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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

Discharge development from point electrodes in air as influenced by a nearby dielectric surface  

Microsoft Academic Search

The interaction between discharges taking place in the stressed air volume of a point-to-point gap and the charge accumulating on a nearby dielectric surface due to these discharges is studied. For the discharge to be confined to one point-electrode of the gap, the tip radius of that electrode is chosen to be much smaller than that of the other electrode.

M. Abdel-Salam; P. Weiss

1990-01-01

4

Arc electrode interaction study  

NASA Technical Reports Server (NTRS)

The project consisted of two parts: (1) the cathode interaction studies which were a continuation of previous work and had the objective of increasing our understanding of the microscopic phenomena controlling cathode erosion in arc jet thrusters, and (2) the studies of the anode attachment in arc jet thrusters. The cathode interaction studies consisted of (1) a continuation of some modeling work in which the previously derived model for the cathode heating was applied to some specific gases and electrode materials, and (2) experimental work in which various diagnostics was applied to the cathode. The specific diagnostics used were observation of the cathode tip during arcing using a Laser Strobe Video system in conjunction with a tele-microscope, a monochromator with an optical multichannel analyzer for the determination of the cathode temperature distribution, and various ex situ materials analysis methods. The emphasis of our effort was shifted to the cathode materials analysis because a parallel project was in place during the second half of 1993 with a visiting scientist pursuing arc electrode materials studies. As a consequence, the diagnostic investigations of the arc in front of the cathode had to be postponed to the first half of 1994, and we are presently preparing these measurements. The results of last year's study showed some unexpected effects influencing the cathode erosion behavior, such as increased erosion away from the cathode tip, and our understanding of these effects should improve our ability to control cathode erosion. The arc jet anode attachment studies concentrated on diagnostics of the instabilities in subsonic anode attachment arc jet thrusters, and were supplemental measurements to work which was performed by one of the authors who spent the summer as an intern at NASA Lewis Research Center. A summary of the results obtained during the internship are included because they formed an integral part of the study. Two tasks for 1994, the diagnostics of the anode closure phenomenon, and the use of arc jet thrusters for the deposition of c-BN, are being prepared.

Zhou, X.; Berns, D.; Heberlein, J.

1994-01-01

5

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

6

Development of a point-electrode conductivity salinometer with high-spatial-resolution for use in very-saline solutions  

Microsoft Academic Search

A conductivity probe and circuit were developed to measure salinities in sodium chloride salt gradient solar ponds. A point electrode salinometer design was chosen to give a spatial resolution of approximately 1 mm. The high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective\\/conductive zone boundaries. The point electrode conductivity instrument was designed

G. F. Jones; D. P. Grimmer; J. Tafoya; T. J. Fitzgerald

1983-01-01

7

Development of a point-electrode conductivity salinometer with high spatial resolution for use in very saline solutions  

Microsoft Academic Search

A conductivity probe and circuit were developed to measure salinities in sodium chloride salt-gradient solar ponds. A point-electrode salinometer design was chosen to give a spatial resolution of approximately 1 mm (0.039 in.). Such high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective\\/conductive zone boundaries. The point-electrode conductivity instrument was designed for

D. P. Grimmer; G. F. Jones; J. Tafoya; T. J. Fitzgerald

1983-01-01

8

Development of a point-electrode conductivity salinometer with high spatial resolution for use in very saline solutions  

Microsoft Academic Search

A conductivity probe and circuit were developed to measure salinities in sodium chloride salt-gradient solar ponds. A point-electrode salinometer design was chosen to give spatial resolution approximately 0.039 in. (1 mm). Such high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective\\/conductive zone interfaces. The point-electrode conductivity instrument was designed for use in

D. P. Grimmer; G. F. Jones; J. Tafoya; T. J. Fitzgerald

1983-01-01

9

Morphological changes at the interface of the nickel-yttria stabilized zirconia point electrode  

Microsoft Academic Search

The Hâ-HâO, Ni\\/YSZ point electrode has been investigated using long-term potential step measurements and impedance spectroscopy at 1,273 K. Morphological and structural changes at the electrode interface were evaluated by electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy ex situ. The anodic current was found to induce a self-catalytic effect on the electrode, and the anodic steady state current

Rolf Jarle Aaberg; R. Tunold; M. Mogensen; R. W. Berg; R. Oedegaard

1998-01-01

10

Nanosecond-pulse gliding discharges between point-to-point electrodes in open air  

NASA Astrophysics Data System (ADS)

In this paper, gliding discharges with a point-to-point electrode geometry were produced by a repetitively pulsed power supply with a rise time of ˜100 ns and a full-width at half-maximum of ˜200 ns. The characteristics of such discharges were investigated by measuring their voltage-current waveforms and taking photographs of their discharge images. Experimental results showed that once the breakdown occurred, the nanosecond-pulse gliding discharges went into a stable stage at all air gaps, behaving in a mode of repetitive sparks. Under certain conditions, a non-stable stage would appear some time after the discharge went into the stable stage, in which the gliding discharges transitioned from repetitive sparks to diffuse discharges. Furthermore, several factors (gap spacing, pulse repetition frequency (PRF) and gas flow rate) influencing the discharge characteristics were investigated. It was observed that both the breakdown voltage and ignition voltage increased with the gap spacing, and a diffuse discharge was absent when the gap spacing was less than 6 mm. The breakdown voltage decreased with the increase in the PRF and its decrease ratio was larger in large gap spacing than in small gap spacing. Discharges would transit from repetitive sparks to diffuse discharges as the flow rate increased. Furthermore, a comparison of nanosecond-pulse and ac gliding discharges was conducted with respect to the power supply. The consumption and energy, the relationship between the power supply and the load, and the time interval between two pulses were three main factors which could lead to different characteristics between the nanosecond-pulse and ac gliding discharges.

Zhang, Cheng; Shao, Tao; Yan, Ping; Zhou, Yuanxiang

2014-06-01

11

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

12

GLAS Spacecraft Pointing Study  

NASA Technical Reports Server (NTRS)

Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 m of the location of the previous repeat ground track. The satellite will be flown in a repeat orbit of 182 days. Operationally, the required pointing information will be determined on the ground using the nominal ground track, to which pointing is desired, and the current propagated orbit of the satellite as inputs to the roll computation algorithm developed by CCAR. The roll profile will be used to generate a set of fit coefficients which can be uploaded on a daily basis and used by the on-board attitude control system. In addition, an algorithm has been developed for computation of the associated command quaternions which will be necessary when pointing at targets of opportunity. It may be desirable in the future to perform the roll calculation in an autonomous real-time mode on-board the spacecraft. GPS can provide near real-time tracking of the satellite, and the nominal ground track can be stored in the on-board computer. It will be necessary to choose the spacing of this nominal ground track to meet storage requirements in the on-board environment. Several methods for generating the roll profile from a sparse reference ground track are presented.

Born, George H.; Gold, Kenn; Ondrey, Michael; Kubitschek, Dan; Axelrad, Penina; Komjathy, Attila

1998-01-01

13

Development of a point-electrode conductivity salinometer with high-spatial-resolution for use in very-saline solutions  

SciTech Connect

A conductivity probe and circuit were developed to measure salinities in sodium chloride salt-gradient solar ponds. A point-electrode salinometer design was chosen to give a spatial resolution of approximately 1 mm (0.039 in.). Such high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective/conductive zone boundaries. The point-electrode conductivity instrument was designed for use in up to 25 wt % salinities with immersion times of about 0.1 year or longer. Drift in the instrument, however, caused principally by changes in the surface condition of the platinum probe tip and reflected by changes in the probe cell constant, required periodic in situ calibration against the measured specific gravity of withdrawn fluid samples.

Jones, G.F.; Grimmer, D.P.; Tafoya, J.; Fitzgerald, T.J.

1983-01-01

14

Carbon nanotube growth on a pointed bulk electrode using femtosecond laser nonlinear lithography  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT) bundles were synthesized on pointed bulk electrodes using femtosecond laser nonlinear lithography. A resist mask of 1.5 ?m diameter was formed on a pointed bulk cathode by translating a laser focus three-dimensionally inside the spherical photoresist. Metal masks obtained by pattern transfers of the resists effectively suppressed CNT growth during plasma-enhanced chemical vapor deposition, resulting in synthesis of CNT bundles only at the electrode tip. Irradiation of field emission currents from the pointed cathode enables local melting and subsequent removal of anode materials. The damaged region size and the threshold voltage for this removal process were reduced by spatial limitations of emission sites using the metal mask.

Nishiyama, Hiroaki; Iba, Tomohiro; Hirata, Yoshinori

2013-11-01

15

Super-resolution imaging using multi- electrode CMUTs: theoretical design and simulation using point targets.  

PubMed

This paper investigates a low computational cost, super-resolution ultrasound imaging method that leverages the asymmetric vibration mode of CMUTs. Instead of focusing on the broadband received signal on the entire CMUT membrane, we utilize the differential signal received on the left and right part of the membrane obtained by a multi-electrode CMUT structure. The differential signal reflects the asymmetric vibration mode of the CMUT cell excited by the nonuniform acoustic pressure field impinging on the membrane, and has a resonant component in immersion. To improve the resolution, we propose an imaging method as follows: a set of manifold matrices of CMUT responses for multiple focal directions are constructed off-line with a grid of hypothetical point targets. During the subsequent imaging process, the array sequentially steers to multiple angles, and the amplitudes (weights) of all hypothetical targets at each angle are estimated in a maximum a posteriori (MAP) process with the manifold matrix corresponding to that angle. Then, the weight vector undergoes a directional pruning process to remove the false estimation at other angles caused by the side lobe energy. Ultrasound imaging simulation is performed on ring and linear arrays with a simulation program adapted with a multi-electrode CMUT structure capable of obtaining both average and differential received signals. Because the differential signals from all receiving channels form a more distinctive temporal pattern than the average signals, better MAP estimation results are expected than using the average signals. The imaging simulation shows that using differential signals alone or in combination with the average signals produces better lateral resolution than the traditional phased array or using the average signals alone. This study is an exploration into the potential benefits of asymmetric CMUT responses for super-resolution imaging. PMID:24158286

You, Wei; Cretu, Edmond; Rohling, Robert

2013-11-01

16

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

17

Study of the near-electrode processes in quasi-steady plasma accelerators with impenetrable electrodes  

SciTech Connect

Near-electrode processes in a coaxial plasma accelerator with equipotential impenetrable electrodes are simulated using a two-dimensional (generally, time-dependent) two-fluid MHD model with allowance for the Hall effect and the plasma conductivity tensor. The simulations confirm the theoretically predicted mechanism of the so-called 'crisis of current' caused by the Hall effect. The simulation results are compared with available experimental data. The influence of both the method of plasma supply to the channel and an additional longitudinal magnetic field on the development of near-electrode instabilities preceding the crisis of current is studied.

Kozlov, A. N. [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation)

2012-01-15

18

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

19

A comparison study of electrodes for neonate electrical impedance tomography  

Microsoft Academic Search

Electrical impedance tomography (EIT) is an imaging technique that has the potential to be used for studying neonate lung function. The properties of the electrodes are very important in multi-frequency EIT (MFEIT) systems, particularly for neonates, as the skin cannot be abraded to reduce contact impedance. In this work, the impedance of various clinical electrodes as a function of frequency

Mohamad Rahal; Joo Moy Khor; Andreas Demosthenous; Andrew Tizzard; Richard Bayford

2009-01-01

20

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

21

Textile Electrodes for EEG Recording — A Pilot Study  

PubMed Central

The overall aim of our research is to develop a monitoring system for neonatal intensive care units. Long-term EEG monitoring in newborns require that the electrodes don’t harm the sensitive skin of the baby, an especially relevant feature for premature babies. Our approach to EEG monitoring is based on several electrodes distributed over the head of the baby, and since the weight of the head always will be on some of them, any type of hard electrode will inevitably cause a pressure-point that can irritate the skin. Therefore, we propose the use of soft conductive textiles as EEG electrodes, primarily for neonates, but also for other kinds of unobtrusive long-term monitoring. In this paper we have tested two types of textile electrodes on five healthy adults and compared them to standard high quality electrodes. The acquired signals were compared with respect to morphology, frequency distribution, spectral coherence, correlation and power line interference sensitivity, and the signals were found to be similar in most respects. The good measurement performance exhibited by the textile electrodes indicates that they are feasible candidates for EEG recording, opening the door for long-term EEG monitoring applications. PMID:23223149

Löfhede, Johan; Seoane, Fernando; Thordstein, Magnus

2012-01-01

22

Quiet Study AssemblyPoint  

E-print Network

AATCem TheRotunda Quiet Study AssemblyPoint On-siteparkingisforpermit holders. Lecture Theatre A TheGraphicsBuilding 1. Seminar Rooms 6,7,8, 9 & 10 2. Time Based Media 3.Graphic Services Centre 10.PhDQuietStudy 11.FineArtStudios/Workshops 12. Mac Suite 1 13. Seminar Room 4 14. Quiet

Molinari, Marc

23

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

24

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

25

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

26

Voltammetric studies of electrodes in contact with ionomeric membranes  

SciTech Connect

Cyclic voltammetry studies were carried out on platinum and gold screen electrodes in contact with Nafion ionomeric membranes. In addition, experiments were carried out on multiple combinations of platinum screens with either graphite felt or gold screen electrodes, with only one of the electrodes in direct contact with th membrane. In the case of platinum and gold screens, it was found that the voltammograms were almost identical to that found for the same screens in acidic aqueous electrolytes. When two platinum screens were used, the adsorption charge on the platinum doubled. Obviously, adsorption can occur on sites remote from the membrane/electrode contact, provided the metal is wetted with water. In the case of platinum, a mechanism based on rapid mobility of absorbed hydrogen and hydroxyl species is proposed. The implications of these findings regarding solid polymer electrolyte electrolyzers and fuel cells are discussed.

McBreen, J.

1985-05-01

27

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

28

Point of zero potential of single-crystal electrode/inert electrolyte interface.  

PubMed

Most of the environmentally important processes occur at the specific hydrated mineral faces. Their rates and mechanisms are in part controlled by the interfacial electrostatics, which can be quantitatively described by the point of zero potential (PZP). Unfortunately, the PZP value of specific crystal face is very difficult to be experimentally determined. Here we show that PZP can be extracted from a single-crystal electrode potentiometric titration, assuming the stable electrochemical cell resistivity and lack of specific electrolyte ions sorption. Our method is based on determining a common intersection point of the electrochemical cell electromotive force at various ionic strengths, and it is illustrated for a few selected surfaces of rutile, hematite, silver chloride, and bromide monocrystals. In the case of metal oxides, we have observed the higher PZP values than those theoretically predicted using the MultiSite Complexation Model (MUSIC), that is, 8.4 for (001) hematite (MUSIC-predicted ~6), 8.7 for (110) rutile (MUSIC-predicted ~6), and about 7 for (001) rutile (MUSIC-predicted 6.6). In the case of silver halides, the order of estimated PZP values (6.4 for AgCl<6.5 for AgBr) agrees well with sequence estimated from the silver halide solubility products; however, the halide anions (Cl(-), Br(-)) are attracted toward surface much stronger than the Ag(+) cations. The observed PZPs sequence and strong anions affinity toward silver halide surface can be correlated with ions hydration energies. Presented approach is the complementary one to the hysteresis method reported previously [P. Zarzycki, S. Chatman, T. Preo?anin, K.M. Rosso, Langmuir 27 (2011) 7986-7990]. A unique experimental characterization of specific crystal faces provided by these two methods is essential in deeper understanding of environmentally important processes, including migration of heavy and radioactive ions in soils and groundwaters. PMID:22277245

Zarzycki, Piotr; Preo?anin, Tajana

2012-03-15

29

A simulation study: effect of the inter-electrode distance, electrode size and shape in transcutaneous electrical stimulation.  

PubMed

Transcutaneous Electrical Stimulation (TES) has been used widely to recover motor functions in neurologically impaired individuals by artificially activating skeletal muscles using superficial electrodes. Some simulation studies have investigated the percentage of fibers activated in denervated skeletal muscles, the comfort and selectivity, and the influence of fat thickness in the case of obese people, to optimize the inter-electrode distance and electrode size. However, the effect of the inter-electrode distance, electrode shape and electrode size might be further analyzed using the selectivity, activation depth and activation volume. In this regard, we developed a 3D multi-layer (skin, fat, muscle, and nerve) thigh model coupled with a mammalian nerve model using a finite element method for optimization of TES therapy. Different evaluation indices (motor threshold, activation depth, selectivity and activation volume) were inspected to compare different TES parameters in terms of nerve activation. The simulation results agreed with experimental data and new insights were obtained: selectivity is better in small electrodes; nevertheless, in high current stimulation, small electrodes and large electrodes have similar selectivity. PMID:23366700

Gomez-Tames, Jose D; Gonzalez, Jose; Yu, Wenwei

2012-01-01

30

Quantitative study of non-covalent interactions at the electrode-electrolyte interface using cyanide-modified Pt(111) electrodes.  

SciTech Connect

Cations at the outer Helmholtz plane (OHP) can interact through non-covalent interactions with species at the inner Helmholtz plane (IHP), which are covalently bonded to the electrode surface, thereby affecting the structure and the properties of the electrochemical double layer. These non-covalent interactions can be studied quantitatively using cyanide-modified Pt(111) electrodes.

Escudero-Escribano, M.; Michoff, M. E. Z.; Leiva, E. P. M.; Markovic, N. M.; Gutierrez, C.; Cuesta, A. (Materials Science Division); (CSIC); (Universidad Nacional de Cordoba)

2011-08-22

31

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

32

X-ray photoelectron and scanning auger electron spectroscopic studies of oxidized graphite electrode surfaces  

Microsoft Academic Search

The surfaces of electrochemically modified graphite electrodes have been studied using ESCA, scanning Auger microscopy, and chemical titration. Quantitative evaluation of surface functionalities after electro-oxidation in sulfuric acid provides an understanding of their mechanistic role in synthetic uses of the carbon electrode. Specifically concentrations of acid and phenolic groups are correlated with the level of oxidation on the electrode. A

Joseph H. Wandass; J. A. Jr. Gardello; N. L. Weinberg; M. E. Bolster; L. Jr. Salvati

1987-01-01

33

Theoretical study of reactions at the electrode-electrolyte interface  

SciTech Connect

Electron transfer rates are predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have produced a new theory for description of the Jahn Teller effect in the solvation shell of the cuprous ion in aqueous solution, have implemented it in a molecular dynamics simulation and compared the results with experimental neutron scattering measurements on solutions containing the cuprous ion. A large amount of numerical data has been collected on the transition state of the ferrous ferric electron transfer reaction at an electrode. Work was completed on a polarizable and dissociable model of water for use in the electron transfer studies. New calculations of the conductivity in models of oxides have shown the existence of impurity conduction bands in such models for the first time.

Halley, J.W.

1993-01-01

34

The buried reference electrode: A critical long term performance study  

SciTech Connect

Accurate monitoring of cathodic protection relies upon the proficiency of the test personnel and the proper operation of the required equipment. The equipment consists of properly insulated test leads, an electronic volt meter with a known internal circuit resistance, and a reference electrode. The proper operation of each piece of equipment is critical to the accuracy of the cathodic protection test results. However, the reference electrode is not often suspected of being responsible for unexpected cathodic protection readings. This paper will provide background on the use of portable reference electrodes and data used to evaluate the performance of buried reference electrodes installed adjacent to a single, catholically protected, underground storage tank. Data accumulated at the test site clearly indicates that not all buried reference electrodes provide identical results.

Leon, T.; Geyer, W. [Steel Tank Inst., Lake Zurich, IL (United States)

1998-12-31

35

A comparative study of solid and liquid inner contact benzalkonium chloride ion-selective electrode membranes.  

PubMed

A comparative study was made between two designs of benzalkonium ion (Bz)-selective electrodes: a silver-coated (solid contact) called electrode A and a PVC membrane (liquid inner contact) called electrode B based on benzalkonium-phosphomolybdate (Bz-PM) as ion-exchanger complex. Electrode A has a linear dynamic range from 2.0×10(-8) to 1.0×10(-2) mol L(-1), with a Nernstian slope of 60±0.3 mV/decade and a detection limit of 2.0×10(-8) mol L(-1). Electrode B shows linearity over the concentration range from 2.0×10(-7) to 1.0×10(-2) mol L(-1), with a Nernstian slope of 55±1.2 mV/decade and a limit of detection of 1.5×10(-7) mol L(-1). Electrode A showed better performance than electrode B. The detection limit of benzalkonium chloride (BzCl) was effectively improved by a solid contact ion-selective electrode (SC-ISE), rather than the traditional liquid inner contact electrode that gives lower detection limits because of diminished ion fluxes. The present electrodes show clear discrimination of BzCl from several inorganic, organic ions, sugars and some common drug excipients. The sensors were applied efficiently for determination of BzCl in its pharmaceutical preparations (eye, ear and nasal drops) using standard addition and the calibration curve methods. PMID:23158314

Abu Shawish, Hazem M; Khedr, Abdalla M; Abed-Almonem, Khalid I; Gaber, M

2012-11-15

36

X-ray photoelectron and scanning auger electron spectroscopic studies of oxidized graphite electrode surfaces  

SciTech Connect

The surfaces of electrochemically modified graphite electrodes have been studied using ESCA, scanning Auger microscopy, and chemical titration. Quantitative evaluation of surface functionalities after electro-oxidation in sulfuric acid provides an understanding of their mechanistic role in synthetic uses of the carbon electrode. Specifically concentrations of acid and phenolic groups are correlated with the level of oxidation on the electrode. A plateau is reached at between 4 and 22 C/cm/sup 2/.

Wandass, J.H.; Gardello, J.A. Jr.; Weinberg, N.L.; Bolster, M.E.; Salvati, L. Jr.

1987-11-01

37

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

E-print Network

/??- alumina were investigated, using Ni, Cu, Co and W as the metal components. Pure metal electrodes (PME) were also studied, including Ta, Ni, Nb, Ir, W and MoRe electrodes. The stability of MIEE/???-alumina solid electrolyte (BASE) interface was studied...

Guo, Yuyan

2009-05-15

38

Lunar libration point flight dynamics study  

NASA Technical Reports Server (NTRS)

Two satellite concepts, Halo and Hummingbird, for a lunar libration point satellite to be used as a tracking and communications link with the far side of the moon were evaluated. Study areas included flight dynamics, communications, attitude control, propulsion, and system integration. Both concepts were proved feasible, but Halo was shown to be the better concept.

1969-01-01

39

Chemistry of carbon polymer composite electrode - An X-ray photoelectron spectroscopy study  

NASA Astrophysics Data System (ADS)

Surface chemistry of the electrodes in a proton exchange membrane fuel cell is of great importance for the cell performance. Many groups have reported that electrode preparation condition has a direct influence on the resulting electrode properties. In this work, the oxidation state of electrode components and the composites (catalyst ionomer mixtures) in various electrode structures were systematically studied with X-ray photoelectron spectroscopy (XPS). Based on the spectra, when catalyst is physically mixed with Nafion ionomer, the resulting electrode surface chemistry is a combination of the two components. When the electrode is prepared with a lamination procedure, the ratio between fluorocarbon and graphitic carbon is decreased. Moreover, ether type oxide content is decreased although carbon oxide is slightly increased. This indicates structure change of the catalyst layer due to an interaction between the ionomer and the catalyst and possible polymer structural change during electrode fabrication. The surface of micro porous layer was found to be much more influenced by the lamination, especially when it is in contact with catalysts in the interphase. Higher amount of platinum oxide was observed in the electrode structures (catalyst ionomer mixture) compared to the catalyst powder. This also indicates a certain interaction between the functional groups in the polymer and platinum surface.

Andersen, Shuang Ma; Dhiman, Rajnish; Skou, Eivind

2015-01-01

40

Raman spectroelectrochemical study of Toluidine Blue, adsorbed and electropolymerized at a gold electrode  

Microsoft Academic Search

The redox dye Toluidine Blue (TB), adsorbed and electropolymerized at a roughened gold electrode, has been studied by Raman spectroscopy at ?ex of 676.4nm in an electrochemical cell. Most of the spectral bands have been assigned based on density functional theory (DFT) calculations. The number and position of the bands, as well as their intensity depend on electrode potential and

Regina Mažeikien?; Gediminas Niaura; Olegas Eicher-Lorka; Albertas Malinauskas

2008-01-01

41

Electron spectroscopic (ESCA) studies of platinum surfaces used for enzyme electrodes  

SciTech Connect

Platinum electrodes which were either thermally or electrochemically treated have been examined by X-ray photoelectron spectroscopy (ESCA). In addition, electrodes that were chemically modified by silane or allylamine coatings were also studied by this technique. The spectra obtained for these samples showed: (a) thermally treated electrodes have less carbonaceous surface contamination than electrochemically conditioned foils; (2) oxidation of the Pt surface is more extensive by electrolysis compared with exposure to an oxidizing natural gas flame; (3) thermal procedures used in this study enhanced migration of bulk contaminants to the electrode surface, in particular silicon was observed; and (4) use of a silane to cover the Pt electrode gives a thicker layer than that obtained using an allylamine binding agent. The study also emphasizes the usefulness of ESCA to prove such surfaces qualitatively while at the same time suggesting caution where quantitative analyses are required. 35 references, 5 figures, 4 tables.

Proctor, A.; Castner, J.F.; Wingard, L.B. Jr.; Hercules, D.M.

1985-07-01

42

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

43

Experimental study on stability of different solid contact arrangements of ion-selective electrodes.  

PubMed

Comparison of potentials stability of different types of solid contact lead selective electrodes is presented. Conducting polymer based sensors (hydrophilic and conducting - poly(3,4-ethylenedioxythiophene) or hydrophobic and semiconducting-polyoctylthiophene) were studied in parallel with coated wire and hydrogel (poly(hydroxyethylmethacrylate)) contact electrodes. The within day and between days potential stability was compared, highlighting the effect of sensor storing conditions. The obtained results clearly demonstrate that different conclusions on stability of sensors' potential can be drawn depending on experimental protocol applied. Polyoctylthiophene based contacts show superior within day stability with no influence of dry storage. On the other hand, a chronopotentiometric method of stability evaluation clearly prefers poly(3,4-ethylenedioxythiophene) based sensors, pointing to smallest resistance and polarizability. It is clearly shown that the choice of experimental conditions applied to test stability can favor particular type of contact used. The inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) experiments conducted for different arrangements tested has shown that for poly(3,4-ethylenedioxythiophene) and poly(hydroxyethylmethacrylate) type contacts longer contact time with lead(II) solution results in changes in the elemental composition of the transducer layer. On the other hand, in line with high stability observed under potentiometric conditions, no changes were seen for polyoctylthiophene based transducer. PMID:20685450

Michalska, Agata; Wojciechowski, Marcin; Bulska, Ewa; Maksymiuk, Krzysztof

2010-06-30

44

Studying the Performance of Conductive Polymer Films as Textile Electrodes for Electrical Bioimpedance Measurements  

NASA Astrophysics Data System (ADS)

With the goal of finding novel biocompatible materials suitable to replace silver in the manufacturing of textile electrodes for medical applications of electrical bioimpedance spectroscopy, three different polymeric materials have been investigated. Films have been prepared from different polymeric materials and custom bracelets have been confectioned with them. Tetrapolar total right side electrical bioimpedance spectroscopy (EBIS) measurements have been performed with polymer and with standard gel electrodes. The performance of the polymer films was compared against the performance of the gel electrodes. The results indicated that only the polypropylene 1380 could produce EBIS measurements but remarkably tainted with high frequency artefacts. The influence of the electrode mismatch, stray capacitances and large electrode polarization impedance are unclear and they need to be clarified with further studies. If sensorized garments could be made with such biocompatible polymeric materials the burden of considering textrodes class III devices could be avoided.

Cunico, F. J.; Marquez, J. C.; Hilke, H.; Skrifvars, M.; Seoane, F.

2013-04-01

45

Neutron reflectometry studies on the lithiation of amorphous silicon electrodes in lithium-ion batteries.  

PubMed

Neutron reflectometry is used to study in situ the intercalation of lithium into amorphous silicon electrodes. The experiments are done using a closed three-electrode electrochemical cell setup. As a working electrode, an about 40 nm thick amorphous silicon layer is used that is deposited on a 1 cm thick quartz substrate coated with palladium as a current collector. The counter electrode and the reference electrode are made of lithium metal. Propylene carbonate with 1 M LiClO4 is used as an electrolyte. The utility of the cell is demonstrated during neutron reflectometry measurements where Li is intercalated at a constant current of 100 ?A (7.8 ?A cm(-2)) for different time steps. The results show (a) that the change in Li content in amorphous silicon and the corresponding volume expansion can be monitored, (b) that the formation of the solid electrolyte interphase becomes visible and (c) that an irreversible capacity loss is present. PMID:23598350

Jerliu, B; Dörrer, L; Hüger, E; Borchardt, G; Steitz, R; Geckle, U; Oberst, V; Bruns, M; Schneider, O; Schmidt, H

2013-05-28

46

A comparative study of nano-scale coatings on gold electrodes for bioimpedance studies of breast cancer cells  

E-print Network

A comparative study of nano-scale coatings on gold electrodes for bioimpedance studies of breast frequency of the cancer cell bioimpedance signal based on the type of electrode coat- ing. The results for different bioimpedance sensing applications. Keywords Gold nanoparticles . Carbon nanotubes . Surface

Heflin, Randy

47

A Study in Enzyme Kinetics Using an Ion-Specific Electrode.  

ERIC Educational Resources Information Center

Describes an undergraduate biochemistry laboratory experiment on enzyme kinetics using the D-amino acid oxidase system and an ammonia electrode. Preparation of an ammonia standard curve, a sample preparation, and inhibition studies are discussed. (YP)

Turchi, Sandra; And Others

1989-01-01

48

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

49

Flash photoelectrochemical studies of transient electrode processes important in solar-energy conversion. Final report  

SciTech Connect

It has been the objective of this research program to apply electroanalytical and spectroscopic measurement techniques to the study of transient photolytic, photoemissive, and photoelectrolytic processes associated with uv-visible irradiation of an electrode/solution interface. Both semiconductor and metallic electrodes have been employed. For the characterization of transient phenomena, the general methodology of flash photolysis was employed (including both xenon flash lamp and tunable pulsed dye laser sources). The novel perspective afforded by transient electroanalytical/spectroscopic measurements of photoinitiated electrode processes has provided more definitive mechanistic insight to solar conversion phenomena in photogalvanic or photoelectrolysis processes.

Perone, S.P.

1982-10-01

50

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

51

Application of Electrode Methods in Studies of Nitric Oxide Metabolism and Diffusion Kinetics  

PubMed Central

Nitric oxide (NO) has many important physiological roles in the body. Since NO electrodes can directly measure NO concentration in the nM range and in real time, NO electrode methods have been generally used in laboratories for measuring NO concentration in vivo and in vitro. This review focuses on the application of electrode methods in studies of NO diffusion and metabolic kinetics. We have described the physical and chemical properties that need to be considered in the preparation of NO stock solution, discussed the effect of several interfering factors on the measured curves of NO concentration that need to be eliminated in the experimental setup for NO measurements, and provided an overview of the application of NO electrode methods in measuring NO diffusion and metabolic kinetics in solution and in biological systems. This overview covers NO metabolism by oxygen (O2), superoxide, heme proteins, cells and tissues. Important conclusions and physiological implication of these studies are discussed. PMID:23730264

Liu, Xiaoping; Zweier, Jay L.

2012-01-01

52

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

53

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

54

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

PubMed

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. PMID:24786208

Gu, Y; Levin, C S

2014-06-01

55

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

56

Engineering study on TiSnSb-based composite negative electrode for Li-ion batteries  

NASA Astrophysics Data System (ADS)

Micrometric TiSnSb is a promising negative electrode material for Li-ion batteries when formulated with carboxymethyl cellulose (CMC) binder and a mixture of carbon black and carbon nanofibers, and cycled in a fluoroethylene carbonate (FEC)-containing electrolyte. Here, other binder systems were evaluated, polyacrylic acid (PAAH) mixed with CMC, CMC in buffered solution at pH 3 and amylopectin. However CMC showed the better performance in terms of cycle life of the electrode. Whatever the binder, cycle life decreases with increasing the active mass loading, which is attributed to both the precipitation of liquid electrolyte degradation products and to the loss of electrical contacts within the composite electrode and with the current collector as a consequence of the active particles volume variations. Furthermore, calendaring the electrode unfortunately decreases the cycle life. The rate performance was studied as a function of the active mass loading and was shown to be determined by the electrode polarization resistance. Finally, full cells cycling tests with Li1Ni1/3Co1/3Mn1/3O2 at the positive electrode were done. 60% of the capacity is retained after 200 cycles at the surface capacity of 2.7 mAh cm-2.

Wilhelm, H. A.; Marino, C.; Darwiche, A.; Soudan, P.; Morcrette, M.; Monconduit, L.; Lestriez, B.

2015-01-01

57

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

58

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

59

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

60

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

61

Applications of porous flow-through electrodes. I - An experimental study on the hydrogen evolution reaction on packed bed electrodes  

NASA Astrophysics Data System (ADS)

The possibility of using porous flow-through electrodes in water electrolysis for the generation of hydrogen is investigated. The chosen electrode was a 2 cm diameter by 2.1 cm long cylindrical copper bed of porosity 0.45, while the electrolyte chosen to suit the material was sulfuric acid. The influence of different variables such as particle size, flow rate, and electrode material and thickness was considered. It was found that the flow rate did not affect the current-polarization relations but that the electrolyte concentration did; this influence is discussed. It is concluded that concentration polarization is negligible, and that polarization characteristics of the electrode depend on activation polarization and on the ohmic potential drop in the pore electrolyte. The effects of electroplated Ag and Pt on the current-polarization relation are also discussed.

Ateya, B. G.; Arafat, E. S.

1983-02-01

62

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

63

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

64

Different Influences of Hematocrit on the Results of Two Point-Of-Care Platelet Function Tests, the VerifyNow Assay and Multiple Electrode Platelet Aggregometry  

PubMed Central

Objective Previous studies have reported a considerable association between the VerifyNow (Accumetrics, San Diego, CA, USA) P2Y12 assay results and hematocrit. No reports, however, have described an association between the multiple electrode platelet aggregometry (MEA; Dynabyte, Munich, Germany) adenosine diphosphate (ADP) assay results and hematocrit. This study was conducted to evaluate the influence of hematocrit on the results of 2 different point-of-care platelet function tests. Methods A total of 462 consecutive patients who were undergoing percutaneous coronary intervention were enrolled. Platelet function was evaluated with both the VerifyNow P2Y12 and MEA ADP assays. Results Anemic patients (n?=?152, 32.9%) demonstrated a significantly higher rate of cardiac death, myocardial infarction, and stroke (5.3% vs. 2.3%, p?=?0.046) during the follow-up (median: 18.8 months). Although the VerifyNow P2Y12 assay results demonstrated a significant inverse correlation with hematocrit (r?=??0.409, p<0.001), there was no such correlation between the MEA ADP assay results and hematocrit (r?=?0.039, p?=?0.401). In the multivariate analysis, anemia was an independent predictor of high on-treatment platelet reactivity, defined as a VerifyNow P2Y12 reaction unit level of ?252.5 (odds ratio?=?2.21, 95% confidence interval?=?1.39–3.52; p?=?0.001). Importantly, this association was independent of an intrinsic change in platelet reactivity as measured by the MEA ADP assay. Adjusting for the influence of hematocrit improved the strength of the correlation between the VerifyNow P2Y12 and MEA ADP assay results. Conclusions Hematocrit significantly influenced the VerifyNow P2Y12 assay results, a phenomenon that was presumably in-vitro. Hematocrit level should therefore be considered when interpreting results of the VerifyNow P2Y12 assay. PMID:25427105

Kim, Yun Gi; Suh, Jung-Won; Park, Jin Joo; Oh, Il-Young; Yoon, Chang-Hwan; Cho, Young-Seok; Youn, Tae-Jin; Chae, In-Ho; Choi, Dong-Ju

2014-01-01

65

Phenothiazine-modified electrodes: a useful platform for protein adsorption study.  

PubMed

Using glucose oxidase (GOx) as a target protein, we studied the adsorption of protein on the phenothiazine-modified electrodes and assessed the potential of using the electrodes in biochemical applications. Experiment results showed that thionine chloride (TC) and its structural analogues, such as toluidine blue and methylene blue, fluoresced under photochemical excitation after being immobilized on indium-doped tin oxide (ITO) electrodes fabricated using either diazotization-reduction or oxidative polymerization. The surface-bound phenothiazines exhibited substantial binding affinities to the protein. At a pH > 5, the adsorbate showed no sign of desorption even the electrodes were electrically biased with voltages between ±0.3 V vs SCE. Thus, emission decay occurred while GOx was injected over the electrodes, which was consistent with the observations made using conductive-mode atomic force microscopy (CM-AFM). Under a quiescent condition, the protein interacted with the immobilized TC via a pseudo-first-order kinetic mechanism. The reaction reached a maximum rate at a pH > 5, at which the rate constant was approximately 7 × 10(-8) L/(U s). Under this condition, the adsorption rate increased as the level of the protein increased, regardless of pH, revealing application potential for GOx quantitation. The adsorption rate, however, decreased with a decrease in pH if the pH < 5. We concluded that static interactions played a crucial role. By monitoring Fe(CN)6(3-/4-) taking place at the TC-modified electrodes in pH 7 solutions, we observed that the adsorption of GOx imposed impedance on Fe(CN)6(3-/4-). The resulting charge-transfer resistance (RCT) increased as the amount of the protein increased, leading to a conclusion that the protein could reach the maximum surface coverage when its concentrations were greater than 100 U/mL. The protein molecules were likely repel each other as approaching the TC sites. Despite this, they maintained the native bioactivity after being adsorbed, enabling the TC-modified electrodes to function as glucose sensors. Glucose concentrations between 1 and 60 mM could be detected. Long-term analysis, in addition, showed that the electrode responses to the analyte were consistent and reproducible. Phenothiazine-modified electrodes are evident as a useful tool for understanding the adsorption of protein on solid surfaces and quantifying proteins. PMID:24460092

Chiou, Bo-Hao; Tsai, Yi-Ting; Wang, Chong Mou

2014-02-18

66

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

67

Two and Three-Electrode Impedance Studies on 18650 Li-Ion Cells  

SciTech Connect

Two and three electrode impedance measurements were made on 18650 Li-ion cells at different QB temperatures ranging from 35 C to {minus}40 C. The ohmic resistance of the cell is nearly constant the temperature range studied although the total cell impedance increases by an order of magnitude in the same temperature range. In contrast to what is commonly believed, we show from our three-electrode impedance results that, the increase in cell impedance comes mostly from the cathode and not from the anode. Further, the anode and cathode contribute to both the impedance loops (in the NyQuist plot).

Nagasubramanian, Ganesan

1999-08-11

68

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 Available online 3 June 2013 Keywords: Magnetic insulation Vacuum electrical breakdown Bacteria-induced electrical breakdown Accelerator a b s t r a c t An experimental program to elucidate the physical causes

Gilson, Erik

69

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 Keywords: Magnetic insulation Vacuum electrical breakdown Bacteria-induced electrical breakdown Accelerator a b s t r a c t An experimental program to elucidate the physical causes of electrical breakdown

Gilson, Erik

70

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-bonding complexes with fluoride ion were modeled and geometry optimized with the B3LYP method and the 6-31G** basis

Ferreira, Márcia M. C.

71

In situ Raman spectroelectrochemical study of electrocatalytic oxidation of ascorbate at polyaniline and sulfonated polyanilinemodified electrodes  

Microsoft Academic Search

Electrocatalytic oxidation of ascorbate at electrodes, covered with polyaniline and sulfonated polyaniline, has been studied by in situ Raman spectroelectrochemistry with the green laser excitation (532nm). Characteristic Raman features have been identified and their changes during electrooxidation of ascorbate have been analysed. It has been shown that an increase of ascorbate concentration causes an increase of the relative content of

R. Mažeikien?; G. Niaura; A. Malinauskas

2006-01-01

72

Degradation of Li/S Battery Electrodes Studied Using X-ray Phase Contrast Tomography  

E-print Network

the Li-ion battery market. This can be explained by their high energy density, high operating voltage1 Degradation of Li/S Battery Electrodes Studied Using X-ray Phase Contrast Tomography L. Zielkea. Zengerlea,f and S. Thielea,g Lithium/sulphur batteries are promising candidates for future energy storage

Schmidt, Volker

73

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

74

Histopathological study of tissue reaction to pacemaker electrodes implanted in the endocardium.  

PubMed

Limited information is available about histopathological reactions to the implanted endocardial electrodes of pacemakers (PM). Gross anatomic and histologic studies of tissue reactions to PM electrodes were made in thirteen autopsy cases (nine men and four women, ages 25 approximately 89 years, mean age 71.8) who died two months to twenty-one years after PM implantation. Nine of them had complete atrioventricular (AV) block, three had sick sinus syndrome, and one had bradycardia-tachycardia syndrome. The direct causes of death were not related to their PM. The tip with projecting tines was implanted in the right ventricle in all patients. At the contact area between the electrode and the endocardium, no tissue reaction was observed in one patient with a history of over sixteen years of PM implantation. However, cardiomyocytes under the tip had been replaced by fibrotic tissue in many other patients. In two patients in particular where the electrode had been implanted at the apex of each right ventricle, all cardiomyocytes had disappeared and only fibrotic tissue and adipose tissue were observed under the tip. These findings suggest that mechanical stress caused by attaching the tip tightly damages cardiomyocytes and brings about changes in the pacing thresholds. In three patients, a space was seen between the tip and the endocardium. A fibrous sheath covering the electrode extended to the tip and formed a thick fibrous cap. This non-excitable fibrous cap acted as a virtual electrode and possibly affected the elevation of the threshold in these patients. In four patients, extensive myocardial fibrosis due to disease, e. g. previous myocardial infarction, dilated cardiomyopathy, amyloidosis, or sarcoidosis, was found in the area surrounding the tip and also might affect the elevation of the threshold. We concluded that elevation of pacing thresholds after PM implantation is not due to reactive endocardial thickening. The space between the tip and the endocardium is occupied by a fibrous sheath, and an overly tight attachment damages cardiomyocytes causing replacement fibrosis. Thus, it is not desirable in some patients to insert the electrodes into the apex, where the myocardium is thin. To avoid the elevation of thresholds, development of further devices is necessary to allow electrode fixation to the endocardium with a more suitable pressure level. PMID:15834208

Mase, Hiroshi; Tamura, Koichi; Hiromoto, Atsushi; Hotta, Masahiro; Hotomi, Saori; Togashi, Mayuko; Fukuda, Yuh; Yajima, Toshimi; Nitta, Takashi; Tanaka, Shigeo; Sugisaki, Yuichi

2005-02-01

75

Motion control of the ankle joint with a multiple contact nerve cuff electrode: a simulation study.  

PubMed

The flat interface nerve electrode (FINE) has demonstrated significant capability for fascicular and subfascicular stimulation selectivity. However, due to the inherent complexity of the neuromuscular skeletal systems and nerve-electrode interface, a trajectory tracking motion control algorithm of musculoskeletal systems for functional electrical stimulation using a multiple contact nerve cuff electrode such as FINE has not yet been developed. In our previous study, a control system was developed for multiple-input multiple-output (MIMO) musculoskeletal systems with little prior knowledge of the system. In this study, more realistic computational ankle/subtalar joint model including a finite element model of the sciatic nerve was developed. The control system was tested to control the motion of ankle/subtalar joint angles by modulating the pulse amplitude of each contact of a FINE placed on the sciatic nerve. The simulation results showed that the control strategy based on the separation of steady state and dynamic properties of the system resulted in small output tracking errors for different reference trajectories such as sinusoidal and filtered random signals. The proposed control method also demonstrated robustness against external disturbances and system parameter variations such as muscle fatigue. These simulation results under various circumstances indicate that it is possible to take advantage of multiple contact nerve electrodes with spatial selectivity for the control of limb motion by peripheral nerve stimulation even with limited individual muscle selectivity. This technology could be useful to restore neural function in patients with paralysis. PMID:24939581

Park, Hyun-Joo; Durand, Dominique M

2014-08-01

76

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

77

Electrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow conditions  

E-print Network

Electrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow November 2013 Available online 18 December 2013 Keywords: Multi-electrode Microbial fuel cells Hydraulic connected microbial fuel cells (MFCs) was compared with the reactors operated using individual electrical

78

High-freezing-point fuel studies  

NASA Technical Reports Server (NTRS)

Considerable progress in developing the experimental and analytical techniques needed to design airplanes to accommodate fuels with less stringent low temperature specifications is reported. A computer technique for calculating fuel temperature profiles in full tanks was developed. The computer program is being extended to include the case of partially empty tanks. Ultimately, the completed package is to be incorporated into an aircraft fuel tank thermal analyser code to permit the designer to fly various thermal exposure patterns, study fuel temperatures versus time, and determine holdup.

Tolle, F. F.

1980-01-01

79

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

80

Material removal rate and electrode wear study on the EDM of silicon carbide  

Microsoft Academic Search

In this work, a material removal rate (MRR) and electrode wear (EW) study on the die-sinking electrical discharge machining (EDM) of siliconised or reaction-bonded silicon carbide (SiSiC) has been carried out. The selection of the above-mentioned conductive ceramic was made taking into account its wide range of applications in the industrial field: high-temperature gas turbines, bearings, seals and lining of

C. J. Luis; I. Puertas; G. Villa

2005-01-01

81

In situ IR spectroscopic study of water at a polycrystalline gold electrode surface  

Microsoft Academic Search

The effect of the electrolyte anions on the water structure at the interface between a polycrystalline gold electrode and aqueous electrolyte solutions was studied using in situ Fourier transform IR reflection absorption spectroscopy (FT-IRAS). Considerably sharp absorption bands due to OH stretching modes of water were observed in the 3600–3500 cm?1 range in solutions containing F?, Cl?, Br?, I?, BF?4,

Fusao Kitamura; Noritoshi Nanbu; Takeo Ohsaka; Koichi Tokuda

1998-01-01

82

A 100 electrode intracortical array: structural variability.  

PubMed

A technique has been developed for fabricating three dimensional "hair brush" electrode arrays from monocrystalline silicon blocks. Arrays consist of a square pattern of 100 penetrating electrodes, with 400 microns interelectrode spacing. Each electrode is 1.5mm in length and tapers from about 100 microns at its base to a sharp point at the tip. The tips of each electrode are coated with platinum and the entire structure, with the exception of the tips, is insulated with polyimide. Electrical connection to selected electrodes is made by wire bonding polyimide insulated 25 microns diameter gold lead wires to bonding pads on the rear surface of the array. As the geometrical characteristics of the electrodes in such an aray will influence their electrical properties (such as impedance, capacitance, spreading resistance in an electrolyte, etc.) it is desirable that such an array have minimal variability in geometry from electrode to electrode. A study was performed to determine the geometrical variability resulting from our micromachining techniques. Measurements of the diameter of each of the 100 electrodes were made at various planes above the silicon substrate of the array. For the array that was measured, the standard deviation of the diameters was approximately 9% of the mean diameter near the tip, 8% near the middle, and 6% near the base. We describe fabrication techniques which should further reduce these variabilities. PMID:2334761

Campbell, P K; Jones, K E; Normann, R A

1990-01-01

83

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

84

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.

85

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

86

A practical method for quickly determining electrode positions in high-density EEG studies.  

PubMed

This report describes a simple and practical method for determining electrode positions in high-density EEG studies. This method reduces the number of electrodes for which accurate three-dimensional location must be measured, thus minimizing experimental set-up time and the possibility of digitization error. For each electrode cap, a reference data set is first established by placing the cap on a reference head and digitizing the 3-D position of each channel. A set of control channels are pre-selected that should be adequately distributed over the cap. A simple choice could be the standard 19 channels of the International 10-20 system or their closest substitutes. In a real experiment, only the 3-D positions of these control channels need to be measured and the position of each of the remaining channels are calculated from the position data of the same channels in the reference data set using a local transformation determined by the nearest three or four pairs of control channels. Six BioSemi ActiveTwo caps of different size and channel numbers were used to evaluate the method. Results show that the mean prediction error is about 2mm and is comparable with the residual uncertainty in direct position measurement using a Polhemus digitizer. PMID:23485737

He, Ping; Estepp, Justin R

2013-04-29

87

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

88

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.

89

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

90

Electrochemical and surface studies of the deposition of mercury and selenium at a gold electrode. [Underpotential  

SciTech Connect

The term underpotential deposition (UPD) refers to the electrodeposition of metal ions from solution onto substrates of noble metals at potentials positive to the thermodynamic Nernst potential for bulk deposition of that particular metal. The research described in this dissertation involves the study of the deposition of Hg(II) and Se(IV) at polycrystalline gold electrodes by cyclic voltammetry, flow-through coulometry and various surface spectroscopies. The work described here has been performed over a higher range of concentration than was previously studied. Also, this work includes investigations utilizing Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), and Electron Spectroscopy for Chemical Analysis (ESCA).

Schadewald, L.A.

1984-01-01

91

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

SciTech Connect

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.; Briand, D.; Rooij, N. F. de [Ecole Polytechnique Fédérale de Lausanne (EPFL) - Institute of Microengineering (IMT) – Sensors, Actuators and Microsystems Laboratory - SAMLAB, 2002 Neuchâtel (Switzerland); Kinkeldei, T.; Tröster, G. [Eidgenössische Technische Hochschule Zürich (ETHZ) – Electronics Laboratory, 8092 Zurich (Switzerland)

2013-11-07

92

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

93

Density functional study of PbTiO3 nanocapacitors with Pt and Au electrodes W. A. Al-Saidi and Andrew M. Rappe  

E-print Network

of the thin films depend not only on the electrode and the FE material but also on the electrode-perovskite accurate properties of bulk ferroelectric FE mate- rials. Pt and Au electrodes are used in our study chemical bonding and charge transfer in stabilizing the FE polar phase. We found that the FE properties

Rappe, Andrew M.

94

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

95

Plasma meniscus and extraction electrode studies of the ISIS H- ion source.  

PubMed

In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H(-) 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. PMID:20192377

Lawrie, S R; Faircloth, D C; Letchford, A P; Gabor, C; Pozimski, J K

2010-02-01

96

Plasma meniscus and extraction electrode studies of the ISIS H- ion sourcea)  

NASA Astrophysics Data System (ADS)

In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H- 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.; Pozimski, J. K.

2010-02-01

97

Hubble Space Telescope Pointing Control System design improvement study  

Microsoft Academic Search

As part of the NASA Controls\\/Structures Integration Program, a study was undertaken to determine if improvements to the performance of the Hubble Space Telescope Pointing Control System could be obtained when advanced control system design techniques were applied using simulation models and telemetry data from the spacecraft. The study was managed through the Marshall Space Flight Center. Four universities and

Angelia P. Bukley

1993-01-01

98

Design and study of the characteristics of a three electrode experimental ionization chamber for gamma ray dosimetry of spent fuel  

NASA Astrophysics Data System (ADS)

The ( I, V) characteristics of two and three electrode ionization chamber filled with argon gas have been studied. To determine the sensitivity and the response with increase in exposure rate, the chamber was tested with a 60Co commercial irradiator. The response is linear up to more than 1.5 krad/h. The experimentally measured sensitivity of the chamber is 1.849×10 -13 A/cm 3 per rad/h when the argon gas pressure in the chamber is 1.24 GPa (180 psi). The effect of transparency of the intermediate electrod on the saturation current due to 137Cs gamma-rays has also been studied. The experimental results show that the electrode with holes of small diameter acts as a better intermediate electrode as compared to the electrodes without holes or with holes of a larger diameter. The chamber has also been teste with fission product gamma-rays from spent fuel elements of a typical pool type research reactor. The results indicate that the presence of an intermediate electrode lowers the operating voltage by 50% and reduces the slope in the plateau region.

Ahmad, N.; Mirza, Nasir M.; Mirza, Sikander M.; Rashid, T.; Tufail, M.; Khan, Liaquat A.

1992-09-01

99

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

100

Fundamental studies of water oxidation at model hematite electrodes prepared by atomic layer deposition  

NASA Astrophysics Data System (ADS)

An increasing global demand for energy, combined with an awareness of anthropogenic climate change, has recently fueled the search for abundant, carbon neutral energy sources. The sun offers an enormous amount of energy that is practically inexhaustible and well distributed across Earth. Thus, it is an ideal source for meeting our future energy needs in a carbon neutral fashion. This work focuses on using hematite and sunlight to oxidize water, which is the rate limiting step of splitting water into the energy dense fuel, hydrogen, and the byproduct, oxygen. Hematite is abundant, absorbs a large fraction of the solar spectrum and has an appropriately placed valence band for water oxidation. However, the often cited poor bulk properties, and slow charge transfer kinetics require large applied potentials to oxidize water. Atomic layer deposition (ALD) was utilized to deposit uniform thin films of hematite on transparent conductive substrates as model electrodes to better understand the nature of the limitations in the bulk and at the surface. Comparison of the oxidation of water to the oxidation of fast redox shuttles allowed for the separation of bulk and surface processes. A combination of electrochemical impedance spectroscopy, photoelectrochemical and electrochemical measurements were employed to determine the cause of the large required applied potential. It was found that photogenerated holes initially oxidize the electrode surface under water oxidation conditions, which is attributed to the first step in water oxidation. A critical number of these surface intermediates need to be generated in order for subsequent hole-transfer steps to proceed. At low applied potentials, these intermediates are subject to recombination from the large concentration of electrons in the conduction band due to low band bending. At higher applied potentials, high band bending eliminates surface recombination and the charge collection efficiency of the electrolyte reaches unity. A water oxidation mechanism is proposed to interpret these results. In addition, fundamental studies of hematite electrodes coated with the phosphate mediated cobalt oxide catalyst were performed. The catalyst was found to reduce the surface recombination mentioned above. However, oxidized cobalt oxide was still subject to electron recombination at low applied potentials. This recombination was reduced with the use of an alumina blocking layer, which resulted in a modified hematite electrode capable of oxidizing water with a near unity charge collection efficiency at low applied potentials.

Klahr, Benjamin M.

101

Surface roughness analysis and magnetic property studies of nickel thin films electrodeposited onto rotating disc electrodes  

NASA Astrophysics Data System (ADS)

Ni films were electrodeposited onto polycrystalline gold substrates mounted on a rotating disc electrode. The effects of rotation speed, film thickness and current density on the kinetic roughening and magnetic properties of the films were investigated. The film surface roughness was imaged using an atomic force microscope (AFM). The results indicate that the film roughness increases as the film thickness or deposition current density increases. We found that the electrodeposited Ni films exhibit anomalous scaling since both local and large-scale roughnesses show a power-law dependence on the film thickness. The effect of electrode rotation speed on the film surface roughness was also investigated. Scanning electron microscopy studies (SEM) had a good agreement with the AFM results. The average crystalline size of the film surfaces is also calculated from X-ray line broadening using (220) peak and Debye-Scherrer formula. The obtained results agree with that of AFM and SEM. The Ni thin films which are grown at different deposition current densities and rotation speeds exhibit in-plane magnetization with coercivities less than 110 Oe.

Hedayati, K.; Nabiyouni, G.

2014-09-01

102

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

103

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

104

The self-discharge of the NiOOH/Ni(OH)2 electrode constant potential study  

NASA Technical Reports Server (NTRS)

Hydrogen oxidation currents at a NiOOH/Ni(OH)2 electrode were measured directly at constant potentials for various hydrogen pressures and states of charge. It was found that the hydrogen oxidation current is linearly proportional to the hydrogen pressure at all electrode potentials and that the logarithm of the anodic current is a linear function of electrode potential. It was also found that hydrogen oxidation on the nickel substrate material was strongly inhibited by the presence of nickel hydroxide on the substrate surface. By comparing the currents for hydrogen oxidation and oxygen evolution on the NiOOH/Ni(OH)2 electrode and a nickel substrate, it is suggested that the self-discharge of the NiOOH/Ni(OH)2 electrode is mainly due to electrochemical oxidation of hydrogen on the active electrode material.

Mao, Z.; White, R. E.

1992-01-01

105

Pointing Treatments Are Task Relevant: A Visuomotor Priming Study  

PubMed Central

The present study focused on priming effects on pointing with everyday objects. In a set of four experiments, a visuomotor priming paradigm was used to investigate the nature of visuomotor processing (automatic versus task relevant). By manipulating congruency of orientation and location we found that location congruency facilitates the initiation time of pointing whereas orientation congruency does not. We provide evidence to show that motor planning is influenced by the goal of the action, and that how visual information is processed and held in memory depends on the task relevance. These data are consistent with the proposed interaction between visuomotor and higher processes during the planning and execution of actions such as pointing. PMID:24777029

Roche, Kevin; Chainay, Hanna

2014-01-01

106

Pointing treatments are task relevant: a visuomotor priming study.  

PubMed

The present study focused on priming effects on pointing with everyday objects. In a set of four experiments, a visuomotor priming paradigm was used to investigate the nature of visuomotor processing (automatic versus task relevant). By manipulating congruency of orientation and location we found that location congruency facilitates the initiation time of pointing whereas orientation congruency does not. We provide evidence to show that motor planning is influenced by the goal of the action, and that how visual information is processed and held in memory depends on the task relevance. These data are consistent with the proposed interaction between visuomotor and higher processes during the planning and execution of actions such as pointing. PMID:24777029

Roche, Kevin; Chainay, Hanna

2014-01-01

107

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

108

Studies of the electrochemical behavior of epinephrine at a homocysteine self-assembled electrode  

Microsoft Academic Search

The self-assembled electrode with the homocysteine monolayer (Hcy\\/Au) has been characterized by infrared spectroscopy and ac impedance spectroscopy in electrolyte. The Hcy\\/Au electrode is demonstrated to promote the electrochemical response of epinephrine (E) by cyclic voltammetry. A pair of well-defined redox waves was obtained and the calculated standard rate constant (ks) is 2.1×10?2 cms?1 at the self-assembled electrode. The reduction

Hui-Min Zhang; Xian-Liang Zhou; Ru-Tai Hui; Nan-Qiang Li; De-Pei Liu

2002-01-01

109

AMTEC system performance studies using the detailed electrode kinetic and transport model  

NASA Technical Reports Server (NTRS)

A detailed electrochemical model of the alkali metal thermoelectric converter (AMTEC) electrode and current collector grid has been developed recently. Comparative evaluations of the resulting differences in model predictions reveal that the new detailed model predicts up to 50 percent higher electrode power densities at condenser operating temperatures above 600 K. The new model, with experimentally determined parameters, was used to recalculate the projected system performance of previously reported 1- and 100-kWe AMTEC space power systems that had incorporated earlier electrolyte/electrode models. It was found that when the detailed model was used to determine the electrode power densities, enhanced specific power and efficiencies are predicted.

Sievers, Robert K.; Williams, Roger M.; Underwood, Mark L.; Jeffries-Nakamura, Barbara; Bankston, C. P.

1992-01-01

110

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

111

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

112

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

113

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

114

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

115

Graphite photoelectrochemistry study of glassy carbon, carbon-fiber and carbon-black electrodes in aqueous electrolytes by photocurrent response  

NASA Astrophysics Data System (ADS)

Photocurrent generation by UV-vis light irradiation of glassy carbon, boronated glassy carbon, carbon-black and carbon-fiber electrodes was studied in comparison with the behavior of HOPG basal plane and edge plane electrodes. The presence of a space charge layer at these electrodes was manifested by photogeneration of electrochemical currents. Both anodic and cathodic photocurrents were observed for all the forms of graphitic materials investigated. An exponential dependence of photocurrent magnitude on electrode potential and on photon energy was found for all the forms of graphitic materials. The exponential response was explained by a model involving the generation of a hot charge carrier by photoexcitation in the space charge layer, transport to the solid-electrolyte interface and subsequent interfacial charge transfer reactions. Studies of photocurrent-potential dependence performed with glassy carbon, boronated glassy carbon and carbon-black electrodes in highly acidic to highly basic aqueous solutions (pH 0-14) revealed a linear dependence of the flat bands potential on pH with a slope of approximately 0.05 V per unit of pH.

Modestov, A. D.; Gun, J.; Lev, O.

1998-11-01

116

Hubble Space Telescope Pointing Control System design improvement study  

NASA Technical Reports Server (NTRS)

As part of the NASA Controls/Structures Integration Program, a study was undertaken to determine if improvements to the performance of the Hubble Space Telescope Pointing Control System could be obtained when advanced control system design techniques were applied using simulation models and telemetry data from the spacecraft. The study was managed through the Marshall Space Flight Center. Four universities and one aerospace company developed controller designs and tested their performance. This paper summarizes the goals and provides an overview of the study.

Bukley, Angelia P.

1993-01-01

117

Rotating ring–disk electrode studies of the oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond electrodes  

Microsoft Academic Search

The stepwise electrochemical oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond (BDD) electrodes was investigated in perchloric acid media using rotating ring–disk electrode (RRDE) and hydrodynamic modulation techniques. Initial oxidation of these compounds to p-benzoquinone at the disk may be confirmed by reduction of the quinone at the ring electrode. Further oxidation, ultimately to CO2, can be followed by the

David Sopchak; Barry Miller; Yitzhak Avyigal; Rafi Kalish

2002-01-01

118

Positive Point-to-Plane Corona Studies in Air  

Microsoft Academic Search

Formative time lags for the development of the positive point-to-plane corona in dry air were measured oscillographically at pressures ranging from atmospheric to a few centimeters of Hg. Studies with a photomultiplier tube show that the observed formative lags are associated with a filamentary streamer type of corona. These corona formative lags are of the order of 10-7 sec even

M. Menes; L. H. Fisher

1954-01-01

119

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

120

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

121

Monochromatic imaging studies of sustained metal vapor arcs burning on 150 mm diameter molten iron electrodes  

SciTech Connect

Monochromatic imaging was used to investigate the excited-state density distributions of Fe and Fe{sup +} in the inter-electrode gap region of a 3,100 A dc metal vapor arc burning between molten iron surfaces in a vacuum arc furnace. Multiple images were acquired at four wavelengths. The images were corrected and Abel inverted to yield the absolute radial intensity distributions for Fe and Fe{sup +} in the inter-electrode gap region. The results show a structured, axisymmetric plasma consisting of a high density `core` of Fe{sup +} emitters centered between the electrode surfaces situated against a relatively broad, flat excited-state Fe distribution.

Williamson, R.L.; Schlienger, M.E.

1996-07-01

122

Working Electrodes  

NASA Astrophysics Data System (ADS)

In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].

Komorsky-Lovri?, Šebojka

123

Field experience and dew point studies of a retrofitted roof  

SciTech Connect

A symposium on insulating materials would not be complete without discussing the effect of the thermal and vapor performance on potential condensation problems in insulated assemblies. Retrofitting the top of an existing insulated roof with an impermeable rigid or foamed insulation can lead to serious condensation-related maintenance problems. Dew point studies in Alaska indicate that the thermal resistance of retrofitted assemblies should be at least two times greater than the existing insulated wall, or roof to avoid condensation in the cavity, depending on local heating degree days. Further, an exterior impervious insulated wall or roof assembly should be provided with some type of natural venting to relieve vapor pressure and allow excess condensate to drain and evaporate. Unfortunately, most condensation problems do not become apparent for 5 to 10 years, long after the one year warranty is null and void. A computer spreadsheet will be presented that simulates dew point conditions in an insulated roof assembly to determine the proper selection and placement of the vapor retarder, insulation, and ventilation of the exterior skin to prevent further deterioration of the roof. This necessitated the computation and tabulation of surface temperatures, dew point temperatures, vapor pressures and relative humidities at various structural components of the insulated assemblies, particularly near the outer skin.

Carlson, A.R. [Univ. of Alaska, Fairbanks, AK (United States). Cooperative Extension Service

1997-11-01

124

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

125

The Surface Organometallic Chemistry of Pd Electrodes: Studies with Aromatic Compounds  

E-print Network

-layer electrochemistry was employed with atomically smooth polycrystalline electrodes to extract information on surface packing densities and adsorbate cross sections. Comparison of the latter with calculated values allowed the determination of the more plausible...

Cruz, Juan

2012-10-19

126

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

127

Study on the electrochemical behavior of dopamine with poly(sulfosalicylic acid) modified glassy carbon electrode  

Microsoft Academic Search

A glassy carbon electrode was modified with electropolymerized films of sulfosalicylic acid in pH 5.5 phosphate buffer solution (PBS) by cyclic voltammetry. The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In PBS of pH 7.4, the oxidation current increased linearly with two concentration intervals of dopamine, one is 5.5×10?7 to 2.2×10?5M, the other is

Hong Zhao; Yuzhong Zhang; Zhuobin Yuan

2001-01-01

128

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

129

Applications of Planar ITO Electrodes for Studying of Some Biochemical Activities  

NASA Astrophysics Data System (ADS)

Trends in disposable and handheld biosensors have called for miniaturized and planar electrodes in the place of conventional bulky ones. In this work, thin tin-doped indium oxide (ITO) film coated on glass were used as a based electrode in a three-electrode electrochemical system to follow some biochemical activities, such as NADH and phenol activity. The reference electrode is made on ITO layer by electro-deposition of thin nickel layer and silver layer, consecutively, followed by chlorination of silver surface by electrochemical potentiostatic method. The plain planar ITO-coated glasses were used as both counter electrode and working electrodes. Cyclic-voltammetry measurements; which follow an oxidation of 200 ?M nicotinamide adenine dinucleotide (NADH) in 0.1 M KCl, show current peak of 8.5 ?A. Another case was also to follow the NADH oxidation but in competition with its coupling activity with flavin mononucleotide (FMN). In this case, cyclic-voltammetry measurements were carried out of 200 ?M NADH in 50 mM sodium phosphate; current peak of 1.3 ?A was observed.

Learngarunsri, P.; Chaiyen, P.; Srikhirin, T.; Veerasai, W.; Dangtip, S.

130

Depth electrode studies in temporal lobe epilepsy: relation to quantitative magnetic resonance imaging and operative outcome.  

PubMed

We performed a retrospective study of 30 patients with presumed intractable temporal lobe epilepsy (TLE) who underwent chronic intracranial EEG monitoring (CIEM). Multicontact depth electrodes were stereotactically implanted through the medial occipital lobe into amygdala and hippocampus. All patients had previously undergone extracranial ictal EEG monitoring that proved inadequate to localize the epileptogenic zone. No morbidity was associated with CIEM in the 30 patients. Twenty-five patients were shown to have exclusively or predominantly unilateral temporal lobe seizures, and 5 patients had bitemporal seizures without unilateral predominance; 24 patients subsequently underwent an anterotemporal lobe cortical resection. Twenty-one patients have been followed a minimum of 1 year postoperatively. Nine patients (43%) had a class I outcome (seizure-free, auras only, or provoked seizures), 3 patients (14%) had a class II outcome (> or = 95% seizure reduction), 4 patients (19%) had a class III outcome (> or = 50% seizure reduction); and 5 patients (24%) had a class IV outcome (< 50% seizure reduction or no change). A prolonged interhemispheric propagation time (p < 0.01) and magnetic resonance imaging (MRI)-identified hippocampal atrophy (p < 0.01) correlated with a favorable surgical outcome. Results of this study may prove useful in counseling patients who undergo CIEM before temporal lobe surgery. PMID:7614905

Cascino, G D; Trenerry, M R; Sharbrough, F W; So, E L; Marsh, W R; Strelow, D C

1995-03-01

131

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

132

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

133

Conversion reaction mechanisms in lithium ion batteries: study of the binary metal fluoride electrodes.  

PubMed

Materials that undergo a conversion reaction with lithium (e.g., metal fluorides MF(2): M = Fe, Cu, ...) often accommodate more than one Li atom per transition-metal cation, and are promising candidates for high-capacity cathodes for lithium ion batteries. However, little is known about the mechanisms involved in the conversion process, the origins of the large polarization during electrochemical cycling, and why some materials are reversible (e.g., FeF(2)) while others are not (e.g., CuF(2)). In this study, we investigated the conversion reaction of binary metal fluorides, FeF(2) and CuF(2), using a series of local and bulk probes to better understand the mechanisms underlying their contrasting electrochemical behavior. X-ray pair-distribution-function and magnetization measurements were used to determine changes in short-range ordering, particle size and microstructure, while high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) were used to measure the atomic-level structure of individual particles and map the phase distribution in the initial and fully lithiated electrodes. Both FeF(2) and CuF(2) react with lithium via a direct conversion process with no intercalation step, but there are differences in the conversion process and final phase distribution. During the reaction of Li(+) with FeF(2), small metallic iron nanoparticles (<5 nm in diameter) nucleate in close proximity to the converted LiF phase, as a result of the low diffusivity of iron. The iron nanoparticles are interconnected and form a bicontinuous network, which provides a pathway for local electron transport through the insulating LiF phase. In addition, the massive interface formed between nanoscale solid phases provides a pathway for ionic transport during the conversion process. These results offer the first experimental evidence explaining the origins of the high lithium reversibility in FeF(2). In contrast to FeF(2), no continuous Cu network was observed in the lithiated CuF(2); rather, the converted Cu segregates to large particles (5-12 nm in diameter) during the first discharge, which may be partially responsible for the lack of reversibility in the CuF(2) electrode. PMID:21894971

Wang, Feng; Robert, Rosa; Chernova, Natasha A; Pereira, Nathalie; Omenya, Fredrick; Badway, Fadwa; Hua, Xiao; Ruotolo, Michael; Zhang, Ruigang; Wu, Lijun; Volkov, Vyacheslav; Su, Dong; Key, Baris; Whittingham, M Stanley; Grey, Clare P; Amatucci, Glenn G; Zhu, Yimei; Graetz, Jason

2011-11-23

134

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

135

A study of direct- and pulse-current chromium electroplating on rotating cylinder electrode (RCE)  

NASA Astrophysics Data System (ADS)

Direct- and pulse-current (DC and PC) chromium electroplating on Cr-Mo steel were performed in a sulfate-catalyzed chromic acid solution at 50 °C using a rotating cylinder electrode (RCE). The electroplating cathodic current densities were at 30, 40, 50 and 60 A dm -2, respectively. The relationship between electroplating current efficiency and the rotating speed of the RCE was studied. The cross-sectional microstructure of Cr-deposit was examined by transmission electron microscope (TEM). Results showed that DC-plating exhibited higher current efficiency than the PC-plating under the same conditions of electroplating current density and the rotating speed. We found the critical rotating speed of RCE used in the chromium electroplating, above this rotating speed the chromium deposition is prohibited. At the same plating current density, the critical rotating speed for DC-plating was higher than that for PC-plating. The higher plating current density is, the larger difference in critical rotating speeds appears between DC- and PC-electroplating. Equiaxed grains, in a nanoscale size with lower dislocation density, nucleate on the cathodic surface in both DC- and PC-electroplating. Adjacent to the equiaxed grains, textured grains were found in other portion of chromium deposit. Fine columnar grains were observed in the DC-electroplated deposit. On the other hand, very long slender grains with high degree of preferred orientation were detected in PC-electroplated deposit.

Chang, J. H.; Hsu, F. Y.; Liao, M. J.; Huang, C. A.

2007-06-01

136

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

137

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

138

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

139

Tunnel magnetoresistance effect and interface study in magnetic tunnel junctions using epitaxial Fe2CrSi Heusler alloy electrode  

NASA Astrophysics Data System (ADS)

We report the studies of magnetic tunnel junctions (MTJs) using epitaxially grown Fe2CrSi (FCS) as a bottom electrode. A tunnel magnetoresistance (TMR) ratio of 2.5% was obtained for MTJ at room temperature. The low TMR ratio is attributed to the oxidation of FCS at the interface with MgO barrier. With the insertion of 0.3 nm Mg layer between the FCS and MgO barrier layers, the TMR ratio increases to 8.1%. X-ray Photoelectron Spectroscopy results show that the FCS film is most likely terminated at Fe and Si atomic layers, which is found to be bonded to oxygen at the interface, while Cr remains at metallic state. Post-annealing effect shows that TMR first increases with annealing temperature (Ta) due to improvement in crystalline structure of MgO and top electrode and then decreases due to oxidation of the bottom electrode. The TMR finally disappears due to the depinning of top electrode induced by Mn diffusion at high Ta.

Wang, Yu-Pu; Han, Gu-Chang; Lu, Hui; Qiu, Jinjun; Yap, Qi-Jia; Ji, Rong; Teo, Kie-Leong

2013-07-01

140

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

141

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

142

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

143

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

144

Advanced electrodes for AMTEC  

SciTech Connect

Texas A&M University has begun an investigation of materials and fabrication methods which will improve AMTEC electrode performance. The study currently involves gathering data on materials which meet the basic requirements of operating in an AMTEC cell, and sorting out candidates possessing characteristics conducive to efficient AMTEC operation. An initial assessment has shown Iridium as a promising metal electrode candidate. Sodium-containing double-oxides, with melting temperatures above AMTEC operating temperatures, including NaNbO{sub 3} and Na{sub 2}Ti{sub 3}O{sub 7}, have been identified as possible electrode dopants, to enhance the sodium conductivity of an electrode. Photo-deposition and Evaporative-deposition will be investigated further as electrode fabrication techniques. {copyright} {ital 1999 American Institute of Physics.}

Fiebig, Brad; Schuller, Michael; Hudson, Patricia [Center for Space Power, Texas AM University, College Station, Texas 77843 (United States); Williams, Roger [Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, California 91109 (United States)

1999-01-01

145

Monochromatic imaging studies of sustained metal vapor arcs burning on 150 mm diameter molten iron electrodes  

SciTech Connect

Monochromatic imaging was used to investigate the excited-state density distributions of Fe and Fe{sup +} in the inter-electrode gap region of a 3,100 A dc metal vapor arc burning between molten iron surfaces in a vacuum arc furnace. Multiple images were acquired at four wavelengths. The images were corrected and Abel inverted to yield the absolute radial intensity distributions for Fe and Fe{sup +} in the inter-electrode gap region. The results show a structured, axisymmetric plasma consisting of a high density {open_quotes}core{close_quotes} of Fe{sup +} emitters centered between the electrode surfaces situated against a relatively broad, flat excited-state Fe distribution.

Williamson, R.L.; Schlienger, M.E. [Sandia National Laboratories, Albuquerque, NM (United States)

1996-12-31

146

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

147

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

PubMed

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. PMID:25413987

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

2014-12-11

148

An in situ x-ray absorption spectroscopy study of InSb electrodes in lithium batteries.  

SciTech Connect

We present a detailed in situ extended X-ray absorption fine-structure spectroscopy (EXAFS) study of structural and compositional changes in InSb intermetallic electrodes under electrochemical cycling conditions in a lithium battery. Analysis of the EXAFS data shows that Li is inserted into and In is extruded from the zinc-blende-type InSb network during the first discharge from 1.5 to 0.5 V, yielding changing Li{sub x+y}In{sub 1-y}Sb compositions (0 < x {le} 2, 0 < y {le} 1), with a lattice parameter that varies between that of InSb (a = 6.478 A) and Li{sub 3}Sb (a = 6.572 A). The structural features of tetragonal metallic In and lithiated (i.e., In depleted) InSb are evident. The fully recharged electrode, at 1.2 V, has a zinc-blende framework closely resembling InSb. However, 40% of the In remains permanently outside the face-centered-cubic Sb lattice, explaining a loss in capacity after the first discharge. After the second discharge, at 0.51 V, Li has replaced about 80% of the indium in the InSb lattice, while the Li{sub x}In{sub y}Sb volume has expanded less than 4% compared to the initial electrode. Finally, as the cell is discharged below 0.51 V, Li reacts with the In metal, forming LiIn. Our results indicate that intermetallic electrodes are promising alternative negative electrodes for Li batteries.

Kropf, A. J.; Tostmann, H.; Johnson, C. S.; Vaughey, J. T.; Thackeray, M. M.; Chemical Engineering; Univ. of Florida

2001-11-01

149

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

150

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

151

Photovoltage response to temperature change at oxide semiconductor electrodes  

NASA Technical Reports Server (NTRS)

A study has been carried out on single crystal electrodes of TiO2, SrTiO3, and alpha-Fe2O3 and polycrystalline WO3 to investigate the effect of cell temperature on the onset potential of n-type oxide semiconductor electrodes. It is found that the change of the onset potential with temperature is due to the potential change across the Helmholtz layer. The amount of this change depends on the point of zero zeta potential (pzzp) of the semiconductor electrode. The possibility of increasing the solar-to-chemical energy conversion efficiency of a photochemical cell by increasing the cell temperature is discussed.

Reichman, B.; Byvik, C. E.

1981-01-01

152

Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes.  

PubMed

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed. PMID:15219243

Sasaki, Satoshi; Yokota, Kazunori; Hanagata, Nobutaka

2004-08-01

153

PET study of pointing with visual feedback of moving hands.  

PubMed

This study was conducted to determine where in the human brain visual feedback of hand movements is processed to allow accurate pointing. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) and H2 15O in nine normal volunteers while performing one control and two reaching tasks. In all tasks, visual stimuli were presented on a head mounted display (HMD). A target board was placed in front of the subjects bearing six red light-emitting diodes (LEDs) aligned on a circle with a green LED at its center. The center green LED and one of the six red LEDs, randomly selected, were repeatedly switched on and off, alternatively. In the control task, subjects were instructed to gaze at the lit LED. In the two reaching tasks, the reaching with visual feedback (RwithF) task and the reaching without visual feedback (RwithoutF) task, they had to point to the lit red LED with their right index fingers. In the RwithF task, their right hands were visible on the HMD before touching the target, whereas in the RwithoutF task, they were not visible. For each subject, subtraction images of each reaching task minus the control and the RwithF task minus the RwithoutF task were calculated after transformation of PET images into the standard brain shape with an adjustable computerized brain atlas. These subtraction rCBF images were then averaged among the subjects, and significant changes of rCBF were identified. Significant increases in rCBF not only in the RwithF task minus control image but also in the RwithF task minus the RwithoutF task image were observed in the supramarginal cortex, the premotor cortex and the posterior cingulate cortex of the left hemisphere, the caudate nucleus and the thalamus of the right hemisphere, and the right cerebellum and vermis. These results indicate that the supramarginal cortex, the premotor cortex, and the posterior cingulate cortex of the left hemisphere and the cerebellum are involved in integrating visual feedback of hand movements and execution of accurate pointing. PMID:9425182

Inoue, K; Kawashima, R; Satoh, K; Kinomura, S; Goto, R; Koyama, M; Sugiura, M; Ito, M; Fukuda, H

1998-01-01

154

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

155

The oxidation of tyrosine and tryptophan studied by a molecular dynamics normal hydrogen electrode.  

PubMed

The thermochemical constants for the oxidation of tyrosine and tryptophan through proton coupled electron transfer in aqueous solution have been computed applying a recently developed density functional theory (DFT) based molecular dynamics method for reversible elimination of protons and electrons. This method enables us to estimate the solvation free energy of a proton (H(+)) in a periodic model system from the free energy for the deprotonation of an aqueous hydronium ion (H(3)O(+)). Using the computed solvation free energy of H(+) as reference, the deprotonation and oxidation free energies of an aqueous species can be converted to pK(a) and normal hydrogen electrode (NHE) potentials. This conversion requires certain thermochemical corrections which were first presented in a similar study of the oxidation of hydrobenzoquinone [J. Cheng, M. Sulpizi, and M. Sprik, J. Chem. Phys. 131, 154504 (2009)]. Taking a different view of the thermodynamic status of the hydronium ion, these thermochemical corrections are revised in the present work. The key difference with the previous scheme is that the hydronium is now treated as an intermediate in the transfer of the proton from solution to the gas-phase. The accuracy of the method is assessed by a detailed comparison of the computed pK(a), NHE potentials and dehydrogenation free energies to experiment. As a further application of the technique, we have analyzed the role of the solvent in the oxidation of tyrosine by the tryptophan radical. The free energy change computed for this hydrogen atom transfer reaction is very similar to the gas-phase value, in agreement with experiment. The molecular dynamics results however, show that the minimal solvent effect on the reaction free energy is accompanied by a significant reorganization of the solvent. PMID:21721644

Costanzo, Francesca; Sulpizi, Marialore; Della Valle, Raffaele Guido; Sprik, Michiel

2011-06-28

156

An electrochemical quartz crystal impedance study on cystine precipitation onto an Au electrode surface during cysteine oxidation in aqueous solution  

Microsoft Academic Search

Electrochemical quartz crystal impedance studies on l-cysteine oxidation in aqueous solutions were conducted. The precipitation of electrogenerated species on the Au electrode surface was found in acetic and phosphate buffers. Changes in the equivalent circuit parameters, resonant frequencies and half peak width of the conductance spectra (?fG1\\/2) obtained simultaneously during electrochemical experiments were discussed. Significant changes in the motional resistance

Qingji Xie; Youyu Zhang; Yu Yuan; Yanghui Guo; Xiangjun Wang; Shouzhuo Yao

2000-01-01

157

Fabrication and heating rate study of microscopic surface electrode ion traps  

Microsoft Academic Search

We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with a trapping height of approximately 240 mum. 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.

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

2011-01-01

158

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

159

Hubble space telescope pointing control system design improvement study results  

Microsoft Academic Search

Unexpected thermally induced disturbances originating in the solar arrays imposed deleterious effects on the pointing performance of the Hubble Space Telescope (HST). A NASA redesign of the onboard pointing control system (PCS) brought the performance back into specification during a majority of the orbit time. As a result of this controller redesign effort, a wealth of flight data was collected

Angelia P. Bukley

1995-01-01

160

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

161

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

162

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

163

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

164

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

165

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

166

Working Electrodes  

Microsoft Academic Search

\\u000a In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can\\u000a be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution;\\u000a however, solid electrolytes and ionic melts can be used as well. The term “electrode” is also used in a technical sense,

Šebojka Komorsky-Lovri?

167

A study of calcium zincate as negative electrode materials for secondary batteries  

Microsoft Academic Search

The properties of calcium zincate as negative electrode materials for secondary batteries were examined by powder microelectrode, cyclic voltammetry, charge–discharge cycle measurements and X-ray diffraction (XRD) analysis. The results show that the cycleability of calcium zincate is obviously superior to that of ZnO and that of the mixture of ZnO and Ca(OH)2 (the molar ratio of Zn:Ca=2:1). Calcium zincate forms

Jingxian Yu; Hanxi Yang; Xinping Ai; Xiaoming Zhu

2001-01-01

168

A rotating disc electrode study of oxygen reduction at platinised nickel and cobalt coatings  

Microsoft Academic Search

Platinized nickel and cobalt coatings, Pt(Ni) and Pt(Co), have been prepared on glassy carbon, GC, rotating disc electrode\\u000a substrates by a two-step room temperature procedure that involved the electrodeposition of nickel and cobalt layers and their\\u000a spontaneous partial replacement by platinum (“transmetalation”) when immersed into a chloroplatinic acid solution. By tuning\\u000a the quantity of initially deposited nickel and cobalt, Pt(Ni)

Andromahi Tegou; Sofia Papadimitriou; Georgios Kokkinidis; Sotirios Sotiropoulos

2010-01-01

169

Thermodynamic studies of LI-GE alloys: application to negative electrodes for molten salt batteries  

SciTech Connect

The objectives of this work are (i) to gain some preliminary understanding of the electrochemical and chemical characteristics of Li-Ge alloys under the conditions present in the lithium-metal sulfide battery system in order to identify the feasibility of using germanium as an additive to lithium alloys currently being investigated for this battery system and (ii) to evaluate the Li-Ge alloy system for its inherent utility as a negative electrode for molten salt batteries. 33 refs.

St. John, M.R.; Furgala, A.J.; Sammells, A.F.

1982-02-01

170

PIV Experimental Study On Electrostatic Spray Of Pressure-swirl Atomizer With Annular Electrode  

Microsoft Academic Search

The middle-size electrostatic spray generated by pressure-swirl atomizer and annular electrode, which could be applied in inside-room disinfections, was investigated through PIV experiment. PIV was applied to measure the flow of charged atomized particles. The flow field of uncharged and charged spray was compared and the change of spray flow filed was analyzed under different charging voltage. The experiment results

Junfeng Wang; Wook Ryol Hwang; Tiqian Luo

2007-01-01

171

Voltammetric study of nifuroxazide at unmodified and Sephadex-modified carbon paste electrodes  

Microsoft Academic Search

The electrooxidation of nifuroxazide was investigated by cyclic and differential-pulse voltammetry at carbon paste and Sephadex-modified\\u000a carbon paste electrodes. Nifuroxazide is irreversibly oxidized at all pH values and gives rise to a well-defined oxidation\\u000a peak. The modification of the carbon paste surface with Sephadex allowed a preconcentration process to take place for nifuroxazide\\u000a such that higher sensitivity was achieved compared

A. Radi

1999-01-01

172

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

173

New Advances in the Study of the Proximal Point Algorithm  

NASA Astrophysics Data System (ADS)

Consider in a real Hilbert space H the inexact, Halpern-type, proximal point algorithm xn+1 = ?nu+(1-?n)J?nxn+en, n = 0,1,…, (H—PPA) where u, x?H are given points, J?n = (I+?na) for a given maximal monotone operator A, and (en) is the error sequence, under new assumptions on ?n?(0,1) and ?n?(0,1). Several strong convergence results for the H—PPA are presented under the general condition that the error sequence converges strongly to zero, thus improving the classical Rockafellar's summability condition on (?en?) that has been extensively used so far for different versions of the proximal point algorithm. Our results extend and improve some recent ones. These results can be applied to approximate minimizers of convex functionals. Convergence rate estimates are established for a sequence approximating the minimum value of such a functional.

Moro?anu, Gheorghe

2010-09-01

174

Topology Study of Photovoltaic Interface for Maximum Power Point Tracking  

Microsoft Academic Search

This paper looks at the performance of photovoltaic modules in nonideal conditions and proposes topologies to minimize the degradation of performance caused by these conditions. It is found that the peak power point of a module is significantly decreased due to only the slightest shading of the module, and that this effect is propagated through other nonshaded modules connected in

Weidong Xiao; Nathan Ozog; William G. Dunford

2007-01-01

175

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

176

A Theoretical Study of Stagnation-Point Ablation  

NASA Technical Reports Server (NTRS)

A simplified analysis is made of ablation cooling near the stagnation point of a two-dimensional or axisymmetric body which occurs as the body vaporizes directly from the solid state. The automatic shielding mechanism Is discussed and the important thermal properties required by a good ablation material are given. The results of the analysis are given in terms of dimensionless parameters.

Roberts, Leonard

1959-01-01

177

Electronic transport properties of carbon chains between Au and Ag electrodes: A first-principles study  

NASA Astrophysics Data System (ADS)

We report first-principles calculations of the current-voltage characteristic and the conductance of carbon-based molecular wires with different length capped with sulfur ends between two metallic electrodes made of different metals. The optimized molecular structure of carbon chain in the junction is presented on the structure of polyyne. The conductance of the polyyne wires shows oscillatory behavior depending on the number of carbon atoms (triple bonds). Current rectification is found and rectification direction presents inversion with the odd and even number of carbon atoms.

Fang, Changfeng; Cui, Bin; Xu, Yuqing; Ji, Guomin; Liu, Desheng; Xie, Shijie

2011-09-01

178

Study of peptide on-line complexation with transition-metal ions generated from sacrificial electrodes in thin-chip polymer microsprays.  

PubMed

A miniaturized polymer electrospray-type interface is used to study metal-ion chelation with model peptides. Taking advantage of the intrinsic electrochemical behavior of electrospray, a sacrificial electrode is used to generate at the same time electrospray and transition-metal ions coming from the anodic dissolution of the electrode. The microspray interface provides enhanced mass transport due to its small dimensions, increasing the yield of possible reactions, in particular complex formation. Transition-metal electrodes, e.g. copper, zinc, nickel, iron and silver, are used to obtain on-line complexation with model peptides. It is demonstrated that the use of in-reservoir sacrificial electrodes is an efficient way to generate metal ions in order to form and study complexes with peptides, avoiding the addition of metallic salts. PMID:15818723

Rohner, Tatiana C; Girault, Hubert H

2005-01-01

179

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

180

Double channel electrode flow cell application to the study of HO 2 ? production on Mn x Co 3? x O 4 (0 ? x ? 1) spinel films  

Microsoft Academic Search

We conducted a study on the electroreduction of O2 in alkaline solution at room temperature on pure thin oxide electrodes of composition MnxCo3?xO4 (0?x?1) using the double channel electrode flow cell (DCEFC). The oxides were prepared at 150°C and deposited by spray pyrolysis onto titanium substrates. The oxygen reduction reaction (orr) occurs through “interactive” and “parallel” pathways, and the ratio

E. Ríos; H. Reyes; J. Ortiz; J. L. Gautier

2005-01-01

181

Synthetic semiconductor diamond electrodes: a study of electrochemical behavior of boron-doped single crystals grown at a high temperature and high pressure  

Microsoft Academic Search

Impedance spectroscopy and electrochemical kinetics in Fe(CN)63?\\/4? and Ce3+\\/4+ redox solutions are investigated for boron-doped `high temperature, high pressure' diamond single crystals of moderate resistivity. The comparison with thin-film chemical-vapor-deposited diamond electrodes studied earlier proved both types of diamond electrode to behave in a similar manner. In particular, a constant phase element is characteristic of their impedance behavior. Redox reactions

Yu. V Pleskov; Yu. E Evstefeeva; M. D Krotova; A. V Laptev

1999-01-01

182

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

183

Z-Pinch Wire-Electrode Contact Resistance Studies Using Weighted and Soft Metal Gasket Contacts*  

NASA Astrophysics Data System (ADS)

The contact made between z-pinch wires and electrodes has a significant effect on both the energy deposited in the wires and the uniformity of the expansion profile of the wires. We have shown that using soft metal gaskets can improve wire-electrode contact significantly over typical weighted contacts. Images of wire expansion profile and wire plasma emission will be presented for single and double wire shots on a 16 kA, 100 kV 4-stage Marx bank with 150 ns risetime. Bench resistance measurements for aluminum, stainless steel, and tungsten wires with diameters ranging from 7.5 um to 30 um will be presented. These measurements utilized both soft metal gasket contacts (gaskets include: indium, silver, aluminum, tin, and lead) and double-ended wire weight contacts (weights ranged from 0.4 g to 1.9 g). *This research was supported by U. S. DoE through Sandia National Laboratories award document numbers 240985, 768225, 790791 and 805234 to the University of Michigan. MRG supported by NNSA Fellowship and JCZ supported by NPSC Fellowship sponsored by Sandia National Labs.

Gomez, M. R.; Zier, J. C.; Thurtell, A. F.; French, D. M.; Gilgenbach, R. M.; Tang, W.; Lau, Y. Y.

2008-11-01

184

Electrode immersion depth determination and control in electroslag remelting furnace  

DOEpatents

An apparatus and method for controlling an electroslag remelting furnace comprising adjusting electrode drive speed by an amount proportional to a difference between a metric of electrode immersion and a set point, monitoring impedance or voltage, and calculating the metric of electrode immersion depth based upon a predetermined characterization of electrode immersion depth as a function of impedance or voltage.

Melgaard, David K. (Albuquerque, NM); Beaman, Joseph J. (Austin, TX); Shelmidine, Gregory J. (Tijeras, NM)

2007-02-20

185

Physiologic Responses to Acupuncture Point Stimulation: A Pilot Study to Evaluate Methods and  

E-print Network

Physiologic Responses to Acupuncture Point Stimulation: A Pilot Study to Evaluate Methods Abstract-- The physiological responses to needle stimulation of an acupuncture point and a nearby control, unexpected noise, etc were annotated. Keywords-- Acupuncture stimulation, physiologic response to acupuncture

186

Improvements and artifact analysis in conductivity images using multiple internal electrodes.  

PubMed

Electrical impedance tomography is an attractive functional imaging method. It is currently limited in resolution and sensitivity due to the complexity of the inverse problem and the safety limits of introducing current. Recently, internal electrodes have been proposed for some clinical situations such as intensive care or RF ablation. This paper addresses the research question related to the benefit of one or more internal electrodes usage since these are invasive. Internal electrodes would be able to reduce the effect of insulating boundaries such as fat and bone and provide improved internal sensitivity. We found there was a measurable benefit with increased numbers of internal electrodes in saline tanks of a cylindrical and complex shape with up to two insulating boundary gel layers modeling fat and muscle. The internal electrodes provide increased sensitivity to internal changes, thereby increasing the amplitude response and improving resolution. However, they also present an additional challenge of increasing sensitivity to position and modeling errors. In comparison with previous work that used point sources for the internal electrodes, we found that it is important to use a detailed mesh of the internal electrodes with these voxels assigned to the conductivity of the internal electrode and its associated holder. A study of different internal electrode materials found that it is optimal to use a conductivity similar to the background. In the tank with a complex shape, the additional internal electrodes provided more robustness in a ventilation model of the lungs via air filled balloons. PMID:24845453

Farooq, Adnan; Tehrani, Joubin Nasehi; McEwan, Alistair Lee; Woo, Eung Je; Oh, Tong In

2014-06-01

187

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

188

Working Electrodes  

Microsoft Academic Search

In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term \\

Sebojka Komorsky-Lovric

2010-01-01

189

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

190

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

191

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 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

192

Chronoamperometric study of membrane electrode assembly operation in continuous flow photoelectrochemical water splitting.  

PubMed

Water splitting was performed in a photoelectrochemical cell (PEC) with water oxidation and hydrogen formation reactions in two separate compartments. A photoanode consisting of carbon paper loaded with TiO2 and a cathode made of Pt dispersed on carbon black spread also on carbon paper were fixed on both sides of a Nafion® membrane and electrically coupled via an external circuit. Anode and cathode compartments with serpentine flow field were operated either in the liquid or vapour phase. Electrical current was monitored with chronoamperometry and D2 formation from deuterated water using mass spectrometry. Mapping the photocurrent under a variety of reaction conditions enabled identification of the limiting factors related to proton and photocarrier transport and reaction product evacuation. This comprehensive research approach to the operation of a PEC will assist future optimisation of cell design and development of membrane electrode assemblies. PMID:23660956

Rongé, Jan; Nijs, Dorien; Kerkhofs, Stef; Masschaele, Kasper; Martens, Johan A

2013-06-21

193

Response mechanism of a neutral carrier Hg(II) polymeric membrane ion-selective electrode. SEM and EDAX study.  

PubMed

Scanning electron microscopy (SEM) and energy dispersive atomic X-ray spectrometry (EDAX) were used to study the response mechanism of a previously reported new Hg membrane ion-selective electrode (ISE) based on 1,3-diphenylthiourea. These techniques allowed the study of the membrane surface characteristics, such as the morphological homogeneity and chemical composition. A 'twice Nernstian' response at pH > or = 7 was explained by the detection of the Hg(OH)+ cation. A normal Nernstian response was found at acidic pH values. Using these techniques, both coordination compounds, [Ligand-Hg-OH] at pH 7 and [Ligand-Hg-Ligand] at pH 4.5, were confirmed on the electrode membrane surface activated with Hg(NO3)2 solution at both pH values. These methods provide results which are independent of the potential measurement data and in agreement with them. A successful response model has explained both independent and unbiased sets of results. These conclusions confirm the proposed response mechanisms for this new Hg membrane sensor. PMID:11340987

Pérez-Marín, L; López-Valdivia, H; Avila-Pérez, P; Otazo-Sánchez, E; Macedo-Miranda, G; Gutiérrez-Lozano, O; Alonzo Chamaro, J; De la Torres-Orozco, J; Carapia-Morales, L

2001-04-01

194

Masking mechanisms of bitter taste of drugs studied with ion selective electrodes.  

PubMed

The masking mechanisms of the bitter taste of propantheline bromide (PB) and oxyphenonium (OB) bromide by native and modified cyclodextrins, saccharides, surfactants, organic acids, nonionic and anionic polymers, and other compounds were investigated with ion selective electrodes. The intensity of the bitter taste for a mixed solution of cyclodextrin with PB or OB was quantitatively explained from the observed electromotive force with the following assumptions: the complex and the masking agent do not have any tastes and the bitter taste is independent of other tastes. Sodium dodecyl sulfate reduced the bitter taste remarkably, and this reduction was also explicable on the basis of the same mechanism. Sodium taurodeoxycholate enhanced the bitter taste, because of its strong bitterness, although it formed 1 : 1 complexes with PB and OB. The masking mechanism of saccharides was ascribed to overcoming the weak bitterness of the drug by the strong sweetness. Lambda-carrageenan suppressed the bitter taste remarkably. This suppression was ascribed to the binding of PB and OB to lambda-carrageenan, the effect of the solution viscosity on the bitter taste, and the covering of the bitter taste receptor by lambda-carrageenan. It was suggested that the moderate masking by other polymers was attributable to the effect of the solution viscosity or the receptor covering. Native and modified beta-cyclodextrins, sodium dodecyl sulfate, lambda-carrageenan, Tween 20, and sodium carboxymethyl cellulose are good masking agents for the bitter tastes of PB and OB. The drug ion selective electrode is a useful tool for understanding of the masking mechanism of the bitter taste, screening of masking agents, and estimation of appropriate concentrations of the masking agents. PMID:16880661

Funasaki, Noriaki; Uratsuji, Ikumi; Okuno, Takashi; Hirota, Shun; Neya, Saburo

2006-08-01

195

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

196

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

197

Studying 21cm power spectrum with one-point statistics  

E-print Network

The redshifted 21cm line signal from neutral hydrogens is a promising tool to probe the cosmic dawn and the epoch of reionization (EoR). Ongoing and future low-frequency radio experiments are expected to detect its fluctuations, especially through the power spectrum. In this paper, we give a physical interpretation of the time evolution of the power spectrum of the 21cm brightness temperature fluctuations, which can be decomposed into dark matter density, spin temperature and neutral fraction of hydrogen fluctuations. From the one-point statistics of the fluctuations, such as variance and skewness, we find that the peaks and dips in the time evolution are deeply related to X-ray heating of the intergalactic gas, which controls the spin temperature. We suggest the skewness of the brightness temperature distribution is a key observable to identify the onset of X-ray heating.

Shimabukuro, Hayato; Takahashi, Keitaro; Yokoyama, Shuichiro; Ichiki, Kiyotomo

2014-01-01

198

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

199

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.

200

Electrode structures  

SciTech Connect

In a sodium sulphur cell, a cathode electrode of annular form comprising a plurality of segments, each of trapezoidal form in cross-section and joined by webs along a longer edge of each segment so that the assembly is foldable to form a substantially annular structure. This electrode may be made by compressing a blanket or sheet of carbon or graphite felt or fibres in a heated mould, which is shaped to produce the segments joined by thin webs, the material being impregnated with sulphur or sodium polysulphide before or after insertion in the mould, and the material being cooled before removal from the mould. Alternatively, the segments may be formed from the blanket or sheet by using shaped rolls, the material being cooled, E.G. By water or air, as it leaves the rolls.

Brennan, M.P.

1981-01-06

201

Use of voltammetric solid-state (micro)electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in situ electrochemical analyzer (ISEA)  

Microsoft Academic Search

Solid-state voltammetric (micro)electrodes have been used in a variety of environments to study biogeochemical processes. Here we show the wealth of information that has been obtained in the study of sediments, microbial mats, cultures and the water column including hydrothermal vents. Voltammetric analyzers have been developed to function with operator guidance and in unattended mode for temporal studies with an

George W. Luther; Brian T. Glazer; Shufen Ma; Robert E. Trouwborst; Tommy S. Moore; Edouard Metzger; Chareonkwan Kraiya; Tim J. Waite; Gregory Druschel; Bjørn Sundby; Martial Taillefert; Donald B. Nuzzio; Timothy M. Shank; Brent L. Lewis; Paul J. Brendel

2008-01-01

202

In situ infrared spectroelectrochemical studies of the corrosion of a nickel electrode as a function of applied potential in cyanate, thiocyanate, and selenocyanate solutions.  

PubMed

This paper presents the first subtractively normalized interfacial Fourier transform infrared spectroscopic (SNIFTIRS) study of the corrosion system Ni/XCN(-) (X=O, S, Se), pH 11, [XCN(-)]=0.05 molL(-1), supporting electrolyte 0.1 molL(-1) KNO(3), for a nickel electrode as a function of applied potential. Cyclic voltammograms, in situ infrared spectra, and current-potential data (recorded while the infrared spectral acquisition was in progress) were recorded for a nickel electrode in a three-electrode thin-layer cell containing the pseudohalides OCN(-), SCN(-), or SeCN(-) ions at pH 11 in a supporting electrolyte of KNO(3). In general, the data showed that all of the pseudohalide ions studied caused corrosion of the nickel electrode by forming the respective nickel-pseudohalide complex ion species as the potential was stepped anodically. Two of the ions, SCN(-) and SeCN(-), caused surface modifications to the electrode which influenced the electrochemical reactions with respect to CO(2) formation. The Ni/SeCN(-) system, for instance, exhibited signs of instability during the spectroelectrochemical experiment, red-brown coatings observed on the electrode caused by the decomposition of the selenocyanate ion to colloidally dispersed elemental selenium. The selenium coated the electrode, hence modifying the surface and consequently the electrochemistry, by causing the "early" appearance of CO(2)-associated IR peaks in SNIFTIRS spectra recorded from the electrode system at potentials lower than those for the Ni/OCN(-) system. In contrast, CO(2) formation at the electrode surface was not observed in the Ni/SCN(-) system, which was likely to have been caused by nickel sulfide poisoning of the electrode surface. In the Ni/SCN(-) and Ni/SeCN(-) systems, IR spectra also indicated the buildup of Ni(SCN)(2) and Ni(SeCN)(2) salts in the thin layer by the appearance of a peak at ca. 2165 cm(-1) at anodic values of the applied potential. PMID:14654398

Mucalo, Michael R; Li, Qiang

2004-01-15

203

Studies on Conducting Polypyrrole/Graphene Oxide Composites as Supercapacitor Electrode  

NASA Astrophysics Data System (ADS)

An electrode material based on polypyrrole (PPy) doped with graphene oxide (GO) sheets was synthesized via in situ polymerization of pyrrole in the presence of GO in various proportions (5% and 10%). The synthesized samples were characterized by Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, and electrical conductivity measurements. FTIR spectroscopy and XRD revealed the interaction between GO and PPy. The direct-current (DC) electrical conductivity (75.8 S/cm) of the prepared composites was dramatically enhanced compared with pure PPy (1.18 S/cm). High specific capacitance of PPy/GO composite of 421.4 F/g was obtained in the potential range from 0 V to 0.50 V at 2 mA compared with 237.2 F/g for pure PPy by galvanostatic charge-discharge analysis. Incorporation of GO into the PPy matrix has a pronounced effect on the electrical conductivity and electrochemical capacitance performance of PPy/GO nanocomposites.

Konwer, Surajit; Boruah, Ratan; Dolui, Swapan K.

2011-11-01

204

A minimal set of electrodes for motor imagery BCI to control an assistive device in chronic stroke subjects: a multi-session study.  

PubMed

The brain-computer interface (BCI) system has been developed to assist people with motor disability. To make the system more user-friendly, it is a challenge to reduce the electrode preparation time and have a good reliability. This study aims to find a minimal set of electrodes for an individual stroke subject for motor imagery to control an assistive device using functional electrical stimulation for 20 sessions with accuracy higher than 90%. The characteristics of this minimal electrode set were evaluated with two popular algorithms: Fisher's criterion and support-vector machine recursive feature elimination (SVM-RFE). The number of calibration sessions for channel selection required for robust control of these 20 sessions was also investigated. Five chronic stroke patients were recruited for the study. Our results suggested that the number of calibration sessions for channel selection did not have a significant effect on the classification accuracy. A performance index devised in this study showed that one training day with 12 electrodes using the SVM-RFE method achieved the best balance between the number of electrodes and accuracy in the 20-session data. Generally, 8-36 channels were required to maintain accuracy higher than 90% in 20 BCI training sessions for chronic stroke patients. PMID:21984520

Tam, Wing-Kin; Tong, Kai-yu; Meng, Fei; Gao, Shangkai

2011-12-01

205

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

206

Readout electrode assembly for measuring biological impedance  

NASA Technical Reports Server (NTRS)

The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.

Montgomery, L. D.; Moody, D. L., Jr. (inventors)

1976-01-01

207

Single and Multidimensional Robustness Studies of the NIF Ignition Point Design  

Microsoft Academic Search

A robustness study of the NIF ignition point-design target is carried out using hydrodynamically equivalent, all-DT direct-drive targets. The direct-drive targets have similar final mass, kinetic energy, implosion velocity, and adiabat of the indirect-drive point design. The direct-drive target has an equivalent one-dimensional ignition-threshold factor [ITF (1-D)] to the indirect-drive point design. A 1-D sensitivity study of ignition is carried

K. S. Anderson; R. Betti; P. Y. Chang; R. Nora; D. Shvarts; M. Fatenejad

2009-01-01

208

Theoretical study of reactions at the electrode-electrolyte interface. Progress report, August 1, 1991--January 31, 1993  

SciTech Connect

Electron transfer rates are predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have produced a new theory for description of the Jahn Teller effect in the solvation shell of the cuprous ion in aqueous solution, have implemented it in a molecular dynamics simulation and compared the results with experimental neutron scattering measurements on solutions containing the cuprous ion. A large amount of numerical data has been collected on the transition state of the ferrous ferric electron transfer reaction at an electrode. Work was completed on a polarizable and dissociable model of water for use in the electron transfer studies. New calculations of the conductivity in models of oxides have shown the existence of impurity conduction bands in such models for the first time.

Halley, J.W.

1993-02-01

209

Experimental and theoretical study of the efficiency of a three-electrode reactor for the removal of NO  

NASA Astrophysics Data System (ADS)

An experimental and theoretical study is presented on the efficiency of the removal of NO in a N2 atmosphere in a novel three-electrode reactor. This reactor combines a dielectric-barrier discharge with a corona discharge, designed to enhance streamer propagation in a relatively large region. Experimentally, the reactor has a good energy yield for the removal of NO, as compared with other discharge methods. A theoretical model is developed for the production of reactive species in the streamers by different reactions that allow to relate simple electrical measurements with the reactor efficiency. This theoretical efficiency resulted in good agreement with the experimental one, validating the model and allowing the evaluation of the contribution of different reactions involved in NO removal.

Gallego, J. L.; Minotti, F.; Grondona, D.

2014-05-01

210

A comparative study of hepatic mitochondrial oxygen consumption in four vertebrates by using Clark-type electrode.  

PubMed

The present study was undertaken to establish a comparative account on hepatic mitochondrial oxygen consumption of Clarias gariepinus (fish), Bufo melanostictus (amphibian), Gallus gallus (bird) and Rattus norvegicus (mammal) and to correlate it with their specific metabolic rate (SMR). Mitochondrial oxygen consumption was measured with a Clarke-type electrode with succinate and pyruvate/malate as substrates. ADP was used to start state-III respiration. The results show that rats and chickens have higher oxygen consumption rate than that of fish and toads. Similarly, a species and substrate specific difference was also noticed in P/O (phosphate utilized per oxygen atom) ratio and respiratory control index. In case of rat, a significant negative correlation was noticed between P/O ratio and SMR with succinate as substrate. It is surmised that the observed difference in the mitochondrial respiration and P/O ratio in the above vertebrates is due to the difference in their metabolic activities. PMID:23739884

Paital, B; Samanta, Luna

2013-06-01

211

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

212

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

213

Experimental and theoretical study of concentration distributions in a model pore electrode; Measurement of two-dimensional concentration gradients in a zinc model pore  

SciTech Connect

The optical probe beam deflection technique has been employed to study two-dimensional concentration gradients within the electrolyte of a zinc model pore. This paper reports that the model pore cell constructed for this study retains the small, confined geometry and two-dimensional character of an actual pore within a porous zinc electrode. Refractive index gradients in the direction of the model pore axis showed that the concentration of zincate ion reaches a maximum between the model pore mouth and a position one-fourth of the distance toward the pore root during the anodic oxidation of the zinc electrode. Also, the variation in the refractive index gradient normal to the electrode along the length of the zinc anode allowed the authors to calculate the local current density within the model pore.

Weaver, J.K.; McLarnon, F.R.; Cairns, E.J. (Applied Science Div., Lawrence Berkeley Lab. and Dept. of Chemical Engineering, Berkeley, CA (US))

1991-09-01

214

Study on electroelastic field concentration around the electrode tip in multilayer ferroelectric actuators of two designs and their optimizations  

Microsoft Academic Search

Distribution of electromechanical field near electrode tips is closely related to the reliability of ferroelectric multilayer actuators. In this paper, the deformation and stress concentrations around the electrode tip in two multilayer actuator designs, partially and fully cofired, are investigated by means of experimental measurement and numerical simulations. The digital speckle correlation method (DSCM) is used to measure the full

X. J. Zhao; B. Liu; D. N. Fang

2010-01-01

215

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

216

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

217

Electrical stimulation and electrode properties. Part 2: pure metal electrodes.  

PubMed

Electrical stimulation can cause significant damage to clinical electrodes as well as patient injury. In this study, the effects of stimulation on pure metal electrodes were investigated without the complexities introduced by the multiple elements that make up the clinical electrode. As with the clinical electrodes, there was significant decomposition of pure stainless steel anodes with no associated significant changes in the cathodes when stimulation employed long pulse durations. Effects of stimulation were greater when the anode and cathode were closer under constant voltage stimulation but were distance independent under constant current stimulation. High ionic content of the solution also increased the degree of damage to the anode as did the presence of chloride in the solution. Electrode composition also influenced the amount damage to the anode. Platinum and platinum-iridium electrodes showed no damage with any stimulus while stainless steel showed the lowest resistance to corrosion for direct current (DC) stimulation. Tungsten electrodes behaved very differently than stainless steel, decomposing with pulse stimulation and resisting decomposition during DC stimulation because of the formation of surface protective layers. Because platinum was able to maintain high levels of current over time, prolonged stimulation produced dramatic increases in the temperature of the solution; however, even short periods of stimulation were sufficient to produce dramatic changes in pH in the neighborhood of the electrode. PMID:21313789

Stevenson, Matthew; Baylor, Kelly; Netherton, Brett L; Stecker, Mark M

2010-12-01

218

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

219

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

220

Mechanistic studies of oxygen reduction at La 0.6Ca 0.4CoO 3-activated carbon electrodes in a channel flow cell  

Microsoft Academic Search

The mechanism of the oxygen reduction reaction (orr) was studied in alkaline media at La0.6Ca0.4CoO3-activated carbon electrodes in a channel flow cell (CFC). The electrodes were made by depositing a mixture of the perovskite (La0.6Ca0.4CoO3) powder as the catalyst, Vulcan XC 72 as the carbon, and Triton X-100 as the binder on Ti substrates. The collection efficiency, N, of the

V Hermann; D Dutriat; S Müller; Ch Comninellis

2000-01-01

221

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

222

Zeolite-modified electrodes in electroanalytical chemistry  

Microsoft Academic Search

This review reports on the analytical applications of chemically modified electrodes involving zeolites or zeolite-like materials. After a brief introduction on zeolites, the implication of these solids in electrochemistry is discussed. The interest of zeolite-modified electrodes (ZMEs) for electroanalytical purpose is pointed out, by classifying the applications into five main categories depending on the detection process. In the last decade,

A. Walcarius

1999-01-01

223

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

224

Study of the optimum level of electrode placement for the evaluation of absolute lung resistivity with the Mk3.5 EIT system  

Microsoft Academic Search

Inter-subject variability has caused the majority of previous electrical impedance tomography (EIT) techniques to focus on the derivation of relative or difference measures of in vivo tissue resistivity. Implicit in these techniques is the requirement for a reference or previously defined data set. This study assesses the accuracy and optimum electrode placement strategy for a recently developed method which estimates

S. Nebuya; M. Noshiro; A. Yonemoto; S. Tateno; B. H. Brown; R. H. Smallwood; P. Milnes

2006-01-01

225

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

226

Alaska Park Science, Volume 8, Issue 2 Genetic Studies Point to Beringia as a Biodiversity  

E-print Network

37 Alaska Park Science, Volume 8, Issue 2 Genetic Studies Point to Beringia as a Biodiversity, Beringia, including Alaska and north-eastern Siberia, has long been a focal point for biogeographical in Beringia are virtually unknown. We analyzed DNA sequence data from various boreal and arctic macrofungi

Wagner, Diane

227

Parametric study on instabilities in a two-layer electromagnetohydrodynamic channel flow confined between two parallel electrodes.  

PubMed

Instabilities in a two-phase electromagnetohydrodynamic (EMHD) flow between a pair of parallel electrodes are explored. A linear stability analysis has been performed based on a coupled Orr-Sommerfeld system generated from the conservation laws. The study shows the presence of a finite-wave-number EMHD mode of instability in addition to the two commonly observed instability modes in the pressure-driven two-layer flows, namely, the long-wave interfacial mode arising from the viscosity or density stratification and the finite-wave-number shear flow mode engendered by the Reynolds stresses. This extra EMHD mode originates from the additional stresses generated by the Lorenz force acting at the liquid layers and is found to exist under all conditions beyond a critical strength of the externally applied magnetic field. The EMHD mode either can exist as a singular dominant mode or can coexist as a dominant or subdominant mode with the conventional interfacial mode or shear flow instabilities in the two-layer flows. The EMHD flow studied here has numerous potential applications in fluid transport, enhanced heat and mass transfer, mixing, and emulsification because of the low energy requirement, flow reversibility, absence of moving parts, and facile control over flow rate. The parametric study presented here on the instabilities in the two-layer EMHD flow will thus be of great practical use. PMID:21517593

Reddy, P Dinesh Sankar; Bandyopadhyay, Dipankar; Joo, Sang Woo; Sharma, Ashutosh; Qian, Shizhi

2011-03-01

228

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

229

Study of the cycling performance of finely dispersed lithium alloy composite electrodes under high Li-utilization  

NASA Astrophysics Data System (ADS)

The cycling behavior of lithium alloy composite electrodes in liquid electrolyte composed of 1 M LiClO 4/EC+DEC (1:1) was examined. The lithium alloys were formed by electrochemical insertion of lithium into metallic host matrices (Al, Sn and SnSb x powders). With a wide potential cut-off between 0.1 and 1.2 V vs. Li/Li +, the capacity retention (ca. 550 mA h/g) of Sn-based electrodes during cycling can be remarkably improved by decreasing the particle size of the host materials to near nano-scale. Moreover, the cycle life performance and coulombic efficiency are also dependent on polymer binder and conducting additive as the other components of the electrodes. Under a similar condition, it was found that an ultra-fine Al powder was not fit for host material due to a strong passivation of the electrode after Li-insertion.

Yang, J.; Takeda, Y.; Imanishi, N.; Ichikawa, T.; Yamamoto, O.

230

Study on the disposable urea biosensors based on PVC-COOH membrane ammonium ion-selective electrodes  

Microsoft Academic Search

A potentiometric urea biosensor is prepared by the immobilization of urease directly onto the surface of a solid-state ammonium ion-selective electrode. The enzyme is immobilized by entrapment method onto a nonactin membrane that incorporated carboxylated polyvinylchloride. The same method of immobilization method is adopted to compare the characteristics of urea biosensors based on ammonium ion-selective electrodes with those based on

Nien Hsuan Chou; Jung Chuan Chou; Tai-Ping Sun; Shen Kan Hsiung

2006-01-01

231

Electrochemical study on the TiO2 porous electrodes for metal-free dye-sensitized solar cells  

Microsoft Academic Search

Nanocrystalline TiO2 porous electrodes were prepared by screen-printing method in order to efficiently control the fabrication process. TiO2 viscous pastes were prepared from commercial TiO2 nano powder using ethyl cellulose as a porosity controlling agent. A metal-free organic dye (indoline dye D102) was used as a sensitizer. TiO2 porous electrodes with different thicknesses were investigated. The optical and physical properties

D. W. Zhang; S. Chen; X. D. Li; Z. A. Wang; J. H. Shi; Z. Sun; X. J. Yin; S. M. Huang

2009-01-01

232

Synthetic semiconductor diamond electrodes: The comparative study of the electrochemical behaviour of polycrystalline and single crystal boron-doped films  

Microsoft Academic Search

Capacitance and potentiodynamic measurements were conducted on single crystal (homoepitaxial) and polycrystalline boron-doped diamond thin-film electrodes. The impedance characteristics and kinetic data in the Ce3+\\/4+ redox system, even if having a great deal of variability, appeared to be similar for the two kinds of diamond electrodes, whereas the kinetics of redox reactions on crystalline diamond and amorphous diamond-like carbon films

Yu. V. Pleskov; Yu. E. Evstefeeva; M. D. Krotova; V. V. Elkin; V. M. Mazin; V. Ya. Mishuk; V. P. Varnin; I. G. Teremetskaya

1998-01-01

233

Response of an ion-selective electrode to butylmethylimidazolium and other ionic liquid cations. Applications in toxicological and bioremediation studies  

Microsoft Academic Search

The response of an ion-selective membrane electrode to 1-butyl-3-methylimidazolium (BMIm) and other ionic liquid cations is presented. The sensing membrane comprised the ionic liquid BMIm-PF6 in a plasticized PVC matrix. The electrode showed a fast, stable and Nernstian response over a wide concentration range. The partition coefficients of the imidazolium cations between water and the membrane were obtained. A relationship

J. A. Ortuño; M. Cuartero; M. S. García; M. I. Albero

2010-01-01

234

A gas electrode - Behavior of the chlorine injection electrode in fused alkali chlorides  

NASA Astrophysics Data System (ADS)

The electroreduction of chlorine in fused alkali chlorides was studied by transient electrochemical techniques on graphite and carbon electrodes. Two types of experiments were carried out. First, on massive electrodes, the separate contributions of dissolved chlorine and of chlorine from bubbles at the electrode surface were detected. Second, injection electrodes were used to improve the efficiency of the reduction; the chlorine gas introduced inside the electrode flowed through the wall of the electrode. A model is presented to describe the behavior of this gas electrode; the model takes into consideration the main parameters which influence the electrode process: the properties of carbon and graphite (density, porosity, pore distribution), the wetting properties or the electrode process, the chlorine pressure, and the temperature.

Lantelme, Frederic; Alexopoulos, Hiraclis; Devilliers, Didier; Chemla, Marius

1991-06-01

235

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

236

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

MedlinePLUS

... and Jobs Three studies point to same risk gene for age-related macular degeneration Listen NIH-funded ... in Nature Genetics have converged on the same gene as a rare, but powerful risk factor for ...

237

Low resistance electrode construction  

DOEpatents

An electrochemical cell having a cathode and an anode in contact with an electrolyte. Both electrodes or one of them has an electrically conducting non-metal receptacle defining a chamber with a first metal having a melting point in the range of from about room temperature to about 800.degree. C. inside said receptacle chamber. A second metal with a melting point greater than about 800.degree. C. is in contact with the first metal inside the receptacle chamber and extends outside of the receptacle chamber to form a terminal for the anode. The electrolyte may include the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides. Metal may be produced at the cathode during operation of the cell and oxygen or chlorine at the anode.

Redey, Laszlo (Downers Grove, IL); Karell, Eric J. (Woodridge, IL)

2002-01-01

238

Study on degradation of solid oxide fuel cell anode by using pure nickel electrode  

NASA Astrophysics Data System (ADS)

In this study, the interactions between Ni and YSZ in solid oxide fuel cell anode and the influence of glass seal to anode performances have been investigated by pure Ni anode sintered on YSZ pellet. The evolution of Ni-YSZ interface in 100 h galvanostatic polarization in hydrogen is studied with different humidities in hydrogen. Electrochemical impedance spectroscopy was applied to analyze the time variation of the anode electrochemical characteristics. The interface microstructural changes were characterized by scanning electron microscopy. The influence of bulk gas humidity, gas-sealing material and Ni coarsening on anode durability was studied. The degradation of pure Ni anode is considered to be determined by the competition among the mechanisms of silicon deposition, YSZ interface morphological change and Ni coarsening.

Jiao, Zhenjun; Shikazono, Naoki; Kasagi, Nobuhide

2011-10-01

239

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

240

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

241

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

E-print Network

coefficient of MgO. The UV photons emitted by the discharge hit the phos- phors deposited on the walls found that wider discharge area results in higher efficiency. In addition, the effect of the insertion by 8%. Finally, a self-erase discharge sustaining waveform is studied. Use of this waveform results

Veronis, Georgios

242

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

243

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

244

A Mixed-Methods Study Investigating the Relationship between Media Multitasking Orientation and Grade Point Average  

ERIC Educational Resources Information Center

The intent of this study was to examine the relationship between media multitasking orientation and grade point average. The study utilized a mixed-methods approach to investigate the research questions. In the quantitative section of the study, the primary method of statistical analyses was multiple regression. The independent variables for the…

Lee, Jennifer

2012-01-01

245

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

NASA Astrophysics Data System (ADS)

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan

2014-07-01

246

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

SciTech Connect

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0?cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electric and Electronic Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-07-15

247

Activated transport in AMTEC electrodes  

SciTech Connect

Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process. 17 refs.

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

1992-01-01

248

Activated transport in AMTEC electrodes  

SciTech Connect

Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process. 17 refs.

Williams, R.M.; Jeffries-Nakamura, B.; Ryan, M.A.; Underwood, M.L.; O`Connor, D.; Kikkert, S.

1992-07-01

249

Experimental and DFT theoretical studies of surface enhanced Raman scattering effect on the silver nano arrays modified electrode.  

PubMed

Well-ordered silver nano arrays, prepared using anodic aluminum oxide (AAO) template by laser molecular beam epitaxy (L-MBE) method, were adhered to the work electrode using conductive adhesive to be a Surface-enhanced Raman scattering (SERS) substrate. Variable SERS signals of paranitrobenzoic acid (PNA) on the electrode modified with silver nano arrays were recorded with electric potential ranging from 0.1 to -0.5 V. The SERS spectra of PNA using DFT-B3PW91 with lanl2dz based on two models were calculated. It indicate that the adsorption orientation of probe molecules on the silver nano arrays with potential change of the electrode. PMID:22495219

Zhang, Lisheng; Fang, Yan; Wang, Peijie

2012-07-01

250

Capacity fading of lithiated graphite electrodes studied by a combination of electroanalytical methods, Raman spectroscopy and SEM  

NASA Astrophysics Data System (ADS)

We present herein Raman spectroscopy and SEM characterizations of composite graphite electrodes in conjunction with classical electroanalytical characterizations (SSCV and EIS) during prolonged cycling. During cycling, graphite particles crack into smaller pieces that are less oriented than the original platelets, with the possible filling of the cracks thus formed by the reduction products of the electrolyte solution. In addition, the average crystalline size (estimated by Raman spectroscopy) decreases as cycling progresses. The borders between the crystallites may possess dangling bonds and generally contain low-energy (or hollow) sites for irreversible interaction with Li-ions and solution species. The redistribution between the hollow and the shallow sites (i.e. the site for reversible Li-ion storage) occurring during electrode cycling is responsible for the moderate decrease of the reversible capacity of graphite electrodes observed during prolonged cycling.

Markervich, E.; Salitra, G.; Levi, M. D.; Aurbach, D.

251

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

252

Electrocatalytic oxidation and adsorption rate of methanol at Pt stepped single-crystal electrodes and effect of Ru step decoration: a DEMS study.  

PubMed

The adsorption and oxidation of methanol at Pt(331) and Ru-step-decorated Pt(331) electrodes are studied recording currents and ion currents by online differential electrochemical mass spectrometry. The CO(2) current efficiencies and the degree of surface poisoning with CO(ad) formed during methanol oxidation are independent of the flow rate, confirming the parallel pathway mechanism. The CO(2) current efficiencies decrease with increasing methanol concentration and increase with increasing potential, whereas those of methyl formate show a reverse trend. At potentials higher than 0.6 V, neither the CO(2) current efficiencies nor the methanol oxidation currents increase with increasing Ru coverage. Instead, methanol oxidation is inhibited due to blocking of the most active platinum step sites. At potentials lower than 0.6 V, however, not only the onset of methanol oxidation shifts negatively, by about 0.1 V, but also the methanol oxidation current and the CO(2) current efficiencies increase. Crucial for the use in fuel cells is the complete oxidation to CO(2), which can be achieved if the reactants first adsorb at the electrode surface along the reaction path with adsorbed CO as an intermediate. Therefore, we directly determine the methanol adsorption rates at Pt(331) as well as at Ru-step-decorated Pt(331), Pt(332), Pt(100), and Pt(11,1,1) electrodes. The methanol adsorption rate is doubled by a double step density in the case of the Pt(331) and Pt(332) electrodes, higher at higher Ru coverages, and increases by a factor of three upon increasing the potential by 0.1 V (corresponding to a Tafel slope of approximately 200 mV?dec(-1)). At Pt(331) electrodes with partial step decoration, stripping of adsorbed CO (from CO gas) reveals two adsorbate states, which are also discernable when the adsorbate formed from methanol dehydrogenation is stripped. PMID:24986467

Mostafa, Ehab; Abd-El-Latif, Abd-El-Aziz A; Baltruschat, Helmut

2014-07-21

253

A Study of Impulsive Multiterm Fractional Differential Equations with Single and Multiple Base Points and Applications  

PubMed Central

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

254

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

255

Improving nickel metal hydride batteries through research in negative electrode corrosion control and novel electrode materials  

E-print Network

IMPROVING NICKEL METAL HYDRIDE BATTERIES THROUGH RESEARCH IN NEGATIVE ELECTRODE CORROSION CONTROL AND NOVEL ELECTRODE MATERIALS A Thesis by MICHAEL SCOTT ALEXANDER Submitted to the Office of Graduate Studies of Texas ARM University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1997 Major Subject: Chemical Engineering IMPROVING NICKEL METAL HYDRIDE BATTERIES THROUGH RESEARCH IN NEGATIVE ELECTRODE CORROSION CONTROL AND NOVEL ELECTRODE...

Alexander, Michael Scott

1997-01-01

256

Comparative study of atmospheric pressure low and radio frequency microjet plasmas produced in a single electrode configuration  

SciTech Connect

Microsize jet-type plasmas were generated in a single pin electrode structure source for two separate input frequencies of 50 kHz and 13.56 MHz in the ambient air. The copper pin electrode radius was 360 {mu}m, and it was placed in a Pyrex tube with a radius of 3 mm for helium gas supply. Due to the input frequency difference, the generated plasmas showed distinct discharge characteristics for their plasma physical appearances, electrical properties, gas temperatures, and optical properties. Strengths and weaknesses of both plasmas were discussed for further applications.

Kim, Dan Bee; Rhee, J. K.; Gweon, B.; Moon, S. Y.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

2007-10-08

257

Advanced treatment of cephalosporin pharmaceutical wastewater by nano-coated electrode and perforated electrode.  

PubMed

The objective of this study was to investigate the degradation of nonbiodegradable organic pollutants in biologically cephalosporin pharmaceutical wastewater using different electrodes such as non-nano-scale electrode (traditional coated), nano-scale (nano-coated) electrode, and perforated electrode after biotreatment. The traditional coated electrode plate, nano-coated electrode plate, and two different perforated titanium dioxide (TiO2) electrode plates with an average pore size of 10 ?m and 20 ?m were chosen as the anode. The results demonstrated that traditional coated electrode, nano-scale electrode, and perforated electrode could effectively remove nonbiodegradable organic pollutants from pharmaceutical wastewater. The perforated electrode with an average pore size of 10 ?m exhibited the best degradation effect with a 90 % decrease in the chemical oxygen demand (COD) (COD content reduced from 320 mg L(-1) to 32 mg L(-1)). During catalytic degradation, the electrical conductivity of pharmaceutical wastewater increased and the pH increased and finally reached equilibrium. It was also found that the perforated TiO2 electrode produced relatively large amounts of dissolved oxygen during the catalytic oxidation process, reaching above 4 mg L(-1), whereas the nano-coated electrode produced little dissolved oxygen. The biotoxicities of all wastewater samples increased firstly then decreased slightly during the electrical catalytic oxidation, but the final biotoxicities were all higher than initial ones. PMID:24967559

Yang, Bo; Zuo, Jiane; Gan, Lili; Yu, Xin; Liu, Fenglin; Tang, Xinyao; Wang, Yajiao

2014-09-19

258

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

259

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... for the degree of MASTER OF SCIENCE August 2001 Major Subject: Mechanical Engineering A STUDY ON THE EFFECT OF INLET TURBULENCE ON GAS MIXING FOR SINGLE POINT AEROSOL SAMPLING A Thesis by ANAND MOHAN Submitted to Texas A&M University in partial...

Mohan, Anand

2012-06-07

260

[Study on water quality monitoring scheme based on non-point source pollution].  

PubMed

In order to improve standardization and normalization of non-point source pollution monitoring, this paper summarized the non-point source pollution monitoring scheme that based on conventional technology condition. The scheme firstly emphasized the preparation work before monitoring, including situation investigation and index selection of the monitoring area and so on; In the process of establishing monitoring scheme, the monitoring area was divided into three types: city, agriculture and watershed. Take urban area monitoring scheme for Xi'an as an example, through dividing function zone setting sampling point, summarized sampling time interval, frequency and sampling methods during a rainfall process. An irrigation district was an example for agricultural monitoring scheme, through unit division, setting sampling point at the approach channel and drain channel, introduced sampling times, interval time and so on in the process of irrigation. Watershed monitoring scheme's example was the Weihe GuanZhong section, raised the setting principle of each sample section, and analyzed each section's sampling law in the process of rainfall. Finally the principal character of different non-point source pollution monitoring areas was discussed, and concluded that non-point source pollution monitoring scheme is the base of non-point source pollution study and control. PMID:23947026

Wu, Xi-Jun; Li, Huai-En; Li, Jia-Ke; Li, Qiang-Kun; Dong, Wen

2013-06-01

261

Influence of the solid electrolyte interphase on the performance of redox shuttle additives in Li-ion batteries - A rotating ring-disc electrode study  

NASA Astrophysics Data System (ADS)

Redox shuttle electrolyte additives (RSAs) can be applied for reversible overcharge protection of batteries. Their successful operation involves their oxidation at the cathode and reduction at the anode. The most common anodes in lithium-ion batteries are graphite or amorphous carbon, which are normally covered with a solid electrolyte interphase (SEI). The reduction of RSAs at these anodes is in apparent contradiction with the common understanding of the SEI, which is thought to be electronically insulating. In this communication the reduction behaviour of ferrocene and 2,5-di-tert-butyl-1,4-dimethoxybenzene is studied at un-filmed and SEI-filmed electrodes. It is found that it depends strongly on the type of RSA and/or composition of the SEI. The rotating ring-disc electrode (RRDE) is introduced as a powerful diagnostic tool to study the reaction mechanism of RSAs in general and the influence of the SEI in particular.

Kaymaksiz, Serife; Wachtler, Mario; Wohlfahrt-Mehrens, Margret

2015-01-01

262

Application of branching point process models to the study of invasive red banana  

E-print Network

Application of branching point process models to the study of invasive red banana plants in Costa species. Here, we apply ETAS models to study the spread of an invasive species of red banana plant (Musa-temporal rate of spread of red banana plants using a space-time ETAS model. Keywords: alien plants, branching

Schoenberg, Frederic Paik (Rick)

263

Time-resolved in situ ATR-SEIRAS study of adsorption and 2D phase formation of uracil on gold electrodes  

Microsoft Academic Search

The adsorption and phase formation of uracil on massive Au[n(111)–(110)] single crystal and Au(111-20 nm) film electrodes in 0.1 M H2SO4 was studied by electrochemical measurements and ATR surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS). At E<0.15 V uracil molecules are disordered and planar oriented, co-adsorbed with weakly hydrogen-bonded interfacial water (region I). Around the potential of zero charge a

S Pronkin; Th Wandlowski

2003-01-01

264

In situ infrared spectroelectrochemical studies of the corrosion of a nickel electrode as a function of applied potential in cyanate, thiocyanate, and selenocyanate solutions  

Microsoft Academic Search

This paper presents the first subtractively normalized interfacial Fourier transform infrared spectroscopic (SNIFTIRS) study of the corrosion system Ni\\/XCN? (X=O, S, Se), pH 11, [XCN?]=0.05 molL?1, supporting electrolyte 0.1 molL?1 KNO3, for a nickel electrode as a function of applied potential. Cyclic voltammograms, in situ infrared spectra, and current–potential data (recorded while the infrared spectral acquisition was in progress) were recorded for

Michael R Mucalo; Qiang Li

2004-01-01

265

Experimental Study on the Influence of Tool Electrode Tip Shape on Electrochemical Micromachining of 304 Stainless Steel  

Microsoft Academic Search

Miniaturization in all emerging areas is rapidly increasing. To meet this need, micromachining is considered as one of the key technologies for the production of miniaturized parts and components. Among the various capable processes, electrochemical micromachining is considered for its advantages of accuracy, no electrode wear, and various ranges of materials that can be machined. An experimental set-up for Electrochemical

R. Thanigaivelan; R. M. Arunachalam

2010-01-01

266

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

267

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

268

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

269

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. 4 figs.

Kronberg, J.W.

1994-05-31

270

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

271

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

272

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

273

High performance cermet electrodes  

DOEpatents

Disclosed is a method of increasing the operating cell voltage of a solid oxide electrochemical cell having metal electrode particles in contact with an oxygen-transporting ceramic electrolyte. The metal electrode is heated with the cell, and oxygen is passed through the oxygen-transporting ceramic electrolyte to the surface of the metal electrode particles so that the metal electrode particles are oxidized to form a metal oxide layer between the metal electrode particles and the electrolyte. The metal oxide layer is then reduced to form porous metal between the metal electrode particles and the ceramic electrolyte.

Isenberg, Arnold O. (Forest Hills Boro, PA); Zymboly, Gregory E. (Penn Hills, PA)

1986-01-01

274

Electronic properties of 1-4, dicyanobenzene and 1-4, phenylene diisocyanide molecules contacted between Pt and Pd electrodes: First-principles study  

NASA Astrophysics Data System (ADS)

Using first-principles calculations, we study the electronic properties of 1-4, dicyanobenzene and 1-4, phenylene diisocyanide molecules sandwiched between two Pt(111) and Pd(111) electrodes. For these metal-molecule-metal systems, we calculate the total and local density of states and the charge transfers. Our results suggest that the tunneling is the dominant mechanism of charge transport. By inducing a shift of the Fermi level of about 2eV via an additional gate electrode, the electronic transmission could be significantly increased through the metal-1-4, phenylene diisocyanide-metal systems, but a higher voltage would be required in the metal-1-4, dicyanobenzene-metal devices.

Morari, C.; Rignanese, G.-M.; Melinte, S.

2007-09-01

275

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

276

Finite element modeling of electrode-skin contact impedance in electrical impedance tomography  

Microsoft Academic Search

In electrical impedance tomography (EIT), the measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through it are both high. Large electrodes were used to provide a more uniform current distribution and reduce the contact impedance. A large electrode differs from a point electrode in that it has shunting and edge effects that

Ping Hua; E. J. Woo; J. G. Webster; W. J. Tompkins

1993-01-01

277

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

278

Local Effects of Biased Electrodes in the Divertor of NSTX  

SciTech Connect

The goal of this paper is to characterize the effects of small non-axisymmetric divertor plate electrodes on the local scrape-off layer plasma. Four small rectangular electrodes were installed into the outer divertor plates of NSTX. When the electrodes were located near the outer divertor strike point and biased positively, there was an increase in the nearby probe currents and probe potentials and an increase in the LiI light emission at the large major radius end of these electrodes. When an electrode located farther outward from the outer divertor strike point was biased positively, there was sometimes a significant decrease in the LiI light emission at the small major radius end of this electrode, but there were no clear effects on the nearby probes. No non-local effects were observed with the biasing of these electrodes.

: S. Zweben, M.D. Campanell, B.C. Lyons, R.J. Maqueda, Y. Raitses, A.L. Roquemore and F. Scotti

2012-05-07

279

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

280

Improved chronic neural stimulation using high surface area platinum electrodes.  

PubMed

We report a novel nano-cluster platinum (NCPt) film that exhibits enhanced performance as an electrode material for neural stimulation applications. Nano-cluster films were deposited using a custom physical vapor deposition process and patterned on a flexible polyimide microelectrode array using semiconductor processing technology. Electrode performance was characterized in vitro using electrochemical impedance spectroscopy and compared with sputtered thinfilm platinum (TFPt) electrodes. We characterized electrode impedance, charge storage capacity, voltage transient properties, and relative surface area enhancement in vitro. Preliminary lifetime testing of the electrode reveals that the NCPt electrodes degrade more slowly than TFPt electrodes. The combination of material biocompatibility, electrochemical performance, and preliminary lifetime results point to a promising new electrode material for neural interface devices. PMID:24109995

Shah, Kedar G; Tolosa, Vanessa M; Tooker, Angela C; Felix, Sarah H; Pannu, Satinderpall S

2013-01-01

281

Electrosynthesis of Cu-Se films on copper electrodes in alkaline media: a voltammetric, electrochemical quartz crystal microbalance and I/t transient study.  

PubMed

The electroformation of Cu-Se phases, obtained by selenizing a thin film of copper deposited on the quartz/gold electrode system, was studied with an electrochemical quartz crystal microbalance (EQCM) and by cyclic voltammetry (CV) in an alkaline solution (0.05 M Na(2)B(4)O(7)) containing selenide ion. Potentiodynamic parameters showed that the formation of the initial Cu-Se phases (Cu(2-x)Se/Cu(3)Se(2)) is ruled by an irreversible diffusion controlled mechanism, where a first electron transfer is the rate-determining step. A CV study was also performed with a bulk copper electrode in 1 M NaOH solution containing selenide ion. The deconvolution of the anodic and cathodic I/E profiles corresponding to the electroformation and electroreduction of the Cu-Se film formed allowed us to establish that, depending on the anodic potential limit of the potentiodynamic scan, the Cu-Se phases formed were either a mixture of Cu(2)(-x)Se/Cu(3)Se(2) or Cu(2-x)Se/Cu(3)Se(2)/CuSe. An EQCM study showed that, during the initial stage of Cu-Se phase electroformation, water molecules were released from the electrode. In advanced stages of the process, when the electrode was completely covered by Cu-Se compounds, selenide anions were adsorbed on the formed phase. When the anodic potential limit was extended to -0.2 V, copper oxide compounds were formed. The analysis of the cathodic charge related to Cu-Se phase electroreduction and Energy Dispersive X-ray Spectroscopy (EDXS) analysis confirmed that when the anodic limit was -0.8 V, a mixture of different Cu-Se phases was formed. A I/t transient study performed with a bulk copper electrode in alkaline solution containing selenide established that the nucleation and growth mechanism (NGM) of the Cu-Se phases takes place through an initial bidimensional-instantaneous nucleation (IN2D), followed by four bidimensional-progressive nucleations (PN2D). These results and atomic force microscopy (AFM) experiences supported that the growth of the Cu-Se films occurs through a layer-by-layer mechanism. PMID:16851343

Córdova, Ricardo; López, Cristina; Orellana, Marco; Grez, Paula; Schrebler, Ricardo; Del Río, Rodrigo

2005-03-01

282

Prevalence of systemic inflammatory response syndrome (SIRS) in hospitalized children: a point prevalence study  

Microsoft Academic Search

BACKGROUND: In accordance with the 1st International pediatric sepsis consensus conference, where sepsis was defined as SIRS associated with suspected or proven infection, we have identified the need to assess the prevalence of SIRS and sepsis in children with abnormal temperatures hospitalized in The Children's Clinical University Hospital in Latvia. METHODS: A descriptive prospective point prevalence study (using two time

Jana Pavare; Ilze Grope; Dace Gardovska

2009-01-01

283

Finite point based numerical study on the unsteady laminar wake behind square cylinders  

Microsoft Academic Search

Purpose – The purpose of this paper is to present numerical study on the behaviour of 2D unsteady incompressible laminar wakes behind square cylinders. Design\\/methodology\\/approach – The numerical method that has been developed is based on a finite point formulation characterised by its weak connectivity requirements. This formulation allows for a patched unstructured approach to computational domain modelling that is

B. Mendez; A. Velazquez

2007-01-01

284

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

285

Interfacial water. The structure of interfacial water on gold electrodes studied by x-ray absorption spectroscopy.  

PubMed

The molecular structure of the electrical double layer determines the chemistry in all electrochemical processes. Using x-ray absorption spectroscopy (XAS), we probed the structure of water near gold electrodes and its bias dependence. Electron yield XAS detected at the gold electrode revealed that the interfacial water molecules have a different structure from those in the bulk. First principles calculations revealed that ~50% of the molecules lie flat on the surface with saturated hydrogen bonds and another substantial fraction with broken hydrogen bonds that do not contribute to the XAS spectrum because their core-excited states are delocalized by coupling with the gold substrate. At negative bias, the population of flat-lying molecules with broken hydrogen bonds increases, producing a spectrum similar to that of bulk water. PMID:25342657

Velasco-Velez, Juan-Jesus; Wu, Cheng Hao; Pascal, Tod A; Wan, Liwen F; Guo, Jinghua; Prendergast, David; Salmeron, Miquel

2014-11-14

286

Electrochemical study on the TiO2 porous electrodes for metal-free dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

Nanocrystalline TiO2 porous electrodes were prepared by screen-printing method in order to efficiently control the fabrication process. TiO2 viscous pastes were prepared from commercial TiO2 nano powder using ethyl cellulose as a porosity controlling agent. A metal-free organic dye (indoline dye D102) was used as a sensitizer. TiO2 porous electrodes with different thicknesses were investigated. The optical and physical properties of the TiO2 films, dye adsorption behavior and performance of dye-sensitized solar cells (DSCs) were investigated systemically. The electronic and ionic processes in DSCs were analysized and discussed by electrochemical impedance spectroscopy (EIS). High conversion efficiencies over 8.00 % under illumination of simulated AM1.5 sunlight (60mW/cm2) were achieved.

Zhang, D. W.; Chen, S.; Li, X. D.; Wang, Z. A.; Shi, J. H.; Sun, Z.; Yin, X. J.; Huang, S. M.

2009-08-01

287

Nanostructured Electrodes For Organic Bulk Heterojunction Solar Cells: Model Study Using Carbon Nanotube Dispersed Polythiophene-fullerene Blend Devices  

SciTech Connect

We test the feasibility of using nanostructured electrodes in organic bulk heterojunction solar cells to improve their photovoltaic performance by enhancing their charge collection efficiency and thereby increasing the optimal active blend layer thickness. As a model system, small concentrations of single wall carbon nanotubes are added to blends of poly(3-hexylthiophene): [6,6]-phenyl-C{sub 61}-butyric acid methyl ester in order to create networks of efficient hole conduction pathways in the device active layer without affecting the light absorption. The nanotube addition leads to a 22% increase in the optimal blend layer thickness from 90 nm to 110 nm, enhancing the short circuit current density and photovoltaic device efficiency by as much as {approx}10%. The associated incident-photon-to-current conversion efficiency for the given thickness also increases by {approx}10% uniformly across the device optical absorption spectrum, corroborating the enhanced charge carrier collection by nanostructured electrodes.

Nam, C.Y.; Wu, Q.; Su, D.; Chiu, C.-y; Tremblay, N.J.; Nuckolls, C,; Black, C.T.

2011-09-19

288

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

289

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

290

A study of electrodeposited negative electrodes for lithium-ion batteries with an emphasis on combinatorial electrodeposition  

NASA Astrophysics Data System (ADS)

When Sn-rich electrodes are cycled in a Li cell to large voltages (>1.4 V) anomalous high-voltage irreversible capacity (AHVIC) can be initiated. AHVIC is detrimental to the cell and should be avoided. A theory describing AHVIC is proposed that teaches ways to eliminate AHVIC. Three ways to avoid AHVIC are: (1) keep the recharge voltage below 1.3 V (vs. Li); (2) cycle the cell at a rate above about 75 mA/cm2 and (3) by alloying Sn with another element (such as Cu). It is shown that advanced negative electrode materials for Li-ion batteries can be made quickly, simply and inexpensively using electrodeposition. In order to investigate a wide range of alloys in a single experiment, combinatorial electrodeposition has been successfully developed and implemented. Electrodes are cut from the composition spread film and tested in Li button cells to determine which composition exhibits both high capacity and good capacity retention. Using combinatorial methods it was determined that a Cu-Sn electrode with 28 atm. % Sn satisfied these criteria. Combinatorial electrodeposition can be applied to many binary systems. Here we look at three binary systems: Cu-Sn, Cu-Zn and Sn-Zn. Composition-spread films were deposited for each system. Composition and crystal structure varied smoothly with position for each system. Combinatorial electrodeposition can also be applied to ternary systems. The Cu-Sn-Zn system is discussed as an example. Combinatorial electrodeposition embodies and even extends the advantages of combinatorial material science: faster, cheaper, better, simpler and scalable. Ingenuity replaces robots and million dollar machines with water guns and buckets.

Beattie, Shane D.

291

AFM studies of the effect of temperature and electric field on the structure of a DMPC-cholesterol bilayer supported on a Au(111) electrode surface.  

PubMed

Atomic force microscopy (AFM) was used to characterize a phospholipid bilayer composed of 70 mol % 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 30 mol % cholesterol, at a Au(111) electrode surface. Results indicate that addition of cholesterol relaxes membrane elastic stress, increases membrane thickness, and reduces defect density. The thickness and thermotropic properties of the mixed DMPC-cholesterol bilayer supported at the gold electrode surface are quite similar to the properties of the mixed membrane in unilamellar vesicles. The stability of the supported membrane at potentials negative to the potential of zero charge E(pzc) was investigated. This study demonstrates that the bilayer supported at the gold electrode surface is stable provided the applied potential (E - E(pzc)) is less than -0.3 V. At larger polarizations, swelling of the membrane is observed. Polarizations larger than -1 V cause electrodewetting of the bilayer from the gold surface. At these negative potentials, the bilayer remains in close proximity to the metal surface, separated from it by a approximately 2 nm thick layer of electrolyte. PMID:19113809

Chen, Maohui; Li, Ming; Brosseau, Christa L; Lipkowski, Jacek

2009-01-20

292

The electroanalysis of mannitol, xylose and lactulose at copper electrodes: voltammetric studies and bioanalysis in human urine by means of HPLC with electrochemical detection.  

PubMed

The electrochemical behavior of mannitol, xylose and lactulose has been investigated at a copper working electrode. A sensitive, accurate and precise method employing HPLC with electrochemical detection in the d.c. amperometric mode, has been developed and validated for the determination of mannitol and lactulose in human urine. The ratio of these probe carbohydrates is altered in conditions that cause damage to the intestinal mucosal barrier. Systematic studies employing cyclic voltammetry indicate that the electrode reaction involves an electrocatalytic oxidation of each carbohydrate in a process yielding a single irreversible anodic wave that is dependent on the ionic strength of the sodium hydroxide supporting electrolyte solution. High performance liquid chromatography with electrochemical detection was performed using a thin-layer cell housing a custom manufactured copper working electrode. The optimized HPLC method can detect 72, 57 and 419 pg of mannitol, xylose and lactulose injected on column, respectively. The corresponding linear calibration ranges are 359 pg-2.24 microgram, 57.4 pg-896 ng and 419 pg-262 ng, respectively. Solid-phase extraction of human urine on polar sorbents, and direct injection after simple 1 + 99 dilution in 0.025 M NaOH were compared for bioanalysis. Direct injection was selected for further method developed as the technique proved robust and simple. The optimized method was validated for the determination of mannitol and lactulose in human urine over the concentration ranges predicted when assessing intestinal permeability (0.25-2.5 mg ml-1 mannitol and 0.05-1.0 mg ml-1 lactulose). Over these ranges intra- and inter-assay bias is < +/- 6.5%, and imprecision (coefficient of variation) is < 9% for each carbohydrate. The validated method provides a useful alternative to HPLC with pulsed-amperometric detection at gold electrodes. PMID:9571539

Wring, S A; Terry, A; Causon, R; Jenner, W N

1998-03-01

293

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

294

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

295

Dielectric elastomer actuators with elastomeric electrodes  

NASA Astrophysics Data System (ADS)

For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.

Bozlar, Michael; Punckt, Christian; Korkut, Sibel; Zhu, Jian; Chiang Foo, Choon; Suo, Zhigang; Aksay, Ilhan A.

2012-08-01

296

Low resistance fuel electrodes  

DOEpatents

An electrode 6 bonded to a solid, ion conducting electrolyte 5 is made, where the electrode 6 comprises a ceramic metal oxide 18, metal particles 17, and heat stable metal fibers 19, where the metal fibers provide a matrix structure for the electrode. The electrolyte 5 can be bonded to an air electrode cathode 4, to provide an electrochemical cell 2, preferably of tubular design.

Maskalick, Nichols J. (Pittsburgh, PA); Folser, George R. (Lower Burrell, PA)

1989-01-01

297

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

298

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

299

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

300

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

301

The ARIES-I high-field-tokamak reactor: Design-point determination and parametric studies  

SciTech Connect

The multi-institutional ARIES study has examined the physics, technology, safety, and economic issues associated with the conceptual design of a tokamak magnetic-fusion reactor. The ARIES-I variant envisions a DT-fueled device based on advanced superconducting coil, blanket, and power-conversion technologies and a modest extrapolation of existing tokamak physics. A comprehensive systems and trade study has been conducted as an integral and ongoing part of the reactor assessment in order to identify an acceptable design point to be subjected to detailed analysis and integration as well as to characterize the ARIES-I operating space. Results of parametric studies leading to the identification of such a design point are presented. 15 refs., 6 figs., 2 tabs.

Miller, R.L.

1989-01-01

302

A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.  

PubMed

Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters. PMID:21828490

Gilbert, C A; Smith, R; Kenny, S D; Murphy, S T; Grimes, R W; Ball, J A

2009-07-01

303

Pain point system scale (PPSS): a method for postoperative pain estimation in retrospective studies  

PubMed Central

Purpose Pain rating scales are widely used for pain assessment. Nevertheless, a new tool is required for pain assessment needs in retrospective studies. Methods The postoperative pain episodes, during the first postoperative day, of three patient groups were analyzed. Each pain episode was assessed by a visual analog scale, numerical rating scale, verbal rating scale, and a new tool – pain point system scale (PPSS) – based on the analgesics administered. The type of analgesic was defined based on the authors’ clinic protocol, patient comorbidities, pain assessment tool scores, and preadministered medications by an artificial neural network system. At each pain episode, each patient was asked to fill the three pain scales. Bartlett’s test and Kaiser–Meyer–Olkin criterion were used to evaluate sample sufficiency. The proper scoring system was defined by varimax rotation. Spearman’s and Pearson’s coefficients assessed PPSS correlation to the known pain scales. Results A total of 262 pain episodes were evaluated in 124 patients. The PPSS scored one point for each dose of paracetamol, three points for each nonsteroidal antiinflammatory drug or codeine, and seven points for each dose of opioids. The correlation between the visual analog scale and PPSS was found to be strong and linear (rho: 0.715; P < 0.001 and Pearson: 0.631; P < 0.001). Conclusion PPSS correlated well with the known pain scale and could be used safely in the evaluation of postoperative pain in retrospective studies. PMID:23152699

Gkotsi, Anastasia; Petsas, Dimosthenis; Sakalis, Vasilios; Fotas, Asterios; Triantafyllidis, Argyrios; Vouros, Ioannis; Saridakis, Evangelos; Salpiggidis, Georgios; Papathanasiou, Athanasios

2012-01-01

304

Single- and Multidimensional Robustness Studies of the NIF Ignition Point Design  

NASA Astrophysics Data System (ADS)

A robustness study of the NIF ignition point-design target is carried out using hydrodynamically equivalent, all-DT direct-drive targets. The direct-drive targets have similar final mass, kinetic energy, implosion velocity, and adiabat of the indirect-drive point design. The direct-drive target has an equivalent one-dimensional ignition-threshold factor [ITF (1-D)] to the indirect-drive point design. A 1-D sensitivity study of ignition is carried out for various hot-spot conditions, gas pressures, and preheat levels. The hot-spot conditions are varied by changing the thermal conductivity. Two-dimensional studies were performed relating the yield over clean (YOC) of a hydro-equivalent THD surrogate target to fusion gain in the DT ignition target. From these studies is found the minimum THD YOC required to demonstrate ignition in the DT campaign. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC02-ER54789 and DE-FC52-08NA28302.

Anderson, K. S.; Betti, R.; Chang, P. Y.; Nora, R.; Shvarts, D.; Fatenejad, M.

2009-11-01

305

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

306

Using GENIE to study a tipping point in the climate system.  

PubMed

We have used the Grid ENabled Integrated Earth system modelling framework to study the archetypal example of a tipping point in the climate system; a threshold for the collapse of the Atlantic thermohaline circulation (THC). eScience has been invaluable in this work and we explain how we have made it work for us. Two stable states of the THC have been found to coexist, under the same boundary conditions, in a hierarchy of models. The climate forcing required to collapse the THC and the reversibility or irreversibility of such a collapse depends on uncertain model parameters. Automated methods have been used to assimilate observational data to constrain the pertinent parameters. Anthropogenic climate forcing leads to a robust weakening of the THC and increases the probability of crossing a THC tipping point, but some ensemble members collapse readily, whereas others are extremely resistant. Hence, we test general methods that have been developed to directly diagnose, from time-series data, the proximity of a 'tipping element', such as the THC to a bifurcation point. In a three-dimensional ocean-atmosphere model exhibiting THC hysteresis, despite high variability in the THC driven by the dynamical atmosphere, some early warning of an approaching tipping point appears possible. PMID:19087945

Lenton, Timothy M; Myerscough, Richard J; Marsh, Robert; Livina, Valerie N; Price, Andrew R; Cox, Simon J; Genie Team

2009-03-13

307

Study of Near-Neighbor Structure of Point Defects in ?-FE by Displacement Cascade  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have been performed to study the primary damage formation in ?-Fe by collision cascades in the recoil energy range 0.5-20 keV. Two near-neighbor analysis methods including the near-neighbor defect density (NPDD) analysis and cluster analysis were introduced to characterize the spatial aggregation of point defects and the morphologies of clusters, respectively. It is found that the NPDD of self-interstitial atom (SIA) and the number of Frenkel pairs show a similar variation trend, while the NPDD of vacancy exhibits a peak at shorter time than that of SIA. Furthermore, we find that the clusters of point defects exist mostly in the form of chainlike structure in the course and the end of cascades, but the proportion of chainlike clusters decreases with increasing the number of point defects included in one cluster. Therefore, the present methods are found to be effective to characterize the aggregation and the near-neighbor structure of point defects by displacement cascades at any time.

Wang, Wei-Lu; Liu, Wei; Wu, Xuebang; Fang, Q. F.; Liu, C. S.; Huang, Qun-Ying; Wu, Y. C.

2012-07-01

308

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

309

Monochromatic imaging studies of a low pressure arc burning on molten Inconel 718 alloy electrodes during vacuum arc remelting  

SciTech Connect

Vacuum arc remelting (VAR) is a melting and solidification process used to produce high quality ingots of chemically reactive or segregation sensitive alloys. Melting is accomplished through the use of a sustained high current (several kiloamperes) dc arc. Energy from the arc is used to melt a consumable electrode (cathode) which is cast from the alloy to be remelted. The molten material drips down into a water-cooled copper crucible (anode) where it solidifies as a larger diameter, homogeneous, porosity-free, cylindrical ingot. Solidification is driven mainly by radial heat extraction from the molten pool atop the ingot and is influenced by magnetically and buoyancy driven fluid flows that are coupled to the arc behavior. The paper reports the initial results of efforts to characterize the VAR furnace arc during remelting of Inconel 718 alloy using monochromatic imaging. This technique allows one to examine how individual atomic species are distributed throughout the arc plasma in the electrode gap. Because only species existing in excited electronic states are able to emit light, the images also give insight into the energy distribution in the gap. Chromium and manganese distributions were investigated. Chromium was chosen to represent one of the major alloy constituents, while manganese represents a highly volatile trace component. 13 refs., 7 figs.

Williamson, R.L.; Zanner, F.J.; Hareland, W.A.

1988-01-01

310

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

311

Electrochemistry at Nanometer-Scaled Electrodes  

ERIC Educational Resources Information Center

Electrochemical studies using nanometer-scaled electrodes are leading to better insights into electrochemical kinetics, interfacial structure, and chemical analysis. Various methods of preparing electrodes of nanometer dimensions are discussed and a few examples of their behavior and applications in relatively simple electrochemical experiments…

Watkins, John J.; Bo Zhang; White, Henry S.

2005-01-01

312

Simultaneous Measurement of Dopamine and Ascorbic Acid at Cnt Electrode  

NASA Astrophysics Data System (ADS)

Electrochemical behaviors of dopamine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for dopamine redox reactions at the carbon nanotube electrode in comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. The important discover was that the carbon nanotube electrode can be used to detect low level of dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution as well.

Hu, C. G.; Wang, W. L.; Feng, B.; Wang, H.

313

Deep brain stimulation electrode anchoring using BioGlue((R)), a protective electrode covering, and a titanium microplate.  

PubMed

The authors present an easily applicable deep brain stimulation (DBS) electrode anchoring technique for use in human and experimental animals. The anchoring technique combines the use of fibrin glue, a two-component surgical adhesive (BioGlue), a protective electrode covering, and a titanium microplate. The BioGlue (CryoLife International, Inc., Kennesaw, GA, USA) hinders unwanted electrode movement during the electrode fixation step and seals the burr hole, while the protective electrode covering protects the electrode under the titanium microplate which keeps the electrode in a permanent position. The described technique further has the advantage of being cosmetically acceptable to the human patient, and furthermore it perfectly adapts to the smaller and irregular-shaped skull in experimental animals. The described technique has clinically been used to implant DBS-electrodes in the subthalamic nucleus for Parkinson disease and is the preferred DBS-electrode anchoring technique for our experimental DBS-studies in the Göttingen minipig. PMID:17953993

Bjarkam, Carsten R; Jorgensen, Rasmus L; Jensen, Kristian N; Sunde, Niels Aa; Sørensen, Jens-Christian H

2008-02-15

314

Auricular Point Acupressure for Chronic Low Back Pain: A Feasibility Study for 1-Week Treatment  

PubMed Central

Objectives. The objective of this one-group, repeated-measures design was to explore the acceptance of auricular point acupressure (APA) to reduce chronic low back pain (CLBP) and estimate minimum clinically important differences (MCIDs) for pain intensity change. Methods. Subjects received 7-day APA treatment. After appropriate acupoints were identified, vaccaria seeds were carefully taped onto each selected auricular point for 7-day. The Brief Pain Inventory Short Form (BPI) was used to collect outcome data. Results. A total of 74 subjects participated in the study. Ten subjects dropped out and the retention rate was 87%. Subjects reported a 46% reduction in BPI worst pain, and over 50% reduction in BPI average pain, overall pain severity and pain interference by the end of study, and 62.5% subjects also reported less pain medication use. The MCIDs for the subscale of BPI ranged from .70 to 1.86 points. The percentage improvement of MCIDs from baseline was between 14.5–24.9%. Discussion. APA appears to be highly acceptable to patients with CLBP. A sham group is needed in order to differentiate the true effects of APA from the possible psychological effects of more frequent visits by the auricular therapist and patients' expectation of the APA treatment. PMID:22811745

Yeh, Chao-Hsing; Chien, Lung-Chang; Chiang, Yi-Chien; Huang, Li-Chun

2012-01-01

315

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.

Murphy, Jr., Robert J. (Bellaire, TX); Jamison, Dale E. (Humble, TX)

1986-01-01

316

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

317

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

318

Enhancing generalisation in biofeedback intervention using the challenge point framework: A case study.  

PubMed

Abstract 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; Mcallister Byun, Tara

2015-01-01

319

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

320

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

321

Robust tracking of a virtual electrode on a coronary sinus catheter for atrial fibrillation ablation procedures  

NASA Astrophysics Data System (ADS)

Catheter tracking in X-ray fluoroscopic images has become more important in interventional applications for atrial fibrillation (AF) ablation procedures. It provides real-time guidance for the physicians and can be used as reference for motion compensation applications. In this paper, we propose a novel approach to track a virtual electrode (VE), which is a non-existing electrode on the coronary sinus (CS) catheter at a more proximal location than any real electrodes. Successful tracking of the VE can provide more accurate motion information than tracking of real electrodes. To achieve VE tracking, we first model the CS catheter as a set of electrodes which are detected by our previously published learning-based approach.1 The tracked electrodes are then used to generate the hypotheses for tracking the VE. Model-based hypotheses are fused and evaluated by a Bayesian framework. Evaluation has been conducted on a database of clinical AF ablation data including challenging scenarios such as low signal-to-noise ratio (SNR), occlusion and nonrigid deformation. Our approach obtains 0.54mm median error and 90% of evaluated data have errors less than 1.67mm. The speed of our tracking algorithm reaches 6 frames-per-second on most data. Our study on motion compensation shows that using the VE as reference provides a good point to detect non-physiological catheter motion during the AF ablation procedures.2

Wu, Wen; Chen, Terrence; Strobel, Norbert; Comaniciu, Dorin

2012-02-01

322

Cooling of extraction electrode of an ion source in long-pulse operation.  

PubMed

Experimental studies were made on the cooling of extraction electrodes of an ion source in the case of long-pulse operation. Copper electrodes with forced water cooling pipes were tested under the condition that an ion beam of 1 to 5 A at 30 keV was extracted for up to 10 s. The average heat loading to the grid are of the electrode was as high as 130 W/cm2. This high heat flux was obtained by a set of electrodes artificially arranged to produce poor beam optics, and hence the high heat loading. Temperature of the ground electrode was measured at two points by thermocouples buried and silver brazed in it, and was kept below 230 degrees C due to a large boiling heat transfer coefficient of the cooling water. No evidences of deformation or deterioration of the electrodes was observed after repetitious beam extraction. This heat loading was still a half of that on the grid of the ion source for the JT-60 NBI. PMID:18699409

Horiike, H; Kondoh, U; Morita, H; Shirakata, H; Sugawara, T; Tanaka, S

1979-11-01

323

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

324

Acupuncture at local and distant points for tinnitus: study protocol for a randomized controlled trial  

PubMed Central

Background Tinnitus is the perception of a sound in the absence of an objective physical source. Up to now, there is no generally accepted view how these phantom sounds come about, and also no efficient treatment. Patients are turning to complementary or alternative medical therapies, such as acupuncture. Based on the theory of traditional Chinese medicine, acupoints located on both the adjacent and distal area of the disease can be needled to treat disease. Furthermore, the way of combining acupoints is for strengthening the curative effect. We aim to evaluate the efficacy of acupuncture at local points in combination with distal points in subjective tinnitus patients. Method This trial is a randomized, single-blind, controlled study. A total of 112 participants will be randomly assigned to one of four treatment groups receiving acupuncture treatment for 4 weeks. The primary outcome measure is subjective tinnitus loudness and annoyance perception, which is graded using the Visual Analogue Scale (VAS). The assessment is at baseline (before treatment initiation), 4 weeks after the first acupuncture session, and 8 weeks after the first acupuncture session. Discussion Completion of this trial will help to identify whether acupuncture at local acupoints in combination with distal acupoints may be more effective than needling points separately. Trial registration International Standard Randomized Controlled Trial Number Register: ISRCTN29230777 PMID:23176350

2012-01-01

325

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

326

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

327

Experimental study of the expansion dynamic of 9 mm Parabellum hollow point projectiles in ballistic gelatin.  

PubMed

We study in this paper the expanding behaviour of hollow point 9 mm Parabellum projectiles (Hornady XTP(®) and Speer Gold Dot(®)). We defined a deformation rate that takes into account both the diameter increase and the length reduction. We plotted the behaviour of this parameter versus impact velocity (we refer to this curve as the expanding law). This expanding law has been plotted for different gelatin weight ratios and different gelatin block lengths. We completed our experiments with a set of high speed movies in order to correlate the deceleration to the state of expansion and size of the temporary cavity. Our results pointed out that full expansion is reached shortly after the projectile fully penetrates the gelatin. This result shows that the key point to accurately simulate human body interaction with a hollow point projectile is to accurately simulate the interface (skin, skull, clothes thoracic walls). Simulating accurately organs is only an issue if a quantitative comparison between penetration depths is required, but not if we only focus on the state of expansion of the projectile. By varying the gelatin parameters, we discovered that the expanding law exhibits a velocity threshold below which no expansion occurs, followed by a rather linear curve. The parameters of that expanding law (velocity threshold and line slope) vary with the gelatin parameters, but our quantitative results demonstrate that these parameters are not extremely critical. Finally, our experiments demonstrate that the knowledge of the expansion law can be a useful tool to investigate a gunshot in a human body with a semi-jacketed projectile, giving an estimation of the impact velocity and thus the shooting distance. PMID:22269130

Bresson, F; Ducouret, J; Peyré, J; Maréchal, C; Delille, R; Colard, T; Demondion, X

2012-06-10

328

Bending properties of nickel electrodes for nickel-hydrogen batteries  

NASA Technical Reports Server (NTRS)

Recent changes in manufacturing have resulted in nickel-hydrogen batteries which fail prematurely by electrical shorting. This is believed to be a result of a blistering problem in the nickel electrodes. This study investigates the bending properties of nickel electrodes in an attempt to correlate the bending properties with the propensity of the electrode to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. Effects of specimen curvature and position within the electrode on the bending strength were studied and within-electrode and batch-to-batch variation were addressed. Two color imaging techniques were employed which allowed differentiation of phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hydroxide surface loading on each electrode, relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading.

Lerch, Bradley

1995-01-01

329

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

330

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

331

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

332

First-principles study of point defects in solar cell semiconductor CuI  

NASA Astrophysics Data System (ADS)

Hybrid density functional theory is used to study the formation energies and transition levels of point defects VCu, VI, ICu, CuI, and OI in CuI. It is shown that the Heyd-Scuseria-Ernzerhof (HSE06) method can accurately describe the band gap of bulk CuI. As a solar cell material, we find that p-type semiconductor CuI can be obtained under the iodine-rich and copper-poor conditions. Our results are in good agreement with experiment and provide an excellent account for tuning the structural and electronic properties of CuI.

Chen, Hui; Wang, Chong-Yu; Wang, Jian-Tao; Wu, Ying; Zhou, Shao-Xiong

2013-03-01

333

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

334

The Friedmann universe of dust by Regge Calculus: study of its ending point  

E-print Network

We develop an evolution scheme, based on Sorkin algorithm, to evolve the most complex regular tridimensional polytope, the 600-cell. This application has been already studied before and all authors found a stop point for the evolution of the spatial section. In our opinion a clear and satisfactory meaning to this behaviour has not been given. In this paper we propose a reason why the evolution of the 600-cell stops when its volume is still far from 0. We find that the 600-cell meets a causality-breaking singularity of space-time. We study the nature of this singularity by embedding the 600-cell into a five-dimensional Lorentzian manifold. We fit 600-cell's evolution with a continuos metric and study it as a solution of Einstein equations.

A. De Felice; E. Fabri

2000-09-27

335

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...

336

Electricity Production by Geobacter sulfurreducens Attached to Electrodes  

Microsoft Academic Search

Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained

Daniel R. Bond; Derek R. Lovley

2003-01-01

337

Microbead-based electrochemical immunoassay with interdigitated array electrodes  

Microsoft Academic Search

The objective of this study was to develop a sensitive and miniaturized immunoassay by coupling a microbead-based immunoassay with an interdigitated array (IDA) electrode. An IDA electrode amplifies the signal by recycling an electrochemically redox-reversible molecule. The microfabricated platinum electrodes had 25 pairs of electrodes with 1.6-?m gaps and 2.4-?m widths. An enzyme-labeled sandwich immunoassay on paramagnetic microbeads with mouse

Jennifer H Thomas; Sang Kyung Kim; Peter J Hesketh; H. Brian Halsall; William R Heineman

2004-01-01

338

Ear acupuncture and fMRI: a pilot study for assessing the specificity of auricular points.  

PubMed

In recent years research explored different acupuncture stimulation techniques but interest has focused primarily on somatic acupuncture and on a limited number of acupoints. As regards ear Acupuncture (EA) there is still some criticism about the clinical specificity of auricular points/areas representing organs or structures of the body. The aim of this study was to verify through (Functional magnetic resonance imaging) fMRI the hypothesis of EA point specificity using two auricular points having different topographical locations and clinical significance. Six healthy volunteers underwent two experimental fMRI sessions: the first was dedicated to the stimulation of Thumb Auricular Acupoint (TAA) and the second to the stimulation of Brain Stem Auricular Acupoint (BSAA). The stimulation of the needle placed in the TAA of the left ear produced an increase in activation bilaterally in the parietal operculum, region of the secondary somatosensory area SII. Stimulation of the needle placed in the BSAA of the left ear showed a pattern that largely overlapped regions belonging to the pain matrix, as shown to be involved in previous somatic acupuncture studies but with local differences in the left amygdala, anterior cingulate cortex, and cerebellum. The differences in activation patterns between TAA and BSAA stimulation support the specificity of the two acupoints. Moreover, the peculiarity of the regions involved in BSAA stimulation compared to those involved in the pain matrix, is in accordance with the therapeutic indications of this acupoint that include head pain, dizziness and vertigo. Our results provide preliminary evidence on the specificity of two auricular acupoints; further research is warranted by means of fMRI both in healthy volunteers and in patients carrying neurological/psychiatric syndromes. PMID:24867864

Romoli, M; Allais, G; Airola, G; Benedetto, C; Mana, O; Giacobbe, M; Pugliese, A M; Battistella, G; Fornari, E

2014-05-01

339

Optimal geometry toward uniform current density electrodes  

NASA Astrophysics Data System (ADS)

Electrodes are commonly used to inject current into the human body in various biomedical applications such as functional electrical stimulation, defibrillation, electrosurgery, RF ablation, impedance imaging, and so on. When a highly conducting electrode makes direct contact with biological tissues, the induced current density has strong singularity along the periphery of the electrode, which may cause painful sensation or burn. Especially in impedance imaging methods such as the magnetic resonance electrical impedance tomography, we should avoid such singularity since more uniform current density underneath a current-injection electrode is desirable. In this paper, we study an optimal geometry of a recessed electrode to produce a well-distributed current density on the contact area under the electrode. We investigate the geometry of the electrode surface to minimize the edge singularity and produce nearly uniform current density on the contact area. We propose a mathematical framework for the uniform current density electrode and its optimal geometry. The theoretical results are supported by numerical simulations.

Song, Yizhuang; Lee, Eunjung; Woo, Eung Je; Seo, Jin Keun

2011-07-01

340

Manufacturing process and electrode properties of palladium-electroded ionic polymer-metal composite  

NASA Astrophysics Data System (ADS)

This paper primarily focuses on the manufacturing process of palladium-electroded ionic polymer-metal composite (IPMC). First, according to the special properties of Pd, many experiments were done to determine several specific procedures, including the addition of a reducing agent and the time consumed. Subsequently, the effects of the core manufacturing steps on the electrode morphology were revealed by scanning electron microscopy studies of 22 IPMC samples treated with different combinations of manufacturing steps. Finally, the effects of electrode characteristics on the electromechanical properties, including the sheet resistivity, the elastic modulus and the electro-active performance, of IPMCs were evaluated experimentally and analyzed according to the electrode morphology.

Chang, Longfei; Chen, Hualing; Zhu, Zicai; Li, Bo

2012-06-01

341

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

342

Electrostatic curved electrode actuators  

Microsoft Academic Search

This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model

Rob Legtenberg; John Gilbert; Stephen D. Senturia; Miko Elwenspoek

1997-01-01

343

Electrostatic curved electrode actuators  

Microsoft Academic Search

In this paper, the design, fabrication, and first experimental results of electrostatic curved electrode actuators are addressed. The actuator design is based upon the deformation of a movable micromechanical structure by electrostatic forces using a fixed curved electrode. When a voltage is applied, an electrostatic force is created that will deform the free structure along the outline of the fixed

Rob Legtenberg; Erwin Berenschot; Miko Elwenspoek; J. H. J. Fluitman

1995-01-01

344

Spinal Cord Electrophysiology II: Extracellular Suction Electrode Fabrication  

PubMed Central

Development of neural circuitries and locomotion can be studied using neonatal rodent spinal cord central pattern generator (CPG) behavior. We demonstrate a method to fabricate suction electrodes that are used to examine CPG activity, or fictive locomotion, in dissected rodent spinal cords. The rodent spinal cords are placed in artificial cerebrospinal fluid and the ventral roots are drawn into the suction electrode. The electrode is constructed by modifying a commercially available suction electrode. A heavier silver wire is used instead of the standard wire given by the commercially available electrode. The glass tip on the commercial electrode is replaced with a plastic tip for increased durability. We prepare hand drawn electrodes and electrodes made from specific sizes of tubing, allowing consistency and reproducibility. Data is collected using an amplifier and neurogram acquisition software. Recordings are performed on an air table within a Faraday cage to prevent mechanical and electrical interference, respectively. PMID:21372792

Garudadri, Suresh; Gallarda, Benjamin; Pfaff, Samuel; Alaynick, William

2011-01-01

345

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

346

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

347

Comprehensive study of the conditions for obtaining hydrogenated amorphous erbium- and oxygen-doped silicon suboxide films, a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket , by dc-magnetron deposition  

SciTech Connect

The results of a comprehensive study of the conditions for growing a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films are presented. The effect of the composition of various erbium-containing targets (a-SiO{sub x}:H , ErO{sub x}, Er{sub 2}SiO{sub 5}, Er{sub 2}O{sub 3}, and Er), substrate temperature, and annealing temperatures in argon, air, and under conditions of SiH{sub 4} + Ar + O{sub 2} plasma glow is studied. In order to obtain a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films with the highest photoluminescence intensity of erbium ions, it is recommended for the following technological conditions to be used: the substrate holder should be insulated from dc-magnetron electrodes and the working gas mixture should include silane, argon, and oxygen. Single-crystal silicon and metal erbium should be used as targets. The erbium target should be placed only in the Si-target erosion zone.

Undalov, Yu. K., E-mail: undalov@mail.ioffe.ru; Terukov, E. I.; Gusev, O. B. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Lebedev, V. M. [Russian Academy of Sciences, Konstantinov Saint Petersburg Institute of Nuclear Physics (Russian Federation); Trapeznikova, I. N. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-12-15

348

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

349

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

350

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

351

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

352

Young’s Modulus Reconstruction for Radio-frequency Ablation Electrode-induced Displacement Fields: A Feasibility Study  

PubMed Central

Radiofrequency (RF) ablation is a minimally invasive treatment for tumors in various abdominal organs. It is effective if good tumor localization and intra-procedural monitoring can be done. In this paper, we investigate the feasibility of using an ultrasound-based Young’s modulus reconstruction algorithm to image an ablated region whose stiffness is elevated due to tissue coagulation. To obtain controllable tissue deformations for abdominal organs during and/or intermediately after the RF ablation, the proposed modulus imaging method is specifically designed for using tissue deformation fields induced by the RF electrode. We have developed a new scheme under which the reconstruction problem is simplified to a two-dimensional problem. Based on this scheme, an iterative Young’s modulus reconstruction technique with edge-preserving regularization was developed to estimate the Young’s modulus distribution. The method was tested in experiments using a tissue-mimicking phantom and on ex vivo bovine liver tissues. Our preliminary results suggest that high contrast modulus images can be successfully reconstructed. In both experiments, the geometries of the reconstructed modulus images of thermal ablation zones match well with the phantom design and the gross pathology image, respectively. PMID:19258195

Jiang, Jingfeng; Varghese, Tomy; Brace, Chris L.; Madsen, Ernest L.; Hall, Timothy J.; Bharat, Shyam; Hobson, Maritza A.; Zagzebski, James A.; Lee, Fred T.

2009-01-01

353

Oxidation of carbon monoxide at a platinum film electrode studied by Fourier transform infrared spectroscopy with attenuated total reflection technique  

SciTech Connect

Fourier transform infrared reflection absorption spectroscopy with the attenuated total reflection technique (ATR-FTIR), coupled with cyclic voltammetry (CV) measurement, is used to observe the oxidation process of adsorbed CO at Pt film sputtered on a silicon prism. The interesting bipolar shape of the linearly bonded CO band is observed at high coverage of CO, although no CO band is included in the reference spectrum. This asymmetric shape is ascribed to Fano resonance. In addition to a linear CO and bridged CO, a new absorption band presumably assigned to a carboxyl radical, was detected. This band may be formed by a heterogeneous reaction between adsorbed CO and H{sub 2}O on the Pt surface in the hydrogen adsorption potential region. The adsorbed carboxyl radical was oxidized at a less positive potential than the adsorbed CO, which can be ascribed to a presumable origin for the pre-peak that appeared in a CV reading prior to the oxidation of such a linear or bridged CO. This oxidation led to the rearrangement of CO ad-layers, especially at high coverage of CO. In the case of the low coverage of CO, the conversion from the bridged CO to the linear CO is ascribed to the potential induced electronic effects of the electrode surface on the adsorption states. A consumption of adsorbed H{sub 2}O and a production of CO{sub 2} were also clearly indicated by the spectroscopy when COOH of CO disappeared from the surface.

Zhu, Yimin; Uchida, Hiroyuki; Watanabe, Masahiro

1999-12-07

354

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

355

Low consistency of four brain connectivity measures derived from intracranial electrode measurements.  

PubMed

Measures of brain connectivity are currently subject to intense scientific and clinical interest. Multiple measures are available, each with advantages and disadvantages. Here, we study epilepsy patients with intracranial electrodes, and compare four different measures of connectivity. Perhaps the most direct measure derives from intracranial electrodes; however, this is invasive and spatial coverage is incomplete. These electrodes can be actively stimulated to trigger electrophysical responses to provide the first measure of connectivity. A second measure is the recent development of simultaneous BOLD fMRI and intracranial electrode stimulation. The resulting BOLD maps form a measure of effective connectivity. A third measure uses low frequency BOLD fluctuations measured by MRI, with functional connectivity defined as the temporal correlation coefficient between their BOLD waveforms. A fourth measure is structural, derived from diffusion MRI, with connectivity defined as an integrated diffusivity measure along a connecting pathway. This method addresses the difficult requirement to measure connectivity between any two points in the brain, reflecting the relatively arbitrary location of the surgical placement of intracranial electrodes. Using a group of eight epilepsy patients with intracranial electrodes, the connectivity from one method is compared to another method using all paired data points that are in common, yielding an overall correlation coefficient. This method is performed for all six paired-comparisons between the four methods. While these show statistically significant correlations, the magnitudes of the correlation are relatively modest (r (2) between 0.20 and 0.001). In summary, there are many pairs of points in the brain that correlate well using one measure yet correlate poorly using another measure. These experimental findings present a complicated picture regarding the measure or meaning of brain connectivity. PMID:25566178

Jones, Stephen E; Beall, Erik B; Najm, Imad; Sakaie, Ken E; Phillips, Michael D; Zhang, Myron; Gonzalez-Martinez, Jorge A

2014-01-01

356

Low Consistency of Four Brain Connectivity Measures Derived from Intracranial Electrode Measurements  

PubMed Central

Measures of brain connectivity are currently subject to intense scientific and clinical interest. Multiple measures are available, each with advantages and disadvantages. Here, we study epilepsy patients with intracranial electrodes, and compare four different measures of connectivity. Perhaps the most direct measure derives from intracranial electrodes; however, this is invasive and spatial coverage is incomplete. These electrodes can be actively stimulated to trigger electrophysical responses to provide the first measure of connectivity. A second measure is the recent development of simultaneous BOLD fMRI and intracranial electrode stimulation. The resulting BOLD maps form a measure of effective connectivity. A third measure uses low frequency BOLD fluctuations measured by MRI, with functional connectivity defined as the temporal correlation coefficient between their BOLD waveforms. A fourth measure is structural, derived from diffusion MRI, with connectivity defined as an integrated diffusivity measure along a connecting pathway. This method addresses the difficult requirement to measure connectivity between any two points in the brain, reflecting the relatively arbitrary location of the surgical placement of intracranial electrodes. Using a group of eight epilepsy patients with intracranial electrodes, the connectivity from one method is compared to another method using all paired data points that are in common, yielding an overall correlation coefficient. This method is performed for all six paired-comparisons between the four methods. While these show statistically significant correlations, the magnitudes of the correlation are relatively modest (r2 between 0.20 and 0.001). In summary, there are many pairs of points in the brain that correlate well using one measure yet correlate poorly using another measure. These experimental findings present a complicated picture regarding the measure or meaning of brain connectivity. PMID:25566178

Jones, Stephen E.; Beall, Erik B.; Najm, Imad; Sakaie, Ken E.; Phillips, Michael D.; Zhang, Myron; Gonzalez-Martinez, Jorge A.

2014-01-01

357

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

358

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

359

Automatic Correspondence on Medical Images: A Comparative Study of Four Methods for Allocating Corresponding Points  

Microsoft Academic Search

The accurate estimation of point correspondences is often required in a wide variety of medical image-processing applications.\\u000a Numerous point correspondence methods have been proposed in this field, each exhibiting its own characteristics, strengths,\\u000a and weaknesses. This paper presents a comprehensive comparison of four automatic methods for allocating corresponding points,\\u000a namely the template-matching technique, the iterative closest points approach, the correspondence

Theodore Economopoulos; Pantelis A. Asvestas; George K. Matsopoulos

2010-01-01

360

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

361

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

362

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

363

Point-contact study of soft magnetic CoSiBFeNb amorphous alloys  

NASA Astrophysics Data System (ADS)

We study magnetotransport in nanoscale point contacts to soft magnetic CoSiBFeNb ribbons. Such ultrasoft amorphous alloys attracted considerable attention previously because they exhibit Giant Magnetoimpedance (GMI) effect - large variations in the electrical impedance as a function of an external magnetic field [see, for instance, M.-H. Phan, H.-X. Peng, Prog. Mater. Sci. 53, 323 (2008) and references therein]. GMI is attributed to the field-induced variations in alloy permeability and has been established through ac measurements on bulk samples which revealed a strong dependence on ac frequency and amplitude but did not show any variations in dc resistance at all. In our experiments, we use nanocontacts to probe magnetotransport in amorphous CoSiBFeNb at the nanoscale. We use point contacts to inject both ac and dc currents into the alloy ribbons prepared by a melt-spinning technique. Measurements with ac currents revealed GMIs similar to those in macroscopic samples. Interestingly, we also observe a dc magnetoresistance which may be attributed to magnetic domain reorientations in a small contact region. Effects of high dc densities on the magnetoresistance are discussed in terms of spin-transfer torque (STT) effect. We thank A. Serebryakov for providing ribbon samples.

Seinige, Heidi; Wang, Cheng; Tsoi, Valerii; Tsoi, Maxim

2013-03-01

364

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

365

Mass Transport and Potential Studies in a Flow-through Porous Electrode Reactor. A Comparative Study of Reticulated Vitreous Carbon and Graphite Felt Used as Cathode  

Microsoft Academic Search

This paper deals with the use of reticulated vitreous carbon (RVC) and graphite felt (GF) as porous electrode for the removal of 20 ppm Cu(II) in 0.5 mol dm -3 Na 2SO 4 at pH 2 (which resembles a rinsing wastewater generated by a plating industry). The experimental mass transport characterization (k ma = bu c ) showed that for

J. L. Nav; A. Recéndiz; L. G. González; G. Carreño; F. Martínez

366

Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes  

PubMed Central

Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Zt) and access resistance (Ra) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between Ra and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation suggesting that the level of stimulation applied was creating localised changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation. PMID:21572219

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Seligman, Peter; Cowan, Robert; Shepherd, Robert

2011-01-01

367

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

368

Study of PTCDI-C12H25-based organic thin film transistors with bottom contact electrode  

NASA Astrophysics Data System (ADS)

A n-type organic semiconductor, N,N'-didodecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C12H25), film crystallizes on various temperature substrates to act as active layer of organic thin-film transistors (OTFTs). The nuclear magnetic resonance 1-D hydrogen spectroscopy (1H-NMR) was used to analyze molecular structure of the PTCDI-C12H25 which was synthesized by us. When the transistors was fabricated on room temperature substrate, the field-effect mobility of the device was about half of that of the transistor fabricated on high temperature substrate. Furthermore, x-ray diffraction analysis gave an account that the higher temperature substrate provided better epitaxial environment for PTCDI-C12H25 thin film growth. The grain size of PTCDI-C12H25 thin films deposited on room temperature and 100 °C substrates were 24.8 and 35.6 nm, respectively, which analyzed by paracrystalline theory. We base that larger grain results in better carrier transport in organic films on the grain boundary model which assumed that the boundary of grain will trap charge carriers when they pass through these grains, and the quality differences of microstructural within a grain can be neglected. The PTCDI-C12H25 based OTFTs were achieved high performances, such as field-effect mobility of 0.10 cm2V-1s -1, threshold voltage 14.5 V, on-off ratio 3.01 × 106 and subthreshold swing 1.24 V/dec, when the active layer was grown under substrate temperature of 100 °C. Additionally, contact resistance analysis reveals that PTCDI-C12H25 thin film on 100 °C substrate has better interface between organic thin film and electrode.

Lin, Yi-Sheng; Chou, Wei-Yang; Chen, Lin-Ni; Cheng, Yao-Chien; Cheng, Horng-Long; Liu, Shyh-Jiun; Tang, Fu-Ching; Yen, Chia-Te

2010-08-01

369

Measuring electrode assembly  

DOEpatents

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture. 2 figs.

Bordenick, J.E.

1988-04-26

370

Measuring electrode assembly  

DOEpatents

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture.

Bordenick, John E. (West Mifflin, PA)

1989-01-01

371

Genetic thinking in the study of social relationships: Five points of entry  

PubMed Central

For nearly a generation, researchers studying human behavioral development have combined genetically informed research designs with careful measures of social relationships: parenting, sibling relationships, peer relationships, marital processes, social class stratifications and patterns of social engagement in the elderly. In what way have these genetically informed studies altered the construction and testing of social theories of human development? We consider five points where genetic thinking is taking hold. First, genetic findings suggest an alternative scenario for explaining social data. Associations between measures of the social environment and human development may be due to genes that influence both. Second, genetic studies add to other prompts to study the early developmental origins of current social phenomena in mid-life and beyond. Third, genetic analyses promise to bring to the surface understudied social systems, such as sibling relationships, that have an impact on human development independent of genotype. Fourth, genetic analyses anchor in neurobiology individual differences in resilience and sensitivity to both adverse and favorable social environments. Finally, genetic analyses increase the utility of laboratory simulations of human social processes and of animal models. PMID:25419225

Reiss, David

2014-01-01

372

Study of the Electrocatalytic Activity of Cerium Oxide and Gold-Studded Cerium Oxide Nanoparticles Using a Sonogel-Carbon Material as Supporting Electrode: Electroanalytical Study in Apple Juice for Babies  

PubMed Central

The present work reports a study of the electrocatalytic activity of CeO2 nanoparticles and gold sononanoparticles (AuSNPs)/CeO2 nanocomposite, deposited on the surface of a Sonogel-Carbon (SNGC) matrix used as supporting electrode and the application of the sensing devices built with them to the determination of ascorbic acid (AA) used as a benchmark analyte. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrocatalytic behavior of CeO2- and AuSNPs/CeO2-modified SNGC electrodes, utilizing different concentrations of CeO2 nanoparticles and different AuSNPs:CeO2 w/w ratios. The best detection and quantification limits, obtained for CeO2 (10.0 mg·mL?1)- and AuSNPs/CeO2 (3.25% w/w)-modified SNGC electrodes, were 1.59 × 10?6 and 5.32 × 10?6 M, and 2.93 × 10?6 and 9.77 × 10?6 M, respectively, with reproducibility values of 5.78% and 6.24%, respectively, for a linear concentration range from 1.5 ?M to 4.0 mM of AA. The electrochemical devices were tested for the determination of AA in commercial apple juice for babies. The results were compared with those obtained by applying high performance liquid chromatography (HPLC) as a reference method. Recovery errors below 5% were obtained in most cases, with standard deviations lower than 3% for all the modified SNGC electrodes. Bare, CeO2- and AuSNPs/CeO2-modified SNGC electrodes were structurally characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). AuSNPs and AuSNPs/CeO2 nanocomposite were characterized by UV-vis spectroscopy and X-ray diffraction (XRD), and information about their size distribution and shape was obtained by transmission electron microscopy (TEM;. The advantages of employing CeO2 nanoparticles and AuSNPs/CeO2 nanocomposite in SNGC supporting material are also described. This research suggests that the modified electrode can be a very promising voltammetric sensor for the determination of electroactive species of interest in real samples. PMID:23584124

Abdelrahim, M. Yahia M.; Benjamin, Stephen R.; Cubillana-Aguilera, Laura Ma; Naranjo-Rodríguez, Ignacio; Hidalgo-Hidalgo de Cisneros, Josè L.; Delgado, Juan Josè; Palacios-Santander, Josè Ma

2013-01-01

373

Multifunctional reference electrode  

DOEpatents

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Redey, Laszlo (Lisle, IL); Vissers, Donald R. (Naperville, IL)

1983-01-01

374

Multifunctional reference electrode  

DOEpatents

A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell are described. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

Redey, L.; Vissers, D.R.

1981-12-30

375

AMTEC electrode development  

NASA Technical Reports Server (NTRS)

The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-alumina solid electrolyte. Progress is reported on a long life, high power, porous electrode. Two electrode compositions were identified which have the potential for long life operation at power densities above 0.5 W/sq cm. Longer lifetime testing is being initiated. Successful optimization and demonstration of very long lifetimes for these electrodes will be a major step toward establishing the feasibility of AMTEC space power systems.

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

1987-01-01

376

Access resistance of stimulation electrodes as a function of electrode proximity to the retina.  

PubMed

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. PMID:25474329

Majdi, Joseph A; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D

2015-02-01

377

Relationship between intracortical electrode design and chronic recording function.  

PubMed

Intracortical electrodes record neural signals directly from local populations of neurons in the brain, and conduct them to external electronics that control prosthetics. However, the relationship between electrode design, defined by shape, size and tethering; and long-term (chronic) stability of the neuron-electrode interface is poorly understood. Here, we studied the effects of various commercially available intracortical electrode designs that vary in shape (cylindrical, planar), size (15 ?m, 50 ?m and 75 ?m), and tethering [electrode connections to connector with (tethered) and without tethering cable (untethered)] using histological, transcriptomic, and electrophysiological analyses over acute (3 day) and chronic (12 week) timepoints. Quantitative analysis of histological sections indicated that Michigan 50 ?m (M50) and Michigan tethered (MT) electrodes induced significantly (p < 0.01) higher glial scarring, and lesser survival of neurons in regions of blood-brain barrier (BBB) breach when compared to microwire (MW) and Michigan 15 ?m (M15) electrodes acutely and chronically. Gene expression analysis of the neurotoxic cytokines interleukin (Il)1 (Il1?, Il1?), Il6, Il17 (Il17a, Il17b, Il17f), and tumor necrosis factor alpha (Tnf) indicated that MW electrodes induced significantly (p < 0.05) reduced expression of these transcripts when compared to M15, M50 and FMAA electrodes chronically. Finally, electrophysiological assessment of electrode function indicated that MW electrodes performed significantly (p < 0.05) better than all other electrodes over a period of 12 weeks. These studies reveal that intracortical electrodes with smaller size, cylindrical shape, and without tethering cables produce significantly diminished inflammatory responses when compared to large, planar and tethered electrodes. These studies provide a platform for the rational design and assessment of chronically functional intracortical electrode implants in the future. PMID:23891081

Karumbaiah, Lohitash; Saxena, Tarun; Carlson, David; Patil, Ketki; Patkar, Radhika; Gaupp, Eric A; Betancur, Martha; Stanley, Garrett B; Carin, Lawrence; Bellamkonda, Ravi V

2013-11-01

378

Understanding performance and corrosion behavior of photo-electrode in terms of energetics of water-derived radicals on Ga-V (V=N,P,As) and GaP:N (110) surfaces: First-principles study  

NASA Astrophysics Data System (ADS)

Holes supplied from sunlight will detach the hydrogen atoms of H2O as protons, leaving energetic O, H, or OH radicals. Therefore energetics of water-derived radicals on photo-electrode surface is important factor which determine its performance. Based on first-principles electronic structure and total energy calculations, we have studied reactions of -H, -O and -OH on the (110) surface of photo-cathode Ga-V and GaP:N materials, where V is N, P, and As. Zero-point energy and chemical potential of H2 and O2 gases are considered after static calculations. We have found that atomic oxygen on the GaN surface prefers being detached as O2 to forming Ga-O. On the other hand, GaP and GaAs surfaces can have a strong Ga-O bond, hindering formation of O2 gas and thus promoting surface corrosion. On GaP and GaAs surfaces hydrogen easily evolves as H2 gas but on GaN not. Doped nitrogen in GaP to improve corrosion resistivity are tend to be clustered specially on the outermost surface region. These surface nitrogen atoms are expected to protect the surface and at the same time reduce hydrogen evolution rate.

Choi, Woon Ih; Turner, John; Kim, Yong-Hyun; Kim, Kwiseon

2010-03-01

379

InGaN working electrodes with assisted bias generated from GaAs solar cells for efficient water splitting.  

PubMed

Hydrogen generation through water splitting by n-InGaN working electrodes with bias generated from GaAs solar cell was studied. Instead of using an external bias provided by power supply, a GaAs-based solar cell was used as the driving force to increase the rate of hydrogen production. The water-splitting system was tuned using different approaches to set the operating points to the maximum power point of the GaAs solar cell. The approaches included changing the electrolytes, varying the light intensity, and introducing the immersed ITO ohmic contacts on the working electrodes. As a result, the hybrid system comprising both InGaN-based working electrodes and GaAs solar cells operating under concentrated illumination could possibly facilitate efficient water splitting. PMID:24514940

Liu, Shu-Yen; Sheu, J K; Lin, Yu-Chuan; Chen, Yu-Tong; Tu, S J; Lee, M L; Lai, W C

2013-11-01

380

Polarization of anthracite electrodes in electrolyte solutions  

SciTech Connect

The regularities of the polarization of anthractie electrodes for the liberation of hydrogen from electrolyte (potassium chloride and hydrogen chloride) solutions were found, and electrode processes occurring at the surface of coals in the Fe{sup 2+}/Fe{sup 3+} redox system were studied. It was found that the deviations of standard electrode potentials from the equilibrium values of redox systems depend on the exchange current densities of electrochemical processes occurring at the surface of coal matter. Low transfer coefficients (0.04-0.051) for the discharge reaction of hydrogen ions on anthracites indicate that the reaction occurs under conditions close to those of an activationless process.

A.N. Lopanov; E.V. Blaido; O.V. Smirnova [Shukhov State Technological Academy, Belgorod (Russian Federation)

2007-10-15

381

Ray tracing to study of waxes around the cloud point by optical absorption tomography  

NASA Astrophysics Data System (ADS)

In optical tomography of parallel projections, the light rays that cross the slice of the object are experimentally approached to suffer minimal refraction, i.e. take refractional limits. Generally, a media is used for immersion whose refractive index rate tied the environment to study, but the geometry of the containment vessels also affects refraction and may be the case that the approach is not subject performed. In this work we make a numerical study of the refraction of a ray of light that enters a typical experimental system for studying the thermodynamic behaviour of a paraffinic wax around their cloud point. Since it has special properties in the heat capacity and refractive index near the phase transition, these results will be used to characterize the transition and is intended to give tomographic information to the study of thermal properties obtained using the T-History calorimetric technique. In this study, we simulate the behaviour of the refraction of parallel rays crossing the T-History test system to find the optimal values of the dimensions of the containment vessels and the index of refraction of the medium for immersion, considering that the optical properties of the sample under study vary with temperature. Thus, we obtain the optimum conditions of minimum refraction technique for which reconstruction of a tomographic slice parallel projection can be applied. The distribution of the linear attenuation coefficient on the slice of the object, typically, is obtained by applying the filtered backprojection algorithm to the set of projections (sinogram) obtained experimentally, which constitutes a way to detect mobile interfacial boundaries in real time. The projections are sequentially measuring the intensity of the wave emerging from the slice of the object at different angles.

Moreno-Alvarez, L.; Meneses-Fabian, C.; Herrera, J. N.; Rodríguez-Zurita, G.

2011-10-01

382

Study of critical points of drugs with different solubilities in hydrophilic matrices.  

PubMed

Hydrophilic matrices are one of the most popular controlled release systems in the world. It is well known that drug solubility increases the osmotic stress in hydrophilic matrices, resulting in higher swelling through the creation of microcavities and influencing the release rate. Drug solubility also affects the drug release mechanism, favouring the diffusion against the erosion mechanism. Nevertheless it has not been studied whether this can modify the critical points of the hydrophilic matrices. The objective of the present work is to estimate the excipient percolation threshold in HPMC K4M hydrophilic matrices containing acetaminophen, theophiline and ranitidine.HCl, and to study the influence of the drug solubility on the excipient percolation threshold. Dissolution assays were performed using the paddle method. Water uptake was examined using the modified Enslin apparatus. In order to estimate the excipient percolation threshold, the behaviour of the kinetic parameters versus the excipient volume fraction plus initial porosity, was studied. The excipient percolation thresholds were situated between 24.8-25.8, 14.7-18.4 and around 31.2% (v/v) HPMC in theophiline, ranitidine.HCl and acetaminophen matrices, respectively. On the other hand, using these and some previously reported values no relation has been found between drug solubility and excipient percolation threshold in hydrophilic matrices. PMID:19766706

Fuertes, Inmaculada; Caraballo, Isidoro; Miranda, Antonia; Millán, Mónica

2010-01-01

383

Electrode contact impedance sensitivity to variations in geometry.  

PubMed

Electrode contact impedance is a crucial factor in physiological measurements and can be an accuracy-limiting factor when performing electroencephalography and electrical impedance tomography. In this work, standard flat electrodes and micromachined multipoint spiked electrodes are characterized with a finite-element method electromagnetic solver and the dependence of the contact impedance on geometrical factors is explored. It is found that flat electrodes are sensitive to changes in the outer skin layer properties related to hydration and thickness, while spike electrodes are not. The impedance as a function of the effective contact area, number of spikes and penetration depth has also been studied and characterized. PMID:22531168

Cardu, Roberto; Leong, Philip H W; Jin, Craig T; McEwan, Alistair

2012-05-01

384

A Study on Amino Acids: Synthesis of Alpha-Aminophenylacetic Acid (Phenylglycine) and Determination of its Isoelectric Point.  

ERIC Educational Resources Information Center

Background information and procedures are provided for an experimental study on aminophenylacetic acid (phenylglycine). These include physical chemistry (determination of isoelectric point by pH measurement) and organic chemistry (synthesis of an amino acid in racemic form) experiments. (JN)

Barrelle, M.; And Others

1983-01-01

385

The bi-variate frequency distribution of two concurrent climatic variables: a study of temperature and dew point  

E-print Network

of the requirements for the degree of MASTER OF SCIENCE December 1991 Major Subject: Meteorology THE BI-VARIATE FREQUENCY DISTRIBUTION OF TWO CONCURRENT CLIMATIC VARIABLES: A STUDY OF TEMPERATURE AND DEW POINT A Thesis by JON WILLIAM ZEITLER Approved... Study of Temperature and Dew Point (December 1991). Jon William Zeitler, B. S. , iowa State University Chair of Advisory Comminee; Prof. John F. Griffiths The bi-variate normal distribution was fitted for the mid-season months of January, April, July...

Zeitler, Jon William

1991-01-01

386

Electrocatalysts for oxygen electrodes  

NASA Astrophysics Data System (ADS)

The overall objective of this research was an in-depth understanding of the factors controlling O2 reduction and generation on various electrocatalysts and the use of this understanding to identify much higher activity, stable catalysts. The following is a brief summary of the research for the period 1 April 1989 to 31 March 1990. (1) Transition metal monomeric and sheet-polymeric macrocycle catalysts -- The iron tetrasulfonated phthalocyanine (FeTsPc) complex adsorbed on an electrode surface has high activity for the 4-electron reduction of O2 to water or OH(exp -) in alkaline solutions. (2) Polymer-modified electrodes -- Poly(4-vinyl pyridine) (PVP)-modified electrodes with adsorbed CoTsPc exhibited much higher catalytic activity for O2 reduction than the electrode with only adsorbed CoTsPc in acid solutions. (3) Transition metal oxide catalysts and bifunctional electrodes -- Anion-exchange membranes were found to greatly improve the performance of the pyrochlore-based bifunctional oxygen electrodes when operating in the O2 generation mode. (4) Catalyst supports -- The use of mildly fluorinated carbon blacks as catalyst supports for platinum was explored in cooperation with the Electrosynthesis Company (ESC).

Yeager, E.

1990-10-01

387

Effect of hole doping on the magnetism of point defects in graphene: A theoretical study  

NASA Astrophysics Data System (ADS)

Using ab initio methods based on the density functional theory, we study the magnetic properties of different point defects in graphene. We consider separately, atomic hydrogen, atomic fluorine, and single vacancies. The three defects have completely different magnetic properties. A local spin one-half magnetic moment is well defined at a hydrogen impurity, while single fluorine adatoms do not induce a well-defined magnetic moment unless there is a fluorine concentration of at least of a 0.5%. In this case, the induced magnetic moment is of the order of 0.45 ?B per defect. This behavior is interpreted as being due to the charge transfer between fluorine and graphene. The case of magnetic moments localized at ? electrons near vacancies is different from both previous cases; the size of the induced magnetic moment decreases with the dilution of defects and it is compatible with zero in the isolated vacancy. The effect of hole doping on these magnetic behaviors is studied and compared with the available experimental data. In the three cases, hole doping inhibits the formation of ? states magnetic moments.

Yndurain, Felix

2014-12-01

388

Two-micron Laser Atmospheric Wind Sounder (LAWS) pointing/tracking study  

NASA Technical Reports Server (NTRS)

The objective of the study was to identify and model major sources of short-term pointing jitter for a free-flying, full performance 2 micron LAWS system and evaluate the impact of the short-term jitter on wind-measurement performance. A fast steering mirror controls system was designed for the short-term jitter compensation. The performance analysis showed that the short-term jitter performance of the controls system over the 5.2 msec round-trip time for a realistic spacecraft environment was = 0.3 micro rad, rms, within the specified value of less than 0.5 micro rad, rms, derived in a 2 micron LAWS System Study. Disturbance modes were defined for: (1) the Bearing and Power Transfer Assembly (BAPTA) scan bearing, (2) the spacecraft reaction wheel torques, and (3) the solar array drive torques. The scan bearing disturbance was found to be the greatest contributing noise source to the jitter performance. Disturbances from the fast steering mirror reaction torques and a boom-mounted cross-link antenna clocking were also considered but were judged to be small compared to the three principal disturbance sources above and were not included in the final controls analysis.

Manlief, Scott

1995-01-01

389

Alternating current cloud point extraction on a microchip: a comprehensive study.  

PubMed

We present a comprehensive study of alternating current cloud point extraction (ACPE) on a microchip. ACPE is an extraction technique for preconcentration of membrane-associated biomolecules. To characterize and optimize ACPE, we carried out ACPE experiments under various experimental conditions including amplitude and frequency of applied voltages, flow velocity, and concentration of surfactant, analyte, and salt. We found that ACPE has an amplitude threshold (15 V(p-p)), above which the extraction was more efficient. The dependence of the extraction on frequency (>5 MHz) was insignificant. Efficient extraction was achieved when the velocity of the test solution was 0.10?0.67 mm s?¹ and the concentration of surfactant was 0.10?1.0%. In contrast, the extraction was independent of the concentration of analytes (0.20?20 ?mol dm?³). The technique was applicable to solutions with a salt concentration of 0.050?0.15 mol dm?³ under temperature control of the devices. Solution temperature in ACPE was also studied. These results provide guidelines for use of the ACPE technique in microfluidic chemical and biochemical analyses. PMID:23027025

Sasaki, Naoki; Takemura, Azusa; Sato, Kae

2012-11-01

390

An Observational Study on the Effectiveness of Point-Of-Use Chlorination  

PubMed Central

Although the efficacy of chlorine disinfection under controlled laboratory conditions is well known, the effectiveness of chlorine under field point-of-use (POU) conditions is still not clearly understood and may be impacted by a variety of factors. This study evaluated the effectiveness of POU chlorine disinfection in rural Ecuador under typical use conditions and compared this effectiveness with the efficacy in controlled laboratory conditions. While reductions of indicator organisms were slightly higher in households that used chlorination, no significant differences were seen between households employing POU chlorination and the households with no chlorination (1–1.5 log10 median reductions for chlorinating households and 0.31–0.55 log10 for nonchlorinating households, depending on the indicator organism). In contrast, significant reduction of all test organisms was found when simulating POU conditions in the laboratory. This study demonstrates that POU chlorination can be considerably less effective under actual field conditions than would be predicted based on its laboratory efficacy (3–5 log10 median reductions for chlorinated and 0–0.3 log10 for non-chlorinated samples). Human factors (including improper storage and chlorine dosing) and uncontrolled water quality effects are hypothesized to impact significantly the effectiveness of chlorine disinfection. PMID:19408433

McLaughlin, Laura A.; Levy, Karen; Beck, Nicola K.; Shin, Gwy-Am; Meschke, J. Scott; Eisenberg, Joseph N.

2010-01-01

391

Performance and kinetics of LiFePO4-carbon bi-material electrodes for hybrid devices: A comparative study between activated carbon and multi-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Activated Carbon (AC) and multi-walled carbon nanotubes (CNT) are investigated as components of LiFePO4 (LFP)-based bi-material electrodes for hybrid devices. Firstly, the influence of their different morphological and porosimetric characteristics is correlated to the electrochemical performance. Furthermore, kinetic aspects are carefully studied (by means of galvanostatic cycling and cyclic voltammetry), in order to address the processes which determine the power performance. The results indicate that, independently from the carbon, under high current loads the electrode kinetics are limited by the transport of reactant to the LFP particles. In such conditions CNT allow, better than AC, rapid electrons and Li+ ions flow through the open network established in the electrode, thus enabling superior high rate performance, especially during pulsed operation.

Varzi, Alberto; Ramirez-Castro, Claudia; Balducci, Andrea; Passerini, Stefano

2015-01-01

392

Multiple-electrode radiofrequency ablations using Octopus® electrodes in an in vivo porcine liver model  

PubMed Central

Objectives The objective of this study was to determine the in vivo efficacy of radiofrequency ablation (RFA) in porcine liver using Octopus® electrodes for creating a large coagulation compared with RFA using clustered electrodes. Methods A total of 39 coagulations were created using a 200-W generator and clustered electrodes or Octopus electrodes during laparotomy in 19 pigs. Radiofrequency was applied to the livers using four protocols: (1) Group A-1, monopolar mode using a clustered electrode (n=11); (2) Group A-2, monopolar mode using an Octopus electrode (n=11); (3) Group B-1, consecutive monopolar mode using three, clustered electrodes (n=8); and (4) Group B-2, switching monopolar mode using two Octopus electrodes (n=9). The energy efficiency, shape, diameters (D) and volume (V) of the coagulation volume were compared in each of the two groups. Results The mean maximum D and V of the coagulations in Group A-2 (4.7 cm and 33.1 cm3, respectively) were significantly larger than those in Group A-1 (4.1 cm and 20.3 cm3, respectively) (p<0.05). Furthermore, the mean minimum D, maximum D and V of the coagulations in Group B-2 were significantly larger than those in Group B-1, i.e. 5.3 vs 4.0 cm, 6.6 vs 4.9 cm and 66.9 vs 30.2 cm3, respectively (p<0.05). The energy efficiencies were also significantly higher in Groups A-2 and B-2 than in Groups A-1 and B-1 (p<0.05). Conclusion The Octopus electrodes were more efficient for creating a large ablation zone than clustered electrodes, and the efficacy of RFA with Octopus electrodes can be amplified in the switching monopolar mode. PMID:22422385

Lee, E S; Lee, J M; Kim, W S; Choi, S H; Joo, I; Kim, M; Yoo, D H; Yoo, R-E; Han, J K; Choi, B I

2012-01-01

393

Integrated electrode/separator structures  

SciTech Connect

An integrated electrode/insulator structure is disclosed for use as part of an electrochemical system of an electrochemical cell. The electrode/insulator structure includes an electrode and an adherent porous layer of an electrically-nonconductive material deposited on the electrode and physically integrated with the electrode. The material of the adherent porous layer is selected so as to be chemically stable with the electrode and with any other components of the electrochemical system of the electrochemical cell in which the integrated electrode/insulator structure is to be used.

Goebel, F.; Schlaikjer, C.R.

1981-08-11

394

Graphene and graphene oxide nanogap electrodes fabricated by atomic force microscopy nanolithography  

Microsoft Academic Search

Nanogap electrodes have been studied intensively both as ideal research tools for molecular electronics and fundamental building blocks for nanodevices. Here, graphene and graphene oxide nanogap electrodes with gap width below 10 nm were fabricated by atomic force microscopy (AFM) nanolithography. It provides a simple and convenient way to fabricate nanogap electrodes and transfer the nanogap electrodes onto any required

Yudong He; Huanli Dong; Tao Li; Chengliang Wang; Wei Shao; Yajie Zhang; Lang Jiang; Wenping Hu

2010-01-01

395

Ionomer Degradation in Electrodes of PEM Fuel Cell  

SciTech Connect

Although PEMFC Membrane Electrode Assembly (MEA) durability related studies have increased dramatically since 2004, studies on ionomer degradation of the composite electrodes has received far less attention than that of the proton exchange membranes, electrocatalysts, and catalyst supports. The catalyst layer ionomer unavoidably gets involved in other components degradation processes since it is subjected to exposure to different operating effects, including the presence of the catalyst, catalyst support, and the porous nature of the electrode layer which includes 2-phase flow. PEMFC durability issues cannot be fully resolved without understanding the contribution of ionomer degradation in electrode to the performance decay in life time. However, addressing the impact of changes to the catalyst layer ionomer during durability tests is experimentally difficult mainly because of the need to separate the ionomer in the electrode from other components during chemical, electrical and materials characterization. The catalyst layer ionomer is essentially chemically identical to the membrane ionomeric material, and is composed of low atomic number elements, making characterization difficult. In the present work, MEAs with different Nafion ionomer types: stabilized and non-stablized ionomer in the electrode layer (Type I) and mixed membrane/ionomer MEAs (Type II) were designed to separate ionomer degradation from membrane degradation, as shown in Figure (1a) and (b) respectively. Stabilized and non stabilized ionomers were 5% Nafion{reg_sign} solutions (Ion Power, New Castle, Delaware). The non-stabilized version is the typical Nafion chemical structure with carboxylic acid (-COOH) end groups; these end groups are thought to be a susceptible point of degradative peroxide attack. The stabilized version replaces the -COOH end groups with -CF{sub 3} end groups to prevent peroxide attack at the end groups. Type I MEAs were designed to compare ionomer degradation and its effect on performance decay. Since F{sup -} ions are released only from PFSA based membranes, and not from non-PFSA based membranes, Type II MEAs use a hydrocarbon membrane with no fluorine with a PFSA (Nafion{reg_sign}) ionomer in the catalyst layer for FER measurements. Any F{sup -} ions measured will then have come only for the catalyst layer ionomer during degradation experiments. Type II MEAs allow more detailed chemical characterization exclusively of the catalyst layer ionomer to better understand its degradation.

Borup, Rodney L. [Los Alamos National Laboratory

2011-01-01

396

A Simulation Study Comparison of Bayesian Estimation with Conventional Methods for Estimating Unknown Change Points  

ERIC Educational Resources Information Center

The main purpose of this research is to evaluate the performance of a Bayesian approach for estimating unknown change points using Monte Carlo simulations. The univariate and bivariate unknown change point mixed models were presented and the basic idea of the Bayesian approach for estimating the models was discussed. The performance of Bayesian…

Wang, Lijuan; McArdle, John J.

2008-01-01

397

Reconstruction of 3-D head geometry from digitized point sets: an evaluation study  

Microsoft Academic Search

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

Juha Koikkalainen; Jyrki Lötjönen

2004-01-01

398

On numerical studies of multi-point boundary value problem and its fold bifurcation  

Microsoft Academic Search

Based upon shooting method, we set up a numerical method for approximating solutions and fold bifurcation solutions of second order multi-point boundary value problems. We prove the equivalence of the regularity of solutions and simple fold bifurcation solutions between the numerical method and the multi-point boundary value problems. Many numerical experiments are carried out to illustrate the theoretical analysis, from

Yongkui Zou; Qingwan Hu; Ran Zhang

2007-01-01

399

In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O(3±?).  

PubMed

Mixed-conducting perovskite-type electrodes which are used as cathodes in solid oxide fuel cells (SOFCs) exhibit pronounced performance improvement after cathodic polarization. The current in situ study addresses the mechanism of this activation process which is still unknown. We chose the new perovskite-type material La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±?) which is a potential candidate for use in symmetrical solid oxide fuel cells (SFCs). We prepared La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±?) thin film model electrodes on YSZ (111) single crystals by pulsed laser deposition (PLD). Impedance spectroscopy (EIS) measurements show that the kinetics of these electrodes can be drastically improved by applying a cathodic potential. To understand the origin of the enhanced electrocatalytic activity the surfaces of operating LSCrM electrodes were studied in situ (at low pressure) with spatially resolving X-ray photoelectron spectroscopy (?-ESCA, SPEM) and quasi static secondary ion mass spectrometry (ToF-SIMS) after applying different electrical potentials in the SIMS chamber. We observed that the electrode surfaces which were annealed at 600 °C are enriched significantly in strontium. Subsequent cathodic polarization decreases the strontium surface concentration while anodic polarization increases the strontium accumulation at the electrode surface. We propose a mechanism based on the reversible incorporation of a passivating SrO surface phase into the LSCrM lattice to explain the observed activation/deactivation process. PMID:22116198

Huber, Anne-Katrin; Falk, Mareike; Rohnke, Marcus; Luerssen, Bjoern; Gregoratti, Luca; Amati, Matteo; Janek, Jürgen

2012-01-14

400

Dynamic behavior of ion-selective electrodes  

Microsoft Academic Search

This book provides a survey of the different techniques employed to study time-dependent processes of ion-selective electrodes. The fundamentals, the impedance field, the polarization field, and the activity step methods are treated in depth with emphasis on the information content of the results provided by the different techniques relevant to the dynamic characteristics of ion-selective electrodes. Within the activity step

E. Pungor; E. Linder; K. Toth

1988-01-01

401

Thermodynamic analysis and experimental study of the effect of atmospheric pressure on the ice point  

SciTech Connect

We present a detailed thermodynamic analysis of the temperature of the ice point as a function of atmospheric pressure. This analysis makes use of accurate international standards for the properties of water and ice, and of available high-accuracy data for the Henry's constants of atmospheric gases in liquid water. The result is an ice point of 273.150 019(5) K at standard atmospheric pressure, with higher ice-point temperatures (varying nearly linearly with pressure) at lower pressures. The effect of varying ambient CO{sub 2} concentration is analyzed and found to be significant in comparison to other uncertainties in the model. The thermodynamic analysis is compared with experimental measurements of the temperature difference between the ice point and the triple point of water performed at elevations ranging from 145 m to 4302 m, with atmospheric pressures from 101 kPa to 60 kPa.

Harvey, A. H. [Thermophysical Properties Division National Institute of Standards and Technology, Boulder, Colorado (United States)] [Thermophysical Properties Division National Institute of Standards and Technology, Boulder, Colorado (United States); McLinden, M. O. [Thermophysical Properties Division, National Institute of Standards and Technology, Boulder, Colorado (United States)] [Thermophysical Properties Division, National Institute of Standards and Technology, Boulder, Colorado (United States); Tew, W. L. [Sensor Science Division National Institute of Standards and Technology, Gaithersburg, Maryland (United States)] [Sensor Science Division National Institute of Standards and Technology, Gaithersburg, Maryland (United States)

2013-09-11

402

Changes in Antimicrobial Use Prevalence in China: Results from Five Point Prevalence Studies  

PubMed Central

Objective The abuse of antimicrobials is a serious concern in China. Several measures have been taken to improve the rational use of antimicrobials, including the establishment of a national surveillance network for antimicrobial use. This study describes the dynamic changes in antimicrobial use in China between 2001 and 2010, with the scope of identifying targets to improve the prescription of antimicrobials. Methods Five point prevalence surveys were performed in hospitals across mainland China in 2001, 2003, 2005, 2008, and 2010. All inpatients who were admitted for at least 24 hours were included in the study. Details regarding antimicrobial use by these patients and the collection of samples for bacterial culture from inpatients administered therapeutic antimicrobials were recorded. Results The surveys encompassed tertiary hospitals from all 31 provinces of mainland China. Antimicrobial use prevalence decreased from 54.79% in 2001 to 46.63% in 2010. While this decline was observed in most hospital departments, antimicrobial use remained stable or increased in others. Antimicrobial use prevalence was relatively high in the Pediatrics departments and general intensive care units, whereas it was lower in the Obstetrics (Neonatal group) departments in each survey. The proportion of patients administered a single antimicrobial increased from 60.78% in 2001 to 70.16% in 2010, while the proportion of administration of two or more antimicrobials declined. The bacterial culture rate increased from 25.22% in 2003 to 34.71% in 2010. Antimicrobial use prevalence (47.96% vs 46.16%), bacterial culture rate (36.40% vs 34.19%), and the proportion of administration of a single antimicrobial (71.41% vs 67.33%) were higher in teaching hospitals than in nonteaching hospitals in 2010. Conclusion Although measures for enhancing the rational use of antimicrobials have been effective, further improvements are required. The findings from this study can promote such improvements. PMID:24376580

Li, Chunhui; Ren, Nan; Wen, Ximao; Zhou, Pengcheng; Huang, Xun; Gong, Ruie; Lv, Yixin; Feng, Li; Wu, Hongman; Liu, Zhenru; Fu, Chenchao; Huang, Xin; Li, Jie; Chen, Yuhua; Zeng, Cui; Zuo, Shuangyan; Xiong, Xinrui; Xu, Xiuhua; Wu, Anhua

2013-01-01

403

Capacitive de-ionization electrode  

DOEpatents

An electrode "cell" for use in a capacitive deionization (CDI) reactor consists of the electrode support structure, a non-reactive conductive material, the electrode accompaniment or substrate and a flow through screen/separator. These "layers" are repeated and the electrodes are sealed together with gaskets between two end plates to create stacked sets of alternating anode and cathode electrodes in the CDI reactor.

Daily, III, William D.

2013-03-19

404

ELECTRODE DEVELOPMENT FOR REVERSIBLE SOLID OXIDE FUEL CELLS  

SciTech Connect

The reversibility of the electrodes for a solid oxide fuel cell with an yttria-stabilized zirconia (YSZ) electrolyte was examined using electrochemical impedance spectroscopy and current interrupt methods. The fuel electrodes were nickel/zirconia cermet and lanthanum-doped strontium titanate/doped ceria composites. The air electrodes were lanthanum strontium ferrite (LSF) and lanthanum strontium copper ferrite (LSCuF). Under the experimental conditions studied all four electrodes were able to operate in both the fuel cell and electrolyzer modes. The titanate/ceria fuel electrode performed substantially better in the electrolyzer mode than state-of-art Ni-YSZ. Moreover, it showed slightly higher activity for water electrolysis as compared to hydrogen oxidation. Air electrodes were less active in the electrolyzer than fuel cell modes. LSF typically provided higher overpotential losses in both modes than copper-substituted LSF. Changes in the defect chemistry of electrode materials under cathodic and anodic polarization are discussed.

Marina, Olga A.; Coffey, Greg W.; Pederson, Larry R.; Rieke, Peter C.; Thomsen, Ed C.; Williams, Mark C.

2004-08-06

405

A polyoxovanadate as an advanced electrode material for supercapacitors.  

PubMed

Polyoxovanadate Na(6)V(10)O(28) is investigated for the first time as electrode material for supercapacitors (SCs). The electrochemical properties of Na(6)V(10)O(28) electrodes are studied in Li(+) -containing organic electrolyte (1?M LiClO(4) in propylene carbonate) by galvanostatic charge/discharge and cyclic voltammetry in a three-electrode configuration. Na(6)V(10)O(28) electrodes exhibit high specific capacitances of up to 354 F?g(-1). An asymmetric SC with activated carbon as positive electrode and Na(6)V(10)O(28) as negative electrode is fabricated and exhibits a high energy density of 73 Wh?kg(-1) with a power density of 312 W?kg(-1), which successfully demonstrates that Na(6)V(10)O(28) is a promising electrode material for high-energy SC applications. PMID:24816786

Chen, Han-Yi; Wee, Grace; Al-Oweini, Rami; Friedl, Jochen; Tan, Kim Soon; Wang, Yuxi; Wong, Chui Ling; Kortz, Ulrich; Stimming, Ulrich; Srinivasan, Madhavi

2014-07-21

406

Ab initio study of oxygen point defects on tungsten trioxide surface  

NASA Astrophysics Data System (ADS)

The gas response of tungsten trioxide (WO3) based sensors strongly depends on the surface properties. Reconstructed surfaces and oxygen point defects at the surface of the monoclinic WO3 are studied using a self-consistent scheme based on first-principle. The oxygen vacancy is found to be the predominant defect independently of the oxygen partial pressure. Indeed, under rich oxygen atmosphere the formation enthalpies are found to be 1.45 eV in LDA (1.28 eV in GGA) for the oxygen vacancy instead of 2.70 eV (2.42 eV) for the oxygen adatom. When the oxygen partial pressure is lowered, the oxygen vacancy formation enthalpy decreases and becomes exothermic under very O-poor condition (- 1.65 eV in LDA and - 1.36 eV in GGA). On the other hand, the formation enthalpy of an oxygen adatom rises. Finally, the oxygen vacancy formation acts as a n-doping by introducing negative charge carriers at the bottom of the conduction band. All these results can be very helpful in order to explain the electrical resistivity measurements.

Lambert-Mauriat, Caroline; Oison, Vincent; Saadi, Lama; Aguir, Khalifa

2012-01-01

407

A computational study of magnesium point defects and diffusion in forsterite  

NASA Astrophysics Data System (ADS)

We have studied the formation and migration of point defects within the magnesium sub-lattice in forsterite using a combination of empirical and quantum mechanical modelling methodologies. Empirical models based on a parameterised force field coupled to a high throughput grid computing infrastructure allow rapid evaluation of a very large number of possible defect configurations. An embedded cluster approach reveals more accurate estimates of defect energetics for the most important defect configurations. Considering all defects in their minimum energy, equilibrium positions, we find that the lowest energy intrinsic defect is the magnesium Frenkel type, where a magnesium atom moves from the M1 site to form a split interstitial defect. This defect has 2 four-co-ordinated magnesium atoms located outside opposite triangular faces of an otherwise vacant M1 octahedron. The split interstitial defect is more stable than regular interstitials where magnesium is located in either of the two structurally vacant octahedral sites in the hexagonally close packed oxygen lattice. M1 vacancies are also found to form when iron(II) oxidises to iron(III). The energy of the defects away from the equilibrium positions allows the energy barrier to diffusion to be calculated. We have considered the migration of both magnesium vacancies and interstitials and find that vacancies are more mobile. When the contribution from the formation energy of the defects is included we arrive at activation energies for vacancy diffusion that are in agreement with experiment.

Walker, Andrew M.; Woodley, Scott M.; Slater, Ben; Wright, Kate

2009-01-01

408

First-principles study of point defects in chalcopyrite ZnSnP2  

NASA Astrophysics Data System (ADS)

Chalcopyrite ZnSnP2 is an alternative photoabsorber material for solar cells because of its controllable band gap, high absorption coefficient, and earth abundant constituents. In this study we systematically investigate its native point defects including vacancies, interstitials, and antisites using first-principles calculations with the Heyd-Scuseria-Ernzerhof hybrid functional. We evaluate the defect formation energies and defect single-particle levels at the dilute limit using finite-size image-charge corrections and compare them with those reported for CuInSe2 and CuGaSe2. The most likely donors and acceptors are cation antisites, Sn-on-Zn and Zn-on-Sn, respectively. Because of their significantly low formation energies, they lead to Fermi level pinning in the band gap under any growth condition, and constrain the carrier concentration. The Sn-on-Zn antisite in the neutral charge state becomes an intrinsic DX center, a complex of the Sn interstitial and Zn vacancy, and shows a deep donor level as reported for CuGaSe2.

Kumagai, Yu; Choi, Minseok; Nose, Yoshitaro; Oba, Fumiyasu

2014-09-01

409

Kinetics and mechanisms of electrode processes  

SciTech Connect

This book examines the kinetics and mechanisms of processes at electrodes and investigates the behavior of double layers at charged interfaces, the state of reacting ions in solution, and the state of solid and liquid surfaces of metals and metal oxide films with regard to their catalytic activity in various processes. Different ways of treating (at a quantum-mechanical level) the reaction mechanics of electron and particle transfer across barriers of atomic dimensions in the double layer at electrode interfaces are discussed. Electron, proton and molecular processes from the point of activation through solvent mode fluctuations coupled with quantum-mechanical aspects of OH vibrations and hydrogen transfer; the kinetics of electrode processes that involve multistep routes; electrocatalysis; cathodic hydrogen evolution; oxygen electrode reactions to a variety of materials; electrolytic metal deposition; the semiconductor-solution interface; molten salt electrochemistry; and the application of electrode process kinetics to mechanisms of the main types of electroorganic reactions are explored. This book is recommended for those working in electrochemistry, materials science, and solid state chemistry.

Conway, B.E.; Bockris, J.O'M.; Khan, S.U.M.; White, R.E.; Yeager, E.

1983-01-01

410

Modiolus-hugging intracochlear electrode array with shape memory alloy.  

PubMed

In the cochlear implant system, the distance between spiral ganglia and the electrodes within the volume of the scala tympani cavity significantly affects the efficiency of the electrical stimulation in terms of the threshold current level and spatial selectivity. Because the spiral ganglia are situated inside the modiolus, the central axis of the cochlea, it is desirable that the electrode array hugs the modiolus to minimize the distance between the electrodes and the ganglia. In the present study, we propose a shape-memory-alloy-(SMA-) embedded intracochlear electrode which gives a straight electrode a curved modiolus-hugging shape using the restoration force of the SMA as triggered by resistive heating after insertion into the cochlea. An eight-channel ball-type electrode array is fabricated with an embedded titanium-nickel SMA backbone wire. It is demonstrated that the electrode array changes its shape in a transparent plastic human cochlear model. To verify the safe insertion of the electrode array into the human cochlea, the contact pressures during insertion at the electrode tip and the contact pressures over the electrode length after insertion were calculated using a 3D finite element analysis. The results indicate that the SMA-embedded electrode is functionally and mechanically feasible for clinical applications. PMID:23762181

Min, Kyou Sik; Jun, Sang Beom; Lim, Yoon Seob; Park, Se-Ik; Kim, Sung June

2013-01-01

411

The point of Corumbau : a case study in emerging market (Brazil) real estate development feasibility analysis  

E-print Network

In 2003, Renata Oliveira, a young Portuguese architect, has re-discovered the Point of Corumbau in Bahia, Brazil, and, like the Portuguese adventurers who had discovered Brazil 500 years earlier in the same location, found ...

Clayton, Paul B., S.M. Massachusetts Institute of Technology

2007-01-01

412

A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme  

Microsoft Academic Search

A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc\\/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of

K. K. Tse; Billy M. T. Ho; Henry Shu-Hung Chung; S. Y. Ron Hui

2004-01-01

413

Electrochemical, neutron reflectivity and in situ PM-FT-IRRAS studies of a monolayer of n-octadecanol at a Au(1 1 1) electrode surface  

Microsoft Academic Search

The horizontal touch and Langmuir–Blodgett techniques have been used to transfer a monolayer of n-octadecanol from the gas–solution interface of a Langmuir trough onto the metal–solution interface of a Au(111) electrode. Chronocoulometry has been used to determine the charge density at the electrode surface covered by the film of n-octadecanol. The surface pressure of this film was calculated from the

I. Zawisza; I. Burgess; G. Szymanski; J. Lipkowski; J. Majewski; S. Satija

2004-01-01

414

Design and evaluation of a highly sensitive nanostructure-based surface modification of glassy carbon electrode for electrochemical studies of hydroxychloroquine in the presence of acetaminophen.  

PubMed

N,N'-bis[(E)-(1-pyridyl) methylidene]-1,3-propanediamine (PMPDA) self-assembled monolayer (SAM) was covalently prepared on a glassy carbon electrode (GCE). The electrode surface modification was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Then GC-PMPDA SAM modified electrode was used to investigate the electrochemical behavior of hydroxychloroquine (HQ) using CV, double potential step chronocoulometry and linear sweep voltammetry (LSV) techniques. Using these techniques, the diffusion coefficient (D), electron transfer coefficient (?) and exchanging current density (j0) for HQ were calculated. Furthermore the modified electrode was applied as a high sensitive biosensor for determination of HQ in the presence of acetaminophen (AC). The GC-PMPDA SAM modified electrode provides two linear responses for HQ in the presence of AC in the concentration ranges from 0.09 to 10.21 ?M and 10.21 to 98.29 ?M by differential pulse voltammetry (DPV). The detection limit (three times the signal blank/slope) was 4.65 nM. Finally the modified electrode was satisfactorily used for determining of HQ in human body fluids. PMID:25456984

Khoobi, Asma; Ghoreishi, Sayed Mehdi; Behpour, Mohsen; Shaterian, Maryam; Salavati-Niasari, Masoud

2014-11-01

415

GPR study of a prehistoric archaeological site near Point Barrow, Alaska  

NASA Astrophysics Data System (ADS)

A ground penetrating radar (GPR) study was performed on the prehistoric Thule cemetery site near Point Barrow, Alaska. The goals of this study were (a) to test this technology in this type of polar environment, and (b) to search for burials and other archaeological features in a location in imminent danger from ocean erosion. The Nuvuk site is currently eroding at an average rate measured at over 6 m/year. Prior archaeological work at the site had recovered over 80 burials with nearly 100 individuals represented, all of which were less than 1 m below surface, and detectable with small test pits. In addition, the first coastal Ipiutak occupation known north of Point Hope had been recently discovered, at a depth of nearly 2m below surface, in the erosion face. The occupation appeared to have been terminated by a large storm which overwashed the site, leaving a strandline immediately superimposed on the living surface. After that, approximately 1.5 m of sterile gravels had been deposited before the surface on which the Thule people were living formed. Both occupations are of considerable scientific interest. The matrix at the site consists of unconsolidated beach gravels, which necessitates opening large surface areas or use of shoring to test even small units to the depths of the Ipiutak deposit (approximately 8m x 8m at the surface to test 1m x 1m at 2m depth). Such excavations promote erosion, and are very costly in terms of time and labor, so a means to detect features buried at depths greater than those exposed by shovel test pits was desirable. GPR seemed a likely candidate, but it had not been used in such conditions before, and thus it was necessary to test it thoroughly prior to relying on GPR to eliminate areas from physical testing. The GPR imaged the subsurface to a depth of 3 meters at a frequency of 500MHz. Meter-deep test pits were placed at 2-meter intervals in the survey area in a grid pattern since the efficacy of the technology had yet to be shown. The results of the test pits and the GPR were in agreement. It was anticipated that there might be few or no remaining burials in this location since the number of burials had been declining with distance from the center of the larger site. Thus it was surprising when the GPR detected an anomaly that turned out to be the deepest burial in the whole site. In fact, it was so deeply buried that the standard shovel test pitting method might not have detected it. It proved to be a very well-preserved individual, with fairly intact garments. In addition to the burial site, the GPR was used to image a number of "strandlines" as well as other deep (>1m) features in this area. These correspond in depth and orientation to two partial Ipiutak features which have been exposed and recorded in the erosion face in two separate field seasons. It was not possible to test to that depth, but subsequent coastal erosion has exposed additional strandline debris at the depth and location predicted by the GPR data. Two- and three-dimensional images of these features will be presented, along with a detailed technical description of the GPR methods used in this environment.

Herman, R. B.; Jensen, A. M.

2012-12-01

416

Porous electrode preparation method  

DOEpatents

A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder of such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity. 2 figs.

Arons, R.M.; Dusek, J.T.

1983-10-18

417

Porous electrode preparation method  

DOEpatents

A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder of such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity.

Arons, Richard M. (Wheaton, IL); Dusek, Joseph T. (Downers Grove, IL)

1983-01-01

418

Composite carbon foam electrode  

DOEpatents

Carbon aerogels used as a binder for granularized materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivty and power to system energy.

Mayer, Steven T. (San Leandro, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

1997-01-01

419

Composite carbon foam electrode  

DOEpatents

Carbon aerogels used as a binder for granulated materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. 1 fig.

Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

1997-05-06

420

Building Better Electrodes for Electrical Resistivity and Induced Polarization Data  

NASA Astrophysics Data System (ADS)

In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles" heal of the resistivity method. Even stainless steel, a commonly used electrode material because of its durability, showed only average results in laboratory tests for electrode noise. Better results have been found with non-polarizing metal-metal salt electrodes, which are widely used as surface electrodes and in IP surveys. But although they produce small measurement errors, they are not durable enough for in-situ borehole resistivity surveys, and often contain compounds that are toxic to the environment. They are also very seldom used as transmitters. In laboratory studies, we are exploring other materials and configurations for low-noise compound electrodes that will be nontoxic, inexpensive, and durable and can be used as both transmitters and receivers. Testing of the electrical noise levels of electrodes is an arduous task involving repeated measurements under varying conditions at field scales. Thus it is important to find methods of sorting out likely candidates from the mass of possible electrode configurations and construction methods. Testing of electrode impedance versus current density appears to provide simple criteria for predicting the suitability of electrodes. The best electrodes show relatively low overall contact impedance, relatively small changes in impedance with increased current density, and relatively small changes in impedance with time. Furthermore it can be shown that resistivity and induced polarization performance of electrodes is strongly correlated, so that methods of finding electrodes with low impedance and good direct current performance usually provide better quality induced polarization data and vice- versa.

Adkins, P. L.; La Brecque, D. J.

2007-12-01

421

Reducing risks to human and environmental health: A case study at Point Lisas Industrial Estate, Trinidad  

SciTech Connect

Waste audits were completed at four industrial plants on the Point Lisas Industrial Estate in Couva, Trinidad to examine the potential for setting up an industrial ecosystem on the estate. There was no legislation in effect to require treatment of any waste materials and, as a consequence, most materials were disposed of into the environment. The objective of this research was to determine possible sources of contamination, the potential effects on human and environmental health and to assess means of reducing the contamination. The four plants produced 50,270,000 tonnes/year of liquid waste, 986,000,000 tonnes/year of gas waste, 5,400,000 tonnes/year of solid waste and 22,000 tonnes/year of sludge waste. Atmospheric emissions were particularly severe at the ammonia/fertilizer and steel producing plants, sufficient to pose a threat to employee health. Liquid wastes, including solvents, were disposed of into the ocean and previous studies had revealed damage to aquatic life. Solid and sludge wastes were either buried on site or sent to landfill. A number of hazardous materials were in use at the plants. Recommendations were made for reducing waste production, reducing the hazardous nature of materials and for treating or co-treating wastes for reuse or recycling on site or for disposal. Unfortunately there appears to be little interest in setting standards for emissions, effluents or waste disposal in Trinidad and further economic data are required to persuade companies that they should consider spending funds on waste management or on establishing an industrial ecosystem.

Boyle, C. [Univ. of British Columbia, Vancouver, British Columbia (Canada); Baetz, B. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Civil Engineering

1995-12-31

422

Point defects in twisted bilayer graphene: A density functional theory study  

NASA Astrophysics Data System (ADS)

We have used ab initio density functional theory, incorporating van der Waals corrections, to study twisted bilayer graphene (TBLG) where Stone-Wales defects or monovacancies are introduced in one of the layers. We compare these results to those for defects in single-layer graphene or Bernal stacked graphene. The energetics of defect formation is not very sensitive to the stacking of the layers or the specific site at which the defect is created, suggesting a weak interlayer coupling. However, signatures of the interlayer coupling are manifested clearly in the electronic band structure. For the "??" Stone-Wales defect in TBLG, we observe two Dirac cones that are shifted in both momentum space and energy. This up/down shift in energy results from the combined effect of a charge transfer between the two graphene layers and a chemical interaction between the layers, which mimics the effects of a transverse electric field. Charge density plots show that states near the Dirac points have significant admixture between the two layers. For Stone-Wales defects at other sites in TBLG, this basic structure is modified by the creation of minigaps at energy crossings. For a monovacancy, the Dirac cone of the pristine layer is shifted up in energy by ˜0.25 eV due to a combination of the requirement of the equilibration of Fermi energy between the two layers with different numbers of electrons, charge transfer, and chemical interactions. Both kinds of defects increase the density of states at the Fermi level. The monovacancy also results in spin polarization, with magnetic moments on the defect of 1.2-1.8 ?B.

Ulman, Kanchan; Narasimhan, Shobhana

2014-06-01