V) oxidation process is observed just prior to the positive potential limit via dc methods. Importantly, the ability of the higher harmonic components of the ac method to discriminate against the irreversible background solvent process allows this (process I) as well as an additional fourth reversible ruthenium based process (J) to be readily identified. The steady-state rotating disk electrode (RDE) method confirmed that all four Ru-centers in Rb(8)K(2)-1(0) are in oxidation state IV. The dc and ac data indicate that reversible potentials of the four ruthenium centers are evenly spaced, which may be relevant to understanding of the water oxidation

  3. There is a Relationship between Resource Expenditures and Reference Transactions in Academic Libraries. A Review of: Dubnjakovic, A. (2012. Electronic resource expenditure and the decline in reference transaction statistics in academic libraries. Journal of Academic Librarianship, 38(2, 94-100. doi:10.1016/j.acalib.2012.01.001

    Directory of Open Access Journals (Sweden)

    Annie M. Hughes

    2013-03-01

    Full Text Available Objective – To provide an analysis of the impact of expenditures on electronic resourcesand gate counts on the increase or decrease in reference transactions.Design – Analysis of results of existing survey data from the National Center for Educational Statistics (NCES 2006 Academic Library Survey(ALS.Setting – Academic libraries in the United States.Subjects – 3925 academic library respondents.Methods – The author chose to use survey data collected from the 2006 ALS conducted bythe NCES. The survey included data on various topics related to academic libraries, but in the case of this study, the author chose to analyze three of the 193 variables included. The three variables: electronic books expenditure, computer hardware and software, and expenditures on bibliographic utilities, were combined into one variable called electronic resource expenditure. Gate counts were also considered as a variable. Electronic resource expenditure was also split as a variable into three groups: low, medium, and high. Multiple regression analysis and general linear modeling, along with tests of reliability, were employed. Main Results – The author determined that low, medium, and high spenders with regard to electronic resources exhibited differences in gate counts, and gate counts have an effect on reference transactions in any given week. Gate counts tend to not have much of an effect on reference transactions for the higher spenders, and higher spenders tend to have a higher number of reference transactions overall. Low spenders have lower gate counts and also a lower amount of reference transactions.Conclusion – The findings from this study show that academic libraries spending more on electronic resources also tend to have an increase with regard to reference transactions. The author also concludes that library spaces are no longer the determining factor with regard to number of reference transactions. Spending more on electronic resources is

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

    Energy Technology Data Exchange (ETDEWEB)

    Jakuba, Rachel Wisniewski [Massachusetts Institute of Technology, Woods Hole Oceanographic Institution Joint Program in Chemical Oceanography, 266 Woods Hole Road, Woods Hole, MA 02543 (United States)], E-mail: jakuba.rachel@epa.gov; Moffett, James W. [Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543 (United States)], E-mail: jmoffett@usc.edu; Saito, Mak A. [Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543 (United States)

    2008-05-05

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

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

    Science.gov (United States)

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

    2008-05-05

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

  6. Detection of food additives by voltammetry at the liquid-liquid interface.

    Science.gov (United States)

    Herzog, Grégoire; Kam, Victor; Berduque, Alfonso; Arrigan, Damien W M

    2008-06-25

    Electrochemistry at the liquid-liquid interface enables the detection of nonredoxactive species with electroanalytical techniques. In this work, the electrochemical behavior of two food additives, aspartame and acesulfame K, was investigated. Both ions were found to undergo ion-transfer voltammetry at the liquid-liquid interface. Differential pulse voltammetry was used for the preparation of calibration curves over the concentration range of 30-350 microM with a detection limit of 30 microM. The standard addition method was applied to the determination of their concentrations in food and beverage samples such as sweeteners and sugar-free beverages. Selective electrochemically modulated liquid-liquid extraction of these species in both laboratory solutions and in beverage samples was also demonstrated. These results indicate the suitability of liquid-liquid electrochemistry as an analytical approach in food analysis.

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

    Science.gov (United States)

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

    2007-03-01

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

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

    Science.gov (United States)

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

    2014-09-15

    During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium

    CERN Document Server

    Hamad, Ibrahim Abou; Novotny, Mark A; Rikvold, Per Arne

    2007-01-01

    We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The Electrochemical first-order reversal curve (EC-FORC) diagram for a discontinuous phase transition (nucleation and growth), such as occurs in underpotential deposition, is characterized by a negative region, while such a region does not exist for a continuous phase transition, such as occurs in the electrosorption of Br on Ag(100). Moreover, for systems with a continuous phase transition, the minima of the individual EC-FORCs trace the equilibrium curve, even at very high scan rates. Since obtaining experimental data for the EC-FORC method would require only a simple reprogramming of the potentiostat used in conventional cyclic-voltammetry experiments, we believe that this method has significant potential for ea...

  10. Cyclic Voltammetry and Impedance Spectroscopy Behavior Studies of Polyterthiophene Modified Electrode

    Directory of Open Access Journals (Sweden)

    Naima Maouche

    2011-01-01

    Full Text Available We present in this work a study of the electrochemical behaviour of terthiophene and its corresponding polymer, which is obtained electrochemically as a film by cyclic voltammetry (CV on platinum electrode. The analysis focuses essentially on the effect of two solvents acetonitrile and dichloromethane on the electrochemical behaviour of the obtained polymer. The electrochemical behavior of this material was investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS. The voltammograms show that the film of polyterthiophene can oxide and reduce in two solutions; in acetonitrile, the oxidation current intensity is more important than in dichloromethane. The impedance plots show the semicircle which is characteristic of charge-transfer resistance at the electrode/polymer interface at high frequency and the diffusion process at low frequency.

  11. Electrochemical-Voltammetry Behavior of Several Aromatic Aldehydes in Acid Solution

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The electrochemical-voltammetry behavior of vanillin, heliotropin, anisaldehyde on the surface ofPt, Au electrodes in acid solution has been studied by means of the electrochemical cyclic voltammetry method. I was found that the electrochemical processes of them are irreversible on both Pt and Au elec-trodes. The electrochemical activity of vanillin is stronger than heliotropin's and heliotropin's is stronger than, anisaldehyde's on Pt electrode. While the electrochemical activity of anisaldehyde is stronger than heliotropin's and vanillin's is the weakest on Au. The results indicate that when they are used as additives for electroplating, they must be consumptive, and it will improve the leveling ability of plating solution and brightness of the deposition layer.

  12. Determination of Norfloxacin by square-wave adsorptive voltammetry on a glassy carbon electrode.

    Science.gov (United States)

    Ghoneim, M M; Radi, A; Beltagi, A M

    2001-05-01

    The adsorptive and electrochemical behavior of norfloxacin on a glassy carbon electrode were investigated by cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated that the process was irreversible and fundamentally controlled by adsorption. To obtain a good sensitivity, the solution conditions and instrumental parameters were studied using square-wave voltammetry. In acetate buffer of pH 5.0, norfloxacin gave a sensitive adsorptive oxidative peak at 0.920 V (versus Ag-AgCl). Applicability to measurement of norfloxacin at submicromolar levels in urine samples was illustrated. The peak current was linear with the norfloxacin concentration in the range 5-50 microg ml(-1) urine. The detection limit was 1.1 microg ml(-1) urine.

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

    Science.gov (United States)

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

    2015-02-01

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

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

    Science.gov (United States)

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

    2014-05-15

    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.

  15. Voltametria de onda quadrada. Segunda parte: aplicações Square wave voltammetry. Second part: applications

    Directory of Open Access Journals (Sweden)

    Djenaine de Souza

    2004-10-01

    Full Text Available The aim of this work is to discuss some selected applications of square wave voltammetry published in the last five years. The applications focused here cover several electroanalytical fields such as: determination of pesticides; molecules with biological activity; metals and other environmental pollutants. Special attention is given to the work developed in the Grupo de Materiais Eletroquímicos e Métodos Eletroanalíticos - IQSC - USP concerning the utilization of square wave voltammetry, with different kinds of electrodes, for the determination of pesticides in natural waters and active principles in pharmaceutical formulations. The new methodology is simple, fast and sensitive when compared with the traditional ones such as chromatography and spectrophotometry. The satisfactory results obtained provide alternative procedures for the quality control of drugs and the monitoring of pesticides in natural environments.

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

    OpenAIRE

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

    2012-01-01

    Fast-scan cyclic voltammetry (FSCV) is a common analytical electrochemistry tool used to measure chemical species. It has recently been adapted for measurement of neurotransmitters such as dopamine in awake and behaving animals (in vivo). Electrode calibration is an essential step in FSCV to relate observed current to concentration of a chemical species. However, existing methods require multiple components, which reduce the ease of calibrations. To this end, a microfluidic flow cell (µFC) wa...

  17. EC-FORC: A New Cyclic Voltammetry Based Method for Examining Phase Transitions and Predicting Equilibrium

    OpenAIRE

    2007-01-01

    We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite accurately recover equilibrium behavior from dynamic analysis of systems with a continuous phase transition. The Electrochemical first-order reversal curve (EC-FORC) diagram for a discontinuous phase transition (nucleation and growth), such as occurs in underpotential deposition, is characterized by a neg...

  18. Detection of heavy metals in biological samples through anodic stripping voltammetry

    OpenAIRE

    Buzea, Vlad; Florescu, Monica; Badea, Mihaela

    2012-01-01

    The toxicological aspects due to the presence of heavy metals in biological samples impose to have accurate and rapid methods for their detection. This paper is aimed to review approaches to anodic stripping voltammetry (ASV) determination of several heavy metals (lead, cadmium, copper, mercury, zinc) in biological matrices (blood, urine, saliva, tissue sample). Analytical performances (LOD, data linearity range, sensitivity) of the reviewed methods were presented for several electrochemical ...

  19. New aspects of the electrochemical-catalytic (EC’) mechanism in square-wave voltammetry

    OpenAIRE

    Gulaboski, Rubin; Mirceski, Valentin

    2015-01-01

    Several new theoretical aspects of the electrocatalytic (regenerative) EC’ mechanism under conditions of square-wave (SWV) and staircase cyclic voltammetry (SCV) are presented. Elaborating the effect of the rate of the catalytic reaction in the diffusion-controlled catalytic mechanism (diffusional EC’ mechanism) and surface catalytic mechanism (surface EC’ mechanism), we refer to several phenomena related to the shift of the position and the half-peak width of the net peak in ...

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

    OpenAIRE

    MARTÍNEZ GIL, PABLO; Laguarda Miró, Nicolás; Soto Camino, Juan; Masot Peris, Rafael

    2013-01-01

    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 count...

  1. Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing

    Science.gov (United States)

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

    1993-01-01

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

  2. The redox status of experimental hemorrhagic shock as measured by cyclic voltammetry.

    Science.gov (United States)

    Mittal, Anubhav; Göke, Friederike; Flint, Richard; Loveday, Benjamin P T; Thompson, Nichola; Delahunt, Brett; Kilmartin, Paul A; Cooper, Garth J S; MacDonald, Julia; Hickey, Anthony; Windsor, John A; Phillips, Anthony R J

    2010-05-01

    Hemorrhagic shock (HS) leads to reactive oxygen species production. However, clinicians do not have access to bedside measurements of the redox status during HS. Cyclic voltammetry (CyV) is a simple electrochemical method of measuring redox status. The aims of this study were to 1) report the first application of cyclic voltammetry to measure the acute changes in serum redox status after HS, 2) to contrast it with another severe systemic disease with a different redox pathology (acute pancreatitis [AP]), and 3) to describe the response of CyV over time in a resolving model of AP. In the acute study, 24 male Wistar rats were randomized into three groups: groups 1 (control), 2 (AP), and 3 (HS). In the time-course study, 28 rats were randomized to a sham-control as well as 6 and 24 h post-AP cohorts, respectively.Cyclic voltammetry was performed using a three-electrode system. In the acute study, the first and second voltammetric peaks increased significantly in HS. In contrast, within the AP group, only the first voltammetric peak showed a significant increase. The first voltammetric peak correlated with plasma protein carbonyls (PCs) and with thiobarbituric acid-reactive substances, whereas the second voltammetric peak correlated positively with plasma protein carbonyls. In the second study, the first voltammetric peak correlated with physiological improvements. Here, we showed that serum CyV could respond to the serum redox change in HS and AP. Cyclic voltammetry warrants evaluation as a potential real-time beside measure of a patient's redox status during shock.

  3. A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects

    OpenAIRE

    Adib J. Samin

    2016-01-01

    In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level ...

  4. Dating copper-based archaeological materials using the voltammetry of microparticles

    OpenAIRE

    Doménech-Carbó, Antonio; Capelo, Sofia; Doménech-Carbó, María Teresa

    2014-01-01

    The voltammetry of microparticles, an electrochemical technique providing information on the composition of archaeological materials using an essentially non invasive analysis [1,2] was previously applied for dating lead-based materials [3,4]. It is described the application of this methodology for dating copper-based archaeological materials based on a theoretical model for long term metal corrosion [5]. Dating is based on the measurement of the voltammetric signals of cuprite and tenorite f...

  5. A pipette-based calibration system for fast-scan cyclic voltammetry with fast response times.

    Science.gov (United States)

    Ramsson, Eric S

    2016-01-01

    Fast-scan cyclic voltammetry (FSCV) is an electrochemical technique that utilizes the oxidation and/or reduction of an analyte of interest to infer rapid changes in concentrations. In order to calibrate the resulting oxidative or reductive current, known concentrations of an analyte must be introduced under controlled settings. Here, I describe a simple and cost-effective method, using a Petri dish and pipettes, for the calibration of carbon fiber microelectrodes (CFMs) using FSCV.

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

    Science.gov (United States)

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

    2014-01-31

    Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Cathodic stripping voltammetry of trace Mn(II) at carbon film electrodes

    OpenAIRE

    Filipe, Olga M. S.; Brett,Christopher M.A.

    2003-01-01

    A sensitive voltammetric method is presented for the determination of tract levels of Mn (II) using carbon film electrodes fabricated from carbon resistors of 2 [Omega]. Determination of manganese was made by square wave cathodic stripping voltammetry (CSV), with deposition of manganese as manganese dioxide. Chronoamperometric experiments were made to study MnO2 nucleation and growth. As a result, it was found to be necessary to perform electrode conditioning at a more positive potential to i...

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

    Science.gov (United States)

    Yosypchuk, B; Novotný, L

    2002-04-01

    Silver and copper solid amalgam electrodes (modified with mercury meniscus and based on amalgamation of fine metallic powder) have been successfully tested for cathodic stripping voltammetry of cysteine. In the case of the silver solid amalgam electrode AgSAE the relative standard deviation (RSD) and the detection limit (3 SD) reached +/-2.3% and 3x10(-9) mol l(-1) cysteine, respectively.

  9. Square-Wave Voltammetry of Cathodic Stripping Reactions. Diagnostic Criteria, Redox Kinetic Measurements, and Analytical Applications

    OpenAIRE

    Gulaboski, Rubin; Mirceski, Valentin; Komorsky-Lovrić, Šebojka; Lovrić, Milivoj

    2004-01-01

    A comparative study of different types of cathodic stripping reactions under conditions of square-wave voltammetry is presented. Cathodic stripping processes involving reactions of second order as well as reactions coupled by adsorption of the reacting ligand are analyzed The inherent parameters, controlling the overall voltammetric behavior of each cathodic stripping electrode reaction are derived. The criteria for qualitative distinguishing of each mechanism are established as w...

  10. Porosity Study of Hybrid Silica Mesostructure in Aluminium Oxide Membrane Columnar by Cyclic Voltammetry Method

    Directory of Open Access Journals (Sweden)

    M.N. Jalil

    2011-12-01

    Full Text Available Silica mesostructure has been grown within with a porous aluminium oxide membrane columnar material (hybrid-AOM. This was prepared using a sol-gel technique with Pluronic P123 triblock copolymer as the structure-directing agent and tetraethyl orthosilicate as the inorganic source. The porosity of the hybrid-AOM after ethanol extraction was calculated from the cyclic voltammetry response of a neutral probe (FcMeOH, using Randles-Sevčik equation.

  11. Preparation and Cyclic Voltammetry Characterization Of Cu-dipyridyl Imprinted Polymer

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Polymer capable of specific binding to Cu-dipyridyl complex was prepared by molecular imprinting technology.The binding specificity of the polymer to the template (Cu-dipyridyl complex) was investigated by cyclic voltametric scanning using the carbon paste electrode modified by polymer particles in phosphate buffer solution.Factors that influence rebinding of the imprinted polymer were explored.The result demonstrated that the cyclic voltammetry was an efficient approach to explore interactions between template and imprinted polymers.

  12. Simultaneous identification of lead pigments and binding media in paint samples using voltammetry of microparticles

    OpenAIRE

    DOMENECH CARBO, ANTONIO; Domenech Carbo, Mª Teresa; Mas Barberà, Xavier; Ciarrocci, Julia

    2007-01-01

    Voltammetry of microparticles is applied to the simultaneous determination of lead pigments and binding media in paint samples. The mechanical attachment of a few nanograms of sample to a paraffin-impregnated graphite electrode produced well-defined square wave voltammetric responses for model paint specimens containing lead white, minium and Naples yellow associated with linseed, sunflower and poppy oils and casein, egg, and bovine gelatin. The use of a multiparametric fitting of the electro...

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

    Science.gov (United States)

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

    2011-12-20

    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 π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-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 π-electron-rich recognition sites being part of a macrocyclic polyether.

  14. Study on the adsorptive catalytic voltammetry of aloe-emodin at a carbon paste electrode

    Institute of Scientific and Technical Information of China (English)

    LI; Ju'nan; GAO; Peng; LI; Xiangling; YAN; Zhihong; MAO; Xu

    2005-01-01

    A new catalytic voltammetric method for the determination of anthraqunone medicines at a carbon paste electrode (CPE) was described for the first time. The mechanism of the catalytic reaction was investigated by using linear sweep voltammetry, cyclic voltammetry, constant potential electrolysis and so on. The experiment results indicate that aloe-emodin was efficiently accumulated at a CPE by adsorption. In the following potential scan, aloe-emodin was reduced to homologous anthrahydroquinone compound, then the compound was immediately oxidized to aloe-emodin by the dissolved oxygen, and the aloe-emodin was again reduced at the CPE. As a result, a cyclic catalytic reaction was established. But a reversible redox reaction of aloe-emodin can only be observed at a mercury electrode, no catalytic reaction occurs there. A sensitive catalytic voltammetric peak of aloe-emodin was obtained at about -0.60 V (vs. SCE) in 0.56 mol/L NH3-NH4Cl buffer (pH 8.9). The proposed method was applied to the determination of aloe-emodin in the Radix Rhei with satisfactory results. The determination results were in good agreement with reference values obtained by the HPLC. The adsorptive catalytic voltammetry for the determination of organic compound at CPE, chemically modified electrode and other solid electrodes could be significant in the studies on pharmacology, pharmacodynamics, toxicity of medicine, clinical medicine and biochemistry.

  15. Alternating current scanning electrochemical microscopy with simultaneous fast-scan cyclic voltammetry.

    Science.gov (United States)

    Koch, Jason A; Baur, Melinda B; Woodall, Erica L; Baur, John E

    2012-11-06

    Fast-scan cyclic voltammetry (FSCV) is combined with alternating current scanning electrochemical microscopy (AC-SECM) for simultaneous measurements of impedance and faradaic current. Scan rates of 10-1000 V s(-1) were used for voltammetry, while a high-frequency (100 kHz), low-amplitude (10 mV rms) sine wave was added to the voltammetric waveform for the ac measurement. Both a lock-in amplifier and an analog circuit were used to measure the amplitude of the resultant ac signal. The effect of the added sine wave on the voltammetry at a carbon fiber electrode was investigated and found to have negligible effect. The combined FSCV and ac measurements were used to provide simultaneous chemical and topographical information about a substrate using a single carbon fiber probe. The technique is demonstrated in living cell culture, where cellular respiration and topography were simultaneously imaged without the addition of a redox mediator. This approach promises to be useful for the topographical and multidimensional chemical imaging of substrates.

  16. Catalytic mechanism in cyclic voltammetry at disc electrodes: an analytical solution.

    Science.gov (United States)

    Molina, Angela; González, Joaquín; Laborda, Eduardo; Wang, Yijun; Compton, Richard G

    2011-08-28

    The theory of cyclic voltammetry at disc electrodes and microelectrodes is developed for a system where the electroactive reactant is regenerated in solution using a catalyst. This catalytic process is of wide importance, not least in chemical sensing, and it can be characterized by the resulting peak current which is always larger than that of a simple electrochemical reaction; in contrast the reverse peak is always relatively diminished in size. From the theoretical point of view, the problem involves a complex physical situation with two-dimensional mass transport and non-uniform surface gradients. Because of this complexity, hitherto the treatment of this problem has been tackled mainly by means of numerical methods and so no analytical expression was available for the transient response of the catalytic mechanism in cyclic voltammetry when disc electrodes, the most popular practical geometry, are used. In this work, this gap is filled by presenting an analytical solution for the application of any sequence of potential pulses and, in particular, for cyclic voltammetry. The induction principle is applied to demonstrate mathematically that the superposition principle applies whatever the geometry of the electrode, which enabled us to obtain an analytical equation valid whatever the electrode size and the kinetics of the catalytic reaction. The theoretical results obtained are applied to the experimental study of the electrocatalytic Fenton reaction, determining the rate constant of the reduction of hydrogen peroxide by iron(II).

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

    Science.gov (United States)

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

    2014-03-17

    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.

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

    Science.gov (United States)

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

    2014-12-16

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

  19. Electrochemical characterisation and anodic stripping voltammetry at mesoporous platinum rotating disc electrodes.

    Science.gov (United States)

    Lozano-Sanchez, Pablo; Elliott, Joanne M

    2008-02-01

    Using the technique of liquid crystal templating a rotating disc electrode (RDE) was modified with a high surface area mesoporous platinum film. The surface area of the electrode was characterised by acid voltammetry, and found to be very high (ca. 86 cm(2)). Acid characterisation of the electrode produced distorted voltammograms was interpreted as being due to the extremely large surface area which produced a combination of effects such as localised pH change within the pore environment and also ohmic drop effects. Acid voltammetry in the presence of two different types of surfactant, namely Tween 20 and Triton X-100, suggested antifouling properties associated with the mesoporous deposit. Further analysis of the modified electrode using a redox couple in solution showed typical RDE behaviour although extra capacitive currents were observed due to the large surface area of the electrode. The phenomenon of underpotential deposition was exploited for the purpose of anodic stripping voltammetry and results were compared with data collected for microelectrodes. Underpotential deposition of metal ions at the mesoporous RDE was found to be similar to that at conventional platinum electrodes and mesoporous microelectrodes although the rate of surface coverage was found to be slower at a mesoporous RDE. It was found that a mesoporous RDE forms a suitable system for quantification of silver ions in solution.

  20. Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.

    Science.gov (United States)

    Barus, C; Romanytsia, I; Striebig, N; Garçon, V

    2016-11-01

    A Square Wave Voltammetry electrochemical method is proposed to measure phosphate in seawater as pulse techniques offer a higher sensitivity as compared to classical cyclic voltammetry. Chronoamperometry cannot be either adapted for an in situ sensor since this method requires to have controlled convection which will be impossible in a miniaturised sensor. Tests and validation of Square Wave Voltammetry parameters have been performed using an open cell and for the first time with a small volume (<400µL) laboratory prototypes. Two designs of prototypes have been compared. Using high frequency (f=250Hz) allows to obtain a linear behaviour between 0.1 and 1µmolL(-1) with a very low limit of detection of 0.05 µmolL(-1) after 60min of complexation waiting time. In order to obtain a linear regression for a larger concentration range i.e. 0.25-4µmolL(-1), a lower frequency of 2.5Hz is needed. A limit of detection of 0.1µmolL(-1) is obtained in this case after 30min of complexation waiting time for the peak measured at E=0.12V. Changing the position of the molybdenum electrode for the complexation step and moving the detection into another electrochemical cell allow to decrease the reaction time down to 5min. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

    2014-06-24

    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 μm(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 μm(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.

  2. Hydrogen-bonding effect on spin-center transfer of tetrathiafulvalene-linked 6-oxophenalenoxyl evaluated using temperature-dependent cyclic voltammetry and theoretical calculations.

    Science.gov (United States)

    Nishida, Shinsuke; Fukui, Kozo; Morita, Yasushi

    2014-02-01

    The stable tetrathiafulvalene (TTF)-linked 6-oxophenalenoxyl neutral radical exhibits a spin-center transfer with a continuous color change in solution caused by an intramolecular electron transfer, which is dependent on solvent and temperature. Cyclic voltammetry measurements showed that addition of 2,2,2-trifluoroethanol (TFE) to a benzonitrile solution of the neutral radical induces a redox potential shift that is favorable for the spin-center transfer. Temperature-dependent cyclic voltammetry of the neutral radical using a novel low-temperature electrochemical cell demonstrated that the redox potentials change with decreasing temperature in a 199:1 CH2Cl2/TFE mixed solvent. Furthermore, theoretical calculation revealed that the energy levels of the frontier molecular orbitals involved in the spin-center transfer are lowered by the hydrogen-bonding interaction of TFE with the neutral radical. These results indicate that the hydrogen-bonding effect is a key factor for the occurrence of the spin-center transfer of TTF-linked 6-oxophenalenoxyl. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 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.

    Science.gov (United States)

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

    2014-03-15

    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 μM to 1129 μM with a sensitivity of 0.266 μA μM(-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.

  4. Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step.

    Science.gov (United States)

    Laffont, Laure; Hezard, Teddy; Gros, Pierre; Heimbürger, Lars-Eric; Sonke, Jeroen E; Behra, Philippe; Evrard, David

    2015-08-15

    Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs-GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs-GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10(-2)M range. Finally, the AuNPs-GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM).

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

    Science.gov (United States)

    Weidner, John W.; Fedkiw, Peter S.

    1991-01-01

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

  6. Cyclic voltammetry and impedance studies of electrodeposited polypyrrole nanoparticles doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahim, Sh. M., E-mail: shebrahim@igsr.alex.edu.e [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Postal Code 21526, Alexandria (Egypt); Latif, M.M. Abd-El [Mubarak City for Scientific Research and Technology Applications, Institute of Advanced Technology and New Materials, Borg El-Arab City, Alexandria (Egypt); Gad, A.M.; Soliman, M.M. [Department of Materials Science, Institute of Graduate Studies and Research, Alexandria University, Postal Code 21526, Alexandria (Egypt)

    2010-05-31

    Electrochemical synthesis of polypyrrole (PPY), doped with 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPSNa), was carried out using chronoamperometric technique. Cyclic voltammetry measurements showed that the electroactivity of PPY films, doped with AMPSNa, increases with the film thickness. Scanning electron microscopy photographs revealed that the PPY particles are in the nano-scale range and that their size depends on the potential at which the PPY has formed. Electrochemical impedance spectroscopy (EIS), in the potential range of + 1.0 and - 1.0 V, revealed in the PPY film charge transfer domination with a semicircle at high frequencies, and anion diffusion dominance at low frequencies. EIS also showed that the charge transfer resistance of PPY film at - 1.0 V is lower than what is expected and that on increasing the thickness of the PPY films, the overall impedance decreases. The proposed equivalent circuit model, based on the double layer capacity and the Warburg impedance, was replaced by two constant-phase elements to fit the experimental work of this study. The values of the fractional exponent of the first constant phase element at approximately 0.5 indicate that the processes have a diffusion-limited nature.

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

    Science.gov (United States)

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

    2014-06-15

    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.

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

    Science.gov (United States)

    Fang, Yishan; Huang, Xinjian; Wang, Lishi

    2015-01-06

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

  9. Substituent Inductive Effects on the Electrochemical Oxidation of Flavonoids Studied by Square Wave Voltammetry and Ab Initio Calculations.

    Science.gov (United States)

    Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo

    2016-10-27

    Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.

  10. Solid-state voltammetry-based electrochemical immunosensor for Escherichia coli using graphene oxide-Ag nanoparticle composites as labels.

    Science.gov (United States)

    Jiang, Xiaochun; Chen, Kun; Wang, Jing; Shao, Kang; Fu, Tao; Shao, Feng; Lu, Donglian; Liang, Jiangong; Foda, M Frahat; Han, Heyou

    2013-06-21

    A new electrochemical immunosensor based on solid-state voltammetry was fabricated for the detection of Escherichia coli (E. coli) by using graphene oxide-Ag nanoparticle composites (P-GO-Ag) as labels. To construct the platform, Au nanoparticles (AuNPs) were first self-assembled on an Au electrode surface through cysteamine and served as an effective matrix for antibody (Ab) attachment. Under a sandwich-type immunoassay format, the analyte and the probe (P-GO-Ag-Ab) were successively captured onto the immunosensor. Finally, the bonded AgNPs were detected through a solid-state redox process in 0.2 M of KCl solution. Combining the advantages of the high-loading capability of graphene oxide with promoted electron-transfer rate of AuNPs, this immunosensor produced a 26.92-fold signal enhancement compared with the unamplified protocol. Under the optimal conditions, the immunosensor exhibited a wide linear dependence on the logarithm of the concentration of E. coli ranging from 50 to 1.0 × 10(6) cfu mL(-1) with a detection limit of 10 cfu mL(-1). Moreover, as a practical application, the proposed immunosensor was used to monitor E. coli in lake water with satisfactory results.

  11. If Information Wants To Be Free...Then Who's Going To Pay for It? [and] A Question of Access: SPARC, BioOne, and Society-Driven Electronic Publishing [and] Who Is Going To Mine Digital Library Resources? And How?

    Science.gov (United States)

    Kaser, Richard T.; Johnson, Richard K.; Rudner, Lawrence

    2000-01-01

    Discusses Fair Use and the public perception; models for funding information services; publishers illusion that information is/should be free; Internet's role in making information freely available; scholarly communication systems: Scholarly Publishing and Academic Resources Coalition (SPARC) and BioOne (an electronic aggregation of bioscience…

  12. If Information Wants To Be Free...Then Who's Going To Pay for It? [and] A Question of Access: SPARC, BioOne, and Society-Driven Electronic Publishing [and] Who Is Going To Mine Digital Library Resources? And How?

    Science.gov (United States)

    Kaser, Richard T.; Johnson, Richard K.; Rudner, Lawrence

    2000-01-01

    Discusses Fair Use and the public perception; models for funding information services; publishers illusion that information is/should be free; Internet's role in making information freely available; scholarly communication systems: Scholarly Publishing and Academic Resources Coalition (SPARC) and BioOne (an electronic aggregation of bioscience…

  13. Impact of two interventions on timeliness and data quality of an electronic disease surveillance system in a resource limited setting (Peru: a prospective evaluation

    Directory of Open Access Journals (Sweden)

    Quispe Jose A

    2009-03-01

    Full Text Available Abstract Background A timely detection of outbreaks through surveillance is needed in order to prevent future pandemics. However, current surveillance systems may not be prepared to accomplish this goal, especially in resource limited settings. As data quality and timeliness are attributes that improve outbreak detection capacity, we assessed the effect of two interventions on such attributes in Alerta, an electronic disease surveillance system in the Peruvian Navy. Methods 40 Alerta reporting units (18 clinics and 22 ships were included in a 12-week prospective evaluation project. After a short refresher course on the notification process, units were randomly assigned to either a phone, visit or control group. Phone group sites were called three hours before the biweekly reporting deadline if they had not sent their report. Visit group sites received supervision visits on weeks 4 & 8, but no phone calls. The control group sites were not contacted by phone or visited. Timeliness and data quality were assessed by calculating the percentage of reports sent on time and percentage of errors per total number of reports, respectively. Results Timeliness improved in the phone group from 64.6% to 84% in clinics (+19.4 [95% CI, +10.3 to +28.6]; p Conclusion Regular phone reminders significantly improved timeliness of reports in clinics and ships, whereas supervision visits led to improved data quality only among clinics. Further investigations are needed to establish the cost-effectiveness and optimal use of each of these strategies.

  14. Metadata for Electronic Information Resources

    Science.gov (United States)

    2004-12-01

    among digital libraries . METS provides an XML DTD that can point to metadata in other schemes by declaring the scheme that is being used. For example...site: www.niso.org/news/Metadata_simpler.pdf International Federation of Library Associations and Institutions (IFLA). (2002). Digital Libraries : Metadata

  15. 基于ASP.NET的电子资源整合系统设计与实现%Design and Realization of an Integrated Electronic Resource System Based on ASP.NET

    Institute of Scientific and Technical Information of China (English)

    冀宪武; 陈晓冬; 何燕; 杨方; 曹宇宾; 潘大丰

    2011-01-01

    电子信息资源的整合是数字图书馆建设中的一个非常重要的环节,论述了数字资源整合的必要性,结合农业图书馆的实际,开展了电子资源整合服务平台的设计与实现。%The integration of electronic information resources is a very important part in digital library construction.In this paper,the necessity for integration of digital resources was discussed,combined with the actuality of the agricultural library,the design and implementation about services platform of electronic resource integration were carried out.

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

    Science.gov (United States)

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

    2007-03-01

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

  17. Theoretical and experimental study of redox processes combined with adsorption phenomena under conditions of square-wave voltammetry

    OpenAIRE

    Gulaboski, Rubin

    2001-01-01

    Theoretical models of four electrode reactions coupled with adsorption phenomena under conditions of square-wave voltammetry are developed: simple surface redox reaction, surface catalytic reaction, cathodic stripping reaction of I order, and cathodic stripping reaction of II order.

  18. Examining the complex regulation and drug-induced plasticity of dopamine release and uptake using voltammetry in brain slices.

    Science.gov (United States)

    Ferris, Mark J; Calipari, Erin S; Yorgason, Jordan T; Jones, Sara R

    2013-05-15

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

  19. Ferrocene-Boronic Acid-Fructose Binding Based on Dual-Plate Generator-Collector Voltammetry and Square-Wave Voltammetry.

    Science.gov (United States)

    Li, Meng; Xu, Su-Ying; Gross, Andrew J; Hammond, Jules L; Estrela, Pedro; Weber, James; Lacina, Karel; James, Tony D; Marken, Frank

    2015-06-10

    The interaction of ferrocene-boronic acid with fructose is investigated in aqueous 0.1 m phosphate buffer at pH 7, 8 and 9. Two voltammetric methods, based on 1) a dual-plate generator-collector micro-trench electrode (steady state) and 2) a square-wave voltammetry (transient) method, are applied and compared in terms of mechanistic resolution. A combination of experimental data is employed to obtain new insights into the binding rates and the cumulative binding constants for both the reduced ferrocene-boronic acid (pH dependent and weakly binding) and for the oxidised ferrocene-boronic acid (pH independent and strongly binding).

  20. Library resources on the Internet

    Science.gov (United States)

    Buchanan, Nancy L.

    1995-07-01

    Library resources are prevalent on the Internet. Library catalogs, electronic books, electronic periodicals, periodical indexes, reference sources, and U.S. Government documents are available by telnet, Gopher, World Wide Web, and FTP. Comparatively few copyrighted library resources are available freely on the Internet. Internet implementations of library resources can add useful features, such as full-text searching. There are discussion lists, Gophers, and World Wide Web pages to help users keep up with new resources and changes to existing ones. The future will bring more library resources, more types of library resources, and more integrated implementations of such resources to the Internet.

  1. The structure and function of quinones in biological solar energy transduction: a cyclic voltammetry, EPR, and hyperfine sub-level correlation (HYSCORE) spectroscopy study of model naphthoquinones.

    Science.gov (United States)

    Coates, Christopher S; Ziegler, Jessica; Manz, Katherine; Good, Jacob; Kang, Bernard; Milikisiyants, Sergey; Chatterjee, Ruchira; Hao, Sijie; Golbeck, John H; Lakshmi, K V

    2013-06-20

    Quinones function as electron transport cofactors in photosynthesis and cellular respiration. The versatility and functional diversity of quinones is primarily due to the diverse midpoint potentials that are tuned by the substituent effects and interactions with surrounding amino acid residues in the binding site in the protein. In the present study, a library of substituted 1,4-naphthoquinones are analyzed by cyclic voltammetry in both protic and aprotic solvents to determine effects of substituent groups and hydrogen bonds on the midpoint potential. We use continuous-wave electron paramagnetic resonance (EPR) spectroscopy to determine the influence of substituent groups on the electronic properties of the 1,4-naphthoquinone models in an aprotic solvent. The results establish a correlation between the presence of substituent group(s) and the modification of electronic properties and a corresponding shift in the midpoint potential of the naphthoquinone models. Further, we use pulsed EPR spectroscopy to determine the effect of substituent groups on the strength and planarity of the hydrogen bonds of naphthoquinone models in a protic solvent. This study provides support for the tuning of the electronic properties of quinone cofactors by the influence of substituent groups and hydrogen bonding interactions.

  2. 基于 EZproxy 日志的电子资源异常访问行为研究%Research on Abnormal Access to Electronic Resources Based on EZproxy Logs

    Institute of Scientific and Technical Information of China (English)

    雷东升; 郭振英

    2016-01-01

    The off - campus access to electronic resources in the library benefits readers a lot .Meanwhile ,some abnormal access behavior arises .The paper analyzed the electronic resources access log with EZproxyog proxy server ,designed and devel-oped the EZproxy log analysis system so as to pretreat ,upload ,count and analyze the access log to electronic resources .To dis-cover the abnormal access behavior of readers on the basis of the characteristics of their access and to classify the abnormal behav -ior , the paper could avoid that IP is temporarily blocked by the supporters of database of electronic resources in the library so that can maintain the readers' rights and improve the efficiency of resource access .%校外访问图书馆电子资源在方便读者的同时也出现一些异常访问行为,利用 EZproxy 代理服务器日志信息分析异常访问行为特征,设计并开发 EZproxy 日志分析系统,完成对电子资源访问日志的预处理、上传、统计和分析,从访问特征发掘读者的异常访问行为,对异常行为情况分类处理,基本避免了异常访问行为导致图书馆电子资源被数据库商临时封掉 IP 的现象出现,维护图书馆读者的合法权利,提高资源访问效率。

  3. Oxidation management of white wines using cyclic voltammetry and multivariate process monitoring.

    Science.gov (United States)

    Martins, Rui C; Oliveira, Raquel; Bento, Fatima; Geraldo, Dulce; Lopes, Vitor V; Guedes de Pinho, Paula; Oliveira, Carla M; Silva Ferreira, Antonio C

    2008-12-24

    The development of a fingerprinting strategy capable to evaluate the "oxidation status" of white wines based on cyclic voltammetry is proposed here. It is known that the levels of specific antioxidants and redox mechanisms may be evaluated by cyclic voltammetry. This electrochemical technique was applied on two sets of samples. One group was composed of normal aged white wines and a second group obtained from a white wine forced aging protocol with different oxygen, SO(2), pH, and temperature regimens. A study of antioxidant additions, namely ascorbic acid, was also made in order to establish a statistical link between voltammogram fingerprints and chemical antioxidant substances. It was observed that the oxidation curve presented typical features, which enables sample discrimination according to age, oxygen consumption, and antioxidant additions. In fact, it was possible to place the results into four significant orthogonal directions, compressing 99.8% of nonrandom features. Attempts were made to make voltammogram fingerprinting a tool for monitoring oxidation management. For this purpose, a supervised multivariate control chart was developed using a control sample as reference. When white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity. Finally, quantification of substances implicated in the oxidation process as reagents (antioxidants) and products (off-flavors) was tried using a supervised algorithmic the partial least square regression analysis. Good correlations (r > 0.93) were observed for ascorbic acid, Folin-Ciocalteu index, total SO(2), methional, and phenylacetaldehyde. These results show that cyclic voltammetry fingerprinting can be used to monitor and diagnose the effects of wine oxidation.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guerreiro, Gabriela V.; Zaitouna, Anita J.; Lai, Rebecca Y., E-mail: rlai2@unl.edu

    2014-01-31

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

  5. Hydrodynamic sono-voltammetry of ferrocene in [Tf2N]- based ionic liquid media.

    Science.gov (United States)

    Costa, Cédric; Doche, Marie-Laure; Hihn, Jean-Yves; Bisel, Isabelle; Moisy, Philippe; Lévêque, Jean-Marc

    2010-02-01

    The present work deals with the hydrodynamic behavior of several room-temperature ionic liquids presenting the same bis(trifluoromethanesulfonyles)imide anion, associated with four different cations: 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, N-trimethyl-N-propylammonium and 1-butyl-1-methylpyrrolidinium cations. Steady state voltammetry was used as an electrochemical technique to characterize mass transfer in both silent and sonicated conditions, using a rotating disk electrode. Results obtained in RTILs media are compared to those acquired in synthetic solutions of controlled viscosity, in order to develop a better understanding of the phenomena involved in such media.

  6. Microfluidic platform for neurotransmitter sensing based on cyclic voltammetry and dielectrophoresis for in vitro experiments.

    Science.gov (United States)

    Mathault, Jessy; Zamprogno, Pauline; Greener, Jesse; Miled, Amine

    2015-08-01

    This paper presents a new microfluidic platform that can simultaneously measure and locally modulate neurotransmitter concentration in a neuron network. This work focuses on the development of a first prototype including a potentiostat and electrode functionalization to detect several neurotransmitter's simultaneously. We tested dopamine as proof of concept to validate functionality. The system is based on 320 bidirectional electrode array for dielectrophoretic manipulation and cyclic voltammetry. Each electrode is connected to a mechanical multiplexer in order to reduce noise interference and fully isolate the electrode. The multiplexing rate is 476 kHz and each electrode can drive a signal with an amplitude of 60 V pp for dielectrophoretic manipulation.

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

    Science.gov (United States)

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

    2015-01-05

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

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

    Directory of Open Access Journals (Sweden)

    Hui Li

    2014-03-01

    Full Text Available 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.

  9. Simultaneous Determination of Bismuth and Copper by Square Wave Voltammetry in The Presence of Ethylenediaminetetraacedic Acid

    OpenAIRE

    HASDEMİR, Erdoğan; KARABODUK, Kuddusi

    2010-01-01

    A sensitive and selective method for the simultaneous determination of copper and bismuth by square wave voltammetry (SWV) was developed using ethylenediaminetetraacedic acid (EDTA) as complexing agent. Factors affecting the pH and concentrations ratios of copper and bismuth were investigated. Optimal analytical conditions were  found to be: pH of 8.0, the ratio of [Cu2+]/[Bi3+] was 0.13-2.5. The limit of detection (3δ) was 1.26 × 10-7 mol dm-3 for copper,  1.30×10...

  10. Rapid Kinetics and Relative Reactivity of Some Five Membered Aromatic Heterocycles using Hydrodynamic Voltammetry

    Directory of Open Access Journals (Sweden)

    S. B. Walke

    2015-12-01

    Full Text Available Kinetics of the bromination of imidazole, pyrazole and thiazole by molecular bromine and N-bromosuccinimide has been studied in aqueous medium. Since the reactions are rapid special technique namely, hydrodyanamic voltammetry has been employed to follow the course of the reactions. These reactions follow second order kinetics. The comparative kinetic data determines the reactivity order for these heterocycles towards the bromination using two different brominating reagents. The study justifies the stereochemical principles ascertaining the relative reactivity of these heterocycles quantitatively using kinetics as an investigational tool.

  11. APPLICATION OF PRINCIPAL COMPONENTS ANALYSIS IN THE STUDY OF ADSORPTIVE VOLTAMMETRY OF METALICS IONS

    Directory of Open Access Journals (Sweden)

    Leandra de Oliveira Cruz da Silva

    2010-01-01

    Full Text Available The adsorptive stripping voltammetry with differential pulse cathodic through the use of a mixture of complexing agents dimethylglyoxime and oxine was used for an exploratory study simultaneously of ions cadmium, cobalt, copper, nickel, lead and zinc. Were obtained voltammograms of the 64 individual solutions used in planning and current data were submitted to principal component analysis (PCA, allowing to characterize the trends of the solutions of metal ions studied. The system can be described in eight principal components that explained 98.32% of variance. Since the first three principal components accumulated approximately 85.46% of the total variance.

  12. General theory of cathodic and anodic stripping voltammetry at solid electrodes: mathematical modeling and numerical simulations.

    Science.gov (United States)

    Ward Jones, Sarah E; Chevallier, François G; Paddon, Christopher A; Compton, Richard G

    2007-06-01

    Theory is presented to describe the voltammetric signals associated with the stripping phase of stripping voltammetry at solid electrodes. Three mathematical models are considered, and the importance of the hemispherical diffusion associated with electrochemical dissolution of particles in the micrometer range is investigated. Model A considers a "monolayer" system where the coverage at a specific point cannot exceed a maximum value. Model B considers a thin layer of metal or metal oxide, but in contrast to model A, the maximum surface coverage is not restricted. Model C represents the stripping of a "thick layer" where the deposition is also unrestricted.

  13. Detection of iron(III)-binding ligands originating from marine phytoplankton using cathodic stripping voltammetry.

    Science.gov (United States)

    Hasegawa, Hiroshi; Maki, Teruya; Asano, Kohnosuke; Ueda, Kentaro; Ueda, Kazumasa

    2004-01-01

    The sample preparation and analytical methodology are described for detecting biologically produced iron(III)-binding ligands in laboratory cultures of coastal marine phytoplankton. The iron(III)-binding ligands from the culture media were purified by passage through a column packing with a hydrophobic absorbent. The concentrations and stability constants of the ligands were determined by adsorptive cathodic stripping voltammetry with competitive ligand equilibration. The analytical results of the cultivated cultures suggest that eukaryotic phytoplankton would produce iron(III)-binding ligands in analogy with other microorganisms.

  14. Anodic stripping voltammetry of nickel ions and nickel hydroxide nanoparticles at boron-doped diamond electrodes

    Science.gov (United States)

    Musyarofah, N. R. R.; Gunlazuardi, J.; Einaga, Y.; Ivandini, T. A.

    2017-04-01

    Anodic stripping voltammetry (ASV) of nickel ions in phosphate buffer solution (PBS) have been investigated at boron-doped diamond (BDD) electrodes. The deposition potential at 0.1 V (vs. Ag/AgCl) for 300 s in 0.1 M PBS pH 3 was found as the optimum condition. The condition was applied for the determination of nickel contained in nickel hydroxide nanoparticles. A linear calibration curve can be achieved of Ni(OH)2-NPs in the concentration range of x to x mM with an estimated limit of detection (LOD) of 5.73 × 10-6 mol/L.

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

    Science.gov (United States)

    Weidner, John W.

    1991-01-01

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

  16. Analysis on the Thinking Modes of Medical Users Utilizing Library Electronic Resources%医药学用户使用图书馆电子资源的思维模式分析

    Institute of Scientific and Technical Information of China (English)

    陈东滨; 应峻; 辛继宾; 徐一新

    2012-01-01

    The paper studies the thinking modes of medical users utilizing electronic resources in college and university libraries. Combining with the questionnaires,in - depth analysis of utilization desire,utilization decision,impact factors of utilization behaviors are compiled,in order to provide references for college and university libraries formulating electronic resources marketing strategies.%研究高校图书馆医药学用户在使用电子资源过程中的思维模式,结合问卷调查结果深入分析思维模式中使用意愿、使用决策、使用行为的影响因素,为高校图书馆制定电子资源营销策略提供依据。

  17. Hydrodynamic Voltammetry as a Rapid and Simple Method for Evaluating Soil Enzyme Activities

    Directory of Open Access Journals (Sweden)

    Kazuto Sazawa

    2015-03-01

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

  18. Combined characterization of bovine polyhemoglobin microcapsules by UV-Vis absorption spectroscopy and cyclic voltammetry.

    Science.gov (United States)

    Knirsch, Marcos Camargo; Dell'Anno, Filippo; Salerno, Marco; Larosa, Claudio; Polakiewicz, Bronislaw; Eggenhöffner, Roberto; Converti, Attilio

    2017-03-01

    Polyhemoglobin produced from pure bovine hemoglobin by reaction with PEG bis(N-succynimidil succinate) as a cross-linking agent was encapsulated in gelatin and dehydrated by freeze-drying. Free carboxyhemoglobin and polyhemoglobin microcapsules were characterized by UV-Vis spectroscopy in the absorption range 450-650 nm and cyclic voltammetry in the voltage range from -0.8 to 0.6 mV to evaluate the ability to break the bond with carbon monoxide and to study the carrier's affinity for oxygen, respectively. SEM used to observe the shape of cross-linked gelatin-polyhemoglobin microparticles showed a regular distribution of globular shapes, with mean size of ~750 nm, which was ascribed to gelatin. Atomic absorption spectroscopy was also performed to detect iron presence in microparticles. Cyclic voltammetry using an Ag-AgCl electrode highlighted characteristic peaks at around -0.6 mV that were attributed to reversible oxygen bonding with iron in oxy-polyhemoglobin structure. These results suggest this technique as a powerful, direct and alternative method to evaluate the extent of hemoglobin oxygenation.

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

    Science.gov (United States)

    Sazawa, Kazuto; Kuramitz, Hideki

    2015-03-04

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

  20. Investigation of antioxidant capacity of the extracts of bilberry (VACCINUM MYRTILLIS L.) by voltammetry

    Science.gov (United States)

    Vtorushina, A. N.; Nikonova, E. D.

    2016-02-01

    This paper deals with the urgent issue of the search of new drugs based on plant raw materials that have an influence on various stages of oxidation processes occurring in the human body. The aim of this paper is to determine the antioxidant activity of the bilberry extracts that are used in the medicine practice by a cathodic voltammetry method. We consider the influence of water and alcohol bilberry extracts on the process of oxygen electroreduction. From these extracts the most activity relation to the process of cathodic oxygen reduction showed alcohol (40%) bilberry extract. It was also stated that the alcohol extract of bilberry has a greater antioxidant activity than other known antioxidants such as ascorbic acid, glucose, dihydroquercetin. Thus, after consideration of a number of plant objects, we showed the possibility of applying the method of cathodic voltammetry for the determination of total antioxidant activity of plant material and identifying and highlighting the most perspective sources of biologically active substances (BAS), as well as the ability of identifying extractants that fully extract BAS from plant raw materials. The activity data of extracts of plant raw materials gives an opportunity of establishing an effective yield phytopreparation based on bilberry that has an antioxidant effect.

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

    Science.gov (United States)

    Keithley, Richard B; Wightman, R Mark

    2011-06-07

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

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

    Science.gov (United States)

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

    2014-11-18

    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 μm. 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.

  3. Flexible software platform for fast-scan cyclic voltammetry data acquisition and analysis.

    Science.gov (United States)

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

    2013-11-05

    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 that 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 transistor-transistor logic-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 subsecond and multiminute time scales. Here we describe and demonstrate the utility of HDCV for in vivo experiments.

  4. DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY FOR DETERMINATION OF SOME HEAVY METALS IN URANIUM

    Directory of Open Access Journals (Sweden)

    Saryati Saryati

    2010-06-01

    Full Text Available The direct determination of some metals impurity in uranium by using differential pulse anodic stripping voltammetry (DPASV method at a hanging mercury drop electrode and in a carbonate buffer media was developed. It was found that the carbonate buffer show the strongest affinity for uranium and gives the best separation between the DPASV peaks of heavy metals impurities. The carbonate concentration markedly affects the oxidation and reduction the major and the minor constituents of the uranium samples. In 0.1 M carbonate buffer solution pH 10, copper, bismuth, thalium, lead, cadmium, zinc, could be determined without the removal of the uranium matrix. Recovery and relative standard deviation (RSD of this method was in the range of 174% - 85.2% for recovery and 36.8% - 1.2% for RSD. The larger error of analytical result was obtained for Zn at low concentration. In general, the analytic results error and RSD decreased with increasing metals concentration.   Keywords: heavy metal determination, differential pulse anodic stripping voltammetry, uranium

  5. Catalytic Adsorptive Stripping Voltammetry at a Carbon Paste Electrode for the Determination of Amiodarone

    Institute of Scientific and Technical Information of China (English)

    LIU Ning; GAO Wei; SONG Jun-Feng

    2006-01-01

    Voltammetry using solid electrodes usually suffers from the contamination due to the deposition of the redox products of analytes on the electrode surface. The contamination has resulted in poor reproducibility and overelaborate operation procedures. The use of the chemical catalysis of oxidant on the reduction product of analyte not only can eliminate the contamination of analyte to solid electrodes but also can improve the faradaic response of analyte. This work introduced both the catalysis of oxidant K2S2O8 and the enhancement of surfactant Triton X-100 on the faraday response of amiodarone into an adsorptive stripping voltammetry at a carbon paste electrode for the determination of amiodarone. The method exhibits high sensitivity, good reproducibility and simple operation procedure. In 0.2 mol·L-1 HOAc-NaOAc buffer (pH=5.3) containing 2.2 × 10-2 mol·L-1 K2S2O8 and 0.002% Triton X-100, the 2.5th-order derivative stripping peak current of the catalytic wave at 0.3 V (vs. Ag/AgCl) is rectilinear to amiodarone concentration in the range of 2.0× 10-10-2.3× 10-8 mol·L-1 with a detection limit of 1.5× l0-10 mol·L-1 after accumulation at 0 V for 30 s.

  6. Determination of copper in whole blood by differential pulse adsorptive stripping voltammetry

    Directory of Open Access Journals (Sweden)

    Tarik Attar

    2014-02-01

    Full Text Available A selective and sensitive method for determination of copper in blood by adsorptive differential pulse cathodic stripping voltammetry is presented. The method is based on adsorptive accumulation of the complexes of Cu (II ions with benzenesulfonyl hydrazide onto hanging mercury drop electrode (HMDE, followed by the reduction of the adsorbed species by differential pulse cathodic stripping voltammetry. The effect of various parameters such as supporting electrolyte, concentration of benzenesulfonyl hydrazide, accumulation potential, accumulation time and stirring rate on the selectivity and sensitivity were studied. The optimum conditions for determination of copper include perchloric acid 0.03 M, concentration of benzenesulfonyl hydrazide 7.5×10-5 M, the accumulation potential of -350 mV (vs. Ag/AgCl, the accumulation time of 50 s, and the scan rate of 50 mV s-1. Under optimized conditions, linear calibration curves were established for the concentration of Cu (II in the range of 0.62-275 ng mL-1, with detection limit of 0.186 ng mL-1 for Cu (II. The procedure was successfully applied to the determination of copper ion in whole blood samples.

  7. Accurate analytical expressions for stripping voltammetry in the Henry adsorption limit.

    Science.gov (United States)

    Calvente, Juan José; Andreu, Rafael

    2011-08-15

    A strategy is developed to derive accurate analytical expressions for low-coverage cathodic stripping voltammetry. The procedure relies on the observation that diffusion affects the location of simulated voltammetric waves but not their shape, provided that physisorption of the analyte is negligible. As a proof of the generality of the proposed approach and having in mind the stripping of thiols, analytical solutions are derived for the cathodic stripping of monomers, dimers, and a mixture of monomers and dimers, whose reliability is proved by their comparison with numerically simulated voltammograms. Application to the deposition and reductive desorption of mercaptoacetic acid at a mercury electrode demonstrates that these approximate solutions can be used to get insights into the interfacial organization of incipient films. For this particular system, a transition from monomeric to dimeric behavior is identified upon increasing the thiol surface concentration. Further generalization of the proposed methodology is achieved by deriving an approximate analytical solution for thin-layer anodic stripping voltammetry, which is satisfactorily compared to the existing summation series solution.

  8. Determination of trace amounts of thallium by adsorptive cathodic stripping voltammetry with xylenol orange.

    Science.gov (United States)

    Shams, Esmaeil; Yekehtaz, Mehdi

    2002-09-01

    Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5-110 ng ml(-1) and 110-2000 ng ml(-1). The limit of detection was 0.2 ng ml(-1). The relative standard deviation for the determination of 80 ng ml(-1) thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.

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

    Science.gov (United States)

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

    2013-02-01

    Zinc (Zn) homeostasis is required for a functional immune system. Critically ill patients often exhibit decreased Zn serum concentrations and could potentially benefit from Zn supplementation as a therapeutic strategy. However, the conventional approaches to monitoring Zn are time consuming and costly. This work reports on detection of Zn by anodic stripping voltammetry (ASV) on bismuth electrodes in a microfabricated electrochemical cell. The working potential window of the electrodeposited bismuth film electrode was investigated by cyclic voltammetry, while square wave ASV was used for measuring Zn in acetate buffer and blood serum. Conditions critical to sensing, such as preconcentration potential, preconcentration time, and buffer pH, were optimized for Zn detection. The sensor was successfully calibrated with pH 6 acetate buffer in the physiologically-relevant range of 5 μM to 50μM 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 (μL vs. μL) and faster turnaround time (hours vs. days) as compared with the conventional spectroscopic methods.

  10. Square wave voltammetry with multivariate calibration tools for determination of eugenol, carvacrol and thymol in honey.

    Science.gov (United States)

    Tonello, Natalia; Moressi, Marcela Beatriz; Robledo, Sebastián Noel; D'Eramo, Fabiana; Marioli, Juan Miguel

    2016-09-01

    The simultaneous determination of eugenol (EU), thymol (Ty) and carvacrol (CA) in honey samples, employing square wave voltammetry (SWV) and chemometrics tools, is informed for the first time. For this purpose, a glassy carbon electrode (GCE) was used as working electrode. The operating conditions and influencing parameters (involving several chemical and instrumental parameters) were first optimized by cyclic voltammetry (CV). Thus, the effects of the scan rate, pH and analyte concentration on the electrochemical response of the above mentioned molecules were studied. The results show that the electrochemical responses of the three compounds are very similar and that the voltammetric traces present a high degree of overlap under all the experimental conditions used in this study. Therefore, two chemometric tools were tested to obtain the multivariate calibration model. One method was the partial least squares regression (PLS-1), which assumes a linear behaviour. The other nonlinear method was an artificial neural network (ANN). In this last case we used a supervised, feed-forward network with Levenberg-Marquardt back propagation training. From the accuracies and precisions analysis between nominal and estimated concentrations calculated by using both methods, it was inferred that the ANN method was a good model to quantify EU, Ty and CA in honey samples. Recovery percentages were between 87% and 104%, except for two samples whose values were 136% and 72%. The analytical methodology was simple, fast and accurate.

  11. Determination of trace amounts of morphine in human plasma by anodic adsorptive stripping differential pulse voltammetry

    Institute of Scientific and Technical Information of China (English)

    Ali Niazi; Ateesa Yazdanipour

    2008-01-01

    New adsorptive anodic differential pulse stripping voltammetry method for the direct determination of morphine at trace levels in human plasma of addicts is proposed.The procedure involves an adsorptive accumulation of morphine on a HMDE,followed by oxidation of adsorbed morphine by voltammetry scan using differential pulse modulation.The optimum conditions for the analysis of morphine are pH 10.5,Eacc of - 100 mV (vs.Ag/AgCl),and tacc of 120 s.The peak current is proportional to the concentration of morphine,and a linear calibration graph is obtained at 0.01-3.10 μg mL-1.A relative standard deviation of 1.06% (n=5) was obtained,and the limit of detection was 3 ng mL- 1.The capability of the method for the analysis of real samples was evaluated by the determination of morphine in spiked human plasma and addicts human plasma with satisfactory results.

  12. Thin-layer voltammetry of soluble species on screen-printed electrodes: proof of concept.

    Science.gov (United States)

    Botasini, S; Martí, A C; Méndez, E

    2016-10-17

    Thin-layer diffusion conditions were accomplished on screen-printed electrodes by placing a controlled-weight onto the cast solution and allowing for its natural spreading. The restricted diffusive conditions were assessed by cyclic voltammetry at low voltage scan rates and electrochemical impedance spectroscopy. The relationship between the weight exerted over the drop and the thin-layer thickness achieved was determined, in such a way that the simple experimental set-up designed for this work could be developed into a commercial device with variable control of the thin-layer conditions. The experimental results obtained resemble those reported for the voltammetric features of electroactive soluble species employing electrodes modified with carbon nanotubes or graphene layers, suggesting that the attainment of the benefits reported for these nanomaterials could be done simply by forcing the solution to spread over the screen-printed electrodic system to form a thin layer solution. The advantages of thin-layer voltammetry in the kinetic characterization of quasi-reversible and irreversible processes are highlighted.

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

    Science.gov (United States)

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

    2013-10-15

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

  14. Review of Researches on the Usage Standard Management of Electronic Resources in China from 2000 to 2010%2000—20l0年我国电子资源使用的规范管理研微

    Institute of Scientific and Technical Information of China (English)

    宛玲; 杜坤

    2012-01-01

    In recent years, electronic resources play an increasingly important role in research, teaching and other works. Through the statistical analysis of the domestic research on the usage standard management of electronic resources from 2000 to 2010, we find that the issue of the usage standard management of electronic resources is increasingly concerned by the public and researchers. But there are still some problems, such as lack of systematic discussion and empirical research, scattered research topics, most research results on guidance proposals, and so on. Our researches about usage standard management of electronic resources should strengthen researches on the user, related technologies, licensing alliance, strengthen the communication between libraries and database providers, and strengthen the analysis and absorption of foreign experience.%目前,电子资源在科研、教学等工作中扮演着越来越重要的角色。通过对2000-2010年我国电子资源使用规范管理研究文献的统计分析发现,虽然公众及科研人员对电子资源使用的规范的关注程度越来越高,但是仍存在缺乏系统性的论述和实证性的研究、研究主题过于分散、研究成果多为指导性建议等问题。我国电子资源使用规范管理研究应加强对用户、相关技术、许可联盟的研究,加强对图书馆与数据库商交流的研究,加强对国外经验的分析与吸收。

  15. 高校图书馆电子资源购买过程中的委托-代理关系探究%Principal-agent Relationship During the Electronic Resources Purchase Process of University Libraries

    Institute of Scientific and Technical Information of China (English)

    桂君; 吴冬曼

    2012-01-01

    The prineipal-agent relationship is throughout the whole process of the electronic resources purchase for university libraries. Based on the asymmetric informatiun theory the issues of information asymmetries in the purchase process of electronic resources for university libraries are analyzed. The major prineipal-agent relationships between the university libraries, the group organizers and the database providers ate studied. The operational characteristics and existing problems in the purchase process of electronic resources for university libraries are also discussed. Taking this opportunity to attention the principal-agent relationships existed in the electronic resources purchase of university libraries, the authors hope to solve some problems caused by the market information asymmetry.%委托-代理关系贯穿了高校图书馆电子资源的购买全过程,,基于信息不对称理论,分析高校图书馆电子资源购买中的信息不对称现象,并以高校图书馆、集团组织者、数据库提供者为主体,研究高校图书馆电子资源采购过程中存在的几种主要委托-代理关系、业务特点和存在的问题、通过对委托-代理关系的研究和分析,合理把握电子资源采购的规律,可以部分解决高校电子资源购买中由市场信息不平衡所带来的问题。

  16. Direct determination of praziquantel in pharmaceutical formulations and human plasma by cathodic adsorptive stripping differential-pulse voltammetry.

    Science.gov (United States)

    Ghoneim, M M; Mabrouk, M M; Tawfik, A

    2002-11-07

    The polarographic and cyclic voltammetric behaviour of praziquantel was studied in B.R. buffers of different pH values. Contradictory to that mentioned in a previously published work, praziquantel is an electro-active compound. Its polarogram exhibited a single 2-electron irreversible reduction wave in B.R. buffer of pH 5, the wave height decreased on the increase of pH till it disappeared in solution of pH >7. This wave was attributed to the reduction of the Cz.dbnd6;O double bond. The quantitative trace determination of bulk praziquantel was studied at a hanging mercury drop electrode by cathodic adsorptive stripping differential-pulse voltammetry. A fully validated sensitive procedure based on controlled adsorptive accumulation of the drug onto a HMDE was developed for its direct determination without derivatization. Accumulation of praziquantel was found to be optimized in 0.1 M Na(2)SO(4) solution as supporting electrolyte under the following conditions: accumulation potential, -1.2 V (vs. Ag/AgCl/KCl(s)); accumulation time, 30 s; scan rate, 10 mV/s and pulse height 100 mV. The proposed procedure was applied successfully for determination of praziquantel in its pharmaceutical formulations and human plasma. The mean recoveries of the drug were 98.85-99.42% and 99.12-100.47% with RSD of 0.49-0.95% and 0.45-0.52% in pharmaceutical formulations and human plasma, respectively. Limits of detection and quantitation of 1.14x10(-9) and 3.80x10(-9) M praziquantel, respectively, were achieved.

  17. Printed Resources and Electronic Resources Integrated Services in Small and Medium-sized Libraries%中小型图书馆印本资源与电子资源一体化服务实践

    Institute of Scientific and Technical Information of China (English)

    刘胜

    2014-01-01

    Through analyzing the integrated service system of library resources, this paper sums up three methods for the integration of printed resources and digital resources including the digital resources catalog, digital resources navigate and open link system, and suggests that the libraries should give priority to books and periodicals integrated retrieval in the integrated service, and carry out the system construction within their capabilities by adopting the methods of making second development, introducing new system, and conducting independent development, etc.%通过对图书馆馆藏一体化服务系统的分析,归纳总结出印本资源与电子资源整合的3种主要模式———电子资源编目、电子资源导航与开放链接,并建议图书馆在进行一体化服务时,优先考虑图书和期刊的整合检索,在系统建设上量力而行,采取二次开发、引进新系统、自主开发等方式。

  18. 基于使用数据的馆藏电子资源评价方法与系统分析%Methods and Systems of Library Electronic Resources Evaluation Analysis Based on Usage Data

    Institute of Scientific and Technical Information of China (English)

    王丹丹

    2014-01-01

    The origin and methods of library electronic resources evaluation were summarized;the statistical standards of library users' us-age data were reviewed. Then four library electronic resources evaluation systems based on library users' usage data which are ScholarlyS-tats,Journal Use Reports,360 Counter and Ustat were compared and contrasted. The related work which librarians need to do and the con-sidering factors about the selection of electronic resources evaluation system was also analyzed.%总结了图书馆馆藏电子资源评价的缘起与方法,梳理了图书馆用户使用数据的统计规范。以此为基础对比了四个基于使用数据的馆藏电子资源评价系统---ScholarlyStats,Journal Use Reports,360 Counter,UStat,分析了图书馆选择电子资源评价系统的考虑因素和需要预先做好的相关工作。

  19. Cyclic voitammetry, convolutive voltammetry, chrono-potentiometry and digital simulation studies of [Pt(C≡C tol)_2(dppm)_2Ir(CO)_2]~+PF_6~- complex

    Institute of Scientific and Technical Information of China (English)

    El-Hallag S Ibrahim

    2009-01-01

    The electrochemical behaviour of the heterobimetallic complex [Pt(C≡C tol)_2(dppm)_2-Ir(CO)_2]~+PF_6~-was studied via cyclic voltammetry, convolutive voltammetry and chronopotentiometry at glassy carbon electrode in dichloromethane solution. The electrochemical parameters calculated from experimental data were tested and confirmed by matching the experimental cyclic voltammograms with the simu-lated data. It was found that convolutive voltammetry provided higher sensitivity, better resolution and more accurate method for determination of the electrochemical parameters than ordinary cyclic volt-ammetry.

  20. Determination of mobile form contents of Zn, Cd, Pb and Cu in soil extracts by combined stripping voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Nedeltcheva, T. [Department of Analytical Chemistry, University of Chemical Technology and Metallurgy, 8 Kl. Ohridsi Blvd., 1756 Sofia (Bulgaria)]. E-mail: nedel@uctm.edu; Atanassova, M. [Department of Analytical Chemistry, University of Chemical Technology and Metallurgy, 8 Kl. Ohridsi Blvd., 1756 Sofia (Bulgaria); Dimitrov, J. [N. Pushkarov Institute of Soil Science and Agroecology, 7 Shosse Bankya St., 1080 Sofia (Bulgaria); Stanislavova, L. [N. Pushkarov Institute of Soil Science and Agroecology, 7 Shosse Bankya St., 1080 Sofia (Bulgaria)

    2005-01-10

    The amount of mobile forms of Zn, Pb, Cd and Cu in extracts obtained by treating soil samples with ammonium nitrate were determined by an appropriate combination of anodic and cathodic stripping voltammetry with hanging mercury drop electrode. Every analysis required three mercury drops: on the first one, zinc was determined; on the second, cadmium and lead; on the third, copper was determined. Zinc, lead and cadmium were determined by conventional differential-pulse anodic stripping voltammetry. For copper determination, adsorptive differential-pulse cathodic stripping voltammetry with amalgamation using chloride ions as a complexing agent was applied. The standard deviation of the results was from 1 to 10% depending on the metal content in the sample. Voltammetric results were in good agreement with the AAS analysis. No microwave digestion of soil extracts was necessary.

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

    Science.gov (United States)

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

    2015-02-09

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

  2. Analysis on Current Situation and Countermeasure of Domestic Electronic Commerce Logistics in the Internet Age——Based on Resource Dependence Theory

    Directory of Open Access Journals (Sweden)

    Zhang Jiapeng

    2017-01-01

    Full Text Available This paper analyzes the status of electric business logistics in the current Internet era in China, and combines the SWOT analysis with AHP to do the empirical analysis, then puts forward the countermeasure that the electric business logistics resource should be shared based on the resource dependence theory. Through the empirical analysis, it is found that the disadvantages and opportunities of the logistics status are important in the Internet era.The resource sharing strategy based on the resource dependence theory is more scientific. The rational use of Internet technology in electric business logistics industry can achieve “sharing”. It is of great significance for its balanced development, intelligent development and optimization and development.

  3. CYCLIC VOLTAMMETRY STUDIES OF COPPER (II AND TELLURIUM (IV IONS IN ACIDIC AQUEOUS SOLUTIONS FOR THIN FILM DEPOSITION

    Directory of Open Access Journals (Sweden)

    SARAVANAN NAGALINGAM

    2014-05-01

    Full Text Available Cyclic voltammetry studies of copper (II and tellurium (IV ions in acidic aqueous solutions were carried out to determine the optimum condition for copper telluride thin film deposition. The voltammetry studies include reversible scans at different solution pH. Based on the voltammogram, suitable deposition conditions was determined to be in the range of -0.35 V to -0.45 V versus Ag/AgCl at pH values between 2.0 to 2.2 under non diffusion-limited conditions.

  4. In situ microliter-droplet anodic stripping voltammetry of copper stained on the gold label after galvanic replacement reaction enlargement for ultrasensitive immunoassay of proteins.

    Science.gov (United States)

    Qin, Xiaoli; Xu, Aigui; Wang, Linchun; Liu, Ling; Chao, Long; He, Fang; Tan, Yueming; Chen, Chao; Xie, Qingji

    2016-05-15

    We report a new protocol for ultrasensitive electrochemical sandwich-type immunosensing, on the basis of signal amplification by gold-label/copper-staining, galvanic replacement reactions (GRRs), and in situ microliter-droplet anodic stripping voltammetry (ASV) after an enhanced cathodic preconcentration of copper. First, a sandwich-type immuno-structure is appropriately assembled at a glassy carbon electrode. Second, copper is selectively stained on the catalytic surfaces of second antibody-conjugated Au nanoparticles through CuSO4-ascorbic acid redox reaction, and the GRRs between HAuCl4 and the stained copper are used to amplify the quantity of copper. Finally, the corresponding antigen is determined based on simultaneous chemical-dissolution/cathodic-preconcentration of copper for in-situ ASV analysis directly at the immunoelectrode. Cyclic voltammetry, electrochemical impedance spectroscopy, quartz crystal microbalance and scanning electron microscopy are used for film characterization and/or process monitoring. Under optimized conditions, ultrasensitive analyses of human immunoglobulin G (IgG) and human carbohydrate antigen 125 (CA125) are achieved. The limits of detection are 0.3 fg mL(-1) (equivalent to 7 IgG molecules in the 6 μL sample employed) for IgG (S/N=3) and 1.3 nU mL(-1) for CA125 (S/N=3), respectively, which are amongst the best reported to date for the two proteins. The theoretical feasibility of such a single-molecule-level amperometric immunoassay is also discussed based on the immunological reaction thermodynamics. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Fiber resources

    Science.gov (United States)

    P. J. Ince

    2004-01-01

    In economics, primary inputs or factors of production define the term ‘resources.’ Resources include land resources (plants, animals, and minerals), labor, capital, and entrepreneurship. Almost all pulp and paper fiber resources are plant materials obtained from trees or agricultural crops. These resources encompass plant materials harvested directly from the land (...

  6. Studies on the Nucleophilicity and Scavenge of Superoxide Ion by Cyclic Voltammetry

    Institute of Scientific and Technical Information of China (English)

    Wei Ying-liang; Dang Xue-ping; Hu Sheng-shui

    2003-01-01

    Superoxide ion was generated by the electrochemical reduction of oxygen at a platinum electrode in dimethylsulphoxide (DMSO). This work was focused on the nucleophilicity and scavenge of electrogenerated-superoxide ion by cyclic voltammetry. The nucleophilic displacement reactions of superoxide ion with ethyl acetate and diethyl adipate were discussed and the reason for remarkable influence of diethyl adipate was elucidated. The scavenging activity of ascorbic acid was evaluated and the result allowed the conclusion that the scavenging ability of ascorbic acid is much lower in DMSO than in aqueous phase. UV-spectrum of electrogenerated superoxide ion in DMSO exhibited a single absorption band with λmax at 275 nm, which certified further that the method of electrogeneration was reliable and superoxide ion was stable in DMSO.

  7. Studies on the Nucleophilicity and Scavenge of Superoxide Ion by Cyclic Voltammetry

    Institute of Scientific and Technical Information of China (English)

    WeiYing-liang; DangXue-ping; HuSheng-shui

    2003-01-01

    Superoxide ion was generated by the electro-chemical reduction of oxygen at a platinum electrode in dimethylsulphoxide (DMSO). This work was focused on the nucleophilicity and scavenge of electrogenemted-superoxide ion by cyclic voltammetry. The nucleophilic displacement reactions of superoxide ion with ethyl acetate and diethyl adipate were discussed and the reason for remarkable influence of diethyl adipate was elucidated. The scavenging activity of ascorbic acid was evaluated and the result allowed the conclusion that the scavenging ability of ascorbic acid is much lower in DMSO than in aqueous phasc UV-spectrum of electrogenerated superoxide ion in DMSO exhibited a single absorption band with λmax at 275 nm, which certified further that the method of electrogeneration was reliable and superoxide ion was stable in DMSO.

  8. Electrochemical characterization of lithium ferrite electrodes through cyclic voltammetry and Raman spectra

    Energy Technology Data Exchange (ETDEWEB)

    Manley, M.; Cook, W. [Univ. of New Brunswick, Dept. of Chemical Engineering, Fredericton, New Brunswick (Canada)

    2013-07-01

    Lithium ferrite, a mixed spinel with the formula, Fe[Li{sub 0.5}Fe{sub 1.5}]O{sub 4} or LiFe{sub 5}O{sub 8}, has been synthesized and characterized in both its ordered (α) and disordered (β) phases. In an effort to scope the electrochemical activity lithium ferrite in lithium hydroxide solutions, the powders produced were compressed into pellets and tested with cyclic voltammetry and the surface of the electrodes were analyzed with laser Raman spectroscopy. Results of the initial electrochemical testing showed good correlation with Nernstian behavior and exhibited quasi-reversible behaviour. The redox mechanism involves the breakdown of lithium ferrite into hematite, a hybrid lithiated-hematite oxide and lithium ions under the alkaline conditions tested. By comparing the equilibrium potential of the redox process with proposed reaction schemes and examining the reaction products using the laser Raman microprobe, the proposed redox mechanism could be verified. (author)

  9. Mathematical Modelling of the Electrode Process of Azithromycin Using Cyclic Voltammetry at Hanging Mercury Drop Electrode

    Directory of Open Access Journals (Sweden)

    Maha F. Tutunji

    2002-11-01

    Full Text Available A theoretical treatment is presented to predict the kinetic behaviour of azithromycin at the surface of hanging mercury drop electrode using cyclic voltammetry. A model is developed to incorporate the occurrence of adsorption of the oxidized and reduced species of azithromycin at the surface of mercury drop electrode. An analytical solution was obtained using MATHEMATICA (V-3, Wolfram Research, Inc. to predict the cyclic voltammetric profiles by calculating the currents resulting after applying variable potentials ranging –1.9 to –1.3 V versus Ag/AgCl. Simulation runs at different initial concentrations of azithromycin and different scan rates showed good agreement with experimental findings. However, this model should be modified to describe a multilayer adsorption with irreversible electrochemical reaction.

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

    Science.gov (United States)

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

    2015-06-25

    The electrochemical properties of gelatinized starch dispersions (GSD; 5% w/w) from different botanical sources were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests over a platinum surface. The phenomenological modelling of EIS data using equivalent circuits indicated that after gelatinization the electrical resistance was determined mainly by the resistance of insoluble material (i.e., ghosts). Sonication of the GSD disrupted the ghost microstructure, and produced an increase in electrical conductivity by reducing the resistance of the insoluble material. The CV data showed three oxidation peaks at potentials where glucose solutions displayed oxidation waves. It is postulated that hydrolysis at the bulk and electrocatalyzed oxidation on the Pt-surface are reactions involved in the starch transformation. Starches peak intensity increased with the amylose content, suggesting that the amylose-rich matrix played an important role in the charge transfer in the electrolytic system. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Monitoring axonal and somatodendritic dopamine release using fast-scan cyclic voltammetry in brain slices.

    Science.gov (United States)

    Patel, Jyoti C; Rice, Margaret E

    2013-01-01

    Brain dopamine pathways serve wide-ranging functions including the control of movement, reward, cognition, learning, and mood. Consequently, dysfunction of dopamine transmission has been implicated in clinical conditions such as Parkinson's disease, schizophrenia, addiction, and depression. Establishing factors that regulate dopamine release can provide novel insights into dopaminergic communication under normal conditions, as well as in animal models of disease in the brain. Here we describe methods for the study of somatodendritic and axonal dopamine release in brain slice preparations. Topics covered include preparation and calibration of carbon-fiber microelectrodes for use with fast-scan cyclic voltammetry, preparation of midbrain and forebrain slices, and procedures of eliciting and recording electrically evoked dopamine release from in vitro brain slices.

  12. Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots.

    Science.gov (United States)

    Osipovich, Nikolai P; Poznyak, Sergei K; Lesnyak, Vladimir; Gaponik, Nikolai

    2016-04-21

    The application of electrochemical methods for the characterization of colloidal quantum dots (QDs) attracts considerable attention as these methods may allow for monitoring of some crucial parameters, such as energetic levels of conduction and valence bands as well as surface traps and ligands under real conditions of colloidal solution. In the present work we extend the applications of cyclic voltammetry (CV) to in situ monitoring of degradation processes of water-soluble CdTe QDs. This degradation occurs under lowering of pH to the values around 5, i.e. under conditions relevant to bioimaging applications of these QDs, and is accompanied by pronounced changes of their photoluminescence. Observed correlations between characteristic features of CV diagrams and the fluorescence spectra allowed us to propose mechanisms responsible for evolution of the photoluminescence properties as well as degradation pathway of CdTe QDs at low pH.

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

    Science.gov (United States)

    Palma, Alberto; Ruiz Montoya, Mercedes; Arteaga, Jesús F; Rodríguez Mellado, Jose M

    2014-01-22

    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, μ10 as the reverse of V10, V10 being the volume necessary to decrease the peak area in DPV by 10%, was selected. Higher μ10 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.

  14. Imprinted Polymeric Film-Based Sensor for the Detection of Dopamine Using Cyclic Voltammetry

    Institute of Scientific and Technical Information of China (English)

    郭洪声; 何锡文; 李一峻

    2003-01-01

    The imprinted polymeric film was synthesized on the glass-carbon electrodes dlrectly. The response to the template molecule-dopamine and other molecules with similar structure was measured by cyclic voltammetry. The response of dopamine on imprinted electrode was much higher than that of other molecules,because of the existing of micro-cavities in polymeric rdm fitting with the size and shape of dopamine in the imprinted polymer.Experimental results showed that dopamlne can be enriched by the imprinted film, therefore increasing the sensitivity of the sensor. The imprinted film could also efface the interference of ascorbic acid, indicating that dopamine can be determined with a large excess of ascorbic acid.

  15. Kinetics and Antioxidant Capacity of Proanthocyanidins Encapsulated in Zein Electrospun Fibers by Cyclic Voltammetry.

    Science.gov (United States)

    Wang, Hualin; Hao, Lilan; Niu, Baicheng; Jiang, Suwei; Cheng, Junfeng; Jiang, Shaotong

    2016-04-20

    The proanthocyanidins encapsulated in zein (zein-PA) fibers was via electrospinning technique. The kinetics and antioxidant capacity of PA from zein fibers was investigated by cyclic voltammetry. Circular dichroism was used to investigate the secondary structure change of zein and its influence on the shape of fibers. The addition of PA caused a significant increase in viscosity and made fibers wider. These hydrogen bonds between zein and PA molecules would favor the α-helix change and decrease the β-folds of zein in electrospinning solutions, leading to a round-shaped tendency of fibers and enhancing the thermal properties slightly. Zein-PA fibers showed high encapsulation efficiency close to 100%, and the encapsulated PA retained its antioxidant capacity in fibers. Zein-PA fibers showed a good controlled release toward PA, and the predominant release of PA from fibers was Fickian diffusion, which could be well described by first-order model and Hixson-Crowell model.

  16. Evaluating the Passivation of Corrosion of API-X100 Steel with Cyclic Voltammetry

    Science.gov (United States)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2017-10-01

    In this research, cyclic voltammetry, in oxygen-free low bicarbonate-carbonate solutions, was used to study the corrosion reactions of a high-strength steel, API-X100. With cycles of different scan ranges, the effects of cycling, transpassivation, and cathodic reduction on the electrochemistry of the passive films were analyzed. It was found that carbonate in higher concentrations reduces the anodic activity and the cathodic reactions of the surface. Bicarbonate in small concentrations in solutions that contained low carbonate concentrations catalyzed dissolution and disrupted the formation of the passive films, in reference to the measured anodic currents. From the experiments, there was electrochemical evidence that with more cycles, the passive films were growing thicker, the transpassivation deteriorated the passive films, and during the cathodic reduction, the dissolution was occurring at lower potentials to facilitate later the passivation at higher potentials.

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

    Science.gov (United States)

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

    2014-12-01

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Determination of diclofenac in pharmaceutical preparations by voltammetry and gas chromatography methods

    Institute of Scientific and Technical Information of China (English)

    Bilal Yilmaz; Ulvihan Ciltas

    2015-01-01

    Rapid, sensitive and specific methods were developed for the determination of diclofenac in pharmaceutical preparations by linear sweep voltammetry (LSV) and gas chromatography (GC) with mass spectrometry (MS) detection. The linearity was established over the concentration range of 5–35μg/mL for LSV and 0.25–5μg/mL for GC–MS method. The intra- and inter-day relative standard deviation (RSD) was less than 4.39% and 4.62% for LSV and GC–MS, respectively. Limits of quantification (LOQ) were determined as 4.8 and 0.15μg/mL for LSV and GC–MS, respectively. No interference was found from tablet excipients at the selected assay conditions. The methods were applied for the quality control of commercial diclofenac dosage forms to quantify the drug and to check the formulation content uniformity.

  19. Selective method for the determination of gold by anodic stripping voltammetry.

    Science.gov (United States)

    Korolczuk, M

    1996-12-01

    A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au(3+) reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5x10(-8) to 1x10(-6) mol/l. The relative standard deviation for 2x10(-7) mol/l HAuCl(4) was 4.2% (n=5). The detection limit was 4x10(-9) mol/l. The accuracy of the method was verified by the determination of gold in reference materials.

  20. Investigation on Concentrated V(IV)/V(V) Redox Reaction by Rotating Disc Voltammetry

    Institute of Scientific and Technical Information of China (English)

    WEN Yue-Hua; ZHANG Hua-Min; QIAN Peng; MA Hai-Peng; YI Bao-Lian; YANG Yu-Sheng

    2007-01-01

    The kinetic characteristics of the concentrated V(IV)/V(V) couple have been studied at a glassy carbon electrode in sulfuric acid using rotating-disc electrode and cyclic voltammetry. The kinetics of the V(IV)/V(V) redox couple reaction was found to be electrochemically quasi-reversible with the slower kinetics for the V(V) reduction than that for the V(IV) oxidation. And, dependence of diffusion coefficients and kinetic parameters of V(IV) species on the V(IV) and H25O4 concentration was investigated. It is shown that the concentration of active species V(IV)centration, the diffusion coefficients of V(IV) were gradually reduced whereas its kinetics was improved considerably,espicially in the case of Ⅴ(Ⅳ)and H2SO4 up to 2 and 4 mol·L-1.

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

    Science.gov (United States)

    Ndungu, Kuria

    2012-07-17

    Trace metal toxicity to aquatic biota is highly dependent on the metaĺs chemical speciation. Accordingly, metal speciation is being incorporated in to water quality criteria and toxicity regulations using the Biotic Ligand Model (BLM) but there are currently no BLM for biota in marine and estuarine waters. In this study, I compare copper speciation measurements in a typical coastal water made using Competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) to model calculations using Visual MINTEQ. Both Visual MINTEQ and BLM use similar programs to model copper interactions with dissolved organic matter-DOM (i.e., the Stockholm Humic Model and WHAM-Windermere Humic Aqueous Model, respectively). The total dissolved (14). The modeled [Cu2+] could be fitted to the experimental values better after the conditional stability constant for copper binding to fulvic acid (FA) complexes in DOM in the SHM was adjusted to account for higher concentration of strong Cu-binding sites in FA.

  2. Cathodic stripping voltammetry of trace Mn(II) at carbon film electrodes.

    Science.gov (United States)

    Filipe, Olga M S; Brett, Christopher M A

    2003-12-04

    A sensitive voltammetric method is presented for the determination of tract levels of Mn (II) using carbon film electrodes fabricated from carbon resistors of 2 Omega. Determination of manganese was made by square wave cathodic stripping voltammetry (CSV), with deposition of manganese as manganese dioxide. Chronoamperometric experiments were made to study MnO(2) nucleation and growth. As a result, it was found to be necessary to perform electrode conditioning at a more positive potential to initiate MnO(2) nucleation. Under optimised conditions the detection limit obtained was 4 nM and the relative standard deviation for eight measurements of 0.22 nM was 5.3%. Interferences from various metal ions on the response CSV of Mn(II) were investigated, namely Cd(II), Ni(II), Cu(II), Cr(VI), Pb(II), Zn(II) and Fe(II). Application to environmental samples was demonstrated.

  3. CO adsorption on electrode of Pt nanoparticles investigated by cyclic voltammetry and in situ FTIR spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Pt nanoparticles were prepared by the chemical reduction method. The average diameter of Pt nanoparticles was determined to be 2.5 nm by TEM. The electrochemical properties of Pt nanoparticles were studied by cyclic voltammetry. In comparison with massive Pt, the oxidation current peak of CO adsorbed on Pt nanoparticles is broader. Twin adsorbates of CO on Pt nanoparticles were determined by in situ FTIRS for the first time. It has revealed that the linear and twin-bonded CO can be converted into bridge-bonded CO with the variation of electrode potential. A series of special properties of Pt nanoparticles, such as enhanced IR absorption of CO adsorbates, were also observed.

  4. The versatility of salicylaldehyde thiosemicarbazone in the determination of copper in blood using adsorptive stripping voltammetry.

    Science.gov (United States)

    Mahajan, Rakesh Kumar; Walia, T P S; Sumanjit; Lobana, T S

    2005-10-15

    The adsorptive cathodic stripping voltammetry technique (AdCSV) is used to determine copper(II) using salicylaldehyde thiosemicarbazone (N, S- donor) as a complexing agent on hanging mercury drop electrode at pH 9.3. Variable factors affecting the response, i.e. the concentration of ligand, pH, adsorption potential and adsorption time are assessed and optimized. The adsorbed complex of copper(II) and salicylaldehyde thiosemicarbazone gives a well defined cathodic stripping peak current at -0.35 V, which has been used for the determination of copper in the concentration range of 7.85 x 10(-9) to 8.00 x 10(-6)M with accumulation time of 360 s at -0.1 V versus Ag/AgCl. This technique has been applied for the determination of copper in various digested samples of whole blood at trace levels.

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

    Science.gov (United States)

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

    2008-01-01

    This paper describes a procedure that has been optimized for the determination of lamotrigine by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using carbon screen-printed electrodes (CSPE) and mercury coated carbon screen-printed electrodes. Selection of the experimental parameters was made using experimental design methodology. The detection limit found was 5.0 × 10-6 M and 2.0 × 10-6 M for the non modified and Hg modified CSPE, respectively. In terms of reproducibility, the precision of the above mentioned methods was calculated in %RSD values at 9.83% for CSPE and 2.73% for Hg-CSPE. The Hg-coated CSPEs developed in this work were successfully applied in the determination of lamotrigine in pharmaceutical preparations. PMID:27879931

  6. Estimation of Heavy Metals in Multivitamin Tablets by Differential Pulse Anodic Stripping Voltammetry

    Directory of Open Access Journals (Sweden)

    Kumar Rohit Raj

    2010-01-01

    Full Text Available Differential pulse anodic stripping voltammetry (DPASV was applied for the simultaneous determination of zinc and copper in multivitamin tablet (supradyn and centrum. Determination of the metals was made in ammonium acetate buffer (pH 4.5 with a scan rate of 0.01 V/s by Hanging Mercury Dropping Electrode (HMDE.The solution was stirred during electrolysis at -1.3 V for 300 s in the potential range of -1.3 to + 0.1 V. Concentrations of zinc and copper in supradyn drug sample were found to be 1.80 and 2.9 mg/tablet and for centrum drug sample were found to be 4.6 and 0.94 mg/tablet respectively.

  7. Detection of aniline at boron-doped diamond electrodes with cathodic stripping voltammetry.

    Science.gov (United States)

    Spătaru, Tanţa; Spătaru, Nicolae; Fujishima, Akira

    2007-09-15

    Boron-doped diamond (BDD) electrodes were used to investigate the possibility of detecting aniline by linear-sweep cathodic stripping voltammetry. It was found that the dimeric species (p-aminodiphenylamine and benzidine) formed by anodic oxidation of aniline during the accumulation period are involved in electrochemically reversible redox processes and, in acidic media, the shape of the stripping voltammetric response is suitable for aniline detection in the micromolar concentration range. The low background current of conductive diamond is an advantage compared to other electrode materials and allows a detection limit of 1muM. Weak adsorption properties and the extreme electrochemical stability are additional advantages of BDD and it was found that, even after long-time measurements, the electrode surface can regain its initial activity by an anodic polarization in the potential region of water decomposition.

  8. Determination of picomolar levels of iron in seawater using catalytic cathodic stripping voltammetry.

    Science.gov (United States)

    Obata, H; van den Berg, C M

    2001-06-01

    A new procedure for the direct determination of picomolar levels of iron in seawater is presented. Cathodic stripping voltammetry (CSV) is preceded by adsorptive accumulation of the iron(III)-2,3-dihydroxynaphthalene (DHN) complex from seawater, containing 20 microM DHN at pH 8.0, onto a static mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is catalytically enhanced by the presence of 20 mM bromate. Optimized conditions include a 60-s adsorption period at -0.1 V and a voltammetric scan using sampled dc modulation at 10 Hz. In these conditions, a detection limit of 13 pM iron in seawater was achieved which can be lowered further by extending the adsorption time to 300 s. The new catalytic CSV method is approximately 5 times more sensitive than existing CSV methods and was tested on samples from the Atlantic Ocean.

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

    Directory of Open Access Journals (Sweden)

    M. Julia Arcos-Martínez

    2008-07-01

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

  10. Lead migration from toys by anodic stripping voltammetry using a bismuth film electrode.

    Science.gov (United States)

    Leal, M Fernanda C; Catarino, Rita I L; Pimenta, Adriana M; Souto, M Renata S; Afonso, Christelle S; Fernandes, Ana F Q

    2016-09-02

    Metals may be released from toys via saliva during mouthing, via sweat during dermal contact, or via gastric and intestinal fluids after partial or whole ingestion. In this study, we determined the lead migration from toys bought on the Portuguese market for children below 3 years of age. The lead migration was performed according to the European Committee for Standardization EN 71-3, which proposes a 2-hour migration test that simulates human gastric conditions. The voltammetric determination of migrated lead was performed by anodic stripping voltammetry (ASV) at a bismuth film electrode (BiFE). For all the analyzed toys, the values of migrated lead did not exceed the limits imposed by the European Committee for Standardization EN 71-3 (90 mg kg(-1)) and by the EU Directive 2009/48/EC (13.5 mg kg(-1)) on the safety of toys.

  11. Square Wave Voltammetry: An Alternative Technique to Determinate Piroxicam Release Profiles from Nanostructured Lipid Carriers.

    Science.gov (United States)

    Otarola, Jessica; Garrido, Mariano; Correa, N Mariano; Molina, Patricia G

    2016-08-04

    A new, simple, and fast electrochemical (EC) method has been developed to determine the release profile of piroxicam, a nonsteroidal anti-inflammatory drug, loaded in a drug delivery system based on nanostructured lipid carriers (NLCs). For the first time, the samples were analyzed by using square wave voltammetry, a sensitive EC technique. The piroxicam EC responses allow us to propose a model that explains the experimental results and to subsequently determine the amount of drug loaded into the NLCs formulation as a function of time. In vitro drug release studies showed prolonged drug release (up to 5 days), releasing 60 % of the incorporated drug. The proposed method is a promising and stable alternative for the study of different drug delivery systems.

  12. Voltammetry and fluorescence studies on the interaction between Eu (phen)33+ and DNA

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The binding mode of Eu(phen) 33+ with DNA is studied by fluorescence and voltammetric methods. From theScatchard graph and the fluorescence quenching phenomenon, it is concluded that the mode of interaction betweenEu(phen) 33+ and DNA is intercalation bind by inserting the phen π-π conjugate surface between the base pairs of theDNA duplex. Voltammetry was used to confirm the results obtained from the fluorescence method, the result from bothmethods agrees with each other. The binding constant (K) and the binding site size (ns) were calculated from voltammetricdata such as the shifts in potential and limiting currents in the process of adding DNA, according to the positive shifts ofpeak potential. It was considered that the complex of the +2 ion interacted more favorably with the nucleotide bases thanthat of the +3 ion by hydrophobic interaction.

  13. Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

    Directory of Open Access Journals (Sweden)

    Chalder Nogueira Nunes

    2016-01-01

    Full Text Available 17α-Ethinyl estradiol (EE2, which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV with a hanging mercury drop electrode (HMDE in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at −1.16±0.02 V versus Ag/AgCl. The experimental parameters were as follows: −0.7 V accumulation potential, 150 s accumulation time, and 60 mV s−1 scan rate. The limit of detection was 0.49 μg L−1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%.

  14. Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry

    Science.gov (United States)

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

    2008-01-01

    A method was developed for assessing ascorbic acid concentration in commercial fruit juice by cyclic voltammetry. The anodic oxidation peak for ascorbic acid occurs at about 490 mV on a Pt disc working electrode (versus SCE). The influence of the potential sweep speed on the peak height was studied. The obtained calibration graph shows a linear dependence between peak height and ascorbic acid concentration in the domain (0.1–10 mmol·L−1). The equation of the calibration graph was y = 6.391x + 0.1903 (where y represents the value of intensity measured for the anodic peak height, expressed as μA and x the analyte concentration, as mmol·L−1, r2 = 0.9995, r.s.d. = 1.14%, n = 10, Cascorbic acid = 2 mmol·L−1). The developed method was applied to ascorbic acid assessment in fruit juice. The ascorbic acid content determined ranged from 0.83 to 1.67 mmol·L−1 for orange juice, from 0.58 to 1.93 mmol·L−1 for lemon juice, and from 0.46 to 1.84 mmol·L−1 for grapefruit juice. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.35% and 104%. Ascorbic acid determination results obtained by cyclic voltammetry were compared with those obtained by the volumetric method with dichlorophenol indophenol. The results obtained by the two methods were in good agreement. PMID:19343183

  15. Bare and Polymer-Coated Indium Tin Oxide as Working Electrodes for Manganese Cathodic Stripping Voltammetry.

    Science.gov (United States)

    Rusinek, Cory A; Bange, Adam; Warren, Mercedes; Kang, Wenjing; Nahan, Keaton; Papautsky, Ian; Heineman, William R

    2016-04-19

    Though an essential metal in the body, manganese (Mn) has a number of health implications when found in excess that are magnified by chronic exposure. These health complications include neurotoxicity, memory loss, infertility in males, and development of a neurologic psychiatric disorder, manganism. Thus, trace detection in environmental samples is increasingly important. Few electrode materials are able to reach the negative reductive potential of Mn required for anodic stripping voltammetry (ASV), so cathodic stripping voltammetry (CSV) has been shown to be a viable alternative. We demonstrate Mn CSV using an indium tin oxide (ITO) working electrode both bare and coated with a sulfonated charge selective polymer film, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-sulfonate (SSEBS). ITO itself proved to be an excellent electrode material for Mn CSV, achieving a calculated detection limit of 5 nM (0.3 ppb) with a deposition time of 3 min. Coating the ITO with the SSEBS polymer was found to increase the sensitivity and lower the detection limit to 1 nM (0.06 ppb). This polymer modified electrode offers excellent selectivity for Mn as no interferences were observed from other metal ions tested (Zn(2+), Cd(2+), Pb(2+), In(3+), Sb(3+), Al(3+), Ba(2+), Co(2+), Cu(2+), Ni(3+), Bi(3+), and Sn(2+)) except Fe(2+), which was found to interfere with the analytical signal for Mn(2+) at a ratio 20:1 (Fe(2+)/Mn(2+)). The applicability of this procedure to the analysis of tap, river, and pond water samples was demonstrated. This simple, sensitive analytical method using ITO and SSEBS-ITO could be applied to a number of electroactive transition metals detectable by CSV.

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

    Science.gov (United States)

    Sun, Y C; Mierzwa, J; Lan, C R

    2000-06-30

    A reliable and very sensitive procedure for the determination of trace levels of molybdenum in seawater is proposed. The complex of molybdenum with 8-hydroxyquinoline (Oxine) is analyzed by cathodic stripping square-wave voltammetry based on the adsorption collection onto a hanging mercury drop electrode (HMDE). This procedure of molybdenum determination was found to be more favorable than differential pulse cathodic stripping voltammetry because of inherently faster scan rate and much better linearity obtained through the one-peak (instead of one-of-two peaks) calibration. The variation of polarographic peak and peak current with a pH, adsorption time, adsorption potential, and some instrumental parameters such as scan rate and pulse height were optimized. The alteration of polarographic wave and its likely mechanism are also discussed. The relationship between peak current and molybdenum concentration is linear up to 150 mug l(-1). Under the optimal analytical conditions, the determination limit of 0.5 mug l(-1) Mo was reached after 60 s of the stirred collection. The estimated detection limit is better than 0.1 mug l(-1) of Mo. The applicability of this method to analysis of seawater was assessed by the determination of molybdenum in two certified reference seawater samples (CASS-2 and NASS-2) and the comparison of the analytical results for real seawater samples (study on a vertical distribution of Mo in the seawater column) with the results obtained by Zeeman-corrected electrothermal atomization atomic absorption spectrometry (Zeeman ETAAS). A good agreement between two used methods of molybdenum determination was obtained.

  17. Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

    Science.gov (United States)

    2016-01-01

    17α-Ethinyl estradiol (EE2), which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs) in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV) with a hanging mercury drop electrode (HMDE) in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at −1.16 ± 0.02 V versus Ag/AgCl. The experimental parameters were as follows: −0.7 V accumulation potential, 150 s accumulation time, and 60 mV s−1 scan rate. The limit of detection was 0.49 μg L−1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%. PMID:27738548

  18. Application of thin-shielded mercury microelectrodes in anodic stripping voltammetry.

    Science.gov (United States)

    Daniele, Salvatore; Bragato, Carlo; Baldo, M Antonietta; Ciani, Ilenia

    2008-10-19

    The performance in anodic stripping voltammetry (ASV) of hemispherical mercury microelectrodes, fabricated by electrodeposition of liquid mercury on the surface of Pt microdisks which were surrounded by a rather thick or thin insulating shield, was compared. The Pt microdisks were produced by sealing a wire of 25 microm diameter into a glass capillary, and by coating the cylindrical length of the Pt wire with a cathodic electrophoretic paint. The ratio of the overall tip radius b, to the basal radius of the electrode a, so-called RG=b/a, was equal to 110+/-10 and 1.52+/-0.01 for the thick- and thin-shielded microdisk, respectively. The mercury microelectrodes were characterized by cyclic voltammetry at 1 mVs(-1), in 1mM Ru(NH(3))(6)(3+) aqueous solution. The steady-state voltammogram recorded with the thin-shielded mercury microelectrode displayed less hysteresis, while the steady-state current was about 30% higher than that of the thicker one. This was a consequence of the additional flux due to diffusion from behind the plane of the electrode. The flux enhancement, which was operative at the thin-shielded mercury microelectrode during the deposition step in the ASV experiments, allowed recording stripping peaks for Cd and Pb, which resulted about 32% larger than those recorded at the thicker shielded mercury microelectrode, under same experimental conditions. The usefulness of the thin-shielded mercury microelectrode for ASV measurements in real samples was verified by determining the content of heavy metal ions released in the pore water (pH 4.5) of a soil slurry.

  19. On the development and the utilization of library holding in electronic resources Taking the Library of Shandong University of Science and Technology%试论电子资源的馆藏发展与利用——以山东科技大学图书馆为例

    Institute of Scientific and Technical Information of China (English)

    陈明华; 马圣芹

    2012-01-01

    通过分析电子资源馆藏发展的意义及模式,对电子资源发展的目标及有效管理进行了探讨,并提出一些提高电子资源利用率的措施。%This paper analyses the mode and the importance of library holding development in electronic resources. It also ex- plores the aim and the affective management in electronic resource development and put forwards some measures to improve the utilization ratio of electronic resources.

  20. Electronic Library: A TERI Experiment.

    Science.gov (United States)

    Kar, Debal C.; Deb, Subrata; Kumar, Satish

    2003-01-01

    Discusses the development of Electronic Library at TERI (The Energy and Resources Institute, New Delhi). Highlights include: hardware and software used; the digital library/Virtual Electronic Library; directory of Internet journals; virtual reference resources; electronic collection/Physical Electronic Library; downloaded online full-length…

  1. Electron transfer in pH-sensitive nitroxide radicals

    Science.gov (United States)

    Barbon, Antonio; Bortolus, Marco; Isse, Abdirisak A.; Reznikov, Vladimir A.; Weiner, Lev

    2016-11-01

    Two pH-sensitive stable nitroxide radicals are characterized by EPR spectroscopy and cyclic voltammetry in aqueous solution at different pH values. The rates of the photochemically-induced electron transfer reactions from the protonated and deprotonated forms of the radicals to a ruthenium complex are determined.

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

    Science.gov (United States)

    Reche, Irene; Gallardo, Iluminada; Guirado, Gonzalo

    2015-01-28

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

  3. Voltammetry and single-molecule in situ scanning tunneling microscopy of laccases and bilirubin oxidase in electrocatalytic dioxygen reduction on Au(111) single-crystal electrodes

    DEFF Research Database (Denmark)

    Climent, Victor; Zhang, Jingdong; Friis, Esben Peter

    2012-01-01

    to elucidate the catalytic mechanism, where laccase (sub)monolayer voltammetry has been a core approach. In this report, we address voltammetry and electrocatalysis of O2 reduction of (sub)monolayers of several laccases in new ways. These are based on the use of single-crystal, atomically planar bare Au(111...... American Chemical Society....

  4. Catalytic monolayer voltammetry and in situ scanning tunneling microscopy of copper nitrite reductase on cysteamine-modified Au(111) electrodes

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Welinder, A.C.; Hansen, Allan Glargaard

    2003-01-01

    We have studied the adsorption and electrocatalysis of the redox metalloenzyme blue copper nitrite reductase from Achromobacter xylosoxidans (AxCuNiR) on single-crystal Au(111)-electrode surfaces modified by a self-assembled monolayer of cysteamine. A combination of cyclic voltammetry and in situ...... biotechnology at the monolayer and toward the single-molecule level....

  5. Catalytic monolayer voltammetry and in situ scanning tunneling microscopy of copper nitrite reductase on cysteamine-modified Au(111) electrodes

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Welinder, A.C.; Hansen, Allan Glargaard

    2003-01-01

    We have studied the adsorption and electrocatalysis of the redox metalloenzyme blue copper nitrite reductase from Achromobacter xylosoxidans (AxCuNiR) on single-crystal Au(111)-electrode surfaces modified by a self-assembled monolayer of cysteamine. A combination of cyclic voltammetry and in situ...

  6. Initial stages of anodic oxidation of silver in sodium hydroxide solution studied by potential sweep voltammetry and ellipsometry

    NARCIS (Netherlands)

    Droog, J.M.M.; Alderliesten, P.T.; Bootsma, G.A.

    1979-01-01

    The first stages of the oxidation of polycrystalline silver electrodes in NaOH solutions were studied by potential sweep voltammetry and ellipsometry. Formation of bulk Ag2O was found to be preceded by dissolution of silver species and deposition of a surface oxide. The equilibrium oxide coverage de

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

    Science.gov (United States)

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

    2001-01-01

    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.

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

    Science.gov (United States)

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

    2014-11-04

    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.

  9. Experimentation and numerical modeling of cyclic voltammetry for electrochemical micro-sized sensors under the influence of electrolyte flow

    DEFF Research Database (Denmark)

    Adesokan, Bolaji James; Quan, Xueling; Evgrafov, A.

    2016-01-01

    In this study, we perform experimental studies as well as simulations for cyclic voltammetry(CV) of the redox couple FeIII(CN)63-/FeII(CN)64- on a gold plated ECC biosensor encapsulated by a microfluidic system. We examine the effect of flow rate, scan rate, varying supporting electrolyte, exchan...

  10. Innovative Resources for Education and Public Information: Electronic Services, Data and Information from NASA's Hubble Space Telescope and Other NASA Missions.

    Science.gov (United States)

    Christian, Carol A.

    The Space Telescope Science Institute (STScI), which supports the operation of the Hubble Space Telescope, is actively investigating and supporting innovative and experimental methods for improving science and math education content. The educational resources on the World Wide Web are derived from the latest data, scientific results, and advances…

  11. An implementation case study. Implementation of the Indian Health Service's Resource and Patient Management System Electronic Health Record in the ambulatory care setting at the Phoenix Indian Medical Center.

    Science.gov (United States)

    Dunnigan, Anthony; John, Karen; Scott, Andrea; Von Bibra, Lynda; Walling, Jeffrey

    2010-01-01

    The Phoenix Indian Medical Center (PIMC) has successfully implemented the Resource and Patient Management System Electronic Health Record (RPMS-EHR) in its Ambulatory Care departments. One-hundred and twenty-six providers use the system for essentially all elements of documentation, ordering, and coding. Implementation of one function at a time, in one clinical area at a time, allowed for focused training and support. Strong departmental leadership and the development of 'super-users' were key elements. Detailed assessments of each clinic prior to implementation were vital, resulting in optimal workstation utilization and a greater understanding of each clinic's unique flow. Each phase saw an increasing reluctance to revert to old paper processes. The success of this implementation has placed pressure on the remainder of the hospital to implement the RPMS-EHR, and has given the informatics team an increased awareness of what resources are required to achieve this result.

  12. 大學圖書館電子資源之需求分析與行銷策略之研究 A Study of Demands Analysis and Marketing Strategy of Electronic Resources in University Library

    Directory of Open Access Journals (Sweden)

    Huang-Yu Liu

    2008-03-01

    Full Text Available 電子資源的出現,使得知識載體有了新的突破,提高了使用者的便利性與即時性。對於圖書館而言,如何使電子資源的使用效益達到最高,必須思考一套有效的行銷策略。電子資源行銷概念應以讀者為導向,尊重讀者的資訊需求,並利用各種宣傳技巧,行銷電子資源,使圖書館能提供更完善的服務。本研究之目的旨在探討讀者的使用需求及電子資源的推廣策略,以獲致最有效益的行銷方式。研究對象以開南大學日間部四學院(商學院、運輸觀光學院、資訊學院、人文社會學院)學生為樣本,佐以缺口分析模型為分析架構,藉以找出個案中讀者/學生對於電子資源使用的真實需求,並進而歸納出提供服務的大學圖書館在其推廣或行銷服務上可有的因應策略。The emergence of electronic resources has made new breakthrough in knowledge carriers because of their ease of use, instant availability, and the characteristic of no time and space constraints. For public libraries to achieve maximum efficiency in its electronic resources, it is necessary to seek the most effective marketing strategies. Therefore, the marketing concept of the electronic resources should be reader oriented, such as respecting and understanding library user’s information needs. Libraries also need to utilize various media and techniques to market the electronic resources, so that more comprehensive services and experiences can be provided to readers. The purpose of this study is to investigate library user’s needs and promotion strategies of electronic resources in order to identify the most effective ways of marketing. This study focuses on the students of the four colleges (College of Business, College of Tourism, College of Information, and College of Humanities and Social Science in Kainan University as subjects in the survey questionnaire. It uses the Gap Analysis

  13. 电子商务系统内的人力资源管理模式解析%The analytic model of human resource management in electronic commerce system

    Institute of Scientific and Technical Information of China (English)

    王斌

    2013-01-01

      企业人力资源管理工作在现代电子商务环境下呈现出多方面的电子化新特征,且较之于传统的人力资源管理工作有非常多显著的优势可言,基本上已经成为了企业获取更大成功的基本导向。电子商务系统内的人力资源管理新模式E-HR就是在这样一种背景下应运而生的,E-HR管理模式不仅已经成为了众多企业发展的趋势,而且在实际应用的过程当中也已经给企业带来了非常多的利益。本文正是在此背景之下对电子商务系统内的人力资源管理模式E-HR进行解析,希望能够对其有更深入的理解并更好的应用到实践当中去。%The enterprise human resources management in modern electronic commerce environment presents many new characteristics of the electron,and compared with the traditional human resource management has many significant advantages,basically has become a basic guide for more successful enterprises.E-HR is a new mode of human resource management system emerge as the times require electronic commerce is in such a background,the E-HR management model not only has become the trend of development of many enterprises, but also in the process of practical application also has to the enterprise has brought a lot of benefits. This paper is analyzed under this background to the electronic commerce system within the human resources management mode of E-HR,the application wishes to have a deeper understanding and better on it into practice.

  14. Positive Perceptions of Access to Online Library Resources Correlates with Quality and Quantity of Scholarly Publications among Finnish Academics. A Review of: Vakkari, Pertti. “Perceived Influence of the Use of Electronic Information Resources on Scholarly Work and Publication Productivity.” Journal of the American Society for Information Science and Technology 59.4 (Feb. 15, 2008: 602-12.

    Directory of Open Access Journals (Sweden)

    Scott Marsalis

    2008-12-01

    Full Text Available Objective – To investigate the relationship between academics’ use of library electronic resources and their opinions regarding how these resources have impacted their work, and to investigate the association between this perceived influence and publication productivity during the previous two years.Design – Two specific questions added to an annual online user-survey questionnaire; additional data mined from surveySetting – Twenty-two Finnish Universities served by FinELib, the Finnish Electronic Library.Subjects – Seven hundred and sixty seven academic staff and full-time doctoral students.Methods – A questionnaire was posted in April 2007 on FinELib’s homepage and advertised on each university library’s mainpage, and focused on respondents’ experience in the previous two years. Participants selected answers either from a list of category choices, or, when measuring perceptions, by rating agreement with statements along a four-point scale. Controlled variables measured were the respondents’ academic position, their discipline, membership in a research group, whether their literature use was discipline-specific or interdisciplinary, and their perception of the availability online of the relevant core literature. The independent variable measured was the scholars’ perception of the impact of the use of electronic library resources on their work. The dependent variable measured was the scholars’ self-reported publications in the two years preceding the survey.Main Results – Participants reported a positive impact on the efficiency of their work, most strongly in areas of ease of access, with lesser impacts in the range of materials available to them and the ease with which they can keep up-to-date in their field. To a lesser extent, the scholars perceived a positive impact on the quality of their work. Upon analysis, the study found that access to online library resources improved scholars’ work by the interconnected

  15. Electronic Properties of Ordered Ladder Polymers

    Science.gov (United States)

    1989-01-01

    DHTAP.X" + NO. Electron Spin Resonance (ESR) spectroscopy will be used to confirm the nature of these later complexes in future studies. Figure...b) stirring of the monomer solution with a magnetic stirring bar; and (c) no air bubbling through the solution and no stirring. The product recovered...The electrochemical properties of BBL film were studied by cyclic voltammetry at neutral pH in non-aqueous electrolyte and as a funtion of pH in aqueous

  16. Reduction of antitumour mitosenes in non-aqueous and aqueous environment. An electron spin resonance and cyclic voltammetry study

    NARCIS (Netherlands)

    Maliepaard, Marc; de Mol, Nico J.; Janssen, Lambert H.M.; Goeptar, Arnold R.; te Koppele, Johan; Vermeulen, Nico P.E.; Verboom, Willem; Reinhoudt, David

    1995-01-01

    Chemical reduction of mitosenes under aerobic conditions in DMSO showed characteristic ESR signals of the mitosene derived semiquinone free radicals. However, these signals diminished strongly upon addition of water to the reaction mixture, indicating a short lifetime of the mitosene semiquinone

  17. Lactation resources for clinicians.

    Science.gov (United States)

    Turner-Maffei, Cynthia

    2007-01-01

    Breastfeeding is widely acknowledged as the optimal infant feeding choice. However, many clinicians working in maternal and child health do not receive adequate university preparation to support breastfeeding. Knowledge and skill are most often gained through on-the-job and personal experience. Myriad resources exist to support clinicians in delivering the best quality care to breastfeeding clients. Among the available resources are policies and protocols of professional organizations, governmental, and health advocacy groups. Breastfeeding-focused academic and continuing education programs are identified. Electronic and other resources for breastfeeding information are available for both professional and consumer audiences.

  18. Renewable energy resources

    DEFF Research Database (Denmark)

    Ellabban, Omar S.; Abu-Rub, Haitham A.; Blaabjerg, Frede

    2014-01-01

    Electric energy security is essential, yet the high cost and limited sources of fossil fuels, in addition to the need to reduce greenhouse gasses emission, have made renewable resources attractive in world energy-based economies. The potential for renewable energy resources is enormous because...... they can, in principle, exponentially exceed the world's energy demand; therefore, these types of resources will have a significant share in the future global energy portfolio, much of which is now concentrating on advancing their pool of renewable energy resources. Accordingly, this paper presents how...... renewable energy resources are currently being used, scientific developments to improve their use, their future prospects, and their deployment. Additionally, the paper represents the impact of power electronics and smart grid technologies that can enable the proportionate share of renewable energy...

  19. Merge of terminological resources

    DEFF Research Database (Denmark)

    Henriksen, Lina; Braasch, Anna

    2012-01-01

    In our globalized world, the amount of cross-national communication increases rapidly, which also calls for easy access to multi-lingual high quality terminological resources. Sharing of terminology resources is currently becoming common practice, and efficient strategies for integration...... – or merging – of terminology resources are strongly needed. This paper discusses prerequisites for successful merging with the focus on identification of candidate duplicates of a subject domain found in the resources to be merged, and it describes automatic merging strategies to be applied to such duplicates...... in electronic terminology resources. Further, some perspectives of manual, supplementary assessment methods supporting the automatic procedures are sketched. Our considerations are primarily based on experience gained in the IATE and EuroTermBank projects, as merging was a much discussed issue in both projects....

  20. Effects of coupled homogeneous chemical reactions on the response of large-amplitude AC voltammetry: extraction of kinetic and mechanistic information by Fourier transform analysis of higher harmonic data.

    Science.gov (United States)

    Lee, Chong-Yong; Bullock, John P; Kennedy, Gareth F; Bond, Alan M

    2010-09-23

    Large-amplitude ac voltammograms contain a wealth of kinetic information concerning electrode processes and can provide unique mechanistic insights compared to other techniques. This paper describes the effects homogeneous chemical processes have on ac voltammetry in general and provides experimental examples using two well-known chemical systems: one simple and one complex. Oxidation of [Cp*Fe(CO)(2)](2) (Cp* = η(5)-pentamethylcyclopentadienyl) in noncoordinating media is a reversible one-electron process; in the presence of nucleophiles, however, the resulting ligand-induced disproportionation changes the process to a multiple step regeneration. The chemical kinetic parameters of the regeneration mechanism were discerned via analysis of the third and higher harmonics of Fourier-transformed ac voltammetry data. Comparison of experimental data to digital simulations provides clear evidence that the reaction proceeds via a rapid pre-equilibrium between the electrogenerated monocation and the coordinating ligand; simultaneous fitting of the first nine harmonics indicates that k(f) = 7500 M(-1) s(-1) and k(r) = 100 s(-1), and that the unimolecular decomposition of the corresponding intermediate occurs with a rate constant of 2.2 s(-1). The rapid cis(+) → trans(+) isomerization of the electrogenerated cis-[W(CO)(2)(dpe)(2)](+), where dpe = 1,2-diphenylphosphinoethane, was examined to illustrate the effects of a simpler EC mechanism on the higher harmonics; a rate constant of 280 s(-1) was determined. These results not only shed new light on the chemistry of these systems, but provide a clear demonstration that the higher harmonics of ac voltammetry provide mechanistic insights into coupled homogeneous processes far more detailed than those that are readily accessible with dc techniques.

  1. Anodic Stripping Voltammetry with Pencil Graphite Electrode for Determination of Chromium (III)

    Science.gov (United States)

    Wyantuti, S.; Hafidza, R. A.; Ishmayana, S.; Hartati, Y. W.

    2017-02-01

    Chromium is required as micronutrient that has roles in insulin metabolism and blood glucose level regulation. Chromium (III) deficiency can cause hyperglycemia and glycosuria. However, a high amount of chromium in body can cause allergic reaction, organ damage, and even death because of its toxicity. Chromium is commonly used in steel industries. Simultaneously with the development of industry, the waste disposal that can endanger environment also increased. Therefore, a sensitive and specific analysis method for chromium detection is required. Stripping voltammetry is one of the voltammetric methods that is commonly used for heavy metal analysis due to the very low limit of detection (sub ppb). The present study was conducted to develop an analysis method for chromium (III) determination using pencil graphite electrode. Quantitative determination was performed for chromium (III) which measured at -0.8 to +1.0 V with deposition time for 60 s and 50 mV/s scan rate. Stripping voltammetric analysis of chromium (III) using pencil graphite electrode gave linear range at 12.5 to 75 ppm with limit of detection of 0.31 ppm.

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

    Science.gov (United States)

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

    2004-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-01

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

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

    Science.gov (United States)

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

    2012-07-07

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

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

    Science.gov (United States)

    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

    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.

  6. Enriched alloy layer on an Al-Cu alloy studied by cyclic voltammetry

    Science.gov (United States)

    García Vergara, S. J.; Blanco Pinzon, C. E.; Skeldon, P.

    2017-01-01

    The behaviour of enriched Al-0.7at.%Cu alloy is investigated using cyclic voltammetry. Enriched alloy layers at the interface between the alloy/oxide film were developed by alkaline etching at 5mAcm-2 in 0.1M sodium hydroxide solution at 298K, with the time of etching determining the extent of enrichment. Cyclic voltammograms were recorded at a scan rate of 10mV s-1 in naturally aerated 0.1M ammonium pentaborate solution at 298K. The current overshoot of the enriched alloys was different from that for non-enriched alloy. The latter material revealed the usual single peaks, which are very similar. In contrast, the overshoot comprised two or more components for the enriched alloys. The behaviour is suggested to be associated with the atomic bonding of aluminium in copper-rich and aluminium-rich regions of the enriched alloy layer, with influence on the activation potentials for oxidation of aluminium.

  7. Determination of Selenium in infant formula by differential pulse cathodic stripping voltammetry

    Directory of Open Access Journals (Sweden)

    "Oveisi MR

    2002-07-01

    Full Text Available Selenium as a nonmetallic chemical element has received high attention of biologists because of its dual role as an essential trace nutrient and a toxic element. This interest has created a need for reliable analytical methods for determination of selenium. In this investigation determination of selenium by differential pulse cathodic stripping voltammetry and the influence of various parameters such as deposition potentials, deposition time. Cu concentration pH, etc. on selenium peak in voltammogram are described. Determination of selenium was accomplished in mixture of acetic acid, hydrochloric acid and sodium chloride buffer (pH=1 with a scan rate of 60 mv/s and a pulse height of 100 my by hanging mercury drop electrode (HMDE as working electrode. The solution was stirred during pre-electrolysis at - 350 mv (vs SCE for 30 s and the potential was scanned between - 350 mv and - 800 mv. The determination limit of the method was 0.005 mg/kg for the sample. The calibration curves were linear in the range of 0-30 μg/L (R2=0.996, p<0.001. Repeatability of the method at concentrations of 30 and 0.5 μg/L were 2.5 and 10.5% respectively.

  8. Relating cyclic voltammetry and impedance analysis in a viologen electrochromic device

    Energy Technology Data Exchange (ETDEWEB)

    Vergaz, Ricardo; Barrios, David; Sanchez-Pena, Jose-Manuel [Grupo de Displays y Aplicaciones Fotonicas, Department Tecnologia Electronica, Universidad Carlos III de Madrid, C/Butarque, 15, E28911 Leganes, Madrid (Spain); Pozo-Gonzalo, Cristina; Salsamendi, Maitane [Centre for Electrochemical Technologies (CIDETEC), Dept. Nuevos Materiales, Parque Tecnologico de San Sebastian - Paseo Miramon, 196, E-20009, San Sebastian (Spain)

    2009-12-15

    Viologens are electrochromic materials that have a wide range of coloration depending on the radical substituents. The results for a new blue viologen-based device, that has recently been patented, with an active area of 8.5 cm{sup 2} is presented in this paper. The characterization techniques used are based on optical measurements, chronoamperometry, cyclic voltammetry, and impedance spectroscopy analysis. A study of the results obtained from these measurements provides both an overview of the reactions taking place and has allowed an equivalent circuit to be developed which relates the different electrochemical parameters. The transmittance is observed to change from 80% to 15% in 600 nm for input voltages ranging from 0 to 2.5 V. However, increasing voltage beyond 1.8 V shows no optical change, thus, maintaining the voltage below this level optimizes the use of electrical current. Voltages and charges used for each redox reaction have been computed and are seen to be linearly related. The equivalent circuit generated to mimic the process has included parameters based on Warburg diffusion and double-layer capacitances. Results from this model are consistent with measurements for up to 1.8 V. Saturation of reduced species has been deduced for input voltages beyond this level. (author)

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

    Science.gov (United States)

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

    2007-12-01

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

  10. Sensitive quantitation of Ochratoxin A in cocoa beans using differential pulse voltammetry based aptasensor.

    Science.gov (United States)

    Mishra, Rupesh K; Hayat, Akhtar; Catanante, Gaëlle; Istamboulie, Georges; Marty, Jean-Louis

    2016-02-01

    In this work, we propose for the first time a sensitive Ochratoxin A (OTA) detection in cocoa beans using competitive aptasensor by differential pulse voltammetry (DPV). In the proposed method, biotin labeled and free OTA competed to bind with immobilized aptamer onto the surface of a screen printed carbon electrode (SPCE), and percentage binding was calculated. The detection was performed after adding avidin-ALP to perform avidin-biotin reaction; the signal was generated through a suitable substrate 1-naphthyl phosphate (1-NP), for alkaline phosphatase (ALP). The cocoa samples were extracted and purified using molecular imprinted polymer (MIP) columns specifically designed for OTA. The developed aptasensor showed a good linearity in the range 0.15-5 ng/mL with the limit of detection (LOD) 0.07 ng/mL and 3.7% relative standard deviation (RSD). The aptasensor displayed good recovery values in the range 82.1-85% with 3.87% RSD, thus, demonstrated the efficiency of proposed aptasensor for such matrices.

  11. Diamond microelectrodes and CMOS microelectronics for wireless transmission of fast-scan cyclic voltammetry.

    Science.gov (United States)

    Roham, Masoud; Halpern, Jeffrey M; Martin, Heidi B; Chiel, Hillel J; Mohseni, Pedram

    2007-01-01

    This paper reports on technology development at the sensor and circuit levels for wireless transmission of fast-scan cyclic voltammetry (FSCV) in neurochemical detection. Heavily conductive, boron-doped diamond is selectively deposited onto the polished tip of a tungsten microelectrode to fabricate versatile, implantable, micro-needle microprobes capable of neurochemical sensing in the brain. In addition, an integrated circuit is fabricated in a 0.5-microm CMOS technology for processing and wireless transmission of the electrochemical signals corresponding to extracellular concentration changes of various neurotransmitters. The chip consists of a current-based, second-order, front-end SigmaDelta ADC and an on-chip, RF-FSK transmitter at the back-end. The ADC core and the transmitter consume 22microA and 400microA, respectively, from a 2.6-V power supply. Major electroactive neurotransmitters such as serotonin and dopamine in micromolar concentration have been wirelessly recorded at 433MHz using 300-V/s FSCV in flow injection analysis experiments.

  12. Overoxidized polypyrrole-coated carbon fiber microelectrodes for dopamine measurements with fast-scan cyclic voltammetry.

    Science.gov (United States)

    Pihel, K; Walker, Q D; Wightman, R M

    1996-07-01

    Thin films of overoxidized polypyrrole have been electro-chemically coated onto carbon fiber microelectrodes and used for dopamine measurements with background-substracted, fast-scan cyclic voltammetry at a scan rate of 300 V/s. The films were stable on the electrode surface only when the electrodes were scanned to high potentials (1400 mV vs SSCE) in pH 7.4 aqueous buffer. Dopamine sensitivity and ascorbate and dihydroxyphenylacetic acid (DOPAC) rejection at the overoxidized polypyrrole-coated electrode were compared to those at carbon fiber electrodes coated with Nafion, a perfluorinated ion-exchange material. At 300 V/s, the overoxidized polypyrrole-coated electrode was almost 3 times more sensitive to dopamine than an uncoated disk electrode. Furthermore, the films were as effective as Nafion in the attenuation of the response to ascorbate and DOPAC, common interferences of dopamine in vivo. Overoxidized polypyrrole-coated electrodes maintained a stable response to dopamine for several hours when implanted in the rat brain. The electrochemical deposition procedure was effective at both elliptical and cylindrical electrodes. This is in contrast to the dip-coating procedures employed with Nafion films that lead to nonuniform coatings at cylindrical electrodes.

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

    Directory of Open Access Journals (Sweden)

    Rene Kizek

    2005-11-01

    Full Text Available The paper describes successful coupling of adsorptive transfer stripping (AdTS andelimination voltammetry with linear scan (EVLS for the resolution of reduction signals of cytosine (Cand adenine (A residues in hetero-oligodeoxynucleotides (ODNs. Short ODNs (9-mers and 20-merswere adsorbed from a small volume on a hanging mercury drop electrode (HMDE. After washing ofthe 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 theelimination function conserving the diffusion current component and eliminating kinetic and chargingcurrent 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 inODN chains. Optimal conditions of elimination experiments such as pH, time of adsorption, and scanrate were found. The combination of EVLS with AdTS procedure can be considered as a newdetection method in a DNA sensor.

  14. Cyclic voltammetry studies of n-type polymers with non-alternant fluoranthene units

    Energy Technology Data Exchange (ETDEWEB)

    Angulo, Gonzalo [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Kapturkiewicz, Andrzej [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland)], E-mail: akaptur@ichf.edu.pl; Palmaerts, Arne [Hasselt University, Institute for Materials Research (IMO), Agoralaan, Building D, B-3590 Diepenbeek (Belgium); Lutsen, Laurence [IMEC, Division IMOMEC, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Cleij, Thomas J. [Hasselt University, Institute for Materials Research (IMO), Agoralaan, Building D, B-3590 Diepenbeek (Belgium); Vanderzande, Dirk [Hasselt University, Institute for Materials Research (IMO), Agoralaan, Building D, B-3590 Diepenbeek (Belgium); IMEC, Division IMOMEC, Wetenschapspark 1, B-3590 Diepenbeek (Belgium)

    2009-02-01

    Poly(p-fluoranthenevinylenes) and their dithiocarbamate precursors have been deposited on indium-tin oxide electrodes and electrochemical properties of the obtained films have been investigated by means of cyclic voltammetry studies in acetonitrile solutions containing 0.1 M (n-C{sub 4}H{sub 9}){sub 4}NBF{sub 4} as supporting electrolyte. It has been found that all investigated polymers display well pronounced n-doping processes. Electrochemical reduction of the dithiocarbamate precursors seems to be associated with C-S bond cleavage with elimination of -SC(S)N(C{sub 2}H{sub 5}){sub 2} group. In view of UV-vis spectroscopic data the obtained products, tentatively identified as polymers containing fluoranthene units connected by -CH{sub 2}-CH{sub 2}- bridges, are somewhat less conjugated than the corresponding poly(p-fluoranthenevinylenes). Reversible electrochemical reduction of poly(p-fluoranthenethanes) occurs at potentials only somewhat (ca. 0.1 V) more negative as found for their poly(p-fluoranthenevinylenes) analogues suggesting relatively weak coupling between fluoranthene kernels in both kinds of investigated polymers.

  15. Fast-scan cyclic voltammetry analysis of dynamic serotonin reponses to acute escitalopram.

    Science.gov (United States)

    Wood, Kevin M; Hashemi, Parastoo

    2013-05-15

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

  16. Fast-scan Cyclic Voltammetry for the Characterization of Rapid Adenosine Release.

    Science.gov (United States)

    Nguyen, Michael D; Venton, B Jill

    2015-01-01

    Adenosine is a signaling molecule and downstream product of ATP that acts as a neuromodulator. Adenosine regulates physiological processes, such as neurotransmission and blood flow, on a time scale of minutes to hours. Recent developments in electrochemical techniques, including fast-scan cyclic voltammetry (FSCV), have allowed direct detection of adenosine with sub-second temporal resolution. FSCV studies have revealed a novel mode of rapid signaling that lasts only a few seconds. This rapid release of adenosine can be evoked by electrical or mechanical stimulations or it can be observed spontaneously without stimulation. Adenosine signaling on this time scale is activity dependent; however, the mode of release is not fully understood. Rapid adenosine release modulates oxygen levels and evoked dopamine release, indicating that adenosine may have a rapid modulatory role. In this review, we outline how FSCV can be used to detect adenosine release, compare FSCV with other techniques used to measure adenosine, and present an overview of adenosine signaling that has been characterized using FSCV. These studies point to a rapid mode of adenosine modulation, whose mechanism and function will continue to be characterized in the future.

  17. Simultaneous measurement and quantitation of 4-hydroxyphenylacetic acid and dopamine with fast-scan cyclic voltammetry.

    Science.gov (United States)

    Shin, Mimi; Kaplan, Sam V; Raider, Kayla D; Johnson, Michael A

    2015-05-07

    Caged compounds have been used extensively to investigate neuronal function in a variety of preparations, including cell culture, ex vivo tissue samples, and in vivo. As a first step toward electrochemically measuring the extent of caged compound photoactivation while also measuring the release of the catecholamine neurotransmitter, dopamine, fast-scan cyclic voltammetry at carbon-fiber microelectrodes (FSCV) was used to electrochemically characterize 4-hydroxyphenylacetic acid (4HPAA) in the absence and presence of dopamine. 4HPAA is a by-product formed during the process of photoactivation of p-hydroxyphenacyl-based caged compounds, such as p-hydroxyphenylglutamate (pHP-Glu). Our data suggest that the oxidation of 4HPAA occurs through the formation of a conjugated species. Moreover, we found that a triangular waveform of -0.4 V to +1.3 V to -0.4 V at 600 V s(-1), repeated every 100 ms, provided an oxidation current of 4HPAA that was enhanced with a limit of detection of 100 nM, while also allowing the detection and quantitation of dopamine within the same scan. Along with quantifying 4HPAA in biological preparations, the results from this work will allow the electrochemical measurement of photoactivation reactions that generate 4HPAA as a by-product as well as provide a framework for measuring the photorelease of electroactive by-products from caged compounds that incorporate other chromophores.

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

    Energy Technology Data Exchange (ETDEWEB)

    Jasinski, G; Jasinski, P, E-mail: gregor@biomed.eti.pg.gda.pl [Gdansk University of Technology, Faculty of Electronics, Telecommunication and Informatics, Narutowicza 11/12, 80-233 Gdansk (Poland)

    2011-10-29

    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 NO{sub 2} and synthetic air are compared.

  19. Failure of Standard Training Sets in the Analysis of Fast-Scan Cyclic Voltammetry Data.

    Science.gov (United States)

    Johnson, Justin A; Rodeberg, Nathan T; Wightman, R Mark

    2016-03-16

    The use of principal component regression, a multivariate calibration method, in the analysis of in vivo fast-scan cyclic voltammetry data allows for separation of overlapping signal contributions, permitting evaluation of the temporal dynamics of multiple neurotransmitters simultaneously. To accomplish this, the technique relies on information about current-concentration relationships across the scan-potential window gained from analysis of training sets. The ability of the constructed models to resolve analytes depends critically on the quality of these data. Recently, the use of standard training sets obtained under conditions other than those of the experimental data collection (e.g., with different electrodes, animals, or equipment) has been reported. This study evaluates the analyte resolution capabilities of models constructed using this approach from both a theoretical and experimental viewpoint. A detailed discussion of the theory of principal component regression is provided to inform this discussion. The findings demonstrate that the use of standard training sets leads to misassignment of the current-concentration relationships across the scan-potential window. This directly results in poor analyte resolution and, consequently, inaccurate quantitation, which may lead to erroneous conclusions being drawn from experimental data. Thus, it is strongly advocated that training sets be obtained under the experimental conditions to allow for accurate data analysis.

  20. Determination of diclofenac using electromembrane extraction coupled with stripping FFT continuous cyclic voltammetry.

    Science.gov (United States)

    Mofidi, Zahra; Norouzi, Parviz; Seidi, Shahram; Ganjali, Mohammad Reza

    2017-06-15

    For the first time, on-line and ultra-sensitive determination of trace amount of diclofenac in whole blood sample was performed by coupling of electromembrane extraction (EME) and stripping fast Fourier transform continuous cyclic voltammetry (SFFTCCV). In SFFTCCV, the potential waveform was continuously applied on a carbon paste electrode and the electrode response was obtained by subtracting the background current and integrating the current in potential range of the analyte oxidation. A central composite design was used for the optimization of the parameters influencing the extraction efficiency. By applying a DC potential of 20 V during 28 min of extraction, diclofenac was migrated from the sample solution (pH 5), into a thin layer of 1-octanol immobilized in the pores of a porous flat sheet membrane and then into the acceptor solution (pH 7). The method presented a good linearity within the range of 5-1000 ng mL(-1) with a determination coefficient of 0.993 in whole blood samples. Limits of detection (LOD) and quantification (LOQ) were found to be 1.0 ng mL(-1) and 5.0 ng mL(-1) respectively. Copyright © 2017 Elsevier B.V. All rights reserved.