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Sample records for charge exchange cell

  1. Effect of ligand exchange of Cu2ZnSnS4 nanocrystals on the charge transport and photovoltaic performance of nanostructured depleted bulk heterojunction solar cell

    Science.gov (United States)

    Zhang, Zhuo-Xi; Zhou, Zheng-Ji; Bai, Bing; Liu, Ming-Hua; Zhou, Wen-Hui; Kou, Dong-Xing; Wu, Si-Xin

    2015-12-01

    Cu2ZnSnS4 (CZTS) nanocrystals combining the advantage of feasible solution-phase synthesis and processing are perceived as promising materials for application in efficient, low-cost photovoltaic technology. Herein, we have got surfactant-free CZTS nanocrystals by a novel ligand exchange method, and the obtained CZTS nanocrystals were deposited onto ZnO nanorod arrays to construct depleted bulk heterojunction solar cell. The all-inorganic CZTS nanocrystal solar cells demonstrated a remarkable improvement in J sc (from 8.14 to 13.97 mA/cm2) and power conversion efficiency (from 1.83 to 3.34 %) compared with surfactant-capped CZTS nanocrystals. Using surface photovoltage spectrum, the influence of ligand exchange of CZTS nanocrystals on the charge transport and photovoltaic performance of the nanostructured CZTS solar cells was discussed.

  2. Hydration shells exchange charge with their protein

    DEFF Research Database (Denmark)

    Abitan, Haim; Lindgård, Per-Anker; Nielsen, Bjørn Gilbert

    2010-01-01

    Investigation of the interaction between a protein and its hydration shells is an experimental and theoretical challenge. Here, we used ultrasonic pressure waves in aqueous solutions of a protein to explore the conformational states of the protein and its interaction with its hydration shells....... In our experiments, the amplitude of an ultrasonic pressure wave is gradually increased (0–20 atm) while we simultaneously measure the Raman spectra from the hydrated protein (β-lactoglobulin and lysozyme). We detected two types of spectral changes: first, up to 70% increase in the intensity...... the presence of an ultrasonic pressure, a protein and its hydration shells are in thermodynamic and charge equilibrium, i.e. a protein and its hydration shells exchange charges. The ultrasonic wave disrupts these equilibria which are regained within 30–45 min after the ultrasonic pressure is shut off....

  3. Ion thruster charge-exchange plasma flow

    Science.gov (United States)

    Carruth, M. R., Jr.; Gabriel, S. B.; Kitamura, S.

    1982-01-01

    The electron bombardment ion thruster has been under development for a number of years and during this time, studies of the plasmas produced by the thrusters and their interactions with spacecraft have been evaluated, based on available data. Due to diagnostic techniques used and facility effects, there is uncertainty as to the reliability of data from these early studies. This paper presents data on the flow of the charge-exchange plasma produced just downstream of the thruster's ion optics. The 'end-effect' of a cylindrical Langmuir probe is used to determine ion density and directed ion velocity. Results are compared with data obtained from a retarding potential analyzer-Faraday cup.

  4. Fine structure of charge exchange lines observed in laboratory plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ida, K.; Nishimura, S. [National Inst. for Fusion Science, Nagoya (Japan); Kondo, K.

    1997-01-01

    The influence of the fine structure of charge exchange lines appears only at the plasma edge or in the recombining phase where the ion temperature is low enough. The observed spectra in Li III and C VI are consistent with the sum of fine-structure components populated by statistical weights (assuming complete l-mixing) not by direct charge exchange cross sections. Some discrepancy was observed in the intensity ratio of fine-structure components between the observation and calculation for C VI in the recombining phase. The fine-structure of charge exchange lines gives an apparent Doppler shift in plasma rotation velocity measurement using charge exchange spectroscopy. (author)

  5. Effects of ammonium concentration and charge exchange on ammonium recovery from high strength wastewater using a microbial fuel cell

    NARCIS (Netherlands)

    Kuntke, P.; Geleij, M.; Bruning, H.; Zeeman, G.; Hamelers, H.V.M.; Buisman, C.J.N.

    2011-01-01

    Ammonium recovery using a 2 chamber microbial fuel cell (MFC) was investigated at high ammonium concentration. Increasing the ammonium concentration (from 0.07 g to 4 g ammonium-nitrogen/L) by addition of ammonium chloride did not affect the performance of the MFC. The obtained current densities by

  6. Progress Towards Charge Exchange Cross-Sections with Highly Charged Ions: Computation and Experiment

    Science.gov (United States)

    Bromley, Steven James

    This thesis is a summary of the computational and experimental progress towards measuring the charge exchange cross-section of highly charged ions (HCIs). Electronic structure calculations were carried out for the molecular ion LiHe+ using NWChem on the Clemson University Palmetto Cluster. Potential energy surfaces for 40 electronic states are presented. The electronic configurations of the six lowest states have been identified by their energies in the separate atom limit, which deviate from experimental values by at most 1.2%. Future work will investigate higher charge states of LiHe and the interaction between low-Z HCIs and neutral gases. Two experimental apparatus were designed and constructed for experiments with HCIs. To aid in the detection of trapped HCIs, a time-of-flight mass spectrometer for radial extraction from Paul traps was constructed and tested using a Mg + source. Lastly, a gas cell was designed and constructed for charge exchange cross-section measurements using HCIs produced in the Clemson University Electron Beam Ion Trap (CUEBIT).

  7. X-ray emission from charge exchange of highly-charged ions in atoms and molecules

    Science.gov (United States)

    Greenwood, J. B.; Williams, I. D.; Smith, S. J.; Chutjian, A.

    2000-01-01

    Charge exchange followed by radiative stabilization are the main processes responsible for the recent observations of X-ray emission from comets in their approach to the Sun. A new apparatus was constructed to measure, in collisions of HCIs with atoms and molecules, (a) absolute cross sections for single and multiple charge exchange, and (b) normalized X-ray emission cross sections.

  8. Laser-assisted H^{-} charge exchange injection in magnetic fields

    Directory of Open Access Journals (Sweden)

    T. Gorlov

    2010-05-01

    Full Text Available The use of stripping foils for charge exchange injection can cause a number of operational problems in high intensity hadron accelerators. A recently proposed three-step method of laser-assisted injection is capable of overcoming these problems. This paper presents advances in the physical model of laser-assisted charge exchange injection of H^{-} beams and covers a wide field of atomic physics. The model allows the calculation of the evolution of an H^{0} beam taking into account spontaneous emission, field ionization, and external electromagnetic fields. Some new data on the hydrogen atom related to the problem are calculated. The numerical calculations in the model use realistic descriptions of laser field and injection beam. Generally, the model can be used for design and optimization of a laser-assisted injection cell within an accelerator lattice. Example calculations of laser-assisted injection for an intermediate experiment at SNS in Oak Ridge and for the PS2 accelerator at CERN are presented. Two different schemes, distinctively characterized by various magnetic fields at the excitation point, are discussed. It was shown that the emittance growth of an injected beam can be drastically decreased by moving the excitation point into a strong magnetic field.

  9. Characterization of an atomic hydrogen source for charge exchange experiments

    Energy Technology Data Exchange (ETDEWEB)

    Leutenegger, M. A. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States); CRESST/University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Beiersdorfer, P.; Brown, G. V.; Magee, E. W. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Betancourt-Martinez, G. L. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States); University of Maryland College Park, College Park, Maryland 20742 (United States); Hell, N. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Dr. Karl-Remeis-Sternwarte and ECAP, FAU Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg (Germany); Kelley, R. L.; Kilbourne, C. A.; Porter, F. S. [NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771 (United States)

    2016-11-15

    We characterized the dissociation fraction of a thermal dissociation atomic hydrogen source by injecting the mixed atomic and molecular output of the source into an electron beam ion trap containing highly charged ions and recording the x-ray spectrum generated by charge exchange using a high-resolution x-ray calorimeter spectrometer. We exploit the fact that the charge exchange state-selective capture cross sections are very different for atomic and molecular hydrogen incident on the same ions, enabling a clear spectroscopic diagnostic of the neutral species.

  10. Mass-charge-heat coupled transfers in a single cell of a proton exchange membrane fuel cell; Transferts couples masse-charge-chaleur dans une cellule de pile a combustible a membrane polymere

    Energy Technology Data Exchange (ETDEWEB)

    Ramousse, J.

    2005-11-15

    Understanding and modelling of coupled mass, charges and heat transfers phenomena are fundamental to analyze the electrical behaviour of the system. The aim of the present model is to describe electrical performances of a PEFMC according to the fluidic and thermal operating conditions. The water content of the membrane and the water distribution in the single cell are estimated according to the coupled simulations of mass transport in the thickness of the single cell and in the feeding channels of the bipolar plates. A microscopic model of a Gas Diffusion Electrode is built up to describe charges transfer phenomena occurring at the electrodes. Completed by a study of heat transfer in the Membrane Electrode Assembly, conditions and preferential sites of water vapor condensation can be highlighted. A set of measurements of the effective thermal conductivity of carbon felts used in fuel cells as porous backing layers have also been performed. Although the value of this parameter is essential for the study of heat transfer, it is still under investigation because of the strong thermal anisotropy of the medium. (author)

  11. Effect of ligand exchange of Cu{sub 2}ZnSnS{sub 4} nanocrystals on the charge transport and photovoltaic performance of nanostructured depleted bulk heterojunction solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhuo-Xi; Zhou, Zheng-Ji, E-mail: zzj@henu.edu.cn; Bai, Bing; Liu, Ming-Hua; Zhou, Wen-Hui; Kou, Dong-Xing; Wu, Si-Xin, E-mail: wusixin@henu.edu.cn [Henan University, Key Laboratory for Special Functional Materials of Ministry of Education (China)

    2015-12-15

    Cu{sub 2}ZnSnS{sub 4} (CZTS) nanocrystals combining the advantage of feasible solution-phase synthesis and processing are perceived as promising materials for application in efficient, low-cost photovoltaic technology. Herein, we have got surfactant-free CZTS nanocrystals by a novel ligand exchange method, and the obtained CZTS nanocrystals were deposited onto ZnO nanorod arrays to construct depleted bulk heterojunction solar cell. The all-inorganic CZTS nanocrystal solar cells demonstrated a remarkable improvement in J{sub sc} (from 8.14 to 13.97 mA/cm{sup 2}) and power conversion efficiency (from 1.83 to 3.34 %) compared with surfactant-capped CZTS nanocrystals. Using surface photovoltage spectrum, the influence of ligand exchange of CZTS nanocrystals on the charge transport and photovoltaic performance of the nanostructured CZTS solar cells was discussed.

  12. Measurement of absorption and charge exchange of $\\pi^+$ on carbon

    CERN Document Server

    Ieki, K; Berkman, S; Bhadra, S; Cao, C; de Perio, P; Hayato, Y; Ikeda, M; Kanazawa, Y; Kim, J; Kitching, P; Mahn, K; Nakaya, T; Nicholson, M; Olchanski, K; Rettie, S; Tanaka, H A; Wilking, M J; Tobayama, S; Yamauchi, T; Yen, S; Yokoyama, M

    2015-01-01

    The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.

  13. Charge exchange spectroscopy as a fast ion diagnostic on TEXTOR

    NARCIS (Netherlands)

    Delabie, E.; Jaspers, R. J. E.; von Hellermann, M. G.; Nielsen, S.K.; Marchuk, O.

    2008-01-01

    An upgraded charge exchange spectroscopy diagnostic has been taken into operation at the TEXTOR tokamak. The angles of the viewing lines with the toroidal magnetic field are close to the pitch angles at birth of fast ions injected by one of the neutral beam injectors. Using another neutral beam for

  14. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    CERN Document Server

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  15. Proton exchange membrane fuel cells

    CERN Document Server

    Qi, Zhigang

    2013-01-01

    Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

  16. Peculiarity of the charge-exchange quadrupole excitation in nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Leonardi, R.; Lipparini, E.; Stringari, S.

    1987-04-01

    The experimental isovector quadrupole strength in the charge exchange channels is smaller than predicted by random phase approximation calculations using conventional nuclear interactions. The introduction of nonlocal components in the interaction combined with the existence of a low-lying 0h-dash-bar..omega.. rotational 2/sup +/ quadrupole state in the daughter nucleus can explain this behavior. These nonlocal interactions do not play a role in the properties of the isovector monopole and dipole resonance.

  17. Charge exchange reactions as tests for structures of exotic nuclei

    CERN Document Server

    Karataglidis, S

    2010-01-01

    Charge exchange reactions serve as alternative tests of the structures of exotic nuclei. Of particular relevance is the (p, n) reaction, which is related to the Gamow-Teller matrix element. The (p, n) reaction is also related to (p, p′) in the case of transitions to the isobaric analogue state (IAS). There are few measurements of (p, n) reactions using exotic beams. We revisit the case of 6He(p, n)6Li and discuss apparent discrepancies with other available data.

  18. Excited State Atom-Ion Charge-Exchange

    Science.gov (United States)

    Li, Ming; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

    2017-04-01

    We theoretically investigate the exothermic charge-exchange reaction between an excited atom and a ground-state positive ion. In particular, we focus on MOT-excited Ca*(4s4p 1P) atoms colliding with ground-state Yb+ ions, which are under active study by the experimental group of E. Hudson at UCLA. Collisions between an excited atom and an ion are guided by two major contributions to the long-range interaction potentials, the induction C4 /R4 and charge-quadrupole C3 /R3 potentials, and their coupling by the electron-exchange interaction. Our model of these forces leads to close-coupling equations for multiple reaction channels. We find several avoided crossings between the potentials that couple to the nearby asymptotic limits of Yb*+Ca+, some of which can possibly provide large charge exchange rate coefficients above 10-10 cm3 / s. We acknowledge support from the US Army Research Office, MURI Grants W911NF-14-1-0378 and the US National Science Foundation, Grant PHY-1619788.

  19. Charge-exchange plasma generated by an ion thruster

    Science.gov (United States)

    Kaufman, H. R.

    1975-01-01

    The use of high voltage solar arrays greatly reduces or eliminates power processing requirements in space electric propulsion systems. This use also requires substantial areas of solar array to be at high positive potential relative to space and most of the spacecraft. The charge exchange plasma conducts electrons from the ion beam to such positive surfaces, and thereby electrically load the high voltage solar array. To evaluate this problem, the charge-exchange plasma generated by an ion beam was investigated experimentally. Based upon the experimental data, a simple model was derived for the charge-exchange plasma. This model is conservative in the sense that both the electron/ion density and the electron current density should be equal to, or less than, the preducted value for all directions in the hemisphere upstream of the ion beam direction. Increasing the distance between a positive potential surface (such as a high voltage solar array) and the thruster is the simplest way to control interactions. Both densities and currents vary as the inverse square of this distance.

  20. Charge exchange in fluid description of partially ionized plasmas

    CERN Document Server

    Vranjes, J; Luna, M

    2015-01-01

    The effects of charge exchange on waves propagating in weakly ionized plasmas are discussed. It is shown that for low-frequency processes, ions and neutrals should be treated as a single fluid with some effective charge on all of them. We have derived a new momentum equation which should be used in such an environment. As a result, the low-frequency magnetic waves can propagate even if particles are not magnetized, which is entirely due to the charge exchange and the fact that it is not possible to separate particles into two different populations as charged and neutral species. So there can be no friction force between ions and neutrals in the usual sense. The mean force per particle is proportional to the ionization ratio $n_i/(n_i+ n_n)$. Regarding the application of the theory to the Alfven wave propagation in the lower solar atmosphere, the results predict that the plane of displacement of the fluid must change by 90 degrees when an Alfven wave propagates from the area where particles are un-magnetized (...

  1. Interdefect charge exchange in silicon particle detectors at cryogenic temperatures

    CERN Document Server

    MacEvoy, B; Hall, G; Moscatelli, F; Passeri, D; Santocchia, A

    2002-01-01

    Silicon particle detectors in the next generation of experiments at the CERN Large Hadron Collider will be exposed to a very challenging radiation environment. The principal obstacle to long-term operation arises from changes in detector doping concentration (N/sub eff/), which lead to an increase in the bias required to deplete the detector and hence achieve efficient charge collection. We have previously presented a model of interdefect charge exchange between closely spaced centers in the dense terminal clusters formed by hadron irradiation. This manifestly non-Shockley-Read-Hall (SRH) mechanism leads to a marked increase in carrier generation rate and negative space charge over the SRH prediction. There is currently much interest in the subject of cryogenic detector operation as a means of improving radiation hardness. Our motivation, however, is primarily to investigate our model further by testing its predictions over a range of temperatures. We present measurements of spectra from /sup 241/Am alpha par...

  2. Exciting baryon resonances in isobar charge-exchange reactions

    Science.gov (United States)

    Benlliure, J.; Rodriguez-Sanchez, J. L.; Vargas, J.; Alavarez-Pol, H.; Aumann, T.; Atkinson, J.; Ayyad, Y.; Beceiro, S.; Boretzky, K.; Chatillon, A.; Cortina, D.; Diaz, P.; Estrade, A.; Geissel, H.; Lenske, H.; Litvinov, Y.; Mostazo, M.; Paradela, C.; Pietri, S.; Prochazka, A.; Takechi, M.; Vidaña, I.; Weick, H.; Winfield, J.

    2017-11-01

    Isobaric charge-exchange reactions induced by different tin isotopes have been investigated at GSI. The high-resolving power of the FRS spectrometer made it possible to separate elastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic component was associated to the in-medium excitation of nucleon resonances such as the Delta and Roper resonances. These data are expected to contribute to better understand the in-medium properties of baryon resonances but also to investigate the abundance of protons and neutrons at the nuclear periphery.

  3. Nucleon charge-exchange reactions at intermediate energy

    Energy Technology Data Exchange (ETDEWEB)

    Alford, W.P. [Western Ontario Univ., London, ON (Canada). Dept. of Physics]|[TRIUMF, Vancouver, BC (Canada); Spicer, B.M. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1997-12-31

    An historical review of the development of ideas pertaining to Gamow-Teller giant resonances is given, and a description of the emergence of techniques for the study of charge exchange reactions - particularly the technical advances which yielded the recent volume of new date. The present status of charge exchange reactions is reviewed and assessed. Evidence is presented from the {sup 14}C(p,n) reaction for the dominance of the spin-isospin component of the nucleon-nucleon interaction in intermediate energy reactions. In (p,n) reactions the Gamow-Teller giant resonance dominates the spectra, with higher multipoles contributing. By contrast, in (n,p) reactions in the heavier nuclei, the Gamow-Teller transitions are substantially Pauli-blocked and the spin dipole resonance dominates, with contributions from higher multipoles. Discussions of the multipole decomposition process, used to obtain from the data the contributions of the different multipoles, and the contributions of the multipoles, are given. 226 refs., 19 figs.

  4. Charge Exchange: Velocity Dependent X-ray Emission Modeling

    Science.gov (United States)

    Cumbee, Renata

    2017-06-01

    Atomic collisions play a fundamental role in astrophysics, plasma physics, and fusion physics. Here, we focus on charge exchange (CX) between hot ions and neutral atoms and molecules. Even though charge exchange calculations can provide vital information, including neutral and ion density distributions, ion temperatures, elemental abundances, and ion charge state distributions in the environments considered, both theoretical calculations and laboratory studies of these processes lack the necessary reliability and/or coverage. In order to better understand the spectra we observe in astrophysical environments in which both hot plasma and neutral gas are present, including comets, the heliosphere, supernova remnants, galaxy clusters, star forming galaxies, the outflows of starburst galaxies, and cooling flows of hot gas in the intracluster medium, a thorough CX X-ray model is needed. Included in this model should be a complete set of X-ray line ratios for relevant ion and neutral interactions for a range of energies.In this work, theoretical charge exchange emission spectra are produced using cross sections calculated with widely applied approaches including the quantum mechanical molecular orbital close coupling (QMOCC), atomic orbital close coupling (AOCC), classical trajectory Monte Carlo (CTMC), and the multichannel Landau-Zener (MCLZ) methods. When possible, theoretical data are benchmarked to experiments. Using a comprehensive, but still far from complete, CX database, new models are performed for a variety of X-ray emitting environments. In an attempt to describe the excess emission in X-rays of the starburst galaxy M82, Ne X CX line ratios are compared to line ratios observed in the region. A more complete XSPEC X-ray emission model is produced for H-like and He-like C-Al ions colliding with H and He for a range of energies; 200 to 5000 eV/u. This model is applied to the northeast rim of the Cygnus Loop supernova remnant in an attempt to determine the

  5. Anion exchangers with negatively charged functionalities in hyperbranched ion-exchange layers for ion chromatography.

    Science.gov (United States)

    Uzhel, Anna S; Zatirakha, Alexandra V; Smirnov, Konstantin N; Smolenkov, Alexandr D; Shpigun, Oleg A

    2017-01-27

    Novel pellicular poly(styrene-divinylbenzene)-based (PS-DVB) anion exchangers with covalently-bonded hyperbranched functional ion-exchange layers containing negatively charged functionalities are obtained and examined. The hyperbranched coating is created on the surface of aminated PS-DVB substrate by repeating the modification cycles including alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE), and amination of the terminal epoxide rings with methylamine (MA) or glycine (Gly). The influence of the position and the number of the layers with glycine, as well as of the total number of the layers of amine in the coating on the chromatographic properties of the obtained stationary phases is investigated. Chromatographic performance of the obtained stationary phases is evaluated using the model mixtures of inorganic and organic anions with hydroxide eluent. It is shown that the best selectivity toward weakly retained organic acids and oxyhalides is possessed by the anion exchanger obtained after 5 modification cycles, with glycine being used in the first one. Such anion exchanger packed in 25-cm long column is capable of separating 22 anions in 58min including 7 standard anions, mono-, di- and trivalent organic acids, oxyhalides, and some other double- and triple-charged anions. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Spermine Sepharose as a clustered-charge anion exchange adsorbent.

    Science.gov (United States)

    Dhamane, Sagar; Ruiz-Ruiz, Federico; Chen, Wen-hsiang; Kourentzi, Katerina; Benavides, Jorge; Rito-Palomares, Marco; Willson, Richard C

    2014-01-10

    We previously showed that the affinity and capacity of ion exchange adsorbents of a given total charge density are improved by immobilization of the charges in pre-ordered clusters, rather than individually in random locations. This previous work used pentalysinamide and pentaargininamide as clustered ligands. This approach allows close control of cluster size, but is uneconomically expensive for some research and most practical applications. In this work, we demonstrate that the inexpensive synthetic analog of the natural polyamine spermine (H2N-CH2-CH2-CH2-NH-CH2-CH2-CH2-CH2-NH-CH2-CH2-CH2-NH2) also can serve as the basis of effective clustered adsorbents. The calcium-depleted form of the protein α-lactalbumin, and RNA from baker's yeast, were adsorbed on a spermine Sepharose adsorbent. This adsorbent exhibited enhanced α-lactalbumin binding capacity (Qmax>1.6 and 1.3-fold higher than those for Qiagen DEAE and GE DEAE Sepharose adsorbents of much greater charge density) and higher initial binding affinity (Qmax/KD 2.4 and 2.1-fold higher, respectively). The new spermine-based matrix exhibited a higher value of the Z parameter, suggesting an increased number of apparent interaction sites between the protein and the resin, and functioned well in column mode. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Charge exchange spectroscopy as a fast ion diagnostic on TEXTOR

    DEFF Research Database (Denmark)

    Delabie, E.; Jaspers, R.J.E.; von Hellermann, M.G.

    2008-01-01

    for active spectroscopy, injected counter the direction in which fast ions injected by the first beam are circulating, we can simultaneously measure a fast ion tail on the blue wing of the D-alpha spectrum while the beam emission spectrum is Doppler shifted to the red wing. An analysis combining the two......An upgraded charge exchange spectroscopy diagnostic has been taken into operation at the TEXTOR tokamak. The angles of the viewing lines with the toroidal magnetic field are close to the pitch angles at birth of fast ions injected by one of the neutral beam injectors. Using another neutral beam...... parts of the spectrum offers possibilities to improve the accuracy of the absolute (fast) ion density profiles. Fast beam modulation or passive viewing lines cannot be used for background subtraction on this diagnostic setup and therefore the background has to be modeled and fitted to the data together...

  8. H^{-} charge-exchange injection without hazardous stripping foils

    Directory of Open Access Journals (Sweden)

    Isao Yamane

    1998-09-01

    Full Text Available A new scheme of H^{-} charge-exchange injection without stripping foils is proposed. It is composed of a neutralizer of the H^{-} beam using Lorentz stripping, the colliding system of a high power laser and the H^{0} beam to excite H^{0} atoms to the 3P state using the Rabi oscillation, and a magnet to strip the H^{0}(3P to a proton beam by Lorentz stripping. The necessary laser wavelength, laser power, magnetic-field gradient, and maximum magnetic field are estimated for a beam energy from 1.0 to 3.0 GeV. The result shows that such a scheme is sufficiently feasible for H^{-} beams with an energy discussed here.

  9. Charge Exchange Cross Sections Measured at Low Energies in Q-Machines

    DEFF Research Database (Denmark)

    Andersen, S. A.; Jensen, Vagn Orla; Michelsen, Poul

    1972-01-01

    A new technique for measurements of charge exchange cross sections at low energies is described. The measurements are performed in a single‐ended Q machine. The resonance charge exchange cross section for Cs at 2 eV was found to be 0.6×10−13 cm2±20%.......A new technique for measurements of charge exchange cross sections at low energies is described. The measurements are performed in a single‐ended Q machine. The resonance charge exchange cross section for Cs at 2 eV was found to be 0.6×10−13 cm2±20%....

  10. XMM-Newton Observations of Solar Wind Charge Exchange Emission

    Science.gov (United States)

    Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

  11. Charge Reduction Potentials of Several Refrigerants Based on Experimentally Validated Micro-Channel Heat Exchangers Performance and Charge Model

    OpenAIRE

    Padilla Fuentes, Yadira; Hrnjak, Predrag S.

    2012-01-01

    This paper presents an experimentally validated simulation model developed to obtain accurate prediction of evaporator microchannel heat exchanger performance and charge. Effects of using various correlations are presented and discussed with focus on serpentine microchannel evaporators. Experiments with propane are used to validate the model. The experimentally validated model is used to compare the charge reduction potential of various refrigerants. The procedure for charge reduction analysi...

  12. Charge-exchange reactions with a secondary triton beam

    CERN Document Server

    Sherrill, B M; Austin, S M; Bazin, D; Berg, A; Berg, G P A; Caggiano, J; Daito, I; Fujimura, H; Fujita, Y; Fujiwara, M; Hara, K; Harakeh, M N; Jänecke, J; Kawabata, T; Navin, A; Roberts, D A; Steiner, M

    1999-01-01

    A secondary triton beam from fragmentation of 560-MeV alpha-particles has been used in a high-resolution (t, sup 3 He) charge-exchange experiment at intermediate bombarding energies. The experiment was carried out at the National Superconducting Cyclotron Laboratory using a sup 4 He beam from the K1200 cyclotron. The radioactive triton beam of (0.5-1.0)x10 sup 6 particles/s with a mean energy of 350 MeV was produced in a production target of the A1200 fragment separator and transported to the target position of the S800 magnetic spectrometer. Ray-tracing and dispersion-matching techniques were employed to detect sup 3 He particles from the sup 1 sup 2 C(t, sup 3 He) sup 1 sup 2 B reaction near 0 deg. . An energy resolution of DELTA E approx 160 keV or DELTA E/E approx 4.6x10 sup - sup 4 (FWHM) was achieved. This is an improvement over our previous results and opens the possibility for studying high-resolution (n,p)-type reactions at intermediate bombarding energies. (author)

  13. Toroidal charge exchange recombination spectroscopy measurements on MST

    Energy Technology Data Exchange (ETDEWEB)

    Magee, R. M.; Den Hartog, D. J.; Fiksel, G.; Kumar, S. T. A. [University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States); Craig, D. [Wheaton College, 501 College Avenue, Wheaton, Illinois 60187 (United States)

    2010-10-15

    Charge exchange recombination spectroscopy measurements of the poloidal component of the C{sup +6} temperature and flow in the Madison Symmetric Torus have been vital in advancing the understanding of the ion dynamics in the reversed field pinch. Recent work has expanded the diagnostic capability to include toroidal measurements. A new toroidal view overcomes a small signal-to-background ratio (5%-15%) to make the first localized measurements of the parallel component of the impurity ion temperature in the core of the reversed field pinch. The measurement is made possible through maximal light collection in the optical design and extensive atomic modeling in the fitting routine. An absolute calibration of the system allowed the effect of Poisson noise in the signal on line fitting to be quantified. The measurement is made by stimulating emission with a recently upgraded 50 keV hydrogen diagnostic neutral beam. Radial localization is {approx}4 cm{sup 2}, and good temporal resolution (100 {mu}s) is achieved by making simultaneous emission and background measurements with a high-throughput double-grating spectrometer.

  14. 76 FR 10498 - Exchange Visitor Program-Fees and Charges

    Science.gov (United States)

    2011-02-25

    ... finds that educational and cultural exchanges are both the cornerstone of U.S. public diplomacy and an... Cultural exchange program. Accordingly, 22 CFR part 62 is amended as follows: PART 62--EXCHANGE VISITOR..., 1977 Comp. p. 200; E.O. 12048 of March 27, 1978; 3 CFR, 1978 Comp. p. 168; the Illegal Immigration...

  15. Gain measurements of the Ca-Xe charge exchange system. [for UV lasers

    Science.gov (United States)

    Michels, C. J.; Chubb, D. L.

    1978-01-01

    Charge-exchange-pumped Ca(+) was studied for possible positive laser gain at 370.6 and 315.9 nm using an Xe MPD arc as the Xe(+) source. The present paper describes the MPD arc, the calcium injection system, the diagnostics for gain, and spontaneous emission measurements and results. No positive gain measurements were observed. A small Xe-Ca charge exchange cross section compared to He-metal laser systems charge exchange cross sections is the most probable reason why the result was negative.

  16. 75 FR 60674 - Exchange Visitor Program-Fees and Charges

    Science.gov (United States)

    2010-10-01

    ... entities to conduct educational and cultural exchange programs pursuant to a broad grant of authority provided by the Mutual Educational and Cultural Exchange Act of 1961, as amended (Fulbright- Hays Act), 22 U.S.C. 2451 et seq.; the Immigration and Nationality Act, 8 U.S.C. 1101(a)(15)(J); the Foreign...

  17. Surface Charge Visualization at Viable Living Cells.

    Science.gov (United States)

    Perry, David; Paulose Nadappuram, Binoy; Momotenko, Dmitry; Voyias, Philip D; Page, Ashley; Tripathi, Gyanendra; Frenguelli, Bruno G; Unwin, Patrick R

    2016-03-09

    Scanning ion conductance microscopy (SICM) is demonstrated to be a powerful technique for quantitative nanoscale surface charge mapping of living cells. Utilizing a bias modulated (BM) scheme, in which the potential between a quasi-reference counter electrode (QRCE) in an electrolyte-filled nanopipette and a QRCE in bulk solution is modulated, it is shown that both the cell topography and the surface charge present at cellular interfaces can be measured simultaneously at high spatial resolution with dynamic potential measurements. Surface charge is elucidated by probing the properties of the diffuse double layer (DDL) at the cellular interface, and the technique is sensitive at both low-ionic strength and under typical physiological (high-ionic strength) conditions. The combination of experiments that incorporate pixel-level self-referencing (calibration) with a robust theoretical model allows for the analysis of local surface charge variations across cellular interfaces, as demonstrated on two important living systems. First, charge mapping at Zea mays root hairs shows that there is a high negative surface charge at the tip of the cell. Second, it is shown that there are distinct surface charge distributions across the surface of human adipocyte cells, whose role is the storage and regulation of lipids in mammalian systems. These are new features, not previously recognized, and their implications for the functioning of these cells are highlighted.

  18. 78 FR 6263 - Exchange Visitor Program-Fees and Charges

    Science.gov (United States)

    2013-01-30

    ... Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) of 1996, Pub. L. 104-208, Div. C, 110... Exchange Act of 1961, as amended (Fulbright-Hays Act), 22 U.S.C. 2451 et seq.; the Immigration and...

  19. Charge exchange from D(n=2) atoms to low-Z receiver ions

    NARCIS (Netherlands)

    Hoekstra, R; Anderson, H; Bliek, FW; von Hellermann, M; Maggi, CF; Olson, RE; Summers, HP

    To elucidate the influence on charge-exchange Spectroscopy of metastable deuterium donors, the corresponding cross sections for state-selective charge transfer have been calculated using the classical trajectory Monte Carlo method. The cross sections for electron capture from D(n = 2) by fully

  20. X-ray Signature of Charge Exchange in the Spectra of L-shell Iron Ions

    Energy Technology Data Exchange (ETDEWEB)

    Beiersdorfer, P; Schweikhard, L; Liebisch, P; Brown, G V

    2007-01-05

    The X-ray signature of charge exchange between highly charged L-shell iron ions and neutral gas atoms was studied in the laboratory in order to assess its diagnostic utility. Significant differences with spectra formed by electron-impact excitation were observed. In particular, a strong enhancement was found of the emission corresponding to n {le} 4 {yields} n = 2 transitions relative to the n = 3 {yields} n = 2 emission. This enhancement was detectable even with relatively low-resolution X-ray instrumentation (E/{Delta}E {approx} 10) and may enable future identification of charge exchange as a line-formation mechanism in astrophysical spectra.

  1. Laboratory simulation of charge exchange-produced X-ray emission from comets.

    Science.gov (United States)

    Beiersdorfer, P; Boyce, K R; Brown, G V; Chen, H; Kahn, S M; Kelley, R L; May, M; Olson, R E; Porter, F S; Stahle, C K; Tillotson, W A

    2003-06-06

    In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory.

  2. Galvanic Cells: Anodes, Cathodes, Signs and Charges

    Science.gov (United States)

    Goodwin, Alan

    2011-01-01

    Electrochemistry is a difficult subject for students at school and beyond and even for their teachers. This article explores the difficult "truth" that, when a current flows from a galvanic cell, positive ions within the cell electrolyte move towards the electrode labelled positive. This seems to contravene the basic rule that like charges repel…

  3. Line reversal, SU$_{3}, and exchange degeneracy in K$\\pm$N charge exchange at 4 GeV/c

    CERN Document Server

    Elvekjaer, F

    1974-01-01

    The recent data on charge exchange reactions K/sup +/n to K/sup 0/p and K/sup -/p to K/sup 0/n are discussed. The data are shown to be consistent with SU/sub 3/ octet symmetry for helicity flip rho and A /sub 2/ quantum-number exchange. The sizeable breaking of line reversal symmetry is not consistent with the standard model which blames the s-channel helicity-non flip amplitude, while supposing that the flip amplitude is EXD and Regge pole like. A model of alpha broken EXD poles may work for the flip amplitude. (20 refs).

  4. Removal of charged micropollutants from water by ion-exchange polymers -- effects of competing electrolytes.

    Science.gov (United States)

    Bäuerlein, Patrick S; Ter Laak, Thomas L; Hofman-Caris, Roberta C H M; de Voogt, Pim; Droge, Steven T J

    2012-10-15

    A wide variety of environmental compounds of concern, e.g. pharmaceuticals or illicit drugs, are acids or bases that may predominantly be present as charged species in drinking water sources. These charged micropollutants may prove difficult to remove by currently used water treatment steps (e.g. UV/H(2)O(2), activated carbon (AC) or membranes). We studied the sorption affinity of some ionic organic compounds to both AC and different charged polymeric materials. Ion-exchange polymers may be effective as additional extraction phases in water treatment, because sorption of all charged compounds to oppositely charged polymers was stronger than to AC, especially for the double-charged cation metformin. Tested below 1% of the polymer ion-exchange capacity, the sorption affinity of charged micropollutants is nonlinear and depends on the composition of the aqueous medium. Whereas oppositely charged electrolytes do not impact sorption of organic ions, equally charged electrolytes do influence sorption indicating ion-exchange (IE) to be the main sorption mechanism. For the tested polymers, a tenfold increased salt concentration lowered the IE-sorption affinity by a factor two. Different electrolytes affect IE with organic ions in a similar way as inorganic ions on IE-resins, and no clear differences in this trend were observed between the sulphonated and the carboxylated cation-exchanger. Sorption of organic cations is five fold less in Ca(2+) solutions compared to similar concentrations of Na(+), while that of anionic compounds is three fold weaker in SO(4)(2-) solutions compared to equal concentrations of Cl(-). Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Transient response of a proton exchange membrane fuel cell

    Science.gov (United States)

    Weydahl, Helge; Møller-Holst, Steffen; Hagen, Georg; Børresen, Børre

    The transient response of a proton exchange membrane fuel cell (PEMFC) supplied with pure hydrogen and oxygen was investigated by load step measurements assisted by electrochemical impedance spectroscopy and chronoamperometry. Using an in-house designed resistance board, the uncontrolled response in both cell voltage and current upon step changes in a resistive load was observed. The PEMFC was found to respond quickly and reproducibly to load changes. The transient PEMFC response was limited by a cathodic charge transfer process with a potential-dependent response time. For load steps to high-current densitities, a second transient process with a constant response time was observed. This transient was offset from the charge transfer transient by a temporarily stable plateau. Results from chronoamperometry indicated that the second transient could be related to a diffusion process. Transient paths were plotted in the V- i diagram, matching a predicted pattern with overshooting cell voltage and current during a load step.

  6. Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra

    Science.gov (United States)

    Patch, R. W.; Lauver, M. R.

    1976-01-01

    Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

  7. Characterization of charge-exchange collisions between ultracold 6Li atoms and 40Ca+ ions

    Science.gov (United States)

    Saito, R.; Haze, S.; Sasakawa, M.; Nakai, R.; Raoult, M.; Da Silva, H.; Dulieu, O.; Mukaiyama, T.

    2017-03-01

    We investigate the energy dependence and the internal-state dependence of the charge-exchange collision cross sections in a mixture of 6Li atoms and 40Ca+ ions. Deliberately excited ion micromotion is used to control collision energy of atoms and ions. The energy dependence of the charge-exchange collision cross section obeys the Langevin model in the temperature range of the current experiment, and the measured magnitude of the cross section is correlated to the internal state of the 40Ca+ ions. Revealing the relationship between the charge-exchange collision cross sections and the interaction potentials is an important step toward the realization of the full quantum control of the chemical reactions at an ultralow-temperature regime.

  8. Study of the pd→→n{pp}s charge-exchange reaction using a polarised deuterium target

    Directory of Open Access Journals (Sweden)

    B. Gou

    2015-02-01

    Full Text Available The vector and tensor analysing powers, Ay and Ayy, of the pd→→n{pp}s charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the S01 state, here denoted by {pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q≥160 MeV/c. These data provide a good continuation of the earlier results at q≤140 MeV/c obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam.

  9. Charge exchange excitations in N not = Z nuclei: Vlasov and hydrodynamic equations

    Energy Technology Data Exchange (ETDEWEB)

    Lipparini, E.; Stringari, S.

    1987-06-01

    Macroscopic equations of motion for charge exchange reactions in N not = Z nuclei are derived starting from the time dependent Hartree-Fock theory. Application is made to the study of the dipole giant resonance in isospin channels and ..mu..- capture in N not = Z nuclei.

  10. A high etendue spectrometer suitable for core charge eXchange recombination spectroscopy on ITER

    NARCIS (Netherlands)

    Jaspers, R.J.E.; Scheffer, M.; Kappatou, A.; Valk, N.C.J. van der; Durkut, M.; Snijders, B.; Marchuk, O.; Biel, W.; Pokol, G.I.; Erdei, G.; Zoletnik, S.; Dunai, D.

    2012-01-01

    A feasibility study for the use of core charge exchange recombination spectroscopy on ITER has shown that accurate measurements on the helium ash require a spectrometer with a high etendue of 1mm 2sr to comply with the measurement requirements [S. Tugarinov, Rev. Sci. Instrum. 74, 2075

  11. Evidence of electron saddle swap oscillations in angular differential ion-atom charge exchange cross sections

    NARCIS (Netherlands)

    Otranto, S.; Blank, I.; Olson, R. E.; Hoekstra, R.

    2012-01-01

    State selective charge exchange processes in 1-10 keV/amu Ne8+ +Na(3s) collisions were measured by means of the magneto-optical trap recoil-ion momentum spectroscopy technique and compared to classical trajectory Monte Carlo calculations. We find that for electron capture to n-levels >= 10, the

  12. Conceptual design of the ITER upper port plug for charge exchange diagnostic

    NARCIS (Netherlands)

    Sadakov, S.; Baross, T.; Biel, W.; Borsuk, V.; Hawkes, N.; Hellermann, M. von; Gille, P.; Kiss, G.; Koning, J.; Knaup, M.; Klinkhamer, J.F.F.; Krasikov, Yu.; Litnovsky, A.; Neubauer, O.; Panin, A.

    2009-01-01

    A plug for the ITER core charge exchange recombination spectroscopy (core CXRS) is located in the upper port 3. It transfers the light emitted by interaction of plasma ions with the diagnostic neutral beam (DNB). The plug consists of a main shell, a shielding cassette and a retractable tube. The

  13. Pion Double Charge Exchange at 50 MeV on 14C

    Science.gov (United States)

    Navon, I.; Leitch, M. J.; Bryman, D. A.; Numao, T.; Schlatter, P.; Azuelos, G.; Poutissou, R.; Burnham, R. A.; Hasinoff, M.; Poutissou, J. M.; MacDonald, J. A.; Spuller, J. E.; Hargrove, C. K.; Mes, H.; Blecher, M.; Gotow, K.; Moinester, M.; Baer, H.

    1984-01-01

    The first measurement of pion double charge exchange at low energy is reported. The reaction 14C(π+,π-)14O was measured at an incident pion energy of 50 MeV. Differential cross sections of the double analog transition are given in the angular range 50°-120°. Strong nonanalog transitions were also observed.

  14. An Integrated Data Analysis model to determine ion effective charge from beam attenuation and charge exchange emission measurements

    Science.gov (United States)

    Nornberg, M. D.; den Hartog, D. J.; Reusch, L. M.

    2017-10-01

    We have created a forward model for charge-exchange impurity density measurements that incorporates neutral beam attenuation measurements self-consistently for determining the ion effective charge Zeff in MST PPCD plasmas. Detailed knowledge of Zeff is critical to determining the resistive dissipation of hot plasmas and requires knowledge of the impurity content and dynamics. Previously, Zeff profiles were determined from soft-x-ray brightness measurements by using charge-exchange impurity density measurements as prior information using an Integrated Data Analysis (IDA) method. The model is extended to include a self-consistent calculation of the neutral beam attenuation and includes measurements of the beam Doppler-shift spectrum and shine-through particle flux. Methods of experimental design are employed to calculate the information gained from different diagnostic combinations. The analysis shows that while attenuation measurements alone do not provide a unique impurity density measurement in the case of a multi-species inhomogeneous plasmas, they do provide a valuable measurement of the Zeff profile and constrain the range of contributing impurity densities. Supported by US DOE.

  15. Achievement of the charge exchange work diminishing of an internal combustion engine in part load

    Directory of Open Access Journals (Sweden)

    Stefan POSTRZEDNIK

    2012-01-01

    Full Text Available Internal combustion engines, used for driving of different cars, occurs not only at full load, but mostly at the part load. The relative load exchange work at the full (nominal engine load is significantly low. At the part load of the IC engine its energy efficiency ηe is significantly lower than in the optimal (nominal field range of the performance parameters. One of the numerous reasons of this effect is regular growing of the relative load exchange work of the IC engine. It is directly connected with the quantitative regulation method commonly used in the IC engines. From the thermodynamic point of view - the main reason of this effect is the throttling process (causing exergy losses occurring in the inlet and outlet channels. The known proposals for solving of this problem are based on applying of the fully electronic control of the motion of inlet, outlet valves and new reference cycles.The idea presented in the paper leads to diminishing the charge exchange work of the IC engines. The problem can be solved using presented in the paper a new concept of the reference cycle (called as eco-cycle of IC engine. The work of the engine basing on the eco-cycle occurs in two 3-stroke stages; the fresh air is delivered only once for both stages, but in range of each stage a new portion of fuel is burned. Normally the charge exchange occurs once during each engine cycle realized. Elaborated proposition bases on the elimination of chosen charge exchange processes and through this the dropping of the charge exchange work can be achieved.

  16. Transport, charge exchange and loss of energetic heavy ions in the earth's radiation belts - Applicability and limitations of theory

    Science.gov (United States)

    Spjeldvik, W. N.

    1981-01-01

    Computer simulations of processes which control the relative abundances of ions in the trapping regions of geospace are compared with observations from discriminating ion detectors. Energy losses due to Coulomb collisions between ions and exospheric neutrals are considered, along with charge exchange losses and internal charge exchanges. The time evolution of energetic ion fluxes of equatorially mirroring ions under radial diffusion is modelled to include geomagnetic and geoelectric fluctutations. Limits to the validity of diffusion transport theory are discussed, and the simulation is noted to contain provisions for six ionic charge states and the source effect on the radiation belt oxygen ion distributions. Comparisons are made with ion flux data gathered on Explorer 45 and ISEE-1 spacecraft and results indicate that internal charge exchanges cause the radiation belt ion charge state to be independent of source charge rate characteristics, and relative charge state distribution is independent of the radially diffusive transport rate below the charge state redistribution zone.

  17. Anion Exchange Capacity As a Mechanism for Deep Soil Carbon Storage in Variable Charge Soils

    Science.gov (United States)

    Dietzen, C.; James, J. N.; Ciol, M.; Harrison, R. B.

    2014-12-01

    Soil is the most important long-term sink for carbon (C) in terrestrial ecosystems, containing more C than plant biomass and the atmosphere combined. However, soil has historically been under-represented in C cycling literature, especially in regards to information about subsurface (>1.0 m) layers and processes. Previous research has indicated that Andisols with large quantities of noncrystalline, variable-charge minerals, including allophane, imogolite, and ferrihydrite, contain more C both in total and at depth than other soil types in the Pacific Northwest. The electrostatic charge of variable-charge soils depends on pH and is sometimes net positive, particularly in acid conditions, such as those commonly developed under the coniferous forests of the Pacific Northwest. However, even soils with a net negative charge may contain a mixture of negative and positive exchange sites and can hold some nutrient anions through the anion exchange capacity. To increase our understanding of the effects of variable-charge on soil organic matter stabilization, deep sampling is under way at the Fall River Long-Term Soil Productivity Site in western Washington. This site has a deep, well-drained soil with few rocks, which developed from weathered basalt and is classified as an Andisol of the Boistfort Series. Samples have been taken to a depth of 3 m at eight depth intervals. In addition to analyzing total soil C, these soils will be analyzed to determine functional groups present, cation exchange capacity, anion exchange capacity, and non-crystalline mineral content. These data will be analyzed to determine any correlations that may exist between these mineralogical characteristics, total soil C, and types of functional groups stored at depth. The most abundant organic functional groups, including carboxylic and phenolic groups, are anionic in nature, and soil positive charge may play an important role in binding and stabilizing soil organic matter and sequestering C.

  18. Surfactant-mediated ion exchange and charge reversal at ionic liquid interfaces.

    Science.gov (United States)

    Chen, Lang G; Lerum, Ronald V; Aranda-Espinoza, Helim; Bermudez, Harry

    2010-09-09

    Room-temperature ionic liquids (ILs) exhibit a unique set of properties due to their charged character, presenting opportunities for numerous applications. Here, we show that the combination of charged surfactants with ILs leads to rich interfacial behavior due to the interplay between electrostatic and surface forces. Using traditional measures of surface activity and X-ray photoelectron spectroscopy (XPS), we find that sodium alkyl sulfates and alkyl trimethylammonium bromides are, indeed, surface-active at the air-IL interfaces of both [EMIM][EtSO(4)] and [BHEDMA][MeSO(3)]. XPS also reveals that surfactant counterions readily dissociate into the bulk, which when combined with the surfactant surface activity has striking consequences. We find that ion exchange occurs between surfactants and like-charged IL ions, with the greatest exchange for short surfactant alkyl chains. The initial negative surface charge of neat [EMIM][EtSO(4)] can be switched to positive by the addition of alkyl trimethylammonium bromides, with the effect most pronounced at short chain lengths. By contrast, the surface charge of [BHEDMA][MeSO(3)] is largely unaffected by the added surfactants, suggesting a key role for the strength of ion-pairing within the IL. The results here illustrate a simple but effective means of manipulating IL interfacial properties.

  19. The coherent weak flavour charge of ordinary matter for neutrino-exchange forces

    Science.gov (United States)

    Segarra, Alejandro

    2017-09-01

    We study the long-range force arising between two aggregates of ordinary matter due to a neutrino-pair exchange, in the limit of zero neutrino mass. Even if matter is neutral of electric charge, it is charged for this weak force. The interaction is described in terms of a coherent charge, which we call the weak flavour charge of aggregated matter. For each one of the interacting aggregates, this charge depends on the neutrino flavour as Q_W{ν _e} = 2Z - N,Q_W{ν _μ } = Q_W{ν _τ } = - N, where Z is the number of protons and N the number of neutrons. Q_W{ν _e} depends explicitly on Z because of the charged current contribution to νee elastic scattering, while the N term in the three charges comes from the universal neutral current contribution. The effective potential describing this force is repulsive and decreases as r -5. Due to its specific behaviour on (Z, N) and r, this interaction is distinguishable from both gravitation and residual electromagnetic forces. As neutrinos are massive and mixed, this potential is valid for r ≲ 1/mν .

  20. Proton exchange membrane fuel cells modeling

    CERN Document Server

    Gao, Fengge; Miraoui, Abdellatif

    2013-01-01

    The fuel cell is a potential candidate for energy storage and conversion in our future energy mix. It is able to directly convert the chemical energy stored in fuel (e.g. hydrogen) into electricity, without undergoing different intermediary conversion steps. In the field of mobile and stationary applications, it is considered to be one of the future energy solutions.Among the different fuel cell types, the proton exchange membrane (PEM) fuel cell has shown great potential in mobile applications, due to its low operating temperature, solid-state electrolyte and compactness.This book pre

  1. ROSAT Observations of Solar Wind Charge Exchange with the Lunar Exosphere

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Benna, M.; Carter, J. A.; Cravens, T. E.; Hills, H. Kent; Hodges, R. R.; Kuntz, K. D.; Porter, F. Scott; Read, A.; hide

    2012-01-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the anti-solar direction. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the count rate increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere. Along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed. This technique can be used to explore the solar wind-lunar interaction.

  2. Analysing powers and spin correlations in deuteron–proton charge exchange at 726 MeV

    Directory of Open Access Journals (Sweden)

    S. Dymov

    2015-05-01

    Full Text Available The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td=726 MeV. By selecting two fast protons at low relative energy Epp, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron–proton charge-exchange amplitudes at a neutron kinetic energy of Tn≈12Td=363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both Epp and the momentum transfer. This lends broad support to the current neutron–proton partial wave solution that was used in the estimation.

  3. Charge-Exchange Neutral Particle Analyzer Diagnostic of TJ-II

    Energy Technology Data Exchange (ETDEWEB)

    Fontdecaba, J. M.; Balbin, R.; Petrov, S.; TJ-II team

    2003-07-01

    A description of the Charge Exchange Neutral Particle Analyzers in operation in the heliac flexible TJ-II is reported. A description of the detectors, as well as the operation characteristics, hardware and software used in the control and analysis of the data obtained with the diagnostic is detailed. Two NPAs are in operation in TJ-II. One of them is a 5-channel analyzer and another one is an Acord-12. The 5-channel analyzer provides measurements of charge exchange neutral fluxes at five energy channels, whereas the Acord-12 can measure simultaneously two different hydrogen isotopes (H and D) at six energy channels. Their lines of sight can be varied poloidally in order to observe the different sections of the plasma. (Author) 10 refs.

  4. Charge exchange contamination of CRIT-II barium CIV experiment. [critical ionization velocity in ionosphere

    Science.gov (United States)

    Swenson, G. R.; Mende, S. B.; Meyerott, R. E.; Rairden, R. L.

    1991-01-01

    Experiments have been recently performed which attempted to confirm critical ionization velocity (CIV) ionization by deploying chemicals at high velocity in the ionosphere. Specifically, the CRIT-II rocket performed a barium release in the ionosphere, where observations of Ba(+) resonant emissions following the release are believed to have resulted from the CIV process. Calculations are presented which suggest a significant fraction (if not all) of the Ba(+) observed likely resulted from charge exchange with the thermosphere ions and not through CIV processes. The results presented here are pertinent to other CIV experiments performed in the ionosphere. It is recommended that laboratory measurements should be made of the charge exchange cross section between O(+) and Ba as well as other metal vapors used in CIV experiments.

  5. Simulation of charge exchange neutrals interactions with gaps in first wall cladding

    Energy Technology Data Exchange (ETDEWEB)

    Kurnaev, V.A. [Moscow Engineering and Physics Institute, Kashirskoe sh. 31, 115409 Moscow (Russian Federation)]. E-mail: kurnaev@plasma.mephi.ru; Matveev, D.I. [Moscow Engineering and Physics Institute, Kashirskoe sh. 31, 115409 Moscow (Russian Federation); Trifonov, N.N. [Moscow Engineering and Physics Institute, Kashirskoe sh. 31, 115409 Moscow (Russian Federation)

    2007-06-15

    Angular distributions of particles impinging PFC in fusion devices with magnetic confinement are briefly discussed. It is shown that simulation of charge exchange neutrals interaction with the first wall should be made for inclined incidence of particles. Particle reflection coefficients and sputtering yields for gaps in Be, C and W first wall cladding are found with Monte Carlo computer simulations for hydrogen isotopes in the energy range {approx}5-5 x 10{sup 3} eV as well as for the flux integrated over the ITER charge exchange neutrals energy spectrum. Trapping of deuterons by the gap in the W wall increases two times (up to {approx}0.6) as compared with the flat surface, while trapping in the Be gap is close to unity. The influence of isotope mass on trapping and sputtering is shown to follow data for the flat surface. Roughness of gap sidewalls taken into account slightly contributes to calculated data.

  6. Measurement of charge exchange cross sections for highly charged xenon and thorium ions with molecular hydrogen in a Penning Ion Trap

    Energy Technology Data Exchange (ETDEWEB)

    Weinberg, G.M.

    1995-12-01

    Highly charged xenon (35+ to 46+) and thorium (72+ to 79+) ions were produced in an Electron Beam Ion Trap (EBIT). The ions were extracted from EBIT in a short pulse. Ions of one charge state were selected using an electromagnet. The ions were recaptured at low energy in a cryogenic Penning trap (RETRAP). As the ions captured electrons from molecular hydrogen, populations of the various charge states were obtained by measuring the image currents induced by the ions on the electrodes of the trap. Data on the number of ions in each charge state vs. time were compared to theoretical rate equations in order to determine the average charge exchange rates. These rates were compared to charge exchange rates of an ion with a known charge exchange cross section (Ar{sup 11+}) measured in a similar manner in order to determine the average charge exchange cross sections for the highly charged ions. The energy of interaction between the highly charged ions and hydrogen was estimated to be 4 eV in the center of mass frame. The mean charge exchange cross sections were 9 {times} 10{sup {minus}14} cm{sup 2} for Xe{sup 43+} to Xe{sup 46+} and 2 {times} 10{sup {minus}13} cm{sup 2} for Th{sup 73+} to Th{sup 79+}. Double capture was approximately 20--25% of the total for both xenon and thorium. A fit indicated that the cross sections were approximately proportional to q. This is consistent with a linear dependence of cross section on q within the measurement uncertainties.

  7. Macroscopic models for charge exchange reactions in N not = Z nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Stringari, S.; Lipparini, E.

    1987-10-19

    Vlasov equations in the isospin channels are derived in the framework of the time dependent Hartree-Fock theory. The local equilibrium (hydrodynamic) approximation is then considered and applied to study isovector giant resonances excited in charge exchange reactions and ..mu../sup -/ inclusive capture in N not = Z nuclei. The theoretical predictions well account for the observed energy splitting between different isospin fragments and for the quenching of the ..delta..T/sub Z/ = +1 strength.

  8. Pion double charge exchange at 50 MeV on /sup 14/C

    Energy Technology Data Exchange (ETDEWEB)

    Navon, I.; Leitch, M.J.; Bryman, D.A.; Numao, T.; Schlatter, P.; Azuelos, G.; Poutissou, R.; Burnham, R.A.; Hasinoff, M.; Poutissou, J.M.

    1984-01-09

    The first measurement of pion double charge exchange at low energy is reported. The reaction /sup 14/C(..pi../sup +/,..pi../sup -/) /sup 14/O was measured at an incident pion energy of 50 MeV. Differential cross sections of the double analog transition are given in the angular range 50/sup 0/--120/sup 0/. Strong nonanalog transitions were also observed.

  9. USING KAPPA FUNCTIONS TO CHARACTERIZE OUTER HELIOSPHERE PROTON DISTRIBUTIONS IN THE PRESENCE OF CHARGE-EXCHANGE

    Energy Technology Data Exchange (ETDEWEB)

    Zirnstein, E. J.; McComas, D. J., E-mail: ezirnstein@swri.edu, E-mail: dmccomas@swri.edu [Southwest Research Institute, San Antonio, TX 78228 (United States)

    2015-12-10

    Kappa functions have long been used in the analysis and modeling of suprathermal particles in various space plasmas. In situ observations of the supersonic solar wind show its distribution contains a cold ion core and power-law tail, which is well-represented by a kappa function. In situ plasma observations by Voyager, as well as observations of energetic neutral atom (ENA) spectra by the Interstellar Boundary Explorer (IBEX), showed that the compressed and heated inner heliosheath (IHS) plasma beyond the termination shock can also be represented by a kappa function. IBEX exposes the IHS plasma properties through the detection of ENAs generated by charge-exchange in the IHS. However, charge-exchange modifies the plasma as it flows through the IHS, and makes it difficult to ascertain the parent proton distribution. In this paper we investigate the evolution of proton distributions, initially represented by a kappa function, that experience losses due to charge-exchange in the IHS. In the absence of other processes, it is no longer representable by a single kappa function due to the energy-dependent, charge-exchange process. While one can still fit a kappa function to the evolving proton distribution over limited energy ranges, this yields fitting parameters (pseudo-density, pseudo-temperature, pseudo-kappa index) that depend on the energy range of the fit. We discuss the effects of fitting a kappa function to the IHS proton distribution over limited energy ranges, its dependence on the initial proton distribution properties at the termination shock, and implications for understanding the observations.

  10. Moving Towards a State of the Art Charge-Exchange Reaction Code

    Science.gov (United States)

    Poxon-Pearson, Terri; Nunes, Filomena; Potel, Gregory

    2017-09-01

    Charge-exchange reactions have a wide range of applications, including late stellar evolution, constraining the matrix elements for neutrinoless double β-decay, and exploring symmetry energy and other aspects of exotic nuclear matter. Still, much of the reaction theory needed to describe these transitions is underdeveloped and relies on assumptions and simplifications that are often extended outside of their region of validity. In this work, we have begun to move towards a state of the art charge-exchange reaction code. As a first step, we focus on Fermi transitions using a Lane potential in a few body, Distorted Wave Born Approximation (DWBA) framework. We have focused on maintaining a modular structure for the code so we can later incorporate complications such as nonlocality, breakup, and microscopic inputs. Results using this new charge-exchange code will be shown compared to the analysis in for the case of 48Ca(p,n)48Sc. This work was supported in part by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through the U.S. DOE Cooperative Agreement No. DE- FG52-08NA2855.

  11. The role of electron capture and energy exchange of positively charged particles passing through matter

    CERN Document Server

    Ulmer, W

    2011-01-01

    The conventional treatment of the Bethe-Bloch equation for protons accounts for electron capture at the end of the projectile track by the small Barkas correction. This is only a possible way for protons, whereas for light and heavier charged nuclei the exchange of energy and charge along the track has to be accounted for by regarding the projectile charge q as a function of the residual energy. This leads to a significant modification of the Bethe-Bloch equation, otherwise the range in a medium is incorrectly determined. The LET in the Bragg peak domain and distal end is significantly influenced by the electron capture. A rather significant result is that in the domain of the Bragg peak the superiority of carbon ions is reduced compared to protons.

  12. Performance of the CERN PSB at 160 MeV with $H^{-}$ charge exchange injection

    CERN Document Server

    AUTHOR|(CDS)2084247; Santoni, Claudio

    As part of the LHC Injectors Upgrade Project, the CERN PS Booster (PSB) will be upgraded with a H- charge exchange injection system and its injection energy will be raised from 50 MeV to 160 MeV to obtain the beam brightness required for the LHC High-Luminosity Upgrade. Space charge effects like beam losses and transverse emittance blow-up at injection are expected to be the main limitations towards the achievement of the required high brightness. Studies of beam dynamics in presence of space charge in order to evaluate the performances of the PSB after the Upgrade have been performed. The first part of the work consists of measurements in the present machine, to study the effects of space charge and its interplay with resonances and to have a good set of data for code benchmarking. The code chosen for the beam tracking in presence of space charge is PTC-Orbit (and PyOrbit). Necessary numerical convergence studies are presented together with a benchmark with the PSB measurements. Once assessed the code and it...

  13. The charge-exchange induced coupling between plasma-gas counterflows in the heliosheath

    Directory of Open Access Journals (Sweden)

    H. J. Fahr

    2003-06-01

    Full Text Available Many hydrodynamic models have been presented which give similar views of the interaction of the solar wind plasma bubble with the counterstreaming partially ionized interstellar medium. In the more recent of these models it is taken into account that the solar and interstellar hydrodynamic flows of neutral atoms and protons are coupled by mass-, momentum-, and energy-exchange terms due to charge exchange processes. We shall reinvestigate the theoretical basis of this coupling here by use of a simplified description of the heliospheric interface and describe the main physics of the H-atom penetration through the more or less standing well-known plasma wall ahead of the heliopause. Thereby we can show that the type of charge exchange coupling terms used in up-to-now hydrodynamic treatments unavoidably leads to an O-type critical point at the sonic point of the H-atom flow, thus not allowing for a continuation of the integration of the hydrodynamic set of differential equations. The remedy for this problem is given by a more accurate formulation of the momentum exchange term for quasi-and sub-sonic H-atom flows. With a refined momentum exchange term derived from basic kinetic Boltzmann principles, we instead arrive at a characteristic equation with an X-type critical point, allowing for a continuous solution from supersonic to subsonic flow conditions. This necessitates that the often treated problem of the propagation of inter-stellar H-atoms through the heliosheath has to be solved using these newly derived, differently effective plasma – gas friction forces. Substantially different results are to be expected from this context for the filtration efficiency of the heliospheric interface.Key words. Interplanetary physics (heliopause and solar wind termination; interstellar gas – Ionosphere (plasma temperature and density

  14. The charge-exchange induced coupling between plasma-gas counterflows in the heliosheath

    Directory of Open Access Journals (Sweden)

    H. J. Fahr

    Full Text Available Many hydrodynamic models have been presented which give similar views of the interaction of the solar wind plasma bubble with the counterstreaming partially ionized interstellar medium. In the more recent of these models it is taken into account that the solar and interstellar hydrodynamic flows of neutral atoms and protons are coupled by mass-, momentum-, and energy-exchange terms due to charge exchange processes. We shall reinvestigate the theoretical basis of this coupling here by use of a simplified description of the heliospheric interface and describe the main physics of the H-atom penetration through the more or less standing well-known plasma wall ahead of the heliopause. Thereby we can show that the type of charge exchange coupling terms used in up-to-now hydrodynamic treatments unavoidably leads to an O-type critical point at the sonic point of the H-atom flow, thus not allowing for a continuation of the integration of the hydrodynamic set of differential equations. The remedy for this problem is given by a more accurate formulation of the momentum exchange term for quasi-and sub-sonic H-atom flows. With a refined momentum exchange term derived from basic kinetic Boltzmann principles, we instead arrive at a characteristic equation with an X-type critical point, allowing for a continuous solution from supersonic to subsonic flow conditions. This necessitates that the often treated problem of the propagation of inter-stellar H-atoms through the heliosheath has to be solved using these newly derived, differently effective plasma – gas friction forces. Substantially different results are to be expected from this context for the filtration efficiency of the heliospheric interface.

    Key words. Interplanetary physics (heliopause and solar wind termination; interstellar gas – Ionosphere (plasma temperature and density

  15. Development of Laboratory Experimental System to Clarify Solar Wind Charge Exchange Mechanism with TES Microcalorimeter

    Science.gov (United States)

    Enoki, T.; Ishisaki, Y.; Akamatsu, H.; Ezoe, Y.; Ohashi, T.; Kanda, T.; Ishida, T.; Tanuma, H.; Ohashi, H.; Shinozaki, K.; Mitsuda, K.

    2012-06-01

    Significant fraction of the cosmic diffuse soft X-ray emission (0.1-1 keV) is caused by the Solar Wind Charge eXchange (SWCX) process between the solar wind ion (C q+, N q+, O q+ etc.) and the interplanetary neutral matter. It is difficult to identify spectral features of SWCX with the spectral resolution of existing X-ray astronomy satellites. We are developing a laboratory experimental system with transition edge sensor (TES) X-ray microcalorimeters, in order to clarify the SWCX mechanism. This experiment is designed to measure Charge eXchange (CX) X-rays using Electron Cyclotron Resonance Ion Source (ECRIS) that generates multi-charged ions. Emission lines (OVIII: 2p→1s; 654 eV) by CX between O8+ and neutral He atom is aimed to be measured with energy resolution better than 10 eV. The TES microcalorimeter is cooled by a double-stage adiabatic demagnetization refrigerator (DADR), however, our TES microcalorimeter are not working potentially due to magnetic field contamination. This paper reports our experimental system, present results, and future prospects.

  16. Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR

    Science.gov (United States)

    Lee, Hyungho; Song, Eun-ji; Park, Young-dong; Oh, Soo-ghee; Ko, Won-Ha

    2011-06-01

    The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 Å (n = 8-7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device (CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2-4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

  17. Organic Charge Carriers for Perovskite Solar Cells.

    Science.gov (United States)

    Völker, Sebastian F; Collavini, Silvia; Delgado, Juan Luis

    2015-09-21

    The photovoltaic field is currently experiencing the "perovskite revolution". These materials have been known for decades, but only recently have they been applied in solid-state solar cells to obtain outstanding power conversion efficiencies. Given that the variety of perovskites used so far is limited, a lot of attention has been devoted to the development of suitable organic charge-transport materials to improve device performance. In this article, we will focus on the most promising materials able to transport electrons or holes from a structural point of view. Thereby, we focus on organic materials owing to their ease of preparation and manipulation, and this is nicely combined with the potential tuning of their properties through chemical synthesis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    Science.gov (United States)

    Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

    2010-04-01

    Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.

  19. Cometary X-rays. Solar wind charge exchange in cometary atmospheres

    Science.gov (United States)

    Bodewits, Dennis

    2007-06-01

    The interaction of the solar wind with the planets and the interstellar medium is of key importance for the evolution of our solar system. The interaction with Earth's atmosphere is best known for the northern light. In case of Mars, the interaction with the solar wind might have lead to the erosion of its atmosphere. Solar wind-atmosphere interactions can be studied particularly well in cometary atmospheres, because in that case the solar wind flow is not attenuated by a planetary magnetic field and interacts directly with its atmosphere, the coma. The size of the cometary atmosphere (in the order of 10(4-10^5) km) allows remote tracking of the ions as they penetrate into the comet's atmosphere, offering a unique window on the cometary atmosphere, the solar wind and the interaction of these two plasmas. When solar wind ions fly through an atmosphere they are neutralized via charge exchange reactions with the neutral gaseous species. These reactions depend strongly on target species and collision velocity. The resulting X-ray and Far-UV emission can therefore be regarded as a fingerprint of the underlying reaction, with many diagnostic qualities. My thesis studies have focussed on all aspects relevant for X-ray emission from comets: experimental studies of state-to-state charge exchange cross sections, observations of X-ray emission from comets with Chandra, XMM, and Swift, and theoretical modelling of the interaction of solar wind ions with cometary gasses and the resulting X-ray emission spectrum. Together, this has greatly improved our understanding of the interaction of the solar wind with solar system objects and in more general, of physical processes in wind-environment collisions. The thorough understanding of cometary charge exchange emission has opened the door to the direct observation of more complex solar wind interactions such as those with Mars and Venus.

  20. Thin Robust Anion Exchange Membranes for Fuel Cell Applications

    Science.gov (United States)

    2014-01-01

    provide inexpensive compact power from a wider variety of fuels than is possible with a proton exchange membrane ( PEM ) fuel cell , has continued to...complexity and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs...release; distribution is unlimited. (Invited) Thin Robust Anion Exchange Membranes for Fuel Cell Applications The views, opinions and/or findings

  1. Correlation between charge transfer and exchange coupling in carbon-based magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Anh Tuan, E-mail: tuanna@hus.edu.vn [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Science and Technology Department, Vietnam National University, Hanoi, 144 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan); Nguyen, Van Thanh; Nguyen, Huy Sinh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Pham, Thi Tuan Anh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, College of Hai Duong, Nguyen Thi Due, Hai Duong (Viet Nam); Do, Viet Thang [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, Haiphong University, 171 Phan Dang Luu, Kien An, Hai Phong (Viet Nam); Dam, Hieu Chi [Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan)

    2015-10-15

    Several forms of carbon-based magnetic materials, i.e. single radicals, radical dimers, and alternating stacks of radicals and diamagnetic molecules, have been investigated using density-functional theory with dispersion correction and full geometry optimization. Our calculated results demonstrate that the C{sub 31}H{sub 15} (R{sub 4}) radical has a spin of ½. However, in its [R{sub 4}]{sub 2} dimer structure, the net spin becomes zero due to antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, eight alternating stacks, R{sub 4}/D{sub 2m}/R{sub 4} (with m = 3-10), were designed. Our calculated results show that charge transfer (Δn) between R{sub 4} radicals and the diamagnetic molecule D{sub 2m} occurs with a mechanism of spin exchange (J) in stacks. The more electrons that transfer from R{sub 4} to D{sub 2m}, the stronger the ferromagnetic spin-exchange in stacks. In addition, our calculated results show that Δn can be tailored by adjusting the electron affinity (E{sub a}) of D{sub 2m}. The correlation between Δn, E{sub a}, m, and J is discussed. These results give some hints for the design of new ferromagnetic carbon-based materials.

  2. Correlation between charge transfer and exchange coupling in carbon-based magnetic materials

    Directory of Open Access Journals (Sweden)

    Anh Tuan Nguyen

    2015-10-01

    Full Text Available Several forms of carbon-based magnetic materials, i.e. single radicals, radical dimers, and alternating stacks of radicals and diamagnetic molecules, have been investigated using density-functional theory with dispersion correction and full geometry optimization. Our calculated results demonstrate that the C31H15 (R4 radical has a spin of ½. However, in its [R4]2 dimer structure, the net spin becomes zero due to antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, eight alternating stacks, R4/D2m/R4 (with m = 3-10, were designed. Our calculated results show that charge transfer (Δn between R4 radicals and the diamagnetic molecule D2m occurs with a mechanism of spin exchange (J in stacks. The more electrons that transfer from R4 to D2m, the stronger the ferromagnetic spin-exchange in stacks. In addition, our calculated results show that Δn can be tailored by adjusting the electron affinity (Ea of D2m. The correlation between Δn, Ea, m, and J is discussed. These results give some hints for the design of new ferromagnetic carbon-based materials.

  3. Phenomenological characteristics of absorption in charge- and hypercharge-exchange reactions

    CERN Document Server

    Sadoulet, B

    1973-01-01

    The author tries to explain in a unique framework charge- and hypercharge-exchange reactions above 3 GeV/c. His approach is based on exchange degenerate and SU(3) symmetric Regge poles to which absorption corrections are applied. In the absence of a firm theoretical basis for the corrections he adopts the approach of fixing the Regge poles through theoretical and phenomenological considerations; he then determines what kind of absorption he should apply. At intermediate energy (around 5 GeV/c) his results indicate complete absorption of the s-wave amplitude. Of the two terms 1 and e /sup -i pi alpha / of the Regge signature factor, the latter should be more strongly absorbed. This effect may explain especially the breaking of line-reversal symmetry for hypercharge-exchange reactions, pi /sup -/p to pi /sup 0/n polarization data, and the difference of peripherality of rho - omega and A/sub 2/-f/sub 0/ contributions. In addition, K-exchange in pp to Lambda Lambda has been studied. (50 refs).

  4. Observation of large enhancements of charge exchange cross sections with neutron-rich carbon isotopes

    Science.gov (United States)

    Tanihata, I.; Terashima, S.; Kanungo, R.; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Knoebel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Takechi, M.; Tanaka, J.; Toki, H.; Vargas, J.; Winfield, J. S.; Weick, H.

    2016-04-01

    Production cross sections of nitrogen isotopes from high-energy (˜ 950 MeV per nucleon) carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes (A = 12 to 19). The fragment separator FRS at GSI was used to deliver C-isotope beams. The cross sections of the production of N-isotopes were determined by charge measurements of forward-going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge-exchange (Cex) reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and/or Fermi transition strength at low excitation energies for neutron-rich carbon isotopes. It was also observed that the Cex cross sections were enhanced much more strongly for neutron-rich isotopes in the C-target data.

  5. Molecular (Feshbach) treatment of charge exchange Li/sup 3 +/+He collisions. II. Cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Errea, L.F.; Martin, F.; Mendez, L.; Riera, A.; Yanez, M.

    1986-05-15

    Using the wave functions calculated in the preceding article, and a common translation factor, the charge exchange cross section for the Li/sup 3 +/+He(1s/sup 2/) reaction is calculated, and the mechanism of the process discussed. We show how small deviations from the Landau--Zener model, which are unrelated to Nikitin's conditions for its validity, lead to a minimum of the cross section at an impact energy Eapprox. =1 keV, and to larger values of sigma at intermediate nuclear velocities.

  6. Towards hot electron mediated charge exchange in hyperthermal energy ion-surface interactions

    DEFF Research Database (Denmark)

    Ray, M. P.; Lake, R. E.; Thomsen, Lasse Bjørchmar

    2010-01-01

    We have made Na + and He + ions incident on the surface of solid state tunnel junctions and measured the energy loss due to atomic displacement and electronic excitations. Each tunnel junction consists of an ultrathin film metal–oxide–semiconductor device which can be biased to create a band of hot...... shows that the primary energy loss mechanism is the atomic displacement of Au atoms in the thin film of the metal–oxide–semiconductor device. We propose that neutral particle detection of the scattered flux from a biased device could be a route to hot electron mediated charge exchange....

  7. Excitation of Nucleon Resonances in Heavy-Ion Charge-Exchange Reactions

    Science.gov (United States)

    Benlliure, J.; Vargas, J.; Alvarez-Pol, H.; Aumann, T.; Atkinson, J.; Ayyad, Y.; Beceiro, S.; Borezky, K.; Chatillon, A.; Cortina, D.; Diaz, P.; Estrade, A.; Geissel, H.; Lenske, H.; Litvinov, Y.; Mostazo, M.; Paradela, C.; Pietri, S.; Prochazka, A.; Taieb, J.; Takechi, M.; Vidaña, I.; Weick, H.; Winfield, J.

    Isobaric charge-exchange reactions induced by different tin isotopes have been investigated at GSI. The high-resolving power of the FRS spectrometer made it possible to separate elastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic component was associated to the in-medium excitation of nucleon resonances such as the Delta and Roper resonances. These data are expected to contribute to better understand the role of subnuclear degrees of freedom in three body forces or the missing strength in Gamow-Teller transitions but also to investigate the abundance of protons and neutrons at the nuclear periphery.

  8. High resolution probe of coherence in low-energy charge exchange collisions with oriented targets

    CERN Document Server

    Leredde, A; Cassimi, A; Hennecart, D; Pons, B

    2013-01-01

    The trapping lasers of a magneto-optical trap (MOT) are used to bring Rb atoms into well defined oriented states. Coupled to recoil-ion momentum spectroscopy (RIMS), this yields a unique MOTRIMS setup which is able to probe scattering dynamics, including their coherence features, with unprecedented resolution. This technique is applied to the low-energy charge exchange processes Na$^+$+Rb($5p_{\\pm 1}$) $\\rightarrow$ Na($3p,4s$)+Rb$^+$. The measurements reveal detailed features of the collisional interaction which are employed to improve the theoretical description. All of this enables to gauge the reliability of intuitive pictures predicting the most likely capture transitions.

  9. A high etendue spectrometer suitable for core charge eXchange recombination spectroscopy on ITER

    Energy Technology Data Exchange (ETDEWEB)

    Jaspers, R. J. E.; Scheffer, M. [Science and Technology of Nuclear Fusion, Eindhoven University of Technology, Eindhoven (Netherlands); Kappatou, A. [FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Nieuwegein (Netherlands); Valk, N. C. J. van der; Durkut, M.; Snijders, B. [TNO Science and Industry, P.O. Box 155, 2600 AD Delft (Netherlands); Marchuk, O.; Biel, W. [Institut fuer Energie und Klimaforschung-IEK-4 Forschungszentrum, Juelich GmbH, 52425 Juelich (Germany); Pokol, G. I. [Institute of Nuclear Techniques, Budapest University of Technology and Economics, EURATOM Association, P. O. Box 91, H-1521 Budapest (Hungary); Erdei, G. [Department of Atomic Physics, Budapest University of Technology and Economics, EURATOM Association, P. O. Box 91, H-1521 Budapest (Hungary); Zoletnik, S.; Dunai, D. [WIGNER RCP, RMKI, EURATOM Association, P. O. Box 91, H-1521 Budapest (Hungary)

    2012-10-15

    A feasibility study for the use of core charge exchange recombination spectroscopy on ITER has shown that accurate measurements on the helium ash require a spectrometer with a high etendue of 1mm{sup 2}sr to comply with the measurement requirements [S. Tugarinov et al., Rev. Sci. Instrum. 74, 2075 (2003)]. To this purpose such an instrument has been developed consisting of three separate wavelength channels (to measure simultaneously He/Be, C/Ne, and H/D/T together with the Doppler shifted direct emission of the diagnostic neutral beam, the beam emission (BES) signal), combining high dispersion (0.02 nm/pixel), sufficient resolution (0.2 nm), high efficiency (55%), and extended wavelength range (14 nm) at high etendue. The combined measurement of the BES along the same sightline within a third wavelength range provides the possibility for in situ calibration of the charge eXchange recombination spectroscopy signals. In addition, the option is included to use the same instrument for measurements of the fast fluctuations of the beam emission intensity up to 2 MHz, with the aim to study MHD activity.

  10. Cold neutral atoms via charge exchange from excited state positronium: a proposal

    CERN Document Server

    Bertsche, W A; Eriksson, S

    2016-01-01

    We present a method for generating cold neutral atoms via charge exchange reactions between trapped ions and Rydberg positronium. The high charge exchange reaction cross section leads to efficient neutralisation of the ions and since the positronium-ion mass ratio is small, the neutrals do not gain appreciable kinetic energy in the process. When the original ions are cold the reaction produces neutrals that can be trapped or further manipulated with electromagnetic fields. Because a wide range of species can be targeted we envisage that our scheme may enable experiments at low temperature that have been hitherto intractable due to a lack of cooling methods. We present an estimate for achievable temperatures, neutral number and density in an experiment where the neutrals are formed at a milli-Kelvin temperature from either directly or sympathetically cooled ions confined on an ion chip. The neutrals may then be confined by their magnetic moment in a co-located magnetic minimum well also formed on the chip. We ...

  11. First measurement of the edge charge exchange recombination spectroscopy on EAST tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y. Y., E-mail: liyy@ipp.ac.cn; Fu, J.; Jiang, D.; Lyu, B.; Hu, C. D.; Wan, B. N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Yin, X. H.; Feng, S. Y. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); School of Nuclear Science and Technology, University of Science and Technology of China, Hefei (China); Shi, Y. J. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei (China); Department of Nuclear Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Yi, Y.; Ye, M. Y. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei (China); Zhou, X. J. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-11-15

    An edge toroidal charge exchange recombination spectroscopy (eCXRS) diagnostic, based on a heating neutral beam injection (NBI), has been deployed recently on the Experimental Advanced Superconducting Tokamak (EAST). The eCXRS, which aims to measure the plasma ion temperature and toroidal rotation velocity in the edge region simultaneously, is a complement to the exiting core CXRS (cCXRS). Two rows with 32 fiber channels each cover a radial range from ∼2.15 m to ∼2.32 m with a high spatial resolution of ∼5-7 mm. Charge exchange emission of Carbon VI CVI at 529.059 nm induced by the NBI is routinely observed, but can be tuned to any interested wavelength in the spectral range from 400 to 700 nm. Double-slit fiber bundles increase the number of channels, the fibers viewing the same radial position are binned on the CCD detector to improve the signal-to-noise ratio, enabling shorter exposure time down to 5 ms. One channel is connected to a neon lamp, which provides the real-time wavelength calibration on a shot-to-shot basis. In this paper, an overview of the eCXRS diagnostic on EAST is presented and the first results from the 2015 experimental campaign will be shown. Good agreements in ion temperature and toroidal rotation are obtained between the eCXRS and cCXRS systems.

  12. A high etendue spectrometer suitable for core charge eXchange recombination spectroscopy on ITERa)

    Science.gov (United States)

    Jaspers, R. J. E.; Scheffer, M.; Kappatou, A.; van der Valk, N. C. J.; Durkut, M.; Snijders, B.; Marchuk, O.; Biel, W.; Pokol, G. I.; Erdei, G.; Zoletnik, S.; Dunai, D.

    2012-10-01

    A feasibility study for the use of core charge exchange recombination spectroscopy on ITER has shown that accurate measurements on the helium ash require a spectrometer with a high etendue of 1mm2sr to comply with the measurement requirements [S. Tugarinov et al., Rev. Sci. Instrum. 74, 2075 (2003)], 10.1063/1.1537443. To this purpose such an instrument has been developed consisting of three separate wavelength channels (to measure simultaneously He/Be, C/Ne, and H/D/T together with the Doppler shifted direct emission of the diagnostic neutral beam, the beam emission (BES) signal), combining high dispersion (0.02 nm/pixel), sufficient resolution (0.2 nm), high efficiency (55%), and extended wavelength range (14 nm) at high etendue. The combined measurement of the BES along the same sightline within a third wavelength range provides the possibility for in situ calibration of the charge eXchange recombination spectroscopy signals. In addition, the option is included to use the same instrument for measurements of the fast fluctuations of the beam emission intensity up to 2 MHz, with the aim to study MHD activity.

  13. Cold neutral atoms via charge exchange from excited state positronium: a proposal

    Science.gov (United States)

    Bertsche, W. A.; Charlton, M.; Eriksson, S.

    2017-05-01

    We present a method for generating cold neutral atoms via charge exchange reactions between trapped ions and Rydberg positronium. The high charge exchange reaction cross section leads to efficient neutralisation of the ions and since the positronium-ion mass ratio is small, the neutrals do not gain appreciable kinetic energy in the process. When the original ions are cold the reaction produces neutrals that can be trapped or further manipulated with electromagnetic fields. Because a wide range of species can be targeted we envisage that our scheme may enable experiments at low temperature that have been hitherto intractable due to a lack of cooling methods. We present an estimate for achievable temperatures, neutral number and density in an experiment where the neutrals are formed at a milli-Kelvin temperature from either directly or sympathetically cooled ions confined on an ion chip. The neutrals may then be confined by their magnetic moment in a co-located magnetic minimum well also formed on the chip. We discuss general experimental requirements.

  14. Determination of plasma ion velocity distribution via charge-exchange recombination spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fonck, R.J.; Darrow, D.S.; Jaehnig, K.P.

    1983-12-01

    Spectroscopy of line radiation from plasma impurity ions excited by charge-exchange recombination reactions with energetic neutral beam atoms is rapidly becoming recognized as a powerful technique for measuring ion temperature, bulk plasma motion, impurity transport, and more exotic phenomena such as fast alpha particle distributions. In particular, this diagnostic offers the capability of obtaining space- and time-resolved ion temperature and toroidal plasma rotation profiles with relatively simple optical systems. Cascade-corrected excitation rate coefficients for use in both fully stripped impurity density studies and ion temperature measurements have been calculated to the principal ..delta..n = 1 transitions of He+, C/sup 5 +/, and O/sup 7 +/ with neutral beam energies of 5 to 100 keV/amu. A fiber optically coupled spectrometer system has been used on PDX to measure visible He/sup +/ radiation excited by charge exchange. Central ion temperatures up to 2.4 keV and toroidal rotation speeds up to 1.5 x 10/sup 7/ cm/s were observed in diverted discharges with P/sub INJ/ less than or equal to 3.0 MW.

  15. Effects of charged particles on human tumor cells

    Directory of Open Access Journals (Sweden)

    Kathryn D Held

    2016-02-01

    Full Text Available The use of charged particle therapy in cancer treatment is growing rapidly, in large part because the exquisite dose localization of charged particles allows for higher radiation doses to be given to tumor tissue while normal tissues are exposed to lower doses and decreased volumes of normal tissues are irradiated. In addition, charged particles heavier than protons have substantial potential clinical advantages because of their additional biological effects including greater cell killing effectiveness, decreased radiation resistance of hypoxic cells in tumors and reduced cell cycle dependence of radiation response. These biological advantages depend on many factors such as endpoint, cell or tissue type, dose, dose rate or fractionation, charged particle type and energy, and oxygen concentration. This review summarizes the unique biological advantages of charged particle therapy and highlights recent research and areas of particular research needs, such as quantification of Relative Biological Effectiveness (RBE for various tumor types and radiation qualities, role of genetic background of tumor cells in determining response to charged particles, sensitivity of cancer stem-like cells to charged particles, role of charged particles in tumors with hypoxic fractions and importance of fractionation, including use of hypofractionation, with charged particles.

  16. Solar wind charge exchange emission in the Chandra deep field north

    Energy Technology Data Exchange (ETDEWEB)

    Slavin, Jonathan D.; Wargelin, Bradford J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koutroumpa, Dimitra [LATMOS/IPSL, CNRS, Université Versailles Saint Quentin, 11 Boulevard d' Alembert, F-78280, Guyancourt (France)

    2013-12-10

    The diffuse soft X-ray background comes from distant galaxies, from hot Galactic gas, and from within the solar system. The latter emission arises from charge exchange between highly charged solar wind ions and neutral gas. This so-called solar wind charge exchange (SWCX) emission is spatially and temporally variable and interferes with our measurements of more distant cosmic emission while also providing important information on the nature of the solar wind-interstellar medium interaction. We present the results of our analysis of eight Chandra observations of the Chandra Deep Field North (CDFN) with the goal of measuring the cosmic and SWCX contributions to the X-ray background. Our modeling of both geocoronal and heliospheric SWCX emission is the most detailed for any observation to date. After allowing for ∼30% uncertainty in the SWCX emission and subtracting it from the observational data, we estimate that the flux of cosmic background for the CDFN in the O VII Kα, Kβ, and O VIII Lyα lines totals 5.8 ± 1.1 photons s{sup –1} cm{sup –2} sr{sup –1} (or LU). Heliospheric SWCX emission varied for each observation due to differences in solar wind conditions and the line of sight through the solar system, but was typically about half as strong as the cosmic background (i.e., one-third of the total) in those lines. The modeled geocoronal emission was 0.82 LU in one observation but averaged only 0.15 LU in the others. Our measurement of the cosmic background is lower than but marginally consistent with previous estimates based on XMM-Newton data.

  17. Design of a strong cation exchange methodology for the evaluation of charge heterogeneity in glatiramer acetate.

    Science.gov (United States)

    Campos-García, Víctor R; López-Morales, Carlos A; Benites-Zaragoza, Eleuterio; Jiménez-Miranda, Armando; Espinosa-de la Garza, Carlos E; Herrera-Fernández, Daniel; Padilla-Calderón, Jesús; Pérez, Néstor O; Flores-Ortiz, Luis F; Medina-Rivero, E

    2017-01-05

    Complex pharmaceuticals are in demand of competent analytical methods able to analyze charge heterogeneity as a critical quality attribute (CQA), in compliance with current regulatory expectations. A notorious example is glatiramer acetate (GA), a complex polypeptide mixture useful for the treatment of relapsing-remitting multiple sclerosis. This pharmaceutical challenges the current state of analytical technology in terms of the capacity to study their constituent species. Thus, a strong cation exchange methodology was designed under the lifecycle approach to support the establishment of GA identity, trough the evaluation of its chromatographic profile, which acts as a charge heterogeneity fingerprint. In this regard, a maximum relative margin of error of 5% for relative retention time and symmetry factor were proposed for the analytical target profile. The methodology met the proposed requirements after precision and specificity tests results, the former comprised of sensitivity and selectivity. Subsequently, method validation was conducted and showed that the method is able to differentiate between intact GA and heterogeneity profiles coming from stressed, fractioned or process-modified samples. In summary, these results provide evidence that the method is adequate to assess charge heterogeneity as a CQA of this complex pharmaceutical. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. The velocity dependence of X-ray emission due to Charge Exchange in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick Dean; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-01-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics for collisions of bare and H-like C to Al ions with H, He, and H2. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31This work was partially supported by NASA grant NNX09AC46G.

  19. Determining the maximum charging currents of lithium-ion cells for small charge quantities

    Science.gov (United States)

    Grimsmann, F.; Gerbert, T.; Brauchle, F.; Gruhle, A.; Parisi, J.; Knipper, M.

    2017-10-01

    In order to optimize the operating parameters of battery management systems for electric and hybrid vehicles, great interest has been shown in achieving the maximum permissible charging currents during recuperation, without causing a cell damage due to lithium plating, in relation to the temperature, charge quantity and state of charge. One method for determining these recuperation currents is measuring the cell thickness, where excessively high charging currents can be detected by an irreversible increase in thickness. It is not possible to measure particularly small charge quantities by employing mechanic dial indicators, which have a limited resolution of 1 μm. This is why we developed a measuring setup that has a resolution limit of less than 10 nm using a high-resolution contactless inductance sensor. Our results show that the permissible charging current I can be approximated in relation to the charge quantity x by a correlating function I =a /√{(x) } which is compliant with the Arrhenius law. Small charge quantities therefore have an optimization potential for energy recovery during recuperation.

  20. Charge-exchange, ionization and excitation in low-energy Li$^{+}-$ Ar, K$^{+}-$ Ar, and Na$^{+}-$He collisions

    CERN Document Server

    Lomsadze, Ramaz A; Kezerashvili, RomanYa; Schulz, Michael

    2016-01-01

    Absolute cross sections are measured for charge-exchange, ionization, and excitation within the same experimental setup for the Li$^{+}-$Ar, K$^{+}-$ Ar, and Na$^{+}-$ He collisions in the ion energy range $0.5-10$ keV. Results of our measurements along with existing experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes are realized with high probabilities and electrons are predominately captured in ground states. The cross section ratio for charge exchange, ionization and excitation processes roughly attains the value $10:2:1$, respectively. The contributions of various partial inelastic channels to the total ionization cross sections are estimated and a primary mechanism for the process is defined. The energy-loss spectrum, in addition, is applied to estimate the relative contribution of different inelastic channels and to determine the mechanisms for the ionization and f...

  1. Molecular (Feshbach) treatment of charge exchange Li/sup 3 +/+He collisions. I. Energies and couplings

    Energy Technology Data Exchange (ETDEWEB)

    Martin, F.; Riera, A.; Yanez, M.

    1986-05-15

    We point out a fundamental difference between the molecular treatment of charge exchange X/sup n/++H(1s) and X/sup n/++He(1s/sup 2/) collisions, which is that the latter process involves molecular states that are formally autoionizing. Then standard ab initio methods do not, in general, yield the relevant wave functions that are needed in the collision treatment, irrespective of whether quasimolecular autoionization be significant or not during the collision. We implement a particularly simple and useful form of the Feshbach formalism to calculate the energies of those two electron systems, and a method to evaluate the corresponding dynamical couplings is presented for the first time. Our implementation of this formalism together with the new computational techniques involved are presented in detail.

  2. Effect of injection energy on residual dose around the charge exchange foil

    Directory of Open Access Journals (Sweden)

    Kazami Yamamoto

    2012-12-01

    Full Text Available The rapid cycling synchrotron (RCS of Japan Proton Accelerator Research Complex (J-PARC and the accumulator ring (AR of Spallation Neutron Source (SNS can be used as high-power pulsed neutron sources. In both cases, the injection region becomes one of the highest activation areas in the ring. However, residual dose distributions have revealed that the highest activation points in the J-PARC RCS and the SNS AR are different in detail. The dose of the charge exchange chamber in the SNS is more than 100 times larger than that of the RCS though the ratio of beam power is less than 10. We investigated the reason of this difference by Geant4 and MARS, and the calculation results indicated that the difference was due to the dependence of the neutron and pion production rate on the injection energy.

  3. Final-state-resolved charge exchange in C5 + collisions with H

    Science.gov (United States)

    Nolte, J. L.; Stancil, P. C.; Liebermann, H. P.; Buenker, R. J.; Hui, Y.; Schultz, D. R.

    2012-12-01

    We report charge exchange cross sections for the collision system C5 + + H using the quantum mechanical molecular-orbital close-coupling method. The multi-reference single- and double-excitation configuration interaction method is used to produce potential and coupling data, and scattering calculations are performed for collision energies between 0.01 eV/u to 1 keV/u for all l,S-resolved states within the n = 3 and 4 manifolds. The n = 5 manifold is represented through the inclusion of the 5s state. To predict cross sections at higher energies, we include new results from atomic-orbital close-coupling and classical trajectory Monte Carlo calculations. We briefly discuss applications to x-ray emission within the solar system.

  4. Non-coherent contributions in charge-exchange reactions and η-η{sup '} mixing

    Energy Technology Data Exchange (ETDEWEB)

    Nekrasov, M.L. [NRC ' ' Kurchatov Institute' ' , Institute for High Energy Physics, Protvino (Russian Federation)

    2017-05-15

    We analyse K{sup -}p → (η,η{sup '},π{sup 0})Λ on the basis of the fit of data in a wide region of energies, and π{sup -}p → (η,η{sup '})n at the energies of GAMS-4π. We show that disagreements between the data and the predictions of Regge theory may be explained by the mode change of summation of intermediate contributions at increasing energy, from coherent to non-coherent. A method of experimental measurement of the non-coherent contributions is proposed. On the basis of available data on the charge-exchange reactions the η-η{sup '} mixing is estimated. (orig.)

  5. High efficiency laser-assisted H- charge exchange for microsecond duration beams

    Science.gov (United States)

    Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin; Aleksandrov, Alexander; Danilov, Viatcheslav; Gorlov, Timofey; Liu, Yun; Long, Cary; Menshov, Alexander; Plum, Michael; Shishlo, Andrei; Webster, Andrew; Johnson, David

    2017-12-01

    Laser-assisted stripping is a novel approach to H- charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. The experiment was performed on the Spallation Neutron Source 1 GeV H- beam using a 1 MW peak power UV laser and resulted in ˜95 % stripping efficiency.

  6. Review of cell performance in anion exchange membrane fuel cells

    Science.gov (United States)

    Dekel, Dario R.

    2018-01-01

    Anion exchange membrane fuel cells (AEMFCs) have recently received increasing attention since in principle they allow for the use of non-precious metal catalysts, which dramatically reduces the cost per kilowatt of power in fuel cell devices. Until not long ago, the main barrier in the development of AEMFCs was the availability of highly conductive anion exchange membranes (AEMs); however, improvements on this front in the past decade show that newly developed AEMs have already reached high levels of conductivity, leading to satisfactory cell performance. In recent years, a growing number of research studies have reported AEMFC performance results. In the last three years, new records in performance were achieved. Most of the literature reporting cell performance is based on hydrogen-AEMFCs, although an increasing number of studies have also reported the use of fuels others than hydrogen - such as alcohols, non-alcohol C-based fuels, as well as N-based fuels. This article reviews the cell performance and performance stability achieved in AEMFCs through the years since the first reports in the early 2000s.

  7. Charge ordering and exchange bias behaviors in Co3O4 porous nanoplatelets and nanorings

    Science.gov (United States)

    Debnath, J. C.; Wang, Jianli; Zeng, R.

    2017-01-01

    We present the synthesis of α-Co3O4 porous nanoplatelets and hexagonal nanorings using microwave-assisted hydrothermal and conventional chemical reaction methods. The x-ray diffraction (XRD) and refinement analyses indicate the α-Co3O4 crystal structure, and the x-ray photoelectron spectrum (XPS) indicates the high purity of the samples. The M-T (including 1/χ-T) curves indicate an antiferromagnetic transition at about 35 K in both kind of samples but the interesting finding was made that a charge-ordered (CO) state appears at 250 K for the nanoplatelets sample whereas it is inattentive for the nanorings. The antiferromagnetic transition temperature TN is lower than that of the bulk α-Co3O4 single crystal due to the nanosized structures. We observed quite significant exchange bias for nanorings. The exchange bias behavior of the α-Co3O4 hexagonal nanorings is consistent with an antiferromagnetic (AFM) Co3O4 core and spin-glass like shell.

  8. Most exchange plans charge lower tobacco surcharges than allowed, but many tobacco users lack affordable coverage.

    Science.gov (United States)

    Kaplan, Cameron M; Graetz, Ilana; Waters, Teresa M

    2014-08-01

    Beginning in 2014, federal guidelines for health plans sold to people in the individual market allow insurers to charge tobacco users up to 50 percent more for premiums, compared to nonusers. We examined variations in tobacco surcharges for plans offered through the state and federal health insurance exchanges, or Marketplaces. The plan with the median surcharge had only 10 percent higher premiums for tobacco users compared to nonusers, and nine in ten plans charged a lower surcharge than allowed. Even with such lower-than-allowed surcharges, tobacco users lacked affordable coverage-defined as access to at least one plan with premiums of less than 8 percent of income after subsidies-in more states than did nonusers. Higher premiums could encourage tobacco users to opt out of coverage. Our results also suggest that the variation in tobacco surcharges may result in the sorting of tobacco users and nonusers into different plans. Project HOPE—The People-to-People Health Foundation, Inc.

  9. X-ray spectroscopic study of charge exchange phenomena in plasma-wall interaction

    Directory of Open Access Journals (Sweden)

    Renner O.

    2013-11-01

    Full Text Available Jets of energetic ions launched at laser-burnt-through foils represent an efficient tool for investigation of plasma interaction with solid surfaces (plasma-wall interaction, PWI and for description of transient phenomena occurring close to the walls. Highly charged ions approaching the secondary target interpenetrate the near surface layer, collide with the counter-propagating matter and capture a large number of electrons. This results in a creation of atoms in highly excited Rydberg states or hollow ions with multiple inner vacancies; plasma jet and target ions may also undergo charge exchange (CE processes. We report PWI experiments with Al/Si(PMMA and Al/C targets irradiated at normal or oblique laser incidence. The distinct dip structures observed in red wings of Al Lyγ self-emission is interpreted in terms of CE between C6+ and Al12+ in the near-wall zone. The spectroscopic identification of CE phenomena is supported by results of analytical and numerical calculations.

  10. Fast charge implications: Pack and cell analysis and comparison

    Science.gov (United States)

    Tanim, Tanvir R.; Shirk, Matthew G.; Bewley, Randy L.; Dufek, Eric J.; Liaw, Bor Yann

    2018-03-01

    This study investigates the effect of 50-kW (about 2C) direct current fast charging on a full-size battery electric vehicle's battery pack in comparison to a pack exclusively charged at 3.3 kW, which is the common alternating current Level 2 charging power level. Comparable scaled charging protocols are also independently applied to individual cells at three different temperatures, 20 °C, 30 °C, and 40 °C, to perform a comparative analysis with the packs. Dominant cell-level aging modes were identified through incremental capacity analysis and compared with full packs to gain a clear understanding of additional key factors that affect pack aging. While the cell-level study showed a minor impact on performance due to direct current fast charging, the packs showed a significantly higher rate of capacity fade under similar charging protocols. This indicates that pack-level aging cannot be directly extrapolated from cell evaluation. Delayed fast charging, completing shortly before discharge, was found to have less of an impact on battery degradation than conventional alternating current Level 2 charging.

  11. Modeling the Magnetospheric X-ray Emission from Solar Wind Charge Exchange with Verification from XMM-Newton Observations

    Science.gov (United States)

    2016-08-26

    Earth (i.e., hydrogen) to a heavy , high charge state, ion in the solarwind. The electron can be captured in an excited state and transition to lower... heavy ions , Geophys Res. Lett., 24, 105–109, doi:10.1029/96GL03780. Cravens, T. E. (2000), Heliospheric X-ray emission associated with charge transfer...quantifying charge exchange from other ions with emission lines around the 1 4 keV band have also been performed, though the lack of cross-sectional

  12. Overview on R&D and design activities for the ITER core charge exchange spectroscopy diagnostic system

    NARCIS (Netherlands)

    Biel, W.; Baross, T.; Bourauel, P.; Dunai, D.; Durkut, M.; Erdei, G.; Hawkes, N.; Hellermann, M. von; Hogenbirk, A.; Jaspers, R.; Kiss, G.; Klinkhamer, J.F.F.; Koning, J.F.; Kotov, V.; Krasikov, Y.; Krimmer, A.; Lischtschenko, O.; Litnovsky, A.; Marchuk, O.; Neubauer, O.; Offermanns, G.; Panin, A.; Patel, K.; Pokol, G.; Schrader, M.; Snijders, B.; Szabo, V.; Valk, N.J.C. van der; Voinchet, R.; Wolters, J.; Zoletnik, S.

    2011-01-01

    The ITER core charge exchange recombination spectroscopy (core CXRS) diagnostic system is designed to provide experimental access to various measurement quantities in the ITER core plasma such as ion densities, temperatures and velocities. The implementation of the approved CXRS diagnostic principle

  13. Impact of exact exchange in the description of the electronic structure of organic charge-transfer molecular crystals

    KAUST Repository

    Fonari, Alexandr

    2014-10-21

    We evaluate the impact that the amount of nonlocal Hartree-Fock (%HF) exchange included in a hybrid density functional has on the microscopic parameters (transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport in high-mobility organic crystals. We consider both crystals based on a single molecule, such as pentacene, and crystals based on mixed-stack charge-transfer systems, such as dibenzo-TTF–TCNQ. In the pentacene crystal, the band gap decreases and the effective masses increase linearly with an increase in the amount of %HF exchange. In contrast, in the charge-transfer crystals, while the band gap increases linearly, the effective masses vary only slightly with an increase in %HF exchange. We show that the superexchange nature of the electronic couplings in charge-transfer systems is responsible for this peculiar evolution of the effective masses. We compare the density functional theory results with results obtained within the G0W0 approximation as a way of benchmarking the optimal amount of %HF exchange needed in a given functional.

  14. Classification of solar cells according to mechanisms of charge separation and charge collection.

    Science.gov (United States)

    Kirchartz, Thomas; Bisquert, Juan; Mora-Sero, Ivan; Garcia-Belmonte, Germà

    2015-02-14

    In the last decade, photovoltaics (PV) has experienced an important transformation. Traditional solar cells formed by compact semiconductor layers have been joined by new kinds of cells that are constituted by a complex mixture of organic, inorganic and solid or liquid electrolyte materials, and rely on charge separation at the nanoscale. Recently, metal organic halide perovskites have appeared in the photovoltaic landscape showing large conversion efficiencies, and they may share characteristics of the two former types. In this paper we provide a general description of the photovoltaic mechanisms of the single absorber solar cell types, combining all-inorganic, hybrid and organic cells into a single framework. The operation of the solar cell relies on a number of internal processes that exploit internal charge separation and overall charge collection minimizing recombination. There are two main effects to achieve the required efficiency, first to exploit kinetics at interfaces, favouring the required forward process, and second to take advantage of internal electrical fields caused by a built-in voltage and by the distribution of photogenerated charges. These principles represented by selective contacts, interfaces and the main energy diagram, form a solid base for the discussion of the operation of future types of solar cells. Additional effects based on ferroelectric polarization and ionic drift provide interesting prospects for investigating new PV effects mainly in the perovskite materials.

  15. Ballard: leading the fuel cell charge

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1999-10-01

    This article outlines the role of Ballard Power Systems in the development of fuel cells, and their strategy in concentrating on fuel cells for cars, buses, trucks, and stationary and portable power plants. Market drivers; costs; the concept of a fuel cell as a component of a power plant, and customers and competition are discussed. California's fuel cell partnership for testing fuel cell vehicles, the shrinking of fuel cell sizes and weights, aspects of piracy and copyright, and fuel types and sources are examined. (UK)

  16. Mechanistic modeling of ion-exchange process chromatography of charge variants of monoclonal antibody products.

    Science.gov (United States)

    Kumar, Vijesh; Leweke, Samuel; von Lieres, Eric; Rathore, Anurag S

    2015-12-24

    Ion-exchange chromatography (IEX) is universally accepted as the optimal method for achieving process scale separation of charge variants of a monoclonal antibody (mAb) therapeutic. These variants are closely related to the product and a baseline separation is rarely achieved. The general practice is to fractionate the eluate from the IEX column, analyze the fractions and then pool the desired fractions to obtain the targeted composition of variants. This is, however, a very cumbersome and time consuming exercise. A mechanistic model that is capable of simulating the peak profile will be a much more elegant and effective way to make a decision on the pooling strategy. This paper proposes a mechanistic model, based on the general rate model, to predict elution peak profile for separation of the main product from its variants. The proposed approach uses inverse fit of process scale chromatogram for estimation of model parameters using the initial values that are obtained from theoretical correlations. The packed bed column has been modeled along with the chromatographic system consisting of the mixer, tubing and detectors as a series of dispersed plug flow and continuous stirred tank reactors. The model uses loading ranges starting at 25% to a maximum of 70% of the loading capacity and hence is applicable to process scale separations. Langmuir model has been extended to include the effects of salt concentration and temperature on the model parameters. The extended Langmuir model that has been proposed uses one less parameter than the SMA model and this results in a significant ease of estimating the model parameters from inverse fitting. The proposed model has been validated with experimental data and has been shown to successfully predict peak profile for a range of load capacities (15-28mg/mL), gradient lengths (10-30CV), bed heights (6-20cm), and for three different resins with good accuracy (as measured by estimation of residuals). The model has been also

  17. Stimulated-healing of proton exchange membrane fuel cell catalyst

    NARCIS (Netherlands)

    Latsuzbaia, R.; Negro, E.; Koper, G.J.M.

    2013-01-01

    Platinum nanoparticles, which are used as catalysts in Proton Exchange Membrane Fuel Cells (PEMFC), tend to degrade after long-term operation. We discriminate the following mechanisms of the degradation: poisoning, migration and coalescence, dissolution, and electrochemical Ostwald ripening. There

  18. X-ray emission from the local hot bubble and solar wind charge exchange

    Science.gov (United States)

    Uprety, Youaraj

    DXL (Diffuse X-rays from the Local galaxy) is a sounding rocket mission to quantify the Solar Wind Charge Exchange (SWCX) X-ray emission in the interplanetary medium, and separate its contribution from the Local Hot Bubble (LHB) emission. The first launch of DXL took place in December 2012. This thesis will describe the DXL instrumentation and calibrations, and discuss the results obtained. The mission uses two large area proportional counters to scan through the Helium Focusing Cone (HFC), a high helium density region in the solar system emitting excess X-rays due to SWCX. Using well determined models of the interplanetary neutral distribution and comparing the DXL results with data from the same region obtained by the ROSAT satellite away from the cone, we calculated that SWCX contributes at most 36% to the ¼ keV ROSAT band and 13% to the ¾ keV ROSAT band, in the galactic plane. This provides a firm proof for existence of a LHB which dominates the Diffuse X-ray Background (DXB) at ¼ keV, while raising new questions on the origin of the ¾ keV emission.

  19. On the Experimental Investigation of the Clamping Pressure Effects on the Proton Exchange Membrane Water Electrolyser Cell Performance

    DEFF Research Database (Denmark)

    Al Shakhshir, Saher; Frensch, Steffen Henrik; Kær, Søren Knudsen

    2017-01-01

    energy sources. The proton exchange membrane water electrolyser(PEMWE) is the most candidate technology to produce hydrogen from renewable energysources. PEMWE cell splits water into hydrogen and oxygen when an electric current is passedthrough it. Electrical current forces the positively charged ions...

  20. Asymmetric intramembrane charge movement in mouse hippocampal pyramidal cells.

    Science.gov (United States)

    Chameau, P; Bournaud, R; Shimahara, T

    1995-12-08

    Intramembrane charge movement was recorded from freshly dissociated hippocampal pyramidal cells from mice using the whole cell clamp technique. Once the ionic currents were suppressed, a depolarizing pulse from a holding potential of -80 mV elicited a capacitive transient outward current at onset and a capacitive inward current at offset of the pulse. The amount of charge displaced at the onset of the pulse (Qon) was equivalent to the charge moved at repolarization (Qoff). The relationship between the amount of charge moved and pulse potential could be expressed by a simple two states Boltzmann equation: Q = Qmax/(1 + exp[-(V-V1/2)/k]), where Qmax is the maximum charge, V1/2 the membrane potential at which Q is half of Qmax and k is a slope factor. On average, Qmax was 10.90 +/- 0.62 nC/microF, V1/2 was 1.70 +/- 2.90 mV, and k was 18.80 +/- 1.20 mV (n = 16). Phenylglyoxal (10 mM), an arginine modifying reagent, reduced the maximum amount of charge movement to 14% of control. The inhibitory effect of phenylglyoxal was time dependent and the decline time course of maximum amount of charge movement could be fitted by a single exponential curve with a time constant of 5.79 min. The dihydropyridine (DHP) receptor antagonist, nifedipine, immobilized 54% of the charge movement. These results suggest that a part of the charge movement reflects the conformational change of the DHP receptors upon membrane depolarization.

  1. Charge exchange and X-ray emission in 70 MeV/u Bi-Au collisions

    Energy Technology Data Exchange (ETDEWEB)

    Verma, P. [GSI, D-64291 Darmstadt (Germany) and Vaish College, Rohtak 124 001 (India) and J. Liebig University, D-35392 Giessen (Germany)]. E-mail: P.Verma@gsi.de; Mokler, P.H. [GSI, D-64291 Darmstadt (Germany); JMI University, New Delhi 110 025 (India); Braeuning-Demian, A. [GSI, D-64291 Darmstadt (Germany); Braeuning, H. [JMI University, New Delhi 110 025 (India); Berdermann, E. [GSI, D-64291 Darmstadt (Germany); Chatterjee, S. [GSI, D-64291 Darmstadt (Germany); Gumberidze, A. [GSI, D-64291 Darmstadt (Germany); Hagmann, S. [J.W. Goethe University, D-60486 Frankfurt (Germany); Kozhuharov, C. [GSI, D-64291 Darmstadt (Germany); Orsic-Muthig, A. [GSI, D-64291 Darmstadt (Germany); Reuschl, R. [J.W. Goethe University, D-60486 Frankfurt (Germany); Schoeffler, M. [J.W. Goethe University, D-60486 Frankfurt (Germany); Spillmann, U. [GSI, D-64291 Darmstadt (Germany); Stoehlker, Th. [GSI, D-64291 Darmstadt (Germany); Stachura, Z. [Institute for Nuclear Physics, PL-31-342 Cracow (Poland); Tashenov, S. [GSI, D-64291 Darmstadt (Germany); Wahab, M.A. [Vaish College, Rohtak 124 001 (India)

    2005-07-01

    Charge exchange and X-ray emission for 70 MeV/u highly charged ions of Bi {sup q+} [77 q 82] colliding with thin Au targets [21 t in {mu}g/cm{sup 2} 225] were measured at the heavy ion synchrotron SIS at GSI. For the innermost shells this beam energy implies a quasiadiabatic collision regime. The charge state distribution of the emerging ions was measured by a position sensitive CVD-diamond detector after being analyzed by a magnet spectrometer. Charge exchange cross sections have been deduced from the target thickness dependence of the charge state distribution. Electron capture at distant collision dominates completely over ionization at close collision. The X-ray emission from the collision partners were measured by solid state detectors, Ge(i). The K X-ray emission for closed and open incoming projectile K vacancies gives access to vacancy transfer in the superheavy quasi-molecule transiently formed during collision for the innermost shells.

  2. Protein adsorption on ion exchange resins and monoclonal antibody charge variant modulation.

    Science.gov (United States)

    Guélat, Bertrand; Khalaf, Rushd; Lattuada, Marco; Costioli, Matteo; Morbidelli, Massimo

    2016-05-20

    A novel multicomponent adsorption equilibrium model for proteins on ion-exchange resins is developed on a statistical thermodynamic basis including surface coverage effects and protein-resin and protein-protein interactions. The resulting model exhibits a general competitive Langmuirian behavior and was applied to the study and optimization of the separation of monoclonal antibody charge variants on two strong cation exchangers. The model accounts explicitly for the effect of both pH and salt concentration, and its parameters can be determined in diluted conditions, that is, through physically sound assumptions, all model parameters can be obtained using solely experiments in diluted conditions, and be used to make predictions in overloaded conditions. The parameterization of the model and optimization of the separation is based on a two-step approach. First, gradient experiments in diluted conditions are undertaken in order to determine the model parameters. Based on these experiments and on information about the proteins of interest and the stationary phase used, all the model parameters can be estimated. Second, using the parameterized model, an initial Pareto optimization is undertaken where overloaded operating conditions are investigated. Experiments from this Pareto set are then used to refine the estimation of the model parameters. A second Pareto optimization can then be undertaken, this time with the refined parameters. This can be repeated until a satisfactory set of model parameters is found. This iterative approach is shown to be extremely efficient and to provide large amounts of knowledge based on only a few experiments. It is shown that due to the strong physical foundation of the model and the very low number of adjustable parameters, the number of iterations is expected to be at most two or three. Furthermore, the model based tool is improved as more experimental knowledge is provided, allowing for better estimations of the chromatographic

  3. Astrophysical Applications for Charge-Exchange with H, He, and H2 Targets

    Science.gov (United States)

    Cumbee, Renata S.; Mullen, Patrick D.; Shelton, Robin L.; Schultz, David R.; Stancil, Phillip C.

    2018-01-01

    When a hot plasma collides with a cold neutral gas, interactions occur between the constituents at the interface of the collision, including charge exchange (CX). CX is a process in which an electron can be transferred from a neutral atom or molecule into an excited energy level of an ion. Following this transfer, the excited electron relaxes to lower energy levels, emitting X-rays. This process has been established as a primary source of X-ray emission within our solar system, such as when the solar wind interacts with cometary and planetary atmospheres, and outside of our solar system, such as in the hot outflows of starburst galaxies.As the CX X-ray emission spectrum varies greatly with collision velocity, it is critical that realistic CX data are included in X-ray spectral models in regions in which CX might be significant so that the ion abundance and plasma velocities can be estimated most accurately. Here, a set of CX X-ray line ratios and spectra will be shown for a variety of collision velocities for C-Cl ions colliding with H, He, and H2. An X-ray emission model including these line ratios performed in XSPEC will be presented for a region of the Cygnus Loop supernova remnant and the starburst galaxy M82 in order to highlight the variation in CX spectral models with collision energy and neutral target species.R. Cumbee’s research was partially supported by an appointment to the NASA Postdoctoral Program at NASA GSFC, administered by Universities Space Research Association under contract with NASA. Work at UGA was partially supported by NASA grants NNX09AC46G and NNG09WF24I.

  4. Charge-exchange collision dynamics and ion engine grid geometry optimization

    Science.gov (United States)

    Morris, Bradford

    The development of a new three-dimensional model for determining the absolute energy distribution of ions at points corresponding to spacecraft surfaces to the side of an ion engine is presented. The ions resulting from elastic collisions, both charge-exchange (CEX) and direct, between energetic primary ions and thermal neutral xenon atoms are accounted for. Highly resolved energy distributions of CEX ions are found by integration over contributions from all points in space within the main beam formed by the primary ions.The sputtering rate due to impingement of these ions on a surface is calculated. The CEX ions that obtain significant energy (10 eV or more) in the collision are responsible for the majority of the sputtering, though this can depend on the specific material being sputtered. In the case of a molybdenum surface located 60 cm to the side of a 30 cm diameter grid, nearly 90% of the sputtering is due to the 5% of ions with the highest collision exit energies. Previous models that do not model collision energetics cannot predict this. The present results agree with other models and predict that the majority of the ion density is due to collisions where little to no energy is transferred.The sputtering model is combined with a grid-structure model in an optimization procedure where the sputtering rate at specified locations is minimized by adjustment of parameters defining the physical shape of the engine grids. Constraints are imposed that require that the deflection of the grid under a specified load does not exceed a maximum value, in order to ensure survivability of the grids during launch. To faciliate faster execution of the calculations, simplifications based on the predicted behavior of the CEX ions are implemented. For diametrically opposed sputtering locations, a rounded barrel-vault shape reduces the expected sputtering rate by up to 30% in comparison to an NSTAR-shaped grid.

  5. Heavy-ion double charge exchange reactions: A tool toward 0 νββ nuclear matrix elements

    Energy Technology Data Exchange (ETDEWEB)

    Cappuzzello, F.; Bondi, M. [Universita di Catania, Dipartimento di Fisica e Astronomia, Catania (Italy); INFN, Laboratori Nazionali del Sud, Catania (Italy); Cavallaro, M.; Agodi, C.; Carbone, D.; Cunsolo, A. [INFN, Laboratori Nazionali del Sud, Catania (Italy); Foti, A. [Universita di Catania, Dipartimento di Fisica e Astronomia, Catania (Italy); INFN, Sezione di Catania, Catania (Italy)

    2015-11-15

    The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial- and final-state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the {sup 40}Ca({sup 18}O,{sup 18}Ne){sup 40}Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0{sup +} → 0{sup +} transition to {sup 40}Ar{sub gs}, at least at very forward angles. (orig.)

  6. CrossRef Large numbers of cold positronium atoms created in laser-selected Rydberg states using resonant charge exchange

    CERN Document Server

    McConnell, R; Kolthammer, WS; Richerme, P; Müllers, A; Walz, J; Grzonka, D; Zielinski, M; Fitzakerley, D; George, MC; Hessels, EA; Storry, CH; Weel, M

    2016-01-01

    Lasers are used to control the production of highly excited positronium atoms (Ps*). The laser light excites Cs atoms to Rydberg states that have a large cross section for resonant charge-exchange collisions with cold trapped positrons. For each trial with 30 million trapped positrons, more than 700 000 of the created Ps* have trajectories near the axis of the apparatus, and are detected using Stark ionization. This number of Ps* is 500 times higher than realized in an earlier proof-of-principle demonstration (2004 Phys. Lett. B 597 257). A second charge exchange of these near-axis Ps* with trapped antiprotons could be used to produce cold antihydrogen, and this antihydrogen production is expected to be increased by a similar factor.

  7. Charge exchange recombination in X-ray spectra of He-like argon measured at the tokamak TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Schlummer, Tobias

    2014-06-16

    Charge exchange recombination between ions and atomic hydrogen is an important atomic process in magnetically confined fusion plasmas. Besides radiative cooling of the plasma edge, charge exchange causes modifications of the ionization balance and the population densities of excited ion states. The central goal of this work is to investigate the influence of charge exchange on X-ray spectra measured at the tokamak TEXTOR. A new 2D X-ray spectrometer developed for future use at the stellarator W7-X was recently installed at TEXTOR. The spectrometer is optimized for measuring the K{sub α}-spectrum of He-like argon (1s2l - 1s{sup 2}) at wavelengths close to 4 Aa. K{sub α}-spectroscopy on He-like impurity ions is an established diagnostic for electron and ion temperature measurements in fusion plasmas. Still, up to now the observed intensity ratios of the K{sub α}-lines and their associated satellites are not fully understood. They show significant deviations from the predictions made by basic corona models. In the past charge exchange with the neutral particle background and radial impurity transport have been discussed as likely explanations. Yet a detailed description of the experimental spectra still has not been achieved. To reconstruct the 2D K{sub α}-spectra measured at TEXTOR the radial argon ion distribution is modeled using an impurity transport code. The model accounts for charge exchange and transport on basis of given radial profiles of the neutral particle density n{sub 0}(r) and the diffusion coefficient D {sub perpendicular} {sub to} (r). The theoretical spectrum is then constructed based on the processes relevant for line emission. Within an iterative procedure n{sub 0}(r) and D {sub perpendicular} {sub to} (r) are varied until consistency between the theoretical and the experimental spectra is achieved. It is shown that the 2D K{sub α}-spectra allow a clear distinction of charge exchange and transport effects, ensuring unique solutions for n

  8. Charge carrier dynamics in thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Strothkaemper, Christian

    2013-06-24

    This work investigates the charge carrier dynamics in three different technological approaches within the class of thin film solar cells: radial heterojunctions, the dye solar cell, and microcrystalline CuInSe{sub 2}, focusing on charge transport and separation at the electrode, and the relaxation of photogenerated charge carriers due to recombination and energy dissipation to the phonon system. This work relies mostly on optical-pump terahertz-probe (OPTP) spectroscopy, followed by transient absorption (TA) and two-photon photoemission (2PPE). The charge separation in ZnO-electrode/In{sub 2}S{sub 3}-absorber core/shell nanorods, which represent a model system of a radial heterojunction, is analyzed by OPTP. It is concluded, that the dynamics in the absorber are determined by multiple trapping, which leads to a dispersive charge transport to the electrode that lasts over hundreds of picoseconds. The high trap density on the order of 10{sup 19}/cm{sup 3} is detrimental for the injection yield, which exhibits a decrease with increasing shell thickness. The heterogeneous electron transfer from a series of model dyes into ZnO proceeds on a time-scale of 200 fs. However, the photoconductivity builds up just on a 2-10 ps timescale, and 2PPE reveals that injected electrons are meanwhile localized spatially and energetically at the interface. It is concluded that the injection proceeds through adsorbate induced interface states. This is an important result because the back reaction from long lived interface states can be expected to be much faster than from bulk states. While the charge transport in stoichiometric CuInSe{sub 2} thin films is indicative of free charge carriers, CuInSe{sub 2} with a solar cell grade composition (Cu-poor) exhibits signs of carrier localization. This detrimental effect is attributed to a high density of charged defects and a high degree of compensation, which together create a spatially fluctuating potential that inhibits charge transport. On

  9. Optimum charge carrier mobility in organic solar cells

    NARCIS (Netherlands)

    Mandoc, M. M.; Koster, L. J. A.; Blom, P. W. M.

    2007-01-01

    In organic semiconductors the recombination mechanism is of the Langevin type, controlled by the mobility of the charge carriers. As a result, in organic solar cells the mobility simultaneously controls both the carrier extraction and the losses via carrier recombination. The authors demonstrate

  10. First successful automated red cell exchange (erythrocytapheresis ...

    African Journals Online (AJOL)

    INTRODUCTION: Despite several documented challenges, Hematopoietic Stem cell Transplantation (HSCT) remains the only curative therapy for Sickle Cell Disease (SCD). However HSCT is expensive with its complications, therefore supportive care remains the main available option to many Nigerians. Frequent blood ...

  11. Solar Wind Charge Exchange Contribution To The ROSAT Sky Survey Maps

    Science.gov (United States)

    Uprety, Y.; Chiao, M.; Collier, M. R.; Cravens, T.; Galeazzi, M.; Koutroumpa, D.; Kuntz, K. D.; Lallement, R.; Lepri, S. T.; Liu, W.; hide

    2016-01-01

    DXL (Diffuse X-ray emission from the Local Galaxy) is a sounding rocket mission designed to estimate the contribution of solar wind charge eXchange (SWCX) to the diffuse X-ray background and to help determine the properties of the Local Hot Bubble. The detectors are large area thin-window proportional counters with a spectral response that is similar to that of the PSPC (Position Sensitive Proportional Counters) used in the ROSAT All Sky Survey (RASS). A direct comparison of DXL and RASS data for the same part of the sky viewed from quite different vantage points in the solar system, and the assumption of approximate isotropy for the solar wind, allowed us to quantify the SWCX contribution to all six RASS bands (R1-R7, excluding R3). We find that the SWCX contribution at l = 140 degrees, b = 0 degrees, where the DXL path crosses the Galactic plane, is 33 percent plus or minus 6 percent (statistical) plus or minus 12 percent (systematic) for R1, 44 percent plus or minus 6 percent plus or minus 5 percent for R2, 18 percent plus or minus 12 percent plus or minus 11 percent for R4, 14 percent plus or minus 11 percent plus or minus 9 percent for R5, and negligible for the R6 and R7 bands. Reliable models for the distribution of neutral H and He in the solar system permit estimation of the contribution of interplanetary SWCX emission over the the whole sky and correction of the RASS maps. We find that the average SWCX contribution in the whole sky is 26 percent plus or minus 6 percent plus or minus 13 percent for R1, 30 percent plus or minus 4 percent plus or minus 4 percent for R2, 8 percent plus or minus 5 percent plus or minus 5 percent for R4, 6 percent plus or minus 4 percent plus or minus 4 percent for R5, and negligible for R6 and R7.

  12. Effect of collisions on dust particle charging via particle-in-cell Monte-Carlo collision

    Science.gov (United States)

    Rovagnati, B.; Davoudabadi, M.; Lapenta, G.; Mashayek, F.

    2007-10-01

    In this paper, the effect of collisions on the charging and shielding of a single dust particle immersed in an infinite plasma is studied. A Monte-Carlo collision (MCC) algorithm is implemented in the particle-in-cell DEMOCRITUS code to account for the collisional phenomena which are typical of dusty plasmas in plasma processing, namely, electron-neutral elastic scattering, ion-neutral elastic scattering, and ion-neutral charge exchange. Both small and large dust particle radii, as compared to the characteristic Debye lengths, are considered. The trends of the steady-state dust particle potential at increasing collisionality are presented and discussed. The ions and electron energy distributions at various locations and at increasing collisionality in the case of large particle radius are shown and compared to their local Maxwellians. The ion-neutral charge-exchange collision is found to be by far the most important collisional phenomenon. For small particle radius, collisional effects are found to be important also at low level of collisionality, as more ions are collected by the dust particle due to the destruction of trapped ion orbits. For large particle radius, the major collisional effect is observed to take place in proximity of the presheath. Finally, the species energy distribution functions are found to approach their local Maxwellians at increasing collisionality.

  13. Lipid exchange between Borrelia burgdorferi and host cells.

    Directory of Open Access Journals (Sweden)

    Jameson T Crowley

    2013-01-01

    Full Text Available Borrelia burgdorferi, the agent of Lyme disease, has cholesterol and cholesterol-glycolipids that are essential for bacterial fitness, are antigenic, and could be important in mediating interactions with cells of the eukaryotic host. We show that the spirochetes can acquire cholesterol from plasma membranes of epithelial cells. In addition, through fluorescent and confocal microscopy combined with biochemical approaches, we demonstrated that B. burgdorferi labeled with the fluorescent cholesterol analog BODIPY-cholesterol or (3H-labeled cholesterol transfer both cholesterol and cholesterol-glycolipids to HeLa cells. The transfer occurs through two different mechanisms, by direct contact between the bacteria and eukaryotic cell and/or through release of outer membrane vesicles. Thus, two-way lipid exchange between spirochetes and host cells can occur. This lipid exchange could be an important process that contributes to the pathogenesis of Lyme disease.

  14. Core-ion temperature measurement of the ADITYA tokamak using passive charge exchange neutral particle energy analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Santosh P.; Ajay, Kumar; Mishra, Priyanka; Dhingra, Rajani D.; Govindarajan, J. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India)

    2013-02-15

    Core-ion temperature measurements have been carried out by the energy analysis of passive charge exchange (CX) neutrals escaping out of the ADITYA tokamak plasma (minor radius, a= 25 cm and major radius, R= 75 cm) using a 45 Degree-Sign parallel plate electrostatic energy analyzer. The neutral particle analyzer (NPA) uses a gas cell configuration for re-ionizing the CX-neutrals and channel electron multipliers (CEMs) as detectors. Energy calibration of the NPA has been carried out using ion-source and {Delta}E/E of high-energy channel has been found to be {approx}10%. Low signal to noise ratio (SNR) due to VUV reflections on the CEMs was identified during the operation of the NPA with ADITYA plasma discharges. This problem was rectified by upgrading the system by incorporating the additional components and arrangements to suppress VUV radiations and improve its VUV rejection capabilities. The noise rejection capability of the NPA was experimentally confirmed using a standard UV-source and also during the plasma discharges to get an adequate SNR (>30) at the energy channels. Core-ion temperature T{sub i}(0) during flattop of the plasma current has been measured to be up to 150 eV during ohmically heated plasma discharges which is nearly 40% of the average core-electron temperature (typically T{sub e}(0) {approx} 400 eV). The present paper describes the principle of tokamak ion temperature measurement, NPA's design, development, and calibration along with the modifications carried out for minimizing the interference of plasma radiations in the CX-spectrum. Performance of the NPA during plasma discharges and experimental results on the measurement of ion-temperature have also been reported here.

  15. Trapped charge-driven degradation of perovskite solar cells

    Science.gov (United States)

    Ahn, Namyoung; Kwak, Kwisung; Jang, Min Seok; Yoon, Heetae; Lee, Byung Yang; Lee, Jong-Kwon; Pikhitsa, Peter V.; Byun, Junseop; Choi, Mansoo

    2016-01-01

    Perovskite solar cells have shown unprecedent performance increase up to 22% efficiency. However, their photovoltaic performance has shown fast deterioration under light illumination in the presence of humid air even with encapulation. The stability of perovskite materials has been unsolved and its mechanism has been elusive. Here we uncover a mechanism for irreversible degradation of perovskite materials in which trapped charges, regardless of the polarity, play a decisive role. An experimental setup using different polarity ions revealed that the moisture-induced irreversible dissociation of perovskite materials is triggered by charges trapped along grain boundaries. We also identified the synergetic effect of oxygen on the process of moisture-induced degradation. The deprotonation of organic cations by trapped charge-induced local electric field would be attributed to the initiation of irreversible decomposition. PMID:27830709

  16. Charge Exchange X-Ray Emission due to Highly Charged Ion Collisions with H, He, and H2: Line Ratios for Heliospheric and Interstellar Applications

    Science.gov (United States)

    Cumbee, R. S.; Mullen, P. D.; Lyons, D.; Shelton, R. L.; Fogle, M.; Schultz, D. R.; Stancil, P. C.

    2018-01-01

    The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, molecular-orbital close-coupling, and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H2 with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.

  17. Electronic circuit model for proton exchange membrane fuel cells

    Science.gov (United States)

    Yu, Dachuan; Yuvarajan, S.

    The proton exchange membrane (PEM) fuel cell is being investigated as an alternate power source for various applications like transportation and emergency power supplies. The paper presents a novel circuit model for a PEM fuel cell that can be used to design and analyze fuel cell power systems. The PSPICE-based model uses bipolar junction transistors (BJTs) and LC elements available in the PSPICE library with some modification. The model includes the phenomena like activation polarization, ohmic polarization, and mass transport effect present in a PEM fuel cell. The static and dynamic characteristics obtained through simulation are compared with experimental results obtained on a commercial fuel cell module.

  18. Removal of charged micropollutants from water by ion-exchange polymers - effects of competing electrolytes

    NARCIS (Netherlands)

    Bäuerlein, P.S.; ter Laak, T.L.; Hofman-Caris, R.C.H.M.; de Voogt, P.; Droge, S.T.J.

    2012-01-01

    A wide variety of environmental compounds of concern, e.g. pharmaceuticals or illicit drugs, are acids or bases that may predominantly be present as charged species in drinking water sources. These charged micropollutants may prove difficult to remove by currently used water treatment steps (e.g.

  19. Removal of charged micropollutants from water by ion-exchange polymers - Effects of competing electrolytes

    NARCIS (Netherlands)

    Bauerlein, P.S.; ter Laak, T.L.; Hofman-Caris, R.C.; Droge, S.T.J.

    2012-01-01

    A wide variety of environmental compounds of concern, e.g. pharmaceuticals or illicit drugs, are acids or bases that may predominantly be present as charged species in drinking water sources. These charged micropollutants may prove difficult to remove by currently used water treatment steps (e.g.

  20. Separation of Flip and Non-Flip parst of Charge Exchange np->pn at energies Tn = 0.5 - 2.0 GeV

    CERN Document Server

    Shindin, R A; Chernykh, E V; Guriev, D K; Nomofilov, A A; Prytkov, V Yu; Sharov, V I; Strunov, L I

    2008-01-01

    The new Delta-Sigma experimental data on the ratio $R_{dp}$ allowed separating the Flip and Non-Flip parts of the differential cross section of $np\\to pn$ charge exchange process at the zero angle by the Dean formula. The PSA solutions for the $np\\to np$ elastic scattering are transformed to the $np\\to pn$ charge exchange representation using unitary transition, and good agreement is obtain.

  1. Fuel cell ion-exchange membrane investigation

    Science.gov (United States)

    Toy, M. S.

    1972-01-01

    The present deficiencies in the fluorocarbon sulfonic acid membrane used as the solid polymer electrolyte in the H2/O2 fuel cell are studied. Considered are: Adhesives selection, elastomeric formulations, scavenger exploration, and membrane characterization. The significant data are interpreted and recommendations are given for both short and long range further investigations in two of the four major areas: membrane adhesives and membrane stabilization.

  2. Solar-induced direct biomass-to-electricity hybrid fuel cell using polyoxometalates as photocatalyst and charge carrier.

    Science.gov (United States)

    Liu, Wei; Mu, Wei; Liu, Mengjie; Zhang, Xiaodan; Cai, Hongli; Deng, Yulin

    2014-01-01

    The current polymer-exchange membrane fuel cell technology cannot directly use biomass as fuel. Here we present a solar-induced hybrid fuel cell that is directly powered with natural polymeric biomasses, such as starch, cellulose, lignin, and even switchgrass and wood powders. The fuel cell uses polyoxometalates as the photocatalyst and charge carrier to generate electricity at low temperature. This solar-induced hybrid fuel cell combines some features of solar cells, fuel cells and redox flow batteries. The power density of the solar-induced hybrid fuel cell powered by cellulose reaches 0.72 mW cm(-2), which is almost 100 times higher than cellulose-based microbial fuel cells and is close to that of the best microbial fuel cells reported in literature. Unlike most cell technologies that are sensitive to impurities, the cell reported in this study is inert to most organic and inorganic contaminants present in the fuels.

  3. Solar-induced direct biomass-to-electricity hybrid fuel cell using polyoxometalates as photocatalyst and charge carrier

    Science.gov (United States)

    Liu, Wei; Mu, Wei; Liu, Mengjie; Zhang, Xiaodan; Cai, Hongli; Deng, Yulin

    2014-02-01

    The current polymer-exchange membrane fuel cell technology cannot directly use biomass as fuel. Here we present a solar-induced hybrid fuel cell that is directly powered with natural polymeric biomasses, such as starch, cellulose, lignin, and even switchgrass and wood powders. The fuel cell uses polyoxometalates as the photocatalyst and charge carrier to generate electricity at low temperature. This solar-induced hybrid fuel cell combines some features of solar cells, fuel cells and redox flow batteries. The power density of the solar-induced hybrid fuel cell powered by cellulose reaches 0.72 mW cm-2, which is almost 100 times higher than cellulose-based microbial fuel cells and is close to that of the best microbial fuel cells reported in literature. Unlike most cell technologies that are sensitive to impurities, the cell reported in this study is inert to most organic and inorganic contaminants present in the fuels.

  4. Charge carrier recombination dynamics in perovskite and polymer solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paulke, Andreas; Kniepert, Juliane; Kurpiers, Jona; Wolff, Christian M.; Schön, Natalie; Brenner, Thomas J. K.; Neher, Dieter [Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476, Potsdam (Germany); Stranks, Samuel D. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Snaith, Henry J. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2016-03-14

    Time-delayed collection field experiments are applied to planar organometal halide perovskite (CH{sub 3}NH{sub 3}PbI{sub 3}) based solar cells to investigate charge carrier recombination in a fully working solar cell at the nanosecond to microsecond time scale. Recombination of mobile (extractable) charges is shown to follow second-order recombination dynamics for all fluences and time scales tested. Most importantly, the bimolecular recombination coefficient is found to be time-dependent, with an initial value of ca. 10{sup −9} cm{sup 3}/s and a progressive reduction within the first tens of nanoseconds. Comparison to the prototypical organic bulk heterojunction device PTB7:PC{sub 71}BM yields important differences with regard to the mechanism and time scale of free carrier recombination.

  5. Ultrafast spin exchange-coupling torque via photo-excited charge-transfer processes

    National Research Council Canada - National Science Library

    Ma, X; Fang, F; Li, Q; Zhu, J; Yang, Y; Wu, Y Z; Zhao, H B; Lüpke, G

    2015-01-01

    .... Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon...

  6. The atmosphere of comet 67P/Churyumov-Gerasimenko diagnosed by charge-exchanged solar wind alpha particles

    Science.gov (United States)

    Simon Wedlund, C.; Kallio, E.; Alho, M.; Nilsson, H.; Stenberg Wieser, G.; Gunell, H.; Behar, E.; Pusa, J.; Gronoff, G.

    2016-03-01

    Context. The ESA/Rosetta mission has been orbiting comet 67P/Churyumov-Gerasimenko since August 2014, measuring its dayside plasma environment. The ion spectrometer onboard Rosetta has detected two ion populations, one energetic with a solar wind origin (H+, He2+, He+), the other at lower energies with a cometary origin (water group ions such as H2O+). He+ ions arise mainly from charge-exchange between solar wind alpha particles and cometary neutrals such as H2O. Aims: The He+ and He2+ ion fluxes measured by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA) give insight into the composition of the dayside neutral coma, into the importance of charge-exchange processes between the solar wind and cometary neutrals, and into the way these evolve when the comet draws closer to the Sun. Methods: We combine observations by the ion spectrometer RPC-ICA onboard Rosetta with calculations from an analytical model based on a collisionless neutral Haser atmosphere and nearly undisturbed solar wind conditions. Results: Equivalent neutral outgassing rates Q can be derived using the observed RPC-ICA He+/He2+ particle flux ratios as input into the analytical model in inverse mode. A revised dependence of Q on heliocentric distance Rh in AU is found to be Rh-7.06 between 1.8 and 3.3 AU, suggesting that the activity in 2015 differed from that of the 2008 perihelion passage. Conversely, using an outgassing rate determined from optical remote sensing measurements from Earth, the forward analytical model results are in relatively good agreement with the measured RPC-ICA flux ratios. Modelled ratios in a 2D spherically-symmetric plane are also presented, showing that charge exchange is most efficient with solar wind protons. Detailed cometocentric profiles of these ratios are also presented. Conclusions: In conclusion, we show that, with the help of a simple analytical model of charge-exchange processes, a mass-capable ion spectrometer such as RPC-ICA can be used as a

  7. Prospects of real-time ion temperature and rotation profiles based on neural-network charge exchange analysis

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, R.W.T.; Von Hellermann, M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Svensson, J. [Royal Inst. of Tech., Stockholm (Sweden)

    1994-07-01

    A back-propagation neural network technique is used at JET to extract plasma parameters like ion temperature, rotation velocities or spectral line intensities from charge exchange (CX) spectra. It is shown that in the case of the C VI CX spectra, neural networks can give a good estimation (better than +-20% accuracy) for the main plasma parameters (Ti, V{sub rot}). Since the neural network approach involves no iterations or initial guesses the speed with which a spectrum is processed is so high (0.2 ms/spectrum) that real time analysis will be achieved in the near future. 4 refs., 8 figs.

  8. A quark model calculation for the short-range contribution in the pion double charge exchange reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zou Bingsong; Jiang Huanqing (Institute of Theoretical Physics and Institute of High Energy Physcis, Academia Sinica, Beijing (CN))

    1989-10-01

    A quark model calculation for the short-range contribution in the pion double charge exchange (DCX) reaction is presented. In the framework of this new model the angular distributions of {sup 18}O({pi}{sup +},{pi}{sup {minus}}){sup 18}Ne(g.s.) at low energies are calculated and compared with the experimental data. It is found that this model can explain the anomalous'' increasing behavior for the DCX reaction around 50 MeV quite well.

  9. Initial Assessment of Electron and X-Ray Production and Charge Exchange in the NDCX-II Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    COHEN, R.H.

    2010-02-18

    The purpose of this note is to provide initial assessments of some atomic physics effects for the accelerator section of NDCX-II. There are several effects we address: the production of electrons associated with loss of beam ions to the walls, the production of electrons associated with ionization of background gas, the possibly resultant production of X-rays when these electrons hit bounding surfaces, and charge exchange of beam ions on background gas. The results presented here are based on a number of caveats that will be stated below, which we will attempt to remove in the near future.

  10. Charge ordering and exchange bias behaviors in Co{sub 3}O{sub 4} porous nanoplatelets and nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, J.C., E-mail: jcd341@uowmail.edu.au [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Wang, Jianli [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Zeng, R. [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); School of Materials Science and Engineering, Faculty of Science, UNSW, Sydney NSW 2052 (Australia)

    2017-01-01

    We present the synthesis of α-Co{sub 3}O{sub 4} porous nanoplatelets and hexagonal nanorings using microwave-assisted hydrothermal and conventional chemical reaction methods. The x-ray diffraction (XRD) and refinement analyses indicate the α-Co{sub 3}O{sub 4} crystal structure, and the x-ray photoelectron spectrum (XPS) indicates the high purity of the samples. The M–T (including 1/χ–T) curves indicate an antiferromagnetic transition at about 35 K in both kind of samples but the interesting finding was made that a charge-ordered (CO) state appears at 250 K for the nanoplatelets sample whereas it is inattentive for the nanorings. The antiferromagnetic transition temperature T{sub N} is lower than that of the bulk α-Co{sub 3}O{sub 4} single crystal due to the nanosized structures. We observed quite significant exchange bias for nanorings. The exchange bias behavior of the α-Co{sub 3}O{sub 4} hexagonal nanorings is consistent with an antiferromagnetic (AFM) Co{sub 3}O{sub 4} core and spin-glass like shell. - Highlights: ●Charge-ordered state appears for the Co{sub 3}O{sub 4} nanoplatelets but absent for the nanorings. ●Quite significant exchange bias is only observed for Co{sub 3}O{sub 4} nanorings. ●Exchange bias behavior of Co{sub 3}O{sub 4} nanorings is consistent with spin-glass like shell. ●Potential for ultrahigh-density magnetic recording and spin valve devices.

  11. Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge-Exchange Cross Sections

    Science.gov (United States)

    Chutjian, A.; Ĉade, I.; Greenwood, J. B.; Mawhorter, R. J.; Smith, S. J.; Lozano, J.

    2002-11-01

    The detection of X-rays from comets such as Hyakutake, Hale-Bopp, d'Arrest, and Linear as they approach the Sun has been both unexpected and exciting. This phenomenon, moreover, should be quite general, occurring wherever a fast solar or stellar wind interacts with neutrals in a comet, a planetary atmosphere, or a circumstellar cloud. Comet-modeling calculations to date have (a) used an approximate, over-barrier expression for the charge-exchange (CE) cross section, (b) assumed a flat energy dependence of cross section, and (c) neglected multiple charge exchanges. In support of the understanding of the X-ray emissions (their intensity and spatial extent) laboratory measurements have been carred out at the JPL Highly-Charged Ion Facility [1]. The projectiles have been partially- and fully-stripped H, He, C, N, O, and Ne ions interacting with the comet molecules He, H2, CO, CO2, and H2O. Absolute CE cross sections have been measured, and normalized X-ray emission cross sections reported for these major HCI components of the solar wind [2-5]. The minor, heavier HCI components will produce high-energy X-rays. A large body of data has been acquired on Fe(5-13)+[6]. The experimental approach will be discussed and results given. Future work will be extended to Mgq+ charge states, and include as well NH3 as the target. R. Mawhorter thanks the National Research Council for a fellowship though the NASA-NRC program. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and was supported under contract with the National Aeronautics and Space Administration.

  12. Effect of Molecular Packing and Charge Delocalization on the Nonradiative Recombination of Charge-Transfer States in Organic Solar Cells

    KAUST Repository

    Chen, Xian Kai

    2016-09-05

    In organic solar cells, a major source of energy loss is attributed to nonradiative recombination from the interfacial charge transfer states to the ground state. By taking pentacene–C60 complexes as model donor–acceptor systems, a comprehensive theoretical understanding of how molecular packing and charge delocalization impact these nonradiative recombination rates at donor–acceptor interfaces is provided.

  13. Symposium GC: Nanoscale Charge Transport in Excitonic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Bommisetty, Venkat [Univ. of South Dakota, Vermillion, SD (United States)

    2011-06-23

    This paper provides a summary only and table of contents of the sessions. Excitonic solar cells, including all-organic, hybrid organic-inorganic and dye-sensitized solar cells (DSSCs), offer strong potential for inexpensive and large-area solar energy conversion. Unlike traditional inorganic semiconductor solar cells, where all the charge generation and collection processes are well understood, these excitonic solar cells contain extremely disordered structures with complex interfaces which results in large variations in nanoscale electronic properties and has a strong influence on carrier generation, transport, dissociation and collection. Detailed understanding of these processes is important for fabrication of highly efficient solar cells. Efforts to improve efficiency are underway at a large number of research groups throughout the world focused on inorganic and organic semiconductors, photonics, photophysics, charge transport, nanoscience, ultrafast spectroscopy, photonics, semiconductor processing, device physics, device structures, interface structure etc. Rapid progress in this multidisciplinary area requires strong synergetic efforts among researchers from diverse backgrounds. Such effort can lead to novel methods for development of new materials with improved photon harvesting and interfacial treatments for improved carrier transport, process optimization to yield ordered nanoscale morphologies with well defined electronic structures.

  14. Proton Exchange Membrane Fuel Cells Applied for Transport Sector

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud

    2010-01-01

    A thermodynamic analysis of a PEMFC (proton exchange membrane fuel cell) is investigated. PEMFC may be the most promising technology for fuel cell automotive systems, which is operating at quite low temperatures, (between 60 to 80℃). In this study the fuel cell motive power part of a lift truck has...... of the electricity will be consumed by pumps and compressors in the system. Generally the whole system can be separated in three parts, cathode circuit, anode circuit and cooling loops. In this paper the effect of operating conditions and anode recirculation on power production as well as system efficiency have been...

  15. Establishment of cell lines from adult T-cell leukemia cells dependent on negatively charged polymers.

    Science.gov (United States)

    Kagami, Yoshitoyo; Uchiyama, Susumu; Kato, Harumi; Okada, Yasutaka; Seto, Masao; Kinoshita, Tomohiro

    2017-07-05

    Growing adult T-cell leukemia/lymphoma (ATLL) cells in vitro is difficult. Here, we examined the effects of static electricity in the culture medium on the proliferation of ATLL cells. Six out of 10 ATLL cells did not proliferate in vitro and thus had to be cultured in a medium containing negatively charged polymers. In the presence of poly-γ-glutamic acid (PGA) or chondroitin sulfate (CDR), cell lines (HKOX3-PGA, HKOX3-CDR) were established from the same single ATLL case using interleukin (IL)-2, IL-4, and feeder cells expressing OX40L (OX40L+HK). Dextran sulfate inhibited growth in both HKOX3 cell lines. Both PGA and OX40L+HK were indispensable for HKOX3-PGA growth, but HKOX3-CDR could proliferate in the presence of CDR or OX40L+HK alone. Thus, the specific action of each negatively charged polymer promoted the growth of specific ATLL cells in vitro.

  16. Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

    Energy Technology Data Exchange (ETDEWEB)

    G. Shvets; N.J. Fisch; J.-M. Rax

    2002-01-18

    The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

  17. Inelastic process observed in charge-exchange reactions of 56Fe at 500 MeV/u

    Directory of Open Access Journals (Sweden)

    Momota S.

    2014-03-01

    Full Text Available The inelastic (IE component of the reaction product, which is produced through charge-exchange reactions at relativistic energies of E ~ 1 GeV/u, is one of the hopeful probes used to study the nuclear medium effect on Δ excitation. In the present study, the longitudinal-momentum (PL distribution of 56Co, produced by bombarding C-and CH2-target with a primary beam of 56Fe at E=500 MeV/u, was observed by means of the spectrometer at HIMAC facility. The IE peak of 56Co, produced from H and C targets, was successfully observed in energy transfer spectrum. The behaviors of the IE peaks are consistent with those observed in previous experiments. A remarkable reduction of the energy transfer for the IE process was also observed with C target compared with H target. The present results have shown the feasibility to investigate the energy transfer in charge-exchange reactions for heavy reaction system at the energy down to 500 MeV/u.

  18. Charge transfer and transport in polymer-fullerene solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Parisi, J.; Dyakonov, V.; Pientka, M.; Riedel, I.; Deibel, C. [Faculty of Physics, Dept. of Energy and Semiconductor Research, Univ. of Oldenburg, Oldenburg (Germany); Brabec, C.J. [Faculty of Physics, Dept. of Energy and Semiconductor Research, Univ. of Oldenburg, Oldenburg (Germany); Siemens AG, CT MM1 Innovative Polymers, Erlangen (Germany); Sariciftci, N.S. [Faculty of Physics, Dept. of Energy and Semiconductor Research, Univ. of Oldenburg, Oldenburg (Germany); Inst. of Physical Chemistry and Linz Inst. of Organic Solar Cells, Univ. of Linz, Linz (Austria); Hummelen, J.C. [Faculty of Physics, Dept. of Energy and Semiconductor Research, Univ. of Oldenburg, Oldenburg (Germany); Stratingh Inst. and Materials Research Center, Univ. of Groningen, Groningen (Netherlands)

    2002-12-01

    The development of polymer-fullerene plastic solar cells has made significant progress in recent years. These devices excel by an efficient charge generation process as a consequence of a photo-induced charge transfer between the photo-excited conjugated polymer donor and acceptor-type fullerene molecules. Due to the paramagnetic nature of the radical species, the photo-induced charge transfer can be analyzed by the help of light-induced electron spin resonance spectroscopy. Upon looking at an interpenetrating donor-acceptor composite consisting of the polymer MDMO-PPV and the fullerene derivative PCBM, we disclose two well separated line groups having a strongly anisotropic structure. The line shape can be attributed to an environmental axial symmetry of the polymer cation and a lower rhombohedric symmetry of the fullerene anion. Since the signals were found to be independent of one another with different spin-lattice relaxation times, the radical species can be discriminated via separate characterization procedures. In order to study the bulk charge transport properties, we carried out admittance spectroscopy on the polymer-fullerene solar cell device including a transparent semiconductor oxide front contact (ITO/PEDOT:PSS) and a metal back contact (Al). The temperature- and frequency-dependent device capacitance clearly uncovers two different defect states, the first, having an activation energy of 9 meV, indicates a shallow trap due to a bulk impurity, the latter, having an activation energy of 177 meV, can be assigned to an interfacial defect state located between the polymer-fullerene composite and the metal back contact. (orig.)

  19. Local charge exchange of He{sup +} ions at Aluminum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Riccardi, P., E-mail: pierfrancesco.riccardi@fis.unical.it [Dipartimento di Fisica, Università della Calabria and INFN – Gruppo collegato di Cosenza, Via P. Bucci cubo 33C, Arcavacata di Rende, Cosenza (Italy); Sindona, A. [Dipartimento di Fisica, Università della Calabria and INFN – Gruppo collegato di Cosenza, Via P. Bucci cubo 33C, Arcavacata di Rende, Cosenza (Italy); Dukes, C.A. [Laboratory for Astrophysics and Surface Physics, Materials Science and Engineering University of Virginia, Charlottesville, VA 22904 (United States)

    2017-04-04

    We report on experiments designed to observe the correlation between the autoionization of doubly excited helium atoms and the Auger decay of 2p vacancies in Al. The autoionizing states are formed when incident He{sup +*} and He{sup ++} are neutralized by resonant electron capture at the surface. 2p excitation in Al occurs in dielectronic charge transfer during the close encounter of an excited helium ion and an Al atom. These results clarify the mechanism for Al-2p excitation in the case of singly charged ground state He{sup +}(1s) ion impact, where the dielectronic transition occurs after promotion of the 1s electron of incoming ions. - Highlights: • We observe the correlation between autoionization of doubly excited helium atoms and the Auger decay of 2p vacancies in Al. • 2p excitation in Al occurs in dielectronic charge transfer during the close encounter of an excited helium ion and an Al atom. • These results clarify the mechanism for Al-2p excitation in the case of singly charged ground state He{sup +}(1s) ion impact.

  20. Highly durable direct hydrazine hydrate anion exchange membrane fuel cell

    Science.gov (United States)

    Sakamoto, Tomokazu; Serov, Alexey; Masuda, Teruyuki; Kamakura, Masaki; Yoshimoto, Koji; Omata, Takuya; Kishi, Hirofumi; Yamaguchi, Susumu; Hori, Akihiro; Horiuchi, Yousuke; Terada, Tomoaki; Artyushkova, Kateryna; Atanassov, Plamen; Tanaka, Hirohisa

    2018-01-01

    The factors influenced on degradation of direct hydrazine hydrate fuel cells (DHFCs) under operation conditions are analyzed by in situ soft X-ray radiography. A durability of DHFCs is significantly improved by multi-step reaction DHFCs (MSR-DHFCs) approach designed to decrease the crossover of liquid fuel. An open circuit voltage (OCV) as well as cell voltage at 5 mA cm-2 of MSR-DHFC construct with commercial anion exchange membrane (AEM) maintained for over of 3500 h at 60 °C. Furthermore, the commercial proton exchange membrane (PEM) is integrated into AEM of MSR-DHFCs resulting in stable power output of MSR-DHFCs for over than 2800 h at 80 °C.

  1. The velocity dependence of X-ray emission due to Charge Exchange: Applications in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-04-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate high-energy astrophysical environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities. Collisions of bare and H-like C to Al ions with H, He, and H2 are considered. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31

  2. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling.

    Science.gov (United States)

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Donohoe, Gregory C; Valentine, Stephen J

    2016-03-01

    Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H](2-) ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H](3-) ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H](2-) ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H](3-) ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

  3. Role of Surface Electric Charge in Red Blood Cell Interactions

    Science.gov (United States)

    Jan, Kung-Ming; Chien, Shu

    1973-01-01

    The role of the surface charge of human red blood cells (RBC's) in affecting RBC aggregation by macromolecules was studied by comparing the behavior of normal RBC's with that of RBC's treated with neuraminidase, which removes the sialic acids from the cell membrane and reduces the zeta potential. RBC aggregation in dextrans with different molecular weights (Dx 20, Dx 40, and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. Dx 20 did not cause aggregation of normal RBC's, but caused considerable aggregation of neuraminidase-treated RBC's. Neuraminidase-treated RBC's also showed stronger aggregation than normal RBC's in Dx 40 and 80. Together with the electron microscopic findings that the intercellular distance in the RBC rouleaux varies with the molecular size of dextrans used, the present study indicates that the surface charge of RBC's inhibits their aggregation by dextrans and that the electrostatic repulsive force between cell surfaces may operate over a distance of 20 nm. PMID:4705641

  4. Proton Exchange Membrane Fuel Cell Reversal: A Review

    Directory of Open Access Journals (Sweden)

    Congwei Qin

    2016-12-01

    Full Text Available The H2/air-fed proton exchange membrane fuel cell (PEMFC has two major problems: cost and durability, which obstruct its pathway to commercialization. Cell reversal, which would create irreversible damage to the fuel cell and shorten its lifespan, is caused by reactant starvation, load change, low catalyst performance, and so on. This paper will summarize the causes, consequences, and mitigation strategies of cell reversal of PEMFC in detail. A description of potential change in the anode and cathode and the differences between local starvation and overall starvation are reviewed, which gives a framework for comprehending the origins of cell reversal. According to the root factor of cell starvation, i.e., fuel cells do not satisfy the requirements of electrons and protons of normal anode and cathode chemical reactions, we will introduce specific methods to mitigate or prevent fuel cell damage caused by cell reversal in the view of system management strategies and component material modifications. Based on a comprehensive understanding of cell reversal, it is beneficial to operate a fuel cell stack and extend its lifetime.

  5. A direct ascorbate fuel cell with an anion exchange membrane

    Science.gov (United States)

    Muneeb, Omar; Do, Emily; Tran, Timothy; Boyd, Desiree; Huynh, Michelle; Ghosn, Gregory; Haan, John L.

    2017-05-01

    Ascorbic Acid (Vitamin C) is investigated as a renewable alternative fuel for alkaline direct liquid fuel cells (DLFCs). The environmentally- and biologically-friendly compound, L-ascorbic acid (AA) has been modeled and studied experimentally under acidic fuel cell conditions. In this work, we demonstrate that ascorbic acid is a more efficient fuel in alkaline media than in acidic media. An operating direct ascorbate fuel cell is constructed with the combination of L-ascorbic acid and KOH as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, metal or carbon black anode materials and metal cathode catalyst. Operation of the fuel cell at 60 °C using 1 M AA and 1 M KOH as the anode fuel and electrolyte, respectively, and oxygen gas at the cathode, produces a maximum power density of 73 mW cm-2, maximum current density of 497 mA cm-2 and an open circuit voltage of 0.90 V. This performance is significantly greater than that of an ascorbic acid fuel cell with a cation exchange membrane, and it is competitive with alkaline DLFCs fueled by alcohols.

  6. Modeling Of Proton Exchange Membrane Fuel Cell Systems

    DEFF Research Database (Denmark)

    Nielsen, Mads Pagh

    The objective of this doctoral thesis was to develop reliable steady-state and transient component models suitable to asses-, develop- and optimize proton exchange membrane (PEM) fuel cell systems. Several components in PEM fuel cell systems were characterized and modeled. The developed component...... cell systems. Consequences of indirectly fueling PEM stacks with hydrocarbons using reforming technology were investigated using a PEM stack model including CO poisoning kinetics and a transient Simulink steam reforming system model. Aspects regarding the optimization of PEM fuel cell systems......- and system models match experimental data from the literature. However, limited data were available for verification so further work is necessary to confirm detailed aspects of the models. It is nonetheless expected that the developed models will be useful for system modeling and optimization of PEM fuel...

  7. Dual capillary tube / heat exchanger in combination with cycle priming for reducing charge migration

    Science.gov (United States)

    Gomes, Alberto Regio; Kuehl, Steven J.; Litch, Andrew D.; Wu, Guolian

    2017-07-04

    A refrigerator appliance including a multi-capacity compressor and a refrigerant circuit with two conduits and pressure reducing devices arranged in parallel between an evaporator and a condenser. Refrigerant can flow through one, both or none of the conduits and pressure reducing devices. The appliance also has a heat exchanger in contact with either one pressure reducing device, or one conduit between the pressure reducing device and the valve system. The appliance also includes a controller for priming the compressor above a nominal capacity for a predetermined or calculated duration at the beginning of an ON-cycle.

  8. Charge exchange recombination detection of low-Z and medium-Z impurities in the extreme UV using a digital lock-in technique.

    Science.gov (United States)

    Brooks, N H; Burrell, K H; Isler, R C; Meyer, O; Pablant, N A

    2010-10-01

    More sensitive detection of charge exchange recombination lines from low-Z elements, and first-time detection from the medium-Z elements nickel and copper, has been achieved in DIII-D plasmas with a digital lock-in technique. That portion of the extreme UV spectrum varying synchronously in time with the square-wave modulation of a high energy, neutral heating beam is extracted by forming a scalar product of a correlation function with the data record of each pixel in the linear array detector. The usual, dense array of collisionally excited, metallic lines from the tokamak plasma is strongly suppressed, leaving only a sparse spectrum of lines dominated by charge exchange recombination transitions from fully stripped, low-Z elements. In plasmas with high metal content, charge exchange recombination lines from the Li-like ions of nickel and copper have been positively identified.

  9. Highly Water Resistant Anion Exchange Membrane for Fuel Cells.

    Science.gov (United States)

    Yang, Zhengjin; Hou, Jianqiu; Wang, Xinyu; Wu, Liang; Xu, Tongwen

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A Novel Unitized Regenerative Proton Exchange Membrane Fuel Cell

    Science.gov (United States)

    Murphy, O. J.; Cisar, A. J.; Gonzalez-Martin, A.; Salinas, C. E.; Simpson, S. F.

    1996-01-01

    A difficulty encountered in designing a unitized regenerative proton exchange membrane (PEM) fuel cell lies in the incompatibility of electrode structures and electrocatalyst materials optimized for either of the two functions (fuel cell or electrolyzer) with the needs of the other function. This difficulty is compounded in previous regenerative fuel cell designs by the fact that water, which is needed for proton conduction in the PEM during both modes of operation, is the reactant supplied to the anode in the electrolyzer mode of operation and the product formed at the cathode in the fuel cell mode. Drawbacks associated with existing regenerative fuel cells have been addressed. In a first innovation, electrodes function either as oxidation electrodes (hydrogen ionization or oxygen evolution) or as reduction electrodes (oxygen reduction or hydrogen evolution) in the fuel cell and electrolyzer modes, respectively. Control of liquid water within the regenerative fuel cell has been brought about by a second innovation. A novel PEM has been developed with internal channels that permit the direct access of water along the length of the membrane. Lateral diffusion of water along the polymer chains of the PEM provides the water needed at electrode/PEM interfaces. Fabrication of the novel single cell unitized regenerative fuel cell and results obtained on testing it are presented.

  11. A GTP-exchange factor required for cell orientation.

    Science.gov (United States)

    Nern, A; Arkowitz, R A

    1998-01-08

    The Rho-family of GTPases and their regulators are essential for cytoskeletal reorganization and transcriptional activation in response to extracellular signals. Little is known about what links these molecules to membrane receptors. In the budding yeast Saccharomyces cerevisiae, haploid cells respond to mating pheromone through a G-protein-coupled receptor and the betagamma subunit of the G protein, resulting in arrest of the cell cycle, transcriptional activation, and polarized growth towards a mating partner. The Rho-family GTPase Cdc42 and its exchange factor Cdc24 have been implicated in the mating process, but their specific role is unknown. Here we report the identification of cdc24 alleles that do not affect vegetative growth but drastically reduce the ability of yeast cells to mate. When exposed to mating pheromone, these mutants arrest growth, activate transcription, and undergo characteristic morphological and actin-cytoskeleton polarization. However, the mutants are unable to orient towards a pheromone gradient, and instead position their mating projection adjacent to their previous bud site. The mutants are specifically defective in the binding of Cdc24 to the G-protein betagamma subunit. Our results demonstrate that the association of an exchange factor and the betagamma subunit of a hetero-trimeric G protein links receptor-mediated activation to oriented cell growth.

  12. Delocalization and dielectric screening of charge transfer states in organic photovoltaic cells

    National Research Council Canada - National Science Library

    Bernardo, B; Cheyns, D; Verreet, B; Schaller, R D; Rand, B P; Giebink, N C

    2014-01-01

    Charge transfer (CT) states at a donor-acceptor heterojunction have a key role in the charge photogeneration process of organic solar cells, however, the mechanism by which these states dissociate efficiently into free...

  13. Chromatography of proteins on charge-variant ion exchangers and implications for optimizing protein uptake rates.

    Science.gov (United States)

    Langford, John F; Xu, Xuankuo; Yao, Yan; Maloney, Sean F; Lenhoff, Abraham M

    2007-09-07

    Intraparticle transport of proteins usually represents the principal resistance controlling their uptake in preparative separations. In ion-exchange chromatography two limiting models are commonly used to describe such uptake: pore diffusion, in which only free protein in the pore lumen contributes to transport, and homogeneous diffusion, in which the transport flux is determined by the gradient in the total protein concentration, free or adsorbed. Several studies have noted a transition from pore to homogeneous diffusion with increasing ionic strength in some systems, and here we investigate the mechanistic basis for this transition. The studies were performed on a set of custom-synthesized methacrylate-based strong cation exchangers differing in ligand density into which uptake of two proteins was examined using confocal microscopy and frontal loading experiments. We find that the transition in uptake mechanism occurs in all cases studied, and generally coincides with an optimum in the dynamic binding capacity at moderately high flow rates. The transition appears to occur when protein-surface attraction is weakened sufficiently, and this is correlated with the isocratic retention factor k' for the system of interest: the transition occurs in the vicinity of k' approximately 3000. This result, which may indicate that adsorption is sufficiently weak to allow the protein to diffuse along or near the surface, provides a predictive basis for optimizing preparative separations using only isocratic retention data.

  14. What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?

    Science.gov (United States)

    Snowden, S. L.

    2008-01-01

    Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.

  15. Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation

    Directory of Open Access Journals (Sweden)

    N. Vaeck

    2002-03-01

    Full Text Available We report the application of the quantum approach, which takes full account of electron translation at low collisional energies, to the charge exchange process H, D + C4+ → H+, D+ + C3+(3s; 3p; 3d. The partial and the total integral cross sections of the process are calculated in the energy range from 1 till 60 eV/amu. It is shown that the present results are independent from the upper integration limit for numerical solution of the coupled channel equations although nonadiabatic couplings remain nonzero up to infinity. The calculated partial and total cross sections are in agreement with the previous low-energy calculations and the available experimental data. It is shown that for low collisional energies the isotopic effect takes place. The observed effect is explained in terms of the nonadiabatic dynamics.

  16. A microscopic approach based on particle-vibration coupling: application to charge-exchange transitions and multiplets in odd nuclei

    Directory of Open Access Journals (Sweden)

    Colò Gianluca

    2016-01-01

    Full Text Available In this contribution, we shall describe a formalism that goes beyond the simple time-dependent mean field and is based on particle-vibration coupling (PVC. Such a formalism has been developed with the idea of being self-consistent. It makes use of Skyrme effective forces, and has been used for several applications. We will focus on charge-exchange transitions, namely we will show that our model describes well both the Gamow-Teller giant resonance width, and the low-lying transitions associated with β-decay. In this latter case, including PVC produces a significant improvement of the half-lives obtained at mean-field level, and leads to a good agreement with experimental data. We will end by discussing particle-phonon multiplets in odd nuclei.

  17. Numerical solutions to a kinetic model for the plasma-sheath problem with charge exchange collisions of ions.

    Science.gov (United States)

    Sternovsky, Z; Downum, K; Robertson, S

    2004-08-01

    A kinetic model of the plasma-sheath problem is presented that includes the effects of charge-exchange collisions of the ion. The collisions are modeled as a sink for accelerated ions and as a source of cold ions. Solutions are obtained by numerical integration of Poisson's equation from a point near the plasma midplane to the wall. In the quasineutral region, these solutions agree with earlier analytic work. As the mean free path is decreased, the current density at the wall decreases and the potential profile in the quasineutral region shows a smooth transition from a parabolic profile to a nearly cubic profile determined by the ion mobility. An approximate expression is found for the ion flux to the wall in the collisional limit.

  18. Charge exchange fluxes of ripple trapped slowing-down ions during L-to-H transition and ELMs

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, W. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Fahrbach, H.U. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Kaufmann, M. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Lackner, K. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Ryter, F. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Zohm, H. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Albrecht, M. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Alexander, M. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Asmussen, K. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Behler, K. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Behringer, K. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Bessenrodt-Weberpals, M. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Bosch, H.S. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Buechl, K. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Carlson, A. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Coster, D. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Blank, H.J. de [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Drube, R. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Dux, R. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Engelhardt, W. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Gehre, O. [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

    1995-06-01

    Neutral fluxes from charge exchange with ripple-trapped particles show a remarkably different behaviour during L and H mode; their measurement provides a new diagnostic for the mode discrimination of the plasma. A possible reason for the changes of the fluxes is the action of a radial electric field. This seems to grow steadily after the L-to-H transition with a strong increase (jump in the ms range) at the transition to the quiescent H-mode. During ELMs the fluxes reduce to L-mode level. Measurements with 100 {mu} time resolution show no action in the fluxes piror to the change in the D{sub {alpha}}-signal at the start of type 1 ELM. (orig.)

  19. Optimization and application of cooled avalanche photodiodes for spectroscopic fluctuation measurements with ultra-fast charge exchange recombination spectroscopy

    Science.gov (United States)

    Truong, D. D.; Fonck, R. J.; McKee, G. R.

    2016-11-01

    The Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic is a highly specialized spectroscopic instrument with 2 spatial channels consisting of 8 spectral channels each and a resolution of ˜0.25 nm deployed at DIII-D to measure turbulent ion temperature fluctuations. Charge exchange emissions are obtained between 528 and 530 nm with 1 μs time resolution to study plasma instabilities. A primary challenge of extracting fluctuation measurements from raw UF-CHERS signals is photon and electronic noise. In order to reduce dark current, the Avalanche Photodiode (APD) detectors are thermo-electrically cooled. State-of-the-art components are used for the signal amplifiers and conditioners to minimize electronic noise. Due to the low incident photon power (≤1 nW), APDs with a gain of up to 300 are used to optimize the signal to noise ratio. Maximizing the APDs' gain while minimizing the excess noise factor (ENF) is essential since the total noise of the diagnostic sets a floor for the minimum level of detectable broadband fluctuations. The APDs' gain should be high enough that photon noise dominates electronic noise, but not excessive so that the ENF overwhelms plasma fluctuations. A new generation of cooled APDs and optimized preamplifiers exhibits significantly enhanced signal-to-noise compared to a previous generation. Experiments at DIII-D have allowed for characterization and optimization of the ENF vs. gain. A gain of ˜100 at 1700 V is found to be near optimal for most plasma conditions. Ion temperature and toroidal velocity fluctuations due to the edge harmonic oscillation in quiescent H-mode plasmas are presented to demonstrate UF-CHERS' capabilities.

  20. Career Development of College Students through Part-Time Work: The Role of Leader-Member Exchange and Taking Charge Behavior

    OpenAIRE

    Tomoki Sekiguchi

    2010-01-01

    This study examines the potential benefit of college students' part-time work on their career development by focusing on leader-member exchange (LMX) and taking charge behavior in the workplace. Using a sample of Japanese college students, results from this study indicate that taking charge behavior in part-time work mediates the relationship between LMX quality with supervisors and career development (focus of career exploration, self-efficacy toward postcollege employment and proactive care...

  1. Durable Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    the selectivity for platinum loading. Fuel cell durability tests in term of performance degradation were performed with acid doped polybenzimidazole membrane fuel cells at temperatures of up to 160°C. The tests were focused on catalyst degradation by means of a potential cycling protocol. The electrochemical......Durability of proton exchange membrane fuel cells (PEMFCs) is recognized as one of the most important issues to be addressed before the commercialization. The failure mechanisms are not well understood, however, degradation of carbon supported noble metal catalysts is identified as a major failure...... mode of PEMFCs. Under idle, load-cycling or start-up/shutdown modes of operation, which are prerequisite for automobile applications, the cathode will experience significantly higher potentials and therefore suffer from serious carbon corrosion, especially at the presence of platinum. The carbon...

  2. Ionic Liquids and New Proton Exchange Membranes for Fuel Cells

    Science.gov (United States)

    Belieres, Jean-Philippe

    2004-01-01

    There is currently a great surge of activity in fuel cell research as laboratories across the world seek to take advantage of the high energy capacity provided by &el cells relative to those of other portable electrochemical power systems. Much of this activity is aimed at high temperature fie1 cells, and a vital component of such &el cells must be the availability of a high temperature stable proton-permeable membrane. NASA Glenn Research Center is greatly involved in developing this technology. Other approaches to the high temperature fuel cell involve the use of single- component or almost-single-component electrolytes that provide a path for protons through the cell. A heavily researched case is the phosphoric acid fuel cell, in which the electrolyte is almost pure phosphoric acid and the cathode reaction produces water directly. The phosphoric acid fie1 cell delivers an open circuit voltage of 0.9 V falling to about 0.7 V under operating conditions at 170 C. The proton transport mechanism is mainly vehicular in character according to the viscosity/conductance relation. Here we describe some Proton Transfer Ionic Liquids (PTILs) with low vapor pressure and high temperature stability that have conductivities of unprecedented magnitude for non-aqueous systems. The first requirement of an ionic liquid is that, contrary to experience with most liquids consisting of ions, it must have a melting point that is not much above room temperature. The limit commonly suggested is 100 C. PTILs constitute an interesting class of non-corrosive proton-exchange electrolyte, which can serve well in high temperature (T = 100 - 250 C) fuel cell applications. We will present cell performance data showing that the open circuit voltage output, and the performance of a simple H2(g)Pt/PTIL/Pt/O2(g) fuel cell may be superior to those of the equivalent phosphoric acid electrolyte fuel cell both at ambient temperature and temperatures up to and above 200 C. My work at NASA Glenn Research

  3. Mechanistic Modeling Based PAT Implementation for Ion-Exchange Process Chromatography of Charge Variants of Monoclonal Antibody Products.

    Science.gov (United States)

    Kumar, Vijesh; Rathore, Anurag S

    2017-09-01

    Process chromatography is typically used to remove product related impurities and variants that have very similar physicochemical properties to the product. Baseline separation may not be achieved in most cases due to high protein loading and thus, pooling of the elution peak can be challenging for maximizing yield and achieving consistency in product quality. Batch-to-batch variability in quality of the feed material also occurs in commercial manufacturing. Mechanistic modeling of process chromatography, though non-trivial, can be an enabler for implementation of Process Analytical Technology. This paper presents one such application involving prediction of the impact of variability in feed quality and in gradient shape on separation of charge variants by cation exchange process chromatography and thereby facilitating feed forward control. Five batches having different compositions of charge variants have been used to demonstrate the proposed pooling strategy based on simulated chromatograms and the outcome has been compared to offline pooling based on fractionation. For all the conditions examined and for the desired target of main product (67%), the proposed approach resulted in remarkable consistency in product quality (67 ± 2%) while delivering a yield of greater than 90%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Experimental investigation of the reaction of helium ions with dimethyl ether: stereodynamics of the dissociative charge exchange process.

    Science.gov (United States)

    Cernuto, Andrea; Tosi, Paolo; Martini, Luca Matteo; Pirani, Fernando; Ascenzi, Daniela

    2017-08-02

    The fate of dimethyl ether (DME, CH3OCH3) in collisions with He+ ions is of high relevance for astrochemical models aimed at reproducing the abundances of complex organic molecules in the interstellar medium. Here we report an investigation on the reaction of He+ ions with DME carried out using a Guided Ion Beam Mass Spectrometer (GIB-MS), which allows the measurement of reactive cross-sections and branching ratios (BRs) as a function of the collision energy. We obtain insights into the dissociative charge (electron) exchange mechanism by investigating the nature of the non-adiabatic transitions between the relevant potential energy surfaces (PESs) in an improved Landau-Zener approach. We find that the large interaction anisotropy could induce a pronounced orientation of the polar DME molecule in the electric field generated by He+ so that at short distances the collision complex is confined within pendular states, a particular case of bending motion, which gives rise to intriguing stereodynamic effects. The positions of the intermolecular potential energy curve crossings indicate that He+ captures an electron from an inner valence orbital of DME, thus causing its dissociation. In addition to the crossing positions, the symmetry of the electron density distribution of the involved DME orbitals turns out to be a further major point affecting the probability of electron transfer. Thus, the anisotropy of the intermolecular interaction and the electron densities of the orbitals involved in the reaction are the key "ingredients" for describing the dynamics of this dissociative charge transfer.

  5. Impurity line emission due to thermal charge exchange in JET edge plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Maggi, C.F.; Horton, L.D.; Koenig, R.; Stamp, M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Summers, H.P. [Strathclyde Univ., Glasgow (United Kingdom)

    1994-07-01

    High n-shell emission from hydrogen-like carbon (C VI, n=8-7) has been routinely observed from the plasma edge of JET. By comparing the measured spectral line intensities with the signals predicted by advanced atomic physics modelling of carbon and hydrogen radiation, integrated with modelling of the divertor and edge plasma, it is concluded that charge transfer from excited state hydrogen donors into fully stripped carbon ions can account for the observed spectral emission, but that the hydrogen distribution and to a lesser extent the carbon distribution away from the strike zone predicted by the transport model are too low. Data presented are those of three upper X-point discharges, where the target material was carbon. 5 refs., 1 fig., 3 tabs.

  6. Charge-exchange-induced two-electron satellite transitions from autoionizing levels in dense plasmas.

    Science.gov (United States)

    Rosmej, F B; Griem, H R; Elton, R C; Jacobs, V L; Cobble, J A; Faenov, A Ya; Pikuz, T A; Geissel, M; Hoffmann, D H H; Süss, W; Uskov, D B; Shevelko, V P; Mancini, R C

    2002-11-01

    Order-of-magnitude anomalously high intensities for two-electron (dielectronic) satellite transitions, originating from the He-like 2s(2) 1S0 and Li-like 1s2s(2) (2)S(1/2) autoionizing states of silicon, have been observed in dense laser-produced plasmas at different laboratories. Spatially resolved, high-resolution spectra and plasma images show that these effects are correlated with an intense emission of the He-like 1s3p 1P-1s(2) 1S lines, as well as the K(alpha) lines. A time-dependent, collisional-radiative model, allowing for non-Maxwellian electron-energy distributions, has been developed for the determination of the relevant nonequilibrium level populations of the silicon ions, and a detailed analysis of the experimental data has been carried out. Taking into account electron density and temperature variations, plasma optical-depth effects, and hot-electron distributions, the spectral simulations are found to be not in agreement with the observations. We propose that highly stripped target ions (e.g., bare nuclei or H-like 1s ground-state ions) are transported into the dense, cold plasma (predominantly consisting of L- and M-shell ions) near the target surface and undergo single- and double-electron charge-transfer processes. The spectral simulations indicate that, in dense and optically thick plasmas, these charge-transfer processes may lead to an enhancement of the intensities of the two-electron transitions by up to a factor of 10 relative to those of the other emission lines, in agreement with the spectral observations.

  7. Structure-property relationships in non-epitaxial chalcogenide heterostructures: the role of interface density on charge exchange

    Science.gov (United States)

    Bauers, S. R.; Ditto, J.; Moore, D. B.; Johnson, D. C.

    2016-07-01

    A homologous series of quasi-2D ([PbSe]1+δ)m(TiSe2)m nanolayered heterostructures are prepared via self-assembly of designed precursors with 1 rock salt structured PbSe layers alternating with TiSe2 layers, and that grain size increases with m. The compounds are all metallic with upturns in resistivity at low temperature suggesting electron localization, with room temperature resistivity of 1-3 10-5 Ω m, negative Hall coefficients and Seebeck coefficients between -50 and -100 μV K-1. A decrease in the mobile carrier concentration with temperature is observed for all m and the rate increases with increasing low-dimensionality. Decreasing the interface density also decreases the average carrier concentration while increasing the electron mobility. The Seebeck coefficients systematically increase in magnitude as m is increased, but the net effect to the power factor is small due to a compensating increase in resistivity. The observed transport behavior is not described by the simple rigid band models with charge transfer between constituents used previously. Charge exchange between constituents stabilizes the intergrowth, but also introduces mobile carriers and interfacial band bending that must play a role in the transport behavior of the heterostructures. As chemical potentials equilibrate in high m heterostructures there is a decrease in total coulombic stabilization as there are fewer interfaces, so m = 1 is likely to be most stable. This rationalizes why the structurally similar misfit layer compounds with m = 1 are often the only intergrowths that can be prepared. Charge transfer and band bending at interfaces should occur in other heterostructures with similar type II broken-gap band alignments and are important considerations regarding both their stability and transport properties.

  8. Anion selective membrane. [ion exchange resins and ion exchange membrane electrolytes for electrolytic cells

    Science.gov (United States)

    Alexander, S. S.; Geoffroy, R. R.; Hodgdon, R. B.

    1975-01-01

    Experimental anion permselective membranes were prepared and tested for their suitability as cell separators in a chemical redox power storage system being developed at NASA-Lewis Research Center. The goals of long-term (1000 hr) oxidative and thermal stability at 80 C in FeCl3 and CrCl3 electrolytes were met by most of the weak base and strong base amino exchange groups considered in the program. Good stability is exhibited by several of the membrane substrate resins. These are 'styrene' divinylbenzene copolymer and PVC film. At least four membrane systems produce strong flexible films with electrochemical properties (resistivity, cation transfer) superior to those of the 103QZL, the most promising commercial membrane. The physical and chemical properties of the resins are listed.

  9. Development of Passive Fuel Cell Thermal Management Heat Exchanger

    Science.gov (United States)

    Burke, Kenneth A.; Jakupca, Ian J.; Colozza, Anthony J.

    2010-01-01

    The NASA Glenn Research Center is developing advanced passive thermal management technology to reduce the mass and improve the reliability of space fuel cell systems for the NASA Exploration program. The passive thermal management system relies on heat conduction within highly thermally conductive cooling plates to move the heat from the central portion of the cell stack out to the edges of the fuel cell stack. Using the passive approach eliminates the need for a coolant pump and other cooling loop components within the fuel cell system which reduces mass and improves overall system reliability. Previous development demonstrated the performance of suitable highly thermally conductive cooling plates that could conduct the heat, provide a sufficiently uniform temperature heat sink for each cell of the fuel cell stack, and be substantially lighter than the conventional thermal management approach. Tests were run with different materials to evaluate the design approach to a heat exchanger that could interface with the edges of the passive cooling plates. Measurements were made during fuel cell operation to determine the temperature of individual cooling plates and also to determine the temperature uniformity from one cooling plate to another.

  10. Proton exchange membrane fuel cell technology for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Swathirajan, S. [General Motors R& D Center, Warren, MI (United States)

    1996-04-01

    Proton Exchange Membrane (PEM) fuel cells are extremely promising as future power plants in the transportation sector to achieve an increase in energy efficiency and eliminate environmental pollution due to vehicles. GM is currently involved in a multiphase program with the US Department of Energy for developing a proof-of-concept hybrid vehicle based on a PEM fuel cell power plant and a methanol fuel processor. Other participants in the program are Los Alamos National Labs, Dow Chemical Co., Ballard Power Systems and DuPont Co., In the just completed phase 1 of the program, a 10 kW PEM fuel cell power plant was built and tested to demonstrate the feasibility of integrating a methanol fuel processor with a PEM fuel cell stack. However, the fuel cell power plant must overcome stiff technical and economic challenges before it can be commercialized for light duty vehicle applications. Progress achieved in phase I on the use of monolithic catalyst reactors in the fuel processor, managing CO impurity in the fuel cell stack, low-cost electrode-membrane assembles, and on the integration of the fuel processor with a Ballard PEM fuel cell stack will be presented.

  11. DNA Charge Transport: From Chemical Principles to the Cell

    Science.gov (United States)

    Arnold, Anna R.; Grodick, Michael A.; Barton, Jacqueline K.

    2016-01-01

    The DNA double helix has captured the imagination of many, bringing it to the forefront of biological research. DNA has unique features that extend our interest into areas of chemistry, physics, material science and engineering. Our laboratory has focused on studies of DNA charge transport (CT), wherein charges can efficiently travel long molecular distances through the DNA helix while maintaining an exquisite sensitivity to base pair π-stacking. Because DNA CT chemistry reports on the integrity of the DNA duplex, this property may be exploited to develop electrochemical devices to detect DNA lesions and DNA-binding proteins. Furthermore, studies now indicate that DNA CT may also be used in the cell by, for example, DNA repair proteins, as a cellular diagnostic, in order to scan the genome to localize efficiently to damage sites. In this review, we describe this evolution of DNA CT chemistry from the discovery of fundamental chemical principles to applications in diagnostic strategies and possible roles in biology. PMID:26933744

  12. Study of charge transfer reactions in a microbial fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Martin, E.; Savadogo, O. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. de Genie Chimique; National Research Council of Canada, Montreal, PQ (Canada). Biotechnology Research Inst.; Tartakovsky, B. [National Research Council of Canada, Montreal, PQ (Canada). Biotechnology Research Inst.

    2008-07-01

    Electron transfer reactions in a microbial fuel cell (MFC) were evaluated. The MFC was inoculated with anaerobic mesophilic sludge and operated with carbon felt, carbon cloth, and platinum (Pt) coated carbon cloth. The MFC was then fed with either acetate or glucose as a source of fuel and operated at a temperature of 25 degrees C and a pH of 7. Scanning electron microscopy (SEM) micrographs demonstrated that the micro-organisms colonized the anodes. Cyclic voltammetry and polarization tests were conducted using different fractions of the anodophilic biofilm in order to determine charge transfer routes. The study characterized the electron transfer mechanisms used by the exoelectrogenic micro-organisms to produce electricity. It was concluded that further research is needed to characterize reaction transfer routes. 2 refs., 1 fig.

  13. Charge Transport in Carbon Nanotubes-Polymer Composite Photovoltaic Cells

    Science.gov (United States)

    Ltaief, Adnen; Bouazizi, Abdelaziz; Davenas, Joel

    2009-01-01

    We investigate the dark and illuminated current density-voltage (J/V) characteristics of poly(2-methoxy-5-(2’-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV)/single-walled carbon nanotubes (SWNTs) composite photovoltaic cells. Using an exponential band tail model, the conduction mechanism has been analysed for polymer only devices and composite devices, in terms of space charge limited current (SCLC) conduction mechanism, where we determine the power parameters and the threshold voltages. Elaborated devices for MEH-PPV:SWNTs (1:1) composites showed a photoresponse with an open-circuit voltage Voc of 0.4 V, a short-circuit current density JSC of 1 µA/cm² and a fill factor FF of 43%. We have modelised the organic photovoltaic devices with an equivalent circuit, where we calculated the series and shunt resistances.

  14. Anion exchange membrane fuel cells: Current status and remaining challenges

    Science.gov (United States)

    Gottesfeld, Shimshon; Dekel, Dario R.; Page, Miles; Bae, Chulsung; Yan, Yushan; Zelenay, Piotr; Kim, Yu Seung

    2018-01-01

    The anion exchange membrane fuel cell (AEMFC) is an attractive alternative to acidic proton exchange membrane fuel cells, which to date have required platinum-based catalysts, as well as acid-tolerant stack hardware. The AEMFC could use non-platinum-group metal catalysts and less expensive metal hardware thanks to the high pH of the electrolyte. Over the last decade, substantial progress has been made in improving the performance and durability of the AEMFC through the development of new materials and the optimization of system design and operation conditions. In this perspective article, we describe the current status of AEMFCs as having reached beginning of life performance very close to that of PEMFCs when using ultra-low loadings of Pt, while advancing towards operation on non-platinum-group metal catalysts alone. In the latter sections, we identify the remaining technical challenges, which require further research and development, focusing on the materials and operational factors that critically impact AEMFC performance and/or durability. These perspectives may provide useful insights for the development of next-generation of AEMFCs.

  15. Charge exchange and energy loss of slowed down heavy ions channeled in silicon crystals; Echanges de charge et perte d'energie d'ions lourds ralentis, canalises dans des cristaux de silicium

    Energy Technology Data Exchange (ETDEWEB)

    Testa, E

    2005-10-15

    This work is devoted to the study of charge exchange processes and of the energy loss of highly charged heavy ions channeled in thin silicon crystals. The two first chapters present the techniques of heavy ion channeling in a crystal, the ion-electron processes and the principle of our simulations (charge exchange and trajectory of channeled ions). The next chapters describe the two experiments performed at the GSI facility in Darmstadt, the main results of which follow: the probability per target atom of the mechanical capture (MEC) of 20 MeV/u U{sup 91+} ions as a function of the impact parameter (with the help of our simulations), the observation of the strong polarization of the target electron gas by the study of the radiative capture and the slowing down of Pb{sup 81+} ions from 13 to 8,5 MeV/u in channeling conditions for which electron capture is strongly reduced. (author)

  16. Reactivation System for Proton-Exchange Membrane Fuel-Cells

    Directory of Open Access Journals (Sweden)

    Roberto Giral

    2012-07-01

    Full Text Available In recent years, Proton-Exchange Membrane Fuel Cells (PEMFCs have been the focus of very intensive researches. Manufacturers of these alternative power sources propose a rejuvenation sequence after the FC has been operating at high power for a certain period of time. These rejuvenation methods could be not appropriate for the reactivation of the FC when it has been out of operation for a long period of time or after it has been repaired. Since the developed reactivation system monitors temperature, current, and the cell voltages of the stack, it could be also useful for the diagnostic and repairing processes. The limited number of published contributions suggests that systems developing reactivation techniques are an open research field. In this paper, an automated system for reactivating PEMFCs and results of experimental testing are presented.

  17. Dock-family exchange factors in cell migration and disease.

    Science.gov (United States)

    Gadea, Gilles; Blangy, Anne

    2014-10-01

    Dock family proteins are evolutionary conserved exchange factors for the Rho GTPases Rac and Cdc42. There are 11 Dock proteins in mammals, named Dock1 (or Dock180) to Dock11 that play different cellular functions. In particular, Dock proteins regulate actin cytoskeleton, cell adhesion and migration. Not surprisingly, members of the Dock family have been involved in various pathologies, including cancer and defects in the central nervous and immune systems. This review proposes an update of the recent findings regarding the function of Dock proteins, focusing on their role in the control of cell migration and invasion and the consequences in human diseases. Copyright © 2014 Elsevier GmbH. All rights reserved.

  18. Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung-Sung; Hong, John; Hou, Bo; Cho, Yuljae; Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk; Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom); Kim, Jong Min [Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom)

    2016-08-08

    We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.

  19. Preparation of Highly Sulfonated Ultra-Thin Proton-Exchange Polymer Membranes for Proton Exchange Membrane Fuel Cells

    Science.gov (United States)

    Jiang, Zhongqing; Meng, Yuedong; Jiang, Zhong-Jie; Shi, Yicai

    Sulfonated ultra-thin proton-exchange polymer membrane carrying pyridine groups was made from a plasma polymerization of styrene, 2-vinylpyridine, and trifluoromethanesulfonic acid by after-glow capacitively coupled discharge technique. Pyridine groups tethered to the polymer backbone acts as a medium through the basic nitrogen for transfer of protons between the sulfonic acid groups of proton exchange membrane. It shows that the method using present technology could effectively depress the degradation of monomers during the plasma polymerization. Spectroscopic analyses reveal that the obtained membranes are highly functionalized with proton exchange groups and have higher proton conductivity. Thus, the membranes are expected to be used in direct methanol fuel cells.

  20. Advanced proton-exchange materials for energy efficient fuel cells.

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, Cy H.; Grest, Gary Stephen; Hickner, Michael A.; Cornelius, Christopher James; Staiger, Chad Lynn; Hibbs, Michael R.

    2005-12-01

    The ''Advanced Proton-Exchange Materials for Energy Efficient Fuel Cells'' Laboratory Directed Research and Development (LDRD) project began in October 2002 and ended in September 2005. This LDRD was funded by the Energy Efficiency and Renewable Energy strategic business unit. The purpose of this LDRD was to initiate the fundamental research necessary for the development of a novel proton-exchange membranes (PEM) to overcome the material and performance limitations of the ''state of the art'' Nafion that is used in both hydrogen and methanol fuel cells. An atomistic modeling effort was added to this LDRD in order to establish a frame work between predicted morphology and observed PEM morphology in order to relate it to fuel cell performance. Significant progress was made in the area of PEM material design, development, and demonstration during this LDRD. A fundamental understanding involving the role of the structure of the PEM material as a function of sulfonic acid content, polymer topology, chemical composition, molecular weight, and electrode electrolyte ink development was demonstrated during this LDRD. PEM materials based upon random and block polyimides, polybenzimidazoles, and polyphenylenes were created and evaluated for improvements in proton conductivity, reduced swelling, reduced O{sub 2} and H{sub 2} permeability, and increased thermal stability. Results from this work reveal that the family of polyphenylenes potentially solves several technical challenges associated with obtaining a high temperature PEM membrane. Fuel cell relevant properties such as high proton conductivity (>120 mS/cm), good thermal stability, and mechanical robustness were demonstrated during this LDRD. This report summarizes the technical accomplishments and results of this LDRD.

  1. Precision evaluation of the Ga-71(nu(e),e(-)) solar neutrino capture rate from the (He-3,t) charge-exchange reaction

    NARCIS (Netherlands)

    Frekers, D.; Adachi, T.; Akimune, H.; Alanssari, M.; Brown, B. A.; Cleveland, B. T.; Ejiri, H.; Fujita, H.; Fujita, Y.; Fujiwara, M.; Gavrin, V. N.; Harakeh, M. N.; Hatanaka, K.; Holl, M.; Iwamoto, C.; Lennarz, A.; Okamoto, A.; Okamura, H.; Suzuki, T.; Tamii, A.

    2015-01-01

    A precision measurement of the Ga-71(He-3,t)Ge-71 charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective

  2. CROSS-SECTIONS FOR HEII(N=4-]N=3) AND CVI(N=7-]N=6) EMISSION FOR CHARGE-EXCHANGE DIAGNOSTICS AT TOKAMAKS

    NARCIS (Netherlands)

    BLIEK, FW; FOLKERTS, HO; MORGENSTERN, R; HOEKSTRA, R; MENG, L; OLSON, RE; FRITSCH, W; VONHELLERMANN, M; SUMMERS, HP

    Charge exchange spectroscopy of fusion plasmas relies on an accurate knowledge of state selective electron capture cross sections. Here we discuss the gathering and evaluation of such cross sections, with emphasis on electron capture by He2+ and C6+. The influence of metastable atoms on the plasma

  3. Chandra observations of comet 2P/Encke 2003 : First detection of a collisionally thin, fast solar wind charge exchange system

    NARCIS (Netherlands)

    Lisse, CM; Christian, DJ; Dennerl, K; Wolk, SJ; Bodewits, Dennis; Hoekstra, Ronnie; Combi, MR; Makinen, T; Dryer, M; Fry, CD; Weaver, H

    2005-01-01

    We report the results of 15 hr of Chandra observations of comet 2P/Encke 2003 on November 24. X-ray emission from comet Encke was resolved on scales of 500-40,000 km, with unusual morphology due to the presence of a low-density, collisionally thin (to charge exchange) coma. A light curve with

  4. Modelling and validation of Proton exchange membrane fuel cell (PEMFC)

    Science.gov (United States)

    Mohiuddin, A. K. M.; Basran, N.; Khan, A. A.

    2018-01-01

    This paper is the outcome of a small scale fuel cell project. Fuel cell is an electrochemical device that converts energy from chemical reaction to electrical work. Proton Exchange Membrane Fuel Cell (PEMFC) is one of the different types of fuel cell, which is more efficient, having low operational temperature and fast start up capability results in high energy density. In this study, a mathematical model of 1.2 W PEMFC is developed and simulated using MATLAB software. This model describes the PEMFC behaviour under steady-state condition. This mathematical modeling of PEMFC determines the polarization curve, power generated, and the efficiency of the fuel cell. Simulation results were validated by comparing with experimental results obtained from the test of a single PEMFC with a 3 V motor. The performance of experimental PEMFC is little lower compared to simulated PEMFC, however both results were found in good agreement. Experiments on hydrogen flow rate also been conducted to obtain the amount of hydrogen consumed to produce electrical work on PEMFC.

  5. The role of surface charge on the uptake and biocompatibility of hydroxyapatite nanoparticles with osteoblast cells.

    Science.gov (United States)

    Chen, Liang; Mccrate, Joseph M; Lee, James C-M; Li, Hao

    2011-03-11

    The objective of this study is to evaluate the effect of hydroxyapatite (HAP) nanoparticles with different surface charges on the cellular uptake behavior and in vitro cell viability and proliferation of MC3T3-E1 cell lines (osteoblast). The nanoparticles' surface charge was varied by surface modification with two carboxylic acids: 12-aminododecanoic acid (positive) and dodecanedioic acid (negative). The untreated HAP nanoparticles and dodecanoic acid modified HAP nanoparticles (neutral) were used as the control. X-ray diffraction (XRD) revealed that surface modifications by the three carboxylic acids did not change the crystal structure of HAP nanoparticles; Fourier transform infrared spectroscopy (FT-IR) confirmed the adsorption and binding of the carboxylic acids on the HAP nanoparticles' surfaces; and zeta potential measurement confirmed that the chemicals successfully modified the surface charge of HAP nanoparticles in water based solution. Transmission electron microscopy (TEM) images showed that positively charged, negatively charged and untreated HAP nanoparticles, with similar size and shape, all penetrated into the cells and cells had more uptake of HAP nanoparticles with positive charge compared to those with negative charge, which might be attributed to the attractive or repulsive interaction between the negatively charged cell membrane and positively/negatively charged HAP nanoparticles. The neutral HAP nanoparticles could not penetrate the cell membrane due to their larger size. MTT assay and LDH assay results indicated that as compared with the polystyrene control, greater cell viability and cell proliferation were measured on MC3T3-E1 cells treated with the three kinds of HAP nanoparticles (neutral, positive, and untreated), among which positively charged HAP nanoparticles showed the strongest improvement for cell viability and cell proliferation. In summary, the surface charge of HAP nanoparticles can be modified to influence the cellular uptake of

  6. Benchmarking charge exchange theory in the dawning era of space-born high-resolution X-ray spectrometers

    Science.gov (United States)

    Betancourt-Martinez, Gabriele

    2017-08-01

    Charge Exchange (CX) is a process in which a highly charged ion captures one or more electrons from a neutral atom or molecule into an excited state during a close interaction. The electron's subsequent radiative cascade to the ground state produces diagnostic line emission in the X-ray band. CX with solar wind ions occurs frequently in the solar system, and CX may also occur astrophysically. In order to properly identify CX in astrophysical spectra and make use of its diagnostic properties, we must be able to model the emission. Theoretical treatments of CX are often computationally expensive, experimental benchmarks at high resolution are fairly scarce, and there is often poor agreement between the two. This dissertation seeks to build a better understanding of the mechanics and spectral signatures of CX through high-resolution experimental data paired with theoretical calculations of CX. Chapter 1 outlines the necessary ingredients for modeling and identifying CX spectra, describes several astrophysical environments in which CX has been observed or postulated to occur, and presents some of the challenges we are facing in identifying and understanding this emission. Chapter 2 describes the theoretical and computational tools used in this work. Chapter 3 discusses the experimental tools and facilities we use, namely an Electron Beam Ion Trap (EBIT) and an X-ray microcalorimeter. Chapter 4 presents experimental K-shell data that highlights both the subtle nature of the CX interaction and the difficulty in including those nuances in spectral synthesis codes. Chapter 5 presents the first high-resolution L-shell CX spectra of Ne-like Ni and describes what we can learn from these results. In Chapter 6, we take these data a step further and present a pipeline to calculate relative state-selective capture cross sections, previously only available from theoretical modeling. We then compare some of our results to theory. In Chapter 7, we discuss several future steps for

  7. Device and Method for Continuously Equalizing the Charge State of Lithium Ion Battery Cells

    Science.gov (United States)

    Schwartz, Paul D. (Inventor); Martin, Mark N. (Inventor); Roufberg, Lewis M. (Inventor)

    2015-01-01

    A method of equalizing charge states of individual cells in a battery includes measuring a previous cell voltage for each cell, measuring a previous shunt current for each cell, calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell, determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages, and calculating a new shunt current for each cell.

  8. Tandem cathode for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Siahrostami, Samira; Björketun, Mårten E.; Strasser, Peter

    2013-01-01

    tandem cathode design where the full oxygen reduction, involving four electron-transfer steps, is divided into formation (equilibrium potential 0.70 V) followed by reduction (equilibrium potential 1.76 V) of hydrogen peroxide. The two part reactions contain only two electron-transfer steps and one......The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel...... reaction intermediate each, and they occur on different catalyst surfaces. As a result they can be optimized independently and the fundamental problem associated with the four-electron catalysis is avoided. A combination of density functional theory calculations and published experimental data is used...

  9. Analysis performance of proton exchange membrane fuel cell (PEMFC)

    Science.gov (United States)

    Mubin, A. N. A.; Bahrom, M. H.; Azri, M.; Ibrahim, Z.; Rahim, N. A.; Raihan, S. R. S.

    2017-06-01

    Recently, the proton exchange membrane fuel cell (PEMFC) has gained much attention to the technology of renewable energy due to its mechanically ideal and zero emission power source. PEMFC performance reflects from the surroundings such as temperature and pressure. This paper presents an analysis of the performance of the PEMFC by developing the mathematical thermodynamic modelling using Matlab/Simulink. Apart from that, the differential equation of the thermodynamic model of the PEMFC is used to explain the contribution of heat to the performance of the output voltage of the PEMFC. On the other hand, the partial pressure equation of the hydrogen is included in the PEMFC mathematical modeling to study the PEMFC voltage behaviour related to the input variable input hydrogen pressure. The efficiency of the model is 33.8% which calculated by applying the energy conversion device equations on the thermal efficiency. PEMFC’s voltage output performance is increased by increasing the hydrogen input pressure and temperature.

  10. A general model of proton exchange membrane fuel cell

    Science.gov (United States)

    Le, Anh Dinh; Zhou, Biao

    In this study, a general model of proton exchange membrane fuel cell (PEMFC) was constructed, implemented and employed to simulate the fluid flow, heat transfer, species transport, electrochemical reaction, and current density distribution, especially focusing on liquid water effects on PEMFC performance. The model is a three-dimensional and unsteady one with detailed thermo-electrochemistry, multi-species, and two-phase interaction with explicit gas-liquid interface tracking by using the volume-of-fluid (VOF) method. The general model was implemented into the commercial computational fluid dynamics (CFD) software package FLUENT ® v6.2, with its user-defined functions (UDFs). A complete PEMFC was considered, including membrane, gas diffusion layers (GDLs), catalyst layers, gas flow channels, and current collectors. The effects of liquid water on PEMFC with serpentine channels were investigated. The results showed that this general model of PEMFC can be a very useful tool for the optimization of practical engineering designs of PEMFC.

  11. Overview on R and D and design activities for the ITER core charge exchange spectroscopy diagnostic system

    Energy Technology Data Exchange (ETDEWEB)

    Biel, W., E-mail: w.biel@fz-juelich.de [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich Gmbh, Association EURATOM-FZJ, member of Trilateral Euregio Cluster, 52425 Juelich (Germany); Baross, T. [KFKI RMKI, EURATOM Association, PO Box 49, H-1521 Budapest (Hungary); Bourauel, P. [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich Gmbh, Association EURATOM-FZJ, member of Trilateral Euregio Cluster, 52425 Juelich (Germany); Dunai, D. [KFKI RMKI, EURATOM Association, PO Box 49, H-1521 Budapest (Hungary); Durkut, M. [TNO Science and Industry, Partner in ITER-NL, P.O. Box 155, 2600 AD Delft (Netherlands); Erdei, G. [BME, EURATOM Association, PO Box 91, H-1521 Budapest (Hungary); Hawkes, N. [Association EURATOM/CCFE, OX14 3DB Abingdon (United Kingdom); Hellermann, M. von [FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, partner in the Trilateral Euregio Cluster and ITER-NL, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Hogenbirk, A. [Nuclear Research and Consultancy Group V.o.F., Petten (Netherlands); Jaspers, R. [Department of Applied Physics, Eindhoven University of Technology (Netherlands); Kiss, G. [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich Gmbh, Association EURATOM-FZJ, member of Trilateral Euregio Cluster, 52425 Juelich (Germany); Klinkhamer, F. [TNO Science and Industry, Partner in ITER-NL, P.O. Box 155, 2600 AD Delft (Netherlands); Koning, J.F. [FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, partner in the Trilateral Euregio Cluster and ITER-NL, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Kotov, V.; Krasikov, Y.; Krimmer, A. [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich Gmbh, Association EURATOM-FZJ, member of Trilateral Euregio Cluster, 52425 Juelich (Germany)

    2011-10-15

    The ITER core charge exchange recombination spectroscopy (core CXRS) diagnostic system is designed to provide experimental access to various measurement quantities in the ITER core plasma such as ion densities, temperatures and velocities. The implementation of the approved CXRS diagnostic principle on ITER faces significant challenges: First, a comparatively low CXRS signal intensity is expected, together with a high noise level due to bremsstrahlung, while the requested measurement accuracy and stability for the core CXRS system go far beyond the level commonly achieved in present-day fusion experiments. Second, the lifetime of the first mirror surface is limited due to either erosion by fast particle bombardment or deposition of impurities. Finally, the hostile technical environment on ITER imposes challenging boundary conditions for the diagnostic integration and operation, including high neutron loads, electro-magnetic loads, seismic events and a limited access for maintenance. A brief overview on the R and D and design activities for the core CXRS system is presented here, while the details are described in parallel papers.

  12. Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

    Science.gov (United States)

    Edley, Michael

    . With these techniques, the extension of the depletion layer from CdSe into ZnO was determined to be vital to suppression of interfacial recombination. However, depletion of the ZnO also restricted the effective diffusion core for electrons and slowed their transport. Thus, materials and geometries should be chosen to allow for a depletion layer that suppresses interfacial recombination without impeding electron transport to the point that it is detrimental to cell performance. Thin film solar cells are another promising technology that can reduce costs by relaxing material processing requirements. CuInxGa (1-x)Se (CIGS) is a well studied thin film solar cell material that has achieved good efficiencies of 22.6%. However, use of rare elements raise concerns over the use of CIGS for global power production. CuSbS2 shares chemistry with CuInSe2 and also presents desirable properties for thin film absorbers such as optimal band gap (1.5 eV), high absorption coefficient, and Earth-abundant and non-toxic elements. Despite the promise of CuSbS2, direct characterization of the material for solar cell application is scarce in the literature. CuSbS2 nanoplates were synthesized by a colloidal hot-injection method at 220 °C in oleylamine. The CuSbS2 platelets synthesized for 30 minutes had dimensions of 300 nm by 400 nm with a thickness of 50 nm and were capped with the insulating oleylamine synthesis ligand. The oleylamine synthesis ligand provides control over nanocrystal growth but is detrimental to intercrystal charge transport that is necessary for optoelectronic device applications. Solid-state and solution phase ligand exchange of oleylamine with S2- were used to fabricate mesoporous films of CuSbS2 nanoplates for application in solar cells. Exchange of the synthesis ligand with S2- resulted in a two order of magnitude increase in 4-point probe conductivity. Photoexcited carrier lifetimes of 1.4 ns were measured by time-resolved terahertz spectroscopy, indicating potential

  13. Water Soluble Polymers as Proton Exchange Membranes for Fuel Cells

    Directory of Open Access Journals (Sweden)

    Bing-Joe Hwang

    2012-03-01

    Full Text Available The relentless increase in the demand for useable power from energy-hungry economies continues to drive energy-material related research. Fuel cells, as a future potential power source that provide clean-at-the-point-of-use power offer many advantages such as high efficiency, high energy density, quiet operation, and environmental friendliness. Critical to the operation of the fuel cell is the proton exchange membrane (polymer electrolyte membrane responsible for internal proton transport from the anode to the cathode. PEMs have the following requirements: high protonic conductivity, low electronic conductivity, impermeability to fuel gas or liquid, good mechanical toughness in both the dry and hydrated states, and high oxidative and hydrolytic stability in the actual fuel cell environment. Water soluble polymers represent an immensely diverse class of polymers. In this comprehensive review the initial focus is on those members of this group that have attracted publication interest, principally: chitosan, poly (ethylene glycol, poly (vinyl alcohol, poly (vinylpyrrolidone, poly (2-acrylamido-2-methyl-1-propanesulfonic acid and poly (styrene sulfonic acid. The paper then considers in detail the relationship of structure to functionality in the context of polymer blends and polymer based networks together with the effects of membrane crosslinking on IPN and semi IPN architectures. This is followed by a review of pore-filling and other impregnation approaches. Throughout the paper detailed numerical results are given for comparison to today’s state-of-the-art Nafion® based materials.

  14. Microbial desalination cells packed with ion-exchange resin to enhance water desalination rate.

    Science.gov (United States)

    Morel, Alexandre; Zuo, Kuichang; Xia, Xue; Wei, Jincheng; Luo, Xi; Liang, Peng; Huang, Xia

    2012-08-01

    A novel configuration of microbial desalination cell (MDC) packed with ion-exchange resin (R-MDC) was proposed to enhance water desalination rate. Compared with classic MDC (C-MDC), an obvious increase in desalination rate (DR) was obtained by R-MDC. With relatively low concentration (10-2 g/L NaCl) influents, the DR values of R-MDC were about 1.5-8 times those of C-MDC. Ion-exchange resins packed in the desalination chamber worked as conductor and thus counteracted the increase in ohmic resistance during treatment of low concentration salt water. Ohmic resistances of R-MDC stabilized at 3.0-4.7 Ω. By contrast, the ohmic resistances of C-MDC ranged from 5.5 to 12.7 Ω, which were 55-272% higher than those of R-MDC. Remarkable improvement in desalination rate helped improve charge efficiency for desalination in R-MDC. The results first showed the potential of R-MDC in the desalination of water with low salinity. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Fouling of proton exchange membrane (PEM) deteriorates the performance of microbial fuel cell.

    Science.gov (United States)

    Xu, Juan; Sheng, Guo-Ping; Luo, Hong-Wei; Li, Wen-Wei; Wang, Long-Fei; Yu, Han-Qing

    2012-04-15

    The fouling characteristics of proton exchange membrane (PEM) in microbial fuel cell (MFC) and the resulting deterioration of MFC performance were explored in this study. It was observed that the ion exchange capacity, conductivity and diffusion coefficients of cations of PEM were reduced significantly after fouling. Imaging analysis coupled with FTIR analysis indicated that the fouling layer attached on PEM consisted of microorganisms encased in extracellular polymers and inorganic salt precipitations. The results clearly demonstrate that PEM fouling deteriorated the performance of MFCs and led to a decrease in electricity generation. Cation transfer limitation might play an important role in the deterioration of MFC performance because of the membrane fouling. This was attributed to the physical blockage of charge transfer in the MFC resulted from the membrane fouling. With the experimental results, the effect of membrane fouling on the electrical generation of MFCs was evaluated. It was found that the decreased diffusion coefficients of cations and cathodic potential loss after membrane fouling contributed mainly to the deterioration of the MFC performance. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Using (18)O/(16)O exchange to probe an equilibrium space-charge layer at the surface of a crystalline oxide: method and application.

    Science.gov (United States)

    De Souza, Roger A; Martin, Manfred

    2008-05-07

    The use of an (18)O/(16)O exchange experiment as a means for probing surface space-charge layers in oxides is examined theoretically and experimentally. On the basis of a theoretical treatment, isotope penetration profiles are calculated for (18)O/(16)O exchange across a gas-solid interface and subsequent diffusion of the labelled isotope through an equilibrium space-charge layer depleted of mobile oxygen vacancies and into a homogeneous bulk phase. Profiles calculated for a range of conditions all have a characteristic shape: a sharp drop in isotope fraction close to the surface followed by a normal bulk diffusion profile. Experimental (18)O profiles in an exchanged (001) oriented single crystal of Fe-doped SrTiO(3) were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS). By extracting the space-charge potential from such profiles, we demonstrate that this method allows the spatially resolved characterization of space-charge layers at the surfaces of crystalline oxides under thermodynamically well-defined conditions.

  17. DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Shamsuddin Ilias

    2001-07-06

    Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for space and electric vehicle applications. Platinum (Pt) catalyst is used for both fuel and air electrodes in PEMFCs. The carbon monoxide (CO) contamination of H{sub 2} greatly affects electrocatalysts used at the anode of PEMFCs and decrease the cell performance. This irreversible poisoning of the anode can happen even in CO concentrations as low as few ppm, and therefore, require expensive scrubbing of the H{sub 2}-fuel to reduce the contaminant concentration to acceptable level. In order to commercialize this environmentally sound source of energy/power system, development of suitable CO-tolerant catalyst is needed. In this work, we have synthesized several novel electrocatalysts (Pt/C, Pt/Ru/C Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell. The concentration of CO in the H{sub 2} fuel varied from 10 ppm to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effect of temperature, catalyst compositions, and electrode film preparation methods on the performance of PEM fuel cell has also been studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalysts (10 wt % Pt/Ru/C, 20 wt % Pt/Mo/C) were more CO-tolerant than 20 wt % Pt catalyst alone. It was also observed that spraying method is better for the preparation of electrode film than the brushing technique. Some of these results are summarized in this report.

  18. Metal Oxides as Efficient Charge Transporters in Perovskite Solar Cells

    KAUST Repository

    Haque, Mohammed

    2017-07-10

    Over the past few years, hybrid halide perovskites have emerged as a highly promising class of materials for photovoltaic technology, and the power conversion efficiency of perovskite solar cells (PSCs) has accelerated at an unprecedented pace, reaching a record value of over 22%. In the context of PSC research, wide-bandgap semiconducting metal oxides have been extensively studied because of their exceptional performance for injection and extraction of photo-generated carriers. In this comprehensive review, we focus on the synthesis and applications of metal oxides as electron and hole transporters in efficient PSCs with both mesoporous and planar architectures. Metal oxides and their doped variants with proper energy band alignment with halide perovskites, in the form of nanostructured layers and compact thin films, can not only assist with charge transport but also improve the stability of PSCs under ambient conditions. Strategies for the implementation of metal oxides with tailored compositions and structures, and for the engineering of their interfaces with perovskites will be critical for the future development and commercialization of PSCs.

  19. Rapid, efficient charging of lead-acid and nickel-zinc traction cells. [for electric vehicles

    Science.gov (United States)

    Smithrick, J. J.

    1978-01-01

    Lead-acid and nickel-zinc traction cells were rapidly and efficiently charged using a high rate taped dc charge (HRTDC) method which could possibly be used for on-the-road service recharge of electric vehicles. The HRTDC method takes advantage of initial high cell charge acceptance and uses cell gassing rate and temperature as an indicator of charging efficiency. On the average, 300 amp-hour nickel-zinc traction cells were given a HRTDC to 78% of rated amp-hour capacity within 53 minutes at an amp-hour efficiency of 92% and an energy efficiency of 52%. Three-hundred amp-hour lead-acid traction cells were charged to 69% of rated amp-hour capacity within 46 minutes at an amp-hour efficiency of 91% with an energy efficiency of 64%.

  20. Cellular uptake and cytotoxicity of positively charged chitosan gold nanoparticles in human lung adenocarcinoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Seon Young; Jang, Soo Hwa [Seoul National University, Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Institute for Veterinary Science (Korea, Republic of); Park, Jin; Jeong, Saeromi; Park, Jin Ho; Ock, Kwang Su [Soongsil University, Department of Chemistry (Korea, Republic of); Lee, Kangtaek [Yonsei University, Department of Chemical and Biomolecular Engineering (Korea, Republic of); Yang, Sung Ik [Kyung Hee University, College of Environment and Applied Chemistry (Korea, Republic of); Joo, Sang-Woo, E-mail: sjoo@ssu.ac.kr [Soongsil University, Department of Chemistry (Korea, Republic of); Ryu, Pan Dong; Lee, So Yeong, E-mail: leeso@snu.ac.kr [Seoul National University, Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Institute for Veterinary Science (Korea, Republic of)

    2012-12-15

    Cellular uptake, cytotoxicity, and mechanisms of cytotoxicity of the positively charged Au nanoparticles (NPs) were examined in A549 cells, which are one of the most characterized pulmonary cellular systems. Positively charged Au NPs were prepared by chemical reduction using chitosan. The dimension and surface charge of Au NPs were examined by transmission electron microscopy (TEM), dynamic light scattering, and zeta potential measurements. The uptake of Au NPs into A549 cells was also monitored using TEM and dark-field microscopy (DFM) and z-stack confocal microRaman spectroscopy. DFM live cell imaging was also performed to monitor the entry of chitosan Au NPs in real time. The cytotoxic assay, using both methylthiazol tetrazolium and lactate dehydrogenase assays revealed that positively charged Au NPs decreased cell viability. Flow cytometry, DNA fragmentation, real-time PCR, and western blot analysis suggest that positively charged chitosan Au NPs provoke cell damage through both apoptotic and necrotic pathways.

  1. Cellular uptake and cytotoxicity of positively charged chitosan gold nanoparticles in human lung adenocarcinoma cells

    Science.gov (United States)

    Choi, Seon Young; Jang, Soo Hwa; Park, Jin; Jeong, Saeromi; Park, Jin Ho; Ock, Kwang Su; Lee, Kangtaek; Yang, Sung Ik; Joo, Sang-Woo; Ryu, Pan Dong; Lee, So Yeong

    2012-12-01

    Cellular uptake, cytotoxicity, and mechanisms of cytotoxicity of the positively charged Au nanoparticles (NPs) were examined in A549 cells, which are one of the most characterized pulmonary cellular systems. Positively charged Au NPs were prepared by chemical reduction using chitosan. The dimension and surface charge of Au NPs were examined by transmission electron microscopy (TEM), dynamic light scattering, and zeta potential measurements. The uptake of Au NPs into A549 cells was also monitored using TEM and dark-field microscopy (DFM) and z-stack confocal microRaman spectroscopy. DFM live cell imaging was also performed to monitor the entry of chitosan Au NPs in real time. The cytotoxic assay, using both methylthiazol tetrazolium and lactate dehydrogenase assays revealed that positively charged Au NPs decreased cell viability. Flow cytometry, DNA fragmentation, real-time PCR, and western blot analysis suggest that positively charged chitosan Au NPs provoke cell damage through both apoptotic and necrotic pathways.

  2. Cathode material comparison of thermal runaway behavior of Li-ion cells at different state of charges including over charge

    Science.gov (United States)

    Mendoza-Hernandez, Omar Samuel; Ishikawa, Hiroaki; Nishikawa, Yuuki; Maruyama, Yuki; Umeda, Minoru

    2015-04-01

    The analysis of Li-ion secondary cells under outstanding conditions, as overcharge and high temperatures, is important to determine thermal abuse characteristics of electroactive materials and precise risk assessments on Li-ion cells. In this work, the thermal runaway behavior of LiCoO2 and LiMn2O4 cathode materials were compared at different state of charges (SOCs), including overcharge, by carrying out accelerating rate calorimetry (ARC) measurements using 18650 Li-ion cells. Onset temperatures of self-heating reactions and thermal runaway behavior were identified, and by using these onset points thermal mapping plots were made. We were able to identify non-self-heating, self-heating and thermal runaway regions as a function of state of charge and temperature. The cell using LiMn2O4 cathode material was found to be more thermally stable than the cell using LiCoO2. In parallel with the ARC measurements, the electrochemical behavior of the cells was monitored by measuring the OCV and internal resistance of the cells. The electrochemical behavior of the cells showed a slightly dependency on SOC.

  3. Protonic conductors for proton exchange membrane fuel cells: An overview

    Directory of Open Access Journals (Sweden)

    Jurado Ramon Jose

    2002-01-01

    Full Text Available At present, Nation, which is a perfluorinated polymer, is one of the few materials that deliver the set of chemical and mechanical properties required to perform as a good electrolyte in proton exchange membrane fuel cells (PEMFCs. However, Nation presents some disadvantages, such as limiting the operational temperature of the fuel system (So°C, because of its inability to retain water at higher temperatures and also suffers chemical crossover. In addition to these restrictions, Nation membranes are very expensive. Reducing costs and using environmentally friendly materials are good reasons to make a research effort in this field in order to achieve similar or even better fuel-cell performances. Glass materials of the ternary system SiO2-ZrO2-P2O5, hybrid materials based on Nation, and nanopore ceramic membranes based on SiO2 TiO2, Al2O3, etc. are considered at present, as promising candidates to replace Nation as the electrolyte in PEMFCs. These types of materials are generally prepared by sol-gel processes in order to tailor their channel-porous structure and pore size. In this communication, the possible candidates in the near future as electrolytes (including other polymers different than Nation in PEMFCs are briefly reviewed. Their preparation methods, their electrical transport properties and conduction mechanisms are considered. The advantages and disadvantages of these materials with respect to Nation are also discussed.

  4. High power density proton exchange membrane fuel cells

    Science.gov (United States)

    Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

    1993-01-01

    Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

  5. Numerical modeling transport phenomena in proton exchange membrane fuel cells

    Science.gov (United States)

    Suh, DongMyung

    To study the coupled phenomena occurring in proton exchange membrane fuel cells, a two-phase, one-dimensional, non-isothermal model is developed in the chapter 1. The model includes water phase change, proton transport in the membrane and electro-osmotic effect. The thinnest, but most complex layer in the membrane electrode assembly, catalyst layer, is considered an interfacial boundary between the gas diffusion layer and the membrane. Mass and heat transfer and electro-chemical reaction through the catalyst layer are formulated into equations, which are applied to boundary conditions for the gas diffusion layer and the membrane. Detail accounts of the boundary equations and the numerical solving procedure used in this work are given. The polarization curve is calculated at different oxygen pressures and compared with the experimental results. When the operating condition is changed along the polarization curve, the change of physicochemical variables in the membrane electrode assembly is studied. In particular, the over-potential diagram presents the usage of the electrochemical energy at each layer of the membrane electrode assembly. Humidity in supplying gases is one of the most important factors to consider for improving the performance of PEMFE. Both high and low humidity conditions can result in a deteriorating cell performance. The effect of humidity on the cell performance is studied in the chapter 2. First, a numerical model based on computational fluid dynamics is developed. Second, the cell performances are simulated, when the relative humidity is changed from 0% to 100% in the anode and the cathode channel. The simulation results show how humidity in the reactant gases affects the water content distribution in the membrane, the over-potential at the catalyst layers and eventually the cell performance. In particular, the rapid enhancement in the cell performance caused by self-hydrating membrane is captured by the simulation. Fully humidifying either H2

  6. A FRET sensor enables quantitative measurements of membrane charges in live cells.

    Science.gov (United States)

    Ma, Yuanqing; Yamamoto, Yui; Nicovich, Philip R; Goyette, Jesse; Rossy, Jérémie; Gooding, J Justin; Gaus, Katharina

    2017-04-01

    Membrane charge has a critical role in protein trafficking and signaling. However, quantification of the effective electrostatic potential of cellular membranes has remained challenging. We developed a fluorescence membrane charge sensor (MCS) that reports changes in the membrane charge of live cells via Förster resonance energy transfer (FRET). MCS is permanently attached to the inner leaflet of the plasma membrane and shows a linear, reversible and fast response to changes of the electrostatic potential. The sensor can monitor a wide range of cellular treatments that alter the electrostatic potential, such as incorporation and redistribution of charged lipids and alterations in cytosolic ion concentration. Applying the sensor to T cell biology, we used it to identify charged membrane domains in the immunological synapse. Further, we found that electrostatic interactions prevented spontaneous phosphorylation of the T cell receptor and contributed to the formation of signaling clusters in T cells.

  7. Pressure, relaxation volume, and elastic interactions in charged simulation cells

    Science.gov (United States)

    Bruneval, Fabien; Varvenne, Céline; Crocombette, Jean-Paul; Clouet, Emmanuel

    2015-01-01

    The ab initio calculation of charged supercells within density-functional theory is a necessary step to access several important properties of matter. The relaxation volume of charged point defects or the partial molar volume of ions in solution are two such examples. However, the total energy and therefore the pressure of charged systems is not uniquely defined when periodic boundary conditions are employed. This problem is tightly related to the origin of the electrostatic potential in periodic systems. This effect can be easily observed by modifying the electrostatic convention or modifying the local ionic potential details. We propose an approach to uniquely define the pressures in charged supercells with the use of the absolute deformation potentials. Only with such a definition could the ab initio calculations provide meaningful values for the relaxation volumes and for the elastic interactions for charged defects in semiconductors or ions in solution. The proposed scheme allows one to calculate sensible data even when charge neutrality is not enforced, thus going beyond the classical force-field-based approaches.

  8. Dielectric process of space-charge polarization for an electrolytic cell with blocking electrodes.

    Science.gov (United States)

    Sawada, Atsushi

    2008-08-14

    The dielectric process of space-charge polarization for an electrolytic cell with blocking electrodes is simulated considering bound charges externally supplied to the electrodes. A numerical calculation is performed to determine the distribution of mobile charges under an ac field satisfying Poisson's equation in which the dielectric constant varies with frequency. An exact frequency-dependent curve of the complex dielectric constant is obtained by including the contribution of bound charges induced by the space-charge polarization itself in Poisson's equation at every frequency. The present model of the space-charge polarization enables one to correctly understand the experimental results on the complex dielectric constant of electrolytic cells in low-frequency regions.

  9. Mathematical and Computational Modeling of Polymer Exchange Membrane Fuel Cells

    Science.gov (United States)

    Ulusoy, Sehribani

    results showed that the fuel performance can be improved by using flow field designs alleviating the reactant depletion along the channels and supplying more uniform reactant distribution. Stepped flow field was found to show better performance when compared to straight and tapered ones. ANSYS FLUENT model is evaluated in terms of predicting the two phase flow in the fuel cell components. It is proposed that it is not capable of predicting the entire fuel cell polarization due to the lack of agglomerate catalyst layer modeling and well-established two-phase flow modeling. Along with the comprehensive modeling efforts, also an analytical model has been computed by using MathCAD and it is found that this simpler model is able to predict the performance in a general trend according to the experimental data obtained for a new novel membrane. Therefore, it can be used for robust prediction of the cell performance at different operating conditions such as temperature and pressure, and the electrochemical properties such as the catalyst loading, the exchange current density and the diffusion coefficients of the reactants. In addition to the modeling efforts, this thesis also presents a very comprehensive literature review on the models developed in the literature so far, the modeling efforts in fuel cell sandwich including membrane, catalyst layer and gas diffusion layer and fuel cell model properties. Moreover, a summary of possible directions of research in fuel cell analysis and computational modeling has been presented.

  10. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  11. $\\beta$- decay of $^{58}$Zn. A critical test for the charge-exchange reaction as a probe for the $\\beta$- decay strength distribution

    CERN Multimedia

    2002-01-01

    % IS353 \\\\ \\\\ Due to its importance in fundamental physics and astrophysics, a great effort both theoretically and experimentally is devoted to study Gamow Teller (GT)-strength. The GT-strength and its distribution play a key role in late stellar evolution. During the pre-supernova core-collapse of massive stars, the electron capture and nuclear $\\beta$ -decay determine the electron-to-baryon ratio, which influences the infall dynamics and the mass of the final core. The cross-section of the charge-exchange reaction at forward angles with energies above 100~MeV is expected to be proportional to the squares of Fermi and GT matrix elements. This proportionality should provide a Q-value free method to probe the weak interaction strength and renormalization effects in nuclei. Thus charge-exchange reactions are often used to determine the experimental GT-strength. However, the connection between the GT-strength and the cross-section of the charge-exchange reaction is partially model-dependent and the question aris...

  12. Modeling and simulation of the dynamic behavior of portable proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, C.

    2005-07-01

    In order to analyze the operational behavior, a mathematical model of planar self-breathing fuel cells is developed and validated in Chapter 3 of this thesis. The multicomponent transport of the species is considered as well as the couplings between the transport processes of heat, charge, and mass and the electrochemical reactions. Furthermore, to explain the oxygen mass transport limitation in the porous electrode of the cathode side an agglomerate model for the oxygen reduction reaction is developed. In Chapter 4 the important issue of liquid water generation and transport in PEMFCs is addressed. One of the major tasks when operating this type of fuel cell is avoiding the complete flooding of the PEMFC during operation. A one-dimensional and isothermal model is developed that is based on a coupled system of partial differential equations. The model contains a dynamic and two-phase description of the proton exchange membrane fuel cell. The mass transport in the gas phase and in the liquid phase is considered as well as the phase transition between liquid water and water vapor. The transport of charges and the electrochemical reactions are part of the model. Flooding effects that are caused by liquid water accumulation are described by this model. Moreover, the model contains a time-dependent description of the membrane that accounts for Schroeder's paradox. The model is applied to simulate cyclic voltammograms. Chapter 5 is focused on the dynamic investigation of PEMFC stacks. Understanding the dynamic behavior of fuel cell stacks is important for the operation and control of fuel cell stacks. Using the single cell model of Chapter 3 and the dynamic model of Chapter 4 as basis, a mathematical model of a PEMFC stack is developed. However, due to the complexity of a fuel cell stack, the spatial resolution and dynamic description of the liquid water transport are not accounted for. These restrictions allow for direct comparison between the solution variables of

  13. Role of the charge transfer state in organic donor-acceptor solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Deibel, Carsten; Strobel, Thomas [Experimental Physics VI, Julius-Maximilians-University of Wuerzburg (Germany); Dyakonov, Vladimir [Experimental Physics VI, Julius-Maximilians-University of Wuerzburg (Germany); Bavarian Centre for Applied, Energy Research (ZAE Bayern), Wuerzburg (Germany)

    2010-10-01

    Charge transfer complexes are interfacial charge pairs residing at the donor-acceptor heterointerface in organic solar cell. Experimental evidence shows that it is crucial for the photovoltaic performance, as both photocurrent and open circuit voltage directly depend on it. For charge photogeneration, charge transfer complexes represent the intermediate but essential step between exciton dissociation and charge extraction. Recombination of free charges to the ground state is via the bound charge transfer state before being lost to the ground state. In terms of the open circuit voltage, its maximum achievable value is determined by the energy of the charge transfer state. An important question is whether or not maximum photocurrent and maximum open circuit voltage can be achieved simultaneously. The impact of increasing the CT energy - in order to raise the open circuit voltage, but lowering the kinetic excess energy of the CT complexes at the same time - on the charge photogeneration will accordingly be discussed. Clearly, the fundamental understanding of the processes involving the charge transfer state is essential for an optimisation of the performance of organic solar cells. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  14. Fault tolerance control for proton exchange membrane fuel cell systems

    Science.gov (United States)

    Wu, Xiaojuan; Zhou, Boyang

    2016-08-01

    Fault diagnosis and controller design are two important aspects to improve proton exchange membrane fuel cell (PEMFC) system durability. However, the two tasks are often separately performed. For example, many pressure and voltage controllers have been successfully built. However, these controllers are designed based on the normal operation of PEMFC. When PEMFC faces problems such as flooding or membrane drying, a controller with a specific design must be used. This paper proposes a unique scheme that simultaneously performs fault diagnosis and tolerance control for the PEMFC system. The proposed control strategy consists of a fault diagnosis, a reconfiguration mechanism and adjustable controllers. Using a back-propagation neural network, a model-based fault detection method is employed to detect the PEMFC current fault type (flooding, membrane drying or normal). According to the diagnosis results, the reconfiguration mechanism determines which backup controllers to be selected. Three nonlinear controllers based on feedback linearization approaches are respectively built to adjust the voltage and pressure difference in the case of normal, membrane drying and flooding conditions. The simulation results illustrate that the proposed fault tolerance control strategy can track the voltage and keep the pressure difference at desired levels in faulty conditions.

  15. The importance of OH − transport through anion exchange membrane in microbial electrolysis cells

    KAUST Repository

    Ye, Yaoli

    2018-01-11

    In two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact electrochemical performance. However, ion transport between the chambers will also impact performance, which is a factor not included in those calculations. To separate the impacts of pH and ion transport on MEC performance, a high molecular weight polymer buffer (PoB), which was retained in the catholyte due to its low AEM transport and cationic charge, was compared to PBS in MECs and abiotic electrochemical half cells (EHCs). In MECs, catholyte pH control was less important than ion transport. MEC tests using the PoB catholyte, which had a higher buffer capacity and thus maintained a lower catholye pH (<8), resulted in a 50% lower hydrogen production rate (HPR) than that obtained using PBS (HPR = 0.7 m3-H2 m−3 d−1) where the catholyte rapidly increased to pH = 12. The main reason for the decreased performance using PoB was a lack of hydroxide ion transfer into the anolyte to balance pH. The anolyte pH in MECs rapidly decreased to 5.8 due to a lack of hydroxide ion transport, which inhibited current generation by the anode, whereas the pH was maintained at 6.8 using PBS. In abiotic tests in ECHs, where the cathode potential was set at −1.2 V, the HPR was 133% higher using PoB than PBS due to catholyte pH control, as the anolyte pH was not a factor in the performance. These results show that maintaining charge transfer to control anolyte pH is more important than obtaining a more neutral pH catholyte.

  16. Reducing nitrogen crossover in microbial reverse-electrodialysis cells by using adjacent anion exchange membranes and anion exchange resin

    KAUST Repository

    Wallack, Maxwell J.

    2015-01-01

    Microbial reverse electrodialysis cells (MRECs) combine power generation from salinity gradient energy using reverse electrodialysis (RED), with power generation from organic matter using a microbial fuel cell. Waste heat can be used to distill ammonium bicarbonate into high (HC) and low salt concentration (LC) solutions for use in the RED stack, but nitrogen crossover into the anode chamber must be minimized to avoid ammonia loses, and foster a healthy microbial community. To reduce nitrogen crossover, an additional low concentration (LC) chamber was inserted before the anode using an additional anion exchange membrane (AEM) next to another AEM, and filled with different amounts of anion or cation ion exchange resins. Addition of the extra AEM increased the ohmic resistance of the test RED stack from 103 Ω cm2 (1 AEM) to 295 Ω cm2 (2 AEMs). However, the use of the anion exchange resin decreased the solution resistance of the LC chamber by 74% (637 Ω cm2, no resin; 166 Ω cm2 with resin). Nitrogen crossover into the anode chamber was reduced by up to 97% using 50% of the chamber filled with an anion exchange resin compared to the control (no additional chamber). The added resistance contributed by the use of the additional LC chamber could be compensated for by using additional LC and HC membrane pairs in the RED stack.

  17. Cell adhesion monitoring of human induced pluripotent stem cell based on intrinsic molecular charges

    Science.gov (United States)

    Sugimoto, Haruyo; Sakata, Toshiya

    2014-01-01

    We have shown a simple way for real-time, quantitative, non-invasive, and non-label monitoring of human induced pluripotent stem (iPS) cell adhesion by use of a biologically coupled-gate field effect transistor (bio-FET), which is based on detection of molecular charges at cell membrane. The electrical behavior revealed quantitatively the electrical contacts of integrin-receptor at the cell membrane with RGDS peptide immobilized at the gate sensing surface, because that binding site was based on cationic α chain of integrin. The platform based on the bio-FET would provide substantial information to evaluate cell/material bio-interface and elucidate biding mechanism of adhesion molecules, which could not be interpreted by microscopic observation.

  18. Powering microbial electrolysis cells by capacitor circuits charged using microbial fuel cell

    KAUST Repository

    Hatzell, Marta C.

    2013-05-01

    A microbial electrolysis cell (MEC) was powered by a capacitor based energy storage circuit using energy from a microbial fuel cell (MFC) to increase MEC hydrogen production rates compared to that possible by the MFC alone. To prevent voltage reversal, MFCs charged the capacitors in a parallel configuration, and then the capacitors were discharged in series to boost the voltage that was used to power the MECs. The optimal capacitance for charging was found to be ∼0.01 F for each MFC. The use of the capacitor charging system increased energy recoveries from 9 to 13%, and hydrogen production rates increased from 0.31 to 0.72 m3 m-3-day-1, compared to coupled systems without capacitors. The circuit efficiency (the ratio of the energy that was discharged to the MEC to the energy provided to the capacitor from the MFCs) was ∼90%. These results provide an improved method for linking MFCs to MECs for renewable hydrogen gas production. © 2012 Elsevier B.V. All rights reserved.

  19. Evaluation of a Passive Heat Exchanger Based Cooling System for Fuel Cell Applications

    Science.gov (United States)

    Colozza, Anthony J.; Burke, Kenneth A.

    2011-01-01

    Fuel cell cooling is conventionally performed with an actively controlled, dedicated coolant loop that exchanges heat with a separate external cooling loop. To simplify this system the concept of directly cooling a fuel cell utilizing a coolant loop with a regenerative heat exchanger to preheat the coolant entering the fuel cell with the coolant exiting the fuel cell was analyzed. The preheating is necessary to minimize the temperature difference across the fuel cell stack. This type of coolant system would minimize the controls needed on the coolant loop and provide a mostly passive means of cooling the fuel cell. The results indicate that an operating temperature of near or greater than 70 C is achievable with a heat exchanger effectiveness of around 90 percent. Of the heat exchanger types evaluated with the same type of fluid on the hot and cold side, a counter flow type heat exchanger would be required which has the possibility of achieving the required effectiveness. The number of heat transfer units required by the heat exchanger would be around 9 or greater. Although the analysis indicates the concept is feasible, the heat exchanger design would need to be developed and optimized for a specific fuel cell operation in order to achieve the high effectiveness value required.

  20. Taking control of charge transfer : strategic design for solar cells

    NARCIS (Netherlands)

    Monti, Adriano

    2015-01-01

    The thesis is focused on the investigation of the electron transfer mechanisms leading to solar fuel production and to the identification of engineering principles that can be used to design materials able to improve charge separation. Molecular systems composed of three or more subunits arranged

  1. Analytical estimation of effective charges at saturation in Poisson-Boltzmann cell models

    CERN Document Server

    Trizac, E; Bocquet, L

    2003-01-01

    We propose a simple approximation scheme for computing the effective charges of highly charged colloids (spherical or cylindrical with infinite length). Within non-linear Poisson-Boltzmann theory, we start from an expression for the effective charge in the infinite-dilution limit which is asymptotically valid for large salt concentrations; this result is then extended to finite colloidal concentration, approximating the salt partitioning effect which relates the salt content in the suspension to that of a dialysing reservoir. This leads to an analytical expression for the effective charge as a function of colloid volume fraction and salt concentration. These results compare favourably with the effective charges at saturation (i.e. in the limit of large bare charge) computed numerically following the standard prescription proposed by Alexander et al within the cell model.

  2. Ion exchange membrane cathodes for scalable microbial fuel cells.

    Science.gov (United States)

    Zuo, Yi; Cheng, Shaoan; Logan, Bruce E

    2008-09-15

    One of the main challenges for using microbial fuel cells (MFCs) is developing materials and architectures that are economical and generate high power densities. The performance of two cathodes constructed from two low-cost anion (AEM) and cation (CEM) exchange membranes was compared to that achieved using an ultrafiltration (UF) cathode, when the membranes were made electrically conductive using graphite paint and a nonprecious metal catalyst (CoTMPP). The best performance in single-chamber MFCs using graphite fiber brush anodes was achieved using an AEM cathode with the conductive coating facing the solution, at a catalyst loading of 0.5 mg/cm2 CoTMPP. The maximum power densitywas 449 mW/ m2 (normalized to the projected cathode surface area) or 13.1 W/m3 (total reactor volume), with a Coulombic efficiency up to 70% in a 50 mM phosphate buffer solution (PBS) using acetate. Decreasing the CoTMPP loading by 40-80% reduced power by 28-56%, with only 16% of the power (72 mW/m2) generated using an AEM cathode lacking a catalyst. Using a current collector (a stainless steel mesh) pressed against the inside surface of the AEM cathode and 200 mM PBS, the maximum power produced was further increased to 728 mW/m2 (21.2 W/m3). The use of AEM cathodes and brush anodes provides comparable performance to similar systems that use materials costing nearly an order of magnitude more (carbon paper electrodes) and thus represent more useful materials for reducing the costs of MFCs for wastewater treatment applications.

  3. A hydrogen-oxygen fuel cell using an ion-exchange membrane as an electrolyte

    NARCIS (Netherlands)

    Duin, P.J. van; Kruissink, C.A.

    1966-01-01

    Using an acidic type of water leached ion exchange membrane, cell current outputs of the order of 100 mA▪cm-2 at 0,6 V cell voltage have been obtained; the removal of produced water largely limits the cell performance. Cells using the alkaline type of membrane exhibit much smaller current densities,

  4. Thermal Analysis of a Fast Charging Technique for a High Power Lithium-Ion Cell

    Directory of Open Access Journals (Sweden)

    Victor Manuel García Fernández

    2016-11-01

    Full Text Available The cell case temperature versus time profiles of a multistage fast charging technique (4C-1C-constant voltage (CV/fast discharge (4C in a 2.3 Ah cylindrical lithium-ion cell are analyzed using a thermal model. Heat generation is dominated by the irreversible component associated with cell overpotential, although evidence of the reversible component is also observed, associated with the heat related to entropy from the electrode reactions. The final charging stages (i.e., 1C-CV significantly reduce heat generation and cell temperature during charge, resulting in a thermally safe charging protocol. Cell heat capacity was determined from cell-specific heats and the cell materials’ thickness. The model adjustment of the experimental data during the 2 min resting period between discharge and charge allowed us to calculate both the time constant of the relaxation process and the cell thermal resistance. The obtained values of these thermal parameters used in the proposed model are almost equal to those found in the literature for the same cell model, which suggests that the proposed model is suitable for its implementation in thermal management systems.

  5. Balance between the physical diffusion and the exchange reaction on binary ionic liquid electrolyte for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Feng; Lin, Hong; Zhang, Jing [State Key Laboratory of New Ceramics and Fine Processing, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); Li, Jianbao [State Key Laboratory of New Ceramics and Fine Processing, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory of Ministry of Education for Application Technology of Chemical Materials in Hainan Superior Resources, Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti Resources, College of Materials Science and Chemical Engineering, Hainan University, Haikou 570228 (China)

    2011-02-01

    A comprehensive characterizations of viscosities, conductivities, triiodide diffusion coefficients, charge-transfer resistances and photovoltaic performance of a potential dye-sensitized solar cell (DSC) electrolyte systems based on binary ionic liquid (IL) mixtures, namely, 1-ethyl-3-methylimidazolium dicyanamide (EMIDCA)/1-methyl-3-propylimidazolium iodide (PMII) with a fixed iodine concentration at varying EMIDCA volume fraction are investigated in the present study. Viscosity and conductivity values are accurately correlated with regard to temperature and EMIDCA volume fraction. The triiodide diffusion coefficients, the predominant electrolyte parameter for limitation of DSC efficiency, are determined by symmetrical cell methods. The physical diffusion and exchange reactions between the iodide and triiodide dominate the apparent triiodide diffusion coefficients at different range of EMIDCA volume fraction. A balance between the viscosity-dependent physical diffusion and the exchange reactions can get at an optimal volume percents of EMIDCA. Impedance spectroscopy and photovoltaic results both support the existence of an optimized binary IL electrolyte composition. Hence, for optimizing an IL-based electrolyte in regards to triiodide transport, a low viscosity is not the exclusive crucial factor since exchange reactions transport effects also play an important role to resolve the diffusion limitation of DSC efficiency. (author)

  6. Validation of a pH gradient-based ion-exchange chromatography method for high-resolution monoclonal antibody charge variant separations.

    Science.gov (United States)

    Rea, Jennifer C; Moreno, G Tony; Lou, Yun; Farnan, Dell

    2011-01-25

    Ion-exchange chromatography is widely used for profiling the charge heterogeneity of proteins, including monoclonal antibodies. Despite good resolving power and robustness, ionic strength-based ion-exchange separations are product-specific and time-consuming to develop. We have previously reported a novel pH-based separation of proteins by cation exchange chromatography that was multi-product, high-resolution, and robust against variations in sample matrix salt concentration and pH. In this study, a pH gradient-based separation method using cation exchange chromatography was evaluated in a mock validation. This method was shown to be robust for monoclonal antibodies and suitable for its intended purpose of charge heterogeneity analysis. Simple mixtures of defined buffer components were used to generate the pH gradients that separated closely related antibody species. Validation characteristics, such as precision and linearity, were evaluated. Robustness to changes in protein load, buffer pH and column oven temperature was demonstrated. The stability-indicating capability of this method was determined using thermally stressed antibody samples. In addition, intermediate precision was demonstrated using multiple instruments, multiple analysts, multiple column lots, and different column manufacturers. Finally, the precision for this method was compared to conventional ion-exchange chromatography and imaged capillary isoelectric focusing. These results demonstrate the superior precision and robustness of this multi-product method, which can be used for the high-throughput evaluation of in-process and final product samples. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. High Performance PbS Quantum Dot/Graphene Hybrid Solar Cell with Efficient Charge Extraction

    Science.gov (United States)

    2016-01-01

    Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion of graphene interlayers is shown to increase power conversion efficiency by 9.18%. It is shown that the inclusion of conductive graphene enhances charge extraction in devices. Photoluminescence shows that graphene quenches emission from the quantum dot suggesting spontaneous charge transfer to graphene. CQD photodetectors exhibit increased photoresponse and improved transport properties. We propose that the CQD/SG hybrid structure is a route to make CQD thin films with improved charge extraction, therefore resulting in improved solar cell efficiency. PMID:27213219

  8. Ion transport resistance in Microbial Electrolysis Cells with anion and cation exchange membranes

    NARCIS (Netherlands)

    Sleutels, T.H.J.A.; Hamelers, H.V.M.; Rozendal, R.A.; Buisman, C.J.N.

    2009-01-01

    Previous studies have shown that Microbial Electrolysis Cells (MECs) perform better when an anion exchange membrane (AEM) than when a cation exchange membrane (CEM) separates the electrode chambers. Here, we have further studied this phenomenon by comparing two analysis methods for

  9. Partial Red Blood Cell Exchange in Children and Young Patients with Sickle Cell Disease: Manual Versus Automated Procedure.

    Science.gov (United States)

    Escobar, Carlos; Moniz, Marta; Nunes, Pedro; Abadesso, Clara; Ferreira, Teresa; Barra, António; Lichtner, Anabela; Loureiro, Helena; Dias, Alexandra; Almeida, Helena

    2017-10-31

    The benefits of manual versus automated red blood cell exchange have rarely been documented and studies in young sickle cell disease patients are scarce. We aim to describe and compare our experience in these two procedures. Young patients (≤ 21 years old) who underwent manual- or automated-red blood cell exchange for prevention or treatment of sickle cell disease complications were included. Clinical, technical and hematological data were prospectively recorded and analyzed. Ninety-four red blood cell exchange sessions were performed over a period of 68 months, including 57 manual and 37 automated, 63 for chronic complications prevention, 30 for acute complications and one in the pre-operative setting. Mean decrease in sickle hemoglobin levels was higher in automated-red blood cell exchange (p red blood cell exchange and access alarm on automated-red blood cell exchange. No major complication or alloimunization was recorded. Automated-red blood cell exchange decreased sickle hemoglobin levels more efficiently than manual procedure in the setting of acute and chronic complications of sickle cell disease, with minor technical concerns mainly due to vascular access. The threshold of sickle hemoglobin should be individualized for clinical and hematological goals. In our cohort of young patients, the need for an acceptable venous access was a limiting factor, but iron-overload was avoided. Automated red blood cell exchange is safe and well tolerated. It permits a higher sickle hemoglobin removal efficacy, better volume status control and iron-overload avoidance.

  10. Improved durability of proton exchange membrane fuel cells by introducing Sn (IV) oxide into electrodes using an ion exchange method

    Science.gov (United States)

    Poulsen, M. G.; Larsen, M. J.; Andersen, S. M.

    2017-03-01

    Electrodes of Proton Exchange Membrane Fuel Cells (PEMFCs), consisting of catalyst-coated gas diffusion layers, were subjected to an optimized ion exchange procedure, in which tin (IV) oxide (SnO2) nanoparticles were introduced into them. Both methanol and sulfuric acid were tested as ion exchange solvents. SnO2 has previously been shown to exhibit radical scavenging abilities towards radicals inside the electrocatalyst layers. Its presence inside the electrodes was confirmed using X-ray photoelectron spectroscopy and X-ray fluorescence. After exposure to an accelerated stress test in a three-electrode setup, the electrodes containing SnO2 were found to have retained approximately 73.0% of their original Pt, while only 53.2% was retained in electrodes treated identically, but without Sn. Similarly, the SnO2-treated electrodes also experienced a smaller loss in electrochemical surface area in comparison to before the accelerated stress test. A membrane electrode assembly (MEA) constructed with a SnO2-containing anode was evaluated over 500 h. The results showed remarkably reduced OCV decay rate and end of test hydrogen crossover compared to the control MEA, indicating that SnO2 aids in impeding membrane thinning and pinhole formation. The results point toward a positive effect of SnO2 on fuel cell durability, by reducing the degradation of the membrane as well as of the ionomer in the electrocatalyst layer.

  11. Folding model study of the charge-exchange scattering to the isobaric analog state and implication for the nuclear symmetry energy

    Energy Technology Data Exchange (ETDEWEB)

    Khoa, Dao T.; Thang, Dang Ngoc [VINATOM, Institute for Nuclear Science and Technique, Hanoi (Viet Nam); Loc, Bui Minh [VINATOM, Institute for Nuclear Science and Technique, Hanoi (Viet Nam); University of Pedagogy, Ho Chi Minh City (Viet Nam)

    2014-02-15

    The Fermi transition (ΔL = ΔS = 0 and ΔT = 1) between the nuclear isobaric analog states (IAS), induced by the charge-exchange (p, n) or ({sup 3}He, t) reaction, can be considered as ''elastic'' scattering of proton or {sup 3}He by the isovector term of the optical potential (OP) that flips the projectile isospin. The accurately measured (p, n) or ({sup 3}He, t) scattering cross section to the IAS can be used, therefore, to probe the isospin dependence of the proton or {sup 3}He optical potential. Within the folding model, the isovector part of the OP is determined exclusively by the neutron-proton difference in the nuclear densities and the isospin dependence of the effective nucleon-nucleon (NN) interaction. Because the isovector coupling explicitly links the isovector part of the proton or {sup 3}He optical potential to the cross section of the charge-exchange (p, n) or ({sup 3}He, t) scattering to the IAS, the isospin dependence of the effective (in-medium) NN interaction can be well tested in the folding model analysis of these charge-exchange reactions. On the other hand, the same isospin- and density-dependent NN interaction can also be used in a Hartree-Fock calculation of asymmetric nuclear matter, to estimate the nuclear matter energy and its asymmetry part (the nuclear symmetry energy). As a result, the fine-tuning of the isospin dependence of the effective NN interaction against the measured (p, n) or ({sup 3}He, t) cross sections should allow us to make some realistic prediction of the nuclear symmetry energy and its density dependence. (orig.)

  12. A numerical model for charge transport and energy conversion of perovskite solar cells.

    Science.gov (United States)

    Zhou, Yecheng; Gray-Weale, Angus

    2016-02-14

    Based on the continuity equations and Poisson's equation, we developed a numerical model for perovskite solar cells. Due to different working mechanisms, the model for perovskite solar cells differs from that of silicon solar cells and Dye Sensitized Solar Cells. The output voltage and current are calculated differently, and in a manner suited in particular to perovskite organohalides. We report a test of our equations against experiment with good agreement. Using this numerical model, it was found that performances of solar cells increase with charge carrier's lifetimes, mobilities and diffusion lengths. The open circuit voltage (Voc) of a solar cell is dependent on light intensities, and charge carrier lifetimes. Diffusion length and light intensity determine the saturated current (Jsc). Additionally, three possible guidelines for the design and fabrication of perovskite solar cells are suggested by our calculations. Lastly, we argue that concentrator perovskite solar cells are promising.

  13. Design of a Fast Neutral He Beam System for Feasibility Study of Charge-Exchange Alpha-Particle Diagnostics in a Thermonuclear Fusion Reactor

    CERN Document Server

    Shinto, Katsuhiro; Kitajima, Sumio; Kiyama, Satoru; Nishiura, Masaki; Sasao, Mamiko; Sugawara, Hiroshi; Takenaga, Mahoko; Takeuchi, Shu; Wada, Motoi

    2005-01-01

    For alpha-particle diagnostics in a thermonuclear fusion reactor, neutralization using a fast (~2 MeV) neutral He beam produced by the spontaneous electron detachment of a He- is considered most promising. However, the beam transport of produced fast neutral He has not been studied, because of difficulty for producing high-brightness He- beam. Double-charge-exchange He- sources and simple beam transport systems were developed and their results were reported in the PAC99* and other papers.** To accelerate an intense He- beam and verify the production of the fast neutral He beam, a new test stand has been designed. It consists of a multi-cusp He+

  14. DXL: A Sounding Rocket Mission for the Study of Solar Wind Charge Exchange and Local Hot Bubble X-Ray Emission

    Science.gov (United States)

    Galeazzi, M.; Prasai, K.; Uprety, Y.; Chiao, M.; Collier, M. R.; Koutroumpa, D.; Porter, F. S.; Snowden, S.; Cravens, T.; Robertson, I.; hide

    2011-01-01

    The Diffuse X-rays from the Local galaxy (DXL) mission is an approved sounding rocket project with a first launch scheduled around December 2012. Its goal is to identify and separate the X-ray emission generated by solar wind charge exchange from that of the local hot bubble to improve our understanding of both. With 1,000 square centimeters proportional counters and grasp of about 10 square centimeters sr both in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-minute flight what cannot be achieved by current and future X-ray satellites.

  15. Measurement of anomalously strong emission from the 1s-9p transition in the spectrum of H-like phosphorus following charge exchange with molecular hydrogen

    CERN Document Server

    Leutenegger, M A; Brown, G V; Kelley, R L; Kilbourne, C A; Porter, F S

    2010-01-01

    We have measured K-shell x-ray spectra of highly ionized argon and phosphorus following charge exchange with molecular hydrogen at low collision energy in an electron beam ion trap using an x-ray calorimeter array with $\\sim$6 eV resolution. We find that the emission at the high-end of the Lyman series is greater by a factor of 2 for phosphorus than for argon, even though the measurement was performed concurrently and the atomic numbers are similar. This does not agree with current theoretical models and deviates from the trend observed in previous measurements.

  16. Differential cross section of the pion-nucleon charge-exchange reaction in the momentum range from 148 to 323 MeV/c

    CERN Document Server

    Sadler, M E; Abaev, V V; Allgower, C; Barker, A; Bekrenev, V; Bircher, C; Briscoe, W J; Cadman, R; Carter, C; Clajus, M; Comfort, J R; Craig, K; Daugherity, M; Draper, B; Grosnick, D P; Hayden, S; Huddleston, J; Isenhower, D; Jerkins, M; Joy, M; Knecht, N; Koetke, D D; Kozlenko, N; Kruglov, S; Kycia, T; Lolos, G J; Lopatin, I; Manley, D M; Manweiler, R; Marusic, A; McDonald, S; Nefkens, B M K; Olmsted, J; Papandreou, Z; Peaslee, D; Peterson, J; Phaisangittisakul, N; Prakhov, S N; Price, J W; Ramírez, A; Robinson, C; Shafi, A; Spinka, H; Stanislaus, S; Starostin, A; Staudenmaier, H M; Strakovsky, I I; Supek, I; Tippens, W B; Watson, S

    2004-01-01

    Measured values of the differential cross section for pion-nucleon charge exchange are presented at momenta 148, 174, 188, 212, 238, 271, 298, and 323 MeV/c, a region dominated by the Delta resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically 2-6%, exceptions being the results at the lowest momentum and at the most forward measurements of the five lowest momenta. We estimate the systematic uncertainties to be 3-6%.

  17. Differential cross sections of the charge-exchange reaction pi- p --> pi0 n in the momentum range from 103 to 178 MeV/c

    CERN Document Server

    Mekterović, D; Abaev, V; Bekrenev, V; Bircher, C; Briscoe, W J; Cadman, R V; Clajus, M; Comfort, J R; Craig, K; Grosnick, D; Isenhover, D; Jerkins, M; Joy, M; Knecht, N; Koetke, D D; Kozlenko, N; Kulbardis, A; Kruglov, S; Lolos, G; Lopatin, I; Manley, D M; Manweiler, R; Marušić, A; McDonald, S; Nefkens, B M K; Olmsted, J; Papandreou, Z; Peaslee, D; Peterson, J; Phaisangittisakul, N; Prakhov, S N; Price, J W; Ramírez, A; Sadler, M E; Shafi, A; Spinka, H; Stanislaus, S; Starostin, A; Staudenmaier, H M; Strakovsky, I; Tippens, W B; Watson, S

    2009-01-01

    Measured values of the differential cross sections for pion-nucleon charge exchange, pi- p --> pi0 n, are presented for pi- momenta of 103, 112, 120, 130, 139, 152, and 178 MeV/c. Complete angular distributions were obtained by using the Crystal Ball detector at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Statistical uncertainties of the differential cross sections vary from 3% to 6% in the backward angle region, and from 6% to about 20% in the forward region with the exception of the two most forward angles. The systematic uncertainties are estimated to be about 3% for all momenta.

  18. Lack of NMDA receptor subunit exchange alters Purkinje cell dendritic morphology in cerebellar slice cultures

    NARCIS (Netherlands)

    Metzger, F; Pieri, [No Value; Eisel, ULM; Pieri, Isabelle

    2005-01-01

    Early postnatal developmental changes in N-methyl-D-aspartate (NMDA) receptor (NR) subunits regulate cerebellar granule cell maturation and potentially Purkinje cell development. We therefore investigated Purkinje cell morphology in slice cultures from mice with genetic subunit exchange from NR2C to

  19. Application of Proton Exchange Membrane Fuel Cell for Lift Trucks

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud

    2011-01-01

    thermodynamically. The system includes a compressor, an air humidifier, set of heat exchangers and a stack which together build up the anode circuit, the cathode circuit and the cooling loop. Since fuel humidification is carried out via water cross over from cathode to anode, there is no humidifier in the anode...

  20. Charge transport and recombination dynamics in organic bulk heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Andreas

    2011-08-02

    The charge transport in disordered organic bulk heterojunction (BHJ) solar cells is a crucial process affecting the power conversion efficiency (PCE) of the solar cell. With the need of synthesizing new materials for improving the power conversion efficiency of those cells it is important to study not only the photophysical but also the electrical properties of the new material classes. Thereby, the experimental techniques need to be applicable to operating solar cells. In this work, the conventional methods of transient photoconductivity (also known as ''Time-of-Flight'' (TOF)), as well as the transient charge extraction technique of ''Charge Carrier Extraction by Linearly Increasing Voltage'' (CELIV) are performed on different organic blend compositions. Especially with the latter it is feasible to study the dynamics - i.e. charge transport and charge carrier recombination - in bulk heterojunction (BHJ) solar cells with active layer thicknesses of 100-200 nm. For a well performing organic BHJ solar cells the morphology is the most crucial parameter finding a trade-off between an efficient photogeneration of charge carriers and the transport of the latter to the electrodes. Besides the morphology, the nature of energetic disorder of the active material blend and its influence on the dynamics are discussed extensively in this work. Thereby, the material system of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C{sub 61}butyric acid methyl ester (PC{sub 61}BM) serves mainly as a reference material system. New promising donor or acceptor materials and their potential for application in organic photovoltaics are studied in view of charge dynamics and compared with the reference system. With the need for commercialization of organic solar cells the question of the impact of environmental conditions on the PCE of the solar cells raises. In this work, organic BHJ solar cells exposed to synthetic air for finite duration are

  1. Alkaline Exchange Membrane (AEM) for High-Efficiency Fuel Cells, Electrolyzers and Regenerative Fuel Cell Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop an alkaline exchange membrane (AEM)for use as a polymer electrolyte in both fuel cell and electrolyzer systems.  The ultimate goal in AEM development is...

  2. Electroluminescence from charge transfer states in Donor/Acceptor solar cells

    DEFF Research Database (Denmark)

    Sherafatipour, Golenaz; Madsen, Morten

    Charge photocurrent generation is a key process in solar energy conversion systems. Effective dissociation of the photo-generated electron-hole pairs (excitons) has a strong influence on the efficiency of the organic solar cells. Charge dissociation takes place at the donor/acceptor interface via...... charge transfer (CT) excitons, which is Coulombically bound interfacial electron- hole pairs residing at the donor/acceptor heterojunctions. The CT state represents an intermediate state between the exciton dissociation and recombination back to the ground state. Since the recombination of photo-generated...... charges is a major limitation for the efficiency of the organic solar cells, a thorough understanding of this loss mechanism is crucial to improve the performance of the devices. Furthermore, examining this interfacial state is of great importance in order to maximize open-circuit voltage and photocurrent...

  3. Correlation between charge transfer exciton recombination and photocurrent in polymer/fullerene solar cells

    NARCIS (Netherlands)

    Hallermann, Markus; Da Como, Enrico; Feldmann, Jochen; Izquierdo, Marta; Filippone, Salvatore; Martin, Nazario; Juechter, Sabrina; von Hauff, Elizabeth

    2010-01-01

    We correlate carrier recombination via charge transfer excitons (CTEs) with the short circuit current, J sc, in polymer/fullerene solar cells. Near infrared photoluminescence spectroscopy of CTE in three blends differing for the fullerene acceptor, gives unique insights into solar cell

  4. AT cells are not radiosensitive for simple chromosomal exchanges at low dose

    Energy Technology Data Exchange (ETDEWEB)

    Hada, Megumi; Huff, Janice L.; Patel, Zarana S. [USRA Division of Life Sciences, Houston, TX 77058 (United States); Kawata, Tetsuya [Department of Radiology, School of Medicine, Keio University, Tokyo (Japan); Pluth, Janice M. [Lawrence Berkeley National Laboratory, Life Sciences Division, One Cyclotron Road, Building 74, Berkeley, CA 94720 (United States); George, Kerry A. [Wyle, 1290 Hercules Drive, Houston, TX 77058 (United States); Cucinotta, Francis A., E-mail: Francis.A.Cucinotta@nasa.gov [NASA, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058 (United States)

    2011-11-01

    Cells deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome) show increased yields of both simple and complex chromosomal aberrations after high doses (>0.5 Gy) of ionizing radiation (X-rays or {gamma}-rays), however less is known on how these cells respond at low dose. Previously we had shown that the increased chromosome aberrations in ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex exchanges. The linear dose-response term for simple exchanges was significantly higher in NBS cells compared to wild type cells, but not for AT cells. However, AT cells have a high background level of exchanges compared to wild type or NBS cells that confounds the understanding of low dose responses. To understand the sensitivity differences for high to low doses, chromosomal aberration analysis was first performed at low dose-rates (0.5 Gy/d), and results provided further evidence for the lack of sensitivity for exchanges in AT cells below doses of 1 Gy. Normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, showed increased numbers of exchanges at a dose of 1 Gy and higher, but were similar to wild type cells at 0.5 Gy or below. These results were confirmed using siRNA knockdown of ATM. The present study provides evidence that the increased radiation sensitivity of AT cells for chromosomal exchanges found at high dose does not occur at low dose.

  5. Field collapse due to band-tail charge in amorphous silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi; Crandall, R.S. [National Renewable Energy Lab., Golden, CO (United States); Schiff, E.A. [Syracuse Univ., NY (United States)

    1996-05-01

    It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.

  6. Computer-aided model analysis for ionic strength-dependent effective charge of protein in ion-exchange chromatography

    DEFF Research Database (Denmark)

    Lim, Young-il; Jørgensen, Sten Bay; Kim, In-Ho

    2005-01-01

    differential algebraic equation (PDAE) system, a fast and accurate numerical method (i.e., conservation element/solution element (CE/SE) method), is proposed. Sensitivity and elasticity of the model parameters (e.g., steric/shape factors, adsorption heat coefficient, effective protein charge, equilibrium...... constant, mass transfer coefficient, axial dispersion coefficient and bed voidage) are analyzed for a BSA-salt system in a low protein concentration range. Within a low concentration range of bovine serum albumin (BSA) where linear adsorption isotherms are shown, the adsorption heat coefficient, shape...... salt concentrations, it is proposed that the effective protein charge could depend upon the salt concentration (or ionic strength). The reason for this dependence may be a steric hindrance of protein binding sites combined with a salt shielding effect neutralizing the surface charges of the protein. (c...

  7. Improved tumor tissue penetration and tumor cell uptake achieved by delayed charge reversal nanoparticles.

    Science.gov (United States)

    Gou, Jingxin; Liang, Yuheng; Miao, Linlin; Guo, Wei; Chao, Yanhui; He, Haibing; Zhang, Yu; Yang, Jingyu; Wu, Chunfu; Yin, Tian; Wang, Yanjiao; Tang, Xing

    2017-10-15

    The high affinity of positively charged nanoparticles to biological interfaces makes them easily taken up by tumor cells but limits their tumor permeation due to non-specific electrostatic interactions. In this study, polyion complex coated nanoparticles with different charge reversal profiles were developed to study the influence of charge reversal profile on tumor penetration. The system was constructed by polyion complex coating using micelles composed of poly (lysine)-b-polycaprolactone (PLys-b-PCL) as the cationic core and poly (glutamic acid)-g- methoxyl poly (ethylene glycol) (PGlu-g-mPEG) as the anionic coating material. Manipulation of charge reversal profile was achieved by controlling the polymer chain entanglement and electrostatic interaction in the polyion complex layer through glutaraldehyde-induced shell-crosslinking. The delayed charge reversal nanoparticles (CTCL30) could maintain negatively charged in pH 6.5 PBS for at least 2h and exhibit pH-responsive cytotoxicity and cellular uptake in an extended time scale. Compared with a faster charge reversal counterpart (CTCL70) with similar pharmacokinetic profile, CTCL30 showed deeper penetration, higher in vivo tumor cell uptake and stronger antitumor activity in vivo (tumor inhibition rate: 72.3% vs 60.2%, compared with CTCL70). These results indicate that the delayed charge reversal strategy could improve therapeutic effect via facilitating tumor penetration. Here, the high tumor penetration capability of PEG-coated nanoparticles and the high cellular uptake of cationic nanoparticles were combined by a delayed charge reversal drug delivery system. This drug delivery system was composed of a drug-loading cationic inner core and a polyion complex coating. Manipulation of charge reversal profile was realized by varying the crosslinking degree of the shell of the cationic inner core, through which changed the strength of the polyion complex layer. Nanoparticles with delayed charge reversal profile

  8. Role of Na+/Ca2+ Exchangers in Therapy Resistance of Medulloblastoma Cells.

    Science.gov (United States)

    Pelzl, Lisann; Hosseinzadeh, Zohreh; Al-Maghout, Tamer; Singh, Yogesh; Sahu, Itishri; Bissinger, Rosi; Schmidt, Sebastian; Alkahtani, Saad; Stournaras, Christos; Toulany, Mahmoud; Lang, Florian

    2017-01-01

    Alterations of cytosolic Ca2+-activity ([Ca2+]i) are decisive in the regulation of tumor cell proliferation, migration and survival. Transport processes participating in the regulation of [Ca2+]i include Ca2+ extrusion through K+-independent (NCX) and/or K+-dependent (NCKX) Na+/Ca2+-exchangers. The present study thus explored whether medulloblastoma cells express Na+/Ca2+-exchangers, whether expression differs between therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells, and whether Na+/Ca2+-exchangers participate in the regulation of cell survival. In therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells transcript levels were estimated by RT-PCR, protein abundance by Western blotting, cytosolic Ca2+-activity ([Ca2+]i) from Fura-2-fluorescence, Na+/ Ca2+-exchanger activity from the increase of [Ca2+]i (Δ[Ca2+]i) and from whole cell current (Ica) following abrupt replacement of Na+ containing (130 mM) and Ca2+ free by Na+ free and Ca2+ containing (2 mM) extracellular perfusate as well as cell death from PI -staining and annexin-V binding in flow cytometry. The transcript levels of NCX3, NCKX2, and NCKX5, protein abundance of NCX3, slope and peak of Δ[Ca2+]i as well as Ica were significantly lower in therapy sensitive D283 than in therapy resistant UW228-3 medulloblastoma cells. The Na+/Ca2+-exchanger inhibitor KB-R7943 (10 µM) significantly blunted Δ[Ca2+]i, and augmented the ionizing radiation-induced apoptosis but did not significantly modify clonogenicity of medulloblastoma cells. Apoptosis was further enhanced by NCX3 silencing. Na+/Ca2+-exchanger activity significantly counteracts apoptosis but does not significantly affect clonogenicity after radiation of medulloblastoma cells. © 2017 The Author(s). Published by S. Karger AG, Basel.

  9. On Lunar Exospheric Column Densities and Solar Wind Access Beyond the Terminator from ROSAT Soft X-ray Observations of Solar Wind Charge Exchange (SWCX)

    Science.gov (United States)

    Collier, M. R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T.; Farrell, W. M.; Fatemi, S.; Hills, H. K.; Hodges, R. R.; Holmstrom, M.; Kuntz, K. D.; Porter, F. S.; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P. M.

    2013-12-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the antisolar point. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears dominated by exospheric species arising from solar wind implantation, this technique can also monitor how the exosphere varies with solar wind conditions. Now along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed.

  10. Cell contact-dependent outer membrane exchange in myxobacteria: genetic determinants and mechanism.

    Directory of Open Access Journals (Sweden)

    Darshankumar T Pathak

    Full Text Available Biofilms are dense microbial communities. Although widely distributed and medically important, how biofilm cells interact with one another is poorly understood. Recently, we described a novel process whereby myxobacterial biofilm cells exchange their outer membrane (OM lipoproteins. For the first time we report here the identification of two host proteins, TraAB, required for transfer. These proteins are predicted to localize in the cell envelope; and TraA encodes a distant PA14 lectin-like domain, a cysteine-rich tandem repeat region, and a putative C-terminal protein sorting tag named MYXO-CTERM, while TraB encodes an OmpA-like domain. Importantly, TraAB are required in donors and recipients, suggesting bidirectional transfer. By use of a lipophilic fluorescent dye, we also discovered that OM lipids are exchanged. Similar to lipoproteins, dye transfer requires TraAB function, gliding motility and a structured biofilm. Importantly, OM exchange was found to regulate swarming and development behaviors, suggesting a new role in cell-cell communication. A working model proposes TraA is a cell surface receptor that mediates cell-cell adhesion for OM fusion, in which lipoproteins/lipids are transferred by lateral diffusion. We further hypothesize that cell contact-dependent exchange helps myxobacteria to coordinate their social behaviors.

  11. Surface charge characteristics of cells from malignant cell lines and normal cell lines of the human hematopoietic system.

    Science.gov (United States)

    Marikovsky, Y; Ben-Bassat, H; Leibovich, S J; Cividalli, L; Fischler, H; Danon, D

    1979-02-01

    Cells from malignant and normal lines of human hematopoietic origin were studied for their surface charge characteristics with the use of the following criteria: 1) the electron microscopic appearance of cell membranes after labeling with cationized ferritin (CF) either before or after glutaraldehyde fixation, 2) electrophoretic mobility, 3) total sialic acid content, and 4) agglutinability with poly-L-lysine (PLL). CF induced a time-dependent redistribution of surface receptors in unfixed malignant cells but not in unfixed normal cells. After 10 seconds of labeling with CF, both normal and malignant unfixed cells showed a uniform and even labeling pattern. After 5 minutes of labeling, malignant cells exhibited a highly pronounced pattern of clusters and patches, as distinct from a random and even pattern exhibited by normal cells. Both normal and malignant cells after fixation exhibited an equivalent random and even labeling pattern with CF, independent of the duration of labeling. The malignant cells studied possessed less sialic acid, had a lower electric mobility, and were agglutinated more readily with PLL than were the normal cells.

  12. Probing Single- to Multi-Cell Level Charge Transport in Geobacter sulfurreducens DL-1

    Science.gov (United States)

    2013-11-08

    autoclaving at 121 C for 15min. Cell cultures for nanoelectrode measurements. Before inoculation of the measurement chamber, the culture media were...3757–3761 (2008). 30. Jiang, X. et al. Probing electron transfer mechanisms in Shewanella oneidensis MR-1 using a nanoelectrode platform and single cell ...ARTICLE Received 10 May 2013 | Accepted 10 Oct 2013 | Published 8 Nov 2013 Probing single- to multi- cell level charge transport in Geobacter

  13. Method of detecting defects in ion exchange membranes of electrochemical cells by chemochromic sensors

    Science.gov (United States)

    Brooker, Robert Paul; Mohajeri, Nahid

    2016-01-05

    A method of detecting defects in membranes such as ion exchange membranes of electrochemical cells. The electrochemical cell includes an assembly having an anode side and a cathode side with the ion exchange membrane in between. In a configuration step a chemochromic sensor is placed above the cathode and flow isolation hardware lateral to the ion exchange membrane which prevents a flow of hydrogen (H.sub.2) between the cathode and anode side. The anode side is exposed to a first reactant fluid including hydrogen. The chemochromic sensor is examined after the exposing for a color change. A color change evidences the ion exchange membrane has at least one defect that permits H.sub.2 transmission therethrough.

  14. Generalized moving boundary model for charge-discharge of LiFePO4/C cells

    Science.gov (United States)

    Khandelwal, Ashish; Hariharan, Krishnan S.; Senthil Kumar, V.; Gambhire, Priya; Kolake, Subramanya Mayya; Oh, Dukjin; Doo, Seokgwang

    2014-02-01

    Lithium ion cells with electrode materials that undergo phase transitions, like LiFePO4, have unique charge-discharge characteristics. In this work a generalized framework of moving boundary approach is proposed to model the path dependent charge-discharge response of porous electrodes that exhibit multi-phase coexistence. Using the Landau transformation the governing equation in moving coordinate is transformed to fixed coordinate and a suitable path dependent algorithm is devised and is implemented in a multi-physics environment. Simulation results show that tangential propagation of the phase front, often seen in experiments, can be addressed by this model. Incorporation of multi-phase diffusion predicts the characteristic phase separation in LiFePO4 particles. The proposed model successfully captures the charge-discharge asymmetry of LiFePO4 based cells. Efficacy of the proposed approach to model the path dependence of cells with phase change electrodes is demonstrated by simulating the response of LiFePO4/graphite cell subjected to a charge-discharge pulse. Numerical studies are performed to study the effect of important model parameters to enhance cell design and to bring out unique features in the cell response due to multi-phase coexistence.

  15. Charge heterogeneity profiling of monoclonal antibodies using low ionic strength ion-exchange chromatography and well-controlled pH gradients on monolithic columns.

    Science.gov (United States)

    Talebi, Mohammad; Nordborg, Anna; Gaspar, Andras; Lacher, Nathan A; Wang, Qian; He, Xiaoping Z; Haddad, Paul R; Hilder, Emily F

    2013-11-22

    In this work, the suitability of employing shallow pH gradients generated using single component buffer systems as eluents through cation-exchange (CEX) monolithic columns is demonstrated for the high-resolution separation of monoclonal antibody (mAb) charge variants in three different biopharmaceuticals. A useful selection of small molecule buffer species is described that can be used within very narrow pH ranges (typically 1 pH unit) defined by their buffer capacity for producing controlled and smooth pH profiles when used together with porous polymer monoliths. Using very low ionic strength eluents also enabled direct coupling with electrospray ionisation mass spectrometry. The results obtained by the developed pH gradient approach for the separation of closely related antibody species appear to be consistent with those obtained by imaged capillary isoelectric focusing (iCE) in terms of both resolution and separation profile. Both determinants of resolution, i.e., peak compression and peak separation contribute to the gains in resolution, evidently through the Donnan potential effect, which is increased by decreasing the eluent concentration, and also through the way electrostatic charges are distributed on the protein surface. Retention mechanisms based on the trends observed in retention of proteins at pH values higher than the electrophoretic pI are also discussed using applicable theories. Employing monolithic ion-exchangers is shown to enable fast method development, short analysis time, and high sample throughput owing to the accelerated mass transport of the monolithic media. The possibility of short analysis time, typically less than 15 min, and high sample throughput is extremely useful in the assessment of charge-based changes to the mAb products, such as during manufacturing or storage. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Faradaic impedance to analyze charge recombination in photoelectrode of dye-sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Itagaki, Masayuki, E-mail: itagaki@rs.noda.tus.ac.jp [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Nakano, Yuya; Shitanda, Isao; Watanabe, Kunihiro [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

    2011-09-30

    Charge transfer on the photoelectrode of dye sensitized solar cell (DSC) is composed of the various processes as follows: photoexcitation of electron in the dye; electron injection from the excited dye into the conduction band of oxide semiconductor; electron diffusion in the oxide semiconductor, reaction between oxidized dye and iodide ions (I{sup -}); and charge recombination. The charge recombination is one of the main factors that limit the efficiency of photoelectric conversion at photoelectrode. It is well known that 4-tert-butyl pyridine (TBP) is the useful additive in order to suppress the charge recombination. The authors fabricated the DSC with two photoelectrode materials such as titanium dioxide (TiO{sub 2}) and zinc oxide (ZnO), and analyzed the charge recombination by using electrochemical impedance spectroscopy. Theoretical equation of Faradaic impedance was derived from the reaction model of photoelectorde, and the charge transfer resistance of the photoelectrode was defined from the Faradaic impedance. In addition, the influence of the charge recombination on the impedance spectrum of the photoelectrode was discussed by the comparison between simulated and experimental results.

  17. Claudins create charge-selective channels in the paracellular pathway between epithelial cells.

    Science.gov (United States)

    Colegio, Oscar R; Van Itallie, Christina M; McCrea, Heather J; Rahner, Christoph; Anderson, James Melvin

    2002-07-01

    Epithelia separate tissue spaces by regulating the passage of ions, solutes, and water through both the transcellular and paracellular pathways. Paracellular permeability is defined by intercellular tight junctions, which vary widely among tissues with respect to solute flux, electrical resistance, and ionic charge selectivity. To test the hypothesis that members of the claudin family of tight junction proteins create charge selectivity, we assessed the effect of reversing the charge of selected extracellular amino acids in two claudins using site-directed mutagenesis. Claudins were expressed in cultured Madin-Darby canine kidney cell monolayers under an inducible promoter, and clones were compared with and without induction for transmonolayer electrical resistance and dilution potentials. Expression and localization of claudins were determined by immunoblotting, immunofluorescence microscopy, and freeze-fracture electron microscopy. We observed that substituting a negative for a positive charge at position 65 in the first extracellular domain of claudin-4 increased paracellular Na+ permeability. Conversely, substituting positive for negative charges at three positions in the first extracellular domain of claudin-15, singly and in combination, reversed paracellular charge selectivity from a preference for Na+ to Cl-. These results support a model where claudins create charge-selective channels in the paracellular space.

  18. Analysis of the charge-exchange reaction $pp \\rightarrow (p\\pi^{+}) (p\\pi^{-}$ and of \\delta^{++}\\delta^{0}$ production at the CERN ISR

    CERN Document Server

    Goggi, Giorgio V; Conta, C; Fraternali, M; Impellizzeri, F; Mantovani, G C; Pastore, F; Rimoldi, A; Rossini, B

    1978-01-01

    The results of a systematic analysis of charge-exchange double dissociation in proton-proton collisions at the CERN Intersecting Storage Rings are presented. The data cover the entire ISR energy range between square root s=23 GeV and square root s=63 GeV at five standard energies. Double resonance production is observed in the Delta /sup ++/ Delta /sup 0/ and Delta /sup ++/N/sup 0/(1688) final states. The mass spectra of the p pi /sup -/ system show more pronounced resonant signals in the backward Jackson hemisphere. A detailed analysis ofdifferential cross sections shows a forward peak typical of absorbed pion exchanges decreasing as s/sup -1.81+or-0.06/, followed by a much gentler exponential behaviour associated with a trajectory typical of rho -A/sub 2/ exchange. The high-energy transition to this regime is also indicated by a dramatic change in the s-dependence of total cross sections as compared with low-energy data. (20 refs).

  19. The critical relation between chemical stability of cations and water in anion exchange membrane fuel cells environment

    Science.gov (United States)

    Dekel, Dario R.; Willdorf, Sapir; Ash, Uri; Amar, Michal; Pusara, Srdjan; Dhara, Shubhendu; Srebnik, Simcha; Diesendruck, Charles E.

    2018-01-01

    Anion exchange membrane fuel cells can potentially revolutionize energy storage and delivery; however, their commercial development is hampered by a significant technological impedance: the chemical decomposition of the anion exchange membranes during operation. The hydroxide anions, while transported from the cathode to the anode, attack the positively charged functional groups in the polymer membrane, neutralizing it and suppressing its anion-conducting capability. In recent years, several new quaternary ammonium salts have been proposed to address this challenge, but while they perform well in ex-situ chemical studies, their performance is very limited in real fuel cell studies. Here, we use experimental work, corroborated by molecular dynamics modeling to show that water concentration in the environment of the hydroxide anion, as well as temperature, significantly impact its reactivity. We compare different quaternary ammonium salts that have been previously studied and test their stabilities in the presence of relatively low hydroxide concentration in the presence of different amounts of solvating water molecules, as well as different temperatures. Remarkably, with the right amount of water and at low enough temperatures, even quaternary ammonium salts which are considered "unstable", present significantly improved lifetime.

  20. Saccharin-induced sister chromatid exchanges in Chinese hamster and human cells

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, S.; Rodin, B.

    1978-05-05

    Since the induction of sister chromatid exchanges in cultured cells has been shown to be the most sensitive mammalian system to detect the effects of mutagenic carcinogens, Chinese hamster ovary cells and human lymphocytes were exposed to the sodium saccharin found to induce bladder cancer in rats. Both that saccharin and a highly purified extract of it increased the yield of sister chromatid exchanges in both types of cells. The results, which were repeatable and statistically highly significant, indicated that the weak carcinogen, saccharin, is also mutagenic in the sense that it induces cytogenetic changes.

  1. Synthesis and characterisation of alkaline anionic-exchange membranes for direct alcohol fuel cells

    CSIR Research Space (South Africa)

    Nonjola, P

    2007-12-01

    Full Text Available of alkaline anionic-exchange membranes for direct alcohol fuel cells P. Nonjola*, M. Mathe, S. Hietkamp Materials Science and Manufacturing, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001, South Africa *snonjola... exchange membranes from poly(arylene ether), by the conventional aromatic nucleophilic displacement route via chloromethylation and quaternary amination. The primary objective was to acquire basic information on structure-property relationships to permit...

  2. Hydroxyl pyridine containing polybenzimidazole membranes for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Xu, Yixin; Zhou, Lu

    2013-01-01

    at 180°C without humidifying. In addition, an improved tensile modulus at elevated temperatures was observed for acid doped OHPyPBI membranes. Fuel cell tests demonstrated the technical feasibility of acid doped OHPyPBI membranes for high temperature proton exchange membrane fuel cells. © 2013 Elsevier B.V....

  3. Self assembled 12-tungstophosphoric acid-silica mesoporous nanocomposites as proton exchange membranes for direct alcohol fuel cells.

    Science.gov (United States)

    Tang, Haolin; Pan, Mu; Jiang, San Ping

    2011-05-21

    A highly ordered inorganic electrolyte based on 12-tungstophosphoric acid (H(3)PW(12)O(40), abbreviated as HPW or PWA)-silica mesoporous nanocomposite was synthesized through a facile one-step self-assembly between the positively charged silica precursor and negatively charged PW(12)O(40)(3-) species. The self-assembled HPW-silica nanocomposites were characterized by small-angle XRD, TEM, nitrogen adsorption-desorption isotherms, ion exchange capacity, proton conductivity and solid-state (31)P NMR. The results show that highly ordered and uniform nanoarrays with long-range order are formed when the HPW content in the nanocomposites is equal to or lower than 25 wt%. The mesoporous structures/textures were clearly presented, with nanochannels of 3.2-3.5 nm in diameter. The (31)P NMR results indicates that there are (≡SiOH(2)(+))(H(2)PW(12)O(40)(-)) species in the HPW-silica nanocomposites. A HPW-silica (25/75 w/o) nanocomposite gave an activation energy of 13.0 kJ mol(-1) and proton conductivity of 0.076 S cm(-1) at 100 °C and 100 RH%, and an activation energy of 26.1 kJ mol(-1) and proton conductivity of 0.05 S cm(-1) at 200 °C with no external humidification. A fuel cell based on a 165 μm thick HPW-silica nanocomposite membrane achieved a maximum power output of 128.5 and 112.0 mW cm(-2) for methanol and ethanol fuels, respectively, at 200 °C. The high proton conductivity and good performance demonstrate the excellent water retention capability and great potential of the highly ordered HPW-silica mesoporous nanocomposites as high-temperature proton exchange membranes for direct alcohol fuel cells (DAFCs).

  4. Thermal diversities of two Na+/H+ exchanges in guinea pig red cells.

    Science.gov (United States)

    Ji, H L

    2001-09-01

    To test the effect of hypothermia on Na+/H+ exchange, activated by shrinkage and cytoplasmic acidosis. Amiloride-sensitive Na+ influx in guinea pig red cells was traced with isotope 22Na and intracellular Na+ concentration was measured by emission flame photometry. Amiloride-sensitive Na+ influx decreased linearly as a function of temperatures (about 37 degrees C) in shrunken cells, but increased in acidified cells. The up-regulation of acid-induced Na+/H+ exchange by elevated temperature was enhanced by hypo-osmolarity. Less sensitivity of intracellular H+ site at 41 degrees C may be the mechanism for the inhibition of shrinkage-induced Na+/H+ exchange by elevated temperature. Heating-mediated explosive increase in the activity of acid-induced Na+/H+ exchange may be due to enhanced extracellular Na+ sensitivity and lower intracellular pH caused by acidic metabolites. Acid-induced Na+/H+ exchange contributes to cytoplasmic Na+ accumulation. These two modes of Na+/H+ exchange with different response to elevated temperature may play different roles in the cellular pathogenesis of heatstroke.

  5. Mathematical model of a plate fin heat exchanger operating under solid oxide fuel cell working conditions

    Science.gov (United States)

    Kaniowski, Robert; Poniewski, Mieczysław

    2013-12-01

    Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.

  6. The Effect of Surface Charges on the Cellular Uptake of Liposomes Investigated by Live Cell Imaging.

    Science.gov (United States)

    Kang, Ji Hee; Jang, Woo Young; Ko, Young Tag

    2017-04-01

    Liposomes have been developed as versatile nanocarriers for various pharmacological agents. The effect of surface charges on the cellular uptake of the liposomes has been studied by various methods using mainly fixed cells with inevitable limitations. Live cell imaging has been proposed as an alternative methods to overcome the limitations of the fixed cell-based analysis. In this study, we aimed to investigate the effects of surface charges on cellular association and internalization of the liposomes using live cell imaging. We studied the cellular association and internalization of liposomes with different surface charge using laser scanning confocal microscopy (LSCM) equipped with live cell chamber system. Flow cytometry was also carried out using flow cytometer (FACS) for comparison. All of the cationic, neutral and anionic liposomes showed time-dependent cellular uptake through specific endocytic pathways. In glioblastoma U87MG cells, the cationic and anionic liposomes were mainly taken up via macropinocytosis, while the neutral liposomes mainly via caveolae-mediated endocytosis. In fibroblast NIH/3T3 cells, all of the three liposomes entered into the cell via clathrin-mediated endocytosis. This study provides a better understanding on the cellular uptake mechanisms of the liposomes, which could contribute significantly to development of liposome-based drug delivery systems.

  7. FUEL CELL PROTON EXCHANGE MEMBRANE - PRESENT AND PERSPECTIVES

    Directory of Open Access Journals (Sweden)

    Victor CIUPINA

    2012-05-01

    Full Text Available The fuel cells could contribute to the reduction of the pollution emission and the fossil fuels due to the conversion efficiency which is higher than the other energy conversion systems. There are many possibilities to improve the efficiency and to reduce the weight of the fuel cells by the integration of new nanostructured materials.

  8. Mast cell synapses and exosomes: membrane contacts for information exchange.

    NARCIS (Netherlands)

    Carroll-Portillo, A.; Surviladze, Z.; Cambi, A.; Lidke, D.S.; Wilson, B.S.

    2012-01-01

    In addition to their central role in allergy, mast cells are involved in a wide variety of cellular interactions during homeostasis and disease. In this review, we discuss the ability of mast cells to extend their mechanisms for intercellular communication beyond the release of soluble mediators.

  9. Hot topics in alkaline exchange membrane fuel cells

    Science.gov (United States)

    Serov, Alexey; Zenyuk, Iryna V.; Arges, Christopher G.; Chatenet, Marian

    2018-01-01

    The tremendous progress from the first discovery of fuel cell principles by Sir William Robert Grove in 1839 [1] and independent observation of electricity generated in electrochemical reaction of hydrogen and air by a Swiss scientist Christian F. Shoenbein [2] to the recent breakthroughs in the fuel cell field resulted in the appearance of this clean energy technology around us. Indeed, fuel cell technology undoubtedly has entered into our life with the first introduction of Toyota Mirai Fuel Cell Vehicle (FCV) by Toyota Motor Co. in December of 2014 [3,4]. This FCV is commercially available and can be purchased in several countries. However, its sticker price of 57,500 substantially limits the number of customers that can purchase it. There are numerous factors that contribute to the high cost of fuel cell stack, however the price of platinum and platinum alloys is the main contributor [5].

  10. Microfluidic device for rapid solution exchange to study kinetics of cell physiology

    Science.gov (United States)

    Hu, Howard; Honnatti, Meghana; Gillis, Kevin

    2006-11-01

    Exchanging the extracellular solution of the cell rapidly (less than 10ms) is an important requirement in study the kinetics of cell physiology. A microfluidic device is developed to exchange the solution around the cells as they flow through a junction at the intersection of two microfluidic channels. The solution exchange time is measured experimentally by fluorescently labeling the cell surface membranes with a styryl dye, FM1-43 or FM 2-10, and then observing the time course of cell fluorescence decay following the rapid drop in the extracellular concentration of the FM dye that occurs as the cell flows past the fluidic junction. A numerical model is developed to guide the experimental design of microfluidic device. In the model, the motion of a single cell through a fluid junction is simulated and the mixing process of the solutions is solved. The model also includes the kinetics of departitioning of FM dyes from the cell membrane. The departitioning time constants for the FM dyes are determined from fitting the measured data of the cell fluorescence decay. This departitioning kinetics is important as FM dyes are commonly used to label cell membranes for the purpose of measuring the release of neurotransmitter from synaptic vesicles via exocytosis and the subsequent reuptake of vesicular membrane by endocytosis.

  11. Doxorubicin-loaded, charge reversible, folate modified HPMA copolymer conjugates for active cancer cell targeting.

    Science.gov (United States)

    Li, Lian; Yang, Qingqing; Zhou, Zhou; Zhong, Jiaju; Huang, Yuan

    2014-06-01

    Although folate exhibits many advantages over other targeting ligands, it has one major defect: poor water solubility. Once it was conjugated to hydrophilic drug carrier such as N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer, the hydrophobic folate may be buried inside the random polymer coil and not exposed to be accessible to its receptor on the cell surface, thus losing its active targeting ability. To address this folate dilemma, the positive charge was introduced in the present study. The obtained cationic folate-functionalized HPMA copolymers exhibited a synergistic enhancing effect on cellular uptake by folate receptor (FR) positive Hela cells via electrostatic absorptive endocytosis and folate receptor-mediated endocytosis, with the involvement of multiple internalization pathways including clathrin-mediated endocytosis, caveolae-mediated endocytosis, macropinocytosis and energy-dependent endocytosis. As demonstrated in binding efficiency study, the FR antibody bound to 71.2% of tested cells in the competition with neutral folate modified HPMA copolymers, while the FR antibody-bounded cells decreased to only 34.0% in competition with cationic folate modified HPMA copolymers, indicating that the positively charge could probably amplify the binding efficiency of folate to its receptor due to close proximity of the conjugates to the cell surface by the electronic adhesion. In addition, the cell uptake study on FR negative A549 cells also confirmed the specific role of folate as targeting ligand. Then, to avoid non-specific binding by positive charge in the circulation, the charge shielding/deshielding approach was further employed. With selective hydrolysis of the charge shielding groups 2,3-dimethylmaleic anhydride (DMA) at tumor extracellular pH 6.8, the conjugates underwent a quick charge-reversible process with more than 80% DMA cleavage within 2 h and endocytosed into the endo/lysosomes much more rapidly than at physiological pH 7.4. And then the

  12. Surfactant functionalization induces robust, differential adhesion of tumor cells and blood cells to charged nanotube-coated biomaterials under flow.

    Science.gov (United States)

    Mitchell, Michael J; Castellanos, Carlos A; King, Michael R

    2015-07-01

    The metastatic spread of cancer cells from the primary tumor to distant sites leads to a poor prognosis in cancers originating from multiple organs. Increasing evidence has linked selectin-based adhesion between circulating tumor cells (CTCs) and endothelial cells of the microvasculature to metastatic dissemination, in a manner similar to leukocyte adhesion during inflammation. Functionalized biomaterial surfaces hold promise as a diagnostic tool to separate CTCs and potentially treat metastasis, utilizing antibody and selectin-mediated interactions for cell capture under flow. However, capture at high purity levels is challenged by the fact that CTCs and leukocytes both possess selectin ligands. Here, a straightforward technique to functionalize and alter the charge of naturally occurring halloysite nanotubes using surfactants is reported to induce robust, differential adhesion of tumor cells and blood cells to nanotube-coated surfaces under flow. Negatively charged sodium dodecanoate-functionalized nanotubes simultaneously enhanced tumor cell capture while negating leukocyte adhesion, both in the presence and absence of adhesion proteins, and can be utilized to isolate circulating tumor cells regardless of biomarker expression. Conversely, diminishing nanotube charge via functionalization with decyltrimethylammonium bromide both abolished tumor cell capture while promoting leukocyte adhesion. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Model-based analysis of anion-exchanger positioning in direct methanol fuel cell systems

    Science.gov (United States)

    Kraus, Maik; Schröder, Daniel; Krewer, Ulrike

    2014-09-01

    In this work we present a model based study to investigate the presence of anion exchangers in direct methanol fuel cell (DMFC) systems. It is well known that environmental or fuel impurities lead to accumulation of harmful anions, such as chloride, in the system. However, due to DMFC anodic reaction, a carbonate system is present. These corbanate anions have to be taken into account for the anion exchanger design and placement as well as for the system operation strategy with and without anion exchanger, which is the objective of this study. For this purpose, the expected amount of harmful chloride ions in a DMFC system is estimated, and that of carbonate ions is calculated with a model of the carbonate system in a DMFC system. The predicition of durability and dimensions of an anion exchanger is based on a monovalent anion exchange model. The design of gas liquid separators in the DMFC system has a major influence on the amount of dissolved carbon dioxide, which is crucial for durability and dimension of a system integrated anion exchanger. Finally, feasible positions of anion exchanger in a DMFC system are elaborated to fulfill the needs for long term and stable DMFC operation.

  14. Rapid Sequential in Situ Multiplexing with DNA Exchange Imaging in Neuronal Cells and Tissues.

    Science.gov (United States)

    Wang, Yu; Woehrstein, Johannes B; Donoghue, Noah; Dai, Mingjie; Avendaño, Maier S; Schackmann, Ron C J; Zoeller, Jason J; Wang, Shan Shan H; Tillberg, Paul W; Park, Demian; Lapan, Sylvain W; Boyden, Edward S; Brugge, Joan S; Kaeser, Pascal S; Church, George M; Agasti, Sarit S; Jungmann, Ralf; Yin, Peng

    2017-10-11

    To decipher the molecular mechanisms of biological function, it is critical to map the molecular composition of individual cells or even more importantly tissue samples in the context of their biological environment in situ. Immunofluorescence (IF) provides specific labeling for molecular profiling. However, conventional IF methods have finite multiplexing capabilities due to spectral overlap of the fluorophores. Various sequential imaging methods have been developed to circumvent this spectral limit but are not widely adopted due to the common limitation of requiring multirounds of slow (typically over 2 h at room temperature to overnight at 4 °C in practice) immunostaining. We present here a practical and robust method, which we call DNA Exchange Imaging (DEI), for rapid in situ spectrally unlimited multiplexing. This technique overcomes speed restrictions by allowing for single-round immunostaining with DNA-barcoded antibodies, followed by rapid (less than 10 min) buffer exchange of fluorophore-bearing DNA imager strands. The programmability of DEI allows us to apply it to diverse microscopy platforms (with Exchange Confocal, Exchange-SIM, Exchange-STED, and Exchange-PAINT demonstrated here) at multiple desired resolution scales (from ∼300 nm down to sub-20 nm). We optimized and validated the use of DEI in complex biological samples, including primary neuron cultures and tissue sections. These results collectively suggest DNA exchange as a versatile, practical platform for rapid, highly multiplexed in situ imaging, potentially enabling new applications ranging from basic science, to drug discovery, and to clinical pathology.

  15. Fullerene-Based Photoactive Layers for Heterojunction Solar Cells: Structure, Absorption Spectra and Charge Transfer Process

    Directory of Open Access Journals (Sweden)

    Yuanzuo Li

    2014-12-01

    Full Text Available The electronic structure and optical absorption spectra of polymer APFO3, [70]PCBM/APFO3 and [60]PCBM/APFO3, were studied with density functional theory (DFT, and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT. Visualized charge difference density analysis can be used to label the charge density redistribution for individual fullerene and fullerene/polymer complexes. The results of current work indicate that there is a difference between [60]PCBM and [70]PCBM, and a new charge transfer process is observed. Meanwhile, for the fullerene/polymer complex, all calculations of the twenty excited states were analyzed to reveal all possible charge transfer processes in depth. We also estimated the electronic coupling matrix, reorganization and Gibbs free energy to further calculate the rates of the charge transfer and the recombination. Our results give a clear picture of the structure, absorption spectra, charge transfer (CT process and its influencing factors, and provide a theoretical guideline for designing further photoactive layers of solar cells.

  16. Efficiently photo-charging lithium-ion battery by perovskite solar cell.

    Science.gov (United States)

    Xu, Jiantie; Chen, Yonghua; Dai, Liming

    2015-08-27

    Electric vehicles using lithium-ion battery pack(s) for propulsion have recently attracted a great deal of interest. The large-scale practical application of battery electric vehicles may not be realized unless lithium-ion batteries with self-charging suppliers will be developed. Solar cells offer an attractive option for directly photo-charging lithium-ion batteries. Here we demonstrate the use of perovskite solar cell packs with four single CH3NH3PbI3 based solar cells connected in series for directly photo-charging lithium-ion batteries assembled with a LiFePO4 cathode and a Li4Ti5O12 anode. Our device shows a high overall photo-electric conversion and storage efficiency of 7.80% and excellent cycling stability, which outperforms other reported lithium-ion batteries, lithium-air batteries, flow batteries and super-capacitors integrated with a photo-charging component. The newly developed self-chargeable units based on integrated perovskite solar cells and lithium-ion batteries hold promise for various potential applications.

  17. Efficiently photo-charging lithium-ion battery by perovskite solar cell

    Science.gov (United States)

    Xu, Jiantie; Chen, Yonghua; Dai, Liming

    2015-08-01

    Electric vehicles using lithium-ion battery pack(s) for propulsion have recently attracted a great deal of interest. The large-scale practical application of battery electric vehicles may not be realized unless lithium-ion batteries with self-charging suppliers will be developed. Solar cells offer an attractive option for directly photo-charging lithium-ion batteries. Here we demonstrate the use of perovskite solar cell packs with four single CH3NH3PbI3 based solar cells connected in series for directly photo-charging lithium-ion batteries assembled with a LiFePO4 cathode and a Li4Ti5O12 anode. Our device shows a high overall photo-electric conversion and storage efficiency of 7.80% and excellent cycling stability, which outperforms other reported lithium-ion batteries, lithium-air batteries, flow batteries and super-capacitors integrated with a photo-charging component. The newly developed self-chargeable units based on integrated perovskite solar cells and lithium-ion batteries hold promise for various potential applications.

  18. Theoretical Energy and Exergy Analyses of Proton Exchange Membrane Fuel Cell by Computer Simulation

    OpenAIRE

    I. D. Gimba; Abdulkareem, A. S.; Jimoh, A.; A. S. Afolabi

    2016-01-01

    A mathematical model of a proton exchange membrane fuel cell (PEMFC) was developed to investigate the effects of operating parameters such as temperature, anode and cathode pressures, reactants flow rates, membrane thickness, and humidity on the performance of the modelled fuel cell. The developed model consisted of electrochemical, heat energy and exergy components which were later simulated using a computer programme. The simulated model for the voltage output of the cell showed good confor...

  19. Diffusion engineering of ions and charge carriers for stable efficient perovskite solar cells

    Science.gov (United States)

    Bi, Enbing; Chen, Han; Xie, Fengxian; Wu, Yongzhen; Chen, Wei; Su, Yanjie; Islam, Ashraful; Grätzel, Michael; Yang, Xudong; Han, Liyuan

    2017-06-01

    Long-term stability is crucial for the future application of perovskite solar cells, a promising low-cost photovoltaic technology that has rapidly advanced in the recent years. Here, we designed a nanostructured carbon layer to suppress the diffusion of ions/molecules within perovskite solar cells, an important degradation process in the device. Furthermore, this nanocarbon layer benefited the diffusion of electron charge carriers to enable a high-energy conversion efficiency. Finally, the efficiency on a perovskite solar cell with an aperture area of 1.02 cm2, after a thermal aging test at 85 °C for over 500 h, or light soaking for 1,000 h, was stable of over 15% during the entire test. The present diffusion engineering of ions/molecules and photo generated charges paves a way to realizing long-term stable and highly efficient perovskite solar cells.

  20. Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation

    Directory of Open Access Journals (Sweden)

    A. Riera

    2002-03-01

    Full Text Available The effect of the anisotropy of the interaction potential on ion-diatom non-adiabatic collisions is analized by considering the influence of the anisotropy on orientation averaged total cross sections for charge transfer in H++H2(X1Σ+g collisions. We discuss the possibility of employing simpli ed methods such as an isotropic approximation, where only the electronic energies and interactions of a single orientation are necessary. The use of several isotropic calculations to evaluate the orientation averaged cross section is analized.

  1. State of charge estimation of high power lithium iron phosphate cells

    Science.gov (United States)

    Huria, T.; Ludovici, G.; Lutzemberger, G.

    2014-03-01

    This paper describes a state of charge (SOC) evaluation algorithm for high power lithium iron phosphate cells characterized by voltage hysteresis. The algorithm is based on evaluating the parameters of an equivalent electric circuit model of the cell and then using a hybrid technique with adequate treatment of errors, through an additional extended Kalman filter (EKF). The model algorithm has been validated in terms of effectiveness and robustness by several experimental tests.

  2. High resolution spectral signatures of X-ray emission following charge exchange recombination between highly charged iron and neutral helium, molecular hydrogen and molecular nitrogen: A comparison between theory and experiment

    Science.gov (United States)

    Brown, Gregory V.; Cumbee, Renata; Gu, Liyi; Kelley, Richard L.; Kilbourne, Caroline; Leutenegger, Maurice A.; Porter, Frederick S.; Beiersdorfer, Peter

    2017-08-01

    We have used the LLNL electron beam ion trap EBIT-I and a NASA/GSFC quantum microcalorimeter to measure the X-ray emission following charge exchange recombination between highly charged Fe25+ and Fe 26+ and neutral helium, molecular hydrogen, and molecular nitrogen. The ~ 5 eV energy resolution of the microcalorimeter has made it possible to measure and resolve n to 1 K-shell transitions from up to n = 14. We compare the measurements to a model based on the Landau-Zener theory and also the models found in SPEX and APEC. Our results include relative intensities of the 1P1 resonance line to the 3S1 forbidden line, commonly referred to as lines w and z. These results are especially useful for interpreting spectra from celestial sources measured with XARM's Resolve and ATHENA's X-IFU. These data have also proved useful in the interpretation of Hitomi's SXS spectrum of the Perseus cluster.Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Charge-exchange dipole excitations in neutron-rich nuclei: -1 ℏ ω0 , anti-analog pygmy and anti-analog giant resonances

    Science.gov (United States)

    Yoshida, Kenichi

    2017-11-01

    The occurrence of low-lying charge-exchange non-spin-flip dipole modes below the giant resonance in neutron-rich nuclei is predicted on the basis of nuclear density functional theory. The ground and excited states are described within the framework of the self-consistent Hartree-Fock-Bogoliubov theory and the proton-neutron quasiparticle-random-phase approximation employing a Skyrme-type energy density functional. The model calculations are performed for the spherical neutron-rich Ca, Ni, and Sn isotopes. It is found that the low-lying states appear sensitive to the shell structure associated with the -1 ℏ ω0 excitation below the Gamow-Teller states. Furthermore, the pygmy resonance emerges below the giant resonance when the neutrons occupy the low-ℓ (ℓ ≤2 -3 ) orbitals analogous to the pygmy resonance seen in the electric-dipole response.

  4. Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Manley, N.B.; Fabrikant, J.I.; Alpen, E.L.

    1988-12-01

    The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. This study concerns the cell population and cell cycle kinetics of the subependymal layer in the mouse brain, and the effects of charged particle irradiations on this cell population. Quantitative high resolution autoradiography was used to study the kinetic parameters in this cell layer. This study should help in understanding the effects of these high-energy heavy ions on normal mammalian brain tissue. The response of the mammalian brain exposure to charged particle ionizing radiation may be extremely variable. It varies from minimal physiological changes to overt tissue necrosis depending on a number of factors such as: the administered dose, dose-rate, the volume of the irradiated tissue, and the biological end-point being examined.

  5. Grazing incidence collisions of ions and atoms with surfaces: from charge exchange to atomic diffraction; Collisions rasantes d'ions ou d'atomes sur les surfaces: de l'echange de charge a la diffraction atomique

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, P

    2006-09-15

    This thesis reports two studies about the interaction with insulating surfaces of keV ions or atoms under grazing incidence. The first part presents a study of charge exchange processes occurring during the interaction of singly charged ions with the surface of NaCl. In particular, by measuring the scattered charge fraction and the energy loss in coincidence with electron emission, the neutralization mechanism is determined for S{sup +}, C{sup +}, Xe{sup +}, H{sup +}, O{sup +}, Kr{sup +}, N{sup +}, Ar{sup +}, F{sup +}, Ne{sup +} and He{sup +}. These results show the importance of the double electron capture as neutralization process for ions having too much potential energy for resonant capture and not enough for Auger neutralization. We have also studied the ionisation of the projectile and of the surface, and the different Auger-like neutralization processes resulting in electron emission, population of conduction band or excited state. For oxygen scattering, we have measured an higher electron yield in coincidence with scattered negative ion than with scattered atom suggesting the transient formation above the surface of the oxygen doubly negative ion. The second study deals with the fast atom diffraction, a new phenomenon observed for the first time during this work. Due to the large parallel velocity, the surface appears as a corrugated wall where rows interfere. Similarly to the Thermal Atom Scattering the diffraction pattern corresponds to the surface potential and is sensitive to vibrations. We have study the H-NaCl and He-LiF atom-surface potentials in the 20 meV - 1 eV range. This new method offers interesting perspectives for surface characterisation. (author)

  6. Proton exchange fuel cell : the design, construction and evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Heinzen, M.R.; Simoes, G.C.; Da Silva, L. [Univ. do Vale do Itajai, Sao Jose, SC (Brazil). Lab. de Pesquisa em Energia; Fiori, M.A.; Paula, M.M.S. [Univ. do Extremo Sul Catarinense, Santa Catarina (Brazil). Lab. de Sintese de Complexos Multifuncionais; Benavides, R. [Centro de Investigacion en Quimica Aplicada, Coahuila (Mexico)

    2010-07-15

    Polymer electrolyte membrane fuel cells (PEMFC) convert the chemical energy stored in the fuel directly into electrical energy without intermediate steps. The PEMFC operates at a relatively low operating temperature making it a good choice for mobile applications, but a high power density is needed in order to decrease the total weight of the vehicles. This paper presented a simple methodology to construct a PEMFC-type fuel cell, with particular reference to the gaseous diffuser, cell structure, the fixing plate, mounting bracket, gas distribution plates, and the membrane electrode assembly (MEA). The geometric design and meshing of the PEMFC were also described. The electrode was made using graphite with flow-field geometry. The PEMFC was tested for 100 hour of continuous work, during which time the current and voltage produced were monitored in order to evaluate the performance of the PEMFC. The materials used in the preparation of the fuel cell proved to be suitable. There was no loss of efficiency during the tests. The most relevant aspects affecting the PEMFC design were examined in an effort to optimize the performance of the cell. 13 refs., 6 figs.

  7. The exchange factor Cdc24 is required for cell fusion during yeast mating.

    Science.gov (United States)

    Barale, Sophie; McCusker, Derek; Arkowitz, Robert A

    2004-08-01

    During Saccharomyces cerevisiae mating, chemotropic growth and cell fusion are critical for zygote formation. Cdc24p, the guanine nucleotide exchange factor for the Cdc42 G protein, is necessary for oriented growth along a pheromone gradient during mating. To understand the functions of this critical Cdc42p activator, we identified additional cdc24 mating mutants. Two mating-specific mutants, the cdc24-m5 and cdc24-m6 mutants, each were isolated with a mutated residue in the conserved catalytic domain. The cdc24-m6 mutant responds normally to pheromone and orients its growth towards a mating partner yet accumulates prezygotes during mating. cdc24-m6 prezygotes have two apposed intact cell walls and do not correctly localize proteins required for cell fusion, despite normal exocytosis. Our results indicate that the exchange factor Cdc24p is necessary for maintaining or restricting specific proteins required for cell fusion to the cell contact region during mating.

  8. Nonadiabatic ionic--covalent transitions. Exponential-linear model for the charge exchange and neutralization reactions Na+H arrow-right-left Na/sup +/+H/sup -/

    Energy Technology Data Exchange (ETDEWEB)

    Errea, L.F.; Mendez, L.; Mo, O.; Riera, A.

    1986-01-01

    A previous study of charge exchange processes taking place through ionic--covalent transitions is extended to the case of Na+H and Na/sup +/+H/sup -/ collisions. A five-state molecular expansion, with the inclusion of two-electron translation factors, is employed to calculate the charge exchange and neutralization cross sections. Transitions at the first two pseudocrossings between the energy curves, practically determine the cross sections in the energy range 0.16--5 keV amu/sup -1/. We also show that the widely used multichannel Landau--Zener theory is totally inadequate, to treat these transitions.

  9. Proton Exchange Membrane (PEM) fuel Cell for Space Shuttle

    Science.gov (United States)

    Hoffman, William C., III; Vasquez, Arturo; Lazaroff, Scott M.; Downey, Michael G.

    1999-01-01

    Development of a PEM fuel cell powerplant (PFCP) for use in the Space Shuttle offers multiple benefits to NASA. A PFCP with a longer design life than is delivered currently from the alkaline fuel will reduce Space Shuttle Program maintenance costs. A PFCP compatible with zero-gravity can be adapted for future NASA transportation and exploration programs. Also, the commercial PEM fuel cell industry ensures a competitive environment for select powerplant components. Conceptual designs of the Space Shuttle PFCP have resulted in identification of key technical areas requiring resolution prior to development of a flight system. Those technical areas include characterization of PEM fuel cell stack durability under operational conditions and water management both within and external to the stack. Resolution of the above issues is necessary to adequately control development, production, and maintenance costs for a PFCP.

  10. Space charge calculations for sub-three-dimensional particle-in-cell code

    Directory of Open Access Journals (Sweden)

    Leonid G. Vorobiev

    2000-11-01

    Full Text Available A novel approach for modeling high-current, charged particle beams in a three-dimensional manner is introduced. While the integration of beam motion equations is done as in completely 3D particle-in-cell codes, the space charge forces are found by an approximately self-consistent inclusion of the transverse and longitudinal fields. The algorithm is dramatically faster than fully 3D algorithms with computational times comparable to 2D field solvers. In addition, a sparser spatial grid and fewer required macroparticles provide significantly reduced memory demands. The proposed sub-3D technique has been verified with good agreement with other independent algorithms.

  11. Improving charge transport property and energy transfer with carbon quantum dots in inverted polymer solar cells

    Science.gov (United States)

    Liu, Chunyu; Chang, Kaiwen; Guo, Wenbin; Li, Hao; Shen, Liang; Chen, Weiyou; Yan, Dawei

    2014-08-01

    Carbon quantum dots (Cdots) are synthesized by a simple method and introduced into active layer of polymer solar cells (PSCs). The performance of doped devices was apparently improved, and the highest power conversion efficiency of 7.05% was obtained, corresponding to a 28.2% enhancement compared with that of the contrast device. The charge transport properties, resistance, impedance, and transient absorption spectrum are systematically investigated to explore how the Cdots affect on PSCs performance. This study reveals the importance of Cdots in enhancing the efficiency of PSCs and gives insight into the mechanism of charge transport improvement.

  12. Commercialization of proton exchange membrane fuel cells for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Wismer, L.

    1996-04-01

    Environmental concerns with air quality and global warming have triggered strict federal ambient ozone air quality standards. Areas on non-attainment of these standards exist across the United States. Because it contains several of the most difficult attainment areas, the State of California has adopted low emission standards including a zero emission vehicle mandate that has given rise to development of hybrid electric vehicles, both battery-powered and fuel-cell powered. Fuel cell powered vehicles, using on-board hydrogen as a fuel, share the non-polluting advantage of the battery electric vehicle while offering at least three times the range today`s battery technology.

  13. Multiple-Trapping Model for the Charge Recombination Dynamics in Mesoporous-Structured Perovskite Solar Cells.

    Science.gov (United States)

    Wang, Hao-Yi; Wang, Yi; Hao, Ming-Yang; Qin, Yujun; Fu, Li-Min; Guo, Zhi-Xin; Ai, Xi-Cheng; Zhang, Jian-Ping

    2017-12-22

    The photovoltaic performance of organic-inorganic hybrid perovskite solar cells has reached a bottleneck after rapid development in last few years. Further breakthrough in this field requires deeper understanding of the underlying mechanism of the photoelectric conversion process in the device, especially the dynamics of charge-carrier recombination. Originating from dye-sensitized solar cells (DSSCs), mesoporous-structured perovskite solar cells (MPSCs) have shown many similarities to DSSCs with respect to their photoelectric dynamics. Herein, by applying the multiple-trapping model of the charge-recombination dynamic process for DSSCs in MPSCs, with rational modification, a novel physical model is proposed to describe the dynamics of charge recombination in MPSCs that exhibits good agreement with experimental data. Accordingly, the perovskite- and TiO 2 -dominating charge-recombination processes are assigned and their relationships with the trap-state distribution are also discussed. An optimal balance between these two dynamic processes is required to improve the performance of mesoporous-structured perovskite devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory

    Science.gov (United States)

    Ndu, Udonna

    2017-01-01

    Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl− ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl− ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl− ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl− reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH. PMID:28464020

  15. Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory.

    Directory of Open Access Journals (Sweden)

    Cristian P Schulthess

    Full Text Available Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl- ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl- ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl- ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl- reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH.

  16. Polymers application in proton exchange membranes for fuel cells (PEMFCs)

    Science.gov (United States)

    Walkowiak-Kulikowska, Justyna; Wolska, Joanna; Koroniak, Henryk

    2017-07-01

    This review presents the most important research on alternative polymer membranes with ionic groups attached, provides examples of materials with a well-defined chemical structure that are described in the literature. Furthermore, it elaborates on the synthetic methods used for preparing PEMs, the current status of fuel cell technology and its application. It also briefly discusses the development of the PEMFC market.

  17. Effects of weakly coupled and dense quantum plasmas environments on charge exchange and ionization processes in Na+ + Rb(5s) atom collisions

    Science.gov (United States)

    Pandey, Mukesh Kumar; Lin, Yen-Chang; Ho, Yew Kam

    2017-02-01

    The effects of weakly coupled or classical and dense quantum plasmas environment on charge exchange and ionization processes in Na+ + Rb(5s) atom collision at keV energy range have been investigated using classical trajectory Monte Carlo (CTMC) method. The interaction of three charged particles are described by the Debye-Hückel screen potential for weakly coupled plasma, whereas exponential cosine-screened Coulomb potential have been used for dense quantum plasma environment and the effects of both conditions on the cross sections are compared. It is found that screening effects on cross sections in high Debye length condition is quite small in both plasma environments. However, enhanced screening effects on cross sections are observed in dense quantum plasmas for low Debye length condition, which becomes more effective while decreasing the Debye length. Also, we have found that our calculated results for plasma-free case are comparable with the available theoretical results. These results are analyzed in light of available theoretical data with the choice of model potentials.

  18. Nearest-neighbor Kitaev exchange blocked by charge order in electron-doped α -RuCl3

    Science.gov (United States)

    Koitzsch, A.; Habenicht, C.; Müller, E.; Knupfer, M.; Büchner, B.; Kretschmer, S.; Richter, M.; van den Brink, J.; Börrnert, F.; Nowak, D.; Isaeva, A.; Doert, Th.

    2017-10-01

    A quantum spin liquid might be realized in α -RuCl3 , a honeycomb-lattice magnetic material with substantial spin-orbit coupling. Moreover, α -RuCl3 is a Mott insulator, which implies the possibility that novel exotic phases occur upon doping. Here, we study the electronic structure of this material when intercalated with potassium by photoemission spectroscopy, electron energy loss spectroscopy, and density functional theory calculations. We obtain a stable stoichiometry at K0.5RuCl3 . This gives rise to a peculiar charge disproportionation into formally Ru2 + (4 d6 ) and Ru3 + (4 d5 ). Every Ru 4 d5 site with one hole in the t2 g shell is surrounded by nearest neighbors of 4 d6 character, where the t2 g level is full and magnetically inert. Thus, each type of Ru site forms a triangular lattice, and nearest-neighbor interactions of the original honeycomb are blocked.

  19. Magnetic charge distribution and stray field landscape of asymmetric néel walls in a magnetically patterned exchange bias layer system

    Science.gov (United States)

    Zingsem, Norbert; Ahrend, Florian; Vock, Silvia; Gottlob, Daniel; Krug, Ingo; Doganay, Hatice; Holzinger, Dennis; Neu, Volker; Ehresmann, Arno

    2017-12-01

    The 3D stray field landscape above an exchange bias layer system with engineered domain walls has been fully characterized by quantitative magnetic force microscopy (qMFM) measurements. This method is based on a complete quantification of the MFM tip’s imaging properties and the subtraction of its contribution from the measured MFM data by deconvolution in Fourier space. The magnetically patterned Ir17Mn83/Co70Fe30-exchange-bias-multilayers have been designed to contain asymmetric head-to-head (hh)/tail-to-tail (tt) Néel walls between domains of different magnetic anisotropies for potential use in guided particle transport. In the current application, qMFM reveals the effective magnetic charge profile on the surface of the sample—with high spatial resolution and in an absolute quantitative manner. These data enable to calculate the magnetostatic potential and the full stray field landscape above the sample surface. It has been successfully tested against: (i) micromagnetic simulations of the magnetization structure of a comparable exchange-bias layer system, (ii) measurements of the magnetization profile across the domain boundary with x-ray photoemission electron microscopy, and (iii) direct stray field measurements obtained by scanning Hall probe microscopy at elevated scan heights. This approach results in a quantitative determination of the stray field landscape at close distances to the sample surface, which will be of importance for remote magnetic particle transport applications in lab-on-a-chip devices. Furthermore, the highly resolving and quantitative MFM approach reveals details of the domain transition across the artificially structured phase boundary, which have to be attributed to a continuous change in the materials parameters across this boundary, rather than an abrupt one.

  20. Charge collection and pore filling in solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Snaith, Henry J; Humphry-Baker, Robin; Chen, Peter; Cesar, Ilkay; Zakeeruddin, Shaik M; Grätzel, Michael

    2008-10-22

    The solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO(2) with the organic hole-transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20 µm. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, ∼2 µm, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the

  1. Charge collection and pore filling in solid-state dye-sensitized solar cells

    Science.gov (United States)

    Snaith, Henry J.; Humphry-Baker, Robin; Chen, Peter; Cesar, Ilkay; Zakeeruddin, Shaik M.; Grätzel, Michael

    2008-10-01

    The solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO2 with the organic hole-transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20 µm. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, ~2 µm, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the process of

  2. PVDF-PZT nanocomposite film based self-charging power cell

    Science.gov (United States)

    Zhang, Yan; Zhang, Yujing; Xue, Xinyu; Cui, Chunxiao; He, Bin; Nie, Yuxin; Deng, Ping; Wang, Zhong Lin

    2014-03-01

    A novel PVDF-PZT nanocomposite film has been proposed and used as a piezoseparator in self-charging power cells (SCPCs). The structure, composed of poly(vinylidene fluoride) (PVDF) and lead zirconate titanate (PZT), provides a high piezoelectric output, because PZT in this nanocomposite film can improve the piezopotential compared to the pure PVDF film. The SCPC based on this nanocomposite film can be efficiently charged up by the mechanical deformation in the absence of an external power source. The charge capacity of the PVDF-PZT nanocomposite film based SCPC in 240 s is ˜0.010 μA h, higher than that of a pure PVDF film based SCPC (˜0.004 μA h). This is the first demonstration of using PVDF-PZT nanocomposite film as a piezoseparator for SCPC, and is an important step for the practical applications of SCPC for harvesting and storing mechanical energy.

  3. Method and tool to reverse the charges in anti-reflection films used for solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Vivek; Tracy, Clarence

    2017-01-31

    A method is provided for making a solar cell. The method includes providing a stack including a substrate, a barrier layer disposed on the substrate, and an anti-reflective layer disposed on the barrier layer, where the anti-reflective layer has charge centers. The method also includes generating a corona with a charging tool and contacting the anti-reflective layer with the corona thereby injecting charge into at least some of the charge centers in the anti-reflective layer. Ultra-violet illumination and temperature-based annealing may be used to modify the charge of the anti-reflective layer.

  4. 160 C PROTON EXCHANGE MEMBRANE (PEM) FUEL CELL SYSTEM DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    L.G. Marianowski

    2001-12-21

    The objectives of this program were: (a) to develop and demonstrate a new polymer electrolyte membrane fuel cell (PEMFC) system that operates up to 160 C temperatures and at ambient pressures for stationary power applications, and (b) to determine if the GTI-molded composite graphite bipolar separator plate could provide long term operational stability at 160 C or higher. There are many reasons that fuel cell research has been receiving much attention. Fuel cells represent environmentally friendly and efficient sources of electrical power generation that could use a variety of fuel sources. The Gas Technology Institute (GTI), formerly Institute of Gas Technology (IGT), is focused on distributed energy stationary power generation systems. Currently the preferred method for hydrogen production for stationary power systems is conversion of natural gas, which has a vast distribution system in place. However, in the conversion of natural gas into a hydrogen-rich fuel, traces of carbon monoxide are produced. Carbon monoxide present in the fuel gas will in time cumulatively poison, or passivate the active platinum catalysts used in the anodes of PEMFC's operating at temperatures of 60 to 80 C. Various fuel processors have incorporated systems to reduce the carbon monoxide to levels below 10 ppm, but these require additional catalytic section(s) with sensors and controls for effective carbon monoxide control. These CO cleanup systems must also function especially well during transient load operation where CO can spike 300% or more. One way to circumvent the carbon monoxide problem is to operate the fuel cell at a higher temperature where carbon monoxide cannot easily adsorb onto the catalyst and poison it. Commercially available polymer membranes such as Nafion{trademark} are not capable of operation at temperatures sufficiently high to prevent this. Hence this project investigated a new polymer membrane alternative to Nafion{trademark} that is capable of operation at

  5. Post-transfusion purpura treated with plasma exchange by haemonetics cell separator. A case report

    DEFF Research Database (Denmark)

    Laursen, B; Morling, N; Rosenkvist, J

    1978-01-01

    A case of post-transfusion purpura in a 61-year-old, multiparous female with a platelet alloantibody (anti-Zwa) in her serum is reported. The patient was successfully treated with plasma exchange by means of a Haemonetics 30 cell separator and corticosteroids. Compared with other therapeutic meas...

  6. Characterization of proton exchange membrane fuel cell anode catalysts prepared by colloid method

    Energy Technology Data Exchange (ETDEWEB)

    Franco, E.G.; Dantas-Filho, P.L.; Burani, G.F. [Universidade de Sao Paulo (IEE/USP), Sao Paulo, SP (Brazil). Instituto de Eletrotecnica e Energia

    2009-07-01

    Full text: Anode catalysts for Proton Exchange Membrane Fuel Cell (PEMFC) were synthesized by the colloid method and their structure was investigated by transmission electron microscopy (TEM), energy dispersive analyses (EDS), X-ray Diffraction (XRD). The electrochemical behavior of the anode catalyst was analyzed by cyclic voltammetry (CV) and polarization curves (UxI). (author)

  7. Bromodeoxyuridine does not contribute to sister chromatid exchange events in normal or Bloom syndrome cells

    NARCIS (Netherlands)

    van Wietmarschen, Niek; Lansdorp, Peter M.

    2016-01-01

    Sister chromatid exchanges (SCEs) are considered sensitive indicators of genome instability. Detection of SCEs typically requires cells to incorporate bromodeoxyuridine (BrdU) during two rounds of DNA synthesis. Previous studies have suggested that SCEs are induced by DNA replication over

  8. Model-based fault detection for proton exchange membrane fuel cell ...

    African Journals Online (AJOL)

    In this paper, an intelligent model-based fault detection (FD) is developed for proton exchange membrane fuel cell (PEMFC) dynamic systems using an independent radial basis function (RBF) networks. The novelty is that this RBF networks is used to model the PEMFC dynamic systems and residuals are generated based ...

  9. Preparation of Stable Pt-Clay Nanocatalysts for Self-humidifying Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Zhang, Wenjing

    One of the critical challenges in making proton exchange membrane (PEM) fuel cells commercially viable is the inability of Nafion (the most used PEM) to conduct protons at low water content level. Both external humidifier and physical seal of the fixture in commercial products increase the cost...

  10. Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

    Science.gov (United States)

    Omasta, T. J.; Wang, L.; Peng, X.; Lewis, C. A.; Varcoe, J. R.; Mustain, W. E.

    2018-01-01

    Anion exchange membrane fuel cells (AEMFCs) offer several potential advantages over proton exchange membrane fuel cells (PEMFCs), most notably to overcome the cost barrier that has slowed the growth and large scale implementation of fuel cells for transportation. However, limitations in performance have held back AEMFCs, specifically in the areas of stability, carbonation, and maximum achievable current and power densities. In order for AEMFCs to contend with PEMFCs for market viability, it is necessary to realize a competitive cell performance. This work demonstrates a new benchmark for a H2/O2 AEMFC with a peak power density of 1.4 W cm-2 at 60 °C. This was accomplished by taking a more precise look at balancing necessary membrane hydration while preventing electrode flooding, which somewhat surprisingly can occur both at the anode and the cathode. Specifically, radiation-grafted ETFE-based anion exchange membranes and anion exchange ionomer powder, functionalized with benchmark benzyltrimethylammonium groups, were utilized to examine the effects of the following parameters on AEMFC performance: feed gas flow rate, the use of hydrophobic vs. hydrophilic gas diffusion layers, and gas feed dew points.

  11. Charge generation in organic solar cell materials studied by terahertz spectroscopy

    KAUST Repository

    Scarongella, M.

    2015-09-09

    We have investigated the photophysics in neat films of conjugated polymer PBDTTPD and its blend with PCBM using terahertz time-domain spectroscopy. This material has very high efficiency when used in organic solar cells. We were able to identify a THz signature for bound excitons in neat PBDTTPD films, pointing to important delocalization in those excitons. Then, we investigated the nature and local mobility (orders of magnitude higher than bulk mobility) of charges in the PBDTTPPD:PCBM blend as a function of excitation wavelength, fluence and pump-probe time delay. At low pump fluence (no bimolecular recombination phenomena), we were able to observe prompt and delayed charge generation components, the latter originating from excitons created in neat polymer domains which, thanks to delocalization, could reach the PCBM interface and dissociate to charges on a time scale of 1 ps. The nature of the photogenerated charges did not change between 0.5 ps and 800 ps after photo-excitation, which indicated that the excitons split directly into relatively free charges on an ultrafast time scale. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  12. Secondary Electron Emission From Solar Cell Coverslides And Its Effect On Absolute Vehicle Charging

    Science.gov (United States)

    Ferguson, Dale C.

    2011-10-01

    It has often been stated that earthed conductive solar cell coverslides are the best way to prevent electrostatic discharges on space solar arrays in GEO. While it is true that such coverslides will prevent differential charging on the solar arrays, it will be shown through NASCAP- 2k simulations that the secondary electron emission of such coverslides is very important for absolute vehicle charging. In particular, carbon nanotube coatings, due to the extremely low secondary electron emission from carbon, may exacerbate absolute vehicle charging. However, if they are earthed, because of their conductivity they may minimize differential charging and the possibility of arcing elsewhere on the spacecraft. Such results may also be true for insulative coverslides if spacecraft thermal blankets are made of materials with high secondary electron emission. Finally, photoemission from coverslides is investigated, with regard to anti-reflection coatings. Surfaces which reflect UV can have low photoemission, while those that absorb may have higher photoemission rates. Thus, anti-reflection coatings may lead to higher absolute spacecraft charging rates. NASCAP-2k simulations will be used to investigate these dependences for realistic spacecraft.

  13. Strontium insertion in methlyammonium lead iodide: long charge carrier lifetime and high fill factor solar cells (Conference Presentation)

    Science.gov (United States)

    Momblona, Cristina; Gil-Escrig, Lidón; Ávila, Jorge; Pérez-Del-Rey, Daniel; Forgács, David; Sessolo, Michele; Bolink, Hendrik J.

    2016-09-01

    Organic-inorganic (hybrid) lead halide perovskites are taking the lead among the emerging photovoltaics technologies, thanks to the demonstration of power conversion efficiencies exceeding 20 %. Hybrid perovskites have a wide spectrum of desirable properties; they are direct bandgap semiconductors with very high absorption coefficients, high and balanced hole and electron mobility, and large diffusion length. A unique feature of these materials is their versatility in terms of bandgap energy, which can be tuned by simple exchange of their components. In this paper we present vacuum and hybrid deposition routes for the preparation of different organic-inorganic lead perovskite thin films, and their incorporation into efficient solar cells. The influence of the type of organic semiconductors used as hole/electron transport layer in p-i-n solar cells will be presented. We also discuss their electroluminescence properties, either for applications in light-emitting diodes or as a diagnostic tool of the optical and electronic quality of perovskite thin films. Finally, the effect of additives and dopants in the perovskite absorber as well as in the charge selective layers will be described.

  14. A hermetic self-sustained microbial solar cell based on Chlorella vulgaris and a versatile charge transfer chain

    Science.gov (United States)

    Pan, Keliang; Zhou, Peijiang

    2015-10-01

    A hermetic noble-metal-free membrane-less microbial solar cell (MSC) is established. The substances decomposition and regeneration in this MSC are carried out only by Chlorella vulgaris simultaneously. The conversion of metabolism types of C. vulgaris is controlled only by illumination. By using a pleiotropic redox mediator and a cupric hexacyanoferrate modified cathode, a two-phase three-stage charge transfer chain is formed. Through this pathway, the one microorganism self-sustained system gets a long-term power output up to 0.04773 mW/cm2 at 0.423 V without any material exchange with external, which is 50 times higher than that obtained from the original system. Benefiting from this electron buffer system, the battery will achieve an electricity generation in both light and dark conditions. There is almost no consumption of any substrates throughout the stabilized process, and no more additions are required. This maintenance-free and extremely inexpensive reactor with a simple structure and a long service life demonstrates the possibility of combining the microbial, chemical and photo cells.

  15. Oxygen release and exchange in niobium oxide MEHPPV hybrid solar cells

    DEFF Research Database (Denmark)

    Lira-Cantu, M.; Norrman, K.; Andreasen, J.W.

    2006-01-01

    exchange was demonstrated using O-18(2)-isotopic labeling in combination with time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging analysis of devices and oxide substrates. TOF-SIMS depth profiling confirmed O-18 incorporation throughout the device in hybrid solar cells. The results...... are discussed in the context of hybrid solar cell stability and illuminate one of the degradation paths....

  16. Elevated sister chromatid exchange phenotype of Bloom syndrome cells is complemented by human chromosome 15.

    OpenAIRE

    McDaniel, L. D.; Schultz, R A

    1992-01-01

    Bloom syndrome (BSx) is a rare autosomal-recessive chromosome-instability disorder manifested by a constellation of clinical features including a significant predisposition to early onset of neoplasia. BSx cells display cytogenetic abnormalities, the pathognomonic feature being an increased rate of spontaneous sister chromatid exchanges (SCEs), 10- to 15-fold more frequent than SCEs seen in control cells. Identification of the primary biochemical defect in BSx and its relationship to SCE freq...

  17. Lead methylammonium triiodide perovskite-based solar cells: an interfacial charge-transfer investigation.

    Science.gov (United States)

    Xu, Xiaobao; Zhang, Hua; Cao, Kun; Cui, Jin; Lu, Jianfeng; Zeng, Xianwei; Shen, Yan; Wang, Mingkui

    2014-11-01

    This work reports on an investigation into interfacial charge transfer in CH3NH3PbI3 perovskite solar cells by using anatase TiO2 nanocuboids enclosed by active {100} and {001} facets. The devices show 6.0 and 8.0% power conversion efficiency with and without hole-transport material. Transient photovoltage/photocurrent decay and charge extraction, as well as impedance spectroscopy measurements, reveal that carbon materials are effective counter electrodes in perovskite solar cells. The photogenerated charges are observed to be stored in mesoporous TiO2 film under illumination and in the CH3NH3PbI3 layer in the dark. The use of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene (spiro-MeOTAD) as a hole-transport material accelerates interfacial charge recombination between the photogenerated electrons and holes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Thermal and water management of low temperature Proton Exchange Membrane Fuel Cell in fork-lift truck power system

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud; Rabbani, Raja Abid

    2013-01-01

    A general zero-dimensional Proton Exchange Membrane Fuel Cell (PEMFC) model has been developed for forklift truck application. The balance of plant (BOP) comprises of a compressor, an air humidifier, a set of heat exchangers and a recirculation pump. Water and thermal management of the fuel cell...

  19. Performance Analysis of Air Breathing Proton Exchange Membrane Fuel Cell Stack (PEMFCS) At Different Operating Condition

    Science.gov (United States)

    Sunil, V.; Venkata siva, G.; Yoganjaneyulu, G.; Ravikumar, V. V.

    2017-08-01

    The answer for an emission free power source in future is in the form of fuel cells which combine hydrogen and oxygen producing electricity and a harmless by product-water. A proton exchange membrane (PEM) fuel cell is ideal for automotive applications. A single cell cannot supply the essential power for any application. Hence PEM fuel cell stacks are used. The effect of different operating parameters namely: type of convection, type of draught, hydrogen flow rate, hydrogen inlet pressure, ambient temperature and humidity, hydrogen humidity, cell orientation on the performance of air breathing PEM fuel cell stack was analyzed using a computerized fuel cell test station. Then, the fuel cell stack was subjected to different load conditions. It was found that the stack performs very poorly at full capacity (runs only for 30 min. but runs for 3 hours at 50% capacity). Hence, a detailed study was undertaken to maximize the duration of the stack’s performance at peak load.

  20. In Vitro Collapsing Colon Cancer Cells by Selectivity of Disulfiram-Loaded Charge Switchable Nanoparticles Against Cancer Stem Cells.

    Science.gov (United States)

    Abu-Serie, Marwa M; El-Rashidy, Fatma H

    2017-01-01

    Different strategies against colon cancer are accompanied by treatment failure, because of drug toxicity toward normal cells and cancer stem cells (CSCs) resistance. However, previous patent evaluated liposome that encapsulated inhibitor of CSCs' aldehyde dehydrogenase (ALDH)1; disulfiram, for targeting breast CSCs. Liposome has disadvantages due to its hydrophobicity. Designing hydrophilic nanoparticles has selectivity to release disulfiram in CC cells rather than in normal colonocytes based on variation in microenvironment between normal and cancer cells. Disulfiram was nanoformulated by its loading into cationic chitosan and coating with anionic albumin. Their selectivity and targeting were investigated using murine and human colon cancer cells compared to normal mice colon cells. Zeta potential of the coated nanoparticles confirmed that albumin-layering confers negative charge (-10.3mv) for disulfiram-loaded chitosan nanoparticles (52.9mv). In slightly acidic medium of tumor, the ionic bond between albumin and chitosan hydrolyzed then the positive charge was reversed (47.6mv). Thus coated nanoparticles showed higher sustain release for disulfiram in tumor microenvironment than neutral pH and their uptake was higher in cancer cells than normal cells. This interpreted the highest selectivity of coated nanoparticles for enhancing apoptosis and eliminating CSCs in cancer cells. These patented coated nanoparticles were the most effective and selective for eradicating colon CSCs without insulting normal stem cells in comparison with disulfiram which was toxic to both normal and CSCs. This novel study that used charge switchable (hydrophilic) nanoparticles for targeting colon CSCs may represent a basis for future in vivo studies. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  1. Human mesenchymal stroma/stem cells exchange membrane proteins and alter functionality during interaction with different tumor cell lines.

    Science.gov (United States)

    Yang, Yuanyuan; Otte, Anna; Hass, Ralf

    2015-05-15

    To analyze effects of cellular interaction between human mesenchymal stroma/stem cells (MSC) and different cancer cells, direct co-cultures were performed and revealed significant growth stimulation of the tumor populations and a variety of protein exchanges. More than 90% of MCF-7 and primary human HBCEC699 breast cancer cells as well as NIH:OVCAR-3 ovarian adenocarcinoma cells acquired CD90 proteins during MSC co-culture, respectively. Furthermore, SK-OV-3 ovarian cancer cells progressively elevated CD105 and CD90 proteins in co-culture with MSC. Primary small cell hypercalcemic ovarian carcinoma cells (SCCOHT-1) demonstrated undetectable levels of CD73 and CD105; however, both proteins were significantly increased in the presence of MSC. This co-culture-mediated protein induction was also observed at transcriptional levels and changed functionality of SCCOHT-1 cells by an acquired capability to metabolize 5'cAMP. Moreover, exchange between tumor cells and MSC worked bidirectional, as undetectable expression of epithelial cell adhesion molecule (EpCAM) in MSC significantly increased after co-culture with SK-OV-3 or NIH:OVCAR-3 cells. In addition, a small population of chimeric/hybrid cells appeared in each MSC/tumor cell co-culture by spontaneous cell fusion. Immune fluorescence demonstrated nanotube structures and exosomes between MSC and tumor cells, whereas cytochalasin-D partially abolished the intercellular protein transfer. More detailed functional analysis of FACS-separated MSC and NIH:OVCAR-3 cells after co-culture revealed the acquisition of epithelial cell-specific properties by MSC, including increased gene expression for cytokeratins and epithelial-like differentiation factors. Vice versa, a variety of transcriptional regulatory genes were down-modulated in NIH:OVCAR-3 cells after co-culture with MSC. Together, these mutual cellular interactions contributed to functional alterations in MSC and tumor cells.

  2. A 2-D Implicit, Energy and Charge Conserving Particle In Cell Method

    Energy Technology Data Exchange (ETDEWEB)

    McPherson, Allen L. [Los Alamos National Laboratory; Knoll, Dana A. [Los Alamos National Laboratory; Cieren, Emmanuel B. [Los Alamos National Laboratory; Feltman, Nicolas [Los Alamos National Laboratory; Leibs, Christopher A. [Los Alamos National Laboratory; McCarthy, Colleen [Los Alamos National Laboratory; Murthy, Karthik S. [Los Alamos National Laboratory; Wang, Yijie [Los Alamos National Laboratory

    2012-09-10

    Recently, a fully implicit electrostatic 1D charge- and energy-conserving particle-in-cell algorithm was proposed and implemented by Chen et al ([2],[3]). Central to the algorithm is an advanced particle pusher. Particles are moved using an energy conserving scheme and are forced to stop at cell faces to conserve charge. Moreover, a time estimator is used to control errors in momentum. Here we implement and extend this advanced particle pusher to include 2D and electromagnetic fields. Derivations of all modifications made are presented in full. Special consideration is taken to ensure easy coupling into the implicit moment based method proposed by Taitano et al [19]. Focus is then given to optimizing the presented particle pusher on emerging architectures. Two multicore implementations, and one GPU (Graphics Processing Unit) implementation are discussed and analyzed.

  3. Long-lived photoinduced charge separation for solar cell applications in supramolecular complexes of multi-metalloporphyrins and fullerenes.

    Science.gov (United States)

    Fukuzumi, Shunichi; Ohkubo, Kei

    2013-12-07

    Monomers, dimers, trimers, dendrimers and oligomers of metalloporphyrins form supramolecular complexes with fullerene derivatives via electrostatic interactions, π-π interactions and coordination bonds. Photoexcitation of the supramolecular complexes resulted in photoinduced electron transfer from the porphyrin moiety to the fullerene moiety to produce the charge-separated states as revealed by laser flash photolysis measurements. The rate constants of photoinduced charge separation and charge recombination in supramolecular complexes of multi-metalloporphyrins and fullerenes were also determined by laser flash photolysis measurements and the results depending on the number of porphyrins in the supramolecular complexes are discussed in terms of efficiency of photoinduced energy transfer and charge separation as well as the lifetimes of charge-separated states. The photoelectrochemical performances of solar cells composed of supramolecular complexes of monomers, dimers, dendrimers and oligomers of metalloporphyrins with fullerenes are compared in relation to the rate constants of photoinduced charge separation and charge recombination.

  4. A nanoscale study of charge extraction in organic solar cells: the impact of interfacial molecular configurations.

    Science.gov (United States)

    Tang, Fu-Ching; Wu, Fu-Chiao; Yen, Chia-Te; Chang, Jay; Chou, Wei-Yang; Gilbert Chang, Shih-Hui; Cheng, Horng-Long

    2015-01-07

    In the optimization of organic solar cells (OSCs), a key problem lies in the maximization of charge carriers from the active layer to the electrodes. Hence, this study focused on the interfacial molecular configurations in efficient OSC charge extraction by theoretical investigations and experiments, including small molecule-based bilayer-heterojunction (sm-BLHJ) and polymer-based bulk-heterojunction (p-BHJ) OSCs. We first examined a well-defined sm-BLHJ model system of OSC composed of p-type pentacene, an n-type perylene derivative, and a nanogroove-structured poly(3,4-ethylenedioxythiophene) (NS-PEDOT) hole extraction layer. The OSC with NS-PEDOT shows a 230% increment in the short circuit current density compared with that of the conventional planar PEDOT layer. Our theoretical calculations indicated that small variations in the microscopic intermolecular interaction among these interfacial configurations could induce significant differences in charge extraction efficiency. Experimentally, different interfacial configurations were generated between the photo-active layer and the nanostructured charge extraction layer with periodic nanogroove structures. In addition to pentacene, poly(3-hexylthiophene), the most commonly used electron-donor material system in p-BHJ OSCs was also explored in terms of its possible use as a photo-active layer. Local conductive atomic force microscopy was used to measure the nanoscale charge extraction efficiency at different locations within the nanogroove, thus highlighting the importance of interfacial molecular configurations in efficient charge extraction. This study enriches understanding regarding the optimization of the photovoltaic properties of several types of OSCs by conducting appropriate interfacial engineering based on organic/polymer molecular orientations. The ultimate power conversion efficiency beyond at least 15% is highly expected when the best state-of-the-art p-BHJ OSCs are combined with present arguments.

  5. Observation of doubly-charged ions of francium isotopes extracted from a gas cell

    Science.gov (United States)

    Schury, P.; Wada, M.; Ito, Y.; Kaji, D.; Haba, H.; Hirayama, Y.; Kimura, S.; Koura, H.; MacCormick, M.; Miyatake, H.; Moon, J. Y.; Morimoto, K.; Morita, K.; Murray, I.; Ozawa, A.; Rosenbusch, M.; Reponen, M.; Takamine, A.; Tanaka, T.; Watanabe, Y. X.; Wollnik, H.

    2017-09-01

    Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a 48Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.

  6. Improving the Performance Of Single Cells In The Design Of Proton Exchange Membrane Fuel Cell (PEMFC) When Using Hydrogen

    OpenAIRE

    - Mulyazmi; Maria Ulfah; Silvi Octavia

    2017-01-01

    A proton Exchange Membrane Fuel Cell (PEMFC) was developed as a potential solution in power supply applications. In this study, the parameter values such as the relative humidity, the temperature, the pressure, the stoichiometric ratio of hydrogen to oxygen and the mass of catalyst used were varied to determine their effects on the single cell performance of PEMFC. The investigation showed that an increase in the temperature from 353 to 363 K resulted in a modest improvement in the single-cel...

  7. Red cell exchange to mitigate a delayed hemolytic transfusion reaction in a patient transfused with incompatible red blood cells.

    Science.gov (United States)

    Irani, Mehraboon S; Karafin, Matthew S; Ernster, Luke

    2017-02-01

    A red cell exchange was performed to prevent a potentially fatal hemolytic transfusion reaction in a patient with anti-e who was transfused with e-antigen unscreened red blood cells during liver transplant surgery. A 64-year-old woman with cirrhosis due to hepatitis C was scheduled to receive a liver transplant. She had a previously documented anti-e, an antibody to the Rh(e)-antigen that is known to cause delayed hemolytic transfusion reactions. Pre-operatively and intra-operatively, she had massive hemorrhage which required transfusion of 34 e-antigen unscreened red blood cells (RBCs) most of which were incompatible. The hemoglobin dropped from 9.1 g/dL on post-operative day (POD)1 to 6.6 g/dL on POD6, with no evidence of blood loss. The bilirubin also increased from 5.0 mg/dL on POD 1 to 11.0 mg/dL on POD 6. As she was also becoming more hemodynamically unstable, a red cell exchange with 10 units of e-negative RBCs was performed on POD 6. She improved clinically and was extubated the following day. A few residual transfused e-positive red cells were detected after the red cell exchange until POD 13. This case illustrates how a red cell exchange can mitigate the potentially harmful effects of a delayed hemolytic transfusion reaction caused by red cell antibodies. With massive intraoperative blood loss it may not be possible to have antigen-negative RBCs immediately available, particularly for the e-antigen, which is present in 98% of the donor population. The ability to perform such a procedure may be life-saving in such patients. J. Clin. Apheresis 32:59-61, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. Charge Transfer from Carbon Nanotubes to Silicon in Flexible Carbon Nanotube/Silicon Solar Cells.

    Science.gov (United States)

    Li, Xiaokai; Mariano, Marina; McMillon-Brown, Lyndsey; Huang, Jing-Shun; Sfeir, Matthew Y; Reed, Mark A; Jung, Yeonwoong; Taylor, André D

    2017-12-01

    Mechanical fragility and insufficient light absorption are two major challenges for thin flexible crystalline Si-based solar cells. Flexible hybrid single-walled carbon nanotube (SWNT)/Si solar cells are demonstrated by applying scalable room-temperature processes for the fabrication of solar-cell components (e.g., preparation of SWNT thin films and SWNT/Si p-n junctions). The flexible SWNT/Si solar cells present an intrinsic efficiency ≈7.5% without any additional light-trapping structures. By using these solar cells as model systems, the charge transport mechanisms at the SWNT/Si interface are investigated using femtosecond transient absorption. Although primary photon absorption occurs in Si, transient absorption measurements show that SWNTs also generate and inject excited charge carriers to Si. Such effects can be tuned by controlling the thickness of the SWNTs. Findings from this study could open a new pathway for designing and improving the efficiency of photocarrier generation and absorption for high-performance ultrathin hybrid SWNT/Si solar cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Matching Charge Extraction Contact for Wide-Bandgap Perovskite Solar Cells.

    Science.gov (United States)

    Lin, Yuze; Chen, Bo; Zhao, Fuwen; Zheng, Xiaopeng; Deng, Yehao; Shao, Yuchuan; Fang, Yanjun; Bai, Yang; Wang, Chunru; Huang, Jinsong

    2017-07-01

    Efficient wide-bandgap (WBG) perovskite solar cells are needed to boost the efficiency of silicon solar cells to beyond Schottky-Queisser limit, but they suffer from a larger open circuit voltage (V OC ) deficit than narrower bandgap ones. Here, it is shown that one major limitation of V OC in WBG perovskite solar cells comes from the nonmatched energy levels of charge transport layers. Indene-C60 bisadduct (ICBA) with higher-lying lowest-unoccupied-molecular-orbital is needed for WBG perovskite solar cells, while its energy-disorder needs to be minimized before a larger V OC can be observed. A simple method is applied to reduce the energy disorder by isolating isomer ICBA-tran3 from the as-synthesized ICBA-mixture. WBG perovskite solar cells with ICBA-tran3 show enhanced V OC by 60 mV, reduced V OC deficit of 0.5 V, and then a record stabilized power conversion efficiency of 18.5%. This work points out the importance of matching the charge transport layers in perovskite solar cells when the perovskites have a different composition and energy levels. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Primary Phenomenon in the Network Formation of Endothelial Cells: Effect of Charge.

    Science.gov (United States)

    Arai, Shunto

    2015-12-07

    Blood vessels are essential organs that are involved in the supply of nutrients and oxygen and play an important role in regulating the body's internal environment, including pH, body temperature, and water homeostasis. Many studies have examined the formation of networks of endothelial cells. The results of these studies have revealed that vascular endothelial growth factor (VEGF) affects the interactions of these cells and modulates the network structure. Though almost all previous simulation studies have assumed that the chemoattractant VEGF is present before network formation, vascular endothelial cells secrete VEGF only after the cells bind to the substrate. This suggests VEGF is not essential for vasculogenesis especially at the early stage. Using a simple experiment, we find chain-like structures which last quite longer than it is expected, unless the energetically stable cluster should be compact. Using a purely physical model and simulation, we find that the hydrodynamic interaction retard the compaction of clusters and that the chains are stabilized through the effects of charge. The charge at the surface of the cells affect the interparticle potential, and the resulting repulsive forces prevent the chains from folding. The ions surrounding the cells may also be involved in this process.

  11. Primary Phenomenon in the Network Formation of Endothelial Cells: Effect of Charge

    Directory of Open Access Journals (Sweden)

    Shunto Arai

    2015-12-01

    Full Text Available Blood vessels are essential organs that are involved in the supply of nutrients and oxygen and play an important role in regulating the body’s internal environment, including pH, body temperature, and water homeostasis. Many studies have examined the formation of networks of endothelial cells. The results of these studies have revealed that vascular endothelial growth factor (VEGF affects the interactions of these cells and modulates the network structure. Though almost all previous simulation studies have assumed that the chemoattractant VEGF is present before network formation, vascular endothelial cells secrete VEGF only after the cells bind to the substrate. This suggests VEGF is not essential for vasculogenesis especially at the early stage. Using a simple experiment, we find chain-like structures which last quite longer than it is expected, unless the energetically stable cluster should be compact. Using a purely physical model and simulation, we find that the hydrodynamic interaction retard the compaction of clusters and that the chains are stabilized through the effects of charge. The charge at the surface of the cells affect the interparticle potential, and the resulting repulsive forces prevent the chains from folding. The ions surrounding the cells may also be involved in this process.

  12. Iron oxide/hydroxide nanoparticles with negatively charged shells show increased uptake in Caco-2 cells.

    Science.gov (United States)

    Jahn, Markus R; Nawroth, Thomas; Fütterer, Sören; Wolfrum, Uwe; Kolb, Ute; Langguth, Peter

    2012-06-04

    The absorption of commonly used ferrous iron salts from intestinal segments at neutral to slightly alkaline pH is low, mainly because soluble ferrous iron is easily oxidized to poorly soluble ferric iron and because ferrous iron, but not ferric iron, is carried by the divalent metal transporter DMT-1. Moreover, ferrous iron frequently causes gastrointestinal side effects. Iron hydroxide nanoparticles with neutral and hydrophilic carbohydrate shells are alternatively used to ferrous salts. In these formulations gastrointestinal side effects are rare because hundreds of ferric iron atoms are safely packed in nanoscaled cores surrounded by the solubilizing shell; nevertheless, iron bioavailability is even worse compared to ferrous salts. In this study the cell uptake of iron hydroxide and iron oxide nanoparticles (FeONP) with negatively charged shells of different chemical types and sizes was compared to the uptake of those with neutral hydrophilic shells, ferrous sulfate and ferric chloride. The nanoparticle uptake was measured in Caco-2 cells with the iron detecting ferrozine method and visualized by transmission electron microscopy. The toxicity was evaluated using the MTT assay. For nanoparticles with a negatively charged shell the iron uptake was about 40 times higher compared to those with neutral hydrophilic carbohydrate shell or ferric chloride and in the same range as ferrous sulfate. However, in contrast to ferrous sulfate, nanoparticles with negatively charged shells showed no toxicity. Two different uptake mechanisms were proposed: diffusion for hydroxide nanoparticles with neutral hydrophilic shell and adsorptive endocytosis for nanoparticles with negatively charged shells. It needs to be determined whether iron hydroxide nanoparticles with negatively charged shells also show improved bioavailability in iron-deficient patients compared to iron hydroxide nanoparticles with a neutral hydrophilic shell, which exist in the market today.

  13. a Calculation of the Doubly Differential Cross Section for Inclusive Pion - HELIUM-4 Double Charge Exchange at Incident Pion Kinetic Energy Less than 270 Mev

    Science.gov (United States)

    Kulkarni, Arun Venkatesh

    Pi-nuclear scattering calculations that use multiple scattering usually require the knowledge not only of the pi-nucleon interaction in free space but also its modification inside a nuclear medium. A relativistic 3-Body model consisting of the pion, the i^ {rm th}-nucleon and the residual nucleus also called the core, is developed. In this model the nucleon core separation in co-ordinate space is approximated by the separation between the center of mass of the pi-i^{rm th} nucleon subsystem called the Composite, and the core. The instant form of dynamics was employed to introduce interactions between the pion and the nucleon and between the pi N Composite and the Core. The Composite-Core Hamiltonian is assumed to admit no bound states. The relativistic 3-Body total Hamiltonian is then diagonalized by nested-separable eigenfunctions. This diagonalization allows the construction of an expression for matrix elements of the medium modified pi N scattering operator tau_ {i} in the lab frame in terms of the CM pi N free space t-matrix elements. Terms that are quadratic in the pi N t -matrix elements in this expression are neglected. The Sequential Single Charge eXchange (SSCX) mechanism contribution to inclusive pi- ^4He Double Charge eXchange (DCX) is calculated using only the double scattering term of the Watson multiple scattering series. The tau-matrix elements obtained from the 3-Body model are used for the first scattering. It contains explicit dependance upon the matrix elements of the Composite-Core scattering operator t_{pi N-C}. This explicit dependance is ignored in the second scattering. The pole of the intermediate pion Green function is fixed from 3-Body model considerations and the requirement that pion be on the mass shell at the pole. The calculated inclusive cross sections {{d^2sigma}over{d Omega dT_pi}} are compared with the Kinney et al. experimental results and essential agreement with the spectrum for incident pion kinetic energy T_sp{pi}{rm In

  14. The effect of interfacial layers on charge transport in organic solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Mbuyise, Xolani G.; Tonui, Patrick; Mola, Genene Tessema, E-mail: mola@ukzn.ac.za

    2016-09-01

    The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.

  15. Efficient Polymer Solar Cells by Lithium Sulfonated Polystyrene as a Charge Transport Interfacial Layer.

    Science.gov (United States)

    Wang, Kai; Zhang, Zhan; Liu, Chang; Fu, Qiang; Xu, Wenzhan; Huang, Chongwen; Weiss, R A; Gong, Xiong

    2017-02-15

    In this paper, we report the highly efficient bulk heterojunction (BHJ) polymer solar cells (PSCs) with an inverted device structure via utilizing an ultrathin layer of lithium sulfonated polystyrene (LiSPS) ionomer to reengineer the surface of the solution-processed zinc oxide (ZnO) electron extraction layer (EEL). The unique lithium-ionic conductive LiSPS contributes to enhanced electrical conductivity of the ZnO/LiSPS EEL, which not only facilitates charge extraction from the BHJ active layer but also minimizes the energy loss within the charge transport processes. In addition, the organic-inorganic LiSPS ionomer well circumvents the coherence issue of the organic BHJ photoactive layer on the ZnO EEL. Consequently, the enhanced charge transport and the lowered internal resistance between the BHJ photoactive layer and the ZnO/LiSPS EEL give rise to a dramatically reduced dark saturation current density and significantly minimized charge carrier recombination. As a result, the inverted BHJ PSCs with the ZnO/LiSPS EEL exhibit an approximatively 25% increase in power conversion efficiency. These results indicate our strategy provides an easy, but effective, approach to reach high performance inverted PSCs.

  16. Effect of health information exchange on recognition of medication discrepancies is interrupted when data charges are introduced: results of a cluster-randomized controlled trial.

    Science.gov (United States)

    Boockvar, Kenneth S; Ho, William; Pruskowski, Jennifer; DiPalo, Katherine E; Wong, Jane J; Patel, Jessica; Nebeker, Jonathan R; Kaushal, Rainu; Hung, William

    2017-11-01

    To determine the effect of health information exchange (HIE) on medication prescribing for hospital inpatients in a cluster-randomized controlled trial, and to examine the prescribing effect of availability of information from a large pharmacy insurance plan in a natural experiment. Patients admitted to an urban hospital received structured medication reconciliation by an intervention pharmacist with (intervention) or without (control) access to a regional HIE. The HIE contained prescribing information from the largest hospitals and pharmacy insurance plan in the region for the first 10 months of the study, but only from the hospitals for the last 21 months, when data charges were imposed by the insurance plan. The primary endpoint was discrepancies between preadmission and inpatient medication regimens, and secondary endpoints included adverse drug events (ADEs) and proportions of rectified discrepancies. Overall, 186 and 195 patients were assigned to intervention and control, respectively. Patients were 60 years old on average and took a mean of 7 medications before admission. There was no difference between intervention and control in number of risk-weighted discrepancies (6.4 vs 5.8, P = .452), discrepancy-associated ADEs (0.102 vs 0.092 per admission, P = .964), or rectification of discrepancies (0.026 vs 0.036 per opportunity, P = .539). However, patients who received medication reconciliation with pharmacy insurance data available had more risk-weighted medication discrepancies identified than those who received usual care (8.0 vs 5.9, P = .038). HIE may improve outcomes of medication reconciliation. Charging for access to medication information interrupts this effect. Efforts are needed to understand and increase prescribers' rectification of medication discrepancies.

  17. Degradation of graphene coated copper in simulated proton exchange membrane fuel cell environment: Electrochemical impedance spectroscopy study

    Science.gov (United States)

    Ren, Y. J.; Anisur, M. R.; Qiu, W.; He, J. J.; Al-Saadi, S.; Singh Raman, R. K.

    2017-09-01

    Metallic materials are most suitable for bipolar plates of proton exchange membrane fuel cell (PEMFC) because they possess the required mechanical strength, durability, gas impermeability, acceptable cost and are suitable for mass production. However, metallic bipolar plates are prone to corrosion or they can passivate under PEMFC environment and interrupt the fuel cell operation. Therefore, it is highly attractive to develop corrosion resistance coating that is also highly conductive. Graphene fits these criteria. Graphene coating is developed on copper by chemical vapor deposition (CVD) with an aim to improving corrosion resistance of copper under PEMFC condition. The Raman Spectroscopy shows the graphene coating to be multilayered. The electrochemical degradation of graphene coated copper is investigated by electrochemical impedance spectroscopy (EIS) in 0.5 M H2SO4 solution at room temperature. After exposure to the electrolyte for up to 720 h, the charge transfer resistance (Rt) of the graphene coated copper is ∼3 times greater than that of the bare copper, indicating graphene coatings could improve the corrosion resistance of copper bipolar plates.

  18. Mass and Heat Transfer in Ion-Exchange Membranes Applicable to Solid Polymer Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Otteroey, M.

    1996-04-01

    In this doctoral thesis, an improved emf method for determination of transference numbers of two counter ions in ion-exchange membranes is presented. Transference numbers were obtained as a continuous function of the composition. The method avoids problems with diffusion by using a stack of membranes. Water transference coefficients in ion-exchange membranes is discussed and reversible and irreversible water transfer is studied by emf methods. Efforts were made to get data relevant to the solid polymer fuel cell. The results support the findings of other researchers that the reversible water transfer is lower than earlier predicted. A chapter on the conductivity of ion-exchange membranes establishes a method to separate the very thin liquid layers surrounding the membranes in a stack. Using the method it was found that the conductivity is obtained with high accuracy and that the liquid layer in a membrane stack can contribute significantly to the total measured resistance. A four point impedance method was tested to measure the conductivity of membranes under fuel cell conditions. Finally, there is a discussion of reversible heat effects and heat transfer in ion-exchange membranes. 155 refs., 45 figs., 13 tabs.

  19. Membrane electrode assembly with enhanced platinum utilization for high temperature proton exchange membrane fuel cell prepared by catalyst coating membrane method

    Science.gov (United States)

    Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Linkov, Vladimir; Pasupathi, Sivakumar

    2014-11-01

    In this work, membrane electrode assemblies (MEAs) prepared by catalyst coating membrane (CCM) method are investigated for reduced platinum (Pt) loading and improved Pt utilization of high temperature proton exchange membrane fuel cell (PEMFC) based on phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB-PBI) membrane. The results show that CCM method exhibits significantly higher cell performance and Pt-specific power density than that of MEAs prepared with conventional gas diffusion electrode (GDE) under a low Pt loading level. In-suit cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show that the MEAs prepared by the CCM method have a higher electrochemical surface area (ECSA), low cell ohmic resistance and low charge transfer resistance as compared to those prepared with GDEs at the same Pt loading.

  20. Highly conductive anion exchange membrane for high power density fuel-cell performance.

    Science.gov (United States)

    Ren, Xiaoming; Price, Samuel C; Jackson, Aaron C; Pomerantz, Natalie; Beyer, Frederick L

    2014-08-27

    Anion exchange membrane fuel cells (AEMFCs) are regarded as a new generation of fuel cell technology that has the potential to overcome many obstacles of the mainstream proton exchange membrane fuel cells (PEMFCs) in cost, catalyst stability, efficiency, and system size. However, the low ionic conductivity and poor thermal stability of current anion exchange membranes (AEMs) have been the key factors limiting the performance of AEMFCs. In this study, an AEM made of styrenic diblock copolymer with a quaternary ammonium-functionalized hydrophilic block and a cross-linkable hydrophobic block and possessing bicontinuous phases of a hydrophobic network and hydrophilic conduction paths was found to have high ionic conductivity at 98 mS cm(-1) and controlled membrane swelling with water uptake at 117 wt % at 22 °C. Membrane characterizations and fuel cell tests of the new AEM were carried out together with a commercial AEM, Tokuyama A201, for comparison. The high ionic conductivity and water permeability of the new membrane reported in this study is attributed to the reduced torturosity of the ionic conduction paths, while the hydrophobic network maintains the membrane mechanical integrity, preventing excessive water uptake.

  1. Alkaline anion exchange membrane fuel cells for cogeneration of electricity and valuable chemicals

    Science.gov (United States)

    Pan, Z. F.; Chen, R.; An, L.; Li, Y. S.

    2017-10-01

    Alkaline anion exchange membrane fuel cells (AAEMFCs) have received ever-increasing attentions due to the enhanced electrochemical kinetics and the absence of precious metal electrocatalysts, and thus great progress has been made in recent years. The alkaline anion exchange membrane based direct alcohol fuel cells, one type of alkaline anion exchange membrane fuel cells utilizing liquid alcohols as fuel that can be obtained from renewable biomass feedstocks, is another attractive point due to its ability to provide electricity with cogeneration of valuable chemicals. Significant development has been made to improve the selectivity towards high added-value chemicals and power output in the past few years. This review article provides a general description of this emerging technology, including fuel-cell setup and potential reaction routes, summarizes the products, performance, and system designs, as well as introduces the application of this concept in the removal of heavy-metal ions from the industrial wastewater. In addition, the remaining challenges and perspectives are also highlighted.

  2. Charge variants characterization of a monoclonal antibody by ion exchange chromatography coupled on-line to native mass spectrometry: Case study after a long-term storage at +5°C.

    Science.gov (United States)

    Leblanc, Y; Ramon, C; Bihoreau, N; Chevreux, G

    2017-03-24

    Numerous putative post-translational modifications may induce variations of monoclonal antibodies charge distribution that can potentially affect their biological activity. The characterization and the monitoring of these charge variants are critical quality requirements to ensure stability and process consistency. Charge variants are usually characterized by preparative ion exchange chromatography, collection of fractions and subsequent reverse-phase liquid chromatography with mass spectrometry analysis. While this process can be automatized by on-line two-dimensional chromatography, it remains often complex and time consuming. For this reason, a straightforward on-line charge variant analysis method is highly desirable and analytical laboratories are actively pursuing efforts to overcome this challenge. In this study, a mixed mode ion exchange chromatographic method using volatile salts and coupled on-line to native mass spectrometry was developed in association with a middle-up approach for a detailed characterization of monoclonal antibodies charge variants. An aged monoclonal antibody, presenting a complex charge variant profile was successfully investigated by this methodology as a case study. Results demonstrate that deamidation of the heavy chain was the major degradation pathway after long-term storage at 5°C while oxidation was rather low. The method was also very useful to identify all the clipped forms of the antibody. Copyright © 2017 LFB Biotechnologies. Published by Elsevier B.V. All rights reserved.

  3. Proton exchange membrane fuel cells for electrical power generation on-board commercial airplanes.

    Energy Technology Data Exchange (ETDEWEB)

    Curgus, Dita Brigitte; Munoz-Ramos, Karina (Sandia National Laboratories, Albuquerque, NM); Pratt, Joseph William; Akhil, Abbas Ali (Sandia National Laboratories, Albuquerque, NM); Klebanoff, Leonard E.; Schenkman, Benjamin L. (Sandia National Laboratories, Albuquerque, NM)

    2011-05-01

    Deployed on a commercial airplane, proton exchange membrane fuel cells may offer emissions reductions, thermal efficiency gains, and enable locating the power near the point of use. This work seeks to understand whether on-board fuel cell systems are technically feasible, and, if so, if they offer a performance advantage for the airplane as a whole. Through hardware analysis and thermodynamic and electrical simulation, we found that while adding a fuel cell system using today's technology for the PEM fuel cell and hydrogen storage is technically feasible, it will not likely give the airplane a performance benefit. However, when we re-did the analysis using DOE-target technology for the PEM fuel cell and hydrogen storage, we found that the fuel cell system would provide a performance benefit to the airplane (i.e., it can save the airplane some fuel), depending on the way it is configured.

  4. Proton Exchange Membrane Fuel Cells for Electrical Power Generation On-Board Commercial Airplanes

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, Joesph W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Klebanoff, Leonard E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Munoz-Ramos, Karina [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Akhil, Abbas A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Curgus, Dita B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schenkman, Benjamin L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2011-05-01

    Deployed on a commercial airplane, proton exchange membrane fuel cells may offer emissions reductions, thermal efficiency gains, and enable locating the power near the point of use. This work seeks to understand whether on-board fuel cell systems are technically feasible, and, if so, if they offer a performance advantage for the airplane as a whole. Through hardware analysis and thermodynamic and electrical simulation, we found that while adding a fuel cell system using today’s technology for the PEM fuel cell and hydrogen storage is technically feasible, it will not likely give the airplane a performance benefit. However, when we re-did the analysis using DOE-target technology for the PEM fuel cell and hydrogen storage, we found that the fuel cell system would provide a performance benefit to the airplane (i.e., it can save the airplane some fuel), depending on the way it is configured.

  5. A study of charge transfer kinetics in dye-sensitized surface conductivity solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Dennis

    2011-05-15

    The efficiency of the quasi-solid-state dye-sensitized solar cell developed by Junghaenel and Tributsch, the so-called Nano Surface Conductivity Solar Cell (NSCSC), was improved from 2% to 3.5% introducing a compact TiO{sub 2} underlayer, modifying the surface of the mesoporous TiO{sub 2} electrode, optimizing the deposition process of the electrolyte film, and replacing the platinum counter electrode by a carbon layer. Space-resolved photocurrent images revealed the importance of a homogeneous distribution of the electrolyte film. An uneven dispersion led to localized areas of high and low photocurrents, whereas the latter were attributed to an insufficient concentration of the redox couple. Impedance spectroscopy was performed on cells containing different concentrations of the redox couple. By modeling the spectra using an equivalent circuit with a transmission line of resistive and capacitive elements, the characteristic parameters of electron transport in the TiO{sub 2}, such as diffusion length and electron lifetime were obtained. The measurements indicated that the transport of the positive charge to the counter electrode is the main process limiting the efficiency of the cells. Excess charge carrier decay in functioning devices was analyzed by contactless transient photoconductance measurements in the microwave frequency range (TRMC). The lifetime of the photogenerated charge carriers was observed to decrease with increasing applied potential, reaching its maximum close to the opencircuit potential of the cell, where the photocurrent density was minimal, i.e. the potential dependent decay observed was limited by the injection of electrons into the front contact. The functioning of this NSCSC indicated that the transport of the positive charge occurs by solid-state diffusion at the surface of the TiO{sub 2} particles. TRMC measurements on subset devices in the form of sensitized TiO{sub 2} layers revealed charge carrier kinetics strongly dependent on the

  6. Nonhumidified High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    Science.gov (United States)

    Kinder, James D.

    2005-01-01

    Fuel cells are being considered for a wide variety of aerospace applications. One of the most versatile types of fuel cells is the proton-exchange-membrane (PEM) fuel cell. PEM fuel cells can be easily scaled to meet the power and space requirements of a specific application. For example, small 100-W PEM fuel cells are being considered for personal power for extravehicular activity suit applications, whereas larger PEM fuel cells are being designed for primary power in airplanes and in uninhabited air vehicles. Typically, PEM fuel cells operate at temperatures up to 80 C. To increase the efficiency and power density of the fuel cell system, researchers are pursuing methods to extend the operating temperature of the PEM fuel cell to 180 C. The most widely used membranes in PEM fuel cells are Nafion 112 and Nafion 117--sulfonated perfluorinated polyethers that were developed by DuPont. In addition to their relatively high cost, the properties of these membranes limit their use in a PEM fuel cell to around 80 C. The proton conductivity of Nafion membranes significantly decreases above 80 C because the membrane dehydrates. The useful operating range of Nafion-based PEM fuel cells can be extended to over 100 C if ancillary equipment, such as compressors and humidifiers, is added to maintain moisture levels within the membrane. However, the addition of these components reduces the power density and increases the complexity of the fuel cell system.

  7. Charge transfer state in DBP:C70 organic solar cells

    DEFF Research Database (Denmark)

    Sherafatipour, Golenaz; Benduhn, Johannes; Spoltore, Donato

    Organic solar cells (OSC) are green solar energy technology, which can be fabricated from organic compounds with cheep techniques and on flexible or transparent substrates such as plastic or glass. OSCs are cost efficient, and lightweight devices that can exhibit high power conversion efficiency...... of the CT states from which the maximum open circuit can be calculated and will set the base for modeling and optimizing the stability of the solar cells. 1. Cao, H. et al. Recent progress in degradation and stabilization of organic solar cells. J. Power Sources 264, 168–183 (2014). 2. Tvingstedt, K. et al....... Electroluminescence from charge transfer states in polymer solar cells. J. Am. Chem. Soc. 131, 11819–11824 (2009)....

  8. On lunar exospheric column densities and solar wind access beyond the terminator from ROSAT soft X-ray observations of solar wind charge exchange

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T. E.; Farrell, W. M.; Fatemi, S.; Hills, H. Kent; Hodges, R. R.; Holmström, M.; Kuntz, K. D.; Porter, F. Scott; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P.; Walsh, B. M.

    2014-07-01

    We analyze the Röntgen satellite (ROSAT) position sensitive proportional counter soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges: two 19° wedges (one north and one south) 13-32° off the terminator toward the dark side and one wedge 38° wide centered on the antisolar direction. The radial profiles of both the north and the south wedges show significant limb brightening that is absent in the 38° wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears to be dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now, along with Mars, Venus, and Earth, the Moon represents another solar system body at which SWCX has been observed.

  9. Deuterium charge exchange recombination spectroscopy from the top of the pedestal to the scrape off layer in H-mode plasmas

    Science.gov (United States)

    Haskey, S. R.; Grierson, B. A.; Stagner, L.; Burrell, K. H.; Chrystal, C.; Groebner, R. J.; Ashourvan, A.; Pablant, N. A.

    2017-10-01

    Recent completion of the thirty two channel main-ion (deuterium) charge exchange recombination spectroscopy (CER) diagnostic on DIII-D [J.L. Luxon, Nucl. Fusion 42 (2002) 614] enables detailed comparisons between impurity and main-ion temperature, density, and toroidal rotation. Sixteen sightlines cover the core of the plasma and another sixteen are densely packed towards the edge, providing high resolution measurements of the pedestal and steep gradient edge region of H-mode plasmas. The complexities of the Dα spectrum require fitting with a comprehensive model, as well as using iterative collisional radiative modeling to determine the underlying thermal deuterium ion properties. Large differences in the structure and magnitude of impurity (C6+) and main-ion (D+) toroidal rotation profiles are seen in the H-mode pedestal. Additionally the D+ temperature can be half the value of the C6+ temperature at the separatrix and shows more of a pedestal structure. Typically only the impurity properties are measured and the main-ion properties are either assumed to be the same, or inferred using neoclassical models, which require validation in the steep gradient region. These measured differences have implications for transport model validation, intrinsic rotation studies, pedestal stability, and the boundary conditions for scrape off layer and plasma material interactions studies.

  10. CHD7, the gene mutated in CHARGE syndrome, regulates genes involved in neural crest cell guidance.

    Science.gov (United States)

    Schulz, Yvonne; Wehner, Peter; Opitz, Lennart; Salinas-Riester, Gabriela; Bongers, Ernie M H F; van Ravenswaaij-Arts, Conny M A; Wincent, Josephine; Schoumans, Jacqueline; Kohlhase, Jürgen; Borchers, Annette; Pauli, Silke

    2014-08-01

    Heterozygous loss of function mutations in CHD7 (chromodomain helicase DNA-binding protein 7) lead to CHARGE syndrome, a complex developmental disorder affecting craniofacial structures, cranial nerves and several organ systems. Recently, it was demonstrated that CHD7 is essential for the formation of multipotent migratory neural crest cells, which migrate from the neural tube to many regions of the embryo, where they differentiate into various tissues including craniofacial and heart structures. So far, only few CHD7 target genes involved in neural crest cell development have been identified and the role of CHD7 in neural crest cell guidance and the regulation of mesenchymal-epithelial transition are unknown. Therefore, we undertook a genome-wide microarray expression analysis on wild-type and CHD7 deficient (Chd7 (Whi/+) and Chd7 (Whi/Whi)) mouse embryos at day 9.5, a time point of neural crest cell migration. We identified 98 differentially expressed genes between wild-type and Chd7 (Whi/Whi) embryos. Interestingly, many misregulated genes are involved in neural crest cell and axon guidance such as semaphorins and ephrin receptors. By performing knockdown experiments for Chd7 in Xenopus laevis embryos, we found abnormalities in the expression pattern of Sema3a, a protein involved in the pathogenesis of Kallmann syndrome, in vivo. In addition, we detected non-synonymous SEMA3A variations in 3 out of 45 CHD7-negative CHARGE patients. In summary, we discovered for the first time that Chd7 regulates genes involved in neural crest cell guidance, demonstrating a new aspect in the pathogenesis of CHARGE syndrome. Furthermore, we showed for Sema3a a conserved regulatory mechanism across different species, highlighting its significance during development. Although we postulated that the non-synonymous SEMA3A variants which we found in CHD7-negative CHARGE patients alone are not sufficient to produce the phenotype, we suggest an important modifier role for SEMA3A in the

  11. POLYSULFONE COMPOSED OF POLYANILINE NANOPARTICLES AS NANOCOMPOSITE PROTON EXCHANGE MEMBRANE IN MICROBIAL FUEL CELL

    OpenAIRE

    Mostafa Ghasemi; Mostafa Rahimnejad; Chakavak Esmaeili; Wan Ramli Wan Daud; Mohd Shahbudin Masdar; Edy Herianto Majlan; Sedky H.A. Hassan; Javed Alam; Manal Ismail; Mansour Saleh Alhoshan

    2012-01-01

    Proton exchange membranes play a critical role in the performance of Microbial Fuel Cells (MFCs) but their high price was always a big deal for commercialization of MFCs. In the present study, doped and undoped polyaniline nanoparticles/polysulfone nanocomposites membranes as a new type of PEM, were fabricated and applied in the MFC and their performance was compared with Nafion 117 as a traditional and expensive PEM. The obtained results show that MFC working by undoped Pani/Ps generated 78....

  12. Synthesis and Characterization of Sulfonated Polyimides as Proton Exchange Membranes for Fuel Cells

    OpenAIRE

    Gunduz, Nazan

    2001-01-01

    Series of homo- and copolyimides containing controlled degrees of sulfonic acid ion conducting pendant groups have been synthesized from both phthalic (five-) and naphthalic (six-membered) dianhydrides and appropriate wholly aromatic diamines and heterocyclic analogues. The goal is to identify thermally and hydrolytically stable ion conducting polymers (ICP) suitable as proton exchange membranes, PEM, for fuel cells. The candidate ICP's have been synthesized and characterized for molecular we...

  13. Tuning charge-discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

    National Research Council Canada - National Science Library

    Zhou, Yong-Ning; Ma, Jun; Hu, Enyuan; Yu, Xiqian; Gu, Lin; Nam, Kyung-Wan; Chen, Liquan; Wang, Zhaoxiang; Yang, Xiao-Qing

    2014-01-01

    .... Here we report such changes in opposite directions for lithium molybdenum trioxide (Li2MoO3). A 'unit cell breathing' mechanism is proposed based on crystal and electronic structural changes of transition metal oxides during charge-discharge...

  14. Solvent Vapor Annealing-Mediated Crystallization Directs Charge Generation, Recombination and Extraction in BHJ Solar Cells

    KAUST Repository

    Babics, Maxime

    2017-12-19

    Small-molecule (SM) donors that can be solution-processed with fullerene acceptors (e.g., PC61/71BM), or their “nonfullerene” counterparts, are proving particularly promising for the realization of high-efficiency bulk-heterojunction (BHJ) solar cells. In several recent studies, solvent vapor annealing (SVA) protocols have been found to yield significant BHJ device efficiency improvements via structural changes in the active layer morphologies. However, the mechanisms by which active layer morphologies evolve when subjected to SVA treatments, and the structural factors impacting charge generation, carrier transport, recombination and extraction in BHJ solar cells with SM donors and fullerene acceptors, remain important aspects to be elucidated. In this report, we show that – in BHJ solar cells with SM donors and fullerene acceptors – selective crystallization promoted by SVA mediates the development of optimized morphologies across the active layers, setting domain sizes and boundaries. Examining BHJ solar cells subjected to various SVA exposure times, with BDT[2F]QdC as the SM donor and PC71BM as the acceptor, we connect those morphological changes to specific carrier effects, showing that crystal growth effectively directs charge generation and recombination. We find that the SM donor-pure domains growing at the expense of a mixed donor-acceptor phase play a determining role, establishing optimum networks with 10-20nm-sized domains during the SVA treatment. Longer SVA times result in highly textured active layers with crystalline domains that can exceed the lengthscale of exciton diffusion, while inducing detrimental vertical morphologies and deep carrier traps. Last, we emphasize the field-dependence charge generation occurring upon SVA-mediated crystallization and link this carrier effect to the mixed phase depletion across the BHJ active layer.

  15. In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Chi-Yuan Lee

    2010-06-01

    Full Text Available The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC that are based on micro-electro-mechanical systems (MEMS. The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

  16. Water removal characteristics of proton exchange membrane fuel cells using a dry gas purging method

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Yeop; Kim, Hyoung-Juhn; Jang, Jong Hyun; Oh, In-Hwan; Cho, Eun Ae; Hong, Seong-Ahn; Lim, Tae-Hoon [Center for Fuel Cell Research, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Sungbuk-gu, Seoul 136-791 (Korea); Kim, Sang-Uk [Center for Fuel Cell Research, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Sungbuk-gu, Seoul 136-791 (Korea); Department of Chemical Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea); Ko, Jaejun; Lim, Tae-Won [Fuel Cell Vehicle Team 1, Hyundai-Kia Corporate Research and Development Division, 104 Mabuk-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-do 446-912 (Korea); Lee, Kwan-Young [Department of Chemical Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea)

    2008-06-01

    Water removal from proton exchange membrane fuel cells (PEMFC) is of great importance to improve start-up ability and mitigate cell degradation when the fuel cell operates at subfreezing temperatures. In this study, we report water removal characteristics under various shut down conditions including a dry gas-purging step. In order to estimate the dehydration level of the electrolyte membrane, the high frequency resistance of the fuel cell stack was observed. Also, a novel method for measuring the amount of residual water in the fuel cell was developed to determine the amount of water removal. The method used the phase change of liquid water and was successfully applied to examine the water removal characteristics. Based on these works, the effects of several parameters such as purging time, flow rate of purging gas, operation current, and stack temperature on the amount of residual water were investigated. (author)

  17. On-line fault diagnostic system for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Riascos, Luis Alberto M. [Federal University of ABC, r. Santa Adelia 166, CEP 09210-170, Santo Andre, Sao Paulo (Brazil); Simoes, Marcelo G. [Colorado School of Mines, 1500 Illinois St, 80401 Golden, CO (United States); Miyagi, Paulo E. [Escola Politecnica, University of Sao Paulo, Av. Prof. Mello Moraes 2231, CEP 05508-900, Sao Paulo (Brazil)

    2008-01-03

    In this paper, a supervisor system, able to diagnose different types of faults during the operation of a proton exchange membrane fuel cell is introduced. The diagnosis is developed by applying Bayesian networks, which qualify and quantify the cause-effect relationship among the variables of the process. The fault diagnosis is based on the on-line monitoring of variables easy to measure in the machine such as voltage, electric current, and temperature. The equipment is a fuel cell system which can operate even when a fault occurs. The fault effects are based on experiments on the fault tolerant fuel cell, which are reproduced in a fuel cell model. A database of fault records is constructed from the fuel cell model, improving the generation time and avoiding permanent damage to the equipment. (author)

  18. On-line fault diagnostic system for proton exchange membrane fuel cells

    Science.gov (United States)

    Riascos, Luis Alberto M.; Simoes, Marcelo G.; Miyagi, Paulo E.

    In this paper, a supervisor system, able to diagnose different types of faults during the operation of a proton exchange membrane fuel cell is introduced. The diagnosis is developed by applying Bayesian networks, which qualify and quantify the cause-effect relationship among the variables of the process. The fault diagnosis is based on the on-line monitoring of variables easy to measure in the machine such as voltage, electric current, and temperature. The equipment is a fuel cell system which can operate even when a fault occurs. The fault effects are based on experiments on the fault tolerant fuel cell, which are reproduced in a fuel cell model. A database of fault records is constructed from the fuel cell model, improving the generation time and avoiding permanent damage to the equipment.

  19. In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

    Science.gov (United States)

    Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

    2010-01-01

    The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse. PMID:22163556

  20. Zizimin and Dock guanine nucleotide exchange factors in cell function and disease.

    Science.gov (United States)

    Pakes, Nicholl K; Veltman, Douwe M; Williams, Robin S B

    2013-01-01

    Zizimin proteins belong to the Dock (Dedicator of Cytokinesis) superfamily of Guanine nucleotide Exchange Factor (GEF) proteins. This family of proteins plays a role in the regulation of Rho family small GTPases. Together the Rho family of small GTPases and the Dock/Zizimin proteins play a vital role in a number of cell processes including cell migration, apoptosis, cell division and cell adhesion. Our recent studies of Zizimin proteins, using a simple biomedical model, the eukaryotic social amoeba Dictyostelium discoideum, have helped to elucidate the cellular role of these proteins. In this article, we discuss the domain structure of Zizimin proteins from an evolutionary viewpoint. We also compare what is currently known about the mammalian Zizimin proteins to that of related Dock proteins. Understanding the cellular functions of these proteins will provide a better insight into their role in cell signaling, and may help in treating disease pathology associated with mutations in Dock/Zizimin proteins.

  1. Adaptive state of charge estimator for lithium-ion cells series battery pack in electric vehicles

    Science.gov (United States)

    Xiong, Rui; Sun, Fengchun; Gong, Xianzhi; He, Hongwen

    2013-11-01

    Due to cell-to-cell variations in battery pack, it is hard to model the behavior of the battery pack accurately; as a result, accurate State of Charge (SoC) estimation of battery pack remains very challenging and problematic. This paper tries to put effort on estimating the SoC of cells series lithium-ion battery pack for electric vehicles with adaptive data-driven based SoC estimator. First, a lumped parameter equivalent circuit model is developed. Second, to avoid the drawbacks of cell-to-cell variations in battery pack, a filtering approach for ensuring the performance of capacity/resistance conformity in battery pack has been proposed. The multi-cells “pack model” can be simplified by the unit model. Third, the adaptive extended Kalman filter algorithm has been used to achieve accurate SoC estimates for battery packs. Last, to analyze the robustness and the reliability of the proposed approach for cells and battery pack, the federal urban driving schedule and dynamic stress test have been conducted respectively. The results indicate that the proposed approach not only ensures higher voltage and SoC estimation accuracy for cells, but also achieves desirable prediction precision for battery pack, both the pack's voltage and SoC estimation error are less than 2%.

  2. Mechanisms of nanoparticle internalization and transport across an intestinal epithelial cell model: effect of size and surface charge.

    Science.gov (United States)

    Bannunah, Azzah M; Vllasaliu, Driton; Lord, Jennie; Stolnik, Snjezana

    2014-12-01

    This study investigated the effect of nanoparticle size (50 and 100 nm) and surface charge on their interaction with Caco-2 monolayers as a model of the intestinal epithelium, including cell internalization pathways and the level of transepithelial transport. Initially, toxicity assays showed that cell viability and cell membrane integrity were dependent on the surface charge and applied mass, number, and total surface area of nanoparticles, as tested in two epithelial cell lines, colon carcinoma Caco-2 and airway Calu-3. This also identified suitable nanoparticle concentrations for subsequent cell uptake experiments. Nanoparticle application at doses below half maximal effective concentration (EC₅₀) revealed that the transport efficiency (ratio of transport to cell uptake) across Caco-2 cell monolayers is significantly higher for negatively charged nanoparticles compared to their positively charged counterparts (of similar size), despite the higher level of internalization of positively charged systems. Cell internalization pathways were hence probed using a panel of pharmacological inhibitors aiming to establish whether the discrepancy in transport efficiency is due to different uptake and transport pathways. Vesicular trans-monolayer transport for both positively and negatively charged nanoparticles was confirmed via inhibition of dynamin (by dynasore) and microtubule network (via nocodazole), which significantly reduced the transport of both nanoparticle systems. For positively charged nanoparticles a significant decrease in internalization and transport (46% and 37%, respectively) occurred in the presence of a clathrin pathway inhibitor (chlorpromazine), macropinocytosis inhibition (42%; achieved by 5-(N-ethyl-N-isopropyi)-amiloride), and under cholesterol depletion (38%; via methyl-β-cyclodextrin), but remained unaffected by the inhibition of lipid raft associated uptake (caveolae) by genistein. On the contrary, the most prominent reduction in

  3. Electrochemical characterization of a polybenzimidazole-based high temperature proton exchange membrane unit cell

    Science.gov (United States)

    Jespersen, Jesper Lebæk; Schaltz, Erik; Kær, Søren Knudsen

    This work constitutes detailed EIS (Electrochemical Impedance Spectroscopy) measurements on a PBI-based HT-PEM unit cell. By means of EIS the fuel cell is characterized in several modes of operation by varying the current density, temperature and the stoichiometry of the reactant gases. Using Equivalent Circuit (EC) modeling key parameters, such as the membrane resistance, charge transfer resistance and gas transfer resistance are identified, however the physical interpretation of the parameters derived from EC's are doubtful as discussed in this paper. The EC model proposed, which is a modified Randles circuit, provides a reasonably good fit at all the conditions tested. The measurements reveal that the cell temperature is an important parameter, which influences the cell performance significantly, especially the charge transfer resistance proved to be very temperature dependent. The transport of oxygen to the Oxygen Reduction Reaction (ORR) likewise has a substantial effect on the impedance spectra, results showed that the gas transfer resistance has an exponential-like dependency on the air stoichiometry. Based on the present results and results found in recent publications it is still not clear what exactly causes the distinctive low frequency loop occurring at oxygen starvation. Contrary to the oxygen transport, the transport of hydrogen to the Hydrogen Oxidation Reaction (HOR), in the stoichiometry range investigated in this study, shows no measurable change in the impedance data. Generally, this work is expected to provide a basis for future development of impedance-based fuel cell diagnostic systems for HT-PEM fuel cell.

  4. Cast and 3D printed ion exchange membranes for monolithic microbial fuel cell fabrication

    Science.gov (United States)

    Philamore, Hemma; Rossiter, Jonathan; Walters, Peter; Winfield, Jonathan; Ieropoulos, Ioannis

    2015-09-01

    We present novel solutions to a key challenge in microbial fuel cell (MFC) technology; greater power density through increased relative surface area of the ion exchange membrane that separates the anode and cathode electrodes. The first use of a 3D printed polymer and a cast latex membrane are compared to a conventionally used cation exchange membrane. These new techniques significantly expand the geometric versatility available to ion exchange membranes in MFCs, which may be instrumental in answering challenges in the design of MFCs including miniaturisation, cost and ease of fabrication. Under electrical load conditions selected for optimal power transfer, peak power production (mean 10 batch feeds) was 11.39 μW (CEM), 10.51 μW (latex) and 0.92 μW (Tangoplus). Change in conductivity and pH of anolyte were correlated with MFC power production. Digital and environmental scanning electron microscopy show structural changes to and biological precipitation on membrane materials following long term use in an MFC. The cost of the novel membranes was lower than the conventional CEM. The efficacy of two novel membranes for ion exchange indicates that further characterisation of these materials and their fabrication techniques, shows great potential to significantly increase the range and type of MFCs that can be produced.

  5. Experimental results with a natural gas cogeneration system using a polymer exchange membrane fuel cell

    Science.gov (United States)

    Radulescu, Mihai; Lottin, Olivier; Feidt, Michel; Lombard, Christophe; Noc, David Le; Doze, Stéphane Le

    This paper reports experimental results of an investigation of five identical CHP (combined heat and power) units using PEMFC (proton exchange membrane fuel cell) and running on natural gas. The natural gas is reformed locally to produce hydrogen. The net electric power is 4.5 kWe and the installations are designed for low temperature heat recovery (6 kW at 60 °C). The performances of the CHP units are analyzed in terms of electrical, thermal and total efficiencies. The electrical efficiency is low and it is shown that this is due mostly to the reforming process and to electric losses, while fuel cell performances are fully satisfying.

  6. Novel niobium carbide/carbon porous nanotube electrocatalyst supports for proton exchange membrane fuel cell cathodes

    Science.gov (United States)

    Nabil, Y.; Cavaliere, S.; Harkness, I. A.; Sharman, J. D. B.; Jones, D. J.; Rozière, J.

    2017-09-01

    Niobium carbide/carbon nanotubular porous structures have been prepared using electrospinning and used as electrocatalyst supports for proton exchange membrane fuel cells. They were functionalised with 3.1 nm Pt particles synthesised by a microwave-assisted polyol method and characterised for their electrochemical properties. The novel NbC-based electrocatalyst demonstrated electroactivity towards the oxygen reduction reaction as well as greater stability over high potential cycling than a commercial carbon-based electrocatalyst. Pt/NbC/C was integrated at the cathode of a membrane electrode assembly and characterised in a single fuel cell showing promising activity and power density.

  7. Continual Energy Management System of Proton Exchange Membrane Fuel Cell Hybrid Power Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Ren Yuan

    2016-01-01

    Full Text Available Current research status in energy management of Proton Exchange Membrane (PEM fuel cell hybrid power electric vehicles are first described in this paper, and then build the PEMFC/ lithium-ion battery/ ultra-capacitor hybrid system model. The paper analysis the key factors of the continuous power available in PEM fuel cell hybrid power electric vehicle and hybrid power system working status under different driving modes. In the end this paper gives the working flow chart of the hybrid power system and concludes the three items of the system performance analysis.

  8. Analysis of capacity fading effect on Lithium Cobalt cells caused by pulse current technique in fast charging methods

    Science.gov (United States)

    Hafiz, S.; Arianto, S.; Yunaningsih, R. Y.; Majid, N.; Prihandoko, B.

    2017-04-01

    Charging a battery in a short time is important for portable devices. Many techniques have been developed to find out the proper method for fast charging. One of those techniques that has been patented in several fast charging methods is pulse current technique. This technique implements pulse current with adjusting pulse wide and voltage threshold in a certain values. In this paper, the capacity fading effects caused by the current pulse in lithium cobalt cells were investigated. The experiment was done by applying pulse current at high-level SOC to charge four cylindrical lithium cobalt cells. The Capacity of each cell was checked every 50 charge-discharge cycles. The experiment result shows that the changing capacity in each cell forms patterns alike. As if there was a slight increament on their capacities at first checking but rapidly decreasing at the next check. Then, their capacities continue to decrease slowly but the more often the charge-discharge cycling, the battery lifetime decreased. This research has provided analysis of pulse current effect on lithium cobalt capacity fading that should be noted as a reference in applying current pulse for fast charging methods.

  9. Serial Charging Test on High Capacity Li-Ion Cells for the Orbiter Advanced Hydraulic Power System

    Science.gov (United States)

    Jeevarajan, Judith A.; Irlbeck, Brad

    2006-01-01

    Although it looks like module level voltage drives the cutoff for charge, the actual cutoff is due to unbalanced cell voltages that drive the module voltage up. Individual cell voltage drives the cutoff for discharge Low resistance cells are the first to reach the low-voltage cutoff Cell-to-Cell voltage differences are generally small and show similar trends for each cycle Increase for a distinct window during charge and at the end of discharge Increase in max to min cell voltage difference with time/cycles Decrease in max to min cell voltage difference during high current pulses with time/cycles Individual cell voltage trends (with respect to other cells) are very repeatable from cycle to cycle, although voltage slowly degrades with time/cycles (resistance growth) Much more difference observed near end of discharge Little change in order of cell voltage (cell with highest voltage to cell with lowest voltage) Temp sensor on the side of cell (between 2 cells) shows much greater rise during discharge than for single cell tests (18 C vs 5 C) Conclusion: Serial Charging of this string of cells is feasible as it has only a minor impact on useful capacity

  10. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells

    Science.gov (United States)

    Setzler, Brian P.; Zhuang, Zhongbin; Wittkopf, Jarrid A.; Yan, Yushan

    2016-12-01

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW-1 in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  11. Steady state and transient simulation of anion exchange membrane fuel cells

    Science.gov (United States)

    Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

    2018-01-01

    We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

  12. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells.

    Science.gov (United States)

    Setzler, Brian P; Zhuang, Zhongbin; Wittkopf, Jarrid A; Yan, Yushan

    2016-12-06

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW(-1) in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  13. Insights into collaborative separation process of photogenerated charges and superior performance of solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiangyang, E-mail: lxy081276@126.com; Wang, Shun; Zheng, Haiwu; Gu, Yuzong [Institute of Microsystems Physics and School of Physics and Electronics, Henan University, Kaifeng 475004 (China)

    2016-07-25

    ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} (ZnO/CBS) and ZnO nanowires/CBS-graphene nanoplates (ZnO/CBS-GNs), as well as two types of solar cells were prepared. The photovoltaic responses of CBS-GNs and ZnO/CBS-GNs can be improved with incorporation of GNs. The transient surface photovoltage (TPV) can provide detailed information on the separation and transport of photogenerated carriers. The multichannel separation process from the TPVs indicates that the macro-photoelectric signals can be attributed to the photogenerated charges separated at the interface of CBS/GNs, rather than CBS/ZnO. The multi-interfacial recombination is the major carrier loss, and the hole selective p-V{sub 2}O{sub 5} can efficiently accelerate the charge extraction to the external circuit. The ZnO/CBS-GNs cell exhibits the superior performance, and the highest efficiency is 10.9%. With the adequate interfaces of CBS/GNs, GNs conductive network, energy level matching, etc., the excitons can easily diffuse to the interface of CBS/GNs, and the separated electrons and holes can be collected quickly, inducing the high photoelectric properties. Here, a facile strategy for solid state solar cells with superior performance presents a potential application.

  14. Relative logic cell placement for mitigation of charge sharing-induced transients

    Science.gov (United States)

    Kiddie, Bradley T.; Robinson, William H.

    2016-10-01

    Design of modern integrated circuits increasingly requires consideration of radiation effects, especially in space and other high-risk environments. With fabrication technologies scaling down both feature sizes and critical charge, a radiation strike in sub-100 nm technologies may affect multiple, physically adjacent nodes. With increasing clock speeds, transient errors in the processing datapath also increase in risk. Modeling single-event multiple-transients (SEMT) for pre-fabrication reliability characterization has become a more common design step, and this work adds to the state-of-the-art by providing a fast and physically-informed characterization flow that captures the effects of single-event multiple-node charge collection through experimentally observed transport mechanisms. Beyond characterization, the study of SEMT vulnerabilities reveals the electronic design automation (EDA) step of standard logic cell placement as a design space for hardening against SEMT-induced errors. This work: (1) analyzes the vulnerability of benchmark circuits against SEMT errors, (2) evaluates the impact of logic on transient propagation, (3) explores EDA placement techniques, and (4) builds an automated design flow for relative placement of cells to mask transient errors, while maintaining compatibility with other radiation hardening techniques. Zero cost to area and marginal impact on timing enable this new cell placement algorithm that masks 30% of SEMT-induced errors.

  15. On electrode pinning and charge blocking layers in organic solar cells

    Science.gov (United States)

    Magen, Osnat; Tessler, Nir

    2017-05-01

    We use device modelling for studying the losses introduced by metallic electrodes in organic solar cells' device structure. We first discuss the inclusion of pinning at the integer charge transfer state in device models, with and without using the image charge potential. In the presence of disorder, the space charge introduced due to the image potential enhances the pinning by more than 0.2 eV. The explicit introduction of the image potential creates band-gap narrowing at the contact, thus affecting both dark leakage current and photo conversion efficiency. We find that there are two regimes in which the contacts may limit the performance. For low (moderate) barriers, the contacts introduce minority carrier recombination at the contacts that adds to the bulk recombination channels. Only for high barriers, the contacts directly limit the open circuit voltage and impose a value that is equal to the contact's energy difference. Examining the device structures with blocking layers, we find that these are mainly useful for the low to moderate contacts' barriers and that for the high barrier case, the enhancement of open circuit voltage may be accompanied by the introduction of serial resistance or S shape.

  16. Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Sourav, E-mail: sourav.bhattacharjee@wur.nl [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Opstal, Edward J. van; Alink, Gerrit M. [Wageningen University, Division of Toxicology (Netherlands); Marcelis, Antonius T. M.; Zuilhof, Han [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Rietjens, Ivonne M. C. M. [Wageningen University, Division of Toxicology (Netherlands)

    2013-06-15

    The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size {approx}45 nm) and polystyrene nanoparticles (PSNPs/size {approx}50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).

  17. Carbon materials for enhancing charge transport in the advancements of perovskite solar cells

    Science.gov (United States)

    Hu, Ruiyuan; Chu, Liang; Zhang, Jian; Li, Xing'ao; Huang, Wei

    2017-09-01

    Organic-inorganic halide perovskite solar cells (PSCs) have become a new favorite in the photovoltaic field, due to the boosted efficiency up to 22.1%. Despite a flow of achievements, there are certain challenges to simultaneously meet high efficiency, large scale, low cost and high stability. Due to the low cost, extensive sources, high electrical conductivity and chemical stability, carbon materials have made undeniable contributions to play positive roles in developing PSCs. Carbon materials not only have the favorable conductivity but also bipolar advantage, which can transfer both electrons and holes. In this review, we will discuss how the carbon materials transfer charge or accelerate charge transport by incorporation in PSCs. Carbon materials can replace transparent conductive oxide layers, and enhance electron transport in electron transport layers. Moreover, carbon materials with continuous structure, especially carbon nanotubes and graphene, can provide direct charge transport channel that make them suitable additives or even substitutes in hole transport layers. Especially, the successful application of carbon materials as counter electrodes makes the devices full-printable, low temperature and high stability. Finally, a brief outlook is provided on the future development of carbon materials for PSCs, which are expected to devote more contributions in the future photovoltaic market.

  18. Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Shanlin [Univ. of Alabama, Tuscaloosa, AL (United States)

    2014-11-16

    Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an

  19. Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Heeger, Alan [Univ. of California, Santa Barbara, CA (United States); Bazan, Guillermo [Univ. of California, Santa Barbara, CA (United States); Nguyen, Thuc-Quyen [Univ. of California, Santa Barbara, CA (United States); Wudl, Fred [Univ. of California, Santa Barbara, CA (United States)

    2015-02-12

    The need for renewable sources of energy is well known. Conversion of sunlight to electricity using solar cells is one of the most important opportunities for creating renewable energy sources. The research carried out under DE-FG02-08ER46535 focused on the science and technology of “Plastic” solar cells comprised of organic (i.e. carbon based) semiconductors. The Bulk Heterojunction concept involves a phase separated blend of two organic semiconductors each with dimensions in the nano-meter length scale --- one a material that functions as a donor for electrons and the other a material that functions as an acceptor for electrons. The nano-scale inter-penetrating network concept for “Plastic” solar cells was created at UC Santa Barbara. A simple measure of the impact of this concept can be obtained from a Google search which gives 244,000 “hits” for the Bulk Heterojunction solar cell. Research funded through this program focused on four major areas: 1. Interfacial effects in organic photovoltaics, 2. Charge transfer and photogeneration of mobile charge carriers in organic photovoltaics, 3. Transport and recombination of the photogenerated charge carriers in organic photovoltaics, 4. Synthesis of novel organic semiconducting polymers and semiconducting small molecules, including conjugated polyelectrolytes. Following the discovery of ultrafast charge transfer at UC Santa Barbara in 1992, the nano-organic (Bulk Heterojunction) concept was formulated. The need for a morphology comprising two interpenetrating bicontinuous networks was clear: one network to carry the photogenerated electrons (negative charge) to the cathode and one network to carry the photo-generated holes (positive charge) to the anode. This remarkable self-assembled network morphology has now been established using Transmission electron Microscopy (TEM) either in the Phase Contrast mode or via TEM-Tomography. The steps involved in delivering power from a solar cell to an external circuit

  20. Effects of propylene, methyl methacrylate and isopropanol poisoning on spatial performance of a proton exchange membrane fuel cell

    Science.gov (United States)

    Reshetenko, Tatyana V.; St-Pierre, Jean

    2018-02-01

    This paper studies the effects of propylene, methyl methacrylate (MMA) and isopropanol (IPA) in air on the spatial performance of proton exchange membrane fuel cells (PEMFCs). The introduction of 100 ppm C3H6 into the oxidant stream resulted in a performance decrease of 130 mV at 1.0 A cm-2, whereas 20 ppm MMA caused a voltage loss of 80 mV. A moderate performance decline of 60 mV was detected in the presence of 5.3ṡ103 ppm IPA in air. Spatial electrochemical impedance spectroscopy (EIS) data showed an increase in charge and mass transfer resistances under exposure to C3H6 and MMA, although IPA did not affect the impedance. The observed PEMFC performances, local current redistributions and EIS data can be explained by the adsorption of contaminants on the Pt surface, their subsequent transformations, and their impacts on the electrochemical surface area and oxygen reduction mechanism. It was assumed that the studied contaminants were oxidized mainly to CO2 via electrochemical and chemical pathways under the operating conditions and at the cathode potential. Self-recovery of PEMFC performance was observed for each contaminant after halting its introduction into the air. Possible contaminant oxidation/reduction mechanisms and their correlations with spatial performance and EIS are presented and discussed.

  1. Dynamic environmental transmission electron microscopy observation of platinum electrode catalyst deactivation in a proton-exchange-membrane fuel cell.

    Science.gov (United States)

    Yoshida, Kenta; Xudong, Zhang; Bright, Alexander N; Saitoh, Koh; Tanaka, Nobuo

    2013-02-15

    Spherical-aberration-corrected environmental transmission electron microscopy (AC-ETEM) was applied to study the catalytic activity of platinum/amorphous carbon electrode catalysts in proton-exchange-membrane fuel cells (PEMFCs). These electrode catalysts were characterized in different atmospheres, such as hydrogen and air, and a conventional high vacuum of 10(-5) Pa. A high-speed charge coupled device camera was used to capture real-time movies to dynamically study the diffusion and reconstruction of nanoparticles with an information transfer down to 0.1 nm, a time resolution below 0.2 s and an acceleration voltage of 300 kV. With such high spatial and time resolution, AC-ETEM permits the visualization of surface-atom behaviour that dominates the coalescence and surface-reconstruction processes of the nanoparticles. To contribute to the development of robust PEMFC platinum/amorphous carbon electrode catalysts, the change in the specific surface area of platinum particles was evaluated in hydrogen and air atmospheres. The deactivation of such catalysts during cycle operation is a serious problem that must be resolved for the practical use of PEMFCs in real vehicles. In this paper, the mechanism for the deactivation of platinum/amorphous carbon electrode catalysts is discussed using the decay rate of the specific surface area of platinum particles, measured first in a vacuum and then in hydrogen and air atmospheres for comparison.

  2. Anion exchange composite membrane based on octa quaternary ammonium Polyhedral Oligomeric Silsesquioxane for alkaline fuel cells

    Science.gov (United States)

    Elumalai, Vijayakumar; Sangeetha, Dharmalingam

    2018-01-01

    A series of novel composite anion exchange membranes were prepared via simple solution casting method using synthesized quaternary ammonium functionalized Polyhedral Oligomeric Silsesquioxane (QA-POSS) with Quaternary polysulfone (QPSU). QA-POSS was synthesized from prepared Cl-POSS and well characterized by FT-IR, NMR, SEM and TEM analyses to confirm the chemical modifications and cubic morphologies. The QA-POSS nano particles have dual role in the membrane providing additional ion conducting groups and reinforcing the membrane in molecular level for the overall improvement of composite membrane. Additionally, the composite membranes were characterized by XRD, SEM, Ion exchange capacity (IEC), water uptake and conductivity to ensure the suitability of its use as an electrolyte in alkaline fuel cell. Finally, membrane electrode assembly (MEA) was fabricated using Pt anode (0.25 mg/cm2), Ag cathode (0.375 mg/cm2) and various synthesized composite membranes, and then it was tested in real time fuel cell setup. The membrane with 15% QA-POSS showed the maximum power density of 321 mW/cm2. The results showed that QA-POSS possess the ability to enhance the performance of the anion exchange membrane significantly.

  3. Multiphase Simulations and Design of Validation Experiments for Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Berning, Torsten

    2013-01-01

    Proton exchange membrane fuel cells directly convert into electricity the chemical energy of hydrogen and oxygen from air. The by-products are just water and waste heat. Depending on the operating conditions the water may be in the liquid or gas phase, and liquid water can hence plug the porous...... media in the fuel cell, and, more importantly, the flow channels and outlet ports of a single cell in a stack. These problems may be avoided if the fuel cell operates in a way that both the anode and cathode outlet stream are exactly fully humidified, i.e. the relative humidity is at 100...... %. Such operation can conceivably be obtained by adjusting the operating conditions using dew point diagrams. In this paper numerical results will be presented of two different flow field arrangements, both using the interdigitated flow field. It will be shown that arranging the gas streams in a counter-flow, “x...

  4. Proton exchange membrane fuel cell diagnosis by spectral characterization of the electrochemical noise

    Science.gov (United States)

    Maizia, R.; Dib, A.; Thomas, A.; Martemianov, S.

    2017-02-01

    Electrochemical noise analysis (ENA) has been performed for the diagnosis of proton-exchange membrane fuel cell (PEMFC) under various operating conditions. Its interest is related with the possibility of a non-invasive on-line diagnosis of a commercial fuel cell. A methodology of spectral analysis has been developed and an evaluation of the stationarity of the signal has been proposed. It has been revealed that the spectral signature of fuel cell, is a linear slope with a fractional power dependence 1/fα where α = 2 for different relative humidities and current densities. Experimental results reveal that the electrochemical noise is sensitive to the water management, especially under dry conditions. At RHH2 = 20% and RHair = 20%, spectral analysis shows a three linear slopes signature on the spectrum at low frequency range (f fuel cell water balance.

  5. Dynamic Model of the High Temperature Proton Exchange Membrane Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2009-01-01

    The present work involves the development of a model for predicting the dynamic temperature of a high temperature proton exchange membrane (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system...... is managed by running the stack at a high stoichiometric air flow. This is possible because of the polybenzimidazole (PBI) fuel cell membranes used and the very low pressure drop in the stack. The model consists of a discrete thermal model dividing the stack into three parts: inlet, middle, and end....... The temperature is predicted in these three parts, where they also are measured. The heat balance of the system involves a fuel cell model to describe the heat added by the fuel cells when a current is drawn. Furthermore the model also predicts the temperatures when heating the stack with external heating...

  6. Performance prediction of a proton exchange membrane fuel cell using the ANFIS model

    Energy Technology Data Exchange (ETDEWEB)

    Vural, Yasemin; Ingham, Derek B.; Pourkashanian, Mohamed [Centre for Computational Fluid Dynamics, University of Leeds, Houldsworth Building, LS2 9JT Leeds (United Kingdom)

    2009-11-15

    In this study, the performance (current-voltage curve) prediction of a Proton Exchange Membrane Fuel Cell (PEMFC) is performed for different operational conditions using an Adaptive Neuro-Fuzzy Inference System (ANFIS). First, ANFIS is trained with a set of input and output data. The trained model is then tested with an independent set of experimental data. The trained and tested model is then used to predict the performance curve of the PEMFC under various operational conditions. The model shows very good agreement with the experimental data and this indicates that ANFIS is capable of predicting fuel cell performance (in terms of cell voltage) with a high accuracy in an easy, rapid and cost effective way for the case presented. Finally, the capabilities and the limitations of the model for the application in fuel cells have been discussed. (author)

  7. A review on the performance and modelling of proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Boucetta, A., E-mail: abirboucetta@yahoo.fr; Ghodbane, H., E-mail: h.ghodbane@mselab.org; Bahri, M., E-mail: m.bahri@mselab.org [Department of Electrical Engineering, MSE Laboratory, Mohamed khider Biskra University (Algeria); Ayad, M. Y., E-mail: ayadmy@gmail.com [R& D, Industrial Hybrid Vehicle Applications (France)

    2016-07-25

    Proton Exchange Membrane Fuel Cells (PEMFC), are energy efficient and environmentally friendly alternative to conventional energy conversion for various applications in stationary power plants, portable power device and transportation. PEM fuel cells provide low operating temperature and high-energy efficiency with near zero emission. A PEM fuel cell is a multiple distinct parts device and a series of mass, energy, transport through gas channels, electric current transport through membrane electrode assembly and electrochemical reactions at the triple-phase boundaries. These processes play a decisive role in determining the performance of the Fuel cell, so that studies on the phenomena of gas flows and the performance modelling are made deeply. This paper gives a comprehensive overview of the state of the art on the Study of the phenomena of gas flow and performance modelling of PEMFC.

  8. New load cycling strategy for enhanced durability of high temperature proton exchange membrane fuel cell

    DEFF Research Database (Denmark)

    Thomas, Sobi; Jeppesen, Christian; Steenberg, Thomas

    2017-01-01

    The objective of this paper is to develop a new operational strategy to increase the lifetime of a high temperature proton exchange membrane (HT-PEMFCs) fuel cell system by using load cycling patterns to reduce the phosphoric acid loss from the fuel cell. Four single cells were operated under...... different current cycling profile, while one cell was operated at constant current density for comparison. Polarization curves and electrochemical impedance spectroscopy measurements were recorded during the course of the tests and analysed. Two different current densities, 0.2 Acm-2 for the lower end and 0.......8 Acm-2 for the higher end, were selected for the load cycling operation. The relaxation time, which is the period of time spent at low current density operation, is varied to understand how the performance over prolonged period behaves. The duration of the high current density operation is selected...

  9. Diffusion-driven proton exchange membrane fuel cell for converting fermenting biomass to electricity.

    Science.gov (United States)

    Malati, P; Mehrotra, P; Minoofar, P; Mackie, D M; Sumner, J J; Ganguli, R

    2015-10-01

    A membrane-integrated proton exchange membrane fuel cell that enables in situ fermentation of sugar to ethanol, diffusion-driven separation of ethanol, and its catalytic oxidation in a single continuous process is reported. The fuel cell consists of a fermentation chamber coupled to a direct ethanol fuel cell. The anode and fermentation chambers are separated by a reverse osmosis (RO) membrane. Ethanol generated from fermented biomass in the fermentation chamber diffuses through the RO membrane into a glucose solution contained in the DEFC anode chamber. The glucose solution is osmotically neutral to the biomass solution in the fermentation chamber preventing the anode chamber from drying out. The fuel cell sustains >1.3 mW cm(-2) at 47°C with high discharge capacity. No separate purification or dilution is necessary, resulting in an efficient and portable system for direct conversion of fermenting biomass to electricity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Microwave Assisted Reduction of Pt-Catalyst by N-Phenyl-p-Phenylenediamine for Proton Exchange Membrane Fuel Cells

    National Research Council Canada - National Science Library

    Ming-Jer Tsai; Tar-Hwa Hsieh; Yen-Zen Wang; Ko-Shan Ho; Chia-Yun Chang

    2017-01-01

    The presence of N-phenyl-p-phenylenediamine (PPDA: a dimer of aniline) during microwave (MW) irradiation can significantly improve Pt-loading on the XC72 carbon matrix as a catalyst support of proton exchange membrane fuel cells...

  11. Study on Corrosion Migrations within Catalyst-Coated Membranes of Proton Exchange Membrane Electrolyzer Cells

    Energy Technology Data Exchange (ETDEWEB)

    Green, Johney [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Mo, Jingke [University of Tennessee; Steen, Stuart [University of Tennessee; Kang, Zhenye [University of Tennessee; Yang, Gaoqiang [University of Tennessee; Taylor, Derrick A. [University of Tennessee; Li, Yifan [University of Tennessee; Toops, Todd J. [Oak Ridge National Laboratory; Brady, Michael P. [Oak Ridge National Laboratory; Retterer, Scott T. [Oak Ridge National Laboratory; Cullen, David A. [Oak Ridge National Laboratory; Zhang, Feng-Yuan [University of Tennessee

    2017-10-09

    The corrosion of low-cost, easily manufactured metallic components inside the electrochemical environment of proton exchange membrane electrolyzer cells (PEMECs) has a significant effect on their performance and durability. In this study, 316 stainless steel (SS) mesh was used as a model liquid/gas diffusion layer material to investigate the migration of corrosion products in the catalyst-coated membrane of a PEMEC. Iron and nickel cation particles were found distributed throughout the anode catalyst layer, proton exchange membrane, and cathode catalyst layer, as revealed by scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The results indicate the corrosion products of 316 SS are transported from anode to cathode through the nanochannels of the Nafion membrane, resulting in impeded proton transport and overall PEMEC performance loss.

  12. Receptor-Mediated Surface Charge Inversion Platform Based on Porous Silicon Nanoparticles for Efficient Cancer Cell Recognition and Combination Therapy.

    Science.gov (United States)

    Zhang, Feng; Correia, Alexandra; Mäkilä, Ermei; Li, Wei; Salonen, Jarno; Hirvonen, Jouni J; Zhang, Hongbo; Santos, Hélder A

    2017-03-22

    Negatively charged surface-modified drug delivery systems are promising for in vivo applications as they have more tendency to accumulate in tumor tissues. However, the inefficient cell uptake of these systems restricts their final therapeutic performance. Here, we have fabricated a receptor-mediated surface charge inversion nanoparticle made of undecylenic acid modified, thermally hydrocarbonized porous silicon (UnTHCPSi) nanoparticles core and sequentially modified with polyethylenimine (PEI), methotrexate (MTX), and DNA aptamer AS1411 (herein termed as UnTHCPSi-PEI-MTX@AS1411) for enhancing the cell uptake of nucleolin-positive cells. The efficient interaction of AS1411 and the relevant receptor nucleolin caused the disintegration of the negative-charged AS1411 surface. The subsequent surface charge inversion and exposure of the active targeting ligand, MTX, enhanced the cell uptake of the nanoparticles. On the basis of this synergistic effect, the UnTHCPSi-PEI-MTX@AS1411 (hydrodynamic diameter is 242 nm) were efficiently internalized by nucleolin-positive MDA-MB-231 breast cancer cells, with an efficiency around 5.8 times higher than that of nucleolin-negative cells (NIH 3T3 fibroblasts). The receptor competition assay demonstrated that the major mechanism (more than one-half) of the internalized nanoparticles in MDA-MB-231 cells was due to the receptor-mediated surface charge inversion process. Finally, after loading of sorafenib, the nanosystem showed efficient performance for combination therapy with an inhibition ratio of 35.6%.

  13. The Fate of a Normal Human Cell Traversed by a Single Charged Particle

    Science.gov (United States)

    Fournier, C.; Zahnreich, S.; Kraft, D.; Friedrich, T.; Voss, K.-O.; Durante, M.; Ritter, S.

    2012-09-01

    The long-term ``fate'' of normal human cells after single hits of charged particles is one of the oldest unsolved issues in radiation protection and cellular radiobiology. Using a high-precision heavy-ion microbeam we could target normal human fibroblasts with exactly one or five carbon ions and measured the early cytogenetic damage and the late behaviour using single-cell cloning. Around 70% of the first cycle cells presented visible aberrations in mFISH after a single ion traversal, and about 5% of the cells were still able to form colonies. In one third of selected high-proliferative colonies we observed clonal (radiation-induced) aberrations. Terminal differentiation and markers of senescence (PCNA, p16) in the descendants of cells traversed by one carbon ion occurred earlier than in controls, but no evidence of radiation-induced chromosomal instability was found. We conclude that cells surviving single-ion traversal, often carrying clonal chromosome aberrations, undergo accelerated senescence but maintain chromosomal stability.

  14. The Fate of a Normal Human Cell Traversed by a Single Charged Particle

    Science.gov (United States)

    Fournier, C.; Zahnreich, S.; Kraft, D.; Friedrich, T.; Voss, K.-O.; Durante, M.; Ritter, S.

    2012-01-01

    The long-term “fate” of normal human cells after single hits of charged particles is one of the oldest unsolved issues in radiation protection and cellular radiobiology. Using a high-precision heavy-ion microbeam we could target normal human fibroblasts with exactly one or five carbon ions and measured the early cytogenetic damage and the late behaviour using single-cell cloning. Around 70% of the first cycle cells presented visible aberrations in mFISH after a single ion traversal, and about 5% of the cells were still able to form colonies. In one third of selected high-proliferative colonies we observed clonal (radiation-induced) aberrations. Terminal differentiation and markers of senescence (PCNA, p16) in the descendants of cells traversed by one carbon ion occurred earlier than in controls, but no evidence of radiation-induced chromosomal instability was found. We conclude that cells surviving single-ion traversal, often carrying clonal chromosome aberrations, undergo accelerated senescence but maintain chromosomal stability. PMID:22966418

  15. Performance of amorphous NiNb-based alloys in a proton exchange membrane fuel cell (PEMFC)

    Energy Technology Data Exchange (ETDEWEB)

    Barranco, J.; Pierna, A.R. [Univ. of the Basque Country, San Sebastien (Spain). Dept. of Chemical Engineering and Environment

    2009-04-15

    A study was conducted to investigate the effectiveness of the spray technique of the different amorphous catalysts nickel niobate (NiNb){sub 9}9 platinum (Pt){sub 1}, and NiNb{sub 9}9 platinum (Pt) tin (Sn){sub 1}, obtained by means of the mechanical alloying, on the polymeric membrane. In particular, it examined the deposition of the catalysts on the proton exchange membrane, which is of significant importance for preparing an efficient membrane electrode assembling, which will be part of a hydrogen fuel cell. The effectiveness of spray was studied by determining the efficacy in hydrogen fuel cells. Different particle sizes were used in the catalytic ink. The deposition over the proton exchange membrane of the alloys was carried out using the airbrush technique, a process of painting the polymeric membrane which offers a homogeneous spread of the catalyst and carbon powders over the polymeric membrane. The paper described the experiment and results. The paper included a characterization of the catalysts and catalytic layers, and described the performance of the simple cells. It was concluded that both cells exhibit better behaviour when the hydrogen flow rate is low. 16 refs., 6 figs.

  16. Heat exchange studies on coconut oil cells as thermal energy storage for room thermal conditioning

    Science.gov (United States)

    Sutjahja, I. M.; Putri, Widya A.; Fahmi, Z.; Wonorahardjo, S.; Kurnia, D.

    2017-07-01

    As reported by many thermal environment experts, room air conditioning might be controlled by thermal mass system. In this paper we discuss the performance of coconut oil cells as room thermal energy storage. The heat exchange mechanism of coconut oil (CO) which is one of potential organic Phase Change Material (PCM) is studied based on the results of temperature measurements in the perimeter and core parts of cells. We found that the heat exchange performance, i.e. heat absorption and heat release processes of CO cells are dominated by heat conduction in the sensible solid from the higher temperature perimeter part to the lower temperature core part and heat convection during the solid-liquid phase transition and sensible liquid phase. The capability of heat absorption as measured by the reduction of air temperature is not influenced by CO cell size. Besides that, the application of CO as the thermal mass has to be accompanied by air circulation to get the cool sensation of the room’s occupants.

  17. H- and He-like Charge-Exchange Induced X-ray Emission due to Ion Collisions with H, He, and H2

    Science.gov (United States)

    Cumbee, Renata; Mullen, Patrick; Miller, Ansley; Lyons, David; Shelton, Robin L.; Schultz, David R.; Stancil, Phillip C.; Leutenegger, Maurice A.

    2017-08-01

    When a hot plasma collides with a cold neutral gas interactions occur between the microscopic constituents including charge exchange (CX). CX is a process in which an electron can be transferred from a neutral atom or molecule into an excited energy level of an ion. Following this transfer, the excited electron relaxes to lower energy levels, emitting X-rays. This process has been established as a primary source of X-ray emission within our solar system, such as when the solar wind interacts with cometary and planetary atmospheres, and outside of our solar system, such as in the hot outflows of starburst galaxies.Since the CX X-ray emission spectrum varies greatly with collision velocity, it is critical that realistic CX data are included in X-ray spectral models of astrophysical environments in which CX might be significant in order to correctly estimate the ion abundance and plasma velocities. Here, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for a variety of collision energies relevant to various astrophysical environments. Collisions of bare and H-like C, N, O, Ne, Mg, Al, Si, P, S, and Cl ions are shown with H, He, and H2 as the neutral collision targets. An X-ray model using line ratios for C-Si ions is then performed within XSPEC for a region of the Cygnus Loop supernova remnant for 8 collision energies in order to highlight the variation in CX spectral models with collision energy.R. Cumbee’s research was partially supported by an appointment to the NASA Postdoctoral Program at NASA GSFC, administered by Universities Space Research Association under contract with NASA. Work at UGA was partially supported by NASA grants NNX09AC46G and NNG09WF24I.

  18. Persistent oxidative stress in human neural stem cells exposed to low fluences of charged particles

    Directory of Open Access Journals (Sweden)

    Janet E. Baulch

    2015-08-01

    Full Text Available Exposure to the space radiation environment poses risks for a range of deleterious health effects due to the unique types of radiation encountered. Galactic cosmic rays are comprised of a spectrum of highly energetic nuclei that deposit densely ionizing tracks of damage along the particle trajectory. These tracks are distinct from those generated by the more sparsely ionizing terrestrial radiations, and define the geometric distribution of the complex cellular damage that results when charged particles traverse the tissues of the body. The exquisite radiosensitivity of multipotent neural stem and progenitor cells found within the neurogenic regions of the brain predispose the central nervous system to elevated risks for radiation induced sequelae. Here we show that human neural stem cells (hNSC exposed to different charged particles at space relevant fluences exhibit significant and persistent oxidative stress. Radiation induced oxidative stress was found to be most dependent on total dose rather than on the linear energy transfer of the incident particle. The use of redox sensitive fluorogenic dyes possessing relative specificity for hydroxyl radicals, peroxynitrite, nitric oxide (NO and mitochondrial superoxide confirmed that most irradiation paradigms elevated reactive oxygen and nitrogen species (ROS and RNS, respectively in hNSC over a 1 week interval following exposure. Nitric oxide synthase (NOS was not the major source of elevated nitric oxides, as the use of NOS inhibitors had little effect on NO dependent fluorescence. Our data provide extensive evidence for the capability of low doses of charged particles to elicit marked changes in the metabolic profile of irradiated hNSC. Radiation induced changes in redox state may render the brain more susceptible to the development of neurocognitive deficits that could affect an astronaut’s ability to perform complex tasks during extended missions in deep space.

  19. Interfacial charge separation and photovoltaic efficiency in Fe(ii)-carbene sensitized solar cells.

    Science.gov (United States)

    Pastore, Mariachiara; Duchanois, Thibaut; Liu, Li; Monari, Antonio; Assfeld, Xavier; Haacke, Stefan; Gros, Philippe C

    2016-10-12

    The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

  20. Elevated sister chromatid exchange phenotype of Bloom syndrome cells is complemented by human chromosome 15.

    Science.gov (United States)

    McDaniel, L D; Schultz, R A

    1992-09-01

    Bloom syndrome (BSx) is a rare autosomal-recessive chromosome-instability disorder manifested by a constellation of clinical features including a significant predisposition to early onset of neoplasia. BSx cells display cytogenetic abnormalities, the pathognomonic feature being an increased rate of spontaneous sister chromatid exchanges (SCEs), 10- to 15-fold more frequent than SCEs seen in control cells. Identification of the primary biochemical defect in BSx and its relationship to SCE frequency and neoplasia have been complicated by reports that BSx cell lines exhibit defects in the structure and/or activity of a number of different enzymes. The rare occurrence of the disorder and lack of informative families have precluded mapping of the primary defect by standard linkage analysis. We have utilized BSx cells as recipients for microcell-mediated chromosome transfer to map a locus that renders complementation of the elevated SCE phenotype. Studies with the BSx cell line GM08505 demonstrated a stable frequency of SCEs 10-fold higher than control values, offering a phenotype suitable for complementation studies. Transfer of different independent human chromosomes from somatic cell hybrids into BSx cells permitted identification of a single chromosome that dramatically reduced the SCE frequency to a level near that seen in control cells. Detailed characterization revealed this complementing element to be human chromosome 15.

  1. Characterization of the basic charge variants of a human IgG1: effect of copper concentration in cell culture media.

    Science.gov (United States)

    Kaschak, Timothy; Boyd, Daniel; Lu, Franklin; Derfus, Gayle; Kluck, Brian; Nogal, Bartek; Emery, Craig; Summers, Christie; Zheng, Kai; Bayer, Robert; Amanullah, Ashraf; Yan, Boxu

    2011-01-01

    We report a case study of an IgG1 with a unique basic charge variant profile caused by C-terminal proline amidation on either one or two heavy chains. The proline amidation was sensitive to copper ion concentration in the production media during cell culture: the higher the Cu ( 2+) ion concentration, the higher the level of proline amidation detected. This conclusion was supported by the analysis of samples that revealed direct correlation between the proline amidation level observed from peptide maps and the level of basic peaks measured by imaged capillary isoelectric focusing and a pH gradient ion-exchange chromatography method. The importance of these observations to therapeutic antibody production is discussed.

  2. Photochemical charges separation and photoelectric properties of flexible solar cells with two types of heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiangyang, E-mail: lxy081276@126.com, E-mail: yzgu@henu.edu.cn; Wang, Shun; Zheng, Haiwu; Cheng, Xiuying; Gu, Yuzong, E-mail: lxy081276@126.com, E-mail: yzgu@henu.edu.cn [Institute of Microsystems Physics and School of Physics and Electronics, Henan University, Kaifeng 475004 (China)

    2015-12-14

    Photochemical charges generation, separation, and transport at nanocrystal interfaces are central to energy conversion for solar cells. Here, Zn{sub 2}SnO{sub 4} nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} (ZTO/CBS), ZTO nanowires/CBS-reduced graphene oxide (ZTO/CBS-RGO), and bulk heterojunction (BHJ) solar cells were measured. The signals of steady state and electric field-induced surface photovoltage indicate that RGO with high electron mobility can evidently improve the photovoltaic response. Besides, ZTO/CBS and ZTO/CBS-RGO cells exhibit the excellent performance and the highest efficiencies of 1.2% and 2.8%, respectively. The internal relations of photoelectric properties to some factors, such as film thickness, direct paths, RGO conductive network, energy level matching, etc., were discussed in detail. Qualitative and quantitative analyses further verified the comprehensive effect of RGO and other factors. Importantly, the fine bendable characteristic of BHJ solar cells with excellent efficiency and facile, scalable production gives the as-made flexible solar cells device potential for practical application in future.

  3. Photochemical charges separation and photoelectric properties of flexible solar cells with two types of heterostructures

    Science.gov (United States)

    Liu, Xiangyang; Wang, Shun; Zheng, Haiwu; Cheng, Xiuying; Gu, Yuzong

    2015-12-01

    Photochemical charges generation, separation, and transport at nanocrystal interfaces are central to energy conversion for solar cells. Here, Zn2SnO4 nanowires/Cu4Bi4S9 (ZTO/CBS), ZTO nanowires/CBS-reduced graphene oxide (ZTO/CBS-RGO), and bulk heterojunction (BHJ) solar cells were measured. The signals of steady state and electric field-induced surface photovoltage indicate that RGO with high electron mobility can evidently improve the photovoltaic response. Besides, ZTO/CBS and ZTO/CBS-RGO cells exhibit the excellent performance and the highest efficiencies of 1.2% and 2.8%, respectively. The internal relations of photoelectric properties to some factors, such as film thickness, direct paths, RGO conductive network, energy level matching, etc., were discussed in detail. Qualitative and quantitative analyses further verified the comprehensive effect of RGO and other factors. Importantly, the fine bendable characteristic of BHJ solar cells with excellent efficiency and facile, scalable production gives the as-made flexible solar cells device potential for practical application in future.

  4. Preparation and properties of high performance nanocomposite proton exchange membrane for fuel cell

    Science.gov (United States)

    Lin, Yu-Feng; Yen, Chuan-Yu; Ma, Chen-Chi M.; Liao, Shu-Hang; Hung, Chih-Hung; Hsiao, Yi-Hsiu

    Various spatially enlarged organoclays were prepared by using poly(oxyproplene)-backboned quaternary ammonium salts of various molecular weights M w 230, 400 and 2000 as the intercalating agents for Na +-montmorillonite. The modified MMT was utilized to improve the compatibility with Nafion ®. Sufficient interaction of the modified MMT with Nafion ® was studied by using X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The performance of the Nafion ®/ m-MMT composite membranes for direct methanol fuel cell (DMFCs) was evaluated in terms of water uptake, ion exchange capacity (IEC), methanol permeability, proton conductivity, and cell performance. The methanol permeability of the composite membrane decreased with the increasing of m-MMT content. The proton conductivity of the membrane was lowered slightly from that of pristine Nafion ® membrane. These results led to an essential improvement in the single-cell performance of DMFCs.

  5. A Review of Metallic Bipolar Plates for Proton Exchange Membrane Fuel Cells: Materials and Fabrication Methods

    Directory of Open Access Journals (Sweden)

    Shahram Karimi

    2012-01-01

    Full Text Available The proton exchange membrane fuel cell offers an exceptional potential for a clean, efficient, and reliable power source. The bipolar plate is a key component in this device, as it connects each cell electrically, supplies reactant gases to both anode and cathode, and removes reaction products from the cell. Bipolar plates have been fabricated primarily from high-density graphite, but in recent years, much attention has been paid to developing cost-effective and feasible alternative materials. Two different classes of materials have attracted attention: metals and composites. This paper offers a comprehensive review of the current research being carried out on metallic bipolar plates, covering materials and fabrication methods.

  6. The direct formate fuel cell with an alkaline anion exchange membrane

    Science.gov (United States)

    Bartrom, Amy M.; Haan, John L.

    2012-09-01

    We demonstrate for the first time an operating Direct Formate Fuel Cell employing formate salts as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, and metal catalysts at the anode and cathode. Operation of the DFFC at 60 °C using 1 M KOOCH and 2 M KOH as the anode fuel and electrolyte and oxygen gas at the cathode produces 144 mW cm-2 of peak power density, 181 mA cm-2 current density at 0.6 V, and an open circuit voltage of 0.931 V. This performance is competitive with alkaline Direct Liquid Fuel Cells (DLFCs) previously reported in the literature and demonstrates that formate fuel is a legitimate contender with alcohol fuels for alkaline DLFCs. A survey of the literature shows that a formate-oxygen fuel cell has a high theoretical potential, and the safe, renewable formate fuel does not poison the anode catalyst.

  7. Performance of organic-inorganic hybrid anion-exchange membranes for alkaline direct methanol fuel cells

    Science.gov (United States)

    Xiong, Ying; Liu, Qing Lin; Zhu, Ai Mei; Huang, Si Meng; Zeng, Qing Hua

    A series of organic-inorganic membranes were prepared through sol-gel reaction of quaternized poly(vinyl alcohol) (QAPVA) with different contents of tetraethoxysilanes (TEOS) for alkaline direct methanol fuel cells. These hybrid membranes are characterized by FTIR, X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDXA) and thermo gravimetric analysis (TGA). The ion exchange content (IEC), water content, methanol permeability and conductivity of the hybrid membranes were measured to evaluate their applicability in fuel cells. It was found that the addition of silica enhanced the thermal stability and reduced the methanol permeability of the hybrid membranes. The hybrid membrane M-5, for which the silica content was 5 wt%, showed the lowest methanol permeability and the highest ion conductivity among the three hybrid membranes. The ratio of conductivity to methanol permeability of the membrane M-5 indicated that it had a high potential for alkaline direct methanol fuel cell applications.

  8. High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

    DEFF Research Database (Denmark)

    Li, Qingfeng; Jensen, Jens Oluf; Savinell, Robert F

    2009-01-01

    havebeenmadeincluding spectroscopy,wateruptake and acid doping, thermal and oxidative stability, conductivity, electro-osmoticwater drag, methanol crossover, solubility and permeability of gases, and oxygen reduction kinetics. Related fuel cell technologies such as electrode and MEA fabrication have been developed......To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid–base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has...... in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characterizations and fuel cell technologies. To optimize the membrane properties, high molecular weight polymers...

  9. The application of Dow Chemical's perfluorinated membranes in proton-exchange membrane fuel cells

    Science.gov (United States)

    Eisman, G. A.

    1989-01-01

    Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes useful as the proton transport medium and separator. Some of the performance characteristics which are typical for such membranes are outlined. The results of tests utilizing a new experimental membrane useful in proton-exchange membrane fuel cells are presented. The high voltage at low current densities can lead to higher system efficiencies while, at the same time, not sacrificing other critical properties pertinent to membrane fuel cell operation. A series of tests to determine response times indicated that on-off cycles are on the order of 80 milliseconds to reach 90 percent of full power. The IR free voltage at 100 amps/sq ft was determined and the results indicating a membrane/electrode package resistance to be .15 ohm-sq cm at 100 amps/sq ft.

  10. Durability Issues of High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    observed under continuous operation with hydrogen and air at 150-160oC, with a fuel cell performance degradation rate of 5-10 µV/h. Improvement of the membrane performance such as mechanical strength, swelling and oxidative stability has achieved by exploring the polymer chemistry, i.e. covalently......To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, phosphoric acid doped polybenzimidazole (PBI) membrane represents an effective approach, which in recent years has motivated extensive research activities with great progress....... As a critical concern, issues of long term durability of PBI based fuel cells are addressed in this talk, including oxidative degradation of the polymer, mechanical failures of the membrane, acid leaching out, corrosion of carbon support and sintering of catalysts particles. Excellent polymer durability has...

  11. Issues associated with modelling of proton exchange membrane fuel cell by computational fluid dynamics

    Science.gov (United States)

    Bednarek, Tomasz; Tsotridis, Georgios

    2017-03-01

    The objective of the current study is to highlight possible limitations and difficulties associated with Computational Fluid Dynamics in PEM single fuel cell modelling. It is shown that an appropriate convergence methodology should be applied for steady-state solutions, due to inherent numerical instabilities. A single channel fuel cell model has been taken as numerical example. Results are evaluated for quantitative as well qualitative points of view. The contribution to the polarization curve of the different fuel cell components such as bi-polar plates, gas diffusion layers, catalyst layers and membrane was investigated via their effects on the overpotentials. Furthermore, the potential losses corresponding to reaction kinetics, due to ohmic and mas transport limitations and the effect of the exchange current density and open circuit voltage, were also investigated. It is highlighted that the lack of reliable and robust input data is one of the issues for obtaining accurate results.

  12. Recovery of infective virus particles in ion-exchange and hydrophobic interaction monolith chromatography is influenced by particle charge and total-to-infective particle ratio.

    Science.gov (United States)

    Sviben, Dora; Forcic, Dubravko; Ivancic-Jelecki, Jelena; Halassy, Beata; Brgles, Marija

    2017-06-01

    Viral particles are used in medical applications as vaccines or gene therapy vectors. In order to obtain product of high purity, potency and safety for medical use purification of virus particles is a prerequisite, and chromatography is gaining increased attention to meet this aim. Here, we report on the use of ion-exchange and hydrophobic interaction chromatography on monolithic columns for purification of mumps virus (MuV) and measles virus (MeV). Efficiency of the process was monitored by quantification of infective virus particles (by 50% cell culture infective dose assay) and total virus particles, and monitoring of their size (by Nanoparticle Tracking Analysis). Ion-exchange chromatography was shown to be inefficient for MuV and best results for MeV were obtained on QA column with recovery around 17%. Purification of MuV and MeV by hydrophobic interaction chromatography resulted in recoveries around 60%. Results showed that columns with small channels (d=1.4μm) are not suitable for MuV and MeV, although their size is below 400nm, whereas columns with large channels (6μm) showed to be efficient and recoveries independent on the flow rate up to 10mL/min. Heterogeneity of the virus suspension and its interday variability mostly regarding total-to-infective particle ratio was observed. Interestingly, a trend in recovery depending on the day of the harvest was also observed for both viruses, and it correlated with the total-to-infective particle ratio, indicating influence of the virus sample composition on the chromatography results. Copyright © 2017. Published by Elsevier B.V.

  13. A small portable proton exchange membrane fuel cell and hydrogen generator for medical applications.

    Science.gov (United States)

    Adlhart, O J; Rohonyi, P; Modroukas, D; Driller, J

    1997-01-01

    Small, lightweight power sources for total artificial hearts (TAH), left ventricular assist devices (LVAD), and other medical products are under development. The new power source will provide 2 to 3 times the capacity of conventional batteries. The implications of this new power source are profound. For example, for the Heartmate LVAD, 5 to 8 hours of operation are obtained with 3 lb of lead acid batteries (Personal Communication Mr. Craig Sherman, Thermo Cardiosystems, Inc TCI 11/29/96). With the same weight, as much as 14 hours of operation appear achievable with the proton exchange membrane (PEM) fuel cell power source. Energy densities near 135 watt-hour/L are achievable. These values significantly exceed those of most conventional and advanced primary and secondary batteries. The improvement is mission dependent and even applies for the short deployment cited above. The comparison to batteries becomes even more favorable if the mission length is increased. The higher capacity requires only replacement of lightweight hydride cartridges and logistically available water. Therefore, when one spare 50 L hydride cartridge weighing 115 g is added to the reactant supply the energy density of the total system increases to 230 watt-hour/kg. This new power source is comprised of a hydrogen fueled, air-breathing PEM fuel cell and a miniature hydrogen generator (US Patent No 5,514,353). The fuel cell is of novel construction and differs from conventional bipolar PEM fuel cells by the arrangement of cells on a single sheet of ion-exchange membrane. The construction avoids the weight and volume penalty of conventional bipolar stacks. The hydrogen consumed by the fuel cell is generated load-responsively in the miniature hydrogen generator, by reacting calcium hydride with water, forming in the process hydrogen and lime. The generator is cartridge rechargeable and available in capacities providing up to several hundred watt-hours of electric power.

  14. Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes

    Science.gov (United States)

    Narayan, Sri R.; Yen, Shiao-Ping S.; Reddy, Prakash V.; Nair, Nanditha

    2012-01-01

    Polymer electrolyte membranes that conduct hydroxide ions have potential use in fuel cells. A variety of polystyrene-based quaternary ammonium hydroxides have been reported as anion exchange fuel cell membranes. However, the hydrolytic stability and conductivity of the commercially available membranes are not adequate to meet the requirements of fuel cell applications. When compared with commercially available membranes, polystyrene-imidazolium alkaline membrane electrolytes are more stable and more highly conducting. At the time of this reporting, this has been the first such usage for imidazolium-based polymeric materials for fuel cells. Imidazolium salts are known to be electrochemically stable over wide potential ranges. By controlling the relative ratio of imidazolium groups in polystyrene-imidazolium salts, their physiochemical properties could be modulated. Alkaline anion exchange membranes based on polystyrene-imidazolium hydroxide materials have been developed. The first step was to synthesize the poly(styrene-co-(1-((4-vinyl)methyl)-3- methylimidazolium) chloride through a free-radical polymerization. Casting of this material followed by in situ treatment of the membranes with sodium hydroxide solutions provided the corresponding hydroxide salts. Various ratios of the monomers 4-chloromoethylvinylbenzine (CMVB) and vinylbenzine (VB) provided various compositions of the polymer. The preferred material, due to the relative ease of casting the film, and its relatively low hygroscopic nature, was a 2:1 ratio of CMVB to VB. Testing confirmed that at room temperature, the new membranes outperformed commercially available membranes by a large margin. With fuel cells now in use at NASA and in transportation, and with defense potential, any improvement to fuel cell efficiency is a significant development.

  15. The study of flow and proton exchange interactions in the cylindrical solid oxide fuel cell

    CERN Document Server

    Saievar-Iranizad, E

    2002-01-01

    The solid oxide fuel cell operates at high temperature of about 1000 deg C. In this temperature, some known materials such as Ni, ... which is abundant in the nature, can be used as a catalyst in the electrodes. The electrolytes of such cell solid oxide fuel cell can be made through non-porous solid ceramics such as Zircon's (ZrO sub 2). It can be stabilized using a doped Yttrium oxide. The importance of Yttria-stabilised Zirconia at high temperature belongs to the transport of oxygen ions through the electrolyte. Oxygen using in the hot cathode side causes a considerable reduction in the concentration of oxygen molecules. The oxygen ions exchange through the electrolyte relates to the molecular oxygen concentration gradient between the anode and cathode. Applying fuels such as hydrogen or natural gas in the anode and its chemical reaction with oxygen ions transfer from cathode through the electrolyte, produce electricity, water and heat. To study the ion exchange and its interaction into solid oxide fuel cel...

  16. A self-sustained, complete and miniaturized methanol fuel processor for proton exchange membrane fuel cell

    Science.gov (United States)

    Yang, Mei; Jiao, Fengjun; Li, Shulian; Li, Hengqiang; Chen, Guangwen

    2015-08-01

    A self-sustained, complete and miniaturized methanol fuel processor has been developed based on modular integration and microreactor technology. The fuel processor is comprised of one methanol oxidative reformer, one methanol combustor and one two-stage CO preferential oxidation unit. Microchannel heat exchanger is employed to recover heat from hot stream, miniaturize system size and thus achieve high energy utilization efficiency. By optimized thermal management and proper operation parameter control, the fuel processor can start up in 10 min at room temperature without external heating. A self-sustained state is achieved with H2 production rate of 0.99 Nm3 h-1 and extremely low CO content below 25 ppm. This amount of H2 is sufficient to supply a 1 kWe proton exchange membrane fuel cell. The corresponding thermal efficiency of whole processor is higher than 86%. The size and weight of the assembled reactors integrated with microchannel heat exchangers are 1.4 L and 5.3 kg, respectively, demonstrating a very compact construction of the fuel processor.

  17. Proton Exchange Membrane fuel cell development with lightweight component materials, phase 1

    Science.gov (United States)

    Abens, Sandors

    1995-07-01

    Although the Proton Exchange Membrane (PEM) fuel cell is a leading candidate for an automobile power source through meeting the zero emission requirement, its power density is currently an order of magnitude below the 400 W/kg criterion proposed by the Department of Energy. The major contributors to stack weight are the bipolar gas distribution plates. This effort, performed jointly by Energy Research Corporation (ERC) and Texas A&M University (TAM U), focused on lightweight alternative bipolar plate materials and designs. The electronic conductivity of various candidate materials was evaluated. The emphasis was on conductive plastic materials and porous graphite. Several plastic materials with specific resistance between 0.5 and 0.8 ohm/cm were identified. Preliminary evaluation of lightweight materials was performed in single cell tests. The emphasis was on atmospheric pressure and internally humidified cell operation as a potential means of system simplification and reduction of PEM fuel cell ancillary equipment complexity and weight. The performance of single cells was nearly the same at 1 and 3 atm pressure. At a cell potential of O.6V, a current density of 230 mA/sq cm was reached at 1.7 stoichiometric air flow rate. With lightweight bipolar plates, the DOE power density target may be achieved with unpressurized, internally humidified cell stacks.

  18. Effect of lipophilic ions on the intramembrane charge movement and intracellular Ca2+ release in fetal mouse skeletal muscle cells.

    Science.gov (United States)

    Inoue, I; Shimahara, T; Bournaud, R

    1997-12-01

    The effects of lipophilic ions on the intramembrane charge movement and intracellular calcium transient were studied using freshly dissociated skeletal muscle cells from mice fetuses. The lipophilic cations Rhodamine 6G and tetraphenylphosphonium (TPP) immobilized part of the intramembrane charge movement in a dose-dependent manner, and inhibited both calcium transient and contraction evoked by membrane depolarization. In contrast, the lipophilic anion 1-anilinonaphthalene-8-sulfonic acid (ANS) had no effect on intramembrane charge movement. We suggest that the lipophilic cations block the voltage-sensing mechanism for the excitation-contraction (E-C) coupling mechanism.

  19. Recent Development of Pd-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Hui Meng

    2015-07-01

    Full Text Available This review selectively summarizes the latest developments in the Pd-based cataysts for low temperature proton exchange membrane fuel cells, especially in the application of formic acid oxidation, alcohol oxidation and oxygen reduction reaction. The advantages and shortcomings of the Pd-based catalysts for electrocatalysis are analyzed. The influence of the structure and morphology of the Pd materials on the performance of the Pd-based catalysts were described. Finally, the perspectives of future trends on Pd-based catalysts for different applications were considered.

  20. A Bayesian network fault diagnostic system for proton exchange membrane fuel cells

    Science.gov (United States)

    Riascos, Luis Alberto M.; Simoes, Marcelo G.; Miyagi, Paulo E.

    This paper considers the effects of different types of faults on a proton exchange membrane fuel cell model (PEMFC). Using databases (which record the fault effects) and probabilistic methods (such as the Bayesian-Score and Markov Chain Monte Carlo), a graphical-probabilistic structure for fault diagnosis is constructed. The graphical model defines the cause-effect relationship among the variables, and the probabilistic method captures the numerical dependence among these variables. Finally, the Bayesian network (i.e. the graphical-probabilistic structure) is used to execute the diagnosis of fault causes in the PEMFC model based on the effects observed.

  1. A Bayesian network fault diagnostic system for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Riascos, Luis Alberto M. [Federal University of ABC, r. Santa Adelia, 166, CEP 09210-170, Santo Andre, SP (Brazil); Simoes, Marcelo G. [Colorado School of Mines, 1500 Illinois Street, 80401, Golden, CO (United States); Miyagi, Paulo E. [Escola Politecnica, University of Sao Paulo, Av. Prof. Mello Moraes, 2231, CEP 05508-900, Sao Paulo (Brazil)

    2007-02-25

    This paper considers the effects of different types of faults on a proton exchange membrane fuel cell model (PEMFC). Using databases (which record the fault effects) and probabilistic methods (such as the Bayesian-Score and Markov Chain Monte Carlo), a graphical-probabilistic structure for fault diagnosis is constructed. The graphical model defines the cause-effect relationship among the variables, and the probabilistic method captures the numerical dependence among these variables. Finally, the Bayesian network (i.e. the graphical-probabilistic structure) is used to execute the diagnosis of fault causes in the PEMFC model based on the effects observed. (author)

  2. Understanding on Interface Contribution to the Electrode Performance of Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Grahl-Madsen, L.

    2016-01-01

    The commercialization of proton exchange membrane fuel cells (PEMFCs) is closer to the reality than ever before. Electrode interface development can bring a boost to the last few steps. Here, we explore electrode properties from its interface structure, especially the ionomer phase. Electrodes...... decreased with the increase of the ionomer. The electrode surface studies surprisingly reveal that the ionomer coverage increases linearly with the ionomer loading/content only up to a certain extent (around 30 wt.% in this case); further increase of the ionomer content triggers ionomer agglomeration, which...

  3. Model of Organic Solar Cell Photocurrent Including the Effect of Charge Accumulation at Interfaces and Non-Uniform Carrier Generation

    DEFF Research Database (Denmark)

    Torto, Lorenzo; Cester, Andrea; Rizzo, Antonio

    2017-01-01

    We developed an improved model to fit the photocurrent density versus voltage in organic solar cells. The model has been validated by fitting data from P3HT:PCBM solar cells. Our model quantitatively accounts for the band bending near the electrodes caused by charge accumulation in the active layer...

  4. Characterization of Tunneling Nanotubes in Wharton's jelly Mesenchymal Stem Cells. An Intercellular Exchange of Components between Neighboring Cells.

    Science.gov (United States)

    Sanchez, Viviana; Villalba, Nerina; Fiore, Luciano; Luzzani, Carlos; Miriuka, Santiago; Boveris, Alberto; Gelpi, Ricardo J; Brusco, Alicia; Poderoso, Juan José

    2017-08-01

    Intercellular communication is one of the most important events in cell population behavior. In the last decade, tunneling nanotubes (TNTs) have been recognized as a new form of long distance intercellular connection. TNT function is to allow molecular and subcellular structure exchange between neighboring cells via the transfer of molecules and organelles such as calcium ions, prions, viral and bacterial pathogens, small lysosomes and mitochondria. New findings support the concept that mesenchymal stem cells (MSCs) can affect cell microenvironment by the release of soluble factors or the transfer of cellular components to neighboring cells, in a way which significantly contributes to cell regulation and tissue repair, although the underlying mechanisms remain poorly understood. MSCs have many advantages for their implementation in regenerative medicine. The TNTs in these cell types are heterogeneous in both structure and function, probably due to their highly dynamic behavior. In this work we report an extensive and detailed description of types, structure, components, dynamics and functionality of the TNTs bridging neighboring human umbilical cord MSCs obtained from Wharton"s jelly. Characterization studies were carried out through phase contrast, fluorescence, electron microscopy and time lapse images with the aim of describing cells suitable for an eventual regenerative medicine.

  5. Parallel Control over Surface Charge and Wettability Using Polyelectrolyte Architecture: Effect on Protein Adsorption and Cell Adhesion.

    Science.gov (United States)

    Guo, Shanshan; Zhu, Xiaoying; Li, Min; Shi, Liya; Ong, June Lay Ting; Jańczewski, Dominik; Neoh, Koon Gee

    2016-11-09

    Surface charge and wettability, the two prominent physical factors governing protein adsorption and cell adhesion, have been extensively investigated in the literature. However, a comparison between these driving forces in terms of their independent and cooperative effects in affecting adhesion is rarely explored on a systematic and quantitative level. Herein, we formulate a protocol that features two-dimensional control over both surface charge and wettability with limited cross-parameter influence. This strategy is implemented by controlling both the polyion charge density in the layer-by-layer (LbL) assembly process and the polyion side-chain chemical structures. The 2D property matrix spans surface isoelectric points ranging from 5 to 9 and water contact angles from 35 to 70°, with other interferential factors (e.g., roughness) eliminated. The interplay between these two surface variables influences protein (bovine serum albumin, lysozyme) adsorption and 3T3 fibroblast cell adhesion. For proteins, we observe the presence of thresholds for surface wettability and electrostatic driving forces necessary to affect adhesion. Beyond these thresholds, the individual effects of electrostatic forces and wettability are observed. For fibroblast, both surface charge and wettability have an effect on its adhesion. The combined effects of positive charge and hydrophilicity lead to the highest cell adhesion, whereas negative charge and hydrophobicity lead to the lowest cell adhesion. Our design strategy can potentially form the basis for studying the distinct behaviors of electrostatic force or wettability driven interfacial phenomena and serve as a reference in future studies assessing protein adsorption and cell adhesion to surfaces with known charge and wettability within the property range studied here.

  6. Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?

    Science.gov (United States)

    Sljukić, Biljana; Morais, Ana L; Santos, Diogo M F; Sequeira, César A C

    2012-07-19

    Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH4) as the fuel, and hydrogen peroxide (H2O2) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH4/H2O2 fuel cells using Pt electrodes is studied at room temperature. Two commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC's performance. Cell polarization, power density, stability, and durability tests are used in the membranes' evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load.

  7. Bromodeoxyuridine does not contribute to sister chromatid exchange events in normal or Bloom syndrome cells.

    Science.gov (United States)

    van Wietmarschen, Niek; Lansdorp, Peter M

    2016-08-19

    Sister chromatid exchanges (SCEs) are considered sensitive indicators of genome instability. Detection of SCEs typically requires cells to incorporate bromodeoxyuridine (BrdU) during two rounds of DNA synthesis. Previous studies have suggested that SCEs are induced by DNA replication over BrdU-substituted DNA and that BrdU incorporation alone could be responsible for the high number of SCE events observed in cells from patients with Bloom syndrome (BS), a rare genetic disorder characterized by marked genome instability and high SCE frequency. Here we show using Strand-seq, a single cell DNA template strand sequencing technique, that the presence of variable BrdU concentrations in the cell culture medium and in DNA template strands has no effect on SCE frequency in either normal or BS cells. We conclude that BrdU does not induce SCEs and that SCEs detected in either normal or BS cells reflect DNA repair events that occur spontaneously. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  8. Polarity governed selective amplification of through plane proton shuttling in proton exchange membrane fuel cells.

    Science.gov (United States)

    Gautam, Manu; Chattanahalli Devendrachari, Mruthyunjayachari; Thimmappa, Ravikumar; Raja Kottaichamy, Alagar; Pottachola Shafi, Shahid; Gaikwad, Pramod; Makri Nimbegondi Kotresh, Harish; Ottakam Thotiyl, Musthafa

    2017-03-15

    Graphene oxide (GO) anisotropically conducts protons with directional dominance of in plane ionic transport (σ IP) over the through plane (σ TP). In a typical H 2 -O 2 fuel cell, since the proton conduction occurs through the plane during its generation at the fuel electrode, it is indeed inevitable to selectively accelerate GO's σ TP for advancement towards a potential fuel cell membrane. We successfully achieved ∼7 times selective amplification of GO's σ TP by tuning the polarity of the dopant molecule in its nanoporous matrix. The coexistence of strongly non-polar and polar domains in the dopant demonstrated a synergistic effect towards σ TP with the former decreasing the number of water molecules coordinated to protons by ∼3 times, diminishing the effects of electroosmotic drag exerted on ionic movements, and the latter selectively accelerating σ TP across the catalytic layers by bridging the individual GO planes via extensive host guest H-bonding interactions. When they are decoupled, the dopant with mainly non-polar or polar features only marginally enhances the σ TP, revealing that polarity factors contribute to fuel cell relevant transport properties of GO membranes only when they coexist. Fuel cell polarization and kinetic analyses revealed that these multitask dopants increased the fuel cell performance metrics of the power and current densities by ∼3 times compared to the pure GO membranes, suggesting that the functional group factors of the dopants are of utmost importance in GO-based proton exchange membrane fuel cells.

  9. Development of large aperture projection scatterometry for catalyst loading evaluation in proton exchange membrane fuel cells

    Science.gov (United States)

    Stocker, Michael T.; Barnes, Bryan M.; Sohn, Martin; Stanfield, Eric; Silver, Richard M.

    2017-10-01

    Widespread commercialization of proton exchange membrane fuel cells remains curbed by various manufacturing and infrastructure challenges. One such technical barrier identified by the U. S. Department of Energy is the need for high-speed, in-line process control of platinum-based catalyst layers in the membrane electrode assembly of the fuel cell. Using multiple reflectivity-based optical methods, such as optical scatterometry and large aperture projection scatterometry, we demonstrate in-line-capable catalyst loading measurements of carbon-supported Pt nanoparticle and Pt-alloy nanostructured thin film catalyst coated membranes. Large aperture projection scatterometry is a new high-throughput approach developed at the National Institute of Standards and Technology specifically for fuel cell manufacturing metrology. Angle- and wavelength-resolved measurements of these fuel cell soft goods validate the ability of reflectivity-based measurements to produce industrially relevant sensitivities to changes in Pt and Pt-alloy loading. The successful application of these optical methods to fuel cell manufacturing metrology directly addresses the shortage of high-throughput process control approaches needed to facilitate performance improvements and manufacturing cost-reductions required to make fuel cells commercially viable.

  10. Study of spin-exchange optically pumped 3He cells with high polarisation and long lifetimes

    Science.gov (United States)

    Parnell, S. R.; Babcock, E.; Nünighoff, K.; Skoda, M. W. A.; Boag, S.; Masalovich, S.; Chen, W. C.; Georgii, R.; Wild, J. M.; Frost, C. D.

    2009-01-01

    We present a detailed investigation into 3He neutron spin filter cells polarised by spin exchange optical pumping (SEOP). We include measurements of the absolute 3He polarisation using neutron transmission and characterisation of both the X-factor and 3He relaxation times ( T1) for a number of cells. For one cell we calculated a maximum 3He polarisation of 79% with a T1 of 633 h. The measured X-factor of this cell, X=0.17±0.01, is low. For all cells polarisations of >71% are observed. In addition we present 3He relaxation data for a new design of magneto-static cavity with a field of high homogeneity ΔB/B0≈3.5×10-4 cm-1. This compact device provides a magnetic field in an orientation suitable for in situ optical pumping that minimises the field inhomogeneity contribution to the T1 to 930 h in a 1 bar cell, the longest reported on beam thus far. The results suggest that high 3He polarisation with long relaxation times can now be routinely obtained with SEOP, enabling time independent incident beam polarisation to be easily implemented across many different neutron scattering instruments.

  11. Culture temperature modulates monoclonal antibody charge variation distribution in Chinese hamster ovary cell cultures.

    Science.gov (United States)

    Zhang, Xintao; Sun, Ya-Ting; Tang, Hongping; Fan, Li; Hu, Dongdong; Liu, Jintao; Liu, Xuping; Tan, Wen-Song

    2015-11-01

    To investigate the effect of lowering culture temperature on monoclonal antibody charge variation distribution in Chinese hamster ovary cell cultures. In both batch and fed-batch cultures, lowering the culture temperature decreased the antibody acidic variant levels. The acidic variant levels (defined as variants eluting earlier than the main peak of an antibody during HPLC) at 32 °C were about 10 % lower than those at 37 °C at the end of both batch and fed-batch cultures. Additionally, lowering the culture temperature increased the lysine variant level, which further increased basic variant level. The lysine variant levels at 32 °C were about 8 % (batch culture) and 3 % (fed-batch culture) higher than those at 37 °C at the end of cultures. Real-time PCR results suggests that the decrease in carboxypeptidase B transcription level might be partially responsible for the increased lysine variant level at sub-physiological temperatures. Culture temperature exhibits noticeable impact on antibody charge variation distribution, especially the acidic variants and lysine variants.

  12. Comparison of dust charging between Orbital-Motion-Limited theory and Particle-In-Cell simulations

    CERN Document Server

    Delzanno, Gian Luca

    2016-01-01

    The Orbital-Motion-Limited (OML) theory has been modified to predict the dust charge and the results were contrasted with the Whipple approximation [Tang and Delzanno, Phys. Plasmas 21, 123708 (2014)]. To further establish its regime of applicability, in this paper the OML predictions (for a non-electron-emitting, spherical dust grain at rest in a collisionless, unmagnetized plasma) are compared with Particle-In-Cell simulations that retain the absorption radius effect. It is found that for large dust grain radius $r_d$ relative to the plasma Debye length $\\lambda_D$, the revised OML theory remains a very good approximation as, for the parameters considered ($r_d/\\lambda_D\\le10$, equal electron and ion temperatures), it yields the dust charge to within $20\\%$ accuracy. This is a substantial improvement over the Whipple approximation. The dust collected currents and energy fluxes, which remain the same in the revised and standard OML theories, are accurate to within $15-30\\%$.

  13. Development and characterization of direct ethanol fuel cells using alkaline anion-exchange membranes

    Science.gov (United States)

    Lim, Peck Cheng

    2009-08-01

    Alkaline membrane fuel cell (AMFC) is a relatively new fuel cell technology that is generating considerable interests. It offers the electrocatalytic advantages of conventional alkaline fuel cells, and the manufacturing and cost advantages of solid polymer electrolyte fuel cells. This project was carried out to develop and characterize high performance membrane electrode assemblies (MEAs) for all-solid-state AMFCs. The primary fuel of interests is ethanol, but hydrogen was used in the development stages to facilitate the diagnostic and evaluation of the fuel cell performance. In the preliminary investigation, AMFC was assembled using off-the-shelf electrodes and anion-exchange membrane (AEM). It was found that the performance of AMFC operating on ethanol fuel was limited by a large high-frequency resistance (HFR) value. The advantage of using non-toxic ethanol fuel was also compromised by the need to add hydrazine and potassium hydroxide to the fuel blend. Subsequently, a high performance MEA was developed for an all-solid-state AMFC, in which liquid electrolyte or other additives were not required during the operation of the fuel cell. Ionomer was incorporated in the formulation of catalyst ink, and the catalyst ink was directly coated on the anion-exchange membrane (AEM). An ionomer content of 20 wt.% was found to be the optimum amount required in the catalyst layers. It was demonstrated that the AMFC generated a maximum power density of 365 mW/cm2 and 213 mW/cm 2 with the use of hydrogen/oxygen and hydrogen/pure air, respectively. The performance of the AMFC was also found to be influenced by exposure to carbon dioxide in the air. Hence, the CCMs were pre-treated in potassium hydroxide solution and pure oxygen was used to condition the fuel cell to maximize the power output from the AMFCs. Although satisfactory performance was demonstrated in the AMFC, its stability during cell operation remains a major issue. The poor stability was attributed to degradation of

  14. Hydroquinone based sulfonated poly (arylene ether sulfone copolymer as proton exchange membrane for fuel cell applications

    Directory of Open Access Journals (Sweden)

    V. Kiran

    2015-12-01

    Full Text Available Synthesis of sulfonated poly (arylene ether sulfone copolymer by direct copolymerization of 4,4'-bis(4-hydroxyphenyl valeric acid, benzene 1,4-diol and synthesized sulfonated 4,4'-difluorodiphenylsulfone and its characterization by using FTIR (Fourier Transform Infrared and NMR (Nuclear Magnetic Resonance spectroscopic techniques have been performed. The copolymer was subsequently cross-linked with 4, 4!(hexafluoroisopropylidenediphenol epoxy resin by thermal curing reaction to synthesize crosslinked membranes. The evaluation of properties showed reduction in water and methanol uptake, ion exchange capacity, proton conductivity with simultaneous enhancement in oxidative stability of the crosslinked membranes as compared to pristine membrane. The performance of the membranes has also been evaluated in terms of thermal stability, morphology, mechanical strength and methanol permeability by using Thermo gravimetric analyzer, Differential scanning calorimetery, Atomic force microscopy, XPERT-PRO diffractometer, universal testing machine and diffusion cell, respectively. The results demonstrated that the crosslinked membranes exhibited high thermal stability with phase separation, restrained crystallinity, acceptable mechanical properties and methanol permeability. Therefore, these can serve as promising proton exchange membranes for fuel cell applications.

  15. Novel fluoropolymer anion exchange membranes for alkaline direct methanol fuel cells.

    Science.gov (United States)

    Zhang, Yanmei; Fang, Jun; Wu, Yongbin; Xu, Hankun; Chi, Xianjun; Li, Wei; Yang, Yixu; Yan, Ge; Zhuang, Yongze

    2012-09-01

    A series of novel fluoropolymer anion exchange membranes based on the copolymer of vinylbenzyl chloride, butyl methacrylate, and hexafluorobutyl methacrylate has been prepared. Fourier transform infrared (FT-IR) spectroscopy and elemental analysis techniques are used to study the chemical structure and chemical composition of the membranes. The water uptake, ion-exchange capacity (IEC), conductivity, methanol permeability, and chemical stability of the membranes are also determined. The membranes exhibit high anionic conductivity in deionized water at 65 °C ranging from 3.86×10(-2) S cm(-1) to 4.36×10(-2) S cm(-1). The methanol permeability coefficients of the membranes are in the range of 4.21-5.80×10(-8) cm(2) s(-1) at 65 °C. The novel membranes also show good chemical and thermal stability. An open-circuit voltage of 0.7 V and a maximum power density of 53.2 mW cm(-2) of alkaline direct methanol fuel cell (ADMFC) with the membrane C, 1 M methanol, 1 M NaOH, and humidified oxygen are achieved at 65 °C. Therefore, these membranes have great potential for applications in fuel cell systems. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Ion transport resistance in Microbial Electrolysis Cells with anion and cation exchange membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sleutels, Tom H.J.A.; Buisman, Cees J.N. [Sub-Department of Environmental Technology, Wageningen University, Bomenweg 2, P.O. Box 8129, 6700 EV Wageningen (Netherlands); Wetsus, Centre of Excellence for Sustainable Water Technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden (Netherlands); Hamelers, Hubertus V.M. [Sub-Department of Environmental Technology, Wageningen University, Bomenweg 2, P.O. Box 8129, 6700 EV Wageningen (Netherlands); Rozendal, Rene A. [Advanced Water Management Centre (AWMC), The University of Queensland, Qld 4072 (Australia)

    2009-05-15

    Previous studies have shown that Microbial Electrolysis Cells (MECs) perform better when an anion exchange membrane (AEM) than when a cation exchange membrane (CEM) separates the electrode chambers. Here, we have further studied this phenomenon by comparing two analysis methods for bio-electrochemical systems, based on potential losses and partial system resistances. Our study reconfirmed the large difference in performance between the AEM configuration (2.1 m{sup 3} H{sub 2} m{sup -3} d{sup -1}) and CEM configuration (0.4 m{sup 3} H{sub 2} m{sup -3} d{sup -1}) at 1 V. This better performance was caused mainly by the much lower internal resistance of the AEM configuration (192 m{omega} m{sup 2}) compared to the CEM configuration (435 m{omega} m{sup 2}). This lower internal resistance could be attributed to the lower transport resistance of ions through the AEM compared to the CEM caused by the properties of both membranes. By analyzing the changes in resistances the limitations in an MEC can be identified which can lead to improved cell design and higher hydrogen production rates. (author)

  17. Graphene-supported platinum catalyst prepared with ionomer as surfactant for anion exchange membrane fuel cells

    Science.gov (United States)

    Zeng, L.; Zhao, T. S.; An, L.; Zhao, G.; Yan, X. H.; Jung, C. Y.

    2015-02-01

    In this work, we have synthesized an ionomer-coated graphene-supported platinum catalyst for anion exchange membrane fuel cells. Unlike the common surfactant stabilized colloidal method, we employ a home-made anion exchange ionomer (AEI), namely quaternary ammonia poly (2, 6-dimethyl-1, 4-phenylene oxide) (QAPPO), as the surfactant. The AEI coated on reduced graphene oxide (rGO) surfaces serves as a stabilizer to anchor the platinum precursor on rGO surfaces due to electrostatic interactions. As a result, platinum nanoparticles (Pt NPs) can be easily deposited onto rGO surfaces with a uniform distribution. The remarkable feature of the present synthesis method is that the surfactant, the coated AEI, does not need to be removed from the catalyst, but serves as hydroxide-conductive paths in the catalyst layer, leading to enhanced triple phase boundaries. It is demonstrated that the use of the catalyst obtained with the present method enables a H2/O2 AEMFC to yield a peak power density of 264.8 mW cm-2 at 60 °C, which is 30% higher than that produced from the same fuel cell but with the use of the catalyst synthesized by the conventional synthesis method.

  18. Transport in Proton Exchange Membranes for Fuel Cell Applications-A Systematic Non-Equilibrium Approach.

    Science.gov (United States)

    Rangel-Cárdenas, Angie L; Koper, Ger J M

    2017-05-25

    We hypothesize that the properties of proton-exchange membranes for fuel cell applications cannot be described unambiguously unless interface effects are taken into account. In order to prove this, we first develop a thermodynamically consistent description of the transport properties in the membranes, both for a homogeneous membrane and for a homogeneous membrane with two surface layers in contact with the electrodes or holder material. For each subsystem, homogeneous membrane, and the two surface layers, we limit ourselves to four parameters as the system as a whole is considered to be isothermal. We subsequently analyze the experimental results on some standard membranes that have appeared in the literature and analyze these using the two different descriptions. This analysis yields relatively well-defined values for the homogeneous membrane parameters and estimates for those of the surface layers and hence supports our hypothesis. As demonstrated, the method used here allows for a critical evaluation of the literature values. Moreover, it allows optimization of stacked transport systems such as proton-exchange membrane fuel cell units where interfacial layers, such as that between the catalyst and membrane, are taken into account systematically.

  19. Transport in Proton Exchange Membranes for Fuel Cell Applications—A Systematic Non-Equilibrium Approach

    Directory of Open Access Journals (Sweden)

    Angie L. Rangel-Cárdenas

    2017-05-01

    Full Text Available We hypothesize that the properties of proton-exchange membranes for fuel cell applications cannot be described unambiguously unless interface effects are taken into account. In order to prove this, we first develop a thermodynamically consistent description of the transport properties in the membranes, both for a homogeneous membrane and for a homogeneous membrane with two surface layers in contact with the electrodes or holder material. For each subsystem, homogeneous membrane, and the two surface layers, we limit ourselves to four parameters as the system as a whole is considered to be isothermal. We subsequently analyze the experimental results on some standard membranes that have appeared in the literature and analyze these using the two different descriptions. This analysis yields relatively well-defined values for the homogeneous membrane parameters and estimates for those of the surface layers and hence supports our hypothesis. As demonstrated, the method used here allows for a critical evaluation of the literature values. Moreover, it allows optimization of stacked transport systems such as proton-exchange membrane fuel cell units where interfacial layers, such as that between the catalyst and membrane, are taken into account systematically.

  20. Analytical Investigation and Improvement of Performance of a Proton Exchange Membrane (Pem) Fuel Cell in Mobile Applications

    OpenAIRE

    Khazaee I.

    2015-01-01

    In this study, the performance of a proton exchange membrane fuel cell in mobile applications is investigated analytically. At present the main use and advantages of fuel cells impact particularly strongly on mobile applications such as vehicles, mobile computers and mobile telephones. Some external parameters such as the cell temperature (Tcell ) , operating pressure of gases (P) and air stoichiometry (λair ) affect the performance and voltage losses in the PEM fuel cell. Because of the exis...

  1. Metal oxide nanoparticles synthesized by pulsed laser ablation for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Dorcioman, G.; Serban, N.; Axente, E.; Sima, F.; Ristoscu, C.; Mihailescu, I.N. [Lasers Department, National Institute for Lasers, Plasma and Radiations Physics, 409 Atomistilor Street, PO Box MG-54, RO-77125, Magurele, Ilfov (Romania); Ebrasu, D. [National Research and Development Institute for Cryogenics and Isotopic Technologies - ICSI Rm. Valcea, RO-240050 (Romania); Enculescu, I. [National Institute of Materials Physics, 105 Bis Atomistilor Street, RO-77125, Magurele, Ilfov (Romania)

    2010-12-01

    We report on the development of a modified gas diffusion layer for fuel cells consisting of a simple or teflonized carbon cloth pulsed laser deposited with metal oxide nanostructures designed to operate both as co-catalyst, and oxidic support for other electrochemically active catalysts. We selected TiO{sub 2}, ZnO and Al{sub 2}O{sub 3} doped (2 wt.%) ZnO which were uniformly distributed over the surface of gas diffusion layers in order to improve the catalytic activity, stability and lifetime, and reduce the production costs of proton exchange membrane fuel cells. We evidenced by scanning electron microscopy and energy dispersive spectroscopy that our depositions consisted of TiO{sub 2} nanoparticles while in the case of ZnO and Al{sub 2}O{sub 3} doped (2 wt.%) ZnO transparent quasi-continuous films were synthesized. (author)

  2. Electrocatalysts and their Supporting Materials for Proton Exchange Membrane Fuel Cells: Activity and Durability Studies

    DEFF Research Database (Denmark)

    Permyakova, Anastasia Aleksandrovna

    This thesis describes investigations conducted exploring the activity, stability and durability of supported nano-particulate, bulk and thin film electrocatalysts used in proton exchange membrane fuel cells (PEMFCs). The effects of different factors and conditions on the reactions involved...... in oxygen reduction, carbon monoxide and methanol electro-oxidation reactions were explored. Employed catalysts were characterized electrochemically and physiochemically using techniques such as: cyclic voltammetry, rotating disk electrode technique, SEM, TEM, EDS, XPS, TGA/DTA, Raman, XRD, FTIR-IR among...... other methods. The thesis begins with an introduction in Chapter 1 providing an overview of fuel cells, their associated reaction mechanisms, catalysts and catalysts supports. Chapter 2 presents the theoretical background to the study including equipment and the techniques used to analyse the catalysts...

  3. High surface area graphite as alternative support for proton exchange membrane fuel cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira-Aparicio, P.; Folgado, M.A. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense 22, E-28040 Madrid (Spain); Daza, L. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense 22, E-28040 Madrid (Spain); Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie, 2 Campus de Cantoblanco, E-28049 Madrid (Spain)

    2009-07-01

    The suitability of a high surface area graphite (HSAG) as proton exchange membrane fuel cell (PEMFC) catalyst support has been evaluated and compared with that of the most popular carbon black: the Vulcan XC72. It has been observed that Pt is arranged on the graphite surface resulting in different structures which depend on the catalysts synthesis conditions. The influence that the metal particle size and the metal-support interaction exert on the catalysts degradation rate is analyzed. Temperature programmed oxidation (TPO) under oxygen containing streams has been shown to be a useful method to assess the resistance of PEMFC catalysts to carbon corrosion. The synthesized Pt/HSAG catalysts have been evaluated in single cell tests in the cathode catalytic layer. The obtained results show that HSAG can be a promising alternative to the traditionally used Vulcan XC72 carbon black when suitable catalysts synthesis conditions are used. (author)

  4. An Equivalent Electrical Circuit Model of Proton Exchange Membrane Fuel Cells Based on Mathematical Modelling

    Directory of Open Access Journals (Sweden)

    Dinh An Nguyen

    2012-07-01

    Full Text Available Many of the Proton Exchange Membrane Fuel Cell (PEMFC models proposed in the literature consist of mathematical equations. However, they are not adequately practical for simulating power systems. The proposed model takes into account phenomena such as activation polarization, ohmic polarization, double layer capacitance and mass transport effects present in a PEM fuel cell. Using electrical analogies and a mathematical modeling of PEMFC, the circuit model is established. To evaluate the effectiveness of the circuit model, its static and dynamic performances under load step changes are simulated and compared to the numerical results obtained by solving the mathematical model. Finally, the applicability of our model is demonstrated by simulating a practical system.

  5. Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    Cleemann, Lars Nilausen; Buazar, F.; Li, Qingfeng

    2013-01-01

    contribution of the membrane degradation to the performance losses during the potential cycling tests. As the major mechanism of the fuel cell performance degradation, the electrochemical active area of the cathodic catalysts showed a steady decrease in the cyclic voltammetric measurements, which was also...... and multi‐walled carbon nanotubes were used as supports for electrode catalysts and evaluated in accelerated durability tests under potential cycling at 150 °C. Measurements of open circuit voltage, area specific resistance and hydrogen permeation through the membrane were carried out, indicating little......Degradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black...

  6. Phosphoric acid doped imidazolium polysulfone membranes for high temperature proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Li, Qingfeng; Jensen, Jens Oluf

    2012-01-01

    A novel acid–base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i...... group is achieved in 85wt% H3PO4 at room temperature. The membranes exhibit a proton conductivity of 0.015–0.022Scm−1 at 130–150°C under 15mol% water vapor in air, and a tensile strength of 5–6MPa at 130°C under ambient humidity. Fuel cell tests show an open circuit voltage as high as 0.96V and a peak...

  7. Fatigue Analysis of Proton Exchange Membrane Fuel Cell Stacks Based on Structural Stress Distribution

    Science.gov (United States)

    Wu, C. W.; Liu, B.; Wei, M. Y.; Liu, L. F.

    2017-05-01

    Proton exchange membrane fuel cell (PEMFC) stack usually undergoes various vibrations during packing, transportation and serving time, in particular for those used in the automobiles and portable equipment. Based on the Miner fatigue damage theory, the fatigue lives of the fuel cell components are first assessed. Then the component fatigue life contours of the stack are obtained under four working conditions, i.e. the three single-axial (in X-, Y- and Z-axis separately) and multi-axial random vibrations. Accordingly, the component damage under various vibrations is evaluated. The stress distribution on the gasket and PEM will greatly affect their fatigue lives. Finally, we compare the fatigue lives of 4-bolt- and 6-bolt-clamping stacks under the same total clamping force, and find that increasing the bolt number could improve the bolt fatigue lives.

  8. Internal transmission coefficient in charges carrier generation layer of graphene/Si based solar cell device

    Energy Technology Data Exchange (ETDEWEB)

    Rosikhin, Ahmad, E-mail: a.rosikhin86@yahoo.co.id; Winata, Toto, E-mail: toto@fi.itb.ac.id [Department of physics, physics of electronic materials research division Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung Jl. Ganesha 10, Bandung 40132, Jawa Barat – Indonesia (Indonesia)

    2016-04-19

    Internal transmission profile in charges carrier generation layer of graphene/Si based solar cell has been explored theoretically. Photovoltaic device was constructed from graphene/Si heterojunction forming a multilayer stuck with Si as generation layer. The graphene/Si sheet was layered on ITO/glass wafer then coated by Al forming Ohmic contact with Si. Photon incident propagate from glass substrate to metal electrode and assumed that there is no transmission in Al layer. The wavelength range spectra used in this calculation was 200 – 1000 nm. It found that transmission intensity in the generation layer show non-linear behavior and partitioned by few areas which related with excitation process. According to this information, it may to optimize the photons absorption to create more excitation process by inserting appropriate material to enhance optical properties in certain wavelength spectra because of the exciton generation is strongly influenced by photon absorption.

  9. Correlation between the Open-Circuit Voltage and Charge Transfer State Energy in Organic Photovoltaic Cells.

    Science.gov (United States)

    Zou, Yunlong; Holmes, Russell J

    2015-08-26

    In order to further improve the performance of organic photovoltaic cells (OPVs), it is essential to better understand the factors that limit the open-circuit voltage (VOC). Previous work has sought to correlate the value of VOC in donor-acceptor (D-A) OPVs to the interface energy level offset (EDA). In this work, measurements of electroluminescence are used to extract the charge transfer (CT) state energy for multiple small molecule D-A pairings. The CT state as measured from electroluminescence is found to show better correlation to the maximum VOC than EDA. The difference between EDA and the CT state energy is attributed to the Coulombic binding energy of the CT state. This correlation is demonstrated explicitly by inserting an insulating spacer layer between the donor and acceptor materials, reducing the binding energy of the CT state and increasing the measured VOC. These results demonstrate a direct correlation between maximum VOC and CT state energy.

  10. Effects of High Temperature and Thermal Cycling on the Performance of Perovskite Solar Cells: Acceleration of Charge Recombination and Deterioration of Charge Extraction.

    Science.gov (United States)

    Sheikh, Arif D; Munir, Rahim; Haque, Md Azimul; Bera, Ashok; Hu, Weijin; Shaikh, Parvez; Amassian, Aram; Wu, Tom

    2017-10-11

    In this work, we investigated the effects of high operating temperature and thermal cycling on the photovoltaic (PV) performance of perovskite solar cells (PSCs) with a typical mesostructured (m)-TiO2-CH3NH3PbI3-xClx-spiro-OMeTAD architecture. After temperature-dependent grazing-incidence wide-angle X-ray scattering, in situ X-ray diffraction, and optical absorption experiments were carried out, the thermal durability of PSCs was tested by subjecting the devices to repetitive heating to 70 °C and cooling to room temperature (20 °C). An unexpected regenerative effect was observed after the first thermal cycle; the average power conversion efficiency (PCE) increased by approximately 10% in reference to the as-prepared device. This increase of PCE was attributed to the heating-induced improvement of the crystallinity and p doping in the hole transporter, spiro-OMeTAD, which promotes the efficient extraction of photogenerated carriers. However, further thermal cycles produced a detrimental effect on the PV performance of PSCs, with the short-circuit current and fill factor degrading faster than the open-circuit voltage. Similarly, the PV performance of PSCs degraded at high operation temperatures; both the short-circuit current and open-circuit voltage decreased with increasing temperature, but the temperature-dependent trend of the fill factor was the opposite. Our impedance spectroscopy analysis revealed a monotonous increase of the charge-transfer resistance and a concurrent decrease of the charge-recombination resistance with increasing temperature, indicating a high recombination of charge carriers. Our results revealed that both thermal cycling and high temperatures produce irreversible detrimental effects on the PSC performance because of the deteriorated interfacial photocarrier extraction. The present findings suggest that the development of robust charge transporters and proper interface engineering are critical for the deployment of perovskite PVs in harsh

  11. Effects of High Temperature and Thermal Cycling on the Performance of Perovskite Solar Cells: Acceleration of Charge Recombination and Deterioration of Charge Extraction

    KAUST Repository

    Sheikh, Arif D.

    2017-09-18

    In this work, we investigated the effects of high operating temperature and thermal cycling on the photovoltaic performance of perovskite solar cells (PSCs) with a typical mesostructured (m)-TiO2-CH3NH3PbI3-xClx-spiro-OMeTAD architecture. After carrying out temperature-dependent grazing incidence wide-angle X-ray scattering (GIWAXS), in-situ X-ray diffraction (XRD) and optical absorption experiments, thermal durability of PSCs was tested by subjecting the devices to repetitive heating to 70 °C and cooling to room temperature (20 °C). An unexpected regenerative effect was observed after the first thermal cycle; the average power conversion efficiency (PCE) increased by approximately 10 % in reference to the as-prepared device. This increase of PCE was attributed to the heating-induced improvement of crystallinity and p-doping in the hole-transporter, Spiro-OMeTAD, which promotes the efficient extraction of photo-generated carriers. However, further thermal cycles produced a detrimental effect on the photovoltaic performance of PSCs with short-circuit current and fill factor degrading faster than the open-circuit voltage. Similarly, the photovoltaic performance of PSCs degraded at high operation temperatures; both short-circuit current and open-circuit voltage decreased with increasing temperature, but the temperature-dependent trend of fill factor was opposite. Our impedance spectroscopy analysis revealed a monotonous increase of charge transfer resistance and a concurrent decrease of charge recombination resistance with increasing temperature, indicating high recombination of charge carriers. Our results revealed that both thermal cycling and high temperatures produce irreversible detrimental effects on the PSC performance due to the deteriorated interfacial photo-carrier extraction. The present findings suggest that development of robust charge transporters and proper interface engineering are critical for the deployment of perovskite photovoltaics in harsh

  12. Lithium polymer batteries and proton exchange membrane fuel cells as energy sources in hydrogen electric vehicles

    Science.gov (United States)

    Corbo, P.; Migliardini, F.; Veneri, O.

    This paper deals with the application of lithium ion polymer batteries as electric energy storage systems for hydrogen fuel cell power trains. The experimental study was firstly effected in steady state conditions, to evidence the basic features of these systems in view of their application in the automotive field, in particular charge-discharge experiments were carried at different rates (varying the current between 8 and 100 A). A comparison with conventional lead acid batteries evidenced the superior features of lithium systems in terms of both higher discharge rate capability and minor resistance in charge mode. Dynamic experiments were carried out on the overall power train equipped with PEM fuel cell stack (2 kW) and lithium batteries (47.5 V, 40 Ah) on the European R47 driving cycle. The usage of lithium ion polymer batteries permitted to follow the high dynamic requirement of this cycle in hard hybrid configuration, with a hydrogen consumption reduction of about 6% with respect to the same power train equipped with lead acid batteries.

  13. A kinetic Monte Carlo model with improved charge injection model for the photocurrent characteristics of organic solar cells

    Science.gov (United States)

    Kipp, Dylan; Ganesan, Venkat

    2013-06-01

    We develop a kinetic Monte Carlo model for photocurrent generation in organic solar cells that demonstrates improved agreement with experimental illuminated and dark current-voltage curves. In our model, we introduce a charge injection rate prefactor to correct for the electrode grid-size and electrode charge density biases apparent in the coarse-grained approximation of the electrode as a grid of single occupancy, charge-injecting reservoirs. We use the charge injection rate prefactor to control the portion of dark current attributed to each of four kinds of charge injection. By shifting the dark current between electrode-polymer pairs, we align the injection timescales and expand the applicability of the method to accommodate ohmic energy barriers. We consider the device characteristics of the ITO/PEDOT/PSS:PPDI:PBTT:Al system and demonstrate the manner in which our model captures the device charge densities unique to systems with small injection energy barriers. To elucidate the defining characteristics of our model, we first demonstrate the manner in which charge accumulation and band bending affect the shape and placement of the various current-voltage regimes. We then discuss the influence of various model parameters upon the current-voltage characteristics.

  14. Molecular semiconductor blends: microstructure, charge carrier transport and application in photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Opitz, Andreas; Wagner, Julia; Ecker, Bernhard; Bruetting, Wolfgang [Institute of Physics, University of Augsburg (Germany); Hinderhofer, Alexander; Schreiber, Frank [Institute of Applied Physics, University of Tuebingen (Germany)

    2009-07-01

    Blends of organic donor and acceptor materials have the potential of an increase of solar cell efficiency. However, the balance between charge carrier transport in phase-separated structures and exciton dissociation at the donor-acceptor interface has to be optimized. To analyze this relation in more detail the following molecular material combinations were investigated: (i) Copper phthalocyanine (CuPc) combined with fullerene C{sub 60} and (ii) CuPc in combination with perfluorinated CuPc (F{sub 16}CuPc). Measurements by X-ray diffraction and scanning force microscopy indicate the formation of phase-separated nanocrystals for blends of CuPc/C{sub 60} and the formation of mixed crystals in the CuPc/F{sub 16}CuPc system. The formation of mixed crystals is an interesting feature for organic blends which has not yet been explored in organic solar cells. We will discuss the implications of the different molecular arrangements on the optical and electrical properties as well as for the solar cell performance.

  15. Proton exchange membrane micro fuel cells on 3D porous silicon gas diffusion layers

    Science.gov (United States)

    Kouassi, S.; Gautier, G.; Thery, J.; Desplobain, S.; Borella, M.; Ventura, L.; Laurent, J.-Y.

    2012-10-01

    Since the 90's, porous silicon has been studied and implemented in many devices, especially in MEMS technology. In this article, we present a new approach to build miniaturized proton exchange membrane micro-fuel cells using porous silicon as a hydrogen diffusion layer. In particular, we propose an innovative process to build micro fuel cells from a “corrugated iron like” 3D structured porous silicon substrates. This structure is able to increase up to 40% the cell area keeping a constant footprint on the silicon wafer. We propose here a process route to perform electrochemically 3D porous gas diffusion layers and to deposit fuel cell active layers on such substrates. The prototype peak power performance was measured to be 90 mW cm-2 in a “breathing configuration” at room temperature. These performances are less than expected if we compare with a reference 2D micro fuel cell. Actually, the active layer deposition processes are not fully optimized but this prototype demonstrates the feasibility of these 3D devices.

  16. Charged particle mutagenesis at low dose and fluence in mouse splenic T cells

    Energy Technology Data Exchange (ETDEWEB)

    Grygoryev, Dmytro [Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239 (United States); Gauny, Stacey [Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Lasarev, Michael; Ohlrich, Anna [Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239 (United States); Kronenberg, Amy [Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Turker, Mitchell S., E-mail: turkerm@ohsu.edu [Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239 (United States); Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239 (United States)

    2016-06-15

    Highlights: • Densely ionizing forms of space radiation induce mutations in splenic T cells at low fluence. • Large interstitial deletions and discontinuous LOH patterns are radiation signature mutations. • Space radiation mutagenesis suggests a cancer risk from deep space travel. - Abstract: High-energy heavy charged particles (HZE ions) found in the deep space environment can significantly affect human health by inducing mutations and related cancers. To better understand the relation between HZE ion exposure and somatic mutation, we examined cell survival fraction, Aprt mutant frequencies, and the types of mutations detected for mouse splenic T cells exposed in vivo to graded doses of densely ionizing {sup 48}Ti ions (1 GeV/amu, LET = 107 keV/μm), {sup 56}Fe ions (1 GeV/amu, LET = 151 keV/μm) ions, or sparsely ionizing protons (1 GeV, LET = 0.24 keV/μm). The lowest doses for {sup 48}Ti and {sup 56}Fe ions were equivalent to a fluence of approximately 1 or 2 particle traversals per nucleus. In most cases, Aprt mutant frequencies in the irradiated mice were not significantly increased relative to the controls for any of the particles or doses tested at the pre-determined harvest time (3–5 months after irradiation). Despite the lack of increased Aprt mutant frequencies in the irradiated splenocytes, a molecular analysis centered on chromosome 8 revealed the induction of radiation signature mutations (large interstitial deletions and complex mutational patterns), with the highest levels of induction at 2 particles nucleus for the {sup 48}Ti and {sup 56}Fe ions. In total, the results show that densely ionizing HZE ions can induce characteristic mutations in splenic T cells at low fluence, and that at least a subset of radiation-induced mutant cells are stably retained despite the apparent lack of increased mutant frequencies at the time of harvest.

  17. Polymer-zeolite nanocomposite membranes for proton exchange membrane fuel cells

    Science.gov (United States)

    Holmberg, Brett Anderson

    2005-07-01

    Proton exchange membrane fuel cells (PEMFCs) have recently received a great deal of attention for their potential as compact, high efficiency power sources for portable, distributed generation, and transportation applications. Unfortunately, current proton exchange membrane (PEM) technology hinders fuel cell performance by limiting fuel cell operation temperature and methanol feed concentration in direct methanol fuel cells (DMFCs). Nafion-zeolite nanocomposite membranes that take advantage of the hydrophilicity, selectivity, and proton conductivity of zeolite nanocrystals have been developed to address these problems. All known zeolite topologies were evaluated as potential additives to Nafion proton exchange membranes. Zeolites Y and beta were determined to have great potential as additives due to their low framework density, three dimensional pore structure, and high hydrophilicity. Zeolite Y nanocrystal syntheses were optimized to enhance yield and produce smaller crystal size. Significant improvement of the acid stability of the zeolite Y nanocrystals was not achieved with both ammonium hexafluorosilicate treatments and direct high silica nanocrystal synthesis. However, control of zeolite Y nanocrystal framework Si/Al ratio was demonstrated in the range of SiO2/Al2O3 = 4.38 to 5.84 by manipulating the tetramethylammonium structure directing agent hydroxide content. Zeolite beta nanocrystals were investigated due to their inherent high silica content and high acid stability. Zeolite beta nanocrystals were hydrothermally synthesized with and without phenethyl (called PE-BEA and BEA respectively) organic functional groups. Sulfonic acid functionalized zeolite beta (SAPE-BEA) was generated by treating the PE-BEA nanocrystals with a concentrated sulfuric acid post synthesis treatment. SAPE-BEA samples demonstrated proton conductivities up to 0.01 S/cm at room temperature under water-saturated conditions using a newly developed characterization technique. With

  18. Coupling ion-exchangers with inexpensive activated carbon fiber electrodes to enhance the performance of capacitive deionization cells for domestic wastewater desalination.

    Science.gov (United States)

    Liang, Peng; Yuan, Lulu; Yang, Xufei; Zhou, Shaoji; Huang, Xia

    2013-05-01

    A capacitive deionization (CDI) cell was built with electrodes made of an inexpensive commercial activated carbon fiber (ACF), and then modified by incorporating ion-exchangers into the cell compartment. Three modified CDI designs were tested: MCDI - a CDI with electrodes covered by ion-exchange membranes (IEMs) of the same polarity, FCDI - a CDI with electrodes covered by ion-exchange felts (IEFs), and R-MCDI - an MCDI with cell chamber packed with ion-exchange resin (IER) granules. The cell was operated in the batch reactor mode with an initial salt concentration of 1000 mg/L NaCl, a typical level of domestic wastewater. The desalination tests involved investigations of two consecutive operation stages of CDIs: electrical adsorption (at an applied voltage of 1.2 V) and desorption [including short circuit (SC) desorption and discharge (DC) desorption]. The R-MCDI showed the highest electric adsorption as measured in the present study by desalination rate [670 ± 20 mg/(L h)] and salt removal efficiency (90 ± 1%) at 60 min, followed by the MCDI [440 ± 15 mg/(L h) and 60 ± 2%, respectively]. The superior desalination performance of the R-MCDI over other designs was also affirmed by its highest charge efficiency (110 ± 7%) and fastest desorption rates at both the SC [1960 ± 15 mg/(L·h)] and DC [3000 ± 20 mg/(L·h)] modes. The desalination rate and salt removal efficiency of the R-MCDI increased from ∼270 mg/(L h) and 83% to ∼650 mg/(L h) and 98% respectively when the applied voltage increased from 0.6 V to 1.4 V, while decreased slightly when lowering the salt water flow rate that fed into the cell. The packing of IER granules in the R-MCDI provided additional surface area for ions transfer; meanwhile, according to the results of electrochemical impedance spectroscopy (EIS) analysis, it substantially lower down the R-MCDI's ohmic resistance, resulting in improved desalination performance. Copyright © 2013 Elsevier Ltd. All

  19. CHARGE syndrome modeling using patient-iPSCs reveals defective migration of neural crest cells harboring CHD7 mutations.

    Science.gov (United States)

    Okuno, Hironobu; Renault Mihara, Francois; Ohta, Shigeki; Fukuda, Kimiko; Kurosawa, Kenji; Akamatsu, Wado; Sanosaka, Tsukasa; Kohyama, Jun; Hayashi, Kanehiro; Nakajima, Kazunori; Takahashi, Takao; Wysocka, Joanna; Kosaki, Kenjiro; Okano, Hideyuki

    2017-11-28

    CHARGE syndrome is caused by heterozygous mutations in the chromatin remodeler, CHD7, and is characterized by a set of malformations that, on clinical grounds, were historically postulated to arise from defects in neural crest formation during embryogenesis. To better delineate neural crest defects in CHARGE syndrome, we generated induced pluripotent stem cells (iPSCs) from two patients with typical syndrome manifestations, and characterized neural crest cells differentiated in vitro from these iPSCs (iPSC-NCCs). We found that expression of genes associated with cell migration was altered in CHARGE iPSC-NCCs compared to control iPSC-NCCs. Consistently, CHARGE iPSC-NCCs showed defective delamination, migration and motility in vitro, and their transplantation in ovo revealed overall defective migratory activity in the chick embryo. These results support the historical inference that CHARGE syndrome patients exhibit defects in neural crest migration, and provide the first successful application of patient-derived iPSCs in modeling craniofacial disorders.

  20. Biodegradation and proton exchange using natural rubber in microbial fuel cells.

    Science.gov (United States)

    Winfield, Jonathan; Ieropoulos, Ioannis; Rossiter, Jonathan; Greenman, John; Patton, David

    2013-11-01

    Microbial fuel cells (MFCs) generate electricity from waste but to date the technology's development and scale-up has been held-up by the need to incorporate expensive materials. A costly but vital component is the ion exchange membrane (IEM) which conducts protons between the anode and cathode electrodes. The current study compares natural rubber as an alternative material to two commercially available IEMs. Initially, the material proved impermeable to protons, but gradually a working voltage was generated that improved with time. After 6 months, MFCs with natural rubber membrane outperformed those with anion exchange membrane (AEM) but cation exchange membrane (CEM) produced 109 % higher power and 16 % higher current. After 11 months, polarisation experiments showed a decline in performance for both commercially available membranes while natural rubber continued to improve and generated 12 % higher power and 54 % higher current than CEM MFC. Scanning electron microscope images revealed distinct structural changes and the formation of micropores in natural latex samples that had been employed as IEM for 9 months. It is proposed that the channels and micropores formed as a result of biodegradation were providing pathways for proton transfer, reflected by the steady increase in power generation over time. These improvements may also be aided by the establishment of biofilms that, in contrast, caused declining performance in the CEM. The research demonstrates for the first time that the biodegradation of a ubiquitous waste material operating as IEM can benefit MFC performance while also improving the reactor's lifetime compared to commercially available membranes.

  1. Solid alkaline membrane fuel cell : what are they advantages and drawbacks compared to proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Coutanceau, C.; Baranton, S.; Simoes, M. [Univ. de Poitiers, Poitiers (France). Laboratoire de Catalyse en Chimie Organique, UMR CNRS

    2010-07-01

    Low temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs) and direct alcohol fuel cells (DAFCs) are promising power sources for portable electronics and transportation applications. However, these fuel cells require high amounts of platinum at the anodes to achieve high cell performance. Although alkaline membrane fuel cells (AFCs) may be an alternative to PEMFCs, the technology of low temperature fuel cells is less developed than that of fuel cells working with a solid acid electrolyte. Interest in solid alkaline membrane fuel cells (SAMFCs) has increased in recent years because it is easier to activate the oxidation and reduction reactions in alkaline medium than in acidic medium. Fewer platinum based catalysts are needed due to higher electrode kinetics. The development of hydroxyl conductive membrane makes this technology available, but the fuel to be used in the system must be considered. Pure hydrogen or hydrogen-rich gases offer high electric efficiency, but their production, storage, and distribution are not sufficient for a large-scale development. This paper discussed the relatively good electroreactivity of polyols such as glycerol and ethylene glycol in a SAMFC, as well as sodium borohydride (NaBH{sub 4}) as an alternative. The working principle of SAMFCs was also presented along with considerations regarding the electrochemical reactions occurring at the electrodes, and requirements concerning the catalysts, the triple phase boundary in the electrode and the anionic membrane. Palladium based catalysts were found to be an interesting alternative to platinum in SAMFCs. In situ FTIR measurements and oxidation products analysis was used to determine the electrooxidation pathways of alcohol and NaBH{sub 4}in alkaline medium. The study also included a comparison with oxidation mechanisms in acid medium. 8 refs.

  2. Conductivity Measurements of Synthesized Heteropoly Acid Membranes for Proton Exchange Membrane Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Record, K.A.; Haley, B.T.; Turner, J.

    2006-01-01

    Fuel cell technology is receiving attention due to its potential to be a pollution free method of electricity production when using renewably produced hydrogen as fuel. In a Proton Exchange Membrane (PEM) fuel cell H2 and O2 react at separate electrodes, producing electricity, thermal energy, and water. A key component of the PEM fuel cell is the membrane that separates the electrodes. DuPont’s Nafion® is the most commonly used membrane in PEM fuel cells; however, fuel cell dehydration at temperatures near 100°C, resulting in poor conductivity, is a major hindrance to fuel cell performance. Recent studies incorporating heteropoly acids (HPAs) into membranes have shown an increase in conductivity and thus improvement in performance. HPAs are inorganic materials with known high proton conductivities. The primary objective of this work is to measure the conductivity of Nafion, X-Ionomer membranes, and National Renewable Energy Laboratory (NREL) Developed Membranes that are doped with different HPAs at different concentrations. Four-point conductivity measurements using a third generation BekkTech conductivity test cell are used to determine membrane conductivity. The effect of multiple temperature and humidification levels is also examined. While the classic commercial membrane, Nafion, has a conductivity of approximately 0.10 S/cm, measurements for membranes in this study range from 0.0030 – 0.58 S/cm, depending on membrane type, structure of the HPA, and the relative humidity. In general, the X-ionomer with H6P2W21O71 HPA gave the highest conductivity and the Nafion with the 12-phosphotungstic (PW12) HPA gave the lowest. The NREL composite membranes had conductivities on the order of 0.0013 – 0.025 S/cm.

  3. Modelling, simulation and control of a proton exchange membrane fuel cell (PEMFC) power system

    Energy Technology Data Exchange (ETDEWEB)

    Al-Dabbagh, Ahmad W.; Lu, Lixuan; Mazza, Antonio [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, ON L1H 7K4 (Canada)

    2010-05-15

    Fuel cell power systems are emerging as promising means of electrical power generation on account of the associated clean electricity generation process, as well as their suitability for use in a wide range of applications. During the design stage, the development of a computer model for simulating the behaviour of a system under development can facilitate the experimentation and testing of that system's performance. Since the electrical power output of a fuel cell stack is seldom at a suitable fixed voltage, conditioning circuits and their associated controllers must be incorporated in the design of the fuel cell power system. This paper presents a MATLAB/Simulink model that simulates the behaviour of a Proton Exchange Membrane Fuel Cell (PEMFC), conditioning circuits and their controllers. The computer modelling of the PEMFC was based on adopted mathematical models that describe the fuel cell's operational voltage, while accounting for the irreversibilities associated with the fuel cell stack. The conditioning circuits that are included in the Simulink model are a DC-DC converter and DC-AC inverter circuits. These circuits are the commonly utilized power electronics circuits for regulating and conditioning the output voltage from a fuel cell stack. The modelling of the circuits is based on relationships that govern the output voltage behaviour with respect to their input voltages, switching duty cycle and efficiency. In addition, this paper describes a Fuzzy Logic Controller (FLC) design that is aimed at regulating the conditioning circuits to provide and maintain suitable electrical power for a wide range of applications. The model presented demonstrates the use of the FLC in conjunction with the PEMFC Simulink model and that it is the basis for more in-depth analytical models. (author)

  4. Direct-hydrogen-fueled proton-exchange-membrane fuel cell system for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Oei, D.; Adams, J.A.; Kinnelly, A.A. [and others

    1997-07-01

    In partial fulfillment of the U.S. Department of Energy Contract No. DE-ACO2-94CE50389, {open_quotes}Direct Hydrogen-Fueled Proton-Exchange-Membrane (PEM) Fuel Cell System for Transportation Applications{close_quotes}, this conceptual vehicle design report addresses the design and packaging of battery augmented fuel cell powertrain vehicles. This report supplements the {open_quotes}Conceptual Vehicle Design Report - Pure Fuel Cell Powertrain Vehicle{close_quotes} and includes a cost study of the fuel cell power system. The three classes of vehicles considered in this design and packaging exercise are the same vehicle classes that were studied in the previous report: the Aspire, representing the small vehicle class; the AIV (Aluminum Intensive Vehicle) Sable, representing the mid-size vehicle; and the E-150 Econoline, representing the van-size class. A preliminary PEM fuel cell power system manufacturing cost study is also presented. As in the case of the previous report concerning the {open_quotes}Pure Fuel Cell Powertrain Vehicle{close_quotes}, the same assumptions are made for the fuel cell power system. These assumptions are fuel cell system power densities of 0.33 kW/ka and 0.33 kW/l, platinum catalyst loading of less than or equal to 0.25 mg/cm{sup 2} total, and hydrogen tanks containing compressed gaseous hydrogen under 340 atm (5000 psia) pressure. The batteries considered for power augmentation of the fuel cell vehicle are based on the Ford Hybrid Electric Vehicle (HEV) program. These are state-of-the-art high power lead acid batteries with power densities ranging from 0.8 kW/kg to 2 kW/kg. The results reported here show that battery augmentation provides the fuel cell vehicle with a power source to meet instant high power demand for acceleration and start-up. Based on the assumptions made in this report, the packaging of the battery augmented fuel cell vehicle appears to be as feasible as the packaging of the pure fuel cell powered vehicle.

  5. Prognostics of Proton Exchange Membrane Fuel Cells stack using an ensemble of constraints based connectionist networks

    Science.gov (United States)

    Javed, Kamran; Gouriveau, Rafael; Zerhouni, Noureddine; Hissel, Daniel

    2016-08-01

    Proton Exchange Membrane Fuel Cell (PEMFC) is considered the most versatile among available fuel cell technologies, which qualify for diverse applications. However, the large-scale industrial deployment of PEMFCs is limited due to their short life span and high exploitation costs. Therefore, ensuring fuel cell service for a long duration is of vital importance, which has led to Prognostics and Health Management of fuel cells. More precisely, prognostics of PEMFC is major area of focus nowadays, which aims at identifying degradation of PEMFC stack at early stages and estimating its Remaining Useful Life (RUL) for life cycle management. This paper presents a data-driven approach for prognostics of PEMFC stack using an ensemble of constraint based Summation Wavelet- Extreme Learning Machine (SW-ELM) models. This development aim at improving the robustness and applicability of prognostics of PEMFC for an online application, with limited learning data. The proposed approach is applied to real data from two different PEMFC stacks and compared with ensembles of well known connectionist algorithms. The results comparison on long-term prognostics of both PEMFC stacks validates our proposition.

  6. Recovery mechanisms in proton exchange membrane fuel cells after accelerated stress tests

    Science.gov (United States)

    Zhang, Xu; Guo, Liejin; Liu, Hongtan

    2015-11-01

    The mechanisms of performance recovery after accelerated stress test (AST) in proton exchange membrane fuel cells (PEMFCs) are systematically studied. Experiments are carried out by incorporating a well-designed performance recovery procedure right after the AST protocol. The experiment results show that the cell performance recovers significantly from the degraded state after the AST procedure. The results from cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements further show that the performance recovery can be divided into kinetic and mass transport recoveries. It is further determined that the kinetic recovery, i.e. the recovery of electrochemical active area (ECA), is due to two distinct mechanisms: the reduction of platinum oxide and the re-attachment of detached platinum nanoparticles onto the carbon surface. The mass transport resistance is probably due to reduction of hydrophilic oxide groups on the carbon surface and the microstructure change that alleviates flooding. Performance comparisons show that the recovery procedure is highly effective, indicating the results of AST significantly over-estimate the true degradation in a PEM fuel cell. Therefore, a recovery procedure is highly recommended when an AST protocol is used to evaluate cell degradations to avoid over-estimating true performance degradations in PEMFCs.

  7. Contact behavior modelling and its size effect on proton exchange membrane fuel cell

    Science.gov (United States)

    Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

    2017-10-01

    Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

  8. A Review on Cold Start of Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Zhongmin Wan

    2014-05-01

    Full Text Available Successful and rapid startup of proton exchange membrane fuel cells (PEMFCs at subfreezing temperatures (also called cold start is of great importance for their commercialization in automotive and portable devices. In order to maintain good proton conductivity, the water content in the membrane must be kept at a certain level to ensure that the membrane remains fully hydrated. However, the water in the pores of the catalyst layer (CL, gas diffusion layer (GDL and the membrane may freeze once the cell temperature decreases below the freezing point (Tf. Thus, methods which could enable the fuel cell startup without or with slight performance degradation at subfreezing temperature need to be studied. This paper presents an extensive review on cold start of PEMFCs, including the state and phase changes of water in PEMFCs, impacts of water freezing on PEMFCs, numerical and experimental studies on PEMFCs, and cold start strategies. The impacts on each component of the fuel cell are discussed in detail. Related numerical and experimental work is also discussed. It should be mentioned that the cold start strategies, especially the enumerated patents, are of great reference value on the practical cold start process.

  9. Superhydrophobic PAN nanofibers for gas diffusion layers of proton exchange membrane fuel cells

    Science.gov (United States)

    Salahuddin, Mohammad; Hwang, Gisuk; Asmatulu, Ramazan

    2016-04-01

    Proton exchange membrane (PEM) fuel cells are considered to be the promising alternatives of natural resources for generating electricity and power. An optimal water management in the gas diffusion layers (GDL) is critical to high fuel cell performance. Its basic functions include transportation of the reactant gas from flow channels to catalyst effectively, draining out the liquid water from catalyst layer to flow channels, and conducting electrons with low humidity. In this study, polyacrylonitrile (PAN) was dissolved in a solvent and electrospun at various conditions to produce PAN nanofibers prior to the stabilization at 280 °C for 1 hour in the atmospheric pressure and carbonization at 850 °C for 1 hour. The surface hydrophobicity values of the carbonized PAN nanofibers were adjusted using superhydrophobic and hydrophilic agents. The thermal, mechanical, and electrical properties of the new GDLs depicted much better results compared to the conventionally used ones. The water condensation tests on the surfaces (superhydrophobic and hydrophilic) of the GDL showed a crucial step towards improved water managements in the fuel cell. This study may open up new possibilities for developing high- performing GDL materials for future PEM fuel cell applications.

  10. A Critical Evaluation of the Influence of the Dark Exchange Current on the Performance of Dye-Sensitized Solar Cells

    Science.gov (United States)

    García-Rodríguez, Rodrigo; Villanueva-Cab, Julio; Anta, Juan A.; Oskam, Gerko

    2016-01-01

    The influence of the thickness of the nanostructured, mesoporous TiO2 film on several parameters determining the performance of a dye-sensitized solar cell is investigated both experimentally and theoretically. We pay special attention to the effect of the exchange current density in the dark, and we compare the values obtained by steady state measurements with values extracted from small perturbation techniques. We also evaluate the influence of exchange current density, the solar cell ideality factor, and the effective absorption coefficient of the cell on the optimal film thickness. The results show that the exchange current density in the dark is proportional to the TiO2 film thickness, however, the effective absorption coefficient is the parameter that ultimately defines the ideal thickness. We illustrate the importance of the exchange current density in the dark on the determination of the current–voltage characteristics and we show how an important improvement of the cell performance can be achieved by decreasing values of the total series resistance and the exchange current density in the dark. PMID:28787833

  11. A Critical Evaluation of the Influence of the Dark Exchange Current on the Performance of Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Rodrigo García-Rodríguez

    2016-01-01

    Full Text Available The influence of the thickness of the nanostructured, mesoporous TiO2 film on several parameters determining the performance of a dye-sensitized solar cell is investigated both experimentally and theoretically. We pay special attention to the effect of the exchange current density in the dark, and we compare the values obtained by steady state measurements with values extracted from small perturbation techniques. We also evaluate the influence of exchange current density, the solar cell ideality factor, and the effective absorption coefficient of the cell on the optimal film thickness. The results show that the exchange current density in the dark is proportional to the TiO2 film thickness, however, the effective absorption coefficient is the parameter that ultimately defines the ideal thickness. We illustrate the importance of the exchange current density in the dark on the determination of the current–voltage characteristics and we show how an important improvement of the cell performance can be achieved by decreasing values of the total series resistance and the exchange current density in the dark.

  12. Sulfonation of cPTFE Film grafted Styrene for Proton Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Yohan Yohan

    2010-10-01

    Full Text Available Sulfonation of γ-ray iradiated and styrene-grafted crosslinked polytetrafluoroethylene film (cPTFE-g-S film have been done. The aim of the research is to make hydropyl membrane as proton exchange membrane fuel cell. Sulfonation was prepared with chlorosulfonic acid in chloroethane under various conditions. The impact of the percent of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film is examinated. The results show that sulfonation of surface-grafted films is incomplete at room  temperature. The increasing of concentration of chlorosulfonic acid and reaction temperature accelerates the reaction but they also add favor side reactions. These will lead to decreasing of the ion-exchange capacity, water uptake, and proton conductivity but increasing the resistance to oxidation in a perhidrol solution. The cPTFE-g-SS membrane which is resulted has stability in a H2O2 30% solution for 20 hours.

  13. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    KAUST Repository

    Liu, Jia

    2014-12-01

    Power production in microbial reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis stack. Typical MRC stacks use non-conductive spacers that block ion transport by the so-called spacer shadow effect. These spacers can be relatively thick compared to the membrane, and thus they increase internal stack resistance due to high solution (ohmic) resistance associated with a thick spacer. New types of patterned anion and cation exchange membranes were developed by casting membranes to create hemispherical protrusions on the membranes, enabling fluid flow between the membranes without the need for a non-conductive spacer. The use of the patterned membrane decreased the MRC stack resistance by ∼22 Ω, resulting in a 38% increase in power density from 2.50 ± 0.04 W m-2 (non-patterned membrane with a non-conductive spacer) to 3.44 ± 0.02 W m-2 (patterned membrane). The COD removal rate, coulombic efficiency, and energy efficiency of the MRC also increased using the patterned membranes compared to the non-patterned membranes. These results demonstrate that these patterned ion exchange membranes can be used to improve performance of an MRC. © 2014 Elsevier B.V. All rights reserved.

  14. Study of operating conditions and cell design on the performance of alkaline anion exchange membrane based direct methanol fuel cells

    Science.gov (United States)

    Prakash, G. K. Surya; Krause, Frederick C.; Viva, Federico A.; Narayanan, S. R.; Olah, George A.

    2011-10-01

    Direct methanol fuel cells using an alkaline anion exchange membrane (AAEM) were prepared, studied, and optimized. The effects of fuel composition and electrode materials were investigated. Membrane electrode assemblies fabricated with Tokuyama® AAEM and commercial noble metal catalysts achieved peak power densities between 25 and 168 mW cm-2 depending on the operating temperature, fuel composition, and electrode materials used. Good electrode wettability at the anode was found to be very important for achieving high power densities. The performance of the best AAEM cells was comparable to Nafion®-based cells under similar conditions. Factors limiting the performance of AAEM MEAs were found to be different from those of Nafion® MEAs. Improved electrode kinetics for methanol oxidation in alkaline electrolyte at Pt-Ru are apparent at low current densities. At high current densities, rapid CO2 production converts the hydroxide anions, necessary for methanol oxidation, to bicarbonate and carbonate: consequently, the membrane and interfacial conductivity are drastically reduced. These phenomena necessitate the use of aqueous potassium hydroxide and wettable electrode materials for efficient hydroxide supply to the anode. However, aqueous hydroxide is not needed at the cathode. Compared to AAEM-based fuel cells, methanol fuel cells based on proton-conducting Nafion® retain better performance at high current densities by providing the benefit of carbon dioxide rejection.

  15. Enhanced visible light absorption and reduced charge recombination in AgNP plasmonic photoelectrochemical cell

    Directory of Open Access Journals (Sweden)

    Samaila Buda

    Full Text Available In this research work, silver nanoparticles (AgNP were synthesized using a simple solvothermal technique, the obtained AgNP were used to prepare a titania/silver (TiO2/Ag nanocomposites with varied amount of Ag contents and used to fabricated a photoanode of dye-sensitized solar cell (DSSC. X-ray photoelectron spectroscopy (XPS was used to ascertain the presence of silver in the nanocomposite. A photoluminance (PL spectra of the nanocomposite powder shows a low PL activity which indicates a reduced election- hole recombination within the material. UV–vis spectra reveal that the Ag in the DSSC photoanode enhances the light absorption of the solar cell device within the visible range between λ = 382 nm and 558 nm nm owing to its surface plasmon resonance effect. Power conversion efficiency was enhanced from 4.40% for the pure TiO2 photoanode based device to 6.56% for the device fabricated with TiO2/Ag due to the improvement of light harvesting caused by the localized surface plasmonic resonance effect of AgNP. The improvement of power conversion was also achieved due to the reduced charge recombination within the photoanode. Keywords: Nanoparticle, Silver, Plasmonic, Power, Photon

  16. Enhanced visible light absorption and reduced charge recombination in AgNP plasmonic photoelectrochemical cell

    Science.gov (United States)

    Buda, Samaila; Shafie, Suhaidi; Rashid, Suraya Abdul; Jaafar, Haslina; Sharif, N. F. M.

    In this research work, silver nanoparticles (AgNP) were synthesized using a simple solvothermal technique, the obtained AgNP were used to prepare a titania/silver (TiO2/Ag) nanocomposites with varied amount of Ag contents and used to fabricated a photoanode of dye-sensitized solar cell (DSSC). X-ray photoelectron spectroscopy (XPS) was used to ascertain the presence of silver in the nanocomposite. A photoluminance (PL) spectra of the nanocomposite powder shows a low PL activity which indicates a reduced election- hole recombination within the material. UV-vis spectra reveal that the Ag in the DSSC photoanode enhances the light absorption of the solar cell device within the visible range between λ = 382 nm and 558 nm nm owing to its surface plasmon resonance effect. Power conversion efficiency was enhanced from 4.40% for the pure TiO2 photoanode based device to 6.56% for the device fabricated with TiO2/Ag due to the improvement of light harvesting caused by the localized surface plasmonic resonance effect of AgNP. The improvement of power conversion was also achieved due to the reduced charge recombination within the photoanode.

  17. Enthalpy analysis and Heat Exchanger Sizing of an Air-cooled Proton Exchange Membrane Fuel Cell System

    DEFF Research Database (Denmark)

    Gao, Xin; Berning, Torsten; Kær, Søren Knudsen

    the warmer exhaust air is used to pre-heat and also humidify the incoming colder and dryer air stream using an enthalpy wheel. It is important to thermodynamically understand such a fuel cell system, and in this work the enthalpy streams and the humidity stream are followed throughout the fuel cell system...... simulations have been carried out to better understand the distribution of the reactant air over the fuel cell stack and the resulting temperature distribution across the stack. These results suggest that the humidifying function of the current enthalpy wheel is negligible and a smaller enthalpy wheel...

  18. Experimental study on the influence of charge exchange on the stopping power in the interaction of chlorine with a gas and a deuterium plasma; Etude experimentale de l`influence des echanges de charges sur le pouvoir d`arret dans l`interaction d`ions chlore avec un gaz et un plasma de deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Nectoux, Marie [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1998-01-06

    This thesis is placed in the context of the physics of energy deposition of a multicharged heavy ion beam in matter at intermediate energies. The experiment gave measurements of energy loss as a function of final charge state for chlorine ions at 1.7 MeV/u in deuterium gas or plasma. In this way, we explore the influence of charge state evolution, depending on experimentally measured capture and ionization cross sections and the electron density of the target, on energy loss. The target is cylindrical and enclosed by two fast valves. The plasma is created in the gas by a discharge, which induces a magnetic perturbation of the beam (lens effect). This effect induces a divergent and misaligned outgoing beam. A simulation including charge state and velocity evolution of the projectile in flight in the magnetic field has been made in order to optimize beam analysis, to reach a precision better than 10{sup -3} in energy measurement. This study led to removal of the target to the `Split Pole`, a refocusing magnetic spectrometer. The first results obtained clearly show the dependence of energy loss on exit charge and especially on its evolution in the target. This is explained in terms of the lengths covered by the projectile in its successive charge states in the target, which depends on target electron density and the medium considered. In plasma, we observed an energy distribution with exit charge twice that observed in gas, because of a strong decrease of charge exchange. A comparison of data obtained in gas with stopping power calculated from Bethe-Bloch-Barkas theory leads to the necessity of including spatial extension of the projectile charge in the theory. (author) 81 refs., 62 figs., 5tabs.

  19. Nanoclay gelation approach toward improved dye-sensitized solar cell efficiencies: an investigation of charge transport and shift in the TiO2 conduction band.

    Science.gov (United States)

    Wang, Xiu; Kulkarni, Sneha A; Ito, Bruno Ieiri; Batabyal, Sudip K; Nonomura, Kazuteru; Wong, Chee Cheong; Grätzel, Michael; Mhaisalkar, Subodh G; Uchida, Satoshi

    2013-01-23

    Nanoclay minerals play a promising role as additives in the liquid electrolyte to form a gel electrolyte for quasi-solid-state dye-sensitized solar cells, because of the high chemical stability, unique swelling capability, ion exchange capacity, and rheological properties of nanoclays. Here, we report the improved performance of a quasi-solid-state gel electrolyte that is made from a liquid electrolyte and synthetic nitrate-hydrotalcite nanoclay. Charge transport mechanisms in the gel electrolyte and nanoclay interactions with TiO(2)/electrolyte interface are discussed in detail. The electrochemical analysis reveals that the charge transport is solely based on physical diffusion at the ratio of [PMII]:[I(2)] = 10:1 (where PMII is 1-propyl-3-methylimidazolium iodide). The calculated physical diffusion coefficient shows that the diffusion of redox ions is not affected much by the viscosity of nanoclay gel. The addition of nitrate-hydrotalcite clay in the electrolyte has the effect of buffering the protonation process at the TiO(2)/electrolyte interface, resulting in an upward shift in the conduction band and a boost in open-circuit voltage (V(OC)). Higher V(OC) values with undiminished photocurrent is achieved with nitrate-hydrotalcite nanoclay gel electrolyte for organic as well as for inorganic dye (D35 and N719) systems. The efficiency for hydrotalcite clay gel electrolyte solar cells is increased by 10%, compared to that of the liquid electrolyte. The power conversion efficiency can reach 10.1% under 0.25 sun and 9.6% under full sun. This study demonstrates that nitrate-hydrotalcite nanoclay in the electrolyte not only solidifies the liquid electrolyte to prevent solvent leakage, but also facilitates the improvement in cell efficiency.

  20. Proton exchange membrane with hydrophilic capillaries for elevated temperature PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xue-Min; Mei, Ping; Mi, Yuanzhu; Gao, Lin; Qin, Shaoxiong [College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434023 (China)

    2009-01-15

    Novel water-retention proton exchange membrane of Nafion-phosphotungstic acid/mesoporous silica with hydrophilic capillaries has been fabricated to improve the elevated temperature performance of the PEM fuel cells. Due to the hydrophilic capillarity of the HPW/meso-SiO{sub 2} mesoporous structure, the Nafion-HPW/meso-SiO{sub 2} composite membrane retained 23.7 wt% of water after being dried in 100 C for 2 h and then exposed in 25 RH% gas for 2 h. As a result, under the condition of elevated temperature of 120 C and low humidity of 25 RH%, the Nafion-HPW/meso-SiO{sub 2} composite membrane showed a steady performance. (author)