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Sample records for point electrode studies

  1. Accurate pointing of tungsten welding electrodes

    NASA Technical Reports Server (NTRS)

    Ziegelmeier, P.

    1971-01-01

    Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Tianhe C.; Grill, Warren M.

    2010-12-01

    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 casestissue anisotropy, a long active electrode and bipolar stimulationwas 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.

  3. Arc electrode interaction study

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  4. Weld electrode cooling study

    NASA Astrophysics Data System (ADS)

    Masters, Robert C.; Simon, Daniel L.

    1999-03-01

    The U.S. auto/truck industry has been mandated by the Federal government to continuously improve their fleet average gas mileage, measured in miles per gallon. Several techniques are typically used to meet these mandates, one of which is to reduce the overall mass of cars and trucks. To help accomplish this goal, lighter weight sheet metal parts, with smaller weld flanges, have been designed and fabricated. This paper will examine the cooling characteristics of various water cooled weld electrodes and shanks used in resistance spot welding applications. The smaller weld flanges utilized in modern vehicle sheet metal fabrications have increased industry's interest in using one size of weld electrode (1/2 inch diameter) for certain spot welding operations. The welding community wants more data about the cooling characteristics of these 1/2 inch weld electrodes. To hep define the cooling characteristics, an infrared radiometer thermal vision system (TVS) was used to capture images (thermograms) of the heating and cooling cycles of several size combinations of weld electrodes under typical production conditions. Tests results will show why the open ended shanks are more suitable for cooling the weld electrode assembly then closed ended shanks.

  5. GLAS Spacecraft Pointing Study

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

  6. Two-point concrete resistivity measurements: interfacial phenomena at the electrode-concrete contact zone

    NASA Astrophysics Data System (ADS)

    McCarter, W. J.; Taha, H. M.; Suryanto, B.; Starrs, G.

    2015-08-01

    Ac impedance spectroscopy measurements are used to critically examine the end-to-end (two-point) testing technique employed in evaluating the bulk electrical resistivity of concrete. In particular, this paper focusses on the interfacial contact region between the electrode and specimen and the influence of contacting medium and measurement frequency on the impedance response. Two-point and four-point electrode configurations were compared and modelling of the impedance response was undertaken to identify and quantify the contribution of the electrode-specimen contact region on the measured impedance. Measurements are presented in both Bode and Nyquist formats to aid interpretation. Concretes mixes conforming to BSEN206-1 and BS8500-1 were investigated which included concretes containing the supplementary cementitious materials fly ash and ground granulated blast-furnace slag. A measurement protocol is presented for the end-to-end technique in terms of test frequency and electrode-specimen contacting medium in order to minimize electrode-specimen interfacial effect and ensure correct measurement of bulk resistivity.

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

    SciTech Connect

    Aaberg, R.J.; Tunold, R.; Mogensen, M.; Berg, R.W.; Oedegaard, R. |

    1998-07-01

    The H{sub 2}-H{sub 2}O, 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 increased to more than twice the initial value with a time constant of about 40 h. In contrast, cathodic polarization reduced the performance of the electrode, and the cathodic current decreased significantly with a time constant of about 20 h. At anodic overpotentials it was observed that Ni was transported to the electrolyte surface, forming a necklace of Ni particles around the electrode/electrolyte contact. At cathodic overpotentials the transfer of Ni to the YSZ was found to be restricted, and it is proposed that agglomeration of dispersed metal particles reduced the three-phase boundary (TPB) length, and accordingly the cathodic current. The catalytic properties of the surfaces were significantly altered as the electrode was polarized. Transformation from cubic to tetragonal YSZ, due to segregation of the material, was observed on the surface of the electrolyte when the sample was kept at working conditions for long periods of time (135 days). The passage of current was not found to generate any permanent phase transformation in the YSZ.

  8. Direct writing electrodes using a ball pen for paper-based point-of-care testing.

    PubMed

    Li, Zedong; Li, Fei; Hu, Jie; Wee, Wei Hong; Han, Yu Long; Pingguan-Murphy, Belinda; Lu, Tian Jian; Xu, Feng

    2015-08-21

    The integration of paper with an electrochemical device has attracted growing attention for point-of-care testing, where it is of great importance to fabricate electrodes on paper in a low-cost, easy and versatile way. In this work, we report a simple strategy for directly writing electrodes on paper using a pressure-assisted ball pen to form a paper-based electrochemical device (PED). This method is demonstrated to be capable of fabricating electrodes on paper with good electrical conductivity and electrochemical performance, holding great potential to be employed in point-of-care applications, such as in human health diagnostics and food safety detection. As examples, the PEDs fabricated using the developed method are applied for detection of glucose in artificial urine and melamine in sample solutions. Furthermore, our developed strategy is also extended to fabricate PEDs with multi-electrode arrays and write electrodes on non-planar surfaces (e.g., paper cup, human skin), indicating the potential application of our method in other fields, such as fabricating biosensors, paper electronics etc. PMID:26079757

  9. Imaging study on acupuncture points

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    PubMed

    You, Wei; Cretu, Edmond; Rohling, Robert

    2013-11-01

    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

  11. Raman structural studies of the nickel electrode

    NASA Technical Reports Server (NTRS)

    Cornilsen, B. C.

    1985-01-01

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

  12. AC impedance study of degradation of porous nickel battery electrodes

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  13. [Radionuclide study of acupuncture points].

    PubMed

    Wu, C C; Jong, S B

    1990-12-01

    During recent years, upon investigation of the meridian which is an important part of the traditional concept in Chinese medicine, we have obtained several significant findings using radionuclide: 1. By subcutaneous injection (SC) of Tc-99m pertechnetate at acupuncture points K-3 and B-60, it was found that certain acupuncture points may be closely related to the venous drainage. 2. A new technique of radionuclide venography, namely SC-RNV of the lower limbs, was established through the above study. The SC-RNV subsequently proved to be clinically available in diagnosis of DVT and calf varicose veins. By SC injection of Tc-99m pertechnetate at various acupuncture points (APP) and nonacupuncture points (non-APP) it seemed that not every APP is closely related to venous drainage, and so is not the non-APP. As for the mechanism of SC-RNV, through SC injection of T1-201 chloride and Ga-67 citrate at K-3 respectively, it was found that the Na-K pumping system may play a major role in the drainage of soft tissue fluid from the APP into th venous flow. We now continue to investigate the meridian with radionuclide and hope to understand more clearly the physiological function of the APP, especially its relationship with the veins. PMID:2176243

  14. Electrode

    SciTech Connect

    Endoh, E.; Oda, Y.; Otouma, H.

    1981-03-10

    An electrode is prepared by etching an alloy substrate comprising a first metallic component selected from the group consisting of chromium, manganese, tantalum, niobium, vanadium, titanium, silicon, zirconium, germanium, scandium, yttrium and lanthanum and a second metallic component selected from the group consisting of iron, nickel, tungsten, copper, silver, cobalt and molybdenum to remove at least part of the first metallic component.

  15. Study of the contributions of the electrode materials to the plasma of a high-current vacuum spark

    SciTech Connect

    Bashutin, O. A.; Vovchenko, E. D.; Dodulad, E. I.; Savjolov, A. S.; Sarantsev, S. A.

    2012-03-15

    The contribution of the electrode material to the formation of the plasma of a low-inductive high-current vacuum spark and its influence on the process of discharge micropinching were studied using X-ray spectroscopy and laser diagnostics. Electrode system configurations are determined in which the contributions of the materials of both electrodes to the plasma emitting X-rays are comparable and in which the contribution of one electrode is dominating. It is found that discharge pinching occurs primarily in the vapor of the pointed electrode independently of its polarity. The experimental results indicate the formation of a suprathermal electron beam in the micropinch region.

  16. Study of Influence of Electrode Geometry on Impedance Spectroscopy

    SciTech Connect

    Ahmed, Riaz; Reifsnider, Kenneth L

    2011-01-01

    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.

  17. Point-Process Analysis of Neural Spiking Activity of Muscle Spindles Recorded from Thin-Film Longitudinal Intrafascicular Electrodes

    PubMed Central

    Citi, Luca; Djilas, Milan; Azevedo-Coste, Christine; Yoshida, Ken; Brown, Emery N.; Barbieri, Riccardo

    2012-01-01

    Recordings from thin-film Longitudinal Intra-Fascicular Electrodes (tfLIFE) together with a wavelet-based de-noising and a correlation-based spike sorting algorithm, give access to firing patterns of muscle spindle afferents. In this study we use a point process probability structure to assess mechanical stimulus-response characteristics of muscle spindle spike trains. We assume that the stimulus intensity is primarily a linear combination of the spontaneous firing rate, the muscle extension, and the stretch velocity. By using the ability of the point process framework to provide an objective goodness of fit analysis, we were able to distinguish two classes of spike clusters with different statistical structure. We found that spike clusters with higher SNR have a temporal structure that can be fitted by an inverse Gaussian distribution while lower SNR clusters follow a Poisson-like distribution. The point process algorithm is further able to provide the instantaneous intensity function associated with the stimulus-response model with the best goodness of fit. This important result is a first step towards a point process decoding algorithm to estimate the muscle length and possibly provide closed loop Functional Electrical Stimulation (FES) systems with natural sensory feedback information. PMID:22254803

  18. Porous nickel electrodes in water electrolysis. I - Electrode preparation and polarisation studies in strong alkali. II - Use of porous nickel electrodes in multicell module

    NASA Astrophysics Data System (ADS)

    Ragunathan, P.; Mitra, S. K.; Nayar, M. G.

    Replacement of 'plate' electrodes in water electrolysis cells by porous nickel electrodes leads to many advantages resulting in reduced specific energy consumption for hydrogen production. This paper describes the techniques developed to prepare the porous electrodes, their physical characteristics and their performance in strong alkali as hydrogen and oxygen gas electrodes. Steady state cell polarization studies over a range of 100 to 10,000 ASM at different temperatures were carried out in 6N K OH solution for different electrode samples prepared by alloy electrodeposition and powder metallurgy methods. Electrodes from these two methods were compared with respect to their electrochemical performance. The current carrying capacity at a given overvoltage was evaluated for different electrode thicknesses. Use of porous electrodes in electrolysis modules permits high current density operation at reduced cell voltages because the specific surface area in porous electrodes increases manifold due to fine pores and large pore densities. But the use of porous electrodes also imposes certain restrictions in design and operation of the module. The increased current densities cause high heat and gas generation fluxes within a small cell space, with the gases being released in the form of very fine bubbles. The above aspects are discussed in detail and the experimental studies carried out on the porous nickel electrodes to determine the bubble size, gas release and separation at different current densities are reported. Description of an electrolyzer of 1.5 cu nm/hr capacity and operation of the module with porous electrodes are given.

  19. Alkali metal thermoelectric converter (AMTEC) electrode lifetime studies

    NASA Technical Reports Server (NTRS)

    Bankston, C. Perry; Williams, Roger M.; Jeffries-Nakamura, Barbara; Colle, Terry

    1987-01-01

    Experimental studies are being conducted at JPL to identify long life, high area power density electrodes for AMTEC. Power versus time measurements are being made in a demountable electrode test cell and, for longer term experiments, a self-contained recirculating cell. The experimental apparatus and procedures are described in detail. The results show that thin film molybdenum electrodes can be designed to produce power near 0.5 W/sq cm for over two hundred hours. Also, platinum/tungsten electrodes exhibit power densities that are stable near 0.5 W/sq cm. If the performance of these electrodes is verified for longer periods (thousands of hours), then practical AMTEC systems will be possible.

  20. Chemically modified electrodes and related solution studies

    SciTech Connect

    Elliott, C.M.

    1993-04-01

    This report is divided into 5 sections: Ru[sub 4]/Fe complexes of tetra(4[prime]-methyl-2,2[prime]-bipyridine)porphyrin--catalytic epoxidation of olefins; water oxidation catalysis by doubly linked [mu]-oxo ruthenium complexes; polymer films formed by oxidation of transition metal electrodes into solutions of bisbipyridinealkane ligands; polymer films containing [CpMo([mu]-S)][sub 2]S[sub 2]CHR dinuclear clusters;and conducting polymer films for catalyst incorporation.

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

    SciTech Connect

    Liu, Wenzheng Sun, Guangliang Li, Chuanhui; Zhang, Rongrong

    2014-04-15

    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.

  2. Raman structural studies of the nickel electrode

    NASA Technical Reports Server (NTRS)

    Cornilsen, Bahne C.

    1994-01-01

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

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

    PubMed

    Zarzycki, Piotr; Preo?anin, Tajana

    2012-03-15

    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

  4. Electrochemical study of thiols and disulfides using modified electrodes

    SciTech Connect

    Linders, C.R.; Patriarche, G.J.; Kauffman, J.M.

    1986-01-01

    The electrochemical oxidative behavior of cysteine and several disulfides, such as cysteine, lipoic acid and disulfiram, have been investigated using a carbon paste (EPC) and a modified carbon paste (EPCM) electrode. The study has permitted the differentiation of the oxidative behavior of the thiol and of the disulfides. Modification of the carbon paste, by incorporating cobalt(II) phthalocyanine, offers interesting properties due to the electrocatalytic capability of the electrode. Using these types of electrodes the different molecules have been quantitatively determined at concentrations as low as 2.10/sup -7/ M. 14 references, 2 figures, 1 table.

  5. Comparative Study between Monopolar Electrodes and Bipolar Electrodes in Hysteroscopic Surgery

    PubMed Central

    Ahmed, Hazem Hashim; Abdella, Ahmed Hshim; Taha, Sayed Ahmed Mohmed

    2015-01-01

    Background The hysteroscopic surgery has become a simple and safe technique, with the use of small hysteroscopes and bipolar energy with trained surgeons, which can prevent abortions and probably increase fertility. Aim The study was conducted to evaluate the outcomes after hysteroscopic surgery by using uninopolar or bipolar electrodes. Setting and Design At the department of Obstetrics and Gynaecology, Qena university hospital and is a prospective non randomized clinical study. Materials and Methods One hundred fifty patients who included in this study were non randomly classified into two groups; one for hysteroscopic surgery by using bipolar electrode and the second group using unipolar electrode. Operative complications; bleeding, perforation, fluid over load and hyponatraemia were recorded. Also, operative time and hospital stay were included. Results There were no statistically significant differences between both groups in patients characteristics, ultrasono-graphic findings, serum sodium levels before surgical interference, perforation and intraoperative bleeding. The fluid overload was significantly higher in unipolar group (p value= 0.03), postoperative hyponatraemia was significantly marked in unipolar group (p<0.05) and the changes of the levels of serum sodium in unipolar group in comparison to bipolar group were significantly different (p = 0.01). The mean operative time was significantly less in the bipolar group when compared to the unipolar group (p = 0.01) and the hospital stay was obviously less for patients of the bipolar group in comparison to unipolar group (p=0.04). Conclusion Operative hysteroscopy using bipolar electrodes associated with significant decrease in hyponatraemia, operative time and postoperative hospital stay. So, it is safe and effective method when compared to using the unipolar electrodes. PMID:26674177

  6. Potentiometric studies at ORNL with hydrogen electrode concentration cells

    SciTech Connect

    Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J.

    1994-12-31

    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.

  7. The development of a micropatterned electrode for studies of zinc electrodeposition

    SciTech Connect

    Sutija, D.P.; Muller, R.H.; Tobias, C.W.

    1986-12-01

    A micropatterned electrode was prepared for the study of electrocrystallization. Using microphotolithography, in conjunction with evaporation and pulse electrodeposition of thin films, a set of artificially roughened electrodes with hemispherical surface features five microns in diameter was developed. Voltammetric studies were conducted to determine the best electrode material. Gold, platinum, and various carbon surfaces were evaluated for zinc nucleation density and hydrogen overpotential. Surface homogeneity was examined by both light and scanning electron microscopy. Gold was determined to possess the best combination of material properties: chemical inertness, low melting point, and a high work function allowing underpotential deposition of zinc which reduces the rate of hydrogen evolution. Stripping coulometry was employed to determine zinc limiting currents, and evaluate effective diffusion coefficients in concentrated zinc chloride solutions. Although the method worked well for dilute zinc chloride and copper sulfate solutions, it failed at higher current densities; the emergence of surface roughness obscured actual limiting current plateaus.

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

    PubMed Central

    2013-01-01

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

  9. In situ STM studies of polycrystalline platinum electrodes

    NASA Astrophysics Data System (ADS)

    Szklarczyk, Marek; Bockris, John O'M.

    1991-01-01

    In situ scanning tunneling microscopy (STM) was applied in a 10 -2M NaClO 4 solution to study topographical changes of a platinum electrode surface due to its oxidation and reduction. Surface morphology depends on the electrode potential. There are two stages in surface reduction: the fast electrochemical charge transfer and the slow crystallographic reconstruction. Reconstruction during surface reduction tends to proceed in the direction of the topography obtained during the annealing process. Methods of avoiding Faradaic current flowing through the STM tip are discussed in detail.

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

    SciTech Connect

    Escudero-Escribano, M.; Michoff, M. E. Z.; Leiva, E. P. M.; Markovic, N. M.; Gutierrez, C.; Cuesta, A.

    2011-08-22

    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.

  11. A study of electrode passivation during aqueous phenol electrolysis

    SciTech Connect

    Gattrell, M.; Kirk, D.W. )

    1993-04-01

    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 30 ms anodic pulse. X-ray photoelectron spectroscopy shows that the passivating polymer film is oxidized incompletely with many hydroxyl groups present. Increased potential increased the polymerization rate, but above 1.0 V vs. SCE film decomposition reactions also occurred. Increased phenol concentration increased the charge required to initiate passivation. Potential steps to the open-circuit potential or to mo9re cathodic values can interfere with the passivation process. Chronamperometric results show that the current decay at the passivated electrode is roughly inversely proportional to time and that the currents for a fixed amount of polymerization reaction follow a Tafel relationship. This t;type of decay is not due to a limitation caused b;y reactant diffusion through, nor IR drop across, a growing film but is more characteristic of electron tunneling through a growing insulating barrier layer. The model proposed for the observed behavior involves the formation of a region of high molecular weight, oxidized material at the electrode surface which blocks further reaction at the electrode. The rate-determining step at the passivated electrode is therefore electron tunneling through this unreactive material.

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

    PubMed

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

    2013-12-01

    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

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

    PubMed Central

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

    2013-01-01

    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

  14. Model electrode structures for studies of electrocatalyst degradation.

    SciTech Connect

    St. Pierre, Jean; Atanassov, Plamen Borissov; Datye, Abhaya K.; Goeke, Ronald S.

    2010-10-01

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

  15. Electrode surface studies by LEED-Auger

    NASA Technical Reports Server (NTRS)

    Ogrady, W. E.; Woo, M. Y. C.; Hagans, P. L.; Yeager, E.

    1977-01-01

    The role the electronic and geometric structures of the metal surface play in electrochemical surface reactions remains as yet an unknown factor. In order to investigate these surface contributions to electrochemical reactions, a low-energy-electron diffraction (LEED) and an Auger electron spectrometer (AES) have been combined with an electrochemical thin-layer cell. The surface to be studied electrochemically is first characterized by LEED-AES and then transferred into a second chamber where it becomes part of the electrochemical thin-layer cell. Electrochemical reactions are then run on this surface. The sample may then be transferred back to the LEED-AES chamber for further characterization. Data on Pt (111) will be presented.

  16. Theoretical modeling of RF ablation with internally cooled electrodes: comparative study of different thermal boundary conditions at the electrode-tissue interface.

    PubMed

    Rivera, Mara J; Molina, Juan A Lpez; Trujillo, Macarena; Berjano, Enrique J

    2009-07-01

    Previous studies on computer modeling of RF ablation with cooled electrodes modeled the internal cooling circuit by setting surface temperature at the coolant temperature (i.e., Dirichlet condition, DC). Our objective was to compare the temperature profiles computed from different thermal boundary conditions at the electrode-tissue interface. We built an analytical one-dimensional model based on a spherical electrode. Four cases were considered: A) DC with uniform initial condition, B) DC with pre-cooling period, C) Boundary condition based on Newton's cooling law (NC) with uniform initial condition, and D) NC with a pre-cooling period. The results showed that for a long time (120 s), the profiles obtained with (Cases B and D) and without (Cases A and C) considering pre-cooling are very similar. However, for shorter times ( 30 s), Cases A and C overestimated the temperature at points away from the electrode-tissue interface. In the NC cases, this overestimation was more evident for higher values of the convective heat transfer coefficient (h). Finally, with NC, when h was increased the temperature profiles became more similar to those with DC. The results suggest that theoretical modeling of RF ablation with cooled electrodes should consider: 1) the modeling of a pre-cooling period, especially if one is interested in the thermal profiles registered at the beginning of RF application; and 2) NC rather than DC, especially for low flow in the internal circuit. PMID:19566131

  17. ECG electrodes. A study of electrical and mechanical long-term properties.

    PubMed

    Ask, P; Oberg, P A; Odman, S; Tenland, T; Skogh, M

    1979-04-01

    The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar. PMID:442948

  18. Studies of Low-Current Back-Discharge in Point-Plane Geometry with Dielectric Layer

    SciTech Connect

    Jaworek, Anatol; Rajch, Eryk; Krupa, Andrzej; Czech, Tadeusz; Lackowski, Marcin

    2006-01-15

    The paper presents results of spectroscopic investigations of back-discharges generated in the point-plane electrode geometry in ambient air at atmospheric pressure, with the plane electrode covered with a dielectric layer. Fly ash from an electrostatic precipitator of a coal-fired power plant was used as the dielectric layer in these investigations. The discharges for positive and negative polarities of the needle electrode were studied by measuring optical emission spectra at two regions of the discharge: near the needle electrode and dielectric layer surface. The visual forms of the discharge were recorded and correlated with the current-voltage characteristics and optical emission spectra. The back-arc discharge was of particular interest in these studies due to its detrimental effects it causes in electrostatic precipitators.

  19. Factors Associated with Incomplete Insertion of Electrodes in Cochlear Implant Surgery: A Histopathologic Study

    PubMed Central

    Lee, Joonhan; Nadol, Joseph B.; Eddington, Donald K.

    2011-01-01

    Objectives Atraumatic and complete insertion of the electrode array is a stated objective of cochlear implant surgery. However, it is known that obstructions within the cochlea such as new bone formation, cochlear otosclerosis, temporal bone fracture, and cochlear anomalies may limit the depth of insertion of the electrode array. In addition, even among patients without obvious clinical or radiographic indicators of obstruction, incomplete insertion may occur. The current study is a histopathologic evaluation of possible sources of resistance to insertion of the electrode array using the temporal bone collection of the Massachusetts Eye and Ear Infirmary. Methods Forty temporal bones from patients who in life had undergone cochlear implantation were evaluated. Temporal bones were removed at autopsy and fixed and prepared for histologic study by standard techniques. Specimens were then serially sectioned and reconstructed by 2-dimensional methods. Two electrode metrics were determined for each bone: the inserted length (IL: the distance measured from the cochleostomy site to the apical tip of the electrode) and the active electrode length (AEL: the distance between the most basal and most apical electrodes on the electrode array). The ratio of these two metrics (IL/AEL) was used to split the temporal bones into two groups: those with incomplete insertion (n = 27, IL/AEL <1.0) and those with complete insertion (n = 13, IL/AEL ≥1.0). Seven possible histopathologic indicators of resistance to insertion of the electrode due to contact with the basilar membrane, osseous spiral lamina and/or spiral ligament were evaluated by analysis of serial sections from the temporal bones along the course of the electrode tracks. Results Obvious obstruction by abnormal intracochlear bone or soft tissue accounted for only 6 (22%) of the 27 partial insertions. Of the remaining 21 bones with incomplete insertions and 13 bones with complete insertions, dissection of the spiral ligament to the lateral cochlear wall was the only histopathologic indicator of insertion resistance identified with significantly higher frequency in the partial-insertion bones than in the complete-insertion bones (p = 0.003). An observed trend for the percentage of complete insertions to decrease with the number of times the electrode penetrated the basilar membrane did not reach significance. In the bones without an obvious obstruction, the most frequently observed indicator of insertion resistance was dissection of the spiral ligament (with no contact of the lateral cochlear wall) identified in 67% (14/21) of partial-insertion bones and in 92% (12/13) of complete-insertion bones. Conclusion These results are consistent with the view that (1) electrode contact with cochlear structures resulting in observable trauma to the basilar membrane, osseous spiral lamina and/or spiral ligament does not necessarily impact the likelihood of complete insertion of the electrode array and (2) once contact trauma to the spiral ligament reaches the point of dissection to the cochlear wall, the likelihood of incomplete insertion increases dramatically. PMID:20571258

  20. Lunar libration point flight dynamics study

    NASA Technical Reports Server (NTRS)

    1969-01-01

    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.

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

    PubMed Central

    Thakore, Vaibhav; Molnar, Peter; Hickman, James J.

    2014-01-01

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

  2. Preliminary results from studies of limited streamer tubes with external electrode readout

    SciTech Connect

    Callegari, G.; DiCapua, E.; Piemontese, L.; Calcaterra, A.; de Sangro, R.; De Simone, P.; Peruzzi, I.; Piccolo, M.; Busza, W.; Cartwright, S.; Friedman, J.; Fuess, S.; Hansl-Kozanecka, T.; Kendall, H.; Lyons, T.; Osborne, L.; Rosenson, L.; Ross, D.; Schneekloth, U.; Taylor, F.; Verdier, R.; Williams, D.; Yamartino, J.; Bacchetta, N.; Bisello, D.; Castro, A.; Loreti, M.; Pescara, L.; Toniolo, D.; Wyss, J.; Alpat, B.; Artemi, C.; Battiston, R.; Bilei, G.M.; Cappelletti, C.; Dell'Orso, R.; Mantovani, G.; Pauluzzi, M.; Servoli, L.; Scarlatella, M.; Beconcini, F.; Castaldi, R.; Cazzola, U.; Vannini, C.; Verdini, P.G.; Messner, R.; Zdarko, R.; Johnson, J.R.

    1987-10-01

    We report initial results from a new multichannel test facility built to study the properties of chambers constructed for the Warm Iron Calorimeter of the SLD detector as they are made. The correlation between the signal on the external electrodes and the wire is observed. A systematic study of the transition between the proportional and streamer modes of operation is given as a function of argonisobutane mixture and high voltage. The pulse height spectrum is correlated with the operational plateau of the chambers and may be used to determine optimum operating points under a variety of conditions.

  3. A morphological study of SEI film on graphite electrodes

    NASA Astrophysics Data System (ADS)

    Zane, D.; Antonini, A.; Pasquali, M.

    Morphological features of the protective layer on the graphitic electrodes, formed by reduction of electrolytic solution components during the first cycle, are investigated by SEM and common electrochemical techniques. As expected, the interaction between electrode and solution is very important, leading to quite different results for different solutions. Here, results for solution of various solvents ratio are reported. It appears that the performances of the electrodes are strongly dependent on their surface chemistry in solutions. We can conclude that the nature of the surface film plays a key role for the electrode stability or to capacity decrease always related to an increase of the electrode itself impedance.

  4. Multi-point Study of Magnetosheath Waves

    NASA Astrophysics Data System (ADS)

    Bates, I.; Balikhin, M.; Alleyne, H.; Yearby, K.; Andre, M.; Dunlop, M.

    Space Systems Group, University of Sheffield, U.K. Swedish Institute of Space Physics, Uppsala, Sweden 3 Imperial College, London, U.K.The magnetosheath is a highly turbulent plasma region. It is important to understand waves in this region as the magnetosheath forms the intermediate region between the solar wind and the Earth's inner Magnetosphere and these waves can be a mechanism for energy transport through the medium. Multi-point measurements, in particular from CLUSTER, enable a technique to be used that can determine the propagation direction of these waves. This enables a comprehensive experimental study of magnetosheath waves. Recent results of these studies are presented in this paper.

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

    PubMed Central

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

    2015-01-01

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

  6. The study of capacitive deionization behavior of a carbon nanotube electrode from the perspective of charge efficiency.

    PubMed

    Li, Haibo; Liang, Sen; Gao, Mangmang; Li, Guolong; Li, Jin; He, Lijun

    2015-01-01

    In this work, the capacitive deionization (CDI) performance of a single-walled carbon nanotube (CNT) electrode has been studied from the point view of charge efficiency theory. It is revealed here that the charge efficiency of a CNT electrode is strongly dependent upon the cell voltage and solution concentration. Either the high cell voltage or the low ionic strength results in a high charge efficiency, implying that CDI is expected to be a promising technique for an aqueous solution with low ionic strength. Additionally, it is found that the high decay constant and high electrical double-layer capacity are beneficial to enhance electrosorption performance. PMID:25607673

  7. Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Diamandis, E. P.; And Others

    1983-01-01

    The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

  8. FEM numerical model study of electrosurgical dispersive electrode design parameters.

    PubMed

    Pearce, John A

    2015-08-01

    Electrosurgical dispersive electrodes must safely carry the surgical current in monopolar procedures, such as those used in cutting, coagulation and radio frequency ablation (RFA). Of these, RFA represents the most stringent design constraint since ablation currents are often more than 1 to 2 Arms (continuous) for several minutes depending on the size of the lesion desired and local heat transfer conditions at the applicator electrode. This stands in contrast to standard surgical activations, which are intermittent, and usually less than 1 Arms, but for several seconds at a time. Dispersive electrode temperature rise is also critically determined by the sub-surface skin anatomy, thicknesses of the subcutaneous and supra-muscular fat, etc. Currently, we lack fundamental engineering design criteria that provide an estimating framework for preliminary designs of these electrodes. The lack of a fundamental design framework means that a large number of experiments must be conducted in order to establish a reasonable design. Previously, an attempt to correlate maximum temperatures in experimental work with the average current density-time product failed to yield a good match. This paper develops and applies a new measure of an electrode stress parameter that correlates well with both the previous experimental data and with numerical models of other electrode shapes. The finite element method (FEM) model work was calibrated against experimental RF lesions in porcine skin to establish the fundamental principle underlying dispersive electrode performance. The results can be used in preliminary electrode design calculations, experiment series design and performance evaluation. PMID:26736814

  9. Study on the Realization of Indium Point

    NASA Astrophysics Data System (ADS)

    Widiatmo, Januarius V.; Yamazawa, Kazuaki; Satou, Kouichi; Tamba, Jun; Arai, Masaru

    Indium point cells are fabricated using ingots of various forms from a variety of sources (manufacturers). Using these cells, newly built indium point furnaces are evaluated and their reliability is confirmed. The indium point realizations based on the single solid-liquid method (SSL method) and multi solid-liquid method (MSL method) are evaluated. The effect of impurities in the ingots is evaluated from the dependency of the slope of the freezing curve on the change in furnace temperature, the indium point depression based on the impurity analysis, and the cell comparison. The results show equality among the cells. Based on the results obtained, the uncertainty in realizing the indium point using the described indium point cells and indium point furnaces is estimated. The new uncertainty budget introduces uncertainties coming from plateau repeatability and chemical impurity derived by the present work, the values of which are significantly lower than those adopted in the current calibration service.

  10. Advances in Studies of Electrode Kinetics and Mass Transport in AMTEC Cells (abstract)

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Previous work reported from JPL has included characterization of electrode kinetics and alkali atom transport from electrodes including Mo, W, WRh(sub x), WPt(sub x)(Mn), in sodium AMTEC cells and vapor exposure cells, and Mo in potassium vapor exposure cells. These studies were generally performed in cells with small area electrodes (about 1 to 5 cm(sup 2)), and device geometry had little effect on transport. Alkali diffusion coefficients through these electrodes have been characterized, and approximate surface diffusion coefficients derived in cases of activated transport. A basic model of electrode kinetic at the alkali metal vapor/porous metal electrode/alkali beta'-alumina solid electrolyte three phase boundary has been proposed which accounts for electrochemical reaction rates with a collision frequency near the three phase boundary and tunneling from the porous electrode partially covered with adsorbed alkali metal atoms. The small electrode effect in AMTEC cells has been discussed in several papers, but quantitative investigations have described only the overall effect and the important contribution of electrolyte resistance. The quantitative characterization of transport losses in cells with large area electrodes has been limited to simulations of large area electrode effects, or characterization of transport losses from large area electrodes with significant longitudinal temperature gradients. This paper describes new investigations of electrochemical kinetics and transport, particularily with WPt(sub 3.5) electrodes, including the influence of electrode size on the mass transport loss in the AMTEC cell. These electrodes possess excellent sodium transport properties making verification of device limitations on transport much more readily attained.

  11. Some Studies into Electrical Discharge Machining of Nimonic75 Super Alloy Using Rotary Copper Disk Electrode

    NASA Astrophysics Data System (ADS)

    Singh, S.; Pandey, A.

    2013-05-01

    The present study reports the rotary disk electrical discharge machining of Nimonic75 super alloy, extensively used in aerospace industries. The experiments have been performed using Taguchi's orthogonal array L18 (21 × 35) with copper disk electrode. The control factors considered were, viz., peak current, pulse on time, pulse off-time, gap voltage, and rotational speed of disk electrode with three levels each, and aspect ratio (AR) of the disk electrode having two levels, as noise factor. The novel approach of this article is to study the effect of the AR of the disk electrode on the performance measures, viz., material removal rate, disk electrode wear rate, and surface roughness. The results based on Taguchi's analysis show that among the considered process parameters, the AR and peak current significantly affect the machining characteristics. Furthermore, the rotating disk electrode easily flushes off the debris, resulting in better machining and reducing the chances of re-solidified layer formation.

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

    NASA Technical Reports Server (NTRS)

    Castro, A.

    1986-01-01

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

  13. Study of impedance spectra for dry and wet EarEEG electrodes.

    PubMed

    Kappel, Simon L; Kidmose, Preben

    2015-08-01

    EarEEG is a novel recordings concept where electrodes are embedded on the surface of an earpiece customized to the individual anatomical shape of the users ear. A key parameter for recording EEG signals of good quality is a stable and low impedance electrode-body interface. This study characterizes the impedance for dry and wet EarEEG electrodes in a study of 10 subjects. A custom made and automated setup was used to characterize the impedance spectrum from 0.1 Hz - 2 kHz. The study of dry electrodes showed a mean (standard deviation) low frequency impedance of the canal electrodes of 1.2MΩ (1.4MΩ) and the high frequency impedance was 230 kΩ (220 kΩ). For wet electrodes the low frequency impedance was 34 kΩ (37 kΩ) and the high frequency impedance was 5.1 kΩ (4.4 kΩ). The high standard deviation of the impedance for dry electrodes imposes very high requirements for the input impedance of the amplifier in order to achieve an acceptable common-mode rejection. The wet electrode impedance was in line with what is typical for a wet electrode interface. PMID:26736963

  14. Astrometric Telescope Facility isolation and pointing study

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  16. Empirical study on human acupuncture point network

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    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.

  17. ICESat Spacecraft Pointing Support Study Grant

    NASA Technical Reports Server (NTRS)

    2000-01-01

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

  18. Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE.

    PubMed

    Grka, B; Nilsson, B; Fernndez-Varea, J M; Svensson, R; Brahme, A

    2006-08-01

    A new dosimeter, based on chemical vapour deposited (CVD) diamond as the active detector material, is being developed for dosimetry in radiotherapeutic beams. CVD-diamond is a very interesting material, since its atomic composition is close to that of human tissue and in principle it can be designed to introduce negligible perturbations to the radiation field and the dose distribution in the phantom due to its small size. However, non-tissue-equivalent structural components, such as electrodes, wires and encapsulation, need to be carefully selected as they may induce severe fluence perturbation and angular dependence, resulting in erroneous dose readings. By introducing metallic electrodes on the diamond crystals, interface phenomena between high- and low-atomic-number materials are created. Depending on the direction of the radiation field, an increased or decreased detector signal may be obtained. The small dimensions of the CVD-diamond layer and electrodes (around 100 microm and smaller) imply a higher sensitivity to the lack of charged-particle equilibrium and may cause severe interface phenomena. In the present study, we investigate the variation of energy deposition in the diamond detector for different photon-beam qualities, electrode materials and geometric configurations using the Monte Carlo code PENELOPE. The prototype detector was produced from a 50 microm thick CVD-diamond layer with 0.2 microm thick silver electrodes on both sides. The mean absorbed dose to the detector's active volume was modified in the presence of the electrodes by 1.7%, 2.1%, 1.5%, 0.6% and 0.9% for 1.25 MeV monoenergetic photons, a complete (i.e. shielded) (60)Co photon source spectrum and 6, 18 and 50 MV bremsstrahlung spectra, respectively. The shift in mean absorbed dose increases with increasing atomic number and thickness of the electrodes, and diminishes with increasing thickness of the diamond layer. From a dosimetric point of view, graphite would be an almost perfect electrode material. This study shows that, for the considered therapeutic beam qualities, the perturbation of the detector signal due to charge-collecting graphite electrodes of thicknesses between 0.1 and 700 microm is negligible within the calculation uncertainty of 0.2%. PMID:16861769

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Guo, Yuyan

    This research focuses on preparation, kinetics, and performance studies of mixed ionic and electronic conducting electrodes (MIEE) applied in an alkali metal thermal to electric converter (AMTEC). Two types of MIEE, metal/sodium titanate and metal/beta″-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/beta″-alumina solid electrolyte (BASE) interface was studied in terms of the chemical potential of Na-Al-Ti-O system at 1100K (typical AMTEC operating temperature). Ni metal was compatible with sodium titanate and BASE and displayed the best initial performance among all tested PMEs. Ni/sodium titanate electrodes with 4/1 mass ratios of metal/ceramic performed best among all tested electrodes. Scanning Electron Microscope (SEM) observations showed that grain agglomeration, which is the main mechanism for electrode degradation, occurred in all tested electrodes. Ceramic components were able to effectively limit the growth of metal grains and resulted in a long lifetime for MIEEs. Ni particles in the MIEE formed a network microstructure that was close to the theoretical morphology of the ideal electrode. A model based on percolation theory was constructed to interpret and predict the performance of MIEEs. The electrode kinetics was studied and a theoretical expression for the interface impedance was derived for both PME and MIEE, using electrochemical impedance spectroscopy (EIS). The conductivity of the Na2Ti 3O7 and Na2Ti6O13 mixture was measured. The average activation energy for the bulk conductivity was 0.87ev. Finally, theoretical analysis clarified that the transfer coefficient alpha value change would cause at most a few percent change in the electrode performance parameter B.

  1. Bright point study. [of solar corona

    NASA Technical Reports Server (NTRS)

    Tang, F.; Harvey, K.; Bruner, M.; Kent, B.; Antonucci, E.

    1982-01-01

    Transition region and coronal observations of bright points by instruments aboard the Solar Maximum Mission and high resolution photospheric magnetograph observations on September 11, 1980 are presented. A total of 31 bipolar ephemeral regions were found in the photosphere from birth in 9.3 hours of combined magnetograph observations from three observatories. Two of the three ephemeral regions present in the field of view of the Ultraviolet Spectrometer-Polarimeter were observed in the C IV 1548 line. The unobserved ephemeral region was determined to be the shortest-lived (2.5 hr) and lowest in magnetic flux density (13G) of the three regions. The Flat Crystal Spectrometer observed only low level signals in the O VIII 18.969 A line, which were not statistically significant to be positively identified with any of the 16 ephemeral regions detected in the photosphere. In addition, the data indicate that at any given time there lacked a one-to-one correspondence between observable bright points and photospheric ephemeral regions, while more ephemeral regions were observed than their counterparts in the transition region and the corona.

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

    PubMed

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

    2013-05-28

    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

  3. Study on the spatial resolution of EEG--effect of electrode density and measurement noise.

    PubMed

    Ryynnen, O; Hyttinen, J; Malmivuo, J

    2004-01-01

    The spatial resolution of electroencephalography (EEG) is studied by means of inverse cortical EEG solution. Special attention is paid to the effect of electrode density and the effect of measurement noise on the spatial resolution. A three-layer spherical head model is used as a volume conductor to obtain the source-field relationship of cortical potentials and scalp potential field. Effect of measurement noise is evaluated with truncated singular value decomposition (TSVD). Also simulations about different electrode systems' ability to separate cortical sources are performed. The results show that as the measurement noise increases the advantage of dense electrode systems decreases. Our results suggest that in clinical measurement environment it is always beneficial to use at least 64 measurement electrodes. In low-noise realistic measurement environment the use of even 256 measurement electrodes is beneficial. PMID:17271283

  4. Anodic iridium oxide films: An UPS study of emersed electrodes

    NASA Astrophysics Data System (ADS)

    Ktz, E. R.; Neff, H.

    1985-09-01

    Formation of anodic iridium oxide films has been monitored using Ultraviolet Photoemission Spectroscopy (UPS) of the emersed electrodes. The potential dependent valence band spectra clearly show the onset of oxide formation at about 0.6 V versus SCE. The density of states at the Fermi level and the positron of the Fermi level with respect to the maximum of the t 2g band of the oxide indicates a transition from metallic to semiconducting behaviour of the oxide. Protonation of the oxide is associated with increased emission from OH species. A linear correlation between electrode potential and workfunction change is observed for the metal as well as for the oxide. Our results confirm known band theory models and provide a fundamental understanding of the electrochromism of anodic iridium oxide films.

  5. Study on the Inter-electrode Process of Aluminum Electrolysis

    NASA Astrophysics Data System (ADS)

    Yang, Youjian; Gao, Bingliang; Wang, Zhaowen; Shi, Zhongning; Hu, Xianwei

    2016-02-01

    The voltage distribution between carbon anode and aluminum cathode in cryolite electrolyte saturated with alumina was determined using a scanning reference electrode to investigate the inter-electrode process during aluminum electrolysis. The results showed that the anode-cathode-distance (ACD) is consisted of three parts: a relatively stable cathode boundary layer, bubble-free electrolyte layer, and gas-liquid layer near the anode. The aluminum diffusion layer with high electronic conductivity as well as the crystallization of cryolite was observed at the cathode boundary layer. The thickness of the aluminum diffusion layer varied with current density, which further determined the critical ACD. The thickness, coverage, and releasing frequency of the bubbles on both laboratory and industrial prebaked cells were derived, and it is found that the average bubble coverage decreases with current density, and the average coverage at 0.8 A cm-2 is approximately 50 pct.

  6. Study on the Inter-electrode Process of Aluminum Electrolysis

    NASA Astrophysics Data System (ADS)

    Yang, Youjian; Gao, Bingliang; Wang, Zhaowen; Shi, Zhongning; Hu, Xianwei

    2015-11-01

    The voltage distribution between carbon anode and aluminum cathode in cryolite electrolyte saturated with alumina was determined using a scanning reference electrode to investigate the inter-electrode process during aluminum electrolysis. The results showed that the anode-cathode-distance (ACD) is consisted of three parts: a relatively stable cathode boundary layer, bubble-free electrolyte layer, and gas-liquid layer near the anode. The aluminum diffusion layer with high electronic conductivity as well as the crystallization of cryolite was observed at the cathode boundary layer. The thickness of the aluminum diffusion layer varied with current density, which further determined the critical ACD. The thickness, coverage, and releasing frequency of the bubbles on both laboratory and industrial prebaked cells were derived, and it is found that the average bubble coverage decreases with current density, and the average coverage at 0.8 A cm-2 is approximately 50 pct.

  7. Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

    PubMed

    Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

    2012-09-01

    In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436

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

    PubMed Central

    Seker, Erkin; Berdichevsky, Yevgeny; Begley, Matthew R; Reed, Michael L; Staley, Kevin J; Yarmush, Martin L

    2011-01-01

    Neural electrodes are essential tools for the study of the nervous system and related diseases. Low electrode impedance is a figure of merit for sensitive detection of neural electrical activity and numerous studies have aimed to reduce impedance. Unfortunately, most of these efforts have been tethered by a combination of poor functional coating adhesion, complicated fabrication techniques, and poor fabrication repeatability. We address these issues with a facile method for reliably producing multiple-electrode arrays with low impedance by patterning highly adherent nanoporous gold films using conventional microfabrication techniques. The high surface area-to-volume ratio of self-assembled nanoporous gold results in a more than 25-fold improvement in the electrode-electrolyte impedance, where at 1 kHz, 850 kΩ impedance for conventional Au electrodes is reduced to 30 kΩ for nanoporous gold electrodes. Low impedance provides a superior signal-to-noise ratio for detection of neural activity in noisy environments. We systematically studied the effect of film morphology on electrode impedance and successfully recorded field potentials from rat hippocampal slices. Here, we present our fabrication approach, the relationship between film morphology and impedance, and field potential recordings. PMID:20203356

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

    ERIC Educational Resources Information Center

    Turchi, Sandra; And Others

    1989-01-01

    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)

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  11. Study of the Properties of Plessey's Electrocardiographic Capacitive Electrodes for Portable Systems

    NASA Astrophysics Data System (ADS)

    Uvarov, A. A.; Lezhnina, I. A.; Overchuk, K. V.; Starchak, A. S.; Akhmedov, Sh D.; Larioshina, I. A.

    2016-01-01

    Cardiac diseases are still most widely spread in all regions of the world. And more and more devices are invented to satisfy increasing requirements of the patients. One of the perspective technologies in cardiac diagnostics is capacitive sensing ECG electrodes. This article describes a study of the properties of electrocardiographic capacitive electrodes PS25255 from Plessey Semiconductors for portable systems as well as some undocumented parameters of these sensors. We developed special cardiograph using Plessey's electrodes and applied to the number of patients with ischemic heart disease. We paid our attention mostly to the correct transition of the ST segment as it has critical impact on the diagnostics of ischemic heart disease.

  12. Electrooxidation of flavonoids at platinum electrode studied by cyclic voltammetry.

    PubMed

    Masek, Anna; Zaborski, Marian; Chrzescijanska, Ewa

    2011-07-15

    Flavonoids are natural vegetable dyes synthesized from phenylalanine. They are responsible for colour of blooming plant portions. Moreover, they are very important for human health due to their activity as free radical acceptors. Cyclic and differential pulse voltammetry was used in the determination of kinetic parameters of flavonoids electrooxidation. Electrochemical measurements of the oxidation of organic compounds can be helpful in understanding how these compounds are metabolised by living organisms. Flavonoids electrochemical oxidation is an irreversible reaction at a platinum electrode. In the case of morin hydrate, rutin, dihydroxyflavone, trihydroxyflavone, hesperidin, quercetin, the first step of the electrooxidation includes an exchange of two electrons during the oxidation of hydroxyl groups in the ring B. Hydroxyl groups in the rings A and C are probably oxidised in subsequent steps. The heterogeneous rate constants (k(bh)) determined for the flavonoids electrooxidation are as follows: morin - 3.5910(-4), rutin - 4.4210(-4), dihydroxyflavone - 4.5410(-4), trihydroxyflavone - 4.1910(-4), hesperidin - 4.5010(-4) and quercetin - 4.6310(-4)cms(-1). Their anodic transition coefficient ranged from 0.63 to 0.48 (n=2). Xanthone and flavone were oxidised easiest and quickest among other substrates at the platinum electrode with the heterogeneous rate constants (k(bh)) of 7.0810(-4) and 6.4610(-4)cms(-1), respectively. PMID:23140722

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  14. High-freezing-point fuel studies

    NASA Technical Reports Server (NTRS)

    Tolle, F. F.

    1980-01-01

    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.

  15. Simultaneous determination of tyrosine and tryptophan by mesoporous silica nanoparticles modified carbon paste electrode using H-point standard addition method.

    PubMed

    Tashkhourian, J; Daneshi, M; Nami-Ana, S F

    2016-01-01

    A simple, selective and sensitive sensor based on mesoporous silica nanoparticles modified carbon paste electrode (MSNs/CPE) is introduced for electrochemical determination of tyrosine (Tyr) and tryptophan (Trp). Compared with the unmodified electrode and commercial SiO2 modified electrode (SiO2/CPE), the oxidation peak current significantly improved for both amino acids. Under optimized experimental conditions, the oxidation peak current of Trp was linear over a concentration range of 5.0נ10(-8) to 4.0נ10(-4)M with a detection limit of 3.4נ10(-8)M. The oxidation peak current of Tyr was linear over a concentration range from 5.0נ10(-7) to 6.0נ10(-4)M with a detection limit of 1.5נ10(-7)M. For simultaneous determination Trp and Tyr, H-point standard addition method was applied to resolve the overlapping of differential pulse voltammetric peaks of Trp and Tyr. The results showed that the method was successfully applied to the simultaneous determination of Trp and Tyr in some synthetic samples. Moreover, the applicability of the method was demonstrated by the recovery tests of Trp and Tyr in artificial urine. PMID:26703257

  16. Coulometric study of ethanol adsorption at a polycrystalline platinum electrode

    NASA Astrophysics Data System (ADS)

    Gilman, Sol

    2012-01-01

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

  17. Results of a study on rate of thickening of nickel electrodes

    NASA Astrophysics Data System (ADS)

    Bernhardt, M. P.; Maurer, D. W.

    A study has been carried out in order to investigate the effect of various operational parameters on the growth of nickel electrodes, a major cause of failure of aerospace Ni/Cd batteries. The variables investigated include: electrode impregnation process, manufacturing lot variations, depth of discharge (DOD), charge rate (CR), trickle charge, reconditioning method, temperature, and electrolyte composition. Electrochemically impregnated electrodes exhibited no growth under any of the conditions tested. The growth rate of chemically impregnated electrodes increases at temperatures both higher and lower than room temperature, suggesting that satellite battery temperature reduction to minimize separator degradation must be tempered by plate growth rate considerations. It is also shown that lot to lot variability in the growth rate of chemically impregnated plates is larger than the effects of most of the other variables.

  18. Study on the distortion of apparent resistivity curves caused by the 'infinite' electrode space of a Pole-Pole array and its correction

    NASA Astrophysics Data System (ADS)

    Xiao, Le-Le; Wei, Jiu-Chuan; Niu, Chao; Shi, Long-Qing; Zhai, Pei-He; Yin, Hui-Yong; Xie, Dao-Lei

    2015-07-01

    The Pole-Pole (PP) array is widely used for measurements that incorporate two-dimensional (2-D) and three-dimensional (3-D) multi-electrode electrical resistivity surveys, although an effective equilibrium has not yet been achieved between two factors, the location of 'infinite' electrodes and the data utilisation of the effective resistivity, which affects the detection accuracy; thus, the data collected under the conditions of 'infinite' electrodes that are as finite as possible are maximally effective. Studies have shown that the optimum 'infinite' electrode distance must be greater than 20 times the current-potential electrode distance AM; this value is much greater than the currently used value of 5 to 10 times AM. However, limitations imposed by landforms and topographic conditions, such as mountainous areas and coal mine roadways, often prevent the 'infinite' condition from being satisfied. In this study, a field test was designed and performed by adopting a particular PP array to collect sounding data under different 'infinite' electrode distances, and the differences were analysed in the apparent resistivity curves calculated with different geometric coefficients. The results reveal that when the 'infinite' electrode space is finite relative to AM, significant distortion may occur, and a minimum inflection point may appear in the sounding curve of apparent resistivity that is calculated with the geometric coefficient Kpp. Although the data past the minimum inflection point of ρs-mpp curve lose their value for the sounding application, a portion of the first segment of the distorted curve can be used, therefore, a correction formula under the condition of non-infinite electrode (Bing and Greenhalgh, 1998) space in a PP array is derived based on traditional electric field theories and formulas of apparent resistivity under different electrode arrays. The error analysis after correction indicates that the data utilisation ratio in the corrected effective apparent resistivity is significantly improved, and all the data that appear before the minimum inflection point can be effectively corrected. Additionally, the error between the corrected apparent resistivity and the value under an ideal state (when BM is at least 20 times AM) is less than 5%. Engineering application cases are conducted to validate the effectiveness of this correction formula, and the results indicate that this formula can be applied to process the resistivity sounding data affected by the 'infinite' electrodes.

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

    PubMed Central

    Gu, Y; Levin, C S

    2014-01-01

    We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3-D positioning Cadmium Zinc Telluride (CZT) 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 mm 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 ns to ~127.5 ns 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 ns 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 V to −80 V w.r.t the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 μm vs. 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

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

    PubMed

    Gu, Y; Levin, C S

    2014-06-01

    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 m) 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

  1. Experimental study and finite element analyses of electrode wear mechanisms during the resistance spot welding of galvannealed steel

    NASA Astrophysics Data System (ADS)

    Lu, Feng

    The wear mechanisms of electrodes used on resistance spot welding of galvannealed steels were studied. The study focused on the inter-relationship among the steel properties, welding parameters and electrode wear. Six different galvannealed steels were studied using a standard constant current welding test. With the same kind of Cu-Zr electrode, the tests were performed with the electrode force fixed at 600 lbs and the welding time fixed at 12 cycles for all the steels studied. The welding current is set at just below the expulsion limit for each of the steels. The microstructure and mechanical properties of these steels were examined by SEM and microhardness tests. The face profiles for electrodes subjected to various numbers of welds were examined using carbon imprint tests and low magnification optical microscopy. The alloys formed on the electrode face were studied by the EDS and WDS quantitative analyses and linescans. Changes in the microhardness of the electrode material near the electrode face during the electrode wear process were also studied. Combined with the experimental examination, a sequentially coupled finite element analysis procedure was used to analyze the detailed distribution and evolution of the electrical current, temperature and stress throughout the process of making a weld. These analyses have greatly enhanced the understanding of the experimental observations. The results of this study indicate that the welding current is the dominant factor influencing electrode life. When the electrode force and the welding time are fixed, the welding current is determined by the steel properties. Thicker steel sheets and higher steel sheet surface hardnesses will result in smaller welding current. When the electrode force and welding time are fixed, steels requiring higher welding currents will yield shorter electrode lives. With increasing welding current, the top and bottom electrodes in this study showed increasingly different wear behaviors. Electrodes used on steels requiring higher welding current developed an edge pit near the top electrode periphery, that gradually evolved into a large pit at the bottom electrode face center. Toward the end of the electrode life, these electrodes result in a "three spots" feature nuggets that are shifted toward the top electrode. This kind of electrode failure is characterized by "nugget shifting". In contrast, under smaller welding current, the top and bottom electrode wear approximately the same. As the electrode face diameter increases gradually, not all the face area is in good contact with the steel sheet during welding. The localized contact areas for the top and bottom electrodes are symmetric and become fragmented gradually toward the end of the electrode life. The fragmentation of the electrode face areas which can be in good contact with the steel sheet results in the shunting of the welding current. When the electrical current density is reduced to a certain level by the shunting effect, the nugget can not be formed and the electrodes are declared to be failed. This kind of electrode failure is characterized by nugget shrinking. The welding current also has a big influence on the other electrode wear mechanism as the electrode mushrooming, face alloying, etc.

  2. Study on the Realization of Zinc Point and the Zinc-Point Cell Comparison

    NASA Astrophysics Data System (ADS)

    Widiatmo, J. V.; Sakai, M.; Satou, K.; Yamazawa, K.; Tamba, J.; Arai, M.

    2011-01-01

    Continuing our study on aluminum, tin, and silver points, a study on the realization of the zinc point was conducted. Zinc-point cells were newly fabricated using 6N-nominal grade zinc samples, impurity elements of which were analyzed extensively based on glow-discharge mass spectrometry (GDMS). The present paper reports the temperature measurements done using the newly fabricated cells during the zinc freezing process, under which the zinc fixed point is defined, and the analysis of the freezing curve obtained. Comparisons of zinc-point temperatures realized by the newly fabricated cells (cell-to-cell comparisons) were also conducted. Zinc-point depression due to impurity elements was calculated based on the sum of individual estimates and the impurity element analysis. One of the cells evaluated was drawn out from its crucible and analyzed by GDMS at four points, namely, at around the center of the top, of the middle, of the bottom, and around the outer part of the middle area. The purpose of this cell disassembly is to see whether or not there has been some difference before and after cell fabrication, as well as difference in impurity element distribution within the ingot. From the aforementioned studies, some findings were obtained. First finding is that the homogeneity of the zinc ingot was within 30%, except for Pb, which was more concentrated in the center part. Second finding is that the cell-to-cell temperature difference changes along with the progressing solidification process. As a consequence, for an accurate cell-to-cell comparison, the locus in the freezing plateau where the comparison is done should be determined. Third finding is that the slope analysis estimates accurately the cell-to-cell comparison, and is consistent with the impurity analysis. This shows that the slope analysis gives extensive information about the effect of impurity to the zinc-point realization, especially after the cell fabrication.

  3. Reference electrode assembly and its use in the study of fluorohydrogenate ionic liquid silicon electrochemistry.

    PubMed

    Shvartsev, Boris; Cohn, Gil; Shasha, Hila; Eichel, Rdiger-A; Ein-Eli, Yair

    2013-11-01

    Silicon electrochemistry in fluorohydrogenate ionic liquids is partly hampered owing to the incapability of producing an accurate and reproducible potential measurement due to a lack of appropriate reference electrodes. This research work describes a simple assembly of a stable external reference electrode enabling accurate studies of silicon electrochemistry in fluorohydrogenate ionic liquids. The electrode configuration is based on the ferrocene/ferrocenium (Fc|Fc(+)) couple dissolved in the EMIm(HF)(2.3)F (1-ethyl-3-methyl-imidazolium fluorohydrogenate)/Carbopol 941 gel. A stable potential of 2.5 wt% Carbopol-based electrode was measured versus a calomel reference electrode at 250 3 mV. By utilizing the constructed electrode, an intensive electrochemical investigation on n-type silicon in EMIm(HF)(2.3)F was conducted. Flat-band and open circuit potentials were measured, along with Si-air half- and full-cell electrochemical measurements. A suggested mechanism for the n-type Si dissolution process in the EMIm(HF)(2.3)F electrolyte, without illumination, is discussed as well. PMID:24045638

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  6. Experimental Studies about Transient Characteristics of a Deeply Buried Grounding Electrode and a Grounding Mesh

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kazuo; Yanagawa, Shunichi; Sekioka, Shozo

    When lightning strikes the tower of a cellular phone base station or other such facilities, power and communication equipments in the vicinity of the tower may suffer extensive damages due to the lightning current flowing backward from the grounding system of the tower. The use of a deeply buried grounding electrode has been proposed recently to suppress such back flow current and a potential rise in the vicinity of the tower. The deeply buried grounding electrode is a bare conductor buried deep in the ground that is connected to a lightning rod on the ground by an insulated wire. When lightning strikes the lightning rod, the lightning current is directed to the electrode from which it diffuses to the ground. The deeply buried grounding electrodes have been installed in cellular phone base stations and other such facilities to solve such problems caused by the back flow current and the potential rise. A grounding mesh is usually laid around such base stations as a grounding system for the facilities on the ground. Therefore, it is important to understand the interactions between the deeply buried grounding electrode and the grounding mesh. In this study, experiments on the interactions between a grounding mesh and a deeply buried grounding electrode have been carried out. Additionally, the transient characteristics of the mesh grounding have researched.

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

    PubMed Central

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

    2012-01-01

    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

  8. Impedance spectroscopy of nonactive metal electrodes at low potentials in propylene carbonate solutions: A comparison to studies of Li electrodes

    SciTech Connect

    Aurbach, D.; Zaban, A. . Dept. of Chemistry)

    1994-07-01

    Surface films formed on nonactive metals (nickel, gold, and silver) in propylene carbonate solutions were investigated using impedance spectroscopy. The salts used included LiClO[sub 4], LiAsF[sub 6], LiBF[sub 4], and LiPF[sub 6], and the impact of their concentration on the properties of the surface films was explored. In addition, the influence of the presence of additives such as O[sub 2], H[sub 2]O, and CO[sub 2] in solutions and the potential of formation on the properties of these surface films was rigorously studied. Using simple methods and simulation programs, it was possible to separate the time constants of the impedance spectra, relate them to different parts of the metal-solution interface, and to calculate the thickness of these surface films from the interfacial capacitances. Following variations of the thickness calculated for the surface films formed in the different systems as a function of applied potential and solution composition, it was possible to study the stability of the surface films, their dissolution rates and the influence of different additives on their stability. For a few systems, ex situ Fourier transform infrared spectroscopy (external reflectance mode) was also applied. The results thus obtained were correlated to previous studies of Li electrodes in the same solutions.

  9. Optical and electrochemical study of model zinc electrode pores in alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Flatt, J. H.; McLarnon, F. R.; Cairns, E. J.

    1985-09-01

    A computer-controlled model single-pore cell has been developed to study zinc electrode discharge behavior in alkaline electrolytes. The cell design allows for simultaneous microscopic and potential performance observations. A quartz-supported, thin-film cadmium reference microelectrode was designed, fabricated and installed in the cell. The cell was designed to create model pores of dimensions comparable to those in commercial zinc electrodes. Zinc electrode discharge behavior was studied in pores of effective radii between 14 and 20 microns at 7 mA/sq cm, 30 mA/sq cm and 1250 mA/sq cm rates of discharge in 7.7M KOH electrolyte. Results are consistent with a dissolution-precipitation discharge reaction mechanism. SEM studies showed significant variations in electrodes surface morphology with location in the pore and rate of discharge. Significant poreOH(-) gradients, with slow relaxation times, were found to exist within the pore at the mA/sq cm rate. Passivation was observed at the 1250 mA/sq cm rate. Zinc electrode discharge behavior in 3.5M KOH-3.4M KF showed a similar discharge reaction mechanism. However, earlier surface film formation in 3.5M KOH-3.4M KF was found to occur. Initial reaction penetration depths in 7.7M KOH and 3.5M KOH-3.4M KF electrolytes were 0.11 cm and 0.10 cm.

  10. Origins of the Human Pointing Gesture: A Training Study

    ERIC Educational Resources Information Center

    Matthews, Danielle; Behne, Tanya; Lieven, Elena; Tomasello, Michael

    2012-01-01

    Despite its importance in the development of children's skills of social cognition and communication, very little is known about the ontogenetic origins of the pointing gesture. We report a training study in which mothers gave children one month of extra daily experience with pointing as compared with a control group who had extra experience with…

  11. Origins of the Human Pointing Gesture: A Training Study

    ERIC Educational Resources Information Center

    Matthews, Danielle; Behne, Tanya; Lieven, Elena; Tomasello, Michael

    2012-01-01

    Despite its importance in the development of children's skills of social cognition and communication, very little is known about the ontogenetic origins of the pointing gesture. We report a training study in which mothers gave children one month of extra daily experience with pointing as compared with a control group who had extra experience with

  12. Toward the development of smart and low cost point-of-care biosensors based on screen printed electrodes.

    PubMed

    Ahmed, Minhaz Uddin; Hossain, Mohammad Mosharraf; Safavieh, Mohammadali; Wong, Yen Lu; Rahman, Ibrahim Abd; Zourob, Mohammed; Tamiya, Eiichi

    2016-06-01

    Screen printing technology provides a cheap and easy means to fabricate disposable electrochemical devices in bulk quantities which are used for rapid, low-cost, on-site, real-time and recurrent industrial, pharmaceutical or environmental analyses. Recent developments in micro-fabrication and nano-characterization made it possible to screen print reproducible feature on materials including plastics, ceramics and metals. The processed features forms screen-printed disposable biochip (SPDB) upon the application of suitable bio-chemical recognition receptors following appropriate methods. Adequacy of biological and non-biological materials is the key to successful biochip development. We can further improve recognition ability of SPDBs by adopting new screen printed electrode (SPE) configurations. This review covers screen-printing theory with special emphasis on the technical impacts of SPE architectures, surface treatments, operational stability and signal sensitivity. The application of SPE in different areas has also been summarized. The article aims to highlight the state-of-the-art of SPDB at the laboratory scale to enable us in envisaging the deployment of emerging SPDB technology on the commercial scale. PMID:25578718

  13. Point and non-point microbial source pollution: A case study of Delhi

    NASA Astrophysics Data System (ADS)

    Jamwal, Priyanka; Mittal, Atul K.; Mouchel, Jean-Marie

    The present study identifies major point and non-point sources of microbial pollution during dry and wet weather in Delhi watershed which is the first prerequisite for planning and management of water quality of the river Yamuna. Fecal coliforms (FC) and fecal streptococci (FS) levels were determined from two types of sources - point source (effluent from sewage treatment plants) and non-point source (stormwater runoff during dry and wet weather). FC and FS levels in the river Yamuna were also monitored, which is an ultimate sink for all microbial loads in Delhi watershed. Effluent from sewage treatment plants (STPs) employing different treatment technologies were evaluated. FC and FS levels greater than the effluent discharge standard (1000 MPN/100 ml) were observed in the effluents from all STPs except “oxidation pond Timarpur”. This study also involved field program for characterization of urban runoff from different land-uses. Results indicated that the microbial quality of urban runoff produced during wet weather from different land-uses was similar to that of raw sewage. Sewage overflows along with human and animal sources were responsible for high FC and FS levels in the runoff samples. Wet weather FC and FS levels in river Yamuna were higher as compared to the dry weather levels suggesting that dilution of the river water during wet weather does not affect its microbiological quality. Thus on the basis of this study it was found that urban runoff also contributes to the microbial quality of the river Yamuna.

  14. Exploring the electrocatalytic sites of carbon nanotubes for NADH detection: an edge plane pyrolytic graphite electrode study.

    PubMed

    Banks, Craig E; Compton, Richard G

    2005-09-01

    The electrocatalytic properties of multi-walled carbon nanotube modified electrodes toward the oxidation of NADH are critically evaluated. Carbon nanotube modified electrodes are examined and compared with boron-doped diamond and glassy carbon electrodes, and most importantly, edge plane and basal pyrolytic graphite electrodes. It is found that CNT modified electrodes are no more reactive than edge plane pyrolytic graphite electrodes with the comparison with edge plane and basal plane pyrolytic graphite electrodes allowing the electroactive sites for the electrochemical oxidation of NADH to be unambiguously determined as due to edge plane sites. Using these highly reactive edge plane sites, edge plane pyrolytic graphite electrodes are examined with cyclic voltammetry and amperometry for the electroanalytical determination of NADH. It is demonstrated that a detection limit of 5 microM is possible with cyclic voltammetry or 0.3 microM using amperometry suggesting that edge plane pyrolytic graphite electrodes can conveniently replace carbon nanotube modified glassy carbon electrodes for biosensing applications with the relative advantages of reactivity, cost and simplicity of preparation. We advocate the routine use of edge plane and basal plane pyrolytic graphite electrodes in studies utilising carbon nanotubes particularly if 'electrocatalytic' properties are claimed for the latter. PMID:16096667

  15. Potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries

    NASA Technical Reports Server (NTRS)

    Le Helloco, Jean-Guy; Bojkov, Hristo; Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.

    1992-01-01

    In a study of electrode activity for hydrogen evolution and hydrogen ionization, knowledge of the detailed kinetics and of the surface coverage by adsorbed hydrogen is essential. In the Ni/H2 battery, the hydrogen electrode is subjected to high hydrogen pressure; elucidation of the variation of kinetic parameters with hydrogen pressure is therefore of interest. Potentiostatic and ac impedance spectroscopic techniques were used in the present study. The equivalent circuit of the reaction, the kinetic parameters, and their pressure dependence have been determined.

  16. 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

    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

    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

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

    PubMed

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

    2014-02-18

    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

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

    PubMed

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

    1999-07-01

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

  19. Studies on Mechanical Alloying of Copper-Tungsten Carbide Composite for Spot Welding Electrode

    NASA Astrophysics Data System (ADS)

    Zuhailawati, H.; Jamaludin, S. B.

    2009-12-01

    This article presents a study on the properties and performance of copper-based composite reinforced with recycled tungsten carbide powder as spot welding electrode. The copper-tungsten carbide composite electrode was prepared by mechanical alloying and powder forging before being machined into truncated cone-face geometry. The welding operation was conducted on galvanized steel using a pedestal-type spot welding machine. Composites with higher density and electrical conductivity were obtained after mechanical alloying for shorter time. In contrast, a higher hardness is shown in the composite, which was mechanically alloyed to longer time. The strength of the welded steel coupon was found to increase with decreasing milling time due to an increase in density and electrical conductivity. The wear behavior of the composite revealed that the deformation of the spot weld electrode increased with increasing milling time.

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

    SciTech Connect

    Nagasubramanian, Ganesan

    1999-08-11

    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).

  1. Electrochemical and spectroscopic studies of carbon electrodes in lithium battery electrolyte systems

    NASA Astrophysics Data System (ADS)

    Chusid, O.; Ein Ely, E.; Aurbach, D.; Babai, M.; Carmeli, Y.

    1993-03-01

    In this work we studied several parameters that influence the intercalation of lithium ions into carbons (e.g. carbon type, binder and solution composition). The carbons investigated included carbon blacks (e.g. acetylene black, Ketjen black), graphite and carbon fibers. The solvents used in this study include methyl formate, propylene and ethylene carbonate, ethers (e.g. tetrahydrofuran) and their mixtures. The salts included LiClO 4, LiAsF 6 and LiBF 4. CO 2 was tested as an additive. The electrochemical behavior of the electrodes in solutions was followed by chronopotentiometry in galvanostatic charge/discharge cycling and their surface chemistry in solutions was investigated using surface sensitive Fourier-transform infrared spectroscopy (FT-IR) in transmittance, attenuated total reflectance and diffuse reflectance modes. It was found that the solvents and salts are reduced on the carbon electrodes at low potentials to form surface films. In general, their surface chemistry is quite similar to that of lithium or noble metal electrodes at low potential (in the same solutions). The electrochemical behavior of the carbon electrodes in terms of degree of intercalation and its reversibility is strongly affected by their surface chemistry. Reversible intercalation was obtained with graphite in methyl formate solutions containing CO 2. Some degree of reversible intercalation was also obtained with graphite in ethers. The presence of propylene carbonate in solution is detrimental for lithium intercalation in graphite. Reversible lithium-carbon intercalation was also obtained with acetylene black and carbonized polyacrylonitrile. The binder types have a strong impact on the electrode's performance. Preliminary guidelines for optimizing the performance of carbon electrodes as anodes in rechargeable lithium battery are discussed.

  2. Electrical characteristics of conductive yarns and textile electrodes for medical applications.

    PubMed

    Rattflt, Linda; Lindn, Maria; Hult, Peter; Berglin, Lena; Ask, Per

    2007-12-01

    Clothing with conductive textiles for health care applications has in the last decade been of an upcoming research interest. An advantage with the technique is its suitability in distributed and home health care. The present study investigates the electrical properties of conductive yarns and textile electrodes in contact with human skin, thus representing a real ECG-registration situation. The yarn measurements showed a pure resistive characteristic proportional to the length. The electrodes made of pure stainless steel (electrode A) and 20% stainless steel/80% polyester (electrode B) showed acceptable stability of electrode potentials, the stability of A was better than that of B. The electrode made of silver plated copper (electrode C) was less stable. The electrode impedance was lower for electrodes A and B than that for electrode C. From an electrical properties point of view we recommend to use electrodes of type A to be used in intelligent textile medical applications. PMID:17929069

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

    SciTech Connect

    Devereux, O.F.

    1981-02-01

    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)

  4. The acetabular point: a morphological and ontogenetic study

    PubMed Central

    RISSECH, C.; SAUDO, J. R.; MALGOSA, A.

    2001-01-01

    The acetabular point was analysed by studying human pelvic bones from 326 individuals ranging from newborns to age 97 y. The bones were categorised into 3 groups according to the degree of fusion for the 3 elements of the pelvis: nonfused (59), semifused (5) and fused (262). The acetabular point in immature pelvic bones is clearly represented by the point of the fusion lines for each bony element at the level of the acetabular fossa. In adult pelvic bones the acetabular fossa has an irregular clover-leaf shape, the superior lobe being smaller than the anterior and posterior lobes. Cross-sectional analysis of acetabular morphology suggested that the acetabular point in adult pelvic bones is always represented by the indentation between the superior and the anterior lobes of the acetabular fossa. PMID:11465866

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

    Park, Hyun-Joo; Durand, Dominique M

    2014-08-01

    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

  7. Implementing "Starting Points": A Follow-Up Study.

    ERIC Educational Resources Information Center

    Borgen, William A.

    1999-01-01

    Describes a follow-up study of the implementation of a group-based needs assessment program for unemployed people titled "Starting Points." Study uses focus group methodology to identify and categorize participant statements into 15 themes. The themes generated suggest that the program was successful in connecting clients with needed resources.

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

    NASA Technical Reports Server (NTRS)

    Fielder, William L.; Singer, Joseph

    1991-01-01

    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.

  9. Adult Cortical Plasticity Studied with Chronically Implanted Electrode Arrays

    PubMed Central

    Abe, Hiroshi; McManus, Justin N.J.; Ramalingam, Nirmala; Li, Wu; Marik, Sally A.; Meyer zum Alten Borgloh, Stephan

    2015-01-01

    The functional architecture of adult cerebral cortex retains a capacity for experience-dependent change. This is seen after focal binocular lesions as rapid changes in receptive field (RF) of the lesion projection zone (LPZ) in the primary visual cortex (V1). To study the dynamics of the circuitry underlying these changes longitudinally, we implanted microelectrode arrays in macaque (Macaca mulatta) V1, eliminating the possibility of sampling bias, which was a concern in previous studies. With this method, we observed a rapid initial recovery in the LPZ and, during the following weeks, 6389% of the sites in the LPZ showed recovery of visual responses with significant position tuning. The RFs shifted ?3 away from the scotoma. In the absence of a lesion, visual stimulation surrounding an artificial scotoma did not elicit visual responses, suggesting that the postlesion RF shifts resulted from cortical reorganization. Interestingly, although both spikes and LFPs gave consistent prelesion position tuning, only spikes reflected the postlesion remapping. PMID:25673865

  10. Electrode-polarization studies in hot corrosion systems. Progress report, June 1, 1982-May 31, 1983

    SciTech Connect

    Devereux, O.F.

    1983-01-01

    Electrode polarization studies in molten sodium sulfide: polarization of nickel electrodes in molten 25% FeS - 75% Na/sub 2/S was found to be linear in current, with the major part due to ohmic electrolyte resistance. Nickel was observed to undergo nonelectrodic dissolution in this electrolyte at the rate of 1.6 x 10/sup -6/g cm/sup -2/sec/sup -1/, with anomalous initial behavior attributed to the presence of polysulfide in the melt. Electrode polarization studies in molten sodium carbonate: this task is proceeding in the direction of a complete mechanistic and kinetic understanding of electrode reactions at the H/sub 2//H/sub 2/S/CO/CO/sub 2/, Ni electrode in molten sodium carbonate. Progress is hampered in working with H/sub 2/S. Gas/metal reactions in mixed oxidants: the kinetics of scale formation on iron in H/sub 2//H/sub 2/S/CO/CO/sub 2/ mixtures at 900/sup 0/C was studied over a range of P/sub O/sub 2// values encompassing thermodynamic stability of FeS and Fe/sub 3/O/sub 4/. All scales, however, were FeS, and all behavior seen could be treated as a perturbation of sulfidation kinetics in H/sub 2//H/sub 2/S alone. During this period a highly successful model was developed which invokes an initial period in which islands of scale form and grow laterally and in thickness. After the surface is entirely covered, i.e., the islands impinge, the scale undergoes a period of diffusion-controlled, parabolic growth, following which the outer portion of the scale ceases to be a diffusion barrier by some process, such as recrystallization, which progresses linearly with time. The inner, barrier portion of the scale thus diminishes in thickness until a steady state condition, with linear scale growth, is attained.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  12. In vivo potentiostatic studies at the electrode tissue interface: filter properties of the monophasic action potential (Ag/AgCl) electrode in living rat heart.

    PubMed

    Chou, H A; Ovadia, M; Moskowitz, M; Zavitz, D H

    2000-03-01

    The monophasic action potential (Franz) catheter is regarded as the criterion standard for high fidelity recording of a class of physiological signals. However, its signal modulation characteristics have never been reported. Broadband impedance spectroscopy was performed in perfused living rat heart in a three-electrode potentiostatic configuration to determine the filtering characteristics of the MAP and model Ag/AgCl electrode-tissue interfaces. The filter transfer function H(f) (attenuation [dB] vs log(f) [log(Hz)]) was derived for the frequency range 10 Hz-10(6) Hz. As a filter, the MAP interface is characterized by two ranges of filtering behavior. At high frequency the MAP interface is a high-pass filter with passband frequency 54 kHz-549 kHz (median 321 kHz) and with -3 dB cutoff points ranging from 10 kHz to 302 kHz. In this high frequency range the transfer function is characterized by decreasing attenuation per decade. However, in the lower frequency range relevant to physiological signals (the monophasic action potential, 0.1-40 Hz), it is a severely attenuating nondiodic high-pass filter element with an average attenuation of 16.87 dB relative to passband. In this physiological range, rolloff is nonlinear with increasing attenuation per decade. While the MAP electrode and model Ag/AgCl electrodes are high-pass filters with robust transfer functions for high frequency signals in the living heart, the attenuation of signals in a frequency range relevant to in vivo physiological recording imparts extreme attenuation that may distort physiological signals unpredictably. This disadvantage may be mitigated by amplitude scaling to a calibrated pure tone signal within the physiological frequency band to recover a reproducible signal. PMID:10750142

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

    ERIC Educational Resources Information Center

    Point Loma Nazarene Coll., San Diego, CA.

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

  14. Study of collinear VHS: point spread function and shift selectivity

    NASA Astrophysics Data System (ADS)

    Sun, Ching-Cherng; Yu, Yeh-Wei; Cheng, Chih-Yuan

    2010-11-01

    We summarize our theoretical study of the collinear volume holographic storage system. Simple formulas with direct physical concepts are developed under paraxial condition with scalar diffraction theory and VOHIL model, which are much helpful in figuring out the characteristics on point spread function (PSF) and the shift selectivity. Accordingly, effective system design is possible.

  15. Design study of floating point systolic VLSI chip

    NASA Astrophysics Data System (ADS)

    Nash, J. G.; Nudd, G. R.

    1984-03-01

    The objective of this program was to investigate the feasibility of building a floating point processor (24-bit mantissa and 8-bit exponent) on a single ship based on the Hughes Research Laboratories (HRL) present 28-bit fixed point chip (Multiplication Oriented Processor or MOP chip). The plan was to generate any necessary cell logic, layout, or simulations in order to estimate the size of the chip and predict its performance. Since division and square root were not included in the HRL MOP chip, arithmetic algorithms for performing these operations were to be studied.

  16. Alternative fuels study: point-of-use component

    SciTech Connect

    1981-12-28

    The purpose of the concept paper is to outline a possible approach to conducting the point-of-use component of the Virginia Electric and Power Company (VEPCO) study of alternative fuels. Alternative measures for point-of-use application (specifically for the residential sector) would include conservation, solar space conditioning and water heating, and heat pumps. An outline is presented of analytical and field work that will provide information on parameters affecting users, the utility, and the market. Six interdependent activities discussed are: performance analysis, market research, utility impact analysis, comparative analysis, strategy planning, and implementation.

  17. Impedance studies of Ni/Cd and Ni/H cells using the cell case as reference electrode

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1989-01-01

    Many impedance studies were carried out on Ni electrodes and Ni/Cd and Ni/H batteries. In order for impedance to become a diagnostic tool, accurate and reproducible measurements must be made, and some way of separating the contributions of the individual electrodes must be found. Using the PAR and the Solartron impedance equipment, studies have found that consistent measurements can be made if the cells or electrodes are equilibrated at the voltage of interest. In the charged state, equilibration times required are short, on the order of a few hours or less, but the equilibration time required becomes progessively longer as the voltage is lowered. The cell case can be used as a reference electrode during impedance measurements. The voltage of the case with respect to the electrodes is unimportant provided that it does not change appreciably during the course of the measurement. Measurements were made with several uncycled Ni/Cd cells, one from a lot which was known to have faulty Cd electrodes and another from a lot which showed excellent cycle life and presumably had good Cd electrodes. The impedances of the Ni electrodes vs. the case were similar, while the impedance of the poor Cd electrodes vs. the case. A 50 AH Ni/H cell was also investigated. After subtraction of the ohmic resistances, the sums of the impedances of the individual electrodes were very close to the impedance of the total cell. This indicates that the method is valid for examining the characteristics of the individual electrodes in situ.

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

    PubMed Central

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

    2012-01-01

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

  19. Voltammetric studies of the behavior of carbon black during phenol oxidation on Ti/Pt electrodes

    SciTech Connect

    Boudenne, J.L.; Cerclier, O.; Bianco, P.

    1998-08-01

    Oxidation of phenol on platinum electrodes rapidly leads to the formation of a passivating film on the surface of these electrodes. Studies of cyclic voltammetry and chronoamperometry combined with high-performance liquid chromatography (HPLC) analyses have shown that the presence of carbon black avoids these phenomena of passivation and thus allows the complete mineralization of phenol. The nature of carbon black and the pH value are two important factors which are studied here. VULCAN XC-72 R, an intrinsic p-type semiconductor, having a large specific area, showed all its efficiency when cyclic voltammetry experiments were carried out in an acid medium (pH 2.2). HPLC analyses revealed the appearance of several by-products such as hydroquinone and benzoquinone, and maleic and fumaric acids.

  20. Chemical redox reactions in ES-MS: Study of electrode reactions

    SciTech Connect

    Zhou, Feimeng; VAn Berkel, G.J.

    1995-12-31

    The authors previously demonstrated that chemical redox reactions can be used to ionize neutral commpounds for electrospray mass spectrometric (ES-MS) detection. Two different compounds, viz, C{sub 60}F{sub 48} and {beta}-carotene were used to demonstrate the utility of chemical redox reactions with on-line ES-MS for the elucidation of mechanisms of complicated electron transfer reactions and for the kinetic study of electrode reactions in which relatively short-lived intermediates are involved.

  1. Electrochemical Studies of Ceramic Carbon Electrodes Prepared with Sulfonated Organosilane Precursors

    NASA Astrophysics Data System (ADS)

    Eastcott, Jennie

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

  2. A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique

    NASA Technical Reports Server (NTRS)

    Donford, M. D.; Ding, R. J.

    1998-01-01

    A study of the corrosion of friction stir welded 2195 Al-Li alloy has been carried out using the scanning reference electrode technique (SRET). The results are compared to those obtained from a study of heterogeneously welded samples.

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

    NASA Astrophysics Data System (ADS)

    Jiang, Junwei

    2005-07-01

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

  4. Characterization and kinetic study of a nanostructured rhodium electrode for the hydrogen oxidation reaction

    NASA Astrophysics Data System (ADS)

    Montero, Mara A.; Fernndez, Jos L.; Gennero de Chialvo, Mara R.; Chialvo, Abel C.

    2014-05-01

    The hydrogen oxidation reaction was studied on a nanostructured rhodium electrode at different rotation rates. The electrode was prepared via sputtering on a glassy carbon disc support and it was characterized by X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and cyclic voltammetry, which allowed verifying the nanostructured morphology and the absence of any phase other than metallic rhodium. The real surface area was evaluated by CO stripping voltammetry. Experimental current density (j) - overpotential (?) curves of the hydrogen oxidation reaction were obtained in the range -0.015 V ? ? ? 0.25 V at different rotation rates in sulphuric acid solution. They were correlated by kinetic expressions derived from the Tafel-Heyrovsky-Volmer mechanism and thus the kinetic parameters were evaluated. It was verified that over this overpotential region the reaction proceeds through the simultaneous occurrence of the Tafel-Volmer and the Heyrovsky-Volmer route.

  5. A semi-automatic method to determine electrode positions and labels from gel artifacts in EEG/fMRI-studies.

    PubMed

    de Munck, Jan C; van Houdt, Petra J; Verdaasdonk, Ruud M; Ossenblok, Pauly P W

    2012-01-01

    The analysis of simultaneous EEG and fMRI data is generally based on the extraction of regressors of interest from the EEG, which are correlated to the fMRI data in a general linear model setting. In more advanced approaches, the spatial information of EEG is also exploited by assuming underlying dipole models. In this study, we present a semi automatic and efficient method to determine electrode positions from electrode gel artifacts, facilitating the integration of EEG and fMRI in future EEG/fMRI data models. In order to visualize all electrode artifacts simultaneously in a single view, a surface rendering of the structural MRI is made using a skin triangular mesh model as reference surface, which is expanded to a "pancake view". Then the electrodes are determined with a simple mouse click for each electrode. Using the geometry of the skin surface and its transformation to the pancake view, the 3D coordinates of the electrodes are reconstructed in the MRI coordinate frame. The electrode labels are attached to the electrode positions by fitting a template grid of the electrode cap in which the labels are known. The correspondence problem between template and sample electrodes is solved by minimizing a cost function over rotations, shifts and scalings of the template grid. The crucial step here is to use the solution of the so-called "Hungarian algorithm" as a cost function, which makes it possible to identify the electrode artifacts in arbitrary order. The template electrode grid has to be constructed only once for each cap configuration. In our implementation of this method, the whole procedure can be performed within 15 min including import of MRI, surface reconstruction and transformation, electrode identification and fitting to template. The method is robust in the sense that an electrode template created for one subject can be used without identification errors for another subject for whom the same EEG cap was used. Furthermore, the method appears to be robust against spurious or missing artifacts. We therefore consider the proposed method as a useful and reliable tool within the larger toolbox required for the analysis of co-registered EEG/fMRI data. PMID:21784161

  6. [Study on the derivation of P300 with reference electrode in the oral cavity].

    PubMed

    Mizuta, Akira; Mitani, Hiroko; Ishiyama, Yoji

    2003-11-01

    The event related potential P300 is useful as an index of the fall of the cognitive function attends by aging and the diagnosis of dementia. If the generator of P300 is assumed to be equivalent current dipole (ECD), the negative wave should be recorded at other sites which polarity differs from the positive wave on the scalp. This study is to determine the most suitable reference electrode site for P300 recording and to improve S/N of P300. In order to record the P300 or N300 potential which spread on the scalp, earlobe (A1), oral (X1) and under site of the nose(X2) was used as a reference electrode. Auditory oddball paradigm which consists of the acoustic sound of 2000 Hz (targets) and 1000 Hz (standards) was used for the measurement of P300. In this results, P300 or N300 was measured by using earlobe(A1) site as a reference electrode. P300 wave was detected by Cz-A1 derivation and also the negative wave of N300 was detected by X1-A1 and X2-A1 derivation. These results demonstrate that there is an ECD which goes to the parietal region from internal focal area as a source of P300, and also suggest that P300 amplitude with Cz-X1 or Cz-X2 derivation is higher than that with Cz-A1 derivation. Therefore, it was speculated that the most suitable reference electrode sites for the improvement of the S/N in the P300 are oral (X1) or under the nose (X2) that show the negative potentials (N300). PMID:14679786

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

    SciTech Connect

    Ticianelli, E.A.; Mukerjee, S.; McBreen, J.; Adzic, G.D.; Johnson, J.R.; Reilly, J.J.

    1998-12-31

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

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

    PubMed Central

    Lin, Jyh-Ling; Hsu, Hsiang-Yi

    2010-01-01

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

  9. Detailed study of heat generation in porous LiCoO2 electrodes

    NASA Astrophysics Data System (ADS)

    Heubner, C.; Schneider, M.; Michaelis, A.

    2016-03-01

    In this work the heat generation in porous LiCoO2 based electrodes for lithium ion batteries is studied in detail. Irreversible heat generation rates due to ohmic resistance, charge transfer and mass transport limitations as well as the reversible heat of the electrode reaction are determined from electrochemical measurements as a function of the C-rate, the temperature and the lithium concentration in the active material. The results show that all the individual heat sources contribute significantly to the total heat generation in the electrode. The heat sources are functions of the C-rate and the temperature as well as the lithium concentration in the active material. The reversible heat contribution was found to be most significant at higher temperatures und lower C-rates, which tend to reduce kinetic limitations and irreversible heats, respectively. The heat generation rate due to mass transport limitations is most influential among the irreversible heats, whereas the ohmic contribution shows a minor impact. The total heat generation was found to increase with increasing C-rate and decreasing temperature. Furthermore, the heat generation is significantly reduced for charging compared to discharging due to the intrinsic asymmetry of the reversible heat and larger kinetic limitations for lithiation compared to delithiation of LiCoO2.

  10. New epicardial mapping electrode with warming/cooling function for experimental electrophysiology studies.

    PubMed

    Tormos, Alvaro; Guill, Antonio; Millet, Jos; Roses, Eduardo J; Trapero, Isabel; Such-Miquel, Luis; Chorro, Francisco J

    2011-06-01

    Cardiac electrical activity is influenced by temperature. In experimental models, the induction of hypothermia and/or hyperthermia has been used for the study of mechanisms of cardiac arrhythmia. A system that allows for localized, controlled induction, besides simultaneously recording electrical activity in the same induced area, needs to be developed ad hoc. This article describes the construction and application of a new system capable of locally modifying the epicardial temperature of isolated hearts and of carrying out cardiac mapping with sufficient spatial resolution. The system is based on a thermoelectric refrigerator and an array of 128 stainless steel unipolar electrodes in encapsulated epoxy of good thermal conductivity. The surface of the electrode is shaped to match the ventricular curvature. The electrode-device was tested on 7 isolated perfused rabbit hearts following the Langendorff technique. Quality recordings were obtained for the left ventricle at temperatures of 37 C, 22 C and 42 C. The effects of temperature were explored in relation to two electrophysiological parameters: the QT interval during sinus rhythm and the VV interval during ventricular fibrillation. The results indicate that this is a suitable method for creating and analyzing electrophysiological heterogeneities induced by temperature in the experimental model. PMID:21256794

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

    NASA Astrophysics Data System (ADS)

    Ereifej, Evon S.

    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 nanopattern on the PDMS pins. Decreases in several inflammatory markers (GFAP, TNFα, IL-1beta) determined from gene expression analysis, was shown with the nanopatterned PDMS pins. Results of this study confirm nanopatterning not only influences cell morphology, but alters molecular cascades within the cells as well. The results of these studies provide essential information for the neural electrode research community. There is a lack of information available in the scientific community on acceptable and effective materials for neural electrode fabrication. The results of the presented studies provide more information which could lead to classifying guidelines to create biocompatible neural electrode materials. This research project was partially supported by the Wayne State University President's Translational Enhancement Award and by the Kales Scholarship for Biomedical Engineering students.

  12. Use of surfactant-specific electrodes in the study of adsorption of cationic amphiphilic ions onto clays

    SciTech Connect

    Gloton, M.P.; Mayaffre, A.; Turmine, M.; Letellier, P.; Suquet, H.

    1995-06-01

    The adsorption isotherms of dodecyltrimethylammonium ions (DTA{sup +}) adsorbed onto a laponite clay colloid were studied in water and in NaBr solution (at 0.1, 0.3, and 0.5 mol/liter), at 298 K, using amphiphilic ion-specific electrodes. This potentiometric method can be used to measure concentrations in situ and to follow the decrease in the amount of surfactant in the solution as the surfactant is adsorbed onto the clay. This paper describes a method for characterizing adsorption isotherms of DTA{sup +} onto laponite by determining the amount adsorbed at a fixed surfactant activity in solution. By repeating this process for various DTA{sup +} activities, the adsorption isotherm can be plotted. Adsorption isotherms obtained with or without NaBr in the solution were continuous curves which increased with the surfactant activity. The field of study is limited by the CMC value for the surfactant and the curves have a common intersection point, which can be attributed to the isoelectrical point of the laponite/adsorbed surfactant system. This method can be generalized to other cations and obviously to other solids.

  13. Comprehensive Study of Microgel Electrode for On-Chip Electrophoretic Cell Sorting

    NASA Astrophysics Data System (ADS)

    Akihiro Hattori,; Kenji Yasuda,

    2010-06-01

    We have developed an on-chip cell sorting system and microgel electrode for applying electrostatic force in microfluidic pathways in the chip. The advantages of agarose electrodes are 1) current-driven electrostatic force generation, 2) stability against pH change and chemicals, and 3) no bubble formation caused by electrolysis. We examined the carrier ion type and concentration dependence of microgel electrode impedance, and found that CoCl2 has less than 1/10 of the impedance from NaCl, and the reduction of the impedance of NaCl gel electrode was plateaued at 0.5 M. The structure control of the microgel electrode exploiting the surface tension of sol-state agarose was also introduced. The addition of 1% (w/v) trehalose into the microgel electrode allowed the frozen storage of the microgel electrode chip. The experimental results demonstrate the potential of our system and microgel electrode for practical applications in microfluidic chips.

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

    SciTech Connect

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

    2013-11-07

    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.

  15. First-principles study of point defects in thorium carbide

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  16. Study of surface dielectric barrier discharge generated using liquid electrodes in different gases

    NASA Astrophysics Data System (ADS)

    Galmiz, O.; Pavlinak, D.; Zemanek, M.; Brablec, A.; Cernak, M.

    2016-02-01

    Surface dielectric barrier discharges with conductive water-solution electrodes were generated at atmospheric pressure air, nitrogen, oxygen, and argon. The discharges were studied by conventional and high-speed camera photography. Plasma rotational and vibrational temperatures and the electron number density were estimated using optical emission spectroscopy. Surprisingly, especially for oxygen, the discharge was found to generate visually diffuse strongly non-isothermal plasma. This observation indicates the interesting application potential of the discharge for surface plasma treatments of, i.e. the inner and outer surfaces of hollow dielectric bodies.

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

    SciTech Connect

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

    2010-02-15

    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.

  18. Sleep and temporal lobe epilepsy: a case study with depth electrodes.

    PubMed

    Montplaisir, J; Laverdire, M; Saint-Hilaire, J M; Walsh, J; Bouvier, G

    1981-10-01

    We studied a patient with hippocampal epilepsy who had frequent nocturnal and diurnal seizures. Depth electrode recording showed that focal seizure discharges in the right hippocampus were of shorter duration in REM and non-REM sleep. However, awakening, especially from REM sleep or shortly after a REM period, facilitated the occurrence of a generalized seizure. There was no ultradian fluctuation in frequency or duration of seizure during diurnal recording. Night terrors (but not nightmares) disappeared after right temporal lobectomy, suggesting that pavor nocturnus was an ictal manifestation in this case. PMID:7202142

  19. A comparative study on electrosorption behavior of carbon nanotubes electrodes fabricated via different methods

    NASA Astrophysics Data System (ADS)

    Zhu, Guang; Wang, Hongyan; Zhang, Li

    2016-04-01

    The carbon nanotubes (CNTs) electrodes were fabricated via electrophoretic deposition (EPD), press and screen printing methods, respectively. The electrochemical properties and electrosorption performance of the CNTs electrodes were tested, respectively. Inhere, screen printing, as a conventional method for fabricating supercapacitor electrodes, was used for fabricating the CDI electrodes for the first time. Such a comparison is reasonably envisaged not only to be used to further understanding the influence of fabrication method on the electrode performance, but also to form a fundamental basis for CDI applications.

  20. Point Contact Andreev Reflection Studies on Iron Pnictide Superconductors

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohang; Saha, S. R.; Butch, N. P.; Kirshenbaum, K.; Paglione, J.; Greene, R. L.; Takeuchi, I.; Oh, Y.-S.; Liu, Y.; Yan, L. Q.; Kim, K.-H.

    2011-03-01

    We have systematically investigated the temperature, doping and the directional dependence of the gap structure for various types of single crystal iron pnictide superconductors by point contact Andreev reflection spectroscopy. Our studies were performed on highly transparent junctions evidenced by sharp and dramatic conductance enhancements at low temperatures. For the 122 family, despite some small features occasionally observed on the spectroscopy curves which may originate from the multiband superconductivity, a more conclusive characteristic of our obtained spectra is the presence of one predominant superconducting gap. By applying the BTK model, we find that the determined gap size scales well with the transition temperature, resulting in the 2 ? / kBTC value of ~ 3.1 for both potassium doped and cobalt doped single crystals. Directional studies suggest that this gap is highly isotropic. Results on chalcogenide and nickel doped 122 superconductors will also be discussed. [X. H. Zhang et al., Phys. Rev. B 81, 024518 (2010)]. Supported by CNAM and NSF DMR-0653535.

  1. Chalk Point auxiliary pump study: 1981. Final report

    SciTech Connect

    Hirshfield, M.F.; Hixson, J.H. III; Perry, E.S.

    1982-03-26

    In July 1981, the Academy of Natural Sciences of Philadelphia undertook a study to examine the numbers of finfish and blue crabs (Callinectes sapidus) entrained through the auxiliary cooling pumps at the Chalk Point Steam Electric Station (SES) operated by the Potomac Electric Power Company. Samples were collected by positioning a net attached to a hinged steel frame directly in the discharge of the auxiliary pumps. Concurrently, impingement rates of fish and blue crabs on the travelling screens were estimated by collecting the organisms washed into the troughs that lead to the discharge canal. A total of 6673 fish and blue crabs, representing 13 species, was collected in auxiliary pump samples at the Chalk Point generating station during July and August 1981. A total of 2154 fish and blue crabs representing seven species was collected in concurrent impingement samples. Blue crabs represented almost all of the total. The numbers of individuals entrained through auxiliary pumps showed a diel effect, with most individuals entrained at night.

  2. Kinetic study of the formation of oxygen vacancy on lanthanum manganite electrodes

    SciTech Connect

    Jiang, Y.; Wang, S.; Zhang, Y.; Yan, J.; Li, W.

    1998-02-01

    Strontium doped lanthanum manganite (LSM) has been considered one of the most promising cathode materials for solid oxide fuel cells (SOFC). The electrochemical reduction of oxygen on lanthanum manganite (LSM) electrodes has been investigated by cyclic voltammetry, alternating current (ac) impedance, and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of oxygen vacancy, which is shown to be the main cause for the reversed hysteresis in cyclic voltammograms and for the increase in the electrochemical activity of oxygen reduction on the cathodically polarized LSM electrode observed in both ac impedance and in potential step experiments. The potential step experiments show that the oxygen vacancy concentration increases exponentially with time when the LSM is under a cathodic polarization. In the present study, the rate controlling step for the formation of oxygen vacancies is the oxygen vacancy generation step. The cathodic current rising from the reaction on oxygen vacancies can make a significant contribution to the total reduction current.

  3. Study of electrode slice forming of bicycle dynamo hub power connector

    NASA Astrophysics Data System (ADS)

    Chen, Dyi-Cheng; Jao, Chih-Hsuan

    2013-12-01

    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.

  4. Electrochemical study of NO conversion from Fe(II)-EDTA-NO complex on Pt electrodes

    SciTech Connect

    Juzeliunas, E.; Juettner, K.

    1998-01-01

    The Fe(II)-ethylenediaminetetraacetic acid (EDTA)-NO complex formed by interaction of gaseous nitrous oxide (ca. 200 ppm) and Fe(II)-EDTA in aqueous solution was found to be convert3ed electrochemically on platinum electrodes at potentials below ca. {minus}0.6 V{sub SCE}, indicating the cathodic reduction of NO. In addition to the previous studies by which the indirect conversion of NO with dithionite as a redox mediator was confirmed, the present results should elucidate the possibility of the direct electrochemical conversion of NO in mediator-free solutions. To clearly separate this process from other reactions in the system, the electrochemical behavior of Fe(II)-EDTA and Fe(III)-EDTA was studied over a wide potential range at different pH values. Five electrode reactions could be identified, which include the oxidation/reduction of Fe{sup 2+}/Fe{sup 3+} in the EDTA complex, the reduction of EDTA, the reduction of protons, the cathodic deposition of iron, and the anodic decomposition of EDTA. The electrochemical deposition of iron from Fe(II)-EDTA at potentials E < {minus}1.0 V{sub SCE} was confirmed by electrochemical quartz crystal microbalance measurements and energy-dispersive x-ray analysis.

  5. 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)

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

    1992-09-01

    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 1.84910 -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.

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

    NASA Astrophysics Data System (ADS)

    Klahr, Benjamin M.

    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.

  7. Studies of acoustic emission from point and extended sources

    NASA Astrophysics Data System (ADS)

    Sachse, W.; Kim, K. Y.; Chen, C. P.

    1986-01-01

    The use of simulated and controlled acoustic emission signals forms the basis of a powerful tool for the detailed study of various deformation and wave interaction processes in materials. The results of experiments and signal analyses of acoustic emission resulting from point sources such as various types of indentation-produced cracks in brittle materials and the growth of fatigue cracks in 7075-T6 aluminum panels are discussed. Recent work dealing with the modeling and subsequent signal processing of an extended source of emission in a material is reviewed. Results of the forward problem and the inverse problem are presented with the example of a source distributed through the interior of a specimen.

  8. Optical Studies of Pure Fluids about Their Critical Points

    NASA Astrophysics Data System (ADS)

    Pang, Kian Tiong

    Three optical experiments were performed on pure fluids near their critical points. In the first two setups, CH_3F and H_2C:CF _2 were each tested in a temperature -controlled, prism-shaped cell and a thin parallel-windows cell. In the prism cell, a laser beam was additionally deflected by the fluid present. From the deflection data, the refractive index was related to the density to find the Lorentz-Lorenz function. Critical temperature (T _{c}), density, refractive index and electronic polarizability were found. In the second experiment, a critically-filled, thin parallel-windows cell was placed in one arm of a Mach-Zehnder interoferometer. Fluid density was monitored by changes in the fringe pattern with changing cell temperature. The aim was to improve on the precision of T_{c}: T_{c}{rm (CH}_3 F) = (44cdot9087 +/- 0cdot0002)C; T _{c}{rm(H}_2C:CF _2) = (29cdot7419 +/- 0cdot0001)C; and, to study the coexistence curve and diameter as close to T_{c} as possible. The critical behaviour was compared to the theoretical renormalization group calculations. The derived coefficients were tested against a proposed three-body interaction to explain the field-mixing term in the diameter near the critical point. It was found that H_2C:CF_2 behaved as predicted by such an interaction; CH _3F (and CHF_3) did not. The third experiment was a feasibility study to find out if (critical) isotherms could be measured optically in a setup which combined the prism and parallel-windows cells. The aim was to map isotherms in as wide a range of pressure and density as possible and to probe the critical region directly. Pressure was monitored by a precise digital pressure gauge. CH_3F and CHF _3 were tested in this system. It was found that at low densities, the calculated second and third virial coefficients agreed with reference values. However, the data around the critical point were not accurate enough for use to calculate the critical exponent, delta . The calculated value was consistently smaller than the expected value. It was believed that the present setup had thermal isolation problems. Suggestions were made as to the improvements of this isotherm cell setup. Lastly, a joint project with the Department of Ophthalmology, UBC to assemble a vitreous fluorophotometer is discussed in Appendix F. The upgrading of the instrument took up the initial two years of this PhD programme.

  9. A preliminary study of the effect of electrode placement in order to define a suitable location for two electrodes and obtain sufficiently reliable ECG signals when monitoring with wireless system.

    PubMed

    Noh, Hyung Wook; Jang, Yongwon; Lee, I B; Song, Yoonseon; Jeong, Ji-Wook; Lee, Sooyeul

    2012-01-01

    Most countries face high and increasing rates of cardiovascular disease. Each year, heart disease kills more Americans than cancer. Therefore, there has been a promising market for portable ECG equipment and it is increasing. To use portable ECG measuring devices, it is essential to define a suitable location for the measuring as we need to reduced electrode size and distance. This research proposes to study how the inter-electrode distance affects the signal and how the electrode pair should be placed on the chest in order to obtain a sufficiently reliable ECG signal to detect heart arrhythmias in any environment, such as home or work. Therefore, we developed a compact, portable patch type ambulatory ECG monitoring system, Heart Tracker, using a microprocessor for preliminary study of signal analysis. To optimize the electrode arrangement in wireless environment, we compared HT and standard 12 lead with changing electrode position. PMID:23366341

  10. Space Shuttle Earth Observation sensors pointing and stabilization requirements study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Jiang, Meng

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

  12. Sodiation kinetics of metal oxide conversion electrodes: A comparative study with lithiation

    SciTech Connect

    He, Kai; Lin, Feng; Zhu, Yizhou; Yu, Xiqian; Li, Jing; Lin, Ruoqian; Nordlund, Dennis; Weng, Tsu Chien; Richards, Ryan M.; Yang, Xiao -Qing; Doeff, Marca M.; Stach, Eric A.; Mo, Yifei; Xin, Huolin L.; Su, Dong

    2015-08-19

    The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations. We found that a crystalline Na₂O reaction layer that was formed at the beginning of sodiation plays an important role in blocking the further transport of sodium ions. In addition, sodiation in NiO exhibits a “shrinking-core” mode that results from a layer-by-layer reaction, as identified by ab initio MD simulations. For lithiation, however, the formation of Li anti-site defects significantly distorts the local NiO lattice that facilitates Li insertion, thus enhancing the overall reaction rate. These observations delineate the mechanistic difference between sodiation and lithiation in metal-oxide conversion materials. More importantly, our findings identify the importance of understanding the role of reaction layers on the functioning of electrodes and thus provide critical insights into further optimizing NIB materials through surface engineering.

  13. Sodiation kinetics of metal oxide conversion electrodes: A comparative study with lithiation

    DOE PAGESBeta

    He, Kai; Lin, Feng; Zhu, Yizhou; Yu, Xiqian; Li, Jing; Lin, Ruoqian; Nordlund, Dennis; Weng, Tsu Chien; Richards, Ryan M.; Yang, Xiao -Qing; et al

    2015-08-19

    The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations. We found that a crystalline Na₂O reaction layer thatmore » was formed at the beginning of sodiation plays an important role in blocking the further transport of sodium ions. In addition, sodiation in NiO exhibits a “shrinking-core” mode that results from a layer-by-layer reaction, as identified by ab initio MD simulations. For lithiation, however, the formation of Li anti-site defects significantly distorts the local NiO lattice that facilitates Li insertion, thus enhancing the overall reaction rate. These observations delineate the mechanistic difference between sodiation and lithiation in metal-oxide conversion materials. More importantly, our findings identify the importance of understanding the role of reaction layers on the functioning of electrodes and thus provide critical insights into further optimizing NIB materials through surface engineering.« less

  14. Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation.

    PubMed

    He, Kai; Lin, Feng; Zhu, Yizhou; Yu, Xiqian; Li, Jing; Lin, Ruoqian; Nordlund, Dennis; Weng, Tsu-Chien; Richards, Ryan M; Yang, Xiao-Qing; Doeff, Marca M; Stach, Eric A; Mo, Yifei; Xin, Huolin L; Su, Dong

    2015-09-01

    The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations. We found that a crystalline Na2O reaction layer that was formed at the beginning of sodiation plays an important role in blocking the further transport of sodium ions. In addition, sodiation in NiO exhibits a "shrinking-core" mode that results from a layer-by-layer reaction, as identified by ab initio MD simulations. For lithiation, however, the formation of Li antisite defects significantly distorts the local NiO lattice that facilitates Li insertion, thus enhancing the overall reaction rate. These observations delineate the mechanistic difference between sodiation and lithiation in metal-oxide conversion materials. More importantly, our findings identify the importance of understanding the role of reaction layers on the functioning of electrodes and thus provide critical insights into further optimizing NIB materials through surface engineering. PMID:26288360

  15. Study of Ion Transfer Coupling with Electron Transfer by Hydrophilic Droplet Electrodes.

    PubMed

    Gu, Jing; Zhao, Wenbo; Chen, Ye; Zhang, Xin; Xie, Xiang; Liu, Shujuan; Wu, Xiaofeng; Zhu, Zhiwei; Li, Meixian; Shao, Yuanhua

    2015-12-01

    In a hydrophilic droplet three-electrode system, electroactive species within the droplet play very important roles in the electron-transfer (ET) process on the solid/electrolyte interface, which can then induce an ion-transfer (IT) reaction at the liquid/liquid interface. In this work, several redox couples and electroactive species are chosen to study ET-IT coupling processes at the water/1,2-dichloroethane (W/DCE) interface by cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV). Among them, the redox couple Ru(NH3)6(3+/2+) has been found to have the widest useful potential window of about 1.2 V. A hydrophilic droplet three-electrode system using a single electroactive molecule instead of a redox couple has been confirmed to be stable and has similar functionality to a redox couple. In addition, the lipophilicity of antiplatelet drug clopidogrel at the W/DCE interface is investigated and its ionic partition diagram has been constructed. Protonated clopidogrel is detected in a linear concentration range of 5.0-50 ?M and the limit of detection (LOD) is calculated to be 3.0 ?M by using the hydrophilic droplet system Ru(NH3)6(3+/2+) and OSWV. PMID:26499518

  16. Surface Enhanced Infrared Studies of 4-Methoxypyridine Adsorption on Gold Film Electrodes.

    PubMed

    Quirk, Amanda; Unni, Bipinlal; Burgess, Ian J

    2016-03-01

    This work uses electrochemical surface sensitive vibrational spectroscopy to characterize the adsorption of a known metal nanoparticle stabilizer and growth director, 4-methoxypyridine (MOP). Surface enhanced infrared absorption spectroscopy (SEIRAS) is employed to study the adsorption of 4-methoxypyridine on gold films. Experiments are performed under electrochemical control and in different electrolyte acidities to identify both the extent of protonation of the adsorbed species as well as its orientation with respect to the electrode surface. No evidence of adsorbed conjugated acid is found even when the electrolyte pH is considerably lower than the pKa. Through an analysis of the transition dipole moments, determined from DFT calculations, the SEIRA spectra support an adsorption configuration through the ring nitrogen which is particularly dominant in neutral pH conditions. Adsorption is dependent on both the electrical state of the Au film electrode as well as the presence of ions in the electrolyte that compete for adsorption sites at positive potentials. Combined differential capacitance measurements and spectroscopic data demonstrate that both a horizontal adsorption geometry and a vertical adsorption phase can be induced, with the former being found on negatively charged surfaces in acidic media and the latter over a wide range of polarizations in neutral solutions. PMID:26862774

  17. [Time-resolved optical studies of charge relaxation and charge transfer at electrode interfaces

    SciTech Connect

    Not Available

    1992-01-01

    Key components were identified in a quantitative model of carrier relaxation in semiconductor electrodes: nonlinear aspects of nonradiative and radiative recombination, effect of space charge field on carrier dynamics, self-absorption effects in direct gas semiconductors, and influence of surface state population kinetics on charge carrier recombination. For CdSe, the first three are operative (no direct proof of the last one). A realistic kinetic model for carrier recombination in the bulk of CdSe was used which includes important nonlinear effects, both radiative and nonradiative. The change in interfacial recombination velocity with the chemical nature of the sinterface was studied (n-CdSe/silane interfaces). Temperature effect (278 to 328 K) on fluorescence decay of n-CdSe in contact with 0.5 M KOH was found to be weak. An analytical solution was obtained for time-resolved fluoresence from electrodes under potential bias, and is being tested. Fluorescence work on a different material, CdS, indicate different recombination kinetics; this material was used to directly pump an optical transition of a surface state.

  18. [Time-resolved optical studies of charge relaxation and charge transfer at electrode interfaces

    SciTech Connect

    Not Available

    1992-12-31

    Key components were identified in a quantitative model of carrier relaxation in semiconductor electrodes: nonlinear aspects of nonradiative and radiative recombination, effect of space charge field on carrier dynamics, self-absorption effects in direct gas semiconductors, and influence of surface state population kinetics on charge carrier recombination. For CdSe, the first three are operative (no direct proof of the last one). A realistic kinetic model for carrier recombination in the bulk of CdSe was used which includes important nonlinear effects, both radiative and nonradiative. The change in interfacial recombination velocity with the chemical nature of the sinterface was studied (n-CdSe/silane interfaces). Temperature effect (278 to 328 K) on fluorescence decay of n-CdSe in contact with 0.5 M KOH was found to be weak. An analytical solution was obtained for time-resolved fluoresence from electrodes under potential bias, and is being tested. Fluorescence work on a different material, CdS, indicate different recombination kinetics; this material was used to directly pump an optical transition of a surface state.

  19. Turbulent mixing and deposition studies for single point aerosol sampling

    NASA Astrophysics Data System (ADS)

    Gupta, Rajiv

    1999-11-01

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

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

    SciTech Connect

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

    1980-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    SciTech Connect

    Jayanta, P.S.; Ishida, Takanobu

    1991-05-01

    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.

  3. A method for direct thalamic stimulation in fMRI studies using a glass-coated carbon fiber electrode.

    PubMed

    Shyu, Bai-Chuang; Lin, Chun-Yu; Sun, Jyh-Jang; Sylantyev, Sergiy; Chang, Chen

    2004-08-15

    Recent fMRI studies are of interest in exploring long-range interactions between different brain structures and the functional activation of specific brain regions by known neuroanatomical pathways. One of the experimental approaches requires the invasive implantation of an intracranial electrode to excite specific brain structures. In the present report, we describe a procedure for the production of a glass-coated carbon fiber electrode and the use of this electrode for direct activation of the brain in fMRI studies. The glass-coated carbon fiber microelectrode was implanted in the medial thalamus of anaesthetized rats and T2*-weighted gradient echo images in the sagittal plane obtained on a 4.7 T system (Biospec BMT 47/40) during electrical stimulation of the medial thalamus. The image quality obtained using this electrode was acceptable without reduction of the signal-to-noise ratio and image distortion. Cross-correlation analysis showed that the signal intensities of activated areas in the ipsilateral anterior cingulate cortex were significantly increased by about 4-5% during medial thalamus stimulation. The present study shows that glass-coated carbon fiber electrodes are suitable for fMRI studies and can be used to investigate functional thalamocingulate activation. PMID:15196834

  4. Point contact spectroscopy studies of the iron based superconductors

    NASA Astrophysics Data System (ADS)

    Arham, Hamood Zafir

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

  5. Virtual electrodes for high-density electrode arrays

    DOEpatents

    Cela, Carlos J.; Lazzi, Gianluca

    2015-10-13

    The present embodiments are directed to implantable electrode arrays having virtual electrodes. The virtual electrodes may improve the resolution of the implantable electrode array without the burden of corresponding complexity of electronic circuitry and wiring. In a particular embodiment, a virtual electrode may include one or more passive elements to help steer current to a specific location between the active electrodes. For example, a passive element may be a metalized layer on a substrate that is adjacent to, but not directly connected to an active electrode. In certain embodiments, an active electrode may be directly coupled to a power source via a conductive connection. Beneficially, the passive elements may help to increase the overall resolution of the implantable array by providing additional stimulation points without requiring additional wiring or driver circuitry for the passive elements.

  6. Study of freezing-point depression of selected food extracts

    SciTech Connect

    Tanaka, Fumihiko; Murata, Satoshi; Habara, Kazuhiro; Amaratunga, K.S.P.

    1996-12-31

    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.

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

    PubMed Central

    2013-01-01

    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

  8. Numerical Studies of Electrode Plasma Formation and Expansion in High Power Charged Particle Beam Diodes

    NASA Astrophysics Data System (ADS)

    Rittersdorf, I. M.; Swanekamp, S. B.; Richardson, A. S.; Allen, R. J.; Schumer, J. W.

    2014-10-01

    High-power diodes that generate intense electron beams are useful in many applications, such as producing x-rays for flash radiography and nuclear weapon effects simulations. Desorption and ionization of gases from electrodes can form a plasma during operation. Expansion of this plasma into the gap leads to a short circuit, which limits the radiation production. It is difficult for particle-in-cell codes to model the surface physics or the subsequent expansion of the plasma. NRL is beginning a multi-year research effort to study such plasmas. This paper will summarize the relevant literature on plasma formation in high-power diodes with a goal of developing dynamic models that describe the formation and expansion of these plasmas that are suitable for PIC codes. This work was supported by the NRL Basic and Applied Research Program.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  10. Vanadium pentoxide thin films used as positive electrode in lithium microbatteries: An XPS study during cycling

    NASA Astrophysics Data System (ADS)

    Benayad, A.; Martinez, H.; Gies, A.; Pecquenard, B.; Levasseur, A.; Gonbeau, D.

    2006-05-01

    Vanadium pentoxide thin films, usable as positive electrode in microbatteries, have been prepared by radio frequency magnetron sputtering in a pure argon or mixed argon/oxygen atmosphere using a V2O5 target. Depending on the oxygen partial pressure in the discharge gas, we have obtained either crystallized or amorphous thin films, with different morphologies. These two kinds of thin films having different electrochemical behavior, an extensive XPS study was carried out. The main redox processes and their reversibility occurring during the 1st, 10th, and 30th discharge charge cycles were discussed in relation with the electrochemical properties. Our results have revealed a good reversibility of the redox process for amorphous thin films and degradation for crystallized ones, in agreement with the discharge capacity evolution. Furthermore, the growth of a surface layer between the cathode and the liquid electrolyte was evidenced upon the discharge as well as its partial dissolution upon the charge.

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

    NASA Astrophysics Data System (ADS)

    K?os, Jacek; Lamperski, Stanis?aw

    2014-02-01

    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.

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

    PubMed

    K?os, Jacek; Lamperski, Stanis?aw

    2014-02-01

    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. PMID:24511964

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

    NASA Astrophysics Data System (ADS)

    Chen, Jia; Selloni, Annabella

    2013-03-01

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

  14. Electrochemical properties of titanium nitride nerve stimulation electrodes: an in vitro and in vivo study

    PubMed Central

    Meijs, Suzan; Fjorback, Morten; Jensen, Carina; Srensen, Sren; Rechendorff, Kristian; Rijkhoff, Nico J. M.

    2015-01-01

    The in vivo electrochemical behavior of titanium nitride (TiN) nerve stimulation electrodes was compared to their in vitro behavior for a period of 90 days. Ten electrodes were implanted in two Gttingen minipigs. Four of these were used for electrical stimulation and electrochemical measurements. Five electrodes were kept in Ringer's solution at 37.5C, of which four were used for electrical stimulation and electrochemical measurements. The voltage transients measured in vivo were 13 times greater than in vitro at implantation and they continued to increase with time. The electrochemical properties in vivo and the tissue resistance (Rtissue) followed a similar trend with time. There was no consistent significant difference between the electrochemical properties of the in vivo and in vitro electrodes after the implanted period. The differences between the in vivo and in vitro electrodes during the implanted period show that the evaluation of electrochemical performance of implantable stimulation electrodes cannot be substituted with in vitro measurements. After the implanted period, however, the performance of the in vivo and in vitro electrodes in saline was similar. In addition, the changes observed over time during the post-implantation period regarding the electrochemical properties of the in vivo electrodes and Rtissue were similar, which indicates that these changes are due to the foreign body response to implantation. PMID:26300717

  15. Study of permeability changes induced by external stimuli on chemically modified electrodes

    NASA Astrophysics Data System (ADS)

    Perera, Dingiri Mudiyanselage Neluni T.

    This research was focused on understanding how external stimuli affect the permeability of the chemically modified electrodes, and how the materials used in modifying the working electrodes respond to the changes in the surface charge. We adopted a voltammetric type electrochemical sensor to investigate the permeability effects induced by pH and organic solvents. The working electrodes used in this research were chemically modified with thioctic acid self assembled monolayer (TA SAM), track etched polycarbonate membranes (TEPCM) and PS-b-PMMA nanoporous films (polystyrene-block-polymethylmethacrylate). We studied the permeability behavior of each of the material upon application of external stimuli. In chapter 3, the permeability changes induced by change in surface charge of thioctic acid SAM was investigated. The surface charge of the monolayer was tuned by changing pH of the medium, which resulted in decrease of redox current of a negatively charged marker due to deprotonation of the surface --COOH groups of TA SAM. Decrease in redox current reflected a decrease in the reaction rate, and by using closed form equations the effective rate constants at several pKa values were extracted. In chapter 4, permeability changes induced by pH in TEPCM were investigated. We assessed the surface charge of these membranes via cyclic voltammetry generated for neutral and charged redox molecules. Limiting current of charged markers were affected by the surface charge induced by pH, where as the redox current for the neutral marker was not affected. Experimental redox currents were larger than the theoretical current, indicating that redox molecules preferentially distributed in a surface layer on the nanopore. Organic solvent induced permeability changes of PS-b-PMMA nanoporous films were investigated via electrochemical impedance spectroscopy and AFM. Higher response of pore resistance in the presence of organic solvents indicated either swelling of the nanoporous film or partitioning of organic solvents in the pores. However AFM data revealed that the permeability changes are due to partitioning of the solvents rather than swelling of the porous film, since there was no appreciable change if the pore diameter in the presence of solvents.

  16. A Newly Developed Perfused Umbrella Electrode for Radiofrequency Ablation: An Ex Vivo Evaluation Study in Bovine Liver

    SciTech Connect

    Bruners, Philipp Pfeffer, Jochen; Kazim, Rana M.; Guenther, Rolf W.; Schmitz-Rode, Thomas; Mahnken, Andreas H.

    2007-09-15

    The purpose of this study was to evaluate the effectiveness of a newly developed perfused monopolar radiofrequency (RF) probe with an umbrella-shaped array. A perfused umbrella-shaped monopolar RF probe based on a LeVeen electrode (Boston Scientific Corp., Natick, MA, USA) with a 3-cm array diameter was developed. Five different configurations of this electrode were tested: (a) perfusion channel/endhole, (b) perfusion channel/endhole + sideholes, (c) 1 cm insulation removed at the tip, (d) 1 cm insulation removed at the tip + perfusion channel/endhole, and (e) 1 cm insulation removed at the tip + perfusion channel/endhole + sideholes. An unmodified LeVeen electrode served as a reference standard. RF ablations were performed in freshly excised bovine liver using a commercial monopolar RF system with a 200-W generator (RF 3000; Boston Scientific Corp.). Each electrode was tested 10 times applying the vendor's recommended ablation protocol combined with the preinjection of 2 ml 0.9% saline. Volumes and shapes of the lesions were compared. Lesions generated with the original LeVeen electrode showed a mean volume of 12.74 {+-} 0.52 cm{sup 3}. Removing parts of the insulation led to larger coagulation volumes (22.65 {+-} 2.12 cm{sup 3}). Depending on the configuration, saline preinjection resulted in a further increase in coagulation volume (25.22 {+-} 3.37 to 31.28 {+-} 2.32 cm{sup 3}). Besides lesion volume, the shape of the ablation zone was influenced by the configuration of the electrode used. We conclude that saline preinjection in combination with increasing the active tip length of the umbrella-shaped LeVeen RF probe allows the reliable ablation of larger volumes in comparison to the originally configured electrode.

  17. Electrochemical study and flow injection analysis of paracetamol in pharmaceutical formulations based on screen-printed electrodes and carbon nanotubes.

    PubMed

    Fanjul-Bolado, Pablo; Lamas-Ardisana, Pedro Jos; Hernndez-Santos, David; Costa-Garca, Agustn

    2009-04-13

    Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical-chemical oxidation mechanism of paracetamol at pH 2.0. Quantitative analysis of paracetamol by using its oxidation process (in a Britton-Robinson buffer solution pH 10.0) at +0.20 V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5x10(-6) M to 1x10(-3) M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1x10(-7) M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10(-5) M acetaminophen and do not present any memory effect. Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products. PMID:19327451

  18. Electrode compositions

    DOEpatents

    Block, J.; Fan, X.

    1998-10-27

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

  19. Electrode compositions

    DOEpatents

    Block, Jacob; Fan, Xiyun

    1998-01-01

    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.

  20. Comparative study of carbon free and carbon containing Li4Ti5O12 electrodes

    NASA Astrophysics Data System (ADS)

    Pohjalainen, Elina; Kallioinen, Jani; Kallio, Tanja

    2015-04-01

    Traditionally electrodes for lithium ion batteries are manufactured using carbon additives to increase the conductivity. However, in case of lithium titanate, Li4Ti5O12 (LTO), carbon free electrodes have gathered some interest lately. Therefore two LTO materials synthesized using the same synthesis but different end milling process resulting in materials with different particle size and surface area are compared here using electrodes manufactured with and without carbon additives. Both LTO samples (LTO-SP with small primary particle size and high surface area, and LTO-LP with larger primary particle size and small surface area) produce similar capacities and voltages with or without carbon additives at low C-rates at the room temperature. However, at high C-rates and/or sub-zero temperatures electrodes with carbon additives produce higher capacities and smaller ohmic losses and this behavior is more pronounced for the LTO electrodes with smaller primary particle size and larger surface area. These results show that the feasibility of carbon free LTO electrodes depends on the properties of LTO affecting the morphology of the electrode and consequently, the transport properties. This is most pronounced under conditions where electron and Li+ ion transfer become limiting (high C-rates and low temperature).

  1. Study of Interdigitated Electrode Arrays Using Experiments and Finite Element Models for the Evaluation of Sterilization Processes.

    PubMed

    Oberlnder, Jan; Jildeh, Zaid B; Kirchner, Patrick; Wendeler, Luisa; Bromm, Alexander; Iken, Heiko; Wagner, Patrick; Keusgen, Michael; Schning, Michael J

    2015-01-01

    In this work, a sensor to evaluate sterilization processes with hydrogen peroxide vapor has been characterized. Experimental, analytical and numerical methods were applied to evaluate and study the sensor behavior. The sensor set-up is based on planar interdigitated electrodes. The interdigitated electrode structure consists of 614 electrode fingers spanning over a total sensing area of 20 mm. Sensor measurements were conducted with and without microbiological spores as well as after an industrial sterilization protocol. The measurements were verified using an analytical expression based on a first-order elliptical integral. A model based on the finite element method with periodic boundary conditions in two dimensions was developed and utilized to validate the experimental findings. PMID:26473883

  2. Study of Interdigitated Electrode Arrays Using Experiments and Finite Element Models for the Evaluation of Sterilization Processes

    PubMed Central

    Oberländer, Jan; Jildeh, Zaid B.; Kirchner, Patrick; Wendeler, Luisa; Bromm, Alexander; Iken, Heiko; Wagner, Patrick; Keusgen, Michael; Schöning, Michael J.

    2015-01-01

    In this work, a sensor to evaluate sterilization processes with hydrogen peroxide vapor has been characterized. Experimental, analytical and numerical methods were applied to evaluate and study the sensor behavior. The sensor set-up is based on planar interdigitated electrodes. The interdigitated electrode structure consists of 614 electrode fingers spanning over a total sensing area of 20 mm2. Sensor measurements were conducted with and without microbiological spores as well as after an industrial sterilization protocol. The measurements were verified using an analytical expression based on a first-order elliptical integral. A model based on the finite element method with periodic boundary conditions in two dimensions was developed and utilized to validate the experimental findings. PMID:26473883

  3. REGIONAL AIR POLLUTION STUDY. POINT SOURCE EMISSION INVENTORY

    EPA Science Inventory

    Emission data from stationary point sources in the St. Louis Interstate Air Quality Control Region were gathered during 1975. Data for 'criteria' pollutants were obtained on an hourly basis. Emissions from large sources were based on hourly, measured values at pertinent operating...

  4. A Theoretical Study of Stagnation-Point Ablation

    NASA Technical Reports Server (NTRS)

    Roberts, Leonard

    1959-01-01

    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.

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

    SciTech Connect

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

    1996-07-01

    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.

  6. A study on transmission characteristics and specific absorption rate using impedance-matched electrodes for various human body communication.

    PubMed

    Machida, Yuta; Yamamoto, Takahiko; Koshiji, Kohji

    2013-01-01

    Human body communication (HBC) is a new communication technology that has presented potential applications in health care and elderly support systems in recent years. In this study, which is focused on a wearable transmitter and receiver for HBC in a body area network (BAN), we performed electromagnetic field analysis and simulation using the finite difference time domain (FDTD) method with various models of the human body. Further we redesigned a number of impedance-matched electrodes to allow transmission without stubs or transformers. The specific absorption rate (SAR) and transmission characteristics S21 of these electrode structures were compared for several models. PMID:24110079

  7. Do we activate specifically somatosensory thin fibres with the concentric planar electrode? A scalp and intracranial EEG study.

    PubMed

    Perchet, Caroline; Frot, Maud; Charmarty, Audran; Flores, Cecilia; Mazza, Stephanie; Magnin, Michel; Garcia-Larrea, Luis

    2012-06-01

    Laser-evoked potentials (LEPs) are acknowledged as the most reliable laboratory tool for assessing thermal and pain pathways. Electrical stimulation with a newly developed planar concentric electrode, delivering stimuli limited to the superficial skin layers, has been suggested to provide selective activation of A? fibres without the inconveniences linked to laser stimulation. The aim of our study was to compare the scalp and intracranial responses to planar concentric electrode stimulation (CE-SEPs) with those of LEPs and standard somatosensory-evoked potentials (SEPs). Sixteen healthy subjects, 6 patients with intracortical electrodes, and 2 patients with selective lesions of the spinothalamic pathway were submitted to Neodymium:Yttrium-Aluminium-Perovskite laser stimulations, and electrical stimulations using standard electrodes or planar concentric electrodes (CE). In both healthy controls and epileptic implanted patients, CE- and standard SEPs showed significantly shorter latencies than LEPs. This is consistent with A?-fibre activation, peripheral activation time being unable to account for longer LEP latencies. In the patients with spinothalamic lesions, LEPs were absent after stimulation of the affected territory, while CE-SEPs were still present. For these 2 reasons, we conclude that the planar CE does not selectively activate the A? and C fibers, but coexcites a significant proportion of large myelinated A? fibres that dominate the ensuing cortical response. The use of CE-SEPs for the detection of spinothalamic system lesions is therefore not warranted; the planar electrode can, however, represent a useful tool to study nociceptive reflexes, which can be reliably elicited even in the presence of A? coactivation. PMID:22497800

  8. Simulation studies of bus electrode effect on discharge and luminous characteristics of plasma display panels

    SciTech Connect

    Lee, Insook; Choi, K.Y.

    2005-03-01

    We have investigated how bus electrodes affect discharge and luminous characteristics of a discharge cell. Three-dimensional simulations have been performed in a coplanar structured alternating current plasma display panel cell, with phosphor saturation effect taken into account. There exists the optimal position of bus electrodes for high luminance and luminous efficiency. Considering bus electrode thickness, we have found that in-bus structure is a promising candidate for high luminance, high luminous efficiency, and fast operation plasma display panels. Our simulation results would be very useful to understand the influence of bus electrode on characteristics of a plasma display panel cell, and would also provide a general guidance to improve its display performances.

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

    PubMed Central

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

    2011-01-01

    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

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

    SciTech Connect

    Bae, Sang-Eun; Kim, Dae-Hyun; Kim, Jong-Yoon; Park, Tae-Hong; Cho, Young Hwan; Yeon, Jei-Won; Song, Kyuseok

    2013-07-01

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

  11. An impedance study of complex Al/Cu-Al2O3 electrode

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

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

    2010-08-01

    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.

  14. Applications of Planar ITO Electrodes for Studying of Some Biochemical Activities

    NASA Astrophysics Data System (ADS)

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

    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.

  15. Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes.

    PubMed

    Costa Rama, Estefana; Biscay, Julien; Gonzlez Garca, Mara Begoa; Julio Reviejo, A; Pingarrn Carrazn, Jos Manuel; Costa Garca, Agustn

    2012-05-30

    Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt-phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211 nA mM(-1)), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05-1.00 mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks. PMID:22560283

  16. A semi-analytical study of positive corona discharge in wire-plane electrode configuration

    NASA Astrophysics Data System (ADS)

    Yanallah, K.; Pontiga, F.; Chen, J. H.

    2013-08-01

    Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables.

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

    PubMed Central

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

    2012-01-01

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

  18. Photovoltaic concentrator pointing dynamics and plasma interaction study

    NASA Technical Reports Server (NTRS)

    Stern, T. G.

    1984-01-01

    The objectives of this experiment are to use the Space Technology Experiments Platform (STEP) system to demonstrate the viability of concentrator photovoltaic arrays by: (1) configuring a deployable mast on the STEP pallet with concentrator mass models and some active photovoltaic modules; (2) measuring the array pointing dynamics under normal rotation as well as disturbance conditions; (3) performing an array plasma interaction experiment to determine the steady-state plasma losses under various voltage conditions; and (4) providing active distributed control of the support truss to determine the improvement in dynamic response. Experiment approach and test control and instrumentation are described.

  19. Liquid electrode

    DOEpatents

    Ekechukwu, Amy A. (Augusta, GA)

    1994-01-01

    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.

  20. Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes

    SciTech Connect

    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

    2015-10-15

    Materials that undergo a conversion reaction with lithium (e.g., metal fluorides MF{sub 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{sub 2}) while others are not (e.g., CuF{sub 2}). In this study, we investigated the conversion reaction of binary metal fluorides, FeF{sub 2} and CuF{sub 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{sub 2} and CuF{sub 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{sup +} with FeF{sub 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{sub 2}. In contrast to FeF{sub 2}, no continuous Cu network was observed in the lithiated CuF{sub 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{sub 2} electrode.

  1. Fluorescent Microspheres as Point Sources: A Localization Study

    PubMed Central

    Chao, Jerry; Lee, Taiyoon; Ward, E. Sally; Ober, Raimund J.

    2015-01-01

    The localization of fluorescent microspheres is often employed for drift correction and image registration in single molecule microscopy, and is commonly carried out by fitting a point spread function to the image of the given microsphere. The mismatch between the point spread function and the image of the microsphere, however, calls into question the suitability of this localization approach. To investigate this issue, we subject both simulated and experimental microsphere image data to a maximum likelihood estimator that localizes a microsphere by fitting an Airy pattern to its image, and assess the suitability of the approach by evaluating the ability of the estimator to recover the true location of the microsphere with the best possible accuracy as determined based on the Cramr-Rao lower bound. Assessing against criteria based on the standard errors of the mean and the variance for an ideal estimator of the microspheres location, we find that microspheres up to 100 nm in diameter can in general be localized using a fixed width Airy pattern, and that microspheres as large as 1 ?m in diameter can in general be localized using a floated width Airy pattern. PMID:26218251

  2. The feasibility of endoscopic transcanal approach for insertion of various cochlear electrodes: a pilot study.

    PubMed

    Migirov, Lela; Shapira, Yisgav; Wolf, Michael

    2015-07-01

    To determine the feasibility of inserting various types of electrode arrays using an endoscopic transcanal approach into the cochlea via the round window membrane (RWM). All the procedures were performed by the first author and started with a cortical mastoidectomy. A six o'clock vertical incision was made in the meatal skin, and a posterior tympano-meatal flap was elevated transmeatally to expose the middle ear cavity using a rigid 0 endoscope (diameter 3 mm, length 14 cm). The chorda tympani nerve (CTN) and body of the incus were exposed. The RWM was incised, and the electrodes were passed through the tunnel from the mastoid to the epitympanum, medial to the CTN and lateral to the incus into the round window (RW) in seven procedures. In the other six cases, an open groove had been drilled, starting superiorly and laterally to the CTN and ending in the mastoid region. After electrodes insertion, the groove was filled with bone dust and covered with a large piece of fascia prior to repositioning of the tympano-meatal flap. Complete electrode insertion (7 Nucleus Contour Advance, 5 Concerto and 1 HiRes90K) via the RW was achieved in all 13 cases. Endoscopic CI was more feasible for insertion of concerto electrode followed by HiRes90K and Nucleus. An assistance of another surgeon was required for removal of stylet in the "off-the-stylet technique" utilized for implantation of nucleus electrode. Endoscopic transcanal implantation of different cochlear electrodes through the RW is feasible in both children and adults and can be used as first surgical option or as a complementary to the traditional posterior tympanotomy approach. PMID:24619204

  3. Understanding capacity fade in silicon based electrodes for lithium-ion batteries using three electrode cells and upper cut-off voltage studies

    NASA Astrophysics Data System (ADS)

    Beattie, Shane D.; Loveridge, M. J.; Lain, Michael J.; Ferrari, Stefania; Polzin, Bryant J.; Bhagat, Rohit; Dashwood, Richard

    2016-01-01

    Commercial Li-ion batteries are typically cycled between 3.0 and 4.2 V. These voltages limits are chosen based on the characteristics of the cathode (e.g. lithium cobalt oxide) and anode (e.g. graphite). When alternative anode/cathode chemistries are studied the same cut-off voltages are often, mistakenly, used. Silicon (Si) based anodes are widely studied as a high capacity alternative to graphite for Lithium-ion batteries. When silicon-based anodes are paired with high capacity cathodes (e.g. Lithium Nickel Cobalt Aluminium Oxide; NCA) the cell typically suffers from rapid capacity fade. The purpose of this communication is to understand how the choice of upper cut-off voltage affects cell performance in Si/NCA cells. A careful study of three-electrode cell data will show that capacity fade in Si/NCA cells is due to an ever-evolving silicon voltage profile that pushes the upper voltage at the cathode to >4.4 V (vs. Li/Li+). This behaviour initially improves cycle efficiency, due to liberation of new lithium, but ultimately reduces cycling efficiency, resulting in rapid capacity fade.

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

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoling; Miley, George H.

    2009-03-01

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

  5. Electrode studies in molten salts: Final report for the period June 1, 1984-May 31, 1986

    SciTech Connect

    Devereux, O.F.

    1986-10-15

    The work performed under this contract consisted primarily of a study of the deterioration of refractory oxide films in molten sodium carbonate. Films were prepared by anodic oxidation of NiAl in sodium carbonate at 1000/sup 0/C. The impedance of the anodized NiAl substrates was found to follow models consisting of resistive and capacitive elements, combined with Warburg or diffusive elements. No evidence, derived from impedance behavior or otherwise, was found of refractory oxide dissolution or ''fluxing'' as a result of immersion in the molten carbonate. Rather, the impedance behavior of the immersed film-covered substrates was consistant with a continued growth of the oxide, whether under cathodic, zero or anodic polarization, interrupted by apparent spalling of the oxide due, presumably, to growth stresses. A secondary task within this program involved an exploratory examination of the behavior of chromium electrodes in molten sodium polysulfide at approx.375/sup 0/C. The anodic behavior of this system was characterized by the formation of a ''blocking'' film of elemental sulfur.

  6. Investigation and Design Studies of SOFC Electrode Performance at Elevated Pressure

    SciTech Connect

    Ted Ohrn; Shung Ik Lee

    2010-07-31

    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.

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

    SciTech Connect

    Ouyang, Jianyong

    2013-12-02

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

  8. Studying 21cm power spectrum with one-point statistics

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    The redshifted 21cm line signal from neutral hydrogens is a promising tool to probe the cosmic dawn and the epoch of reionization. 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.

  9. A study on the ignition characteristics of inductively coupled electrode-less lamp

    NASA Astrophysics Data System (ADS)

    Uetsuki, Tadao; Fujita, Masao; Saimi, Motohiro; Kakehashi, Hidenori

    2009-10-01

    Almost twenty years have passed since the first electrode-less lamp operated at 13.56MHz was put on the market. Since then, it has come to be expected that the lumen output and the efficiency of these lamp systems would be improved. The present electrode-less lamp system operated at 135kHz has higher efficiency and output than the high pressure mercury lamp system which is very popular in the market. However, the ignition mechanism of the electrode-less lamp has not yet been completely worked out. To grasp the ignition voltage and time is very important for designing this lamp system, because these influence the cost of the system. The authors investigated how to reduce the ignition time. With regard to the ignition for magnetic coupled electrode-less lamp, it was reported that there are theoretically two types of ignition, E-discharge and H-discharge. However, the definition of the ignition actually is regarded as the time when the H-discharge occurs. The authors observed the starting state of the electrode-less lamp and found that the performance of the circuit influenced the transition from E- discharge to H- discharge. The large current is necessary for the smooth transition from E- discharge to H- discharge right after the E- discharge occurs.

  10. Feasibility Study of a Novel Electrode Concept for a Neuroprosthesis for Augmentation of Impaired Finger Functions

    PubMed Central

    Jnasson, Skli r; Sigrsson, Haraldur; Helgason, rur

    2014-01-01

    The project Finger Rehabilitation aims to design a neuroprosthesis with integrated electronics. The neuroprosthesis should enable spinal cord injured people, with injury at cervical vertebrae level, to increase finger mobility and activity with the use of functional electrical stimulation. The equipment is based on several integrated factors. The user has to be independent from any external help and has to be able to put it on, control the electrical stimulation and remove it by himself. The neuroprosthesis has to be both flexible and stable for the electrodes to remain firmly on the skin. In this part of the project, new electrodes which do not get stuck on the skin are described. The electrodes are small and have low impedance. A sleeve, made from glass fibres, is also described. The electrode matrices are integrated in the sleeve. The neuroprosthesis fits a patient with spinal cord injury at C5-C6. In this work, a novel electrode concept integrated in a glass fibre sleeve is tested on its ability for use in an independent user neuroprosthesis for finger movement rehabilitation.

  11. 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)

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

    2010-03-01

    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.

  12. Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles.

    PubMed

    Asadian, Elham; Iraji Zad, Azam; Shahrokhian, Saeed

    2016-01-01

    By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable decrease in its reduction overpotential. These results can be attributed to the incredible enlargement in the microscopic surface area of the electrode due to the presence of graphene nanosheets together with strong adsorption of Aza on its surface. The effect of experimental parameters such as accumulation time, the amount of modifier suspension and pH of the supporting electrolyte were also optimized toward obtaining the maximum sensitivity. Under the optimum conditions, the calibration curve studies demonstrated that the peak current increased linearly with Aza concentrations in the range of 7 10(-7) to 1 10(-4)mol L(-1) with the detection limit of 68 nM. Further experiments revealed that the modified electrode can be successfully applied for the accurate determination of Aza in pharmaceutical preparations. PMID:26478409

  13. Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

    NASA Astrophysics Data System (ADS)

    Embong, Zaidi; Johar, Saffuwan; Tajudin, Saiful Azhar Ahmad; Sahdan, Mohd Zainizan

    2015-04-01

    Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangau soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 μR/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si2+ and Al2+ cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.

  14. Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

    SciTech Connect

    Embong, Zaidi; Johar, Saffuwan; Tajudin, Saiful Azhar Ahmad; Sahdan, Mohd Zainizan

    2015-04-29

    Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangau soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 μR/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si{sup 2+} and Al{sup 2+} cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.

  15. Study of Copper and Purine-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry

    PubMed Central

    Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek

    2008-01-01

    Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes.

  16. Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source

    SciTech Connect

    Jung, Bong-Ki; Chung, Kyoung-Jae; Dang, Jeong-Jeung; Hwang, Y. S.

    2012-02-15

    A high monatomic beam fraction is an important factor in a hydrogen ion source to increase the application efficiency. The monatomic fraction of hydrogen plasmas with different plasma electrode materials is measured in a helicon plasma ion source, and aluminum shows the highest value compared to that with the other metals such as copper and molybdenum. Formation of an aluminum oxide layer on the aluminum electrode is determined by XPS analysis, and the alumina layer is verified as the high monatomic fraction. Both experiments and numerical simulations conclude that a low surface recombination coefficient of the alumina layer on the plasma electrode is one of the most important parameters for increasing the monatomic fraction in hydrogen plasma ion sources.

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

    SciTech Connect

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

    2013-08-12

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

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

    SciTech Connect

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

    1986-01-01

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

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

    PubMed

    Sasaki, Satoshi; Yokota, Kazunori; Hanagata, Nobutaka

    2004-08-01

    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

  1. Superconducting molybdenum-rhenium electrodes for single-molecule transport studies

    SciTech Connect

    Gaudenzi, R.; Island, J. O.; Bruijckere, J. de; Burzurí, E.; Zant, H. S. J. van der; Klapwijk, T. M.

    2015-06-01

    We demonstrate that electronic transport through single molecules or molecular ensembles, commonly based on gold (Au) electrodes, can be extended to superconducting electrodes by combining gold with molybdenum-rhenium (MoRe). This combination induces proximity-effect superconductivity in the gold to temperatures of at least 4.6 K and magnetic fields of 6 T, improving on previously reported aluminum based superconducting nanojunctions. As a proof of concept, we show three-terminal superconductive transport measurements through an individual Fe{sub 4} single-molecule magnet.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  3. Effect of silicate ions on electrode overvoltage

    NASA Technical Reports Server (NTRS)

    Gras, J. M.; Seite, C.

    1979-01-01

    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.

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

    SciTech Connect

    Devereux, O.F.

    1980-02-01

    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.

  5. Nanogap-enabled study of electrode reactions by scanning electrochemical microscopy

    NASA Astrophysics Data System (ADS)

    Nioradze, Nikoloz

    The nanogap quasi-steady-state voltammetry, developed in my work, presents the way to monitor and study rapid electron transfer reactions on macroscopic substrates of scanning electrochemical microscopy (SECM). It combines the cyclic voltammetry and SECM and monitors substrate reaction as a tip current. The resulting plot of iT versus ES features the retraceable sigmoidal shape of a quasi-steady state voltammogram although a transient peak-shape voltammogram is obtained simultaneously at the macroscopic substrate. This simplifies measurement and analysis of a quasi-steady-state voltammogram and gives information about thermodynamic as well as kinetic parameters of the reaction taking place at the interface. No charging current at the amperometric tip, high and adjustable mass transport under the tip and high spatial resolution are all advantages of quasi-steady-state voltammetry. I also introduced generalized theory for nanoscale iT-ES voltammetry of substrate reactions with arbitrary reversibility and mechanism under comprehensive experimental conditions including any substrate potential and both SECM modes (feedback and substrate generation tip collection, SG/TC). I nanofabricated submicrometer size highly reliable Pt SECM tips and found the way of protection of these tiny electrodes from the damage caused either by electrostatic discharge or electrochemical etching. Subsequent application of quasi-steady-state voltammetry and reliable nanofabricated SECM probes enabled sensitive detection of adsorption of organic impurities from air and ultrapure water to the HOPG surface as evidenced by redox reaction of ferrocenylmethyl)trimethyl ammonium (FcTMA +). Study revealed that hydrophobic contaminant layer slows down the access of hydrophilic aqueous redox species to the underlying HOPG surface, thereby yielding a lower standard rate constant, k 0. Moreover, this barrier effects stronger to a more charged form (FcTMA2+) of a redox couple so that the electron-transfer reaction of the more hydrophilic form is slower to yield a lower k 0 value.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

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

    PubMed

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

    2015-01-14

    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

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

    SciTech Connect

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

    2001-11-01

    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.

  9. A Study on the Optimal Positions of ECG Electrodes in a Garment for the Design of ECG-Monitoring Clothing for Male.

    PubMed

    Cho, Hakyung; Lee, Joo Hyeon

    2015-09-01

    Smart clothing is a sort of wearable device used for ubiquitous health monitoring. It provides comfort and efficiency in vital sign measurements and has been studied and developed in various types of monitoring platforms such as T-shirt and sports bra. However, despite these previous approaches, smart clothing for electrocardiography (ECG) monitoring has encountered a serious shortcoming relevant to motion artifacts caused by wearer movement. In effect, motion artifacts are one of the major problems in practical implementation of most wearable health-monitoring devices. In the ECG measurements collected by a garment, motion artifacts are usually caused by improper location of the electrode, leading to lack of contact between the electrode and skin with body motion. The aim of this study was to suggest a design for ECG-monitoring clothing contributing to reduction of motion artifacts. Based on the clothing science theory, it was assumed in this study that the stability of the electrode in a dynamic state differed depending on the electrode location in an ECG-monitoring garment. Founded on this assumption, effects of 56 electrode positions were determined by sectioning the surface of the garment into grids with 6 cm intervals in the front and back of the bodice. In order to determine the optimal locations of the ECG electrodes from the 56 positions, ECG measurements were collected from 10 participants at every electrode position in the garment while the wearer was in motion. The electrode locations indicating both an ECG measurement rate higher than 80.0 % and a large amplitude during motion were selected as the optimal electrode locations. The results of this analysis show four electrode locations with consistently higher ECG measurement rates and larger amplitudes amongst the 56 locations. These four locations were abstracted to be least affected by wearer movement in this research. Based on this result, a design of the garment-formed ECG monitoring platform reflecting the optimal positions of the electrode was suggested. PMID:26254250

  10. Advanced electrodes for AMTEC

    SciTech Connect

    Fiebig, Brad; Schuller, Michael; Hudson, Patricia; Williams, Roger

    1999-01-01

    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.}

  11. Surface-enhanced Raman spectroscopy of surfactants on silver electrodes

    SciTech Connect

    Sun, Soncheng; Birke, R.L.; Lombardi, J.R. )

    1990-03-08

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

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

    NASA Astrophysics Data System (ADS)

    Amro, Abdulaziz Nabil

    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.

  13. Development of electrokinetic remediation for caesium: A feasibility study of 2D electrode configuration system

    NASA Astrophysics Data System (ADS)

    Syah Putra, Rudy

    2016-02-01

    Agar matrix was artificially contaminated with caesium and subjected to rapid assessment of electrokinetic treatment on the basis of the 2D electrode configuration. The effect of caesium concentration on the process was investigated using different electrode configuration (i.e. rectangular, hexagonal and triangular). During treatment the in situ pH distribution, the current flow, and the potential distribution were monitored. At the end of the treatment, the caesium concentration distribution was measured. The results of these experiments showed that for caesium contamination, pH control is essential in order to create a suitable environment throughout the agar matrix to enable contaminant removal. It was found that the type of electrode configuration used to control the pH affected the rate of caesium accumulation. All of the electrode configurations tested was effective, but the highest caesium extraction was achieved when the hexagonal pattern was used to control the pH. After 72 h of treatment at 50 mA, the concentration of caesium decreased gradually from the second and first layer of agar matrix throughout the cell, suggesting that most of the caesium was concentrated on the cathode part.

  14. In-situ Studies of Structures and Processes at Model Battery Electrode/Electrolyte Interfaces

    NASA Astrophysics Data System (ADS)

    Fenter, Paul

    2015-03-01

    The ability to understand and control materials properties within electrochemical energy storage systems is a significant scientific and technical challenge. This is due, at least in part, to the extreme conditions present within these systems, and the significant structural and chemical changes that take place as lithium ions are incorporated in the active electrode material. In particular, the behavior of interfaces in such systems is poorly understood, notably the solid-liquid interface that separates the electrode and the liquid electrolyte. I will review our recent work in which we seek to isolate and understand the role of interfacial reactivity in these systems through in-situ, real-time, observations of electrochemically driven lithiation/delithation reactions. This is achieved by observing well-defined model electrode-electrolyte interfaces using X-ray reflectivity. These results reveal novel understandings of interfacial reactivity in conversion reactions (e.g., Si, SixCr, Ge, NiO) that can be used to control the complex reaction lithiation pathway through the use of thin-film and multilayer electrode structures. This work was supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, in collaboration with T. Fister, A. Gewirth, M.J. Bedzyk and others.

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

    PubMed

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

    2014-05-01

    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

  16. Experimental study of plasma energization at magnetic neutral points

    NASA Astrophysics Data System (ADS)

    Deaconu, Stelu S.

    2002-09-01

    A new experiment of magnetic field diffusion through plasma was performed with static, time varying, quadrupole magnetic fields created by a dual coil device. The experiment was designed to answer some of the questions raised by the process of plasma energization at magnetic neutral points. Prior experimental and theoretical work offers controversial views regarding the possibility of efficient plasma energization in these conditions. Thus, the investigation concentrated on the evaluation of the effectiveness of plasma energization (heating and acceleration) when starting from a hydrostatic initial condition, and the identification of actual mechanisms of energy transfer and dissipation. The possibility that the energy transfer process involves magnetic field line reconnection was also discussed. Parallel to the experimental work, an unsteady analytic model was proposed. The analysis presented two views of the process: (a) a fluid model describing the energization of fully ionized plasmas, and (b) a kinetic model adequate for describing the energization of weakly ionized plasmas. Experimentally, the investigation was limited to the case of weakly ionized plasma. The experimental data showed good agreement with the model and with some results from past experiments. Thus, the experiment demonstrated that the diffusion of variable magnetic fields through (weakly ionized) plasma leads to one or two orders of magnitude increase in the ionization fraction, to plasma heating, and to plasma motion. A distinct result of the MDE experiment is the detection of low frequency (kHz range) ion acoustic waves. The analysis shows that the generation of ion acoustic waves is the main mechanism of energy dissipation, in the plasma, during the slow decline of the magnetic field. In terms of energy transfer, the experiment showed that the weak coupling between the magnetic field and the low conductivity plasma is directly responsible for a small energy conversion efficiency. It is concluded, however, that the process may prove useful in engineering applications (involving plasma ionization and acceleration), if certain conditions are met. The data also showed that, in the configuration tested, magnetic field line reconnection is an unlikely mechanism for plasma energization.

  17. Ionization EM calorimetry with accordion electrodes and liquid krypton or argon

    SciTech Connect

    Radeka, V.

    1993-11-01

    The results of a study and tests of a liquid krypton/argon electromagnetic calorimeter with accordion electrode structure are briefly summarized. This includes the calorimeter response to electrons and muons, energy, pointing and timing resolution, and a measurement by multiple sampling. The electrode layout with fine segmentation is illustrated.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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 (H3O+). Using the computed solvation free energy of H+ as reference, the deprotonation and oxidation free energies of an aqueous species can be converted to pKa 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)], 10.1063/1.3250438. 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 pKa, 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.

  19. A spatiotemporal study of gliosis in relation to depth electrode tracks in drug-resistant epilepsy.

    PubMed

    Goc, Joanna; Liu, Joan Y W; Sisodiya, Sanjay M; Thom, Maria

    2014-06-01

    Key questions remain regarding the processes governing gliogenesis following central nervous system injury that are critical to understanding both beneficial brain repair mechanisms and any long-term detrimental effects, including increased risk of seizures. We have used cortical injury produced by intracranial electrodes (ICEs) to study the time-course and localization of gliosis and gliogenesis in surgically resected human brain tissue. Seventeen cases with ICE injuries of 4-301 days age were selected. Double-labelled immunolabelling using a proliferative cell marker (MCM2), markers of fate-specific transcriptional factors (PAX6, SOX2), a microglial marker (IBA1) and glial markers (nestin, GFAP) was quantified in three regions: zone 1 (immediate vicinity: 0-350 ?m), zone 2 (350-700 ?m) and zone 3 (remote ?2000 ?m) in relation to the ICE injury site. Microglial/macrophage cell densities peaked at 28-30 days post-injury (dpi) with a significant decline in proliferating microglia with dpi in all zones. Nestin-expressing cells (NECs) were concentrated in zones 1 and 2, showed the highest regenerative capacity (MCM2 and PAX6 co-expression) and were intimately associated with capillaries within the organizing injury cavity. There was a significant decline in nestin/MCM2 co-expressing cells with dpi in zones 1 and 2. Nestin-positive fibres remained in the chronic scar, and NECs with neuronal morphology were noted in older injuries. GFAP-expressing glia were more evenly distributed between zones, with no significant decline in density or proliferative capacity with dpi. Colocalization between nestin and GFAP in zone 1 glial cells decreased with increasing dpi. In conclusion, NECs at acute injury sites are a proliferative, transient cell population with capacity for maturation into astrocytes with possible neuronal differentiation observed in older injuries. PMID:24666402

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

    SciTech Connect

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

    2011-06-28

    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{sup +}) in a periodic model system from the free energy for the deprotonation of an aqueous hydronium ion (H{sub 3}O{sup +}). Using the computed solvation free energy of H{sup +} as reference, the deprotonation and oxidation free energies of an aqueous species can be converted to pK{sub 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{sub 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.

  1. A spatiotemporal study of gliosis in relation to depth electrode tracks in drug-resistant epilepsy

    PubMed Central

    Goc, Joanna; Liu, Joan Y W; Sisodiya, Sanjay M; Thom, Maria

    2014-01-01

    Key questions remain regarding the processes governing gliogenesis following central nervous system injury that are critical to understanding both beneficial brain repair mechanisms and any long-term detrimental effects, including increased risk of seizures. We have used cortical injury produced by intracranial electrodes (ICEs) to study the time-course and localization of gliosis and gliogenesis in surgically resected human brain tissue. Seventeen cases with ICE injuries of 4301days age were selected. Double-labelled immunolabelling using a proliferative cell marker (MCM2), markers of fate-specific transcriptional factors (PAX6, SOX2), a microglial marker (IBA1) and glial markers (nestin, GFAP) was quantified in three regions: zone 1 (immediate vicinity: 0350?m), zone 2 (350700?m) and zone 3 (remote ?2000?m) in relation to the ICE injury site. Microglial/macrophage cell densities peaked at 2830days post-injury (dpi) with a significant decline in proliferating microglia with dpi in all zones. Nestin-expressing cells (NECs) were concentrated in zones 1 and 2, showed the highest regenerative capacity (MCM2 and PAX6 co-expression) and were intimately associated with capillaries within the organizing injury cavity. There was a significant decline in nestin/MCM2 co-expressing cells with dpi in zones 1 and 2. Nestin-positive fibres remained in the chronic scar, and NECs with neuronal morphology were noted in older injuries. GFAP-expressing glia were more evenly distributed between zones, with no significant decline in density or proliferative capacity with dpi. Colocalization between nestin and GFAP in zone 1 glial cells decreased with increasing dpi. In conclusion, NECs at acute injury sites are a proliferative, transient cell population with capacity for maturation into astrocytes with possible neuronal differentiation observed in older injuries. PMID:24666402

  2. Photovoltage response to temperature change at oxide semiconductor electrodes

    NASA Technical Reports Server (NTRS)

    Reichman, B.; Byvik, C. E.

    1981-01-01

    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.

  3. First-principles study of high-conductance DNA sequencing with carbon nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Chen, X.; Rungger, I.; Pemmaraju, C. D.; Schwingenschlgl, U.; Sanvito, S.

    2012-03-01

    Rapid and cost-effective DNA sequencing at the single nucleotide level might be achieved by measuring a transverse electronic current as single-stranded DNA is pulled through a nanometer-sized pore. In order to enhance the electronic coupling between the nucleotides and the electrodes and hence the current signals, we employ a pair of single-walled close-ended (6,6) carbon nanotubes (CNTs) as electrodes. We then investigate the electron transport properties of nucleotides sandwiched between such electrodes by using first-principles quantum transport theory. In particular, we consider the extreme case where the separation between the electrodes is the smallest possible that still allows the DNA translocation. The benzene-like ring at the end cap of the CNT can strongly couple with the nucleobases and therefore it can both reduce conformational fluctuations and significantly improve the conductance. As such, when the electrodes are closely spaced, the nucleobases can pass through only with their base plane parallel to the plane of CNT end caps. The optimal molecular configurations, at which the nucleotides strongly couple to the CNTs, and which yield the largest transmission, are first identified. These correspond approximately to the lowest energy configurations. Then the electronic structures and the electron transport of these optimal configurations are analyzed. The typical tunneling currents are of the order of 50 nA for voltages up to 1 V. At higher bias, where resonant transport through the molecular states is possible, the current is of the order of several ?A. Below 1 V, the currents associated to the different nucleotides are consistently distinguishable, with adenine having the largest current, guanine the second largest, cytosine the third and, finally, thymine the smallest. We further calculate the transmission coefficient profiles as the nucleotides are dragged along the DNA translocation path and investigate the effects of configurational variations. Based on these results, we propose a DNA sequencing protocol combining three possible data analysis strategies.

  4. THE STUDY OF LANGUAGES--A POINT OF VIEW.

    ERIC Educational Resources Information Center

    EDGERTON, M., JR.

    FOREIGN LANGUAGE STUDY IN SCHOOLS SHOULD BE PREDICATED ON THE NEED OF SOCIETIES TO COEXIST WITH OTHER CONTEMPORARY NATIONAL CULTURES. IN A WORLD THAT CONSISTS OF A LARGE NUMBER OF HISTORICALLY DETERMINED, SEPARATE CULTURES, LANGUAGE ALONE CAN PRESENT THE LINGUISTICALLY CONDITIONED THOUGHT PATTERNS, THE "REALITY," OF A SPECIFIC CULTURE. LANGUAGE

  5. Space tug point design study. Volume 4: Program requirements

    NASA Technical Reports Server (NTRS)

    1973-01-01

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

  6. Liquid electrode

    DOEpatents

    Ekechukwu, A.A.

    1994-07-05

    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.

  7. Terminal electrode

    SciTech Connect

    Zagrodnik, J.P.; Bowen, G.K.

    1990-08-14

    This paper discusses a bipolar flow battery. It comprises a series of half cells in electrical communication with one another, the cells being defined by partitions comprising alternating electrodes and separators, each partition being secured to each adjacent partition about a common perimeter therewith, the series of half cells having a terminal electrode at an end thereof; an endblock, disposed at an end of the series of half cells, the endblock being secured to the terminal electrode; an electrolyte manifold in hydraulic communication with the half cells; and an electrolyte pump for urging electrolyte through the manifold and into the half cells.

  8. A Cross-Cultural Study of Reference Point Adaptation: Evidence from China, Korea, and the US

    ERIC Educational Resources Information Center

    Arkes, Hal R.; Hirshleifer, David; Jiang, Danling; Lim, Sonya S.

    2010-01-01

    We examined reference point adaptation following gains or losses in security trading using participants from China, Korea, and the US. In both questionnaire studies and trading experiments with real money incentives, reference point adaptation was larger for Asians than for Americans. Subjects in all countries adapted their reference points more

  9. A Cross-Cultural Study of Reference Point Adaptation: Evidence from China, Korea, and the US

    ERIC Educational Resources Information Center

    Arkes, Hal R.; Hirshleifer, David; Jiang, Danling; Lim, Sonya S.

    2010-01-01

    We examined reference point adaptation following gains or losses in security trading using participants from China, Korea, and the US. In both questionnaire studies and trading experiments with real money incentives, reference point adaptation was larger for Asians than for Americans. Subjects in all countries adapted their reference points more…

  10. Principal Point Classification: Applications to Differentiating Drug and Placebo Responses in Longitudinal Studies

    PubMed Central

    Tarpey, Thaddeus; Petkova, Eva

    2009-01-01

    Principal points are cluster means for theoretical distributions. A discriminant methodology based on principal points is introduced. The principal point classification method is useful in clinical trials where the goal is to distinguish and differentiate between different treatment effects. Particularly, in psychiatric studies where placebo response rates can be very high, the principal point classification is illustrated to distinguish specific drug responders from non-specific placebo responders. PMID:20563220

  11. An electrochemical study of the oxidation of hydrogen at platinum electrodes in several room temperature ionic liquids.

    PubMed

    Silvester, Debbie S; Aldous, Leigh; Hardacre, Christopher; Compton, Richard G

    2007-05-10

    The electrochemical oxidation of dissolved hydrogen gas has been studied in a range of room-temperature ionic liquids (RTILs), namely [C(2)mim][NTf(2)], [C(4)mim][NTf(2)], [N(6,2,2,2)][NTf(2)], [P(14,6,6,6)][NTf(2)], [C(4)mpyrr][NTf(2)], [C(4)mim][BF(4)], [C(4)mim][PF(6)], [C(4)mim][OTf], and [C(6)mim]Cl on a platinum microdisk electrode of diameter 10 microm. In all cases, except [C(6)mim]Cl, a broad quasi-electrochemically reversible oxidation peak between 0.3 to 1.3 V vs Ag was seen prior to electrode activation ([C(6)mim]Cl showed an almost irreversible wave). When the electrode was pre-anodized ("activated") at 2.0 V vs Ag for 1 min, the peak separations became smaller, and the peak shape became more electrochemically reversible. It is thought that the electrogenerated protons chemically combine with the anions (A-) of the RTIL. The appearance and position of the reverse (reduction) peak on the voltammograms is thought to depend on three factors: (1) the stability of the protonated anion, HA, (2) the position of equilibrium of the protonation reaction HA<==> H+ + A- , and (3) any follow-up chemistry, e.g., dissociation or reaction of the protonated anion, HA. This is discussed for the five different anions studied. The reduction of HNTf(2) was also studied in two [NTf(2)]- -based RTILs and was compared to the oxidation waves from hydrogen. The results have implications for the defining of pKa in RTIL media, for the development of suitable reference electrodes for use in RTILs, and in the possible amperometric sensing of H2 gas. PMID:17284067

  12. Study of the voltammetric behaviour of maleic hydrazide and its determination at a hanging mercury drop electrode.

    PubMed

    Ni, Yongnian; Qiu, Ping; Kokot, Serge

    2004-06-17

    Voltammetric behaviour of maleic hydrazide pesticide dissolved in a Britton-Robertson buffer was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the process at the Hg electrode was diffusion controlled; the reaction was irreversible and involved a change of one proton and a transfer of one electron. A quantitative differential pulse voltammetric method for determination of maleic hydrazide was developed on the basis of these studies involving the reduction of the compound at a hanging mercury drop electrode. A linear calibration was obtained in the range of 0.5-5.5mgl(-1), and the developed DPV methodology was then applied for the determination of maleic hydrazide in spiked vegetable samples by the standard addition method. Satisfactory percentage R.S.D. ( approximately 2%), percentage recovery values ( approximately 85%) and LOD (0.215mgl(-1)) were obtained. These compared well with the results from the alternative spectrophotometric method. PMID:18969469

  13. Alloy corrosion studied by a combination of stripping voltammetry and the rotating ring-disk electrode. Lead-cadmium alloy

    SciTech Connect

    Zhdanov, V.V.; Filanovskii, B.K.

    1984-08-01

    The authors have used the rotating ring-disk electrode (RRDE) in combination with stripping voltammetry (SVA) at solid electrodes in order to determine partial dissolution rates of alloy components in the vicinity of the steady potential and also under cathodic and anodic polarization. The method of SVA is used in the analytical determination of trace amounts of heavy metals dissolved in electrolytes. The method was used to investigate the electrolytic dissolution of lead-cadmium alloy in the vicinity of the steady potential and under cathodic polarization. Results obtained when studying the corrosion behavior of the lead-cadmium alloy are given. The results indicate that selective cadmium dissolution occurs initially, but then this is replaced by uniform alloy dissolution. The data shows that the partial currents of alloy component dissolution can be determined by a combination of SVA and RRDE.

  14. Space tug point design study. Volume 1: Summary

    NASA Technical Reports Server (NTRS)

    1972-01-01

    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.

  15. Numerical study on the spark ignition characteristics of a methane-air mixture using detailed chemical kinetics. Effect of equivalence ratio, electrode gap distance, and electrode radius on MIE, quenching distance, and ignition delay

    SciTech Connect

    Han, Jilin; Yamashita, Hiroshi; Hayashi, Naoki

    2010-07-15

    The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. Even though the formation of flame kernels in quiescent methane-air mixtures has been simulated numerically, the ignition mechanism has never been satisfactorily explained. This study investigated the spark ignition of methane-air mixtures through a numerical analysis using detailed chemical kinetics consisting of 53 species and 325 elementary reactions while considering the heat loss to the electrode. The simulation was used to investigate the quenching distance and the effects on the MIE of the electrode size, electrode gap distance, ignition duration, and equivalence ratio. The effect of the equivalence ratio on the ignition delay time was also examined. The simulated results showed the same trend as previous experimental results. (author)

  16. Chemically modified electrodes and related solution studies. Final technical report, January 15, 1991--January 14, 1992

    SciTech Connect

    Elliott, C.M.

    1993-04-01

    This report is divided into 5 sections: Ru{sub 4}/Fe complexes of tetra(4{prime}-methyl-2,2{prime}-bipyridine)porphyrin--catalytic epoxidation of olefins; water oxidation catalysis by doubly linked {mu}-oxo ruthenium complexes; polymer films formed by oxidation of transition metal electrodes into solutions of bisbipyridinealkane ligands; polymer films containing [CpMo({mu}-S)]{sub 2}S{sub 2}CHR dinuclear clusters;and conducting polymer films for catalyst incorporation.

  17. Electrochemical characteristics of nanostructured platinum electrodes--a cyclic voltammetry study.

    PubMed

    Daubinger, P; Kieninger, J; Unmssig, T; Urban, G A

    2014-05-14

    Platinum surfaces play a decisive role in catalysis in sensors, fuel cells, solar cells and other applications like neuronal stimulation and recording. Technical advances in nanotechnology contributed tremendously to the progress in these fields. A fundamental understanding of the chemical and physical interactions between the nanostructured surfaces and electrolytes is essential, but was barely investigated up to now. In this article, we present a wet-chemical process for the deposition of nanostructures on polycrystalline platinum surfaces. The electrochemically active surface area was increased by a factor of over 1000 times with respect to the geometrical surface. The influence of the nanostructures was examined in different acidic, alkaline, and neutral electrolytes. Comparing cyclic voltammograms of nanostructured and planar polycrystalline platinum revealed new insights into the microenvironment at the electrode-electrolyte interface. The characteristic features of the cyclic voltammograms were altered in their shape and strongly shifted with respect to the applied potential. In neutral buffered and unbuffered electrolytes the water window was expanded from 1.4 V to more than 2 V. The shifts were interpreted as local pH-changes and exhausted buffer capacity in direct proximity of the electrode surface due to the strong release and binding of protons, respectively. These polarized electrodes induce significant changes in the electrochemical potential of the electrolyte due to the high roughness of their surface. The electrochemical phenomena and the observed voltage shifts are crucial for the understanding of the basic mechanism at nanostructured electrodes and mandatory for designing fuel cells, sensors and many other devices. PMID:24664444

  18. Improved performances of nanosilicon electrodes using the salt LiFSI: a photoelectron spectroscopy study.

    PubMed

    Philippe, Bertrand; Dedryvre, Rmi; Gorgoi, Mihaela; Rensmo, Hkan; Gonbeau, Danielle; Edstrm, Kristina

    2013-07-01

    Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery. PMID:23763546

  19. Characterization of dry biopotential electrodes.

    PubMed

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

    2013-01-01

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

  20. In-situ acoustic emission study of Si-based electrodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Tranchot, A.; Etiemble, A.; Thivel, P.-X.; Idrissi, H.; Roué, L.

    2015-04-01

    The mechanical degradation of a Si powder (∼2 μm) based electrode is investigated by acoustic emission (AE). AE signals are mainly detected during the first lithiation, suggesting that electrode cracking mainly occurs during this period. The formation of the solid electrolyte interface (SEI) is not very acoustically emissive, in contrast to the Si particle cracking which is initiated in the early stage of the lithiation in accordance with a core-shell lithiation mechanism. An increase of the AE activity is observed at the end of the discharge when the c-Li15Si4 phase is formed and during the charge when the potential reaches ∼0.45 V, corresponding to the delithiation of c-Li15Si4. From a clustering procedure, three types of signals are identified: type-1 signals consisting of a succession of very short waveforms with high peak frequency (∼700 kHz) are primarily detected when the Si lithiation is initiated and are ascribed to the nucleation of surface microcracks on the Si particles; type-2 signals (peak frequency ∼400 kHz), present all during the Si lithiation, are attributed to the propagation of cracks through the Si particles and into the composite film; type-3 signals (peak frequency ∼200 kHz), detected when the potential reaches 60 mV, are ascribed to the accentuation of the electrode cracking due to the c-Li15Si4 formation.

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

    SciTech Connect

    Pickett, D.F. Jr.; Scoles, D.L.; Johnson, Z.W.; Hayden, J.W.; Pennington, R.D.

    1997-12-31

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  3. Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes

    SciTech Connect

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

    2012-11-01

    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.

  4. Control of electrode depth in electroslag remelting

    DOEpatents

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

    2002-01-01

    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.

  5. PM-IRRAS Studies of DMPC Bilayers Supported on Au(111) Electrodes Modified with Hydrophilic Monolayers of Thioglucose.

    PubMed

    Matyszewska, Dorota; Bilewicz, Renata; Su, ZhangFei; Abbasi, Fatemah; Leitch, J Jay; Lipkowski, Jacek

    2016-02-23

    A phospholipid bilayer composed of 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine (d54-DMPC) was deposited onto the Au(111) electrode modified with a self-assembled monolayer of 1-thio-β-d-glucose (β-Tg) via the Langmuir-Blodgett and Langmuir-Schaefer (LB-LS) techniques. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements were used to characterize structural and orientational changes in this model biological membrane on a hydrophilic surface modified gold electrode. The results of the spectroscopic measurements showed that the tilt angle of acyl chains obtained for deuterated DMPC bilayers supported on the β-Tg-modified gold is significantly lower than that reported previously for DMPC bilayers deposited directly on Au(111) electrodes. Moreover, tilt angles of ∼18° were obtained for d54-DMPC bilayers on β-Tg self-assembled monolayers (SAMs) at positive potentials, which are similar to the values calculated for h-DMPC deposited on bare gold in the desorbed state and to those observed for a stack of hydrated DMPC bilayers. This data confirms that the β-thioglucose SAM promotes the formation of a water cushion that separates the phospholipid bilayer from the metal surface. As a result, the DMPC polar heads are not in direct contact with the electrode and can adopt a zigzag configuration, which strengthens the chain-chain interactions and allows for an overall decrease in the tilt of the acyl chains. These novel supported model membranes may be especially useful in studies pertaining to the incorporation of peptides and proteins into phospholipid bilayers. PMID:26829620

  6. Comprehensive Study of an Earth-Abundant Bifunctional 3D Electrode for Efficient Water Electrolysis in Alkaline Medium.

    PubMed

    Sharifi, Tiva; Gracia-Espino, Eduardo; Jia, Xueen; Sandstrm, Robin; Wgberg, Thomas

    2015-12-30

    We report efficient electrolysis of both water-splitting half reactions in the same medium by a bifunctional 3D electrode comprising Co3O4 nanospheres nucleated on the surface of nitrogen-doped carbon nanotubes (NCNTs) that in turn are grown on conductive carbon paper (CP). The resulting electrode exhibits high stability and large electrochemical activity for both oxygen and hydrogen evolution reactions (OER and HER). We obtain a current density of 10 mA/cm(2) in 0.1 M KOH solution at overpotentials of only 0.47 and 0.38 V for OER and HER, respectively. Additionally, the experimental observations are understood and supported by analyzing the Co3O4:NCNT and NCNT:CP interfaces by ab initio calculations. Both the experimental and the theoretical studies indicate that firm and well-established interfaces along the electrode play a crucial role on the stability and electrochemical activity for both OER and HER. PMID:26629887

  7. The study of electrolyte solutions based on ethylene and diethyl carbonates for rechargeable Li batteries. 2: Graphite electrodes

    SciTech Connect

    Aurbach, D.; Ein-Eli, Y.; Markovsky, B.; Zaban, A.; Luski, S.; Carmeli, Y.; Yamin, H.

    1995-09-01

    The electrochemical behavior of Li-graphite intercalation anodes in ethylene and diethyl carbonates (EC-DEC) solutions was studied using surface sensitive Fourier transform infrared spectroscopy (FTIR) and impedance spectroscopy in conjunction with standard electrochemical techniques. Three different solvent combinations, four different salts: LiBF{sub 4}, LiPF{sub 6}, LiClO{sub 4}, and LiAsF{sub 6}, and the influence of the presence of CO{sub 2} were investigated. Graphite electrodes could be cycled hundreds of times obtaining a reasonable reversible capacity. The best electrolyte was found to be LiAsF{sub 6} and the presence of CO{sub 2} in solutions considerably increased the reversible capacity upon cycling. This improved performance is due to precipitation of the ethylene carbonate reduction product, (CH{sub 2}OCO{sub 2}Li){sub 2}, which is an excellent passivating agent, on the electrode surface. Aging processes of these surface films and their influence on the electrode properties are discussed.

  8. 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

    2013-01-01

    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

  9. Do Changes in Electrical Skin Resistance of Acupuncture Points Reflect Menstrual Pain? A Comparative Study in Healthy Volunteers and Primary Dysmenorrhea Patients

    PubMed Central

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

    2014-01-01

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

  10. A study on oxidized glassy carbon sheets for bipolar supercapacitor electrodes

    SciTech Connect

    Braun, A.; Baertsch, M.; Geiger, F.

    2000-07-01

    Electrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GC) electrodes, are being developed in this laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation on active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. The authors show that this effect is correlated with the opening, the growth and the coalescence of the pores.

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

    PubMed

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

    2014-10-01

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

  12. Surface-enhanced resonance hyper-Raman scattering and surface-enhanced resonance Raman scattering of dyes adsorbed on silver electrode and silver colloid: a comparison study

    NASA Astrophysics Data System (ADS)

    Li, Wu-Hu; Li, Xiao-Yuan; Yu, Nai-Teng

    1999-10-01

    Surface-enhanced resonance hyper-Raman scattering (SERHRS) and surface-enhanced resonance Raman scattering (SERRS) of three dyes, rhodamine 6G, crystal violet and basic fuchsin, are studied comparatively on electrochemically roughened silver electrode and silver colloid, respectively. All three dyes show a better SERHRS efficiency on the silver colloid than on the silver electrode, a phenomenon just opposite to what we have recently observed for pyridine and pyrazine [Chem. Phys. Lett. 305 (1999) 303]. These results suggest that the efficiency of SEHRS depends not only on the active surfaces employed (colloidal metals versus roughened electrodes) but also on the types of the adsorbed molecules.

  13. Cermet electrode

    DOEpatents

    Maskalick, Nicholas J. (Pittsburgh, PA)

    1988-08-30

    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.

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

    PubMed Central

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

    2014-01-01

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

  15. Photoelectrochemical electrodes

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  16. Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes

    NASA Astrophysics Data System (ADS)

    Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.

    2015-03-01

    Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.

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

    SciTech Connect

    Daniel A Scherson

    2013-03-14

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

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

    NASA Astrophysics Data System (ADS)

    Whitney, Scott M.

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

  19. Density functional theory study of the electrochemical interface between a Pt electrode and an aqueous electrolyte using an implicit solvent method

    NASA Astrophysics Data System (ADS)

    Sakong, Sung; Naderian, Maryam; Mathew, Kiran; Hennig, Richard G.; Gro, Axel

    2015-06-01

    We present a computational study of the interface of a Pt electrode and an aqueous electrolyte employing semi-empirical dispersion corrections and an implicit solvent model within first-principles calculations. The electrode potential is parametrized within the computational hydrogen electrode scheme. Using one explicit layer, we find that the most realistic interface configuration is a water bilayer in the H-up configuration. Furthermore, we focus on the contribution of the dispersion interaction and the presence of water on H, O, and OH adsorption energies. This study demonstrates that the implicit water scheme represents a computationally efficient method to take the presence of an aqueous electrolyte interface with a metal electrode into account.

  20. Electrode immersion depth determination and control in electroslag remelting furnace

    SciTech Connect

    Melgaard, David K.; Beaman, Joseph J.; Shelmidine, Gregory J.

    2007-02-20

    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.

  1. Turning Points during the Life of Student Project Teams: A Qualitative Study

    ERIC Educational Resources Information Center

    Raes, Elisabeth; Kyndt, Eva; Dochy, Filip

    2015-01-01

    In this qualitative study a more flexible alternative of conceptualising changes over time in teams is tested within student project teams. The conceptualisation uses turning points during the lifespan of a team to outline team development, based on work by Erbert, Mearns, & Dena (2005). Turning points are moments that made a significant…

  2. Extracurricular Activities and Their Effect on the Student's Grade Point Average: Statistical Study

    ERIC Educational Resources Information Center

    Bakoban, R. A.; Aljarallah, S. A.

    2015-01-01

    Extracurricular activities (ECA) are part of students' everyday life; they play important roles in students' lives. Few studies have addressed the question of how student engagements to ECA affect student's grade point average (GPA). This research was conducted to know whether the students' grade point average in King Abdulaziz University,

  3. A multi-electrode velocity-map imaging apparatus to study laser induced molecular dynamics

    NASA Astrophysics Data System (ADS)

    de, S.; Ray, D.; Johnson, N. G.; Bocharova, I.; Magrakvelidze, M.; Cocke, C. L.; Litvinyuk, I. V.; Znakovskaya, I.; Wirth, A.; Kling, M. F.

    2009-05-01

    We have designed and built a multi-electrode VMI spectrometer capable of detecting up to 300 eV electrons with good momentum resolution. The spectrometer is based on an original design which utilizes a multiple electrostatic lens system to contain the high energy electrons, while maintaining good volume focusing. The spectrometer is used together with super-sonic atomic and molecular jet gas targets in the J. R. Macdonald Laboratory. We measured 3D momentum distributions of ATI electrons produced by intense femtosecond laser pulses to determine the resolution of the spectrometer experimentally and compare the result to Simion calculations. We will present first results on using this device to record phase dependent control of electron localization in the dissociative ionization of simple molecules in two-color intense laser fields and the dynamic alignment and orientation of carbon monoxide after excitation by a two-color laser field.

  4. Os layers spontaneously deposited on the Pt(111) electrode : XPS, STM and GIF-XAS study.

    SciTech Connect

    Rhee, C. K.; Wakisaka, M.; Tolmachev, Y.; Johnston, C.; Haasch, R.; Attenkofer, K.; Lu, G. Q.; You, H.; Wieckowski, A.; Univ. of Illinois Champaigh-Urbana

    2003-01-01

    Scanning tunneling microscopy (STM) characterized adlayers of spontaneously deposited osmium on a Pt(111) electrode were investigated using ex-situ X-ray photoemission spectroscopy (XPS) and in-situ grazing incidence fluorescence X-ray absorption spectroscopy (GIF-XAS). After a single spontaneous deposition, monoatomic (or nearly monoatomic) nanoislands of osmium are formed. The island diameter varies from 2 to 5 nm depending on the Os coverage, which in turn is adjusted by varying the concentration of the Os precursor salt (OsCl3) in the deposition bath and/or by the deposition time. XPS reveals three oxidation states: a metallic Os (the 4f7/2 core level binding energy of 50.8 eV), Os(IV) (51.5 eV) and Os(VIII) (52.4 eV). The metallic osmium exists at potentials below 500 mV (vs. RHE) while above 500 mV osmium is oxidized to Os(IV). Electrodissolution of osmium begins above 900 mV and occurs simultaneously with platinum oxidation. At ca. 1200 mV V versus the RHE reference, the oxidation state of some small amounts of osmium that survive dissolution is the Os(VIII). We demonstrate, for the first time, that mixed or odd valencies of osmium exist on the platinum surface at potentials higher that 800 mV. In-situ GIF-XAS measurements of an Os LIII edge also reveal the presence of three Os oxidation states. Namely, below the electrode potential of 400 mV, the X-ray fluorescent energy at maximum absorption is 10.8765 keV, and is characteristic of the metallic Os. In the potential range between 500 and 1000 mV this energy is gradually shifted to higher values, assignable to higher valencies of osmium, like Os(IV). This tendency continues to higher potentials consistent with the third, highly oxidized osmium form present, most likely Os(VIII). The variation of the 'raw edge jump height' of Os with the electrode potential, which is equivalent to a drop in osmium surface concentration, demonstrates that the electrochemical stripping of Os begins below 1.0 V versus RHE, as expected from voltammetry. Also, the observed intensity of the white line of Os in the 100-400 mV region is larger than the value reported for metallic bulk Os. This discrepancy may result from the difference in the electronic properties of the metallic Os layers on Pt(111) and the metallic bulk Os: in the potential region between 100 and 400 mV, the 5d electrons in Os and Pt form a mixed electronic band, and the density of electronic states near the Fermi level, the main factor determining the white line intensity, may not be the same as in metallic bulk. The presented results on osmium adlayers are much more comprehensive than those available in our previous work due to the combined STM, GIF-XAS and XPS investigations. A nearly perfect convergence of the in situ and ex situ data is one of the main research outcomes of this project. Finally, platinum XPS spectra taken in the context of Os electrooxidation from the electrode surface are also presented and conclusions are made, that up to 900 mV platinum remain metallic, irrespective of a significant osmium oxidation on its surface.

  5. Production and study of megawatt air-nitrogen plasmatron with divergent channel of an output electrode

    NASA Astrophysics Data System (ADS)

    Isakaev, E. H.; Chinnov, V. F.; Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Konovalov, P. V.

    2015-11-01

    Megawatt generator of high-enthalpy air plasma jet (H ≥ 30 kJ/g) is constructed. Plasmatron belongs to the class of plasma torches with thermionic cathode, tangential swirl flow and divergent channel of an output electrode-anode. Plasma torch ensures the formation of the slightly divergent (2α = 12°) air plasma jet with the diameter D = 50 mm. The current-voltage characteristics of the plasma torch has virtually unchanged voltage relative to its current with enhanced (compared with arcs in cylindrical channels) stable combustion zone. Preliminary analysis of the obtained air plasma spectra shows that at a current of 1500 A near-axis zone of the plasma jet is characterized by a temperature of up to 15000 K, and the peripheral radiating area has a temperature of 8000-9000 K.

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

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1995-01-01

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

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

    PubMed

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

    2006-08-01

    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

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

    PubMed

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

    2014-02-01

    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. PMID:24593429

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

    SciTech Connect

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

    1988-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

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

    SciTech Connect

    Kishii, Y. Kawasaki, S.; Kitagawa, A.; Muramatsu, M.; Uchida, T.; Graduate School of Interdisciplinary New Science, Toyo University, 2100 Kujirai, Kawagoe 350-8585

    2014-02-15

    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.

  12. Tetracycline-selective electrode for content determination and dissolution studies of pharmaceuticals by flow-injection analysis (FIA).

    PubMed

    Sales, M G; Montenegro, M C

    2001-08-01

    The present work describes the construction and evaluation of different tetracycline (TC)-selective electrodes without inner reference solution and with polymer membranes. The several electrodes were prepared with poly(vinyl chloride) or ethylene(vinyl acetate) membranes comprising o-nitrophenyl octyl ether or bis(2-ethylhexyl)sebacate as mediator solvents and tetracycline tetrakis(4-clorophenyl)borate as ion exchanger. The best performance was recorded for the poly(vinyl chloride) membranes with bis(2-ethylhexyl)sebacate. Using solutions with adjusted ionic strength, this type of electrode presented a slope of 57.4 mV decade(-1) and a reproducibility of +/-0.3 mV day(-1), for an analytical range from 1.2 x 10(-4) to 1.0 x 10(-2) M. The pH working range was 2.0-3.8. Tubular-shaped potentiometric detectors based on the same selective membrane were also constructed. When TC solutions with adjusted ionic strength of concentrations ranging from 1.0 x 10(-4) to 1.0 x 10(-2) M were injected into a single-channel flow manifold, the detectors presented a slope of 56.6 mV decade(-1) and a reproducibility of +/-0.5 mV day(-1). The pH working range was 1.9-3.9. Both batch and flow procedures were applied to the potentiometric analysis of oral dosage forms. Average recoveries were within 98.6 to 100.3% and the t test indicated the accuracy of these results in comparison to an independent methodology. The flow system with the potentiometric detector was employed in dissolution studies as well. PMID:11536217

  13. Semiclassical Green's functions of magnetic point contacts

    NASA Astrophysics Data System (ADS)

    Useinov, N. Kh.

    2015-05-01

    We propose a method for constructing the semiclassical symmetric and antisymmetric Green's functions of magnetic point contacts with uniform magnetization of different ferromagnetic electrodes. The obtained antisymmetric Green's function permits studying the ballistic and diffusion transport of electrons through the magnetic contact with the electrochemical potential inhomogeneity taken into account.

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

    NASA Astrophysics Data System (ADS)

    Wu, Jingjie

    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 33.5 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.

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

    PubMed Central

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

    2015-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

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

    PubMed

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

    2014-06-01

    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

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

    SciTech Connect

    Wilcox, James D.

    2008-12-18

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

  1. Electrode structures

    SciTech Connect

    Brennan, M.P.

    1981-01-06

    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.

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

    NASA Astrophysics Data System (ADS)

    Batra, Arunabh

    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 vacuum. We find that the halogen atoms cleave from the precursors at surprisingly low temperatures of <100C, and find that the resulting radicals bind to Au, forming Au-C and Au-Br bonds. We show that the Br desorbs at relatively low temperatures of <250C, and that polymerization of the precursor molecules to form nanoribbons proceeds only after the debrominization of the surface. Finally, with Angle-Resolved Photoemission and Density Functional Theory calculations, we quantify the interaction strength of the resulting nanoribbons with the underlying gold substrate. Taken together, the results presented in this thesis offer a mechanistic understanding of the formation of electrode-molecule bonds, and also an insight into the high-bias behavior of molecular junctions as a function of electrode-molecule coupling. In addition, our work in developing tunable, functional electronic devices serves as a framework for future technological advances towards molecule-based computation.

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

    PubMed

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

    2014-11-21

    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 μm 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 μm and 5 μm 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 μM), 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

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

    SciTech Connect

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

    2013-01-01

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

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

    PubMed Central

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  7. Sorption of polluting metal ions on a palm tree frond sawdust studied by the means of modified carbon paste electrodes.

    PubMed

    Nouacer, Sana; Hazourli, Sabir; Despas, Christelle; Hébrant, Marc

    2015-11-01

    Water remediation by adsorption of the metal ions on a low cost sorbent is the frame of the present study. The metal ions adsorption properties of sawdust of palm tree fronds (PTF sawdust) are investigated by both equilibrium measurements and modified carbon paste electrode. The ability to adsorb Cu(II), Cr(VI) and As(III) in significant quantities is demonstrated. Carbon paste electrodes modified by incorporation of PTF sawdust (PTF-CPE) or, for comparison, an organically modified silica for the detection of copper(II) are investigated in term of sensitivity, estimation of number of possible reuses, repeatability and interference effect. A detection limit for Cu(II) analysis of 1.0×10(-8) M has been achieved after 5 min preconcentration and a single PTF-CPE can be used for up to 10 preconcentration-analysis-regeneration cycles. The relative standard deviation (n=9) for the determination of a 10(-6) M Cu(II) solution (pH=5) was about 26%. The effects of Ca(II), As(III) and Cr(VI) on the copper detection are investigated: calcium ions were shown to compete with copper on the same adsorption sites, arsenic(III) has no effect on the copper detection whereas chromium(VI) was shown to enhance the copper detection. PMID:26452828

  8. In Situ Potentiodynamic Analysis of the Electrolyte/Silicon Electrodes Interface Reactions - A Sum Frequency Generation Vibrational Spectroscopy Study.

    PubMed

    Horowitz, Yonatan; Han, Hui-Ling; Ross, Philip N; Somorjai, Gabor A

    2016-01-27

    The key factor in long-term use of batteries is the formation of an electrically insulating solid layer that allows lithium ion transport but stops further electrolyte redox reactions on the electrode surface, hence solid electrolyte interphase (SEI). We have studied a common electrolyte, 1.0 M LiPF6/ethylene carbonate (EC)/diethyl carbonate (DEC), reduction products on crystalline silicon (Si) electrodes in a lithium (Li) half-cell system under reaction conditions. We employed in situ sum frequency generation vibrational spectroscopy (SFG-VS) with interface sensitivity in order to probe the molecular composition of the SEI surface species under various applied potentials where electrolyte reduction is expected. We found that, with a Si(100)-hydrogen terminated wafer, a Si-ethoxy (Si-OC2H5) surface intermediate forms due to DEC decomposition. Our results suggest that the SEI surface composition varies depending on the termination of Si surface, i.e., the acidity of the Si surface. We provide the evidence of specific chemical composition of the SEI on the anode surface under reaction conditions. This supports an electrochemical electrolyte reduction mechanism in which the reduction of the DEC molecule to an ethoxy moiety plays a key role. These findings shed new light on the formation mechanism of SEI on Si anodes in particular and on SEI formation in general. PMID:26651259

  9. Electrochemical behavior of sodium azide at Pt and Au electrodes in sodium sulfate electrolyte: A DEMS study

    SciTech Connect

    Dalmia, A.; Wasmus, S.; Savinell, R.F.; Liu, C.C.

    1995-11-01

    Azides are widely used in chemical technology for a large variety of applications, such as detonators (Pb(N{sub 3}){sub 2}), getters in electric discharge tubes, anticorrosive agents, or additives for the production of foam rubber. The electro-oxidation and -reduction of sodium azide at porous painted platinum and gold electrodes was studied using the multipurpose electrochemical mass spectrometry (MPEMS) which was operated in the differential electrochemical mass spectrometry (DEMS) mode. The platinum electrode was found to be active for electro-oxidation as well as for electroreduction. Above 0.3 V vs. Hg/Hg{sub 2}SO{sub 4}, azide is oxidized to give N{sub 2}, NO, NO{sub 2}, and N{sub 2}O. Reduction of azide takes place below {minus}0.9 V forming N{sub 2}, N{sub 2}H{sub 4}, and possibly NH{sub 3}. In contrast to platinum, gold showed only activity for the electro-oxidation of azide leading to the formation of N{sub 2}, NO, NO{sub 2}, and N{sub 2}O above 0.5 V. Evidence for a reaction without evolution of volatile products was also found taking place above 0.1 V. A reaction mechanism is discussed emphasizing the role of adsorbed hydrogen and oxygen.

  10. Rotating Ring-Disk Electrode and Quantum-Chemical Study of the Electrochemical Reduction of Monoiodoacetic Acid and Iodoform.

    PubMed

    Ma, Jing; Yan, Mingquan; Kuznetsov, Andrey M; Masliy, Aleksey N; Ji, Guodong; Korshin, Gregory V

    2015-11-17

    This study examined the electrochemical (EC) reduction of monoiodoacetic acid (MIAA) and iodoform (CHI3), which are typical iodine-containing disinfection byproducts (I-DBPs). Experiments carried out using the method of a rotating ring-disk electrode (RRDE) with a gold working electrode showed that the reduction of CHI3 and MIAA is diffusion-controlled. The MIAA diffusion coefficient was determined to be (1.86 ± 0.24)·10(-5) cm(2) s(-1). The yield of the iodide ion formed as a result of MIAA or CHI3 reduction was affected by the presence of dissolved organic matter (DOM) and resorcinol. Increasing concentrations of DOM or resorcinol did not affect the EC reduction of the examined I-DBPs, but the formation of iodide was suppressed. This indicated that free iodine, ·I, was formed as a result of the first step in the EC reduction of MIAA and CHI3. This also indicated that the pathway of the EC reduction of MIAA and CHI3 was different from that typical for the reduction of Br- and Cl-containing DBPs, in which case Br(-) or Cl(-) tend to be formed as a result of the electron transfer. Quantum-chemical (QC) calculations confirmed the thermodynamic likelihood of and possible preference to the formation of free iodine species as a result of the EC reduction of MIAA, CHI3, and other I-DBPs. PMID:26496660

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

    NASA Astrophysics Data System (ADS)

    Yilmaz, M.; Gullu, M.

    2014-06-01

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

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

    PubMed

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

    2014-11-25

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

  13. Parametric Study of Plasma Torch Operation Using a MHD Model Coupling the Arc and Electrodes

    NASA Astrophysics Data System (ADS)

    Alaya, M.; Chazelas, C.; Vardelle, A.

    2015-10-01

    Coupling of the electromagnetic and heat transfer phenomena in a non-transferred arc plasma torch is generally based on a current density profile and a temperature imposed on the cathode surface. However, it is not possible to observe the current density profile experimentally and so the computations are grounded on an estimation of current distribution at cathode tip. To eliminate this boundary condition and be able to predict the arc dynamics in the plasma torch, the cathode was included in the computational domain, the arc current was imposed on the rear surface of the cathode, and the electromagnetism and energy conservation equations for the fluid and the electrode were coupled and solved. The solution of this system of equations was implemented in a CFD computer code to model various plasma torch operating conditions. The model predictions for various arc currents were consistent and indicated that such a model could be applied with confidence to plasma torches of different geometries, such as cascaded-anode plasma torches.

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

    SciTech Connect

    Saha, Dipendu; Li, Yunchao; Bi, Zhonghe; Chen, Jihua; Keum, Jong Kahk; Hensley, Dale K; Grappe, Hippolyte A.; Meyer III, Harry M; Dai, Sheng; Paranthaman, Mariappan Parans; Naskar, Amit K

    2014-01-01

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

  15. Parametric Study of Plasma Torch Operation Using a MHD Model Coupling the Arc and Electrodes

    NASA Astrophysics Data System (ADS)

    Alaya, M.; Chazelas, C.; Vardelle, A.

    2016-01-01

    Coupling of the electromagnetic and heat transfer phenomena in a non-transferred arc plasma torch is generally based on a current density profile and a temperature imposed on the cathode surface. However, it is not possible to observe the current density profile experimentally and so the computations are grounded on an estimation of current distribution at cathode tip. To eliminate this boundary condition and be able to predict the arc dynamics in the plasma torch, the cathode was included in the computational domain, the arc current was imposed on the rear surface of the cathode, and the electromagnetism and energy conservation equations for the fluid and the electrode were coupled and solved. The solution of this system of equations was implemented in a CFD computer code to model various plasma torch operating conditions. The model predictions for various arc currents were consistent and indicated that such a model could be applied with confidence to plasma torches of different geometries, such as cascaded-anode plasma torches.

  16. The point-to-point test: A new diagnostic tool for measuring lumbar tactile acuity? Inter and intra-examiner reliability study of pain-free subjects.

    PubMed

    Adamczyk, Wacław; Sługocka, Anna; Saulicz, Oskar; Saulicz, Edward

    2016-04-01

    A two-point discrimination test (TPD) is commonly used to investigate lumbar tactile acuity. However, low inter-examiner reliability and difficulties in execution significantly limit its application. Therefore the aim of this study was to compare the inter- and intra-examiner reliability of a new approach, the point-to-point test (PTP), with the TPD. Twenty-one pain-free subjects attended the inter-examiner stage of the study. Eighteen of them were further recruited into an intra-examiner (reproducibility and repeatability) reliability study. PTP was performed on the three points plotted at the L3 spinal level. Point '0' overlapped with the L3 spinous process, from which points '1' and '2' were horizontally separated by 5 and 10 cm, respectively. Participants manually indicated a point previously touched by the examiner, while the distance (error) was measured. Reliability was determined with the intraclass correlation coefficient (ICC2,3). The results revealed good and moderate inter- and intra-examiner reliability at point '1' (ICC2,3 = 0.68-0.84) and good reliability at point '2' (ICC2,3 = 0.84-0.86). At point '0', reliability was moderate to poor (ICC2,3 = 0.13-0.63). TPD was characterised by a poor to moderate level of inter- (ICC2,1 = 0.51; ICC2,3 = 0.56) and intra-examiner reliability (ICC(2,1) = 0.50; ICC2,3 = 0.74). Our findings suggest that PTP is more reliable than TPD at two investigated points at the L3 spinal level. However, further research on PTP validity data is strongly warranted. PMID:26797175

  17. Mediated Knowledge: Reexamining Six Classic Community Studies from a Woman's Point of View

    ERIC Educational Resources Information Center

    Zimmerman, Julie N.

    2011-01-01

    Six studies published in the 1940s have become classics in the analysis of rural community and change: the community stability/instability studies. One of their less recognized features is that their analyses included women. This article revisits these six studies, but from a different vantage point. As a socially constructed enterprise, the

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

    ERIC Educational Resources Information Center

    Lee, Jennifer

    2012-01-01

    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

  19. Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.

    PubMed

    Puurtinen, Merja M; Komulainen, Satu M; Kauppinen, Pasi K; Malmivuo, Jaakko A V; Hyttinen, Jari A K

    2006-01-01

    Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes. The aim was to study how the electrode size and preparation of the electrode (dry electrode/wet electrode/electrode covered with hydrogel membrane) affect the measurement noise, and the skin-electrode impedance. The measurement noise and skin-electrode impedance were determined from surface biopotential measurements. These preliminary results indicate that noise level increases as the electrode size decreases. The noise level is high in dry textile electrodes, as expected. Yet, the noise level of wet textile electrodes is quite low and similar to that of textile electrodes covered with hydrogel. Hydrogel does not seem to improve noise properties, however it may have effects on movement artifacts. Thus, it is feasible to use textile embedded sensors in physiological monitoring applications when moistening or hydrogel is applied. PMID:17946734

  20. A study of the fatigue properties of small diameter wires used in intramuscular electrodes.

    PubMed

    Scheiner, A; Mortimer, J T; Kicher, T P

    1991-05-01

    Single and multi-strand stainless steel and cobalt-nickel alloy wires, with strand diameters from 26 to 46 microns, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi-stranded wires have the same average fatigue life as their individual constituent strands, but the variance of that life is smaller. (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure. (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life. PMID:1869576

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

    PubMed Central

    Liu, Yuji; Ahmad, Bashir

    2014-01-01

    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

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

    PubMed

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

    2013-06-01

    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

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

    SciTech Connect

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

    2014-04-15

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

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

    PubMed

    Paital, B; Samanta, Luna

    2013-06-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  7. Readout electrode assembly for measuring biological impedance

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  8. Fabrication of ion-conducting carbon-polymer composite electrodes by spin-coating

    NASA Astrophysics Data System (ADS)

    Pldsalu, Inga; Mndmaa, Sven-Erik; Peikolainen, Anna-Liisa; Keskla, Arko; Aabloo, Alvo

    2015-04-01

    We report a fabricating method for ion-conducting carbon electrodes on top of industrially produced PVDF membrane by spin-coating. Spin-coating is desirable due to its potential application in large-scale actuator manufacturing and its possibility to produce very thin electrodes. The industrial grade membrane was chosen in order to investigate more accurately the results of spin-coating without considering the deviations present in a hand-made membrane. Spin-coating and surface resistivity measurements via four-point probe were described in further detail. The production process of electrode suspension and suspension dispensing were developed and fine-tuned. The spin coater was programmed to obtain electrodes with uniform electrical properties. The arrangement of the spin coater was slightly altered to remove swelling and bubble formation effects concurrent with usage of the porous membrane. Electrodes produced with the developed method were measured and analyzed. Thickness of the film was measured with micrometer screw gauge and four-point probe was used to measure sheet resistivity, in addition film was studied under scanning electron microscope. In best cases the coefficient of variation for sheet conductivity was 6.2%. For all electrode sheet conductivities the median coefficient of variation was 7%. The thickness of the electrodes varied from 6 to 23 ?m. As a proof of concept for the developed method a working actuator with spin-coated electrodes was produced.

  9. Poly(3-methylthiophene)/palladium sub-micro-modified sensor electrode. Part II: Voltammetric and EIS studies, and analysis of catecholamine neurotransmitters, ascorbic acid and acetaminophen.

    PubMed

    Atta, Nada F; El-Kady, Maher F

    2009-08-15

    Promising voltammetric sensors based on the modification of Pt and poly(3-methylthiophene) (PMT) electrodes with Pd nanoparticles were achieved for the determination of catecholamine neurotransmitters, ascorbic acid and acetaminophen. Electrochemistry of the indicated compounds was studied at these electrodes and interesting electrocatalytic effects were found. Furthermore, simple, easily prepared one electrochemical step Pd-modified Pt electrode (Pt/Pd) is reported for the first time. Cyclic voltammetry (CV) and chronocoulometry (CC) were used for the determination of the apparent diffusion coefficients in different electrolytes at these electrodes and the values are in the range from 10(-4) to 10(-5)cm(2)s(-1). Furthermore, it was found that the method of polymer formation had a substantial effect on the synergism between the polymer film and the loaded metal particles towards the oxidation of dopamine (DA) in different supporting electrolytes. This was confirmed by the CV, CC and EIS (electrochemical impedance spectroscopy) as well as SEM (Scanning Electron Microscopy) results. Pt and PMT electrodes modified with Pd nanoparticles showed excellent results for the simultaneous determination of tertiary and quaternary mixtures of the studied compounds. PMID:19576424

  10. Skimming Electronic Newspaper Headlines: A Study of Typeface, Point Size, Screen Resolution, and Monitor Size.

    ERIC Educational Resources Information Center

    Kingery, David; Furuta, Richard

    1997-01-01

    Describes a study that suggests the perception of words while skimming a newspaper headline on a computer screen is affected by typeface, point size, screen resolution, and monitor size. Limitations of the study are discussed and further research is suggested. (LRW)

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    NASA Technical Reports Server (NTRS)

    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

    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

  14. Preliminary numerical modeling results - cone penetrometer (CPT) tip used as an electrode

    SciTech Connect

    Ramirez, A L

    2006-12-19

    Figure 1 shows the resistivity models considered in this study; log10 of the resistivity is shown. The graph on the upper left hand side shows a hypothetical resisitivity well log measured along a well in the upper layered model; 10% Gaussian noise has been added to the well log data. The lower model is identical to the upper one except for one square area located within the second deepest layer. Figure 2 shows the electrode configurations considered. The ''reference'' case (upper frame) considers point electrodes located along the surface and along a vertical borehole. The ''CPT electrode'' case (middle frame) assumes that the CPT tip serves as an electrode that is electrically connected to the push rod; the surface electrodes are used in conjuction with the moving CPT electrode. The ''isolated CPT electrode'' case assumes that the electrode at the CPT tip is electrically isolated from the pushrod. Note that the separate CPT push rods in the middle and lower frames are shown separated to clarify the figure; in reality, there is only one pushrod that is changing length as the probe advances. Figure 3 shows three pole-pole measurement schemes were considered; in all cases, the ''get lost'' electrodes were the leftmost and rightmost surface electrodes. The top frame shows the reference scheme where all surface and borehole electrodes can be used. The middle frame shows two possible configurations available when a CPT mounted electrode is used. Note that only one of the four poles can be located along the borehole at any given time; electrode combinations such as the one depicted in blue (upper frame) are not possible in this case. The bottom frame shows a sample configuration where only the surface electrodes are used. Figure 4 shows the results obtained for the various measurement schemes. The white lines show the outline of the true model (shown in Figure 1, upper frame). The starting initial model for these inversions is based on the electrical resistivity log shown on the upper left. The results in the lower frame show what would be observed if the data collected by the CPT electrode have been corrected for the effects of the push rod. Figure 5 shows the results obtained when the starting initial model is a homogeneous half-space with a resistivity of 20 ohm-m. This figure can be compared with Figure 4 to see the effect that different starting models have on the inversion. Figure 6 shows results that are analogous to those in Figure 4. In this case, the true model is the one shown in the lower frame of Figure 1. Figure 7 compares corrected and uncorrected results. Both results only used data that can be collected when CPT electrodes are used. The top frame shows results when data is collected with point electrodes (no correction used). The bottom frame shows results when data is collected using a CPT electrode; a correction was applied to remove the effects of the electrically conducting pushrod. Figure 8 compares data collected using the CPT electrodes to data collected with point electrode. The blue diamonds represent the uncorrected CPT data and the red squares represent the corrected CPT data. The top frame (electrical gap = 0.0 m) corresponds to the case where the CPT electrode and the pushrod are connected together thorigh the metal. The bottom frame corresponds to the case where the CPT electrode and pushrod are separated by a 1.0 m gap; the electrical connection between rod and electrode is through the soil.

  15. Single camera photogrammetry system for EEG electrode identification and localization.

    PubMed

    Baysal, U?ur; Sengl, Gkhan

    2010-04-01

    In this study, photogrammetric coordinate measurement and color-based identification of EEG electrode positions on the human head are simultaneously implemented. A rotating, 2MP digital camera about 20 cm above the subject's head is used and the images are acquired at predefined stop points separated azimuthally at equal angular displacements. In order to realize full automation, the electrodes have been labeled by colored circular markers and an electrode recognition algorithm has been developed. The proposed method has been tested by using a plastic head phantom carrying 25 electrode markers. Electrode locations have been determined while incorporating three different methods: (i) the proposed photogrammetric method, (ii) conventional 3D radiofrequency (RF) digitizer, and (iii) coordinate measurement machine having about 6.5 mum accuracy. It is found that the proposed system automatically identifies electrodes and localizes them with a maximum error of 0.77 mm. It is suggested that this method may be used in EEG source localization applications in the human brain. PMID:20186487

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  18. Study on turbulent natural convection in LNG carrier cofferdam with heating points

    SciTech Connect

    Chung, H.S.; Jeong, H.M.; Kim, K.K.; Kwon, S.S.

    1999-07-01

    The turbulent natural convection in the membrane type LNG carrier cofferdam with heating points has been studied by numerical and experimental methods. The parameters considered for numerical study are number and capacity of heating points, i.e., 1 {le} Ns {le} 12 and 1.0 x 10{sup 5} {le} Qs(W/m{sup 3}) {le} 5.0 x 10{sup 10}. The results of the isotherms and velocity vectors have been represented for various parameters. The temperature and velocity at upper position in the space are shown to be higher than those at lower position. for obtaining the optimal temperatures, 20{approximately}30 C in the cofferdam space, the heating capacities how 2.0 x 10{sup 7}{approximately}4.0 x 10{sup 7} W/m{sup 3} at 8-heating points and 1.0 x 10{sub 7} at 12-points. Based on the numerical data, the mean temperature in the cofferdam space can be expressed as a function of number and capacity of heating points.

  19. Study on the Impurity Effect in the Realization of Silver Fixed Point

    NASA Astrophysics Data System (ADS)

    Tsai, S. F.

    2016-03-01

    The application of a thermal analysis model to estimate the temperature depression from the ideal fixed-point temperature is important, especially when the chemical analysis of the sample in a cell is insufficient or the cell might have been contaminated during fabrication. This study extends previous work, on thermal analysis with the tin point, to an investigation of the impurity dependence of the silver-point temperature. Close agreement was found between the temperature depression (-0.36 mK) inferred from the thermal analysis of the measured fixed-point plateau and the temperature depression (-0.32 mK) inferred using the sum of individual estimates (SIE) method with an impurity analysis based on glow discharge mass spectrometry. Additionally, the results of the thermal analysis manifest no significant dependence on the rate of solidification, and the scatter of observed gradients was within 0.36 mK among five plateaux with different temperature settings of the furnace. Although the results support the application of both the SIE method and thermal analysis for the silver point, further experiments with cell-to-cell comparisons linked to thermal analysis, a study of the thermometer-furnace systematic effects, the oxygen effect, and the locus of the freezing plateau should be investigated to reach a firm conclusion.

  20. Study of structural break points in global and hemispheric temperature series by piecewise regression

    NASA Astrophysics Data System (ADS)

    Werner, Rolf; Valev, Dimitar; Danov, Dimitar; Guineva, Veneta

    2015-12-01

    The study of climate trends taking into consideration possible structural changes is important for understanding climate development characterized by a stochastic trend or by a determined one. In the paper global and hemisphere temperature anomalies are modeled by piecewise linear regression and break points in the temperature evolution are found. It was demonstrated that the used method allowed finding of breaks characterized by long time trends (low frequency processes) as well as abrupt changes (fast frequency processes). The obtained break points for slow temperature change are close to the ones found by other authors however additional conditions (as segment length, gradient and others) are not used here. The results for higher break point numbers are like the ones of step slope models. It was demonstrated that the successive phases of warming and cooling and most of the break points subdividing these periods in the Northern Hemisphere are introduced by the Atlantic multidecadal oscillation. Because the strong quasi periodicity of the Atlantic multidecadal oscillation the authors recommend the removal of its influence on the temperature from the temperature series before studies of trends or structural changes. The Northern Hemisphere temperature data after the removal of the Atlantic multidecadal oscillation influence show structures like the Southern Hemisphere temperatures. Model selection by the Schwarz-Bayesian Information Criterion developed by Liu, Wu and Zidek (LWZ criterion) shows that models with only one break point are to be preferred.

  1. Plated Metal Powders for Electrode Pastes

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.

    1984-01-01

    Metal grains to be sintered precoated with frit metal. Coated metal powders used to make ink-like electrode pastes for printing and sintering electrode-fabrication process. Grains of base metal coated with lowmelting-point--, lead or tin-- by electroless deposition.

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

    PubMed Central

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

    2015-01-01

    In the search for optimized cathode materials for high-temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6Sr0.4FeO3−δ (LSF) thin film electrodes. Under cathodic polarization the formation of Fe0 on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. PMID:25557533

  3. Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.

    PubMed

    Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki

    2009-11-01

    To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096

  4. Impedance studies of Ni/Cd and Ni/H2 cells using the cell case as a reference electrode

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1989-01-01

    Impedance measurements have been made on several Ni/Cd and Ni/H2 flightweight 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 voltages of the cell cases with respect to the individual electrodes differ from cell to cell even at the same overall cell voltage, but they remains 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.

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

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1990-01-01

    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.

  6. Radiofrequency Ablation with an Internally Cooled Monopolar Directional Electrode: Ex Vivo and in Vivo Experimental Studies in the Liver.

    PubMed

    Yu, Mi Hye; Lee, Jae Young; Jun, Su Ryoung; Kim, Kyung Won; Kim, Se Hyung; Han, Joon Koo; Choi, Byung Ihn

    2016-02-01

    Purpose To evaluate the feasibility of using an internally cooled directional electrode (ICDE) to create sufficient directional ablation in the desired area and to investigate whether use of the ICDE reduces thermal injury to the adjacent organs. Materials and Methods The animal care and use committee approved this animal study. In ex vivo studies of bovine livers and colons, temperature was measured in both ablation and nonablation directions with the ICDE, temperature at the liver-colon interface and the presence of burns on the colon were evaluated with each ICDE and internally cooled conventional electrode (ICCE), and the ablation area with the use of three ICDEs in the switching multichannel mode was evaluated. In an in vivo study of 10 pigs, 11 ablations were performed by using three ICDEs in the switching multichannel mode. In addition, the difference in thermal injury to the gallbladder and stomach was compared between use of the ICDE and the ICCE. Mann-Whitney test and the Fisher exact test were used for statistical analysis. Results In the ex vivo study, the hepatic temperature in the nonablation direction was lower than 50C; temperature higher than 47C was maintained for less than 3 minutes, even 0.5 cm away from the ICDE; and the temperature at the liver-colon interface did not increase above 50C. In the switching multichannel mode, a fused coagulation zone was created. In the in vivo study, confluent ablation was created in the inner circle of three ICDEs with a mean interelectrode distance of less than 2.6 cm. Use of the ICDE did not create a moderate-to-severe gallbladder wall injury in any of the pigs, but use of the ICCE caused injury in three of the five pigs (P > .05). The ICDE caused moderate-to-severe gastric wall injury at one of eight ablations, and the ICCE caused injury at eight of nine ablations (P < .05). Conclusion Use of an ICDE can create a sufficient ablation in the desired direction and can decrease thermal injury to the adjacent organs. () RSNA, 2015. PMID:26172531

  7. Electromagnetic Initiation and Propagation of Bipolar Radiofrequency Tissue Reactions via Invasive Non-Insulated Microneedle Electrodes

    PubMed Central

    Na, Jongju; Zheng, Zhenlong; Dannaker, Christopher; Lee, Sang Eun; Kang, Jin-Soo; Cho, Sung Bin

    2015-01-01

    Radiofrequency (RF) energy can be emitted into the skin, either non- or invasively, via a monopolar mode that utilizes an active electrode and a grounded electrode or via a bipolar mode that employs two active electrodes. In this experimental study of RF tissue reactions, bipolar RF energy was emitted in vivo to micropig skin at varying microneedle penetration depths, signal amplitudes, and conduction times. Immediately after RF treatment, skin samples exhibited RF-induced coagulation columns of thermal injury, separately generated around each microneedle in the dermis. In ex vivo bovine liver tissue, the thermal coagulation columns were found to be concentrated maximally around the pointed tips of each electrode. After a RF conduction time of 2 seconds, the individual areas of thermal coagulation began to converge with neighboring RF-induced coagulation columns; the convergence of coagulation columns was found to start from the tips of neighboring electrodes. PMID:26563971

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

    ERIC Educational Resources Information Center

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

    2008-01-01

    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.…

  9. Contingency Management to Increase Grade Point Average among Fraternity Members: A Feasibility Study

    ERIC Educational Resources Information Center

    Van Patten, Ryan A.; Irons, Jessica G.; Apple, Kevin J.

    2015-01-01

    Contingency management is an incentive-based intervention strategy that has been demonstrated to be effective for inducing behavior change among a variety of populations and for a variety of behaviors. The current study examined whether contingency management techniques can help students change behaviors in an effort to raise their grade point

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

    ERIC Educational Resources Information Center

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

    2008-01-01

    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.

  11. Retrospective study using MRI to measure depths of acupuncture points in neck and shoulder region

    PubMed Central

    Chou, Pei-Chi; Huang, Yu-Chuen; Hsueh, Chun-Jen; Lin, Jaung-Geng; Chu, Heng-Yi

    2015-01-01

    Objectives There are safety issues associated with acupuncture treatment. Previous studies regarding needling depth of acupuncture points revealed inconsistent results due to vague depth definition, acupuncture point localisation and measuring tools. The objective of this study is to find and compare the differences of the mean depths of 11 acupuncture points in the neck and shoulder region between subjects, with variables including gender and body mass index (BMI). Setting This study was conducted at a single medical center in Taiwan. Participants Three hundred and ninety-four participants were included in this study. Participants were grouped according to gender and BMI. Acupuncture points were localised by WHO standard and measured by MRI. Outcome measures The distance from the needle insertion point (surface of the skin) to any tissues that would cause possible/severe complications. Results Mean depths of 11 points were obtained in groups of different BMI and gender. Mean depths of all participants regardless of BMI and gender are as follows, in centimetres: GB21=5.6, SI14=5.2, SI15=8.8, GV15=4.9, GV16=4.6, GB20=5.0, ST9=1.6, SI16=1.8, SI17=2.4, TE16=3.1, LI18=1.3. Participants with higher BMI had greater measured depths in both gender groups. Male participants had larger mean depths than female participants regardless of BMI except in SI17 and LI18. When taking BMI into consideration, depths in male participants are greater than in female participants in most of the points except the following: GB21, TE16 in obesity group; ST9 in underweight and obesity group; SI16 in ideal body weight, overweight and obesity group; SI17, LI18 in each group. Conclusions Participants with higher BMI had greater measured depths and males tended to have greater depths in most of the points. Clinical practitioners are recommended to consider this information to prevent complications when applying acupuncture treatment to their patients. PMID:26224017

  12. Study on the RF Set Point for the PEFP DTL by using a phase scan method

    NASA Astrophysics Data System (ADS)

    Jang, Ji-Ho; Kwon, Hyeok-Jung; Cho, Yong-Sub

    2012-12-01

    The drift tube linac (DTL) is used to accelerate proton beams from 20 MeV to 100 MeV in the linear accelerator of the Proton Engineering Frontier Project (PEFP). The phase scan signature method is a common technique to determine the radio-frequency (rf) set point, including the rf amplitude and phase, in DTL tanks. In this work, we applied the phase scan method to the first tank of the PEFP's DTL in order to study the procedure for determining the rf set point by using artificial experimental data generated by using the PARMILA code.

  13. Inexpensive and Disposable pH Electrodes

    ERIC Educational Resources Information Center

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

    2010-01-01

    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

  14. Inexpensive and Disposable pH Electrodes

    ERIC Educational Resources Information Center

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

    2010-01-01

    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…

  15. Retina-on-a-chip: a microfluidic platform for point access signaling studies.

    PubMed

    Dodson, Kirsten H; Echevarria, Franklin D; Li, Deyu; Sappington, Rebecca M; Edd, Jon F

    2015-12-01

    We report on a microfluidic platform for culture of whole organs or tissue slices with the capability of point access reagent delivery to probe the transport of signaling events. Whole mice retina were maintained for multiple days with negative pressure applied to tightly but gently bind the bottom of the retina to a thin poly-(dimethylsiloxane) membrane, through which twelve 100?m diameter through-holes served as fluidic access points. Staining with toluidine blue, transport of locally applied cholera toxin beta, and transient response to lipopolysaccharide in the retina demonstrated the capability of the microfluidic platform. The point access fluidic delivery capability could enable new assays in the study of various kinds of excised tissues, including retina. PMID:26559199

  16. Retina-on-a-chip: a microfluidic platform for point access signaling studies

    PubMed Central

    Dodson, Kirsten H.; Echevarria, Franklin D.; Li, Deyu; Sappington, Rebecca M.; Edd, Jon F.

    2016-01-01

    We report on a microfluidic platform for culture of whole organs or tissue slices with the capability of point access reagent delivery to probe the transport of signaling events. Whole mice retina were maintained for multiple days with negative pressure applied to tightly but gently bind the bottom of the retina to a thin poly-(dimethylsiloxane) membrane, through which twelve 100 μm diameter through-holes served as fluidic access points. Staining with toluidine blue, transport of locally applied cholera toxin beta, and transient response to lipopolysaccharide in the retina demonstrated the capability of the microfluidic platform. The point access fluidic delivery capability could enable new assays in the study of various kinds of excised tissues, including retina. PMID:26559199

  17. HPLC/EC studies of selected explosive components, nitroanilines, and nitrophenols with dual electrode electrochemical detection. Final report

    SciTech Connect

    Manning, D.L.; Maskarinec, M.P.

    1986-10-01

    The dual electrode electrochemical detector has greatly enhanced high pressure liquid chromatography/electrochemical detection (HPLC/EC) capability. The most fruitful mode of operation is in the dual parallel electrode configuration. The ability to assess peak purity in real samples is very beneficial. Simultaneous recording of cathodic and anodic chromatograms to look for possible impurities and munition decomposition products is an added technique to ascertain sample purity. The extent of electrode ''crosstalk'' can be minimized by repeating the experiment with the Au/Hg electrode ''OFF.'' In view of the low collection efficiencies encountered, the dual series mode of operation, at present, is of limited practical value for these types of electroactive substances. 5 refs., 9 figs., 2 tabs.

  18. Stable ?-MnS thin film deposited by two-electrode cell: synthesis, structural characterization and photoemission spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Taleatu, Bidini A.; Arbab, Elhadi A. A.; Mola, Genene T.

    2015-09-01

    Stable MnS thin film was deposited from catalyst-free inorganic solution by electrochemical cell. The film was characterized by some surface profiling techniques. Morphology revealed that film's particles were fairly distributed across substrate's surface. Crystallinity and surface growth height/roughness were observed before and after post-deposition annealing. Optical studies further showed that annealing has improved film transmittance across visible wavelength region. Reflections from planes associated with only rock salt structure of MnS were prominently identified by diffraction studies. An estimated average crystal size of 17.40 nm suggested that the deposited film is mainly composed of nanocrystalline particles. Film durability was appraised by core-level profiling of Mn and S binding energy (BE) positions during X-ray photoemission spectroscopy (XPS). The results indicated that before and after vacuum annealing, chemical states of Mn and S remained the same suggesting that the film did not undergo any form of transformation after long exposure to ambient environment. This study demonstrated sustainability of MnS electrode in extreme environmental condition.

  19. Results of blue crab studies at Chalk Point. Final report 1978-1979

    SciTech Connect

    Souza, P.A.; Polgar, T.T.; Miller, R.E.; Holland, A.F.

    1980-11-01

    This report summarizes the findings of two years of blue crab tagging studies conducted in the Patuxent estuary near the Chalk Point power plant. This report is organized in the following manner: An introduction and objectives section defines the objectives of the blue crab study, discusses the modes of interaction between blue crabs and power plant operations, and discusses the life history characteristics of blue crabs. A study methods section provides detailed information on tagging and capture operations and on analysis methods. A results section presents the major findings of the study. A discussion and conclusions section interprets and discusses major findings and defines the impacts of power plant operations at Chalk Point on blue crab populations in the Patuxent estuary. A list of references is included.

  20. 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)

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

    2013-10-01

    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.

  1. A Theoretical Study of the Two-Dimensional Point Focusing by Two Multilayer Laue Lenses.

    SciTech Connect

    Yan,H.; Maser, J.; Kang, H.C.; Macrader, A.; Stephenson, B.

    2008-08-10

    Hard x-ray point focusing by two crossed multilayer Laue lenses is studied using a full-wave modeling approach. This study shows that for a small numerical aperture, the two consecutive diffraction processes can be decoupled into two independent ones in respective directions. Using this theoretical tool, we investigated adverse effects of various misalignments on the 2D focus profile and discussed the tolerance to them. We also derived simple expressions that described the required alignment accuracy.

  2. Noise characteristics of stainless-steel surface electrodes.

    PubMed

    Godin, D T; Parker, P A; Scott, R N

    1991-11-01

    Bioelectric events measured with surface electrodes are subject to noise components which may be significant in comparison with low-level biological signals such as evoked neuroelectric potentials, and myoelectric potentials. In an effort to better understand noise arising from these electrodes, electrode and measurement system noise is modelled. The effect of electrode surface area on electrode impedance and noise is studied using circular stainless-steel electrodes of varying diameters. The main contributions of the work are the development of a model for stainless-steel electrode noise as a function of electrode area, and demonstrating that, for the band-width of interest to evoked neuroelectric and myoelectric signals (8-10,000 Hz), the primary noise components are thermal and amplifier current generated. The magnitudes of both of these depend on the electrode impedance magnitude. Electrode impedance is shown to be a power function of both electrode diameter and frequency, consistent with a capacitive electrode model. PMID:1813753

  3. Low resistance electrode construction

    DOEpatents

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

    2002-01-01

    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.

  4. Low Resistance Electrode Construction

    SciTech Connect

    Redey, Laszlo; Karell, Eric

    2000-01-20

    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 C inside said receptacle chamber. A second metal with a melting point greater than about 800 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.

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

    PubMed

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

    2009-07-01

    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

  6. Studying the Contact Point and Interface Moving in a Sinusoidal Tube with Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Fang, Hai-Ping; Fan, Le-Wen; Wang, Zuo-Wei; Lin, Zhi-Fang; Qian, Yue-Hong

    The multicomponent nonideal gas lattice Boltzmann model by Shan and Chen (S-C) is used to study the immiscible displacement in a sinusoidal tube. The movement of interface and the contact point (contact line in three-dimension) is studied. Due to the roughness of the boundary, the contact point shows ``stick-slip'' mechanics. The ``stick-slip'' effect decreases as the speed of the interface increases. For fluids that are non-wetting, the interface is almost perpendicular to the boundaries at most time, although its shapes at different position of the tube are rather different. When the tube becomes narrow, the interface turns a complex curves rather than remains simple menisci. The velocity is found to vary considerably between the neighbor nodes close to the contact point, consistent with the experimental observation that the velocity is multi-values on the contact line. Finally, the effect of three boundary conditions is discussed. The average speed is found different for different boundary conditions. The simple bounce-back rule makes the contact point move fastest. Both the simple bounce-back and the no-slip bounce-back rules are more sensitive to the roughness of the boundary in comparison with the half-way bounce-back rule. The simulation results suggest that the S-C model may be a promising tool in simulating the displacement behaviour of two immiscible fluids in complex geometry.

  7. Studies of carbon as negative electrode materials for secondary lithium batteries

    NASA Astrophysics Data System (ADS)

    Yang, Han-Xi; Ai, Xin-Ping; Lei, Ming; Li, Sheng-Xian

    1993-04-01

    A number of carbon materials was investigated as lithium storage anodes. The discharge/charge characteristics of the carbon anodes and its dependence on solvents were evaluated. The results from this study demonstrated that pyrolytic and carbon coke carbon in a mixed solvent of propylene carbonate (PC) + dimethoxyethane (DME) have high discharge/charge capacity, superior cycling efficiency and good rechargeability, suitable for use as lithium intercalating negatives in lithium ion cells.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    PubMed Central

    Payrau, Bernard; Qur, Nadine; Bois, Danis

    2011-01-01

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

  10. Kinetics, isothermal and thermodynamics studies of electrocoagulation removal of basic dye rhodamine B from aqueous solution using steel electrodes

    NASA Astrophysics Data System (ADS)

    Adeogun, Abideen Idowu; Balakrishnan, Ramesh Babu

    2015-09-01

    Electrocoagulation was used for the removal of basic dye rhodamine B from aqueous solution, and the process was carried out in a batch electrochemical cell with steel electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process, were investigated. Equilibrium was attained after 10 min at 30 °C. Pseudo-first-order, pseudo-second-order, Elovich and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analysed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich and Sips isotherms and it was found that the data fitted well with Sips isotherm model. The study showed that the process depends on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (Δ G^circ ,Δ H^circ {text{and}}Δ S{^circ } ) indicated that the process is spontaneous and endothermic in nature.

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

    PubMed

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

    2009-03-13

    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

  12. Parametric study of two-body floating-point wave absorber

    NASA Astrophysics Data System (ADS)

    Amiri, Atena; Panahi, Roozbeh; Radfar, Soheil

    2016-03-01

    In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter's efficiency when considering specific conditions.

  13. Interactive graphics system for locating plunge electrodes in cardiac MRI images

    NASA Astrophysics Data System (ADS)

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

    1991-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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 Ω, compared to more than 400 Ω 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.

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

    SciTech Connect

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

    2014-07-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  17. Damage states in laminated composite three-point bend specimens: An experimental-analytical correlation study

    NASA Technical Reports Server (NTRS)

    Starbuck, J. Michael; Guerdal, Zafer; Pindera, Marek-Jerzy; Poe, Clarence C.

    1990-01-01

    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.

  18. Research on rechargeable oxygen electrodes

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

    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.

  19. Cyclic voltammetric study on stoichiometric spinel LiMn 2O 4 electrode at elevated temperature

    NASA Astrophysics Data System (ADS)

    Ma, Shuhua; Noguchi, Hideyuki; Yoshio, Masaki

    The high-temperature electrochemical cell behavior of Li-stoichiometric Li-Mn-O spinel material, LiMn 2O 4.014, has been studied by cyclic voltammetry and coulometric titration curve measurement methods. A split of the reduction peak at x>0.5, in Li xMn 2O 4.014, during Li + insertion was found at 85C. Correspondingly, three plateaus appeared in its coulometric titration curve, which manifest itself as three peaks in d Q/d V- V plot. The peak split phenomenon was also found for oxygen deficient spinel, LiMn 2O 3.986, prepared at 900C in both reduction and oxidation branches at room and elevated temperatures using a lower scan rate of 0.02 mV/s. The disproportionation dissolution of stoichiometric spinel LiMn 2O 4.014 intensified by the elevated temperature in slightly acidic electrolyte is considered responsible for the occurrence of the phenomenon. The finding gives a piece of evidence for oxygen deficient spinel LiMn 2O 4- z as the insoluble product of disproportionation dissolution.

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

    SciTech Connect

    Vadlamani, Bhaskar S; An, Ke; Jagannathan, M.; Ravi Chandran, K.

    2014-01-01

    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.

  1. Point and 5-year period prevalence of neuropsychiatric symptoms in dementia: the Cache County Study

    PubMed Central

    Steinberg, Martin; Shao, Huibo; Zandi, Peter; Lyketsos, Constantine G.; Welsh-Bohmer, Kathleen A.; Norton, Maria C.; Breitner, John C.S.; Steffens, David C.; Tschanz, JoAnn T.

    2010-01-01

    SUMMARY Background Neuropsychiatric symptoms are nearly universal in dementia, yet little is known about their longitudinal course in the community. Objective To estimate point and 5-year period prevalence of neuropsychiatric symptoms in an incident sample of 408 dementia participants from the Cache County Study. Methods The Neuropsychiatric Inventory assessed symptoms at baseline and at 1.5 years, 3.0 years, 4.1 years, and 5.3 years. Point prevalence, period prevalence and mean symptom severity at each time point were estimated. Results Point prevalence for delusions was 18% at baseline and 3438% during the last three visits; hallucinations, 10% at baseline and 1924% subsequently; agitation/aggression fluctuated between 13% and 24%; depression 29% at baseline and 4147% subsequently; apathy increased from 20% at baseline to 51% at 5.3 years; elation never rose above 1%; anxiety 14% at baseline and 2432% subsequently; disinhibition fluctuated between 2% and 15%; irritability between 17% and 27%; aberrant motor behavior gradually increased from 7% at baseline to 29% at 5.3 years. Point prevalence for any symptom was 56% at baseline and 7687% subsequently. Five-year period prevalence was greatest for depression (77%), apathy (71%), and anxiety (62%); lowest for elation (6%), and disinhibition (31%). Ninety-seven percent experienced at least one symptom. Symptom severity was consistently highest for apathy. Conclusions Participants were most likely to develop depression, apathy, or anxiety, and least likely to develop elation or disinhibition. Give converging evidence that syndromal definitions may more accurately capture neuropsychiatric co-morbidity in dementia, future efforts to validate such syndromes are warranted. PMID:17607801

  2. Ion-Selective Electrodes.

    ERIC Educational Resources Information Center

    Arnold, Mark A.; Meyerhoff, Mark E.

    1984-01-01

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

  3. Fundamental electrode kinetics

    NASA Technical Reports Server (NTRS)

    Elder, J. P.

    1968-01-01

    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

  4. Ion-Selective Electrodes.

    ERIC Educational Resources Information Center

    Arnold, Mark A.; Meyerhoff, Mark E.

    1984-01-01

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

  5. Use of platinum electrodes for the electrochemical detection of bacteria

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.

    1978-01-01

    Platinum electrodes with surface area ratios of four to one were used to detect and enumerate a variety of gram-positive and gram-negative organisms. Linear relationships were established between inoculum size and detection time. End points for platinum electrodes were similar to those obtained with a platinum-reference electrode combination. Shape of the overall response curves and length of detection times for gram-positive organisms were markedly different than those for the majority of gram-negative species. Platinum electrodes are better than the platinum-reference electrode combination because of cost, ease of handling, and clearer definition of the end point.

  6. Interactions between point defects and dislocations in Al: An ab initio study

    NASA Astrophysics Data System (ADS)

    Lu, Gang; Zhang, Qing; Kioussis, Nicholas; Kaxiras, Efthimios

    2001-06-01

    Interactions of point defects (vacancies and interstitials) and dislocations play an important role in materials mechanical properties. In this paper, we employ the semidiscrete variational Peierls-Nabarro model to study the core properties of various dislocations in Al with and without point defects. In specific, the point defects we study in this paper are vacancy and interstitial H. The material parameters, including elastic constants and generalized stacking fault energy surfaces entering the model are calculated from ab initio approaches with large supercells to simulate the low concentration of vacancy and H interstitial (less than 5 at.properties, such as core energy, Peierls stress and core structure are calculated with and without the point defects and the interactions between them are thus revealed. We find although there is a strong binding between H interstitial and dislocation cores, a weak repulsion is observed for vacancy and dislocations. Moreover while the binding energy of H at dislocation cores increases from screw to edge dislocations, the repulsion between vacancy and dislocations remains almost the same for the various dislocations we studied. The critical stress to move a dislocation, Peierls stress, is calculated and we find that both vacancy and H interstitial can reduce the Peierls stress significantly, while the latter has a more dramatic effect (orders of magnitude), strongly supporting the H-enhanced local plasticity theory of H-embrittlement. For the static dislocation core structure, we find vacancy can facilitate dislocations to dissociate into two partials, with distances between them ranging from 5 to 11 depending on the dislocation characters, while H interstitial can only increase the dislocation width but without any dissociation.

  7. Novel electrodes for underwater ECG monitoring.

    PubMed

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

    2014-06-01

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

  8. Photoelectrocatalytic study of water oxidation at n-RuS{sub 2} electrodes

    SciTech Connect

    Salvador, P.; Alonso-Vante, N.; Tributsch, H.

    1998-01-01

    A kinetic study of the photocatalytic oxidation of water at a n-RuS{sub 2} semiconducting single crystal has been undertaken on the basis of photocurrent transients (photocurrent-time behavior as a function of the polarization potential, illumination intensity, and temperature) and electrolyte electroreflectance experiments. The main factor defining the catalytic activity of RuS{sub 2} for water oxidation, both in the dark and under illumination, is a low overpotential ({eta} {approx} 0.3 V), which is comparable to that of the RuO{sub 2} catalyst for oxygen evolution at darkness. Evidence has been given that {eta} is determined by the E{sup o}(Ru{sub s}-OH{sup 0}/Ru{sub s}-H{sub 2}O) redox potential, which strongly depends on the bonding energy of Ru surface species with OH{sup o} radicals generated by direct oxidation of adsorbed water molecules (interfacial Ru-peroxo-type complex formation). This bonding energy increases as the RuS{sub 2} surface becomes oxidized under anodic polarization and reaches its maximum value at the potential of the S{sub 2}RuO{sub 2}/RuS{sub 2} transition (VIII Ru oxidation state). Further oxidation of the Ru-peroxo-type complexes leads to oxygen evolution at a rate which increases with the degree of oxidation of the Ru surface active centers. Although O{sub 2} evolution probably already takes place on Ru(VI) surface sites, high evolution rates (current densities) are only reached under oxidation state VIII. However, in this state (idealized S{sub 2}Ru(VIII)O{sub 2}) Ru-S surface bonds are weakened and occasionally broken, contributing to RuS{sub 2} dissolution with generation of volatile RuO{sub 4} and SO{sub 4}{sup 2{minus}} soluble ions as the main corrosion products. This phenomenon may be attributed to the reaction in acidic medium of H{sub 2}O molecules with Ru(VIII) surface species, giving rise to the formation of unstable intermediate complexes.

  9. Studies of 18650 cylindrical cells made with doped LiNiO 2 positive electrodes for military applications

    NASA Astrophysics Data System (ADS)

    Fan, Jiang

    We studied GP 18650 cylindrical cells made with doped LiNiO 2 positive electrode for military application. The studied cells should deliver about 184 Wh/kg according to the military specification MIL-PRF-320521 while it delivers about 201 Wh/kg according to the general commercial standard. The difference in the cell specific energy is mainly caused by the difference in the charging voltage. It is 4.1 V in the military specification compared to 4.2 V in the general commercial standard. Clearly, to take full advantage of the commercial lithium-ion cell, either the military increases the voltage limit to 4.2 V from 4.1 V or the cell manufacturers redesign their cells according to the 4.1 V charging voltage limit. The studied cell exceeds all major military requirements including high rate discharging, high current pulse discharging, low temperature discharging, cycle life, high temperature storage, and abuse tolerances such as the overcharging, forced discharging, and external short. Specifically, the capacity of the cell exceeds the requirement by 51% at a high discharging rate (3.3 A) and by 39% with a high current (6 A) pulse. The cell can discharge not only 62% of the expected capacity at -30 C but also 47% at -40 C and at 0.67 A, which means that the military can extend their specification to -40 C. The cell still retained 1.97 Ah (or 92%) after 224 cycles, which exceeds the requirement by 9%. The cell retained 1.95 Ah (or 95%) after one-week storage at 50 C and at 4.1 V, which exceeds the requirement by 8%. The abuse tolerance is also very high. The maximum cell temperature ranged only from 62 to 70 C during overcharging, external short, and forced discharging. Directions for the improvement are also discussed.

  10. Understanding Semiotic Technology in University Classrooms: A Social Semiotic Approach to PowerPoint-Assisted Cultural Studies Lectures

    ERIC Educational Resources Information Center

    Zhao, Sumin; van Leeuwen, Theo

    2014-01-01

    In this paper, we propose a social semiotic approach to studying PowerPoint in university classrooms. Our approach is centred on two premises: (1) PowerPoint is a semiotic technology that can be integrated into the pedagogical discourse of classrooms, and (2) PowerPoint technology encompasses three interrelated dimensions of social semiotic…

  11. Understanding Semiotic Technology in University Classrooms: A Social Semiotic Approach to PowerPoint-Assisted Cultural Studies Lectures

    ERIC Educational Resources Information Center

    Zhao, Sumin; van Leeuwen, Theo

    2014-01-01

    In this paper, we propose a social semiotic approach to studying PowerPoint in university classrooms. Our approach is centred on two premises: (1) PowerPoint is a semiotic technology that can be integrated into the pedagogical discourse of classrooms, and (2) PowerPoint technology encompasses three interrelated dimensions of social semiotic

  12. Reading Different Orthographic Structures in the Shallow-Pointed Hebrew Script: A Cross-Grade Study in Elementary School

    ERIC Educational Resources Information Center

    Shany, Michal; Bar-On, Amalia; Katzir, Tami

    2012-01-01

    Hebrew-speaking children learn to read using a transparent, pointed writing system, but by grade three, they gradually begin using the non-pointed version of Hebrew script. The current study examined the development of reading, in the pointed script, of a nationally representative sample of children in grades two, four, and six. Rate and accuracy

  13. Molecular dynamics study of polarizable point dipole models for molten sodium iodide

    NASA Astrophysics Data System (ADS)

    Alcaraz, Olga; Bitrin, Vicente; Trulls, Joaquim

    2007-10-01

    The structure, the ionic transport properties, and the dynamics of long-wavelength charge-density fluctuations, for two polarizable point dipole models of molten NaI, have been studied by molecular dynamics simulations. These models are based on a rigid ion potential to which the induced dipole polarization of the anions is added. The polarization is added in such a way that point dipoles are induced on the anions by both local electric field and short-range damping interactions that oppose the electrically induced dipole moments. The two polarizable ion models differ only in the range of the damping polarization interactions. The influence of the induced anion polarization on the different properties of simulated molten NaI is discussed.

  14. Molecular dynamics study of polarizable point dipole models for molten sodium iodide.

    PubMed

    Alcaraz, Olga; Bitrin, Vicente; Trulls, Joaquim

    2007-10-21

    The structure, the ionic transport properties, and the dynamics of long-wavelength charge-density fluctuations, for two polarizable point dipole models of molten NaI, have been studied by molecular dynamics simulations. These models are based on a rigid ion potential to which the induced dipole polarization of the anions is added. The polarization is added in such a way that point dipoles are induced on the anions by both local electric field and short-range damping interactions that oppose the electrically induced dipole moments. The two polarizable ion models differ only in the range of the damping polarization interactions. The influence of the induced anion polarization on the different properties of simulated molten NaI is discussed. PMID:17949174

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

    PubMed Central

    HITCHCOCK, ELAINE R.; BYUN, TARA McALLISTER

    2014-01-01

    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

  16. First-principles studies of intrinsic point defects in magnesium silicide

    NASA Astrophysics Data System (ADS)

    Kato, Akihiko; Yagi, Takeshi; Fukusako, Naoto

    2009-05-01

    We have studied intrinsic point defects in magnesium silicide, Mg2Si, by density-functional theory. Evaluating the formation energies of point defects, we show that n-type electric conductivity of Mg2Si originates from formations of positively charged Mg ions at interstitial sites, regardless of the chemical composition in crystal growth. Moreover, we have calculated the Born effective charge tensors and the valence charge density distribution. They show Mg2Si is an ionic crystal composed of Mg2+ and Si4- which have very different ionic radii, 0.6 and 2.1 , respectively. We have concluded that the unfavorable antisite defect, MgSi, is due to the dissimilar ionic radii.

  17. HSPES membrane electrode assembly

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  18. Microscopic study on magnetocaloric and electrocaloric effects near the critical point

    NASA Astrophysics Data System (ADS)

    Honmi, Hitoshi; Hashizume, Yoichiro; Nakajima, Takashi; Okamura, Soichiro

    2015-09-01

    Adiabatic temperature changes of magnetocaloric/electrocaloric effects are analytically investigated. The analytical studies are based on the microscopic statistical models such as Husimi-Temperley model and Slater model. As a result, we show the characteristic scales of the adiabatic processes correspond to microscopic parameters, namely exchange couplings and Slater energy. The scaled parameter dependence become stronger near the critical point. Furthermore, using a general Hamiltonian method, we clarify the adiabatic temperature changes depend on the relative ratio of characteristic scales. The present study may propose a useful aspect for applications.

  19. Neural Stimulation via Fractal Electrodes

    NASA Astrophysics Data System (ADS)

    Montgomery, Rick; Watterson, William; Pilgrim, Ian; Fairley, Kurtis; Johnson, Darren; Linke, Heiner; Taylor, Richard

    2013-03-01

    A host of physical phenomena exhibit fractal geometry and benefit from its enhanced properties, which can include large surface area-to-volume ratios and high network connectivity. These properties are exploited in a fractal electrode designed for neural stimulation and recording. Presented are electric field studies of a fractal electrode with an emphasis on applications in retinal implants. Air Force Research Laboratory FA8650-05-1-5041

  20. Satisfaction with the local service point for care: results of an evaluation study

    PubMed Central

    Esslinger, Adelheid Susanne; Macco, Katrin; Schmidt, Katharina

    2009-01-01

    Purpose The market of care increases and is characterized by complexity. Therefore, service points, such as the Zentrale Anlaufstelle Pflege (ZAPf) in Nuremberg, are helpful for clients to get orientation. The purpose of the presentation is to show the results of an evaluation study about the clients' satisfaction with the offers of ZAPf. Study Satisfaction with service may be measured with the SERVQUAL concept introduced by Parasuraman et al. (1988). They found out five dimensions of quality (tangibles, reliability, responsiveness, assurances and empathy). We took these dimensions in our study. The study focuses on the quality of service and the benefits recognized by clients. In spring 2007, we conducted 67 interviews by phone, based on a half standardized questionnaire. Statistical analysis was conducted using SPSS. Results The clients want to get information about care in general, financial and legal aspects, alternative care arrangement (e.g. ambulant, long-term care) and typical age-related diseases. They show a high satisfaction with the service provided. Their benefits are to get information and advice, to strengthen the ability of decision taking, to cope with changing situations in life, and to develop solutions. Conclusions The results show that the quality of service is on a high level. Critical success factors are the interdisciplinary cooperation at the service point, based on a regularly and open exchange of information. Every member focuses on an optimal individual solution for the client. Local professional service points act as networkers and brokers. They serve not only for the clients' needs but also support the effective and efficient provision of optimized care.

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

    PubMed Central

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

    2014-01-01

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

  2. Potential Controls the Interaction of Liposomes with Octadecanol-Modified Au Electrodes: An in Situ AFM Study.

    PubMed

    Musgrove, Amanda; Bizzotto, Dan

    2015-11-24

    The formation of supported lipid bilayers using liposomes requires interaction with the solid surface, rupture of the liposome, and spreading to cover the surface with a lipid bilayer. This can result in a less-than-uniform coating of the solid surface. Presented is a method that uses the electrochemical poration of an adsorbed lipid-like layer on a Au electrode to control the interaction of 100 nm DOPC liposomes. An octadecanol-coated Au-on-mica surface was imaged using tapping-mode AFM during the application of potential in the presence or absence of liposomes. When the substrate potential was made negative enough, defects formed in the adsorbed layer and new taller features were observed. More features were observed and existing features increased in size with time spent at this negative poration potential. The new features were 1.8-2.0 nm higher than the octadecanol-coated gold surface, half the thickness of a DOPC bilayer. These features were not observed in the absence of liposomes when undergoing the same potential perturbation. In the presence of liposomes, the application of a poration potential was needed to initiate the formation of these taller features. Once the applied potential was removed, the features stopped growing and no new regions were observed. The size of these new regions was consistent with the footprint of a flattened 100 nm liposome. It is speculated that the DOPC liposomes were able to interact with the defects and became soluble in the octadecanol, creating a taller region that was limited in size to the liposome that adsorbed and became incorporated. This AFM study confirms previous in situ fluorescence measurements of the same system and illustrates the use of a potential perturbation to control the formation of these regions of increased DOPC content. PMID:26528884

  3. Composite electrode structures for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Ahn, Soonho; Tatarchuk, Bruce J.

    In this study, fibrous carbon-stainless-steel composite electrodes have been fabricated for use as cathodes in alkaline fuel cells. The performances of the composite electrodes were assessed during the oxygen reduction in a KOH half-cell. ac impedance was utilized to obtain the ohmic, kinetic, and mass transport characteristics of the composite electrode at imposed dc potentials. The effects of composition and structure on the performance of the electrode were investigated. Compared to a commercial Teflon-bonded electrode, the composite electrode showed less polarization loss at higher current densities and lower ohmic and mass-transfer resistances. These attributes of the composite electrode, its high electrical conductivity, its mechanical flexibility, and its open accessible structure appear promising for various fuel cell applications.

  4. The secondary alkaline zinc electrode

    NASA Astrophysics Data System (ADS)

    McLarnon, Frank R.; Cairns, Elton J.

    1991-02-01

    The worldwide studies conducted between 1975 and 1990 with the aim of improving cell lifetimes of secondary alkaline zinc electrodes are overviewed. Attention is given the design features and characteristics of various secondary alkaline zinc cells, including four types of zinc/nickel oxide cell designs (vented static-electrolyte, sealed static-electrolyte, vibrating-electrode, and flowing-electrolyte); two types of zinc/air cells (mechanically rechargeable consolidated-electrode and mechanically rechargeable particulate-electrode); zinc/silver oxide battery; zinc/manganese dioxide cell; and zinc/ferric cyanide battery. Particular consideration is given to recent research in the fields of cell thermodynamics, zinc electrodeposition, zinc electrodissolution, zinc corrosion, electrolyte properties, mathematical and phenomenological models, osmotic pumping, nonuniform current distribution, and cell cycle-life perforamnce.

  5. 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)

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

    2015-01-01

    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.

  6. High frequency reference electrode

    DOEpatents

    Kronberg, James W. (Aiken, SC)

    1994-01-01

    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.

  7. Controlled porosity in electrodes

    SciTech Connect

    Chiang, Yet-Ming; Bae, Chang-Jun; Halloran, John William; Fu, Qiang; Tomsia, Antoni P.; Erdonmez, Can K.

    2015-06-23

    Porous electrodes in which the porosity has a low tortuosity are generally provided. In some embodiments, the porous electrodes can be designed to be filled with electrolyte and used in batteries, and can include low tortuosity in the primary direction of ion transport during charge and discharge of the battery. In some embodiments, the electrodes can have a high volume fraction of electrode active material (i.e., low porosity). The attributes outlined above can allow the electrodes to be fabricated with a higher energy density, higher capacity per unit area of electrode (mAh/cm.sup.2), and greater thickness than comparable electrodes while still providing high utilization of the active material in the battery during use. Accordingly, the electrodes can be used to produce batteries with high energy densities, high power, or both compared to batteries using electrodes of conventional design with relatively highly tortuous pores.

  8. Flexible retinal electrode array

    DOEpatents

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

    2006-10-24

    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.

  9. Micromachined electrode array

    DOEpatents

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

    2007-12-11

    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.

  10. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    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.

  11. Cohort protocol paper: The Pain and Opioids In Treatment (POINT) study

    PubMed Central

    2014-01-01

    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 12weeks). 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 (Australias 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

  12. Point Contact Spectroscopy Study of the New Superconductor Nb2 PdxSe5

    NASA Astrophysics Data System (ADS)

    Jiang, Yeping; Zhang, Xiaohang; Takeuchi, Ichiro; Greene, Richard; Khim, Seunghyun; Lee, Bumsung; Kim, Kee-Hoon

    2014-03-01

    We have systematically investigated the temperature dependence of the energy gap structure for the new quasi-one-dimensional superconductor Nb2PdxSe5 by point contact spectroscopy (PCS). Our studies were performed on highly transparent Andreev reflection junctions evidenced by sharp and dramatic conductance enhancements at low temperatures. By applying the BTK model, we find that the energy gap scales with the transition temperature (Tc =5.5 K) in a BCS-like manner. Details of this and a few anomalous features of the PCS will be presented. Supported by NSF DMR-1104256 and AFOSR-MURI FA9550-09-1-0603.

  13. First-principles study of point defects at a semicoherent interface

    PubMed Central

    Metsanurk, E.; Tamm, A.; Caro, A.; Aabloo, A.; Klintenberg, M.

    2014-01-01

    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

  14. Structural transformations from point to extended defects in silicon: A molecular dynamics study

    SciTech Connect

    Marques, Luis A.; Pelaz, Lourdes; Santos, Ivan; Lopez, Pedro; Aboy, Maria

    2008-11-15

    We use classical molecular dynamics simulation techniques to study how point defects aggregate to form extended defects in silicon. We have found that <110> chains of alternating interstitials and bond defects, a generalization of the Si di-interstitial structure, are metastable at room temperature but spontaneously transform into (311) defects when annealed at higher temperatures. Obtained atomic configurations and energetics are in good agreement with experiments and previous theoretical calculations. We have found a (311) structural unit which consists of two interstitial chains along <110> but arranged differently with respect to the known (311) units.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  16. Understanding the Global Epidemiology of Pediatric Critical Illness: The Power, Pitfalls, and Practicalities of Point Prevalence Studies

    PubMed Central

    Faustino, Edward Vincent; Festa, Marino S.; Fink, Ericka L.; Jouvet, Philippe; Bush, Jenny L.; Kissoon, Niranjan; Marshall, John; Nadkarni, Vinay M.; Thomas, Neal J.

    2014-01-01

    Objective The point prevalence methodology is a valuable epidemiological study design that can optimize patient enrollment, prospectively gather individual-level data, and measure practice variability across a large number of geographic regions and health care settings. The objective of this manuscript is to review the design, implementation, and analysis of recent point prevalence studies investigating the global epidemiology of pediatric critical illness. Data Sources Literature review and primary datasets. Study Selection Multicenter, international point prevalence studies performed in pediatric intensive care units since 2007. Data Extraction Study topic, number of sites, number of study days, patients screened, prevalence of disease, use of specified therapies, and outcomes. Data Synthesis Since 2007, five point prevalence studies have been performed on acute lung injury, neurological disease, thromboprophylaxis, fluid resuscitation, and sepsis in pediatric intensive care units. These studies were performed in 59 to 120 sites in seven to 28 countries. All studies accounted for seasonal variation in pediatric disease by collecting data over multiple study days. Studies screened up to 6,317 patients and reported data on prevalence and therapeutic variability. Three studies also reported short-term outcomes, a valuable but atypical data element in point prevalence studies. Using these five studies as examples, the advantages and disadvantages and approach to designing, implementing, and analyzing point prevalence studies are reviewed. Conclusions Point prevalence studies in pediatric critical care can efficiently provide valuable insight on the global epidemiology of disease and practice patterns for critically ill children. PMID:24751790

  17. Cloud point, fluorimetric and 1H NMR studies of ibuprofen-polymer systems

    NASA Astrophysics Data System (ADS)

    Khan, Iqrar Ahmad; Anjum, Kahkashan; Koya, P. Ajmal; Qadeer, Atiytul; Kabir-ud-Din

    2014-01-01

    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 (δ) varies with the nature of the polymer.

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

    PubMed

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

    2014-05-01

    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

  19. Structure and energy of point defects in TiC: An ab initio study

    NASA Astrophysics Data System (ADS)

    Sun, Weiwei; Ehteshami, Hossein; Korzhavyi, Pavel A.

    2015-04-01

    We employ first-principles calculations to study the atomic and electronic structure of various point defects such as vacancies, interstitials, and antisites in the stoichiometric as well as slightly off-stoichiometric Ti1 -cCc (including both C-poor and C-rich compositions, 0.49 ≤c ≤0.51 ). The atomic structure analysis has revealed that both interstitial and antisite defects can exist in split conformations involving dumbbells. To characterize the electronic structure changes caused by a defect, we introduce differential density of states (dDOS) defined as a local perturbation of the density of states (DOS) on the defect site and its surrounding relative to the perfect TiC. This definition allows us to identify the DOS peaks characteristic of the studied defects in several conformations. So far, characteristic defect states have been discussed only in connection with carbon vacancies. Here, in particular, we have identified dDOS peaks of carbon interstitials and dumbbells, which can be used for experimental detection of such defects in TiC. The formation energies of point defects in TiC are derived in the framework of a grand-canonical formalism. Among the considered defects, carbon vacancies and interstitials are shown to have, respectively, the lowest and the second-lowest formation energies. Their formation energetics are consistent with the thermodynamic data on the phase stability of nonstoichiometric TiC. A cluster type of point defect is found to be next in energy, a titanium [100] dumbbell terminated by two carbon vacancies.

  20. High performance cermet electrodes

    DOEpatents

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

    1986-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The formation of resistance-free or Ohmic contacts at metal/organic interfaces remains a significant challenge for achieving high-performance organic electronic devices such as organic light-emitting diodes. Several oxides have recently been reported to yield extremely low-voltage devices and thus have excited a renewed interest in developing the next generation of contacting electrodes. In this paper, major metal oxides, CuO, Cu2O , Ni2O3 , Co3O4 , WO3 , MoO3 , V2O5 , and indium tin oxide, have been systematically studied to compare their relative performance as hole injection anodes, as well as to provide an experimental database for theoretical analysis of current-voltage (IV) characteristics with a diverse range of injection barrier heights. Contrary to previous reports in the literature, none of the oxides studied in this work were found to form a true Ohmic contact with commonly used hole transport layers, such as N,N-diphenyl-N, N-bis-1-naphthyl-1-1-biphenyl-4,4-diamine ( ? -NPD). This discrepancy is attributed to incorrect IV data analysis of the quasi-Ohmic injection regimethe region in between space-charge limited current (SCLC) and injection limited current (ILC)in previous studies. It is found that the quasi-Ohmic regime is much larger (i.e., covers a greater range of injection barrier height) than has previously been expected. A criterion that defines Ohmic, quasi-Ohmic, and injection limited contacts has been quantified based on a time-domain simulation of charge transport across ? -NPD single-carrier devices. This criterion includes the effects of the electric field dependent mobility, organic layer thickness, and charge-injection barrier height. The effects of the built-in potential on the IV characteristics are also evaluated. A barrier-thickness-voltage phase diagram that defines the regions of SCLC, quasi-Ohmic, and ILC for ? -NPD is presented.

  2. Auricular point acupressure as an adjunct analgesic treatment for cancer patients: a feasibility study.

    PubMed

    Yeh, Chao Hsing; Chien, Lung-Chang; Chiang, Yi Chien; Ren, Dianxu; Suen, Lorna Kwai-Ping

    2015-06-01

    This study aimed (1) to examine the feasibility of an auricular point acupressure (APA) research protocol in terms of recruitment and for the assessment and management of pain and (2) to examine the potential APA analgesic effects for cancer patients. This study was a repeated-measures one-group design. Participants were recruited from the cancer center follow-up clinic affiliated with a large university hospital in the northeastern United States. Participants included 50 patients aged 55-87 years with a diagnosis of cancer. Participants received 7 days of APA treatment for their pain. After appropriate acupoints were identified, vaccaria seeds were carefully taped onto each selected auricular point on each ear. The study recruitment and retention rates were 92% and 91%, respectively. Importantly, the study found preliminary evidence for the analgesic effects of APA for cancer pain management. For example, by the end of the 7-day study, APA reduced pain intensity more than 55% for "worst pain" and about 57% for "average pain" and "pain intensity." Moreover, the use of pain medication was reduced during the APA treatment (e.g., 78% of patients [n = 39] took less pain medication than before the treatment). APA appears to be highly acceptable to patients with cancer-related pain. However, without a placebo control, we cannot draw conclusive evidence for the analgesic effect of APA for cancer patients. A sham group must be added to future studies to differentiate the true effects of APA from the possible psychological effects of the APA treatment. PMID:25439120

  3. A study of the turning points of a nems shuttle using td-scc-dftb

    SciTech Connect

    Huldt, C.; Kinaret, J.; Koskinen, P.

    2009-01-21

    Nanoelectromechanical systems, of which the shuttle is one of the most fundamental, have theoretically been described mainly with phenomenological models with simplified interactions between the mobile part and the electrodes. Many microscopic methods, which in principle can give a more realistic picture of the shuttling process, are poorly suited for the dynamic non-equilibrium problem at hand. This is primarily due to the presence of several timescales associated with the mechanical motion, electronic relaxation within subsystems, and charge transfer between the mobile shuttle and the electrodes. The last timescale varies by many orders of magnitude during a shuttling cycle, which complicates many of the standard approaches. To overcome these difficulties, we use a TD-SCC-DFTB code developed in the Fraunhofer Institute for Mechanics of Materials (IWM) in Freiburg. The method, which is a well-tested approximation to TDDFT, couples the reliability of DFT with the efficiency of the TB approach.

  4. A compiled BASIC program for analysis of spatial point patterns: application to retinal studies.

    PubMed

    Fernández, E; Cuenca, N; De Juan, J

    1993-10-01

    The pattern of distribution of a population of cells is of considerable interest to biologists and neurobiologists. However, the labor involved in collecting and analyzing the data often requires a significant amount of time. This paper presents a compiled BASIC program written using the Microsoft QuickBasic compiler for Apple Macintosh to facilitate such studies. The program allows collection and analysis of data that can be introduced either with the aid of a digitizing tablet of directly imported as x,y coordinates from different sources as, for example, word processors or image analysis software. Subsequently the program provides a quick, easy and interactive way of access to statistical, mathematical and graphical techniques used in the analysis of spatial point patterns. These techniques include several measures of dispersion (quadrat count, nearest neighbor and a 2-dimensional point autocorrelogram analysis) and arrangement. Although the program has been tested on spatial organization of retinal cells, it can be used to study the distribution of other cells in the nervous system and for different projects, as for example the distribution of microtubules and neurofilaments inside the axons. This software is available from the authors. PMID:8277777

  5. Study of the diffusion of points defects in crystalline silicon using the kinetic ART method

    NASA Astrophysics Data System (ADS)

    Trochet, Mickael; Brommer, Peter; Beland, Laurent-Karim; Joly, Jean-Francois; Mousseau, Normand

    2013-03-01

    Because of the long-time scale involved, the activated diffusion of point defects is often studied in standard molecular dynamics at high temperatures only, making it more difficult to characterize complex diffusion mechanisms. Here, we turn to the study of point defect diffusion in crystalline silicon using kinetic ART (kART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building based on the activation-relaxation technique (ART nouveau). By generating catalogs of diffusion mechanisms and fully incorporating elastic and off-lattice effects, kART is a unique tool for characterizing this problem. More precisely, using kART with the standard Stillinger-Weber potential we consider the evolution of crystalline cells with 1 to 4 vacancies and 1 to 4 interstitials at various temperatures and to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics in addition to identifying special configurations such as a 2-interstitial super-diffuser.

  6. Ab initio study of radiation effects on the Li4Ti5O12 electrode used in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Samin, Adib; Kurth, Michael; Cao, Lei

    2015-04-01

    Lithium-ion batteries are currently in wide use owing to their high energy density and enhanced capabilities. Li4Ti5O12 is a promising anode material for lithium-ion batteries because of its advantageous properties. Lithium-ion batteries could be exposed to radiation occurring in various conditions such as during outer space exploration and nuclear accidents. In this study, we apply density functional theory to explore the effect of radiation damage on this electrode and, ultimately, on the performance of the battery. It was found that radiation could affect the structural stability of the material. Furthermore, the electrode was shown to undergo a transition from insulator to metal, following the defects due to radiation. In addition, the effect of radiation on the intercalation potential was found to be highly dependent on the nature of the defect induced.

  7. Viewing another person's body as a target object: a behavioural and PET study of pointing.

    PubMed

    Cleret de Langavant, Laurent; Trinkler, Iris; Remy, Philippe; Thirioux, Brangre; McIntyre, Joseph; Berthoz, Alain; Dupoux, Emmanuel; Bachoud-Lvi, Anne-Catherine

    2012-07-01

    Humans usually point at objects to communicate with other persons, although they generally avoid pointing at the other's body. Moreover, patients with heterotopagnosia after left parietal damage cannot point at another person's body parts, although they can point at objects and at their own body parts and although they can grasp the others' body parts. Strikingly, their performance gradually improves for figurative human body targets. Altogether, this suggests that the body of another real person holds a specific status in communicative pointing. Here, we test in healthy individuals whether performance for communicative pointing is influenced by the communicative capacity of the target. In Experiment 1, pointing at another real person's body parts was compared to pointing at objects, and in Experiment 2, the person was replaced by a manikin. While reaction times for pointing at objects were shorter compared to pointing at other person's body parts, they were similar for objects and manikin body parts. By adapting Experiment 1 to PET-scan imaging (Experiment 3), we showed that, compared to pointing at objects, the brain network for pointing at other person's body parts involves the left posterior intraparietal sulcus, lesion of which could cause heterotopagnosia. Taken together, our results indicate that the specificity of pointing at another person's body goes beyond the visuo-spatial features of the human body and might rather rely on its communicative capacity. PMID:22579967

  8. A disposable paper-based electrochemical sensor with an addressable electrode array for cancer screening.

    PubMed

    Ge, Shenguang; Ge, Lei; Yan, Mei; Song, Xianrang; Yu, Jinghua; Huang, Jiadong

    2012-09-28

    A novel addressable electrode array based on paper was assembled on the crossing points of the row/column electrodes to form a 4 6 sensor array by a facile home-made device-holder, one paper layer contained the sensing sites, the other paper layer the printed counter electrode and reference electrode. PMID:22889917

  9. Nonlinear Seismic Analysis of Morrow Point Dam: A Study for the United States Bureau of Reclamation

    SciTech Connect

    Noble, C R; Solberg, J

    2004-02-20

    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.

  10. Carbon paste electrodes modified with biosolids, soils and biocomposites utilized to study the interaction between organic matter and copper.

    PubMed

    Flores-lvarez, J M; Gonzlez, I; Garca-de la Rosa, L A; Mancilla-Pea, F; Reyes-Gmez, J

    2011-03-01

    Carbon paste electrodes (CPEs) modified with a biosolid, two types of soils with different amounts of organic matter (OM), and two biocomposites (soils mixed with a biosolid) were used to assess and compare the Cu(II) ion retention properties of the organic matter contained in the samples. The accumulation of Cu(II) on the surface of the modified carbon paste electrodes (MCPEs) was performed under open-circuit conditions. When comparing the response of the MCPEs while assessing parameters such as pH, preconcentration time, and adsorption/desorption capacity, it was found that the reaction mechanism of the two soils is different between the soils and dissimilar from the biosolid; while the biocomposites show reaction mechanisms that are intermediate between those of the soils and the biosolid. This was proven with the use of infrared spectroscopy, since the FTIR spectra show similarities between the two soils and significant differences between the soils and the biosolid. PMID:21044813

  11. Evolution of the negative electrode (tin/silicate) for Li-ion batteries studied by 119 Sn Mssbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Mouyane, M.; Lippens, P.-E.; Womes, M.; Ducourant, B.; Olivier-Fourcade, J.; Jumas, J.-C.

    2008-11-01

    A novel tin composite Sn/CaSiO3 for the anode of Li-ion batteries was prepared by solid-state reaction. The CaSiO3 matrix was synthesized by a sol-gel route. The crystalline structures and morphology were determined by X-ray diffraction (XRD) and 119Sn Mssbauer spectroscopy; the electrochemical properties were evaluated by galvanostatic charge and discharge. The results obtained show that the Sn/CaSiO3 composite presents very interesting electrochemical performances in terms of specific capacity in the first discharge (591 mAh/g) and a good reversibility due to both the formation of an interface between active and inactive materials and the reversible formation of Li x Sn alloys. We have also highlighted, by 119Sn Mssbauer spectroscopy, the various tin species constituting the material of the starting electrode, as well as the chemical evolutions occurring during the discharge and the charge of the electrode.

  12. Space science/space station attached payload pointing accommodation study: Technology assessment white paper

    NASA Technical Reports Server (NTRS)

    Lin, Richard Y.; Mann, Kenneth E.; Laskin, Robert A.; Sirlin, Samuel W.

    1987-01-01

    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.

  13. Experimental study on magnetically insulated transmission line electrode surface evolution process under MA/cm current density

    NASA Astrophysics Data System (ADS)

    Zhang, PengFei; Hu, Yang; Yang, HaiLiang; Sun, Jiang; Wang, Liangping; Cong, Peitian; Qiu, Aici

    2016-03-01

    The design of high-current density magnetically insulated transmission line (MITL) is a difficult problem of current large-scale Z-pinch device. In particular, a thorough understanding of the MITL electrode surface evolution process under high current density is lacking. On the "QiangGuang-I" accelerator, the load area possesses a low inductance short-circuit structure with a diameter of 2.85 mm at the cathode, and three reflux columns with a diameter of 3 mm and uniformly distributed circumference at the anode. The length of the high density MITL area is 20 mm. A laser interferometer is used to assess and analyze the state of the MITL cathode and anode gap, and their evolution process under high current density. Experimental results indicate that evident current loss is not observed in the current density area at pulse leading edge, and peak when the surface current density reaches MA/cm. Analysis on electrode surface working conditions indicates that when the current leading edge is at 71.5% of the peak, the total evaporation of MITL cathode structure can be realized by energy deposition caused by ohmic heating. The electrode state changes, and diffusion conditions are reflected in the laser interferometer image. The MITL cathode area mainly exists in metal vapor form. The metal vapor density in the cathode central region is higher than the upper limit of laser penetration density (˜4 × 1021/cm3), with an expansion velocity of ˜0.96 km/s. The metal vapor density in the electrode outer area may lead to evident distortion of fringes, and its expansion velocity is faster than that in the center area (1.53 km/s).

  14. Corneal-shaping electrode

    DOEpatents

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

    1982-01-01

    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.

  15. Improved biomedical electrode

    NASA Technical Reports Server (NTRS)

    Frost, J. D., Jr.

    1972-01-01

    Newly designed electrode is prefilled, disposable, electrolyte-saturated spong. New design permits longe periods of storage without deterioration, and readiness in matter of seconds. Electrodes supply signals for electroencephalogram, electro-oculogram, and electrocardiogram.

  16. Corneal-shaping electrode

    SciTech Connect

    Doss, J.D.; Hutson, R.L.

    1982-04-27

    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.

  17. Acupuncture point injection treatment of primary dysmenorrhoea: a randomised, double blind, controlled study

    PubMed Central

    Wade, C; Wang, L; Zhao, W J; Cardini, F; Kronenberg, F; Gui, S Q; Ying, Z; Zhao, N Q; Chao, M T; Yu, J

    2016-01-01

    Objective To determine if injection of vitamin K3 in an acupuncture point is optimal for the treatment of primary dysmenorrhoea, when compared with 2 other injection treatments. Setting A Menstrual Disorder Centre at a public hospital in Shanghai, China. Participants Chinese women aged 14–25 years with severe primary dysmenorrhoea for at least 6 months not relieved by any other treatment were recruited. Exclusion criteria were the use of oral contraceptives, intrauterine devices or anticoagulant drugs, pregnancy, history of abdominal surgery, participation in other therapies for pain and diagnosis of secondary dysmenorrhoea. Eighty patients with primary dysmenorrhoea, as defined on a 4-grade scale, completed the study. Two patients withdrew after randomisation. Interventions A double-blind, double-dummy, randomised controlled trial compared vitamin K3 acupuncture point injection to saline acupuncture point injection and vitamin K3 deep muscle injection. Patients in each group received 3 injections at a single treatment visit. Primary and secondary outcome measures The primary outcome was the difference in subjective perception of pain as measured by an 11 unit Numeric Rating Scale (NRS). Secondary measurements were Cox Pain Intensity and Duration scales and the consumption of analgesic tablets before and after treatment and during 6 following cycles. Results Patients in all 3 groups experienced pain relief from the injection treatments. Differences in NRS measured mean pain scores between the 2 active control groups were less than 1 unit (−0.71, CI −1.37 to −0.05) and not significant, but the differences in average scores between the treatment hypothesised to be optimal and both active control groups (1.11, CI 0.45 to 1.78) and (1.82, CI 1.45 to 2.49) were statistically significant in adjusted mixed-effects models. Menstrual distress and use of analgesics were diminished for 6 months post-treatment. Conclusions Acupuncture point injection of vitamin K3 relieves menstrual pain rapidly and is a useful treatment in an urban outpatient clinic. Trial registration number NCT00104546; Results. PMID:26733563

  18. A Randomized Clinical Trial of Auricular Point Acupressure for Chronic Low Back Pain: A Feasibility Study

    PubMed Central

    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

    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

  19. Forced Magnetic Reconnection at an X-point: A Fully Kinetic Study

    NASA Astrophysics Data System (ADS)

    Wang, L.; Bhattacharjee, A.; Bessho, N.; Germaschewski, K.

    2012-12-01

    We will present electromagnetic Particle-In-Cell (PIC) simulation of the current sheet formation and resulting magnetic reconnection at an X-point of an initially potential field closed by conducting wall boundaries. The reconnection we study is driven by forcing that is far from the initial separatrices and is slow compared to a characteristic Alfvn speed. The effects of two types of forcing will be investigated separately: (i) convergent flows at two opposite boundaries, and (ii) enhanced pressure gradient in two spatial domains on opposite sides of the initial separatrix. For both cases, we will present the time dependence of the reconnecting electric field (suitably normalized), energy partitioning, and dependence on system size. Our results will be compared with fluid simulations of the same setup to seek suitable closure relation with necessary kinetic effects in the fluid models. This challenge problem is carried out under the auspices of a Focus Team in the NASA Living With a Star Targeted Research and Technology Program.; Reconnecting electric field Ey in the case of forcing by boundary convergent flows. Change of sign of Ey is observed. Note that the value shown is unnormalized and that if normalized by upstream B and outflow velocity, the value can be of order 0.1. ; The out-of-plane current along two axes passing the X-point at two times. The signs are opposite for the two times. The length of the current sheet is in tens of di while the width is about 1di.

  20. An experimental-theoretical study of free vibrations of plates on elastic point supports

    NASA Technical Reports Server (NTRS)

    Leuner, T. R.

    1972-01-01

    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.

  1. Low resistance fuel electrodes

    DOEpatents

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

    1989-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  3. In situ SERS and X-ray photoelectron spectroscopy studies on the pH-dependant adsorption of anthraquinone-2-carboxylic acid on silver electrode

    NASA Astrophysics Data System (ADS)

    Li, Dan; Jia, Shaojie; Fodjo, Essy Kouadio; Xu, Hu; Wang, Yuhong; Deng, Wei

    2016-03-01

    In this study, in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) are used to investigate the redox reaction and adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on an Ag electrode at different pH values. The obtained results indicate that AQ-2-COOH is adsorbed tilted on the Ag electrode through O-atom of ring carbonyl in a potential range from -0.3 to -0.5 V vs. SCE, but the orientation turns to more tilted orientation with both O-atom of the ring carbonyl and carboxylate group in positive potential region for pH 6.0 and 7.4. However, at pH 10.0, the orientation adopts tilted conformation constantly on the Ag electrode with both O-atom of the anthraquinone ring and carboxylate group in the potential range from -0.3 to -0.5 V vs. SCE or at positive potentials. Moreover, the adsorption behavior of AQ-2-COOH has been further confirmed by AR-XPS on the Ag surface. Proposed reasons for the observed changes in orientation are presented.

  4. A Simple Hydrogen Electrode

    ERIC Educational Resources Information Center

    Eggen, Per-Odd

    2009-01-01

    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

  5. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg (East Lansing, MI); Fischer, Anne (Arlington, VA),; Bennett, Jason (Lansing, MI); Lowe, Michael (Holt, MI)

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  6. A Simple Hydrogen Electrode

    ERIC Educational Resources Information Center

    Eggen, Per-Odd

    2009-01-01

    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…

  7. Lightweight composite cadmium electrodes

    NASA Technical Reports Server (NTRS)

    Sutula, R. A.; Ferrando, W.

    1981-01-01

    The design and fabrication of the electrodes are discussed. The electrode efficiency of different impregnations of plaques is reported. The chemical impregnation for commercial use has the lowest efficiency, and for aerospace application it has higher efficiency. The electrochemically impregnated electrode is the most efficient.

  8. Insulated ECG electrodes

    NASA Technical Reports Server (NTRS)

    Portnoy, W. M.; David, R. M.

    1973-01-01

    Insulated, capacitively coupled electrode does not require electrolyte paste for attachment. Other features of electrode include wide range of nontoxic material that may be employed for dielectric because of sputtering technique used. Also, electrode size is reduced because there is no need for external compensating networks with FET operational amplifier.

  9. Near-electrode imager

    DOEpatents

    Rathke, Jerome W.; Klingler, Robert J.; Woelk, Klaus; Gerald, II, Rex E.

    2000-01-01

    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.

  10. Fuel cell electrodes

    DOEpatents

    Strmcnik, Dusan; Cuesta, Angel; Stamenkovic, Vojislav; Markovic, Nenad

    2015-06-23

    A process includes patterning a surface of a platinum group metal-based electrode by contacting the electrode with an adsorbate to form a patterned platinum group metal-based electrode including platinum group metal sites blocked with adsorbate molecules and platinum group metal sites which are not blocked.

  11. Longitudinal discharge laser electrodes

    DOEpatents

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

    1994-01-01

    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.

  12. Longitudinal discharge laser electrodes

    DOEpatents

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

    1994-08-23

    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.

  13. Multiscale porous fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Wen, Hao

    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.

  14. First-principles study of point defects in solar cell semiconductor CuInS2

    NASA Astrophysics Data System (ADS)

    Chen, Hui; Wang, Chong-Yu; Wang, Jian-Tao; Hu, Xiao-Ping; Zhou, Shao-Xiong

    2012-10-01

    The formation energies and transition levels of point defects VCu, VIn, VS, InCu, CuIn, and OS in CuInS2 are studied using the hybrid density functional theory. It is found that the Heyd-Scuseria-Ernzerhof method can accurately describe the electronic structure and gives a band gap of 1.40 eV, in good agreement with the experimental value. On the other hand, we conclude that p-type semiconductor CuInS2 can be obtained under sulfur-rich condition with a certain copper and indium content, while n-type semiconductor CuInS2 can be easily obtained under the copper-rich, indium-rich, sulfur-poor, and non-oxygen conditions. These results provide an excellent account for the modification of the structural and electronic properties of CuInS2.

  15. Study to define points of entry for potential contaminants in limestone aquifers. [in Alabama

    NASA Technical Reports Server (NTRS)

    Doyle, F. L.

    1973-01-01

    Visual examinations of both prints and transparencies from ERTS 1 and U-2 aircraft imagery provided a method for discovering possible points of entry of potential contaminants into the limestone aquifer in Madison County, Alabama. Knowledge of the locations at which contaminants could enter the aquifer is an important consideration in water quality management, particularly for regions that depend, at least partially, on ground water for their water supply. ERTS 1 imagery recorded on December 28, 1972 in the Multispectral Scanner-5 (MSS-5) and MSS-7 bands, and a false-color composite of the MSS-4 (green), MSS-5 (red), and MSS-7 (near infrared) bands were the principal materials used, along with thermography recorded by an RS-7 infrared scanner onboard a U-2 aircraft. The results of the study are discussed in detail, providing information on prominent lineations and major fracture trends which are related to aquifer contamination. Maps depicting the observations are also presented.

  16. A pilot reactor study on the effect of the naphtha boiling point properties in catalytic reforming

    SciTech Connect

    Moliord, K.; Tanem, I.; Grande, K.

    1995-12-31

    Three naphthas with different initial and three naphthas with different final boiling points were compared by testing in a pilot reactor. The pilot reactor unit consisted of isothermal, once-through 200 cm{sup 2} reactors with on-line GCs for full product analysis and octane number determination. Octane numbers, reformate yields and composition, gas and hydrogen yields were measured as function of reaction temperature at 16 bar reaction pressure and a molar H{sub 2}/HC ratio of 4.23. Catalyst deactivation was studied over 2 weeks periods at high seventy conditions, i.e. 102.4 RON and a H{sub 2}/HC ratio of 2.2. Test results, with emphasis on the yields of benzene and other aromatics, hydrogen yields as well as catalyst deactivation, are presented.

  17. Probabilistic Safety Study Applications Program for inspection of the Indian Point Unit 3 Nuclear Power Plant

    SciTech Connect

    Taylor, J.H.; Fullwood, R.; Fresco, A.

    1986-03-01

    By prioritizing the various areas of interest for inspection and by better defining inspection needs, the NRC expects to make more effective use of finite inspection resources by concentrating on those potential areas most significant to safety. Through review and application of the Indian Point Unit 3 Probabilistic Safety Study's numerical data and event tree modeling, and by utilizing related documents, a technical basis for prioritizing areas for NRC inspection has been developed. This was then tested at the plant site for the NRC Operating Reactor Inspection Program, I and E Manual Chapter 2515. Inspection activities addressed include normal operations, system and component testing, maintenance and surveillance. A computer program entitled NSPKTR, which was developed specifically for this program, modeled the internal plant states to the system level and performed the risk and importance calculations. 17 refs., 21 tabs.

  18. Fault tree application to the study of systems interactions at Indian Point 3

    SciTech Connect

    Youngblood, R.; Hanan, N.; Fitzpatrick, R.; Xue, D.; Bozoki, G.; Fresco, A.; Papazoglou, I.; Mitra, S.; MacDonald, G.; Mazour, T.

    1986-01-01

    This report describes an application of fault tree methods to search for systems interactions at Indian Point 3. This project was carried out in support of the resolution of Unresolved Safety Issue A-17 on Systems Interaction. Here, the methods are introduced, the findings are presented, and comments on the methods are offered. Findings are presented in the following manner. Systems interactions which may qualitatively violate regulatory requirements (regardless of their probability) are discussed; additionally, a probabilistically ranked list of system interactions is provided. This study resulted in the discovery of a previously undetected active single failure causing loss of low pressure injection. After verifying this finding, the licensee took immediate corrective actions, including a design modification to the switching logic for one of the safety buses, as well as procedural changes.

  19. Study on the tie point selection for DEM extraction from stereo PRISM images

    NASA Astrophysics Data System (ADS)

    Kawata, Yoshiyuki; Funatsu, Yukihiro; Yoshii, Satoshi; Takemata, Kazuya

    2012-10-01

    The accuracy of DEM extraction was analyzed from the view of tie point selection in the stereo ALOS/PRISM images, using PCI Geomatica software. In the analysis we considered three different parameters in the automatic tie point selection, namely, 1) the number of tie points, 2) the image correlation coefficient of tie points, and 3) the spatial resolution of DEM extraction. We found that a better DEM extraction accuracy was possible when we adopted a single tie point with large image correlation coefficient (around 0.8) and the spatial resolution of 2.5 (m) in the automatic tie point selection from the stereo PRISM images. In addition, we examined the dependence of the DEM extraction accuracy on the tie point's elevation in the manual tie point selection. However, no clear dependence on the tie point's elevation was found because of large DEM noises at tie points in the mountain area. Finally, some preliminary analysis results of DEM extraction accuracy were presented from the stereo QuickBird images.

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

    PubMed Central

    Reiss, David

    2014-01-01

    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

  1. Electrode potential studies of liquid-solid equilibrium in Na{sub 3}Bi-saturated Na-Bi melts

    SciTech Connect

    Yan, X.Y.; Langberg, D.E.; Rankin, W.J.

    2000-04-01

    Liquid binary Na-Bi alloys have been studied extensively because of the interest in possible uses as electrochemically active couples in regenerative electrochemical cells, in high-energy batteries, and as potential heat-transfer media in nuclear reaction processes. Techniques used previously for thermodynamic measurements on the system have included the transpiration method, quasi-static and boiling point methods, the electromotive force (emf) method using molten salt mixtures and various solid electrolytes, and thermal analysis. Most of the thermodynamic data on Bi-Na alloys were recently assessed by Sangster and Pelton. However, no experimental thermodynamic data for liquid-solid equilibrium in liquid Na-Bi alloys saturated with solid Na{sub 3}Bi have been reported in the literature. The aim of the present work was to investigate experimentally the equilibrium between Na-Bi melts and solid Na{sub 3}Bi by the emf method in the range 638 to 973 K.

  2. Silver nanowires embedded gel electrodes

    NASA Astrophysics Data System (ADS)

    Abe, Yuta; Gong, Jin; Furukawa, Hidemitsu

    2013-04-01

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

  3. Design of a Wireless EEG System for Point-of-Care Applications

    PubMed Central

    Jia, Wenyan; Bai, Yicheng; Sun, Mingui; Sclabassi, Robert J.

    2014-01-01

    This study aims to develop a wireless EEG system to provide critical point-of-care information about brain electrical activity. A novel dry electrode, which can be installed rapidly, is used to acquire EEG from the scalp. A wireless data link between the electrode and a data port (i.e., a smartphone) is established based on the Bluetooth technology. A prototype of this system has been implemented and its performance in acquiring EEG has been evaluated. PMID:25419099

  4. A Study of Point of View and Character in Preparation for Oral Performance of Cuttings from "The Optimist's Daughter."

    ERIC Educational Resources Information Center

    Snow, Nancy Hill

    In the process of perfecting oral performances of selected scenes from Eudora Welty's "The Optimist's Daughter," it is important to study point of view and character as they pertain to the play. Four aspects should be considered to understand the point of view: (1) the character's story, (2) the position from which the narrator speaks, (3) the…

  5. Experimental and Analytical Studies of Shielding Concepts for Point Sources and Jet Noises.

    NASA Astrophysics Data System (ADS)

    Wong, Raymond Lee Man

    This analytical and experimental study explores concepts for jet noise shielding. Model experiments centre on solid planar shields, simulating engine-over-wing installations, and 'sugar scoop' shields. Tradeoff on effective shielding length is set by interference 'edge noise' as the shield trailing edge approaches the spreading jet. Edge noise is minimized by (i) hyperbolic cutouts which trim off the portions of most intense interference between the jet flow and the barrier and (ii) hybrid shields--a thermal refractive extension (a flame); for (ii) the tradeoff is combustion noise. In general, shielding attenuation increases steadily with frequency, following low frequency enhancement by edge noise. Although broadband attenuation is typically only several dB, the reduction of the subjectively weighted perceived noise levels is higher. In addition, calculated ground contours of peak PN dB show a substantial contraction due to shielding: this reaches 66% for one of the 'sugar scoop' shields for the 90 PN dB contour. The experiments are complemented by analytical predictions. They are divided into an engineering scheme for jet noise shielding and more rigorous analysis for point source shielding. The former approach combines point source shielding with a suitable jet source distribution. The results are synthesized into a predictive algorithm for jet noise shielding: the jet is modelled as a line distribution of incoherent sources with narrow band frequency (TURN)(axial distance)('-1). The predictive version agrees well with experiment (1 to 1.5 dB) up to moderate frequencies. The insertion loss deduced from the point source measurements for semi-infinite as well as finite rectangular shields agrees rather well with theoretical calculation based on the exact half plane solution and the superposition of asymptotic closed-form solutions. An approximate theory, the Maggi-Rubinowicz line integral, is found to yield reasonable predictions for thin barriers including cutouts if a certain correction is applied. The more exact integral equation approach (solved numerically) is applied to a more demanding geometry: a half round sugar scoop shield. It is found that the solutions of integral equation derived from Helmholtz formula in normal derivative form show satisfactory agreement with measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    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.

  7. a Comparative Study Between Pair-Point Clique and Multi-Point Clique Markov Random Field Models for Land Cover Classification

    NASA Astrophysics Data System (ADS)

    Hu, B.; Li, P.

    2013-07-01

    Markov random field (MRF) is an effective method for description of local spatial-temporal dependence of image and has been widely used in land cover classification and change detection. However, existing studies only use pair-point clique (PPC) to describe spatial dependence of neighbouring pixels, which may not fully quantify complex spatial relations, particularly in high spatial resolution images. In this study, multi-point clique (MPC) is adopted in MRF model to quantitatively express spatial dependence among pixels. A modified least squares fit (LSF) method based on robust estimation is proposed to calculate potential parameters for MRF models with different types. The proposed MPC-MRF method is evaluated and quantitatively compared with traditional PPCMRF in urban land cover classification using high resolution hyperspectral HYDICE data of Washington DC. The experimental results revealed that the proposed MPC-MRF method outperformed the traditional PPC-MRF method in terms of classification details. The MPC-MRF provides a sophisticated way of describing complex spatial dependence for relevant applications.

  8. What is the point of the point-of-care? A case study of user resistance to an e-health system.

    PubMed

    Whittaker, Louise; Van Zyl, Jaco; Soicher, Antony S

    2011-01-01

    The purpose of this article is to explore the response of nurses to a point-of-care e-health system that was implemented in a large private hospital in South Africa, to determine why the nursing staff rejected the implementation of the system. The study examines user responses with reference to a model designed to account for the use and adoption of mobile handheld devices, having adapted the model for an e-health context. In addition to the input features of technological characteristics and individual differences identified in the model, the added features of nursing culture and group differences were found to be influential factors in fuelling the nurses' resistance to the point-of-care system. Nurses perceived a lack of cultural fit between the system and their work. Their commitment to their nursing culture meant that they were not prepared to adapt their processes to integrate the system into their work. The study shows that the model is useful for understanding adoption in an organizational context and also that the additional elements of nursing culture and group differences are important in an e-health context. PMID:21294686

  9. Negative electrode composition

    DOEpatents

    Kaun, Thomas D. (New Lenox, IL); Chilenskas, Albert A. (Western Springs, IL)

    1982-01-01

    A secondary electrochemical cell and a negative electrode composition for use therewith comprising a positive electrode containing an active material of a chalcogen or a transiton metal chalcogenide, a negative electrode containing a lithium-aluminum alloy and an amount of a ternary alloy sufficient to provide at least about 5 percent overcharge capacity relative to a negative electrode solely of the lithium-aluminum alloy, the ternary alloy comprising lithium, aluminum, and iron or cobalt, and an electrolyte containing lithium ions in contact with both of the positive and the negative electrodes. The ternary alloy is present in the electrode in the range of from about 5 percent to about 50 percent by weight of the electrode composition and may include lithium-aluminum-nickel alloy in combination with either the ternary iron or cobalt alloys. A plurality of series connected cells having overcharge capacity can be equalized on the discharge side without expensive electrical equipment.

  10. Advances in lightweight nickel electrode technology

    NASA Technical Reports Server (NTRS)

    Coates, Dwaine; Paul, Gary; Daugherty, Paul

    1989-01-01

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

  11. Advances in lightweight nickel electrode technology

    NASA Technical Reports Server (NTRS)

    Coates, Dwaine; Paul, Gary; Wheeler, James R.; Daugherty, Paul

    1989-01-01

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

  12. 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

    Undalov, Yu. K. Terukov, E. I.; Gusev, O. B.; Lebedev, V. M.; Trapeznikova, I. N.

    2011-12-15

    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.

  13. 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

    Thomas E. Springer

    1998-01-30

    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.

  14. Studies of Point Defects and Defect Interactions in Metals Using Perturbed Gamma Gamma Angular Correlations

    NASA Astrophysics Data System (ADS)

    Shropshire, Steven Leslie

    Point defects in plastically deformed Au, Pt, and Ni were studied with atomic-scale sensitivity using the perturbed gamma-gamma angular correlations (PAC) technique by monitoring formation and transformation of complexes of vacancy defects with very dilute ^{111}In/ ^{111}Cd solute probes. Three topics were investigated: (1) Production of vacancy defects during plastic deformation of Au was investigated to differentiate models of defect production. Concentrations of mono-, di-, and tri-vacancy species were measured in Au, and the ratio of mono- to di-vacancies was found to be independent of the amount of deformation. Results indicate that point defects are produced in correlated lattice locations, such as in "strings", as a consequence of dislocation interactions and not at random locations. (2) Hydrogen interactions with vacancy-solute complexes were studied in Pt. From thermal detrapping experiments, binding of hydrogen in complexes with mono-, di- and tri-vacancies was determined using a model for hydrogen diffusing in a medium with traps, with enthalpies all measured in the narrow range 0.23-0.28 eV, proving that the binding is insensitive to the precise structure of small vacancy clusters. Nuclear relaxation of the probe in a trivacancy complex in Pt was studied as a function of temperature, from which an activation energy of 0.34 eV was measured. This value is inconsistent with relaxation caused by diffusion or trapping of hydrogen, but explainable by dynamical hopping of the PAC probe atom in a cage of vacancies. (3) By observing transformations between vacancy-solute complexes induced by annihilation reactions, it was demonstrated that interstitials are produced during plastic deformation. The evolution of concentrations of the different vacancy complexes under an interstitial flux was measured and analyzed using a kinetic-rate model, from which interstitial capture cross-sections for the different vacancy complexes and the relative quantities of interstitial species in the flux were determined. Deformation of Au was found to produce only mono- and di-interstitial fluxes in a 1:2 ratio. Cross-sections increased rapidly with the number of vacancies, which is attributed to the amount of relaxation of lattice strains around solute-vacancy complexes.

  15. Design and baseline characteristics of the Incremental Decrease in End Points through Aggressive Lipid Lowering study.

    PubMed

    Pedersen, Terje R; Faergeman, Ole; Kastelein, John J P; Olsson, Anders G; Tikkanen, Matti J; Holme, Ingar; Larsen, Mogens Lytken; Bendiksen, Fredrik S; Lindahl, Christina; Palmer, Gary

    2004-09-15

    The Incremental Decrease in End Points through Aggressive Lipid Lowering (IDEAL) study is an investigator-initiated trial designed to determine whether additional clinical benefit might be gained through a strategy that decreases levels of low-density lipoprotein cholesterol levels better than those currently achieved with established statin therapy in patients who have coronary heart disease. IDEAL is a multicenter prospective, randomized, open-label, blinded, end point classification study. Patients who had myocardial infarction were randomized to prescription treatment with 80 mg/day of atorvastatin or 20 mg/day of simvastatin (the dose was increased to 40 mg/day at week 24 in those patients whose plasma total cholesterol remained >5.0 mmol/L, or 190 mg/dl, or whose low-density lipoprotein cholesterol remained >3.0 mmol/L, or 115 mg/dl). The primary clinical outcome variable is the time to initial occurrence of a major coronary event, which is defined as nonfatal acute myocardial infarction, coronary death, or resuscitated cardiac arrest. The study is designed to have a power of 90% to detect a relative decrease of 20% in the atorvastatin-group compared with the simvastatin-group in the number of major events caused by coronary heart disease over approximately 5.5 years. The 8,888 randomized patients had the following characteristics: mean age 61.7 +/- 9.5 years, 19.1% women (mean age 64.0 +/- 9.5 years), baseline total cholesterol 5.1 +/- 1.0 mmol/L (197 mg/dl), low-density lipoprotein cholesterol 3.2 +/- 0.9 mmol/L (124 mg/dl), and high-density lipoprotein cholesterol 1.2 +/- 0.3 mmol/L (46 mg/dl). Drug treatment before randomization consisted of statins in 77% of patients, aspirin in 78.9%, beta blockers in 75.1%, and angiotensin-converting enzyme inhibitors in 30%. PMID:15374773

  16. A CMB foreground study in WMAP data: Extragalactic point sources and zodiacal light emission

    NASA Astrophysics Data System (ADS)

    Chen, Xi

    The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. It serves as a primary tool to understand the global properties, content and evolution of the universe. Since 2001, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite has been napping the full sky anisotropy with unprecedented accuracy, precision and reliability. The CMB angular power spectrum calculated from the WMAP full sky maps not only enables accurate testing of cosmological models, but also places significant constraints on model parameters. The CMB signal in the WMAP sky maps is contaminated by microwave emission from the Milky Way and from extragalactic sources. Therefore, in order to use the maps reliably for cosmological studies, the foreground signals must be well understood and removed from the maps. This thesis focuses on the separation of two foreground contaminants from the WMAP maps: extragalactic point sources and zodiacal light emission. Extragalactic point sources constitute the most important foreground on small angular scales. Various methods have been applied to the WMAP single frequency maps to extract sources. However, due to the limited angular resolution of WMAP, it is possible to confuse positive CMB excursions with point sources or miss sources that are embedded in negative CMB fluctuations. We present a novel CMB-free source finding technique that utilizes the spectrum difference of point sources and CMB to form internal linear combinations of multifrequency maps to suppress the CMB and better reveal sources. When applied to the WMAP 41, 64 and 94 GHz maps, this technique has not only enabled detection of sources that are previously cataloged by independent methods, but also allowed disclosure of new sources. Without the noise contribution from the CMB, this method responds rapidly with the integration time. The number of detections varies as 0( t 0.72 in the two-band search and 0( t 0.70 in the three-band search from one year to five years, separately, in comparison to t 0.40 from the WMAP catalogs. Our source catalogs are a good supplement to the existing WMAP source catalogs, and the method itself is proven to be both complementary to and competitive with all the current source finding techniques in WMAP maps. Scattered light and thermal emission from the interplanetary dust (IPD) within our Solar System are major contributors to the diffuse sky brightness at most infrared wavelengths. For wavelengths longer than 3.5 mm, the thermal emission of the IPD dominates over scattering, and the emission is often referred to as the Zodiacal Light Emission (ZLE). To set a limit of ZLE contribution to the WMAP data, we have performed a simultaneous fit of the yearly WMAP time-ordered data to the time variation of ZLE predicted by the DIRBE IPD model (Kelsallet al. 1998) evaluated at 240 mm, plus [cursive l] = 1 - 4 CMB components. It is found that although this fitting procedure can successfully recover the CMB dipole to a 0.5% accuracy, it is not sensitive enough to determine the ZLE signal nor the other multipole moments very accurately.

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

    PubMed Central

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

    2013-01-01

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

  18. Studies on the relationship between the point mutation of ras oncogenes and the prognosis of patients with gastric cancer

    PubMed Central

    Fang, Dian-Chun; Luo, Yuan-Hui; Lu, Rong; Liu, Wei-Wen

    1997-01-01

    AIM: To study the relationship between the point mutation of ras oncogenes and the prognosis of patients with gastric cancer. METHODS: The point mutations at codon 12 and 61 of c-Ha-ras, at codon 12 and 13 of K-ras, and at codon 12 of N-ras were studied with PCR-RFLP in 88 formalin fixed and paraffin embedded specimens of gastric cancer. RESULTS: It was found that the overall rate of point mutation of ras oncogenes was 18.2% and the positivity of the point mutation of ras oncogenes was related to the cancerous invasion of the serosa, the status of lymph node metastasis, the stage of cancer and the survival time after surgery. CONCLUSION: The findings suggest that the determination of point mutations of ras oncogenes can be used to determine the prognosis of patients with gastric cancer. PMID:27006577

  19. Research on rechargeable oxygen electrodes.

    NASA Technical Reports Server (NTRS)

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

    1970-01-01

    A research program is described which consisted of studying the effects of electrode cycling in very pure KOH solutions, with and without controlled additions of impurities, on oxide formation, oxygen evolution kinetics, oxygen reduction kinetics (including hydrogen peroxide formation), and changes in electrode structure. Bright platinum, platinized platinum, and Teflon-bonded platinum black electrodes were studied. Three main problem areas are identified: the buildup of a refractory anodic layer on prolonged cycling, which leads to a degradation of performance; the dissolution and subsequent deposition of dendritic platinum in the separator, leading to short-circuit ing and loss of electrocatalyst; and the disruptive effect of bubbling during gas evolution on charge. Each of these problem areas is analyzed, and remedial solutions are proposed.

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

    NASA Technical Reports Server (NTRS)

    Manlief, Scott

    1995-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Yndurain, Felix

    2014-12-01

    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.

  2. A water quality modeling study of non-point sources at recreational marine beaches.

    PubMed

    Zhu, Xiaofang; Wang, John D; Solo-Gabriele, Helena M; Fleming, Lora E

    2011-04-01

    A model study was conducted to understand the influence of non-point sources including bather shedding, animal fecal sources, and near shore sand, as well as the impact of the environmental conditions, on the fate and transport of the indicator microbe, enterococci, at a subtropical recreational marine beach in South Florida. The model was based on an existing finite element hydrodynamic and transport model, with the addition of a first order microbe deactivation function due to solar radiation. Results showed that dog fecal events had a major transient impact (hundreds of Colony Forming Units/100 ml [CFU/100 ml]) on the enterococci concentration in a limited area within several hours, and could partially explain the high concentrations observed at the study beach. Enterococci released from beach sand during high tide caused mildly elevated concentration for a short period of time (ten to twenty of CFU/100 ml initially, reduced to 2 CFU/100 ml within 4 h during sunny weather) similar to the average baseline numbers observed at the beach. Bather shedding resulted in minimal impacts (less than 1 CFU/100 ml), even during crowded holiday weekends. In addition, weak current velocity near the beach shoreline was found to cause longer dwelling times for the elevated concentrations of enterococci, while solar deactivation was found to be a strong factor in reducing these microbial concentrations. PMID:21477839

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

    SciTech Connect

    Harvey, A. H.; McLinden, M. O.; Tew, W. L.

    2013-09-11

    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.

  4. Effect of electrode coating on the response curve of dose calibrators for nuclear medicine: A computer simulation study

    NASA Astrophysics Data System (ADS)

    Kleeven, Willem J. G. M.; Wijnhoven, Gerd P. J.

    1985-07-01

    For most types of re-entrant ionization chambers filled with nobel gases, the response is relatively low in the energy region between ca 100 and 500 keV. By coating the electrode with a thin high- Z metal layer, the response in this region can be considerably increased. The influence of thickness and Z number of the coating on the response is calculated with a computer model for ?-energies up to 1000 keV. Calculations are carried out for a spherical model geometry of the ionization chamber. Using a lead coating of 200 ?m and krypton gas filling, an improvement in response of a factor 3 around 350 keV can be achieved. Although the model is not suited for calculation of the response of actual dose calibrators, it enables a better understanding of the influence of dimensions, construction materials, gas filling and particularly electrode coating on the final shape of the response curve. It may be seen as an onset for more complicated models for the achievement of dose calibrators with a flat response curve.

  5. Infrared cameras are potential traceable "fixed points" for future thermometry studies.

    PubMed

    Yap Kannan, R; Keresztes, K; Hussain, S; Coats, T J; Bown, M J

    2015-01-01

    The National physical laboratory (NPL) requires "fixed points" whose temperatures have been established by the International Temperature Scale of 1990 (ITS 90) be used for device calibration. In practice, "near" blackbody radiators together with the standard platinum resistance thermometer is accepted as a standard. The aim of this study was to report the correlation and limits of agreement (LOA) of the thermal infrared camera and non-contact infrared temporal thermometer against each other and the "near" blackbody radiator. Temperature readings from an infrared thermography camera (FLIR T650sc) and a non-contact infrared temporal thermometer (Hubdic FS-700) were compared to a near blackbody (Hyperion R blackbody model 982) at 0.5 °C increments between 20-40 °C. At each increment, blackbody cavity temperature was confirmed with the platinum resistance thermometer. Measurements were taken initially with the thermal infrared camera followed by the infrared thermometer, with each device mounted in turn on a stand at a fixed distance of 20 cm and 5 cm from the blackbody aperture, respectively. The platinum thermometer under-estimated the blackbody temperature by 0.015 °C (95% LOA: -0.08 °C to 0.05 °C), in contrast to the thermal infrared camera and infrared thermometer which over-estimated the blackbody temperature by 0.16 °C (95% LOA: 0.03 °C to 0.28 °C) and 0.75 °C (95% LOA: -0.30 °C to 1.79 °C), respectively. Infrared thermometer over-estimates thermal infrared camera measurements by 0.6 °C (95% LOA: -0.46 °C to 1.65 °C). In conclusion, the thermal infrared camera is a potential temperature reference "fixed point" that could substitute mercury thermometers. However, further repeatability and reproducibility studies will be required with different models of thermal infrared cameras. PMID:26468981

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

    ERIC Educational Resources Information Center

    Barrelle, M.; And Others

    1983-01-01

    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)

  7. Mechanical characterization of Cu-Zn wire electrode base used in EDM and study of influence of the process of machining on its properties

    NASA Astrophysics Data System (ADS)

    Sedjal, H.; Amirat, B.; Aichour, M.; Marouf, T.; Chitroub, M.

    2015-03-01

    This work is part of a Research National project (PNR) carried out by the group of research of the engineering and material sciences laboratory of the polytechnic national school at Algiers in collaboration with company BCR, which relates to "the characterization of the wire intended for the EDM of matrices metal. The goal of this work is to bring metallographic explanations on the wire electrode used by the machine ROBOFIL 290P, mechanically characterized this wire as of knowing of advantage about the process of its manufacturing (wiredrawing, .) The methods of studies used are it micro Vickers pyramid hardness, the tensile test, optical microscopy and scan electronic microscopy SEM.

  8. Mechanical characterization of Cu-Zn wire electrode base used in EDM and study of influence of the process of machining on its properties

    SciTech Connect

    Sedjal, H. Amirat, B.; Aichour, M.; Marouf, T.; Chitroub, M.

    2015-03-30

    This work is part of a Research National project (PNR) carried out by the group of research of the engineering and material sciences laboratory of the polytechnic national school at Algiers in collaboration with company BCR, which relates to “the characterization of the wire intended for the EDM of matrices metal. The goal of this work is to bring metallographic explanations on the wire electrode used by the machine ROBOFIL 290P, mechanically characterized this wire as of knowing of advantage about the process of its manufacturing (wiredrawing, .) The methods of studies used are it micro Vickers pyramid hardness, the tensile test, optical microscopy and scan electronic microscopy SEM.

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

    PubMed Central

    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

    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

  10. An Evaluation of Surgical Prophylaxis Procedures in Turkey: A Multi-Center Point Prevalence Study

    PubMed Central

    Kaya, Selcuk; Aktas, Seyhan; Senbayrak, Seniha; Tekin, Recep; Oztoprak, Nefise; Aksoy, Firdevs; Firat, Pinar; Yenice, Sevinc; Oncul, Ahsen; Gunduz, Alper; Solak, Semiha; Kadanali, Ayten; Cakar, Sule Eren; Caglayan, Derya; Yilmaz, Hava; Bozkurt, Ilkay; Elmaslar, Tulin; Tartar, Ayse Sagmak; Aynioglu, Aynur; Kocyigit, Nilgun Fidan; Koksal, Iftihar

    2016-01-01

    Objective: The purpose of this study was to evaluate compliance with guidelines in surgical prophylaxis (SP) procedures in Turkey. Materials and Methods: A point prevalence study involving 4 university, 5 education and research and 7 public hospitals was performed assessing compliance with guidelines for antibiotic use in SP. Compliance was based on the “Clinical Practice Guidelines for Antimicrobial Surgery (CPGAS) 2013” guideline. Results: Sixteen centers were included in the study, with 166 operations performed at these being evaluated. Parenteral antibiotic for SP was applied in 161 (96.9%) of these. Type of antibiotic was inappropriate in 66 (40.9%) cases and duration of use in 47 (29.1%). The main antibiotics used inappropriately in SP were ceftriaxone, glycopeptides and aminoglycosides. No significant difference was observed between secondary and tertiary hospitals in terms of inappropriate selection. Duration of prophylaxis was also incompatible with guideline recommendations in approximately half of surgical procedures performed in both secondary and tertiary hospitals, however statistical significance was observed between institutions in favor of tertiary hospitals. Conclusion: Antibiotics are to a considerable extent used in a manner incompatible with guidelines even in tertiary hospitals in Turkey. It must not be forgotten that several pre-, intra- and postoperative factors can be involved in the development of surgical site infections (SSI), and antibiotics are not the only option available for preventing these. A significant improvement can be achieved in prophylaxis with close observation, educational activities, collaboration with the surgical team and increasing compliance with guidelines. All health institutions must establish and apply their own SP consensus accompanied by the guidelines in order to achieve success in SP.

  11. Do Owners Have a Clever Hans Effect on Dogs? Results of a Pointing Study

    PubMed Central

    Schmidjell, Teresa; Range, Friederike; Huber, Ludwig; Virnyi, Zsfia

    2012-01-01

    Dogs are exceptionally successful at interpreting human pointing gestures to locate food hidden in one of two containers. However, it has repeatedly been questioned whether dogs rely on the pointing gesture or their success is increased by subtle cues from their human handler. In two experiments we used a standard two-way object-choice task to focus on this potential Clever Hans effect. We investigated if and how owners knowledge and beliefs influenced their dogs performance. In two experiments, as is typical in such pointing tasks, the owners sat behind their dogs, in close auditory and tactile contact with them. In Experiment 1, we systematically manipulated the owners knowledge of whether or not their dog should follow the pointing gesture, but at the same time instructed the owners to refrain from influencing the choice of their dog. We found no influence of subtle cues from the owners, if indeed they existed: dogs in the different groups followed the pointing uniformly. Furthermore, in the absence of pointing dogs chose randomly, even though the owners had been informed about the location of the reward. In Experiment 2, owners were instructed to actively influence the choice of their dogs, and they, indeed, succeeded in sending their dogs to the container they believed to be baited. However, their influence was significantly weaker if the experimenter had previously pointed to the other location. Overall the pointing gesture seems to have a strong effect on the choice of dogs in an object-choice task. Pointing can lead the dogs to success without help from their owners as well as it can counteract clear directional instructions provided by the owners. PMID:23272000

  12. First-principles study of native point defects in Bi2Se3

    NASA Astrophysics Data System (ADS)

    Xue, L.; Zhou, P.; Zhang, C. X.; He, C. Y.; Hao, G. L.; Sun, L. Z.; Zhong, J. X.

    2013-05-01

    Using first-principles method within the framework of the density functional theory, we study the influence of native point defect on the structural and electronic properties of Bi2Se3. Se vacancy in Bi2Se3 is a double donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi) is always an active donor in the system because its donor level (ɛ(+1/0)) enters into the conduction band. Interestingly, Bi antisite (BiSe1) in Bi2Se3 is an amphoteric dopant, acting as a donor when μe < 0.119 eV (the material is typical p-type) and as an acceptor when μe > 0.251 eV (the material is typical n-type). The formation energies under different growth environments (such as Bi-rich or Se-rich) indicate that under Se-rich condition, SeBi is the most stable native defect independent of electron chemical potential μe. Under Bi-rich condition, Se vacancy is the most stable native defect except for under the growth window as μe > 0.262 eV (the material is typical n-type) and ΔμSe < -0.459 eV (Bi-rich), under such growth window BiSe1 carrying one negative charge is the most stable one.

  13. Numerical, experimental, and theoretical study of convective instability of flows over pointed bodies at incidence

    NASA Technical Reports Server (NTRS)

    Degani, David; Tobak, Murray

    1991-01-01

    A study is conducted to investigate whether the behavior of the asymmetric mean flow observed on pointed bodies of revolution at incidence remains consistent with the presence of a convective instability of an original symmetric flow, even in the incidence range where virtually bistable behavior of the asymmetric flow is observed. By means of a retractable wire located near the tip, it is determined experimentally that for all angles of attack tested (30 to 60 degs), changing the size or location of the controlled disturbance results in a finite change in the asymmetric flow field, even to the extent of reversing the sign of the side force or becoming almost symmetric. The process is reversible; returning the wire to an original position likewise restores the corresponding flow field and mean side force. The effect of wire location (roll angle and distance from the tip) as well as angle of attack and flow conditions are evaluated experimentally by means of flow visualization and side-force measurements for a generic ogive-cylinder model in a low-speed wind tunnel. Evaluation of the results in the light of computational observations and theoretical considerations yields an affirmative answer to the question posed.

  14. C/NOFS and the Air Force Research Laboratory's Conjugate Point Study

    NASA Astrophysics Data System (ADS)

    Gentile, L. C.; Cooke, D. L.; Huang, C.; Huang, C. Y.; Roddy, P. A.; Sutton, E. K.; Mishin, E. V.; Dao, E. V.; Martinis, C. R.; Burke, W. J.; Lai, P. C.; Pradipta, R.; Valladares, C. E.

    2014-12-01

    The Air Force Research Laboratory's Conjugate Point Study (CPS) seeks to leverage a unique opportunity with the Communication/Navigation Outage Forecasting System (C/NOFS) to make coincident measurements from the satellite and an ever-expanding network of ground stations that can be used to specify effects of atmospheric wave activity on the structure of the ionospheric F-layer. The primary objective of CPS is to integrate plasma density and drift measurements from C/NOFS with ground-based observations of disturbances within magnetic flux tubes to address outstanding scientific questions regarding relationships between plasma fluctuations in the topside ionosphere and wave-like structures generated at bottomside altitudes where satellites have little or no direct access. This project has the potential to generate new insights into the dynamics of ionosphere-neutral atmosphere interactions known to affect operational systems. This could prove particularly valuable in areas where there are no ground stations. Initial results are quite promising, but there is still much work to be done in understanding the mechanisms that couple the topside and bottomside of the ionosphere.

  15. Modification of the in vivo four-point loading model for studying mechanically induced bone adaptation.

    PubMed

    Forwood, M R; Bennett, M B; Blowers, A R; Nadorfi, R L

    1998-09-01

    We modified the noninvasive, in vivo technique for strain application in the tibiae of rats (Turner et al., Bone 12:73-79, 1991). The original model applies four-point bending to right tibiae via an open-loop, stepper-motor-driven spring linkage. Depending on the magnitude of applied load, the model produces new bone formation at periosteal (Ps) or endocortical surfaces (Ec.S). Due to the spring linkage, however, the range of frequencies at which loads can be applied is limited. The modified system replaces this design with an electromagnetic vibrator. A load transducer in series with the loading points allows calibration, the loaders' position to be adjusted, and cyclic loading completed under load control as a closed servo-loop. Two experiments were conducted to validate the modified system: (1) a strain gauge was applied to the lateral surface of the right tibia of 5 adult female rats and strains measured at applied loads from 10 to 60 N; and (2) the bone formation response was determined in 28 adult female Sprague-Dawley rats. Loading was applied as a haversine wave with a frequency of 2 Hz for 18 sec, every second day for 10 days. Peak bending loads were applied at 33, 40, 52, and 64 N, and a sham-loading group was included at 64 N. Strains in the tibiae were linear between 10 and 60 N, and the average peak strain at the Ps.S at 60 N was 2664 +/- 250 microstrain, consistent with the results of Turner's group. Lamellar bone formation was stimulated at the Ec.S by applied bending, but not by sham loading. Bending strains above a loading threshold of 40 N increased Ec lamellar bone formation rate, bone forming surface, and mineral apposition rate with a dose response similar to that reported by Turner et al. (J Bone Miner Res 9:87-97, 1994). We conclude that the modified loading system offers precision for applied loads of between 0 and 70 N, versatility in the selection of loading rates up to 20 Hz, and a reproducible bone formation response in the rat tibia. Adjustment of the loader also enables study of mechanical usage in murine tibia, an advantage with respect to the increasing variety of transgenic strains available in bone and mineral research. PMID:9737355

  16. Seepage study of the Rocky Point Canal and the Grey Mountain-Pleasant Valley Canal systems, Duchesne County, Utah

    USGS Publications Warehouse

    Cruff, R.W.; Hood, J.W.

    1976-01-01

    This report describes the study of the Rocky Point Canal system in the vicinity of Duchesne and the Grey Mountain-Pleasant Valley Canal system between Duchesne and Myton, in the Uinta Basin, Duchesne County, Utah. The Rocky Point Canal diverts from the left bank of the Duchesne River about 4 mi north of Duchesne. This canal splits into the upper Rocky Point Canal and the lower Rocky Point Canal about 5.2 mi below its head. The Grey Mountain Canal diverts from the right bank of the Duchesne River about 6 mi east of Duchesne. At a point about 7.6 mi below the head, the Pleasant Valley Canal diverts from the right bank of the Grey Mountain Canal.

  17. CROSS-SECTIONAL STUDY ON DIFFERENT ENTRY POINTS FOR ANTEROGRADE FEMORAL INTRAMEDULLARY OSTEOSYNTHESIS

    PubMed Central

    Kanas, Michel; Wajnsztejn, Andre; Roucourt, Danilo; Fiorentino, Eduardo; Fernandes, Hélio Jorge Alvachian; dos Reis, Fernando Baldy

    2015-01-01

    Objective: To analyze the degree of knowledge among professionals who treat fractures using the recommended technique, with regard to correlating the nail with the entry point that is considered appropriate. Methods: A questionnaire that presented five types of nail and simulated a transverse diaphyseal fracture of the femur was developed. Results: Responses regarding the entry points corresponding to choosing the type of nail were obtained from 370 orthopedists who were participating in the 41st Brazilian Congress of Orthopedics and Traumatology. It was observed that only 20% correctly identified the entry point and that there was no difference between the professionals within the specialty of Traumatology and the others. Conclusion: It was concluded that the majority of the physicians attending the congress were unaware of the entry points.

  18. Electrode holder useful in a corrosion testing device

    DOEpatents

    Murphy, Jr., Robert J.; Jamison, Dale E.

    1986-01-01

    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.

  19. Electrode holder useful in a corrosion testing device

    DOEpatents

    Murphy, R.J. Jr.; Jamison, D.E.

    1986-08-19

    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.

  20. Origin of Capacity Fading in Nano-Sized Co3O4Electrodes: Electrochemical Impedance Spectroscopy Study

    PubMed Central

    2008-01-01

    Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.