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1

Complete electrode model in EEG: relationship and differences to the point electrode model  

NASA Astrophysics Data System (ADS)

In electroencephalography (EEG) source analysis, a primary current density generated by the neural activity of the brain is reconstructed from external electrode voltage measurements. This paper focuses on accurate and effective simulations of EEG through the complete electrode model (CEM). The CEM allows for the incorporation of the electrode size, shape and effective contact impedance into the forward simulation. Both neural currents in the brain and shunting currents between the electrodes and the skin can affect the measured voltages in the CEM. The goal of this study was to investigate the CEM by comparing it with the point electrode model (PEM), which is the current standard electrode model for EEG. We used a three-dimensional, realistic and high-resolution finite element head model as the reference computational domain in the comparison. The PEM could be formulated as a limit of the CEM, in which the effective impedance of each electrode goes to infinity and the size tends to zero. Numerical results concerning the forward and inverse errors and electrode voltage strengths with different impedances and electrode sizes are presented. Based on the results obtained, limits for extremely high and low impedance values of the shunting currents are suggested.

Pursiainen, S.; Lucka, F.; Wolters, C. H.

2012-02-01

2

Surface-electrode point Paul trap  

E-print Network

We present a model as well as experimental results for a surface electrode radiofrequency Paul trap that has a circular electrode geometry well suited for trapping single ions and two-dimensional planar ion crystals. The ...

Chuang, Isaac L.

3

Surface-electrode point Paul trap  

SciTech Connect

We present a model as well as experimental results for a surface electrode radiofrequency Paul trap that has a circular electrode geometry well suited for trapping single ions and two-dimensional planar ion crystals. The trap design is compatible with microfabrication and offers a simple method by which the height of the trapped ions above the surface may be changed in situ. We demonstrate trapping of single {sup 88}Sr{sup +} ions over an ion height range of 200-1000 {mu}m for several hours under Doppler laser cooling and use these to characterize the trap, finding good agreement with our model.

Kim, Tony Hyun; Herskind, Peter F.; Chuang, Isaac L. [Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Kim, Taehyun; Kim, Jungsang [Department of Electrical and Computer Engineering, Duke University Durham, North Carolina 27708 (United States)

2010-10-15

4

Modeling deep brain stimulation: point source approximation versus realistic representation of the electrode  

NASA Astrophysics Data System (ADS)

Deep brain stimulation (DBS) has emerged as an effective treatment for movement disorders; however, the fundamental mechanisms by which DBS works are not well understood. Computational models of DBS can provide insights into these fundamental mechanisms and typically require two steps: calculation of the electrical potentials generated by DBS and, subsequently, determination of the effects of the extracellular potentials on neurons. The objective of this study was to assess the validity of using a point source electrode to approximate the DBS electrode when calculating the thresholds and spatial distribution of activation of a surrounding population of model neurons in response to monopolar DBS. Extracellular potentials in a homogenous isotropic volume conductor were calculated using either a point current source or a geometrically accurate finite element model of the Medtronic DBS 3389 lead. These extracellular potentials were coupled to populations of model axons, and thresholds and spatial distributions were determined for different electrode geometries and axon orientations. Median threshold differences between DBS and point source electrodes for individual axons varied between -20.5% and 9.5% across all orientations, monopolar polarities and electrode geometries utilizing the DBS 3389 electrode. Differences in the percentage of axons activated at a given amplitude by the point source electrode and the DBS electrode were between -9.0% and 12.6% across all monopolar configurations tested. The differences in activation between the DBS and point source electrodes occurred primarily in regions close to conductor-insulator interfaces and around the insulating tip of the DBS electrode. The robustness of the point source approximation in modeling several special cases—tissue anisotropy, a long active electrode and bipolar stimulation—was also examined. Under the conditions considered, the point source was shown to be a valid approximation for predicting excitation of populations of neurons in response to DBS.

Zhang, Tianhe C.; Grill, Warren M.

2010-12-01

5

Corona in atmospheric air between negative point and plane electrodes  

Microsoft Academic Search

The phenomena of corona between negative point and plane electrodes in atmospheric air have been found to consist of Trichel pulses above onset. Results of experimental investigations on negative point plane corona in air at atmospheric pressure for DC voltage applications are reported in this paper. The diameter of the hemispherical tip used in these investigations varied from 1.0 mm

G. R. Gurumurthy; J. Amarnath; B. R. Natarajan

2004-01-01

6

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

PubMed

We report on the effect of electrode geometry on alternating current cloud point extraction (ACPE). ACPE is a technique utilized to extract membrane-associated biomolecules in an electrode-integrated microfluidic channel. In this study, we investigated the effect of gap size (4?22 ?m) between microband electrodes on ACPE. A decrease in gap size resulted in efficient and rapid concentration of fluorescent-labeled phospholipids, a model of membrane-associated biomolecules. We also investigated the effect of applied voltage amplitude on ACPE using devices with decreased electrode gap size. When the gap was small, ACPE was achieved with low applied voltages. ACPE of membrane proteins extracted from HeLa cells was also studied to demonstrate the applicability of the ACPE to real samples. The results provide a guideline to improve the performance of ACPE and facilitate application of the ACPE technique as part of an overall analytical process. PMID:25224325

Sasaki, Naoki; Maekawa, Chisaki; Sato, Kae

2015-02-01

7

Experimental study of cylindrical air electrodes  

NASA Astrophysics Data System (ADS)

The electrodes studied here are cylindrical and prepared to be placed inside the inner surface of a sintered brass tube, which is nickel-plated. Previously we have reported on the preparation of flat air electrodes and also on long run tests carried out with these electrodes. The electrode material was prepared by the so-called wet method to obtain a carbon dough which is easy to handle. The material preparation remains the same, but owing to the different geometrical shape, the preparation of the electrode itself is quite different. We have studied here the long-term performance of these new cylindrical air electrodes and at the same time measured the carbonate content of the electrolyte. We have also analyzed by comparative methods which property of the electrode lowers the performance after a fairly long period.

Viitanen, M.; Lamminen, J.; Lampinen, M. J.

1991-11-01

8

Discharges in air from point electrodes in the presence of dielectric plates-experimental results  

Microsoft Academic Search

The effect of a dielectric plate on characteristics of discharges in air from a point electrode was investigated experimentally. Experiments have been carried out with either 250\\/2500 ?s switching impulse, or DC voltage applied to the point electrode in the presence of a Plexiglas, (PMMA) dielectric plate. The dielectric plate was charged positively, irrespective of the polarity of the applied

M. Abdel-Salam; P. Weiss; B. Lieske

1992-01-01

9

Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning.  

PubMed

The aim of the study was to investigate the uniformity of the muscle motor point location for lower limb muscles in healthy subjects. Fifty-three subjects of both genders (age range: 18-50 years) were recruited. The muscle motor points were identified for the following ten muscles of the lower limb (dominant side): vastus medialis, rectus femoris, and vastus lateralis of the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus of the hamstring muscles, tibialis anterior, peroneus longus, lateral and medial gastrocnemius. The muscle motor point was identified by scanning the skin surface with a stimulation pen electrode and corresponded to the location of the skin area above the muscle in which an electrical pulse evoked a muscle twitch with the least injected current. For each investigated muscle, 0.15 ms square pulses were delivered through the pen electrode at low current amplitude (<10 mA) and frequency (2 Hz). 16 motor points were identified in the 10 investigated muscles of almost all subjects: 3 motor points for the vastus lateralis, 2 motor points for rectus femoris, vastus medialis, biceps femoris, and tibialis anterior, 1 motor point for the remaining muscles. An important inter-individual variability was observed for the position of the following 4 out of 16 motor points: vastus lateralis (proximal), biceps femoris (short head), semimembranosus, and medial gastrocnemius. Possible implications for electrical stimulation procedures and electrode positioning different from those commonly applied for thigh and leg muscles are discussed. PMID:21796408

Botter, Alberto; Oprandi, Gianmosè; Lanfranco, Fabio; Allasia, Stefano; Maffiuletti, Nicola A; Minetto, Marco Alessandro

2011-10-01

10

Raman structural studies of the nickel electrode  

NASA Technical Reports Server (NTRS)

Raman spectroscopy is sensitive to empirically controlled nickel electrode structural variations, and has unique potential for structural characterization of these materials. How the structure relates to electrochemical properties is examined so that the latter can be more completely understood, controlled, and optimized. Electrodes were impregnated and cycled, and cyclic voltammetry is being used for electrochemical characterization. Structural variation was observed which has escaped detection using other methods. Structural changes are induced by: (1) cobalt doping, (2) the state of change or discharge, (3) the preparation conditions and type of buffer used, and (4) the formation process. Charged active mass has an NiOOH-type structure, agreeing with X-ray diffraction results. Discharged active mass, however, is not isostructural with beta-Ni(OH)2. Chemically prepared alpha phases are not isostructural either. A disordered structural model, containing point defects, is proposed for the cycled materials. This model explains K(+) incorporation. Band assignments were made and spectra interpreted for beta-Ni(OH)2, electrochemical NiOOH and chemically precipitated NiOOH.

Cornilsen, B. C.

1985-01-01

11

AC impedance study of degradation of porous nickel battery electrodes  

NASA Technical Reports Server (NTRS)

AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.

Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.

1987-01-01

12

Imaging study on acupuncture points  

NASA Astrophysics Data System (ADS)

The topographic structures of acupuncture points were investigated by using the synchrotron radiation based Dark Field Image (DFI) method. Four following acupuncture points were studied: Sanyinjiao, Neiguan, Zusanli and Tianshu. We have found that at acupuncture point regions there exists the accumulation of micro-vessels. The images taken in the surrounding tissue out of the acupuncture points do not show such kind of structure. It is the first time to reveal directly the specific structure of acupuncture points by X-ray imaging.

Yan, X. H.; Zhang, X. Y.; Liu, C. L.; Dang, R. S.; Ando, M.; Sugiyama, H.; Chen, H. S.; Ding, G. H.

2009-09-01

13

AC-impedance studies on metal hydride electrodes  

SciTech Connect

The metal hydride (MH{sub x}) electrode is the negative electrode in one of the most advanced rechargeable batteries (i.e. nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydriding reaction in the battery, using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MH{sub x} electrode reaction is proposed. The rate capabilities of charge/discharge reaction of MH{sub x} electrode are determined by the kinetics of charge transfer reaction at the alloy surface. Transient and pseudo steady-state analyses (cyclic voltammetry and potential vs. current density behavior) qualitatively and quantitatively support the EIS results. EIS studies on electrodes with (i) three types of binding additives, (ii) varying amounts of active material, and (iii) two types of alloys as active materials demonstrate the usefulness of this technique to develop electrodes with the optimum compositions and structures.

Zhang, W.; Kumar, M.P.S.; Visintin, A.; Srinivasan, S. [Texas A and M Univ., College Station, TX (United States)

1994-12-31

14

Study of electric discharges between moving electrodes in air  

SciTech Connect

A barrier electric discharge excited between a fixed electrode and a rotating electrode covered with a dielectric layer in atmospheric-pressure air is studied experimentally. A distinctive feature of this type of discharge is that it operates at a constant voltage between the electrodes. An advantage of the proposed method for plasma generation in the boundary layer of the rotating electrode (e.g., for studying the influence of plasma on air flows) is the variety of forms of the discharge and conditions for its initiation, simplicity of the design of the discharge system, and ease of its practical implementation.

Andreev, V. V.; Pichugin, Yu. P.; Telegin, V. G.; Telegin, G. G. [Chuvash State University (Russian Federation)

2011-12-15

15

Study of Influence of Electrode Geometry on Impedance Spectroscopy  

SciTech Connect

Electrochemical Impedance Spectroscopy (EIS) is a powerful and proven tool for analyzing AC impedance response. A conventional three electrode EIS method was used to perform the investigation in the present study. Saturated potassium chloride solution was used as the electrolyte and three different material rods were used as working electrodes. Different configurations of electrode area were exposed to the electrolyte as an active area to investigate electrode geometry effects. Counter to working electrode distance was also altered while keeping the working electrode effective area constant to explore the AC response dependence on the variation of ion travel distance. Some controlled experiments were done to validate the experimental setup and to provide a control condition for comparison with experimental results. A frequency range of 100 mHz to 1 MHz was used for all experiments. In our analysis, we have found a noteworthy influence of electrode geometry on AC impedance response. For all electrodes, impedance decreases with the increase of effective area of the electrolyte. High frequency impedance is not as dependent on geometry as low frequency response. The observed phase shift angle drops in the high frequency region with increased working electrode area, whereas at low frequency the reverse is true. Resistance and capacitive reactance both decrease with an increase of area, but resistance response is more pronounce than reactance. For lower frequencies, small changes in working area produce very distinctive EIS variations. Electrode material as well as geometry was systematically varied in the present study. From these and other studies, we hope to develop a fundamental foundation for understanding specific changes in local geometry in fuel cell (and other) electrodes as a method of designing local morphology for specific performance.

Ahmed, Riaz; Reifsnider, Kenneth L

2011-01-01

16

Behavior of Air Bubble Attaching to a Point Electrode in Liquid Dielectrics  

NASA Astrophysics Data System (ADS)

Using a new technique which was able to attach a bubble to a point electrode, the behavior of a bubble in insulating liquids (silicone oil and hexane) was investigated under a negative point condition. Above a threshold voltage, successive pulsed discharges were produced in the bubble; these were very similar to Trichel corna in gases. The interval of the pulse was almost constant at a certain voltage, but decreased with increasing applied voltage. The discharge could induce a mechanical vibration with a frequency that was much higher than that of the discharge pulse. The vibration might be sustained by a pressure change in the bubble or a small displacement of liquid inside a fine insulating pipe for suppling the bubble.

Arii, Kiyomitsu; Kitani, Isamu

1986-10-01

17

A study of the glow discharge characteristics of contact electrodes at atmospheric pressure in air  

SciTech Connect

Electric field distributions and discharge properties of rod-rod contact electrodes were studied under the condition of DBD for the steady generation of atmospheric pressure glow discharge plasma (APGD) in air. We found that under the effect of the initial electrons generated in a nanometer-scale gap, the rod-rod cross-contact electrodes yielded APGD plasma in air. Regarding the rod-rod cross-contact electrodes, increasing the working voltage expanded the strong electric field area of the gas gap so that both discharge area and discharge power increased, and the increase in the number of contact points kept the initial discharge voltage unchanged and caused an increase in the plasma discharge area and discharge power. A mesh-like structure of cross-contact electrodes was designed and used to generate more APGD plasma, suggesting high applicability.

Liu, Wenzheng, E-mail: wzhliu@bjtu.edu.cn; Sun, Guangliang, E-mail: 11121659@bjtu.edu.cn; Li, Chuanhui; Zhang, Rongrong [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China)] [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China)

2014-04-15

18

Raman structural studies of the nickel electrode  

NASA Technical Reports Server (NTRS)

The objectives of this investigation have been to define the structures of charged active mass, discharged active mass, and related precursor materials (alpha-phases), with the purpose of better understanding the chemical and electrochemical reactions, including failure mechanisms and cobalt incorporation, so that the nickel electrode may be improved. Although our primary tool has been Raman spectroscopy, the structural conclusions drawn from the Raman data have been supported and augmented by three other analysis methods: infrared spectroscopy, powder X-ray Diffraction (XRD), and x-ray absorption spectroscopy (in particular EXAFS, Extended X-ray Absorption Fine Structure spectroscopy).

Cornilsen, Bahne C.

1994-01-01

19

Study of multi-electrodes structure in CdTe nuclear radiation detectors  

Microsoft Academic Search

We studied CdTe nuclear radiation detectors with multi-electrodes structure. The detector consists of a common cathode, while the anode has been separated into three electrodes: the central collecting anode, a guard ring electrode, and a guiding electrode. The detector was biased in such a way that the central anode collects electrons while the guiding electrode repel electrons and guide them

Madan Niraula; Yasunori Agata; Kazuhito Yasuda

2004-01-01

20

A study of electrode passivation during aqueous phenol electrolysis  

Microsoft Academic Search

The process of electrode passivation during phenol electrolysis at a platinum electrode was studied in a sulfuric acid electrolyte (pH0-1). Passive film growth and the effects of concentration and potential were investigated using chronoamperometry, x-ray photoelectron spectroscopy, and gel permeation chromatography. The main products of the phenol oxidation are oligomers\\/polymers with weight-averaged molecular weights typically around 1000 g\\/mol after a

M. Gattrell; D. W. Kirk

1993-01-01

21

Spectroelectrochemical studies of metallophthalocyanines adsorbed on electrode surfaces  

SciTech Connect

Co(II) and Fe(II)-phthalocyanines adsorbed on platinum and various carbon electrode surfaces have been studied by spectroelectrochemical techniques. The metallophthalocyanine (MPc) films were prepared on substrate electrodes by a drop-dry method after dissolving them in pyridine. While not much change in the spectroscopic properties is observed for MPcs adsorbed at the platinum electrode, both the Soret and Q bands were significantly broadened when adsorbed on the carbon electrodes. Also, the metal-ligand charge-transfer (MLCT) bands are observed from CoPc films adsorbed on carbon substrates even if they are not reduced. These observations lead to the conclusion that the MPc molecules not only undergo oligomerization but also interact strongly with carbon surfaces by perhaps sharing the {pi}-electrons of carbon. MPcs have been used as effective catalysts for oxygen reduction, which is used as a cathode reaction in fuel cells and metal-air batteries.

Mho, S.; Ortiz, B.; Park, S.M. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry; Ingersoll, D.; Doddapaneni, N. [Sandia National Labs., Albuquerque, NM (United States)

1995-05-01

22

Potentiometric studies at ORNL with hydrogen electrode concentration cells  

SciTech Connect

The absence of suitably stable reference electrodes for and to 300 C led ORNL to develop hydrogen electrode concentration cells for studies of equilibria of interest in reactor and steam generator systems to about 300 C during the late 1960`s and seventies. During the intervening two dozen years over twenty scientists have participated in potentiometric studies at Oak Ridge and much of that work will be summarized in this paper. A description of hydrogen electrode concentration cells developed in the late sixties and currently in use at Oak Ridge is given. The method of measurement, data interpretation, and published results are reviewed for studies of acid-base ionization, metal ion hydrolysis, and metal complexation reactions using principally such cells in titration or flow modes. 41 refs.

Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

1994-12-31

23

Model electrode structures for studies of electrocatalyst degradation.  

SciTech Connect

Proton exchange membrane fuel cells are being extensively studied as power sources because of their technological advantages such as high energy efficiency and environmental friendliness. The most effective catalyst in these systems consists of nanoparticles of Pt or Pt-based alloys on carbon supports. Understanding the role of the nanoparticle size and structure on the catalytic activity and degradation is needed to optimize the fuel cell performance and reduce the noble metal loading. One of the more significant causes of fuel cell performance degradation is the cathode catalyst deactivation. There are four mechanisms considered relevant to the loss of electrochemically active surface area of Pt in the fuel cell electrodes that contribute to cathode catalyst degradation including: catalyst particle sintering such as Ostwald ripening, migration and coalescence, carbon corrosion and catalyst dissolution. Most approaches to study this catalyst degradation utilize membrane electrode assemblies (MEAs), which results in a complex system where it is difficult to deconvolute the effects of the metal nanoparticles. Our research addresses catalyst degradation by taking a fundamental approach to study electrocatalyst using model supports. Nanostructured particle arrays are engineered directly onto planar glassy carbon electrodes. These model electrocatalyst structures are applied to electrochemical activity measurements using a rotating disk electrode and surface characterization by scanning electron microscopy. Sample transfer between these measurement techniques enables examination of the same catalyst area before and after electrochemical cycling. This is useful to probe relationships between electrochemical activity and catalyst structure such as particle size and spacing. These model systems are applied to accelerated aging studies of activity degradation. We will present our work demonstrating the mechanistic aspects of catalyst degradation using this simplified geometric system. The active surface area loss observed in repeated cyclic voltammetry is explained through characterization and imaging of the same RDE electrode structures throughout the aging process.

St. Pierre, Jean (University of South Carolina); Atanassov, Plamen Borissov (University of New Mexico); Datye, Abhaya K. (University of New Mexico); Goeke, Ronald S. (University of New Mexico)

2010-10-01

24

Electrochemical studies of cobalt hydroxide — an additive for nickel electrodes  

Microsoft Academic Search

The electrochemical behavior of chemically precipitated cobalt hydroxide is studied by cyclic voltammetry and galvanostatic charge\\/discharge cycling. When cycled in the potential range between the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), the electrode undergoes two pairs of reactions. The pair of current peaks close to the OER is attributed to quasi-reversible oxidation of Co(OH)2 to CoOOH,

P. Elumalai; H. N. Vasan; N. Munichandraiah

2001-01-01

25

Comparison of resistive switching characteristics using copper and aluminum electrodes on GeOx/W cross-point memories  

PubMed Central

Comparison of resistive switching memory characteristics using copper (Cu) and aluminum (Al) electrodes on GeOx/W cross-points has been reported under low current compliances (CCs) of 1 nA to 50 ?A. The cross-point memory devices are observed by high-resolution transmission electron microscopy (HRTEM). Improved memory characteristics are observed for the Cu/GeOx/W structures as compared to the Al/GeOx/W cross-points owing to AlOx formation at the Al/GeOx interface. The RESET current increases with the increase of the CCs varying from 1 nA to 50 ?A for the Cu electrode devices, while the RESET current is high (>1 mA) and independent of CCs varying from 1 nA to 500 ?A for the Al electrode devices. An extra formation voltage is needed for the Al/GeOx/W devices, while a low operation voltage of ±2 V is needed for the Cu/GeOx/W cross-point devices. Repeatable bipolar resistive switching characteristics of the Cu/GeOx/W cross-point memory devices are observed with CC varying from 1 nA to 50 ?A, and unipolar resistive switching is observed with CC >100 ?A. High resistance ratios of 102 to 104 for the bipolar mode (CCs of 1 nA to 50 ?A) and approximately 108 for the unipolar mode are obtained for the Cu/GeOx/W cross-points. In addition, repeatable switching cycles and data retention of 103 s are observed under a low current of 1 nA for future low-power, high-density, nonvolatile, nanoscale memory applications. PMID:24305116

2013-01-01

26

Pressure-independent point in current-voltage characteristics of coplanar electrode microplasma devices operated in neon  

SciTech Connect

We introduce the idea of a pressure-independent point (PIP) in a group of current-voltage curves for the coplanar electrode microplasma device (CEMPD) at neon pressures ranging from 15 to 95 kPa. We studied four samples of CEMPDs with different sizes of the microcavity and observed the PIP phenomenon for each sample. The PIP voltage depends on the area of the microcavity and is independent of the height of the microcavity. The PIP discharge current, I{sub PIP}, is proportional to the volume (Vol) of the microcavity and can be expressed by the formula I{sub PIP}=I{sub PIP0}+DxVol. For our samples, I{sub PIP0} (the discharge current when Vol is zero) is about zero and D (discharge current density) is about 3.95 mA mm{sup -3}. The error in D is 0.411 mA mm{sup -3} (less than 11% of D). When the CEMPD operates at V{sub PIP}, the discharge current is quite stable under different neon pressures.

Meng Lingguo; Lin Zhaojun [School of Physics, Shandong University, Jinan 250100 (China); Xing Jianping [School of Information Science and Engineering, Shandong University, Jinan 250100 (China); Liang Zhihu; Liu Chunliang [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China)

2010-05-10

27

Wire beam electrode: a new tool for studying localised corrosion and other heterogeneous electrochemical processes  

Microsoft Academic Search

Heterogeneous electrochemical processes are very common in industry and are important, but difficult topics in electrochemical and corrosion science studies. Traditional electrochemical techniques which employ a conventional one-piece electrode have major limitations in studying heterogeneous electrochemical processes since the one-piece electrode has major difficulties in measuring electrochemical parameters from local areas of the electrode surface. In order to overcome this

Yong-Jun Tan

1998-01-01

28

Alternative Electrode Materials and Ceramic Filter Minimize Disinfection Byproducts in Point-of-Use Electrochemical Water Treatment  

PubMed Central

Abstract Effects of various electrodes and prefiltration to minimize disinfection byproducts (DBPs) in electrochemical water disinfection was evaluated. The target microorganism, Escherichia coli O157:H7, was effectively inactivated even applying a solar-charged storage battery for the electrolysis process. Extent of microbial inactivation decreased with lower water temperature and higher pH in the free chlorine disinfection system. The RuO2/Ti electrode was most efficient because it produced the lowest concentration of chlorate and the highest generation of free chlorine. Prefiltration using a ceramic filter inhibited formation of halogenated DBPs because it removed precursors of DBPs. For safe point-of-use water treatment, the use of a hybrid prefiltration stage with the electrolysis system is strongly recommended to reduce risks from DBPs. The system is particularly suited to use in developing regions. PMID:24381482

Yoon, Yeojoon; Jung, Youmi; Kwon, Minhwan; Cho, Eunha; Kang, Joon-Wun

2013-01-01

29

An optimization-based study of equivalent circuit models for representing recordings at the neuron-electrode interface.  

PubMed

Extracellular neuroelectronic interfacing is an emerging field with important applications in the fields of neural prosthetics, biological computation, and biosensors. Traditionally, neuron-electrode interfaces have been modeled as linear point or area contact equivalent circuits but it is now being increasingly realized that such models cannot explain the shapes and magnitudes of the observed extracellular signals. Here, results were compared and contrasted from an unprecedented optimization-based study of the point contact models for an extracellular "on-cell" neuron-patch electrode and a planar neuron-microelectrode interface. Concurrent electrophysiological recordings from a single neuron simultaneously interfaced to three distinct electrodes (intracellular, "on-cell" patch, and planar microelectrode) allowed novel insights into the mechanism of signal transduction at the neuron-electrode interface. After a systematic isolation of the nonlinear neuronal contribution to the extracellular signal, a consistent underestimation of the simulated suprathreshold extracellular signals compared to the experimentally recorded signals was observed. This conclusively demonstrated that the dynamics of the interfacial medium contribute nonlinearly to the process of signal transduction at the neuron-electrode interface. Further, an examination of the optimized model parameters for the experimental extracellular recordings from sub- and suprathreshold stimulations of the neuron-electrode junctions revealed that ionic transport at the "on-cell" neuron-patch electrode is dominated by diffusion whereas at the neuron-microelectrode interface the electric double layer (EDL) effects dominate. Based on this study, the limitations of the equivalent circuit models in their failure to account for the nonlinear EDL and ionic electrodiffusion effects occurring during signal transduction at the neuron-electrode interfaces are discussed. PMID:22695342

Thakore, V; Molnar, P; Hickman, J J

2012-08-01

30

Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes.  

PubMed

In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications. PMID:22107487

Park, Hyesung; Brown, Patrick R; Bulovi?, Vladimir; Kong, Jing

2012-01-11

31

A neural cell culture study on thin film electrode materials.  

PubMed

Functional neural stimulation requires good interface between the neural cells and the electrode surfaces. In order to study the effect of electrode materials and surface structure on cell adhesion and biocompatibility, we cultured cortical neurons on thin films of platinum and iridium oxide. We used both flat, as-deposited and laser micro-structured films. The laser micro-structuring consisted of creating regular arrays of micro-bumps or holes with diameters of 4-5 mum and height of about 1.5 mum. The micro-bumps were fabricated onto platinum and iridium film surfaces deposited on borosilicate glass substrates, using mask-projection irradiation with single nano-second pulses from a KrF excimer laser (lambda = 248 nm). Amorphous and crystalline (deposited at 250 degrees C) IrO(2) films were deposited onto the laser micro-structured iridium films by pulsed-DC reactive sputtering to obtain micro-structured IrO(2) films. Cortical neurons isolated from rat embryo brain were cultured onto these film surfaces. Our results indicate that flat and micro-structured film surfaces are biocompatible and non-toxic for neural cell growth. The use of poly-D: -lysine as a mediator for cell adhesion onto the thin film surfaces is also discussed. PMID:17483885

Thanawala, Sachin; Palyvoda, Olena; Georgiev, Daniel G; Khan, Saida P; Al-Homoudi, Ibrahim A; Newaz, Golam; Auner, Gregory

2007-09-01

32

A computer program GEZ for determination of the equivalence point of the acid-base titration and E 0 of the glass electrode  

Microsoft Academic Search

A computer program GEZ has been described for determination of the equivalence point, concentration of the free acid and E0 of the glass electrode at the acid-base titration. The program works in three steps. In the first step, using the Gran method, GEZ calculates the equivalence point and the concentration of the free acid, HGran. In the second step it

Nikola B. Mili?

1996-01-01

33

A computer study of uniform-field electrodes  

Microsoft Academic Search

The departures from uniformity of the electric field, expressed as (E - E0)\\/E0, have been calculated for fields produced by 90° Rogowski, 120° Rogowski and Bruce electrodes. The fields on the axes of the electrodes were found to be uniform to better than 1 part in 107 for the Rogowski profiles and to better than 1% for the Bruce profile.

J A Harrison

1967-01-01

34

Contribution to the study of the electric arc: Erosion of metallic electrodes. Thesis  

NASA Technical Reports Server (NTRS)

A procedure is described for determining the extent of arc electrode erosion (excluding erosion due to transfer of material) from measurements of emitted spectral beam intensity. The relation between emission intensity and plasma temperature is ascertained. Experimental study of several combinations of monometallic electrodes shows that the method is suitable for determining cathode erosion, although the anode metal affects the extent of erosion. Combinations of electrodes which lead to low erosion of silver are reported.

Castro, A.

1986-01-01

35

Vibrational spectroscopic studies of electrode surfaces and technologically important electrolyte solutions. Final report, 1987-1990  

Microsoft Academic Search

Laser Raman spectroscopy has been coupled with electrochemical techniques such as chronocoulometry and cyclic voltammetry to study the species adsorbed on electrode surfaces and to monitor processes which occur with changes in electrode potential, solvent properties, laser exciting line wavelength, solute and other variables. Lithium metal surfaces have been studied with the Raman microprobe; decomposition products, polymerization and conditions for

1991-01-01

36

Study of molybdenum electrodes for hydrogen evolution reaction  

Microsoft Academic Search

The molybdenum electrode, Mo, has been investigated for hydrogen production via water electrolysis in 10vol.% aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF4) using electrochemical impedance spectroscopy (EIS). The EIS measurements show that the Mo system has much higher interfacial capacitance, and correspondently the electrical double layer formed on this electrode is thicker than those formed on nickel or platinum. The positive

Janine Carvalho Padilha; Emilse Maria Agostini Martini; Cauã Brum; Michèle Oberson de Souza; Roberto Fernando de Souza

2009-01-01

37

Characterization of piezoresistive PEDOT:PSS pressure sensors with inter-digitated and cross-point electrode structures.  

PubMed

The piezoresistive characteristics of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pressure sensors with inter-digitated (IDE) and cross-point electrode (CPE) structures have been investigated. A small variation of the resistance of the pressure sensors with IDE without bottom indium-tin-oxide (b-ITO) film and with CPE structures was observed owing to the single carrier-conducting pathway. For the IDE pressure sensors with b-ITO, the piezoresistive characteristics at low and high pressure were similar to those of the pressure sensors with IDE without b-ITO and with CPE structures, respectively, leading to increased piezoresistive pressure sensitivity as the PEDOT:PSS film thickness decreased. A maximum sensitivity of more than 42 k?/Pa was achieved. When the normal pressure was applied, the increased number of conducting points or the reduced distance between the PEDOT oligomers within the PEDOT:PSS film resulted in a decrease of the resistance. The piezoresistive pressure sensors with a single carrier-conducting pathway, i.e., IDE without b-ITO and CPE structures, exhibited a small relaxation time and a superior reversible operation, which can be advantageous for fast piezoresistive response applications. PMID:25569756

Wang, Jer-Chyi; Karmakar, Rajat Subhra; Lu, Yu-Jen; Huang, Chiung-Yin; Wei, Kuo-Chen

2015-01-01

38

Characterization of Piezoresistive PEDOT:PSS Pressure Sensors with Inter-Digitated and Cross-Point Electrode Structures  

PubMed Central

The piezoresistive characteristics of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pressure sensors with inter-digitated (IDE) and cross-point electrode (CPE) structures have been investigated. A small variation of the resistance of the pressure sensors with IDE without bottom indium-tin-oxide (b-ITO) film and with CPE structures was observed owing to the single carrier-conducting pathway. For the IDE pressure sensors with b-ITO, the piezoresistive characteristics at low and high pressure were similar to those of the pressure sensors with IDE without b-ITO and with CPE structures, respectively, leading to increased piezoresistive pressure sensitivity as the PEDOT:PSS film thickness decreased. A maximum sensitivity of more than 42 k?/Pa was achieved. When the normal pressure was applied, the increased number of conducting points or the reduced distance between the PEDOT oligomers within the PEDOT:PSS film resulted in a decrease of the resistance. The piezoresistive pressure sensors with a single carrier-conducting pathway, i.e., IDE without b-ITO and CPE structures, exhibited a small relaxation time and a superior reversible operation, which can be advantageous for fast piezoresistive response applications. PMID:25569756

Wang, Jer-Chyi; Karmakar, Rajat Subhra; Lu, Yu-Jen; Huang, Chiung-Yin; Wei, Kuo-Chen

2015-01-01

39

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid  

NASA Astrophysics Data System (ADS)

The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.

Zhou, Yuan; Hao, Miao; Chen, George; Wilson, Gordon; Jarman, Paul

2014-07-01

40

Stimulation of the Human Lumbar Spinal Cord With Implanted and Surface Electrodes: A Computer Simulation Study  

Microsoft Academic Search

Human lumbar spinal cord networks controlling stepping and standing can be activated through posterior root stimulation using implanted electrodes. A new stimulation method utilizing surface electrodes has been shown to excite lumbar posterior root fibers similarly as with implants, an unexpected finding considering the distance to these target neurons. In the present study we apply computer modeling to compare the

Josef Ladenbauer; Karen Minassian; Ursula S. Hofstoetter; Milan R. Dimitrijevic; Frank Rattay

2010-01-01

41

The fabrication of low-impedance nanoporous gold multiple-electrode arrays for neural electrophysiology studies  

E-print Network

for sensitive detection of neural electrical activity and numerous studies have aimed to reduce impedance method for reliably producing multiple-electrode arrays with low impedance by patterning highly adherent gold electrodes. Low impedance provides a superior signal-to-noise ratio for detection of neural

Seker, Erkin

42

Studies of the vacuum breakdown behavior using refractory-metal thin film coated electrodes  

NASA Astrophysics Data System (ADS)

A reliable operation of ICRF antennas in fusion devices is often limited by its breakdown threshold. Surface conditions of electrodes during high voltage operations have played a key role in affecting breakdowns. In this work, the effects of coating electrodes with refractory-metal thin films to improve on the reliability and power delivered by ICRF antennas have been investigated. Using the Surface Plasma Arcs by Radiofrequency - Control Study (SPARCS) facility at the Center for Plasma-Material Interactions which is designed as a DC system, the current and voltage breakdown patterns and the measured energy in the arc at an electric field of up to 150 MW/m were studied. Experiments with electrodes coated with W, Mo and Ta operated at high temperature of 600 ^oC and above were explored. Surface studies were also conducted on the electrodes to determine the electrode conditions and other surface reactions after the breakdown.

Flauta, Randolph; Kionka, John; Neumann, Martin John; Ruzic, David; Caughman, John

2009-11-01

43

Electrochemical studies on nanometal oxide-activated carbon composite electrodes for aqueous supercapacitors  

NASA Astrophysics Data System (ADS)

In present study, the electrochemical performance of eco-friendly and cost-effective titanium oxide (TiO2)-based and zinc oxide-based nanocomposite electrodes were studied in neutral aqueous Na2SO3 electrolyte, respectively. The electrochemical properties of these composite electrodes were studied using cyclic voltammetry (CV), galvanostatic charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that these two nanocomposite electrodes achieve the highest specific capacitance at fairly low oxide loading onto activated carbon (AC) electrodes, respectively. Considerable enhancement of the electrochemical properties of TiO2/AC and ZnO/AC nanocomposite electrodes is achieved via synergistic effects contributed from the nanostructured metal oxides and the high surface area mesoporous AC. Cations and anions from metal oxides and aqueous electrolyte such as Ti4+, Zn2+, Na+ and SO32- can occupy some pores within the high-surface-area AC electrodes, forming the electric double layer at the electrode-electrolyte interface. Additionally, both TiO2 and ZnO nanoparticles can provide favourable surface adsorption sites for SO32- anions which subsequently facilitate the faradaic processes for pseudocapacitive effect. These two systems provide the low cost material electrodes and the low environmental impact electrolyte which offer the increased charge storage without compromising charge storage kinetics.

Ho, Mui Yen; Khiew, Poi Sim; Isa, Dino; Chiu, Wee Siong

2014-11-01

44

Radio-frequency ablation electrode displacement elastography: A phantom study  

PubMed Central

This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio-frequency (rf) ablation-induced lesions. The method involves use of the radio-frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easyin vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single-inclusion tissue-mimicking phantom containing a radio-frequency ablation electrode rigidly attached to the inclusion center. Full-frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One-dimensional cross-correlation analysis between pre-and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast-to-noise ratio, and signal-to-noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single-inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue-mimicking phantom and on in vitro rf-ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation. PMID:18649476

Bharat, Shyam; Varghese, Tomy; Madsen, Ernest L.; Zagzebski, James A.

2008-01-01

45

Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study Ramya Balachandran1  

E-print Network

Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study-invasive technique, called percutaneous cochlear implantation (PCI), has been proposed that involves drilling: Percutaneous cochlear implantation, microstereotactic frame, minimally-invasive surgery. 1. INTRODUCTION

Webster III, Robert James

46

Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter  

E-print Network

This research focuses on preparation, kinetics, and performance studies of mixed ionic and electronic conducting electrodes (MIEE) applied in an alkali metal thermal to electric converter (AMTEC). Two types of MIEE, metal/sodium titanate and metal...

Guo, Yuyan

2009-05-15

47

Study of nickel hydroxide electrodes. 2: Oxidation products of nickel (2) hydroxides  

NASA Technical Reports Server (NTRS)

Pure phases of some oxidized Ni oxides were prepared galvanimetrically with the Ni(2) hydroxide electrode of an alkaline battery. The crystallographic data of these phases, their chemical behavior, and conditions of transition were studied.

Bode, H.; Demelt, K.; White, J.

1986-01-01

48

Immobilization of DNA at Glassy Ccarbon Electrodes: A Critical Study of Adsorbed Layer  

PubMed Central

In this work we present a critical study of the nucleic acid layer immobilized at glassy carbon electrodes. Different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface. The adsorption and electrooxidation of DNA demonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. The DNA layer immobilized at a freshly polished glassy carbon electrode was very stable even after applying highly negative potentials. The electron transfer of potassium ferricyanide, catechol and dopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlled potential conditions) and thick (obtained by casting the glassy carbon surface with highly concentrated DNA solutions) DNA layers was slower than that at the bare glassy carbon electrode, although this effect was dependent on the thickness of the layer and was not charge selective. Raman experiments showed an important decrease of the vibrational modes assigned to the nucleobases residues, suggesting a strong interaction of these residues with the electrode surface. The hybridization of oligo(dG)21 and oligo(dC)21 was evaluated from the guanine oxidation signal and the reduction of the redox indicator Co(phen)33+. In both cases the chronopotentiometric response indicated that the compromise of the bases in the interaction of DNA with the electrode surface is too strong, preventing further hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in a direct and very sensitive way, but not to be used for the preparation of biorecognition layers by direct adsorption of the probe sequence on the electrode surface for detecting the hybridization event.

Pedano, M. L.; Rivas, G. A.

2005-01-01

49

A systematic study of BNL's 3D-Trench Electrode detectors  

NASA Astrophysics Data System (ADS)

New types of silicon pixel detectors have been proposed because of the need for more radiation hard semiconductor devices for the high luminosity tracking detector upgrades at the Large Hadron Collider. A novel type of 3D Si pixel detectors is proposed, with each cell of the 3D-Trench Electrode pixel detector featuring a concentric trench electrode surrounding the central collecting column electrode. The pixel sensor is an array of those individual cells. Systematic 3D simulations using Silvacos TCAD programs have been carried out to study the characteristics of this novel 3D pixel design and to compare to the traditional 3D column electrode pixel design. The 3D simulations show a much lower depletion voltage and a more uniform electric field in the new 3D-Trench Electrode pixel detectors as compared to the traditional 3D column Electrode detectors. The first prototype 3D-Trench Electrode pixel detectors have been manufactured at the Centro Nacional De Microelectronica. Preliminary electrical measurements are discussed and charge collection efficiency measurements are presented.

Montalbano, A.; Bassignana, D.; Li, Z.; Liu, S.; Lynn, D.; Pellegrini, G.; Tsybychev, D.

2014-11-01

50

Point-process analysis of neural spiking activity of muscle spindles recorded from thin-film longitudinal intrafascicular electrodes  

E-print Network

Recordings from thin-film Longitudinal Intra-Fascicular Electrodes (tfLIFE) together with a wavelet-based de-noising and a correlation-based spike sorting algorithm, give access to firing patterns of muscle spindle afferents. ...

Citi, Luca

51

Advanced PowerPoint Self Study  

NSDL National Science Digital Library

In order to recieve credit for the Advanced PowerPoint Night, you will need to complete *ALL* of the following activities. 1. Please search for of Advanced PowerPoint Features on Google. These examples demonstrate how PowerPoint can function in other ways besides a linear presentation. (Notice how button and hyperlinks are used to navigate through the slideshows.) 2. Read pages 1-8 in your Advanced PowerPoint Module . ...

Rachel Murphy

2005-11-28

52

Voltammetric studies of porous molybdenum electrodes for the alkali metal thermoelectric converter  

NASA Technical Reports Server (NTRS)

Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from about 600 to 1000 K revealed a series of redox processes within the AMTEC operational voltage range which can be used to establish the electronic and ionic conductivities of these electrodes. Improved estimates of the free energies of formation of Na2Mo3O6, NaMoO2, and Na3MoO4 are obtained. Evidence is provided for the slow corrosive attack by Na2MoO4 on molybdenum. The ionic conductivity of Na2MoO4 is found to be sufficiently large at temperatures of greater than 700 K to explain the observed electrochemical phenomena in addition to the enhanced sodium transport in AMTEC electrodes below the freezing point of Na2MoO4.

Williams, R. M.; Bankston, C. P.; Khanna, S. K.; Cole, T.

1986-01-01

53

Morphology and capacity of a cadmium electrode - Studies on a simulated pore.  

NASA Technical Reports Server (NTRS)

Conditions in a single pore of a battery plate were simulated by using a cadmium chip of millimeter dimensions covered with an electrolyte film of micron thickness. In situ microscopy was applied to study changes in the electrode morphology during charge and discharge. Passivation and increases in particle sizes due to precipitation and electrodeposition of dissolved cadmium species were found to cause profound loss in electrode capacity on repeated charge and discharge.

Will, F. G.; Hess, H. J.

1973-01-01

54

Development and electrochemical studies of gas diffusion electrodes for polymer electrolyte fuel cells  

Microsoft Academic Search

Electrochemical studies on low catalyst loading gas diffusion electrodes for polymer electrolyte fuel cells are reported. The best performance is obtained with an electrode formed from 20 wt% Pt\\/C, 0.4 mg Pt cm-2 and 1.1 mg Nafion® cm-2 in the catalyst layer and 15% PTFE in a diffusion layer of 50 µm thickness, for both the cathode and the anode.

V. A. Paganin; E. A. Ticianelli; E. R. Gonzalez

1996-01-01

55

Simulation studies of optimized electrode designs for a cylindrical IEC  

SciTech Connect

The cylindrical version (c-device) of the single grid inertial electrostatic confinement (IEC) device is of strong interest for various neutron activation analysis (NAA) applications. The present version produces {approximately} 10{sup 6} D-D fusion neutron/s steady-state, and a higher yield pulsed version is under development. In both designs the grid configuration must be optimized for maximum neutron yield. An ion tracking code, SIMION has been adapted for this purpose. While it includes several key approximations (e.g., neglects self-fields and collisions), it still predicts trends well for the present regime of operation, and provides improved physical insight. Recent simulations have examined variations of the reference electrode design, covering a wide range of diameters and lengths. Thus, for example, with a 10-cm long cathode and 3-cm long anodes the optimum diameter is predicted to be 60--80 mm. As the diameter is reduced further, the ion beam focus is lost. Further, the plasma sheath at the inside cathode wall begins to distort the beam path. These simulations will be described along with results for several novel designs, including a modular cathode and multiple segmented electrode concept will be presented.

Miley, G.H.; DeMora, J.; Stubbers, R.A.; Zich, R. [Univ. of Illinois, Urbana, IL (United States). Fusion Studies Lab.; Sved, J. [DASA, Bremmen (Germany); Anderl, R.; Hartwell, J. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1997-12-31

56

Modeling of Solid Oxide Fuel Cell functionally graded electrodes and a feasibility study of fabrication techniques for functionally graded electrodes  

NASA Astrophysics Data System (ADS)

With the large energy demands, finite natural resources, and concern about carbon emissions, a more efficient method to produce energy for the electrical power grid is needed. Solid Oxide Fuel Cells (SOFC) have demonstrated nearly 70% efficiency in full scale trials. Much time has been spent reducing the cost of SOFCs, but little investigative focus has been put on optimal power output based on electrode microstructure. Moreover, it appears that no modeling has investigated optimization behavior of functionally graded SOFC electrodes. Also, nonlinear functional grading of SOFC electrodes has not been explored. In this work, a complete SOFC electrode model from literature was adapted for use in analyzing and comparing the losses between homogeneous, linearly, and nonlinearly graded electrodes. The model is based on a coupled differential equation system that was iteratively solved for three dependent variables: voltage, electronic current, and reactant gas pressure. It was found that particle size and porosity functional grading reduce diffusion losses near the electrode's free surface, while decreasing activation loss levels near the electrolyte interface. A range of particle sizes was identified around the optimal homogenous electrode particles size, where particle size grading is beneficial. Outside of this range, homogeneous structured electrodes show better performance. Nonlinear porosity grading shows an improvement over linear grading in voltage losses at small particle diameters (300 nm); little to no benefit is seen for larger particle diameters (3 mum). This work discusses (1) relative loss contribution in a SOFC electrode, (2) particle size and porosity grading ranges and their associated grading profiles for optimal performance, and (3) design criteria for the efficacy of particle size graded verses homogeneous electrodes. This work can be used to further explore the contribution of individual losses in a SOFC electrode. This information can then be used to further understand how to optimize SOFCs.

Flesner, Reuben Richard

2009-12-01

57

Study of electrode pattern design for a CZT-based PET detector  

NASA Astrophysics Data System (ADS)

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (˜26 to ˜127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (˜34 to ˜83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips’ weighting functions, which indicated a stronger ‘small pixel’ effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.

Gu, Y.; Levin, C. S.

2014-06-01

58

Coulometric study of ethanol adsorption at a polycrystalline platinum electrode  

NASA Astrophysics Data System (ADS)

For the first time, use of a novel pre-conditioning sequence and measurements of hydrogen blockage during fast cathodic scans has enabled the determination of rates of accumulation of ethanolic species on the surface of a platinum electrode under well-controlled conditions of surface cleanliness/activity and mass transport. For dilute solutions of ethanol in 1 N perchloric acid (HClO4), oxidative adsorption rates maximize at 0.3 V, drop off at more cathodic potentials due to competition with adsorbed hydrogen and drop off at more anodic potentials due to oxidative processes that produce products released to the electrolyte. The time and concentration dependence of adsorption follows relationships that are common for adsorption on a heterogeneous surface. Some evidence are presented supporting a mechanism for production of soluble products that does not involve the adsorbed species that are detected through the measurement of blockage of hydrogen adsorption sites.

Gilman, Sol

2012-01-01

59

Numerical Study of the Buoyancy-Driven Flow in a Four-Electrode Rectangular Electrochemical Cell  

NASA Astrophysics Data System (ADS)

Two-dimensional numerical simulation is done on the buoyancy-driven flow in a four-electrode rectangular electrochemical cell. Two kinds of electrode layouts, the anode-cathode-cathode-anode (ACCA) and the cathode-anode-anode-cathode (CAAC) layouts, are studied. In the ACCA layout, the two anodes are placed close to the channel outlets while the two cathodes are located between the two anodes. The CAAC layout can be converted from the ACCA layout by applying higher electric potential on the two middle electrodes. Density gradient was generated by the electrodic reaction I3^-+2e^- =3I^-. When the electrochemical cell is accelerated axially, buoyancy-driven flow occurs. In our model, electro-neutrality is assumed except at the electrodes. The Navier-Stokes equations with the Boussinesq approximation and the Nernst-Planck equations are employed to model the momentum and mass transports, respectively. It is found that under a given axial acceleration, the electrolyte density between the two middle electrodes determines the bulk flow through the electrochemical cell. The cathodic current difference is found to be able to measure the applied acceleration. Other important electro-hydrodynamic characteristics are also discussed.

Sun, Zhanyu; Agafonov, Vadim; Rice, Catherine; Bindler, Jacob

2009-11-01

60

Dithiooxamide Modified Glassy Carbon Electrode for the Studies of Non-Aqueous Media: Electrochemical Behaviors of Quercetin on the Electrode Surface  

PubMed Central

Electrochemical oxidation of quercetin, as an important biological molecule, has been studied in non-aqueous media using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. To investigate the electrochemical properties of quercetin, an important flavonoid derivative, on a different surface, a new glassy carbon electrode has been developed using dithiooxamide as modifier in non-aqueous media. The surface modification of glassy carbon electrode has been performed within the 0.0 mV and +800 mV potential range with 20 cycles using 1 mM dithioxamide solution in acetonitrile. However, the modification of quercetin to both bare glassy carbon and dithiooxamide modified glassy carbon electrode surface was carried out in a wide +300 mV and +2,800 mV potential range with 10 cycles. Following the modification process, cyclic voltammetry has been used for the surface characterization in aqueous and non-aqueous media whereas electrochemical impedance spectroscopy has been used in aqueous media. Scanning electron microscopy has also been used to support the surface analysis. The obtained data from the characterization and modification studies of dithioxamide modified and quercetin grafted glassy carbon electrode showed that the developed electrode can be used for the quantitative determination of quercetin and antioxidant capacity determination as a chemical sensor electrode. PMID:22666010

Mülaz?mo?lu, Ay?en Demir; Y?lmaz, Ecir; Mülaz?mo?lu, ?brahim Ender

2012-01-01

61

Study of RPC bakelite electrodes and detector performance for INO-ICAL  

E-print Network

The Resistive Plate Chambers (RPCs) are going to be used as the active detectors in the India-based Neutrino Observatory (INO)-Iron Calorimeter (ICAL) experiment for the detection and study of atmospheric neutrinos. In this paper, an extensive study of structural and electrical properties for different kind of bakelite RPC electrodes is presented. RPCs fabricated from these electrodes are tested for their detector efficiency and noise rate. The study concludes with the variation of efficiency, leakage current and counting rate over the period of operation with different gas compositions and operational conditions like temperature and relative humidity.

Ashok Kumar; Ankit Gaur; Md. Hasbuddin; Praveen Kumar; Purnendu Kumar; Daljeet Kaur; Swati Mishra; Md. Naimuddin

2014-09-19

62

Study of RPC bakelite electrodes and detector performance for INO-ICAL  

NASA Astrophysics Data System (ADS)

The Resistive Plate Chambers (RPCs) are going to be used as the active detectors in the India-based Neutrino Observatory (INO)-Iron Calorimeter (ICAL) experiment for the detection and study of atmospheric neutrinos. In this paper, an extensive study of structural and electrical properties for different kind of bakelite RPC electrodes is presented. RPCs fabricated from these electrodes are tested for their detector efficiency and noise rate. The study concludes with the variation of efficiency, leakage current and counting rate over the period of operation with different gas compositions and operational conditions like temperature and relative humidity.

Kumar, A.; Gaur, A.; Hasbuddin, Md.; Kumar, P.; Kumar, P.; Kaur, D.; Mishra, S.; Naimuddin, Md.

2014-10-01

63

Influence of the pre-ionization background and simulation of the optical emission of a streamer discharge in preheated air at atmospheric pressure between two point electrodes  

NASA Astrophysics Data System (ADS)

This paper presents simulations of positive and negative streamers propagating between two point electrodes in preheated air at atmospheric pressure. As many discharges have occurred before the simulated one, seed charges are taken into account in the interelectrode gap. First, for a pre-ionization background of 109 cm-3, we have studied the influence of the data set used for transport parameters and reaction rates for air on the simulation results. We have compared results obtained in 1997 using input parameters from Morrow and Lowke and from Kulikovsky. Deviations as large as 20% of streamer characteristics (i.e. electric field in the streamer head and body, streamer velocity, streamer radius, streamer electron density) have been observed for this point-to-point configuration. Second, we have studied the influence of the pulsed voltage frequency on the discharge structure. For the studied discharge regime, a change in the applied voltage frequency corresponds to a change in the pre-ionization background. In this work, we have considered a wide range of pre-ionization values from 104 and up to 109 cm-3. We have noted that the value of the pre-ionization background has a small influence on the electron density, electric field and location of the negative streamer head. Conversely, it has a significant influence on the positive streamer characteristics. Finally, we have compared instantaneous and time-averaged optical emissions of the three band systems of N2 and N_2^+ (1PN2, 2PN2 and 1NN_2^+ ) during the discharge propagation. We have shown that the emission of the 2PN2 is the strongest of the three bands, in agreement with experimental observations. It is interesting to note that even with a short time averaging of a few nanoseconds, which corresponds to currently used instruments, the structure of the time-averaged emission of the 2PN2 is different from the instantaneous one and shows negative and positive streamers with smaller radial expansions and more diffuse streamer heads.

Bourdon, A.; Bonaventura, Z.; Celestin, S.

2010-06-01

64

Astrometric Telescope Facility isolation and pointing study  

NASA Technical Reports Server (NTRS)

The Astrometric Telescope Facility (ATF), an optical telescope designed to detect extrasolar planetary systems, is scheduled to be a major user of the Space Station's Payload Pointing System (PPS). However, because the ATF has such a stringent pointing stability specification and requires + or - 180 deg roll about its line of sight, mechanisms to enhance the basic PPS capability are required. The ATF pointing performance achievable by the addition of a magnetic isolation and pointing system (MIPS) between the PPS upper gimbal and the ATF, and separately, by the addition of a passive isolation system between the Space Station and the PPS base was investigated. The candidate MIPS can meet the ATF requirements in the presence of a 0.01 g disturbance. It fits within the available annular region between the PPS and the ATF while meeting power and weight limitations and providing the required roll motion, payload data and power services. By contrast, the passive base isolator system must have an unrealistically low isolation bandwidth on all axes to meet ATF pointing requirements and does not provide roll about the line of sight.

Hibble, William; Allen, Terry; Jackson, Louis; Medbery, James; Self, Richard

1988-01-01

65

The study the erosion of the electrodes under the influence moving electric arc  

NASA Astrophysics Data System (ADS)

The paper presents the results of experimental study of the processes of interaction of a moving arc with electrodes pulsed plasma generator in the range of parameters I = 60÷500 A, U = 30÷70 V, G = 0÷155 l/min, dE = 4÷14 mm and LE = 2÷20 mm. In this article the results of the study traces left by moving arc on the electrode surfaces are described, and the impact velocity of the arc on the form and sizes these traces, ranging VD = 7÷130 m / s. We show the research results of the heating and erosion of the electrodes under the influence of high-current arc moving.

Gabdrakhmanov, A. T.; Israphilov, I. H.; Galiakbarov, A. T.

2014-11-01

66

Structural and electrochemical study of positive electrode materials for rechargeable lithium ion batteries  

Microsoft Academic Search

The research presented in this dissertation focuses on a combined study of the electrochemistry and the structure of positive electrode materials for Li ion batteries. Li ion batteries are one of the most advanced energy storage systems and have been the subject of numerous scientific studies in recent decades. They have been widely used for various mobile devices such as

Meng Jiang

2008-01-01

67

Surface enhanced Raman spectroscopy study of the potential dependence of thymine on silver electrodes  

Microsoft Academic Search

The potential-induced changes in thymine coordination on polycrystalline silver electrodes are studied by surface enhanced Raman spectroscopy (SERS) for potentials positive to the potential of zero charge up to the end of the double layer range. Two distinct sets of spectra could be obtained in the range of potentials studied. Both states correspond to chemisorbed phases of thymine on silver,

Frederico Cunha; J. Raul Garcia; Francisco C. Nart; Paola Corio; Márcia Temperini

2003-01-01

68

Empirical study on human acupuncture point network  

NASA Astrophysics Data System (ADS)

Chinese medical theory is ancient and profound, however is confined by qualitative and faint understanding. The effect of Chinese acupuncture in clinical practice is unique and effective, and the human acupuncture points play a mysterious and special role, however there is no modern scientific understanding on human acupuncture points until today. For this reason, we attend to use complex network theory, one of the frontiers in the statistical physics, for describing the human acupuncture points and their connections. In the network nodes are defined as the acupuncture points, two nodes are connected by an edge when they are used for a medical treatment of a common disease. A disease is defined as an act. Some statistical properties have been obtained. The results certify that the degree distribution, act degree distribution, and the dependence of the clustering coefficient on both of them obey SPL distribution function, which show a function interpolating between a power law and an exponential decay. The results may be helpful for understanding Chinese medical theory.

Li, Jian; Shen, Dan; Chang, Hui; He, Da-Ren

2007-03-01

69

ICESat Spacecraft Pointing Support Study Grant  

NASA Technical Reports Server (NTRS)

The Geodetic Laser Altimeter System (GLAS) mission is designed to measure changes in the elevations of the polar ice sheets. The ICESat satellite will carry the GLAS altimeter, and will have a nominal orbit altitude of 600 km and orbit inclination of 94deg. The groundtrack repeat period is 182 days and will be maintained to less than 1 km at the equator via routine orbit adjustments. Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 meters of a predetermined reference groundtrack. As the actual ICESat groundtrack drifts away from the reference groundtrack, the attitude must be controlled such that the altimeter boresight is pointed, crosstrack, at the reference groundtrack. This orientation may be described by a rotation, theta, about the instantaneous geodetic local horizontal direction vector, which lies in the orbit plane and is oriented in the direction of motion of the satellite. The attitude is further complicated by requirements related to thermal and power considerations for various instruments, spacecraft components, and solar array orientation. In order to keep battery temperatures within the specified operating range, and maintain near normal pointing of the solar array with respect to the sunline direction vector as the orbit precesses relative to the sun, the satellite will be oriented in one of four fixed yaw modes. Each of these yaw modes depends upon the angle between the orbit plane and the sunline direction vector; this angle is designated Beta'. Table 1 shows the satellite yaw angle, Psi, for a given Beta' range. The angle Psi represents a rotation about the satellite z-axis, which points in the geodetic nadir direction; for Psi = 0deg the satellite x-axis points in the direction of motion.

2000-01-01

70

Metallic electrodes and leads in simultaneous EEG-MRI: specific absorption rate (SAR) simulation studies.  

PubMed

The purpose of this study was to investigate the changes in specific absorption rate (SAR) in human-head tissues while using nonmagnetic metallic electroencephalography (EEG) electrodes and leads during magnetic resonance imaging (MRI). A realistic, high resolution (1 mm(3)) head model from individual MRI data was adopted to describe accurately thin tissues, such as bone marrow and skin. The RF power dissipated in the human head was evaluated using the FDTD algorithm. Both surface and bird cage coils were used. The following numbers of EEG electrodes/leads were considered: 16, 31, 62, and 124. Simulations were performed at 128 and 300 MHz. The difference in SAR between the electrodes/leads and no-electrodes conditions was greater with the bird cage coil than with the surface coil. The peak 1 g averaged SAR values were highest at 124 electrodes, increasing to as much as two orders of magnitude (x172.3) at 300 MHz compared to the original value. At 300 MHz, there was a fourfold (x3.6) increase of SAR averaged over the bone marrow, and a sevenfold (x7.4) increase in the skin. At 128 MHz, there was a fivefold (x5.6) increase of whole head SAR. Head models were obtained from two different subjects, with an inter-subject whole head SAR variability of 3%. . PMID:15114638

Angelone, Leonardo M; Potthast, Andreas; Segonne, Florent; Iwaki, Sunao; Belliveau, John W; Bonmassar, Giorgio

2004-05-01

71

The chemistry of Li/SOCl2 cells - An ESR study of carbon electrodes  

NASA Technical Reports Server (NTRS)

Carbon electrodes from Li/SOCl2 cells were studied by electron spin resonance after various stages of discharge. Different behavior was observed in the temperature-dependent part of the ESR linewidth, defined as 'intrinsic linewidth', Delta H(int), when two different electrolytes were used. With one electrolyte, 1.5M LiAlCl4/SoCl2, the Delta H(int) value stayed constant or slightly decreased whereas with another electrolyte, 1.0M LiAlCl4/14 percent BrClin SOCl2, the value increased as discharge progressed. The carbon electrodes are modified differently during discharge with these two electrolytes, and it is speculated that this may be due to changes in the carbon matrix functional groups. This difference in the carbon electrodes may explain the claimed differences in safety performance of the cells.

Kim, S. S.; Carter, B. J.; Tsay, F. D.

1985-01-01

72

Cyclic voltammetric studies of porous iron electrodes in alkaline solutions used for alkaline batteries  

NASA Astrophysics Data System (ADS)

Cyclic voltammetric studies have been conducted in order to develop a suitable method for characterizing the performance of sintered porous iron electrodes in 5.35 M KOH with 0.65 M LiOH solution. The separation of peak potential ( ?Ep) and the ratio of cathodic to anodic charges ( Qc/ Qa) of the Fe/Fe(II) and Fe(II)/Fe(III) couples at zero sweep rates are used to evaluate the reversibility of the porous iron and iron-sulfur electrodes. The influence of additives to the solution (i.e., 0.05 M thiourea, 0.025 M ethylenediaminetetraacetic acid (EDTA), 0.01 M hexamine and 0.01 M Na 2S) on the electrode reversibility is also examined.

Periasamy, P.; Babu, B. Ramesh; Iyer, S. Venkatakrishna

73

Studies on 1:12 phosphomolybdic heteropoly anion film modified carbon paste electrode.  

PubMed

A 1:12 phosphomolybdic anion film modified carbon paste electrode (PMo(12) electrode) is prepared by electrochemical deposition and its application is studied by cyclic voltammetry. The film modified electrode can adsorb PMo(12) selectively and thus be used for the determination of trace phosphorus. In a solution containing 2 mug ml(-1) phosphorus, the relative standard deviation is 4.69% (n=4), the peak height also varies linearly with the concentration of phosphorus over the range 0.4-25 mug ml(-1), and the detection limit is 0.04 mug ml(-1). The method is convenient and rapid. It has been used for the determination of inorganic phosphorus in phytic acid directly with satisfactory results. PMID:18967625

Guanghan, L; Xiaogang, W; Yanhua, L; Shenlai, Y

1999-07-01

74

In situ STM studies of electrochemically polished Cd(0001) electrode in aqueous electrolyte solutions  

NASA Astrophysics Data System (ADS)

The in situ STM studies of electrochemically polished Cd(0001) electrode in the H3PO4 aqueous solution have been performed under negative electrode potentials from - 1.4 to - 0.9 V (versus Ag|AgCl in sat. KCl aqueous solution) in the 0.1 M Na2SO4 + 1 × 10- 5 M H2SO4 aqueous solution. The atomic resolution parameters of Cd(0001) surface have been calculated. The in situ STM data show that there are no surface reconstruction processes and the surface structure of electrochemically polished Cd(0001) is stable within the potential region investigated.

Pikma, P.; Grozovski, V.; Kasuk, H.; Lust, E.

2014-10-01

75

QSPR Study of Passivation by Phenolic Compounds at Platinum and Boron-Doped Diamond Electrodes  

E-print Network

QSPR Study of Passivation by Phenolic Compounds at Platinum and Boron-Doped Diamond Electrodes Campinas, 13083-852 Campinas, SP, Brazil Blocking polycrystalline platinum Pt and boron-doped diamond BDD,8,9 In electrochemical processes, the electro-oxidation of phenolic compounds begins with the formation of the phenoxyl

Ferreira, Márcia M. C.

76

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes  

E-print Network

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes L concen- tration, and reducing the use of materials in, for instance, accelerator insulator columns, which or electric field. They also had in common that no matter which combination of techniques was used, new

Gilson, Erik

77

Electrode-polarization studies in hot-corrosion systems. Progress report, 1 June 1980-31 May 1981  

SciTech Connect

The following tasks are reported on: electrode polarization studies in molten sodium carbonate, liquid line corrosion, and gas/metal reactions in mixed oxidants. Two previously unpublished papers are included as appendices: Reactions at the CO, CO/sub 2//Ni electrode in Molten Sodium Carbonate; and Reactions at the Corroding Nickel Electrode in Molten Sodium Carbonate under CO, CO/sub 2/ Atmospheres. (DLC)

Devereux, O.F.

1981-02-01

78

Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon nanotube dispersed polythiophene-fullerene  

E-print Network

Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon://jap.aip.org/about/rights_and_permissions #12;Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon for organic pseudo-bilayer solar cells J. Appl. Phys. 112, 084511 (2012) Addition of regiorandom poly(3

Hone, James

79

Operando studies of all-vanadium flow batteries: Easy-to-make reference electrode based on silver-silver sulfate  

NASA Astrophysics Data System (ADS)

In-depth evaluation of the electrochemical performance of all-vanadium redox flow batteries (VRFBs) under operando conditions requires the insertion of a reliable reference electrode in the battery cell. In this work, an easy-to-make reference electrode based on silver-silver sulfate is proposed and described for VRFBs. The relevance and feasibility of the information obtained by inserting the reference electrode is illustrated with the study of ammoxidized graphite felts. In this case, we show that the kinetic of the electrochemical reaction VO2+/VO2+ is slower than that of V2+/V3+ at the electrode. While the slow kinetics at the positive electrode limits the voltage efficiency, the operating potential of the negative electrode, which is outside the stability widow of water, reduces the coulombic efficiency due to the hydrogen evolution.

Ventosa, Edgar; Skoumal, Marcel; Vázquez, Francisco Javier; Flox, Cristina; Morante, Joan Ramon

2014-12-01

80

An improved cochlear implant electrode array for use in experimental studies.  

PubMed

Experimental studies play an important role in establishing the safety and efficacy of cochlear implants and they continue to provide insight into a new generation of electrode arrays and stimulation strategies. One drawback has been the limited depth of insertion of an electrode array in experimental animals. We compared the insertion depth and trauma associated with the insertion of Cochlear Ltd's Hybrid-L (HL) array with a standard 8 ring array in cat cochleae. Both arrays were inserted into cadaver cochleae and an X-ray recorded their anatomical location. The implanted cochlea was serially sectioned and photographed at 300 ?m intervals for evidence of electrode insertion trauma. Subsequently two cats were chronically implanted with HL arrays and electrically-evoked potentials recorded over a three month period. Mean insertion depth for the HL arrays was 334.8° (SD = 21°; n = 4) versus 175.5° (SD = 6°; n = 2) for the standard array. This relates to ?10.5 mm and 6 mm respectively. A similar insertion depth was measured in a chronically implanted animal with an HL array. Histology from each cadaver cochleae showed that the electrode array was always located in the scala tympani; there was no evidence of electrode insertion trauma to the basilar membrane, the osseous spiral lamina or the spiral ligament. Finally, evoked potential data from the chronically implanted animals exhibited significantly lower thresholds compared with animals implanted with a standard 8 ring array, with electrical thresholds remaining stable over a three-month observation period. Cochlear Ltd's HL electrode array can be safely inserted ?50% of the length of the cat scala tympani, placing the tip of the array close to the 4 kHz place. This insertion depth is considerably greater than is routinely achieved using a standard 8-ring electrode array (?12 kHz place). The HL array evokes low thresholds that remain stable over three months of implantation. This electrode array has potential application in a broad area of cochlear implant related research. PMID:21540098

Shepherd, Robert; Verhoeven, Kristien; Xu, Jin; Risi, Frank; Fallon, James; Wise, Andrew

2011-07-01

81

A study of Na(x)Pt3O4 as an O2 electrode bifunctional electrocatalyst  

NASA Technical Reports Server (NTRS)

The present study suggests that polytetrafluoroethylene (PTFE) bonded Na(X)Pt3O4 gas porous diffusion electrodes may be a viable candidate for bifunctional O2 reduction and evolution activity. The electrodes exhibited Tafel slopes of about 0.06 V/decade for both O2 reduction an evolution. For O2 reduction, the 0.06 slope doubled to 0.12 V/decade at larger current densities. Preliminary stability testing at 24 C suggest that the Na(x)Pt3O4 electrodes were relatively stable at reducing and oxidizing potentials typically encountered at the O2 electrodes in a regenerative fuel cell.

Fielder, William L.; Singer, Joseph

1991-01-01

82

Electrochemical reduction of an anion for ionic-liquid molecules on a lithium electrode studied by first-principles calculations  

NASA Astrophysics Data System (ADS)

We report ab initio molecular dynamics studies with electric field that reveal chemical stability of room temperature ionic liquid for charge transfer from lithium and nickel electrodes. Bis(trifluoromethanesulfonyl)imide (TFSI) is oxidized on the nickel electrode under a high positive bias condition as expected. However, TFSI is reduced on the lithium electrode under both positive and negative bias conditions, because the lithium electrode acts as a strong reductant. The decomposition of TFSI anion might induce the formation of LiF as a solid electrolyte interphase, which could restrain the TFSI reduction. The stability of an cation under reductant conditions is presented.

Ando, Yasunobu; Kawamura, Yoshiumi; Ikeshoji, Tamio; Otani, Minoru

2014-09-01

83

Point-to-Point Car Racing: an Initial Study of Evolution Versus Temporal Difference Learning  

E-print Network

Point-to-Point Car Racing: an Initial Study of Evolution Versus Temporal Difference Learning Simon, jtogel}@essex.ac.uk Abstract-- This paper considers variations on an extremely simple form of car racing-evaluation neural networks, and these were greatly superior to human drivers. Keywords: Car racing, reinforcement

Togelius, Julian

84

Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study  

NASA Astrophysics Data System (ADS)

Cochlear implantation is a surgical procedure for treating patients with hearing loss in which an electrode array is inserted into the cochlea. The traditional surgical approach requires drilling away a large portion of the bone behind the ear to provide anatomical reference and access to the cochlea. A minimally-invasive technique, called percutaneous cochlear implantation (PCI), has been proposed that involves drilling a linear path from the lateral skull to the cochlea avoiding vital structures and inserting the implant using that drilled path. The steps required to achieve PCI safely include: placing three bone-implanted markers surrounding the ear, obtaining a CT scan, planning a surgical path to the cochlea avoiding vital anatomy, designing and constructing a microstereotactic frame that mounts on the markers and constrains the drill to the planned path, affixing the frame on the markers, using it to drill to the cochlea, and inserting the electrode through the drilled path. We present in this paper a cadaveric study demonstrating the PCI technique on three temporal bone cadaveric specimens for inserting electrode array into the cochlea. A custom fixture, called a Microtable, which is a type of microstereotactic frame that can be constructed in less than five minutes, was fabricated for each specimen and used to reach the cochlea. The insertion was successfully performed on all three specimens. Postinsertion CT scans confirm the correct placement of the electrodes inside the cochlea without any damage to the facial nerve.

Balachandran, Ramya; Mitchell, Jason E.; Noble, Jack; Schurzig, Daniel; Blachon, Grégoire; McRackan, Theodore R.; Webster, Robert J.; Dawant, Benoit M.; Fitzpatrick, J. Michael; Labadie, Robert F.

2011-03-01

85

In Situ X-Ray Absorption Spectroscopy Study of the LiNiO2 Electrode  

Microsoft Academic Search

LiNiO2 is one of the most promising active material for the development of novel 4V rechargeable lithium batteries. Recent x-ray diffraction studies showed that the electrochemical reactivity of this electrode is sensitive to the structure of the starting material as well as the charged products. To further examine this material, we have conducted an x-ray absorption spectroscopy (XAS) study to

A. N. Mansour; J. McBreen; C. A. Melendres

1997-01-01

86

Adult cortical plasticity studied with chronically implanted electrode arrays.  

PubMed

The functional architecture of adult cerebral cortex retains a capacity for experience-dependent change. This is seen after focal binocular lesions as rapid changes in receptive field (RF) of the lesion projection zone (LPZ) in the primary visual cortex (V1). To study the dynamics of the circuitry underlying these changes longitudinally, we implanted microelectrode arrays in macaque (Macaca mulatta) V1, eliminating the possibility of sampling bias, which was a concern in previous studies. With this method, we observed a rapid initial recovery in the LPZ and, during the following weeks, 63-89% of the sites in the LPZ showed recovery of visual responses with significant position tuning. The RFs shifted ?3° away from the scotoma. In the absence of a lesion, visual stimulation surrounding an artificial scotoma did not elicit visual responses, suggesting that the postlesion RF shifts resulted from cortical reorganization. Interestingly, although both spikes and LFPs gave consistent prelesion position tuning, only spikes reflected the postlesion remapping. PMID:25673865

Abe, Hiroshi; McManus, Justin N J; Ramalingam, Nirmala; Li, Wu; Marik, Sally A; Borgloh, Stephan Meyer Zum Alten; Gilbert, Charles D

2015-02-11

87

Part I: A comparative study of bismuth-modified screen-printed electrodes for lead detection.  

PubMed

Lead determination was carried out in the frame of the European Union project Biocop (www.biocop.org) using a bismuth-modified screen-printed electrode (Bi-SPE) and the stripping analysis technique. In order to choose a sensitive Bi-SPE for lead detection, an analytical comparative study of electrodes modified by Bi using "in situ", "ex situ" and "bulk" procedures was carried out. On the basis of the results obtained, we confirmed that the "in situ" procedure resulted in better analytical performances with respect to not only "ex situ" but also to "Bi(2)O(3) bulk" modified electrodes, allowing for a linear range of lead ion concentration from 0.5 to 100 ?g L(-1) and a detection limit of 0.15 ?g L(-1). We demonstrated that, before the Bi film deposition, an oxidative electrochemical pre-treatment of the working electrode could be useful because it eliminates traces of lead in the graphite-ink, as shown with stripping measurements. It also improves the electrochemical performance of the electrodes as demonstrated with Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of different analytical parameters, such as the electrolyte solution composition (acetate buffer, chloridric acid, nitric acid, perchloric acid) and the ionic strength was investigated in order to evaluate how to treat the sample before the analysis. The morphology of prepared "in situ" Bi-SPEs was also characterized by Atomic Force Microscopy (AFM). Finally, the Bi-SPEs were used to determine the concentration of lead ions in tap and commercial water samples obtaining satisfactory values of the recovery percentage (81% and 98%). PMID:22027135

Quintana, Josefina Calvo; Arduini, Fabiana; Amine, Aziz; Punzo, Francesco; Destri, Giovanni Li; Bianchini, Chiara; Zane, Daniela; Curulli, Antonella; Palleschi, Giuseppe; Moscone, Danila

2011-11-30

88

Numerical study of dc-biased ac-electrokinetic flow over symmetrical electrodes  

PubMed Central

This paper presents a numerical study of DC-biased AC-electrokinetic (DC-biased ACEK) flow over a pair of symmetrical electrodes. The flow mechanism is based on a transverse conductivity gradient created through incipient Faradaic reactions occurring at the electrodes when a DC-bias is applied. The DC biased AC electric field acting on this gradient generates a fluid flow in the form of vortexes. To understand more in depth the DC-biased ACEK flow mechanism, a phenomenological model is developed to study the effects of voltage, conductivity ratio, channel width, depth, and aspect ratio on the induced flow characteristics. It was found that flow velocity on the order of mm/s can be produced at higher voltage and conductivity ratio. Such rapid flow velocity is one of the highest reported in microsystems technology using electrokinetics. PMID:22662084

Yang Ng, Wee; Ramos, Antonio; Cheong Lam, Yee; Rodriguez, Isabel

2012-01-01

89

Cyanide adsorption on gold electrodes: a combined surface enhanced Raman spectroscopy and density functional theory study  

Microsoft Academic Search

A combined SERS and DFT study of cyanide adsorption on a gold electrode is presented. From our analysis, the high-frequency mode at ?2100 cm?1 is ascribed to the C–N stretching frequency at (100) and (110) sites. The lower frequency modes at ?370 and ?300 cm?1 are ascribed to the Au–CN stretching and bending modes, respectively. The Stark tuning slopes of

G. L Beltramo; T. E Shubina; S. J Mitchell; M. T. M Koper

2004-01-01

90

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

Microsoft Academic Search

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a J×B torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in ?1 ?s, which is much faster than any of

S. P. Gerhardt; D. T. Anderson; F. S. B. Anderson; J. N. Talmadge

2004-01-01

91

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

Microsoft Academic Search

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a J×B torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in ~1 mus, which is much faster than any of

S. P. Gerhardt; D. T. Anderson; F. S. B. Anderson; J. N. Talmadge

2004-01-01

92

Electrochemical Studies of Ceramic Carbon Electrodes Prepared with Sulfonated Organosilane Precursors  

NASA Astrophysics Data System (ADS)

State-of-the-art electrodes for proton exchange membrane fuel cells (PEMFCs) contain platinum catalyst and a Nafion proton-conducting binder. Optimal conditions for Nafion functionality are at 80°C and 100% relative humidity (RH). Ceramic carbon electrodes (CCEs), consisting of carbon particles supported by ceramic binder network, may be an alternative electrode structure which replaces Nafion with organosilane materials. CCEs are also attractive for their high surface area and durable nature. CCEs have been fabricated via an in-situ sol-gel polymerization process. Development of a novel electrode fabrication procedure included direct spray-deposition of CCEs onto a microporous/gas diffusion layer to facilitate adhesion and facile electrode preparation. CCEs were composed of commercial carbon-supported platinum catalyst and 3-trihydroxysilyl-1-propanesulfonic acid (TPS) or TPS and tetraethylorthosilicate (TEOS) to vary the level of sulfonation. CCEs were initially tested electrochemically in a half-cell set-up to evaluate electrode functionality. An optimal loading of 42-48 wt% silane was determined for CCEs with only TPS to provide the highest electrochemically active surface area (ECSA) of platinum and proton conductivity. BET surface areas were low due to restriction of pore sizes by the sulfonated side chain. Composite CCEs of TPS/TEOS had enhanced electrochemical performance and high BET surface areas (>400 m 2 g-1), indicating high porosity. Excellent electrochemical results were obtained for the CCE with a TPS:TEOS ratio of 4:96 (40 wt% total silane). The sulfonated TPS/TEOS CCE (SS-CCE) was further evaluated in a fuel cell. Electrochemical studies showcased higher accessibility of catalyst sites and good proton conductivity compared to Nafion-containing cathodes. At 80°C and 100% relative humidity (RH), CCEs performed similarly to Nafion electrodes at low current density but suffered from mass transport limitations due to flooding at high current density. Investigation at lower %RH conditions revealed superior performance for membrane electrode assemblies (MEAs) with SS-CCE cathodes compared to Nafion-based cathodes, resulting from back-diffusion of water from the cathode to the membrane. SS-CCE durability was demonstrated over multiple start-up/shut-down conditions and 300 hours of continuous load testing. Carbon corrosion and silane backbone degradation were not observed, though ECSA was reduced. Transport phenomena related to performance losses were evaluated compared to Nafion cathodes. No performance drop was observed when air was the oxidant (vs. oxygen), suggesting excellent oxygen transport capabilities for SS-CCE cathodes. Oxygen diffusivity through the catalyst layer is enhanced by the silane-based ionomer, and the major contribution to performance loss is related to pore flooding, which could be alleviated under low humidity conditions. Keywords: proton exchange membrane fuel cell, ceramic carbon electrode, electrochemistry, sulfonated organosilane, sol-gel, carbon-supported catalysts, microporous layer, relative humidity, durability, cyclic voltammetry, electrochemical impedance spectroscopy.

Eastcott, Jennie

93

Thermal-stability studies of electrode materials for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ? x ? 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ? y ? 1/4, 1/6 ? z ? 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

Jiang, Junwei

2005-07-01

94

In Situ X-Ray Absorption Spectroscopy Study of the LiNiO2 Electrode  

NASA Astrophysics Data System (ADS)

LiNiO2 is one of the most promising active material for the development of novel 4V rechargeable lithium batteries. Recent x-ray diffraction studies showed that the electrochemical reactivity of this electrode is sensitive to the structure of the starting material as well as the charged products. To further examine this material, we have conducted an x-ray absorption spectroscopy (XAS) study to determine the structure of this electrode as a function of its charge state. Specifically, the x-ray absorption Ni K-edge energy, the pre-edge structure, and local structure parameters such as bond lengths, coordination numbers and disorders were investigated at various states of charge corresponding to Li_(1-x)NiO2 for x values of 0.0, 0.11, 0.23, 0.34, 0.45, 0.82, and 0.99. The charging which proceeds via lithium de-intercalation was conducted using constant current anodization at 0.5 mA in a non aqueous electrolyte consisting of 1M LiPF6 in 1:1:3 propylene ! carbonate, ethylene carbonate and dimethyl carbonate. The XAS results for this electrode will be compared with those of ?-NiOOH and KNiIO_6, the latter being used as a reference for quadrivalent nickel.

Mansour, A. N.; McBreen, J.; Melendres, C. A.

1997-03-01

95

A Study of Preconditioners for Network Interior Point Methods  

Microsoft Academic Search

We study and compare preconditioners available for network interior point methods. We derive upper bounds for the condition number of the preconditioned matrices used in the solution of systems of linear equations defining the algorithm search directions. The preconditioners are tested using PDNET, a state-of-the-art interior point code for the minimum cost network flow problem. A computational comparison using a

Joaquim J. Júdice; João Patricio; Luis F. Portugal; Mauricio G. C. Resende; Geraldo Veiga

2003-01-01

96

Studying the glial cell response to biomaterials and surface topography for improving the neural electrode interface  

NASA Astrophysics Data System (ADS)

Neural electrode devices hold great promise to help people with the restoration of lost functions, however, research is lacking in the biomaterial design of a stable, long-term device. Current devices lack long term functionality, most have been found unable to record neural activity within weeks after implantation due to the development of glial scar tissue (Polikov et al., 2006; Zhong and Bellamkonda, 2008). The long-term effect of chronically implanted electrodes is the formation of a glial scar made up of reactive astrocytes and the matrix proteins they generate (Polikov et al., 2005; Seil and Webster, 2008). Scarring is initiated when a device is inserted into brain tissue and is associated with an inflammatory response. Activated astrocytes are hypertrophic, hyperplastic, have an upregulation of intermediate filaments GFAP and vimentin expression, and filament formation (Buffo et al., 2010; Gervasi et al., 2008). Current approaches towards inhibiting the initiation of glial scarring range from altering the geometry, roughness, size, shape and materials of the device (Grill et al., 2009; Kotov et al., 2009; Kotzar et al., 2002; Szarowski et al., 2003). Literature has shown that surface topography modifications can alter cell alignment, adhesion, proliferation, migration, and gene expression (Agnew et al., 1983; Cogan et al., 2005; Cogan et al., 2006; Merrill et al., 2005). Thus, the goals of the presented work are to study the cellular response to biomaterials used in neural electrode fabrication and assess surface topography effects on minimizing astrogliosis. Initially, to examine astrocyte response to various materials used in neural electrode fabrication, astrocytes were cultured on platinum, silicon, PMMA, and SU-8 surfaces, with polystyrene as the control surface. Cell proliferation, viability, morphology and gene expression was measured for seven days in vitro. Results determined the cellular characteristics, reactions and growth rates of astrocytes grown on PMMA resembled closely to that of cells grown on the control surface, thus confirming the biocompatibility of PMMA. Additionally, the astrocyte GFAP gene expressions of cells grown on PMMA were lower than the control, signifying a lack of astrocyte reactivity. Based on the findings from the biomaterials study, it was decided to optimize PMMA by changing the surface characteristic of the material. Through the process of hot embossing, nanopatterns were placed on the surface in order to test the hypothesis that nanopatterning can improve the cellular response to the material. Results of this study agreed with current literature showing that topography effects protein and cell behavior. It was concluded that for the use in neural electrode fabrication and design, the 3600mm/gratings pattern feature sizes were optimal. The 3600 mm/gratings pattern depicted cell alignment along the nanopattern, less protein adsorption, less cell adhesion, proliferation and viability, inhibition of GFAP and MAP2k1 compared to all other substrates tested. Results from the initial biomaterials study also indicated platinum was negatively affected the cells and may not be a suitable material for neural electrodes. This lead to pursuing studies with iridium oxide and platinum alloy wires for the glial scar assay. Iridium oxide advantages of lower impedance and higher charge injection capacity would appear to make iridium oxide more favorable for neural electrode fabrication. However, results of this study demonstrate iridium oxide wires exhibited a more significant reactive response as compared to platinum alloy wires. Astrocytes cultured with platinum alloy wires had less GFAP gene expression, lower average GFAP intensity, and smaller glial scar thickness. Results from the nanopatterning PMMA study prompted a more thorough investigation of the nanopatterning effects using an organotypic brain slice model. PDMS was utilized as the substrate due to its optimal physical properties. Confocal and SEM imaging illustrated cells from the brain tissue slices were aligned along the nanopatt

Ereifej, Evon S.

97

A finite-element study of the effects of electrode position on the measured impedance change in impedance cardiography.  

PubMed

Traditional impedance cardiography (ICG) technique uses band electrodes both for delivering current to and measuring impedance change in the thorax. The use of spot electrodes increases the ease of electrode placement and comfort level for patients. Research has shown that changes in thoracic impedance can have multiple causes. In this study, we used finite element modeling to investigate the sources of impedance change for both band-electrode and spot-electrode ICG, and focused on how differences in electrode location affect the contribution of different sources to changes in impedance. The ultimate purpose is to identify the optimal electrode type and placement for the sensing of stroke volume (SV). Our models were built on sets of end-diastolic and end-systolic magnetic resonance images of a healthy human subject. The results showed that the effect of ventricular contraction is opposite to that of the other changes in systole: the expansion of major vessels, decrease in blood resistivity due to increased blood flow velocity, and decrease in lung resistivity due to increased blood perfusion. Ventricular contraction, the only factor that tends to increase systolic impedance, has a larger effect than any of the other factors. When spot electrodes are placed on the anterior chest wall near the heart, ventricular contraction is so dominant that the measured impedance increases from end-diastole to end-systole, and the change represents 82% of the contribution from ventricular contraction. When using the common band-electrode configuration, the change in measured impedance is a more balanced combination of the four effects, and ventricular contraction is overcome by the other three factors so that the impedance decreases. These results suggest that the belief that ICG can be used to directly measure SV based on the change in the whole thoracic impedance may be invalid, and that spot electrodes may be more useful for understanding local physiological events such as ventricular volume change. These findings are supported by previously reported experimental observations. PMID:11759920

Wang, Y; Haynor, D R; Kim, Y

2001-12-01

98

Surface-enhanced Raman spectroscopy of surfactants on silver electrodes  

Microsoft Academic Search

Surface-enhanced Raman spectroscopy (SERS) has been used to study different kinds of surfactants (cationic, anionic, and nonionic surfactants) adsorbed on a roughened Ag electrode. Spectral assignments are made for the SERS spectrum of cetylpyridinium chloride (CPC), and it is shown that the molecule is oriented with its pyridinium ring end-on at the electrode surface at potentials positive to the point

Soncheng. Sun; Ronald L. Birke; John R. Lombardi

1990-01-01

99

Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide  

PubMed Central

The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10?4 M to 1 M, and 29.96 mV/decade for 10?7 M to 10?4 M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10?4 M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 10?5 M and 10?4 M. PMID:22294900

Lin, Jyh-Ling; Hsu, Hsiang-Yi

2010-01-01

100

REACTION KINETICS AND X-RAY ABSORPTION SPECTROSCOPY STUDIES OF YTTRIUM CONTAINING METAL HYDRIDE ELECTRODES  

SciTech Connect

This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)}, (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.

TICIANELLI,E.A.; MUKERJEE,S.; MCBREEN,J.; ADZIC,G.D.; JOHNSON,J.R.; REILLY,J.J.

1998-11-01

101

Reaction kinetics and x-ray absorption spectroscopy studies of yttrium containing metal hydride electrodes  

SciTech Connect

This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)} Y{sub x}Ni{sub 4.7}Sn{sub 0.3} (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.

Ticianelli, E.A.; Mukerjee, S.; McBreen, J.; Adzic, G.D.; Johnson, J.R.; Reilly, J.J. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science

1998-12-31

102

Lung Radiofrequency Ablation: In Vivo Experimental Study with Low-Perfusion-Rate Multitined Electrodes  

SciTech Connect

The purpose of this study was to investigate the feasibility and safety of lung radiofrequency (RF) ablation by using low-perfusion-rate, expandable, multitined electrodes in an in vivo animal model. Ten New Zealand White rabbits underwent RF ablation using low-perfusion-rate, expandable, multitined electrodes (Starburst Talon; RITA Medical Systems, Mountain View, CA) and a 200-W RF generator. The electrode was positioned under fluoroscopy guidance and a single percutaneous RF ablation was performed. Saline perfusate was doped with nonionic iodinated contrast agent to render it visible on computed tomography (CT). The pump infused the saline doped with contrast agent into the lateral tines at a rate of 0.1ml/min. The planned ablation was of 3 min, with the hooks deployed to 2 cm at a target temperature of 105{sup o}C. An immediate posttreatment CT scan documented the distribution of the doped saline and the presence of immediate complications. The animals were monitored for delayed complications and sacrificed within 72 h (n = 4), 2 weeks (n = 3), or 4 weeks (n = 3). Assessment of ablation zone and adjacent structures was done at autopsy. Major complications consisted of pneumothorax requiring drainage (n = 2) and skin burn (n = 1). Immediately after the procedure the area of ablation was depicted at CT as a round, well-demarcated area, homogeneously opacified by iodinated contrast medium (mean size, 2.3 {+-} 0.8 cm). The presence of a sharply demarcated area of coagulation necrosis (mean size, 2.1 {+-} 0.4 cm) without severe damage to adjacent structures was confirmed at autopsy. In one case, euthanized at 4 weeks, in whom pneumothorax and pleural effusion were depicted, pleural fibrinous adhesions were demonstrated at autopsy. In conclusion, lung RF ablation performed in an in vivo animal model using low-perfusion-rate, expandable, multitined electrodes is feasible and safe. No severe damage to adjacent structures was demonstrated.

Crocetti, Laura, E-mail: l.crocetti@med.unipi.it; Lencioni, Riccardo; Bozzi, Elena [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplant and Advanced Technologies in Medicine (Italy); Sbrana, Alberto [University of Pisa (Italy); Bartolozzi, Carlo [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplant and Advanced Technologies in Medicine (Italy)

2008-05-15

103

Chemisorption and anodic oxidation of aromatic molecules on Pd electrode surfaces: studies by UHV-EC-STM  

E-print Network

The chemisorption and anodic oxidation of hydroquinone (H2Q) and benzoquinone (BQ) at palladium electrode surfaces was studied by a combination of electrochemistry (EC), Auger electron spectroscopy (AES), high-resolution electron...

Chen, Xiaole

2006-04-12

104

Electrochemical Behavior and Li Diffusion Study of LiCoO? Thin Film Electrodes Prepared by PLD  

E-print Network

Preferred c-axis oriented LiCoO? thin films were prepared on the SiO?/Si (SOS) substrates by pulsed laser deposition (PLD). Thin film electrodes without carbon and binder are ideal samples to study the electrochemical ...

Xia, H.

105

Theoretical and experimental study of the bending influence on the capacitance of interdigitated micro-electrodes patterned on flexible substrates  

NASA Astrophysics Data System (ADS)

Interdigitated electrodes are common structures in the fields of microelectronics and MEMS. Recent developments in flexible electronics compel an understanding of such structures under bending constraints. In this work, the behavior of interdigitated micro-electrodes when subjected to circular bending has been theoretically and experimentally studied through changes in capacitance. An analytical model has been developed to calculate the expected variation in capacitance of such structures while undergoing outward and inward bending along the direction perpendicular to the electrodes. The model combines conformal mapping techniques to account for the electric field redistribution and fundamental aspects of solid mechanics in order to define the geometrical deformation of the electrodes while bending. To experimentally verify our theoretical predictions, several interdigitated electrode structures with different geometries were fabricated on polymeric substrates by means of photolithography. The samples, placed in a customized bending setup, were bent to controlled radii of curvature while measuring their capacitance. A maximum variation in capacitance of less than 3% was observed at a minimum radius of curvature of 2.5 mm for all the devices tested with very thin electrodes whereas changes of up to 7% were found on stiffer, plated electrodes. Larger or smaller variations would be possible, in theory, by adjusting the geometry of the device. This work establishes a useful predictive tool for the design and evaluation of truly flexible/bendable electronics consisting of interdigitated structures, allowing one to tune the bending influence on the capacitance value through geometrical design.

Molina-Lopez, F.; Kinkeldei, T.; Briand, D.; Tröster, G.; de Rooij, N. F.

2013-11-01

106

Numerical study on the electron—wall interaction in a Hall thruster with segmented electrodes placed at the channel exit  

NASA Astrophysics Data System (ADS)

Electron—wall interaction is always recognized as an important physical problem because of its remarkable influences on thruster discharge and performance. Based on existing theories, an electrode is predicted to weaken electron—wall interaction due to its low secondary electron emission characteristic. In this paper, the electron—wall interaction in an Aton-type Hall thruster with low-emissive electrodes placed near the exit of discharge channel is studied by a fully kinetic particle-in-cell method. The results show that the electron—wall interaction in the region of segmented electrode is indeed weakened, but it is significantly enhanced in the remaining region of discharge channel. It is mainly caused by electrode conductive property which makes equipotential lines convex toward channel exit and even parallel to wall surface in near-wall region; this convex equipotential configuration results in significant physical effects such as repelling electrons, which causes the electrons to move toward the channel center, and the electrons emitted from electrodes to be remarkably accelerated, thereby increasing electron temperature in the discharge channel, etc. Furthermore, the results also indicate that the discharge current in the segmented electrode case is larger than in the non-segmented electrode case, which is qualitatively in accordance with previous experimental results.

Qing, Shao-Wei; E, Peng; Duan, Ping; Xu, Dian-Guo

2013-08-01

107

Simulation studies on the fuel electrode of a methanol air polymer electrolyte fuel cell  

SciTech Connect

A macro-homogeneous porous electrode model that describes the reactions and transport within the catalyst zone of the methanol electrode was developed. The model treats the catalyst zone as a porous electrode structure flooded with polymer electrolyte. The interactions of potential dependent reaction kinetics, diffusion of gases and ohmic losses are taken into consideration. The effects of catalyst zone thickness, catalyst loading and polymer electrolyte loading on the performance of the electrode are discussed.

Wang, J.; Savinell, R.E. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Chemical Engineering

1994-12-31

108

Plasma meniscus and extraction electrode studies of the ISIS H{sup -} ion source  

SciTech Connect

In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H{sup -} ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.

Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Gabor, C. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Pozimski, J. K. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Department of Physics, Imperial College of Science and Technology, London SW7 2AZ (United Kingdom)

2010-02-15

109

Application of drug selective electrode in the drug release study of pH-responsive microgels.  

PubMed

The colloidal phenomenon of soft particles is becoming an important field of research due to the growing interest in using polymeric system in drug delivery. Previous studies have focused on techniques that require intermediate process step such as dialysis or centrifugation, which introduces additional errors in obtaining the diffusion kinetic data. In this study, a drug selective electrode was used to directly measure the concentration of procaine hydrochloride (PrHy) released from methacrylic acid-ethyl acrylate (MAA-EA) microgel, thereby eliminating the intermediate process step. PrHy selective membrane constructed using a modified poly (vinyl chloride) (PVC) membrane and poly (ethylene-co-vinyl acetate-co-carbon monoxide) as plasticizer exhibited excellent reproducibility and stability. The response was reproducible at pH of between 3 to 8.5 and the selectivity coefficients against various organic and inorganic cations were evaluated. Drug release was conducted using the drug electrode under different pHs and the release rate increased with pH. The release behavior of the system under different pH exhibited obvious gradient release characteristics. PMID:17250922

Tan, Jeremy P K; Tam, Kam C

2007-03-12

110

Study of electrode slice forming of bicycle dynamo hub power connector  

NASA Astrophysics Data System (ADS)

Taiwan's bicycle industry has been an international reputation as bicycle kingdom, but the problem in the world makes global warming green energy rise, the development of electrode slice of hub dynamo and power output connector to bring new hope to bike industry. In this study connector power output to gather public opinion related to patent, basis of collected documents as basis for design, structural components in least drawn to power output with simple connector. Power output of this study objectives connector hope at least cost, structure strongest, highest efficiency in output performance characteristics such as use of computer-aided drawing software Solid works to establish power output connector parts of 3D model, the overall portfolio should be considered part types including assembly ideas, weather resistance, water resistance, corrosion resistance to vibration and power flow stability. Moreover the 3D model import computer-aided finite element analysis software simulation of expected the power output of the connector parts manufacturing process. A series of simulation analyses, in which the variables relied on first stage and second stage forming, were run to examine the effective stress, effective strain, press speed, and die radial load distribution when forming electrode slice of bicycle dynamo hub.

Chen, Dyi-Cheng; Jao, Chih-Hsuan

2013-12-01

111

Study of Waverider-based Point-to-Point Suborbital Rocketplane  

NASA Astrophysics Data System (ADS)

As a high-speed manned transportation system in the future, point-to-point (P2P) suborbital rocketplane is currently studied in Japan Aerospace Exploration Agency (JAXA) space transportation mission directorate. The vehicle was designed on the basis of the concept of waverider allowing high L/D in hypersonic regime, which is required for longer flight range and smaller load factor. Compared with an ideal waverider, the designed P2P suborbital rocketplane has outer wings for the improvement of the low-speed aerodynamic performance, finite thickness in the leading edge for the reduction of the aerodynamic heating, and twin vertical tails for directional stability. The aerodynamic performance of the P2P vehicle was investigated through numerical simulation of both subsonic and hypersonic flows, and the baseline aerodynamic shape of the P2P vehicle was discussed. The L/D in the trim condition at hypersonic speed was 2.6.

Takama, Yoshiki; Ishimoto, Shinji

112

Structural and electrochemical study of positive electrode materials for rechargeable lithium ion batteries  

NASA Astrophysics Data System (ADS)

The research presented in this dissertation focuses on a combined study of the electrochemistry and the structure of positive electrode materials for Li ion batteries. Li ion batteries are one of the most advanced energy storage systems and have been the subject of numerous scientific studies in recent decades. They have been widely used for various mobile devices such as cell phones, laptop computers and power tools. They are also promising candidates as power sources for automotive applications. Although intensive research has been done to improve the performance of Li ion batteries, there are still many remaining challenges to overcome so that they can be used in a wider range of applications. In particular, cheaper and safer electrodes are required with much higher reversible capacity. The series of layered nickel manganese oxides [NixLi 1/3-2x/3Mn2/3- x/3]O2 (0 < x < 1/2) are promising alternatives for Li2CoO2, the commercial positive electrode materials in Li ion batteries, because of their lower cost and higher safety and abuse tolerance, when lithium is removed from their structure. Compounds with x<1/2, in which the total Li content is higher than transition metal content, are referred as "Li-excess" materials. The "Li2MnO3-like" region is always present in this type of materials, and the overcapacity is obtained in the first charge process, which is not reversible in the following cycles. A combined X-ray diffraction, solid state nuclear magnetic resonance and X-ray absorption spectroscopy study is performed to investigate the effect of synthetic methods on the structure, to probe the structural change of the materials during cycling and to understand the electrochemical reaction mechanism. The conversion compounds are also investigated because of their high capacities. Since the various compounds have different voltage windows, they can have potential applications as both cathodes and anodes. Solid state nuclear magnetic resonance is used to study the change in the local environment of the structure during the cycling process. Two systems are included in this work, including iron fluorides and Cu-containing materials. A comparison study has been performed on FeF3 and FeF2. Different discharge reaction mechanisms are clarified for each compound, and possible phase transitions are proposed as well. As for the Cu-containing systems, three compounds were chosen with different anions: CuS, CuO and CuF2. The reaction mechanisms are studied by 63Cu, 7Li and 19F NMR and supported by powder X-ray diffraction.

Jiang, Meng

113

MoS2 Field Effect Transistors with different polarity: study of electrode work functions  

NASA Astrophysics Data System (ADS)

The transfer characteristics of Molybdenum disulfide (MoS2) field effect transistors (FETs) depend on the Schottky barrier formed between the metal electrode and the semiconducting MoS2. We obtained p-type behavior for Pd-contacted MoS2 FETs and n-type with both Au and Nb [1] contacts. We study the work function of these electrode metals to understand their effect on the Schottky barrier and therefore the polarity of the MoS2 FETs. The work function of the above metals is measured using a non-contact Kelvin Probe technique under different ambient conditions. We will discuss the observed n-type and p-type behavior of MoS2 FETs in relation to the measured metal work functions.[4pt] [1] M. Fontana, T. Deppe, A. Boyd, M. Rinzan, A. Liu, M. Paranjape, P. Barbara, Photovoltaic effect in gated MoS2 Schottky junctions, in, arXiv:1206.6125v1 [cond-mat.mtrl-sci

Dube, Isha; Boyd, Anthony K.; Fontana, Marcio; Gayduchenko, Igor; Fedorov, Georgy; Liu, Amy; Paranjape, Makarand; Barbara, Paola

2013-03-01

114

An impedimetric study of DNA hybridization on paper-supported inkjet-printed gold electrodes.  

PubMed

In this study, two different supramolecular recognition architectures for impedimetric detection of DNA hybridization have been formed on disposable paper-supported inkjet-printed gold electrodes. The gold electrodes were fabricated using a gold nanoparticle based ink. The first recognition architecture consists of subsequent layers of biotinylated self-assembly monolayer (SAM), streptavidin and biotinylated DNA probe. The other recognition architecture is constructed by immobilization of thiol-functionalized DNA probe (HS-DNA) and subsequent backfill with 11-mercapto-1-undecanol (MUOH) SAM. The binding capacity and selectivity of the recognition architectures were examined by surface plasmon resonance (SPR) measurements. SPR results showed that the HS-DNA/MUOH system had a higher binding capacity for the complementary DNA target. Electrochemical impedance spectroscopy (EIS) measurements showed that the hybridization can be detected with impedimetric spectroscopy in picomol range for both systems. EIS signal indicated a good selectivity for both recognition architectures, whereas SPR showed very high unspecific binding for the HS-DNA/MUOH system. The factors affecting the impedance signal were interpreted in terms of the complexity of the supramolecular architecture. The more complex architecture acts as a less ideal capacitive sensor and the impedance signal is dominated by the resistive elements. PMID:24522116

Ihalainen, Petri; Pettersson, Fredrik; Pesonen, Markus; Viitala, Tapani; Määttänen, Anni; Österbacka, Ronald; Peltonen, Jouko

2014-03-01

115

An impedimetric study of DNA hybridization on paper-supported inkjet-printed gold electrodes  

NASA Astrophysics Data System (ADS)

In this study, two different supramolecular recognition architectures for impedimetric detection of DNA hybridization have been formed on disposable paper-supported inkjet-printed gold electrodes. The gold electrodes were fabricated using a gold nanoparticle based ink. The first recognition architecture consists of subsequent layers of biotinylated self-assembly monolayer (SAM), streptavidin and biotinylated DNA probe. The other recognition architecture is constructed by immobilization of thiol-functionalized DNA probe (HS-DNA) and subsequent backfill with 11-mercapto-1-undecanol (MUOH) SAM. The binding capacity and selectivity of the recognition architectures were examined by surface plasmon resonance (SPR) measurements. SPR results showed that the HS-DNA/MUOH system had a higher binding capacity for the complementary DNA target. Electrochemical impedance spectroscopy (EIS) measurements showed that the hybridization can be detected with impedimetric spectroscopy in picomol range for both systems. EIS signal indicated a good selectivity for both recognition architectures, whereas SPR showed very high unspecific binding for the HS-DNA/MUOH system. The factors affecting the impedance signal were interpreted in terms of the complexity of the supramolecular architecture. The more complex architecture acts as a less ideal capacitive sensor and the impedance signal is dominated by the resistive elements.

Ihalainen, Petri; Pettersson, Fredrik; Pesonen, Markus; Viitala, Tapani; Määttänen, Anni; Österbacka, Ronald; Peltonen, Jouko

2014-03-01

116

Point Loma Nazarene College, San Diego, Self-Study Report.  

ERIC Educational Resources Information Center

Point Loma Nazarene College's self-study report for reaffirmation of accreditation, which was submitted to the Western Association of Schools and Colleges, is presented. A description about the history and demographics of the college is provided, along with information on: institutional integrity; institutional purposes; governance and…

Point Loma Nazarene Coll., San Diego, CA.

117

Stereo Visual Servoing with a Single Point: a Comparative Study  

Microsoft Academic Search

A comparative study of a stereo visual servoing sys- tem is presented. The visual feature is the pair of images of an object, for which there not exists a ge- ometrical model. Instead, the image of the object is segmented, and its center of gravity is computed. The developed control laws use either the raw image points, or the estimated

E. Cervera; F. Berry; P. Martinet Robotic; Blaise Pascal

118

Preparation of polymer-modified electrodes: A literature and experimental study  

SciTech Connect

A literature review is presented on the field of polymer modified electrodes which can be electrochemically generated. It is suggested that a possible application of these polymer modified electrodes is as a regeneratable catalysis packing material for use in couter-current exchange columns. Secondly, there is a presentation of experimental results dealing with possible electrode modification using difluoro- and dimethyl- phenols and fluorinated derivatives of styrene, benzoquinone and hydroquinone. It appears that dimethylphenol shows the most potential of the monomers experimentally tested in providing a stable polymer modified electrode surface. 170 refs., 31 figs., 1 tab.

Jayanta, P.S.; Ishida, Takanobu

1991-05-01

119

Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries  

SciTech Connect

Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous oxidation of Fe{sup 2+} and Mn{sup 2+} in a small range of compositions. Black-Right-Pointing-Pointer Surface analysis from XPS allows reveals slight differences at the surface of the electrode with respect to the bulk.

Perea, A. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Castro, L. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Aldon, L., E-mail: laurent.aldon@um2.fr [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Stievano, L. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Dedryvere, R.; Gonbeau, D. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Tran, N.; Nuspl, G. [Sued-Chemie AG, Ostenriederstr. 15, D-85368 Moosburg (Germany); Breger, J.; Tessier, C. [SAFT, 111-113 bd. Alfred Daney, 33074 Bordeaux, Cedex (France)

2012-08-15

120

In situ surface enhanced Raman spectroscopic studies of solid electrolyte interphase formation in lithium ion battery electrodes  

NASA Astrophysics Data System (ADS)

The use of surfaced-enhanced Raman spectroscopy (SERS) in lithium-ion battery (LIB) and Li-O2 battery studies has proven to be a powerful tool for observing solid electrolyte interphase (SEI) growth, on the electrode's surface, that is crucial in determining the battery's electrochemical performance. Here, we report the use of SiO2-coated Au nanoparticles for in situ SERS studies during electrochemical cycling to directly observe SEI formation on the electrode. The comparison of silicon electrodes with and without the electrolyte additive vinylene carbonate (VC) shows the formation of VC-related reduction products on the electrode's surface before the reduction of ethylene carbonate. Further observation, using normal Raman and SERS, of the silicon band intensity shows different amorphization rates between bulk and surface. These successful proof-of-concept experiments should allow this technique to be extended to other electrode material studies in conjunction with other surface sensitive techniques to further our understanding of surface reactions that heavily influence overall battery performance.

Hy, Sunny; Felix; Chen, Yi-Hsiu; Liu, Jyong-yue; Rick, John; Hwang, Bing-Joe

2014-06-01

121

A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells  

PubMed Central

This study describes a systematic approach of TiO2/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO2 and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO2 to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized. PMID:23672498

2013-01-01

122

Analytical study of the structure of chaos near unstable points  

E-print Network

In a 2D conservative Hamiltonian system there is a formal integral $\\Phi$ besides the energy H. This is not convergent near a stable periodic orbit, but it is convergent near an unstable periodic orbit. We explain this difference and we find the convergence radius along the asymptotic curves. In simple mappings this radius is infinite. This allows the theoretical calculation of the asymptotic curves and their intersections at homoclinic points. However in more complex mappings and in Hamiltonian systems the radius of convergence is in general finite and does not allow the theoretical calculation of any homoclinic point. Then we develop a method similar to analytic continuation, applicable in systems expressed in action-angle variables, that allows the calculation of the asymptotic curves to an arbitrary length. In this way we can study analytically the chaotic regions near the unstable periodic orbit and near its homoclinic points.

G. Contopoulos; C. Efthymiopoulos; M. Katsanikas

2014-10-10

123

Combined NMR and PDF studies of positive electrode materials for rechargeable lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Layered lithium nickel manganese oxides are promising, inexpensive and nontoxic alternative positive electrodes materials to the commercial LiCoO 2 electrode used in Li-ion batteries. Among these materials, Li(NiMn) 0.5O2 is particularly attractive due to its high theoretical capacity (280 mAh/g). The motivation for the research presented here was to understand the detailed long-range and short-range structure of these materials, particularly Li(NiMn)0.5O2, both as-synthesised and upon cycling. It is indeed important to know what the cation environments are, especially for the Li ions, since they strongly affect the electrochemical performance. The local environments and short-range ordering of Li(NiMn)0.5O 2, a potential Li-ion battery positive electrode material, were investigated by using a combination of X-ray and neutron diffraction and isotopic substitution (NDIS) techniques, 6Li Magic Angle Spinning (MAS) NMR spectroscopy and, for the first time, X-ray and neutron Pair Distribution Function (PDF) analysis, associated with Reverse Monte Carlo (RMC) calculations. Two Li(NiMn) 0.5O2 samples were studied in detail: one obtained from regular solid-state synthesis (SS), and another one obtained from ion-exchange routes (IE). 6Li MAS NMR experiments showed less Li/Ni site exchange (between the Li and the Ni/Mn layers) for the IE compound than for the SS compound, explaining its improved Li diffusivity and rate capability. For the SS compound, the Ni/Ni and Mn/Mn repulsion seen by PDF/RMC and the Li/Mn proximity seen by NMR were consistent with an ordering scheme intermediate between the ideal structures proposed so far (the "honey-comb" and "flower" structures). Ordering of Ni and Mn atoms in the transition metal layers was also detected in IE-Li(NiMn)0.5O2: Ni atoms tend to be surrounded by more Mn atoms in the first coordination shell, while the second coordination shell shows that zigzag ordering scheme is preferred over the chain. Ex-situ neutron diffraction and, for the first time on battery materials, in-situ X-ray PDF experiments were also performed to study the evolution of the cation arrangement during cycling. Based on this work, many applications of this joint NMR-PDF analysis approach to many battery systems may be readily envisaged.

Breger, Julien

124

Binding studies and anion-selective electrodes with neutral isophthalamide-based receptors.  

PubMed

Two acyclic isophthalamide-based hosts have been synthesised and their anion binding properties have been evaluated by (1)H-NMR titrations. Different binding modes have been detected for the series of tested anions. The attachment of aminomethylpyrrole groups resulted in an improved binding selectivity. Additionally, the receptors have been incorporated as ionophores in plasticised polymeric membrane-based anion-selective electrodes. The potentiometric studies were in agreement with the NMR experiments and revealed a good sensing ability, considering the structural simplicity of the receptors and their interactions purely based on hydrogen bonding. These preliminary experiments have revealed an interesting selectivity towards highly hydrophilic anions such as fluoride and sulfate. Moreover, a particularly low detection limit (9 × 10(-7) M) has been determined for the fluoride anion. PMID:25368872

Más-Montoya, Miriam; Cuartero, María; Curiel, David; Ortuño, Joaquín A; Soledad García, M; Tárraga, Alberto

2015-01-01

125

Monte Carlo study of molten salt with charge asymmetry near the electrode surface  

NASA Astrophysics Data System (ADS)

Results of the Monte Carlo simulation of the electrode | molten salt or ionic liquid interface are reported. The system investigated is approximated by the primitive model of electrolyte being in contact with a charged hard wall. Ions differ in charges, namely anions are divalent and cations are monovalent but they are of the same diameter d = 400 pm. The temperature analysis of heat capacity at a constant volume Cv and the anion radial distribution function, g2-/2-, allowed the choice of temperature of the study, which is T = 2800 K and corresponds to T* = 0.34 (definition of reduced temperature T* in text). The differential capacitance curve of the interface with the molten salt or ionic liquid at c = 5.79 M has a distorted bell shape. It is shown that with increasing electrolyte concentration from c = 0.4 to 5 M the differential capacitance curves undergo transition from U shape to bell shape.

K?os, Jacek; Lamperski, Stanis?aw

2014-02-01

126

Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study  

NASA Astrophysics Data System (ADS)

There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.

Chen, Jia; Selloni, Annabella

2013-03-01

127

Studies of localized corrosion in welded aluminum alloys by the scanning reference electrode technique  

NASA Technical Reports Server (NTRS)

Localized corrosion in welded samples of 2219-T87 Al alloy (2319 filler), 2090 Al-Li alloy (4043 and 2319 fillers), and 2195 Al-Li alloy (4043 and 2319 fillers) has been investigated using the relatively new scanning reference electrode technique. The weld beads are cathodic in all cases, leading to reduced anode/cathode ratios. A reduction in anode/cathode ratio leads to an increase in the corrosion rates of the welded metals, in agreement with results obtained in previous electrochemical and stress corrosion studies involving the overall corrosion rates of welded samples. The cathodic weld beads are bordered on both sides by strong anodic regions, with high propensity for corrosion.

Danford, M. D.; Nunes, A. C.

1995-01-01

128

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

SciTech Connect

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a JxB torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in {approx}1 {mu}s, which is much faster than any of the plasma time scales; the electrode current is terminated on a similar time scale at the end of the electrode pulse. A pair of multitipped Mach probes have been designed to measure the plasma flows in a magnetic surface with good spatial and time resolution ({delta}t>20 {mu}s). The unmagnetized model by Hutchinson is used to analyze the Mach probe data, and radial force balance is found to be well satisfied during electrode bias. These probes allow for measurements of the transient response of the plasma flows and floating potential when the electrode is energized. An example of using the system for the estimation of viscous damping times in HSX is provided.

Gerhardt, S.P.; Anderson, D.T.; Anderson, F.S.B.; Talmadge, J.N. [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53703 (United States)

2004-11-01

129

Electrode compositions  

DOEpatents

An electrode composition for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C.sub.8 -C.sub.15 alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5-4.5 volts.

Block, Jacob (Rockville, MD); Fan, Xiyun (Orange, TX)

1998-01-01

130

Electrode compositions  

DOEpatents

An electrode composition is described for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C{sub 8}-C{sub 15} alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5--4.5 volts.

Block, J.; Fan, X.

1998-10-27

131

Near infrared photoresponse study of large area multi-walled carbon nanotube film with different electrode spacing  

NASA Astrophysics Data System (ADS)

Photoconductivity of carbon nanotube have generated considerable debate in terms of whether the photoresponse is (i) due to photon induced charge carrier (excitonic), (ii) due to heating of the CNT network (bolometric), or (iii) caused by photodesorption of oxygen molecules at the surface of the CNT. In addition, the role of the metal electrode -- CNT contact's effect on the photoresponse has also been debated. In this talk, we will present near -infrared photoresponse study of multi-walled carbon nanotube (MWCNT) film with different electrode spacings. We found that there is a large enhancement of photocurrent upon laser illumination and the photocurrent strongly depends on the position of the laser spot with maximum response occurring at the metal -- film interface. We also show that the photoresponse is rather slow (˜1s) and increases with increasing electrode spacing. We will discuss the origin of the position dependent photocurrent and slow time response.

Sarker, Biddut; Arif, M.; Stokes, Paul; Kabir, Alamgir; Khondaker, Saiful I.

2009-03-01

132

Olivine electrode engineering impact on the electrochemical performance of lithium-ion batteries.  

SciTech Connect

High energy and power density lithium iron phosphate was studied for hybrid electric vehicle applications. This work addresses the effects of porosity in a composite electrode using a four-point probe resistivity analyzer, galvanostatic cycling, and electrochemical impedance spectroscopy (EIS). The four-point probe result indicates that the porosity of composite electrode affects the electronic conductivity significantly. This effect is also observed from the cell's pulse current discharge performance. Compared to the direct current (dc) methods used, the EIS data are more sensitive to electrode porosity, especially for electrodes with low porosity values.

Lu, W.; Jansen, A.; Dees, D.; Henriksen, G.; Chemical Sciences and Engineering Division

2010-08-01

133

Photoelectrocatalytic study and scaling up of titanium dioxide electrodes for wastewater treatment.  

PubMed

Different TiO2 photoelectrodes have been characterized and tested for the photoelectrocatalytic oxidation of methanol. Particulate electrodes (TiO2/Ti and TiO2/ITO) have been shown to notably favour charge-carrier transfer at the electrolyte interface while a thermal electrode (Ti) has been shown to favour charge-carrier separation when applying an electric potential bias according to cyclic voltammetry technique, as a consequence of differences in TiO2 surface between particulate and thermal electrodes. Particulate electrodes lead to a higher photoelectrocatalytic activity for methanol oxidation compared to that of the thermal electrode, probably due to the pure-rutile TiO2 phase composition of the latter and its lower surface area. TiO2/Ti electrode has been shown to be the most effective photoelectrode tested for methanol oxidation since its activity was improved by the combination of the particulate TiO2 layer and the high electrical conductivity of the support. Generally, photocurrent density measured in the photoelectrochemical cell seems to correlate with activity, whereas this correlation is not observed when using a larger photoelectrocatalytic reactor. In contrast, the activity obtained for the scaled-up electrode is found to be similar in terms of surface kinetic constant to that obtained at laboratory scale. PMID:24037149

Pablos, C; van Grieken, R; Marugán, J; Adán, C; Osuna, M; Palma, J

2013-01-01

134

Ancient Astronomy: A Study of the Point Remove Mound Complex  

NASA Astrophysics Data System (ADS)

Artificial solstice markers are a common thread across many early civilizations. With the beginnings of early agriculture, the need to be able to predict the changes in season became an issue of utmost importance. Many Native American groups used artificial mounds to mark different astronomical events. Toltec Mounds (located southeast of Little Rock, AR) is a complex set of structures left behind by the area's native people that is known to have alignments with the summer and winter solstice as well as an equinox alignment. The Point Remove mound complex (located outside Morrilton, Arkansas, also known as site 3CN4) is a known archeological site that has not been well studied, therefore has never been checked for any form of astronomical alignment. The purpose of this project is to study the Point Remove Mound site and look for features of astronomical significance. Study of Toltec Mounds will serve as a baseline for comparison. Study of the site consists of aerial photographs, topographic maps, and GPS measurements. In addition to studying alignments within the site, the location of the mound complex will be studied with respect to other known complexes like Toltec Mounds and Spiro Mounds (Oklahoma).

Hankins, Matt; Burris, D. L.

2012-01-01

135

A novel electrode array for diameter-dependent control of axonal excitability: a simulation study.  

PubMed

Electrical extracellular stimulation of peripheral nerve activates the large-diameter motor fibers before the small ones, a recruitment order opposite the physiological recruitment of myelinated motor fibers during voluntary muscle contraction. Current methods to solve this problem require a long-duration stimulus pulse which could lead to electrode corrosion and nerve damage. The hypothesis that the excitability of specific diameter fibers can be suppressed by reshaping the profile of extracellular potential along the axon using multiple electrodes is tested using computer simulations in two different volume conductors. Simulations in a homogenous medium with a nine-contact electrode array show that the current excitation threshold (Ith) of large diameter axons (13-17 microm) (0.6-3.0 mA) is higher than that of small-diameter axons (2-7 microm) (0.4-0.7 mA) with 200-microm axon-electrode distance and 10-micros stimulus pulse. The electrode array is also tested in a three-dimensional finite-element model of the sacral root model of dog (ventral root of S3). A single cathode activates large-diameter axons before activating small axons. However, a nine-electrode array activates 50% of small axons while recruiting only 10% of large ones and activates 90% of small axons while recruiting only 50% of large ones. The simulations suggest that the near-physiological recruitment order can be achieved with an electrode array. The diameter selectivity of the electrode array can be controlled by the electrode separation and the method is independent of pulse width. PMID:15248540

Lertmanorat, Zeng; Durand, Dominique M

2004-07-01

136

Industrial hygiene study at the Anvil Points oil shale facility  

SciTech Connect

An industrial study was performed at the Department of Energy Anvil Points Oil Shale Mine and Retorting Facility near Rifle, Colorado. This study considered the potential industrial hygiene problems associated with the Paraho direct combustion retorting process and the related mining, crushing, disposal, and auxiliary operations. Air samples did not indicate any personal exposures in excess of existing industrial hygiene standards. However, area sampling did show that some operations would present significant exposures to some employees should such employees work full time in these areas. Commercial scale operations will require industrial hygiene control measures to control these potentially hazardous situations.

Garcia, L.L.; Schulte, H.F.; Ettinger, H.J.

1981-11-01

137

Durability study of electrospray deposited Pt film electrode for hydrogen production in PV assisted water electrolysis system  

Microsoft Academic Search

We studied the durability of the previously reported low mass loaded, highly efficient electrospray deposited Pt film as a cathode and Ni mesh as anode electrode in PV assisted water electrolysis system for 1000 h. This assembly showed no detectable decline in performance for initial 200 h, but thereafter it started to decline with time and showed 18% decline after 1000 h. For

Sang-Youn Chae; Jyotiprakash B. Yadav; Kang-Jin Kim; Oh-Shim Joo

2011-01-01

138

Electrochemical and morphological study of the effect of temperature on the restructuring and loss of capacity of alkaline battery electrodes. Final report  

SciTech Connect

The degradation processes occurring within porous nickel battery electrodes were investigated during charge/discharge cycling at temperatures in the range 0 to 100/sup 0/C. The ac impedance of two types of porous nickel electrodes (sintered electrodes and rolled and bonded electrodes) in a 8 m KOH solution was measured, and the data were analyzed in terms of a transmission line model (TLM). In addition, cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on nickel electrodes during charging. Impedance data of planar, non-porous electrodes were obtained over a range of potentials and temperatures in order to provide an equivalent circuit to model the pore-wall and backing-plate interfacial impedance components in the TLM. Parameters in the TLM were curve-fitted to experimental impedance data obtained for porous electrodes at different stages of cycling. Changes in these parameters with cycling time for rolled and bonded electrodes were consistent with experimental observations, and could be attributed to various degradation processes. The principal changes found to occur with increasing cycle number were that the average pore effective length decreases and the average solid-phase resistivity increases. The impedance data for sintered electrodes do not change during galvanostatic cycling and failures occur abruptly after a relatively large number of cycles. Consequently, the TLM provides little insight into cycle-dependent degradation phenomena on sintered electrodes.

Macdonald, D.D.; Pound, B.G.; Lenhart, S.J.

1984-11-01

139

Numerical study of the cathode electrode in the Microfluidic Fuel Cell using agglomerate model  

NASA Astrophysics Data System (ADS)

Simulation of the cathode electrode of a Microfluidic Fuel Cell (hereafter MFC) is performed with focus on the electrochemical reaction. Oxygen transport phenomena are modeled from the microchannel inlet to the reaction sites surface (on the platinum particles) in the catalyst layer. The dissolved oxygen in sulfuric acid and the formic acid are considered as the oxidant and the fuel, respectively. The cathode catalyst layer is modeled using the agglomerate model versus the homogenous model which is incapable of predicting concentration loss at high current densities. The results are validated versus the experiments of Choban et al. published in 2004. A set of parametric study is performed to investigate the influence of operating and structural parameters on the cell performance; at the end, a sensitivity analysis is implemented to rank the studied parameters with rank 1 for the most influential parameters. The results indicate that oxygen concentration at the inlet of microchannel within the range 0.1 M-0.7 M is the most influential parameter, and the cell performance can enhance by 2.615 W m-2 at the studied range. The results could be used by the microfluidic fuel cell manufacturers to overcome the current drawbacks of the MFCs.

Moein-Jahromi, M.; Movahed, S.; Kermani, M. J.

2015-03-01

140

An impedance study of complex Al/Cu-Al2O3 electrode  

NASA Astrophysics Data System (ADS)

Electrochemical impedance spectroscopy (EIS) was used to investigate different Cu deposition regimes on Al surface obtained by internal electrolysis and to characterize properties of fabricated electrodes. EIS experimental data confirmed that Cu deposition by internal electrolysis is realized and the complex electrode system is obtained. The main difficulty in preparation of Al/Cu electrodes is to prevent aluminium oxidation before and during electrochemical deposition of Cu particles. In this work NaCl, CH3COONa, K2SO4, mono- and diammonium citrate electrolytes were examined to determine their suitability for impedance measurements. Al/Cu-Al2O3 electrode composition was approved by equivalent circuit analysis, optical and scanning electron microscope methods. The most optimal Cu deposition mode using internal electrolysis was determined. The obtained results are promising for future electrochemical fabrication of nanostructures directly on Al surfaces by internal electrolysis.

Denisova, J.; Katkevics, J.; Erts, D.; Viksna, A.

2011-06-01

141

Simulation studies of the coplanar electrode and other plasma display panel cell designs  

E-print Network

the plates is filled with an inert gas mixture. A protective MgO layer is deposited above the dielectric film color, red, green, or blue. The most common type of color plasma display is the coplanar-electrode PDP

Veronis, Georgios

142

Carbon Paste Electrodes Made from Different Carbonaceous Materials: Application in the Study of Antioxidants  

PubMed Central

This work describes the sensing properties of carbon paste electrodes (CPEs) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, l-ascorbic acid and l-glutathione have been analyzed and compared. It has been demonstrated that the electrodes based on carbon microspheres show the best performances in terms of kinetics and stability, whereas G-CPEs presented the smallest detection limit for all the antioxidants analyzed. An array of electrodes has been constructed using the three types of electrodes. As demonstrated by means of Principal Component Analysis, the system is able to discriminate among antioxidants as a function of their chemical structure and reactivity. PMID:22319354

Apetrei, Constantin; Apetrei, Irina Mirela; De Saja, Jose Antonio; Rodriguez-Mendez, Maria Luz

2011-01-01

143

Electrochemical study of uranium cations in LiCl-KCl melt using a rotating disk electrode  

SciTech Connect

A rotating disk electrode (RDE) measurement technique was employed to investigate the electrochemical REDOX reactions of actinide (An) and lanthanide (Ln) ions in LiCl-KCl molten salt. By using RDE, it is possible to access more exact values of the diffusion coefficient, Tafel slope, and exchange current density. In this work, we constructed RDE setup and electrodes for RDE measurements in high temperature molten salt and measured the electrochemical parameters of the An and Ln ions. The RDE setup is composed of a Pine model MSRX rotator equipped with a rod type of W electrode. The active electrode area was confined to the planar part of the W rod by making meniscus at the LiCl-KCl melt surface.

Bae, Sang-Eun; Kim, Dae-Hyun; Kim, Jong-Yoon; Park, Tae-Hong; Cho, Young Hwan; Yeon, Jei-Won; Song, Kyuseok [Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute,989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of)

2013-07-01

144

Fabrication and heating rate study of microscopic surface electrode ion traps  

E-print Network

We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with a trapping height of approximately 240 ?m. Using the Doppler recooling method, we characterize the trap heating rates ...

Daniilidis, N.

145

A Comparative Electrochemical Behaviour Study and Analytical Detection of the p-Nitrophenol Using Silver Solid Amalgam, Mercury, and Silver Electrodes  

PubMed Central

This work reports a comparative electrochemical behaviour study and p-nitrophenol analytical detection using silver solid amalgam, hanging dropping mercury, and silver electrodes. For this, square wave voltammetry was employed, where the analytical responses and the redox mechanisms could be compared for reduction processes of 4-nitrophenol by analysis of the voltammetric responses. The analytical performance of the electrode was evaluated and detection and quantification limits, recovery percentages, repeatability, and reproducibility for the silver solid amalgam and hanging dropping mercury electrodes presented similar values; the results presented for the silver electrode indicated worse analytical parameters than the other electrodes. The results indicate that the silver solid amalgam electrode can be considered a suitable tool and an interesting alternative for the analytical determination of 4-nitrophenol, as well as for the determination of other biological and environmentally interesting compounds that present analytical responses on mercury surfaces. PMID:21647286

De Souza, Djenaine; Mascaro, Lucia H.; Fatibello-Filho, Orlando

2011-01-01

146

Solid state NMR and pair distribution function studies of silicon electrodes for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The universally used negative electrode material in a LIB is carbon, because of its moderate capacity (372 mAhg-1 for graphite), cyclability and high rate capability. However, new, low cost, safe electrode materials with higher capacities are still urgently required for both portable and transportation applications. Silicon anodes are particularly attractive alternatives to carbon with extremely high gravimetric energy densities (3572 mAhg-1). Compared to graphite, silicon has a massive volumetric capacity of 8322 mAhcm-3 (calculated based on the original volume of silicon) which is approximately ten times that graphite. At room temperature, upon electrochemical lithiation, silicon undergoes a crystalline to amorphous phase transition forming a lithiated amorphous silicide phase. Unfortunately, due to the amorphous nature of the lithiated silicides, it is not possible to monitor all the structural changes that occur during lithium insertion/removal with conventional methods such as diffraction. The short range order of the amorphous materials remains unknown, preventing attempts to optimize performance based on electrochemical-structure correlations. In this work, a combination of local structure probes, ex-situ 7Li nuclear magnetic resonance (NMR) studies and pair distribution function (PDF) analysis of X-ray data was applied to investigate the changes in short range order that occur during the initial charge and discharge cycles. The distinct electrochemical profiles observed subsequent to the 1 st discharge have been shown to be associated with the formation of distinct amorphous lithiated silicide structures. A (de)lithiation model consisting of four different mechanisms, each being valid for regions of the charge or discharge process is proposed to explain the hysteresis and the steps in the electrochemical profile observed during lithiation and delithiation of Si. A spontaneous reaction of the fully lithiated lithium silicide with the electrolyte is directly observed in the in situ NMR experiments; this mechanism results in self-discharge, and potentially capacity loss. The rate of this self-discharge process is much slower when CMC (carboxymethylcellulose) is used as the binder. Previous work has shown that the electrochemical performance of nanoparticulate crystalline silicon is different from the bulk. The lithiation and delithiation mechanisms of nano-Si for lithium ion batteries are studied by using ex-situ solid state MAS NMR and PDF analysis. The main differences vs. bulk lithiation and delithiation are identified by characterizing the amorphous phases formed.

Key, Baris

147

A Printed Superoxide Dismutase Coated Electrode for the Study of Macrophage Oxidative Burst  

PubMed Central

The miniaturization of electrochemical sensors allows for the minimally invasive and cost effective examination of cellular responses at a high efficacy rate. In this work, an ink-jet printed superoxide dismutase electrode was designed, characterized, and utilized as a novel microfluidic device to examine the metabolic response of a 2D layer of macrophage cells. Since superoxide production is one of the first indicators of oxidative burst, macrophage cells were exposed within the microfluidic device to phorbol myristate acetate (PMA), a known promoter of oxidative burst, and the production of superoxide was measured. A 46 ± 19% increase in current was measured over a 30 min time period demonstrating successful detection of sustained macrophage oxidative burst, which corresponds to an increase in the superoxide production rate by 9 ± 3 attomoles/cell/sec. Linear sweep voltammetry was utilized to show the selectivity of this sensor for superoxide over hydrogen peroxide. This novel controllable microfluidic system can be used to study the impact of multiple effectors from a large number of bacteria or other invaders along a 2D layer of macrophages, providing an in vitro platform for improved electrochemical studies of metabolic responses. PMID:22257735

Hiatt, Leslie A.; McKenzie, Jennifer R.; Deravi, Leila F.; Harry, Reese S.; Wright, David W.; Cliffel, David E.

2012-01-01

148

Motor point delineation of the gluteus medius muscle for functional electrical stimulation: an in vivo anatomic study.  

PubMed

The purpose of this study was to delineate the motor point region of the gluteus medius muscle to aid in placing epimysial electrodes for functional electrical stimulation. Seven surgically dissected gluteus medius muscles were studied in five patients. The lateral surface of the muscle was sequentially probed with an electrical stimulator. The motor point region, which responded maximally to an applied electric current, was located on the posterolateral aspect of the muscle, adjacent to the superior margin of the piriformis, 3 cm lateral to the greater sciatic notch; it was rectangular or oval, measuring approximately 3.5 cm by 3.0 cm. The mean threshold current that produced a contraction was 14 mA (range = 2 to 26 mA). The mean minimum current required to produce a maximum contraction was 34 mA (range = 11 to 60 mA). This information provides guidelines for the placement of electrodes for functional electrical stimulation of this deeply situated muscle, and it provides electrical stimulation parameters required for adequate muscle activation. PMID:1991010

Botte, M J; Nakai, R J; Waters, R L; McNeal, D R; Rubayi, S

1991-02-01

149

Electron transfer at the contact between Al electrode and gold nanoparticles of polymer: Nanoparticle resistive switching devices studied by alternating current impedance spectroscopy  

SciTech Connect

Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO{sub 3}/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.

Ouyang, Jianyong, E-mail: mseoj@nus.edu.sg [Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore)] [Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore)

2013-12-02

150

A new disposable electrode for electrochemical study of leukemia K562 cells and anticancer drug sensitivity test.  

PubMed

Developing cost-effective and simple analysis tools is of vital importance for practical applications in bioanalysis. In this work, a new disposable electrochemical cell sensor with low cost and simple fabrication was proposed to study the electrochemical behavior of leukemia K562 cells and the effect of anticancer drugs on cell viability. The analytical device was integrated by using ITO glass as the substrate of working electrodes and paper as the electrolytic cell. The cyclic voltammetry of the K562 cells at the disposable electrode exhibited an irreversible anodic peak and the peak current is proportional to the cell number. This anodic peak is attributed to the oxidation of guanine in cells involving two protons per transfer of two electrons. For the drug sensitivity tests, arsenic trioxide and cyclophosphamide were added to cell culture media. As a result, the electrochemical responses of the K562 cells decreased significantly. The cytotoxicity curves and results obtained corresponded well with the results of CCK-8 assays. In comparison to conventional methods, the proposed method is simple, rapid and inexpensive. More importantly, the developed sensor is supposed to be a single-use disposable device and electrodes were prepared "as new" for each experiment. We think that such disposable electrodes with these characteristics are suitable for experimental study with cancer cells or other types of pathogens for disease diagnosis, drug selection and on-site monitoring. PMID:24140828

Yu, Chunmei; Zhu, Zhenkun; Wang, Li; Wang, Qiuhong; Bao, Ning; Gu, Haiying

2014-03-15

151

Impedance spectroscopy study of a catechol-modified activated carbon electrode as active material in electrochemical capacitor  

NASA Astrophysics Data System (ADS)

Modified activated carbon (Norit S-50) electrodes with electrochemical double layer (EDL) capacitance and redox capacitance contributions to the electric charge storage were tested in 1 M H2SO4 to quantify the benefit and the limitation of the surface redox reactions on the electrochemical performances of the resulting pseudo-capacitive materials. The electrochemical performances of an electrochemically anodized carbon electrode and a catechol-modified carbon electrode, which make use both EDL capacitance of the porous structure of the carbon and redox capacitance, were compared to the performances obtained for the pristine carbon. Nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the BET surface area, pore size distribution, pore volume and average pore diameter. The electrochemical behavior of carbon materials was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The EIS data were discussed by using a complex capacitance model that allows defining the characteristic time constant, the global capacitance and the frequency at which the maximum charge stored is reached. The EIS measurements were achieved at different dc potential values where a redox activity occurs and the evolution of the capacitance and the capacitive relaxation time with the electrode potential are presented. Realistic galvanostatic charge/discharge measurements performed at different current rates corroborate the results obtained by impedance.

Cougnon, C.; Lebègue, E.; Pognon, G.

2015-01-01

152

First-principles study of point defects in thorium carbide  

NASA Astrophysics Data System (ADS)

Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

Pérez Daroca, D.; Jaroszewicz, S.; Llois, A. M.; Mosca, H. O.

2014-11-01

153

Microparticle electrodes and single particle microbatteries: electrochemical and in situ microRaman spectroscopic studies.  

PubMed

Studies of the intrinsic electrochemical, structural, and electronic propertiesof microparticles of energy storage materials can provide much needed insight into the factors that control various aspects of the performance of technical electrodes for battery applications. This Account summarizes efforts made in our laboratories toward the development and implementation of methods for the in situ electrical, optical, and spectroscopic characterization of microparticles of a variety of such materials, including Ni hydroxide, Zn, carbon, and lithiated Mn and Co oxides. In the case of Ni hydroxide, the much darker appearance of NiOOH compared to the virtually translucent character of virgin Ni(OH)2 allowed for the spatial and temporal evolution of charge flow within spherical microparticles of Ni(OH)2 to be monitored in real time during the first scan toward positive potentials using computer-controlled video imaging. In situ Raman scattering measurements involving single microparticles of Zn harvested from a commercial Zn|MnO2 battery revealed that passive films formed in strongly alkaline solutions by stepping the potential from 1.55 V to either 0.7 or 0.8 V vs SCE displayed a largely enhanced feature at ca. 565 cm(-1) ascribed to a longitudinal optical phonon mode of ZnO, an effect associated with the presence of interstitial Zn and oxygen deficiencies in the lattice. In addition, significant amounts of crystalline ZnO could be detected only for passive films formed at the same two potentials after the electrodes had been roughened by a single passivation-reduction step. Quantitative correlations were found in the case of LiMn2O4 and KS-44 graphite between the Raman spectral properties and the state of charge. In the case of KS-44, a chemometrics analysis of the spectroscopic data in the potential region in which the transition between dilute phase 1 and phase 4 of lithiated graphite is known to occur made it possible to determine independently the fraction of each of the two phases present as a function of potential without relying on the coulometric information. Also featured in this Account are methods we developed for the assembly and electrochemical characterization of Zn|MnO2 and nickel|metal-hydride Ni|MH alkaline batteries incorporating single microparticles of the active materials. As evidenced from the data collected, the voltage-time profiles for constant current operation for both types of devices were found to be similar to those of commercially available batteries involving the same chemistries. The ability to monitor the state of charge of individual particles based strictly on spectroscopic data is expected to open exciting new prospects for visualizing the flow of charge within electrodes in Li-ion batteries, an area that is being vigorously pursued in our laboratories. PMID:23530836

Jebaraj, Adriel Jebin Jacob; Scherson, Daniel A

2013-05-21

154

A mortality cohort study among workers in a graphite electrode production plant in Italy  

PubMed Central

Aims: To investigate mortality from cancer and other diseases among workers in a graphite electrode production plant in Italy. Methods: A total of 1291 males actively employed between 1 January 1950 and 31 December 1989 who had worked at the plant for at least one year were studied. The follow up extended from 1950 to 1997. Standardised mortality ratios (SMR) and their 95% confidence intervals (CI) were computed using mortality rates for the Italian and regional male population. Results: Excess mortality was observed for all causes (SMR 1.44, CI 1.32 to 1.56), all cancers (SMR 1.27, CI 1.07 to 1.50), liver cancer (SMR 4.19, CI 2.68 to 6.23), silicosis (SMR 66.39, CI 52.56 to 82.7), and cirrhosis and other chronic diseases of the liver (SMR 1.87, CI 1.31 to 2.59) in comparison with the national male population. When regional rates were used to calculate the number of expected deaths, SMRs remained higher for silicosis (SMR 57.32, 42.11 to 76.22), and liver cancer (SMR 2.57, 1.57 to 3.97). Mortality from silicosis was increased in workers hired at young ages (<25 years, SMR 81.79; 25–34 years, SMR 82.73), and in workers aged <45 at death (SMR 333.3, CI 159.8 to 613). Mortality from liver cancer increased threefold (SMR 3.11, CI 1.78 to 5.05) in workers with more than 10 years of employment at the plant during the manufacture of Karbate products. Conclusions: Results support the association between excess mortality from silicosis and occupational exposure to siliceous sands experienced during graphite electrode manufacturing. The observed excess mortality from liver cancer is compatible, to some extent, with exposures that may have occurred during the manufacture of phenolic and furfuryl resins treated products, although a role of lifestyle factors and viral infections cannot be excluded. PMID:14739393

Merlo, D; Garattini, S; Gelatti, U; Simonati, C; Covolo, L; Ceppi, M; Donato, F

2004-01-01

155

Liquid electrode  

DOEpatents

A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.

Ekechukwu, Amy A. (Augusta, GA)

1994-01-01

156

Empirical study of unipolar and bipolar configurations using high resolution single multi-walled carbon nanotube electrodes for electrophysiological probing of electrically excitable cells  

NASA Astrophysics Data System (ADS)

Identifying the neurophysiological basis underlying learning and memory in the mammalian central nervous system requires the development of biocompatible, high resolution, low electrode impedance electrophysiological probes; however, physically, electrode impedance will always be finite and, at times, large. Herein, we demonstrate through experiments performed on frog sartorius muscle that single multi-walled carbon nanotube electrode (sMWNT electrode) geometry and placement are two degrees of freedom that can improve biocompatibility of the probe and counteract the detrimental effects of MWNT/electrolyte interface impedance on the stimulation efficiency and signal-to-noise ratio (SNR). We show that high aspect ratio dependent electric field enhancement at the MWNT tip can boost stimulation efficiency. Derivation of the sMWNT electrode's electrical equivalent indicates that, at low stimulus voltage regimes below 1 V, current conduction is mediated by charge fluctuation in the double layer obviating electrolysis of water, which is potentially toxic to pH sensitive biological tissue. Despite the accompanying increase in electrode impedance, a pair of closely spaced sMWNT electrodes in a two probe (bipolar) configuration maintains biocompatibility and enhances stimulation efficiency and SNR compared to the single probe (unipolar) configuration. For stimulus voltages below 1 V, the electrical equivalent verifies that current conduction in the two probe configuration still proceeds via charge fluctuation in the double layer. As an extracellular stimulation electrode, the two sMWNT electrodes comprise a current dipole that concentrates the electric field and the current density in a smaller region of sartorius; consequently, the bipolar configuration can elicit muscle fiber twitching at low voltages that preclude electrolysis of water. When recording field potentials, the bipolar configuration subtracts the potential between two points allowing for the detection of higher signal amplitudes. As a result, SNR is improved. These results indicate that use of the high aspect ratio MWNT in a bipolar configuration can achieve a biocompatible electrode that offers enhanced stimulation efficiency and higher SNR.

de Asis, Edward D., Jr.; Leung, Joseph; Wood, Sally; Nguyen, Cattien V.

2010-03-01

157

Investigation and Design Studies of SOFC Electrode Performance at Elevated Pressure  

SciTech Connect

An experimental program was set forth to study fuel cell performance at pressure and under various compositions. Improvement in cathode electrode performance is on the order of 33-40% at pressures of 6.4 Bara compared to atmospheric pressure. Key cathode operational parameters are the concentration and partial pressure of O2, and temperature. The effect of partial pressure of oxygen (PO2) decreases the activation polarization, although there appears to be a secondary effect of absolute pressure as well. The concentration of oxygen impacts the diffusion component of the polarization, which is largely insensitive to absolute pressure. The effect of pressure was found to reduce the total polarization resistance of full fuel-cells beyond the reduction determined for the cathode alone. The total reduction in ASR was on the order of 0.10 ohm-cm2 for a pressure increase from 1 to 6.5 Bara, with about 70% of the improvement being realized from 1 to 4 Bara. An important finding was that there is an effect of steam on the cathode that is highly temperature dependent. The loss of performance at temperatures below 850 C was very large for the standard LSM + YSZ cathodes.

Ted Ohrn; Shung Ik Lee

2010-07-31

158

Study of methods to increase cluster/dislocation loop densities in electrodes  

NASA Astrophysics Data System (ADS)

Recent research has developed a technique for imbedding ultra-high density deuterium ``clusters'' (50 to 100 atoms per cluster) in various metals such as Palladium (Pd), Beryllium (Be) and Lithium (Li). It was found the thermally dehydrogenated PdHx retained the clusters and exhibited up to 12 percent lower resistance compared to the virginal Pd samplesootnotetextA. G. Lipson, et al. Phys. Solid State. 39 (1997) 1891. SQUID measurements showed that in Pd these condensed matter clusters approach metallic conditions, exhibiting superconducting propertiesootnotetextA. Lipson, et al. Phys. Rev. B 72, 212507 (2005ootnotetextA. G. Lipson, et al. Phys. Lett. A 339, (2005) 414-423. If the fabrication methods under study are successful, a large packing fraction of nuclear reactive clusters can be developed in the electrodes by electrolyte or high pressure gas loading. This will provide a much higher low-energy-nuclear- reaction (LENR) rate than achieved with earlier electrodeootnotetextCastano, C.H., et al. Proc. ICCF-9, Beijing, China 19-24 May, 2002..

Yang, Xiaoling; Miley, George H.

2009-03-01

159

DEMS study of gas evolution at thick graphite electrodes for lithium-ion batteries: the effect of ?-butyrolactone  

NASA Astrophysics Data System (ADS)

Differential electrochemical mass spectrometry (DEMS) was used to study the reductive decomposition of an electrolyte based on ethylene carbonate/dimethyl carbonate (EC/DMC), as well as the formation of a solid electrolyte interphase (SEI) in this electrolyte, at thick (75-100 ?m) porous graphite composite electrodes. A number of graphite electrodes differing in their electrochemical lithium intercalation properties were investigated in potential-sweep experiments. They proved to be similar with respect to the evolution of ethylene and hydrogen gas during the first two charge/discharge cycles. Due to an incomplete coulombic conversion, a high irreversible capacity, as well as slow diffusion kinetics and an enhanced ohmic resistance of the electrodes, SEI formation on these thick electrodes was not yet complete after the first charge/discharge cycle. Undesired gas evolution can be reduced by adding ?-butyrolactone (GBL) as an electrolyte co-solvent. The amount of ethylene and hydrogen gas evolved decreases with increasing percentages of GBL in an EC/DMC electrolyte, indicating that the SEI layer is built up from GBL rather than from EC decomposition products.

Lanz, Martin; Novák, Petr

160

Carbon nanotube detectors for microchip CE: comparative study of single-wall and multiwall carbon nanotube, and graphite powder films on glassy carbon, gold, and platinum electrode surfaces.  

PubMed

The performance of microchip electrophoresis/electrochemistry system with carbon nanotube (CNT) film electrodes was studied. Electrocatalytic activities of different carbon materials (single-wall CNT (SWCNT), multiwall CNT (MWCNT), carbon powder) cast on different electrode substrates (glassy carbon (GC), gold, and platinum) were compared in a microfluidic setup and their performance as microchip electrochemical detectors was assessed. An MWCNT film on a GC electrode shows electrocatalytic effect toward oxidation of dopamine (E(1/2) shift of 0.09 V) and catechol (E(1/2) shift of 0.19 V) when compared to a bare GC electrode, while other CNT/carbon powder films on the GC electrode display negligible effects. Modification of a gold electrode by graphite powder results in a strong electrocatalytic effect toward oxidation of dopamine and catechol (E(1/2) shift of 0.14 and 0.11 V, respectively). A significant shift of the half-wave potentials to lower values also provide the MWCNT film (E(1/2) shift of 0.08 and 0.08 V for dopamine and catechol, respectively) and the SWCNT film (E(1/2) shift of 0.10 V for catechol) when compared to a bare gold electrode. A microfluidic device with a CNT film-modified detection electrode displays greatly improved separation resolution (R(s)) by a factor of two compared to a bare electrode, reflecting the electrocatalytic activity of CNT. PMID:17366488

Pumera, Martin; Merkoçi, Arben; Alegret, Salvador

2007-04-01

161

Effect of silicate ions on electrode overvoltage  

NASA Technical Reports Server (NTRS)

The influence of the addition of a silicate to a caustic solution (KOH) is studied in order to determine the degree to which silicates inhibit the corrosion of chrysotile under conditions of electrolysis at working temperatures of 100 C and above. In an alkaline solution containing various silicate concentrations, current density was increased and electrode overvoltage was measured. Results show that silicate ion concentrations in the electrolyte increase with temperature without effecting electrochemical performance up to 115 C at 700 MA/sqcm. At this point the concentration is about 0.5 g Si/100 g KOH. Beyond this limit, electrolytic performance rapidly degenerates due to severe oxidation of the electrodes.

Gras, J. M.; Seite, C.

1979-01-01

162

Surface-enhanced Raman spectroscopy of surfactants on silver electrodes  

SciTech Connect

Surface-enhanced Raman spectroscopy (SERS) has been used to study different kinds of surfactants (cationic, anionic, and nonionic surfactants) adsorbed on a roughened Ag electrode. Spectral assignments are made for the SERS spectrum of cetylpyridinium chloride (CPC), and it is shown that the molecule is oriented with its pyridinium ring end-on at the electrode surface at potentials positive to the point of zero charge (pzc) on Ag.

Sun, Soncheng; Birke, R.L.; Lombardi, J.R. (City Univ. of New York, NY (USA))

1990-03-08

163

Effects of Electrode Position on Spatiotemporal Auditory Nerve Fiber Responses: A 3D Computational Model Study  

PubMed Central

A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance. PMID:25755675

2015-01-01

164

Theoretical and experimental studies of the electrochemistry of p-aminophenol on a golden electrode  

NASA Astrophysics Data System (ADS)

The geometric parameters, vibrational frequencies, and thermochemical values of p-quinonimine ( p-AQ) and p-aminophenol ( p-AP) were computed ab initio (IIF) and by the density functional theory (DFT) method with the 6-31G( d, p) basis set. Cyclic voltammetry with a golden electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.728 V. The standard electrode potentials of half reactions for p-QI and p-AP were calculated using the free energies and solvation energies of p-QI, p-AP, p-benzoquinone ( p-BQ), and hydroquinone ( p-HQ). The results showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.743 V at the B3LYP/6-31G( d, p) level and 0.755 V at the HF/6-31G( d, p) level. The standard electrode potentials computed at the B3LYP/6-31G( d, p) and HF/6-31G( d, p) levels were close to their experimental values.

Song, Y. Z.; Xie, J. M.; Song, Y.; Ye, Y.

2007-10-01

165

Microtitrimetry by differential electrolytic potentiometry using metallic electrodes and nanomaterials modified metallic electrodes  

NASA Astrophysics Data System (ADS)

For the first time silver wire electrodes have been coated with carbon nanotubes using floating catalyst chemical vapor deposition (CVD) method. The production of CNTs has been conducted in a horizontal tubular reactor. Acetylene gas was used as a carbon source. Ferrocene has been used as a catalyst precursor for the growth of CNT. Different parameters have been optimized to get a high yield of CNTs and ensure their growth on the silver electrodes using univariate method. The parameters studied include the hydrogen flow rate, acetylene flow rate, temperature of the furnace, time of the reaction and the location of the electrodes in the reactor tube. The optimum conditions for those parameters were: for hydrogen and acetylene, the flow rates were 25 mL /min and 75 mL / min respectively. The furnace temperature was found to be 700 °C and the reaction time was 15 minutes. Regarding the location of the silver wires it should be located in the first 10 cm of the front side of the tube. Scanning electron microscopy (SEM) and transition electron microscopy (TEM) have been used to characterize carbon on silver electrodes. According to the experimental results, TEM figures show that CNT produced on Silver wire is multiwall carbon nanotubes MWCNT. Silver electrodes either pure or coated with CNT were used as indicating systems in micro titration using both dc differential electrolytic potentiometry (DEP) and mark-space bias DEP techniques. All types of titrimetric reactions were investigated using different types of electrodes like Pt and gold for oxidation reduction titrations, antimony electrodes for acid base titrations, silver electrodes for precipitation titrations in addition to Ag-CNT electrodes. End points at volumes of 1 microL were determined. Different parameters were optimized like the current density, the percentage bias, the volume of the sample and the concentrations of the reactants. Microtitrimetry has been applied on several types of analytes; Ferrous, Ascorbic acid, chloride, Cyanide, Sodium Bicarbonate and Ketoconazole in aqueous and non- aqueous medium. The performance of Ag-CNT electrodes was found to be much better than the normal silver electrodes. The differential titration curves obtained were symmetrical with significant heights. For silver electrodes coated with CNT the first derivative of the potential was found to give better curves than the normal differential curves, hence the end point location was successfully achieved. A micro liter injector that can deliver volumes at a micro liter level was designed and fabricated. Microtitrimetry which requires volumes of reagents at the micro liter level can offer a solution to the large consumption of reagents in all classical titrimetric processes. Hence, large savings in reagents as well as less waste will reach the environment.

Amro, Abdulaziz Nabil

166

Chalk Point steam electric station studies Patuxent Estuary studies: ichthyoplankton population studies, 1979. Final report  

SciTech Connect

Two years of riverwide ichthyoplankton data were collected as a part of a series of studies at the Chalk Point Steam Electric Station (SES) to contribute data necessary to evaluate information to be presented in the 316 variance demonstration document scheduled for Units 1 and 2 of this facility during 1981. These studies also provided information on the regional spatial and temporal distribution of fish eggs and larvae required to put nearfield studies conducted by the Potomac Electric Power Company into regional context. The principal species collected were white perch, striped bass, bay anchovy, sliversides, naked goby, yellow perch, and clupeids.

Mihursky, J.A.; Wood, K.V.; Kerig, S.; Setzler-Hamilton, E.M.

1980-04-01

167

On the Origins of Pointing in Infancy: A Pilot Study.  

ERIC Educational Resources Information Center

Observations were made of the incidence of pointing behavior among infants differing in age when a radio-controlled truck entered the room in which mother and infant were seated. Infants' reactions over 5 to 6 minutes were recorded on videotape. Recordings were analyzed to establish the incidence of pointing, handedness of pointing, whether…

Butterworth, George; Adamson-Macedo, Elvidina

168

Study on Edge Detection of LIDAR Point Cloud  

Microsoft Academic Search

The LIDAR points should be interpolated to grids by the method of the edge detection with images directly. That will damage the position precision of the edge points. This paper proposes methods of using height difference and the spatial structure information of points cloud. The methods transition from 2D level to 3D level, they get a clear edge, retains the

Rongrong Wang; Xudong Lai; Wenguang Hou

2011-01-01

169

Enhanced capacitance of composite TiO2 nanotube/boron-doped diamond electrodes studied by impedance spectroscopy  

NASA Astrophysics Data System (ADS)

We report on novel composite nanostructures based on boron-doped diamond thin films grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (~200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of the Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman spectroscopy. The composite electrodes TiO2/BDD are characterized by a significantly higher capacitive current compared to BDD films deposited directly onto a Ti substrate. The novel composite electrode of TiO2 nanotube arrays overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver a specific capacitance of 2.10, 4.79, and 7.46 mF cm-2 at a scan rate of 10 mV s-1 for a [B]/[C] ratio of 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and the excellent rate capability could be attributed to the synergistic effect of TiO2 treatment in CH4 : H2 plasma and the high electrical conductivity of BDD layers. The analysis of electrochemical impedance spectra using an electric equivalent circuit allowed us to determine the surface area on the basis of the value of constant phase element.

Siuzdak, K.; Bogdanowicz, R.; Sawczak, M.; Sobaszek, M.

2014-12-01

170

A structural study of solid electrolyte interface on negative electrode of lithium-Ion battery by electron microscopy.  

PubMed

For the last decades, the performance of the lithium-ion battery (LIB) has been significantly improved and its applications have been expanding rapidly. However, its performance has yet to be enhanced.In the lithium-ion battery development, it is important to elucidate the electrode structure change in detail during the charge and discharge cycling. In particular, solid electrolyte interface (SEI) formed by decomposition of the electrolytes on the graphite negative electrode surface should play an important role for battery properties. Therefore, it is essential to control the structure and composition of SEI to improve the battery performance. Here, we conducted a scanning electron microscope (SEM) and transmission electron microscope (TEM) study to elucidate the structures of the SEI during the charge and discharge process using LiNi1/3Co1/3Mn1/3O2 [1] cathode and graphite anode. [2] Since SEI is a lithium-containing compound with high activity, it was observed without being exposed to the atmosphere. The electrodes including SEI were sampled after dismantling batteries with cutoff voltages of 3V and 4.2V for the charge process and 3V for the discharge process. Fig.1 shows SEM images of the graphite electrode surface during the charge and discharge process. The change of the SEI structure during the process was clearly observed. Further, TEM images showed that the SEI grew thicker during the charge process and becomes thinner when discharged. These results with regard to the reversible SEI structure could give a new insight for the battery development.jmicro;63/suppl_1/i21/DFU056F1F1DFU056F1Fig. 1.SEM images of the graphite electrode surface:(a) before charge process;(b) with charge-cutoff voltage of 3.0V; (c) with charge-cutoff voltage of 4.2V; (d) with discharge-cutoff voltage of 3.0V. PMID:25359815

Matsushita, Tadashi; Watanabe, Jiro; Nakao, Tatsuya; Yamashita, Seiichi

2014-11-01

171

Application of iron electrode corrosion enhanced electrokinetic-Fenton oxidation to remediate diesel contaminated soils: A laboratory feasibility study  

NASA Astrophysics Data System (ADS)

SummaryDiesel soil contamination on gas stations or refinery plants is a worldwide environmental problem. The main objectives of this study were to (1) evaluate the efficiency of electrokinetic (EK) by using different electrode materials (graphite and iron rods) and electrolytes (tap water, 0.01 M NaCl, and 0.1 M NaCl) on the remediation of diesel contaminated soils, and (2) evaluate the feasibility of total petroleum hydrocarbon-diesel (TPH-D) reducing in soils via EK-Fenton oxidation enhanced by corroded iron electrode. The EK and EK-Fenton experiments were conducted in batch and sand box experiments, respectively. Batch experiments reveal that the most appropriate electrolyte was 0.1 M NaCl when iron electrode was used in the EK system. Sand box experiments indicate that the TPH-D concentration dropped from 10,000 to 300 mg kg -1 when amorphous iron/total iron (Fe o/Fe t) ratio increased from 0.1 to 0.33, with the addition of 8% of H 2O 2 and 0.1 M NaCl after 60 days of EK-Fenton operation. Electrokinetically enhanced oxidation with the presence of both H 2O 2 and Fe 3O 4 (iron electrode corrosion) resulted in higher TPH-D removal efficiency (97%) compared to the efficiencies observed from EK (55%) or Fenton oxidation (27%) alone. This demonstrates that EK-Fenton oxidation catalyzed by iron electrode corrosion is a valuable direction to efficiently and effectively remediate diesel contaminated soils.

Tsai, Tzai-Tang; Sah, Jygau; Kao, Chih-Ming

2010-01-01

172

Study of the ultraviolet emission of the electrode coatings of arc welding.  

PubMed

The optical emission properties of several minerals components employed in electrode coatings of arc welding have been investigated. The X-ray diffraction analysis shows that the composition of 14 commercial electrode coatings collected from different countries (Spain, France, UK, Poland, Argentina and Germany), consists of quartz, calcite, sodium and potassium rich feldspars, muscovite and rutile. The natural thermal stimulated luminescence (TSL) of these mineral phases, measured in the range of 200-800 nm at different temperatures (from room temperature to 400 degrees C) displays UV-A (wavelengths of 320 nm to 400 nm) and UV-B (from 280 nm to 320 nm) emissions, with the exception of rutile. The UV-B radiation, commonly described as the most dangerous form of radiation to human life, is here associated with structural defects in the crystallographic lattice of the mineral components of electrode coatings. PMID:15369993

Garcia-Guinea, J; Correcher, V; Lombardero, M; Gonzalez-Martin, R

2004-08-01

173

Application of Gold Electrodes for the Study of Nickel Based Homogeneous Catalysts for Hydrogen Oxidation  

SciTech Connect

Gold and glassy carbon working electrode materials are compared as suitable substrates for the hydrogen oxidation reaction with Ni(PCy2Nt-Bu2)2(BF4)2 used as a catalyst. Voltammetric responses showing electrocatalytic hydrogen oxidation mediated by the homogeneous electrocatalyst Ni(PCy2Nt-Bu2)2(BF4)2 are identical at glassy carbon and gold electrodes, which shows that gold electrode can be used for hydrogen oxidation reaction. This work is supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under FWP 56073.

Nepomnyashchii, Alexander B.; Liu, Fei; Roberts, John A.; Parkinson, Bruce A.

2013-08-12

174

In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium  

NASA Astrophysics Data System (ADS)

Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque time curves presente saw-tooth fashion. The maximum torque has a range of 0.3 1.9 N mm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.

Zhang, Xiangming; Ma, Nianke; Fan, Hualin; Niu, Guodong; Yang, Wei

2007-06-01

175

Electrode polarization studies in hot corrosion systems. Progress report, 1 June 1979-31 April 1980  

SciTech Connect

Work on the following discrete tasks is reported: Electrode Polarization Studies in Molten Sodium Carbonate: A comprehensive set of tests has been performed on iron, nickel, and types 304 and 316 stainless steel in gas mixtures of controlled CO, CO/sub 2/, H/sub 2/, and H/sub 2/S pressures at a total pressure of one atmosphere and in a temperature range of 900 to 1000/sup 0/C. The polarization curves thus derived have been reduced to a set of empirical kinetic constants via computer modelling. Gas/Metal Reactions in Mixed Oxidants: Oxidation of iron in gas mixtures of controlled P/sub CO/, P/sub CO//sub 2/, P/sub H//sub 2/ and P/sub H//sub 2//sub S/ at a total pressure of one atmosphere and a temperature of 900/sup 0/C has been studied. In the P/sub S//sub 2/ and P/sub O//sub 2/ ranges employed sulfide scales were formed; P/sub O//sub 2/ influenced the short term sulfidation kinetics. Specimen geometry was seen as a significant factor influencing long term kinetics. Liquid Line Corrosion: A reproducible corrosive attack is seen at the metal/molten carbonate/gas phase junction. This attack can be quantitatively evaluated and explained in terms of a diffusion model. Evaluation of Reaction Kinetics from Polarization Data (addendum): previous modelling procedures have been expanded to include one or more anodic reactions displaying passive behavior.

Devereux, O.F.

1980-02-01

176

Point-to-Point Car Racing: an Initial Study of Evolution Versus Temporal Difference Learning  

Microsoft Academic Search

This paper considers variations on an extremely simple form of car racing, the challenge being to visit as many way-points as possible in a fixed amount of time. The simplicity of the models enables a very thorough evaluation of various learning algorithms and control architectures, and enables other researchers to work on the same models with relative ease. The models

Simon M. Lucas; Julian Togelius

2007-01-01

177

Point defect structures in gallium arsenide studied by positron spectroscopies  

NASA Astrophysics Data System (ADS)

Positron spectroscopies were used to examine the point defect structure of gallium arsenide. Experiments to investigate the properties of native defects in as-grown GaAs were performed. The defect production during electron irradiation, hydrogen implantation and plastic deformation of GaAs was studied by positron techniques. New information is obtained especially on the properties of vacancy defects. In as-grown GaAs, the ionization levels of arsenic vacancies are determined. In semi-insulation GaAs, the metastable state of the EL2 defect is shown to contain a monovacancy. The introduction of vacancies and antisite defects to the gallium sublattice is observed in electron irradiation of GaAs. In deformed GaAs, the simultaneous formation of vacancies, antisites and vacancy complexes is detected. The depth distributions of vacancies are determined after hydrogen implantation in semi-insulating GaAs, and the recovery of the implantation damage during isochronal annealing is investigated.

Saarinen, Kimmo

178

Platinum loss and migration in porous gas diffusion fuel cell electrodes as studied by Rutherford backscattering  

SciTech Connect

Long-term operation of phosphoric acid fuel cell produces severe migration of the highly dispersed electrocatalyst, Pt, from the cathode to the anode. We have examined, before and after extended operation, the porous gas diffusion electrode assemblies by conventional Rutherford backscattering spectrometry using the ion beam facility at Los Alamos. In addition, we have made computer simulations to the data that give catalyst concentration as a function of depth. The data demonstrate that after extended operation (500 to 2000 hours), Pt is lost from the cathode and is redeposited at the outermost surface layers of the anode electrode structure. This loss is significant and several factors contributing to it are discussed.

Borodovsky, L.; Beery, J.G.; Paffett, M.

1986-01-01

179

Turbulent mixing and deposition studies for single point aerosol sampling  

NASA Astrophysics Data System (ADS)

A generic mixing system has been developed which creates suitable conditions for single point stack sampling of effluent air emission points. Results show that the system performance is well within the EPA mixing criteria---the COVs for velocity, tracer gas concentration and 10 mum AD aerosol particles are less than half of the EPA permissible level of 20%. Experiments were conducted to characterize the degree of mixing at downstream locations as affected by several types of flow disturbances, including 90° elbows and commercial static mixing devices. It was found that the mixing is impacted by the upstream flow turbulence and that the use of static mixing elements can greatly enhance the mixing process. A stack system has been characterized which creates conditions suitable for single point representative sampling. The stack system could be used in both existing and new stack or duct configurations. It could also be used as an aerosol wind tunnel for testing various sampling devices. Results show that the system performance is well within the EPA permissible limits. A mixing model has been developed which can predict mixing of tracer gas in turbulent air flows in piping systems comprised of a series of 90° elbows. The model uses the concept of an equivalent length of straight pipe that would produce the same degree of mixing as the mixing element under consideration. There is good agreement between experimental and predicted results. Aerosol penetration through flow splitters was experimentally and numerically investigated. A surface plot was generated from the experimental data to predict aerosol penetration as a function of the Stokes number and the bifurcation angle between the two outlets of the splitters. The developed correlation is valid in the ranges of 0.034 ? Stk ? 1.248; 2,556 ? Re ? 13,630; and, 30° ? theta ? 180°, and should be a useful sub-model for predicting aerosol particle losses in flow splitters in software programs, e.g., DEPOSITION. Numerical studies were conducted with a commercial computational fluid dynamics (CFD) software, FLUENT, and a Lagrangian particle tracking code. Good agreement was found between the experimental and numerical results.

Gupta, Rajiv

1999-11-01

180

A novel electrode array for diameter-dependent control of axonal excitability: a Simulation study  

Microsoft Academic Search

Electrical extracellular stimulation of peripheral nerve activates the large-diameter motor fibers before the small ones, a recruitment order opposite the physiological recruitment of myelinated motor fibers during voluntary muscle contraction. Current methods to solve this problem require a long-duration stimulus pulse which could lead to electrode corrosion and nerve damage. The hypothesis that the excitability of specific diameter fibers can

Zeng Lertmanorat; Dominique M. Durand

2004-01-01

181

Structural modifications in chronic microwire electrodes for cortical neuroprosthetics: a case study  

Microsoft Academic Search

Long-term viability of chronic invasive neural probes is a necessary condition for extracting robust control signals directly from neural tissue. Although immune\\/tissue response is a leading factor in the degradation of single neuron recording, we investigate a second component of signal degradation connected to the structural changes associated with microwire electrodes chronically exposed to extracellular environments in vivo. Scanning electron

J. C. Sanchez; N. Alba; T. Nishida; C. Batich; P. R. Carney

2006-01-01

182

Structural Modifications in Chronic Microwire Electrodes for Cortical Neuroprosthetics: A Case Study  

Microsoft Academic Search

Long-term viability of chronic invasive neural probes is a nec- essary condition for extracting robust control signals directly from neural tissue. Although immune\\/tissue response is a leading factor in the degrada- tion of single neuron recording, we investigate a second component of signal degradation connected to the structural changes associated with microwire electrodes chronically exposed to extracelluar environments in vivo.

J. H. Callicott; N. F. Ramsey; K. Tallent; A. Bertolino; M. B. Knable; R. Coppola; T. Goldberg; P. Van Gelderen; V. S. Mattay; J. A. Frank; C. T. W. Moonen; D. R. Weinberger

183

Modeling of EEG electrode artifacts and thermal ripples in human radiofrequency exposure studies.  

PubMed

The effects of radiofrequency (RF) exposure on wake and sleep electroencephalogram (EEG) have been in focus since mobile phone usage became pervasive. It has been hypothesized that effects may be explained by (1) enhanced induced fields due to RF coupling with the electrode assembly, (2) the subsequent temperature increase around the electrodes, or (3) RF induced thermal pulsing caused by localized exposure in the head. We evaluated these three hypotheses by means of both numerical and experimental assessments made with appropriate phantoms and anatomical human models. Typical and worst-case electrode placements were examined at 900 and 2140?MHz. Our results indicate that hypothesis 1 can be rejected, as the induced fields cause <20% increase in the 10?g-averaged specific absorption rate (SAR). Simulations with an anatomical model indicate that hypothesis 2 is also not supported, as the realistic worst-case electrode placement results in a maximum skin temperature increase of 0.31?°C while brain temperature elevations remained <0.1?°C. These local short-term temperature elevations are unlikely to change brain physiology during the time period from minutes to several hours after exposure. The maximum observed temperature ripple due to RF pulses is <0.001?°C for GSM-like signals and <0.004?°C for 20-fold higher pulse energy, and offers no support for hypothesis 3. Thus, the mechanism of interaction between RF and changes in the EEG power spectrum remains unknown. PMID:24523224

Murbach, Manuel; Neufeld, Esra; Christopoulou, Maria; Achermann, Peter; Kuster, Niels

2014-05-01

184

Space Shuttle Earth Observation sensors pointing and stabilization requirements study  

NASA Technical Reports Server (NTRS)

The shuttle orbiter inertial measurement unit (IMU), located in the orbiter cabin, is used to supply inertial attitude reference signals; and, in conjunction with the onboard navigation system, can provide a pointing capability of the navigation base accurate to within plus or minus 0.5 deg for earth viewing missions. This pointing accuracy can degrade to approximately plus or minus 2.0 deg for payloads located in the aft bay due to structural flexure of the shuttle vehicle, payload structural and mounting misalignments, and calibration errors with respect to the navigation base. Drawbacks to obtaining pointing accuracy by using the orbiter RCS jets are discussed. Supplemental electromechanical pointing systems are developed to provide independent pointing for individual sensors, or sensor groupings. The missions considered and the sensors required for these missions and the parameters of each sensor are described. Assumptions made to derive pointing and stabilization requirements are delineated.

1976-01-01

185

Tricritical point in ferroelastic ammonium titanyl fluoride: NMR study  

SciTech Connect

Ionic mobility and phase transitions in ammonium titanyl pentafluoride (NH{sub 4}){sub 3}TiOF{sub 5} were studied using the {sup 19}F and {sup 1}H NMR data. The high-temperature phase (I) is characterized by spherically symmetric (isotropic) reorientation of [TiOF{sub 5}]{sup 3-} anions and by uniaxial reorientation of these anions in the ferroelastic phase II. A previously unknown second-order phase transition to the low-temperature modification (NH{sub 4}){sub 3}TiOF{sub 5}(III) was found at 205 K. The transition is accompanied by hindering of uniaxial rotations of [TiOF{sub 5}]{sup 3-} anions and by noticeable change of {sup 19}F magnetic shielding tensor associated with the influence of pseudo-Jahn-Teller effect. A pressure-induced tricritical point with coordinates p{sub TCR{approx}}2 kbar and T{sub TCR{approx}}170 K is estimated on the base of {sup 19}F NMR chemical shift data, and previously studied p-T diagram of (NH{sub 4}){sub 3}TiOF{sub 5}. - Graphical abstract: p-T phase diagram of (NH{sub 4}){sub 3}TiOF{sub 5}.

Kavun, V.Ya. [Institute of Chemistry, FEB RAS, Ave. Stoletiya, 159, 690022 Vladivostok (Russian Federation); Kozlova, S.G., E-mail: sgk@niic.nsc.r [Nikolaev Institute of Inorganic Chemistry, SB RAS, Ave. Lavrenteva, 3, 630090 Novosibirsk (Russian Federation); Laptash, N.M; Tkachenko, I.A. [Institute of Chemistry, FEB RAS, Ave. Stoletiya, 159, 690022 Vladivostok (Russian Federation); Gabuda, S.P [Nikolaev Institute of Inorganic Chemistry, SB RAS, Ave. Lavrenteva, 3, 630090 Novosibirsk (Russian Federation)

2010-09-15

186

Study of Cobalt(III) Corrole as the Neutral Ionophore for Nitrite and Nitrate Detection via Polymeric Membrane Electrodes  

PubMed Central

Cobalt(III) 5, 10, 15-tris(4-tert-butylphenyl) corrole was synthesized and incorporated into plasticized poly(vinyl chloride) membranes and studied as a neutral carrier ionophore via potentiometry. This cobalt(III) complex has binding affinity to nitrite, and the resulting membrane electrode yields reversible and Nernstian response toward nitrite. Enhanced nitrite selectivity is observed over other anions, including lipophilic anions such as thiocyanate and perchlorate when an appropriate amount of lipophilic cationic sites are added to the membrane phase. Detection limit to nitrite is ca. 5 µM. Using tributylphosphate as the plasticizer with the cobalt(III) corrole species yields electrodes with enhanced nitrate selectivity. PMID:25422577

Yang, Si; Meyerhoff, Mark E.

2014-01-01

187

Characterization of dry biopotential electrodes.  

PubMed

Driven by the increased interest in wearable long-term healthcare monitoring systems, varieties of dry electrodes are proposed based on different materials with different patterns and structures. Most of the studies reported in the literature focus on proposing new electrodes and comparing its performance with commercial electrodes. Few papers are about detailed comparison among different dry electrodes. In this paper, printed metal-plate electrodes, textile based electrodes, and spiked electrodes are for the first time evaluated and compared under the same experimental setup. The contact impedance and noise characterization are measured. The in-vivo electrocardiogram (ECG) measurement is applied to evaluate the overall performance of different electrodes. Textile electrodes and printed electrodes gain comparable high-quality ECG signals. The ECG signal obtained by spiked electrodes is noisier. However, a clear ECG envelope can be observed and the signal quality can be easily improved by backend signal processing. The features of each type of electrodes are analyzed and the suitable application scenario is addressed. PMID:24109978

Xie, Li; Yang, Geng; Xu, Linlin; Seoane, Fernando; Chen, Qiang; Zheng, Lirong

2013-01-01

188

Liquid electrode  

DOEpatents

A dropping electrolyte electrode is described for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions. 2 figures.

Ekechukwu, A.A.

1994-07-05

189

Point contact spectroscopy studies of the iron based superconductors  

NASA Astrophysics Data System (ADS)

Point contact spectroscopy (PCS) is used to probe both the normal and superconducting phases of the iron based superconductors. It is shown that apart from probing superconductors by Andreev reflection, PCS is also a useful technique to study exotic electron matter in correlated materials. The point contact junctions are made by two separate techniques: needle-anvil PCS and soft PCS. dI/dV measured in the superconducting phase is sensitive to the magnitude and symmetry of the superconducting order parameter. Andreev reflection spectra for the 122 and 111 families of the iron based superconductors is presented. The 122 crystals probed include electron doped Ba(Fe1-x Cox)2As2 (x = 0.05, 0.055, 0.07, 0.08), hole doped Ba0.8K0.2Fe2As2, and isoelectronic doped BaFe2(As1-xPx)2 (x = 0.24, 0.43). The 111 crystals studied are electron doped NaFe 1-xCoxAs (x = 0.02, 0.06). The Andreev spectra show clear features corresponding to multiple, nodeless superconducting gaps. The dI/dV curves are fit to the independent two band BTK model assuming isotropic s-wave order parameters. The normal state spectra of certain iron based superconductors shows a conductance enhancement around zero bias above the structural transition temperature, TS. Theoretical analysis showing that this enhancement is likely a consequence of orbital fluctuations is discussed. The nonsuperconducting compounds probed are AEFe2As2 (AE = Ca,Sr,Ba) and Fe1+yTe. For AE = Sr,Ba orbital fluctuations are detected above TS while for AE = Ca these fluctuations start below TS. Co doping preserves the orbital fluctuations while K doping suppresses it. The fluctuations are only seen at those dopings and temperatures where for detwinned crystals, an in-plane resistive anisotropy is known to exist. The normal state spectra thus provides evidence that PCS is sensitive to orbital fluctuations in the iron based superconductors. A thorough analysis of Ba(Fe1-xCo x)2As2 is performed and a new region on the phase diagram is defined where PCS picks up orbital fluctuations. Diagnostics performed to ensure the quality of the PCS junctions are discussed in detail. Preliminary data for dI/dV under applied magnetic field and compressive stress is also presented.

Arham, Hamood Zafir

190

Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes  

SciTech Connect

Under precisely controlled conditions, atomic gold electrodes with even or odd number of Au atoms per polyaniline repeat unit (Pt/PANI/AuN for 0 electrodes is compared with that of macro gold and PANI coated platinum electrodes by testing electrochemical oxidation of n-propanol and iso-propanol. This study allowed us to separate the behavior dominated by that of macroscopic gold in strongly alkaline medium and by that of the quantized odd–even effect of atomic gold. Within this overarching scope, there is a specific oxidation pattern attributable to the structural differences between the two isomers of propanol. The significance of this research lies in the recognition of high specific catalytic activity of atomic gold, which is at least three orders of magnitude higher than that of bulk gold for the oxidation of alcohols. It points to a substantial saving of the precious metal without the loss of catalytic activity, which is important in fuel cells and in other energy conversion device applications.

Schwartz, Ilana; Jonke, Alex P.; Josowicz, Mira A.; Janata, Jiri

2012-11-01

191

Rotational thromboelastometry and multiple electrode platelet aggregometry in four patients with abnormal routine coagulation studies before removal of epidural catheters after major surgery: a case series and research study  

PubMed Central

Introduction Routine coagulation tests have a low predictability for perioperative bleeding complications, and spinal hematoma after removal of epidural catheters is very infrequent. Thromboelastometry and point-of-care platelet aggregometry may improve hemostatic monitoring but have not been studied in the context of safety around epidural removal. Methods Twenty patients who received an epidural catheter for major thoracoabdominal and abdominal surgery were included prospectively. In addition to routine coagulation tests, rotational thromboelastometry and multiple electrode platelet aggregometry were carried out. Results A coagulation deficit was suggested by routine coagulation tests on the intended day of epidural catheter removal in four out of 20 patients. Prothrombin time-international normalized ratio was elevated to 1.5 in one patient (normal range: 0.9 to 1.2) while rotational thromboelastometry and multiple electrode platelet aggregometry parameters were within normal limits. Activated partial thromboplastin time was elevated to 47 to 50 seconds in the remaining three patients (normal range 28 to 45 seconds). Rotational thromboelastometry showed that one of the patients’ results was due to heparin effect: the clotting time with the HEPTEM® activator was 154 seconds as compared to 261 seconds with INTEM. The three remaining patients with prolonged routine coagulation test results had all received over 1L of hydroxyethyl starch (Venofundin®) and thrombosis prophylaxis with low-molecular-weight heparin (enoxaparin). Rotational thromboelastometry and multiple electrode platelet aggregometrygave normal or hypercoagulative signals in most patients. Conclusions This case series is new in that it examines rotational thromboelastometry and multiple electrode platelet aggregometry postoperatively in the context of epidural analgesia and shows that they may be clinically useful. These methods should be validated before they can be used for standard patient care. PMID:24377397

2013-01-01

192

Control of electrode depth in electroslag remelting  

DOEpatents

A method of and apparatus for controlling an electroslag remelting furnace by driving the electrode at a nominal speed based upon melting rate and geometry while making minor proportional adjustments based on a measured metric of the electrode immersion depth. Electrode drive speed is increased if a measured metric of electrode immersion depth differs from a set point by a predetermined amount, indicating that the tip is too close to the surface of a slag pool. Impedance spikes are monitored to adjust the set point for the metric of electrode immersion depth based upon one or more properties of the impedance spikes.

Melgaard, David K. (Albuquerque, NM); Shelmidine, Gregory J. (Tijeras, NM); Damkroger, Brian K. (Albuquerque, NM)

2002-01-01

193

Subdural Electrodes  

PubMed Central

Subdural electrodes are frequently used to aid in the neurophysiological assessment of patients with intractable seizures. We review the indications for these, their uses for localizing epileptogenic regions and for localizing cortical regions supporting movement, sensation, and language. PMID:20573543

Lesser, Ronald P.; Crone, Nathan E.; Webber, W.R.S.

2010-01-01

194

Lifetime studies of high power rhodium/tungsten and molybdenum electrodes for application to AMTEC (alkali metal thermal-to-electric converter)  

NASA Technical Reports Server (NTRS)

A detailed and fundamental model for the electrochemical behavior of AMTEC electrodes is developed which can aid in interpreting the processes which occur during prolonged operation of these electrodes. Because the sintering and grain growth of metal particles is also a well-understood phenomenon, the changes in electrode performance which accompany its morphological evolution may be anticipated and modeled. The grain growth rate observed for porous Mo AMTEC electrodes is significantly higher than that predicted from surface diffusion data obtained at higher temperatures and incorporated into the grain growth model. The grain growth observed under AMTEC conditions is also somewhat higher than that measured for Mo films on BASE (beta-alumina solid electrolyte) substrates in vacuum or at similar temperatures. Results of modeling indicate that thin Mo electrodes may show significant performance degradation for extended operation (greater than 10,000 h) at higher operating temperatures (greater than 1150 K), whereas W/Rh and W/Pt electrodes are expected to show adequate performance at 1200 K for lifetimes greater than 10,000 h. It is pointed out that current collection grids and leads must consist of refractory metals such as Mo and W which do not accelerate sintering or metal migration.

Williams, R. M.; Jeffries-Nakamura, B.; Underwood, M. L.; O'Connor, D.; Ryan, M. A.; Kikkert, S.; Bankston, C. P.

1990-01-01

195

Streamer initiation in mineral oil. Part I: electrode surface effect under impulse voltage  

Microsoft Academic Search

Presents a study of streamer inception in mineral transformer oil, in point-plane and rod-plane geometry under impulse voltage. The measurements performed with points and rods over a wide range of tip radii show a marked decrease of initiation fields when the electrode radius is increased. The initiation field is divided by 30 over the investigated range (from 1 ?m points

O. Lesaint; T. V. Top

2002-01-01

196

Study of freezing-point depression of selected food extracts  

SciTech Connect

The phenomenon of freezing-point depression that accompanies the solute concentration of selected food extracts was investigated to reveal the characteristics of solid-liquid phase equilibrium. The freezing curves of various food extracts did not exhibit ideal solution behavior in the higher concentration range. The experimental data were fitted to new freezing-point depression equations by the method of nonlinear least squares, and the results clearly indicated that the calculated freezing points at various concentrations were in good agreement with the experimental data. Furthermore, by using the determined parameters, the freezing ratio and the activation coefficient were derived.

Tanaka, Fumihiko [Kagoshima Univ. (Japan). Dept. of Agricultural Systems Engineering; Murata, Satoshi; Habara, Kazuhiro; Amaratunga, K.S.P. [Kyushu Univ., Fukuoka (Japan). Dept. of Agricultural Engineering

1996-12-31

197

Radiofrequency electrode vibration-induced shear wave imaging for tissue modulus estimation: A simulation study  

PubMed Central

Quasi-static electrode displacement elastography, used for in-vivo imaging of radiofrequency ablation-induced lesions in abdominal organs such as the liver and kidney, is extended in this paper to dynamic vibrational perturbations of the ablation electrode. Propagation of the resulting shear waves into adjoining regions of tissue can be tracked and the shear wave velocity used to quantify the shear (and thereby Young’s) modulus of tissue. The algorithm used utilizes the time-to-peak displacement data (obtained from finite element analyses) to calculate the speed of shear wave propagation in the material. The simulation results presented illustrate the feasibility of estimating the Young’s modulus of tissue and is promising for characterizing the stiffness of radiofrequency-ablated thermal lesions and surrounding normal tissue. PMID:20968329

Bharat, Shyam; Varghese, Tomy

2010-01-01

198

Study of the spectral response of CZT multiple-electrode detectors  

Microsoft Academic Search

Cadmium zinc telluride (CZT) is a promising material for room temperature X-ray and gamma-ray detectors. The high atomic number and the wide band-gap give high quantum efficiency and good room temperature performances. Due to hole trapping, particular electrode structures have been developed to provide single-charge carrier collection (electrons), exploiting the excellent charge transport properties of the electrons. In this work,

L. Abbene; S. Del Sordo; F. Fauci; G. Gerardi; A. La Manna; G. Raso; A. Cola; E. Perillo; A. Raulo; V. Gostilo; S. Stumbo

2007-01-01

199

Rotating disc electrode study of the electropolishing mechanism of NiTi in methanolic sulfuric acid  

Microsoft Academic Search

The mechanism during electropolishing of NiTi in methanolic 3M sulfuric acid is elucidated based on the investigations carried out using a rotating disc electrode (RDE). The influence of the rotation rate, temperature and the addition of Ni and Ti ions in solution on the dissolution kinetics are investigated and analysed. The dissolution of NiTi during electropolishing exhibits Levich behaviour confirming

Lakshman Neelakantan; Achim Walter Hassel

2007-01-01

200

Thermal-stability studies of electrode materials for lithium-ion batteries  

Microsoft Academic Search

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes

Junwei Jiang

2005-01-01

201

The cone electrode: ultrastructural studies following long-term recording in rat and monkey cortex.  

PubMed

The achievement of long-term recording of neural signals from the central nervous system has potential clinical and investigative application. To facilitate long-term recording, a novel cone electrode composed of an insulated gold wire within a hollow glass cone had been developed. Cone electrodes containing sciatic nerve or neurotrophic medium were implanted into cerebral cortex in rats and monkeys. Electrophysiologic recordings had been previously obtained from cone tissue for as long as 15 months following implantation and this tissue contained silver-positive processes. We now extend these observations to characterize the fine structural features of the tissue within these long-term implants. Electron microscopy revealed central myelinated axons, dendrites, synaptic profiles, blood vessels, and glia; peripheral nerve was not found in the cones in which sciatic nerve had been placed. These observations further suggest ingrowth of cortical neurites and elements into the hollow glass tip of the cone and support the feasibility of long-term recording using this electrode. PMID:1407726

Kennedy, P R; Mirra, S S; Bakay, R A

1992-08-01

202

Study of nickel electrode oxidation as a function of 80% depth of discharge cycling  

SciTech Connect

Oxidation of nickel sinter used in nickel oxide electrodes in aerospace nickel cadmium cells leads to hydrogen gassing and the potential for cell rupture. The oxidation is directly related to loss of overcharge protection built into the cell during manufacturing. In nickel hydrogen cells, excessive oxidation of the nickel sinter can eventually lead to a burst before leak situation and is a potential source of failure. It is well known that nickel cadmium cells having nylon separators contribute to loss of overcharge via a hydrolysis reaction of the nylon in the potassium hydroxide electrolyte environment in the cell. The hydrolysis reaction produces lower chain organics which are oxidized by the positive electrode and oxygen. Oxidation of the organics diminishes the overcharge protection. With introduction of the Super NiCd{trademark} and the Magnum{trademark} nickel cadmium cells the nylon hydrolysis reaction is eliminated, but any reducing agent in the cell such as nickel or an organic additive can contribute to loss of overcharge protection. The present effort describes chemical analyses made to evaluate the extent of overcharge protection loss in nickel cadmium cells which do not have nylon hydrolysis, and quantifies the amount of hydrogen buildup in nickel hydrogen cells which are subjected to 80% depth of discharge cycling with and without the presence of cadmium in the positive electrode.

Pickett, D.F. Jr.; Scoles, D.L.; Johnson, Z.W.; Hayden, J.W.; Pennington, R.D. [Eagle-Picher Industries, Inc., Colorado Springs, CO (United States)

1997-12-31

203

A study of the electrochemistry of nickel hydroxide electrodes with various additives  

NASA Astrophysics Data System (ADS)

Nickel composite electrodes (NCE) with various additives are prepared by a chemical impregnation method from nitrate solutions on sintered porous plaques. The electrochemical properties, such as utilization of active material, swelling and the discharge potential of the nickel oxide electrode (NOE) are determined mainly through the composition of the active material and the characteristics of nickel plaques. Most additives (Mg, Ca, Sr, Ba, Zn, Cd, Co, Li and Al hydroxide) exert effects on the discharge potential and swelling of the NOE. Chemical co-precipitation with the addition of calcium, zinc, magnesium and barium hydroxide increases the discharge potential by more than 20 mV, but that with zinc hydroxide results in an obvious decrease of active-material utilization and that with calcium and magnesium hydroxide produces a larger increase of electrode thickness. The effects of anion additives are also examined. Less than 1% mol of NiS in the active material increases the discharge potential. Cadmium, cobalt and zinc hydroxide are excellent additives for preventing swelling of the NCE. Slow voltammetry (0.2 mV s -1) in 6 M KOH is applied to characterize the oxygen-evolving potential of the NCE. The difference between the oxygen-evolution potential and the potential of the oxidation peak for the NCE with additives of calcium, lithium, barium and aluminium hydroxide is at least + 60 mV.

Zhu, Wen-Hua; Ke, Jia-Jun; Yu, Hong-Mei; Zhang, Deng-Jun

204

Study on the influence of the B4C layer thickness on the neutron flux and energy distribution shape in multi-electrode ionisation chamber.  

PubMed

A model of a multi-electrode ionisation chamber, with polypropylene electrodes coated with a thin layer of B4C was created within Monte Carlo N-Particle Transport Code (MCNPX) and Fluktuierende Kaskade (FLUKA) codes. The influence of the layer thickness on neutron absorption in B4C and on the neutron spectra in the consecutive intra-electrode gas volumes has been studied using the MCNPX and FLUKA codes. The results will be used for designing the new type of the ionisation chamber. PMID:24729596

Tymi?ska, K; Maciak, M; O?ko, J; Tulik, P; Zielczy?ski, M; Gryzi?ski, M A

2014-10-01

205

Pathological Alterations and Stress Responses near DBS Electrodes after MRI Scans at 7.0T, 3.0T and 1.5T: An In Vivo Comparative Study  

PubMed Central

Objective The purpose of this study was to investigate the pathological alterations and the stress responses around deep brain stimulation (DBS) electrodes after magnetic resonance imaging (MRI) scans at 7.0T, 3.0T and 1.5T. Materials and Methods DBS devices were stereotactically implanted into the brains of New Zealand rabbits, targeting the left nucleus ventralis posterior thalami, while on the right side, a puncture passage pointing to the same target was made. MRI scans at 7.0T, 3.0T and 1.5T were performed using transmit/receive head coils. The pathological alterations of the surrounding tissue were evaluated by hematoxylin and eosin staining (H&E staining) and transmission electron microscopy (TEM). The levels of the 70 kDa heat shock protein (HSP-70), Neuronal Nuclei (NeuN) and Caspase-3 were determined by western-blotting and quantitative polymerase chain reaction (QPCR) to assess the stress responses near the DBS electrodes. Results H&E staining and TEM showed that the injury around the DBS electrodes was featured by a central puncture passage with gradually weakened injurious alterations. Comparisons of the injury across the groups manifested similar pathological alterations near the DBS electrodes in each group. Moreover, western-blotting and QPCR assay showed that the level of HSP-70 was not elevated by MRI scans (p>0.05), and the levels of NeuN and Caspase-3 were equal in each group, regardless of the field strengths applied (p>0.05). Conclusions Based on these findings, it is reasonable to conclude that in this study the MRI scans at multiple levels failed to induce additional tissue injury around the DBS electrodes. These preliminary data furthered our understanding of MRI-related DBS heating and encouraged revisions of the current MRI guidelines for patients with DBS devices. PMID:24988329

Meng, Da-Wei; Li, Shao-Wu; Liu, Huan-Guang; Li, Jun-Ju; Wang, Xiu; Zhang, Xin; Zhang, Jian-Guo

2014-01-01

206

Experimental study of bulk storage ignition by hot points Agns Jans*, Douglas Carson  

E-print Network

Experimental study of bulk storage ignition by hot points Agnès Janès*, Douglas Carson INERIS.janes@ineris.fr An experimental study of ignition risk due to hot points in the storage of bulk materials is required to ensure and temperature, type and size of hot point, etc. The aim of this study is to determine critical ignition

Paris-Sud XI, Université de

207

A potentiometric study of the behavior of a carbon-freon (C, CF/sub 4/) electrode in fluorine-containing halide melts  

SciTech Connect

It was previously noted that a graphite carbon electrode washed with gaseous carbon tetrafluoride should, at high temperatures, be reversible to fluoride ion in fluoride-containing melts. Its equilibrium potential should be determined by the partial pressure of the gaseous carbon tetrafluoride and by the activity of the fluoride ion in the melt. Since there was no previous information on specific studies in the electrochemical behavior of this carbon-freon electrode in halide melts, the authors conducted a potentiometric study of the electrochemical cells shown in this paper. In the experiments, the authors used analytical reagent-grade potassium fluoride (dihydrate), ultrapure sodium fluoride, and analytical reagent-grade lithium fluoride and ammonium fluoride. It is shown that the carbon-freon (C,CF/sub 4/) electrode is a reversible, second-order electrode in melts containing fluoride. Measurements using it give stable, reproducible results in fluoride or fluoride-chloride melts with a high fluoride content.

Nekrasov, V.N.; Cherepanov, V.B.; Ivanovskii, L.E.; Zaikov, Yu.P.

1985-09-01

208

Study Points to Acid Rain in Decline of Songbirds  

NSDL National Science Digital Library

New research from the Cornell Lab of Ornithology points to acid rain as a major cause of songbird decline, where previous research focused on forest fragmentation. This Web site is a brief article highlighting the research findings from the Atlanta Journal-Constitution, published on the Natural Resources Defense Council's Web page.

Seabrook, Charles.

2002-01-01

209

Two-point bend studies of glass fibers  

NASA Astrophysics Data System (ADS)

The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of glasses, including glass composition, thermal history of melts and environmental conditions during the failure tests. Understanding how these conditions affect failure helps us understand how glass fails. In this dissertation, failure strains for many different silicate and borate glasses were measured under a variety of experimental conditions. Failure stresses for various silicate glasses were calculated using values of the nonlinear elastic moduli reported in the literature. Inert intrinsic strengths for alkali silicate glasses were related to the structure and corresponding bond strengths, and the dependence of the inert strengths on faceplate velocity is discussed. Inert failure strains were also obtained for sodium borate glasses. Up to ˜40% failure strain was measured for vitreous B2O 3. The addition of soda to boron oxide increases the dimensionality and connectivity of the glass structure and hence increases its resistance to deformation, as was observed in elasticity and brittleness measurements reported in the literature. The increase in deformation resistance produces lower failure strains, a behavior also seen for alkali silicate and aluminosilicate glasses where the reduction of non-bridging oxygen increases the structure stiffness and leads to lower inert failure strain. Fatigue effects on silicate glasses were studied by measuring the failure strains in water at different temperatures and at different loading rates, and in air with a range of relative humidities. The dominant fatigue reaction for cross-linked network glasses is bond hydrolysis, whereas for alkali modified depolymerized glasses is ion-exchange reaction between alkali ions and water species. The fatigue mechanism difference results in the difference in the humidity sensitivity of the reaction rate. The dominant fatigue reaction also changes at around 50% relative humidity.

Tang, Zhongzhi

210

Preliminary Study of Electrophoretic Deposition of Vertically Aligned Mwcnt on Metallic Electrode  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes films formed randomly aligned laterally by electrophoresis. Multi-walled carbon nanotubes with lengths of about 10 ? was shortened and functionalized by a mixture of sulfuric and nitric acid. The functional groups on carbon nanotubes were elaborated by FT-IR. Chemically shortened MWCNTs disperse in organic and aqueous solvent and deposited on electrode vertically-aligned by applying a constant DC electric field. The alignment of MWCNTs was observed by scanning electron microscopy. It also the effect of various substrates on alignment of multi-walled carbon nanotubes was investigated.

Khabazian, Siavash; Sanjabi, Sohrab

211

Studies on CuTAPc-nanotube-modified electrodes as chemical sensors for NO.  

PubMed

Poly-copper tetraaminophthalocyanine (CuTAPc) nanotubes were successfully fabricated on porous alumina templates by electropolymerization. Their high surface area and simple preparation protocol made them potential candidates as the modification layer of electrodes for sensor application. High sensitivities and improved linear ranges were obtained through different measurements such as differential pulse voltammetry (DPV), differential potential amperometric (DPA) and electrochemical impedance spectroscopy (EIS). Detection limits as low as 10 nM were demonstrated in common voltammetric analysis with ultra-high response current in the microA range. PMID:19581690

Gu, Feng; Xu, Guo Qin; Ang, Siau Gek

2009-07-29

212

Study on stainless steel electrode based on dynamic aluminum liquid corrosion mechanism.  

PubMed

Scanning electrion microscope (SEM) was performed for investigations on the corrosion mechanism of stainless steel electrode in dynamic melting aluminum liquid. Microstructures and composition analysis was made by electron probe analysis (EPA) combined with metallic phase analysis. It can be concluded that the corrosion process is mainly composed of physical corrosion (flowing and scouring corrosion) and chemical corrosion (forming FeAl and Fe2Al5) and the two mechanisms usually exist simultaneously. The corrosion interface thickness is about 10 ?m, which is different to usual interface width of hundreds ?m in the static melting Al with iron matrix. PMID:25084422

Hou, Hua; Yang, Ruifeng

2009-01-01

213

Neutron Depth Profiling benchmarking and analysis of applications to lithium ion cell electrode and interfacial studies research  

NASA Astrophysics Data System (ADS)

The role of the lithium ion cell is increasing with great intensity due to global concerns for the decreased use of fossil fuels as well as the growing popularity of portable electronics. With the dramatic increase in demand for these cells follows an outbreak of research to optimize the lithium ion cells in terms of safety, cost, and also performance. The work shown in this dissertation sets out to distinguish the role of Neutron Depth Profiling (NDP) in the expanding research of lithium ion cells. Lithium ions play the primary role in the performance of lithium ion batteries. Moving from anode to cathode, and cathode to anode, the lithium ions are constantly being disturbed during the cell's operation. The ability to accurately determine the lithium's behavior within the electrodes of the cell after different operating conditions is a powerful tool to better understand the faults and advantages of particular electrode compositions and cell designs. NDP has this ability through the profiling of 6Li. This research first validates the ability of The University of Texas NDP (UT-NDP) facility to accurately profile operated lithium ion cell electrodes to a precision within 2% over 10 mum for concentration values, and with a precision for depth measurements within 77 nm. The validation of the UT-NDP system is performed by comparing UT-NDP profiles to those from the NIST-NDP system, from the Secondary Ion Mass Spectrometry (SIMS) technique, and also from Monte Carlo n-Particle (MCNPX) code simulations. All of the comparisons confirmed that the UT-NDP facility is fully capable of providing accurate depth profiles of lithium ion cell electrodes in terms of depth, shape of distribution, and concentration. Following the validation studies, this research investigates three different areas of lithium ion cell research and provides analysis based on NDP results. The three areas of investigation include storage of cells at temperature, cycling of cells, and the charging of cells at different current rates. The results conclude that NDP is a valuable asset to the characterization of the Solid Electrolyte Interface (SEI) growth as a function of storage time. The NDP results were able to conclude that LiFePO4 cell anodes have a factor of 21 times slower rate of SEI growth than anodes from LiFePSO 4. This indicates that the capacity fade of the LiFePO4 cell will be less than that of the LiFePSO4 cell due to storage at 50°C. Furthermore, NDP was able to conclude that cycling of cells had little effect on the lithium concentration within the cathode materials. The lithium concentration was found to be uniform throughout the first 10 mum of the LiFePO4 and LiNi1/3Mn1/3Co1/3O 2 cathodes. These measurements agreed with the initial hypothesis. However, NDP analysis of cells charged at different current rates found that lithium was concentrating within the first 2 mum of the cathode's surface at the electrode-electrolyte interface. This was an unexpected conclusion, but the results also concluded that effect of the lithium concentrating near the surface is amplified by charging the cells at higher current rates. The ultimate conclusion of this research was that NDP is capable of providing invaluable insight to the behavior of lithium within the electrodes of lithium ion cells. It is the author's conclusion that NDP may be most useful in the investigation of SEI layers and their variation according to electrode composition, electrolyte compositions, and the conditions, such as temperature, to which the cells are exposed.

Whitney, Scott M.

214

Cermet electrode  

DOEpatents

Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.

Maskalick, Nicholas J. (Pittsburgh, PA)

1988-08-30

215

Photoelectrochemical electrodes  

NASA Technical Reports Server (NTRS)

The surface of a moderate band gap semiconductor such as p-type molybdenum sulfide is modified to contain an adherent film of charge mediating ionene polymer containing an electroactive unit such as bipyridimium. Electron transport between the electrode and the mediator film is favorable and photocorrosion and recombination processes are suppressed. Incorporation of particles of catalyst such as platinum within the film provides a reduction in overvoltage. The polymer film is readily deposited on the electrode surface and can be rendered stable by ionic or addition crosslinking. Catalyst can be predispersed in the polymer film or a salt can be impregnated into the film and reduced therein.

Williams, R. M.; Rembaum, A. (inventors)

1983-01-01

216

Mass Transfer Studies of Geobacter sulfurreducens Biofilms on Rotating Disk Electrodes  

PubMed Central

Electrochemical impedance spectroscopy has received significant attention recently as a method to measure electrochemical parameters of Geobacter sulfurreducens bio-films. Here, we use electrochemical impedance spectroscopy to demonstrate the effect of mass transfer processes on electron transfer by G.sulfurreducens biofilms grown in situ on an electrode that was subsequently rotated. By rotating the biofilms up to 530 rpm, we could control the microscale gradients formed inside G.sulfurreducens biofilms. A 24% increase above a baseline of 82 ?A could be achieved with a rotation rate of 530 rpm. By comparison, we observed a 340% increase using a soluble redox mediator (ferrocyanide) limited by mass transfer. Control of mass transfer processes was also used to quantify the change in biofilm impedance during the transition from turnover to non-turnover. We found that only one element of the biofilm impedance, the interfacial resistance, changed significantly from 900 to 4,200 ? under turnover and non-turnover conditions, respectively. We ascribed this change to the electron transfer resistance overcome by the biofilm metabolism and estimate this value as 3,300 ?. Additionally, under non-turnover, the biofilm impedance developed pseudocapacitive behavior indicative of bound redox mediators. Pseudocapacitance of the biofilm was estimated at 740 ?F and was unresponsive to rotation of the electrode. The increase in electron transfer resistance and pseudocapacitive behavior under non-turnover could be used as indicators of acetate limitations inside G.sulfurreducens biofilms. PMID:23996084

Babuta, Jerome T.; Beyenal, Haluk

2014-01-01

217

In-situ Spectroscopic and Structural Studies of Electrode Materials for Advanced Battery Applications  

SciTech Connect

Techniques have been developed and implemented to gain insight into fundamental factors that affect the performance of electrodes in Li and Li-ion batteries and other energy storage devices. These include experimental strategies for monitoring the Raman scattering spectra of single microparticles of carbon and transition metal oxides as a function of their state of charge. Measurements were performed in electrolytes of direct relevance to Li and Li-Ion batteries both in the static and dynamic modes. In addition, novel strategies were devised for performing conventional experiments in ultrahigh vacuum environments under conditions which eliminate effects associated with presence of impurities, using ultrapure electrolytes, both of the polymeric and ionic liquid type that display no measurable vapor pressure. Also examined was the reactivity of conventional non aqueous solvent toward ultrapure Li films as monitored in ultrahigh vacuum with external reflection Fourier transform infrared spectroscopy. Also pursued were efforts toward developing applying Raman-scattering for monitoring the flow of charge of a real Li ion battery. Such time-resolved, spatially-resolved measurements are key to validating the results of theoretical simulations involving real electrode structures.

Daniel A Scherson

2013-03-14

218

A study of purely astrometric selection of extragalactic point sources  

E-print Network

Selection of extragalactic point sources, e.g. QSOs, is often hampered by significant selection effects causing existing samples to have rather complex selection functions. We explore whether a purely astrometric selection of extragalactic point sources, e.g. QSOs, is feasible with the ongoing Gaia mission. Such a selection would be interesting as it would be unbiased in terms of colours of the targets and hence would allow selection also with colours in the stellar sequence. We have analyzed a total of 18 representative regions of the sky by using \\textit{GUMS}, the simulator prepared for ESAs Gaia mission, both in the range of $12\\le G \\le 20$ mag and $12\\le G \\le 18$ mag. For each region we determine the density of apparently stationary stellar sources, i.e. sources for which Gaia cannot measure a significant proper motion. The density is contrasted with the density of extragalactic point sources, e.g. QSOs, in order to establish in which celestial directions a pure astrometric selection is feasible. When ...

Heintz, Kasper E; Høg, Erik

2015-01-01

219

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

SciTech Connect

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

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

1988-01-01

220

A study on prevention of an electric discharge at an extraction electrode of an electron cyclotron resonance ion source for cancer therapy  

SciTech Connect

A compact ECR ion source has utilized for carbon radiotherapy. In order to increase beam intensity with higher electric field at the extraction electrode and be better ion supply stability for long periods, electric geometry and surface conditions of an extraction electrode have been studied. Focusing attention on black deposited substances on the extraction electrode, which were observed around the extraction electrode after long-term use, the relation between black deposited substances and the electrical insulation property is investigated. The black deposited substances were inspected for the thickness of deposit, surface roughness, structural arrangement examined using Raman spectroscopy, and characteristics of electric discharge in a test bench, which was set up to simulate the ECR ion source.

Kishii, Y., E-mail: Ando.Yasuto@ct.MitsubishiElectric.co.jp; Kawasaki, S. [Energy Systems Center, Mitsubishi Electric Corporation, 1-1-2 Wadasaki-cho, Hyogo-ku, Kobe 652-8555 (Japan)] [Energy Systems Center, Mitsubishi Electric Corporation, 1-1-2 Wadasaki-cho, Hyogo-ku, Kobe 652-8555 (Japan); Kitagawa, A.; Muramatsu, M. [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan)] [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Uchida, T. [Bio-Nano Electronics Research Center, Toyo University, 2100 Kujirai, Kawagoe 350-8585 (Japan) [Bio-Nano Electronics Research Center, Toyo University, 2100 Kujirai, Kawagoe 350-8585 (Japan); Graduate School of Interdisciplinary New Science, Toyo University, 2100 Kujirai, Kawagoe 350-8585 (Japan)

2014-02-15

221

A study on prevention of an electric discharge at an extraction electrode of an electron cyclotron resonance ion source for cancer therapy  

NASA Astrophysics Data System (ADS)

A compact ECR ion source has utilized for carbon radiotherapy. In order to increase beam intensity with higher electric field at the extraction electrode and be better ion supply stability for long periods, electric geometry and surface conditions of an extraction electrode have been studied. Focusing attention on black deposited substances on the extraction electrode, which were observed around the extraction electrode after long-term use, the relation between black deposited substances and the electrical insulation property is investigated. The black deposited substances were inspected for the thickness of deposit, surface roughness, structural arrangement examined using Raman spectroscopy, and characteristics of electric discharge in a test bench, which was set up to simulate the ECR ion source.

Kishii, Y.; Kawasaki, S.; Kitagawa, A.; Muramatsu, M.; Uchida, T.

2014-02-01

222

Comparison between different thickness umbrella-shaped expandable radiofrequency electrodes (SuperSlim and CoAccess): Experimental and clinical study  

PubMed Central

The purpose of the present study was to compare the size and configuration of the ablation zones created by SuperSlim and CoAccess electrodes, using various ablation algorithms in ex vivo bovine liver and in clinical cases. In the experimental study, we ablated explanted bovine liver using 2 types of electrodes and 4 ablation algorithms (combinations of incremental power supply, stepwise expansion and additional low-power ablation) and evaluated the ablation area and time. In the clinical study, we compared the ablation volume and the shape of the ablation zone between both electrodes in 23 hepatocellular carcinoma (HCC) cases with the best algorithm (incremental power supply, stepwise expansion and additional low-power ablation) as derived from the experimental study. In the experimental study, the ablation area and time by the CoAccess electrode were significantly greater compared to those by the SuperSlim electrode for the single-step (algorithm 1, p=0.0209 and 0.0325, respectively) and stepwise expansion algorithms (algorithm 2, p=0.0002 and <0.0001, respectively; algorithm 3, p= 0.006 and 0.0407, respectively). However, differences were not significant for the additional low-power ablation algorithm. In the clinical study, the ablation volume and time in the CoAccess group were significantly larger and longer, respectively, compared to those in the SuperSlim group (p=0.0242 and 0.009, respectively). Round ablation zones were acquired in 91.7% of the CoAccess group, while irregular ablation zones were obtained in 45.5% of the SuperSlim group (p=0.0428). In conclusion, the CoAccess electrode achieves larger and more uniform ablation zones compared with the SuperSlim electrode, though it requires longer ablation times in experimental and clinical studies. PMID:22977647

KODA, MASAHIKO; TOKUNAGA, SHIHO; MATONO, TOMOMITSU; SUGIHARA, TAKAAKI; NAGAHARA, TAKAKAZU; MURAWAKI, YOSHIKAZU

2011-01-01

223

Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs//Li4Ti5O12  

NASA Astrophysics Data System (ADS)

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li4Ti5O12 (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3 V HSC device exhibits maximum volumetric energy density of ~4.38 mWh cm-3, much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5 V/100 mF supercapacitor (can be operated within 3 s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems.

Zuo, Wenhua; Wang, Chong; Li, Yuanyuan; Liu, Jinping

2015-01-01

224

Directly grown nanostructured electrodes for high volumetric energy density binder-free hybrid supercapacitors: a case study of CNTs//Li4Ti5O12.  

PubMed

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li(4)Ti(5)O(12) (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3 V HSC device exhibits maximum volumetric energy density of ~4.38 mWh cm(-3), much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5 V/100 mF supercapacitor (can be operated within 3 s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems. PMID:25586374

Zuo, Wenhua; Wang, Chong; Li, Yuanyuan; Liu, Jinping

2015-01-01

225

Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs//Li4Ti5O12  

PubMed Central

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li4Ti5O12 (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3?V HSC device exhibits maximum volumetric energy density of ~4.38?mWh cm?3, much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5?V/100?mF supercapacitor (can be operated within 3?s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems. PMID:25586374

Zuo, Wenhua; Wang, Chong; Li, Yuanyuan; Liu, Jinping

2015-01-01

226

Nonlinearity of Cardiac Pacemaker Electrodes  

Microsoft Academic Search

Nonlinear properties of electrodes immersed in saline were studied in the time domain and frequency domain. Three electrode materials were tested: platinum-iridium, Elgiloy, and stainless steel. For time domain measurements, current pulses of 1.0 to 2.0 ms duration and varying amplitudes were applied to the electrodes. Frequency domain measurements of polarization impedance were made with an impedance bridge, utilizing sinusoidal

Dov Jaron; Stanley A. Briller; Herman P. Schwan; David B. Geselowitz

1969-01-01

227

Chronically implanted intrafascicular recording electrodes  

Microsoft Academic Search

A newly designed intrafascicular electrode for chronic neural recording was studied by implanting 12 electrodes in the radial\\u000a nerves of 6 cats for 6 months. Action potentials were monitored at specified intervals throughout the experiment. The number\\u000a and size of the signals recorded suggest that this type of electrode provides information that is appropriate for feedback\\u000a control in functional electrical

Todd Lefurge; Eleanor Goodall; Kenneth Horch; Larry Stensaas; Andrew Schoenberg

1991-01-01

228

Fabrication and heating rate study of microscopic surface electrode ion traps  

E-print Network

We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with trapping height of approximately 240 micron. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found in the literature and possible relation of anomalous heating to sources of noise and dissipation in other systems, namely impurity atoms adsorbed on metal surfaces and amorphous dielectrics.

N. Daniilidis; S. Narayanan; S. A. Möller; R. Clark; T. E. Lee; P. J. Leek; A. Wallraff; St. Schulz; F. Schmidt-Kaler; H. Häffner

2010-09-15

229

Study of localized corrosion in aluminum alloys by the scanning reference electrode technique  

NASA Technical Reports Server (NTRS)

Localized corrosion in 2219-T87 aluminum (Al) alloy, 2195 aluminum-lithium (Al-Li) alloy, and welded 2195 Al-Li alloy (4043 filler) have been investigated using the relatively new scanning reference electrode technique (SRET). Anodic sites are more frequent and of greater strength in the 2195 Al-Li alloy than in the 2219-T87 Al alloy, indicating a greater tendency toward pitting for the latter. However, the overall corrosion rates are about the same for these two alloys, as determined using the polarization resistance technique. In the welded 2195 Al-Li alloy, the weld bean is entirely cathodic, with rather strongly anodic heat affected zones (HAZ) bordering both sides, indicating a high probability of corrosion in the HAZ parallel to the weld bead.

Danford, M. D.

1995-01-01

230

Infrared spectroelectrochemical study of dissociation and oxidation of methanol at a palladium electrode in alkaline solution.  

PubMed

The dissociative adsorption and electrooxidation of CH(3)OH at a Pd electrode in alkaline solution are investigated by using in situ infrared spectroscopy with both internal and external reflection modes. The former (ATR-SEIRAS) has a higher sensitivity of detecting surface species, and the latter (IRAS) can easily detect dissolved species trapped in a thin-layer-structured electrolyte. Real-time ATR-SEIRAS measurement indicates that CH(3)OH dissociates to CO(ad) species at a Pd electrode accompanied by a "dip" at open circuit potential, whereas deuterium-replaced CH(3)OH doesn't, suggesting that the breaking of the C-H bond is the rate-limiting step for the dissociative adsorption of CH(3)OH. Potential-dependent ATR-SEIRAS and IRAS measurements indicate that CH(3)OH is electrooxidized to formate and/or (bi)carbonate, the relative concentrations of which depend on the potential applied. Specifically, at potentials negative of ca. -0.15 V (vs Ag/AgCl), formate is the predominant product and (bi)carbonate (or CO(2) in the thin-layer structure of IRAS) is more favorable at potentials from -0.15 to 0.10 V. Further oxidation of the CO(ad) intermediate species arising from CH(3)OH dissociation is involved in forming (bi)carbonate at potentials above -0.15 V. Although the partial transformation from interfacial formate to (bi)carbonate may be justified, no bridge-bonded formate species can be detected over the potential range under investigation. PMID:23311730

Yang, Yao-Yue; Ren, Jie; Zhang, Han-Xuan; Zhou, Zhi-You; Sun, Shi-Gang; Cai, Wen-Bin

2013-02-01

231

Microfluidic device with tunable post arrays and integrated electrodes for studying cellular release.  

PubMed

In this paper, we describe the development of a planar, pillar array device that can be used to image either side of a tunable membrane, as well as sample and detect small molecules in a cell-free region of the microchip. The pores are created by sealing two parallel PDMS microchannels (a cell channel and a collector channel) over a gold pillar array (5 or 10 ?m in height), with the device being characterized and optimized for small molecule cross-over while excluding a flowing cell line (here, red blood cells, RBCs). The device was characterized in terms of the flow rate dependence of analyte cross-over and cell exclusion as well as the ability to perform amperometric detection of catechol and nitric oxide (NO) as they cross-over into the collector channel. Using catechol as the test analyte, the limits of detection (LOD) of the cross-over for the 10 ?m and 5 ?m pillar array heights were shown to be 50 nM and 105 nM, respectively. Detection of NO was made possible with a glassy carbon detection electrode (housed in the collector channel) modified with Pt-black and Nafion, to enhance sensitivity and selectivity, respectively. Reproducible cross-over of NO as a function of concentration resulted in a linear correlation (r(2) = 0.995, 7.6-190 ?M), with an LOD for NO of 230 nM on the glassy carbon/Pt-black/0.05% Nafion electrode. The applicability of the device was demonstrated by measuring the NO released from hypoxic RBCs, with the device allowing the released NO to cross-over into a cell free channel where it was detected in close to real-time. This type of device is an attractive alternative to the use of 3-dimensional devices with polycarbonate membranes, as either side of the membrane can be imaged and facile integration of electrochemical detection is possible. PMID:25105251

Selimovic, Asmira; Erkal, Jayda L; Spence, Dana M; Martin, R Scott

2014-11-21

232

Electrochemical, interfacial, and surface studies of the conversion of carbon dioxide to liquid fuels on tin electrodes  

NASA Astrophysics Data System (ADS)

The electrochemical reduction of carbon dioxide (CO2) into liquid fuels especially coupling with the intermittent renewable electricity offers a promising means of storing electricity in chemical form, which reduces the dependence on fossil fuels and mitigates the negative impact of anthropogenic CO2 emissions on the planet. Although converting CO2 to fuels is not in itself a new concept, the field has not substantially advanced in the last 30 years primarily because of the challenge of discovery of structural electrocatalysts and the development of membrane architectures for efficient collection of reactants and separation of products. An efficient catalyst for the electrochemical conversion of CO2 to fuels must be capable of mediating a proton-coupled electron transfer reaction at low overpotentials, reducing CO2 in the presence of water, selectively converting CO 2 to desirable chemicals, and sustaining long-term operations (Chapter 1). My Ph.D. research was an investigation of the electroreduction of CO2 on tin-based electrodes and development of an electrochemical cell to convert CO2 to liquid fuels. The initial study focused on understanding the CO2 reduction reaction chemistry in the electrical double layer with an emphasis on the effects of electrostatic adsorption of cations, specific adsorption of anion and electrolyte concentration on the potential and proton concentration at outer Helmholtz plane at which reduction reaction occurs. The variation of potential and proton concentration at outer Helmholtz plane accounts for the difference in activity and selectivity towards CO2 reduction when using different electrolytes (Chapter 2). Central to the highly efficient CO2 reduction is an optimum microstructure of catalyst layer in the Sn gas diffusion electrode (GDE) consisting of 100 nm Sn nanoparticles to facilitate gas diffusion and charge transfer. This microstructure in terms of the proton conductor fraction and catalyst layer thickness was optimized to maximize the triple phase boundary length for simultaneous high current density and selectivity towards formate formation (Chapter 3). The Sn GDEs was incorporated into a home-designed scalable full electrochemical cell which features a buffer layer of circulating liquid electrolyte mediating the proton concentration at cathode electrode surface. The Sn GDEs exhibited excellent short-term performance for CO2 reduction with high selectivity towards formate formation at low overpotentials in the full electrochemical cell. Additionally, coupling water oxidation and CO2 reduction was demonstrated in this full electrochemical cell to mimic biosynthesis (Chapter 4). The rapid degradation of selectivity towards formate formation on Sn GDEs in the full electrochemical cell, however, was observed during long-term operation. The degradation mechanism was unraveled due to the decrease of electrode potential resulted from substantial increase of internal ohmic resistance of the full electrochemical cell. The unexpected rise of internal ohmic resistance was attributed to the pulverization of 100 nm Sn nanoparticles due to the hydrogen diffusion induced stress. Based on the understanding of the origin of Sn nanoparticles pulverization, SnO2 nanoparticles of 3˜3.5 nm close to the critical size were utilized and reduced in situ to form Sn catalyst for electrochemical reduction of CO2. The pulverization was suppressed and subsequently a stable performance of electrodes was obtained (Chapter 5). Due to the affinity to oxygen, Sn nanoparticle surface is covered by a native thin oxide layer. The performance of Sn GDEs towards CO2 reduction strongly depends on the initial thickness of the surface oxide layer. The selectivity towards formate production dropped while the hydrogen yield increased as the initial thickness of the oxide layer increased (Chapter 6). These results suggest the underlying of surface structure on the selectivity of Sn electrode for CO2 reduction and provide insight into the development of more efficient catalysts.

Wu, Jingjie

233

Numerical Studies and Equipment Development for Single Point Incremental Forming  

NASA Astrophysics Data System (ADS)

This paper summarizes the achievements obtained so far in the context of a research project carried out at the University of Aveiro, Portugal on both numerical and experimental viewpoints concerning Single Point Incremental Forming (SPIF). On the experimental side, the general guidelines on the development of a new SPIF machine are detailed. The innovation features are related to the choice of a six-degrees-of-freedom, parallel kinematics machine, with a high payload, to broad the range of materials to be tested, and allowing for a higher flexibility on tool-path generation. On the numerical side, preliminary results on simulation of SPIF processes resorting to an innovative solid-shell finite element are presented. The final target is an accurate and fast simulation of SPIF processes by means of numerical methods. Accuracy is obtained through the use of a finite element accounting for three-dimensional stress and strain fields. The developed formulation allows for an unlimited number of integration points through its thickness direction, which promotes accuracy without loss of CPU efficiency. Preliminary results and designs are shown and discussions over the obtained solutions are provided in order to further improve the research framework.

Marabuto, S. R.; Sena, J. I. V.; Afonso, D.; Martins, M. A. B. E.; Coelho, R. M.; Ferreira, J. A. F.; Valente, R. A. F.; de Sousa, R. J. Alves

2011-05-01

234

Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes  

PubMed Central

Background We aimed to investigate the effect of cell-cell dipole interactions in the equilibrium distributions in dielectrophoretic devices. Methods We used a three dimensional coupled Monte Carlo-Poisson method to theoretically study the final distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. The simulated distributions have been compared with experimental ones observed in the case of MDA-MB-231 cells in the same operating conditions. Results The real and simulated distributions are consistent. In both cases the cells distribution near the electrodes is dominated by cell-cell dipole interactions which generate long chains. Conclusions The agreement between real and simulated cells’ distributions demonstrate the method’s reliability. The distribution are dominated by cell-cell dipole interactions even at low density regimes (105 cell/ml). An improved estimate for the density threshold governing the interaction free regime is suggested. PMID:24903282

2014-01-01

235

Strain-based in-situ study of anion and cation insertion into porous carbon electrodes with different pore sizes  

SciTech Connect

The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in-situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Also, the influence of potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into experimental results, which is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.

Black, Jennifer M [ORNL] [ORNL; Feng, Guang [ORNL] [ORNL; Fulvio, Pasquale F [ORNL] [ORNL; Hillesheim, Patrick C [ORNL] [ORNL; Dai, Sheng [ORNL] [ORNL; Gogotsi, Yury G. [Drexel University] [Drexel University; Cummings, Peter T [ORNL] [ORNL; Kalinin, Sergei V [ORNL] [ORNL; Balke, Nina [ORNL] [ORNL

2013-01-01

236

Potential dependence of self-assembled porphyrin layers on a Cu(111) electrode surface: In-situ STM study  

NASA Astrophysics Data System (ADS)

The adsorption of redox-active 5,10,15,20-Tetrakis(4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate) molecules, abbreviated as [H2TTMAPP]4+, on a chloride pre-covered Cu(111) electrode surface was studied in an electrochemical environment by means of combined cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). The [H2TTMAPP]4+ molecules adsorb spontaneously on the c(p ×?{ 3}) Cl/Cu(111) surface and form a highly ordered 2D monolayer once the supporting electrolyte (10 mM HCl) is replaced by the molecule containing electrolyte (10 mM HCl + 0.1 mM H2TTMAPP) at a potential of E = + 20 mV vs. RHE (reversible hydrogen electrode). This ordered phase undergoes a phase transition into a disordered one once the [H2TTMAPP]4+ molecules pass through the first reduction step at negative potentials. In contrast, at positive potentials, the copper corrosion process, taking place at step-edges with predominant < 2 bar 11 > directions, is not prevented by the presence of the [H2TTMAPP]4+ adlayer.

Phan, Thanh Hai; Kosmala, Tomaz; Wandelt, Klaus

2015-01-01

237

Investigation of the effects of shear on arc-electrode erosion using a modified arc-electrode mass loss model  

NASA Astrophysics Data System (ADS)

The electrodes are the attachment points for an electric arc where electrons and positive ions enter and leave the gas, creating a flow of current. Electrons enter the gas at the cathode and are removed at the anode. Electrons then flow out through the leads on the anode and are replenished from the power supply through the leads on the cathode. Electric arc attachment to the electrode surface causes intensive heating and subsequent melting and vaporization. At that point a multitude of factors can contribute to mass loss, to include vaporization (boiling), material removal via shear forces, chemical reactions, evaporation, and ejection of material in jets due to pressure effects. If these factors were more thoroughly understood and could be modeled, this knowledge would guide the development of an electrode design with minimal erosion. An analytic model was developed by a previous researcher that models mass loss by melting, evaporation and boiling with a moving arc attachment point. This pseudo one-dimensional model includes surface heat flux in periodic cycles of heating and cooling to model motion of a spinning arc in an annular electrode where the arc periodically returns to the same spot. This model, however, does not account for removal of material due to shear or pressure induced effects, or the effects of chemical reactions. As a result of this, the model under-predicts material removal by about 50%. High velocity air flowing over an electrode will result in a shear force which has the potential to remove molten material as the arc melts the surface on its path around the electrode. In order to study the effects of shear on mass loss rate, the model from this previous investigator has been altered to include this mass loss mechanism. The results of this study have shown that shear is a viable mechanism for mass loss in electrodes and can account for the mismatch between theoretical and experimental rates determined by previous investigators. The results of a parametric study of arc attachment factors - including spot size, fall voltage, arc spot rotation rate, ambient bore heat rate, and air mass flow rate - are presented. The parametric study resulted in improving estimates of both the arc spot size and electrode fall voltage, two critical factors affecting electrode heating. Little sensitivity of electrode erosion rate to ambient bore heat rate and rotation rate was found. The erosion rate is found to be sensitive to the mass flow rate of air injected in the arc heater and validation of the model by comparison with more run condition data should be carried out as the data become available.

Webb, Bryan T.

238

STUDIES ON TWO CLASSES OF POSITIVE ELECTRODE MATERIALS FOR LITHIUM-ION BATTERIES  

SciTech Connect

The development of advanced lithium-ion batteries is key to the success of many technologies, and in particular, hybrid electric vehicles. In addition to finding materials with higher energy and power densities, improvements in other factors such as cost, toxicity, lifetime, and safety are also required. Lithium transition metal oxide and LiFePO{sub 4}/C composite materials offer several distinct advantages in achieving many of these goals and are the focus of this report. Two series of layered lithium transition metal oxides, namely LiNi{sub 1/3}Co{sub 1/3-y}M{sub y}Mn{sub 1/3}O{sub 2} (M=Al, Co, Fe, Ti) and LiNi{sub 0.4}Co{sub 0.2-y}M{sub y}Mn{sub 0.4}O{sub 2} (M = Al, Co, Fe), have been synthesized. The effect of substitution on the crystal structure is related to shifts in transport properties and ultimately to the electrochemical performance. Partial aluminum substitution creates a high-rate positive electrode material capable of delivering twice the discharge capacity of unsubstituted materials. Iron substituted materials suffer from limited electrochemical performance and poor cycling stability due to the degradation of the layered structure. Titanium substitution creates a very high rate positive electrode material due to a decrease in the anti-site defect concentration. LiFePO{sub 4} is a very promising electrode material but suffers from poor electronic and ionic conductivity. To overcome this, two new techniques have been developed to synthesize high performance LiFePO{sub 4}/C composite materials. The use of graphitization catalysts in conjunction with pyromellitic acid leads to a highly graphitic carbon coating on the surface of LiFePO{sub 4} particles. Under the proper conditions, the room temperature electronic conductivity can be improved by nearly five orders of magnitude over untreated materials. Using Raman spectroscopy, the improvement in conductivity and rate performance of such materials has been related to the underlying structure of the carbon films. The combustion synthesis of LiFePO4 materials allows for the formation of nanoscale active material particles with high-quality carbon coatings in a quick and inexpensive fashion. The carbon coating is formed during the initial combustion process at temperatures that exceed the thermal stability limit of LiFePO{sub 4}. The olivine structure is then formed after a brief calcination at lower temperatures in a controlled environment. The carbon coating produced in this manner has an improved graphitic character and results in superior electrochemical performance. The potential co-synthesis of conductive carbon entities, such as carbon nanotubes and fibers, is also briefly discussed.

Wilcox, James D.

2008-12-18

239

A Comparative Study of Mobility Anchor Point Selection Schemes in Hierarchical Mobile IPv6 Networks  

E-print Network

A Comparative Study of Mobility Anchor Point Selection Schemes in Hierarchical Mobile IPv6 Networks IPv6 networks, how an mobile node select an appropriate mobility anchor point (MAP) has a vital effect Terms Algorithms, Performance, Standardization Keywords Hierarchical Mobile IPv6, mobility anchor point

240

Ion-selective micro-electrode studies of the electrochemical potentials in trout urinary bladder.  

PubMed Central

Intracellular micro-electrode techniques were used to measure the electrical resistances of the cell membranes and the shunt pathway and intracellular ionic activities in trout urinary bladder when the tissue was incubated in Ringer solution and in the presence of the polyene antibiotic ionophore amphotericin B. In control conditions the transepithelial potential was zero and the intracellular potential was -56 mV. The intracellular ionic activities measured with single- and double-barrel ion-sensitive micro-electrodes for the first time in a fish bladder (aiNa = 16 mM, aiK = 87 mM, and aiCl = 21 mM) indicate an active accumulation of K and Cl ions and an active extrusion of Na ions by the cell. The maintenance of intracellular Cl activity above its equilibrium value depended on the presence of Na ions in the mucosal medium, but was independent of the presence of K ions. Flat cable analysis yielded values for transepithelial, apical, basolateral and shunt resistances of 197, 2790, 1986 and 205 omega cm-2 respectively. Equivalent circuit analysis using amphotericin B yielded similar values for shunt resistance. The paracellular pathway accounts for 96% of transepithelial current flow and this epithelium may be classified as 'leaky'. The cells are electrically coupled with a space constant of 354 micron. Amphotericin B when added to the mucosal solution induced an immediate serosa positive transepithelial potential of about 9 mV and a short-circuit current of 64 microA cm-2. The Vt was ouabain sensitive and dependent on mucosal Na concentration. The origin of the antibiotic induced transepithelial potential was an increase in the sum of the cell membrane electromotive forces. The apical membrane potential depolarized to -7 mV and its resistance fell to 433 omega cm-2. During the first 10 min of exposure aiNa increased to 80 mM and aiK decreased to 7 mM with only a small change in aiCl. The changes in cellular Na+ and K+ activities were in accordance with their passive redistribution down their electrochemical gradients. PMID:2420979

Harvey, B J; Lahlou, B

1986-01-01

241

Accuracy Study of a 2-Component Point Doppler Velocimeter (PDV)  

NASA Technical Reports Server (NTRS)

A two-component Point Doppler Velocimeter (PDV) which has recently been developed is described, and a series of velocity measurements which have been obtained to quantify the accuracy of the PDV system are summarized. This PDV system uses molecular iodine vapor cells as frequency discriminating filters to determine the Doppler shift of laser light which is scattered off of seed particles in a flow. The majority of results which have been obtained to date are for the mean velocity of a rotating wheel, although preliminary data are described for fully-developed turbulent pipe flow. Accuracy of the present wheel velocity data is approximately +/- 1 % of full scale, while linearity of a single channel is on the order of +/- 0.5 % (i.e., +/- 0.6 m/sec and +/- 0.3 m/sec, out of 57 m/sec, respectively). The observed linearity of these results is on the order of the accuracy to which the speed of the rotating wheel has been set for individual data readings. The absolute accuracy of the rotating wheel data is shown to be consistent with the level of repeatability of the cell calibrations. The preliminary turbulent pipe flow data show consistent turbulence intensity values, and mean axial velocity profiles generally agree with pitot probe data. However, there is at present an offset error in the radial velocity which is on the order of 5-10 % of the mean axial velocity.

Kuhlman, John; Naylor, Steve; James, Kelly; Ramanath, Senthil

1997-01-01

242

Do changes in electrical skin resistance of acupuncture points reflect menstrual pain? A comparative study in healthy volunteers and primary dysmenorrhea patients.  

PubMed

Electrical skin resistance (ESR) measurements were performed with a four-electrode impedance detector at 10 points bilaterally on the first day of and the third day after menstruation in 48 healthy volunteers and 46 primary dysmenorrhea (PD) patients, to assess whether ESR changes of acupuncture points can reflect menstrual pain or not. The results showed statistical reductions in ESR imbalance ratio between left and right side that were detected at SP8 (Diji) and GB39 (Xuanzhong) (P < 0.05), and a statistical increase was detected at SP6 (Sanyinjiao) (P = 0.05) on the first day of menstruation compared with those values on the third day after menstruation in dysmenorrhea group. No significant differences were detected at other points within and between two groups (P > 0.05). This study showed that the imbalance of ESR at uterine-relevant points in PD patients is not significantly different from those of healthy women on both the 1st day of and the 3rd day after menstruation. The ESR imbalance ratio of certain points can either be lower or higher during menstruation in PD patients. The ESR property of acupuncture points needs to be investigated in further clinical trials with appropriate points, diseases, larger sample sizes, and optimal device. PMID:24876879

She, Yan-Fen; Ma, Liang-Xiao; Qi, Cong-Hui; Wang, Yan-Xia; Tang, Ling; Li, Chun-Hua; Yuan, Hong-Wen; Liu, Yu-Qi; Song, Jia-Shan; Zhu, Jiang

2014-01-01

243

Accelerating rate calorimetry studies of the reactions between ionic liquids and charged lithium ion battery electrode materials  

Microsoft Academic Search

Using accelerating rate calorimetry (ARC), the reactivity between six ionic liquids (with and without added LiPF6) and charged electrode materials is compared to the reactivity of standard carbonate-based solvents and electrolytes with the same electrode materials. The charged electrode materials used were Li1Si, Li7Ti4O12 and Li0.45CoO2. The experiments showed that not all ionic liquids are safer than conventional electrolytes\\/solvents. Of

Yadong Wang; K. Zaghib; A. Guerfi; Fernanda F. C. Bazito; Roberto M. Torresi; J. R. Dahn

2007-01-01

244

Study of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries  

Microsoft Academic Search

Graphite and nano-silicon-based negative electrodes in lithium-ion batteries with low binder content were evaluated. The effectiveness of styrene butadiene rubber (SBR) and various types of cellulose containing electrodes were compared to standard electrodes containing PVdF as binder. The cycling performance of lithium-based half cells in EC:DMC (1:1), 1M LiPF6 shows that styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (Na-CMC), or

H. Buqa; M. Holzapfel; F. Krumeich; C. Veit; P. Novák

2006-01-01

245

Atomic resolution study of reversible conversion reaction in metal oxide electrodes for lithium-ion battery.  

PubMed

Electrode materials based on conversion reactions with lithium ions have shown much higher energy density than those based on intercalation reactions. Here, nanocubes of a typical metal oxide (Co3O4) were grown on few-layer graphene, and their electrochemical lithiation and delithiation were investigated at atomic resolution by in situ transmission electron microscopy to reveal the mechanism of the reversible conversion reaction. During lithiation, a lithium-inserted Co3O4 phase and a phase consisting of nanosized Co-Li-O clusters are identified as the intermediate products prior to the subsequent formation of Li2O crystals. In delithiation, the reduced metal nanoparticles form a network and breakdown into even smaller clusters that act as catalysts to prompt reduction of Li2O, and CoO nanoparticles are identified as the product of the deconversion reaction. Such direct real-space, real-time atomic-scale observations shed light on the phenomena and mechanisms in reaction-based electrochemical energy conversion and provide impetus for further development in electrochemical charge storage devices. PMID:25337887

Luo, Langli; Wu, Jinsong; Xu, Junming; Dravid, Vinayak P

2014-11-25

246

Studies on Supercapacitor Electrode Material from Activated Lignin-Derived Mesoporous Carbon  

SciTech Connect

We synthesized mesoporous carbon from pre-cross-linked lignin gel impregnated with a surfactant as the pore-forming agent, and then activated the carbon through physical and chemical methods to obtain activated mesoporous carbon. The activated mesoporous carbons exhibited 1.5- to 6-fold increases in porosity with a maximum BET specific surface area of 1148 m2/g and a pore volume of 1.0 cm3/g. Slow physical activation helped retain dominant mesoporosity; however, aggressive chemical activation caused some loss of the mesopore volume fraction. Plots of cyclic voltammetric data with the capacitor electrode made from these carbons showed an almost rectangular curve depicting the behavior of ideal double-layer capacitance. Although the pristine mesoporous carbon exhibited the same range of surface-area-based capacitance as that of other known carbon-based supercapacitors, activation decreased the surface-area-based specific capacitance and increased the gravimetric-specific capacitance of the mesoporous carbons. Surface activation lowered bulk density and electrical conductivity. Warburg impedance as a vertical tail in the lower frequency domain of Nyquist plots supported good supercapacitor behavior for the activated mesoporous carbons. Our work demonstrated that biomass-derived mesoporous carbon materials continue to show potential for use in specific electrochemical applications.

Saha, Dipendu [ORNL] [ORNL; Li, Yunchao [ORNL] [ORNL; Bi, Zhonghe [ORNL] [ORNL; Chen, Jihua [ORNL] [ORNL; Keum, Jong Kahk [ORNL] [ORNL; Hensley, Dale K [ORNL] [ORNL; Grappe, Hippolyte A. [Oak Ridge Institute for Science and Education (ORISE)] [Oak Ridge Institute for Science and Education (ORISE); Meyer III, Harry M [ORNL] [ORNL; Dai, Sheng [ORNL] [ORNL; Paranthaman, Mariappan Parans [ORNL] [ORNL; Naskar, Amit K [ORNL] [ORNL

2014-01-01

247

Particle Transportation Using Programmable Electrode Arrays  

E-print Network

This study presents a technique to manipulate particles in microchannels using arrays of individually excitable electrodes. These electrodes were energized sequentially to form a non-uniform electric field that moved along ...

Kua, C.H.

248

Mechanistic Studies of Charge Injection from Metallic Electrodes into Organic Semiconductors Mediated by Ionic Functionalities: Final Report  

SciTech Connect

Metal-organic semiconductor interfaces are important because of their ubiquitous role in determining the performance of modern electronics such as organic light emitting diodes (OLEDs), fuel cells, batteries, field effect transistors (FETs), and organic solar cells. Interfaces between metal electrodes required for external wiring to the device and underlying organic structures directly affect the charge carrier injection/collection efficiency in organic-based electronic devices primarily due to the mismatch between energy levels in the metal and organic semiconductor. Environmentally stable and cost-effective electrode materials, such as aluminum and gold typically exhibit high potential barriers for charge carriers injection into organic devices leading to increased operational voltages in OLEDs and FETs and reduced charge extraction in photovoltaic devices. This leads to increased power consumption by the device, reduced overall efficiency, and decreased operational lifetime. These factors represent a significant obstacle for development of next generation of cheap and energy-efficient components based on organic semiconductors. It has been noticed that introduction of organic materials with conjugated backbone and ionic pendant groups known as conjugated poly- and oligoelectrolytes (CPEs and COEs), enables one to reduce the potential barriers at the metal-organic interface and achieve more efficient operation of a device, however exact mechanisms of the phenomenon have not been understood. The goal of this project was to delineate the function of organic semiconductors with ionic groups as electron injection layers. The research incorporated a multidisciplinary approach that encompassed the creation of new materials, novel processing techniques, examination of fundamental electronic properties and the incorporation of the resulting knowledgebase into development of novel organic electronic devices with increased efficiency, environmental stability, and reduced cost. During the execution of the project, main efforts were focused on the synthesis of new charge-bearing organic materials, such as CPEs and COEs, and block copolymers with neutral and ionic segments, studies of mechanisms responsible for the charge injection modulation in devices with ionic interlayers, and use of naturally occurring charged molecules for creation of enhanced devices. The studies allowed PIs to demonstrate the usefulness of the proposed approach for the improvement of operational parameters in model OLED and FET systems resulting in increased efficiency, decreased contact resistance, and possibility to use stable metals for fabrication of device electrodes. The successful proof-of-the-principle results potentially promise development of light-weight, low fabrication cost devices which can be used in consumer applications such as displays, solar cells, and printed electronic devices. Fundamental mechanisms responsible for the phenomena observed have been identified thus advancing the fundamental knowledgebase.

Nguyen, Thuc-Quyen [UCSB; Bazan, Guillermo [UCSB; Mikhailovsky, Alexander [UCSB

2014-04-15

249

First-Principles Study of Point Defects in LaAlO?  

E-print Network

In this study, the native point defects including oxygen vacancy and interstitial, metal (La, Al) vacancy and interstitial, and metal antisite in perovskite LAO are studied. Defect formation energies are studied as a ...

Zheng, J.X.

250

Space tug point design study. Volume 4: Program requirements  

NASA Technical Reports Server (NTRS)

A study was conducted to determine the configuration of a space tug and to predict the performance parameters. The program plans and planning data generated in support of the tug development program are presented. The preliminary plans and supporting planning data emphasize the following requirements: (1) maintenance and refurbishment, (2) technology development, (3) production, (4) test facilities, (5) quality control, and (6) scheduling.

1973-01-01

251

Electrochemical studies of thin films of conducting polymers and conducting polymer composites deposited on metal and semiconductor electrodes  

NASA Technical Reports Server (NTRS)

Electrochemical studies indicate that poly(Isothianaphthene) or PITN, can be p-doped only. Electrochemical properties of PITN and Nafion-PITN in acetonitrile solutions containing tetra-phenyl Phosphonium chloride as supporting electrolyte are compared. In both cases, the electrochemical behavior of thin films are different from that of thick films. In addition, Nafion does not seem to alter the electrochemical properties of PITN. Cyclic voltammetric and chronocoulometric measurements were made to compute the diffusion coefficient of the counter ions. Electrochemical behavior of both PITN and Nafion-PITN in acetonitrile solution containing different counter ions are described. PITN, when electrochemically deposited, apparently neither passivates surface states present nor forms ohmic contacts with p-Si or p(+)Si single-crystal electrodes.

Nagasubramanian, G.; Di Stefano, S.; Moacanin, J.

1987-01-01

252

A comparative study of carbon felt and activated carbon based electrodes for sodium polysulfide\\/bromine redox flow battery  

Microsoft Academic Search

Carbon felt (CF) and activated carbon (AC) based electrodes for sodium polysulfide\\/bromine redox flow battery (PSB) were prepared and compared with a laboratory scale PSB flow cell in terms of structure and application performances. The structural properties of the two types of electrodes were characterized by filamentary analog and BET analysis, respectively. Catalyst coating, discharge behavior analysis and thermogravimetric analysis-mass

Hantao Zhou; Huamin Zhang; Ping Zhao; Baolian Yi

2006-01-01

253

Muscle channelopathies and critical points in functional and genetic studies  

PubMed Central

Muscle channelopathies are caused by mutations in ion channel genes, by antibodies directed against ion channel proteins, or by changes of cell homeostasis leading to aberrant splicing of ion channel RNA or to disturbances of modification and localization of channel proteins. As ion channels constitute one of the only protein families that allow functional examination on the molecular level, expression studies of putative mutations have become standard in confirming that the mutations cause disease. Functional changes may not necessarily prove disease causality of a putative mutation but could be brought about by a polymorphism instead. These problems are addressed, and a more critical evaluation of the underlying genetic data is proposed. PMID:16075040

Jurkat-Rott, Karin; Lehmann-Horn, Frank

2005-01-01

254

The Effect of Electrode Coupling on Single Molecule Device Characteristics: An X-Ray Spectroscopy and Scanning Probe Microscopy Study  

NASA Astrophysics Data System (ADS)

This thesis studies electronic properties of molecular devices in the limiting cases of strong and weak electrode-molecule coupling. In these two limits, we use the complementary techniques of X-Ray spectroscopy and Scanning Tunneling Microscopy (STM) to understand the mechanisms for electrode-molecule bond formation, the energy level realignment due to metal-molecule bonds, the effect of coupling strength on single-molecule conductance in low-bias measurements, and the effect of coupling on transport under high-bias. We also introduce molecular designs with inherent asymmetries, and develop an analytical method to determine the effect of these features on high-bias conductance. This understanding of the role of electrode-molecule coupling in high-bias regimes enables us to develop a series of functional electronic devices whose properties can be predictably tuned through chemical design. First, we explore the weak electrode-molecule coupling regime by studing the interaction of two types of paracyclophane derivates that are coupled 'through-space' to underlying gold substrates. The two paracyclophane derivatives differ in the strength of their intramolecular through-space coupling. X-Ray photoemission spectroscopy (XPS) and Near-Edge X-ray Absorbance Fine Structure (NEXAFS) spectroscopy allows us to determine the orientation of both molecules; Resonant Photoemission Spectroscopy (RPES) then allows us to measure charge transfer time from molecule to metal for both molecules. This study provides a quantititative measure of charge transfer time as a function of through-space coupling strength. Next we use this understanding in STM based single-molecule current-voltage measurements of a series of molecules that couple through-space to one electrode, and through-bond to the other. We find that in the high-bias regime, these molecules respond differently depending on the direction of the applied field. This asymmetric response to electric field direction results in diode-like behavior. We vary the length of these asymmetrically coupled molecules, and find that we can increase the rectifying characteristics of these molecules by increasing length. Next, we explore the strong-coupling regime with an X-Ray spectroscopy study of the formation of covalent gold-carbon bonds using benzyltrimethyltin molecules on gold surfaces in ultra high vacuum conditions. Through X-ray Photoemission Spectroscopy (XPS) and X-ray absorption measurements, we find that the molecule fragments at the Sn-Benzyl bond when exposed to gold and the resulting benzyl species only forms covalent Au-C bonds on less coordinated Au surfaces like Au(110). We also find spectroscopic evidence for a gap state localized on the Au-C bond that results from the covalent nature of the bond. Finally, we use Density Functional Theory based Nudged Elastic Band methods to find reaction pathways and energy barriers for this reaction. We use our knowledge of the electronic structure of these bonds to create single-molecule junctions containing Au-C bonds in STM-based break junction experiments. In analogy with our approach for the weakly coupled 'through-space' systems, we study the high-bias current-voltage characteristics of molecules with one strong Au-C bond, and one weaker donor-acceptor bond. These experiments reveal that the 'gap state' created due to the covalent nature of the Au-C bond remains essentially pinned to the Fermi level of its corresponding electrode, and that most of the electric potential drop in the junction occurs on the donor-acceptor bond; as a result, these molecules behave like rectifiers. We use this principle to create a series of three molecular rectifiers, and show that the unique properties of the Au-C bond allow us to easily tune the rectification ratio by modifying a single electronic parameter. We then explore the process of molecular self-assembly to create organic electronic structures on metal surfaces. Specifically, we study the formation of graphene nanoribbons using a brominated precursor deposited on Au(111) surface in ultra high vacuu

Batra, Arunabh

255

Space tug point design study. Volume 1: Summary  

NASA Technical Reports Server (NTRS)

The design and characteristics of a space tug are discussed. The primary objective of the study is to verify the performance capability of a baseline design to deliver and retrieve payloads between 100 nautical miles, 28.5 degrees inclination, and geosynchronous. The space tug is ground based, reusable for 20 mission cycles, and is shuttled to and from low earth orbit by an earth orbital shuttle (EOS) with a 65,000 pound payload capability. It is shown that the baseline concept can meet the target performance goals. The design analysis encompassed: (1) definition of the vehicle primary structure, (2) thermal control, (3) meteoroid protection, (4) propulsion and mechanical subsystems, and (5) avionics including power generation and distribution.

1972-01-01

256

A weighted least squaes study of robustness in interior point linear programming  

Microsoft Academic Search

This paper studies the robustness of interior point linear programming algorthims with respect to initial iterates that are too close to the boundary. Weighted least squares analysis is used in studying the near-boundary behavior of the affine scaling and Newton centering directions, which are often combined by interior point methods. This analysis leads to the develoment of a modified Newton

Alexander L. Hipolito

1993-01-01

257

A study on the determination of chromium as chromate at a carbon paste electrode modified with surfactants.  

PubMed

A procedure for the determination of chromium is described based on synergistic pre-concentration of the chromate anion at a carbon paste electrode modified in situ with quarternary ammonium salts such as 1-ethoxycarbonylpentadecyltrimethylammonium bromide (Septonex((R))), cetyltrimethylammonium bromide (CTAB) or cetylpyridinium bromide (CPB). The proper electrochemical detection utilises the reduction Cr(VI) --> Cr(III) performed in the differential pulse cathodic voltammetric mode. In discussion, considerable attention has been paid to the accumulation mechanism at the carbon paste electrode in the presence of surfactants. Furthermore, after optimising the corresponding experimental conditions (0.1-0.3M HCl + 0.1M NaCl as the supporting electrolyte, 2.5-25muM as the total concentration of modifier, pre-concentration at +0.7V versus Ag/AgCl and the stripping from +0.7 to -0.4V), the analytical performance of the method has been evaluated. The signal of interest was reproducible within +/-8% and proportional to the concentration in a range of 0.5-50muM CrO(4)(2-), with a limit of detection (S/N = 3:1) of about 5x10(-8)M CrO(4)(2-) (with accumulation for 300s). Interference studies were focused mainly on the species capable of forming ion-pairs with the modifier; i.e., TlCl(4)(-), AuCl(4)(-), PdCl(4)(2-), PtCl(6)(2-), VO(4)(3-), MnO(4)(-) and I(-). Practical applicability of the method was tested on model solutions via the recovery rates (typically 90-110%) or using selected certified reference materials (tea, bush leaves, clover) and two samples of black tea when the respective results were compared to those obtained by the reference determinations with ICP-AES. PMID:18969679

Svancara, Ivan; Foret, Petr; Vytras, Karel

2004-11-15

258

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors  

NASA Astrophysics Data System (ADS)

A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120 °C and 1 kgf/cm2 for 2 min, followed by a 10 min post-baking at 100 °C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-? titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon (˜0.01 cm2/V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

Cavallari, Marco Roberto; Zanchin, Vinicius Ramos; Pojar, Mariana; Seabra, Antonio Carlos; de Assumpção Pereira-da-Silva, Marcelo; Fonseca, Fernando Josepetti; de Andrade, Adnei Melges

2014-05-01

259

The future of labor studies, from a labor lawyer's point of view. 1.How might future labor studiesevolve, from a French labor lawyer's point of view?  

E-print Network

The future of labor studies, from a labor lawyer's point of view. 1.How might future labor studiesevolve, from a French labor lawyer's point of view? I would first point out several factors that may an improvement. We may add that, following German lawyers, Mitbestimmung, which used to be very criticized few

Paris-Sud XI, Université de

260

Experimental Study of Saddle Point of Attachment in Laminar Juncture Flow  

NASA Technical Reports Server (NTRS)

An experimental study of laminar horseshoe vortex flows upstream of a cylinder/flat plate juncture has been conducted to verify the existence of saddle-point-of-attachment topologies. In the classical depiction of this flowfield, a saddle point of separation exists on the flat plate upstream of the cylinder, and the boundary layer separates from the surface. Recent computations have indicated that the topology may actually involve a saddle point of attachment on the surface and additional singular points in the flow. Laser light sheet flow visualizations have been performed on the symmetry plane and crossflow planes to identify the saddle-point-of-attachment flowfields. The visualizations reveal that saddle-point-of-attachment topologies occur over a range of Reynolds numbers in both single and multiple vortex regimes. An analysis of the flow topologies is presented that describes the existence and evolution of the singular points in the flowfield.

Coon, Michael D.; Tobak, Murray

1995-01-01

261

Enhancing Electrochemical Water-Splitting Kinetics by Polarization-Driven Formation of Near-Surface Iron(0): An In?Situ XPS Study on Perovskite-Type Electrodes.  

PubMed

In the search for optimized cathode materials for high-temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6 Sr0.4 FeO3-? (LSF) thin film electrodes. Under cathodic polarization the formation of Fe(0) on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. PMID:25557533

Opitz, Alexander K; Nenning, Andreas; Rameshan, Christoph; Rameshan, Raffael; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; Rupprechter, Günther; Fleig, Jürgen; Klötzer, Bernhard

2015-02-23

262

Electrochemical and Photon Polarization Modulation Infrared Reflection Absorption Spectroscopy Study of the Electric Field Driven Transformations of a Phospholipid Bilayer Supported at a Gold Electrode Surface  

PubMed Central

Electrochemistry and polarization modulation Fourier transform infrared reflection absorption spectroscopy (PM-FTIRRAS) was employed to investigate fusion of small unilamellar vesicles of 1,2dioyl-sn-glycero-3-phosphatidyl choline (DOPC) onto the Au(111) electrode. Electrochemical studies demonstrated that the DOPC vesicles fuse and spread onto the gold electrode surface at small charge densities ?8 ?C cm?2 < ?M < 0 ?C cm?2(if the static electric field is <2 × 108 V/m) to form a bilayer. At ?M < ?8 ?C cm?2, the film is detached from the electrode surface; however, the film remains in close proximity to the surface. The PM-FTIRRAS experiments demonstrated that the field-driven transformation of the film involves changes in hydration, orientation, and conformation in the polar headgroup region and that changes in the packing and tilt of the acyl chains are consequences of the headgroup rearrangements. PMID:14645094

Zawisza, I.; Lachenwitzer, A.; Zamlynny, V.; Horswell, S. L.; Goddard, J. D.; Lipkowski, J.

2003-01-01

263

A rotating disk electrode for kinetic studies of superoxide dismutases: applicability in a wide pH range and for continuous monitoring of enzyme inactivation.  

PubMed

A rotating disk electrode coated with a thin mercury film is described. It is suitable for electrochemical determinations of the catalytic constant of superoxide dismutase in a much wider pH range than that accessible to polarographic methods. In particular this is the only direct method, except for pulse radiolysis, that allows mechanistic studies of the enzyme in the physiological pH range. Furthermore, the continuous response of this electrode allows enzyme activity changes characterized by half-lives in the range from a few to 10(3) s. to be followed. PMID:6312832

Argese, E; De Carli, B; Orsega, E; Rigo, A; Rotilio, G

1983-07-01

264

Inexpensive and Disposable pH Electrodes  

ERIC Educational Resources Information Center

Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H[superscript +] concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH…

Goldcamp, Michael J.; Conklin, Alfred; Nelson, Kimberly; Marchetti, Jessica; Brashear, Ryan; Epure, Emily

2010-01-01

265

Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter  

NASA Technical Reports Server (NTRS)

Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.

Wheeler, B. L.; Williams, R. M.; Jeffries-Nakamura, B.; Lamb, J. L.; Loveland, M. E.; Bankston, C. P.; Cole, T.

1988-01-01

266

A Raman spectroscopic study of the carbon deposition mechanism on Ni/CGO electrodes during CO/CO2 electrolysis.  

PubMed

In situ and ex situ Raman analyses of porous Ni/CGO electrodes reveal differences in the amount, location and type of carbon formed during CO/CO2 electrolysis. The results demonstrate the limitations of optical in situ techniques applied to Solid Oxide Cells (SOCs) operated in electrolysis conditions. Increased carbon deposition close to the electrode-electrolyte interface is likely to be the result of high charge-transfer current in that area. The positive effect of a CGO interlayer on reducing carbon formation on the fuel electrode is demonstrated. PMID:24871047

Duboviks, V; Maher, R C; Kishimoto, M; Cohen, L F; Brandon, N P; Offer, G J

2014-07-14

267

Impedance studies of nickel/cadmium and nickel/hydrogen cells using the cell case as a reference electrode  

NASA Technical Reports Server (NTRS)

Impedance measurements have been made on several Ni/Cd and Ni/H2 flight-weight cells using the case as a reference electrode. For these measurements, the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltage of the cell cases with respect to the individual electrodes differ from cell to cell, even at the same overall cell voltage, but they remain stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.

Reid, Margaret A.

1990-01-01

268

sensor electrodes  

NASA Astrophysics Data System (ADS)

In this work, an ultrafast and facile method is developed to synthesize Au(I)-dodecanethiolate nanotubes (Au(I)NTs) with the assistance of glycyl-glycyl-glycine (G-G-G). Transmission electron microscopy (TEM) images reveal that the as-prepared Au(I)NTs can be obtained in a 2-h reaction instead of a previous 24-h reaction and are uniform with a hollow structure and smooth surface by virtue of the G-G-G peptide tubular template. According to structural analysis, a possible preparative mechanism is proposed that the G-G-G peptide could help to curl into tube-like morphology in alkaline situation spontaneously to accelerate the formation of Au(I)NTs. Meanwhile, PVDF-stabilized Au(I)NT-modified glassy carbon electrodes present their promising potential for Hg2+ detection.

Zhang, Zhiqiang; Ma, Congcong; He, Lian; Zhu, Shijin; Hao, Xiaodong; Xie, Wanyi; Zhang, Wei; Zhang, Yuxin

2014-11-01

269

Electrochemical lithiation and passivation mechanisms of iron monosulfide thin film as negative electrode material for lithium-ion batteries studied by surface analytical techniques  

NASA Astrophysics Data System (ADS)

The lithiation/delithiation reaction mechanism of iron monosulfide (troilite Fe(1-x)S, x = 0.07) as negative electrode material for lithium-ion batteries and the electrode passivation induced by reductive decomposition of the electrolyte were studied by combining surface (X-ray photoelectron spectroscopy, XPS, and time-of-flight secondary ion mass spectrometry, ToF-SIMS) and electrochemical analysis (cyclic voltammetry, CV) of thin films grown by thermal sulfidation of metal iron substrate. XPS analysis performed at different stages of the first lithiation/delithiation cycle shows that the reversible formation of metallic iron and lithium sulfide is not solely limited to the principal cathodic/anodic peaks at 1.23/1.89 V and that disulfide products, possibly Li2FeS2, are also formed at lower cathodic potentials. ToF-SIMS depth profiling of the thin film electrode confirms an incomplete process of conversion/deconversion and reveals an expansion/shrinkage of the material induced by electrochemical lithiation/delithiation. The solid electrolyte interphase (SEI) layer formed on the iron monosulfide thin film electrode is mostly composed of Li2CO3 with some presence of ROCO2Li. For the first time, it is shown that the SEI layer thickness varies upon conversion/deconversion, between 9 and 4.5 nm in the lithiated and delithiated states, respectively, on a conversion-type electrode. Moreover, the electrolyte decomposition products penetrate the bulk electrode until the current collector owing to pulverization/cracking caused by expansion and shrinkage of the thin film material upon cycling.

Liao, Feng; ?wiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Klein, Lorena H.; Zanna, Sandrine; Marcus, Philippe

2013-10-01

270

CETF Space Station payload pointing system design and analysis feasibility study. [Critical Evaluation Task Force  

NASA Technical Reports Server (NTRS)

The expected pointing performance of an attached payload coupled to the Critical Evaluation Task Force Space Station via a payload pointing system (PPS) is determined. The PPS is a 3-axis gimbal which provides the capability for maintaining inertial pointing of a payload in the presence of disturbances associated with the Space Station environment. A system where the axes of rotation were offset from the payload center of mass (CM) by 10 in. in the Z axis was studied as well as a system having the payload CM offset by only 1 inch. There is a significant improvement in pointing performance when going from the 10 in. to the 1 in. gimbal offset.

Smagala, Tom; Mcglew, Dave

1988-01-01

271

Structural investigations of LiFePO 4 electrodes and in situ studies by Fe X-ray absorption spectroscopy  

Microsoft Academic Search

Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on electrodes containing LiFePO4 to determine the local atomic and electronic structure and their stability with electrochemical cycling. A versatile electrochemical in situ cell has been constructed for long-term soft and hard X-ray experiments for the structural investigation on battery electrodes during

Aniruddha Deb; Uwe Bergmann; S. P. Cramer; Elton J. Cairns

2005-01-01

272

STUDIES OF THE CARDIAC-LIKE ACTION POTENTIAL IN CRAYFISH GIANT AXONS INDUCED BY PLATINIZED TUNGSTEN METAL ELECTRODES  

Microsoft Academic Search

SUMMARY A lightly platinized tungsten (Pt-W) wire electrode, axially inserted into a crayfish giant axon, causes the development of cardiac-like action potentials with durations of up to 4 s. The plateau in membrane potential typically occurs within lOmin of the start of action potential elongation. The effect occurs without passing current through the Pt-W electrode and is temporally related to

LISTON A. ORR; EDWARD M. LIEBERMAN

273

Behaviour of a fluorine-doped tin oxide electrode: a study by quartz crystal microbalance in propylene carbonate  

Microsoft Academic Search

Fluorine-doped tin oxide (FTO) was deposited onto a gold electrode evaporated onto a quartz crystal. The FTO material was cycled in propylene carbonate in the presence of 1 M LiClO4. Voltammetric and gravimetric responses of the FTO electrode were recorded between +2.75 and +0.75 V vs. Li|Li+ for 180 cycles. During the first few cycles, reduction of trace water was

M. Székely; C. Mathieu; N. E. Moulayat; M. Herlem; H. Cachet; M. Keddam; H. Perrot; B. Fahys; B. Eid; E. Caillot

1996-01-01

274

resterilizable electrode for electrosurgery  

NASA Technical Reports Server (NTRS)

Required properties of flexibility, electrical conductivity, tensile strength, and tear resistance of electrosurgical electrodes is retained through utilization of flexible-polymer/conductive particle composites for electrodes.

Engstrom, E. R.; Houge, J. C.

1979-01-01

275

Electrode-Skin contact impedance: In vivo measurements on an ovine model  

NASA Astrophysics Data System (ADS)

The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 ?, compared to more than 400 ? measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and non-invasive cases. This further prompted us to design a flexible electrode belt using the novel multi-point electrodes for lung EIT on animal models.

Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Jin, C.; Oh, T. I.; Thiagalingam, A.; McEwan, A.

2013-04-01

276

Interactive graphics system for locating plunge electrodes in cardiac MRI images  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms of ventricular fibrillation and defibrillation requires analysis of epicardial and endocardial potentials throughout the heart. Plunge electrodes permit recording of cardiac potentials at epicardial and endocardial sites, and allow determination of electrical gradients. They also enable us to determine the arrhythmia recurrence sites following failed defibrillation; these sites may be epicardial or endocardial. Therefore, it is necessary to relate the position of the plunge electrodes to the cardiac geometry. We have developed an interactive, computer graphics based system that allows us to locate plunge electrodes on digitized MRI slices of a heart. The system, which can work with any type of image, allows us to identify the epicardial and endocardial points of each plunge electrode on the different MRI slices. Up to 128 different plunge electrodes may be identified to the system. Normalized 3-D coordinates for each epicardial and endocardial electrode point are computed and stored in data files on the computer. Geometry information obtained from this system permits a more thorough understanding of the electrical signals recorded by the plunge electrodes. This information can be used in the study of cardiac excitation and arrhythmias and could help in the development of a more effective lead system for ventricular defibrillation.

Laxer, Cary; Johnson, G. A.; Kavanagh, Katherine M.; Simpson, Edward V.; Ideker, Raymond E.; Smith, William M.

1991-05-01

277

ELLIPSOMETRIC AND ELECTROCHEMICAL STUDIES OF THE STATE OF THE SURFACE OF COBALT, NICKEL AND INDIUM ELECTRODES  

E-print Network

ELLIPSOMETRIC AND ELECTROCHEMICAL STUDIES OF THE STATE OF THE SURFACE OF COBALT, NICKEL AND INDIUM'ellipsométrie est utilisée pour suivre le comportement anodique du cobalt, du nickel et de l'indium en solution

Paris-Sud XI, Université de

278

Localization of neurosurgically implanted electrodes via photograph-MRI-radiograph coregistration  

PubMed Central

Intracranial electroencephalography (iEEG) is clinically indicated for medically refractory epilepsy and is a promising approach for developing neural prosthetics. These recordings also provide valuable data for cognitive neuroscience research. Accurate localization of iEEG electrodes is essential for evaluating specific brain regions underlying the electrodes that indicate normal or pathological activity, as well as for relating research findings to neuroimaging and lesion studies. However, electrodes are frequently tucked underneath the edge of a craniotomy, inserted via a burr hole, or placed deep within the brain, where their locations cannot be verified visually or with neuronavigational systems. We show that one existing method, registration of postimplant CT with preoperative MRI, can result in errors exceeding 1 cm. We present a novel method for localizing iEEG electrodes using routinely acquired surgical photographs, X-ray radiographs, and magnetic resonance imaging (MRI) scans. Known control points are used to compute projective transforms that link the different image sets, ultimately allowing hidden electrodes to be localized, in addition to refining the location of manually registered visible electrodes. As the technique does not require any calibration between the different image modalities, it can be applied to existing image databases. The final result is a set of electrode positions on the patient’s rendered MRI yielding locations relative to sulcal and gyral landmarks on individual anatomy, as well as MNI coordinates. We demonstrate the results of our method in eight epilepsy patients implanted with electrode grids spanning the left hemisphere. PMID:18657573

Dalal, Sarang S.; Edwards, Erik; Kirsch, Heidi E.; Barbaro, Nicholas M.; Knight, Robert T.; Nagarajan, Srikantan S.

2008-01-01

279

Research on rechargeable oxygen electrodes  

NASA Technical Reports Server (NTRS)

Studies were carried out on a number of factors which may influence the behavior of the platinum electrocatalyst of oxygen electrodes for use in rechargeable metal-oxygen batteries or hydrogen-oxygen fuel cells. The effects of pretreatments for various potentials and added ionic species, which could be present in such systems, were studied with reguard to: (1) the state of surface oxidation, (2) platinum dissolution, (3) the kinetics of oxygen evolution and reduction (including the role of hydrogen peroxide), and (4) changes in porous electrode structure. These studies were carried out on smooth platinum, platinized platinum, and Teflon-bonded platinum black electrodes in carefully purified electrolyte solutions. The main factors which appear to affect rechargeable oxygen electrode performance and life are: (1) the buildup of a refractory anodic layer on extended cycling, and (2) the dissolution of platinum.

Giner, J.; Malachesky, P. A.; Holleck, G.

1971-01-01

280

Three Studies Point to Same Risk Gene for Age-Related Macular Degeneration  

MedlinePLUS

... Training and Jobs Three studies point to same risk gene for age-related macular degeneration Listen NIH- ... the same gene as a rare, but powerful risk factor for age-related macular degeneration (AMD), a ...

281

Study of infrared point source simulator for generating the multi-decoy  

NASA Astrophysics Data System (ADS)

The hardware-in-loop test system for infrared point-type guide missile was introduced;The decoy irradiation and motion characteristics were analyzed; multi-decoy generation mode and principle were studied.

Zeng, Chang-e.; Yang, Di; Su, Jian-gang; Huang, Yan-jun; Wang, Zhi-sheng

2013-08-01

282

AN ELECTROANALYTICAL STUDY OF ELECTRODE REACTIONS ON CARBON ANODES DURING ELECTROLYTIC PRODUCTION OF ALUMINUM  

E-print Network

OF ALUMINUM Hongmin Zhu and Donald R. Sadoway Department of Materials Science and Engineering Massachusetts production of aluminum the anodic reactions have been studied on carbon microelectrodes by voltammetry electrolysis in a laboratory-scale aluminum reduction cell. When the voltage exceeds a critical value (about 3

Sadoway, Donald Robert

283

transparent electrode  

NASA Astrophysics Data System (ADS)

We report a new semitransparent inverted polymer solar cell (PSC) with a structure of glass/FTO/nc-TiO2/P3HT:PCBM/MoO3/Ag/MoO3. Because high-temperature annealing which decreased the conductivity of indium tin oxide (ITO) must be handled in the process of preparation of nanocrystalline titanium oxide (nc-TiO2), we replace glass/ITO with a glass/fluorine-doped tin oxide (FTO) substrate to improve the device performance. The experimental results show that the replacing FTO substrate enhances light transmittance between 400 and 600 nm and does not change sheet resistance after annealing treatment. The dependence of device performances on resistivity, light transmittance, and thickness of the MoO3/Ag/MoO3 film was investigated. High power conversion efficiency (PCE) was achieved for FTO substrate inverted PSCs, which showed about 75% increase compared to our previously reported ITO substrate device at different thicknesses of the MoO3/Ag/MoO3 transparent electrode films illuminated from the FTO side (bottom side) and about 150% increase illuminated from the MoO3/Ag/MoO3 side (top side).

Li, Fumin; Chen, Chong; Tan, Furui; Li, Chunxi; Yue, Gentian; Shen, Liang; Zhang, Weifeng

2014-10-01

284

A study on the effect of inlet turbulence on gas mixing for single point aerosol sampling  

E-print Network

A STUDY ON THE, EI I'ECT OF INI, FT TURBULENCE ON GAS MIXING FOR SINGLE POINT AEROSOL SAMPLING A Thesis by ANAND MOHAN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of thc requirements... favorably with the data. The correlation incorporates the idea of a history ol' intensity influencing the mixing at. any downstream point and is much better than an earlier correlation which failed to incorporate thc history of fluctuations. It could...

Mohan, Anand

2001-01-01

285

Partially filled electrodes for digital microfluidic devices  

NASA Astrophysics Data System (ADS)

As digital microfluidics technology evolves, the need for integrating additional elements (e.g., sensing/detection and heating elements) on the electrode increases. Consequently, electrode area for droplet actuation is reduced to create space for accommodating these additional elements, which undesirably affects force generation. Electrodes cannot simply be scaled larger to compensate for this loss of force, as this would also increase droplet volume and thereby compromise the advantages thought in miniaturization. Here, we present a study evaluating, numerically with preliminary experimental verification, different partially filled electrode designs and suggesting designs that combine high actuation forces with a large reduction in electrode area.

Pyne, D. G.; Salman, W. M.; Abdelgawad, M.; Sun, Y.

2013-07-01

286

A Novel In-situ Electrochemical Cell for Neutron Diffraction Studies of Phase Transitions in Small Volume Electrodes of Li-ion Batteries  

SciTech Connect

The design and performance of a novel in-situ electrochemical cell that greatly facilitates the neutron diffraction study of complex phase transitions in small volume electrodes of Li-ion cells, is presented in this work. Diffraction patterns that are Rietveld-refinable could be obtained simultaneously for all the electrodes, which demonstrates that the cell is best suited to explore electrode phase transitions driven by the lithiation and delithiation processes. This has been facilitated by the use of single crystal (100) Si sheets as casing material and the planar cell configuration, giving improved signal-to-noise ratio relative to other casing materials. The in-situ cell has also been designed for easy assembly and to facilitate rapid experiments. The effectiveness of cell is demonstrated by tracking the neutron diffraction patterns during the charging of graphite/LiCoO2 and graphite/LiMn2O4 cells. It is shown that good quality neutron diffraction data can be obtained and that most of the finer details of the phase transitions, and the associated changes in crystallographic parameters in these electrodes, can be captured.

Vadlamani, Bhaskar S [ORNL; An, Ke [ORNL; Jagannathan, M. [University of Utah; Ravi Chandran, K. [University of Utah

2014-01-01

287

[Preparation of OMC-Au/L-Lysine/Au modified glassy carbon electrode and the study on its detection response to hydroquinone and catechol].  

PubMed

Ordered mesoporous carbon-Au nanoparticles (OMC-Au) nanocomposites were synthesized by a one-step chemical reduction route, and an OMC-Au/L-Lysine/Au composite film-modified glassy carbon electrode (GCE) was constructed. The microstructure of OMC and OMC-Au/L-Lysine/Au composite films were characterized by SEM, and the preparation process of OMC-Au/L-Lysine/Au modified glassy carbon electrode was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic oxidation of hydroquinone and catechol on the modified electrode was discussed by differential pulse voltammetry in this study, and a sensor for separate determination of hydroquinone and catechol based on OMC-Au/L-Lysine/Au modified glassy carbon electrode was developed. Under the optimal conditions, the cathodic peak current was linearly related to hydroquinone concentration over ranges from 1.0 x 10(-6) mol x L(-1) to 8.0 x 10(-4) mol x L(-1) with a detection limit of 3.0 x 10(-7) mol x L(-1), and linearly related to catechol concentration from 1.0 x 10(-7) mol x L(-1) to 8.0 x 10(-5) mol x L(-1) with a detection limit of 8.0 x 10(-7) mol x L(-1). PMID:23745436

Zhou, Yao-Yu; Tang, Lin; Li, Zhen; Liu, Yuan-Yuan; Yang, Gui-De; Wu, Meng-Shi; Lei, Xiao-Xia; Zheng, Guang-Ming

2013-03-01

288

Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

289

Electrocatalysts and Electrode Design for Bifunctional Oxygen/Air Electrodes  

NASA Astrophysics Data System (ADS)

Electrocatalysts and appropriate electrode designs have been studied with respect to the development of Bifunctional Air/Oxygen Electrode (BAE). Three groups of catalysts have been prepared: (i) CuxCo3-xO4; (ii) thin films of Co-Ni-Te-O and Co-Te-O and (iii) CoxOv/ZrO2 films. Different catalysts deposited on classical and originally designed GDE were compared by their electrochemical performances.

Nikolova, V.; Iliev, P.; Petrov, K.; Vitanov, T.; Zhecheva, E.; Stoyanova, R.; Valov, I.; Stoychev, D.

290

Novel electrodes for underwater ECG monitoring.  

PubMed

We have developed hydrophobic electrodes that provide all morphological waveforms without distortion of an ECG signal for both dry and water-immersed conditions. Our electrode is comprised of a mixture of carbon black powder (CB) and polydimethylsiloxane (PDMS). For feasibility testing of the CB/PDMS electrodes, various tests were performed. One of the tests included evaluation of the electrode-to-skin contact impedance for different diameters, thicknesses, and different pressure levels. As expected, the larger the diameter of the electrodes, the lower the impedance and the difference between the large sized CB/PDMS and the similarly-sized Ag/AgCl hydrogel electrodes was at most 200 k?, in favor of the latter. Performance comparison of CB/PDMS electrodes to Ag/AgCl hydrogel electrodes was carried out in three different scenarios: a dry surface, water immersion, and postwater immersion conditions. In the dry condition, no statistical differences were found for both the temporal and spectral indices of the heart rate variability analysis between the CB/PDMS and Ag/AgCl hydrogel (p > 0.05) electrodes. During water immersion, there was significant ECG amplitude reduction with CB/PDMS electrodes when compared to wet Ag/AgCl electrodes kept dry by their waterproof adhesive tape, but the reduction was not severe enough to obscure the readability of the recordings, and all morphological waveforms of the ECG signal were discernible even when motion artifacts were introduced. When water did not penetrate tape-wrapped Ag/AgCl electrodes, high fidelity ECG signals were observed. However, when water penetrated the Ag/AgCl electrodes, the signal quality degraded to the point where ECG morphological waveforms were not discernible. PMID:24845297

Reyes, Bersain A; Posada-Quintero, Hugo F; Bales, Justin R; Clement, Amanda L; Pins, George D; Swiston, Albert; Riistama, Jarno; Florian, John P; Shykoff, Barbara; Qin, Michael; Chon, Ki H

2014-06-01

291

A study of the relationship between the effect on polarization of iron electrodes and the inhibitor efficiencies for some organic amines in acid solution  

E-print Network

of the polarized cathodes and to their inhibitor efficiencies? as deterained by corros1on rate studies, Xt has been found that, for the anines investigated and ewer the concentration ranges employed, the per cent of electrode surfaoe area sacked as detersined... by scans of the electrolysis bridge is approxinately proportional to the per cent inhibitor efficiencies, as detersined by corrosion rate studies. PAGE I Int redact i on ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ i ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 II Literature Surrey r ~ ~ ~ ~ o...

Burns, Lawrence Raymond

1956-01-01

292

Soft X-ray absorption spectroscopic studies with different probing depths: Effect of an electrolyte additive on electrode surfaces  

NASA Astrophysics Data System (ADS)

A solid electrolyte interphase (SEI) formed on a model LiCoO2 electrode was analyzed by the ultra-soft X-ray absorption spectroscopy (XAS). The data of Li K-, B K-, C K-, O K-, and Co L-edges spectra for the SEI film on the electrode were collected using three detection methods with different probing depths. The electrode was prepared by a pulsed laser deposition method. All the spectral data consistently indicated that the SEI film containing lithium carbonate was instantly formed just after the soak of the electrode into the electrolyte solution and that it decomposed during the repeated charge-discharge reactions. The decomposition of the SEI film seems to cause the deterioration in lithium ion battery cycle performance. By adding lithium bis(oxalate) borate (LiBOB) to the electrolyte the decomposition could be suppressed leading to longer cycle life. It was found that some of the Co ions at the electrode surface were reduced to Co(II) during the charge-discharge reactions and this reaction could also be suppressed by the addition of LiBOB.

Yogi, Chihiro; Takamatsu, Daiko; Yamanaka, Keisuke; Arai, Hajime; Uchimoto, Yoshiharu; Kojima, Kazuo; Watanabe, Iwao; Ohta, Toshiaki; Ogumi, Zenpachi

2014-02-01

293

Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO2) electrodes  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO2), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode, notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.

Wei, Jun-Jun; Zhu, Xiu-Ping; Lü, Fan-Xiu; Ni, Jin-Ren

2011-10-01

294

Ion-Selective Electrodes.  

ERIC Educational Resources Information Center

Literature on ion-selective electrodes (ISEs) is reviewed in seven sections: books, conferences, reviews; potentiometric membrane electrodes; glass and solid-state membrane electrodes; liquid and polymer membrane ISEs; coated wire electrodes, ion-selective field effect transistors, and microelectrodes; gas sensors and selective bioelectrode…

Arnold, Mark A.; Meyerhoff, Mark E.

1984-01-01

295

Comparative study of protonic conducting polymers incorporated in the oxygen electrode of the PEMFC  

NASA Astrophysics Data System (ADS)

The kinetics of the reduction of oxygen at the surface of a platinum disc covered with thin layers of polymer has been studied in 0.5 M H 2SO 4 at ambient temperature in order to establish to what extent the polymer affects the reaction mechanism. Experiments were performed particularly to determine the oxygen permeability DfCf (product of the diffusion coefficient and the oxygen concentration in the film) for Nafion ® and other polymers such as sulfonated polyimide (PIS), sulfonated polyetherketone (PEEKs) and non-sulfonated polybenzimidazole (PBI). The product DfCf depends on the nature of the polymer. Furthermore, how well the active layer works depends markedly on the amount of polymer it contains.

Ayad, A.; Bouet, J.; Fauvarque, J. F.

296

The sensitivity comparison of bar electrode and disposable ring electrode for recording of lateral femoral cutaneous nerve  

PubMed Central

Objectives: To compare the sensitivity of bar electrode and disposable ring electrode for recording of lateral femoral cutaneous (LFCN) Materials and Methods: A total of 23 subjects (13 females, 10 males, mean age: 49.6 ± 9.6 (range: 29-63) were recruited in the study. A total of 36 recordings were obtained with each electrode (with bar and disposable ring electrodes) from the subjects. The comparison of data was performed with percentages and student T-table test. Results: The response rate was 98% (35 out of 36 recordings) with bar electrode and 88% (32 out of 36 recordings) with disposable ring electrode. Although the sensitivity rate of bar electrode is slightly higher than of disposable ring electrode, there were no statistically significant differences in detecting the onset latency, peak latency, and amplitude of LFCN. Conclusion: The recording sensitivity of LFCN is higher with bar electrode than disposable ring electrode. However, disposable ring electrode can be used alternatively. PMID:25024568

Burakgazi, Ahmet Z.; Russo, Mary; Richardson, Perry K.

2014-01-01

297

A comparative study for the estimation of geodetic point velocity by artificial neural networks  

NASA Astrophysics Data System (ADS)

Space geodesy era provides velocity information which results in the positioning of geodetic points by considering the time evolution. The geodetic point positions on the Earth's surface change over time due to plate tectonics, and these changes have to be accounted for geodetic purposes. The velocity field of geodetic network is determined from GPS sessions. Velocities of the new structured geodetic points within the geodetic network are estimated from this velocity field by the interpolation methods. In this study, the utility of Artificial Neural Networks (ANN) widely applied in diverse fields of science is investigated in order to estimate the geodetic point velocities. Back Propagation Artificial Neural Network (BPANN) and Radial Basis Function Neural Network (RBFNN) are used to estimate the geodetic point velocities. In order to evaluate the performance of ANNs, the velocities are also interpolated by Kriging (KRIG) method. The results are compared in terms of the root mean square error (RMSE) over five different geodetic networks. It was concluded that the estimation of geodetic point velocity by BPANN is more effective and accurate than by KRIG when the points to be estimated are more than the points known.

Yilmaz, M.; Gullu, M.

2014-06-01

298

Study Abroad Office Key Data Points Academic Years 2007/08 -2012/13  

E-print Network

Study Abroad Office Key Data Points Academic Years 2007/08 - 2012/13 Students Participating 1,261 students have studied abroad over the past 6 years, a number that has increased about 7% per year hours have been earned by study abroad students: 46% were in the student's major or minor. All

Illinois at Chicago, University of

299

Study on the sonic point in unsteady shock reflections via numerical flowfield analysis  

NASA Astrophysics Data System (ADS)

A current literature review revealed that unsteady shock reflection is an active research field in terms of the number of still unanswered questions in this area. One of the unresolved aspects of unsteady shock reflection is the relationship between the catch-up and sonic points. In a recent experiment, Skews and Kleine found that the catch-up point is reached at a higher wall angle than the theoretical sonic point predicted by the steady-state two-shock theory. This thesis attempts to shed some light on these matters via numerical flowfield analysis of unsteady shock reflections. Two-dimensional computations are performed using a locally adaptive unstructured unsteady Euler/Navier-Stokes code. At the first stage, a general guideline for numerical modeling of shock wave front structure using the Navier-Stokes equations on adaptive unstructured grid is presented. Obtained results can be directly used for selection of grid resolution required to study shock reflection problems in a viscous flowfields. Then, various techniques for determination of the location of the sonic/catch-up points in unsteady shock reflection based on numerical flowfield analysis are introduced. The results obtained with these techniques regarding the sonic/catch-up points locations are not in agreement with the experimental results of Skews and Kleine. The causes of this disagreement between the experiments and the present CFD study are studied by imitating the experimental technique used for catch-up point determination. It is shown that the reason for this disagreement is that the shock thickness captured in experimental images exceeds the shock physical thickness by a few orders of magnitude, which leads to detection of the catch-up point at higher wall angles. Three flow models are studied to investigate the location of the sonic/catch-up points on a circular cylinder. The first model is based on the Euler (inviscid, non-heat-conducting) equations and an ideal reflecting surface (impermeable wall boundary condition). The computational experiment for this case shows that the sonic and catch-up points are actually the same points, which approach to the theoretical sonic point with grid refinement. The other two models are intend to study the effect of viscosity on the sonic/catch-up points. At first, the ideal reflecting surface (slip boundary condition) is considered. It is shown that for this case the sonic and catch-up points are again the same points, but the viscous effects (finite shock thickness) cause the sonic/catch-up point to be delayed (to occur at lower wall angles) as compared to the two-shock theory predictions. The final model employs the non-slip reflecting surface. Since in this model the flow velocity at the wall is zero, the sonic point cannot be obtained on the reflection surface; however, the catch-up point can be defined and analyzed. The results of the simulations show that even larger delay for the catch-up point is obtained for the viscous case with the non-slip reflecting surface (in the presence of the boundary layer) as compared to the viscous case with the ideal reflecting surfaces.

Hakkaki-Fard, Ali

300

HSPES membrane electrode assembly  

NASA Technical Reports Server (NTRS)

An improved fuel cell electrode, as well as fuel cells and membrane electrode assemblies that include such an electrode, in which the electrode includes a backing layer having a sintered layer thereon, and a non-sintered free-catalyst layer. The invention also features a method of forming the electrode by sintering a backing material with a catalyst material and then applying a free-catalyst layer.

Kindler, Andrew (Inventor); Yen, Shiao-Ping (Inventor)

2000-01-01

301

An experimental and computational study of solid oxide fuel cell electrodes  

NASA Astrophysics Data System (ADS)

Composite nano-LSCF-GDC cathodes were sythesized using an infiltration method achieving polarization resistances as low as 0.2 Ocm 2 at 600°C. Instead of firing both the LSCF and GDC phase in one step, as is done conventionally, the processing of each phase was separate, allowing for individual control to optimize the microstructure of each phase. It was found that firing the GDC scaffold at 1100°C followed by infiltrating LSCF and firing at 800°C yielded optimal performance. The resulting microstructure was a sub-micron scale GDC matrix covered with a nano-scaled LSCF particle network. It was also found that up to 12 vol% LSCF (the highest loading tested), the performance of the cathodes continually improved. A simple model relating the performance of the cathodes to the surface area of the LSCF, electrocatalyst phase showed good agreement with experimental results without the use of fitting parameters at 600°C. Based on the knowledge that the surface area of the LSCF directly impacts the performance, coarsening was then assumed to be the primary degradation mechanism of the cathode. An accelerated testing method was developed, where the cathodes were aged at high temperatures (650--850°C), and impedance measurements were taken at 600°C. This data was fit to a power-law model for coarsening of a 3D particle on a 2D surface. The fit was very good indicating that coarsening was in fact responsible for the decrease in performance. SEM images in the same location after various aging treatments also showed a loss of surface area in the LSCF phase. An activation energy range was found from fitting the power-law model, and predicted degradation over 40,000h was between 39--74%. Finally, a dual infiltration of both LSCF and GDC into a GDC matrix showed decreased degradation, likely because the GDC particles were acting to pin the LSCF and slow the coarsening. Additionally, a phase field model was developed to describe the growth and coarsening of electrocatalyst particles. Both bulk and surface diffusion were accounted for in this model, and a method for relating the mobility at the surface to the surface diffusion coefficient was developed. Since the diffusion coefficients of this novel system remain unknown, a parametric study of diffusion coefficients was done revealing how various ratios of bulk and surface diffusion in the substrate and particle affect the microstructural evolution of the anode.

Shah, Megna Narendra

2011-12-01

302

Preheated ignition and work function studies on alkaline earth metal oxides coated tungsten electrodes of fluorescent lamps  

NASA Astrophysics Data System (ADS)

This paper describes measurements on the alkaline earth (Ba, Sr, Ca) oxide layers utilized as emitting material in fluorescent lamp electrodes. In a first approach we compared the emission capabilities of the different materials (BaO, SrO and CaO coatings on tungsten filaments) by their ability to facilitate the start of a lamp. In a second investigation the work function was measured quantitatively by means of a Kelvin probe. Basically, the results of both measurements coincide. The impact of sample geometry on measurement results of a Kelvin probe applied for work function measurements of lamp electrodes are discussed in detail.

Langer, Reinhard; Dar, Farrukh; Hilscher, Achim; Horn, Siegfried; Tidecks, Reinhard

2015-03-01

303

Analysis of non-point and point source pollution in China: case study in Shima Watershed in Guangdong Province  

NASA Astrophysics Data System (ADS)

China economy has been rapidly increased since 1978. Rapid economic growth led to fast growth of fertilizer and pesticide consumption. A significant portion of fertilizers and pesticides entered the water and caused water quality degradation. At the same time, rapid economic growth also caused more and more point source pollution discharge into the water. Eutrophication has become a major threat to the water bodies. Worsening environment problems forced governments to take measures to control water pollution. We extracted land cover from Landsat TM images; calculated point source pollution with export coefficient method; then SWAT model was run to simulate non-point source pollution. We found that the annual TP loads from industry pollution into rivers are 115.0 t in the entire watershed. Average annual TP loads from each sub-basin ranged from 0 to 189.4 ton. Higher TP loads of each basin from livestock and human living mainly occurs in the areas where they are far from large towns or cities and the TP loads from industry are relatively low. Mean annual TP loads that delivered to the streams was 246.4 tons and the highest TP loads occurred in north part of this area, and the lowest TP loads is mainly distributed in middle part. Therefore, point source pollution has much high proportion in this area and governments should take measures to control point source pollution.

Fang, Huaiyang; Lu, Qingshui; Gao, Zhiqiang; Shi, Runhe; Gao, Wei

2013-09-01

304

A study of impulsive multiterm fractional differential equations with single and multiple base points and applications.  

PubMed

We discuss the existence and uniqueness of solutions for initial value problems of nonlinear singular multiterm impulsive Caputo type fractional differential equations on the half line. Our study includes the cases for a single base point fractional differential equation as well as multiple base points fractional differential equation. The asymptotic behavior of solutions for the problems is also investigated. We demonstrate the utility of our work by applying the main results to fractional-order logistic models. PMID:24578623

Liu, Yuji; Ahmad, Bashir

2014-01-01

305

A Numerical Study of Active-Set and Interior-Point Methods for Bound Constrained Optimization  

Microsoft Academic Search

This papers studies the performance of several interior-point and active-set methods on bound constrained optimization problems.\\u000a The numerical tests show that the sequential linear-quadratic programming (SLQP) method is robust, but is not as effective\\u000a as gradient projection at identifying the optimal active set. Interior-point methods are robust and require a small number\\u000a of iterations and function evaluations to converge. An

Long Hei; Jorge Nocedal; Richard A. Waltz

306

Satellite Power Systems (SPS) concept definition study: SPS point design definition update  

NASA Technical Reports Server (NTRS)

The Rockwell International Photovoltaic Satellite Based Satellite Power System (SPS) Point Design as it is defined through July 1978 is described. The point design to be presented is the result of a series of trade studies. The data established during the period May through July 1978 is incorporated in this summary document. The system relationship of the total Satellite Power System is depicted. This document discusses only the first two elements: the satellite and ground systems.

Hanley, G. M.

1978-01-01

307

Experimental study of adaptive pointing and tracking for large flexible space structures  

NASA Technical Reports Server (NTRS)

This paper describes an experimental study of adaptive pointing and tracking control for flexible spacecraft conducted on a complex ground experiment facility. The algorithm used in this study is based on a multivariable direct model reference adaptive control law. Several experimental validation studies were performed earlier using this algorithm for vibration damping and robust regulation, with excellent results. The current work extends previous studies by addressing the pointing and tracking problem. As is consistent with an adaptive control framework, the plant is assumed to be poorly known to the extent that only system level knowledge of its dynamics is available. Explicit bounds on the steady-state pointing error are derived as functions of the adaptive controller design parameters. It is shown that good tracking performance can be achieved in an experimental setting by adjusting adaptive controller design weightings according to the guidelines indicated by the analytical expressions for the error.

Boussalis, D.; Bayard, D. S.; Ih, C.; Wang, S. J.; Ahmed, A.

1991-01-01

308

A simulation study of the micro-grooved electrode structure for back-contact back-junction silicon solar cell  

NASA Astrophysics Data System (ADS)

A micro-grooved electrode structure is investigated to illustrate its advantages when applied to the back-contact back-junction (BC–BJ) silicon solar cell. The finite element analysis shows that the micro-grooved electrodes enhances the photo-carrier collection and weakens the dependence of collection ability on pitch distance. The geometries of micro-groove are found to have little impact on the cell performance. These advantages open possibilities for the implementation of low cost fabrication methods. As a demonstration, a process involving laser doping and screen printing techniques are proposed and analyzed. The simulation results show that the laser induced lattice damage causes negligible deterioration of device electrical properties and the presence of parasitic metal insulator semiconductor structure near the screen printed electrodes actually leads to a performance improvement rather than degradation. Our preliminary results indicate that the micro-grooved electrode structure is promising for fabricating low cost high efficiency BC–BJ silicon solar cells.

Zhang, Bo; Yang, Jianfeng

2015-01-01

309

Modeling defibrillation electrode performance.  

PubMed

A Boundary Element (BE) model was developed of the electric potential field in the heart arising from electric potentials applied on implanted defibrillator electrodes. The model solved Laplace's equation for potential and was implemented using the BE method with realistic torso structures. An efficient out-of-core solver was developed, allowing any size problem to be solved, subject only to computer speed and time available. A method was also developed that allowed matrices calculated in one problem to be used in other, similar problems, often reducing calculation times by an order of magnitude. Model validation included comparison with myocardial potentials from a finite element model and clinically found voltage and resistance at defibrillation threshold from 29 patients. The model was used in investigations of transvenous electrode configurations, with potential found for reduction in defibrillation voltage and energy. The BE model was successful in modelling the electric field in the torso, in predicting implantable defibrillator performance and in finding application in electrode performance studies. PMID:17281079

Gale, Timothy

2005-01-01

310

Briefing Points: Total Remuneration Study General Campus Ladder-rank Faculty (8-8-14)  

E-print Network

#12;Briefing Points: Total Remuneration Study General Campus Ladder-rank Faculty (8-8-14) Background · In July, 2013, then President Mark Yudof approved a total remuneration study of general campus the consultants in December 2013 and worked with them from January through July 2014. · This Total Remuneration

Rose, Michael R.

311

Micromachined electrode array  

DOEpatents

An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

2007-12-11

312

Flexible retinal electrode array  

DOEpatents

An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2006-10-24

313

High frequency reference electrode  

DOEpatents

A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

Kronberg, James W. (Aiken, SC)

1994-01-01

314

Weighted total least squares for rigid body transformation and comparative study on heteroscedastic points  

NASA Astrophysics Data System (ADS)

Aligning two point clouds is the iterated closest point algorithm which starts with two point clouds to estimate three translates and rotations. Traditional registration are searching the optimal solutions at the cost function of the minimum residual squares without consideration of points covariance. Closed-form or iterative least squares methods are performed to search the solutions, and total least squares (TLS) methods are introduced in recent years. The ordinary least squares (OLS) and OTLS methods can not work on the heteroscedastic cases. So element-wise weighted TLS (EWTLS) and row-wise weighted TLS (RWTLS) methods are introduced to solve the rigid body transformation problem after the initial values obtained by Procrustes analysis method. Comparative studies are made with the weighted and unweighted estimators of OLS, TLS, mixed OLS and TLS, EWTLS and RWTLS. The results indicate that the RWTLS method is the highest accuracy estimator, and be much more accurate than the unweighted OLS and TLS methods.

Zhou, Yongjun; Deng, Caihua; Zhu, Jianjun

2011-10-01

315

Computational Study on Subdural Cortical Stimulation - The Influence of the Head Geometry, Anisotropic Conductivity, and Electrode Configuration  

PubMed Central

Subdural cortical stimulation (SuCS) is a method used to inject electrical current through electrodes beneath the dura mater, and is known to be useful in treating brain disorders. However, precisely how SuCS must be applied to yield the most effective results has rarely been investigated. For this purpose, we developed a three-dimensional computational model that represents an anatomically realistic brain model including an upper chest. With this computational model, we investigated the influence of stimulation amplitudes, electrode configurations (single or paddle-array), and white matter conductivities (isotropy or anisotropy). Further, the effects of stimulation were compared with two other computational models, including an anatomically realistic brain-only model and the simplified extruded slab model representing the precentral gyrus area. The results of voltage stimulation suggested that there was a synergistic effect with the paddle-array due to the use of multiple electrodes; however, a single electrode was more efficient with current stimulation. The conventional model (simplified extruded slab) far overestimated the effects of stimulation with both voltage and current by comparison to our proposed realistic upper body model. However, the realistic upper body and full brain-only models demonstrated similar stimulation effects. In our investigation of the influence of anisotropic conductivity, model with a fixed ratio (1?10) anisotropic conductivity yielded deeper penetration depths and larger extents of stimulation than others. However, isotropic and anisotropic models with fixed ratios (1?2, 1?5) yielded similar stimulation effects. Lastly, whether the reference electrode was located on the right or left chest had no substantial effects on stimulation. PMID:25229673

Kim, Donghyeon; Seo, Hyeon; Kim, Hyoung-Ihl; Jun, Sung Chan

2014-01-01

316

Cryogenic Propellant Storage and Transfer Technology Demonstration: Prephase A Government Point-of-Departure Concept Study  

NASA Technical Reports Server (NTRS)

The primary purpose of this study was to define a point-of-departure prephase A mission concept for the cryogenic propellant storage and transfer technology demonstration mission to be conducted by the NASA Office of the Chief Technologist (OCT). The mission concept includes identification of the cryogenic propellant management technologies to be demonstrated, definition of a representative mission timeline, and definition of a viable flight system design concept. The resulting mission concept will serve as a point of departure for evaluating alternative mission concepts and synthesizing the results of industry- defined mission concepts developed under the OCT contracted studies

Mulqueen, J. A.; Addona, B. M.; Gwaltney, D. A.; Holt, K. A.; Hopkins, R. C.; Matis, J. A.; McRight, P. S.; Popp, C. G.; Sutherlin, S. G.; Thomas, H. D.; Baysinger, M. F.; Maples, C. D.; Capizzo, P. D.; Fabisinski, L. L.; Hornsby, L. S.; Percy, T. K.; Thomas, S. D.

2012-01-01

317

Post-test evaluation of oxygen electrodes from solid oxide electrolysis stacks.  

SciTech Connect

The oxygen electrodes from two solid oxide electrolysis stacks that performed high-temperature steam electrolysis (HTSE) and produced hydrogen for 1000 and 2000 h, respectively, were examined using X-ray fluorescence, X-ray absorption near edge structure (XANES), four-point resistivity, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Raman micro-spectroscopy to determine possible causes for the degradation in stack performance over the test periods. These techniques yielded information such as elemental distribution, oxidation state, phases present, electrode delamination, and porosity within the electrode layers. From these studies, we found two phenomena that were likely the cause of increasingly poor oxygen electrode performance over time. The first source of degradation was chromium substitution into the oxygen electrode bond layer, which serves to bond the cell to the flow field and interconnect. This is caused by migration of a chromium species from the bipolar plate. The effect of this is a significant increase in the electrical resistance of the bond layer material. The other source of degradation identified was oxygen electrode delamination. The cause of electrode delamination, which is locally catastrophic to the operation of the cell, is unclear; however, we will discuss two possible mechanisms that might cause this phenomenon.

Mawdsley, J. R.; Carter, J. D.; Kropf, A. J.; Yildiz, B.; Maroni, V. A.; Massachusetts Inst. of Tech.

2009-05-01

318

A quantitative study on accumulation of age mass around stagnation points in nested flow systems  

NASA Astrophysics Data System (ADS)

The stagnant zones in nested flow systems have been assumed to be critical to accumulation of transported matter, such as metallic ions and hydrocarbons in drainage basins. However, little quantitative research has been devoted to prove this assumption. In this paper, the transport of age mass is used as an example to demonstrate that transported matter could accumulate around stagnation points. The spatial distribution of model age is analyzed in a series of drainage basins of different depths. We found that groundwater age has a local or regional maximum value around each stagnation point, which proves the accumulation of age mass. In basins where local, intermediate and regional flow systems are all well developed, the regional maximum groundwater age occurs at the regional stagnation point below the basin valley. This can be attributed to the long travel distances of regional flow systems as well as stagnancy of the water. However, when local flow systems dominate, the maximum groundwater age in the basin can be located around the local stagnation points due to stagnancy, which are far away from the basin valley. A case study is presented to illustrate groundwater flow and age in the Ordos Plateau, northwestern China. The accumulation of age mass around stagnation points is confirmed by tracer age determined by 14C dating in two boreholes and simulated age near local stagnation points under different dispersivities. The results will help shed light on the relationship between groundwater flow and distributions of groundwater age, hydrochemistry, mineral resources, and hydrocarbons in drainage basins.

Jiang, Xiao-Wei; Wan, Li; Ge, Shemin; Cao, Guo-Liang; Hou, Guang-Cai; Hu, Fu-Sheng; Wang, Xu-Sheng; Li, Hailong; Liang, Si-Hai

2012-12-01

319

Lithium-ion drifting: Application to the study of point defects in floating-zone silicon  

SciTech Connect

The use of lithium-ion (Li{sup +}) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li{sup +} drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li{sup +} drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li{sup +} compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

Walton, J.T.; Wong, Y.K. [Lawrence Berkeley National Lab., CA (United States); Zulehner, W. [Wacker-Siltronic GmbH, Burghausen (Germany)] [and others

1997-04-01

320

Lithium-ion drifting: Application to the study of point defects in floating-zone silicon  

NASA Technical Reports Server (NTRS)

The use of lithium-ion (Li(+)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(+) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li(+) drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li(+) compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

Walton, J. T.; Wong, Y. K.; Zulehner, W.

1997-01-01

321

Electrodes for long-term esophageal electrocardiography.  

PubMed

The emerging application of long-term and high-quality ECG recording requires alternative electrodes to improve the signal quality and recording capability of surface skin electrodes. The esophageal ECG has the potential to overcome these limitations but necessitates novel recorder and lead designs. The electrode material is of particular interest, since the material has to ensure conflicting requirements like excellent biopotential recording properties and inertness. To this end, novel electrode materials like PEDOT and silver-PDMS as well as established electrode materials such as stainless steel, platinum, gold, iridium oxide, titanium nitride, and glassy carbon were investigated by long-term electrochemical impedance spectroscopy and model-based signal analysis using the derived in vitro interfacial properties in conjunction with a dedicated ECG amplifier. The results of this novel approach show that titanium nitride and iridium oxide featuring microstructured surfaces did not degrade when exposed to artificial acidic saliva. These materials provide low electrode potential drifts and insignificant signal distortion superior to surface skin electrodes making them compatible with accepted standards for ambulatory ECG. They are superior to the noble and polarizable metals such as platinum, silver, and gold that induced more signal distortions and are superior to esophageal stainless steel electrodes that corrode in artificial saliva. The study provides rigorous criteria for the selection of electrode materials for prolonged ECG recording by combining long-term in vitro electrode material properties with ECG signal quality assessment. PMID:23649132

Niederhauser, Thomas; Haeberlin, Andreas; Marisa, Thanks; Jungo, Michael; Goette, Josef; Jacomet, Marcel; Abacherli, Roger; Vogel, Rolf

2013-09-01

322

Internal reflection flash photolysis study of the photochemistry of eosin at TiO sub 2 semiconductor electrodes  

SciTech Connect

It is shown that the photoelectrochemical data on eosin Y sensitized TiO{sub 2} single-crystal electrodes cannot be interpreted unambiguously without concomitant data from flash photolysis measurements on this system. By use of a combination of internal reflection spectroscopy and laser flash photolysis, electron exchange with TiO{sub 2} was observed for the excited singlet state, the triplet state, and the cation radical of the dye. With a temporal resolution of 100 ns, the kinetics of the charge transfer are compared with those of the dye in solution and used to interpret the photoelectrochemistry of the dye at the electrode. Spectroscopic evidence revealed photocurrent production by the triplet state and a reduction of the eosin cation radical by electrons from the TiO{sub 2} conduction band and by hydroquinone.

Ryan, M.A.; Fitzgerald, E.C.; Spitler, M.T. (Polaroid Corp., Cambridge, MA (USA))

1989-08-10

323

Corneal-shaping electrode  

DOEpatents

The disclosure relates to a circulating saline electrode for changing corneal shape in eyes. The electrode comprises a tubular nonconductive electrode housing having an annular expanded base which has a surface substantially matched to a subject corneal surface. A tubular conductive electrode connected to a radiofrequency generating source is disposed within the electrode housing and longitudinally aligned therewith. The electrode has a generally hemispherical head having at least one orifice. Saline solution is circulated through the apparatus and over the cornea to cool the corneal surface while radiofrequency electric current emitted from the electrode flows therefrom through the cornea to a second electrode, on the rear of the head. This current heats the deep corneal stroma and thereby effects corneal reshaping as a biological response to the heat.

Doss, James D. (Los Alamos, NM); Hutson, Richard L. (Los Alamos, NM)

1982-01-01

324

High potential durability of LiNi0.5Mn1.5O4 electrodes studied by surface sensitive X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Phenomena at electrode/electrolyte interface of LiNi0.5Mn1.5O4 are studied by in situ total-reflection fluorescence X-ray absorption spectroscopy (TRF-XAS), ex situ X-ray photoelectron spectroscopy (XPS), and electrochemical tests. Flat and well-defined thin films of LiNi0.5Mn1.5O4 prepared by pulsed laser deposition (PLD) are used as model electrodes to facilitate the observation of the interface. The thin-film LiNi0.5Mn1.5O4 electrode showed good cycling characteristics at around 4.7 V vs. Li/Li+. The TRF-XAS measurements reveal that nickel and manganese species at the surface have almost the same chemical states and local environments as those in the bulk when in contact with organic electrolyte solutions (1 mol dm-3 LiClO4 in a 1:1 volumetric mixture of ethylene carbonate and diethyl carbonate). This is in sharp contrast to the behavior of a LiCoO2 electrode, in which the surface cobalt species is irreversibly reduced by soaking to the organic electrolyte solutions, leading to gradual material deterioration during the delithiation/lithiation cycling (D. Takamatsu et al., Angew. Chem. Int. Edit., 51 (2012) 11597). It is suggested that the electrolyte decomposition products detected by XPS form a protective layer to restrict the reduction of the surface species of LiNi0.5Mn1.5O4, leading to good cycling characteristics of LiNi0.5Mn1.5O4 in spite of its high operating potential.

Kawaura, Hiroyuki; Takamatsu, Daiko; Mori, Shinichiro; Orikasa, Yuki; Sugaya, Hidetaka; Murayama, Haruno; Nakanishi, Kouji; Tanida, Hajime; Koyama, Yukinori; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi

2014-01-01

325

Multiscale porous fuel cell electrodes  

NASA Astrophysics Data System (ADS)

Porous electrodes are widely used in fuel cells to enhance electrode performance due to their high surface area. Increasingly, such electrodes are designed with both micro-scale and nano-scale features. In the current work, carbon based porous materials have been synthesized and utilized as bioelectrode support for biofuel cells, analysis of such porous electrodes via rotating disk electrode has been enhanced by a numerical model that considers diffusion and convection within porous media. Finally, porous perovskite metal oxide cathodes for solid oxide fuel cell have been modeled to simulate impedance response data obtained from symmetric cells. Carbon fiber microelectrodes (CFME) were fabricated to mimic the microenvironment of carbon fiber paper based porous electrodes. They were also miniature electrodes for small-scale applications. As observed by scanning electron microscopy (SEM), carbon nanotubes (CNTs) formed a homogeneously intertwined matrix. Biocatalysts can fully infiltrate this matrix to form a composite, with a significantly enhanced glucose oxidation current---that is 6.4 fold higher than the bare carbon fiber electrodes. Based on the CNT based porous matrix, polystyrene beads of uniform diameter at 500 nm were used as template to tune the porous structure and enhance biomolecule transport. Focused ion beam (FIB) was used to observe the morphology both at the surface and the cross-section. It has been shown that the template macro-pores enhanced the fuel transport and the current density has been doubled due to the improvement. Like commonly used rotating disk electrode, the porous rotating disk electrode is a system with analytically solved flow field. Although models were proposed previously with first order kinetics and convection as the only mass transport at high rotations, some recent findings indicated that diffusion could play an important role at all disk rotation rates. In the current proposed model, enzymatic kinetics that follow a Ping Pong Bi Bi mechanism was considered, diffusional transport included, and the electrolyte transport of substrate outside the porous media discussed as well. Composite solid oxide fuel cells have good power generation due to enhanced ion conductivity in the cathode achieved by inclusion of high oxygen ion conductivity materials. Impedance spectroscopies of such cathodes were modeled to study the underlying transport and kinetic mechanisms. The effects of electronic conductor loading were studied, including loading values below the percolation threshold. The conductivity and oxygen surface exchange reaction rate were fitted to experimental data and percolation theory was utilized to explain the fitted trends.

Wen, Hao

326

Analysis of charge-injection characteristics at electrode-organic interfaces: Case study of transition-metal oxides  

Microsoft Academic Search

The formation of resistance-free or Ohmic contacts at metal\\/organic interfaces remains a significant challenge for achieving high-performance organic electronic devices such as organic light-emitting diodes. Several oxides have recently been reported to yield extremely low-voltage devices and thus have excited a renewed interest in developing the next generation of contacting electrodes. In this paper, major metal oxides, CuO, Cu2O ,

Z. B. Wang; M. G. Helander; M. T. Greiner; J. Qiu; Z. H. Lu

2009-01-01

327

Electrochemical studies of ceramic carbon electrodes for fuel cell systems: A catalyst layer without sulfonic acid groups  

Microsoft Academic Search

Ceramic carbon electrodes (CCEs) have been produced via the sol–gel process using 20% Pt on Vulcan XC72 carbon black and tetra ethyl orthosilicate (TEOS) as the organosilane precursor. This process produces a homogenous distribution of SiO2 and carbon supported Pt catalyst. Electrochemical experiments (cyclic voltammetry, electrochemical impedance spectroscopy) were performed to determine the effect of SiO2 loading on the active

Jennie I. Eastcott; E. Bradley Easton

2009-01-01

328

Low-temperature study of lithium-ion cells using a Li ySn micro-reference electrode  

Microsoft Academic Search

Lithium-ion batteries are considered to be the next battery system for hybrid electric vehicles (HEVs) due to their high power density. However, their power is severely limited at ?30°C and the concern exists that lithium metal could plate on the negative electrode during regen (charge) pulses. The goal of this work is to determine the reason for this poor low-temperature

Andrew N. Jansen; Dennis W. Dees; Daniel P. Abraham; Khalil Amine; Gary L. Henriksen

2007-01-01

329

Study of the contribution of cobalt additive to the behavior of the nickel oxy-hydroxide electrode by potentiodynamic techniques  

Microsoft Academic Search

Using stepwise potentiodynamic cycling with observations of the chronoamperometric responses, we demonstrated different behaviors for Co additives in nickel oxy-hydroxides electrodes (NOE), depending on their form: either co-precipitated or post-added as a coating. First, we show that for pure Co(OH)2, oxidation occurs at 0.9 V directly in a solid-state process or through a dissolution re-crystallization process, depending on the oxidation

V Pralong; Y Chabre; A Delahaye-Vidal; J.-M Tarascon

2002-01-01

330

A comparative study of the electrochemical behavior of complementary polymer electrochromic devices based on different counter-electrodes  

NASA Astrophysics Data System (ADS)

8,11-di-(4-thiophen-2-yl)acenaphtho[1,2-b]quinoxaline (DTAQ) was successfully synthesized via a Stille coupling reaction and the corresponding polymer (PDTAQ) was prepared electrochemically. The spectroelectrochemical and electrochromic properties of the polymer film reveal that PDTAQ film shows distinct color states (purple in the neutral state and blue in the oxidized state), and optical contrast (?T%) of 45.16% at 772 nm and 49.39% at 1100 nm with switching times of 2.5 and 0.5 s. Complementary electrochromic devices, which are based on the PDTAQ film as the working electrode, Prussian blue (PB) and V2O5 as counter-electrodes, respectively, and LiClO4/PC solution as the electrolyte, were assembled and characterized. The results illustrate that the properties of the PDTAQ/PB and PDTAQ/V2O5 devices (including the absorption, color changes, ?T% and response times) can be modified by the counter-electrodes. Furthermore, the PDTAQ/V2O5 device exhibits a significantly higher contrast ratio in the visible region (34.92% at 771 nm) and much faster response time (0.4 s) than the PDTAQ/PB device (21.32% at 552 nm).

Du, Qing; Mi, Sai; Zheng, Jianming; Xu, Chunye

2013-12-01

331

Quantitative femtosecond charge transfer dynamics at organic/electrode interfaces studied by core-hole clock spectroscopy.  

PubMed

Organic semiconductor materials have important applications in organic electronics and other novel hybrid devices. In these devices, the transport of charge carriers across the interfaces between organic molecules and electrodes plays an important role in determining the device performance. Charge transfer dynamics at the organic/electrode interface usually occurs at the several femtoseconds timescale, and quantitative charge transfer dynamics data can been inferred using synchrotron-based core-hole clock (CHC) spectroscopy. In this research news, we have reviewed recent progress in the applications of CHC spectroscopy on the quantitative characterization of charge transfer dynamics at organic/electrode interfaces. By examining charge transfer dynamics at different types of interface, from weakly interacting van der Waals-type interfaces to interfaces with strong covalent bonds, we discuss a few factors that have been found to affect the charge transfer dynamics. We also review the application of CHC spectroscopy to quantify through-bonds and through-space charge transport in organic molecules. PMID:24692009

Cao, Liang; Gao, Xing-Yu; Wee, Andrew T S; Qi, Dong-Chen

2014-12-10

332

Innovations fields from corporate studies to socio-ecological indicators : a point of review  

E-print Network

), environmental management (i.e. ISO 14,000, EMAS), organisation of economic activities and corporate social for sustainability is to manage consumption without increasing its resource use and environmental impact (Daly 2004Innovations fields from corporate studies to socio-ecological indicators : a point of review

Boyer, Edmond

333

Points to Consider about Recruitment and Retention While Preparing a Clinical Research Study  

E-print Network

with the community. Points to Consider Examples/Suggestions Community Engagement · Have you identified the communities that you would like to engage? · What relationships have you established with communities in order to facilitate your study? What relationships will you need to establish? · How will you maintain

Bandettini, Peter A.

334

CSci 4651 Spring 2012 Final paper (50 points): study of programming languages design.  

E-print Network

type system (or a combination?) What are guarantees about run-time type errors after staticCSci 4651 Spring 2012 Final paper (50 points): study of programming languages design. Due at a scheduled time outside of the class. Presenting a paper results in extra credit (the exact amount

Machkasova, Elena

335

Impact of Field of Study, College and Year on Calculation of Cumulative Grade Point Average  

ERIC Educational Resources Information Center

A consistent finding from many reviews is that undergraduate Grade Point Average (uGPA) is a key predictor of academic success in medical school. Curiously, while uGPA has established predictive validity, little is known about its reliability. For a variety of reasons, medical schools use different weighting schemas to combine years of study.…

Trail, Carla; Reiter, Harold I.; Bridge, Michelle; Stefanowska, Patricia; Schmuck, Marylou; Norman, Geoff

2008-01-01

336

Cosmic-Ray Detectors With Interdigitated Electrodes  

NASA Technical Reports Server (NTRS)

Detectors measure both positions of incidence and energies of incident charged particles. Stack of detector wafers intercept cosmic ray. Measure positions of incidence to determine cosmic-ray trajectory and charge generated within them (proportional to cosmic-ray energy dissipated within them). Interdigital electrode pattern repeated over many rows and columns on tops of detector wafers in stack. Electrode pattern defines pixels within which points of incidence of incident cosmic rays located.

Cunningham, Thomas J.; Mazed, Mohammed; Holtzman, Melinda J.; Fossum, Eric R.

1995-01-01

337

A Simple Hydrogen Electrode  

ERIC Educational Resources Information Center

This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements…

Eggen, Per-Odd

2009-01-01

338

Near-electrode imager  

DOEpatents

An apparatus, near-electrode imager, for employing nuclear magnetic resonance imaging to provide in situ measurements of electrochemical properties of a sample as a function of distance from a working electrode. The near-electrode imager uses the radio frequency field gradient within a cylindrical toroid cavity resonator to provide high-resolution nuclear magnetic resonance spectral information on electrolyte materials.

Rathke, Jerome W. (Lockport, IL); Klingler, Robert J. (Westmont, IL); Woelk, Klaus (Wachtberg, DE); Gerald, II, Rex E. (Brookfield, IL)

2000-01-01

339

Longitudinal discharge laser electrodes  

DOEpatents

The improved longitudinal discharge laser electrode with IR baffle includes an electrode made up of washers spaced along the laser axis in order to form inter-washer spaces for hollow cathode discharge to take place and for IR radiation to be trapped. Additional IR baffles can be placed between the electrode ann the window.

Warner, Bruce E. (Livermore, CA); Miller, John L. (Dublin, CA); Ault, Earl R. (Dublin, CA)

1994-01-01

340

Longitudinal discharge laser electrodes  

DOEpatents

The improved longitudinal discharge laser electrode with IR baffle includes an electrode made up of washers spaced along the laser axis in order to form inter-washer spaces for hollow cathode discharge to take place and for IR radiation to be trapped. Additional IR baffles can be placed between the electrode ann the window. 2 figs.

Warner, B.E.; Miller, J.L.; Ault, E.R.

1994-08-23

341

Silver nanowires embedded gel electrodes  

NASA Astrophysics Data System (ADS)

The polyelectrolyte of high-strength gels was made to improve the mechanical properties in our previous study. In the field of electronic devices, the demand of polymer electrodes, which have high conductivity, high flexibility and transparence, is increasing. In this study, we attempt to make a transparent polymer electrode by laminating polymer thin film and silver nanowire (AgNW). High transparenct poly(methyl methacrylate) (PMMA) film, which is produced by using solvent cast method is used. AgNW is prepared by reacting Silver chloride (AgCl) with Silver nitrate (AgNO3) based on previous study. The AgNWs taking on different shapes were obtained. Fibrous AgNWs are formed by using high molecular weight polyvinylpyrrolidone (PVP). These results showed a possibility of developing the polymer electrode with high conductivity, high flexibility and transparence.

Abe, Yuta; Gong, Jin; Furukawa, Hidemitsu

2013-04-01

342

Advances in lightweight nickel electrode technology  

NASA Technical Reports Server (NTRS)

Studies are currently underway to further the development of lightweight nickel electrode technology. Work is focused primarily on the space nickel-hydrogen system and nickel-iron system but is also applicable to the nickel-cadmium and nickel-zinc systems. The goal is to reduce electrode weight while maintaining or improving performance, thereby increasing electrode energy density. Two basic electrode structures are being investigated. The first is the traditional nickel sponge produced from sintered nickel-carbonyl powder. The second is a new material for this application which consists of a non-woven mat of nickel fiber. Electrodes are being manufactured, tested, and evaluated at the electrode and cell level.

Coates, Dwaine; Paul, Gary; Daugherty, Paul

1989-01-01

343

Graphical techniques to assist in pointing and control studies of orbiting spacecraft  

NASA Technical Reports Server (NTRS)

Computer generated graphics are developed to assist in the modeling and assessment of pointing and control systems of orbiting spacecraft. Three-dimensional diagrams are constructed of the Earth and of geometrical models which resemble the spacecraft of interest. Orbital positioning of the spacecraft model relative to the Earth and the orbital ground track are then displayed. A star data base is also available which may be used for telescope pointing and star tracker field-of-views to visually assist in spacecraft pointing and control studies. A geometrical model of the Hubble Space Telescope (HST) is constructed and placed in Earth orbit to demonstrate the use of these programs. Simulated star patterns are then displayed corresponding to the primary mirror's FOV and the telescope's star trackers for various telescope orientations with respect to the celestial sphere.

Howell, L. W.; Ruf, J. H.

1986-01-01

344

Ion-exchange studies on poly-o-anisidine Sn(IV) phosphate nano composite and its application as Cd(II) ion-selective membrane electrode  

Microsoft Academic Search

An organic-inorganic composite, poly-o-anisidine Sn(IV) phosphate, was chemically synthesized by mixing ortho-anisidine into\\u000a gels of Sn(IV) phosphate with different mixing volume ratios. Studies on the effect of eluant concentration, elution behavior\\u000a and separation of metal ions were carried out to understand the ion-exchange capabilities. Due to Cd(II) selective nature\\u000a of composite, revealed by distribution studies, Cd(II) ion selective membrane electrode

Asif Ali Khan; Anish Khan

2010-01-01

345

Cervical Detachment Using Monopolar SupraLoop™ Electrode versus Monopolar Needle in Laparoscopic Supracervical Hysterectomy (LSH): An Interventional, Comparative Cohort Study  

PubMed Central

Objective: Currently available monopolar loop electrodes are difficult to handle in laparoscopic supracervical hysterectomy (LSH) and are entirely disposable devices, generating additional operating costs. The aim of this interventional study was the comparison of the efficiency and safety of cervical detachment with a newly developed monopolar loop electrode (SupraLoop™) with a conventional method of cervical detachment in LSH. Material and Methods: Our study sample included 1598 patients; 1070 patients that underwent LSH with cervical detachment using the monopolar SupraLoop™ (study group) and 528 patients that underwent LSH with cervical detachment using the monopolar needle (control group). We also assessed cervical detachment time and total device application and cutting time in a subgroup of 49 patients (23 patients from the study group and 26 patients from the control group). Results: Total operation time for LSH was significantly shorter among SupraLoop™ patients (93?±?41 minutes) when compared to patients in whom cervical detachment was performed with the needle (105?±?44 minutes) (p?electrode (SupraLoop™) is both an effective and safe instrument for cervical detachment in laparoscopic supracervical hysterectomy, and performed better than the needle, offering a significantly shorter operating time and less complications for the hysterectomy compared to the conventional method. PMID:24771898

Brucker, S.; Rothmund, R.; Krämer, B.; Neis, F.; Schönfisch, B.; Zubke, W.; Taran, F. A.; Wallwiener, M.

2013-01-01

346

Task 1: Modeling Study of CO Effects on Polymer Electrolyte Fuel Cell Anodes Task 2: Study of Ac Impedance as Membrane/Electrode Manufacturing Diagnostic Tool  

SciTech Connect

Carbon monoxide poisoning of polymer electrolyte fuel cell anodes is a key problem to be overcome when operating a polymer electrolyte fuel cell (PEFC) on reformed fuels. CO adsorbs preferentially on the precious metal surface leading to substantial performance losses. Some recent work has explored this problem, primarily using various Pt alloys in attempts to lower the degree of surface deactivation. In their studies of hydrogen oxidation on Pt and Pt alloy (Pt/Sn, Pt/Ru) rotating disk electrodes exposed to H{sub 2}/CO mixtures, Gasteiger et al. showed that a small hydrogen oxidation current is observed well before the onset of major CO oxidative stripping (ca. 0.4 V) on Pt/Ru. However, these workers concluded that such current observed at low anode overpotentials was too low to be of practical value. Nonetheless, MST-11 researchers and others have found experimentally that it is possible to run a PEFC, e.g., with a Pt/Ru anode, in the presence of CO levels in the range 10--100 ppm with little voltage loss. Such experimental results suggest that, in fact, PEFC operation at significant current densities under low anode overpotentials is possible in the presence of such levels of CO, even before resorting to air bleeding into the anode feed stream. The latter approach has been shown to be effective in elimination of Pt anode catalyst poisoning effects at CO levels of 20--50 ppm for cells operating at 80 C with low Pt catalyst loading. The effect of oxygen bleeding is basically to lower P{sub CO} down to extremely low levels in the anode plenum thanks to the catalytic (chemical) oxidation of CO by dioxygen at the anode catalyst. In this modeling work the authors do not include specific description of oxygen bleeding effects and concentrate on the behavior of the anode with feed streams of H{sub 2} or reformate containing low levels of CO. The anode loss is treated in this work as a hydrogen and carbon monoxide electrode kinetics problem, but includes the effects of dilution of the feedstream with significant fractions of carbon dioxide and nitrogen and of mass transport losses in the gas diffusion backing. Not included in the anode model are ionic resistance and diffusion losses in the catalyst layer. They are looking to see if the overall pattern of polarization curves calculated based on such a purely kinetic model indeed mimics the central features of polarization curves observed for PEFCs operating on hydrogen with low levels of CO.

Thomas E. Springer

1998-01-30

347

Vascular Fasciatherapy Danis Bois Method: a Study on Mechanism Concerning the Supporting Point Applied on Arteries  

PubMed Central

Background A first study on vascular fasciatherapy enabled us to observe the turning of a turbulent blood flow into a laminar one, and a questioning on the process involved in this transformation emerged. The first question was: What is the nature of artery from the point of view of fascia? And a second question was: Which is the link permitting the observed process working in our first study? So this time, we are investigating a specific aspect of the big question that polarizes the interest of many researchers: “What is fascia?” Methods Following Donald Ingber’s statement, “It is necessary to understand how tissues and organs are structured across multiple size scales”, our research methods have been established in order to collect information on what is artery and what is fascia. Concerning these two organs, we have questioned science across the scales of embryology, anatomy, histology and cytology. Beyond the knowledge on structure, the functional link between artery and fascia is the necessary complement of this study whose starting point is in fact a questioning on process. As an application of this study, vascular fasciatherapy Danis-Bois Method and mechanotransduction have been investigated in theoretical and in research aspects to improve the understanding of how they work. Results The embryological approach points out a common origin and a histofunctional community of connective tissue and artery. As organs, arteries are sheathed by the adventia-fascia, and are penetrated by connective tissue extensions in media and intima. Furthermore, the functional point of view of this study reports the knowledge on mechanotransduction involving artery, both from the connective side and from the luminal side. Functional anatomy, surgery, histology, and cytology integrating the theory of the extended cytoskeleton, underline continuity from the static and functional points of view, with tensegrity being the architectural principle linking molecules to the entire body. Conclusion By answering these questions, we are attempting a better understanding of the mechanisms occurring in the progress of the arterial supporting point. One could presume that it relaxes adventitia and media, locally and all along the arterial network. Its action could also extend inward to the intima and on blood, as well as outwards to the neighboring connective tissue. By its local and remote action, it may be useful when diseases associate general perturbations and arterial disorders, like in high blood pressure or in aging. PMID:22211153

Payrau, Bernard; Quéré, Nadine; Bois, Danis

2011-01-01

348

Feasibility studies for the detection of organic surface and subsurface water contaminants by surface-enhanced Raman spectroscopy on silver electrodes  

Microsoft Academic Search

Fundamental components of various families of organic contaminants that are found in surface and subsurface waters have been investigated by surface-enhanced Raman spectroscopy (SERS). The SERS substrate was a silver electrode maintained at various electrode potentials. The limit of detection for pyridine was calculated to be 8.5 pg. Variation of the electrode potential and excitation wavelength was used to qualitatively

Michael M. Carrabba; Robert B. Edmonds; R. David. Rauh

1987-01-01

349

Single-Point Magnetic Resonance Imaging Study of Water Adsorption in Pellets of Zeolite 4A  

Microsoft Academic Search

The water uptake process in commercial type particles of zeolite 4A has been studied using a single-point MRI method. True proton density,T1,T2, andT*2relaxation times were obtained with submillimetric resolution, overcoming the restrictions of shortT*2signals. The molecular mobility in nonequilibrium conditions has been characterized by relaxation time mapping. A clear reduction of the water sorption rate was observed by comparing MRI

Pablo J. Prado; Bruce J. Balcom; Mohamed Jama

1999-01-01

350

Toxicogenomic Studies of the Rat Brain at an Early Time Point Following Acute Sarin Exposure  

Microsoft Academic Search

We have studied sarin-induced global gene expression patterns at an early time point (2 h: 0.5×LD50) using Affymetrix Rat Neurobiology U34 chips and male Sprague–Dawley rats. A total of 46 genes showed statistically significant alterations from control levels. Three gene categories contained more of the altered genes than any other groups: ion channel (8 genes) and calcium channel and binding proteins

Tirupapuliyur V. Damodaran; Stephen T. Greenfield; Anand G. Patel; Holly K. Dressman; Siomon K. Lin; Mohamed B. Abou-Donia

2006-01-01

351

Partial nephrectomy using radiofrequency incremental bipolar generator with multi electrode probe: experimental study in bench pig kidneys  

PubMed Central

Background The aim of this research project was the realization of an incremental bipolar radiofrequency generator with inline 4-electrode probe for partial renal resection without clamping of the vessels. Methods The experimentation was carried out across two phases: the preliminary realization of a specific generator and an inline multielectrode probe for open surgery (Phase 1); system testing on 27 bench kidneys for a total of 47 partial resection (Phase 2). The parameters evaluated were: power level, generator automatisms, parenchymal coagulation times, needle caliber, thickness of the coagulated tissue “slice”, charring, ergonomy, feasibility of the application of “bolster” stitches. Results The analysis of the results referred to the homogeneity and thickness of coagulation, energy supply times with reference to the power level and caliber of the needles. The optimal results were obtained by using needles of 1.5 mm caliber at power level 5, and with coagulation times of 54 seconds for the first insertion and 30 seconds for the second. Conclusions The experimentation demonstrated that the apparatus, consisting of a generator named “LaparoNewPro” and fitted with a dedicated probe for open surgery, is able to carry out a coagulation of the line of resection of the renal parenchyma in a homogeneous manner, in short times, without tissue charring, and with the possibility of stitching both on coagulated tissue and the caliceal system. The generator automatism based on the flow of the current supplied by each electrode is reliable, and the cessation of energy supply coincides with optimal coagulation. PMID:24410789

2014-01-01

352

Reading Different Orthographic Structures in the Shallow-Pointed Hebrew Script: A Cross-Grade Study in Elementary School  

ERIC Educational Resources Information Center

Hebrew-speaking children learn to read using a transparent, pointed writing system, but by grade three, they gradually begin using the non-pointed version of Hebrew script. The current study examined the development of reading, in the pointed script, of a nationally representative sample of children in grades two, four, and six. Rate and accuracy…

Shany, Michal; Bar-On, Amalia; Katzir, Tami

2012-01-01

353

Agglomeration in Li-Al alloy electrodes  

Microsoft Academic Search

Lithium-aluminum alloy negative electrodes have shown excellent promise for meeting the performance requirements of high temperature lithium\\/iron sulfide batteries being developed for electric vehicle propulsion. However, it appears that under certain conditions, capacity retention by these electrodes can be affected by agglomeration of the active material. To study agglomeration, its causes, and its electrochemical effects on cell performance, an experimental

A. K. Fischer; D. R. Vissers

1980-01-01

354

Damage states in laminated composite three-point bend specimens: An experimental-analytical correlation study  

NASA Technical Reports Server (NTRS)

Damage states in laminated composites were studied by considering the model problem of a laminated beam subjected to three-point bending. A combination of experimental and theoretical research techniques was used to correlate the experimental results with the analytical stress distributions. The analytical solution procedure was based on the stress formulation approach of the mathematical theory of elasticity. The solution procedure is capable of calculating the ply-level stresses and beam displacements for any laminated beam of finite length using the generalized plane deformation or plane stress state assumption. Prior to conducting the experimental phase, the results from preliminary analyses were examined. Significant effects in the ply-level stress distributions were seen depending on the fiber orientation, aspect ratio, and whether or not a grouped or interspersed stacking sequence was used. The experimental investigation was conducted to determine the different damage modes in laminated three-point bend specimens. The test matrix consisted of three-point bend specimens of 0 deg unidirectional, cross-ply, and quasi-isotropic stacking sequences. The dependence of the damage initiation loads and ultimate failure loads were studied, and their relation to damage susceptibility and damage tolerance of the mean configuration was discussed. Damage modes were identified by visual inspection of the damaged specimens using an optical microscope. The four fundamental damage mechanisms identified were delaminations, matrix cracking, fiber breakage, and crushing. The correlation study between the experimental results and the analytical results were performed for the midspan deflection, indentation, damage modes, and damage susceptibility.

Starbuck, J. Michael; Guerdal, Zafer; Pindera, Marek-Jerzy; Poe, Clarence C.

1990-01-01

355

Electrode holder useful in a corrosion testing device  

DOEpatents

The present invention is directed to an apparatus and method for holding one or more test electrodes of precisely known exposed surface area. The present invention is particularly useful in a device for determining the corrosion properties of the materials from which the test electrodes have been formed. The present invention relates to a device and method for holding the described electrodes wherein the exposed surface area of the electrodes is only infinitesimally decreased. Further, in the present invention the exposed, electrically conductive surface area of the contact devices is small relative to the test electrode surface area. The holder of the present invention conveniently comprises a device for contacting and engaging each test electrode at two point contacts infinitesimally small in relation to the exposed surface area of the electrodes. 4 figs.

Murphy, R.J. Jr.; Jamison, D.E.

1986-08-19

356

Regenerative scaffold electrodes for peripheral nerve interfacing.  

PubMed

Advances in neural interfacing technology are required to enable natural, thought-driven control of a prosthetic limb. Here, we describe a regenerative electrode design in which a polymer-based thin-film electrode array is integrated within a thin-film sheet of aligned nanofibers, such that axons regenerating from a transected peripheral nerve are topographically guided across the electrode recording sites. Cultures of dorsal root ganglia were used to explore design parameters leading to cellular migration and neurite extension across the nanofiber/electrode array boundary. Regenerative scaffold electrodes (RSEs) were subsequently fabricated and implanted across rat tibial nerve gaps to evaluate device recording capabilities and influence on nerve regeneration. In 20 of these animals, regeneration was compared between a conventional nerve gap model and an amputation model. Characteristic shaping of regenerated nerve morphology around the embedded electrode array was observed in both groups, and regenerated axon profile counts were similar at the eight week end point. Implanted RSEs recorded evoked neural activity in all of these cases, and also in separate implantations lasting up to five months. These results demonstrate that nanofiber-based topographic cues within a regenerative electrode can influence nerve regeneration, to the potential benefit of a peripheral nerve interface suitable for limb amputees. PMID:23033438

Clements, Isaac P; Mukhatyar, Vivek J; Srinivasan, Akhil; Bentley, John T; Andreasen, Dinal S; Bellamkonda, Ravi V

2013-07-01

357

Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode  

PubMed Central

Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200?nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. PMID:24170960

Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

2013-01-01

358

Design of a Wireless EEG System for Point-of-Care Applications.  

PubMed

This study aims to develop a wireless EEG system to provide critical point-of-care information about brain electrical activity. A novel dry electrode, which can be installed rapidly, is used to acquire EEG from the scalp. A wireless data link between the electrode and a data port (i.e., a smartphone) is established based on the Bluetooth technology. A prototype of this system has been implemented and its performance in acquiring EEG has been evaluated. PMID:25419099

Jia, Wenyan; Bai, Yicheng; Sun, Mingui; Sclabassi, Robert J

2013-04-01

359

Design of a Wireless EEG System for Point-of-Care Applications  

PubMed Central

This study aims to develop a wireless EEG system to provide critical point-of-care information about brain electrical activity. A novel dry electrode, which can be installed rapidly, is used to acquire EEG from the scalp. A wireless data link between the electrode and a data port (i.e., a smartphone) is established based on the Bluetooth technology. A prototype of this system has been implemented and its performance in acquiring EEG has been evaluated. PMID:25419099

Jia, Wenyan; Bai, Yicheng; Sun, Mingui; Sclabassi, Robert J.

2014-01-01

360

Two-craft Coulomb formation study about circular orbits and libration points  

NASA Astrophysics Data System (ADS)

This dissertation investigates the dynamics and control of a two-craft Coulomb formation in circular orbits and at libration points; it addresses relative equilibria, stability and optimal reconfigurations of such formations. The relative equilibria of a two-craft tether formation connected by line-of-sight elastic forces moving in circular orbits and at libration points are investigated. In circular Earth orbits and Earth-Moon libration points, the radial, along-track, and orbit normal great circle equilibria conditions are found. An example of modeling the tether force using Coulomb force is discussed. Furthermore, the non-great-circle equilibria conditions for a two-spacecraft tether structure in circular Earth orbit and at collinear libration points are developed. Then the linearized dynamics and stability analysis of a 2-craft Coulomb formation at Earth-Moon libration points are studied. For orbit-radial equilibrium, Coulomb forces control the relative distance between the two satellites. The gravity gradient torques on the formation due to the two planets help stabilize the formation. Similar analysis is performed for along-track and orbit-normal relative equilibrium configurations. Where necessary, the craft use a hybrid thrusting-electrostatic actuation system. The two-craft dynamics at the libration points provide a general framework with circular Earth orbit dynamics forming a special case. In the presence of differential solar drag perturbations, a Lyapunov feedback controller is designed to stabilize a radial equilibrium, two-craft Coulomb formation at collinear libration points. The second part of the thesis investigates optimal reconfigurations of two-craft Coulomb formations in circular Earth orbits by applying nonlinear optimal control techniques. The objective of these reconfigurations is to maneuver the two-craft formation between two charged equilibria configurations. The reconfiguration of spacecraft is posed as an optimization problem using the calculus of variations approach. The optimality criteria are minimum time, minimum acceleration of the separation distance, minimum Coulomb and electric propulsion fuel usage, and minimum electrical power consumption. The continuous time problem is discretized using a pseudospectral method, and the resulting finite dimensional problem is solved using a sequential quadratic programming algorithm. The software package, DIDO, implements this approach. This second part illustrates how pseudospectral methods significantly simplify the solution-finding process.

Inampudi, Ravi Kishore

361

Study on cloud points of Triton X-100-cationic gemini surfactants mixtures: a spectroscopic approach.  

PubMed

This study investigates the effects of various cationic surfactants on the cloud point (CP) of the nonionic surfactant Triton X-100 (TX-100) in aqueous solutions. Instead of visual observation, a spectrophotometer was used for measurement of the cloud point temperatures. The values of CPs for Triton X-100 can be measured directly because TX-100 has an average number of oxyethylene units per molecule of p approximately 9.5 and a CP=66.0 degrees C. Quaternary ammonium dimeric surfactants (m-s-m, m=10, 12, and 16, and s=2, 6, and 10) were synthesized and used. The melting temperature T(M) and the Krafft temperature T(K) were measured for 1 wt% aqueous solutions of these synthesized surfactants. The melting temperature of the solid gemini surfactants increased with the carbon number of the alkyl chain. The results showed that additions of the gemini surfactants (which are infinitely miscible with water) to Triton X-100 increased the cloud point of the TX-100 solutions. All salts tested in these studies had a large effect on the CPs of nonionic surfactants due to their effect on water structure and their hydrophilicity. The effect of the alkyl chain length of the gemini surfactant on the CP of Triton X-100 is therefore more important than the spacer chain length. PMID:20034845

Akba?, Halide; Boz, Mesut; Batigöç, Ci?dem

2010-02-01

362

Reconstruction of 3-D head geometry from digitized point sets: an evaluation study.  

PubMed

In this paper, we evaluate different methods to estimate patient-specific scalp, skull, and brain surfaces from a set of digitized points from the target's scalp surface. The reconstruction problem is treated as a registration problem: An a priori surface model, consisting of the scalp, skull, and brain surfaces, is registered to the digitized surface points. The surface model is generated from segmented magnetic resonance (MR) volume images. We study both affine and free-form deformation (FFD) registration, the use of average models, the averaging of individual registration results, a model selection procedure, and statistical deformation models. The registration algorithms are mainly previously published, and the objective of this paper is to evaluate these methods in this particular application with sparse data. The main interest of this paper is to generate geometric head models for biomedical applications, such as electroencephalography and magnetoencephalographic. However, the methods can also be applied to other anatomical regions and to other application areas. The methods were validated using 15 MR volume images, from which the scalp, skull, and brain were manually segmented. The best results were achieved by averaging the results of the FFD registrations of the database: the mean distance from the manually segmented target surface to a deformed a priori model surface for the studied anatomical objects was 1.68-2.08 mm, depending on the point set used. The results support the use of the evaluated methods for the reconstruction of geometric models in applications with sparse data. PMID:15484443

Koikkalainen, Juha; Lötjönen, Jyrki

2004-09-01

363

Feasibility study on twisted nematic liquid-crystal cell with two cross-embedded wire-grid polarizers as alignment and electrode for projection displays.  

PubMed

For this study, twisted nematic liquid crystals (TN-LCs) are sandwiched between two cross-embedded wire-grid polarizers (WGPs) as alignment and electrodes for projection displays. In the proposed device, the WGPs replace not only the sheet polarizers in a conventional TN-LC cell, but also the front and rear alignment layers and transparent electrodes. It is found that the structure of a WGP microgroove is suitable for alignment; however, the proposed TN-LC cell exhibits a multidomain phenomenon because there is no apparent pretilt angle on the two WGPs. The multidomain phenomenon can be solved by the annealing method and by blending chiral material with the TN-LC for twisting the LC in the same direction. In addition, the surface resistance of the aluminum WGP is two orders lower than the indium-tin-oxide glass substrates, so that it is suitable for electric conductivity and for use as a transparent electrode. Also, metallic WGPs exhibit a higher heat resistance characteristic than plastic sheet polarizers, making them robust. As a result, the threshold voltages, the saturation voltages, and the response time of the proposed TN-LC cell are almost identical to the conventional TN-LC cell. The contrast ratio of the LCD projector with the proposed TN-LC cell and the quarter-wave plate exhibit the best characteristics in comparisons with the other LCD projectors. Thus, the proposed TN-LC cell represents a simple and feasible solution for the next generation of high-brightness projection display devices. PMID:19956310

Chen, Chin-Yu; Lo, Yu-Lung

2009-12-01

364

Enhancing generalisation in biofeedback intervention using the challenge point framework: a case study.  

PubMed

Biofeedback intervention can help children achieve correct production of a treatment-resistant error sound, but generalisation is often limited. This case study suggests that generalisation can be enhanced when biofeedback intervention is structured in accordance with a "challenge point" framework for speech-motor learning. The participant was an 11-year-old with residual /r/ misarticulation who had previously attained correct /r/ production through a structured course of ultrasound biofeedback treatment but did not generalise these gains beyond the word level. Treatment difficulty was adjusted in an adaptive manner following predetermined criteria for advancing, maintaining, or moving back a level in a multidimensional hierarchy of functional task complexity. The participant achieved and maintained virtually 100% accuracy in producing /r/ at both word and sentence levels. These preliminary results support the efficacy of a semi-structured implementation of the challenge point framework as a means of achieving generalisation and maintenance of treatment gains. PMID:25216375

Hitchcock, Elaine R; Byun, Tara McAllister

2015-01-01

365

An experimental-theoretical study of free vibrations of plates on elastic point supports  

NASA Technical Reports Server (NTRS)

A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. An experiment is conducted in which the bending stiffness of horizontal beams is used to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured and is compared with results from a theoretical model in which a Rayleigh-Ritz analysis is used which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modeled both as massless translational springs and springs with tip masses, which are included to better represent the experimental supports.

Leuner, T. R.

1974-01-01

366

Enhancing generalisation in biofeedback intervention using the challenge point framework: A case study  

PubMed Central

Biofeedback intervention can help children achieve correct production of a treatment-resistant error sound, but generalisation is often limited. This case study suggests that generalisation can be enhanced when biofeedback intervention is structured in accordance with a “challenge point” framework for speech-motor learning. The participant was an 11-year-old with residual /r/ misarticulation who had previously attained correct /r/ production through a structured course of ultrasound biofeedback treatment but did not generalise these gains beyond the word level. Treatment difficulty was adjusted in an adaptive manner following predetermined criteria for advancing, maintaining, or moving back a level in a multidimensional hierarchy of functional task complexity. The participant achieved and maintained virtually 100% accuracy in producing /r/ at both word and sentence levels. These preliminary results support the efficacy of a semi-structured implementation of the challenge point framework as a means of achieving generalisation and maintenance of treatment gains. PMID:25216375

HITCHCOCK, ELAINE R.; BYUN, TARA McALLISTER

2014-01-01

367

Nanoscopic electrode molecular probes  

DOEpatents

The present invention relates to a method and apparatus for enhancing the electron transport property measurements of a molecule when the molecule is placed between chemically functionalized carbon-based nanoscopic electrodes to which a suitable voltage bias is applied. The invention includes selecting a dopant atom for the nanoscopic electrodes, the dopant atoms being chemically similar to atoms present in the molecule, and functionalizing the outer surface and terminations of the electrodes with the dopant atoms.

Krstic, Predrag S. (Knoxville, TN); Meunier, Vincent (Knoxville, TN)

2012-05-22

368

Bioselective Membrane Electrode Probes  

NASA Astrophysics Data System (ADS)

The use of intact bacterial cells or tissue slices of plant and animal origin as immobilized biocatalysts has extended the possible range of potentiometric bioselective membrane electrodes beyond that of conventional enzyme electrodes. The use of such materials as biocatalysts offers advantages in situations where isolated enzymes are not available or where multistep reaction paths are required. The resulting bioselective electrodes also offer exceptional ease of preparation, time stability, and low cost.

Rechnitz, Garry A.

1981-10-01

369

Longitudinal vascular dynamics following cranial window and electrode implantation measured with speckle variance optical coherence angiography  

PubMed Central

Speckle variance optical coherence angiography (OCA) was used to characterize the vascular tissue response from craniotomy, window implantation, and electrode insertion in mouse motor cortex. We observed initial vasodilation ~40% greater than original diameter 2-3 days post-surgery (dps). After 4 weeks, dilation subsided in large vessels (>50 µm diameter) but persisted in smaller vessels (25-50 µm diameter). Neovascularization began 8-12 dps and vessel migration continued throughout the study. Vasodilation and neovascularization were primarily associated with craniotomy and window implantation rather than electrode insertion. Initial evidence of capillary re-mapping in the region surrounding the implanted electrode was manifest in OCA image dissimilarity. Further investigation, including higher resolution imaging, is required to validate the finding. Spontaneous lesions also occurred in many electrode animals, though the inception point appeared random and not directly associated with electrode insertion. OCA allows high resolution, label-free in vivo visualization of neurovascular tissue, which may help determine any biological contribution to chronic electrode signal degradation. Vascular and flow-based biomarkers can aid development of novel neural prostheses. PMID:25136505

Hammer, Daniel X.; Lozzi, Andrea; Abliz, Erkinay; Greenbaum, Noah; Agrawal, Anant; Krauthamer, Victor; Welle, Cristin G.

2014-01-01

370

Longitudinal vascular dynamics following cranial window and electrode implantation measured with speckle variance optical coherence angiography.  

PubMed

Speckle variance optical coherence angiography (OCA) was used to characterize the vascular tissue response from craniotomy, window implantation, and electrode insertion in mouse motor cortex. We observed initial vasodilation ~40% greater than original diameter 2-3 days post-surgery (dps). After 4 weeks, dilation subsided in large vessels (>50 µm diameter) but persisted in smaller vessels (25-50 µm diameter). Neovascularization began 8-12 dps and vessel migration continued throughout the study. Vasodilation and neovascularization were primarily associated with craniotomy and window implantation rather than electrode insertion. Initial evidence of capillary re-mapping in the region surrounding the implanted electrode was manifest in OCA image dissimilarity. Further investigation, including higher resolution imaging, is required to validate the finding. Spontaneous lesions also occurred in many electrode animals, though the inception point appeared random and not directly associated with electrode insertion. OCA allows high resolution, label-free in vivo visualization of neurovascular tissue, which may help determine any biological contribution to chronic electrode signal degradation. Vascular and flow-based biomarkers can aid development of novel neural prostheses. PMID:25136505

Hammer, Daniel X; Lozzi, Andrea; Abliz, Erkinay; Greenbaum, Noah; Agrawal, Anant; Krauthamer, Victor; Welle, Cristin G

2014-08-01

371

Origin of Capacity Fading in Nano-Sized Co3O4Electrodes: Electrochemical Impedance Spectroscopy Study  

PubMed Central

Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.

2008-01-01

372

A combination of in situ ESR and in situ NMR spectroelectrochemistry for mechanistic studies of electrode reactions: the case of p-benzoquinone.  

PubMed

A combined in situ NMR and in situ ESR spectroelectrochemical study of a reaction mechanism is presented detecting and describing the whole number of paramagnetic and diamagnetic intermediates and final products in an electrode reaction. While in situ NMR spectroelectrochemistry provides a powerful method for the study of structural or electronic changes of diamagnetic molecules in any electrochemical reaction mechanism, in situ ESR spectroelectrochemistry is the method of choice to detect paramagnetic structures and to characterise their electronic state via the g-value and hyperfine splitting in redox reactions. To demonstrate the power of this combination of magnetic spectroscopies in electrochemistry, the reduction of p-benzoquinone to hydroquinone is followed by both these spectroelectrochemical methods at selected pH values, thus considering the influence of the proton on the reaction mechanism. The results of both in situ spectroelectrochemical methods at the same redox system are used to get the complete reaction mechanism of p-benzoquinone at electrodes in aqueous solutions. PMID:21972011

Klod, Sabrina; Dunsch, Lothar

2011-11-01

373

Structural in situ study of the thermal behavior of manganese dioxide materials: toward selected electrode materials for supercapacitors.  

PubMed

The thermal behavior of a series of MnO2 materials was investigated toward MnO2 microstructures under inert atmospheres. The byproduct formed during MnO2 heat treatments from the room temperature to 800 °C were characterized by in situ X-ray diffraction analyses. It was found that annealing spinel and ramsdellite phases caused the formation of MnO2 pyrolusite at 200 °C, Mn2O3, at 400 °C, and then Mn3O4 at higher temperatures. In the case of cryptomelane and birnessite phases, the heating process resulted in the formation of K0.51Mn0.93O2 at 600 °C, while Mn3O4 was also formed and still present up to 800 °C. Heat-treating Ni-todorokite and OMS-5 up to about 450 °C led to the formation of NiMn2O4 and NaxMnO2, respectively, and again Mn3O4 at higher temperatures. All of these structural transformations were correlated to resulting weight losses of MnO2 powders, measured by thermogravimetric analyses, during the heating process. Cyclic voltammetry measurements were performed in the presence of 0.5 M K2SO4 aqueous solution for annealed cryptomelane, K0.51Mn0.93O2, and Mn3O4-based electrodes. It was found that MnO2 cryptomelane is electrochemically stable upon heating. The long-term charge/discharge voltammetric cycling revealed that the specific capacitance of Mn3O4-based electrode is significantly improved from 14 F·g(-1) (after 20 cycles) to 123 F·g(-1) (after 500 cycles). PMID:21114252

Ghodbane, Ouassim; Pascal, Jean-Louis; Fraisse, Bernard; Favier, Frédéric

2010-12-01

374

Sulfur Tolerant Solid Oxide Fuel Cell for Coal Syngas Application: Experimental Study on Diverse Impurity Effects and Fundamental Modeling of Electrode Kinetics  

NASA Astrophysics Data System (ADS)

With demand over green energy economy, fuel cells have been developed as a promising energy conversion technology with higher efficiency and less emission. Solid oxide fuel cells (SOFC) can utilize various fuels in addition to hydrogen including coal derived sygas, and thus are favored for future power generation due to dependence on coal in electrical industry. However impurities such as sulfur and phosphorous present in coal syngas in parts per million (p.p.m.) levels can severely poison SOFC anode typically made of Ni/yttria-stabilized-zirconia (Ni-YSZ) and limit SOFC applicability in economically derivable fuels. The focus of the research is to develop strategy for application of high performance SOFC in coal syngas with tolerance against trace impurities such as H2S and PH3. To realize the research goal, the experimental study on sulfur tolerant anode materials and examination of various fuel impurity effects on SOFC anode are combined with electrochemical modeling of SOFC cathode kinetics in order to benefit design of direct-coal-syngas SOFC. Tolerant strategy for SOFC anode against sulfur is studied by using alternative materials which can both mitigate sulfur poisoning and function as active anode components. The Ni-YSZ anode was modified by incorporation of lanthanum doped ceria (LDC) nano-coatings via impregnation. Cell test in coal syngas containing 20 ppm H2S indicated the impregnated LDC coatings inhibited on-set of sulfur poisoning by over 10hrs. Cell analysis via X-ray photon spectroscopy (XPS), X-ray diffraction (XRD) and electrochemistry revealed LDC coatings reacted with H2S via chemisorptions, resulting in less sulfur blocking triple--phase-boundary and minimized performance loss. Meanwhile the effects of PH3 impurity on SOFC anode is examined by using Ni-YSZ anode supported SOFC. Degradation of cell is found to be irreversible due to adsorption of PH3 on TPB and further reaction with Ni to form secondary phases with low melting point. The feasibility of mixed ionic and electronic conductive (MIEC) metal oxides with perovskite structure (ABO3) as alternative ceramic SOFC anodes in coal syngas has been examined by PH3 exposure test. The study found although perovskite anodes can be generally more tolerant against H2S, further examination on PH3 tolerance is indispensable before their extensive application in coal syngas. On the theoretical end it is this research's initiative that oxygen reduction reaction at mixed ionic and electronic conductive (MIEC) cathode is a key factor controlling SOFC performance at intermediate temperature (700˜850°C). It is generally recognized that the overall charge-transfer process could occur through both surface pathway at triple-phase boundary (3PB) and bulk pathway at electrolyte/cathode interface (2PB). A modified one-dimensional model is thus developed to predict defect evolution of MIEC cathode under overpotential by incorporating multi-step charge-transfer into the bi-pathway continuum model. Finite volume control method is applied to obtain solutions for the model. The simulation predicted kinetics transition from 3PB control to 2PB control as cathodic overpotential stepping from -0.2V to -0.4V, depending on the material properties parameters. Meanwhile significant activation behavior of the MIEC electrode was also observed as indicated by extension of reaction region towards gas-exposed oxide surface. This model addressed contribution from electrochemical-controlled rate-limiting steps (RLSs) on the reduction kinetics, and identified the role played by multiple material property parameters such as surface oxygen ion concentration and bulk vacancy concentration on the kinetics transition. Combined academic knowledge gained through experimental investigation and theoretical simulation in this research would benefit the future design, development and application strategy of high-performance SOFC in coal syngas fuels.

Gong, Mingyang

375

Pocket ECG electrode  

NASA Technical Reports Server (NTRS)

A low noise electrode suited for sensing electrocardiograms when chronically and subcutaneously implanted in a free ranging subject is described. The electrode comprises a pocket shaped electrically conductive member with a single entrance adapted to receive body fluids. The exterior of the member and the entrance region is coated with electrical insulation so that the only electrolyte/electrode interface is within the member, remote from artifact-generating tissue. Cloth straps are bonded to the member to permit the electrode to be sutured to tissue and to provide electrical lead flexure relief.

Lund, G. F. (inventor)

1980-01-01

376

Pocket ECG electrode  

NASA Technical Reports Server (NTRS)

A low-noise electrode suited for sensing electrocardiograms when chronically and subcutaneously implanted in a free-ranging subject. The electrode comprises a pocket-shaped electrically conductive member with a single entrance adapted to receive body fluids. The exterior of the member and the entrance region is coated with electrical insulation so that the only electrolyte/electrode interface is within the member remote from artifact-generating tissue. Cloth straps are bonded to the member to permit the electrode to be sutured to tissue and to provide electrical lead flexure relief.

Lund, Gordon F. (Inventor)

1982-01-01

377

[Temperature distribution and geometry of the electrodes in RF interstitial hyperthermia using circular and interstitial electrodes].  

PubMed

To evaluate the feasibility of clinical application of a newly developed interstitial hyperthermia system, which consists of an 8 MHz radiofrequency generator, interstitial needle electrodes, and a superficial circular electrode, we conducted preclinical experiments using an agar phantom and VX-2 carcinoma in the rabbit. In the experiment with an agar phantom, four 4 cm needle electrodes were placed in a square array at intervals of 1.0, 1.5, and 2.0 cm. Thermography demonstrated homogeneous temperature distribution at electrode intervals of 1.0 and 1.5 cm, but hot spots around the electrodes at an interval of 2.0 cm. When electrode deviation was less than 8 degrees from the parallel plane, no temperature deviation was observed. Using two 2 cm electrodes and two 4 cm electrodes in square array, thermography demonstrated a homogeneous temperature distribution in the area surrounded by the electrodes. Even if the electrodes were located at the periphery of the agar phantom, a homogeneous temperature distribution was obtained in the area surrounded by the electrodes. Using four 4 cm electrodes at intervals of 1.5 cm in VX-2 carcinoma in the rabbit, ideal heating was obtained: 42 degrees C at the periphery of the tumor and 43 degrees C at the center. These data suggest that the newly developed interstitial hyperthermia apparatus provides homogeneous heat distribution at electrode intervals of 1.5 cm or less and can be used in a Phase I study for deep-seated or superficial tumors. PMID:1508637

Kataoka, M; Nishiyama, Y; Fujii, T; Kawamura, M; Mogami, H; Itoh, H; Iio, A; Hamamoto, K

1992-05-25

378

Electrode surface roughness initiated breakdown in compressed SF6 gas  

Microsoft Academic Search

The effect of electrode roughness on the behaviour of a SF6 gaseous gap is studied analytically in this paper by introducing an elongated protrusion in the form of a fixed small conducting needle on an ideally smooth electrode surface. This effect is discussed by applying the streamer theory of breakdown. The breakdown characteristics for elongated protrusions on the coaxial electrode

S. M. El-Makkawy

1994-01-01

379

Construction of an electrode for intraoperative nerve stimulation.  

PubMed

The electrode described in this paper consist of a barrel or handle with its conducting cable and a detachable stimulating tip. It is constructed of inexpensive and commercially available materials and is disposable. During the course of a stimulation study, electrode tips of different lengths or curvatures may be substituted without the need to replace the electrode barrel and cable. PMID:1942021

Ashley, R A; Wee, A S

1991-07-01

380

Plastic Membrane Sensor from a Disposed Combined Glass Electrode  

ERIC Educational Resources Information Center

The construction of combined plastic membrane electrode for hydralazinium cation from a disposed glass electrode is described. A variety of electrodes could be prepared by students using other types of polymers, plasticizers, or exchangers which could also help to study effects of pH and temperature, or environmental investigations.

Marafie, Hayat M.; Shoukry, Adel F.; Alshatti, Laila A.

2007-01-01

381

Improving Electrode Durability of PEF Chamber by selecting suitable material  

Technology Transfer Automated Retrieval System (TEKTRAN)

Corrosion resistance of four materials - titanium, platinized titanium, stainless steel, and boron carbide - as electrodes in a Pulsed Electric Field (PEF) system was studied to reduce electrode material migration into the food by electrode corrosion. The PEF process conditions were 28 kV/cm field s...

382

Application of double-impedance system and cyclic voltammetry to study the adsorption of fullerols (C60(OH)n) on biological peptide-adsorbed gold electrode.  

PubMed

The adsorption of fullerols (C60(OH)n) on glutathione-adsorbed gold electrode was characterized by using double-impedance system, i.e., electrochemical quartz crystal impedance and electrochemical impedance spectroscopy, and cyclic voltammetry. The time courses of piezoelectric parameters were used to reflect the changes of interfacial physical properties, such as mass, density-viscosity, and dielectric constant, during the adsorptions of peptide and fullerols onto electrode. The electrochemical impedance based on the simple equivalent electric network were also simultaneously measured and provided electrochemical interface information, e.g., double-layer capacitance and charge-transfer resistance. It was found that the double-impedance responses were varied with the forms of glutathione. It was also shown that the frequency curves due to the adsorption of oxidized (GSSG) and reduced (GSH) glutathione could be exhibited as different kinetic equations. The heterogeneous charge-transfer rate constants of ferricyanide/ferrocyanide before and after the peptide and fullerols adsorption were determined by CV and EIS methods. The results showed that the proposed method has potential applications in interfacial studies of biomaterials, since these combined techniques have advantages in real time providing multidimensional piezoelectric and electrochemical impedance information. PMID:11516084

Zhou, A; Zhang, J; Xie, Q; Yao, S

2001-09-01

383

CEREBRAL CORRELATES OF MULTIMODAL POINTING: AN FMRI STUDY OF PROSODIC FOCUS, SYNTACTIC  

E-print Network

, DIGITAL- AND OCULAR- POINTING Hélène Loevenbruck1 , Coriandre Vilain1 , Francesca Carota1,2 , Monica Baciu of pointing including: 1) index finger pointing, 2) eye pointing, 3) prosodic focus production, 4) syntactic extraction (during speech production). Fifteen subjects were examined while they gave digital, ocular

Boyer, Edmond

384

Point-prevalence study of inappropriate antibiotic use at a tertiary Australian hospital.  

PubMed

A point-prevalence study at a tertiary Australian hospital found 199 of 462 inpatients (43%) to be receiving antibiotic therapy. Forty-seven per cent of antibiotic use was discordant with guidelines or microbiological results and hence considered inappropriate. Risk factors for inappropriate antibiotic prescribing included bone/joint infections, the absence of infection, creatinine level >120 µmol/L, carbapenem or macrolide use and being under the care of the aged care/rehabilitation team. In the setting of finite antimicrobial stewardship resources, identification of local determinants for inappropriate antibiotic use may enable more targeted interventions. PMID:22697156

Ingram, P R; Seet, J M; Budgeon, C A; Murray, R

2012-06-01

385

First-principles study of point defects at a semicoherent interface.  

PubMed

Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. We show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. We give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials. PMID:25524061

Metsanurk, E; Tamm, A; Caro, A; Aabloo, A; Klintenberg, M

2014-01-01

386

Cohort protocol paper: The Pain and Opioids In Treatment (POINT) study  

PubMed Central

Background Internationally, there is concern about the increased prescribing of pharmaceutical opioids for chronic non-cancer pain (CNCP). In part, this is related to limited knowledge about the long-term benefits and outcomes of opioid use for CNCP. There has also been increased injection of some pharmaceutical opioids by people who inject drugs, and for some patients, the development of problematic and/or dependent use. To date, much of the research on the use of pharmaceutical opioids among people with CNCP, have been clinical trials that have excluded patients with complex needs, and have been of limited duration (i.e. fewer than 12 weeks). The Pain and Opioids In Treatment (POINT) study is unique study that aims to: 1) examine patterns of opioid use in a cohort of patients prescribed opioids for CNCP; 2) examine demographic and clinical predictors of adverse events, including opioid abuse or dependence, medication diversion, other drug use, and overdose; and 3) identify factors predicting poor pain relief and other outcomes. Methods/Design The POINT cohort comprises around 1,500 people across Australia prescribed pharmaceutical opioids for CNCP. Participants will be followed-up at four time points over a two year period. POINT will collect information on demographics, physical and medication use history, pain, mental health, drug and alcohol use, non-adherence, medication diversion, sleep, and quality of life. Data linkage will provide information on medications and services from Medicare (Australia’s national health care scheme). Data on those who receive opioid substitution therapy, and on mortality, will be linked. Discussion This study will rigorously examine prescription opioid use among CNCP patients, and examine its relationship to important health outcomes. The extent to which opioids for chronic pain is associated with pain reduction, quality of life, mental and physical health, aberrant medication behavior and substance use disorders will be extensively examined. Improved understanding of the longer-term outcomes of chronic opioid therapy will direct community-based interventions and health policy in Australia and internationally. The results of this study will assist clinicians to better identify those patients who are at risk of adverse outcomes and who therefore require alternative treatment strategies. PMID:24646721

2014-01-01

387

Single-Point Magnetic Resonance Imaging Study of Water Adsorption in Pellets of Zeolite 4A  

NASA Astrophysics Data System (ADS)

The water uptake process in commercial type particles of zeolite 4A has been studied using a single-point MRI method. True proton density,T1,T2, andT*2relaxation times were obtained with submillimetric resolution, overcoming the restrictions of shortT*2signals. The molecular mobility in nonequilibrium conditions has been characterized by relaxation time mapping. A clear reduction of the water sorption rate was observed by comparing MRI profiles of a loosely packed bed and gravimetric measurements of spread particles from the same sieved zeolite batch.

Prado, Pablo J.; Balcom, Bruce J.; Jama, Mohamed

1999-03-01

388

First-principles study of point defects at a semicoherent interface  

PubMed Central

Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. We show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. We give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials. PMID:25524061

Metsanurk, E.; Tamm, A.; Caro, A.; Aabloo, A.; Klintenberg, M.

2014-01-01

389

Point defects in crystalline zircon (zirconium silicate), ZrSiO4: electron paramagnetic resonance studies  

NASA Astrophysics Data System (ADS)

This article outlines the present state of knowledge of paramagnetic defects in crystalline zircon as obtained mainly, but not exclusively, from electron paramagnetic resonance (EPR) studies in crystalline zircon (zirconium silicate, ZrSiO4). The emphasis is on single-crystal studies where, in principle, unambiguous analysis is possible. Firstly, the crystallography of zircon is presented. Secondly, the relationships between available crystal-site symmetries and the symmetries of observed paramagnetic species in zircon, and how these observations lead to unambiguous assignments of point-group symmetries for particular paramagnetic species are detailed. Next, spin-Hamiltonian (SH) analysis is discussed with emphasis on the symmetry relationships that necessarily exist amongst the Laue classes of the crystal sites in zircon, the paramagnetic species occupying those sites and the SH itself. The final sections of the article then survey the results of EPR studies on zircon over the period 1960-2002.

Tennant, W. C.; Claridge, R. F. C.; Walsby, C. J.; Lees, N. S.

390

Cloud point, fluorimetric and 1H NMR studies of ibuprofen-polymer systems  

NASA Astrophysics Data System (ADS)

Influence of six polymers viz. hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), sodium carboxy methyl cellulose (NaCMC) and dextran sulfate (DxS) on solution properties of amphiphilic drug ibuprofen (IBF) has been described in this work. As only HPMC showed the clouding behavior (among the polymers employed herein), its cloud point (CP) was studied in detail in presence of varying amounts of IBF containing different fixed concentrations of inorganic salts (NaCl, NaNO3, Na2SO4, KBr and KNO3). Presence of all these salts had CP reducing effect. By means of steady state fluorescence quenching studies, average aggregation number of IBF aggregates (Nagg) in the presence of varying amounts of the mentioned polymers were evaluated and discussed. 1H NMR studies show that the magnitude of chemical shifts (?) varies with the nature of the polymer.

Khan, Iqrar Ahmad; Anjum, Kahkashan; Koya, P. Ajmal; Qadeer, Atiytul; Kabir-ud-Din

2014-01-01

391

Auricular Point Acupressure as an Adjunct Analgesic Treatment for Cancer Patients: A Feasibility Study.  

PubMed

This study aimed (1) to examine the feasibility of an auricular point acupressure (APA) research protocol in terms of recruitment and for the assessment and management of pain and (2) to examine the potential APA analgesic effects for cancer patients. This study was a repeated-measures one-group design. Participants were recruited from the cancer center follow-up clinic affiliated with a large university hospital in the northeastern United States. Participants included 50 patients aged 55-87 years with a diagnosis of cancer. Participants received 7 days of APA treatment for their pain. After appropriate acupoints were identified, vaccaria seeds were carefully taped onto each selected auricular point on each ear. The study recruitment and retention rates were 92% and 91%, respectively. Importantly, the study found preliminary evidence for the analgesic effects of APA for cancer pain management. For example, by the end of the 7-day study, APA reduced pain intensity more than 55% for "worst pain" and about 57% for "average pain" and "pain intensity." Moreover, the use of pain medication was reduced during the APA treatment (e.g., 78% of patients [n = 39] took less pain medication than before the treatment). APA appears to be highly acceptable to patients with cancer-related pain. However, without a placebo control, we cannot draw conclusive evidence for the analgesic effect of APA for cancer patients. A sham group must be added to future studies to differentiate the true effects of APA from the possible psychological effects of the APA treatment. PMID:25439120

Yeh, Chao Hsing; Chien, Lung-Chang; Chiang, Yi Chien; Ren, Dianxu; Suen, Lorna Kwai-Ping

2014-10-31

392

Long term flight electrodes  

NASA Technical Reports Server (NTRS)

The reproducibility, stability, and methods of preparation for the various types and forms of biomedical electrodes are discussed. A critical and selective compilation of information on biological and/or physiological electrodes is presented. A discussion of plant hydrocolloids, clays, hydrophyllic colloids, synthetic waxes, and acrylic polymers is included.

Mosier, B.

1975-01-01

393

Novel nanostructured electrodes  

Microsoft Academic Search

Nanotechnology provides an effective and direct way to create novel properties and phenomena through the reduction in material sizes without changing the materials’ chemical composition. A number of routes to the preparation of novel nanostructured electrodes were investigated in this thesis. These involve the formation of nanoporous opaline electrodes, three dimensional nanofibrous networks and the synthesis of flexible nanoelectrodes based

Yong Liu

2007-01-01

394

Membrane Bioprobe Electrodes  

ERIC Educational Resources Information Center

Describes the design of ion selective electrodes coupled with immobilized enzymes which operate either continuously or on drop-sized samples. Cites techniques for urea, L-phenylalanine and amygdalin. Micro size electrodes for use in single cells are discussed. (GH)

Rechnitz, Garry A.

1975-01-01

395

Application of Ultrasound-Guided Trigger Point Injection for Myofascial Trigger Points in the Subscapularis and Pectoralis Muscles to Post-Mastectomy Patients: A Pilot Study  

PubMed Central

Purpose To investigate the therapeutic effectiveness of ultrasound (US)-guided trigger point injection for myofascial trigger points (MTrPs) in the internal rotator muscles of the shoulder in post-mastectomy patients. Materials and Methods This pilot study was a non-controlled, prospective, clinical trial. Nineteen post-mastectomy patients with a diagnosis of at least one active MTrP in the subscapularis and/or pectoralis muscles were included. We performed trigger point injections into the subscapularis muscle deep behind the scapula as well as the pectoralis muscle for diagnostic and therapeutic purpose by the newly developed US-guided method. Results Visual analogue scale and range of motion of the shoulder for external rotation and of abduction showed significant improvement immediately after the first injection and 3 months after the last injection compared with baseline (p<0.05 for both). Duration from onset to surgery and duration of myofascial pain syndrome in the good responder group were significantly shorter than in the bad responder group (p<0.05). Patients did not report any complications related to the procedure or serious adverse events attributable to the treatment. Conclusion In post-mastectomy patients with shoulder pain, US-guided trigger point injections of the subscapularis and/or pectoralis muscles are effective for both diagnosis and treatment when the cause of shoulder pain is suspected to originate from active MTrPs in these muscles, particularly, the subscapularis. PMID:24719150

Shin, Hyuk Jai; Shin, Ji Cheol; Kim, Wan Sung; Chang, Won Hyuk

2014-01-01

396

Access resistance of stimulation electrodes as a function of electrode proximity to the retina  

NASA Astrophysics Data System (ADS)

Objective. Epiretinal prostheses seek to effectively stimulate the retina by positioning electrode arrays close to its surface so current pulses generate narrow retinal electric fields. Our objective was to evaluate the use of the electrical impedance of insulated platinum electrodes as a measure of the proximity of insulated platinum electrodes to the inner surface of the retina. Approach. We examined the impedance of platinum disk electrodes, 0.25 mm in diameter, insulated with two widths (0.8 and 1.6 mm outer diameter) of transparent fluoropolymer in a rabbit retinal eyecup preparation. Optical coherence tomography measured the electrode’s proximity to the retinal surface which was correlated with changes in the voltage waveform at the electrode. Electrode impedance changes during retinal deformation were also studied. Main results. When the 1.6 mm diameter insulated electrodes advanced towards the retinal surface from 1000 ?m, their voltage step at current pulse onset increased, reflecting an access resistance increase of 3880 ± 630 ?, with the 50% midpoint averaging 30 ?m, while thin 0.8 mm insulated electrode advancement showed an access resistance increase 50% midpoint averaging 16 ?m. Using impedance spectroscopy, electrode–retina proximity differences were seen in the 1.6 mm insulated electrode impedance modulus between 1 and 100 kHz and the waveform phase angle at 0.3–10 kHz, while thin 0.8 mm insulated electrode advancement produced smaller impedance modulus changes with retinal proximity between 3 and 100 kHz. These impedance changes with retinal proximity may reflect different sized zones of eye wall being coupled in series with the insulated platinum electrode. Significance. The proximity of stimulus electrodes to neural tissue in fluid-filled spaces can be estimated from access resistance changes in the stimulus pulse waveform. Because many prosthetic devices allow back telemetry communication of the stimulus electrode waveform, it is possible these series resistance increases observed with retinal proximity could be used as a metric of stimulus electrode placement.

Majdi, Joseph A.; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D.

2015-02-01

397

Bifunctional catalytic electrode  

NASA Technical Reports Server (NTRS)

The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

2005-01-01

398

Electrodes for microfluidic applications  

DOEpatents

An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

Crocker, Robert W. (Fremont, CA); Harnett, Cindy K. (Livermore, CA); Rognlien, Judith L. (Livermore, CA)

2006-08-22

399

A study on fabrication of sulfonated poly(ether ether ketone)-based membrane-electrode assemblies for polymer electrolyte membrane fuel cells  

Microsoft Academic Search

The porosity effect of catalyst electrodes in membrane-electrode assemblies (MEAs) using a hydrocarbon-based polymer as electrolyte and ionomer was investigated on physical and electrochemical properties by varying the content of ionomer binder (dry condition) in the catalyst electrodes. The MEAs were compared with the Nafion®-based MEA using Nafion® 112 and 5wt.% ionomer solution (EW=1100) in terms of porosity values, scanning

Jin-Soo Park; Palanichamy Krishnan; Seok-Hee Park; Gu-Gon Park; Tae-Hyun Yang; Won-Yong Lee; Chang-Soo Kim

2008-01-01

400

3-D effects of polarization switching on interdigitated electroded ferroelectrics  

NASA Astrophysics Data System (ADS)

Interdigitated electrodes are used to obtain an in-plane d33 coupling from patch actuators. Existing design tools do not take into consideration the three dimensional effects of polarization reorientation. This work presents a 3-D finite element code that utilizes a micromechancial constitutive law with full ferroelectric switching. The code is used to explore the design of interdigitated electrode devices. The results point to several parameters that are important to the design of these devices. These include electrode spacing, electrode width, specimen thickness, and specimen depth.

Pisani, David M.; Lynch, C. S.

2011-04-01

401

Feasibility studies for the detection of organic surface and subsurface water contaminants by surface-enhanced Raman spectroscopy on silver electrodes  

SciTech Connect

Fundamental components of various families of organic contaminants that are found in surface and subsurface waters have been investigated by surface-enhanced Raman spectroscopy (SERS). The SERS substrate was a silver electrode maintained at various electrode potentials. The limit of detection for pyridine was calculated to be 8.5 pg. Variation of the electrode potential and excitation wavelength was used to qualitatively determine a two-component mixture of contaminants. The in situ type of conditions of low ionic strengths and humic materials was found not to inhibit the SERS effect on the silver electrode.

Carrabba, M.M.; Edmonds, R.B.; Rauh, R.D.

1987-11-01

402

Electrolysis-reducing electrodes for electrokinetic devices.  

PubMed

Direct current electrokinetic systems generally require Faradaic reactions to occur at a pair of electrodes to maintain an electric field in an electrolyte connecting them. The vast majority of such systems, e.g. electrophoretic separations (capillary electrophoresis) or electroosmotic pumps (EOPs), employ electrolysis of the solvent in these reactions. In many cases, the electrolytic products, such as H+ and OH? in the case of water, can negatively influence the chemical or biological species being transported or separated, and gaseous products such as O? and H? can break the electrochemical circuit in microfluidic devices. This article presents an EOP that employs the oxidation/reduction of the conjugated polymer poly(3,4-ethylenedioxythiophene), rather than electrolysis of a solvent, to drive flow in a capillary. Devices made with poly(3,4-ethylenedioxythiophene) electrodes are compared with devices made with Pt electrodes in terms of flow and local pH change at the electrodes. Furthermore, we demonstrate that flow is driven for applied potentials under 2?V, and the electrodes are stable for potentials of at least 100?V. Electrochemically active electrodes like those presented here minimize the disadvantage of integrated EOP in, e.g. lab-on-a-chip applications, and may open new possibilities, especially for battery-powered disposable point-of-care devices. PMID:21425174

Erlandsson, Per G; Robinson, Nathaniel D

2011-03-01

403

Study of the hidden-order of URu2Si2 by point contact tunnel junctions  

NASA Astrophysics Data System (ADS)

URu2Si2 presents superconductivity at temperatures below 1.5 K and a hidden order (HO) at about 17.5 K. Both electronic phenomena are influenced by Fano and Kondo resonances. At 17.5 K the HO was related in the past to a Peierls distortion that produces an energy gap deformed by the resonances. This order has been studied for more than 20 years and still there is no clear understanding. In this work we studied the electronic characteristics of URu2Si2 in a single crystal, with tunneling and metallic point contact spectroscopies. In the superconducting state, we determined the energy gap, which shows the influence of the Fano and Kondo resonances. At temperatures where HO is observed, the tunnel junctions spectra show the influence of the two resonances. Tunnel junction characteristics show that the Fermi surface nesting depends on the crystallographic direction.

Escudero, R.; López-Romero, R. E.; Morales, F.

2015-01-01

404

Nonlinear Seismic Analysis of Morrow Point Dam: A Study for the United States Bureau of Reclamation  

SciTech Connect

This research and development project was sponsored by the United States Bureau of Reclamation (USBR), who are best known for the dams, power plants, and canals it constructed in the 17 western states. The mission statement of the USBR's Dam Safety Office, located in Denver, Colorado, is ''to ensure Reclamation dams do not present unacceptable risk to people, property, and the environment.'' The Dam Safety Office does this by quickly identifying the dams which pose an increased threat to the public, and quickly completing the related analyses in order to make decisions that will safeguard the public and associated resources. The research study described in this report constitutes one element of USBR's research and development work to advance their computational and analysis capabilities for studying the response of dams to strong earthquake motions. This project focused on the seismic response of Morrow Point Dam, which is located 263 km southwest of Denver, Colorado.

Noble, C R; Solberg, J

2004-02-20

405

Study of the hidden-order of URu?Si? by point contact tunnel junctions.  

PubMed

URu2Si2 presents superconductivity at temperatures below 1.5 K and a hidden order (HO) at about 17.5 K. Both electronic phenomena are influenced by Fano and Kondo resonances. At 17.5 K the HO was related in the past to a Peierls distortion that produces an energy gap deformed by the resonances. This order has been studied for more than 20 years and still there is no clear understanding. In this work we studied the electronic characteristics of URu2Si2 in a single crystal, with tunneling and metallic point contact spectroscopies. In the superconducting state, we determined the energy gap, which shows the influence of the Fano and Kondo resonances. At temperatures where HO is observed, the tunnel junctions spectra show the influence of the two resonances. Tunnel junction characteristics show that the Fermi surface nesting depends on the crystallographic direction. PMID:25469859

Escudero, R; López-Romero, R E; Morales, F

2015-01-14

406

Polyethyleneimine as a promoter layer for the immobilization of cellobiose dehydrogenase from Myriococcum thermophilum on graphite electrodes.  

PubMed

Cellobiose dehydrogenase (CDH) is a promising enzyme for the construction of biofuel cell anodes and biosensors capable of oxidizing aldoses as cellobiose as well as lactose and glucose and with the ability to connect to an electrode through a direct electron transfer mechanism. In the present study, we point out the beneficial effect of a premodification of spectrographic graphite electrodes with the polycation polyethyleneimine (PEI) prior to adsorption of CDH from Myriococcum thermophilum (MtCDH). The application of PEI shifts the pH optimum of the response of the MtCDH modified electrode from pH 5.5 to 8. The catalytic currents to lactose were increased up to 140 times, and the K(M)(app) values were increased up to 9 times. The previously investigated, beneficial effect of divalent cations on the activity of CDH was also present for graphite/PEI/MtCDH electrodes but was less pronounced. Polarization curves revealed a second unexpected catalytic wave for graphite/PEI/MtCDH electrodes especially pronounced at pH 8. Square wave voltammetric studies revealed the presence of an unknown redox functionality present at 192 mV vs Ag|AgCl (0.1 M KCl) at pH 8, probably originating from an oxidized adenosine derivative. Adenosine is a structural part of the flavin adenine dinucleotide (FAD) cofactor of the dehydrogenase domain of CDH. It is suggested that for some enzyme molecules FAD leaks out from the active site, adsorbs onto graphite, and is oxidized on the electrode surface into a product able to mediate the electron transfer between CDH and the electrode. PEI is suggested and discussed to act in several manners by (a) increasing the surface loading of the enzyme, (b) possibly increasing the electron transfer rate between CDH and the electrode, and (c) facilitating the creation or immobilization of redox active adenosine derivatives able to additionally mediate the electron transfer between CDH and the electrode. PMID:24746119

Schulz, Christopher; Ludwig, Roland; Gorton, Lo

2014-05-01

407

Activation of the hypothalamus characterizes the acupuncture stimulation at the analgesic point in human: a positron emission tomography study  

Microsoft Academic Search

We performed a positron emission tomography study, using regional cerebral blood flow as the index of brain activity, to address the specificity of brain activation pattern by acupuncture stimulation of short duration at the classical analgesic point. Needling manipulation at 2 Hz was performed at a classical point of prominent analgesic efficacy (Li 4, Heku) and a near-by non-classical\\/non-analgesic point,

Jen-Chuen Hsieh; Chung-Haow Tu; Fang-Pey Chen; Min-Chi Chen; Tzu-Chen Yeh; Hui-Cheng Cheng; Yu-Te Wu; Ren-Shyan Liu; Low-Tone Ho

2001-01-01

408

Electrodes for sealed secondary batteries  

NASA Technical Reports Server (NTRS)

Self-supporting membrane electrode structures, in which active ingredients and graphite are incorporated in a polymeric matrix, improve performance of electrodes in miniature, sealed, alkaline storage batteries.

Boies, D. B.; Child, F. T.

1972-01-01

409

Layered electrode for electrochemical cells  

DOEpatents

There is provided an electrode structure comprising a current collector sheet and first and second layers of electrode material. Together, the layers improve catalyst utilization and water management.

Swathirajan, Swathy (West Bloomfield, MI); Mikhail, Youssef M. (Sterling Heights, MI)

2001-01-01

410

A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS  

NASA Astrophysics Data System (ADS)

We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm2), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.

Faria, Paula; Hallett, Mark; Cavaleiro Miranda, Pedro

2011-12-01

411

A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS  

PubMed Central

We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e., the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the CSF, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25–35 cm2), one of the electrodes should be placed just “behind” the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5 to 12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode. PMID:22086257

Faria, Paula; Hallett, Mark; Miranda, Pedro Cavaleiro

2012-01-01

412

Changes in blood flow and cellular metabolism at a myofascial trigger point with trigger point release (ischemic compression): a proof-of-principle pilot study  

PubMed Central

Objective To demonstrate proof-of-principle measurement for physiological change within an active myofascial trigger point (MTrP) undergoing trigger point release (ischemic compression). Design Interstitial fluid was sampled continuously at a trigger point before and after intervention. Setting A biomedical research clinic at a university hospital. Participants Two subjects from a pain clinic presenting with chronic headache pain. Interventions A single microdialysis catheter was inserted into an active MTrP of the upper trapezius to allow for continuous sampling of interstitial fluid before and after application of trigger point therapy by a massage therapist. Main Outcome Measures Procedural success, pain tolerance, feasibility of intervention during sample collection, determination of physiologically relevant values for local blood flow, as well as glucose and lactate concentrations. Results Both patients tolerated the microdialysis probe insertion into the MTrP and treatment intervention without complication. Glucose and lactate concentrations were measured in the physiological range. Following intervention, a sustained increase in lactate was noted for both subjects. Conclusions Identifying physiological constituents of MTrP’s following intervention is an important step toward understanding pathophysiology and resolution of myofascial pain. The present study forwards that aim by showing proof-of-concept for collection of interstitial fluid from an MTrP before and after intervention can be accomplished using microdialysis, thus providing methodological insight toward treatment mechanism and pain resolution. Of the biomarkers measured in this study, lactate may be the most relevant for detection and treatment of abnormalities in the MTrP. PMID:22975226

Moraska, Albert F.; Hickner, Robert C.; Kohrt, Wendy M.; Brewer, Alan

2012-01-01

413

Fundamental aspects of electrocatalysis of the hydrogen electrode reaction and oxygen electrode reaction on platinum  

Microsoft Academic Search

This dissertation work studies the fundamental aspects of the electrocatalysis of the hydrogen electrode reaction (HER) and oxygen electrode reaction (OER) on platinum over a wide temperature range from ambient up to 220°C. Previously, the majority of the work reported was restricted to temperatures below 70°C due to apparatus constraints, whereas the current operation temperature for proton exchange membrane fuel

Jianer Bao

2007-01-01

414

Space science/space station attached payload pointing accommodation study: Technology assessment white paper  

NASA Technical Reports Server (NTRS)

Technology assessment is performed for pointing systems that accommodate payloads of large mass and large dimensions. Related technology areas are also examined. These related areas include active thermal lines or power cables across gimbals, new materials for increased passive damping, tethered pointing, and inertially reacting pointing systems. Conclusions, issues and concerns, and recommendations regarding the status and development of large pointing systems for space applications are made based on the performed assessments.

Lin, Richard Y.; Mann, Kenneth E.; Laskin, Robert A.; Sirlin, Samuel W.

1987-01-01

415

An experimental-theoretical study of free vibrations of plates on elastic point supports  

NASA Technical Reports Server (NTRS)

A theoretical and experimental study is made to investigate the effect on plate vibrations of varying the stiffness of corner elastic point supports. A theoretical model is developed using a Rayleigh-Ritz analysis which approximates the plate mode shapes as products of free-free beam modes. The elastic point supports are modelled both as massless translational springs, and springs with tip masses. The tip masses are included to better represent the experimental supports. An experiment is constructed using the bending stiffness of horizontal beams to support a square plate at its four corners. The stiffness of these supports can be varied over such a range that the plate fundamental frequency is lowered to 40% of the rigid support frequency. The variation with support stiffness of the frequencies of the first eight plate modes is measured, and compared with the theoretical results. The plate mode shapes for rigid supports are analyzed using holographic interferometry. There is excellent agreement between the theoretical and experimental results, except for high plate modes where the theoretical model is demonstrated to be inadequate.

Leuner, T. R.

1972-01-01

416

Point defects engineering in graphene/h-BN bilayer: A first principle study  

NASA Astrophysics Data System (ADS)

Point defects engineering in a new type hetero bilayer consisting of graphene and hexagonal boron-nitrogen (h-BN) sheet, including vacancy, substitutional C/B/N doping and the possible combinations of the former two, was theoretically studied using first-principles calculations. The optimized geometry, formation energy, magnetic moment, and electronic property of these systems are discussed. It was found that N vacancy is more likely to form than B vacancy in graphene/h-BN bilayer and their electronic properties exhibit n-type and p-type conductivity, respectively. Divacancy of N and C in hetero bilayer shows high stability and induces direct band gap in up and down spin, respectively. Combined by N substitutional doping in graphene and B vacancy in h-BN layer, this substitution-vacancy combination shows low formation energy and changes the semiconductor property of pristine graphene/h-BN bilayer to metallic. In contrast, the graphene/h-BN bilayer with the combinated defect of C-substitution in B site and C vacancy in graphene shows half-metallic electronic property. The calculated magnetic moments are in reasonable agreement with the available theoretical analysis on atomic charge distribution. This work reveals that the electronic and magnetic properties of graphene/h-BN bilayer can be effectively tuned by above proposed point defects engineering.

Yuan, Jianmei; Wei, Zhe; Zhong, Jianxin; Huang, Yanping; Mao, Yuliang

2014-11-01

417

Theoretical study on tethered polymers with explicit grafting points in ?-solvent  

NASA Astrophysics Data System (ADS)

Systematic studies on the polymers chemically grafted onto a solid substrate with various grafting densities are presented based on the self-consistent mean-field theory (SCMFT). The distribution of the grafting points is explicitly included and all the three coordinates of each grafting point are fixed during the calculations. The existence of solvent molecules is also explicitly considered in the model and the case of ?-solvent is investigated. The structure of the system is derived by solving the SCMFT equations in three-dimensional space. For the cases of low grafting density, the system is highly inhomogeneous and typical mushroom-like structures are derived. On the other hand, when the grafting density is high enough, the system is nearly homogeneous along the substrate and the polymer concentration profile is consistent with the numerical results of one dimensional SCMFT calculations. The crossover between "mushroom" regime and polymer brush is obtained by tuning the grafting density. In addition, in brush limit, while the root-mean-squared thickness of the brush is linearly dependent on the degree of polymerization, its dependency on the grafting density is in general more complicated than a simple power law.

Suo, Tongchuan; Yan, Dadong

2011-02-01

418

A Randomized Clinical Trial of Auricular Point Acupressure for Chronic Low Back Pain: A Feasibility Study  

PubMed Central

Objectives. This prospective, randomized clinical trial (RCT) was designed to investigate the feasibility and effects of a 4-week auricular point acupressure (APA) for chronic low back pain (CLBP). Methods. Participants were randomized to either true APA (true acupoints with taped seeds on the designated ear points for CLBP) or sham APA (sham acupoints with taped seeds but on different locations than those designated for CLBP). The duration of treatment was four weeks. Participants were assessed before treatment, weekly during treatment, and 1 month following treatment. Results. Participants in the true APA group who completed the 4-week APA treatment had a 70% reduction in worst pain intensity, a 75% reduction in overall pain intensity, and a 42% improvement in disability due to back pain from baseline assessment. The reductions of worst pain and overall pain intensity in the true APA group were statistically greater than participants in the sham group (P < 0.01) at the completion of a 4-week APA and 1 month followup. Discussion. The preliminary findings of this feasibility study showed a reduction in pain intensity and improvement in physical function suggesting that APA may be a promising treatment for patients with CLBP. PMID:23554825

Yeh, Chao Hsing; Chien, Lung Chang; Balaban, Devora; Sponberg, Rebecca; Primavera, Jaclyn; Morone, Natalia E.; Glick, Ronald; Albers, Kathryn M.; Cohen, Susan M.; Ren, Dianxu; Huang, Li Chun; Suen, Lorna Kwai-Ping

2013-01-01

419

One electron oxygen reduction in room temperature ionic liquids: A comparative study of Butler-Volmer and Symmetric Marcus-Hush theories using microdisc electrodes  

E-print Network

The voltammetry for the reduction of oxygen at a microdisc electrode is reported in two room temperature ionic liquids: 1-butyl-1-methylpyyrolidinium bis(trifluoromethylsulfonyl) imide ([Bmpyrr][NTf2]) and trihexyltetradecylphosphonium bis9trifluoromethylsulfonyl) imide ([P14,6,6,6][NTf2]) at 298 K. Simulated voltammograms using Butler-Volmer theory and Symmetric Marcus-Hush (SMH) theory were compared with experimental data. Butler-Volmer theory consistently provided experimental parameters with a higher level of certainty than SMH theory. A value of solvent reorganisation energy for oxygen reduction in ionic liquids was inferred for the first time as 0.4-0.5 eV, which is attributable to inner-sphere reorganisation with a negligible contribution from solvent reorganisation. The developed Butler-Volmer and Symmetric Marcus-Hush programs are also used to theoretically study the possibility of kinetically limited steady state currents, and to establish an approximate equivalence relationship between microdisc el...

Tanner, Eden E L; Barnes, Edward O; Compton, Richard G

2015-01-01

420

Auricular point acupressure for chronic pain: a feasibility study of a 4-week treatment protocol.  

PubMed

This 1-group, 4-week observational study aimed to (1) assess the feasibility of recruiting, retention, and completion of a 4-week auricular point acupressure (APA) treatment protocol for chronic pain in adult patients and (2) assess the effects of APA in pain reduction (pain severity and pain interference) among these patients. The participants received a 4-week APA treatment protocol in weekly cycles. Each weekly cycle included 5 days with APA seeds taped onto the ear and 2 days without. Each participant was called every day to monitor adherence to the treatment protocol (the actual times the participant pressed the seeds each day and the duration of applied pressure), to answer analgesic use, and to answer the pain intensity questionnaire. Thirty participants were initially enrolled in this study, but 5 did not continue. The retention rate was 83% (n = 25). Approximately 60% of the participants (n = 15) adhered to the 4-week APA and completed all data assessments. At baseline assessment, only 40% of all participants (n = 12 of 30) were confident that APA would reduce and eliminate pain; nonetheless, all participants reported fewer episodes of pain occurrences and pain intensity with the APA treatment. For the participants who completed the 4-week APA protocol (n = 15), 96% (n = 14) decreased analgesic medication intake and 88% (n = 13) felt "much better" after the APA treatment. Participants reported an average reduction of 63% in the worst pain intensity at day 7. By the end of the 4-week APA protocol, an even greater reduction in pain intensity was reported (66%, n = 10, at day 28). The participants who did not complete the treatment protocol reported an average pain reduction of 29%, which fluctuated to 22% before they dropped out. Auricular point acupressure is feasible for patients with chronic pain. The preliminary findings of this feasibility study show a reduction in pain intensity and improvement in physical function, which demonstrate the potential for APA as a treatment option for patients with chronic pain. PMID:24722613

Yeh, Chao Hsing; Chien, Lung-Chang; Huang, Li Chun; Suen, Lorna Kwai-Ping

2014-01-01

421

A study on roof point extraction based on robust estimation from airborne LIDAR data  

Microsoft Academic Search

The airborne LIDAR scanning system is a whole new surveying technique that captures extremely detailed and abundant terrain surface information. Terrain information is implied in airborne LIDAR data. Roof points are especially important in airborne LIDAR data for 3?D building reconstruction. The key point for automatically and reliably extracting roof points from airborne LIDAR data is how to exclude irrelevant

2008-01-01